Toner and image forming method

Abstract

Provided is a toner, wherein bleed-out of a mold release agent does not easily occur even in a high temperature and high humidity environment, printing defects do not easily occur even when using the toner stored for a long period of time in the high temperature and high humidity environment, continuous printing can be performed while suppressing the occurrence of printing defects in both a low temperature and low humidity environment and high temperature and high humidity environment, and fluctuations in a charge amount due to environmental changes are suppressed. The toner contains a binder resin, a colorant, colored resin particles containing a positively-chargeable charge control resin and a mold release agent, and an external additive, the toner containing, as the positively-chargeable charge control resin, copolymer A containing a functional group-containing monomer unit in a proportion of 1.50-6.00 mass%, and copolymer B containing a functional group-containing monomer unit in a proportion of 0.10 mass% or more and less than 1.50 mass%, and the colored resin particles further containing a polar resin having an acid value of 0.5-8.0 mgKOH / g.

Description

Toner and image forming 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 to an image forming method using 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 or during long-term storage, which may result in a deterioration in the shelf life of the toner. Therefore, there is a demand for toners with improved low-temperature fixability without impairing shelf life.

[0003] As a toner having an excellent balance between storage stability and low-temperature fixability, for example, Patent Document 1 discloses a toner containing colored resin particles containing a binder resin, a colorant, and a release agent, and an external additive, in which the colored resin particles further contain a styrene-based thermoplastic elastomer, and the release agent contains a fatty acid ester compound having a number average molecular weight (Mn) of 500 or more but less than 2,000 in an amount of 2 to 20 parts by mass per 100 parts by mass of the binder resin.

[0004] Patent Document 2 discloses a toner containing colored resin particles that include a binder resin, a colorant, a charge control agent, and a release agent, wherein the colored resin particles further contain an additive having a polydiene structure whose solubility in styrene at a temperature of 40°C is 3 to 40 g / 100 g, and the number of crystalline domains of the release agent having an aspect ratio in the range of 2 to 10 present in the colored resin particles is within a specific range, or the storage modulus G'(60) of the colored resin particles at 60°C, as determined by dynamic viscoelasticity measurement, is within a specific range.

[0005] Patent Document 3 discloses a toner containing colored resin particles containing a binder resin, a colorant, and a softener (releasing agent), as well as an external additive, wherein the colored resin particles further contain, as a fixing aid, a copolymer of at least one of an acrylic acid ester and a methacrylic acid ester and at least one of acrylic acid and methacrylic acid, the copolymer having an acid value of 0.5 to 7 mgKOH / g, a weight average molecular weight Mw of 6,000 to 50,000, and a glass transition temperature of 60 to 85°C.

[0006] International Publication No. WO 2019 / 065868 International Publication No. WO 2020 / 045664 International Publication No. WO 2014 / 133032

[0007] All of the toners disclosed in Patent Documents 1 to 3 contain a release agent. The release agent improves the toner's releasability from the fixing roll, thereby improving the toner's low-temperature fixability. However, release agents tend to bleed out, and the bled-out release agent can contaminate printing components such as photoreceptors, causing print defects such as fogging. Therefore, there is a demand for toners that are less susceptible to release agent bleed-out. However, the higher the temperature and humidity of the toner storage environment, the faster the release agent, which is compatible with the binder resin, migrates to the toner surface, making the release agent more likely to bleed out. The toners disclosed in Patent Documents 1 to 3 have difficulty adequately suppressing release agent bleed-out in high-temperature, high-humidity environments exceeding 45°C. Furthermore, storing conventional toners in such high-temperature, high-humidity environments can easily cause print defects such as fogging when printing with the stored toner. Furthermore, in recent years, cartridges with large toner filling volumes have become more common in order to reduce component costs. If the toner is loaded with a large amount of toner, the toner will be subjected to mechanical stress for a longer period of time during continuous printing. Therefore, if continuous printing is performed using a cartridge with a large toner load, the charge level of the toner in the cartridge will decrease, causing printing problems and resulting in a large amount of unusable toner remaining.

[0008] An object of the present disclosure is to provide a toner that is less likely to cause bleeding out of a release agent even in a high-temperature, high-humidity environment, is less likely to cause printing defects even when used with a toner that has been stored for a long period of time in a high-temperature, high-humidity environment, and when used with a cartridge with a large toner load, is capable of performing continuous printing while suppressing the occurrence of printing defects until the remaining toner amount becomes low in both a low-temperature, low-humidity environment and a high-temperature, high-humidity environment, and further, suppresses fluctuations in charge amount due to changes in temperature and humidity, and to provide an image forming method using the toner.

[0009] The present inventors have conducted extensive research to solve the above problems, and have found that by using two types of positively charging charge control resins with different amounts of functional groups in combination with a polar resin having a specific acid value, bleeding out of the release agent in the toner can be suppressed even in a high-temperature, high-humidity environment, printing defects can be suppressed after the toner is stored for a long period of time in a high-temperature, high-humidity environment, or in a low-temperature, low-humidity environment and a high-temperature, high-humidity environment, and further fluctuations in the charge amount of the toner due to changes in the environment can be suppressed.

[0010] That is, the present disclosure provides a toner containing colored resin particles containing a binder resin, a colorant, a positively charged charge control resin and a release agent, and an external additive, wherein the positively charged charge control resin contains a copolymer A containing functional group-containing monomer units in a proportion of 1.50 mass % or more and 6.00 mass % or less, and a copolymer B containing functional group-containing monomer units in a proportion of 0.10 mass % or more and less than 1.50 mass %, and the colored resin particles further contain a polar resin having an acid value of 0.5 mgKOH / g or more and 8.0 mgKOH / g or less. The present disclosure also provides a toner containing colored resin particles containing a binder resin, a colorant, a positively charged charge control resin, and a release agent, as well as an external additive, wherein the positively charged charge control resin contains a copolymer A containing functional group-containing monomer units in a proportion of 1.50% by mass or more and 6.00% by mass or less, and a copolymer B containing functional group-containing monomer units in a proportion of 0.10% by mass or more and less than 1.50% by mass, and the colored resin particles further contain a polar resin having an acid value of 0.5 mgKOH / g or more and 5.0 mgKOH / g or less.

[0011] In the toner of the present disclosure, when the proportion (mass%) of functional group-containing monomer units in each copolymer contained as the positively charged charge control resin is F and the content (parts by mass) of the copolymer relative to 100 parts by mass of the binder resin is m, it is preferable that the sum of the products (F×m) of F and m calculated for each copolymer is 2.00 or more and 6.00 or less.

[0012] In the toner of the present disclosure, the acid value (mgKOH / g) of the polar resin is represented by X, and the content (parts by mass) of the polar resin relative to 100 parts by mass of the binder resin is represented by m Ｐ The proportion (mass%) of functional group-containing monomer units in the copolymer A is F Ａ The content (parts by mass) of the copolymer A relative to 100 parts by mass of the binder resin is m Ａ When X and m ｐ The product of (X × m Ｐ ) and F Ａ and m Ａ The product of (F Ａ ×m Ａ ) and the absolute value of the difference (|X × m Ｐ -F Ａ ×m Ａ |) is preferably 2.50 or less.

[0013] In the toner of the present disclosure, it is preferable that the release agent contains a fatty acid ester compound having a number average molecular weight (Mn) of 500 or more and less than 2,000 in a ratio of 5 parts by mass or more to 30 parts by mass or less with respect to 100 parts by mass of the binder resin.

[0014] In the toner of the present disclosure, it is preferable that the colored resin particles further contain a styrene-based thermoplastic elastomer in an amount of 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the binder resin.

[0015] The image forming method of the present disclosure is characterized by using the toner of the present disclosure.

[0016] According to the present disclosure as described above, a toner is provided that is less likely to cause bleeding out of a release agent even in a high-temperature, high-humidity environment, is less likely to cause printing defects even when a toner that has been stored in a high-temperature, high-humidity environment for a long period of time is used, and when a cartridge with a large toner load is used, can perform continuous printing while suppressing the occurrence of printing defects until the remaining toner amount is low in both a low-temperature, low-humidity environment and a high-temperature, high-humidity environment, and further, suppresses fluctuations in charge amount due to changes in temperature and humidity. Furthermore, by using this toner, an image forming method is provided in which printing defects are less likely to occur.

[0017] The toner of the present disclosure is a toner containing colored resin particles containing a binder resin, a colorant, a positively charged charge control resin and a release agent, and an external additive, wherein the positively charged charge control resin contains a copolymer A containing functional group-containing monomer units in a proportion of 1.50 mass % or more and 6.00 mass % or less, and a copolymer B containing functional group-containing monomer units in a proportion of 0.10 mass % or more and less than 1.50 mass %, and the colored resin particles further contain a polar resin having an acid value of 0.5 mg KOH / g or more and 8.0 mg KOH / g or less, preferably a polar resin having an acid value of 0.5 mg KOH / g or more and 5.0 mg KOH / g or less.

[0018] The toner of the present disclosure contains, in the colored resin particles, a combination of copolymer A having a relatively high proportion of functional group-containing monomer units (sometimes simply referred to as "functional group amount" in the present disclosure) and copolymer B having a relatively low functional group amount, as positively charged charge control resins, and further contains a polar resin having an acid value within the above-mentioned specific range. As a result, bleed-out of the release agent is unlikely to occur even in a high-temperature, high-humidity environment of more than 45°C, and printing defects such as fogging are unlikely to occur even when a toner stored for a long period of time in such a high-temperature, high-humidity environment is used. When a cartridge with a large toner load is used, continuous printing can be performed while suppressing the occurrence of printing defects until the remaining toner amount becomes low, both in a low-temperature, low-humidity environment and a high-temperature, high-humidity environment. Furthermore, this toner is one in which fluctuations in charge amount due to changes in temperature and humidity are suppressed.

[0019] Copolymers containing functional groups used as positively charged charge control resins exhibit a higher charge-imparting effect the greater the amount of functional groups. On the other hand, polar resins with an acid value reduce the charge of toner. This is because the acidic groups contained in polar resins leak charge due to moisture absorption. If the charge of toner is too high, the amount of toner transferred is insufficient, resulting in insufficient print density. On the other hand, if the charge of toner is too low, the electrostatic repulsion force of toner particles against the photoreceptor decreases, making toner particles more likely to adhere to the photoreceptor. Adhesion of toner particles to the photoreceptor can cause fogging. Furthermore, the charge of toner tends to increase in low-temperature, low-humidity environments and decrease in high-temperature, high-humidity environments. Furthermore, toners containing polar resins are prone to charge leakage due to the acidic groups of the polar resins easily absorbing moisture in high-temperature, high-humidity environments, making them more likely to lose charge. In contrast, the toner of the present disclosure contains a combination of copolymers A and B, each having a functional group content within the above-mentioned specific range, and a polar resin having an acid value within the above-mentioned specific range, thereby providing an appropriate charge amount, and therefore less likely to cause printing defects such as insufficient print density or fogging in both low-temperature, low-humidity and high-temperature, high-humidity environments. Furthermore, the toner of the present disclosure is also likely to maintain an appropriate charge amount even when environmental changes occur or when continuous printing is performed. When continuous printing is performed using a cartridge with a large toner load, the toner is subjected to mechanical stress for a longer period of time. However, the toner of the present disclosure is likely to maintain an appropriate charge amount, and therefore, when a cartridge with a large toner load is used, continuous printing can be performed until the remaining toner amount is low, both in low-temperature, low-humidity and high-temperature, high-humidity environments, while suppressing printing defects. Furthermore, because the acid value of the polar resin contained in the toner of the present disclosure is not too high, the toner of the present disclosure is also less likely to decrease in charge amount even in high-temperature, high-humidity environments, and the charge amount does not fluctuate much with changes in temperature and humidity.

[0020] Furthermore, the higher the functional group content or the acid value of the copolymer containing functional groups and the polar resin having an acid value, the more likely they are to be unevenly distributed on the surface side of the colored resin particles. The toner of the present disclosure contains a combination of copolymers A and B, each having a functional group content within the above-mentioned specific range, and a polar resin having an acid value within the above-mentioned specific range. This uneven distribution of these copolymers on the surface side of the colored resin particles results in the formation of a dense resin layer on the surface of the colored resin particles. This presumably suppresses release agent bleed-out even in high-temperature, high-humidity environments exceeding 45°C. Fog is likely to occur when printing is performed using a toner in which release agent bleed-out has occurred. When the release agent in the toner bleeds out, the release agent migrates from the toner to a regulating blade or the like during the printing process, and the release agent adhering to the regulating blade or the like causes fog. While insufficient toner charge may be a contributing factor to the occurrence of fog when conventional toners are used in printing after long-term storage in high-temperature, high-humidity environments, the release agent bled out during storage is a major factor. In contrast, the toner of the present disclosure is less likely to cause bleeding out of the release agent even when stored for a long period of time in a high-temperature, high-humidity environment, and has an appropriate amount of charge. Therefore, even when a toner of the present disclosure is used that has been stored for a long period of time in a high-temperature, high-humidity environment, printing defects such as fogging are less likely to occur.

