JPH06295146A - Image forming device - Google Patents

Abstract

PURPOSE:To suppress the formation of black specks and to obtain image quality stable over a long period of time by constituting a fur brush to rub the surface of an image carrying member of a material which is triboelectrostatically charged to the same polarity as the electrostatic charge polarity of additives. CONSTITUTION:A cleaning device 9 includes the fur brush 11 to rub the surface of a photosensitive body 1 which is one constituting example of the image carrying member as a means for cleaning the surface of the photosensitive body after transfer of toner images. The fur brush 11 is constituted of the material to be triboelectrostatically charged to the same polarity as the electrostatic charge polarity of the fine powder additives by contact with the photosensitive body 1. More specifically, the fur brush 11 is constituted of the fibers of, for example, a polyester resin or fluororesin. The respective materials are strongly electrostatically charged to the negative polarity in the triboelectrostatic charge system. Namely, the fine powder additives are electrostatically charged to the same negative polarity if the toners are assumed to be electrostatically charged to the negative polarity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus equipped with a cleaning device using a fur brush.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer or a facsimile, an electrostatic latent image is formed on an image carrier,
In the one that visualizes this electrostatic latent image as a toner image,
After the toner image is transferred to the recording medium, the toner that has not contributed to the transfer remains on the surface of the image carrier, and thus the adhered toner is cleaned and removed from the image carrier to be collected.

FIG. 5 shows a schematic structure of an electrophotographic image forming apparatus provided with a cleaning device for cleaning an image bearing member, while explaining an image forming process of the image forming apparatus. The conventional problems will be clarified below.

In FIG. 1, reference numeral 1 denotes a drum-shaped photosensitive member which is an example of the structure of an image bearing member. First, the surface of the photosensitive member 1 is uniformly charged by a charging charger 2, and an exposure optical system 3 is provided. The photoconductor 1 is imagewise exposed by the photoconductor 1
An electrostatic latent image is formed on it. Next, the eraser 4 removes unnecessary electric charges in the non-image areas corresponding to the inter-recording medium area and the outer areas of both ends of the recording medium, and then the developing device 5 supplies toner to the electrostatic latent image, and the photoconductor A toner image is formed on 1. That is, the electrostatic latent image on the photoconductor 1 is visualized as a toner image by the developer.

On the other hand, a recording medium (not shown) such as plain paper is sent out from the paper feeding cassette 30 by a paper feeding roller 31, the recording medium is guided by a guide plate 32, and is temporarily stopped by a pair of registration rollers 33. Then, the toner image on the photoconductor 1 is sent to the transfer portion while being synchronized with the toner image.

The transfer charger 6 charges the recording medium by corona discharge to transfer the toner image on the photoconductor onto the recording medium, and the separation charger 7 discharges the recording medium by corona discharge to transfer the toner image through the toner image. The recording medium electrostatically attracted to the photoconductor 1 is easily separated. afterwards,
The recording medium is guided by the guide plate 34 and the conveying device 35 and conveyed to the fixing device 36. After the toner image on the recording medium is fixed by heat and pressure, the recording medium is discharged to the discharge tray 38 by the discharge roller 37. .

The toner remaining on the photoconductor 1 without being transferred in the transfer process is removed by the cleaning device 9. After the toner is removed, the photoconductor 1 is electrostatically initialized by being subjected to corona discharge by the charge removal charger 15 and light irradiation by the charge removal lamp 16, and is repeatedly used.

Here, the cleaning device 9 will be described in more detail with reference to FIG. 1 showing an embodiment of the present invention. The toner remaining on the photoconductor 1 passes through the seal 10 on the entrance side of the cleaning device 9, and the toner is removed from the photoconductor 1 by mechanical rubbing of the cleaning fur brush 11. The fur brush 11 is a core metal roller 1.
The cored bar roller 11a is rotationally driven in a clockwise direction together with the fur brush 11 by a drive motor (not shown). The fur brush 11 that rubs against the surface of the photoconductor 1 in this way constitutes means for cleaning the surface of the photoconductor 1 after the toner image is transferred. Since the residual toner cannot be completely removed, the toner that cannot be completely removed is scraped off on the fur brush 11 by mechanical rubbing of the cleaning blade 23 arranged on the downstream side of the fur brush 11.

