JPH09304974A - Carrier for developing electrostatic charge image, developer and developing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain image disturbance due to charging failure so as to stably obtain a high-grade output image over a long period by setting the sphericity of carrier in a specified range. SOLUTION: Carrier is obtained by immobilizing resin particles on the surface of carrier formed by coating the magnetic particle surface with polyolefine, and the sphericity of the carrier is in the range of 1.0-25.0. This constitution improves unstableness of applying electric charges to toner due to bad fluidity in the case of using carrier coated with polyolefine resin so as to obtain carrier by which crush of characters and fog of background part are not caused under high temperature and high humidity environment. Further, it is possible to obtain carrier, a developer and a developing method which can be applied to an image forming method adopting a toner recycle system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carrier for developing an electrostatic image, a developer and a developing method used in electrophotography, electrostatic photography, electrostatic printing and the like.

[0002]

2. Description of the Related Art Two-component developers comprising a carrier and a toner are widely used in copying machines utilizing electrophotography.
In addition, usually, in order to impart durability and charging stability, a carrier is often used in which the surface of the magnetic particles is coated with a resin.

As a resin for coating the surface of a carrier, a polyolefin-based resin has attracted attention. Since the polyolefin resin is excellent in water repellent property and releasability, the carrier surface is less likely to be contaminated. Then, a proposal of a carrier coated with a polyolefin resin is disclosed in JP-A-52-154.
639, JP-A-54-35735, and JP-A-2-187770.

However, a carrier coated with a polyolefin resin has poor fluidity, and it is difficult to sufficiently stably mix it with a toner when used as a developer. Therefore, especially in a high temperature and high humidity environment, there is a problem that charging is not stably applied to the toner, characters are crushed, and fog occurs on the background portion.

To solve these problems, Japanese Patent Laid-Open No.
Japanese Patent Publication No. 266168 proposes to seal the irregularities on the surface of the carrier with functional fine particles. However, only by sealing the irregularities on the surface of the carrier with fine particles, it is not possible to improve the poor fluidity of the carrier coated with the polyolefin resin and it is not possible to prevent the above problems.

Further, in order to improve the chargeability of the carrier, a technique of incorporating a charge controllable material has been proposed. For example, it is described in Japanese Patent Laid-Open No. 53-100242, Japanese Patent Laid-Open No. 1-202764, and the like. However, this technique is intended to increase the saturated charge amount of the carrier, and the effect of improving the charging rise is not found. I can't.

Further, Japanese Patent Laid-Open Publication No. 61-9661 discloses that
In order to improve the fluidity of the developer, a microcarrier in which a fluidity improver is added to a magnetic powder dispersion type carrier has been proposed, but this is a technology unique to magnetic powder dispersion type microcarriers. Add a property improver to the carrier,
It is being stirred. Therefore, it is completely different from the technique of immobilizing fine particles on the surface of a resin-coated carrier using a polyolefin resin as provided in the present invention.

[0008]

By improving the poor fluidity of the carrier coated with polyolefin, the toner charging start-up is improved, image disturbance due to poor charging is suppressed, and high-quality output is achieved for a long period of time. It is an object of the present invention to provide a carrier, a developer and a developing method that can stably obtain an image.

Another object of the present invention is to provide a carrier, a developer and a developing method which can be applied to an image forming method equipped with a toner recycling system by improving poor fluidity of the carrier.

[0010]

[Means for Solving the Problems] This is a carrier in which resin particles are fixed on the surface of a carrier in which the surface of magnetic particles is coated with polyolefin, and the sphericity α of the carrier is 1.
The above problems can be solved by using a carrier characterized by being in the range of 0 to 25.0, a developer using the carrier, and a developing method.

That is, according to the present invention, instability of imparting charge to the toner due to poor fluidity when a carrier coated with a polyolefin-based resin is used is improved, and in a high temperature and high humidity environment. It is possible to obtain a carrier, a developer and a developing method which do not cause the characters to be crushed and the background to be fogged.

Similarly, it is possible to obtain a carrier, a developer and a developing method which can be applied to an image forming method equipped with a toner recycling system.

The structure of the present invention will be described below.

(Magnetic Particles) As the magnetic particles usable in the present invention, a substance which is strongly magnetized in its direction by a magnetic field can be used.

Specifically, iron, ferrite, magnetite, and other metals exhibiting ferromagnetism such as nickel and cobalt or alloys or compounds containing these metals can be used. The term “ferrite” as used herein is a general term for magnetic compounds containing iron and is not limited to spinel type.

