Magnetic one-component toner and image forming apparatus using the same

Abstract

The present invention provides a magnetic one-component toner that has low-temperature fixing properties and excellent heat resistance and heat stress resistance over long periods, as well as an image forming apparatus using the same. [Solution] The magnetic one-component toner comprises toner matrix particles containing at least a binder resin and magnetic powder, and an external additive attached to the surface of the toner matrix particles. The binder resin comprises an amorphous polyester resin and a crystalline polyester resin containing an aliphatic diol with 3 to 9 carbon atoms, and the amount of crystalline polyester resin added is 5% by mass or less relative to the amorphous polyester resin. When the glass transition point at the first heating, measured by differential scanning calorimeter, is Tg1, and the glass transition point measured when the temperature is raised again after cooling after measuring Tg1 is Tg2, Tg(45) and Tg(25), which are Tg1 measured after being left at 45°C and 25°C for 100 hours, are 0

Description

Technical Field

[0001] The present invention relates to a magnetic one-component toner and an image forming apparatus using a magnetic one-component developing method using the magnetic one-component toner.

Background Art

[0002] Generally, in electrophotography, after the surface of an electrostatic latent image carrier is charged by corona discharge or the like, it is exposed by a laser or the like to form an electrostatic latent image. The formed electrostatic latent image is developed with toner to form a toner image. Further, the formed toner image is transferred onto a recording medium to obtain a high-quality image.

[0003] As methods for developing an electrostatic latent image with toner, a magnetic one-component developing method using only a magnetic toner and a two-component developing method using a two-component developer containing a non-magnetic toner and a magnetic carrier are known. Since magnetic toner is less expensive than a two-component developer, the magnetic one-component developing method is widely used in monochrome printers.

[0004] In the magnetic one-component developing method, in order to increase the speed of the image forming apparatus and improve the compatibility with various media, further improvement in low-temperature fixing property of the toner is required, and various studies have been conducted. For example, a technique for improving the low-temperature fixing property by containing a crystalline polyester as a plasticizer in an amorphous polyester resin is known. On the other hand, when the crystalline polyester is compatible with the amorphous polyester, the effect of lowering the glass transition point (Tg) is high, so the storage stability of the toner may deteriorate.

[0005] As a means for suppressing the decrease in the glass transition point (Tg), Patent Document 1 discloses a method of preventing the amorphous polyester and the crystalline polyester from being compatible and the glass transition point (Tg) from decreasing by using a plasticizer different from the crystalline polyester and the amorphous polyester.

[0006] Patent Document 2 discloses a toner in which, in a cross-section observed with a transmission electron microscope, vinyl resin constitutes the matrix and amorphous polyester and crystalline polyester constitute the domains, and when the integral value of the stress of the toner is taken as f1 in measurements using a tacking tester, f1 is 5.9 g·m / sec or less, and when the glass transition point obtained by differential scanning calorimetry of the toner during the first heating is taken as Tg1 (°C) and the glass transition point during the second heating is taken as Tg2 (°C), the value of Tg1 is 50°C or higher and the value of Tg1-Tg2 is 5°C or higher. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2020-95272 [Patent Document 2] Japanese Patent Publication No. 2018-4880 [Overview of the project] [Problems that the invention aims to solve]

[0008] The toner described in Patent Document 1 had a problem in that the plasticizer was detached during the grinding of the toner, resulting in insufficient effectiveness. The toner described in Patent Document 2 has a lower Tg2 temperature than Tg1, which makes the toners more easily deformed during melting, promoting adhesion between toners on paper and between toners themselves, thus improving fixation. However, the Tg1 > Tg2 relationship also affected the toner after fixation, resulting in a problem in that the shelf life of printed materials deteriorated.

[0009] In view of the above problems, the present invention aims to provide a magnetic one-component toner that has low-temperature fixing properties and excellent heat resistance and heat stress resistance over a long period of time, and an image forming apparatus using the same. [Means for solving the problem]

[0010] To achieve the above objective, the first configuration of the present invention is a magnetic one-component toner comprising toner particles comprising toner matrix particles containing at least a binder resin and magnetic powder, and an external additive attached to the surface of the toner matrix particles. The binder resin comprises an amorphous polyester resin and a crystalline polyester resin, wherein the amount of crystalline polyester resin added is 5% by mass or less relative to the amorphous polyester resin. The crystalline polyester resin contains one or more aliphatic diols having 3 to 9 carbon atoms. When the glass transition point at the first heating, measured by differential scanning calorimeter, is Tg1, and the glass transition point measured when the temperature is raised again after cooling following the measurement of Tg1, is Tg(45), which is Tg1 measured after being left at 45°C for 100 hours, and Tg(25), which is Tg1 measured after being left at 25°C for 100 hours, satisfy the following equations (1) and (2). 0 <Tg2-Tg(45)<5 ···(1) 4 <Tg2-Tg(25)<10 ···(2) [Effects of the Invention]

[0011] According to the first configuration of the present invention, a magnetic single-component toner is obtained that has low-temperature fixing properties and excellent heat resistance and heat stress resistance over a long period of time. Therefore, it can be suitably used in magnetic single-component development methods with particularly high process line speeds. [Brief explanation of the drawing]

[0012] [Figure 1] Schematic cross-sectional view of an image forming apparatus 100 using the magnetic one-component toner of the present invention. [Modes for carrying out the invention]

[0013] [1. Overall configuration of the image forming apparatus] Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a schematic cross-sectional view of an image forming apparatus 100 in which the magnetic one-component toner of the present invention is used. In the image forming apparatus (e.g., a monochrome printer) 100, when printing is performed, an electrostatic latent image is formed in the image forming unit 9 within the image forming apparatus 100 based on original image data transmitted from a higher-level device (not shown), such as a personal computer, and toner is attached to the electrostatic latent image by the developing device 4 to form a toner image. Toner is supplied to the developing device 4 from the toner container 5. In the image forming apparatus 100, the image forming process on the photoreceptor drum 1 is performed while the photoreceptor drum 1 is rotated clockwise in Figure 1.

