Toner, developer, developer storage container, image forming method, and image forming apparatus

Abstract

To provide a toner that is excellent in fluidity and electrification characteristics and can prevent a deterioration in image quality.SOLUTION: A toner includes a binder resin, a colorant, and an external additive. The external additive contains titanium oxide fine particles subjected to hydrophobic treatment with a silane coupling agent including n-octyl triethoxy silane. The titanium oxide fine particles are rutile-type titanium oxide having a particle diameter of 10 nm or more and 35 nm or less.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] It has been known that fine particles with an average primary particle size of several nanometers to several tens of nanometers have been used as external additives for toners for developing electrostatic latent images (toners for electrophotography). For example, hydrophobized silica fine particles are used from the viewpoint of imparting chargeability, fluidity, and hydrophobicity, while hydrophobized titanium oxide fine particles are commonly used from the viewpoint of maintaining chargeability under usage and storage conditions and suppressing fluctuations in the amount of retained charge.

[0003] Titanium oxide comes in several crystalline forms, but the two main types of titanium oxide used for electrophotography are anatase titanium oxide and rutile titanium oxide. Because anatase-type titanium oxide has a spherical shape, it is less likely to cause a decrease in fluidity due to the shape of titanium oxide when added to toner. However, rutile-type titanium oxide has a scaly to needle-like shape, and may cause problems such as a decrease in fluidity when added to toner. Therefore, these issues can be reduced to a negligible level by performing a surface treatment that provides high lubricity, or by using external additives such as silica that have high fluidity and lubricity. However, it has been desired to give rutile titanium dioxide high fluidity through surface treatment.

[0004] For example, Patent Document 1 discloses that by surface-treating rutile-type titanium oxide fine particles with a fluorine-containing silane coupling agent and using the resultant as an external additive for toner, a toner with excellent hydrophobicity, fluidity, and charging properties can be obtained.

[0005] However, since fluorine-containing silane coupling agents have a large environmental impact, it is desired to treat the surface of rutile-type titanium oxide fine particles with a surface treatment agent that does not contain fluorine. Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a toner that is excellent in fluidity and chargeability and can suppress deterioration of image quality. [Means for solving the problem]

[0007] The toner of the present invention as a means for solving the problems is a toner containing a binder resin, a colorant, and an external additive, wherein the external additive contains titanium oxide fine particles that have been hydrophobized with a silane coupling agent containing n-octyltriethoxysilane, and the titanium oxide fine particles are rutile titanium oxide having a particle size of 10 nm or more and 35 nm or less. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a toner that is excellent in fluidity and chargeability and that can suppress deterioration of image quality. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing an example of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing an example of a process cartridge according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] (toner) The toner of the present invention comprises toner base particles containing a binder resin and a colorant, and an external additive that coats the toner base particles. The toner base particles may further contain other components such as a release agent and a charge control agent, as required.

[0011] [External additives] The external additive contained in the toner of the present invention includes titanium oxide fine particles that have been hydrophobized with a silane coupling agent containing n-octyltriethoxysilane, and may further contain other external additives as needed. By using other external additives in combination, for example, the fluidity, developability, chargeability, etc. of the toner can be further improved, and the toner can exhibit more effective functions.

[0012] <Titanium oxide particles> The titanium oxide particles used in the present invention are rutile titanium oxide. Rutile titanium oxide has a scale-to-acicular shape, and compared with anatase titanium oxide, which has a spherical shape, rutile titanium oxide is less likely to be embedded in the toner due to friction and provides excellent toner charge stability, although it has inferior toner fluidity when used as an external additive.

[0013] The particle diameter of the titanium oxide fine particles used in the present invention is 10 nm or more and 35 nm or less. By having a particle diameter of 10 nm or more, aggregation of the titanium oxide fine particles is suppressed, and a toner with excellent charge stability is obtained. Furthermore, by having a particle diameter of 35 nm or less, a toner with excellent dispersibility is obtained.

[0014] Rutile titanium oxide may be a commercially available product or may be appropriately prepared. Examples of methods for producing rutile titanium oxide include a method in which ilmenite ore is reacted with sulfuric acid to form a water-soluble sulfate, impurities are removed, and a rutile transformation promoter is added during hydrolysis or calcination to cause rutile transformation, thereby obtaining rutile titanium oxide.

[0015] <Silane coupling agent> The titanium oxide fine particles used in the present invention are characterized by being hydrophobized with a silane coupling agent. n Six 4-n (wherein n is an integer of 0 to 3, R represents a hydrogen atom or an organic group such as an alkyl group, and X represents a hydrolyzable group such as an alkoxy group). The silane coupling agent in the present invention contains at least n-octyltriethoxysilane, and if necessary, further contains a short-chain silane coupling agent having a molecular weight of 160 or less.

[0016] By including n-octyltriethoxysilane as the silane coupling agent used in the hydrophobic treatment of titanium oxide fine particles, a toner having excellent fluidity and chargeability can be obtained without using a fluorine-containing silane coupling agent.

[0017] <<Short-chain silane coupling agent>> The silane coupling agent preferably further contains a short-chain silane coupling agent having a molecular weight of not more than 160. After the titanium oxide fine particles are hydrophobized with n-octyltriethoxysilane, the untreated hydroxyl group sites can be hydrophobized with the short-chain silane coupling agent, thereby obtaining a toner with superior hydrophobicity.

[0018] There are no particular restrictions on the short-chain silane coupling agent as long as it has a molecular weight of 160 or less, and it can be selected appropriately depending on the purpose. Examples include dimethyldimethoxysilane (molecular weight 120), methyltrimethoxysilane (molecular weight 136), and dimethyldiethoxysilane (molecular weight 148).

[0019] <Other external additives> The external additive of the toner of the present invention may further contain other external additives in addition to the hydrophobized titanium oxide fine particles. The other external additives are not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include hydrophobic silica treated with hexamethyldisilazane or silicone oil, metal oxides such as strontium titanate, zinc oxide, and tin oxide, fatty acid metal salts such as zinc stearate and calcium stearate, and layered double hydroxides such as hydrotalcite. These may be used alone or in combination of two or more. Among these, hydrophobic silica is preferred from the viewpoint of improving the fluidity of the toner.

[0020] [Binder resin] The binder resin contained in the toner of the present invention is not particularly limited and can be appropriately selected depending on the purpose, but it is preferable that the toner contains a crystalline resin.

[0021] <Crystalline resin> Crystalline is defined as a substance in which atoms or molecules are arranged in a spatially repeating pattern, and is defined as a substance that shows a diffraction pattern using a general X-ray diffraction device. Crystalline resins exhibit thermal melting properties that show a sudden change in viscosity near the fixing start temperature, and therefore can impart low-temperature fixing properties to electrophotographic toners.

[0022] The crystalline resin is not particularly limited as long as it has crystallinity and can be appropriately selected depending on the purpose. Examples include polyester resin (crystalline polyester resin), polyurethane resin, polyurea resin, polyamide resin, polyether resin, vinyl resin, modified crystalline resin, etc. These may be used alone or in combination of two or more. Among these, polyester resin (crystalline polyester resin) is particularly preferred.

