JPH10161396A - Electrostatic charging member and electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive electrostatic charging member having excellent environmental stability and durability and an electrophotographic device having the same. SOLUTION: The coating layer of the electrostatic charging member having a conductive elastic layer and the coating layer on this conductive elastic layer has single or >=2 layers of tube layers. The change in the weight of the tubes used for the tube layers in contact with the conductive elastic layer after immersing in a softening agent added to the conductive elastic layer and resting is <=and the change in the volumetric resistivity thereof is within two times. The electrophotographic device has the electrostatic charging member described above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member and an electrophotographic apparatus having the same. More specifically, the present invention relates to a charging member that applies a voltage to charge a surface of an object to be charged to a predetermined potential, and an electrophotographic apparatus having the same.

[0002]

2. Description of the Related Art An electrophotographic apparatus includes a step of uniformly charging an object to be charged to a predetermined potential. In recent years, as a charging method, a contact charging device has been proposed (for example,
JP-A-63-167380). This charging method is
Compared with the conventionally used corona charging method, there are advantages that the applied voltage can be reduced, the amount of generated ozone is small, and the device can be downsized.

FIG. 1 shows a configuration example in which a contact charging device using a charging roller is used in an image forming apparatus. A charging roller 2 serving as a charging member is brought into contact with an electrophotographic photoreceptor 1 (hereinafter, referred to as a photoreceptor) 1 as a member to be charged at a constant pressure and is driven to rotate. The surface of the photoconductor is charged.

More specifically, since charging is performed by discharging from a charging member to a member to be charged, charging is started by applying a voltage equal to or higher than a certain threshold. For example, when a charging roller is pressed against an OPC photosensitive member having a thickness of 25 μm, the surface potential of the photosensitive member starts to increase when a voltage of about 650 V or more is applied, and thereafter, A straight line having a slope of 1 with respect to the applied voltage is formed. Hereinafter, this threshold voltage is defined as a charging start voltage Vth. That is, in order to obtain the required surface potential Vd of the photoconductor,
A DC voltage of d + Vth is required. The method of applying only a DC voltage to the charging member and charging the charged body to a predetermined potential in this manner is called a DC charging method. Also,
An AC charging method using a superimposed voltage of a DC voltage and an AC voltage having a peak-to-peak voltage which is about twice the charging start voltage Vth when the DC voltage is applied to the charging member for uniform charging is also a special feature. It is disclosed in, for example, JP-A-63-149669. This is for the purpose of the potential leveling effect of the alternating current, and the potential of the charged body converges to the Vd value at the center of the peak of the alternating voltage.

[0005] The structure of a general charging roller is such that a conductive elastic layer, an intermediate layer and a surface layer are provided on a conductive support. A conductive material such as stainless steel, iron and copper is used for the conductive support, and a conductive pigment such as carbon is used for the conductive elastic layer to secure a sufficient nip width with the member to be charged and to control the resistance. A dispersed rubber material is used. The intermediate layer and the surface layer are obtained by dissolving a conductive pigment dispersed in a resin in an organic solvent, and coating the elastic layer surface with a dipping method or a roll coating method.

[0006] However, when a material made into a paint is formed on the elastic layer by various coating methods, the following problems exist.

Since the material of each layer must be dissolved in an organic solvent to form a coating, the material is limited.

After drying the lower layer (intermediate layer), the surface layer is coated and dried, resulting in poor productivity.

[0009] Since the solubility coefficients are different, the adhesion of each layer is poor, and floating and wrinkles are caused.

In some cases, a primer is used to increase the adhesion, which causes an increase in cost.

[0011] Each layer is likely to have uneven thickness and it is difficult to finish the surface smoothly. Particularly, when a foam is used for the purpose of reducing the charging noise of the elastic layer, it is easily affected by irregularities on the surface of the foam. A smooth surface of the charging member cannot be obtained.

