JP2002328494A - Carrier for electrophotographic developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carrier which has a small particle size and which exhibits high image quality (namely, good dot-and highlight reproducibility, high image density and little staining), high durability, and little induction type carrier adhesion in the use for a long time, to provide a developer, and a developer container which contains the above developer, to further provide an image forming device having the above developer container installed therein and to provide a method for producing the carrier. SOLUTION: The carrier for electrophotographic developer which consists of magnetic core material particles and a resin layer which covers the particle surface has a weight average particle diameter Dw of 25 to 45 μm. The content ratio of particles which have a particle size smaller than 44 μm in the carrier is 70 wt.% or greater, and the content ratio of the particles which have a particle size smaller than 22 μm is 7.0 wt.% or less. The carrier resistance (LogΩ.cm) is 12.0 or greater, and the resistance of the resin coating layer of a portion near the carrier core material is greater than the resistance of the coating layer of the carrier surface layer part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a carrier for an electrophotographic developer, a developer, a developer container, an image forming apparatus, a developing method, and a method of manufacturing a carrier.

[0002]

2. Description of the Related Art An electrophotographic developing system includes a so-called one-component developing system using only toner as a main component, a glass bead, a magnetic carrier, or a coat carrier having their surfaces covered with a resin or the like. There is a two-component developing method using a mixture with a toner. The two-component developing method uses a carrier and has a large frictional charging area with respect to the toner. Therefore, compared to the one-component method, the two-component developing method has stable charging characteristics and is advantageous for maintaining high image quality for a long time. . Further, since the toner supply capacity to the developing area is high, it is often used particularly for high-speed machines. A digital electrophotographic system that forms an electrostatic latent image on a photoreceptor with a laser beam and visualizes this latent image,
A two-component developing system utilizing the above-mentioned features is widely used.

In recent years, the minimum unit (1 dot) of a latent image has been minimized and its density has been increased in order to cope with an increase in resolution, highlight reproducibility, colorization, and the like. A development system that can faithfully develop (dots) has become an important issue. For this reason, various proposals have been made in terms of both process conditions and developer (toner, carrier, etc.). On the process side, it is effective to make the development gap closer, make the photoreceptor thinner, and reduce the writing beam diameter, but there are still significant problems in terms of cost increase and reliability.

[0004] The use of a small particle size toner greatly improves dot reproducibility. However, the developer containing the small particle size toner may cause background contamination, insufficient image density, toner spent on a carrier, and the like. There remains a problem to be solved. In the case of a full-color toner, a resin having a low softening point is used to obtain a sufficient color tone.
The amount of spent on the carrier is increased, the developer is deteriorated, and toner scattering and background contamination are likely to occur.

Various uses of small particle size carriers have also been proposed. For example, Japanese Patent No. 2832013 discloses that an electrostatic latent image formed on a latent image holding member having an organic photoconductor layer is developed while applying a bias electric field having an AC component and a DC component in a developing section. A reversible development by a magnetic brush of a two-component developer having a toner and a carrier carried on a developer carrier and having the same polarity as the charge polarity of the electrostatic latent image, wherein the carrier comprises ferrite. The surface of the carrier core having particles is coated with 0.1 to 5.0% by weight of the electrically insulating resin based on the weight of the carrier core, and after being coated with the electrically insulating resin. Has a weight average particle diameter of 30 to 65 μm.
m, and the average pore size on the surface of the carrier core material is from 1,500 to 30,000 °.

[0006] Japanese Patent No. 3029180 discloses that
In an electrophotographic carrier having carrier particles, the carrier has a 50% average particle size (D ₅₀ ) of 15 to 45 μm, and the carrier contains 1 to 20% of carrier particles smaller than 22 μm, and has a particle size of 16 μm. 3% or less of smaller carrier particles, 2 to 15% of carrier particles of 62 μm or more, and 2% or less of carrier particles of 88 μm or more,
Specific surface area S of the carrier measured by an air permeation method
₁ and the following formula

[0007]

The specific surface area S _{2 of the} carrier calculated by S ₂ = (6 / ρ · D ₅₀ ) × 10 ⁴ (ρ is the specific gravity of the carrier)

[0008]

## EQU2 ## An electrophotographic carrier characterized by satisfying the condition of 1.2 ≦ S ₁ / S ₂ ≦ 2.0 is described.

Japanese Patent Application Laid-Open No. Hei 10-198077 discloses a carrier used for an electrostatic latent image developer, wherein the carrier has a 50% diameter (D50) of the volume average particle diameter of 30 to 30%.
80%, and 10% of the volume average particle diameter (D1
0) and the 50% diameter of the volume average particle diameter (D50 / D1).
0) is 1.8 or less, and 90% of the volume average particle diameter (D
90) and the ratio of 50% of the volume average particle size (D90 / D5)
0) is 1.8 or less, the carrier having a volume particle size of 20 μm or less is less than 3%, and 1 kOe of the carrier
The carrier for electrostatic latent image developer is characterized in that the magnetization of the toner is in the range of 52 to 65 emu / g.

When using this small particle size carrier,
The following advantages are obtained. (1) Since the surface area is large, sufficient frictional charge can be given to each toner, and the generation of low charge amount toner and reverse charge amount toner is small. As a result, background stains are less likely to occur, and toner remnants and bleeding around the dots are reduced and dot reproducibility is improved. (2) Since the surface area is large and the soil is hardly generated,
The average charge amount of the toner can be reduced, and a sufficient image density can be obtained. (3) Even when a small particle size toner is used, the coverage of the toner with respect to the carrier does not increase, which is particularly effective in compensating for a defect in using the small particle size toner and extracting advantages. (4) The small particle size carrier forms a dense magnetic brush,
In addition, since the spikes have good fluidity, they have features such as hardly causing spike marks on images.

[0011] However, the conventional small particle size carrier is
A major problem is that carrier adhesion is extremely likely to occur, which causes damage to the photoreceptor and flaws in the fixing roller. The present inventors have examined the carrier particle size of the carrier adhered to the small particle size carrier, and found that the carrier having the smaller particle size tends to preferentially adhere to the original particle size distribution. It has been found that the ratio of particles having a particle size of less than 22 μm is overwhelmingly large in the attached carrier. Furthermore, it was also clarified that there was a large variation in the state of the film formation on the carrier surface and that there were many carriers in which a part of the core material was exposed. The small particle size carrier has a small magnetic moment per unit, so it is easy to adhere to the carrier originally, but by adding the above state,
Induced carrier deposition has occurred. Further, when used for a long period of time, abrasion or the like of the film occurs, so that the resistance is lowered. As a result, the adhesion of the inductive carrier is amplified, so that an effective means for preventing this is required.

