JP2011197568A - Carrier for electrostatic charge image development, electrostatic charge image developer, process cartridge, image forming apparatus and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carrier for electrostatic charge image development which suppresses the occurrence of voids of an image.SOLUTION: The carrier for electrostatic charge image development comprises a core particle and a resin coating layer containing niobium-doped titanium dioxide particles and coating the core particle; and the carrier has a water content of 0.1 mass% or more, and 2.0 mass% or less.

Description

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

  Conventionally, in electrophotography, an electrostatic charge image is formed on an electrostatic latent image holding member (photosensitive member) or electrostatic recording member using various means, and electrostatic particles called toner are attached to the electrostatic latent image. A method of developing a charge image is used. In developing an electrostatic charge image, toner and carrier are mixed and triboelectrically charged to give an appropriate amount of positive or negative charge to the toner. Carriers are generally classified into a coated carrier having a coating layer on the surface and an uncoated carrier having no coating layer, and the coated carrier is excellent in consideration of the developer life and the like.

  Although there are various characteristics required for the coat carrier, it is required to impart an appropriate charge amount (charge amount or charge distribution) to the toner and maintain the charge amount over a long period of time. For this purpose, it is important not to change the chargeability of the toner even in response to environmental changes such as the impact resistance, friction resistance, temperature and humidity of the carrier, and various coated carriers have been proposed.

  For example, a copolymer of a nitrogen-containing fluorinated alkyl (meth) acrylate and a vinyl monomer or a copolymer of a fluorinated alkyl (meth) acrylate and a nitrogen-containing vinyl monomer is coated on the surface of the carrier core, It has been proposed to obtain a long-life coat carrier (see, for example, Patent Document 1 or Patent Document 2).

  With the development of color in electrophotographic technology, when a developer containing a carrier with carbon black added to the resin coating layer on the surface of the carrier is used, the resin coating layer is scraped off due to the long-term use of the developer. When mixed with toner and developed, color smear of the printed image and color reproducibility may be deteriorated. For this reason, in the resin coating layer, a carbon black concentration gradient is applied from the vicinity of the core to the surface to eliminate the carbon black on the surface layer (see, for example, Patent Document 3), or the resin coating layer has a two-layer structure and carbon black is formed as an inner layer. The use of white conductive powder for the outer layer (for example, see Patent Document 4) has been studied.

  Further, as white conductive powder, oxides such as titanium oxide, alumina, silica, etc., metal oxides such as zinc oxide and tin oxide having relatively low electric resistance, and metal oxides doped with metal to further reduce electric resistance, for example, Antimony-doped tin oxide (see, for example, Patent Document 5), tin-doped indium oxide, aluminum-doped zinc oxide, and the like have been reported. In view of reducing the electric resistance, indium oxide is most preferably used.

JP 61-80161 A JP 61-80162 A JP-A-8-179570 JP-A-8-286429 JP 2007-248614 A

  An object of the present invention is to provide a carrier for developing an electrostatic image in which occurrence of white spots in an image is suppressed.

  That is, the invention according to claim 1 includes core material particles and a resin coating layer that includes titanium dioxide particles doped with niobium and covers the core material particles, and the water content is 0.1% by mass. The electrostatic charge image developing carrier has a content of 2.0% by mass or less.

  The invention according to claim 2 is the electrostatic image developing carrier according to claim 1, wherein the molar ratio of niobium and titanium contained in the titanium dioxide particles doped with niobium is 1: 200 to 1: 5. is there.

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

  The invention according to claim 4 is the electrostatic charge image developer according to claim 3, wherein the electrostatic charge image developing toner has a shape factor SF1 of 110 or more and 145 or less.

The invention according to claim 5 contains the electrostatic charge image developer according to claim 3 or claim 4 and develops the electrostatic charge image formed on the surface of the latent image holding body with the electrostatic charge image developer. Developing means for forming a toner image;
At least one selected from the group consisting of a latent image holder, a charging means for charging the surface of the latent image holder, and a cleaning means for removing toner remaining on the surface of the latent image holder. It is a process cartridge that can be attached to and detached from the image forming apparatus.

  According to a sixth aspect of the present invention, there is provided a latent image holding member, a charging unit that charges the surface of the latent image holding member, an electrostatic charge image forming unit that forms an electrostatic charge image on the surface of the latent image holding member, and the electrostatic charge. A developing means for developing an image with the electrostatic charge image developer according to claim 3 to form a toner image, a transfer means for transferring the toner image to a recording medium, and the toner image on the recording medium. An image forming apparatus comprising: a fixing unit that fixes

  The invention according to claim 7 is the charging step for charging the surface of the latent image holding member, the electrostatic charge image forming step for forming an electrostatic charge image on the surface of the latent image holding member, and the electrostatic charge image according to claim 3 or claim. A development step of developing the electrostatic image developer according to Item 4 to form a toner image, a transfer step of transferring the toner image to a recording medium, and a fixing step of fixing the toner image to the recording medium; Is an image forming method.

  According to the first aspect of the present invention, there is provided an electrostatic charge image developing carrier in which the occurrence of white spots in an image is suppressed.

  According to the invention which concerns on Claim 2, the resistance of the titanium dioxide particle doped with niobium is adjusted to a desirable range.

  According to the third aspect of the present invention, there is provided an electrostatic charge image developer in which occurrence of white spots in an image is suppressed.

  According to the fourth aspect of the present invention, an image having excellent resolution can be formed as compared with a case where the shape factor SF1 of the electrostatic charge image developing toner is out of the range of 110 to 145.

  According to the fifth aspect of the present invention, it is possible to facilitate the handling of the electrostatic charge image developer in which the occurrence of white spots in the image is suppressed, and the adaptability to various image forming apparatuses can be enhanced.

  According to the sixth aspect of the present invention, there is provided an image forming apparatus using an electrostatic charge image developer that suppresses occurrence of white spots in an image.

  According to the seventh aspect of the present invention, there is provided an image forming method using an electrostatic charge image developer that suppresses occurrence of white spots in an image.

1 is a schematic configuration diagram illustrating an image forming apparatus according to a first embodiment. It is a schematic block diagram which shows the image forming apparatus which concerns on 2nd embodiment. It is a schematic block diagram which shows an example of the process cartridge which concerns on this embodiment.

  Hereinafter, embodiments of an electrostatic charge image developing carrier, an electrostatic charge image developer, a process cartridge, an image forming apparatus, and an image forming method according to the present invention will be described in detail.

  The electrostatic image developing carrier according to the present embodiment (hereinafter, sometimes simply referred to as “carrier”) includes core particles and titanium dioxide particles doped with niobium (hereinafter referred to as specific titanium dioxide particles). And a resin coating layer that covers the core particles, and the moisture content is 0.1% by mass or more and 2.0% by mass or less.

  In recent years, as the use situation of electrophotography is diversified, the use situation is stressful to carriers. In particular, when an image is output continuously for a long time in a high-temperature and high-humidity environment, the carrier absorbs moisture, so that acidic components in the resin are easily eluted in the resin coating layer. Here, as an acidic component in the resin, an unreacted monomer that contains an acid group such as a carboxyl group, or an acid group such as a carboxyl group generated by hydrolysis of the resin, which is an unreacted product of the constituent resin. Examples include substances. Even when indium oxide with excellent resistance controllability is added as a conductive agent in the resin coating layer due to the elution of acidic components in the resin, it loses conductivity by reacting with the acidic component, and the resin coating layer conducts. As a result, the carrier resistance deteriorates. For this reason, in such a situation, the occurrence of white spots in the image called starvation may be a problem.

