JP5326464B2 - Electrostatic charge developing carrier, electrostatic charge developing developer, electrostatic charge developing developer cartridge, process cartridge, and image forming apparatus - Google Patents

Description

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

  In electrophotography, an electrostatic charge image is formed on an electrostatic latent image holding member (photoreceptor) by a charging process and an exposure process, developed in a developing process to form a developed image, and the developed image is transferred onto a transfer body. In the fixing step, the image is fixed by heating or the like. An electrostatic charge image developer (hereinafter sometimes referred to as “developer”) used in such an electrophotographic method is a one-component developer and a toner that use a toner in which a colorant is dispersed in a binder resin. And a two-component developer composed of a carrier. The two-component developer has a relatively large carrier surface area so that it can be easily charged with toner, and by using magnetic particles for the carrier, it can be relatively easily transported by a mag roll or the like. Is currently widely used.

Under such circumstances, various proposals have been made regarding carriers.
For example, a magnetic particle-dispersed carrier has been proposed in that the stress on the toner is relatively small and the change in the toner surface structure can be reduced, and at least magnetic particles having a number average primary particle size of 0.1 to 1.0 μm are resin. There has been proposed a resin-dispersed carrier in which 50-80% by mass is dispersed and contained therein (see, for example, Patent Document 1).

A carrier combining magnetite (ferromagnetism) and hematite (high resistance) has been proposed (see, for example, Patent Document 2).
Further, magnetite particles containing 0.1 to 5.0% by mass of P with respect to Fe, 0.1 to 5.0% by mass of Al with respect to Fe, and 5.0% by mass or less of Si with respect to Fe. A carrier containing powder has been proposed (see, for example, Patent Document 3).
JP-A-8-30037 JP 2001-343790 A Japanese Patent Laid-Open No. 10-101339

  A resin-dispersed carrier comprising magnetic particles having a number-average primary particle size of 0.1 to 1.0 μm dispersed in a resin in an amount of 50 to 80% by mass is formed to stabilize developer transport and replenishment. However, due to its low specific gravity, the number of magnetizations per unit is likely to be low, and because of its narrow particle size and shape distribution, magnetic brushes are likely to be thin and long, especially for low density printing. The carrier scatters easily. In addition, the carrier scattering may be scattered in a daisy chain, and image defects such as white spots and streaks may remarkably appear.

In addition, a carrier combining magnetite and hematite is a carrier for controlling electric resistance, but magnetization tends to be lowered with an increase in the hematite component, and images such as white spots and streaks are similar to the proposed carrier. Defects may occur.
Further, magnetite particles containing 0.1 to 5.0% by mass of P with respect to Fe, 0.1 to 5.0% by mass of Al with respect to Fe, and 5.0% by mass or less of Si with respect to Fe. The carrier containing the powder has a low residual magnetic flux density and includes a magnetite particle powder that is a hexahedron, octahedron, or tetrahedron polyhedron, but the magnetization tends to be low, and, similar to the proposed carrier, Image defects such as streaks may occur, and this tendency becomes more prominent with low density and high speed printing.

The present invention provides an electrostatic charge developing carrier that suppresses the occurrence of image defects even when an image having a low density is formed at high speed, and an electrostatic charge developing developer including the electrostatic charge developing carrier. With the goal.
Another object of the present invention is to provide an electrostatic charge developing developer cartridge, a process cartridge, and an image forming apparatus that suppress the occurrence of image defects even when a low-density image is formed at high speed. .

The above-mentioned subject is achieved by the following present invention.
That is, the invention according to claim 1
A core material composed of magnetic particles dispersed in a resin, and a coating layer containing a styrene acrylic copolymer and covering the core material,
As the magnetic particles, containing magnetoplumbite type ferrite containing strontium element ,
Wherein the iron element in the magnetic particles molar ratio of the strontium element which forms magnetoplumbite ferrite (iron: strontium element) is 100: 0.4-100: 1.7 and Do characterized Rukoto The electrostatic charge developing carrier.

The invention according to claim 2
The electrostatic charge developing carrier according to claim 1, further comprising magnetite as the magnetic particles.

The invention according to claim 3
Toner and a electrostatic latent image developing developer comprising a a electrostatic latent image developing carrier according to claim 1 or claim 2.

The invention according to claim 4
A developer that is detachable from the image forming apparatus and that is supplied to a developing unit that develops the electrostatic latent image formed on the surface of the electrostatic latent image holding member and forms a toner image is stored. A developer cartridge for developing electrostatic charge according to claim 3 , wherein the developer cartridge is for developing electrostatic charge.

The invention according to claim 5
A developing means for accommodating the developer for developing electrostatic charge according to claim 3 and forming a toner image from the electrostatic latent image formed on the surface of the electrostatic latent image holding member, and holding the electrostatic latent image And at least one selected from the group consisting of a charging means for charging the surface of the electrostatic latent image holding body, and a cleaning means for removing toner remaining on the surface of the electrostatic latent image holding body,
Is a process cartridge.

The present invention according to claim 6 provides:
An electrostatic latent image carrier;
Charging means for charging the surface of the electrostatic latent image holding member;
An electrostatic latent image forming means for forming an electrostatic latent image on the surface of the electrostatic latent image holding member;
Developing means for developing the electrostatic latent image with a developer to form a toner image;
Transfer means for transferring the toner image to a recording medium;
Cleaning means for removing toner remaining on the latent image carrier, fixing means for fixing the toner image on the recording medium,
With
An image forming apparatus, wherein the developer is the electrostatic charge developing developer according to claim 3 .

