JP2006171309A - Method for manufacturing carrier for electrophotographic developer, carrier for electrophotographic developer, electrophotographic developer, and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a carrier for an electrophotographic developer which keeps the electric resistance of a carrier coating layer low, is provided with an effect of preventing an edge effect and carrier adhesion, is free of deterioration in color characteristics such as color clouding, and is less fluctuated in electrostatic charge due to wear of the coating layer and spent toner composition. <P>SOLUTION: The method for manufacturing the carrier for the electrophotographic developer having the resin coating layer wherein at least conductive carbon is dispersed on the surface of magnetic substance particles includes a process of separating the easily separable conductive carbon on the carrier surface by using a vibration sieving machine with an ultrasonic vibrator oscillator laminated and installed with at least two sheets of mesh materials in tight contact with each other on the ultrasonic vibrator, transmitting the vibration received by the mesh material on the lower layer side from the ultrasonic vibrator to the mesh material on the upper layer side, and subjecting the carrier fed onto the uppermost layer of mesh material to an vibration treatment. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an improved method for producing an electrophotographic developer carrier, a carrier produced by the production method, an electrophotographic developer using the carrier, and an image forming method and process using the electrophotographic developer. It relates to the cartridge.

As a carrier used in an electrophotographic developer, a carrier core material surface made of a magnetic material is coated with a silicone resin or the like. Since the surface of such a resin-coated carrier is covered with a low surface energy substance, it is difficult for the toner to become spent during development (the toner component adheres to the carrier), resulting in a stable charge amount and development. There is an advantage that the life of the agent can be extended. On the other hand, since the carrier is insulated with the resin coating and does not function as a developing electrode, there is a drawback that an edge effect is likely to occur particularly in a solid image portion. In addition, since the counter charge at the time of toner detachment is excessive, the carrier is easily developed on the non-image portion, that is, carrier adhesion is likely to occur.
In order to solve this problem, for example, a resin-coated carrier in which conductive carbon is dispersed as a conductive agent in a carrier coating layer has been proposed (for example, see Patent Document 1).

  However, when such a carrier is used, as a developer, a part of the conductive carbon containing resin floating in the atmosphere adheres to the surface of the coating layer. The adhering carbon is detached from the surface of the carrier coating layer due to the collision or the like, and adheres to the toner particles or is developed as it is. This phenomenon is not so much a problem when forming a copy image such as black characters using black toner, but it appears remarkably as a problem of color turbidity in a developer combined with a color toner, particularly a yellow toner.

JP-A-56-75659

  The present invention has been made in view of the above-mentioned problems, and its problem is to suppress the electrical resistance of the carrier coating layer, to provide an edge effect and an action to prevent carrier adhesion, and there is no color characteristic deterioration such as color turbidity. In addition, the present invention provides a method for producing a carrier for an electrophotographic developer that is less subject to electrification fluctuation due to wear of the coating layer or spent toner composition, and a carrier produced by the production method, an electrophotographic developer using the carrier, An object is to provide an image forming method using the electrophotographic developer.

That is, the said subject is solved by (1)-(16) of this invention.
(1) In the method for producing a carrier for an electrophotographic developer having a resin coating layer in which at least conductive carbon is dispersed on the surface of magnetic particles, the production method comprises at least two sheets on an ultrasonic vibrator. Using a vibration sieve machine with an ultrasonic vibrator oscillator in which the mesh materials are closely stacked, the vibration received by the lower mesh material from the ultrasonic vibrator is transmitted to the upper mesh material, and the uppermost mesh A method for producing a carrier for an electrophotographic developer, comprising a step of separating the conductive carbon that is easily released from the surface of the carrier by subjecting the carrier supplied on the material to vibration treatment ”;
(2) "The method for producing a carrier for an electrophotographic developer according to item (1) above, wherein the uppermost mesh material of at least two mesh materials is a resin mesh";
(3) The above-mentioned (1), wherein as at least two mesh materials, a mesh material with a small mesh is installed on the upper layer side and a mesh material with a large mesh is installed on the lower layer side Or a method for producing a carrier for an electrophotographic developer according to item (2);
(4) “This vibration sieve machine with an ultrasonic vibrator oscillator uses a resonance member fixedly installed on a mesh material, transmits ultrasonic vibration to the resonance member to resonate, and then uses the mesh member as an upper layer mesh material. The method for producing a carrier for an electrophotographic developer according to any one of (1) to (3) above,
(5) “A carrier for an electrophotographic developer having a resin coating layer in which at least conductive carbon is dispersed on the surface of magnetic particles, wherein at least two mesh members are adhered to the ultrasonic vibrator. It is manufactured by the manufacturing method according to any one of the items (1) to (4), wherein the vibration processing is performed by a vibration sieving machine with an ultrasonic transducer oscillator that is stacked. Characterized carrier for electrophotographic developer "
(6) “The electrophotographic developer carrier according to (5) above, wherein the conductive carbon has a specific surface area of 1000 m ² / g or more”;
(7) The carrier for an electrophotographic developer according to (5) or (6) above, wherein the resin covering the surface of the magnetic particles contains at least a silanol-condensable silicone resin ";
(8) The electrophotographic developer according to any one of (5) to (7) above, wherein the resin coating layer is baked at 160 ° C. to 300 ° C. Career ";
(9) “The resin coating layer includes fine particles made of an oxide of Si, Ti, or Al,” according to any one of the above items (5) to (8). "Electrophotographic developer carrier"
(10) “The carrier for an electrophotographic developer according to (9) above, wherein the particle diameter of the fine particles contained in the resin coating layer is 0.01 to 0.4 μm”;
(11) “The carrier has a weight average particle diameter Dw of 22 to 32 μm, a content of particles having a particle diameter of less than 36 μm is 90 to 100% by weight, a content of particles having a particle diameter of less than 20 μm is 7% by weight or less, And the ratio Dw / Dp of the weight average particle diameter Dw to the number average particle diameter Dp is 1.0 to 1.3, in any one of (5) to (10) above The carrier for electrophotographic developer according to the description;
(12) Any one of the above items (5) to (11), wherein the magnetic particles have a magnetic moment of 50 to 150 emu / g when a magnetic field of 1000 oersted is applied. The carrier for an electrophotographic developer according to 1);
(13) The electrophotographic developer according to any one of (5) to (12) above, wherein LogR of electric resistivity R (Ωcm) of the carrier is 11 to 16 Career ";
(14) "The electrophotographic developer comprising the toner according to any one of (5) to (13) as the carrier in an electrophotographic developer comprising a toner and a carrier";
(15) “At least a developing step of developing an electrostatic latent image formed on the surface of the photoreceptor with an electrophotographic developer, and a transfer step of transferring the image developed on the photoreceptor to an image recording medium; A cleaning step of wiping off the developer remaining on the surface of the photoreceptor, wherein the developing step uses the developer described in item (14) above;
(16) “Photoconductor, charging brush for charging the surface of the photoconductor, a developing unit for developing an electrostatic latent image formed on the surface of the photoconductor with an electrophotographic developer, and the surface of the photoconductor Among the blades for wiping off the developer remaining on the substrate, the process cartridge includes at least a developing portion and is integrally supported, and holds the electrophotographic developer described in (14) as the developer. "Featured process cartridge".

