Toner and method for producing same

Abstract

Provided are a toner having good low-temperature fixability and preservability, and a method for producing the toner. The toner contains colored resin particles including a binder resin, a colorant and a softener. The binder resin contains a polymer comprising a monomer unit derived from a dicarboxylic acid dialkyl ester having a radically polymerizable double bond, wherein the dicarboxylic acid dialkyl ester is at least one selected from the group consisting of a dialkyl fumarate and a dialkyl maleate. The toner contains an ester wax as the softener.

Description

Toner and its manufacturing method

[0001] The present disclosure relates to a toner used to develop electrostatic latent images in electrophotography, electrostatic recording, electrostatic printing, and the like, and a method for producing the toner.

[0002] In image forming devices such as electrophotographic devices, electrostatic recording devices, and electrostatic printing devices, an electrostatic latent image formed on a photoreceptor is developed with toner, the toner image is transferred to a transfer material such as paper, and then fixed by heating or the like to form a fixed image. The toner fixing process typically requires heating the fixing roll to a temperature of 150°C or higher during fixing, which requires a large amount of power. With increasing demands for reduced energy consumption and faster printing speeds in image forming devices, there is a demand for toners that can maintain a high fixing rate even at low fixing temperatures, i.e., toners with excellent low-temperature fixability. However, toners with improved low-temperature fixability may be prone to blocking at high temperatures, which may result in reduced toner shelf life. Therefore, there is a demand for toners with improved low-temperature fixability without impairing shelf life.

[0003] Patent Document 1 discloses a toner containing, as a binder resin, a styrene-acrylic resin obtained by polymerizing a monomer mixture containing dialkyl maleate, dialkyl fumarate, and / or dialkyl itaconate.

[0004] Patent Document 2 discloses core-shell type resin particles for toner, which have a shell layer made of a resin containing structural units of vinyl acetate and other vinyl monomers, and a core layer made of at least one resin selected from polyester resin, polyurethane resin, epoxy resin, and specific vinyl resin. Patent Document 2 also describes that a dialkyl fumarate ester can be used as the other vinyl monomer used in the shell layer.

[0005] Patent Document 3 discloses a toner containing a styrene-(meth)acrylic acid ester copolymer as a binder resin and a specific linear diester wax.

[0006] However, the toners disclosed in Patent Documents 1 to 3 are insufficient in at least one of low-temperature fixability and storage stability.

[0007] Japanese Patent Laid-Open No. 6-19192 Japanese Patent Laid-Open No. 2007-56241 Japanese Patent Laid-Open No. 2010-85909

[0008] An object of the present disclosure is to provide a toner having good low-temperature fixability and storage stability, and a method for producing the toner.

[0009] As a result of extensive research into solving the above problems, the present inventors have found that when a specific dicarboxylic acid dialkyl ester is introduced into a binder resin and an ester wax is used as a softener, a toner having an excellent balance of low-temperature fixability and storage stability can be obtained, leading to the present disclosure.

[0010] That is, the present disclosure provides the following toners. [1] A toner containing colored resin particles including a binder resin, a colorant, and a softener, wherein the binder resin contains a polymer containing a monomer unit derived from a dicarboxylic acid dialkyl ester having a radically polymerizable double bond, the dicarboxylic acid dialkyl ester being at least one selected from the group consisting of a fumaric acid dialkyl ester and a maleic acid dialkyl ester, and the softener contains an ester wax. [2] The toner according to [1], wherein the alkyl group in the dicarboxylic acid dialkyl ester is an alkyl group having 10 or more carbon atoms. [3] The toner according to [1] or [2], wherein the content of the monomer unit derived from the dicarboxylic acid dialkyl ester is 2 to 20 mass% based on 100 mass% of the polymer. [4] The toner according to any one of [1] to [3], wherein the polymer is a styrene-acrylic resin. [5] The toner according to any one of [1] to [4], wherein the colored resin particles further contain a charge control agent, the charge control agent containing a quaternary ammonium base-containing copolymer, and the toner is a positively charged toner.

[0011] The present disclosure also provides the following toner manufacturing method: [6] The toner manufacturing method according to any one of [1] to [5], comprising the steps of: preparing a polymerizable monomer composition containing at least a polymerizable monomer, a colorant, and a softener; preparing a suspension in which droplets of the polymerizable monomer composition are dispersed in an aqueous medium containing a dispersion stabilizer; and subjecting the suspension to a polymerization reaction, wherein the polymerizable monomer contains a dicarboxylic acid dialkyl ester having a radically polymerizable double bond, which is at least one selected from the group consisting of a fumaric acid dialkyl ester and a maleic acid dialkyl ester; and containing an ester wax as the softener.

[0012] According to the present disclosure as described above, a toner having good low-temperature fixability and storage stability can be provided.

[0013] The toner of the present disclosure and the method for producing the toner of the present disclosure will be described below in order. In this disclosure, the term "to" in a numerical range means that the numerical values ​​before and after it are included as the lower and upper limits. Furthermore, among the numerical values ​​described to explain this disclosure, numerical values ​​that may contain decimal places are, unless otherwise specified, numerical values ​​obtained by rounding off the digit that is one place smaller than the lowest digit included in the numerical value.

[0014] 1. Toner The toner of the present disclosure is a toner containing colored resin particles including a binder resin, a colorant, and a softener, wherein the binder resin contains a polymer containing a monomer unit derived from a dicarboxylic acid dialkyl ester having a radically polymerizable double bond, the dicarboxylic acid dialkyl ester being at least one selected from the group consisting of a fumaric acid dialkyl ester and a maleic acid dialkyl ester, and the softener contains an ester wax.

[0015] The toner of the present disclosure is a toner that is excellent in both low-temperature fixability and storage stability. While the low-temperature fixability and storage stability of a toner are usually in a trade-off relationship, the toner of the present disclosure uses a specific dialkyl dicarboxylic acid ester as a polymerizable monomer that forms the binder resin, and an ester wax as a softener, thereby improving the compatibility between the binder resin and the softener and improving the dispersibility of the softener in the colored resin particles. As a result, the softener's effects are more easily exerted, and the low-temperature fixability can be improved while suppressing a decrease in the storage stability of the toner. Therefore, the toner of the present disclosure is excellent in both low-temperature fixability and storage stability.

[0016] The toner of the present disclosure contains colored resin particles containing a binder resin, a colorant, and a softener. The colored resin particles may further contain other additives such as a charge control agent and a polar resin, as necessary, and may have a shell layer.

[0017] (Binder Resin) The toner of the present disclosure contains, as a binder resin, a polymer containing a monomer unit derived from a dicarboxylic acid dialkyl ester having a radical polymerizable double bond. That is, the binder resin contains, as a polymer, a polymer of a polymerizable monomer containing the dicarboxylic acid dialkyl ester.

[0018] <Polymerizable Monomer> In the present disclosure, a polymerizable monomer refers to a monomer capable of radical polymerization, and the polymerizable monomer is polymerized to form a binder resin. In the present disclosure, the polymerizable monomer includes at least one dicarboxylic acid dialkyl ester having a radically polymerizable double bond, which is at least one selected from the group consisting of a dialkyl fumarate ester and a dialkyl maleate ester. The dicarboxylic acid dialkyl ester is a monovinyl monomer. Note that a monovinyl monomer refers to a monomer having only one functional group capable of radical polymerization.

[0019] In the present disclosure, the dicarboxylic acid dialkyl ester is at least one dicarboxylic acid dialkyl ester selected from the group consisting of a fumaric acid dialkyl ester and a maleic acid dialkyl ester. Among them, a fumaric acid dialkyl ester is preferred because it can easily improve the low-temperature fixability and storage stability of the toner in a well-balanced manner.

[0020] Each of the two alkyl groups in the dicarboxylic acid dialkyl ester is preferably, but not particularly limited to, an alkyl group having 10 or more carbon atoms. The lower limit of the number of carbon atoms in the alkyl group is more preferably 14 or more, even more preferably 16 or more, and still more preferably 18 or more, and the upper limit is preferably 24 or less, more preferably 22 or less. When the number of carbon atoms in the alkyl group in the dicarboxylic acid dialkyl ester is within the above range, the dispersibility of the ester wax in the binder resin can be improved while suppressing a decrease in the melting temperature of the binder resin, and therefore the low-temperature fixability and storage stability of the toner can be improved in a more balanced manner.

[0021] Preferred examples of dialkyl fumarate esters include dimyristyl fumarate, dipalmityl fumarate, distearyl fumarate, diarachidyl fumarate, dibehenyl fumarate, and dilignoceryl fumarate. Preferred examples of dialkyl maleate esters include dimyristyl maleate, dipalmityl maleate, distearyl maleate, diarachidyl maleate, dibehenyl maleate, and dilignoceryl maleate. Among these, at least one selected from the group consisting of dimyristyl fumarate, distearyl fumarate, dibehenyl fumarate, dimyristyl maleate, distearyl maleate, and dibehenyl maleate is preferred, and at least one selected from the group consisting of distearyl fumarate, dibehenyl fumarate, distearyl maleate, and dibehenyl maleate is particularly preferred.

[0022] The content of the dicarboxylic acid dialkyl ester is preferably 2 to 20 parts by weight, more preferably 3 to 10 parts by weight, and even more preferably 4 to 6 parts by weight, per 100 parts by weight of the total amount of polymerizable monomers. That is, the content of the monomer units derived from the dicarboxylic acid dialkyl ester is preferably 2 to 20% by weight, more preferably 3 to 10% by weight, and even more preferably 4 to 6% by weight, per 100% by weight of the polymer. When the content of the dicarboxylic acid dialkyl ester is equal to or greater than the lower limit, the low-temperature fixability of the toner is further improved. When the content is equal to or less than the upper limit, the decrease in the glass transition temperature (Tg) of the binder resin is suppressed, thereby suppressing deterioration of the toner storage stability. Furthermore, when the content of the dicarboxylic acid dialkyl ester is within the above range, the dispersibility of the ester wax in the binder resin is improved, thereby further improving the low-temperature fixability of the toner.

[0023] In the present disclosure, it is preferable that the polymerizable monomer that becomes the binder resin contains, as a main component, a monovinyl monomer other than the dicarboxylic acid dialkyl esters. Examples of the monovinyl monomer other than the dicarboxylic acid dialkyl esters include aromatic vinyl monomers such as styrene and styrene derivatives such as vinyltoluene and α-methylstyrene; acrylic acid esters such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and dimethylaminoethyl acrylate; methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, and dimethylaminoethyl methacrylate; (meth)acrylic monomers such as acrylic acid and methacrylic acid; nitrile compounds such as acrylonitrile and methacrylonitrile; amide compounds such as acrylamide and methacrylamide; and olefins such as ethylene, propylene, and butylene. These monovinyl monomers can be used alone or in combination of two or more. In the present disclosure, monovinyl monomers other than the above-mentioned dicarboxylic acid dialkyl esters may be referred to as "other monovinyl monomers."

[0024] The content of the other monovinyl monomer is not particularly limited, but is preferably 80 to 98 parts by mass, more preferably 90 to 97 parts by mass, and even more preferably 94 to 96 parts by mass, relative to 100 parts by mass of the total amount of polymerizable monomers. That is, the content of monomer units derived from the other monovinyl monomers in 100% by mass of the polymer is preferably 80 to 98% by mass, more preferably 90 to 97% by mass, and even more preferably 94 to 96% by mass. When the content of the other monovinyl monomer is at least the lower limit, the balance between the storage stability and low-temperature fixability of the toner is good. When the content is at most the upper limit, the dicarboxylic acid dialkyl ester can be used in a sufficient amount, thereby further improving the storage stability and low-temperature fixability of the toner.