[0021] Hereinafter, a method for producing the colored resin particles contained in the toner of the present disclosure, the colored resin particles obtained by the production method, and the toner of the present disclosure will be described in order. Note that in this disclosure, the term "to" in a numerical range means that the numerical values ​​before and after it are included as the lower limit and upper limit, respectively.

[0022] 1. Manufacturing Method of Colored Resin Particles Generally, manufacturing methods of colored resin particles are roughly divided into dry methods such as pulverization methods, and wet methods such as emulsion polymerization aggregation methods, suspension polymerization methods, and dissolution suspension methods, with wet methods being preferred because they are more likely to produce 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 are more likely to produce toners with a relatively small particle size distribution on the order of microns, and among polymerization methods, suspension polymerization is more preferred.

[0023] 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.

[0024] The colored resin particles contained in the toner of the present disclosure can be produced by adopting a wet method or a dry method. When the colored resin particles are produced by adopting (A) suspension polymerization method, which is preferable among wet methods, or (B) pulverization method, which is typical among dry methods, the following process is carried out.

[0025] (A) Suspension Polymerization Method (A-1) Preparation Step of Polymerizable Monomer Composition First, a polymerizable monomer composition is prepared by mixing a polymerizable monomer, a colorant, a positively charged charge control resin, a polar resin, a release agent, and, if necessary, other additives such as a styrene-based thermoplastic elastomer and a molecular weight modifier. The mixing when preparing the polymerizable monomer composition is carried out using a disperser such as an in-line type emulsifying disperser or a media type emulsifying disperser.

[0026] (Polymerizable Monomer) In the present disclosure, a polymerizable monomer refers to a monomer containing a polymerizable functional group, and the polymerizable monomer polymerizes to form a binder resin. It is preferable to use a monovinyl monomer as the main component of the polymerizable monomer. Examples of monovinyl monomers include styrene; styrene derivatives such as vinyltoluene and α-methylstyrene; acrylic acid and methacrylic acid; 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; 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. Among these, styrene, styrene derivatives, and acrylic acid esters or methacrylic acid esters are preferably used as the monovinyl monomer. Among these, it is particularly preferable to use at least one selected from styrene and styrene derivatives in combination with at least one selected from acrylic acid esters and methacrylic acid esters as the main component of the polymerizable monomer. By using such a polymerizable monomer, colored resin particles containing a styrene-acrylic resin as a binder resin can be obtained. The term "main component" refers to a component whose content exceeds 50% by mass. The styrene-acrylic resin has negative charging properties. Toners containing negatively charged binder resins are more susceptible to mechanical stress during continuous printing than negatively charged toners, and the surfaces of the colored resin particles are more likely to wear, resulting in a decrease in charge amount. In contrast, the toner of the present disclosure, which is a positively charged toner, is less susceptible to a decrease in charge due to abrasion of the surfaces of the colored resin particles, even when containing a negatively charged binder resin.The toner of the present disclosure contains copolymers A and B, which are positively charged charge control resins with different amounts of functional groups, and has a distribution in which copolymer A is concentrated toward the surface of the colored resin particles and copolymer B is concentrated relatively toward the center of the colored resin particles, which is thought to be why the colored resin particles have excellent abrasion resistance.

[0027] To improve hot offset and storage stability, it is preferable to use an optional crosslinkable polymerizable monomer together with the monovinyl monomer. A crosslinkable polymerizable monomer refers to a monomer having two or more polymerizable functional groups. 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. In the present disclosure, the crosslinkable polymerizable monomer is typically used in a ratio of 0.1 to 5 parts by mass, preferably 0.3 to 2 parts by mass, per 100 parts by mass of the monovinyl monomer.

[0028] 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 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.

[0029] 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.

[0030] (Colorant) The colorant can be appropriately selected from colorants conventionally used in toners and is not particularly limited. When preparing a color toner, black, cyan, yellow, or magenta colorants can be used. Examples of black colorants that can be used include carbon black, titanium black, and magnetic powders such as iron zinc oxide and iron nickel oxide. Examples of cyan colorants that can be used 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. 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 yellow colorants that can be used 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, 214; C.I. Solvent Yellow 98, 162, etc. 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 colorants 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. The colorants can be used alone or in combination of two or more.

[0031] The content of the colorant is not particularly limited, but from the viewpoint of obtaining sufficient image density, it 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 in the toner 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. In the present disclosure, 100 parts by mass of the binder resin is the same as 100 parts by mass of the polymerizable monomer used to obtain the binder resin, and in the case of core-shell type colored resin particles, it is the same as 100 parts by mass of the polymerizable monomer used to obtain the core layer.

[0032] (Positively Charging Charge Control Resin) As the positively charging charge control resin, a combination of copolymer A containing functional group-containing monomer units in a proportion of 1.50% by mass or more and 6.00% by mass or less and copolymer B containing functional group-containing monomer units in a proportion of 0.10% by mass or more and less than 1.50% by mass is used. In the copolymers A and B, the functional group-containing monomer units are monomer units containing functional groups that impart positive charging properties. The amount of functional groups in copolymer A is preferably 1.60% by mass or more, more preferably 1.80% by mass or more, from the viewpoint of improving the effect of suppressing bleed-out of the release agent. On the other hand, the amount of functional groups is preferably 4.00% by mass or less, more preferably 3.00% by mass or less, from the viewpoint of easily achieving an appropriate charge amount of the toner, and in particular, suppressing a decrease in print density due to an excessively high charge amount of the toner. The amount of functional groups in the copolymer B is preferably 0.40% by mass or more, more preferably 0.50% by mass or more, from the viewpoint that the toner charge amount is likely to be appropriate, and in particular, the occurrence of fogging due to the toner charge amount being too low is suppressed. On the other hand, the amount of functional groups in the copolymer B is preferably 1.40% by mass or less, more preferably 1.20% by mass or less, from the viewpoint that the toner charge amount is likely to be appropriate, and in particular, the decrease in print density due to the toner charge amount being too high is suppressed.

[0033] The copolymers A and B are preferably copolymers containing a monomer unit containing a functional group that imparts positive chargeability, an aromatic vinyl monomer unit, and a (meth)acrylate monomer unit. Here, the aromatic vinyl monomer unit and the (meth)acrylate monomer unit do not contain a functional group that imparts positive chargeability. The copolymers have excellent compatibility with binder resins, which makes it easy to achieve a uniform charge amount for the toner. Furthermore, from the viewpoint of dispersibility in the polymerizable monomer composition, the copolymers A and B are preferably those that dissolve in the aromatic vinyl monomer. In this disclosure, (meth)acrylate refers to both acrylate and methacrylate.

[0034] Examples of functional groups that provide positive charging include pyridinium groups, amino groups, quaternary ammonium groups, and quaternary ammonium bases. Quaternary ammonium bases are preferred because they function effectively even in non-magnetic one-component developers and tend to provide a uniform amount of charge on the toner. The quaternary ammonium base is preferably a -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, an alkyl group in which one hydrogen atom is substituted with a halogen ion, or —SO ３ － , -PO ３ － Or -BO ３ － Examples of the hydrocarbon group include an alkyl group, an aromatic hydrocarbon group, and a substituted aromatic hydrocarbon group. 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 group having the formula:

[0035] The copolymers A and B may be copolymers obtained by copolymerizing a vinyl monomer containing a functional group that imparts positive chargeability with another vinyl monomer copolymerizable therewith, or may be copolymers obtained by polymerizing a vinyl monomer that does not contain a functional group that imparts positive chargeability and then modifying it to introduce a functional group that imparts positive chargeability.The copolymers preferably used as the copolymers A and B, which contain a monomer unit containing a quaternary ammonium salt group, an aromatic vinyl monomer unit, and a (meth)acrylate monomer unit, are not particularly limited, and can be obtained, for example, by the following method.The polymerization method is not limited, and known polymerization methods such as emulsion polymerization, dispersion polymerization, suspension polymerization, and solution polymerization can be used.

[0036] (i) A method in which an aromatic vinyl monomer, a (meth)acrylate monomer, and an N,N-disubstituted aminoalkyl (meth)acrylate monomer are copolymerized in the presence of a polymerization initiator, and then the amino group is quaternized using a quaternizing agent such as a halogenated organic compound or an acid ester compound. (ii) A method in which an aromatic vinyl monomer, a (meth)acrylate monomer, and an N,N-disubstituted aminoalkyl (meth)acrylate monomer are copolymerized in the presence of a polymerization initiator with a monomer obtained by converting the monomer into a quaternary ammonium salt using a quaternizing agent such as a halogenated organic compound or an acid ester compound.

[0037] Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2-propylstyrene, 3-propylstyrene, 4-propylstyrene, 2-isopropylstyrene, 3-isopropylstyrene, 4-isopropylstyrene, 2,4-diisopropylstyrene, 2,4-dimethylstyrene, 4-butylstyrene, 4-t-butylstyrene, 5-t-butyl-2-methylstyrene, 2-chlorostyrene, 3-chlorostyrene, 4-chlorostyrene, 2-methyl-α-methylstyrene, 3-methyl-α-methylstyrene, 4-methyl-α-methylstyrene, 4-bromostyrene, 2-methyl-4,6-dichlorostyrene, 2,4-dibromostyrene, and vinylnaphthalene. Among these, styrene and α-methylstyrene are preferred. These may be used alone or in combination of two or more.

[0038] As the (meth)acrylate monomer, for example, an alkyl (meth)acrylate monomer which may have a hydroxyl group is preferably used. Examples of the alkyl (meth)acrylate monomer which may have a hydroxyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-amyl (meth)acrylate, isoamyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, hydroxypropyl (meth)acrylate, and dodecyl (meth)acrylate. These may be used alone or in combination of two or more. In the alkyl (meth)acrylate monomer, 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)acrylate monomers which do not have a substituent are particularly preferred.

[0039] Examples of the N,N-disubstituted aminoalkyl (meth)acrylate monomer include dimethylaminomethyl (meth)acrylate, diethylaminomethyl (meth)acrylate, dipropylaminomethyl (meth)acrylate, diisopropylaminomethyl (meth)acrylate, ethylmethylaminomethyl (meth)acrylate, methylpropylaminomethyl (meth)acrylate, dimethylamino-1-ethyl (meth)acrylate, diethylamino-1-ethyl (meth)acrylate, and dipropylamino-1-ethyl (meth)acrylate. These can be used alone or in combination of two or more. In the N,N-disubstituted aminoalkyl (meth)acrylate monomer, the number of carbon atoms in the alkyl group is not particularly limited, but is preferably 1 to 3.

[0040] Examples of halogenated organic compounds used as quaternizing agents include linear, branched, or cyclic alkyl halides having 1 to 6 carbon atoms, such as chloromethane, dichloromethane, and trichloromethane; and aromatic halides, such as chlorobenzene, 4-chlorotoluene, and 1-chloronaphthalene. Examples of acid ester compounds used as quaternizing agents include alkyl sulfonates, such as methyl methylsulfonate and ethyl methylsulfonate; alkyl benzenesulfonates, such as methyl benzenesulfonate; alkyl paratoluenesulfonates, such as methyl paratoluenesulfonate; phosphoric acid esters, such as trimethylphosphate; and boric acid esters, such as trimethoxyborane. These quaternizing agents can be used alone or in combination of two or more.

[0041] The monomer unit containing a quaternary ammonium salt group contained in the copolymer is preferably a structural unit represented by the following formula [I]:

[0042] [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 R３ ~R ５ are 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 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:

[0043] X － is a halogen ion or may have at least one substituent selected from a linear, branched or cyclic alkyl group having 1 to 6 carbon atoms and a halogen atom; —SO ３ － , -PO ３ － Or -BO ３ － The toner is preferably benzene or naphthalene having either of the following: X － is more preferably an aromatic sulfonate anion which may have the above-mentioned substituent. Examples of the aromatic sulfonate anion include a benzenesulfonate anion and a paratoluenesulfonate anion.

[0044] Specific examples of the structural unit represented by formula [I] include structural units corresponding to quaternary ammonium base-containing monomers 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-dimethylethaneammonium 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-dimethylethaneammonium paratoluenesulfonate. Among these, a structural unit corresponding to N,N-diethyl-N-methyl-2-(methacryloyloxy)ethylammonium paratoluenesulfonate is preferred.