[0012]

SUMMARY OF THE INVENTION The main object of the present invention is to provide high image quality (that is, image quality with good dot reproducibility and highlight reproducibility, high image density, and low background smear). It is an object of the present invention to provide a small-diameter carrier and a developer which are durable and do not cause induction type carrier adhesion even during long-term use. Another object of the present invention is to
An object of the present invention is to provide a developer container in which the developer is stored. Another object of the present invention is to provide an image forming apparatus equipped with the developer container. Still another object is to provide a method for manufacturing the carrier.

[0013]

According to the present invention, there are provided a carrier for an electrophotographic developer, a developer, a developing container, an image forming apparatus, a developing method, and a method of manufacturing a carrier as described below. That is, an object of the present invention is to provide (1) a carrier for an electrophotographic developer comprising (1) a core material particle having magnetism and a resin layer covering the surface of the particle, wherein the carrier has a weight average particle diameter Dw of 25. ４５45 μm, and 44
When the content ratio of particles having a particle size smaller than 22 μm is 70% by weight or more and the content ratio of particles having a particle size smaller than 22 μm is 7.0% by weight or less, the carrier resistance (LogΩ)
(Cm) is 12.0 or more, and the resistance of the resin coating layer in a portion close to the carrier core material is higher than the resistance of the coating layer in the surface layer portion of the carrier. " (2) “A carrier for an electrophotographic developer according to the above (1), wherein the magnetic moment at 1 KOe is 76 emu / g or more”, (3)
"A carrier for an electrophotographic developer according to the above item (1) or (2), wherein the content of particles having a particle size smaller than 22 μm in the carrier is 3% by weight or less" (4) The method according to any one of the above (1) or (2), wherein the content of particles having a particle size smaller than 22 μm in the carrier is 1% by weight or less. Carrier for electrophotographic developer ", (5)" 6
(1) The carrier for an electrophotographic developer according to any one of the above (1) to (4), wherein particles having a particle size of 2 μm or more are less than 1% by weight. the paragraph (1), second (5) the electrophotographic carrier for developer according to any one of Items "(7)" carrier core Mn but is characterized in that at 2.2 g / cm ³ or more (8) The carrier for electrophotographic developer according to any one of the above items (1) to (6), wherein the carrier core material is magnetite. (9) The carrier according to any one of the above (1) to (6), wherein the coating layer is a silicone resin. The carrier for an electrophotographic developer according to any one of Items to (8) ”, (1 0) According to the “electrophotographic developer carrier according to any one of the above items (1) to (9), wherein the resin layer is made of a resin containing an aminosilane coupling agent”. Achieved.

Another object of the present invention is to provide (11) an electrophotographic developer comprising a toner and a carrier, wherein the carrier is any one of the items (1) to (10). Wherein the carrier described in (1) is used.

[0015] The object of the present invention is (12) a developer container containing a developer according to the present invention, wherein the developer is the developer according to the above (11). Developer container ".

According to a third aspect of the present invention, there is provided an image forming apparatus equipped with a developer container, wherein the developer container is the developer container described in the above item (12). Characteristic image forming apparatus ".

The above object is also achieved by (14) a "developing method using a developer, wherein the developing method according to the above (11) is used as the developer". Achieved.

Another object of the present invention is to provide (15) a method for producing a carrier for electrophotographic development according to the present invention, wherein (i) classifying the pulverized particles of the magnetic material so that the weight average particle diameter is 25 to 45 μm, the content ratio of particles having a particle size smaller than 44 μm is 70% by weight or more and 22 μm
The content ratio of particles having a smaller particle size is 7.0% by weight.
(Ii) a step of obtaining core particles having the following properties; and (ii) coating the resin-coated carrier with a resistance (LogR · Ωcm) of 12.0 or more and a portion close to the carrier core material on the surface of the core particles. Any one of the above-mentioned items (1) to (10), comprising a step of forming a resin film having a resistance of the layer larger than a resistance of the coating layer of the carrier surface layer portion.
Method for producing a carrier for electrophotographic development according to
(16) The method for producing an electrophotographic carrier, wherein (i) the resistance of the resin coating layer on the surface of the pulverized magnetic material particles near the carrier core is the resistance of the coating layer on the carrier surface layer. Forming a larger resin coating to obtain resin-coated particles, and (ii) classifying the resin-coated particles to obtain particles having a weight average particle size of 25 to 45 μm and a particle size smaller than 44 μm. When the content ratio is 70% by weight or more,
The electrophotography according to any one of the above items (1) to (10), comprising a step of obtaining a carrier in which a content ratio of particles having a particle size smaller than 22 μm is 7% by weight or less. Method for Manufacturing Carrier for Development ", (1
7) “A method for producing a carrier for electrophotographic development according to the above (15), wherein a vibrating sieve equipped with an ultrasonic oscillator is used to classify the pulverized particles of the magnetic material.” (18) “A method for producing a carrier for electrophotographic development according to the above (16), wherein a vibrating sieve equipped with an ultrasonic oscillator is used to classify the resin-coated particles”, (19) The electronic device according to the above (17) or (18), wherein the vibrating sieve has a structure for transmitting ultrasonic vibrations to a wire mesh surface by a resonance ring installed in the sieve. Production method of carrier for photographic development ".

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The carrier for an electrophotographic developer of the present invention (hereinafter also simply referred to as a carrier) comprises core material particles having magnetism and a resin layer covering the surface thereof.

In the carrier of the present invention, the weight average particle diameter Dw is in the range of 25 μm to 45 μm, preferably in the range of 30 μm to 45 μm. Weight average particle size D
If w is larger than the above range, carrier adhesion is unlikely to occur, but if the toner concentration is increased in order to obtain a high image density, the background smear rapidly increases. Also, when the dot diameter of the latent image is small, the variation in the dot diameter becomes large.
Further, the content ratio of particles having a particle size smaller than 44 μm is 70% by weight or more, preferably 75% by weight or more. If it is less than 70% by weight, the variation in dot diameter is still large. The content ratio of the particles having a particle size smaller than 22 μm is 7% by weight or less, preferably 3% by weight or less, more preferably 1% by weight or less.

