Toner

Abstract

To provide a toner that has excellent fixability, can be charged to a desired charge amount even when images are continuously formed in various environments such as a normal-temperature and normal-humidity environment, a high-temperature and high-humidity environment, and a low-temperature and low-humidity environment, and can form an image with little fogging and a desired density.SOLUTION: The toner includes toner particles. The toner particles each include a toner core. The toner cores contain a binder resin, a black colorant, and carbon nanotubes. The toner cores have a carbon nanotube content of at least 0.10% by mass and no greater than 1.00% by mass.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a toner. [Background technology]

[0002] In order to satisfy low-temperature fixability in a recycling system, Patent Document 1 discloses a toner containing a binder resin containing a predetermined low-molecular-weight resin component, a colorant, and a release agent. The resin softening coefficient A of the predetermined low-molecular-weight resin component satisfies the formula "A>0.165." The storage modulus G'(Tfb) of the predetermined low-molecular-weight resin component, when the flow-start temperature measured by a high-speed flow tester is Tfb, satisfies the formula "G'(Tfb)≦1×10 4 " is satisfied. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2012 / 101875 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the toner described in Patent Document 1 is insufficient in terms of stably charging the toner and forming high-quality images when the environment, such as temperature and humidity, changes.

[0005] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a toner that has excellent fixing properties, can be charged to a desired charge amount, and can form images of a desired density with little fog, even when images are continuously formed under various environments such as a normal temperature and normal humidity environment, a high temperature and high humidity environment, and a low temperature and low humidity environment. [Means for solving the problem]

[0006] The toner of the present invention includes toner particles. The toner particles have a toner core. The toner core contains a binder resin, a black colorant, and carbon nanotubes. The content of the carbon nanotubes in the toner core is 0.10% by mass or more and 1.00% by mass or less. [Effects of the Invention]

[0007] The toner of the present invention has excellent fixing properties, and can be charged to a desired charge amount even when images are continuously formed under various environments such as a normal temperature and normal humidity environment, a high temperature and high humidity environment, and a low temperature and low humidity environment, and can form images of a desired density with little fog. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing a cross-sectional structure of a non-capsule toner particle, which is an example of a toner particle contained in a toner according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing a cross-sectional structure of a capsule toner particle, which is another example of a toner particle contained in a toner according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] The following describes in detail the embodiments of the present invention, but the present invention is not limited to the following embodiments and can be implemented with appropriate modifications within the scope of the object of the present invention. Note that redundant explanations may be omitted as appropriate, but this does not limit the gist of the invention.

[0010] First, the terms used in this embodiment will be explained. A toner is an aggregate of toner particles (for example, powder). An external additive is an aggregate of external additive particles (for example, powder). Unless otherwise specified, the evaluation results (values ​​indicating shape, physical properties, etc.) of a powder (more specifically, powder of toner particles, powder of external additive particles, etc.) are the number average of values ​​measured for each of a considerable number of particles selected from the powder. Volume median diameter (D 50Unless otherwise specified, the mean diameter is the median diameter measured using a laser diffraction / scattering particle size analyzer (LA-950, manufactured by Horiba, Ltd.). Unless otherwise specified, the number-average primary particle diameter is the number-average value of the equivalent circle diameters of primary particles (Heywood diameter: the diameter of a circle having the same area as the projected area of ​​a primary particle) measured using a field emission scanning electron microscope (JEOL Ltd., JSM-6700F). The number-average primary particle diameter is the number-average value of the equivalent circle diameters of, for example, 50 primary particles. Unless otherwise specified, the softening point (Tm) is a value measured using a high-speed flow tester (CFT-500D, manufactured by Shimadzu Corporation). In the S-shaped curve (horizontal axis: temperature, vertical axis: stroke) measured using the high-speed flow tester, the temperature at which "(baseline stroke value + maximum stroke value) / 2" is obtained corresponds to Tm (softening point). The glass transition point (Tg) is a value determined from the change point in the specific heat of the binder resin using a differential scanning calorimeter (DSC). More specifically, the glass transition point of the object to be measured can be determined by measuring the endothermic curve of the object to be measured using a differential scanning calorimeter (Seiko Instruments Inc.'s "DSC-6220") as the measuring device. 10 mg of the object to be measured is placed in an aluminum pan. An empty aluminum pan is used as a reference. Measurement is performed at room temperature and normal humidity under conditions of a measurement temperature range of 25°C to 200°C and a heating rate of 10°C / min. The glass transition point of the object to be measured can be determined from the obtained endothermic curve. Unless otherwise specified, the acid value is a value measured in accordance with JIS (Japanese Industrial Standards) K0070-1992. Unless otherwise specified, the number average molecular weight (Mn) and mass average molecular weight (Mw) are values ​​measured using gel permeation chromatography (GPC). For example, the number average molecular weight (Mn) and mass average molecular weight (Mw) can be determined using a calibration curve prepared in advance using a standard polystyrene resin. Unless otherwise specified, the nitrogen adsorption specific surface area is a value measured in accordance with JIS (Japanese Industrial Standards) K6217. Unless otherwise specified, the DBP absorption amount is a value measured in accordance with JIS (Japanese Industrial Standards) K6221. Unless otherwise specified, the relative humidity is a value measured in accordance with JIS (Japanese Industrial Standards) Z8806:2001.The compound name may be followed by "based" to refer to the compound and its derivatives in a comprehensive manner. When the compound name is followed by "based" to refer to the name of a polymer, it means that the repeating unit of the polymer is derived from the compound or its derivative. Acrylic and methacrylic may be collectively referred to as "(meth)acrylic." Acrylonitrile and methacrylonitrile may be collectively referred to as "(meth)acrylonitrile." Acrylate and methacrylate may be collectively referred to as "(meth)acrylate." Unless otherwise specified, each component described in this specification may be used alone or in combination of two or more. The terms used in this embodiment have been explained above.

[0011] [toner] The toner of this embodiment includes toner particles. The toner particles have a toner core. The toner core contains a binder resin, a black colorant, and carbon nanotubes. The carbon nanotube content in the toner core is 0.10% by mass or more and 1.00% by mass or less.

[0012] The toner of the present embodiment, having the above-described configuration, has excellent fixability (for example, low-temperature fixability and fixation rate to a recording medium), and can be charged to a desired charge amount even when images are continuously formed under various environments such as a normal temperature and normal humidity environment, a high temperature and high humidity environment, and a low temperature and low humidity environment, and can form images with a desired density and little fog. The reason for this is presumed to be as follows.

[0013] In this embodiment, the toner core contains carbon nanotubes. The carbon nanotube content in the toner core is 0.10% by mass or more. Because carbon nanotubes have high conductivity, when toner particles are triboelectrically charged in the developing unit of an image forming apparatus, they are triboelectrically charged well even under various environments. As a result, even when images are continuously formed under various environments, the toner can be charged to a desired charge amount, and images of a desired density can be formed. Furthermore, because carbon nanotubes have high conductivity, charge transfer occurs quickly between toner particles even under various environments. As a result, the toner has a sharp charge distribution, and images with less fogging can be formed even when images are continuously formed under various environments.

[0014] On the other hand, if the carbon nanotube content in the toner core is too high, the charge will be excessively removed from the frictionally charged toner. Therefore, the carbon nanotube content in the toner core is set to 1.00% by mass or less. As a result, excessive charge removal from the frictionally charged toner can be suppressed, and excessive reduction in the charge amount of the toner can be suppressed.

[0015] In addition to high electrical conductivity, carbon nanotubes also have high thermal conductivity. Therefore, when fixing toner to a recording medium, the heat of the fixing device of the image forming apparatus is quickly transferred to the toner. As a result, the low-temperature fixability of the toner and the fixation rate of the toner to the recording medium are improved.

[0016] The above has explained why the toner of this embodiment has excellent fixing properties, and can be charged to the desired charge amount and can form images of the desired density with little fog, even when images are continuously formed in various environments such as a normal temperature and normal humidity environment, a high temperature and high humidity environment, and a low temperature and low humidity environment.

[0017] The toner of this embodiment is suitably used, for example, as a positively charged toner, for developing electrostatic latent images. The toner may be used as a single-component developer. The toner may be mixed with a carrier using a mixing device (e.g., a ball mill) and used as a two-component developer. When used as a single-component developer, the toner is charged by friction with a developing sleeve or a toner charging member in a developing device. An example of a toner charging member is a doctor blade. When used as a two-component developer, the toner is charged by friction with a carrier in a developing device. Details of the toner of this embodiment will be further described below.

[0018] <Toner particle structure> The toner particles are non-encapsulated toner particles or encapsulated toner particles. The structure of the toner particles contained in the toner will be described below with reference to FIGS. 1 and 2. FIG. 1 shows the cross-sectional structure of a non-encapsulated toner particle 1, which is an example of a toner particle contained in the toner of this embodiment. FIG. 2 shows the cross-sectional structure of an encapsulated toner particle 10, which is another example of a toner particle contained in the toner of this embodiment.

