Toner for developing electrostatic images and method for producing the same

Abstract

To provide an electrostatic charge image developing toner and electrostatic charge image developing toner manufacturing method that are excellent in anti-folding property of a printed material while satisfying fixability at low temperature.SOLUTION: An electrostatic charge image developing toner of the present invention is the electrostatic charge image developing toner that includes a toner base particle containing binder resin and colorant, in which the toner base particle contains a polymer that has a first structure unit to be represented by at least a following general formula (1). As shown below, in the general formula (1), R1 and R2 respectively represent an alkyl group having a hydrogen atom or carbon number of 1 to 4, independently.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a toner for developing electrostatic images and a method for producing the toner for developing electrostatic images, and more particularly to a toner for developing electrostatic images that has satisfactory low-temperature fixability and excellent bending resistance for printed matter, and a method for producing the same. [Background technology]

[0002] In the printing field where images are formed by electrophotography, there has been a demand in recent years for toners for developing electrostatic images (hereinafter also simply referred to as "toner") that can meet the demands of reduced power consumption, faster printing speeds, diversification of image formation media, higher image quality, and reduced environmental impact. The characteristics required for such toner include low-temperature fixability, which allows toner images to be fixed at lower temperatures than conventional toners, and improved fixing strength. Furthermore, as toners expand beyond the traditional office market into the light printing market, there is a demand for improved stability in the image quality of printed products.

[0003] Toners typically contain a binder resin (hereinafter also referred to as "toner binder") that functions as a binder, and hybrid resins such as styrene-acrylic resins, polyester resins, and polyester resins having grafted acrylic polymer segments are known to be used as binder resins. In response to the above-mentioned requirements, techniques are known for improving low-temperature fixability by improving these toner binders (see, for example, Patent Documents 1 to 3).

[0004] In addition, not only in the light printing market, but also in other markets, there is a demand for smaller toner particle size to achieve higher image quality in printed materials, and toner production methods are shifting from the conventional pulverization method to chemical methods. By reducing the toner particle size, the toner can adhere more uniformly to the electrostatic latent image, thereby achieving higher image quality. In this way, by adopting a binder resin that can be fixed at a lower temperature and by reducing the toner particle diameter, it is possible to reduce power consumption, increase printing speed, improve image quality, and reduce the environmental impact.

[0005] On the other hand, there has been active expansion into the light printing market, and there is an increasing demand for no toner peeling (spine cracks) caused by folding or bending, which is a common problem when printing small lot booklets, etc. To address this issue, post-processing such as lamination using polypropylene (PP) film is being used to improve folding and bending resistance. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-279714 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-287229 [Patent Document 3] Japanese Patent Application Laid-Open No. 2010-15159 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in consideration of the above problems and circumstances, and the problem to be solved is to provide a toner for developing electrostatic images that has satisfactory low-temperature fixability and excellent bending resistance of printed matter, and a method for producing the same. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the present inventors have investigated the causes of the above-mentioned problems and have found that by including a polymer having a specific structural unit as a binder resin, it is possible to provide a toner for developing electrostatic images that has satisfactory low-temperature fixability and excellent bending resistance of printed matter, and have arrived at the present invention. That is, the above-mentioned problems of the present invention are solved by the following means.

[0009] 1. A toner for developing electrostatic images, comprising toner base particles containing a binder resin and a colorant, The toner base particles contain, as the binder resin, ,under The first structural unit represented by the general formula (1) and other secondary structural units The copolymer contains death, The second structural unit is at least n-butyl acrylate, 2-ethylhexyl acrylate, or methyl methacrylate. 1. A toner for developing electrostatic images, comprising: [ka] [In general formula (1), R1 and R2 each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.]

[0010] 2. The toner for developing electrostatic images according to item 1, wherein R1 and R2 in the general formula (1) each independently represent a hydrogen atom or a methyl group.

[0011] 3. The toner for developing electrostatic images according to item 1 or 2, wherein R1 in the general formula (1) represents a methyl group and R2 represents a hydrogen atom.

[0015] 4. The binder resin contains 5 to 30% by mass of a crystalline polyester resin. 3 Item 1. The toner for developing electrostatic images according to any one of items 1 to 9.

[0016] 5. The crystalline polyester resin is a hybrid crystalline polyester resin formed by chemically bonding a polyester polymer segment and a vinyl polymer segment. 4 Item 1. The toner for developing electrostatic images according to item 1.

[0017] 6. A method for producing a toner for developing electrostatic images, the toner comprising toner base particles containing a binder resin and a colorant, comprising: A first polymerizable monomer having at least a structure represented by the following general formula (2): and other secondary structural units The present invention has a step of preparing a resin particle dispersion containing a polymer obtained by copolymerizing death, The second structural unit is at least n-butyl acrylate, 2-ethylhexyl acrylate, or methyl methacrylate. 1. A method for producing a toner for developing electrostatic images, comprising: [ka] [In general formula (2), R1 and R2 each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.] [Effects of the Invention]

[0018] According to the above-mentioned means of the present invention, it is possible to provide a toner for developing electrostatic images which has satisfactory low-temperature fixability and excellent bending resistance of printed matter, and a method for producing the same. Although the mechanism by which the effects of the present invention are manifested or the mechanism of action has not been clarified, it is speculated as follows: Note that the following mechanism is based on speculation, and the present invention is not limited to the following mechanism in any way. In the following description, the polymer having the first structural unit represented by the general formula (1) is also referred to as the "polymer according to the present invention." Conventional toners containing styrene-acrylic resins are primarily composed of structural units derived from styrene, methyl methacrylate, and n-butyl acrylate. In order to reduce power consumption during printing, efforts are being made to lower the Tg (glass transition temperature) and molecular weight, thereby achieving so-called low-temperature fixing. On the other hand, there is a limit to the level at which low-temperature fixation, particularly low Tg, can be reduced because blocking is likely to occur during toner transport. Furthermore, as the molecular weight decreases, the interaction between polymer chains decreases, making it difficult to withstand stress caused by bending, resulting in breakage and making it difficult to retain images on the medium. Thus, achieving low-temperature fixation while ensuring bending resistance is a difficult challenge, and achieving both is required, particularly in the field of commercial printing. The reason why the toner of the present invention is able to satisfy the low-temperature fixing requirement while ensuring bending resistance is thought to be due to the change in the interaction between polymer chains caused by the introduction of a specific structural unit (first structural unit). By incorporating a polymer having the first structural unit represented by the general formula (1) into a toner binder, a resin structure is formed in which bulky substituents are directly bonded to the main chain. This results in a mixture of rigid portions where the main chain becomes more rigid, and portions where the freedom of movement of the main chain is increased due to steric hindrance caused by the bulky substituents. This is thought to be why the stress generated by bending the printed material can be converted into thermal energy, improving bending resistance. DETAILED DESCRIPTION OF THE INVENTION

[0019] The toner for developing electrostatic images of the present invention is a toner for developing electrostatic images comprising toner base particles containing a binder resin and a colorant, and is characterized in that the toner base particles contain, as the binder resin, at least a polymer having a first structural unit represented by the following general formula (1): This feature is a technical feature common to or corresponding to each of the following embodiments.

[0020] In an embodiment of the present invention, it is preferable that R1 and R2 in the general formula (1) each independently represent a hydrogen atom or a methyl group, since this allows for a better balance between low-temperature fixability and bending resistance.

[0021] In addition, it is preferable that R1 in the general formula (1) represents a methyl group and R2 represents a hydrogen atom, in order to achieve both low-temperature fixability and bending resistance.

