Toner, toner storage unit, image forming apparatus, and image forming method

Abstract

To provide a toner that has good fluidity, can achieve both heat-resistant storage property and low temperature fixability, and can form high-quality images for a long period.SOLUTION: A toner includes toner base particles including a binder resin, a mold release agent, and a charge control agent, and an external additive. The toner base particles have an average circularity of 0.95 or less. The external additive includes polymethyl silsesquioxane particles subjected to hydrophobic treatment. The polymethyl silsesquioxane particles have an average particle diameter of 0.050 μm or more and 0.150 μm or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a toner, a toner container unit, an image forming apparatus, and an image forming method.

Background Art

[0002] Conventionally, in electrophotographic toners, fine particles having an average primary particle diameter of several nm to several tens of nm are known to be used as external additives in order to obtain fluidity and charging characteristics. In recent years, with the diversification, high speed, and high image quality of the usage purposes of image forming apparatuses, the demand for low-temperature fixing of toners has been increasing.

[0003] When using a toner material specialized for low-temperature fixing, in order to ensure the storage stability of the toner, it has been reported that high coating with external additives or the use of large-particle-size external additive particles is effective. However, since existing large-particle-size external additive particles have a large true specific gravity, it is impossible to avoid the desorption of the external additive from the toner surface due to mechanical stress received in the developing device, and adverse effects have occurred due to the transfer of the external additive to the carrier and the photoreceptor.

[0004] On the other hand, in order to suppress the desorption of large-particle-size external additive particles from the toner surface, a toner having hydrophobic external additive particles obtained by simultaneously subjecting a mixture containing small-particle-size inorganic fine particles and large-particle-size inorganic fine particles to a hydrophobic treatment in the same treatment tank has been proposed. By this, it has been proposed to uniformly disperse the small-particle-size inorganic fine particles and the large-particle-size inorganic fine particles as primary particles on the toner surface and make it difficult to desorb with a small addition amount (for example, see Patent Document 1). In addition, in order to suppress the passing through of spherical silica particles desorbed from the toner surface, a toner using spherical silica particles in combination with non-spherical silica particles has been proposed (for example, see Patent Document 2).

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention aims to provide a toner that has good fluidity, achieves both heat resistance and low-temperature fixation, and can form high-quality images over the long term. [Means for solving the problem]

[0006] The toner of the present invention, as a means for solving the above-mentioned problems, is a toner comprising toner matrix particles containing a binder resin, a release agent, and a charge control agent, and an external additive, wherein the average circularity of the toner matrix particles is 0.95 or less, and the external additive contains hydrophobized polymethylsilsesquioxane particles, and the average particle diameter of the polymethylsilsesquioxane particles is 0.050 μm or more and 0.150 μm or less. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a toner that has good fluidity, achieves both heat resistance and low-temperature fixation, and can form high-quality images over the long term. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram showing an example of a tandem-type image forming apparatus according to the present invention. [Figure 2] Figure 2 is a magnified view of a portion of Figure 1. [Modes for carrying out the invention]

[0009] (toner) The toner of the present invention comprises toner matrix particles containing a binder resin, a release agent, and a charge control agent, an external additive, and further contains other components as needed. The average circularity of the toner matrix particles is 0.95 or less, the external additive contains hydrophobized polymethylsilsesquioxane particles, and the average particle diameter of the polymethylsilsesquioxane particles is 0.050 μm or more and 0.150 μm or less. The aforementioned toner may sometimes be referred to as "electrophotographic toner."

[0010] The toner of the present invention is based on the inventors' discovery of the problems of the prior art, namely, that in the toner of the prior art which contains external additive particles with a particle size of 50 nm or more, although the large particle size of the external additive contributes to improved shelf life, the ease with which the external additive is released due to its shape can hinder the transfer of charge between the toner and the carrier when the external additive adheres to the carrier, making it impossible to increase the amount of external additive added and necessitating the prevention of external additive release. In addition, the inventors have found that the size of the external additive particles can adversely affect fluidity. The present inventors, in order to solve the problems of the prior art described above, conducted diligent research and found that a toner comprising toner matrix particles containing a binder resin, a release agent, and a charge control agent, and an external additive, wherein the average circularity of the toner matrix particles is 0.95 or less, the external additive contains hydrophobized polymethylsilsesquioxane particles, and the average particle diameter of the polymethylsilsesquioxane particles is 0.050 μm or more and 0.150 μm or less, thereby providing a toner that has good fluidity, achieves both heat resistance and low-temperature fixation, and can form high-quality images over the long term, thus completing the present invention.

[0011] <Toner matrix particles> The toner matrix particles (hereinafter sometimes referred to as "toner matrix" or "matrix particles") contain a binder resin, a release agent, and a static charge control agent, and preferably contain a colorant, and further contain other components as needed.

[0012] [Average circularity of toner matrix particles] The average circularity of the toner matrix particles is 0.95 or less, and preferably between 0.890 and 0.945. If the average circularity of the toner matrix particles is 0.95 or less, systems employing blade cleaning or the like can prevent cleaning failures on the photoreceptor and transfer belt, which can cause smudges on the image. For example, in development and transfer with a low image area ratio, there is little residual toner, so cleaning failures are not a problem. However, in the case of color photographs with a high image area ratio, or when untransferred images are formed due to paper feeding problems, toner may be generated as residual toner on the charged surface such as the photoreceptor, and if it accumulates, it can cause smudges on the background of the image. In addition, it can contaminate the charging rollers that contact charge the charged surface such as the photoreceptor, preventing them from performing their original charging ability. If the average circularity of the toner matrix particles is 0.95 or less, these problems can be prevented.

[0013] The average circularity of the toner matrix particles can be measured, for example, using a flow particle image analyzer (FPIA-3000) manufactured by Sysmex Corporation. The specific measurement method involves adding 0.1 mL to 0.5 mL of a surfactant, preferably alkylbenzene sulfonate, as a dispersant to 100 mL to 150 mL of water from which impurities have been removed beforehand, and then adding 0.1 g to 0.5 g of toner matrix particles as the measurement sample. The suspension containing the dispersed toner matrix particles is subjected to dispersion treatment in an ultrasonic disperser for 1 to 3 minutes, and the dispersion concentration is set to 3,000 particles / μL to 10,000 particles / μL. The shape of the toner matrix particles is then measured using the above apparatus, and the circularity is determined.

[0014] <<Binding resin>> The binder resin is not particularly limited and can be appropriately selected from known resins depending on the purpose. Examples include styrene-based resins (monopolymers or copolymers containing styrene or styrene-substituted products) such as styrene, poly-α-stylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylate ester copolymer, styrene-α-methyl chloroacrylate copolymer, and styrene-acrylonitrile-acrylic acid ester copolymer; epoxy resin, vinyl chloride resin, rosin-modified maleic acid resin, phenolic resin, polyethylene resin, polypropylene resin, petroleum resin, polyurethane resin, ketone resin, ethylene-ethyl acrylate copolymer, xylene resin, and polyvinyl butyrate resin. These may be used individually or in combination of two or more. Among these, polyester resin is preferred because it allows for low-temperature fixing while maintaining resistance to high temperature and high humidity storage.

[0015] There are no particular limitations on the method for producing the binder resin, and it can be appropriately selected depending on the purpose. Examples include bulk polymerization, solution polymerization, emulsion polymerization, and suspension polymerization.

