JP2002049219A - Electrostatic charging member and electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic member, capable of obtaining stable and satisfactory uniformly charging property and output image quality, and to pro vide electrophotographic device using the same. SOLUTION: This electrostatic charging member is charged by bringing into contact with a body to be charged and applying voltage thereon; the charging member is provided with at least a support member and the conductive coating member; and the conductive coating member is a seamless tube incorporating carbon black at least more than one kind, that lies respectively in the maximum area, the intermediate area, and the minimum area whose conductivity index of carbon black lies respectively in the range of 10 to 500 (preferably 12 to 480). Moreover, the same is used also for the electrophotographic device.

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 apparatus and an electrophotographic apparatus.

[0002]

2. Description of the Related Art An electrophotographic apparatus such as an electronic copying machine and an electrostatic recording apparatus includes a step of uniformly charging an object to be charged.
As a charging method, a corona charging method is generally used. However, the corona charging method often generates products such as ozone, and requires additional means and a mechanism to cope with the problem. There is a problem that it is easy to increase the size and cost.

Therefore, recently, a contact charging method has been studied as a new charging method replacing the corona charging method, and some of them have been put to practical use.

In the contact charging method, a charging member to which a voltage is applied is brought into contact with a charged body with a predetermined pressing force to charge the charged body. Since the generation of ozone is greatly reduced as compared with the corona charging method, there is an advantage that the corona charging method does not require any additional means and mechanism. As the applied voltage, a voltage obtained by superimposing a DC voltage or an AC voltage is used.

The charging member is usually provided with a conductive support, a conductive elastic layer formed of a rubber or a foam formed around the conductive support, and further thereon, for example, an improvement in abrasion resistance and an improvement in photoreceptor contamination resistance. Depending on the purpose, etc., a structure provided with one or more conductive coating layers is often used.

Means for providing a conductive coating layer include:
(1) a method of thinly coating a paint provided with conductivity by dipping, spraying, or the like; (2) coating a tube formed into a tube with conductivity, or
There is a method of extrusion molding directly on the elastic layer.

When the means for providing the conductive coating layer or the like is a coating, (3) the material must be dissolved in a solvent to form a coating, so that there are restrictions on the materials used. (4) Since the manufacturing process is complicated as compared with the tube coating, the manufacturing cost is increased. (5) It is difficult to finish the surface smoothly as compared with tube coating. In particular, when a foam is used for the support, it is easily affected by unevenness on the surface. If the smoothness of the surface is insufficient, the charging becomes non-uniform, which may result in an image defect or an increase in the discharge amount, which may result in increased drum abrasion.

[0008] Therefore, as a solution to the above problems,
A method has been proposed in which a conductive coating member is processed into a tube shape using an extrusion molding machine or an inflation molding machine, and the obtained tube is coated on a conductive support member and a conductive elastic layer to obtain a charged member. . For example, Japanese Patent Application Laid-Open No. 5-09
No. 2466 discloses a multi-layer roller in which a multi-layer tube serving as a resistance layer is coated on a conductive rubber elastic body. According to this, there is an advantage that a multilayer roller can be obtained at a low cost by a simple manufacturing method as compared with the related art.

[0009] Such a charging member coated with a tube needs to have a function of keeping the charged object at a predetermined potential, and therefore, it is important to control the electric resistance of the tube within a certain range.

For controlling the resistance, a conductive pigment such as carbon black is usually used. It is common to use carbon black in terms of cost and the like. Those powder resistance of 10 ^-2 ~10 ⁰ Ω · cm is used for the carbon black.

[0011]

However, the charging device using the charging member has the following problems.

Main constituent materials of a tube as a covering member
Are resins, especially thermoplastic elastomers and pigments. resin
In particular, the volume resistivity of thermoplastic elastomers is at least
Also 10 ^TenΩ · cm. Such high volume resistivity
Imparts conductivity to resins that exhibit high resistance, especially thermoplastic elastomers
Powder resistance to 10^-2-10⁰Ω · cm carb
Disperse black and white. For this reason, microscopically
High and low resistance values in the layer, that is, resistance
There is unevenness. Therefore, having such a constituent layer
In an electrophotographic apparatus using a contact charging member, a member to be charged is
In the case of electric treatment, the potential on the surface of the charged
Is likely to occur, which causes spot-like black spots on the image.
Image failure may occur. Especially in the halftone image area
It is remarkable in the area.

