JP5678649B2 - Electrostatic charge image developing carrier, electrostatic charge image developing developer, developer cartridge, process cartridge, image forming apparatus, and image forming method - Google Patents

Description

  The present invention relates to an electrostatic charge image developing carrier, an electrostatic charge image developing developer, a developer cartridge, a process cartridge, an image forming apparatus, and an image forming method.

  A method for visualizing image information through an electrostatic latent image (electrostatic image) such as electrophotography is currently used in various fields. In electrophotography, an electrostatic latent image formed on a photoreceptor by charging and exposure processes contains an electrostatic charge image developing toner (hereinafter sometimes referred to simply as “toner”). It is developed with an agent (hereinafter sometimes simply referred to as “developer”), and visualized through a transfer and fixing process. As a developer used for development, a two-component developer including a toner and a carrier for developing an electrostatic image (hereinafter sometimes simply referred to as “carrier”) and a toner used alone such as a magnetic toner are used. There are component developers, but the two-component developer has characteristics such as good controllability because the carrier shares functions such as stirring, transport and charging of the developer and is separated as a developer. Is currently widely used.

  Carriers are generally classified into resin-coated carriers having a resin coating layer on the surface of magnetic particles (core particles) and uncoated carriers having no coating layer on the surface. Developers using resin-coated carriers are generally charged. It has excellent controllability and is relatively easy to improve environmental dependency and stability over time. So far, it has been studied to improve the characteristics of the carrier by mixing particles in the resin coating layer of the resin-coated carrier.

  For example, Japanese Patent Application Laid-Open No. H10-260260 makes it possible to quickly charge a particularly small-diameter toner with a carrier containing conductive composite particles containing conductive particles on or near the surface in a resin coating layer. Thus, it is described that an image can be stably formed even in a small high-speed machine.

  In Patent Document 2, in a method for producing a carrier for an electrophotographic developer having a resin coating layer in which at least conductive carbon is dispersed on the surface of magnetic particles, at least two mesh members are provided on an ultrasonic vibrator. Using a vibration sieve machine with an ultrasonic transducer oscillator installed in close contact, the vibration received by the mesh material on the lower layer side from the ultrasonic transducer is transmitted to the mesh material on the upper layer side. By oscillating the supplied carrier, by separating the conductive carbon that is easily released from the surface of the carrier, the electrical resistance of the carrier coating layer is kept low, and the edge effect and the carrier adhesion preventing action are provided. It is described that a carrier can be obtained which has no color characteristic deterioration such as color turbidity and is less subject to electrification fluctuation due to coating layer wear or spent toner composition. That.

  Patent Document 3 discloses a magnetic carrier having a coating layer obtained by coating at least a binder resin and an inorganic fine powder on the surface of a magnetic carrier core containing a magnetic material, wherein the inorganic fine powder is at least titanic acid. By containing strontium, it prevents image flow in the toner non-image area after standing for a long time in a high humidity environment, and without reducing developability even in long-term image formation under a high humidity environment, It is described that fogging and changes in image density are suppressed through long-term image formation (durability).

JP 2005-181935 A JP 2006-171309 A JP 2010-014854 A

  An object of the present invention is to provide an electrostatic charge image developing carrier capable of stably obtaining a high-quality image over a long period of time, an electrostatic charge image developing developer containing the carrier, a developer cartridge using the developer, a process cartridge, An object of the present invention is to provide an image forming apparatus and an image forming method.

The invention according to claim 1 includes a carrier core material, and a resin coating layer that contains a coating resin and conductive particles and covers the surface of the carrier core material, and the resin coating layer is for at least an inner layer. a two-layer structure of an inner layer and outer layer are formed by using the coating liquid and the coating liquid for the outer layer, at least a portion of the conductive particles is exposed on the surface of the outer layer, the outer the number-average aggregate diameters of the exposed conductive particles domains on the surface of the layer (Da) is much larger than the number-average aggregate diameter (Db) of the conductive particles domains contained within said layer, the conductive particles domain The number average aggregate diameters Da and Db are electrostatic charge image developing carriers in the range of 5 nm to 1,000 nm .

The invention according to claim 2 is characterized in that the number average aggregate diameters Da and Db of the conductive particle domains are 0 . 2. The electrostatic charge image developing carrier according to claim 1, wherein 005 ≦ (Db / Da) <1.

  A third aspect of the present invention is an electrostatic charge image developing developer containing the electrostatic charge image developing carrier according to the first or second aspect.

  The invention according to claim 4 is a developer cartridge containing the developer for developing an electrostatic charge image according to claim 3.

  According to a fifth aspect of the present invention, there is provided an image carrier, and a developing unit that develops an electrostatic latent image formed on the surface of the image carrier using a developer to form a toner image, and the development The agent is a process cartridge which is the developer for developing an electrostatic image according to claim 3.

  According to a sixth aspect of the present invention, there is provided an image carrier, a charging unit that charges the surface of the image carrier, a latent image forming unit that forms an electrostatic latent image on the surface of the image carrier, and the image carrier. A developing unit that develops the electrostatic latent image formed on the surface of the toner using a developer to form a toner image; and a transfer unit that transfers the developed toner image to a transfer target. The agent is an image forming apparatus which is the developer for developing an electrostatic image according to claim 3.

  The invention according to claim 7 is formed on a surface of the image carrier, a charging step for charging the surface of the image carrier, a latent image forming step for forming an electrostatic latent image on the surface of the image carrier. A developing step of developing the electrostatic latent image using a developer to form a toner image; and a transferring step of transferring the developed toner image to a transfer target, wherein the developer is claimed in claim 3. An image forming method, which is the developer for developing an electrostatic image described in 1.

  According to the first aspect of the present invention, there is provided an electrostatic charge image developing carrier capable of stably obtaining a high-quality image over a long period of time as compared with the case without this configuration.

  According to the second aspect of the present invention, there is provided an electrostatic charge image developing carrier capable of more stably obtaining a high-quality image over a long period of time as compared with the case without this configuration.

  According to the third aspect of the present invention, there is provided a developer for developing an electrostatic charge image that can stably obtain a high-quality image over a long period of time as compared with the case without this configuration.

  According to the fourth aspect of the present invention, there is provided a developer cartridge capable of stably obtaining a high-quality image over a long period of time as compared with the case where this configuration is not provided.

  According to the fifth aspect of the present invention, there is provided a process cartridge capable of stably obtaining a high-quality image over a long period of time as compared with the case where this configuration is not provided.

  According to the sixth aspect of the present invention, there is provided an image forming apparatus capable of stably obtaining a high-quality image over a long period of time as compared with the case where this configuration is not provided.