[0016] <<<Polyester resin>>> There are no particular restrictions on the polyester resin, and it can be appropriately selected depending on the purpose. Examples include amorphous polyester resin, modified polyester resin, and crystalline polyester resin. These may be used individually or in combination of two or more types. Among these, amorphous polyester resins obtained by reacting polyols with polycarboxylic acids are preferred.

[0017] Examples of the aforementioned polyols include diols and polyols with a valentity of three or higher. Examples of the diol include glycols such as ethylene glycol, diethylene glycol, triethylene glycol, and propylene glycol; etherified bisphenols such as 1,4-bis(hydroxymethyl)cyclohexane and bisphenol A; alkylene (C2-C3) oxide (average addition mole number 1-10) adducts of bisphenol A such as polyoxypropylene(2.2)-2,2-bis(4-hydroxyphenyl)propane and polyoxyethylene(2.2)-2,2-bis(4-hydroxyphenyl)propane; hydrogenated bisphenol A, and alkylene (C2-C3) oxide (average addition mole number 1-10) adducts of hydrogenated bisphenol A, etc. Examples of the alcohol having a valence of 3 or more include glycerin, pentaerythritol, trimethylolpropane, etc. These may be used alone or in combination of two or more.

[0018] Examples of the polycarboxylic acid include dicarboxylic acids and polycarboxylic acids having a valence of 3 or more. Examples of the dicarboxylic acid include alkyl groups having 1-20 carbon atoms such as adipic acid, phthalic acid, isophthalic acid, terephthalic acid, fumaric acid, maleic acid, succinic acid, malonic acid, dodecenyl succinic acid, and octyl succinic acid; succinic acid substituted with an alkenyl group having 2-20 carbon atoms, etc. Examples of the carboxylic acid having a valence of 3 or more include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,5-benzenetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methylenecarboxypropane, 1,2,7,8-octanetetracarboxylic acid, or their acid anhydrides, etc. These may be used alone or in combination of two or more.

[0019] The molecular weight of the polyester resin is not particularly limited and can be appropriately selected according to the purpose, but it is preferably in the following range. The weight-average molecular weight (Mw) of the polyester resin is preferably 10,000 to 100,000, and more preferably 30,000 to 50,000. The peak top molecular weight of the polyester resin is preferably 10,000 to 60,000, and more preferably 10,000 to 16,000. The aforementioned molecular weight can be measured by GPC (gel permeation chromatography).

[0020] The glass transition temperature (Tg) of the polyester resin is preferably 50°C to 75°C, and more preferably 60°C to 72°C. When the Tg is 50°C or higher, the heat resistance of the toner during storage and its durability against stress such as agitation in the developing machine are improved. On the other hand, when the Tg is 75°C or lower, deformation due to heating and pressurization during toner fixing is improved, resulting in improved low-temperature fixing performance.

[0021] There are no particular restrictions on the content of the polyester resin, and it can be appropriately selected depending on the purpose, but it is preferably 50 parts by mass or more and 95 parts by mass or less, and more preferably 60 parts by mass or more and 90 parts by mass or less, per 100 parts by mass of the toner matrix particles. When the content is 50 parts by mass or more, the dispersibility of the colorant and release agent in the toner is obtained, and image blurring and distortion can be suppressed. When it is 95 parts by mass or less, it is advantageous in terms of high image quality and excellent low-temperature fixing properties.

[0022] <<Release agent>> There are no particular restrictions on the mold release agent (wax) and it can be appropriately selected from known types depending on the purpose, such as natural waxes and synthetic waxes. These may be used individually or in combination of two or more types.

[0023] Examples of the aforementioned natural waxes include plant-based waxes such as carnauba wax, cotton wax, and wood wax; animal-based waxes such as beeswax and lanolin; mineral-based waxes such as ozokerite and cerucine; and petroleum waxes such as paraffin, microcrystalline, and petrolatum. Examples of the synthetic waxes include synthetic hydrocarbon waxes such as Fischer-Tropsch wax, polyethylene, and polypropylene; fatty acid amide compounds such as esters, ketones, ethers, 12-hydroxystearic acid amide, stearic acid amide, phthalimide anhydride, and chlorinated hydrocarbons; homopolymers or copolymers of polyacrylates such as poly-n-stearyl methacrylate and poly-n-lauryl methacrylate, which are low molecular weight crystalline polymer resins (for example, copolymers of n-stearyl acrylate and ethyl methacrylate); and crystalline polymers having long alkyl groups in their side chains.

[0024] Among these, carnauba wax, montan wax, and oxidized rice wax are preferred. These can be used individually or in combination of two or more types. The carnauba wax is preferably microcrystalline, has an acid value of 5 or less, and has a particle size of 1 μm or less when dispersed in the fixing resin. The aforementioned montane wax generally refers to montane-based wax refined from minerals, and is preferably microcrystalline with an acid value of 5 to 14. The oxidized rice wax is obtained by air oxidation of rice bran wax, and its acid value is preferably 10 to 30.

[0025] There are no particular restrictions on the content of the release agent, and it can be appropriately selected depending on the purpose, but it is preferably 1 to 20 parts by mass, and more preferably 2 to 10 parts by mass, per 100 parts by mass of toner. If the content is 1 part by mass or more, it is possible to prevent problems such as poor resistance to high temperature offset and poor low temperature fixing during fixing, and if it is 20 parts by mass or less, it is possible to prevent problems such as reduced heat resistance for storage and increased likelihood of image blurring.

[0026] <<Static Control Agent>> The aforementioned charge control agent is not particularly limited and can be appropriately selected depending on the purpose. Examples include nigrosine dyes, metal complex salt dyes (metal azo dyes), and salicylic acid metal complexes. These may be used individually or in combination of two or more. Among these, metal complexes containing a metal with a valency of 3 or higher that can adopt a 6-coordinate configuration are preferred. Examples of such metals include Al, Fe, Cr, and Zr. Among these, metal complexes having non-toxic Fe as the central metal are preferred. Specifically, azo iron dyes represented by the following structural formula (1) are preferred. [ka] In structural formula (1), A + This represents the ammonium ion. The azo iron dye of structural formula (1) may be a commercially available product, and can be obtained as T-77 (manufactured by Hodogaya Chemical Co., Ltd.).

[0027] The content of the charge control agent is preferably 0.5 parts by mass or more and 3.0 parts by mass or less, and more preferably 0.5 parts by mass or more and 2.0 parts by mass or less, per 100 parts by mass of the binder resin. When the content is 0.5 parts by mass or more, it functions as a charge control agent, and when it is 3.0 parts by mass or less, it can suppress toner cracking and chipping, reduce blade sticking and photoreceptor filming, and suppress image quality degradation such as charging failure, supply failure and background staining.

[0028] <<Coloring agent>> There are no particular restrictions on the coloring agents, and they can be appropriately selected depending on the purpose. Examples include carbon black, lamp black, iron black, aniline blue, phthalocyanine blue, phthalocyanine green, Hansa yellow G, rhodamine 6C lake, chalcioyl blue, chrome yellow, quinacridone, benzidine yellow, rose bengal, and triallylmethane-based dyes. These may be used individually or in combination of two or more. The aforementioned colorant can be used as both a black toner and a full-color toner.

[0029] There are no particular restrictions on the content of the coloring agent, and it can be appropriately selected depending on the purpose, but it is preferably 1 to 35 parts by mass, and more preferably 3 to 20 parts by mass, per 100 parts by mass of toner.

