JP2000284571A - Electrostatic charging member and electrophotographic image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic charging member provided with a resistance layer being free from the occurrence of an image defect as a result of resistance unevenness, and an electrophotographic device forming a uniform and faithful image being free from unevenness, even adopting thermoplastic resin or elastomer for a resistance layer of an electrostatic charging member. SOLUTION: In the electrostatic charging member consisting by laminating in an order of a conductive elastic layer the resistance layer on a conductive support, this electrophotographic image forming device is provided with the resistance layers, composed by the resin composition composed of (A) at least, at one hand of terminal of ethylene-butylene copolymer, the copolymer resin composed by bonding block polymer selected from a group consisting of styrene block polymer and olefin block polymer, (B) polyolefin resin of average molecular weight beyond 10,000, (C) the polyolefin resin of average molecular weight below 10,000, and provided with these charging member.

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 using the same, and more particularly, to a charging member for charging a surface of a member to be charged to a predetermined potential by applying a voltage, and using the same. The present invention relates to an electrophotographic apparatus.

[0002]

2. Description of the Related Art Conventionally, many methods are known as electrophotography. In general, an electrostatic latent image is formed on a photoreceptor by various means using a photoconductive substance, and then the latent image is formed. The image is developed with a powder developer (toner) to produce a visible image.
After transferring the toner image to a transfer material such as paper as necessary,
This is to obtain a copy by fixing a toner image on a transfer material by heat and pressure. Further, toner particles remaining on the photoconductor without being transferred onto the transfer material are removed from the photoconductor by a cleaning process.

Conventionally, as a charging device for electrophotography,
A corona charger using a corona charger has been used, but in recent years, a contact charger has been put to practical use instead. The contact charging device has advantages that a lower voltage can be used, the amount of generated ozone is small, and the device can be miniaturized, as compared with the corona charging device. Among them, a roller charging method using a conductive roller as a charging member is preferably used in the contact charging device from the viewpoint of charging stability.

FIG. 1 schematically shows a configuration example of a contact charging device using a charging roller.

In the roller charging method, a conductive elastic roller 1 (charging roller) is brought into pressure contact with a photoreceptor 2 to be charged, and a voltage is applied thereto to apply a voltage to the surface of the photoreceptor 2. Charging is performed.

More specifically, since the charging is performed by discharging from the charging member to the member to be charged, the charging is started by applying a voltage equal to or higher than a certain threshold value. For example, thickness 2
When the charging roller 1 is pressed against the 5 μm OPC photosensitive member 2, the surface potential of the photosensitive member 2 starts to rise when a voltage of about 650 V or more is applied. As a result, the surface potential of the photoconductor 2 increases on the straight line having the slope 1. Hereinafter, this threshold voltage is defined as a charging start voltage (Vth).

That is, in order to obtain the photosensitive member surface potential Vd required for electrophotography, the charging roller needs to have a voltage of {Vth + V
Although a DC voltage of d｝ is required, a DC charging method of applying only a DC voltage to such a contact charging member to charge the photosensitive member to a predetermined potential has come into practical use.

However, in the DC charging method, the electric resistance value of the contact charging member fluctuates depending on the use environment (temperature and humidity), or the film thickness fluctuates due to abrasion of the photoreceptor, and Vth fluctuates. Therefore, it was difficult to set the surface potential of the photoconductor to a desired value.

On the other hand, Japanese Patent Application Laid-Open No. 63-149669 discloses that a DC potential corresponding to a desired photoconductor surface potential Vd is V
A so-called AC charging system in which a superimposed voltage with an AC voltage having a peak-to-peak voltage of twice or more than th is applied to a contact charging member is described. This AC charging method has an effect of leveling the potential by the AC voltage, and the potential of the photoconductor converges to Vd, which is the median of the peaks of the AC voltage, so that the charging is uniform without being affected by disturbances such as the environment. This is the expected method.

