JPS63135984A - Image forming device - Google Patents

Abstract

PURPOSE:To eliminate potential nonuniformity generated by transfer electrification, and to obtain an image with high definition, by supplying electrification which supplies a potential with polarity opposite to that of primary electrification and exposure on a photosensitive body prior to the application of the primary electrification. CONSTITUTION:A pre-exposure and pre-electrification means 20 to perform the cleaning of residual potential on the photosensitive body is provided at the front of an electrification means 2 which applies the primary electrification on the photosensitive body 1. The pre- exposure and pre-electrification means 20 consists of a pre-exposure device 22 and a pre- electrification device 24. Also, the pre-electrification device 24 is a device to add the potential with the same polarity as that of a transfer electrification means on the photosensitive body, and sets the potential of the surface of the photosensitive body at the polarity opposite to that of the primary electrification by the electrification means 2. Furthermore, it is necessary that the exposure by the pre-exposure device can erase the potential with the same polarity as that of the primary electrification left on the surface of the photosensitive body, and it is preferable that the exposure is performed simultaneously with the electrification by the pre-electrifier 24, or prior to that. In such way, it is possible to eliminate the potential nonuniformity on the photosensitive body after the transfer electrification, to supply uniform surface potential on the photosensitive body, and to obtain the image with high fidelity.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic image forming apparatus using an electrophotographic photoreceptor, and particularly to an electrophotographic image forming apparatus that is characterized by cleaning the residual potential of the photoreceptor prior to image formation. The present invention relates to a photographic image forming apparatus.

Conventional 1 In an image forming apparatus such as an electrophotographic copying apparatus, a latent image is formed on an electrophotographic photoreceptor by at least a charging means and an exposure means, and the latent image or the latent image is is visualized by a developing means and transferred to a transfer material such as paper to obtain a permanent image.

In addition, in general, such an image forming apparatus disposes a transfer charger facing the photoreceptor when transferring an image to a transfer material,
The transfer charger applies a transfer charge to the transfer material side that is opposite in polarity to the charge by the charging means when forming an image on the photoreceptor, that is, the primary charge, and forms a latent image or a visualized toner image. A format is used in which the image is transferred onto a transfer material.

According to research conducted by the present inventor, in an image forming apparatus with such a configuration, the transfer charger is normally in a discharge state, and therefore there are cases where a transfer material is present between the photoreceptor and the transfer charger, and times when there is no transfer material. The amount of potential of the photoconductor charged by the transfer charger differs depending on the case (opposite polarity to the primary charge), and for this reason, even if a predetermined primary charge for image formation is performed after transfer charging, the photoconductor In many cases, it is not possible to make the surface potential uniform, and as a result, when the surface potential of the photoreceptor is uneven, the latent image obtained by irradiating the light image with the exposure means will have uneven potential. However, it was found that it was not possible to obtain images of good quality.

In other words, generally speaking, if there is no transfer material and a transfer charge is applied directly to the photoconductor, the potential of that part of the photoconductor will be low, and as a result, the latent image of that part will be transferred to other parts. The potential is lower than that of the latent image, resulting in uneven image development.

An object of the present invention is to provide an image forming apparatus that can eliminate potential unevenness on a photoreceptor after transfer charging as described above, provide a uniform surface potential on the photoreceptor, and obtain a high-quality image. The goal is to provide the following.

. - Fortune-telling - The above object is achieved by an image forming apparatus according to the present invention.

To summarize, the present invention provides an image forming apparatus having an electrophotographic photoreceptor, forming an image on the photoreceptor using at least a charging means and an exposure means, and transferring the image to a transfer material. Image formation characterized in that a pre-exposure and pre-charging means is provided for performing pre-exposure and pre-charging on the photoreceptor with a polarity different from the polarity of the pre-exposure and the primary charging before performing the primary charging by the charging means. It is a device. Preferably, the photoreceptor is charged to a predetermined potential with a polarity different from the primary charging by the pre-exposure and pre-charging means.

