JPS6149666B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic apparatus using a photoreceptor having an insulating layer.

Electrophotographic methods include primary charging of a photoreceptor having a conductive support, a photoconductive layer, and an insulating layer, secondary charging with opposite polarity to the primary charging, simultaneous image exposure with AC static elimination, uniform exposure over the entire surface, etc. When applied, the following 10 to 20 memories occur in areas that have been charged with opposite polarity in the dark due to primary charging and reverse polarity secondary charging or AC static elimination.
It remains until the number of copies is made, causing image unevenness and the like. An object of the present invention is to prevent memory by providing light to a region charged with an opposite polarity in the dark. For this purpose, a special light source is provided or the above-mentioned means for uniform exposure over the entire surface is provided.

Hereinafter, the present invention will be described in detail with reference to examples.

FIG. 1 shows a conventional electrophotographic apparatus using a photosensitive drum body constructed in three layers. Reference numeral 1 represents a photosensitive drum body comprising a conductive support layer, a photoconductive layer, and an insulating layer. First, a high voltage power source of 6.0 Kv is applied to the photosensitive drum body 1 by the primary charging means 2, and the surface is charged with +
Apply primary charging of 1500V. Next, an AC corona of 7.6 Kv is applied by the AC charging means 3, and at the same time, image exposure is performed through the optical means 4, and then uniform exposure is performed over the entire surface by the light source 5 to obtain a contrast of about 500V. Next, a powder image is formed by the developing means 6, and a transfer paper 8 conveyed in synchronization with the photoconductor drum 1 is brought into close contact with the position of the photoconductor drum 1 where the development has been completed, and the back surface of the transfer paper 8 in the contact area is A transfer accelerating voltage of +6.5 Kv is applied from the side by the corona discharge unit 7 to transfer the toner image onto the transfer paper 8. The toner remaining on the photosensitive drum body 1 is wiped off by the cleaning means 9 and made available for reuse. At this time, charging and uniform exposure over the entire surface generally continue while the photosensitive drum is rotating. Almost at the same time as the photosensitive drum stops, charging and uniform exposure of the entire surface also stop. If the rotation of the photosensitive drum is delayed after the charging and uniform exposure of the entire surface is stopped, and the photosensitive drum stops after the primarily charged area has passed the AC charging means 3, the drum will stop during the first rotation of the next photosensitive drum. At this time, the surface potential of 1500 V given by the primary charging means passes through the developing means 6 without being neutralized, resulting in developer adhesion. Therefore, it is important to use a drum brake to cause the photosensitive drum to stop to coincide with the stop of the uniform exposure of the charged surface.

By the way, in this embodiment, as shown in FIG.
The exposure is carried out through a slit 7 having a width of about mm, and the light for uniform exposure over the entire surface is also blocked by the rail 8 supporting the AC static eliminator, so that there is a portion A on the photosensitive drum where the light does not reach. While the photosensitive drum is rotating, this part A will be the part where light continuously reaches from the uniform exposure source 5, so there is no problem, but when the photosensitive drum stops, the part A will be reversely charged in a dark place. The problem is that if left untreated, memory will be generated and the following phenomena will occur. In other words, if a drum that has been reversely charged in the dark is left in a stopped state for a certain period of time and then an image is formed again according to the process described above, the image will be created using the parts of the photosensitive drum that were reversely charged in the dark. A phenomenon in which the concentration becomes thinner is observed. As shown in Figure 3, this decrease in image density is closely related to the time the photosensitive drum is left in a stopped state, and although there is a large difference depending on the photosensitive plate, it becomes noticeable when the photosensitive drum is left for more than 30 seconds. It reaches its maximum in ~5 minutes. Furthermore, when images are taken continuously after the drum has been stopped for a certain period of time, the decrease in image density gradually recovers, as shown in Figure 4, and this phenomenon disappears after about 10 to 20 copies have been made. It disappears. The speed of recovery also depends on the time the photosensitive drum is left standing.

