JPH08179591A - Electrifying member - Google Patents

Abstract

PURPOSE: To prevent the melt-sticking of a developer to the surface of an image carrier, its shaving caused by the rubbing of an electrifying member and the surface of the image carrier, contamination, the generation of a noise, etc., by providing a resistant layer of a single layer incorporating a magnetic material, in contact with a conductive substrate. CONSTITUTION: The electrifying member 1 is constituted so that its surface faces the surface of the image carrier 5 with a gap and provided with the resistant layer 3 of the single layer obtained in such a manner that the magnetic material whose powder resistance is preferably >=1×10<3> Ωcm is dispersed in resin or sintered, in the position facing the image carrier 5, of the electrifying member 1, to enable uniform electrification with the gap. The resistant layer 3 of the single layer is in contact with the conductive substrate 2, in the position facing the surface of the image carrier 5 with the gap and formed like a roller or a plate. The surface of the image carrier 5 is uniformly electrified by a discharge from the surface of a layer incorporating the magnetic material of the electrifying member 1. Therefore, all problems caused by the fact that the electrifying member 1 is in contact with a member to be electrified can be eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member used in an electrophotographic image forming apparatus as a charging member for primary charging, a charging member for transfer charging, a charging member for static elimination charging and the like.

[0002]

2. Description of the Related Art Recently, a contact charging device has been proposed which charges a surface by directly contacting (contacting) the surface of an image bearing member (member to be charged). For example, as described in Japanese Patent Laid-Open No. 63-7380, the charging member is formed into a roller shape and is contact driven on the surface of the image bearing member (member to be charged) for charging. This device has an advantage that the applied voltage can be suppressed low and at the same time, the ozone generation amount is extremely low. In addition to this, there is a method using a conductive brush, as proposed in Japanese Patent Laid-Open No. 64-24264. This method has the advantages that uniform charging is realized and that the charging device does not wear even if there is a drum defect or the like. Further, as described in JP-A-1-93760, there has been proposed a system in which an electrode is arranged on an elastic blade having conductivity and the tip of this blade is pressed against the photoconductor.

[0003]

However, since the charging roller is in contact with and driven by the surface of the image bearing member (member to be charged), the developer is fused to the surface of the image bearing member (member to be charged) and the image bearing is carried. It may also induce adverse effects such as scraping of the surface of the body (body to be charged). Further, as the applied bias of the charging roller, an AC voltage having a peak-to-peak voltage that is at least twice the discharge start voltage (Vth) is superimposed on a DC voltage corresponding to the desired surface potential of the surface of the image carrier (charged body). Generally, it is applied, and in order to obtain a higher definition image as in today's day, the frequency of the applied AC voltage is increased to compensate for the narrow discharge area of the charging roller, and more discharge opportunities are created. I have to give it. Also in this case, since the charging roller is in contact with the surface of the image carrier (charged), the vibration of the charging roller due to the oscillating electric field is transmitted to the surface of the image carrier (charged),
Noise (charging sound) having a frequency twice the applied frequency is generated. Further, in the case of writing image information by line scanning to form an image, there is a drawback that moire occurs due to mutual interference when the spacing between scanning lines and the applied frequency are close to each other.

On the other hand, the above-mentioned charging member is manufactured by a process of coating a core metal, which is a conductive base material, with an elastic layer / resistive layer / protective layer (surface layer) in this order. Be seen. That is, first, in order to obtain a sufficient nip with the surface of the image bearing member (charged member), it is common to use rubber in which the conductive pigment is dispersed in the elastic layer. Next, a resistance layer is required for the purpose of making the electric resistance of the charging roller semi-conductive and for preventing current concentration even if there is a defect such as a pinhole on the surface of the image bearing member (member to be charged). Furthermore, rubber requires several kinds of plasticizers and activators to exert its elasticity and prevent deterioration, and it is not uncommon to use a dispersion aid to disperse the conductive pigment. . In addition, the surface of the image bearing member (charged member) is an amorphous resin such as polycarbonate or acryl, which is very weak against these plasticizers, activators and dispersion aids. Therefore, a protective layer is required to prevent these leaks. That is, the charging roller has a multi-layered structure as described above, and the desired performance can be obtained for the first time by exhibiting the function of each layer. Therefore, the manufacturing process is complicated, and the charging roller is likely to be very expensive.