The manufacturing method according to claim 1 uses a vibration sieving machine with an ultrasonic transducer oscillator in which at least two mesh materials are closely stacked on the ultrasonic transducer, and the mesh on the lower layer side from the ultrasonic transducer. Is transmitted to the mesh material on the upper layer side, and the carrier supplied on the uppermost mesh material is subjected to vibration treatment, thereby separating the conductive carbon that is easily released from the carrier surface. In addition, the present invention provides an excellent effect that a carrier excellent in color characteristic deterioration prevention, edge effect prevention, and carrier adhesion prevention is provided.
According to the second aspect of the invention, since the uppermost mesh material of at least two mesh materials is a resin mesh and subjected to vibration treatment, a carrier excellent in preventing color characteristic deterioration can be provided at a low cost. Show the effect.
Claim 3 is extremely excellent in that a carrier excellent in color characteristic deterioration prevention and carrier adhesion prevention is provided by installing a mesh material having a small mesh on the upper layer side and a mesh material having a large mesh on the lower layer side. Show the effect.
According to the fourth aspect of the present invention, the resonance member is fixedly installed on the mesh material, and the ultrasonic vibration is transmitted to the resonance member to resonate, and then transmitted to the upper mesh material, thereby further preventing color characteristic deterioration and carrier adhesion. It is extremely effective in providing a good carrier.

The carrier according to claim 5, wherein at least conductive carbon is dispersed in the resin coating layer, and at least two mesh members are closely stacked on the ultrasonic vibrator, and the vibration with an ultrasonic vibrator is provided. Since it has been vibrated by a sieving machine, it exhibits extremely excellent effects of preventing color characteristic deterioration, preventing edge effects, and preventing carrier adhesion.
The carrier according to claim 6 exhibits an extremely excellent effect of further preventing deterioration of color characteristics by setting the specific surface area of the conductive carbon to 1000 m ² / g or more.

The carrier according to claim 7 exhibits an extremely excellent effect of suppressing the charge fluctuation with the passage of time because the resin covering the carrier surface contains at least a silanol condensable silicone resin.
Since the carrier resin coating layer is fired at 160 ° C. to 300 ° C., the carrier according to claim 8 exhibits an extremely excellent effect of suppressing electrification fluctuation over time.
According to the ninth aspect of the present invention, since oxide fine particles of any one of Si, Ti, and Al are added to the coating layer, the extremely excellent effect of suppressing the time-dependent charging fluctuation is exhibited.
According to the tenth aspect of the present invention, when the particle diameter of the fine particles is 0.01 to 0.4 μm, an extremely excellent effect that fluctuations in electrification with time can be further suppressed is exhibited.

Since the particle size distribution of the carrier is within a predetermined range, the eleventh aspect exhibits an extremely excellent effect of improving the image quality.
According to the twelfth aspect, since the magnetic moment of the magnetic particles is 50 to 150 emu / g, an extremely excellent effect of further preventing carrier adhesion is exhibited.
According to the thirteenth aspect, since the LogR of the electrical resistivity R of the carrier is 11 to 16, the carrier adhesion can be further prevented, and an extremely excellent effect of improving the image quality is exhibited.
According to a fourteenth aspect of the present invention, there is provided an electrophotographic developer which is a combination of the carrier and the toner of the present invention, has no deterioration in color characteristics, has an edge effect and an effect of preventing carrier adhesion, and has little fluctuation in electrification with time. It is extremely effective to be provided.
According to the fifteenth and sixteenth aspects, an extremely excellent image forming method and process cartridge using the electrophotographic developer of the present invention are provided.

Hereinafter, embodiments of the present invention will be described.
Note that it is easy for a person skilled in the art to make other embodiments by changing or correcting the present invention within the scope of the claims, and these changes and modifications are included in the scope of the claims. The following description is an example of the best mode of the present invention, and does not limit the scope of the claims.

The electrophotographic developer carrier according to the present invention (hereinafter also simply referred to as a carrier) comprises magnetic core particles and a resin coating layer in which at least conductive carbon is dispersed on the surface thereof.
The carrier according to the present invention has been subjected to a vibration treatment using a vibration sieving machine equipped with an oscillator including an ultrasonic vibrator, and as the vibration sieving machine, at least two mesh materials are disposed on the ultrasonic vibrator. Is used, and the vibration received by the lower layer mesh material from the ultrasonic transducer is transmitted to the upper layer mesh material, and the carrier supplied on the uppermost mesh material is added. Manufactures by shaking and adhering substances that cause color stains such as floating carbon adhering to the carrier surface to the mesh material by shaking treatment, or by screening substances that cause color stains from the carrier itself. be able to.

  It is preferable that at least two mesh materials in close contact with each other should be set so that the mesh material has a small opening on the upper layer side and a smaller lower layer side, and the mesh material with a small mesh opening removes floating carbon adhering to the carrier surface. The mesh material with a large mesh size has the function of receiving vibration directly from the ultrasonic vibrator and transmitting the vibration to the mesh material on the upper layer side, and substantially supporting the weight of the carrier. When performing vibration treatment with a vibration sieve, the load on the mesh material on the upper layer side is reduced, and it can withstand long-term use, and the life can be extended significantly.

As the mesh material on the lower layer side, a material having a wire diameter and an opening of, for example, knitted with a thick thread, which transmits ultrasonic vibrations efficiently and does not easily wear or break, is desirable. Further, the opening is preferably larger than the maximum particle diameter of the carrier particles.
For example, when processing a carrier having a weight average particle diameter Dw of 22 to 45 μm, it is sufficient that the mesh of the lower layer side mesh material is 62 μm (250 mesh) or more.

On the other hand, since ultrasonic vibration is difficult to be transmitted if the wire diameter of the mesh material becomes too large, in the case of an electrophotographic carrier having a Dw of 22 to 45 μm, an opening of about 104 μm (150 mesh) is particularly preferable.
Further, the material of the mesh material on the lower layer side is preferably a metallic material that transmits ultrasonic vibration efficiently and is strong, and the mesh material may have two or more layers.
The mesh material on the upper layer side only needs to have a mesh size suitable for the carrier particle size to be processed. Since the mesh material on the lower layer side is installed, the mesh material on the upper side can use a material having a large opening ratio.