  According to the seventh aspect of the present invention, there is provided an image forming method capable of stably obtaining a high-quality image over a long period of time as compared with the case where this configuration is not provided.

It is a schematic structure figure showing an example of a process cartridge concerning an embodiment of the present invention. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention.

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

<Carrier for developing electrostatic image>
A carrier according to an embodiment of the present invention includes a carrier core material, a resin coating layer that contains a coating resin and conductive particles and covers the surface of the carrier core material, and at least a part of the conductive particles is The number average aggregate diameter (Da) of the conductive particle domains exposed on the surface of the resin coating layer and exposed on the surface of the resin coating layer is the number average aggregate diameter of the conductive particle domains contained in the resin coating layer. It is larger (Da> Db) than (Db).

  With this configuration, even if the resin coating layer of the resin-coated carrier is worn out after a long period of use, the number average aggregate diameter (Da) of the conductive particle domains exposed on the surface of the resin coating layer is contained in the resin coating layer. Since the conductive particle domain is larger than the number average aggregate diameter (Db), the resistance variation of the carrier is suppressed. Since the triboelectric charge amount between the toner and the carrier is stably maintained, a high-quality image can be stably obtained over a long period of time. Further, the occurrence of toner contamination inside the copying machine is suppressed.

  In general, when a resin-coated carrier is used over a long period of time, the resin coating layer wears out, the exposure and removal of additives, the exposure of the carrier core progress, and the fine line reproducibility due to the decrease in carrier resistance and charge amount. Deterioration of images and image defects such as white spots are likely to occur. Conductive particles such that the number average aggregate diameter (Da) of the conductive particle domains exposed on the surface of the resin coating layer is larger than the number average aggregate diameter (Db) of the conductive particle domains contained in the resin coating layer. If this is placed, even if the surface of the resin coating layer wears and the carrier core material is exposed, the area of the conductive particles exposed on the surface of the resin coating layer is reduced, so fluctuations in carrier resistance are suppressed. In addition, since the triboelectric charge amount between the toner and the carrier is stably maintained, a high-quality image can be stably obtained over a long period of time.

  In the carrier according to the present embodiment, the number average aggregate diameters Da and Db of the conductive particle domains are preferably in the range of 5 nm to 1,000 nm, and more preferably in the range of 10 nm to 1,000 nm. . When the number average agglomerated diameters Da and Db of the conductive particle domains are less than 5 nm, the carrier resistance control effect may be lost. .

  In the carrier according to the present embodiment, 0.005 ≦ (Db / Da) <1 is preferable, and 0.010 ≦ (Db / Da) <1 is more preferable. If (Db / Da) is less than 0.005, the carrier resistance may increase even if the resin coating layer is worn. If it exceeds 1, the effect of suppressing fluctuation in carrier resistance is not exhibited.

  The conductive particles are not particularly limited as long as they are conductive particles, and are selected from metal particles such as metal oxide particles, carbon black, carbon fibers, and metal compound particles. In order to configure the number average aggregate diameter of the conductive particle domains as described above, a plurality of conductive particles having different compositions may be used, or conductive particles having a single composition and different aggregate forms may be used. Exactly the same conductive particles may be used. Since the number average agglomerated diameter of the conductive particle domains varies depending on the type of conductive particles used, etc., the number average agglomerated diameter of the conductive particle domains after forming the resin coating layer on the surface of the carrier core material is confirmed in advance by a test. It is preferable to keep it. By appropriately selecting the type of conductive particles to be used, the number average aggregate diameter (Da> Db) of the conductive particle domains as described above is configured.

  As content of electroconductive particle, the range of 2.5 mass% or more and 20 mass% or less of a resin coating layer is preferable. When the amount is less than 2.5% by mass, the effect of controlling the carrier resistance may be lost. When the amount exceeds 20% by mass, it is difficult to control the dispersion of particles in the resin coating layer, and it becomes difficult to control the electric resistance. There is.

  The coating resin is not particularly limited as long as it is a resin that coats the carrier core material. However, contamination of the surface of the resin coating layer of the resin-coated carrier by the toner constituent material and adhesion of the toner itself are suppressed, and mechanical resin is used. A resin that is excellent in strength and resistant to abrasion and breakage is preferable. Specifically, polyolefin resin, polyvinyl and polyvinylidene resin, (meth) acrylic resin, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether, polyvinyl ketone, polyester, polyurethane , Polycarbonate, amino resin, epoxy resin, vinyl chloride / vinyl acetate copolymer, styrene / acrylic copolymer, silicone resin containing an organosiloxane bond and modified products thereof, fluorine resin, polystyrene resin, methacrylic acid, and the like. Particularly preferred are polystyrene resins, (meth) acrylic resins, and styrene / acrylic copolymers. When these resins are used, the strength of the resin coating layer is high, and the dispersion state of the conductive particles can be easily controlled.

Examples of the carrier core material (core particle) include known magnetic particles such as iron powder, magnetite, and ferrite. A ferrite core is particularly preferable. In particular, the ferrite core as the most suitable magnetic core material is mainly composed of an oxide containing one or more elements selected from Li, Mg, Ca, Mn, Ni, Cu, Zn, and Sr, and Fe ₂ O _2. Examples thereof include particles formed by granulation and sintering. This ferrite core is excellent in adhesiveness with the coating resin and is easy to control the surface shape of the core, and therefore suitable for precise control of the aggregate diameter of the conductive particles.

  In order to configure the number average aggregation diameter (Da> Db) of the conductive particle domains in the resin coating layer of the carrier according to this embodiment, in addition to the method of selecting the type of conductive particles, for example, the resin coating layer Alternatively, a two-layer structure including an inner layer including conductive particle domains having a smaller number average aggregate diameter and an outer layer including conductive particle domains having a larger number average aggregate diameter may be employed. In this case, it is preferable that the number average aggregate diameter of the conductive particle domains after forming the resin coating layer on the surface of the carrier core material is confirmed in advance by a test. The resin coating layer is not limited to a two-layer configuration, and may be configured to have three or more layers so that the number average aggregation diameter of the conductive particle domains is changed stepwise so that Da> Db.

  The resin-coated carrier can be produced by, for example, a method in which conductive particles are added to a solution in which a coating resin is dissolved, stirred and dispersed, and a resin coating layer forming solution is applied to the surface of the carrier core and coated. Good.

  In the present embodiment, any type of coating apparatus may be used as a coating apparatus used to coat the surface of the carrier core material with a coating resin. Examples of such a coating apparatus include a fluidized bed, spray drying, a high-speed rotary mixer, a planetary coating apparatus, and a kneader coating apparatus.

