JPH11316487A - Electrifying member, electrifying device, process cartridge and intermediate transfer body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the peeling in a contact electrifying member using a water- based resin as a material for a surface layer, even when the member is left in a high-temperature high-humidity environment and to obtain stable electrification capability in the use under a high-humidity environment. SOLUTION: An electrifying roller 10 as an electrifying member, on a conductive supporting body 11 serving also as a feeder electrode, is formed by providing an elastic layer 12, a resistance control layer 13 and a surface layer 14 successively. The surface layer 14 is formed by the use of a dispersion of a water-based fluorocarbon resin adding carbon, a vinylidene emulsion and a butyral resin, through dipping and air-drying. The weight change rate (water absorption) of the material due to absorption of water accompanied with the environmental change from 23 deg.C air temperature and 50% relative humidity to 40 deg.C temperature and 95% relative humidity is made to less than or equal to 3%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine or a printer.
The present invention relates to a charging member, a charging device, a process cartridge, and an intermediate transfer member that perform charging by being brought into contact with an electrophotographic photosensitive member as a member to be charged.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, as a charging device for performing a primary charging process of a photosensitive member as an image carrier, a high voltage is applied to a wire to generate a corona discharge, and the corona is applied to the wire. Corona chargers that expose a member to be charged have been widely used.

In recent years, the development of a contact charging type charging device, that is, a charging device in which a charging member is arranged in contact with a member to be charged and a voltage is applied thereto to charge the surface of the member to be charged has been developed. Contact charging is advantageous in that, compared to non-contact type corona charging, the applied voltage required to obtain a desired potential on the charged body surface is low, and the amount of ozone generated during charging is small. In particular, a conductive roller is used as a charging member, and an AC having a DC voltage equal to the potential on the surface of a desired charged body and a peak-to-peak voltage of twice or more the discharge start voltage.
An AC contact charging method in which a voltage is superimposed and applied is preferable in terms of charging stability, and is widely used.

FIGS. 13 and 1 show an example of a charging roller as a charging member in a conventional electrophotographic image forming apparatus.
It is shown in FIG.

The charging member 1 comprises a conductive shaft 2 also serving as a power supply electrode, an elastic layer 3, a resistance adjusting layer 4, and a surface layer 5. Examples of the resin for the elastic layer 3 include solid rubber such as styrene-butadiene rubber (SBR), isoprene rubber, and silicone rubber. By dispersing a conductive agent such as carbon black or metal powder in these resins, It has conductivity.

[0006] The resistance adjusting layer 4 is a layer provided for imparting an appropriate resistance to the charging member 1. Examples of the material include acrylic resin, hydrin rubber, urethane, and silicone rubber. By dispersing an appropriate amount of a conductive agent such as metal powder, appropriate conductivity can be imparted.

The surface layer 5 is provided to ensure the surface properties of the charging member 1 and to prevent contamination of the surface of the photoconductor by the material of the resistance adjusting layer 4. Examples of the material include an acrylic resin, a nylon-based synthetic resin material such as N-methoxymethylated nylon, and an acrylic modified urethane.

At this time, the surface layer 5 must not disturb the resistance imparted evenly by the resistance adjusting layer 4, but if the surface layer 5 is made conductive, pinholes or the like may be formed on the surface of the photoreceptor. When a low-resistance portion is generated, a leak is likely to occur, so that the resistance adjustment layer 4 needs to have the same level of resistance. That is, the surface layer 5 must be a uniform material with no resistance unevenness, and have good dispersibility of the conductive agent.

The purpose of ensuring the surface properties of the charging member by the surface layer 5 is to prevent resistance unevenness caused by contamination of the charging member due to durability. Therefore, for the purpose of lowering the surface energy of the surface layer 5, it has been studied to disperse a material containing fluorine (for example, ethylene tetrafluoride powder) in the material of the surface layer 5.