(Resin coating method) The method for producing the carrier used in the present invention is not particularly limited, and a known coating method can be applied.

Specifically, for example, a. A method of dissolving the coating resin in a suitable solvent and spray coating the surface of the magnetic particles, b. A method in which a resin powder for coating is electrostatically adhered to the surface of the magnetic particles, and is mechanically fixed while being heated to a temperature close to or higher than the melting point of the resin material, c. A method described in JP-A-60-106808 (surface polymerization coating method) in which a monomer of a coating resin is polymerized and grown on the surface of the magnetic particles to coat the particles can be applied.

Two or more of these methods may be used in combination.

Among these coating methods, c. When a method of coating by polymerizing and growing a monomer of the coating resin on the surface of the magnetic particles is used, a resin coating layer having a sufficient thickness can be uniformly formed, so that a developer having more stable characteristics can be obtained. It is preferable in that it can be obtained.

That is, the resin coating layer contains a titanium and / or zirconium-containing highly active catalyst component soluble in a hydrocarbon solvent, magnetic particles and an organoaluminum compound, and is coated with a coating resin on the surface of the magnetic particles. This is a method of polymerizing and growing a monomer to form a resin coating layer. Although an olefin monomer is selected as a monomer to which this resin coating method is applied, particularly when an ethylene monomer is used, good results can be obtained.

(Adjustment of Carrier Volume Resistance) Further, a conductive material or a semiconductive material may be added to the coating resin of the carrier used in the present invention, if necessary.

Specific examples of the conductive material or semiconductive material that can be introduced into the coating resin include fine metal particles such as iron, aluminum, nickel and tungsten, various carbon blacks such as furnace black and acetylene black, and conductive titanium oxide. , Silicon oxide, silicon carbide, tin oxide,
It is preferable to use fine particles such as aluminum oxide.

The average primary particle size is preferably 1/50 or less of the weight average particle size of the carrier.

As the volume resistivity of the carrier,
It is preferably in the range of 1 × 10 ⁸ to 1 × 10 ¹⁵ Ωcm.

(Fine Resin Particles Immobilized on Carrier) As the resin particles to be fixed on the carrier surface of the present invention, fine particles made of known materials can be used.

For example, styrene resin, acrylic resin, styrene / acrylic copolymer resin, fluorine resin, silicone resin, carbonate resin, epoxy resin, ester resin, olefin resin, acetal resin, ketone resin. Fine particles made of a resin, a phenol resin, a melamine resin, an amide resin, a vinyl resin, or the like can be used.

(Shape of Resin Fine Particles) The shape of the resin fine particles may be any shape such as a true sphere, a sphere, a plate, an irregular shape, or a needle shape. Of these,
It is particularly preferable to use true spherical or spherical resin fine particles, because immobilization can be performed more uniformly.

It is more preferable to use fine resin particles having a cross-linked molecular structure.

Specifically, a resin having a molecular chain bonded in a mesh shape, such as a silicone resin, a cross-linking acrylic resin, a phenol resin, or a melamine resin, can be preferably used.

Since the fine particles of the crosslinkable resin itself are unlikely to be deformed, the resin fine particles can be fixed to the surface of the carrier reliably with a sufficient depth.

(Particle Diameter of Resin Fine Particles) The average primary particle diameter of the resin fine particles is 0.
It is preferable that the ratio is in the range of 0001 to 0.01. If the particle size of the resin fine particles to be used is excessive, it can be used by adjusting the particle size to an appropriate value by pulverization, classification, or the like.

(Thermophysical Properties of Resin Fine Particles) It is preferable that the resin fine particles to be used have a melting point higher than that of the carrier coating resin. The melting point of the resin can be measured, for example, by measuring an endothermic peak by the DSC method.

(Addition amount of resin fine particles) The addition amount of the resin fine particles to be immobilized on the surface of the carrier is slightly different depending on the particle diameter and the specific gravity of the resin fine particles to be used, but is 0.01 to the total weight of the carrier. It is preferably in the range of 10.0% by weight.

(Method for Immobilizing Resin Particles) As a method for immobilizing resin particles on the carrier surface, specifically,
The above-mentioned resin-coated carrier is mixed with a necessary amount of resin fine particles, and the resin fine particles are attached and arranged on the carrier surface. Then, a method of applying mechanical or mechanical / thermal stress to the carrier surface to firmly fix the resin fine particles to the carrier surface can be used.

