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

Abstract

A magnetic single-component toner capable of suppressing electrostatic offset by reducing the adhesion force between the fixing belt and the toner, and an image forming apparatus using the same. [Solution] The magnetic single-component toner consists of toner particles comprising toner matrix particles and an external additive attached to the surface of the toner matrix particles. The external additive includes conductive particles with a resistivity of 1.0E+4 [Ω·cm] or less, resin particles with a number-average primary particle diameter of 50 nm to 100 nm, and silica particles. The resin particles are formed from a specific vinyl resin having formula (1), etc. JPEG2026066830000010.jpg5786

Description

[Technical Field]

[0001] The present invention relates to a magnetic one-component toner used in image forming apparatuses such as photocopiers, printers, and facsimile machines, and to an image forming apparatus using a magnetic one-component toner. [Background technology]

[0002] In belt-type fixing devices that use a fixing belt as the rotating body to be heated, a method is known in which the fixing belt is heated by a surface heater that slides against the fixing belt. In such a configuration, it is necessary to reduce the sliding load between the fixing belt and the surface heater.

[0003] Patent Document 1 discloses a fixing device in which a planar heater for heating the fixing belt is provided between the inner surface of the fixing belt and a pressing member, and a lubricant holding portion for holding lubricant is provided on the part of the pressing member facing the planar heater. Patent Document 2 discloses a fixing device in which, in the contact area of ​​the planar heater that contacts the inner circumferential surface of the fixing belt, a groove is formed in the region outside the heating resistor in the longitudinal direction of the holder, such that the lubricant interposed between the fixing belt and the planar heater flows toward the center of the holder as it flows toward the downstream side in the rotational direction of the fixing belt.

[0004] On the other hand, a magnetic single-component development method is known for image forming apparatuses that use an electrophotographic process, which uses a magnetic single-component developer consisting of a magnetic single-component toner. However, when a belt-type fixing apparatus and a magnetic single-component system are combined as described above, there is a problem that toner tends to adhere to the fixing belt, and electrostatic offset is likely to occur.

[0005] Patent Document 3 discloses a magnetic toner that contains multiple resin particles as an external toner additive, and by allowing the resin particles to function as spacers between toner particles, the adhesion of the toner in a high-temperature, high-humidity environment is reduced.

[0006] Patent Document 4 discloses a magnetic one-component toner in which toner matrix particles and resin particles and silica particles as external additives are set within a predetermined range for the isoelectric points of the resin particles, the toner matrix particles, and the toner particles. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2019-120779 [Patent Document 2] Japanese Patent Publication No. 2019-197142 [Patent Document 3] Japanese Patent Publication No. 2019-45754 [Patent Document 4] Japanese Patent Publication No. 2022-7125 [Overview of the project] [Problems that the invention aims to solve]

[0008] The toner described in Patent Document 3 has the problem that, because it does not specify the electrostatic properties of the resin particles or add conductive particles, when combined with a belt-type fixing device, it has an insufficient effect in suppressing toner adhesion to the fixing belt. The toner described in Patent Document 4 has the problem that, although the isoelectric point and particle size of the resin particles are specified, the material of the resin particles is not specified, resulting in an insufficient effect in suppressing toner adhesion to the fixing belt.

[0009] In view of the above problems, the present invention aims to provide a magnetic one-component toner that can suppress the occurrence of electrostatic offset by reducing the adhesion force between the fixing belt and the toner, 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 used in an image forming apparatus, comprising: a developing device for developing an electrostatic latent image formed on an image carrier into a toner image using a magnetic one-component toner; a transfer device for transferring the toner image developed by the developing device onto a recording medium; an endless fixing belt heated by a heating device; a nip-forming member disposed radially inside the fixing belt and sliding with the inner circumferential surface of the fixing belt; and a pressing member that presses against the nip-forming member with a predetermined pressure, sandwiching the fixing belt, thereby forming a fixing nip portion between itself and the fixing belt, and a fixing device for fixing the toner image transferred onto the recording medium by the transfer device onto the recording medium. The magnetic one-component toner consists of 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 external additive includes conductive particles with a resistivity of 1.0E+4 [Ω·cm] or less, resin particles with a number-average primary particle diameter of 50 nm or more and 100 nm or less, and silica particles. The resin particles are formed using an anionic surfactant and are made of a vinyl resin having repeating units represented by the following general formula (1), repeating units represented by the following general formula (2), and repeating units derived from a sulfo-group-containing vinyl compound, wherein the content of repeating units derived from the sulfo-group-containing vinyl compound in the vinyl resin is 2.0 mol% or more and 5.0 mol% or less relative to the total repeating units in the vinyl resin. [ka] [ka] (In formula (1), R 11 , R 12 Each independently represents a hydrogen atom, a halogen atom, or an alkyl group which may have a substituent. 13 R represents an alkylene group having a hydroxyl group. In formula (2), R 21 ~R 27 Each of these independently represents a hydrogen atom, a halogen atom, a hydroxyl group, an optionally substituted alkyl group, an optionally substituted alkoxy group, an optionally substituted alkoxyalkyl group, or an optionally substituted aryl group.