[0025] As the polymerizable monomer for the binder resin, it is preferable to use a monovinyl monomer and any crosslinkable polymerizable monomer in order to improve the hot offset resistance and storage stability of the toner. A crosslinkable polymerizable monomer refers to a monomer having two or more functional groups capable of radical polymerization. Examples of crosslinkable polymerizable monomers include aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, and derivatives thereof; ester compounds in which two or more carboxylic acids having carbon-carbon double bonds are ester-bonded to alcohols having two or more hydroxyl groups, such as ethylene glycol dimethacrylate and diethylene glycol dimethacrylate; other divinyl compounds such as N,N-divinylaniline and divinyl ether; and compounds having three or more vinyl groups. These crosslinkable polymerizable monomers can be used alone or in combination of two or more. When the polymerizable monomer contains the crosslinkable polymerizable monomer, the content of the crosslinkable polymerizable monomer is not particularly limited, but is usually 0.1 to 5 parts by mass, and preferably 0.3 to 2 parts by mass, per 100 parts by mass of the monovinyl monomer.

[0026] Furthermore, using a macromonomer as part of the polymerizable monomer is preferable because it improves the balance between the storage stability and low-temperature fixability of the resulting toner. Examples of macromonomers include reactive oligomers and polymers having a polymerizable carbon-carbon unsaturated double bond at the end of the molecular chain, typically having a number-average molecular weight of 1,000 to 30,000. Examples of the macromonomer include styrene macromonomers, styrene-acrylonitrile macromonomers, polyacrylic acid ester macromonomers, and polymethacrylic acid ester macromonomers. Among these, at least one selected from the group consisting of polyacrylic acid ester macromonomers and polymethacrylic acid ester macromonomers is preferably used. Examples of acrylic acid esters used in polyacrylic acid ester macromonomers include the same acrylic acid esters usable as the monovinyl monomers described above. Examples of methacrylic acid esters used in polymethacrylic acid ester macromonomers include the same methacrylic acid esters usable as the monovinyl monomers described above. As the macromonomer, it is preferable to appropriately select and use a macromonomer that, when incorporated into the polymerizable monomer, results in a binder resin with a higher glass transition temperature (Tg) than when not incorporated. Commercially available macromonomers may be used. Examples of commercially available macromonomers include the macromonomer series AA-6, AS-6, AN-6S, AB-6, and AW-6S manufactured by Toagosei Co., Ltd. These macromonomers may be used alone or in combination of two or more. When the polymerizable monomer contains the macromonomer, the content of the macromonomer is not particularly limited, but is preferably 0.03 to 5 parts by mass, more preferably 0.05 to 1 part by mass, per 100 parts by mass of the monovinyl monomer.

[0027] The polymer of the polymerizable monomer is preferably a styrene-acrylic resin. This allows the effects of introducing the dicarboxylic acid dialkyl ester to be particularly exhibited. Here, the styrene-acrylic resin is a copolymer containing a monomer unit derived from an aromatic vinyl monomer and a monomer unit derived from a (meth)acrylic monomer. The (meth)acrylic monomer is a monomer containing at least one selected from the group consisting of an acryloyl group and a methacryloyl group. Furthermore, in the present disclosure, (meth)acrylate refers to each of acrylate and methacrylate, and (meth)acrylic refers to each of acrylic and methacrylic. The polymerizable monomer used in the styrene-acrylic resin preferably contains at least a monovinyl monomer and may further contain a macromonomer or a crosslinkable polymerizable monomer.

[0028] The styrene-acrylic resin used in the present disclosure is a polymer of polymerizable monomers including an aromatic vinyl monomer, a (meth)acrylic monomer, and the above-mentioned dicarboxylic acid dialkyl ester, and other monomers may be further copolymerized within the scope of the present disclosure. In the present disclosure, the polymerizable monomer used in the styrene-acrylic resin preferably contains, as monovinyl monomers, the above-mentioned aromatic vinyl monomer, the above-mentioned (meth)acrylic monomer, and the above-mentioned dicarboxylic acid dialkyl ester. Furthermore, the above-mentioned aromatic vinyl monomer preferably contains styrene, and the above-mentioned (meth)acrylic monomer preferably contains at least one selected from the group consisting of acrylic acid esters and methacrylic acid esters. From the viewpoint of achieving a good balance between the storage stability and low-temperature fixability of the toner, the acrylic acid ester used in the styrene-acrylic resin may be an alkyl acrylate ester having an alkyl group of 1 to 12 carbon atoms, an alkyl acrylate ester having an alkyl group of 1 to 10 carbon atoms, or an alkyl acrylate ester having an alkyl group of 1 to 8 carbon atoms, of which at least one selected from the group consisting of butyl acrylate, propyl acrylate, and 2-ethylhexyl acrylate is preferred. From the same viewpoint as above, the methacrylic acid ester used in the styrene-acrylic resin may be an alkyl methacrylate ester having an alkyl group of 1 to 12 carbon atoms, an alkyl methacrylate ester having an alkyl group of 1 to 10 carbon atoms, or an alkyl methacrylate ester having an alkyl group of 1 to 8 carbon atoms, of which at least one selected from the group consisting of methyl methacrylate, butyl methacrylate, propyl methacrylate, and 2-ethylhexyl methacrylate is preferred. In addition, in the polymerizable monomers used in the styrene-acrylic resin, the mass ratio of the aromatic vinyl monomer to the (meth)acrylic monomer (aromatic vinyl monomer / (meth)acrylic monomer) is preferably 0.1 to 0.9, and more preferably 0.2 to 0.8.Furthermore, the total content of the aromatic vinyl monomer and the (meth)acrylic monomer relative to 100% by mass of the total amount of polymerizable monomers used in the styrene-acrylic resin is preferably 85 to 99% by mass, more preferably 90 to 98% by mass, and even more preferably 93 to 96% by mass.

[0029] The structure and ratio of each monomer unit constituting the polymer contained in the colored resin particles can be determined from the composition of the polymerizable monomer used when producing the colored resin particles. １ It can be determined from the integral value obtained by H-NMR measurement.

[0030] Other binder resins that can be used include polystyrene, polyester resins, and epoxy resins, which have been widely used in toners. In the present disclosure, the content of the styrene-acrylic resin is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 99% by mass or more, and particularly preferably 100% by mass, relative to 100% by mass of the total amount of binder resins. This tends to improve the balance between the storage stability and low-temperature fixability of the toner.

[0031] The binder resin used in the present disclosure preferably has a glass transition temperature (Tg) of 20 to 100°C, more preferably 30 to 90°C. When the Tg of the binder resin is within the above range, the balance between the storage stability and low-temperature fixability of the toner of the present disclosure is good. In the present disclosure, the glass transition temperature (Tg) of the resin can be determined, for example, in accordance with ASTM D3418-82. Specifically, a sample is heated at a heating rate of 10°C / min using a differential scanning calorimeter (such as SSC5200 manufactured by Seiko Electronics Industries, Ltd.), and the temperature showing the maximum endothermic peak in the DSC curve obtained during this process can be taken as the glass transition temperature.

[0032] The content of the binder resin contained in the colored resin particles is not particularly limited, but is preferably 60 parts by mass or more, more preferably 65 parts by mass or more, and even more preferably 70 parts by mass or more, relative to 100 parts by mass of the colored resin particles. In order to ensure that the colorant, softener, and the like are sufficiently contained, the content is preferably 95 parts by mass or less, more preferably 90 parts by mass or less, and even more preferably 85 parts by mass or less.

[0033] (Colorant) The colorant can be appropriately selected from colorants conventionally used in toners and is not particularly limited. When preparing a color toner, white, black, cyan, yellow, or magenta colorants can be used. The white colorant is not particularly limited, but titanium dioxide is preferably used from the viewpoint of hiding power. In addition to titanium dioxide, examples of white colorants include zinc white, antimony white, zinc sulfide, and barium sulfate, and these may be used in combination with titanium dioxide. Titanium dioxide may be in any crystalline form, such as anatase, rutile, or brookite. Examples of black colorants include carbon black, titanium black, and magnetic powders such as iron zinc oxide and iron nickel oxide. Examples of cyan colorants include phthalocyanine pigments such as copper phthalocyanine pigments and their derivatives, cyan pigments such as anthraquinone pigments, and cyan dyes. Specific examples include C.I. Examples of the yellow colorant include C.I. Pigment Blue 2, 3, 6, 15, 15:1, 15:2, 15:3, 15:4, 16, 17:1, and 60; C.I. Solvent Blue 70, and the like. Examples of the yellow colorant include azo pigments such as monoazo pigments and disazo pigments, yellow pigments such as condensed polycyclic pigments, and yellow dyes. Specific examples include C.I. Pigment Yellow 3, 12, 13, 14, 15, 17, 62, 65, 73, 74, 83, 93, 97, 120, 138, 155, 180, 181, 185, 186, 213, and 214; C.I. Solvent Yellow 98 and 162, and the like. Examples of magenta colorants that can be used include azo pigments such as monoazo pigments and disazo pigments, magenta pigments such as condensed polycyclic pigments such as quinacridone pigments, and magenta dyes.Specifically, for example, C.I. Pigment Red 31, 48, 57:1, 58, 60, 63, 64, 68, 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 144, 146, 149, 150, 163, 170, 184, 185, 187, 202, 206, 207, 209, 237, 238, 251, 254, 255, 269; C.I. Pigment Violet 19; C.I. Solvent Red 1, 3, 8, 23, 24, 25, 27, 30, 49, 81, 82, 83, 84, 100, 109, 121; C.I. Disperse Red 9; C.I. Examples of the colorant include Solvent Violet 8, 13, 14, 21, and 27; C.I. Disperse Violet 1; C.I. Basic Red 1, 2, 9, 12, 13, 14, 15, 17, 18, 22, 23, 24, 27, 29, 32, 34, 35, 36, 37, 38, 39, and 40; and C.I. Basic Violet 1, 3, 7, 10, 14, 15, 21, 25, 26, 27, and 28. These colorants can be used alone or in combination of two or more.

[0034] The content of the colorant is not particularly limited, but is preferably 5 to 15 parts by mass, more preferably 7 to 13 parts by mass, relative to 100 parts by mass of the binder resin. The content of the colorant is also preferably 5 to 15 parts by mass, more preferably 7 to 13 parts by mass, relative to 100 parts by mass of the monovinyl monomer. When the content of the colorant is equal to or greater than the lower limit, the image density can be increased, and when the content is equal to or less than the upper limit, deterioration of the toner fixability can be suppressed.

[0035] (Softener) The toner of the present disclosure contains an ester wax as a softener. Ester wax has good compatibility with the binder resin and excellent dispersibility in colored resin particles, and is therefore highly effective in improving low-temperature fixability while suppressing deterioration of the toner's storage stability. Furthermore, by including an ester wax as the primary softener, the toner's hot offset resistance can be improved more than, for example, by including a hydrocarbon wax as the primary softener. Among the ester waxes, synthetic ester waxes obtained by esterifying alcohol and carboxylic acid are particularly preferred. The ester wax may be a monoester having only one ester bond in its structure or a polyfunctional ester having two or more ester bonds in its structure. However, at least one selected from the group consisting of a monoester and a polyfunctional ester having three or more ester bonds in its structure is preferred because it can more easily exhibit the effects of the dicarboxylic acid dialkyl ester. Furthermore, monoesters are preferred because they can easily improve the low-temperature fixability of the toner, while polyfunctional esters having three or more ester bonds in their structure are preferred because they can suppress deterioration of the toner's storage stability. Among the polyfunctional esters, trifunctional to octafunctional esters, i.e., polyfunctional esters having 3 to 8 ester bonds in the structure of one molecule, are more preferred. These ester waxes can be used alone or in combination of two or more.

