JPH06110253A - Electrostatic image developer carrier, its production and image forming method - Google Patents

Abstract

PURPOSE:To provide a carrier for electrostatic development without containing amorphous magnetic fine powder which causes wear of a cleaning member or scratch on a photosensitive body surface, and to provide the production method of this carrier and the image forming method using this carrier. CONSTITUTION:This carrier for electrostatic development consists of magnetic particles each having a resin coating layer formed on the particle surface by dry coating method. The magnetic particles contains 0.1-1.0 pt.wt. P and/or As to 100 pts.wt. of ferrite component expressed by (MO)x(Fe2O3)y. In formula, M is Zn or Cu, x and y are the number of mols. The image forming method includes a process to remove a toner remaining on the photosensitive body with a cleaning device equipped with a blade 11 and to recover the removed toner to a toner replenisher hopper or a developing device for reuse. In this process, the carrier of this invention is used.

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 method for manufacturing the carrier, and an image forming method.

[0002]

2. Description of the Related Art A two-component developer used in electrophotography or the like comprises a toner and a carrier, and the carrier is used for the purpose of imparting a triboelectric charge having a proper polarity and a proper amount to the toner. It is something.

As such a carrier, a resin-coated carrier having a resin coating layer on the surface of magnetic particles is used for various purposes.

As a technique for producing such a resin-coated carrier, for example, a spray coating method, a dip coating method, a sinter coating method and the like are known, but it is to produce a carrier having excellent durability by a simple means. Therefore, the dry coating method is preferably performed.

In the dry coating method, a mechanical impact force is repeatedly applied to a mixture obtained by mixing and stirring magnetic particles and coating resin fine particles by, for example, a rotary blade type mixing and stirring device. A method of forming a resin coating layer by spreading and adhering resin particles on the surface of magnetic particles.

[0006]

However, in the dry coating method, when a mechanical impact force is applied to the mixture of the magnetic particles and the resin fine particles for coating, the magnetic particles are subjected to an impact contact and a magnetic material. Due to the shocking contact between the particles and the rotating blade member of the mixing and stirring device, the magnetic substance constituents are separated from the surface of the magnetic substance particles or the magnetic substance particles themselves are destroyed, and along with this, the fine amorphous magnetism Fine powder is generated.
Therefore, the amorphous magnetic fine powder is mixed in the resin-coated carrier obtained by the dry coating method as described above.

However, since the amorphous magnetic fine powder mixed in the resin-coated carrier has a particle size of about several μm to 30 μm, which is considerably small, it can be removed from the developing device (development ear) during development by the image forming apparatus. Easily transferred to the surface of the photoconductor.

The amorphous magnetic fine powder transferred onto the photoconductor is
Usually, after the completion of the transfer process, the residual toner on the photoconductor is removed together with the cleaning device by a cleaning device. However, during this cleaning, the irregular magnetic substance fine powder
The cleaning blade and the cleaning guide roller are abraded in the gap between the cleaning blade and the photoconductor or the gap between the cleaning guide roller and the photoconductor that are used together, and the cleaning blade and the cleaning guide roller are worn away. Causes abrasion along the direction. As a result, an image defect due to poor cleaning occurs in the formed image, and streaky roughness particularly occurs in the halftone portion.

Further, in an image forming apparatus equipped with a toner recycling system in which the toner removed from the photoconductor by the cleaning device is collected in a toner replenishing hopper or a developing device and reused, the irregular magnetic fine powder is a toner. The image defects and streaky roughness are particularly likely to occur because they are repeatedly collected and transferred to the photoconductor, the blade and the guide roller are abraded, and the photoconductor is rubbed repeatedly.

To solve such a problem, by adopting a (CuO)-(ZnO)-(Fe ₂ O ₃ ) composition as the ferrite composition and controlling the production conditions of the ferrite particles, a magnetic material by impact contact is obtained. Although the destruction of the particles themselves can be suppressed to some extent, it is not sufficient, and even if the production conditions are controlled, the separation of the magnetic substance constituents from the surface of the magnetic substance particles cannot be suppressed.