SUMMARY OF THE INVENTION An object of the present invention is to provide a charging member capable of obtaining stable and good uniform charging characteristics and output image quality.

[0014]

That is, the present invention is a charging member for charging by applying a voltage to a member to be charged, the charging member having at least a support member and a conductive coating member. The conductive coating member has a carbon black conductivity index of 10 to 500 (preferably 12 to 48).
A charging member characterized by having a seamless tube containing at least one or more types of carbon black in each of an upper limit region, a middle region and a lower limit region of the range 0). Carbon black has a conductivity index of 200 to 500.
(Preferably 220 to 480) and 40 to 100 (preferably 40 to 80), or 200 to 500
(Preferably 220 to 480) and 10 to 30 (preferably 12 to 28), or 200 to 500 (preferably 220 to 480), 40 to 100 (preferably 40 to 80) and 10 to 30 (preferably Are used in combination.

[0015] The conductivity index of carbon black (see "Filler Utilization Dictionary", Taiseisha, edited by the Filler Study Group) is defined from the specific surface area, DBP oil absorption, and volatile content of carbon black, as shown by equation (1). Is what is done.

Conductivity index = ｛specific surface area (m ² / g) × DB
P oil absorption (ml / 100 g)｝ ^0.5 / {1 + volatile content (%)} Formula (1) As described above, carbon black having a conductivity index in the upper limit region, the middle region and the lower limit region are used in combination. As a result, two or more types of carbon blacks having different conductivity are interconnected, thereby eliminating resistance unevenness in the coated conductive member, stabilizing the resistance characteristic, and achieving uniform charging.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The conductive coating member of the present invention has a thermal conductivity of 10 to 500 (preferably 12 to 480), and contains two or more carbon blacks having different conductivity indices. It is a seamless tube formed of a plastic elastomer.

Carbon black has a conductivity index of 10 to 10.
It is made of two or more types of carbon black having a range of 500 (preferably 12 to 480) and different conductivity indices.

Specifically, a highly conductive carbon black having a carbon black conductivity index in the range of 200 to 500 (preferably 220 to 480);
(Preferably 40 to 80) medium to low conductive carbon black in the range of 10 to 30 (preferably 12 to 28)
In combination with both or one of the low-conductivity carbon blacks.

The present invention relates to an electrophotographic apparatus having a photosensitive member, a latent image forming unit, a unit for developing the formed latent image, and a unit for transferring the developed image to a transfer material, wherein the photosensitive member is used as the latent image forming unit. An electrophotographic apparatus characterized in that the above charging member is used to perform a charging process.

The conductivity index of the carbon black is 2
Examples of the highly conductive carbon black in the range of 00 to 500 include Ketjen Black EC and Ketjen EC60.
0JD (manufactured by Lion Akzo), PRINTEX XE2
(Made by Degussa), Black Pearls-2000 (made by Cabot) and the like.

The conductivity index of carbon black is 40-1.
As the medium conductive carbon black in the range of 00,
Toka Black Series (made by Tokai Carbon), Seast Series (made by Tokai Carbon) and the like.

The conductivity index of carbon black is 10 to 3
Examples of the low conductive carbon black in the range of 0 include Special Black Series (manufactured by Degussa), Black Pearls-1400, Black Pearls-1300, and Black Pearls-1000 (manufactured by Cabot).

The proportion of the carbon black used is, for example, by weight ratio, high conductive carbon black: medium conductive carbon black: low conductive carbon black = 1: 2: 3 to
1: 3: 5. Highly conductive carbon black: medium conductive carbon black = 1: 1 to 1: 5, more preferably 1: 2 to 1: 4. Highly conductive carbon black: lowly conductive carbon black = 1: 1 to 1:11, more preferably 1: 2 to 1:10. The compounding ratio of carbon black is 10 to 3 with respect to the total weight.
0% by weight. If the compounding ratio of the carbon black is more than this, the hardness of the binder resin increases, and it becomes difficult to form a tube. In addition, if it is less than this, conductivity cannot be exhibited or conductivity becomes non-uniform, making charging difficult.