[0030] <External additives> The aforementioned external additive comprises hydrophobized polymethylsilsesquioxane particles and, if necessary, other external additives.

[0031] <<Hydrophobic treated polymethylsilsesquioxane particles>> The aforementioned polymethylsilsesquioxane is a polymer of methyltrimethoxysilane. The aforementioned polymethylsilsesquioxane is a silicone resin polymerized by cross-linking methyltrimethoxysilane in a three-dimensional network structure, and is composed of spherical microparticles. Therefore, it is referred to as "polymethylsilsesquioxane particles." The hydrophobized polymethylsilsesquioxane particles can be obtained by hydrophobizing polymethylsilsesquioxane particles.

[0032] The average particle size of the polymethylsilsesquioxane particles is 0.050 μm or more and 0.150 μm or less, and preferably 0.100 μm or more and 0.135 μm or less. If the average particle size is greater than 0.150 μm, the adhesion to the toner surface is weak, causing the particles to roll off the toner surface. The average particle size of the polymethylsilsesquioxane particles can be measured using a known method. Specifically, polymethylsilsesquioxane particles or toner to which the polymethylsilsesquioxane particles have been added are measured using a scanning electron microscope SU8200 series (Hitachi High-Technologies Corporation). The obtained images are processed using image processing software A-Image-kun (Asahi Kasei Engineering Corporation) to recognize the additive particles by binarization, and the circularity, equivalent circle diameter, and particle area are calculated. The equivalent circle diameter is assumed to be the value obtained above, which is the circular area, and is converted to a diameter value. In the case of measuring polymethylsilsesquioxane particles, the measurement is performed on a substrate on which the particles are dispersed, and in the case of measuring toner, the measurement is performed on the toner surface. There is no designated area for observation, but any three or more points in the field of view are checked, the equivalent circle diameter of approximately 100 particles is calculated, and the average value is taken as the average particle diameter.

[0033] [Method for producing polymethylsilsesquioxane particles] The polymethylsilsesquioxane particles can be produced by mixing and condensing a hydrolysis solution containing a hydrolysate of methyltrimethoxysilane and an anionic surfactant with a precipitate solution containing water, a base catalyst, and an anionic surfactant.

[0034] Examples of the anionic surfactants include carboxylic acid-type anionic surfactants such as aliphatic monocarboxylates, polyoxyethylene alkyl ether carboxylates, and fatty acid oils; sulfonic acid-type anionic surfactants such as dialkyl sulfosuccinates, polyoxyethylene alkyl sulfosuccinates, alkanesulfonates, linear alkylbenzene sulfonates, branched alkylbenzene sulfonates, naphthalene sulfonate-formaldehyde condensates, and alkylnaphthalene sulfonates; sulfate ester-type anionic surfactants such as alkyl sulfates, polyoxyalkylene alkyl ether sulfates, and oil sulfates; and phosphate ester-type anionic surfactants such as alkyl phosphates, alkyl phosphate esters, polyoxyethylene alkyl ether phosphates, and polyoxyethylene alkylaryl ether phosphates. Among these, sulfonic acid-type anionic surfactants, sulfate ester-type anionic surfactants, and sulfate ester-type anionic surfactants are preferred.

[0035] The hydrolysis solution preferably further contains an acid catalyst such as an organic acid or an inorganic acid. Examples of the organic acids include formic acid, acetic acid, propionic acid, oxalic acid, and citric acid. Examples of the inorganic acids include hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid.

[0036] By mixing the hydrolysis solution and the precipitate, a condensation reaction of silanol groups proceeds, and polymethylsilsesquioxane particles are produced. Polymethylsilsesquioxane particles can be obtained from the polymethylsilsesquioxane particle dispersion obtained by the above reaction by methods such as membrane separation and centrifugation. Surface treatment with HMDS or the like can also be performed in the solution before separation to impart hydrophobicity.

[0037] The hydrophobized polymethylsilsesquioxane particles can be obtained by hydrophobizing the surface of the polymethylsilsesquioxane particles with a hydrophobizing agent. Examples of the hydrophobic treatment agent include known organosilicon compounds having alkyl groups (e.g., methyl group, ethyl group, propyl group, butyl group, etc.). Specific examples include silazane compounds (e.g., silane compounds such as methyltrimethoxysilane, dimethyldimethoxysilane, trimethylchlorosilane, trimethylmethoxysilane, hexamethyldisilazane, tetramethyldisilazane, etc.). These may be used individually or in combination of two or more. Among these, organosilicon compounds having a trimethyl group, such as trimethylmethoxysilane and hexamethyldisilazane, are preferred. Other methods include silicone oil treatment. Hydrophobic treatment suppresses particle aggregation and improves dispersibility in the toner matrix. It also reduces environmental fluctuations such as high temperature and humidity, and low temperature and humidity, resulting in stable and high image quality.

[0038] The content of the polymethylsilsesquioxane particles is preferably 0.05 parts by mass or more and 3 parts by mass or less per 100 parts by mass of toner. When the content is 3 parts by mass or less, filming can be prevented, and when it is 0.05 parts by mass or more, fluctuations in fluidity and chargeability over a long period can be suppressed, which is advantageous in that high image quality can be obtained.

[0039] <<Other external additives>> The toner of the present invention has at least polymethylsilsesquioxane particles, but can be used in combination with two or more other external additives other than polymethylsilsesquioxane particles.

[0040] Other external additives include, for example, fluidity improvers and hydrophobic treatment agents. Examples of the fluidity improvers include silicon oxide, titanium oxide, silicon carbide, aluminum oxide, and barium titanate. Among these, hydrophobic silica that has undergone hydrophobic treatment is particularly preferred.

[0041] [Toner manufacturing method] The toner can be manufactured by a known manufacturing method comprising: a melt-kneading step of melting and kneading toner material; a grinding step of grinding the obtained melt-kneaded product; a classification step of classifying the ground product obtained by the grinding; and an external addition step of adding an external additive to the obtained toner matrix particles.

[0042] In the melt-mixing step, the toner material is mixed, and the resulting mixture is fed into a melt-mixing machine for melt-mixing. As the melt-mixing machine, for example, a single-screw or twin-screw continuous mixer or a batch-type mixer using a roll mill can be used. For example, the KTK twin-screw extruder manufactured by Kobe Steel, Ltd., the TEM type extruder manufactured by Toshiba Machine Co., Ltd., the twin-screw extruder manufactured by KCK Corporation, the PCM type twin-screw extruder manufactured by Ikegai Co., Ltd., and the Conninder manufactured by Buss Co., Ltd. are preferably used. The melt-kneading process is preferably carried out under appropriate conditions that do not cleave the molecular chains of the binder resin. Specifically, the melt-kneading temperature is preferably set with reference to the softening point of the binder resin. If the temperature is too high, severe cleavage may occur, and if the temperature is too low, dispersion may not proceed properly.

[0043] In the grinding step, the kneaded material obtained in the melt-kneading step is ground. In this grinding step, it is preferable to first coarsely grind the kneaded material, and then finely grind it. Suitable grinding methods include, for example, grinding by impacting the material against an impact plate in a jet stream, grinding by impacting particles against each other in a jet stream, and grinding in a narrow gap between a mechanically rotating rotor and stator.