Advantages of the Invention

[0011] According to the first configuration of the present invention, when used in an image forming apparatus employing a belt fixing system, it is possible to reduce the electrostatic adhesion force to the fixing belt and to suppress the occurrence of image contamination due to electrostatic offset, resulting in a magnetic one-component toner.

Brief Description of the Drawings

[0012] [Figure 1] Schematic cross-sectional view of an image forming apparatus 100 in which the magnetic one-component toner of the present invention is used [Figure 2] Side cross-sectional view of a fixing device 8 mounted in an image forming apparatus 100

Embodiments for Carrying Out the Invention

[0013] [1. Overall Configuration of the Image Forming Apparatus] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 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 an image forming apparatus (e.g., a monochrome printer) 100, when performing a printing operation, in an image forming section 9 within the image forming apparatus 100, an electrostatic latent image is formed based on manuscript image data transmitted from a host device (not shown) such as a personal computer, and toner is attached to the electrostatic latent image by a developing device 4 to form a toner image. The toner is supplied to the developing device 4 from a toner container 5. In the image forming apparatus 100, while rotating the photosensitive drum 1 in the clockwise direction in FIG. 1, an image forming process for the photosensitive drum 1 is executed.

[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.

[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 forms a toner image by attaching toner to the electrostatic latent image on the photoreceptor drum 1. In this embodiment, a magnetic one-component toner (magnetic one-component developer) is contained in the developing device 4. Further details of the developing device 4 will be described later. The cleaning device 7 is equipped with cleaning rollers and cleaning blades that make linear contact with the photoreceptor drum 1 in the longitudinal direction (the direction perpendicular to the paper surface in Figure 1), and removes any toner remaining on the surface of the photoreceptor drum 1 after the toner image has been transferred to the paper.

[0017] As described above, paper is transported from the paper storage unit 10 to the image forming unit 9 via the paper transport path 11 and the registration roller pair 13 at a predetermined timing, towards the photoreceptor drum 1 on which the toner image has been formed. The transfer roller 6 contacts the photoreceptor drum 1 to form a nip (transfer nip), and without disturbing the toner image formed on the surface of the photoreceptor drum 1, the toner is transferred to the paper passing through the transfer nip. Subsequently, in preparation for the formation of a new electrostatic latent image, the cleaning device 7 removes residual toner from the surface of the photoreceptor drum 1, and the static eliminator removes residual charge.

[0018] The paper onto which the toner image has been transferred is separated from the photoreceptor drum 1 and transported to the fuser unit 8, where it is heated and pressurized to fix the toner image onto the paper. The paper that has passed through the fuser unit 8 passes through the discharge roller pair 14 and is discharged to the paper discharge unit 15.

[0019] [2. Configuration of the fixing device] Figure 2 is a side cross-sectional view of the fixing device 8 mounted on the image forming apparatus 100. The fixing device 8 is a belt fixing type and comprises a fixing belt 20, a pressure roller (pressure member) 21, a heater (heating device) 23, a support stay 25, and a nip forming member 27. Note that the housing of the fixing device 8 is omitted from Figure 2.

[0020] The fixing belt 20 is an endless belt made up of multiple layers, including a base layer provided on the innermost side (heater 23 side) and a release layer provided on the outermost side (pressure roller 21 side). The fixing belt 20 is subjected to a predetermined tension by a nip forming member 27 and a belt support guide (not shown).

[0021] Furthermore, the width dimension of the fixing belt 20 (in the direction of the rotation axis, perpendicular to the plane of the paper in Figure 2) is set to be wider than the maximum width of the paper S that passes through the fixing nip section N. As a result, the fixing belt 20 can cover the entire surface of the paper S regardless of the paper size, thus preventing unfixed toner from adhering to the nip forming member 27.

[0022] The pressure roller 21 is made of a cylindrical core metal 21a made of a material such as metal, with an elastic layer 21b made of silicone rubber laminated on its outer surface, and the surface of the elastic layer 21b covered with a release layer (not shown) such as a fluororesin coating. The pressure roller 21 is pressed against the fixing belt 20 at a predetermined pressure.

[0023] The support stay 25 is a hollow, rectangular tubular member made of metal. The nip forming member 27 is supported on the lower surface of the support stay 25. Both ends of the support stay 25 are fixed to the housing side plates (not shown) of the fixing device 8.

[0024] The nip-forming member 27 contacts the pressure roller 21 via the fixing belt 20, thereby forming a fixing nip section N through which the paper S is inserted. The nip-forming member 27 is made of a heat-resistant resin such as liquid crystal polymer or an elastic material such as silicone rubber, and an elastomer may be placed on the surface facing the fixing belt 20.

