JPH03132678A - Electronic photographing type printer - Google Patents

Abstract

PURPOSE:To clearly perform printing immediately after the printing is restarted by providing a shielding means which shields between a corona discharger and a photosensitive material. CONSTITUTION:An endless belt 10 is driven with a motor at both an electrification part and a transfer part in the printing so as to be rotated at the same speed in the same direction as that of a photosensitive drum 1 as coming in contact with the photosensitive drum 1. Therefore, a part between a charger 2 comprised of the corona discharger, a transfer device 5 and the photosensitive drum 1 is shielded with the endless belt 10. Thereby, no activated material generated from the corona discharger arrives at the photosensitive drum 1 even after the printing is completed as a matter of course while the printing is being performed. In such a way, it is possible to prevent a print defect occurring such as a thin printed result at a time when the printing is restarted after the stoppage of the printing continues for prescribed time or more.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic printer using a photoconductor made of amorphous silicon, and particularly to an electrophotographic printer that prevents printing defects that occur when printing is resumed after stopping printing for a predetermined period of time. It is related to printers.

[Background of the invention]

Amorphous silicon is Se, which is a conventional photoreceptor material.
Because it has a higher surface hardness than , CdS, etc., there is extremely little wear due to contact with paper or cleaning brushes, and it is expected to be a maintenance-free photoreceptor material.

However, amorphous silicon photoreceptors have the following problems. In other words, if printing is restarted after approximately 10 hours or more have passed since printing ended, the initial 20
By the time 0 to 300 sheets are printed, a printing defect occurs in which the print result becomes pale and unclear. At the initial stage of occurrence, the printing blur area is 10 to 20 mm in the circumferential direction of the photosensitive drum and approximately 3/4 of the total length of the photosensitive drum in the length direction.
It is fairly elongated and occurs locally. If printing is continued further, the blurred areas will disappear and the entire surface will be printed clearly.

Note that a printing defect in which the printed result after printing is restarted occurs with good reproducibility if the printing stop time continues for a predetermined period of time or more. Furthermore, if printing, stopping printing for a predetermined period of time or more, and printing are repeated, blurred printing spots that initially appeared locally will begin to appear over the entire area of the photosensitive drum.

According to experiments conducted by the inventors of the present invention, it has been found that the blurred portion of the print corresponds to the position of the photosensitive drum facing the charger and the transfer device. It was also found that negative ions are strongly generated in the portion of the photosensitive drum that faces the corona discharger that generates negative ions.

From the results of this experiment, we found that the activation substance generated by the corona discharger that constitutes the transfer device and charger remains inside the transfer device and charger even after the end of corona discharge, that is, the end of printing, and becomes photosensitive due to a diffusion phenomenon. It is presumed that the particles reach and adhere to the drum surface and form a layer of foreign atoms or molecules, deteriorating the properties of the photoreceptor and making printing unclear.

[Purpose of the invention]

An object of the present invention is to eliminate the above-mentioned problems of the prior art and to enable clear printing immediately after restarting printing. Focusing on the fact that the corona discharge occurs at a location facing the corona discharger, the present invention is characterized by providing a shielding means for shielding between the corona discharger and the photoreceptor. The present invention will be explained below with reference to the drawings.

[Embodiments of the invention]

FIG. 1 shows the state during printing, in which a photosensitive drum 1 made of amorphous silicon is surrounded by a charger 2, an exposure source 3 such as a semiconductor laser or an LED array, a developer 4, and a transfer device 5.
A cleaning brush 6 and the like are provided. The charger 2 and the transfer device 5 are constituted by corona dischargers as described above.

An endless belt 10 provided so as to surround the charger 2 and the transfer device 5 is brought into contact with the photosensitive drum 1 by two driving rollers 1 and a tension applying guide roller 12.
It is quickly moved so that it rotates in the same direction and at the same speed as the rotation direction. One of the drive rollers 11 is connected to a motor (not shown), and the other serves as an idle roller.

As shown in FIG. 2, both sides of the endless belt 10 are covered by covers 1.
It is sealed by 3.

Examples of materials for the endless belt 10 include nitrile rubber,
Chloroprene rubber, butyl rubber, fluorine rubber, silicone rubber, imprene rubber, styrene butadiene rubber, urethane rubber, polyacrylic rubber, chlorosulfonated polyethylene rubber, polysulfide rubber, ethylene propylene rubber, epichlorohydrin rubber, polybutadiene rubber, etc. are used. If possible, it is preferable to disperse and mix metal powder such as chromium, molybdenum, tungsten, etc. into these to give them semiconducting properties, and on top of that, tetrafluoroethylene resin, tetrafluoroethylene/hexafluoropropylene resin, The endless belt 10 may be coated with a perfluoroalkoxy polymer or the like to improve the abrasion resistance of the endless belt 10. In addition, so that the surface of the photosensitive drum 1 can be polished by the endless belt 10, Sin, TiOx, A1. Oa, Si, N,
, SiC, TiC1TiN, artificial diamond, etc., may be coated or dispersed in the belt material.

During printing, the endless belt 10 is driven by the motor so as to rotate at the same speed in the same direction as the rotational direction of the photosensitive drum 1 while contacting the photosensitive drum 1 in both the charging section and the transfer section. . As is well known, since the printing paper 7 needs to come into contact with the photosensitive drum 1 at the transfer section, it is fed between the photosensitive drum 1 and the endless belt 10.

