JPH07104606B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus for forming an image based on an electrophotographic recording system such as a printer, a copying machine, and a facsimile, and particularly to an image on a photosensitive drum or the like. The present invention relates to an image forming apparatus that visualizes an electrostatic latent image formed on a surface of a carrier using a one-component toner.

"Prior Art" Based on a so-called electrophotographic recording method, an electrostatic latent image formed on an image carrier formed as a photoconductor drum is visualized with a one-component toner, and then the toner image is exposed. An image forming apparatus such as a printer that transfers a recording sheet inserted on the peripheral surface of a body drum to form a predetermined image is known, and a transfer apparatus used in this type of apparatus has a rear side of the recording sheet. There are those that transfer a toner image onto a recording paper by performing corona discharge having a polarity opposite to that of the toner, and those that transfer the toner image by using the compression pressure of a transfer roller. Even in the above device, 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 with each other, the paper dust or the like separated from the recording paper is exposed during the transfer step. Body drum Will adhere to.

Therefore, in the conventional apparatus, the paper dust and the like are removed together with the residual toner by the cleaning blade located on the downstream side of the transfer process, but unlike the toner, the paper dust is not particulate but fibrous. Therefore, it is difficult to completely scrape 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 dust adhered on the drum has hygroscopicity, the surface of the photoconductor drum is absorbed by the paper dust and the surface resistance is lowered. As a result, the latent image charge formed on the drum surface is moved, and Flow may occur.

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).

"Problems to be Solved by the Invention" However, in the former case, since the protective layer is formed by the developer, the protective layer cannot be formed unless the image formation is completed, and the paper dust generated during the image formation. There is no defense against image flow due to adhesion, and in the latter case, it cannot be applied to a device that visualizes with a developer, especially one-component toner that does not use carrier liquid (dry developing method),
Further, since the thin film is liquid, paper dust is more likely to adhere during the transfer process, and in any case, there is a problem that insufficient cleaning due to the paper dust adhesion 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 Problems] In order to achieve the technical problem, the present invention provides an image forming apparatus that visualizes an electrostatic latent image formed on the surface of an image bearing member using a one-component toner. An image having essential constitutional requirements that a non-water-absorbing particle group is mixed in the developing container together with the toner, and that the particle group is configured to have a polarity opposite to the charging polarity of the toner at the developing position. A forming device is proposed.

In this case, the particle group is configured so that it can have a polarity opposite to the charging polarity of the toner at the developing position, for example, a hydrophobic silica having a strong negative charging property or a silica having a positive charging property having been subjected to aminosilane treatment. As described above, a particle group having a polarity opposite to that of the toner may be used, or a particle group having a different triboelectrification series from that of the toner may be used. It may be configured to inject a charge having a polarity opposite to the charging polarity of the toner.

In addition to the mutual frictional charging of the toner and the particle group, in the image forming apparatus configured to inject charges of different polarities into the particle group and the toner by frictional charging of the toner layer thickness regulating member, It is preferable that the charging system of the regulating member is located between the triboelectrification system of toner and particles.

The polarities of the toner and the particle group described above differ depending on the photoconductor drum used and the development method such as reversal development or regular development, and the relationship between them is shown in the following table.

[Operation] According to the technical means, since the particle group has a polarity opposite to the charging polarity of the toner at the developing position, the toner is present on the latent image forming portion and the non-latent image forming surface (background portion) is present. The particle groups adhere to each other, and the entire surface of the image carrier is hidden by the toner and the particle groups in the transfer process located on the downstream side, so that the recording paper does not come into direct contact with the image carrier.

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 plate located on the downstream side and the residual toner can be easily scraped together with the particle group by scraping operation, thereby completely trapping the paper dust between the blade and the image carrier. Therefore, the insufficient cleaning due to the paper dust being caught is eliminated.

Since both the particle group and the toner are fine particles and are not fibrous, there is no risk of biting between the blade and the image carrier, and when the particle group rubs against the blade. Therefore, it is possible to prevent the image carrier from being damaged due to the rubbing of the blade.

On the other hand, since the particle group is non-water-absorbing, even when the paper powder absorbs moisture, it is possible to prevent water in the paper powder from leaching on the surface of the image carrier, and the particle group is also absent. Function as a protective layer that prevents corona products generated by corona discharge during the transfer process from adhering to the photoconductor drum, thus completely preventing moisture absorption of the image carrier during the transfer process. Therefore, a clear image with no image deletion can be formed.

Further, since the particle group has a polarity opposite to that of the toner, in other words, the same polarity that repels the polarity of corona discharge during the transfer step, there is no fear that the particle group is transferred to the recording paper side. Various adverse effects due to the adhesion of the 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.

If the mixing ratio of the particle groups is high, the toner may not be sufficiently adhered to the latent image forming portion. Therefore, the mixing ratio of the particle groups and the toner is preferably about 10% or less.

