JPS63109460A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the adhesion of dispersed toner based upon image exposure to a dust preventing glass by arranging an electric field forming member for forming a DC field between the member and the surface of a photosensitive body in the vicinity of an image exposing device. CONSTITUTION:A slit electrode 9 as an electric field forming means is arranged under a frame body 8 of the image exposing device 6. Voltage with the same polarity as toner is impressed to the electrode 9, and especially in case of reverse development, the voltage is set up to the same polarity as that of the surface potential of the photosensitive body and the potential level is set up to the same or more as the surface potential to mechanically suppress the infiltration of toner into the dust preventing glass 4. Since an electric field providing no force to the toner or moving the toner to the side of the photosensitive body 5 is generated between the electrode 9 and the surface of the photosensitive body 5, toner dispersion is suppressed and toner infiltration into the glass 4 can be electrically suppressed. When a distance between the electrode 9 and the surface of the photosensitive body 5 is set up to a sufficiently large value, the dispersed toner can be sufficiently decelerated or inverted by air resistance or the like before its arrival at the slit electrode 9.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is directed to the application of second and subsequent colors in an image forming apparatus that superimposes color toner images on a photoreceptor to form a multicolor toner image and then transfers the image to a transfer material. This invention relates to an improvement in means for preventing toner scattering during image exposure.

(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 4# charging, exposure, and development are repeated many times, after the toner image formed in the first process is charged, the vicinity of the toner image is When exposed to light, the electric field distribution near the image changes rapidly, so the toner scatters due to the repulsive force between the toner particles and adheres to areas where the Coulomb force acts. This tendency for toner to scatter is particularly noticeable in the case of reversal development or in the case of irradiation with spot-like exposure light in which the electric field distribution changes abruptly.

FIG. 4 is an explanatory diagram of causes of toner scattering.

The vertical axis in FIGS. 4(a) to 4(e) indicates the negative potential of the surface of the photoreceptor. In the following description, uniform charging is assumed to be negative charging. ), the horizontal axis indicates the position of the surface of the photoreceptor (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 by is exposed to light, and the potential of that area becomes close to 0 volts. Figure (c) shows that when the exposed portion of the photoreceptor passes through the developing device, the negatively charged toner from the developing sleeve, which has approximately the same potential as the photoreceptor's °-uniform electric potential, is transferred to the photoreceptor. The toner image of the first color is formed on the surface of the photoreceptor, and the surface of the photoreceptor remains in the state where the toner image is formed. A second uniform charging is applied.

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

Then, image exposure is performed using an image signal corresponding to the second color. In FIG.
The light is emitted and the potential of that part is close to 0 volts (
In other words, the potential of the L' portion is higher than that of the L portion.

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 diagram showing a situation where a part of the toner adhering to the portion L where the potential is -E volts tries to move to the portion L' where the potential is close to 0 volts and scatters.

In this way, if toner scatters when a photoconductor on which a toner image has previously been formed is exposed for the next color, 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. 5 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.

As a solution to this problem, a method of preventing adhesion using airflow may be considered, but in this case, a duct, a fan, a filter, etc. are required, resulting in problems such as large size and fan noise.

In order to solve the above-mentioned problems, an object of the present invention is to provide an electric field forming member that forms a DC electric field between the image exposure device and the photoreceptor in the vicinity of the image exposure device, so that the scattered toner caused by the image exposure can be removed from the image exposure device. It is an object of the present invention to provide an image forming apparatus that can prevent dust particles from adhering to dust-proof glass and thereby form high-quality images without causing a decrease in exposure amount or uneven exposure.

(Means for solving the problems) In order to achieve the above object, the present invention has the following means configuration. That is, the image forming apparatus of the present invention includes a photoreceptor;
a charger that uniformly charges the surface of the photoreceptor; an image exposure device that performs image exposure on the uniformly charged surface of the photoreceptor to form a latent image; and an image exposure device that is provided near the image exposure device and that charges the photoreceptor. an electric field forming member that forms a direct current electric field between; a plurality of developing devices that apply toner to the latent image formed on the surface of the photoreceptor and develop it; A control means for repeating a series of steps of exposure and development a plurality of times according to a predetermined number of colors, and forming a plurality of color toner images in a superimposed manner on a photoreceptor; Forming Apparatus 6 (Function) The image forming apparatus of the present invention is provided with an electric field forming member that forms a DC electric field between it and the photoreceptor in the vicinity of the image exposure device. Therefore, by applying a DC voltage to this electric field forming 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 toner is directed toward the photoreceptor, toner scattering can be suppressed, and even if the toner has already been scattered, it can be prevented from reaching the image exposure device. If the charged polarity of the toner is negative, the toner receives electric force in the direction of higher potential, so first, the voltage that makes the potential of the photoreceptor higher, that is, the potential of the electric field forming member It is better to apply a voltage such that the voltage 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 equivalent to this adsorption force, toner scattering prevention effects can be achieved.

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 main parts of a first embodiment of the present invention. In the structure shown in FIG. 5, a slit electrode &9 is provided at the lower part of the frame 8 of the image exposure device 6 as an electric field forming means. The image exposure device 6 is an image exposure device that performs spot-like exposure using laser light.