[0023] <<Crystalline polyester resin>>

[0024] The crystalline polyester resin is not particularly limited and can be appropriately selected depending on the purpose. For example, a crystalline polyester resin synthesized by reacting a diol component selected from saturated aliphatic diol compounds having 2 to 12 carbon atoms, particularly 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, or derivatives thereof, with a dicarboxylic acid component selected from dicarboxylic acids having 2 to 12 carbon atoms and having a double bond (C=C bond), or saturated dicarboxylic acids having 2 to 12 carbon atoms, particularly fumaric acid, 1,4-butanedioic acid, 1,6-hexanedioic acid, 1,8-octanedioic acid, 1,10-decanedioic acid, 1,12-dodecanedioic acid, or derivatives thereof, is preferred.

[0025] The content of the crystalline polyester resin is preferably 1 part by mass or more and 30 parts by mass or less per 100 parts by mass of the toner base particles. A content of 1 part by mass or more is preferred in that a sufficient low-temperature fixing effect can be obtained. A content of 30 parts by mass or less is preferred in that a decrease in image quality, a decrease in developer fluidity, and a decrease in image density can be suppressed, sufficient chargeability of the toner can be maintained for a long period of time, and the environmental stability of the toner can be improved.

[0026] <Other resins> The binder resin may contain other resins in addition to the crystalline resin. The other resins are not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include homopolymers of styrene and its substituted derivatives, such as polystyrene, poly(p-chlorostyrene), and polyvinyltoluene; styrene-p-chlorostyrene copolymers, styrene-propylene copolymers, styrene-vinyltoluene copolymers, styrene-methyl acrylate copolymers, styrene-ethyl acrylate copolymers, styrene-methacrylic acid copolymers, styrene-methyl methacrylate copolymers, styrene-ethyl methacrylate copolymers, styrene-butyl methacrylate copolymers, styrene-α-chloromethyl methacrylate copolymers, styrene-acrylonitrile copolymers, styrene-vinyl methyl ether copolymers, styrene-vinyl methyl ketone copolymers, styrene-butadiene copolymers, styrene-isoprene copolymers, and styrene-maleic acid ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polyesters, polyurethanes, epoxy resins, polyvinyl butyral, polyacrylic acid, rosin, modified rosin, terpene resins, phenolic resins, aliphatic or aromatic hydrocarbon resins, and aromatic petroleum resins. These may be used alone or in combination of two or more.

[0027] [Coloring agent] The colorant used as the toner material constituting the toner base particles is not particularly limited and can be appropriately selected from known dyes and pigments depending on the purpose, and examples thereof include carbon black, nigrosine dye, iron black, naphthol yellow S, Hansa yellow (10G, 5G, G), cadmium yellow, yellow iron oxide, yellow ochre, lead yellow, titanium yellow, polyazo yellow, oil yellow, Hansa yellow (GR, A, RN, R), pigment yellow L, benzidine yellow (G, GR), permanent yellow (NCG), and Vulcan fast yellow (5G, R). ), Tartrazine Lake, Quinoline Yellow Lake, Anthrazan Yellow BGL, Isoindolinone Yellow, Bengala, Red Lead, Cinnabar, Cadmium Red, Cadmium Mercury Red, Antimony Vermilion, Permanent Red 4R, Para Red, Faise Red, p-Chloro-o-Nitroaniline Red, Lithol Fast Scarlet G, Brilliant Fast Scarlet, Brilliant Carnmin BS, Permanent Red (F2R, F4R, FRL, FRLL, F4RH), Fast Scarlet VD, Belkan Fast Rubin B, Brilliant Toscarlet G, Lithol Rubin GX, Permanent Red F5R, Brilliant Carmine 6B, Pigment Scarlet 3B, Bordeaux 5B, Toluidine Maroon, Permanent Bordeaux F2K, Helio Bordeaux BL, Bordeaux 10B, Bon Maroon Light, Bon Maroon Medium, Eosin Lake, Rhodamine Lake B, Rhodamine Lake Y, Alizarin Lake, Thioindigo Red B, Thioindigo Maroon, Oil Red, Quinacridone Red, Pyrazolone Red, Polyazo Red, Chrome Vermilion, Benzidine Orange, Perinone Orange Di, Oil Orange, Cobalt Blue, Cerulean Blue, Alkali Blue Lake, Peacock Blue Lake, Victoria Blue Lake, Metal-free Phthalocyanine Blue, Phthalocyanine Blue, Fast Sky Blue, Indanthrene Blue (RS, BC), Indigo, Ultramarine Blue, Prussian Blue, Anthraquinone Blue, Fast Violet B, Methyl Violet Lake, Cobalt Purple, Manganese Purple, Dioxane Violet, Anthraquinone Violet, Chrome Green, Zinc Green, Chromium Oxide, Pyridian, Emerald Green, Pigment Green B,Examples of the pigments include naphthol green B, green gold, acid green lake, malachite green lake, phthalocyanine green, anthraquinone green, titanium oxide, zinc oxide, and lithopone, and these can be used alone or in combination.

[0028] The content of the colorant in the toner base particles is preferably 1% by mass or more and 15% by mass or less, and more preferably 3% by mass or more and 10% by mass or less.

[0029] The colorant may be used as a masterbatch combined with a resin. The resin used for the masterbatch is not particularly limited and can be appropriately selected from known resins depending on the purpose, and examples thereof include homopolymers of styrene or its substituted derivatives, styrene copolymers, polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, epoxy resins, epoxy polyol resins, polyurethanes, polyamides, polyvinyl butyral, polyacrylic acid, rosin, modified rosin, terpene resins, aliphatic hydrocarbon resins, alicyclic hydrocarbon resins, aromatic petroleum resins, chlorinated paraffins, paraffins, etc., and these can be used alone or in combination of two or more.

[0030] [Release agent] The release agent is not particularly limited and can be appropriately selected from known agents depending on the purpose. For example, waxes can be used. Examples of waxes include waxes having a carbonyl group, polyolefin waxes, and long-chain hydrocarbons, which can be used alone or in combination of two or more kinds, with waxes having a carbonyl group being preferred. Examples of waxes having a carbonyl group include polyalkanoic acid esters, polyalkanol esters, polyalkanoic acid amides, polyalkylamides, and dialkyl ketones, with polyalkanoic acid esters being particularly preferred. Examples of polyalkanoic acid esters include carnauba wax, montan wax, trimethylolpropane tribehenate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, and 1,18-octadecanediol distearate. Examples of polyalkanol esters include tristearyl trimellitate and distearyl maleate. Examples of polyalkanoic acid amides include dibehenylamide, etc. Examples of polyalkylamides include trimellitic acid tristearylamide, etc. An example of the dialkyl ketone is distearyl ketone. Examples of polyolefin waxes include polyethylene wax and polypropylene wax. Examples of long-chain hydrocarbons include paraffin wax and sazol wax.

[0031] The melting point of the release agent is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 45° C. or higher and 120° C. or lower. If the melting point is lower than 45° C., the release agent may adversely affect the heat-resistant storage stability, and if it exceeds 120° C., cold offset may be more likely to occur during fixation at low temperatures.

[0032] The melt viscosity of the release agent, as measured at a temperature 20° C. higher than the melting point of the release agent, is preferably 5 cps to 1,000 cps, more preferably 10 cps to 100 cps. If the melt viscosity is less than 5 cps, the release properties may be reduced, and if it exceeds 1,000 cps, the effects of improving hot offset resistance and low-temperature fixability may not be obtained.

[0033] The content of the release agent in the toner base particles is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 1% by mass to 40% by mass, more preferably 3% by mass to 30% by mass. If the content exceeds 40% by mass, the fluidity of the toner may decrease.

