JP2005301105A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-quality image by regulating the roughness of the surface layer of an ETB, thereby realizing ETB cleaning by an OPC electrostatic recovery system where the difference of circumferential speed is applied. <P>SOLUTION: In the image forming apparatus having a plurality of image forming units having at least an image carrier, a charging means for charging the image carrier to have a prescribed polarity, and a developing device for visualizing an electrostatic latent image formed on the image carrier with developer, and a transfer member stretched and laid by a plurality of members, the surface roughness of the transfer member is set within the prescribed range of 0.05<Ra<0.2[μm] in center line average roughness Ra. Then, the image forming apparatus adopts an in-line system where the plurality of different image forming units are arranged in series and a developed image is transferred to transfer material transported by the transfer member at a time. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, or a facsimile machine that forms an image by an electrophotographic system, an electrostatic recording system, or the like.

As conventional image forming apparatuses, various systems such as an electrophotographic system, a thermal transfer system, and an ink jet system are used. this house,
Electrophotographic methods are superior to other methods in terms of high speed, high image quality, and quietness, and have become popular in recent years. This electrophotography is also divided into various systems. For example, in addition to the well-known multiple transfer system and intermediate transfer body system, an image is formed by superimposing a color image on the surface of the photoreceptor and then transferring it all at once. Multiple development system,
There is an in-line method in which a plurality of image forming units (process stations) of different colors are arranged in series and a developed image is transferred onto a transfer material conveyed by a transfer belt. Among these, the inline method has an example as described in Patent Document 1,
It is an excellent method because it can speed up and is advantageous in image quality because the number of times of image transfer is small.

  FIG. 1 shows an inline configuration.

In FIG. 1, an electrostatic attraction conveyance belt (hereinafter abbreviated as ETB) 8 is stretched by each of a driving roller 102, an adsorption facing roller and a stretching roller 101.
The direction indicated by the arrow movement rotates at a predetermined peripheral speed. Process stations Y (yellow), C (cyan), M (magenta), and K (black) of different colors are arranged in a row on the peripheral surface of the ETB8, and the photoconductor of each process station is transferred via the ETB8. It is in contact with the roller 3. Further, the suction roller 7 is disposed upstream of the process station and is in contact with the suction counter roller 101. Here, the transfer material is electrostatically attracted to the ETB 8 by being applied with a bias when passing through the nip formed by the suction roller 7 and the suction counter roller 101, and is conveyed in the direction indicated by the arrow. The

Conventionally, as ETB8, the thickness is 50 to 200 μm,
Resin films such as PVdF, ETFE, polyimide, PET, polycarbonate, etc. having a volume resistivity of about 10 ⁹ to 10 ¹⁶ Ω, or a thickness of about 0.5 to 2 mm,
For example, a material obtained by dispersing a fluororesin such as PTFE in urethane rubber as a surface layer on a rubber base layer such as EPDM is used.

  Here, the image forming process will be described.

First, an image forming process in the process station will be described. The explanation uses a yellow process station,
The same applies to other color stations.

  The photosensitive drum 11 is uniformly charged by the charging roller 21, and a latent image is formed by scanning light by the exposure optical system 31. This latent image is developed by the developing device 41 to form a toner image on the photosensitive drum 11. The untransferred toner that has not been transferred in the transfer process is scraped off by the cleaning blade and stored in the waste toner container 61.

  Next, the transfer process will be described.

  In a generally used reversal development method, when the photosensitive member is, for example, a negative-polarity OPC (photo organic semiconductor) photosensitive member, a negative-polarity toner is used when developing the exposed portion. Accordingly, a positive transfer bias is applied to the transfer rollers 51 to 54 from the bias power sources 51 'to 54'.

In the actual printing process, considering the moving speed of the ETB 8 and the distance between the transfer positions of each process station,
Image formation, transfer process, and transfer material conveyance at the process station are performed at the timing when the positions of the toner images of the respective colors formed on the transfer material coincide with each other. A toner image is completed. After the toner image is completed on the transfer material,
The transfer material is passed through the fixing device 9, and the toner image is fixed on the transfer material, thereby completing the image.

