JP2002169355A - Electrifying roll and electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrifying roll and an electrophotographic device using the same where an image defect is not caused by the fusion of toner. SOLUTION: This electrifying roll coming into contact with a body to be electrified and electrifying it by the application of voltage is formed so that the component value of the surface free energy of the surface layer of the electrifying roll may be γsd<30 mN/m and γsp<20 mN/m and the ten-point average roughness of the surface may be <=2.0 μm. Fluororesin is added to thermoplastic elastomer in order to adjust the surface free energy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a charging roll and an electrophotographic apparatus using the same.

[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 processing method, but in general corona charging method is used, the corona charging method is more likely to occur in the product such as ozone, and requires the additional means for coping, a mechanism, therefore device 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 needs to have a function of keeping the member to be charged at a predetermined potential. Therefore, it is important to control the electrical resistance of the member within a certain range. Usually, a conductive filler such as carbon black or tin oxide is used for the resistance control. Powder resistance of carbon black is 10 ^-2 or more
Of 10 ⁰ [Omega] cm things, tin oxide, those powder resistance of 10 ¹ to 10 ² [Omega] cm for titanium oxide, are widely used.

[0005]

In the case of a contact charging member which performs charging by contacting a member to be charged, foreign matter easily enters a contact surface with the member to be charged. For example, in an electrophotographic apparatus,
When the contact charging member in the form of a roll is used, the remaining toner, paper dust, and the like are picked up from the photosensitive drum, which is the member to be charged, and the surface of the charging member becomes dirty as the durability increases. In particular, in a severe environment such as high temperature and high humidity, the resistance of the charging member increases due to severe contamination, and the charging potential of the photosensitive drum may decrease.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a charging roll which does not cause an image defect due to toner fusion or the like in an electrophotographic apparatus, and an electrophotographic apparatus using the same.

[0007]

Means for Solving the Problems That is, the present invention is in contact with the member to be charged, in a charging roll which performs charging by applying a voltage, component values of the surface free energy of the surface layer of the charging roll, gamma ^{_{s d <30mN / m, γ}} s p <20mN / m
And the above-mentioned problem is solved by a charging roll having a surface having a ten-point average roughness of 2.0 μm or less.

Further, the present invention includes a photoreceptor, a latent image forming means,
In an electrophotographic apparatus having a means for developing a formed latent image and a means for transferring a developed image to a transfer material, the use of the charging member as the latent image forming means when charging the photosensitive member is excellent. An electrophotographic apparatus is provided.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a voltage applied to a charging member, any of a DC voltage and a voltage obtained by superimposing an AC voltage can be used.

FIGS. 1 and 2 are sectional views of an example of the charging roll of the present invention.

FIG. 3 is a schematic diagram showing an example of an electrophotographic apparatus (copier) using a charging roll according to the present invention. The charging roll includes a metal core (2a) for applying a DC voltage or a superimposed voltage of a DC voltage and an AC voltage, an elastic layer (2b), and a surface layer (coating layer) (2c). An intermediate layer (2d) is provided between 2b) and the surface layer (2c).

The component value of the surface free energy of the surface layer is
Variance components γ _s ^d <30mN / m, a polar component (including hydrogen bonding ^{_{component) γ s p <20mN / m}} , and, if the ten-point average roughness Rz of the surface 2.0μm or less, the durability Since the surface is not stained, fusion does not occur and charging is stable.
Regarding surface free energy, surface free energy analysis software EG issued by Kyowa Interface Science Co., Ltd.
References were made to literature such as -11 type instruction manual.

If γ _s ^d is greater than 30 mN / m, the surface is soiled due to durability, so that the resistance of the charging roll increases and the surface potential of the member to be charged decreases. Particularly in a low humidity environment, the resistance value of the fouling substance increases, and further poor charging occurs.

[0014] gamma _s ^p is larger than 20 mN / m, soiling substances attached to the surface of the charging member is migrated latent image is disturbed member to be charged. Especially in a high humidity environment, the resistance of the fouling substance is low,
The problem of so-called image deletion is likely to occur.