In the case of a small particle size carrier, most of the carrier adhering to the carrier is fine particles of less than 22 μm. The present inventors have found that the weight average particle size Dw is 25 μm to 45 μm.
The carrier adhesion was evaluated by changing the weight ratio of the particles smaller than 22 μm in the carrier having a small particle diameter of μm. If the particles having the particle diameter of 22 μm or less were 7% by weight or less, there was no problem, but 3% by weight. , And further 1% by weight, the carrier adhesion was further improved.

The carrier adhesion indicates a phenomenon in which the carrier adheres to an image portion or a background portion of the electrostatic latent image. The stronger the respective electric fields, the more easily the carriers adhere. Since the electric field is weakened in the image area by developing the toner, carrier adhesion is less likely to occur than in the background area. Carrier adhesion is
This is not preferable because it causes inconveniences such as damage to the photosensitive drum and the fixing roller.

In the carrier of the present invention, the resistivity L
og · Ωcm is 12.0 or more, more preferably 13.
0 or more. If the resistivity of the carrier is lower than the above range, for example, the developing gap (the closest distance between the photoconductor and the developing sleeve) becomes narrow, and if the electric field strength becomes large, electric charges are induced in the carrier and carrier adhesion easily occurs. Become. When the linear velocity of the photoreceptor and the linear velocity of the developing sleeve are high, there is a tendency for deterioration.

In addition, those having a large variation in the formation of the coating on the carrier surface and those having a part of the core material exposed tend to easily adhere to the carrier. Furthermore, it has been found that when a resin-coated carrier is used for a long period of time, the film is gradually scraped or peeled off, resulting in carrier adhesion. It is considered that this is also due to the induction of charges in the carriers. In response to this phenomenon, if the resistance of the resin coating layer near the carrier core material is set higher than the resistance of the coating layer on the surface layer of the carrier, carrier adhesion hardly occurs even after long-time use, and the small particle size It has been confirmed that this is an effective means as a method for preventing carrier adhesion to carriers. As the method, a high-resistance layer may be provided on the surface of the core material, or the resistance in the coating layer may be gradually changed so that the core material side becomes higher. To gradually change the resistance of the resin coating, apply multiple layers of different resistance coatings, or
The resistance can be achieved by gradually lowering the resistance of the coating liquid to be applied with respect to the application time.

The adjustment of the resistance can be controlled by adjusting the resistance of the coating resin on the core material particles, controlling the film thickness, and the like.
Further, for the purpose of adjusting the carrier resistance, it is also possible to add a conductive fine powder to the coating resin layer and use it. Examples of the conductive fine powder include metal or metal oxide powder such as conductive ZnO and Al, SnO ₂ prepared by various methods or SnO ₂ , TiB ₂ , ZnB ₂ , and Mo doped with various elements.
Borides of ₂ such as B, silicon carbide, polyacetylene, polyparaphenylene, poly (para - phenylene sulfide)
Examples thereof include conductive polymers such as polypyrrole and polyethylene, and carbon blacks such as furnace black, acetylene black, and channel black.

These conductive fine powders are prepared by the following method, that is, after charging the conductive fine powder into a solvent used for coating or a resin solution for coating, a dispersing machine using a medium such as a ball mill or a bead mill, or a high-speed dispersing machine. Uniform dispersion can be achieved by using a stirrer with rotating blades.

The resistivity of the carrier is measured by the following method. As shown in FIG. 2, the carrier (1) is placed in a cell (11) composed of a fluororesin container containing electrodes (12a) and (12b) having a distance between electrodes of 2 mm and a surface area of 2 × 4 cm.
3), and a DC voltage of 100 V is applied between both electrodes, and a high resistance meter 4329A (4329A
+ LJK 5HVLVWDQFH OHWHU (manufactured by Yokogawa Hewlett-Packard Co., Ltd.) to measure the DC resistance and calculate the electrical resistivity Log · Ωcm.

The particles having a size of 62 μm or more are less than 3% by weight, preferably less than 1% by weight. The greater the content of particles of 62 μm or more, the greater the variation in dot diameter. 62
The slight difference in the weight of the carrier over μm is 44 μm to 6 μm.
It is considered that this has a large effect on the weight% of the carrier in the range of 2 μm.

At the same time, when the magnetic moment at 1 KOe was 76 emu / g or more, carrier adhesion was greatly improved.

The carrier of the present invention is obtained by pulverizing a magnetic material,
Classify the pulverized particles so as to obtain a predetermined particle size,
It can be obtained by forming a resin film on the surface of the core material particles obtained by this classification. The classification includes air classification and sieving (sieving). A vibrating sieve is preferably used for the production of the carrier core particles. However, in a vibrating sieve generally used in the related art, in order to classify particles having a small particle size, a small mesh of the sieve (wire mesh) is used. However, the workability for classification is very poor because of the inconvenience that the particles are immediately clogged.

The present inventors have conducted various studies to develop a method capable of cutting small-sized particles efficiently and sharply. When classifying the particles using a sieving machine, ultrasonic vibration was applied to the wire mesh. It has been found that, by giving, small particles of less than 22 μm can be efficiently and sharply cut.

Ultrasonic vibration for vibrating the wire mesh can be obtained by supplying a high-frequency current to a converter and converting it into ultrasonic vibration. The converter in this case is PZ
It consists of a T oscillator. In order to vibrate the wire net by ultrasonic vibration, the ultrasonic vibration generated by the converter is
The light is transmitted to the resonance member fixed to the wire mesh. The resonance member to which the ultrasonic vibration has been transmitted resonates due to the ultrasonic vibration, and vibrates the wire mesh fixed to the resonance member. The frequency at which the wire net is vibrated is 20 to 50 kHz, preferably 30 to 40 kHz. The shape of the resonance member is
Any shape suitable for vibrating the wire netting may be used, and it is usually a ring shape. The vibration direction for vibrating the wire mesh is preferably a vertical direction.

FIG. 1 is an explanatory structural view of a vibrating sieve with an ultrasonic oscillator. In FIG. 1, (1) is a vibrating sieve,
(2) a cylindrical container, (3) a spring, (4) a base (support), (5) a wire mesh, (6) a resonance ring,
(7) is a high-frequency current cable, (8) is a converter,
(9) shows a ring-shaped frame. To operate the vibrating sieve (circular sieve) with the ultrasonic oscillator shown in FIG. 1, 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. Converter (8)
The ultrasonic vibration generated in (1) vibrates the resonance ring (8) to which the converter (8) is fixed and the ring-shaped frame (9) connected thereto in the vertical direction. Due to the vibration of the resonance ring (6), the resonance ring (6) and the wire mesh (5) fixed to the frame (9) vibrate vertically. A vibration sifter equipped with an ultrasonic oscillator is sold, and is available, for example, under the product name "Ultrasonic" from Koei Sangyo Co., Ltd.