[0019] First, a case where the toner particles are non-encapsulated toner particles 1 will be described. As shown in FIG. 1, non-encapsulated toner particles 1 have toner base particles 2 and external additive particles 3. Hereinafter, "toner base particles 2 possessed by non-encapsulated toner particles 1" may be referred to as "non-encapsulated toner base particles 2." The external additive particles 3 adhere to the surface of the non-encapsulated toner base particles 2. The non-encapsulated toner base particles 2 have toner cores 2a. The non-encapsulated toner base particles 2 do not have a shell layer 2b (see FIG. 2), and the toner cores 2a correspond to the non-encapsulated toner base particles 2. In other words, the toner cores 2a that are not covered with the shell layer 2b correspond to the non-encapsulated toner base particles 2.

[0020] Next, a case where the toner particles are encapsulated toner particles 10 will be described. As shown in FIG. 2, the encapsulated toner particles 10 include toner base particles 20 and external additive particles 3. Hereinafter, the "toner base particles 20 included in the encapsulated toner particles 10" may be referred to as the "encapsulated toner base particles 20." The external additive particles 3 are attached to the surfaces of the encapsulated toner base particles 20. The encapsulated toner base particles 20 include a toner core 2a and a shell layer 2b that covers the surface of the toner core 2a. The shell layer 2b may cover the entire surface of the toner core 2a. The shell layer 2b may not have any irregularities. The thickness of the shell layer 2b is not particularly limited, but is preferably 0.03 μm to 1 μm, more preferably 0.04 μm to 0.7 μm, particularly preferably 0.05 μm to 0.5 μm, and most preferably 0.05 μm to 0.3 μm.

[0021] Although the structure of the toner particles has been described above, the structure of the toner particles contained in the toner of the present embodiment is not limited to the structure shown in FIGS. 1 and 2. For example, the non-encapsulated toner particles 1 may not have external additive particles 3. When the non-encapsulated toner particles 1 do not have external additive particles 3, the non-encapsulated toner base particles 2 correspond to the non-encapsulated toner particles 1. For example, the encapsulated toner particles 10 may not have external additive particles 3. When the non-encapsulated toner particles 10 do not have external additive particles 3, the encapsulated toner base particles 20 correspond to the encapsulated toner particles 10. For example, the shell layer 2b may cover only a portion of the surface of the toner core 2a, rather than the entire surface of the toner core 2a. The adhesion state of the external additive particles 3 and the coating state of the shell layer 2b can be confirmed using a scanning electron microscope (SEM). For example, the surface of the shell layer 2b may have irregularities. When the shell layer 2b is made of resin particles, irregularities due to the shape of the resin particles are formed on the surface of the shell layer 2b. The degree of smoothness of the shell layer 2b can be confirmed by observing the cross section of the encapsulated toner particle 10 using a transmission electron microscope (TEM). Hereinafter, the non-encapsulated toner particle 1 and the encapsulated toner particle 10 may be collectively referred to as "toner particles." Furthermore, the non-encapsulated toner base particle 2 and the encapsulated toner base particle 20 may be collectively referred to as "toner base particles." Above, the structure of the toner particles contained in the toner has been described with reference to FIGS. 1 and 2. Below, the toner core, shell layer, external additives, and a method for producing the toner will be described.

[0022] <Toner core> The toner core of the toner particle contains a binder resin, a black colorant, and carbon nanotubes. The toner core may further contain an internal additive (for example, at least one of a release agent, a charge control agent, a magnetic powder, and other known additives) as needed. In order to obtain a toner suitable for image formation, the volume median diameter (D 50 ) is preferably 4 μm or more and 9 μm or less.

[0023] (binder resin) Examples of binder resins include thermoplastic resins. Examples of thermoplastic resins include styrene resins, acrylic resins, styrene-acrylic resins, polyethylene resins, polypropylene resins, vinyl chloride resins, polyester resins, polyamide resins, polyurethane resins, polyvinyl alcohol resins, vinyl ether resins, N-vinyl resins, and styrene-butadiene resins. Among these resins, polystyrene resins and polyester resins are preferred in terms of the dispersibility of the black colorant in the binder resin, the chargeability of the toner, and the fixability to the recording medium. Polystyrene resins and polyester resins will be described below.

[0024] Polystyrene resins may be styrene homopolymers or copolymers with other monomers copolymerizable with styrene. Examples of other copolymerizable monomers copolymerizable with styrene include p-chlorostyrene, vinylnaphthalene, ethylenically unsaturated monoolefins, vinyl halides, vinyl esters, (meth)acrylic acid esters, other acrylic acid derivatives, vinyl ketones, and N-vinyl compounds. Examples of ethylenically unsaturated monoolefins include ethylene, propylene, butylene, and isobutylene. Examples of vinyl halides include vinyl chloride, vinyl bromide, and vinyl fluoride. Examples of vinyl esters include vinyl acetate, vinyl propionate, vinyl benzoate, and vinyl butyrate. Examples of (meth)acrylic acid esters include methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, α-methyl chloroacrylate, methyl methacrylate, ethyl methacrylate, and butyl methacrylate. Examples of other acrylic acid derivatives include acrylonitrile, methacrylonitrile, and acrylamide. Examples of vinyl ethers include vinyl methyl ether and vinyl isobutyl ether. Examples of vinyl ketones include vinyl methyl ketone, vinyl ethyl ketone, and methyl isopropenyl ketone. Examples of N-vinyl compounds include N-vinylpyrrole, N-vinylcarbazole, N-vinylindole, and N-vinylpyrrolidone.

[0025] The polyester resin can be obtained by polycondensation of a divalent or trivalent or higher alcohol monomer and a divalent or trivalent or higher carboxylic acid monomer.

[0026] Examples of dihydric alcohol monomers include diols and bisphenols. Examples of diols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 2-butene-1,4-diol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. Examples of bisphenols include bisphenol A, hydrogenated bisphenol A, bisphenol A ethylene oxide adduct, and bisphenol A propylene oxide adduct.

[0027] Examples of trihydric or higher alcohol monomers include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene.

[0028] Examples of dicarboxylic acid monomers include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, alkylsuccinic acids (more specifically, n-butylsuccinic acid, isobutylsuccinic acid, n-octylsuccinic acid, n-dodecylsuccinic acid, isododecylsuccinic acid, etc.), and alkenylsuccinic acids (more specifically, n-butenylsuccinic acid, isobutenylsuccinic acid, n-octenylsuccinic acid, n-dodecenylsuccinic acid, isododecenylsuccinic acid, etc.).

[0029] Examples of trivalent or higher carboxylic acid monomers include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra(methylenecarboxyl)methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, and empol trimer acid.

[0030] The divalent, trivalent or higher carboxylic acid monomer may be used after being derivatized into an ester-forming derivative (more specifically, an acid halide, an acid anhydride, a lower alkyl ester, etc.). Here, the term "lower alkyl" refers to an alkyl group having 1 to 6 carbon atoms.

[0031] The polyester resin is preferably a condensation polymer of at least one bisphenol, at least one dicarboxylic acid monomer, and at least one tricarboxylic acid monomer, and more preferably a condensation polymer of a bisphenol A ethylene oxide adduct, a bisphenol A propylene oxide adduct, terephthalic acid, alkenyl succinic acid, and trimellitic acid.

[0032] The softening point of the binder resin is preferably 70°C or higher and 130°C or lower, and more preferably 80°C or higher and 120°C or lower.

[0033] The glass transition temperature (Tg) of the binder resin is preferably 40° C. or higher and 70° C. or lower. The lower the glass transition temperature, the better the low-temperature fixability of the toner tends to be. The higher the glass transition temperature, the better the heat-resistant storage stability of the toner tends to be.

[0034] The mass average molecular weight (Mw) of the binder resin is not particularly limited, but is preferably 20,000 or more and 300,000 or less, and more preferably 30,000 or more and 200,000 or less.

[0035] Furthermore, when the binder resin is a polystyrene resin, the polystyrene resin preferably has peaks in both a low molecular weight region and a high molecular weight region in its molecular weight distribution measured by gel permeation chromatography or the like. Specifically, the peak in the low molecular weight region preferably exists in a molecular weight range of 3,000 to 20,000, and the peak in the high molecular weight region preferably exists in a molecular weight range of 300,000 to 1,500,000. Furthermore, for a polystyrene resin having such a molecular weight distribution, the ratio (Mw / Mn) of the number average molecular weight (Mn) to the mass average molecular weight (Mw) is preferably 10 or more. When the polystyrene resin has peaks in the low molecular weight region and the high molecular weight region within such ranges in its molecular weight distribution, a toner having excellent low-temperature fixing properties and capable of suppressing high-temperature offset can be obtained.