[0034] [Charge control agent] As the toner material constituting the toner base particles, a charge control agent or the like can be used as required. There are no particular limitations on the charge control agent, and a positive or negative charge control agent can be appropriately selected and used depending on whether the charge on the photosensitive member is positive or negative. As the negative charge control agent, for example, a resin or compound having an electron-donating functional group, an azo dye, a metal complex of an organic acid, or the like can be used. Specific examples include Bontron (product numbers: S-31, S-32, S-34, S-36, S-37, S-39, S-40, S-44, E-81, E-82, E-84, E-86, E-88, A, 1-A, 2-A, 3-A) (all manufactured by Orient Chemical Industry Co., Ltd.), Kayacharge (product numbers: N-1, N-2), Kayaset Black (product numbers: T-2, 004) (all manufactured by Nippon Kayaku Co., Ltd.), Aizenspiron Black (T-37, T-77, T-95, TRH, TNS-2) (all manufactured by Hodogaya Chemical Co., Ltd.), FCA-1001-N, FCA-1001-NB, FCA-1001-NZ (all manufactured by Fujikura Kasei Co., Ltd.), and the like. These can be used alone or in combination of two or more. Positive charge control agents that can be used include, for example, basic compounds such as nigrosine dyes, cationic compounds such as quaternary ammonium salts, and metal salts of higher fatty acids. Specific examples include Bontron (product numbers N-01, N-02, N-03, N-04, N-05, N-07, N-09, N-10, N-11, N-13, P-51, P-52, and AFP-B) (all manufactured by Orient Chemical Industry Co., Ltd.), TP-302, TP-415, and TP-4040 (all manufactured by Hodogaya Chemical Co., Ltd.), Copy Blue PR, and Copy Charge (product number PX-VP-435 , NX-VP-434) (all manufactured by Hoechst), FCA (product numbers: 201, 201-B-1, 201-B-2, 201-B-3, 201-PB, 201-PZ, 301) (all manufactured by Fujikura Chemical Co., Ltd.), PLZ (product numbers: 1001, 2001, 6001, 7001) (all manufactured by Shikoku Chemicals Corporation), and the like, which can be used alone or in combination of two or more.

[0035] The amount of charge control agent added is determined by the type of binder resin and the method of manufacturing the toner base particles, including the dispersion method, and is not uniquely limited, but is preferably 0.05% by mass or more and 1.0% by mass or less relative to the total amount of binder resin. If the amount added exceeds 1.0% by mass, the toner becomes too chargeable, reducing the effect of the charge control agent and increasing the electrostatic attraction to the developing roller, which can lead to reduced developer fluidity and reduced image density. If the amount added is less than 0.05% by mass, the charge buildup and charge amount are insufficient, which can affect the toner image.

[0036] [Toner manufacturing method] The toner can be produced by a known production method (pulverization method) including a melt-kneading step of melting and kneading toner materials, a pulverization step of pulverizing the resulting melt-kneaded mixture, a classification step of classifying the pulverized mixture obtained by the pulverization, and an external addition step of externally adding an external additive to the resulting toner base particles.

[0037] In the melt-kneading step, the toner materials are mixed, and the resulting mixture is placed in a melt-kneader and melt-kneaded. Examples of the melt-kneader that can be used include a single-screw or twin-screw continuous kneader and a batch kneader using a roll mill. Suitable examples include a KTK twin-screw extruder manufactured by Kobe Steel, Ltd., a TEM extruder manufactured by Toshiba Machine Co., Ltd., a KCK twin-screw extruder, a PCM twin-screw extruder manufactured by Ikegai Corporation, and a Co-kneader manufactured by Buss.

[0038] The melt-kneading is preferably carried out under appropriate conditions so as not to sever 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 above the softening point, severe severing may occur, and if the temperature is too low, dispersion may not proceed.

[0039] In the pulverization step, the kneaded product obtained in the melt-kneading step is pulverized. In this pulverization, it is preferable to first coarsely pulverize the kneaded product and then finely pulverize it. Suitable pulverization methods include, for example, a method of pulverizing particles by colliding them with an impingement plate in a jet stream, a method of pulverizing particles by colliding them with each other in a jet stream, and a method of pulverizing them in a narrow gap between a mechanically rotating rotor and stator.

[0040] In the classification step, the pulverized material obtained in the pulverization step is classified to adjust the particles to a predetermined particle size. Examples of the classification method include a method of removing fine particles using a cyclone, decanter, centrifugal separator, etc. After the pulverization step and the classification step are completed, the pulverized material is classified in an airflow by centrifugal force, etc., to produce toner base particles of a predetermined particle size.

[0041] In the external addition step, an external additive is externally added to the toner base particles obtained in the classification step. The toner base particles and the external additive are mixed and stirred using a mixer, whereby the external additive is crushed and coated on the surfaces of the toner base particles. By mixing and stirring and applying a mechanical impact force, the external additive can be attached to the toner base particles. Examples of methods for applying a mechanical impact force include a method in which an impact force is applied to particles using a blade rotating at high speed, and a method in which particles are introduced into a high-speed airflow and accelerated, causing the particles to collide with each other or the composite particles with an appropriate collision plate, thereby applying an impact force. Examples of devices that apply mechanical impact force include an Ang Mill (manufactured by Hosokawa Micron Corporation), a modified I-type Mill (manufactured by Nippon Pneumatic Co., Ltd.) with reduced grinding air pressure, a Hybridization System (manufactured by Nara Machinery Works), a Cryptron System (manufactured by Kawasaki Heavy Industries, Ltd.), and an automatic mortar.

[0042] When toner base particles are obtained by emulsifying or dispersing a toner material liquid (oil phase) in an aqueous medium (aqueous phase) (wet method), the process includes a step of preparing a toner material liquid (oil phase) by dissolving or dispersing toner materials including a binder resin and / or a binder resin precursor, a colorant, and, if necessary, a release agent in an organic solvent, and a step of emulsifying or dispersing the oil phase in an aqueous medium (aqueous phase) and then removing the solvent to obtain toner base particles, and then external addition can be performed in an external addition step similar to the step in the pulverization method described above.

[0043] The volume average particle size (Dv) of the toner base particles produced by either the pulverization method or the wet method is preferably 3.0 μm or more and less than 6.0 μm, and the ratio (Dv / Dn) of the volume average particle size (Dv) to the number average particle size (Dn) of the toner base particles is preferably 1.05 or more and 1.25 or less. If the volume average particle size (Dv) is smaller than 3.0 μm, in the case of a two-component developer (consisting of toner and carrier), the toner will fuse to the surface of the carrier during long-term stirring in the developing device, making it easier for the carrier's charging ability to decrease.If used as a one-component developer, the toner will easily film on the developing roller and fuse to components such as blades used to thin the toner layer. If the volume average particle diameter (Dv) is greater than 6.0 μm, it becomes difficult to obtain high-resolution, high-quality images, and the toner particle diameter often fluctuates greatly when the toner balance in the developer is performed. The same is true if the ratio of volume average particle diameter (Dv) to number average particle diameter (Dn) (Dv / Dn) is greater than 1.25. Furthermore, if the Dv / Dn is less than 1.05, this is desirable in terms of stabilizing toner behavior and uniforming the charge amount, but it may not only be impossible to sufficiently charge the toner, but may also deteriorate cleaning properties.

