JPH03103879A - Contact electrifying device - Google Patents

Abstract

PURPOSE:To achieve stable, uniform electrification by providing an electrifying member with two or more facing surfaces, from which the surface of a body to be electrified is gradually separated toward a downstream side, in the direction in which the surface to be electrified moves, from abutting parts on the body. CONSTITUTION:The electrifying member 2a is provided with first and second parts 01 and 02, in which the member 2 abuts on the surface of the body 1, in the front and rear part, respectively, on the upstream and downstream sides, respectively, in the direction in which the surface of the body 1 moves. Also, the electrifying member 2 is provided with the first and second facing surfaces 7a and 7b, from both of which the surface of the body is gradually separated toward the downstream side in the direction in which each of the first and second abutting part 01 and 02 moves on the surface of the body. Accordingly, since there are two facing surfaces, two discharge areas, first and second discharge areas X and Y, are present thereon. Therefore, the surface of the body 1 can be electrified in the first and second discharge areas X and Y, by the single electrifying member. Thus, the stable, uniform electrification can be achieved.

Description

Detailed Description of the Invention (Industrial field in Icheon) The invention is a contact charging device, that is, a charging member to which a voltage is applied (contact charging member), which is brought into contact with the surface of the object to be charged to perform charging (neutralization) on the surface of the object to be charged. {1} Including electrical equipment.

(Prior Art) For convenience, an image forming apparatus such as an electrophotographic copying apparatus or an electrostatic recording apparatus will be used as an example for explanation. In the image forming process of electrophotography and electrostatic recording, there is a drum 1 driven by rotation or lijl motion or k-line drive, an electrophotographic photoreceptor of type endless belt type, winding reweb type, sheet type, etc., and electrostatic photoreceptor. This includes a step of uniformly charging the surface of an image carrier (an object to be charged) such as a recording dielectric.

Conventionally, as a means for uniformly charging the surface of such an image carrier, a corona discharge device such as a corotron or a scoro I-ron, which has good uniform charging properties, has been widely used. However, the corona discharger requires an expensive high-voltage power supply, requires space for itself and the shield space for the high-voltage power supply, and often generates corona products such as ozone. This has problems, such as increasing the size and cost of the device.

Therefore, in recent years, consideration has been given to adopting a contact charging method instead of a corona discharger, which has many problems. In contact charging, a voltage (for example, 1 to 2 KV) is applied to the surface of an image carrier as a charged body by a power source.
By contacting a conductive member (charging member) to which a DC voltage of approximately 100% or a superimposed voltage of a DC voltage and an AC voltage, etc.) is applied, charge is directly transferred (injected) to the image carrier surface. This is a device that charges the battery to a predetermined potential, and includes roller charging type (JP-A No. 58-91253), plate Teiden type (#KOKAI No. 56-1! 94349, and No. 80-1477).
58 Publication), and a combination IP cleaning type (Japanese Patent Application Laid-Open No. 511-516B) have been devised.

One of the problems when using this type of contact charging method is
One of them is the occurrence of charging unevenness.

{;}Proposals for removing electric unevenness and obtaining uniform {1} electric power include, for example, the following.

■Applying an oscillating voltage (a voltage whose voltage value changes periodically with time) having a peak-to-peak voltage that is more than twice the charging start voltage of the charged object to the contact charging member, the photosensitive drum as an image carrier is Charge uniformity is obtained by performing charge transfer and reverse movement between
.

■ Vibration that has a step in which the contact charging member gradually separates from the surface of the charged object in the downstream direction of the surface movement direction of the charged object, and during this process has a peak-to-peak voltage that is more than twice the charging start voltage of the charged object. A device that obtains uniform charging properties by applying a voltage (Japanese Patent Application Laid-Open No. 1498/1983).

(2) A device that eliminates charging unevenness by providing a plurality of contact charging members (Japanese Patent Application Laid-open No. 104349/1983).

(Problem to be solved by the invention) As in the above example, the subject {;F electric body? tF start voltage 2
Charging unevenness can be improved by applying an oscillating voltage (AC) with a peak-to-peak voltage that is more than double that to the contact charging member, but this is because the charging member is in the form of a rotating roller, etc. In the case of plane movement with respect to the charged body, charging uniformity that poses no practical problem can be obtained.

However, in the case of a fixed contact charging member that does not move relative to the object to be charged, for example, a plate-shaped one, the above-mentioned AC superimposed bias application is not sufficient. There was a drawback that iF electrical uniformity could not be obtained and vertical streaks may occur on the image.