[0036] The thermoplastic resins mentioned above are preferred as binder resins because they have good fixability to recording media. However, instead of using a thermoplastic resin alone, a crosslinking agent or a thermosetting resin may be added to the thermoplastic resin. By adding a crosslinking agent or a thermosetting resin to introduce a partial crosslinked structure into the binder resin, the heat-resistant storage stability and durability of the toner can be improved without reducing the fixability of the toner. When a thermosetting resin is used, the amount of crosslinked portions (gel amount) of the binder resin extracted using a Soxhlet extractor is preferably 10% by mass or less, more preferably 0.1% by mass or more and 10% by mass or less, based on the mass of the binder resin.

[0037] Examples of thermosetting resins that can be used together with the thermoplastic resin include epoxy resins and cyanate resins, with epoxy resins being preferred. Examples of epoxy resins include bisphenol A epoxy resins, hydrogenated bisphenol A epoxy resins, novolac epoxy resins, polyalkylene ether epoxy resins, and cycloaliphatic epoxy resins.

[0038] (black colorant) Examples of black colorants include carbon black and aniline black. Carbon black is classified into furnace black, acetylene black, lamp black, and channel black depending on the production method. Furnace black is produced by the furnace method. Acetylene black is produced by the acetylene method. Lamp black is produced by the lamp smoke method. Channel black is produced by the channel method.

[0039] The black colorant is preferably carbon black, and more preferably furnace black or acetylene black. Furnace black is easy to mass-produce with high yield and is relatively inexpensive. Therefore, using furnace black as a black colorant can improve cost benefits in toner production. On the other hand, acetylene black has high conductivity and also functions as a conductivity imparting agent. Therefore, by using a combination of highly conductive carbon nanotubes and highly conductive acetylene black, it is possible to suitably charge to a desired charge amount even when images are continuously formed under various environments.

[0040] A masterbatch in which a black colorant is dispersed in advance in a resin such as a thermoplastic resin can also be used. When a masterbatch of a black colorant is used, the resin contained in the masterbatch is preferably the same resin as the binder resin.

[0041] The number average primary particle diameter of the black colorant is preferably 1 nm or more and 50 nm or less, and more preferably 20 nm or more and 30 nm or less. The nitrogen adsorption specific surface area of ​​the black colorant is 50 m 2 / g or more 200m 2 / g or less, and 2 / g or more 140m 2 / g or less. The DBP absorption of the black colorant is preferably 50 cm 3 / 100g or more 200cm 3 / 100g or less is preferable, and 90cm 3 / 100g or more 110cm3 It is more preferable that the amount is 100g or less.

[0042] The content of the black colorant is preferably 4% by mass or more and 10% by mass or less, and more preferably 5% by mass or more and 9% by mass or less, based on the mass of the toner core.

[0043] The presence of the black colorant can be confirmed by observing the cross section of the toner particle using a transmission electron microscope (TEM). In order to achieve a desired color tone, the toner core may further contain a colorant of a color other than black.

[0044] (carbon nanotubes) As already mentioned, the toner core of the toner particles contains carbon nanotubes. Because the carbon nanotubes are less susceptible to environmental changes, it is preferable that the carbon nanotubes are added internally to the toner base particles (particularly the toner core), but not externally to the toner base particles. In other words, it is preferable that the toner particles do not contain carbon nanotubes as an external additive.

[0045] As already mentioned, the carbon nanotube content in the toner core is 0.10% by mass or more and 1.00% by mass or less. In order to achieve excellent fixability, charge to a desired amount even when images are continuously formed under various environments, and form images with a desired density and little fog, the carbon nanotube content in the toner core is preferably 0.20% by mass or more and 0.90% by mass or less, more preferably 0.30% by mass or more and 0.80% by mass or less, and even more preferably 0.40% by mass or more and 0.70% by mass or less.

[0046] In order to achieve the desired color tone, the ratio WCN / WBK of the mass of carbon nanotubes WCN to the mass WBK of the black colorant is preferably 0.010 or more and 0.150 or less, more preferably 0.020 or more and 0.120 or less, and even more preferably 0.050 or more and 0.100 or less.

[0047] In order to achieve excellent fixability, chargeability to a desired charge amount even when images are continuously formed under various environments, and formation of images of a desired density with little fog, the content of carbon nanotubes is preferably 0.10 parts by mass or more and 1.20 parts by mass or less, more preferably 0.12 parts by mass or more and 1.00 parts by mass or less, and even more preferably 0.40 parts by mass or more and 0.80 parts by mass or less, relative to 100.0 parts by mass of binder resin.

[0048] The carbon nanotubes are preferably single-walled carbon nanotubes or multi-walled carbon nanotubes. Single-walled carbon nanotubes have a single cylindrical structure. Multi-walled carbon nanotubes have a structure in which multiple (e.g., two or more) cylinders with different diameters are nested together.

[0049] The inner diameter of the carbon nanotubes is preferably 5 nm to 50 nm, more preferably 7 nm to 40 nm. The length of the carbon nanotubes is preferably 1 μm to 10 μm. However, since the carbon nanotubes are cut to some extent by kneading and pulverizing in the toner core formation step during toner production, carbon nanotubes longer than 10 μm can also be used. The carbon nanotubes can be confirmed by observing the cross section of the toner particles using a transmission electron microscope (TEM).

[0050] (mold release agent) For the purpose of improving fixability and offset resistance, the toner core preferably contains a release agent. The release agent is not particularly limited, but wax is preferred from the viewpoint of more efficiently suppressing the occurrence of offset and image smearing (i.e., staining around the image when the image is rubbed). Examples of waxes include carnauba wax, synthetic ester wax, polyethylene wax, polypropylene wax, fluororesin wax, Fischer-Tropsch wax, paraffin wax, montan wax, and rice wax.

[0051] When a polyester resin is used as the binder resin, from the viewpoint of compatibility, one or more release agents selected from the group consisting of carnauba wax, synthetic ester wax, and polyethylene wax are preferably used as the release agent.

[0052] When a polystyrene resin is used as the binder resin, one or more release agents selected from the group consisting of Fischer-Tropsch wax and paraffin wax are preferably used as the release agent, also from the viewpoint of compatibility. Fischer-Tropsch wax is a linear hydrocarbon compound with few isostructural molecules and few side chains. Fischer-Tropsch wax is produced by utilizing the Fischer-Tropsch reaction, which is a catalytic hydrogenation reaction of carbon monoxide.

[0053] The Fischer-Tropsch wax is preferably one having a mass average molecular weight of 1,000 or more and a bottom temperature of the endothermic peak observed by DSC measurement in the range of 100° C. to 120° C. Examples of such Fischer-Tropsch wax include Sasolwax C1 (bottom temperature of the endothermic peak: 106.5° C.), Sasolwax C105 (bottom temperature of the endothermic peak: 102.1° C.), and Sasolwax SPRAY (bottom temperature of the endothermic peak: 102.1° C.), all of which are available from Sasol.

[0054] The content of the release agent is preferably 1% by mass or more and 10% by mass or less relative to the mass of the toner core. The higher the content of the release agent, the more effectively the occurrence of offset and image smearing in the formed image can be suppressed. On the other hand, the lower the content of the release agent, the less likely the toner particles are to fuse together, improving the heat-resistant storage stability of the toner.

[0055] (charge control agent) In order to improve the charge level and charge rise characteristics of the toner and obtain a toner with excellent durability and stability, the toner core preferably contains a charge control agent. The charge rise characteristics of the toner are an index of whether the toner can be charged to a predetermined charge level in a short time. When developing by positively charging the toner, a positively charging charge control agent is used. On the other hand, when developing by negatively charging the toner, a negatively charging charge control agent is used.

[0056] Examples of positively charging charge control agents include azine compounds, direct dyes, nigrosine compounds, acid dyes, metal salts of naphthenic acid, metal salts of higher fatty acids, alkoxylated amines, alkylamides, and quaternary ammonium salt compounds. Examples of azine compounds include pyridazine, pyrimidine, pyrazine, 1,2-oxazine, 1,3-oxazine, 1,4-oxazine, 1,2-thiazine, 1,3-thiazine, 1,4-thiazine, 1,2,3-triazine, 1,2,4-triazine, 1,3,5-triazine, 1,2,4-oxadiazine, 1,3,4-oxadiazine, 1,2,6-oxadiazine, 1,3,4-thiadiazine, 1,3,5-thiadiazine, 1,2,3,4-tetrazine, 1,2,4,5-tetrazine, 1,2,3,5-tetrazine, 1,2,4,6-oxatriazine, 1,3,4,5-oxatriazine, phthalazine, quinazoline, and quinoxaline. Examples of direct dyes include Azin Fast Red FC, Azin Fast Red 12BK, Azin Violet BO, Azin Brown 3G, Azin Light Brown GR, Azin Dark Green BH / C, Azin Deep Black EW, and Azin Deep Black 3RL. Examples of nigrosine compounds include nigrosine, nigrosine salts, and nigrosine derivatives. Examples of acid dyes include Nigrosine BK, Nigrosine NB, and Nigrosine Z. Examples of quaternary ammonium salt compounds include benzyldecylhexylmethylammonium chloride and decyltrimethylammonium chloride. Among these positively charged charge control agents, quaternary ammonium salt compounds are preferred because they provide a more rapid charge buildup.