The present invention according to claim 7 provides:
The image forming apparatus according to claim 6 , wherein the cleaning unit includes a cleaning blade, and the rebound resilience of the leaning blade is 60 to 75%.

According to the first aspect of the invention, there can be obtained an electrostatic charge developing carrier that suppresses the occurrence of image defects even when an image having a low density is formed at high speed.
According to the invention of claim 2, the balance between saturation magnetization and residual magnetization becomes good .

According to the third aspect of the invention, it is possible to obtain an electrostatic charge developing developer that suppresses the occurrence of image defects even when a low density image is formed at high speed.

According to the fourth aspect of the present invention, there can be obtained an electrostatic charge developing developer cartridge that suppresses the occurrence of image defects even when a low density image is formed at high speed.

According to the fifth aspect of the present invention, it is possible to obtain a process cartridge that suppresses the occurrence of image defects even when a low density image is formed at high speed.

According to the sixth aspect of the present invention, an image forming apparatus that suppresses the occurrence of image defects even when a low density image is formed at high speed can be obtained.

According to the seventh aspect of the present invention, the cleaning blade is prevented from being turned over against the deposit, and the scattered carrier removal is excellent.

<Carrier for electrostatic charge development>
The electrostatic charge developing carrier of the present embodiment (hereinafter sometimes referred to as “the carrier of the present embodiment”) includes a core material in which magnetic particles are dispersed in a resin, and a coating that covers the core material. And a magnetoplumbite-type ferrite as the magnetic particles.
In general, a so-called resin-dispersed carrier having a core material in which magnetic particles are dispersed in a resin has a narrow particle size distribution and shape distribution and a low specific gravity. And stable images can be obtained. However, since the resin-dispersed carrier has a low specific gravity, the magnetization per unit number tends to be low, and since the particle size and shape distribution are narrow, the magnetic brush is likely to be formed thin and long. In particular, when an image having a low density is formed at a high speed, the carrier easily scatters to the photosensitive member (electrostatic latent image holding member). In addition, the carrier may be scattered in a daisy chain, and image defects such as white spots and streaks tend to appear remarkably.

In response to the above problems, the carrier of the present embodiment contains a magnetoplumbite type ferrite as the magnetic particles, so that the carrier magnetization retention force and residual magnetization are increased, and the shape of the magnetic brush becomes thicker and shorter. By making it easier, you can prevent carrier scattering. In addition, since the electrical resistance is increased, carrier scattering due to charge injection from the toner hardly occurs. As a result, while taking advantage of the resin-dispersed carrier such as light specific gravity, particle size, and narrow shape distribution, carrier scattering at high speed and low density can be suppressed, and high speed and low density images can be obtained. Even in the case of formation, the occurrence of image defects is suppressed over a long period of time.
Hereinafter, the carrier of this embodiment is demonstrated for every component.

(Core material)
The core material in the carrier of the present embodiment is configured by dispersing magnetic particles in a resin, and at least magnetoplumbite type ferrite is used as the magnetic particles. Here, the magnetoplumbite type ferrite means a ferrite having a composition represented by “AFe ₁₂ O ₁₉ ”. Examples of A include Ba, Sr, Ca, and Pb. Ba, Sr, and Ca are preferable, and Sr and Ca are more preferable. In this embodiment, magnetoplumbite type ferrite containing a strontium element is used.

The magnetic particles containing the magnetoplumbite type ferrite can be produced, for example, as follows.
Magnetic particles containing magnetoplumbite-type ferrite can be obtained by mixing strontium, iron oxide or hydroxide, firing and wet grinding as described below, and adjusting the particle size by sieving.
First, the molar ratio of strontium and iron is calculated, and an appropriate amount of each oxide or hydroxide is weighed and pulverized and mixed with a wet ball mill.
Next, after drying with a spray dryer, baking is performed at a temperature of 1000 ° C. for 1 hour. Again, after pulverizing with a wet ball mill, temporary baking is performed at a temperature of 800 ° C. for 10 hours, and then main baking is performed at a temperature of 1200 ° C. for 2 hours.

In this way, a large amount of strontium components are easily distributed on the inside by performing a long time treatment at a low temperature after a short time treatment at a high temperature.
Thereafter, by firing, a large amount of the magnetite component is distributed outside the particles, whereby high electric field resistance is high and magnetization is high, but residual magnetization does not increase so much and good physical properties can be obtained.
After firing, magnetic particles containing the desired magnetoplumbite type ferrite can be obtained by grinding with a wet ball mill and adjusting the particle size by sieving.

  Further, barium or calcium may be used instead of strontium. Furthermore, strontium, barium, and calcium may be arbitrarily combined.

The core material in the carrier of the present embodiment may be used in combination with magnetic particles (other magnetic particles) other than magnetoplumbite type ferrite. Other magnetic particles are not particularly limited as long as they are magnetic particles such as spinel type ferrite and magnetite iron powder, but spinel type ferrite and magnetite are preferable, and magnetite is more preferable. Here, the spinel type ferrite means a ferrite having a composition represented by “BFe ₂ O ₄ ”. Examples of B include Mn, Co, Ni, Cu, Zn, Li, and Mg, and Li, Mn, and Mg are preferable.

  When the other magnetic particles are spinel type ferrite or magnetite, the balance between saturation magnetization and residual magnetization becomes good. As a result, when the developer containing the carrier of the present embodiment is magnetized on the developer holding body, which will be described later, a good heading state is formed, and even if the developer is separated from the developer holding body, the present embodiment is performed. In the carrier of the form, some magnetization remains, the contact between the toner and the carrier during stirring is promoted, and the charging ability is improved.