Starvation is a phenomenon in which a thin white portion of toner is generated at the rear end portion in the output direction of an image, and is presumed to occur for the following reason.
When the toner held by the carrier moves to the photoconductor, the reverse charge of the charge of the toner is accumulated in the carrier. When the reverse charge is accumulated in the carrier in this way, a part of the toner is attracted by the charge and may adhere to the carrier again. As a result, it is assumed that white spots occur. White spots are more likely to occur because the higher the carrier resistance, the more difficult the charges are removed. On the other hand, a non-uniform glen structure or a structure with element variations is less likely to cause starvation because reverse charge accumulation is less likely to occur.
Starvation is likely to occur at an edge portion where an image changes from a low density image to a high density image in the sub-scanning direction, for example. In this case, the density at the rear end of the low density image is lowered. This is presumably because the toner adhering to the low density image portion is pulled back to the developer side by the electric field of the high density image portion.

  The present inventors dispersed niobium-doped titanium dioxide particles having higher acid resistance than indium and resistance control similar to indium in a coating resin, and coated the core particles with the coating resin. A resin-coated carrier was used. As a result, when continuously outputting images over a long period of time in a high-temperature and high-humidity environment, the resin coating layer is stable without causing deterioration in conductivity due to acidic components in the resin eluted by moisture absorbed. By maintaining the conductivity, the occurrence of white spots in the image could be suppressed.

  A method for producing the specific titanium dioxide particles used in the present embodiment is not particularly limited, but a dry vapor phase method such as a physical method such as pulverization, a flame method, a plasma method, a vacuum deposition method, or a sputtering method. In addition, wet liquid phase methods such as coprecipitation method, uniform precipitation method, metal alkoxy method, spray drying method and the like can be mentioned. From the viewpoint of controllability of particle diameter, the dry gas phase method is preferable.

  As a specific method for producing titanium dioxide particles, for example, titanium tetrabutoxide is used as a titanium raw material, niobium pentaboxide is used as a niobium raw material, ethanol is added if necessary, the viscosity of the solution is lowered, and the film is covered with a film or the like And stirring with a stirrer or the like while avoiding contact with moisture, and blowing these liquid raw materials into an ultra-high temperature plasma in an argon atmosphere using an argon carrier gas.

  The carrier according to this embodiment using specific titanium dioxide particles as a conductive agent exhibits stable resistance controllability. The reason is not clear, but it seems to be due to the faster flow of electrons due to the doped metal.

  The amount of niobium to be doped is preferably 1: 200 to 1: 5, more preferably 1: 100 to 1:10, in the molar ratio of niobium and titanium contained in the specific titanium dioxide particles. When the amount of niobium is less than 1: 200, the effect of lowering the electric resistance is less than that of titanium oxide, and when the amount of niobium is increased from 1: 5, no further effect of reducing the resistance can be obtained. In addition, it is difficult to produce niobium more than 1: 5.

  The volume average particle diameter of the specific titanium dioxide particles is preferably 10 nm or more and 1000 nm or less, and more preferably 15 nm or more and 200 nm or less. When the volume average particle diameter of the specific titanium dioxide particles is smaller than 10 nm, it is difficult to disperse the specific titanium dioxide particles in the resin coating layer, and the strength of the resin coating layer may be lowered. When the volume average particle diameter of the specific titanium dioxide particles is larger than 1000 nm, the specific titanium dioxide particles are easily exposed from the resin coating layer.

  The volume average particle diameter of specific titanium dioxide particles is measured using a nanoparticle analyzer Delsa Nano S (manufactured by Beckman Coulter).

  Surface treatment may be performed on specific titanium dioxide particles for dispersibility control and resistance control. Examples of the compound used for such treatment include a silane coupling agent, an aluminum coupling agent, a titanium coupling agent, a silicone oil, or a surfactant. The treatment amount at that time is preferably 1% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 10% by mass or less with respect to the particles.

Measurement of the amount of niobium doped in specific titanium dioxide particles (molar ratio of niobium and titanium contained in specific titanium dioxide particles) is determined by the following method.
Specific titanium dioxide particles containing niobium are dissolved in a mixed solution of sulfuric acid and hydrofluoric acid, and then analyzed by a plasma emission spectroscopic analyzer to measure the molar ratio. Separately prepare niobium oxide and titanium oxide mixture with the same molar ratio of this particle and this particle to niobium and titanium, and use an X-ray diffraction analyzer to oxidize with the intensity of titanium oxide and niobium oxide using CuKα ray X-ray. The amount of niobium is measured and the amount of doped niobium is measured.
Examples of a method for extracting specific titanium dioxide particles from the carrier according to the present embodiment include the following methods.
A carrier weighed in a beaker is mixed with a coating resin-soluble organic solvent (for example, chloroform) and ultrasonicated with an ultrasonic dispersing device, and a magnet is applied to the bottom of the beaker to coat the organic solvent containing the coating resin and titanium dioxide particles. to recover. This operation is repeated three times to completely separate the core particles. The collected organic solvent is centrifuged to dry the precipitate, and titanium dioxide particles are extracted.

  The moisture content of the carrier according to the present embodiment is 0.1% by mass or more and 2.0% by mass or less. Desirably, it is 0.5 mass% or more and 1.5 mass% or less. When the water content is less than 0.1% by mass, the effect of the conductive agent is exerted too much, and resistance control may be difficult. If the water content is more than 2.0% by mass, the adverse effect due to the water may be greater than the effect of the conductive agent, leading to a decrease in carrier resistance.

  The moisture content of the carrier according to this embodiment is adjusted to a desired range by adjusting the drying conditions (drying time, drying temperature, etc.) of the kneader when the resin coating layer is formed by the kneader coater method described later. Is done.

  The moisture content of the carrier is measured using a Karl Fischer moisture meter (MKA-610; manufactured by Kyoto Electronics Industry Co., Ltd.) after leaving the carrier for 1 hour in a high temperature and high humidity environment (30 ° C., 85% RH). Carried out.

  The carrier according to the present embodiment is a resin-coated carrier having core material particles and a resin coating layer that coats the core material particles. Examples of the core particles used here include magnetic metals such as iron, steel, nickel and cobalt, magnetic oxides such as ferrite and magnetite, and glass beads.

  The resin constituting the resin coating layer of the carrier according to this embodiment includes polyolefin resins such as polyethylene and polypropylene; polystyrene, acrylic resin, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl Polyvinyl or polyvinylidene resins such as ether and polyvinyl ketone; vinyl chloride / vinyl acetate copolymer, styrene / acrylic acid copolymer; straight silicone resin composed of organosiloxane bond or modified product thereof; polytetrafluoroethylene, polyfluoride Fluorine resins such as vinyl fluoride, polyvinylidene fluoride, and polychlorotrifluoroethylene; polyester; polyurethane; polycarbonate; urea / formaldehyde resin, etc. Mino resins; and epoxy resins. Among these, in order to suppress the contamination of the carrier surface, it is desirable to contain a polymer or silicone resin containing fluorine which is a low surface energy material.

  In particular, the fluorine-containing polymer is, as a monomer, perfluorooctylethyl acrylate, perfluorooctylethyl methacrylate, perfluorohexylethyl acrylate, perfluorohexylethyl methacrylate, or other fluorine-containing acrylic acid ester or methacrylic acid ester, Alternatively, a resin obtained by polymerizing polyvinylidene fluoride is preferable. Further, when positive chargeability is imparted, it is desirable to use an acrylic monomer. Specifically, a resin obtained by polymerizing methacrylic acid ester or acrylic acid ester such as methyl methacrylate, methyl acrylate, ethyl methacrylate, ethyl acrylate, butyl methacrylate, butyl acrylate and the like is preferable.