[0045] In the copolymer, the copolymerization ratio of the aromatic vinyl monomer and the (meth)acrylate monomer is not particularly limited, but from the viewpoints of solubility in the polymerizable monomer and dispersibility in the binder resin, the mass ratio of the (meth)acrylate monomer unit to the aromatic vinyl monomer unit ((meth)acrylate monomer unit / aromatic vinyl monomer unit) is preferably 0.05 to 0.35, more preferably 0.10 to 0.30, and even more preferably 0.15 to 0.25.

[0046] In the present disclosure, the content of copolymer A containing functional group-containing monomer units in a proportion of 1.50% by mass or more and 6.00% by mass or less is not particularly limited, but the lower limit is preferably 0.50 parts by mass or more, more preferably 0.80 parts by mass or more, and even more preferably 1.00 parts by mass or more, relative to 100 parts by mass of binder resin, and the upper limit is preferably 3.00 parts by mass or less, more preferably 2.50 parts by mass or less, and even more preferably 2.00 parts by mass or less. When the content of copolymer A is equal to or greater than the lower limit, the effect of suppressing bleed-out of the release agent is improved, and the toner charge amount is likely to be appropriate, particularly, the occurrence of fogging due to an excessively low toner charge amount is suppressed. When the content of copolymer A is equal to or less than the upper limit, the toner charge amount is likely to be appropriate, particularly, the decrease in print density due to an excessively high toner charge amount is suppressed.

[0047] In the present disclosure, the content of copolymer B containing functional group-containing monomer units in a proportion of 0.10% by mass or more and less than 1.50% by mass is not particularly limited, but the lower limit is preferably 0.50 parts by mass or more, more preferably 0.60 parts by mass or more, and even more preferably 0.80 parts by mass or more, relative to 100 parts by mass of binder resin, and the upper limit is preferably 5.00 parts by mass or less, more preferably 3.00 parts by mass or less, and even more preferably 2.00 parts by mass or less. When the content of copolymer B is equal to or greater than the lower limit, the effect of suppressing bleed-out of the release agent is improved. When the content of copolymer B is equal to or less than the upper limit, the toner charge amount is likely to be appropriate, and in particular, a decrease in print density due to an excessively high toner charge amount is suppressed.

[0048] The ratio of the content of copolymer A to the content of copolymer B (content of copolymer A / content of copolymer B) is not particularly limited, but the lower limit is preferably 0.3 or more, more preferably 0.5 or more, and even more preferably 1.0 or more, and the upper limit is preferably 3.0 or less, more preferably 2.5 or less, and even more preferably 2.0 or less. When the ratio (content of copolymer A / content of copolymer B) is equal to or greater than the lower limit and equal to or less than the upper limit, the effect of suppressing bleed-out of the release agent is enhanced, and the toner charge amount tends to be appropriate. In particular, when the ratio is equal to or greater than the lower limit, the occurrence of fogging due to an excessively low toner charge amount is suppressed, and when the ratio is equal to or less than the upper limit, the decrease in print density due to an excessively high toner charge amount is suppressed.

[0049] In the present disclosure, the positively chargeable charge control resin may contain at least one type of the copolymer A and at least one type of the copolymer B. In terms of easily achieving the effects of the present disclosure, it is preferable that the copolymer A and the copolymer B each consist of a copolymer having the same monomer unit composition. Note that 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.

[0050] In the present disclosure, when the proportion (mass%) of functional group-containing monomer units in each copolymer contained as a positively chargeable charge control resin is F and the content (parts by mass) of the copolymer relative to 100 parts by mass of the binder resin is m, the sum of the products of F and m (F×m) calculated for each copolymer is preferably 1.80 or more and 6.00 or less, more preferably 2.00 or more and 6.00 or less. That is, for example, when one type each of the copolymer A and the copolymer B is contained as a positively chargeable charge control resin, the proportion (mass%) of functional group-containing monomer units in copolymer A is F Ａ The content (parts by mass) of copolymer A relative to 100 parts by mass of binder resin is m Ａ , the proportion (mass%) of functional group-containing monomer units in copolymer B is F Ｂ The content (parts by mass) of copolymer B relative to 100 parts by mass of binder resin is m Ｂ When the above formula is set, the calculated F for copolymer A isＡ and m Ａ The product of (F Ａ ×m Ａ ) and F calculated for copolymer B Ｂ and m Ｂ The product of (F Ｂ ×m Ｂ ) and the sum (F Ａ ×m Ａ +F Ｂ ×m Ｂ ) is preferably 1.80 or more and 6.00 or less, and more preferably 2.00 or more and 6.00 or less. When the sum of the above products is equal to or greater than the lower limit, the toner charge is sufficiently high, thereby suppressing the occurrence of fog. When the sum of the above products is equal to or less than the upper limit, the toner charge is not too high, thereby suppressing a decrease in print density. Furthermore, when the sum of the above products is equal to or less than the upper limit, the amount of charge control resin present on the surface of the colored resin particles is not too large, and a sufficient amount of polar resin is unevenly distributed on the surface of the colored resin particles, thereby improving the heat resistance of the toner and the effect of suppressing bleed-out of the release agent, and suppressing the occurrence of fog when using toner stored for a long period of time in a high-temperature, high-humidity environment. The sum of the product of F and m (F × m) calculated for each of the above copolymers has a lower limit of more preferably 2.50 or more, even more preferably 3.00 or more, and an upper limit of more preferably 5.50 or less, even more preferably 5.00 or less.

[0051] Proportion F of functional group-containing monomer units in copolymer A Ａ (mass%) and the proportion F of functional group-containing monomer units of copolymer B Ｂ (mass%) (F Ａ -F Ｂ ) is not particularly limited, but in order to easily obtain the effects of the present disclosure, the lower limit is preferably 0.30 or more, more preferably 0.50 or more, and even more preferably 0.70 or more, and the upper limit is preferably 5.90 or less, more preferably 5.00 or less, and even more preferably 1.50 or less. In addition, when a plurality of types of copolymers A are contained, the difference (F Ａ -F Ｂ ) used to calculate F ＡWhen a plurality of copolymers B are contained, the difference (F Ａ -F Ｂ ) used to calculate F Ｂ As the functional group content, the value of the functional group content in copolymer B, which has the smallest functional group content, is used.

[0052] The weight-average molecular weight (Mw) of the copolymers A and B is not particularly limited, but is preferably 8,000 to 28,000, more preferably 10,000 to 25,000, and even more preferably 15,000 to 23,000. When the weight-average molecular weight (Mw) is at least the lower limit, deterioration in storage stability and print durability can be suppressed, while when it is at or below the upper limit, deterioration in fixability can be suppressed. Furthermore, when the weight-average molecular weight (Mw) 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 imparted 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.

[0053] The polymerizable monomer composition may further contain a charge control agent different from the copolymers A and B, as long as the effects of the present disclosure are not impaired. In this case, in order to easily obtain the effects of the present disclosure, the content of the copolymers A and B is preferably 90 parts by mass or more, more preferably 95 parts by mass or more, and even more preferably 99 parts by mass or more, per 100 parts by mass of the total amount of the charge control agent.

[0054] (Polar Resin) As the polar resin, a resin having an acid value of 0.5 mgKOH / g or more and 8.0 mgKOH / g or less is used, and preferably a resin having an acid value of 0.5 mgKOH / g or more and 5.0 mgKOH / g or less is used. As the polar resin, it is preferable to use an acrylate copolymer having an acidic group in order to suppress printing defects in high-temperature and high-humidity environments. As the acrylate copolymer having an acidic group, for example, a copolymer of a (meth)acrylic acid ester and (meth)acrylic acid is preferably used. In this disclosure, (meth)acrylic represents both acrylic and methacrylic. A copolymer of a (meth)acrylic acid ester and (meth)acrylic acid is a copolymer of at least one selected from an acrylic acid ester and a methacrylic acid ester and at least one selected from acrylic acid and methacrylic acid. Examples of the copolymer include a copolymer of an acrylic acid ester and acrylic acid, a copolymer of an acrylic acid ester and methacrylic acid, a copolymer of a methacrylic acid ester and acrylic acid, a copolymer of a methacrylic acid ester and methacrylic acid, a copolymer of an acrylic acid ester, a methacrylic acid ester and acrylic acid, a copolymer of an acrylic acid ester, a methacrylic acid ester and methacrylic acid, and a copolymer of an acrylic acid ester, a methacrylic acid ester, an acrylic acid and a methacrylic acid, etc. Among these, a copolymer of an acrylic acid ester, a methacrylic acid ester and acrylic acid is preferred.

[0055] Examples of the (meth)acrylic acid ester 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, isopentyl (meth)acrylate, neopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, neohexyl (meth)acrylate, sec-hexyl (meth)acrylate, and tert-hexyl (meth)acrylate, etc. Of these, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, and n-butyl acrylate are preferred, with ethyl acrylate and n-butyl acrylate being more preferred. Of the methacrylic acid esters, methyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, and n-butyl methacrylate are preferred, with methyl methacrylate being more preferred.

[0056] The mass ratio of each monomer unit in the acrylate copolymer is preferably adjusted so as to satisfy the acid value, weight average molecular weight Mw, and glass transition temperature described below.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 the upper limit is preferably 1.0% by mass or less, more preferably 0.6% by mass or less, and even more preferably 0.5% 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 99.0% by mass or more, more preferably 99.4% by mass or more, and even more preferably 99.5% by mass or more, and the upper limit 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.

[0057] The acrylate copolymer may contain other monomer units different from (meth)acrylic acid ester units and (meth)acrylic acid units, as long as the effects of the present disclosure are 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 parts by mass or less, more preferably 2 parts by mass or less, and most preferably 0 parts by mass, per 100 parts by mass of (meth)acrylic acid ester units.

[0058] The acid value of the polar resin may be 0.5 mgKOH / g or more and 8.0 mgKOH / g or less, preferably 0.5 mgKOH / g or more and 5.0 mgKOH / g or less. The lower limit is more preferably 1.0 mgKOH / g or more, even more preferably 2.0 mgKOH / g or more, and the upper limit is more preferably 4.0 mgKOH / g or less, even more preferably 3.0 mgKOH / g or less. When the acid value of the polar resin is equal to or greater than the lower limit, the charge amount of the toner can be appropriately reduced, thereby suppressing a decrease in print density. When the acid value of the polar resin is equal to or less than the upper limit, fluctuations in the charge amount of the toner due to changes in temperature and humidity are suppressed. In the present disclosure, the acid value of the resin is measured in accordance with JIS K 0070.

[0059] 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 the lower limit or more, the effect of suppressing bleed-out of the release agent is improved, and when it is the upper limit or less, the decrease in heat resistance of the toner is suppressed, and the occurrence of fogging when a toner that has been stored for a long period of time in a high-temperature, high-humidity environment is used is suppressed.

[0060] 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, and even more preferably 77°C or lower. When the glass transition temperature Tg of the polar resin is within the above range, the deterioration of the heat resistance of the toner is suppressed, and the occurrence of fogging is suppressed when using a toner that has been stored for a long period of time in a high-temperature, high-humidity environment. In the present disclosure, the glass transition temperature Tg can be determined in accordance with ASTM D3418-82.

[0061] The content of the polar resin, relative to 100 parts by mass of the binder resin, is preferably 0.30 parts by mass or more, more preferably 0.40 parts by mass or more, and even more preferably 0.50 parts by mass or more, and is preferably 3.00 parts by mass or less, more preferably 2.00 parts by mass or less, and even more preferably 1.50 parts by mass or less. When the content of the polar resin is equal to or greater than the lower limit, the effect of suppressing bleed-out of the release agent is improved. When the content of the polar resin is equal to or less than the upper limit, the toner charge amount tends to be appropriate, and in particular, the occurrence of fogging due to an excessively low toner charge amount is suppressed, and fluctuations in the toner charge amount due to changes in temperature and humidity are suppressed.

[0062] 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. A typical example of a method for producing the polar resin is as follows. Note that the method for producing the polar resin is not limited to the following typical example. First, a solvent is appropriately added to a reaction vessel, the atmosphere inside 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 into 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.