[0014] The image forming unit 9 is equipped with a charging device 2, an exposure unit 3, a developing device 4, a transfer roller 6, a cleaning device 7, and a static elimination device (not shown) along the rotation direction (clockwise) of the photoreceptor drum 1. The photoreceptor drum 1 is, for example, an aluminum drum with a photosensitive layer laminated on its surface (outer surface). The surface (outer surface) of the photoreceptor drum 1 is uniformly charged by the charging device 2. Then, an electrostatic latent image is formed on the surface that receives a light beam from the exposure unit 3, which will be described later, with the charge attenuated. The photosensitive layer is not particularly limited, but amorphous silicon (a-Si), which has excellent durability, is preferred. The linear velocity of the photoreceptor drum 1 (i.e., the process linear velocity of the image forming apparatus 100) is 250 mm / sec or more.

[0015] The charging device 2 uniformly charges the surface of the photoreceptor drum 1. The charging device 2 is a corona discharge device that discharges electricity by applying a high voltage using, for example, a thin wire as an electrode. Alternatively, a contact-type charging device may be used, in which a voltage is applied while a charging member, such as a charging roller, is in contact with the surface of the photoreceptor drum 1. The exposure unit 3 irradiates the photoreceptor drum 1 with a light beam (for example, a laser beam) based on the image data, forming an electrostatic latent image on the surface of the photoreceptor drum 1.

[0016] The developing device 4 adheres toner to the electrostatic latent image on the photoreceptor drum 1 to form a toner image. In this embodiment, a magnetic single-component toner (magnetic single-component developer) is housed in the developing device 4. The developing device 4 has a regulating blade 4b that is non-contact with the developing roller 4a and has a mechanism for charging the toner via the developing roller 4a, which is a magnetic single-component jumping development method. The cleaning device 7 includes a cleaning blade 7a that makes line contact in the longitudinal direction of the photoreceptor drum 1 (the direction perpendicular to the paper surface of FIG. 1), and after the toner image is transferred (transferred) to the paper, the cleaning blade 7a removes the toner remaining on the surface of the photoreceptor drum 1.

[0017] Toward the photoreceptor drum 1 on which the toner image is formed as described above, the paper is conveyed from the paper storage unit 10 to the image forming unit 9 at a predetermined timing via the paper conveyance path 11 and the registration roller pair 13. The transfer roller 6 contacts the photoreceptor drum 1 to form a nip portion (transfer nip portion), and transfers (transfers) the toner image formed on the surface of the photoreceptor drum 1 to the paper passing through the transfer nip portion without disturbing it. Thereafter, in preparation for the formation of a new electrostatic latent image that is subsequently performed, the cleaning device 7 removes the residual toner on the surface of the photoreceptor drum 1, and the discharging device removes the residual charge.

[0018] The paper onto which the toner image is transferred is separated from the photoreceptor drum 1, conveyed to the fixing device 8, and heated and pressurized so that the toner image is fixed to the paper. The paper that has passed through the fixing device 8 passes through the discharge roller pair 14 and is discharged to the paper discharge unit 15.

[0019] [2. Basic Configuration of Toner] Hereinafter, the magnetic one-component toner of the present invention (hereinafter also simply referred to as toner) used in the image forming apparatus 100 will be described in detail. In addition, the evaluation results (values indicating shape or physical properties, etc.) regarding powder (more specifically, toner core particles, toner mother particles, external additives, or toner, etc.) are, if not otherwise specified, the number average of the values measured for each of a considerable number of average particles selected from the powder. Further, the number average particle diameter of the powder is, if not otherwise specified, the number average value of the equivalent circle diameter of the primary particles (the diameter of a circle having the same area as the projected area of the particles) measured using a microscope. Also, the measured value of the volume median diameter (D50) of the powder is, if not otherwise specified, the value measured using a laser diffraction / scattering particle size distribution measuring device ("LA-750" manufactured by Horiba, Ltd.). Further, the measured value of each of the acid value and the hydroxyl value is, if not otherwise specified, the value measured according to "JIS (Japanese Industrial Standard) K0070-1992". Also, the measured value of each of the number average molecular weight (Mn) and the mass average molecular weight (Mw) is, if not otherwise specified, the value measured using gel permeation chromatography.

[0020] Hereinafter, when comprehensively referring to a compound and its derivatives by attaching "system" after the compound name, it may be done in some cases. When representing a polymer name by attaching "system" after the compound name, it means that the repeating unit of the polymer is derived from the compound or its derivative. Also, acrylic and methacrylic may be comprehensively referred to as "(meth)acrylic" in some cases. Also, acryloyl (CH 2 =CH-CO-) and methacryloyl (CH 2 =C(CH 3 )-CO-) may be comprehensively referred to as "(meth)acryloyl" in some cases.

[0021] The toner according to the present embodiment can be suitably used for developing an electrostatic latent image as a positively chargeable toner. The toner of the present embodiment is a powder containing a plurality of toner particles (particles each having a configuration described later). The toner contains magnetic powder and is used as a one-component developer.

[0022] The toner particles contained in this embodiment comprise toner matrix particles and an external additive attached to the surface of the toner matrix particles. The toner matrix particles contain at least a binder resin and magnetic powder. The toner matrix particles may also contain a release agent, a charge control agent, etc., in addition to the binder resin as needed. The toner matrix particles include amorphous polyester resin and crystalline polyester resin as the binder resin.

[0023] When the amount of crystalline polyester resin added increases, the amorphous polyester resin and crystalline polyester resin become compatible, lowering the glass transition temperature (Tg). As a result, problems such as a decrease in the heat resistance of the toner occur. Therefore, in the toner of the present invention, the amount of crystalline polyester resin added relative to the toner matrix particles (total amount of amorphous polyester resin, amorphous polyester resin, and magnetic powder) is 5% by mass or less.

