JPH0695264B2 - Electrostatic recording device - Google Patents

Description

The present invention relates to an electrostatic recording apparatus, in particular, an electrophotographic printer, which performs development cleaning with the same magnetic brush to obtain one image in two rotations.

[Conventional technology]

Since the electrophotographic process for obtaining one image by two rotations requires few constituent elements, it has been proposed so far in JP-A-50-155233. That is, Japanese Patent Application Laid-Open No. 50-155233 is characterized in that development and cleaning are performed with a magnetic brush. Moreover, if the same magnetic brush is used for both of the above processes, it is considered that it is not necessary to separately form a cleaning unit, so the cost can be reduced.

However, in practice, it is difficult to perform cleaning with only the magnetic brush, and it is disclosed in Japanese Patent Laid-Open No. 53-1310 on the upstream side of the magnetic brush.
No. 50, a blade is provided in JP-A-56-38073, and a method is proposed in which the toner is once removed from the photoconductor and the magnetic brush collects the toner.

FIG. 3 is a schematic configuration diagram of a conventional electrostatic recording apparatus in the process of obtaining one image by two rotations. The photoreceptor 1 is uniformly charged, for example, negatively by the strip electrode 2a (FIG. 4 (a)), and the exposure device 3 erases the charge in the non-image area to form a latent image (FIG. 4 (b)). Then, the latent image becomes a toner image by the magnetic brush device 4 (FIG. 4 (c)). Next, the toner image is transferred onto the transfer paper by the transfer pole 5 (FIG. 4 (d)). After the transfer, some toner remains on the photoconductor, so the toner passes through the magnetic brush again to be cleaned and the next cycle is started.

The photoconductor after transfer is very strongly charged by the corona of the transfer pole 5 (Fig. 4 (e)), and it cannot be cleaned by passing through the magnetic brush as it is. It is necessary to generate a corona to neutralize the surface of the photoconductor or to neutralize by light (FIG. 4 (f)).

Through such a process, cleaning with a magnetic brush is started (FIG. 4 (g)).

The transfer paper is pulled out from the cassette 7 by the supply roller 8, receives the image transfer through the guide chute 9 and the transfer pole 5, passes through the guide chute 10, and is fixed by the fixing device 11 to be collected after the electrostatic recording is completed. It

[Problems to be solved by the invention]

As described above, in the prior art, it is difficult to erase the charge under the toner layer when attempting to eliminate the charge with light, and particularly when a jam occurs and the toner image is not transferred, the toner becomes more difficult and cleaning failure tends to occur. . In this case, charge can be removed even from the top of the toner layer by removing charge with AC corona, but a power supply and a corona discharger for the charge removal corona electrode for cleaning are required, and a space for that is also required, making the device complicated and complicated. It will be large and costly.

An object of the present invention is to eliminate such drawbacks. In the case of an electrostatic recording apparatus which performs reversal development, the polarity of charging is the same as the polarity of charge of toner, and after development, the toner image on the photoreceptor is developed. The toner image is transferred to the recording paper by the transfer electrode of the opposite polarity to that of the above, and paying attention to the residual charge of this polarity, the device is simplified by sharing the charging corona electrode for static elimination before cleaning. It is a measure.

[Means for solving problems]

The purpose of this is to rotate the photoconductor, apply an electric charge to the surface of the photoconductor by a charger, form an electrostatic latent image by imagewise exposure, and make the electrostatic latent image a visible image by a magnetic brush developing device. In an electrostatic recording device in which the surface of the photoconductor is cleaned by the magnetic brush developing device after the transfer to the recording paper, a scorotron is used as the charger, and a potential having the same polarity as the electric charge applied by the scorotron is applied. After reversal development by the magnetic brush developing device and transferring this image to recording paper, the DC voltage of the same polarity is applied to the scorotron before cleaning by the magnetic brush developing device on the surface of the photoreceptor after the transfer process. The electrostatic recording apparatus is characterized in that a charge having a polarity opposite to that of the transfer step is applied to attenuate the potential on the surface of the photoconductor to eliminate the charge.

〔Example〕

One embodiment of the present invention will be described with reference to a schematic configuration diagram of FIG. 1 and a model diagram of each process of FIG. Members having the same functions as those of the conventional example shown in FIG. 3 have the same numbers and names.