As the binder used for the seamless tube, a resin, especially a thermoplastic elastomer, may be used.

Specific examples include styrene elastomers, olefin elastomers, urethane elastomers, vinyl chloride elastomers, polyester elastomers, polyamide elastomers and the like. Also,
These may be blended.

The additives to be added to the binder include, if necessary, a conductive filler, an antioxidant, a softener,
Examples include a plasticizer, a reinforcing agent, a filler, and the like. As the conductive filler, the above-described carbon black is an essential component, and in addition, graphite and metal oxides may be used. Examples of the metal oxide include titanium oxide and zinc oxide.

Next, a method for manufacturing the conductive coating member of the present invention will be described. The binder resin is kneaded with two or more types of carbon black and necessary additives, and then pelletized. The obtained pellet is made into a seamless tube by an extruder. Further, the seamless tube may be a multilayer seamless tube formed by a multilayer tube extruder. The support member is coated with the formed seamless tube to form a charging member.

The inner diameter of the seamless tube is made larger than the outer diameter of the support to be covered, and the tube is physically and thermally shrunk to fit, for example, by heat, or the inner diameter of the seamless tube is made smaller than the outer diameter of the support to be covered. Means are taken to push or expand the tube by air pressure. As an example, there is JP-A-10-228156.
The upper limit of the thickness of the seamless tube is 1 mm or less, preferably 500 μm or less, and more preferably 300 μm or less. Although the lower limit of the thickness is not particularly defined, for example, considering the manufacturing process and the difficulty of handling, 10 μm or more,
Preferably, the lower limit is 100 μm or more.

The structure, material, or manufacturing method of the support member to be coated used in the present invention will be exemplified.

As the form, an elastic roller, an elastic blade and the like are used. As the material, for example, in the case of a roller, there is disclosed in, for example, Japanese Patent Application Laid-Open No. 1-211799. However, as a conductive substrate, a metal such as iron, copper and stainless steel, a carbon-dispersed resin, a metal-dispersed or A resin or the like is used, and the shape thereof may be a rod shape, a plate shape, or the like. For example, as the configuration of the elastic roller, a conductive base and an elastic layer on which a conductive layer and a resistance layer are provided are used. As the roller elastic layer, chloroprene rubber, isoprene rubber, EPDM rubber, and polyurethane rubber are used. And rubbers such as epoxy rubber and butyl rubber or sponges, and thermoplastic resins such as styrene, butadiene, polyurethane, polyester and ethylene-vinyl acetate.

As a means for developing conductivity, for example, a metal deposited film, a conductive particle-dispersed resin, a conductive resin, and the like are used. Specific examples include a deposited film of aluminum, indium, nickel, copper, iron, and the like. Examples of the conductive particle-dispersed resin include those in which conductive particles such as carbon, aluminum, nickel, and titanium oxide are dispersed in a resin such as urethane, polyester, vinyl acetate-vinyl chloride copolymer, and polymethyl methacrylate. Is mentioned. Examples of the conductive resin include quaternary ammonium salt-containing polymethyl methacrylate, polyvinylaniline, polyvinylpyrrole, polydiacetylene, and polyethyleneimine.
For the resistance layer, a conductive resin, a conductive particle-dispersed insulating resin, or the like can be used. As the conductive resin, resins such as ethyl cellulose, nitrocellulose, methoxymethylated nylon, ethoxymethylated nylon, copolymerized nylon, polyvinyl hydrin, and casein are used. Examples of the conductive particle-dispersed resin include a small amount of conductive particles such as carbon, aluminum, indium oxide and titanium oxide in an insulating resin such as urethane, polyester, vinyl acetate-vinyl chloride copolymer and polymethyl methacrylate. Dispersed materials and the like can be mentioned.