Next, in the method using a conductive brush, since the contact pressure of the wire of the brush is low, foreign matter or the like is likely to enter the charging area. In addition, since the wire rods are aligned in a certain direction at each location, there is a problem that charging defects are likely to occur and that the wire rods easily fall off from the carrier due to contact with the surface of the image bearing member (charged member). There is. Further, the surface of the wire is easily contaminated by oxides generated during discharge, so that its life is limited and it is difficult to maintain constant performance for a long period of time.

Further, the elastic blade method does not cause the above-mentioned problems such as the dropping of the wire rod, but has a problem that it is easily affected by the inclusion of foreign matter because the charging area is narrow. In addition, during discharge, fine powder toner and paper powder that have rubbed through the cleaner adhere to the surface due to the action of collecting the oscillating electric field generated by the AC component, which causes uneven resistance and easily causes image defects. In addition, since its tip constantly rubs against the photoconductor, it wears severely and its life is limited.

All the problems associated with each charging member as described above are caused by the charging member being in contact with the surface of the image bearing member (member to be charged). Therefore, 1) fusion of the developer to the surface of the image bearing member (charged member). 2) Wear of the charging member and abrasion of the surface of the image bearing member (charged member) due to rubbing between the charging member and the surface of the image bearing member (charged member). 3) Contamination of the surface of the image bearing member (charged member). 4) When a voltage in which an AC voltage is superimposed on a DC voltage is applied, the vibration of the charging member is transmitted to the surface of the image bearing member (object to be charged), and noise (charging sound) having a frequency twice the applied frequency.
Occurs. With the problem said.

An object of the present invention is to provide a charging member capable of solving all the problems caused by the contact between the charging member and the member to be charged as described above.

[0009]

According to the present invention, there is provided at least a conductive substrate and a single resistance layer containing a magnetic substance, which is in contact with the conductive substrate. A member is provided.

That is, the charging member according to the present invention opposes the surface of the charging member and the surface of the image bearing member (object to be charged) via a gap, and enables uniform charging through this gap. A single resistance layer obtained by dispersing or sintering a magnetic material having a powder resistance of 1 × 10 ³ Ωcm or more in a resin is preferably provided at a position facing the image bearing member (charged member) of the member. I have.

More specifically, in the charging member according to the present invention, a single resistance layer obtained by dispersing or sintering a magnetic material having a powder resistance of 1 × 10 ³ Ωcm or more in a resin is preferably conductive. Image carrier (charged body) in contact with substrate
A charging member which is present at a position facing a surface with a gap therebetween and has a shape of a roller or a plate.

That is, in the charging member according to the present invention, the surface of the charging member and the surface of the image bearing member (member to be charged) are opposed to each other with a gap, and the image bearing is carried by discharge from the surface of the layer containing the magnetic material of the charging member. Since the surface of the body (object to be charged) is uniformly charged, it is possible to eliminate all the problems as described above due to the contact between the charging member and the member to be charged.

The problem with the charging member according to the present invention is that
It is how to secure the void. As described below, when the surface of the image bearing member is charged to a constant potential via the void, it directly affects the increase / decrease of the applied voltage, so that it is preferably as small as possible. However, in consideration of the accuracy of the charging member and the tolerance in mass production, it is actually 100
It is very difficult to develop below μm. Therefore, the charging member according to the present invention is 100 .mu.
It is intended to provide a charging member capable of being uniformly charged even when a void of m or more is secured.

Here, the discharge start voltage through the air gap is an approximate expression of the dielectric breakdown voltage derived from Paschen's law Vth (discharge start voltage) = 312 + 6.2d (d = gap; μm where d = 8 μm or more ). That is, theoretically, when the gap is 100 μm, the discharge start voltage (Vth) is 932 V, and if a DC voltage of a value obtained by adding a desired surface potential of the image carrier (charged member) is applied to the image carrier, (Charge object) The surface can be charged to a desired potential. Similarly, when the gap is 200 μm, the discharge start voltage (Vth) is 1552 v, and when only the DC voltage is applied, by applying the DC voltage of a value including the desired surface potential of the image carrier (charged body). The surface of the image bearing member (charged member) can be charged to a desired surface potential.

When a voltage obtained by superimposing an AC voltage on a DC voltage is applied, the DC voltage corresponding to the desired surface potential of the image bearing member (charged member) is changed to the discharge start voltage (Vth) for the air gap at that time. By applying an AC voltage having a peak-to-peak voltage that is twice or more at a constant frequency, it is possible to charge to a desired surface potential. That is, the image carrier (charged body) surface can be charged to a desired surface potential simply by increasing the applied voltage as the voids are expanded. It was discovered that there was spot-like unevenness in the charged state of the surface of the image bearing member (charged member), that is, the surface potential, and the unevenness increased especially when the voids exceeded 100 μm, and the voltage corresponding to the voids was simply applied. It was confirmed that uniform charging cannot be obtained only by applying.

