JPH10104893A - Electrostatic latent image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an excellent electrostatic latent image on uniformizing a surface potential of a photoreceptor after exposing, and to manufacture at a low cost by disposing electrification adjusting exposure means capable of uniformizing the electrification potential on the photoreceptor surface prior the exposure by exposing means. SOLUTION: As for this device, an electrifying unit 20 uniformly electrifies the photoreceptor 10 surface upto about -1200V. The low energy exposing device 30 uniformly exposes the surface of the photoreceptor 10 by means of the low energy exposure 301. In such a manner, the surface potential of the photoreceptor 10 is lowered to about -800V, and the electrification potential is uniformized. The high energy exposing device 40 makes an exposure section on the photoreceptor 10 surface lowered to about -100V and makes the non- exposure part kept as the usual potential by making the exposure quantity of the high energy exposure 402 turned on/off, based on the image data imparted by a host device. In such a manner, the electrostatic latent image provided with a specific potential pattern is formed on the photoreceptor 10 surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic latent image forming apparatus for forming an electrostatic latent image on the surface of a photoreceptor by exposing the charged surface of the photoreceptor based on image data. More specifically, the present invention relates to an electrostatic latent image forming apparatus capable of forming a favorable electrostatic latent image by uniformly adjusting a charging potential on a photosensitive member surface.

[0002]

2. Description of the Related Art Generally, in an image forming apparatus such as an electrophotographic printer or a facsimile, a corotron charger including a wire electrode, a scorotron charger having a grid electrode such as a mesh plate, or a roller charger is used. To uniformly charge the surface of the photoreceptor before exposure. Since these chargers are generally arranged at a distance from the surface of the photoreceptor, the surface of the photoreceptor can be uniformly formed with a desired accuracy by the distance from the surface of the photoreceptor to each electrode and uneven wiring of wire electrodes. It is difficult to charge.

FIG. 5 is a graph showing a potential profile on a photosensitive member surface in a conventional electrostatic latent image forming apparatus.
(A) shows a potential profile immediately after charging, and (b) shows a potential profile after exposure. Prior to the exposure, the surface of the photoreceptor is -8 as shown in FIG.
It is charged to about 00V. Next, the photoconductor surface is
As shown in FIG. 5B, exposure is performed by an exposure 401 according to print image data output from a higher-level device. As a result, the non-exposed portion maintains the previous potential, and the exposed portion drops to, for example, about -100 V, thereby forming an electrostatic latent image on the surface of the photoconductor. The formed electrostatic latent image is formed into a toner image, which is transferred onto a medium such as paper. In the charger, it is important that the surface of the photoreceptor can be charged to a uniform potential. With this uniform charging potential, a good electrostatic latent image and, therefore, a clear image can be formed.

Generally, the surface of a photoreceptor is easily affected by the environment such as the temperature and humidity of a space, and the amount of charge given by a charger varies from place to place. Has variations as exemplified in FIG. Such a non-uniform potential profile results in a non-uniform potential profile in a non-exposed portion, and impairs the quality of an image to be formed. For this reason, an electrostatic latent image forming apparatus capable of forming a potential profile as uniform as possible has conventionally been desired.

Japanese Patent Application Laid-Open No. 4-003180 discloses a conventional charger (first charging means) for performing charging before exposure,
After the exposure step, the charger (second
Charging means). The second charging unit lowers the potential of the non-exposed portion of the photoreceptor surface to make the potential uniform, thereby preventing extra carrier from adhering, thereby obtaining a clear image on a print medium.

[0006]

In the electrostatic latent image forming apparatus having the second charging means proposed above, the excess charge of the non-exposed portion after exposure is removed from the surface of the photoreceptor by the second charging means. However, at the same time, there arises a problem that the charge amount of the exposed portion is also reduced. In other words, there is a problem that a place where the charging potential is abnormally low occurs on the surface of the photoreceptor in the exposed portion, and excessive toner adheres.

Here, in order to increase the potential of the exposed portion after the exposure, the second charging means may be controlled by a scorotron charger or the like. However, when the scorotron charger is used, the mesh plate is easily contaminated, and it is difficult to stably control the potential for a long time.

The present invention has been made in view of the problems of the above-described conventional electrostatic latent image forming apparatus, and has a uniform surface potential of a photoreceptor after exposure so that a good electrostatic latent image can be stably formed, and can be manufactured at low cost. It is an object of the present invention to provide an electrostatic latent image forming apparatus capable of performing the above.

