JPH0535122A - Electrophotographic device - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to obtain a good image in which no transfer omission occurs by preventing leakage of the bias applied to the transfer roller in an electrophotographic apparatus of the bias roller transfer type. By providing an insulating member 14 having a high resistance, which is provided on the surface of the intermediate transfer member 9 corresponding to the positions of both ends of the transfer roller 13, the leak of the portion where the electric field is most concentrated and the voltage leaks easily. It is possible to prevent the occurrence of a transfer failure image and to improve the reliability with high transfer efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bias roller transfer type electrophotographic apparatus.

[0002]

2. Description of the Related Art Conventionally, electrophotographic apparatuses have been used in copying machines, laser printers and the like.

A conventional electrophotographic apparatus will be described below. As shown in FIGS. 2 and 3, an organic optical semiconductor belt (hereinafter, referred to as an OPC) 1 is wound around an OPC driving roller 2 and is stretched and driven. Reference numeral 4 denotes a charger that uniformly charges the surface of the OPC belt 1 mounted near the OPC belt 1, and 7 denotes OPC according to image information.
It is a laser irradiator that irradiates the belt 1 with light. Developing device 8
Is a developing device 8a that attaches black toner to the electrostatic latent image formed on the OPC belt 1 to make it visible, and cyan toner attaches the toner to the electrostatic latent image formed on the OPC belt 1. Develop the developing device 8b and magenta toner to O
A developing device 8c for adhering to visualize the electrostatic latent image formed on the PC belt 1 and a developing device for adhering yellow toner to the electrostatic latent image formed on the OPC belt 1 to visualize it. It is composed of 8d. Belt-shaped intermediate transfer member 9
Are wound around the intermediate transfer belt drive roller 3 and are stretched and driven. Reference numeral 11 denotes an intermediate transfer roller for transferring the toner attached to the OPC belt 1 to the intermediate transfer body 9, and 5 denotes O after the transfer.
An OPC cleaning device for scraping and cleaning the residual toner on the PC belt 1, 6 is an OP after cleaning
It is a static eliminator that eliminates electric charges on the C-belt 1. The transfer roller 13 presses the transfer paper 12 conveyed by the conveyance roller 17 from the paper cassette 16 to the intermediate transfer body 9 and applies a transfer voltage to transfer the toner adhering to the intermediate transfer body 9 to the transfer paper 12. 10 is a cleaning device for scraping off the residual toner on the intermediate transfer body 9 after transfer, 15 is a fixing device for fixing the toner transferred to the transfer paper 12, and 14 is a meandering preventing member for the belt-shaped intermediate transfer body 9. .

The operation of the image forming apparatus having the above structure will be described below. First, while the OPC belt 1 is rotationally driven by the OPC driving roller 2, the charger 4
When a voltage is applied to the surface of the OPC belt 1, a laser beam that gives black image information to the surface of the OPC belt 1 is irradiated by the laser irradiator 7, and the irradiated portion of the surface of the OPC belt 1 loses its electric charge to form an electrostatic latent image. To be done.

Next, the electrostatic latent image formed on the surface of the OPC belt 1 by the developing device 8a is visualized by black toner, and the black toner is transferred by the intermediate transfer roller 11 to which a transfer voltage is applied. OPC of the intermediate transfer member 9
When the belt 1 is pressed, it is transferred to the intermediate transfer body 9. The residual toner remaining on the surface of the OPC belt 1 is OPC.
The residual toner scraped off by the cleaning device 5 is collected inside the OPC cleaning device 5, and the OPC belt 1 from which the residual toner is scraped off is neutralized by the static eliminator 6. By the same operation as the black image information, the cyan image information is transferred so as to be superimposed on the black toner image of the intermediate transfer body 9 to which the toner image developed by the developing device 8b has been transferred previously. Similarly, a color toner image is temporarily stored on the intermediate transfer member 9 with a total of four color toners in the order of magenta and yellow. The transport roller 17 transports the transfer paper 12 from the paper cassette 16 to the toner image on the intermediate transfer body 9 while transporting it between the intermediate transfer body 9 and the transfer roller 13 at the same transport speed as the intermediate transfer body 9. Then, a voltage having a polarity opposite to the charging polarity of the toner particles forming the toner image is applied to the transfer roller 13 from the back surface side of the transfer paper 12 as seen from the toner image on the intermediate transfer member 9 in close contact with the intermediate transfer member 9. By performing roller transfer, the toner image on the intermediate transfer body 9 is transferred to the transfer paper 12. The residual toner remaining on the surface of the intermediate transfer body 9 is scraped off by the cleaning device 10, and the scraped residual toner is collected inside the cleaning device 10. The toner image transferred to the transfer paper 12 is fixed by the fixing device 15.