Next, a configuration example of the contact charging member will be described.

FIG. 2 is a schematic sectional view of a charging member (roller). The charging roller has a conductive elastic layer 1b necessary for forming a uniform contact portion with the member to be charged on a conductive support (core bar) 1a, and further has a resistance adjustment and abrasion resistance. The resistance layer 1c is provided for the purpose of improving the photoconductor contamination prevention property and the like. The conductive elastic layer 1 b and the resistive layer 1 c
And an intermediate layer may be provided between them.

The conductive elasticity 1b is usually made of EPDM, B
It has a configuration in which a conductive agent such as conductive carbon black is dispersed in synthetic rubber such as R, IR, SBR, NBR, silicone rubber, urethane rubber, or fluorine rubber.

The resistance layer 1c is usually made of a synthetic resin such as a polyamide resin, a polyurethane resin or a fluororesin, in which a conductive agent such as conductive carbon black, conductive titanium oxide or conductive tin oxide is dispersed for resistance adjustment. Having a configuration.
At this time, the resistance layer is adjusted to have a low hardness for the purpose of preventing the powder developer from fusing to the surface of the photoreceptor. Further, a configuration using a seamless tube made of a conductive thermoplastic resin or a thermoplastic elastomer as the resistance layer 1c has also been proposed.

However, when a seamless tube made of a thermoplastic resin or a thermoplastic elastomer is used in the resistance layer of the conventional charging member described above, there is a problem that unevenness in resistance of the tube generated during extrusion molding appears in an image. . For example, density unevenness of the charging roller pitch may occur on an image due to resistance unevenness in the circumferential direction of the tube. One of the causes is the uneven flow of material in the mold that occurs when manufacturing tubes by extrusion.
It is considered that the conductive agent is unevenly distributed.

[0015]

SUMMARY OF THE INVENTION An object of the present invention is to provide a charging member having a resistance layer which does not cause an image defect due to resistance unevenness even when a thermoplastic resin or an elastomer is used for the resistance layer of the charging member. is there.

Another object of the present invention is to provide an electrophotographic apparatus which forms a uniform and faithful image without unevenness.

[0017]

According to the present invention, in a charging member comprising a conductive elastic layer and a resistance layer sequentially laminated on a conductive support, the resistance layer comprises (A) an ethylene / butylene copolymer. A copolymer resin obtained by bonding a block polymer selected from the group consisting of a styrene block polymer and an olefin block polymer to at least one terminal, (B) a polyolefin resin having an average molecular weight of 10,000 or more,
(C) A charging member formed of a resin composition containing a polyolefin resin having an average molecular weight of less than 10,000 is provided.

According to the present invention, there is provided 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. An electrophotographic apparatus having the charging member for charging a photoreceptor as a forming unit is provided.

[0019]

Embodiments of the present invention will be described below in detail.

The charging member shown in FIG. 2 has a configuration in which a conductive elastic layer 1b is provided on a conductive support (core bar) 1a and a resistance layer 1c is provided on the elastic layer 1b. In the operation of the photograph, a predetermined voltage is applied to the cored bar 1a to charge the surface of the photoconductor (photosensitive drum) 2 in FIG.

The resistance layer 1c comprises (A) a copolymer resin having a block polymer selected from the group consisting of a styrene block polymer and an olefin block polymer at at least one end of an ethylene / butylene copolymer; It is formed of a resin composition containing two or more types of polyolefin resins having different molecular weights.

As described above, the resin (A) is a copolymer resin having a styrene block polymer and an olefin block polymer at at least one end of an ethylene / butylene copolymer. ,
"Dynalon", a thermoplastic elastomer manufactured by Nippon Synthetic Rubber Co., Ltd .; "Clayton", a thermoplastic elastomer manufactured by Shell Japan Co., Ltd .; And the like.