  Examples of the method of forming the resin coating layer on the surface of the core material particles include, for example, an immersion method in which the core material particles are immersed in the resin coating layer forming solution and spraying the resin coating layer forming solution on the surface of the core material particles. A fluidized bed method in which a resin coating layer forming solution is sprayed in a state in which core particles are fluidized in a fluidized bed, and a kneader in which the core material particles and the resin coating layer forming solution are mixed in a kneader coater to remove the solvent. Examples of the coater method include a kneader coater method.

  The solvent used for the resin coating layer forming solution is not particularly limited as long as it dissolves the coating resin. Specifically, aromatic hydrocarbons such as toluene and xylene; ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran and dioxane are used.

  The film thickness of the resin coating layer in the carrier according to this embodiment is preferably 0.1 μm or more and 10 μm or less, and more preferably 0.3 μm or more and 5 μm or less. The average particle diameter of the core material particles of the carrier according to this embodiment is desirably 10 μm or more and 500 μm or less, and more desirably 30 μm or more and 150 μm or less. The amount of the specific titanium dioxide particles is preferably 3% by mass or more and 20% by mass or less, more preferably 5% by mass or more and 10% by mass or less, with respect to the resin component constituting the resin coating layer.

  The volume average particle diameter of the carrier according to this embodiment is preferably 15 μm or more and 510 μm or less.

  Moreover, you may use together other conductive materials other than specific titanium dioxide particle for the resin coating layer of the carrier which concerns on this embodiment. For example, metals such as gold, silver, copper, titanium oxide, zinc oxide, tin oxide, barium sulfate, aluminum borate, potassium titanate, tin oxide, tin oxide doped with antimony, tin-doped indium oxide, Examples include zinc oxide doped with aluminum, resin particles coated with metal, and carbon black.

<Electrostatic image developer>
The electrostatic image developer according to the exemplary embodiment (hereinafter, simply referred to as “developer”) may be referred to as a carrier and an electrostatic image developing toner according to the exemplary embodiment (hereinafter, simply referred to as “toner”). A). The developer according to this embodiment is prepared by mixing the carrier and toner according to this embodiment at an appropriate blending ratio. The carrier content ((carrier) / (carrier + toner) × 100) is preferably in the range of 85% by mass to 99% by mass, more preferably in the range of 87% by mass to 98% by mass, and still more preferably 89%. The range is from mass% to 97 mass%.

Hereinafter, the toner used for the electrostatic charge image developer according to the exemplary embodiment will be described.
The toner according to the exemplary embodiment includes a binder resin and a colorant as main components. Binder resins used include styrenes such as styrene and chlorostyrene; monoolefins such as ethylene, propylene, butylene, and isobutylene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, and vinyl acetate; Α-methylene aliphatic monocarboxylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, dodecyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate Vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether; homopolymers or copolymers such as vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropenyl ketone, etc.

  In particular, typical binder resins include polystyrene, styrene / alkyl acrylate copolymer, styrene / alkyl methacrylate copolymer, styrene / acrylonitrile copolymer, styrene / butadiene copolymer, styrene / maleic anhydride. Examples include copolymers, polyethylene, and polypropylene. Further examples include polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin, and waxes. Among these, polyester is particularly effective as a binder resin. Specifically, a polyester resin made of a polycondensate containing bisphenol A and polyvalent aromatic carboxylic acid as main monomer components is desirable.

  The binder resin has a softening temperature of 70 ° C. or higher and 150 ° C. or lower, a glass transition temperature of 40 ° C. or higher and 70 ° C. or lower, a number average molecular weight of 2000 or higher and 50000 or lower, a weight average molecular weight of 8000 or higher and 150,000 or lower, and an acid value of 5 or higher. It is desirable that the hydroxyl value is in the range of 30 or less and 5 or more and 40 or less.

  Typical toner colorants include carbon black, nigrosine, aniline blue, calcoil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, Rose Bengal, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 57: 1, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 12, C.I. I. Pigment blue 15: 1, C.I. I. Pigment blue 15: 3.

The toner particles are produced, for example, by a kneading and pulverizing method in which a binder resin, a colorant, and a release agent, a charge control agent, and the like are kneaded, pulverized, and classified; A method of changing the shape by mechanical impact force or thermal energy; a dispersion obtained by emulsifying and dispersing a binder resin; and a dispersion of a colorant and, if necessary, a release agent and a charge control agent Emulsion aggregation method in which toner particles are obtained by mixing, aggregating and heat-fusing to obtain toner particles; a dispersion monomer formed by emulsion polymerization of a binder resin polymerizable monomer, a colorant, and a release agent as required An emulsion polymerization aggregation method in which toner particles are obtained by mixing with a dispersion of a charge control agent, etc., and agglomerating and heat-fusing; a polymerizable monomer to obtain a binder resin, a colorant, and if necessary Suspension polymerization method in which a solution of a mold release agent, charge control agent, etc. is suspended in an aqueous solvent and polymerized; Agent, and a release agent, if necessary, a dissolution suspension method and a solution such as a charge control agent granulated suspended in an aqueous solvent; or the like is used.
Further, a manufacturing method may be performed in which the toner particles obtained by the above method are used as a core, and resin particles are further adhered and heat-fused to have a core-shell structure. Among these, the toner according to the exemplary embodiment is desirably a toner (emulsion aggregation toner) obtained by an emulsion aggregation method or an emulsion polymerization aggregation method.

These toner particles may be added with a fluidizing agent such as silica, titania or alumina, or an external additive such as a cleaning aid or a transfer aid such as polystyrene particles, polymethylmethacrylate particles or polyvinylidene fluoride particles. Good. A toner is obtained by adding an external additive to the toner particles. In particular, hydrophobic silica having a primary average particle size of 5 nm to 30 nm is preferably used.

  Additives include ingredients such as salicylic acid metal salts, metal-containing azo compounds, charge control agents such as nigrosine and quaternary ammonium salts, and anti-offset agents such as low molecular weight polypropylene, low molecular weight polyethylene and high molecular alcohol. May be. In particular, a low molecular weight polypropylene having a weight average molecular weight of 500 or more and 5000 or less is desirable. The average particle diameter of the toner according to the exemplary embodiment is less than 30 μm, and preferably in the range of 4 μm to 20 μm.

The toner according to the exemplary embodiment preferably has a shape factor SF1 of 110 or more and 145 or less, more preferably 115 or more and 140 or less, and still more preferably 120 or more and 135 or less. When the shape factor SF1 is 110 or more and 145 or less, an image having excellent resolution is formed.
The shape factor SF1 is quantified mainly by analyzing a microscope image or a scanning electron microscope image with an image analyzer, and is obtained as follows, for example. For measurement of the shape factor SF1, first, an optical microscope image of toner spread on a slide glass is taken into a Luzex image analyzer through a video camera, and SF1 of the following formula is calculated for 50 or more particles to obtain an average value. Can be obtained.

SF1 = (ML ² / A) × (π / 4) × 100
Here, ML is the absolute maximum length of the particle, and A is the projected area of the particle.