[0012] Therefore, as a solution to the above problem, an intermediate layer and a surface layer are processed into a tube shape using an extrusion molding machine or an inflation molding machine, and the obtained tube is formed on a conductive support member and a conductive elastic layer. A method for obtaining a charging member by coating the surface of a member has been proposed. For example, Japanese Patent Application Laid-Open No. 5-0924
No. 66 discloses a multilayer roller in which a multilayer 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 simpler manufacturing method than in the related art.

[0013]

However, when the above-described structure is used for a charging member, environmental stability and durability are not sufficient unless a layer in contact with the elastic layer is limited in material. May be. This is the case where oil such as process oil or vegetable oil, which is a softening agent mixed in the rubber material constituting the elastic layer, leaks to the surface of the elastic layer and transfers the oil to the tube in contact with the elastic body. In the tube in which the oil has migrated and swollen, the resistance of the tube itself increases, and the resistance of the charging member increases, which may cause image failure (so-called image fog) due to charging failure. In addition, there is also a disadvantage that the tube expands due to a decrease in the tensile strength and the adhesion to the lower elastic layer is reduced. This phenomenon is observed even in a low-temperature and low-humidity environment, but is particularly remarkable in a high-temperature and high-humidity environment.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a charging member which prevents the above-mentioned phenomenon, stably obtains a uniform charge over a long period of time, and which can be manufactured at low cost, and an electrophotographic apparatus having the same. .

[0015]

According to a first aspect of the present invention, there is provided a charging member having a conductive elastic layer and a coating layer on the conductive elastic layer, wherein the coating layer comprises a single layer or two or more tube layers. The weight change rate of a tube used for a tube layer in contact with the conductive elastic layer after being immersed and left in a softener added to the conductive elastic layer is 5% or less,
The charging member is characterized in that the change in volume resistivity is within twice.

According to a second aspect of the present invention, there is provided an electrophotographic apparatus comprising a photosensitive member, an electrostatic latent image forming unit, a unit for developing the formed electrostatic latent image, and a unit for transferring the developed image to a transfer material.
An electrophotographic apparatus comprising the charging member for charging a photosensitive member as the electrostatic latent image forming means.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

The conductive elastic layer constituting the charging member needs to satisfy characteristics such as stabilization of the nip width between the member to be charged, resistance control, and withstand voltage. Vulcanizing agents, vulcanization accelerators, vulcanization accelerators, anti-aging agents,
It has a composition including compounding agents such as antioxidants, antiozonants, fillers, softeners, plasticizers, lubricants, dispersants, and foaming agents.

Above all, the softener imparts plasticity to the rubber to assist in the incorporation and dispersion of the compounding agent, improves workability such as rolling and extrusion, increases the tackiness of the unvulcanized rubber, and facilitates molding.
And it is blended in order to perform reforming such as lowering the hardness of the vulcanized product.

However, when oil such as process oil or vegetable oil as a softener leaks to the surface of the elastic layer and moves to a tube in contact with the elastic layer, the tube swells with the oil, and the resistance of the tube itself increases, In some cases, the charging member has increased resistance and causes image defects (so-called image fog) due to charging failure. In addition, there is also an adverse effect such that the tube expands due to a decrease in the tensile strength and the adhesion to the lower elastic layer is deteriorated. This phenomenon is observed even in a low-temperature and low-humidity environment, but is particularly remarkable in a high-temperature and high-humidity environment.

On the other hand, an amorphous resin such as an acrylic resin or a polycarbonate resin is used on the surface of the photoreceptor which is a member to be charged in contact with the charging member to secure light transmission. When the softener in the layer leaks, the surface of the photoreceptor is contaminated or deteriorated, and image defects such as horizontal stripes at the pitch of the circumference of the photoreceptor may occur.

For this reason, in order to prevent the above-mentioned problem, a material having a small change in characteristics with respect to the softener in the elastic layer is selected for the tube used for the layer in contact with the elastic layer. Suppress resistance rise due to swelling,
In addition, it is necessary to prevent the softener in the elastic layer from migrating to the photoreceptor.