[0063] The acid value (mgKOH / g) of the polar resin is X, and the content (parts by mass) of the polar resin relative to 100 parts by mass of the binder resin is m Ｐ The proportion (mass%) of functional group-containing monomer units in the copolymer A is F Ａ The content (parts by mass) of the copolymer A relative to 100 parts by mass of the binder resin is m Ａ When X and m ｐ The product of (X × m Ｐ ) and F Ａ and m Ａ The product of (F Ａ ×m Ａ ) and the absolute value of the difference (|X × m Ｐ -F Ａ ×m Ａ It is preferable that the absolute value of the difference (|X×m Ｐ -F Ａ ×m Ａ |) is more preferably 2.00 or less, and even more preferably 1.00 or less. The lower limit is not particularly limited and may be 0, but may be, for example, 0.20 or more. When a plurality of polar resins are contained, the "X × m Ｐ " is the "X × m Ｐ When multiple types of copolymers A are contained, the "F" used in the above formula is the sum of Ａ ×m Ａ " is the "F" calculated for each copolymer A. Ａ ×m Ａ "

[0064] (Styrenic Thermoplastic Elastomer) The polymerizable monomer composition preferably contains a styrene-based thermoplastic elastomer. This improves the dispersibility of the release agent, making it less likely for the release agent to bleed out. In this disclosure, the styrene-based thermoplastic elastomer refers to a random, block, graft, or other copolymer of a styrene-based monomer, i.e., an aromatic vinyl monomer, with another monomer copolymerizable with the aromatic vinyl monomer, as well as a hydrogenated product of such a copolymer. A thermoplastic elastomer is typically a material whose volume can be deformed by a small external force at room temperature (20°C) to 200% by volume, assuming its original volume to be 100% by volume, and which returns to less than 130% by volume when the external force is removed.

[0065] As the styrene-based thermoplastic elastomer, for example, a conjugated diene-aromatic vinyl-based thermoplastic elastomer can be preferably used. Among these, an unhydrogenated conjugated diene-aromatic vinyl-based thermoplastic elastomer is particularly preferred. Here, the conjugated diene-aromatic vinyl-based thermoplastic elastomer is a polymer having structural units derived from a conjugated diene monomer and structural units derived from an aromatic vinyl monomer. Examples of the conjugated diene-aromatic vinyl-based thermoplastic elastomer include random, block, and graft copolymers of a conjugated diene monomer, an aromatic vinyl monomer, and optionally other monomers copolymerizable therewith, as well as hydrogenated products of such copolymers. Among these, a block copolymer containing at least one aromatic vinyl polymer block and at least one conjugated diene polymer block is preferred from the viewpoint of improving the fixing property of the toner.

[0066] Hereinafter, a block copolymer containing at least one aromatic vinyl polymer block and at least one conjugated diene polymer block (hereinafter, sometimes simply referred to as a "block copolymer"), which is a typical example of a styrene-based thermoplastic elastomer, will be described. The block copolymer contains at least one aromatic vinyl polymer block obtained by polymerizing an aromatic vinyl monomer and at least one conjugated diene polymer block obtained by polymerizing a conjugated diene monomer.

[0067] Examples of aromatic vinyl monomers used in the aromatic vinyl polymer block include those similar to those usable in the charge control resin, with styrene being preferred. In each aromatic vinyl polymer block of the block copolymer, the aromatic vinyl monomers can be used alone or in combination of two or more. Furthermore, when the block copolymer has multiple aromatic vinyl polymer blocks, each aromatic vinyl polymer block may be composed of the same aromatic vinyl monomer unit or different aromatic vinyl monomer units.

[0068] The aromatic vinyl polymer block may contain other monomer units as long as aromatic vinyl monomer units are the main repeating units. Examples of other monomers that can be used in the aromatic vinyl polymer block include conjugated diene monomers such as 1,3-butadiene and isoprene (2-methyl-1,3-butadiene), α,β-unsaturated nitrile monomers, unsaturated carboxylic acid or acid anhydride monomers, unsaturated carboxylic acid ester monomers, and non-conjugated diene monomers. The content of monomer units other than aromatic vinyl monomer units in the aromatic vinyl polymer block is preferably 20% by mass or less, more preferably 10% by mass or less, and particularly preferably 0% by mass.

[0069] Examples of conjugated diene monomers used in the conjugated diene polymer blocks include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene. Among these, from the viewpoint of highly effective improvements in storage stability and low-temperature fixability, it is preferable to use at least one selected from 1,3-butadiene and isoprene, and it is particularly preferable to use isoprene. In each conjugated diene polymer block contained in the block copolymer, these conjugated diene monomers can be used alone or in combination of two or more. Furthermore, when the block copolymer has multiple conjugated diene polymer blocks, each conjugated diene polymer block may be composed of the same conjugated diene monomer units or different conjugated diene monomer units. Furthermore, a hydrogenation reaction may be performed on a portion of the unsaturated bonds in each conjugated diene polymer block.

[0070] The conjugated diene polymer block may contain other monomer units as long as the conjugated diene monomer units are the main repeating units. Examples of other monomers that can be used in the conjugated diene polymer block include aromatic vinyl monomers such as styrene and α-methylstyrene, α,β-unsaturated nitrile monomers, unsaturated carboxylic acid monomers, unsaturated carboxylic anhydride monomers, unsaturated carboxylic ester monomers, and non-conjugated diene monomers. The content of monomer units other than conjugated diene monomer units in the conjugated diene polymer block is preferably 20% by mass or less, more preferably 10% by mass or less, and particularly preferably 0% by mass.

[0071] The vinyl bond content of the conjugated diene polymer block (the proportion of 1,2-vinyl bond units and 3,4-vinyl bond units in all conjugated diene monomer units in the conjugated diene polymer block) is not particularly limited, but is preferably 1 to 20 mol %, more preferably 2 to 15 mol %, and particularly preferably 3 to 10 mol %.

[0072] The block copolymer is not particularly limited in the number of each polymer block and the bonding form thereof, as long as it contains at least one aromatic vinyl polymer block and at least one conjugated diene polymer block. Specific examples of the block copolymer include the following. In the following specific examples, Ar represents an aromatic vinyl polymer block, D represents a conjugated diene polymer block, X represents a residue of a coupling agent, and n represents an integer of 2 or more. (a) An aromatic vinyl-conjugated diene block copolymer represented as Ar-D. (b) Ar-D-Ar or (Ar-D). ｎ (c) Aromatic vinyl-conjugated diene-aromatic vinyl block copolymer represented by -X (D-Ar-D or (D-Ar) ｎ (d) an aromatic vinyl-conjugated diene-aromatic vinyl-conjugated diene block copolymer represented by Ar-D-Ar-D; and (e) a block copolymer composition obtained by arbitrarily combining two or more of the above (a) to (d).

[0073] In order to improve fixability, the toner of the present disclosure preferably contains at least the above-mentioned (b) as a styrene-based thermoplastic elastomer, and more preferably contains at least the above-mentioned (a) and (b). When the above-mentioned (b) is contained as the styrene-based thermoplastic elastomer, the content of the above-mentioned (b) relative to 100% by mass of the styrene-based thermoplastic elastomer is preferably 2% by mass or more, more preferably 5% by mass or more, and preferably 60% by mass or less, more preferably 50% by mass or less. When the above-mentioned (a) is contained as the styrene-based thermoplastic elastomer, the content of the above-mentioned (a) relative to 100% by mass of the styrene-based thermoplastic elastomer is preferably 40% by mass or more, more preferably 50% by mass or more, and more preferably 55% by mass or more, and although not particularly limited, the upper limit is preferably 98% by mass or less, more preferably 95% by mass or less. Furthermore, when the styrene-based thermoplastic elastomer contains the above (a) and (b), the content of the above (b) is preferably 2 to 60 parts by mass, more preferably 5 to 50 parts by mass, relative to 100 parts by mass of the total mass of the above (a) and (b). When the contents of the above (a) and (b) are within the above ranges, the fixability of the toner is improved, thereby suppressing a decrease in print density, and the charge amount of the toner is likely to be appropriate, making it easier to suppress bleeding out of the release agent.

[0074] In the above (a), the weight average molecular weight (Mw(Ar)) of the aromatic vinyl polymer block Ar is not particularly limited, but is preferably 10,000 to 50,000, more preferably 15,000 to 30,000. In the above (a), the weight average molecular weight (Mw(D)) of the conjugated diene polymer block D is not particularly limited, but is preferably 50,000 to 200,000, more preferably 60,000 to 150,000.

[0075] In the above (b), the weight average molecular weight (Mw(Ar)) of the aromatic vinyl polymer block Ar is not particularly limited, but is preferably 20,000 to 70,000, more preferably 25,000 to 50,000. In the above (b), the weight average molecular weight (Mw(D)) of the conjugated diene polymer block D is not particularly limited, but is preferably 100,000 to 300,000, more preferably 120,000 to 250,000.

[0076] The content of aromatic vinyl monomer units in the block copolymer relative to the total monomer units is preferably 10 to 30% by mass, more preferably 12 to 25% by mass, and even more preferably 15 to 25% by mass. By setting the content of aromatic vinyl monomer units within the above range, the affinity of the block copolymer for the release agent and the affinity of the block copolymer for the binder resin can be well balanced, resulting in a toner with excellent storage stability and low-temperature fixability. Regarding the content of aromatic vinyl monomer units in a block copolymer, if all polymer components constituting the block copolymer are composed only of aromatic vinyl monomer units and conjugated diene monomer units, the block copolymer can be ozonolyzed and then reduced with lithium aluminum hydride according to the method described in Rubber Chem. Technol., 45, 1295 (1972), whereby the conjugated diene monomer unit portion is decomposed and only the aromatic vinyl monomer unit portion is isolated, thereby easily measuring the total aromatic vinyl monomer unit content.

[0077] The weight average molecular weight (Mw) of the aromatic vinyl polymer block in the block copolymer is not particularly limited, but is preferably 10,000 to 50,000, and more preferably 20,000 to 40,000. The weight average molecular weight (Mw) of the conjugated diene polymer block in the block copolymer is not particularly limited, but is preferably 50,000 to 200,000, and more preferably 60,000 to 180,000.

[0078] The melt index (MI) of the block copolymer is not particularly limited, but is selected, for example, from the range of 1 to 1000 g / 10 min, and preferably from 5 to 30 g / 10 min, as a value measured in accordance with ASTM D-1238 (G conditions, 200°C, 5 kg).

[0079] The block copolymer can be produced by a conventional method, for example, by anionic living polymerization, in which an aromatic vinyl monomer and a conjugated diene monomer are sequentially polymerized to form polymer blocks, and then, if necessary, a coupling agent is added to the polymer blocks to couple them.

[0080] A mixture containing at least the above (a) and (b), which is preferably used as the block copolymer, can be produced, for example, by the following method. First, an aromatic vinyl monomer is polymerized by an anionic living polymerization method, and then a conjugated diene monomer is added and polymerized to obtain a diblock copolymer having an active end. Next, a coupling agent in an amount less than 1 molar equivalent relative to the active end of the diblock copolymer having an active end is added to cause a coupling reaction with a portion of the diblock copolymer having an active end, thereby producing (Ar-D). ｎ One example of such a method is to obtain an aromatic vinyl-conjugated diene-aromatic vinyl block copolymer represented by -X, and then add a polymerization terminator to inactivate the diblock copolymer having the remaining active terminals, thereby obtaining a diblock copolymer represented by Ar-D. In this case, by using a bifunctional coupling agent such as dichlorosilane, monomethyldichlorosilane, dimethyldichlorosilane, diphenyldimethoxysilane, diphenyldiethoxysilane, dichloroethane, dibromoethane, methylene chloride, or dibromomethane as the coupling agent, an aromatic vinyl-conjugated diene-aromatic vinyl block copolymer represented by Ar-D-Ar (D includes a residue of the coupling agent).

[0081] Furthermore, as the styrene-based thermoplastic elastomer, instead of the above-mentioned block copolymer, a random copolymer of an aromatic vinyl monomer and a conjugated diene monomer can also be used. The random copolymer of an aromatic vinyl monomer and a conjugated diene monomer can be produced, for example, by living anionic polymerization using an organic alkali metal compound as a polymerization initiator. Examples of the organic alkali metal compound include organolithium compounds, organosodium compounds, and organopotassium compounds. Specific examples include organomonolithium compounds such as n-butyllithium, sec-butyllithium, t-butyllithium, hexyllithium, phenyllithium, and stilbenelithium; organic polyvalent lithium compounds such as dilithiomethane, 1,4-dilithiobutane, 1,4-dilithio-2-ethylcyclohexane, 1,3,5-trilithiobenzene, and 1,3,5-tris(lithiomethyl)benzene; organosodium compounds such as sodium naphthalene; and organopotassium compounds such as potassium naphthalene. Among these organometallic compounds, n-butyllithium is preferably used.

