JP2000141758A - Method for correcting electrophotograph density gradient and image-forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To apply a gradient of an electrostatic attractive force to a surface of a photosensitive drum and correct a density gradient by changing an irradiation amount of laser light depending on expose points on the photosensitive drum to correct the density gradient of a toner image on the photosensitive drum. SOLUTION: An exposing means is provided with a means for changing an irradiation amount of a laser light 3 depending on expose points on a photosensitive drum 1 to correct a density gradient of a toner image 7 on the photosensitive drum 1. The exposing means changes a laser exposure amount in an appropriate distribution according to the density gradient of the toner image 7 on the photosensitive drum 1 which is primarily caused by an irregular toner hold amount on a sleeve of a developing device, thereby correcting the density gradient of the toner image 7 on the photosensitive drum 1. Concretely, the laser exposure amount is changed in the appropriate distribution with use of an irradiation amount control signal applied to the laser light 3. The density gradient of the toner image 7 on the photosensitive drum 1 can be corrected in this manner. A beautiful image with no density gradient can be expressed on a printed image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming technique, and more particularly, to a method for correcting an electrophotographic density gradient used in an electrophotographic process having a laser exposure process for performing exposure while scanning the surface of a photosensitive drum with a laser beam. Further, the present invention relates to an image forming apparatus using an electrophotographic process including a laser exposure process for performing exposure while scanning the surface of a photosensitive drum with laser light.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic density gradient correction technology used in an electrophotographic process having a laser exposure process for performing exposure while scanning the surface of a photosensitive drum with a laser beam, a density gradient caused by a developing device is not corrected. Improvements have been made by changing the toner conveyance path inside the developing device, changing the mounting method of the toner amount regulating blade, and the like. However, in reality, a conspicuous density gradient appeared on the image. It is considered that the reason is that it is difficult to completely eliminate the density gradient mechanically in the developing device, and that means for compensating the density gradient at a location outside the developing device is not provided. As a conventional technique for solving such a problem, for example, there is a technique disclosed in Japanese Patent Application Laid-Open No. 63-18320. That is, an illumination optical system that forms an image on a photosensitive member with a modulated laser beam corresponding to image information and scans the photosensitive member, and a storage unit that stores variation characteristics of the intensity of the modulated laser beam on the surface of the photosensitive member in the main scanning direction. And correcting means for changing the intensity of the modulated laser beam under the same modulation to have the same set value in the main scanning direction based on the modulation characteristics stored in the storage means.

[0003]

However, if the intensity of the modulated laser beam under the same modulation is changed so as to have the same set value in the main scanning direction based on the modulation characteristics stored in the storage means, it is not practical. Has a problem that it is difficult to sufficiently suppress the density gradient on the image.

The present invention has been made in view of such a problem, and an object of the present invention is to generate a gradient in a laser exposure amount using a radiation amount control signal corresponding to a density gradient that can occur. Accordingly, an object of the present invention is to provide an electrophotographic density gradient correction method and an image forming apparatus for correcting a density gradient by giving a gradient of electrostatic attraction to the surface of a photosensitive drum.

In addition, the surface of the photosensitive drum is provided with a gradient of electrostatic attraction by generating a gradient in laser exposure using an optical filter having an appropriate transmittance distribution according to the amount of density gradient that can occur. An object of the present invention is to provide an electrophotographic density gradient correction method and an image forming apparatus for performing correction.

[0006]