In addition, when a vibrating screen with an ultrasonic oscillator used in the processing method of the present invention is used in which the resonant member is fixedly installed on the mesh material, the ultrasonic vibration from the resonant member is effectively applied to the mesh material surface. This is preferable because the processing efficiency is improved.
The ultrasonic vibration that vibrates the mesh material can be obtained by supplying a high-frequency current to the converter and converting it into ultrasonic vibration. The converter in this case consists of a PZT vibrator.
In order to vibrate the mesh material by ultrasonic vibration, the ultrasonic vibration generated by the converter is transmitted to the resonance member fixedly installed on the mesh material, the resonance member resonates by the ultrasonic vibration, and The mesh fixed to the resonance member is vibrated.
In this case, the frequency for vibrating the mesh material is 20 to 50 kHz, preferably 30 to 40 kHz.
The shape of the resonance member may be a shape suitable for vibrating the mesh material, and is usually a ring shape. The vibration direction for vibrating the mesh material is preferably a vertical direction.

FIG. 1 is a conceptual diagram for explaining an example of a vibration sieving machine with an ultrasonic oscillator used in the processing method of the present invention.
In FIG. 1, reference numeral (1) is a vibrating screen, (2) is a cylindrical container, (3) is a spring, (4a) is a base (support), and (5) is a mesh material of two or more layers adhered to each other. A mesh with a large opening is installed on the lower side, (6) is a resonance member (in this case, ring-shaped), (7) is a high-frequency current cable, (8) is a converter, and (9) is a ring-shaped frame Indicates.
In order to operate the vibratory sieve with an ultrasonic oscillator (circular sieve) shown in FIG. 1, first, a high frequency current is supplied to the converter (8) via the cable (7). The high-frequency current supplied to the converter (8) is converted into ultrasonic vibration.
The ultrasonic vibration generated in the converter (8) vibrates the resonant member (6) to which the converter (8) is fixed and the ring-shaped frame (9) provided in the vertical direction in the vertical direction. Due to the vibration of the resonance member (6), the mesh member (5) fixed to the resonance member (6) and the frame (9) vibrates in the vertical direction.

A commercial product can be used as the vibration sieve machine equipped with an ultrasonic oscillator, and for example, “Ultrasonic” (product name) manufactured by Sakae Sangyo Co., Ltd. is available.
The material of the mesh material on the upper layer side can be applied not only with metal but also with resin. As the mesh material, a material made by knitting a thin line or a material having holes formed by laser, etching, or the like can be used.
However, since the carrier is approximately spherical, clogging is likely to occur when the hole shape is circular. Therefore, a fibrous mesh material knitted with each material is more preferable.

A mesh material knitted with a resin thread is preferable because it has a slight degree of freedom in the direction perpendicular to the fine line than a stainless steel mesh material, and is less likely to clog.
A mesh material knitted with a fine stainless steel wire takes a lot of time and becomes very expensive when the mesh opening becomes small. For example, when the mesh size is about 20 μm, the cost per unit area is 20 times or more compared to a fiber type knitted with resin yarn.
A resin mesh material with a small mesh opening may not be suitable for use as a mesh material for ultrasonic vibration sieves because the strength may be insufficient if no mesh is installed on the lower layer side. In such a case, it was confirmed that sufficient strength and durability can be obtained by using the above-described double pasting method.

The resin mesh material is not particularly limited in terms of production method and material. As long as the mesh material can be produced, a known resin such as a nylon resin, a polyester resin, an acrylic resin, or a fluorine resin can be used.
Among these, nylon resins are preferable because they are excellent mesh materials in terms of durability and chemical resistance, and polyester resins are preferable in terms of durability and weather resistance.
In addition, when the carrier vibration treatment according to the present invention is continuously performed for a long time, the uppermost mesh material is likely to be contaminated with the mesh material due to floating carbon migrated from the carrier surface and the carrier itself is clogged. The uppermost mesh material is removed from the ring-shaped frame, washed with a generally used ultrasonic cleaner, and the mesh material can be used repeatedly by removing dirt and carrier clogging.

  By containing conductive carbon in the carrier coating layer in a dispersed manner, it is possible to adjust the carrier electric resistance in a wide range at a low cost. Examples of the conductive carbon include furnace black (as commercially available products include Black, Pearls 2000, Carbolac 1 manufactured by Cabot; Ketjen Black EC, Ketjen Black EC-600JD, etc. manufactured by Lion Akzo), and acetylene black (as commercially available products). Can be used Denka black granular form, Denka black powder form manufactured by Denki Kagaku Kogyo Co., Ltd .;

The specific surface area of the conductive carbon is preferably 1000 m ² / g or more. When the specific surface area is less than 1000 m ² / g, the dispersibility of the conductive carbon in the carrier coating layer is poor, and the conductive carbon is likely to be detached from the carrier coating layer, and color stains are likely to occur. In addition, the content of the conductive carbon in the coating layer is appropriately selected based on the process conditions using the developer, and is 0.1% to 20% by weight ratio with respect to the resin component in the coating layer, preferably It is selected from the range of 1% to 10%. When the conductive agent content is 0.1% or less, charge-up is likely to occur during development, and image density reduction and carrier adhesion are likely to occur. On the other hand, if it is 20% or more, the developer charge amount is likely to be left unattended, and toner scattering and background contamination are likely to occur.

  As the resin used for the carrier coating layer, various conventionally known resins can be used, and a silanol condensable silicone resin containing a repeating unit represented by the following formula is preferably used.

上記式中、Ｒ^１は水素原子、ハロゲン原子、ヒドロキシ基、メトキシ基、炭素数１〜４の低級アルキル基、またはアリール基（フェニル基、トリル基など）を示し、Ｒ^２は炭素数１〜４のアルキレン基、またはアリーレン基（フェニレン基など）を示す。
上記式のアリール基において、その炭素数は６〜２０、好ましくは６〜１４である。このアリール基には、ベンゼン由来のアリール基（フェニル基）の他、ナフタレンやフェナンスレン、アントラセン等の縮合多環式芳香族炭化水素由来のアリール基及びビフェニルやターフェニル等の鎖状多環式芳香族炭化水素由来のアリール基等が包含される。
該アリール基には、各種の置換基が結合していてもよい。

In the above formula, R ¹ represents a hydrogen atom, a halogen atom, a hydroxy group, a methoxy group, a lower alkyl group having 1 to 4 carbon atoms, or an aryl group (such as a phenyl group or a tolyl group), and R ² represents 1 to C atoms. 4 alkylene group or an arylene group (such as a phenylene group).
In the aryl group of the above formula, the carbon number thereof is 6 to 20, preferably 6 to 14. This aryl group includes an aryl group derived from benzene (phenyl group), an aryl group derived from a condensed polycyclic aromatic hydrocarbon such as naphthalene, phenanthrene, and anthracene, and a chain polycyclic aromatic such as biphenyl and terphenyl. An aryl group derived from a group hydrocarbon is included.
Various substituents may be bonded to the aryl group.

In the arylene group of the above formula, the carbon number thereof is 6 to 20, preferably 6 to 14. These arylene groups include benzene-derived arylene groups (phenylene groups), arylene groups derived from condensed polycyclic aromatic hydrocarbons such as naphthalene, phenanthrene, and anthracene, and chain polycyclic aromatics such as biphenyl and terphenyl. An arylene group derived from a group hydrocarbon is included.
Various substituents may be bonded to the arylene group.