The resin fine particles may be mixed and fixed at the same time, or the mixing and the fixation may be repeated if necessary.

As a method for immobilizing resin fine particles,
Specifically, a method of applying mechanical stress to the carrier surface by rotating the mixing container itself in which the carrier and the resin particles are charged, charging the carrier and the resin particles together with the mixing medium into the apparatus, and utilizing the motion of the mixing medium. To apply mechanical stress to the carrier surface, to rotate the stirring blade installed in the mixing container to mix the carrier and the resin particles, and to apply mechanical stress to the carrier surface. A method of fluidizing the mixture with an air stream or a liquid stream to bring the carriers into contact with each other to apply mechanical stress, passing the mixture in which the carrier and the resin fine particles have been mixed in advance or circulating the apparatus with the air stream or the liquid stream, Method of applying mechanical stress to the inner wall of the device, collision plate, or by contacting carriers with each other. The mixture which had been mixed with fat particles fall freely, it is possible to use a method of applying mechanical stresses by contacting the inner walls of the apparatus and the collision plate, and the like.

Among these methods, it is particularly preferable to rotate the stirring blade to fix it because the strength of immobilization can be adjusted relatively easily and the apparatus configuration is simple and the maintainability is good. This is a method of performing a chemical conversion process.

When performing the above-mentioned immobilization treatment, if the apparatus itself and the inflowing gas or liquid are simultaneously heated as required, the immobilization treatment of the resin fine particles may be completed in a short time. it can. In that case, good results can be obtained by setting the carrier temperature by heating within the range of the melting point of the coating resin ± 50 ° C.

When the resin fine particles are fixed by the above method, the carrier sphericity α is used as an index of the fixed state.
Should be in the range of 1.0 to 25.0. In a more preferable range, the sphericity α is 5.0 to 20.0.

By keeping the sphericity α of the carrier within an appropriate range, not only the resin fine particles can be sufficiently fixed on the carrier surface, but also the mechanical frictional force between the carriers can be reduced, so that the resin fine particles can be removed. It can be sufficiently prevented.

(Method of measuring sphericity) The sphericity α of the resin fine particle-immobilized carrier can be calculated by the following formula.

The sphericity alpha = (measured specific surface area) / (theoretical specific surface _{area) = (S B) / [} 6 / (D · ρ)] [-] Here, S _B: BET value [m ² / G] D: Weight average particle diameter [μm] ρ: True density [g / cm ³ ] In the formula, the BET value S _B is the specific surface area obtained by the N ₂ gas adsorption method. In the present invention, the FLOWSORBII230
0 (manufactured by Micromeritics) is used as the value measured under the following conditions.

Measurement method: 1-point method specific surface area Supply gas: N ₂ 30% / He 70% mixed gas Gas pressure: About 1 kgf / cm ² Gas flow rate: About 20 cm ³ / min Gas flow path: SHORT PATH Cooling medium: Liquid nitrogen Degassing temperature: 25 ° C. (room temperature) Further, the weight average particle diameter D is a value obtained by a laser diffraction method, and in the present invention, D50% measured under the following conditions with HELOS SYSTEM (manufactured by Sympatech). The value is used as the weight average particle size.

Measurement method: SUSPENSION CELL Focal length: 100 mm Medium: Water + surfactant Ultrasonic wave application time: 20 sec Resting time: 10 sec Measurement time: 15 sec The true density ρ is determined by the gas phase displacement method. It is a value obtained by a pressure comparison method, and in the present invention, a high precision automatic volume meter VM-
The value measured under the following conditions at 100 (manufactured by STEC Co., Ltd.) is used.

Carrier gas: He Supply pressure: Approximately 1.0 kgf / cm ² Measurement environment: 25 ° C./50% RH Number of measurements: 4 times (calculate average value) (toner) The toner used in the present invention is known. Can be used. Specifically, it is a toner including at least a binder resin and a colorant, and may be a toner to which a release agent, a charge control agent, a fluidizing agent, and a magnetic material are further added as necessary. Known materials can be used for the constituent materials.

Specifically, as the binder resin, a styrene resin, an acrylic resin, a styrene-acrylic copolymer resin, a polyester resin, an epoxy resin, a vinyl resin or the like can be used.

As the colorant, various carbon blacks,
Magnetic powder, various dyes and pigments can be used.

The weight average particle diameter of the toner used in the present invention is 1/4 to 1/2 of the weight average particle diameter of the carrier used.
Those in the range of 0 are preferred.

