toner

Abstract

The present invention provides a toner that offers excellent fixation properties and can be charged to the desired amount and form images of the desired density with minimal fogging, even when images are continuously formed in various environments such as normal temperature and humidity, high temperature and high humidity, and low temperature and low humidity. [Solution] The toner contains toner particles. The toner particles have a toner core. The toner core contains a binder resin, magnetic particles, and carbon nanotubes. The magnetic particle content in the toner core is 30.0% by mass or more and 50.0% by mass or less, and the carbon nanotube content is 0.10% by mass or more and 1.00% by mass or less.

Description

[Technical Field]

[0001] This invention relates to toner. [Background technology]

[0002] To satisfy low-temperature fixation requirements in a recycling system, Patent Document 1 discloses a toner comprising 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 outflow start temperature measured by a high-efficiency flow tester is Tfb, satisfies the formula "G'(Tfb) ≤ 1 × 10⁴". [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2012 / 101875 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, the toner described in Patent Document 1 is insufficient in that it can stably charge the toner and form high-quality images when environmental conditions such as temperature and humidity change.

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

[0006] The toner of the present invention contains toner particles. The toner particles have a toner core. The toner core contains a binder resin, magnetic particles, and carbon nanotubes. The content of magnetic particles in the toner core is 30.0% by mass or more and 50.0% by mass or less, and the content of carbon nanotubes 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 amount even when images are continuously formed in various environments such as normal temperature and humidity, high temperature and high humidity, and low temperature and low humidity, and can form images of a desired density with minimal fogging. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows a cross-sectional structure of non-encapsulated toner particles, which are an example of toner particles contained in the toner of an embodiment of the present invention. [Figure 2] This figure shows a cross-sectional structure of capsule toner particles, which is another example of toner particles contained in the toner according to an embodiment of the present invention. [Modes for carrying out the invention]

[0009] The embodiments of the present invention will be described in detail below, but the present invention is not limited in any way to the embodiments described below, and can be implemented with appropriate modifications within the scope of the object of the present invention. In addition, explanations may be omitted where necessary to avoid repetition, but this does not limit the gist of the invention.

[0010] First, let's explain the terminology used in this embodiment. Toner is an aggregate of toner particles (e.g., powder). Magnetic particles are an aggregate of magnetic particles (e.g., powder). External additives are an aggregate of external additive particles (e.g., powder). Unless otherwise specified, the evaluation results (values ​​indicating shape, physical properties, etc.) for powders (more specifically, toner particle powders, external additive particle powders, etc.) are the number average of the values ​​measured for each of the particles selected from the powder. Volume median diameter (D 50 Unless otherwise specified, the primary particle diameter is the median diameter measured using a laser diffraction / scattering particle size distribution analyzer (LA-950, Horiba, Ltd.). Unless otherwise specified, the number-average primary particle diameter is the number-average value of the equivalent circle diameter (Haywood diameter: the diameter of a circle with the same area as the projected area of ​​the primary particle) of primary particles measured using a field emission scanning electron microscope (JSM-6700F, JEOL Ltd.). The number-average primary particle diameter is, for example, the number-average value of the equivalent circle diameter of 50 primary particles.

[0011] The softening point (Tm), unless otherwise specified, is the value measured using a high-temperature flow tester (Shimadzu Corporation "CFT-500D"). In the S-curve (horizontal axis: temperature, vertical axis: stroke) measured by the high-temperature flow tester, the temperature at which "(baseline stroke value + maximum stroke value) / 2" corresponds to Tm (softening point). The glass transition point (Tg) is the value obtained from the point of change in the specific heat of the binder resin using a differential scanning calorimeter (DSC). More specifically, the glass transition point of the sample can be determined by using a differential scanning calorimeter (Seiko Instruments Inc. "DSC-6220") as the measuring device and measuring the endothermic curve of the sample using the following method: Place 10 mg of the sample into an aluminum pan. Use an empty aluminum pan as a reference. By measuring under normal temperature and humidity conditions with 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 can be determined from the obtained endothermic curve.

[0012] Unless otherwise specified, the acid value is measured according to JIS (Japanese Industrial Standards) K0070-1992. Unless otherwise specified, the number-average molecular weight (Mn) and mass-average molecular weight (Mw) are 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 standard polystyrene resin. Unless otherwise specified, the nitrogen adsorption specific surface area is measured according to JIS (Japanese Industrial Standards) K6217. Unless otherwise specified, the DBP absorption amount is measured according to JIS (Japanese Industrial Standards) K6221. Unless otherwise specified, the relative humidity is measured according to JIS (Japanese Industrial Standards) Z8806:2001.

[0013] The term "system" may be added after a compound name to comprehensively refer to the compound and its derivatives. When "system" is added after a compound name to represent a polymer name, it means that the repeating unit of the polymer originates from the compound or its derivative. Acrylics and methacrylics may be comprehensively referred to as "(meth)acrylics." Acrylonitriles and methacrylonitriles may be comprehensively referred to as "(meth)acrylonitriles." Acrylates and methacrylates may be comprehensively referred to as "(meth)acrylates." Unless otherwise specified, each component described herein may be used alone or in combination of two or more. The terms used in this embodiment have now been explained.

[0014] [toner] The toner of this embodiment contains toner particles. The toner particles have a toner core. The toner core contains a binder resin, magnetic particles, and carbon nanotubes. The magnetic particle content in the toner core is 30.0% by mass or more and 50.0% by mass or less, and the carbon nanotube content is 0.10% by mass or more and 1.00% by mass or less.

[0015] The toner of the present embodiment, having the above configuration, is excellent in fixability (for example, low-temperature fixability and fixing 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, so that an image with a desired density and less fog can be formed. The reason is presumed as follows.

[0016] In the present embodiment, the toner core contains carbon nanotubes. Further, the content of carbon nanotubes in the toner core is 0.10% by mass or more. Since carbon nanotubes have high conductivity, when the toner is triboelectrically charged in the developing unit of an image forming apparatus, the toner particles are favorably triboelectrically charged 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 an image with a desired density can be formed. In addition, since carbon nanotubes have high conductivity, electric charge moves rapidly between toner particles even under various environments. As a result, the charge amount distribution of the toner becomes sharp, and an image with less fog can be formed even when images are continuously formed under various environments.

[0017] On the other hand, if the content of carbon nanotubes in the toner core is excessively high, excessive electric charge leaks from the triboelectrically charged toner. Therefore, the content of carbon nanotubes in the toner core is set to 1.00% by mass or less. As a result, excessive leakage of electric charge from the triboelectrically charged toner can be suppressed, and an excessive decrease in the charge amount of the toner can be suppressed.

[0018] In addition, carbon nanotubes have high thermal conductivity in addition to high conductivity. Therefore, when the toner is fixed to a recording medium, the heat from the fixing device of the image forming apparatus is rapidly conducted to the toner. As a result, the low-temperature fixability of the toner and the fixing rate of the toner to the recording medium are improved.

[0019] The above explains why the toner of this embodiment has excellent fixing properties and can be charged to the desired charge level and form images of the desired density with minimal fogging, even when continuously forming images in various environments such as normal temperature and humidity, high temperature and high humidity, and low temperature and low humidity.