The fur brush 11 that has captured the toner comes into contact with the flick cover 24, and the impact force of the fur brush 11 separates the toner from the fur brush 11 or weakens the adhesion force, and electrostatically attracts it to the bias roller 12. To be done. The toner on the bias roller 12 is the scraper member 1
It is scraped off mechanically by 3, and is discharged to a predetermined place by the rotation of the discharge coil 14.

By the way, various properties are required for the developer used for visualizing the electrostatic latent image, but if the fluidity is particularly bad, the toner is supplied from the developing device 5 to the photosensitive member 1. However, the smoothness may be impaired, or the transfer performance may be deteriorated.

Therefore, a developing device using a developer containing at least a toner and a fine powder additive to be adhered to the surface of the toner is used as the developer of this type. Here, the additive is an additive that improves the fluidity of the developer.

In the developing device 5 shown in FIG. 5, in addition to the toner and the fine powder additive, a two-component type developer having a carrier that does not transfer to the photoreceptor 1 is used. The present invention can be applied to an image forming apparatus using a one-component developer having no carrier.

When the image forming apparatus as described above is used for a long period of time, the toner component in the developer adheres to the surface of the photoconductor. In particular, when a developer containing a fine powder additive is used on the toner surface, the fine powder additive is also released from the toner surface and easily adheres to the surface of the photoreceptor. If such a fine powder additive adheres to the surface of the photoconductor, it becomes difficult to scrape it off with the fur brush 11, the cleaning blade 23, or the like.

When the fine powder additive is left behind and remains attached to the surface of the photoconductor, the resin, which is the main component of the toner, gradually adheres to the fine powder additive on the photoconductor using the core as a core, thereby forming a spindle shape. Grows to the spots. These spots retain their charge on this surface area during the charging process,
Since the charge is not removed in the exposure step, it is developed with toner, resulting in black spots, which greatly impairs image quality. Also, when the spots pass through the cleaning blade,
This blade edge portion is easily scratched, resulting in poor cleaning.

Therefore, for the purpose of solving such a problem, a technique for subjecting the fine powder additive to a surface treatment has been proposed. However, when the surrounding environment becomes, for example, a low humidity state, the fine powder additive may be extremely removed from the toner. It becomes easy to be released and it becomes difficult to suppress the generation of black spots. A technique for surface-treating the fine powder additive is disclosed in, for example, JP-A-2-308173.
The gazette etc. have already been proposed.

Generally, as the fine powder additive of this kind, one which is charged to the same polarity as the toner is selected in order to stabilize the charging characteristics of the toner itself. In order to increase the charge amount of both the additive and
The electrostatic repulsion force between the two increases, and the fine powder additive easily separates from the toner.

Liquid is present in the fine gap between the toner particles and this kind of fine powder additive, and the adhesive force is generated due to the surface tension of the liquid itself, but in a low humidity environment. If so, the adhesive force is reduced, and the fine powder additive is more likely to be released from the toner surface.

In recent years, in order to achieve higher image quality,
Although there is a tendency to use a toner having a smaller particle diameter, the amount of the fine powder additive added is further increased in order to compensate for the decrease in the fluidity of the toner caused by the toner. Under such circumstances, the amount of the fine powder additive liberated becomes very large, and black spots are likely to appear.

The problem of the image forming apparatus of the type in which the toner image formed on the image carrier made of the photoconductor is directly transferred to the recording medium has been described above. Even in an image forming apparatus of a type in which the toner image is transferred to an image carrier made of a transfer body and then the toner image is transferred to a recording medium, black spots are formed on the photoconductor and the intermediate transfer body for the same reason as described above. Therefore, the above problem occurs.

[0020]

SUMMARY OF THE INVENTION The object of the present invention is to suppress the generation of black spots and to provide stable image quality for a long period of time even in a situation where an additive for facilitating the flow of a developer is easily liberated. It is to provide an image forming apparatus to be obtained.

[0021]

In order to achieve the above object, the present invention is an image forming apparatus which visualizes an electrostatic latent image as a toner image with a developer, wherein the developer is a toner and a toner. In an image forming apparatus using a developer containing at least an additive to be adhered to the toner surface, and using an additive that improves the fluidity of the developer as the additive, As a means for cleaning the surface of the image carrier, a fur brush that slides on the surface of the image carrier is provided, and the fur brush is made of a material that is triboelectrically charged to the same polarity as the charge polarity of the additive. It is a proposal.

It is effective to form the fur brush with a material of polyester resin or fluorine resin.