As a method for producing the toner, a known method can be used. Specifically, the constituent materials are mixed, melted and kneaded, and then subjected to a cooling step, pulverization and classification to obtain a toner, and a pulverization method for obtaining a toner, or emulsion polymerization, suspension polymerization, etc. to obtain a toner. A polymerization method or the like can be used.

(Developer) The developer used in the present invention is
Although it is composed of a carrier and a toner, a third component such as a lubricant, a cleaning aid and a fluidizing agent may be mixed if necessary.

The mixing ratio of the toner to the entire developer is
It is preferably in the range of 3.0 to 15.0% by weight.

When mixing the magnetic carrier and the toner, a conventionally known mixer can be used.
It is preferable that the stress applied to the developer at that time is small. Specifically, a rotation type mixer such as a V-type mixer, a W-cone mixer, and a rocking mixer can obtain better results.

(Developing Device) As the developing device which can be used in the present invention, a known developing device which can be applied to a magnetic brush developing method in which a magnetic brush is formed and a developer is conveyed to a developing area can be used.

The developing device used in the present invention is composed of two mechanisms, namely, a stirring unit for stirring the newly supplied toner with the carrier and a transport unit for transporting the developer to the developing area.

The developer stirring section stirs the carrier with the replenished toner or the so-called recycled toner which collects and reuses the toner remaining on the photoconductor after the image formation, so that the toner has the desired polarity. It is a mechanism for charging.

As the stirring member used for stirring the toner and the carrier, known stirring members such as a screw type, a water wheel type, and a stirring spatula type can be used.

The developer carrying section is composed of a magnetic pole column in which a plurality of magnetic poles are arranged, a cylindrical sleeve covering the circumference thereof, and a restricting member for restricting the developer carrying amount to an appropriate amount. . Then, in order to convey the developer, one or both of the cylindrical sleeve and the inner magnetic pole is rotated.

A known sleeve can be used as the cylindrical sleeve. Aluminum, stainless steel, etc. can be used as the material. Further, in order to stably convey the developer to the developing area, it is effective to subject the sleeve surface to a surface roughening treatment such as a thermal spraying treatment, a sandblasting treatment, and a grooving treatment.

If the total number of magnetic poles of the magnetic pole columns inside the sleeve is at least 4, preferably 5 to 10, the developer transportability is very stable.

Further, as the member for regulating the developer transport amount, a known system can be used. Specifically, a magnetic rod or magnetic blade that has magnetism and regulates the developer conveyance amount by magnetic force, or a non-magnetic material that is mechanically pressed onto the sleeve or has a certain gap to convey the developer conveyance amount. A non-magnetic rod or a non-magnetic blade that regulates can be used.

As the material for the non-magnetic regulating member, known materials can be used. Specifically, metal materials such as aluminum, stainless steel, etc., elastic bodies such as urethane rubber, silicone rubber, etc., or a combination thereof are used. Can be used. Further, when an elastic body such as rubber is used as the regulation member, a conductive material such as carbon black may be compounded in order to impart conductivity to the regulation member.

In the present invention, the magnetic brush is formed and the developer is conveyed to the developing area. However, in the developing section, the magnetic brush comes into contact with the photosensitive member on which the electrostatic latent image is formed and develops. It can be applied to both the developing method and the non-contact developing method in which the developing is performed without contacting with the photoreceptor.

[0063]

【Example】

[Manufacture of carrier 1] A spira coater (Okada Seiko Co., Ltd.) was prepared by dissolving polyethylene in toluene by heating.
The surface of the magnetic particles (magnetite sintered particles; volume average particle size 65 μm) was coated with a resin to obtain a polyethylene-coated carrier 1.

Next, with respect to the obtained polyethylene-coated carrier 1, crosslinked styrene acrylic copolymer resin fine particles (Microgel P-5002; average particle size 0.05 μm).
(manufactured by Nippon Paint Co., Ltd.) 1.0% by weight and added to MechanoMill (Okada Seiko Co., Ltd.), which is a high-speed stirring type mixing device, and then 10 at a stirring blade rotation speed of 1000 rpm at room temperature. The mixture was stirred and mixed for 1 minute to obtain Carrier 2.

Then, the mixture was stirred and mixed under heating at 100 ° C. for 1 hour under the condition of a stirring blade rotation speed of 2000 rpm, and a polyethylene-coated carrier 3 was obtained through a cooling process.

Similarly, a polyethylene-coated carrier 3
Carriers 4 and 5 were obtained by further extending the stirring and mixing time of 1 hour and 2 hours.