[0022] It is preferable that the toner base particles contain a copolymer having the first structural unit and another second structural unit as the binder resin, in that the effects of the present invention can be exhibited more efficiently.

[0023] Furthermore, it is preferable that the other second structural unit is at least a structural unit derived from styrene, acrylic acid, an acrylic acid ester, methacrylic acid, or a methacrylic acid ester, and particularly that the second structural unit is at least styrene, n-butyl acrylate, 2-ethylhexyl acrylate, methacrylic acid, or methyl methacrylate, in that this makes it easier to adjust the glass transition temperature of the polymer according to the present invention.

[0024] The binder resin preferably contains crystalline polyester resin in the range of 5 to 30% by mass. Crystalline polyester resin has a faster melting rate than styrene-acrylic resin and can improve the fixation of toner to paper. Therefore, when crystalline polyester resin is contained in an amount of 5% by mass or more, the fixation improvement effect is significant, and when it is contained in an amount of 30% by mass or less, the charge retention ability of the toner is not reduced and it can be used as a toner. Therefore, from the viewpoint of achieving both fixation and charge retention, it is preferable to contain it in the range of 5 to 30% by mass.

[0025] It is preferable that the crystalline polyester resin is a hybrid crystalline polyester resin formed by chemically bonding a polyester polymerization segment and a vinyl polymerization segment, because the hybrid crystalline polyester resin is partially compatible with the polymer having the first structural unit represented by the general formula (1) and is finely dispersed in the toner, thereby obtaining excellent low-temperature fixability.

[0026] The method for producing a toner for developing electrostatic images of the present invention is a method for producing a toner for developing electrostatic images comprising toner base particles containing a binder resin and a colorant, and is characterized by comprising a step of preparing a resin particle dispersion containing a polymer obtained by copolymerizing at least a first polymerizable monomer having a structure represented by the following general formula (2): This makes it possible to produce a toner having good low-temperature fixability and excellent bending resistance.

[0027] The present invention, its components, and embodiments and modes for carrying out the present invention will be described below. In this application, the symbol "to" is used to mean that the numerical values ​​before and after it are included as lower and upper limits.

[0028] [Toner for developing electrostatic images of the present invention] The toner for developing electrostatic images (hereinafter also simply referred to as "toner") of the present invention is a toner for developing electrostatic images comprising toner base particles containing a binder resin and a release agent, and is characterized in that the toner base particles contain, as the binder resin, at least a polymer having a first structural unit represented by the following general formula (1): In this specification, "toner base particles" refer to the base of "toner particles." "Toner base particles" contain at least a binder resin and a release agent, and may contain other components such as a colorant and a charge control agent as necessary. "Toner base particles" are called "toner particles" when external additives are added. "Toner" refers to an aggregate of "toner particles."

[0029] <Binder resin> The binder resin according to the present invention contains a polymer having a first structural unit represented by the following general formula (1). [ka]

[0030] [In general formula (1), R1 and R2 each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.]

[0031] (Polymer having a first structural unit represented by general formula (1)) In the general formula (1), R1 and R2 each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Specific examples thereof include a methyl group, an n-butyl group, and an iso-butyl group. From the viewpoint of further improving low-temperature fixability and bending resistance, it is preferable that R1 and R2 each independently represent a hydrogen atom or a methyl group, and it is particularly preferable that R1 represents a methyl group and R2 represents a hydrogen atom.

[0032] The polymer having the first structural unit represented by the general formula (1) can be synthesized by polymerizing a monomer having a structure represented by the following general formula (2) (hereinafter also referred to as "first polymerizable monomer"). [ka]

[0033] [In general formula (2), R1 and R2 each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.] R1 and R2 have the same meanings as R1 and R2 in the general formula (1). The first polymerizable monomer may be used alone or in combination of two or more kinds. Specific examples of the first polymerizable monomer include, but are not limited to, the following exemplary compounds M1 to M8. [ka]

[0034] The first polymerizable monomer may be a commercially available product or a synthetic product. The polymerization method for the first polymerizable monomer is not particularly limited, but from the viewpoint of easy synthesis, a method of radically polymerizing the monomer using a known oil-soluble or water-soluble radical polymerization initiator is preferred. That is, a method for producing a toner according to a preferred embodiment of the present invention includes the steps of (radical) polymerizing a first polymerizable monomer having a structure represented by the general formula (2) to synthesize a polymer having a first structural unit represented by the general formula (1), and preparing a resin particle dispersion containing the polymer.

[0035] Specific examples of oil-soluble polymerization initiators used in radical polymerization include the following azo or diazo polymerization initiators and peroxide polymerization initiators. If necessary, known chain transfer agents such as n-octyl mercaptan and n-octyl-3-mercaptopropionate may also be used. Examples of the azo or diazo polymerization initiator include 2,2'-azobis-(2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, and azobisisobutyronitrile. Examples of peroxide polymerization initiators include benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide, 2,2-bis-(4,4-t-butylperoxycyclohexyl)propane, and tris-(t-butylperoxy)triazine.

[0036] Furthermore, when the polymer having the first structural unit represented by the general formula (1) according to the present invention is formed by emulsion polymerization, a water-soluble radical polymerization initiator can be used. Examples of the water-soluble radical polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate, azobisaminodipropane acetate, azobiscyanovaleric acid and its salts, and hydrogen peroxide. The polymerization temperature varies depending on the types of monomers and polymerization initiators used, but is preferably within a range of 50 to 100° C., and more preferably within a range of 55 to 90° C. The polymerization time also varies depending on the types of monomers and polymerization initiators used, but is preferably, for example, 1 to 12 hours.

[0037] (Polymers with other structural units) The polymer having the first structural unit represented by the general formula (1) according to the present invention may be a polymer obtained only from a polymerizable monomer having a structure represented by the general formula (2) (first polymerizable monomer). However, from the viewpoint of more efficiently exerting the effects of the present invention, it is preferable that the polymer is a copolymer of the first polymerizable monomer with another polymerizable monomer copolymerizable with the first polymerizable monomer (also referred to as a "second polymerizable monomer") as described below.

[0038] Examples of the second polymerizable monomer include styrene-based monomers such as styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o-methoxystyrene, p-methoxystyrene, m-methoxystyrene, o-ethylstyrene, m-ethylstyrene, p-ethylstyrene, o-acetoxystyrene, m-acetoxystyrene, and p-acetoxystyrene; methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, tert-butyl acrylate, isobutyl acrylate (isobutyl acrylate), acrylic acid, acrylic acid esters ... acrylates such as n-octyl methacrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, and phenyl acrylate; and methacrylates such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, and diethylaminoethyl methacrylate. Among these, from the viewpoint of facilitating adjustment of the glass transition temperature of the polymer, at least one selected from styrene and acrylic acid esters is preferred, at least one selected from the group consisting of styrene, n-butyl acrylate, 2-ethylhexyl acrylate, and methyl methacrylate is more preferred, and at least one of styrene and n-butyl acrylate is even more preferred.

[0039] Furthermore, a polymerizable monomer having an ionically dissociable group may be used as the second polymerizable monomer. The polymerizable monomer having an ionically dissociable group is, for example, one having a group such as a carboxy group, a sulfonic acid group, or a phosphate group. Specific examples include acrylic acid, methacrylic acid, maleic acid, itaconic acid, and fumaric acid. Of these, acrylic acid or methacrylic acid is preferred. These second polymerizable monomers can be used alone or in combination of two or more.

