JPH0619277A - Contact electrifying member, contact electrifier, and process cartridge - Google Patents

Abstract

PURPOSE:To effectively eliminate the problem of the generation of an electrifying noise on contact electrification, without having the different inconvenience of electrification uneveness, the degradation of an image, the rising of cost, etc. CONSTITUTION:A contact electrifying member 2 is for a contact electrifier executing electrification in such a manner that the electrifying member 2 is abutted on a body to be electrified 1, and composed of, at least, a supporting member 2a, an electrifying layer 2c being in contact with the body to be electrified 1, direct, or via other layers, and an inside foamed member 2b on the side opposite to the side of the body to be electrified 1 of the electrifying layer 2c, as a characteristic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact charging member, a contact charging device, and a process cartridge of an image forming apparatus using them.

[0002]

2. Description of the Related Art For convenience, an image forming apparatus such as an electrophotographic apparatus (copier, printer, etc.), electrostatic recording apparatus, etc. will be described as an example.

In an image forming apparatus such as an electrophotographic apparatus,
Conventionally, a corona discharger which is a non-contact charging system has been mainly used as a means for charging (including discharging) an image carrier such as an electrophotographic photoreceptor or an electrostatic recording dielectric.

Although the corona discharger has an advantage of being uniformly charged, it requires an expensive high-voltage power source, requires a space such as itself and a shield space for the high-voltage power source, and generates corona products such as ozone. However, there is a problem that an additional means / mechanism is required to deal with the problem, which is a factor for increasing the size and cost of the device.

Therefore, recently, instead of the corona discharger, which has many problems, a contact charging type charging means is being adopted. The contact charging is to charge the surface of the body to be charged to a predetermined polarity and potential by bringing a charging member (conductive member) to which a voltage is applied into contact with the body to be charged, which can lower the power supply and generate corona such as ozone. There are advantages such as less material generation, simple structure, and cost reduction.

A roller charging type using a roller body as a contact charging member (JP-A-56-91253) and a blade charging type using a blade body (JP-A-56-194349).
JP-A-56-1), a charging / cleaning combined type (JP-A-56-1).
No. 65166) has been devised.

The applicant of the present invention has previously proposed (Japanese Patent Laid-Open No. 63-1
No. 49669, etc.), an oscillating electric field (alternating electric field / AC electric field) having a peak-to-peak voltage (PEAK TO PEAK) that is more than twice the charging start voltage of the charged body when a DC voltage is applied to the contact charging member. A method of forming an electric field or voltage whose voltage value periodically changes with time between the contact charging member and the body to be charged, and charging the surface of the body to be charged (including a charge removing process) (hereinafter, AC application method) Is effective because it is possible to carry out uniform charging treatment.

The oscillating electric field (voltage) is an oscillating voltage component (hereinafter,
AC component) or a superimposed electric field or voltage of AC component and DC component (voltage corresponding to target charging potential, hereinafter referred to as DC component), and the waveform of AC component is sine wave, rectangular wave, triangular wave, etc. It is appropriate. It may be a rectangular wave voltage formed by periodically turning on and off a DC power supply.

FIG. 23 shows a schematic structure of an example of an image forming apparatus which employs the above-mentioned AC application type contact charging means as the charging means of the image bearing member. The image forming apparatus of this example is a laser printer using an electrophotographic process.

Reference numeral 1 denotes a drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) as an image bearing member, which has a predetermined peripheral speed (process speed, for example, 40 m) in a clockwise direction indicated by an arrow A.
(m / sec).

Reference numeral 20 denotes a charging roller as a contact charging member, and a cored bar 21 as a support member, and a conductive solid charging layer 22 (for example, concentrically formed on the outer periphery of the cored bar 21 in a roller shape). It is a so-called integral charging roller composed of a carbon-dispersed conductive rubber layer such as EPDM).

The charging roller 20 is arranged substantially parallel to the photosensitive drum 1 so that both ends of the cored bar 21 are held by bearing members (not shown), and a pressing spring 23 presses and urges the photosensitive drum 1 toward the photosensitive drum 1. It is pressed against the surface of the photosensitive drum 1 with a predetermined pressing force, and in the case of this example, the photosensitive drum 1 is driven to rotate as the photosensitive drum 1 rotates.

To the charging roller 20, the AC component having a peak-to-peak voltage which is more than twice the charging start voltage of the photosensitive member and the target charging are supplied from the power source 4 through the sliding electrode 24 which is brought into contact with the mandrel 21. An oscillating voltage (V _ac + V _dc ) superposed with a DC component of a voltage corresponding to the potential is applied. As a result, the peripheral surface of the rotary photosensitive drum 1 is uniformly contact-charged by the AC application method.

Next, a laser beam, which is modulated and output from a laser scanner (not shown) corresponding to a time-series electric digital pixel signal of target print (image) information, is output to the charging surface of the rotary photosensitive drum 1. By performing the scanning exposure by 5, the print information is written and an electrostatic latent image of the print information is formed.

The latent image is visualized (developed) as a toner image by reversal development by the developing sleeve 6 of the developing device, and the toner image is pressed from the paper feeding portion (not shown) to the pressure nip portion between the photosensitive drum 1 and the transfer roller 8. The images are sequentially transferred onto the transfer material 7 fed to the (transfer site) at a predetermined timing.

The transfer material 7 to which the toner image has been transferred is separated from the surface of the photosensitive drum 1 and conveyed to a fixing means (not shown), where it is subjected to toner image fixing and is output as an image-formed product. After the transfer material is separated, the surface of the rotary photosensitive drum 1 is cleaned by the cleaning blade 9 of the cleaning device (cleaner) to remove residual adhering substances such as transfer residual toner, and is repeatedly used for image formation.

[0017]

By the way, as a problem of the AC charging type contact charging means, generation of vibration noise called "charging sound" due to the AC component of the charging bias applied to the contact charging member can be mentioned.

The mechanism of generation of this charging sound will be described with reference to the model diagram of FIG.

Reference numeral 1 is a photosensitive drum as a member to be charged,
Reference numeral 1b is a grounded conductive base layer (substrate) made of aluminum, and 1a is a photosensitive layer formed on the outer surface of the base layer.
Reference numeral 20 is a charging roller as a contact charging member which is pressed against the surface of the photosensitive drum 1, 21 is a core metal, and 22 is a solid charging layer made of a conductive rubber material such as carbon-dispersed EPDM.

[0020]. Applied vibration voltage (V _ac
The AC component of + V _dc induces a positive charge on the charging layer 22 side and a negative charge on the base layer 1b side across the photosensitive layer 1a as shown by the thick solid line in (a) at a certain moment.

[0021]. Since these positive and negative charges are attracted to each other, the surface of the charging layer 22 is attracted to the photosensitive drum 1 side against the elasticity of the charging layer 22 and is thick from the position of the thick solid line to the position of the thin solid line ((b) is thick). (Solid line position)
Move to.

.. Then, when the AC electric field starts reversing, the positive charges on the side of the charging layer 22 and the negative charges on the side of the base layer 1b start to be canceled by the charges of opposite polarities respectively induced.

When the AC electric field just changes from positive to negative, the positive charge on the charging layer 22 side,
The negative charge on the base layer 1b side disappears. (B) shows the state at the time of disappearance.

[0024]. As a result, the surface of the charging layer 22 is released from the attracting force against the elasticity of the charging layer 22, and the elastic return force causes the elastic returning force to change from the position indicated by the thick solid line in (b) to the position indicated by the thin solid line ((a)). It will return to the position of the solid line).

[0025]. Further, when the AC electric field goes to a negative peak, as shown in (c), negative charges are induced on the charging layer 22 side and positive charges are induced on the base layer 1b side. Therefore, due to the attraction force of both the negative and positive charges, the surface of the charging layer 22 is again attracted to the photosensitive drum 1 side against the elasticity of the charging layer 22 and moves from the position of the thick solid line to the position of the thin solid line. .

In this way, the surface of the charging layer 22 corresponds to the repeated positive and negative reversals of the AC electric field.
The charging member 20 vibrates with the application of the oscillating voltage due to the repeated phenomenon of the movement of pulling the photosensitive drum 1 toward the photosensitive drum 1 side against the elasticity of 2 and the returning movement by releasing the pulling force. It is considered that the photosensitive drum 1 is hit for the first time, and as a result, "charging noise" is generated.

Assuming that the frequency of the AC electric field (voltage) is f and the vibration frequency of the charging member 20 is F, the charging member 20 vibrates twice during one cycle of the AC voltage, as is clear from the above description. Therefore, there is the following relationship between both f and F.

2f (H _Z ) = F (c / s) The charging sound is not limited to the case where the contact charging member is the charging roller, but is generated by the charging blade, the charging pad or the like by the same mechanism.

As a charging noise reducing measure, an oscillating voltage (V _ac + V _dc ) which is a charging bias applied to the contact charging member 20.
If the peak-to-peak voltage V _PP of the AC component is less than twice the charging start voltage of the body to be charged, the charging noise can be improved to a considerably low level.

However, in the contact charging of the AC application system,
Lowering the peak-to-peak voltage V _PP of the AC component means A
A so-called "leveling effect" that allows uniform charging by applying C component
As a result, the uniform charging cannot be obtained on the body to be charged, and spot-like uneven charging occurs. This is because the contact surface between the charging member 20 and the member to be charged 1 is microscopically uneven, and an ideal contact surface cannot be obtained.

In the electrophotographic image forming process, the spot-shaped uneven charging state of the photosensitive drum 1, which is the member to be charged, causes spot-shaped black spot image unevenness corresponding to the spot-shaped uneven charging in the output image, which is high. I can't get a quality image.