  Further, in the process of printing an image, a process of cleaning the toner remaining on the ETB is necessary. The ETB cleaning process will be described below.

As a means for removing the toner remaining on the ETB, a method of scraping the residual toner on the belt with a blade or the like, an OPC electrostatic recovery method in which the transfer member reversely transfers the toner to the photosensitive member and collects it in a cleaning container in the cartridge, etc. There is. The method of scraping the residual toner on the belt with the blade has a drawback that the belt is scraped due to wear because the belt and the blade are in contact with each other. On the other hand, in the OPC electrostatic recovery system, only a reverse polarity bias is applied during cleaning, and there is no adverse effect such as belt scraping due to wear.
Here, the OPC electrostatic recovery system will be described with reference to FIG.

  In order to efficiently transfer the toner on the ETB 8 back to the photosensitive drums 11 to 14, the negative and positive voltages are sequentially applied alternately to the transfer portions of the four stations. Assuming the first to fourth stations in order from the upstream station, the negative voltage is applied to the first and third stations, the negative toner is applied, and the positive voltage is applied to the second and fourth stations, respectively. By reverse transfer to the photosensitive drum, the toner is collected in the cleaning containers 61 to 64 in the same manner as the untransferred toner.

At this time, by giving a circumferential speed difference Δv12 [%] between the moving speed v1 of the belt and the moving speed v2 of the OPC,
By rubbing the residual toner on the belt, and encouraging charging of the toner sandwiched between the belt and the photosensitive drum, and forcibly moving the residual toner by the rubbing force,
The influence of van der Waals force is weakened, and the residual toner moves in the direction of the force received by the electric field generated between the photosensitive drum and the transfer roller. Accordingly, the chance of collecting the residual toner on the belt is increased, and the mechanism can be efficiently cleaned.

  The moving speed difference Δv12 [%] is defined by the following equation.

Δv12 [%] = (v1−v2) / v2 * 100
JP 2000-219354 A

  However, at the time of ETB cleaning when the OPC electrostatic recovery method is adopted, especially when a peripheral speed difference is provided between the ETB and the photosensitive drum, both the belt surface layer and the photosensitive drum are smooth, so that the ETB- The area of the contact surface between the photosensitive drums is increased, and as a result, a large frictional force is generated. For this reason, the ETB is rotated with respect to the rotation of the photosensitive drum, and it becomes impossible to perform ETB cleaning with a difference in peripheral speed.

  However, since the contact surface area between the ETB and the photoconductive drum is reduced by making the belt surface layer rough, a large frictional force is not generated, and the ETB does not follow the rotation of the photoconductive drum. As a result, a peripheral speed difference can be provided between the ETB and the photosensitive drum, and effective ETB cleaning becomes possible.

  On the other hand, by roughening the belt surface layer, toner external additives or paper powder is embedded in the belt surface. It is impossible to recover the toner embedded on the ETB surface by the OPC electrostatic recovery method, and as a result, there is a possibility of causing an image defect due to the uncollected toner.

  Therefore, the present invention has an object to provide ETB cleaning by an OPC electrostatic recovery system having a peripheral speed difference by providing the roughness of the ETB surface layer and to provide a high-quality image. .

  In order to achieve the above object, the invention described in claim 1 develops at least an image carrier, charging means for charging the image carrier to a predetermined polarity, and an electrostatic latent image formed on the image carrier. In an image forming apparatus having a plurality of image forming units having a developing device visualized by an agent and a transfer member stretched by a plurality of members, the surface roughness of the transfer member is 0.05 in terms of centerline average roughness Ra <Ra <0.2 [μm] is within the specified range.

  The invention described in claim 2 employs an in-line method in which a plurality of different image forming units are arranged in series in the invention described in claim 1 and a developed image is transferred onto a transfer material conveyed by a transfer member at a time. It is characterized by being.