In the present invention, a straight silicone resin can be used as the silicone resin. Examples thereof include KR271, KR272, KR282, KR252, KR255, KR152 (manufactured by Shin-Etsu Chemical Co., Ltd.), SR2400, SR2406 (manufactured by Toray Dow Corning Silicone).
In the present invention, a modified silicone resin can also be used as the silicone resin. Examples of such materials include epoxy-modified silicone, acrylic-modified silicone, phenol-modified silicone, urethane-modified silicone, polyester-modified silicone, and alkyd-modified silicone.

Specific examples of the modified silicone resin include epoxy modified product: ES-1001N, acrylic modified silicone: KR-5208, polyester modified product: KR-5203, alkyd modified product: KR-206, urethane modified product: KR-305 ( As mentioned above, Shin-Etsu Chemical Co., Ltd.), epoxy-modified product: SR2115, alkyd-modified product: SR2110 (manufactured by Toray Dow Corning Silicone), and the like.
Furthermore, in the present invention, the following can be used alone or mixed with the silicone resin.

  Polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, Styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer) Polymer, styrene-phenyl acrylate copolymer, etc.), styrene-methacrylate copolymer (styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, Styrene-phenyl methacrylate copolymer, etc.) Styrene resins such as styrene-α-chloromethyl acrylate copolymer, styrene-acrylonitrile-acrylate copolymer, epoxy resin, polyester resin, polyethylene resin, polypropylene resin, ionomer resin, polyurethane resin, ketone resin, ethylene -Ethyl acrylate copolymer, xylene resin, polyamide resin, phenol resin, polycarbonate resin, melamine resin, fluorine resin and the like.

As a method for forming the coating layer on the surface of the carrier core particles, a known method such as a spray drying method, a dipping method, or a powder coating method can be used.
In particular, the method using a fluidized bed type coating apparatus is effective for forming a uniform coating layer.
The thickness of the coating layer on the surface of the carrier core particles is usually 0.02-1 μm, preferably 0.03-0.8 μm. Since the thickness of the coating layer is very small, the carrier having the coating layer formed on the surface of the core particle and the carrier core particle have substantially the same particle size.
By adding an aminosilane coupling agent to the carrier coating layer containing the silicone resin, a carrier having further excellent durability can be obtained.
Examples of the aminosilane coupling agent used in the present invention include the following. The content is preferably 0.001 to 30% by weight.

The carrier coating layer resin containing at least a silanol condensation type silicone resin can be easily condensed by firing the carrier, and the firing temperature is preferably 160 to 300 ° C. When the firing temperature is less than 160 ° C., the condensation does not proceed sufficiently, so that the coating layer is easily scraped and color stains are likely to occur over time. On the other hand, when the firing temperature is higher than 300 ° C., the condensation proceeds excessively, so that the coating layer becomes brittle and color stains easily occur over time.

The particle size of the inorganic oxide fine particles contained in the carrier coating layer is preferably 0.01 to 0.4 μm, more preferably 0.01 to 0.3 μm. When the particle size is larger than 0.4 μm, the fine particles are easily detached from the coating layer, and when it is less than 0.01 μm, the wear resistance effect of the coating layer is reduced.
Further, the content of the inorganic oxide contained in the coating layer is preferably 5% to 70%, more preferably 20 to 40%. If it is 5% or less, the wear resistance effect of the coating layer is hardly exhibited, and if it exceeds 70%, the particles are likely to be detached.

  In the carrier of the present invention, the weight average particle diameter Dw is 22 to 32 μm, preferably 23 to 30 μm. When the weight average particle diameter Dw is larger than the above range, carrier adhesion is less likely to occur, but the toner is not developed faithfully with respect to the latent image, so that the variation in dot diameter increases and the graininess decreases. Further, when the toner concentration is increased, the background is likely to be stained. The carrier adhesion indicates a phenomenon that the carrier adheres to the image portion or the background portion of the electrostatic latent image. The stronger each electric field, the easier the carrier adheres. In the image area, the electric field is weakened by developing the toner, so that carrier adhesion is less likely to occur compared to the background area. Carrier adhesion is not preferable because it causes inconveniences such as damage to the photosensitive drum and the fixing roller.

The content of particles having a particle size of less than 20 μm is 7% by weight or less, preferably 5% by weight or less, more preferably 3% by weight or less. When the particles smaller than 20 μm are more than 7% by weight, the particle size distribution is widened, and particles having a small magnetic moment are present throughout the magnetic brush. Carrier adhesion suddenly worsens.
Further, the content ratio of the carrier particles having a particle size smaller than 20 μm is preferably 0.5% by weight or more. When it exceeds 0.5% by weight, a desired value can be obtained without cost.

  Further, the magnetic particle having a sharp particle size distribution in which particles smaller than 36 μm are 90% by weight or more, more preferably 92% by weight or more with respect to the particle size distribution in the core material particles having a weight average particle size Dw of 22 to 32 μm. By covering the surface of the body with a resin, a carrier for an electrophotographic developer in which the spread of the magnetic moment of each particle was suppressed was obtained, and carrier adhesion could be greatly improved.

In the present invention, the weight average particle diameter Dw and the number average particle diameter Dp referred to for the carrier, the carrier core material, and the toner are based on the particle diameter distribution (relationship between the number frequency and the particle diameter) of the particles measured on a number basis. It is calculated.
In this case, the weight average particle diameter Dw and the number average diameter Dp are expressed by the following equations.

In the above formula, D represents the representative particle size (μm) of particles present in each channel, n represents the total number of particles present in each channel, and N represents the total number of particles measured. The channel indicates a length for equally dividing the particle size range in the particle size distribution diagram. In the present invention, a length of 2 μm is adopted.
As a particle size analyzer for measuring the particle size distribution in the present invention, a Microtrac particle size analyzer (model HRA9320-X100: manufactured by Honeywell) was used.
The ratio of the weight average particle diameter Dw and the number average particle diameter Dp of the carrier, the value of Dw / Dp approaches 1.0 as the particle diameter distribution of the carrier is sharper, and the particle diameter distribution is broader. The index is larger than 1.0, and in the present invention, it is necessary to be in the range of 1.0 to 1.3. If it exceeds 1.3, the particle size distribution of the carrier becomes broad and the image quality is lowered.

  The core particles used in the carrier of the present invention are crushed particles of magnetic material, or in the case of core materials such as ferrite and magnetite, the primary granulated product before classification is classified, and the sintered particles are classified. It can be obtained by mixing a plurality of particle powders after classification into particle powders having different particle size distributions by treatment.