On the other hand, in Japanese Unexamined Patent Publication No. 60-227265, for a (MgO)-(ZnO)-(Fe ₂ O ₃ ) type ferrite component, among the group V elements of the periodic table,
A technique for suppressing the peeling phenomenon and the breakage phenomenon of a crystal by introducing 0.01 to 5% by weight of one or more oxides of P, As, Sb, Bi and V is introduced.

[0012] However, as a result of the studies by the present inventors, the carrier of the above technique can suppress the surface peeling phenomenon and the damage phenomenon to some extent against the mechanical impact force received in the developing device. However, it was confirmed that they do not have sufficient impact resistance against the mechanical impact force applied during the dry coating method. Therefore, the resin-coated carrier obtained by treating the carrier of the above technique by the dry coating method still has the above-mentioned problems.

Further, the present inventors have tried a separating operation by a sieve or air classification to remove only the irregular magnetic substance fine powder from the resin-coated carrier in which the irregular magnetic substance fine powder is mixed. However, the amorphous magnetic fine powder has a small particle size and is electrostatically attached to the resin-coated carrier, so that the separation efficiency is extremely low and it cannot be completely removed.

The present invention has been made based on the above circumstances, and a first object of the present invention is to provide an amorphous magnetic fine powder which causes abrasion of a cleaning member and abrasion on the surface of a photoreceptor. It is to provide a carrier for developing an electrostatic image which is not mixed. A second object of the present invention is to provide a method for producing a carrier for developing an electrostatic image, which does not generate fine particles of an amorphous magnetic substance even by a mechanical impact force applied when performing a dry coating method. A third object of the present invention is to provide an image forming method which does not cause image defects due to poor cleaning and streaky roughness in the halftone portion.

[0015]

Means for Solving the Problems As a result of intensive investigations by the present inventors, as a result of the Cu--Zn ferrite component,
It has been found that magnetic particles having remarkably excellent impact resistance can be obtained by containing P and / or As in a group V element of the periodic table at a specific ratio, and the present invention is based on such findings. Was completed.

That is, the carrier for electrostatic image development of the present invention repeatedly imparts a mechanical impact force to a mixture of magnetic particles and coating resin fine particles so that the surface of the magnetic particles is coated with the coating resin fine particles. In the electrostatic image developing carrier obtained by a dry coating method for forming a resin coating layer, the magnetic particles have a composition formula: (MO) _x (Fe ₂ O ₃ ) _y [M represents Zn and Cu, and x , Y represents the number of moles. ] It is characterized by containing 0.1 to 1.0 part by weight of P and / or As with respect to 100 parts by weight of the ferrite component.

In the method for producing a carrier for electrostatic image development of the present invention, a mechanical impact force is repeatedly applied to a mixture of magnetic particles and coating resin fine particles so that the surface of the magnetic particles is coated with the coating resin fine particles. In the method for producing a carrier for electrostatic image development by a dry coating method for forming a resin coating layer according to, the magnetic particles are the magnetic particles described above.

According to the image forming method of the present invention, the electrostatic image on the photoconductor is developed with a two-component developer consisting of toner and carrier to form a toner image, and the toner image is transferred to a transfer material. An image forming method including a step of removing the toner remaining on the photoconductor by using a cleaning device equipped with a cleaning blade, and collecting the removed toner in a toner replenishing hopper or a developing device for reuse.
The carrier is the electrostatic image developing carrier described above.

The ferrite composition of the magnetic particles forming the above electrostatic image developing carrier is (CuO) 5.
30 mol%, (ZnO) 5 to 30 mol%, (Fe
₂ O ₃ ) It is preferably in the range of 55 to 70 mol%.