Further, it is effective to form the fur brush into a loop shape.

Further, it is effective to use at least one of silicon oxide, silicon carbide and titanium oxide as an additive.

[0025]

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

FIG. 1 shows a schematic structure of a cleaning device provided in an image forming apparatus according to an embodiment of the present invention, and the cleaning device 9 of this embodiment also has a structure of an image carrier after transfer of the toner image described above. As a means for cleaning the surface of the photoconductor 1 which is a structural example, a fur brush 11 that rubs against the surface of the photoconductor is provided. It is made of a material that is triboelectrically charged to the same polarity as the charging polarity.

More specifically, the fur brush 11 is made of, for example, fibers of polyester resin or fluorine resin, and these materials are strongly negatively charged in the triboelectric charging series. Conventionally, in this type of cleaning device, an acrylic fiber in which carbon is dispersed is generally used as the fur brush.

The other structure of this example is substantially the same as the image forming apparatus described above with reference to FIGS. 1 and 5. Therefore, in order to avoid duplication of description, description of the same configuration will be omitted, and in the following description, FIG. 5 will be referred to as necessary.

As described above, in order to stabilize the charging characteristics of the toner itself, the one which is charged to the same polarity as the toner is selected as the fine powder additive. Here, the toner has a negative polarity. In this case, the fine powder additive is charged to the same negative polarity. The above-mentioned polyester resin or fluorine resin material is triboelectrically charged to the same negative polarity as the fine powder additive.

As a result of research conducted by the present inventors, the fur brush 11 is triboelectrically charged in the same polarity as the fine powder additive, and for example, the more strongly the brush 11 is negatively charged by triboelectrification,
It has been found that black spots are less likely to occur on the photoconductor 1. The fur brush 11 in the form of a loop made of polyester fiber showed the best results.

If a material such as silicon oxide, silicon carbide, or titanium oxide is used as the fine powder additive of the developer used in the developing device 5 shown in FIG. 5, the fluidity of the developer can be significantly improved. Although it is possible, several toners to which such additives have been added were subjected to a paper passing test in a low temperature and low humidity environment using fur brushes with different materials, morphology, etc. When the fur brush was used, black spots were not always generated on the photoconductor. Thus, it is particularly advantageous to use at least one of silicon oxide, silicon carbide and titanium oxide as an additive.

The fur brush material evaluated here was prepared by dispersing carbon in the above-mentioned materials, as well as polyester fibers, insulating fibers such as acrylic fibers, fluorine fibers, nylon fibers, polypropylene fibers, and the like. Although the obtained conductive fibers and fibers made of stellenless, etc., preferable results were not obtained when a fur brush made of a material other than polyester resin or fluorine resin was used. In particular, the conductive fibers have their electric charges canceled by frictional electrification, so that even polyester fibers are not sufficiently effective.

FIG. 3 shows the form of the fur brush.
The loop-shaped fur brush 11 shown in FIG. 4 has generally obtained better results than the straight-hair fur brush 11 shown in FIG. 4, but the straight-fur fur brush 11 also has a sharp tip portion. This is because the triboelectric charge leaks due to the electric discharge phenomenon. Thus, it is particularly preferable to use a fur brush having a loop shape.

The polyester fiber fur brush used in this embodiment has a flock density of 600 loops / inch ² ,
The fiber thickness is 360 denier / 24 filaments, the number of twists of the fiber is 6 times / inch, the bristle length is 5 mm, and the amount of bite into the photoreceptor is 1.5 mm. However, these conditions do not affect the generation of the black spots so much and may be determined in consideration of the hardness of the surface of the photoconductor to be used, the drive torque of the fur brush, and the like.

By the way, the fur brush 11 scrapes off and removes the toner remaining on the photoreceptor after the toner image transfer step, or removes the toner filming layer, and further, the toner of the pattern for image density detection. Etc. are removed, and in any case, cleaning the surface of the photoconductor is the same. In the case of a well-known color copying machine, the amount of toner adhered on the photoconductor is large, and the residual toner cannot be completely removed from the surface of the photoconductor by the cleaning blade 23 alone. Is widely used. That is,
As described above, before the residual toner on the photoconductor 1 is input to the cleaning blade 23, the fur brush 11 removes some residual toner. A conductive fur brush is used as the fur brush 11, and a bias voltage having a polarity opposite to that of the residual toner is applied to the cored bar roller 11a to electrostatically adsorb the residual toner on the fur brush 11 side and expose it. Removed from the body.

