JPH0720685A - Electrifying member - Google Patents

Abstract

PURPOSE:To eliminate occurrence of a defective image caused by the unevenness of the resistance value of an electrifying roller. CONSTITUTION:The electrifying roller 2 is allowed to abut on a photoreceptor 1 rotating in a direction shown by arrow R1 and rotated in a direction shown by arrow R2. Bias is impressed on the roller 2 by a power source 3 to electrify the surface of the photoreceptor 1. The roller 2 is provided with a core bar 2a, an elastic layer 2b and an intermediate layer 2c. Either the elastic layer 2b or the intermediate layer 2c is made a resistance control layer. The resistance control layer includes a conductive filler and an insulating filler, and its resistance value is adjusted by adjusting the content of the filler. Since it includes the fillers such as the conductive and the insulating ones, the fine adjustment of the resistance value is facilitated and the uniformity of the resistance value is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact type charging member which is used in an electrophotographic image forming apparatus and contacts a charged body to uniformly charge the surface of the charged body.

[0002]

2. Description of the Related Art An image forming apparatus such as an electronic copying machine and an electrostatic recording apparatus includes a charging process for uniformly charging the surface of an object to be charged in the image forming process. A corona charging method is generally used as the charging method, but it is known that the corona charging method often produces products such as ozone. Therefore, it is indispensable to install additional means and mechanism for treating the product, and there is a problem that the device tends to be large and costly.

Therefore, recently, a contact charging method has been studied as a new charging method which replaces the corona charging method, and has been partially put into practical use.

In the contact charging method, a charging member to which a voltage is applied is brought into contact with a member to be charged with a predetermined pressing force to charge the member to be charged. According to this method, the generation of ozone is significantly reduced as compared with the corona charging method, so that there is an advantage that the additional means and mechanism which are indispensable in the conventional corona charging method are unnecessary. In this contact charging method, the voltage applied to the charging member is a superimposed voltage of a DC voltage and an AC voltage having a peak-to-peak voltage that is about twice the charging start voltage when the DC voltage is applied to the charging member. There are many. The charging member is required to have a function of holding the body to be charged at a predetermined potential, and therefore it is important to control the electric resistance of the charging member within a certain range. For this resistance control, a conductive filler such as carbon black, tin oxide or titanium oxide is usually used. Powder resistance is 10 ^-2 ~10 ⁰ Ω · cm order for carbon black, also tin oxide,
The powder resistance of titanium oxide is 10 ¹ to 10 ² Ω.
Those with a size of about cm are generally widely used.

[0005]

However, the above charging member has the following problems.

The preferable resistance of the charging member as a whole is 1.
0 × 10 ^{4 to} 1.0 × 10 ⁸ Ω, and in order to control the resistance in this range, the volume resistivity should be at least 1.0 × 10 ³
A resistance control layer formed of a material of 1.0 × 10 ⁹ Ω · cm is required. However, the resistance value in this region is
Since it greatly changes with a slight fluctuation in the amount of filler added, resistance adjustment is performed using only the above-mentioned conductive filler,
Therefore, it is difficult to stably produce the charging member.

For the resistance control layer for controlling the resistance of the charging member, a dry film of a paint mixed with a conductive filler, a vulcanized molded rubber having carbon black dispersed therein and the like are often used.

In the former case, a slight variation in the filler distribution tends to occur, and in the latter case, in addition to this, uneven resistance values are likely to occur in the material due to differences in molding method, vulcanization conditions and the like. Therefore, in the electrophotographic image forming apparatus using such a material for the contact type charging member,
When an attempt is made to charge the photoconductor, which is the member to be charged, to a predetermined potential, the potential on the photoconductor becomes uneven, which causes image defects.

Therefore, in the present invention, the resistance control layer contains a conductive filler and an insulating filler,
An object of the present invention is to provide a charging member which is capable of forming a good image by eliminating unevenness in resistance value.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and is a charging device that contacts a charged body and applies a charging voltage to uniformly charge the charged body. In the member, the charging member has a resistance control layer containing at least a conductive filler and an insulating filler, the resistance control layer, by changing the content of the conductive filler and the insulating filler, resistance It is characterized by adjusting the value.