[0020] The toner of this embodiment is suitably used for developing electrostatic latent images, for example, as a positively charged toner. The toner may be used as a one-component developer. The toner may also be used as a two-component developer by mixing it with a carrier using a mixing device (e.g., a ball mill). When used as a one-component developer, the toner becomes charged by friction with a developing sleeve or toner charging member within the developing device. An example of a toner charging member is a doctor blade. When used as a two-component developer, the toner becomes charged by friction with a carrier within the developing device. The details of the toner of this embodiment will be further described below.

[0021] <Structure of toner particles> The toner particles are either unencapsulated toner particles or encapsulated toner particles. The structure of the toner particles contained in the toner will be described below with reference to Figures 1 and 2. Figure 1 shows the cross-sectional structure of unencapsulated toner particle 1, an example of toner particles contained in the toner of this embodiment. Figure 2 shows the cross-sectional structure of encapsulated toner particle 10, another example of toner particles contained in the toner of this embodiment.

[0022] First, let's explain the case where the toner particle is a non-encapsulated toner particle 1. As shown in Figure 1, the non-encapsulated toner particle 1 has a toner base particle 2 and an external additive particle 3. Hereinafter, "the toner base particle 2 that the non-encapsulated toner particle 1 has" may be referred to as "non-encapsulated toner base particle 2". The external additive particle 3 is attached to the surface of the non-encapsulated toner base particle 2. The non-encapsulated toner base particle 2 has a toner core 2a. The non-encapsulated toner base particle 2 does not have a shell layer 2b (see Figure 2), and the toner core 2a corresponds to the non-encapsulated toner base particle 2. That is, the toner core 2a that is not covered by the shell layer 2b corresponds to the non-encapsulated toner base particle 2.

[0023] Next, we will describe the case where the toner particles are capsule toner particles 10. As shown in Figure 2, the capsule toner particles 10 have toner mother particles 20 and external additive particles 3. Hereinafter, "toner mother particles 20 of the capsule toner particles 10" may be referred to as "capsule toner mother particles 20". The external additive particles 3 are attached to the surface of the capsule toner mother particles 20. The capsule toner mother particles 20 have 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. Also, the shell layer 2b does not have to have irregularities. The thickness of the shell layer 2b is not particularly limited, but is preferably 0.03 μm or more and 1 μm or less, more preferably 0.04 μm or more and 0.7 μm or less, particularly preferably 0.05 μm or more and 0.5 μm or less, and most preferably 0.05 μm or more and 0.3 μm or less.

[0024] The structure of toner particles has been described above, but the structure of toner particles contained in the toner of this embodiment is not limited to the structure shown in Figures 1 and 2. For example, non-capsulated toner particles 1 do not have external additive particles 3. If external additive particles 3 are not present, non-capsulated toner mother particles 2 correspond to non-capsulated toner particles 1. Also, for example, encapsulated toner particles 10 do not have external additive particles 3. If external additive particles 3 are not present, encapsulated toner mother particles 20 correspond to encapsulated toner particles 10. Furthermore, for example, the shell layer 2b may cover only a part 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 covering state of the shell layer 2b can be confirmed using a scanning electron microscope (SEM). Furthermore, for example, the surface of the shell layer 2b may have irregularities. When the shell layer 2b is composed of resin particles, irregularities caused by 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 capsule toner particles 10 using a transmission electron microscope (TEM). Hereinafter, the uncapsulated toner particles 1 and the capsule toner particles 10 may be collectively referred to as "toner particles." Similarly, the uncapsulated toner matrix particles 2 and the capsule toner matrix particles 20 may be collectively referred to as "toner matrix particles." The structure of the toner particles contained in the toner has been explained above with reference to Figures 1 and 2. The toner core, shell layer, external additives, and toner manufacturing method will be explained below.

[0025] <Toner Core> The toner core of the toner particles contains a binder resin, magnetic particles, and carbon nanotubes. The toner core may further contain internal additives as needed (e.g., at least one of a mold release agent, a charge control agent, and other known additives). To obtain a toner suitable for image formation, the median diameter (D) of the toner core is set. 50 The particle size is preferably 4 μm or more and 9 μm or less.

[0026] (Binding resin) Examples of binder resins include thermoplastic resins. Examples of thermoplastic resins include styrene resin, acrylic resin, styrene-acrylic resin, polyethylene resin, polypropylene resin, vinyl chloride resin, polyester resin, polyamide resin, polyurethane resin, polyvinyl alcohol resin, vinyl ether resin, N-vinyl resin, and styrene-butadiene resin. Among these resins, polystyrene resin and polyester resin are preferred in terms of the dispersibility of magnetic particles in the binder resin, the chargeability of the toner, and the fixation to the recording medium. Polystyrene resin and polyester resin will be described below.

[0027] Polystyrene resin may be a homopolymer of styrene or a copolymer of styrene with other copolymerizable monomers. Examples of other copolymerizable monomers with styrene include p-chlorostyrene, vinylnaphthalene, ethylene unsaturated monoolefins, vinyl halides, vinyl esters, (meth)acrylic acid esters, other acrylic acid derivatives, vinyl ketones, and N-vinyl compounds. Examples of ethylene 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, dothoyl acrylate, n-octyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, α-methyl chloroacrylate, methyl methacrylate, ethyl methacrylate, and butyl methacrylate. Other examples of 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-vinylpyrrolidene.

[0028] Polyester resins are obtained by condensation polymerization of a divalent or trivalent or higher alcohol monomer and a divalent or trivalent or higher carboxylic acid monomer.

[0029] Examples of divalent 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.

[0030] Examples of alcohol monomers with a valency of 3 or higher 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.

[0031] Examples of divalent carboxylic 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, alkyl succinic acids (more specifically, n-butyl succinic acid, isobutyl succinic acid, n-octyl succinic acid, n-dodecyl succinic acid, and isododecyl succinic acid, etc.), and alkenyl succinic acids (more specifically, n-butenyl succinic acid, isobutenyl succinic acid, n-octenyl succinic acid, n-dodecenyl succinic acid, and isododecenyl succinic acid, etc.).

[0032] Examples of trivalent or higher carboxylic acid monomers include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalentricarboxylic acid, 1,2,4-naphthalentricarboxylic 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 acids.

[0033] Divalent or trivalent or higher carboxylic acid monomers may also be used after being derivatized into ester-forming derivatives (more specifically, acid halides, acid anhydrides, and lower alkyl esters, etc.). Here, "lower alkyl" means an alkyl group having 1 to 6 carbon atoms.

[0034] As the polyester resin, a condensation polymer of at least one bisphenol, at least one divalent carboxylic acid monomer, and at least one trivalent or higher carboxylic acid monomer is preferred. As the polyester resin, a condensation polymer of bisphenol A ethylene oxide adduct, bisphenol A propylene oxide adduct, terephthalic acid, alkenyl succinic acid, and trimellitic acid is more preferred.

[0035] The softening point of the binder resin is preferably 70°C to 130°C, and more preferably 80°C to 120°C.