In order to prevent these drawbacks, controlling the ON/OFF of the corona discharge means eliminates the situation where image density decreases and is completely effective, but it complicates the sequence and increases the cost. do.

The present invention has been devised to eliminate the above-mentioned drawbacks, and is to prevent memory of the photosensitive drum by irradiating light for a certain period of time after the drum is stopped on the A section, where reverse charging was conventionally performed in the dark. That is, the first method is to install light source B in FIG.
1sec) to erase memory. That is, the light source B is off while the photosensitive drum is rotating, turned on when the photosensitive drum stops, and turned off again after a certain period of time.

As a second method, as shown in Fig. 6, the entire surface uniform exposure source 5 is turned on for a certain period of time (15 to 30 seconds) even after the photosensitive drum has stopped, and the flare light is used to reversely charge the photosensitive drum in the dark. This is to erase the memory.

In this case, in order to enhance the effect of uniform exposure over the entire surface, a reflecting plate C shown in FIG. 6 may be provided. However, it is necessary to regulate the direction of reflection so that the flare light reaches the drum without disturbing the image. In these methods, if the light source is turned on continuously,
It is desirable to turn on the lamp for a predetermined period of time because the area directly irradiated with light may turn white due to optical fatigue or appear as a black band due to optical quenching.

These methods eliminate the conventionally unavoidable portions of the photosensitive drum that are left to be reversely charged in a dark place, and the above-mentioned decrease in image density can be prevented.

In the detailed description of the present invention described above, the dark reverse charging portion of the photosensitive drum has been described as an AC neutralization section, but the present invention can also be applied to other copying processes in which dark reverse charging is performed.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an example of an electrophotographic apparatus to which the present invention can be applied, FIG. 2 is an enlarged view illustrating the drawbacks of the conventional apparatus, and FIG. A graph showing an example of the image density of the charged part in the dark. Figure 4 is a graph showing an example of the image density of the charged part in the dark during copying after the photosensitive drum has stopped for 3 minutes. Figures 5 and 6 are the graphs of the image density of the charged part in the dark. Examples for erasing are shown below. 1 is a photosensitive drum, 2 is a charging means, 3 is a corona discharge means, 4 is an optical means, 5 is an entire surface uniform exposure source, 6
7 represents a developing means, 7 represents a transfer charging means, A represents a portion to be charged in the dark, B represents a light source, and C represents a reflecting plate.

Claims (1)

[Scope of Claims] 1. A movable photoreceptor whose basic components are a conductive support layer, a photoconductive layer, and an insulating layer, a first charging means for primarily charging the photoreceptor, and a movable photoreceptor that is connected to the first charging means. a second charging means for applying a corona discharge having a polarity component opposite to that of the first charging means to the photoreceptor;
In an electrophotographic apparatus, the operation of the first and second charging means is stopped substantially simultaneously with the stop of rotation of the photoreceptor,
An electrophotographic apparatus comprising a light irradiation means for applying light irradiation to a portion of the photoreceptor that has been subjected to the action of the second charging means in the dark for a predetermined period of time after the rotation of the photoreceptor has stopped. 2. A movable photoreceptor whose basic components are a conductive support layer, a photoconductive layer, and an insulating layer, a first charging means for primarily charging this photoreceptor, and subsequent to the first charging means image exposure of the photoreceptor. At the same time, it has a second charging means that applies a corona discharge having a polarity component opposite to that of the first charging means, and an entire surface exposure means that exposes the entire surface of the photoreceptor following the second charging means, and the photoreceptor rotates. In an electrophotographic apparatus, in which the operation of the first and second charging means is stopped substantially simultaneously with the stop of the photoreceptor, the entire surface of the photoreceptor is exposed after the rotation of the photoreceptor is stopped, after the photoreceptor has stopped rotating. An electrophotographic apparatus characterized in that a means applies light irradiation for a predetermined period of time.