JPH0683163A - Electrifier - Google Patents

Abstract

PURPOSE:To obtain an electrifier having an advantage over the uniform electrificatin of a photosensitive body and high electrostatic chargeability, without the bare part of an electrode. CONSTITUTION:The electrifier 10 is composed of a substrate 12 made of an insulator such as a glass, plural electrodes 14 provided on the substrate 12 and a high resistant layer 16 provided on the substrate 12 so as to cover the electrodes 14. In an actual using state, the electrifier 10 comes into contact with the photosensitive body 22 via a spacer 20 provided on both ends of the electrifier 10 and presses its both ends by a spring to keep an interval from the photosensitive body 22 100-800mum. Further, power sources 26a and 26b are provided so as to apply voltages different each other in the electrodes of the central part and an end part, on plural electrodes 14.

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 in an electrophotographic apparatus or the like for charging the surface of an object to be charged.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic apparatus, for example, a device called a scorotron charger has been put into practical use as a charging device for charging a photosensitive member for carrying an electrostatic latent image to a predetermined initial potential. . This scorotron charger is composed of a wire having a diameter of 100 μm or less, a grid provided so as to face the photoconductor, and a case that integrally holds them. In this charger, when a high voltage of about -5 kV is applied to the wire, corona discharge occurs around the wire. The charge generated by this discharge can be controlled by a voltage of about -500 V applied to the grid to uniformly charge the photoconductor to a voltage substantially equal to the voltage applied to the grid.

As described above, the scorotron charger has the feature that the charging potential can be controlled by the voltage applied to the grid and that the charging potential is excellent in uniformity, but a high voltage is applied to the wire. Ozone is generated to cause corona discharge. This ozone not only emits a peculiar odor and makes the user of the electrophotographic apparatus uncomfortable, but also has a property of being highly chemically active, which invades organic substances such as rubber and adversely affects the human body.

Therefore, in order to further suppress the generation of ozone, a contact charging system has been proposed and put into practical use. As a typical example of the contact charging method, there is JP-A-63-14966.
Roller having conductivity as shown in Japanese Patent No.
A charging method using a so-called charging roller can be mentioned. Therefore, the configuration and operation of the charging roller will be described with reference to FIG.

The charging roller 40 has a diameter of 20 m as a whole.
A urethane foam rubber layer 44 in which carbon is dispersed so as to have a volume resistance value of about 10 5 is formed around a stainless steel rod 42 as a core metal in a cylindrical shape of about m. Further, the stainless rod 42 has a voltage of 1 to 2 kV.
A voltage applying device 46 for applying a bias voltage on which an AC voltage having a peak-to-peak voltage is superimposed is provided.

Next, the operation of the charging roller 40 will be described. The charging roller 40 is a photoconductor drum 48 in which a photoconductor layer 48b made of an organic photoconductor or amorphous silicon is formed on a conductive substrate 48a such as aluminum.
The surface is in contact with a predetermined pressure. Then, the photosensitive drum 48 is rotating in the direction of the arrow X, and the charging roller 40
Rotates in the direction of the arrow Y as the photosensitive drum 48 rotates. At this time, the voltage application device 46 applies a bias voltage on which the AC voltage is superimposed to the charging roller 40, and the surface of the photosensitive drum 48 is uniformly charged to a predetermined potential.

The charging process of the surface of the photosensitive drum 48 by the charging roller 40 at this time includes frictional charging between the roller and the photosensitive member surface, charge injection from the charging roller surface to the photosensitive member, and charging roller. And the surface of the photoreceptor contact
Air discharge phenomenon in the minute gap between the two when they dissociate,
and so on. Of these, the greatest contribution to the charging of the surface of the photoconductor is the atmospheric discharge phenomenon, so ozone is generated even though the contact charging method using a charging roller is used. It is considerably smaller than the amount generated from the charger using.

However, such a contact charging system has the following drawbacks. That is, since the roller is contacted for charging, the surface of the roller is easily soiled by the toner and the like remaining on the surface of the photoconductor, which easily causes charging failure on the surface of the photoconductor. Further, some of the components of the charging roller are deposited at the contact portion and are rubbed against the surface of the photoconductor to be attached, resulting in image defects such as image deletion.