In order to satisfy these severe conditions and obtain a surface layer 5 having good surface properties and no resistance unevenness, at present,
A layer of a coating material in which a material resin, a conductive agent, a material containing fluorine, and the like are dispersed in an organic solvent is formed on the resistance adjusting layer 4.
The surface layer 5 is obtained by air drying at a low temperature of about 20 ° C. or less.

It is known that when such a material is dried at a high temperature of 120 ° C. or more, wrinkles and cracks are formed on the surface, and the surface property is impaired. In addition, when drying is performed at a high temperature, the base layer and the like are deformed by the heat, and the surface property may be impaired.

Further, in recent years, a charging member using an aqueous resin as a material of the resistance adjusting layer 4 and the surface layer 5 instead of a conventional organic solvent-soluble resin has been devised. This is because when an organic solvent-soluble resin is used when forming the resistance adjusting layer 4 on the elastic layer 3, the organic solvent swells the elastic layer 3 as a foam body, and impairs the surface smoothness. This is to prevent it.

The use of an aqueous resin eliminates the need for organic solvent management, has advantages in terms of cost, and has advantages such as easy management and handling.

[0014]

However, when a water-based material is used, the charging member 1 sticks to the image carrier in a high temperature and high humidity environment when the charging member 1 is actually used. When the image carrier is driven, the surface layer 5
May occur (hereinafter referred to as peeling) and a phenomenon in which an appropriate charging ability may not be obtained due to fluctuations in the resistance characteristics of the charging member due to the use environment (hereinafter referred to as "environmental fluctuation"). I know it.

The following mechanism is considered as a cause of peeling.

Since the material of the surface layer 5 is water-based, in a high temperature and high humidity environment, the material of the surface layer 5 absorbs moisture and adheres to the image carrier side, so that the surface layer 5 of the charging member 1 and the surface of the image carrier are separated. Sticking occurs between them.

In particular, when dew condensation occurs on the surface of the charging member 1 and the image carrier and the dew surfaces contact each other, moisture is trapped in the contact nip portion between the charging member 1 and the image carrier, and It has been found that the adhesion between the image carrier and the surface layer 5 of the charging member 1 becomes particularly large because the image carrier is easily welded.

When the adhesive force exceeds the adhesive force between the surface layer 5 and the resistance adjusting layer 4, the adhered portion of the surface layer 5 is peeled off from the resistance adjusting layer 4 and remains on the image carrier.

When peeling occurs, the charging member 1
In the portion where the material of the surface layer 5 adheres to the surface of the image carrier,
The toner image cannot be satisfactorily formed, and appears as an abnormal image.

Further, since the resistance of the charging member 1 is different from that of the other portions in the portion where the surface layer 5 has been peeled off on the charging member 1, uneven charging occurs and appears as an abnormal image.

Further, since the surface layer 5 is lost, a portion where the resistance adjusting layer 4 is exposed is formed. If the portion is left in contact with the image carrier, the surface of the image carrier is further contaminated. May be

The following mechanism is considered for environmental change.

It is known that when the surface layer 5 absorbs moisture in a high-humidity environment, the resistance of the entire charging member decreases because the moisture has low resistance. Therefore, the amount of current flowing when the same voltage is applied increases in a high humidity environment.

The moisture absorption of the surface layer 5 also affects the water absorption of the underlying resistance adjusting layer 4. Since the moisture that has passed through the surface layer 5 is further absorbed by the resistance adjusting layer 4, the resistance of the charging member is greatly affected by the water absorption of the surface layer 5.

At this time, when the power supply for charging is controlled at a constant current, the voltage applied to the charging member is reduced even if the power supply is controlled with the same amount of current. In addition, even in the case of the constant voltage control, a current larger than usual must be supplied, so that the power of the power supply is insufficient, and the voltage applied to the charging member may be reduced as a result.

As described above, when the voltage applied to the charging member is reduced, a voltage required for charging cannot be obtained, resulting in poor charging and an abnormal image.