  According to a third aspect of the present invention, in the first or second aspect of the invention, when the developer remaining on the transfer member is removed, a cleaning bias having a different bias polarity is applied to the transfer member so as to be applied to the transfer member. The remaining transfer material is removed.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein when the developer remaining on the transfer member is removed, the movement speed v1 [mm / s] of the surface of the elephant carrier is The moving speed difference Δv12 [%] (Δv12 = (v1−v2) / v2 * 100) with respect to the moving speed v2 [mm / s] of the transfer member is changed, and the speed difference | Δv12 | It is within the specified range of | Δv12 | <500 [%].

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the transfer member has an endless belt shape.

  The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the transfer member has a structure of at least two layers.

  A seventh aspect of the invention is characterized in that, in the invention of any one of the first to sixth aspects, the transfer member is a transfer conveyance material that electrostatically adsorbs and conveys a transfer material.

  According to the present invention, by defining the center line average roughness Ra on the ETB surface layer, it is possible to perform ETB cleaning with a difference in peripheral speed between the ETB and the photosensitive drum, and to achieve stable and high image quality. It became possible to achieve images.

  Examples of the present invention will be described below with reference to the accompanying drawings, but the embodiments of the present invention are not limited thereto. Only the characteristic part of the invention will be described.

<Embodiment 1>
An image forming apparatus according to Embodiment 1 of the present invention will be described.

  In this embodiment, a single layer PVdF resin film having a peripheral length of 800 mm and a thickness of 100 μm was used as the ETB. The belt surface layer is polished with wrapping paper, and the roughness Ra of the ETB surface layer is changed as shown in Table 1.

  Here, the photosensitive drum has a diameter of 30 mm, and the process speed of the image forming apparatus of the present embodiment is 181 mm / s. The ETB is rotated by a driving roller, and the transfer roller located at a position facing the photosensitive drum rotates following the ETB.

  At the time of ETB cleaning, the residual toner on the ETB is rubbed and efficiently collected in the cleaning container in the cartridge, so that the photosensitive drum moving speed v1 is -60% of the peripheral speed difference with respect to the belt moving speed v2. Is given.

ここで、中心線平均粗さの測定方法は以下の通りである。

Here, the measuring method of the center line average roughness is as follows.

Measurement parameters:
Cut-off value: 0.8mm
Measuring range: 2.5mm
Measurement speed: 0.1 mm / s
* For measurement, ETB was cut out in 5 cm square, placed on a smooth glass plate and stretched, and measured with a contact-type surface roughness meter.

  In Table 1, when the ETB surface layer roughness is as smooth as 0.03 [μmRa], the contact area between the ETB and the photosensitive drum is widened. As a result, a large frictional force is generated between the ETB and the photosensitive drum. Arise. For this reason, the ETB is rotated with respect to the rotation of the photosensitive drum, and it is impossible to perform the ETB cleaning by the OPC electrostatic recovery system having a peripheral speed difference.

  On the other hand, when the surface layer of the ETB is intentionally roughened with wrapping paper (Ra ≧ 0.05 [μm] ˜), the contact area between the ETB and the photosensitive drum decreases, and the ETB-photosensitive drum The friction force generated between the two is reduced. Therefore, the ETB does not follow the rotation of the photosensitive drum, and it is possible to perform ETB cleaning with a difference in peripheral speed.

  On the other hand, when the ETB surface layer is roughened to 0.25 [μm Ra], toner external additives having a particle size of about several μm, or paper dust slightly generated due to paper scraping during the print sequence, etc., are generated on the ETB surface layer. The embedded external additive or paper powder could not be recovered by the OPC electrostatic recovery method.

  Therefore, the roughness of the ETB surface layer is defined in the following range from the viewpoints of preventing the accompanying rotation of the ETB with respect to the rotation of the photosensitive drum, and the cleaning failure due to the toner external additive, paper dust and the like.

0.05 <Ra <0.2 [μm]
Lower limit: Prevention of follow-up of ETB with respect to rotation of photosensitive drum Upper limit: Prevention of cleaning failure due to toner additive, paper powder, etc. <Embodiment 2>
Next, a second embodiment of the present invention will be described.