As described above, there is a difference in charging unevenness when the charging member is a roller type and when it is a plate type, and the reason for this is as follows.

■In the case of a roller, the charging member itself moves in plane, so the entire outer circumferential surface of the roller contributes to charging, whereas in the case of a plate, the charging member is fixed, so one part of the surface of the plate contributes to charging. Only that portion contributes to constant charging.

Therefore, if one portion contributing to Teiden becomes unstable, charging unevenness (particularly vertical streaks) will occur. In the case of a roller, there will be no vertical streaks but roller bit charging unevenness, but if the unevenness is minute, it cannot be recognized in a normal image and will not be a substantial unevenness.

■In the case of a roller, charging is possible in both the upstream and downstream areas of the moving direction of the surface of the charged object, where the charging member is in contact with the charged object, but in the case of a plate, the charged object can be charged If it is brought into contact in the forward direction with respect to the direction of body surface movement,
Only the upstream side of the contact part can be charged, and if the contact is made in the counter direction, only the downstream side of the contact part can be charged. Therefore, whereas a roller is charged twice in two different areas, a plate is charged only once. Therefore, with respect to charging unevenness, a roller that can be charged twice provides better results than a roller that can be charged only once.

In this way, when the contact charging member is in the form of a plate or the like and is fixed and does not move relative to the object to be charged (a fixed type contact charging device such as a plate), the contact charging member is a rotating roller or a rotating member. Compared to those in the form of moving belts, running webs, etc. that move in a plane relative to the object to be charged (contact charging devices using a plane movement method such as rollers), the latitude of charging unevenness is narrower.

However, compared to surface-moving contact charging devices such as rollers, fixed-type contact charging devices such as plates: ■ have a simpler configuration and are less expensive; ■ have a simpler bias application method; ■ In the case of rollers. , The contact pressure tends to vary due to shaft deflection, etc., but with fixed plates, etc., it is relatively easy to set the contact conditions, and stable contact can be obtained even if the contact pressure is low. It also has great benefits, such as being able to create a contact surface shape.

As described above, the fixed type contact charging means has many advantages, but it has the disadvantage that if a plurality of plates etc. are provided to eliminate charging unevenness, the structure becomes complicated and the cost increases.

The present invention has been proposed in view of the above, and is an object of improving Teiden unevenness in a fixed type contact charging device such as a plate with an inexpensive and simple configuration.

(Means for Solving the Problems) The present invention is a contact charging device that charges the surface of an object to be charged by bringing a charging member to which a voltage is applied into contact with the surface of the object to be charged that moves in plane. The 417 member is a fixed conductive member that does not move relative to the object to be charged, and has an opposing surface that gradually separates from the surface of the object to be charged on the downstream side in the direction of movement of the surface of the object to be charged than the contact portion with respect to the object to be charged. This is a contact charging device characterized in that at least two or more of the following are present in the same member.

Further, in the contact charging device of the present invention, the portion of the resistive member that statically influences the 41'f electric body is coated with one or more types of resistive layer having an electrical resistance value higher than that of the conductive member. The voltage applied to the charging member is a DC voltage with an AC (vibration) component superimposed, and the peak-to-peak voltage of the AC component is at least twice the charging start voltage of the charged object. One thing is that the charging member is made of an elastic material,
This contact charging device is characterized by the fact that it is in the shape of a plate that contacts the object to be charged using the elastic force of the charging member itself.

(for production) This will be explained using the schematic diagram shown in FIG.

Let l be an object to be charged that is moving in plane in the direction of arrow A. For example, rotating drum type ◆ Rotating belt type ● in contact charging equipment
Traveling web type ●Conveying sheet-like image carriers (photoreceptors, dielectrics, etc.).

2a is a charging member that is pressed against the surface of the charged object with a predetermined pressing force. Assume that is applied. The charging member 2a shown in the figure has first and second abutting portions 01 and 02 for the surface of the charged object 1 at two locations on the upstream and downstream sides in the surface movement direction of the charged object 1. Then, the first and second opposing surfaces 7a and 7a are arranged so that the surfaces of the charged object are gradually separated from each other on the downstream side in the moving direction of the charged object surface of the first and second abutting portions 01@02.
7b is provided.

A bias voltage is applied to the 111F electric member 2a from the outside, and the charged object 1 surface and the first and fiS2 of the member 2a
A strong electric field is generated in the tapered minute gap formed between the facing surfaces 7a and 7b.