[0025] The heater 23 is a planar heater in which a resistive layer is coated on a ceramic substrate, and heat is generated when current is passed through this resistive layer. The heater 23 is positioned between the fixing belt 20 and the nip forming member 27, and a glass layer is laminated on the surface of the resistive layer facing the inner circumferential surface of the fixing belt 20. The heat generated in the resistive layer heats the fixing belt 20 via the glass layer. The glass layer is in contact with the inner circumferential surface of the fixing belt 20, ensuring electrical insulation and sliding properties with the inner circumferential surface of the fixing belt 20.

[0026] A fixing drive motor 30 is connected to one end of the core metal 21a via a drive input gear (not shown). When the driving force is transmitted from the fixing drive motor 30 to the core metal 21a, the pressure roller 21 rotates in the counterclockwise direction as shown in Figure 2. Due to the frictional force between the pressure roller 21 and the outer surface of the fixing belt 20, the nip forming member 27 (heater 23) and the inner surface of the fixing belt 20 slide against each other, causing the fixing belt 20 to rotate in the clockwise direction as shown in Figure 2. A fixing nip portion N is formed where the fixing belt 20 and the pressure roller 21 come into contact with each other while rotating in opposite directions.

[0027] The paper S is transported from the upstream side in the paper transport direction (right side in Figure 2) to the fixing nip section N, where the toner powder on the paper S is heated and pressurized by the fixing belt 20 and pressure roller 21, causing it to melt and be fixed. After the fixing process, the paper S is separated from the surface of the fixing belt 20 by a separation claw (not shown) and then transported downstream of the fixing device 8 in the paper transport direction (left side in Figure 2).

[0028] [3. Basic Configuration of Single-Component Magnetic Toner] The magnetic one-component toner of the present invention (hereinafter also simply referred to as toner) used in the image forming apparatus 100 comprises 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 colorant, a charge control agent, etc., in the binder resin as needed.

[0029] The toner of the present invention comprises conductive particles and resin particles as external additives that adhere to the surface of toner matrix particles. The conductive particles are adjusted to have a resistance of 1.0E+4Ω·cm or less. The resin particles are formed from a vinyl resin having repeating units derived from a sulfo group-containing vinyl compound.

[0030] [2. Toner Materials] The following describes the silica particles that constitute the binder resin, magnetic powder, release agent, charge control agent, colorant, 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.

[0031] (Binding resin) The toner matrix particles constituting the toner of the present invention include a binder resin. The binder resin that can be contained in the toner matrix particles is not particularly limited as long as it is a resin that has been conventionally used as a binder resin for toner. Specific examples of binder resins include thermoplastic resins such as styrene resins, acrylic resins, styrene-acrylic resins, polyethylene resins, polypropylene resins, vinyl chloride resins, polyester resins, polyamide resins, polyurethane resins, polyvinyl alcohol resins, vinyl ether resins, N-vinyl resins, and styrene-butadiene resins. Among these resins, it is preferable to contain at least one of polyester resin and styrene-acrylic acid resin, with polyester resin being more preferable, from the viewpoint of dispersibility of the colorant in the binder resin, the electrostatic properties of the toner, and the fixation to paper. Polyester resin will be described below.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] When the binder resin is a polyester resin, 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.

[0036] As the binder resin, a thermoplastic resin is preferable because it has good adhesion to paper. However, thermoplastic resins can be used alone, or crosslinking agents or thermosetting resins can be added to them. By adding crosslinking agents or thermosetting resins and introducing a partially crosslinked structure into the binder resin, the heat resistance, storage properties, 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.

[0037] Epoxy resins and cyanate resins are preferred thermosetting resins that can be used with thermoplastic 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.

[0038] The glass transition temperature (Tg) of the binder 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.

[0039] The glass transition point of a binder resin can be determined 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 binder resin can be determined by measuring the endothermic curve of the binder resin using a differential scanning calorimeter (DSC-6200, manufactured by Seiko Instruments Corporation) as the measuring device. A 10 mg sample is placed in an aluminum pan, and an empty aluminum pan is used as a reference. The glass transition point of the binder resin can be determined from the endothermic curve obtained by measuring the binder resin at room temperature and humidity with a temperature range of 25°C to 200°C and a heating rate of 10°C / min.

[0040] 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.

[0041] (magnetic powder) The toner matrix contains magnetic powder in the binder resin. Suitable materials for the magnetic powder include, for example, ferromagnetic metals (more specifically, iron, cobalt, nickel, or alloys containing one or more of these metals), ferromagnetic metal oxides (more specifically, ferrite, magnetite, or chromium dioxide), or materials that have undergone ferromagnetic treatment (more specifically, carbon materials to which ferromagnetism has been imparted by heat treatment). To suppress the elution of metal ions (e.g., iron ions) from the magnetic powder, it is preferable to use surface-treated magnetic particles as the magnetic powder. One type of magnetic powder may be used alone, or multiple types of magnetic powder may be used in combination.

[0042] 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 0.1 μm or more and 1.0 μm or less, and more preferably 0.1 μm or more and 0.5 μm or less. When using magnetic powder with such particle size, it is easier to uniformly disperse the magnetic powder in the binder resin.

[0043] 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.

