JPH0627782A - Charger - Google Patents

Abstract

PURPOSE:To reduce dirt, improve reliability and uniformity of charging, and to increase safety and at the same time to reduce the generation of ozone by arranging face to face a conductive fiber-like member connected to a power supply and an electrostatic latent image forming body at an interval. CONSTITUTION:This charger is constituted of a roundish metal support member 1 provided in the corner of the opposed side of an electrostatic latent image forming body 5, a conductive fiber-like member 2 bonded with a conductive bonding agent 3 on the surface of the opposed side of the metal support member 1 to the electrostatic latent image forming body 5 and a power supply 4 connected to the metal support member 1, and the conductive fiber-like member 2 and the electrostatic latent image forming body 5 are arranged face to face at an interval Gap G. Then, when a conductive fiber-like material is used for the conductive fiber-like member 2, the material is not particularly limited, for example, non-woven cloth and regularly woven cloth-like materials are preferably used, and non-woven cloth and regularly woven cloth to which the conduction treatment of plating, metal coating and conductive polymer coating is applied is taken for instance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device for charging an electrostatic latent image forming body in an apparatus for forming an image by an electrophotographic method using the electrostatic latent image forming body.

[0002]

2. Description of the Related Art Conventionally, copying machines, laser printers, fax machines and the like have been known as apparatuses for forming images by electrophotography using an electrostatic latent image forming body such as a photoconductor. In most of them, the electrostatic latent image forming body, for example, the photoconductor is uniformly charged, and the reflected light from the original is exposed according to the image information to form the electrostatic latent image on the photoconductor, and then the developer is used. There is a method called indirect electrophotography, which involves developing, transferring to a recording medium such as plain paper, fixing under heat and pressure, and outputting an image.

There is also a direct electrophotographic method in which the recording medium itself is an electrostatic latent image forming body, and the recording medium is also uniformly charged, and then exposed, developed and fixed, and then output. In either case, there is a process for uniformly charging the electrostatic latent image forming body in forming the electrostatic latent image. on the other hand,
An electrostatic recording method is used to form an electrostatic latent image from the beginning without being uniformly charged, that is, as an electrostatic latent image forming body, for example, a dielectric is dot-charged to form an electrostatic latent image. There are developing, transferring, fixing or developing, fixing, but the charged part is complicated and expensive, and there are many problems in practical use due to variations in the charged part at each place, and in reality it is rarely used. is there. Therefore, most of the image forming apparatuses using the electrostatic latent image forming body that have been put into practical use use the electrophotographic method.

In the electrophotographic method, it is necessary to uniformly charge the electrostatic latent image forming body prior to exposure, but the charging devices currently in use are roughly classified into corona discharge charging, brush charging, and Roller charging is known. Corona discharge charging is performed by corona discharge from a wire connected to a high-voltage power supply. Actually, it is absolutely necessary for tungsten or Au-plated tungsten wire placed inside a shield with an opening on the side of the object to be charged. As a value, a high voltage of 4 to 7 kV is applied to cause corona discharge,
It is to be charged. There is also a scorotron type in which a grid electrode is provided between the wire and the object to be charged in order to achieve more uniform charging and stable charging. Brush charging is
A conductive brush (metal brush or conductive resin brush) connected to the power supply for application is charged by contacting the object to be charged, and unlike the corona discharge mentioned above, a voltage of about the same potential as the target charge level is applied. It is charged while being applied. In roller charging, a roller with a single layer or multiple layers of conductive rubber is attached to a metal shaft to apply a voltage while pressing it against an object to be charged, and the applied voltage can be as low as brush charging. Moreover, there is an advantage that the generation of ozone is small.

[0005]

However, each of these charging devices has the following problems. In corona discharge charging, first, a high voltage of 4 to 7 kV in absolute value is required to be applied, and attention must be paid in practical use such as connection of wiring and distinction from other wiring. In addition, ozone is generated with corona discharge, and particularly with negative corona discharge, more than 10 times more ozone is generated than with positive corona discharge, which not only affects the material selection and reliability of parts inside the device,
There is a problem of arranging or replacing the ozone filter for suppressing the release of ozone to the outside of the device, and thus increasing the cost. Further, the discharge performance is deteriorated by the products on the wire surface due to the corona discharge, and there remains a problem in the reliability of the charging device itself.

