JPH04285979A - Developing device - Google Patents

Abstract

PURPOSE:To provide an elastic developer carrier which is most appropriate for developing by contact or developing with pressurized contact, is soft, and where developing bias can be obtained stably for an electrophotographic developing device. CONSTITUTION:The elastic layer 11 of the developer carrier 9 is made to be foamed material. A electrically conductive layer 12 is formed on a circumferential periphery surface of the elastic layer 11. The vicinity of the edge surface is made to be the electrically conductive elastic layer 11a by processing to be electrically conductive, and the electrically conductive layer 12 and a shaft 10 are connected electrically. Because the vicinity of the edge surface is made to be electrically conductive, the construction is made integral, the manufacture is facilitated, and the electrically conductive layer is not cut off. Furthermore, even when a corner of the developer carrier is damaged, the developing bias can be obtained. If the elastic layer is made to be a continuous foamed body, variation of shape due to temperature or pressure of the environment is made small.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device that uses a developer based on electrophotographic principles as an image forming means, and more particularly to a developing device that conveys the developer using an elastic developer carrier for development.

0002

2. Description of the Related Art In conventional developing devices, particularly those using a developer carrier made of an elastic material, a method has been proposed or realized in which the developer carrier is brought into contact with or pressed against the latent image carrier to perform development. There is. These methods have the characteristic that high-resolution printing can be performed because the developing electrode is close to the latent image carrier. However, when the contact pressure at the contact portion between the developer carrier and the latent image carrier changes, the development characteristics also change, and when the contact pressure increases, damage to the developer and the latent image carrier occurs. Therefore, there is a need for a developer carrier that has a small contact pressure and is difficult to change, that is, a developer carrier that is made of an elastic material that is as flexible as possible. Specifically, solid soft materials such as low-hardness solid rubber and solid foam, and foamed materials such as foamed rubber and foamed foam have been proposed. In particular, foams are suitable as materials for developer carriers because they can provide flexibility that cannot be achieved with solid soft materials. In addition, for development, it is necessary to form a development electrode and apply a development bias, and for this purpose, it is possible to use the elastic material itself as a conductive material or to form a conductive layer on the surface of the developer carrier. It is being

0003

[Problem to be Solved by the Invention] However, in order to make the elastic material itself conductive, it is necessary to disperse conductive substances such as carbon or metal fine powders or fine fibers into the elastic material. I had lost my sexuality. Furthermore, when using a foam such as foam rubber as the conductive material, there is also a method of impregnating the foam with a conductive paint. However, in this case as well, the flexibility of the foam was impaired by the influence of the conductive substance or binder in the conductive paint.

When a conductive layer is formed on the surface of the developer carrier, the conductive layer is formed on the circumferential surface and end surfaces of the developer carrier to establish electrical connection with the shaft. Because of the edge shape of the boundary ridge line, it was easily damaged and the reliability of the electrical connection was low. As a countermeasure to this problem, as disclosed in Japanese Patent Application Laid-Open No. 2-37378, the following methods have been proposed: ■ A method of chamfering or curved connection edges; ■ A method of arranging a conductive elastic body at both ends of the elastic body and electrically connecting it to the conductive layer. However, in the former case, it is difficult to accurately chamfer or curve the flexible elastic body. In the latter case, the number of parts increases, and furthermore, processing is required to align the circumferential surfaces of the two after placing the conductive elastic body at both ends of the elastic body, and if the interface between the two is not sufficiently joined, the boundary There was a high possibility that the electrical connection between the conductive layer and the conductive elastic body would be broken due to separation of the surfaces.

The present invention is intended to solve these problems, and its purpose is to realize a developer carrier with a simple structure and manufacturing method, thereby achieving low cost, high reliability, and contact development. It is an object of the present invention to provide a developing device suitable for the development method or the pressure contact development method.

[0006]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a developing device that transports a developer by a developer carrier and develops the developer on a latent image carrier. An elastic layer made of an elastic material having pores is arranged at least on the outer periphery of a shaft made of a conductive rigid body, a conductive layer is formed on the surface of the elastic layer, and the vicinity of the axial end surface of the elastic layer is treated to be conductive. It is also characterized in that it is electrically connected to the conductive layer.