  In order to configure the number average aggregation diameter (Da> Db) of the conductive particle domains in the resin coating layer of the carrier according to the present embodiment, for example, a plurality of coating apparatuses may be used, or a single coating apparatus may be used. May be used. Moreover, it may be manufactured by changing the conditions of the coating process stepwise, or may be manufactured by changing continuously.

  In addition to the coating resin, the resin coating layer forming solution may appropriately contain conductive particles, a charge control agent used as necessary, and the like. The solvent for dissolving the coating resin is not particularly limited as long as it dissolves the coating resin. For example, aromatic hydrocarbons such as xylene and toluene, ketones such as acetone and methyl ethyl ketone, tetrahydrofuran, Ethers such as dioxane and halides such as chloroform and carbon tetrachloride may be used.

  The resin coating layer may contain a negative charge control agent. Negative charge control agents include trimethylethane dyes, metal complexes of salicylic acid, metal complexes of benzylic acid, copper phthalocyanine, perylene, quinacridone, azo pigments, metal complex azo dyes, azochrome complexes, etc. Examples include dyes, calixarene type phenolic condensates, cyclic polysaccharides, resins containing at least one of carboxyl groups and sulfonyl groups.

  The content of the negative charge control agent is preferably in the range of 0.001% by mass to 1.0% by mass with respect to the mass of the core particles, and is 0.01% by mass to 0.8% by mass. More preferably, it is the range. When the content of the negative charge control agent is less than 0.001% by mass with respect to the mass of the core particles, there is a case where there is no effect on the toner charge rising property. It may inhibit the charging ability.

  The resin coating layer of the carrier may contain a wax. Waxes are usually hydrophobic, are relatively soft at room temperature, and have low film strength. This originates from the molecular structure of the wax, but due to this characteristic, when wax is present in the resin coating layer, toner components such as external additives added to the toner surface or toner bulk components are added to the carrier surface. Hard to adhere. Even if it adheres, the surface of the carrier is renewed by peeling off the wax at the adhesion level at the molecular level, and the carrier surface is not easily contaminated.

  The wax is not particularly limited, and examples thereof include paraffin wax and derivatives thereof, montan wax and derivatives thereof, microcrystalline wax and derivatives thereof, Fischer-Tropsch wax and derivatives thereof, polyolefin wax and derivatives thereof, and the like. Derivatives include oxides, polymers with vinyl monomers, and graft modified products. In addition, alcohol, fatty acid, plant wax, animal wax, mineral wax, ester wax, acid amide, and the like may be used. Moreover, you may use another well-known thing. The melting point of the wax is preferably 60 ° C. or higher and 200 ° C. or lower. More preferably, the melting point of the wax is 80 ° C. or higher and 150 ° C. or lower. If it is less than 60 degreeC, the fluidity | liquidity as a carrier may deteriorate.

  Moreover, in order to improve the adhesiveness between the core particle surface and the coating resin, the core particles may be subjected to a coupling treatment. Examples of coupling agents include silane coupling agents, silicone oils, titanate coupling agents, and aluminum coupling agents. These may be used individually by 1 type and may use 2 or more types together. Of these, silane coupling agents are preferred.

  As the silane coupling agent, any type of chlorosilane, alkoxysilane, silazane, and special silylating agent may be used. Specifically, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, tetraethoxysilane, Methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltrimethoxysilane, decyltrimethoxysilane, hexamethyldisilazane, N, O- (bistrimethylsilyl) acetamide, N, N-bis (Trimethylsilyl) urea, tert-butyldimethylchlorosilane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxy Silane, γ-methacryloxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-mercapto Examples include propyltrimethoxysilane, γ-chloropropyltrimethoxysilane, and γ-aminopropyltriethoxysilane.

  Examples of titanate coupling agents include “Plenact KR TTS”, “Plenact KR 46B”, “Plenact KR 55”, “Plenact KR 41B”, “Plenact KR 38S”, “Plenact KR 138S”, “Prenact K”. ”,“ Plenact 338X ”,“ Plenact KR 44 ”,“ Plenact KR 9SA ”,“ Plenact KR ET ”(all of which are manufactured by Ajinomoto Fine Techno Co., Ltd.) and the like. Examples include acetoacetate aluminum diisopropylate (“Plenact AL-M” manufactured by Ajinomoto Fine Techno Co., Ltd.).

  The thickness of the resin coating layer is preferably in the range of 0.1 to 5 μm, more preferably in the range of 0.2 to 3 μm. If the thickness of the resin coating layer is smaller than 0.1 μm, it may be difficult to form a resin coating layer that is as uniform and flat as possible on the surface of the core particles. On the other hand, if the thickness is greater than 5 μm, the carriers may aggregate to make it difficult to obtain a carrier that is as uniform as possible.

<Toner for electrostatic image development>
The toner is not particularly limited, and a known toner containing a binder resin and a colorant as main components and containing a release agent or the like as necessary may be used. The toner may be produced by a dry production method such as a kneading and pulverization method, or may be produced by a wet production method such as an emulsion polymerization aggregation method, a dissolution suspension method, or a suspension polymerization method. . A toner produced by a wet production method such as an emulsion polymerization agglomeration method is preferred from the standpoint that the surface exposure of the colorant and the release agent is small and the stability of the image is good.

  Such toner has a relatively spherical particle shape, a narrow particle size distribution, a relatively uniform toner surface, high chargeability, and a narrow and favorable charge distribution. Since this toner has a narrow particle size distribution, the occurrence of fogging is small.

  As the binder resin for the toner, styrenes such as styrene and chlorostyrene; monoolefins such as ethylene, propylene, butylene, and isobutylene; vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate, methyl acrylate, acrylic acid Esters of α-methylene aliphatic monocarboxylic acids such as ethyl, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate; vinyl methyl ether, Homopolymers or copolymers of vinyl ethers such as vinyl ethyl ether and vinyl butyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropenyl ketone, and particularly representative binding As fat, polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyethylene, polypropylene Etc. Furthermore, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin waxes and the like can be mentioned.

  Examples of the colorant include carbon black, chrome yellow, hansa yellow, benzidine yellow, sren yellow, quinoline yellow, permanent orange GTR, pyrazolone orange, vulcan orange, watch young red, permanent red, brillianthamine 3B, and brillianthamine. 6B, DuPont Oil Red, Pyrazolone Red, Resol Red, Rhodamine B Lake, Lake Red C, Rose Bengal, Aniline Blue, Ultramarine Blue, Calco Oil Blue, Methylene Blue Chloride, Phthalocyanine Blue, Phthalocyanine Green, Malachite Green Oxalate, etc. Or acridine, xanthene, azo, benzoquinone, azine, anthraquinone, thio Various dyes such as Ndico, Dioxazine, Thiazine, Azomethine, Indico, Thioindico, Phthalocyanine, Aniline Black, Polymethine, Triphenylmethane, Diphenylmethane, Thiazine, Thiazole, and Xanthene Or in combination of two or more.