Below a certain gap, air dielectric breakdown occurs and a discharge phenomenon occurs. Due to this discharge phenomenon, the surface of the charged object 1 is charged, and the surface potential on the charged object 1 increases. As the surface potential on the charged object l increases, the potential difference between the first and second opposing surfaces 7a and 7b of the member 2a and the surface of the charged object l becomes smaller, and the electric field also weakens. Therefore, at some point the discharge stops.

In FIG. 1, the region in which the discharge occurs is conceptually indicated by an arrow. The discharge region between the first opposing surface 7a of the member 2a and the first surface of the charged object is called a first discharge region X, and the discharge region between the second opposing surface 7b and the first surface of the charged object is called a second discharge region. Let's call it Castle Y.

In conventional charging rollers or counter-contact charging plates, there is only one surface that gradually separates from the contact area of the charged object, and therefore there is only one discharge area. ．． The member 2a has two surfaces, a first opposing surface 7a and a second opposing surface 7b, which are gradually separated from the charged object contact portion, and therefore the discharge area is also divided into the first and second discharge regions x.
There are two, I1Y. For this reason, it is possible to charge one surface of the object to be charged in two regions, the first discharge region X and the second discharge region Y, in one charging member, making it possible to perform more stable and uniform charging. Become.

l1 The member 2a is not limited to two as shown in the schematic diagram, but may be provided with a plurality of contact portions for the surface of the charged object and subsequent opposing surfaces as described above, and the number of discharge regions increases.
More uniform '41F electricity is possible.

If there is a defect such as a hole in the surface of the charged object, the applied voltage of the charging member that is in contact with the surface of the charged object may break down, or the charged object may be exposed to light in electrophotography or electrostatic recording. If the image carrier is a body, dielectric, or the like, horizontal white streaks may occur in the output image due to charge loss.

Therefore, the charging member has a form in which the portion that electrostatically affects the object to be charged is coated with one or more types of resistance layer having a higher electrical resistance value than the conductive member (base material of the charging member). Even if there is a defect on the surface of the object to be charged, the above-mentioned resistance layer can prevent phenomena such as breakdown of the applied voltage and loss of charge. Furthermore, it can be used even if the resistance value varies within the conductive base layer that is the base material of the charging member.

The voltage applied to the charging member has an alternating current (vibration) component. If the peak-to-peak voltage value of the alternating current component is at least twice the charging start voltage of the object to be charged, the effect is even better in combination with the above-mentioned effect due to the form of the charging member having the above-mentioned specific configuration. A uniform charging effect can be obtained.

By making the charging member a plate-shaped member made of an elastic material, the elastic force of the charging member itself allows the member to be brought into stable and good contact with the surface of the charged object with a predetermined pressing force. In particular, there is no need to provide pressure means such as a spring, and the structure is simplified.

(Example) Example 1 (Figure 2) 1 is an electromagnetic object, for example, a drum-shaped electrophotographic photosensitive member that is rotated at a predetermined circumferential speed (process speed) in the diagonal direction of arrow A. (hereinafter referred to as photosensitive drum).

2 is a general code of a contact charging device for uniformly charging the circumferential surface of the photosensitive drum l. 2a is a conductive charging member that comes into contact with the surface of the photosensitive drum 1, and 2b is a support member for this charging member. The support member 2b is fitted into a guide frame 4 that is fixedly supported by a stationary member (not shown), and a pressure spring 3 is compressed between the guide frame 4 and the support member 2b, so that the charging member 2a is constantly pressed against the surface of the photosensitive drum l with a predetermined pressure.

In the case of a wooden case, the support member 2b is made of a conductive member,
It is electrically connected to the conductive charging member 2a. Further, the pressure spring 3 is also made of a conductive material, and one end thereof is in contact with the support member 2b, and the other end is in contact with the conductive electrode 5.

Reference numeral 6 denotes a high-voltage power source for charging, which applies a bias voltage for charging to the conductive electrode 5 via a lead wire. Is the applied voltage passed through the conduction 8i5 → correction spring 3 → support member 2b?
tF is applied to the electric member 2a.

The charging member 2'a is similar to the one shown in the schematic diagram of FIG.
Contact portion 01 *02 and first and second opposing surfaces 7a and 7
b, and the surface of the photosensitive drum is sequentially charged at two locations in the first and second discharge regions X-Y by the same action as explained in the above (effect) section. , stable and uniform charging processing becomes possible.