"Dinalon" includes a styrene block polymer at one of both ends of an ethylene / butylene copolymer,
Styrene-ethylene-butylene-olefin copolymer (SEBC), the other being an olefin block polymer
And an olefin-ethylene-butylene-olefin copolymer (CEBC) in which both terminals of the ethylene-butylene copolymer are olefin block polymers.
Further, “Clayton” and “Tuftec” include a styrene-ethylene-butylene-styrene copolymer (SEBS) in which both ends of an ethylene-butylene copolymer are styrene block polymers. These resins have a preferable flexibility in the resin itself, and softening oils such as paraffin oil and naphthenic oil and phthalic acid derivatives (for example, DOP,
These are soft resins that do not require the addition of a plasticizer such as DBP, DEP).

In the resistance layer 1c, a polyolefin resin (B) having an average molecular weight of 10,000 or more and a polyolefin resin having an average molecular weight of 10,000 or less are contained in the ethylene / butylene-block polymer copolymer resin (A). (C) is mixed and used. These polyolefin resins (B) and (C) are mixed and used in the proportions of 5 to 50 parts by weight and 5 to 30 parts by weight, respectively, per 100 parts by weight of the ethylene / butylene-block polymer copolymer resin (A). It is extremely important.

If the amount of the polyolefin resin (B) having an average molecular weight of 10,000 or more is less than 5 parts by weight, the adhesion of the resistance layer to the photosensitive member is insufficient, and if it exceeds 50 parts by weight, the hardness of the resistance layer is increased. Undesirably rises sharply. A desirable amount is 5 to 50 parts by weight. The amount of the polyolefin resin (C) having an average molecular weight of 10,000 or less is 5
If the amount is less than 10 parts by weight, the resistance unevenness in the circumferential direction cannot be reduced in the extrusion molding of the seamless tube. Desirable usage is 5 to
The range is 30 parts by weight.

The polyolefin resin is preferably a resin which is compatible with the above-mentioned ethylene / butylene-block polymer copolymer resin and can prevent sticking.
For example, polyethylene resin, ethylene propylene copolymer, ethylene butylene copolymer, ethylene octene copolymer, ethylene ethyl acrylate copolymer (EEA), ethylene methyl methacrylate copolymer (EMMA), ethylene Vinyl acetate copolymer (EV
A) or an olefin resin such as a polypropylene resin is included. Further, as the polyethylene resin, low density polyethylene (LDPE), high density polyethylene (HDP)
E), very low density polyethylene (VLDPE), linear low density polyethylene resin (LLDPE) and the like are preferably used.

The polyolefin resin having an average molecular weight of less than 10,000 is preferably a polypropylene resin or a polyethylene resin produced by a method such as a decomposition method or a polymerization method, from the viewpoint of compatibility with the polyolefin resin having an average molecular weight of 10,000 or more. Can be

Further, the resistance layer 1c comprises (A) a resin having a block polymer selected from the group consisting of a styrene block polymer and an olefin block polymer at at least one end of an ethylene / butylene-block polymer copolymer; The resistance is adjusted by mixing and dispersing a conductive agent in a resin composition containing (a) a polyolefin resin having an average molecular weight of 10,000 or more and (C) a polyolefin resin having an average molecular weight of less than 10,000. Examples of the conductive agent include conductive carbon black, conductive carbon graphite, conductive titanium oxide, conductive tin oxide, metal oxides such as conductive zinc oxide, and metal powders such as gold, silver, copper, and nickel. These can be used alone or in combination of two or more.

The resistance value of the resistance layer 1c is 1 × 10 ⁵
It is preferably in the range of Ω · cm to 1 × 10 ¹¹ Ω · cm. When the resistance value is lower than 1 × 10 ⁵ Ω · cm, if there are surface defects such as pinholes and scratches on the photosensitive drum,
The current is concentrated, so-called pinhole leak occurs. When the resistance exceeds 1 × 10 ¹¹ Ω · cm,
The applied voltage drops, the chargeability of the photosensitive drum is reduced, and so-called sand fog in which black dots appear on a white background occurs.