[0020]

(1) The magnetic particles constituting the electrostatic image developing carrier of the present invention contain P and / or As in a specific ratio with respect to the Cu-Zn ferrite component. The particles are excellent in impact resistance as will be apparent from the examples described later. Therefore, the mechanical impact force applied when performing the dry coating method does not cause separation of the magnetic substance constituents or destruction of the magnetic substance particles themselves, and accompanying this, amorphous magnetic fine powder is generated.・ There is no mixture. (2) Since the amorphous magnetic fine powder, which causes abrasion of the cleaning member and scratches on the surface of the photoconductor, is not mixed in the resin-coated carrier, an image such as an image defect or streaky roughness is formed in the formed image. Defects are prevented.

The present invention will be specifically described below. The electrostatic image developing carrier of the present invention is a resin-coated carrier in which a resin coating layer is formed on the surface of magnetic particles, and the magnetic particles constituting the carrier have a Cu-Zn-based ferrite component. And is characterized in that it contains P and / or As in a specific ratio.

The ferrite component of the magnetic particles has a composition formula:
(CuO) _a (ZnO) _b (Fe ₂ O ₃ ) _c [a, b and c each represent a number of moles. ] Cu-Z shown by
It is an n-type ferrite. In the above composition formula, the preferable molar ratio is “a: b: c” of 5 to 30: 5 to 30:
It is preferably in the range of 55 to 70 and preferably "(a + b) <c".

Further, the magnetic particles contain P at a ratio of 0.1 to 1.0 parts by weight with respect to 100 parts by weight of the ferrite component.
And / or As is contained. The magnetic particles containing P and / or As in this proportion have significantly improved impact resistance, and the particles themselves are destroyed even by the mechanical impact force applied during the dry coating method. And surface peeling does not occur. P and / or A
If the content of s is less than 0.1 parts by weight, the impact resistance of the magnetic particles will not be sufficient, and irregular magnetic fine particles will be generated and mixed after dry coating. On the other hand, even if P and / or As is contained in a ratio exceeding 1.0 part by weight,
The effect of improving impact resistance commensurate with the content is not exhibited.

As a method of adding P and / or As to the magnetic particles, for example, a ferrite component is mixed with a binder, a dispersant and a dispersion medium,
It is added in the form of a simple substance, an oxide, a hydroxide, or a salt in the slurry-like mixture before firing.

The magnetic particles thus obtained have an average particle size of 30 to 200 μm and a specific resistance of 1 × 10 ^7.
~9 × 10 ⁹ Ω · cm, it is preferable saturation magnetization in the external magnetic field 1000Oe is 40~70emu / g. By using the magnetic particles having such preferable characteristics, more excellent developability can be obtained.

In the present invention, a resin coating layer is formed on the surface of the magnetic particles by a dry coating method. Here, the “dry coating method” means that, without using a coating liquid, the coating resin fine particles and the magnetic particles are mixed and agitated, and mechanical impact force is repeatedly applied to the mixed resin fine particles to give magnetic particles. It is a method of forming a film of a coating resin on the surface, and since resin fine particles adhere and spread on the surface of magnetic particles, it is possible to obtain a resin-coated carrier that is difficult to peel off and has excellent durability. . Here, the coating resin is not particularly limited and can be a conventionally known resin,
For example, styrene-acrylic copolymer resin, fluorine resin, silicone resin, etc. can be used. Also,
The mixing weight ratio of the magnetic particles and the resin fine particles for coating varies depending on the specific gravity of the magnetic material and cannot be specified unconditionally, but is preferably about 100: 1 to 100: 10, for example.

The carrier for developing an electrostatic image of the present invention develops an electrostatic image on a photoreceptor with a two-component developer comprising a toner and a carrier to form a toner image, and the toner image is used as a transfer material. After transfer, remove the toner remaining on the photoconductor using a cleaning device equipped with a blade or a cleaning device that also functions as a blade and guide roller, and collect the removed toner in the toner replenishment hopper or developer. Then, it can be suitably used for an image forming method including a step of recycling.

[0028]

EXAMPLES Examples of the present invention will be described below together with comparative examples, but the present invention is not limited thereto. In the following, "part" means "part by weight".