In particular, in the case of the AC contact charging system, by setting the AC peak-to-peak voltage to twice or more of the discharge starting voltage, a destructive discharge is generated between the charging member and the image carrier, thereby stably charging. As the AC voltage decreases, the peak-to-peak voltage of AC becomes 2 times of the discharge starting voltage.
It is known that the charging state is not stable, the charging state becomes unstable, and charging failure occurs. At this time, the image has a phenomenon that a black spot in the form of a sand on a white background or a halftone occurs throughout the image (hereinafter referred to as “sand”). In an extreme case, no charging is performed, and the entire image is stained black. It will be.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a contact charging member using an aqueous resin as a material of a surface layer when the contact charging member is left in a high temperature and high humidity environment. Also, no peeling occurs, and even when used in a high-humidity environment, a charging member, a charging device and a process cartridge capable of obtaining a stable charging ability,
Another object of the present invention is to provide an intermediate transfer member having similar characteristics.

[0029]

The above object is achieved by a charging member, a charging device, a process cartridge and an intermediate transfer member according to the present invention. In summary, the present invention has at least a base layer and a surface layer on a conductive support, which contacts a member to be charged and charges the member to be charged by applying a voltage between the member and the member to be charged. In a charging member having a plurality of structures of two or more layers, the surface layer is formed by air-drying a dispersion of an aqueous resin, and the material forming the surface layer has a temperature of 23 ° C. and a relative humidity of 50% to a temperature of 40 ° C. A charging member characterized in that a weight change rate due to water absorption accompanying an environmental change to a humidity of 95% is 3.0% or less. According to the present invention, the surface layer is made of a material containing at least a fluororesin. The charging member has a roller shape. Alternatively, the charging member has a blade shape.

Further, the present invention is a charging device for an image forming apparatus, wherein the charging member described above is incorporated.
Further, there is provided a process cartridge of an image forming apparatus incorporating the charging member described above. Further, in an intermediate transfer member in an image forming apparatus of an intermediate transfer system, the intermediate transfer member has a plurality of structures of two or more layers having at least a base layer and a surface layer on a conductive support, and the surface layer has an aqueous system. A material formed by air drying of a resin dispersion and forming the surface layer has a temperature of 23 ° C. and a relative humidity of 50% to a temperature of 40 ° C. and a relative humidity of 95%.
% By weight due to water absorption due to environmental change to 3.0%
% Or less. The surface layer is made of a material containing at least a fluororesin.

[0031]

Embodiments of the present invention will be described below in more detail with reference to the drawings.

Embodiment 1 FIG. 1 is a sectional view showing a charging member according to an embodiment of the present invention. In this embodiment, the charging member 10 has a roller shape, that is, a charging roller.

In FIG. 1, reference numeral 11 denotes a shaft-shaped conductive support made of metal or plastic which also serves as a power supply electrode. The charging roller 10 sequentially has an elastic layer 12, a resistance adjustment layer 13, and a surface layer 14 on a conductive support 11,
It has an outer diameter of about 14 mm.

In this embodiment, urethane foam is used as the elastic layer 12. A metal oxide is added to the foam as a conductive agent for imparting conductivity.

The resistance adjusting layer 13 is formed by adding carbon to a dispersion of an aqueous acrylic resin and a butyral resin,
Stir and disperse, about 300μ by dipping
m and dried in an environment at a temperature of 100 ° C. for 5 to 6 hours.

As the surface layer 14, a dispersion of a water-based fluororesin to which carbon is added, a vinylidene emulsion and a butyral resin is formed to a thickness of about 10 μm by dipping. Furthermore, temperature 1
Drying is carried out by leaving it in an environment of 00 ° C. for 5 to 6 hours.

FIG. 2 shows the charging roller 10 in this embodiment.
Shows the water absorption of the material of the surface layer 14 of FIG.

Here, the water absorption indicates the rate of change in weight when a single material is brought from an environment at a temperature of 23 ° C. and a relative humidity of 50% to an environment at a temperature of 40 ° C. and a relative humidity of 95%.
A higher water absorption indicates that the material absorbs moisture.