The carrier according to the present embodiment is such that the content ratio of magnetoplumbite ferrite with respect to the total content of magnetic particles including other magnetic particles is different from that of other magnetic particles in that the occurrence of image defects is suppressed without impairing fluidity. Molar ratio of iron element in the whole magnetic particle containing iron and other metal element forming the magnetoplumbite type ferrite (metal element corresponding to A of magnetoplumbite type ferrite) (iron element: other metal element) However, it is preferable that it is 100: 0.4-100: 4.0, and it is more preferable that it is 100: 1.0-100: 3.0. In this embodiment, the molar ratio (iron element: strontium element) between the iron element in the magnetic particles and the strontium element forming the magnetoplumbite ferrite is 100: 0.4 to 100: 1.7. It is.
The composition and content of the magnetic particles can be measured by quantification with fluorescent X-rays. A sample whose content is known in advance is prepared, and an element content in the magnetic particles is measured by preparing a calibration curve for each element.

  The volume average particle diameter of the magnetic particles is preferably 0.05 μm or more and 5.0 μm or less, and more preferably 0.1 μm or more and 1.0 μm or less in that the magnetization per carrier becomes good. The volume average particle diameter of the magnetic particles is measured with a laser diffraction / scattering particle size distribution measuring apparatus. In the case of a carrier hardened with a resin, the magnetic particles can be taken out by dissolving the resin with an organic solvent or by burning the resin part at a high temperature. Moreover, the particle size of the resin particles can be obtained from the cross section of the carrier by embedding the carrier with a curable resin and creating a section thereof. In this case, in order to confirm that the cross section of the magnetic particle is the center, it is necessary to observe while slightly shaving.

  The resin constituting the core material by dispersing the magnetic particles is not particularly limited, but styrene resin, acrylic resin, phenol resin, melamine resin, epoxy resin (, urethane resin, polyester resin, silicone) Curable resins are preferable from the viewpoint of chargeability, and phenolic resins, melamine resins, epoxy resins, and urethane resins are preferable.

The total content of magnetic particles (including other magnetic particles) in the core is preferably 80% by mass or more and 99% by mass or less, more preferably 95% by mass or more and 99% by mass or less in terms of magnetization per piece. preferable. The ratio of the magnetic particles in the core material is obtained by dividing the mass when the core material is burned and carbonized by the mass of the original core material and multiplying by 100.
Further, the core material may further contain other components according to the purpose. Examples of other components include a charge control agent and fluorine-containing particles.
The ratio of the magnetic particles in the core material can be determined from the change in weight by raising the temperature to 600 ° C. using a differential scanning calorimeter (DSC).

The method for producing the core of the magnetic particle-dispersed carrier includes, for example, melting and kneading magnetic particles and a resin constituting the core by dispersing the magnetic particles using a Banbury mixer, a kneader, etc., and cooling. A suspension is prepared by pulverizing and classifying a melt-kneading method (Japanese Patent Publication No. Sho 59-24416, Japanese Patent Publication No. 8-3679, etc.) or dispersing a binder resin monomer unit and magnetic particles in a solvent. There are known suspension polymerization methods for polymerizing this suspension (JP-A-5-1000049, etc.) and spray-drying methods in which magnetic particles are mixed and dispersed in a resin solution and then spray-dried.
In any of the melt kneading method, suspension polymerization method, and spray drying method, magnetic particles are prepared in advance by some means, the magnetic particles and the resin solution are mixed, and the magnetic particles are dispersed in the resin solution. Including the step of

(Coating layer)
The carrier in the present embodiment has a coating layer that covers the core material.
A known matrix resin can be used for the coating layer as long as it is used as a material for the carrier coating layer, and two or more types of resins may be blended. The matrix resin constituting the coating layer is roughly classified into a charge imparting resin for imparting chargeability to the toner and a resin having a low surface energy used for preventing the toner component from being transferred to the carrier. It is done. In the present embodiment, the coating layer contains a styrene acrylic copolymer.

Here, examples of the charge imparting resin for imparting negative chargeability to the toner include amino resins such as urea-formaldehyde resin, melamine resin, benzoguanamine resin, urea resin, polyamide resin, and epoxy resin. Furthermore, polystyrene resins such as polyvinyl and polyvinylidene resins, acrylic resins, polymethyl methacrylate resins, styrene acrylic copolymer resins, polyacrylonitrile resins, polyvinyl acetate resins, polyvinyl acetate resins, polyvinyl alcohol resins, polyvinyl butyral resins, ethyl cellulose resins And the like.
Examples of the charge imparting resin for imparting positive chargeability to the toner include polystyrene resins, halogenated olefin resins such as polyvinyl chloride, polyester resins such as polyethylene terephthalate resins and polybutylene terephthalate resins, and polycarbonate resins. Can be mentioned.

  Examples of the resin having a low surface energy used for preventing the transfer of the toner component to the carrier include polyethylene resin, polyvinyl fluoride resin, polyvinylidene fluoride resin, polytrifluoroethylene resin, polyhexafluoropropylene resin, fluororesin. Fluoroterpolymers such as copolymers of vinylidene fluoride and acrylic monomers, copolymers of vinylidene fluoride and vinyl fluoride, terpolymers of tetrafluoroethylene, vinylidene fluoride and non-fluorinated monomers, And silicone resin.