The carrier of the present invention is obtained by forming a resin film on the surface of the pulverized particles of a magnetic material to obtain resin-coated particles.
It can also be produced by classifying the resin-coated particles. In this case, the classification of the resin-coated particles is preferably performed using the above-described vibration sieve equipped with an ultrasonic oscillator.

As the material of the core particles constituting the carrier of the present invention, various conventionally known magnetic materials are used. In the carrier core material particles used in the present invention, 100
The magnetic moment when a magnetic field of 0 Oe (Oe) is applied is 55 emu / g or more, more preferably 76 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 material particles is smaller than the above range, carrier adhesion is likely to occur, which is not preferable.

The magnetic moment can be measured as follows. BH tracer (BHU-6
0 / manufactured by Riken Denshi Co., Ltd.) and 1.0 g of carrier core material particles are packed in a cylindrical cell and set in an apparatus. Gradually increase the magnetic field, change to 3000 Oersteds,
Next, after gradually decreasing the value to zero, the magnetic field in the opposite direction is gradually increased to 3000 Oe. Furthermore, after gradually reducing the magnetic field to zero, a magnetic field is applied in the same direction as the first. In this manner, the BH curve is illustrated, and the magnetic moment of 1000 Oe is calculated from the figure.

The core material particles used in the carrier of the present invention and having an epsilon of 55 emu / g or more when a magnetic field of 1000 Oe is applied include, for example, ferromagnetic substances such as iron and cobalt, magnetite, hematite, and Li-based ferrite. , Mn-Zn ferrite, Cu-Zn ferrite, Ni-Zn ferrite, Ba ferrite, Mn
Series ferrite. Ferrite is a sintered body generally represented by the following formula.

[0038]

(MO) _x (NO) _y (Fe ₂ O ₃ ) z where x + y + z = 100 mol%, and M and N are Ni, Cu, Zn, Li, Mg, Mn, and S, respectively.
r, Ca and the like, and is composed of a complete mixture of a monovalent, divalent metal oxide and a trivalent iron oxide. In the present invention, the magnetic moment when a more preferably used magnetic field of 1000 Oersted is applied is 76 emu /
Examples of the core material particles of g or more include iron-based, magnetite-based, Mn-Mg-Sr-based ferrite, and Mn-based ferrite.

The bulk density of the carrier is at least 2.1 g / cm ³ , preferably at least 2.2 g / cm ³ , more preferably at least 2.3 g / cm ³ . A large bulk density is advantageous for preventing carrier adhesion. A core material having a low bulk density has large porosity or large surface irregularities. If the bulk density is small,
Even if the magnetic moment (emu / g) of 1 KOe is large, the value of the substantial magnetic moment per particle becomes small, which is disadvantageous for carrier adhesion. Also,
If the irregularities are large, the thickness of the coat resin varies depending on the location, and the charge amount and the resistance are likely to be non-uniform, which affects durability over time, carrier adhesion, and the like.

The carrier of the present invention is produced by forming a resin layer on the surface of the core particles. As a resin for forming the resin layer, various conventionally known resins used for manufacturing a carrier can be used.
In the present invention, a silicone resin containing a repeating unit represented by the following formula can also be preferably used.

[0041]

Embedded image 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 (phenyl group, tolyl group, etc.);
² represents an alkylene group having 1 to 4 carbon atoms or an arylene group (such as a phenylene group).

In the present invention, a straight silicone resin can be used. As such, KR2
71, KR272, KR282, KR252, KR25
5, KR152 (manufactured by Shin-Etsu Chemical Co., Ltd.), SR2400,
SR2406 (manufactured by Toray Dow Corning Silicone Co., Ltd.) and the like.

In the present invention, a modified silicone resin can be used. Examples of such a material 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 an epoxy-modified product: ES-1001N, an acrylic-modified silicone: KR-5208, and a polyester-modified product: K
R-5203, alkyd modified product: KR-206, urethane modified product: KR-305 (above, manufactured by Shin-Etsu Chemical Co., Ltd.), epoxy modified product: SR2115, alkyd modified product: SR2110 (manufactured by Toray Dow Corning Silicone Co., Ltd.) and the like. No.

The silicone resin that can be used in the present invention contains an aminosilane coupling agent in an appropriate amount (from 0.001 to 0.001).
30% by weight), such as the following. H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃ MW 179.3 H ₂ N (CH ₂ ) ₃ Si (OC ₂ H ₅ ) ₃ MW 221.4 H ₂ NCH ₂ CH ₂ CH ₂ Si (CH ₃ ) ₂ (OC ₂ H ₅ ) MW 161.3 H ₂ NCH ₂ CH ₂ CH ₂ Si (CH ₃ ) (OC ₂ H ₅ ) ₂ MW 191.3 H ₂ NCH ₂ CH ₂ NHCH ₂ Si (OCH ₃ ) _{3 MW 194.3 H 2 NCH 2 CH 2} NHCH 2 CH 2 CH 2 Si (CH 3) (OCH 3) 2 MW 206.4 H 2 NCH 2 CH 2 NHCH 2 CH 2 CH 2 Si (OCH 3) 3 MW 224 _{.4 (CH 3) 2 NCH 2} CH 2 CH 2 Si (CH 3) (OC 2 H 5) 2 MW 219.4 (C 4 H 9) 2 NC 3 H 6 Si (OCH 3) 3 MW 291.6

Further, in the present invention, as the resin for coating the surface of the carrier core material particles, the following resin may be used alone or in combination with the above-mentioned 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-acrylate 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-based 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, etc.

As a method for forming the resin layer on the surface of the carrier core material particles, a known method such as a spray drying method, an immersion method, or a powder coating method can be used. In particular, the method using a fluidized bed type coating apparatus is as follows.
It is effective for forming a uniform coating film.

The thickness of the resin layer formed on the surface of the carrier core material particles is usually 0.02 to 1 μm, preferably 0.03 to 1 μm.
０．８0.8 μm. Since the thickness of the resin layer is extremely small, the particle size distribution of the carrier composed of the core particles coated with the resin layer and the particle size distribution of the carrier core particles are substantially the same.

The carrier core material of the present invention may be a so-called resin-dispersed carrier having a form in which magnetic powder is dispersed in a known resin such as a phenol resin, an acrylic resin, and a polyester resin. Using this as a carrier core material
The carrier of the present invention can also be obtained by forming a resin coating layer such that the resistance of the resin coating layer near the core material is greater than the resistance of the coating layer on the carrier surface layer.