As shown in FIG. 2, the water absorption of the surface layer 14 starts to increase immediately after standing, and reaches a saturated state in about 5 to 20 hours. According to FIG. 2, the water absorption of the surface layer 14 is about 2.3% at the time of saturation.

FIG. 3 is a sectional view showing a photosensitive drum as an image carrier in the present embodiment.

The photosensitive drum 40 has an undercoat layer 42 on an aluminum cylinder 41 having a diameter of 30 mm, a charge generation layer 43 on the undercoat layer, and a charge transport using bisphenol Z type polycarbonate resin as a resin on the charge generation layer. Layer 4
And 4 having an organic photoreceptor layer.

The charging roller 10 is connected to the photosensitive drum 40
Then, as shown in FIG. 4, a load was applied to both ends of the charging roller 10 by a spring 52 using a charging roller terminal 51. At this time, the load of the charging roller terminal 51 on one side is 700
g weight, and a total load of 1400 g weight was applied to the charging roller 10.

As described above, when the charging roller 10 is in contact with the photosensitive drum 40, the temperature is 40 ° C. and the relative humidity is 95%.
After leaving in the environment for one month, no peeling occurred and no particular problem occurred on the image.

Further, when the charging roller 10 and the photosensitive drum 40 are dew-condensed and the dew surfaces are in contact with each other, the charging roller 10 and the photosensitive drum 40 are left in an environment of 32.5 ° C. and 80% relative humidity for 2 weeks. Surface layer 14 of roller 10
And the photosensitive drum 40 were in close contact with each other, but could be easily peeled off, and no peeling occurred.

The relationship between the current flowing through the charging roller and the voltage between the AC peaks applied to the charging roller when the charging roller is incorporated in an image forming apparatus is shown as follows: temperature 23 ° C., relative humidity 50%, and temperature 32.5. The measurement was performed in two environments at 80 ° C. and a relative humidity of 80%. The result is shown in FIG.

The image forming apparatus of this embodiment performs a constant current control of 900 μA. Therefore, the voltage between AC peaks in an environment with a temperature of 23 ° C. and a relative humidity of 50% is 2.0 k.
V, and the AC peak-to-peak voltage in an environment where the temperature is 32.5 ° C. and the relative humidity is 80% is 1.8 kV. In this example,
The discharge starting voltage is about 750V. According to this, even in an environment with a temperature of 32.5 ° C. and a relative humidity of 80%, the AC peak-to-peak voltage exceeds 1.5 kV, which is twice the discharge starting voltage, so that image abnormality such as sandy ground does not appear.

Actually, the charging roller was heated at a temperature of 32.5 ° C.
In an environment with a relative humidity of 80%, incorporated into the image forming apparatus,
When the image was output, the state of the image was good.

Example 2 In Example 1, the amount of butyral resin in the material of the surface layer 14 was increased by 1.25 times while keeping the material of the resistance adjusting layer 13 and the drying conditions unchanged.

FIG. 6 shows the transition of the water absorption of the charging roller 10 at this time. As shown in FIG. 6, the water absorption is about 3.0% at the time of saturation.

The charging roller 10 is brought into contact with the photosensitive drum 40 in the same manner as in the first embodiment.
When left in the environment for one month, the charging roller 10 and the photosensitive drum 40 came into close contact with each other, and although there was resistance when the photosensitive drum 40 was turned by hand, it was relatively easy to turn by hand, and peeling occurred. I didn't.

Further, the charging roller 10 and the photosensitive drum 40 are dew-condensed, and the dew surface is brought into contact with the condensing roller. Then, the charging roller 10 is left in an environment of a temperature of 32.5 ° C. and a relative humidity of 80% for 2 weeks. Although peeling occurred at a very small portion at the end in the longitudinal direction, no problem occurred on the image because it was outside the image area.

The relationship between the current flowing through the charging roller and the voltage between the AC peaks applied to the charging roller when the charging roller is incorporated in an image forming apparatus is shown as follows: temperature 23 ° C., relative humidity 50%, and temperature 32.5. The measurement was performed in two environments at 80 ° C. and a relative humidity of 80%. FIG. 7 shows the result.