[0036] The glass transition temperature (Tg) of the binder resin is preferably between 40°C and 70°C. A lower glass transition temperature tends to improve the low-temperature fixing properties of the toner. A higher glass transition temperature tends to improve the heat-resistant storage properties of the toner.

[0037] The mass-average molecular weight (Mw) of the binder resin is not particularly limited, but is preferably 20,000 to 300,000, and more preferably 30,000 to 200,000.

[0038] Furthermore, when the binder resin is polystyrene resin, it is preferable that the polystyrene resin has peaks in both the low molecular weight region and the high molecular weight region on the molecular weight distribution measured by gel permeation chromatography or the like. Specifically, it is preferable that the peak in the low molecular weight region is in the range of 3,000 to 20,000 molecular weights, and that the peak in the high molecular weight region is in the range of 300,000 to 1,500,000 molecular weights. In addition, for polystyrene resin with such a molecular weight distribution, it is preferable that the ratio of the number average molecular weight (Mn) to the mass average molecular weight (Mw) (Mw / Mn) is 10 or more. By having peaks in the low molecular weight region and the high molecular weight region in such ranges on the molecular weight distribution of the polystyrene resin, it is possible to obtain a toner that has excellent low-temperature fixation and can suppress high-temperature offset.

[0039] Because of its good adhesion to recording media, the thermoplastic resin mentioned above is preferred as the binder resin. However, thermoplastic resins may be used alone, or a crosslinking agent or thermosetting resin may be added to the thermoplastic resin. By adding a crosslinking agent or thermosetting resin to introduce a partially crosslinked structure into the binder resin, the heat resistance and durability of the toner can be improved without reducing the toner's adhesion. When using a thermosetting resin, the amount of crosslinked portion (gel amount) of the binder resin extracted using a Soxhlet extractor is preferably 10% by mass or less, and more preferably 0.1% by mass or more and 10% by mass or less, relative to the mass of the binder resin.

[0040] Examples of thermosetting resins that can be used with thermoplastic resins include epoxy resins and cyanate resins, with epoxy resins being preferred. Examples of epoxy resins include bisphenol A type epoxy resins, hydrogenated bisphenol A type epoxy resins, novolac type epoxy resins, polyalkylene ether type epoxy resins, and cyclic aliphatic type epoxy resins.

[0041] (Carbon nanotubes) As already mentioned, the toner core of toner particles contains carbon nanotubes. Because carbon nanotubes are less susceptible to environmental changes, it is preferable that they are internally added to the toner matrix particles (especially the toner core) but not externally added to the toner matrix particles. In other words, it is preferable that toner particles do not contain carbon nanotubes as an external additive.

[0042] 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 fixation and to be able to charge to the desired amount even when images are formed continuously under various conditions, and to form images of the desired density with little fogging, 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.

[0043] In order to achieve excellent fixation, and to be able to charge to the desired amount even when images are formed continuously under various environmental conditions, and to form images of the desired density with little fogging, the carbon nanotube content 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, per 100.0 parts by mass of binder resin.

[0044] 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 cylinders of different diameters (for example, two or more) are stacked on top of each other like a nest.

[0045] The inner diameter of the carbon nanotube is preferably between 5 nm and 50 nm, and more preferably between 7 nm and 40 nm. The length of the carbon nanotube is preferably between 1 μm and 10 μm. However, since the carbon nanotube is cut to some extent by kneading and pulverizing during the toner core formation process when manufacturing toner, carbon nanotubes longer than 10 μm can also be used. The carbon nanotube can be confirmed by observing the cross-section of the toner particle using a transmission electron microscope (TEM).

[0046] (Coloring agent) The toner of the present invention is normally black because it contains magnetic powder. For this reason, the toner may contain a black coloring agent to adjust the formed image formed using the toner of the present invention to a more preferred black hue, to the extent that it does not hinder the objective of the present invention. Examples of black coloring agents include carbon black and aniline black. Carbon black is classified into furnace black, acetylene black, lamp black, and channel black depending on the manufacturing method. Furnace black is manufactured by the furnace process. Acetylene black is manufactured by the acetylene process. Lamp black is manufactured by the soot process. Channel black is manufactured by the channel process.

[0047] The black coloring agent is preferably carbon black, and more preferably furnace black or acetylene black. Furnace black is easy to mass-produce in high yield and is relatively inexpensive. Therefore, using furnace black as the black coloring agent can enhance cost advantages in toner manufacturing. 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 the desired amount even when images are continuously formed under various environmental conditions.

[0048] 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.

[0049] 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 and 200 m 2 / g or less, and preferably 110 m 2 / g or more and 140 m 2 / g or less, more preferably. The DBP absorption of the black colorant is 50 cm 3 / 100g or more and 200 cm 3 / 100g or less, and preferably 90 cm 3 / 100g or more and 110 cm 3 / 100g or less, more preferably.

[0050] 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, relative to the mass of the toner core.

[0051] The black colorant can be confirmed by observing a cross-section of toner particles using a transmission electron microscope (TEM). Further, in order to adjust the toner to a desired color, a colorant of a color other than black may be further contained in the toner core.

[0052] In order to adjust the toner to a desired color, the ratio of the mass of carbon nanotubes to the mass 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 still more preferably 0.050 or more and 0.100 or less.

[0053] (Release Agent) To improve adhesion and resistance to offset, 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., smearing 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.

[0054] When 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.

[0055] When 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 release agents, also from the viewpoint of compatibility. Fischer-Tropsch wax is a straight-chain hydrocarbon compound with few iso (iso) structural molecules and side chains. Furthermore, Fischer-Tropsch wax is produced using the Fischer-Tropsch reaction, which is a catalytic hydrogenation reaction of carbon monoxide.

[0056] Preferred Fischer-Tropsch waxes have a mass-average molecular weight of 1,000 or more, and the bottom temperature of the endothermic peak observed by DSC measurement is in the range of 100°C to 120°C. Examples of such Fischer-Tropsch waxes include Sazol wax C1 (bottom temperature of endothermic peak: 106.5°C), Sazol wax C105 (bottom temperature of endothermic peak: 102.1°C), and Sazol wax SPRAY (bottom temperature of endothermic peak: 102.1°C), all available from Sazol.

[0057] The release agent content is preferably 1% to 10% by mass relative to the mass of the toner core. The higher the release agent content, the more effectively offset and image smearing in the formed image can be suppressed. On the other hand, the lower the release agent content, the less likely the toners are to fuse together, improving the heat resistance of the toner during storage.

[0058] (Charge control agent) To improve the toner's charge level and charge rise characteristics, and to obtain a toner with excellent durability and stability, it is preferable that the toner core contains a charge control agent. The toner's charge rise characteristics are an indicator of whether or not it can be charged to a predetermined charge level in a short time. When developing the toner with a positive charge, a positively charging charge control agent is used. On the other hand, when developing the toner with a negative charge, a negatively charging charge control agent is used.

[0059] Examples of positively charged charge control agents include azine compounds, direct dyes, nigrosine compounds, acid dyes, metal salts of naphthenic acids, 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-thiaidine, 1,3-thiaidine, 1,4-thiaidine, 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 faster charge rise.