[0057] Resins having a quaternary ammonium salt, a carboxylate, or a carboxy group as a functional group can also be used as positively charged charge control agents. More specifically, examples include styrene resins having a quaternary ammonium salt, acrylic resins having a quaternary ammonium salt, styrene-acrylic resins having a quaternary ammonium salt, polyester resins having a quaternary ammonium salt, styrene resins having a carboxylate, acrylic resins having a carboxylate, styrene-acrylic resins having a carboxylate, polyester resins having a carboxylate, styrene resins having a carboxylate, acrylic resins having a carboxylate, styrene-acrylic resins having a carboxylate, and polyester resins having a carboxylate. The molecular weight of these resins is not particularly limited, and they may be oligomers or polymers.

[0058] Among resins that can be used as positively charged charge control agents, styrene-acrylic resins having a quaternary ammonium salt as a functional group are more preferred because the charge amount can be easily adjusted to a value within a desired range. In styrene-acrylic resins having a quaternary ammonium salt as a functional group, examples of acrylic acid monomers copolymerizable with styrene include (meth)acrylic acid alkyl esters. Examples of (meth)acrylic acid alkyl esters include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, and isobutyl methacrylate.

[0059] Examples of quaternary ammonium salt monomers that can be used in copolymerization of styrene-acrylic resins having a quaternary ammonium salt as a functional group include dialkylaminoalkyl(meth)acrylates, dialkyl(meth)acrylamides, and monomers derived from dialkylaminoalkyl(meth)acrylamides via a quaternization process. Examples of dialkylaminoalkyl(meth)acrylates include dimethylaminoethyl(meth)acrylate, diethylaminoethyl(meth)acrylate, dipropylaminoethyl(meth)acrylate, and dibutylaminoethyl(meth)acrylate. Examples of dialkyl(meth)acrylamides include dimethylmethacrylamide. Examples of dialkylaminoalkyl(meth)acrylamides include dimethylaminopropylmethacrylamide. Hydroxy group-containing polymerizable monomers (more specifically, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate, N-methylol(meth)acrylamide, etc.) can also be used in combination during polymerization.

[0060] Examples of negatively chargeable charge control agents include organometallic complexes, chelate compounds, monoazo metal complexes, acetylacetone metal complexes, aromatic hydroxycarboxylic acids, aromatic dicarboxylic acid metal complexes, aromatic monocarboxylic acids, aromatic polycarboxylic acids, aromatic monocarboxylic acids, aromatic polycarboxylic acids, and phenol derivatives (more specifically, bisphenols, etc.). The aromatic monocarboxylic acids and aromatic polycarboxylic acids may each be their metal salts, anhydrides, or ester derivatives. Among these, organometallic complexes and chelate compounds are preferred. As organometallic complexes and chelate compounds, acetylacetone metal complexes (more specifically, aluminum acetylacetonate and iron(II) acetylacetonate, etc.), salicylic acid metal complexes (more specifically, chromium 3,5-di-tert-butylsalicylate, etc.), and salicylic acid metal salts are more preferred.

[0061] The content of the charge control agent is preferably 0.1% by mass or more and 10% by mass or less relative to the mass of the toner core. The higher the content of the charge control agent, the easier it is to stably charge the toner to a predetermined polarity and obtain an image of the desired density. Furthermore, the higher the content of the charge control agent, the easier it is to uniformly disperse the charge control agent, making it less likely that fog will occur in the formed image and effectively suppressing contamination of the image carrier by toner components. On the other hand, the lower the content of the charge control agent, the easier it is to ensure sufficient charging properties even under high temperature and high humidity conditions.

[0062] (magnetic powder) The toner of this embodiment can be used as a magnetic one-component developer by optionally incorporating magnetic powder into the toner core. The magnetic powder is not particularly limited, but examples thereof include iron (more specifically, ferrite, magnetite, etc.), ferromagnetic metals (more specifically, cobalt, nickel, etc.), alloys containing iron and / or ferromagnetic metals, compounds containing iron and / or ferromagnetic metals, ferromagnetic alloys that have been subjected to ferromagnetic treatment (more specifically, heat treatment, etc.), and chromium dioxide.

[0063] The particle size of the magnetic powder is not particularly limited, but is preferably 0.1 μm to 1.0 μm, and more preferably 0.1 μm to 0.5 μm. When magnetic powder with a particle size in this range is used, it is easy to uniformly disperse the magnetic powder in the binder resin.

[0064] For the purpose of improving dispersibility in the binder resin, magnetic powder that has been surface-treated with a surface treatment agent (more specifically, a titanium coupling agent, a silane coupling agent, or the like) may be used.

[0065] When magnetic powder is contained in the toner core, the content of the magnetic powder is preferably 0.1% by mass or more and 5% by mass or less, and more preferably 0.1% by mass or more and 3% by mass or less, relative to the mass of the toner core. The lower the content of magnetic powder, the easier it is to improve the fixability of the toner, and the easier it is to form images of the desired density when forming images continuously for a long period of time. On the other hand, the higher the content of magnetic powder, the less likely fog will occur in the formed image, and the more likely it is that a decrease in image density will be suppressed when forming images continuously for a long period of time.

[0066] <Shell layer> The shell layer is formed of, for example, resin particles. Hereinafter, the "resin particles forming the shell layer" may be referred to as "shell resin particles."

[0067] <Shell resin particles> The shell resin particles contain a resin. Hereinafter, the "resin contained in the shell resin particles" may be referred to as the "shell resin." The content of the shell resin in the shell resin particles is preferably 90% by mass or more, more preferably 95% by mass or more, and particularly preferably 100% by mass.

[0068] The shell resin is preferably a charge control resin. By forming the shell layer from a charge control resin, the toner can be charged to a desired charge amount even when images are continuously formed in various environments, such as a normal temperature and normal humidity environment, a high temperature and high humidity environment, and a low temperature and low humidity environment. As a result, images of a desired density can be suitably formed in various environments.

[0069] The shell resin is preferably a polymer of a monomer having an unsaturated bond, since this facilitates the formation of a shell layer having a predetermined structure. When the shell resin is a charge-controlling resin, the charge-controlling resin is preferably a copolymer of a monomer having an unsaturated bond and a chargeable functional group that imparts chargeability to the shell resin, and a monomer having an unsaturated bond but no chargeable functional group.

[0070] When the shell resin is to be made positively chargeable, examples of the positively chargeable functional group include a nitrogen-containing polar functional group such as a quaternary ammonium group, while when the shell resin is to be made negatively chargeable, examples of the negatively chargeable functional group include a fluorine-substituted hydrocarbon group or a sulfo group.

[0071] The monomer having an unsaturated bond is not particularly limited as long as it can synthesize a resin having sufficient physical properties as a shell layer. A vinyl monomer is preferred as the monomer having an unsaturated bond. The α-position of the vinyl group contained in the vinyl monomer may be substituted with an alkyl group. The alkyl group that the vinyl group may have is preferably an alkyl group having 1 to 6 carbon atoms, more preferably a methyl group or an ethyl group, and particularly preferably a methyl group. The vinyl group contained in the vinyl monomer may also be substituted with a halogen atom. The halogen atom that the vinyl group may have is preferably a chlorine atom or a bromine atom, more preferably a chlorine atom.

[0072] As the monomer having an unsaturated bond but not having a chargeable functional group, a vinyl monomer having no chargeable functional group is preferred. As the monomer having a chargeable functional group and an unsaturated bond, a vinyl monomer having a chargeable functional group is preferred. When imparting positive chargeability to the shell resin, as the vinyl monomer having a chargeable functional group, a vinyl monomer having a positive chargeable functional group is preferred. When imparting negative chargeability to the shell resin, as the vinyl monomer having a chargeable functional group, a vinyl monomer having a negative chargeable functional group is preferred.

[0073] Examples of vinyl monomers that do not have a chargeable functional group include styrene, styrene derivatives (more specifically, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, p-methoxystyrene, p-ethoxystyrene, p-phenylstyrene, p-chlorostyrene, and 3,4-dichlorostyrene), ethylenically unsaturated monoolefins (more specifically, ethylene, propylene, butylene, and isobutylene), vinyl halides (more specifically, vinyl chloride, vinylidene chloride, vinyl bromide, and vinyl fluoride), vinyl esters (more specifically, vinyl acetate, propylene, and the like), and vinyl esters (more specifically, vinyl esters such as vinyl esters, ... Examples of suitable vinyl esters include vinyl propionate, vinyl benzoate, and vinyl butyrate, (meth)acrylic acid esters (more specifically, methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, propyl (meth)acrylate, n-octyl (meth)acrylate, dodecyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, 2-chloroethyl (meth)acrylate, phenyl (meth)acrylate, and methyl α-chloroacrylate, acrylonitrile, vinyl ethers (more specifically, vinyl methyl ether, vinyl ethyl ether, and vinyl isobutyl ether, etc.), vinyl ketones (more specifically, vinyl methyl ketone, vinyl hexyl ketone, and methyl isopropenyl ketone, etc.), and vinyl naphthalene. Among these, styrene and (meth)acrylic acid esters are preferred. As the (meth)acrylic acid ester, a (meth)acrylic acid alkyl ester is preferred, butyl (meth)acrylate is more preferred, and n-butyl (meth)acrylate is even more preferred.