  In the toner according to the exemplary embodiment, the content of the colorant is preferably in the range of 1 part by mass to 30 parts by mass with respect to 100 parts by mass of the binder resin. It is also effective to use a surface-treated colorant or a pigment dispersant as necessary. By appropriately selecting the type of the colorant, yellow toner, magenta toner, cyan toner, black toner and the like can be obtained.

  Examples of mold release agents include low molecular weight polyolefins such as polyethylene, polypropylene and polybutene; silicones having a softening point upon heating; fatty acid amides such as oleic acid amide, erucic acid amide, ricinoleic acid amide and stearic acid amide; Plant waxes such as ester wax, carnauba wax, rice wax, candelilla wax, tree wax, jojoba oil, etc .; animal waxes such as beeswax; montan wax, ozokerite, ceresin, paraffin wax, microcrystalline wax, fisher Mineral waxes such as Tropsch wax, petroleum waxes, and modified products thereof may be used. The addition amount of the release agent may be added in the range of 50% by mass or less with respect to the toner.

  In addition, as an internal additive, a magnetic material such as a metal such as ferrite, magnetite, reduced iron, cobalt, nickel, or manganese, an alloy thereof, or a compound containing the metal may be used. As the charge control agent, a quaternary ammonium salt, a nigrosine compound, a dye composed of a complex such as aluminum, iron, or chromium, or various commonly used charge control agents such as a triphenylmethane pigment may be used. A charge control agent that is difficult to dissolve in water is suitable for controlling the ionic strength that affects the stability during aggregation and fusion integration and reducing wastewater contamination.

  Examples of inorganic particles to be wet-added include silica, alumina, titania, calcium carbonate, magnesium carbonate, and tricalcium phosphate, all of which are usually used as external additives on the toner surface, such as ionic surfactants and What is necessary is just to disperse | distribute with a polymeric acid and a polymeric base, and to add wet.

  Surfactants used for emulsion polymerization, seed polymerization, pigment dispersion, resin particles, release agent dispersion, aggregation, or stabilization in the toner manufacturing process by a wet manufacturing method include sulfate ester salts, sulfonate salts, phosphorus Examples thereof include anionic surfactants such as acid esters and soaps, and cationic surfactants such as amine salts and quaternary ammonium salts, and also polyethylene glycols, alkylphenol ethylene oxide adducts, polyhydric alcohols. It is also effective to use a nonionic surfactant such as a system together.

  Moreover, what is necessary is just to use well-known external additives, such as an inorganic particle and an organic particle, as an external additive (external additive) used in this embodiment. Among these, inorganic particles such as silica, titania, alumina, cerium oxide, strontium titanate, calcium carbonate, magnesium carbonate and calcium phosphate, metal soap such as zinc stearate, fluorine-containing resin particles, silica-containing resin particles and nitrogen Organic resin particles such as containing resin particles are preferred. Moreover, you may surface-treat on the surface of an external additive according to the objective. Examples of the surface treatment agent include a silane compound, a silane coupling agent, and a silicone oil for performing a hydrophobic treatment.

  The volume average particle size of the toner according to the exemplary embodiment is preferably in the range of 4 μm to 8 μm, and more preferably in the range of 5 μm to 7 μm. If the volume average particle diameter of the toner is less than 4 μm, the amount of fine powder increases, so that toner fog and poor cleaning are likely to occur.

  The volume average particle size distribution index GSDv of the toner according to the exemplary embodiment is preferably in the range of 1.1 to 1.3, more preferably in the range of 1.1 to 1.27. More preferably, it is in the range of 1.15 or more and 1.24 or less. When the GSDv exceeds 1.3, the presence of coarse particles and fine powder particles increases, so that the toner is agglomerated and tends to cause charging failure and transfer failure. Moreover, when GSDv is less than 1.1, it will be quite difficult to manufacture.

The volume average particle size D50v and the volume average particle size distribution index GSDv are measured using a Coulter-Multisizer-II type (manufactured by Beckman-Coulter) with an aperture diameter of 100 μm. At this time, the measurement is performed after the toner is dispersed in an electrolyte aqueous solution (Isoton II aqueous solution) and dispersed by ultrasonic waves for 30 seconds or more. For the particle size range (channel) divided based on the measured particle size distribution of the toner, a cumulative distribution is drawn from the small diameter side for each of the volume and number, and the particle size that becomes 16% is the volume D16v and the cumulative is 50%. The particle diameter to be defined is defined as volume D50v, and the particle diameter to be accumulated 84% is defined as volume D84v. At this time, D50v represents the volume average particle diameter, and the volume average particle size distribution index (GSDv) is obtained as (D84v / D16v) ^1/2 .

  In addition, the toner shape factor SF1 represented by the following formula of the toner for developing an electrostatic charge image according to the exemplary embodiment is preferably in the range of 110 to 140, and more preferably in the range of 115 to 135. More preferably, it is in the range of 120 to 130. If the toner shape factor SF1 is less than 110, the toner particles are close to a spherical shape, which may cause a cleaning failure after transfer. On the other hand, when the toner shape factor SF1 exceeds 140, not only the transfer efficiency and the image quality are deteriorated, but also the shape range of the toner particles obtained by a low-temperature manufacturing method may be exceeded.

SF1 = (ML ² / A) × (π / 4) × 100
(In the above formula, ML represents the maximum length (μm) of toner, and A represents the projected area (μm ² ) of toner.)

  The toner shape factor SF1 is measured as follows using a Luzex image analyzer (manufactured by Nireco Corporation, FT). First, an optical microscope image of the toner spread on the slide glass is taken into a Luzex image analyzer through a video camera, and the maximum length (ML) and the projected area (A) of 50 toners are measured. SF1 is calculated, and an average of these values is obtained as the toner shape factor SF1.

<Developer for developing electrostatic image>
The developer for developing an electrostatic charge image according to the exemplary embodiment includes a toner and a carrier, and the carrier is the carrier for developing an electrostatic charge image. That is, the developer for developing an electrostatic charge image according to the exemplary embodiment is a two-component developer including a toner and a carrier.