Therefore, as a non-contact charging system having a higher charge generation efficiency and less ozone generation than the above-mentioned scorotron charger, a charging device using a proximity discharge element is disclosed in Japanese Patent Laid-Open No. 60-157183. 62-2961
It is proposed in Japanese Patent Publication No. 74 and the like.

The structure of the charging device using the proximity discharge element is as follows.
For example, it has a structure as shown in FIG. Charging device 6
0 is a high resistance layer 62 formed by various metal oxides or metal nitrides so that the volume resistance value is 10 6 to 10 13 Ωcm, and the high resistance layer 62.
The electrode 64 provided on one surface of the
The power supply 66 is provided so as to apply a positive or negative voltage of about kV. The high resistance layer 62
On the surface opposite to the surface on which the electrode 64 is provided
Are installed close to each other, and the distance is 500 μm.
It is kept at about 2 mm. High-resistance layer 62 photoconductor 6
The surface facing 8 is treated to be smooth.

Next, the operation of the charging device 60 will be described. The photoconductor 68 rotates in the direction of the arrow,
The high resistance layer 6 at an appropriate timing to charge the surface thereof.
A voltage is applied from a power supply 66 through the electrode 64 provided on the second electrode 2. By doing so, the high resistance layer 62 and the photoconductor 68 are
Corona discharge is generated between them, and as a result, the surface of the photoconductor 68 is uniformly charged.

In the case of the charging device using such a proximity discharge element, the applied voltage is lower than the voltage applied to the wire of the scorotron charger, and the inflow current required to charge the surface of the photoconductor is small. Therefore, the amount of ozone generated can be suppressed. Further, since it is a non-contact charging method, it can be said that it is an advantageous charging method that can eliminate the defects of the contact charging method such as abrasion and contamination of the surface of the photoconductor.

[0013]

However, the proximity discharge device having the above structure has the following drawbacks.

As shown in FIG. 4, the proximity discharge element has a two-layer structure of a high resistance layer 62 and an electrode 64, but since the electrode portion is exposed on the side surface, this exposed portion. Then, non-uniform spark discharge is generated from the surface of the photosensitive member, which leaks charges on the surface of the photoconductor, making it difficult to perform uniform charging. Alternatively, when the photoconductor as the member to be charged has a cylindrical shape, it is effective because the distance between the photoconductor and the proximity discharge element, which has a substantially planar shape, changes along the circumferential direction of the photoconductor. The area of the proximity discharge element capable of performing proper charging becomes small and the charging efficiency deteriorates.

The present invention has been made in order to solve the above-mentioned problems, and provides a charging device which has a simple structure and can prevent discharge from electrodes and edge parts, and has a large effective charging area and high charging efficiency. Is to provide.

[0016]

In order to achieve the above-mentioned object, a charging device of the present invention is opposed to a surface of an object to be charged with a predetermined interval, and the surface of the object to be charged has a predetermined polarity and potential. And a plurality of electrodes provided on the surface of the high resistance layer opposite to the surface of the high resistance layer facing the charged body. And a voltage applying means capable of applying different voltages to each of the plurality of electrodes.

[0017]

In the charging device of the present invention having the above-mentioned structure, by applying a predetermined voltage to each of the plurality of electrodes, a voltage distribution is generated on the surface of the high resistance layer facing the surface of the body to be charged, Corona discharge is generated from the electrode, and the charged body is charged to a predetermined potential without spark discharge from the electrode covered with the high resistance layer.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an electrophotographic apparatus such as a laser printer, which is used as a charging device for charging a surface of a photoconductor as an image carrier to a uniform potential.
It is the figure which showed one Example of the charging device of this invention.

The charging device 10 includes a substrate 12 made of an insulating material such as glass, and a plurality of electrodes 1 provided thereon.
4 and a high resistance layer 16 provided on the substrate 12 so as to cover those electrodes 14. In actual use, the charging device 10 contacts the photoconductor 22 via the spacers 20 provided at both ends thereof, and presses both ends with springs (not shown) so that the gap between the photoconductor 22 and the photoconductor 22 is 100 or 100. It is kept at 800 μm. Further, the plurality of electrodes 14 are provided with power supplies 26a and 26b so that different voltages can be applied to the central electrode and the end electrodes, respectively.

The material of the high resistance layer 16 is a nitride or oxide of various metals, for example, tantalum nitride, silicon nitride, tantalum oxide, silicon oxide or the like. Then, the high resistance layer 16 is formed by a manufacturing method called sputtering.