As a method of classifying the core particles, conventionally known classification methods such as a sieving machine, a gravity classifier, a centrifugal classifier, and an inertia classifier can be used, but the productivity is easy and the classification point can be easily changed. Therefore, it is preferable to use an air classifier such as a gravity classifier, a centrifugal classifier, or an inertia classifier.
The inventors of the present invention have examined the magnetization M related to the magnetic binding force Fm of the carrier by making a sample having a different size, and the magnetic moment when a magnetic field of 1000 oersted (Oe) is applied is 50 emu / It has been found that carrier adhesion is improved by setting it to g or more, more preferably 70 emu / g or more. The upper limit is not particularly limited, but is usually about 150 emu / g.
If the magnetic moment of the carrier core particles is smaller than the above range, carrier adhesion tends to occur, which is not preferable.

The magnetic moment can be measured as follows.
Using a BH tracer (BHU-60 / manufactured by Riken Denshi Co., Ltd.), 1 g of carrier core particles are packed in a cylindrical cell and set in an apparatus. The magnetic field is gradually increased and changed to 3000 oersted, then gradually reduced to zero, and then the opposite magnetic field is gradually increased to 3000 oersted. Further, after gradually reducing the magnetic field to zero, a magnetic field is applied in the same direction as the first. In this way, the BH curve is illustrated, and the magnetic moment of 1000 oersted is calculated from the figure.
Examples of the core particles that are 50 emu / g or more when a magnetic field of 1000 oersted used in the carrier of the present invention is applied include, for example, ferromagnetic materials such as iron and cobalt, magnetite, hematite, Li-based ferrite, Mn- Examples thereof include Zn-based ferrite, Cu—Zn-based ferrite, Ni—Zn-based ferrite, Ba-based ferrite, and Mn-based ferrite.
Ferrite is a sintered body generally represented by the following formula.

但し、ｘ＋ｙ＋ｚ＝１００ｍｏｌ％であって、Ｍ、Ｎはそれぞれ、Ｎｉ、Ｃｕ、Ｚｎ、Ｌｉ、Ｍｇ、Ｍｎ、Ｓｒ、Ｃａなどであり、２価の金属酸化物と３価の鉄酸化物との完全混合物から構成されている。

However, x + y + z = 100 mol%, and M and N are Ni, Cu, Zn, Li, Mg, Mn, Sr, Ca, etc., respectively, and the divalent metal oxide and the trivalent iron oxide Consists of a complete mixture.

  In the present invention, the core particles having a magnetic moment of 70 emu / g or more when a 1000 oersted magnetic field is used more preferably are, for example, iron-based, magnetite-based, Mn-Mg-Sr-based ferrite, Mn-based ferrite Etc.

In the carrier of the present invention, since a part of the conductive carbon containing the resin floating in the atmosphere adheres to the surface of the coating layer at the time of manufacture, when used as a developer, Conventionally, the carbon adhering to the carrier coating layer is detached from the surface of the carrier coating layer due to friction or collision, and adheres to the toner particles or is developed as it is, which causes problems such as color turbidity especially in a developer combined with yellow toner. Unlike the above, there is no adhering carbon, and therefore no problems such as color turbidity due to this are caused. Therefore, the carrier of the present invention is visually confirmed with a developer that is actually mixed and stirred with a yellow toner by the method described in JP-A-2004-109159, and L ^* a ^* b ^{* of} JIS Z8730 ^. Can be identified by color difference ΔE ^* _ab depending on the color system or by the value of the supernatant transmittance, that is, 3 g of a 0.1% aqueous solution of a surfactant polyoxyethylene (10) octylphenyl ether Add 0.3 g of carrier and shake for 30 seconds, then let it stand on the magnetic material, settle the carrier particles by magnetic force, and remove the remaining supernatant liquid in a measuring cell with an optical path length of 10 mm. Can be identified by the value of the supernatant transmittance measured with a spectrophotometer (V-560, manufactured by JASCO Corporation).

In the carrier of the present invention, Log R of resistivity R (Ω · cm) is preferably 11 to 16, more preferably 12 to 14.
When LogR of the carrier resistivity R is lower than 11, when the developing gap (the closest distance between the photosensitive member and the developing sleeve) becomes narrow, charges are induced in the carrier and carrier adhesion is likely to occur. When the linear velocity of the photosensitive member and the linear velocity of the developing sleeve are large, a tendency of deterioration is observed. In addition, it is remarkable when an AC bias is applied. Usually, a color toner developing carrier is generally used having a low resistance in order to obtain a sufficient toner adhesion amount. It has been found that a sufficient image density can be obtained by using a carrier having the above resistance range under an appropriate toner charge amount.
On the other hand, when LogR is larger than 16, charges having a polarity opposite to that of the toner are likely to be accumulated, and the carrier is charged and the carrier is easily attached.

The carrier resistivity can be measured by the following method.
As shown in FIG. 2, a cell (101) made of a fluororesin container containing electrodes (102a) and (102b) having an electrode distance of 2 mm and a surface area of 2 × 4 cm is filled with a carrier (103), A DC voltage of 100 V is applied, the DC resistance is measured with a high resistance meter 4329A (4329A + LJK 5HVLVWDQFH OHWHU; manufactured by Yokogawa Hewlett-Packard Co., Ltd.), and an electrical resistivity R (Ω · cm) is calculated.

After filling the cell until it overflows into the cell, tapping the entire cell 20 times and then using a horizontal spatula made of non-magnetic top surface of the cell along the top edge of the cell. Scrape flat in one operation.
The resistivity of the carrier can be adjusted by adjusting the resistance of the coating resin on the core particles and controlling the thickness of the coating layer. Further, it is also possible to adjust the amount of conductive carbon black such as furnace black, acetylene black, channel black, etc. for carrier resistance adjustment.
These conductive carbon blacks can be obtained by the following methods, that is, a dispersion machine using a medium such as a ball mill or a bead mill after a conductive fine powder is added to a solvent used for coating or a resin solution for coating, or a blade rotating at high speed. Can be uniformly dispersed.

The developer of the present invention comprises the carrier and toner.
The toner used in the present invention contains a colorant, fine particles, a charge control agent, a release agent and the like in a binder resin mainly composed of a thermoplastic resin. Can be used. This toner can be an amorphous or spherical toner prepared by various toner production methods such as a polymerization method and a granulation method. Either magnetic toner or non-magnetic toner can be used.

As the binder resin for the toner, the following can be used alone or in combination.
Styrene binder resins such as polystyrene, polyvinyltoluene and other styrene and substituted homopolymers, styrene-p-chlorostyrene copolymers, styrene-propylene copolymers, styrene-vinyltoluene copolymers, styrene-acrylic Acid methyl copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate Copolymer, styrene-α-chloromethacrylic acid methyl copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene -Isoprene copolymer, styrene- Styrene copolymers such as oleic acid copolymers and styrene-maleic acid ester copolymers; examples of acrylic binders include polymethyl methacrylate and polybutyl methacrylate. In addition, polyvinyl chloride, polyvinyl acetate, polyethylene, Polypropylene, polyester, polyurethane, epoxy resin, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or aliphatic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin wax, etc. Is mentioned.