If Rz is greater than 2.0 μm, even if the surface free energy is controlled, the surface is soiled by durability, so that the resistance of the charging roll increases and the surface potential of the member to be charged decreases. In particular, the higher the resistance of the fouling substances in a low-humidity environment, to generate a further charging failure.

As the material of the surface layer of the charging roll of the present invention, for example, thermoplastic elastomers such as styrene, olefin, PVC, urethane, ester and amide can be used. Generally, the thermoplastic elastomer is used in the form of a conductive filler added to control the resistance. Styrene-based thermoplastic elastomers include styrene-ethylene-butylene-olefin copolymer resins, olefin-based thermoplastic elastomers include polyethylene, and amide-based thermoplastic elastomers include polyamide-polyether copolymer resins.

[0017] As fluorine resin to be blended in order to achieve the surface free energy value of the present invention, polytetrafluoroethylene (PTFE), tetrafluoroethylene - perfluoroalkyl vinyl ether copolymer (PFA),
Tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-hexafluoropropylene-perfluoroalkylvinyl ether copolymer (EPE), tetrafluoroethylene-ethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-
Ethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PV
F) and the like.

The addition amount of the fluororesin to the material of the surface layer is preferably from 10 to 50 parts by mass, more preferably from 10 to 50 parts by mass, per 100 parts by mass of the thermoplastic elastomer.
The range is 40 parts by mass. The addition amount is less than 10 parts by weight, gamma _s ^d and gamma _s ^p is not lowered until the desired value, sufficient effect of preventing contamination of toner fusion, etc. soiling or the charged member surface such as toner contamination of the charging member surface Instead, if it exceeds 50 parts by mass,
The surface layer, that is, the surface layer of the charging member becomes brittle and easily broken, or it becomes difficult to form a tube as the surface layer. Specifically, problems such as an increase in the surface roughness of the tube occur, which is not preferable. Further, if the fluorine resin has an extremely high powder resistance value and exceeds 50 parts by mass, it becomes difficult to adjust the resistance of the surface layer to the medium resistance region, and since the surface layer resistance is high, charging failure is likely to occur. Absent.

In FIG. 3, reference numeral 1 denotes a rotating drum type electrophotographic photosensitive member as a member to be charged (hereinafter referred to as a photosensitive drum).
And is driven to rotate at a predetermined peripheral speed (process speed) in the clockwise direction indicated by the arrow. 1a is the photosensitive drum 1
The conductive drum substrate 1b made of aluminum or the like is a photosensitive layer formed on the outer peripheral surface of the drum substrate 1a.

Reference numeral 2 denotes a contact charging roll. This embodiment is a roll (charging roll) which is disposed in parallel with the surface of the photosensitive drum 1 with a predetermined pressing force in a direction substantially parallel to the drum generatrix. The rotation follows the rotation.

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

The surface of the photosensitive drum 1 which has been uniformly primary-charged to a predetermined potential by the charging roll 2 is subjected to laser beam scanning exposure 4 of target image information by a laser scanner (image exposure means) (not shown), and a developing unit 5 The steps of toner development and transfer of the formed toner image to the transfer material 7 by the transfer means 6 are sequentially performed, and the transfer material 7 that has been transferred from the surface of the photosensitive drum 1 after receiving the toner image is introduced into a fixing means (not shown). It is outputted 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 8 to remove contaminants adhering to untransferred toner, and is repeatedly used for image formation.

[0023]

The present invention will be described in more detail with reference to the following examples.

(Example 1) (Molding of surface layer tube) Styrene resin (styrene-ethylene / butylene-olefin copolymer resin, trade name: Dinalon, manufactured by JSR Corporation) 100 as a material for the surface layer
Parts by mass, 20 parts by mass of polyethylene (trade name: Petrocene, manufactured by Tosoh Corporation), 30 parts by mass of carbon black (trade name: Toka Black, manufactured by Tokai Carbon Co., Ltd.), 10 parts by mass of magnesium oxide, 1 part by mass of calcium stearate, and poly 30 parts by mass of tetrafluoroethylene (trade name: Lubron, manufactured by Daikin Industries, Ltd.) was mixed with a V-type blender for several minutes. Next, at 190 ° C. using a pressure kneader,
The mixture was melt-kneaded for 0 minutes. Furthermore, after cooling, pulverize with a pulverizer,
Pelletized with a single screw extruder.