In this case, the volume resistivity of the resistance control layer is 1.0 × 10 ³ Ω · cm or more and 1.0 × 10 ⁹ Ω.
・ It is preferable to set it to not more than cm.

The powder resistance of the conductive filler is preferably 1.0 × 10 ⁶ Ω · cm or more, and the powder resistance of the insulating filler is preferably 1.0 × 10 ¹² Ω · cm or more.

The insulating filler may be a metal oxide.

[0014]

With the above structure, the resistance control layer of the charging member contains at least the conductive filler and the insulating filler, so that the resistance value can be finely adjusted and the uniformity of the resistance value is improved.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. <Example 1> In the present invention, a contact type charging member has a layer for controlling resistance (hereinafter referred to as "resistance control layer"), and the resistance control layer includes a conductive filler and an insulating filler. It is characterized by containing.

FIG. 4 is a vertical sectional view showing a schematic structure of an example of an image forming apparatus (copier) using the charging member according to the present invention.

This image forming apparatus has a photosensitive layer 1b on the surface of a cylindrical base 1a, and a photosensitive member (material to be charged) 1 which is driven to rotate in the direction of arrow R1. A charging roller (charging member) 2 is pressed against the photoconductor 1 with an appropriate pressing force. A bias is applied to the charging roller 2 by the power source 3, and the charging roller 2 is driven to rotate in the direction of the arrow R2 as the photoreceptor 1 rotates in the direction of the arrow R1.
The surface of the photoconductor 1 is uniformly charged. After that, an electrostatic latent image is formed on the photoconductor 1 by exposure 5, and the electrostatic latent image becomes a toner image with toner attached by the developing device 6. The toner image on the photoconductor 1 is transferred onto the transfer material P by the transfer device 7, and then fixed by a fixing device (not shown).

On the other hand, the residual toner on the photoconductor 1 is removed by the cleaner 9.

The voltage applied to the charging roller 2 is a DC voltage, or a DC voltage, an AC voltage and a superimposed voltage,
Any of these can be used.

Next, FIGS. 1, 2 and 3 show different embodiments of the charging roller (charging member). It should be noted that all of these figures are vertical cross-sectional views in the axial direction of the charging roller.

The charging roller has a cored bar 2a to which a DC voltage or a superimposed voltage of a DC voltage and an AC voltage is applied, and an elastic layer 2b (see FIGS. 1 to 3), and if necessary, an intermediate layer. 2c (see FIGS. 1 and 2) and a coating layer 2d (see FIG. 1) outside the intermediate layer 2c. Of these layers, at least one layer serves as the resistance control layer.

The conductive filler used in the present invention has a powder resistance of 1.0 × 10 ⁶ Ω · cm or less, such as titanium oxide, tin oxide, indium oxide, iron oxide, zinc oxide, calcium oxide, There are fillers made of metal oxides such as zirconium oxide and cesium oxide, and carbon black. The insulating filler has a powder resistance of 1.0 ×.
There are metal oxides of 10 ¹² Ω · cm or more, such as zinc oxide, magnesium oxide, tin oxide, iron oxide, titanium oxide, lead oxide, beryllium oxide, cesium oxide, calcium oxide, zirconium oxide, etc., each alone or 2 You may use it in combination of 2 or more types. As a usage method, a conductive filler and an insulating filler are mixed, and a material added to a binder is used for the resistance control layer. An example of actual addition is shown in FIGS. FIG. 5 shows a change in resistance value when only the conductive filler (carbon black) is added to the binder (polyamide resin), and FIG. 6 shows that the insulating filler (oxidizing magnesium) is added after the conductive filler (carbon black) is added. Indicates the change in resistance value when Figure 5,
As shown in FIG. 6, when only the conductive filler is used, the change gradient around the required resistance value (10 ⁴ Ω to 10 ⁸ Ω) is large, so it is very difficult to adjust the resistance. The change in resistance around this becomes gentle,
It has an advantage that the resistance value is stabilized even if the amount of the insulating filler added fluctuates to some extent. Further, when the conductive filler and the insulating filler are mixed and used, the uniformity of the resistance in the material is significantly improved as compared with the case where the conductive filler is used alone.

