JP2023029104A - Charging member, charging device, process cartridge, and image forming device - Google Patents

Abstract

To provide an image forming device capable of suppressing wear of an electrophotographic photoreceptor and appearance of white spots.SOLUTION: An image forming device provided herein features a discharge width in a range of 0.5-0.6 mm, inclusive, between a charging member and an electrophotographic photoreceptor.SELECTED DRAWING: Figure 4

Description

The present invention relates to charging members, charging devices, process cartridges, and image forming apparatuses.

In Patent Document 1, "an electrophotographic photosensitive member, a conductive support, a conductive elastic layer disposed on the conductive support, and a surface layer disposed on the conductive elastic layer, When measured by the AC impedance method in the range from 1 MHz to 1 mHz, the product of the high frequency resistance component (Ω m) from 10 kHz to 100 Hz and the high frequency capacitance (F / m) is 7.0 × 10 ^-6 ( Ω·F) or more and 7.0×10 ⁻⁵ (Ω·F) or less, and charging the surface of the electrophotographic photosensitive member by a contact charging method in which only a DC voltage is applied to the charging member. means, an electrostatic latent image forming means for forming an electrostatic latent image on the surface of the charged electrophotographic photosensitive member, and a developer containing toner to form an electrostatic latent image on the surface of the electrophotographic photosensitive member. An image forming apparatus comprising developing means for developing a toner image to form a toner image, and transfer means for transferring the toner image to the surface of a recording medium.

JP 2017-62435 A

An object of the present invention is to solve an image forming apparatus including an electrophotographic photoreceptor and a charging device having a charging member that charges the surface of the electrophotographic photoreceptor in contact with the electrophotographic photoreceptor. An object of the present invention is to provide an image forming apparatus which suppresses the occurrence of white spots as well as the wear of an electrophotographic photosensitive member, compared to when the discharge width is less than 0.5 mm or more than 0.6 mm.

Specific means for solving the above problems include the following aspects.

<1>
an electrophotographic photoreceptor;
a charging device having a charging member that contacts and charges the surface of the electrophotographic photosensitive member;
an electrostatic latent image forming device for forming an electrostatic latent image on the surface of the charged electrophotographic photosensitive member;
a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image;
a transfer device for transferring the toner image onto a surface of a recording medium;
with
An image forming apparatus, wherein a discharge width generated between the charging member and the electrophotographic photosensitive member is 0.5 mm or more and 0.6 mm or less.
<2>
The image forming apparatus according to <1>, wherein the discharge width is 0.5 mm or more and 0.55 mm or less.
<3>
The image forming apparatus according to <1> or <2>, wherein the total amount of discharge light generated between the charging member and the electrophotographic photosensitive member is 25 mV or more and 30 mV or less.
<4>
The image forming apparatus according to <3>, wherein the total amount of discharge light is 28 mV or more and 30 mV or less.
<5>
The charging device has an applying unit that applies a superimposed voltage obtained by superimposing a DC voltage and an AC voltage to the charging member,
When the discharge start voltage value is V0 and the peak-to-peak voltage value of the output voltage during image formation is Vpp, ((Vpp−(2×V0))/(2×V0))×100≧30 is satisfied. The image forming apparatus according to any one of <1> to <4>, wherein the superimposed voltage is applied to the charging member.
<6>
The charging member includes a conductive substrate, an elastic layer provided on the conductive substrate and having a storage elastic modulus G of 5.0 MPa or less at 100 Hz, and a surface layer provided on the elastic layer; and in the Cole-Cole plot obtained by measuring the charging member in the range from 1 MHz to 0.1 Hz by the AC impedance method, the resistance component Ra of the capacitive semicircle containing 2.5 kHz is 6.3 The image forming apparatus according to any one of <1> to <5>, wherein the resistance is ×10 ⁴ Ω or less.
<7>
The image forming apparatus according to <6>, wherein the elastic layer of the charging member has a storage elastic modulus G of 3.0 MPa or less at 100 Hz.
<8>
The image forming apparatus according to <6> or <7>, wherein the elastic layer contains an elastic material containing epichlorohydrin-alkylene oxide copolymer rubber, carbon black, and an inorganic filler.
<9>
The image forming apparatus according to <8>, wherein the content of the carbon black is 3 parts by mass or less with respect to 100 parts by mass of the elastic material.
<10>
The image forming apparatus according to <8> or <9>, wherein the content of the inorganic filler is 30 parts by mass or less with respect to 100 parts by mass of the elastic material.
<11>
The image formation according to any one of <8> to <10>, wherein the content of structural units derived from alkylene oxide is 55% by mass or more with respect to the entire epichlorohydrin-alkylene oxide copolymer rubber. Device.
<12>
an electrophotographic photoreceptor;
a charging device having a charging member that contacts and charges the surface of the electrophotographic photosensitive member, the charging member having a width of discharge between the electrophotographic photosensitive member and the electrophotographic photosensitive member of 0.5 mm or more and 0.6 mm or less;
and a process cartridge detachable from the image forming apparatus.

According to the invention of <1> or <8>, in an image forming apparatus comprising an electrophotographic photoreceptor and a charging device having a charging member that contacts and charges the surface of the electrophotographic photoreceptor, the charging member Provided is an image forming apparatus that suppresses the occurrence of white spots along with wear of the electrophotographic photoreceptor, compared to the case where the discharge width generated between the electrophotographic photoreceptor is less than 0.5 mm or more than 0.6 mm.

According to the invention relating to <2>, there is provided an image forming apparatus that suppresses the occurrence of white spots as well as the wear of the electrophotographic photosensitive member compared to the case where the discharge width is less than 0.5 mm or more than 0.55 mm. .
According to the invention according to <3>, compared with the case where the total discharge light amount of the discharge generated between the electrophotographic photoreceptor is less than 25 mV or more than 30 mV, the electrophotographic photoreceptor wears and white spots are suppressed. There is provided an image forming apparatus that performs
According to the invention pertaining to <4>, compared with the case where the total amount of discharge light generated between the electrophotographic photoreceptor is less than 28 mV or more than 30 mV, abrasion of the electrophotographic photoreceptor and generation of white spots are suppressed. There is provided an image forming apparatus that performs

According to the invention according to <5>, white spots are less likely to occur than when a superimposed voltage is applied to the charging member so as to satisfy ((Vpp−(2×V0))/(2×V0))×100<30. An image forming apparatus that suppresses the occurrence is provided.

According to the invention relating to <6>, the electrophotographic photoreceptor has a higher storage elastic modulus G than 5.0 MPa or a resistance component Ra of more than 6.3×10 ⁴ Ω in the elastic layer of the charging member. An image forming apparatus that reduces wear is provided.
According to the invention relating to <7>, there is provided an image forming apparatus that suppresses abrasion of the electrophotographic photosensitive member as compared with the case where the storage elastic modulus G of the elastic layer of the charging member exceeds 3.0 MPa.

According to the invention relating to <9>, there is provided a charging member that suppresses abrasion of the electrophotographic photosensitive member as compared with the case where the carbon black content exceeds 3 parts by mass.
According to the invention according to <10>, there is provided a charging member that suppresses abrasion of the electrophotographic photosensitive member as compared with the case where the content of the inorganic filler exceeds 30 parts by mass.
According to the invention according to <11>, there is provided a charging member that suppresses abrasion of an electrophotographic photosensitive member as compared with the case where the content of structural units derived from alkylene oxide is less than 55% by mass.