The charging member of the present invention having a support member and a seamless tube as the charging member is excellent in production stability, and can stably produce a medium resistance region which has been conventionally difficult to produce stably.

FIG. 1 is a schematic structural view of an example of an image forming apparatus using the charging member of the present invention.

In FIG. 1, reference numeral 1 denotes a rotating drum type electrophotographic photosensitive member (hereinafter, referred to as a photosensitive drum) as a member to be charged, which is rotationally driven at a predetermined peripheral speed (process speed) in a clockwise direction indicated by an arrow. Is done.

Reference numeral 2 denotes a contact charging member, which in this embodiment is a roller body (hereinafter referred to as a charging roll) which is disposed substantially parallel to the surface of the photosensitive drum 1 and in contact with a predetermined pressing force. The photosensitive drum 1 is driven to rotate.

As shown in FIG. 2, the charging roll 2 of the present embodiment includes a conductive core 2a and an elastic layer 2b of a conductive rubber or the like formed concentrically and integrally with the core by a molding or the like into a roller shape. And a conductive coating member 2d formed on the outer periphery thereof. Further, if necessary, an intermediate layer 2c can be provided between the elastic layer 2b and the conductive covering member 2d. In the charging roll 2 of the present embodiment, two or more types of carbon blacks having different conductivity indices are used for the conductive coating member 2d, which is a layer in contact with the surface of the photosensitive drum 1, which is a member to be charged. Further, two or more types of carbon blacks having different conductivity indices can also be used as the conductive pigment of the intermediate layer 2c.

Reference numeral 3 denotes a power supply for applying a voltage to the charging roll 2. By applying a predetermined voltage from the power supply to the core 2 a of the charging roll 2, the peripheral surface of the rotating photosensitive drum 1 has a predetermined polarity and potential. It is charged by a contact charging method.

The voltage applied to the charging roll 2 may be only a DC voltage. However, in order to uniformly charge the surface of the photosensitive drum 1 as a member to be charged, it is preferable to apply a superimposed voltage (oscillation voltage) of a DC voltage and an AC voltage. Is preferred.

Laser beam scanning exposure (image exposure means) of target image information by a laser scanner (image exposure means) (not shown) is performed on the surface of the photosensitive drum 1 which has been uniformly primary-charged to a predetermined potential from the charging roll 2. 4) The steps of toner development by a developing device (developing means) 5 and transfer of a formed toner image onto a transfer material 7 by a transfer means 6 are sequentially performed, and the transfer material separated from the photosensitive drum 1 by receiving the toner image transfer 7 is introduced into a fixing unit (not shown) and output as an image-formed product (print). After the transfer of the toner image, the surface of the photosensitive drum 1 is cleaned by a cleaning device (cleaning means) 8.
Then, the contaminants adhering to the transfer residual toner are removed, the surface is cleaned, and the image is repeatedly provided.

[0041]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. Although the embodiment has been described using a contact-type charging roll, the present invention is not limited to the embodiment.

[Example 1] (Preparation of elastic body) A vulcanizing agent and a foaming agent were mixed with EPDM rubber in which conductive carbon was dispersed by a Banbury mixer with two rolls, and formed into a tube by extrusion. did. When this tube-shaped molded product was foamed in a vulcanizing can, a sponge tube having a length of 240 mm, an inner diameter of 5 mm, and an outer diameter of 15 mm was obtained.

(Adhesion of core metal and elastic body) A core metal having a length of 240 mm and an outer diameter of 6 mm to which an adhesive was applied was inserted into the inside of the sponge tube, and the core metal and the elastic body were adhered in a heat oven. An elastic layer was formed.

(Adjustment of the shape of the elastic layer)
The sponge elastic layer was adjusted to a length of 220 mm so that both ends of the core remained 10 mm each. The elastic layer with the metal core was polished to obtain an outer diameter of 10.70 mm at the end and an outer diameter of 11.70 at the center.
Finished in a 35 mm crown shape.

(Preparation of Intermediate Layer) A thermoplastic urethane elastomer (Kuramilon U, manufactured by Kuraray) in which conductive carbon was dispersed was formed into a seamless tube having an inner diameter of 10.2 mm and an average thickness of 400 μm by extrusion molding. A seamless tube was obtained.

(Preparation of Conductive Coated Member) The conductivity index of carbon black is 5% by weight of Ketjen Black EC of 358, 10% by weight of Toka Black # 5500 of 78, and 14% by weight of Special Black 4 of 15 Styrene-based thermoplastic elastomer in which is dispersed (Dinalon, J
SR) was formed into a seamless tube having an inner diameter of 10.6 mm and an average wall thickness of 200 μm by extrusion molding to obtain a seamless tube serving as a conductive coating member. The volume resistance of this seamless tube was measured to be 3 × 10 ⁷ Ω
cm.

(Coating of Intermediate Layer and Conductive Coating Member) The inside diameter of the intermediate layer is widened by pressurized air, the elastic layer is inserted inside the elastic layer, the air is shut off, and the elastic layer is coated with the intermediate layer. did. Similarly, the conductive coating member was coated on the intermediate layer.

As described above, a charging member having a three-layer structure was manufactured.

Each of the charging members manufactured as described above was brought into contact with the photosensitive member by applying a pressing force of 500 g to both ends of the cored bar to obtain a contact type charging device.

When this contact-type charging device was incorporated in an electrophotographic device (laser beam printer, laser jet 4000 manufactured by Hewlett-Packard), and the image was evaluated in a high-temperature and high-humidity environment, the image was good over the entire charging area. Further, even when 8,000 sheets of A4 size were continued for image evaluation, a poor image did not occur and a good image was obtained.

Example 2 (Production of Elastic Body) Same as Example 1. (Adhesion of core metal and elastic body) Same as in Example 1. (Adjustment of Shape of Elastic Layer) Same as in Example 1. (Preparation of Intermediate Layer) Same as Example 1. (Production of conductive coating member) The conductivity index of carbon black was 466 Ketjen Black EC600JD.
The same as Example 1 except that 10% by weight of Toka Black # 4500 of 62% by weight and 16% by weight of Black Pearls-1400 of 15 were used. The volume resistance of this seamless tube was measured to be 1 × 10 ⁷ Ωcm.

(Coating of Intermediate Layer and Conductive Coating Member) Same as in Example 1.

As described above, a charging member having a three-layer structure was manufactured.

Each of the charging members manufactured as described above was brought into contact with the photosensitive member by applying a pressing force of 500 g to both ends of the cored bar, thereby obtaining a contact type charging device.

When this contact-type charging device was incorporated in an electrophotographic device (laser beam printer, Laser Jet 4000 manufactured by Hewlett-Packard), and the image was evaluated in a high-temperature and high-humidity environment, the image was good over the entire charging area. Further, even when 8,000 sheets of A4 size were continued for image evaluation, a poor image did not occur and a good image was obtained.

Example 3 (Preparation of Elastic Body) Same as Example 1. (Adhesion of core metal and elastic body) Same as in Example 1. (Adjustment of Shape of Elastic Layer) Same as in Example 1. (Preparation of Intermediate Layer) Same as Example 1.

(Preparation of Conductive Coating Member) The conductivity index of carbon black was the same as that of Example 1 except that Ketjen Black EC of 358 was 7% by weight and Toka Black # 5500 of 78 was 13% by weight. the same. The volume resistance of this seamless tube was measured to be 2 × 10 ⁸ Ωc
m.

(Coating of Intermediate Layer and Conductive Coating Member) As in Example 1.

As described above, a charging member having a three-layer structure was manufactured.

Each of the charging members manufactured as described above was brought into contact with the photosensitive member by applying a pressing force of 500 g to both ends of the cored bar, thereby obtaining a contact type charging device.

This contact-type charging device was incorporated in an electrophotographic device (laser beam printer, laser jet 4000 manufactured by Hewlett-Packard), and image evaluation was performed in a high-temperature, high-humidity environment. As a result, the image was good over the entire charging area. Further, even when 8,000 sheets of A4 size were continued for image evaluation, a poor image did not occur and a good image was obtained.

Example 4 (Preparation of Elastic Body) Same as Example 1. (Adhesion of core metal and elastic body) Same as in Example 1. (Adjustment of Shape of Elastic Layer) Same as in Example 1. (Preparation of Intermediate Layer) Same as Example 1.

(Preparation of Conductive Coated Member) The conductivity index of carbon black was the same as that of Example 1 except that 6% by weight of Ketjen Black EC of 358 and 6% by weight of Talker Black # 4300 were used. the same. When the volume resistance of this seamless tube was measured, it was 2 × 10 ⁹ Ωc.
m.

(Coating of Intermediate Layer and Conductive Coating Member) As in Example 1.

As described above, a charging member having a three-layer structure was manufactured.

Each of the charging members manufactured as described above was brought into contact with the photosensitive member by applying a pressing force of 500 g to both ends of the cored bar, to obtain a contact type charging device.

This contact-type charging device was incorporated in an electrophotographic device (laser beam printer, Laser Jet 4000 manufactured by Hewlett-Packard), and image evaluation was performed in a high-temperature and high-humidity environment. Further, even when 8,000 sheets of A4 size were continued for image evaluation, a poor image did not occur and a good image was obtained.

Example 5 (Preparation of Elastic Body) Same as Example 1. (Adhesion of core metal and elastic body) Same as in Example 1. (Adjustment of Shape of Elastic Layer) Same as in Example 1. (Preparation of Intermediate Layer) Same as Example 1.

(Preparation of Conductive Coating Member) The same as Example 1 except that the conductivity index of carbon black used was 9% by weight of Ketjen Black EC of 358 and 17% by weight of Special Black 4 of 15. . The volume resistance of this seamless tube was measured and found to be 2 × 10 ⁷ Ωcm.

(Coating of Intermediate Layer and Conductive Coating Member) Same as in Example 1.

As described above, a charging member having a three-layer structure was manufactured.

Each of the charging members manufactured as described above was brought into contact with the photosensitive member by applying a pressing force of 500 g to both ends of the metal core, to obtain a contact-type charging device.

This contact-type charging device was incorporated in an electrophotographic device (laser beam printer, laser jet 4000 manufactured by Hewlett-Packard), and the image was evaluated in a high-temperature and high-humidity environment. As a result, the image was good over the entire charging area. Further, even when 8,000 sheets of A4 size were continued for image evaluation, a poor image did not occur and a good image was obtained.

Example 6 (Preparation of Elastic Body) Same as Example 1. (Adhesion of core metal and elastic body) Same as in Example 1. (Adjustment of Shape of Elastic Layer) Same as in Example 1. (Preparation of Intermediate Layer) Same as Example 1.

(Production of Conductive Coating Member)
Black Pearls-200 with a conductivity index of 233
0 to 4% by weight and 25 color black FW2000 to 2
Same as Example 1 except that 6% by weight was used. This sea
When the volume resistance of the mules tube was measured, it was 8 × 10
⁹Ωcm.

(Coating of Intermediate Layer and Conductive Coating Member) Same as in Example 1.

As described above, a charging member having a three-layer structure was manufactured.

Each of the charging members manufactured as described above was brought into contact with the photoreceptor by applying a pressing force of 500 g to both ends of the metal core, to obtain a contact-type charging device.

This contact-type charging device was incorporated in an electrophotographic device (laser beam printer, laser jet 4000 manufactured by Hewlett-Packard), and the image was evaluated in a high-temperature and high-humidity environment. As a result, the image was good over the entire charging area. Further, even when 8,000 sheets of A4 size were continued for image evaluation, a poor image did not occur and a good image was obtained.

Example 7 (Preparation of Elastic Body) Same as Example 1. (Adhesion of core metal and elastic body) Same as in Example 1. (Adjustment of Shape of Elastic Layer) Same as in Example 1.