Further, in the developing device of the present invention, the elastic layer of the developer carrier has a depth of 0.5 mm from the end surface in the vicinity of the axial end surface.
It is characterized by being subjected to conductive treatment over the above range.

Further, the developing device of the present invention is characterized in that the vicinity of the axial end face of the elastic layer of the developer carrier outside the image forming area is subjected to conductive treatment.

[0009]

Embodiments (Embodiment 1) FIG. 1 is a cross-sectional schematic view of an image forming apparatus using a developing device of the present invention. The latent image carrier 1 is
A photosensitive layer 3 is coated with an organic or inorganic photoconductive material on a conductive support 2, and the photosensitive layer 3 is coated with a charger 4 such as a corona charger or a charging roller. After being charged, light emitted from a light source 5 such as a laser or LED is selectively irradiated onto the photosensitive layer 3 according to the image through an imaging optical system 6 to obtain a potential contrast and form an electrostatic latent image. . On the other hand, the developing device 7 conveys and develops the developer 8, and the developer carrier 9 that conveys the developer 8 has an elastic layer 11 and a conductive layer 12 arranged concentrically around the outer periphery of the shaft 10. The developer 8 is frictionally charged with a plate-shaped elastic blade 13 made of metal or resin, and the developer 8 is conveyed in a thin layer by rotating the developer carrier 9 while controlling the amount to an appropriate amount. It is something. The developer carrier 9 is pressed against the latent image carrier 1 at a predetermined pressure, and the developer 8 is pressed up to the pressure contact portion.
When the latent image carrier 1 is conveyed, a developing electric field is formed by the potential contrast and developing bias applying means 14 of the latent image carrier 1, and the developer 8 charged according to the developing electric field adheres to the latent image carrier 1, forming an electrostatic latent image. Be visualized. Furthermore, the image formed by the developer 8 is transferred onto the recording paper 16 using a transfer device 15 such as a corona transfer device or a transfer roller, and the developer 8 is fixed on the recording paper 16 using heat or pressure to form a desired image. This is what is obtained on the recording paper 16.

FIG. 2 is an axial cross-sectional view of the developer carrier 9 used in the developing device 7 of FIG. An elastic layer 11 and a conductive layer 12 are arranged concentrically around the outer periphery of a metal shaft 10. The vicinity of the end face in the axial direction of the elastic layer is subjected to conductive treatment to form a conductive elastic layer 11a. The elastic layer 10 is made of foamed rubber, specifically silicone, urethane,
Various rubbers including fluorine, ethylene propylene, and chloroprene can be used, but the material is not limited to rubber as long as it is a soft material that can be foamed.
For example, flexible foams such as polyurethane, polystyrene, polyethylene, and elastomer may be used. The method of forming the elastic layer 11 on the outer periphery of the shaft 10 includes a method of integrally forming it by insert molding using a foam molding machine;
There is a method in which only the cylindrical elastic layer 11 is formed and the shaft 10 is inserted into the center. The conductive layer 12 can be easily formed by applying a conductive paint. Alternatively, this can also be achieved by covering it with a conductive shrink tube. The conductive elastic layer 11a can be formed by immersing the vicinity of the axial end face of the elastic layer 10 in a conductive paint. In FIG. 2, conductive elastic layers 11a are formed on both end faces, but
This may be done only on one end side. As a result, shaft 1
0 and the conductive layer 12 are electrically connected via the conductive elastic layer 11a.

[0011] Also, the elastic layer 1 as shown in the present invention is made of foam.
1, the surface is sometimes made into a solid surface layer (skin), but since this solid surface layer also has minute pores, the conductive paint spreads on the surface of the pores, and the conductive elastic layer 11a is formed by the conductive treatment. Formation and conductive elastic layer 11a
There is no problem with the electrical connection between the conductive layer 12 and the conductive layer 12. Since the solid surface layer portion has a smooth surface condition, it is preferable as a base for forming the conductive layer 12 and a surface for carrying the developer.