[0074] Examples of vinyl monomers having a positively charged functional group include N-vinyl compounds, aminoacrylic acid monomers, (meth)acrylonitrile, and (meth)acrylamide.

[0075] Examples of N-vinyl compounds include N-vinylpyrrole, N-vinylcarbazole, N-vinylindole, and N-vinylpyrrolidone.

[0076] An example of an aminoacrylic acid monomer is a compound represented by formula (1) "CH2=C(R1)-(CO)-XN(R2)(R3)". In formula (1), R1 represents hydrogen or a methyl group. In formula (1), R2 and R3 each represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. X represents -O-, -OQ-, or -NH. Q represents an alkylene group having 1 to 10 carbon atoms, a phenylene group, or a combination of these groups.

[0077] In formula (1), examples of alkyl groups having 1 to 20 carbon atoms represented by R2 and R3 include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a tert-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, a 2-ethylhexyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group (lauryl group), an n-tridecyl group, an n-tetradecyl group, an n-pentadecyl group, an n-hexadecyl group, an n-heptadecyl group, an n-octadecyl group (stearyl group), an n-nonadecyl group, and an n-icosyl group.

[0078] In formula (1), examples of alkylene groups having 1 to 10 carbon atoms represented by Q include methylene, 1,2-ethanediyl, 1,1-ethylene, propane-1,3-diyl, propane-2,2-diyl, propane-1,1-diyl, propane-1,2-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl, heptane-1,7-diyl, octane-1,8-diyl, nonane-1,9-diyl, and decane-1,10-diyl. In formula (1), examples of phenylene groups represented by Q include p-phenylene, m-phenylene, o-phenylene, and divalent groups obtained by removing a hydrogen atom from the 4-position of the phenyl group contained in a benzyl group.

[0079] Examples of aminoacrylic acid monomers represented by formula (1) include N,N-dimethylamino(meth)acrylate, N,N-dimethylaminomethyl(meth)acrylate, N,N-diethylaminomethyl(meth)acrylate, 2-(N,N-methylamino)ethyl(meth)acrylate, 2-(N,N-diethylamino)ethyl(meth)acrylate, 3-(N,N-dimethylamino)propyl(meth)acrylate, 4-(N,N-dimethylamino)butyl(meth)acrylate, and pN,N-dimethylaminophenyl(meth)acrylate. , pN,N-diethylaminophenyl (meth)acrylate, pN,N-dipropylaminophenyl (meth)acrylate, pN,N-di-n-butylaminophenyl (meth)acrylate, pN-laurylaminophenyl (meth)acrylate, pN-stearylaminophenyl (meth)acrylate, (pN,N-dimethylaminophenyl)methyl (meth)acrylate, (pN,N-diethylaminophenyl)methyl (meth)acrylate, (pN,N-di-n-propylaminophenyl)methyl (meth)acrylate, (pN,N- Di-n-butylaminophenyl)methylbenzyl (meth)acrylate, (pN-laurylaminophenyl)methyl (meth)acrylate, (pN-stearylaminophenyl)methyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylamide, N,N-diethylaminoethyl (meth)acrylamide, 3-(N,N-dimethylamino)propyl (meth)acrylamide, 3-(N,N-diethylamino)propyl (meth)acrylamide, pN,N-dimethylaminophenyl (meth)acrylamide, pN,N-diethylamino ethylaminophenyl (meth)acrylamide, pN,N-di-n-propylaminophenyl (meth)acrylamide, pN,N-di-n-butylaminophenyl (meth)acrylamide, pN-laurylaminophenyl (meth)acrylamide, pN-stearylaminophenyl (meth)acrylamide, (pN,N-dimethylaminophenyl)methyl (meth)acrylamide, (pN,N-diethylaminophenyl)methyl (meth)acrylamide, (pN,N-di-n-propylaminophenyl)methyl (meth)acrylamide, (pN,Examples of the aminoacrylic acid monomer represented by formula (1) include (N-di-n-butylaminophenyl)methyl(meth)acrylamide, (pN-laurylaminophenyl)methyl(meth)acrylamide, and (pN-stearylaminophenyl)methyl(meth)acrylamide. As the aminoacrylic acid monomer represented by formula (1), 2-(N,N-diethylamino)ethyl(meth)acrylate is preferred, and 2-(N,N-diethylamino)methacrylate is preferred.

[0080] Examples of negatively chargeable functional groups include fluorine-substituted hydrocarbon groups and sulfo groups. Examples of vinyl monomers having negatively chargeable functional groups include vinyl monomers having fluorine-substituted hydrocarbon groups and vinyl monomers having sulfo groups. Examples of vinyl monomers having fluorine-substituted hydrocarbon groups include fluoroalkyl (meth)acrylates (more specifically, 2,2,2-trifluoroethyl acrylate, 2,2,3,3-tetrafluoropropyl acrylate, 2,2,3,3,4,4,5,5-octafluoroamyl acrylate, and 1H,1H,2H,2H-heptadecafluorodecyl acrylate), trifluorochloroethylene, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, trifluoropropylene, hexafluoropropene, and hexafluoropropylene. Examples of vinyl monomers having a sulfo group include 2-acrylamido-2-methylpropanesulfonic acid, sodium styrenesulfonate, and sulfoalkyl(meth)acrylic acids (more specifically, sulfoethylacrylic acid, sulfoethylmethacrylic acid, sodium sulfoethylmethacrylate, etc.).

[0081] The method for addition polymerization of the monomer having an unsaturated bond is not particularly limited, and any method such as solution polymerization, bulk polymerization, emulsion polymerization, or suspension polymerization can be selected.

[0082] Examples of polymerization initiators that can be used in the addition polymerization of vinyl monomers include potassium persulfate, sodium peroxodisulfate, potassium peroxodisulfate, ammonium peroxodisulfate, acetyl peroxide, decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, azobisisobutyronitrile, azobismethylbutyronitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, t-butylperoxy-2-ethylhexanoate, t-butylperbenzoate, dicyclohexyl peroxide, and dicumyl peroxide. The amount of these polymerization initiators used is preferably 0.1% by mass or more and 15% by mass or less relative to the total mass of the monomers.

[0083] When an aqueous medium is used to add-polymerize a monomer having an unsaturated bond, such as emulsion polymerization or suspension polymerization, a surfactant can be used. The surfactant is not particularly limited and can be appropriately selected from the group consisting of anionic surfactants, cationic surfactants, and nonionic surfactants. Examples of anionic surfactants include sulfate ester salt surfactants, sulfonate salt surfactants, phosphate ester salt surfactants, and soap. Examples of cationic surfactants include amine salt surfactants and quaternary ammonium salt surfactants. Examples of nonionic surfactants include polyethylene glycol surfactants, alkylphenol ethylene oxide adduct surfactants, and polyhydric alcohol surfactants (more specifically, glycerin, sorbitol, sorbitan, etc.).

[0084] When the charge control resin is a copolymer of a monomer having an electrostatically charged functional group and an unsaturated bond and a monomer having an unsaturated bond but no electrostatically charged functional group, the content of repeating units derived from the monomer having an electrostatically charged functional group and an unsaturated bond in all repeating units of the charge control resin is preferably 0.1 mol % or more and 10 mol % or less, and more preferably 0.3 mol % or more and 7 mol % or less.

[0085] The content of the charge control resin in the shell resin is preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 100% by mass.

[0086] The shell layer may be formed using a mixture of a charge-control resin and a non-charge-control resin (a resin that does not have a charge-capable functional group). The non-charge-control resin may be at least one polymer of a vinyl monomer that does not have a charge-capable functional group. Examples of methods for mixing the charge-control resin and the non-charge-control resin include a method of melt-kneading these resins using a melt-kneading device such as a twin-screw extruder, and a method of dissolving these resins in an organic solvent and removing the organic solvent from the resulting resin solution.

[0087] The shell layer may be formed using shell resin particles containing a charge control resin and shell resin particles containing a resin other than a charge control resin. In this case, the ratio of the mass of the shell resin particles containing the charge control resin to the total mass of the shell resin particles used to form the shell layer is preferably 80 mass% or more, more preferably 90 mass% or more.

[0088] The glass transition point of the shell resin is preferably 45°C or higher and 90°C or lower, and more preferably 50°C or higher and 80°C or lower. The softening point of the shell resin is preferably 100°C or higher and 250°C or lower, and more preferably 110°C or higher and 240°C or lower. The softening point of the shell resin is preferably higher than that of the binder resin contained in the toner core, and more preferably 10°C or higher and 140°C or lower than that of the binder resin. By setting the temperature characteristics of the shell resin within this range, the portions of the shell resin particles in contact with the toner core are less likely to deform when the shell resin particles are embedded in the toner core, and therefore, convex portions derived from the shape of the shell resin particles before they change into the shell layer are more likely to be formed on the inner surface of the shell layer.