<Image Forming Apparatus, Image Forming Method, and Process Cartridge>
The image forming apparatus according to the present embodiment includes a latent image holding member, a charging unit that charges the surface of the latent image holding member, an electrostatic charge image forming unit that forms an electrostatic charge image on the surface of the latent image holding member, Developing means for developing an electrostatic charge image with the electrostatic charge image developer according to the present embodiment to form a toner image, transfer means for transferring the toner image to a recording medium, and fixing the toner image on the recording medium Fixing means. The image forming apparatus according to the present embodiment may include a cleaning unit or the like for removing toner remaining on the surface of the latent image holding member as necessary.

  In this image forming apparatus, for example, the portion including the developing unit may be a cartridge structure (process cartridge) that can be attached to and detached from the main body of the image forming apparatus, and the process cartridge is related to the present embodiment. A developing means for storing an electrostatic charge image developer and developing the electrostatic charge image formed on the surface of the latent image holding body with the electrostatic charge image developer to form a toner image, a latent image holding body, and the latent image holding At least one selected from the group consisting of a charging means for charging the surface of the body and a cleaning means for removing the toner remaining on the surface of the latent image holding body. The process cartridge according to the embodiment is preferably used.

  A charging process for charging the surface of the latent image holding body, an electrostatic charge image forming process for forming an electrostatic charge image on the surface of the latent image holding body, and the electrostatic charge image according to the present embodiment. A developing step of developing with the electrostatic charge image developer according to the invention to form a toner image, a transfer step of transferring the toner image to a recording medium, and a fixing step of fixing the toner image to the recording medium. The image forming method according to the embodiment is performed.

Hereinafter, an example of the image forming apparatus according to the present embodiment will be described, but the present invention is not limited thereto.
FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus according to the first embodiment. The image forming apparatus 301 includes a charging unit 310, an exposure unit 312, an electrophotographic photosensitive member 314 that is a latent image holding member, a developing unit 316, a transfer unit 318, a cleaning unit 320, and a fixing unit 322. .

  In the image forming apparatus 301, around the electrophotographic photosensitive member 314, a charging unit 310 that is a charging unit that charges the surface of the electrophotographic photosensitive member 314 and the charged electrophotographic photosensitive member 314 are exposed according to image information. An exposure unit 312 that is an electrostatic image forming unit that forms an electrostatic image, a developing unit 316 that is a developing unit that develops the electrostatic image with a developer to form a toner image, and the surface of the electrophotographic photoreceptor 314 The transfer unit 318 that is a transfer unit that transfers the toner image formed on the surface of the recording medium 324 and foreign matters such as toner remaining on the surface of the electrophotographic photosensitive member 314 after the transfer are removed to remove the toner image. A cleaning unit 320 which is a cleaning means for cleaning the surface of the substrate is arranged in this order. A fixing unit 322 that is a fixing unit that fixes the toner image transferred to the recording medium 324 is disposed on the side of the transfer unit 318.

  The operation of the image forming apparatus 301 according to this embodiment will be described. First, the surface of the electrophotographic photosensitive member 314 is charged by the charging unit 310 (charging process). Next, light is applied to the surface of the electrophotographic photosensitive member 314 by the exposure unit 312, and the charged charge in the exposed part is removed, and an electrostatic image is formed according to image information (electrostatic image formation). Process). Thereafter, the electrostatic charge image is developed by the developing unit 316, and a toner image is formed on the surface of the electrophotographic photosensitive member 314 (development process). For example, in the case of a digital electrophotographic copying machine using an organic photoconductor as the electrophotographic photoconductor 314 and using a laser beam as the exposure unit 312, the surface of the electrophotographic photoconductor 314 is negatively charged by the charging unit 310. Then, a digital latent image is formed in a dot shape by the laser beam light, and a toner is applied to a portion irradiated with the laser beam light by the developing unit 316 to be visualized. In this case, a negative bias is applied to the developing unit 316. Next, a recording medium 324 such as paper is superimposed on the toner image at the transfer unit 318, and a charge having a polarity opposite to that of the toner is applied to the recording medium 324 from the back side of the recording medium 324. 324 is transferred (transfer process). The transferred toner image is heated and pressed by a fixing member in the fixing unit 322, and is fused and fixed to the recording medium 324 (fixing step). On the other hand, foreign matters such as toner remaining on the surface of the electrophotographic photosensitive member 314 without being transferred are removed by the cleaning unit 320 (cleaning step). One cycle is completed in a series of processes from charging to cleaning. In FIG. 1, the toner image is directly transferred to the recording medium 324 such as paper by the transfer unit 318, but may be transferred via a transfer body such as an intermediate transfer body.

  Hereinafter, a charging unit, a latent image holding member, an electrostatic charge image forming unit (exposure unit), a developing unit, a transfer unit, a cleaning unit, and a fixing unit in the image forming apparatus 301 of FIG. 1 will be described.

(Charging means)
As the charging unit 310 serving as a charging unit, 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 electrophotographic photosensitive member 314 or may apply an alternating current superimposed thereon. For example, such a charging unit 310 charges the surface of the electrophotographic photosensitive member 314 by generating a discharge in a minute space near the contact portion with the electrophotographic photosensitive member 314. 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.

(Latent image carrier)
The latent image holding member has a function of forming at least a latent image (electrostatic charge image). As the latent image holding member, an electrophotographic photosensitive member is preferably exemplified. The electrophotographic photoreceptor 314 has a coating film containing an organic photoreceptor or the like on the outer peripheral surface of a cylindrical conductive substrate. The coating film is a substrate in which a subbing layer and a photosensitive layer including a charge generating layer containing a charge generating material and a charge transporting layer containing a charge transporting material are formed in this order, if necessary. is there. 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. It may be a single layer type photoreceptor included in the above layer, and is preferably a laminated type photoreceptor. Further, an intermediate layer may be provided between the undercoat layer and 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.

(Static charge image forming means)
There is no particular limitation on the exposure unit 312 which is an electrostatic charge image forming unit (exposure unit). And optical system equipment that exposes the light.

(Development means)
The developing unit 316 that is a developing unit has a function of developing a latent image formed on the latent image holding member with a developer containing toner to form a toner image. Such a developing device is not particularly limited as long as it has the above-described function, and may be selected according to the purpose. For example, an electrostatic image developing toner is electrophotographic using a brush, a roller, or the like. A known developing device having a function of adhering to the photoreceptor 314 may be used. The electrophotographic photosensitive member 314 normally uses a DC voltage, but may be used with an AC voltage superimposed thereon.

(Transfer means)
As the transfer unit 318 serving as a transfer unit, for example, a charge having a polarity opposite to that of the toner is applied to the recording medium 324 from the back side of the recording medium 324 as illustrated in FIG. A transfer roll and a transfer roll pressing device using a conductive roll or a semiconductive roll that transfers directly in contact with the recording medium 324 may be used. A direct current may be applied to the transfer roll as a transfer current applied to the latent image holding member, 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. As a transfer method, a method of directly transferring to a recording medium 324 such as paper or a method of transferring to a recording medium 324 via an intermediate transfer member may be used.

  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, blend material of PC / PAT, and the like can be mentioned. From the viewpoint of mechanical strength, an intermediate transfer belt using a thermosetting polyimide resin is desirable.

(Cleaning means)
As the cleaning unit 320 serving as a cleaning unit, a blade cleaning method, a brush cleaning method, a roll cleaning method, or the like may be selected as long as it cleans foreign matter such as residual toner on the latent image holding member. Absent.

(Fixing means)
The fixing unit 322 as a fixing unit (image fixing device) fixes a toner image transferred to the recording medium 324 by heating, pressing, or heating and pressing, and includes a fixing member.