In addition, it is desirable to add conductive particles (volume resistance of 10 ⁵ Ωcm or less, preferably 10 ² Ωcm or less) to the coating layer for the purpose of adjusting the resistance. In this embodiment, there may be two or more coating layers. In that case, it is desirable that the outermost layer contains conductive particles.
Examples of the conductive particles include metal powder, carbon black, titanium oxide, tin oxide, and zinc oxide. Among these, carbon black is preferable. These conductive particles preferably have a volume average particle size of 1 μm or less. Furthermore, a plurality of conductive particles can be used in combination as necessary.
The content of the conductive particles in the coating layer (each layer including conductive particles in the case of two or more coating layers) is 1 mass from the viewpoint of maintaining the strength of the coating layer and adjusting the resistance of the carrier. % To 50% by mass, more preferably 3% to 20% by mass.

Furthermore, the coating layer may contain resin particles for the purpose of charge control. As the resin constituting the resin particles, a thermoplastic resin or a thermosetting resin can be used.
In the case of thermoplastic resins, polyolefin resins, such as polyethylene, polypropylene; polyvinyl and polyvinylidene resins, such as polystyrene, acrylic resin, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl Ether and polyvinyl ketone; vinyl chloride-vinyl acetate copolymer; styrene-acrylic acid copolymer; straight silicone resin composed of an organosiloxane bond or a modified product thereof; fluororesin such as polytetrafluoroethylene, polyvinyl fluoride, polyfluoride And vinylidene chloride, polychlorotrifluoroethylene; polyester; polycarbonate and the like.

  Examples of thermosetting resins include phenol resins; amino resins such as urea-formaldehyde resins, melamine resins, benzoguanamine resins, urea resins, polyamide resins; epoxy resins and the like.

The volume average particle size of the resin particles is preferably 0.1 μm or more and 1.5 μm or less. If the particle size is less than 0.1 μm, the dispersibility is poor and the particles are aggregated in the coating layer, the exposure rate on the surface of the carrier core material becomes unstable, and it may be difficult to keep the charging characteristics stable. Moreover, since the film | membrane intensity | strength of a coating layer falls in an aggregate interface, a coating layer may become easy to break.
On the other hand, when the particle size of the resin particles exceeds 1.5 μm, the resin particles are likely to be detached from the coating layer, and the charge imparting function may not be exhibited. In addition, the strength of the coating layer may be reduced depending on the particle size.

The coating amount of the coating layer in the carrier of the present embodiment is preferably 1% by mass or more and 5% by mass or less, and more preferably 1.5% by mass or more and 3% by mass or less in terms of charging and resistance. .
The coating amount can be determined from the remaining amount of the coating resin dissolved in an organic solvent such as toluene and the weight date of the original carrier.

The formation method of the coating layer in the carrier is not particularly limited, and a conventionally known carrier production method can be used.
That is, a coating layer forming solution (a solution containing conductive particles (conductive powder) and the like in addition to a matrix resin for forming a coating layer in a solvent) is prepared, and a core material is placed in the coating layer forming solution. Immersion method to immerse, spray method to spray the coating layer forming solution on the surface of the core material, fluidized bed method to spray the coating layer forming solution in a state where the core material is suspended by flowing air, core material in a kneader coater And a coating layer forming solution, and then a kneader coater method in which the solvent is removed. However, it is not particularly limited to those using the solution. For example, depending on the type of the core material of the carrier, a powder coating method in which the core material and the resin powder are heated and mixed together can be appropriately employed. Furthermore, after forming a coating layer, it can also heat-process with apparatuses, such as an electric furnace and a kiln.

  The solvent used in the coating layer forming solution for forming the coating layer is not particularly limited as long as it dissolves the resin. For example, aromatic hydrocarbons such as xylene and toluene , Ketones such as acetone and methyl ethyl ketone, ethers such as tetrahydrofuran and dioxane, halides such as chloroform and carbon tetrachloride, and the like can be used.

In addition, the saturation magnetization of the carrier of this embodiment is preferably 50 emu / g or more, and more preferably 56 emu / g or more.
As a device for measuring magnetic properties, a vibrating sample type magnetic measuring device VSMP10-15 (manufactured by Toei Kogyo Co., Ltd.) is used. The measurement sample is packed in a cell having an inner diameter of 7 mm and a height of 5 mm and set in the apparatus. The measurement applies an applied magnetic field and sweeps up to 1000 oersted. Next, the applied magnetic field is decreased to create a hysteresis curve on the recording paper. Saturation magnetization, residual magnetization, and coercive force are obtained from the curve data. In the present invention, saturation magnetization refers to magnetization measured in a 1000 oersted field.

<Developer for electrostatic charge development>
The developer for developing an electrostatic charge image of the present embodiment (hereinafter sometimes referred to as “developer of the present embodiment”) includes a toner and the carrier of the present embodiment described above, so-called two-component development. It is an agent.
Hereinafter, the toner will be described.
The toner used in the exemplary embodiment is not particularly limited, but contains at least a binder resin and a colorant.

As the binder resin contained in the toner, a known resin that can be used for the toner can be appropriately selected. Specifically, for example, monoolefins such as ethylene, propylene, butylene, and isoprene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, and vinyl butyrate; methyl acrylate, phenyl acrylate, octyl acrylate, Α-methylene aliphatic monocarboxylic esters such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether; vinyl methyl ketone, vinyl hexyl ketone And homopolymers or copolymers of vinyl ketone such as vinyl isopropenyl ketone.
Among these, particularly typical binder resins include polystyrene, styrene-alkyl acrylate copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polystyrene, polypropylene, and the like. Furthermore, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin and the like can be mentioned.