As another method for reducing the charging noise,
It has been proposed to insert a vibration isolating member made of rubber or the like into the photosensitive drum 1 which is the member to be charged, but there are drawbacks in terms of deformation, weight increase and manufacturing cost of the photosensitive drum 1,
It has not been put to practical use.

Further, it has been proposed that the charging roller 20 be hollow so that the charging mass (striking force, striking energy) of the charging roller 20 on the photosensitive drum 1 is reduced to reduce charging noise. 25 and 26 show this embodiment, FIG. 25 is a cross-sectional model view of the hollow charging roller 20, and FIG. 26 is a vertical cross-sectional model view.

That is, the conductive rubber roller portion which is the charging layer 22 is a hollow body. 25 shows the hollow part. In such a configuration, by setting the wall thickness t of the hollow conductive rubber roller portion, which is the charging layer 22, to about 1 mm, an oscillating voltage as a charging bias is applied and the charging roller 20 vibrates by the mechanism described above. Also, since the mass of hitting the photosensitive drum 1 is small, the charging sound can be suppressed to a level at which there is no problem.

However, when the charging roller 20 is pressed by the pressure spring 23 on both ends of the cored bar 21 and pressed against the photosensitive drum 1, a part of the hollow charging layer 22 is indicated by a chain double-dashed line 22 'in FIG. Since it floats from the surface of the photosensitive drum 1 as shown in FIG.
The charging failure portion a corresponding to the rotation cycle of No. 1 occurred. This phenomenon was not a problem in the A4 size machine in which the axial length of the charging roller 2 is short, but it becomes remarkable in the A3 size machine in which the axial length of the charging roller 2 is long.

Therefore, an object of the present invention is to effectively solve the problem of generation of charging noise in contact charging without causing other inconveniences such as uneven charging, deterioration of image quality and high cost.

[0037]

SUMMARY OF THE INVENTION The present invention is a contact charging member, a contact charging device, and a process cartridge having the following features.

(1) A contact charging member of a contact charging device for charging a charging member by bringing it into contact with a member to be charged. The contact charging member includes at least a support member and a direct or other layer on the member to be charged. 1. A contact charging member comprising a charging layer that is in contact with the surface of the charging layer and an inside foaming member that is opposite to the side of the member to be charged of the charging layer.

(2) A contact charging member of a contact charging device for charging by charging a charging member to which an oscillating voltage is applied to a member to be charged, the contact charging member including at least a supporting member and a member to be charged. 1. A contact charging member comprising a charging layer that is in direct contact with another layer or another layer, and an inside foaming member that is the side opposite to the charged body side of this charging layer.

(3) The contact charging member as described in (1) or (2), wherein the foaming member is made of polystyrene, polyolefin, polyester, polyurethane, or polyamide foaming material.

(4) In a contact charging device for charging a charging member by bringing it into contact with a member to be charged, the contact charging member is at least a supporting member and a charging layer which is in contact with the member to be charged directly or through another layer. And a foaming member on the inner side of the charging layer opposite to the side of the body to be charged, the contact charging device.

(5) In the contact charging device for charging by charging the charging member to which the oscillating voltage is applied to the member to be charged, the contact charging member is at least supported by the support member and directly or through another layer. A contact charging device comprising: a charging layer in contact with the charging layer; and a foaming member on the inner side of the charging layer opposite to the charged body side.

(6) In a process cartridge that includes at least an image carrier and a charging unit for the image carrier and is attached to and detached from an image forming apparatus, the charging unit brings the charging member into contact with the image carrier. The charging device is a contact charging device that performs charging by means of at least the supporting member, a charging layer that is in contact with the body to be charged directly or through another layer, and the side of the charging layer opposite to the body to be charged. A process cartridge comprising an inner foam member.

(7) A contact charging member of a contact charging device for charging by charging a charging member to an object to be charged, the contact charging member including at least a support member and a direct or another layer on the object to be charged. The charging layer is in contact with the charging layer, the conductive layer on the inner side of the charging layer opposite to the charging target side, and the foaming member inside the charging layer.The conductive layer is biased to charge the charging target. Is applied, and the charging layer has a higher volume resistivity than the conductive layer.

(8) A contact charging member of a contact charging device for charging by charging a charging member to which an oscillating voltage is applied to a member to be charged, the contact charging member being at least a support member and a member to be charged. A charging layer that is in direct contact with another layer or through another layer, an inner conductive layer that is the opposite side of the charging layer to the charged body, and a foaming member inside the charging layer. The contact charging member is characterized in that a bias is applied to perform the charging, and the charging layer has a higher volume resistivity than the conductive layer.

(9) In a contact charging device for charging a charging member by bringing it into contact with a member to be charged, the contact charging member includes at least a support member and a charging layer in contact with the member to be charged directly or through another layer. , An electrically conductive layer on the opposite side of the charged layer from the side of the body to be charged, and a foam member inside the electrically conductive layer,
The contact charging device is characterized in that a bias is applied to the conductive layer to charge the charged body, and the charging layer has a higher volume resistivity than the conductive layer.

(10) In a contact charging device for charging by charging a charging member to which an oscillating voltage is applied to a member to be charged, the contact charging member is at least supported by the support member and directly or through another layer. A charging layer in contact with the charging layer, a conductive layer on the inner side of the charging layer opposite to the charged body side, and a foaming member inside the charging layer, and a bias is applied to the conductive layer to charge the charged body. A contact charging device characterized in that the applied charging layer has a higher volume resistivity than the conductive layer.

(11) In a process cartridge including at least an image carrier and a charging unit for the image carrier, which is attached to and detached from an image forming apparatus, the charging unit brings the charging member into contact with the image carrier. The charging device is a contact charging device that performs charging by means of at least the supporting member, a charging layer that is in contact with the body to be charged directly or through another layer, and the side of the charging layer opposite to the body to be charged. It is characterized by comprising an inner conductive layer and a foamed member further inside thereof, a bias is applied to the conductive layer to charge an object to be charged, and the charging layer has a higher volume resistivity than the conductive layer. Process cartridge.

(12) A contact charging member of a contact charging device for charging by charging a charging member to an object to be charged, the contact charging member including at least a support member and a direct or other layer on the object to be charged. The charging layer is in contact with the charging layer, the conductive layer on the opposite side of the charging layer to the body to be charged, and a layer including a foam layer composed of at least one layer further inside. A contact charging member having a volume resistivity lower than that of a layer containing the same.

(13) A contact charging member of a contact charging device for charging by charging a charging member to an object to be charged, the contact charging member including at least a support member and a direct or another layer on the object to be charged. The charging layer is in contact with the charging layer, the conductive layer on the opposite side of the charging layer to the body to be charged, and a layer including a foam layer composed of at least one layer further inside. A contact charging member having a layer thickness smaller than that of a layer containing the same.

(14) A contact charging member of a contact charging device for charging a charging member by bringing it into contact with a member to be charged, the contact charging member including at least a supporting member and a direct or another layer on the member to be charged. The charging layer is in contact with the charging layer, the conductive layer on the inner side of the charging layer opposite to the charging target side, and the foaming member inside the charging layer.The conductive layer is biased to charge the charging target. Is applied, the charging layer has a higher volume resistivity than the conductive layer, and the foaming member has a volume resistivity equal to or lower than that of the conductive layer.

(15) A contact charging member of a contact charging device for charging by charging a charging member to which an oscillating voltage is applied to a member to be charged, the contact charging member being at least a supporting member,
A charging layer that is in contact with the charged body directly or through another layer, and an inner conductive layer that is the side opposite to the charged body side of this charging layer,
Furthermore, a biasing member is applied to the conductive layer to charge the body to be charged, the charging layer has a higher volume resistivity than the conductive layer, and the foaming member has a conductive layer and a volume resistivity. Of the same or lower than that of the conductive layer.

(16) The contact charging member according to (14) or (15), wherein the foaming member is made of polystyrene, polyolefin, polyester, polyurethane, or polyamide foaming material.

(17) The contact charging member according to (14) or (15), wherein the foamed member has a layer thickness larger than that of the conductive layer.

(18) The contact charging member according to (14) or (15), wherein the foaming member has a foaming ratio of 70% or more.

(19) In a contact charging device for charging by charging a charging member to a member to be charged, the contact charging member includes at least a support member and a charging layer which is in contact with the member to be charged directly or through another layer. , A conductive layer on the inner side of the charged layer opposite to the charged body side, and a foaming member inside the charged layer. A bias is applied to the conductive layer to charge the charged body. Has a higher volume resistivity than the conductive layer, and the foamed member has a volume resistivity equal to or lower than that of the conductive layer.

(20) In the contact charging device for charging by charging the charging member to which the oscillating voltage is applied to the member to be charged, the contact charging member is at least directly connected to the support member and the member to be charged or through another layer. A charging layer in contact with the charging layer, a conductive layer on the inner side of the charging layer opposite to the charged body side, and a foaming member inside the charging layer, and a bias is applied to the conductive layer to charge the charged body. Applied, the charging layer has a higher volume resistivity than the conductive layer, the foamed member has a volume resistivity equal to that of the conductive layer,
Alternatively, the contact charging device is characterized by being lower than the conductive layer.

(21) The contact charging device as described in (19) or (20), wherein the foamed member has a layer thickness larger than that of the conductive layer.

(22) The contact charging device as described in (19) or (20), wherein the foaming member has a foaming rate of 70% or more.

(23) In a process cartridge that includes at least an image carrier and a charging unit for the image carrier and is attached to and detached from an image forming apparatus, the charging unit brings the charging member into contact with the image carrier. The charging device is a contact charging device that performs charging by means of at least the supporting member, a charging layer that is in contact with the body to be charged directly or through another layer, and the side of the charging layer opposite to the body to be charged. It is composed of an inner conductive layer and a foamed member inside the inner layer. A bias is applied to the conductive layer to charge an object to be charged. The charged layer has a higher volume resistivity than the conductive layer, and the foamed member is A process cartridge having a volume resistivity equal to or lower than that of the conductive layer.

