JPH05307279A - Electrostatic charging method - Google Patents

Abstract

PURPOSE:To prevent the damage and unequal electrostatic charge of a member to be electrostatically charged by impressing alternating voltages superposed with a DC voltage and a low-frequency AC voltage between members via a specific air gap. CONSTITUTION:A power source 3 impresses the alternating voltages superposed with a DC voltage and a low-frequency AC voltage between an electrode member 2 and the member 1 to be electrostatically charged. On the member 1 to be electrostatically charged, a light image is projected in accordance with a copying process, by that, the electrostatic image is formed thereon. After this image is visualized by a toner, the image is transferred to a transfer material, such as paper and is fixed, by that, a copy is formed. The member 1 to be electrostatically charged is cleaned and destaticized and is repetitively used. As the air gap G of the electrode member 2 from the surface of the member 1 to be electrostatically charged, the shortest distance between the two members is made to be 120mum or less in order to obtain the uniform electrostatic charge in such a case. A double-layered roller of silicone rubber, etc., or roller coated with a plastic material, etc., having 10<3> to 10<13>OMEGA.cm electric resistance are used as the electrode member 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging method, and more particularly to a charging method for a photoconductor which is preferably used in an electrophotographic copying machine or the like.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic copying machine or the like, the surface of a photoconductor (member to be charged) is uniformly charged to a specific polarity by corona discharge means, and then the charge on the photoconductor is selectively exposed by image exposure. Disappears to form an electrostatic image, and the developer is supplied to the surface of the photoconductor by the developer supplying body to which an appropriate developing bias is applied to develop the electrostatic image. However, the device using the corona discharge means is easily affected by the use environment such as humidity and dust, and has a problem of odor and harmfulness to human body due to release of ozone accompanying corona discharge. In order to solve this problem, for example, Japanese Patent Laid-Open No. 63-1496.
As disclosed in JP-A-68, JP-A-63-149669, JP-A-64-73367, JP-A-64-73364, and the like, conductivity in which a voltage obtained by superimposing an AC voltage on a DC voltage is applied. A method of charging the surface of the member to be charged by bringing the elastic member into contact with the surface of the member to be charged has been proposed.

[0003]

However, in such a contact charging method, when a relatively hard foreign substance such as a carrier adheres to the surface of the member to be charged or the surface of the electrically conductive member, the electrically conductive member does not contact the foreign substance. Since it comes into contact with the surface of the member to be charged with the intervening contact between them, these foreign substances can damage the surface of the member to be charged or the surface of the conductive member, or can correspond to the portion of the conductive member to which the foreign substance adheres. As a result, inconvenience occurs such that uneven charging occurs in the part to be charged. Further, it is necessary to bring the conductive member into contact with the surface of the member to be charged with a uniform pressure along the width direction.
For this reason, the conductive member is practically manufactured from an elastic material such as rubber, but it has the drawback that it is very difficult to obtain mechanical accuracy in mass production and it is economically expensive. Further, there is a drawback that stable use for a long time cannot be expected due to the scratches on the conductive member or the adhesion of foreign matter as described above.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the drawbacks of the conventional means, in which the electrode member is arranged with an air gap of 120 μm or less with respect to the surface of the charged member to be moved, It is characterized in that the member to be charged is charged by applying an alternating voltage in which a DC voltage and a low-frequency AC voltage are superposed between these members.

In particular, the electrode member is composed of a rotating roller, and preferably 10 ³ to 10 ^{3 on the} surface of the roller-shaped conductive substrate.
A coating layer made of a plastic material of 10 ¹³ Ωcm is formed.

[0006]

By such means, the surface of the member to be charged is discharged and charged by the electrode member.