[0044] (developer) The developer of the present invention may be either a one-component developer consisting of the toner of the present invention alone, or a two-component developer consisting of the toner of the present invention and a carrier. However, when used in a high-speed printer or the like that can handle increased information processing speeds, it is preferable to use a two-component developer in terms of lifespan, etc. The mixing ratio of the toner and the carrier in the two-component developer is preferably 1 part by mass or more and 10 parts by mass or less of the toner with respect to 100 parts by mass of the carrier.

[0045] When the toner of the present invention is used as a one-component developer, even if the toner is balanced, there is little fluctuation in the particle size of the toner, there is no toner filming on the developing roller, and there is no toner fusion to components such as blades used to thin the toner layer, and good and stable developability and images can be obtained even with long-term use (stirring) of the developing device. Furthermore, in the case of a two-component developer using the toner of the present invention, even if the toner is balanced over a long period of time, there is little fluctuation in the toner particle size in the developer, and good and stable developability can be obtained even with long-term stirring in the developing device.

[0046] [Career] The carrier is not particularly limited and can be appropriately selected depending on the purpose, but preferably has a core material and a resin layer that covers the core material.

[0047] <Core material> The core material is not particularly limited and can be appropriately selected from known materials. For example, manganese-strontium (Mn-Sr)-based materials and manganese-magnesium (Mn-Mg)-based materials with a molecular weight of 50 emu / g to 90 emu / g are preferred. To ensure image density, highly magnetic materials such as iron powder (100 emu / g or more) and magnetite (75 emu / g to 120 emu / g) are preferred. Furthermore, weakly magnetic materials such as copper-zinc (Cu-Zn)-based materials (30 emu / g to 80 emu / g) are preferred because they can weaken the impact of the standing toner on the photoreceptor, which is advantageous for achieving high image quality. These materials can be used alone or in combination.

[0048] The weight-average particle diameter of the core material is preferably 10 μm to 200 μm, more preferably 40 μm to 100 μm. If the weight-average particle diameter is less than 10 μm, the carrier contains a large amount of fine powder components, which may reduce the magnetization per particle and cause carrier scattering. If the weight-average particle diameter is more than 150 μm, the specific surface area may decrease, causing toner scattering. In full-color printers with many solid areas, the reproducibility of the solid areas may be particularly poor.

[0049] <Resin layer> The material for the resin layer is not particularly limited and can be appropriately selected from known resins depending on the purpose. Examples include amino resins, polyvinyl resins, polystyrene resins, halogenated olefin resins, polyester resins, polycarbonate resins, polyethylene, polyvinyl fluoride, polyvinylidene fluoride, polytrifluoroethylene, polyhexafluoropropylene, copolymers of vinylidene fluoride and an acrylic monomer, copolymers of vinylidene fluoride and vinyl fluoride, fluoro terpolymers such as terpolymers of tetrafluoroethylene, vinylidene fluoride and a non-fluorinated monomer, and silicone resins, and these can be used alone or in combination of two or more.

[0050] Examples of the amino resins include urea-formaldehyde resins, melamine resins, benzoguanamine resins, urea resins, polyamide resins, and epoxy resins. Examples of polyvinyl resins include acrylic resins, polymethyl methacrylate, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, and polyvinyl butyral. Examples of polystyrene resins include polystyrene and styrene-acrylic copolymers. Examples of halogenated olefin resins include polyvinyl chloride. Examples of polyester resins include polyethylene terephthalate and polybutylene terephthalate.

[0051] If necessary, a conductive powder or the like may be added to the resin layer. Examples of conductive powder include metal powder, carbon black, titanium oxide, tin oxide, and zinc oxide. The average particle size of the conductive powder is preferably 1 μm or less. If the average particle size exceeds 1 μm, it may be difficult to control the electrical resistance.

[0052] The resin layer can be formed, for example, by dissolving a silicone resin or the like in a solvent to prepare a coating solution, then uniformly applying the coating solution to the surface of the core material by a known coating method, drying, and then baking. Examples of the coating method include dipping, spraying, and brush coating.

[0053] The solvent is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, methyl cellosolve, and butyl acetate.

[0054] The baking method is not particularly limited, and may be either an external heating method or an internal heating method. Examples include methods using a fixed electric furnace, a fluidized electric furnace, a rotary electric furnace, a burner furnace, etc., and methods using microwaves.

[0055] The content of the resin layer in the carrier is preferably 0.01% by mass or more and 5.0% by mass or less. If the content is less than 0.01% by mass, it may not be possible to form a uniform resin layer on the surface of the core material, and if it exceeds 5.0% by mass, the resin layer may become too thick, causing granulation of the carrier particles.

[0056] As described above, the developer of the present invention can be suitably used for image formation by various known electrophotographic methods such as a magnetic one-component development method, a non-magnetic one-component development method, and a two-component development method, and since it contains the toner of the present invention, when an image is formed by an electrophotographic method using the developer, a high-quality image having excellent cleaning properties, image quality, and durability is formed.

[0057] (Developer container) The developer container in the present invention refers to a container that contains a developer. Here, examples of the developer storage container include a developer container, a developing unit, and a process cartridge. The developer container refers to a container that contains a developer. The developing device is a device that contains a developer and has a means for developing. The process cartridge is a unit that integrates at least an electrostatic latent image carrier and a developing means, and is detachably mountable to an image forming apparatus.

[0058] The developing means has at least a developer container that contains the developer of the present invention and a developer carrier that carries and transports the developer contained in the developer container. The developing means may further have a regulating member or the like for regulating the thickness of the developer carried.

[0059] (Image forming method and image forming apparatus) The image forming method of the present invention includes an electrostatic latent image forming step of forming an electrostatic latent image on an electrostatic latent image carrier, a developing step of developing the electrostatic latent image with the developer of the present invention to form a visible image, a transferring step of transferring the visible image to the surface of a transfer recipient, and a fixing step of fixing the visible image transferred to the surface of the transfer recipient, and may further include other steps as necessary. Other processes include a charge removal process in which a charge removal bias is applied to the electrostatic latent image carrier to remove charge, a cleaning process in which toner remaining on the electrostatic latent image carrier is removed, a recycling process in which the toner removed in the cleaning process is recycled to the developing unit, and a control process in which each of the above processes is controlled.

[0060] The image forming apparatus of the present invention comprises an electrostatic latent image carrier, an electrostatic latent image forming unit that forms an electrostatic latent image on the electrostatic latent image carrier, a developing unit that develops the electrostatic latent image using the developer of the present invention to form a visible image, a transfer unit that transfers the visible image to the surface of a transfer recipient, and a fixing unit that fixes the visible image transferred to the surface of the transfer recipient, and may further comprise other units as necessary. Other parts include a charge removal unit that applies a charge removal bias to the electrostatic latent image carrier to remove charge, a cleaning unit that removes toner remaining on the electrostatic latent image carrier, a recycling unit that recycles the toner removed in the cleaning process to the developing unit, and a control unit that controls each of the above processes.

[0061] [Electrostatic latent image forming process and electrostatic latent image forming unit] In the electrostatic latent image forming step, an electrostatic latent image is formed on an electrostatic latent image carrier, and the electrostatic latent image forming step can be suitably carried out by an electrostatic latent image forming unit included in the image forming apparatus of the present invention.

[0062] The electrostatic latent image forming unit includes, for example, a charging unit that uniformly charges the surface of the electrostatic latent image carrier by applying a voltage to the surface, and an exposure unit that imagewise exposes the surface of the electrostatic latent image carrier charged by the charging unit.

