JPH0559468U - Charging device - Google Patents

Abstract

(57) [Summary] [Object] To provide a charging device capable of preventing discharge from an electrode with a simple structure and consequently performing uniform charging. A charging device 10 has a high resistance as an electrode plate 12 serving as a voltage applying electrode, and a solid electrode formed so as to cover the periphery of the electrode plate 12 and having a surface facing the photoconductor 14 formed into a flat surface. It is composed of a layer 16 and a power source 18 for applying a predetermined voltage to the electrode plate 12.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a charging device.

[0002]

[Prior Art]

 Conventionally, in an electrophotographic apparatus, a device called a scorotron charger has been put into practical use as a charging device that charges 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. When a high voltage of about -5 kV is applied to the wire in this charger, corona discharge is generated around the wire. By controlling the electric charges generated by this discharge with a voltage of about -500 V applied to the grid, it is possible to uniformly charge the surface of the photoconductor to a voltage almost equal to the voltage applied to the grid.

As described above, the scorotron charger has a 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 because it causes corona discharge. This ozone not only emits a peculiar odor and makes the user of the electrophotographic apparatus uncomfortable, but due to its rich chemical activity, it also damages organic substances such as rubber and adversely affects the human body.

Therefore, in order to further suppress the amount of ozone generated, a contact charging type charging device has been proposed and put into practical use. As a typical example of the contact charging method, there is a charging method using a roller having conductivity as described in JP-A-63-149669, that is, a so-called charging roller. Therefore, the configuration and operation of the charging roller will be described below with reference to FIG.

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

Next, the operation of the charging roller 40 will be described. The charging roller 40 is in contact with the surface of the photosensitive drum 48 having a photosensitive layer 48b made of an organic photosensitive body or amorphous silicon on a conductive substrate 48a such as aluminum under a predetermined pressure. The photosensitive drum 48 rotates in the arrow X direction, and the charging roller 40 rotates in the arrow Y direction as the photosensitive drum 48 rotates. At this time, the voltage applying device 46 applies to the charging roller 40 a bias voltage in which the above-described alternating voltage is superimposed, 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 surface of the photosensitive member, charge injection from the surface of the charging roller to the photosensitive member, and charging roller. And an air discharge phenomenon in a minute gap between the photoconductor surface and the photoconductor surface when they contact and dissociate. Of these, the largest contribution to the charging of the surface of the photoconductor is the air discharge phenomenon, so that ozone is also generated in the contact charging method using a charging roller. However, the amount of ozone generated is considerably smaller than the amount generated from a charger using a scorotron wire.

However, such a contact charging method has the following drawbacks. That is, since the roller is brought into contact with the toner for charging, the abrasion of the photoconductor is remarkable as compared with the non-contact charging method, and as a result, the life is shortened. Further, some of the components of the charging roller are deposited at the contact portion and are rubbed and adhered to the surface of the photoreceptor, resulting in image defects such as image deletion.

Therefore, as a non-contact charging method that has higher charge generation efficiency and less ozone generation than the scorotron charger described above, a charging device using a proximity discharge element is disclosed in Japanese Patent Laid-Open No. 60-157183. It is proposed in Japanese Laid-Open Patent Publication No. 62-296174.

The structure of the charging device using the proximity discharge element has a structure as shown in FIG. 3, for example. The charging device 60 is made of various metal oxides or metal nitrides, and has a high resistance layer 62 whose volume resistance is controlled to be about 10 ⁸ Ωcm, and one surface of the high resistance layer 62. The electrode 64 is provided, and the power source 66 is provided so as to apply a positive or negative voltage of about 1 to 2 kV to the electrode 64. The high resistance layer 62 is provided with the surface opposite to the surface on which the electrode 64 is provided close to the photoconductor 68, and the distance between them is kept at about 500 μm to 2 mm. The surface of the high resistance layer 62 facing the photoconductor 68 is processed to be smooth. Next, the operation of the charging device 60 will be described. Although the photoconductor 68 is rotating in the direction of the arrow, a voltage is applied from a power source 66 through an electrode 64 provided on the high resistance layer 62 at an appropriate timing to charge the surface thereof. By doing so, corona discharge occurs between the high resistance layer 62 and the photoconductor 68, 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. In addition, since it is a non-contact charging method, it can be said that it is an advantageous charging method that can eliminate the drawbacks of the contact charging method such as abrasion and contamination of the surface of the photoconductor.

[0012]

[Problems to be solved by the device]

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

The proximity discharge element has a two-layer structure of a high resistance layer 62 and an electrode 64. Since the electrode portion is exposed on the side surface, non-uniform spark discharge is generated from this exposed portion. Occurs, and the charge on the surface of the photoconductor is leaked, making it difficult to perform uniform charging.