[Production of Carrier 2] In an autoclave, 500 ml of dehydrated n-hexane and 450 g of magnetic particles (MnMg ferrite, volume average particle size 65 μm) previously dried under reduced pressure are put and stirred. Next, 2.0 mmol of Ziegler-Natta catalyst was added and stirred to carry the catalyst on the surface of the magnetic particles.

Next, 0.22 g of carbon black was charged from the nozzle in the upper part of the autoclave. The carbon black used was one that had been previously dried under reduced pressure and mixed with dehydrated n-hexane to form a slurry.

After that, pressure is applied and the mixture is heated at 90 ° C. for 5 minutes.
By continuously supplying ethylene gas for 0 minutes, ethylene was polymerized on the surface of the magnetic particles to obtain a magnetite- and carbon black-containing polyethylene composition. Further, the polyethylene composition obtained here is opened 106
A carbon black-containing polyethylene-coated carrier 6 was obtained by removing aggregates with a sieve of μm and removing free polyethylene particles with a sieve of 38 μm.

Next, with respect to the obtained polyethylene-coated carrier 6, crosslinked melamine resin fine particles (EPOSTA) were used.
RS: average particle size 0.3 μm; manufactured by Nippon Shokubai Co., Ltd.) 2.0
The resulting mixture was added to a mechano-mill (manufactured by Okada Seiko Co., Ltd.), which is a high-speed stirring type mixing device, and then stirred and mixed at room temperature for 10 minutes under the condition of a stirring blade rotation speed of 1000 rpm to obtain a carrier 7.

Then, the mixture was stirred and mixed for 1 hour under heating at 100 ° C. under the condition of a stirring blade rotation speed of 2000 rpm, and a polyethylene-coated carrier 8 was obtained through a cooling process.

Similarly, a polyethylene-coated carrier 8
Carriers 9 and 10 were obtained by further extending the stirring and mixing time of 2 to 4 hours.

[Production of Carrier 3] For the polyethylene-coated carrier 6 obtained in Production of Carrier 2, crosslinked silicone resin fine particles (Tospearl 105; average particle size of 0.
5 μm; Toshiba Silicone Co., Ltd.) 3.0% by weight was added, and MechanoMill (Okada Seiko Co., Ltd.) which is a high-speed stirring type mixing device.
Manufactured). Then, the mixture was stirred and mixed under heating at 100 ° C. for 2 hours under the condition of a stirring blade rotation speed of 2000 rpm, and a polyethylene-coated carrier 11 was obtained through a cooling process.

[Production of Carrier 4] Fine particles of cross-linked styrene-acrylic copolymer resin (Microgel P-
3101; average particle size 0.3 μm; Nippon Paint Co., Ltd.)
1.5% by weight was added, and the mixture was put into MechanoMill (manufactured by Okada Seiko Co., Ltd.) which is a high-speed stirring type mixing device. Then 100
1 under the condition of stirring blade rotation speed 2000 rpm under heating at ℃
After stirring and mixing for a period of time, and a cooling process, a polyethylene-coated carrier 12 was obtained.

[Manufacture of carrier 5] The polyethylene-coated carrier 6 obtained in the manufacture of carrier 2 was crosslinked phenolic resin fine particles (Bellpearl R-900; classified to have an average particle size of 2.0 μm; 5.0)
The mixture was added by weight% and put into a mechano-mill (manufactured by Okada Seiko Co., Ltd.) which is a high-speed stirring type mixing device. Then, the mixture was stirred and mixed under heating at 100 ° C. under the condition of a stirring blade rotation speed of 2000 rpm for 3 hours, and a polyethylene-coated carrier 13 was obtained through a cooling process.

[Manufacture of Carrier 6] Manganese (III) oxide Mn ₂ O ₃ inorganic fine particles (average particle size 1.0 μm) were added to the polyethylene-coated carrier 1 obtained in Manufacture 1 of Carrier.
m) 5.0 wt% was added, and the mixture was put into MechanoMill (manufactured by Okada Seiko Co., Ltd.) which is a high-speed stirring type mixing device. afterwards,
The polyethylene-coated carrier 14 was obtained by heating and stirring at 100 ° C., stirring and mixing for 1 hour under the condition of the rotation speed of the stirring blade of 2000 rpm, and cooling.

