JP2001066851A - Electrostatic charging device, and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the surface of an image carrier stably charged, even if any defect such as a pin hole is present on a photosensitive layer, at the time of electrostatically charging the surface of the image carrier by bringing a charging member in a sheet shape held into contact with the surface of the image carrier that the photosensitive layer is formed thereon. SOLUTION: In this electrostatic charging device the surface on the image carrier 10 charged by applying voltage from a power source 22 on this charging member 21 in the sheet shape being held is brought into contact with the surface of the image carrier 10 that the photosensitive layer 11 is formed thereon. At the time thereof, the device is provided with a resistor 23 between the charging member 21 and the power source 22 so that the next numerical formula is satisfied, Rc+Rf+<=2+0.1|Vc-Vs|/d, when assuming resistance value of this resistor 23 as Rc(MΩ), the resistance value of the charging member 21 as Rf(MΩ), the voltage applied from the power source 22 on the charging member 21 as Vc(V), surface potential on the image carrier 10 before conducted to the charging member 21 as Vs(V), and the layer thickness of the photosensitive layer 11 on the surface of the image carrier 10 as d(μm).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device used for charging the surface of an image carrier having a photosensitive layer formed thereon in an image forming apparatus such as a copying machine or a printer, and an image using the charging device. In particular, in contacting the sheet-shaped charging member with the surface of the image carrier on which the photosensitive layer is formed, and applying a voltage from a power source to the charging member to charge the surface of the image carrier. Even when defects such as pinholes are present in the photosensitive layer formed on the surface of the image carrier, the surface of the image carrier is appropriately charged,
The feature is that stable image formation can be performed.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer, the surface of an image carrier on which a photosensitive layer is formed is generally charged by a charging device, and the surface of the image carrier thus charged is charged. After forming an electrostatic latent image according to the image information, toner is supplied to the surface of the image carrier on which the electrostatic latent image has been formed in this way, and the surface corresponding to the electrostatic latent image is formed on the surface of the image carrier. A toner image is formed, and the toner image thus formed is transferred from a surface of the image carrier to a transfer medium such as a recording paper to form an image. On the other hand, a blade or the like is removed from the surface of the image carrier after the transfer. The members are brought into contact with each other to remove toner and the like remaining on the surface of the image carrier after transfer.

[0003] In charging the surface of the image bearing member on which the photosensitive layer is formed as described above with a charging device, a corona charging device such as a corotron or a scorotron utilizing corona discharge is generally used. Was.

Here, such a corona charger has an advantage that the surface of the image carrier can be stably charged. However, since the discharge is performed at a certain distance from the surface of the image carrier, the discharge is performed. Along with the necessity of a high voltage, ozone is generated at the time of discharge, which has been a problem in terms of safety and environmental preservation.

For this reason, in recent years, various charging members, such as a sheet, a roller, and a brush, are brought into contact with the surface of the image carrier, and a voltage is applied to the charging member from a power source to cause the charging member to contact the image carrier. A device was developed that discharges at the part where the body is separated and charges the surface of the image carrier, and in particular, stably contacts the surface of the image carrier and stabilizes the surface of the image carrier. A sheet-shaped charging member is widely used because it can be charged by charging.

Here, when the charging member is brought into contact with the surface of the image carrier and the discharge is performed in a portion where the charging member and the image carrier are separated from each other, the charging member and the image carrier are located at an extremely close position. Since the discharge is performed, the voltage required for the discharge can be reduced, and the generation of ozone is reduced.

However, when charging is performed by bringing the charging member into contact with the surface of the image carrier as described above, if a defect such as a pinhole is present in the photosensitive layer formed on the surface of the image carrier, such a defect is caused. There is a problem in that the current flows from the charging member in a concentrated manner at the portion, causing a leak, thereby destroying the photosensitive layer of the charging member or the image carrier.

In recent years, in order to reduce the size of an image forming apparatus such as a copying machine or a printer, the toner image formed on the surface of the image carrier as described above is transferred to a transfer medium and then transferred to a transfer medium. 2. Description of the Related Art An image forming apparatus has been used in which a removing member for removing toner and the like remaining on the surface of an image carrier by contacting the surface of the image carrier is not provided.