[0044] In the classification step, the pulverized material obtained in the grinding step is classified and adjusted to particles of a predetermined particle size. Examples of classification methods include removing fine particles using a cyclone, decanter, centrifuge, etc. After the grinding and classification steps are completed, the pulverized material can be separated into an airflow using centrifugal force or the like to produce toner matrix particles of a predetermined particle size.

[0045] In the external additive step, the external additive is added to the toner matrix particles obtained in the classification step. The toner matrix particles and the external additive are mixed and stirred using a mixer, causing the external additive to break down and coat the surface of the toner matrix particles.

[0046] (Developer) The developer of the present invention comprises at least the toner, and further comprises other components as appropriate, such as a carrier, if necessary. When using the toner of the present invention as a developer, it may be used as a one-component developer consisting only of toner, or as a two-component developer mixed with a carrier, and is not particularly limited. However, when used in high-speed printers and the like to accommodate the recent increase in information processing speed, a two-component developer is preferred from the viewpoint of improving lifespan and other factors.

[0047] When the developer is a two-component developer comprising the toner of the present invention and a carrier, the carrier may be a magnetic carrier or a non-magnetic carrier, depending on the two-component development method. Examples of the magnetic carriers include magnetite, spinel ferrites such as gamma iron oxide, spinel ferrites containing one or more metals other than iron (such as Mn, Ni, Zn, Mg, Cu, etc.), magnetoplanvite-type ferrites such as barium ferrite, and particles of iron or alloys having an oxide layer on their surface. The shape of the magnetic carrier may be granular, spherical, or needle-shaped. Among these, when high magnetization is required, it is preferable to use ferromagnetic fine particles such as iron, and in terms of chemical stability, magnetite, magnetoplanbite-type ferrites such as spinel ferrite containing magnetite or gamma iron oxide, or barium ferrite are preferred. Suitable examples of the aforementioned magnetoplanbite-type ferrites include MFL-35S, MFL-35HS (manufactured by Powdertec Co., Ltd.); DFC-400M, DFC-410M, and SM-350NV (manufactured by DOWA IP Creation Co., Ltd.).

[0048] As the magnetic carrier, a resin carrier containing magnetic fine particles such as ferromagnetic fine particles, which has a desired magnetization when their type and content are selected, can also be used. The magnetic properties of the resin carrier are preferably such that the magnetization strength at 1,000 Ørsted is 30 emu / g to 150 emu / g.

[0049] Examples of methods for producing the resin carrier include: a method of producing it by spraying a molten mixture of magnetic fine particles and an insulating binder resin using a spray dryer; a method of producing a resin carrier in which magnetic fine particles are dispersed in a condensation-type binder resin by reacting and curing a monomer or prepolymer in an aqueous medium in the presence of magnetic fine particles; and a method of producing a resin carrier by fixing positively or negatively charged fine particles or conductive fine particles to the surface of the magnetic carrier, coating the surface of the magnetic carrier with a resin, or coating the surface of the magnetic carrier with a resin containing positively or negatively charged fine particles or conductive fine particles. The chargeability can be controlled as appropriate by these methods. Examples of the resins used for the coating include silicone resins, acrylic resins, epoxy resins, and fluororesins. Among these, silicone resins and acrylic resins are preferred.

[0050] The carrier content in the two-component developer is preferably 85% by mass or more and less than 98% by mass. If the content is 85% by mass or more, it is possible to suppress the occurrence of defective images due to toner scattering from the developing device. If the content is less than 98% by mass, it is possible to suppress an excessive increase in the charge amount of the electrophotographic toner and an insufficient supply of electrophotographic toner, thereby effectively preventing a decrease in image density and the occurrence of defective images.

[0051] (Toner storage unit) In the present invention, the toner storage unit refers to a unit having the function of storing toner, in which the toner of the present invention described above is stored. Examples of the toner storage unit include a toner storage container, a developer, and a process cartridge. The toner container mentioned above refers to a container that contains the toner. The aforementioned developing unit refers to a unit having means for storing and developing the toner. The process cartridge refers to a cartridge that integrates at least an image carrier and a developing means, contains the toner, and is detachable from the image forming apparatus. The process cartridge may further include at least one selected from a charging means, an exposure means, and a cleaning means. The toner storage unit of the present invention stores the toner of the present invention. By mounting the toner storage unit of the present invention in an image forming apparatus and performing image formation, image formation is performed using the toner of the present invention, resulting in excellent low-temperature fixability and heat-resistant storage, and obtaining a superior image.

[0052] (Image forming apparatus and image forming method) The image forming apparatus of the present invention comprises at least an electrostatic latent image carrier, an electrostatic latent image forming means, a developing means, a transfer means, and a fixing means, and further comprises other means as appropriate, such as a static elimination means, a cleaning means, a recycling means, a control means, etc. The image forming method of the present invention includes at least an electrostatic latent image formation step, a development step, a transfer step, and a fixing step, and further includes other steps as appropriate, such as an electrostatic discharge step, a cleaning step, a recycling step, a control step, etc.

[0053] The image forming method of the present invention can be suitably carried out by the image forming apparatus of the present invention, the electrostatic latent image formation step can be carried out by the electrostatic latent image forming means, the development step can be carried out by the development means, the transfer step can be carried out by the transfer means, the fixing step can be carried out by the fixing means, and the other steps can be carried out by the other means.

[0054] <Electrostatic latent image formation process and electrostatic latent image formation means> The electrostatic latent image formation step is a step of forming an electrostatic latent image on an electrostatic latent image carrier. The electrostatic latent image forming means is a means for forming an electrostatic latent image on an electrostatic latent image carrier. The electrostatic latent image carrier (sometimes referred to as a "photoconductive insulator," "electrophotographic photoreceptor," or "photoreceptor") is not particularly limited in terms of its material, shape, structure, size, etc., and can be appropriately selected from known materials. However, a drum shape is preferred, and examples of materials include inorganic photoreceptors such as amorphous silicon and selenium, and organic photoreceptors such as polysilane and phthalopolymethine. Among these, amorphous silicon and the like are preferred in terms of long lifespan.

[0055] The formation of the electrostatic latent image can be carried out, for example, by uniformly charging the surface of the electrostatic latent image carrier and then exposing it to image-like light, and can be performed by the electrostatic latent image forming means. The electrostatic latent image forming means includes, for example, a charger that uniformly charges the surface of the electrostatic latent image carrier, and an exposure unit that exposes the surface of the electrostatic latent image carrier to an image-like state.

[0056] The charging can be performed, for example, by applying a voltage to the surface of the electrostatic latent image carrier using the charger. There are no particular limitations on the aforementioned charger, and it can be appropriately selected according to the purpose. Examples include contact chargers that are known in themselves and equipped with conductive or semiconductive rollers, brushes, films, rubber blades, etc., and non-contact chargers that utilize corona discharge such as Corotron and Scorotron.

[0057] Preferably, the charger is positioned in contact with or without contact with the electrostatic latent image carrier, and charges the surface of the electrostatic latent image carrier by superimposing a DC voltage and an AC voltage. Alternatively, the charger is a charging roller positioned in close proximity to the photoreceptor via a gap tape, and charges the surface of the photoreceptor by superimposing a DC voltage and an AC voltage on the charging roller.

