JPH0895344A - Conductive brush and electrifying device using that - Google Patents

Abstract

PURPOSE: To stabilize the discharge from a conductive fiber to a photosensitive body and to avoid such problems that the conductive part is exposed by wear or the like and a toner remaining and depositing on the top end of the brush causes irregular electrification, by covering the fiber with a protective layer comprising a high resistance material. CONSTITUTION: This conductive brush 1 consists of a base cloth 3, conductive fiber 5 and base body 7. The base cloth 3 is applied to the base body 7 and the conductive fiber 5 is implanted to the base cloth 3. This conductive fiber consists of a fiber 51 and a protective layer 52. Since it is necessary that charges can easily move, the fiber 51 is preferably made to have rather low resistance as <=10<10> Ωcm volume resistance (R1). On the other hand, it is preferable that the protective layer 52 has rather high resistance to stabilize discharge so that a material having high resistance as >=10<9> Ωcm volume resistance (R2) is used. The protective layer 52 is formed to 0.7-15μm thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic system for information equipment such as copiers, printers and facsimiles.
The present invention relates to a conductive brush used for charging and the like and a charging device using the same.

[0002]

2. Description of the Related Art After performing uniform initial charging on a moving electrostatic image carrier, the initial charging on the electrostatic image carrier is partially erased to form an electrostatic charge pattern. In an image forming apparatus that develops this electrostatic charge pattern and transfers it to a transfer material, the corona charging method has been widely used from the past due to advantages such as a non-contact method as a charging method and a simple configuration. There is. On the other hand, however, this method has a problem that ozone is generated during corona discharge and a problem that a high voltage must be applied because the efficiency is low. A contact charging method has been proposed as a method for solving such a problem, and in this contact charging method, a roller, a brush, a blade, or the like exists as a contact member. As the brush charging method, for example, conductive fibers are folded into a lower cloth, and the conductive fibers are cut and aligned to have a predetermined length. The brush charging method has advantages such as less ozone generation and better charging efficiency than the corona charging method, but has a problem that uneven charging is likely to occur. As a countermeasure against this, Japanese Patent Laid-Open No. 6-13
As disclosed in Japanese Patent No. 8751, a structure in which only the tip end portion of the conductive fiber is covered with an insulating material is used to uniformize the charge action from the conductive fiber to the photoreceptor. However, in the brush charging method with this structure, since the electrically conductive fiber tip is charged by the portion covered with the insulating material, the thickness of the insulating portion cannot be increased so much. The conductive part is exposed due to wear, etc.,
There is also a problem that residual toner adheres to the tip and uneven charging occurs.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The discharge from the conductive fiber to the photosensitive member is stabilized, the conductive portion is not exposed due to abrasion, etc., and the residual toner adheres to the tip to cause uneven charging. It is an object of the present invention to provide a brush charging device capable of reducing charging unevenness that does not occur.

[0004]

The present invention has found that the above problems can be solved by the following constitutions. That is, in the first invention, the volume resistance of the fiber is 10 ¹⁰ Ωcm or less, and the volume resistance of the fiber is 10 ⁹ Ωcm or less.
A conductive brush comprising a conductive fiber coated with a protective layer made of a high resistance material having an Ωcm or more. A second invention is the conductive brush, wherein the volume resistance (R1) of the fiber and the volume resistance (R2) of the high resistance member of the protective layer are R1 <R2. A third invention is a conductive brush, wherein the protective layer has a layer thickness of 0.7 to 15 μm. A fourth aspect of the present invention is the conductive brush, wherein the protective layer has a large thickness at the tip of the conductive fiber in the protective layer. A fifth aspect of the present invention is a conductive brush, wherein the conductive fiber tip is covered with a high resistance member having a higher resistance. A sixth aspect of the present invention is a brush charging device comprising the conductive brush, and means for contacting the brush with a body to be charged and charging and discharging the body to be charged. A seventh aspect of the present invention is the brush charging device according to the seventh aspect, characterized in that it has means for vibrating the conductive brush in a direction parallel to the charged body and at a right angle to the moving direction of the charged body. An eighth invention is a brush charging device characterized in that a piezoelectric element is arranged on a base of a conductive brush and the brush is vibrated by applying a voltage to the piezoelectric element.

The embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows the configuration of the conductive brush of the present invention. The conductive brush 1 shown in the figure comprises a base cloth 3, a conductive fiber 5, and a base 7. The base cloth 3 is provided on the base 7, and the conductive fiber 5 is applied to the base cloth 3. It has been planted. A known method can be used as a method for implanting the conductive fibers 5 in the base fabric 3. Base 7 is conductive fiber 5
Is for fixing the erected base fabric 3, and is made of, for example, aluminum, stainless steel, copper, brass or the like. Figure 2
Shows a configuration of a charging device using the conductive brush of the present invention. The member to be charged 11 shown in the figure comprises a cored bar 11a and a photosensitive layer 11b provided on the cored bar. Although the charged body 11 has a drum shape in the drawing, it may have a belt shape or an insulating sheet shape, and the shape thereof is not limited. Further, the base 7 in the figure functions as an electrode when a voltage 13 is applied to the conductive brush 1. 3 to 5 are enlarged cross-sectional views of the conductive fiber 5 which constitutes the conductive brush of the present invention. The conductive fiber 5 shown in each drawing is composed of a fiber 51 and a protective layer 52. Further, in FIG. 5, the fiber tip portion is composed of a second protective layer made of a member having higher resistance.

Since the fibers 51 are required to easily transfer charges, it is preferable that the fibers 51 have a somewhat low resistance value, and it is necessary that the fibers 51 are formed of a low resistance member. A low resistance material having R1) of 10 ¹⁰ Ωcm or less, for example, a material mixed with conductive carbon or the like can be used. On the other hand, the protective layer 52 preferably has a somewhat high resistance value in order to stabilize the discharge, and needs to be formed of a high resistance member. Specifically, the volume resistance (R2) is 10 ⁹ Ωcm or more. A resistance substance can be used, and a substance having an insulating property is particularly preferable. For example, a fluororesin may be used. As shown in FIG. 3, the protective layer is formed so as to completely cover the tip portion 53 of the fiber. Further, in order to perform the discharge more stably, it is preferable that the electric charge is accumulated between the protective layer and the fiber. For that purpose, the relationship between the volume resistance (R1) of the low resistance material of the fiber and the volume resistance (R2) of the high resistance material of the protective layer is R1 <R2. The shape of the cross section of the fiber need not be a perfect circle, and may be an ellipse or the like. Further, when electric discharge occurs between the conductive fiber and the body to be charged, if the surface of the conductive fiber 5 has a low resistance, unstable abnormal discharge (streamer) occurs, and uneven charging occurs. . However, by providing the protective layer 52 having a high resistance on the fiber surface like the conductive fiber of the present invention, the occurrence of abnormal discharge can be suppressed, so that stable discharge can be performed and uneven charging can be suppressed.

As a method for forming the protective layer 52 on the fiber, it is possible to use a conventionally known method such as dipping, coating, double extrusion or drawing formation. The layer thickness of the protective layer is not particularly specified, but if it is too thin, the conductive fibers 51 are exposed due to wear or the like, and abnormal discharge occurs from there, which is not preferable. In addition, the surface of the protective layer must hold a sufficient electric potential to generate an electric discharge, and thus it is not preferable even if the layer thickness is too thick because a problem occurs. Table 1 shows the results of studying the relationship between the layer thickness of the protective layer and the uneven charging by changing the layer thickness of the protective layer. The fiber used was a low resistance material in which fluorocarbon resin was mixed with conductive carbon. The volume resistance R1 of this low resistance material is 5 × 10 ⁸ Ωcm.
Met. The diameter of the fiber was 100 μm. As the high resistance material of the protective layer 52, only fluororesin was used. The volume resistance R2 of this high resistance material was 10 ¹⁵ Ωcm or more. As a method of measuring the uneven charging, a mylar sheet with aluminum surface deposited on one side of a substrate is
After charging with a conductive fiber applied with a voltage of 2 Kv,
Cascade development was carried out with a negative polarity toner, and uneven charging was observed.