<Production Example of Ferrite Particles> “CuO: Z
A ferrite component of “nO: Fe ₂ O ₃ = 23.5: 23.5: 53.0 (molar ratio)” was mixed with a binder, a dispersant, and a dispersion medium to prepare a slurry mixture. Then, according to the formulation shown in Table 1 below, each element or compound was added and baked at 1120 ° C. to form Cu--
Zn-based ferrite particles [ferrite particles 1 to 5 (for the present invention) and ferrite particles 6 to 8 (for comparison)] were produced. In Table 1, the "addition amount" indicates "the number of parts per 100 parts of the ferrite component".

The Cu--Zn ferrite particles 1 to 8 produced as described above were measured for specific surface area, crushed amount, current value, static resistance and saturation magnetization. The results are also shown in Table 1. In addition, these measuring methods are as follows. (1) Specific Surface Area Specific Surface Area Measuring Device "Micromeritics Flowsorb II230
It was measured using "Type 0" (manufactured by Shimadzu Corporation). (2) Crushing amount The particle size distribution of ferrite particles is 0 when the volume average particle size is 80 μm, 105 μm or more and 44 μm or less, respectively.
% (Trace). A mechanical impact force was applied to each of these ferrite particles by a pulverizer "Mill MK-52M" (manufactured by National Corp.) for 10 minutes, and then the weight ratio of the generated particles of 44 µm or less was measured. (3) Electric current value The electric current value of each ferrite particle was measured using the apparatus as shown in FIG. In the figure, 1 is a developing device, 2 is a developing brush, 3 is a photosensitive drum, 4 is a resistance (1 kΩ), 5 is a voltmeter, and 6 is a DC power supply. 1 kg
The ferrite particles (sample) of No. 1 were filled in the developing device 1, and the developing brush 2 and the photosensitive drum 3 were rotated. The electromotive force of the DC power supply 6 is set to 260V, and the voltage V between a and b is set.
_Ab (mV) was measured and the current value was calculated by the following equation.
Formula) Current value (μA) = V _ab / 1000 The measurement conditions are as follows. Rotational speed of developing brush: 160 rpm Rotational speed of photosensitive drum: 30 rpm Measurement temperature and humidity: 20 to 25 ° C., 50 + 5%
(RH) (4) Static resistance The static resistance of each ferrite particle was measured using an apparatus as shown in FIG. In the figure, F is a ferrite particle layer (sample layer), 7 is an insulating pipe, and 8
Is a brass weight, 9 is a brass bottom plate, and 10 is an insulation resistance meter. The static resistance was determined by the following formula from the reading R (Ω) of the insulation resistance meter, the cross-sectional area S (cm ² ) of the sample layer, and the thickness t (cm) of the sample layer. Formula) Static resistance (Ω-cm) = R
× S / t (5) Saturation magnetization DC magnetization characteristic automatic recorder “Ty
pe3257-36 "(manufactured by Yokogawa Hokushin Electric Co., Ltd.), an electromagnet type magnetizer" Type3261-15 "(manufactured by the same company) and a pickup coil" Type3256-20 "(manufactured by the same company). was calculated.

[0031]

[Table 1]

[MgO: ZnO: Fe ₂ O ₃ = 20.
5: 24.5: 55.0 (molar ratio) "was mixed with a binder, a dispersant, and a dispersion medium to prepare a slurry mixture. Next, 1.0 part of P is added to 100 parts of the ferrite component, and 1240 ° C
Mg-Zn ferrite particles 9 (for comparison)
Was produced.

The specific surface area, crushing amount, current value, static resistance and saturation magnetization of the thus prepared Mg—Zn ferrite particles 9 were measured in the same manner as above, and the specific surface area was 0.058 m. ² / g, crushed amount is 4.
7% by weight, current value 12 μA, static resistance 8 × 10 ⁹ Ω-
cm, and the saturation magnetization (σs) was 64 emu / g.

