Positively charged magnetic one-component toner

Abstract

This invention provides a positively charged magnetic single-component toner that suppresses image density degradation and image fogging after durable printing, as well as layer distortion of the toner layer after toner installation. [Solution] The positively charged 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. When standard carrier P-01 and toner are mixed for 10 minutes, the mass mixing ratio of toner to carrier is x (x = 0.2, 0.4, 0.6, 0.8, 1.0), and the charge amount of the carrier is y. The approximate formula for the charge amount of the carrier is y = b*x a However, this satisfies 0.3 ≤ a ≤ 1 and -7 ≤ b ≤ -3.

Description

Technical Field

[0001] The present invention relates to a positively charged 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. Usually, for toner applied to such electrophotography, after a colorant, a charge control agent, a release agent, a magnetic material, etc. are mixed with a binder resin such as a thermoplastic resin, kneading, pulverization, and classification are performed to obtain toner particles (toner mother particles) having an average particle size of 5 μm or more and 10 μm or less. And for the purpose of imparting fluidity to the toner, imparting suitable charging performance to the toner, or improving the cleaning property of the toner from the photoreceptor drum, inorganic fine powders such as silica and titanium oxide are externally added to the toner mother particles.

[0003] Patent Document 1 discloses a magnetic toner containing at least one compound selected from metallic soaps, higher fatty acids, fatty acid amides, higher alcohols, hydrocarbon-based lubricants, and ester-based lubricants as a toner component, and heat-treated at a temperature higher than the softening point of the toner thermoplastic resin after mixing, kneading, and pulverization.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a magnetic single-component development system using a magnetic single-component toner, ensuring image quality requires that the toner particles within the toner chain have an appropriate amount of charge, maintain a certain charge distribution, and suppress variations in the shape of the toner chain. Narrowing the charge distribution is influenced by how easily charge can be transferred from the bottom layer of toner, which is triboelectrically charged with the developing roller, to the upper layers of toner. Charge transfer within the toner chain is promoted by increasing the dielectric properties of the toner, but at the same time, the design of the charging performance must prevent the bottom layer of toner from becoming excessively charged and hindering charge transfer.

[0006] In view of the above problems, the present invention aims to provide a positively charged magnetic single-component toner that can suppress the decrease in image density and the occurrence of image fogging after durable printing, as well as suppress the disorder of the toner layer after toner installation. [Means for solving the problem]

[0007] To achieve the above objective, the first configuration of the present invention is a positively charged 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. When standard carrier P-01 and toner are mixed for 10 minutes, the mass mixing ratio of toner to carrier is x, and the charge amount of the carrier is y, and the approximate formula for the charge amount of the carrier is y = b*x a However, it satisfies the following conditions (1) and (2). 0.3 ≤ a ≤ 1 ···(1) -7≦b≦-3 ···(2) however, x = 0.2, 0.4, 0.6, 0.8, 1.0 That is the case. [Effects of the Invention]

[0008] According to the first configuration of the present invention, a positively charged magnetic single-component toner is obtained that has excellent charge stability, suppresses the decrease in image density and the occurrence of image fringing after durable printing, and also suppresses layer disorder of the toner layer after toner installation. [Brief explanation of the drawing]

[0009] [Figure 1] Graph showing the relationship between carrier charge amount and toner concentration (T / C). [Figure 2] Electron microscope image showing the state of toner and carrier after mixing when the toner concentration is 10%. [Figure 3] Electron microscope image showing the state of toner and carrier after mixing when the toner concentration is 20%. [Figure 4] Electron microscope image showing the state of toner and carrier after mixing when the toner concentration is 40%. [Figure 5] Electron microscope image showing the state of toner and carrier after mixing when the toner concentration is 60%. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described in detail below. Unless otherwise specified, the evaluation results (values ​​indicating shape or physical properties, etc.) for the powder (more specifically, toner core particles, toner mother particles, external additives, or toner, etc.) are the number average of the values ​​measured for each of the average particles selected from the powder. Unless otherwise specified, the number average particle diameter of the powder is the number average of the equivalent circle diameter (diameter of a circle having the same area as the projected area of ​​the particle) of the primary particles measured using a microscope. Unless otherwise specified, the measured value of the median volume diameter (D50) of the powder is the value measured using a laser diffraction / scattering particle size distribution analyzer ("LA-750" manufactured by Horiba, Ltd.). Unless otherwise specified, the measured values ​​of the acid value and hydroxyl value are the values ​​measured according to "JIS (Japanese Industrial Standards) K0070-1992". Furthermore, unless otherwise specified, the measured values ​​for number-average molecular weight (Mn) and mass-average molecular weight (Mw) are those obtained using gel permeation chromatography.