[0008]

[Table 1]

In the table, ⊚ does not cause uneven charging and there is no change in charging potential. In the case of ○, uneven charging did not occur, but the charging potential was slightly lowered. A part of the triangle is not charged. It means that.

As is clear from the results shown in Table 1, the protective layer 52 made of this high resistance material has a layer thickness T ₁ of 0.7 to
It is understood that it is preferable to set the thickness to about 15 μm. However,
The layer thickness of the protective layer is preferably 1 μm or more in order to uniformly charge the layer uniformly, and the layer thickness of the protective layer is preferably 10 μm or less in order to prevent a decrease in the charging potential. Therefore, in order to sufficiently satisfy both characteristics, it is preferably 1 to 10 μm, particularly preferably 3 to 8 μm.
It is suitable to adjust the layer thickness to μm, but in actual use, it varies depending on factors such as the layer thickness of the photoconductor and the characteristics of the residual toner, and is not particularly limited to this value.

In the conductive fiber forming the conductive brush shown in FIG. 3, most of the charging is generated at the tip of the fiber. Therefore, there are cases in which minute uneven charging occurs due to the influence of the layer thickness and surface condition of the protective layer and the adhesion of residual toner, which causes the discharge to be slightly closer to the root than the tip 54 of the fiber 5. It can be improved by generating it in the trunk portion 53. It is considered that this is because the discharge gap is increased by the same configuration, the influence of the surface state of the protective layer 52 is reduced, and the influence of the residual toner is almost eliminated.

To this end, only the surface potential of the tip portion 53 of the fiber 5 needs to be lowered. This can be achieved by increasing the thickness of the protective layer 52 at the tip portion as shown in FIG. 4 or as shown in FIG. The second protective layer 9 may be further provided on 53. In the present invention, the output of the image is obtained by performing uniform initial charging on the electrostatic image bearing member and then partially erasing the initial charging on the electrostatic image bearing member to form an electrostatic charge pattern. This electrostatic charge pattern is developed and transferred to the material to be transferred. At this time, by vibrating the entire brush with a small amplitude, it is possible to improve the streak unevenness corresponding to the fiber density of the brush. it can. At this time, the vibrating direction is preferably a plane shape parallel to the charged body and a direction perpendicular to the moving direction of the charged body. The optimum method for vibrating is to use a piezoelectric element. The piezoelectric element is the most preferable in the present invention because it has a good frequency followability, can reproduce a minute displacement with high accuracy, consumes less power, and does not generate noise. FIG. 6 shows an outline of an apparatus for vibrating a brush using a piezoelectric element. In the device shown in the figure, the piezoelectric element 12 is composed of a spring 13 for holding the brush 1 and a support base 14 for holding the brush 1. The piezoelectric element 12 vibrates at a certain frequency f when a bias is applied from a power source (not shown). When the vibration frequency f of the image formed on the charged body 11 is ΔL and the moving speed is VL when the distance between dots in the moving direction of the charged body 11 is VL, and when f> VL / ΔL is satisfied, No charge unevenness appears on the image. Therefore, if this condition is satisfied, the conductive brush 1 vibrates in one cycle or more while the charged object moves by a distance of ΔL, and thus uneven charging according to the vibration cycle does not appear on the image. You can Although the above description is for the case of using as a charging brush, the conductive brush of the present invention may be arranged on the surface of the conductive roller and used as a charging roller. In this case, by providing a roller cleaning member, it is possible to easily clean the residual toner adhering to the conductive fibers 5.

Further, by changing the moving speed between the conductive fiber and the member to be charged, there is a merit that efficient charging becomes possible. Similarly to the charging brush, it is possible to remove minute charging unevenness by vibrating the roller using a piezoelectric element or the like, and it is also possible to displace the piezoelectric element in another displacement direction. is there.

[0014]

EXAMPLES The present invention will be specifically described below based on examples.