The first opposing surface 7a faces the photosensitive drum surface at an angle θ1 with respect to the photosensitive drum tangent line Il at the first contact portion 01,
The second opposing surface 7b contacts the photosensitive drum at the contact portion 02!
iiiI2 and faces the photosensitive drum surface at an angle θ2.

The values of θl and θ2 are 45″ or less, more preferably 30° or less, and θl≧
02 is desirable.

In this example, θ1=02=15'. Charging 7 The member 2a is made of carbon-dispersed EPDM having a volume resistance of 10ΩCl1, and the applied voltage is -1. When charging was carried out at 3 KV and a circumferential speed of the photosensitive drum 1 of 501 Il/SeC, the photosensitive drum surface potential was -700 V and a good image without charging unevenness was obtained. OPC was used as the photosensitive drum 1.

Furthermore, when a voltage obtained by superimposing a DC voltage on an AC voltage described in JP-A-83-149888 was applied as the applied voltage, the unevenness was further improved, and even if small dust etc. entered the charged area, there was no streak. Stable and uniform charging was obtained. In the experiment, the AC voltage was set to 1. 6-2
-4KV. When the test was carried out under the same conditions as above, with a DC voltage of -750 V, the surface potential of the photosensitive drum was -720 cm, and a uniform image was obtained.

Although a photosensitive drum is used as an example of the image carrier (charged body), the image carrier is not limited to the drum shape, and may be a belt-shaped photosensitive member. Further, the present invention is not limited to rotational driving, and a flat photoreceptor may be moved in parallel.

As long as the structure allows the voltage of the charging member 2 to be applied, the support member 2b may be an insulator.

In the charging member 2a shown in FIG. 1 and FIG. 2, the first and second opposing surfaces 7a and 7b are flat surfaces, but they may of course be curved surfaces such as cylindrical surfaces.

l6? Example 2 (FIG. 3) In this example, a conductive charging member 2a is connected to a photosensitive drum l as a heavy body to be charged, and a portion surface that has an electrostatic influence is a conductive member serving as a base layer (base material) of the charging member 2a. This shows an example of a configuration in which one or more types of resistance layers 8 having a higher electrical resistance value are stirred. Resistance layer. ,) The resistance value is ■. 7Qcyo～■0”Q c1,
a,? /0 is preferably 10-10Ωcm. The provision of the electric conductor 8, which is the base layer of the charging member 2a, is made easier. The electrical member may have any resistance value of 10Ω14 or less.

When the conductive charging member 2a, which is not provided with a resistance layer, is in contact with the photosensitive drum l, if the resistance value of the conductive charging member 72a is 10Ωcm or less, the photosensitive drum l
If there is a defect on the top, the applied voltage will break down or horizontal white lines will appear due to so-called charge loss. Further, when the resistance value reaches approximately 10ΩC1, a voltage drop occurs within the conductive charging member even if a bias is applied, and it becomes impossible to form a sufficient electric field necessary for charging. Therefore, I. Q. Only a very narrow range of materials with a resistance value of -10Qc■ can be used.

On the other hand, in the case of this embodiment, by providing the resistance layer 8 on the surface layer, the conductive 4iF electric member 2a can be used as long as the resistance l value is 10 Ωcm or less, and the resistance l value 11 inside the member 2a can be used. It can be used even if it falls apart.

As the material for the resistance layer 8, in addition to Torezin (trade name), Amilan (trade name), and other materials, various polymeric materials can be used. Further, it is better to select a material with excellent sliding properties such as a fluororesin or a material with high wear resistance for the resistance layer 8.

The thickness of the resistive layer is 20 mm, which is a level that does not cause dielectric breakdown of the film.
~30 p. A thickness of rs or more is required. Further, when a material with a high resistance value of about 10Ωcm is selected for the resistance layer, the thickness is desirably 100 ILIm or less so as not to cause a large voltage drop inside the resistance layer 8.

Example 8 (Figures 4 and 5) Another example is shown in Figure 4. In FIG. 4, the photosensitive drum 1 as an object to be charged rotates in the clockwise direction of arrow A. In FIG. A charging plate lO as a charging member is in contact with the photosensitive drum l. Further, the charging plate 10 is attached to a plate supporting metal plate 11 and is electrically connected to the supporting metal plate 11.

A bias application terminal l2 is attached to the plate support metal plate 11, and a bias voltage of {+F
The necessary voltage is applied to the current.