[0011] In the following, the compound name may be followed by "system" to comprehensively refer to the compound and its derivatives. When "system" is followed by a compound name to represent a polymer name, it means that the repeating unit of the polymer originates from the compound or its derivative. Also, acrylic and methacrylic may be comprehensively referred to as "(meth)acrylic". Furthermore, acryloyl (CH) 2 =CH-CO-) and methacryloyl (CH 2 =C(CH 3 The terms )-CO-) are sometimes collectively referred to as "(meth)acryloyl".

[0012] The toner according to this embodiment can be suitably used as a positively charged toner for developing electrostatic latent images. The toner of this embodiment is a powder containing a plurality of toner particles (each having a configuration described later). The toner contains magnetic powder and is used as a one-component developer.

[0013] The toner particles contained in this embodiment comprise toner mother particles and an external additive attached to the surface of the toner mother particles. That is, toner particles before the external additive is attached are referred to as toner mother particles. Furthermore, if the toner mother particles have a shell layer, the particles before the shell layer is formed are referred to as toner core particles. If the toner mother particles do not have a shell layer, the toner mother particles are also referred to as toner core particles.

[0014] The toner according to this embodiment can be used, for example, to form images in an electrophotographic apparatus (image forming apparatus). An example of an image forming method using an electrophotographic apparatus will be described below.

[0015] First, an electrostatic latent image is formed on a photoreceptor (for example, the surface layer of a photoreceptor drum) based on image data. Next, the formed electrostatic latent image is developed using a magnetic one-component toner. In the developing process, toner (for example, toner charged by friction with a blade) on a developing sleeve (for example, the surface layer of a developing roller in a developing device) disposed near the photoreceptor is attached to the electrostatic latent image to form a toner image on the photoreceptor. Then, in the subsequent transfer process, the toner image on the photoreceptor is directly transferred to a recording medium (for example, paper). Alternatively, after primary transfer to an intermediate transfer body (for example, a transfer belt), the toner image on the intermediate transfer body is further secondarily transferred to the recording medium. Thereafter, the toner is heated to fix the toner on the recording medium. As a result, an image is formed on the recording medium.

[0016] <.. [1. Basic Composition of Toner] The magnetic one-component toner of the present invention (hereinafter, also simply referred to as toner) includes toner mother particles and external additives attached to the surface of the toner mother particles. The toner mother particles contain at least a binder resin, magnetic powder, and a release agent. The release agent contains a long-chain fatty acid having 24 or more carbon atoms. Further, the toner mother particles may contain a colorant, a charge control agent, etc. in the binder resin as necessary.

[0017] The toner of the present invention has a release agent containing at least a long-chain fatty acid having 24 or more carbon atoms inside the toner mother particles, and as external additives attached to the surface of the toner mother particles, positively charged dry silica particles and wet silica particles whose surfaces are subjected to positive and negative electrification treatments are used in combination. As the wet silica particles, those obtained by treating a precipitation method silica base material having a high dielectric constant with a positively charged aminosilane for increasing the dielectric constant and a negatively charged silane for canceling its time change are used.

[0018] [2. Materials of Toner] Hereinafter, the binder resin, magnetic powder, release agent, charge control agent, colorant, charge control agent for forming the toner mother particles, and silica particles constituting the external additives externally added to the toner mother particles, and the manufacturing method of the toner of the present invention will be described in order.

[0019] (Binder 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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 Seiko Instruments Inc. DSC-6200 differential scanning calorimeter 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.

[0028] 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.

[0029] (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.

[0030] 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 magnetic powder with such particle size is used, it is easy to uniformly disperse the magnetic powder in the binder resin.