In this case, if the toner or the like remaining on the surface of the image carrier after the transfer is not removed by the removing member, the toner and the paper powder remaining on the surface of the image carrier after the transfer are removed. Is guided by the above-described charging member and clogged, and the clogged toner or paper dust damages the photosensitive layer, or the toner or paper dust is embedded in the photosensitive layer. As in the case of defects such as holes, there is a problem in that current flows from the charging member in a concentrated manner and leaks, and the charging member and the photosensitive layer are destroyed.

[0010]

SUMMARY OF THE INVENTION The present invention relates to an image forming apparatus such as a copying machine or a printer, in which a sheet-shaped charging member is brought into contact with the surface of an image carrier having a photosensitive layer formed thereon, It is an object of the present invention to solve the above-mentioned problem when the surface of the image carrier is charged by applying a voltage from a power source to the image carrier.

That is, in the present invention, a sheet-shaped charging member is brought into contact with the surface of the image carrier on which the photosensitive layer is formed, and a voltage is applied from a power source to the charging member to change the surface of the image carrier. In charging, even when a defect such as a pinhole is present in the photosensitive layer on the surface of the image carrier, it is possible to suppress a current from being concentrated and flowing from the charging member to the defective portion and to prevent a leak from occurring. And an image forming apparatus in which the photosensitive layer of the image carrier is prevented from being destroyed by a leak, and in particular, the toner remaining on the surface of the image carrier after transfer is not removed by a removing member. It is an object of the present invention to stably charge the surface and to perform stable image formation.

[0012]

In the charging device according to the present invention, in order to solve the above-mentioned problems, a sheet-shaped charging member is brought into contact with the surface of an image carrier on which a photosensitive layer is formed, In a charging device for charging the surface of the image carrier by applying a voltage from a power supply to the charging member, a resistor is provided between the charging member and the power supply, and a resistance value Rc (MΩ) of the resistor and a charging member Resistance value Rf (MΩ)
A voltage Vc (V) applied from the power supply to the charging member;
Surface potential Vs (V) of the image carrier before being guided to the charging member
And the thickness d (μm) of the photosensitive layer on the surface of the image carrier satisfies the condition of Rc + Rf ≧ 2 + 0.1 | Vc−Vs | / d.

Here, when a resistor is provided between the sheet-shaped charging member to be brought into contact with the surface of the image carrier and the power source as in the charging device of the present invention, the current flowing through the charging member is changed by the resistance. Is reduced,
When the surface of the image carrier is charged by the charging member so as to satisfy the above-described conditions, even if a defect such as a pinhole exists in the photosensitive layer on the surface of the image carrier, this defect is eliminated. The occurrence of leakage due to current flowing from the charging member to the portion is suppressed, the charging member and the photosensitive layer of the image carrier are prevented from being destroyed by the leak, and the surface of the image carrier is stabilized by the charging member. And become charged.

According to another aspect of the present invention, there is provided an image forming apparatus comprising: at least one charging device for charging a surface of an image carrier having a photosensitive layer formed thereon; A latent image forming apparatus for forming an electrostatic latent image on the surface of a body, a developing device for supplying toner to an image carrier to form a toner image corresponding to the electrostatic latent image formed on the surface, and an image carrier A transfer device for transferring a toner image formed on the surface of the body to a transfer medium, and an image forming apparatus without a removing member for removing remaining toner and the like by contacting the surface of the image carrier after transfer In the apparatus, the above-described charging device according to the present invention is used as one of the charging devices.

When the toner or the like remaining on the surface of the image carrier after the transfer is not removed from the surface of the image carrier by the removing member as in the image forming apparatus of the present invention, the toner or the like is removed from the image carrier. Even if the surface of the image carrier is damaged due to clogging between the surface and the charging member, and toner or the like is embedded in the surface of the image carrier, when the surface of the image carrier is charged by the charging device described above, ,
The occurrence of leakage due to the flow of current from the charging member to such defective portions is suppressed, and the surface of the image carrier is stably charged, so that stable image formation can be performed.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a charging device and an image forming apparatus according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings.

In the charging device and the image forming apparatus according to this embodiment, as shown in FIGS. 1 and 2, a drum-shaped image carrier 10 having a photosensitive layer 11 formed on the surface thereof.
Is rotated, and the surface of the image carrier 10 is charged by the charging device 20.

Here, when the surface of the image carrier 10 is charged by the charging device 20, in this embodiment, the surface of the image carrier 10 on which the photosensitive layer 11 is formed as described above is formed into a sheet. The charging member 21 is contacted, and a resistor 23 is provided between the charging member 21 and the power supply 22.
1, a voltage is applied to the charging member 21 and the image carrier 10
A discharge is performed in a part where the image carrier 10 is separated from the image carrier 10 so that the surface of the image carrier 10 is uniformly charged.