The present inventors considered this phenomenon as follows. The material of the discharge surface of the conventional charging member causes a significant voltage drop of the applied voltage from the lower limit resistance that can prevent current concentration (leakage) even when there is a pinhole on the surface of the image carrier (member to be charged). 1 as the range up to the upper limit of resistance
The volume resistivity range of × 10 ⁵ to 1 × 10 ¹⁰ Ωcm is empirically known. In order to adjust the material in such a so-called medium resistance range, the material itself falls within the above resistance range, and the conductive material (conductive carbon, conductive tin oxide, conductive titanium oxide, AL, etc.) is used as the insulating material. Powder, Cu powder, Ni powder, etc.) is used to adjust the electric resistance. However, the former is small in number and the resistance fluctuation due to the atmosphere is large, so the latter is generally widely used. It was Here, when a material in which a conductive pigment is dispersed in an insulating material is used as the discharge surface, the applied voltage reaches the surface through the conductive pigment in the material. In other words, there are innumerable fine needle electrodes.

In the space, electrons gain energy from the applied electric field and are ionized from the surface of the resistance layer. Further, the ionized electrons adhere to the gas forming the space and form charged particles. Since the energy is high near the discharge surface, the concentration of charged particles is also high. These particles repeatedly collide and diffuse from a high density area to a low density area (image carrier surface direction) and finally reach the image carrier surface. The charged particles give an electric charge to the surface of the image carrier to become neutral particles. A large number of electrons are supplied to the discharge space by the applied electric field, and the time interval of the supply is within the space travel time of the electrons, and when the electrons are supplied at a constant time interval, a plurality of electrons travel in the space. The stable diffusion condition is always satisfied. Therefore, the drum surface is uniformly charged. And the result that the upper limit of the voids at that time was 100 μm was obtained. On the other hand, the gap is 10
When it is 0 μm or more, the voltage applied to the discharge surface increases. Here, the material used for the discharge surface is one in which a conductive pigment is dispersed, and the conductive path of this conductive pigment is regarded as an assembly of needle electrodes. It is considered that the number of times of ionization of electrons becomes extremely large and the density thereof becomes excessive as well. Therefore, electrons flow into the charged particles one after another to form a plasma portion.

Such a state is generally called a streamer. In other words, the discharge start voltage increases due to the expansion of the air gap, and the applied voltage rises correspondingly, and the diffusion state required for uniform charging is destroyed by the increase in the electric field applied to the needle electrode that forms the discharge surface, forming a streamer. As a result, the potential on the surface of the image bearing member (the member to be charged) becomes spotted unevenness. The void that becomes this boundary is 100μ
m, and when a high voltage corresponding to the discharge start voltage in a void of 100 μm + the desired surface potential of the image bearing member (charged member) is applied, a streamer is formed in the conductive pigment that has been conventionally used. He came to the conclusion that he could not be suppressed.

As a result of intensive studies based on this idea, the present inventors have found a solution to the electric resistance itself of the conductive pigment. In other words, the conductive pigments that have been conventionally used (conductive carbon, conductive tin oxide, conductive titanium oxide, AL powder, Cu
Powder, Ni powder, etc.) has a powder resistance of 100 Ωcm or less,
Since the conductivity is too high, the number of times of ionization of electrons becomes extremely large due to a large applied electric field, so that the formation of the plasma portion which is caused by the successive inflow of electrons into the charged particles cannot be suppressed. Therefore, the present inventors decided to use conductive powder having a relatively high powder resistance for the discharge surface. Specifically, the inventors have reached the result that it is most desirable to use a magnetic material in consideration of resistance stability, particle size and shape stability, cost, and the like. This is because when the void is 100 μm or more, the powder resistance itself is high even when a large applied electric field corresponding to the discharge start voltage + the surface potential of the surface of the image carrier (charged body) is applied.
That is, the magnetic material converts the current energy generated excessively due to the high resistance of the needle electrode itself into heat energy,
The generation of excessive electrons can be suppressed and the number of times of electron ionization can be suppressed,
Therefore, it is considered that the formation of the plasma part which is caused by the inflow of electrons into the charged particles one after another is suppressed.