The above pellets were extruded into a tube using an extruder, cooled with water at an appropriate temperature, and taken out. Thus, a surface tube having an outer diameter of about 11 mm and a thickness of 250 μm was obtained.

(Molding of middle layer tube) As a material for the middle layer, 100 parts by mass of a polyurethane resin (trade name: Kuramilon, manufactured by Kuraray Co., Ltd.), 17 parts by mass of carbon black (Ketjen Black EC), 10 parts by mass of magnesium oxide, and calcium stearate One part by mass was pelletized in the same process as the surface layer material.

The above pellets were extruded into a tube using an extruder, cooled with water at an appropriate temperature, and taken out. Thus, a middle-layer tube having an outer diameter of about 11 mm and a thickness of 400 μm was obtained.

(Formation of a foamed elastic body layer)
A vulcanizing agent and a foaming agent were blended into a hose-shaped foamed elastic body (EPDM rubber) having an outer diameter of 11.5 mm, and the mixture was formed into a hose shape by an extruder and foamed in a vulcanizing can. A cored bar (metal layer) having a diameter of 5 mm and a length of 260 mm was inserted into a cut piece having a length of 225 mm.

In addition, the above-mentioned middle-layer tube has a length of 228.
The material cut into mm was coated with a tube coating device, and was pressure-adhered to the foamed elastic material layer.

Next, the above-mentioned surface layer tube is cut into a length of 230 mm on the one coated with the middle layer tube. A member was manufactured. Using a contact angle meter CA-X manufactured by Kyowa Interface Science Co., Ltd., the contact angle was measured by a droplet method using water, methylene iodide, and ethylene glycol as a liquid sample, and based on the extended Fowkes theory, was determined component values of the surface free energy of the charging member surface ^{_{layer, γ s d = 26.8mN / m}} , γ s p =
0.0mN / m. Surface roughness is JIS B06
01 is the ten-point average roughness, and Rz = 1.
It was 80 μm.

This charging member was attached to a primary charger of an LBP (laser beam printer, laser jet 4000 manufactured by Canon Inc.), and intermittent durability was performed in a high-temperature, high-humidity environment. A good image was obtained without performing the test.

Further, after the durability test, an image was output under a low-temperature and low-humidity environment, and the quality of the output image was visually evaluated. As a result, no abnormality was observed. Table 1 shows the results.

Example 2 (Molding of Surface Tube) As a material for the surface layer, 100 parts by mass of an amide resin (polyamide-polyether copolymer resin, trade name: Pebax, manufactured by Toray Industries, Inc.), carbon black (trade name) Toka Black, manufactured by Tokai Carbon Co., Ltd.) 30
Parts by mass, 10 parts by mass of magnesium oxide, 1 part by mass of calcium stearate, and 20 parts by mass of polytetrafluoroethylene (trade name: Lubron, manufactured by Daikin Industries, Ltd.)
Mix for several minutes in a mold blender. Next, the mixture was melt-kneaded at 190 ° C. for 10 minutes using a pressure kneader. Furthermore, after cooling, it was pulverized by a pulverizer and pelletized by a single screw extruder.

The above pellets were extruded into a tube using an extruder, cooled with water at an appropriate temperature, and taken out. Thus, a surface tube having an outer diameter of about 11 mm and a thickness of 250 μm was obtained.

(Molding of middle layer tube) As a material for the middle layer, 100 parts by mass of a polyurethane resin (trade name: Kuramilon, manufactured by Kuraray Co., Ltd.), 17 parts by mass of carbon black (Ketjen Black EC), 10 parts by mass of magnesium oxide, and calcium stearate One part by mass was pelletized in the same process as the surface layer material.

The pellets were extruded into a tube using an extruder, cooled with water at an appropriate temperature, and taken out. Thus, a middle-layer tube having an outer diameter of about 11 mm and a thickness of 400 μm was obtained.