On the other hand, although ozone is hardly generated by brush charging or roller charging, since it is in contact with an object to be charged, it is easy to scratch the object. In addition, the conductive brush etc. becomes dirty due to poor cleaning of the charged object or mixing of the developer and paper powder in the device,
It has been pointed out that the charging potential is lowered, and uneven charging occurs due to non-uniformity during manufacturing and mounting. In particular, in the case of brush charging, there are many problems in practical application in terms of uniform charging and reliability, such as a problem of brush density, a problem of brush bristling, and a problem of setting contact conditions. Although multi-stage brush charging has been proposed as a countermeasure, cost and space problems still arise.

Roller charging can solve many problems found in brush charging to some extent, and uniform production of rollers and uniform pressure contact with an object to be charged are relatively easy to carry out, and have been put into practical use. However, once the roller surface is scratched, that portion has different charging performance from the others, which causes image deterioration. In addition, there is a question whether it is possible to secure a more uniform charging performance for future image densification, and in the color superposition development process that forms a color image on the charged object for contact charging. It has also been pointed out that there are drawbacks such as not being able to adapt. Therefore, in view of the above points, an object of the present invention is simple and non-contact with an object to be charged, more specifically, an electrostatic latent image forming member, without applying a high voltage of 4 to 7 kV in absolute value. An object of the present invention is to provide a charging device that can be realized at a low device cost by configuring the device.

[0008]

SUMMARY OF THE INVENTION In a charging device of the present invention, in a device for charging an electrostatic latent image forming body, a conductive fibrous member connected to a power source is arranged to face the electrostatic latent image forming body with a gap. It is characterized by being. Also,
The conductive fibrous member can be achieved by using a conductive-treated non-woven fabric, a regular woven fabric, or electric flocking. Further, the gap between the conductive fibrous member and the electrostatic latent image forming body is 0.15 to 1.5 mm.

[0009]

In the charging device of the present invention, the electrostatic latent image forming body is charged by applying a voltage to the conductive fibrous members which are arranged to face each other with a gap from the electrostatic latent image forming body. Since the surface of the conductive fibrous member is an ultrafine fiber of several μm, it has a structure that can be said to be an assembly of small lightning rods, and thus charging is performed by needle discharge from these small lightning rods.

[0010]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. FIG. 1 shows a schematic view of a charging device according to the first embodiment. That is, the metal support 1 having rounded corners on the side facing the electrostatic latent image forming body 5, and the conductive adhesion on the surface of the metal support facing the electrostatic latent image forming body It is composed of a conductive fibrous member 2 bonded by an agent 3 and a power source 4 connected to the metal support, and the conductive fibrous member faces the electrostatic latent image forming body with a gap of Gap G. It is arranged.

The conductive fibrous member used here is not particularly limited as long as it is a conductive fibrous substance. For example, a non-woven fabric, a cloth woven with regularity, or electric flocking is subjected to a conductive treatment. Those that have been used are preferably used. For example, a non-woven fabric, a cloth woven with regularity,
Examples thereof include those subjected to a conductive treatment by plating, a metal coat, or a conductive polymer coat. When electric flocking is used, the electric flock may be provided on the support and then subjected to a conductive treatment.

Specifically, when a nonwoven fabric is used, PET,
A non-woven fabric made of fibers having a diameter of several μm or less based on a single substance or a composite substance of PP, rayon, nylon, acrylic, etc., is plated with a metal such as Ni, Cu or the like, or contains a metal filler, carbon. A conductive non-woven fabric can be obtained by making it conductive with a conductive polymer coat. For the production of the nonwoven fabric itself, a short fiber dispersed in water by a spinning method is dehydrated and dried to finish it, a raw material is formed into a web by ordinary spinning or special spinning such as parallel method, and melted, chemically, mechanically. Either a dry method of bonding by adhesion or entanglement may be used.

Also when a regular woven cloth is used, a cloth made of fibers based on a single material or a composite material of PET, PP, rayon, nylon, acrylic, etc. is similarly prepared as described above. It can be used by making it conductive in the same manner as in the case of a non-woven fabric. When electric flocking is used, it is possible to use an electric flock provided on a support such as aluminum or SUS and then subjected to a conductive treatment with a metal coat or a conductive polymer coat.