[0082] In the random copolymer of an aromatic vinyl monomer and a conjugated diene monomer, the content ratio of the aromatic vinyl monomer units to all the monomer units is not particularly limited, but is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less. By setting the content ratio of the aromatic vinyl monomer units to the above upper limit or less, it is possible to achieve a high level of balance between the affinity of the random copolymer to the release agent and the affinity of the block copolymer to the binder resin, and the resulting toner can have excellent storage stability and low-temperature fixability.

[0083] The weight average molecular weight (Mw) of the styrene-based thermoplastic elastomer is not particularly limited, but is preferably 60,000 to 350,000, and more preferably 80,000 to 250,000. When the weight average molecular weight (Mw) of the styrene-based thermoplastic elastomer is within the above range, the storage stability and low-temperature fixability of the toner can be improved, and the occurrence of printing defects can be suppressed.

[0084] The content of the styrene-based thermoplastic elastomer, relative to 100 parts by mass of the binder resin, is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, and is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, as the upper limit. When the content of the styrene-based thermoplastic elastomer is equal to or greater than the lower limit, the effect of suppressing bleed-out of the release agent is improved. When the content of the styrene-based thermoplastic elastomer is equal to or less than the upper limit, the toner easily spreads during fixing, thereby suppressing a decrease in print density.

[0085] (Release Agent) The release agent can be any one that is generally used as a release agent or softener for toner, but a fatty acid ester compound having a number average molecular weight (Mn) of 500 or more and less than 2,000 is preferred because the effect of suppressing bleed-out by the combination of the positively charged charge control resin and the polar resin described above is likely to be effectively exhibited. Here, the term "fatty acid ester compound" refers to a product obtained by an ester reaction between at least one alcohol selected from monohydric alcohols and polyhydric alcohols and at least one fatty acid selected from saturated fatty acids and unsaturated fatty acids.

[0086] Examples of monohydric alcohols include saturated monohydric 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, stearyl alcohol, and behenyl alcohol; unsaturated monohydric 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. 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, polyglycerin, etc. Among these monohydric alcohols and polyhydric alcohols, monohydric to tetrahydric saturated aliphatic alcohols are preferred, with behenyl alcohol and pentaerythritol being particularly preferred.

[0087] The carbon number of the fatty acid used as the raw material for the fatty acid ester compound is preferably 12 or more, more preferably 14 or more, and even more preferably 16 or more, as a lower limit, and preferably 24 or less, more preferably 22 or less, and even more preferably 18 or less, as an upper limit. When the carbon number of the fatty acid is equal to or more than the above lower limit, bleeding out of the fatty acid ester compound is easily suppressed. When the carbon number of the fatty acid is equal to or less than the above upper limit, deterioration in the heat resistance of the toner is suppressed, and the occurrence of fogging when using a toner stored for a long period of time in a high-temperature, high-humidity environment is suppressed. Furthermore, saturated fatty acids with a carbon number within the above range are particularly preferred, since a fatty acid ester compound having a number average molecular weight (Mn) of 500 or more but less than 2,000 can be easily obtained.

[0088] The saturated fatty acid is not particularly limited, but examples thereof include 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 (20 carbon atoms), and behenic acid (22 carbon atoms). Of these, behenic acid (22 carbon atoms), stearic acid (18 carbon atoms), and arachidic acid (20 carbon atoms) are preferred.

[0089] The unsaturated fatty acids are not particularly limited, but examples thereof include: 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). The above fatty acids can be used either alone or in combination of two or more.

[0090] The esterification rate of the fatty acid ester compound 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 fatty acid ester compound. The esterification rate of the fatty acid ester compound is the ratio of the number of hydroxyl groups ester-bonded to a fatty acid to the total number of hydroxyl groups possessed by the raw material alcohol of the fatty acid ester compound. The esterification rate of the fatty acid ester compound can be calculated by measuring the saponification value (SV), hydroxyl value (OHV), and acid value (AV) of the fatty acid ester compound, respectively, and using the following formula: Esterification rate (%) = [(SV - AV) / (SV - AV + OHV)] x 100. The saponification value (SV) and acid value (AV) of the fatty acid ester compound are measured in accordance with JIS K 0070, and the hydroxyl value (OHV) of the fatty acid ester compound is measured in accordance with JIS K 1557.

[0091] The fatty acid ester compound may be any of monoesters, diesters, triesters, tetraesters, and polyesters. However, monoesters are preferred because they improve the storage stability of the toner and suppress toner aggregation under high-temperature, high-humidity environments. Toner aggregates land on the developing roller in an uncharged state and cause fogging, so suppressing toner aggregation can suppress the occurrence of fogging. Furthermore, while monoesters are typically prone to bleed-out, the toner of the present disclosure suppresses bleed-out of the release agent. Therefore, using a monoester as a release agent effectively demonstrates the effects of the present disclosure. Examples of monoesters include behenyl palmitate, behenyl stearate, behenyl eicosanoate, behenyl behenate, eicosyl palmitate, eicosyl stearate, eicosyl eicosanoate, eicosyl behenate, stearyl stearate, stearyl eicosanoate, stearyl behenate, hexadecyl eicosanoate, and hexadecyl behenate. Among these, behenyl stearate, behenyl palmitate, and stearyl behenate are preferred, and behenyl stearate is particularly preferred, because they improve the low-temperature fixability of the toner, make the toner more likely to melt and spread during fixation, and increase the hiding power on the paper surface, thereby improving print density.

[0092] The number average molecular weight (Mn) of the fatty acid ester compound is preferably 500 or more, more preferably 550 or more, as a lower limit from the viewpoint of improving the low-temperature fixability of the toner and suppressing bleed-out of the fatty acid ester compound, and is preferably less than 2,000, more preferably 1,500 or less, even more preferably 1,000 or less, and still more preferably 700 or less, as it allows the toner to easily spread during fixation and suppresses a decrease in print density. Furthermore, fatty acid ester compounds having a number average molecular weight (Mn) within the above range are prone to bleed-out, but in the toner of the present disclosure, bleed-out of the release agent is suppressed, and therefore, when a fatty acid ester compound having a number average molecular weight (Mn) within the above range is used as a release agent, the effects of the present disclosure are particularly effectively exhibited.

[0093] The melting point of the release agent is preferably within the range of 50 to 90°C, more preferably within the range of 60 to 85°C, and even more preferably within the range of 65 to 75°C.

[0094] The fatty acid ester compound may be a commercially available product, such as "WEP2," "WEP3," "WEP4," "WEP5," "WE6," or "WE11" (all of which are trade names) manufactured by NOF Corporation.

[0095] In the present disclosure, other release agents can also be used in combination with the fatty acid ester compound. Specific examples of the other release agents include low-molecular-weight polyolefin waxes and modified waxes thereof; natural plant waxes such as jojoba; petroleum waxes such as paraffin; mineral waxes such as ozokerite; and synthetic waxes such as Fischer-Tropsch wax. The other release agents can be used alone or in combination of two or more.

[0096] The content of the release agent, relative to 100 parts by mass of the binder resin, is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more, 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 release agent is equal to or greater than the above-mentioned lower limit, a toner with excellent low-temperature fixability is obtained, and the toner easily spreads during fixation, thereby suppressing a decrease in print density. When the content of the release agent is equal to or less than the above-mentioned upper limit, bleeding out of the release agent is suppressed. Furthermore, the content of the fatty acid ester compound per 100 parts by mass of the release agent is preferably 90 parts by mass or more, more preferably 95 parts by mass or more, and even more preferably 99 parts by mass or more.

[0097] (Molecular Weight Regulator) In the polymerizable monomer composition, it is preferable to use a molecular weight regulator as another additive when polymerizing the polymerizable monomer. The molecular weight regulator is not particularly limited as long as it is one that is generally used as a molecular weight regulator for toner, 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 regulators 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, based on 100 parts by mass of the monovinyl monomer.

[0098] (A-2) Suspension step for obtaining a suspension (droplet formation step) Next, the polymerizable monomer composition is dispersed in an aqueous medium containing a dispersion stabilizer, and a polymerization initiator is added thereto, followed by droplet formation of the polymerizable monomer composition. As described above, the polymerization initiator may be added after the polymerizable monomer composition is dispersed in the aqueous medium and before droplet formation, or may be added to the polymerizable monomer composition before it is dispersed in the aqueous medium.

[0099] 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 the resulting toner has excellent print durability. 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.

[0100] The amount of the polymerization initiator used for polymerization of the polymerizable monomer composition 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 monovinyl monomer.

[0101] 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 dispersion stabilizers include inorganic compounds such as 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; and organic compounds such as water-soluble polymers such as polyvinyl alcohol, methyl cellulose, and gelatin; anionic surfactants; nonionic surfactants; and amphoteric surfactants. The dispersion stabilizers can be used alone or in combination of two or more.

[0102] Among the dispersion stabilizers, inorganic compounds, particularly colloids of poorly water-soluble metal hydroxides, are preferred. By using inorganic compounds, particularly colloids of poorly water-soluble metal hydroxides, the particle size distribution of the colored resin particles can be narrowed and the amount of dispersion stabilizer remaining after washing can be reduced, resulting in a toner that can clearly reproduce images and has excellent environmental stability. The colloids of poorly water-soluble metal hydroxides can be prepared, for example, by reacting at least one selected from 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 may be any water-soluble polyvalent metal salt other than the compounds corresponding to the alkaline earth metal hydroxides, and examples thereof include magnesium metal salts such as magnesium chloride, magnesium phosphate, magnesium sulfate, etc.; calcium metal salts such as calcium chloride, calcium nitrate, calcium acetate, calcium sulfate, etc.; aluminum metal salts such as aluminum chloride, aluminum sulfate, etc.; barium salts such as barium chloride, barium nitrate, barium acetate, etc.; zinc salts such as zinc chloride, zinc nitrate, zinc acetate, etc. 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.

[0103] 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, and 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. 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 so as not to coalesce in the suspension. 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, and the problem of the suspension clogging in the granulator can be avoided. Furthermore, the content of the dispersion stabilizer is typically 1 to 15 parts by mass, and preferably 1 to 8 parts by mass, relative to 100 parts by mass of the aqueous medium.

[0104] The polymerizable monomer composition is introduced into an aqueous medium containing a dispersion stabilizer, and the mixture is vigorously stirred to obtain a suspension in which droplets of the polymerizable monomer composition are dispersed in the aqueous medium. The vigorous stirring for forming droplets of the polymerizable monomer composition is not particularly limited, and can be performed using a disperser such as a horizontal or vertical in-line disperser such as Milder (trade name) manufactured by Pacific Machinery Works, Ltd., Cavitron (trade name) manufactured by Eurotec Co., Ltd., or an in-line disperser manufactured by IKA (e.g., DISPAX-REACTOR (registered trademark) DRS (trade name)); or an emulsifying disperser such as a homomixer MARK II series manufactured by Primix Corporation. The stirring time in the suspension step is adjusted appropriately depending on the amount of the polymerizable monomer composition, and is not particularly limited.

[0105] (A-3) Polymerization Step After droplets of the polymerizable monomer composition are formed as in (A-2) above, the polymerizable monomer composition is subjected to a polymerization reaction in the presence of a polymerization initiator to form colored resin particles. That is, the suspension in which droplets of the polymerizable monomer composition are dispersed is heated to promote the polymerization reaction of the polymerizable monomer, thereby obtaining an aqueous dispersion of colored resin particles. The heating temperature when subjecting the suspension to the polymerization reaction is not particularly limited, but is preferably 50°C or higher, more preferably 60°C or higher, from the viewpoint of rapidly promoting the polymerization reaction. On the other hand, it is preferably 95°C or lower, from the viewpoint of suppressing rapid polymerization reaction and stabilizing the quality of the resulting toner. The polymerization reaction time is preferably 1 hour to 20 hours, more preferably 2 hours to 15 hours. In order to carry out polymerization in a state in which droplets of the polymerizable monomer composition are stably dispersed, in this polymerization step as well, the polymerization reaction may be carried out while performing a dispersion treatment by stirring following the suspension step (droplet formation step) for obtaining the suspension (A-2) above.

[0106] In the present disclosure, the colored resin particles obtained by the polymerization process may be used as a toner by adding an external additive. However, it is preferable to use the colored resin particles obtained by the polymerization process as the core layer of so-called core-shell type (also called "capsule type") colored resin particles. Core-shell type colored resin particles have a structure in which the outside of the core layer is coated with a shell layer formed of a material different from the core layer. By coating a core layer made of a material with a low softening point with a material with a higher softening point, the low-temperature fixability and storage stability of the toner can be improved in a well-balanced manner. Furthermore, core-shell type colored resin particles are preferable because the shell prevents the external additive from being embedded, thereby suppressing toner deterioration due to the embedded external additive. As a result, the toner charge amount is easily maintained during continuous printing, and the occurrence of printing defects is suppressed.