[0024] Furthermore, when the toner of the present invention is heated from 30°C to 170°C at a rate of 10°C / min, the glass transition point of the toner measured by a differential scanning calorimeter is defined as Tg1, and when the toner is cooled to 30°C at a rate of 100°C / min after measuring Tg1, and then heated again from 30°C to 170°C at a rate of 10°C / min, the glass transition point of the toner measured by a differential scanning calorimeter is defined as Tg2. In this case, Tg(45), which is Tg1 after the toner has been left at 45°C for 100 hours, and Tg(25), which is Tg1 after the toner has been left at 25°C for 100 hours, satisfy the following relationships (1) and (2). 0 <Tg2-Tg(45)<5 ···(1) 4 <Tg2-Tg(25)<10 ···(2)

[0025] This allows for lower Tg1 than Tg2 to maintain low-temperature fixing properties, while keeping the difference between Tg1 and Tg2 within a predetermined range, thereby improving toner stability in high-temperature environments. As a result, it becomes a magnetic single-component toner that is suitable for high-speed processes with high thermal storage and stress resistance, despite having low-temperature fixing properties, and can withstand significant stress in the development system.

[0026] [3. Toner materials] The binder resin, magnetic powder, colorant, release agent, charge control agent, and external additives added to the toner matrix particles, as well as the method for manufacturing the toner of the present invention, will be described below in order.

[0027] (Binding resin) The toner matrix particles constituting the toner of the present invention contain a binder resin. The toner matrix particles contain a polyester resin as the binder resin. More specifically, the toner matrix particles contain an amorphous polyester resin and a crystalline polyester resin as the binder resin. By including a crystalline polyester resin in the toner matrix particles, sharp melt properties can be imparted to the toner matrix particles.

[0028] Polyester resins can be obtained by condensation polymerization or copolymerization of a divalent or trivalent or higher alcohol component with a divalent or trivalent or higher carboxylic acid component. The following alcohol and carboxylic acid components are examples of components used in the synthesis of polyester resins.

[0029] Specific examples of divalent or trivalent or higher alcohol components include diols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; bisphenol A, hydrogenated bisphenol A, and polyoxyethylene Examples include bisphenols such as bisphenol A and polyoxypropylene bisphenol A; and trivalent or higher alcohols such as 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.

[0030] Specific examples of divalent or trivalent or higher carboxylic acid components include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebatic acid, azelaic acid, malonic acid, or divalent alkyl or alkenyl succinic acids such as n-butylsuccinic acid, n-butenylsuccinic acid, isobutylsuccinic acid, isobutenylsuccinic acid, n-octylsuccinic acid, n-octenylsuccinic acid, n-dodecylsuccinic acid, n-dodecenylsuccinic acid, isododecylsuccinic acid, and isododecenylsuccinic acid. Carboxylic acids include trivalent or higher carboxylic acids such as 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,5-benzenetricarboxylic 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 trimeric acid. These divalent or trivalent or higher carboxylic acid components may be used as ester-forming derivatives such as acid halides, acid anhydrides, and lower alkyl esters. Here, "lower alkyl" means an alkyl group having 1 to 6 carbon atoms.

[0031] Suitable examples of amorphous polyester resins include polymers of one or more bisphenols (specifically, bisphenol A ethylene oxide adduct or bisphenol A propylene oxide adduct, etc.) and one or more dicarboxylic acids (specifically, terephthalic acid, fumaric acid, or alkyl succinic acid, etc.).

[0032] A suitable example of a crystalline polyester resin is a polymer of one or more aliphatic dicarboxylic acids having 10 to 15 carbon atoms (specifically, suberic acid, adipic acid, or succinic acid, etc.) and one or more aliphatic diols having 3 to 9 carbon atoms (specifically, ethylene glycol, propanediol, butanediol, pentanediol, or hexanediol, etc.). When an aliphatic diol having 10 or more carbon atoms (for example, 1,12-dodecanediol) is used, the heat stress resistance of the toner decreases, as shown in the examples described later.

[0033] More preferred examples of crystalline polyester resins include copolymers of one or more aliphatic dicarboxylic acids having 10 to 15 carbon atoms, one or more aliphatic diols having 3 to 9 carbon atoms, and one or more aromatic dicarboxylic acids.

[0034] The degree of crystallinity of crystalline polyester resin is defined as 0% at the start of the annealing process and 100% when the annealing process is carried out until the degree of crystallinity is saturated. The degree of crystallinity of crystalline polyester resin is a value measured based on the X-ray diffraction intensity of the target peak (the peak originating from the crystalline polyester resin) in the X-ray diffraction spectrum.

[0035] The glass transition temperature (Tg) of polyester resin is preferably between 40°C and 70°C. If the glass transition temperature is too high, the low-temperature fixability of the toner tends to decrease. If the glass transition temperature is too low, the heat resistance of the toner tends to decrease.

[0036] The glass transition point of polyester resin can be determined from the point of change in the specific heat of the polyester resin using a differential scanning calorimeter (DSC). More specifically, the glass transition point of polyester resin can be determined by measuring the endothermic curve of the polyester resin using a differential scanning calorimeter (DSC-6200, manufactured by Seiko Instruments Inc.) as the measuring device. 10 mg of the sample is placed in an aluminum pan, and an empty aluminum pan is used as a reference. The glass transition point of the polyester resin can be determined from the endothermic curve obtained by measuring the polyester resin at room temperature and humidity within a measurement temperature range of 25°C to 200°C at a heating rate of 10°C / min.

[0037] The softening point of the polyester resin is preferably 70°C to 130°C, and more preferably 80°C to 120°C. To improve the strength of the toner matrix particles and the fixation of the toner, the number-average molecular weight (Mn) of the polyester resin is preferably 1000 to 2000. The molecular weight distribution of the polyester resin (ratio of mass-average molecular weight (Mw) to number-average molecular weight (Mn) Mw / Mn) is preferably 9 to 21.