[0044] 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 30% to 60% by mass, and more preferably 40% to 60% by mass, relative to the total mass of toner. If the amount of magnetic powder used is excessive, it may become difficult to form an image with the desired image density over a long period of time, or the toner's adhesion to the paper may be severely reduced. If the amount of magnetic powder used is insufficient, the formed image may be prone to blurring, or it may become difficult to form an image with the desired image density over a long period of time.

[0045] (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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] (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.

[0051] 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.

[0052] Furthermore, a coloring agent can also be used as a masterbatch in which the coloring agent is pre-dispersed in a resin material such as a thermoplastic resin. When using a coloring agent as a masterbatch, it is preferable that the resin contained in the masterbatch is the same type of resin as the binder resin.

[0053] (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.

[0054] 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 azine compounds such as 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-oxatriazine, 1,3,4,5-oxatriazine, phthalazine, quinazoline, and quinoxaline; azine compounds Examples include direct dyes consisting of azine compounds such as Stread 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; 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; 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 rise. Two or more of these positively charged charge control agents can be used in combination.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] The amount of charge control agent used is not particularly limited as long as it does not hinder the objectives of the present invention. Typically, the amount of charge control agent used is preferably 0.1% by mass or more and 10% by mass or less, relative to the total mass of toner matrix particles. If the amount of charge control agent used is insufficient, it is difficult to stably charge the toner to a predetermined polarity, which may result in the image density of the formed image falling below the desired value or making it difficult to maintain the image density over a long period of time. In addition, because the charge control agent is difficult to disperse uniformly, the formed image is more prone to blurring, and contamination of the latent image-carrying area by toner components is more likely to occur. If the amount of charge control agent used is excessive, the environmental resistance deteriorates, making it easier for image defects in the formed image due to poor charging under high temperature and high humidity conditions, and contamination of the latent image-carrying area by toner components to occur.

[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 is obtained by treating the surface of toner matrix particles with an external additive. The toner of the present invention includes conductive particles, resin particles, and silica particles as external additives.

[0061] (Conductive particles) Conductive particles are manufactured by applying ATO (antimond-doped tin oxide) treatment and hydrophobic treatment with coupling agents to a metal oxide substrate such as titanium oxide or alumina. For hydrophobic treatment, surface treatment with silane coupling agents, titanate coupling agents, etc., is performed to improve environmental stability.

[0062] The resistance (conductivity) of the conductive particles can be adjusted by the amount of ATO processing. In this embodiment, the resistivity of the conductive particles is adjusted to 1.0E+4 [Ω·cm] or less by ATO processing. This reduces the electrostatic adhesion between the fuser belt and the toner.

[0063] Silane coupling agents used in hydrophobic treatment include hexamethyldisilazane, trimethylsilane, trimethylchlorsilane, trimethylethoxysilane, dimethyldichlorsilane, methyltrichlorsilane, allyldimethylchlorsilane, allylphenyldichlorsilane, benzyldimethylchlorsilane, brommethyldimethylchlorsilane, α-chloroethyltrichlorsilane, β-chloroethyltrichlorsilane, chlormethyldimethylchlorsilane, and triorganosilyl mercapta. Examples include trimethylsilyl mercaptan, triorganosilyl acrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divinyltetramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane, and dimethylpolysiloxane, which has 2 to 12 siloxane units per molecule and contains one hydroxyl group bonded to Si at each terminal unit.

[0064] Hydrophobic treatment may be performed with a nitrogen-containing silane coupling agent, which is particularly preferred for positively charged toners. Examples of nitrogen-containing silane coupling agents include aminopropyltrimethoxysilane, aminopropyltriethoxysilane, dimethylaminopropyltrimethoxysilane, diethylaminopropyltrimethoxysilane, dipropylaminopropyltrimethoxysilane, dibutylaminopropyltrimethoxysilane, monobutylaminopropyltrimethoxysilane, dioctylaminopropyltrimethoxysilane, dibutylaminopropyldimethoxysilane, dibutylaminopropylmonomethoxysilane, dimethylaminophenyltrimethoxysilane, trimethoxysilyl-γ-propylphenylamine, trimethoxysilyl-γ-propylbenzylamine, trimethoxysilyl-γ-propylpiperidine, trimethoxysilyl-γ-propylmorpholine, and trimethoxysilyl-γ-propylimidazole. These treatment agents can be used individually, in mixtures of two or more, or in combination or multiple treatments. Silicone oil may also be used for hydrophobic treatment together with the silane coupling agent or alone.

[0065] The number average primary particle diameter of the conductive particles is preferably 0.1 μm or more and 0.5 μm or less. The addition amount of the conductive particles is preferably 0.3% by mass or more and 2% by mass or less with respect to the mass of the toner mother particles.

[0066] (Resin particles) The resin particles are formed of a vinyl resin having a repeating unit represented by the following general formula (1), a repeating unit represented by the following general formula (2), and a repeating unit derived from a sulfonic acid group-containing vinyl compound. The content of the repeating unit derived from the sulfonic acid group-containing vinyl compound in the vinyl resin is 2.0 mol% or more and 5.0 mol% or less with respect to all the repeating units in the vinyl resin.