[0031] 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.

[0032] 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.

[0033] (Release agent) The toner matrix particles contain a release agent to improve adhesion and offset resistance. The release agent contains long-chain fatty acids with 24 or more carbon atoms. The type of release agent that can be added to the toner matrix particles is not particularly limited as long-chain fatty acids with 24 or more carbon atoms are included. 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 a release agent 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] (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.

[0039] 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.

[0040] 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.

[0041] (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.

[0042] The type of charge control agent that can be contained in the toner matrix particles is not particularly limited as long as it does not hinder the objective 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; and Azinfastred F Examples include direct dyes consisting of azine compounds such as C, 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; 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] (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 contains dry silica and wet silica as external additives.

[0049] (Dry silica particles) Dry silica particles can achieve a high charge due to their low silanol group count. They are produced by methods such as gas-phase hydrolysis of silane halides like silicon tetrachloride at high temperatures (flame hydrolysis method), and by reducing silica sand with coke in an electric furnace, vaporizing it, and then oxidizing the resulting gas (heating method). Dry silica particles are typically surface-treated with hydrophobic agents such as alkylsilanes. Specific examples of alkylsilanes include alkylhalosilanes (more specifically, trichloro(methyl)silane, dichlorodimethylsilane, chlorotrimethylsilane, or tert-butyldimethylchlorosilane, etc.), phenylhalosilanes (more specifically, phenyltrichlorosilane, or dichlorodiphenylsilane, etc.), vinylhalosilanes (more specifically, vinyltrichlorosilane, etc.), tetraalkoxysilanes (more specifically, tetramethoxysilane, or tetraethoxysilane, etc.), alkylalkoxysilanes (more specifically, trimethoxy(methyl)silane, dimethoxydimethylsilane, triethoxymethylsilane, diethoxydimethylsilane, isobutyltrimethoxysilane, or decyltrimethoxysilane, etc.), and halogenated alkylalkoxysilanes (more specifically, 3-chloropropyltrimethoxysilane, etc.) Examples include silanes (such as lanes), phenylalkoxysilanes (more specifically, trimethoxyphenylsilane, dimethoxydiphenylsilane, triethoxyphenylsilane, or diphenyldiethoxysilane), vinylalkoxysilanes (more specifically, vinyltrimethoxysilane or vinyltriethoxysilane), silane coupling agents having a (meth)acryloyl group (more specifically, 3-(trimethoxysilyl)propyl methacrylate), silane coupling agents having an epoxy group (more specifically, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidyloxypropyltrimethoxysilane, or 3-glycidyloxypropylmethyldiethoxysilane), or silane coupling agents having a mercapto group (more specifically, 3-mercaptopropyltrimethoxysilane).Furthermore, by using dry silica particles that have been hydrophobized with a positively charged hydrophobic treatment agent, such as aminosilane, in which an amino group is introduced into a silane compound, the positive charge of the dry silica particles is improved, making it easier to suppress the decrease in the amount of charge of toner under high temperature and high humidity conditions.

[0050] Silicone oils can also be used as hydrophobic treatment agents for dry silica particles. The type of silicone oil is not particularly limited as long as the desired hydrophobic effect can be obtained, and various silicone oils that have been conventionally used as hydrophobic treatment agents can be used. As for the silicone oil, those having a linear siloxane structure are preferred, and both non-reactive and reactive silicone oils can be used. Specific examples of silicone oils include dimethyl silicone oil, phenylmethyl silicone oil, chlorophenyl silicone oil, alkyl silicone oil, chlorosilicone oil, polyoxyalkylene-modified silicone oil, fatty acid ester-modified silicone oil, methyl hydrogen silicone oil, silanol group-containing silicone oil, alkoxy group-containing silicone oil, acetoxy group-containing silicone oil, amino-modified silicone oil, carboxylic acid-modified silicone oil, and alcohol-modified silicone oil.

[0051] Methods for hydrophobizing dry silica particles include adding or spraying a hydrophobic agent such as alkylsilane, aminosilane, and silicone oil while rapidly stirring the dry silica particles, and adding the dry silica particles to an organic solvent solution of the stirred hydrophobic agent. After the hydrophobic treatment, heating is performed to obtain hydrophobic dry silica particles. When adding or spraying the hydrophobic agent, the agent can be used as is or diluted with an organic solvent.