[0038] As the binder resin, amorphous polyester resins and crystalline polyester resins that have good adhesion to paper are used. However, polyester resins can be used alone, or crosslinking agents and thermosetting resins can be added to them. By adding crosslinking agents and thermosetting resins and introducing a partially crosslinked structure into the binder resin, it is possible to improve the heat resistance, storage durability, etc. of the toner without reducing the toner's adhesion.

[0039] The toner matrix particles may contain other binder resins in addition to the polyester resin described above. Examples of other binder resins include thermoplastic resins and thermosetting resins. Examples of thermoplastic resins that can be used with polyester 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. Two or more of these thermoplastic resins can be used in combination.

[0040] Epoxy resins and cyanate resins are preferred thermosetting resins that can be used with polyester resins. Specific examples of suitable thermosetting resins include bisphenol A type epoxy resins, hydrogenated bisphenol A type epoxy resins, novolac type epoxy resins, polyalkylene ether type epoxy resins, cyclic aliphatic type epoxy resins, and cyanate resins. Two or more of these thermosetting resins can be used in combination.

[0041] The mass-average molecular weight (Mw) of the binder resin is not particularly limited as long as it does not hinder the objectives of the present invention. Typically, the mass-average molecular weight (Mw) of the binder resin is preferably 20,000 to 300,000, and more preferably 30,000 to 2,000,000. The mass-average molecular weight of the binder resin can be determined by gel permeation chromatography (GPC) using a calibration curve prepared in advance using standard polystyrene resin.

[0042] (magnetic powder) The toner matrix particles contain magnetic powder in the binder resin. Examples of magnetic powder materials include magnetic iron oxides such as magnetite, maghemite, and ferrite, or compounds of divalent metals and iron oxides, powders of metals such as iron, cobalt, and nickel, or alloys of these metals such as aluminum, cobalt, copper, lead, magnesium, tin, zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten, and vanadium, and mixtures of these powders.

[0043] The particle size of the magnetic powder is not limited as long as it does not hinder the objective of the present invention. Specifically, the particle size of the magnetic powder is preferably 0.05 to 2.0 μm, and more preferably 0.1 μm or more and 1.0 μm or less. When using magnetic powder with such particle size, it is easy to uniformly disperse the magnetic powder in the binder resin.

[0044] Magnetic powders can be surface-treated using surface treatment agents such as titanium-based coupling agents or silane-based coupling agents, for purposes such as improving the dispersibility of magnetic powders in the binder resin.

[0045] The amount of magnetic powder used is not particularly limited as long as it does not hinder the objective of the present invention. Specifically, the amount of magnetic powder used is preferably about 10 to 150 parts by weight, and more preferably 30 to 60 parts by weight, per 100 parts by weight of binder resin. If the amount of magnetic powder is excessive, it may become difficult to form an image with the desired image density over a long period, or the toner's adhesion to the paper may be severely reduced. If the amount of magnetic powder is insufficient, image fogging may occur more easily, or it may become difficult to form an image with the desired image density over a long period.

[0046] (Coloring agent) Since toner matrix particles contain magnetic powder as an essential component, they are usually black. Therefore, the toner may contain known dyes or pigments as colorants for the purpose of adjusting 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 objectives of the present invention. Specifically, carbon black is an example of a pigment, and acid violet is an example of a dye.

[0047] The amount of colorant used is not particularly limited as long as it does not hinder the objective of the present invention. Specifically, the amount of colorant used is preferably 1% by mass or more and 10% by mass or less, and more preferably 2% by mass or more and 7% by mass or less, relative to the total mass of toner matrix particles.

[0048] Furthermore, a colorant can also be used as a masterbatch in which the colorant is pre-dispersed in a resin material such as a thermoplastic resin. When using a colorant as a masterbatch, it is preferable that the resin contained in the masterbatch is the same type of resin as the binder resin.

[0049] (Release agent) Toner matrix particles may contain a release agent to improve adhesion and offset resistance. The type of release agent that can be added to the toner matrix particles is not particularly limited. Wax is preferred as such a release agent, and 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. Two or more of these release agents can be used in combination. By adding such release agents to the toner matrix particles, the occurrence of offset and image smearing (smudges around the image when the image is rubbed) can be suppressed more efficiently.

[0050] 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. Similarly, when polystyrene resin is used as the binder resin, from the viewpoint of compatibility, Fischer-Tropsch wax and / or paraffin wax are preferably used as the release agent.

[0051] Fischer-Tropsch wax is a straight-chain hydrocarbon compound with few iso-structure molecules or side chains, produced using the Fischer-Tropsch reaction, which is a catalytic hydrogenation reaction of carbon monoxide.

[0052] Among Fischer-Tropsch waxes, those with a mass-average molecular weight of 1,000 or more and whose endothermic peak bottom temperature observed by DSC measurement is in the range of 100°C to 120°C are more preferable. Examples of such Fischer-Tropsch waxes include Sazol wax C1 (endothermic peak bottom temperature: 106.5°C), Sazol wax C105 (endothermic peak bottom temperature: 102.1°C), and Sazol wax SPRAY (endothermic peak bottom temperature: 102.1°C), all available from Sazol.

[0053] The amount of release agent used is not particularly limited as long as it does not hinder the objectives of the present invention. Preferably, the amount of release agent used is 1% by mass or more and 10% by mass or less, relative to the total mass of toner matrix particles. If the amount of release agent used is too little, the desired effect of suppressing offset and image smearing in the formed image may not be obtained, and if the amount of release agent used is too much, the heat resistance of the toner may decrease due to fusion of toners.

[0054] (Charge control agent) The toner matrix particles may contain a charge control agent to improve the charge level of the toner and the charge rise characteristics, which are indicators of whether or not it can be charged to a predetermined charge level in a short time, and in order to obtain a toner with excellent durability and stability. Since the toner of the present invention is a positively charged toner, a positively charged charge control agent is used.