[0010]

To achieve the above object, an electrostatic latent image forming apparatus according to the present invention comprises a photosensitive member, a charger for charging the surface of the photosensitive member to a predetermined potential, and a charged photosensitive member. An electrostatic latent image forming apparatus having an exposure device that exposes the surface in a predetermined pattern based on print image data;
A charge adjusting exposure unit for equalizing the charge potential on the surface of the photoreceptor before exposure by the exposure device (first invention); or
The exposure apparatus includes a light amount adjusting unit that controls the amount of light to be emitted from the exposure apparatus to high energy exposure and low energy exposure according to image data.

According to the image forming apparatus of the present invention, the charged potential of the exposed portion and the non-exposed portion of the surface of the photoreceptor can be made uniform. Thereby, formation of a white background image particularly obtained in a non-exposed portion is improved, and a clear image can be obtained by preventing fogging failure on the image due to potential unevenness.

The charge adjusting exposure means for equalizing the potential of the photoreceptor surface before exposure of the exposure apparatus performs, for example, exposure with predetermined energy smaller than the energy used in normal exposure according to image data. It is configured as a low-energy exposure device that equalizes the charged potential on the surface of the photoconductor.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail based on embodiments of the present invention. FIG. 1 is a block diagram illustrating an entire image forming apparatus including an electrostatic latent image forming apparatus according to a first embodiment of the present invention. The image forming apparatus includes the electrostatic latent image forming apparatus of the present embodiment, a developing device 50, and a transfer device 60. The electrostatic latent image forming device includes a photoconductor 10, a charger 20, A low energy exposure device 30 serving as a charge adjustment exposure unit, and a high energy exposure device 40 for image formation.

The photoreceptor 10 has a substantially cylindrical shape and rotates at a constant speed clockwise in the figure at a peripheral speed equal to the paper traveling speed. The charger 20 is connected to a charging power supply 21 and applies a negative charge to the surface of the photoconductor 10 to uniformly charge the surface of the photoconductor 10 to about -1200V. The low-energy exposure device 30 uniformly exposes the surface of the photoconductor 10 with the low-energy exposure 301, thereby lowering the surface potential of the photoconductor 10 to about -800 V and making the charging potential uniform. .

The high-energy exposure device 40 turns the exposure amount of the high-energy exposure 402 on and off based on the image data given from the host device, thereby reducing the exposed portion of the surface of the photoconductor 10 to about -100V. And the unexposed portion is maintained at the previous potential. This allows
An electrostatic latent image having a predetermined potential pattern is formed on the surface of the photoconductor 10. The developing device 50 includes a developing chamber 51 for storing toner, a developing roller 52 disposed in the developing chamber 51, and a bias power supply 53 for applying a bias potential to the developing roller 52, and supplies toner to the surface of the photoconductor 10. And
A toner pattern is formed based on the electrostatic latent image on the photoreceptor surface. The transfer device 60 is connected to a transfer power supply 61 and transfers the toner pattern on the surface of the photoconductor 10 onto a print medium 70 such as paper.

FIGS. 2 (a) to 2 (c) show, in chronological order, a potential pattern on the surface of the photoreceptor in the electrostatic latent image forming apparatus of FIG. 1, and FIG. FIG.
FIG. 4C shows the state after the adjustment of the charging potential, and FIG. 5C shows the state after the high energy exposure. Here, the horizontal axis represents the position on the surface of the photoreceptor, and the vertical axis represents the potential (V). As shown in FIG. 2A, the surface of the photoreceptor is charged to a potential of about -1200 V, as shown in FIG. This potential distribution varies as shown in the figure, depending on the environmental conditions.

As shown in FIG. 2B, the surface of the photoreceptor is adjusted by low-energy exposure 301 using a low-energy exposure device so that the charging potential drops to about -800 V and the potential profile becomes uniform. You. The photoreceptor surface is then exposed by an exposure pattern 402 from a high energy exposure device according to the print image data, and FIG.
As shown in (c), the exposed portion drops to about -100 V, and the unexposed portion is maintained at the previous potential of -800 V, whereby an electrostatic latent image is formed. Here, the irradiation light amount of the high energy exposure 402 in the exposed portion is made uniform.

In the obtained electrostatic latent image, the charged potential is precisely-
Since it is formed as a potential pattern of 800 V or -100 V, problems such as excessive toner adhesion are prevented in the toner image formed by the developing device 50. As a result, a clear print image is formed on the paper without any obstacle such as printing fog.