[0060] Resins having quaternary ammonium salts, carboxylates, or carboxyl groups as functional groups can also be used as positively charged charge control agents. More specifically, examples include styrene resins having quaternary ammonium salts, acrylic resins having quaternary ammonium salts, styrene-acrylic resins having quaternary ammonium salts, polyester resins having quaternary ammonium salts, styrene resins having carboxylates, acrylic resins having carboxylates, styrene-acrylic resins having carboxylates, polyester resins having carboxylates, styrene resins having carboxyl groups, acrylic resins having carboxyl groups, styrene-acrylic resins having carboxyl groups, and polyester resins having carboxyl groups. The molecular weight of these resins is not particularly limited and they may be oligomers or polymers.

[0061] Among resins that can be used as positively charged charge control agents, styrene-acrylic resins having quaternary ammonium salts as functional groups are more preferred because the amount of charge can be easily adjusted to a value within a desired range. Examples of acrylic acid monomers copolymerizable with styrene in styrene-acrylic resins having quaternary ammonium salts as functional groups include alkyl (meth)acrylates. Examples of alkyl (meth)acrylates include methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, and iso-butyl methacrylate.

[0062] Furthermore, examples of quaternary ammonium salt monomers that can be used in copolymerization of styrene acrylic resins having quaternary ammonium salts as functional groups 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. An example of dialkyl(meth)acrylamide is dimethylmethacrylamide. An example of dialkylaminoalkyl(meth)acrylamide is dimethylaminopropylmethacrylamide. In addition, polymerizable monomers containing hydroxyl groups (more specifically, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate, and N-methylol(meth)acrylamide, etc.) can also be used in combination during polymerization.

[0063] Examples of negatively charged charge control agents include organometallic complexes, chelate compounds, monoazometallic 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, bisphenol, etc.). 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. More preferred organometallic complexes and chelate compounds include 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.

[0064] The content of the charge control agent is preferably 0.1% to 10% by mass 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 the easier it is to obtain an image of the desired density. Also, the higher the content of the charge control agent, the easier it is to uniformly disperse the charge control agent, so fogging is less likely to occur in the formed image, and contamination of the image carrier by toner components can be effectively suppressed. On the other hand, the lower the content of the charge control agent, the easier it is to ensure sufficient charging even under high temperature and high humidity conditions.

[0065] (magnetic particles) Magnetic particles are not particularly limited, but examples include iron (more specifically, ferrite and magnetite, etc.), ferromagnetic metals (more specifically, cobalt and nickel, etc.), alloys containing iron and / or ferromagnetic metals, compounds containing iron and / or ferromagnetic metals, ferromagnetic alloys that have undergone ferromagnetic treatment (more specifically, heat treatment, etc.), and chromium dioxide.

[0066] The particle size of the magnetic particles 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 particles with a particle size within this range are used, it is easy to uniformly disperse the magnetic particles in the binder resin.

[0067] To improve dispersibility in the binder resin, magnetic particles that have been surface-treated with a surface treatment agent (more specifically, titanium coupling agents and silane coupling agents, etc.) may be used.

[0068] When magnetic particles are included in the toner core, the magnetic particle content must be between 30.0% and 50.0% by mass relative to the mass of the toner core, and more preferably between 35.0% and 45.0% by mass. The lower the magnetic particle content, the easier it is to improve the toner's fixation and the easier it is to form an image of the desired density when forming an image continuously over a long period of time. On the other hand, the higher the magnetic particle content, the less likely fogging is to occur in the formed image and the more the decrease in image density can be suppressed when forming an image continuously over a long period of time.

[0069] <Shell layer> The shell layer is formed, for example, by resin particles. Hereinafter, "resin particles that form the shell layer" may be referred to as "shell resin particles."

[0070] <Shell resin particles> The shell resin particles contain resin. Hereinafter, "the resin contained in the shell resin particles" may be referred to as "shell resin." The content of 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.

[0071] The shell resin is preferably a charge-controlled resin. By having the shell layer composed of a charge-controlled resin, the toner can be charged to the desired level of charge even when continuously forming images in various environments, such as normal temperature and humidity, high temperature and high humidity, and low temperature and low humidity. As a result, images of the desired density can be suitably formed in various environments.

[0072] The shell resin is preferably a polymer of monomers having unsaturated bonds, as it facilitates the formation of a shell layer with a predetermined structure. When the shell resin is a charge-controlled resin, the charge-controlled resin is preferably a copolymer of a monomer having an electrostatic functional group and unsaturated bonds that impart electrostatic properties to the shell resin, and a monomer that does not have an electrostatic functional group but has unsaturated bonds.

[0073] When imparting positive charge properties to a shell resin, examples of positive charge functional groups include nitrogen-containing polar functional groups such as quaternary ammonium groups. On the other hand, when imparting negative charge properties to a shell resin, examples of negative charge functional groups include fluorine-substituted hydrocarbon groups or sulfo groups.

[0074] The monomer having an unsaturated bond is not particularly limited as long as it can synthesize a resin with sufficient physical properties as a shell layer. Vinyl monomers are preferred as monomers having an unsaturated bond. The α-position of the vinyl group 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 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, and more preferably a chlorine atom.

[0075] As monomers that do not have electrostatic functional groups but have unsaturated bonds, vinyl monomers without electrostatic functional groups are preferred. As monomers that have electrostatic functional groups and unsaturated bonds, vinyl monomers having electrostatic functional groups are preferred. When imparting positive charge properties to a shell resin, vinyl monomers having positive charge properties are preferred. When imparting negative charge properties to a shell resin, vinyl monomers having negative charge properties are preferred.

[0076] Examples of vinyl monomers that do not have electrostatic functional groups 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, etc.), ethylenically unsaturated monoolefins (more specifically, ethylene, propylene, butylene, and isobutylene, etc.), vinyl halides (more specifically, vinyl chloride, vinylidene chloride, vinyl bromide, and vinyl fluoride, etc.), and vinyl esters (more specifically, vinyl acetate, provinyl chloride, vinyl fluoride, etc.). Examples include vinyl pionate, vinyl benzoate, and vinyl butyrate, etc., (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, etc.), 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 vinylnaphthalene. Among these, styrene and (meth)acrylic acid esters are preferred. As the (meth)acrylic acid ester, alkyl (meth)acrylate ester is preferred, butyl (meth)acrylate is more preferred, and n-butyl (meth)acrylate is even more preferred.

[0077] Examples of vinyl monomers having positively charged functional groups include N-vinyl compounds, aminoacrylic acid monomers, (meth)acrylonitrile, and (meth)acrylamide.

[0078] Examples of N-vinyl compounds include N-vinylpyrrole, N-vinylcarbazole, N-vinylindole, and N-vinylpyrrolidone.

[0079] Examples of aminoacrylic acid monomers include compounds 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, a phenylene group, or a combination of these groups having 1 to 10 carbon atoms.

[0080] Examples of alkyl groups having 1 to 20 carbon atoms represented by R2 and R3 in formula (1) include methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, iso-pentyl group, tert-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, 2-ethylhexyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group (lauryl group), n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group (stearyl group), n-nonadecyl group, and n-icosyl group.