[0036] The alcohol used as a raw material for the ester wax may be at least one alcohol selected from the group consisting of monohydric alcohols and polyhydric alcohols, of which monohydric alcohols are preferred for obtaining monoester waxes, and trihydric or higher polyhydric alcohols are preferred for obtaining polyfunctional ester waxes having three or more ester bonds in the structure. These alcohols may be used alone or in combination of two or more. Examples of monohydric alcohols include monohydric saturated aliphatic alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1-pentanol, 1-hexanol, octanol, 2-ethyl-1-hexanol, nonyl alcohol, lauryl alcohol, cetyl alcohol (palmityl alcohol), stearyl alcohol, and behenyl alcohol; monohydric unsaturated aliphatic alcohols such as allyl alcohol, methallyl alcohol, crotyl alcohol, and oleyl alcohol; monohydric alicyclic alcohols such as cyclohexanol; and monohydric aromatic alcohols such as phenol, phenylmethanol (benzyl alcohol), methylphenol (cresol), p-ethylphenol, dimethylphenol (xylenol), nonylphenol, dodecylphenol, phenylphenol, and naphthol. Among these, monohydric saturated aliphatic alcohols are preferred, monohydric linear saturated aliphatic alcohols are more preferred, and monohydric linear saturated aliphatic alcohols having 12 to 24 carbon atoms are particularly preferred. Examples of polyhydric alcohols include dihydric saturated aliphatic alcohols such as ethylene glycol and propylene glycol, dihydric aromatic alcohols such as catechol and hydroquinone, and trihydric or higher saturated aliphatic alcohols such as glycerin, pentaerythritol, dipentaerythritol, diglycerol, triglycerol, tetraglycerol, pentaglycerol, hexaglycerol, and polyglycerin. Among these, trihydric or higher saturated aliphatic alcohols are preferred, and at least one selected from the group consisting of pentaerythritol, hexaglycerol, and polyglycerin is particularly preferred.

[0037] The carboxylic acid used as a raw material for the ester wax may be at least one selected from the group consisting of monocarboxylic acids and polycarboxylic acids, with monocarboxylic acids being preferred. The carboxylic acid may also be at least one fatty acid selected from the group consisting of saturated fatty acids and unsaturated fatty acids, with saturated fatty acids being preferred. That is, saturated aliphatic monocarboxylic acids are particularly preferred. These carboxylic acids may be used alone or in combination of two or more.

[0038] Examples of monocarboxylic acids include saturated aliphatic monocarboxylic acids (saturated fatty acids) such as lauric acid (12 carbon atoms), myristic acid (14 carbon atoms), pentadecylic acid (15 carbon atoms), palmitic acid (16 carbon atoms), margaric acid (17 carbon atoms), stearic acid (18 carbon atoms), arachidic acid (eicosanoic acid) (20 carbon atoms), and behenic acid (22 carbon atoms); and fatty acids such as the following unsaturated aliphatic monocarboxylic acids (unsaturated fatty acids): palmitoleic acid (CH ３ (CH ２ ) ５ CH=CH(CH ２ ) ７ COOH) oleic acid (CH ３ (CH ２ ) ７ CH=CH(CH ２ ) ７ COOH) vaccenic acid (CH ３ (CH ２ ) ５ CH=CH(CH ２ ) ９ COOH) Linoleic acid (CH ３ (CH ２ ) ３ (CH ２ CH=CH) ２ (CH ２ ) ７ COOH) (9,12,15)-linolenic acid (CH ３ (CH ２ CH=CH) ３ (CH ２ ) ７ COOH) (6,9,12)-linolenic acid (CH ３(CH ２ ) ３ (CH ２ CH=CH) ３ (CH ２ ) ４ COOH) Eleostearic acid (CH ３ (CH ２ ) ３ (CH=CH) ３ (CH ２ ) ７ COOH) and arachidonic acid (CH ３ (CH ２ ) ３ (CH ２ CH=CH) ４ (CH ２ ) ３ COOH)

[0039] Examples of polycarboxylic acids include aliphatic dicarboxylic acids such as oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenylsuccinic acid, adipic acid, sebacic acid, and cyclohexanedicarboxylic acid; aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, and naphthalenedicarboxylic acid; and trivalent or higher carboxylic acids such as trimellitic acid and pyromellitic acid.

[0040] The carbon number of the fatty acid used as a raw material for the ester wax has a lower limit of preferably 12 or more, more preferably 16 or more, and even more preferably 18 or more, and an upper limit of preferably 30 or less, more preferably 24 or less, and even more preferably 22 or less. When the carbon number of the fatty acid is equal to or more than the lower limit, deterioration in the storage stability of the toner is suppressed, and when the carbon number is equal to or less than the upper limit, the low-temperature fixability of the toner is improved.

[0041] Furthermore, the monoester used as the ester wax is not particularly limited, but is preferably an ester of an alcohol having 10 or more carbon atoms and a carboxylic acid having 10 or more carbon atoms, since the effect of combining it with the dicarboxylic acid dialkyl ester is easily exhibited. From the same viewpoint as above, the number of carbon atoms in the alcohol used in the monoester may be 12 or more, 14 or more, 16 or more, or 18 or more, and the upper limit of the carbon number is preferably 30 or less, 24 or less, or 22 or less. From the same viewpoint as above, the number of carbon atoms in the carboxylic acid used in the monoester may be 12 or more, 14 or more, 16 or more, or 18 or more, and the upper limit of the carbon number is preferably 30 or less, 24 or less, or 22 or less.

[0042] The polyfunctional ester used as the ester wax is not particularly limited, but is preferably an ester of a polyhydric alcohol and a carboxylic acid having 10 or more carbon atoms, since the effect of the combination with the dicarboxylic acid dialkyl ester is easily exhibited. For the same reasons as above, the number of carbon atoms in the carboxylic acid used in the polyfunctional ester may be 12 or more, 14 or more, 16 or more, or 18 or more, and the upper limit of the carbon number is preferably 30 or less, 24 or less, or 22 or less.

[0043] The hydroxyl value of the ester wax is not particularly limited, but from the viewpoint of suppressing deterioration of the storage stability of the toner, it is preferably 10.0 mgKOH / g or less, more preferably 5.0 mgKOH / g or less, and even more preferably 3.0 mgKOH / g or less. The acid value of the ester wax is not particularly limited, but from the viewpoint of suppressing deterioration of the storage stability of the toner, it is preferably 1.0 mgKOH / g or less, more preferably 0.7 mgKOH / g or less, and even more preferably 0.5 mgKOH / g or less. The hydroxyl value and acid value of the softener are values ​​measured in accordance with JIS K 0070, which is a standard method for analyzing fats and oils established by the Japanese Industrial Standards Committee (JICS).

[0044] The esterification rate of the ester wax is preferably 92% or more, more preferably 95% or more, and even more preferably 97% or more, from the viewpoint of improving the low-temperature fixability of the toner due to the sharp melting properties of the ester wax. The esterification rate of the ester wax is the ratio of the number of hydroxyl groups ester-bonded to a carboxylic acid (e.g., a fatty acid) to the total number of hydroxyl groups possessed by the raw material alcohol of the ester wax. The esterification rate of the ester wax can be calculated by measuring the saponification value (SV), hydroxyl value (OHV), and acid value (AV) of the ester wax, respectively, and using the following formula: Esterification rate (%) = [(SV - AV) / (SV - AV + OHV)] × 100. The saponification value (SV) and acid value (AV) of the ester wax are measured in accordance with JIS K 0070, and the hydroxyl value (OHV) of the ester wax is measured in accordance with JIS K 1557.

[0045] The molecular weight of the ester wax is not particularly limited, but is preferably 300 to 3000, more preferably 400 to 2800, and even more preferably 500 to 2700. When the molecular weight of the ester wax is equal to or greater than the above lower limit, the low-temperature fixability of the toner is improved and bleed-out of the ester wax is suppressed, and when the molecular weight is equal to or less than the above upper limit, deterioration of the low-temperature fixability of the toner is suppressed, the toner spreads easily during fixation, and a decrease in print density is suppressed.

[0046] Furthermore, the melting point of the ester wax is preferably within a range of 50 to 90°C, more preferably within a range of 60 to 85°C, and even more preferably within a range of 65 to 80°C, from the viewpoint of improving the storage stability and low-temperature fixability of the toner in a well-balanced manner.

[0047] As long as the object of the present disclosure is not impaired, the toner may further contain a softener other than the ester wax. Examples of softeners other than the ester wax include hydrocarbon waxes such as polyethylene wax, polypropylene wax, Fischer-Tropsch wax, and petroleum wax; natural waxes such as jojoba; and mineral waxes such as ozokerite. When the toner of the present disclosure contains a softener other than the ester wax, the content of the ester wax in 100% by mass of the softener is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more.

[0048] The content of the softener is not particularly limited, but the lower limit is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, relative to 100 parts by mass of the binder resin, and the upper limit is preferably 30 parts by mass or less, more preferably 25 parts by mass or less. Furthermore, the lower limit of the content of the softener is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, relative to 100 parts by mass of the monovinyl monomer, and the upper limit is preferably 30 parts by mass or less, more preferably 25 parts by mass or less. When the content of the softener is equal to or greater than the lower limit, low-temperature fixability is improved, and the toner easily spreads during fixation, thereby suppressing a decrease in print density. When the content of the softener is equal to or less than the upper limit, deterioration in storage stability and hot offset resistance is suppressed.

[0049] (Charge Control Agent) The colored resin particles preferably contain a positively or negatively charged charge control agent. This can improve the chargeability of the toner. The charge control agent is not particularly limited as long as it is a charge control agent that is generally used as a charge control agent for toner. Among charge control agents, a positively or negatively charged charge control resin is preferred because it has high compatibility with the binder resin and can impart stable chargeability (charge stability) to the toner particles.

[0050] A functional group-containing copolymer can be used as a positively or negatively charged charge control resin. Positively charged charge control resins include functional group-containing copolymers containing structural units containing functional groups such as amino groups, quaternary ammonium groups, or quaternary ammonium salt-containing groups, such as polyamine resins, quaternary ammonium group-containing copolymers, and quaternary ammonium base-containing copolymers. Negatively charged charge control resins include functional group-containing copolymers containing structural units containing functional groups such as sulfonic acid groups, sulfonate salt-containing groups, carboxylic acid groups, or carboxylate salt-containing groups, such as sulfonic acid group-containing copolymers, sulfonate salt group-containing copolymers, carboxylic acid group-containing copolymers, and carboxylate salt group-containing copolymers. These charge control resins can be used alone or in combination of two or more.

[0051] The glass transition temperature (Tg) of the charge control resin is preferably 60 to 90° C., more preferably 65 to 85° C., and even more preferably 70 to 80° C. When the Tg of the charge control resin is within the above range, the balance between the storage stability and fixability of the toner is good.