[0040] In the polymer according to the present invention, the content of the structural units derived from the first polymerizable monomer is, for example, preferably in the range of 10 to 60 mass %, and more preferably in the range of 20 to 50 mass %, where the total structural units of the polymer according to the present invention is 100 mass %. In the polymer according to the present invention, the content of the structural unit derived from the second polymerizable monomer is not particularly limited, and can be adjusted appropriately depending on the type of the structural unit. For example, when the second polymerizable monomer is the above-mentioned styrene-based monomer, the content of the structural units derived from the styrene-based monomer in the polymer according to the present invention is preferably in the range of 10 to 50 mass%, and more preferably in the range of 20 to 40 mass%, with the total structural units of the polymer according to the present invention being 100 mass%. When the second polymerizable monomer is an acrylic acid ester or a methacrylic acid ester, the content of structural units derived from the acrylic acid ester or the methacrylic acid ester in the polymer according to the present invention is preferably within a range of 5 to 50 mass %, and more preferably within a range of 10 to 40 mass %, with the total structural units of the polymer according to the present invention being 100 mass %. When a polymerizable monomer having an ionically dissociable group is used, the content of the structural unit is preferably within a range of 3 to 8% by mass, with the total structural units of the polymer according to the present invention being 100% by mass.

[0041] The method for synthesizing the polymer of the present invention using the first polymerizable monomer and the second polymerizable monomer is the same as the polymerization method for the first polymerizable monomer described above, and therefore, description thereof will be omitted here.

[0042] The polymer according to the present invention preferably has a peak molecular weight obtained from the molecular weight distribution measured by gel permeation chromatography (GPC) in terms of polystyrene within the range of 3500 to 35000, more preferably within the range of 10000 to 30000. A peak molecular weight within such a range is preferable because the polymer has an appropriate melt viscosity during fixing, enabling both good fixing properties and offset resistance to be achieved. The peak molecular weight is the molecular weight corresponding to the elution time of the peak top in the molecular weight distribution. When there are multiple peaks in the molecular weight distribution, it refers to the molecular weight corresponding to the elution time of the peak top with the largest peak area ratio.

[0043] The peak molecular weight of a polymer can be measured by the following method. Specifically, using an apparatus "HLC-8220" (manufactured by Tosoh Corporation) and a column "TSKguard column + TSKgel Super HZM-M triple column" (manufactured by Tosoh Corporation), the column temperature is maintained at 40°C, tetrahydrofuran (THF) is passed as a carrier solvent at a flow rate of 0.2 ml / min, and the measurement sample is dissolved in tetrahydrofuran to a concentration of 1 mg / ml under dissolution conditions of 5 minutes of treatment using an ultrasonic disperser at room temperature (25°C). Next, the sample solution is obtained by processing it with a membrane filter with a pore size of 0.2 μm, and 10 μl of this sample solution is injected into the device together with the above-mentioned carrier solvent, and detected using a refractive index detector (RI detector).The molecular weight distribution of the measurement sample is measured.

[0044] From the viewpoint of a balance between low-temperature fixability and bending resistance, the content of the polymer according to the present invention is preferably in the range of 65 to 99% by mass, and more preferably in the range of 70 to 95% by mass, with the total mass of the binder resin being 100% by mass.

[0045] The binder resin according to the present invention may contain other resins in addition to the polymer according to the present invention, and resins generally used as binder resins constituting toner can be used without any restrictions. Specific examples include polyester resins, silicone resins, polyolefin resins, polyamide resins, epoxy resins, etc. These other resins can be used alone or in combination of two or more.

[0046] The polyester resin that can be used as the binder resin will be described below. (polyester resin) The polyester resin is a known polyester resin obtained by polycondensation reaction of a divalent or higher carboxylic acid (a polycarboxylic acid component) and a divalent or higher alcohol (a polyhydric alcohol component). The polyester resin may be amorphous or crystalline. The valence of the polycarboxylic acid component and the polyhydric alcohol component is preferably 2 to 3, and particularly preferably 2. Therefore, a particularly preferred embodiment in which the valence is 2 (i.e., a dicarboxylic acid component and a diol component) will be described.

[0047] Examples of the dicarboxylic acid component include saturated aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid (dodecanedioic acid), 1,11-undecanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,13-tridecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,16-hexadecanedicarboxylic acid, and 1,18-octadecanedicarboxylic acid; methylenesuccinic acid; Examples of suitable dicarboxylic acids include unsaturated aliphatic dicarboxylic acids such as fumaric acid, maleic acid, 3-hexenedioic acid, 3-octenedioic acid, and dodecenylsuccinic acid; and unsaturated aromatic dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, t-butylisophthalic acid, tetrachlorophthalic acid, chlorophthalic acid, nitrophthalic acid, p-phenylenediacetic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, and anthracenedicarboxylic acid. Lower alkyl esters and acid anhydrides of these dicarboxylic acids can also be used. The dicarboxylic acid components may be used alone or in combination. In addition, trivalent or higher polyvalent carboxylic acids such as trimellitic acid and pyromellitic acid, anhydrides of the above carboxylic acid compounds, or alkyl esters having 1 to 3 carbon atoms can also be used.

[0048] Examples of the diol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,18-octadecanediol, 1,20-eicosanediol, and neopentane. Examples of the diol component include saturated aliphatic diols such as ethylene glycol; unsaturated aliphatic diols such as 2-butene-1,4-diol, 3-butene-1,4-diol, 2-butyne-1,4-diol, 3-butyne-1,4-diol, and 9-octadecene-7,12-diol; and aromatic diols such as bisphenols such as bisphenol A and bisphenol F, and alkylene oxide adducts of bisphenols such as ethylene oxide adducts and propylene oxide adducts of these bisphenols. Derivatives of these diols can also be used. The diol component may be used alone or in combination of two or more.

[0049] The method for producing the polyester resin is not particularly limited, and the polyester resin can be produced by polycondensing (esterifying) the polycarboxylic acid component and the polyhydric alcohol component using a known esterification catalyst. Catalysts that can be used in producing polyester resins include alkali metal compounds such as sodium and lithium, compounds containing Group 2 elements such as magnesium and calcium, compounds of metals such as aluminum, zinc, manganese, antimony, titanium, tin, zirconium, and germanium, phosphorous compounds, phosphoric acid compounds, and amine compounds. Specific examples of tin compounds include dibutyltin oxide (dibutyltin oxide), tin octoate, tin dioctoate, and salts thereof.

[0050] Examples of titanium compounds include titanium alkoxides such as tetra-normal-butyl titanate (Ti(On-Bu)4), tetraisopropyl titanate, tetramethyl titanate, and tetrastearyl titanate; titanium acylates such as polyhydroxytitanium stearate; and titanium chelates such as titanium tetraacetylacetonate, titanium lactate, and titanium triethanolamine.

[0051] The germanium compound may include germanium dioxide. Further, examples of the aluminum compound include polyaluminum hydroxide, aluminum alkoxide, tributylaluminate, etc. These may be used alone or in combination of two or more.

[0052] The polymerization temperature is not particularly limited, but is preferably within the range of 70 to 250° C. The polymerization time is also not particularly limited, but is preferably 0.5 to 10 hours. During the polymerization, the reaction system may be reduced in pressure as necessary. The polyester resin may be a hybrid crystalline polyester resin having a graft copolymer structure of a polyester polymer segment (also referred to as a "polyester resin segment") and a vinyl polymer segment (also referred to as a "styrene-acrylic polymer segment" or "amorphous resin segment"). This allows the hybrid crystalline polyester resin to have a vinyl resin segment, which is the main component of the binder resin, and thus the hybrid crystalline polyester resin is partially compatible with the polymer according to the present invention and finely dispersed in the toner, thereby achieving excellent low-temperature fixability. Furthermore, the composition ratio of the polyester polymerization segment to the vinyl polymerization segment in the hybrid crystalline polyester resin is preferably 85 to 95% by mass of the polyester polymerization segment and 5 to 15% by mass of the vinyl polymerization segment, and more preferably 90 to 95% by mass of the polyester polymerization segment and 5 to 10% by mass of the vinyl polymerization segment.