(Formation of foamed elastic layer)
A hose-shaped foamed elastic body with an outer diameter of 11.5 mm (a compound obtained by blending a vulcanizing agent and a foaming agent with EPDM rubber, forming the mixture into a hose shape using an extruder, and foaming in a vulcanizing can. Cut into pieces with a length of 225 mm and a diameter of 5 mm and a length of 2
A 60 mm core (metal layer) was inserted.

[0038] This length of the above middle tube 228
Those cut in mm, coated by a tube coated device was compacted wearing elastic foam layer.

Next, the middle tube was covered with
Cut the above surface layer tube to a length of 230 mm, and
Turn the core metal arrangement upside down when coating the tube
It was coated with a coating device to prepare a charging member. Example 1
Of the surface free energy of the charging member surface layer
When the component values were determined, γ_s ^d= 17.0 mN / m, γ _s ^p
= 18.1 mN / m. The ten-point average roughness Rz is 1.
It was 51 μm.

The charging roll was used as an LBP (laser beam printer, Laser Jet 4000 manufactured by Canon Inc.).
When the battery was attached to the primary charger and subjected to intermittent durability in a high-temperature, high-humidity environment, good images were obtained without occurrence of charging failure even after 10,000 sheets.

Further, after the durability test, an image was output in a low-temperature and low-humidity environment, and the quality of the output image was visually evaluated. As a result, no abnormality was observed. Table 1 shows the results.

Comparative Example 1 (Molding of Surface Tube) As a material for the surface layer, 100 parts by mass of a styrene-based resin (styrene-ethylene / butylene-olefin copolymer resin, trade name: Dinalon, manufactured by JSR), polyethylene ( Trade name: Petrocene, manufactured by Tosoh Corporation 20 parts by mass, carbon black (trade name: Denka Black, manufactured by Denki Kagaku Kogyo)
30 parts by mass, 10 parts by mass of magnesium oxide, 1 part by mass of calcium stearate, and 60 parts by mass of polytetrafluoroethylene (trade name: Lubron, manufactured by Daikin Industries, Ltd.) were mixed for several minutes using a V-type blender. Next, the mixture was melt-kneaded at 190 ° C. for 10 minutes using a pressure kneader. Furthermore,
After cooling, the mixture was pulverized by a pulverizer and pelletized by a single screw extruder.

[0043] was taken off by means of an extruder and cooling the pellets extruded into a tube at a suitable temperature of the water. Thus, a surface tube having an outer diameter of about 11 mm and a thickness of 250 μm was obtained.

(Formation of Middle Tube) Same as in Example 1.

[0045] (formation of the foamed elastic layer) Same as Example 1.

In addition, the above-mentioned middle-layer tube is 228
The material cut into mm was coated with a tube coating device, and was pressure-adhered to the foamed elastic material layer.

Next, the above-mentioned surface tube was cut into a length of 230 mm on the one coated with the middle layer tube, and the core metal arrangement at the time of coating the middle layer tube was reversed upside down, and the tube was coated with a tube coating device and charged. A roll was made. When the component value of the surface free energy of the charging roll surface layer was determined in the same manner as in Example 1, γ _s ^d = 25.4 mN / m,
It was γ _s ^p = 0.0mN / m. The ten-point average roughness Rz was 1.77 μm.

The charging roll was used as an LBP (laser beam printer, Laser Jet 4000 manufactured by Canon Inc.).
Attached to the primary charger, good image without generating faulty charging such even after 10,000 sheets was conducted intermittent endurance was obtained by high-temperature and high-humidity environment.

After the endurance test, an image was output in a low-temperature and low-humidity environment, and the quality of the output image was visually evaluated. As a result, almost no abnormality was recognized. Confirmed only in toned images. Table 1 shows the results.

(Comparative Example 2) (Molding of Surface Tube) As a material for the surface layer, a styrene-based resin (styrene-ethylene / butylene-olefin copolymer resin, trade name: Dinalon, manufactured by JSR Corporation) 100
Parts by weight of carbon black (trade name talker black,
30 parts by mass of Tokai Carbon Co., Ltd., magnesium oxide 10
Parts by mass and 1 part by mass of calcium stearate were mixed for several minutes in a V-type blender. Next, the mixture was melt-kneaded at 190 ° C. for 10 minutes using a pressure kneader. After cooling,
It was pulverized by a pulverizer and pelletized by a single screw extruder.