The developer of the present invention comprises the above carrier and toner. The toner used in the present invention contains a binder resin containing a thermoplastic resin as a main component, a coloring agent, fine particles, a charge control agent, a release agent, and the like. Can be used. The toner can be an irregular or spherical toner produced by various toner production methods such as a polymerization method and a granulation method. Further, both magnetic toners and non-magnetic toners can be used.

The following binder resins can be used alone or as a mixture. As the styrene-based binder resin, polystyrene, a homopolymer of styrene such as polyvinyltoluene and a substituted product thereof, styrene-
p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer,
Styrene-methyl methacrylate copolymer, styrene-
Ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl Styrene-based copolymers such as methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer; Methyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, epoxy resin, polyvinyl butyral, polyacrylic resin, rosin, modified rosin, terpene resin, pheno Le resins, aliphatic or aliphatic hydrocarbon resins, aromatic petroleum resins, chlorinated paraffin, and paraffin wax.

Further, the polyester resin can further lower the melt viscosity while securing the stability during storage of the toner as compared with the styrene or acrylic 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 and 1,4-butenediol. , 1,4-bis (hydroxymethyl) cyclohexane, bisphenol A, hydrogenated bisphenol A,
Etherified bisphenols such as polyoxyethylenated bisphenol A and polyoxypropylene-modified bisphenol A, dihydric alcohol units obtained by substituting these with a saturated or unsaturated hydrocarbon group having 3 to 22 carbon atoms, and other divalent alcohols Sorbitol, 1,2,2
3,6-hexanetetrol, 1,4-sorbitan, pentaethritol dipentaethritol, tripentaethritol, sucrose, 1,2,4-butanetriol,
1,2,5-pentanetriol, glycerol, 2-
Methylpropanetriol, 2-methyl-1,2,4-
Examples thereof include trivalent or higher alcoholic monomers such as butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene.

The carboxylic acids used for obtaining the polyester resin include, for example, monocarboxylic acids such as palmitic acid, stearic acid and oleic acid, maleic acid, fumaric acid, mesaconic acid, citraconic acid, terephthalic acid and cyclohexanedicarboxylic acid. Acids, succinic acid, adipic acid, sebacic acid, malonic acid, which have 3 to 22 carbon atoms
Divalent organic acid monomers substituted with saturated or unsaturated hydrocarbon groups, anhydrides of these acids, dimers of lower alkyl esters and linoleic acid, 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,2
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. Trivalent or higher polycarboxylic acid monomers can be exemplified.

Examples of the epoxy resin include a polycondensate of bisphenol A and epochlorohydrin. Examples of the epoxy resin include epomic R362, R364, R365, and R36.
6, R367, R369 (all manufactured by Mitsui Petrochemical Industries, Ltd.), Epotote YD-011, YD-012,
YD-014, YD-904, YD-017, (the above,
Toto Kasei Co., Ltd.) Epcot 1002, 1004, 1
007 (both manufactured by Shell Chemical Co., Ltd.) and the like.

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

It is also possible to incorporate a magnetic substance into the toner to form a magnetic toner. As the magnetic material, a ferromagnetic material such as iron and cobalt, magnetite, hematite, L
i-based ferrite, Mn-Zn-based ferrite, Cu-Zn
Fine powders such as system ferrite, Ni-Zn ferrite, and Ba ferrite can be used.

In order to sufficiently control the triboelectrification of the toner, so-called charge control agents such as metal complexes of monoazo dyes, nitrohumic acid and its salts, salicylic acid, naphthoic salts, and dicarboxylic acids such as Co, Cr and Fe Complex amino compounds, quaternary ammonium compounds, organic dyes and the like can be contained.

Further, a releasing agent may be added to the toner used in the present invention, if necessary. Release materials include low molecular weight polypropylene, low molecular weight polyethylene,
Carnauba wax, microcrystalline wax,
Jojoba wax, rice wax, montanic acid wax or the like can be used alone or in combination, but is not limited thereto.

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 fine particles of a hydrophobic metal oxide or a fine particle such as a lubricant as a fluidity improving material, and use a metal oxide, an organic resin fine particle, a metal soap or the like as an additive. It can be used. Specific examples of these additives include:
Fluororesins such as polytetrafluoroethylene, lubricating agents such as zinc stearate, and polishing agents such as cerium oxide and silicon carbide; for example, SiO ₂ , TiO with a hydrophobic surface
Fluidity imparting agents such as an inorganic oxide ₂ and the like; what are known as anti-caking agents, and, thereof, and the like surface-treated. In order to improve the fluidity of the toner, hydrophobic silica is particularly preferably used.

The toner used in the present invention has a weight average particle size Dt of 9.0 to 4.0 μm, preferably 8.5.
４4.5 μm. The ratio of the toner to the carrier is 2 to 25 parts by weight, preferably 4 to 15 parts by weight, per 100 parts by weight of the carrier.

In the present invention, the weight average particle diameter Dw of the carrier, the carrier core material and the toner is the particle diameter distribution of particles measured on a number basis (relation between number frequency and particle diameter).
Is calculated based on The weight average particle diameter Dw in this case is represented by the following equation.

[0063]

Dw = {1 / {(nD ³ )} × {(nD ⁴ )} In the above formula, D represents a representative particle diameter (μm) of particles present in each channel, and n represents Shows the total number of particles present. The channel indicates a length for equally dividing the particle size range in the particle size distribution diagram. In the case of the present invention, a length of 2 μm is adopted. The lower limit of the particle diameter stored in each channel was adopted as the representative particle diameter of the particles present in each channel.

As a particle size analyzer for measuring the particle size distribution, a Microtrac particle size analyzer (model HRA93) is used.
20-X100: manufactured by Honeywell). The measurement conditions are as follows. (1) Particle size range: 100-8 μm (2) Channel length (channel width): 2 μm (3) Number of channels: 46

The electrophotographic developer container of the present invention is a container in which the developer of the present invention is stored in a container for storing the developer. In this case, various known containers can be used.

The image forming apparatus of the present invention is an image forming apparatus equipped with a developing container, wherein the developing container of the present invention is used as the developing container. As the image forming apparatus in this case, various conventionally known apparatuses can be used.