[0053] Examples of the synthesis method for the hybrid crystalline polyester resin include the following synthesis methods (a), (b) and (c). (a) A method in which a bireactive monomer is reacted with a crystalline polyester polymer segment prepared in advance, and then a vinyl monomer, which is a raw material for vinyl resin, is reacted to chemically bond the vinyl polymer segment to the crystalline polyester polymer segment. (b) A method in which a bireactive monomer is reacted with a vinyl resin prepared in advance, and then a polycarboxylic acid monomer and a polyhydric alcohol monomer, which are raw materials for a crystalline polyester resin, are reacted to chemically bond the crystalline polyester polymer segment to the vinyl polymer segment. (c) A method in which a crystalline polyester resin and a vinyl resin are reacted with a bireactive monomer to chemically bond the crystalline polyester polymer segment and the vinyl polymer segment to each other.

[0054] The bireactive monomer is a monomer that bonds a crystalline polyester resin and a vinyl resin, and has, in its molecule, a substituent such as a hydroxy group, a carboxy group, an epoxy group, a primary amino group, or a secondary amino group that can react with a crystalline polyester resin, and an ethylenically unsaturated group that can react with an amorphous resin. Among these, vinyl carboxylic acids having a hydroxy group or a carboxy group and an ethylenically unsaturated group are preferred. As the bireactive monomer, for example, (meth)acrylic acid, fumaric acid, maleic acid, etc. can be used, and hydroxyalkyl (having 1 to 3 carbon atoms) esters of these acids may also be used. From the viewpoint of reactivity, acrylic acid, methacrylic acid, or fumaric acid is preferred.

[0055] From the viewpoint of improving the low-temperature fixability, hot offset resistance, and durability of the toner, the amount of the bireactive monomer used is preferably within a range of 1 to 10 parts by mass, and more preferably within a range of 4 to 8 parts by mass, relative to 100 parts by mass of the total amount of the monomers used to form the vinyl-based polymerization segment.

[0056] From the viewpoint of interaction with the polymer according to the present invention, the polyester resin is preferably a crystalline polyester, and the number of carbon atoms in the linear hydrocarbon structure of the aliphatic carboxylic acid is preferably 6 to 16, more preferably 10 to 14. The hydrocarbon structure of the aliphatic carboxylic acid may be partially branched. In this case, the hydrocarbon chain sandwiched between two carboxy groups is specified as the linear hydrocarbon structure. The number of carbon atoms in the linear hydrocarbon structure of the aliphatic diol is preferably 2 to 12, more preferably 4 to 6. The hydrocarbon structure of the aliphatic diol may be partially branched. In this case, the hydrocarbon chain sandwiched between oxygen atoms derived from two alcohols is specified as the linear hydrocarbon structure.

[0057] From the viewpoint of achieving both fixability and charge retention, the content of the polyester resin is preferably in the range of 5 to 30% by mass, and more preferably in the range of 5 to 20% by mass, with the total mass of the binder resin being 100% by mass.

[0058] <Release agent> The toner base particles according to the present invention contain a release agent, and the release agent contains a fatty acid ester and / or a hydrocarbon wax.

[0059] Examples of fatty acid esters contained in the release agent include, for example, behenyl behenate (behenyl behenate), stearyl stearate (stearyl stearate), behenyl stearate, stearyl behenate, butyl stearate, propyl oleate, hexadecyl palmitate (hexadecyl palmitate), methyl lignocerate (methyl lignocerate), glycerin monostearate (glyceryl stearate), diglyceryl distearate (diglyceryl distearate), pentaerythritol, and the like. Examples of the fatty acid ester include pentaerythritol tetrabehenate (pentaerythritol tetrabehenate ester), diethylene glycol monostearate, dipropylene glycol distearate, sorbitan monostearate, cholesteryl stearate, trimethylolpropane tribehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, tristearyl trimellitate (tristearyl trimellitate), distearyl maleate, methyl triacontanate (methyl triacontanoate), etc. These fatty acid esters can be used alone or in combination of two or more. These fatty acid esters may be commercially available products or synthetic products.

[0060] Examples of hydrocarbon waxes include polyolefin waxes such as low molecular weight polyethylene and low molecular weight polypropylene, branched chain hydrocarbon waxes such as microcrystalline wax, long chain hydrocarbon waxes such as paraffin wax and sazol wax, dialkyl ketone waxes such as distearyl ketone, and fatty acid amide waxes such as ethylenediamine behenylamide and trimellitic acid tristearylamide.

[0061] From the viewpoint of a balance between fixability and offset resistance, the content of the release agent is preferably in the range of 1 to 25% by mass, and more preferably in the range of 5 to 20% by mass, with the total mass of the polymer according to the present invention being 100% by mass.

[0062] The toner base particles used in the present invention may contain a colorant and a charge control agent, if necessary.

[0063] <Coloring agent> The toner base particles according to the present invention may contain a colorant, which may be a commonly known dye or pigment. Examples of colorants for obtaining black toner include carbon black, magnetic materials, iron-titanium composite oxide black, etc. Examples of carbon black include channel black, furnace black, acetylene black, thermal black, lamp black, etc. Examples of magnetic materials include ferrite, magnetite, etc.

[0064] Examples of colorants for obtaining yellow toner include dyes such as CI Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, and 162; and pigments such as CI Pigment Yellow 14, 17, 74, 93, 94, 138, 155, 180, and 185.

[0065] Examples of colorants for obtaining magenta toner include dyes such as CI Solvent Red 1, 49, 52, 58, 63, 111, and 122; and pigments such as CI Pigment Red 5, 48:1, 53:1, 57:1, 122, 139, 144, 149, 166, 177, 178, and 222.

[0066] Examples of colorants for obtaining cyan toner include dyes such as CI Solvent Blue 25, 36, 60, 70, 93, and 95; and pigments such as CI Pigment Blue 1, 7, 15, 60, 62, 66, and 76.

[0067] The colorants for obtaining the toner of each color may be used alone or in combination of two or more kinds for each color. The content of the colorant is preferably in the range of 0.5 to 20% by mass, and more preferably in the range of 2 to 10% by mass, with the total mass of the toner base particles being 100% by mass.

[0068] <Charge control agent> The toner base particles according to the present invention may contain a charge control agent. The charge control agent used is not particularly limited as long as it is a substance that can impart a positive or negative charge through frictional charging and is colorless, and various known positively charged charge control agents and negatively charged charge control agents can be used.

[0069] Specifically, examples of positively charged charge control agents include nigrosine dyes such as "Nigrosine Base EX" (manufactured by Orient Chemical Industry Co., Ltd.), quaternary ammonium salts such as "Quaternary Ammonium Salt P-51" (manufactured by Orient Chemical Industry Co., Ltd.) and "Copy Charge PX VP435" (manufactured by Hoechst Japan), alkoxylated amines, alkylamides, molybdic acid chelate pigments, and imidazole compounds such as "PLZ1001" (manufactured by Shikoku Chemical Industry Co., Ltd.).