The method for producing the resistance layer 1c is, for example, an ethylene / butylene-block polymer copolymer resin (A),
After a predetermined amount of each of the resin (B) and the resin (C) is dry-mixed with a conductive agent using a mixer such as a Henschel mixer, a V-type blender or a cylindrical blender, a pressure-type kneader extruder and a hot roll are used. Melt and mix using a kneader. Further, pelletization into a predetermined shape is performed by an extruder and a pelletizer. Next, a tube can be manufactured by a molding method using an extruder equipped with a predetermined tube molding die, for example, free extrusion, vacuum extrusion, pressure sizing, and internal calibration.

The obtained tubular resistance layer is coated on the conductive elastic layer 1b. If the tube has heat shrinkability, the inner diameter of the tube is formed larger than the outer diameter of the conductive elastic layer. After inserting the conductive elastic layer into the tube, the tube can be covered by heat shrinkage. When the tube did not have heat shrinkability, the inner diameter of the tube-shaped resistance layer was molded slightly smaller than the outer diameter of the conductive elastic layer, and air or nitrogen gas was blown to expand using the elasticity of the resin. Thereafter, it can be coated on the conductive elastic layer.

Materials for forming the conductive elastic layer 1b include ethylene propylene rubber (EPDM), styrene butadiene rubber (SBR), butadiene rubber (BR),
Isoprene rubber (IR), chloroprene rubber (CR),
Synthetic rubber such as acrylic rubber (ACM), acrylonitrile butadiene rubber (NBR), epichlorohydrin rubber, silicone rubber, fluoro rubber, urethane rubber, or polyolefin, polystyrene, polyamide,
Solid or foamed thermoplastic elastomers such as polyester and polyvinyl chloride are suitable. Further, for the purpose of resistance adjustment, the conductive agents listed for the resistance layer 1c can be mixed with these materials and used.

The resistance value of the conductive elastic layer 1b is 1 × 10 ⁹
It is preferably Ω · cm or less. Resistance value is 1 × 10
^If it exceeds ⁹ Ω · cm, the applied voltage drops in the conductive elastic layer 1b, and the chargeability deteriorates, which is inconvenient.

Further, the conductive support (core metal) 1a of the present invention
Metal rods such as iron, copper, nickel, stainless steel and brass may be used as they are, or they may be subjected to surface treatment such as chemical nickel plating or chromium plating for rust prevention and scratch resistance. However, it is important not to impair conductivity.

Next, an electrophotographic apparatus using the charging member of the present invention will be described with reference to FIGS.

A conductive drum support 2a made of aluminum or the like
The electrophotographic photosensitive member 2 of a rotating drum type as a member to be charged having a photosensitive layer 2b formed on the outer peripheral surface thereof is rotationally driven at a predetermined peripheral speed (process speed) in a clockwise direction indicated by an arrow.

The contact charging member 1 is a roller body (hereinafter referred to as a charging roller) which is disposed substantially in parallel with the surface of the photosensitive drum 2 in a direction parallel to the drum gene line and is brought into contact with the photosensitive drum 2 at a predetermined suppression pressure. The rotation follows the rotation. Of course, charging roller 1
May be driven using some kind of driving means.

The charging roller 1 of the present embodiment has a conductive core 1a.
And a conductive elastic layer 1b made of a conductive rubber or the like formed concentrically and integrally with the core metal by injection molding, transfer molding, or the like, and a resistance layer 1c formed on the outer periphery thereof. . Further, if necessary, an intermediate layer may be provided between the conductive elastic layer 1b and the resistance layer 1c.

In the charging roller 1, a mixture of the above-described thermoplastic elastomer material and polyolefin resin is usually used for the resistance layer 1c, which is a material layer in contact with the surface of the photosensitive drum 1, which is a member to be charged.

In electrophotography, a predetermined voltage is applied from a voltage applying power source 3 to a metal core 1a of the charging roller 1, and the outer peripheral surface of the rotating photosensitive drum 2 is charged to a predetermined polarity and potential.

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

The surface of the photosensitive drum 1 which has been subjected to primary charging processing to a predetermined potential uniformly by the charging roller 1 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. Are sequentially performed by the transfer means 6 of the formed toner image on the transfer material 7 (for example, paper), and the transfer material 7 separated from the surface of the photosensitive drum 1 by receiving the toner image is not shown. Image formed matter (print) introduced into fixing means
Is output as The surface of the photosensitive drum 1 after the transfer of the toner image is cleaned and cleaned by the cleaning device 8 to remove the remaining toner adhered to the transfer, and repeatedly used for image formation.

[0043]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in further detail with reference to embodiments.

Example 1 <Preparation of Conductive Elastic Layer of Charging Member>
The mixture was kneaded for 20 minutes with two rolls whose temperature was adjusted to prepare a compound.

EPDM 100 parts by weight Zinc oxide 5 parts by weight Higher fatty acid 1 part by weight Conductive carbon black 5 parts by weight Paraffin oil 10 parts by weight Sulfur 2 parts by weight Vulcanization accelerator (MTB) 1 part by weight Vulcanization accelerator (TMTD) 1 part by weight Vulcanization accelerator (ZnMDC) 1.5 parts by weight Blowing agent (sodium bicarbonate) 10 parts by weight

Further, the above compound was heated and cured at 150 ° C. for 30 minutes around a stainless steel cored bar having an outer diameter of 6 mm to form a foaming roller having a 3 mm thick conductive elastic layer (12 mm outer diameter). I got

Next, the electric resistance value of the foamed roller was measured in an environment of a temperature of 23 ° C. and a relative humidity of 60%.
It was 0.08 MΩ. The measurement is performed on the outer circumference of the foaming roller.
A 0-mm-wide aluminum foil (thickness: 50 μm) is tightly wound and a DC voltage of 25 is applied between the metal core and the aluminum foil.
0V is applied and the resistance value after 10 seconds is measured with a resistance meter (trade name: 3119 DIGITAL MΩ, manufactured by Hioki Electric Co., Ltd.)
HITESTER).

<Preparation of Resistive Layer of Charging Member> 100 parts by weight of a styrene-ethylene / butylene-styrene copolymer resin (SEBS, manufactured by Shell Japan K.K., trade name: Clayton G1652), a low-density polyethylene resin (LDPE) , Average molecular weight of about 80,000), 5 parts by weight of polyethylene resin (manufactured by Sanyo Chemical Industries, Ltd., trade name: Sunwax 151-P, average molecular weight of about 2,000), 14 parts by weight of conductive carbon black, calcium stearate One part by weight was dry mixed in a V-type blender for 5 minutes.

Then, using a pressure type kneader,
For 10 minutes. Furthermore, after cooling these mixtures and pulverizing them with a pulverizer, a single screw extruder (screw diameter 3
(0 mm, L / D = 30, resin temperature 190 ° C.). Furthermore, a die having an inner diameter of 12 mm and an outer diameter of 11 mm
Using a crosshead extruder (screw diameter 28 mm, L / D = 30, resin temperature 190 ° C.) equipped with a nipple of 1 mm, a seamless tube having an inner diameter of 11.5 mm and a wall thickness of about 200 μm was produced.

<Preparation of Charging Roller> Air was blown into the seamless tube (resistance layer) to expand the inner diameter of the tube, and then the foam roller was inserted. A charging roller of Example 1 was obtained. Next, when the resistance value of the charging roller was measured in an environment of a temperature of 23 ° C. and a relative humidity of 60%, it was 0.7 MΩ. The measurement was performed by the same method as the resistance measurement of the conductive elastic layer.