  In the present embodiment, as shown in FIG. An ETB having a two-layer structure in which a PVdF resin film having a peripheral length of 800 mm and a thickness of 100 μm was coated with an acrylic resin having a thickness of 1 μm was used as the ETB.

In addition, as an acrylic resin, what applied the UV curable solution to the PVdF sheet is used. Further, the roughness Ra of the belt surface layer is changed as shown in Table 2 by mixing silica, PMMA, and glass beads with several microns of commas into the coating material.
As in the first embodiment, the photosensitive drum has a diameter of 30 mm, and the process speed of the image forming apparatus of the present embodiment is 181 mm / s. The ETB is rotated by a driving roller, and the transfer roller located at a position facing the photosensitive drum rotates following the ETB.

  At the time of ETB cleaning, the residual toner on the ETB is rubbed and efficiently collected in the cleaning container in the cartridge. Therefore, the photosensitive drum moving speed v1 is -60% of the peripheral speed difference with respect to the ETB moving speed v2. Is given.

ここで、中心線平均粗さの測定方法は実施の形態１と同様であるので省略する。

Here, since the measuring method of the center line average roughness is the same as that of the first embodiment, the description thereof is omitted.

  In Table 2, when the particles were not added to the coating agent and the roughness of the ETB surface layer was as smooth as 0.03 [μmRa], the contact area between the ETB and the photosensitive drum was increased, and as a result, the ETB- A large frictional force is generated between the photosensitive drums. For this reason, the ETB is rotated with respect to the rotation of the photosensitive drum, and it is impossible to perform the ETB cleaning by the OPC electrostatic recovery system having a peripheral speed difference.

  On the other hand, when the coating agent is mixed with particles such as silica, PMMA, glass beads and the like having a particle size of about a few microns, and the ETB surface layer is rough (Ra ≧ 0.05 [μm]), ETB- The contact area between the photosensitive drums is reduced, and the frictional force generated between the ETB and the photosensitive drum is reduced. Therefore, the ETB does not follow the rotation of the photosensitive drum, and it is possible to perform ETB cleaning with a difference in peripheral speed.

  On the other hand, when the ETB surface layer is roughened to 0.25 [μmRa], toner external additives having a particle size of about several microns, or paper dust generated slightly due to paper scraping during the print sequence, etc., are present on the ETB surface layer. The embedded external additive or paper powder could not be recovered by the OPC electrostatic recovery method.

  Therefore, in the coating two-layer belt, the following relationship is necessary for the roughness of the ETB surface layer from the viewpoints of prevention of follow-up of the ETB with respect to the rotation of the photosensitive drum, and poor cleaning due to the toner external additive, paper dust and the like.

0.05 <Ra <0.2 [μm]
Lower limit: prevention of rotation of ETB with respect to rotation of photosensitive drum Upper limit: prevention of poor cleaning due to toner additive, paper powder, etc. <Embodiment 3>
Next, a third embodiment of the present invention will be described.

  In the present embodiment, as shown in FIG. 2, a belt having a two-layer structure in which a PVdF resin film having a circumferential length of 800 mm and a thickness of 100 μm is coated with an acrylic resin having a thickness of 1 μm is used as an ETB. As the acrylic resin, a UV curable solution coated on a PVdF sheet is used.

  The roughness of the ETB surface layer is changed as shown in Table 3 by providing irregularities on the inner surface of the mold during belt molding.

  As in the first embodiment, the photosensitive drum has a diameter of 30 mm, and the process speed of the image forming apparatus of the present embodiment is 181 mm / s. The ETB is rotated by a driving roller, and the transfer roller located at a position facing the photosensitive drum rotates following the belt.

  At the time of ETB cleaning, the residual toner on the ETB is rubbed and efficiently collected in the cleaning container in the cartridge. Therefore, the photosensitive drum moving speed v1 is -60% of the peripheral speed difference with respect to the ETB moving speed v2. Is given.