[0052] The average particle size of the dry silica particles is preferably between 10 nm and 150 nm. The amount of dry silica particles added is preferably between 0.8% and 1.6% by mass, and more preferably between 0.8% and 1.4% by mass, relative to the mass of the toner matrix particles. By setting the amount of dry silica particles added within the above range, it becomes particularly easier to suppress the occurrence of image fogging when the toner is subjected to mechanical stress in the developer.

[0053] (Wet-processed silica particles) Wet silica particles are produced using methods such as the wet synthesis of silica nanoparticles by hydrolysis of alkoxysilanes, or by methods such as the precipitation method or sol-gel method that obtain silica nanoparticles from sodium silicate in a wet manner. Since wet silica is obtained in a form where primary particles have undergone secondary aggregation, it is difficult to obtain fluidity.

[0054] Furthermore, wet silica particles, like dry silica, have their surfaces hydrophobicated using alkylsilanes, aminosilanes (alkylsilanes with an amino group introduced), and hydrophobic agents such as silicone oil. The method for hydrophobicating wet silica particles is the same as for dry silica. In addition, wet silica particles may be surface-treated with a negatively charged silane. Examples of negatively charged silanes include fluorine-containing silanes such as trimethoxy(3,3,3-trifluoropropyl)silane.

[0055] The average particle size of the wet silica particles is preferably between 10 nm and 150 nm. The amount of wet silica particles added is preferably between 0.2% and 0.4% by mass, and more preferably between 0.2% and 0.3% by mass, relative to the mass of the toner matrix particles. By setting the amount of wet silica particles added within the above range, it becomes particularly easier to suppress the occurrence of image fogging when the toner is subjected to mechanical stress in the developer. In addition, it becomes easier to obtain toner with a fluidity change rate of 5% or less.

[0056] The external additive may include dry silica particles and wet silica particles, as well as other external additives other than silica particles. Preferred other external additives are particles of metal oxides (more specifically, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, or barium titanate, etc.) or resin particles. The other external additives may be surface-treated. The average particle size of the other external additives is not particularly limited as long as it does not hinder the objectives of the present invention, but is preferably 0.01 μm or more and 1.0 μm or less.

[0057] [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. 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.

[0058] (Method for manufacturing toner matrix particles) The method for producing toner matrix particles is not particularly limited, as long as 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.

[0059] 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 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 core 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.

[0060] 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 desired particle size is achieved. 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 core particles with the desired particle size.

[0061] (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. [3. Toner charge distribution]

[0062] Next, the method for defining the charge distribution of the toner according to the present invention will be described. In the present invention, as a simple method for representing the charge distribution within the toner chain, the change in the carrier charge relative to the T / C ratio when toner and carrier are mixed at a toner concentration (T / C; ratio of toner mass to carrier mass) of an amount greater than or equal to the amount of toner that can 100% cover the surface of the carrier is measured and used as a surrogate index.

[0063] Figure 1 is a graph showing the relationship between carrier charge and toner concentration (T / C). In Figure 1, for eight types of toners A to H prepared in the examples described later, 10g of standard carrier P-01 (distributed by the Image Society of Japan) was placed in a 10cc poly container, and one of toners A to H was added so that the mass mixing ratio (=T / C) of toner to carrier P-01 was 0.2, 0.4, 0.6, 0.8, and 1.0, respectively. The carrier charge was measured and plotted after mixing for 10 minutes using a Turbra shaker mixer (manufactured by Shinmaru Enterprises). The carrier charge was measured using a charge measuring device (Q / m meter, MODEL 212HS, manufactured by TRek). Since toner is positively charged, the carrier charge is a negative value, but here it is calculated as a positive value in order to obtain the approximation formula described later.

[0064] The standard carrier P-01 is a positively charged carrier whose charge value has been calibrated so that anyone can measure the toner charge in accordance with the Japanese Society of Image Science's standard toner charge measurement method.