(recoding media)
Examples of the recording medium 324 to which the toner image is transferred include plain paper, an OHP sheet, and the like used for electrophotographic copying machines, printers, and the like. In order to further improve the smoothness of the image surface after fixing, the surface of the recording medium is also preferably smooth. For example, coated paper with the surface of plain paper coated with resin, art paper for printing, etc. are used. May be.

  Further, in combination with trickle development proposed in Japanese Examined Patent Publication No. 2-21591, stable image formation can be achieved for a long time.

  FIG. 2 is a schematic configuration diagram illustrating a four-tandem color image forming apparatus that is an image forming apparatus according to the second embodiment. The image forming apparatus shown in FIG. 2 is a first to first electrophotographic method that outputs yellow (Y), magenta (M), cyan (C), and black (K) images based on color-separated image data. Fourth image forming units 10Y, 10M, 10C, and 10K (image forming means) are provided. These image forming units (hereinafter sometimes simply referred to as “units”) 10Y, 10M, 10C, and 10K are arranged in parallel at a predetermined distance from each other in the horizontal direction. The units 10Y, 10M, 10C, and 10K may be process cartridges that are detachable from the main body of the image forming apparatus.

Above each of the units 10Y, 10M, 10C, and 10K, an intermediate transfer belt 20 as an intermediate transfer member is extended through each unit. The intermediate transfer belt 20 is provided by being wound around a driving roller 22 and a support roller 24 that are in contact with the inner surface of the intermediate transfer belt 20 that are spaced apart from each other from the left to the right in the drawing. The vehicle travels in the direction toward the unit 10K. A force is applied to the support roller 24 in a direction away from the drive roller 22 by a spring or the like (not shown), and tension is applied to the intermediate transfer belt 20 wound around the both. Further, an intermediate transfer member cleaning device 30 is provided on the side of the image carrier of the intermediate transfer belt 20 so as to face the driving roller 22.
Further, each of the developing devices (developing means) 4Y, 4M, 4C, and 4K of the units 10Y, 10M, 10C, and 10K has yellow, magenta, cyan, and black contained in the toner cartridges 8Y, 8M, 8C, and 8K. The four colors of toner are supplied.

  Since the first to fourth units 10Y, 10M, 10C, and 10K described above have the same configuration, here, the first image that forms the yellow image disposed on the upstream side in the intermediate transfer belt traveling direction is formed. The unit 10Y will be described as a representative. Note that the second to fourth components are denoted by reference numerals with magenta (M), cyan (C), and black (K) instead of yellow (Y) in the same parts as the first unit 10Y. Description of the units 10M, 10C, and 10K will be omitted.

The first unit 10Y includes a photoreceptor 1Y that functions as an image holding member. Around the photosensitive member 1Y, a charging roller 2Y for charging the surface of the photosensitive member 1Y to a predetermined potential, and the charged surface is exposed by a laser beam 3Y based on the color-separated image signal to form an electrostatic charge image. An exposure device (electrostatic image forming means) 3 for forming, a developing device (developing means) 4Y for supplying the charged toner to the electrostatic image and developing the electrostatic image, and transferring the developed toner image onto the intermediate transfer belt 20 A primary transfer roller 5Y (primary transfer unit) that performs the transfer and a photoconductor cleaning device (cleaning unit) 6Y that removes toner remaining on the surface of the photoconductor 1Y after the primary transfer are sequentially arranged.
The primary transfer roller 5Y is disposed inside the intermediate transfer belt 20, and is provided at a position facing the photoreceptor 1Y. Further, a bias power source (not shown) for applying a primary transfer bias is connected to each of the primary transfer rollers 5Y, 5M, 5C, and 5K. Each bias power source varies the transfer bias applied to each primary transfer roller under the control of a control unit (not shown).

Hereinafter, an operation of forming a yellow image in the first unit 10Y will be described. First, prior to the operation, the surface of the photoreceptor 1Y is charged to a potential of about −600V to −800V by the charging roller 2Y.
The photoreceptor 1Y is formed by laminating a photosensitive layer on a conductive substrate (volume resistivity at 20 ° C .: 1 × 10 ⁻⁶ Ωcm or less). This photosensitive layer usually has a high resistance (a resistance equivalent to that of a general resin), but has a property that the specific resistance of the portion irradiated with the laser beam changes when irradiated with the laser beam 3Y. Therefore, a laser beam 3Y is output to the surface of the charged photoreceptor 1Y via the exposure device 3 in accordance with yellow image data sent from a control unit (not shown). The laser beam 3Y is applied to the photosensitive layer on the surface of the photoreceptor 1Y, whereby an electrostatic charge image of a yellow print pattern is formed on the surface of the photoreceptor 1Y.

The electrostatic charge image is an image formed on the surface of the photoreceptor 1Y by charging, and the specific resistance of the irradiated portion of the photosensitive layer is lowered by the laser beam 3Y, and the charged charge on the surface of the photoreceptor 1Y flows. On the other hand, this is a so-called negative latent image formed by the charge remaining in the portion not irradiated with the laser beam 3Y.
The electrostatic charge image formed on the photoreceptor 1Y in this way is rotated to a predetermined development position as the photoreceptor 1Y travels. At this development position, the electrostatic charge image on the photoreceptor 1Y is visualized (developed image) by the developing device 4Y.

In the developing device 4Y, for example, an electrostatic charge image developer containing at least yellow toner and a carrier is accommodated. The yellow toner is triboelectrically charged by being agitated inside the developing device 4Y, and has a charge of the same polarity (negative polarity) as the charged charge on the photoreceptor 1Y, and a developer roll (developer holder). Is held on. As the surface of the photoreceptor 1Y passes through the developing device 4Y, the yellow toner is electrostatically attached to the latent image portion on the surface of the photoreceptor 1Y, and the latent image is developed with the yellow toner. .
From the viewpoint of development efficiency, image graininess, gradation reproducibility, and the like, a bias potential (development bias) in which an AC component is superimposed on a DC component may be applied to the developer holder. Specifically, when the developer holder DC applied voltage Vdc is −300 to −700 V, the developer holder AC voltage peak width Vp-p may be in the range of 0.5 to 2.0 kV.
The photoreceptor 1Y on which the yellow toner image is formed continues to run at a predetermined speed, and the toner image developed on the photoreceptor 1Y is conveyed to a predetermined primary transfer position.

When the yellow toner image on the photoreceptor 1Y is conveyed to the primary transfer position, a primary transfer bias is applied to the primary transfer roller 5Y, and electrostatic force directed from the photoreceptor 1Y to the primary transfer roller 5Y is applied to the toner image. As a result, the toner image on the photoreceptor 1 </ b> Y is transferred onto the intermediate transfer belt 20. The transfer bias applied at this time is a (+) polarity opposite to the polarity (−) of the toner, and is controlled to about +10 μA by the control unit (not shown) in the first unit 10Y, for example.
On the other hand, the toner remaining on the photoreceptor 1Y is removed and collected by the cleaning device 6Y.