The gist of the present invention is to provide an electrophotographic density gradient used in an electrophotographic process having a laser exposure process for performing exposure while scanning the surface of a photosensitive drum with a laser beam. A correction method, wherein a charging step of charging the surface of the photosensitive drum to a predetermined surface potential, and changing the irradiation amount of the laser light according to an exposure location on the photosensitive drum, with respect to the charged photosensitive drum An exposure step of performing laser exposure to form an electrostatic latent image, and a developing step of forming a toner image by supplying a developer to the photosensitive drum on which the electrostatic latent image has been formed. The present invention resides in a method for correcting an electrophotographic density gradient.
The gist of claim 2 of the present invention is that the exposure step comprises: irradiating the laser light in accordance with an exposure position on the photosensitive drum so as to correct a density gradient of a toner image on the photosensitive drum. 2. The method according to claim 1, further comprising the step of: The gist of claim 3 of the present invention is that the exposing step is performed in accordance with a density gradient of a toner image on the photosensitive drum, which is caused mainly by unevenness of a toner holding amount on a developing device sleeve. 2. An electrophotographic density gradient correction method according to claim 1, wherein the density gradient of the toner image on the photosensitive drum is corrected by changing the laser exposure amount with an appropriate distribution. The gist of claim 4 of the present invention is characterized in that in the exposing step, the laser exposure amount is changed with an appropriate distribution using an irradiation amount control signal applied to laser light. 4. An electrophotographic density gradient correction method according to any one of 1 to 3. The gist of claim 5 of the present invention is that the exposure step changes the laser exposure amount with an appropriate distribution using an optical filter having an appropriate transmittance distribution. 3. An electrophotographic density gradient correction method according to any one of 3. According to another aspect of the present invention, there is provided an image forming apparatus using an electrophotographic process including a laser exposure process for performing exposure while scanning the surface of a photosensitive drum with laser light, wherein Charging means for charging the surface to a predetermined surface potential; and performing laser exposure on the charged photosensitive drum while changing the irradiation amount of the laser light in accordance with an exposure location on the photosensitive drum, thereby forming an electrostatic latent image. An image forming apparatus includes: an exposure unit that forms an image; and a developing unit that supplies a developer to the photosensitive drum on which the electrostatic latent image is formed to form a toner image. The gist of claim 7 of the present invention is that the exposure unit adjusts the irradiation amount of the laser beam in accordance with an exposure position on the photosensitive drum so as to correct a density gradient of a toner image on the photosensitive drum. 7. The image forming apparatus according to claim 6, further comprising: means for changing the image forming apparatus. Further, the gist of the present invention is that the exposure unit is configured to perform the exposure in accordance with a density gradient of a toner image on the photosensitive drum which is mainly caused by an uneven toner holding amount on a developing device sleeve. 7. An image forming apparatus according to claim 6, further comprising means for changing a laser exposure amount with an appropriate distribution to correct a density gradient of the toner image on the photosensitive drum. The gist of the ninth aspect of the present invention is that the exposure means changes the laser exposure amount with an appropriate distribution using an irradiation amount control signal applied to the laser light. An image forming apparatus according to any one of claims 6 to 8. The gist of claim 10 of the present invention is that the exposure unit changes the laser exposure amount with an appropriate distribution using an optical filter having an appropriate transmittance distribution. 8. The image forming apparatus according to claim 8, wherein

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(First Embodiment) With reference to FIG. 1, an embodiment of an image forming apparatus for executing an electrophotographic density gradient correcting method of the present invention will be described using an image forming process of an electrophotographic printing apparatus. FIG. 1 shows an image forming process of an electrophotographic printing apparatus which is an embodiment of an image forming apparatus that executes the electrophotographic density gradient correction method of the present invention.

The image forming process includes a charging step, an exposing step, a developing step, a transferring step, a cleaning step, and a discharging step. In the image forming process, first, the photosensitive drum 1 rotates in the rotation direction 24, and the image forming process is performed in the rotation. First, the surface of the photosensitive drum 1 is charged to about -800 V by the discharge from the charging unit (charging means) 2 (charging step). Second
On the basis of the image data, the laser light 3 is turned on and off while scanning, and the potential of the surface of the photosensitive drum 1 drops to about -100 V at the location where the laser is irradiated to form an electrostatic latent image 4. (Exposure step). Third, about -500V
The toner component of the developer 6 on the developing sleeve (developing means) 5 having the potential of 5 adheres to the portion of the photosensitive drum 1 where the potential drops, forming a toner image 7 (developing step). Fourth, the toner image 7 on the photosensitive drum 1 is transferred by electric force onto the paper 9 running at the same speed as the peripheral speed of the photosensitive drum 1 by the operation of the transfer unit (transfer unit) 8 (see FIG. 4). Transfer step). Fifth, the residual toner image 11 is mechanically removed by the operation of the cleaning blade (cleaning means) 10 (cleaning step). Sixth, the residual electrostatic latent image 13 is removed by the operation of the charge removing lamp (charge removing means) 12 (charge removing step).