(24) The process cartridge according to (23), wherein the foamed member has a layer thickness larger than that of the conductive layer.

(25) The process cartridge according to (23), wherein the foaming member has a foaming rate of 70% or more.

[0063]

[Operation] The foaming member is a foaming member made of polystyrene, polyolefin, polyester, polyurethane, polyamide or the like, and may be one in which conductive powder such as carbon or tin oxide is dispersed and blended to impart conductivity, The above-mentioned charging member is mainly composed of the foamed member and a thin charging layer (conductive layer), which is much lighter than the conventional solid charging member and has a low hardness.

In the case of such a light charging member having low hardness, as in the hollow charging roller 20 shown in FIGS. 25 and 26, even if the AC component of the applied vibration voltage causes the vibration phenomenon by the mechanism described above, it is not affected. Since the mass that hits the charged body is small,
The generated charging noise is at a level that does not cause a problem (a level that does not bother you,
For example, it is reduced to 50 dB or less). This is similar to the fact that tapping a drum with a light, soft Styrofoam or rolled newspaper, is more quiet than hitting a drum with a heavy, hard oak tree.

.. Further, since the charging layer has a foamed member inside thereof, it can be backed up well even if it is thin, so that even if the charging member is pressed against the surface of the member to be charged, it is asymmetrically deformed and becomes a space between the member and the surface to be charged. Since it does not come into contact with the surface of the charged body over the entire length without causing a floating portion,
Even if the axial length of the charging member is lengthened, no defective charging occurs.

According to the experiment, if the thickness t of the charging layer is too thin (5 μm or less), the rigidity of the charging layer disappears and the charging layer easily vibrates when an oscillating voltage is applied. As a result, the charging layer floats from the surface of the body to be charged according to the oscillating voltage, and charging failure occurs. If the thickness t is too thick (10000 μm or more), the charging layer vibrates when an oscillating voltage is applied and the force to hit the body to be charged becomes large. As a result, the charging noise becomes loud and exceeds the allowable level of 50 dB.

Therefore, it is desirable that the thickness t of the charging layer is set to be larger than 5 μm and smaller than 10000 μm.

.. To be able to reduce the generated charging noise means to be able to increase the frequency of the AC component of the vibration voltage applied to the contact charging member, which is a problem with the scanning laser light called "moiré" which was a problem at low frequencies. It has become possible to eliminate the occurrence of moire interference fringes on an image due to interference with uneven charging due to the AC component frequency.

.. In the image forming apparatus, since the contact charging member weakens the force of hitting the image bearing member as the charged member, it is possible to suppress the "toner fusion" phenomenon that occurs when the toner remaining after cleaning is pressed against the image bearing member surface. Became possible.

.. By increasing the expansion ratio and making the cells coarser (the ones with larger outer diameters), the overall weight of the charging member can be made lighter and the height can be lowered. The energy of the charging member during vibration can be further reduced, and the generated charging noise can be further reduced.

.. However, when the outer diameter of the bubbles of the foaming member is larger than a certain level, it becomes difficult for the charges to wrap around to the charging layer portion where the large bubbles are approaching, and defective charging is observed.

Therefore, as in the contact charging member, the contact charging device, and the process cartridge of the above (7) to (13), the conductive layer is interposed between the foam layer and the charging layer of the charging member. Due to the presence of the conductive layer, electric charges can easily wrap around to the charging layer portion where large bubbles of the foaming member are approaching, and the wraparound charge amount of each portion of the charging layer is made uniform, and the foaming member has a foaming ratio. Even if the air bubbles are large and the bubbles are coarse, the charging failure due to the large outer diameter of the bubbles of the foaming member does not occur.

.. When the foamed member has a higher volume resistivity than the conductive layer and the foamed member has a foaming rate of 70% or more, the movement of the electric charge passing through the foamed layer is very poor and does not reach the conductive layer, resulting in charging failure. easy.

Therefore, like the contact charging member, the contact charging device, and the process cartridge of (14) to (25), the volume resistivity of the foam layer of the charging member is made lower than that of the conductive layer.
No matter how many large bubbles there are in the foamed member, the charge can easily pass through the foamed layer, and the presence of the conductive layer makes it possible to charge the charged layer portion where the large bubbles in the foamed member are approaching. Can easily wrap around, the amount of wraparound charges in each part of the charging layer can be made uniform, and charging failure due to the large outer diameter of the bubbles of the foaming member does not occur.

[0075]

【Example】

A. Examples 1 to 6 below are examples of a contact charging member, a contact charging device, or a process cartridge, which is characterized by the configurations described in (1) to (6) above.

<Embodiment 1> (FIGS. 1 to 3) FIG. 1 is a cross-sectional model view of a contact charging member or a contact charging device of this embodiment, and FIG. 2 is a vertical cross-sectional model view of one end side.

Reference numeral 1 is a rotary photosensitive drum having a negative or positive charging polarity as a member to be charged.

Reference numeral 2 is a charging roller as a contact charging member. The charging roller 2 includes a metal cored bar 2a made of stainless steel or the like as a supporting member, and a foaming member (foaming layer) 2b formed concentrically and integrally on the outer periphery of the cored bar 2a.
The charging member 2c has a triple-layer structure in which the outer peripheral surface and both end surfaces of the foam member 2b are covered.

The foam member 2b is a polystyrene / polyolefin / polyester / polyurethane / polyamide foam member or a flexible / low specific gravity member in which conductive powder such as carbon / tin oxide is dispersed and foamed in EPDM or urethane. In this embodiment, it is expanded polystyrene (styrofoam). 2b 'is a bubble portion (air,
Enclosed bubbles such as nitrogen and argon gas).

In this embodiment, the charging layer 2c is a conductive rubber material layer such as carbon-dispersed EPDM. t is this charging layer 2
It shows the thickness of c and is set in the range of 5 μm <t <10000 μm.

If the conductive charging layer 2c on the outer periphery of the foam member 2b extends to the end face of the foam member 2b and is electrically connected to the conductive core metal 2a as shown in FIG. 2, the foam member 2b is strongly conductive. It doesn't have to be sex.

The specifications of the charging roller 2 in this embodiment are as follows.

Core metal 2a; diameter 9 mm, length 332.
mm stainless round bar Foam member 2b; Styrofoam, specific gravity 0.3 Volume resistance value 10 ⁸ Ωcm Layer thickness 2.3 mm, length 310 mm Charging layer 2c; Carbon dispersed EPDM conductive rubber material layer Volume resistance value 10 ⁵ Ωcm layer Thickness t 80 μm, charging roller 2 weight 177 g, hardness 35 degrees (ASKER
-C) This charging roller 2 is also the conventional charging roller 2 of FIG.
As in the case of 0, both ends of the cored bar 2a are held by bearing members (not shown), and the pressure spring 23 presses and urges the photosensitive drum 1 toward the photosensitive drum 1. In this case, they are pressed against each other at a total pressure of 1000 g, and are driven to rotate with the rotation of the photosensitive drum 1 (it may be positively or reversely driven). An AC voltage V _ac is supplied to the charging roller 2 from a power source 4 via a sliding electrode 24 which is brought into contact with the charging roller core 2a; in this embodiment, 2.0 KV _PP , 600 H.
_Z , DC voltage V _dc ; superimposed vibration voltage (V _ac + V _dc ) with DC voltage corresponding to target charging potential is applied. As a result, the peripheral surface of the rotary photosensitive drum 1 is uniformly contact-charged to the target charging potential by the AC application method.

(A) In the charging roller 2, the outer member of the cored bar 2a is composed of the foaming member 2b and the thin charging layer 2c, and the charging roller as a whole is much lighter than the conventional solid charging roller 20 of FIG. Also, the hardness is low.

For example, as a conventional solid integral charging roller 20, a cored bar 21; a stainless steel rod having a diameter of 9 mm and a length of 332 mm; a charging layer 22; a carbon-dispersed solid EPDM conductive rubber, a specific gravity of 1.0 and a volume resistance value. A charging roller 20 having a thickness of 10 ⁵ Ωcm, a layer thickness of 2.5 mm, and a length of 310 mm has a weight of 185 g and a hardness of 60 degrees (A
SKER-C). Therefore, similarly to the hollow charging roller 20 of FIGS. 25 and 26, the charging roller 2 of the present embodiment has a small mass that strikes the photosensitive drum 1 even if the AC phenomenon of the applied vibration voltage causes the vibration phenomenon by the mechanism described above. Therefore, the generated charging noise is reduced to a level at which there is no problem.

The contact charging device of this example was set in an anechoic chamber, and the generated noise (charging sound) was measured under the above-mentioned oscillating voltage application conditions. The measurement was carried out in accordance with ISO 7779, item 6. As a result, the generated charging noise was as low as 33 dB.

(B) Further, since the charging layer 2c has the foaming member 2b on the inner side thereof, it can be backed up even if the wall thickness is thin (5 μm or more) and the shape can be maintained well, so that the charging roller 2 is pressed against the surface of the photosensitive drum 1. Even when the charging roller 2 is pressed, since it does not come into contact with the surface of the photosensitive drum 1 and comes into pressure contact with the surface of the photosensitive drum over the entire length, even if the axial length of the charging roller 2 is increased, the hollow portion shown in FIGS. The charging failure portion a (FIG. 27) corresponding to the rotation cycle of the charging roller such as the charging roller 20 is not observed.

(C) The contact charging device shown in FIGS. 1 and 2 was set in an anechoic chamber, and the generated charging noise was measured when the thickness t of the charging layer 2c of the charging roller 2 was variously changed.

The measurement was carried out in accordance with ISO 7779, item 6. The result is shown in FIG.

In FIG. 3, the vertical line on the right side shows the degree of charging failure, 1 indicates a level at which no charging failure is observed on the output image sample, and 2 indicates a level at which a charging failure is slightly recognized. 3 shows a level at which a poor charging is clearly recognized.

As can be seen from this result, when the thickness t of the charging layer 2c is too thin (5 μm or less), the charging layer 2c loses its rigidity and the charging layer 2c easily vibrates when an oscillating voltage is applied. Will end up. As a result, the charging layer 2c floats from the surface of the photosensitive drum 1 according to the oscillating voltage, and charging failure occurs.

In FIG. 3, the vertical line on the left side indicates the sound pressure level,
As is clear from the figure, the thickness t is too thick (10
000 μm or more), the charging layer 2c vibrates when an oscillating voltage is applied, and the force for hitting the photosensitive drum 1 becomes large like the conventional solid charging roller. as a result,
The charging noise becomes loud and exceeds the allowable level of 50 dB.

From the above results, the thickness t of the charging layer 2c is 5
It is desirable that the thickness is larger than μm and smaller than 10000 μm.

The ratio of the thickness of the foam member 2b to the thickness of the charging layer 2c is
Generally, it is set in the range of 10: 1 to 1000: 1.

(D) The fact that the generated charging noise can be reduced means that the frequency of the AC component of the oscillating voltage applied to the contact charging member can be increased, which causes "moire" which is a problem at low frequencies. It has become possible to eliminate the occurrence of moire interference fringes on an image due to interference of so-called scanning laser light and uneven charging caused by the AC component frequency.

(E) Charging roller 2 as a contact charging member
Since the force of hitting the photosensitive drum 1 is weakened, it is possible to suppress the "toner fusion" phenomenon that occurs when the toner remaining after cleaning is pressed against the surface of the photosensitive drum 1.

<Embodiment 2> (FIGS. 4 and 5) In this embodiment, a high resistance layer 2d such as epichlorohydrin rubber or paper is further provided on the outer periphery of the charging layer 2c of the charging roller 2.

In this embodiment, the foam member 2b is a polystyrene foam molded into a roller shape. Metal flanges 2e each having a shaft portion serving as a supporting member are adhered and attached to both end surfaces thereof. In this embodiment, the charging layer 2c is formed on the outer peripheral surface of the roller foam member 2b and the metal flanges 2e on both ends, and the high resistance layer 2d is further provided on the outer periphery thereof.

The specifications of the charging roller 2 in this embodiment are as follows.

Foamed member 2b: Styrofoam, specific gravity 0.3 Volume resistance value 10 ⁸ Ωcm Diameter 13 mm, length 310 mm Charging layer 2c; Carbon dispersion EPDM conductive rubber layer Volume resistance value 10 ⁵ Ωcm Layer thickness 80 μm High resistance layer 2d Epichlorohydrin rubber, volume resistance value 10 ¹⁰ Ωcm, layer thickness 80 μm, charging roller 2 weight 50 g, hardness 30 ° (ASKER-
C) The charging roller 2 holds the shafts of the flanges 2e on both ends by bearing members (not shown) and presses and urges the pressure spring 23 toward the photosensitive drum 1 to press the surface of the photosensitive drum 1 in a predetermined manner. Pressure, in this embodiment, total pressure of 300 g,
It rotates following the rotation of the photosensitive drum 1. An oscillating voltage (V _ac + V _dc ) similar to that of the first embodiment is applied to the charging roller 2 from the power source 4 via the pressure spring 23 and the metal flange 2e. The applied bias is guided through the metal flange 2e to the charging layer 2c electrically connected to the metal flange 2e.

The high resistance layer 2d is formed when the charging roller faces a low withstand voltage defect portion such as a pinhole portion on the photosensitive drum 1,
It works to prevent the electric current from leaking intensively to the pinholes and the like and causing the abnormal discharge.

This charging roller 2 also produces a small charging noise as in the first embodiment (applied oscillating voltage is the same as in the first embodiment). Further, in the present embodiment, the supporting member is not the core metal 2a that penetrates the entire length of the roller as in the first embodiment but the flange members 2e provided only at both ends, so that the charging roller becomes lighter and the cost is reduced. did.

A bleeding-preventing layer such as nylon for preventing contamination of the photosensitive drum 1 due to bleeding of a plasticizer or the like from the inside of the charging roller may be further provided outside the high resistance layer 2d.

As for the thickness t of the charging layer 2c, when the high resistance layer 2d and the exudation preventing layer are further provided on the outer side of this layer, the thickness t is set by adding all of these layers. Good to do.

<Embodiment 3> (FIG. 6) In this embodiment, the contact charging member is a blade type (charging blade).
FIG. 6 is a schematic cross-sectional view of the charging blade 2A or the contact charging device. Charging blade 2A
The contact charging device using can have a simpler configuration than that using a charging roller.

In the case of this embodiment, the charging blade 2A is
A foamed member (core material) 2b of foamed polypropylene, a charging layer 2c which covers the outer peripheral surface of the foamed member 2b and is made by dispersing conductive powder such as carbon and tin oxide in EPDM / polyurethane, and the like. It is composed of an electrode plate 2g as a supporting member which is attached and supported via a conductive adhesive 2f.

The tip of the charging blade 2A is appropriately pressed against the surface of the photosensitive drum 1 against the waist of the blade, and the electrode plate 2g as a supporting member is attached and fixed to the immovable member 30. Is provided.

An oscillating voltage (V _ac + V _dc ) is applied to the charging blade 2A from the power source 4 through the supporting member 2g as an electrode plate, and the surface of the rotating photosensitive drum 1 is uniformly contact-charged by the AC application method. It

In this example, the charging noise generated when the charging blade 2A having the following specifications was used was 40 dB (the applied oscillating voltage was the same as that in Example 1). .

Foamed member 2b; Foamed polypropylene, specific gravity 0.3, volume resistance value 10 ⁷ Ωcm, length 10 mm, length 310 mm, thickness 3 mm Charging layer 2c; carbon dispersed EPDM conductive rubber material layer, volume resistance value 10 ¹⁰ Ωcm layer Thickness t500 μm Hardness of charging blade 2A is 40 degrees (ASKER-C) Free length of charging blade 2A is L5 mm Total pressure of pressing on photosensitive drum 1 is 700 g Therefore, charging noise can be reduced also in charging blade 2A, and charging blade 2A There is an advantage that the pressure applied to the photosensitive drum 1 can be controlled by utilizing the waist of the blade.

<Embodiment 4> (FIGS. 7 and 8) It is possible to make the foaming member 2b conductive and apply a bias for charging the charging target 1 to the charging layer 2c through the conductive foaming member. It is possible.

Further, the foaming member 2b is made to have a large foaming ratio to make the bubbles coarse (the outer diameter of the bubbles is large), so that the overall weight of the charging member 2 (2A) is made lighter, and The hardness can be reduced, and as a result, the energy at the time of vibration of the charging member 2 (2A) can be further reduced and the generated charging noise can be further reduced.

However, as shown in FIG. 28, if the bubbles 2b 'of the foaming member 2b are roughened to a certain extent or more, large bubbles 2b will be generated.
It becomes difficult for the charge to wrap around to the charging layer portion B where ′ is approaching, and due to the portion B, the charging failure portion b corresponding to the rotation cycle of the charging roller 2 as shown in FIG.
Will occur.

FIGS. 7 and 8 show the structure of the charging roller 2 which solves such a problem, in which the charging layer 2c is provided on the conductive foam member 2b via the conductive layer 2h. The specific specifications are as follows.

Core metal 2a; diameter 9 mm, length 332 m
m stainless round bar Foaming member 2b; Conductive foaming member in which electroconductive powder such as carbon / tin oxide is dispersed in EPDM or urethane Specific gravity 0.4 Volume resistance value 10 ⁵ Ωcm Layer thickness 2.3 μm, length 310 mm Conductive layer 2h; large amount of carbon in EPDM and urethane
Dispersion of conductive powder such as tin oxide Volume resistance value 10 ² Ωcm Layer thickness 80 μm Charging layer 2c; Carbon dispersion EPDM conductive rubber material layer Volume resistance value 10 ¹⁰ Ωcm (larger than conductive layer 2h) Layer Thickness 80 μm Charging roller 2 weighs 177 g and hardness 35 degrees (ASKER
-C) Pressing force on photosensitive drum 1 Total pressure 1000 g Applied vibration voltage AC voltage Vac; 2.0 KVpp, 6
00 Hz DC voltage Vdc; DC voltage corresponding to target charging potential Measurement result of charging noise generated by the charging roller 2 (ISO 7
779, item 6) was as small as 33 dB.

Since the conductive layer 2h is interposed between the conductive foam member 2b and the charging layer 2c, the electric charge can be easily applied to the charging layer portion B in which the large bubbles of the foam member 2b are in close proximity. The outer diameter of the bubbles of the foaming member is large even if the foaming member 2b has coarse bubbles 2b 'with a large expansion ratio. The resulting charging failure does not occur.

The core metal 2a and the conductive layer 2 to which voltage is applied
The foam member 2b is not necessarily conductive as long as it is electrically connected to h, and may be insulative. Also in this case, by increasing the foaming ratio of the foaming member 2b, it is possible to obtain the effect of reducing the charging noise generated by reducing the weight and hardness of the charging roller 2.

<Embodiment 5> (FIG. 9) In this embodiment, in the charging blade 2A, the charging layer 2c is formed on the foaming member 2b (blade core material) having a high expansion ratio through the conductive layer 2h. The specific specifications are as follows.