  The colorant is not particularly limited. 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, Pigment Blue 15: 3, etc. can be used.

  Further, the toner may contain other known components such as a release agent such as low molecular weight polypropylene, low molecular weight polyethylene, and wax. As the above wax, 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 can be used. Derivatives include oxides, polymers with vinyl monomers, graft modified products, and the like. In addition, alcohols, fatty acids, plant waxes, animal waxes, mineral waxes, ester waxes, acid amides, and the like can be used.

  Furthermore, a charge control agent can be added to the toner as needed. When a charge control agent is added to the color toner, a colorless or light-color charge control agent that does not affect the color tone is preferable. As the charge control agent, known ones can be used, but azo metal complexes, salicylic acid or alkylsalicylic acid metal complexes or metal salts are preferably used.

In the exemplary embodiment, an external additive may be included in the toner in order to improve transferability, fluidity, cleaning properties, and charge amount controllability, particularly fluidity. The external additive refers to inorganic particles attached to the toner particle surface.
_{SiO 2, TiO 2, Al 2} O 3 as _the inorganic _{particles, CuO, ZnO, SnO 2,} CeO 2, Fe 2 O 3, MgO, BaO, CaO, K 2 O, Na 2 O, ZrO 2, CaO · SiO ₂ , K ₂ O. (TiO ₂ ) _n , Al ₂ O ₃ .2SiO ₂ , CaCO ₃ , MgCO ₃ , BaSO ₄ , MgSO _{4 and the} like can be used. Among these, silica particles and titania particles are particularly preferable because fluidity is improved.

  The surface of the inorganic particles of the external additive is preferably subjected to a hydrophobic treatment in advance. This hydrophobization treatment improves the powder flowability of the toner, and is effective for the environmental dependency of charging and the resistance to carrier contamination. The hydrophobic treatment can be performed by immersing inorganic particles in a hydrophobic treatment agent. The hydrophobizing agent is not particularly limited, and examples thereof include silane coupling agents, silicone oils, titanate coupling agents, aluminum coupling agents and the like. These may be used individually by 1 type and may use 2 or more types together. Of these, silane coupling agents are preferred.

  The volume average particle diameter of the toner is preferably 2 μm to 12 μm, more preferably 3 μm to 10 μm, and still more preferably 4 μm to 9 μm. When the volume average particle size of the toner particles is less than 2 μm, the fluidity is remarkably lowered, so that the developer layer is not sufficiently formed by the layer regulating member or the like, and the image may be fogged or dirtied. On the other hand, if it exceeds 12 μm, the resolution is lowered and a high-quality image cannot be obtained, or the charge amount per developer unit weight is lowered, and the layer formation maintenance property of the developer layer is lowered. Fog and dirt may occur.

As a method for measuring the volume average particle diameter of toner particles, 0.5 mg to 50 mg of a measurement sample is added to 2 ml of a 5% by weight aqueous solution of a surfactant, preferably sodium alkylbenzene sulfonate, as a dispersant, and this electrolyte solution Added in 100 ml to 150 ml. The electrolyte solution in which the measurement sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 minute, and the above-mentioned Coulter Multisizer II type (manufactured by Beckman Coulter, Inc.) The particle size distribution of particles having a diameter in the range of 2.0 μm to 60 μm is measured. The number of particles to be measured is 50,000.
For the particle size range (channel) obtained by dividing the obtained particle size distribution, the volume cumulative distribution is subtracted from the small particle size side, and the particle size that becomes 50% cumulative is defined as the volume average particle size D50v.

  The method for producing the toner is not particularly limited, and a known method such as a dry production method such as a kneading pulverization method or a wet granulation method such as a melt suspension method, an emulsion aggregation method, or a dissolution suspension method may be appropriately applied. it can.

  The mixing ratio (mass ratio) of the toner and the carrier in the developer of the exemplary embodiment is preferably toner: carrier = 1: 100 to 30: 100, and more preferably 3: 100 to 20: 100.

<Electrostatic charge developing developer cartridge, image forming apparatus, process cartridge>
Next, the developer cartridge for electrostatic charge development according to this embodiment (hereinafter sometimes abbreviated as “cartridge”) will be described. The cartridge according to the present embodiment is detachable from the image forming apparatus, and at least for developing the electrostatic latent image formed on the surface of the electrostatic latent image holding member to supply to a developing unit that forms a toner image. A developer is accommodated, and the developer is the developer of the present embodiment described above.

  Therefore, in the image forming apparatus having a configuration in which the cartridge can be attached and detached, by using the cartridge of the present embodiment in which the developer of the present embodiment is accommodated, the strength of the image when folded is high, and the friction resistance, It is possible to form an image excellent in scratch resistance and processing such as punching and cutting.

  The image forming apparatus according to the present embodiment includes an electrostatic latent image holding member, a charging unit that charges the surface of the electrostatic latent image holding member, and an electrostatic latent image that forms an electrostatic latent image on the surface of the electrostatic latent image holding member. An image forming unit, a developing unit that develops the electrostatic latent image with a developer to form a toner image, a transfer unit that transfers the toner image to a recording medium, and a fixing unit that fixes the toner image on the recording medium. At least, the developer is the developer for electrostatic charge development of the present embodiment described above.

  Therefore, by using the image forming apparatus of this embodiment using the developer of this embodiment, the occurrence of image defects is suppressed.