The above pellets were extruded into a tube using an extruder, cooled with water at an appropriate temperature, and taken out. Thus, a surface tube having an outer diameter of about 11 mm and a thickness of 250 μm was obtained.

[0052] (Forming of middle tube) Same as Example 1.

(Formation of Foamed Elastic Layer) Same as in Example 1.

In addition, the above-mentioned middle-layer tube is connected to a length 228.
The material cut into mm was coated with a tube coating device, and was pressure-adhered to the foamed elastic material layer.

Next, the above-described surface layer tube was cut into a length of 230 mm on the one coated with the middle layer tube, and the core metal arrangement at the time of coating the middle layer tube was reversed upside down, and the tube was coated with a tube coating device and charged. A roll was made. When the component value of the surface free energy of the charging roll surface layer was determined in the same manner as in Example 1, γ _s ^d = 34.7 mN / m,
It was γ _s ^p = 0.0mN / m. The ten-point average roughness Rz was 2.49 μm.

The charging roll was used as an LBP (laser beam printer, Laser Jet 4000 manufactured by Canon Inc.).
When the battery was attached to the primary charger and subjected to intermittent durability in a high-temperature, high-humidity environment, good images were obtained without occurrence of charging failure even after 10,000 sheets.

After the endurance test, an image was output in a low-temperature and low-humidity environment, and the quality of the output image was visually evaluated. As a result, almost no abnormality was recognized. Confirmed only in toned images. Table 1 shows the results.

[0058] (Comparative Example 3) (molding surface tube) surface layer material, styrene-based resin (styrene - ethylene butylene - olefin copolymer resin, trade name Dynaron, produced by JSR Corporation) 100 parts by weight of polyethylene ( Trade name Petrocene, manufactured by Tosoh Corporation 20 parts by mass, carbon black (trade name Denka Black, manufactured by Denki Kagaku Kogyo)
30 parts by mass, 10 parts by mass of magnesium oxide, and 1 part by mass of calcium stearate were mixed in a V-type blender for several minutes. Next, 10 minutes at 190 ° C. using a pressure kneader.
Melted and kneaded for minutes. Furthermore, after cooling, it was pulverized by a pulverizer and pelletized by a single screw extruder.

The pellets were extruded into a tube using an extruder, cooled with water at an appropriate temperature, and taken out. Thus, a surface tube having an outer diameter of about 11 mm and a thickness of 250 μm was obtained.

(Formation of Middle Tube) Same as in Example 1.

(Formation of Foamed Elastic Layer) Same as in Example 1.

In addition, the above-mentioned middle-layer tube has a length of 228.
The material cut into mm was coated with a tube coating device, and was pressure-adhered to the foamed elastic material layer.

Next, those obtained by coating the middle tube, the above-mentioned surface layer tube was cut to a length 230 mm, by upside down metal core arrangement at the time of the previous intermediate tube coated, covered by a tube covering device charging A roll was made. When the component value of the surface free energy of the charging roll surface layer was determined in the same manner as in Example 1, γ _s ^d = 36.0 mN / m,
It was γ _s ^p = 0.0mN / m. The ten-point average roughness Rz was 2.58 μm.

The charging roll is used for LBP (laser beam printer, Laser Jet 4000 manufactured by Canon Inc.).
When the battery was attached to the primary charger and subjected to intermittent durability in a high-temperature and high-humidity environment, charging failure due to contamination of the charging roll occurred after 100,000 sheets had passed. Table 1 shows the results.

(Comparative Example 4) (Molding of Surface Tube) As a material for the surface layer, an amide-based resin (polyamide-polyether copolymer resin, trade name: Pebax, manufactured by Toray Industries, Inc.) 1
00 parts by mass, 30 parts by mass of carbon black (trade name: Denka Black, manufactured by Denki Kagaku Kogyo), 10 parts by mass of magnesium oxide, and 1 part by mass of calcium stearate
Mix for several minutes in a mold blender. Next, the mixture was melt-kneaded at 190 ° C. for 10 minutes using a pressure kneader. Furthermore, after cooling, it was pulverized by a pulverizer and pelletized by a single screw extruder.