The inventors of the present invention have conducted intensive studies, and as a result, the tube used for the layer in contact with the conductive elastic layer was immersed and left in the softener added to the conductive elastic layer. By specifying the rate of change in weight and the change in volume resistivity, the occurrence of the above-mentioned phenomenon was prevented, and a charging member capable of achieving both environmental stability, durability stability, and non-staining property of the member to be charged was successfully obtained.

That is, the tube used for the layer in contact with the conductive elastic layer has a weight change rate of 5% or less after being immersed and left in the softening agent added to the conductive elastic layer, and The change in resistivity is less than twice.

If the change in the volume resistivity of the tube exceeds twice, the resistance of the charging member is increased. Further, even if the change in volume resistivity is less than 2 times, if the change in weight exceeds 5%, the tube itself expands, so that the adhesion to the lower elastic layer is reduced, and as a result, a high charge as a charging member is obtained. It causes resistance and causes poor charging.

In the present invention, the change in the weight change rate [%] and the change in the volume resistivity with respect to the softener are determined according to JIS-K7114.
It was measured as follows based on the standard.

First, a diameter of 50 ± 1 mm and a thickness of 3 ± 0.2
A test piece prepared in the form of a disk having a diameter of 1 mm is prepared. After removing the stain on the surface of the test piece with an appropriate liquid, the mass and volume resistivity are measured. As for the volume resistivity, a high resta manufactured by Mitsubishi Yuka was used, the sample was sandwiched between electrodes from both sides, a DC voltage of 100 V was applied, and the value of the volume resistivity one minute later was adopted.

The test piece was placed in a glass bottle at 23 ° C. ±
Immerse in the test solution at a temperature of 2 ° C. The container should be large enough to completely immerse the test piece, closed and closed.
Leave sealed for days. After 7 days, remove the test piece from the test solution, immediately rinse with running water or a suitable solution, and wipe off the solution adhering to the surface of the test piece with dry gauze or filter paper. Thereafter, the mass and volume resistivity were measured immediately under the same conditions as before the test, and compared with the results before the test.

The rate of change in weight is calculated as follows:
_{When 1} [mg] and mass after test M ₂ [mg] are calculated from the following formula.

Weight change rate M [%] = ｛(M ₂ −M ₁ )
/ M ₁ ｝ × 100

The coating layer of the charging member in the present invention is composed of a single layer or a tube of two or more layers. As a result of intensive studies, it has been concluded that the following materials are desirable.

The material constituting the coating layer is made of a thermoplastic elastomer, specifically, a polyolefin-based thermoplastic elastomer (TPO), a urethane-based thermoplastic elastomer (TPU), a polystyrene-based thermoplastic elastomer (TPS), or a fluoroelastomer-based. Thermoplastic elastomer, polyester-based thermoplastic elastomer (TPEE), polyamide-based thermoplastic elastomer (TPA), polybutadiene-based thermoplastic elastomer (PB), ethylene-vinyl acetate-based thermoplastic elastomer (EVA), polyvinyl chloride-based thermoplastic elastomer ( PVC) and chlorinated polyethylene-based thermoplastic elastomer (CM). These materials may be used alone or as a mixture of two or more, and may be a copolymer.

These are processed into a tube shape by means such as extrusion molding, injection molding, blow molding and injection molding. When an extruder is used, the inner diameter and the film thickness are adjusted by using a means for winding a continuously formed tube and a means for reducing the sizing or external pressure. In the case of injection molding, a tube-shaped mold is filled with resin in advance, and in the case of blow molding, the outer diameter is defined and the film thickness is controlled by the amount of resin. In the case of the inflation molding, the molded product extruded into a tube shape is mixed with air to expand and molded together with sizing or the like.

The coating layer is formed by dispersing a conductive pigment to form an electric resistor.
Anti 1 × 10^-2~ 1 × 10¹²Semi-conductivity in the range of [Ωcm]
It is preferably adjusted to be electrically conductive. More preferably 1 ×
10 ⁶~ 1 × 10^Ten[Ω · cm].

As the conductive pigment, carbon black, graphite, carbon fiber, metal powder (gold, silver,
Examples thereof include copper, nickel, and aluminum) and metal oxides (tin oxide, titanium oxide, zinc oxide, and magnesium oxide), and any of these may be used. These conductive pigments may be used as a mixture of two or more, but are not particularly limited.

