JPH0572920A - Electrophotographic device - Google Patents

Abstract

(57) [Summary] [Object] To provide a transfer method capable of ensuring a good image without transfer omission by preventing a bias leak of a bias applied to a transfer roller in a bias roller transfer method. The width of the transfer roller in the axial direction of the bias roller is made equal to or smaller than the width of the chargeable area of the latent image carrier. [Effect] It is possible to provide a highly reliable bias roller transfer system in which a transfer blank image does not occur and the toner transfer efficiency does not fluctuate significantly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus.

[0002]

2. Description of the Related Art Conventionally, electrophotographic apparatuses have been used in copying machines, laser printers and the like. The conventional electrophotographic apparatus will be described below. FIG. 3 is a schematic configuration diagram of a conventional electrophotographic apparatus, and FIG. 4 is an enlarged view of a main part of the conventional electrophotographic apparatus. In FIG. 3, 1 is an organic optical semiconductor drum (hereinafter, OP
Abbreviated as C drum. ) 2 is a charger for uniformly charging the surface of the OPC drum 1 mounted close to the OPC drum 1, 3 is a laser irradiator for irradiating the OPC drum 1 with light according to image information, and 4 is OPC for toner This is a developing device that visualizes an electrostatic latent image formed on the drum 1 by adhering it. Reference numeral 5 is a bias roller for transferring the toner adhering to the OPC drum 1 to a transfer sheet, 6 is a cleaning device for scraping and cleaning the residual toner on the OPC drum 1 after transfer, and 7 is a charge for the OPC belt 1 after cleaning. A static eliminator that eliminates static electricity. Reference numeral 8 is a transfer paper, 9 is a paper cassette for storing the transfer paper, and 10 is a carrying roller for carrying the transfer paper 8. A fixing device 11 fixes the toner transferred onto the transfer paper 8.

The operation of the image forming apparatus configured as described above will be described below. First, OPC drum 1
When a voltage is applied to the charger 2 while being driven to rotate,
When the laser irradiation device 3 irradiates the surface of the PC drum 1 with laser light having image information, electric charges disappear in the irradiated portion of the surface of the OPC drum 1 and an electrostatic latent image is formed.
The formed electrostatic latent image is visualized with toner, and then the transport roller 10 aligns the transfer paper 8 from the paper cassette 9 with the visualized toner image on the OPC drum 1 while the OPC drum is aligned. OPC at the same transport speed as 1
It is conveyed between the drum 1 and the bias roller 5 and brought into close contact with the OPC drum 1, and a voltage having a polarity opposite to the charging polarity of the toner particles forming the toner image is applied to the bias roller 5 from the back side of the transfer paper 8 and transferred. The toner image on the OPC drum 1 is transferred to the transfer paper 8 by performing the above, the residual toner remaining on the surface of the OPC drum 1 is scraped off by the cleaning device 6, and the scraped residual toner is inside the cleaning device 6. Be recovered to. The toner image transferred to the transfer paper 8 is fixed by the fixing device 11.

[0004]

However, in the above-mentioned conventional structure, when the toner image on the latent image carrier is transferred to the transfer sheet by corona transfer or bias roller transfer, the timing is adjusted by the paper feed roller. However, the transfer sheet is brought into close contact with the toner image on the OPC drum at the same conveyance speed as the OPC drum while aligning the image position. A so-called bias roller transfer (hereinafter abbreviated as a transfer roller method) is performed by applying a corona charge having a polarity to a transfer sheet to perform a corona transfer of a toner image or a transfer roller to which a voltage having a polarity opposite to that of toner particles is applied. It was common to do But in the case of corona transfer,
Due to the generation of ozone due to corona discharge, there is a concern that the electrical characteristics of the photoconductor will deteriorate and the life of the photoconductor will be shortened, or the operating environment will be adversely affected. In order to solve the above-mentioned problems associated with corona transfer, the transfer roller system has recently been reviewed again. The transfer roller system transfers the toner image on the intermediate transfer member from the back surface of the transfer sheet by bringing the transfer roller, to which a bias having a polarity opposite to that of the toner is applied, into contact with the transfer roller with an appropriate pressure contact force. Compared to the corona transfer method, the transfer roller method has a large margin for setting conditions regarding the paper thickness of the transfer paper and the method of guiding the paper to enter the transfer area, but on the other hand, the contact mechanism and the contact mechanism for transferring the toner image are used. Timing, a cleaning mechanism for removing toner adhering to the surface of the transfer roller, and a bias voltage is likely to occur when a high voltage is applied to the transfer roller and brought into contact with the OPC photosensitive member. There is a problem that an image defect called transfer blank is likely to occur.