[0070] Examples of negatively charged charge control agents include metal complexes such as "Bontron (registered trademark) S-22," "Bontron (registered trademark) S-34," "Bontron (registered trademark) E-81," and "Bontron (registered trademark) E-84" (all manufactured by Orient Chemical Industry Co., Ltd.) and "Spiron Black TRH" (manufactured by Hodogaya Chemical Co., Ltd.), thioindigo pigments, quaternary ammonium salts such as "Copy Charge NX VP434" (manufactured by Hoechst Japan), calixarene compounds such as "Bontron (registered trademark) E-89" (manufactured by Orient Chemical Industry Co., Ltd.), boron compounds such as "LR147" (manufactured by Nippon Carlit Co., Ltd.), and fluorine compounds such as magnesium fluoride and carbon fluoride. In addition to the above, metal complexes usable as negatively chargeable charge control agents include those having various structures such as oxycarboxylic acid metal complexes, dicarboxylic acid metal complexes, amino acid metal complexes, diketone metal complexes, diamine metal complexes, azo group-containing benzene-benzene derivative skeleton metal complexes, and azo group-containing benzene-naphthalene derivative skeleton metal complexes. By configuring the toner base particles to contain a charge control agent in this way, the chargeability of the toner is improved.

[0071] The content of the charge control agent in the toner base particles is preferably within a range of 0.01 to 30% by mass, and more preferably within a range of 0.1 to 10% by mass.

[0072] The form of the toner base particles according to the present invention is not particularly limited, and may be, for example, a so-called single-layer structure (a homogeneous structure that is not a core-shell type), a core-shell structure, a multi-layer structure of three or more layers, a domain-matrix structure, or the like.

[0073] <External additives> In order to improve the fluidity, chargeability, cleaning properties, etc. of the toner, the toner of the present invention may be constructed by adding external additives such as a fluidizing agent, a cleaning aid, etc., which are so-called post-treatment agents, to the toner base particles. Examples of external additives include inorganic oxide particles such as silica particles, alumina particles, and titanium oxide particles, inorganic stearic acid compound particles such as aluminum stearate particles and zinc stearate particles, and inorganic titanic acid compound particles such as strontium titanate particles and zinc titanate particles. These can be used alone or in combination of two or more. These inorganic particles may be surface-treated with a silane coupling agent, a titanium coupling agent, a higher fatty acid, a silicone oil, or the like to improve heat-resistant storage properties and environmental stability. The amount of the external additive added is preferably within a range of 0.05 to 5 parts by mass, and more preferably within a range of 0.1 to 3 parts by mass, per 100 parts by mass of the toner base particles.

[0074] <Average particle size of toner> The average particle size of the toner is preferably in the range of 4 to 10 μm, more preferably 5 to 9 μm, in terms of volume-based median diameter (D50). When the volume-based median diameter (D50) is in the above range, transfer efficiency is increased, improving halftone image quality and the image quality of fine lines, dots, etc.

[0075] In the present invention, the volume-based median diameter (D50) of the toner is measured and calculated using a measuring device consisting of a "Coulter Counter 3" (manufactured by Beckman Coulter, Inc.) connected to a computer system (manufactured by Beckman Coulter, Inc.) equipped with data processing software "Software V3.51." Specifically, 0.02 g of the measurement sample (toner) is added to 20 mL of surfactant solution (a surfactant solution prepared by diluting, for example, a neutral detergent containing surfactant components 10 times with pure water in order to disperse the toner particles), and after mixing, ultrasonic dispersion is carried out for 1 minute to prepare a toner dispersion. This toner dispersion is then pipetted into a beaker containing an "ISOTON II" (manufactured by Beckman Coulter, Inc.) in the sample stand until the concentration indicated on the measuring device reaches 8%. By setting the concentration within this range, reproducible measurement values ​​can be obtained. The measurement device counts 25,000 particles and sets the aperture diameter to 50 μm. The measurement range of 1 to 30 μm is divided into 256 parts to calculate the frequency value. The particle diameter of the largest 50% of the volume fraction is taken as the volume-based median diameter (D50).

[0076] [Toner manufacturing method] The toner manufacturing method of the present invention is a method for manufacturing a toner for developing electrostatic images, which includes toner base particles containing a binder resin and a colorant, and is characterized by comprising a step of preparing a resin particle dispersion containing a polymer obtained by copolymerizing at least a first polymerizable monomer having a structure represented by the following general formula (2): That is, the method comprises a step of polymerizing a first polymerizable monomer having a structure represented by the following general formula (2) to synthesize a polymer having a first structural unit represented by the general formula (1), and preparing a resin particle dispersion containing the polymer.

[0077] [ka] [In general formula (2), R1 and R2 each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.]

[0078] The method for producing the toner of the present invention is not particularly limited as long as it includes a step of preparing a resin particle dispersion containing the polymer of the present invention. For example, the polymer according to the present invention, a release agent, and optionally a colorant, etc. are melt-kneaded, and then pulverized, classified, etc. to obtain a toner. Alternatively, a toner can be obtained by an emulsion aggregation method in which polymer particles are prepared by emulsion polymerization, mini-emulsion polymerization, or the like of a polymerizable monomer in an aqueous medium, and the polymer particles, release agent particles, and, if necessary, dispersed particles such as colorant particles are aggregated and fused together. As the emulsion aggregation method, the methods described in JP-A Nos. 5-265252, 6-329947, and 9-15904 can be used. Furthermore, the production method may be a suspension polymerization method described in JP-A-2010-191043. Among these, a production method utilizing emulsion aggregation is preferred from the viewpoints that particle size and shape can be easily controlled and energy costs during production can be reduced.

[0079] Such a production method using emulsion aggregation is as follows: (1A) A resin particle dispersion preparation step for preparing a resin particle dispersion containing the polymer according to the present invention (1B) Polyester particle dispersion preparation step of preparing a polyester particle dispersion (1C) Colorant particle dispersion liquid preparation step of preparing a colorant particle dispersion liquid (1D) A release agent particle dispersion liquid preparation step for preparing a release agent particle dispersion liquid (2) An association step in which a flocculant is added to an aqueous medium containing resin particles containing the polymer according to the present invention, polyester particles, colorant particles, and release agent particles, and salting out is promoted while simultaneously flocculation and fusion are carried out to form associated particles. (3) A ripening process to form toner particles by controlling the shape of aggregated particles (4) A filtering and washing process for filtering toner particles from the aqueous medium and removing surfactants and the like from the toner particles. (5) Drying process to dry the washed toner particles (6) Adding external additives to the dried toner particles It is preferable that the method includes the steps of: The steps (1A) to (1D) will be explained below.

[0080] (1A) Step of preparing a resin particle dispersion containing the polymer according to the present invention In this step, resin particles are formed by a conventionally known emulsion polymerization, etc. As an example, polymerizable monomers (the first polymerizable monomer and the second polymerizable monomer) constituting the binder resin are introduced into an aqueous medium and dispersed therein, and these polymerizable monomers are polymerized using a polymerization initiator to prepare a dispersion of the resin particles containing the polymer according to the present invention. In addition to the method of polymerizing a polymerizable monomer in an aqueous medium using a polymerization initiator, examples of methods for obtaining the resin particle dispersion include a method of performing a dispersion treatment in an aqueous medium without using a solvent, and a method of dissolving a polymer in an organic solvent such as ethyl acetate to prepare a solution, emulsifying and dispersing the solution in an aqueous medium using a disperser, and then performing a solvent removal treatment. In this case, if necessary, a release agent may be added to the resin in advance. For dispersion, it is also preferable to carry out the polymerization in the presence of a known surfactant (e.g., anionic surfactants such as polyoxyethylene (2) dodecyl ether sodium sulfate, sodium dodecyl sulfate, and sodium dodecylbenzenesulfonate). The volume-based median diameter of the resin particles in the dispersion is preferably within a range of 50 to 300 nm. The volume-based median diameter of the resin particles in the dispersion can be measured by dynamic light scattering using a "Microtrac UPA-150" (manufactured by Nikkiso Co., Ltd.).