The constituent material of the conductive elastic layer of the present invention is made of a rubber material in order to obtain a necessary nip width with the member to be charged, and the materials used are ethylene propylene rubber (EPDM), nitrile Rubber (NBR), styrene butadiene rubber (SBR), butadiene rubber (B
R), isoprene rubber (IR), chloroprene rubber (C
R), acrylic rubber (ACM), silicone rubber, fluorine rubber and the like.

In particular, if the conductive elastic layer is made of a foam, even if an oscillating electric field (an AC voltage is superimposed on a DC voltage) is applied, the vibration depending on the frequency of the AC voltage causes the foaming. This is more preferable because the vibration absorbed by the body can be prevented from being transmitted to the member to be charged, and high-frequency noise (so-called charging noise) generated during the charging operation can be reduced.

The electric resistance of the conductive elastic layer is 1 × 10 ^3.
It is necessary to have a conductivity of about 1 × 10 ¹⁰ [Ω · cm], and is filled with a conductive pigment such as carbon black or metal oxide to secure the conductivity.

The 10-point average surface roughness (Rz, JIS-B0601) of the charging member surface of the present invention is preferably 7 [μm] or less. More preferably, it is 5 [μm] or less. If it exceeds the above range, the amount of discharge increases and erodes the photoreceptor, which is the member to be charged, so that so-called photoreceptor scraping is promoted and the life of the photoreceptor may be shortened.

The hardness of the charging member of the present invention is JIS-K63.
In the spring-type hardness test specified in No. 01, the hardness measured by an A-type tester is preferably 90 degrees or less. If the hardness exceeds 90 degrees, the chargeability is good, but the developer (toner) is easily fused to the photoreceptor, which may cause an image defect.

FIG. 1 is a block diagram showing an example of an electrophotographic apparatus to which the charging device according to the present invention is applied. In FIG. 1, 2
Denotes a charging roller as a charging member, and the conductive cored bar 2a
And a conductive elastic layer 2b made of conductive rubber or the like formed concentrically and integrally with the core metal by molding or the like, and a surface layer 2d formed on the outer periphery of the conductive elastic layer 2b. Further, if necessary, an intermediate layer 2c can be provided between the elastic layer 2b and the surface layer 2d. Reference numeral 1 denotes a photosensitive member, which is a member to be charged, and is rotated at a predetermined peripheral speed (process speed) in a clockwise direction indicated by an arrow. Both ends of the charging roller 2 are in contact with the photosensitive member with a constant load by a pressing spring, and are driven to rotate by rotation of the photosensitive member.

Reference numeral 3 denotes a power supply for applying voltage to the charging roller. When a predetermined voltage is applied to the core 2a of the charging roller 2 from the power supply, the peripheral surface of the rotating photosensitive member 1 comes into contact with a predetermined polarity and potential. It is charged by a charging method. The voltage applied to the charging roller 2 is either a DC voltage or a superimposed voltage of a DC voltage and an AC voltage. The surface of the photoreceptor 1 which has been uniformly primary-charged to a predetermined potential by the charging roller 2 is subjected to laser inspection 4 of target image information by a laser scanner (image exposure means: not shown), toner development by a developing device 5, The transfer material 7 from the formed toner image transfer unit 6 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 photoreceptor 2 is cleaned by a cleaning device 8 to remove contaminants adhering to the toner remaining after transfer, and is repeatedly used for image formation. [Examples] The present invention will be described below with reference to examples. (Example 1) For 100 parts by weight of EPDM, 40 parts by weight of conductive carbon black, 50 parts by weight of paraffin oil, and an appropriate amount of a foaming agent, a crosslinking agent and other compounding agents were added and kneaded to prepare a conductive compound 1. Next, 6m in diameter
After the compound was vulcanized and molded on a m stainless steel core, the outer diameter was polished to produce an elastic layer 1 as a foam having a thickness of 3 mm.