However, when a fur brush made of polyester fiber is used to prevent the generation of black spots in such a system, it becomes an insulating fur brush, so that the toner removing ability is greatly lowered and the cleaning blade 23 is used. It is also conceivable that the toner removal capability in the above will be exceeded. Therefore, in the case of such a system, as shown in FIG.
As shown in FIG. 3, a pre-cleaning charger 8 is provided on the upstream side of the fur brush 11, and the charger 8 performs corona discharge having the same polarity as the triboelectric charging polarity of the polyester fur brush, that is, a negative polarity, and thereby the residual toner T
The surface layer portion of is charged negatively. On the other hand, a negative polarity charged toner T is electrostatically applied to the fur brush 11 by applying a bias voltage having a polarity opposite to the charging polarity of the toner, that is, a positive polarity bias voltage to the core metal 11a supporting the polyester fur brush 11.
Adsorb on the side of and remove. The residual toner that cannot be completely removed is removed by the cleaning blade 23 located downstream.

As described above, even if the fur brush 11 is made of an insulating material such as a polyester resin, the pre-cleaning charger 8 is provided to cooperate with the cleaning blade 23 to remove a large amount of residual toner. Not only can it be removed efficiently, but black spots can also be prevented from occurring.

It is needless to say that the present invention can be widely applied to an image forming apparatus using a belt-shaped photosensitive member as an image bearing member and an image forming apparatus using an image bearing member other than such a photosensitive member.

In particular, a toner image is formed on an image carrier composed of a latent image carrier such as a photoconductor in the same manner as in the above-described embodiment, and this toner image is then carried by an intermediate transfer member. When the toner image is transferred to a body, the toner image is transferred to a recording medium, and the residual toner on the intermediate transfer body after the transfer is applied to an image forming apparatus that cleans with a fur brush, the latent image carrier described above is used. The image carrier including the image carrier and the image carrier including the intermediate transfer member are also targets of the image carrier according to the present invention. That is, in this case, the fur brush for the intermediate transfer member is also made of a material that is triboelectrically charged to the same polarity as the charge polarity of the developer additive.

[0040]

According to the image forming apparatus of the first, second and fourth aspects, even in a situation where the additive for improving the fluidity of the developer, which is a component in the toner, is likely to be released, the image forming member is not affected. The generation of black spots can be suppressed, and stable image quality can be obtained for a long period of time.

According to the cleaning device of the third aspect, the leakage of triboelectric charges at the tip of the brush is less likely to occur, and the generation of black spots can be suppressed more effectively.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a cleaning device provided in an image forming apparatus according to an exemplary embodiment of the present invention, and is a diagram that is also used for explaining a conventional example.

FIG. 2 is a schematic configuration diagram of a cleaning device according to another embodiment.

FIG. 3 is a configuration perspective view of a fur brush having a loop shape.

FIG. 4 is a perspective view showing a fur brush having a straight bristle shape.

FIG. 5 is a schematic configuration diagram of an electrophotographic image forming apparatus used for explaining the related art, and is also a diagram that is provided for explaining one embodiment of the present invention.

[Explanation of symbols]

 11 fur brush

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyuki Sugimoto 1-3-6 Nakamagome, Ota-ku, Tokyo Stock company Ricoh Company (72) Hiroshi Ono 1-3-6 Nakamagome, Ota-ku, Tokyo Share Company Ricoh

Claims (4)

[Claims] 1. An image forming apparatus that visualizes an electrostatic latent image as a toner image with a developer, the developer comprising:
A toner image in an image forming apparatus using a developer containing at least a toner and an additive to be adhered to the surface of the toner, and using an additive that improves the fluidity of the developer as the additive. As a means for cleaning the surface of the image bearing member after transfer, a fur brush that rubs against the surface of the image bearing member is provided, and this fur brush is made of a material that is triboelectrically charged to the same polarity as the charge polarity of the additive. An image forming apparatus characterized by. 2. The image forming apparatus according to claim 1, wherein the fur brush is made of a material of polyester resin or fluorine resin. 3. The image forming apparatus according to claim 1, wherein the fur brush has a loop shape. 4. The image forming apparatus according to claim 1, wherein at least one of silicon oxide, silicon carbide and titanium oxide is used as the additive.