[0077]

[Table 1]

[Production of Toner and Developer] 100 parts by weight of styrene / acrylic copolymer resin (glass transition point: 58 ° C., softening point: 138 ° C.) was used as a releasing agent for low molecular weight polypropylene (Viscor 660P: Sanyo Kasei Co., Ltd.). 2 parts by weight) and 10 parts by weight of carbon black (Black Pearl L: manufactured by Cabot Co., Ltd.) as a colorant were mixed and melt-kneaded with a biaxial kneader.

Then, after cooling and coarse crushing steps, fine pulverization and air classification were carried out to obtain colored particles having a weight average particle diameter of 6.0 μm. After that, as a fluidizing agent, hydrophobic silica fine particles (R-974: Nippon Aerosil Co., Ltd.) were used for the colored particles.
(Manufactured by Co., Ltd.) was externally mixed in an amount of 1.0 part by weight to obtain a toner used in Examples of the present invention.

[Performance Evaluation 1] (Charge Rise of Developer) Toner 1.
8g and 28.2g of carrier are put into a ball mill, and NN
100 rpm in the environment (20 ° C, 50% RH)
Mix at rpm. At that time, the charge buildup was evaluated by measuring the change with time of the charge amount.

The charge amount was measured by a blow-off powder charge amount measuring device TB-200 (manufactured by Toshiba Chemical Co., Ltd.) for a mixing time of 1 minute, 2 minutes, 5 minutes, 10 minutes and 5/20 minutes.
When the charging point reached the saturation point of the charge amount within 5 minutes, it was determined that the charge rise was good. The evaluation is shown in Table 2 as ⊚ or ×.

[0082]

[Table 2]

[Performance Evaluation 2] Toner 48 obtained above
g and 752 g of carrier were put into a V-type mixer and mixed for 20 minutes to obtain a two-component developer.

A commercially available digital copying machine Konica 7050 equipped with a toner recycling system for this developer.
(Manufactured by Konica Corp.) in a high temperature and high humidity environment (30 ° C,
80,000 RH), 100,000 continuous live-action images were evaluated.

In the digital copying machine Konica 7050 used in this embodiment, the cylindrical sleeve rotates around the fixed magnetic pole column to convey the developer and at the same time.
It is equipped with a developing system that forms a magnetic brush of developer.

(Image Density) A solid image having an original density of 1.30 was copied, and the relative reflection density of the output image with respect to a blank sheet was measured. Macbeth densitometer RD-9
18 (manufactured by Macbeth Co., Ltd.) was used, and an image density of 1.30 or more was judged to be good. The evaluation was performed twice for the first copy and at the end.

(Background Fog Density) A blank paper original was copied after the initial copying and after the copying, and the relative reflection density of the output image with respect to the blank paper was measured. A Macbeth densitometer was used for density measurement, and image density of 0.005 or less was judged to be good.

(Character Collapse) After completion of copying, a character original was copied and the reproducibility of output characters was visually evaluated. Here, it was judged that if the 4-point character was output without being crushed, it was excellent (⊚), if the 5-point character was output without being crushed, it was good (∘), and otherwise it was defective (x).

[0089]

[Table 3]

As is clear from the above results, when a carrier coated with a polyolefin resin is used,
It can be seen that the fluidity is improved, the charge imparted to the toner is stabilized, and the characters are not crushed and the background is not fogged even in a high temperature and high humidity environment.

Similarly, it was possible to obtain a carrier, a developer and a developing method which can be applied to an image forming method equipped with a toner recycling system.

[0092]

EFFECT OF THE INVENTION The instability of imparting charge to the toner due to poor fluidity when using a carrier coated with a polyolefin resin is improved, and characters are crushed even in a high temperature and high humidity environment. It was possible to obtain a carrier, a developer and a developing method which are free from fog on the background portion.

Similarly, it is possible to obtain a carrier, a developer and a developing method applicable to an image forming method equipped with a toner recycling system.

Claims (3)

[Claims] 1. A carrier in which resin particles are fixed on the surface of a carrier having magnetic particles coated with polyolefin, and the sphericity α of the carrier is in the range of 1.0 to 25.0. Characteristic electrostatic charge image developing carrier. 2. A two-component developer comprising a carrier for developing an electrostatic charge image and a toner, wherein the carrier covers the surface of magnetic particles with a polyolefin, and resin fine particles are fixed on the surface of the carrier. Sphere α is 1.0 to 2
A two-component developer, which is a carrier in the range of 5.0. 3. A two-component magnetic brush developing method using a carrier for electrostatic image development and a toner, wherein the two-component magnetic brush developing method according to claim 2 is used.