ここで、中心線平均粗さの測定方法は実施の形態１と同様であるので省略する。

Here, since the measuring method of the center line average roughness is the same as that of the first embodiment, the description thereof is omitted.

  In Table 3, when the roughness of the belt surface layer is as smooth as 0.03 [μmRa] without unevenness on the inner surface of the mold at the time of belt molding, the contact area between the ETB and the photosensitive drum becomes wide, As a result, a large frictional force is generated between the ETB and the photosensitive drum. For this reason, the ETB is rotated with respect to the rotation of the photosensitive drum, and it is impossible to perform the ETB cleaning by the OPC electrostatic recovery system having a peripheral speed difference.

  On the other hand, when the uneven surface is intentionally formed on the inner surface of the mold and the surface of the ETB is rough (Ra ≧ 0.05 [μm] ˜), the contact area between the ETB and the photosensitive drum is reduced, and the ETB is reduced. -The frictional force generated between the photosensitive drums is reduced. Therefore, the ETB does not follow the rotation of the photosensitive drum, and it is possible to perform ETB cleaning with a difference in peripheral speed.

  On the other hand, when the ETB surface layer is roughened to 0.25 [μmRa], toner external additives having a particle size of about several microns, or paper dust generated slightly due to paper scraping during the print sequence, etc., are present on the ETB surface layer. The embedded external additive or paper powder could not be recovered by the OPC electrostatic recovery method.

  Therefore, in the coating two-layer belt, the following relationship is necessary for the roughness of the belt surface layer from the viewpoints of prevention of follow-up of the ETB with respect to the rotation of the photosensitive drum, and poor cleaning due to the toner external additive, paper dust and the like.

0.05 <Ra <0.2 [μm]
Lower limit: Prevention of ETB rotation with respect to photosensitive drum rotation Upper limit: Prevention of poor cleaning due to toner external additives, paper dust, etc.

  The present invention can be applied to an image forming apparatus such as a copying machine, a printer, or a facsimile machine that forms an image by an electrophotographic system, an electrostatic recording system, or the like.

1 is a cross-sectional view of a main part of an image forming apparatus according to the present invention. 2 is a cross-sectional view of a transfer roller portion of the image forming apparatus according to the present invention.

Explanation of symbols

11, 12, 13, 14 Photosensitive drum 21, 22, 23, 24 Charging roller 31, 32, 33, 34 Exposure device 41, 42, 43, 44 Developing device 51, 52, 53, 54 Transfer roller 61, 62, 63 , 64 Photoconductor cleaning device 7 Adsorption roller 8 ETB
9 Fixing device 97 Pressure roller

Claims (7)

A plurality of image forming units having at least an image carrier, a charging unit that charges the image carrier to a predetermined polarity, and a developing device that visualizes an electrostatic latent image formed on the image carrier with a developer; In an image forming apparatus having a transfer member stretched by a plurality of members,
An image forming apparatus, wherein the surface roughness of the transfer member is within a specified range of 0.05 <Ra <0.2 [μm] at the center line average roughness Ra.   The image forming apparatus according to claim 1, wherein a plurality of different image forming units are arranged in series, and an in-line method is employed in which the developed image is transferred at once to a transfer material conveyed by a transfer member.   The transfer material remaining on the transfer member is removed by applying a cleaning bias having a different bias polarity to the transfer member when removing the developer remaining on the transfer member. Image forming apparatus.   When the developer remaining on the transfer member is removed, the difference between the moving speed v1 [mm / s] of the surface of the elephant carrier and the moving speed v2 [mm / s] of the transfer member Δv12 [%] (Δv12 = (V1-v2) / v2 * 100), and the speed difference | Δv12 | is within a specified range of 5 <| Δv12 | <500 [%]. The image forming apparatus according to any one of?   The image forming apparatus according to claim 1, wherein the transfer member has an endless belt shape.   The image forming apparatus according to claim 1, wherein the transfer member has a configuration of at least two layers.   The image forming apparatus according to claim 1, wherein the transfer member is a transfer conveyance material that electrostatically attracts and conveys a transfer material.

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