Here, the sputtering will be described. Sputtering is a method of producing a thin film by hitting the surface of a metal target with an ionized gas in a high vacuum, giving energy to metal atoms to cause them to fly, and depositing the metal atoms on a substrate. High resistance layer 16
In the production of, since its volume resistance value should desirably be a value in the range of 10 7 to 10 9 Ωcm, nitrogen or oxygen introduced at a partial pressure of several mTorr is combined during sputtering. And form a nitride or an oxide to form a stack.

Further, the electrode 14 may be formed by laminating a metal thin film instead of being formed by sputtering, or may be formed by embedding a metal thin wire such as tungsten in the substrate 12. Further, the high resistance layer 16 may be formed by applying an organic substance having a desired volume resistance value by a method called dipping, instead of forming by sputtering as described above.

Next, the operation of the charging device 10 will be described. With the start of the electrophotographic process, the photoconductor 2
2 starts moving in the direction of the arrow in the figure. The power supplies 26a and 26b are turned on in conjunction with the operation, and a voltage is applied to the high resistance layer 16 of the charging device 10. And the high resistance layer 1
Corona discharge is generated from the surface of 6, and the surface of the photoconductor 22 is charged to a predetermined potential.

The magnitude of the voltage to be applied to the high resistance layer 16 is affected by the width of the gap between the high resistance layer 16 and the photosensitive member 22, and the wider the gap, the more the high voltage is not applied to cause the discharge. Since the surface of the high resistance layer 16 is flat, the interval changes in the circumferential direction when facing the photoconductor 22 having a cylindrical shape and having a predetermined curvature. That is,
The high-resistance layer has a narrow interval at the center in the circumferential direction and a wide interval at the ends. Therefore, if the same potential is uniformly applied to the surface of the high resistance layer 16, only a part of the high resistance layer 16 satisfies the discharge condition regarding the gap and the applied voltage, resulting in poor charging efficiency and uniform charging. It is a disadvantage.

In order to prevent this, in the charging device 10 of FIG. 1 which is an embodiment of the present invention, a plurality of voltage applying electrodes are provided, and the applied voltage at the central portion and the end portion is changed to form a pattern on the surface of the high resistance layer 16, for example By giving a voltage distribution as shown in 2,
Corona discharge can be generated from the entire surface of the high resistance layer 16 and charges can be efficiently applied to the surface of the photoconductor 22.

Further, in the charging device 10, due to its structure,
As described above, since the periphery of the electrode 14 is covered with the high resistance layer 16, it is possible to eliminate the exposed portion of the electrode 14 at the position close to the photoconductor 20. Therefore, even if a voltage is applied when charging the photoconductor 20, the spark discharge phenomenon is unlikely to occur, which is advantageous for uniform charging of the surface of the photoconductor 20.

The present invention is not limited to the above-described examples, and modifications can be made without departing from the spirit of the invention. For example, the electrodes may be provided inside the high resistance layer.

[0028]

As is apparent from the above description, the charging device of the present invention has a high resistance layer provided so as to face the body to be charged, and the high resistance layer faces the body to be charged. By providing a plurality of electrodes provided on the surface opposite to the surface and a voltage applying means capable of applying a voltage of a different value to each of the plurality of electrodes, it is possible to realize a simple structure from electrodes or edge portions. It is possible to provide a charging device that can prevent discharge and has a large effective charging area and high charging efficiency.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a main part in an embodiment embodying a charging device of the present invention.

FIG. 2 is a diagram showing a state of a voltage applied to the surface of the high resistance layer of the charging device of the present invention.

FIG. 3 is a diagram showing a conventional example of a charging device using a contact charging roller.

FIG. 4 is a diagram showing a conventional example of a charging device using a proximity discharge element.

[Explanation of symbols]

 10 Charging Device 14 Electrode 16 High Resistance Layer 22 Photoreceptor 26a Power Supply 26b Power Supply

Claims (1)

[Claims] 1. A charging device that faces a surface of an object to be charged with a predetermined gap and charges the surface of the object to be charged to a predetermined polarity and potential. The charging device is provided so as to face the object to be charged. A resistance layer, a plurality of electrodes provided on the surface of the high resistance layer opposite to the surface facing the body to be charged, and a voltage applying means capable of applying different voltages to each of the plurality of electrodes. A charging device comprising: