JPS6358482A - Electrophotographic copying method - Google Patents

Abstract

PURPOSE:To obtain sharp copied images without generating fogging, etc., in the copied images of the 2nd and subsequent sheets even in the case of retention copying by projecting light onto a photosensitive body through transfer paper right after the start of the peeling of the transfer paper transferred with the image from the photosensitive body. CONSTITUTION:The light is projected onto the surface of the photosensitive body 1 through the transfer paper 9 by an eraser 5 upon the transfer right after the start of the peeling of the transfer paper from the photosensitive body 1 after the end of the copying stage. More specifically, only the background part of the photosensitive body 1 surface is irradiated with the light. The potential in the background part electrically charged by the peeling discharge is thus decreased to the developing bias potential or below by the projection of the light with the eraser 5 after the transfer. The disturbance in the electrostatic latent image by the peeling discharge is thereby cancelled at every end of the respective transfer stages; therefore, the sharp copied images are obtd. without generating the fogging, etc, even in the copied images of the 2nd and ensuing sheets.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to an electrophotographic copying method, more specifically a single latent image multiple copying method (hereinafter referred to as " The present invention relates to an electrophotographic copying method (referred to as "retention copying").

[Prior Art] Electrophotographic copying methods using retention copying have been known. In this copying method, a static 1f image is placed on the surface of the photoreceptor.
An electrostatic latent image formation process to form a fi latent image, a development process to develop the electrostatic latent image, a transfer process to transfer the image obtained in the development process to transfer paper, and the development process and transfer process are repeated in sequence. Each step is performed one or more times.

[Problems to be Solved by the Invention] Generally, in an electrophotographic copying process, when a transfer paper, which is a copy of a toner image formed on a photoreceptor and transferred to a transfer paper, is peeled off from the photoreceptor, the photoreceptor and the transfer paper are It is known that a peeling discharge occurs between the two. This peeling discharge occurs because the gap between the transfer paper and the photoreceptor widens, and the potential difference therebetween sharply increases due to a decrease in capacitance.

When this peeling discharge occurs, the electrostatic latent image formed on the surface of the photoreceptor is disturbed. If this latent image disturbance is extreme, it causes disturbance in the image area, but even if it is not so, it causes disturbance in the back shadow area (which is prone to discharge because the potential is lower than the image area).

In the case of the usual one-latent-image-one-sheet copying method, since an electrostatic latent image is formed for each transfer, it is not necessary to take into account the disturbance of one electrostatic latent image due to peeling discharge. However, in the case of retention copying, there is a problem in that the rise in potential at the background portion appears as a fog in the second and subsequent copies, resulting in significant deterioration of the copied images.

The present invention solves the above-mentioned problems, and provides an electrophotographic copying method that can obtain clear copied images without causing fogging or the like in the second and subsequent copied images even when using retention copying. The purpose is to

[Means for Solving the Problems] The electrophotographic copying method of the present invention is characterized in that a static image is formed on the surface of a photoreceptor. Ti
The electrostatic latent image formation process to form a latent image, the development process to develop the electrostatic latent image, the transfer process to transfer the image obtained in the development process to transfer paper, and the development process and transfer process are roughly operated sequentially. In an electrophotographic copying method that includes the steps of turning the image and transferring the image one or more times, immediately after the transfer paper on which the image has been transferred starts to peel off from the photoreceptor, light is irradiated onto the photoreceptor through the transfer paper to charge the surface of the photoreceptor by peeling. The present invention is characterized in that it includes a peeling charge removal step of removing electricity from a portion corresponding to the portion not transferred to the transfer paper.

The peeling charge elimination process that characterizes the present invention is to eliminate the potential of the back shadow portion of the photoreceptor surface, which has been charged by peeling discharge, by irradiating it with light.

That is, after the transfer process, immediately after the transfer paper is peeled off from the photoreceptor surface, the charge is selectively removed by irradiating light through the transfer paper. In this case, immediately after the transfer paper is peeled off,
The toner image on the transfer paper and the image area on the photoreceptor are located at substantially corresponding positions. Also, the light transmittance is different between the toner image part and the non-toner image part of the transfer paper, and the light transmittance in the toner layer is 5%.
That's about it. Therefore, the charge in the back shadow area is removed without substantially lowering the potential of the image area on the surface of the photoreceptor.