Further, the primary transfer bias applied to the primary transfer rollers 5M, 5C, and 5K after the second unit 10M is also controlled according to the first unit.
Thus, the intermediate transfer belt 20 onto which the yellow toner image has been transferred by the first unit 10Y is sequentially conveyed through the second to fourth units 10M, 10C, and 10K, and the toner images of the respective colors are superimposed and transferred in a multiple manner. The

  The intermediate transfer belt 20 onto which the four color toner images have been transferred through the first to fourth units is arranged on the image transfer surface side of the intermediate transfer belt 20, the support roller 24 in contact with the inner surface of the intermediate transfer belt 20. The secondary transfer roller (secondary transfer means) 26 is connected to a secondary transfer portion. On the other hand, a recording paper (recording medium) P is fed at a predetermined timing into a gap where the secondary transfer roller 26 and the intermediate transfer belt 20 are pressed against each other via a supply mechanism, and the secondary transfer bias is supplied to the support roller. 24. The transfer bias applied at this time is a (−) polarity that is the same polarity as the polarity (−) of the toner, and an electrostatic force from the intermediate transfer belt 20 toward the recording paper P is applied to the toner image, and the transfer bias is applied to the intermediate transfer belt 20. The toner image is transferred onto the recording paper P. Note that the secondary transfer bias at this time is determined according to the resistance detected by a resistance detecting means (not shown) for detecting the resistance of the secondary transfer portion, and is voltage-controlled.

  Thereafter, the recording paper P is fed to the pressure contact portion (nip portion) of the pair of fixing rolls in the fixing device (roll-type fixing means) 28, the toner image is heated, and the color-superposed toner image is melted to record the recording paper. Fixed onto P.

  Examples of the recording medium to which the toner image is transferred include plain paper and OHP sheet used for electrophotographic copying machines, printers, and the like.

The recording paper P on which the color image has been fixed is carried out toward the discharge unit, and a series of color image forming operations is completed.
The image forming apparatus exemplified above is configured to transfer the toner image onto the recording paper P via the intermediate transfer belt 20, but the present invention is not limited to this configuration, and the toner image is directly transferred from the photoconductor. It may be a structure that is transferred to a recording sheet.

FIG. 3 is a schematic configuration diagram showing an embodiment of a preferred example of a process cartridge containing an electrostatic charge image developer according to this embodiment. The process cartridge 200 combines the developing device 111 with the photosensitive member 107, the charging roller 108, the photosensitive member cleaning device 113, the opening 118 for exposure, and the opening 117 for static elimination exposure using the mounting rail 116. , And integrated. In FIG. 3, reference numeral 300 denotes a recording medium.
The process cartridge 200 is detachable from an image forming apparatus main body including a transfer device 112, a fixing device 115, and other components (not shown). It forms a forming apparatus.

  The process cartridge 200 shown in FIG. 3 includes a photosensitive member 107, a charging device 108, a developing device 111, a cleaning device 113, an opening 118 for exposure, and an opening 117 for static elimination exposure. The devices may be selectively combined. In addition to the developing device 111, the process cartridge according to the present embodiment may include at least one selected from the group consisting of the photosensitive member 107, the charging device 108, and the cleaning device (cleaning means) 113.

  Next, the toner cartridge will be described. The toner cartridge is detachably attached to the image forming apparatus, and contains at least toner to be supplied to a developing unit provided in the image forming apparatus. The toner cartridge only needs to contain at least toner, and may contain developer, for example, depending on the mechanism of the image forming apparatus.

  2 is an image forming apparatus having a configuration in which the toner cartridges 8Y, 8M, 8C, and 8K can be attached and detached, and the developing devices 4Y, 4M, 4C, and 4K are respectively the developing devices ( And a toner supply pipe (not shown). Further, when the toner stored in the toner cartridge becomes low, the toner cartridge is replaced.

  Hereinafter, although an Example and a comparative example are given and this embodiment is described in detail in detail, this embodiment is not limited to the following examples. Unless otherwise specified, “part” and “%” are based on mass.

(Production of specific titanium dioxide particles 1)
Using titanium tetrabutoxide as the titanium raw material and niobium pentaboxide as the niobium raw material, mixing so that the molar ratio of niobium and titanium is 5:95, adding ethanol, and covering with a film while avoiding contact with moisture Stir with a stirrer. Then, specific titanium dioxide particles 1 were obtained by blowing the mixture into an ultra-high temperature plasma in an argon atmosphere using an argon carrier gas. The obtained particles had a volume average particle diameter of 35 nm.

(Production of specific titanium dioxide particles 2)
The specific titanium dioxide particles 2 were obtained in the same manner as the specific titanium dioxide particles 1 except that the molar ratio of niobium and titanium was changed to 1:79. The obtained particles had a volume average particle diameter of 34 nm.

(Production of specific titanium dioxide particles 3)
The specific titanium dioxide particles 3 were obtained in the same manner as the specific titanium dioxide particles 1 except that the molar ratio of niobium and titanium was changed to 0.5: 99.5. The volume average particle diameter of the obtained particles was 36 nm.

(Production of specific titanium dioxide particles 4)
Except for changing the molar ratio of niobium and titanium to 1: 7, specific titanium dioxide particles 4 were obtained in the same manner as in the production method of specific titanium dioxide particles 1. The obtained particles had a volume average particle diameter of 37 nm.

(Production of specific titanium dioxide particles 5)
The specific titanium dioxide particles 5 were obtained in the same manner as the specific titanium dioxide particles 1 except that the molar ratio of niobium and titanium was changed to 1: 170. The volume average particle diameter of the obtained particles was 38 nm.

(Manufacture of carrier 1)
Ferrite particles (Powdertech, F300, average particle size 50 μm)
100 parts Toluene 15 parts Styrene / methyl methacrylate copolymer (polymerization ratio 30/70, Mw: 80000)
2.5 parts Specific titanium dioxide particles 1 0.7 parts The above components excluding ferrite particles were dispersed with a homomixer for 10 minutes to prepare a resin coating layer forming solution, and this solution and ferrite particles were maintained at 60 ° C. After stirring for 30 minutes with a vacuum degassing kneader, the pressure was reduced at 5 kPa for 60 minutes to distill off the toluene and form a resin coating layer to obtain a carrier 1. The moisture content of the obtained carrier was measured and found to be 0.75%.

(Manufacture of carrier 2)
Ferrite particles (Powdertech, F300, average particle size 50 μm)
100 parts Toluene 15 parts Styrene / methyl methacrylate copolymer (polymerization ratio 30/70, Mw: 80000)
2.5 parts Specific titanium dioxide particles 2 0.7 parts The above components excluding ferrite particles were dispersed with a homomixer for 10 minutes to prepare a resin coating layer forming solution, and this solution and ferrite particles were maintained at 60 ° C. After stirring for 30 minutes with a vacuum degassing type kneader, the pressure was reduced at 5 kPa for 60 minutes, and toluene was distilled off to form a resin coating layer, whereby Carrier 2 was obtained. The moisture content of the obtained carrier was measured and found to be 0.74%.

(Manufacture of carrier 3)
Ferrite particles (Powdertech, F300, average particle size 50 μm)
100 parts Toluene 15 parts Styrene / methyl methacrylate copolymer (polymerization ratio 30/70, Mw: 80000)
2.5 parts Specific titanium dioxide particles 3 0.7 parts The above components excluding ferrite particles were dispersed with a homomixer for 10 minutes to prepare a resin coating layer forming solution, and this solution and ferrite particles were maintained at 60 ° C. After stirring for 30 minutes with a vacuum degassing kneader, the pressure was reduced at 5 kPa for 60 minutes, and toluene was distilled off to form a resin coating layer, whereby Carrier 3 was obtained. The moisture content of the obtained carrier was measured and found to be 0.70%.

(Manufacture of carrier 4)
Ferrite particles (Powdertech, F300, average particle size 50 μm)
100 parts Toluene 15 parts Styrene / methyl methacrylate copolymer (polymerization ratio 30/70, Mw: 80000)
2.5 parts Specific titanium dioxide particles 1 0.7 parts The above components excluding ferrite particles were dispersed with a homomixer for 10 minutes to prepare a resin coating layer forming solution, and this solution and ferrite particles were maintained at 60 ° C. After stirring for 30 minutes with a vacuum degassing type kneader, the pressure was reduced at 5 kPa for 15 minutes and toluene was distilled off to form a resin coating layer, whereby a carrier 4 was obtained. The moisture content of the obtained carrier was measured and found to be 2.1%.

