JPS6146831B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an electrophotographic apparatus.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic apparatus that is capable of selectively developing a part of a light image exposed to a photoreceptor while not selectively developing a part of the light image. The purpose is to

First, before describing embodiments of the present invention, the principle of electrophotography applied to the present invention will be explained using FIGS. 1 and 2.

FIG. 1 shows an electrophotographic copying machine to which the electrophotographic method disclosed in Japanese Patent Publication No. 42-23910 is applied, and FIG. 2 is a graph showing changes in the surface potential of the photoreceptor in the above-mentioned copying machine. A line 1a indicates a change in the surface potential of the photoreceptor in a non-exposed area when the opening/closing member described later is in an open state, and a line 1b indicates a change in the surface potential of the photoreceptor when the opening/closing member is in a closed state. Further, a line 2a indicates a change in the surface potential of the photoreceptor when the opening/closing member, which will be described later, is in an open state at the second exposure section, and a line 2b indicates a change in the surface potential of the photoreceptor when the opening/closing member is in a closed state.

In FIG. 1, a photoreceptor 1 is formed by laminating a conductive support 2, a photoconductive layer 3, and an insulating layer 4 in this order, and is provided on the circumferential surface of a rotating drum 13 that rotates in the direction of the arrow. The photoreceptor 1 is first pre-charged by a pre-charging corona discharger 5, and then by a simultaneous exposure discharger 6.
Simultaneously with projecting the original image through the insulating layer 4, an electrostatic image is formed on the insulating layer 4 by applying an alternating current corona discharge.

After that, a tungsten lamp 7 is used to increase the contrast of the electrostatic latent image in the image area of the photoreceptor 1.
The insulating layer 4 is uniformly exposed to light through an opening/closing member 15 such as a shutter.

Through this uniform exposure, an electrostatic latent image is formed on the photoreceptor 1 in accordance with the brightness and darkness pattern of the original image. Note 1
Reference numeral 4 indicates a light shielding member for shielding the lamp 7 from light.
If this is shown in the surface potential curve of FIG. 2, the dark part of the original image is line 1a, and the bright part is line 2a. Note that the latent image of the desired original image is formed as described above, but if the original image is not exposed and the photoreceptor is uniformly exposed by the lamp 7, the original image will appear in the dark area over the entire surface of the photoreceptor. The surface potential becomes high. If this was developed using the later developing device 8, the toner would be wasted.

Therefore, in the non-image area as described above, the opening/closing member 15 is closed to prevent the surface potential of the photoreceptor from becoming high. If this is shown in FIG. 2, the dark portion of the original image is line 1b and the bright portion is line 2b. The latent image on the photoreceptor 1 created as described above is transferred to the developing device 8.
The image is developed and visualized using a magnetic brush 9 mainly containing toner. Note that since the toner is positively charged, it does not attract to the latent image surface having a negative potential.

That is, the original image is exposed and only the portion uniformly exposed by the lamp 7 can be developed. Next, a corona discharge having a polarity opposite to that of the charged particles is applied to the transfer paper 10, which moves in contact with the visible powder image, by a transfer accelerating corona discharger 11, thereby transferring the visible powder image. Thereafter, the peripheral surface of the photoreceptor 1 is cleaned of remaining powder images by a cleaning means such as a cleaning blade 12, and is then prepared for the copying process.

As described above, even when no copying operation is performed, the corona discharger and developer, which are the components of the copying machine, are in operation, but the lamp 7, which exposes uniformly, is closed by the opening/closing member 15. As shown by lines 1b and 2b in FIG. 2, the surface potential of the photoreceptor is kept below the developing voltage.

When actually copying, the exposure lamp is turned on by turning on a switch to expose the original image onto the photoreceptor. At the same time, the opening/closing member changes from the closed state to the open state, and the surface potential of the photoreceptor becomes lines 1a and 1b in FIG. 2, forming a developable electrostatic latent image in accordance with the original image.

After the desired electrostatic latent image is created as described above, the opening/closing member becomes closed, thereby stopping uniform exposure of the photoreceptor.

As a result, as described above, only a latent image with a low surface potential that cannot be developed is formed on the photoreceptor, making it possible to prevent excessive use of toner.

As is clear from the foregoing, the present invention takes advantage of the fact that even the portion of the photoreceptor to which the original image has been exposed does not reach a potential that can be developed unless the entire surface is exposed. A second light having a pattern in which a portion of the first light image corresponding to a portion to be developed becomes a bright portion, and a portion of the first light image corresponding to a portion not to be developed becomes a dark portion. It exposes the image.

An embodiment of the present invention will be explained with reference to FIGS. 3 and 4.

That is, as in the embodiment shown in FIG. 3, the light from the lamp 7 is transmitted through the film-like control member 16 and applied to the photoreceptor 1, or as in the embodiment shown in FIG. By applying reflected light to the photoreceptor 1, it is possible to form only a portion of the document into a developable electrostatic latent image. More specifically, when the original image is exposed to the photoreceptor as shown in FIG. 5, and the photoreceptor is irradiated with light through the film-like control member shown in FIG. As shown in the figure, a developable electrostatic latent image is formed on the photoreceptor only in the area exposed to light. In FIG. 6, 18 indicates a portion that does not transmit light, and 19 indicates a portion that transmits light.
In addition, in FIGS. 3 and 4, 20 is a document, 21 is a lamp for illuminating the document, 22 is an optical system such as a lens,
Further, reference numeral 23 indicates lamps for illuminating the sheet-shaped control member 17, respectively.

According to the present invention, only the necessary portion of the first optical image can be developed.

[Brief explanation of the drawing]

FIG. 1 is an electrophotographic copying apparatus for explaining the principle of electrophotography applied to the present invention, FIG. 2 is a surface potential curve of a photoreceptor by the copying apparatus of FIG. 1, and FIGS. 3 and 4 are according to the present invention. FIGS. 5 to 7 are diagrams showing a document image film-like control member and a formed electrostatic image in the embodiment of FIG. 3, respectively. DESCRIPTION OF SYMBOLS 1...Photoreceptor, 5...Corona discharger, 6...Discharger for simultaneous exposure, 7...Lamp, 8...Developer,
DESCRIPTION OF SYMBOLS 10...Transfer paper, 11...Corona discharger for promoting transfer, 15...Opening/closing member, 16...Film-shaped control member, 17...Sheet-shaped control member, 22...
…lens.

Claims (1)

[Scope of Claims] 1. A first corona discharge means for applying a corona discharge of a predetermined polarity to the surface of the photoreceptor, and a first optical image that exposes the surface of the photoreceptor on which the first corona discharge means is applied. an exposure means; a second corona discharge means for applying alternating current corona discharge to the surface of the photoreceptor simultaneously with the exposure of the first light image; and a second light image on the surface of the photoreceptor on which the second corona discharge means is applied , having a pattern in which a portion of the first optical image corresponding to a portion to be developed becomes a bright portion, and a portion of the first optical image corresponding to a portion not to be developed becomes a dark portion. Second
an electrophotographic apparatus comprising: a second optical image exposing means for exposing an optical image;