[0081] Examples of alkylene groups with 1 to 10 carbon atoms represented by Q in formula (1) include methylene group, 1,2-ethane-diyl group, 1,1-ethylene group, propane-1,3-diyl group, propane-2,2-diyl group, propane-1,1-diyl group, propane-1,2-diyl group, butane-1,4-diyl group, pentane-1,5-diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, nonane-1,9-diyl group, and decane-1,10-diyl group. Examples of phenylene groups represented by Q in formula (1) include p-phenylene group, m-phenylene group, o-phenylene group, and the divalent group obtained by removing hydrogen from the 4th position of the phenyl group contained in the benzyl group.

[0082] 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-diethylaminophenyl(meth)acrylamide (pN,) methylaminophenyl(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,Examples 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.

[0083] Examples of negatively charged functional groups include fluorine-substituted hydrocarbon groups or sulfo groups. Examples of vinyl monomers having negatively charged 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, etc.), 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 acid (more specifically, sulfoethylacrylic acid, sulfoethyl methacrylic acid, and sulfoethyl methacrylate sodium, etc.).

[0084] The addition polymerization method for monomers having unsaturated bonds is not particularly limited, and any method such as solution polymerization, bulk polymerization, emulsion polymerization, or suspension polymerization can be selected.

[0085] Examples of polymerization initiators that can be used for 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-butyl perbenzoate, dicyclohexyl peroxide, and dicumyl peroxide. The amount of these polymerization initiators used is preferably 0.1% to 15% by mass relative to the total mass of the monomer.

[0086] When additive polymerization of monomers having unsaturated bonds is carried out using an aqueous medium, such as emulsion polymerization or suspension polymerization, surfactants 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 type surfactants, sulfonate type surfactants, phosphate ester type surfactants, and soaps. Examples of cationic surfactants include amine salt type surfactants and quaternary ammonium salt type surfactants. Examples of nonionic surfactants include polyethylene glycol type surfactants, alkylphenol ethylene oxide adduct type surfactants, and polyhydric alcohol type surfactants (more specifically, glycerin, sorbitol, and sorbitan, etc.).

[0087] When the charge-controlled resin is a copolymer of a monomer having an electrostatic functional group and an unsaturated bond and a monomer that does not have an electrostatic functional group but has an unsaturated bond, the content of repeating units derived from the monomer having an electrostatic functional group and an unsaturated bond in the total repeating units of the charge-controlled 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.

[0088] The content of the charge-controlling 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.

[0089] A shell layer may be formed using a mixture of a charge-controlled resin and a non-charge-controlled resin (a resin without charge-positive functional groups). As the non-charge-controlled resin, at least one polymer of vinyl monomer without charge-positive functional groups can be used. Methods for mixing the charge-controlled resin and the non-charge-controlled resin include melt-kneading these resins using a melt-kneading device such as a twin-screw extruder, and removing the organic solvent from a resin solution obtained by dissolving these resins in an organic solvent.

[0090] A shell layer may be formed using shell resin particles containing a charge-controlled resin and shell resin particles containing a non-charge-controlled resin. In this case, the ratio of the mass of shell resin particles containing the charge-controlled resin to the total mass of shell resin particles used to form the shell layer is preferably 80% by mass or more, and more preferably 90% by mass or more.

[0091] The glass transition temperature of the shell resin is preferably 45°C to 90°C, and more preferably 50°C to 80°C. The softening temperature of the shell resin is preferably 100°C to 250°C, and more preferably 110°C to 240°C. The softening temperature of the shell resin is preferably higher than the softening temperature of the binder resin contained in the toner core, and more preferably 10°C to 140°C higher than the softening temperature of the binder resin. By setting the temperature characteristics of the shell resin within this range, when the shell resin particles are embedded in the toner core, the portion of the shell resin particles that comes into contact with the toner core is less likely to deform, making it easier for convex portions originating from the shape of the shell resin particles before they transformed into the shell layer to form on the inner surface of the shell layer.

[0092] The mass-average molecular weight (Mw) of the shell resin is preferably between 20,000 and 1,500,000.

[0093] 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 using shell resin particles with such number-average primary particle diameters, it is easy to uniformly coat the surface of the toner core with a single layer of shell resin particles, and it is easy to form a shell layer with a desired structure. The larger the number-average primary particle diameter of the shell resin particles, the easier it is to form a shell layer of sufficient thickness on the surface of the toner core, improving the heat resistance 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 adhere the shell resin particles to the surface of the toner core. Therefore, it is easy to form a shell layer with a predetermined structure. 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, grinding method, and classification method.

[0094] The content of shell resin particles is preferably 1 to 20 parts by mass, and more preferably 3 to 15 parts by mass, per 100 parts by mass of toner core. The higher the content of shell resin particles, the easier it is to coat the entire surface of the toner core with shell resin particles. By coating the entire surface of the toner core with shell resin particles, the toner is less likely to aggregate during storage at high temperatures, and the heat-resistant storage properties are easily improved. The lower the content of shell resin particles, the thinner the shell layer becomes, and it is easier to obtain toner with excellent fixation properties.

[0095] <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, and barium titanate, etc.). As already mentioned, it is preferable that the toner particles do not contain carbon nanotubes as external additives. The surface of the external additive particles may be subjected to either or both positive charging treatment and / or 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.

[0096] The content of the external additive is preferably 0.1 parts by mass to 10.0 parts by mass, and more preferably 0.2 parts by mass to 5.0 parts by mass, per 100.0 parts by mass of toner matrix particles. The higher the content of the external additive, the easier it is to improve the hydrophobicity of the toner. As a result, it is less affected by water molecules in the air in high temperature and high humidity environments, sufficient chargeability of the toner can be ensured, and an image of the desired density can be formed. The fluidity of the toner can also be improved. Furthermore, the lower the content of the external additive, the more the decrease in image density due to toner charge-up can be suppressed.

[0097] <Toner manufacturing method> The toner of this embodiment can be manufactured, for example, by performing a toner core formation step, a shell layer formation step, and an external additive step. Note that the shell layer formation step can be omitted when manufacturing non-encapsulated toner particles. Furthermore, the external additive step can be omitted if the toner particles do not contain external additives.

[0098] (Toner core formation process) In the toner core formation process, a binder resin, magnetic particles, carbon nanotubes, and an optional internal additive are mixed using a mixing device to obtain a mixture. The mixture is then melt-kneaded using a kneader such as a single-screw or twin-screw extruder to obtain a kneaded product. The kneaded product is then pulverized to obtain a pulverized product. If it is necessary to reduce the diameter of the pulverized product, it is further pulverized. If it is necessary to standardize the particle size of the pulverized product, it is classified. Through the above methods, the toner core, which is the pulverized product, is obtained.

[0099] (Shell layer formation process) In the shell layer formation process, a shell layer is formed using shell resin particles. The shell resin particles are, for example, spherical. The toner core and the shell resin particles are mixed using a mixing device or the like, and the shell resin particles are attached to the surface of the toner core. Through this attachment, a shell layer composed of shell resin particles is formed on the surface of the toner core.

[0100] In order to form a thin, 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 perpendicularly to the surface of the toner core.