A latent image forming device 30 such as a laser device is placed on the surface of the image carrier 10 uniformly charged as described above.
To form an electrostatic latent image corresponding to the image information, and a toner 41 is supplied from the developing device 40 to the surface of the image carrier 10 on which the electrostatic latent image has been formed in this manner. To form a toner image corresponding to the electrostatic latent image.

Next, the image carrier 1 rotating as described above
0 guides the toner image formed on the surface to a position facing the transfer device 50 such as a transfer roller, and guides a transfer medium 51 such as recording paper between the transfer device 50 and the image carrier 10. The toner image formed on the surface of the image carrier 10 is transferred to the transfer medium 51 to form an image on the transfer medium 51.

Then, the toner image is transferred to the transfer medium 5 as described above.
After the transfer, the surface of the image carrier 10 is charged by the charging device 20 as described above without removing the toner and the like remaining on the surface of the image carrier 10. Is to be repeated.

In this embodiment, the sheet-shaped charging member 21 is brought into contact with the surface of the image carrier 10 as described above, and a voltage is applied to the charging member 21 from a power supply 22 via a resistor 23. When applying the voltage to charge the surface of the image carrier 10, the resistance value Rc (MΩ) of the resistor 23 between the charging member 21 and the power source 22 and the charging member 21
, The voltage Vc (V) applied from the power supply 22 to the charging member 21, the surface potential Vs (V) of the image carrier 10 before being guided to the charging member 21, and the image carrier 1
0, the thickness d (μm) of the photosensitive layer 11 on the surface of R
The condition of c + Rf ≧ 2 + 0.1 | Vc−Vs | / d is satisfied.

When the surface of the image carrier 10 is charged in this way, even if a defect such as a pinhole exists in the photosensitive layer 11 on the surface of the image carrier 10, the charging member 21 The occurrence of leakage due to current flowing from the image carrier 10 is suppressed, and the surface of the image carrier 10 is
As a result, the toner is stably charged.

Next, in the apparatus shown in FIGS. 1 and 2, the resistance 23 between the charging member 21 and the power source 22 is set.
Resistance Rc (MΩ) and the resistance Rf (M
Ω), the voltage Vc applied from the power supply 22 to the charging member 21
(V), the surface potential Vs (V) of the image carrier 10 before being guided to the charging member 21 and the thickness d (μm) of the photosensitive layer 11 on the surface of the image carrier 10 are changed to change the image carrier 10 An experiment was conducted in which the surface of the photosensitive member 11 was charged by the charging member 21. In the case of the embodiment satisfying the above conditions shown in the present invention, even when the photosensitive layer 11 has a defect such as a pinhole, the image carrier It will be clarified that the surface of the battery 10 is stably charged by the charging member 21.

Here, in this experiment, the photosensitive layer 11
Using an image carrier 10 having defects such as pinholes
As shown in Table 1 below, the voltage Vc applied from the power supply 22 to the charging member 21 is changed in the range of −400 V to −1500 V, and the surface potential Vs of the image carrier 10 before being guided to the charging member 21 is changed. 0 V and 100 V, the thickness d of the photosensitive layer 11 on the surface of the image carrier 10 is changed in the range of 10 μm to 30 μm, and the resistance R of the resistor 23 between the charging member 21 and the power supply 22 is changed.
The surface of the image carrier 10 is charged by the charging member 21 by changing the sum (Rc + Rf) of c and the resistance value Rf of the charging member 21 in the range of 3 MΩ to 10 MΩ.

When the surface of the image carrier 10 was charged in this manner, the presence or absence of leakage was examined. The results are shown in Table 1 below.

[0027]

[Table 1]

As is apparent from the results, the above Rc + Rf ≧ 2 + 0.1 | Vc−Vs | /
In Examples 1 to 5 in which the surface of the image carrier 10 is charged by the sheet-shaped charging member 21 so as to satisfy the condition d, the photosensitive layer 11 on the surface of the image carrier 10 is used. Even when a defect such as a pinhole exists in the surface of the image carrier 10, no leakage occurs when the surface of the image carrier 10 is charged by the charging member 21, but Rc + Rf ≧ 2 + 0.1 | Vc−Vs In the cases of Comparative Examples 1 and 2 not satisfying the condition of | / d, if the photosensitive layer 11 on the surface of the image carrier 10 has a defect such as a pinhole, the surface of the image carrier 10 is charged by the charging member 21.
Caused leakage when charged.