In such an image forming process, the electrophotographic density gradient correction method of the present embodiment employs the photosensitive drum 1
Correction method used in an electrophotographic process including a laser exposure process of performing exposure while scanning the surface of the substrate with a laser beam 3, wherein the charging step performed by the charging unit, the exposure step performed by the exposure unit, and the development unit performed. Developing step.

In the charging step, the surface of the photosensitive drum 1 is charged to a predetermined surface potential.

In the exposure step, an electrostatic latent image is formed by performing laser exposure on the charged photosensitive drum 1 while changing the irradiation amount of the laser beam 3 in accordance with the exposure location on the photosensitive drum 1.

In the developing step, a developer is supplied to the photosensitive drum 1 on which the electrostatic latent image has been formed to form a toner image 7.

The exposing step includes a step of changing the irradiation amount of the laser beam 3 in accordance with the exposure position on the photosensitive drum 1 so as to correct the density gradient of the toner image 7 on the photosensitive drum 1.

In the exposing step, the laser exposure amount is appropriately distributed according to the density gradient of the toner image 7 on the photosensitive drum 1 which is mainly caused by the non-uniformity of the toner holding amount on the developing device sleeve (developing means). To correct the density gradient of the toner image 7 on the photosensitive drum 1. Specifically, the laser exposure amount is changed with an appropriate distribution using the irradiation amount control signal 32 applied to the laser beam 3.

The image forming apparatus of the present embodiment shown in FIG.
An apparatus using an electrophotographic process including a laser exposure process for performing exposure while scanning the surface of the photosensitive drum 1 with a laser beam 3, comprising: a charging unit (charging unit 2);
Exposure means (laser oscillator 30, polygonal rotating mirror 31)
A, lenses 31B, an irradiation amount control signal generator (not shown), developing means (developer sleeve 5, developer 6, developing device 35), transfer means (transfer unit 8), cleaning means (cleaning blade 10) ), And a static elimination means (static elimination lamp 12). The charging unit charges the surface of the photosensitive drum 1 to a predetermined surface potential.

The exposure means forms an electrostatic latent image by performing laser exposure on the charged photosensitive drum 1 while changing the irradiation amount of the laser beam 3 in accordance with the exposure location on the photosensitive drum 1. The developing unit supplies a developer to the photosensitive drum 1 on which the electrostatic latent image has been formed to form a toner image 7.

The exposure means has means for changing the irradiation amount of the laser beam 3 in accordance with the exposure position on the photosensitive drum 1 so as to correct the density gradient of the toner image 7 on the photosensitive drum 1.

The exposure means adjusts the laser exposure amount appropriately in accordance with the density gradient of the toner image 7 on the photosensitive drum 1 which is mainly caused by the unevenness of the toner holding amount on the developing device sleeve (developing means). There is provided a means for correcting the density gradient of the toner image 7 on the photosensitive drum 1 by changing the distribution. Specifically, the laser exposure amount is changed with an appropriate distribution using the irradiation amount control signal 32 applied to the laser beam 3.

FIG. 2 is a perspective view of an image forming section of an electrophotographic printing apparatus for explaining an embodiment of the electrophotographic density gradient correcting method according to the present invention. The laser light 3 has a function of being turned on by a laser light 27 having a high laser exposure amount in a specific area 26 of the photosensitive drum 1 and being turned on by a laser light 29 having a standard laser exposure amount in a standard area 28.