According to the invention pertaining to <12>, in the process cartridge including the electrophotographic photosensitive member and the charging device having the charging member that contacts and charges the surface of the electrophotographic photosensitive member, the charging member and the electrophotographic photosensitive member Provided is a process cartridge that suppresses the occurrence of white spots as well as the wear of an electrophotographic photosensitive member, as compared with the case where the discharge width occurring between the two is less than 0.5 mm or more than 0.6 mm.

1 is a schematic configuration diagram showing an example of an image forming apparatus according to an embodiment; FIG. FIG. 2 is a schematic configuration diagram showing another example of the image forming apparatus according to the embodiment; 1 is a schematic configuration diagram showing an example of a process cartridge according to this embodiment; FIG. FIG. 4 is a schematic diagram for explaining a discharge width between a charging member and a photoreceptor;

An embodiment that is an example of the present invention will be described below. These descriptions and examples are illustrative of embodiments and do not limit the scope of the invention.
In the numerical ranges described stepwise in this specification, the upper limit or lower limit described in one numerical range may be replaced with the upper limit or lower limit of the numerical range described in other steps. good. Moreover, in the numerical ranges described in this specification, the upper and lower limits of the numerical ranges may be replaced with the values shown in the examples.

When referring to the amount of each component in the composition in this specification, if there are multiple types of substances corresponding to each component in the composition, unless otherwise specified, the multiple types present in the composition means the total amount of substances in
In this specification, the "electrophotographic photoreceptor" is also simply referred to as the "photoreceptor."
In this specification, the "axial direction" of the charging member means the direction in which the rotating shaft of the charging member extends. "Circumferential direction" means the direction of rotation of the charging member.
In addition, the term “conductivity” as used herein means that the volume resistivity at 20° C. is 1×10 ¹⁴ Ωcm or less.

<Image forming apparatus>
The image forming apparatus according to this embodiment includes:
an electrophotographic photoreceptor;
a charging device having a charging member that contacts and charges the surface of an electrophotographic photosensitive member;
an electrostatic latent image forming device for forming an electrostatic latent image on the surface of the charged electrophotographic photosensitive member;
a developing device that develops an electrostatic latent image formed on the surface of an electrophotographic photosensitive member with a developer containing toner to form a toner image;
a transfer device that transfers the toner image onto the surface of a recording medium;
Prepare.
The discharge width generated between the charging member and the electrophotographic photosensitive member is 0.5 mm or more and 0.6 mm or less.

Here, in an image forming apparatus using a contact charging type charging unit, discharge occurs in a minute gap (also called a "minute gap") in the vicinity of the contact portion between the photosensitive member and the charging member, so that the surface of the photosensitive member is is charged. When the load due to the discharge is large, the surface of the electrophotographic photoreceptor is likely to deteriorate, and abrasion of the surface of the electrophotographic photoreceptor may be accelerated due to rubbing with a cleaning blade or the like to scrape off the deteriorated region. In particular, when a superimposed voltage obtained by superimposing a DC voltage and an AC voltage is applied to the charging member, the load due to the discharge tends to increase, and the wear of the surface of the photoreceptor tends to be accelerated.
On the other hand, when the voltage applied to the charging member is lowered, the discharge load is reduced, but the voltage applied to the discharge area is weak and non-uniform, resulting in white spots (that is, dot-like image defects) caused by uneven charging. This may occur in images. Therefore, it is preferable to apply a voltage necessary for suppressing white spots to the charging member.

On the other hand, by narrowing the discharge width between the charging member and the photoreceptor to 0.6 mm or less, the discharge load on the photoreceptor is reduced and wear of the photoreceptor is suppressed.
On the other hand, if the discharge width between the charging member and the photoreceptor is too narrow, charging unevenness will occur and white spots (that is, dot-like image defects) will occur. That's it.

As described above, in the image forming apparatus according to the present embodiment, the abrasion of the photoreceptor and the occurrence of white spots are suppressed by the above configuration.

In the image forming apparatus according to the present embodiment, the discharge width between the charging member and the photoreceptor is preferably 0.5 mm or more and 0.55 mm, more preferably 0.52 mm or more and 0.52 mm or more, from the viewpoint of suppressing abrasion of the photoreceptor and generation of white spots. 55 mm is more preferred.

Here, the "discharge width between the charging member and the photoreceptor" refers to the discharge area generated in a minute gap around the contact portion between the photoreceptor and the charging member on each of the upstream side and the downstream side in the rotational direction of the photoreceptor. The length is the length along the circumferential direction of the photosensitive member (see Ld in FIG. 4).
In FIG. 4, PH indicates the photosensitive member, CM indicates the charging member, and Lc indicates the contact width (that is, the nip portion) between the charging member and the photosensitive member.

Specifically, the "discharge width between the charging member and the photoreceptor" is measured as follows.
By outputting an image with an image density of 0% in a state in which a voltage obtained by superimposing an alternating current component (AC) and a direct current component (DC) shown below is applied to the charging member, only the portions where the discharge phenomenon occurs are developed. It can be measured as discharge width.
The application state of the AC voltage applied to the charging member repeats ON/OFF with a certain period. When the AC voltage is applied, the charging member secures the potential of the photoreceptor, so that it is not developed, but it is extremely short. By turning off the application of the AC voltage and turning on the application of the DC voltage (that is, the application of the voltage for +charging) for a certain period of time, +charging occurs only in the discharge area corresponding to the width of the discharge, creating an electrostatic latent image. can be done. At this time, no discharge phenomenon occurs at the contact portion of the charging member and the photoreceptor (hereinafter also referred to as the nip portion). It retains the potential it had when the DC voltage was applied and no electrostatic latent image is created. After that, when the electrostatic latent image formed on the upstream side of the nip portion in the rotation direction of the photoreceptor passes through the discharge region on the downstream side of the nip portion in the rotation direction of the photoreceptor, the application of the AC voltage is turned on again, thereby It is possible to form an electrostatic latent image only in the discharge areas on both the upstream side and the downstream side in the rotation direction of the photosensitive member, and print it as a discharge width.
The measurement conditions were set to ON time of voltage application: 8.44 ms and OFF time of voltage application: 5.97 ms for each voltage application time in the evaluation machine driven at 308 mm/s.

In the image forming apparatus according to this embodiment, the total amount of discharge light generated between the charging member and the electrophotographic photosensitive member is preferably 25 mV or more and 30 mV or less, more preferably 28 mV or more and 30 mV or less.
By setting the total discharge amount to 25 mV or more, the occurrence of charging unevenness is suppressed, and the occurrence of white spots is easily suppressed.
By setting the total discharge amount to 30 mV or less, the discharge load on the photoreceptor is reduced, and wear of the photoreceptor is easily suppressed.

The "total amount of discharge light generated between the charging member and the electrophotographic photosensitive member" is the amount of discharge generated in a minute gap around the contact portion between the photosensitive member and the charging member, and is the upstream side in the rotating direction of the photosensitive member. and the total amount of discharge on the downstream side.
Specifically, the "total amount of discharge light generated between the charging member and the electrophotographic photosensitive member" is measured as follows.
An optical sensor using a photomultiplier tube detects discharge light generated in a minute gap around the nip portion between the photoreceptor and the charging member from outside the nip portion (that is, from the upstream side and downstream side of the nip portion in the rotation direction of the photoreceptor). According to "H10721-110 (Hamamatsu Photonics)", the sum of the emission intensity/the number of data measured at a sampling pitch of 0.5 μs and a sampling time of 50 ms is measured as the total amount of discharge light.
That is, the total amount of discharge light is calculated by the formula: total amount of discharge light=total sum of emission intensity/number of data.

In the image forming apparatus according to this embodiment, the charging device may further include a charging member cleaning member that cleans the outer peripheral surface of the charging member.
The charging device has a method of applying only a DC voltage (DC charging method), a method of applying only an AC voltage to the charging member (AC charging method), and a method of applying a voltage obtained by superimposing an AC voltage on a DC voltage to the charging member ( AC/DC charging method) may be used.
The charging device may be a charging device further comprising an applying section for applying only a DC voltage to the charging member, or may be a charging device further comprising an applying section for applying only an AC voltage to the charging member. The charging device may further include an applying section that applies a superimposed voltage obtained by superimposing the voltage and the AC voltage to the charging member.

In particular, the charging device further includes an applying unit that applies a superimposed voltage of a DC voltage and an AC voltage to the charging member. When the peak-to-peak voltage value of the output voltage is Vpp (unit V), the superimposed voltage is set so as to satisfy ((Vpp-(2×V0))/(2×V0))×100≧30 (unit %). It is preferably applied to the charging member.

If the value of "((Vpp-(2*V0))/(2*V0))" is decreased, the discharge load is reduced, the abrasion of the photoreceptor is suppressed, and white spots due to uneven charging are likely to occur.
However, even if the value of "((Vpp-(2*V0))/(2*V0))" is increased to 30 or more, the discharge width between the charging member and the photosensitive member can be narrowed to 0.6 mm or less. While the load is reduced and photoreceptor wear is suppressed, the occurrence of white spots due to charging unevenness is easily suppressed.

The image forming apparatus according to the present embodiment includes a fixing device that fixes a toner image onto a recording medium; a cleaning device that cleans the surface of a photoreceptor after the toner image is transferred but before charging; A known image forming apparatus further comprising at least one selected from the group consisting of: a static eliminator that irradiates the surface of the body with light to eliminate static electricity.

The image forming apparatus according to the present embodiment includes a direct transfer type apparatus for directly transferring a toner image formed on the surface of an electrophotographic photosensitive member to a recording medium, and a toner image formed on the surface of the electrophotographic photosensitive member. Any intermediate transfer type apparatus that primarily transfers the toner image onto the surface of the intermediate transfer body and then secondarily transfers the toner image transferred onto the surface of the intermediate transfer body onto the surface of the recording medium may be used.

The configuration of the image forming apparatus according to this embodiment will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing an example of an image forming apparatus according to this embodiment. FIG. 1 is a schematic diagram showing a direct transfer type image forming apparatus. FIG. 2 is a schematic configuration diagram showing another example of the image forming apparatus according to this embodiment. FIG. 2 is a schematic diagram showing an intermediate transfer type image forming apparatus.

The image forming apparatus 200 shown in FIG. an example), a charging member cleaning member 218 that cleans the outer peripheral surface of the charging member 208, an exposure device 206 (an example of an electrostatic latent image forming device) that exposes the surface of the photoreceptor 207 to form a latent image, and a photoreceptor A developing device 211 that develops the latent image on the body 207 with a developer containing toner, a transfer device 212 that transfers the toner image on the photosensitive member 207 to the recording medium 500, and a fixing device that fixes the toner image on the recording medium 500. It includes a device 215 , a cleaning device 213 that removes toner remaining on the photoreceptor 207 , and a neutralization device 214 that neutralizes the surface of the photoreceptor 207 . The static eliminator 214 may not be provided.
Here, in the image forming apparatus 200 , a charging device is configured by the charging member 208 , the power source 209 and the charging member cleaning member 218 .

The image forming apparatus 210 shown in FIG. A primary transfer member 212a and a secondary transfer member 212b that transfer onto the medium 500, a fixing device 215, and a cleaning device 213 are provided. The image forming apparatus 210 may be provided with a neutralization device like the image forming apparatus 200 .
Here, in the image forming apparatus 210, the charging member 208, the power source 209, and the charging member cleaning member 218 constitute a charging device.

An electrostatic latent image is formed on the photosensitive member 207 by charging and exposure, and a toner image is formed by development. A well-known photoreceptor is applied to the photoreceptor 207 .

The charging member 208 is a contact charging type charging member that is formed of a roll-shaped charging member and contacts the surface of the photoreceptor 207 to charge the surface of the photoreceptor 207 . To the charging member 208 , a DC voltage alone, an AC voltage alone, or a voltage obtained by superimposing an AC voltage on a DC voltage is applied from a power source 209 . Details of the charging member 208 will be described later.

Examples of the exposure device 206 include an optical system device having a light source such as a semiconductor laser or an LED (light emitting diode).

The developing device 211 is a device that supplies toner to the photoreceptor 207 . The developing device 211 , for example, brings a roll-shaped developer holding member into contact with or close to the photoreceptor 207 to adhere toner to the latent image on the photoreceptor 207 to form a toner image.

Examples of the transfer device 212 include a corona discharge generator and a conductive roll that presses the photosensitive member 207 through the recording medium 500 .

An example of the primary transfer member 212a is a conductive roll that rotates in contact with the photoreceptor 207 . As the secondary transfer member 212b, for example, a conductive roll that presses the primary transfer member 212a through the recording medium 500 can be used.

The fixing device 215 may be, for example, a heat fixing device that includes a heating roll and a pressure roll that presses the heating roll.

Examples of the cleaning device 213 include a device including a blade, brush, roll, or the like as a cleaning member. Examples of materials for the cleaning blade include urethane rubber, neoprene rubber, and silicone rubber.

The static elimination device 214 is, for example, a device that irradiates the surface of the photoreceptor 207 after transfer with light to eliminate the residual potential of the photoreceptor 207 . The static eliminator 214 may not be provided.

FIG. 3 is a schematic diagram showing an example of the process cartridge according to this embodiment. A process cartridge 300 shown in FIG. 3 is detachable from, for example, an image forming apparatus having an exposure device, a transfer device, and a fixing device.

In the process cartridge 300 , the photosensitive member 207 , the charging member 208 , the charging member cleaning member 218 , the developing device 211 and the cleaning device 213 are integrated by the housing 301 . The housing 301 is provided with a mounting rail 302 for attaching/detaching to/from the image forming apparatus, an opening 303 for exposure, and an opening 304 for static elimination exposure.

<Charging device>
The charging device will be described below. In addition, the code|symbol is abbreviate|omitted and demonstrated.
The charging device has, for example, a charging member that charges the surface of the photoreceptor, a power source (an example of an application unit) connected to the charging member, and a charging member cleaning member that cleans the outer peripheral surface of the charging member.

In the charging device, from the viewpoint of suppressing abrasion of the photoreceptor, the charging member comprises a conductive substrate, an elastic layer provided on the conductive substrate and having a storage elastic modulus G of 5.0 MPa or less at 100 Hz, and a surface layer provided on the elastic layer, and including 2.5 kHz in a Cole-Cole plot obtained by measuring the charging member in a range from 1 MHz to 0.1 Hz by an AC impedance method. It is preferable that the resistance component Ra of the capacitive semicircle is 6.3×10 ⁴ Ω or less.