[0107] The method for producing core-shell type colored resin particles using the colored resin particles obtained by the polymerization step is not particularly limited, and they 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.

[0108] A method for producing core-shell type colored resin particles by in situ polymerization is described below: A polymerizable monomer for forming a shell layer (shell polymerizable monomer) and a polymerization initiator are added to an aqueous dispersion in which colored resin particles are dispersed, and the resulting mixture is polymerized to obtain core-shell type colored resin particles.

[0109] The polymerizable monomer for the shell may be the same as the polymerizable monomer described above. Among these, it is preferable to use monomers capable of yielding polymers with a Tg exceeding 80°C, such as styrene, acrylonitrile, and methyl methacrylate, either singly or in combination. The amount of the polymerizable monomer for the shell is not particularly limited, but the lower limit is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and the upper limit is preferably 5 parts by mass or less, more preferably 4 parts by mass or less, relative to 100 parts by mass of the binder resin. The mass of the binder resin is the same as the mass of the polymerizable monomer used in the core layer. When the amount of the polymerizable monomer for the shell is equal to or greater than the lower limit, the heat resistance of the toner is suppressed from decreasing, and the occurrence of fogging is suppressed when the toner is stored for a long period of time in a high-temperature, high-humidity environment. When the amount of the polymerizable monomer for the shell is equal to or less than the upper limit, the toner easily spreads during fixing, thereby suppressing a decrease in print density. Furthermore, when the amount of the polymerizable monomer for the shell added is within the above range, the storage stability and low-temperature fixability of the toner are improved.

[0110] Examples of the polymerization initiator used in the polymerization of the shell polymerizable monomer 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 shell polymerizable monomer.

[0111] The polymerization temperature for the shell layer is not particularly limited, but from the viewpoint of rapidly progressing the polymerization reaction, it is preferably 50° C. or higher, more preferably 60° 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.

[0112] (A-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 a conventional manner, which are repeated several times as necessary.

[0113] 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 inorganic 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.

[0114] 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.

[0115] (B) Pulverization Method When colored resin particles are produced using the pulverization method, the process is, for example, as follows. First, the binder resin, colorant, positively charged charge control resin, polar resin, release agent, and other additives, such as a styrene-based thermoplastic elastomer, are mixed using a mixer such as a ball mill, V-type mixer, FM Mixer (trade name, manufactured by Nippon Coke & Engineering Co., Ltd.), high-speed dissolver, internal mixer, or Fallberg mixer. Next, the mixture obtained above is kneaded while heating using a pressure kneader, a twin-screw extrusion mixer, a roller, or the like. The resulting kneaded product is coarsely pulverized using a pulverizer such as a hammer mill, cutter mill, or 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, thereby obtaining colored resin particles by the pulverization method.

[0116] The binder resin, colorant, positively charged charge control resin, polar resin, release agent, and styrene-based thermoplastic elastomer used in the pulverization method can be the same as those listed in the (A) suspension polymerization method. In addition to the binder resins listed above, resins that have been widely used in toners, such as polystyrene, polyester-based resins, and epoxy-based resins, can also be used as the binder resin. Furthermore, the colored resin particles obtained by the pulverization method can also be made into core-shell type colored resin particles by a method such as in situ polymerization, just like the colored resin particles obtained by the (A) suspension polymerization method.

[0117] 2. Colored Resin Particles Colored resin particles can be obtained by a manufacturing method such as (A) a wet method such as a suspension polymerization method or (B) a dry method such as a pulverization method. The colored resin particles contained in the toner will be described below. Note that the colored resin particles described below include both core-shell type and non-core-shell type particles.

[0118] The volume average particle size (Dv) of the colored resin particles is not particularly limited, but is preferably 3 to 15 μm, more preferably 4 to 12 μm. When Dv is within the above range, there is little risk of a decrease in toner fluidity, deterioration in transferability, a decrease in image density, or a decrease in image resolution.

[0119] The ratio (Dv / Dn) of the volume average particle diameter (Dv) to the number average particle diameter (Dn) of the colored resin particles is preferably 1.0 to 1.3, and more preferably 1.0 to 1.2. When Dv / Dn is within the above range, there is little risk of deterioration in transferability, image density, and resolution. The volume average particle diameter and number average particle diameter of the colored resin particles can be measured using, for example, a particle size analyzer (manufactured by Beckman Coulter, trade name: Multisizer) or the like.

[0120] From the viewpoint of image reproducibility, the average circularity of the colored resin particles is preferably 0.96 to 1.00, more preferably 0.97 to 1.00, and even more preferably 0.98 to 1.00. When the average circularity of the colored resin particles is within the above range, excellent thin line reproducibility of printed characters is achieved.

[0121] 3. Toner The toner of the present disclosure is obtained by mixing and stirring the colored resin particles obtained by the above-mentioned method with an external additive to perform an external addition treatment. The toner of the present disclosure has the external additive attached to the surface of the colored resin particles, and can be used as a one-component toner (developer). The one-component toner may also be further mixed and stirred with carrier particles to form a two-component developer.

[0122] The method of external addition treatment for attaching the external additive to the surface of the colored resin particles can be any known external addition treatment 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 FM Mixer (trade name, manufactured by Nippon Coke and Engineering Co., Ltd.), Super Mixer (trade name, manufactured by Kawada Manufacturing Co., Ltd.), Q Mixer (trade name, manufactured by Nippon Coke and Engineering Co., Ltd.), Mechanofusion System (trade name, manufactured by Hosokawa Micron Co., Ltd.), and Mechano Mill (trade name, manufactured by Okada Seiko Co., Ltd.).

[0123] 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 soap such as zinc stearate or 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 preferred to use two or more of them in combination.

[0124] 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 can be determined, for example, by weighing out approximately 0.1 g of a measurement sample, placing it in a beaker, and adding 0.1 mL of an alkylbenzenesulfonic acid aqueous solution (manufactured by Fujifilm Corporation, product name: Drywell) as a dispersant. 10 to 30 mL of a diluent (trade name: Isoton II, manufactured by Beckman Coulter, Inc.) is further added to the beaker, and the mixture is dispersed for 3 minutes using a 20 W (Watt) ultrasonic disperser. Thereafter, the mixture is measured using a particle size measuring device (trade name: Multisizer, manufactured by Beckman Coulter, Inc.) under the conditions of an aperture diameter of 100 μm, a medium: Isoton II, and a number of particles measured: 100,000.

[0125] 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.

[0126] The toner of the present disclosure is a toner that is resistant to bleeding of the release agent even in a high-temperature, high-humidity environment. Therefore, after storing the toner of the present disclosure for 30 days in a high-temperature, high-humidity environment at a temperature of 47°C and a humidity of 80% RH, the bleeding rate calculated as the percentage of the number of bled-out toner particles (B) to the number of total toner particles (A) can be less than 15%, and in a more preferred embodiment, less than 10%, and in an even more preferred embodiment, less than 5%. Note that the bleeding rate of the toner can be determined specifically by the same method as the evaluation of the bleeding rate in the examples described below.

[0127] When the toner of the present disclosure is used, continuous printing can be performed using a cartridge with a large toner load, suppressing printing defects until the toner level becomes low, both in low-temperature, low-humidity environments and high-temperature, high-humidity environments. Therefore, when a print durability test is performed using the toner of the present disclosure under a high-temperature, high-humidity environment, the number of continuous prints that can maintain image quality with a fog value of 2.0 or less can be 10,000 or more, more preferably 15,000 or more, and even more preferably more than 20,000. Furthermore, when a print durability test is performed under a high-temperature, high-humidity environment with 500 g of the toner of the present disclosure filled into a cartridge, the amount of toner used that can maintain image quality with a fog value of 2.0 or less can be until the toner residual rate in the cartridge reaches 60% or less, more preferably 50% or less, and even more preferably 40% or less. The toner residual rate can be calculated using the following formula, where X (g) is the cartridge weight after continuous printing and Y (g) is the cartridge weight before the toner is filled. Toner Residual Rate (%) = {(X-Y) / Y} x 100. Printing durability tests under high-temperature, high-humidity environments and the determination of fog values ​​can be performed using the same method as in the HH durability test described in the Examples below. When a printing durability test is performed under a low-temperature, low-humidity environment using a toner of the present disclosure, the number of continuous prints that can maintain an image quality with a print density (reflection density) of 1.3 or higher can be 10,000 or more sheets, more preferably 15,000 or more sheets, and even more preferably, more than 20,000 sheets. When a printing durability test is performed under a low-temperature, low-humidity environment using a cartridge filled with 500 g of the toner of the present disclosure, the amount of toner used that can maintain an image quality with a print density of 1.3 or higher can be determined until the toner residual rate in the cartridge reaches 60% or less, more preferably, until the toner residual rate reaches 50% or less, and even more preferably, until the toner residual rate reaches 40% or less. Printing durability tests under a low-temperature, low-humidity environment and the determination of print density can be performed using the same method as in the LL durability test described in the Examples below.

[0128] The toner of the present disclosure is less likely to cause printing defects even when used after long-term storage in a high-temperature, high-humidity environment. Therefore, when a printing durability test is conducted in a high-temperature, high-humidity environment using the toner of the present disclosure after 30 days of storage in a high-temperature, high-humidity environment at a temperature of 47°C and a humidity of 80% RH, the number of consecutive prints that can maintain an image quality with a fog value of 2.0 or less can be 10,000 or more, and in a more preferred embodiment, 15,000 or more, and in an even more preferred embodiment, more than 20,000.

[0129] The toner of the present disclosure has reduced fluctuations in charge amount due to changes in temperature and humidity. Therefore, the difference (Q1 - Q2) between the toner charge amount Q1 (μC / g) when 100 sheets are continuously printed using the toner of the present disclosure in a low-temperature, low-humidity environment and the toner charge amount Q2 (μC / g) when 100 sheets are continuously printed using the toner of the present disclosure in a high-temperature, high-humidity environment can be less than 25 μC / g, and in a more preferred embodiment, less than 20 μC / g, and in an even more preferred embodiment, less than 15 μC / g. Note that the determination of the continuous printing and the toner charge amounts Q1 and Q2 in a low-temperature, low-humidity environment or a high-temperature, high-humidity environment can be performed using a method similar to that used to evaluate "charge fluctuations due to environment" in the examples described below.

[0130] 4. Image Forming Method When a cartridge with a large toner load is used, the toner of the present disclosure enables continuous printing while suppressing the occurrence of printing defects until the remaining toner amount is low, both in a low-temperature, low-humidity environment and a high-temperature, high-humidity environment. Therefore, in an image forming method using the toner of the present disclosure, the effects of the toner of the present disclosure are effectively exhibited when a cartridge with a large toner load is used. In the image forming method of the present disclosure, the toner load in the cartridge is preferably 300 g or more, more preferably 400 g or more, and even more preferably 500 g or more. The toner load in the cartridge is typically 1,000 g or less. Furthermore, in the image forming method of the present disclosure, the amount of toner used without causing printing defects to an unusable level can be limited to a level where the toner residual rate in the cartridge is 60% or less, and in a more preferred embodiment, the toner residual rate can be limited to a level where the toner residual rate is 50% or less, and in an even more preferred embodiment, the toner residual rate can be limited to a level where the toner residual rate is 40% or less.

[0131] The image forming method using the toner of the present disclosure may be a general image forming method, and is not particularly limited, except for the above-mentioned toner filling amount in the cartridge and toner residual rate, and may include, for example, an image forming method having a charging step, an exposure step, a developing step, a transfer step, a cleaning step, and a fixing step.

[0132] The charging step is a step of uniformly charging the surface of the photoreceptor positively or negatively using a charging member. Examples of charging methods using a charging member include contact charging methods using a charging roll, fur brush, magnetic brush, blade, etc., and non-contact charging methods using corona discharge.

[0133] The exposure process is a process in which an exposure device irradiates the surface of the photoconductor with light corresponding to an image signal, thereby forming an electrostatic latent image on the uniformly charged surface of the photoconductor. Examples of exposure devices include a laser irradiation device and an LED irradiation device.

[0134] The development process is a process in which a developer applies toner to the electrostatic latent image formed on the surface of the photoconductor during the exposure process to form a visible image. In reversal development, toner is applied only to the exposed areas, while in normal development, toner is applied only to the non-exposed areas.

[0135] The transfer process is a process in which a visible image formed on the surface of the photoreceptor by a developing device is transferred to a recording material such as paper. Transfer is usually performed using a transfer roll, but other transfer methods include belt transfer and corona transfer.