  The image forming apparatus of the present embodiment includes at least the above-described electrostatic latent image holding member, a charging unit, an electrostatic latent image forming unit, a developing unit, a transfer unit, and a fixing unit. There is no particular limitation as long as it is a thing, but a cleaning means, a static elimination means, and the like may be included as necessary.

  The developing means is housed in the developer containing container for containing the developer of the present embodiment, the developer supplying means for supplying the developer to the developer containing container, and the developer containing container. A configuration including a developer discharging means for discharging at least a part of the developer, that is, a trickle developing method may be employed.

  If the image forming apparatus of this embodiment using the developer of this embodiment is used, the occurrence of image defects can be suppressed even when a low density image is formed at high speed.

  The process cartridge according to the present embodiment accommodates the developer according to the present embodiment, is detachable from the image forming apparatus, includes a developing unit, and is selected from an electrostatic latent image holding member, a charging unit, and a cleaning unit. It is characterized by providing at least one kind. In addition, the process cartridge according to the present embodiment may include other members such as a charge removing unit as necessary.

  Therefore, by using the process cartridge of this embodiment in an image forming apparatus having a configuration in which the process cartridge can be attached and detached, the occurrence of image defects can be suppressed even when a low density image is formed at high speed. The

  Hereinafter, specific examples of the image forming apparatus and the process cartridge of the present invention will be specifically described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to the present invention (a four-drum tandem full-color image forming apparatus). The image forming apparatus shown in FIG. 1 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 simply referred to as “units”) 10Y, 10M, 10C, and 10K are juxtaposed at a predetermined distance 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. It is designed to travel in the direction toward 10K. The support roller 24 is biased in a direction away from the drive roller 22 by a spring or the like (not shown), and a predetermined tension is applied to the intermediate transfer belt 20 wound around 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 includes yellow, magenta, cyan, and black contained in the toner cartridges 8Y, 8M, 8C, and 8K. The four color toners can be supplied.

  Since the first to fourth units 10Y, 10M, 10C, and 10K described above have the same configuration, here, the first unit that forms a yellow image disposed on the upstream side in the intermediate transfer belt traveling direction. 10Y will be described as a representative. Note that the second to fourth units 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 10M, 10C, 10K is omitted.

The first unit 10Y has a photoreceptor 1Y that acts as an electrostatic latent image holding body. Around the photosensitive member 1Y, a charging roller (charging means) 2Y that charges 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, thereby forming an electrostatic charge. An exposure device 3 that forms an image; a developing device (developing means) 4Y that supplies charged toner to the electrostatic image and develops the electrostatic image; a primary transfer roller that transfers the developed toner image onto the intermediate transfer belt 20; 5Y (primary transfer unit) and a photoconductor cleaning device (cleaning unit) 6Y for removing 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 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, yellow toner having a volume average particle diameter of 7 μm including at least a yellow colorant and a binder resin and the carrier of this embodiment are 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. . 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, a predetermined primary transfer bias is applied to the primary transfer roller 5Y, and the electrostatic force directed from the photoreceptor 1Y to the primary transfer roller 5Y generates a toner image. 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.

  In the present embodiment, the cleaning device 6Y has a cleaning blade, and the rebound resilience of the cleaning blade is preferably 60 to 75%, more preferably 60 to 70%. When the impact resilience of the cleaning blade is 60 to 75%, the leaning blade is prevented from turning up against the deposits and excellent in removing scattered carriers (particularly, this effect becomes remarkable during high-speed operation). If it is less than 60, the leaning blade may be turned over. If it exceeds 75, the blade may be chipped.

  Here, the specific method for measuring the impact resilience conforms to the Lücke impact resilience test of the impact resilience test method for JIS K6255 vulcanized rubber and thermoplastic rubber. When measuring the impact resilience, the sample to be measured is preliminarily under the temperature (when the impact resilience at 10 ° C. is measured, in a 10 ° C. environment) so that the sample is at the measurement measurement temperature. It is desirable to leave the sample sufficiently. The material of the specific resilience cleaning blade is not particularly limited as long as it is an elastic body satisfying the above physical properties, and various elastic bodies can be used. Specific elastic bodies include elastic bodies such as polyurethane elastic bodies, silicone rubber, and chloroprene rubber.

  As the polyurethane elastic body, a polyurethane synthesized through an addition reaction of an isocyanate with a polyol and various hydrogen-containing compounds is generally used. This uses a polyether polyol such as polypropylene glycol and polytetramethylene glycol as a polyol component, and a polyester polyol such as an adipate polyol, a polycaprolactam polyol, and a polycarbonate polyol, and a tolylene diisocyanate as an isocyanate component. Aromatic polyisocyanates such as 4,4′-diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, toluidine diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, dicyclohexylmethane diisocyanate; Prepare a urethane prepolymer, add a curing agent to it, and pour it into the mold. And, after crosslinking and curing, it is prepared by aging at room temperature. As the curing agent, a dihydric alcohol such as 1,4-butanediol and a trihydric or higher polyhydric alcohol such as trimethylolpropane or pentaerythritol are usually used in combination.

