JPS63172179A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent scattering of a toner and sticking of the scattered toner to dustproof glass by arranging plural electric field generating electrodes along an optical path between the dustproof glass of an image exposure device and a photosensitive body. CONSTITUTION:Two electrodes provided with slits in optical path parts are provided between the image exposure device and the photosensitive body in an image forming device. An electric field stronger than that between a first electrode 11 and the photosensitive body is generated in the left part of the first electrode corresponding to the aperture part of a slit 14. That is, the electric field generated between the first electrode and a second electrode 10 and that between a photosensitive body 5 and the second electrode are synthesized to obtain the electric field stronger than that for the absence of the second electrode. Since the electric field is especially strong in the aperture part of the slit and in the vicinity under this part, the scattered toner is satisfactorily prevented from penetrating the slit. Thus, an image of high quality which is free from reduction of the exposure and unevenness of exposure is formed because the toner is prevented from sticking to the dustproof glass.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention forms a multicolor toner image on the surface of a photoreceptor by repeating a series of steps of uniform charging, image exposure, and development multiple times on the photoreceptor. The purpose of the present invention is to improve a means for preventing scattering of toner caused by image exposure of the second and subsequent colors in an image forming apparatus and preventing the scattered toner from adhering to the dust-proof glass of the image exposing apparatus.

(Prior Art) In an image forming apparatus that repeats the steps of uniform charging, image exposure, and development multiple times on a photoconductor to form multiple color toner images in a layered manner, and transfers this to a transfer material, The surface of the photoreceptor, which has been subjected to color development, is uniformly charged again by a charger, and then image exposure is performed using an image signal corresponding to the second color, and the latent image thus formed is stored in the toner of the second color. Using the developing device, a second color toner image is formed so as to be superimposed on the surface of the photoreceptor on which a first color toner image has already been formed. Thereafter, when there is a third color and a fourth color, the same process is repeated to form toner images of each color so as to overlap each other.

After a superimposed toner image of a preset color is thus formed, this is transferred to a transfer material to form a color image.

As mentioned above, in the multiple toner image forming process in which charging, exposure, and development are repeated many times, if the toner image formed in the first process is charged and then exposed to light, the electric field near the image Because the distribution changes rapidly, the toner scatters due to the repulsive force between the toner particles and adheres to areas where Coulomb force is applied. This tendency is particularly noticeable in the case of reversal development.

FIG. 5 is an explanatory diagram of causes of toner scattering.

The vertical axis in FIGS. 5(a) to 5(e) indicates the negative potential of the surface of the photoreceptor. In the following description, uniform charging is assumed to be negative charging. ), and the horizontal axis indicates the position of the surface of the photoreceptor. Figure (a) shows a state in which the surface of the photoreceptor is uniformly charged to a potential of -E volts by a charger.

Figure (b) shows that the area of the photoreceptor shown is exposed and the potential of that area becomes close to 0 volts. Figure (c) shows that the exposed area of the photoreceptor is exposed to the developing device. When passing, negatively charged toner from the developing sleeve, which has approximately the same potential as the uniformly charged potential of the photoconductor, flies toward the exposed area of the photoconductor, adheres to the exposed area, and is developed. The surface of the photoreceptor on which the first color toner image is thus formed is uniformly charged for the second time by a charger while the toner image is still formed.

Figure (d) shows the potential during the second uniform charging.

Next, in Figure 0 (e), image exposure is performed using an image signal corresponding to the second color, image exposure is performed in the vicinity L' of the first color toner image, and the potential of that portion is close to 0 volts (i.e., (The potential of the L' part is higher than that of the L part.)
Show that.

By the way, each toner particle of the first color toner image adheres to the surface of the photoreceptor due to Coulomb force between it and the photoreceptor, but since the toner particles are charged with the same polarity, they are not electrically charged. has a repulsive force acting on it. On the other hand, since toner particles are negatively charged, if there is a location where the potential is higher than the current location, a force acts to move the toner particles toward the lower potential along the direction of the electric field formed there. If this force to move the toner is larger, the toner will fly out toward the higher potential. FIG. 2 is a diagram showing a situation where a part of the light scatters as it tries to move to a portion L where the potential is close to 0 volts.

In this way, if toner scatters when image exposure corresponding to the next color is performed on a photoconductor on which a toner image has previously been formed, some of the scattered toner will adhere to the dust-proof glass in the image exposure device. As a result, there is a problem that the transmittance of the imagewise exposure light is lowered or unevenness is caused.