[0052] The weight-average molecular weight (Mw) of the charge control resin is preferably 5,000 to 30,000, more preferably 10,000 to 25,000, and even more preferably 15,000 to 23,000. When the weight-average molecular weight (Mw) of the charge control resin is at or above the lower limit, deterioration in the toner's storage stability and print durability can be suppressed. When it is at or below the upper limit, deterioration in the toner's fixability can be suppressed. Furthermore, when the weight-average molecular weight (Mw) of the charge control resin is within the above range, the charge control resin can be suitably dispersed in the polymerizable monomer composition, making it easier to obtain a toner with a stable charge amount over time. In this disclosure, the weight-average molecular weight (Mw) is a polystyrene-equivalent value measured by gel permeation chromatography (GPC) using tetrahydrofuran (THF).

[0053] As the charge control resin, a functional group-containing copolymer having a content ratio of functional group-containing monomer units (sometimes simply referred to as "functional group amount" in the present disclosure) of 0.4 to 10% by mass is preferably used in order to impart the desired chargeability to the toner. The lower limit of the functional group amount of the functional group-containing copolymer is more preferably 1% by mass or more, and even more preferably 2% by mass or more, and the upper limit is more preferably 9% by mass or less, and even more preferably 8% by mass or less.

[0054] The toner of the present disclosure is preferably a positively charged toner containing a positively charged charge control agent, since the effect of the dicarboxylic acid dialkyl ester is easily exhibited. As the positively charged charge control agent, the above-mentioned positively charged charge control resin is preferred, and a positively charged functional group-containing copolymer is more preferred. As the functional group contained in the positively charged functional group-containing copolymer, for example, a functional group that imparts positive chargeability, such as a pyridinium group, an amino group, a quaternary ammonium group, or a quaternary ammonium salt-containing group, is preferred. Among these, from the viewpoint of imparting the desired chargeability to the toner and improving the dispersibility of the colorant, a quaternary ammonium group and a quaternary ammonium salt-containing group are preferred, and a quaternary ammonium salt-containing group is more preferred. That is, the toner of the present disclosure particularly preferably contains a quaternary ammonium base-containing copolymer, i.e., a functional group-containing copolymer containing a quaternary ammonium salt-containing group, as the charge control agent. Furthermore, the toner of the present disclosure is particularly preferably a positively charged toner containing a quaternary ammonium base-containing copolymer as the charge control agent. The quaternary ammonium salt-containing group is preferably -NR ３ ＋ ・X － In this ionic structure, the three R's are each independently a hydrogen atom or a substituent such as an alkyl group, and among these, a hydrogen atom or a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms is preferred. X － represents a halogen ion, a hydrocarbon in which one hydrogen atom is substituted with a halogen ion, or —SO ３ － , -PO ３ － Or -BO ３ － Examples of hydrocarbons include aliphatic hydrocarbons such as alkanes, aromatic hydrocarbons, and substituted aromatic hydrocarbons. X － Among these, —SO 2 in which at least one hydrogen atom may be substituted with a halogen atom is preferred, in that the charge amount of the toner is easily maintained during continuous printing and printing defects are less likely to occur. ３ －Preferably, the anion is a hydrocarbon having the formula (I), more preferably an aromatic sulfonate anion which may have at least one substituent selected from the group consisting of a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms and a halogen atom, and even more preferably a benzenesulfonate anion or a paratoluenesulfonate anion.

[0055] From the viewpoint of compatibility with the polymerizable monomer, the functional group-containing copolymer is preferably a styrene-acrylic resin, more specifically, a copolymer containing a functional group-containing monomer unit, an aromatic vinyl monomer unit, and a (meth)acrylic monomer unit. Here, the aromatic vinyl monomer unit and the (meth)acrylic monomer unit do not contain a functional group that imparts chargeability. Such a copolymer has excellent compatibility with the binder resin, and therefore tends to produce a uniform charge amount of the toner. Furthermore, from the viewpoint of dispersibility in the polymerizable monomer composition, the functional group-containing copolymer is preferably one that dissolves in the aromatic vinyl monomer.

[0056] The functional group-containing copolymer may be, for example, a copolymer obtained by copolymerizing a monomer containing a functional group with another monomer copolymerizable therewith, or may be a copolymer obtained by polymerizing a monomer not containing a functional group and then introducing a functional group by a modification treatment.

[0057] In a copolymer containing a monomer unit containing a quaternary ammonium salt-containing group, an aromatic vinyl monomer unit, and a (meth)acrylic monomer unit, which is preferably used as a positively chargeable functional group-containing copolymer, the monomer unit containing a quaternary ammonium salt-containing group is preferably a structural unit represented by the following formula [I]:

[0058] [In the above formula [I], R １ is a hydrogen atom or a methyl group, and R ２ is a linear or branched alkylene group having 1 to 3 carbon atoms in which at least one hydrogen atom may be substituted with a halogen atom, and R ３ ~R ５are each independently a hydrogen atom or a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms; X － may have at least one substituent selected from the group consisting of a halogen ion, a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms, and a halogen atom; —SO ３ － , -PO ３ － Or -BO ３ － Benzene or naphthalene having either of the following:

[0059] Specific examples of the structural unit represented by formula [I] include structural units corresponding to monomers containing a quaternary ammonium salt-containing group, such as N,N-diethyl-N-methyl-2-(methacryloyloxy)ethylammonium chloride, 2-(methacryloyloxy)ethyltrimethylammonium chloride (DMC; methacrylic acid dimethylaminoethyl methyl chloride), 2-(methacryloyloxy)-N-benzyl-N,N-dimethylethane ammonium chloride (DML; methacrylic acid dimethylaminoethyl benzyl chloride), and N,N-diethyl-N-methyl-2-(methacryloyloxy)ethylammonium paratoluenesulfonate, 2-(methacryloyloxy)ethyltrimethylammonium paratoluenesulfonate, and 2-(methacryloyloxy)-N-benzyl-N,N-dimethylethane ammonium paratoluenesulfonate. Among these, a structural unit corresponding to N,N-diethyl-N-methyl-2-(methacryloyloxy)ethylammonium paratoluenesulfonate is preferred.

[0060] As the aromatic vinyl monomer, for example, styrene and α-methylstyrene are preferred. These can be used alone or in combination of two or more. As the (meth)acrylic monomer, for example, alkyl(meth)acrylates which may have a hydroxyl group are preferably used, and can be used alone or in combination of two or more. In the alkyl(meth)acrylate, the number of carbon atoms in the alkyl group is not particularly limited, but is preferably 1 to 12, more preferably 1 to 8, and even more preferably 1 to 6. Furthermore, alkyl(meth)acrylates which do not have a substituent are particularly preferred.

[0061] In the functional group-containing copolymer, the copolymerization ratio of the aromatic vinyl monomer and the (meth)acrylic monomer is not particularly limited, but from the viewpoint of dispersibility in the binder resin, the mass ratio of the (meth)acrylic monomer units to the aromatic vinyl monomer units ((meth)acrylic monomer units / aromatic vinyl monomer units) is preferably 0.05 to 0.35, more preferably 0.10 to 0.30, and even more preferably 0.15 to 0.25.

[0062] Furthermore, from the viewpoint of improving print density, it is also preferable to include a combination of copolymer A and copolymer B as the charge control resin. Here, copolymer A and copolymer B are functional group-containing copolymers with different amounts of functional groups, with copolymer A having a greater amount of functional groups than copolymer B. By including a combination of copolymer A, which has a relatively high amount of functional groups, and copolymer B, which has a relatively low amount of functional groups, as the charge control resin in the colored resin particles, the toner can be imparted with the desired chargeability while improving the dispersibility of the colorant. Therefore, the colorant can be incorporated at a high concentration, resulting in improved print density. When copolymer A and copolymer B are used in combination as charge control agents, the difference in functional group amounts is thought to result in a distribution in which copolymer B is unevenly distributed relatively toward the center of the colored resin particles, while copolymer A is unevenly distributed toward the surface of the colored resin particles. Since copolymer A has a higher amount of functional groups than copolymer B, it has a stronger charge-imparting effect and is unevenly distributed toward the surface of the colored resin particles, and therefore the chargeability of the toner is thought to be mainly influenced by copolymer A. On the other hand, copolymer B not only exhibits a charge-imparting effect, but is also thought to be more effective at dispersing the colorant within the colored resin particles. It is presumed that the action of such copolymer A and copolymer B imparts the desired chargeability to the toner and improves the dispersibility of the colorant.

[0063] The amount of functional groups in the copolymer A is preferably 1% by mass or more, more preferably 2% by mass or more as a lower limit, and preferably 10% by mass or less, and more preferably 9% by mass or less as an upper limit, from the viewpoint of imparting a desired chargeability to the toner and improving the dispersibility of the colorant. The amount of functional groups in the copolymer B is preferably 0.4% by mass or more, more preferably 0.5% by mass or more as a lower limit, and preferably less than 5% by mass, more preferably 4% by mass or less, and even more preferably 3% by mass or less as an upper limit, from the viewpoint of imparting a desired chargeability to the toner and improving the dispersibility of the colorant.

[0064] The difference between the amount of functional groups in the copolymer A and the amount of functional groups in the copolymer B (amount of functional groups in copolymer A - amount of functional groups in copolymer B) is preferably 0.5 to 9% by mass, more preferably 1 to 8% by mass, from the viewpoint of imparting a desired chargeability to the toner and improving the dispersibility of the colorant.

[0065] In addition, from the viewpoint of imparting the desired chargeability to the toner and improving the dispersibility of the colorant, the functional group contained in the copolymer A and the functional group contained in the copolymer B preferably have the same structure, and more preferably are the same and are a quaternary ammonium group or a quaternary ammonium salt-containing group. From the same viewpoint, it is preferable that the copolymer A and the copolymer B each consist of a copolymer having the same monomer unit composition. Incidentally, copolymers having the same monomer unit composition mean that the types and copolymerization ratios of the monomers used in the synthesis of the copolymers are the same. In other words, when the copolymer A and the copolymer B are contained in combination, it is preferable to contain only one type of the copolymer A and only one type of the copolymer B.

[0066] In a toner containing a combination of copolymer A and copolymer B, the ratio of the content of copolymer A to the content of copolymer B (copolymer A content / copolymer B content) is not particularly limited, but from the viewpoints of imparting a desired chargeability to the toner, improving the dispersibility of the colorant, and improving the heat resistance of the toner, the lower limit is preferably 0.5 or more, more preferably 0.8 or more, even more preferably 1.0 or more, and still more preferably 1.5 or more, and the upper limit is preferably 15 or less, more preferably 10 or less, even more preferably 5 or less, and still more preferably 3 or less. When the ratio is equal to or greater than the lower limit, toner quality can be easily controlled, and when the ratio is equal to or less than the upper limit, the dispersibility of the colorant in particular is improved, making it possible to easily improve print density.

[0067] The charge control agent may contain a substance other than the charge control resin. Examples of charge control agents other than the positively chargeable charge control resin include nigrosine dyes, quaternary ammonium salts, triaminotriphenylmethane compounds, and imidazole compounds. Examples of charge control agents other than the negatively chargeable charge control resin include azo dyes containing metals such as Cr, Co, Al, and Fe, salicylic acid metal compounds, and alkylsalicylic acid metal compounds. Note that the charge control agents other than the charge control resin may be used alone or in combination of two or more.