The image forming apparatus of this embodiment performs a constant current control of 900 μA. Therefore, the voltage between AC peaks in an environment with a temperature of 23 ° C. and a relative humidity of 50% is 2.0 k.
V, and the AC peak-to-peak voltage in an environment with a temperature of 32.5 ° C. and a relative humidity of 80% is 1.6 kV. In this example,
The discharge starting voltage is about 750V. According to this, even in an environment with a temperature of 32.5 ° C. and a relative humidity of 80%, the AC peak-to-peak voltage exceeds 1.5 kV, which is twice the discharge starting voltage, so that image abnormality such as sandy ground does not appear.

Actually, the charging roller was heated at a temperature of 32.5 ° C.
In an environment with a relative humidity of 80%, incorporated into the image forming apparatus,
When the image was output, the state of the image was good.

Comparative Example 1 In this comparative example, the amount of butyral resin in the material of the surface layer 14 of the charging member 10 used in Example 1 was set to 1.5.
The same charging roller as in Example 1 was used except that the charging roller was doubled.

FIG. 8 shows the charging roller 10 in this comparative example.
3 shows the transition of the water absorption of the material of the surface layer 14 of FIG. According to FIG. 8, the water absorption of the material of the charging roller surface layer 14 in this comparative example is about 3.2% when saturated.

The charging roller 10 of Comparative Example 1 was brought into contact with the photosensitive drum 40 in the same manner as in Example 1, and was left for one month in an environment at a temperature of 40 ° C. and a relative humidity of 95%. It was difficult to rotate the photosensitive drum 40 by hand, but when the photosensitive drum 40 was forcibly rotated,
No peeling had occurred.

Further, the charging roller 10 and the photosensitive drum 40 are dew-condensed, and the dew surface is brought into contact with the condensing roller. Then, the charging roller 10 is left in an environment of a temperature of 32.5 ° C. and a relative humidity of 80% for 2 weeks. When the photosensitive drum was forcibly rotated, peeling occurred in the image area at the end in the longitudinal direction. When this charging roller was installed in an image forming apparatus and an image was output, a portion where peeling occurred appeared as an image defect.

The relationship between the current value flowing through the charging roller and the voltage between the AC peaks applied to the charging roller when the charging roller is incorporated in an image forming apparatus is as follows: temperature 23 ° C .; 5 ℃, relative humidity 80% 2
Measured in one environment. FIG. 9 shows the result.

The image forming apparatus of this embodiment performs a constant current control of 900 μA. Therefore, the voltage between AC peaks in an environment with a temperature of 23 ° C. and a relative humidity of 50% is 2.0 k.
V, and the AC peak-to-peak voltage in an environment where the temperature is 32.5 ° C. and the relative humidity is 80% is 1.5 kV. In this example,
The discharge starting voltage is about 750V. According to this, even in an environment with a temperature of 32.5 ° C. and a relative humidity of 80%, the AC peak-to-peak voltage is almost the same as 1.5 kV, which is twice the discharge starting voltage.

When this charging roller was incorporated in an image forming apparatus in an environment of a temperature of 32.5 ° C. and a relative humidity of 80%, and an image was output, a little sand was generated. This is because, while the charging roller as a whole is leveled, an AC peak-to-peak voltage of 1.5 kV is obtained, but the AC peak-to-peak voltage is locally reduced to 1.5 kV due to uneven resistance in the circumferential and longitudinal directions of the charging roller. This is because a lower portion has occurred.

Comparative Example 2 In this comparative example, a cross-linking agent was blended into the material of the surface layer 14 of the charging roller 10 of the example. As a crosslinking agent,
Bifunctional diisocyanates were used. Others were the same as Example 2.

FIG. 10 shows the charging roller 1 in this comparative example.
The transition of the water absorption of the material of the surface layer 14 of 0 is shown. According to FIG. 10, the water absorption of the material of the charging roller surface layer 14 in this comparative example is about 4.0% when saturated.