FIG. 6 is a diagram showing a situation in which scattered toner adheres to the dustproof glass. That is, when the toner 7 of the toner image formed on the surface of the photoreceptor 5 is exposed to the image by the laser beam 3, a part of the toner scattered as shown in the figure is transferred to the frame 8.
or even reach the dustproof glass 4 and adhere thereto.

In this way, there is a problem in that not only the interior of the machine gets dirty, but also the toner adhering to the dustproof glass prevents the laser beam 3 from passing through.

In order to solve this problem, the inventors of the present invention sought to solve the problem in Figure 3 (a).
) and slit electrode 9' in FIG. 3(b) are provided, and an electric field forming means for preventing toner scattering is provided.
The present applicant has developed an invention that suppresses the scattering of toner due to image exposure and has an arrangement structure that makes it difficult for the scattered toner to reach the dust-proof glass.

In FIG. 3(a), a slit electrode 9 having a slit 14 is provided, and this slit electrode 9 is provided with a potential having the same polarity as the charging polarity of the photoreceptor and an absolute value of which is the same as or larger than the absolute value of the charging potential of the photoreceptor 5. By applying , an electric field is formed between the photoreceptor 5 and the surface of the photoreceptor 5 to suppress scattering of toner. This electric field suppresses toner scattering, and if a voltage whose absolute value is larger than the absolute value of the charged potential of the photoreceptor 5 is applied, the scattered toner is pulled back toward the photoreceptor 5. A force acts.

Further, since the slit 14 is a narrow passage, there is an effect that scattered toner is difficult to reach the dustproof glass 4.

FIG. 3(b) is the same as FIG. 3(a) except that the slit electrode 9' is flat.

(Problems with the prior art) In this way, electric field forming means (hereinafter referred to as
By providing a toner scattering prevention electrode), toner scattering from the photoreceptor surface can be suppressed, and once scattered toner can be returned to the photoreceptor, so when the toner scattering prevention electrode is not used. However, since no electrode is provided at the slit opening, the electric field at the slit opening is weaker than at the area where the toner scattering prevention electrode is present, as shown in FIG.
For this reason, once the toner has flown into the slit opening, there is a problem that it is not possible to sufficiently prevent the toner from entering the inside of the slit. Then, there is a problem that the oppositely charged toner adheres to the toner scattering prevention electrode or is drawn into the slit.

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an object of the present invention is to arrange a plurality of electrodes along an image exposure optical path between the dustproof glass of an image exposure device and a photoreceptor, and to set the electrodes at a predetermined potential. By setting it to It is an object of the present invention to provide an image forming apparatus capable of forming high-quality images without causing a decrease in exposure amount or uneven exposure by preventing the particles from reaching and adhering to the surface.

(Means for Solving the Problems) The present invention has the following means configuration to achieve the above object. That is, the image forming apparatus of the present invention provides the photoreceptor with the following:
An image forming apparatus that forms a multicolor toner image on the surface of a photoreceptor by repeating a series of steps of uniform charging, image exposure, and development multiple times, the optical path between the dust-proof glass of the image exposure device and the photoreceptor. This is an image forming apparatus characterized in that a plurality of electric field forming electrodes are arranged along.

(Function) In the image forming apparatus of the present invention, an image exposure optical path (hereinafter simply referred to as optical path) between the image exposure device dustproof glass and the photoreceptor is provided.
multiple electric field forming electrodes (hereinafter simply referred to as electrodes) along the
is provided, so when the photoreceptor and each of the plurality of electrodes are set to different potentials, the electric field near the optical path is equal to the electric field formed between the photoreceptor and each electrode and the electric field formed between each electrode. It becomes a composite electric field. Therefore, if the direction of the electric field between each electrode along the optical path and the direction of the electric field formed between the photoreceptor and each electrode are the same, for example, the electrode facing the photoreceptor is set as the first electrode, The electrodes provided along the optical path toward the dust-proof glass side are used as the second and third electrodes, and the potential of each electrode is lowered in the order of the first, second, and third with respect to the potential of the photoreceptor. In such cases, the direction of the electric field is almost the same, so it is possible to make the electric field near the optical path stronger than the electric field formed between the first electrode and the photoreceptor in areas other than the optical path. can. Therefore, in this case, even if negatively charged toner scatters near the optical path, the force of this electric field can sufficiently suppress the scattered toner from heading toward the dustproof glass. When the toner used is positively charged, if the potential of the first, second, and third electrodes is increased in sequence with respect to the potential of the photoreceptor, the scattered toner will be removed from the dust-proof glass as in the case described above. It is possible to sufficiently suppress the movement toward the direction of the object.