<Method of Measuring the Resistance Unevenness in the Circumferential Direction of the Charging Roller> The charging roller was brought into contact with a stainless steel drum having an outer diameter of 30 mm with a load of 1 kg, and the drum was rotated 17 times per minute.
The charging roller is driven to rotate. Next, a DC voltage of -250 V was applied from one end of the metal core of the charging roller, and a current value flowing to the ground of the stainless steel drum at this time was measured by a recorder. The maximum value and the minimum value of the current were read from the recorded current chart for one round of the sample, and from the calculation, (maximum resistance value / minimum resistance value) = resistance unevenness in the circumferential direction of the charging roller. The measurement was performed in an environment of a temperature of 23 ° C. and a relative humidity of 60%. Before coating the resistance layer (seamless tube), the resistance unevenness in the circumferential direction of the conductive elastic layer was measured by the same method. FIG. 3 schematically shows a method of measuring the resistance unevenness in the circumferential direction of the charging roller.

In FIG. 3, 9 is a stainless steel drum, 1
0 is a measurement power supply, 11 is a standard resistance (1 KΩ), and 12 is a recorder.

As a result, the resistance unevenness of the charging roller was 1.4.
And the resistance unevenness of the conductive elastic layer was 1.1 times. The relationship between the two resistances is the resistance of the charging roller (0.7 MΩ)
> Since the resistance value of the conductive elastic layer (0.08 MΩ),
The resistance unevenness of the charging roller obtained by the measurement is the resistance unevenness caused by the resistance layer (seamless tube).

<Evaluation Method of Charging Roller> This charging roller was used as a laser printer (manufactured by Canon Inc., trade name: LB)
Attached to the primary charger of a process cartridge (product name: EP-E cartridge) used for P-8MarkII), and applied a superimposed voltage of -670 V DC, 2000 V AC (peak-to-peak voltage), and 650 Hz frequency from an external power supply. , Low temperature and low humidity environment (temperature 15 ° C / relative humidity 1)
(0%), the image obtained was visually observed to evaluate the image. As a result, a good image was obtained.

Example 2 In Example 1, a styrene-ethylene / butylene-styrene copolymer (trade name: Clayton G16, manufactured by Shell Japan K.K.) was used.
52) 100 parts by weight, low density polyethylene resin (LDP
E, an average molecular weight of about 100,000) 10 parts by weight, polypropylene resin (manufactured by Sanyo Chemical Industry Co., Ltd., trade name: Viscol 55)
0-P, average molecular weight about 4000) 5 parts by weight and 1 part by weight of calcium stearate were prepared in the same manner as in Example 1 to prepare a charging roller of Example 2.

In the same manner as in Example 1, the resistance value of the charging roller and the resistance unevenness of the resistance layer in the circumferential direction were measured. The resistance value was 0.4 MΩ, and the resistance unevenness was 1.3 times. Furthermore, as a result of performing initial image evaluation under a low temperature and low humidity environment under the same conditions as in Example 1, a good image was obtained.

Example 3 In Example 1, the material of the resistance layer was a styrene-ethylene / butylene / styrene copolymer (trade name: Clayton G16, manufactured by Shell Japan K.K.).
52) 100 parts by weight, 10 parts by weight of polypropylene resin (PP, average molecular weight of about 60,000), 5 parts by weight of polypropylene resin (trade name: Viscol 550-P, manufactured by Sanyo Chemical Industries, Ltd., average molecular weight of about 4000), steer A charging roller of Example 3 was produced in the same manner as in Example 1, except that 1 part by weight of calcium phosphate was used.

In the same manner as in Example 1, the resistance value of the charging roller and the resistance unevenness of the resistance layer in the circumferential direction were measured. The resistance value was 0.6 MΩ, and the resistance unevenness was 1.5 times. Furthermore, as a result of performing initial image evaluation under a low temperature and low humidity environment under the same conditions as in Example 1, a good image was obtained.