The thickness of such a conductive fibrous member is usually 40 to 3000 μm, preferably 500 to 1000 μm, and the weight is 20 to 2 when it is adhered on a support.
It is 000 g / m ² , preferably 90 to 200 g / m ² . The fiber thickness of the conductive fibrous member is usually 0.02 to
The thickness is 50 μm, preferably 0.1 to 10 μm. If the thickness of the fiber is thinner than 0.02 μm, it is difficult to form a needle electrode structure, and if it is thicker than 50 μm, it may be difficult to handle when it is made into a cloth, and the attachment to the support may be uneven. The electrical resistance of the conductive fibrous member may be usually 10 ⁶ Ωcm or less as volume resistance, and preferably 10 ⁶ Ωcm or less.
Ωcm or less.

As the metallic support in the first embodiment, Fe, Al, SUS or the like is used, and it is not particularly limited. Although FIG. 1 shows an example in which the corners on the side facing the electrostatic latent image forming member are rounded from the viewpoint of uneven discharge, the shape is not limited to this. Examples of the conductive adhesive include a silver (Au) filler-containing epoxy adhesive and a carbon filler-containing acrylic adhesive, and any of these may be used. The conductive fibrous member is uniformly adhered to the surface of the metal support facing the electrostatic latent image forming body by the conductive adhesive as described above. Further, the adhesion of the non-woven fabric to the metal support is such that the non-woven fabric itself is conductive and there are many voids in the non-woven fabric due to the structure of the non-woven fabric. It is also possible to impregnate and bond the conductive fibers of the bonding example so that they come into contact with the counterpart at the time of bonding.

The conductive fibrous member is an electrostatic latent image forming member G
They are arranged opposite to each other with a gap of ap G, and the gap is 0.15 to 1.5 mm, preferably about 0.25 to 1.0 mm. FIG. 2 shows the experimental results when an experiment was performed using the charging device according to the present embodiment. The charged position was changed according to the gap of Gap G and the applied voltage (-applied). The smaller the gap between Gap G and the higher the applied voltage, the higher the absolute potential of the charged potential. However, if the gap is too narrow (less than 0.15 mm), the fibers forming the conductive fibrous member may come into contact with the electrostatic latent image forming body, so it is desirable to keep them to some extent. On the other hand, if the distance exceeds 1.5 mm, the charging becomes insufficient, which is not preferable.

The applied voltage is Gap as shown in FIG.
Although it varies depending on the gap of G, when the charge potential of the negative photosensitive member is −600V to −700V, it is usually −1100V to
It is necessary to apply about -1500V. For example, from FIG. 2, when the gap of Gap G is 0.5 mm, 1250 V may be applied. The power source is connected to the metal support, and the conductive fibrous member is applied through the metal support.

The electrostatic latent image forming body is not particularly limited as long as it is used in a usual electrophotographic method, and can be used for charging any type of electrostatic latent image forming body. In the electrostatic latent image forming body, a photosensitive layer is usually provided on a base material such as Al, and in general, Al is grounded. The photosensitive layer is formed by forming a metal optical semiconductor such as Se or an organic optical semiconductor in a single layer or a multilayer. When such an electrostatic latent image forming body is discharged, when it is conveyed to a position facing the charging device of the present invention, the conductive fibrous member connected to the power source forms an aggregate of needle electrodes having a small surface. Since it can be said, minute discharge is generated to the electrostatic latent image forming body through the gap of Gap G, and the electrostatic latent image forming body is charged. In the first embodiment, the potential polarity with respect to the negative photoconductor is shown as an example, but needless to say, the present invention can be applied to the positive photoconductor without being limited to the polarity.