[0055] The types of charge control agents that can be contained in the toner matrix particles are not particularly limited as long as they do not hinder the objectives of the present invention, and can be appropriately selected from charge control agents conventionally used in toners. Specific examples of positively charged charge control agents include pyridazine, pyrimidine, pyrazine, orthoxazine, metaoxazine, paraoxazine, orthothiaidine, metathiaidine, parathiaidine, 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-oxadiazine2,4,6-oxadiazine, 1,2,3,4-thiadiazine, 1,2,4,6-oxadiazine, 1,2,3,4-tetrazine, 1,2,4,6-oxadiazine, 1,2,3,4-tetrazine, 1,2,4,6-oxadiazine, 1,2,3,4-tetrazine, 1,2,4,6-oxadiazine, 1,2,3,4-tetrazine, 1,2,4 Examples include direct dyes consisting of azine compounds such as din, 1,3,4,5-oxatriazine, phthalazine, quinazoline, and quinoxaline; nigrosine compounds such as nigrosine, nigrosine salts, and nigrosine derivatives; acid dyes consisting of nigrosine compounds such as nigrosine BK, nigrosine NB, and nigrosine Z; metal salts of naphthenic acid or higher fatty acids; triphenylmethane-based dyes; alkoxylated amines; alkylamides; and quaternary ammonium salts such as benzylmethylhexyldecylammonium and decyltrimethylammonium chloride. Among these positively charged charge control agents, nigrosine compounds are particularly preferred because they provide a faster charge onset. Two or more of these positively charged charge control agents can be used in combination.

[0056] 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 as long as it does not hinder the objectives of the present invention, and they may be oligomers or polymers.

[0057] 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. Specific examples of preferred acrylic comonomers copolymerized with styrene units in styrene-acrylic resins having quaternary ammonium salts as functional groups include alkyl (meth)acrylates such as 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.

[0058] Furthermore, as quaternary ammonium salts, dialkylaminoalkyl(meth)acrylates, dialkyl(meth)acrylamides, or units derived from dialkylaminoalkyl(meth)acrylamides through a quaternization process can be used. Specific examples of dialkylaminoalkyl(meth)acrylates include dimethylaminoethyl(meth)acrylate, diethylaminoethyl(meth)acrylate, dipropylaminoethyl(meth)acrylate, and dibutylaminoethyl(meth)acrylate. Specific examples of dialkyl(meth)acrylamides include dimethylmethacrylamide, and specific examples of dialkylaminoalkyl(meth)acrylamides include dimethylaminopropylmethacrylamide. In addition, hydroxyl group-containing polymerizable monomers such as hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate, and N-methylol(meth)acrylamide can be used in combination during polymerization.

[0059] The toner matrix particles may be toner matrix particles without a shell layer (non-capsulated toner matrix particles) or toner matrix particles with a shell layer (capsulated toner matrix particles). Capsulated toner matrix particles can be manufactured by forming a shell layer on the surface of non-capsulated toner matrix particles (toner core particles). The shell layer may consist substantially of thermosetting resin only, substantially of thermoplastic resin only, or may contain both thermoplastic resin and thermosetting resin.

[0060] (External additive) The toner of the present invention may have its toner matrix particles treated with an external additive. The type of external additive added to the toner of the present invention is not particularly limited as long as it does not hinder the objective of the present invention, and can be appropriately selected from external additives conventionally used for toner. Specific examples of suitable external additives include silica, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, and metal oxides such as barium titanate. Two or more of these external additives can be used in combination.

[0061] The particle size of the external additive is not particularly limited as long as it does not hinder the objective of the present invention, but is typically preferably 0.01 μm or more and 1.0 μm or less.

[0062] The amount of external additive used is not particularly limited as long as it does not hinder the objectives of the present invention. Preferably, the amount of external additive used is 0.1% to 10% by mass, and more preferably 0.2% to 5% by mass, relative to the total mass of toner matrix particles. If the amount of external additive used is insufficient, the hydrophobicity of the toner tends to decrease. As a result, it becomes more susceptible to the influence of water molecules in the air under high temperature and high humidity environments, which can easily lead to problems such as a decrease in image density of the formed image due to an extreme decrease in the charge amount of the toner, and a decrease in toner fluidity. Conversely, if the amount of external additive used is excessive, it may lead to a decrease in image density due to excessive toner charge buildup.

[0063] [4. Toner manufacturing method] Next, the method for manufacturing the toner of the present invention will be described. The method for manufacturing the toner includes a method for manufacturing toner matrix particles and an external additive treatment method for attaching an external additive to the surface of the toner matrix particles. The method for manufacturing the toner matrix particles is not particularly limited as long as the toner matrix particles are formed to have a predetermined structure. In addition, toner matrix particles coated with a shell layer may be used as needed. As a preferred method for manufacturing the positively charged toner described above, the method for manufacturing the toner matrix particles and the external additive treatment method will be described in order below.

[0064] (Method for manufacturing toner matrix particles) The method for producing toner matrix particles is not particularly limited as long as the magnetic powder and any components such as colorants, release agents, and charge control agents can be well dispersed in the binder resin. Suitable methods for producing toner matrix particles include, for example, grinding or agglomeration.

[0065] The pulverization method involves mixing the binder resin with components such as magnetic powder, colorants, release agents, and charge control agents using a mixer, then melt-kneading the binder resin and the components to be incorporated into the binder resin using a kneader such as a single-screw or twin-screw extruder, and finally pulverizing and classifying the cooled kneaded material. The average particle size of the toner mother particles is not particularly limited as long as it does not hinder the objectives of the present invention, but is generally preferably 5 μm to 10 μm.

[0066] The agglutination method involves agglutinating fine particles of various components, such as a binder resin, magnetic powder, colorant, release agent, and charge control agent, in an aqueous medium until the particles reach a desired size. This forms agglutinated particles containing the binder resin, release agent, charge control agent, and colorant. Subsequently, the resulting agglutinated particles are heated to unify the components contained within them. This yields toner matrix particles with the desired particle size.