[0081] (1B) Polyester particle dispersion preparation process In this step, a polyester particle dispersion is prepared by a conventionally known method. One example is a method in which a polyester resin is dissolved in a solvent such as methyl ethyl ketone, the solution is emulsified and dispersed in an aqueous medium using a disperser, and then the solvent is removed. For dispersion, it is preferable to disperse the resin in the presence of a known surfactant (e.g., anionic surfactants such as polyoxyethylene (2) dodecyl ether sodium sulfate, sodium dodecyl sulfate, and sodium dodecylbenzenesulfonate), and an aqueous sodium hydroxide solution may be added to control particle size.

[0082] The volume-based median diameter of the binder resin particles in the dispersion is preferably within a range of 50 to 300 nm. The volume-based median diameter of the binder resin particles in the dispersion can be measured by dynamic light scattering using a "Microtrac UPA-150" (manufactured by Nikkiso Co., Ltd.).

[0083] (1C) Colorant particle dispersion preparation process This colorant particle dispersion preparation step is a step of dispersing a colorant in the form of fine particles in an aqueous medium to prepare a colorant particle dispersion. The colorant can be dispersed using mechanical energy. The volume-based median diameter of the colorant particles in the dispersion is preferably within a range of 10 to 300 nm, and more preferably within a range of 50 to 200 nm. The volume-based median diameter of the colorant particles in the dispersion can be measured by dynamic light scattering using a "Microtrac UPA-150" (manufactured by Nikkiso Co., Ltd.) in the same manner as above.

[0084] (1D) Release agent particle dispersion liquid preparation process The release agent particle dispersion preparation step is a step of dispersing the release agent in the form of fine particles in an aqueous medium to prepare a dispersion of the release agent particles. The release agent can be dispersed by utilizing mechanical energy. The volume-based median diameter of the release agent particles in the dispersion is preferably within a range of 100 to 1000 nm, and more preferably within a range of 200 to 700 nm. The volume-based median diameter of the release agent particles in the dispersion can be measured, for example, by a laser diffraction particle size distribution measuring instrument LA-750 (manufactured by Horiba, Ltd.).

[0085] (aqueous medium) The aqueous medium used in steps (1A) to (1D) may be water, or an aqueous medium containing water as the main component (50% by mass or more) and optionally containing water-soluble solvents such as alcohols and glycols, surfactants, dispersants, etc. The aqueous medium used is preferably a mixture of water and surfactants. Examples of the water-soluble solvent include methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, tetrahydrofuran, etc. Among these, alcohols such as methanol, ethanol, isopropanol, and butanol, which are organic solvents that do not dissolve the polymer, are preferred.

[0086] Examples of surfactants include cationic surfactants, anionic surfactants, and nonionic surfactants. Examples of cationic surfactants include dodecyl ammonium chloride, dodecyl ammonium bromide, dodecyl trimethyl ammonium bromide, dodecyl pyridinium chloride, dodecyl pyridinium bromide, and hexadecyl trimethyl ammonium bromide. Examples of anionic surfactants include fatty acid soaps such as sodium stearate and sodium dodecanoate, sodium dodecyl benzene sulfonate, and sodium dodecyl sulfate. Examples of nonionic surfactants include polyoxyethylene dodecyl ether, polyoxyethylene hexadecyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl ether, polyoxyethylene sorbitan monooleate ether, and monodecanoyl sucrose. These surfactants can be used alone or in combination of two or more. Among the surfactants, anionic surfactants are preferred, and sodium dodecylbenzenesulfonate and sodium dodecyl sulfate are more preferred. The amount of surfactant added is preferably within a range of 0.01 to 10 parts by mass, and more preferably within a range of 0.04 to 2 parts by mass, relative to 100 parts by mass of the aqueous medium.

[0087] The steps from (2) association step to (6) external additive addition step can be carried out according to various conventionally known methods. The flocculant used in the association step (2) is not particularly limited, but is preferably selected from metal salts.

[0088] Examples of metal salts include monovalent metal salts such as salts of alkali metals such as sodium, potassium, and lithium; divalent metal salts such as calcium, magnesium, manganese, and copper; and trivalent metal salts such as iron and aluminum. Specific examples of metal salts include sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, zinc chloride, copper sulfate, magnesium sulfate, manganese sulfate, and polyaluminum chloride. Among these, it is particularly preferable to use divalent or trivalent metal salts, since they can promote aggregation with smaller amounts. These can be used alone or in combination of two or more.

[0089] [Developer] The toner of the present invention can be suitably used in various cases, for example, when it contains a magnetic material and is used as a one-component magnetic toner, when it is mixed with a so-called carrier and is used as a two-component developer, or when it is used alone as a non-magnetic toner.

[0090] As the magnetic material, for example, magnetite, γ-hematite, or various ferrites can be used. As the carrier constituting the two-component developer, magnetic particles made of conventionally known materials such as metals such as iron, steel, nickel, cobalt, ferrite, and magnetite, and alloys of these metals with metals such as aluminum and lead can be used. As the carrier, it is preferable to use a coated carrier in which the surface of magnetic particles is coated with a coating agent such as resin, or a so-called resin-dispersed carrier in which magnetic powder is dispersed in a binder resin.

[0091] The resin for coating is not particularly limited, but examples thereof include olefin resin, styrene resin, styrene-acrylic resin, silicone resin, polyester resin, and fluororesin. Furthermore, the resin for constituting the resin dispersion type carrier is not particularly limited and any known resin can be used, such as acrylic resin, styrene-acrylic resin, polyester resin, fluororesin, and phenolic resin.

[0092] The volume-based median diameter of the carrier is preferably within the range of 20 to 100 μm, and more preferably within the range of 25 to 60 μm. The volume-based median diameter of the carrier can be measured typically by a laser diffraction particle size distribution measuring device "HELOS" (manufactured by SYMPATEC) equipped with a wet disperser. The amount of toner mixed with the carrier is preferably within the range of 2 to 10% by mass, with the total mass of the toner and carrier being 100% by mass.

[0093] [Image forming method] The toner of the present invention can be suitably used in an image forming method including a fixing step using a heat and pressure fixing method in which heat and pressure are applied, particularly in an image forming method in which the fixing step is performed at a relatively low fixing temperature in which the surface temperature of the heating member in the fixing nip is in the range of 80 to 110°C, preferably 80 to 95°C. Furthermore, it can also be suitably used in an image forming method with high-speed fixing in which the fixing linear speed is within the range of 200 to 600 mm / sec.

[0094] Specifically, in this image forming method, an electrostatic image formed on a photoreceptor is developed using the toner of the present invention as described above to obtain a toner image, which is then transferred to an image support, and the toner image transferred to the image support is then fixed to the image support by a heat and pressure fixing process, thereby obtaining a printed matter on which a visible image is formed.

[0095] The toner of the present invention can be used in a monochrome image forming method and a full-color image forming method. The full-color image forming method can be applied to any image forming method, such as a four-cycle image forming method consisting of four types of color developing devices for yellow, magenta, cyan, and black, and one photosensitive body, or a tandem image forming method in which image forming units having color developing devices and photosensitive bodies for each color are installed, one for each color. [Example]

[0096] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In the following examples, unless otherwise specified, operations were carried out at room temperature (25°C). Furthermore, unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass," respectively.