In the image forming apparatus of the embodiment shown in FIG. 1, when charging the surface of the image carrier 10, the sheet-shaped charging member 21 is attached to the image carrier 10.
The charging device 20 is configured to contact the surface of the charging device 21 and apply a voltage from the power supply 22 to the charging member 21. However, as shown in FIG. A charging device 20a using a roller-shaped charging member 21a; a brush-shaped charging member 2a;
1b, the charging members 21 and 22 in such charging devices 20, 20a and 20b are used.
1a and 21b are brought into contact with the surface of the image carrier 10, and respective charging members 21 and 22 are supplied from respective power sources 22, 22a and 22b.
It is also possible to charge the surface of the image carrier 10 by applying a voltage to 1a and 21b.

[0030]

As described above in detail, in the charging device according to the present invention, a sheet-shaped charging member is brought into contact with the surface of the image carrier on which the photosensitive layer is formed, and a voltage is applied from the power supply to the charging member. Is applied to charge the surface of the image carrier, a resistor is provided between the charging member and the power source, and the resistance value Rc (MΩ) of the resistance and the resistance value Rf of the charging member
(MΩ) and the voltage Vc applied from the power supply to the charging member
(V), the surface potential Vs (V) of the image carrier before being guided to the charging member, and the thickness d of the photosensitive layer on the surface of the image carrier.
(Μm) is Rc + Rf ≧ 2 + 0.1 | Vc−Vs |
/ D, the current flowing through the charging member is reduced by the resistance, and even if a defect such as a pinhole is present in the photosensitive layer on the surface of the image carrier, the charging member is located at the defective portion. Current is prevented from flowing and leakage is prevented, the photosensitive layer of the charging member and the image carrier is prevented from being destroyed, and the surface of the image carrier can be stably charged by the charging member. Now you can.

Further, in the image forming apparatus according to the present invention, the photosensitive layer is formed in the image forming apparatus in which the removing member for removing the remaining toner by contacting the surface of the image carrier after the transfer is not provided. Since one of the above-described charging devices is used as one of the charging devices for charging the surface of the image carrier, toner and the like remaining on the surface of the image carrier after transfer are transferred to the surface of the image carrier and the charging member. Even if the surface of the image carrier is damaged or toner or the like is embedded in the surface of the image carrier, when the surface of the image carrier is charged, such a defective portion is charged by the charging member. Thus, the occurrence of leakage due to the flow of current is suppressed, the surface of the image carrier is stably charged, and stable image formation can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing a charging device and an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a partial explanatory view showing a state where the surface of the image carrier on which the photosensitive layer is formed is charged by the charging device of the embodiment.

FIG. 3 is a partial explanatory view showing a state in which a surface of an image bearing member on which a photosensitive layer is formed is charged by a plurality of charging devices in the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Image carrier 11 Photosensitive layer 20 Charging device 21 Sheet-shaped charging member 22 Power supply 23 Resistance 30 Latent image forming device 40 Developing device 41 Toner 50 Transfer device 51 Transfer medium 20a, 20b Other charging devices

Claims (2)

[Claims] 1. A charging apparatus for charging a sheet-shaped charging member to a surface of an image carrier on which a photosensitive layer is formed, and applying a voltage from a power source to the charging member to charge the surface of the image carrier. A resistor is provided between the charging member and the power supply, and a resistance value Rc (MΩ) of the resistor, a resistance value Rf (MΩ) of the charging member, and a voltage Vc (V) applied from the power supply to the charging member. The surface potential Vs (V) of the image carrier before being guided to the charging member and the thickness d (μm) of the photosensitive layer on the surface of the image carrier are: Rc + Rf ≧ 2 + 0.1 | Vc−Vs | / d A charging device that satisfies the following conditions. 2. One or more charging devices for charging a surface of an image carrier on which a photosensitive layer is formed, a latent image forming device for forming an electrostatic latent image on the surface of the charged image carrier, and an image carrier A developing device that supplies toner to the body to form a toner image corresponding to the electrostatic latent image formed on the surface thereof, and a transfer device that transfers the toner image formed on the surface of the image carrier to a transfer medium. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus does not include a removing member that removes residual toner and the like by contacting the surface of the image carrier after transfer.
An image forming apparatus using the charging device described in (1).