[0063] <Electrostatic latent image carrier> The electrostatic latent image carrier is not particularly limited in terms of material, shape, structure, size, etc., and can be appropriately selected from known ones, but the shape is preferably drum-shaped. Examples of the electrostatic latent image carrier include inorganic photoconductors such as amorphous silicon and selenium, and organic photoconductors (OPCs) such as polysilane and phthalopolymethine.

[0064] Examples of organic photoreceptors include multilayer photoreceptors having a laminated structure in which a layer (charge generation layer) in which a charge generation material such as metal-free phthalocyanine, titanyl phthalocyanine, or gallium phthalocyanine is dispersed in a binder resin and a layer (charge transport layer) in which a charge transport material is dispersed in a binder resin are stacked on a support such as an aluminum drum, and single-layer photoreceptors having a single-layer photosensitive layer in which both a charge generation material and a charge transport material are dispersed in a binder resin on a support. In single-layer photoreceptors, a hole transport agent and an electron transport agent can also be added to the photosensitive layer as charge transport materials. An undercoat layer may also be provided between the support and the charge generation layer of the multilayer photoreceptor, or between the support and the photosensitive layer of the single-layer photoreceptor.

[0065] <Charging section> The charging unit is not particularly limited and can be appropriately selected depending on the purpose. Examples include known contact chargers equipped with conductive or semiconductive rolls, brushes, films, rubber blades, etc., and non-contact chargers utilizing corona discharge, such as corotrons and scorotrons. The charging unit is preferably arranged in contact with or without contact with the electrostatic latent image carrier, and charges the surface of the electrostatic latent image carrier by applying a superimposed DC voltage and an AC voltage. The charging unit is preferably a charging roller arranged in close proximity to the electrostatic latent image carrier but not in contact with it via a gap tape, and charges the surface of the electrostatic latent image carrier by applying a superimposed DC voltage and an AC voltage to the charging roller. The charging unit may be installed in a process cartridge containing the developer of the present invention.

[0066] <Exposure section> The exposure unit is not particularly limited as long as it can imagewise expose the surface of the electrostatic latent image carrier charged by the charging unit, and can be appropriately selected depending on the purpose. Examples include a copying optical system, a rod lens array system, a laser optical system, and a liquid crystal shutter optical system. A backlight system in which imagewise exposure is performed from the back side of the electrostatic latent image carrier may also be used. The exposure unit may be provided in a process cartridge containing the developer of the present invention.

[0067] [Developing process and developing section] In the developing step, the electrostatic latent image formed in the electrostatic latent image forming step is developed with the developer of the present invention to form a visible image. The developing step can be suitably carried out by a developing unit included in the image forming apparatus of the present invention.

[0068] The developing unit is not particularly limited as long as it can develop using the developer of the present invention, and can be appropriately selected from known ones. For example, it can be a unit that contains the developer of the present invention and has at least a developer carrier that can apply the developer to an electrostatic latent image in a contact or non-contact manner, and it is preferable that it is provided with a developer storage container (developer-containing container) that can be attached and detached.

[0069] The developing unit may be either a dry or wet developing system, and may be either a monochromatic or multicolor developing device. For example, it may include a device having a stirrer that charges the developer by friction and a rotatable magnet roller. In the developing device, for example, toner and carrier are mixed and stirred, and the toner is charged by friction and held in a standing state on the surface of the rotating magnet roller, forming a magnetic brush. Because the magnet roller is located near the electrostatic latent image carrier, a portion of the toner constituting the magnetic brush formed on the surface of the magnet roller is transferred to the surface of the electrostatic latent image carrier by electrical attraction. As a result, the electrostatic latent image is developed by the toner, forming a visible image on the surface of the electrostatic latent image carrier. It is preferable to apply an alternating electric field when transferring the toner to the surface of the electrostatic latent image carrier.

[0070] Alternatively, a premix development method may be adopted, in which a premix developer in which toner and carrier are mixed in advance is replenished. In the premix development method, the developer in the developing device can be gradually refreshed by discharging the excess carrier in the developing device as excess developer. This has the effect of extending the replacement cycle associated with developer deterioration and eliminating the effort required for developer replacement.

[0071] [Transfer process and transfer section] In the transfer step, the visible image formed in the development step is transferred onto the surface of a transfer-receiving material. The transfer step can be suitably carried out by a transfer unit included in the image-forming apparatus of the present invention.

[0072] The transfer step preferably uses an intermediate transfer member, and after the visible image is primarily transferred onto the intermediate transfer member, the visible image is secondarily transferred onto the transferee. Furthermore, a preferred embodiment uses two or more colors of toner, preferably full-color toner, and includes a primary transfer step in which the visible image is transferred onto the intermediate transfer member to form a composite transfer image, and a secondary transfer step in which the composite transfer image is transferred onto the transferee. The visible image can be transferred, for example, by charging the electrostatic latent image carrier using a transfer charger.

[0073] The transfer unit preferably has a primary transfer unit that transfers a visible image onto an intermediate transfer member to form a composite transfer image, and a secondary transfer unit that transfers the composite transfer image onto a transfer-receiving member. The transfer unit (primary transfer unit, secondary transfer unit) preferably has at least a transfer device that peels and charges the visible image formed on the electrostatic latent image carrier onto the transfer-receiving member. The transfer unit may be one or two or more. Examples of the transfer device include a corona transfer device that uses corona discharge, a transfer belt, a transfer roller, a pressure transfer roller, and an adhesive transfer device.

[0074] [Fixing process and fixing section] In the fixing step, the visible image transferred to the surface of the transfer medium in the transfer step is fixed, and the fixing step can be suitably carried out by a fixing unit included in the image forming apparatus of the present invention.

[0075] In the fixing step, the toner of each color may be fixed each time it is transferred onto the transfer receiving material, or the toners of each color may be laminated and fixed at the same time.

[0076] The fixing unit is not particularly limited and can be appropriately selected depending on the purpose, but it is preferable to use a known fixing member that performs heat and pressure fixing. The fixing member is preferably in the form of a roller or belt, and examples thereof include a combination of a heating roller and a pressure roller, or a combination of a heating roller, a pressure roller, and an endless belt. In this case, the heating temperature is preferably 80°C or higher and 200°C or lower.

[0077] In the present invention, the fixing section can be a means having a heating element having a heat generating element, a film in contact with the heating element, and a pressure member that is in pressure contact with the heating element via the film, and passing a transfer object on which an unfixed image has been formed between the film and the pressure member to heat, pressurize, and fix the image. Depending on the purpose, for example, a known optical fixing device may be used together with or instead of the fixing unit.

[0078] [Static elimination process and static elimination unit] In the charge removal step, a charge removal bias is applied to the electrostatic latent image bearing member to remove the charge, which can be suitably performed by a charge removal unit that the image forming apparatus of the present invention has as needed.

[0079] The charge removing unit is not particularly limited as long as it can apply a charge removing bias to the electrostatic latent image bearing member, and can be appropriately selected from known charge removers, such as a charge removing lamp.

[0080] [Cleaning process and cleaning department] In the cleaning step, the toner remaining on the electrostatic latent image bearing member is removed, and the cleaning step can be suitably carried out by a cleaning unit that the image forming apparatus of the present invention has as needed.