[0058] The exposure can be performed, for example, by exposing the surface of the electrostatic latent image carrier in an image-like manner using the exposure device. The aforementioned exposure device is not particularly limited as long as it can expose the surface of a photoreceptor charged by a charger in an image-like manner, and can be appropriately selected according to the purpose. Examples include copying optical systems, rod lens array systems, laser optical systems, and liquid crystal shutter optical systems. A back-facing method in which the back side of the photoreceptor is exposed in an image-like manner may also be employed.

[0059] <Developing process and developing means> The development step is a step of developing the electrostatic latent image using the toner or developer of the present invention to form a visible image. The developing means is a means for developing the electrostatic latent image using the toner or developer of the present invention to form a visible image. The formation of the visible image can be performed, for example, by developing the electrostatic latent image using the toner or developer of the present invention, and can be carried out by the developing means. The developing means is not particularly limited as long as it can develop using the toner to developer of the present invention, and can be appropriately selected from known ones. For example, a preferred developing means is one that has at least a developing unit that contains the toner to developer of the present invention and can apply the toner to the electrostatic latent image by contact or non-contact, and a developing unit that is detachably equipped with the toner container of the present invention is more preferred.

[0060] The developer may be of the dry developing type or the wet developing type, and may be a single-color developer or a multi-color developer. For example, a suitable example is one having an agitator that frictionally agitates and charges the toner or developer, and a rotatable magnetic roller.

[0061] In the developing unit, for example, the toner and the carrier are mixed and stirred, and the friction during this process causes the toner to become charged and is held in a pile-like state on the surface of a rotating magnetic roller, forming a magnetic brush. Since the magnetic roller is positioned near the electrostatic latent image carrier, a portion of the toner constituting the magnetic brush formed on the surface of the magnetic roller moves to the surface of the electrostatic latent image carrier by electrical attraction. As a result, the electrostatic latent image is developed by the toner and a visible image is formed on the surface of the electrostatic latent image carrier. It is preferable to apply an alternating electric field when moving the toner to the surface of the electrostatic latent image carrier.

[0062] <Transfer process and transfer means> The transfer step is a step of transferring the visible image onto a recording medium. The transfer means is a means for transferring the visible image onto a recording medium. The transfer step is preferably carried out using an intermediate transfer body, first transferring a visible image onto the intermediate transfer body, and then second transferring the visible image onto the recording medium. More preferably, the toner is two or more colors, preferably full-color toner, and the transfer step includes a first transfer step of transferring a visible image onto the intermediate transfer body to form a composite transfer image, and a second transfer step of transferring the composite transfer image onto the recording medium. The transfer of the visible image can be performed, for example, by charging the electrostatic latent image carrier using a transfer charger, and can be carried out by the transfer means. The transfer means preferably comprises a first transfer means for transferring the visible image onto an intermediate transfer body to form a composite transfer image, and a second transfer means for transferring the composite transfer image onto a recording medium. The transfer means (primary transfer means, secondary transfer means) preferably includes at least a transfer device that exfoliates and charges the visible image formed on the electrostatic latent image carrier toward the transfer target. There may be one transfer means or two or more. Examples of transfer devices include corona discharge transfer devices, transfer belts, transfer rollers, pressure transfer rollers, and adhesive transfer devices. There are no particular restrictions on the intermediate transfer body, and it can be appropriately selected from known transfer bodies depending on the purpose. For example, a transfer belt is a suitable example. The material to be transferred is not particularly limited and can be appropriately selected from known recording media (recording paper).

[0063] <Fixing process and fixing means> The fixing process is a process of fixing the visible image transferred to the recording medium. The fixing means is a means for fixing the visible image transferred to the recording medium. The fixing process may be performed each time a toner of each color is transferred to the recording medium, or it may be performed simultaneously on all the toners of each color in a stacked state. The fixing means is not particularly limited and can be appropriately selected according to the purpose, but known heating and pressing means are preferred. Examples of the fixing means include a combination of a heating roller and a pressing roller; a combination of a heating roller, a pressing roller and an endless belt; and a means having a heating element equipped with a heating element, a film in contact with the heating element, and a pressing member that presses against the heating element via the film, wherein a transfer object on which an unfixed image has been formed is passed between the film and the pressing member to heat, press, and fix the image. The heating in the fixing means is usually preferably 80°C to 200°C. In addition, in the present invention, depending on the purpose, a known optical fuser may be used together with or instead of the fixing step and fixing means.

[0064] <Other processes and other means> The static discharge step is a step of discharging static electricity by applying a static discharge bias to the electrostatic latent image carrier, and can be suitably carried out by static discharge means. There are no particular limitations on the static elimination means; it is sufficient that a static elimination bias can be applied to the electrostatic latent image carrier, and it can be appropriately selected from known static eliminators, for example, a static elimination lamp is a suitable example.

[0065] The cleaning step is a step of removing the electrophotographic toner remaining on the electrostatic latent image carrier, and can be suitably carried out by a cleaning means. The cleaning means is not particularly limited and only needs to be able to remove the electrophotographic toner remaining on the electrostatic latent image carrier. It can be appropriately selected from known cleaners, and suitable examples include magnetic brush cleaners, electrostatic brush cleaners, magnetic roller cleaners, blade cleaners, brush cleaners, web cleaners, etc.

[0066] The recycling step is a step of recycling the electrophotographic toner removed by the cleaning step to the developing means, and can be suitably carried out by the recycling means. There are no particular restrictions on the recycling means, and examples include well-known transport methods.

[0067] The control step is a step that controls each of the above steps, and can be suitably carried out by control means. The control means are not particularly limited as long as they can control the movement of each of the means, and can be appropriately selected according to the purpose. Examples include devices such as sequencers and computers.

[0068] Next, with reference to Figure 1, other embodiments of the image forming method of the present invention will be described. The image forming apparatus shown in Figure 1 is a tandem-type color image forming apparatus. This image forming apparatus comprises a copy unit body 150, a paper feed table 200, a scanner 300, and an automatic document feeder (ADF) 400. The main body 150 of the copying device has an endless belt-shaped intermediate transfer body 50 in its center. The intermediate transfer body 50 is stretched over support rollers 14, 15, and 16 and is rotatable clockwise in Figure 2. Near the support roller 15, an intermediate transfer body cleaning device 17 is located for removing residual toner from the intermediate transfer body 50. On the intermediate transfer body 50 stretched over the support rollers 14 and 15, an image forming means 120 is arranged, with four image forming means 18 for yellow, cyan, magenta, and black facing each other along the transport direction. Near the image forming means 120, an exposure device 21 is located. On the side of the intermediate transfer body 50 opposite to the side where the image forming means 120 is located, a secondary transfer device 22 is located. In the secondary transfer device 22, an endless belt, the secondary transfer belt 24, is stretched over a pair of rollers 23, and the transfer paper and the intermediate transfer body 50 transported on the secondary transfer belt 24 can come into contact with each other. A fixing device 25 is located near the secondary transfer device 22. The fixing device 25 comprises a fixing belt 26, which is an endless belt, and a pressure roller 27 that is positioned under pressure from the fixing belt. In the tandem image forming apparatus, a sheet reversing device 28 is located near the secondary transfer device 22 and the fixing device 25 to reverse the transfer paper in order to form an image on both sides of the transfer paper.

[0069] Next, the formation of a full-color image (color copy) using the image forming means 120 will be described. Specifically, first, the original document is placed on the document tray 130 of the automatic document feeder (ADF) 400, or the automatic document feeder 400 is opened and the original document is placed on the contact glass 32 of the scanner 300, and then the automatic document feeder 400 is closed.