[0007]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 shows an example in which the method according to the present invention is embodied. In the figure, reference numeral 1 is a member to be charged which rotates in the direction of arrow A,
Reference numeral 2 indicates an electrode member, and 3 indicates a power source. For example, when the present invention is applied to an electrophotographic copying machine or the like, the member to be charged 1 is an electrophotographic photosensitive member such as OPC (organic photoconductor) and is applied or coated on a grounded electrode drum. It is worn and provided. The member to be charged 1 charged according to the present invention as described below is projected with an optical image to form an electrostatic image according to a known copying process, visualized with toner, and then transferred to a transfer material such as paper. , Fix, and form a copy. The member 1 to be charged is cleaned and discharged to be provided for repeated use.

The electrode member 2 has a roller shape, and is arranged apart from the surface of the member to be charged 1 with an air gap G interposed therebetween. From experiments, it is desirable that the air gap G of the electrode member 2 with respect to the surface of the member to be charged 1 be 120 μm or less at the shortest distance between both members in order to obtain uniform charging. The electrode member 2 has an electric resistance of 10 ³
Single-layer or multi-layer rollers such as EPDM, silicon rubber, NBR, etc. of -10 ¹³ Ωcm, or rollers formed by coating a conductive material such as metal with a plastic material having an electric resistance of 10 ³ -10 ¹³ Ωcm. Is used. The electrode member 2 is optimally rotated in the arrow B direction. In various experiments, although it was extremely rare, uneven charge could be observed under some conditions when the electrode member was stationary.

The power source 3 applies an alternating voltage between the electrode member 2 and the member to be charged 1 in which an AC voltage is superimposed on a DC voltage. As the AC voltage, a low frequency of 150 Hz to 3 KHz is used, and optimally 1 KHz is used.

Experimental Example 1 As shown in FIG. 2, a member to be charged (OPC) having a diameter of about 30 mm was used.
The photoconductor 1 and the electrode member 2 having a diameter of about 12 mm are about 80 μm.
When a low-frequency AC voltage is applied between the two members while rotating the two members, the charging potential shown in FIG. 3 is obtained on the surface of the member to be charged 1. It was The horizontal axis represents V _PP of the applied AC voltage, and the vertical axis represents the surface potential of the charged member measured at the position C. Discharge starts from about 1100V _PP and uniform charge is 140
It was obtained in the range of 0V _pp ~2100V _PP. 2100V
It was confirmed that if it is more than _PP, it becomes non-uniformly charged. As the electrode member 2, a roller in which a plastic material selected from 10 ³ to 10 ¹³ Ωcm is used as the SUS material is used, but the charging voltage is only slightly changed depending on the resistance value of the surface coating material, If the resistance value is within the above range, uniform charging was obtained in the range of 1400 V _{PP to} 2000 V _PP of the AC applied voltage. It is considered that the negative side is charged in spite of the AC voltage because the output waveform of the low frequency output AC power supply used in the experiment is slightly higher at the negative pole than at the positive pole.

Experimental Example 2 As shown in FIG. 4, a voltage obtained by superimposing a low frequency AC voltage on a DC voltage is applied between the member 1 to be charged and the electrode member. The other conditions are the same as in Experimental Example 1. DC400 as DC voltage
When the same voltage as in Experimental Example 1 was used as the V and AC voltages for superposition, it was confirmed that the charging potential was as shown in FIG. Similar to the case of Experimental Example 1, uniform charging was obtained when the AC voltage was in the range of 1400 V _{PP to} 2100 V _PP . It is experimental example 1 that the charging potential becomes 400 V or more.
It is considered that this is due to the difference in the voltage of the low-frequency AC power source as well.

Experimental Example 3 Under the numerical conditions of Experimental Examples 1 and 2, an electrode member (having a resistance value of 10 ³ to 10 ¹³ Ω, EPDM, silicon rubber, NBR) was brought into contact with the surface of the member 1 to be charged and repeated in the same manner. An experiment was conducted. In the initial number of times, the same results as in Experimental Example 1 and Experimental Example 2 were obtained for both the charging start voltage and the uniform charging region, but when several hundreds of repetitions were performed, the initial number of times was the uniform charging region. The part became unevenly charged.