[0081] The cleaning unit is not particularly limited as long as it can remove toner remaining on the electrostatic latent image carrier, and can be appropriately selected from known cleaners, such as a magnetic brush cleaner, electrostatic brush cleaner, magnetic roller cleaner, blade cleaner, brush cleaner, web cleaner, etc. The cleaning unit may be provided in a process cartridge containing the developer of the present invention.

[0082] [Recycling Process and Recycling Department] In the recycling step, the toner removed in the cleaning step is recycled to the developing unit, which can be suitably carried out by a recycling unit that the image forming apparatus of the present invention has as needed.

[0083] The recycling section is not particularly limited, and examples thereof include known conveying means.

[0084] [Control process and control section] In the control step, the above steps are controlled, and the control step can be suitably performed by a control unit that the image forming apparatus of the present invention has as needed.

[0085] The control unit is not particularly limited as long as it can control the movements of each step, and can be appropriately selected depending on the purpose. Examples of the control unit include devices such as a sequencer and a computer.

[0086] The present invention will now be described in more detail with reference to the drawings.

[0087] FIG. 1 is a diagram showing an example of an image forming apparatus according to an embodiment of the present invention. Although a printer is shown as an example of the image forming apparatus in this embodiment, the image forming apparatus is not particularly limited as long as it is capable of forming an image using toner, such as a copier, facsimile, or multifunction device. The image forming apparatus 200 includes a paper feed section 210, a conveying section 220, an image forming section (electrostatic latent image forming section and developing section) 230, a transfer section 240, and a fixing device (fixing section) 250. The paper feed section 210 includes a paper feed cassette 211 in which the paper P to be fed is stacked, and a paper feed roller 212 that feeds the paper P stacked in the paper feed cassette 211 one sheet at a time.

[0088] The conveying section 220 includes a roller 221 that conveys the paper P fed by the paper feed roller 212 toward the transfer section 240, a pair of timing rollers 222 that hold the leading end of the paper P conveyed by the roller 221 and wait, sending the paper to the transfer section 240 at a predetermined timing, and a paper discharge roller 223 that discharges the paper P with the fixed color toner image onto a paper discharge tray 224.

[0089] The image forming section 230 includes, at a predetermined interval from left to right in the drawing, an image forming unit 180Y that forms an image using a developer containing yellow toner, an image forming unit 180C that uses a developer containing cyan toner, an image forming unit 180M that uses a developer containing magenta toner, an image forming unit 180K that uses a developer containing black toner, a charger 232, and an exposure unit 233. The exposure unit 233 has a light source 233a and a polygon mirror 233b. It should be noted that when referring to any one of the image forming units (180Y, 180C, 180M, 180K), it is referred to as the image forming unit.

[0090] The developer contains toner and carrier. The four image forming units (180Y, 180C, 180M, 180K) have substantially the same mechanical configuration, except for the developer used in each unit.

[0091] The transfer unit 240 includes a drive roller 241, a driven roller 242, an intermediate transfer belt 243 that can rotate counterclockwise in the drawing as the drive roller 241 is driven, primary transfer rollers (244Y, 244C, 244M, 244K) that are provided opposite the electrostatic latent image carrier 231 with the intermediate transfer belt 243 in between, and a secondary opposing roller 245 and secondary transfer roller 246 that are provided opposite each other with the intermediate transfer belt 243 in between at the position where the toner image is transferred to paper. The transfer unit 240 also includes a cleaning device 236 that removes residual toner remaining on the surface of the electrostatic latent image carrier 231. In this embodiment, an elastic intermediate transfer belt can also be used as the intermediate transfer belt 243. As the elastic intermediate transfer belt, for example, one in which a flexible elastic layer is laminated on a rigid base layer that can provide relatively flexibility can be used. In order to prevent the intermediate transfer belt 243 from meandering, a guide member for preventing the intermediate transfer belt 243 from shifting may be provided on the inner peripheral surface of the intermediate transfer belt 243 .

[0092] The fixing unit 250 has a heater installed inside and is equipped with a fixing belt 251 that heats the paper P, and a pressure roller 252 that forms a nip by rotatably applying pressure to the fixing belt 251. This applies heat and pressure to the color toner image on the paper P, fixing the color toner image. The paper P with the fixed color toner image is discharged to a paper discharge tray 224 by a paper discharge roller 223, completing the series of image formation processes.

[0093] FIG. 2 is a diagram showing an example of a process cartridge according to the present invention. The process cartridge 110 includes a photosensitive drum 10 , a corona charger 58 , a developing device 40 , a transfer roller 80 and a cleaning device 90 . [Example]

[0094] Examples of the present invention will be described below, but the present invention is not limited to these examples in any way.

[0095] -Preparation of titanium oxide fine particles A- 100 parts by mass of untreated rutile-type titanium oxide with an average primary particle diameter of 15 nm was dispersed in a toluene solvent, and 15 parts by mass of n-octyltriethoxysilane was added. The mixture was then dispersed to prevent the titanium oxide particles from agglomerating and coalescing, dried, and crushed to obtain titanium oxide microparticles A.

[0096] -Preparation of titanium oxide fine particles B- 100 parts by mass of untreated rutile-type titanium dioxide with an average primary particle diameter of 15 nm was dispersed in a toluene solvent, and 10 parts by mass of n-octyltriethoxysilane was added, followed by a dispersion treatment to prevent the titanium dioxide particles from agglomerating and unifying. Subsequently, 6 parts by mass of dimethyldimethoxysilane was added, followed by a dispersion treatment, followed by drying and crushing to obtain titanium dioxide microparticles B.

[0097] -Preparation of titanium oxide fine particles C- 100 parts by mass of untreated rutile-type titanium dioxide with an average primary particle diameter of 35 nm was dispersed in a toluene solvent, and 8 parts by mass of n-octyltriethoxysilane was added, followed by a dispersion treatment to prevent the titanium dioxide particles from aggregating and coalescing. Subsequently, 8 parts by mass of dimethyldiethoxysilane was added, followed by a dispersion treatment, followed by drying and crushing to obtain titanium dioxide microparticles C.

[0098] -Preparation of titanium oxide particles D- 100 parts by mass of untreated rutile-type titanium oxide with an average primary particle diameter of 35 nm was dispersed in a toluene solvent, and 8 parts by mass of n-octyltriethoxysilane was added.Then, a dispersion treatment was carried out to prevent the titanium oxide particles from agglomerating and coalescing, followed by drying and crushing to obtain titanium oxide microparticles D.

[0099] -Preparation of titanium oxide fine particles E- 100 parts by mass of untreated rutile-type titanium dioxide with an average primary particle diameter of 15 nm was dispersed in a toluene solvent, and 12 parts by mass of dimethyldimethoxysilane was added, followed by a dispersion treatment to prevent the titanium dioxide particles from agglomerating and coalescing. Subsequently, 8 parts by mass of dimethyldiethoxysilane was added, followed by a dispersion treatment, followed by drying and crushing to obtain titanium dioxide fine particles E.

[0100] -Preparation of titanium oxide fine particles F- 100 parts by mass of untreated rutile-type titanium oxide with an average primary particle diameter of 15 nm was dispersed in a toluene solvent, and 20 parts by mass of silicone oil with an average molecular weight of approximately 1500 was added.Then, a dispersion treatment was carried out to prevent the titanium oxide particles from agglomerating and coalescing, and the mixture was dried and crushed to obtain titanium oxide microparticles F.

