JPH05297683A - Electrostatic charge device - Google Patents

Abstract

PURPOSE:To obstruct the occurrence of streamer electric discharge caused by the secondary discharge of an electron and to uniformly electrostatically charge a photosensitive body by arranging an electrostatic charge electrode having specified volume resistivity by being deposed to be opposed to the photosensitive body. CONSTITUTION:An impressing electrode 2 is provided on the bottom surface of a pan 1 made of an insulating substance such as plastic. The pan 1 is filled with the liquid electrostatic charge electrode whose volume resistivity is high electric resistivity to the extent of 10<5>-10<13>OMEGAcm. Besides, a high-voltage power source 5 is connected to the electrode 2 and the electrode 2 is constituted so that corona discharge occurs between the electrode 3 and a photosensitive drum 4. By allowing the electrode 3 and the drum 4 to forcibly spark by using such an electrostatic charge device, a defect caused by a pin hole or the like is prevented from occurring because the thickness of the electrode 3 is sufficient.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device applicable to a copying machine or a laser printer to which an electrophotographic process is applied.

[0002]

2. Description of the Related Art Conventionally, a scorotron charging device as shown in FIGS. 4 and 5 has been used as a charging device used in an electrophotographic apparatus such as a copying machine or a laser printer.

In this scorotron charging device 50, insulating blocks 54a and 54b are provided at both ends of a shield case 52 having a U-shaped cross section.
A discharge wire 56 is stretched between 4b so as to be located substantially in the center of the shield case 52, and a grid electrode 58 is provided on the opening surface of the shield case 52.

The grid electrode 58 is grounded via a shield case 52 and a varistor 60 having a varistor voltage of about 680V.

When charging is performed using the scorotron charging device 50 having the above structure, the opening (the surface on which the grid electrode 58 is provided) of the shield case 52 is formed on the photosensitive drum 62 as shown in FIG. -6kV to discharge wire 56 facing each other
Apply a direct current voltage of about a constant current. Then, corona discharge is generated around the discharge wire 56, the ions generated by the corona discharge reach the photoconductor drum 62, and the surface of the photoconductor drum 62 is -6 which is equivalent to the standard of the varistor 60.
It is charged to about 80V. At this time, the grid electrode 58 controls the corona ion flow flowing to the photoconductor drum 62, and the photoconductor drum 62 is uniformly charged.

However, such a scorotron charging device has various problems as described below.

First, as an environmental hygiene problem, there is the generation of ozone by ionizing oxygen molecules in the atmosphere by corona discharge. In particular, a negatively charged device such as used in a laser printer has an ozone generation amount one digit higher than that of positively charged device. The amount of ozone generated is determined by the value of the current flowing through the discharge wire, but in order to obtain the drum inflow current of several tens of μA required for charging the photosensitive drum, the discharge wire needs to have -4
It is necessary to supply a current as high as 00 to 500 μA, and therefore a large amount of ozone is generated. Therefore, in a normal printer device, exhaust is performed from the exhaust duct through the ozone filter.

Further, in terms of cost, since the current utilization efficiency is poor as described above, a large high-voltage power source is required, and an ozone filter, an exhaust fan, etc. are also required as measures against ozone, which significantly increases the cost. ..

On the maintenance side, the silicone oil of the fixing device may be oxidized and adhered to the surface of the wire, and the initial potential of the photosensitive drum may be lowered to adversely affect printing.

In order to solve the above problems, therefore, a charging device using a solid surface discharge element as shown in FIG. 3 has been proposed.

In this solid surface discharge charging device, an applying electrode 87 made of a conductor such as aluminum is provided on the surface of a substrate 86 made of an insulator such as glass, and a semi-conductor made of tantalum nitride is provided on the surface of the applying electrode 87. The film 88 is provided, and the film 88 is arranged at a position facing the photoconductor drum 84 at a constant interval.

A voltage is applied to the applying electrode 87 by a high voltage power source 85 to generate planar corona discharge on the surface of the semiconductive film 88 to generate ions, and the ions are used to charge the photosensitive drum 84. Is.

As a method of manufacturing this solid surface discharge element,
For example, aluminum is vapor-deposited on the glass surface to apply the electrode 8
7, and a tantalum nitride semiconductive film 88 is further formed on the surface of the application electrode 87.

Since the charging device using the solid surface discharge element has a high current utilization efficiency, it has advantages that the ozone generation amount is small and the high voltage power supply 85 can be made small.

[0015]

However, in this solid surface discharge charging device, since the semiconductive film 88 is formed on the surface of the application electrode 87, defects such as pinholes and the like are generated when the semiconductive film 88 is formed. When this occurs, a current flows from the back-side application electrode 87 to the surface of the semiconductive film 88, and electric field concentration occurs in that part, resulting in streamer discharge due to secondary emission of electrons and uniformly charging the photosensitive drum 84. I can't.

When dust or the like adheres to the surface of the semiconductive film 88 and spark discharge occurs between the semiconductive film 88 and the photosensitive drum 84, a part of the semiconductive film 88 evaporates. However, there is a problem in that the photosensitive drum 84 cannot be uniformly charged in the same manner as when a defect such as a pinhole occurs when the semiconductive film 88 is formed.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a charging device capable of preventing streamer discharge in advance.