[0101] To adjust the smoothness of the shell layer, a mechanical 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 force, the greater the degree of smoothing of the outer surface of the shell layer. One method of applying a mechanical force is to create an impact force on the toner mother particles by collisions between them as the toner core (i.e., toner mother particles) with the external additive attached moves at high speed through the confined space inside the mixing device. Another method of applying a mechanical force is to create an impact force on the toner mother particles by collisions between the toner mother particles and the inner wall of the device, the rotor, or the stator as the toner core (i.e., toner mother particles) with the external additive attached moves at high speed through the confined space inside the mixing device.

[0102] (External addition process) In the external additive process, toner particles are obtained by attaching an external additive to the surface of toner matrix particles. One method for attaching the external additive to the surface of the toner matrix particles is to agitate the toner matrix particles and the external additive using a mixing device (more specifically, an FM mixer and a Nauter mixer®, etc.). It is preferable to adjust the processing conditions so that the external additive particles do not become embedded in the toner matrix particles. [Examples]

[0103] The present invention will be described in more detail below using examples. However, the present invention is not limited in any way to the scope of the examples.

[0104] [Synthesis of binding resins] A polyester resin (BR1) used as a binder resin in the toner core formation process was synthesized by the following method. 1960 g of bisphenol A propylene oxide adduct, 780 g of bisphenol A ethylene oxide adduct, 257 g of dodecenyl succinic anhydride, 770 g of terephthalic acid, and 4 g of dibutyltin oxide were charged into a reaction vessel. The reaction vessel was placed under a nitrogen atmosphere, and the temperature inside the vessel was raised to 235°C while stirring. The reaction was then carried out at this temperature for 8 hours, after which the pressure inside the reaction vessel was reduced to 8.3 kPa and the reaction was carried out for 1 hour. After that, the reaction mixture was cooled to 180°C, and trimellitic anhydride was added to the reaction vessel so that the acid value was 7 mg KOH / g. The temperature of the reaction mixture was then raised at a rate of 10°C / hour to 210°C, and the reaction was carried out at this temperature. After the reaction was complete, the contents of the reaction vessel were removed and cooled to obtain the polyester resin (BR1).

[0105] [Carbon nanotubes] The commercially available carbon nanotubes used in the toner core formation process are shown below. Carbon nanotubes (CN-A): Single-walled carbon nanotubes (ZEONANO® SG101, manufactured by Zeon Corporation) Carbon nanotubes (CN-B): Single-walled carbon nanotubes (SWNTSO, manufactured by Meijo Nanocarbon Co., Ltd.) Carbon nanotubes (CN-C): Multi-walled carbon nanotubes (MWNT, manufactured by Meijo Nanocarbon Co., Ltd.)

[0106] [Synthesis of resin particles] The resin particles (A) used in the shell layer formation process were synthesized by the following method. A flask equipped with a stirrer, thermometer, condenser, and nitrogen inlet tube was used as the reaction vessel. 180 g of isobutanol, a solvent, was placed in the reaction vessel. 16 g of diethylaminoethyl methacrylate and 16 g of methyl p-toluenesulfonate were further 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 contents of the reaction vessel were stirred at a stirring speed of 100 rpm while the internal temperature of the reaction vessel was raised to 80°C. The contents of the reaction vessel were continued to be stirred at a stirring speed of 100 rpm for 1 hour at the same temperature to carry out the quaternization reaction. After the quaternization reaction, 214 g of styrene, 72 g of butyl acrylate, and 12 g of t-butyl peroxy-2-ethylhexanoate (manufactured by Arkema Yoshitomi Co., Ltd.), a peroxide-based initiator, 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 at a stirring speed of 100 rpm for 3 hours. Next, 6 g of t-butyl peroxy-2-ethylhexanoate was added to the reaction vessel. Then, the contents of the reaction vessel were 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 size of resin particles (A) was 0.10 μm.

[0107] [Toner manufacturing] The toners shown in Tables 1 to 3 below were manufactured using the following methods.

[0108] [Table 1]

[0109] [Table 2]

[0110] [Table 3]

[0111] The abbreviations used in Tables 1 to 3 are shown below. BK: Magnetic particles CN: Carbon nanotube Part: Mass part %:mass% -: The relevant ingredient was not added, or the relevant value was not present. BK content: The content of magnetic particles in the toner core (For details, the content is calculated using the formula: "Magnetic particle content in toner core = 100 × amount of magnetic particles added / mass of toner core = 100 × amount of magnetic particles added / (amount of binder resin added + amount of release agent added + amount of charge control agent added + amount of magnetic particles added + amount of carbon nanotubes added)"). CN content: The carbon nanotube content in the toner core (For details, the content is calculated using the formula: "Carbon nanotube content in toner core = 100 × amount of carbon nanotube added / mass of toner core = 100 × amount of carbon nanotube added / (amount of binder resin added + amount of release agent added + amount of charge control agent added + amount of magnetic particles added + amount of carbon nanotube added)").

[0112] <Manufacturing of toner (T-A1)> (Toner core formation process) A mixture was obtained by mixing 53.50 parts by mass of polyester resin (BR1) as a binder resin, 5.00 parts by mass of a release agent (polypropylene wax, "Viscol® 660-P" manufactured by Sanyo Chemical Industries, Ltd.), 1.00 part by mass of a charge control agent (quaternary ammonium salt compound, "BONTRON® P-51" manufactured by Orient Chemical Industries, Ltd.), 40.00 parts by mass of magnetic particles (BK-a) (TN-15 (manufactured by Mitsui Mining & Smelting Co., Ltd.)), and 0.50 parts by mass of carbon nanotubes (CN-A) using a mixing device. The mixture was melt-kneaded using a twin-screw extruder to obtain a kneaded product. The kneaded product was coarsely pulverized using a pulverizer ("Rotoplex®" manufactured by Toa Machinery Works Co., Ltd.) to obtain a coarse pulverized product. The coarse pulverized product was finely pulverized using a mechanical pulverizer ("Turbo Mill" manufactured by Freund Turbo Co., Ltd.) to obtain a fine pulverized product. The finely ground material was classified using a classifier ("Elbow Jet" manufactured by Nippon Steel Mining Co., Ltd.) to obtain toner cores. The median diameter of the obtained toner cores was 7.0 μm. The obtained toner cores were used as toner matrix particles.

[0113] (External addition process) 100.0 parts by mass of the toner matrix particles obtained above, 2.0 parts by mass of titanium oxide particles (EC-100, manufactured by Titanium Industries 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 speed of 30 m / sec using an FM mixer (manufactured by Nippon Coke Industries Co., Ltd.). This allowed the external additives (titanium oxide particles and hydrophobic silica particles) to adhere to the surface of the toner matrix particles, thereby obtaining toner (T-A1).

[0114] <Manufacturing of toner cartridges (T-A2) to (T-A3) and (T-B1) to (T-B2)> Except for the amount of carbon nanotubes added in the toner core formation process as shown in Tables 1 and 3, toners (T-A2) to (T-A3) and (T-B1) to (T-B2) were manufactured using the same method as for toner (T-A1).

