JPS6229790B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a charging device for charging a photoreceptor of, for example, an electrophotographic copying machine.

Corona chargers are currently used in most electrophotographic copying machines, but corona chargers use high pressure, are dangerous, pollute the atmosphere and equipment due to ozone generation, and are expensive. There was a problem in making it a reality. On the other hand, charging devices using rollers or brushes, which have been tried in various ways for a long time, have had the problem of mechanically damaging the photoreceptor or electrically damaging it.

Therefore, in order to solve the above-mentioned problems, the present applicant has already filed an application as Japanese Patent Application No. 55-30093. Figure 1 shows the schematic structure of the above application, where a is a photoreceptor such as ZnO, b is an electrode with a moderate resistance, c is an electric resistor like a cloth with dense piles, and d is a DC power supply that applies a DC voltage to the electrode b, e is an AC power supply that applies an AC voltage to the electrode b via a capacitor f, and g is a capacitor for attenuating the AC electric field. When a DC voltage and an AC voltage are applied to the contact charging device configured in this way, as shown in Figure 2, the AC voltage becomes highest at point A in Figure 1, and as it moves toward point B, as shown in Figure 2. AC voltage is attenuated, but DC voltage is
It features an almost constant potential distribution between A and B, and very good results have been obtained in repeatedly charging the photoreceptor a.

However, in this case, the zinc oxide photoreceptor is advantageous in terms of stabilizing its charging potential, but if the AC voltage at the part B is too large, it will cause uneven charging, as shown in FIG. It was necessary to give a slope to the AC voltage. However, in this case, alternating current constantly flows through the electrodes, which is wasteful and has the drawback of being directly affected by electrode resistance.

This invention was made in view of the above-mentioned circumstances, and its purpose is to provide a contact layer with a first electrode layer for applying a DC voltage and a second electrode layer for applying an AC voltage. The object of the present invention is to provide a charging device that can obtain stable charging characteristics even when the current is small.

The present invention will be explained below based on an embodiment shown in the drawings. FIG. 3 shows the basic configuration of an electronic copying machine, where 1 is the main body. A document mounting table 2 is provided on the upper surface of the main body 1, and is configured to reciprocate by a drive motor 3 provided within the main body 1. A drum-shaped zinc oxide-resin dispersant photoreceptor 4, which rotates synchronously with the mounting table 2 and serves as a charged member, is pivotally supported approximately at the center of the main body 1. An exposure system 7 including a lamp 5, a focusing light transmitter 6, etc. is located between the photoreceptor 4 and the original table 2.
is provided to irradiate the document placed on the document table 2 and guide the reflected light to the photoreceptor 4 to form an image of the document. From this image forming position, in order along the rotational direction of the photoreceptor 4, a developing device 8, a transfer device 9, a cleaning device 10, and a charging device 11, which will be described later.
is installed. The developing device 8 visualizes the latent image of the document formed on the surface of the photoreceptor 4 by the exposure system 7. The transfer device 9 transfers the original toner image formed on the photoreceptor 4 onto the copy paper p, and the cleaning device 10 transfers the original toner image formed on the photoreceptor 4 to the copy paper p.
This removes toner remaining on the surface of the
Further, at the bottom of the main body 1, there is provided a paper feeding device 14 consisting of a removable cassette 12 for storing copy paper p, and a paper feed roller 13 for feeding the copy paper p. The transfer device 9 also includes a transfer roller 1.
5 and a transfer belt 17 having an insulating property such as Mylar (trade name), which is stretched between a plurality of guide rollers 16, 16. and,
This transfer belt 17 is in contact with a part of the outer circumferential surface of the photoreceptor 4, and this transfer belt 17
7, a transfer charging device 18 having basically the same structure as the charging device 11 and a cleaning rate 19 are in contact with each other. Further, a fixing device 20 and a delivery roller 21 are provided on the delivery end side of the transfer belt 17, and the copy paper p onto which the image has been transferred by the transfer device 9 is fixed, and then delivered to the tray 22. ing. Note that 23 is a control device.

The motor 3 is a motor equipped with an exhaust fan, and is designed to exhaust heat generated in the exposure system 7 as the motor rotates to the outside of the main body 1. The photoreceptor 4 is formed by coating a thin aluminum drum with a thickness of 0.8 mm and a diameter of about 80 mm with a binder type photoreceptor of zinc oxide-resin dispersant sensitized with a dye such as rose bengal. It is something. Further, the cleaning blade 19 described above cleans the transfer belt 17 by scraping off toner and the like adhering to the transfer belt 17.