The magnetic substance is a substance which is magnetized by applying a magnetic field. The magnetic substance used in the charging member according to the present invention has a powder resistance of 1 × 1 regardless of the presence or absence of magnetization.
If it is 0 ³ Ωcm or more, the effect is exhibited, and specifically, iron oxide, ferrite or the like is used. One method of forming the resistance layer used for the charging member according to the present invention is a method of forming a resistance layer by dispersing a magnetic material in a binder resin. In that case, it is desired that the magnetic material be uniformly dispersed in the binder resin, but there is no particular restriction on the magnetic material. Therefore, the shape of the magnetic body may be spherical, octahedral or needle-like. The amount of the magnetic substance added to the binder resin (weight percent; wt%) is in the range of 30 wt% or more, preferably 50 wt% or more. If the added amount is less than 30 wt%, the magnetic substance is too small to form a conductive path in the binder resin, so that a so-called fine needle electrode cannot be obtained. In the method of forming such a resistance layer, it is desired that the binder resin used has little resistance variation due to the atmosphere. Specific examples thereof include those appropriately selected from resins such as polyester, polyurethane, nylon, silicon, acryl, polyolefin and phenol.

The method of forming the resistance layer used in the present invention is as follows.
A method of sintering a magnetic material to obtain a desired shape may be used. However, regarding the surface roughness of the resistance layer obtained by each of the above-mentioned preparation methods, it is desirable that the surface average roughness (Ra) is 0.5 μm or less. It is necessary that the resistance value of the obtained resistance layer is set to 10 ⁵ to 10 ¹⁰ Ωcm by satisfying these conditions and adjusting the addition amount depending on the level of the powder resistance of the magnetic material used. If the volume resistivity is less than 1 × 10 ⁵ Ωcm, the applied voltage cannot be uniformly divided and a local conduction circuit is formed, so that uniform charging cannot be performed. On the other hand, if the volume resistivity exceeds 1 × 10 ¹⁰ Ωcm, a voltage drop of the applied voltage is caused and sufficient discharge cannot be performed. Therefore, since the number of times of ionization of electrons is extremely reduced, the charging performance is significantly reduced. It should be noted that two or more kinds of magnetic materials may be used in combination under the above conditions.

The charging member according to the present invention will be described below with reference to FIGS. 1 and 2. The charging member 1 of the present invention has a structure in which a single-layer resistance layer 3 is provided on one surface of a conductive base plate 2 made of an appropriate metal, which is an elongated plate in this example. Thus, it is arranged at a position facing the surface of the image carrier 5 (member to be charged) with a predetermined gap 6 therebetween.

In order to enable uniform charging through the voids 6, the magnetic powder having a powder resistance of 1 × 10 ³ Ωcm or more is located at a position facing the surface of the image bearing member 5 (charged member) of the charging member. It has a single resistance layer 3 obtained by dispersing or sintering the body in a resin.

More specifically, in the charging member 1 of the present invention, a magnetic material having a powder resistance of 1 × 10 ³ Ωcm or more is dispersed in a resin,
Alternatively, a single resistance layer 3 obtained by sintering is provided in contact with a conductive substrate, and is arranged at a position facing the surface of the image bearing member (member to be charged) 5 with a gap.

The conductive substrate 2 is made of a metal material having high rigidity so that the space between the shape of the charging member 1 and the surface of the image bearing member (charged member) 5 is always kept constant.

The charging member of the present invention may have a flat plate shape as shown in FIGS. 1 and 2, or FIG.
Also, as shown in FIG. 4, it may be roller-shaped.

Whether the charging member 1 has a roller shape or a flat plate shape, spacer members 4 are provided at both ends of the charging member 1 in order to secure a predetermined space between the charging member 1 and the member 5 to be charged. Is provided. The spacer member 4 is preferably made of a material having a low friction coefficient such as Teflon, high molecular weight polyethylene, or POM.

In the charging member of the present invention, a voltage is applied to the conductive substrate from the installed power source. The applied voltage is transmitted to the single resistance layer in contact with the conductive substrate, and the surface of the image bearing member (charged member) 5 is uniformly charged by the discharge from the surface.

[0029]

EXAMPLES The present invention will be described below based on examples.

Example 1 Nylon-12 resin was blended with 70 wt% of needle-shaped iron oxide having a powder resistance of 1 × 10 ⁵ Ωcm, a diameter of 0.2 μm and a length of 5 μm. Was melt-kneaded to prepare a semiconductive material having a resistance value of 1 × 10 ⁸ Ωcm. Using this material, a sheet having a thickness of 500 μm was continuously prepared by melt extrusion using an extruder. The surface average roughness (Ra) was 0.
It was 08 μm.