[0065] Figures 2 to 5 are electron microscope images showing the state after mixing toner and carrier, representing toner concentrations (T / C) of 10%, 20%, 40%, and 60%, respectively. As shown in Figures 2 to 5, the toner particles aggregate more as the toner concentration increases due to the enantiomer forces acting between them. In other words, at toner concentrations exceeding the amount of toner that can 100% cover the surface of the carrier, the change in carrier charge is thought to depend on the charge transfer between toner particles.

[0066] As shown in Figure 1, the relationship between carrier charge and toner concentration (T / C dependence of carrier charge) is positively correlated. More specifically, when x is the mass mixing ratio of toner to carrier and y is the carrier charge, the following approximate equation (1) is satisfied (the equation in Figure 1 shows the approximate equation for toner A). y = b * x a ...(1) however, a; Rate of change of carrier charge relative to toner concentration b; constant That is the case.

[0067] The above equation (1) is calculated from the following equations (2) and (3). Ln(y) = a * Ln(x) + b' ... (2) b = EXP(b') ... (3)

[0068] Here, the easier it is for charge transfer to occur between toner particles, the closer the rate of change a of the carrier charge relative to the mass mixing ratio x (=T / C) of toner to carriers will be to 1. If no charging occurs between toner particles at all, the rate of change a of the carrier charge will be 0.

[0069] In the toner of the present invention, the charge distribution of the toner is defined such that the approximate formula (1) satisfies 0.3 ≤ a ≤ 1 and -7 ≤ b ≤ -3 (where x is 0.2, 0.4, 0.6, 0.8, and 1.0). This makes it possible to maintain the image density after durable printing, as shown in the examples described later, and to effectively suppress the occurrence of image fogging and disturbances in the toner layer on the developing roller.

[0070] The toner of the present invention, as described above, can be charged to a desired level of charge 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, thereby enabling the formation of images of a desired density. Furthermore, it can effectively suppress image fogging after durable printing and the occurrence of toner layer disturbance during toner installation in low temperature and low humidity environments. For this reason, the toner of the present invention can be suitably used in various image forming apparatuses. 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 these examples. [Examples]

[0071] [Manufacturing Example 1] (Manufacturing of toner matrix particles) As a binder resin, 1984g of polyester resin (Tuffton NE-8000, manufactured by Kao Corporation, a mixture of three types of resins), 60g of polyester resin (KD-C8, manufactured by Kao Corporation), 1600g of magnetic powder (MRO-15A, manufactured by Toda Kogyo Co., Ltd., resistance value 200Ω·m), 200g of charge control agent (FCA-482PLV, manufactured by Fujikura Kasei Co., Ltd.), and 120g of montane wax (WARADUR_S, manufactured by Ferpke AG) as a release agent 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 the mixture.

[0072] 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 finely ground and classified using a pulverizer and classifier (Jetmill MJT-1, manufactured by Hosokawa Micron Corporation) to obtain toner mother particles A containing long-chain fatty acids with 24 or more carbon atoms.

[0073] Except for adding ester wax (WEP-3, manufactured by NOF Corporation) instead of montan wax, toner mother particle B, which does not contain long-chain fatty acids with 24 or more carbon atoms, was obtained using the same method as toner mother particle A.

[0074] [Manufacturing Example 2] (Wet-process silica particle manufacturing) In a 20L stainless steel jacketed reaction vessel equipped with a stirrer, two dropping nozzles, a thermometer, and a circulation pump, 10L of a 50% aqueous solution of sodium silicate No. 3 (SiO2 concentration 25% by mass, SiO2 / Na2O molar ratio 3.3) and a 40% aqueous sulfuric acid solution were mixed to obtain a silica hydrosol by reducing the excess sulfuric acid to 0.6N. After allowing the silica hydrosol to stand for a while to gel, it was subjected to hydrothermal treatment at 90°C and pH 9.5 for 12 hours. Then, sulfuric acid was added to remove the alkali until the excess sulfuric acid reached 0.03N, and the mixture was left to stand at 60°C for another hour. After that, it was thoroughly washed with water to obtain a pure silica hydrogel.