Next, the charging device 11 will be explained based on FIGS. 4 and 5. 24 is a charger base which is a base body. The back electrical unit base 24 is made of a resin material such as acrylic or ABS and is formed into a prismatic shape.
A mounting member 26 having a diameter of 5 is fixed. The engagement groove 25 of the attachment member 26 is slidably engaged and supported by a guide frame 27 provided on the main body 1. Further, a sheet-like polymer 28 is detachably attached to the front portion of the charger base 24. This polymer 28 has a contact layer 29, a first electrode layer 30, a dielectric layer 31, and a second electrode layer 32 polymerized in order from the front side thereof, that is, the side in contact with the photoreceptor 4. The contact layer 29 is made of velveteen-like cloth, and the base cloth 33 is made of carbon-dispersed rayon fibers (manufactured by Unitika), length 3 mm, thickness 5 denier, density 16,000 fibers/
By implanting the hair body 34 of cm ² , the resistance value is
It is set to 10 ⁷ Ω・cm. In addition, the first electrode layer 30 is made of carbon (Cabon Co., Ltd. VULCAN-XC-
72) Conductive rubber consisting of +SBR (Asahi Kasei Corporation Toughprene) + xylene resin (Mitsubishi Gas Chemical Corporation Nicanol), and the resistance value is set to 10 ⁶ Ωcm. Further, the dielectric layer 31 is formed of a polyester film (trade name: Mylar) with a thickness of 12 μm.
Furthermore, the second electrode layer 32 has the same components as the first electrode layer 30, but its resistance value is set to 10 ² Ω·cm. Polymer 2 configured in this way
The first electrode layer 30 of No. 8 is connected to a DC power source 35, a second
The electrode layers 32 are each connected to an AC power source 36, so that a DC voltage and an AC voltage are applied thereto.

When copying the original on the original platen 2, by pressing the copy start button, each device discharges the copy paper p on which the original copy image has been obtained to the tray 22 by a known operation. be able to.

Here, according to the applicant's experiments, the photoreceptor 4 is
25μ zinc oxide, DC voltage applied to the first electrode layer 30 -
When an AC voltage of 80 V and 50 Hz was applied to the second electrode layer 32 and the photoreceptor 4 was charged at a peripheral speed of 80 mm/sec, a stable potential of -400 to -450 V was obtained, and it was environmentally friendly. There was stability. In this case, it has been found that the appropriate AC voltage is 10 to 20% of the DC voltage, and that if it is lower than this, the potential will not ride well, and if it is higher, uneven charging will easily occur.

Further, the above-mentioned charging phenomenon is caused by too much alternating current flowing at the charging end point B.
However, this charging unevenness can be prevented by the following procedure.

That is, FIG. 6 shows another embodiment of the present invention, in which a first electrode layer 30 and a second electrode layer 32
A side of the dielectric layer 31 between the contactor layer 2
9 has a thin wall on the side that first contacts the photoreceptor 4, and has a thick wall on the opposite side B. With this configuration, the flow of AC voltage can be controlled,
The appropriate range of AC voltage can be expanded, and more stable charging can be obtained by increasing the AC voltage.

Note that in the multilayer structure of the first electrode layer, dielectric layer, and second electrode layer, another layer may be provided between each layer. For example, dielectric layers with different dielectric constants may be superposed, or the first electrode layer may be multilayered, and a dielectric layer may be provided between them.
Different AC voltages may be applied to the plurality of first electrode layers.

As explained above, this invention provides a first electrode layer and a second electrode layer having a lower resistance than the first electrode layer on the contact layer in contact with the object to be charged, and applies a DC voltage to the first electrode layer.
Since an alternating current voltage is applied to the second electrode layer, charging with stable charging characteristics can be achieved with a small power supply current, resulting in an economical effect.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing the principle of a contact charging device, FIG. 2 is an explanatory diagram also showing the voltage distribution applied to the photoreceptor, and FIG. 3 is a schematic diagram of an electronic copying machine employing the charging device of the present invention. FIG. 4 is a cross-sectional view showing one embodiment of the charging device of the present invention, FIG. 5 is a cross-sectional view of the same main part, and FIG. 6 is a cross-sectional view showing another embodiment of the present invention. 4... Photoreceptor (charged body), 29... Contact layer, 30... First electrode layer, 31... Dielectric layer,
32...Second electrode layer.

Claims (1)

[Claims] 1. A first electrode layer on the first surface of the flexible contact layer;
A second electrode layer having a lower resistance than the dielectric layer and the first electrode layer.
The first electrode layer is formed by sequentially polymerizing the electrode layers in a layered manner.
A charging device characterized in that a DC voltage is applied to an electrode layer, an AC voltage is applied to a second electrode layer, and the second surface of the contact layer is brought into contact with a charged object to charge the object. 2. The charging device according to claim 1, wherein the dielectric layer is thinner at the portion where the contact first contacts the object to be charged, and thicker at the opposite portion.