The single resistance layer thus prepared was punched into a predetermined size and attached to a parallel plate made of stainless steel via a conductive primer. Further, a POM spacer member formed so that the surface of the image bearing member (charged member) and the resistance layer of a single layer has a gap of 100 μm is attached to both ends of a parallel plate made of stainless steel, and a target charging member is obtained. Got

The charging member thus obtained was attached to the position of the primary charger of the electrophotographic apparatus shown in FIG. In FIG. 5, 1 is a charging member, 5 is an image carrier, 12 is a charging power source,
13 is a developing device, 14 is a cleaner, 15 is a transfer roller, 1
Reference numeral 6 is a transferred material.

A spring was actuated between the surface of the image bearing member (charged member) 5 and the spacer member (not shown) so that the contact pressure was 10 g. The contact pressure is a value obtained by sandwiching an aluminum sheet having a width of 1 cm between the surface of the image carrier 5 and the spacer member 4 and measuring the force when the aluminum sheet is pulled out.

From the power supply 12 to the charging member 1, -1650v
DC voltage (Vth in the air gap of 100 μm is −932 v, and the set surface potential of the image carrier used is −650.
v) is applied, and the standard environment (23 ° C.) / (55
%), High temperature (32.5 ° C.) / High humidity (85%), and low temperature (15 ° C.) / Low humidity (10%), 10,000 sheets were subjected to durability evaluation.

As a result, in all environments, there was almost no change in the image at the initial stage and after the durability test, and a good image was obtained. Further, no problems such as fusion of the developer on the surface of the image bearing member, wear of the charging member, abrasion of the surface of the image bearing member (member to be charged), and noise (charging noise) were observed.

(Embodiment 2) The spacer of the charging member prepared in Embodiment 1 is arranged so that the image bearing member (the member to be charged) and the surface of the single resistance layer have voids of 200 μm and 300 μm, respectively. Changed to -2200v and -2850 respectively
A DC voltage of v was applied and the durability test was carried out in the same manner as in Example 1.

As a result, under all conditions, there was almost no change in the image in the initial stage and after the endurance under all environments, and a good image was obtained. Further, no problems such as fusion of the developer on the surface of the image bearing member, wear of the charging member, abrasion of the surface of the image bearing member (member to be charged), and noise (charging noise) were observed.

(Example 3) Using the charging member prepared in Example 1, an AC voltage having a peak-to-peak voltage of 2500 vpp was superposed on a DC voltage of -650 V at a frequency of 200 Hz, and a durability test was conducted as in Example 1. I went to

As a result, a good image was obtained under almost all environments, with almost no image change at the initial stage and after the durability test. Further, no problems such as fusion of the developer on the surface of the image bearing member, wear of the charging member, abrasion of the surface of the image bearing member (member to be charged), and noise (charging noise) were observed.

Further, when the charging sound at that time was measured with a sound level meter, it was 45 dB, which was extremely quiet.

Example 4 Powder resistance is 1 × 10 ⁷ Ωc
A nickel-zinc-based ferrite having an average particle size of 30 μm and a diameter of 30 μm was pressed into a plate having a predetermined size and sintered at 600 ° C. to form a single resistance layer. The surface average roughness (R
a) was 0.15 μm. Then, it was attached to a parallel plate made of stainless steel via a conductive primer. Furthermore, the surface of the image bearing member (charged member) and the single resistance layer is 100μ.
Spacer members made of POM prepared so as to have voids of m were attached to both ends of a parallel plate made of stainless steel to obtain a target charging member. The same tests as in Example 1 were performed below.

As a result, good images were obtained under almost all environments, with almost no image change at the initial stage and after the durability test. Further, no problems such as fusion of the developer on the surface of the image bearing member, wear of the charging member, abrasion of the surface of the image bearing member (member to be charged), and noise (charging noise) were observed.

[0043] (Example 5) Powder resistance in the polyester resin is 1 × 10 ⁴ Ωcm, average particle size of 1μm iron oxide 65
wt% was blended and melt-kneaded with a pressure kneader to prepare a semiconductive material having a resistance value of 1 × 10 ⁷ Ωcm.
This material was injection-molded on the outer circumference of a φ6 mm stainless steel cored bar, and then polished to form a φ12 mm single-layer roller. The surface average roughness (Ra) is 0.10 μm.
It was m. Then, the POM was prepared so that the surface of the image bearing member (the member to be charged) and the single resistance layer had a void of 100 μm.
A spacer member made of was attached to both ends of the single-layer roller to obtain an intended charging member.

