JPS63109461A - Image forming device - Google Patents

Abstract

PURPOSE:To suppress the dispersion of toner and to prevent the adhesion of toner to a dust preventing glass and other parts in a device by arranging an electrode member on the photosensitive periphery of a photosensitive body and impressing voltage to the member to form an electric field between the member and the surface of the photosensitive body. CONSTITUTION:A resin-made slit member 10 having an exposing slit 14 is arranged over a range from the lower part of the image exposing device 6 up to the front part of a developing sleeve 15 with several mm separation from the surface of the photosensitive body 15 along a curved face and an electrode 11 is formed by applying conductive paint to the photosensitive body side face of the slit member 10. When a voltage is impressed to the electrode 11, an electric field is generated between the electrode 11 and the surface of the photosensitive body 15. Consequently, toner dispersion can be prevented and the inside of the device can be prevented from dirt.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image forming apparatus that superimposes color toner images on a photoconductor to form a multicolor toner image, and then transfers the multicolor toner image to a transfer material. The present invention relates to a means for preventing a phenomenon in which when a latent image is formed by imagewise exposure, toner of a toner image previously formed on a photoreceptor is scattered due to the influence of an electric field.

(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.

(Problems with the Prior Art) As described above, in the multiple toner image forming process in which charging, exposure, and development are repeated many times, after the toner image formed in the first process is charged, the vicinity of the image is exposed to light. If this occurs, the electric field distribution near the image changes rapidly, and the toner scatters due to the repulsive force between the toner particles and adheres to the area where the Coulomb force acts. This tendency is particularly pronounced in the case of reversal development.

FIG. 3 is an explanatory diagram of causes of toner scattering.

The vertical axis in FIGS. 3(a) to 3(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 part is close to O 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 photoreceptor surface mainly due to Coulomb force and van der Waals force acting between it and the photoreceptor, but the toner particles are charged with the same polarity between each other. Therefore, electrical repulsion is acting. 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 higher potential along the direction of the electric field formed there. When this force for movement becomes large enough, the toner will fly out in the direction of higher potential. Figure (f>) is a situation diagram in which a part of the toner adhering to the area where the potential is -E volts tries to move to the area L' where the potential is close to 0 volts and scatters.

In this way, when a latent image is formed by image exposure on a photoreceptor on which a toner image has previously been formed, the toner adhesion becomes unstable due to changes in the electric field due to the latent image, and some of the toner may scatter. Become.

FIG. 4 is a diagram showing the state of toner scattering in the image forming apparatus. When the surface of the photoreceptor 5 on which a toner image is formed is exposed to the laser beam 3, toner adhesion becomes unstable and the toner 7 scatters.

This unstable state moves as the photoreceptor 5 rotates.
A portion of the toner scattered on the lower side of the image exposure device 6 adheres to the dustproof glass 4 and obstructs the transmission of laser light. In addition, the other part adheres to the frame 8 and the like, causing dirt inside the machine. Since the photoreceptor 5 rotates in this unstable state, the toner scattering is not limited to the area facing the image exposure device, but is scattered over a wide area as shown on the right side of FIG. causing internal defilement.

A possible means of collecting such scattered toner is to create an air flow within the device and suck the toner.
This method requires ducts, fans, and filters, which increases the size of the device and increases noise.Furthermore, the above-mentioned scattered toner is not just floating toner, but scattering caused by Coulomb force, so it is not just floating toner. There is also the problem that the effect on toners is not as high as that for toners.

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an object of the present invention is to prevent toner scattering by applying a voltage around the photoreceptor surface to form an electric field between the photoreceptor surface and the photoreceptor surface, thereby preventing the toner from forming an image. It is an object of the present invention to provide an image forming apparatus that does not adhere to the dust-proof glass of an exposure device and prevent the transmission of exposure light or stain the inside of the apparatus.