As shown in FIG. 3, instead of the transfer roller 13, a corona discharge device 18 applies a corona charge having an electric polarity opposite to the charging polarity of the toner particles from the back side of the transfer paper 12 as seen from the toner image. In the conventional example in which the toner image is corona-transferred by applying to No. 12, there is a problem that the generation of ozone due to corona discharge has a problem of shortening the life due to the deterioration of the electrical characteristics of the photoconductor and adversely affecting the use environment. Recently, the roller transfer method has been reviewed again.

[0007]

However, in the above-mentioned conventional structure, although there is a large margin for setting conditions regarding the thickness of the transfer paper 12 and the method of guiding the paper entry into the transfer area, it is necessary to transfer the toner image. The contact mechanism and its timing, a cleaning mechanism for removing the toner adhering to the surface of the transfer roller 13, and the transfer roller 13 for increasing the efficiency of transferring the toner image onto the transfer paper 12,
A high voltage is applied, but especially at both ends of the transfer roller 13, a leak is likely to occur between the transfer roller 13 and the intermediate transfer body 9 composed of a dielectric member having a medium electric resistance, and as a result, the transfer roller 13 is applied. The generated high voltage drops in voltage, and the toner image corresponding to the dropped portion is not transferred to the transfer paper 12 and an image defect called transfer omission is liable to occur.

The present invention solves the above-mentioned problems of the prior art, prevents voltage leak, eliminates transfer bias drop of the transfer roller, does not cause image defects such as transfer defects, and fluctuates toner transfer efficiency. It is an object of the present invention to provide an electrophotographic apparatus having a high transfer rate and a high reliability with a small number of defects.

[0009]

To achieve this object, the electrophotographic apparatus of the present invention is provided with an insulating member having a high resistance, which is provided on the surface of the intermediate transfer member corresponding to the positions of both ends of the transfer roller. It is a thing.

[0010]

With this configuration, the electric field is most concentrated at both ends of the transfer roller, and the leak is prevented at the portion where the voltage leaks easily.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

The basic structure and basic operation of one embodiment of the present invention are similar to those of the conventional example described with reference to FIG.

As shown in FIG. 1, the intermediate transfer member 9 is a polycarbonate or polyethylene phthalate having a uniform and appropriate electric resistance which is hardly affected by changes in ambient temperature and humidity, and an appropriate electric resistance provided by dispersion of carbon black or the like. The insulating member 14 having a high resistance is provided on the surface of the intermediate transfer body 9 corresponding to both end portions of the transfer roller 13, which is made of a dielectric material or a conductive material.

As described above, according to this embodiment, in the state where the transfer roller 13 to which the high voltage opposite to the charging electrode property of the toner particles is applied to the intermediate transfer member 9 is abutted via the transfer paper 12. Also, the surface of the intermediate transfer member 9 that directly abuts both ends of the transfer roller 13 has a high electrical resistance insulating member 1
By covering with No. 4, it is possible to prevent leakage of voltage from the transfer roller 13 and obtain a good image without transfer omission.

In the conventional corona transfer method and bias roller transfer method from the back surface of the transfer paper 12, the transfer paper 12 absorbs moisture when the ambient temperature and humidity become high, and the electric resistance and the dielectric constant of the transfer paper 12 are increased. However, the stable transfer efficiency of the toner could not be maintained due to the change of the transfer electric field due to the change, and the stable transfer efficiency can be maintained in the present embodiment, and the transfer failure due to the transfer failure occurs. It is possible to achieve high image quality without deterioration of image quality such as color unevenness in images and color images.

[0016]

As is apparent from the above description of the embodiment, the present invention has a structure including an insulating member having a high resistance, which is provided on the surface of the intermediate transfer member corresponding to the positions of both ends of the transfer roller. Achieves a highly reliable and excellent electrophotographic device that can prevent voltage leakage, eliminate the transfer bias drop of the transfer roller, prevent image defects such as missing transfer, and have little fluctuation in toner transfer efficiency. It is possible.

[Brief description of drawings]

FIG. 1 is a front view showing a configuration of an intermediate transfer member and a transfer roller of an electrophotographic apparatus according to an embodiment of the present invention.

FIG. 2 is a side view showing the concept of the configurations of the electrophotographic apparatus of the present invention and the conventional example.

FIG. 3 is a front view showing a configuration of an intermediate transfer member and a transfer roller of a conventional electrophotographic apparatus.

FIG. 4 is a side view showing the concept of the configuration of another conventional electrophotographic apparatus.

[Explanation of symbols]

 3 Drive Roller 9 Intermediate Transfer Body 11 Intermediate Transfer Roller 12 Transfer Paper 13 Transfer Roller 14 Insulation Member

Claims (1)

Claim: What is claimed is: 1. A latent image carrier provided with charging, exposing, developing and cleaning devices, and a toner image on the latent image carrier transferred to an intermediate transfer member. An image forming apparatus that holds a toner image and then fixes the toner image on a transfer paper by a biased transfer roller,
An electrophotographic apparatus comprising an insulating member provided on the surface of the intermediate transfer member that is in contact with both ends of the transfer roller.