Example 4 In Example 1, the material of the resistance layer was styrene-ethylene / butylene-styrene copolymer (trade name: Clayton G16, manufactured by Shell Japan K.K.).
52) 100 parts by weight, 10 parts by weight of polypropylene resin (average molecular weight: about 60,000), 5 parts by weight of polyethylene resin (trade name: Sunwax 161-P, manufactured by Sanyo Chemical Industries, Ltd., average molecular weight: about 5000), calcium stearate A charging roller of Example 4 was produced in the same manner as in Example 1, except that 1 part by weight was used.

In the same manner as in Example 1, the resistance value of the charging roller and the resistance unevenness in the circumferential direction of the resistance layer were measured. The resistance value was 0.6 MΩ, and the resistance unevenness was 1.5 times. Furthermore, as a result of performing initial image evaluation under a low temperature and low humidity environment under the same conditions as in Example 1, a good image was obtained.

(Example 5) In Example 1, 100 parts by weight of a styrene-ethylene / butylene-olefin copolymer (SEBC, manufactured by Nippon Synthetic Rubber Co., Ltd., trade name: Dinalon 4600P) were used as the resistance layer material, 10 parts by weight of polyethylene resin (average molecular weight: about 80,000), propylene resin (manufactured by Sanyo Chemical Industries, Ltd., trade name: Viscol 660-)
P, average molecular weight: about 3000) A charging roller of Example 5 was produced in the same manner as in Example 1, except that 5 parts by weight and 1 part by weight of calcium stearate were used.

In the same manner as in Example 1, the resistance value of the charging roller and the resistance unevenness in the circumferential direction of the resistance layer were measured. The resistance value was 0.5 MΩ, and the resistance unevenness was 1.2 times. Furthermore, as a result of performing initial image evaluation under a low temperature and low humidity environment under the same conditions as in Example 1, a good image was obtained.

(Example 6) In Example 1, 100 parts by weight of an olefin-ethylene-butylene-olefin copolymer (CEBC, manufactured by Nippon Synthetic Rubber Co., Ltd., trade name: Dinalon 6200P) was used as a resistance layer material. 10 parts by weight of polyethylene resin (HDPE, average molecular weight of about 50,000), 5 parts by weight of propylene resin (trade name: Sunwax 161-P, manufactured by Sanyo Chemical Industries, Ltd., average molecular weight of about 5000), and 1 part by weight of calcium stearate. Example 1 except that
In the same manner as in Example 6, a charging roller of Example 6 was produced.

The resistance value of the charging roller and the resistance unevenness in the circumferential direction of the resistance layer were measured in the same manner as in Example 1. The resistance value was 0.7 MΩ, and the resistance unevenness was 1.5 times. Furthermore, as a result of performing initial image evaluation under a low temperature and low humidity environment under the same conditions as in Example 1, a good image was obtained.

(Example 7) In Example 1, 100 parts by weight of a styrene-ethylene / butylene-olefin copolymer (SEBC, manufactured by Nippon Synthetic Rubber Co., Ltd., trade name: Dinalon 6100P) was used as a resistive layer material. 10 parts by weight of propylene copolymer resin (EP, average molecular weight of about 30,000), 5 parts by weight of propylene resin (trade name: Biscol 550-P, average molecular weight of about 5000, manufactured by Sanyo Chemical Industries, Ltd.), and 1 part by weight of calcium stearate Example 1 except that
In the same manner as in the above, a charging roller of Example 7 was produced.

In the same manner as in Example 1, the resistance value of the charging roller and the resistance unevenness in the circumferential direction of the resistance layer were measured. The resistance value was 0.3 MΩ, and the resistance unevenness was 1.7 times. Furthermore, as a result of performing initial image evaluation under a low temperature and low humidity environment under the same conditions as in Example 1, a good image was obtained.

