JPH07104607B2 - Image forming method - Google Patents

Description

The present invention relates to an image forming method for forming an image by transferring a toner image carried by an image forming portion on the surface of an image carrier to a recording paper, and further to an image forming method. More specifically, the present invention relates to an image forming method for preventing paper dust from adhering to the surface of an image carrier during a transfer process.

"Prior Art" A printer or a facsimile that forms an image by transferring a toner image carried by an image forming portion on the surface of an image carrier formed as a photoconductor drum onto a recording paper based on a so-called electrophotographic recording system. An image forming apparatus such as a copying machine is known, and in this type of apparatus, after the toner is carried on the latent image forming portion of the photosensitive drum, the recording paper is inserted on the peripheral surface of the drum with timing. For example, the toner image is transferred onto the recording paper by performing corona discharge having a polarity opposite to that of the toner from the back side thereof.

[Problems to be Solved by the Invention] However, in such a transfer step, since the non-image forming surface of the photosensitive drum on which the toner is not carried and the recording paper are in direct contact, the paper separated from the recording paper is The powder and the like are easily attached to the photosensitive drum, and therefore the paper powder and the like are configured to be removed together with the residual toner by using a cleaning blade located on the downstream side of the transfer process. Since it is fibrous, it is difficult to completely scrape it off by a mechanical scraping method by pressing the blade, and biting easily occurs between the blade and the drum.

Moreover, since a slight gap is generated between the blade and the drum due to the biting, paper dust further enters the gap,
In particular, in an image forming machine with a high conveyance speed such as a laser printer, the above-mentioned bite spreads rapidly, which may cause cleaning failure, resulting in black streaks on the image surface, partial charging failure, and exposure failure. Image distortion is likely to occur due to.

On the other hand, since the paper powder adhering to the drum has hygroscopicity, the surface of the photoconductor drum may be absorbed by the paper powder and the surface resistance may decrease. As a result, the latent image charge formed on the drum surface may move. However, image deletion occurs.

It should be noted that such an image flow is caused by nitrogen oxides generated due to ozone generated by corona discharge during the transfer process and the charging process, which are attached to the photoconductor drum, and It also occurs when the hygroscopicity of the drum surface increases, but as a countermeasure against this, for example, a technique of forming a protective layer of a developer on the entire surface of the photosensitive member or a required portion after image formation (Japanese Patent Laid-Open No. 61-53679). ), Or a technique of forming a thin film on the entire surface of the photoreceptor by a developer, especially a carrier liquid before the charging step (JP-A-60-136756).

However, in the former case, since the protective layer is formed by the developer, the protective layer cannot be formed until after the image formation is completed, and the image flow due to the paper dust adhesion during image formation is completely unprotected. Further, in the latter, not only can it be applied to an image forming apparatus using a developer, especially a carrier liquid, but since the thin film is a liquid, paper powder tends to adhere during the transfer process. In any case, there arises a problem that the insufficient cleaning caused by the adhesion of the paper dust is rather increased.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and an object of the present invention is to provide an image forming apparatus capable of preventing image deletion and insufficient cleaning caused by adhesion of paper dust.

"Means for Solving the Problems" In order to achieve the technical problem, the present invention provides a non-image forming surface which is not covered with at least a toner image on the surface of the image carrier at the transfer position where the paper powder is attached. , Non-water-absorbing particles preferably having a particle size smaller than the average particle diameter of the toner, that is, the particles are positively attached mainly to the non-image forming surface of the image carrier on the upstream side of the transfer position. It is characterized by making it.

And as shown in the following table and "Note", the particles are attached to the image carrier by using particles that can have a polarity opposite to the charge polarity of the toner, and the roller, brush, air It can be easily achieved by attaching by means such as spraying or bias application.

The adhering means may be provided at any position on the upstream side of the transfer position, but the present invention is characterized by positively adhering the particle groups to the non-image forming surface. As described above, it is preferable that the image carrier is provided between the latent image writing position and the transfer position.

In this case, the adhering means does not necessarily have to be formed as an independent device. For example, the toner is mixed in a developing container at a predetermined ratio with the toner, and the toner acts on the image forming portion or the particle group due to the bias applied during the developing process. It may be configured to adhere to the non-imaging surface.

Further, the present invention is characterized by positively adhering the particle group to the non-image forming surface, but the coating of the particle group is not necessarily limited to only the non-image forming surface, and image bearing The case of hiding the entire body surface is also included in the technical scope of the present invention.

[Operation] According to the technical means, at the transfer position, since the image forming portion is hidden by the toner image and the image non-forming portion is hidden by the particle group, the recording paper comes into direct contact with the image carrier. There is no fear.

As a result, even if the electrostatic attraction force acts on the paper powder separated from the recording paper due to corona discharge during the transfer, the paper powder adheres to the image carrier side through the particle group. The particle group of the cleaning blade located on the downstream side and the residual toner can be easily scraped together with the particle group by the scraping operation, thereby completely trapping the paper dust between the blade and the image carrier. Can be prevented. As a result, it is possible to eliminate the insufficient cleaning caused by the paper dust being caught.

Further, since the particle group is a fine particle and is not fibrous, there is no risk of biting between the blade and the image carrier, and the particle group serves as a lubricant when the blade slides. This makes it possible to prevent the image carrier from being scratched due to the blade rubbing.

