JPH0157785B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a printing method applying the principles of electrophotographic copying, that is, an electronic printing method, and particularly to an electrostatic printing method that is excellent in uniformly reproducing images having a certain size.

Printing by electrophotography has been known for a long time. Known examples include the zero printing method in U.S. Patent No. 2,576,047;
Or the electronic printing device of Special Publication No. 1554/1973. This is done by forming a powder image on a photoconductive plate and fusing or fixing it to form a non-photosensitive insulating image figure, that is, a printing master, on the photoconductive plate by an electrostatographic method, and then This printing master is uniformly charged and further uniformly irradiated with light. The charge is thereby retained only on the non-photosensitive image areas and discharged on the photosensitive areas, so that a charged powder is deposited on the partially charged plate to form a powder image;
This is a method of transferring a powder image onto a suitable image support, and the above steps are repeated.

In particular, Japanese Patent Publication No. 43-1554 shows a device as shown in Figure 1. In the figure, reference numeral 1 denotes a rotating drum, which has presser claws around it to support the photosensitive paper 10. Surrounding the rotating drum 1 are a cleaning device 8, a charger 4, a uniform exposure lamp B, Developing machine 5, transfer corotron 6, photosensitive paper 1
Facilities such as an infrared fixing device 7 for fixing the toner image on 0 are arranged.

The printing master is created after the photosensitive paper 10 is wrapped and supported on the rotating drum 1, charged with the charger 4, and then illuminated with the original illumination lamp 14 on the original platen 3. It is projected onto photosensitive paper 10 to form an electrostatic latent image. Next, the latent image is visualized by a developing device 5, and the toner image is fused and fixed onto photosensitive paper 10 by an infrared fixing device 7, thereby forming a printing master.

Electrostatic printing of a large number of sheets using such a printing master is performed as follows. A printing master having a toner image on photosensitive paper is charged by a charger 4, and further exposed uniformly over the entire surface by a uniform exposure lamp 13.
The charge on the uniformly charged photosensitive paper 10 is drained away by uniform exposure leaving only the toner image portions which are insensitive and non-photoconductive. Therefore, a printing master is formed in which only the toner image portion has an electric charge, and the developing machine 5
It is visualized by. Next, the transfer paper 11 is sent to the transfer section in synchronization with the rotation of the rotary drum 1, and the toner image on the print master is transferred to the transfer paper by the transfer corotron 6, and then becomes a fixed image by the fixing device 9. , and output to the paper output tray to obtain a copy. On the other hand, residual toner on the print master after transfer is cleaned by a cleaning device 8,
One print cycle ends. The printing cycle is then repeated for the number of copies required.

However, in this method, development is performed using the same developing device, that is, under the same developing conditions, both in the process of creating a print master and in the printing process of creating multiple prints on transfer paper using the print master. Therefore, it is difficult to obtain good copies. In other words, depending on the rotating direction of the developing device's magnetic brush developing roll relative to the rotating direction of the photosensitive paper,
There is a drawback that poor development occurs at the leading or trailing edge of the surface image, and this defect is multiplied and multiplied at the time of printing master formation and printing. It is difficult to obtain things. The present invention eliminates the above drawbacks and
The objective is to provide an electrostatic printing method that is excellent in reproducing surface images with uniform density.

The present invention is capable of reproducing a uniform surface image by reversing the rotating direction of the magnetic brush developing roll in the developing device when creating a print master and when printing multiple prints from the master. be.

A specific example of the present invention will be explained with reference to FIG.

In FIG. 2, the developing device 51 is composed of a magnetic brush developing roll 15, developer regulating members 16, 17, a toner supply device 19 for replenishing toner, and a developer stirring device 18, and a rotating drum. 1
A photoconductive plate, such as photosensitive paper 10, supported on the surface of
It is designed to develop the electrostatic image above. First, when developing an electrostatic image on photosensitive paper when creating a printing master, the magnetic brush developing roll rotates counterclockwise. At this time, the first developer regulating member 16 functions to provide only a constant and appropriate amount of developer for development, and the surface image on the photosensitive paper has an insufficiently developed portion at the front end. Thereafter, the toner image on the photosensitive paper is fixed by an infrared fixing device to create a print master. When printing is performed using the printing master next time, the magnetic brush developing roll 15 is rotated clockwise, which is the opposite direction from when the printing master was created. The developer regulating member used at this time is the second developer regulating member 17. Since the development characteristics at this time have a characteristic in which the rear end of the surface image is insufficiently developed, it overlaps with the characteristics of creating a printing master, and as a result, it becomes possible to reproduce a uniform surface image.

Further, the rotating directions of the magnetic brush developing roll 15 during printing master creation and printing may be opposite to those described above.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the configuration of an electronic printing device, and FIG. 2 is a sectional view of essential parts in which the developing device of the present invention is applied to the printing device.
3... Original table, 4... Charger, 5... Developer, 6... Transfer corotron, 7... Infrared fixing device, 8... Cleaning device, 9... Fixing device, 10... Photoconductive plate, 11
...Transfer paper, 12... Paper discharge tray, 13... Uniform exposure lamp, 14... Original illumination lamp.

Claims (1)

[Claims] 1. A step of charging a photoconductive plate, imagewise exposing it, developing it, and fixing it to create a printing master on which a toner image is fixed; and a step of charging the printing master, uniformly exposing it to light, and developing it in the step of creating the printing master. In an electrostatic printing method comprising a printing step of transferring a toner image on a printing master after developing with the same developing device as the device, the magnetic brush of the developing device is used in the printing master creation step and the printing step. An electrostatic printing method characterized by developing by rotating developing rolls in opposite directions.