FIG. 5 is a schematic enlarged view of the abutting portion of the charging plate IO in FIG. 4. Similarly to FIG. 4, the photosensitive drum 1 rotates as indicated by arrow A, and the charging blade 10 contacts the photosensitive drum 1 at two contact nips P] and P2. In Figure 5, ? The t'fitt plate lO has a two-layer structure consisting of a {1+f electric plate base layer l3 and a charging plate top layer 14 covering its surface layer, but it may be a single layer conductive plate.

19 The charging plate 1O has two surfaces 7a and 7b that are gradually separated from the surface of the photosensitive drum 1. That is, the surface 7a continuing from the contact nip P1 to the downstream side in the surface movement direction of the photosensitive drum.
and a surface 7b continuing downstream from the nip P2. A strong electric field is generated in the minute gap formed between these two surfaces 7a and 7b and the surface of the photosensitive drum 1. Therefore, below a certain gap, air dielectric breakdown occurs and a discharge phenomenon occurs. The region where this discharge phenomenon occurs is schematically indicated by the arrow in FIG. Contact nip P in Figure 5
The discharge area immediately downstream of the contact nip P2 is referred to as the first discharge area X', and the discharge area immediately downstream of the contact nip P2 is referred to as the second discharge area Y. Since the photosensitive drum l is rotating in the direction of arrow A in the figure,
First, after passing through the contact nip Pl, it is uniformly charged in the first discharge region X'. Thereafter, it passes through the abutment nip P2, but at this time, the electric charge on the irradiated light drum l that was electrically charged at the abutment nip P2 is not removed. After passing through this contact nip P2, it again enters the second discharge region Y'.

What if this match is 20? If the charged potential on the photosensitive drum 1 is uniformly charged to a predetermined value, the surface of the photosensitive drum remains as it is in the second discharge area Y'; If the potential is too high than the potential of the photosensitive drum I, the charge is removed, and if the potential charged on the photosensitive drum l is too lower than the predetermined potential, the potential is reduced to the predetermined potential.

In this way, by providing the charging plate 10 with two surfaces 7a and 7b that are gradually separated from the surface of the photosensitive drum 1, it is possible to charge in two regions f and Y', thereby making it more stable. A uniform charge can be obtained. Furthermore, by forming the charging plate into a charging plate shape, the member can be brought into contact with the surface of the photosensitive drum with the required pressure by the elastic force of the member itself, so there is no need to provide any particular pressure means such as a spring.

In this embodiment, the charging plate base layer 13 is lOrΩc
m (7) The thickness of the CR conductive rubber plate was 1.51111 (7), and the plate top fil4 was made of 30 μl of Torezin (trade name) waste {The iP electric plate 10 had a contact angle of about 15° and a contact pressure of 15 g/cm. the applied voltage is 1.
．． Applying a DC precept to an AC voltage with a peak-to-peak voltage of 6KV -
When image output was performed using a 700V superimposed voltage, a good image without image unevenness was obtained.

In this embodiment, there are two contact surfaces 7a and 7b that are gradually separated from the surface of the photosensitive drum 1, but it is of course possible to have three or more contact surfaces.

Embodiment 4 (FIG. 6) This embodiment is a schematic diagram of an example of an electrophotographic copying apparatus using a contact charging device according to the present invention as a primary charging means for a photoreceptor. The example is an electrophotographic copying machine with a removable process cartridge.

In the figure, reference numeral 1 denotes a drum-type electrophotographic photoreceptor (hereinafter abbreviated as photoreceptor) as an image carrier that is rotated around a support shaft 1a in the direction of arrow A at a predetermined circumferential speed. 1O is a contact charging plate (having the same configuration as the plate-type ?iF charging device shown in FIGS. 4 and 5) as a means for uniformly charging the circumferential surface of the photoreceptor. 15 is a short focus lens array as a light image exposure means, 16 is a developing device, 17 is a transfer device, and 21 is a transfer material conveyed one sheet from a paper feed unit (not shown) to the rotation of photoreceptor L and rotation. Then, remove the photoreceptor 1 and the transfer device 1.
7, a timing roller 22 is a transfer material guide member disposed between the timing roller 2l and the transfer device 17, and l8 is a transfer material guide member that passes between the photoreceptor l and the transfer device l7 to transfer the image. A conveyance device 9 introduces the received transfer material P to a fixing device (not shown), and a cleaning device 9 cleans the surface of the photoreceptor 1 after image transfer.