Foaming member 2b: Foamed polypropylene in which conductive powder is dispersed, specific gravity 0.3, volume resistance value 10 ⁶ Ωcm, length 10 mm, length 310 mm, thickness 3 mm Conductive layer 2h; a large amount of carbon in EPDM or urethane
Conductive powder such as tin oxide dispersed Volume resistance value 10 ² Ωcm Layer thickness 80 μm Charging layer 2c; Carbon dispersion EPDM conductive rubber material layer Volume resistance value 10 ¹⁰ Ωcm Layer thickness 80 μm Charging blade 2A hardness 40 Degree (ASKER-C) Free length L5 mm of charging blade 2A Total pressure of pressing on photosensitive drum 1 700 g Measurement result of charging noise generated by this charging blade 2A (ISO
The item (6th item of 7779) was as small as 40 dB.

Since the conductive layer 2h is interposed between the conductive foam member 2b and the charging layer 2c, the electric charge can be easily applied to the charging layer portion of the foam member 2b where the large bubbles closely correspond to each other. It is possible to wrap around, the amount of wraparound charges in each part of the charging layer 2c is made uniform, and even if the foaming member 2b is a coarse bubble 2b 'with a large expansion ratio, the outside diameter of the bubbles of the foaming member is large. Does not cause poor charging.

The electrode 2g and the conductive layer 2 to which a voltage is applied
The foam member 2b is not necessarily conductive as long as it is electrically connected to h, and may be insulative. Also in this case, by increasing the foaming ratio of the foaming member 2b, it is possible to obtain the effect of reducing the charging noise generated due to the weight reduction and the hardness reduction of the charging blade 2A.

<Embodiment 6> (FIG. 10) This embodiment is a process cartridge of an image forming apparatus using a contact charging member or a contact charging device according to the present invention as a charging means of an image carrier.

The process cartridge according to the present embodiment includes four process devices including a rotary drum type electrophotographic photosensitive member 1 as an image carrier, a charging roller 2 as a contact charging member, a developing device 60 and a cleaning device 90. It will be.

The charging roller 2 is the same as the first or second embodiment or the second embodiment.
It has the same configuration as.

In the developing device 60, 6 is a developing sleeve,
61 is a container for storing the developer (toner) T, and 62 is the container 6
The toner stirring bar in 1 serves to stir the toner T and to send it out toward the developing sleeve. Reference numeral 63 denotes a developing blade for coating the developing sleeve 6 with the toner T in a uniform thickness.

In the cleaning device 90, 9 is a cleaning blade, and 91 is a toner reservoir for accumulating the toner collected by the cleaning blade 9.

Reference numeral 11 denotes a drum shutter of the process cartridge, which can be opened and closed freely from a closed state shown by a solid line to an opened state as shown by a chain double-dashed line. When the process cartridge is taken out from the image forming apparatus main body (not shown), it is in the closed state shown by the solid line, and the externally exposed part surface of the photosensitive drum 1 is hidden to protect the photosensitive drum surface.

When the process cartridge is attached to the main body of the image forming apparatus, the shutter 11 is opened as shown by the chain double-dashed line, or the shutter 11 automatically opens during the process of attaching the process cartridge, When properly mounted, the exposed surface of the photosensitive drum 1 comes into pressure contact with the transfer roller 8 on the image forming apparatus main body side.

Further, the process cartridge and the image forming apparatus main body are mechanically and electrically coupled to each other, and the driving mechanism on the image forming apparatus main body side includes the photosensitive drum 1 on the process cartridge side, the developing sleeve 6, the stirring rod 62 and the like. Driving is possible, and an electric circuit on the image forming apparatus main body side makes it possible to apply a charging bias to the charging roller 2 on the process cartridge side, a developing bias to the developing sleeve 6, and the like, so that an image forming operation can be executed. become.

Reference numeral 12 denotes an exposure passage provided between the cleaning device 90 and the developing device 60 of the process cartridge, which is a laser scanner (not shown) on the image forming apparatus main body side.
The output laser beam 5 from the laser beam enters the process cartridge through the exposure passage 12 to scan and expose the surface of the rotary photosensitive drum 1.

As described above, the charging roller 2 hardly generates a charging sound even when an oscillating voltage is applied, so that it is possible to construct a very compact process cartridge having substantially no charging sound.

B. The following Embodiments 7 and 8 are based on the above (7) to
It is an example of a contact charging member characterized by the configuration described in (13).

<Embodiment 7> (FIGS. 11 and 12) In this embodiment, a charging layer 2c is formed on a conductive foam member 2b of a charging roller 2 via a conductive layer 2h, and a protective layer 2i is formed on the outer peripheral surface thereof. Is provided. The specific specifications are as follows.

Foaming member 2b: Foamed epichlorohydrin rubber, specific gravity 0.3, diameter 12 mm, length 310 mm, thickness 3 mm Volume resistance value 10 ⁶ to 10 ⁹ Ωcm Further, on the core metal side below this, vibration absorption with a higher foaming rate is achieved. A layer may be provided Conductive layer 2h; EPDM or urethane containing a large amount of carbon
Conductive powder such as tin oxide dispersed Volume resistance value 10 ¹ to 10 ⁴ Ωcm Layer thickness 80 μm Charging layer 2c; Epichlorohydrin rubber Volume resistance value 10 ¹⁰ Ωcm, Wall thickness 80 μm Protective layer 2i; N-methoxymethylated Nylon (trade name; resin, manufactured by Teikoku Chemical Industry Co., Ltd.) Volume resistance value 10 ⁹ Ωcm, layer thickness 30 μm Charging roller 2 weight 177 g, hardness 35 degrees (ASKER-C) Pressing force on photosensitive drum 1 Total pressure 1000 g Applied vibration Voltage AC voltage Vac; 2.0KVpp, 6
00 Hz DC voltage Vdc; DC voltage corresponding to target charging potential Measurement result of charging noise generated by the charging roller 2 (ISO 7
779, item 6) was as small as 33 dB.

Protective layer 2i provided on the outer peripheral surface of charging layer 2c
By using a material having a good compatibility with the surface layer of the photosensitive drum 1, it is possible to prevent the surface layer of the photosensitive drum 1 and the charging roller 2 from being contaminated.

A conductive layer 2h having a volume resistance value lower than that of the conductive foam material 2b is provided between the conductive foam material 2b and the charging layer 2c.
By interposing, the electric charge can easily sneak into the charging layer portion B corresponding to the large bubbles of the foaming member 2b, and the amount of sneaking charge in each portion of the charging layer 2c becomes uniform. Even if the foaming member 2b has coarse bubbles 2b having a large expansion ratio, the charging failure due to the large outer diameter of the bubbles of the foaming member does not occur.

The core metal 2a and the conductive layer 2 to which a voltage is applied
The foam member 2b is not necessarily conductive as long as it is electrically connected to h, and may be insulative. Also in this case, by increasing the foaming ratio of the foaming member 2b, it is possible to obtain the effect of reducing the charging noise generated by reducing the weight and hardness of the charging roller 2.

<Embodiment 8> (FIGS. 13 and 14) In the charging roller 2 of this embodiment, the conductive foam member 2b is covered with the tube 2j, and the charging layer 2c is formed on the tube 2j via the conductive layer 2h. Further, a protective layer 2i is provided on the outer peripheral surface thereof.
Is provided. The specific specifications are as follows.

Foaming member 2b; Foamed epichlorohydrin rubber, specific gravity 0.3, volume resistance value 10 ⁶ to 10 ⁹ Ωcm, diameter 12 mm, length 310 mm, thickness 3 mm Tube 2j; polyurethane thermoplastic elastomer, volume resistance value 10 ⁵ to 10 ⁸ Ωcm Layer thickness 300 μm Conductive layer 2h; Large amount of carbon in EPDM and urethane
Conductive powder such as tin oxide dispersed Volume resistance value 10 ¹ to 10 ⁴ Ωcm Layer thickness 80 μm Charging layer 2c; Epichlorohydrin rubber Volume resistance value 10 ¹⁰ Ωcm Layer thickness 80 μm Protective layer 2i; N-methoxymethylated nylon (Trade name; resin, manufactured by Teikoku Chemical Industry Co., Ltd.) Volume resistance value 10 ⁹ Ωcm, layer thickness 30 μm Charge roller 2 weight 177 g, hardness 35 degrees (ASKER-C) Pressure on photosensitive drum 1 Total pressure 1000 g Applied vibration voltage AC voltage Vac; 2.0 KVpp, 6
00 Hz DC voltage Vdc; DC voltage corresponding to target charging potential In such a configuration, a method is used in which a foam member 2b in which epichlorohydrin rubber is foamed is first prepared, and a core metal 2a and a tube 2j are inserted into the foam member 2b. There is a method in which a cored bar 2a is erected inside 2j, and epichlorohydrin rubber, which is a raw material of the foaming member 2b, is inserted into the cored bar 2a and foamed in a fixed state.

The tube 2j covering the conductive foam member 2b is substantially separated from the conductive foam member 2b. The same applies to the core metal 2a and the conductive foam member 2b. Furthermore, in order to prevent axial displacement, the tube 2
It is also possible to fix j and the conductive foam member 2b, and the cored bar 2a and a part of the conductive foam member 2b. As a result, even when an AC voltage is applied to the cored bar 2a, the heavy cored bar 2a does not vibrate, but only the light conductive foam member 2b and the tube 2j vibrate to strike the photosensitive drum 1, and the energy thereof is It becomes smaller and the charging noise becomes smaller. In this case, the measurement result of the charging sound generated by the charging roller 2 (6th item of ISO 7779) is 30 dB.
It was smaller than that without the tube (Example 7).

Protective layer 2i provided on the outer peripheral surface of charging layer 2c
By using a material having a good compatibility with the surface layer of the photosensitive drum 1, it is possible to prevent the surface layer of the photosensitive drum 1 and the charging roller 2 from being contaminated.