[0068] The content of the charge control agent is not particularly limited, but is preferably 0.1 to 10 parts by mass, more preferably 0.3 to 5 parts by mass, and even more preferably 0.6 to 3 parts by mass, per 100 parts by mass of the binder resin. The content of the charge control agent is also preferably 0.1 to 10 parts by mass, more preferably 0.3 to 5 parts by mass, and even more preferably 0.6 to 3 parts by mass, per 100 parts by mass of the monovinyl monomer. When the content of the charge control agent is within the above range, printing performance tends to be improved. When the content of the charge control agent is equal to or greater than the above lower limit, the occurrence of fogging is suppressed, and when it is equal to or less than the above upper limit, print smearing is suppressed.

[0069] (Polar Resin) The colored resin particles may contain a polar resin. The polar resin tends to be unevenly distributed on the surface side of the colored resin particles, reinforcing the particle surface and suppressing deterioration of the colored resin particles, thereby improving the storage stability and print durability of the toner.

[0070] In the present disclosure, a polar resin is a polymer containing a repeating unit containing a heteroatom. Specific examples of such polar resins include acrylic resins, polyester resins, and vinyl resins containing heteroatoms. The polar resin may be a homopolymer or copolymer of a heteroatom-containing monomer, or a copolymer of a heteroatom-containing monomer and a non-heteroatom-containing monomer. When the polar resin is a copolymer of a heteroatom-containing monomer and a non-heteroatom-containing monomer, the proportion of heteroatom-containing monomer units in 100% by mass of all repeating units constituting the copolymer is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more, since the heteroatom-containing monomer units tend to be unevenly distributed on the surface side of the colored resin particles.

[0071] Examples of heteroatom-containing monomers used in the polar resin include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, sec-pentyl (meth)acrylate, and isopentyl (meth)acrylate. acrylate, alkyl (meth)acrylates such as neopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, neohexyl (meth)acrylate, sec-hexyl (meth)acrylate, tert-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl (meth)acrylate, as well as 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate Examples of suitable monomers include (meth)acrylic acid esters such as 4-hydroxybutyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, glycidyl (meth)acrylate, and 4-hydroxybutyl acrylate glycidyl ether, as well as monomers having a (meth)acryloyl group such as (meth)acrylic acid, i.e., (meth)acrylic monovinyl monomers; aromatic vinyl monomers containing heteroatoms such as halogenated styrenes and styrene sulfonic acids; vinyl carboxylic acid ester monomers such as vinyl acetate; halogenated vinyl monomers such as vinyl chloride; halogenated vinylidene monomers such as vinylidene chloride; vinylpyridines; carboxyl group-containing monomers such as ethylenically unsaturated carboxylic acid monomers such as crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, and butenetricarboxylic acid; and epoxy group-containing monomers such as allyl glycidyl ether. These heteroatom-containing monomers can be used alone or in combination of two or more.The polar resin used for the positively chargeable toner preferably has a copolymerization ratio of 0.1% by mass or less of a monomer containing a functional group that imparts positive chargeability and is selected from a pyridinium group, an amino group, a quaternary ammonium group, and a quaternary ammonium salt-containing group, and the polar resin used for the negatively chargeable toner preferably has a copolymerization ratio of 0.1% by mass or less of a monomer containing a functional group that imparts negative chargeability and is selected from a sulfonic acid group, a sulfonate-containing group, a carboxyl group, and a carboxylate-containing group, which can improve the charge stability of the toner.

[0072] Examples of heteroatom-free monomers used in the polar resin include aromatic vinyl monomers that do not contain heteroatoms, such as styrene, vinyltoluene, α-methylstyrene, and p-methylstyrene; monoolefin monomers, such as ethylene, propylene, and butylene; and diene monomers, such as butadiene and isoprene. These heteroatom-free monomers can be used alone or in combination of two or more.

[0073] In particular, the polar resin preferably contains a polar group-containing monomer unit containing at least one polar group selected from the group consisting of an acidic group such as a carboxyl group and a sulfonic acid group, a hydroxyl group, an amino group, a polyoxyethylene group, and an epoxy group, in order to facilitate uneven distribution on the surface side of the colored resin particles. Among these, the polar group is preferably at least one selected from the group consisting of an acidic group and a hydroxyl group, and more preferably at least one selected from the group consisting of a carboxyl group and a hydroxyl group. Examples of polar group-containing monomers include carboxyl group-containing monomers such as ethylenically unsaturated carboxylic acid monomers such as acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, and butenetricarboxylic acid; hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; sulfonic acid group-containing monomers such as styrenesulfonic acid; amino group-containing monomers such as dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate; polyoxyethylene group-containing monomers such as methoxypolyethylene glycol (meth)acrylate; and epoxy group-containing monomers such as glycidyl (meth)acrylate, allyl glycidyl ether, and 4-hydroxybutyl acrylate glycidyl ether. These polar group-containing monomers can be used alone or in combination of two or more.

[0074] Furthermore, an acidic group-containing copolymer is preferably used as the polar resin. The acid value of the acidic group-containing copolymer is not particularly limited, but the lower limit is preferably 0.5 mgKOH / g or more, more preferably 1.0 mgKOH / g or more, and even more preferably 2.0 mgKOH / g or more, and the upper limit is preferably 10.0 mgKOH / g or less, more preferably 7.0 mgKOH / g or less, and even more preferably 5.0 mgKOH / g or less. When the acid value is within the above range, a toner having excellent low-temperature fixability and storage stability is easily obtained. In the present disclosure, the acid value of the resin is measured in accordance with JIS K 0070.

[0075] Among the acidic group-containing copolymers, acrylate copolymers having acidic groups are preferred. As the acrylate copolymer having acidic groups, for example, a copolymer of a (meth)acrylic acid ester and (meth)acrylic acid is preferably used. The copolymer of a (meth)acrylic acid ester and (meth)acrylic acid is a copolymer of at least one selected from the group consisting of an acrylic acid ester and a methacrylic acid ester and at least one selected from the group consisting of an acrylic acid and a methacrylic acid. Examples of such copolymers include a copolymer of an acrylic acid ester and an acrylic acid, a copolymer of an acrylic acid ester and an methacrylic acid, a copolymer of a methacrylic acid ester and an acrylic acid, a copolymer of an acrylic acid ester and an methacrylic acid, a copolymer of an acrylic acid ester, an methacrylic acid ester and an acrylic acid, a copolymer of an acrylic acid ester, an methacrylic acid ester and an acrylic acid, a copolymer of an acrylic acid ester, an methacrylic acid ester and an acrylic acid, and a copolymer of an acrylic acid ester, an methacrylic acid ester, an acrylic acid and an methacrylic acid. Of these, a copolymer of an acrylic acid ester, an methacrylic acid ester and an acrylic acid is preferred.

[0076] Among the acrylic acid esters, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, and n-butyl acrylate are preferred, with ethyl acrylate and n-butyl acrylate being more preferred. Among the methacrylic acid esters, methyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, and n-butyl methacrylate are preferred, with methyl methacrylate being more preferred.

[0077] The mass ratio of each monomer unit constituting the acrylate copolymer is preferably adjusted to satisfy a preferred acid value and glass transition temperature Tg.The content of (meth)acrylic acid units in 100% by mass of all monomer units constituting the acrylate copolymer is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.3% by mass or more, and is preferably 2.0% by mass or less, more preferably 1.0% by mass or less, and even more preferably 0.8% by mass or less.The content of (meth)acrylic acid ester units in 100% by mass of all monomer units constituting the acrylate copolymer is preferably 98.0% by mass or more, more preferably 99.0% by mass or more, and even more preferably 99.2% by mass or more, and is preferably 99.95% by mass or less, more preferably 99.9% by mass or less, and even more preferably 99.7% by mass or less.

[0078] The acrylate copolymer may contain other monomer units different from (meth)acrylic acid ester units and (meth)acrylic acid units, as long as the object of the present disclosure is not impaired. Examples of such other monomers include styrene derivatives, nitrile compounds, and amide compounds, which are exemplified as the monovinyl monomers constituting the binder resin. In the acrylate copolymer, the content of the other monomer units is preferably 10% by mass or less, more preferably 2% by mass or less, and most preferably 0% by mass, relative to 100% by mass of (meth)acrylic acid ester units.

[0079] The weight average molecular weight (Mw) of the polar resin is not particularly limited, but the lower limit is preferably 6,000 or more, more preferably 7,000 or more, and even more preferably 9,000 or more, and the upper limit is preferably 50,000 or less, more preferably 45,000 or less, and even more preferably 40,000 or less. When the weight average molecular weight (Mw) of the polar resin is within the above range, a toner having excellent low-temperature fixability and storage stability is easily obtained.

[0080] The glass transition temperature Tg of the polar resin is not particularly limited, but the lower limit is preferably 60° C. or higher, more preferably 65° C. or higher, and even more preferably 70° C. or higher, and the upper limit is preferably 85° C. or lower, more preferably 80° C. or lower. When the glass transition temperature Tg of the polar resin is within the above range, a toner having excellent low-temperature fixability and storage stability is easily obtained.

[0081] The content of the polar resin, relative to 100 parts by mass of the binder resin, is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more, as a lower limit, and preferably 5 parts by mass or less, and more preferably 3 parts by mass or less. Furthermore, the content of the polar resin, relative to 100 parts by mass of the monovinyl monomer, is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more, as an upper limit, and preferably 5 parts by mass or less, and more preferably 3 parts by mass or less. When the content of the polar resin is within the above range, the toner charge amount tends to be appropriate, and in particular, a decrease in the toner charge amount is suppressed, and a decrease in production stability and a decrease in low-temperature fixability are suppressed.

[0082] The polar resin may be commercially available, or may be produced by known polymerization methods such as solution polymerization, aqueous solution polymerization, ionic polymerization, high-temperature / high-pressure polymerization, and suspension polymerization. Typical examples of the method for producing the polar resin are as follows. Note that the method for producing the polar resin is not limited to the following typical examples. First, an appropriate amount of solvent is added to a reaction vessel, the atmosphere in the reaction vessel is replaced with an inert atmosphere, the temperature is raised, and raw material monomers are added to the reaction vessel. At this time, it is preferable to add a polymerization initiator as well. It is also preferable to gradually dropwise add a mixture of the raw material monomers and the polymerization initiator to the reaction vessel. Next, the temperature is raised to a temperature at which the polymerization reaction proceeds, and polymerization is initiated. After completion of polymerization, the desired polar resin is obtained by appropriately distilling off the solvent. Furthermore, when the polar resin is a copolymer, the copolymer may be any of a random copolymer, a block copolymer, or a graft copolymer, but a random copolymer is preferred. It is also preferable that the polar resin be more finely pulverized to improve solubility.

[0083] (Shell Layer) The colored resin particles may be so-called core-shell type (also called "capsule type") colored resin particles having a core layer containing the binder resin and a shell layer covering the core layer. In the core-shell type colored resin particles, the softening point of the shell layer is preferably higher than that of the core layer. This allows the toner to have a better balance between low-temperature fixability and storage stability.

[0084] The shell layer may contain, for example, a polymer of a polymerizable monomer for the shell. The polymerizable monomer for the shell can be the same as the polymerizable monomer described above that is the raw material for the binder resin contained in the core layer. Among these, it is preferable to use, as the polymerizable monomer for the shell, polymerizable monomers that can give a polymer with a Tg of more than 80°C, such as styrene, acrylonitrile, and methyl methacrylate, either alone or in combination.