In this way, the electric field near the optical path can be strengthened without increasing the electric field strength between the first pole and the photoreceptor.
The electric field strength can be set to a level that does not cause adverse effects due to scattering of the oppositely charged toner or adhesion to the electrodes.

The strength of the electric field near the optical path can be controlled in various ways by setting the potential of each electrode, so it can be set to an appropriate strength taking various other conditions into consideration.

(Example) Hereinafter, an example of the present invention will be described based on the drawings. 1st
The figure is a configuration diagram in which two electrodes each having a slit in the optical path are provided between the image exposure device and the photoreceptor of the image forming apparatus of the present invention.

In this embodiment, the photoreceptor is charged to -470V, the first electrode is set to -600V, the second electrode is set to -1000V, and the developing toner is negatively charged.

FIG. 2 is a diagram showing the electric field near the photoreceptor and each electrode. Since the electric field is symmetrical with respect to the optical path in FIG. 1, only the space on the right side of the optical path is shown.

The curves in the figure indicate the lines of electric force, and the arrows indicate the direction of the electric field.The narrower the interval between the lines of electric force, the stronger the electric field strength. A stronger electric field is formed in the left side of the electrode than in the area between the first electrode and the photoreceptor. This is due to the combination of the electric field formed between the first electrode and the second electrode and the electric field formed between the photoreceptor and the second electrode, compared to when the second electrode is not present. This is due to the fact that a stronger electric field can be obtained.

Now, when negatively charged toner is scattered from the surface of the photoconductor due to the second and subsequent image exposures, the toner receives a force that pushes it back toward the photoconductor in the opposite direction to the arrow of the lines of electric force. . In particular, since the electric field is strong near the slit opening and its lower part, it is possible to sufficiently suppress the scattered toner from entering into the slit.

On the other hand, the strength of the electric field on the surface of the photoreceptor is
That is, in this embodiment, since the strength is not strong enough to induce scattering of positively charged toner, there is no adverse effect due to scattering of oppositely charged toner.

If you try to make the electric field near the slit opening as strong as this example using only the first electrode and the photoreceptor without using the second electrode, the potential of the first electrode will be lowered even further, for example, from -800V to -1000V. Although this is still insufficient considering the direction of the electric field, the electric field on the surface of the photoreceptor becomes stronger, causing the oppositely charged toner to scatter, causing adhesion to the first electrode. Adverse effects such as intrusion into the slit occur.

In this example, by providing the second electrode,
Without causing the above-mentioned adverse effects, it is possible to effectively prevent scattered toner from entering the slit due to imagewise exposure and further from adhering to the dust-proof glass.

(Effects of the Invention) As explained above, since the image forming apparatus of the present invention has a plurality of electric field forming electrodes along the optical path between the dustproof glass of the image exposure device and the photoreceptor, In the image exposure optical path, the strength of the electric field near the electrode facing the photoreceptor, that is, the part closest to the photoreceptor, can be made stronger than when no other electrode is present. Even if the potential difference between the electrode and the photoreceptor is not so large as to induce the scattering of oppositely charged toner, it is possible to effectively suppress the intrusion of scattered toner toward the dust-proof glass due to image exposure, and the toner adheres to the dust-proof glass. This has the advantage that it is possible to provide an image forming apparatus that can form a high-quality image without causing a decrease in exposure amount or uneven exposure.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the main components of an embodiment of the device of the present invention;
Figure 2 is an explanatory diagram of electric field formation in the embodiment of Figure 1;
The figure is a configuration diagram when only the toner scattering prevention electrode is used, Figure 4 is an illustration of electric field formation in the example of Figure 3, Figure 5 is an illustration of the cause of toner scattering, and Figure 6 is an explanation of the situation of toner scattering. It is a diagram. 1... Charger, 2... Mirror, 3
...Laser light, 4...Dust-proof glass,
5... Photoreceptor, 6... Image exposure device,
7... Toner, 8... Frame, 9.
9′...Slit electrode, 10...Second
Electrode, 11...First electrode, 12...
・Electrode holding member, 13... Insulator, 14...
····slit. Agent Patent Attorney Yoshihiro Hachiman Figure 2 (S Tsurumitsu & (-470v) Figure 3 (a) (b) Figure 4

Claims (2)

[Claims] (1) An image forming apparatus that forms a multicolor toner image on the surface of a photoreceptor by repeating a series of steps of uniform charging, image exposure, and development multiple times on the photoreceptor, the dust-proof glass of the image exposure device An image forming apparatus characterized in that a plurality of electric field forming electrodes are arranged along an optical path between a photoreceptor and a photoreceptor. (2) The image forming apparatus according to claim (1), wherein two electrodes having a slit as an optical path are arranged in the optical path direction.