As the light irradiation means in this case, for example, a tungsten lamp, a light emitting diode, etc. can be used.

Further, the light irradiation can also be carried out by detecting the light transmittance of each transfer paper before transferring, and irradiating the surface of the photoreceptor with an appropriate amount of light depending on the light transmittance.

In the electrophotographic copying method of the present invention, conventional electrostatic latent image forming steps, developing steps, and transfer steps can be applied as they are.

[Operations and Effects of the Invention] In the electrophotographic copying method of the present invention, an electrostatic m-image forming step, a developing step, a transfer step, and a peeling charge removal step are sequentially performed during one rotation of the photoreceptor. Then, the photoreceptor continues to rotate roughly a predetermined number of times, and the development process, transfer process, and peeling/charging/discharging process are sequentially repeated for each rotation. At this time, in the peel-off charge elimination step, immediately after the transfer paper starts peeling off from the photoreceptor, light is irradiated through the transfer paper to eliminate static on the back shadow portion of the photoreceptor surface that is charged by peel-off discharge. Therefore, even in the second and subsequent copies, clear copied images can be obtained without causing inconveniences such as fogging.

[Example] Hereinafter, specific embodiments of the present invention will be described based on the drawings.

(Example 1) FIG. 1 is a schematic diagram of an apparatus related to the copying method of Example 1, and FIG. 2 is a schematic diagram of its main parts. This device includes a drum-shaped photoreceptor 1, a charger 2, and a developing device 3, which are arranged in the following order facing the surface of the photoreceptor.
, a transfer charger 4, a post-transfer eraser 5, a separation charger 6, a cleaner 7, and an eraser lamp 8.

The photoreceptor 1 is an organic photoreceptor with a diameter of 80 mm,
An electrostatic latent image is sequentially formed on this surface by an exposure device (not shown). This photoreceptor 1 is rotationally driven in the direction of arrow (a) in the figure (counterclockwise direction).

The charger 2 is placed above the photoreceptor and applies a predetermined charge onto the surface of the photoreceptor 1.

The developing device 3 is of a magnetic brush type.

That is, a charge of opposite polarity to the charge charged on the surface of the photoconductor 1 is applied to the powder toner, and this toner is sequentially attached to the electrostatic latent image portion on the surface of the rotating photoconductor 1, and is developed as a toner image. do.

The transfer static elimination charger 4 is disposed toward a portion where the transfer paper 9 that is sent to the surface of the photoreceptor 1 comes into contact with the photoreceptor 1 .

This transfer static elimination charger 4 may be a normal DC corotron, but an AC scorotron as shown in FIG. 2 is preferable. This AC sufrotron divides the grid electrode into two parts near the starting point B of approximately 111 m, and the upstream side applies an electric charge to the transfer paper 9 via the transfer grid 4a with the opposite polarity to the toner, and transfers the toner image to the transfer paper 9. to be transcribed. On the downstream side, a static eliminating grid 5a applies a voltage of the same polarity as the toner, 0, or the opposite polarity and smaller in absolute value than the 7T copying grid 4a.

The post-transfer eraser 5 is placed toward a position immediately after passing a peeling start point B where the transfer paper 9 peels off from the photoreceptor 1.

Note that the eraser 5 after transfer is 1 to 1.5 liters on the photoreceptor 1.
A device with ux-sea irradiation ability is used.

The separation charger 6 is arranged adjacent to the transfer static elimination charger 4. This separation charger 6 separates the transferred transfer paper 9 from the photoreceptor 1.

The cleaner 7 is of a blade type and removes toner remaining on the surface of the photoreceptor after the transfer process.

The eraser lamp 8 erases the electrostatic latent image formed on the surface of the photoreceptor 1, and is activated after a predetermined number of transfer steps are completed.

The apparatus according to the copying method of this embodiment is configured as described above. Note that the transfer paper 9 is provided in a paper feed cassette (not shown).
The route shown by the two-dot chain line in the figure is indicated by the arrow (b).
conveyed in the direction.