Example 1 A mixture of fluorocarbon resin and conductive carbon was used as the low resistance material 51, the volume resistance was 5 × 10 ⁸ Ωcm, the diameter was 100 μm, the fluorocarbon resin was used as the protective layer 52, and the coating thickness t was used. ₁ was about 5 μm. Second protective layer 9
Is also made of a fluororesin, and has a thickness of 100 μm and a length of 2 mm. The conductive fibers had a length of 2 cm and a fiber density of 5000 fibers / cm ² . When a bias of −2 kv was applied to this conductive brush to charge the photoconductor, a charging potential of −1.2 kv was obtained and no charging unevenness occurred. When the image was visualized with colored particles (toner), the unevenness of the brush sweep was slightly observed in the halftone image.

Example 2 A laminated piezoelectric element was attached to the base of the charging brush used in Example 1 and vibrated at 50 kHz in the axial direction of the photoconductor,
-2 kv was applied. When the photosensitive member was moved at a moving speed of 100 m / s, the charging potential was -1.2 as in Example 1.
kv was obtained. When visualized with colored particles (toner), no charge unevenness was observed.

[0017]

[Effects] By using the conductive brush according to claim 1, in the charging device using the conductive fiber, by stabilizing the discharge from the conductive fiber to the photoreceptor,
It is possible to reduce uneven charging. By using the conductive brush according to claim 3, in the charging device using the conductive fiber, the coating layer on the surface of the conductive fiber is not deteriorated by abrasion or the like, and the surface of the conductive fiber is generated so that discharge is generated. It is possible to sufficiently raise the potential of, the stable discharge occurs, and the uneven charging is reduced. By using the conductive brush according to the fourth and fifth aspects, in the charging device using the conductive fiber, it is possible to reduce the uneven charging by preventing discharge at the tip of the conductive fiber. By using the conductive brush according to the seventh aspect, it is possible to prevent sweep-like charge unevenness in the charging device using the conductive fiber. By using the conductive brush according to claim 8, when the conductive fiber is vibrated to prevent sweeping charge unevenness, it is possible to stably vibrate the fiber, and charge with less unevenness is obtained. it can.

[Brief description of drawings]

FIG. 1 is a diagram showing a conductive brush of the present invention.

FIG. 2 is a diagram showing a state in which the conductive brush of the present invention is used for charging.

FIG. 3 is an enlarged cross-sectional view of a conductive fiber 5 of a first example which constitutes the conductive brush of the present invention.

FIG. 4 is an enlarged cross-sectional view of a conductive fiber 5 of a second example which constitutes the conductive brush of the present invention.

FIG. 5 is an enlarged cross-sectional view of a conductive fiber 5 of a third example which constitutes the conductive brush of the present invention.

FIG. 6 is a diagram showing a specific example of an apparatus used in the recording method of the present invention.

[Explanation of symbols]

 1 Conductive Brush 3 Base Fabric 5 Conductive Fiber 7 Base 9 Second Protective Layer 11 Charged Member 11a Core Bar 11b Photosensitive Layer 12 Piezoelectric Element 13 Voltage 14 Supporting Base 51 Fiber 52 Protective Layer

 ─────────────────────────────────────────────────── --Continued front page (72) Inventor Yutaka Ebi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (8)

[Claims] 1. A conductive material characterized in that the volume resistance of the fiber is 10 ¹⁰ Ωcm or less, and the fiber is made of a conductive fiber coated with a protective layer made of a high resistance material having a volume resistance of 10 ⁹ Ωcm or more. brush. 2. The conductive brush according to claim 1, wherein the volume resistance (R1) of the fibers and the volume resistance (R2) of the high resistance member of the protective layer are R1 <R2. 3. The conductive brush according to claim 1, wherein the protective layer has a layer thickness of 0.7 to 15 μm. 4. The conductive brush according to claim 1, wherein the conductive brush has a thick protective layer at the tip of the conductive fiber. 5. The conductive brush according to claim 1, wherein the tip of the conductive fiber is covered with a high resistance member having higher resistance. 6. A conductive brush according to claim 1, and means for charging and discharging the charged body by bringing the brush into contact with the charged body. Characteristic brush charging device. 7. The charging device according to claim 6, further comprising means for vibrating the conductive brush in a direction parallel to the charged body and perpendicular to the moving direction of the charged body. Brush charging device. 8. A piezoelectric element is arranged on the base of a conductive brush,
The brush charging device according to claim 7, wherein the brush is vibrated by applying a voltage to the piezoelectric element.