FIG. 3 is a block diagram showing an image forming apparatus including an electrostatic latent image forming apparatus according to a second embodiment of the present invention. The electrostatic latent image forming apparatus of the present embodiment has an adjustment exposure apparatus 80 for performing controlled high energy exposure instead of the low energy exposure apparatus 30 and the high energy exposure apparatus 40 of the first embodiment. Is the same as the configuration of the electrostatic latent image forming apparatus of the first embodiment.

The adjustment exposure device 80 includes an exposure unit 81 and a light amount control circuit 82. The light amount control circuit 82 prints the amount of exposure of the surface of the photoreceptor 10 by the exposure unit 81 by printing from a higher-level device (not shown). Control is performed between high energy exposure and low energy exposure according to image data. That is, the high density portion of the print image is exposed with high energy, and the low density portion corresponding to the background color of the paper is exposed with low energy.

FIG. 4 shows a potential pattern on the surface of the photoreceptor in the electrostatic latent image forming apparatus shown in FIG. 3, wherein FIG. 4A shows a state immediately after charging, and FIG. 4B shows a state after exposure. I have. As shown in FIG. 4A, the surface of the photoreceptor after being charged by the charger is charged with a certain variation up to a potential of about -1200V.

After being exposed by the exposure 403 from the adjustment exposure device, as shown in FIG. 2B, the high-density portion of the surface of the photosensitive member irradiated by the high-energy exposure has a charging potential of about-.
The low-density portion of the photoreceptor surface irradiated with the low-energy exposure, which has been lowered to 100 V, has a uniformly adjusted potential profile while the charging potential has dropped to about -800 V. As a result, an electrostatic latent image having a uniform potential pattern is formed on the photoconductor surface. The formed electrostatic latent image is
As in the first embodiment, the toner image is transferred onto a sheet after being formed on a toner image.

As described above, the present invention has been described based on the preferred embodiments. However, the present invention is not limited to the configuration of the above-described embodiment, and various modifications may be made from the configuration of the above-described embodiment. The modified electrostatic latent image forming apparatus is also included in the scope of the present invention.

[0024]

As described above, according to the electrostatic latent image forming apparatus of the present invention, by adjusting the charging potential on the surface of the photoreceptor with low energy exposure, the surface of the photoreceptor can be uniformly charged without uneven charging. Correction to a charged potential having a profile becomes possible, and the obtained image is a clear image without obstruction of print fog.

[Brief description of the drawings]

FIG. 1 is a block diagram of an image forming apparatus including an electrostatic latent image forming apparatus according to a first embodiment of the present invention.

FIGS. 2A, 2B, and 2C are graphs showing potential patterns at respective stages on the surface of a photoconductor in the electrostatic latent image forming apparatus of FIG. 1;

FIG. 3 is a block diagram of an image forming apparatus including an electrostatic latent image forming apparatus according to a second embodiment of the present invention.

4 (a) and 4 (b) are graphs showing potential patterns at respective stages on the surface of a photoreceptor in the electrostatic latent image forming apparatus of FIG. 3, respectively.

FIGS. 5A and 5B are graphs showing a potential pattern at each stage of a photosensitive member surface in a conventional electrostatic latent image forming apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 photoconductor 20 charger 21 charging power supply 30 low energy exposure device 40 high energy exposure device 50 developing device 51 developing chamber 52 developing roller 53 bias power supply 60 transfer device 61 transfer power supply 70 paper 80 adjustment exposure device 81 exposure unit 82 light intensity Control circuit 301 Low energy exposure 401, 402, 403 Exposure pattern

Claims (3)

[Claims] An electrostatic latent device comprising: a photoreceptor; a charger for charging the surface of the photoreceptor to a predetermined potential; and an exposure device for exposing the charged photoreceptor surface in a predetermined pattern based on print image data. An electrostatic latent image forming apparatus comprising: an image forming apparatus; and a charge adjusting exposure unit for equalizing a charged potential on a surface of a photosensitive member prior to exposure by an exposure apparatus. 2. The electrostatic latent image forming apparatus according to claim 1, wherein the charging adjustment exposure unit uniformly irradiates the surface of the photoconductor with a predetermined energy light. 3. An electrostatic latent device comprising: a photoreceptor; a charger for charging the surface of the photoreceptor to a predetermined potential; and an exposure device for exposing the charged photoreceptor surface in a predetermined pattern based on print image data. In the image forming apparatus, the exposure apparatus includes a light amount adjusting unit that controls a light amount to be irradiated from the exposure apparatus to a high energy exposure and a low energy exposure according to image data. .