Next, each process in which retention copying is performed by the above-mentioned apparatus will be explained in order.

In the electrostatic latent image forming step, first, the photoconductor 1 is rotated at a constant speed in the direction of the arrow (a), and the electrostatic charge core 2 is rotated in the direction of the arrow (a).
A charge of -600V is applied. Next, an exposure device continuously exposes the image in a slit shape from the direction of arrow (A) to form an electrostatic latent image.

In the developing step, first, the developing device 3 applies charges to the toner having the opposite polarity to the charges charged on the surface of the photoreceptor 1. Then, the toner is electrically attached to the electrostatic latent image on the surface of the photoreceptor 1. As a result, the static 1i latent image appears as a toner image.

In the transfer process, the toner image on the surface of the photoreceptor 1 is sequentially transferred by the transfer static elimination charger 4 to the transfer paper 9 conveyed from the paper feed cassette onto the surface of the rotating photoreceptor 1. The transfer static elimination charger 4 applies a charge having the opposite polarity to the charge applied to the toner to the transfer paper 9, thereby attracting the toner to the transfer paper 9, thereby transferring a toner image onto the transfer paper 9.

Then, the transfer paper 9 on which the toner image has been transferred is sequentially separated from the photoreceptor 1 by the static eliminating section of the transfer static eliminating charger 4 and the separation charge cell. At this time, as shown in FIGS. 4 and 5, peel! 1Iit11. The electric charge moves from the transfer paper 9 to the surface of the photoreceptor 1. As a result, the potential of the back shadow portion on the surface of the photoreceptor 1 becomes about -300 to -350V, and increases to a developing bias potential (-200V> or more).

In the peeling static electricity removal process, immediately after the transfer paper 9 passes the peeling start point (B) where it peels off from the photoreceptor 1 after the transfer process, light is irradiated by the transfer eraser 5 onto the surface of the photoreceptor 1 through the transfer paper 9. carried out by FIG. 6 shows the change in potential at this time. This transfer pattern eraser 5 is irradiated onto the photoreceptor 1 at 1 to 1.51 ux-sec. As a result, as shown in the bright decay curve of the organic photoreceptor in FIG. 7, when the potential of the back shadow area after peeling discharge is -300 to -350 V, it can be made lower than the developing bias potential (-200 V).

On the other hand, the irradiation m of the image area is about 0.05 to 0.11 uX -SeC due to light being absorbed by the toner image area of the transfer paper 9, and the potential drop due to this is 20 to 30 V, which has almost no effect and is not a problem. It won't happen. By this light irradiation,
The back shadow area is neutralized to a potential below the development bias potential,
The state is approximately the same as before the first development step and transfer step are performed.

Note that the transfer paper 9 separated from the photoreceptor 1 is conveyed to a fixing device (not shown).

After the stripping and static electricity removal process is completed, the photoreceptor 1 is removed by the cleaner 7.
Any residual toner on the surface is removed. The photoreceptor 1 continues to rotate with the eraser lamp 8, the charger 2, and the exposure device turned off, and the development process, transfer process, and peeling/discharging process are repeated in order to continue retention copying. After a predetermined number of transfer steps are completed, the eraser lamp 8 is turned on, and the electrostatic latent images formed on the surface of the photoreceptor 1 are sequentially erased, thereby completing the entire process of retention copying.

In the first embodiment, immediately after the transfer paper starts peeling off from the photoreceptor 1 after the transfer process, the post-transfer eraser 5 irradiates light onto the surface of the photoreceptor 1 through the transfer paper 9. That is, only the back shadow portion of the surface of the photoreceptor 1 is selectively irradiated with light.

Thereby, by light irradiation with the post-transfer eraser 5, the potential of the back shadow portion charged by peeling discharge can be lowered to below the development bias potential. Therefore, after each transfer process, the disturbance of the electrostatic latent image due to peeling discharge is canceled,
Even in the second and subsequent copies, clear copies can be obtained without fogging or the like.