(Preparation of Multilayer Seamless Tube Consisting of Intermediate Layer and Conductive Coated Member) Using a vertical extruder,
The conductivity index of carbon black is 6% by weight of Ketjen Black EC of 358, and Talker Black # 43 of 40
The thermoplastic urethane elastomer (Kuramilon U, manufactured by Kuraray Co., Ltd.) in which 20 wt.
The styrene-based thermoplastic elastomer (Dynalon, manufactured by JSR) in which the conductivity index of carbon black is 358 Ketjen Black EC dispersed by 6% by weight and 14 Special Black 250 dispersed by 12% by weight is the outside (surface layer). ) To form a two-layer structure with a single crosshead so that the inner diameter is 10.2 mm, the outer diameter is 11.4 mm, and the average thickness is 600 μm (intermediate layer thickness 400 μm, surface layer thickness 200 μm). A seamless tube of layers was obtained. When the volume resistance of this seamless tube was measured, it was 3 ×
It was 10 ⁸ Ωcm.

(Coating of Multi-layer Seamless Tube) The inner diameter of the multi-layer seamless tube was widened by pressurized air, the elastic layer was inserted inside the tube, the air was shut off, and the elastic layer was coated with the multi-layer seamless tube.

As described above, a charging member having a three-layer structure was manufactured.

Each of the charging members manufactured as described above was brought into contact with the photosensitive member by applying a pressing force of 500 g to both ends of the metal core to obtain a contact type charging device.

This contact-type charging device was incorporated in an electrophotographic device (laser beam printer, laser jet 4000 manufactured by Hewlett-Packard), and image evaluation was performed in a high-temperature and high-humidity environment. Further, even when 8,000 sheets of A4 size were continued for image evaluation, a poor image did not occur and a good image was obtained.

Comparative Example 1 (Preparation of Elastic Body) Same as Example 1. (Adhesion of core metal and elastic body) Same as in Example 1. (Adjustment of Shape of Elastic Layer) Same as in Example 1. (Preparation of Intermediate Layer) Same as Example 1.

(Preparation of Conductive Coating Member) The same as in Example 1 except that only 10% by weight of Ketjen Black EC having a carbon black conductivity index of 358 was used. When the volume resistance of this seamless tube was measured, it was 2
× 10 ⁸ Ωcm.

(Coating of Intermediate Layer and Conductive Coating Member) Same as in Example 1.

As described above, a charging member having a three-layer structure was manufactured.

Each of the charging members manufactured as described above was brought into contact with the photoreceptor by applying a pressing force of 500 g to both ends of the metal core to obtain a contact type charging device.

This contact-type charging device was incorporated in an electrophotographic device (laser beam printer, laser jet 4000 manufactured by Hewlett-Packard) and image evaluation was performed in a high-temperature and high-humidity environment. A spot-like black image defect due to unevenness occurred in the halftone image.

Comparative Example 2 (Preparation of Elastic Body) Same as in Example 1. (Adhesion of core metal and elastic body) Same as in Example 1. (Adjustment of Shape of Elastic Layer) Same as in Example 1. (Preparation of Intermediate Layer) Same as Example 1.

(Preparation of Conductive Coating Member) The same as Example 1 except that only 26% by weight of Toka Black # 4500 having a carbon black conductivity index of 62 was used. When the volume resistance of this seamless tube was measured, it was 8
× 10 ⁶ Ωcm.

(Coating of Intermediate Layer and Conductive Coating Member) Same as in Example 1.

As described above, a charging member having a three-layer structure was manufactured.

Each of the charging members manufactured as described above was brought into contact with the photosensitive member by applying a pressing force of 500 g to both ends of the cored bar to obtain a contact type charging device.

This contact-type charging device was incorporated in an electrophotographic device (laser beam printer, laser jet 4000 manufactured by Hewlett-Packard), and image evaluation was performed in a high-temperature and high-humidity environment. A spot-like black image defect due to unevenness occurred in the halftone image. Further, when the image evaluation was continued, black dot image defects did not disappear until 8,000 sheets of A4 size were printed.