Here, the resistance component Ra is the resistance component of a capacitive semicircle including 2.5 kHz in the Cole-Cole plot obtained by measuring the charging member in the range from 1 MHz to 0.1 Hz by the AC impedance method. be. In the Cole-Cole plot obtained by measuring a charging member having a conductive substrate, an elastic layer and a surface layer, a capacitive semicircle containing 2.5 kHz is considered to originate from the elastic layer. By reducing the resistance component Ra of the capacitive semicircle derived from the elastic layer, the proportion of the voltage applied to the charging member consumed by the elastic layer of the charging member is reduced. Even if is reduced, dot-like image omissions are less likely to occur. That is, the AC voltage required to suppress the generation of dot-like image defects is reduced. Therefore, by applying a low AC voltage to the charging member to form an image, the discharge load applied to the electrophotographic photosensitive member is reduced.

Moreover, the storage elastic modulus G is the storage elastic modulus of the elastic layer at 100 Hz. The charging member in the image forming apparatus generally operates at a high rotational speed of 100 Hz or more. In other words, a low storage elastic modulus G means that the elastic layer of the charging member operating at a high rotational speed of 100 Hz or higher has a low storage elastic modulus. When the storage elastic modulus G is low, the electrophotographic photosensitive member bites into the charging member at the contact portion between the charging member and the electrophotographic photosensitive member. It is thought that the separation angle becomes steeper and the width of the minute gap becomes narrower. That is, the discharge width becomes narrow. Therefore, the discharge load applied to the electrophotographic photosensitive member is reduced.

As described above, in the charging member, by setting the storage elastic modulus G of the elastic layer to 5.0 MPa or less and the resistance component Ra of the charging member to 6.3×10 ⁴ Ω or less, discharge to the photoreceptor is achieved. It is presumed that the wear of the electrophotographic photoreceptor is easily suppressed because the load on the electrophotographic photoreceptor is reduced.

The storage elastic modulus G at 100 Hz of the elastic layer is 5.0 MPa or less, preferably 4.0 MPa or less, more preferably 3.0 MPa or less from the viewpoint of suppressing wear of the electrophotographic photoreceptor. preferable. The storage elastic modulus G is preferably 1.0 MPa or more, more preferably 1.5 MPa or more, more preferably 2.0 MPa, from the viewpoint of forming a uniform minute gap between the contact portion between the photoreceptor and the charging roll. It is more preferable that it is above. The storage elastic modulus G is preferably 1.0 MPa or more and 5.0 MPa or less, more preferably 1.5 MPa or more and 4.0 MPa or less, and even more preferably 2.0 MPa or more and 3.0 MPa or less.

The resistance component Ra of the capacitive semicircle containing 2.5 kHz in the Cole-Cole plot obtained by measuring the charging member by the AC impedance method is 6.3×10 ⁴ Ω or less. is preferably 5.0×10 ⁴ Ω or less, and more preferably 4.0×10 ⁴ Ω or less. The resistance component Ra is preferably 1.0×10 ⁴ Ω or more, more preferably 1.5×10 ⁴ Ω, from the viewpoint of suppressing deterioration of chargeability due to current flow at the contact portion between the charging roll and the photoreceptor. Ω or more is more preferable, and 2.0×10 ⁴ Ω or more is even more preferable.

Here, the storage elastic modulus G of the elastic layer is obtained as follows.
An elastic layer of 24 mm in length, 2 mm in width, and 0.5 mm in thickness was cut out from the charging member to be measured, and measured with a dynamic viscoelasticity measuring machine RHEOVIBRON (manufactured by Orientec) at a temperature of 24° C. and a distance between chucks of 20 mm. , a load of 10 gf, an amplitude of 80 μm, and an automatic sweep from a frequency of 0.1 Hz to 100 Hz.

The resistance component Ra is obtained as follows.
In the measurement by the AC impedance method, SI 1260 impedance/gain phase analyzer (manufactured by Toyo Technica Co., Ltd.) is used as a power source and ammeter, and 1296 dielectric interface (manufactured by Toyo Technica Co., Ltd.) is used as a current amplifier.
An AC voltage of 1 Vp-p with a frequency of 1 MHz to 0.1 Hz was applied to the conductive base material of the charging member to be measured for impedance as a cathode, and an aluminum plate having a width of 1.5 cm wrapped around the outer peripheral surface of the charging member as an anode. to measure the AC impedance of the charging member to be measured. Of the Cole-Cole plot graph obtained from this measurement, by fitting a capacitive semicircle containing 2.5 kHz to an RC parallel equivalent circuit, the resistance component Ra (unit: Ω) and the capacitance component Ca (Unit: F).

Methods for controlling the resistance component Ra and the storage elastic modulus G within the above ranges include, for example, a method of controlling by adjusting the blending ratio of the components contained in the elastic layer, and manufacturing conditions of the elastic layer (e.g., cross-linking conditions, etc.). ), and the like.
Specifically, for example, when the elastic layer contains an inorganic filler such as calcium carbonate, the resistance component Ra and the storage elastic modulus G may be controlled by adjusting the content of the inorganic filler. By decreasing the content of the inorganic filler, the value of the resistance component Ra tends to decrease, and the value of the storage elastic modulus G also tends to decrease.
Further, for example, when the elastic layer contains carbon black, the resistance component Ra and the storage elastic modulus G may be controlled by adjusting the carbon black content. By decreasing the content of carbon black, the value of the resistance component Ra tends to decrease, and the value of the storage elastic modulus G also tends to decrease.
Further, for example, when the elastic layer contains an epichlorohydrin-alkylene oxide copolymer rubber, the resistance component Ra may be controlled by adjusting the polymerization ratio of the copolymer rubber. By increasing the polymerization ratio of the alkylene oxide component in the copolymer rubber, the value of the resistance component Ra tends to decrease.
For example, when an elastic layer is obtained through a cross-linking reaction, the resistance component Ra may be controlled by reducing the amount of a cross-linking agent, lowering the heating temperature during cross-linking, shortening the heating time during cross-linking, or the like.

Details of the charging member will be described below.

As long as the charging member has a conductive base material, an elastic layer formed on the conductive base material, and a surface layer provided on the elastic layer, the layer structure is not particularly limited. It may also have other layers. Other layers include, for example, one or more adhesive layers provided between the conductive substrate and the elastic layer, and one or more intermediate layers provided between the elastic layer and the surface layer. The shape of the charging member according to the embodiment is not particularly limited, but a roll-shaped charging member, that is, a so-called charging roll is preferable.
Each configuration of the charging member will be mainly described.

(Conductive substrate)
The conductive substrate functions as an electrode and support for the charging member.
Examples of conductive substrates include metals or alloys such as aluminum, copper alloys, and stainless steel; iron plated with chromium, nickel, etc.; and substrates made of conductive materials such as conductive resins. Used. The conductive substrate in the present embodiment functions as an electrode and a support member of the charging roll, and is made of metals such as iron (free-cutting steel, etc.), copper, brass, stainless steel, aluminum, nickel, and the like. is mentioned. In the present embodiment, the conductive base material is a conductive rod-shaped member, and the conductive base material may be a member (for example, a resin or a ceramic member) whose outer peripheral surface is plated, or a conductive agent. A dispersed member (for example, a resin or a ceramic member) may also be used. The conductive substrate may be a hollow member (cylindrical member) or a non-hollow member.