Thereafter, a durability test was conducted in the same manner as in Example 1.
As a result, good images were obtained under almost all environments, with almost no image change at the initial stage and after the durability test. Further, no problems such as fusion of the developer on the surface of the image bearing member, wear of the charging member, abrasion of the surface of the image bearing member (member to be charged), and noise (charging noise) were observed.

Comparative Example 1 Nylon-12 resin was blended with 50 wt% of conductive titanium oxide having a powder resistance of 2 Ωcm and an average particle size of 0.2 μm, melted and kneaded with a pressure kneader, and the resistance value was obtained. A semiconducting material having a value of 1 × 10 ⁷ Ωcm was prepared. This material was melt extruded with an extruder to continuously form a sheet having a thickness of 500 μm. The surface average roughness (Ra) was 0.12 μm. The single-layer resistance layer thus formed was punched out to a predetermined size and attached to a parallel plate made of stainless steel via a conductive primer. Further, spacer members made of POM prepared so that the image carrier (charged body) and the surface of the single resistance layer have a gap of 100 μm are attached to both ends of a parallel plate made of stainless steel to obtain a charging member. It was The same test as in Example 1 was performed below, but a spot-like unevenness was frequently generated, and a good image could not be obtained.

(Comparative Example 2) 10 wt% of conductive carbon having a powder resistance of 1 × 10 ^-1 Ωcm and an average particle size of 0.1 μm was mixed with polyester resin, melted and kneaded with a pressure kneader, and the resistance was measured. A semiconductive material having a value of 1 × 10 ⁶ Ωcm was prepared. This material was injection-molded on the outer circumference of a φ6 mm stainless steel cored bar, and then polished to form a φ12 mm single-layer roller. The surface average roughness (Ra)
Was 0.09 μm. Next image carrier (charged body)
A charging member was obtained in which spacer members made of POM prepared so that the surface of the single resistance layer had voids of 100 μm were attached to both ends of the single layer roller. The same test as in Example 1 was carried out, but spotty unevenness frequently occurred, and a good image could not be obtained.

[0047]

EFFECT OF THE INVENTION The charging member according to the present invention discharges from the surface of the layer in which the magnetic material is dispersed, so that uniform charging can be achieved even when a space of 100 μm or more is secured on the surface of the image bearing member (charged member). It is a possible charging member. Therefore, 1) fusion of the developer to the surface of the image bearing member (charged member). 2) Wear of the charging member and abrasion of the surface of the image bearing member (charged member) due to rubbing between the charging member and the surface of the image bearing member (charged member). 3) Contamination of the surface of the image bearing member (charged member). 4) When a voltage in which an AC voltage is superimposed on a DC voltage is applied, the vibration of the charging member is transmitted to the surface of the image bearing member (the member to be charged), and noise (charging sound) having a frequency twice the applied frequency.
Occurs. It is possible to solve all such problems.

Moreover, since the structure is a simple structure in which the magnetic material is dispersed or sintered on the metal base material, a single resistance layer is present, so that it is possible to provide a charging member at an extremely low cost. Becomes

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of an example of an image forming apparatus using a charging member according to the present invention.

FIG. 2 is a horizontal and vertical sectional view of the image forming apparatus of FIG.

FIG. 3 is a schematic vertical sectional view of an example of an image forming apparatus using another charging member according to the present invention.

4 is a horizontal and vertical sectional view of the image forming apparatus of FIG.

FIG. 5 is a schematic vertical sectional view of an image forming apparatus to which a charging member according to the present invention is attached.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Charging member 2 Conductive substrate 3 Resistive layer 4 Spacer 5 Image carrier 6 Void 12 Power source 13 Developing device 14 Cleaning means 16 Transfer roller 17 Transfer material

Claims (4)

[Claims] 1. A charging member comprising at least a conductive substrate, and a single-layer resistance layer containing a magnetic material, which is in contact with the conductive substrate. 2. The powder resistance of the magnetic material is 1 × 10 ³ Ωc.
The charging member according to claim 1, which is at least m. 3. The charging member according to claim 1, wherein the resistance layer is arranged at a position facing the surface of the member to be charged with a gap therebetween. 4. A roller-shaped or flat-shaped roller.
The charging member according to any one of 3 above.