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 intermediate transfer belt 20 onto which the four color toner images have been transferred in multiple layers through the first to fourth units is disposed on the image transfer surface side of the intermediate transfer belt 20 and 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 sheet (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 a predetermined 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 sent to a fixing device (fixing means) 28, where the toner image is heated, and the color-superposed toner image is melted and fixed on the recording paper P. 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. 2 is a schematic configuration diagram showing a preferred example of a process cartridge containing the developer for developing an electrostatic charge according to the present invention. The process cartridge 200, together with a photosensitive member (electrostatic latent image holding member) 107, a charging roller (charging unit) 108, a developing device (developing unit) 111, a photosensitive member cleaning device (cleaning unit) 113, and an opening for exposure. 118 and an opening 117 for static elimination exposure are combined and integrated using the mounting rail 116.
The process cartridge 200 is detachable from an image forming apparatus main body including a transfer device (transfer means) 112, a fixing device (fixing means) 115, and other components not shown. The image forming apparatus is configured together with the image forming apparatus main body. Reference numeral 300 denotes a recording sheet.

  The process cartridge shown in FIG. 2 includes a charging device 108, a developing device 111, a cleaning device (cleaning means) 113, an opening 118 for exposure, and an opening 117 for static elimination exposure. Can be selectively combined. In the process cartridge of the present invention, in addition to the photosensitive member 107, from the charging device 108, the developing device 111, the cleaning device (cleaning means) 113, the opening 118 for exposure, and the opening 117 for static elimination exposure. It comprises at least one selected from the group comprising.

Hereinafter, although this embodiment is described in detail using an example, this embodiment is not limited only to the example shown below. In the following examples, “part” means “part by mass” unless otherwise specified. Moreover, in the following description, Examples 3-7 are Reference Examples 3-7.

(Preparation of magnetic particles 1)
Iron (III) oxide and strontium hydroxide were weighed out so that the molar ratio of iron to strontium was 8: 2, and pulverized and mixed with a wet ball mill. Next, it was dried and solidified with a spray dryer, and further oxidized at a temperature of 1000 ° C. for 1 hour.
The obtained oxide was pulverized with a surfactant and cellulose resin by a wet ball mill until the volume average particle size became 0.2 μm. This slurry was granulated and dried with a spray dryer, and calcined for 10 hours at a temperature of 800 ° C. using a rotary kiln. Next, the temperature was increased from 1200 ° C. to 1300 ° C. under the condition of 1 ° C. for 1 minute, and main firing was performed for 100 minutes. Further, the obtained magnetic powder was pulverized by a wet ball mill, and magnetic particles 1 having a volume average of 0.3 μm were obtained by an airflow type sieving machine.

(Magnetic particles 2)
In the production of the magnetic particles 1, the magnetic properties are the same as the production of the magnetic particles 1 except that the strontium hydroxide is changed to barium hydroxide, the temporary firing temperature is 900 ° C., the main firing temperature is 1350 ° C., and the main firing time is 150 minutes. Particle 2 was obtained.

(Preparation of core material 1)
Phenol 40 parts, formalin 60 parts, magnetite (volume average particle size 0.2 μm) 400 parts, magnetic particles 1 40 parts, ion-exchanged water 60 parts, ammonia water 12 parts using a dissolver at 85 ° C. with mixing and stirring. The temperature was gradually raised to 4 hours, followed by reaction and curing. Thereafter, cooling, filtration, and washing with ion exchange water were performed. Next, the temperature was gradually raised to 180 ° C. and dried to obtain a core material 1 (volume average particle size 38 μm) in which magnetic particles were dispersed with a phenol-based resin. In addition, the molar ratio of the iron element in a magnetic particle and strontium was 100: 1.7.

(Preparation of core material 2)
In preparation of the core material 1, the core material 2 was obtained like the preparation of the core material 1 except having changed the usage-amount of the magnetic particle 1 into 10 parts. The molar ratio of the iron element in the magnetic particles to strontium was 100: 0.4.

(Preparation of core material 3)
In preparation of the core material 1, the core material 3 was obtained similarly to preparation of the core material 1 except having changed the usage-amount of the magnetic particle 1 into 100 parts. The molar ratio of the iron element in the magnetic particles to strontium was 100: 3.8.

(Preparation of core material 4)
In preparation of the core material 1, the core material 4 was obtained similarly to preparation of the core material 1 except having changed the usage-amount of the magnetic particle 1 into 7 parts. The molar ratio of the iron element in the magnetic particles to strontium was 100: 0.3.

(Preparation of core material 5)
In preparation of the core material 1, the core material 5 was obtained like the preparation of the core material 1 except having changed the usage-amount of the magnetic particle 1 into 120 parts. The molar ratio of the iron element in the magnetic particles to strontium was 100: 4.4.

(Preparation of core material 6)
In the production of the core material 1, the core material 6 was obtained in the same manner as in the production of the core material 1, except that 400 parts of magnetite was changed to 400 parts of manganese ferrite (Fe: Mn = 80: 20 molar ratio). The molar ratio of the iron element and strontium in the magnetic particles was 100: 2.4.

(Preparation of core material 7)
In the production of the core material 1, the core material 7 was obtained in the same manner as the production of the core material 1, except that 40 parts of the magnetic particles 1 were changed to 40 parts of the magnetic particles 2. The molar ratio of the iron element in the magnetic particles was 100: 1.5.

(Preparation of core material 8)
In the production of the core material 1, the core material 8 is obtained in the same manner as the production of the core material 1 except that 40 parts of the magnetic particles 1 are changed to 40 parts of manganese ferrite (Fe: Mn = 80: 20 molar ratio). It was.

(Preparation of coating solution for coating layer formation)
Styrene acrylic resin (styrene / methyl methacrylate: 20 mol% / 80 mol%): 50 parts Carbon black (VXC72, manufactured by Cabot): 9 parts Toluene (Wako Pure Chemical Industries): 531 parts The above components and glass beads (Particle size: 1 mm, the same amount as toluene) was charged into a sand mill manufactured by Kansai Paint Co., Ltd., and stirred at a rotational speed of 1200 rpm for 30 minutes to prepare a coating solution for forming a coating layer having a solid content of 10%.