On the other hand, since the particle group is non-water-absorbing, even if the paper powder absorbs moisture, it is possible to prevent the water in the paper powder from leaching to the surface of the image carrier, and the particle group Is
Since it also functions as a protective layer that prevents the corona products generated by corona discharge during the transfer step from adhering to the photosensitive drum, it completely prevents the image carrier from absorbing moisture during the transfer step. As a result, a clear image with no image deletion can be formed.

Further, since the particle group has a polarity opposite to that of the toner, as a result, it has the same polarity as that of the corona discharge during the transfer step and repels each other. As a result, there is no fear that the particle group is transferred to the recording paper side. Various adverse effects resulting from the adhesion of the particle group to the recording paper can be prevented.

Further, the presence of the particle group on the non-image forming surface may cause image disturbance at the boundary with the image forming portion, that is, the image edge portion, but the particle group is a particle group smaller than the toner average particle diameter. By forming it, such problems can be solved.

[Embodiment] Hereinafter, a preferred embodiment of the present invention will be exemplarily described in detail with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of the components described in this embodiment are not intended to limit the scope of the present invention only thereto, but merely illustrative examples. Nothing more than.

The drawings are schematic views showing an image forming apparatus according to an embodiment of the present invention. As is well known, the photosensitive drum 1 around which a photoconductive layer is formed of amorphous silicon, OPC, or the like is arranged in the rotation direction of the drum 1. An optical system 2 for writing a latent image on the drum 1 sequentially, a developing device 3 for visualizing the latent image, and a toner image visualized by the developing device 3 is transferred onto a recording paper 4. A transfer device 5 including a corona discharger, a cleaning blade 6 for removing residual toner, an eraser 7 for removing the charge on the drum 1 surface, and a charger 8 for uniformly charging the drum 1 after the charge removal are provided. Therefore, the toner image is repeatedly transferred to the recording paper 4 inserted on the peripheral surface of the photoconductor drum 1 above the transfer device 5 at a constant timing to form a predetermined image.

The particle group attaching device 10, which is the gist of the present invention, is provided between the developing device 3 and the optical system 2 when the developing device 3 causes the toner to fly and adhere to the latent image forming portion of the photosensitive drum 1. Alternatively, it is arranged either between the developing device 3 and the transfer device 5, or on the peripheral surface of the drum 1 between the developing device 3 and the transfer device 5 when toner is attached by a magnetic brush.

The particle group attaching device 10 is a container 12 for containing the particle group 11.
And a roller 13 for transporting the particle group 11 in the container 12 onto the peripheral surface of the drum 1, and a thin plate-like member arranged on the peripheral surface of the roller 13 upstream of the drum 1 attachment position so as to be slidable with the roller 13. The flexible member 14 is configured so that a charge having a polarity opposite to that of the toner can be injected into the particle group 11 by frictional charging between the flexible member 14 and the particle group 11.

As the particle group 11 accommodated in the adhering device 10, the particle group 11 having the charging polarity as shown in the following table is selected depending on the type of the photosensitive drum 1 and the difference in the developing method such as the reversal phenomenon or the normal phenomenon. The particle size of the particle group 11 is 5 μm or less when the average particle size of the toner is 5 μm. That is, a particle group having a particle size smaller than the average particle size of the toner is used.

Next, the operation of this embodiment will be described.

First, on the photosensitive drum 1 on which a latent image is formed by the optical system 2, the particle group 11 is uniformly attached to the non-latent image forming surface (background portion) by the adhering device 10 and moves to the developing position. Then, after the toner image A is carried on the latent image forming portion here, only the toner image A is transferred to the recording paper 4 side by performing corona discharge having a polarity opposite to that of the toner image at the transfer position.

After the transfer of the toner image A, the residual toner and the particle group 11
Is scraped off by the cleaning blade 6, the peripheral surface of the drum 1 is cleaned, the charge is erased by the eraser 7, the entire surface is charged by the charger 8, the latent image is written again by the optical system 2, and so on.

It is not always necessary to provide the adhering device 10 independently, and under the conditions described in Note 1) and Note 2) in the above table, the particle group 11 having a different charging system from that of the toner, for example, 5 is added to the toner.
The same effect as that of the above-mentioned embodiment can be obtained by mixing about%.

[Advantages of the Invention] As described above, according to the present invention, image flow caused by adhesion of paper dust during the transfer step, insufficient cleaning caused by paper dust being caught by a cleaning blade, and black caused by insufficient cleaning It is possible to obtain a clear image at all times by preventing the generation of streaks, charging and poor exposure.

It has various remarkable effects.

[Brief description of drawings]

The drawings are schematic views showing an image forming apparatus according to an embodiment of the present invention.

Claims (4)

[Claims] 1. An image forming method for forming an image by transferring a toner image carried by an image forming portion on the surface of an image carrier to a recording paper, wherein at least a non-image forming surface of the image carrier at the transfer position is Image forming method characterized by coating with non-water-absorbing particles 2. The image forming method according to claim 1, wherein the particle group is a particle group smaller than a toner average particle diameter. 3. The image forming method according to claim 1, wherein the group of particles is a group of particles that can have a polarity opposite to the charging polarity of the toner when the image carrier is attached. 4. The coating means for adhering the particle group to the image bearing member side is located on the image bearing member between the latent image writing step and the transfer step. The image forming method according to any one of items 1 to 3.