  The ratio of the toner when preparing the developer by mixing the toner and the carrier is in the range of 1% by mass to 15% by mass, preferably 3% by mass to 12% by mass of the entire developer.

If the toner ratio is less than 1% by mass, it may be difficult to obtain a sufficient image density, or a solid image may not be uniform. On the other hand, if the amount exceeds 15% by mass, the toner coverage on the carrier surface exceeds 100% and the charge amount decreases (when the absolute value of the average charge amount is less than 15 μC / g). Fog) A high-quality color image may not be obtained. For example, when the amount exceeds 15% by mass, the toner coverage on the carrier surface approaches 100%, and the resistance value as a developer increases, and the range is 1 × 10 ⁵ Ω · cm to 1 × 10 ⁸ Ω · cm. In some cases, it is difficult to obtain a good and high-quality color image such as blurring of an image edge portion.

  However, in a low humidity environment, if the toner ratio is less than 1% by mass, a high charge amount (the absolute value of the average charge amount exceeds 25 μC / g) tends to occur, and it may be difficult to obtain a sufficient image density. Therefore, it is preferable to select the toner ratio so that the absolute value of the charging property is in the range of 15 μC / g or more and 50 μC / g or less according to the environment.

<Developer cartridge>
The developer cartridge according to the present embodiment is not particularly limited as long as it contains the electrostatic charge image developing developer including the electrostatic charge image developing carrier of the present embodiment. For example, the developer cartridge is attached to or detached from an image forming apparatus including a developing unit, and the developer cartridge includes the electrostatic image developing carrier of the present embodiment as a developer to be supplied to the developing unit. A developer is stored.

<Process cartridge>
The process cartridge according to the present embodiment includes an image carrier and developing means for developing a latent electrostatic image formed on the surface of the image carrier using a developer to form a toner image. The process cartridge according to the present embodiment includes a charging unit that charges the surface of the image holding member, a latent image forming unit that forms a latent image on the surface of the charged image holding member, and a surface of the image holding member, as necessary. Transfer means for transferring the formed toner image to the transfer body, image holding body cleaning means for removing residual toner remaining on the surface of the image holder after transfer, and cleaning, and transferred to the transfer body You may provide at least 1 selected from the group which consists of a fixing means for fixing a toner image.

  A schematic configuration of an example of a process cartridge according to an embodiment of the present invention is shown in FIG. 1, and the configuration will be described. The process cartridge 1 includes a photoconductor (electrophotographic photoconductor) 14 as an image carrier on which an electrostatic latent image is formed, a charging device 10 as a charging unit that charges the surface of the photoconductor 14, and a photoconductor 14. A developing device 16 as a developing means for forming a toner image by attaching toner to the electrostatic latent image formed on the surface, and the surface of the photoconductor 14 are contacted, and the residual remaining on the surface of the photoconductor 14 after transfer A cleaning blade 20 as an image carrier cleaning means that removes toner and cleans it is integrally supported, and is detachable from the image forming apparatus. When mounted on the image forming apparatus, an exposure device 12 as a latent image forming means for forming an electrostatic latent image on the surface of the photosensitive member 14 around the photosensitive member 14 by the charging device 10, laser light or reflected light of the document. The developing device 16, the transfer roll 18 serving as transfer means for transferring the toner image on the surface of the photoreceptor 14 to the recording paper 24 as a transfer target, and the cleaning blade 20 are arranged in this order. In FIG. 1, description of functional units normally required in other electrophotographic processes is omitted.

  The operation of the process cartridge 1 according to this embodiment will be described.

  First, the surface of the photoreceptor 14 is charged by the charging device 10 (charging process). Next, light is applied to the surface of the photoconductor 14 by the exposure device 12, and the charged charges in the exposed portion are removed, and an electrostatic latent image (electrostatic charge image) is formed according to the image information ( Latent image forming step). Thereafter, the electrostatic latent image is developed by the developing device 16, and a toner image is formed on the surface of the photoreceptor 14 (developing step). For example, in the case of a digital electrophotographic copying machine using an organic photosensitive member as the photosensitive member 14 and using a laser beam as the exposure device 12, the surface of the photosensitive member 14 is given a negative charge by the charging device 10, and the laser beam A digital latent image is formed in the form of dots by light, and toner is applied to the portion irradiated with the laser beam by the developing device 16 to be visualized. In this case, a negative bias is applied to the developing device 16. Next, a recording sheet 24 as a transfer object is superimposed on the toner image by the transfer roll 18, and the charge opposite in polarity to the toner is given to the recording sheet 24 from the back side of the recording sheet 24, and the toner image is formed by electrostatic force. It is transferred onto the recording paper 24 (transfer process). The transferred toner image is subjected to heat and pressure in a fixing device having a fixing roll 22 as fixing means, and is fused and fixed to the recording paper 24 (fixing step). On the other hand, the residual toner such as toner remaining on the surface of the photoconductor 14 without being transferred is removed by the cleaning blade 20 (image carrier cleaning step). One cycle is completed in a series of processes from the charging step to the image carrier cleaning step. In FIG. 1, the toner image is directly transferred to the recording paper 24 by the transfer roll 18, but may be transferred via an intermediate transfer member such as an intermediate transfer belt.

  As the charging device 10 that is a charging means, for example, a charger such as a corotron as shown in FIG. 1 is used, but a conductive or semiconductive charging roll may be used. A contact charger using a conductive or semiconductive charging roll may apply a direct current to the photoreceptor 14 or may apply an alternating current superimposed thereon. For example, the charging device 10 charges the surface of the photoconductor 14 by generating a discharge in a minute space near the contact portion with the photoconductor 14. Normally, it is charged to −300V or more and −1000V or less. The conductive or semiconductive charging roll may have a single layer structure or a multiple structure. Further, a mechanism for cleaning the surface of the charging roll may be provided.

  The photoreceptor 14 has a function of forming at least an electrostatic latent image (electrostatic charge image). In the electrophotographic photosensitive member, an undercoat layer, a charge generation layer containing a charge generation material, and a charge transport layer containing a charge transport material are formed in this order on the outer peripheral surface of a cylindrical conductive substrate as necessary. It is a thing. The order of stacking the charge generation layer and the charge transport layer may be reversed. These are laminated photoconductors in which a charge generation material and a charge transport material are contained in separate layers (charge generation layer, charge transport layer), but both the charge generation material and the charge transport material are the same. A single-layer type photoreceptor included in the above layer may be used, and a laminated photoreceptor is preferable. Further, an intermediate layer may be provided between the undercoat layer and the photosensitive layer. Further, a protective layer may be provided on the photosensitive layer. In addition, other types of photosensitive layers such as an amorphous silicon photosensitive film may be used in addition to the organic photoreceptor.