[0089] The mass average molecular weight (Mw) of the shell resin is preferably 20,000 or more and 1,500,000 or less.

[0090] The number-average primary particle diameter of the shell resin particles is preferably 0.03 μm to 1 μm, more preferably 0.04 μm to 0.7 μm, particularly preferably 0.05 μm to 0.5 μm, and most preferably 0.05 μm to 0.3 μm. When shell resin particles with such a number-average primary particle diameter are used, the surfaces of the toner cores are easily uniformly coated with the shell resin particles in a single layer, and a shell layer with a desired structure is easily formed. The larger the number-average primary particle diameter of the shell resin particles, the easier it is to form a shell layer with sufficient thickness on the surfaces of the toner cores, improving the heat-resistant storage stability of the toner. On the other hand, the smaller the number-average primary particle diameter of the shell resin particles, the easier it is to uniformly attach the shell resin particles to the surfaces of the toner cores. Therefore, a shell layer with a predetermined structure is easily formed. The number-average primary particle diameter of the shell resin particles can be adjusted, for example, by appropriately changing at least one of the polymerization conditions, the pulverization method, and the classification method.

[0091] The content of the shell resin particles is preferably 1 part by mass or more and 20 parts by mass or less, and more preferably 3 parts by mass or more and 15 parts by mass or less, per 100 parts by mass of the toner core. The higher the content of the shell resin particles, the easier it is to coat the entire surface of the toner core with the shell resin particles. By coating the entire surface of the toner core with the shell resin particles, the toner is less likely to aggregate when stored at high temperatures, and heat-resistant storage stability is easily improved. The lower the content of the shell resin particles, the thinner the shell layer, making it easier to obtain a toner with excellent fixability.

[0092] <External additives> The external additive is not particularly limited and can be appropriately selected from known external additives used in toner. Examples of external additives include silica and metal oxides (more specifically, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, barium titanate, etc.). As already mentioned, it is preferable that the toner particles do not contain carbon nanotubes as an external additive. The surfaces of the external additive particles may be subjected to one or both of a positive charging treatment and a hydrophobic treatment. The number-average primary particle diameter of the external additive particles is preferably 0.01 μm or more and 1.0 μm or less.

[0093] The content of the external additive is preferably 0.1 to 10.0 parts by weight, and more preferably 0.2 to 5.0 parts by weight, per 100.0 parts by weight of the toner base particles. The higher the content of the external additive, the easier it is to improve the hydrophobicity of the toner. As a result, the toner is less susceptible to the effects of water molecules in the air in high-temperature, high-humidity environments, ensuring sufficient toner charging properties and enabling the formation of images with the desired density. The fluidity of the toner can also be improved. Furthermore, the lower the content of the external additive, the more effectively the reduction in image density due to toner charge-up can be suppressed.

[0094] <Toner manufacturing method> The toner of this embodiment can be produced, for example, by carrying out a toner core forming step, a shell layer forming step, and an external addition step. Note that when non-capsule toner particles are produced, the shell layer forming step can be omitted. Furthermore, when the toner particles do not contain an external additive, the external addition step can be omitted.

[0095] (Toner core formation process) In the toner core formation process, a binder resin, a black colorant, carbon nanotubes, and optional internal additives are mixed in a mixer or the like to obtain a mixture. The mixture is melted and kneaded in a kneader such as a single-screw or twin-screw extruder to obtain a kneaded product. The kneaded product is pulverized to obtain a pulverized product. If the pulverized product needs to be made smaller in diameter, the pulverized product is further pulverized. If the pulverized product needs to have a uniform particle size, the pulverized product is classified. By the above method, a pulverized product, i.e., a toner core, is obtained.

[0096] (Shell layer forming process) In the shell layer forming process, a shell layer is formed using shell resin particles. The shell resin particles are, for example, spherical. The toner cores and the shell resin particles are mixed using a mixer or the like, and the shell resin particles are adhered to the surfaces of the toner cores. As a result of the adhesion, a shell layer made of the shell resin particles is formed on the surfaces of the toner cores.

[0097] In order to form a thin and uniform shell layer, it is preferable to attach the shell resin particles to the surface of the toner core so that they do not overlap in the direction perpendicular to the surface of the toner core.

[0098] To adjust the smoothness of the shell layer, a mechanical external force may be applied to the outer surface of the shell resin particles attached to the surface of the toner core, thereby deforming the shell resin particles. The stronger the mechanical external force, the greater the degree of smoothness of the outer surface of the shell layer. One method for applying a mechanical external force is to apply an impact force to the toner cores (i.e., toner base particles) to which an external additive has been attached by colliding with each other when the toner cores (i.e., toner base particles) move at high speed through a narrow space in a mixing device. Another method for applying a mechanical external force is to apply an impact force to the toner cores (i.e., toner base particles) to which an external additive has been attached by colliding with the inner wall, rotor, or stator of the mixing device when the toner cores (i.e., toner base particles) move at high speed through a narrow space in a mixing device.

[0099] (External addition process) In the external addition step, toner particles are obtained by adhering an external additive to the surface of toner base particles. Examples of methods for adhering an external additive to the surface of toner base particles include a method of stirring the toner base particles and the external additive in a mixer (more specifically, an FM mixer, a Nauta mixer (registered trademark), or the like). It is preferable to adjust the processing conditions so that the external additive particles are not embedded in the toner base particles. [Example]

[0100] The present invention will be described in more detail below using examples, but the present invention is not limited to the scope of the examples.

[0101] [Synthesis of binder resin] A polyester resin (BR1) used as a binder resin in the toner core formation process was synthesized using the following method. 1960 g of propylene oxide adduct of bisphenol A, 780 g of ethylene oxide adduct of bisphenol A, 257 g of dodecenyl succinic anhydride, 770 g of terephthalic acid, and 4 g of dibutyltin oxide were charged into a reaction vessel. A nitrogen atmosphere was created inside the reaction vessel, and the temperature inside the reaction vessel was raised to 235°C while stirring. The reaction was continued at this temperature for 8 hours, after which the pressure inside the reaction vessel was reduced to 8.3 kPa and the reaction was continued for 1 hour. The reaction mixture was then cooled to 180°C, and trimellitic anhydride was added to the reaction vessel so that the acid value became 7 mgKOH / g. The temperature of the reaction mixture was then raised to 210°C at a rate of 10°C / hour, and the reaction was continued at this temperature. After the reaction was completed, the contents of the reaction vessel were removed and cooled to obtain polyester resin (BR1).

[0102] [Black colorant] Commercially available black colorants used in the toner core formation process are listed below. Black colorant (BK-a): Carbon black (Mitsubishi Chemical Corporation "MA100", classification: furnace black, number-average primary particle diameter: 24 nm, nitrogen adsorption specific surface area: 110 m 2 / g, DBP absorption: 100cm 3 / 100g) Black colorant (BK-b): Carbon black (DENKA BLACK Li 435 manufactured by Denka Co., Ltd., classification: acetylene black, number average primary particle diameter: 23 nm, nitrogen adsorption specific surface area: 133 m 2 / g)

[0103] [Carbon nanotubes] The commercially available carbon nanotubes used in the toner core formation process are listed below. Carbon nanotubes (CN-A): Single-walled carbon nanotubes (ZEON Corporation's "ZEONANO (registered trademark) SG101") Carbon nanotubes (CN-B): Single-walled carbon nanotubes ("SWNTSO" manufactured by Meijo Nano Carbon Co., Ltd.) Carbon nanotubes (CN-C): Multi-walled carbon nanotubes ("MWNT" manufactured by Meijo Nano Carbon Co., Ltd.)

[0104] [Synthesis of resin particles] Resin particles (A) used in the shell layer formation process were synthesized using the following method. A flask equipped with a stirrer, thermometer, condenser, and nitrogen inlet tube was used as a reaction vessel. 180 g of isobutanol, a solvent, was placed in the reaction vessel. 16 g of diethylaminoethyl methacrylate and 16 g of methyl paratoluenesulfonate were then added to the reaction vessel. The reaction vessel was placed on a mantle heater, and nitrogen gas was introduced into the reaction vessel through the nitrogen inlet tube to create an inert atmosphere inside the reaction vessel. Next, the internal temperature of the reaction vessel was raised to 80°C while stirring the contents of the reaction vessel at a stirring speed of 100 rpm. The contents of the reaction vessel were stirred at the same temperature for 1 hour at a stirring speed of 100 rpm to carry out a quaternization reaction. After the quaternization reaction, 214 g of styrene, 72 g of butyl acrylate, and 12 g of the peroxide initiator t-butylperoxy-2-ethylhexanoate (manufactured by Arkema Yoshitomi Co., Ltd.) were added to the reaction vessel. The internal temperature of the reaction vessel was raised to 95°C (polymerization temperature), and the contents of the reaction vessel were stirred for 3 hours at a stirring speed of 100 rpm. Next, 6 g of t-butylperoxy-2-ethylhexanoate was further added to the reaction vessel. The contents of the reaction vessel were then stirred at 95°C for 3 hours at a stirring speed of 100 rpm to complete the polymerization reaction. In this way, a resin particle dispersion was obtained. The obtained resin particle dispersion was freeze-dried to obtain powdered resin particles (A). The number-average primary particle diameter of the resin particles (A) was 0.10 μm.