The photosensitive drum 1 is charged by the charger 2 via the endless belt 10, and the transfer by the transfer device 5 is also carried out via the endless belt 10.

According to the above embodiment, the endless belt 1 is connected between the charger 2 constituted by a corona discharger, the transfer device 5, and the photosensitive drum 1.
0, the activation substance generated from the corona discharger will not reach the photosensitive drum 1 not only during printing but also after printing is completed, and printing will not continue for more than a predetermined time. There is no longer a problem with printing defects where the print result becomes faint when printing is restarted later.

That is, when the process of continuously printing for 12 hours and then stopping printing for 12 hours was repeated, no printing defects occurred even after printing several million pages.

Note that when the endless belt 10 is rotated at a different speed or in the opposite direction to the photosensitive drum 1 after printing is completed to create a speed difference, the surface of the photosensitive drum 1 can be polished by the abrasive material on the endless belt 10. Since the deteriorated portion of the surface of the photosensitive drum 1 is removed, the print result after printing is restarted can be made even clearer. During such abrasive cleaning, the endless belt 10 only needs to rotate at a speed difference with the photosensitive drum 1, but according to experiments conducted by the present inventors,
It has been found that good abrasive cleaning can be achieved by setting the speed of the endless belt 10 to about twice the speed of the photosensitive drum 1 and by setting the number of rotations of the photosensitive drum 1 to 20 times.

FIG. 3 shows another embodiment of the part for the present invention, in which one cover 13 that covers both sides of the endless belt 10 is provided with a large number of air supply ports 30, and the other cover 13 includes a dust suction device (not shown), etc. A gas exhaust port 31 connected to the endless belt 10 is provided to prevent activated substances generated by the corona discharger from accumulating in the endless belt 10. As a result, the activation substance does not accumulate in the endless belt 10, so that the risk of printing defects is further reduced.

In the above embodiment, the charger 2 and the transfer device 5 are provided at positions facing the photosensitive drum 1, but the endless belt 1
Since charging and transfer are performed through the belt 10, there is no need to provide them at opposite positions, and it is sufficient to provide them at any position facing the endless belt 10.

Furthermore, the surface of the photosensitive drum 1 is polished by the endless belt 10 surrounding the charger 2 and the transfer device 5 after printing is completed, that is, during non-printing. The surface of the photosensitive drum 1 may be polished, and in this case, compared to the conventional method of polishing with a cleaning brush 6, since the polishing is performed during non-printing, the contact pressure can be increased, and the contact area with the photosensitive drum 1 is large, so the polishing efficiency can be improved. This can have the effect of improving performance.

Furthermore, both sides of the endless belt 10 are covered with covers 13 to keep it sealed at all times, but as explained in the embodiment of FIG.
In order to eliminate the activation substance generated by the corona discharger, it may be left open during printing and covered after printing is completed.

〔Effect of the invention〕

According to the present invention, since the activation substance generated by the corona discharger does not reach the photoreceptor, printing defects such as thin print results are avoided even when printing is restarted after printing has stopped for a predetermined period of time or more. This will no longer occur, and clear printing will be possible immediately after printing is resumed.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention. FIG. 1 is a side view showing an electrophotographic printer, FIG. 2 is an exploded perspective view showing the area around the transfer section, and FIG. FIG. 7 is a developed perspective view showing another embodiment. In the figure, 1 is a photosensitive drum, 2 is a charger, 3 is an exposure source, 4 is a developer, 5 is a transfer device, 6 is a cleaning brush,
7 is a printing paper, 10 is an endless belt, 11 is a transparent moving roller, 12 is a guide roller, 13 is a cover 30 is an air supply port, and 31 is a gas exhaust port. Engraving of drawings (no changes to content)

Claims (1)

[Scope of Claims] 1. After the surface of a photoreceptor made of amorphous silicon is charged to a constant potential by a charger, a printed image is exposed by an exposure means to form an electrostatic latent image, and the electrostatic latent image is formed by a developing machine. Printing is performed by repeating a series of processes in which toner is attached to the image, developed, and the toner attached to the photoreceptor is suctioned and transferred onto the paper by a transfer device facing the photoreceptor through the paper. 1. An electrophotographic printer in which a charger or a transfer device is a corona discharger, and further comprising a shielding means for shielding between the corona discharger and a photoreceptor. 2. The shielding means surrounds the corona discharger, and the portion located between the photoreceptor and the corona discharger is constituted by an endless belt that moves along the circumferential direction of the photoreceptor. electrophotographic printer. 3. The electrophotographic printer according to claim 2, wherein both sides of the endless belt are covered by cover members. 4. The electrophotographic printer according to claim 3, wherein one and the other of said cover members are provided with an air supply port and a gas exhaust port, respectively. 5. Claim 2, characterized in that the endless belt has an abrasive material, and when not printing, the endless belt is rotated at a speed difference with respect to the photoreceptor, and the surface of the photoreceptor is polished by the endless belt.
The electrophotographic printer described. 6. An electrophotographic printer characterized in that when not printing, the surface of the photoreceptor is polished by an endless belt that rotates at a speed difference with the photoreceptor while contacting the photoreceptor.