FIG. 3 is a perspective view of the image forming section for explaining the operation of the electrophotographic printing apparatus of FIG. The laser light 3 oscillated from the laser oscillator 30 is used for the lenses 3
1B, the shape and size of the photosensitive drum 1 are adjusted, and the surface of the photosensitive drum 1 is scanned by the polygon rotating mirror 31A. At this time, the output value of the laser oscillator 30 changes due to the function of the irradiation amount control signal (modulation signal) 32, and the laser light 27 is irradiated with a high laser exposure amount in the longitudinal end region 33 of the photosensitive drum 1. , Toward the center, the laser exposure gradually decreases, and
Is applied with a laser beam 29 having a standard laser exposure amount.
The surface of the photosensitive drum 1 irradiated with the laser has a strong electrostatic attraction in the end region irradiated with the high laser exposure amount by the above-described laser exposure amount control, and has a central region 34 irradiated with the standard laser exposure amount. Has a standard electrostatic attraction.

FIG. 4 shows the appearance of the developing unit 35 provided in the electrophotographic printing apparatus of FIG. The developing device sleeve (developing means) 5 should originally hold a uniform amount of toner (developer 6) in the longitudinal direction. Is reduced, and as a result, the toner image 7 formed on the photosensitive drum 1 has a density gradient at both ends and the center. By grasping in advance the amount of density reduction at the end with respect to the center and increasing the laser exposure applied to the end of the photosensitive drum 1 to an appropriate value, the electrostatic attraction at the end of the photosensitive drum 1 increases, and Can be applied, and as a result, the density gradient on the print image surface can be reduced.

The first embodiment can be summarized as follows.
The irradiation amount control signal (corresponding to the density gradient of the toner image 7 on the photosensitive drum 1 which is mainly caused by the non-uniformity of the toner holding amount on the developing device sleeve (developing means) 5 which may occur due to the structural reason 5) The density gradient of the toner image 7 on the photosensitive drum 1 can be corrected by changing the laser irradiation amount with an appropriate distribution using the modulation signal 32. As a result, there is an effect that a beautiful image having no density gradient can be expressed on a print image.

(Second Embodiment) FIG. 5 is a perspective view of an image forming section for explaining an electrophotographic printing apparatus which is a second embodiment of the image forming apparatus for executing the electrophotographic density gradient correction method of the present invention. FIG. The image forming apparatus according to the second embodiment includes:
An apparatus using an electrophotographic process including a laser exposure process for performing exposure while scanning the surface of the photosensitive drum 1 with a laser beam 3, comprising: a charging unit (charging unit 2);
Exposure means (laser oscillator 30, polygonal rotating mirror 31)
A, lenses 31B, irradiation amount control signal generator (not shown), optical filter 36), developing unit (developing unit sleeve 5, developer 6, developing unit 35), transfer unit (transfer unit 8), cleaning unit (Cleaning blade 1
0), a static elimination means (static elimination lamp 12). The charging unit charges the surface of the photosensitive drum 1 to a predetermined surface potential.

Exposure means forms an electrostatic latent image by performing laser exposure on the charged photosensitive drum 1 while changing the irradiation amount of the laser beam 3 in accordance with the exposure location on the photosensitive drum 1. The developing unit supplies a developer to the photosensitive drum 1 on which the electrostatic latent image has been formed to form a toner image 7.

The exposure means has a means for changing the irradiation amount of the laser beam 3 in accordance with the exposure position on the photosensitive drum 1 so as to correct the density gradient of the toner image 7 on the photosensitive drum 1.

The exposure means appropriately adjusts the laser exposure amount in accordance with the density gradient of the toner image 7 on the photosensitive drum 1 which is mainly caused by the unevenness of the toner holding amount on the developing device sleeve (developing means) 5. Means for correcting the density gradient of the toner image 7 on the photosensitive drum 1 by changing the distribution in an appropriate manner. Specifically, the amount of laser exposure is changed with an appropriate distribution using the optical filter 36 having an appropriate transmittance distribution.

According to the electrophotographic density gradient correction method of this embodiment, the correction used in the electrophotographic process provided with a laser exposure process in which the surface of the photosensitive drum 1 is scanned with the laser beam 3 in the above-described image forming process. The method includes a charging step performed by a charging unit, an exposure step performed by an exposing unit, and a developing step performed by a developing unit. In the charging step, the surface of the photosensitive drum 1 is charged to a predetermined surface potential.