[0085] The content of the shell layer is not particularly limited, but is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 7 parts by mass, and even more preferably 1 to 5 parts by mass, relative to 100 parts by mass of the binder resin. The content of the polymerizable monomer for the shell is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 7 parts by mass, and even more preferably 1 to 5 parts by mass, relative to 100 parts by mass of the monovinyl monomer. The content of the polymer of the polymerizable monomer for the shell contained in 100% by mass of the shell layer is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more. It is particularly preferred that the shell layer be made of a polymer of the polymerizable monomer for the shell.

[0086] 1-2. External Additives The toner of the present disclosure may be composed of the above-described colored resin particles, but preferably further contains an external additive, from the viewpoint of improving the fluidity of the toner and improving the low-temperature fixability and storage stability of the toner in a balanced manner. Examples of external additives include inorganic fine particles such as silica, titanium oxide, aluminum oxide, zinc oxide, tin oxide, strontium titanate, calcium carbonate, calcium phosphate, or cerium oxide; organic fine particles such as polymethyl methacrylate resin, silicone resin, or melamine resin; and fine particles of metal soaps such as zinc stearate and magnesium stearate. Among these, inorganic fine particles are preferred, and among inorganic fine particles, silica fine particles and titanium oxide fine particles are preferred, with silica fine particles being particularly suitable. These external additives can be used alone, but it is preferable to use two or more of them in combination.

[0087] The external additive preferably contains inorganic fine particles A having a number-average primary particle size of 5 nm to 14 nm and inorganic fine particles B having a number-average primary particle size of 15 nm to 90 nm. When the inorganic fine particles A and B are contained as the external additive, the mass ratio of the inorganic fine particles A to B (inorganic fine particles A:inorganic fine particles B) is not particularly limited and may be, for example, 20:80 to 80:20. The number-average primary particle size of the external additive is measured, for example, by weighing out about 0.1 g of a measurement sample, placing it in a beaker, adding 0.1 mL of an alkylbenzenesulfonic acid aqueous solution (manufactured by Fujifilm Corporation, product name: Drywell) as a dispersant, further adding 10 to 30 mL of a diluent (manufactured by Beckman Coulter, product name: Isoton II) to the beaker, and dispersing the mixture for 3 minutes using a 20 W (Watt) ultrasonic disperser. Thereafter, the number-average primary particle size is measured using a particle size distribution analyzer (manufactured by Beckman Coulter, product name: Multisizer) under the conditions of an aperture diameter of 100 μm, a medium: Isoton II, and a measurement particle count of 100,000.

[0088] The content of the external additive is not particularly limited, but is preferably 0.05 to 6 parts by mass, and more preferably 0.2 to 5 parts by mass, relative to 100 parts by mass of the colored resin particles. When the content of the external additive is within the above range, transfer residue and fogging are easily suppressed.

[0089] The toner of the present disclosure may be used as a one-component toner (developer), or may be further mixed and stirred with carrier particles to be used as a two-component developer.

[0090] The toner manufacturing method of the present disclosure includes at least the step of manufacturing the colored resin particles described above, and may further include a step of mixing and stirring the obtained colored resin particles with an external additive to perform an external addition treatment, thereby adhering the external additive to the surfaces of the colored resin particles. The method of manufacturing the colored resin particles and the external addition treatment method will be described below in order.

[0091] <Method for producing colored resin particles> The method for producing the colored resin particles contained in the toner of the present disclosure is not particularly limited as long as it is a method that can obtain the colored resin particles described above. Generally, methods for producing colored resin particles are broadly divided into dry methods such as pulverization methods, and wet methods such as emulsion polymerization aggregation methods, suspension polymerization methods, and solution suspension methods. Wet methods are preferred because they make it easier to obtain toners with excellent printing properties such as image reproducibility. Among the wet methods, polymerization methods such as emulsion polymerization aggregation methods and suspension polymerization methods are preferred because they make it easier to obtain toners with a relatively small particle size distribution on the order of microns, and among polymerization methods, suspension polymerization is more preferred.

[0092] The emulsion polymerization aggregation method involves polymerizing an emulsified polymerizable monomer to obtain a resin fine particle emulsion, which is then aggregated with a colorant dispersion or the like to produce colored resin particles. The solution suspension method involves forming droplets of a solution in which toner components such as a binder resin and a colorant are dissolved or dispersed in an organic solvent in an aqueous medium, and then removing the organic solvent to produce colored resin particles. Any known method can be used for either method.

[0093] When producing colored resin particles by a pulverization method, first, a binder resin, a colorant, a softener, and optionally other additives are mixed using a mixer such as a ball mill, a V-type mixer, an FM mixer (trade name, manufactured by Nippon Coke & Engineering Co., Ltd.), a high-speed dissolver, or an internal mixer. Next, the resulting mixture is kneaded while heating using a pressure kneader, a twin-screw extrusion kneader, a roller, or the like. The resulting kneaded product is coarsely pulverized using a pulverizer such as a hammer mill, a cutter mill, or a roller mill. The resulting mixture is then finely pulverized using a pulverizer such as a jet mill or a high-speed rotary pulverizer, and then classified to the desired particle size using a classifier such as an air classifier or an airflow classifier to obtain colored resin particles produced by the pulverization method.

[0094] The colored resin particles contained in the toner of the present disclosure can be produced by a wet method or a dry method, and are not particularly limited. However, a preferred method for producing the colored resin particles contained in the toner of the present disclosure is a method including the following steps using a suspension polymerization method. That is, as a method for producing the toner of the present disclosure, the steps for producing the colored resin particles can include, for example, (1) a step of preparing a polymerizable monomer composition containing at least a polymerizable monomer, a colorant, and a softener (polymerizable monomer composition preparation step), (2) a step of preparing a suspension in which droplets of the polymerizable monomer composition are dispersed in an aqueous medium containing a dispersion stabilizer (suspension step), and (3) a step of subjecting the suspension to a polymerization reaction (polymerization step). Each step for producing the colored resin particles will be described in detail below.

[0095] (1) Preparation of Polymerizable Monomer Composition First, a polymerizable monomer, a colorant, a softener, and optionally other additives such as a charge control agent, a polar resin, and a molecular weight modifier are mixed to prepare a polymerizable monomer composition. The polymerizable monomer, colorant, softener, charge control agent, and polar resin are as described above. Mixing during preparation of the polymerizable monomer composition is performed using a disperser such as an in-line emulsion disperser or a media emulsion disperser. The polymerizable monomer composition is preferably prepared, for example, by mixing the polymerizable monomer, colorant, polar resin, and molecular weight modifier using a media disperser and wet-grinding the mixture, followed by adding the charge control agent, the softener, and further mixing. This method facilitates the production of a toner with excellent low-temperature fixability and storage stability.

[0096] In the polymerizable monomer composition, the content of the polymerizable monomer is not particularly limited, but is preferably 60 to 95 parts by mass, more preferably 65 to 90 parts by mass, and even more preferably 70 to 85 parts by mass, relative to 100 parts by mass of the total solid content contained in the polymerizable monomer composition. In the present disclosure, the solid content refers to all components other than the solvent, and includes liquid monomers and the like.

[0097] The polymerizable monomer composition preferably contains a molecular weight modifier as another additive when polymerizing the polymerizable monomer. The molecular weight modifier is not particularly limited as long as it is a molecular weight modifier that is generally used for toners, and examples thereof include mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, n-octyl mercaptan, and 2,2,4,6,6-pentamethylheptane-4-thiol; and thiuram disulfides such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, N,N'-dimethyl-N,N'-diphenylthiuram disulfide, and N,N'-dioctadecyl-N,N'-diisopropylthiuram disulfide. These molecular weight modifiers may be used alone or in combination of two or more. The content of the molecular weight modifier is usually 0.01 to 10 parts by mass, preferably 0.1 to 5 parts by mass, relative to 100 parts by mass of the polymerizable monomer. The content of the molecular weight modifier is usually 0.01 to 10 parts by mass, preferably 0.1 to 5 parts by mass, relative to 100 parts by mass of the monovinyl monomer.

[0098] The polymerizable monomer composition may further contain a polymerization initiator, which may be added in the suspension step described below. From the viewpoint of easy control of the molecular weight of the polymer, the polymerization initiator is preferably added in the suspension step described below after the polymerizable monomer composition is dispersed in an aqueous medium and before droplet formation.

[0099] (2) Suspension Step (Droplet Formation Step) Next, a suspension is prepared in which droplets of the polymerizable monomer composition obtained above are dispersed in an aqueous medium containing a dispersion stabilizer. The method for forming droplets of the polymerizable monomer composition is not particularly limited, but examples thereof include a method in which the mixed solution obtained by mixing the polymerizable monomer composition with an aqueous medium containing a dispersion stabilizer is vigorously stirred. Apparatuses capable of vigorously stirring the mixture are not particularly limited, but examples thereof include horizontal or vertical in-line dispersers such as Milder (trade name) manufactured by Pacific Machinery Works, Ltd., Cavitron (trade name) manufactured by Eurotec Co., Ltd., and an in-line disperser manufactured by IKA (e.g., DISPAX-REACTOR (registered trademark) DRS (trade name)); and emulsifying dispersers such as the Homomixer MARK II series manufactured by Primix Corporation.

[0100] In the present disclosure, the aqueous medium refers to a medium containing water as a main component, typically water. It is preferable that the aqueous medium contains a dispersion stabilizer. Examples of the dispersion stabilizer include sulfates such as barium sulfate and calcium sulfate; carbonates such as barium carbonate, calcium carbonate, and magnesium carbonate; phosphates such as calcium phosphate; metal oxides such as aluminum oxide and titanium oxide; metal hydroxides such as aluminum hydroxide, magnesium hydroxide, and ferric hydroxide; inorganic compounds such as silicon dioxide; water-soluble polymers such as polyvinyl alcohol, methyl cellulose, and gelatin; anionic surfactants; nonionic surfactants; amphoteric surfactants; and other organic compounds. These dispersion stabilizers can be used alone or in combination of two or more.

[0101] Among the dispersion stabilizers, inorganic compounds are preferred, colloids of poorly water-soluble inorganic compounds are more preferred, and colloids of poorly water-soluble metal hydroxides are particularly preferred. By using an inorganic compound, preferably a colloid of a poorly water-soluble inorganic compound, and particularly preferably a colloid of a poorly water-soluble metal hydroxide, the particle size distribution of the colored resin particles can be narrowed and the amount of dispersion stabilizer remaining after washing can be reduced. The colloid of poorly water-soluble metal hydroxide can be prepared, for example, by reacting at least one selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides with a water-soluble polyvalent metal salt (excluding alkaline earth metal hydroxides) in an aqueous medium. Examples of alkali metal hydroxides include lithium hydroxide, sodium hydroxide, and potassium hydroxide. Examples of alkaline earth metal hydroxides include barium hydroxide and calcium hydroxide. The water-soluble polyvalent metal salt is a water-soluble polyvalent metal salt other than the above-mentioned alkaline earth metal hydroxides. Examples of water-soluble polyvalent metal salts include magnesium metal salts such as magnesium chloride, magnesium phosphate, and magnesium sulfate; calcium metal salts such as calcium chloride, calcium nitrate, calcium acetate, and calcium sulfate; aluminum metal salts such as aluminum chloride and aluminum sulfate; barium salts such as barium chloride, barium nitrate, and barium acetate; and zinc salts such as zinc chloride, zinc nitrate, and zinc acetate. Among these, magnesium metal salts, calcium metal salts, and aluminum metal salts are preferred, magnesium metal salts are more preferred, and magnesium chloride is particularly preferred. The method for reacting at least one selected from the group consisting of the alkali metal hydroxides and alkaline earth metal hydroxides with the water-soluble polyvalent metal salt in an aqueous medium is not particularly limited, but includes mixing an aqueous solution of at least one selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides with an aqueous solution of the water-soluble polyvalent metal salt. Furthermore, colloidal silica can also be used as a colloid of a poorly water-soluble inorganic compound, i.e., a colloidal dispersion containing colloidal particles of a poorly water-soluble inorganic compound.

