JP2003280283A - Electrophotographic carrier and developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic carrier and a developer which do not cause sticking of a toner to the surface of the carrier core or peeling of a coating layer comprising a binder resin, and therefore, which can stably maintain the electrification property for a long time and can suppress fog on the base or scattering of the toner with time. <P>SOLUTION: The electrophotographic carrier has a coating layer of a binder resin comprising acrylic resin on the core surface. The coating layer contains particles having the particle size d satisfying 0.2<(d/D)×100<2.0 with respect to the core material diameter D. The electrophotographic developer uses the above carrier. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Of the electrophotographic processes using a two-component developer, a general electrophotographic process is shown in FIGS.
Will be explained. The photosensitive member indicated by reference numeral 11 in the drawing is formed by applying a photosensitive layer on the peripheral surface of the body, and rotates in the direction of the arrow in the drawing by a driving mechanism (not shown). The rotating photoconductor is first uniformly charged to a desired potential by the charging device 12, and then exposed by the exposure device 13 to form an electrostatic latent image corresponding to the image. The electrostatic latent image formed on the photoconductor is visualized by using the developing device 14 described below. The developing device contains a developer consisting of toner and carrier used for development,
A rotatable screw 15 is arranged in the developer accommodating chamber. The developer circulates uniformly in the developing device by the rotating screw, the toner is uniformly dispersed at a desired concentration, and the toner is frictionally charged with the carrier.

Further, a developing sleeve is rotatably disposed above the screw so as to face the photoconductor with a predetermined distance. A magnet roller 17 having N / S magnetic poles is fixedly arranged inside the developing sleeve 16, and the developer is pumped up by rotating the developing sleeve by a driving device (not shown). Further, on the developing sleeve, a developer amount regulating member 18 for scraping off an excessive amount is provided so that only a desired amount of the developer is conveyed to a developing area formed between the photoconductor and the developing sleeve. There is. A voltage is applied to the developing sleeve by a power source 19, and an electric field corresponding to the image is formed between the developing sleeve and the electrostatic latent image on the photosensitive member. The electric field draws the charged toner in the developer drawn up on the developing sleeve. Adhere to the photoconductor to form a toner image. The toner image developed as described above is
The image is transferred from the photoconductor onto the recording paper by the transfer device 20, and is fixed on the paper by heat and pressure while the recording paper passes through the fixing device 22. On the other hand, the toner remaining on the photoconductor without being transferred to the recording paper is removed by the cleaning device 21.

Toner is consumed as the development is carried out, and the toner concentration in the developer is lowered, but a necessary amount is replenished by a toner replenishing mechanism (not shown), and image formation is repeatedly carried out in the above steps. While the image forming apparatus is used for a long period of time, the developer continues to receive a great deal of stress from the mixing and stirring for a long time and the pumping amount regulating member. The carrier that is not replaced in the developing container is most affected by repeating image formation under the above stress, and as a result of being continuously stirred with the toner that is constantly replaced, deterioration as a carrier occurs, Abrasion of core material coating layer, peeling of core material surface coating layer,
Crushing of core material particles, reduction of toner charge amount due to adhesion of toner particle component to carrier particle surface, transition from desired electric resistance, debris, abrasion powder, etc. This causes deterioration of image quality such as generation of background fog and deterioration of resolution, occurrence of physical and electrical scratches on the image bearing member, and deterioration of the image forming system such as contamination of the charging member. In particular, in recent years, development of toners that attach importance to low-temperature fixability has progressed from the viewpoint of energy saving, and further, toner particle components are more likely to stick to the carrier surface, and background fog and toner scattering due to a decrease in charge amount over time of use are prevented. It's a big problem. As an image forming apparatus, an output image is required to have high quality in terms of sharpness, gradation and graininess, and at the same time, high durability and long life as a developing apparatus are essential. Many proposals have been made as carriers that satisfy the requirements.

Among them, as a proposal from the viewpoint of strengthening the carrier coating layer, in Japanese Patent Laid-Open No. 9-31504, the surface of a spherical composite core particle composed of iron oxide particle powder and a hardened phenol resin is hardened. By having a coating layer made of a phenol resin containing an amino group and defining the iron oxide particle content and the amino group content,
Stable triboelectric charging and durability can be obtained. Also,
In Japanese Unexamined Patent Publication (Kokai) No. 9-31105, one or more kinds selected from a melamine resin, an aniline resin and a urea resin and a phenol resin are formed on the surface of a spherical composite core particle composed of iron oxide particle powder and a hardened phenol resin. It is composed of a cured coating layer, and stable triboelectric charging and durability can be obtained. Further, in Japanese Patent Publication No. 2825295, it is possible to obtain a magnetic carrier having high electric resistance and small bulk density by coating the surface of particles composed of ferromagnetic fine particles and cured phenol resin with melamine resin. Patent Publication 290556
According to the publication No. 3, the surface of particles made of ferromagnetic fine particles and hardened phenol resin is uniformly coated with a polyamide layer to obtain a magnetic carrier having high electric resistance and small bulk density.