[0105] [Toner manufacturing] The toners shown in Tables 1 and 2 below were produced by the following method.

[0106] [Table 1]

[0107] [Table 2]

[0108] The abbreviations used in Tables 1 and 2 are as follows: BK: Black colorant CN: Carbon nanotube Part: Mass part %:mass% -: The relevant ingredient was not added or there is no relevant value CN content: The content of carbon nanotubes in the toner core (specifically, the content calculated from the formula "carbon nanotube content in the toner core = 100 x amount of carbon nanotubes added / mass of toner core = 100 x amount of carbon nanotubes added / (amount of binder resin added + amount of release agent added + amount of charge control agent added + amount of black colorant added + amount of carbon nanotubes added)" CN / BK: Ratio of the mass of carbon nanotubes to the mass of black colorant (specifically, calculated using the formula "Ratio of the mass of carbon nanotubes to the mass of black colorant = Amount of carbon nanotubes added / Amount of black colorant added").

[0109] <Toner (T-A1) Production> (Toner core formation process) 86.50 parts by weight of a polyester resin (BR1) binder resin, 5.00 parts by weight of a release agent (polypropylene wax, manufactured by Sanyo Chemical Industries, Ltd., "Viscol (registered trademark) 660-P"), 1.00 parts by weight of a charge control agent (quaternary ammonium salt compound, manufactured by Orient Chemical Industries, Ltd., "BONTRON (registered trademark) P-51"), 7.00 parts by weight of a black colorant (BK-a), and 0.50 parts by weight of carbon nanotubes (CN-A) were mixed in a mixer to obtain a mixture. The mixture was melt-kneaded in a twin-screw extruder to obtain a kneaded product. The kneaded product was coarsely pulverized in a grinder (manufactured by Toa Machinery Works, Ltd., "Rotoplex (registered trademark)") to obtain a coarsely pulverized product. The coarsely pulverized product was finely pulverized in a mechanical grinder (manufactured by Freund-Turbo Corporation, "Turbo Mill") to obtain a finely pulverized product. The finely pulverized product was classified using a classifier (manufactured by Nittetsu Mining Co., Ltd., "Elbow Jet") to obtain toner cores. The volume median diameter of the obtained toner core was 7.0 μm.The obtained toner core was used as the toner base particle.

[0110] (External addition process) 100.0 parts by mass of the toner base particles obtained above, 2.0 parts by mass of titanium oxide particles ("EC-100" manufactured by Titanium Kogyo Co., Ltd.), and 1.0 part by mass of hydrophobic silica particles ("RA-200H" manufactured by Nippon Aerosil Co., Ltd.) were mixed for 5 minutes at a rotational peripheral speed of 30 m / s using an FM mixer (manufactured by Nippon Coke and Engineering Co., Ltd.) to adhere the external additives (titanium oxide particles and hydrophobic silica particles) to the surfaces of the toner base particles, thereby obtaining toner (T-A1).

[0111] <Production of Toners (T-A2) to (T-A3) and (T-B1) to (T-B2)> Toners (T-A2) to (T-A3) and (T-B1) to (T-B2) were produced in the same manner as toner (T-A1), except that the amounts of carbon nanotubes added in the toner core formation process were as shown in Tables 1 and 2.

[0112] <Production of Toner (T-A4) to (T-A5)> Toners (T-A4) to (T-A5) were produced in the same manner as in the production of toner (T-A1), except that the types of carbon nanotubes used in the toner core formation step were as shown in Table 1.

[0113] <Toner (T-A6) Manufacturing> Toner (T-A6) was produced in the same manner as in the production of toner (T-A1), except that the type of black colorant used in the toner core formation step was as shown in Table 2.

[0114] <Toner (T-B3) Manufacturing> Toner (T-B3) was produced in the same manner as toner (T-A1), except that carbon nanotubes were not added in the toner core formation step.

[0115] <Toner (T-A7) Manufacturing> Toner (T-A7) was produced in the same manner as in the production of toner (T-A1), except that the shell layer forming step described below was carried out after the toner core forming step and before the external addition step.

[0116] (Shell layer forming process) A powder processing device (Nippon Coke & Engineering Co., Ltd., "Multi-Purpose Mixer MP Type") was used to form the shell layer. 100 g of toner cores (specifically, toner cores obtained in the toner core formation step of the toner (T-A1) production) and 10 g of resin particles (A) were placed in the processing tank of the powder processing device and processed at a rotation speed of 8,000 rpm for a processing time of 15 minutes. During processing, the powder processing device was controlled so that the temperature inside the tank was in the range of 50°C to 60°C. Through the above processing, the toner cores were coated with resin particles (A), and a shell layer was formed on the surface of the toner cores. As a result, toner base particles having toner cores and a shell layer coating the toner cores were obtained. The obtained toner base particles were used in the external addition step.

[0117] [Measurement method] <Volume Median Diameter> The volume median diameter of the toner core was measured using a Coulter Counter Multisizer 4e (manufactured by Beckman Coulter, Inc.).

[0118] <Number average primary particle size> The number-average primary particle diameter of the resin particles was measured according to the following method. First, a photograph of the resin particles was taken at a magnification of 100,000 times using a field emission scanning electron microscope (JSM-6700F, manufactured by JEOL Ltd.). The electron microscope photograph was further enlarged as necessary, and the primary particle diameters of 50 resin particles were measured using a ruler, calipers, etc. The number-average primary particle diameter of the 50 resin particles was taken as the number-average primary particle diameter of the resin particles.

[0119] [Evaluation machine] The evaluation machine used in the following evaluation was a color printer ("FS-C5300DN" manufactured by Kyocera Document Solutions Inc.) modified so that the fixing temperature could be adjusted.

[0120] [Evaluation of fixation] The fixability (specifically, the minimum fixation temperature and fixation rate) of each toner was evaluated by the following method, and the evaluation results are shown in Tables 3 and 4 below.

[0121] <Minimum fixing temperature> Under normal temperature and humidity conditions (temperature 20°C and relative humidity 65%), one sheet of paper (monochrome and color compatible paper, Mondi "Color Copy 90", basis weight: 90 g / m²) was printed using an evaluation machine. 2 A solid image (specifically, an unfixed toner image) was formed on the paper with a toner amount of 0.8 mg / cm2. 2 The solid image was 30 mm x 30 mm in size. Subsequently, the paper on which the solid image was formed was passed through a fixing device of the evaluation machine.

[0122] The fixing temperature of the fixing device was set to a temperature between 90°C and 135°C. Specifically, the fixing temperature of the fixing device was increased in 1°C increments from 90°C, and the minimum temperature (minimum fixing temperature) at which a solid image (unfixed toner image) could be fixed to paper was measured. Whether or not the unfixed toner image could be fixed was confirmed by the following rubbing test.

[0123] The paper passed through the fixing device was folded so that the side with the solid image formed was facing inward. More specifically, the paper was folded so that the fold line passed through approximately the center of the solid image. A 1 kg weight covered with fabric was used to rub the folded paper back and forth 10 times along the crease so that only the weight of the weight was applied to the paper. The paper was then unfolded, and the length of toner peeling (peeling length) in the folded part of the paper where the solid image was fixed was measured. If the peeling length was 1 mm or less, it was determined that the unfixed toner image had been successfully fixed. The minimum fixing temperature was evaluated according to the following criteria. Note that the lower the minimum fixing temperature of the toner, the better the toner's low-temperature fixing ability.

[0124] (Minimum fixing temperature standard) A (good): The minimum fixing temperature is 120° C. or less. B (bad): The minimum fixing temperature is more than 120°C and less than 125°C. C (particularly poor): The minimum fixing temperature is 125° C. or higher.

[0125] <Retention rate> The fixing temperature of the fixing device of the evaluation machine was set to 150°C. Under normal temperature and humidity conditions (temperature 20°C and relative humidity 65% ​​RH), one sheet of paper (monochrome / color compatible copy paper "C2" manufactured by Fujifilm Business Innovation Co., Ltd., basis weight: 70 g / m) was printed using the evaluation machine. 2 ), Image A (toner amount on paper 0.5 mg / cm 2 A solid image (30 mm x 30 mm in size) was formed. The formed image was used as an evaluation image. The image density (ID before rubbing) of the evaluation image was measured using a spectrodensitometer / colorimeter (SpectroEye (registered trademark) manufactured by X-Rite).