(Manufacture of carrier 5)
Ferrite particles (Powdertech, F300, average particle size 50 μm)
100 parts Toluene 15 parts Styrene / methyl methacrylate copolymer (polymerization ratio 30/70, Mw: 80000)
2.5 parts Specific titanium dioxide particles 1 0.7 parts The above components excluding ferrite particles were dispersed with a homomixer for 10 minutes to prepare a resin coating layer forming solution, and this solution and ferrite particles were maintained at 60 ° C. After stirring for 30 minutes with a vacuum degassing type kneader, the pressure was reduced at 5 kPa for 120 minutes and toluene was distilled off to form a resin coating layer, whereby Carrier 5 was obtained. When the moisture content of the obtained carrier was measured, it was 0.09%.

(Manufacture of carrier 6)
Ferrite particles (Powdertech, F300, average particle size 50 μm)
100 parts Toluene 15 parts Styrene / methyl methacrylate copolymer (polymerization ratio 30/70, Mw: 80000)
2.5 parts indium oxide added particles (EC-700; manufactured by Titanium Industry Co., Ltd.,
(Average particle diameter 99 nm) 0.7 part The above components excluding ferrite particles were dispersed with a homomixer for 10 minutes to prepare a resin coating layer forming solution, and this solution and ferrite particles were maintained at 60 ° C. in a vacuum degassing kneader After stirring for 30 minutes, the pressure was reduced at 5 kPa for 60 minutes and toluene was distilled off to form a resin coating layer, whereby a carrier 6 was obtained. The moisture content of the obtained carrier was measured and found to be 0.75%.

(Manufacture of carrier 7)
Ferrite particles (Powdertech, F300, average particle size 50 μm)
100 parts Toluene 15 parts Styrene / methyl methacrylate copolymer (polymerization ratio 30/70, Mw: 80000)
2.5 parts indium oxide added particles (EC-700; manufactured by Titanium Industry Co., Ltd.,
(Average particle diameter 99 nm) 0.7 part The above components excluding ferrite particles were dispersed with a homomixer for 10 minutes to prepare a resin coating layer forming solution, and this solution and ferrite particles were maintained at 60 ° C. in a vacuum degassing kneader After stirring for 30 minutes, the pressure was reduced at 5 kPa for 120 minutes, and toluene was distilled off to form a resin coating layer, whereby a carrier 7 was obtained. When the moisture content of the obtained carrier was measured, it was 0.09%.

(Manufacture of carrier 8)
Ferrite particles (Powdertech, F300, average particle size 50 μm)
100 parts Toluene 15 parts Styrene / methyl methacrylate copolymer (polymerization ratio 30/70, Mw: 80000)
2.5 parts titanium oxide particles (MT150AW; manufactured by Teika Co., Ltd., average particle size 15 nm)
0.7 parts The above components excluding ferrite particles were dispersed with a homomixer for 10 minutes to prepare a resin coating layer forming solution, and this solution and ferrite particles were stirred for 30 minutes with a vacuum degassing kneader maintained at 60 ° C. Thereafter, the pressure was reduced at 5 kPa for 60 minutes, and toluene was distilled off to form a resin coating layer, whereby a carrier 8 was obtained. The moisture content of the obtained carrier was measured and found to be 0.75%.

(Manufacture of carrier 9)
Ferrite particles (Powdertech, F300, average particle size 50 μm)
100 parts Toluene 15 parts Styrene / methyl methacrylate copolymer (polymerization ratio 30/70, Mw: 80000)
2.5 parts Specific titanium dioxide particles 1 0.7 parts The above components excluding ferrite particles were dispersed with a homomixer for 10 minutes to prepare a resin coating layer forming solution, and this solution and ferrite particles were maintained at 60 ° C. After stirring for 30 minutes with a vacuum degassing type kneader, the pressure was reduced at 5 kPa for 45 minutes and toluene was distilled off to form a resin coating layer, whereby a carrier 9 was obtained. The moisture content of the obtained carrier was measured and found to be 1.1%.

(Manufacture of carrier 10)
Ferrite particles (Powdertech, F300, average particle size 50 μm)
100 parts Toluene 15 parts Styrene / methyl methacrylate copolymer (polymerization ratio 30/70, Mw: 80000)
2.5 parts Specific titanium dioxide particles 1 0.7 parts The above components excluding ferrite particles were dispersed with a homomixer for 10 minutes to prepare a resin coating layer forming solution, and this solution and ferrite particles were maintained at 60 ° C. After stirring for 30 minutes with a vacuum degassing type kneader, the pressure was reduced at 5 kPa for 70 minutes to distill off toluene and form a resin coating layer to obtain a carrier 10. The moisture content of the obtained carrier was measured and found to be 1.5%.

(Manufacture of carrier 11)
Ferrite particles (Powdertech, F300, average particle size 50 μm)
100 parts Toluene 15 parts Styrene / methyl methacrylate copolymer (polymerization ratio 30/70, Mw: 80000)
2.5 parts Specific titanium dioxide particles 4 0.7 parts The above components excluding ferrite particles were dispersed with a homomixer for 10 minutes to prepare a resin coating layer forming solution, and this solution and ferrite particles were maintained at 60 ° C. After stirring for 30 minutes with a vacuum degassing type kneader, the pressure was reduced at 5 kPa for 60 minutes, and toluene was distilled off to form a resin coating layer, whereby a carrier 11 was obtained. The moisture content of the obtained carrier was measured and found to be 1.4%.

(Manufacture of carrier 12)
Ferrite particles (Powdertech, F300, average particle size 50 μm)
100 parts Toluene 15 parts Styrene / methyl methacrylate copolymer (polymerization ratio 30/70, Mw: 80000)
2.5 parts Specific titanium dioxide particles 5 0.7 parts The above components excluding ferrite particles were dispersed with a homomixer for 10 minutes to prepare a resin coating layer forming solution, and this solution and ferrite particles were maintained at 60 ° C. After stirring for 30 minutes with a vacuum degassing kneader, the pressure was reduced at 5 kPa for 60 minutes and toluene was distilled off to form a resin coating layer, whereby a carrier 12 was obtained. The moisture content of the obtained carrier was measured and found to be 1.3%.
The compositions of carriers 1 to 12 are summarized in Table 1.

(Manufacture of toner)
(Preparation of Colorant Particle Dispersion 1)
・ Cyan pigment: Copper phthalocyanine B15: 3 (manufactured by Dainichi Seika Kogyo Co., Ltd.) 50 parts ・ Anionic surfactant: Neogen SC (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 5 parts ・ Ion-exchanged water 200 parts The mixture was mixed and dispersed for 5 minutes with an Ultra-Turrax manufactured by IKA and for 10 minutes with an ultrasonic bath to obtain a colorant particle dispersion 1 having a solid content of 21%. It was 160 nm when the volume average particle diameter was measured with a Horiba Seisakusho particle size measuring instrument LA-700.