[0075] The obtained silica hydrogel was dried in a dryer until the moisture content reached 10%, then pulverized using a superheated steam jet mill (PJM-100NP, manufactured by Nippon Pneumatic Mfg. Co., Ltd.), and further classified using an air classifier. The resulting reaction product was filtered using a filter press and washed with water to obtain silica cake. The obtained silica cake was slurryed using a reciprocating rotary agitator (Agitator AP04 type: manufactured by Shimazaki Engineering Co., Ltd.), and 2.0% by mass of polyoxyalkylene alkyl ether nonionic surfactant (Neugen XL-61, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., HLB: 13) was added relative to the silica. After further stirring, it was spray-dried in a disc-type spray dryer (Spray Dryer AN-40R type: manufactured by Ashizawa Niloatomizer Co., Ltd.) at an outlet temperature of 110°C, then pulverized in a jet mill (PJM-100NP: manufactured by Nippon Pneumatic Mfg. Co., Ltd.), and coarse particles were removed using an air-powered classifier (Classil N-5 type: manufactured by Seishin Kigyo Co., Ltd.) to obtain 1.2 kg of silica substrate.

[0076] Next, 100 g of the obtained silica substrate was placed in a 1 L stainless steel jacketed reaction vessel equipped with a stirrer and thermometer. In this reaction vessel, 5 g of N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane as surface treatment agent 1 (positively charged surface treatment agent) and 5 g of trimethoxy(3,3,3-trifluoropropyl)silane as surface treatment agent 2 (negatively charged surface treatment agent) (both manufactured by Shin-Etsu Chemical Co., Ltd.) were dissolved in 50 g of toluene, and the diluted solution, diluted 10 times, was gradually added dropwise while stirring, and the mixture was irradiated with ultrasound for 30 minutes to form a mixture. After heating this mixture in a constant temperature bath at 150°C, the toluene was removed using a rotary evaporator, and the obtained solid was dried using a vacuum dryer at a set temperature of 50°C until no further weight loss occurred. Furthermore, it was heat-treated in an electric furnace under a nitrogen stream at 200°C for 3 hours. The obtained powder was crushed using a jet mill (PJM-100NP, manufactured by Nippon Pneumatic Mfg. Co., Ltd.) and collected with a bag filter to obtain silica particles A.

[0077] Silica particles B were obtained using the same procedure as for silica particles A, except that 10 g of isopropyl titanium triisostearate (manufactured by Ajinomoto Fine Techno Co., Ltd.) was used instead of 5 g of trimethoxy(3,3,3-trifluoropropyl)silane as surface treatment agent 2.

[0078] Silica particles C were obtained using the same procedure as for silica particles A, except that 5 g of 3-aminopropyltriethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) was used instead of 5 g of N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane as surface treatment agent 1.

[0079] Silica particles D were obtained using the same procedure as for silica particles C, except that 5 g of trimethoxy(3,3,3-trifluoropropyl)silane was not added as surface treatment agent 2.

[0080] [Manufacturing Example 3] (Manufacturing of dry silica particles) A silicon tetrachloride compound was introduced into the mixing chamber of a combustion device (burner) along with nitrogen gas. Hydrogen and air were then introduced into the mixing chamber, and all the introduced gases were combusted and reacted in the reaction chamber of the combustion device at 11200°C. Subsequently, the reaction products were collected using a 1 μm pore size filter at a combustion exhaust gas temperature of 450°C.

[0081] 100 g of the obtained solid was placed in a reaction vessel, and nitrogen gas was introduced into the vessel to create a nitrogen atmosphere. Next, a surface treatment solution containing 15 g of 3-aminopropyltriethoxysilane, 15 g of hexamethyldisilazane, and 1 g of water was sprayed onto the solid in the reaction vessel, and the temperature inside the reaction vessel was raised to 200°C. The contents were stirred for 2 hours under a nitrogen atmosphere. Furthermore, the contents were heated at 250°C under a nitrogen atmosphere while being stirred for 3 hours to dry them. After that, the contents were cooled to obtain silica particles E.