The device shown in the example is configured as a process cartridge 20 in which four process devices: a photoreceptor l, a contact charging plate 10, a developing device 16, and a cleaning device 9 are assembled together in a predetermined arrangement relationship. ,
The cartridge 20 is mounted on a support rail l9 within the main body of the copying apparatus.
●It can be inserted and installed along l9, and conversely, it can be removed and removed from the main body of the copying machine.

By fully inserting and mounting the process cartridge 20 into the main body of the copying apparatus, the main body of the copying apparatus 23 and the process cartridge 20 are mechanically and electrically coupled to each other, and the copying apparatus becomes operable.

During the rotation process, the circumferential surface of the photoreceptor 1 is sequentially and uniformly charged by the contact charging plate 10, and then passes through the optical image exposure means 15 and is sequentially subjected to optical image exposure L (slit exposure of the original image). By receiving the exposure light, electrostatic latent images are sequentially formed corresponding to the exposure light image pattern. Reference numeral 23 denotes a light transmitting window opening in a wall portion of the cartridge housing corresponding to the optical image exposure means 15.

The optical image exposure L can also be performed by laser beam operation. In the case of an electrostatic recording device, latent images are sequentially formed on the photoreceptor surface by means such as an electrode array that selectively removes static electricity from the photoreceptor surface.

The latent image formed on the surface of the photoreceptor 1 is then sequentially developed (developed) as a toner image by a developing device l6, and the toner image on the surface of the photoreceptor is transferred between the transfer device 17 and the photoreceptor l by a transfer device. One sheet of paper is conveyed from the paper feeding section shown in the figure, and transferred to the surface of the transfer material P, which is fed by the timing roller 2l in synchronization with the rotation of the photoreceptor 24l.
be logged.

The transfer material P that has passed through the transfer device l7 and has received the image transfer is sequentially separated from the surface of the photoreceptor, is introduced into a fixing device (not shown) by the conveyance device 18, undergoes image fixation, and is output as an image-formed material. Ru.

On the other hand, the surface of the photoreceptor 1 after the image transfer is cleaned by a cleaning device 9 to remove residual toner, transfer material paper powder, and other adhered contaminants, and is used repeatedly for image formation.

(Effects of the Invention) As described above, according to the present invention, it has become possible to provide a fixed type contact charging device such as a plate that can perform uniform charging treatment without charging unevenness. Another object of the present invention is to provide a simple, inexpensive, and uniformly charged contact charging device that does not require a complex configuration such as a movable contact charging means such as roller charging or a configuration in which charging plates are provided in multiple stages. became possible.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram illustrating the uniform charging action of the charging device of the present invention. FIG. 2 is a schematic diagram of the structure of the charging device of the first embodiment. FIG. 3 is the same diagram as above of the main parts of the charging device of the second embodiment. FIG. 4 is a schematic diagram of the configuration of a charging device according to a third embodiment. Figure 5 is a partially enlarged view of the main part. FIG. 6 is a schematic diagram of an example of an electrophotographic copying apparatus using the charging device shown in FIGS. 4◆5. 1 is an image carrier such as a photosensitive drum as a charged body, 2 is a general code of a contact charging device, 2a*10 is a contact charging member,
011102●PI@P2 is the contact part for the charged object,
7a and 7b are opposing parts, and X, X', Y-Y' are discharge areas. younger sister

Claims (4)

[Claims] (1) A contact charging device that charges the surface of the object to be charged by bringing a charging member to which a voltage is applied into contact with the surface of the object to be charged, which is moving in plane, and the charging member is a fixed type that does not move in plane with respect to the object to be charged. The electrically conductive member has at least two opposing surfaces in the same member that are gradually separated from the surface of the charged object on the downstream side in the direction of movement of the charged object surface from the contact portion with respect to the charged object. Contact charging device with special features. (2) A portion of the charging member that electrostatically affects the charged object is coated with one or more types of resistance layer having a higher electrical resistance value than the conductive member.
Contact charging device as described. (3) The voltage applied to the charging member is a DC voltage with an AC component superimposed, and the peak-to-peak voltage value of the AC component is at least twice the charging start voltage of the charged object.
The contact charging device according to claim 1 or 2, characterized in that: (4) The charging member is made of an elastic body, and has a plate shape that is in contact with the object to be charged by the elastic force of the charging member itself. Contact charging device as described.