[0067] [Chemical formula]

[0068] [Chemical formula]

[0069] In formula (1), R 11 , R 12 each independently represents a hydrogen atom, a halogen atom, or an alkyl group which may have a substituent. R 13 represents an alkylene group having a hydroxyl group.

[0070] R 11 , R 12 are each independently preferably a hydrogen atom or a methyl group, and a combination in which R 11 is a hydrogen atom and R 12 is a hydrogen atom or a methyl group is particularly preferable. R 13 is preferably an alkylene group having a hydroxyl group with 1 to 6 carbon atoms, and particularly preferably an alkylene group having a hydroxyl group with 1 to 4 carbon atoms. In the repeating unit derived from 2-hydroxyethyl methacrylate, R 11 is a hydrogen atom, R 12 is a methyl group, R 13These represent (-(CH2)2-OH).

[0071] In formula (2), R 21 ~R 27 Each of these independently represents a hydrogen atom, a halogen atom, a hydroxyl group, an optionally substituted alkyl group, an optionally substituted alkoxy group, an optionally substituted alkoxyalkyl group, or an optionally substituted aryl group.

[0072] R 21 ~R 27 Preferably, each of these is independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or an alkoxyalkyl group having 2 to 6 carbon atoms (more specifically, the total number of carbon atoms of the alkoxy and alkyl groups). 26 , R 27 For each of these, a hydrogen atom or a methyl group is preferred, R 27 is a hydrogen atom, R 26 A combination of hydrogen atoms or methyl groups is particularly preferred. In addition, for repeating units derived from styrene, R 21 ~R 27 Each of these represents a hydrogen atom.

[0073] The resin particles are manufactured using an anionic surfactant. The use of anionic surfactants imparts a weak negative charge to the resin microparticles. This reduces the electrostatic adhesion between the fuser belt and the toner without adversely affecting the toner's positive charge.

[0074] The number-average primary particle diameter of the resin particles is between 50 nm and 100 nm. If the number-average primary particle diameter of the resin particles is less than 50 nm, the resin particles tend to become embedded in the toner matrix particles. As a result, the effectiveness of the resin particles as spacer particles decreases, making it difficult for the toner to come into contact with the surface of the fixing belt. If the number-average primary particle diameter of the resin particles exceeds 100 nm, the amount of resin particles detaching from the toner matrix particles increases, and the spacer effect cannot be obtained. The amount of resin particles added is preferably between 0.05% by mass and 2% by mass relative to the mass of the toner matrix particles.

[0075] (Silica particles) The external additive includes conductive particles and resin particles, as well as silica particles to improve the fluidity of the toner. The silica particles may be treated with a surface treatment agent such as a silane coupling agent or silicone oil. The number-average primary particle diameter of the silica particles is preferably between 10 nm and 30 nm.

[0076] Furthermore, when the number-average primary particle diameter of conductive particles is r1, the number-average primary particle diameter of resin particles is r2, and the number-average primary particle diameter of silica particles is r3, it is preferable that r1 > r2 > r3 is satisfied. Because the surfaces of silica particles and toner matrix particles are strongly positively charged, the electrostatic adhesion force with the fixing belt (negatively charged) is high. By actively bringing the surface of the fixing belt and the conductive particles into contact, the potential difference between the toner and the surface of the fixing belt is reduced, and the effect of reducing the electrostatic adhesion force of the toner to the fixing belt is greatly increased. Therefore, by maximizing the number-average primary particle diameter r1 of the conductive particles, the frequency of contact between the conductive particles and the fixing belt is increased, and an effect of further reducing the electrostatic adhesion force is obtained.

[0077] [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 core particles and an external additive treatment method for attaching an external additive to the surface of 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.

[0078] (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.

[0079] 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.

[0080] 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.

[0081] (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 the external additive using a mixer such as a Henschel mixer or a Nauter mixer.

[0082] As described above, the toner of the present invention maintains its chargeability (positive charge) as much as possible, and has low electrostatic adhesion to the fixing belt. Therefore, it can effectively suppress the occurrence of electrostatic offset, which tends to occur when a belt fixing system, which has excellent low-temperature fixing performance, is used in combination with a magnetic single-component developing system. 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]

[0083] [Manufacturing Example 1] (Manufacturing of toner matrix particles) As a binder resin, 100 parts by mass of polyester resin (HP-313, manufactured by Nippon Synthetic Chemical Co., Ltd.), 80 parts by mass of magnetic powder (TN-15, manufactured by Mitsui Mining & Smelting Co., Ltd.), 4 parts by mass of charge control agent (FCA-201-PS, manufactured by Fujikura Chemical Co., Ltd.), and 4 parts by mass of release agent (carnauba wax, manufactured by Toa Chemical Co., Ltd.) were mixed using an FM mixer (FM-20B, manufactured by Nippon Coke Industries Co., Ltd.) at a rotation speed of 2000 rpm for 5 minutes to obtain a mixture.

[0084] The obtained mixture was melt-kneaded using a twin-screw extruder (TEM-26SS, manufactured by Toshiba Machine Co., Ltd.) to obtain a kneaded product. The melt-kneading was performed under the conditions of a cylinder temperature of 120°C, a shaft rotation speed of 100 rpm, and a processing rate of 90 g / min. After the kneaded product was cooled, it was coarsely ground using a pulverizer (Rotoplex 16 / 8 type, manufactured by Hosokawa Micron Corporation). The obtained coarsely ground product was ground using a mechanical pulverizer (Turbomill TA, manufactured by Freund Turbo) to obtain a pulverized product. The pulverized product was classified using an air classifier (EJ-L-3 (LABo) type, manufactured by Nippon Steel Mining Co., Ltd.) to obtain toner matrix particles with a number mean primary particle diameter of 7.0 μm.

[0085] [Manufacturing Example 2] (Manufacturing of conductive particles) Titanium dioxide (CR-EL, manufactured by Ishihara Sangyo Co., Ltd.) was dispersed in water to form a 100 g / L titanium dioxide suspension, which was heated to 70°C. To this suspension, a solution of 24 g of tin chloride (SnCl2 / 5H2O) and 8 g of antimony chloride (SbCl2) dissolved in 2N hydrochloric acid aqueous solution, along with a 10% by mass sodium hydroxide aqueous solution, was added over 1 hour while maintaining a pH of 2-3. A conductive layer consisting of hydrated tin oxide and antimony oxide was formed on the surface of the titanium dioxide particles. Subsequently, the suspension was filtered and washed, then calcined at 600°C, and crushed with a jet mill to obtain titanium dioxide particles with the conductive layer formed on them.

[0086] The obtained titanium dioxide particles and 3.0% by mass of isopropyltriisostearoyl titanate relative to the titanium dioxide particles were placed in a Henschel mixer (manufactured by Nippon Coke Industries Co., Ltd.), mixed at a temperature of 130°C to induce a coupling reaction, and then dried and crushed to obtain conductive particles C-1.

[0087] Conductive particle C-2 was obtained using the same method as above, except that the amount of tin chloride (SnCl2 / 5H2O) added was changed to 12g and the amount of antimony chloride (SbCl2) added to 4g.

[0088] Conductive particle C-3 was obtained using the same method as described above, except that the amount of tin chloride (SnCl2 / 5H2O) added was changed to 8g and the amount of antimony chloride (SbCl2) added to 3g.

[0089] [Manufacturing Example 3] (Manufacturing of resin particles) In a 1L four-necked flask equipped with a stirring blade, condenser, thermometer, and nitrogen inlet tube, 600g of deionized water, 6g of anionic surfactant (sodium dodecylbenzenesulfonate), 100g of n-butyl methacrylate, 20g of styrene, 35g of divinylbenzene (a mixture of m-divinylbenzene and p-divinylbenzene), 15g of polymerization initiator (benzoyl peroxide), and 5g of 2-acrylamido-2-methylpropanesulfonic acid were added while stirring the contents at a rotation speed of 100 rpm.

[0090] Next, while stirring the contents at a rotation speed of 100 rpm, nitrogen gas was introduced into the flask to replace the atmosphere with nitrogen. Furthermore, while stirring the contents at a rotation speed of 100 rpm, the temperature of the contents was raised to 90°C under a nitrogen atmosphere. Subsequently, under a nitrogen atmosphere and at a temperature of 90°C, the contents were reacted (polymerized) for 3 hours while stirring at a rotation speed of 100 rpm to obtain an emulsion containing the reaction product (resin particles). Subsequently, the obtained emulsion was cooled and solid-liquid separated, and the resulting solid was dried at a temperature of 80°C for 18 hours to obtain resin particle R-1 powder.

[0091] By changing the stirring rate during the polymerization reaction and the amount of 2-acrylamido-2-methylpropanesulfonic acid added, powdered resin particles R-2 to R-9 with different number-average primary particle sizes and sulfo-group-containing vinyl compound content (mol%) were obtained.

[0092] [Manufacturing Example 4] (Toner manufacturing) The toner matrix particles obtained in Production Example 1, 1.0 mass% conductive particles C-1 obtained in Production Example 2, 0.5 mass% resin particles R-1 obtained in Production Example 3, and silica particles (REA200, manufactured by Nippon Aerosil Co., Ltd., number mean primary particle diameter: 12 nm) were mixed using a Henschel mixer (manufactured by Mitsui Miike Industries Co., Ltd.) at a rotation speed of 2120 rpm for 15 minutes, causing the conductive particles, resin particles, and silica particles to adhere (externally add) to the toner matrix particles. Subsequently, the mixture was sieved using a 100-mesh sieve (mesh opening 150 μm) to obtain toner 1.

[0093] Toners 2 to 12 were obtained using the same method as for toner 1, except that the types of conductive particles and resin particles were changed.

[0094] [Measurement of resistivity of conductive particles] Resistivity was measured under conditions of 25°C and 50% RH. 5g of conductive particles were placed in the cylindrical measuring cell of an electrical resistance meter (R6561, Advantest). The measuring cell used had a metal electrode base and a fluororesin cylinder. The electrodes of the electrical resistance meter were connected to the conductive particles filled in the measuring cell. A 1kg load was applied to these electrodes, and a DC voltage of 10V was applied between the two electrodes. The electrical resistance of the conductive particles was measured 1 minute after the start of the voltage application. The 1kg load was continuously applied to the electrodes from the start of the voltage application until the end of the measurement. Based on the measured electrical resistance value and the dimensions of the conductive particles (specifically, the conductive particles filled in the measuring cell) at the time of electrical resistance measurement, the resistivity (volume resistivity) was calculated using the following formula. Resistivity [Ω·cm] = Electrical resistance value × Cross-sectional area of ​​the current path / Length of the current path

[0095] [Measurement of the number-average primary particle diameter of conductive particles and resin particles] Surface images of toner particles were captured at 30,000x magnification using a scanning electron microscope (JSM-6700F, JEOL Ltd.). Using image analysis software (WinROOF, Mitani Corporation), the equivalent circular diameters of 100 conductive particles and resin particles attached to the surface of the toner particles were measured from the captured cross-sectional images, and the average value was defined as the number-average primary particle diameter. Conductive particles, resin particles, and silica particles attached to the toner particles can be distinguished by the size of each particle. Table 1 shows the substrate, number-average primary particle diameter, and resistivity of conductive particles C-1 to C-3. Table 2 shows the surfactant, number-average primary particle diameter, and sulfo-group-containing vinyl compound content of resin particles R-1 to R-9.

[0096] [Table 1]

[0097] [Table 2]

[0098] [Evaluation of electrostatic offset (image contamination)] The toners 1-12 obtained in Manufacturing Example 4 were installed in the developer unit of a belt-fixing evaluation machine (monochrome printer ECOSYS PA6000x, manufactured by Kyocera Document Solutions). After toner installation, 50,000 images with a print density of 2% were printed in a normal temperature and humidity environment (temperature 23°C, humidity 65%RH). After printing 50,000 images, one evaluation image was printed containing a 30mm x 30mm black solid image (image density 100%) and a 30mm x 30mm black halftone image (image density 37.5%). The printed paper on which the evaluation image was formed was visually observed to determine whether or not electrostatic offset occurred. The evaluation criteria are shown below. ○: No stains caused by toner adhering to the fuser belt (stains that appear with each rotation cycle of the fuser belt) were observed on the printed paper. ×; Stains caused by toner adhering to the fuser belt (stains appearing with each rotation cycle of the fuser belt) were observed on the printed paper.

[0099] Table 3 shows the evaluation results of electrostatic offset (image staining) when using toners 1 to 5 (inventions 1 to 5) and when using toners 6 to 12 (comparative examples 1 to 7), along with the types of conductive particles and resin particles used as external additives.

[0100] [Table 3]

[0101] As is clear from Table 3, in toners 1 to 5 of the present invention, which used conductive particles C-1 and C-2 with a resistivity of 1.0E+4 [Ω·cm] or less, and resin particles R-1 to R-4 in which the content of sulfogroup-containing vinyl compounds in the vinyl resin is 2.0 mol% to 5.0 mol%, no image staining due to electrostatic offset was observed.

[0102] In contrast, in Comparative Example 1, which used toner 6 to which conductive particles C-3 with a resistivity of 7.0E+04 [Ω·cm] were added externally, the electrostatic adhesion between the fixing belt and the toner was not sufficiently reduced, resulting in image smudges due to electrostatic offset. In Comparative Examples 2 and 3, which used toners 7 and 8 to which resin particles R-5 and R-6 with sulfogroup-containing vinyl compounds of 1.0 mol% and 7.5 mol% in the vinyl resin were added externally, image smudges due to electrostatic offset occurred because the content of the sulfogroup-containing vinyl compound was not appropriate.

[0103] Furthermore, in Comparative Example 4, which used toner 9 with resin particles R-7 having an average primary particle diameter of 40 nm added externally, the resin particles were too small, causing them to become embedded in the toner particles, resulting in a lack of spacer effect and image fouling due to electrostatic offset. On the other hand, in Comparative Example 5, which used toner 10 with resin particles R-8 having an average primary particle diameter of 120 nm added externally, a large amount of resin particles detached from the toner particles, resulting in a lack of spacer effect and image fouling due to electrostatic offset.

[0104] Furthermore, in Comparative Example 6, which used toner 11 to which resin particles R-9 manufactured using a cationic surfactant were added externally, it was not possible to give the resin fine particles a weakly negative charge, and therefore the electrostatic adhesion force between the fixing belt and the toner could not be reduced, resulting in image staining due to electrostatic offset.