[0101] -Preparation of titanium oxide fine particles G- 100 parts by mass of untreated rutile-type titanium oxide with an average primary particle diameter of 55 nm was dispersed in a toluene solvent, and 8 parts by mass of n-octyltriethoxysilane was added. After that, a dispersion treatment was carried out to prevent the titanium oxide particles from agglomerating and coalescing, followed by drying and crushing to obtain titanium oxide microparticles G.

[0102] -Preparation of titanium oxide fine particles H- 100 parts by mass of untreated anatase-type titanium oxide with an average primary particle diameter of 15 nm was dispersed in a toluene solvent, and 20 parts by mass of silicone oil with an average molecular weight of approximately 1500 was added. After that, a dispersion treatment was carried out to prevent the titanium oxide particles from agglomerating and coalescing, followed by drying and crushing to obtain titanium oxide microparticles H.

[0103] -Preparation of titanium oxide particles I- 100 parts by mass of untreated rutile-type titanium oxide with an average primary particle diameter of 35 nm was dispersed in a toluene solvent, and 8 parts by mass of hexamethyldisilazane was added. After that, a dispersion treatment was carried out to prevent the titanium oxide particles from agglomerating and coalescing, followed by drying and crushing to obtain titanium oxide microparticles I.

[0104] Table 1 shows the conditions for producing titanium oxide particles A to I.

[0105] [Table 1]

[0106] -Preparation of crystalline polyester resin A- Fumaric acid and 1,6-hexanediol were charged into a 5 L four-neck flask equipped with a nitrogen inlet tube, dehydration tube, stirrer, and thermocouple so that the OH / COOH ratio of the mixture was 0.9, and reacted together with titanium tetraisopropoxide (500 ppm relative to the resin components) at 180°C for 10 hours, then heated to 200°C and reacted for 3 hours, and then reacted for an additional 2 hours at a pressure of 8.3 kPa to obtain crystalline polyester resin A. The melting point of crystalline polyester resin A was 60°C to 80°C, and the weight average molecular weight was 5500 to 6500.

[0107] -Preparation of amorphous polyester resin B- The monomer species shown in Table 2 below and tetrabutoxy titanate as a condensation catalyst were placed in a reaction vessel equipped with a condenser, a stirrer, and a nitrogen inlet tube, and the reaction was carried out at 230°C for 6 hours under a nitrogen stream while distilling off the water produced. Next, the reaction was carried out for 1 hour under a reduced pressure of 5 mmHg to 20 mmHg, yielding amorphous polyester resin B. In Table 2, the "25 mol%" shown for bisphenol A (2,2) propylene oxide refers to the proportion of the alcohol component when the acid component and alcohol component are 50 mol% and 50 mol%, respectively.

[0108] [Table 2]

[0109] -Production of toner base particles- The following raw materials were used in producing the toner base particles. [Binder resin] Amorphous polyester resin B: 79 parts by mass Crystalline polyester resin A: 8 parts by mass [Coloring agent] Carbon black (Mitsubishi Chemical Corporation, #44): 11 parts by mass [Release agent] Fischer-Tropsch wax: 5 parts by mass [Charge control agent] ·Azo iron compound (manufactured by Hodogaya Chemical Industry Co., Ltd., T-77): 1 part by mass

[0110] The above raw materials were premixed using a Henschel mixer (Mitsui Miike Chemical Engineering Co., Ltd., FM20B) and then melted and kneaded at 120°C in a twin-screw kneader (Ikegai Corporation, PCM-30). The resulting kneaded material was rolled to a thickness of 2.7 mm using a roller, cooled to room temperature using a belt cooler, and coarsely pulverized to 200 μm to 300 μm using a hammer mill. Next, it was finely pulverized using a supersonic jet pulverizer, Labojet (Nippon Pneumatic Mfg. Co., Ltd.), and then classified using an air classifier (Nippon Pneumatic Mfg. Co., Ltd., MDS-I) while appropriately adjusting the louver opening to obtain a weight average particle size of 5.8±0.2 μm, to obtain toner base particles to be used for evaluation.

[0111] Example 1 Toner 1 of Example 1 was obtained by adding 0.8 parts by mass of titanium oxide fine particles A and 1.3 parts by mass of hydrophobic silica (H2000T, manufactured by Wacker) to 100 parts by mass of toner base particles and stirring and mixing them in a Henschel mixer.

[0112] Example 2 Toner 2 of Example 2 was obtained in the same manner as in Example 1, except that titanium oxide particles A were changed to titanium oxide particles B.

[0113] Example 3 Toner 3 of Example 3 was obtained in the same manner as in Example 1, except that titanium oxide particles A were changed to titanium oxide particles C and the amount of hydrophobic silica added was changed from 1.3 parts by mass to 2.1 parts by mass.

[0114] Example 4 Toner 4 of Example 4 was obtained in the same manner as in Example 1, except that titanium oxide particles A were changed to titanium oxide particles D and the amount of hydrophobic silica added was changed from 1.3 parts by mass to 1.8 parts by mass.

[0115] (Comparative Example 1) Toner 5 of Comparative Example 1 was obtained in the same manner as in Example 1, except that titanium oxide particles E were used instead of titanium oxide particles A.

[0116] (Comparative Example 2) Toner 6 of Comparative Example 2 was obtained in the same manner as in Example 1, except that titanium oxide particles A were changed to titanium oxide particles F.

[0117] (Comparative Example 3) Toner 7 of Comparative Example 3 was obtained in the same manner as in Example 1, except that titanium oxide particles A were changed to titanium oxide particles G and the amount of hydrophobic silica added was changed from 1.3 parts by mass to 2.2 parts by mass.

[0118] Comparative Example 4 Toner 8 of Comparative Example 4 was obtained in the same manner as in Example 1, except that titanium oxide particles A were changed to titanium oxide particles H.

[0119] (Comparative Example 5) Toner 9 of Comparative Example 5 was obtained in the same manner as in Example 1, except that titanium oxide particles A were changed to titanium oxide particles I and the amount of hydrophobic silica added was changed from 1.3 parts by mass to 2.1 parts by mass.

[0120] Table 3 shows the compositions of toners 1 to 9.

[0121] [Table 3]

[0122] 5% by mass of the toner and 95% by mass of the coated ferrite carrier were uniformly mixed for 5 minutes at 48 rpm using a Turbula mixer (manufactured by Willy & Bachofen (WAB)) to prepare a developer. The prepared developer was evaluated using the evaluation methods described below.

[0123] <Cleaning ability> Cleaning performance was evaluated by running 5,000 sheets of paper through an image forming apparatus (manufactured by Ricoh Co., Ltd.) in a test room at 10°C and 15% RH. After that, the blank image was stopped while the paper was running, and the residual toner remaining on the photoreceptor that had passed the cleaning process was transferred to a blank piece of paper using Scotch tape (manufactured by Sumitomo 3M Co., Ltd.), which was then measured with a Macbeth reflection densitometer RD514. A rating of "△" or better was deemed acceptable for practical use. [Evaluation criteria] ○: Difference from blank is less than 0.01 △: Difference from blank is 0.01 or more and 0.02 or less ×: Difference from blank exceeds 0.02

[0124] <Image quality> The image quality was evaluated by comprehensively assessing the deterioration of image quality after paper feed (specifically, the occurrence of transfer failure and background staining). Transfer failure was evaluated by running 5,000 sheets of paper through an image forming apparatus (manufactured by Ricoh Co., Ltd.), then running a black solid image through the paper, and visually ranking the level of transfer failure of the image. For background smear images, 5,000 sheets were passed through an image forming apparatus (manufactured by Ricoh Co.), and then the blank image was stopped during development, and the developer on the photosensitive drum after development was transferred with Scotch tape (manufactured by Sumitomo 3M Co.), and the difference in image density from the untransferred tape was measured and quantitatively evaluated with a spectrodensitometer (manufactured by X-Rite Co.), with a difference of less than 0.30 being rated as good, and 0.30 or more being poor. Combining these two, good image quality was rated as ○, image quality that was not good but acceptable was △, and image quality that was poor was rated as ×.