[0102] The content of the dispersion stabilizer is appropriately adjusted so as to obtain a toner having the desired particle size. While not particularly limited, it is preferably 0.5 to 10 parts by mass, more preferably 1.0 to 8.0 parts by mass, relative to 100 parts by mass of the polymerizable monomer in the polymerizable monomer composition. The content of the dispersion stabilizer is preferably 0.5 to 10 parts by mass, more preferably 1.0 to 8.0 parts by mass, relative to 100 parts by mass of the monovinyl monomer. The content of the dispersion stabilizer is typically 1 to 15 parts by mass, preferably 1 to 8 parts by mass, relative to 100 parts by mass of the aqueous medium. By ensuring that the content of the dispersion stabilizer is equal to or greater than the lower limit, droplets of the polymerizable monomer composition can be sufficiently dispersed in the suspension so as not to coalesce. On the other hand, by ensuring that the content of the dispersion stabilizer is equal to or less than the upper limit, an increase in the viscosity of the suspension during granulation can be prevented, thereby avoiding problems such as the suspension clogging in the granulator.

[0103] The polymerization initiator is preferably added after the polymerizable monomer composition is dispersed in an aqueous medium and before droplets are formed. Examples of the polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate; azo compounds such as 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)propionamide), 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobisisobutyronitrile; and organic peroxides such as di-t-butyl peroxide, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylbutanoate, t-hexylperoxy-2-ethylbutanoate, t-butylperoxydiethylacetate, diisopropylperoxydicarbonate, di-t-butylperoxyisophthalate, and t-butylperoxyisobutyrate. Among these, organic peroxides are preferred because they can reduce the amount of residual polymerizable monomers and provide excellent print durability for the resulting toner. Among the organic peroxides, peroxyesters are preferred because they have good initiator efficiency and can reduce the amount of residual polymerizable monomers, and non-aromatic peroxyesters, i.e., peroxyesters without an aromatic ring, are more preferred. These polymerization initiators can be used alone or in combination of two or more.

[0104] The amount of the polymerization initiator used in the polymerization of the polymerizable monomer composition is not particularly limited, but is preferably 0.1 to 20 parts by mass, more preferably 0.3 to 15 parts by mass, and even more preferably 1 to 10 parts by mass, relative to 100 parts by mass of the polymerizable monomer. The amount of the polymerization initiator added is also preferably 0.1 to 20 parts by mass, more preferably 0.3 to 15 parts by mass, and even more preferably 1 to 10 parts by mass, relative to 100 parts by mass of the monovinyl monomer.

[0105] (3) Polymerization Step: By subjecting the suspension obtained above to a polymerization reaction, the polymerizable monomer polymerizes to form a binder resin, resulting in a dispersion in an aqueous medium of particles containing the binder resin, colorant, and softener, as well as other additives such as a charge control agent and a polar resin added to the polymerizable monomer composition. The particles obtained by subjecting the suspension to a polymerization reaction may be used directly as colored resin particles, or the particles obtained by subjecting the suspension to a polymerization reaction may form a core layer, and the surface of the core layer may be coated with a shell layer to form colored resin particles. The polymerization reaction of the polymerizable monomer contained in the suspension can be carried out, for example, by heating the suspension. The polymerization temperature is not particularly limited, but is preferably 60°C or higher, more preferably 70°C or higher, from the viewpoint of rapidly progressing the polymerization reaction. On the other hand, it is preferably 95°C or lower, from the viewpoint of suppressing rapid progress of the polymerization reaction and stabilizing the quality of the resulting toner. The polymerization reaction time is preferably 1 to 20 hours, more preferably 2 to 15 hours.

[0106] The method for producing core-shell type colored resin particles having a core layer obtained by subjecting a suspension to a polymerization reaction and a shell layer covering the core layer is not particularly limited, and the particles can be produced by a conventionally known method. In terms of production efficiency, an in situ polymerization method or a phase separation method is preferred.

[0107] A method for producing core-shell type colored resin particles by in situ polymerization is described below. The suspension is subjected to a polymerization reaction to obtain particles, and then a polymerizable monomer for forming a shell layer (shell polymerizable monomer) and a polymerization initiator are added to the resulting aqueous dispersion, followed by polymerization to obtain core-shell type colored resin particles.

[0108] The polymerizable monomer for the shell is as described above. Examples of the polymerization initiator used in the polymerization of the polymerizable monomer for the shell include water-soluble polymerization initiators such as metal persulfates, such as potassium persulfate and ammonium persulfate; and azo initiators, such as 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)propionamide) and 2,2'-azobis-(2-methyl-N-(1,1-bis(hydroxymethyl)2-hydroxyethyl)propionamide). These can be used alone or in combination of two or more. The amount of the polymerization initiator is preferably 0.1 to 30 parts by mass, more preferably 1 to 20 parts by mass, per 100 parts by mass of the polymerizable monomer for the shell.

[0109] The polymerization temperature for the shell layer is not particularly limited, but from the viewpoint of rapidly progressing the polymerization reaction, it is preferably 60° C. or higher, more preferably 70° C. or higher, and from the viewpoint of suppressing volatilization of the polymerizable monomer for the shell, it is preferably 95° C. or lower. The reaction time for polymerization of the shell layer is preferably 1 hour to 20 hours, more preferably 2 hours to 15 hours.

[0110] (4) Washing, Filtration, Dehydration, and Drying Steps After the polymerization is completed, the aqueous dispersion of colored resin particles obtained by polymerization is preferably subjected to a series of operations of washing, filtration, dehydration, and drying in accordance with a conventional method, which are repeated several times as necessary.

[0111] As for the above-mentioned washing method, when an inorganic compound is used as the dispersion stabilizer, it is preferable to add an acid or alkali to the aqueous dispersion of the colored resin particles to dissolve and remove the dispersion stabilizer in water. When a poorly water-soluble metal hydroxide colloid is used as the dispersion stabilizer, it is preferable to add an acid to adjust the pH of the aqueous dispersion of the colored resin particles to 6.5 or less. The acid to be added may be an inorganic acid such as sulfuric acid, hydrochloric acid, or nitric acid, or an organic acid such as formic acid or acetic acid, but sulfuric acid is particularly preferred because of its high removal efficiency and small burden on the production equipment.

[0112] The dehydration and filtration methods can be any of various known methods, and are not particularly limited. Examples include centrifugal filtration, vacuum filtration, pressure filtration, etc. The drying method is also not particularly limited, and various methods can be used.

[0113] <External Addition Treatment Method> The toner manufacturing method of the present disclosure may further include a step of mixing and stirring the obtained colored resin particles with an external additive to perform an external addition treatment, thereby adhering the external additive to the surface of the colored resin particles. The external addition treatment method for adhering the external additive to the surface of the colored resin particles may be a known method, and is not particularly limited. For example, the external addition treatment can be performed by mixing and stirring the colored resin particles and the external additive using a mixer capable of mixing and stirring, such as a Henschel Mixer (trade name, manufactured by Mitsui Mining Co., Ltd.), an FM Mixer (trade name, manufactured by Nippon Coke and Engineering Co., Ltd.), a Super Mixer (trade name, manufactured by Kawada Manufacturing Co., Ltd.), a Q Mixer (trade name, manufactured by Nippon Coke and Engineering Co., Ltd.), a Mechanofusion System (trade name, manufactured by Hosokawa Micron Co., Ltd.), or a Mechano Mill (trade name, manufactured by Okada Precision Industries, Ltd.).

[0114] 3. Toner Performance Since the toner of the present disclosure has excellent storage stability, the heat resistance temperature is preferably 53° C. or higher, more preferably 55° C. or higher, and even more preferably 57° C. or higher. In the present disclosure, the heat resistance temperature of the toner is defined as the highest temperature at which the mass of the toner that aggregates becomes 2.5% by mass or less of the total amount of the toner when the toner is stored at a constant temperature for 8 hours.

[0115] The toner of the present disclosure has excellent low-temperature fixability, and therefore its minimum fixation temperature is preferably less than 155°C, more preferably less than 150°C, and even more preferably less than 145°C. In this disclosure, the minimum fixation temperature of a toner refers to the lowest temperature at which, when a solid image is printed on paper using a printer and a rubbing test is performed on the solid area, a fixation rate of 85% or more is obtained, calculated using the following formula as the ratio of the image density after the rubbing test (ID(after)) to the image density before the rubbing test (ID(before)): Fixation rate (%) = [ID(after) / ID(before)] x 100. The rubbing test is performed by attaching the measurement area to a fastness tester with adhesive tape, placing a 500g load on it, and rubbing five times back and forth with a rubbing terminal wrapped in cotton cloth. In this disclosure, a solid area refers to an area controlled so that developer adheres to all of the (virtual) dots (controlled by the printer control unit) within that area.

[0116] From the viewpoint of hot offset resistance, the toner of the present disclosure has a maximum fixing temperature of preferably 200° C. or higher, more preferably 210° C. or higher, and even more preferably 220° C. or higher. In the present disclosure, the maximum fixing temperature of the toner refers to the highest fixing temperature at which it is determined that offset does not occur.

[0117] The present disclosure will be described in more detail below with reference to examples and comparative examples, but the present disclosure is not limited to these examples. Note that parts and percentages are by mass unless otherwise specified.

[0118] [Production Example 1: Synthesis of Polar Resin P1] 200 parts of toluene were added to a reaction vessel, and the atmosphere in the reaction vessel was thoroughly replaced with nitrogen while stirring the toluene. The toluene was then heated to 90 ° C., and a mixed solution of 97.0 parts of methyl methacrylate, 2.2 parts of ethyl acrylate, 0.8 parts of acrylic acid, and 3 parts of t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, trade name: Perbutyl O) was added dropwise to the reaction vessel over 2 hours. The mixture was then held under toluene reflux for 10 hours to complete the polymerization, and the solvent was then distilled off under reduced pressure. Polar Resin P1 (MMA / EA / AA) was thus obtained. The resulting polar resin P1 had an acid value of 5.0 mgKOH / g, a Tg of 78 ° C., and an Mw of 10,500.

[0119] Example 1 1. Production of Colored Resin Particles 1-1. Preparation of Polymerizable Monomer Composition 72.2 parts of styrene, 22.8 parts of n-butyl acrylate, and 5 parts of distearyl fumarate as monovinyl monomers, 9 parts of carbon black (manufactured by Mitsubishi Chemical Corporation, product name: #25B) as a black colorant, 0.55 parts of divinylbenzene as a crosslinkable polymerizable monomer, 1.0 part of tetrabenzyl thiuram disulfide as a molecular weight modifier, and 3.0 parts of polar resin P1 obtained in Production Example 1 above as a polar resin were mixed and wet-pulverized using a media-type emulsifying disperser. Thereafter, 1.6 parts of CCR-A1 (copolymerization ratio of monomers containing quaternary ammonium salt-containing groups: 2.00%) as Copolymer A, which is a positively chargeable charge control resin, 1.0 part of CCR-B1 (copolymerization ratio of monomers containing quaternary ammonium salt-containing groups: 1.00%) as Copolymer B, which is a positively chargeable charge control resin, and 20 parts of behenyl stearate (melting point 68°C) as an ester wax were mixed to obtain a polymerizable monomer composition. Specifically, the CCR-A1 was a copolymer of 82% styrene, 16% butyl acrylate, and 2% quaternary ammonium salt monomer. Specifically, the CCR-B1 was a copolymer of 82% styrene, 17% butyl acrylate, and 1% quaternary ammonium salt monomer.