[0136] The cleaning process is a process for removing toner remaining on the surface of the photoreceptor after the transfer process. For example, a cleaning blade is pressed against the photoreceptor to scrape off the toner remaining on the surface of the photoreceptor. The scraped toner is usually collected by a recovery device.

[0137] The fixing process is a process for fixing the visible toner image transferred to the recording material, and is carried out, for example, by rotating at least one of a heated roll heated by a heating means and a support roll, and applying heat and pressure to the recording material while passing it between them. Known fixing methods include heating, pressure, heating and pressure, and solvent vapor, and among these, the heating and pressure method using a heated roll as described above is the most widely used.

[0138] 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.

[0139] [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, 2.6 parts of ethyl acrylate, 0.4 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. In this way, polar resin P1 (MMA / EA / AA) was obtained. The resulting polar resin P1 had an acid value of 2.5 mg KOH / g, a Tg of 74 ° C., and an Mw of 12,600.

[0140] [Production Example 2: Synthesis of polar resin P2] Polar resin P2 (MMA / EA / AA) was obtained in the same manner as in Production Example 1, except that 97.3 parts of methyl methacrylate, 2.6 parts of ethyl acrylate, and 0.1 parts of acrylic acid were used. The obtained polar resin P2 had an acid value of 0.5 mgKOH / g, a Tg of 74°C, and an Mw of 12,500.

[0141] [Production Example 3: Synthesis of polar resin P3] Polar resin P3 (MMA / EA / AA) was obtained in the same manner as in Production Example 1, except that 96.6 parts of methyl methacrylate, 2.6 parts of ethyl acrylate, and 0.8 parts of acrylic acid were used. The obtained polar resin P3 had an acid value of 5.0 mgKOH / g, a Tg of 74°C, and an Mw of 12,300.

[0142] [Production Example 4: Synthesis of polar resin P4] Polar resin P4 (MMA / EA / AA) was obtained in the same manner as in Production Example 1, except that 95.9 parts of methyl methacrylate, 2.5 parts of ethyl acrylate, and 1.6 parts of acrylic acid were used. The obtained polar resin P4 had an acid value of 10.0 mgKOH / g, a Tg of 74°C, and an Mw of 12,700.

[0143] [Production Example 5: Synthesis of SIS Composition] 23.2 kg of cyclohexane, 1.5 mmol of N,N,N',N'-tetramethylethylenediamine (TMEDA), and 1.70 kg of styrene were added to a pressure-resistant reactor and stirred at 40°C. 99.1 mmol of n-butyllithium was added, and the resulting mixture was polymerized for 1 hour while heating to 50°C. The polymerization conversion of styrene was 100% by mass. Subsequently, 6.03 kg of isoprene was continuously added to the reactor over 1 hour while controlling the temperature to maintain 50 to 60°C. After the addition of isoprene was completed, polymerization was continued for another 1 hour to obtain a styrene-isoprene diblock copolymer (a) (copolymer (a) represented by Ar-D). The polymerization conversion of isoprene was 100% by mass. Next, 15.0 mmol of dimethyldichlorosilane was added as a coupling agent, and a coupling reaction was carried out for 2 hours to form a styrene-isoprene-styrene triblock copolymer (b) (copolymer (b) represented by Ar-D-Ar). Thereafter, 198 mmol of methanol was added as a polymerization terminator and the mixture was thoroughly mixed to terminate the reaction, thereby obtaining a reaction solution containing a styrene-isoprene-styrene triblock copolymer (SIS) composition containing the block copolymers (a) and (b). A portion of the resulting reaction solution was removed, and the weight-average molecular weight Mw of each block, the weight-average molecular weight Mw of each block copolymer, the weight-average molecular weight Mw of the entire SIS composition, the content of each block copolymer, the styrene unit content, and the vinyl bond content of the conjugated diene block were determined. The results are shown in Table 1. 0.3 parts of 2,6-di-tert-butyl-p-cresol was added as an antioxidant to 100 parts of the reaction liquid obtained in this manner (containing 30 parts of the polymer component), and the mixture was mixed. The mixed solution was added dropwise in small amounts to warm water heated to 85 to 95°C to volatilize the solvent, obtaining a precipitate. This precipitate was then pulverized and dried with hot air at 85°C to recover an SIS composition. The melt index of the obtained SIS composition was measured. The results are shown in Table 1. In Tables 3 to 5, the SIS composition is simply referred to as "SIS."

[0144] [Production Example 6: Synthesis of SBS composition] A styrene-1,3-butadiene-styrene triblock copolymer (SBS) composition was obtained in the same manner as in Production Example 5, except that the amount of styrene added was changed to 2.32 kg and 5.41 kg of butadiene was used instead of 6.03 kg of isoprene. In Tables 3 to 5, the SBS composition is simply referred to as "SBS."

[0145]

[0146] Example 1 1. Production of Colored Resin Particles 70 parts of styrene and 30 parts of n-butyl acrylate as monovinyl monomers, 9 parts of carbon black (manufactured by Mitsubishi Chemical Corporation, product name: #25B) as a black colorant, 0.7 parts of divinylbenzene as a crosslinkable polymerizable monomer, 1.0 part of t-dodecyl mercaptan as a molecular weight modifier, and 1.00 parts of the polar resin P1 obtained in Production Example 1 above as a polar resin were mixed and wet-pulverized using a media-type emulsifying disperser. Subsequently, 1.5 parts of CCR-A1 (copolymerization ratio of a monomer containing a quaternary ammonium base: 2.00%) as Copolymer A, which is a positively chargeable charge control resin, 1.0 part of CCR-B1 (copolymerization ratio of a monomer containing a quaternary ammonium base: 1.00%) as Copolymer B, which is a positively chargeable charge control resin, and behenyl stearate (molecular formula: C) as a mold release agent were added. １７ H ３５ -COO-C ２２ H ４５ 20 parts of a styrene-based thermoplastic elastomer having a melting point of 70°C, an acid value of 0.1 mgKOH / g, a hydroxyl value of 0.3 mgKOH / g, and an esterification rate of 98%), and 5.0 parts of the SIS composition obtained in Production Example 5 as a styrene-based thermoplastic elastomer were further added and mixed to obtain a polymerizable monomer composition. The monomer units and copolymerization ratios (mass%) constituting CCR-A1 and CCR-B1 are as shown in Table 2.

[0147] Separately, in a stirring tank at room temperature, an aqueous solution prepared by dissolving 4.1 parts of sodium hydroxide in 50 parts of ion-exchanged water was gradually added under stirring to an aqueous solution prepared by dissolving 7.4 parts of magnesium chloride in 250 parts of ion-exchanged water, to prepare a magnesium hydroxide colloidal dispersion (3.0 parts of magnesium hydroxide).

[0148] The polymerizable monomer composition was added to the magnesium hydroxide colloidal dispersion obtained above at room temperature and stirred until droplets were stabilized. Five parts of t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, trade name: Perbutyl O) was added as a polymerization initiator, and then the mixture was stirred with high shear at a rotation speed of 15,000 rpm using an in-line emulsifying disperser (manufactured by Pacific Machinery Works, Ltd., trade name: Milder) to form droplets of the polymerizable monomer composition.

[0149] The suspension (polymerizable monomer composition dispersion) 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 as a shell polymerizable monomer was added to the reactor. 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.

[0150] 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 6.5 or less. The resulting solid was then filtered and separated, and 500 parts of ion-exchanged water was added to the resulting solid to form a reslurry. This water washing treatment (washing, filtration, and dehydration) was repeated several times. The resulting solid was then placed in a dryer and dried at 45°C for 48 hours to obtain dried colored resin particles.

[0151] To 100 parts of the above colored resin particles, 0.7 parts of silica fine particles A having a number-average primary particle size of 10 nm and 1 part 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 & Engineering Co., Ltd., product name: FM Mixer) and subjected to external addition treatment to prepare the toner of Example 1.

[0152] [Examples 2 to 21 and Comparative Examples 1 to 8] Toners of Examples 2 to 21 and Comparative Examples 1 to 8 were obtained in the same manner as in Example 1, except that the materials added to the polymerizable monomer composition in Example 1 were changed according to Tables 3 to 5. The monomer units and copolymerization ratios (mass%) constituting the copolymers A, B, and C used in each of the examples and comparative examples are shown in Table 2.

[0153]

[0154] [Evaluation] The toners of each example and each comparative example, and the colored resin particles used in these toners, were evaluated. Details are as follows.

[0155] (1) Evaluation of Colored Resin Particles a. Volume Average Particle Size (Dv), Number Average Particle Size (Dn), and Particle Size Distribution (Dv / Dn) Approximately 0.1 g of colored resin particles was weighed and placed in a beaker, and 0.1 mL of a surfactant aqueous solution (manufactured by Fujifilm Corporation, product name: Drywell) was added as a dispersant. 10 to 30 mL of Isoton II was further added to the beaker, and the mixture was dispersed for 3 minutes using a 20 W ultrasonic disperser. The volume average particle size (Dv) and number average particle size (Dn) of the colored resin particles were measured using a particle size analyzer (manufactured by Beckman Coulter, product name: Multisizer) under the following conditions: aperture diameter: 100 μm, medium: Isoton II, number of particles measured: 100,000, and the particle size distribution (Dv / Dn) was calculated.

[0156] b. Average Circularity 10 mL of ion-exchanged water was placed in a container, 0.02 g of a surfactant was added as a dispersant, and 0.02 g of colored resin particles were then added. The water was dispersed for 3 minutes at 60 W using an ultrasonic disperser. The colored resin particle concentration at the time of measurement was adjusted to 3,000 to 10,000 particles / μL, and 5,000 to 10,000 colored resin particles with a circle-equivalent diameter of 0.4 μm or more were measured using a flow particle image analyzer (manufactured by CIMEX Corporation, product name: FPIA-3000). The average circularity was calculated from the measured values. The circularity is shown in the following formula 1, and the average circularity is the number average. Formula 1: (Circularity) = (Perimeter of a circle equal to the projected area of ​​the particle) / (Perimeter of the projected image of the particle)

[0157] (2) Toner Evaluation a. Bleed Rate First, as the stored toner, a toner sample was prepared after being stored for 30 days under an environment of 47°C and 80% RH. The stored toner sample was observed using an SEM. Ten images of the toner were photographed at a magnification of 2,000x. Next, for each photographed toner image, the number of all toner particles (A) in the image and the number of toner particles (B) to which bled-out release agent had adhered were counted. Note that toner particles to which bled-out release agent had adhered were defined as toner particles in the image for which it was confirmed that the release agent had adhered with a maximum length of more than 0.3 μm. Then, for each toner image, the number of toner particles (B) was divided by the number of toner particles (A) and then multiplied by 100 to calculate a value. The average of the values ​​calculated for the 10 toner images was defined as the bleed rate (%) of the toner. Based on the bleed rate, the bleed-out suppression effect was evaluated according to the following evaluation criteria. (Evaluation criteria) A: Less than 5% B: 5% or more and less than 10% C: 10% or more and less than 15% D: 15% or more

[0158] b. Printing durability test under high temperature and high humidity environment (HH durability test) A commercially available non-magnetic single-component development printer (printing speed: 40 A4 size sheets / minute) was used for the printing durability test. The printing durability test under high temperature and high humidity environment was performed as follows. First, 500 g of toner was placed in the toner cartridge of the development device. After leaving the printer in a high temperature and high humidity environment at a temperature of 33.5°C and a humidity of 82% RH for 24 hours, continuous printing was performed under the same environment up to 20,000 sheets at a print rate of 5%. Every 500 sheets, five solid prints (100% print rate) were performed, followed by solid white prints (0% print rate). The printer was stopped midway through the solid white prints, and the toner in the non-image areas on the photoreceptor after development was attached to adhesive tape (manufactured by Sumitomo 3M Limited, product name: Scotch Mending Tape 810-3-18), which was then attached to the print paper. Next, the whiteness (B) of the printing paper with the adhesive tape attached was measured using a whiteness meter (manufactured by Nippon Denshoku Industries Co., Ltd.). Similarly, unused adhesive tape alone was attached to printing paper, and the whiteness (A) was measured. The difference in whiteness (B - A) was taken as the fog value. A smaller value indicates less fog and better quality. The number of continuous prints that could maintain image quality with a fog value of 2.0 or less was determined. Based on this number of continuous prints, the print durability under a high-temperature, high-humidity environment was evaluated according to the following evaluation criteria. (Evaluation Criteria) A: More than 20,000 sheets B: 15,000 to 20,000 sheets C: 10,000 to less than 15,000 sheets D: Less than 10,000 sheets Furthermore, the toner residual rate was calculated using the following formula from the cartridge weight X (g) at the time when image quality with a fog value of 2.0 or less could no longer be maintained and the cartridge weight Y (g) before toner was added. Toner residual rate (%)={(X−Y) / Y}×100

[0159] c. Printing durability test in a low-temperature, low-humidity environment (LL durability test) Using the same printer as in the HH durability test, a printing durability test in a low-temperature, low-humidity environment was conducted using the following procedure. First, 500 g of toner was placed in the toner cartridge of the developing device. After leaving the printer in a low-temperature, low-humidity environment (temperature 10°C, humidity 20% RH) for 24 hours, continuous printing was performed under the same environment at a printing rate of 5% up to 20,000 sheets. Every 500 sheets, five solid prints (100% printing rate) were printed, and the print density (reflection density) of the solid print area was measured using a reflective image densitometer (manufactured by Macbeth, product name: RD918). The number of continuous prints that could maintain an image quality of 1.3 or higher was determined. Based on the number of continuous prints, the printing durability in a low-temperature, low-humidity environment was evaluated according to the following evaluation criteria. (Evaluation criteria) A: More than 20,000 sheets B: 15,000 to 20,000 sheets C: 10,000 to 15,000 sheets D: Less than 10,000 sheets In addition, the toner residual rate was calculated in the same manner as above from the cartridge weight X (g) at the time when image quality with a print density of 1.3 or more could no longer be maintained and the cartridge weight Y (g) before the toner was added.