[0097] The peak molecular weight of the polymer in the resin particle dispersion was measured as follows: The measurement results are shown in Table I below. Using an apparatus "HLC-8220" (manufactured by Tosoh Corporation) and a column "TSKguard column + TSKgel Super HZM-M triple column" (manufactured by Tosoh Corporation), the column temperature was maintained at 40°C, and tetrahydrofuran (THF) was passed as a carrier solvent at a flow rate of 0.2 ml / min. The measurement sample was dissolved in tetrahydrofuran to a concentration of 1 mg / ml under dissolution conditions of 5 minutes of treatment using an ultrasonic disperser at room temperature (25°C). Next, the sample solution was obtained by processing it with a membrane filter with a pore size of 0.2 μm, and 10 μl of this sample solution was injected into the device together with the above-mentioned carrier solvent, and detected using a refractive index detector (RI detector). The molecular weight distribution of the measured sample was determined.

[0098] <Preparation of Resin Particle Dispersion 1> A surfactant solution prepared by dissolving 8 parts by mass of sodium dodecyl sulfate in 3,000 parts by mass of ion-exchanged water was placed in a 5 L stainless steel kettle (SUS kettle) equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introducing device, and the liquid temperature was raised to 80°C while stirring at a stirring speed of 230 rpm under a nitrogen stream. To this surfactant solution was added an initiator solution prepared by dissolving 10 parts by mass of potassium persulfate in 200 parts by mass of ion-exchanged water, and the temperature was raised to 80°C. Then, the following monomer mixture was added dropwise over 100 minutes, and the system was heated and stirred at 80°C for 2 hours to carry out polymerization, thereby preparing resin particle dispersion 1: -Monomer mixture- Exemplary compound M1 250.0 parts by mass Styrene (St) 253.0 parts by mass n-Butyl acrylate (nBA) 258.0 parts by mass Methacrylic acid (MAA) 44.0 parts by mass n-Octyl-3-mercaptopropionate 5.5 parts by mass The volume-based median diameter of the binder resin particles in the obtained binder resin particle dispersion 1 was measured by dynamic light scattering using "Microtrac UPA-150" (manufactured by Nikkiso Co., Ltd.) and was found to be 128 nm.

[0099] <Preparation of Resin Particle Dispersions 2 to 9> Resin particle dispersions 2 to 9 were prepared in the same manner as in the preparation of Resin particle dispersion 1, except that the combinations and amounts of monomers added were changed to those shown in Table I below. In Table I below, St represents styrene, MMA represents methyl methacrylate, nBA represents n-butyl acrylate, iBA represents iso-butyl acrylate, 2EHA represents 2-ethylhexyl acrylate, MAA represents methacrylic acid, and AA represents acrylic acid.

[0100] [Table 1]

[0101] <Preparation of Polyester Particle Dispersion 1> (Synthesis of crystalline polyester resin 1) The raw material monomers for the amorphous resin segment (styrene-acrylic resin) and polymerization initiator listed below were placed in a dropping funnel. Styrene 21.7 parts by mass n-Butyl acrylate 8.0 parts by mass Acrylic acid 1.8 parts by mass Polymerization initiator (di-t-butyl peroxide) 4.0 parts by mass Meanwhile, the raw material monomers for the crystalline polyester resin segment (crystalline polyester resin) described below were placed in a four-neck flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer and a thermocouple, and heated to 170°C to dissolve. Tetradecanedioic acid 440 parts by mass Butanediol 135 parts by mass Next, with stirring, the raw material monomer for the amorphous resin segment was added dropwise from the dropping funnel over 90 minutes, and the mixture was aged for 60 minutes. After that, unreacted addition polymerization monomer was removed under reduced pressure (8 kPa). Note that the amount of monomer removed was very small compared to the amount of raw material monomer added. Then, 0.8 g of Ti(OBu)4 was added as an esterification catalyst, and the mixture was heated to 235°C and reacted at normal pressure for 5 hours and then under reduced pressure (8 kPa) for 1 hour. The mixture was then cooled to 200°C and reacted under reduced pressure (20 kPa) for 1 hour to obtain crystalline polyester resin (hybrid crystalline polyester resin) 1.

[0102] (Preparation of Polyester Particle Dispersion 1) 82 parts by weight of the hybrid crystalline polyester resin 1 obtained as described above was dissolved in 82 parts by weight of methyl ethyl ketone by stirring at 70°C for 30 minutes. Next, 2.5 parts by weight of a 25% by weight aqueous sodium hydroxide solution was added to this solution. This solution was placed in a reaction vessel equipped with a stirrer, and 236 parts by weight of water heated to 70°C was added dropwise over 70 minutes while stirring. The liquid in the vessel became cloudy during the addition, and a uniform emulsion was obtained after the entire amount was added. The particle size of the oil droplets in this emulsion was measured using a laser diffraction particle size distribution analyzer "LA-750 (manufactured by HORIBA)" and found to have a volume average particle size of 124 nm. Next, while keeping this emulsion at 70°C, it was stirred for 3 hours under a reduced pressure of 15 kPa using a diaphragm vacuum pump "V-700" (manufactured by BUCHI) to distill off the methyl ethyl ketone, thereby preparing crystalline polyester particle dispersion 1 (solid content 25% by mass) in which fine particles of crystalline polyester resin 1 were dispersed. As a result of measurement using the particle size distribution measuring instrument, the volume average particle size of the crystalline polyester particles in crystalline polyester particle dispersion 1 was found to be 200 nm.

[0103] <Preparation of Polyester Particle Dispersions 2 and 3> Polyester particle dispersions 2 and 3 were prepared in the same manner as in the preparation of polyester particle dispersion 1, except that the crystalline polyester resins were synthesized by changing the amounts of monomers shown in Table II below.

[0104] [Table 2]

[0105] <Preparation of Colorant Particle Dispersion 1> Colorant: Carbon black (Mogul (registered trademark) L manufactured by Cabot Corporation) 10 parts by mass Anionic surfactant (20% aqueous solution of sodium dodecylbenzenesulfonate) 1.5 parts by mass Ion-exchanged water 90 parts by mass The above components were mixed and dispersed in an SC mill to obtain colorant particle dispersion 1. The volume-based median diameter of the colorant particles in the dispersion was measured by dynamic light scattering using a Microtrac UPA-150 (manufactured by Nikkiso Co., Ltd.) and was found to be 155 nm.

[0106] <Preparation of Release Agent Particle Dispersion 1> Behenyl behenate 100 parts by mass Sodium dodecyl sulfate 5 parts by mass Ion-exchanged water 240 parts by mass The above components were dispersed in a round stainless steel flask for 10 minutes using a homogenizer "Ultra Turrax (registered trademark) T50" (manufactured by IKA Corporation), and then dispersed using a pressure discharge homogenizer to obtain a release agent particle dispersion 1. The volume-based median diameter of the release agent particles in the dispersion was measured using a laser diffraction particle size distribution analyzer LA-750 (manufactured by Horiba, Ltd.) and was found to be 530 nm.