In the exposure step, an electrostatic latent image is formed by performing laser exposure on the charged photosensitive drum 1 while changing the irradiation amount of the laser beam 3 in accordance with the exposure location on the photosensitive drum 1.

In the developing step, a developer is supplied to the photosensitive drum 1 on which the electrostatic latent image has been formed to form a toner image 7.

The exposing step includes a step of changing the irradiation amount of the laser beam 3 in accordance with the exposure position on the photosensitive drum 1 so as to correct the density gradient of the toner image 7 on the photosensitive drum 1.

In the exposure step, the laser exposure amount is appropriately adjusted according to the density gradient of the toner image 7 on the photosensitive drum 1 which is mainly caused by the unevenness of the toner holding amount on the developing device sleeve (developing means) 5. The density gradient of the toner image 7 on the photosensitive drum 1 is corrected by changing the distribution. Specifically, the amount of laser exposure is changed with an appropriate distribution using the optical filter 36 having an appropriate transmittance distribution.

That is, instead of the irradiation amount control signal (modulation signal) 32 used in the first embodiment, the transmittance at both ends is 100% at a position just before irradiation to the photosensitive drum 1.
The optical filter 36 having an appropriate transmittance distribution characteristic is arranged such that the transmittance is attenuated toward the center. The laser oscillator is designed so that the laser light 29 attenuated by the optical filter 36 has a standard electrostatic attraction near the center of the photosensitive drum 1 and the laser light 27 with the laser exposure amount which is not attenuated has a strong electrostatic attraction at both ends. The output value of 30 and the attenuation rate distribution of the optical filter 36 are adjusted. This makes it possible to realize a dose distribution without performing output control of the laser oscillator 30 by the dose control signal (modulation signal) 32.

The second embodiment is summarized as follows.
5 has an appropriate transmittance distribution corresponding to the density gradient of the toner image 7 on the photosensitive drum 1 which is mainly caused by the unevenness of the toner holding amount on the developing device sleeve (developing means) 5 which may occur due to the structural reason. By causing the laser exposure to tilt using the optical filter 36, the density gradient of the toner image 7 on the photosensitive drum 1 can be corrected. As a result, there is an effect that a beautiful image having no density gradient can be expressed on a print image.

In the present embodiment, the present invention is not limited to an electrophotographic printing apparatus, but may be applied to an electrophotographic facsimile, an electrophotographic copying machine, and the like suitable for applying the present invention. it can. Further, the number, position, shape, and the like of the constituent members are not limited to the above-described embodiment, and can be set to numbers, positions, shapes, and the like suitable for carrying out the present invention. In each drawing, the same components are denoted by the same reference numerals.

[0036]

According to the present invention, the laser irradiation is performed in accordance with the density gradient of the toner image on the photosensitive drum which is mainly caused by the non-uniformity of the toner holding amount on the developing device sleeve which may occur due to the structural reason of the developing device. By changing the amount with an appropriate distribution, the density gradient of the toner image on the photosensitive drum can be corrected. As a result, there is an effect that a beautiful image having no density gradient can be expressed on a print image.

Further, an appropriate transmittance distribution can be obtained in accordance with the density gradient of the toner image on the photosensitive drum, which is mainly caused by the non-uniformity of the toner holding amount on the developing device sleeve, which may occur due to the structure of the developing device. By generating an inclination in laser exposure using an optical filter, the inclination of the density of the toner image on the photosensitive drum can be corrected. As a result, there is an effect that a beautiful image having no density gradient can be expressed on a print image.

[Brief description of the drawings]

FIG. 1 shows an image forming process of an electrophotographic printing apparatus which is a first embodiment of an image forming apparatus that executes an electrophotographic density gradient correction method of the present invention.

FIG. 2 is a perspective view of an image forming unit of an electrophotographic printing apparatus for describing an embodiment of an electrophotographic density gradient correction method according to the present invention.

FIG. 3 is a perspective view of an image forming unit for explaining an operation of the electrophotographic printing apparatus of FIG. 1;

FIG. 4 shows an appearance of a developing unit 35 provided in the electrophotographic printing apparatus of FIG.