(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 is an image forming apparatus that forms toner images of different colors on a photoreceptor by repeating a series of steps of uniform charging, image exposure, and development multiple times. This image forming apparatus is characterized in that an electrode member is disposed around the surface to form an electric field between the photosensitive surface and the photosensitive surface by applying a voltage.

(Function) Hereinafter, the function of the image forming apparatus of the present invention having the above configuration will be described.

In the image forming apparatus of the present invention, an electrode member that can form an electric field between the electrode member and the photoreceptor surface is provided around the photoreceptor surface of the photoreceptor. Therefore, by applying a DC voltage to this electrode member, a DC electric field can be formed between it and the surface of the photoreceptor.

The charged toner receives an electric force from this DC electric field. The direction of this force is the direction of the electric field if the toner is positively charged, and the direction opposite to the electric field if the toner is negatively charged.

The charged toner on the photoreceptor is generated by a combination of the electric field formed between this electric field forming member and the photoreceptor, the electric field generated by the distribution of the charged toner itself, and the electric field due to the mirror image effect due to the presence of a conductor on the photoreceptor. The force from the electric field and the van der Waals force that tries to attract the toner to the photoreceptor act.

Therefore, whether the force of the electric field to direct the toner from the photoconductor toward the electric field forming member is smaller than the van der Waals force, or
If the direction directs the toner toward the photoreceptor, toner scattering can be suppressed, and even once scattered toner can be prevented from reaching the image exposure device. For example, if the charging polarity of the toner is negative, the toner receives electric force toward the higher potential, so the voltage that makes the potential of the photoreceptor higher is the voltage of the electrode member. It is better to apply a voltage such that the potential is lower than the potential of the photoreceptor.

Furthermore, since there is adsorption power due to van der Waals force,
As long as the potential is lower than the potential point higher than the potential of the photoreceptor by an amount corresponding to this adsorption force, toner scattering prevention is effective.

On the other hand, when the toner has positive charge polarity, the toner receives electric force in the direction of lower potential. It is better to apply a voltage that is higher than the potential of the body.

Further, in this case as well, toner scattering can be prevented as long as the potential is higher than the potential point lower than the potential of the photoreceptor by an amount corresponding to the adsorption force due to van der Waals force.

Specifically, the optimum voltage will be determined depending on the shape of the electric field forming member, the position where it is provided, etc.

(Example) Hereinafter, an example of the image forming apparatus of the present invention will be described based on the drawings.

FIG. 1 is a diagram showing the configuration of the main parts of a first embodiment of the present invention. A resin slit member 10 provided with an exposure slit 14 is inserted into the developing sleeve 15 from the lower part of the image exposure device 6.
The front portion of the photoreceptor 5 is provided along a curved surface at a distance from the surface of the photoreceptor 5 by several distances. The electric field is formed by applying conductive paint to the surface of the resin slit member 10 on the photoreceptor 5 side. A voltage having the same polarity as the surface potential of the photoreceptor 5 and having a similar absolute value or a larger voltage is applied to the electrode 11 . This suppresses the scattering of toner on the surface of the photoreceptor, and when the absolute value of the potential is large, a force acts on the scattered toner to push it back toward the photoreceptor. Further, by increasing the distance between the surface of the photoreceptor 5 and the electrode to a certain extent, there is an effect that the scattered toner is difficult to reach the electrode due to air resistance.

Furthermore, since the electrode members are disposed one after the other in the range from the image exposure area to the front of the developing device, scattering is suppressed in all areas where toner is scattered due to exposure, and the interior of the machine is also prevented from becoming dirty in that area.

Furthermore, since the electrode member is arranged along the curved surface of the photoreceptor surface, changes in conditions related to toner scattering, such as electric fields and air currents, can occur over a range from the image exposure area to the front of the developing device. It is small and can exhibit stable toner scattering prevention ability.