The pellets were extruded into a tube using an extruder, cooled with water at an appropriate temperature, and taken out. In this way, a surface tube having an outer diameter of about 11 mm and a thickness of 250 μm was obtained, but the mechanical strength was low.

(Formation of Middle Tube) Same as in Example 1.

(Formation of Foamed Elastic Layer) Same as in Example 1.

In addition, the above-mentioned middle-layer tube is set to a length of 228.
The material cut into mm was coated with a tube coating device, and was pressure-adhered to the foamed elastic material layer.

Next, the above-mentioned surface layer tube was cut into a length of 230 mm on the one coated with the middle layer tube, and the arrangement of the core metal at the time of coating the middle layer tube was turned upside down. A roll was made. When the component value of the surface free energy of the charging roll surface layer was determined in the same manner as in Example 1, γ _s ^d = 10.1 mN / m,
It was γ _s ^p = 27.2mN / m. The ten-point average roughness Rz was 2.43 μm. Table 1 shows the results.

[0071] The charging roll LBP (laser beam printer, manufactured by Canon Inc. Laser Jet 4000)
When the battery was attached to the primary charger and subjected to intermittent durability in a high-temperature, high-humidity environment, charging failure occurred due to contamination of the charging roll after 1,000 sheets.

[0072]

[Table 1]

[0073]

According to the present invention, in a charging roll which contacts a member to be charged and charges by applying a voltage, the component value of the surface free energy of the surface layer of the charging roll is γ _s ^d <30 mN / m, γ
a _s ^p <20mN / m, and that the ten-point average roughness of the surface used charging roller is 2.0μm or less, eliminating image defects caused by toner fusion, etc. of the charging roller in an electrophotographic apparatus it has become possible.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an example of a charging roll of the present invention.

FIG. 2 is a sectional view of an example of the charging roll of the present invention.

FIG. 3 is a schematic configuration diagram of an example of an electrophotographic apparatus using the charging roll of the present invention.

[EXPLANATION OF SYMBOLS] 1 photoconductor drum 1a conductive drum base 1b photosensitive layer 2 charging roll 2a metal core 2b elastic layer 2c surface layer 2d intermediate layer 3 voltage source 4 laser beam scanning exposure 5 developing device 6 transferring means 7 the transfer material 8 Cleaning equipment

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 27:12) C08L 27:12) F-term (Reference) 2H003 AA01 BB11 CC05 3J103 AA02 AA13 AA14 AA23 AA72 EA01 FA18 GA57 GA58 GA60 HA20 HA43 4J002 BB021 BB041 BB151 BD122 BD152 BP011 CL071 GP00 GQ00 GS00 GT00

Claims (7)

[Claims] 1. A charging roll which contacts a member to be charged and charges by applying a voltage, wherein the component value of the surface free energy of the surface layer of the charging roll is γ _s ^d <30 mN / m, γ
_s ^p <a 20 mN / m, and charging roll ten-point average roughness of the surface is equal to or is 2.0μm or less. 2. The charging roll according to claim 1, wherein said surface layer comprises a thermoplastic elastomer extruded tube containing a conductive filler. 3. The thermoplastic elastomer according to claim 1, wherein the thermoplastic elastomer is a styrene-based thermoplastic elastomer.
The charging roll according to claim 2, wherein the charging roll is selected from the group consisting of olefin-based and amide-based thermoplastic elastomers. 4. The charging roll according to claim 2, wherein the extruded tube comprises 10 to 50 parts by mass of a fluororesin and 100 parts by mass of the thermoplastic elastomer. 5. The charging roll according to claim 2, wherein the extruded tube comprises 10 to 40 parts by mass of a fluororesin and 100 parts by mass of the thermoplastic elastomer. 6. The charging roll according to claim 4, wherein the fluororesin is polytetrafluoroethylene. 7. An electrophotographic apparatus comprising a photoconductor, 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 latent image is charged when the photoconductor is charged. An electrophotographic apparatus using the charging roll according to claim 1 as an image forming unit.