(Example 2) A schematic diagram of an apparatus related to the copying method of Example 2 is shown in FIG. This device is the same as the device of Embodiment 1 above, and also has a transfer paper 1.
A light emitting element 21 for detecting a light transmittance of 9, a light receiving element 22, and a control section 23 are provided. This light emitting element 21
The light-receiving element 22 is placed on the transfer paper conveyance path from the transfer paper cassette (not shown) to the transfer position of the photoreceptor 11.
They are arranged so that the transfer paper 19 is sandwiched between both sides. il
The l111 section 23 is electrically connected to the light receiving element 22 and the post-transfer eraser 15. This t(J 101 section 23 calculates the post-transfer eraser 15 based on the light transmittance of each transfer paper 19 detected by the light emitting element 21 and the light receiving element 22.
When the irradiation light passes through each transfer paper 19 and is irradiated onto the surface of the photoreceptor 11, the amount of irradiation is controlled to be approximately constant.

The device according to the second embodiment configured as described above is as follows:
Retention copying is performed in the same manner as in the first embodiment.

However, in this case, the post-transfer eraser 15 is irradiated with light in accordance with the light transmittance of the transfer paper 19 in the peel-off and charge removal process after the electrostatic 1ltfil formation process, development process, and transfer process. Therefore, i! III
Moderate illumination 0 made by III tlO by 111 part 23
1! I is irradiated. By this light irradiation, the potential of the back shadow portion on the surface of the photoreceptor 11 can be lowered to a substantially constant potential below the development bias potential even if the potential increases due to peeling discharge. In the further repeated development process and peel-off charge removal process after the transfer process, the post-transfer eraser 15 applies an appropriate amount of irradiation depending on the light transmittance of each transfer paper. Therefore, the disturbance of the electrostatic latent image on the photoreceptor 11 is canceled even in the second and subsequent development steps and transfer steps. Therefore, even if the type of transfer paper is different, a good copy image can always be obtained.

Note that if the transfer paper is thick paper or the like and has extremely poor light transmittance, the retention copying mode can be canceled and the normal one-latent-image one-sheet copying mode can be set.

[Brief explanation of the drawing]

1 to 2 are diagrams showing an apparatus related to the copying method of Example 1, FIG. 1 is a schematic diagram thereof, FIG. 2 is a schematic diagram of the main part of FIG. 1, and FIG. 3 is an embodiment. 4 to 6 are diagrams showing the potential movement between the transfer material and the photoconductor due to peeling discharge and light irradiation, and FIG. 4 shows the transfer area. FIG. 5 is a diagram immediately after the beginning of minute #J, FIG. 6 is a diagram at the time of light irradiation, and FIG. 7 is a diagram showing the bright decay curve of the organic photoreceptor. 1.11... Photoreceptor 2.12... Charger 3.13... Developing device 4.14... Transfer neutralization charger 4a... Transfer grid 5.15... Post-transfer eraser 5a ... Static elimination grid 6.16 ... Separation charger 7.17 ... Cleaner 8.18 ... Eraser lamp 9.19 ... Transfer paper 21 ... Light emitting element 22 ... Light receiving element 23・・・υノomibe Patent Applicant Minolta Camera Co., Ltd. Figure 1 Figure 7 Dew 9 (juX-5ec)

Claims (3)

[Claims] (1) An electrostatic latent image forming step to form an electrostatic latent image on the surface of the photoreceptor, a developing step to develop the electrostatic latent image, and a transfer step to transfer the image obtained in the developing step to transfer paper. In an electrophotographic copying method further comprising the steps of sequentially repeating the developing step and the transferring step one or more times each, the transferring step is performed immediately after the transfer paper to which the image has been transferred starts peeling off from the photoreceptor. An electrophotographic copying method comprising a peel-off charge elimination step of irradiating light onto the photoreceptor through paper to eliminate charge on a portion of the surface of the photoreceptor that corresponds to a portion that was not transferred to the transfer paper during peel-off charge. . (2) The light irradiation is performed by detecting the light transmittance of each transfer paper before the image is transferred to each transfer paper, and controlling the amount of light irradiation based on the light transmittance. Electrophotographic copying method. (3) The amount of irradiation is controlled based on the light transmittance of the transfer paper detected by light-emitting elements and light-receiving elements arranged on both sides of the conveyance path of the transfer paper sent onto the photoreceptor. The electrophotographic copying method according to scope 2.