The photoconductor is composed of a photoconductor belt 1 stretched endlessly on drums 1a and 1b. This photosensitive belt 1 is
As shown in FIG. 2 (a), it is uniformly charged negatively by the scorotron 2, and the print exposure device 3a erases the charge in the printing portion as shown in FIG. 2 (b) to obtain a latent image. Two
It is developed as shown in FIG. At this time, reversal development is performed so that the toner adheres to the place where the electric charge is erased.

The surface potential of the photoconductor is -600V in the background part (white area) and almost 0V in the printing part (black part), and the potential applied to the magnetic brush sleeve 4a is about -500 to -550V. If it is made negative, reversal development becomes possible.

The toner image thus formed on the photosensitive belt 1 is transferred onto the transfer paper by the transfer electrode 5 as shown in FIG. In this embodiment, the positive corona discharge is performed by the transfer electrode 5 from the back side of the transfer paper.

+500 due to the transfer corona on the photoconductor belt 1 after the transfer.
It is charged to ~ + 1000V, so it is necessary to remove the charge before cleaning. The grid 6 of the scorotron 2 is set to zero potential and a negative corona is irradiated. Since the scorotron is a device that charges the photoconductor so that the potential of the photoconductor becomes substantially equal to the potential of the grid, if the grid has a zero potential, the photoconductor also has a substantially zero potential, and therefore static elimination is possible.
Since the grid 6 needs to be set to about -600 V at the time of charging, the potential of the grid 6 is switched by the switch 6a at the time of charging and at the time of cleaning as shown in FIG. In this way, the scorotron 2 eliminates the charge on the photosensitive belt 1 as shown in FIG. 2 (f).

Although a scorotron is used in this embodiment, it may be a corotron. In this case, the current value should be set so as to cancel the electric charges on the photoconductor charged by the transfer corona.
Therefore, it is desirable that the current value at the time of charging and the current value at the time of discharging be switched.

Then, when the photoconductor passes through the sleeve 4a of the magnetic brush, the photoconductor belt 1 and the residual toner on the belt become the second
It is not charged as shown in FIG. When the sleeve is set to almost 0 potential, the toner on the photoconductor is attracted to the sleeve.

For example, in the case of a one-component magnetic toner, the force of pulling the toner onto the sleeve is a magnetic force generated by a magnet contained in the sleeve.

When two components are used, they are attracted to the carrier due to mutual friction between the carrier and the toner.

As described above, in the present invention, it is possible to make one scorotron have both the functions of the charging and the pre-cleaning charge removal by paying attention to the fact that the polarity of the charge and the transfer are different by performing the reversal development. There is no need to install a separate mechanism.

In the present embodiment, the belt-shaped photosensitive member is used, but a drum-shaped photosensitive member may be used.

〔The invention's effect〕

According to the present invention, a single scorotron can be used for both charging and charge removal before cleaning, and an electrostatic recording apparatus can be obtained which has a simplified mechanism and is capable of highly cleaning the photoconductor.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention, FIG. 2 is a schematic diagram of each process thereof, FIG. 3 is a schematic configuration diagram of a conventional electrostatic recording apparatus, and FIG. 4 is a model of each process thereof. It is a figure. 1 ... Photosensitive belt, 2 ... Scorotron 2a ... Charging device 2b ... Charging negative potential applying power supply 3 ... Exposure device, 3a ... Printing exposure device 4 ... Developing device, 4a ... Sleeve 5 ... Transfer Electrode 5a …… Transfer pole positive potential applying power source 5b …… Transfer pole negative potential applying power source 6 …… Grid 6a …… Grid potential changeover switch 6b …… Grid potential applying power source 12 …… Exceptive electrode

Claims (2)

[Claims] 1. A photoconductor is rotated to apply an electric charge to the surface of the photoconductor by a charger, and an electrostatic latent image is formed by imagewise exposure, and the electrostatic latent image is visualized by a magnetic brush developing device. After transferring this onto recording paper, in an electrostatic recording device in which the surface of the photoconductor is cleaned by the magnetic brush developing device, a scorotron is used as the charging device, and a potential having the same polarity as the electric charge applied by the scorotron is applied. Then, the image is reversely developed by the magnetic brush developing device, the image is transferred to a recording sheet, and the DC voltage of the same polarity is applied to the scorotron before cleaning the surface of the photoreceptor after the transfer process by the magnetic brush developing device. The electrostatic recording apparatus is characterized in that an electric charge having a polarity opposite to that of the transfer step is applied to attenuate the potential on the surface of the photoconductor to remove the electric charge. 2. The electrostatic recording apparatus according to claim 1, wherein the grid potential of the scorotron is connected to a DC power source during charging and grounded during static elimination.