[0070] When the start switch (not shown) is pressed, if a document is placed in the automatic document transporter 400, the document is transported and moved onto the contact glass 32. If a document is placed on the contact glass 32, the scanner 300 is driven immediately, and the first travel body 33 and the second travel body 34 move. At this time, the first travel body 33 irradiates light from the light source, and the mirror on the second travel body 34 reflects the reflected light from the document surface. This light is received by the reading sensor 36 through the imaging lens 35, and the color document (color image) is read and converted into image information in black, yellow, magenta, and cyan. Next, each image information is transmitted to each image forming unit 18 in the image forming means 120, and visible images of black, yellow, magenta, and cyan are formed.

[0071] The image information for black, yellow, magenta, and cyan is then transmitted to each image forming means 18 (black image forming means, yellow image forming means, magenta image forming means, and cyan image forming means) in the tandem image forming means 120, and the black, yellow, magenta, and cyan toner images are formed in each image forming means. Specifically, each of the image forming means 18 for each color in the image forming means 120 (image forming means for black, image forming means for yellow, image forming means for magenta, and image forming means for cyan), as shown in Figure 2, comprises an electrostatic latent image carrier 10, a charging device 160 for uniformly charging the electrostatic latent image carrier 10, an exposure device for exposing the electrostatic latent image carrier to each color image corresponding to an image (L in Figure 2) based on each color image information and forming an electrostatic latent image on the electrostatic latent image carrier, a developing device 61 for developing the electrostatic latent image using each color toner (black toner, yellow toner, magenta toner, and cyan toner) to form a toner image using each color toner, a transfer charger 62 for transferring the toner image onto an intermediate transfer body 50, a cleaning device 63, and a static eliminator 64, and is capable of forming each single-color image (black image, yellow image, magenta image, and cyan image) based on the image information of each color. The black image, yellow image, magenta image, and cyan image thus formed are sequentially transferred (primary transfer) onto an intermediate transfer body 50 that is rotated by support rollers 14, 15, and 16. The black image formed on the black electrostatic latent image carrier 10K, the yellow image formed on the yellow electrostatic latent image carrier 10Y, the magenta image formed on the magenta electrostatic latent image carrier 10M, and the cyan image formed on the cyan electrostatic latent image carrier 10C are then superimposed on the intermediate transfer body 50 to form a composite color image (color transfer image).

[0072] Meanwhile, in the paper feed table 200, one of the paper feed rollers 142 is selectively rotated to feed a sheet (recording paper) from one of the multi-stage paper feed cassettes 144 in the paper bank 143, separate it one sheet at a time with the separation roller 145 and send it to the paper feed path 146, transport it with the transport roller 147 and guide it to the paper feed path 148 in the copier body 150, where it is stopped by the registration roller 49. Alternatively, the paper feed roller 142 is rotated to feed a sheet (recording paper) from the manual feed tray 54, separate it one sheet at a time with the separation roller 145 and put it into the manual feed path 53, where it is stopped by the registration roller 49. The registration roller 49 is generally used in a grounded state, but it may also be used with a bias applied to remove paper dust from the sheet. Then, the register roller 49 is rotated in time with the composite color image (color transfer image) synthesized on the intermediate transfer body 50, and a sheet (recording paper) is fed between the intermediate transfer body 50 and the secondary transfer device 22. The secondary transfer device 22 then transfers the composite color image (color transfer image) onto the sheet (recording paper) (secondary transfer), thereby transferring and forming a color image on the sheet (recording paper). After image transfer, any residual toner on the intermediate transfer body 50 is cleaned by the intermediate transfer body cleaning device 17.

[0073] The sheet (recording paper) on which the color image has been transferred and formed is transported by the secondary transfer device 22 and sent to the fixing device 25, where the composite color image (color transfer image) is fixed onto the sheet (recording paper) by heat and pressure. After that, the sheet (recording paper) is switched by the switching claw 55 and discharged by the discharge roller 56 and stacked on the paper output tray 57, or it is switched by the switching claw 55 and inverted by the sheet inversion device 28 and guided back to the transfer position, where an image is recorded on the back side as well, before being discharged by the discharge roller 56 and stacked on the paper output tray 57.

[0074] According to the image forming apparatus and image forming method of the present invention, since the toner of the present invention, which has excellent fluidity, heat resistance, low-temperature fixability, and print durability is used, high-quality images can be provided over the long term. [Examples]

[0075] The present invention will be described more specifically below based on examples, but the present invention is not limited to the following examples. Unless otherwise specified, the term "parts" refers to parts by mass.

[0076] <Example of Polyester Resin 1 Production> The acid and alcohol components shown in Table 1 were placed in a 1 L four-necked round-bottom flask equipped with a thermometer, stirrer, condenser, and nitrogen gas inlet tube. This flask was then placed on a mantle heater, and nitrogen gas was introduced through the nitrogen gas inlet tube to maintain an inert atmosphere inside the flask while the temperature was raised. Subsequently, 0.05 g of dibutyltin oxide was added, and the reaction was carried out while maintaining the temperature at 200°C to obtain polyester resin 1.

[0077] Table 1 shows the various physical properties of polyester resin 1. In the table, the polycarboxylic acid component and polyol component are expressed in "parts by mass," "Mw" represents the weight-average molecular weight, and the value of "peak top molecular weight" represents the molecular weight of the main peak.

[0078] <Example of Polyester Resin 2 Production> Polyester resin 2 was obtained in the same manner as in the example of polyester resin 1, except that the types and mass parts of the polycarboxylic acid and polyol components were changed as shown in Table 1. The various physical properties of polyester resin 2 are also shown in Table 1.

[0079] [Table 1]

[0080] (Example 1) <Manufacturing of Toner Base A> The mixture of the following composition was stirred and mixed in a Henschel mixer (FM20B, manufactured by Mitsui Miike Chemical Machinery Co., Ltd.) at a rotation speed of 3,000 rpm for 5 minutes, and then melt-kneaded in a twin-screw extruder (TEM-18SS, manufactured by Toshiba Machine Co., Ltd.) at a rotation speed of 600 rpm and a barrel temperature of 100°C to 160°C. The resulting kneaded material was rolled to an average thickness of 1.7 mm using rollers, cooled to room temperature, and then crushed and classified using a jet mill (IDS-2, manufactured by Nippon Pneumatic Industries Co., Ltd.) and a rotor classifier (100TTSP, manufactured by Hosokawa Micron Corporation) to obtain toner matrix A with a volume average particle size of 7.5 μm and an average roundness of 0.935.

[0081] -composition- • Polyester resin 150 parts • Polyester resin 250 units Carnauba wax (WA05TS, manufactured by Toa Chemical Co., Ltd.) 3 parts • Carbon black (MOGUL L, manufactured by Cabot) 10 units ·Metal azo dye (T-77, manufactured by Hodogaya Chemical Industry Co., Ltd.) 1.8 parts

[0082] <Measurement of the average circularity of the toner base material> The average circularity of the toner matrix was measured as follows: Specifically, 0.1 mL of alkylbenzene sulfonate was added as a dispersant to 100 mL of water from which impurities had been removed beforehand, and then 0.08 g of toner matrix particles as the measurement sample was added. The suspension containing the dispersed toner matrix particles was subjected to two 1-minute dispersion treatments using an ultrasonic disperser, and the dispersion concentration was adjusted from 3,000 particles / μL to 10,000 particles / μL. The shape of the toner matrix particles was measured using the above apparatus, and the circularity was determined.