[0018]

To achieve this object, the present invention provides a charging electrode of a liquid high electric resistance body having a volume resistance of 10 ⁵ to 10 ¹³ Ωcm, and an applied voltage for applying a voltage to the charging electrode. It consists of means.

[0019]

The charging device of the present invention having the above structure is arranged so that the charging electrode faces the photoconductor. When a voltage is applied to the charging electrode by the voltage applying means, corona discharge occurs between the charging electrode and the photoconductor, and the photoconductor is charged.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

First, an electrophotographic process using the charging device of the present invention will be described with reference to FIG.

The photoconductor drum 4 is charged by the charging device 24, which will be described in detail later, and the original 20 placed on the original table 21 is illuminated by the illumination lamp 22, passes through the lens 23, and the optical path is rotated 90 ° by the mirror 33. After being bent, an image is formed on the photosensitive drum 4, and an electrostatic latent image is formed on the photosensitive drum 4.

A developing device 25 attaches a developer to the electrostatic latent image on the photosensitive drum 4 to form a visible image.

The sheet 31 sent from the sheet cassette 32 is superposed on the photosensitive drum 4, and the developer on the photosensitive drum 4 is transferred to the sheet 31 by applying ions by the transfer charging device 26.
Is transcribed to.

Subsequently, the peeling charging device 27 removes the electric charge of the paper 31 and peels the paper 31 from the photosensitive drum 4.

The developer on the sheet 31 is fixed on the sheet 31 by the fixing device 28 to form a copied image.

The charges on the photoconductor drum 4 are removed by the charge removing charging device 29, and the remaining developer on the photoconductor drum 4 is cleaned by the cleaner 30.

Next, the charging device 24 will be described in detail. The charging device 24 is configured as described below.

As shown in FIG. 1, an application electrode 2 is provided on the bottom surface of a tray 1 made of an insulating material such as plastic. Further, the saucer 1 has a volume resistance of 10 ⁵
10 ^{1 3} charging electrode 3 of a liquid comprising a liquid Ωcm as high electric resistor are met.

A high voltage power source 5 is connected to the application electrode 2 so that a corona discharge is generated between the charging electrode 3 and the photosensitive drum 4.

Next, a method of making the charging device 24 will be described.

In this embodiment, an applying electrode 2 made of an aluminum plate having a thickness of 0.1 mm is attached to the bottom of a polycarbonate tray 1 having an inner width of 10 mm, and a high voltage power source 5 is connected to the end face of the applying electrode 2. did.

Next, 1 part of Mitsubishi Kasei conductive carbon black (# 3750) was added to 1 part of dimethyl silicone oil (TSF451-50) manufactured by Toshiba Silicone Co., Ltd., and after stirring well, a saucer was prepared. 1 was filled to a thickness of 0.2 mm.

Charging device 24 manufactured by the above manufacturing method
Using a laminated organic photoconductor in which a carrier generation layer (CGL) and a carrier transport layer (CTL) are laminated on a φ35 mm aluminum tube as the photoconductor drum 4, most of the charging electrode 3 and the photoconductor drum 4 are used. Keep 0.3mm in close proximity,
When -5.0 kV was applied by the high voltage power source 5, the photosensitive drum 4 was uniformly charged to -850V.

Further, the charging electrode 3 was filled with glycerin having a purity of 97% so that the pan 1 had a thickness of 0.3 mm, and the photosensitive drum 4 had an aluminum tube of φ35 mm, a carrier generation layer (CGL), and carrier transport. Using a multi-layer type organic photoconductor in which layers (CTL) are laminated, the position where the charging electrode 3 and the photoconductor drum 4 are closest to each other is kept at 0.3 mm, and -3.5 kV is applied by the high voltage power source 5 Body drum 4
Was uniformly charged to -800V.

When a spark discharge was forcibly generated on the charging electrode 3 and the photosensitive belt drum 4 by using the above charging device 24, a small dent was generated but the applying electrode 2 was not exposed. After leaving for a minute, the dent disappeared.

The present invention is not limited to the embodiments described in detail above, and changes can be made without departing from the spirit of the invention.

[0038]

As is apparent from the above description, in the charging device of the present invention, since the thickness of the charging electrode is sufficient, pinhole hitting defects do not occur, and therefore the streamer due to the secondary emission of electrons is used. No discharge occurs and the photoconductor can be uniformly charged.

Further, even if a defect occurs in the charging electrode due to spark discharge or the like, the self-repair function allows the defect to be repaired.
The streamer discharge due to the secondary emission of electrons does not occur and the photoconductor can be uniformly charged.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a charging device of this embodiment.

FIG. 2 is a configuration diagram of an electrophotographic apparatus of this embodiment.

FIG. 3 is a sectional view of a conventional surface discharge charging device.

FIG. 4 is a perspective view of a conventional scorotron charging device.

FIG. 5 is a sectional view of a conventional scorotron charging device.

[Explanation of symbols]

 2 Application electrode 3 Charging electrode 4 Photoreceptor drum 5 High voltage power source

Claims (2)

[Claims] 1. A charging device for discharging by causing a charging electrode to face an electrostatic latent image support, which is a charge acceptor, and a charging electrode of a liquid high electric resistance, and a voltage applying means for applying a voltage to the charging electrode. A charging device comprising: 2. The volume resistance of the liquid high electrical resistance element is 10
The charging device according to claim 1, wherein the charging device has a thickness of ⁵ to 10 ¹³ Ωcm.