Next, 14.5 parts by weight of conductive carbon black was blended with 10 parts by weight of an ether-based thermoplastic urethane elastomer (JIS-A hardness: 85) and melt-kneaded at 180 ° C. for 10 minutes using a pressure kneader. . After further cooling, the mixture was pulverized by a pulverizer and then pelletized by using a single screw extruder.

Using an extruder, the pellets are processed to an inner diameter of 1
A seamless tube having a thickness of 0.5 [mm] and a thickness of 250 [μm] was obtained. This tube is hereinafter referred to as tube A.

Further, using the same pellets, a disk-shaped sheet having a diameter of 5 mm and a thickness of 3 mm was prepared by hot pressing.
The elastic layer 1 was immersed in paraffin oil as a softener for 7 days. When the weight change rate and the volume resistivity before and after standing on this sheet were measured, the weight change rate was 0.03%.
The volume resistivity is 1.9 × 10 ⁶ Ωcm before standing,
After standing, there was almost no change of 2.0 × 10 ⁶ Ωcm.

Separately, a thermoplastic elastomer (J) in which a polystyrene molecular chain is bound to one end of an ethylene butylene rubber molecular chain and an olefin crystal is bound to the other end by a covalent bond.
IS-A hardness: 76) 14 parts by weight of 100 parts by weight of conductive carbon black were blended, and 20 parts were mixed using a pressure kneader.
The mixture was melt-kneaded at 0 ° C. for 10 minutes. After further cooling, the mixture was pulverized by a pulverizer and then pelletized by using a single screw extruder. The pellets were further extruded using an extruder to an inner diameter of 11.0.
[Mm] and a seamless tube having a thickness of 250 [μm] were obtained. This tube is hereinafter referred to as tube B.

Subsequently, after the air is blown into the tube A to expand the outer diameter, the elastic layer 1 is inserted to cover the tube, and then the tube B is coated on the outside in the same manner to obtain the charging roller 1. Was.

The characteristics of the obtained charging roller 1 were as follows.

Electric resistance value: low temperature and low humidity environment (temperature 15 ° C., humidity 10%, hereinafter L / L environment)
1.2MΩ High temperature and high humidity environment (Temperature 32.5 ° C, Humidity 80%, below H / H environment) 1.0MΩ Surface hardness: 76 degrees (JIS-A) Surface roughness: 4.8 μm (10-point average surface roughness Rz) )

The electric resistance value is 10
mm aluminum foil is wound in close contact with it and a DC voltage of 250 V is applied between the cored bar and the aluminum foil, and a resistance meter HIO is used.
KI3119 DIGITAL MΩ HITESTE
It is a value measured using R (manufactured by Hioki Electric).

The surface roughness (10-point average surface roughness Rz) is as follows:
This is an average value obtained by measuring three arbitrary points using a surf coder SE3400 manufactured by Kosaka Laboratory Co., Ltd.

The surface hardness (JIS-A) is JIS-K6
It is a value measured by a spring type hardness tester A type according to the method specified in 301.

The charging roller 1 thus obtained
To a laser beam printer (Laser Jet)
4plus, manufactured by Hewlett-Packard Co., Ltd.), attached to the primary charger position of the cartridge, and superimposed and applied with a DC voltage of -670 V, an AC peak-to-peak voltage of 2000 V, and a frequency of 650 Hz. A durability test of 10,000 sheets was performed under the environment.

As a result, under each environment, a good image was obtained with little image change at the initial stage and after the endurance. The electric resistance value of the charging roller after endurance is 1.6 MΩ in an L / L environment, and H / H
It was 1.4 MΩ in the environment.

The charging sound was measured using a sound level meter in a simple non-room (with a sound pressure level of 35 dB or less) by superimposing and applying a DC voltage of -670 V, an AC peak-to-peak voltage of 2000 V and a frequency of 1000 Hz. , 52dB and very quiet.

(Example 2) 20 parts by weight of conductive carbon black, 30 parts by weight of dimethyl silicone oil, an appropriate amount of a foaming agent, a crosslinking agent and other compounding agents were added to 100 parts by weight of silicone rubber. An elastic layer 2 was produced in the same manner as in Example 1.

The tubes A and B were the same as in Example 1, and the immersion test of the elastic layer 2 in dimethyl silicone oil as a softening agent was carried out using the same pellets as the tubes A. The weight change rate before and after standing was 0.02%, the volume resistivity was 1.9 × 10 ⁶ Ωcm before standing, and 1.
There was almost no change at 95 × 10 ⁶ Ωcm.

Subsequently, after the air is blown into the tube A to expand the outer diameter, the elastic layer 2 is inserted to cover the tube, and then the tube B is coated on the outside in the same manner to obtain the charging roller 2. Was.

The characteristics of the obtained charging roller 2 were measured in the same manner as in Example 1, and the results were as follows.

Electric resistance value: L / L environment: 1.1 MΩ H / H environment: 1.0 MΩ Surface hardness: 78 degrees (JIS-A) Surface roughness: 5.1 μm (10-point average surface roughness Rz)

The charging roller 2 thus obtained
Was evaluated in the same manner as in Example 1. As a result, under each environment, a good image was obtained with little image change at the initial stage and after the endurance. The electric resistance value of the charging roller after endurance is L /
The value was 1.5 MΩ in the L environment and 1.4 MΩ in the H / H environment.

The charging noise was very quiet at 50 dB or less.

Example 3 Styrene butadiene rubber (S
BR) 20 parts by weight of conductive carbon black, 20 parts by weight of naphthenic oil, a foaming agent, a cross-linking agent and other compounding agents were added in appropriate amounts to 100 parts by weight of rubber to form an elastic layer 3 as a foam. It was prepared in the same manner as described above.

The tube A and the tube B were the same as those in Example 1, and the immersion test of the elastic layer 3 in naphthenic oil, which is a softening agent, was carried out on a sample made of the same pellets as the tube A. As a result, the change in weight was 0.04% before and after standing, and the volume resistivity was 1.9 × 10 ⁶ Ωcm before leaving, and 2.05 × 1 after leaving.
Most changes 0 ⁶ Ωcm was not.

Subsequently, after the air is blown into the tube A to expand the outer diameter, the elastic layer 3 is inserted to cover the tube, and then the tube B is coated on the outside in the same manner to obtain the charging roller 3. Was.

The characteristics of the obtained charging roller 3 were measured in the same manner as in Example 1, and the results were as follows.

Electric resistance value: L / L environment 1.2 MΩ H / H environment 0.9 MΩ Surface hardness: 81 degrees (JIS-A) Surface roughness: 4.7 μm (10-point average surface roughness Rz)

The charging roller 3 thus obtained
Was evaluated in the same manner as in Example 1. As a result, under each environment, a good image was obtained with little image change at the initial stage and after the endurance. The electric resistance value of the charging roller after endurance is L /
It was 1.7 MΩ in the L environment and 1.5 MΩ in the H / H environment.

The charging noise was also very quiet at 52 dB.

(Example 4) The tube A shown in Example 1
Of the tube A 'by changing the inner diameter of the tube from 10.5 mm to 11 mm, the weight of carbon from 14.5 parts by weight to 13.0 parts by weight, and the inner diameter of the tube B to 11.0 mm
From 14.0 parts by weight to 15.0 parts by weight, and the tube B '
And the elastic layer 2 shown in Example 2 is used.

Next, a immersion test in dimethyl silicone oil as a softening agent for the elastic layer 2 was performed on a sample formed into a sheet with the same pellet as the tube B. Was 1.4% before and after standing, and the volume resistivity was 3.3 × 10 ⁶ Ωcm before standing and 4.25 × 10 ⁶ Ωcm after standing, which was almost unchanged.

Subsequently, air is blown into the tube B 'to expand the outer diameter, and the elastic layer 2 is inserted to cover the tube. After that, the tube A' is coated on the outside in the same manner, and the charging roller 4 is moved. Obtained.

The characteristics of the obtained charging roller 4 were measured in the same manner as in Example 1, and the results were as follows.