Example 1 Ferrite particles 1 (average particle size 60
μm) 100 parts by weight of resin fine particles A for coating [methyl methacrylate-styrene copolymer (copolymerization molar ratio 6:
4) Porous secondary particles composed of primary resin particles, Tg1
02 ° C, volume average particle size 2.2 μm, BET specific surface area 78
m ² /g)...2 parts by weight The above-mentioned carrier raw material is charged into a high-speed stirring mixer, and the material temperature does not exceed Tg of the coating resin, and the peripheral speed of the stirring blade is 10 m / sec for 10 minutes. The mixture was stirred and mixed for a period of time to obtain a mixture in which the coating resin fine particles A were uniformly attached to the surface of the ferrite particles 1. Then, while maintaining the stirring peripheral speed at 10 m / s, the material temperature was increased to 107
By increasing the temperature to 0 ° C. and stirring for 30 minutes to repeatedly apply mechanical impact force to the surface of the magnetic particles 1,
A carrier 1A of the present invention in which a resin coating layer of the resin fine particles A for coating was formed was produced.

Examples 2 to 5 Instead of the ferrite particles 1,
Carrier 2A of the present invention in the same manner as in Example 1 except that ferrite particles 2 to 5 (average particle size 60 μm) were used.
5A was manufactured.

Comparative Examples 1 to 4 Instead of the ferrite particles 1,
Comparative carriers 6A to 9A in the same manner as in Example 1 except that ferrite particles 6 to 9 (average particle size 60 μm) were used.
Was manufactured.

Example 6 Ferrite particles 1 (average particle size 80
.mu.m) 100 parts by weight of resin fine particles B for coating [a porous secondary particle composed of a primary resin particle of a copolymer of a monomer represented by the following chemical formula 1 and methyl methacrylate (copolymerization molar ratio of 6: 4), Tg 84 ° C, volume average particle diameter 2.6 μm,
BET specific surface area 71 m ² /g)...2 parts by weight The above-mentioned carrier raw materials are charged into a high-speed stirring mixer, and the Tg of the coating resin is
Ferrite particles 1 were mixed by stirring for 10 minutes at a material temperature not exceeding 10 and a peripheral speed of a stirring blade of 8 m / sec.
A mixture was obtained in which the coating resin fine particles B were uniformly attached to the surface of the. Next, while maintaining the stirring peripheral speed at 8 m / s, the material temperature was raised to 90 ° C., and the material was stirred for 30 minutes to repeatedly give a mechanical impact force, whereby the surface of the magnetic particles 1 was coated with a coating resin. A carrier 1B of the present invention having a resin coating layer formed of the fine particles B was produced.

[0038]

[Chemical 1]

Examples 7 to 10 Carrier 2 of the present invention was prepared in the same manner as in Example 6 except that ferrite particles 2 to 5 (average particle size 80 μm) were used instead of ferrite particles 1.
B-5B were produced.

Comparative Examples 5-8 Instead of the ferrite particles 1,
Comparative carriers 6B to 9B in the same manner as in Example 6 except that ferrite particles 6 to 9 (average particle size 80 μm) were used.
Was manufactured.

<Evaluation of Halftone Roughness> (1) Carriers 1A to 9A The carrier 1A to 9A of the present invention was used by using an electrophotographic copying machine "UBix-5070" (manufactured by Konica Corporation) equipped with a photosensitive body. 5A and comparative carrier 6
Regarding A to 9A, the occurrence of scratches and halftone roughening of the photoconductor was evaluated. Resin coated carrier 1A-9
Only A (average particle diameter of 60 μm) was charged into each developing device, and the surface of the photosensitive member was rubbed with the resin-coated carrier by continuously rotating the photosensitive member and the developing device. The cleaning blade was replaced with a new one every 5 hours. After the predetermined time (rubbing time) shown in Table 2 below,
The presence or absence of scratches on the surface of the photoreceptor was confirmed. Then
The developer for "UBix-5070" was replaced with a developing device to form a copy image, and the occurrence of halftone roughness was evaluated. The results are shown in Table 2. In Table 2, when neither scratch nor halftone roughness is observed on the surface of the photoconductor, "○" is given. When scratching on the surface of the photoconductor is seen, but no halftone roughness is found, "△" is given. The case where both scratches and halftone roughness on the body surface are recognized is indicated by "x", and the case where the halftone roughness is significantly recognized is indicated by "xx".