  The exposure apparatus 12 is not particularly limited. For example, a laser optical system that exposes a light source such as semiconductor laser light, LED (Light Emitting Diode) light, and liquid crystal shutter light on the surface of the photoconductor 14 in a desired image manner, Examples include optical system devices such as LED arrays.

  The developing unit has a function of developing the electrostatic latent image formed on the photoreceptor 14 with a one-component developer or a two-component developer containing an electrostatic charge image developing toner to form a toner image. Such a developing device is not particularly limited as long as it has the above-described functions, and may be appropriately selected depending on the purpose. Even a system in which the toner layer is in contact with the photoconductor 14 is not in contact with the system. It may be a thing. For example, as shown in FIG. 1, a developing device having a function of attaching toner for developing an electrostatic image to the photosensitive member 14 using the developing device 16, or developing having a function of attaching the toner to the photosensitive member 14 using a brush or the like. And a known developing device.

  As a transfer device as a transfer means, for example, a charge opposite in polarity to the toner is applied to the recording paper 24 from the back side of the recording paper 24, and the toner image is transferred to the recording paper 24 by electrostatic force, or as shown in FIG. A transfer roll and a transfer roll pressing device using a conductive or semiconductive roll or the like that directly transfers to the surface of the recording paper 24 via the recording paper 24 may be used. A direct current may be applied to the transfer roll as a transfer current applied to the image carrier, or an alternating current may be applied in a superimposed manner. The transfer roll may be arbitrarily set according to the width of the image area to be charged, the shape of the transfer charger, the opening width, the process speed (circumferential speed), and the like. Further, a single layer foam roll or the like is suitably used as a transfer roll for cost reduction. The transfer method may be a method of transferring directly to the recording paper 24 or a method of transferring to the recording paper 24 via an intermediate transfer member.

  A known intermediate transfer member may be used as the intermediate transfer member. Materials used for the intermediate transfer member include polycarbonate resin (PC), polyvinylidene fluoride (PVDF), polyalkylene phthalate, PC / polyalkylene terephthalate (PAT) blend material, ethylene tetrafluoroethylene copolymer (ETFE) / PC, ETFE / PAT, PC / PAT blend materials, and the like can be mentioned. From the viewpoint of mechanical strength, an intermediate transfer belt using a thermosetting polyimide resin is preferable.

  The image carrier cleaning means may be selected as appropriate as long as it removes residual toner on the image carrier and cleans it, and employs a blade cleaning method, a brush cleaning method, a roll cleaning method, or the like. . Among these, it is preferable to use a cleaning blade. Examples of the material for the cleaning blade include urethane rubber, neoprene rubber, and silicone rubber. Among them, it is particularly preferable to use a polyurethane elastic body because of its excellent wear resistance.

  The fixing device as the fixing unit is not particularly limited as long as the toner image transferred onto the recording paper 24 is fixed by heating, pressing, or heating and pressing. For example, a fixing device including a heating roll and a pressure roll is used.

  Examples of the recording paper 24 that is a transfer target to which the toner image is transferred include plain paper, an OHP sheet, and the like used in electrophotographic copying machines and printers. In order to further improve the smoothness of the image surface after fixing, it is preferable that the surface of the transfer material is as smooth as possible. For example, coated paper in which the surface of plain paper is coated with resin, art paper for printing, etc. Preferably used.

<Image forming apparatus>
An image forming apparatus according to the present embodiment includes an image carrier, a charging unit that charges the surface of the image carrier, a latent image forming unit that forms an electrostatic latent image on the surface of the image carrier, and an image carrier. The image forming apparatus includes a developing unit that develops the electrostatic latent image formed on the surface using a developer to form a toner image, and a transfer unit that transfers the developed toner image to a transfer target. The image forming apparatus according to the present exemplary embodiment removes residual toner and the like remaining on the surface of the image holding member after transfer, and a fixing unit for fixing the toner image transferred to the transfer target, as necessary. And at least one selected from the group consisting of an image carrier cleaning means for cleaning. The image forming apparatus according to the present embodiment may use the process cartridge.

  FIG. 2 shows a schematic configuration of an example of the image forming apparatus according to the present embodiment, and the configuration will be described. The image forming apparatus 3 includes a photosensitive member 14 as an image carrier on which an electrostatic latent image is formed, a charging device 10 as a charging unit that charges the surface of the photosensitive member 14, and laser light or reflected light of a document. An exposure device 12 as a latent image forming unit that forms an electrostatic latent image on the surface of the photoconductor 14 and a developing unit that forms a toner image by attaching toner to the electrostatic latent image formed on the surface of the photoconductor 14. A developing device 16, a transfer roll 18 as a transfer means for transferring the toner image on the surface of the photoconductor 14 to a recording paper 24 as a transfer target, and the surface of the photoconductor 14, and the photoconductor after transfer. And a cleaning blade 20 as an image carrier cleaning means for removing residual toner and the like remaining on the surface of the image 14 for cleaning. In the image forming apparatus 3, a charging device 10, an exposure device 12, a developing device 16, a transfer roll 18, and a cleaning blade 20 are arranged around the photoconductor 14 in this order. In addition, a fixing device having a fixing roll 22 is provided as fixing means. In FIG. 2, functional units normally required in other electrophotographic processes are omitted. Each configuration of the image forming apparatus 3 and the operation during image formation are the same as those of the process cartridge 1 of FIG.

  The configurations of the process cartridge and the image forming apparatus according to the present embodiment are not limited to these, and conventionally known configurations may be applied as the configurations of the electrophotographic process cartridge and the image forming apparatus. That is, conventionally known ones are appropriately employed as necessary for the charging unit, latent image forming unit, developing unit, transfer unit, image carrier cleaning unit, charge eliminating unit, sheet feeding unit, transport unit, image control unit, and the like. The These configurations are not particularly limited in the present embodiment.

  Hereinafter, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples.

<Example 1>
[Preparation of dispersion for forming resin coating layer]
4 parts by mass of a styrene / acrylic resin (styrene: methyl methacrylate = 50: 50 (molar ratio), Mw: 30,000) was added to 40 parts by mass of toluene to prepare a resin lacquer 1. 0.5 parts by mass of titanium oxide (manufactured by Teika, MT-01) was added to 134 parts by mass of this resin lacquer, and stirred at 5,000 rpm for 10 minutes using a homogenizer (manufactured by IKA, Ultra Turrax). Thus, a dispersion 1 for forming a resin coating layer was produced. Also, 2 parts by mass of aluminum oxide (Cabot, SpectrA151) was added to 10 parts by mass of the resin lacquer 1 and stirred for 10 minutes at 5,000 rpm using a homogenizer to prepare a dispersion 2 for forming a resin coating layer. .