[0120] 1-2. Preparation of aqueous dispersion medium Separately, in a stirring tank at room temperature, an aqueous solution prepared by dissolving 6.2 parts of sodium hydroxide in 50 parts of ion-exchanged water was gradually added under stirring to an aqueous solution prepared by dissolving 8.8 parts of magnesium chloride in 250 parts of ion-exchanged water, to prepare a magnesium hydroxide colloidal dispersion (4.5 parts of magnesium hydroxide).

[0121] The polymerizable monomer composition was added to the magnesium hydroxide colloidal dispersion obtained above at room temperature, and the mixture was stirred until droplets were stabilized. 4 parts of t-butylperoxydiethyl acetate (manufactured by NOF Corporation, trade name: Perbutyl EB) was added as a polymerization initiator, and then droplets of the polymerizable monomer composition were formed by high-shear stirring at a rotation speed of 15,000 rpm using an in-line emulsifying disperser (manufactured by Pacific Machinery Works, Ltd., trade name: Milder).

[0122] 1-4. Polymerization Step The suspension containing dispersed droplets of the polymerizable monomer composition obtained above was placed in a reactor equipped with a stirring blade, and the temperature was raised to 90°C to initiate the polymerization reaction. When the polymerization conversion rate reached nearly 100%, 3.0 parts of methyl methacrylate was added to the reactor as a polymerizable monomer for the shell. The temperature was then maintained at 90°C for an additional 3 hours to continue polymerization, and the reaction was then stopped by water cooling to obtain an aqueous dispersion of colored resin particles.

[0123] 1-5. Post-treatment step The aqueous dispersion of colored resin particles obtained above was washed with acid by adding sulfuric acid dropwise at room temperature while stirring until the pH reached 5.5 or less. Next, filtration was performed, and 500 parts of ion-exchanged water was added to the obtained solid to form a reslurry, and water washing treatment (washing, filtration, and dehydration) was repeated several times. Next, filtration was performed, and the obtained solid was placed in a container of a dryer and dried at 45°C for 48 hours to obtain dried colored resin particles.

[0124] 2. External Addition Treatment To 100 parts of the above colored resin particles, 1.0 part of silica fine particles A having a number-average primary particle size of 10 nm and 1.4 parts of silica fine particles B having a number-average primary particle size of 55 nm that had been hydrophobized with amino-modified silicone oil were added, and the mixture was mixed using a high-speed mixer (manufactured by Nippon Coke and Engineering Co., Ltd., product name: FM Mixer) to perform external addition treatment, thereby producing the toner of Example 1.

[0125] [Examples 2 to 10 and Comparative Examples 1 to 4] The toners of Examples 2 to 10 and Comparative Examples 1 to 4 were obtained in the same manner as in Example 1, except that the type or amount of polymerizable monomer added, or the type or amount of softener added, was changed according to Table 1. Details of the softeners shown in Table 1 are as follows: Behenyl stearate, melting point 68°C Behenyl behenate, melting point 75°C Palmityl behenate, melting point 63°C Polyglycerin polybehenate (manufactured by NOF Corporation, trade name "WEP-7"), melting point 71°C Pentaerythritol tetrastearate (manufactured by NOF Corporation, trade name "WE-6"), melting point 78°C

[0126] [Evaluation] 1. Toner Volume Average Particle Size (Dv) The toner volume average particle size Dv was measured using a particle size distribution analyzer (manufactured by Beckman Coulter, Inc., trade name: Multisizer). Measurements using this Multisizer were performed under the following conditions: aperture diameter: 100 μm, dispersion medium: Isoton II (trade name), concentration: 10%, and number of particles measured: 100,000. Specifically, 0.2 g of a toner sample was placed in a beaker, and a surfactant aqueous solution (manufactured by Fujifilm Corporation, trade name: Drywell) was added as a dispersant. 2 ml of dispersion medium was further added to wet the toner, and then 10 ml of dispersion medium was added. The mixture was dispersed in an ultrasonic disperser for 1 minute, and then measurement was performed using the particle size distribution analyzer.

[0127] 2. Heat-Resistant Temperature (Storage Stability) 20 g of toner was placed in a 100 mL polyethylene container and sealed. The container was then submerged in a thermostatic water bath set at a predetermined temperature and removed after 8 hours. The toner was transferred from the container onto a 42-mesh sieve while minimizing vibration and then set in a powder measuring instrument (manufactured by Hosokawa Micron Corporation, product name: Powder Tester (registered trademark) PT-R). The sieve amplitude was set to 1.0 mm, and the sieve was vibrated for 30 seconds. The mass of the toner remaining on the sieve was measured, and this was taken as the mass of the aggregated toner. The maximum temperature at which the mass of the aggregated toner became 0.5 g or less was taken as the heat-resistant temperature of the toner. The higher the heat-resistant temperature, the less likely the toner is to block during storage, and the better the storage stability. (Evaluation criteria) A: Heat resistant temperature is 57°C or higher B: Heat resistant temperature is 55°C or higher but lower than 57°C C: Heat resistant temperature is 53°C or higher but lower than 55°C D: Heat resistant temperature is lower than 53°C

[0128] 3. Minimum Fixing Temperature (Low-Temperature Fixability) A commercially available non-magnetic single-component development printer (30 sheets per minute; print speed = 30 sheets per minute) was modified to allow the temperature of the fixing roll to be varied. The temperature of the fixing roll was changed in 5°C increments, and the toner fixation rate was measured at each temperature. The temperature-fixation rate relationship was determined, and the lowest temperature at which a fixation rate of 85% or higher was obtained was defined as the minimum fixing temperature of the toner. The lower the minimum fixing temperature, the better the toner's low-temperature fixability. The fixation rate was calculated from the image density ratio before and after a rubbing test on a solid area of ​​test paper printed with the printer. If the image density before the rubbing test is ID(before) and the image density after the rubbing test is ID(after), then the fixation rate (%) = [ID(after) / ID(before)] × 100. The rubbing test was performed by attaching the test paper to a fastness tester with adhesive tape, placing a 500g load on the paper, and rubbing it back and forth five times with a rubbing pin wrapped in cotton cloth. (Evaluation Criteria) A: Minimum fixing temperature is less than 145°C B: Minimum fixing temperature is 145°C or more and less than 150°C C: Minimum fixing temperature is 150°C or more and less than 155°C D: Minimum fixing temperature is 155°C or more and less than 160°C E: Minimum fixing temperature is 160°C or more

[0129] 4. Maximum Fixing Temperature (Hot Offset Resistance) A commercially available non-magnetic single-component developing printer (30 sheets; printing speed = 30 sheets / min) was modified to change the temperature of the fixing roll, and the temperature of the fixing roll was changed in 5°C increments to print an image in which a 5 cm area from the leading edge was a solid image area and the rest was solid white. In the solid white area of ​​the printouts produced at each temperature, the temperature at which residual toner deposits that had offset onto the fixing roll could be confirmed was taken as the offset temperature, and the highest temperature at which offset did not occur was taken as the maximum fixing temperature of the toner. For prints that did not occur even when the fixing roll temperature was raised up to 220°C, the maximum fixing temperature was taken as 220°C. (Evaluation Criteria) A: Maximum fixing temperature is 220°C or higher B: Maximum fixing temperature is 210°C or higher but lower than 220°C C: Maximum fixing temperature is 200°C or higher but lower than 210°C D: Maximum fixing temperature is lower than 200°C

[0130]

[0131] [Discussion] The toners of Examples 1 to 10 contained a polymer containing a monomer unit derived from at least one selected from the group consisting of a dialkyl fumarate ester and a dialkyl maleate ester as a binder resin, and an ester wax as a softener, and therefore were toners with a well-balanced and excellent low-temperature fixability and storage stability. Furthermore, Examples 1 to 4 demonstrated that the low-temperature fixability and storage stability of the toner can be improved by adjusting the carbon number of the alkyl group of the dialkyl fumarate ester or dialkyl maleate ester. Examples 1, 5, and 6 demonstrated that the low-temperature fixability and storage stability of the toner can be improved in a well-balanced manner by adjusting the content of at least one selected from the group consisting of a dialkyl fumarate ester and a dialkyl maleate ester. Furthermore, when the toner of Example 1 containing a monoester as the ester wax and the toners of Examples 9 and 10 containing a polyfunctional ester were compared with the toners of Comparative Examples 1, 3, and 4 containing the same ester wax, it was found that regardless of which ester wax was used, the toners of the examples had improved low-temperature fixability and storage stability due to the incorporation of at least one selected from the group consisting of dialkyl fumarate and dialkyl maleate as the binder resin. Furthermore, the toner of Comparative Example 2, which used paraffin wax as the softener, had poor storage stability and hot offset resistance despite the use of dialkyl fumarate as the binder resin. This demonstrates that even in toners containing a polymer containing at least one monomer unit selected from the group consisting of dialkyl fumarate and dialkyl maleate as the binder resin, the effects of the present disclosure cannot be obtained unless the softener used in combination is an ester wax. Furthermore, it has been revealed that the toner of the present disclosure has improved hot offset resistance by including an ester wax as a softening agent, and further has well-balanced improved low-temperature fixability and storage stability by including in the binder resin a monomer unit derived from at least one selected from the group consisting of a dialkyl ester of fumaric acid and a dialkyl ester of maleic acid.

Claims

1. A toner containing colored resin particles including a binder resin, a colorant, and a softener, wherein the binder resin contains a polymer containing a monomer unit derived from a dicarboxylic acid dialkyl ester having a radically polymerizable double bond, and the dicarboxylic acid dialkyl ester is at least one selected from the group consisting of a fumaric acid dialkyl ester and a maleic acid dialkyl ester, and the softener contains an ester wax.

2. The toner according to claim 1, wherein the alkyl group of said dicarboxylic acid dialkyl ester is an alkyl group having 10 or more carbon atoms.

3. The toner according to claim 1 or 2, wherein the content of the monomer unit derived from the dicarboxylic acid dialkyl ester is 2 to 20% by mass based on 100% by mass of the polymer.

4. The toner according to claim 1 or 2, wherein the polymer is a styrene-acrylic resin.

5. The toner according to claim 1 or 2, wherein the colored resin particles further contain a charge control agent, the charge control agent containing a quaternary ammonium salt group-containing copolymer, and the toner is a positively charged toner.

6. A method for producing a toner according to claim 1 or 2, comprising the steps of: preparing a polymerizable monomer composition containing at least a polymerizable monomer, a colorant, and a softener; preparing a suspension in which droplets of the polymerizable monomer composition are dispersed in an aqueous medium containing a dispersion stabilizer; and subjecting the suspension to a polymerization reaction, wherein the polymerizable monomer comprises a dicarboxylic acid dialkyl ester having a radically polymerizable double bond, which is at least one selected from the group consisting of a fumaric acid dialkyl ester and a maleic acid dialkyl ester; and the softener comprises an ester wax.

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