Experimental Example 4 In the same manner as in Experimental Examples 1 and 2, the electrode member 1 used in Experimental Example 3 has a distance of about 80 μm between the surface of the member 1 to be charged and the electrode member 2.
An air gap of m was provided and the charging potential was measured. As a result, the same results as in Experimental Examples 1 and 2 were obtained.

Experimental Example 5 The same experiment as Experimental Example 1 and Experimental Example 2 was conducted using an electrode member 2 having an electric resistance of 10 ¹⁴ Ωcm or more. In this case, relatively uniform charging was obtained, but a high value of charging potential could not be obtained.

Experimental Example 6 An experiment similar to Experimental Example 1 and Experimental Example 2 was conducted using an electrode member 2 having a resistance of 10 ² Ωcm or less. As a result, the discharge was unstable and a non-uniform charging potential was obtained. ..

Experimental Example 7 In Experimental Examples 1 to 6, charging was performed by changing the frequency of the AC voltage applied to the electrode member 2 in the range of 150 Hz to 3 KHz. The uniformly charged region had almost the same value as in the above experimental example, but at 1 KHz or more, a strange sound was heard due to the audible frequency.

Experimental Example 8 In Experimental Example 1 and Experimental Example 2, the member 1 to be charged and the electrode member 2 were charged.
I changed the air gap with. Air gap is 120
When the thickness was more than μm, the charge potential was formed, but as the gap increased, the discharge became unstable and uniform charge could not be obtained.

As described above, the electric resistance of the electrode member 2 is from 10 ³ to
Using a roller of 10 ¹³ Ωcm, the charged member 1 and the electrode member 2
The shortest air gap between them is set to 120 μm or less, and the frequency is 150 Hz to 3 KHz and the voltage is 1.4.
The KV _PP ~2.1KV _PP voltage obtained by superimposing an AC voltage on a DC voltage of, uniform charging the member to be charged surface is performed by applying between the charging member 1 and the electrode member 2.
The charging potential is substantially determined by the value of the DC component, and a charging potential almost equal to the DC voltage can be obtained.

In the above example, the electrode of the member to be charged is grounded and the electrode member is applied to the power source 3. However, a voltage is applied to the electrode side of the member to be charged and the electrode member 1 is grounded for charging. Needless to say, in this case, the charging potential and the applied voltage are superimposed to form an amplitude potential. In the experiment, the polarity of the DC voltage was negative, but if the positive polarity was used, the charging polarity would be positive.

[0020]

According to the present invention, uniform charging can be performed without causing damage or uneven charging due to foreign matter adhering to the member to be charged or the electrode member.

[0021]

[Brief description of drawings]

FIG. 1 is a diagram showing an example in which a charging method according to the present invention is embodied.

FIG. 2 is a diagram showing an example of an apparatus that was tested to explain the present invention.

FIG. 3 is a diagram showing an experimental result by the apparatus of FIG.

FIG. 4 is a diagram showing another example of a device that was tested to explain the present invention.

5 is a diagram showing an experimental result by the apparatus example of FIG.

[Explanation of symbols]

 1 charged member 2 electrode member 3 power supply

Claims (4)

[Claims] 1. The surface of a moving member to be charged is 120.
A charging method characterized in that an electrode member is arranged with an air gap of not more than μm, and an alternating voltage obtained by superimposing a DC voltage and a low-frequency AC voltage is applied between these members to charge the member to be charged. .. 2. The charging method according to claim 1, wherein the electrode member is a rotating roller. 3. The charging method according to claim 1, wherein the electrode member is formed by forming a coating layer made of a plastic material of 10 ³ to 10 ¹³ Ωcm on the surface of the roller-shaped conductive substrate. 4. A drum-shaped electrophotographic photosensitive member is provided with 10 parts.
^An electrode roller made of ³ to 10 ¹³ Ωcm is arranged with an air gap of 120 μm or less at the shortest distance, and an alternating voltage obtained by superimposing a DC voltage and a low-frequency AC voltage is applied between these members. A charging method characterized by performing charging.