The charging roller 10 of Comparative Example 1 was brought into contact with the photosensitive drum 40 in the same manner as in Example 1 and left for one month in an environment at a temperature of 40 ° C. and a relative humidity of 95%. Since the photosensitive drum 40 was in close contact with the photosensitive drum 40 and could not be rotated by hand, the photosensitive drum and the charging roller were directly installed in the image forming apparatus and rotated forcibly. As a result, peeling occurred in a straight line in the longitudinal direction.

The condensation test in Comparative Example 2 was omitted because peeling had already occurred.

The relationship between the value of the current flowing through the charging roller and the voltage between the AC peaks applied to the charging roller when the charging roller was incorporated in the image forming apparatus was determined as follows: temperature 23 ° C., relative humidity 50%, temperature 32. 5 ℃, relative humidity 80% 2
Measured in one environment. The result is shown in FIG.

At this time, the AC peak-to-peak voltage in an environment where the temperature is 23 ° C. and the relative humidity is 50% is 2.0 kV,
The AC peak-to-peak voltage in an environment of 2.5 ° C. and a relative humidity of 80% is 1.4 kV. Further, in this example, the discharge starting voltage is about 750V. According to this, even in an environment of a temperature of 32.5 ° C. and a relative humidity of 80%, the AC peak-to-peak voltage is lower than 1.5 kV which is twice the discharge start voltage.

When this charging roller was incorporated in an image forming apparatus in an environment of a temperature of 32.5 ° C. and a relative humidity of 80%, and an image was output, sand was formed on the entire image. This is because the resistance is too low over the entire circumference of the charging roller and a sufficient A
This is because the voltage between C peaks has not been obtained.

The results from Example 1 to Comparative Example 2 are summarized in the following table.

[0070]

[Table 1] From these results, it is understood that if the water absorption of the surface layer 14 is within 3.0%, a charging roller having no practical problem can be formed.

Embodiment 3 This embodiment is characterized in that a blade-shaped member is used as a charging member with the same material configuration as in Embodiment 1.

As shown in FIG. 12, a blade-shaped member
That is, the charging blade 100 includes a conductive support 101 made of metal or plastic, also serving as a power supply electrode, a base material 102 of urethane foam, a resistance adjusting layer 103, and a surface layer 104. Resistance adjustment layer 103, surface layer 10
The material, forming conditions, and the like of No. 4 are the same as those of the resistance adjusting layer 13 and the surface layer 14 of the charging roller 10 in the first embodiment.

The charging blade 100 is fixed by a fixing member (not shown) at both ends in the longitudinal direction of the support 101 in the same direction as the longitudinal direction of the photosensitive drum 100. Nip width and contact pressure are obtained. The charging blade 100 has a linear pressure of 4
The position was adjusted and fixed so as to be 3 g weight / cm.

The charging blade 100 was kept in contact with the photosensitive drum 40 at a temperature of 40 ° C.
When left in an environment with a relative humidity of 95% for one month, no close contact occurred between the charging blade 100 and the photosensitive drum 40, and no abnormality occurred on the image.

Further, both the charging blade 100 and the photosensitive drum 40 are dew-condensed, and the dew surface is brought into contact with the condensing blade. Blade 100 and photosensitive drum 40
Although slight adhesion occurred between the two, no peeling occurred and there was no particular abnormality on the image.

Further, when the charging blade 100 is incorporated into an image forming apparatus,
When the relationship between the AC peak voltages applied to the charging blade was measured in two environments of a temperature of 23 ° C., a relative humidity of 50%, and a temperature of 32.5 ° C. and a relative humidity of 80%, the same characteristics as in Example 1 were obtained. Was. In the constant current control of 900 μA, the AC peak-to-peak voltage exceeds 1.5 kV, which is twice the discharge starting voltage, even in an environment with a temperature of 32.5 ° C. and a relative humidity of 80%.

Actually, when the charging blade 100 was incorporated in an image forming apparatus and an image was output in an environment of a temperature of 32.5 ° C. and a relative humidity of 80%, the image state was good.