Electric resistance value: L / L environment 1.2 MΩ H / H environment 0.9 MΩ Surface hardness: 86 degrees (JIS-A) Surface roughness: 6.1 μm (10-point average surface roughness Rz)

The charging roller 4 thus obtained
Was evaluated in the same manner as in Example 1. As a result, under each environment, a good image was obtained with little image change at the initial stage and after the endurance. The electric resistance value of the charging roller after endurance is L /
It was 1.8 MΩ in the L environment and 2.2 MΩ in the H / H environment.

The charging noise was very quiet, less than 50 dB.

Example 5 Olefinic thermoplastic elastomer (soft segment EPDM rubber dynamic vulcanization system,
JIS-A hardness: 73) 14.0 parts by weight of conductive carbon black was blended with 10 parts by weight and melt-kneaded at 180 ° C. for 10 minutes using a pressure kneader. After further cooling, the mixture was pulverized by a pulverizer and then pelletized by using a single screw extruder.

Using an extruder, the pellets are adjusted to an inner diameter of 1
A seamless tube having a thickness of 0.5 [mm] and a thickness of 250 [μm] was obtained. This tube is hereinafter referred to as tube C.

Next, a disc-shaped sheet having a diameter of 5 mm and a thickness of 3 mm was prepared by hot pressing using the same pellets prepared as the tube C, and immersed in paraffin oil as a softener for the elastic layer 1 for 7 days. did. When the weight change rate and the volume resistivity before and after standing on this sheet were measured, the weight change rate was 4.2%, and the volume resistivity before the standing was 2.
It was 6 × 10 ⁶ Ωcm, and after standing, it was 4.4 × 10 ⁶ Ωcm.

Using the tube C thus obtained, the tube B shown in Example 1, and the elastic layer 1, a charging roller is manufactured. First, the charging roller 5 was obtained by blowing air into the tube C to expand the outer diameter, inserting the elastic layer 1 to cover the tube, and coating the tube B on the outside in the same manner.

The characteristics of the obtained charging roller 5 were measured in the same manner as in Example 1, and the results were as follows.

Electric resistance value: L / L environment 1.1 MΩ H / H environment 0.9 MΩ Surface hardness: 71 degrees (JIS-A) Surface roughness: 6.3 μm (10-point average surface roughness Rz)

The charging roller 5 thus obtained
Was evaluated in the same manner as in Example 1. As a result, under each environment, a good image was obtained with little image change at the initial stage and after the endurance. The electric resistance value of the charging roller after endurance is L /
The value was 1.8 MΩ in the L environment and 2.6 MΩ in the H / H environment.

The charging noise was very quiet at 50 dB or less.

(Comparative Example 1) The elastic layer 1 shown in Example 1
A charging roller is manufactured using the tubes A 'and B' shown in the fourth embodiment. First, the air was blown into the tube B 'to expand the outer diameter, and the elastic layer 1 was inserted to cover the tube. Then, the outside of the tube A' was coated in the same manner to obtain the charging roller 6. The electric resistance value of the charging roller 6 was 1.2 MΩ in an L / L environment and 1.2 MΩ in an H / H environment.

Next, a disc-shaped sheet having a diameter of 5 mm and a thickness of 3 mm was prepared by hot pressing using the same pellets from which the tube B 'was prepared, and immersed in paraffin oil as a softener for the elastic layer 7 for 7 days. I left it. When the weight change rate and volume resistivity before and after standing on this sheet were measured,
The weight change rate is 6.6%, and the volume resistivity is 1.6 × 10 ⁶ Ωcm before standing, and 8.2 × 10 ⁶ Ωcm after standing.
Met.

The thus obtained charging roller 6
Was evaluated in the same manner as in Example 1. As a result, in an H / H environment, poor charging (so-called image fogging) due to the high resistance of the charging member occurred in the image after the end of the durability. When the electric resistance value of the charging roller after the endurance was measured, it was 7.2 MΩ in the L / L environment and 52 MΩ in the H / H environment.
The resistance had risen to Ω.