[0042]

[Table 2]

As shown in Table 2, the carrier (1
In Nos. A to 5A), even after rubbing for 50 hours, scratches and halftone roughness on the surface of the photoconductor did not occur, and the formed copy image was good.
On the other hand, in the comparative carriers containing no P or As (6A to 8A), scratching and halftone roughening occurred on the surface of the photoconductor only after rubbing for 5 hours. Further, in the Mg-Zn-based comparative carrier 9A, scratches and halftone roughness were remarkably generated on the surface of the photoconductor only after rubbing for 5 hours. When the surface of the comparative carrier collected in the cleaning unit was observed, a large number of irregular scale-like particles generated by core crushing were observed. A scanning electron microscope (SEM) photograph showing this state is shown in FIG.

(2) Carriers 1B-9B Electrophotographic copying machine "UBix-5070" equipped with a negatively charged organic photoreceptor.
Using a modified machine, the occurrence status of scratches and halftone roughness of the photoconductors was evaluated for the carriers 1B to 5B of the present invention and the comparative carriers 6B to 9B. Only the resin-coated carriers 1B to 9B (average particle size 80 μm) were put into the respective developing devices, and the surface of the photosensitive member was rubbed with the resin-coated carrier by continuously rotating the photosensitive member and the developing device. The cleaning blade was replaced with a new one every 5 hours. After a predetermined time (rubbing time) shown in Table 3 below, the presence or absence of scratches on the surface of the photoreceptor was confirmed. Next, the developer for "UBix-3035" was replaced with a developing device to form a copy image, and the occurrence of halftone roughness was evaluated. The results are shown in Table 3. In Table 3, when neither scratches nor halftone roughness on the surface of the photoconductor is observed, "○" is given. When scratches on the surface of the photoconductor are seen but no halftone roughness is found, "△" is given. The case where both scratches and halftone roughness on the body surface are recognized is indicated by "x", and the case where the halftone roughness is significantly recognized is indicated by "xx".

[0045]

[Table 3]

As shown in Table 3, the carrier (1
In Nos. B to 5B), even after rubbing for 50 hours, scratches and halftone roughness on the surface of the photoconductor did not occur, and the formed copy image was good.
On the other hand, in the comparative carriers (6B to 8B) containing no P or As, rubbing on the surface of the photoconductor was caused only by rubbing for 5 hours, and halftone roughness was caused when rubbing for 10 hours. It was In addition, Mg-Zn
In the comparative carrier 9B, which is a system, when it was rubbed for 10 hours, a remarkable halftone roughness occurred. When the surface of the comparative carrier collected in the cleaning unit was observed, a large number of irregular scale-like particles generated by core crushing were observed. An SEM photograph showing this state is shown in FIG.

<Actual shooting test> (A-): The comparative carrier 6A and the toner for "UBix-5070" are mixed at a toner density such that the initial image has an appropriate density, and the electrophotographic copying machine "UBix-5070" is mixed. The test for forming a copy image was conducted to evaluate the actual shooting performance. The mounted cleaning unit has a structure in which the blade 11 and the guide roller 12 are used together as shown in FIG. In FIG. 1, 13 is a scraper, 14 is a toner conveying screw, and 30 is a photosensitive drum. In this actual shooting test, the blade 11 was replaced with a new one when an image defect occurred in the copy image. As a result, image defects due to defective cleaning (toner slippage) occurred at the time of copying 27,000 times and copying 52,000 times. In addition, when the copy image was sampled for every 10,000 copies and the occurrence of halftone roughness was observed, a slight halftone roughness was observed at the time of 20,000 copies, and halftone was found at the time of 50,000 copies. The image quality was significantly impaired by the roughness. The live-action test was stopped at the time of copying 60,000 copies. At the time of copying 60,000 times,
When a copy image was formed using an orange chart original, many streaks were observed in the circumferential direction of the photoconductor.