The developing method of the present invention is a method using the above-mentioned developer of the present invention as the developer. in this case,
When a voltage obtained by superimposing an AC voltage on a DC voltage is applied as a developing bias applied from the outside, the image density is high,
High image quality with little background dirt can be obtained. In particular, dot reproducibility and highlight reproducibility are improved. When the above-described developing bias is applied, the substantial developing potential and the background potential become larger than when only the DC bias is applied. For this reason, carrier adhesion has conventionally been apt to occur, but the carrier of the present invention has made compatibility possible.

[0068]

The present invention will be described below with reference to examples and comparative examples. In the following, "parts" represents parts by weight.

Production Example of Toner (Toner Production Example 1) 100 parts of polyester resin 4 parts of copper phthalocyanine pigment 3 parts of zinc salt of salicylate 3 parts of the above components were sufficiently mixed by a blender and then melt-kneaded by a twin-screw extruder. After cooling, the mixture was coarsely pulverized by a cutter mill, finely pulverized by a jet stream type pulverizer, and further classified by an air classifier to obtain a weight average average particle size of 7.
4 μm toner base particles were obtained. Further, 0.8 part of hydrophobic silica fine particles (R972: manufactured by Nippon Aerosil Co., Ltd.) was added to 100 parts of the toner base particles, and mixed with a Henschel mixer to obtain Toner I.

Manufacturing Example of Carrier (Carrier Manufacturing Example 1) Silicone resin (SR2411)
(Toray Dow Corning Silicone Co., Ltd.) was diluted to obtain a silicone resin solution a having a solid content of 5%. Using a fluidized bed type coating apparatus, the above-mentioned silicone resin solution a was applied on the surface of each 5 kg of carrier core material particles (Cu-Zn ferrite, magnetic moment of 61 KOe 61 emu / g) having the properties shown in Table 1. Was applied at a rate of 40 g / min in an atmosphere of 100 ° C. to obtain a carrier having a thickness of 0.10 μm. On the other hand, to the same silicone resin solution a having a solid content of 5% as described above, carbon black (Ketjen Black EC-DJ600 manufactured by Lion Akzo Co., Ltd.) was added at 4% by weight based on the resin solid content, and a ball mill was used. For 60 minutes to prepare a silicone resin solution b. The resin solution b was continuously applied to the above-mentioned carrier having a thickness of 0.10 μm at a rate of 40 g / min without a time interval, and further heated at 220 ° C. for 2 hours to obtain a total thickness of 0.1 μm. 35 μm of carrier A was obtained. The adjustment of the film thickness was performed by the amount of the coating solution.

(Carrier Production Example 2) The same silicone resin solution b as that prepared in Example 1 was applied to a carrier core material particle 5 shown in Table 1 using a fluidized bed type coating apparatus.
Kg on each particle surface in an atmosphere of 100 ° C.
min., and heated at 210 ° C. for 2 hours to obtain a comparative carrier B having a thickness of 0.35 μm. The adjustment of the film thickness was performed by the amount of the coating solution.

(Carrier Production Example 3) A comparative carrier C having a thickness of 0.33 μm was obtained in the same manner as in Production Example 1 except that the carrier core particles shown in Table 1 were used.

(Carrier Production Example 4) A comparative carrier D having a thickness of 0.33 μm was obtained in the same manner as in Production Example 1 except that the carrier core particles shown in Table 1 were used.

(Carrier Production Example 5) A comparative carrier E having a thickness of 0.33 μm was obtained in the same manner as in Production Example 1 except that the carrier core particles shown in Table 1 were used.

(Carrier Production Example 6) A carrier was produced in exactly the same manner as in Production Example 1 except that the amount of carbon based on the resin solid content of the silicone resin solution b in Example 1 was changed to 2% by weight, and the mixture was heated and baked at 240 ° C for 2 hours. Was prepared, and a carrier F having a thickness of 0.34 μm was obtained.

(Carrier Production Example 7) Silicone resin (S
R2411 manufactured by Toray Dow Corning Silicone Co., Ltd.)
I got Next, to 300 g of the resin solution a, 7% by weight of carbon black (Ketjen Black EC-DJ600 manufactured by Lion Akzo Co., Ltd.) based on the resin solid content was added,
Using a ball mill, the mixture was dispersed for 60 minutes to prepare a silicone resin solution c. Using a fluidized bed type coating device,
Carrier core particles having the properties shown in Table 1 (Cu-Z
n-type ferrite, 1KOe magnetic moment 61 emu
/ G) On a surface of each particle of 5 kg, the above-mentioned silicone resin solution a was applied at a rate of 20 g / min in an atmosphere of 100 ° C. Simultaneously with the start of coating, the silicone resin solution c was added at a rate of 10 g / min to the silicone resin solution a.
The mixture was applied at a rate of 20 g / min in an atmosphere of 100 ° C. while being uniformly dispersed, and further heated at 200 ° C. for 2 hours to obtain a carrier G having a thickness of 0.36 μm.

(Carrier Production Example 8) Carrier core particles (MnMgSr ferrite, 1) having the properties shown in Table 1
A carrier H having a thickness of 0.37 μm was obtained in exactly the same manner as in Production Example 1 except that the magnetic moment of KOe (78 emu / g) was used.

(Carrier Production Example 9) Carrier core particles (Cu—Zn ferrite, 2
Carrier I having a thickness of 0.36 μm was obtained in exactly the same manner as in Production Example 1 except that 2.6% by weight of particles having a particle size of less than 2 μm was used.

(Carrier Production Example 10) Carrier core material particles (Cu—Zn ferrite,
Carrier J having a thickness of 0.35 μm was obtained in exactly the same manner as in Production Example 1 except that particles having a particle size of less than 22 μm were 0.4% by weight.

(Carrier Production Example 11) Carrier core material particles (Cu—Zn ferrite,
Production Example 1 except that a bulk density of 2.34 g / cm ³ ) was used.
In the same manner as above, a carrier K having a thickness of 0.34 μm was obtained.

(Carrier Production Example 12) Except that the carrier core particles (Mn ferrite, magnetic moment of 1KOe is 82 emu / g, bulk density 2.33 g / cm ³ ) of Table 1 were used, the procedure was exactly the same as in Production Example 1. 0.36μ
m carriers L were obtained.

(Carrier Production Example 13) Carrier core material particles X (magnetite, magnetic moment of 1 KOe is 80 emu / g, bulk density 2.36 g / cm ³ ) shown in Table 1 are used in exactly the same manner as in Production Example 1 except that they are used. 0.37μm thick
Was obtained.