  Further, the polyester resin can further reduce the melt viscosity while ensuring the stability during storage of the toner, as compared with the styrene-based or acrylic-based resin. Such a polyester resin can be obtained, for example, by a polycondensation reaction between an alcohol and a carboxylic acid.

  Examples of the alcohol include diols such as polyethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-propylene glycol, neopentyl glycol, 1,4-butenediol, , 4-Bis (hydroxymethyl) cyclohexane, bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A and other etherified bisphenols, which are saturated or unsaturated having 3 to 22 carbon atoms Divalent alcohol units substituted with a hydrocarbon group, other divalent alcohol units, sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaesitol, dipentaes Tolu, tripentaerythritol, sucrose, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, tri Mention may be made of trihydric or higher alcohol monomers such as methylolethane, trimethylolpropane and 1,3,5-trihydroxymethylbenzene.

  Examples of the carboxylic acid used to obtain the polyester resin include monocarboxylic acids such as palmitic acid, stearic acid, and oleic acid, maleic acid, fumaric acid, mesaconic acid, citraconic acid, terephthalic acid, cyclohexanedicarboxylic acid, and succinic acid. Acids, adipic acid, sebacic acid, malonic acid, divalent organic acid monomers in which these are substituted with saturated or unsaturated hydrocarbon groups having 3 to 22 carbon atoms, anhydrides of these acids, lower alkyl esters and Dimer from linolenic acid, 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1, 2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl 2-methylenecarboxypropane, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid embol trimer acid, anhydrides of these acids, etc. The body can be mentioned.

  Epoxy resins include polycondensates of bisphenol A and epochrohydrin, such as epomic R362, R364, R365, R366, R367, R369 (above, manufactured by Mitsui Petrochemical Co., Ltd.), Epotot YD-011, YD-012, YD-014, YD-904, YD-017 (above, manufactured by Tohto Kasei Co., Ltd.) Epochs 1002, 1004, 1007 (above, manufactured by Shell Chemical Co., Ltd.) Things.

  Examples of the colorant used in the present invention include carbon black, lamp black, iron black, ultramarine, nigrosine dye, aniline blue, phthalocyanine blue, Hansa Yellow G, rhodamine 6G lake, calco oil blue, chrome yellow, quinacridone, and benzidine yellow. Conventionally known dyes such as rose bengal, triallylmethane dyes, monoazo dyes, disazo dyes, and dyes can be used alone or in combination.

  It is also possible to make a magnetic toner by adding a magnetic material to the toner. As the magnetic material, fine powders such as ferromagnetic materials such as iron and cobalt, magnetite, hematite, Li-based ferrite, Mn—Zn-based ferrite, Cu—Zn-based ferrite, Ni—Zn ferrite, and Ba ferrite can be used.

For the purpose of sufficiently controlling the triboelectric chargeability of the toner, so-called charge control agents such as metal complex salts of monoazo dyes, nitrohumic acid and its salts, salicylic acid, naphthoic salts, dicarboxylic acid Co, Cr, Fe and other metal complex amino compounds , A quaternary ammonium compound, an organic dye, and the like can be contained.
Furthermore, a release agent may be added to the toner used in the present invention as necessary.

As the release material, low molecular weight polypropylene, low molecular weight polyethylene, carnauba wax, microcrystalline wax, jojoba wax, rice wax, montanic acid wax and the like can be used alone or in combination, but are not limited thereto. is not.
Additives can be added to the toner. In order to obtain a good image, it is important to impart sufficient fluidity to the toner. For this purpose, it is generally effective to externally add hydrophobized metal oxide fine particles and fine particles such as lubricants as fluidity improvers, and metal oxides, organic resin fine particles, metal soaps and the like as additives. It is possible to use. Specific examples of these additives include fluorine resins such as polytetrafluoroethylene, lubricants such as zinc stearate, abrasives such as cerium oxide and silicon carbide; for example, inorganic surfaces such as SiO ₂ and TiO ₂ whose surfaces are hydrophobized. Examples thereof include fluidity-imparting agents such as oxides; those known as anti-caking agents, and surface-treated products thereof. In order to improve the fluidity of the toner, hydrophobic silica is particularly preferably used.

In the toner used in the present invention, the weight average particle diameter Dt is 9.0 to 3.0 μm, preferably 7.5 to 3.5 μm. The ratio of the toner to the carrier is 2 to 25 parts by weight, preferably 3 to 20 parts by weight, per 100 parts by weight of the carrier.
The toner particle size was measured using a Coulter counter (manufactured by Coulter Counter).

The electrophotographic developer of the present invention can be obtained by mixing the toner and the carrier for an electrophotographic developer according to the present invention. For mixing, all known mixing means such as a ball mill, a turbula mixer, a rocking mixer, and a V-type blender can be used.
Further, the toner concentration in the developer is in the range of 2 to 20% by weight, preferably 5 to 15% by weight. If the toner concentration is too high, the carrier cannot hold the toner and toner scattering occurs.

Next, an example of the process cartridge of the present invention will be described.
FIG. 3 is a schematic view showing a configuration example of the process cartridge according to the present invention. The process cartridge (image forming unit) of this example has a charging means (25) around a photoconductor (25) which is a typical example of an image carrier. 24) The developing means (20) using the developer of the present invention and the cleaning means (27) are arranged, and are detachably mounted on an image forming apparatus (not shown) having an exposure means and a transfer means. The
An electrophotographic developer using the carrier described above can be used for the process cartridge. As a result, it is possible to speed up the charging of the toner by mixing and stirring with a small amount of carrier and with a small force, and the process cartridge can be lightened. In addition, a larger amount of toner can be accommodated, and the time until replacement of the process cartridge can be lengthened. The burden on the electrophotographic developer can be reduced, the wear of the carrier coating layer can be reduced, the carrier can have a long life, and the life of the process cartridge can be extended. In addition, a high-quality image free from background stains can be obtained by using an electrophotographic developer whose toner charge amount varies little due to environmental variations. Further, scattering of toner into the machine can be suppressed. Further, in the apparatus using the process cartridge, since the life of the process cartridge is long, it is possible to extend the process cartridge replacement cycle of the image forming apparatus and reduce the labor of replacement. Further, in an apparatus using a plurality of these process cartridges, the above advantages are further emphasized, and the operability and maintainability can be greatly improved.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The present invention is not limited to these examples. Moreover, a part represents a weight part.
<Example of carrier production>
(Production Example 1)
For a silicone resin (SR2411: manufactured by Toray Dow Corning Silicone), a liquid prepared by adjusting a conductive carbon having a specific surface area of 1270 m ² / g to a solid content of 7% by weight using a homogenizer for 30 minutes After the dispersion, the dispersion is diluted to a solid content of 10% by weight, and an aminosilane coupling agent (NH ₂ (CH ₂ ) ₃ Si (OCH ₃ )) is further added to the solid content of the silicone resin. The carrier coating layer coating solution was obtained by adding and mixing 3%.
Next, with respect to the magnetic particles (Cu—Zn ferrite, magnetic moment 66 emu / g in 1 KOe), the dispersion is applied at a rate of 50 g / min in an atmosphere at 100 ° C. using a fluidized bed type coating apparatus. It was applied with. Further, the carrier was heated at 250 ° C. for 2 hours to obtain a carrier having an average coating layer thickness of 0.6 μm. The thickness of the carrier coating layer was determined by crushing the carrier and observing the cross section with a scanning electron microscope.