(A-): An actual copying test was conducted in the same manner as in (A-) except that the comparative carrier 9A (Mg-Zn system) was used in place of the comparative carrier 6A. As a result, image defects due to defective cleaning (toner slippage) occurred at the time of copying 190000 times and copying 370000 times. Moreover, when the copy image was sampled for every 10,000 copies and the state of occurrence of halftone roughness was observed, a slight halftone roughness was observed at the time of 13,000 copies, and at the time of 40,000 copies. Image quality was severely compromised by halftone roughness. The live-action test was stopped at the time of copying 50,000 times. At the time of copying 50,000 times, when a copy image was formed using an orange chart original, many streaks were observed in the circumferential direction of the photoconductor.

(A-): A live-copy test was conducted in the same manner as in (A-) except that the carrier 3A of the present invention was used in place of the comparative carrier 6A. The initial image quality was maintained without any problems.

(A-): A live-copy test was carried out using the comparative carrier 6A in the same manner as in (A-) except that the mounted cleaning unit had a structure as shown in FIG. In FIG. 2, 21 is a blade, 24
Is a toner conveying screw, 25 is a toner collecting plate, and 30 is a photosensitive drum. In addition, in this live-action test,
The blade 21 was replaced with a new one when an image defect occurred in the copy image. As a result, an image defect due to cleaning failure occurred at the time of copying 340000 times and copying 608,000 times. Further, a slight halftone roughness was recognized at the time of copying 50,000 times, and the image quality was significantly impaired by the halftone roughness at the time of copying 80,000 times.
The live-action test was stopped at the time of copying 80,000 times. At the time of copying 80,000 times, when a copy image was formed using an orange chart original, many streaks were observed in the circumferential direction of the photoconductor.

(A-): A live-copy test was conducted in the same manner as in (A-) except that the carrier 3A of the present invention was used in place of the comparative carrier 6A. The initial image quality was maintained without any problems.

(B-): Comparative carrier 6B and "UB
ix-3035 "toner is mixed at a toner concentration such that the initial image has an appropriate concentration, and a copy image is formed by a modified electrophotographic copying machine" UBix-5070 "equipped with a negatively charged organic photoconductor. Then, the live-action performance was evaluated. The cleaning unit has a structure as shown in FIG. 1, and the blade 11 was replaced with a new one when an image defect occurred in the copy image. As a result, 3.
At the time of 10,000 copies, 670000 copies and 890000 copies, image defects due to cleaning defects (toner slippage) occurred. Also, when the copy image was sampled for every 10,000 copies and the occurrence of halftone roughness was observed, a slight halftone roughness was observed at the time of 60,000 copies, and halftone was found at the time of 90,000 copies. The image quality was significantly impaired by the roughness. The live-action test was stopped when 90,000 copies were made. At the time of copying 60,000 times, when a copy image was formed using an orange chart original, many streaks were recognized in the circumferential direction of the photoconductor.

(B-): An actual copying test was conducted in the same manner as (B-) except that the comparative carrier 9B (Mg-Zn type) was used in place of the comparative carrier 6B. As a result, image defects due to cleaning defects (toner slippage) occurred at the time of copying 26,000 times and copying 54,000 times. When the copy image was sampled for every 10,000 copies and the occurrence of halftone roughness was observed, a slight halftone roughness was observed at the time of 50,000 copies, and halftone at the time of 70,000 copies. The image quality was significantly impaired by the roughness. The live-action test was stopped at the time of copying 70,000 times. At the time of copying 50,000 times,
When a copy image was formed using an orange chart original, many streaks were observed in the circumferential direction of the photoconductor.

(B-): A live-copy test was conducted in the same manner as in (B-) except that the carrier 3B of the present invention was used in place of the comparative carrier 6B. The initial image quality was maintained without any problems.