[0082] [Manufacturing Example 4] (Toner manufacturing) 1.8 kg of toner matrix particles A obtained in Production Example 1, 4 g of silica particles A obtained in Production Example 2, and 8 g of silica particles E obtained in Production Example 3 were mixed for 15 minutes at a rotation speed of 2120 rpm using an FM mixer (FM-10C, manufactured by Nippon Coke Industries Co., Ltd.) to attach (add externally) silica particles A and silica particles E to toner matrix particles A. Then, the mixture was sieved using a 100-mesh sieve (mesh opening 150 μm) to obtain toner A of the present invention 1.

[0083] Except for changing the types and amounts of wet and dry silica particles, toners B to D of Invention 2 to 4 and toners E to H of Comparative Examples 1 to 4 were obtained by the same method as the toner of Invention 1. Table 1 shows the carrier charge amount and the coefficients of the related equations when toners B to D of Invention 1 to 4 and toners E to H of Comparative Examples 1 to 4 are mixed with carrier P-01, along with the toner composition.

[0084] [Table 1] *1; N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane *2; Trimethoxy(3,3,3-trifluoropropyl)silane *3; Isopropyl titanium triisostearate *4;3-aminopropyltriethoxysilane

[0085] [Evaluation of image density, image fogging, and toner layer disturbance on the developing roller] The image density, image fogging, and toner layer disturbance on the developing roller were evaluated using the toners of Invention 1 to 4 and the toners of Comparative Examples 1 to 4 according to the method described below. (Image density) The toners of Invention 1-4 and Comparative Examples 1-4 obtained in Manufacturing Example 4 were installed in the developer unit of an evaluation machine (monochrome printer ECOSYS PA6000x, manufactured by Kyocera Document Solutions). After toner installation, three test images with a print density of 2% were printed intermittently: 100,000 pages in a normal temperature and humidity environment (NN environment, temperature 23°C, humidity 65%RH), 10,000 pages in a high temperature and high humidity environment (HH environment, temperature 28°C, humidity 80%RH), and 10,000 pages in a low temperature and low humidity environment (LL environment, temperature 10°C, humidity 20%RH). Image density (ID) was measured using a reflectance densitometer (TC-6DX, manufactured by Tokyo Denshoku Co., Ltd.) immediately after the start of printing (initial), after printing 100,000 pages in the NN environment, after printing 10,000 pages in the HH environment, and after printing 10,000 pages in the LL environment. The evaluation criteria for image density are shown below. ○: ID ≥ 1.2 (Excellent, practical level) △; 1.0 ≤ ID < 1.2 (Good, practical level) ×; ID < 1.0 (Defective, outside of usable range)

[0086] (Image overlap) The fog density (FD) of the white areas of printed materials after 100,000 prints in a NN environment was measured using a reflectance densitometer (TC-6DX, manufactured by Tokyo Denshoku Co., Ltd.). The fog density (FD) was calculated using the following formula (1). FD = (Reflectance density of the white area of ​​the printed paper) - (Reflectance density of the unprinted paper). The evaluation criteria for image haze are shown below. ○: FD < 0.01 (Practical level) ×: FD ≥ 0.01 (outside the practical range)

[0087] (Disorder in the toner layer on the developing roller) The toner layer disturbance on the developing roller after toner installation in an LL environment was visually evaluated. The evaluation criteria for toner layer disturbance are shown below. ○; No toner layer distortion occurred (practical level). ×; Toner layer irregularities may occur (outside of practical use range).

[0088] Table 2 shows the evaluation results of image density, image fogging, and toner layer disturbance on the developing roller when using the toners of Invention 1 to 4 and Comparative Examples 1 to 4. The values ​​in Table 2 represent the measured values ​​of image density (ID) and fogging density (FD).

[0089] [Table 2]

[0090] As is clear from Table 2, the approximate formula for carrier charge is y = b*x a In the toners of the present invention 1 to 4, the conditions 0.3 ≤ a ≤ 1 and -7 ≤ b ≤ -3 were satisfied, and both wet silica particles and dry silica particles were included as external additives applied to the surface of the toner matrix particles. In all cases, the image density (ID) was 1.0 or higher at the initial stage under an NN environment, after 100,000 prints, after 10,000 prints under an HH environment, and after 10,000 prints under an LL environment, which was excellent. Furthermore, the fogging density (FD) after 100,000 prints under an NN environment was 0.01 or lower, and no image fogging was observed. In addition, no toner layer disturbance was observed on the developing roller after toner installation under an LL environment.