[0126] The paper was then folded so that the side on which the solid image was formed was facing inward. More specifically, the paper was folded so that the fold line passed through approximately the center of the solid image. A 1 kg weight covered with fabric was rubbed back and forth 10 times along the crease of the folded paper so that only the weight of the weight was applied to the paper. The image density of the evaluation image after rubbing (post-rub ID) was measured using a spectrodensitometer / colorimeter (SpectroEye (registered trademark) manufactured by X-Rite).

[0127] The adhesion rate (unit: %) was calculated according to the formula "Adhesion rate = (ID after friction / ID before friction) x 100." The adhesion rate was judged according to the following criteria.

[0128] (Retention rate criteria) A (Good): The adhesion rate is 95% or more. B (Poor): The adhesion rate is 90% or more but less than 95%. C (particularly poor): The adhesion rate is less than 90%.

[0129] [Table 3]

[0130] [Table 4]

[0131] [Evaluation of image density, toner charge amount, and fog in a normal temperature and humidity environment] The initial image density, toner charge amount, and fogging were evaluated for each toner using the following methods. The image density and toner charge amount after continuous image formation were also evaluated for each toner using the following methods. The evaluation environment was a normal temperature and humidity environment (temperature 20°C and relative humidity 65% ​​RH, hereinafter referred to as "NN environment"). The evaluation results are shown in Tables 5 and 6 below.

[0132] <Image formation> The fixing temperature of the fixing device of the evaluation machine was set to 150° C. Using the evaluation machine, one sheet of paper (monochrome / color dual-use copy paper "C2" manufactured by Fujifilm Business Innovation Co., Ltd., basis weight: 70 g / m 2 ), Image A (toner amount on paper 0.5 mg / cm 2 A solid image (30 mm x 30 mm in size) was formed on one sheet of paper using the evaluation machine, and this was used as an initial image. Next, image B (blank image) was formed on one sheet of paper using the evaluation machine, and this was used as an image for fog evaluation. Next, image C (image with a printing rate of 4%) was continuously formed on 2,500 sheets of paper using the evaluation machine. Next, image A was again formed on one sheet of paper using the evaluation machine, and this was used as an image after printing.

[0133] <Image density> The image density of the initial image obtained by the image formation (initial ID) was measured using a reflection densitometer (X-Rite "RD914"). The image density of the image obtained by the image formation after printing (post-printing ID) was measured using a reflection densitometer (X-Rite "RD914"). The image density was determined according to the following criteria.

[0134] (Image density standard) A (good): ID is 1.25 or more. B (bad): ID is 1.20 or more and less than 1.25. C (particularly poor): ID is less than 1.20.

[0135] <Focus> The reflection density DA of the image for fog evaluation (blank image) obtained by the image formation described above was measured using a reflection densitometer ("RD914" manufactured by X-Rite). The reflection density DB of unprinted paper was also measured using a reflection densitometer ("RD914" manufactured by X-Rite). The fog density (FD) was calculated from the formula "Fog density = Reflection density DA - Reflection density DB". Fog was evaluated according to the following criteria.

[0136] (Fog standard) A (good): FD is 0.010 or less. B (poor): FD is more than 0.010.

[0137] <Toner charge amount> After forming an initial image in the above image formation, the charge amount (initial charge amount) of the toner in the development unit of the evaluation machine was measured using a charge amount measuring device (Trek Q / M Meter 210HS). After forming a post-printing image in the above image formation, the charge amount (post-printing charge amount) of the toner in the development unit of the evaluation machine was measured using a charge amount measuring device (Trek Q / M Meter 210HS). The toner charge amount was judged according to the following criteria.

[0138] (Toner charge amount standard) A (good): The charge amount is 20.0 μC / g or more and 25.0 μC / g or less. B (poor): The charge amount is 19.0 μC / g or more and less than 20.0 μC / g, or more than 25.0 μC / g and 26.0 μC / g or less. C (particularly poor): The charge amount is less than 19.0 μC / g or more than 26.0 μC / g.

[0139] [Table 5]

[0140] [Table 6]

[0141] [Evaluation of image density, toner charge amount, and fog in a high-temperature, high-humidity environment] The image density, toner charge amount, and fog in the HH environment were evaluated in the same manner as in the NN environment, except that the evaluation environment was changed from the NN environment to a high temperature and high humidity environment (temperature 32.5°C and relative humidity 80% RH, hereinafter referred to as the "HH environment"). The evaluation results are shown in Tables 7 and 8 below.

[0142] [Table 7]

[0143] [Table 8]

[0144] In Table 8, "-" indicates that the evaluation machine was not operating properly and the evaluation could not be performed.

[0145] [Evaluation of image density, toner charge amount, and fog in a low-temperature, low-humidity environment] The image density, toner charge amount, and fog in the LL environment were evaluated in the same manner as in the NN environment, except that the evaluation environment was changed from the NN environment to a low-temperature, low-humidity environment (temperature 10°C and relative humidity 20% RH, hereinafter referred to as the "LL environment"). The evaluation results are shown in Tables 9 and 10 below.

[0146] [Table 9]

[0147] [Table 10]

[0148] In Table 10, "-" indicates that the evaluation machine was not operating properly and the evaluation could not be performed.

[0149] The toner (T-B1) had a carbon nanotube content of less than 0.10% by mass in the toner core. The fixability of the toner (T-B1) was evaluated as poor. The charge amount of the toner (T-B1) after repeated printing in an LL environment was evaluated as poor. The image density of the toner (T-B1) after repeated printing in an NN environment and an LL environment was evaluated as poor.

[0150] The toner (T-B2) had a carbon nanotube content of more than 1.00% by mass in the toner core. The evaluation of the initial charge amount of the toner (T-B2) in the NN environment was poor. The evaluation of the charge amount of the toner (T-B2) after repeated printing in the NN environment was particularly poor. The evaluation of the initial fogging of the toner (T-B2) in the NN environment was poor. Furthermore, when the toner (T-B2) was used, the evaluation machine did not operate properly in the HH and LL environments, and evaluation was not possible.

[0151] The toner core of toner (T-B3) did not contain carbon nanotubes. The evaluation of the fixing property of toner (T-B3) was particularly poor. The evaluation of the initial charge amount of toner (T-B3) in the NN environment, HH environment, and LL environment was poor or particularly poor. The evaluation of the charge amount of toner (T-B3) after repeated printing in the NN environment and LL environment was poor or particularly poor. The evaluation of the initial image density of toner (T-B3) in the NN environment and LL environment was poor. The evaluation of the image density of toner (T-B3) after repeated printing in the NN environment, HH environment, and LL environment was poor.

[0152] On the other hand, toners (T-A1) to (T-A7) each contained toner particles. The toner particles had a toner core. The toner core contained a binder resin, a black colorant, and carbon nanotubes. The carbon nanotube content in the toner core was 0.10% by mass or more and 1.00% by mass or less. Evaluations of the fixability of toners (T-A1) to (T-A7), evaluations of the charge amount at the initial stage and after repeated printing in various environments (e.g., NN environment, HH environment, and LL environment), evaluations of the image density at the initial stage and after repeated printing in various environments (e.g., NN environment, HH environment, and LL environment), and evaluations of the initial fog in various environments (e.g., NN environment, HH environment, and LL environment) were all favorable.

[0153] From the above, it is concluded that the toners of the present invention, including toners (T-A1) to (T-A7), have excellent fixing properties, and can be charged to a desired charge amount even when images are continuously formed under various environments such as a normal temperature and normal humidity environment, a high temperature and high humidity environment, and a low temperature and low humidity environment, and can form images of a desired density with little fog. [Industrial Applicability]

[0154] The toner of the present invention can be used to form images in, for example, a copier, a printer, or a multifunction machine. [Explanation of symbols]

[0155] 1: Non-capsule toner particles 2: Toner base particles (non-capsule toner base particles) 2a: Toner core 2b: Shell layer 3: External additive particles 10: Capsule toner particles 20: Toner base particles (capsule toner base particles)

Claims

1. A toner comprising toner particles, the toner particles have a toner core; the toner core contains a binder resin, a black colorant, and carbon nanotubes; The toner, wherein the content of the carbon nanotubes in the toner core is 0.10% by mass or more and 1.00% by mass or less.

2. 2. The toner according to claim 1, wherein a ratio of the mass of the carbon nanotubes to the mass of the black colorant is 0.010 or more and 0.150 or less.

3. The toner according to claim 1 or 2, wherein the carbon nanotubes are single-walled carbon nanotubes or multi-walled carbon nanotubes.

4. 3. The toner according to claim 1, wherein the black colorant is furnace black or acetylene black.

5. the toner particles are capsule toner particles having the toner core and a shell layer covering the surface of the toner core, 3. The toner according to claim 1, wherein the toner particles are non-capsule toner particles having the toner core but not having the shell layer.

6. The toner according to claim 1 , wherein the toner particles do not contain the carbon nanotubes as an external additive.

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