Further, between the tube 2j and the charging layer 2c,
By interposing the conductive foam material 2b having a volume resistance value lower than that of the tube 2j and the conductive layer 2h, the electric charge easily wraps around to the charging layer portion B to which the large bubbles of the foaming member 2b correspond closely. Even if the foaming member 2b has coarse bubbles 2b having a large expansion ratio, charging due to the large outer diameter of the bubbles of the foaming member can be achieved. Does not cause defects.

The core metal 2a and the conductive layer 2 to which voltage is applied
The foam member 2b is not necessarily conductive as long as it is electrically connected to h, and may be insulative. In this case, by increasing the foaming ratio of the foaming member 2b, it is possible to obtain the effect of reducing the charging noise generated by reducing the weight and hardness of the charging roller 2.

C. The following Examples 9 to 14 are based on the above (14)
It is an example of a contact charging member, a contact charging device, and a process cartridge, which are characterized by the configurations described in (25) to (25).

<Embodiment 9> (FIGS. 15 and 16) A charging roller 2 as a contact charging member of this embodiment has a foam member (foam layer) 2b formed concentrically and integrally on the outer periphery of a core metal 2a. The outer peripheral surface of the foam member 2b is covered with the conductive layer 2h, and the outer peripheral surface thereof is covered with the charging layer 2c.

Here, when the foam member 2b has a higher volume resistivity than the conductive layer 2h and the foam ratio of the foam member 2b is 70% or more, the movement of the charges passing through the foam layer 2b becomes very bad and the conductive layer 2h. Since it does not spread all over the place, poor charging is likely to occur.

Therefore, the volume resistivity of the foam layer 2b is determined by the conductive layer 2
By making it lower than h, no matter how many large bubbles in the foam member 2b exist, electric charges can easily pass through the foam layer 2b, and the presence of the conductive layer 2h allows the large bubbles in the foam member 2b to approach. The charges can easily sneak into the charging layer portion that is in charge, the amount of the sneak charge in each portion of the charging layer 2c becomes uniform, and charging failure occurs due to the large outer diameter of the bubbles of the foaming member 2b. Absent.

For the above reason, the foam member 2b is made of the conductive layer 2h.
Volume resistivity is lower than that of the charging layer 2c, and the charging layer 2c has higher volume resistivity than the conductive layer 2h.

The foam member 2b is made of polystyrene / polyolefin / polyester / polyurethane / polyamide foam material or a flexible / low specific gravity material made of EPDM or urethane foam and dispersed with conductive powder such as carbon / tin oxide. A member having a low volume resistivity.

In this embodiment, carbon is dispersed in foamed polyurethane. 2b 'is a bubble portion (enclosed bubble of air, nitrogen, argon gas, etc.) of the foam member 2b.

The charging layer 2c is epichlorohydrin rubber in this embodiment. The thickness t of the charging layer 2c is 5 μm <t <
It is set in the range of 10 ⁴ μm.

The specifications of the charging roller 2 in this embodiment are as follows.

Core 2a; diameter 9 mm, length 332 m
m stainless round bar Foaming member 2b; carbon dispersed foaming polyurethane, specific gravity 0.3 10 volume resistance value 10 ³ Ωcm layer thickness 2.3 mm, length 310 mm conductive layer 2h; EPDM and urethane with a large amount of carbon
Conductive powder such as tin oxide dispersed Volume resistance value 10 ⁵ Ωcm Layer thickness 80 μm Charging layer 2c; Epichlorohydrin rubber Volume resistance value 10 ⁹ Ωcm Layer thickness t80 μm Charging roller 2 weight 177 g, hardness 35 degrees (ASKER- C) This charging roller 2 is also the conventional charging roller 2 shown in FIG.
Similarly to 0, both ends of the cored bar 2a are held by bearing members (not shown), and the pressure spring 23 presses and urges the photosensitive drum 1 toward the photosensitive drum 1 so that a predetermined pressing force is applied to the photosensitive drum 1 surface. The photosensitive drum 1 is pressed under a total pressure of 1000 g and is driven to rotate as the photosensitive drum 1 rotates (it may be positively or normally driven to rotate normally). An AC voltage Vac is applied to the charging roller 2 from a power source 4 via a sliding electrode in contact with the charging roller core metal 2a; in this embodiment, 2.0 KVpp, 600.
Hz DC voltage Vdc; superimposed vibration voltage (Vac + Vdc) of DC voltage corresponding to target charging potential is applied. As a result, the peripheral surface of the rotary photosensitive drum 1 is uniformly contact-charged to the target charging potential by the AC application method.

In the charging roller 2, the outer member of the cored bar 2a comprises a foaming member 2b, a thin conductive layer 2h, and a charging layer 2c.
Conventional solid charging roller 2 illustrated in the first embodiment.
The charging roller as a whole is much lighter than 0 (FIG. 23) and has a low hardness.

Therefore, like the hollow charging roller 20 of FIGS. 25 and 26, the charging roller 2 of this embodiment strikes the photosensitive drum 1 even when the AC component of the applied vibration voltage causes the vibration phenomenon by the mechanism described above. Since the mass is small, the generated charging noise is reduced to a level at which there is no problem.

The contact charging device of this example was set in an anechoic chamber, and the generated noise (charging sound) was measured under the above oscillating voltage application conditions. The measurement was carried out in accordance with ISO 7779, item 6. As a result, the generated charging noise was as low as 33 dB.

The charging layer 2c has a conductive layer 2 inside thereof.
Since the foaming member 2b is present, the thin roller (5 μm or more) can be backed up and good shape retention can be achieved.
Is pressed against the surface of the photosensitive drum 1 and comes into pressure contact with the surface of the photosensitive drum over the entire length without forming a floating portion between the surface of the photosensitive drum 1 and the surface of the photosensitive drum 1. Therefore, even if the axial length of the charging roller 2 is increased, Hollow charging roller 20 of FIGS. 25 and 26
Defective charging a corresponding to the rotation cycle of the charging roller such as
(Fig. 27) does not occur.

Charge generated when the contact charging device of this embodiment is set in an anechoic chamber and the thickness t of the charging layer 2c of the charging roller 2 is variously changed as in the case of the charging roller of the first embodiment. The sound was measured (ISO 7779, item 6). The result is similar to that of the charging roller of Example 1 (FIG. 3).
Met.

That is, as in the case of the charging roller 2 of Example 1, the thickness t of the charging layer 2c is too thin (5 μm or less).
As a result, the charging layer 2c loses its rigidity, and the charging layer 2c easily vibrates when an oscillating voltage is applied. As a result, the charging layer 2c floats from the surface of the photosensitive drum 1 according to the oscillating voltage, and charging failure occurs.

The thickness t is too thick (10000 μm).
m or more), the charging layer 2c vibrates when an oscillating voltage is applied, and the force for hitting the photosensitive drum 1 becomes large as in the case of the conventional solid charging roller. As a result, the charging noise becomes loud and exceeds the allowable level of 50 dB.

From the above results, the thickness t of the charging layer 2c is 5
It is desirable that the thickness is larger than μm and smaller than 10000 μm.

The thickness ratio between the foam member 2b and the charging layer 2c is
Generally, it is set in the range of 10: 1 to 1000: 1.

The fact that the generated charging noise can be reduced means that
It is possible to increase the AC component frequency of the oscillating voltage applied to the contact charging member, which causes a moire on the image due to the interference between the scanning laser light and the charging unevenness due to the AC component frequency, which has been a problem at a low frequency. It has become possible to eliminate the occurrence of interference fringes.

Since the charging roller 2 as the contact charging member weakens the force of striking the photosensitive drum 1, it is possible to suppress the "toner fusion" phenomenon which occurs when the toner remaining after cleaning is pressed against the surface of the photosensitive drum 1. It has become possible.

<Embodiment 10> (FIG. 17) In this embodiment, the contact charging member of Embodiment 9 is a blade type (charging blade) 2A. The charging blade 2A of the present embodiment has a foamed member (core material) 2b of carbon-dispersed polyurethane foam and an EPD on the outer peripheral surface of the foamed member 2b.
A conductive layer 2h made by dispersing a large amount of conductive powder such as carbon or tin oxide in M or urethane, and a charge layer 2c of epichlorohydrin rubber coated on the outer peripheral surface of the conductive layer 2h. It is composed of an electrode plate 2g as a supporting member which is attached and supported via 2f.

The charging blade 2A is attached and fixed to the immovable member 30 with the tip of the charging blade 2A pressed against the surface of the photosensitive drum 1 against the waist of the blade, and then fixed. 2A is provided.

An oscillating voltage (Vac + Vd) is applied to the charging blade 2A from the power source 4 via the supporting member 2g as an electrode plate.
c) is applied, and the surface of the rotary photosensitive drum 1 is uniformly contact-charged by the AC application method.

In this example, the charging noise generated when the charging blade 2A having the following specifications was used was 40 dB (the applied oscillating voltage was the same as in Example 9).

Foaming member 2b: Foamed epichlorohydrin rubber of carbon dispersion, specific gravity 0.3, volume resistance value 10 ³ Ωcm, length 10 mm, length 310 mm, thickness 3 mm. A conductive layer 2h may be provided; a large amount of carbon in EPDM or urethane
Conductive powder such as tin oxide dispersed Volume resistance value 10 ⁵ Ωcm Layer thickness 80 μm Charging layer 2c; Epichlorohydrin rubber Volume resistance value 10 ⁹ Ωcm Layer thickness t500 μm Charging blade 2A hardness 40 degrees (ASKER-C) Charging Free length L5mm of blade 2A Total pressure of pressing on photosensitive drum 1 700g Therefore, charging noise can be reduced also in charging blade 2A, and pressing pressure of charging blade 2A to photosensitive drum 1 can be applied to the waist of the blade. It has the advantage that it can be controlled.