In the developer carrier 9 manufactured in this manner, the hardness is slightly increased only in the vicinity of the axial end face of the elastic layer 11 due to the conductive treatment, but since the conductive elastic layer 11a is only in a small area, the elasticity is increased. The flexibility of the layer as a whole is not impaired. In particular, if the conductive elastic layer 11a is placed outside the image forming area, there is no problem with the flexibility required for development characteristics. Also, among the elastic layers 11, the conductive elastic layer 1
1a has an appropriate depth, so even if the boundary ridgeline between the circumferential surface and the end surface of the elastic layer 11 is damaged due to use, the conductive layer 11
The electrical connection between the shaft 10 and the shaft 10 is maintained. To obtain this effect, the depth from the end surface of the conductive elastic layer 11a should be 0.5 mm.
The above is preferable. In addition, since the elastic layer 11 is originally made of a single piece of material, the interface between the portion of the elastic layer 11 that has not been made conductive and the conductive elastic layer 11a will not separate, and conductivity will occur on the extension of the interface. The layer 12 is not cut. Furthermore, since the elastic layer 11 is originally composed of a single piece of material, the circumferential surface of the elastic layer 11 including the conductive elastic layer 11a can always be molded or processed at the same time. Man-hours can be reduced. Furthermore, there are two types of foam: single cells and open cells. If the elastic layer 11 is an open cell, the pores inside the elastic layer 11 will communicate with the outside air via the conductive elastic layer 11a, so changes in temperature and pressure will occur. It is possible to prevent deformation of the developer carrier 9 due to the above.

(Embodiment 2) FIG. 3 shows another embodiment of the present invention in which a magnetic layer 17 is formed on the conductive layer 12 of the developer carrier 9 shown in FIG. The magnetic layer 17 can be formed by applying magnetic paint. According to this configuration, by magnetizing the magnetic layer 17 and using a magnetic developer, the binding force of the magnetic developer to the developer carrier 9 is increased, so that fogging of the developer on the latent image carrier can be suppressed. can. In FIG. 3, the conductive layer 12 and the magnetic layer 17 are separated, but it is clear that only one layer may be formed if a conductive magnetic paint or a magnetic conductive paint is used.

[0014]

Effects of the Invention As explained above, the present invention provides an elastic layer made of an elastic material having pores on the outer periphery of a shaft made of a conductive rigid body, and a conductive layer is formed on the surface of the elastic layer. A developing device using a developer carrier characterized in that the vicinity of the axial end face of the layer is treated to be electrically conductive so that an electrical connection between the conductive layer and the shaft is established, and the device has a simple structure, is easy to manufacture, and has a long life. A highly reliable developing device can be provided over a long period of time. Further, according to the present invention, since a developer carrier having a flexible elastic layer and a highly reliable conductive layer can be obtained, it is possible to provide a developing device suitable for a contact development method or a pressure development method. High-resolution printing can be achieved stably.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional schematic diagram of an image forming apparatus using a developing device of the present invention.

FIG. 2 is an axial cross-sectional view of a developer carrier used in the developing device of the present invention.

FIG. 3 is an axial cross-sectional view of a developer carrier in another embodiment of the present invention.

[Explanation of symbols] 1 Latent image carrier 2 Conductive support part 3 Photosensitive layer 4 Charger 5 Light source 6 Imaging optical system 7 Developing device 8. Developer 9 Developer carrier 10 Shaft 11 Elastic layer 11a Conductive elastic layer 12 Conductive layer 13 Elastic blade 14 Development bias application means 15　Transfer device 16 Recording paper 17 Magnetic layer

Claims (3)

[Claims] [Claim 1] A developer is transported by a developer carrier,
A developing device that develops the developer onto a latent image carrier,
The developer carrier has an elastic layer made of an elastic material having pores disposed on the outer periphery of at least a shaft made of a conductive rigid body, a conductive layer is formed on the surface of the elastic layer, and a conductive layer is formed on the surface of the elastic layer. A developing device characterized in that the vicinity of the directional end face is treated to be conductive, and the conductive layer and the shaft are electrically connected. 2. The developing device according to claim 1, wherein the vicinity of the axial end face of the elastic layer is treated to be electrically conductive to a depth of 0.5 mm or more from the end face. 3. The developing device according to claim 1, wherein the vicinity of the axial end face of the elastic layer outside the image forming area is subjected to a conductive treatment.