[0055]

The magnetic particles constituting the carrier according to the present invention have a P content of Cu-Zn based ferrite component.
And / or As is contained in a specific ratio, and the particles are extremely excellent in impact resistance. Therefore,
(1) According to the first and fourth aspects of the present invention, there is provided an electrostatic image developing carrier in which the irregular magnetic substance fine powder that causes abrasion of the cleaning member and abrasion on the surface of the photoconductor is not mixed. You can (2) According to the second and fifth aspects of the present invention, a method for manufacturing an electrostatic image developing carrier that does not generate irregular magnetic fine particles even by a mechanical impact force applied when performing the dry coating method. Can be provided. (3) According to the third and sixth aspects of the invention, it is possible to provide an image forming method that does not cause image defects due to poor cleaning and streaky roughness in the halftone portion.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of a cleaning unit mounted on an electrophotographic copying machine used for a live-copy test.

FIG. 2 is an explanatory diagram showing another example of a cleaning unit mounted on an electrophotographic copying machine used for a live-copy test.

FIG. 3 is an SEM photograph showing a surface state of a comparative carrier collected in a cleaning unit.

FIG. 4 is an SEM photograph showing a surface state of a comparative carrier collected in a cleaning unit.

FIG. 5 is a schematic view of an apparatus used to measure the current value of ferrite particles.

FIG. 6 is a schematic view of an apparatus used to measure the static resistance of ferrite particles.

[Explanation of symbols]

11 Blade 12 Guide Roller 13 Scraper 14 Toner Conveying Screw 21 Blade 24 Toner Conveying Screw 25 Toner Collection Plate 30 Photoreceptor Drum

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location G03G 21/00 112

Claims (6)

[Claims] 1. A dry coating method in which a mixture of magnetic particles and coating resin fine particles is repeatedly subjected to a mechanical impact to form a resin coating layer of the coating resin fine particles on the surface of the magnetic particles. In the electrostatic image developing carrier, the magnetic particles have a composition formula: (MO) _x (Fe ₂ O
₃ ) _y [M represents Zn and Cu, and x and y represent the number of moles. ] 0.1-1.0 weight part of P and / or As is contained with respect to 100 weight part of the ferrite component shown by these, The carrier for electrostatic image development characterized by the above-mentioned. 2. A dry coating method in which a mechanical coating force is repeatedly applied to a mixture of magnetic particles and coating resin particles to form a resin coating layer of the coating resin particles on the surface of the magnetic particles. A method for producing a carrier for electrostatic image development, wherein the magnetic particles are the magnetic particles according to claim 1. 3. A two-component developer comprising a toner and a carrier is used to develop an electrostatic image on a photoconductor to form a toner image, the toner image is transferred to a transfer material, and a cleaning blade is provided. The image forming method including the step of removing the toner remaining on the photoconductor using a cleaning device, and collecting the removed toner in a toner replenishing hopper or a developing device for reuse, wherein the carrier is An image forming method, which is the electrostatic image developing carrier as described in 1. 4. The electrostatic image developing carrier according to claim 1, wherein the ferrite composition of the magnetic particles constituting the carrier is (CuO) 5 to 30 mol%, (ZnO) 5
A resin-coated carrier for developing an electrostatic image, wherein the carrier content is in the range of ˜30 mol% and (Fe ₂ O ₃ ) 55 to 70 mol%. 5. The method for manufacturing a carrier for electrostatic image development according to claim 2, wherein the ferrite composition of the magnetic particles used for manufacturing the carrier is (CuO) 5 to 30 mol%.
(ZnO) 5 to 30 mol%, (Fe ₂ O ₃ ) 55 to 70
A method for producing a resin-coated carrier for electrostatic image development, which is in the range of mol%. 6. The image forming method according to claim 3, wherein the ferrite composition of the magnetic particles constituting the carrier used in the image forming method is (CuO) 5 to 30 mol%, (ZnO) 5 to 30 _{mol%, (Fe 2 O 3)} 55~
An image forming method characterized by being in the range of 70 mol%.