[0160] d. Print durability test of toner after storage in a high-temperature, high-humidity environment under a high-temperature, high-humidity environment (HH durability test after high-temperature storage) First, as the toner after storage in a high-temperature, high-humidity environment, a toner after storage for 30 days in an environment at a temperature of 47°C and a humidity of 80% RH was prepared. Using this stored toner, a print durability test was conducted under the same conditions as the HH durability test described above, and the number of continuous prints that could maintain image quality with a fog value of 2.0 or less was determined. Based on the number of continuous prints, the print durability of the toner after storage in a high-temperature, high-humidity environment under a high-temperature, high-humidity environment was evaluated according to the following evaluation criteria. (Evaluation criteria) A: More than 20,000 sheets B: 15,000 to 20,000 sheets C: 10,000 to 15,000 sheets D: Less than 10,000 sheets

[0161] e. Environmental Charge Variation Using the same printer as used in the HH durability test, toner was placed in the toner cartridge of the developing device and left for 24 hours in a low-temperature, low-humidity environment (temperature 10°C, humidity 20% RH). Then, under the same environment, continuous printing of up to 100 sheets was performed at a print rate of 5%. After printing 100 sheets, the charge amount and toner suction amount of the toner on the developing roll were measured using a suction-type actual charge amount meter. The charge amount was divided by the toner suction amount to determine the toner charge amount Q1 (μC / g). Similarly, the toner charge amount Q2 (μC / g) was measured under a high-temperature, high-humidity environment (temperature 33.5°C, humidity 82% RH). The difference between Q1 and Q2 (Q1 - Q2) was calculated as an index of environmental charge variation, and the environmental charge variation was evaluated based on this difference (Q1 - Q2) according to the following evaluation criteria. Note that the smaller the difference between Q1 and Q2, the less the toner charge amount varies due to changes in temperature and humidity. (Evaluation criteria) A: Less than 15 μC / g B: 15 μC / g or more and less than 20 μC / g C: 20 μC / g or more and less than 25 μC / g D: 25 μC / g or more

[0162]

[0163]

[0164]

[0165] In Table 5, in Comparative Examples 2 and 3, |X×m Ｐ -F Ａ ×m Ａ Instead of |, |X×m Ｐ -F Ｂ ×m Ｂ In Comparative Example 7, F Ａ -F Ｂ Instead of F Ｃ -F Ｂ Calculate |X×m Ｐ -F Ａ ×m Ａ Instead of |, |X×m Ｐ -F Ｃ ×m Ｃ | was calculated.

[0166] [Discussion] When either the copolymers A and B as the positively chargeable charge control resin or the polar resin was missing, it was difficult to suppress bleeding of the release agent while suppressing printing defects. In Comparative Examples 1 and 6, only the copolymer A was used as the positively chargeable charge control resin, so when the toner was stored for 30 days in a high-temperature, high-humidity environment at a temperature of 47°C and a humidity of 80% RH, bleeding of the release agent was likely to occur, and in a print durability test under a high-temperature, high-humidity environment using the toner after such storage, fog was likely to occur. In Comparative Examples 1 and 6, only the copolymer A was used as the positively chargeable charge control resin, and the amount of the copolymer A was adjusted so that the toner had an appropriate charge amount. This is thought to be because the amount of resin unevenly distributed on the surface of the colored resin particles was insufficient, and a dense resin layer was not formed. In Comparative Examples 2 and 3, because only the copolymer B was used as the positively chargeable charge control resin, when the toner was stored for 30 days in a high-temperature, high-humidity environment at a temperature of 47°C and a humidity of 80% RH, bleed-out of the release agent was likely to occur, and fog was likely to occur in a print durability test conducted under a high-temperature, high-humidity environment using the toner after storage. Furthermore, fog was also likely to occur in a print durability test conducted under a high-temperature, high-humidity environment using the toner before storage. Since the amount of functional groups in the copolymer B is relatively small, it has a lower charge-imparting effect than the copolymer A, and is less likely to be unevenly distributed on the surface side of the colored resin particles. In Comparative Examples 2 and 3, because only the copolymer B was used as the positively chargeable charge control resin, the amount of resin unevenly distributed on the surface of the colored resin particles was insufficient, preventing the formation of a dense resin layer and failing to sufficiently increase the charge amount of the toner. In Comparative Example 4, because no polar resin was used, when the toner was stored for 30 days in a high-temperature, high-humidity environment at a temperature of 47°C and a humidity of 80% RH, bleeding out of the release agent was likely to occur, and in a print durability test under a high-temperature, high-humidity environment using the toner after the storage, fog was likely to occur, and further, in a print durability test under a low-temperature, low-humidity environment using the toner before the storage, print density was likely to decrease. In Comparative Example 4, because no polar resin was used, the amount of resin unevenly distributed on the surface of the colored resin particles was insufficient, a dense resin layer was not formed, and the charge amount of the toner was presumably too high.

[0167] In Comparative Example 5, a polar resin with an acid value exceeding 8.0 mgKOH / g was used, so the charge amount of the toner changed significantly with changes in temperature and humidity, and fog was likely to occur in a print durability test under a high-temperature, high-humidity environment. It is presumed that the toner of Comparative Example 5 was likely to suffer from charge leakage due to moisture absorption by the acid groups under a high-temperature, high-humidity environment due to the large amount of acid groups in the polar resin.

[0168] In Comparative Example 7, a copolymer having a functional group content of more than 6.0% by mass was used instead of the above-mentioned copolymer A, and therefore the print density was likely to decrease in a print durability test under a low-temperature, low-humidity environment. In Comparative Example 7, the copolymer having a functional group content of more than 6.0% by mass was likely to be unevenly distributed on the surface of the colored resin particles, and therefore, although a dense resin layer was formed, the charge amount of the toner became too high.

[0169] In Comparative Example 8, a copolymer having no functional groups was used instead of the copolymer B. Therefore, when the toner was stored for 30 days in a high-temperature, high-humidity environment at a temperature of 47°C and a humidity of 80% RH, bleeding of the release agent was likely to occur, and in a print durability test using the toner after such storage in a high-temperature, high-humidity environment, fog was likely to occur. The copolymer having no functional groups does not have a charge-imparting effect and is unlikely to be unevenly distributed on the surface side of the colored resin particles. Therefore, it is thought that in Comparative Example 8, the amount of resin unevenly distributed on the surface of the colored resin particles was insufficient because a copolymer having no functional groups was used instead of the copolymer B, and a dense resin layer was not formed.

[0170] In contrast, in each example, a positively chargeable charge control resin was used: copolymer A having a functional group content of 1.50% by mass or more and 6.00% by mass or less; copolymer B having a functional group content of 0.10% by mass or more and less than 1.50% by mass; and a polar resin having an acid value of 0.5 mgKOH / g or more and 5.0 mgKOH / g or less. Therefore, even when the toner was stored for 30 days in a high-temperature, high-humidity environment (temperature 47°C, humidity 80%), bleed-out of the release agent was suppressed. In a print durability test using the toner after storage in a high-temperature, high-humidity environment, the occurrence of fog was suppressed. Furthermore, in a print durability test using a cartridge filled with 500 g of toner, continuous printing was possible until the remaining toner amount was low, suppressing the occurrence of printing defects, both in a low-temperature, low-humidity environment and a high-temperature, high-humidity environment. Furthermore, changes in the charge amount of the toner due to changes in temperature and humidity were suppressed.

[0171] Furthermore, comparing Examples 1, 16, and 17, Examples 1 and 17, which used a monoester as a release agent, suppressed the occurrence of fogging in a high-temperature, high-humidity environment compared to Example 16, which used a diester. This is presumably because the monoester is more effective in suppressing toner aggregation in a high-temperature, high-humidity environment. Comparing Examples 1 and 17, Example 1, which used behenyl stearate as a release agent, suppressed the decrease in print density in a low-temperature, low-humidity environment compared to Example 17, which used behenyl behenate as a release agent. This is presumably because behenyl stearate is more effective in improving the low-temperature fixability of the toner, making it easier for the toner to melt and spread during fixation, thereby suppressing the decrease in print density.

[0172] Comparing Example 1 and Example 18, Example 1, which used an SIS composition as the styrene-based thermoplastic elastomer, suppressed bleeding of the release agent when the toner was stored in a high-temperature, high-humidity environment compared to Example 18, which used an SBS composition. This was because the use of the SIS composition improved the dispersibility of the release agent when the toner was used after storage.

[0173] Comparing Example 1 and Example 19, Example 1, which used core-shell type colored resin particles, suppressed the occurrence of printing defects in high temperature and high humidity environments and low temperature and low humidity environments compared to Example 19, which used colored resin particles without a shell. This is presumably because, in the print durability test, the shell suppressed the embedding of the external additive, thereby suppressing changes in the charge amount due to toner deterioration.

Claims

1. A toner containing a binder resin, a colorant, a positively charged charge control resin, and a release agent, as well as colored resin particles and an external additive. The positively charged charge-controlling resin contains copolymer A, which contains functional group-containing monomer units in a proportion of 1.50% by mass or more and 6.00% by mass or less, and copolymer B, which contains functional group-containing monomer units in a proportion of 0.10% by mass or more and less than 1.50% by mass. The toner further contains a polar resin having an acid value of 0.5 mg KOH / g or more and 8.0 mg KOH / g or less, wherein the colored resin particles further contain a polar resin.

2. A toner containing a binder resin, a colorant, a positively charged charge control resin, and a release agent, as well as colored resin particles and an external additive. The positively charged charge-controlling resin contains copolymer A, which contains functional group-containing monomer units in a proportion of 1.50% by mass or more and 6.00% by mass or less, and copolymer B, which contains functional group-containing monomer units in a proportion of 0.10% by mass or more and less than 1.50% by mass. The toner further contains a polar resin having an acid value of 0.5 mg KOH / g or more and 5.0 mg KOH / g or less, wherein the colored resin particles further contain a polar resin.

3. The toner according to claim 1 or 2, wherein in each copolymer contained as the positively charged charge control resin, when F is the proportion (mass%) of functional group-containing monomer units and m is the content (parts by mass) of the copolymer relative to 100 parts by mass of the binder resin, the sum of the products of F and m (F × m) calculated for each copolymer is 2.00 or more and 6.00 or less.

4. Let X be the acid value (mgKOH / g) of the polar resin, and m be the content (parts by mass) of the polar resin with respect to 100 parts by mass of the binder resin. Ｐ Let F be the ratio (mass %) of the functional group-containing monomer unit in the copolymer A. Ａ Let m be the content (parts by mass) of the copolymer A with respect to 100 parts by mass of the binder resin. Ａ When X and m ｐ The product of (X × m Ｐ ), and F Ａ And m Ａ The product of (F Ａ × m Ａ ), the absolute value of the difference (|X × m Ｐ − F Ａ × m Ａ |) is 2.50 or less. The toner according to claim 1 or 2.

5. The toner according to claim 1 or 2, wherein the mold release agent contains a fatty acid ester compound having a number average molecular weight (Mn) of 500 or more and less than 2,000 in a proportion of 5 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the binder resin.

6. The toner according to claim 1 or 2, wherein the colored resin particles further contain a styrene-based thermoplastic elastomer in a proportion of 1 to 10 parts by mass per 100 parts by mass of the binder resin.

7. Image forming method using the toner described in claim 1 or 2.