FIG. 3 is a schematic view of a charging device according to the second embodiment of the present invention. In this example, the tape-shaped conductive fibrous member 2 is spirally wound around the metal shaft 6 to form a roll, and the conductive latent image forming member 5 and the electrostatic latent image forming body 5 arranged to face each other on both sides of the metal shaft 6 are electrically conductive. Insulating Gap maintaining roller 7 for maintaining a gap of Gap G between the surface of the fibrous member 2
The insulating Gap maintaining roller 7 and the metal shaft 6 rotate integrally with the movement of the electrostatic latent image forming body 5. A pressure spring 8 for applying the insulating Gap maintaining roller 7 to the electrostatic latent image forming body 5 is provided on both sides of the metal shaft 6. The power source 4 is connected to the metal shaft 6.

FIG. 4 shows the mounting cross section of the conductive fibrous member 2 on the metal shaft 6. The conductive fibrous member is adhered to the metal support by a conductive adhesive in the first embodiment. Similarly, it is bonded to the outer peripheral surface of the metal shaft with a conductive adhesive. A power supply 2 is connected to the metal shaft 6, and the conductive fiber member and the electrostatic latent image forming member are Gap.
The G gap is the same as in the apparatus according to the first embodiment, and the charging is performed in the same manner, but with the movement of the electrostatic latent image forming body, the insulating Gap maintaining roller, the metal shaft, Since the conductive fibrous member rotates, the surface of the conductive fibrous member facing the electrostatic latent image forming member changes,
More stable charging is performed than in the first embodiment. That is, if the surface of the conductive fibrous member is the same, and if there are stains or defects, the charging will not be performed uniformly, but in the present embodiment, the surface of the conductive fibrous member changes one after another. Therefore, uniform and stable charging is performed. The peripheral speed of the conductive fibrous member formed into a roller shape in this manner is not particularly limited and can be set arbitrarily, but when more uniformity is required, the peripheral speed is higher than that of the electrostatic latent image forming body. It is good to speed up. Also in this embodiment, as the conductive fibrous member, a non-woven fabric that has been subjected to a conductive treatment as in the case of the first embodiment, a cloth woven with regularity, or electric flocking is used. In addition, Gap
The same applies to the conditions such as the G gap and the applied voltage.

FIG. 5 is a schematic view of a charging device according to the third embodiment of the present invention. FIG. 6 shows a sectional view thereof. In this example, the device of the second embodiment is provided with a metallic shield 9, to which the power supply 4 is connected. The operation is similar to that of the second embodiment, but the provision of the metallic shield suppresses, for example, aerial discharge to other than the electrostatic latent image forming body, so that more efficient charging is performed. Become. In the above embodiments, only direct current is shown as the applied power source, but it is effective to superimpose alternating current in order to improve the environmental stability of charging.

[0022]

EFFECT OF THE INVENTION Since the charging device of the present invention can be charged without contact with the electrostatic latent image forming member, it is superior in dirt, reliability and uniform charging property to the conventional contact type. In addition, since the applied voltage can be made lower than that of the conventional corona charging, not only the safety aspect, but also the ozone generation can be significantly reduced. In addition, the structure is simple, installation and replacement are easy, and the cost is as low as the conventional roller charging.

[Brief description of drawings]

FIG. 1 is a schematic view of a charging device according to a first embodiment.

FIG. 2 is a diagram showing a relationship between Gap G and a charging position when charging is performed by using the charging device according to the first exemplary embodiment.

FIG. 3 is a schematic view of a charging device according to a second embodiment.

FIG. 4 is a cross-sectional view of mounting the conductive fibrous member on a metal shaft in the charging device shown in FIG.

FIG. 5 shows a schematic view of a charging device according to a third embodiment.

6 is a sectional view of the charging device shown in FIG.

[Explanation of symbols]

 1 Metal Support 2 Conductive Fibrous Member 3 Conductive Adhesive 4 Power Supply 5 Electrostatic Latent Image Former 6 Metal Shaft 7 Insulating Gap Maintaining Roller 8 Pressure Spring 9 Metal Shield

Claims (3)

[Claims] 1. A charging device for charging an electrostatic latent image forming body, wherein a conductive fibrous member connected to a power source is arranged to face the electrostatic latent image forming body with a gap. 2. The charging device according to claim 1, wherein the conductive fibrous member is a non-woven fabric that has been subjected to a conductive treatment, a cloth woven with regularity, or electric flocking. 3. The charging device according to claim 1, wherein the gap between the conductive fibrous member and the electrostatic latent image forming member is 0.15 to 1.5 mm.