Further, for example, in Japanese Unexamined Patent Publication (Kokai) No. 5-273789, one in which an additive is attached to the surface of a carrier is used, and in Japanese Unexamined Patent Publication No. 9-160304, conductive particles larger than the coating film thickness are coated. There are disclosed those using the one contained in the film. In addition, JP-A-8
No. 6307 discloses that a benzoguanamine-n-butyl alcohol-formaldehyde copolymer is used as a main component in a carrier coating material, and is disclosed in Japanese Patent No. 268.
Japanese Patent No. 3624 discloses the use of a crosslinked product of a melamine resin and an acrylic resin as a carrier coating material. However, since the toner component tends to adhere more easily to the carrier surface due to the lower melting point and the smaller particle size of the toner material in recent years, even if the above-mentioned method is used, there is a margin for adhesion of the toner component to the carrier surface. Is not yet at a satisfactory level, and it is difficult to suppress background fogging due to a decrease in the amount of charge with time, image deterioration due to toner scattering, and the like.

[0007]

Therefore, the present invention has been made in view of the above circumstances, and it is possible to prevent the toner from being fixed on the surface of the carrier core material and the binder resin of the coating layer from being scraped off.
An object of the present invention is to provide an electrophotographic carrier and a developer, which can keep the chargeability stable for a long period of time and can suppress background fog and toner scattering even over time.

[0008]

In order to achieve the above object, the present invention provides (1) an electrophotographic carrier having a coating layer made of a binder resin containing an acrylic resin on the surface of a core material, the coating comprising: The layer has a particle diameter D of 0.2 <(d /
D) A carrier for electrophotography, which comprises particles having a particle diameter d satisfying the relationship of × 100 <2.0, and (2) the coating layer has a thickness h of the particle diameter d. On the other hand, the carrier for electrophotography according to (1) above, which has a relationship of h <d, and (3) the weight of the particles contained in the coating layer is the weight of the core material of the carrier. In the electrophotographic carrier according to (1) or (2) above, the content is 0.2 to 5.0 wt%, and (4) the particles are inorganic fine particles. (5) The electrophotographic carrier according to any one of (1) to (3) above, wherein (5) the coating layer contains a silicone resin. (6) At least a binder resin, a pigment , A wax toner,
An electrophotographic developer comprising the carrier according to any one of (1) to (5) above,
(7) The toner is achieved by using the electrophotographic developer according to the above (6), which is a color toner.

The present invention will be described in more detail below. In a resin-coated carrier having at least a binder resin as a coating layer containing an acrylic resin and particles, the diameter d of the inorganic fine particles and the carrier core diameter D are 0.2 <(d / D).
By satisfying × 100 <2.0, the effect of incorporating the inorganic fine particles into the binder resin is most exerted. As the core material of the carrier, at least 20 μm of the core material particle size is used from the viewpoint of preventing the carrier from adhering (scattering) to the photoreceptor forming the electrostatic latent image.
In order to prevent occurrence of carrier streaks and the like and to prevent deterioration of image quality, a size of at most 100 μm is used. As a specific material, a well-known two-component electrophotographic carrier, for example, ferrite, magnetite, iron, nickel or the like may be appropriately selected and used according to the use and purpose of use of the carrier.

Further, the particles in the coating resin are inorganic fine particles, and alumina, titanium oxide, zinc oxide or the like can be used, and the effect is obtained by using one of them surface-treated alone or in plural. Is remarkable. Further, by making the carrier coating layer film thickness h smaller than the particle diameter d,
The particles are exposed on the surface of the coating film, so that the above-described improvement effect can be better obtained. Further, it is preferable that the above particles are contained in the carrier coating layer in the range of 0.2 to 5.0 wt% with respect to the weight of the carrier core material. The effect of including the particles in the carrier coating layer is to protect the carrier coating layer from an external force applied to the carrier surface, and to form an uneven shape on the carrier surface, and then the carriers contact each other to form a carrier. The unevenness of the surface is to scrape off the toner components fixed to each other's surface, and the particles listed above are tough against external force because they have tough properties,
It is possible to protect the coating layer for a long period of time without causing cracking or abrasion, and to form irregularities on the surface to maintain the carrier surface in the same manner as in the initial stage. is there. More specifically,
If the particles are too small with respect to the carrier core material, it is difficult to obtain the effect. If the particles are too large, it is difficult to retain the particles on the carrier core material, and the particles are easily released, which is not preferable. Further, when the film thickness of the coating layer is not less than the particles, the particles are not projected from the coating layer and the effect cannot be obtained. Similarly, if the amount is too small, it is difficult to obtain the effect, and if it is too large, the particles are strongly detached from the carrier coating layer, which is not preferable.

Furthermore, the particles are preferably present in the acrylic resin, and the strong adhesiveness of the acrylic resin enables the particles to be retained for a long period of time. Further, the effect of the present invention can be more remarkably obtained because the binder resin is the coating layer containing the silicone resin in addition to the acrylic resin. Acrylic resin has excellent adhesiveness and low brittleness, so it has very good abrasion resistance, but on the other hand, it has a high surface energy, so when used in combination with a toner that easily spends, toner component spent accumulates. May cause a decrease in charge. Therefore, this problem can be solved by using a silicone resin which has a low surface energy and is hard to spend the toner component, and the film is easily scraped so that the spent component does not easily accumulate.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The color image forming apparatus of this embodiment will be described below with reference to the drawings. The present embodiment is a tandem type color image forming apparatus that forms an image using an electrophotographic process, but the present invention is not limited to the image forming apparatus described below. FIG. 1 is a side view showing an outline of the entire tandem type color image forming apparatus that forms an image using an electrophotographic process. Transfer paper 3
The sheet passing path 3 for guiding the sheet 1 is a recording material conveying belt that is stretched between a belt driving roller 32 that is driven by a driving source (not shown) to rotate and a rotatable belt driven roller 33. The transfer belt 34 of FIG. Then, on the transfer belt 34, four developing devices for yellow Y, magenta M, cyan C, and black K, 14Y, 14M, are arranged in this order from the upstream side in the transporting direction of the transfer paper 31.
14C and 14K are installed in order. These developing devices are composed of a photoconductor that contacts the transfer belt, a charging device 7, an image exposure device 10, and a cleaning device CL, which are sequentially arranged around the photoconductor 6. Further, the sheet passing path 4 is provided at a position where the transfer belt 34 is removed and provided with the fixing device 4. In the color image forming apparatus having such a configuration, each developing device motivates the transfer paper 31 guided and conveyed by the transfer belt 34 through the paper passing path 4 to form an image on the photoconductor and transfer the image. A full-color image is obtained on the paper 31. The color image forming apparatus of the present embodiment is
Each unit is drive-controlled by a controller of a microcomputer configuration for controlling each unit (not shown) and an engine control unit.

[0013]

EXAMPLES Next, the present invention will be described with reference to Examples and Comparative Examples.
However, the present invention is not limited to these.
Not a thing. (Example 1)Carrier manufacturing example Acrylic resin solution (solid content 50% by weight): 56.0 parts,
Guanamine solution (solid content 70% by weight): 15.6 parts,
Lumina particles (particle size (representing the weight average particle size):
0.1 μm): 160.0 parts (1.
Amount equivalent to 5 wt%), toluene: 900 parts, butyl
Losolve: 900 parts were dispersed with a homomixer for 10 minutes,
Obtain an acrylic resin coating film forming solution containing alumina particles
It was Core material particle size (representing the weight average diameter of the core material) 35 μm
The above coating film forming solution is used on the core material surface using synthetic ferrite powder.
Spiral coater (Okada
It was applied and dried by Seiko. Obtained carrier
It baked in the electric furnace at 150 degreeC for 1 hour. cooling
After that, use the ferrite powder bulk with a sieve with an opening of 106 μm.
It was crushed and used as a carrier. Binder resin film thickness is transparent
By observing the carrier cross section with an electron microscope,
Since you can observe the coating film that covers the surface of the carrier,
The average value of the film thickness was defined as the film thickness. This carrier cover
The characteristics of the film layer are shown in Table 1.

[0014]Toner manufacturing example Polyester resin (bisphenol A ethylene oxalate
Id-added alcohol, propylene phenol of bisphenol A
Quicide-added alcohol, terephthalic acid, trimellit
Condensation polymer of acid: Mw = about 12000, glass transition point =
About 60 ° C: 79 parts, carbon black (trade name # 4)
4: Mitsubishi Carbon Co., Ltd.): 15 parts, charge control agent: chromium
Metal-containing dye (Product name: AZON SPIRON BLA
(CK: Hodogaya Chemical Co., Ltd.): 1 part, Karnauba Wack
S (made by Noda Wax Co., Ltd.): 2 parts of a mixture having a composition of 5 parts
After kneading for 30 minutes with a roll kneader, mechanical crusher and air flow
Adjust the crushing and classification conditions with a powder classifier to make toner base particles
Got a child Further, for 100 parts of toner base particles, 1
Hydrophobic silica whose surface is treated with dimethylsilane in proportions of parts
Add fine particles and use a Henschel mixer to make a total
The mixture was mixed for 2 minutes to obtain toner particles T1 for testing. toner
Particle size distribution of particles T1 with Coulter Counter TAII
When measured, the weight-average diameter D50 = 5.9 μm, cumulative
Number basis 10% calculated from number distribution = 2.2 μm
there were.

[0015]Developer manufacturing example 5 parts of the toner thus obtained and 95 parts of the carrier are mixed.
By stirring, a developer having a toner concentration of 5 wt% was obtained.Durability test A digital full-color copying machine (made by Ricoh Co., Ltd.)
ipsio Color 8000) and set
5% image area 5% continuous chart
A durability test was performed to output 0 sheets, and the capacity before and after the test was checked.
Changes in rear charging ability, background fogging, toner scattering
(In-machine toner stain) was evaluated. Background fog is 5%
With a developing unit for the background of the chart and toner scattering
The near toner stain was visually evaluated. Career here
To measure the charging capacity, the carrier weight is 95 wt% and the toner is
Samples that were mixed and triboelectrified at a ratio of 5 wt% were generally used.
The amount of charge measured by the simple blow-off method.
As with the carrier, the carrier after the test is in the developer
From the carrier obtained by removing the toner
Similarly, the charge amount was measured. The target value of the amount of change is 5 μC / g
It is the following. The results of the durability test are shown in Table 2.

(Example 2)Carrier manufacturing example Alumina particles (heavy metal) are added to the particles contained in the carrier coating layer.
Amount average diameter: 0.3 μm): 160.0 parts (in weight of core material)
The amount corresponding to 2.0 wt%) and the film thickness is 0.1
The procedure is the same as in Example 1 except that the thickness is 5 μm.
Manufactured. The characteristics of this carrier coating layer are shown in Table 1.
Show.Developer manufacturing example / Durability test A developer having a toner concentration of 5 wt% is obtained by using the toner particles T1.
It was The results of the durability test are shown in Table 2.

(Example 3)Carrier manufacturing example Acrylic resin solution (solid content 50% by weight): 21.0 parts,
Guanamine solution (solid content 70% by weight): 6.4 parts, al
Mina particles (weight average diameter: 0.5 μm): 121.0 parts
(Amount equivalent to 3.0 wt% with respect to the weight of the core material), silicon
Resin solution (solid content 23% by weight: 65.0 parts, amino acid
Orchid (solid content 100% by weight): 0.3 part, toluene: 3
00 parts, butyl cellosolve: 300 parts with a homomixer
Acrylic resin containing alumina particles dispersed for 10 minutes and
A silicone resin blend coating film forming solution was obtained. Core material grain
Formation of the above coating film using fired ferrite powder with a diameter of 35 μm
Except that the solution has a thickness of 0.3 μm on the surface of the core material
A carrier was manufactured in the same manner as in Example 1. This cap
The characteristics of the rear coating layer are shown in Table 1.Developer manufacturing example / Durability test Next, using toner particles T1, developing with a toner concentration of 5 wt%
I got an agent. The results of the durability test are shown in Table 2.

(Example 4)Carrier manufacturing example Alumina is prepared by using fired ferrite powder with a core particle size of 50 μm.
Particles (weight average diameter: 0.3 μm): 160 parts (core material weight
The amount corresponding to 1.3 wt%)
Same as Example 1 except that the thickness was adjusted to 0.15 μm.
Then, the carrier was manufactured. The characteristics of this carrier coating layer
It shows in Table 1.Developer manufacturing example / Durability test Next, using toner particles T1, developing with a toner concentration of 5 wt%
I got an agent. The results of the durability test are shown in Table 2.

(Example 5)Carrier manufacturing example Alumina is prepared by using fired ferrite powder with a core particle size of 50 μm.
Particles (weight average diameter: 0.5 μm): 130.0 parts (core material
The amount corresponding to 2.5 wt% of the weight)
Was set to 0.3 μm as in Example 3.
Then, the carrier was manufactured. The characteristics of this carrier coating layer
It shows in Table 1.Developer manufacturing example / Durability test Next, using toner particles T1, developing with a toner concentration of 5 wt%
I got an agent. The results of the durability test are shown in Table 2.

(Example 6)Carrier manufacturing example Using sintered ferrite powder with a core particle size of 50 μm, titanium oxide
Particles (weight average diameter: 0.5 μm): 130.0 parts (core
The amount corresponding to 4.0 wt% of the material weight)
Same as Example 3 except that the thickness is 0.4 μm.
Then, a carrier was manufactured. Properties of this carrier coating layer
Is shown in Table 1.Developer manufacturing example / Durability test Next, using toner particles T1, developing with a toner concentration of 5 wt%
I got an agent. The results of the durability test are shown in Table 2.

(Embodiment 7)Carrier manufacturing example Using fired ferrite powder with a core material particle size of 65 μm,
Particles (weight average diameter: 0.3 μm): 120.0 parts (core
The amount corresponding to 0.7 wt% of the material weight)
Same as Example 1 except that the thickness was set to 0.15 μm.
The carrier was manufactured in this manner. The characteristics of this carrier coating layer
The sex is shown in Table 1.Developer manufacturing example / Durability test Next, using toner particles T1, developing with a toner concentration of 5 wt%
I got an agent. The results of the durability test are shown in Table 2.

(Embodiment 8)Carrier manufacturing example Zinc oxide is used with calcined ferrite powder with a core particle size of 65 μm.
Particles (weight average diameter: 0.5 μm): 121.0 parts (core material
The amount corresponding to 1.2 wt% of the weight)
Was set to 0.3 μm as in Example 3.
Then, the carrier was manufactured. The characteristics of this carrier coating layer
It shows in Table 1.Developer manufacturing example / Durability test Next, using toner particles T1, developing with a toner concentration of 5 wt%
I got an agent. The results of the durability test are shown in Table 2.

(Comparative Example 1)Carrier manufacturing example Alumina particles (weight average diameter: 0.7 μm): 2
00.0 parts (corresponding to 5.5 wt% with respect to the weight of the core material
Except that the film thickness is 0.5 μm.
A carrier was manufactured in the same manner as in Example 3. This carry
Table 1 shows the characteristics of the coating layer.Developer manufacturing example / Durability test Next, using toner particles T1, developing with a toner concentration of 5 wt%
I got an agent. The results of the durability test are shown in Table 2.

(Comparative Example 2)Carrier manufacturing example Alumina is used with calcined ferrite powder with a core particle size of 65 μm.
Particles (weight average diameter: 0.1 μm): 90.0 parts (core material weight
The amount corresponding to 0.1 wt% of the amount)
Same as Example 3 except that the thickness was 0.05 μm.
Then, the carrier was manufactured. The characteristics of this carrier coating layer
It shows in Table 1.Developer manufacturing example / Durability test Next, using toner particles T1, developing with a toner concentration of 5 wt%
I got an agent. The results of the durability test are shown in Table 2.

(Comparative Example 3)Carrier manufacturing example Alumina particles with 50 μm fired ferrite powder as the core material
Child (weight average diameter: 0.3 μm): 121.0 parts (core material weight
The amount corresponding to 2.0 wt% of the amount)
Same as Example 3 except that the thickness was 0.4 μm.
Manufactured a carrier. The characteristics of this carrier coating layer are shown below.
Shown in 1.Developer manufacturing example / Durability test Next, using toner particles T1, developing with a toner concentration of 5 wt%
I got an agent. The results of the durability test are shown in Table 2.

[0026]

[Table 1] <Table 1: Characteristics of carrier coating layer>

[0027]

[Table 2] <Table 2: Results of durability test>

In Table 2, the values of the carrier charge amount before and after the test and the changes thereof, as well as background fog and toner scattering, are ⊚: very good, ◯: good, Δ: acceptable, ×: not acceptable. The evaluation results are shown. From Table 1 and Table 2, the core material particle size is 35 μm, the particle size in the coating film is 0.1 μm,
In Example 1 in which ((d / D) × 100) was 0.29 and the acrylic resin coating film thickness was 0.05 μm, the amount of charge reduction before and after the test was 2.0 μC / g, which was the target value. And the results of background fog and toner scattering were both good. Furthermore, Example 2 in which the particle diameter in the coating film is 0.3 μm and ((d / D) × 100) is 0.86
In regard to the charge reduction amount, 2.7 μC / g, background fog, and toner scattering were more favorable. Also,
In Example 3, acrylic resin and silicone resin are used,
When the particle size was 0.5 μm, ((d / D) × 10
0) was 1.43, the amount of reduction in electrification was further reduced, and results similar to those in Example 1 were obtained with respect to background fog and toner scattering. Use a core material with a particle size of 50 μm,
Also in Example 4 in which ((d / D) × 100) was 0.6, good results were obtained as in Examples 1 to 3. Also, in Examples 5 and 6 in which the weight of the core material was 2.5 wt% and 4.0 wt% using titanium oxide having a particle diameter of 0.5 μm, the charge reduction did not occur, and background fog and toner scattering occurred. There wasn't. Furthermore, Examples 7 and 8 in which the core material particle size was set to 65 μm
In each of the above, the values of ((d / D) × 100) are 0.46 and 0.77, respectively, and the charging stability, background fog,
Good results were obtained regarding toner scattering.

On the other hand, alumina particles having a particle size of 0.7 μm and a core material particle size of 35 μm are used with respect to the core material weight of 5.5.
In Comparative Example 1 in which the coating film thickness of the acrylic resin and the silicone resin is 0.5 μm and the value of ((d / D) × 100) is 2.0, the electrostatic charge is drastically reduced and the background fogging is caused. Also, the result of toner scattering was very bad. Further, Comparative Example 2 in which alumina particles having a core particle size of 65 μm and a particle size of 0.1 μ are coated with acrylic resin and silicon resin at 0.05 μm, and ((d / D) × 100) is 0.15.
However, as in Comparative Example 1, the charge was drastically reduced, and the background fog and toner scattering were also very bad. Also, in Comparative Example 3 in which alumina having a particle diameter of 0.3 μm is coated with acrylic resin and silicon resin at 0.4 μm with respect to a core material particle diameter of 50 μm, a decrease in charge amount, background fogging, and toner scattering occur, and the carrier is used. The satisfactory effect was not obtained.

[0030]

As is clear from the detailed and specific description above, in the electrophotographic carrier and developer of the present invention, toner components are not fixed to the carrier surface and the carrier coating layer is not scraped at all. For this reason, a stable charge amount can be obtained even during long-term use, so that the deterioration of image quality due to an increase in the number of image-formed sheets can be significantly improved, and good image quality can be maintained for a long period of time.

[Brief description of drawings]

FIG. 1 is a side view schematically showing the entire tandem type color image forming apparatus that forms an image using an electrophotographic process.

FIG. 2 is a schematic diagram showing a configuration for explaining a general electrophotographic process.

FIG. 3 is a schematic diagram showing a configuration for explaining a general electrophotographic process.

[Explanation of symbols]

11 photoconductor 12 Charging device 13 Exposure equipment 14 Developing device 15 screws 16 Development sleeve 17 Magnet roller 18 Developer amount control member 19 power supply 20 Transfer device 21 Cleaning device 22 Fixing device 31 transfer paper 32 belt drive roller 33 Belt driven roller 34 Transfer belt

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masahide Yamashita             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Kosuke Suzuki             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Tomomi Tamura             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh F-term (reference) 2H005 AA21 BA02 BA06 BA07 CA02                       CA12 CB04 CB07 EA05 EA07                       EA10

Claims (7)

[Claims] 1. A carrier for electrophotography having a coating layer of a binder resin containing an acrylic resin on the surface of a core material, wherein the coating layer has a particle diameter D of the core of 0.2 <(d / D)
A carrier for electrophotography, comprising particles having a particle diameter d satisfying the relationship of × 100 <2.0. 2. The electrophotographic carrier according to claim 1, wherein the coating layer has a thickness h of h <d with respect to a particle diameter d. 3. The weight of the particles contained in the coating layer is 0.2 to 5.0 wt% with respect to the weight of the core material of the carrier. Electrophotographic carrier. 4. The electrophotographic carrier according to claim 1, wherein the particles are inorganic fine particles. 5. The electrophotographic carrier according to claim 1, wherein the coating layer contains a silicone resin. 6. An electrophotographic developer comprising a toner comprising at least a binder resin, a pigment and a wax, and the carrier according to any one of claims 1 to 5. 7. The electrophotographic developer according to claim 6, wherein the toner is a color toner.