(elastic layer)
The elastic layer includes, for example, a conductive layer containing an elastic material and a conductive agent. The elastic layer may contain inorganic fillers and other additives as needed.

The elastic layer may be a single layer or a laminated body in which a plurality of layers are laminated. The elastic layer may be a conductive foamed elastic layer, a conductive non-foamed elastic layer, or a laminate of a conductive foamed elastic layer and a conductive non-foamed elastic layer.

-Elastic material-
Examples of elastic materials include epichlorohydrin rubber, polyurethane, nitrile rubber, isoprene rubber, butadiene rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, chloroprene rubber, chlorine Examples include polyisoprene, hydrogenated polybutadiene, butyl rubber, silicone rubber, fluororubber, natural rubber, and elastic materials obtained by mixing these. Among these elastic materials, epichlorohydrin rubbers, acrylonitrile-butadiene rubbers, styrene-butadiene rubbers, chloroprene rubbers, polyurethanes, silicone rubbers, nitrile rubbers, ethylene-propylene-diene rubbers, and elastic materials in which these are mixed are preferable. .

Among these elastic materials, the elastic layer preferably contains at least epichlorohydrin rubber from the viewpoint of resistance uniformity.
The epichlorohydrin-based rubber is a polymer rubber containing at least structural units derived from epichlorohydrin (hereinafter also referred to as "epichlorohydrin component"). Epichlorohydrin-based rubbers include epichlorohydrin homopolymers and multi-copolymers (binary copolymers, terpolymers, etc.). Examples of multicomponent copolymers include epichlorohydrin-allyl glycidyl ether copolymer rubber, epichlorohydrin-alkylene oxide (ethylene oxide, propylene oxide, or both) copolymer rubber, and the like.

The elastic layer preferably contains a multi-component copolymer containing an epichlorohydrin component, and more preferably contains an epichlorohydrin-alkylene oxide copolymer rubber from the viewpoint of facilitating control of the resistance component Ra. .
The epichlorohydrin-alkylene oxide copolymer rubber may contain an epichlorohydrin component and a structural unit derived from an alkylene oxide (hereinafter also referred to as an "alkylene oxide component"), and other polymerization components. It may contain a structural unit derived from. Other polymerizable components include, for example, allyl glycidyl ether. The epichlorohydrin-alkylene oxide copolymer rubber may be an epichlorohydrin-alkylene oxide rubber consisting of an epichlorohydrin component and an alkylene oxide component, wherein the epichlorohydrin component, the alkylene oxide component and allyl glycidyl It may be an epichlorohydrin-alkylene oxide-allyl glycidyl ether rubber containing structural units derived from ether.

When the elastic layer contains epichlorohydrin-alkylene oxide copolymer rubber, the content of the alkylene oxide component with respect to the entire epichlorohydrin-alkylene oxide copolymer rubber is preferably 45% by mass or more, and 50% by mass. It is more preferably 70% by mass or more, and even more preferably 55% by mass or more and 65% by mass or less. When the content of the alkylene oxide component is within the above range, it becomes easier to control the resistance component Ra to a lower value than when the content is less than the above range. In addition, when the content of the alkylene oxide component is within the above range, it is easier to control the resistance component Ra to a lower value than when it is more than the above range, and the resistance fluctuation due to the environment (temperature and humidity) is small. There is

The ratio of the epichlorohydrin-based rubber to the entire elastic material contained in the elastic layer is preferably 80% by mass or more, more preferably 90% by mass or more, from the viewpoint of resistance uniformity. More preferably, it is 95% by mass or more.

-Conductive agent-
Examples of conductive agents include electronic conductive agents and ionic conductive agents.
Examples of electronic conductive agents include carbon black such as furnace black, thermal black, channel black, ketjen black, acetylene black, and color black; pyrolytic carbon; graphite; metals or alloys such as aluminum, copper, nickel, and stainless steel; Metal oxides such as tin, indium oxide, titanium oxide, tin oxide-antimony oxide solid solution, and tin oxide-indium oxide solid solution; substances obtained by treating the surface of an insulating material to make it conductive; powders of the like.
Ionic conductive agents include perchlorates or chlorates such as tetraethylammonium, lauryltrimethylammonium, and benzyltrialkylammonium; perchlorates or chlorates of alkali metals or alkaline earth metals such as lithium and magnesium; etc.
Conductive agents may be used singly or in combination of two or more.

Among these conductive agents, the elastic layer preferably contains at least carbon black from the viewpoint of moldability, and suppresses resistance fluctuations due to the environment (temperature and humidity) while controlling the resistance component Ra and the storage elastic modulus G. From a viewpoint, it is preferable to contain carbon black and an ion conducting agent.

The arithmetic mean particle size of carbon black is preferably 1 nm or more and 200 nm or less, more preferably 10 nm or more and 200 nm or less, and even more preferably 10 nm or more and 100 nm or less, from the viewpoint of resistance controllability and kneadability. , 30 nm or more and 70 nm or less.
The arithmetic mean particle size of carbon black is the number average particle size obtained by measuring the particle size distribution using a laser diffraction particle size distribution analyzer (for example, LS13 320 manufactured by Beckman Coulter). In the obtained particle size distribution, the cumulative distribution of the number of particles is subtracted from the small particle size side of each peak for the divided particle size range (channel), and the particle size at which the cumulative 50% of all particles in each peak is The arithmetic mean particle diameter of the corresponding particles.
The arithmetic average particle diameter of carbon black is calculated by observing the sample cut out from the elastic layer with an electron microscope, measuring the diameter (maximum diameter) of 100 conductive agents, and averaging the diameters. good too. Also, the arithmetic mean particle size may be measured using, for example, Zetasizer Nano ZS manufactured by Sysmex Corporation.

When the elastic layer contains carbon black, the content of carbon black is preferably 10 parts by mass or less with respect to 100 parts by mass of the elastic material from the viewpoint of controlling the resistance component Ra and the storage elastic modulus G within the above ranges. , 5 parts by mass or less, more preferably 3 parts by mass or less. From the standpoint of moldability, the content of carbon black is preferably 1 part by mass or more with respect to 100 parts by mass of the elastic material.
The content of carbon black is preferably 10 parts by mass or less, more preferably 1 part by mass or more and 5 parts by mass or less, and 1 part by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the elastic material. is more preferred.

From the viewpoint of maintaining image quality over a long period of time regardless of the environment, the ion conductive agent contained in the elastic layer includes quaternary ammonium salt compounds, alkali metal or alkaline earth metal salts of perchloric acid, and chloric acid. It is preferably at least one compound selected from the group consisting of alkali metal or alkaline earth metal salts, more preferably a quaternary ammonium salt compound.

When the elastic layer contains an ion-conducting agent, the content of the ion-conducting agent is preferably 0.1 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the elastic material from the viewpoint of resistance controllability and bleeding suppression. It is preferably 0.5 parts by mass or more and 3 parts by mass or less, and further preferably 1 part by mass or more and 2 parts by mass or less.
When the elastic layer contains carbon black and an ion conductive agent, the content of carbon black is preferably 0.1 to 10 times, and 0.3 to 5 times the content of the ion conductive agent. is more preferably 0.5 times or more and 2 times or less.

-Inorganic filler-
The elastic layer may contain an inorganic filler as needed. By containing an inorganic filler in the elastic layer, there is an advantage that moldability is improved.
Examples of inorganic fillers include calcium carbonate, silica, clay minerals, etc. Among them, calcium carbonate is preferable from the viewpoint of moldability and kneadability.
The content of the inorganic filler is preferably 40 parts by mass or less, and preferably 35 parts by mass or less, relative to 100 parts by mass of the elastic material, from the viewpoint of controlling the resistance component Ra and the storage elastic modulus G within the above ranges. is more preferable, and 30 parts by mass or less is even more preferable. From the viewpoint of moldability, the content of the inorganic filler is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and 15 parts by mass or more with respect to 100 parts by mass of the elastic material. It is even more preferable to have
The content of the inorganic filler is preferably 5 parts by mass or more and 40 parts by mass or less, more preferably 10 parts by mass or more and 35 parts by mass or less, and 15 parts by mass or more and 30 parts by mass with respect to 100 parts by mass of the elastic material. It is more preferably not more than parts by mass.

－Other Additives－
The elastic layer may contain other additives as needed.
Other additives blended in the elastic layer include, for example, softeners, plasticizers, curing agents, vulcanizing agents, vulcanization accelerators, vulcanization accelerator aids, antioxidants, surfactants, coupling agents, and the like. is mentioned.

-Characteristics of elastic layer-
The thickness of the elastic layer is preferably 1 mm or more and 10 mm or less, more preferably 2 mm or more and 5 mm or less.
The volume resistivity of the elastic layer is preferably 1×10 ³ Ωcm or more and 1×10 ¹⁴ Ωcm or less.
The volume resistivity of the elastic layer is a value measured by the following method.
A sheet-like measurement sample is taken from the elastic layer, and the measurement sample is measured according to JIS K 6911 (1995) with a measuring jig (R12702A/B resistivity chamber: manufactured by Advantest) and a high resistance measuring instrument (R8340A digital Using a high resistance/micro current meter: Advantest Co., Ltd.), after applying a voltage adjusted so that the electric field (applied voltage/composition sheet thickness) is 1000 V / cm for 30 seconds, from the current value, the following formula Calculated using
Volume resistivity (Ωcm) = (19.63 × applied voltage (V)) / (current value (A) × measurement sample thickness (cm))

-Formation of elastic layer-
As a method for forming the elastic layer on the conductive substrate, for example, an elastic layer-forming composition obtained by mixing an elastic material, a conductive agent, and optionally an inorganic filler and other additives, and a cylindrical are extruded together from an extruder to form a layer of the elastic layer-forming composition on the outer peripheral surface of the conductive substrate, and then the layer of the elastic layer-forming composition is heated. A method for forming an elastic layer by cross-linking with an endless belt-shaped conductive base material; for forming an elastic layer by mixing an elastic material, a conductive agent, and optionally an inorganic filler and other additives on the outer peripheral surface of an endless belt-shaped conductive base material. The composition is extruded from an extruder to form a layer of the elastic layer-forming composition on the outer peripheral surface of the conductive substrate, and then the layer of the elastic layer-forming composition is heated to undergo a cross-linking reaction to form an elastic layer. and the like; The conductive substrate may have an adhesive layer on its outer peripheral surface.

When a cross-linking reaction is performed in forming the elastic layer, in addition to the elastic material, the conductive agent, and the inorganic filler and other additives used as necessary, a cross-linking agent, a cross-linking accelerator, and a vulcanization accelerator aid may also be used. etc. may be used.
In general, types of cross-linking using a cross-linking agent include sulfur cross-linking, peroxide cross-linking, quinoid cross-linking, phenol resin cross-linking, amine cross-linking, and metal oxide cross-linking. Cross-linking with sulfur is preferred from the viewpoints of ease of application and flexibility of the cross-linked rubber.
Cross-linking accelerators include thiazole-based, thiuram-based, sulfenamide-based, thiourea-based, dithiocarbamate-based, guanidine-based, aldehyde-ammonia-based, and mixtures thereof.
As a cross-linking accelerator auxiliary agent, zinc oxide or the like may be added.
In the case of performing a cross-linking reaction in forming the elastic layer, from the viewpoint of controlling the resistance component Ra within the above range, cross-linking can be achieved by reducing the amount of the cross-linking agent, lowering the heating temperature during cross-linking, or shortening the heat time during cross-linking. Conditions may be adjusted.

(Surface layer)
Examples of the surface layer include a layer containing a binder resin. The surface layer may contain conductive particles for controlling the resistivity of the surface layer, unevenness-forming particles for controlling the unevenness of the outer peripheral surface, and other additives, if necessary.

- Binder resin -
Examples of binder resins include acrylic resins, fluorine-modified acrylic resins, silicone-modified acrylic resins, cellulose resins, polyamide resins, copolymerized nylon, polyurethane resins, polycarbonate resins, polyester resins, polyimide resins, epoxy resins, silicone resins, polyvinyl Alcohol resin, polyvinyl butyral resin, cellulose resin, polyvinyl acetal resin, ethylenetetrafluoroethylene resin, melamine resin, polyethylene resin, polyvinyl resin, polyarylate resin, polythiophene resin. Polyethylene terephthalate resin (PET), fluorine resin (polyvinylidene fluoride resin, tetrafluoroethylene resin, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), etc. ). Further, the binder resin may be obtained by curing or cross-linking a curable resin with a curing agent or a catalyst. Also, the binder resin may be an elastic material.
The binder resin may be used alone, or two or more of them may be mixed or copolymerized for use. If it is a crosslinkable resin, it may be used after being crosslinked.
Here, the copolymerized nylon is a copolymer containing one or more of 610 nylon, 11 nylon, and 12 nylon as polymer units. The copolymerized nylon may contain other polymerized units such as 6-nylon and 66-nylon.

Among these, from the viewpoint of durability, polyvinylidene fluoride resin, tetrafluoroethylene resin, and polyamide resin are preferred, and polyamide resin is more preferred as the binder resin. Polyamide resins are less prone to triboelectrification due to contact with a member to be charged (for example, an image carrier), and tend to suppress adhesion of toner and external additives.

Polyamide resins include polyamide resins described in Polyamide Resin Handbook (Osamu Fukumoto, Nikkan Kogyo Shimbun Ltd.). Among these, the polyamide resin is preferably an alcohol-soluble polyamide, more preferably an alkoxymethylated polyamide (alkoxymethylated nylon), and a methoxymethylated polyamide ( methoxymethylated nylon) is more preferred.

The number average molecular weight of the binder resin (polymer material) is preferably in the range of 1,000 to 100,000, more preferably in the range of 10,000 to 50,000.

-Conductive particles-
Examples of the conductive particles contained in the surface layer include particles having a particle size of 3 μm or less and a volume resistivity of 10 ⁹ Ωcm or less. substances, particles made of their alloys, carbon black, and the like. Among these, the conductive particles are preferably carbon black from the viewpoint of resistance controllability. The conductive particles may be used singly or in combination of two or more.

When the surface layer contains conductive particles, the content of the conductive particles is, for example, 3 parts by mass or more and 25 parts by mass or less with respect to 100 parts by mass of the binder resin. From the viewpoint of controlling the resistance value Rd obtained by measuring the member, it is preferably 5 parts by mass or more and 20 parts by mass or less, more preferably 10 parts by mass or more and 15 parts by mass or less.

- Particles for forming irregularities -
The material of the unevenness-forming particles contained in the surface layer is not particularly limited, and may be inorganic particles or organic particles.
Specific examples of the irregularity-forming particles contained in the surface layer include inorganic particles such as silica particles, alumina particles, and zircon (ZrSiO ₄ ) particles, and resin particles such as polyamide particles, fluororesin particles, and silicone resin particles. is mentioned.
Among them, the irregularity-forming particles contained in the surface layer are more preferably resin particles, and more preferably polyamide particles, from the viewpoint of dispersibility and durability.
The unevenness-forming particles may be contained singly or in combination of two or more in the surface layer.

When the surface layer contains unevenness-forming particles, unevenness is formed from the viewpoint of controlling the "ten-point average roughness Rz on the outer peripheral surface of the charging member" and the "average spacing of unevenness on the outer peripheral surface of the charging member Sm", which will be described later. As the particles for unevenness, it is preferable to contain 5 parts by mass or more and 30 parts by mass or less of unevenness-forming particles having a volume average particle diameter of 5 μm or more and 20 μm or less with respect to 100 parts by mass of the binder resin. Further, it is more preferable to contain 8 parts by mass or more and 20 parts by mass or less of unevenness-forming particles having a volume average particle diameter of 5 μm or more and 10 μm or less with respect to 100 parts by mass of the binder resin.

The method of measuring the volume average particle diameter of the unevenness-forming particles is to use a sample cut out from a layer, observe it with an electron microscope, measure the diameter (maximum diameter) of 100 particles, and calculate the volume average. do. Also, the average particle size may be measured using, for example, Zetasizer Nano ZS manufactured by Sysmex Corporation.

－Other Additives－
The surface layer may contain other additives. Other additives include well-known additives such as curing agents, vulcanizing agents, vulcanization accelerators, antioxidants, dispersants, surfactants and coupling agents.

-Characteristics of the surface layer-
The thickness of the surface layer is preferably 1 μm or more and 20 μm or less, more preferably 3 μm or more and 15 μm or less, and even more preferably 5 μm or more and 13 μm or less.
When the thickness of the surface layer is not uniform (for example, when the outer peripheral surface of the surface layer has unevenness), the above-mentioned thickness is determined by means the thickness of the part.
The volume resistivity of the surface layer is preferably 1×10 ⁵ Ωcm or more and 1×10 ⁸ Ωcm or less.

-Formation of surface layer-
The surface layer is formed by dispersing or dissolving the above components in a solvent to prepare a coating liquid, applying this coating liquid on the previously prepared elastic layer, and drying it. Examples of methods for applying the coating liquid include roll coating, blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.
Solvents used in the coating liquid are not particularly limited and common solvents are used. Examples include alcohols such as methanol, ethanol, propanol and butanol; ketones such as acetone and methyl ethyl ketone; tetrahydrofuran; Solvents such as ethers may be used.

In the case where the surface layer contains conductive particles, an immersion method is used as a method for applying the coating liquid, from the viewpoint of controlling the "resistance value Rd obtained by measuring the charging member by the DC method" described later. It is preferable to adjust the dispersion state of the conductive particles by changing the solvent volatilization speed by setting the dew point, wind speed, etc. at the time of air drying immediately after.

(adhesive layer)
The charging member according to this embodiment may have an adhesive layer between the conductive substrate and the elastic layer.
Examples of the adhesive layer interposed between the elastic layer and the conductive substrate include resin layers, and specific examples include polyolefin, acrylic resin, epoxy resin, polyurethane, nitrile rubber, chlorine rubber, vinyl chloride resin, and acetic acid. Resin layers such as vinyl resins, polyesters, phenol resins, and silicone resins can be used. The adhesive layer may contain a conductive agent (for example, the aforementioned electronic conductive agent or ionic conductive agent).

From the viewpoint of adhesion, the thickness of the adhesive layer is preferably 1 μm or more and 100 μm or less, more preferably 2 μm or more and 50 μm or less, and particularly preferably 5 μm or more and 20 μm or less.

The embodiments of the invention will be described in detail below with reference to examples, but the embodiments of the invention are not limited to these examples. In the following description, "parts" are based on mass unless otherwise specified.

<Preparation of charging member (hereinafter referred to as charging roll)>
(Charging roll 1)
-Preparation of conductive substrate-
A substrate made of SUM23L was plated with electroless nickel to a thickness of 5 μm, and then hexavalent chromic acid was applied to obtain a conductive substrate having a diameter of 8 mm.

-Formation of adhesive layer-
Next, the following mixture was mixed in a ball mill for 1 hour and then brushed to form an adhesive layer having a thickness of 10 μm on the surface of the conductive substrate.
・ Chlorinated polypropylene resin (maleic anhydride chlorinated polypropylene resin, Superchron 930, manufactured by Nippon Paper Chemicals Co., Ltd.): 100 parts ・ Epoxy resin (EP4000, manufactured by ADEKA Co., Ltd.): 10 parts ・ Conductive agent (carbon black , Ketjen Black EC, manufactured by Ketjen Black International): 2.5 parts Toluene or xylene was used to adjust the viscosity.

-Formation of elastic layer-
・Epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber (EPION301, manufactured by Osaka Soda Co., Ltd., content of ethylene oxide component 59% by mass): 100 parts by mass ・Carbon black (3030B, manufactured by Mitsubishi Chemical Corporation, arithmetic Average particle diameter 55 nm): 1 part by mass Calcium carbonate (Viscoexcel30, manufactured by Shiraishi Calcium Co., Ltd.): 30 parts by mass Ion conductive agent (BTEAC, manufactured by Lion Corporation): 1.4 parts by mass Vulcanization accelerator (Crosslinking accelerator): stearic acid (manufactured by NOF Corporation): 1 part by mass Vulcanizing agent (crosslinking agent): Sulfur (Palnoc R, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.): 1 part by mass, vulcanization Sulfurization accelerator (crosslinking acceleration aid): zinc oxide: 1.5 parts by mass The mixture having the above composition was kneaded using a tangential pressure kneader and passed through a strainer to prepare a rubber composition. The obtained rubber composition was kneaded with an open roll, and after forming a roll having a diameter of 12 mm on the surface of the prepared conductive substrate via an adhesive layer using an extruder, the roll was heated at 165° C. for 50 minutes. , to obtain a roll-shaped elastic layer. The resulting elastic layer had a thickness of 2 mm and a volume resistivity of 4×10 ⁶ Ωcm.

-Formation of surface layer-
・Binder resin: N-methoxymethylated nylon 1 (trade name: Fine Resin FR101, manufactured by Namiichi Co., Ltd.): 100 parts by mass ・Conductive agent: carbon black (volume average particle diameter: 43 nm, trade name: MONAHRCH1000, Cabot Corporation): 5 parts by mass Concavo-convex forming particles: Polyamide particles (volume average particle diameter 5 μm, trade name: Orgasol 2001UDNat1, manufactured by Arkema): 25 parts by mass distributed according to the conditions.
・Bead material: Glass ・Bead diameter: 1.3mm
・Propeller speed: 2,000 rpm
・Dispersion time: 60 minutes After the dispersion liquid obtained above was applied to the surface of the elastic layer by a dipping method, it was dried by heating at 150°C for 30 minutes to form a surface layer having a thickness of 10 µm. Obtained.

(Charging roll 2)
Charging roll 2 was obtained in the same manner as charging roll 1 except that the amount of carbon black mixed in the elastic layer was changed to 2 parts by mass, and the elastic layer was heated at 165° C. for 60 minutes.

(Charging roll 3)
Charging roll 3 was obtained in the same manner as charging roll 1 except that the amount of carbon black mixed in the elastic layer was changed to 3 parts by mass and the elastic layer was heated at 165° C. for 70 minutes.

(Charging roll 4)
A charging roll 4 was obtained in the same manner as charging roll 1 except that the amount of calcium carbonate compounded in the elastic layer was 25 parts by mass and the vulcanization conditions for the elastic layer were changed to 165° C. for 40 minutes.

(Charging roll 5)
In forming the elastic layer, 50 parts by mass of epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber (EPION301, manufactured by Osaka Soda Co., Ltd.) and epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer are used as elastic materials. Using a mixture of 50 parts by mass of rubber (CG102, manufactured by Osaka Soda Co., Ltd., content of ethylene oxide component: 37% by mass), 6 parts by mass of carbon black, and 40 parts by mass of calcium carbonate. A charging roll 5 was obtained in the same manner as charging roll 1 except that the amount of the ion conductive agent was changed to 1.6 parts by mass and the vulcanization conditions of the elastic layer were changed to 165° C. for 70 minutes.

(Charging roll 6)
A charging roll 5 was obtained in the same manner as charging roll 1 except that the amount of calcium carbonate compounded in the elastic layer was changed to 20 parts by mass and the vulcanization conditions for the elastic layer were changed to 165° C. for 30 minutes.

<Examples 1 to 5, Comparative Examples 1 to 2>
In the combination shown in Table 1, the photosensitive member and charging roll were mounted in an image forming apparatus "DocuCentre-VI C7771" manufactured by Fuji Film Business Innovation Co., Ltd.
Using this apparatus as the image forming apparatus of each example, the following evaluation was carried out. However, the following evaluation was carried out under the following conditions shown in Table 1.
・Discharge width generated between the charging member and the photoreceptor (referred to as “discharge width” in the table)
・Total amount of discharge light generated between the charging member and the electrophotographic photosensitive member (referred to as "total amount of discharge light" in the table)
・((Vpp−(2×V0))/(2×V0))×100 value (in the table) where the discharge start voltage value is V0 and the peak-to-peak voltage value of the output voltage during image formation is Vpp , written as “Vpp margin”)

<Abrasion Rate of Photoreceptor>
Using the image forming apparatus of each example, 1,000 sheets of A4 size J paper were fed and run. A superimposed voltage of a DC voltage and an AC voltage was applied to the charging roll to run the paper.
Then, the initial film thickness of the photoreceptor (that is, the film thickness before running the paper) and the film thickness after running (that is, the film thickness after running 1,000 sheets of paper) were measured. and the reduced film thickness (unit: nm/kcyc) was calculated.

<Image quality defect evaluation of white spots>
Under an environment of 10° C. temperature and 15 RH% humidity, the image forming apparatus of each example printed out one black halftone image with a density of 50% on A4 paper. Then, the output image was observed and evaluated according to the following evaluation criteria.
G0: No white spots are observed.
G1: 1 or more and 10 or less white spots with a diameter of 0.15 mm or more are observed.
G2: 11 to 30 white spots with a diameter of 0.15 mm or more are observed.
G3: 31 or more white spots with a diameter of 0.15 mm or more are observed.

From the above results, it can be seen that in the present example, as compared with the comparative example, the occurrence of white spots is suppressed as well as the abrasion of the photoreceptor.

200, 210, 220 image forming apparatus, 206 exposure device, 207 electrophotographic photoreceptor (photoreceptor), 208 charging member, 209 power supply, 211 developing device, 212 transfer device, 212a primary transfer member, 212b secondary transfer member, 213 cleaning device, 214 static elimination device, 215 fixing device, 218 charging member cleaning member, 500 recording medium

300 process cartridge, 301 housing, 302 mounting rail, 303 opening for exposure, 304 opening for static elimination exposure

Claims (12)

an electrophotographic photoreceptor;
a charging device having a charging member that contacts and charges the surface of the electrophotographic photosensitive member;
an electrostatic latent image forming device for forming an electrostatic latent image on the surface of the charged electrophotographic photosensitive member;
a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image;
a transfer device for transferring the toner image onto a surface of a recording medium;
with
An image forming apparatus, wherein a discharge width generated between the charging member and the electrophotographic photosensitive member is 0.5 mm or more and 0.6 mm or less. 2. The image forming apparatus according to claim 1, wherein said discharge width is 0.5 mm or more and 0.55 mm or less. 3. The image forming apparatus according to claim 1, wherein a total amount of discharge light generated between the charging member and the electrophotographic photosensitive member is 25 mV or more and 30 mV or less. 4. The image forming apparatus according to claim 3, wherein the total amount of discharge light is 28 mV or more and 30 mV or less. The charging device has an applying unit that applies a superimposed voltage obtained by superimposing a DC voltage and an AC voltage to the charging member,
Assuming that the discharge start voltage value is V0 and the peak-to-peak voltage value of the output voltage during image formation is Vpp, ((Vpp−(2×V0))/(2×V0))×100≧ 5. The image forming apparatus according to any one of claims 1 to 4, wherein the superimposed voltage is applied to the charging member so as to satisfy 30. The charging member includes a conductive substrate, an elastic layer provided on the conductive substrate and having a storage elastic modulus G of 5.0 MPa or less at 100 Hz, and a surface layer provided on the elastic layer; and in the Cole-Cole plot obtained by measuring the charging member in the range from 1 MHz to 0.1 Hz by the AC impedance method, the resistance component Ra of the capacitive semicircle containing 2.5 kHz is 6.3 The image forming apparatus according to any one of claims 1 to 5, wherein the resistance is ×10 ⁴ Ω or less. 7. The image forming apparatus according to claim 6, wherein the elastic layer of the charging member has a storage elastic modulus G of 3.0 MPa or less at 100 Hz. 8. The image forming apparatus according to claim 6, wherein the elastic layer contains an elastic material containing epichlorohydrin-alkylene oxide copolymer rubber, carbon black, and an inorganic filler. 9. The image forming apparatus according to claim 8, wherein the content of said carbon black is 3 parts by mass or less with respect to 100 parts by mass of said elastic material. 10. The image forming apparatus according to claim 8, wherein the content of said inorganic filler is 30 parts by mass or less with respect to 100 parts by mass of said elastic material. The image formation according to any one of claims 8 to 10, wherein the content of structural units derived from alkylene oxide is 55% by mass or more with respect to the epichlorohydrin-alkylene oxide copolymer rubber as a whole. Device. an electrophotographic photoreceptor;
a charging device having a charging member that contacts and charges the surface of the electrophotographic photosensitive member, the charging member having a width of discharge between the electrophotographic photosensitive member and the electrophotographic photosensitive member of 0.5 mm or more and 0.6 mm or less;
and a process cartridge detachable from the image forming apparatus.

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