(Preparation of release agent particle dispersion 1)
-Paraffin wax: 19 parts of HNP-9 (Nippon Seiwa Co., Ltd.)-Anionic surfactant: 1 part of Neogen SC (Daiichi Kogyo Seiyaku Co., Ltd.)-80 parts of ion-exchanged water And the mixture was heated to 90 ° C. and stirred for 30 minutes. Next, the molten liquid is circulated from the bottom of the container to the gorin homogenizer, and under a pressure condition of 5 MPa, a circulation operation corresponding to 3 passes is performed. Then, the pressure is increased to 35 MPa, and further a circulation operation corresponding to 3 passes is performed. It was. The emulsion thus prepared was cooled in the heat-resistant solution to 40 ° C. or lower to obtain a release agent particle dispersion 1. It was 240 nm when the volume average particle diameter was measured with a particle size measuring instrument LA-700 manufactured by Horiba, Ltd.

(Preparation of resin particle dispersion 1)
<Oil layer>
・ Styrene (Wako Pure Chemical Industries, Ltd.) 30 parts ・ N-butyl acrylate (Wako Pure Chemical Industries, Ltd.) 10 parts ・ β-carboxyethyl acrylate (Rhodia Nikka Co., Ltd.) 1.3 Part / Dodecanethiol (manufactured by Wako Pure Chemical Industries, Ltd.) 0.4 part <Water layer 1>
・ Ion-exchanged water 17 parts ・ Anionic surfactant (DAWFAX 2A1, manufactured by Dow Chemical Co., Ltd.) 0.4 part <Aqueous layer 2>
・ Ion-exchanged water 40 parts ・ Anionic surfactant (DAWFAX 2A1, manufactured by Dow Chemical Co.) 0.05 part ・ Ammonium peroxodisulfate (manufactured by Wako Pure Chemical Industries, Ltd.) 0.4 part The above oil layer components and water layer 1 Were put into a flask and mixed by stirring to obtain a monomer emulsified dispersion. The components of the aqueous layer 2 were charged into the reaction vessel, the inside of the vessel was replaced with nitrogen, and the reaction system was heated to 75 ° C. with an oil bath while stirring. The above monomer emulsified dispersion was gradually dropped into the reaction vessel over 3 hours to carry out emulsion polymerization. Polymerization was further continued at 75 ° C. after completion of the dropping, and the polymerization was terminated after 3 hours to obtain a resin particle dispersion 1.

(Preparation of Toner 1)
・ Resin particle dispersion 1 150 parts ・ Colorant particle dispersion 1 30 parts ・ Releasing agent particle dispersion 1 40 parts ・ Polyaluminum chloride 0.4 part The above components are manufactured by IKA Ultrata in a stainless steel flask. After mixing and dispersing using Lux, the flask was heated to 48 ° C. with stirring in an oil bath for heating. After holding at 48 ° C. for 80 minutes, 70 parts of the resin particle dispersion 1 was added thereto.
Then, after adjusting the pH in the system to 6.0 using an aqueous solution of sodium hydroxide having a concentration of 0.5 mol / L, the stainless steel flask is sealed, and the stirring shaft seal is magnetically sealed while stirring is continued. Heat to 97 ° C. and hold for 3 hours. After completion of the reaction, the temperature lowering rate was cooled at 1 ° C./min, and solid-liquid separation was performed by Nutsche suction filtration. This was further redispersed using 3,000 parts of ion exchange water at 40 ° C., and stirred and washed at 300 rpm for 15 minutes. This washing operation was further repeated 5 times, and No. 1 was obtained by Nutsche suction filtration. Solid-liquid separation was performed using 5A filter paper. Next, vacuum drying was continued for 12 hours to obtain toner particles.

To the toner particles, silica (SiO ₂ ) particles having a primary particle average particle diameter of 40 nm and subjected to a surface hydrophobization treatment with hexamethyldisilazane (hereinafter sometimes referred to as “HMDS”), metatitanic acid and isobutyltrimethoxysilane The metatitanic acid compound particles having an average primary particle diameter of 20 nm, which is the reaction product of the above, were added so that the coverage of the surface of the toner particles was 40% and mixed with a Henschel mixer to prepare toner 1.

(Preparation of developer and its evaluation)
100 parts of each of the carriers 1 to 12 and 6 parts of the toner were mixed to prepare developers of Examples 1 to 7 and developers of Comparative Examples 1 to 5. Using these developers, an output test was performed using a modified DocuCenter Color400 (manufactured by Fuji Xerox Co., Ltd.), and the image quality after outputting 10,000 images in an environment of high temperature and high humidity (30 ° C., 85% RH). Evaluation was performed.
X when the clear white portion of the toner is clearly visually confirmed at the rear end of the output direction of the image, Δ when barely visually confirmed, ○ when unable to visually confirm, and even when using a 25 × magnifier The case was evaluated with ◎. The obtained results are shown in Table 2. In addition, it is possible to accept up to ○.

1Y, 1M, 1C, 1K, 107, 314 photoconductor (electrophotographic photoconductor)
2Y, 2M, 2C, 2K, 108, 310 Charging roller (charging unit)
3Y, 3M, 3C, 3K Laser beam 3, 110, 312 Exposure apparatus (exposure unit)
4Y, 4M, 4C, 4K, 111, 316 Development device (development unit)
5Y, 5M, 5C, 5K, 318 Primary transfer roller (transfer section)
6Y, 6M, 6C, 6K, 113, 320 Photoconductor cleaning device (cleaning unit)
8Y, 8M, 8C, 8K Toner cartridge 10Y, 10M, 10C, 10K Unit 20 Intermediate transfer belt 22 Drive roller 24 Support roller 26 Secondary transfer rollers 28, 115, 322 Fixing device (fixing unit)
30 Intermediate transfer member cleaning device 112 Transfer device 116 Mounting rail 117 Opening 118 for static elimination exposure Opening 200 for exposure Process cartridge,
P, 300, 324 Recording paper (recording medium)

Claims (7)

  A core material particle and a resin coating layer containing niobium-doped titanium dioxide particles and covering the core material particle, and having a moisture content of 0.1% by mass or more and 2.0% by mass or less. Carrier for developing charge image.   2. The electrostatic charge image developing carrier according to claim 1, wherein the molar ratio of niobium to titanium contained in the niobium-doped titanium dioxide particles is 1: 200 to 1: 5.   An electrostatic charge image developer comprising the electrostatic charge image developing carrier according to claim 1 or 2, and an electrostatic charge image developing toner.   The electrostatic charge image developer according to claim 3, wherein the electrostatic charge image developing toner has a shape factor SF1 of 110 or more and 145 or less. A developing means for accommodating the electrostatic charge image developer according to claim 3 or 4 and developing the electrostatic charge image formed on the surface of the latent image carrier with the electrostatic charge image developer to form a toner image. ,
At least one selected from the group consisting of a latent image holder, a charging means for charging the surface of the latent image holder, and a cleaning means for removing toner remaining on the surface of the latent image holder. A process cartridge attached to and detached from the image forming apparatus.   The latent image holding member, a charging unit that charges the surface of the latent image holding member, an electrostatic charge image forming unit that forms an electrostatic charge image on the surface of the latent image holding member, and the electrostatic charge image. Developing means for developing a toner image by developing with the electrostatic image developer according to claim 4, transfer means for transferring the toner image to a recording medium, and fixing means for fixing the toner image to the recording medium. An image forming apparatus.   5. The electrostatic charge image according to claim 3, wherein the electrostatic charge image is formed on the surface of the latent image holding member, the electrostatic charge image forming step of forming an electrostatic charge image on the surface of the latent image holding member, and the electrostatic charge image. An image forming method comprising: a developing step of developing with a developer to form a toner image; a transferring step of transferring the toner image onto a recording medium; and a fixing step of fixing the toner image on the recording medium.