[0125] <Photoconductor damage> Using an image forming device (manufactured by Ricoh Co., Ltd.), 100,000 A4 images with a density of 4% were printed, and the occurrence of scratches on the photoreceptor was evaluated. [Evaluation criteria] ◯: No scratches or only small scratches on the photosensitive member. △: There are scratches on the photosensitive member, but the printed image is not defective. ×: There are scratches on the photoreceptor, causing defects in the printed image, or there are scratches that cannot be repaired.

[0126] <Charging stability> The developer was conditioned overnight in an environment of 35°C temperature and 85% humidity. After conditioning, the developer was stirred for 1 minute with a magnetic roller, and then the charge amount was measured with a blow-off charge amount measuring device (TB-200 model, manufactured by Toshiba Chemical Co., Ltd.) to obtain the charge amount Q(1). In addition, the charge amount was similarly measured for a sample that was stirred for 60 minutes with a ball mill instead of stirring for 1 minute with a magnetic roller, and the charge amount Q(60) was obtained. The charge amount Q(1) after 1 minute of stirring was defined as the initial charge amount, and the charge amount Q(60) after 60 minutes of stirring was defined as the charge amount after deterioration, and the stability of the charge amount under high temperature and high humidity conditions was evaluated using the following formula. A rating of "Fair" or better was deemed to be acceptable for practical use. Formula: |1-(Q(60) / Q(1))|×100=Qst [Evaluation criteria] 〇: Qst is less than 20 △: Qst is 20 or more and less than 40 ×: Qst is 40 or more

[0127] <Development process durability> After continuous printing, the printed solid images and blank images were visually inspected for the occurrence of abnormal images such as white or black streaks and fading of images, and were evaluated according to the following criteria: A rating of "good" or better was deemed acceptable for practical use. [Evaluation criteria] ◎: No abnormal images occur. ◯: Abnormal images are generated to a level that is not noticeable to the user. △: Signs of a problem are present, but they are not present in the output image at a problematic level. ×: Clearly abnormal images are generated.

[0128] Table 4 shows the evaluation results for the toners of the examples and comparative examples.

[0129] [Table 4]

[0130] The evaluation results of Examples 1 to 4 show that by using titanium oxide microparticles, which are rutile-type titanium oxide particles having a particle size of 10 nm or more and 35 nm or less and which have been hydrophobized with a silane coupling agent containing n-octyltriethoxysilane, as an external additive, a toner having excellent fluidity and charging stability and capable of suppressing deterioration in image quality can be obtained.

[0131] The embodiments of the present invention are as follows, for example. <1> A toner comprising a binder resin, a colorant, and an external additive, the external additive contains titanium oxide fine particles that have been hydrophobized with a silane coupling agent containing n-octyltriethoxysilane; The toner is characterized in that the titanium oxide fine particles are rutile type titanium oxide having a particle size of 10 nm or more and 35 nm or less. <2> The silane coupling agent further contains a short-chain silane coupling agent having a molecular weight of 160 or less. <1> The toner is as described above. <3> The short-chain silane coupling agent is any one of dimethyldimethoxysilane, methyltrimethoxysilane, and dimethyldiethoxysilane. <2> The toner is as described in <4> The external additive further contains hydrophobic silica. <1> from <3> 1. The toner according to any one of claims 1 to 9. <5> The binder resin contains a crystalline resin. <1> from <4> 1. The toner according to any one of claims 1 to 9. <6> <1> from <5> 10. A developer containing the toner according to any one of claims 1 to 9. <7> <6> 10. A developer container characterized by containing the developer described above. <8> an electrostatic latent image forming step of forming an electrostatic latent image on an electrostatic latent image carrier; The electrostatic latent image is <6> a developing step of forming a visible image by developing with the developer according to a transfer step of transferring the visible image onto a surface of a transfer-receiving material; and a fixing step of fixing the visible image transferred onto the surface of the transfer medium. <9> an electrostatic latent image carrier; an electrostatic latent image forming unit that forms an electrostatic latent image on the electrostatic latent image carrier; The electrostatic latent image is <6> a developing section which develops a visible image by using the developer according to the present invention; a transfer unit that transfers the visible image onto a surface of a transfer target; and a fixing section for fixing the visible image transferred onto the surface of the transfer medium. [Explanation of symbols]

[0132] 10 Photosensitive drum 40 Developer 58 Corona charger 80 Transfer roller 90 Cleaning Device 95 Paper 110 Process cartridge 160 Sub Hopper 180 Image forming unit 200 Image forming device 210 Paper feed section 211 Paper cassette 212 Paper feed roller 220 Conveyor 221 Laura 222 Timing roller 223 Paper ejection roller 224 Paper output tray 230 Imaging unit (electrostatic latent image forming unit and developing unit) 231 Electrostatic latent image carrier 233 Exposure device 233a light source 233b Polygon mirror 234 Toner bottle 236 Cleaning Device 240 Transcription Unit 241 Drive roller 242 driven roller 243 Intermediate transfer belt 244 Primary transfer roller 245 Secondary opposing roller 246 Secondary transfer roller 250 Fixing unit (fixing section) 251 Fixing belt 252 pressure roller L writing light P paper [Prior art documents] [Patent documents]

[0133] [Patent Document 1] Patent No. 4373631

Claims

1. A toner comprising a binder resin, a colorant, and an external additive, the external additive contains titanium oxide fine particles that have been hydrophobized with a silane coupling agent containing n-octyltriethoxysilane; The toner is characterized in that the titanium oxide fine particles are rutile type titanium oxide having a particle size of 10 nm or more and 35 nm or less.

2. 2. The toner according to claim 1, wherein the silane coupling agent further comprises a short-chain silane coupling agent having a molecular weight of 160 or less.

3. 3. The toner according to claim 2, wherein the short-chain silane coupling agent is any one of dimethyldimethoxysilane, methyltrimethoxysilane, and dimethyldiethoxysilane.

4. The toner according to claim 1 , wherein the external additive further comprises hydrophobic silica.

5. 2. The toner according to claim 1, wherein the binder resin contains a crystalline resin.

6. A developer comprising the toner according to any one of claims 1 to 5.

7. A developer container containing the developer according to claim 6.

8. an electrostatic latent image forming step of forming an electrostatic latent image on an electrostatic latent image carrier; a developing step of developing the electrostatic latent image with the developer according to claim 6 to form a visible image; a transfer step of transferring the visible image onto a surface of a transfer-receiving material; and a fixing step of fixing the visible image transferred onto the surface of the transfer medium.

9. an electrostatic latent image carrier; an electrostatic latent image forming unit that forms an electrostatic latent image on the electrostatic latent image carrier; a developing section for developing the electrostatic latent image with the developer according to claim 6 to form a visible image; a transfer unit that transfers the visible image onto a surface of a transfer target; and a fixing unit for fixing the visible image transferred onto the surface of the transfer medium.

Images