[0067] (External processing method) The method for treating toner matrix particles with external additives is not particularly limited, and the toner matrix particles can be treated according to conventionally known methods. Specifically, the treatment conditions are adjusted so that the particles of the external additive do not become embedded in the toner matrix particles, and the toner matrix particles are treated with external additives using a mixer such as a Turbuler mixer, Henschel mixer, Nauter mixer, or V-type mixer.

[0068] The toner of the present invention, as described above, has excellent fixability and heat resistance for storage. When forming images over a long period of time in various environments such as high temperature and high humidity environments or low temperature and low humidity environments, the toner can be charged to a desired amount of charge, thereby enabling the formation of images of a desired density. For this reason, the electrostatic latent image developing toner of the present invention can be suitably used in various image forming apparatuses. In particular, it is preferable to use it in an image forming apparatus 100 with a process linear velocity of 250 mm / sec or higher, as shown in Figure 1, because it can suppress the deterioration of heat stress resistance and fixability. The effects of the present invention will be described in more detail below with reference to examples. However, the present invention is not limited in any way by the examples. [Examples]

[0069] [Manufacturing Example 1] (Manufacturing of crystalline polyester resin C-1) In a 2L four-necked flask equipped with a thermometer, a glass nitrogen inlet tube, a stirrer (stainless steel stirring blades), and a drop-flow condenser (heat exchanger), 50 moles of 1,9-nonanediol, 45 moles of 1,10-decanedicarboxylic acid, 5 moles of terephthalic acid, and 0.05 moles of catalyst (tetra-n-butoxytitanium) were placed. Next, the flask was placed on a mantle heater, and nitrogen gas was introduced into the flask through the nitrogen inlet tube to create a nitrogen atmosphere (inert atmosphere). Subsequently, under the nitrogen atmosphere, the contents of the flask were heated to 200°C while being stirred, and the reaction (condensation polymerization reaction) was carried out under the conditions of a nitrogen atmosphere and 200°C while stirring the contents of the flask. After that, the contents of the flask were removed into a stainless steel container (tray) and cooled to 25°C at room temperature to obtain crystalline polyester resin C-1.

[0070] (Manufacturing of crystalline polyester resin C-2) Crystalline polyester resin C-2 was obtained by the same method as for crystalline polyester resin C-1, except that 50 mole parts of 1,12-dodecanediol were used instead of 50 mole parts of 1,9-nonanediol, and the reaction temperature was changed from 200°C to 220°C.

[0071] [Manufacturing Example 2] (Manufacturing of amorphous polyester resin A-1) In a 2L four-necked flask equipped with a thermometer, a glass nitrogen inlet tube, a stirrer (stainless steel stirring blades), and a drop-flow condenser (heat exchanger), 43 moles of ethylene glycol, 42 moles of terephthalic acid, and 5 moles of 1,2,4-benzenetricarboxylic acid anhydride were placed. The flask was then placed on a mantle heater, and nitrogen gas was introduced into the flask through the nitrogen inlet tube to create a nitrogen atmosphere (inert atmosphere). Subsequently, under the nitrogen atmosphere, the contents of the flask were heated to 230°C while being stirred, and the reaction (condensation polymerization reaction) was carried out for 6 hours under the conditions of a nitrogen atmosphere and 230°C while stirring. After that, the contents of the flask were removed into a stainless steel container (tray) and cooled to 25°C at room temperature to obtain amorphous polyester resin A-1.

[0072] (Manufacturing of amorphous polyester resin A-2) Amorphous polyester resin A-2 was obtained by the same method as for amorphous polyester resin A-1, except that the reaction was carried out for 8 hours under conditions of a nitrogen atmosphere and 230°C.

[0073] (Manufacturing of amorphous polyester resin A-3) Amorphous polyester resin A-3 was obtained by the same method as for amorphous polyester resin A-1, except that the reaction was carried out for 4 hours under conditions of a nitrogen atmosphere and 230°C.

[0074] [Manufacturing Example 3] (Manufacturing of magnetic powder) Fe at a concentration of 2.0 mol / L 2+30 L of ferrous sulfate aqueous solution containing [the substance] and 28 L of 4.5 N (normality) sodium hydroxide aqueous solution were added to a reaction vessel and mixed. Subsequently, the contents of the vessel were heated to 90°C, and then the pH of the contents of the vessel was adjusted to 10.5 using the sodium hydroxide aqueous solution. Next, under conditions of pH 10.5 and 90°C, air was blown into the vessel at a rate of 80 L / min for 100 minutes to allow the oxidation reaction of the ferrous sulfate in the vessel to proceed. Subsequently, sulfuric acid aqueous solution was added to the vessel to adjust the pH of the contents of the vessel to 7. Then, the temperature of the contents of the vessel was maintained at 90°C, and air was blown into the vessel at a rate of 80 L / min for 10 minutes. As a result, magnetite particles were generated in the liquid, and a suspension containing magnetite particles was obtained. After that, the magnetite particles (powder) were filtered off from the obtained suspension. Subsequently, the obtained magnetite particles (powder) were washed with water and dried to obtain aggregates of magnetite particles. Next, the obtained aggregates were crushed to obtain a magnetic powder containing numerous octahedral magnetite particles. The number-average primary particle size of the obtained magnetic powder was 0.2 μm. Furthermore, the coercivity at an external magnetic field of 796 kA / m was 8.5 kA / m, and the saturation magnetization was 82 Am. 2 / kg, remanent magnetization is 5.0 Am 2 It was / kg.