(Carrier Production Example 14) In the silicone resin solution b of Example 1, 3% by weight of the aminosilane coupling agent H ₂ N (CH ₂ ) ₃ Si (OC ₂ H) with respect to the resin solid content was added.
₅ ) A carrier N having a thickness of 0.36 μm was obtained in exactly the same manner as in Production Example 1, except that ₃ was added, and the mixture was further heated and baked at 280 ° C. for 2 hours.

(Carrier Example 15) The carrier core material XI having the properties shown in Table 1 was obtained by vibrating 5 kg of the carrier core material shown in Table 1 with a vibration sieve having an ultrasonic oscillator for 6 minutes. The vibrating sieve has the structure shown in FIG. 1, and directly attaches to a 70 cmφ wire mesh (635 mesh) (5) supported on a frame (9) to attach a resonance ring (6). Is a sieve device (1) provided with a vibrator (8) that oscillates ultrasonic waves of 36 KHz. Wire mesh (5) is spring (3) on base (4)
And is disposed in a cylindrical container (2) supported through the inside. A vibration motor (not shown) is installed in the base (4), and a high-frequency current generated by driving the vibration motor is a vibration (8) attached to a resonance ring (6) via a cable (7).
And the ultrasonic wave is oscillated. The ultrasonic wave causes the resonance ring (6) to vibrate, and the vibration causes a vertical vibration of the entire mesh surface (5). The carrier core material supplied on the wire mesh (5) in the cylindrical container (2) was subjected to a sieving process, and then collected as the carrier core material XI on the wire mesh of the cylindrical container (2). There was no clogging of the mesh at all.
By using the vibration sieving machine (1) equipped with an ultrasonic oscillator, the ratio of less than 22 μm could be reduced to an extremely small amount of 6.3% by weight to 0.3% by weight. The yield is about 93
% By weight. Using this carrier core material XI, a coated carrier O having a thickness of 0.35 μm was obtained in exactly the same manner as in Carrier Production Example 1.

(Carrier Manufacturing Example 16) Carrier Manufacturing Example 5
, A sieve apparatus (1) using a carrier E for comparison obtained using a carrier core material in a carrier production example 15
(A fine particle was cut) to obtain a carrier E ′ having a particle size characteristic shown in Table 1 and a thickness of 0.34 μm of the present invention. Although the core material of the carrier E contained 8.3% by weight of particles having a particle size of less than 22 μm, the content of the particles having a particle size of less than 22 μm in the carrier E ′ was 0.5% by sieving.
% By weight. There was no clogging of the mesh during sieving.

(Production and Evaluation of Developer) The toner I obtained in the above toner production example 1 and the carrier production examples 1 to 16
Various developers were produced using the carriers A to E ′ obtained in the above. Further, an image was formed using the obtained developer, and its image quality was confirmed, and a characteristic test such as a reliability test was performed. The images were created using Imagio Color 4000 (a digital color copier / printer multifunction printer manufactured by Ricoh) under the following development conditions.・ Development gap (photoconductor-development sleeve): 0.43 m
m • Doctor gap (developing sleeve-doctor): 0.
65 mm, photoconductor linear speed 200 mm / sec, (developing sleeve linear speed / photoconductor linear speed) = 1.73, writing density: 600 dpi, charging potential (Vd): -600 V, and exposure of a portion corresponding to an image portion (solid document). Later potential (V
l): -100 V Development bias: DC-500 V / AC bias component:
4 kHz, -100 V to -900 V, 30% duty Quality evaluation was performed on transfer paper. However, the state of carrier adhesion was observed on the photoreceptor after development and before transfer.

The test methods employed in the following image forming examples are as follows. (1) Average dot diameter / variance of dispersion: A 1-dot image was created under the above-mentioned development conditions, and 16 dots
The measurement was performed at each part, and the average diameter of a total of 80 dots and the variation (dispersion: σ) of the average diameter of those dots were measured. (In the printer mode, a latent image was formed as ● ○○ ● ○○ ... so that both main scanning and sub-scanning become 200 lines.) (2) Uniformity of highlight part: rank sample was created for graininess And evaluated. Rank 10 is best. (3) Image density: 30 mm × 3 under the above development conditions
The center of the solid portion of 0 mm is measured at five places with an X-Rite 938 spectrocolorimeter, and the average value is obtained. (4) Background stain: The background stain under the above-mentioned developing conditions was evaluated on a scale of 1 to 10. The higher the rank, the less dirt on the ground,
Rank 10 is best. While replenishing the cyan toner I used for producing the initial image, 100,000 copies were run on a character image chart having an image area ratio of 6% under the above-mentioned developing conditions, and the background stain was evaluated. (5) Carrier Attachment: Background Potential = Vb-Vd When carrier attachment occurs, it causes damage to the photosensitive drum and the fixing roller, resulting in deterioration of image quality. Even if the carrier adhered, only a part of the carrier was transferred to the paper. Therefore, the carrier adhesion was directly observed and evaluated on the photosensitive drum. In addition, since the manner of carrier adhesion varies depending on the image pattern, the following method was used to evaluate the difficulty of carrier adhesion. The developing bias (Vb) is DC-500V
And the charging potential (Vd) is -600, -650,-
700, gradually changing the background area (⇒ unexposed area)
Is developed and the charging potential (V
d) was determined. The value of Vb-Vd was calculated and used as the background potential of the occurrence of carrier adhesion. The larger the value, the more difficult it is for the carrier to adhere. As an AC bias component, ± 400 V was superimposed on the DC bias (frequency: 4 kHz, 30% duty). The above measurement was performed at the initial stage and at the time of image output after 100,000 copies.

(Example 1) To 100 parts of carrier A, 8 parts of toner I was added, and the mixture was stirred with a ball mill for 20 minutes to prepare a developer. The charge amount of the toner was −26 μc / g. Next, the image quality was first checked by the above-described measurement and evaluation method using Ricoh's Imagio Color 4000 under the above development conditions. The image density was 1.63, the background dirt was rank 9, and the variance was 0.17. The background potential at which carrier adhesion began to occur was 250V. Subsequently, 100,000 sheets of running evaluation were performed on a character image chart having an image area ratio of 6%. After running 100,000 sheets, the carrier adhesion start voltage and the background dirt rank were confirmed. The carrier adhesion start voltage was 220 V, the background dirt was at a good level of rank 7, and the photoreceptor had few scratches even after 100,000 sheets.
High image quality was maintained.