<Embodiment 11> (FIGS. 18 and 19) In this embodiment, a conductive foam member 2b is used for the charging roller 2.
Further, the charging layer 2c is formed on the conductive layer 2h via the conductive layer 2h, and the protective layer 2i is further provided on the outer peripheral surface thereof. The specific specifications are as follows.

Foaming member 2b; carbon-dispersed polyurethane foam, specific gravity 0.3 volume resistance 10 ³ Ωcm layer thickness 2.3 mm, length 310 mm length 10 mm, length 310 mm, thickness 3 mm. , A vibration absorbing layer having a higher foaming rate may be provided Conductive layer 2h; A large amount of carbon in EPDM or urethane
Conductive powder such as tin oxide dispersed Volume resistance value 10 ⁵ Ωcm Layer thickness 80 μm Charging layer 2c; Epichlorohydrin rubber Volume resistance value 10 ⁹ Ωcm Layer thickness 80 μm Protective layer 2i; N-methoxymethylated nylon volume resistance value 10 ⁹ Ωcm Layer thickness 30 μm Weight of charging roller 2 is 177 g, hardness is 35 degrees (ASKER-C) Pressure on photosensitive drum 1 Total pressure 1000 g Applied vibration voltage AC voltage Vac; 2.0 KVpp, 6
00 Hz DC voltage Vdc; DC voltage corresponding to target charging potential Measurement result of charging noise generated by the charging roller 2 (ISO 7
779, item 6) was as small as 33 dB.

Protective layer 2i provided on the outer peripheral surface of charging layer 2c
By using a material having a good compatibility with the surface layer of the photosensitive drum 1, it is possible to prevent the surface layer of the photosensitive drum 1 and the charging roller 2 from being contaminated.

Further, since the electric charge cannot be supplied to the charging layer portion of the conductive foam material 2b in contact with the large bubbles, the charging layer portion becomes defective in charging. However, since the conductive layer 2h is interposed between the conductive foam material 2b and the charging layer 2c, the electric charge can be easily applied to the charging layer portion B in which the large bubbles of the foaming member 2b correspond closely. It is possible to wrap around, the amount of wraparound charge in each part of the charging layer 2c is made uniform, and even if the foam member 2b is a coarse bubble 2b 'with a large expansion ratio, the outside diameter of the bubbles of the foam member is large. Does not cause poor charging.

<Embodiment 12> (FIG. 20) In this embodiment, in the charging blade 2A, the charging layer 2c is formed on the conductive foam member 2b (blade core material) through the conductive layer 2h.
And a protective layer 2i is further provided on the outer peripheral surface thereof. The specific specifications are as follows.

Foaming member 2b: Polyurethane foam in which conductive powder is dispersed, specific gravity 0.3, volume resistance value 10 ³ Ωcm, length 10 mm, length 310 mm, thickness 3 mm Conductive layer 2h; EPDM or urethane containing a large amount of carbon
Conductive powder such as tin oxide dispersed Volume resistance value 10 ⁵ Ωcm Layer thickness 80 μm Charging layer 2c; Epichlorohydrin rubber Volume resistance value 10 ⁹ Ωcm Layer thickness 100 μm Protective layer 2i; N-Methoxymethylated nylon volume resistance value 10 ⁹ Ωcm Layer thickness 30 μm Charging blade 2A hardness 40 ° (ASKER-C) Charging blade 2A free length L5 mm Total pressing pressure on photosensitive drum 1 700 g Measurement result of charging noise generated by this charging blade 2A (ISO
The item (6th item of 7779) was as small as 40 dB.

Protective layer 2i provided on the outer peripheral surface of charging layer 2c
By using a material having a good compatibility with the surface layer of the photosensitive drum 1, it is possible to prevent the surface layer of the photosensitive drum 1 and the charging roller 2 from being contaminated.

Further, since the electric charge cannot be supplied to the charging layer portion in which the large bubbles of the conductive foam material 2b are in contact, the charging layer portion becomes defective in charging. However, since the conductive layer 2h is interposed between the conductive foam material 2b and the charging layer 2c, the electric charge easily wraps around to the charging layer portion where the large bubbles of the foaming member 2b closely correspond. Even if the foamed member 2b has coarse bubbles 2b 'with a large expansion ratio, the outer diameter of the bubbles of the foamed member 2b is large because the amount of charge sneaking around each part of the charging layer is made uniform. Does not cause poor charging.

<Embodiment 13> (FIGS. 21 and 22) In this embodiment, the electrically conductive foam member 2b is used for the charging roller 2.
Is covered with a tube 2j, and a conductive layer 2h is formed on the tube 2j.
The charging layer 2c is formed through the above, and the protective layer 2i is further provided on the outer peripheral surface thereof. The specific specifications are as follows.

Foaming member 2b: Foamed epichlorohydrin rubber of carbon dispersion, specific gravity 0.3 volume resistance value 10 ³ Ωcm length 10 mm, length 310 mm, thickness 3 mm tube 2j; polyurethane thermoplastic elastomer volume resistance value 10 ⁷ Ωcm layer thickness 300 μm Conductive layer 2h; large amount of carbon in EPDM and urethane
Conductive powder such as tin oxide dispersed Volume resistance value 10 ⁵ Ωcm Layer thickness 80 μm Charging layer 2c; Epichlorohydrin rubber Volume resistance value 10 ⁹ Ωcm Layer thickness 80 μm Protective layer 2i; N-methoxymethylated nylon volume resistance value 10 ⁹ Ωcm Layer thickness 30 μm Weight of charging roller 2 is 177 g, hardness is 35 degrees (ASKER-C) Pressure on photosensitive drum 1 Total pressure 1000 g Applied vibration voltage AC voltage Vac; 2.0 KVpp, 6
00 Hz DC voltage Vdc; DC voltage corresponding to target charging potential In such a configuration, a method is used in which a foam member 2b in which epichlorohydrin rubber is foamed is first prepared, and a core metal 2a and a tube 2j are inserted into the foam member 2b. There is a method in which a cored bar 2a is erected inside 2j, and epichlorohydrin rubber, which is a raw material of the foaming member 2b, is inserted into the cored bar 2a and foamed in a fixed state.

The tube 2j covering the conductive foam member 2b is substantially separated from the conductive foam member 2b. The same applies to the core metal 2a and the conductive foam member 2b. Furthermore, in order to prevent axial displacement, the tube 2j
And conductive foam material 2b, and core metal 2a and conductive foam member 2
You may fix a part of b. As a result, even when an AC voltage is applied to the cored bar 2a, the heavy cored bar 2a does not vibrate, but only the light conductive foam member 2b and the tube 2j vibrate to strike the photosensitive drum 1, and the energy thereof is It becomes smaller and the charging noise becomes smaller. In this case, the measurement result of the charging sound generated by the charging roller 2 (6th item of ISO 7779) is 30 dB.
It was smaller than that without the tube (Example 11).

Protective layer 2i provided on the outer peripheral surface of charging layer 2c
By using a material having a good compatibility with the surface layer of the photosensitive drum 1, it is possible to prevent the surface layer of the photosensitive drum 1 and the charging roller 2 from being contaminated.

Further, since the electric charge cannot be supplied to the charging layer portion in which the large bubbles of the conductive foam material 2b are in contact, the charging layer portion becomes defective in charging. However, the volume resistance value between the tube 2j and the charging layer 2c is
Since the lower conductive layer 2h is interposed, the foam member 2
The electric charge can easily sneak into the charging layer portion B to which a large bubble b corresponds, and the amount of sneaking charges in each portion of the charging layer 2c is made uniform, and the foaming member 2b has a large expansion ratio. Even if the bubbles 2b 'are coarse, the charging failure due to the large outer diameter of the bubbles of the foam member 2b does not occur.

<Embodiment 14> The charging roller 2 or the charging blade 2A of Embodiments 9 to 13 is also the charging roller 2.
As described above, since the charging sound is hardly generated even when the oscillating voltage is applied, as in the case of the sixth embodiment, a very compact process cartridge having substantially no charging sound can be configured. It is possible.

[0184]

As described above, according to the present invention, it is possible to effectively solve the problem of the generation of charging noise in contact charging without causing other inconvenient situations such as uneven charging, deterioration of image quality and high cost. Can be resolved.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a contact charging member (charging roller) or a contact charging device according to a first embodiment.

FIG. 2 is a vertical sectional model view of one end side of the device.

FIG. 3 is a graph showing the relationship between the thickness of the charging layer, the level of charging failure, and the generated charging noise.

FIG. 4 is a schematic cross-sectional view of a contact charging member (charging roller) or a contact charging device according to the second embodiment.

FIG. 5 is a vertical sectional model view of one end side of the device.

FIG. 6 is a schematic cross-sectional view of a contact charging member (charging blade) or a contact charging device of Example 3.

FIG. 7 is a schematic cross-sectional view of a contact charging member (charging roller) or a contact charging device according to the fourth embodiment.

FIG. 8 is a vertical sectional model view of one end side of the device.

FIG. 9 is a schematic cross-sectional view of a contact charging member (charging blade) or a contact charging device of Example 5.

FIG. 10 is a schematic cross-sectional view of the process cartridge of Example 6

FIG. 11 is a schematic cross-sectional view of a contact charging member (charging roller) or a contact charging device of Example 7.

FIG. 12 is a vertical sectional model view of one end side of the device.

FIG. 13 is a schematic cross-sectional view of a contact charging member (charging roller) or a contact charging device of Example 8.

FIG. 14 is a vertical sectional model view of one end side of the device.

FIG. 15 is a schematic cross-sectional view of a contact charging member (charging roller) or a contact charging device of Example 9.

FIG. 16 is a vertical sectional model view of one end side of the device.

FIG. 17 is a schematic cross-sectional view of a contact charging member (charging blade) or a contact charging device of Example 10.