[0075] [Manufacturing Example 4] (Manufacturing of Toner T-1) (Manufacturing of toner matrix particles) Fifty parts by mass of amorphous polyester resin A-1 obtained in Production Example 2, two parts by mass of crystalline polyester resin C-1 obtained in Production Example 1, forty-two parts by mass of magnetic powder obtained in Production Example 3, one part by mass of a first charge control agent (BONTRON N-77, manufactured by Orient Chemical Industry Co., Ltd., component: azine compound), three parts by mass of a second charge control agent (Acrybes FCA-207P, manufactured by Fujikura Chemical Co., Ltd., component: styrene-acrylic acid resin containing repeating units derived from quaternary ammonium salt), and two parts by mass of ester wax (Nissan Electrol WEP-3, manufactured by NOF Corporation) as a release agent were mixed using an FM mixer (FM-20, manufactured by Nippon Coke Industries Co., Ltd.) at a rotation speed of 2000 rpm for four minutes. Next, the obtained mixture was melt-kneaded using a twin-screw extruder (PCM-30, manufactured by Ikegai Co., Ltd.) under the following conditions: melt-kneading temperature (cylinder temperature) of 120°C, rotation speed of 150 rpm, and processing speed of 100 g / min.

[0076] After cooling the resulting mixture, it was coarsely ground to a set particle size of 2 mm using a pulverizer (Rotoplex, manufactured by Hosokawa Micron). The resulting coarsely ground material was then finely ground using a mechanical pulverizer (Turbomill T250, manufactured by Freund Turbo). The resulting finely ground material was classified using an air-powered classifier (Elbowjet EJ-LABO type, manufactured by Nippon Steel Mining Co., Ltd.). As a result, toner matrix particles with a median volume diameter (D50) of 8 μm were obtained.

[0077] (External addition process) To 100 parts by mass of the obtained toner matrix particles, 0.8 parts by mass of positively charged silica particles (AEROSIL RA200, manufactured by Nippon Aerosil Co., Ltd.: dry silica particles with hydrophobic and positively charged properties imparted by surface treatment, surface treatment agents: hexamethyldisilazane (HMDS) and aminosilane, average primary particle size: approximately 12 nm) and 0.8 parts by mass of conductive titanium oxide particles (EC-100, manufactured by Titanium Industries Co., Ltd., base material: TiO2, coating layer: Sb-doped SnO2 film, average primary particle size: approximately 0.35 μm) were added as external additives. The mixture was then mixed for 5 minutes at a rotation speed of 2000 rpm using an FM mixer (FM-20, manufactured by Nippon Coke Industries Co., Ltd.) to adhere (add) the external additives (positively charged silica particles and conductive titanium oxide particles) to the toner matrix particles. Subsequently, the mixture was sieved using a 300-mesh (48 μm opening) sieve to obtain toner T-1.

[0078] (Manufacturing of Toner T-2) Toner T-2 was obtained using the same method as for toner T-1, except that the melting and mixing temperature was changed to 110°C.

[0079] (Manufacturing of Toner T-3) Toner T-3 was obtained using the same method as for toner T-1, except that the melting and mixing temperature was changed to 140°C.

[0080] (Manufacturing of Toner T-4) Toner T-4 was obtained using the same method as toner T-1, except that amorphous polyester resin A-1 was replaced with amorphous polyester resin A-2.

[0081] (Manufacturing of Toner T-5) Toner T-5 was obtained using the same method as toner T-1, except that amorphous polyester resin A-1 was replaced with amorphous polyester resin A-3.

[0082] (Manufacturing of Toner T-6) Toner T-6 was obtained using the same method as for toner T-1, except that the amount of crystalline polyester resin C-1 added was changed to 2.4 parts by mass.

[0083] (Manufacturing of Toner T-7) Toner T-7 was obtained using the same method as for toner T-1, except that the amount of crystalline polyester resin C-1 added was changed to 1.2 parts by mass.

[0084] (Manufacturing of Toner T-8) Toner T-8 was obtained using the same method as for toner T-1, except that the amount of crystalline polyester resin C-1 added was changed to 0.1 parts by mass.

[0085] (Manufacturing of Toner T-9) Toner T-9 was obtained using the same method as toner T-1, except that amorphous polyester resin A-1 was replaced with amorphous polyester resin A-2 and the melt-mixing temperature was changed to 140°C.

[0086] (Manufacturing of Toner T-10) Toner T-10 was obtained using the same method as for toner T-1, except that amorphous polyester resin A-1 was replaced with amorphous polyester resin A-3 and the melt-mixing temperature was changed to 140°C.

[0087] (Manufacturing of Toner T-11) Toner T-11 was obtained using the same method as for toner T-1, except that amorphous polyester resin A-1 was replaced with amorphous polyester resin A-2 and the melt-mixing temperature was changed to 110°C.

[0088] (Manufacturing of Toner T-12) Toner T-12 was obtained using the same method as toner T-1, except that amorphous polyester resin A-1 was replaced with amorphous polyester resin A-3 and the melt-mixing temperature was changed to 110°C.

[0089] (Manufacturing of Toner T-13) Toner T-13 was obtained using the same method as for toner T-1, except that the amount of crystalline polyester resin C-1 added was changed to 1.2 parts by mass and the melt-mixing temperature was changed to 140°C.

[0090] (Manufacturing of Toner T-14) Toner T-14 was obtained using the same method as toner T-1, except that crystalline polyester resin C-1 was replaced with crystalline polyester resin C-2.

[0091] Table 1 shows the melting and mixing temperatures, types of amorphous and crystalline polyester resins, and the ratio (mass%) of crystalline polyester resin to amorphous polyester resin for toners T-1 to T-14.

[0092] [Table 1]

[0093] (Measurement of glass transition temperatures Tg(25), Tg(45), and Tg2 of toner) Approximately 1g of toner was placed in an open 20cc plastic container and exposed to a constant temperature chamber at 45°C for 100 hours. The extracted toner was designated as the 45°C sample. Similarly, toner exposed to a constant temperature chamber at 25°C for 100 hours was designated as the 25°C sample.