[Preparation of resin-coated carrier 1]
22.5 parts by mass of the dispersion liquid 1 for forming a resin coating layer was mixed with 100 parts by mass of ferrite particles having a volume average particle size of 70 μm. Furthermore, this mixture was put into a vacuum degassing kneader, stirred for 30 minutes while being heated to 80 ° C., and further stirred under reduced pressure to remove the solvent, thereby obtaining coated particles 1. Next, 100 parts by mass of coating particles 1 were charged in a composite fluidized bed coating apparatus (MP01 SFP, manufactured by Paulek), screen mesh 0.5 mm, rotating impeller 1,000 rpm, exhaust air volume 1.2 m ³ / min, coating speed 2 The coating particles 1 were coated with the resin coating layer-forming dispersion 2 under the conditions of 0.5 g / min, temperature of 80 ° C., and time of 60 minutes. After taking out from the apparatus, sieving was performed with a 105 μm mesh to remove agglomerates to obtain a resin-coated carrier 1.

[Measurement of number average agglomerated diameter of conductive particle domain]
The number average aggregate diameter of the conductive particle domains was measured by the following method. The conductive particle domain exposed on the surface of the resin-coated layer of the resin-coated carrier was photographed with a magnification of 300,000 times using an electron microscope (manufactured by Hitachi High-Technologies Corporation, S4100), and image analysis was performed from the photograph. Using an apparatus (manufactured by Nireco, LUZEX AP), the agglomerated diameter of the conductive particles was measured by a horizontal ferret diameter (FIRE H). The number of conductive particles measured is 50, and if one field of view is insufficient, the number of fields is increased until the number of measurements reaches 50, and the average value of the 50 particles is exposed on the surface of the resin coating layer. The number average agglomeration diameter of the active particle domain was used. The number average agglomerated diameter of the conductive particle domains contained in the resin coating layer is obtained by preparing a thin piece of a resin-coated carrier using a microtome and using the electron microscope (S4100) at a magnification of 300,000 times. A cross-section of the sample was taken, and the aggregate diameter of the conductive particles was measured with a horizontal ferret diameter (FIRE H) using an image analyzer (LUZEX AP) from the photograph, and 50 pieces obtained in the same procedure. The average value was defined as the number average aggregation diameter of the conductive particle domains contained in the resin coating layer.

  The number average aggregate diameter Da of the conductive particle domains exposed on the surface of the resin coating layer of the resin-coated carrier 1 is 98 nm, and the number average aggregate diameter Db of the conductive particle domains contained in the resin coating layer is 20 nm. It was Db / Da = 0.204.

[Production of Toner 1]
Linear polyester (linear polyester obtained from terephthalic acid, bisphenol A, glycerin: number average molecular weight Mn = 3,500, weight average molecular weight Mw = 12,000)
90 parts by mass Magenta pigment (CI Pigment Red 57-1, manufactured by Dainichi Seika Kogyo Co., Ltd.) 3 parts by mass Paraffin wax (manufactured by Nippon Seiwa Co., Ltd., HNP-9) 7 parts by mass After the above materials were premixed The obtained slab was kneaded with an extruder, rolled, cooled, crushed and then pulverized with a jet mill. Further, the coarse powder and fine powder classified by a wind classifier were removed to obtain toner particles 1 having a volume average particle size of 9.0 μm.

  1. 0.5 parts by mass of rutile type titania having a number average particle size of 35 nm obtained by surface treatment of toner particles 1 with HMDS (hexamethyldisilazane) and silica particles having a volume average particle size of 60 nm obtained by surface treatment with silicone oil. Toner 1 was obtained by adding 5 parts by mass and stirring and mixing with a Henschel mixer. The volume average particle diameter D50v of this toner was measured and found to be 9.5 μm.

[Preparation of Developer 1]
8 parts by mass of the obtained toner 1 and 100 parts by mass of the resin-coated carrier 1 were mixed to prepare a two-component developer.

[Image quality evaluation]
Using a color image forming device (manufactured by Fuji Xerox, DocuCentreColor500 modified machine), image formation is performed on paper (Fuji Xerox, C2 paper) at a development process speed of 200 mm / sec. The state was visually evaluated according to the following criteria. The results are shown in Table 1.
○: Image level with no problem in actual use △: Output image is low quality ×: Output image is low quality, and toner contamination occurs inside the copier

<Example 2>
The homogenizer rotational speed of the dispersion liquid 1 for resin coating layer formation is 7,000 rpm, the aluminum oxide of the dispersion liquid 2 for resin coating layer formation is titanium oxide (Fuji Titanium, TA-500), and the homogenizer rotational speed is 7,000 rpm. A resin-coated carrier 2 was produced in the same manner as in Example 1 except that. The number average aggregation diameter Da of the conductive particle domains exposed on the surface of the resin coating layer 2 of the resin-coated carrier 2 is 682 nm, and the number average aggregation diameter Db of the conductive particle domains contained in the resin coating layer is 12 nm. And Db / Da = 0.018. A developer was prepared in the same manner as in Example 1, and the image quality was evaluated. The results are shown in Table 1.

<Example 3>
Resin-coated carrier in the same manner as in Example 1 except that the titanium oxide of the dispersion liquid 1 for forming the resin coating layer is aluminum oxide (SpectrAl51) and the homogenizer rotational speed of the dispersion liquid 2 for forming the resin coating layer is 3,000 rpm. 3 was produced. The number average aggregation diameter Da of the conductive particle domains exposed on the surface of the resin coating layer 3 of the resin-coated carrier 3 is 154 nm, and the number average aggregation diameter Db of the conductive particle domains contained in the resin coating layer is 97 nm. And Db / Da = 0.630. A developer was prepared in the same manner as in Example 1, and the image quality was evaluated. The results are shown in Table 1.

<Example 4>
A resin-coated carrier 4 was produced in the same manner as in Example 1, except that the homogenizer rotation speed of the dispersion liquid 1 for resin coating layer formation was 7,000 rpm. The number average aggregation diameter Da of the conductive particle domains exposed on the resin coating layer surface of the resin-coated carrier 4 is 98 nm, and the number average aggregation diameter Db of the conductive particle domains contained in the resin coating layer is 12 nm. It was Db / Da = 0.122. A developer was prepared in the same manner as in Example 1, and the image quality was evaluated. The results are shown in Table 1.