(Comparative Example 2) Olefinic thermoplastic elastomer (general simple blend type, JIS-A hardness: 6)
9) 14.0 parts by weight of conductive carbon black was blended with 10 parts by weight and melt-kneaded at 180 ° C. for 10 minutes using a pressure kneader. After further cooling, the mixture was pulverized by a pulverizer and then pelletized by using a single screw extruder.

The pellets having an inner diameter of 1 were extruded using an extruder.
A seamless tube having a thickness of 0.5 [mm] and a thickness of 250 [μm] was obtained. This tube is hereinafter referred to as tube D.

Using the tube D thus obtained, the tube B shown in Example 1, and the elastic layer 1, a charging roller is manufactured. First, the charging roller 7 was obtained by blowing air into the tube D to expand the outer diameter, inserting the elastic layer 1 to cover the tube, and coating the tube B on the outside in the same manner. The electric resistance value of the charging roller 7 was 1.2 MΩ in the L / L environment and 1.1 MΩ in the H / H environment.

Next, a disc-shaped sheet having a diameter of 5 mm and a thickness of 3 mm was prepared by hot pressing using the same pellets prepared as the tube D, and immersed in paraffin oil as a softener of the elastic layer 1 for 7 days. did. When the weight change rate and the volume resistivity before and after standing on this sheet were measured, the weight change rate was 4.8%, and the volume resistivity was 1.
It was 9 × 10 ⁶ Ωcm, and 7.7 × 10 ⁶ Ωcm after standing.

The charging roller 7 thus obtained
Was evaluated in the same manner as in Example 1. As a result, in an H / H environment, poor charging (so-called image fogging) due to the high resistance of the charging member occurred in the image after the end of the durability.

When the electric resistance value of the charging roller after the endurance was measured, it was 6.6 MΩ in an L / L environment and 28 MΩ in an H / H environment.
The resistance had risen to MΩ.

Table 1 shows the results of the above image evaluation.

[0095]

[Table 1]

[0096]

As described above, the present invention relates to a charging member having a conductive elastic layer and a coating layer on the conductive elastic layer, wherein the coating layer has a single layer or two or more tube layers. The rate of weight change of the tube used for the tube layer in contact with the conductive elastic layer after being immersed and left in the softener added to the conductive elastic layer is 5% or less, and the change in volume resistivity is not more than 5%. A charging member characterized by being within two times, and an electrophotographic apparatus having the same. By using this charging member, it is possible to obtain an effect that the object to be charged can be charged uniformly over a long period of time with excellent environmental stability.

[Brief description of the drawings]

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging roller 2a Core metal 2b Elastic layer 2c Intermediate layer 2d Surface layer 3 Voltage application power supply 4 Image exposure means 5 Developing means 6 Transfer means 7 Transfer material 8 Cleaning device

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Seiji Tsuru 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroyoshi Suzuki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Naoki Fuui 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc.

Claims (7)

[Claims] 1. A charging member having a conductive elastic layer and a coating layer on the conductive elastic layer, wherein the coating layer has a single layer or two or more tube layers, and a tube in contact with the conductive elastic layer. The tube used for the layer has a weight change rate of 5% or less after being immersed and left in a softening agent added to the conductive elastic layer, and a change in volume resistivity is within 2 times. Charging member. 2. The charging member according to claim 1, wherein said conductive elastic layer is a foam. 3. The charging member according to claim 1, wherein the tube is a seamless tube. 4. The charging member according to claim 1, wherein the tube is a seamless tube containing a thermoplastic elastomer. 5. The charging member according to claim 1, wherein the surface of the charging member has a 10-point average surface roughness (Rz) of 7 μm or less. 6. The charging member according to claim 1, wherein a surface hardness of the charging member is 90 degrees or less. 7. An electrophotographic apparatus comprising an electrophotographic photosensitive member, an electrostatic latent image forming unit, a unit for developing the formed electrostatic latent image, and a unit for transferring the developed image to a transfer material. 2. The method according to claim 1, wherein the photosensitive member is charged.
An electrophotographic apparatus, comprising the charging member according to any one of claims 6 to 6.