[0094] A differential scanning calorimeter (DSC) DSC7020 (manufactured by Seiko Instruments) was used. Approximately 10 mg of the sample, left at 45°C, was placed in an aluminum dish and then set in the DSC's measurement unit. The measurement start temperature was set to 30°C, and the temperature was increased to 170°C at a rate of 10°C / min to measure Tg(45). After measuring Tg(45), the sample was cooled to 30°C at a rate of 100°C / min. Then, the sample was heated from 30°C to 170°C at a rate of 10°C / min to measure Tg2. Similarly, Tg8(25) and Tg2 were measured using a sample left at 25°C.

[0095] [Evaluation of toner's heat stress resistance and fixation properties] The heat stress resistance and fixation performance of toners T-1 to T-14 were evaluated according to the method described below. (Heat stress resistance) As an evaluation machine, an experimental machine was used, which was a modified monochrome printer (ECOSYS MA6000, manufactured by Kyocera Document Solutions) with adjustable voltage applied to the development system. Toners T-1 to T-14 obtained in Manufacturing Example 4 were installed in the development unit of the evaluation machine. In addition, replenishment toner (the same toner as that installed in the development unit) was installed in the toner container of the evaluation machine. After toner installation, 2000 images with a print density of 5% were printed in a high temperature and high humidity environment (32°C, 80%RH), and then 25% half-print images were printed to obtain measurement images. The thermal stress resistance of the toner was confirmed using these images. If the thermal stress resistance of the toner is low, white streaks will appear in the image due to toner aggregation. The evaluation criteria for thermal stress resistance are shown below. ○: No vertical white streaks present. ×; One or more vertical white streaks appear.

[0096] (Persistence) In a normal temperature and humidity environment (20°C, 50%RH), the evaluation unit was cooled for 10 minutes with the power off, then the power was turned on, and a fixed pattern solid image (toner amount 1.5 mg / cm²) was obtained. 2 Five consecutive prints of the image were obtained to obtain a measurement image. This measurement image was rubbed 10 times back and forth using a weight (1 kg) wrapped in cotton cloth. The image density before and after this operation was measured with a Macbeth reflectance densitometer (RD914, manufactured by Gretag Macbeth), and the ratio of the image density before and after the operation was calculated to determine the fixation. The evaluation criteria for fixation are shown below. ○: Retention rate of 95% or higher △: Retention rate is between 90% and 95% ×: Retention rate less than 90%

[0097] Table 2 shows the evaluation results of the heat stress resistance and fixation properties of toners T-1 to T-8 (Invention 1 to 8) and toners T-9 to T-14 (Comparative Examples 1 to 6), along with the values ​​of Tg(45), Tg(25), Tg2, Tg2-Tg(45), and Tg2-Tg(25).

[0098] [Table 2]

[0099] As is clear from Table 2, in Toners T-1 to T-8 of the present invention 1 to 8 satisfying 0 < Tg2 - Tg(45) < 5 and 4 < Tg2 - Tg(25) < 10, the evaluations of heat stress resistance and fixing property were all good.

[0100] On the other hand, in Toner T-9 of Comparative Example 1 where Tg2 - Tg(25) was 3.5, which was less than the lower limit value, and in Toner T-12 of Comparative Example 4 where Tg2 - Tg(45) was 5.4, which exceeded the upper limit value, the heat stress resistance was poor. On the other hand, in Toner T-11 of Comparative Example 3 where Tg2 - Tg(25) was 10.6, which exceeded the upper limit value, in Toner T-10 of Comparative Example 2 where Tg2 - Tg(45) was -0.1, which was less than the lower limit value, and in Toner T-13 of Comparative Example 5 where it was -0.2, the fixing property was poor.

[0101] Also, in Toner T-14 of Comparative Example 6 where crystalline polyester resin C-2 was used instead of crystalline polyester resin C-1 as the binder resin of the toner mother particles, the heat stress resistance was poor.

[0102] From the above results, by using an aliphatic diol having 3 to 9 carbon atoms as the raw material of the crystalline polyester resin constituting the toner mother particles and making the relationship between the glass transition points Tg(45), Tg(25), and Tg2 satisfy 0 < Tg2 - Tg(45) < 5 and 4 < Tg2 - Tg(25) < 10, it was confirmed that a magnetic one-component toner excellent in heat stress resistance and fixing property can be obtained.

Industrial Applicability

[0103] The present invention can be used for a positively charged magnetic one-component toner used in an electrophotographic method. By using the present invention, a magnetic one-component toner having low-temperature fixing property and excellent in heat storage stability and heat stress resistance can be provided.

Claims

1. Toner matrix particles containing at least a binder resin and magnetic powder, The external additive adhering to the surface of the toner matrix particles, A magnetic one-component toner consisting of toner particles containing, The binder resin comprises an amorphous polyester resin and a crystalline polyester resin, wherein the amount of crystalline polyester resin added is 5% by mass or less relative to the amorphous polyester resin. The crystalline polyester resin contains one or more aliphatic diols having 3 to 9 carbon atoms. When the glass transition point measured by a differential scanning calorimeter during the first heating is denoted as Tg1, and the glass transition point measured after cooling and heating again after measuring Tg1 is denoted as Tg2, A magnetic one-component toner characterized in that Tg(45), which is Tg1 measured after being left at 45°C for 100 hours, and Tg(25), which is Tg1 measured after being left at 25°C for 100 hours, satisfy the following formulas (1) and (2). 0<Tg2-Tg(45)<5...(1) 4<Tg2-Tg(25)<10...(2)

2. The magnetic one-component toner according to claim 1, characterized in that the crystalline polyester resin is a copolymer of the aliphatic diol, one or more aliphatic dicarboxylic acids having 10 to 15 carbon atoms, and one or more aromatic dicarboxylic acids.

3. A developing apparatus comprising a developing device that develops an electrostatic latent image formed on an image carrier into a toner image using a magnetic one-component toner according to claim 1 or claim 2, An image forming apparatus in which the linear velocity of the image carrier is 250 mm / sec or more.

Images