Comparative Example 1 In Example 1, the material of the resistance layer was styrene-butadiene-styrene copolymer (SB).
S, Shell Japan Co., Ltd., Clayton D-KX6
5) 100 parts by weight of low density polyethylene resin (LDP
E, an average molecular weight of about 80,000) A charging roller of Comparative Example 1 was produced in the same manner as in Example 1, except that 10 parts by weight and 1 part by weight of calcium stearate were used.

In the same manner as in Example 1, the resistance value of the charging roller and the resistance unevenness in the circumferential direction of the resistance layer were measured. The resistance value was 0.3 MΩ, and the resistance unevenness was 5.1 times. Further, the initial image evaluation was performed under the same conditions as in Example 1 under a low-temperature and low-humidity environment. As a result, horizontal black stripes having a charging roller pitch (about 38 mm pitch) were generated on the halftone image.

Comparative Example 2 In Example 1, the material of the resistance layer was styrene-butadiene-styrene copolymer (SB).
S, Shell Japan Co., Ltd., Clayton D-KX6
5) Same as Example 1 except that 100 parts by weight, 10 parts by weight of high density polyethylene resin (average molecular weight of about 70,000), 10 parts by weight of polypropylene resin (average molecular weight of about 60,000) and 1 part by weight of calcium stearate were used. Thus, a charging roller of Comparative Example 2 was produced.

In the same manner as in Example 1, the resistance value of the charging roller and the resistance unevenness in the circumferential direction of the resistance layer were measured. The resistance value was 0.4 MΩ, and the resistance unevenness was 3.9 times. Furthermore, the initial image evaluation was performed under the same conditions as in Example 1 under a low-temperature and low-humidity environment. As a result, horizontal black stripes of the charging roller pitch were generated on the image.

[0071]

According to the resistance layer of the charging member of the present invention, the resistance unevenness of the resistance layer generated during extrusion molding can be reduced, and as a result, uniform charging performance can be obtained. Further, the electrophotographic apparatus of the present invention can obtain stable image quality by uniform charging, and has excellent practicality.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view illustrating an example of the configuration of the charging member of the present invention.

FIG. 3 is a diagram schematically illustrating a method for measuring resistance unevenness of a resistance layer used in the present invention.

[Explanation of symbols]

 Reference Signs List 1 charging member (charging roller) 1a conductive support (core bar) 1b conductive elastic layer 1c resistive layer 2 photoconductor (photosensitive drum) 3 power supply 4 exposure means 5 developing means 6 transfer means 7 transfer paper 8 cleaning means 9 stainless steel Drum 10 Power supply for measurement 11 Standard resistance 12 Recorder

Continued on the front page F term (reference) 2H003 BB11 CC05 4J002 BB032 BB033 BB052 BB053 BB062 BB063 BB072 BB073 BB122 BB123 BB152 BB153 BP011 BP031 DA026 DA036 DA076 DA086 DE096 DE106 DE136 GFD116G00

Claims (4)

[Claims] 1. A charging member in which a conductive elastic layer and a resistance layer are sequentially laminated on a conductive support, the resistance layer comprising: (A) styrene at least one end of an ethylene / butylene copolymer A copolymer resin obtained by bonding a block polymer selected from the group consisting of a block polymer and an olefin block polymer; (B) a polyolefin resin having an average molecular weight of 10,000 or more; and (C) a polyolefin resin having an average molecular weight of less than 10,000. A charging member characterized by being formed from a resin composition comprising: 2. The resin composition is prepared by adding the resin (B) and the resin (C) to 100 parts by weight of the resin (A) in an amount of 5 parts by weight.
2. The charging member according to claim 1, wherein the charging member is mixed in a proportion of 50 to 50 parts by weight and 5 to 30 parts by weight. 3. The charging member according to claim 1, wherein the polyolefin resin having an average molecular weight of less than 10,000 is at least one resin selected from the group consisting of a polyethylene resin and a polypropylene resin. 4. 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. Claims 1 to 3 for charging the photoreceptor
An electrophotographic apparatus using the charging member according to any one of the above.