[0083] <Toner Manufacturing> To 100 parts of toner matrix A, 1 part of hexamethyldisilazane-treated (HMDS-treated) hydrophobic silica (H2000, manufactured by Wacker Corporation) with an average particle size of 12 nm and 0.5 parts of hydrophobized polymethylsilsesquioxane particles (Sunseal MP-01, manufactured by Tokuyama Corporation) with an average particle size of 0.050 μm were added, and the mixture was stirred and mixed in a Henschel mixer to obtain toner 1 of Example 1.

[0084] <Manufacturing of Carrier 1> A mixture with the following composition was dispersed in a homomixer for 10 minutes to prepare a resin solution for forming the resin layer. -composition- • 2,100 units of silicone resin solution • Toluene 6,100 copies • Aminosilane 30 parts • Carbon Black 30 copies

[0085] Using ferrite particles (DFC-400M, manufactured by DOWA IP Creation Co., Ltd.) with a weight-average particle size of 35 μm as the carrier core material, the above resin liquid was applied to the surface of the core material to a thickness of 0.50 μm using a fluidized bed coating apparatus under a 60°C atmosphere, and then dried. The obtained carrier was calcined in an electric furnace at 180°C for 2 hours, and after cooling, it was crushed using a sieve with a mesh size of 100 μm to obtain carrier 1.

[0086] <Preparation of two-component developer> The toner 1 and carrier 1 obtained above were uniformly mixed and charged at 48 rpm for 5 minutes using a turbler mixer (manufactured by Willy e Bakkofen (WAB)) to prepare developer 1 of Example 1 as a two-component developer. The toner and carrier mixing ratio was adjusted to match the toner concentration of the initial developer in the evaluation machine, which was 4% by mass.

[0087] (Example 2) In Example 1, the hydrophobized polymethylsilsesquioxane particles with an average particle size of 0.050 μm were replaced with 1.0 part of polymethylsilsesquioxane particles with an average particle size of 0.085 μm (Sunseal MP-01, manufactured by Tokuyama Corporation). Except for this change, the toner 2 and developer 2 of Example 2 were obtained in the same manner as in Example 1.

[0088] (Example 3) In Example 1, the hydrophobized polymethylsilsesquioxane particles with an average particle size of 0.050 μm were replaced by 1.5 parts of polymethylsilsesquioxane particles with an average particle size of 0.120 μm (Sunseal MP-01, manufactured by Tokuyama Corporation). Except for this change, the toner 3 and developer 3 of Example 3 were obtained in the same manner as in Example 1.

[0089] (Example 4) In Example 1, the hydrophobized polymethylsilsesquioxane particles with an average particle size of 0.050 μm were replaced with 1.5 parts of polymethylsilsesquioxane particles with an average particle size of 0.150 μm (Sunseal MP-01, manufactured by Tokuyama Corporation). Except for this change, the toner 4 and developer 4 of Example 4 were obtained in the same manner as in Example 1.

[0090] (Example 5) In Example 5, toner 5 and developer 5 were obtained in the same manner as in Example 3, except that one part of a silicon oil-treated hydrophobic silica (NY50, manufactured by Nippon Aerosil Co., Ltd.) with an average particle size of 25 nm was further added.

[0091] (Example 6) In Example 6, the toner 6 and developer 6 were obtained in the same manner as in Example 3, except that the amount of polymethylsilsesquioxane particles was changed from 1.5 parts to 4.0 parts.

[0092] (Example 7) In Example 3, the toner 7 and developer 7 of Example 7 were obtained in the same manner as in Example 3, except that toner base A was replaced with toner base B manufactured as follows.

[0093] <Manufacturing of Toner Base B> Toner base B was obtained in the same manner as toner base A, except that carnauba wax was replaced with rice wax (TOWAX-3F16, manufactured by Toa Chemical Co., Ltd.), resulting in an average circularity of 0.920.

[0094] (Comparative Example 1) In Comparative Example 1, toner 8 and developer 8 were obtained in the same manner as in Example 1, except that hydrophobized polymethylsilsesquioxane particles were not added.

[0095] (Comparative Example 2) In Example 5, the toner 9 and developer 9 of Comparative Example 2 were obtained in the same manner as in Example 5, except that hydrophobized polymethylsilsesquioxane particles were not added.

[0096] (Comparative Example 3) The toner 10 and developer 10 of Comparative Example 3 were obtained in the same manner as in Comparative Example 1, except that a portion of HMDS-treated hydrophobic silica with an average particle size of 120 nm was further added.

[0097] (Comparative Example 4) In Comparative Example 4, toner 11 and developer 11 were obtained in the same manner as in Example 1, except that the hydrophobized polymethylsilsesquioxane particles with an average particle size of 0.050 μm were replaced with 1.5 parts of polymethylsilsesquioxane particles with an average particle size of 0.030 μm (Sunseal MP-01, manufactured by Tokuyama Corporation).

[0098] (Comparative Example 5) In Comparative Example 5, toner 12 and developer 12 were obtained in the same manner as in Example 1, except that hydrophobized polymethylsilsesquioxane particles with an average particle size of 0.050 μm were replaced with 1.5 parts of polymethylsilsesquioxane particles with an average particle size of 0.20 μm (Sunseal MP-01, manufactured by Tokuyama Corporation).

[0099] (Comparative Example 6) In Example 3, the toner 13 and developer 13 of Comparative Example 6 were obtained in the same manner as in Example 3, except that toner base A was replaced with toner base C manufactured as follows.

[0100] <Manufacturing of Toner Base C> Toner base C was obtained in the same manner as toner base A, except that the jet mill was changed to a turbo mill (T250, Matsubo Co., Ltd.), resulting in an average circularity of 0.955.

[0101] (Comparative Example 7) In Comparative Example 7, toner 14 and developer 14 were obtained in the same manner as in Example 3, except that the hydrophobized polymethylsilsesquioxane particles were replaced with unhydrophobized polymethylsilsesquioxane particles (average particle size 0.120 μm).

[0102] (evaluation) The toners and developers obtained in Examples 1-7 and Comparative Examples 1-7 were evaluated as follows. The evaluation results are shown in Table 2.

[0103] <Measurement of average particle size of polymethylsilsesquioxane particles> The average particle size of polymethylsilsesquioxane particles was measured using the following procedure. Specifically, the toner was measured using a scanning electron microscope SU8200 series (Hitachi High-Technologies Corporation). The obtained images were processed using image processing software A-Image-kun (Asahi Kasei Engineering Corporation) to recognize the external additive particles through binarization, and the circularity was calculated. Three arbitrary points in the field of view on the toner surface were examined, and the equivalent circular diameter of approximately 100 particles was calculated. The average value of these values ​​was then determined as the average particle diameter.