Embodiment 4 In this embodiment, a charging member according to the present invention is provided by using a photosensitive drum,
It is characterized in that it is configured as a process cartridge of an image forming apparatus, which is incorporated in an integral housing together with functional components such as a cleaning device and a developing device.

FIG. 13 shows a process cartridge 110 in this embodiment. As the charging member in this embodiment, the same charging roller 10 as in the first embodiment was used. The configuration of the photosensitive drum 40 as an image carrier is also the same as in the first embodiment.

The developing device 111 includes a developing sleeve 112,
It is composed of a developing blade 113. Developing sleeve 11
The toner 114 held on the developing blade 113
Is regulated to a certain thickness. Developing sleeve 112
Is applied with a power supply (not shown), and the toner on the developing sleeve 112 flies toward the photosensitive drum 40, and selectively and electrostatically adheres to the electrostatic latent image formed on the photosensitive drum 40. As a result, a toner image is formed.

The cleaning device 115 comprises a cleaning blade 116 and a waste toner container 117. The residual toner that is not transferred after the image formation is scraped off by the cleaning blade 116 of the cleaning device 115 and collected in the waste toner container 117.

The photosensitive drum 40 and the charging member 10 are assembled together with the developing device 111 and the cleaning device 115 in an integrated housing 118, and are configured as a process cartridge that is detachably attached to an image forming apparatus (not shown).

In the process cartridge 110,
As in the case of the first embodiment, the charging roller 10 receives a load of a total pressure of 1400 g at both ends by the charging roller terminal 51 and the spring 52.

When the process cartridge 110 is set
When left for one month in an environment of 0 ° C. and a relative humidity of 95%, no close contact occurred between the photosensitive drum 40 and the charging roller 10,
No abnormalities occurred on the image.

Further, the charging roller 10 and the photosensitive drum 40 were dew-condensed, and left in an environment of a temperature of 32.5 ° C. and a relative humidity of 80% for two weeks in a state where the dew surfaces were in contact with each other. Although slight adhesion was observed between the photosensitive drum 40 and the photosensitive drum 40, no peeling occurred and no particular abnormality occurred on the image.

The relationship between the current flowing through the charging roller and the voltage between the AC peaks applied to the charging roller when this process cartridge was incorporated in the image forming apparatus was determined as follows: temperature 23 ° C., relative humidity 50%, temperature 32.degree. When measured in two environments of 5 ° C. and a relative humidity of 80%, the same characteristics as in Example 1 were obtained. In the constant current control of 900 μA, the AC peak-to-peak voltage exceeds 1.5 kV, which is twice the discharge starting voltage, even in an environment with a temperature of 32.5 ° C. and a relative humidity of 80%.

Actually, this process cartridge was incorporated in an image forming apparatus, and the temperature was 32.5 ° C. and the relative humidity was 80%.
The image was output in the environment, but the state of the image was good.

In each of the above embodiments, the primary charging member for applying a uniform potential to the photosensitive drum before exposure is described as the charging member. However, the present invention is not limited to this. The present invention can be applied to a transfer charging member used to transfer the toner image formed thereon by applying a charge to the transfer material. Also, the shape can be various shapes such as a roller shape, a belt shape, and a blade shape.

Further, before transferring the toner image of each color formed on the photoreceptor to the intermediate transfer member used in the intermediate transfer type color image forming apparatus, the toner image of each color is transferred onto the intermediate transfer member. The present invention can also be applied to an intermediate transfer member that is used to transfer the toner image of each color onto the transfer material and temporarily carry the toner image on the transfer material. The shape of the intermediate transfer member may be various shapes such as a drum shape and a belt shape.