(Creation of carrier)
(Preparation of carrier 1)
1000 parts of the core material 1 is charged into a composite fluidized bed coating apparatus MP01-SFP (manufactured by POWREC), a coating liquid for forming a coating layer is 0.5 mm of screen mesh, a rotary impeller of 1000 rpm, an exhaust air amount of 1.2 m ³ / min, Under the conditions of a coating speed of 10 g / min and a temperature of 65 ° C., the core material 1 was coated for 24 minutes to obtain a carrier 1. The coverage of the carrier 1 by the coating layer was 2.4%.

(Production of carriers 2 to 8)
In preparation of the carrier 1, the core material 1 was changed into the core materials 2-8, and the carriers 2-8 were each produced.

(Production of developers 1 to 8)
Each of Carriers 1 to 8 and cyan toner for DCC (DocuCenter Color 400 manufactured by Fuji Xerox Co., Ltd.) were mixed so that the toner concentration was 8% by mass to obtain Developers 1 to 8, respectively.

<Examples 1 to 7, Comparative Example 1>
Print density Cin 1%, except that the developer shown in Table 1 was printed on A4 paper at a printing speed of 60 ppm (page per min) at a printing speed of 60 ppm (page per min) and a print density Cin of 75% using the developer shown in Table 1. Printed 10,000 sheets. The 10th and 10000th printed images printed at a printing density Cin of 75% were compared, and white spots were evaluated according to the following criteria. The results are shown in Table 1. The DCC400 remodeling machine includes an electrostatic latent image holder, a charging unit, an electrostatic latent image forming unit, a developing unit, a transfer unit, and a fixing unit. Further, the DCC400 remodeling machine includes a cleaning unit having a cleaning blade having a rebound resilience of 70%.
A: The image has no white spots and is good.
○: A range in which there are a few light-colored points in the image but no problem in practical use.
Δ: Slight white spots appear in the image, but there is no practical problem.
X: Level in which many white spots are confirmed in the image and there is a problem in practical use.

<Example 8>
In Example 1, the cleaning blade included in the cleaning means included in the DCC400 remodeling machine was evaluated in the same manner as in Example 1 except that the cleaning blade had a rebound resilience of 55%. The results are shown in Table 1.

<Example 9>
In Example 1, evaluation was performed in the same manner as in Example 1 except that the cleaning blade included in the cleaning means included in the DCC400 remodeling machine was changed to a cleaning blade having a rebound resilience of 85%. The results are shown in Table 1.

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

Explanation of symbols

1Y, 1M, 1C, 1K, 107 photoconductor (image carrier)
2Y, 2M, 2C, 2K, 108 Charging roller 3Y, 3M, 3C, 3K Laser beam 3 Exposure device 4Y, 4M, 4C, 4K, 111 Developing device (developing means)
5Y, 5M, 5C, 5K Primary transfer rollers 6Y, 6M, 6C, 6K, 113 Photoconductor cleaning device (cleaning means)
8Y, 8M, 8C, 8K Toner cartridge 10Y, 10M, 10C, 10K Unit 20 Intermediate transfer belt 22 Drive roller 24 Support roller 26 Secondary transfer roller (transfer means)
28, 115 Fixing device (fixing means)
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 Recording paper (transfer object)

Claims (7)

A core material composed of magnetic particles dispersed in a resin, and a coating layer containing a styrene acrylic copolymer and covering the core material,
As the magnetic particles, containing magnetoplumbite type ferrite containing strontium element ,
Wherein the iron element in the magnetic particles molar ratio of the strontium element which forms magnetoplumbite ferrite (iron: strontium element) is 100: 0.4-100: 1.7 and Do characterized Rukoto An electrostatic charge developing carrier.   The electrostatic charge developing carrier according to claim 1, further comprising magnetite as the magnetic particles. Toner and an electrostatic image developing developer comprising a a electrostatic latent image developing carrier according to claim 1 or claim 2. A developer that is detachable from the image forming apparatus and that is supplied to a developing unit that develops the electrostatic latent image formed on the surface of the electrostatic latent image holding member and forms a toner image is stored. The developer cartridge for electrostatic charge development according to claim 3 , wherein the developer cartridge is for electrostatic charge development. A developing means for accommodating the developer for developing electrostatic charge according to claim 3 and forming a toner image from the electrostatic latent image formed on the surface of the electrostatic latent image holding member, and holding the electrostatic latent image And at least one selected from the group consisting of a charging means for charging the surface of the electrostatic latent image holding body, and a cleaning means for removing toner remaining on the surface of the electrostatic latent image holding body,
A process cartridge comprising: An electrostatic latent image carrier;
Charging means for charging the surface of the electrostatic latent image holding member;
An electrostatic latent image forming means for forming an electrostatic latent image on the surface of the electrostatic latent image holding member;
Developing means for developing the electrostatic latent image with a developer to form a toner image;
Transfer means for transferring the toner image to a recording medium;
Cleaning means for removing toner remaining on the latent image carrier, fixing means for fixing the toner image on the recording medium,
With
An image forming apparatus, wherein the developer is the electrostatic charge developing developer according to claim 3 . The image forming apparatus according to claim 6 , wherein the cleaning unit includes a cleaning blade, and the rebound resilience of the cleaning blade is 60 to 75%.