  This carrier was supplied at a rate of 0.1 Kg / min to a vibration sieve equipped with an ultrasonic oscillator having the structure shown in FIG. Two mesh materials were attached to the frame (9). The two mesh materials were attached by attaching a stainless steel mesh having a mesh size of 104 μm (150 mesh) on the lower layer side and a polyester mesh (PES30 manufactured by SEFAR) having a mesh size of 30 μm on the upper layer side. Processing was performed under the condition that the frequency of the ultrasonic oscillator (8) was 36 KHz, and carrier A was obtained.

When the particle size distribution of carrier A was measured with a Microtrac particle size analyzer (model HRA9320-X100), the weight average diameter Dw was 36.9 μm, the number average particle diameter Dp was 31.6 μm, and the content of particles less than 36 μm was 54. The content of 3% by weight and particles less than 20 μm was 0.9% by weight and Dw / Dp = 1.17.
In addition, Log R of electric resistivity R (Ωcm) of carrier A was 14.3.

(Production Example 2)
In Production Example 1, a carrier B was obtained in exactly the same manner except that the vibration treatment was not carried out with a vibration sieve equipped with an ultrasonic oscillator, and sieving was carried out with a conventional mechanical sieve having an opening of the same size. .
When the particle size distribution of the carrier B was measured, the weight average diameter Dw was 35.8 μm, the number average particle diameter Dp was 26.7 μm, the content of particles less than 36 μm was 59.2 wt%, and the content of particles less than 20 μm was 8 It was 1% by weight and Dw / Dp = 1.34.

(Production Example 3)
Carrier C was prepared in exactly the same manner as in Production Example 1 except that the specific surface area of the conductive carbon was 800 m ² / g.
The Log R of the electric resistivity R (Ωcm) of the carrier C was 15.1.

(Production Example 4)
In Production Example 3, the carrier D was obtained in exactly the same manner except that the vibration treatment was not carried out using a vibration sieve equipped with an ultrasonic oscillator, and sieving was carried out using a conventional mechanical sieve having an opening of the same size. .

(Production Example 5)
For a silicone resin (SR2411: manufactured by Toray Dow Corning Silicone), a liquid prepared by adjusting a conductive carbon having a specific surface area of 1270 m ² / g to a solid content of 7% by weight using a homogenizer for 30 minutes Distributed. A liquid in which Al oxide fine particles having a weight average particle diameter of 0.35 μm were added to this dispersion so as to be 20% by weight based on the solid content of the silicone resin was further dispersed for 30 minutes by a homogenizer. The dispersion was diluted to a solid content of 10% by weight, and an aminosilane coupling agent (NH ₂ (CH ₂ ) ₃ Si (OCH ₃ )) was further added to the dispersion to 3% of the solid content of the silicone resin. A carrier coating layer coating solution was obtained by addition and mixing.
Thereafter, the same processing as in Production Example 1 was performed to obtain carrier E.
The Log R of the electrical resistivity (Ωcm) of the carrier E was 14.1.

(Production Example 6)
A carrier coating layer coating solution was obtained in the same manner as in Production Example 1.
Next, the magnetic particles (Mn ferrite, magnetic moment 80 emu / g in 1 KOe) were coated and heated in the same manner as in Production Example 1 to obtain a carrier having an average coating layer thickness of 0.3 μm.
This carrier was supplied to the same vibration sieve equipped with an ultrasonic oscillator as in Production Example 1 at a rate of 0.1 Kg / min, and subjected to a vibration treatment. Of the two mesh members attached to the frame (9), the upper layer side mesh member was a nylon mesh (NY20-HC manufactured by SEFAR) having a mesh size of 20 μm, and was attached in close contact with the lower layer side stainless mesh. Processing was performed under the condition that the frequency of the ultrasonic oscillator (8) was 36 KHz, and carrier F was obtained.
When the particle size distribution of the carrier F was measured, the weight average particle diameter Dw was 27.2 μm, the number average particle diameter Dp was 24.1 μm, the particle content less than 36 μm was 90.1% by weight, and the particle content less than 20 μm was 6.8. % By weight and Dw / Dp was 1.13.
The Log R of the electrical resistivity R (Ωcm) of the carrier F was 13.4.

<Manufacture of developer>
Example 1
The standard yellow toner for Imagio Color 4000 and the carrier A prepared in Production Example 1 were adjusted at a ratio such that the carrier coverage with the toner was 50%, and stirred with a turbula mixer to prepare a developer. This developer is mounted on an Imagio Color 4000, and after being stirred for 10 minutes in the single color mode, the color stain, granularity, background stain, degree of carrier adhesion to the photoconductive drum, and background stain after running 100,000 sheets. Evaluation was performed by the following methods and criteria.

(Evaluation)
(1) The color stain of the image was evaluated by visual observation and the color difference ΔE ^* _ab according to the L ^* a ^* b ^* color system of JIS Z8730.
[1] When the visual evaluation was performed, the following criteria were used.
◎: Very good, ○: Good, ×: Bad (× is an unacceptable level)
[2] When evaluating the color difference ΔE ^* _ab , a standard yellow developer for Imagio Color 4000 was mounted on Imagio Color 4000, and the image after stirring for 10 minutes in the single color mode was used as a reference color.
The color difference ΔE ^* _ab according to L ^* a ^* b ^* color system of JIS Z8730 is expressed by the following formula.

（ΔＬ^＊、Δａ^＊、Δｂ^＊は基準色と評価サンプルの明度Ｌ^＊の差、および色座標ａ^＊、ｂ^＊の差）
一般に色差ΔＥ^＊ _ａｂが２．５以下であれば、サンプルを離して判定したときにほぼ同一と認めることができる、といわれている。

(ΔL ^* , Δa ^* , Δb ^* are the difference between the lightness L ^* of the reference color and the evaluation sample, and the difference between the color coordinates a ^* , b ^* )
In general, it is said that when the color difference ΔE ^* _ab is 2.5 or less, it can be recognized that the samples are almost the same when judged by separating the samples.

(2) The granularity (brightness range: 50 to 80) defined by the following formula was measured, and the numerical values were replaced with ranks as described below for evaluation.