[0104] <Toner fluidity> Fluidity was determined by the degree of toner aggregation. Toner cohesion is an indicator of the adhesive strength between toners; a higher value indicates greater adhesion between toners and poorer development performance. To measure toner cohesion, a powder tester (manufactured by Hosokawa Micron Corporation) was used. Sieves with mesh sizes of 75 μm, 45 μm, and 22 μm were arranged in that order from top to bottom. 2 g of toner was placed in the 75 μm sieve, and the sieve was vibrated at an amplitude of 1 mm for 30 seconds. After vibration, the toner mass on each sieve was measured, multiplied by "0.5", "0.3", and "0.1", respectively, and the values ​​were added together to calculate a percentage. The results were then evaluated according to the following criteria. [Evaluation Criteria] ○: Toner coagulation degree is 15% or less △: Toner aggregation level is between 15% and 20%. ×: Toner coagulation rate exceeds 20%

[0105] <Heat-resistant storage stability> Heat resistance was measured using a penetration tester (manufactured by Nikko Engineering Co., Ltd.). Specifically, 10g of each toner was weighed and placed in a 30ml glass container (screw vial) at a temperature of 20°C to 25°C and 40-60% RH, and the lid was closed. After tapping the glass container with the toner 100 times, it was left in a constant temperature bath set to 50°C for 24 hours. Then, the penetration depth was measured using a penetration depth tester, and the heat resistance storage was evaluated according to the evaluation criteria below. A higher penetration depth value indicates better heat resistance storage. [Evaluation Criteria] ◎: Needle penetration depth of 30mm or more ○: Needle penetration depth of 25mm or more and less than 30mm △: Needle penetration depth is 20mm or more but less than 25mm ×: Needle penetration less than 20mm

[0106] <Low temperature retention> A modified fuser unit from a Ricoh MF2200 copier (manufactured by Ricoh Co., Ltd.) using a Teflon® roller as the fuser roller was used. Type 6200 paper (also manufactured by Ricoh Co., Ltd.) was loaded into this unit, and copying tests were performed using various developers. The cold offset temperature (lower limit of the fixing temperature) was determined by varying the fixing temperature. The evaluation conditions for low-temperature fixing were a paper feed linear speed of 120 mm / sec to 150 mm / sec and a surface pressure of 1.2 kgf / cm². 2 The nip width was set to 3mm. [Evaluation Criteria] ○: The minimum fixing temperature is 140°C or higher and less than 150°C. △: The minimum fixing temperature is 150°C or higher but less than 160°C. ×: The minimum fixing temperature is 160°C or higher.

[0107] <Image Quality> Image quality was determined by comprehensively assessing the deterioration of image quality after paper feeding (specifically, the occurrence of transfer failures and photoreceptor cleaning failures). Transfer defects were evaluated by visually ranking the level of transfer defects in each image using a commercially available image forming machine (manufactured by Ricoh Co., Ltd.). The output images were A4 landscape format with 1,000 vertical stripe images (2 cm wide), followed by a solid black image.

[0108] Furthermore, to assess poor photoreceptor cleaning, 1,000 images of vertical bands 2 cm wide on A4 landscape paper were fed through the machine. Then, during the development of a solid black band image, the process was stopped, and the toner on the photoreceptor after cleaning by the cleaning unit was transferred to Scotch tape and attached to a blank sheet of paper. The toner was then measured using a spectrophotometer (X-Rite938). On the other hand, only the Scotch tape was attached to the same blank sheet of paper and measured using a spectrophotometer. The combined image density (ID) of the toner, tape, and blank paper was subtracted from the combined image density (ID) of the Scotch tape and blank paper to obtain the difference value, and the poorness of the photoreceptor cleaning was evaluated. A smaller difference value indicates better cleaning performance. Image quality was evaluated based on the following criteria.

[0109] [Evaluation Criteria] ○: No abnormal images found △: Minor image density reduction due to transfer defects or minor image smudges due to cleaning defects are observed, but this is within the range of practical use. ×: Image density reduction or loss due to poor transfer, and image staining due to poor cleaning are observed.

[0110] [Table 2]

[0111] [Table 3]

[0112] [Table 4]

[0113] From the above, it has become clear that the toner of the present invention, by adding hydrophobized polymethylsilsesquioxane particles, provides high fluidity, suppresses charge changes due to environmental differences, and enables the formation of high-quality images over the long term.

[0114] Examples of the present invention are as follows: <1> A toner comprising toner matrix particles containing a binder resin, a release agent, and a charge control agent, and an external additive, The average circularity of the toner matrix particles is 0.95 or less. The aforementioned external additive contains hydrophobized polymethylsilsesquioxane particles, The toner is characterized in that the average particle size of the polymethylsilsesquioxane particles is 0.050 μm or more and 0.150 μm or less. <2> The content of the hydrophobized polymethylsilsesquioxane particles is 0.05 parts by mass or more and 3 parts by mass or less per 100 parts by mass of toner. <1> This is the toner described in [the document]. <3> The aforementioned <1> from <2> This toner storage unit is characterized by containing toner as described in any of the above. <4> Electrostatic latent image carrier, An electrostatic latent image forming means for forming an electrostatic latent image on the electrostatic latent image carrier, The electrostatic latent image formed on the electrostatic latent image carrier, <1> from <2> A developing means that develops using toner described in any of the above to form a visible image, A transfer means for transferring the visible image onto a transfer material, The image forming apparatus is characterized by having at least a fixing means for fixing a visible image transferred onto the transfer material. <5> An electrostatic latent image formation step in which an electrostatic latent image is formed on an electrostatic latent image carrier, The electrostatic latent image formed on the electrostatic latent image carrier, <1> from <2> A developing step in which a visible image is formed by developing using a toner described in any of the following, A transfer step of transferring the visible image onto a transfer material, The image forming method is characterized by comprising at least a fixing step of fixing the visible image transferred onto the transfer material.

[0115] The aforementioned <1> from <2> Toner as described in any of the above <3> The toner storage unit described above, <4> The image forming apparatus described above, and the <5> The image forming method described above can solve the aforementioned problems of the conventional method and achieve the objectives of the present invention. [Prior art documents] [Patent Documents]

[0116] [Patent Document 1] Japanese Patent Publication No. 2005-060214 [Patent Document 2] Japanese Patent Publication No. 2014-077930

Claims

1. A toner comprising toner matrix particles containing a binder resin, a release agent, and a charge control agent, and an external additive, The aforementioned binder resin contains polyester resin, The average circularity of the toner matrix particles is 0.890 or more and 0.945 or less. The aforementioned external additive comprises hydrophobized polymethylsilsesquioxane particles and hydrophobic silica. A toner characterized in that the average particle size of the polymethylsilsesquioxane particles is 0.050 μm or more and 0.150 μm or less.

2. The toner according to claim 1, wherein the content of the hydrophobized polymethylsilsesquioxane particles is 0.05 parts by mass or more and 3 parts by mass or less per 100 parts by mass of toner.

3. A toner storage unit characterized by containing the toner described in any one of claims 1 to 2.

4. Electrostatic latent image carrier, An electrostatic latent image forming means for forming an electrostatic latent image on the electrostatic latent image carrier, A developing means for developing the electrostatic latent image formed on the electrostatic latent image carrier using the toner described in any one of claims 1 to 2 to form a visible image, A transfer means for transferring the visible image onto a transfer material, An image forming apparatus characterized by comprising at least a fixing means for fixing the visible image transferred onto the transfer material.

5. An electrostatic latent image formation step in which an electrostatic latent image is formed on an electrostatic latent image carrier, A developing step to develop the electrostatic latent image formed on the electrostatic latent image carrier using the toner described in any one of claims 1 to 2 to form a visible image, A transfer step of transferring the visible image onto a transfer material, An image forming method characterized by comprising at least a fixing step of fixing the visible image transferred onto the transfer material.

Images