FIG. 18 is a contact charging member (charging roller) of Example 11.
Or a cross-sectional model view of the contact charging device

FIG. 19 is a vertical sectional model view of one end side of the device.

FIG. 20 is a schematic cross-sectional view of a contact charging member (charging blade) or a contact charging device of Example 12.

FIG. 21 is a contact charging member (charging roller) of Example 13.
Or a cross-sectional model view of the contact charging device

FIG. 22 is a vertical sectional model view of one end side of the device.

FIG. 23 is a schematic configuration diagram of an example of an image forming apparatus using a contact charging device.

24 (a), (b), and (c) are explanatory views of the mechanism of charging noise generation.

FIG. 25 is a schematic cross-sectional view of a hollow charging roller

[Fig. 26] Similarly, a vertical cross-section model diagram

FIG. 27 is a diagram showing a charging failure portion that occurs due to irregular deformation of the hollow charging roller in correspondence with the rotation cycle of the charging roller.

FIG. 28 is an explanatory diagram of how the charge flows to the charging layer when the conductive foam member has large bubbles.

FIG. 29 is a diagram showing a defective charging portion that occurs corresponding to the rotation cycle of the charging roller due to uneven charge flow.

[Explanation of symbols]

1 Photosensitive Drum as Charged Member 2.2A / 20 Charging Roller or Charging Blade as Contact Charging Member 2a / 2g Core Metal or Electrode Plate as Supporting Member 2b Foaming Member 2c Charging Layer 2h Conductive Layer 4 Power Supply for Charging Bias

Claims (25)

[Claims] 1. A contact charging member of a contact charging device for charging a charging member by bringing the charging member into contact with a member to be charged, the contact charging member being at least a support member and directly or through another layer to the member to be charged. A contact charging member comprising a charging layer in contact with the charging layer and a foaming member on the inner side of the charging layer opposite to the charged body side. 2. A contact charging member of a contact charging device for charging by charging a charging member to which an oscillating voltage is applied to a member to be charged, the contact charging member being at least a support member and directly to the member to be charged. Alternatively, a contact charging member comprising a charging layer that is in contact with another layer via another layer, and an inside foaming member that is the side opposite to the charged body side of this charging layer. 3. The contact charging member according to claim 1, wherein the foam member is made of polystyrene, polyolefin, polyester, polyurethane, or polyamide foam material. 4. A contact charging device for charging a charging member by bringing it into contact with a member to be charged, the contact charging member being at least a support member and a charging layer which is in contact with the member to be charged directly or through another layer. A contact charging device comprising a foaming member on the inner side of the charging layer opposite to the side to be charged. 5. In a contact charging device for charging by charging a charging member to which an oscillating voltage is applied to a member to be charged, the contact charging member is at least directly connected to the support member and the member to be charged or through another layer. 1. A contact charging device comprising a charging layer in contact with the charging layer and a foaming member on the inner side of the charging layer opposite to the charged body side. 6. In a process cartridge including at least an image carrier and a charging unit for the image carrier, which is attached to and detached from an image forming apparatus, the charging unit brings a charging member into contact with the image carrier. Is a contact charging device that charges by
The contact charging member is composed of at least a supporting member, a charging layer that is in contact with the body to be charged directly or through another layer, and a foaming member on the inner side opposite to the side of the body to be charged of the charging layer. Process cartridge. 7. A contact charging member of a contact charging device for charging by charging a charging member to an object to be charged, the contact charging member being at least a support member and directly or through another layer to the object to be charged. A charging layer in contact with the charging layer, a conductive layer on the inner side of the charging layer opposite to the charged body side, and a foaming member inside the charging layer, and a bias is applied to the conductive layer to charge the charged body. A contact charging member, characterized in that the applied charging layer has a higher volume resistivity than the conductive layer. 8. A contact charging member of a contact charging device for charging by charging a charging member to which an oscillating voltage is applied to a member to be charged, wherein the contact charging member is at least directly on the support member and the member to be charged. Alternatively, the charging layer is in contact with another layer via another layer, the conductive layer on the inner side of the charging layer opposite to the side to be charged, and the foaming member inside the charging layer. A contact charging member, characterized in that a bias is applied to do so and the charging layer has a higher volume resistivity than the conductive layer. 9. A contact charging device for charging a charging member by bringing it into contact with a member to be charged, the contact charging member being at least a support member and a charging layer which is in contact with the member to be charged directly or through another layer. An electrically conductive layer on the opposite side of the charging layer from the side of the body to be charged, and a foam member inside the electrically conductive layer,
The contact charging device is characterized in that a bias is applied to the conductive layer to charge the charged body, and the charging layer has a higher volume resistivity than the conductive layer. 10. In a contact charging device for charging by charging a charging member to which an oscillating voltage is applied to a member to be charged, the contact charging member is at least directly supported by the support member and the member to be charged or through another layer. It consists of a charging layer in contact, a conductive layer on the inside of the charging layer opposite to the side of the body to be charged, and a foaming member inside the layer. A bias is applied to the conductive layer to charge the body. The contact charging device is characterized in that the charging layer has a higher volume resistivity than the conductive layer. 11. In a process cartridge including at least an image carrier and a charging unit for the image carrier, which is attached to and detached from an image forming apparatus, the charging unit brings a charging member into contact with the image carrier. Is a contact charging device that performs charging by means of at least a support member, a charging layer that is in contact with a member to be charged directly or through another layer, and an inner side of the charging layer opposite to the member to be charged. And a foamed member inside the conductive layer, a bias is applied to the conductive layer to charge the charged body, and the charged layer has a higher volume resistivity than the conductive layer. Process cartridge. 12. A contact charging member of a contact charging device for charging by charging a charging member to a member to be charged, the contact charging member being at least a support member and directly or through another layer to the member to be charged. And a charging layer in contact with each other, a conductive layer on the inner side of the charging layer opposite to the side to be charged, and a layer including a foam layer composed of at least one layer further inside, and the conductive layer includes the foam layer. A contact charging member having a volume resistivity lower than that of a layer. 13. A contact charging member of a contact charging device for charging by charging a charging member to an object to be charged, the contact charging member being at least a support member and directly or through another layer to the object to be charged. And a charging layer in contact with each other, a conductive layer on the inner side of the charging layer opposite to the side to be charged, and a layer including a foam layer composed of at least one layer further inside, and the conductive layer includes the foam layer. A contact charging member having a layer thickness smaller than a layer. 14. A contact charging member of a contact charging device for charging by charging a charging member to an object to be charged, the contact charging member being at least a support member and directly or through another layer to the object to be charged. A charging layer in contact with the charging layer, a conductive layer on the inner side of the charging layer opposite to the charged body side, and a foaming member inside the charging layer, and a bias is applied to the conductive layer to charge the charged body. The contact charging member, wherein the charged layer has a higher volume resistivity than the conductive layer and the foamed member has a volume resistivity equal to or lower than that of the conductive layer. 15. A contact charging member of a contact charging device for charging by charging a charging member to which an oscillating voltage is applied to a member to be charged, the contact charging member being at least directly on the support member and the member to be charged. Alternatively, the charging layer is in contact with another layer via another layer, the conductive layer on the inner side of the charging layer opposite to the side to be charged, and the foaming member inside the charging layer. The contact charging member is characterized in that a bias is applied to perform the charging, the charging layer has a higher volume resistivity than the conductive layer, and the foaming member has a volume resistivity equal to or lower than that of the conductive layer. 16. The foam member according to claim 14, wherein the foam member is made of polystyrene, polyolefin, polyester, polyurethane, or polyamide foam material.
The contact charging member according to. 17. The contact charging member according to claim 14, wherein the foamed member has a layer thickness larger than that of the conductive layer. 18. The contact charging member according to claim 14 or 15, wherein the foaming member has a foaming rate of 70% or more. 19. A contact charging device for charging a charging member by bringing it into contact with a member to be charged, the contact charging member being at least a support member, and a charging layer in contact with the member to be charged directly or through another layer. An electrically conductive layer on the opposite side of the charging layer from the side of the body to be charged, and a foam member inside the electrically conductive layer,
A bias is applied to the conductive layer to charge the body to be charged, the charging layer has a higher volume resistivity than the conductive layer, and the foamed member has a volume resistivity equal to or lower than that of the conductive layer. A contact charging device characterized by. 20. In a contact charging device for charging by charging a charging member to which an oscillating voltage is applied to a member to be charged, the contact charging member is at least supported by the support member and directly or via another layer. It consists of a charging layer in contact, a conductive layer on the inside of the charging layer opposite to the side of the body to be charged, and a foaming member inside the layer. A bias is applied to the conductive layer to charge the body. The contact charging device is characterized in that the charging layer has a higher volume resistivity than the conductive layer, and the foamed member has a volume resistivity equal to or lower than that of the conductive layer. 21. The contact charging device according to claim 19, wherein the foam member has a layer thickness larger than that of the conductive layer. 22. The contact charging device according to claim 19, wherein the foaming member has a foaming rate of 70% or more. 23. In a process cartridge including at least an image carrier and a charging unit for the image carrier, which is attached to and detached from an image forming apparatus, the charging unit brings a charging member into contact with the image carrier. Is a contact charging device that performs charging by means of at least a support member, a charging layer that is in contact with a member to be charged directly or through another layer, and an inner side of the charging layer opposite to the member to be charged. And a foamed member inside thereof, a bias is applied to the conductive layer in order to charge the body to be charged, the charging layer has a higher volume resistivity than the conductive layer, and the foamed member is made of a conductive material. A process cartridge having a volume resistivity equal to that of the layer or lower than that of the conductive layer. 24. The process cartridge according to claim 23, wherein the foam member has a layer thickness larger than that of the conductive layer. 25. The process cartridge according to claim 23, wherein the foaming member has a foaming rate of 70% or more.