(Comparative Example 1) Toner I (8 parts) was added to carrier B (100 parts), and the mixture was stirred with a ball mill for 20 minutes to prepare a developer. The toner charge amount is -27μc
/ G. When evaluation was carried out in the same manner as in Example 1 using Imagio Color 4000, the background potential at which carrier adhesion began to occur was 260 V, but the dot variation was as large as 0.24. Also,
When 100,000 sheets were run, the carrier deposition start voltage was lowered to 160 V, and carrier deposition was likely to occur. The dirt on the ground was slightly worse at rank 6.
Observation of the photoreceptor revealed that the surface had more scratches than in Example 1.

(Examples 2 to 12 and Comparative Examples 2 to 4) Production Example 3 (Carrier C) to Production Example 16 using toner I
Example 1 A developer was prepared using (Carrier E ′), and Example 1 was used.
In exactly the same way, Ricoh Imagio Color 4000
Was used to perform an image quality test. Table 2 shows the quality evaluation results in each of the comparative examples and examples.

[0091]

[Table 1-1]

[0092]

[Table 1-2]

[0093]

[Table 2-1]

[0094]

[Table 2-2] TC is fixed at 7 Wt%. (Note 1) Background potential at which carrier adhesion starts to occur = DC bias voltage (Vb)-charging potential (Vd)

[0095]

As described above, according to the present invention, according to the present invention, a small particle having a specific particle size distribution and a carrier resistance (Log Ω · cm) of 12.0 or more can be obtained. Yes, and the resistance of the resin coating layer of the portion close to the carrier core material, by using a carrier having a property larger than the resistance of the coating layer of the carrier surface layer portion, by using a developer,
In particular, it has a feature that carrier adhesion hardly occurs over time. Further, the present invention has an extremely excellent effect that high image quality and high reliability can be obtained by combining the powder characteristics and the magnetic characteristics of the carrier.

[Brief description of the drawings]

FIG. 1 is a structural diagram showing an explanation of a vibration sieving machine with an ultrasonic oscillator according to the present invention.

FIG. 2 is a perspective view of a resistance measuring cell used for measuring the electrical resistivity of the carrier.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vibration sieve machine 2 Cylindrical container 3 Spring 4 Base 5 Wire mesh 6 Resonance ring 7 Cable 8 Converter (vibrator) 9 Ring frame 11 Cell 12a Electrode 12b Electrode 13 Carrier

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahide Yamashita 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Hiroaki Takahashi 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh F-term (reference) 2H005 BA06 BA11 BA15 CA12 CA26 CB03 CB04 EA01 EA02 EA05 EA10

Claims (19)

[Claims] 1. A carrier for an electrophotographic developer comprising magnetic core particles and a resin layer covering the particle surface, wherein the weight average particle diameter Dw of the carrier is 25 to 45 μm.
When the content of particles having a particle size smaller than 44 μm in the carrier is 70% by weight or more and the content of particles having a particle size smaller than 22 μm is 7.0% by weight or less, the carrier resistance (LogΩ) (Cm) is 12.0 or more, and the resistance of the resin coating layer in a portion close to the carrier core material is higher than the resistance of the coating layer in the surface layer portion of the carrier. 2. The magnetic moment at 1 KOe is 76
The carrier for an electrophotographic developer according to claim 1, wherein the carrier is not less than emu / g. 3. The carrier for an electrophotographic developer according to claim 1, wherein a content ratio of particles having a particle size smaller than 22 μm in the carrier is 3% by weight or less. 4. The carrier for an electrophotographic developer according to claim 1, wherein a content ratio of particles having a particle size smaller than 22 μm in the carrier is 1% by weight or less. 5. The carrier for an electrophotographic developer according to claim 1, wherein particles having a size of 62 μm or more are less than 1% by weight. 6. The method according to claim 1, wherein the bulk density of the carrier is 2.2 g / cm ³ or more.
3. The carrier for an electrophotographic developer according to item 1. 7. The carrier for an electrophotographic developer according to claim 1, wherein the carrier core material is Mn ferrite. 8. The carrier for an electrophotographic developer according to claim 1, wherein the carrier core material is magnetite. 9. The carrier for an electrophotographic developer according to claim 1, wherein the coating layer is a silicone resin. 10. The method according to claim 1, wherein the resin layer is made of a resin containing an aminosilane coupling agent.
10. The carrier for an electrophotographic developer according to any one of items 1 to 9. 11. An electrophotographic developer comprising a toner and a carrier, wherein the carrier is used as the carrier.
A developer for electrophotography, comprising using the carrier according to any one of the above. 12. A developer container containing a developer, wherein the developer is the developer according to claim 11. 13. An image forming apparatus equipped with a developer container, wherein the developer container is the developer container according to claim 12. 14. A developing method using a developer, wherein the developer according to claim 11 is used as the developer. 15. A method for producing a carrier for electrophotographic development, wherein (i) a pulverized particle of a magnetic material is classified to have a weight average particle diameter of 25 to 45 μm and 44 μm.
obtaining a core material particle having a content ratio of particles having a particle size smaller than m of 70% by weight or more and a content ratio of particles having a particle size of less than 22 μm of 7.0% by weight or less;
(Ii) The resistance (LogΩ · cm) of the resin-coated carrier is 1
A step of forming a resin coating on the surface of the core particles, in which the resistance of the resin coating layer at a portion close to the carrier core material is greater than the resistance of the coating layer on the surface layer of the carrier. 11. The method according to claim 1, wherein:
4. The method for producing a carrier for electrophotographic development according to item 1. 16. A method for producing a carrier for electrophotography, wherein (i) the resistance of the resin coating layer on the surface of the pulverized magnetic material particles near the carrier core is determined by the resistance of the coating layer on the carrier surface layer. (Ii) classifying the resin-coated particles to obtain particles having a weight average particle size of 25 to 45 μm and a particle size smaller than 44 μm. When the content ratio is 70% by weight or more,
The method for producing a carrier for electrophotographic development according to any one of claims 1 to 10, comprising a step of obtaining a carrier having a content ratio of particles having a particle size smaller than 22 µm of 7% by weight or less. . 17. The method for producing a carrier for electrophotographic development according to claim 15, wherein a vibration sieve equipped with an ultrasonic oscillator is used to classify the pulverized particles of the magnetic material. 18. The method for producing a carrier for electrophotographic development according to claim 16, wherein a vibrating sieve equipped with an ultrasonic oscillator is used to classify the resin-coated particles. 19. The vibration sieve machine according to claim 17, wherein said vibrating sieve has a structure for transmitting ultrasonic vibration to a wire mesh surface by means of a resonance ring installed in said sieve machine.
4. The method for producing a carrier for electrophotographic development according to item 1.