[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 drawing is a schematic view showing an image forming apparatus by a reversal development method according to an embodiment of the present invention. As is well known, a photosensitive drum 1 having a photoconductive layer formed by OPC is formed around the photosensitive drum 1 along the rotation direction of the drum 1. Sequentially, an optical system 2 for writing a latent image on the drum 1, 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. In order to explain the configuration of the present embodiment sequentially focusing on its action, first, a latent image in which the negative charge is erased by the optical system 2 is formed on the photosensitive drum 1 which is negatively charged by the charger 8. Formation (thus negative charge is formed in the background) After made), the visible image by following the developing device 3 of the latent image by the rotation of the drum 1.

The developing device 3 is accommodated in a container 11 in which a toner and a particle group described later are mixed in a predetermined ratio, and due to mutual frictional charging of both and frictional charging with the layer thickness regulating member 12, the toner is negatively charged or particles. The group includes a mixture of positively charged mixed particles with a developing roll 13
Is guided to the developing position in accordance with the rotation of the developing roller 13 and is made to fly toward the photoconductor drum 1 side by the bias applied to the developing roller 13 at the developing position. Since they are negatively charged with the same polarity, they are attached to the latent image forming portions from which the charge has been erased.

When the toner image A and the particle group layer B adhering to the photosensitive drum 1 are guided to the transfer position, the recording paper 4 inserted on the peripheral surface of the photosensitive drum 11 above the transfer device 5 at a constant timing. Only the toner image is transferred to the recording paper 4 side by corona discharge having a positive polarity from the back side, and the recording paper 4 on which the toner image A is transferred is sent to an image fixing device (not shown) for image fixing.

On the other hand, the photosensitive drum 1 after the transfer is further rotated and the cleaning blade 6 causes the drum 1 together with the residual toner.
The particles adhering to the top and the paper dust adhering to the particles are scraped off, and the drum 1 is cleaned.

Then, the drum 1 is discharged to the charger 8 after the entire surface of the drum 1 is discharged by the eraser 7, and this is repeated thereafter.

Next, toner in the developing device 3, particles and a layer thickness regulating member
12, the toner is a magnetic toner containing polystyrene resin as a main component, and the toner container 11
It can be charged negatively and has an average particle size of 10 ~
Use a 20 μm one.

For the particle group, an acrylic resin, such as polyacrylonitrile, which is positively charged by mutual friction with the toner is used, the particle size is set to about 5 μm, and the mixing ratio with the toner is 100 (toner): 5 (particles). Group) Set before and after.

The layer thickness regulating member 12 is formed of a flexible member having a thickness of 100 μm, and is slightly inclined toward the downstream side of the developing roll 13 from the wall surface of the magnet blade 14 that forms a repulsive magnetic field on the developing roll 13. While being stretched, its free end side is configured to be capable of being pressed onto the developing roll 13 at a predetermined contact pressure,
Triboelectric charging is also performed between the regulation member 12 and the toner and particle groups.

Therefore, the layer thickness regulating member 12 is formed of polychlorinated butadiene or the like to maintain the relationship of triboelectric charging series of particle group> triboelectric charging series of toner regulating member> triboelectric charging series of toner. As a result, even when the layer thickness regulating member 12 is triboelectrically charged, the particle group is positively charged and the toner is negatively charged, thereby further satisfying the effect of the present invention.

Then, based on such an example, an experiment was conducted with a laser printer (F1010) manufactured by our company, and using a PPC plain paper with a large amount of paper powder peeling as the recording paper in an environment of 100% humidity.
No image distortion due to image deletion or insufficient cleaning occurred at any time of recording 000 sheets or 10,000 sheets, and a clear image was always obtained even at the edge of the image.

[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 prevent the generation of streaks, charging and poor exposure and always obtain a clear image, and to mix particle groups into the conventional developing container 11 without the need for a special particle group adhesion device. There are no restrictions on miniaturization.

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 (6)

[Claims] 1. An image forming apparatus for visualizing an electrostatic latent image formed on an image bearing member surface by using a one-component toner, wherein a non-water-absorbing particle group is mixed together with the toner into a developing container, An image forming apparatus characterized in that the group of particles can have a polarity opposite to the charging polarity of the toner at the developing position. 2. The image forming apparatus according to claim 1, wherein a particle group having a polarity opposite to that of the toner is mixed. 3. A patent in which a group of particles having a different triboelectric charge series from that of the toner is used, and a charge having a polarity opposite to that of the toner is injected into the group of particles by mutual frictional charging between the group of particles and the toner. The image forming apparatus according to claim 1. 4. An image forming apparatus configured to inject charges of different polarities into the particle group and the toner by frictional charging of a toner layer thickness regulating member, in addition to mutual frictional charging of the toner and the particle group. 4. The image forming apparatus according to claim 3, wherein the charge series of the layer thickness regulating member is located between the triboelectric series of toner and particles. 5. The image forming apparatus according to any one of claims 1 to 4, wherein the particle group is a particle group having a size smaller than a toner average particle size. 6. The image forming apparatus according to claim 1, wherein the particle group is mixed and present in the developing container at a mixing ratio of 10% or less of the toner.