[0107] [Production of Toner 1] <Preparation of Toner Base Particle Dispersion 1> A reaction vessel equipped with a stirrer, a temperature sensor, and a cooling tube was charged with 346 parts by mass (solids content) of resin particle dispersion 1, 8 parts by mass of colorant particle dispersion 1, 43.25 parts by mass of release agent particle dispersion 1, and 2000 parts by mass of ion-exchanged water. At room temperature, a 5 mol / L aqueous solution of sodium hydroxide was added to adjust the pH to 10. Next, a solution of 60 parts by mass of magnesium chloride dissolved in 60 parts by mass of ion-exchanged water was added over 10 minutes at 30°C while stirring. After leaving it for 3 minutes, the temperature was raised to 80°C over 60 minutes. After reaching 80°C, 43.25 parts by mass (solid content equivalent) of Polyester Particle Dispersion 1 was added over 20 minutes. The stirring speed was adjusted so that the particle size growth rate was 0.01 μm / min, and the particles were allowed to grow until the volume-based median diameter measured with a Coulter Multisizer 3 (Coulter-Beckman, Inc.) reached 6.0 μm. Thereafter, an aqueous solution of 190 parts by mass of sodium chloride dissolved in 760 parts by mass of ion-exchanged water was added to stop particle growth. The temperature was then raised to 80°C and the mixture was stirred to promote particle fusion until the average circularity of the toner particles reached 0.970. Thereafter, the mixture was cooled to 30°C or below to obtain toner base particle dispersion 1.

[0108] <Cleaning and drying process> The toner base particle dispersion 1 was subjected to solid-liquid separation using a basket-type centrifuge "MARKIII Model No. 60 × 40" (manufactured by Matsumoto Kikai Hanbai Co., Ltd.) to form a wet cake of toner base particles. The wet cake was washed with ion-exchanged water at 45°C until the electrical conductivity of the filtrate from the basket-type centrifuge reached 5 μS / cm, and then transferred to a "Flash Jet Dryer" (manufactured by Seishin Enterprise Co., Ltd.) and dried until the moisture content reached 0.5% by mass, yielding toner base particles.

[0109] <External additive treatment of toner base particles> To 100 parts by mass of the toner base particles obtained above, 1 part by mass of hydrophobic silica (number average primary particle diameter = 12 nm) and 0.3 parts by mass of hydrophobic titania (number average primary particle diameter = 20 nm) were added, and mixed using a Henschel mixer (registered trademark) to perform external additive treatment, thereby producing toner 1.

[0110] [Production of Toners 2 to 18] Toners 2 to 18 were produced in the same manner as in the production of Toner 1, except that toner base particles were produced using the resin particle dispersion and polyester particle dispersion in the combinations shown in Table III below. In Table III, the polyester resin ratio represents the content (mass %) of polyester resin in the binder resin.

[0111] [Table 3]

[0112] [Preparation of two-component developer] 100 parts by mass of ferrite particles (volume-based median diameter: 50 μm (manufactured by Powder Tech Co., Ltd.)) and 4 parts by mass of methyl methacrylate-cyclohexyl methacrylate copolymer resin (volume-based median diameter of primary particles: 85 nm) were placed in a horizontal impeller-type high-speed mixer and mixed for 15 minutes at an impeller peripheral speed of 8 m / s and a temperature of 30°C, after which the temperature was raised to 120°C and stirring was continued for 4 hours. The mixture was then cooled, and fragments of the methyl methacrylate-cyclohexyl methacrylate copolymer resin were removed using a 200-mesh sieve to produce a resin-coated carrier. This resin-coated carrier was mixed with each of the above toners 1 to 18 so that the toner concentration was 7% by mass relative to the total mass of the toner and carrier, thereby preparing two-component developers 1 to 18.

[0113] [evaluation] ·Image forming method For image evaluation, a commercially available color multifunction printer "bizhub PRESS (registered trademark) C6000 (manufactured by Konica Minolta, Inc.)" was modified to create a modified machine A so that the fixing temperature, toner adhesion amount, and system speed could be freely set. The developers prepared above were sequentially loaded into the developing device of this modified machine A and evaluation was performed.

[0114] (1) Low-temperature fixability (UO) Low temperature fixation (under offset) Under normal temperature and humidity conditions (temperature 20°C, humidity 50% RH), toner adhesion amount is 8 g / m 2 The temperature of the lower fixing roller was set 20°C lower than that of the upper fixing belt, and the temperature of the upper fixing belt was increased in 5°C increments from 110°C up to 200°C. This experiment was carried out at a fixing speed of 300 mm / sec. A4 size NPI wood-free 127.9 g / m 2 (manufactured by Nippon Paper Industries Co., Ltd.) was used for evaluation. Under-offset refers to an image defect in which the toner layer is not sufficiently melted by the applied heat when passing through a fixing machine, causing the image to peel off from the transfer material such as recording paper. When an image is formed using the above method, the minimum fixing temperature of the upper fixing belt at which under-offset does not occur was evaluated and used as an index of low-temperature fixability. The lower this minimum fixing temperature, the better the fixability, and a temperature of less than 140°C was considered acceptable.

[0115] (2) Bending resistance Under normal temperature and humidity conditions (temperature 20°C, humidity 50% RH), toner adhesion amount is 8 g / m 2 The temperature of the lower fixing roller was set 20°C lower than that of the upper fixing belt, and the temperature of the upper fixing belt was increased in 5°C increments from 110°C up to 200°C. This experiment was carried out at a fixing speed of 300 mm / sec. A4 size paper with a basis weight of 350 g / m 2 The fixed solid image was folded using a folding machine, and air at 0.35 MPa was blown onto it. The state of the fold was evaluated on a 5-point scale with reference to a limit sample, with ranks 3 to 5 being considered acceptable. (standard) Rank 5: No peeling at the fold Rank 4: Some peeling along folds Rank 3: Thin linear peeling along the fold Rank 2: Thick peeling along the fold Rank 1: Large peeling on the image

[0116] [Table 4]

[0117] As is clear from the results shown in Table IV above, it was found that by containing a polymer having a first structural unit represented by the general formula (1), the toners 1 to 15 of the present invention exhibit excellent performance in both low-temperature fixability and bending resistance. On the other hand, toners 16 to 18, which do not contain a polymer having the first structural unit represented by the general formula (1), have good low-temperature fixability but poor bending resistance, and it has been found that it is difficult to achieve both low-temperature fixability and bending resistance.

Claims

1. A toner for developing electrostatic images, comprising toner base particles containing a binder resin and a colorant, the toner base particles contain, as the binder resin, a copolymer having a first structural unit represented by the following general formula (1) and another second structural unit, Electrostatic image developing toner, wherein the second structural unit is at least n-butyl acrylate, 2-ethylhexyl acrylate or methyl methacrylate. 【Chemical 1】 [In general formula (1), R １ and R ２ each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

2. R in the general formula (1) １ and R ２ 2. The toner for developing electrostatic images according to claim 1, wherein each independently represents a hydrogen atom or a methyl group.

3. R in the general formula (1) １ is a methyl group, R ２ 3. The toner for developing electrostatic images according to claim 1, wherein represents a hydrogen atom.

4. 4. The toner for developing electrostatic images according to claim 1, wherein the binder resin contains 5 to 30% by mass of a crystalline polyester resin.

5. 5. The toner for developing electrostatic images according to claim 4, wherein the crystalline polyester resin is a hybrid crystalline polyester resin formed by chemically bonding a polyester polymer segment and a vinyl polymer segment.

6. A method for producing a toner for developing electrostatic images, the toner comprising toner base particles containing a binder resin and a colorant, comprising: The method includes a step of preparing a resin particle dispersion liquid containing a polymer obtained by copolymerizing at least a first polymerizable monomer having a structure represented by the following general formula (2) and another second structural unit, A method for producing a toner for developing electrostatic images, wherein the second structural unit is at least n-butyl acrylate, 2-ethylhexyl acrylate, or methyl methacrylate. 【Chemistry 2】 [In general formula (2), R １ and R ２ each independently represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

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