FIG. 5 is a perspective view of an image forming unit for explaining an electrophotographic printing apparatus which is a second embodiment of the image forming apparatus that executes the electrophotographic density gradient correction method of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum 2 charging unit (charging means) 3 laser light 4 electrostatic latent image 5 developing device sleeve (developing means) 6 developer (developing means) 7 toner image 8 transfer unit (transfer means) 9) Paper 10 ... Cleaning blade (cleaning means) 11 ... Residual toner image 12 ... Static elimination lamp (static elimination means) 13 ... Residual electrostatic latent image 24 ... Rotation direction 26 ... Specific area of photosensitive drum 27 ... High laser exposure Laser light 28 ... Standard area 29 ... Laser light of standard laser exposure amount 30 ... Laser oscillator (exposure means) 31A ... Polygon rotating mirror (exposure means) 31B ... Lens (exposure means) 32 ... Irradiation amount control signal (exposure) 33) Longitudinal end region 34 Central region 35 Developing device (developing device) 36 Optical filter (exposure device)

Claims (10)

[Claims] 1. An electrophotographic density gradient correction method used in an electrophotographic process including a laser exposure process for performing exposure while scanning the surface of a photosensitive drum with a laser beam, wherein the surface of the photosensitive drum has a predetermined surface potential. And an exposure step of forming an electrostatic latent image by performing laser exposure on the charged photosensitive drum while changing the irradiation amount of the laser light according to an exposure location on the photosensitive drum. And a developing step of supplying a developer to the photosensitive drum on which the electrostatic latent image is formed to form a toner image. 2. The method according to claim 1, wherein the exposing step includes a step of changing an irradiation amount of the laser beam in accordance with an exposure position on the photosensitive drum so as to correct a density gradient of a toner image on the photosensitive drum. 2. The electrophotographic density gradient correction method according to claim 1, wherein: 3. The method according to claim 1, wherein the exposing step changes the laser exposure amount with an appropriate distribution according to a density gradient of the toner image on the photosensitive drum, which is mainly caused by unevenness of the toner holding amount on the developing device sleeve. 2. The method according to claim 1, wherein the density gradient of the toner image on the photosensitive drum is corrected. 4. The method according to claim 1, wherein in the exposing step, the laser exposure amount is changed with an appropriate distribution using an irradiation amount control signal applied to the laser beam. The described electrophotographic density gradient correction method. 5. The method according to claim 1, wherein in the exposing step, the laser exposure amount is changed with an appropriate distribution by using an optical filter having an appropriate transmittance distribution. Electrophotographic density gradient correction method. 6. An image forming apparatus using an electrophotographic process including a laser exposure process for performing exposure while scanning the surface of a photosensitive drum with a laser beam, wherein the surface of the photosensitive drum is charged to a predetermined surface potential. A charging unit, an exposure unit configured to perform laser exposure on the charged photosensitive drum while changing an irradiation amount of the laser beam according to an exposure location on the photosensitive drum to form an electrostatic latent image; An image forming apparatus, comprising: developing means for supplying a developer to the photosensitive drum on which an electrostatic latent image is formed to form a toner image. 7. The exposure device according to claim 1, wherein the exposure unit includes a unit that changes an irradiation amount of the laser light according to an exposure location on the photosensitive drum so as to correct a density gradient of a toner image on the photosensitive drum. The image forming apparatus according to claim 6. 8. The exposure means changes the laser exposure amount with an appropriate distribution in accordance with a density gradient of a toner image on the photosensitive drum which is mainly caused by unevenness of a toner holding amount on a developing device sleeve. The image forming apparatus according to claim 6, further comprising a unit configured to correct a density gradient of the toner image on the photosensitive drum. 9. The method according to claim 6, wherein the exposure unit changes the laser exposure amount with an appropriate distribution using an irradiation amount control signal applied to the laser beam. The image forming apparatus as described in the above. 10. The apparatus according to claim 6, wherein the exposure unit changes the laser exposure amount with an appropriate distribution using an optical filter having an appropriate transmittance distribution. Image forming device.