[0105] Based on the above results, it was confirmed that a magnetic one-component toner capable of suppressing image contamination due to electrostatic offset can be obtained by including, as an external additive, conductive particles with a resistivity of 1.0E+4 [Ω·cm] or less, repeating units represented by general formula (1), repeating units represented by general formula (2), and repeating units derived from a sulfo-group-containing vinyl compound, resin particles having a sulfo-group-containing vinyl compound content of 2.0 mol% to 5.0 mol% in the vinyl resin and a number-average primary particle diameter of 50 nm to 100 nm, and silica particles. [Industrial applicability]

[0106] The present invention is applicable to image forming apparatuses using a magnetic single-component developing method and a belt fixing method. By using the present invention, it is possible to provide an image forming apparatus that can suppress the occurrence of electrostatic offset by reducing the adhesion force between the fixing belt and the magnetic single-component toner. [Explanation of Symbols]

[0107] 1. Photoconductor drum 4. Developing device 6. Transfer roller (transfer device) 8. Fixing device 9 Image forming unit 20 Fixing belt 21 Pressure Roller 23 Heater 25 Support stay 27 Nip forming member 100 Image forming apparatus S Paper (recording medium)

Claims

1. A developing apparatus that develops an electrostatic latent image formed on an image carrier using a magnetic one-component toner into a toner image, A transfer device for transferring the toner image developed by the developing device onto a recording medium, An endless fixing belt heated by a heating device, A nip-forming member is positioned radially inward of the fixing belt and slides against the inner circumferential surface of the fixing belt, A pressing member that is pressed against the nip forming member with a predetermined pressure, sandwiching the fixing belt, thereby forming a fixing nip portion between itself and the fixing belt, A fixing device having the above transfer device which fixes the toner image transferred onto the recording medium onto the recording medium, A magnetic one-component toner used in an image forming apparatus equipped with, Toner matrix particles containing at least a binder resin and magnetic powder, The external additive adhering to the surface of the toner matrix particles, It consists of toner particles equipped with, The aforementioned external additive is Conductive particles with a resistivity of 1.0E+4 [Ω·cm] or less, Resin particles having a number-average primary particle diameter of 50 nm or more and 100 nm or less, Silica particles and Includes, The aforementioned resin particles are formed using an anionic surfactant, It is formed from a vinyl resin having repeating units represented by the following general formula (1), repeating units represented by the following general formula (2), and repeating units derived from a sulfo group-containing vinyl compound. A magnetic one-component toner characterized in that the content of repeating units derived from the sulfo group-containing vinyl compound in the vinyl resin is 2.0 mol% or more and 5.0 mol% or less relative to the total repeating units in the vinyl resin. 【Chemistry 1】 【Chemistry 2】 (In formula (1), R 11 , R 12 Each independently represents a hydrogen atom, a halogen atom, or an alkyl group which may have a substituent. 13 R represents an alkylene group having a hydroxyl group. In formula (2), R 21 , R 27 Each of these independently represents a hydrogen atom, a halogen atom, a hydroxyl group, an optionally substituted alkyl group, an optionally substituted alkoxy group, an optionally substituted alkoxyalkyl group, or an optionally substituted aryl group.

2. The magnetic one-component toner according to claim 1, characterized in that when r1 is the number-average primary particle diameter of the conductive particles, r2 is the number-average primary particle diameter of the resin particles, and r3 is the number-average primary particle diameter of the silica particles, r1 > r2 > r3 is satisfied.

3. The magnetic one-component toner according to claim 1, characterized in that the conductive particles are adjusted to have a resistivity of 1.0E+4 [Ω・cm] or less by ATO treatment.

4. The magnetic one-component toner according to claim 1, characterized in that the resin particles are such that the content of repeating units derived from the sulfo group-containing vinyl compound in the vinyl resin is adjusted to 2.0 mol% or more and 5.0 mol% or less relative to the total repeating units in the vinyl resin by the amount of 2-acrylamido-2-methylpropanesulfonic acid added.

5. The magnetic one-component toner according to claim 1, characterized in that the number-average primary particle diameter of the conductive particles is 0.1 μm or more and 0.5 μm or less.

6. The magnetic one-component toner according to claim 1, characterized in that the amount of conductive particles added is 0.3% by mass or more and 2% by mass or less relative to the mass of the toner matrix particles.

7. The magnetic one-component toner according to claim 1, characterized in that the amount of resin particles added is 0.05% by mass or more and 2% by mass or less relative to the mass of the toner matrix particles.

8. A developing apparatus that develops an electrostatic latent image formed on an image carrier using a magnetic one-component toner into a toner image, A transfer device for transferring the toner image developed by the developing device onto a recording medium, An endless fixing belt heated by a heating device, A nip-forming member is positioned radially inward of the fixing belt and slides against the inner circumferential surface of the fixing belt, A pressing member that is pressed against the nip forming member with a predetermined pressure, sandwiching the fixing belt, thereby forming a fixing nip portion between itself and the fixing belt, A fixing device having the above transfer device which fixes the toner image transferred onto the recording medium onto the recording medium, Equipped with, An image forming apparatus using a magnetic one-component toner according to any one of claims 1 to 7.

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