The present invention has been made to solve the above-mentioned problems, and provides a charging device capable of preventing discharge from an electrode with a simple structure, and as a result, capable of performing uniform charging. The purpose is to

[0015]

[Means for Solving the Problems]

In order to achieve this object, a charging device of the present invention comprises a voltage applying electrode, a high resistance solid electrode formed so as to cover the voltage applying electrode, and a power source for applying a voltage to the voltage applying electrode. Consists of The volume resistance value of the solid electrode is preferably 10 ⁶ to 10 ¹³ Ωcm.

[0016]

[Action]

 The charging device of the present invention having the above-described configuration is arranged so as to face the body to be charged, and a predetermined voltage is applied to the voltage application electrode by the power source, so that corona discharge is generated from the solid electrode and The body is charged to a predetermined potential.

[0017]

【Example】

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

First, the configuration of the charging device 10 of this embodiment will be described with reference to FIG. The charging device 10 includes an electrode plate 12 as a voltage applying electrode, and a high resistance layer 16 as a solid electrode which is formed so as to cover the periphery of the electrode plate 12 and has a flat surface facing the photoconductor 14. , A power source 18 for applying a predetermined voltage to the electrode plate 12.

For the high resistance layer 16, nitride or oxide of various metals, or amorphous silicon doped with impurities is used. For example, sputtered films of tantalum nitride, silicon nitride, aluminum, silicon oxide and the like.

Here, a method of manufacturing the charging device 10 will be described. A metal flat plate such as stainless steel or aluminum is used as the electrode plate 12, and the high resistance layer 16 is attached to the surface of the metal flat plate by sputtering. That is, nitrogen is flowed into the order of 10 ^{@ 7} Torr vacuum at a gas pressure of a few m Torr, nitrogen ions collide with the metal target by applying a bias voltage to the metal target, such as tantalum, metal atoms sputtered To be ringed. The sputtered metal atoms react with nitrogen gas in a nitrogen atmosphere to become metal nitride and adhere to the electrode plate 12. At this time, by rotating the electrode plate 12 at an appropriate speed, the high resistance layer 16 is formed so as to cover the periphery of the electrode plate 12.

The high resistance layer 16 has a layer thickness of several thousand angstroms, and its volume resistance value is about 10 ⁴ to 10 ¹⁰ Ωcm. These values are controlled by the sputtering time, the gas pressure of nitrogen gas during sputtering, and the value of the bias voltage applied to the metal target.

The charging device 10 manufactured as described above is provided with a distance of less than 1 mm from the photoconductor 14.

Next, the operation will be described. A voltage of about 1 to 2 kV having a predetermined polarity is applied to the electrode plate 12 from the power source 18. When a voltage is applied, corona discharge is generated from the surface of the high resistance layer 16 and the photoconductor 14 is charged to a uniform potential.

In this charging device 10, since the periphery of the electrode plate 12 is covered with the high resistance layer 16 as described above, it is possible to eliminate the exposed portion of the electrode plate 12 at the position close to the photoconductor 14. it can. Therefore, even if a voltage is applied when charging the photoconductor 14, the spark discharge phenomenon is unlikely to occur, so that the surface of the photoconductor 14 can be uniformly charged.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention. For example, as for the manufacturing method thereof, the high resistance layer may be formed not by sputtering but by plasma CVD or the like. If the high resistance layer is made of an organic resin having an appropriate resistance, it can be formed by a manufacturing method such as dipping.

[0026]

[Effect of the device]

 As is clear from the above description, in the charging device of the present invention, since the voltage application electrode is not exposed to the outside, spark discharge is unlikely to occur, and the body to be charged can be uniformly charged.

[Brief description of drawings]

FIG. 1A is a side view of a charging device of this embodiment.
(B) is the same perspective view.

FIG. 2 is a perspective view of a conventional contact charging roller type charging device.

FIG. 3A is a side view of a conventional proximity discharge device type charging device. (B) is the same perspective view.

[Explanation of symbols]

 10 Charging device 12 Electrode plate 16 High resistance layer 18 Power supply

Claims (2)

[Scope of utility model registration request] 1. A charging device comprising: a voltage applying electrode; a high-resistance solid electrode formed so as to cover the voltage applying electrode; and a power supply for applying a voltage to the voltage applying electrode. .. 2. The volume resistance value of the solid electrode is 10 ⁴ to 1
The charging device according to claim 1, wherein the charging device is 0 ¹³ Ωcm.