The charging roller 2 will be described in more detail. [Adjustment of compound for elastic layer (material for resistance control layer)] E
PDM 100 parts by weight, zinc oxide 5 parts by weight, higher fatty acid 1 part by weight, conductive carbon black 8 parts by weight, magnesium oxide 5 parts by weight, paraffin oil 10 parts by weight, sulfur 2 parts by weight, vulcanization accelerator MBT 1 part by weight. ,
Vulcanization accelerator TMTD 1 part by weight, vulcanization accelerator ZnMD
While cooling C 1.5 parts by weight with two rolls, 20
The mixture was mixed for a minute to make a compound. [Preparation of coating material for coating layer] Methylol nylon 100
Nylon resin coating material was prepared by dissolving parts by weight in a mixed solvent of methanol 420 parts by weight and toluene 150 parts by weight. [Preparation and Evaluation of Charging Roller] First, the elastic layer compound was applied to a stainless steel core having a diameter of 10 mm at 150 ° C. for 15 minutes.
It was heated and vulcanized for a minute to obtain a rubber roller having an elastic layer with a thickness of 3 mm. When the resistance of the rubber roller was measured at three locations in the longitudinal direction, it was 2.5 × 10 ⁵ , 2.4 × 10 ⁵ , and
It was 2.6 × 10 ⁵ Ω. The compound for the elastic layer, which is the material for the resistance control layer, was molded into a sheet and the volume resistivity was measured to be 1.7 × 10 ⁶ Ω · cm.

Next, the above coating material (nylon coating material) was similarly dip-coated on this charging roller, and dried by heating at 120 ° C. for 1 hour to obtain a charging roller having a coating layer with a thickness of 3 μm. . When the resistance of the charging roller was measured at three locations in the longitudinal direction, they were 2.6 × 10 ⁵ and 2.5, respectively.
It was x10 ⁵ , 2.7 x 10 ⁵ Ω.

An analog copying machine (NP2
When it was attached to the position of the primary charger of 020 Canon Inc. and image formation was performed under a bias condition of -1500V _DC, no image defect occurred and a good image was obtained. (Comparative Example 1) [Adjustment of compound for elastic layer (material for resistance control layer)] E
PDM 100 parts by weight, zinc oxide 5 parts by weight, higher fatty acid 1 part by weight, conductive carbon black 5 parts by weight, paraffin oil 10 parts by weight, sulfur 2 parts by weight, vulcanization accelerator MBT 1 part by weight, vulcanization accelerator TMTD 1 part by weight and 1.5 parts by weight of vulcanization accelerator ZnMDC were mixed for 20 minutes while cooling with a two-roll mill to prepare a compound. [Preparation of coating material for coating layer] Same as in Example 1.

First, the elastic layer compound was heated and vulcanized at 150 ° C. for 15 minutes on a stainless steel core having a diameter of 10 mm to obtain a rubber roller having an elastic layer having a thickness of 3 mm.
When the resistance of the rubber roller was measured at three locations in the longitudinal direction,
2.9 × 10 ⁵ , 2.8 × 10 ⁴ , 1.8 × 1 respectively
It was 0 ⁵ Ω. The compound for elastic layer, which is a material for the resistance control layer, was sheet-molded and the volume resistivity was measured to be 9.6 × 10 ⁵ Ω · cm.

Next, the above coating composition (nylon coating composition) was similarly applied by dip coating onto the charging roller and dried by heating at 120 ° C. for 1 hour to obtain a charging roller having a coating layer with a thickness of 3 μm. When the resistance of the charging roller was measured at three locations in the longitudinal direction, it was 3.0 × 10 ⁵ , 2.9 ×, respectively.
It was 10 ⁴ , 1.85 × 10 ⁵ Ω.

An analog copying machine (NP2
When it was attached to the position of the primary charger of 020 Canon Inc. and image formation was carried out under a bias condition of -1500V _DC , density unevenness in the roller cycle and light density at both ends of the image occurred in a solid black image.

It has been found that when a rubber material using only a conductive filler is used for the resistance control layer, image defects are likely to occur due to the nonuniform resistance. <Example 2> [Preparation of compound for elastic layer] 100 parts by weight of EPDM, 5 parts by weight of zinc oxide, 1 part by weight of higher fatty acid, 10 parts by weight of conductive carbon black, paraffin oil
10 parts by weight, sulfur 2 parts by weight, vulcanization accelerator MBT 1 part by weight, vulcanization accelerator TMTD 1 part by weight, vulcanization accelerator Zn
While cooling 1.5 parts by weight of MDC with 2 rolls, 2
Mix for 0 minutes to make a compound. [Preparation of coating material for coating layer (material for resistance control layer)] 100 parts by weight of methylolated nylon, conductive carbon black
3 parts by weight, magnesium oxide 5 parts by weight, methanol
420 parts by weight and 150 parts by weight of toluene were kneaded using a small bead mill to prepare a nylon paint. [Preparation and Evaluation of Charging Roller] First, the above-mentioned compound for elastic layer was formed on a stainless steel core having a diameter of 10 mm at 150 ° C.
It was heated and vulcanized for 5 minutes to obtain a rubber roller having an elastic layer with a thickness of 3 mm. When the resistance of the rubber roller was measured,
It was 5.0 × 10 ² Ω.

Next, the above coating material (nylon coating material) was similarly applied by dip coating on this charging roller, and dried by heating at 120 ° C. for 1 hour to obtain a charging roller having a coating layer with a thickness of 20 μm. When the resistance of the charging roller was measured at three locations in the longitudinal direction, they were 1.5 × 10 ⁶ and 1.4, respectively.
The values were × 10 ⁶ and 1.45 × 10 ⁶ Ω. The surface layer coating material, which is the material for the resistance control layer, was applied onto an aluminum sheet and the volume resistivity of the dried film was measured to be 5.6 ×
It was 10 ⁸ Ω · cm.

An analog copying machine (NP2
020 Canon Inc.) was attached to the position of the primary charger, and image formation was performed under a bias condition of -1500 _VDC , and a good image was obtained. (Comparative Example 2) [Adjustment of compound for elastic layer] Same as in Example 2 [Adjustment of coating material for coating layer (material for resistance control layer)] 100 parts by weight of methylolated nylon, conductive carbon black
1.5 parts by weight, methanol 420 parts by weight, toluene
Nylon paint was prepared by kneading 150 parts by weight using a small bead mill. [Preparation and Evaluation of Charging Roller] First, the above-mentioned compound for elastic layer was formed on a stainless steel core having a diameter of 10 mm at 150 ° C.
It was heated and vulcanized for 5 minutes to obtain a rubber roller having an elastic layer with a thickness of 3 mm. When the resistance of the rubber roller was measured at three locations in the longitudinal direction, it was 5.0 × 10 ² Ω. Then, the above coating material (nylon coating material) was similarly applied onto this charging roller by dip coating, and dried by heating at 120 ° C. for 1 hour to obtain a charging roller having a coating layer with a thickness of 20 μm.
When the resistance of the charging roller was measured at three locations in the longitudinal direction,
1.05 × 10 ⁶ , 8.25 × 10 ⁶ , 3.3
It was 0 × 10 ⁶ Ω. The surface layer coating material, which is a material for the resistance control layer, was applied onto an aluminum sheet and the volume resistivity of the dried film was measured and found to be 4.3 × 10 ⁸ Ω · cm.

An analog copying machine (NP2
When it was attached to the position of the primary charger of 020 Canon Inc. and image formation was carried out under a bias condition of -1500V _DC , a partially thin density was observed in the solid black image at the roller cycle.

It has been found that when a material using only a conductive filler is used as the resistance control layer, the resistance unevenness in the layer is large and a charging failure is likely to occur. <Example 3> [Adjustment of compound for elastic layer] The same as Example 2. [Preparation of paint for intermediate layer (material for resistance control layer)] 100 parts by weight of hydrin rubber, 2 parts by weight of ethylenethiourea, 5 parts by weight of lead oxide, 2.5 parts by weight of fatty acid metal salt, 80 parts by weight of conductive titanium oxide, magnesium oxide 20 parts by weight are kneaded for 20 minutes while cooling with an open roll,
A compound was made. This compound was diluted with toluene and dissolved to prepare a hydrin rubber paint having a solid content of 5%. [Preparation of coating material for coating layer] Same as in Example 1. [Preparation and Evaluation of Charging Roller] First, the above-mentioned compound for elastic layer was formed on a stainless steel core having a diameter of 10 mm at 150 ° C.
It was heated and vulcanized for 5 minutes to obtain a rubber roller having an elastic layer with a thickness of 3 mm. When the resistance of the rubber roller was measured, 6.
It was 0 × 10 ³ Ω. Next, the intermediate layer coating material (hydrin rubber coating material) was dip-coated on this roller and dried by heating at 160 ° C. for 1 hour to obtain a charging roller having an intermediate layer having a thickness of 105 μm. When the resistance of the charging roller was measured at three locations in the longitudinal direction, each was 1.25 × 10.
^The values were ⁶ , 1.3 × 10 ⁶ and 1.3 × 10 ⁶ Ω. The coating material for the intermediate layer, which is a material for the resistance control layer, was applied onto an aluminum sheet, and the volume resistivity of the dried film was measured and found to be 4.3 × 10 ⁷ Ω · cm.

Next, the above coating material (nylon coating material) was similarly applied onto this charging roller by dip coating, and dried by heating at 120 ° C. for 1 hour to obtain a charging roller having a coating layer with a thickness of 3 μm. . When the resistance of the charging roller was measured at three locations in the longitudinal direction, they were 1.3 × 10 ⁶ and 1.3, respectively.
It was 5 × 10 ⁶ and 1.35 × 10 ⁶ Ω.

An analog copying machine (NP2
When the image was formed under the bias condition of -1500V _DC by being attached to the position of the primary charger of 020 Canon Inc., good images were obtained without abnormalities such as charging failure. Comparative Example 3 [Adjustment of Elastic Compound] Same as Example 2. [Preparation of paint for intermediate layer (material for resistance control layer)] 100 parts by weight of hydrin rubber, 2 parts by weight of ethylenethiourea, 5 parts by weight of lead oxide, 2.5 parts by weight of fatty acid metal salt, and 60 parts by weight of titanium oxide were used as an open roll. 2 while cooling
The mixture was kneaded for 0 minutes to prepare a compound. This compound was diluted with toluene and dissolved to prepare a hydrin rubber paint having a solid content of 5%. [Preparation of coating material for coating layer] Same as in Example 1. [Preparation and Evaluation of Charging Roller] First, the above-mentioned compound for elastic layer was formed on a stainless steel core having a diameter of 10 mm at 150 ° C.
It was heated and vulcanized for 5 minutes to obtain a rubber roller having an elastic layer with a thickness of 3 mm. When the resistance of the rubber roller was measured, 6.
It was 0 × 10 ³ Ω. Next, the above-mentioned intermediate layer coating material was dip-coated on this roller and dried by heating at 120 ° C. for 1 hour to obtain a charging roller having a resistance control layer with a thickness of 98 μm. When the resistance of the charging roller was measured at three locations in the longitudinal direction, they were 1.00 × 10 ⁶ and 2.05 × 10, respectively.
^{5 was} 1.85 × 10 ⁶ Ω. In addition, when the paint for the intermediate layer, which is a material for the resistance control layer, was applied to an aluminum sheet and the resistance of the dry film was measured, it was 9.3 × 10 ⁷ Ω · cm.
Met.

Next, the above coating material (nylon coating material) was similarly applied by dip coating on this charging roller, and dried by heating at 120 ° C. for 1 hour to obtain a charging roller having a coating thickness of 3 μm. When the resistance of the charging roller was measured at three locations in the longitudinal direction, they were 1.10 × 10 ⁶ and 2.2, respectively.
It was 0 × 10 ⁵ , 1.95 × 10 ⁶ Ω.

An analog copying machine (NP2
When it was attached to the position of the primary charger of 020 Canon Inc. and image formation was carried out under a bias condition of -1500V _DC , a partially thin density was observed in the solid black image at the roller cycle.

It has been found that when a material using only a conductive filler is used as the resistance control layer, there is uneven resistance in the layer, which is likely to cause poor charging. (Example 4) [Adjustment of compound for elastic layer] The same as Example 2. [Preparation of intermediate layer paint (resistance control layer material)] 100 parts by weight of hydrin rubber, 2 parts by weight of ethylenethiourea, 5 parts by weight of lead oxide, 2.5 parts by weight of fatty acid metal salt, 80 parts by weight of conductive titanium oxide, 20 of magnesium oxide A part was mixed for 20 minutes while cooling with an open roll to prepare a compound. This compound was diluted with toluene and dissolved to prepare a hydrin rubber paint having a solid content of 5%. [Preparation of coating material for coating layer (resistance control layer material)] The same as Example 2. [Preparation and Evaluation of Charging Roller] First, the above-mentioned compound for elastic layer was formed on a stainless steel core having a diameter of 10 mm at 150 ° C.
It was heated and vulcanized for 5 minutes to obtain a rubber roller having an elastic layer with a thickness of 3 mm. When the resistance of the rubber roller was measured, 6.
It was 0 × 10 ² Ω. Next, the intermediate layer coating material (hydrin rubber coating material) was dip-coated on this roller and dried by heating at 160 ° C. for 1 hour to obtain a charging roller having an intermediate layer having a thickness of 105 μm. When the resistance of the charging roller was measured at three locations in the longitudinal direction, it was 1.30 × 10 each.
⁶ , 1.35 × 10 ⁶ , and 1.35 × 10 ⁶ Ω.
When the coating material for the intermediate layer, which is a material for the resistance control layer, was applied onto an aluminum sheet and the resistance of the dried film was measured, it was 5.3 × 10 ⁷ Ω · cm.

Next, the above coating material (nylon coating material) was similarly applied by dip coating on the charging roller and dried by heating at 120 ° C. for 1 hour to obtain a charging roller having a coating layer with a thickness of 20 μm. When the resistance of the charging roller was measured at three locations in the longitudinal direction, 2.70 × 10 ⁶ and 2.
It was 80 × 10 ⁶ and 2.75 × 10 ⁶ Ω. Also, the surface layer coating material, which is a material for the resistance control layer, was applied onto an aluminum sheet and the volume resistivity of the dried film was measured.
It was 3 × 10 ⁸ Ω · cm.

An analog copying machine (NP2
When the image was formed under the bias condition of -1500V _DC by being attached to the position of the primary charger of 020 Canon Inc., good images were obtained without abnormalities such as charging failure. <Embodiment 5> The charging roller manufactured in Embodiment 1 was attached to the position of the primary charger of an analog copying machine (NP2020 Canon Inc.), and a bias of DC voltage -700V _DC and AC voltage 1.5kV _PP 1.2kHz was applied. When images were formed under the conditions, no image defects occurred and good images were obtained.

[0041]

As described above, according to the present invention,
Since the resistance control layer of the charging member contains at least a conductive filler and an insulating filler, by appropriately adjusting the content of these, it is possible to finely adjust the resistance value, and also the resistance value Uniformity is improved. As a result, it is possible to effectively eliminate image defects caused by uneven resistance values of the charging member.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing the configuration of a charging roller according to the present invention.

FIG. 2 is a vertical sectional view showing the configuration of another charging roller of the same.

FIG. 3 is a longitudinal sectional view showing the structure of still another charging roller.

FIG. 4 is a vertical cross-sectional view schematically showing the configuration of an image forming apparatus equipped with a charging roller.

FIG. 5 is a diagram showing a change in resistance of the charging roller when only a conductive filler is added.

FIG. 6 is a diagram showing a change in resistance of a charging roller when a conductive filler and an insulating filler are used together.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Charged object (photoreceptor) 1a Substrate 1b Photosensitive layer 2 Charging member (charging roller) 2a Core metal 2b Elastic layer 2c Intermediate layer 2d Covering layer 3 Power supply 5 Exposure 6 Developer 7 Transfer device 9 Cleaner P Transfer material

Claims (4)

[Claims] 1. A charging member that contacts an object to be charged and uniformly charges the object to be charged by applying a charging voltage, wherein the charging member contains at least a conductive filler and an insulating filler. A charging member comprising a resistance control layer, wherein the resistance control layer adjusts the resistance value by changing the contents of the conductive filler and the insulating filler. 2. The volume specific resistance value of the resistance control layer is:
The charging member according to claim 1, wherein the charging member is 1.0 × 10 ³ Ω · cm or more and 1.0 × 10 ⁹ Ω · cm or less. 3. The powder resistance of the conductive filler is 1.0.
× 10 ⁶ Ω · cm is more than, the powder resistance of the insulating filler is 1.0 × 10 ¹² Ω · cm or more, the charging member according to claim 2, wherein a. 4. The charging member according to claim 1, wherein the insulating filler is a metal oxide.