[0115] <Manufacturing of toner cartridges (T-A4) to (T-A5)> Except for the type of carbon nanotube used in the toner core formation process shown in Table 1, toners (T-A4) to (T-A5) were manufactured using the same method as toner (T-A1).

[0116] <Manufacturing of toner cartridges (T-A6) to (T-A7)> Except for the amount of magnetic particles used in the toner core formation process, as shown in Table 2, toners (T-A6) to (T-A7) were manufactured using the same method as toner (T-A1).

[0117] <Manufacturing of toner (T-A8)> Except for using MTS-106 (manufactured by Toda Kogyo Co., Ltd.) as the type of magnetic particle (BK-b) used in the toner core formation process, toner (T-A8) was manufactured using the same method as toner (T-A1).

[0118] <Manufacturing of toner cartridges (T-B3) to (T-B4)> Except for the amount of magnetic particles used in the toner core formation process as shown in Table 2, toners (T-B3) to (T-B4) were manufactured using the same method as toner (T-A1).

[0119] <Manufacturing of toner (T-B5)> Toner (T-B5) was manufactured using the same method as toner (T-A1), except that carbon nanotubes were not added during the toner core formation process.

[0120] <Manufacturing of toner (T-A9)> Toner (T-A9) was manufactured in the same manner as toner (T-A1), except that the shell layer formation process described below was performed after the toner core formation process and before the external addition process.

[0121] (Shell layer formation process) A powder processing device (a "Multi-Purpose Mixer MP type" manufactured by Nippon Coke Industries Co., Ltd.) was used to form the shell layer. 100g of toner core (specifically, the toner core obtained in the toner core formation process of the toner (T-A1) manufacturing process) and 10g of resin particles (A) were placed in the processing tank of the powder processing device and processed at a rotation speed of 8000 rpm and 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 process, the toner core was coated with resin particles (A), forming a shell layer on the surface of the toner core. As a result, toner mother particles having a toner core and a shell layer covering the toner core were obtained. The obtained toner mother particles were used in the external addition process.

[0122] [Measurement method] <Medium Diameter> The median diameter of the toner core described above was measured using a Coulter Counter Multisizer 4e (manufactured by Beckman Coulter).

[0123] <Number-average primary particle diameter> The number-average primary particle diameter of the above-mentioned resin particles was measured according to the following method. First, a photograph of the resin particles was taken at a magnification of 100,000x using a field emission scanning electron microscope (JSM-6700F (manufactured by JEOL Ltd.)). The electron microscope images were further magnified as needed, and the primary particle diameter of 50 resin particles was measured using a ruler, calipers, etc. The number-average value of the primary particle diameters of the 50 resin particles was taken as the number-average primary particle diameter of the resin particles.

[0124] [Evaluation unit] The evaluation equipment used for the following evaluations is a modified color printer (manufactured by Kyocera Document Solutions Corporation) with adjustable fixing temperature. We used "ECOSYS(registered trademark) LS-2100DN".

[0125] [Evaluation of retention] The fixing performance (specifically, minimum fixing temperature and fixing rate) of each toner was evaluated using the following method. The evaluation results are shown in Tables 4 to 6 below.

[0126] <Minimum fixing temperature> Under normal temperature and humidity conditions (temperature 20°C and relative humidity 65%RH), the evaluation machine was used to test one sheet of paper (monochrome / color compatible paper, FUJI XEROX "CC90", basis weight: 90g / m²). 2 A solid image (more specifically, an image of unfixed toner) was formed on the paper surface. The solid image was formed with a toner amount of 1.0 mg / cm² on the paper surface. 2 Furthermore, it was a solid image with a size of 30mm x 30mm. Next, the paper on which the solid image was formed was passed through the fixing device of the evaluation machine.

[0127] The fixing temperature of the fuser unit was set to a temperature between 100°C and 145°C. Specifically, the fixing temperature of the fuser unit was increased by 1°C increments starting from 100°C, and the lowest temperature at which a solid image (unfixed toner image) could be fixed to the paper (minimum fixing temperature) was measured. Whether or not the unfixed toner image could be fixed was confirmed by the folding and rubbing test shown below.

[0128] The paper, after being passed through the fuser, was folded so that the side with the solid image was facing inward. More specifically, the paper was folded so that the fold line passed approximately through the center of the solid image. A 1 kg weight covered with cloth was used to rub the folded paper back and forth 10 times along the fold, so that only the weight of the weight itself was applied to the paper. After that, the paper was unfolded, and the length of the toner peeling (peeling length) in the part of the folded paper where the solid image had been fixed was measured. If the peeling length was 1 mm or less, it was determined that the unfixed toner image had been fixed. The minimum fixing temperature was determined according to the following criteria. Note that a lower minimum fixing temperature of the toner indicates better low-temperature fixing properties of the toner.

[0129] (Criteria for minimum fixing temperature) A (Good): The minimum fixing temperature is 130°C or lower. B (Defective): The minimum fixing temperature is greater than 130°C but less than 135°C. C (particularly poor): Minimum fixing temperature is 135°C or higher.

[0130] <Retention Rate> The fixing temperature of the fixing device in the evaluation machine was set to 160°C. Under normal temperature and humidity conditions (temperature 20°C and relative humidity 65%RH), the evaluation machine was used to print one sheet of paper (Fujifilm Business Innovation Co., Ltd. monochrome / color copy paper "C2", basis weight: 70g / m²). 2 Image A (a solid image with a print density of 4%) was formed on the surface. The formed image was used as the evaluation image. The image density (ID before friction) of the evaluation image was measured using a spectrophotometer ("SpectroEye®" manufactured by X-Rite).

[0131] Next, the paper was folded so that the side forming the solid image was facing inward. More specifically, the paper was folded so that the fold line passed approximately through the center of the solid image. A 1 kg weight covered with cloth was rubbed back and forth 10 times along the fold of the folded paper, so that only the weight of the weight itself was applied to the paper. The image density (post-friction ID) of the evaluation image after friction was measured using a spectrophotometer (X-Rite's "SpectroEye®").

[0132] The retention rate (in %) was calculated according to the formula "Retention Rate = (ID after friction / ID before friction) × 100". The retention rate was determined based on the following criteria.

[0133] (Retention rate criteria) A (Good): The retention rate is 95% or higher. B (Poor): The adhesion rate is between 90% and 95%. C (particularly poor): The adhesion rate is less than 90%.

[0134] [Table 4]

[0135] [Table 5]

[0136] [Table 6]

[0137] [Evaluation of image density, toner charge amount, and fogging in a normal temperature and humidity environment] The initial image density, toner charge, and fogging were evaluated for each toner using the following method. Furthermore, the image density and toner charge after continuous image formation were evaluated for each toner using the following method. The evaluation environment was a normal temperature and humidity environment (temperature 20°C and relative humidity 65%RH, hereinafter referred to as the "NN environment"). The evaluation results are shown in Tables 7 to 9 below.