L: Average brightness f: Spatial frequency (cycle / mm)
WS (f): brightness fluctuation power spectrum VTF (f): visual spatial frequency characteristics a, b: coefficient

Rank ◎ (very good): 0 or more and less than 0.1 ○ (good): 0.1 or more and less than 0.2 △ (usable): 0.2 or more and less than 0.3 × (unusable): 0.3 or more (× is an unacceptable level)
(3) As for the background stain, the stain on the background portion on the image was visually evaluated. The symbols described in the table are ◎: very good, ○: good, ×: poor (× is an unacceptable level).
(4) If carrier adhesion occurs, it may cause damage to the photosensitive drum and the fixing roller, resulting in a decrease in image quality. Even if carrier adhesion occurs on the photosensitive drum, only a part of the carrier is transferred to the paper.
An image pattern of 2 dot lines (100 lpi / inch) is created in the sub-scanning direction, developed by applying a DC bias of 400 V, and transferred with adhesive tape between the two dot line lines (area 100 cm ² ). Then, the number was visually observed and evaluated.
The symbols described in the table are ◎: very good, ○: good, Δ: usable, x: defective (x is an unacceptable level).
(5) Background stains after running 100,000 sheets are the same standard as (3) above after running 100,000 sheets on a character image chart with an image area ratio of 6% while replenishing standard yellow toner for Imagio Color 4000 Evaluation of soiling was performed.

Examples 2 to 4, Comparative Examples 1 and 2
An electrophotographic developer was prepared and evaluated in the same manner as in Example 1 using Carriers B to F. The evaluation results are summarized in Table 1.

  As shown in Table 1, the images output using the developers of Examples 1 to 4 containing the carrier of the present invention showed good results for color stain, granularity, background stain, and carrier adhesion. On the other hand, in Comparative Examples 1 and 2 using a developer that is a combination of a carrier and a yellow toner that has not been subjected to vibration treatment by a vibration sieve equipped with an ultrasonic oscillator, the granularity, background stain, and carrier adhesion are good or usable. However, results inferior to color stains were obtained.

  The yellow toners in the developers of Examples 1 to 4 and Comparative Examples 1 and 2 were collected and observed with an optical microscope. As a result, black fine powder was found in the yellow toners of Comparative Examples 1 and 2 compared to Examples 1 to 4. It was confirmed that there was an extremely large amount of foreign matter. When this black foreign material was elementally analyzed by X-ray microanalysis (EPMA), C, O, and Si were detected uniformly from the entire black foreign material, but Fe was not detected. From this, it was found that the black foreign matter was formed by removing the conductive carbon adhering to the carrier surface.

The explanatory structural view of the vibration sieve machine with an ultrasonic oscillator of the present invention is shown. An explanatory view of a cell for measuring carrier electric resistivity is shown. 1 is a schematic view showing a configuration of a process cartridge of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vibrating sieve machine 2 Cylindrical container 3 Spring 4a Base 5 Mesh material of two or more layers 6 Resonant ring 7 Cable 8 Converter (vibrator)
9 Ring-shaped frame 101 Cell 102a Electrode 102b Electrode 103 Carrier 20 Developing device 22 Image forming unit 24 Charging device 25 Photoconductor (image carrier)
27 Cleaning means

Claims (16)

  In the method for producing a carrier for an electrophotographic developer having a resin coating layer in which at least conductive carbon is dispersed on the surface of magnetic particles, the production method includes at least two mesh members adhered to an ultrasonic vibrator. Using the vibration sieve machine with ultrasonic vibrator oscillator installed in layers, the vibration received by the lower mesh material from the ultrasonic vibrator is transmitted to the upper mesh material and supplied onto the uppermost mesh material. A method for producing a carrier for an electrophotographic developer, comprising the step of separating the conductive carbon that is easily released from the surface of the carrier by subjecting the carrier to vibration treatment.   The method for producing a carrier for an electrophotographic developer according to claim 1, wherein the uppermost mesh material is a resin mesh among at least two mesh materials.   3. The electron according to claim 1, wherein the mesh material having a small mesh is installed on the upper layer side and the mesh material having a large mesh is installed on the lower layer side as at least two mesh materials. A method for producing a carrier for a photographic developer.   The vibration sieving machine with an ultrasonic transducer oscillator uses a resonance member fixedly installed on a mesh material, transmits ultrasonic vibration to the resonance member to resonate, and then transmits it to the upper mesh material. A method for producing a carrier for an electrophotographic developer according to any one of claims 1 to 3.   A carrier for an electrophotographic developer having a resin coating layer in which at least conductive carbon is dispersed on the surface of magnetic particles, wherein at least two mesh members are closely stacked on an ultrasonic vibrator. An electrophotographic developer carrier produced by the production method according to any one of claims 1 to 4, wherein the carrier is vibrated by a vibrating sieve equipped with an ultrasonic vibrator. The carrier for an electrophotographic developer according to claim 5, wherein the conductive carbon has a specific surface area of 1000 m ² / g or more.   The carrier for an electrophotographic developer according to claim 5 or 6, wherein the resin coating the surface of the magnetic particles contains at least a silanol condensable silicone resin.   The carrier for an electrophotographic developer according to any one of claims 5 to 7, wherein the resin coating layer is fired at 160 ° C to 300 ° C.   The carrier for an electrophotographic developer according to any one of claims 5 to 8, wherein the resin coating layer contains fine particles made of an oxide of Si, Ti, or Al.   The carrier for an electrophotographic developer according to claim 9, wherein the particle diameter of the fine particles contained in the resin coating layer is 0.01 to 0.4 µm.   The carrier has a weight average particle diameter Dw of 22 to 32 μm, a content of particles having a particle diameter of less than 36 μm is 90 to 100% by weight, a content of particles having a particle diameter of less than 20 μm is 7% by weight or less, and the weight average particle 11. The electrophotographic developer carrier according to claim 5, wherein a ratio Dw / Dp of the diameter Dw to the number average particle diameter Dp is 1.0 to 1.3.   The carrier for an electrophotographic developer according to any one of claims 5 to 11, wherein the magnetic particles have a magnetic moment of 50 to 150 emu / g when a magnetic field of 1000 oersted is applied.   The carrier for an electrophotographic developer according to any one of claims 5 to 12, wherein LogR of the electrical resistivity R (Ωcm) of the carrier is 11 to 16.   An electrophotographic developer comprising a toner and a carrier, wherein the carrier according to any one of claims 5 to 13 is used as the carrier.   At least a developing step of developing an electrostatic latent image formed on the surface of the photosensitive member with an electrophotographic developer, a transferring step of transferring an image developed on the photosensitive member to an image recording medium, and a surface of the photosensitive member 15. A method for forming an image, comprising: a cleaning step of wiping away the developer remaining on the substrate, wherein the developing step uses the developer according to claim 14. A photoconductor, a charging brush for charging the surface of the photoconductor, a developing unit for developing an electrostatic latent image formed on the surface of the photoconductor with an electrophotographic developer, and a development remaining on the surface of the photoconductor A process cartridge comprising at least a developing portion and integrally supported among blades for wiping off the agent, wherein the electrophotographic developer according to claim 14 is held as the developer.

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