[0091] In particular, the toners of the present invention 1 and 2, in which the release agent added to the toner matrix particles contains long-chain fatty acids with 24 or more carbon atoms, and N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane is used as the surface treatment agent for wet silica particles, both showed extremely good image density (ID) of 1.2 or higher after printing 10,000 sheets under HH and LL environments.

[0092] In contrast, the toners in Comparative Examples 1 and 4, which did not satisfy the condition 0.3 ≤ a ≤ 1 and only dry silica particles were added as an external additive, all exhibited a fogging density (FD) of 0.01 or higher after printing 100,000 sheets under an NN environment, indicating image fogging. In particular, Comparative Example 4, in which the release agent added to the toner matrix particles did not contain long-chain fatty acids with 24 or more carbon atoms, had an image density (ID) of less than 1.0 after printing 10,000 sheets under an HH environment, indicating insufficient image density. Furthermore, the fogging density (FD) was 0.033, resulting in significant image fogging.

[0093] On the other hand, in Comparative Example 2, the toner did not satisfy -7 ≤ b ≤ -3, and only wet silica particles surface-treated with 3-aminopropyltriethoxysilane and trimethoxy(3,3,3-trifluoropropyl)silane were added as external additives. The image density (ID) after printing 10,000 sheets in an HH environment was less than 1.0, indicating that sufficient image density could not be obtained.

[0094] Furthermore, in Comparative Example 3, which contained only wet silica particles surface-treated with 3-aminopropyltriethoxysilane as an external additive, toner layer disturbance was observed on the developing roller after toner installation in an LL environment. Therefore, durable printing in an LL environment was not performed using the toner from Comparative Example 3.

[0095] Based on the above results, the approximate formula for carrier charge is y = b*x a It was confirmed that a magnetic single-component toner is produced that satisfies 0.3≦a≦1 and -7≦b≦-3, and includes both wet silica particles treated with positive charging treatment and a fluorine-containing negative charging surface treatment agent, and positively charged dry silica particles as an external additive applied to the surface of the toner matrix particles, thereby maintaining image density under normal temperature and humidity, high temperature and high humidity, and low temperature and low humidity conditions, while also suppressing image fogging after durable printing and disturbance of the toner layer on the developing roller after toner installation under low temperature and low humidity conditions. [Industrial applicability]

[0096] This invention is applicable to positively charged, single-component magnetic toners used in electrophotographic systems. By utilizing this invention, it is possible to provide a single-component magnetic toner that suppresses image density reduction and image fogging after durable printing, as well as layer distortion of the toner layer after toner installation.

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 positively charged magnetic one-component toner comprising toner particles having the following characteristics: When standard carrier P-01 and the toner are mixed for 10 minutes, if the mass mixing ratio of the toner to the carrier is x and the charge amount of the carrier is y, then the approximate formula for the charge amount of the carrier is y = b * x a However, a positively charged magnetic one-component toner characterized by satisfying the following conditions (1) and (2). 0.3 ≤ a ≤ 1 ... (1) -7 ≤ b ≤ -3 ... (2) however, x=0.2, 0.4, 0.6, 0.8, 1.0 That is the case.

2. The amount of charge of the carrier is measured after mixing 10 g of the standard carrier P-01 and an amount of the toner such that the mass mixing ratio x of the toner is 0.2, 0.4, 0.6, 0.8, or 1.0 in a container with a capacity of 10 cc using the positively charged magnetic one-component toner turbler shaker mixer described in claim 1 for 10 minutes.

3. The positively charged magnetic one-component toner according to claim 1, characterized in that the toner matrix particles contain a release agent containing a long-chain fatty acid having 24 or more carbon atoms.

4. The aforementioned external additive is Dry silica and Wet silica in which the particle surface is treated with positively charged silane and negatively charged silane, A positively charged magnetic one-component toner according to claim 1, characterized by including the following:

5. The positively charged magnetic one-component toner according to claim 4, characterized in that the wet silica particles have their surface treated with aminosilane and fluorine-containing silane.

Images