[0005]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention sets the roller width of the bias roller in the axial direction to a latent image carrier such as an optical semiconductor drum (hereinafter, referred to as “O”).
Abbreviated as PC drum. ) Or less than the width of the chargeable region.

[0006]

According to the present invention, the toner image formed on the OPC drum is brought into contact with the OPC drum through the transfer sheet by the bias roller to which a high voltage opposite to the charging polarity of the toner particles is applied. Even in this state, the photoconductor region of the OPC drum that is in contact with the bias roller has a high resistance surface electrical characteristic in the dark,
Leakage of voltage applied to the bias roller is made by narrowing the width of the bias roller so that the photosensitive layer on both ends of the C drum cannot be brought into contact with an area having a thin and uneven electric resistance. It is possible to prevent the occurrence of the transfer voltage drop of the bias roller, and as a result, the transfer of the toner image onto the paper by the bias roller is favorably performed.

[0007]

1 is a schematic structural view of an electrophotographic apparatus according to an embodiment of the present invention, and FIG. 2 is an enlarged view of essential parts of the electrophotographic apparatus according to an embodiment of the present invention. In FIG. 1, 1 is an OPC drum, 2 is a charging device, 6 is a cleaning device, 7 is a static eliminator, 3 is a laser irradiation device, 4 is a developing device, and 5a.
Is a bias roller, 8 is a transfer paper, 11 is a fixing device, 9 is a paper cassette, and 10 is a conveying roller. These are similar to the configuration of the conventional example, and therefore detailed description thereof is omitted.
The operation of the electrophotographic apparatus of the present invention configured as above will be described below. After a potential is applied to the OPC drum 1 by the charger 2 to a predetermined charge potential, laser exposure is performed by the laser irradiator 3. Then, after the developing device 4 develops the toner, the transfer paper 8 sent while aligning the toner image on the OPC drum 1 by the carrying roller 10 has the same carrying speed as the OPC drum 1. When the bias roller 5a is conveyed to a transfer position between the bias roller 5a and the bias roller 5a, a high voltage having a polarity opposite to the charging polarity of the toner particles forming the toner image is applied to the bias roller 5a via the transfer paper 8. The toner image is transferred onto the transfer paper 8 by applying it with an appropriate pressing force. Here, a high voltage is applied to the bias roller 5a in order to improve the transfer efficiency of the toner image onto the transfer paper 8. However, as shown in FIG. 4, both end portions of the bias roller 5a are located at both end portions of the OPC drum. When the photoconductor coating layer is thin and in a non-uniform area, voltage leakage is likely to occur, and as a result, the high voltage applied to the bias roller 5a drops, and the toner image corresponding to the voltage drop portion is generated. Is not transferred to the transfer paper 8 and a transfer missing image occurs. Therefore, as shown in FIG. 2, the width of the bias roller 5a is set to be narrower than that of the non-uniform area of the photoconductor coating layer on both ends of the OPC drum.
It is possible to prevent leakage of voltage from the device, and it is possible to obtain a good image without transfer omission. Next, the toner image transferred to the transfer paper 8 is fixed by the fixing device 11. This embodiment can maintain stable transfer efficiency,
It is possible to achieve high image quality without deterioration of image quality such as a transfer-missing image due to transfer failure.

[0008]

As described above, the electrophotographic apparatus of the present invention is
Even when the bias roller, to which a high voltage is applied, is brought into contact with the latent image carrier through the transfer sheet, the width of the bias roller is set to be equal to or less than the width of the chargeable region on the surface of the latent image carrier. It is possible to avoid contact with the low resistance areas at both ends and eliminate the transfer bias drop of the bias roller. As a result, there is no occurrence of transfer missing images and there is little fluctuation in toner transfer efficiency. An electrophotographic apparatus having high transfer efficiency and high reliability can be provided.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an electrophotographic apparatus according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of an electrophotographic apparatus according to an embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of a conventional electrophotographic apparatus.

FIG. 4 is an enlarged view of a main part of a conventional electrophotographic apparatus.

[Explanation of symbols]

 1 OPC Drum 2 Charging Device 3 Laser Irradiator 4 Developing Device 5 Transfer Device 6 Cleaning Device 7 Charge Eliminating Device 8 Transfer Paper 9 Paper Cassette 10 Conveying Roller 11 Fixing Device 12 OPC Drum Non-Chargeable Area

Claims (1)

[Claims] 1. A latent image carrier for carrying an electrostatic latent image, developing means for developing the electrostatic latent image with toner, and transfer means for transferring a toner image onto a transfer sheet by a bias roller. The electrophotographic transfer device is characterized in that the roller width in the axial direction of the bias roller is set to be equal to or less than the width of the chargeable region of the latent image carrier.