The slit member 10 is made of resin, which has the advantages of being easy to mold, lightweight, and inexpensive. In this example, the distance between the electrode 11 and the photoconductor 5 is set to 5, the voltage applied to the electrode 11 is -500V for the photoconductor charging potential of -470V, and the linear velocity of the photoconductor is 70 m+a.
/ set to form images using the reversal development method, there were white streaks up to 1000 copies (if toner adhered to the dust-proof glass, the laser light would not pass through that area, so the photoconductor would not be exposed, and therefore the toner would not be exposed even after development). When the present invention was not applied, the result was that the phenomenon in which the white part did not adhere and the white part appeared in the form of a line did not appear.
Since white streaks appear at the copying level, a significant improvement can be obtained. In addition, contamination inside the device was significantly reduced.

FIG. 2 is a diagram showing the configuration of the main parts of a second embodiment of the present invention. The difference from the example shown in FIG.
A groove 13 is provided in the slit member 10' to create a mounting structure that can slide in the vertical direction of the paper surface of the figure, and an electrode 11' is provided on the surface (back surface) of the resin slit member 10' opposite to the photoreceptor 5. It is a point. The sliding structure makes it easy to attach and detach from the front of the device, improving maintainability.

Further, since the electrode 11' is provided on the back side, the photoreceptor 5
This eliminates the risk of coming into contact with high voltage during maintenance work after removing the battery, improving safety.

Furthermore, in the slit 14 portion, since the electrode 11' is provided at the back of the slit, that is, closer to the dustproof glass 4, the scattered toner is less likely to reach the dustproof glass 4 compared to the example shown in FIG. Results are being obtained. When image formation was carried out with the voltage applied to the electrode 11' ranging from 1400 V to -600 V and other conditions set as in the first embodiment, it was found that white sushi did not appear until 5000 copies were made. Obtained. Further, contamination inside the device was significantly reduced as in the first example.

(Effects of the Invention) As described above, the image forming apparatus of the present invention provides an electrode member around the photoreceptor surface of the photoreceptor, applies a voltage to the electrode member, and connects the electrode member to the photoreceptor surface. An electric field is created that exerts a force that suppresses toner scattering of the toner image formed on the toner image or pushes the scattered toner back toward the photoreceptor. It is possible to prevent toner from adhering to other parts of the apparatus, and as a result, there are advantages in that it is possible to prevent uneven exposure such as white smudges, and it is also possible to prevent staining inside the apparatus.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of the main part of the first embodiment of the present invention, FIG. 2 is a diagram showing the configuration of the main part of the second embodiment of the invention, and FIG. 3 is the cause of toner scattering. The explanatory diagram, FIG. 4, is a diagram showing the state of toner scattering. 1... Charger, 2... Mirror,
3... Laser light, 4... Dust-proof glass, 5... Photoreceptor, 6... Image exposure device, 7... Toner, 8...Frame body,
10.10'...Resin slit member, 11.
11'... Electrode, 12... Rail,
13...Groove, 14...Slit,
15...Developing sleeve, 16...
Insulating material. Agent: Yoshihiro Yahata, Patent Attorney / Figure 3

Claims (5)

[Claims] (1) An image forming apparatus that forms toner images of different colors on a photoconductor by repeating a series of steps of uniform charging, image exposure, and development multiple times, and applies voltage around the photoconductor surface of the photoconductor. An image forming apparatus characterized in that an electrode member is disposed to form an electric field between the image forming apparatus and the photosensitive surface. (2) The image forming apparatus according to claim (1), wherein development is performed by a reversal development method. (3) Claim (1) characterized in that the voltage applied to the electrode member has the same polarity as the uniformly charged polarity of the photoreceptor, and the absolute value is the same as or larger than the uniformly charged potential. or (2). (4) According to any one of claims (1) to (3), wherein the electrode member is disposed over a range from the image exposure area to the front of the developing device. image forming device. (5) An image forming apparatus characterized in that the electrode member is arranged along the curved surface of the photoreceptor surface.