1. Next, the image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

FIG. 1 shows an embodiment of an image forming apparatus according to the present invention.According to this embodiment, an electrophotographic photoreceptor l is formed into a drum shape (cylindrical shape) and is rotated in the direction of the arrow. . Around the photoreceptor 1, there is an electrophotographic image forming means, for example, a charging means 2 for uniformly charging the photoreceptor 1. Exposure means 4 scans a laser beam modulated in accordance with the recorded information signal using, for example, a laser optical system to form a latent image on the photoreceptor 1; A developing device 6 that attaches toner to the exposed portion to make it visible, a transfer charging device 8 that transfers the image on the photoreceptor to the transfer material P, and a fixing device 10 that fixes the image on the transfer material P. A cleaning means 12 and the like for cleaning residual toner on the photoreceptor l are arranged. Since the electrophotographic imaging process is well known to those skilled in the art, further detailed explanation will be omitted. Furthermore, the present invention is not limited to such an electrophotographic process, and any electrophotographic image forming process having at least a charging step and an exposure step may be used.

According to the present invention, a pre-exposure and pre-charging means 20 is provided in front of a charging means 2 for applying uniform, so-called primary charging to the photoreceptor 1 in order to clean the residual potential of the photoreceptor.

The pre-exposure and pre-charging means 20 consists of a pre-exposure device 22 and a pre-charging device 24, and the light source of the pre-exposure device 22 may be a halogen lamp, LED, laser light, etc. as long as it contains a wavelength to which the photoreceptor is sensitive. In addition, the pre-charger 24 may be of the same polarity as the transfer charging means (therefore, the
A potential with a polarity opposite to that of the secondary charging is applied, and the potential on the surface of the photoreceptor is made to have a polarity opposite to that of the primary charging by the charging means 2.

To explain further, according to the present invention, the exposure by the pre-exposure device needs to be of a level that can erase the potential of the same polarity as the primary charge remaining on the surface of the photoreceptor, and the charging by the pre-charger 24 It is preferable to expose to light at the same time or before charging by the pre-charger 24. When the exposure is performed at the same time as the charging by the pre-charger 24, as shown in FIG. It is preferable to remove the back shield and expose from the back shield side. or,
The amount of light required for pre-exposure varies depending on the photoconductive material of the photoreceptor 1 used, but is usually 20 to 1001 ux, s.
ec level is preferable.

To explain the present invention more specifically, a photoreceptor 1 is manufactured using an actual photoconductor such as phthalocyanine OPC as a photoconductive material, and a discharge electrode of a charger 2 is charged with a primary charge from a high-voltage power source. The photoreceptor was set to be charged to 15oOV.

The amount of exposure from the exposure means 4 was set to 9.5 pJ/crn', and was set so that the potential of the bright area on the photoreceptor was -100V and the potential of the dark area was -300V.

Further, a voltage having a polarity opposite to the primary charging polarity was applied to the transfer charger 8 from a high-voltage power supply, and the photoreceptor was set to be charged to +1100V.

The pre-exposure amount of the pre-exposure and pre-charging means 20 is 301 uXas
ec, and the pre-charging amount was set so that the photoreceptor was charged to +1500V.

In the apparatus set as described above, when pre-charging is not used, a transfer material is placed between the transfer charger 8 and the photoreceptor 1.
In this experiment, when paper P exists and when it does not exist,
The potential unevenness on the photoconductor after primary charging was 55V, while
It was confirmed that when pre-exposure and pre-charging were used, the potential unevenness was 5V or less. Furthermore, when actually making a visible image, density unevenness occurs when pre-exposure and pre-charging are not performed, whereas density unevenness hardly occurs when pre-exposure and pre-charging are performed according to the present invention.

As explained above, according to the present invention, by applying a charge and exposing the photoreceptor to a potential of the opposite polarity to the primary charging before performing secondary charging, the potential generated by transfer charging is reduced. The advantage is that unevenness can be removed and high quality images can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of an embodiment of an image forming apparatus according to the present invention. l: Electrophotographic photoreceptor 2: Charging means 4: Exposure means 8: Transfer charging means 20: @Exposure and pre-charging means

Claims (1)

[Scope of Claims] 1) An image forming apparatus having an electrophotographic photoreceptor, forming an image on the photoreceptor using at least a charging means and an exposure means, and transferring the image to a transfer material, An image characterized in that a pre-exposure and pre-charging means is provided for pre-exposure and pre-charging the photoreceptor with a polarity different from the polarity of the pre-exposure and the primary charging before performing the primary charging by the charging means. Forming device. 2) The apparatus according to claim 1, wherein the photoreceptor is charged to a polarity different from the primary charging by the pre-exposure and pre-charging means. 3) Forming a latent image on the photoreceptor using charging means and exposure means,
A patent claim in which the latent image is made visible by a developing means, and the visible image is transferred to a transfer material by a transfer charging means, and the charging polarity of the transfer charging means is different from the polarity of the primary charging. The device according to item 1 or 2 of the scope.