[0138] <Image Formation> The fixing temperature of the fixing device in the evaluation machine was set to 160°C. Using the evaluation machine, one sheet of paper (Fujifilm Business Innovation Co., Ltd. monochrome / color copy paper "C2", basis weight: 70g / m²) was used. 2 Image A (a solid image with a print density of 4%) was formed on a sheet of paper and used as the initial image. Next, using the evaluation machine, Image B (a blank image) was formed on one sheet of paper and used as the image for fogging evaluation. Next, using the evaluation machine, Image C (an image with a print density of 4%) was formed continuously on 2500 sheets of paper. Next, using the evaluation machine, Image A was formed again on one sheet of paper and used as the image after printing.

[0139] <Image density> The image density (initial ID) of the initial image obtained through the above image formation process was measured using a reflectance densitometer (X-Rite "RD914"). The image density (post-printing ID) of the post-printing image obtained through the above image formation process was also measured using a reflectance densitometer (X-Rite "RD914"). The image density was determined according to the following criteria.

[0140] (Image density standards) A (Good): The ID is 1.25 or higher. B (Defective): The ID is between 1.20 and 1.25. C (Especially defective): The ID is less than 1.20.

[0141] <cover> The reflectance density DA of the image obtained for fogging evaluation (blank image) using the above image formation method was measured using a reflectance densitometer (X-Rite "RD914"). The reflectance density DB of unprinted paper was also measured using a reflectance densitometer (X-Rite "RD914"). The fogging density (FD) was calculated using the formula "Fogging density = Reflectance density DA - Reflectance density DB". Fogging was judged according to the following criteria.

[0142] (Criteria for overlap) A (Good): FD is 0.010 or less. B (Defective): FD is greater than 0.010.

[0143] <Toner charge amount> In the image formation process described above, after forming the initial image, the charge amount (initial charge amount) of the toner in the developer section of the evaluation machine was measured using a charge amount measuring device (Trek Q / M Meter 210HS). In the image formation process described above, after forming the post-printing image, the charge amount (post-printing charge amount) of the toner on the developer roll of the evaluation machine was measured using a charge amount measuring device (Trek Q / M Meter 210HS). The toner charge amount was determined according to the following criteria.

[0144] (Toner charge level standard) A (Good): The charge is between 20.0 μC / g and 25.0 μC / g. B (Defective): The charge level is 19.0 μC / g or more and less than 20.0 μC / g, or greater than 25.0 μC / g and 26.0 μC / g or less. C (particularly defective): The charge level is less than 19.0 μC / g or greater than 26.0 μC / g.

[0145] [Table 7]

[0146] [Table 8]

[0147] [Table 9]

[0148] [Evaluation of image density, toner charge amount, and fogging in high-temperature, high-humidity environments] Except for changing the evaluation environment from the NN environment to a high-temperature, high-humidity environment (an environment with a temperature of 32.5°C and a relative humidity of 80%RH, hereinafter referred to as the "HH environment"), the image density, toner charge amount, and fogging in the HH environment were evaluated using the same methods as those used for evaluating them in the NN environment. The evaluation results are shown in Tables 10 to 12 below.

[0149] [Table 10]

[0150] [Table 11]

[0151] [Table 12]

[0152] In Table 12, "-" indicates that the evaluation machine did not function properly and the evaluation could not be performed.

[0153] [Evaluation of image density, toner charge amount, and fogging in low-temperature, low-humidity environments] Except for changing the evaluation environment from the NN environment to a low-temperature, low-humidity environment (an environment with a temperature of 10°C and a relative humidity of 20%RH, hereinafter referred to as the "LL environment"), the image density, toner charge amount, and fogging in the LL environment were evaluated using the same methods as those used for evaluating them in the NN environment. The evaluation results are shown in Tables 13 to 15 below.

[0154] [Table 13]

[0155] [Table 14]

[0156] [Table 15]

[0157] The toner (T-B1) had a carbon nanotube content of less than 0.10% by mass in the toner core. The adhesion performance of the toner (T-B1) was evaluated as poor.

[0158] The toner (T-B2) had a carbon nanotube content of over 1.00 mass% in the toner core. The evaluation of the initial charge level of the toner (T-B2) in an NN environment was poor. The evaluation of the charge level of the toner (T-B2) after printing in both an NN and HH environment was particularly poor. The evaluation of the initial fogging of the toner (T-B2) in an NN environment was poor.

[0159] The toner (T-B3) had a magnetic particle content of less than 30.0% by mass in the toner core. The evaluation of the initial charge amount of the toner (T-B3) in an HH environment was poor. The evaluation of the initial image density of the toner (T-B3) in an HH environment was particularly poor. The evaluation of the image density of the toner (T-B3) after printing in an HH environment was particularly poor. The evaluation of the charge amount of the toner (T-B3) after printing in an HH environment was particularly poor. The evaluation of the initial fogging of the toner (T-B3) in NN, LL, and HH environments was particularly poor.

[0160] The toner (T-B4) had a magnetic particle content exceeding 50.0% by mass in the toner core. The fixation performance of the toner (T-B4) was evaluated as poor.

[0161] The toner (T-B5) did not contain carbon nanotubes in its toner core. The adhesion performance of the toner (T-B5) was particularly poor.

[0162] On the other hand, toners (T-A1) to (T-A9) each contained toner particles. The toner particles had a toner core. The toner core contained a binder resin, magnetic particles, and carbon nanotubes. The magnetic particle content in the toner core was 30.0% by mass or more and 50.0% by mass or less, and the carbon nanotube content was 0.10% by mass or more and 1.00% by mass or less. The evaluation of the fixation performance of toners (T-A1) to (T-A9), the evaluation of the initial and post-printing charge amount in various environments (e.g., NN environment, HH environment, and LL environment), the evaluation of the initial and post-printing image density in various environments (e.g., NN environment, HH environment, and LL environment), and the evaluation of the initial fogging in various environments (e.g., NN environment, HH environment, and LL environment) were all good.

[0163] From the above, it is determined that the toners of the present invention, including toners (T-A1) to (T-A9), have excellent fixing properties and can be charged to the desired amount and form images of the desired density with less fogging, even when images are continuously formed in various environments such as normal temperature and humidity, high temperature and high humidity, and low temperature and low humidity. [Industrial applicability]

[0164] The toner of the present invention can be used, for example, to form images in a copier, printer, or multifunction device. [Explanation of Symbols]

[0165] 1: Non-encapsulated toner particles 2: Toner matrix particles (non-encapsulated toner matrix particles) 2a: Toner core 2b: Shell layer 3: External additive particles 10: Capsule toner particles 20: Toner matrix particles (capsule toner matrix particles)

Claims

1. Toner containing toner particles, The toner particles have a toner core, The toner core contains a binder resin, magnetic particles, and carbon nanotubes. A toner in which the content of magnetic particles in the toner core is 30.0% by mass or more and 50.0% by mass or less, and the content of carbon nanotubes is 0.10% by mass or more and 1.00% by mass or less.

2. The toner according to claim 1, wherein the carbon nanotube is a single-walled carbon nanotube or a multi-walled carbon nanotube.

3. The toner particles are Capsule toner particles having the toner core and a shell layer covering the surface of the toner core, The toner according to claim 1 or 2, wherein the toner particles are non-encapsulated toner particles having the toner core and not having the shell layer.

4. The toner according to claim 1 or 2, wherein the toner particles do not contain carbon nanotubes as an external additive.

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