[0090]

As described above, according to the present invention,
By applying a voltage between the member and the member to be charged in contact with the member to be charged, a surface layer of the charging member having a plurality of structures for charging the member to be charged is formed by air-drying a dispersion of an aqueous resin, and Temperature 23 of the material forming the surface layer
Since the weight change rate (water absorption rate) due to water absorption due to environmental changes from 50 ° C. and 50% relative humidity to 40 ° C. and 95% relative humidity was 3.0% or less, the charging member was brought into a high-temperature and high-humidity environment. In this case, the adhesion between the surface layer and the member to be charged is kept relatively small, and peeling of the surface layer can be prevented. It became possible to perform charging. Also,
When the dispersion of the water-based resin forming the surface layer contains a fluororesin, the surface properties of the charging member can be improved and excellent durability can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a charging roller according to a first embodiment of the present invention.

FIG. 2 is a graph showing changes in the water absorption of the surface layer of the charging roller according to the first embodiment of the present invention.

FIG. 3 is a sectional view showing a photosensitive drum.

FIG. 4 is a diagram illustrating a contact state between a charging roller and a photosensitive drum.

FIG. 5 is a graph showing a relationship between a current value applied to a charging roller and an AC peak-to-peak voltage in the first embodiment of the present invention.

FIG. 6 is a graph showing a change in water absorption of a surface layer of a charging roller according to a second embodiment of the present invention.

FIG. 7 is a graph showing a relationship between a current value applied to a charging roller and an AC peak-to-peak voltage in a second embodiment of the present invention.

FIG. 8 is a graph showing a change in water absorption of the surface layer of the charging roller in Comparative Example 1 of the present invention.

FIG. 9 is a graph showing a relationship between a current value applied to a charging roller and an AC peak-to-peak voltage in Comparative Example 1 of the present invention.

FIG. 10 is a graph showing a change in water absorption of a surface layer of a charging roller in Comparative Example 2 of the present invention.

FIG. 11 is a graph showing a relationship between a current value applied to a charging roller and an AC peak-to-peak voltage in Comparative Example 2 of the present invention.

FIG. 12 is a sectional view showing a charging blade according to a third embodiment of the present invention.

FIG. 13 is a sectional view illustrating a process cartridge according to a fourth embodiment of the present invention.

FIG. 14 is a sectional view showing a conventional charging roller.

FIG. 15 is a perspective view showing a conventional charging roller.

DESCRIPTION OF SYMBOLS 10 Charging roller 11 Support shaft 12 Elastic layer 13 Resistance adjustment layer 14 Surface layer 40 Photosensitive drum 100 Charging blade 103 Resistance adjustment layer 104 Surface layer 110 Process cartridge

Continued on the front page. (72) Inventor Ken Sunahara 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc.

Claims (8)

[Claims] 1. A layer comprising at least two layers having at least a base layer and a surface layer on a conductive support, wherein the layer is charged by applying a voltage between the layer and a member to be charged in contact with the member to be charged. Wherein the surface layer is formed by air-drying a dispersion of an aqueous resin, and the material forming the surface layer has an air temperature of 23 ° C. and a relative humidity of 50.
A charging member, wherein a weight change rate due to water absorption due to an environmental change from% to an ambient temperature of 40 ° C. and a relative humidity of 95% is 3.0% or less. 2. The charging member according to claim 1, wherein said surface layer is made of a material containing at least a fluororesin. 3. The charging member according to claim 1, wherein said charging member has a roller shape. 4. The charging member according to claim 1, wherein the charging member has a blade shape. 5. A charging device for an image forming apparatus, wherein the charging member according to claim 1 is incorporated therein. 6. A process cartridge for an image forming apparatus, wherein the charging member according to claim 1 is incorporated therein. 7. An intermediate transfer member in an intermediate transfer type image forming apparatus, wherein the intermediate transfer member has a plurality of two or more structures having at least a base layer and a surface layer on a conductive support. Is formed by air-drying of a dispersion of an aqueous resin, and the temperature of the material forming the surface layer is 23 ° C. and the relative humidity is 50% to 40 ° C.
An intermediate transfer member, wherein a weight change rate due to water absorption due to an environmental change to a relative humidity of 95% is 3.0% or less. 8. The intermediate transfer member according to claim 7, wherein said surface layer is made of a material containing at least a fluororesin.