Comparative Example 3 (Preparation of Elastic Body) Same as in Example 1. (Adhesion of core metal and elastic body) Same as in Example 1. (Adjustment of Shape of Elastic Layer) Same as in Example 1. (Preparation of Intermediate Layer) Same as Example 1.

(Preparation of Conductive Coating Member) A special index of carbon black having a conductivity index of 15
Same as Example 1 except that only% by weight was used. When the volume resistance of this seamless tube was measured, it was 8 × 1
Was 0 ⁹ Ωcm.

(Coating of Intermediate Layer and Conductive Coating Member) Same as in Example 1.

As described above, a charging member having a three-layer structure was manufactured.

Each of the charging members manufactured as described above was brought into contact with the photoreceptor by applying a pressing force of 500 g to both ends of the metal core, to obtain a contact-type charging device.

This contact-type charging device was incorporated into an electrophotographic device (laser beam printer, laser jet 4000 manufactured by Hewlett-Packard), and image evaluation was performed in a high-temperature and high-humidity environment. A defect has occurred. Further, when the image evaluation was continued, black dot image defects did not disappear until 8,000 sheets of A4 size were printed.

[0104]

As described above, according to the present invention, there is provided a charging member for performing charging by applying a voltage to a member to be charged, the charging member having at least a support member and a conductive coating member. The conductive coating member is a seamless tube containing at least one or more types of carbon black in which the conductivity index of the carbon black is in an upper range, an intermediate range, and a lower range of 10 to 500. The use of the member makes it possible to control the influence of the conductivity and the amount of carbon black added on the tube hardness, thereby ensuring uniform charging characteristics and output image quality, and is effective as a charging member of a contact charging device.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an example of an electrophotographic apparatus using a charging member according to the present invention.

FIG. 2 is a sectional view showing an example of a charging member according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging roll 2a Core metal 2b Elastic layer 2c Intermediate layer 2d Conductive coating member 3 Voltage application power supply 4 Image exposure means 5 Developing means 6 Transfer means 7 Transfer material 8 Cleaning means

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kazuyuki Shishizuka 1888-2 Kusazaki, Kusazaki-cho, Inashiki-gun, Ibaraki F-term in Canon Chemical Co., Ltd. HA60

Claims (10)

[Claims] 1. A charging member having at least a support member and a conductive coating member, wherein the conductive coating member has a carbon black conductivity index of 200 to 500, 40 to 100.
And at least one of 10 to 30 carbon blacks. 2. The charging member has at least a support member and a conductive coating member, and the conductive coating member has a carbon black conductivity index of at least each of 220 to 480, 40 to 80, and 12 to 28. A charging member comprising one type of carbon black. 3. The charging member has at least a support member and a conductive covering member, and the conductive covering member has a carbon black conductivity index of 200 to 500 and 40 to 10
0. A charging member comprising at least one kind of carbon black. 4. The charging member has at least a support member and a conductive coating member, and the conductive coating member has a carbon black conductivity index of 220 to 480 and 12 to 28.
A charging member containing at least one kind of carbon black. 5. The charging member has at least a support member and a conductive coating member, and the conductive coating member has a carbon black conductivity index of 200 to 500 and 10 to 30.
A charging member containing at least one kind of carbon black. 6. The charging member has at least a support member and a conductive covering member, and the conductive covering member has a carbon black conductivity index of 220 to 480 and 12 to 28.
A charging member containing at least one kind of carbon black. 7. The electrification according to claim 1, wherein the content of at least one type of carbon black having a different conductivity index is 10 to 30% by weight in total. Element. 8. The conductive coating member having a volume resistance of 10
The charging member according to claim 1, wherein the charging member has a thickness of ⁶ to 10 ¹¹ Ωcm. 9. The charging member according to claim 1, wherein the conductive covering member is a seamless tube. 10. An electrophotographic apparatus having a photoconductor, a latent image forming unit, a unit for developing a formed latent image, and a unit for transferring a developed image to a transfer material, wherein the photoconductor is charged as the latent image forming unit. 10. Any one of claims 1 to 9 for processing
An electrophotographic apparatus, comprising using the charging member described in the above item.