FIG. 2 shows an example of the cross-sectional shape of the slit electrode 9. The slit 14 is a gap space through which the image exposure light passes. The longer and narrower the slit is, the more difficult it is for the scattered toner to reach the dust-proof glass.The slit electrode 9 is made of aluminum, and the part that comes into contact with the image exposure device is insulated with Mylar film, etc. It is fixed so that it is more than north away and approximately parallel to the surface of the photoreceptor. A voltage having the same polarity as that of the toner is applied to the slit electrode [9, and in particular, in the case of reversal development, the voltage is set to have the same polarity as the photoreceptor surface potential and to be the same or larger in magnitude. With the above configuration, first of all, structurally speaking, the toner is stored on the dustproof glass 4.
Infiltration is suppressed. And slit electric 5!9
Since an electric field that does not apply force to the toner or an electric field that moves the toner toward the photoreceptor is generated between the surface of the photoreceptor 5 and the surface of the photoreceptor 5, toner scattering is suppressed and toner entry into the dust-proof glass 4 is prevented from occurring. is suppressed. Furthermore, by making the distance between the slit electrode 9 and the surface of the photoreceptor 5 sufficiently large, the scattered toner can be prevented from reaching the slit electrode.
It can be sufficiently decelerated or reversed due to air resistance, etc.

In experiments, a clear effect was observed when the distance was 31111 or more.

FIG. 3 is a diagram showing the configuration of the main parts of the second embodiment of the present invention.

The difference from the embodiment shown in FIG. 1 is that the cross-sectional shape is thick near the slit 14 and becomes thinner as the distance from the slit 14 increases. has been established.

The slit electrode 9 is attached to a rail 12 provided on the frame 8 of the image exposure device 6 and a groove 1 provided on the slit electrode 9.
It is fixed by fitting 3 and can be detached from the front of the image forming apparatus main body.

With the above configuration, when a voltage is applied to move the toner toward the photoreceptor, the slit 14
Increasing the electric field strength in the vicinity suppresses toner from entering into the slit 14.

Also, as the length of the slit 14 increases, the slit 14
The rate at which toner that has entered the slit adheres to the inner wall of the slit 14 increases, and as a result, the amount of toner that adheres to the dustproof glass 4 decreases.

In addition, in the space between the slit electrode 9 and the photoreceptor 5, there is often an air flow due to the rotation of the photoreceptor 5 or an exhaust fan attached to the device, but the slit electrode 9 has a smooth shape. This reduces turbulence around the slit electrode and prevents floating toner from adhering.

As mentioned above, in all the examples, remarkable effects were obtained when the development method was a reversal development method.

(Effects of the Invention) As explained above, in the image forming apparatus of the present invention, by providing an electric field forming member that forms a DC electric field between the image exposure device and the surface of the photoreceptor, the electric field A voltage is applied to the forming member to weaken the electric field that acts on the toner that has adhered to the photoreceptor due to previous development, or to force it toward the photoreceptor. By forming an electric field on which a force acts,
It is possible to suppress the toner from scattering due to image exposure, and if an electric field is created that exerts a force that presses the toner toward the photoconductor even if the toner has already scattered, the photoconductor can be prevented from scattering. A force that causes the toner to return to the body is applied, which prevents the toner from adhering to the dust-proof glass of the image exposure device, and prevents the exposure amount from decreasing or becoming uneven over time. This has the advantage of providing an image forming apparatus that can stably form high-quality images over a long period of time.

Further, by suppressing toner scattering, there is an advantage that dirt inside the machine can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the configuration of the main parts of the first embodiment of the present invention, Fig. 2 is a diagram showing an example of the cross-sectional shape of the slit electrode, and Fig. 3 is the main part of the second embodiment of the invention. FIG. 4 is a diagram illustrating the cause of toner scattering, and FIG. 5 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,
9... Slit electrode, 10... Resin slit member, 11... Conductive electrode member, 12... Rail, 13... groove. Agent: Patent Attorney Yoshihiro Yahata / Figure 2 Figure 3 Figure 5

Claims (5)

[Claims] (1) A photoreceptor; a charger that uniformly charges the surface of the photoreceptor; an image exposure device that performs image exposure on the uniformly charged surface of the photoreceptor to form a latent image; a vicinity of the image exposure device established in
an electric field forming member that forms a DC electric field between the photoreceptor; a plurality of developing devices that apply toner to the latent image formed on the photoreceptor surface and develop the image;
A control means for repeating a series of steps of uniform charging, image exposure, and development multiple times according to a predetermined number of colors to form a plurality of color toner images overlappingly on the photoreceptor; An image forming apparatus characterized by: (2) Claim No. 1, characterized in that the image exposure device is an image exposure device that irradiates spot-like exposure light.
). (3) The electric field forming means has a slit so that the imagewise exposure light can pass through.
The image forming apparatus according to item 1) or item (2). (4) The image forming apparatus according to any one of claims (1) to (3), wherein the developing device is of a reversal developing type. (5) The electric field forming member is disposed at a distance of 3 mm or more from the surface of the photoreceptor.
The image forming apparatus according to any one of items 1) to (4).