<Example 5>
A resin-coated carrier 5 was produced in the same manner as in Example 1 except that the aluminum oxide of the dispersion liquid 2 for forming the resin coating layer was changed to titanium oxide (TA-500, manufactured by Fuji Titanium Co., Ltd.). The number average aggregate diameter Da of the conductive particle domains exposed on the surface of the resin coating layer 5 of the resin-coated carrier 5 is 987 nm, and the number average aggregate diameter Db of the conductive particle domains contained in the resin coating layer is 20 nm. And Db / Da = 0.020. A developer was prepared in the same manner as in Example 1, and the image quality was evaluated. The results are shown in Table 1.

<Comparative Example 1>
[Preparation of dispersion for forming resin coating layer]
5 parts by mass of titanium oxide (manufactured by Teika, MT-01) was added to the resin lacquer 1 and stirred for 10 minutes at 5,000 rpm using a homogenizer to prepare a dispersion for forming a resin coating layer.

[Preparation of resin-coated carrier 2]
22.5 parts by mass of the dispersion liquid for forming a resin coating layer was mixed with 100 parts by mass of ferrite particles having a volume average particle size of 70 μm. Furthermore, this mixture was put into a vacuum degassing type kneader, stirred for 30 minutes while being heated to 80 ° C., and further stirred under reduced pressure to remove the solvent. After taking out from the apparatus, sieving was carried out with a 105 μm mesh to remove aggregates, and a resin-coated carrier 6 was obtained.

  The number average aggregation diameter Da of the conductive particle domains exposed on the surface of the resin coating layer 6 of the resin-coated carrier 6 is 38 nm, and the number average aggregation diameter Db of the conductive particle domains contained in the resin coating layer is 46 nm. It was Db / Da = 1.21.

  A developer was prepared in the same manner as in Example 1, and the image quality was evaluated. The results are shown in Table 1.

<Comparative example 2>
The titanium oxide of the dispersion liquid 1 for forming the resin coating layer is carbon black (Regal 330 manufactured by Cabot Corporation), the homogenizer rotation speed is 7,000 rpm, and the aluminum oxide of the dispersion liquid 2 for forming the resin coating layer 2 is titanium oxide (manufactured by Fuji Titanium Corporation). TA-500), and resin-coated carrier 7 was produced in the same manner as in Example 1 except that the rotation speed of the homogenizer was 3,000 rpm. The number average aggregate diameter Da of the conductive particle domains exposed on the resin coating layer surface of the resin coated carrier 7 is 1,850 nm, and the number average aggregate diameter Db of the conductive particle domains contained in the resin coating layer is 4 nm and Db / Da = 0.002. A developer was prepared in the same manner as in Example 1, and the image quality was evaluated. The results are shown in Table 1.

<Comparative Example 3>
Resin-coated carrier 8 was produced in the same manner as in Example 1, except that the titanium oxide of dispersion liquid 1 for forming the resin coating layer was carbon black (Regal 330, manufactured by Cabot Corporation) and the homogenizer rotation speed was 7,000 rpm. The number average aggregate diameter Da of the conductive particle domains exposed on the surface of the resin coating layer of the resin-coated carrier 8 is 98 nm, and the number average aggregate diameter Db of the conductive particle domains contained in the resin coating layer is 4 nm. It was Db / Da = 0.041. A developer was prepared in the same manner as in Example 1, and the image quality was evaluated. The results are shown in Table 1.

<Comparative Example 4>
The resin-coated carrier 9 was prepared in the same manner as in Example 1 except that the aluminum oxide in the dispersion liquid 2 for resin coating layer formation was titanium oxide (TA-500, manufactured by Fuji Titanium Co., Ltd.) and the homogenizer rotation speed was 3,000 rpm. Produced. The number average aggregation diameter Da of the conductive particle domains exposed on the surface of the resin coating layer 9 of the resin coated carrier 9 is 1,850 nm, and the number average aggregation diameter Db of the conductive particle domains contained in the resin coating layer is 20 nm and Db / Da = 0.111. A developer was prepared in the same manner as in Example 1, and the image quality was evaluated. The results are shown in Table 1.

  As described above, the developers of Examples 1 to 5 stably obtained high-quality images over a long period of time as compared with the developers of Comparative Examples 1 to 4.

  DESCRIPTION OF SYMBOLS 1 Process cartridge, 3 Image forming apparatus, 10 Charging apparatus, 12 Exposure apparatus, 14 Photoconductor, 16 Developing apparatus, 18 Transfer roll, 20 Cleaning blade, 22 Fixing roll, 24 Recording paper.

Claims (7)

A carrier core,
A resin coating layer containing a coating resin and conductive particles, and covering the surface of the carrier core material;
Have
The resin coating layer has a two-layer structure of an inner layer and an outer layer formed by using at least a coating liquid for an inner layer and a coating liquid for an outer layer,
At least a portion of the conductive particles is exposed on the surface of the outer layer,
The number-average aggregate diameters of the exposed conductive particles domains on the surface of the outer layer (Da) is much larger than the number-average aggregate diameter (Db) of the conductive particles domains contained within said layer,
A carrier for developing an electrostatic charge image, wherein the number average aggregation diameters Da and Db of the conductive particle domains are in the range of 5 nm to 1,000 nm . The number average aggregation diameters Da and Db of the conductive particle domains are 0 . The carrier for developing an electrostatic charge image according to claim 1, wherein 005 ≦ (Db / Da) <1.   An electrostatic charge image developing developer comprising the electrostatic charge image developing carrier according to claim 1.   A developer cartridge comprising the developer for developing an electrostatic charge image according to claim 3. An image carrier, and developing means for developing the electrostatic latent image formed on the surface of the image carrier using a developer to form a toner image,
The process cartridge according to claim 3, wherein the developer is an electrostatic charge image developing developer according to claim 3. An image carrier,
Charging means for charging the surface of the image carrier;
Latent image forming means for forming an electrostatic latent image on the surface of the image carrier;
Developing means for developing the electrostatic latent image formed on the surface of the image carrier using a developer to form a toner image;
Transfer means for transferring the developed toner image to a transfer medium;
With
The image forming apparatus according to claim 3, wherein the developer is a developer for developing an electrostatic image according to claim 3. A charging step for charging the surface of the image carrier;
A latent image forming step of forming an electrostatic latent image on the surface of the image carrier;
A developing step of developing the electrostatic latent image formed on the surface of the image carrier using a developer to form a toner image;
A transfer step of transferring the developed toner image to a transfer target;
With
The image forming method according to claim 3, wherein the developer is a developer for developing an electrostatic image according to claim 3.

Images