JP2011128419A - Developing device, process cartridge, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent occurrence of an image defect caused by toner sticking to by preventing toner from sticking onto a developer carrier. <P>SOLUTION: The developing device 1 is provided with: two-component developer made of toner and carrier; and a plurality of developing rollers 4a, 4b, and 4c for conveying developer and forming a toner image on an electrostatic latent image formed on a latent image carrier 6. In the developing device 1, a coating layer of molybdenum disulfide is formed on the surface of at least one of the developing rollers 4a and 4b other than the developing roller 4c which finally develops a toner image among a plurality of the developing rollers 4a, 4b, and 4c. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a developing device, a process cartridge, and an image forming apparatus, and more particularly, a two-component developer composed of toner and a carrier, and a toner image on an electrostatic latent image formed on a latent image carrier by conveying the developer. The present invention relates to a developing device including a plurality of developer carriers to be formed, a process cartridge, and an image forming apparatus equipped with these.

  As is well known, in an image forming apparatus, a predetermined electrostatic latent image is formed on a latent image carrier made of, for example, a photoconductor, and this electrostatic latent image is visualized as a toner image. As a developing device that achieves such a visible image forming function, there is one that uses a two-component developer having a toner and a carrier.

  By the way, when such a developing device is used for a long time, the developing device may be abnormal due to wear of components and toner adhesion to components in the developing device (developing roller or doctor). The developing device abnormality here refers to a mechanical failure of the developing device, a developed image abnormality such as density unevenness or band-like unevenness, developer leakage, and the like.

  As described above, when the toner adheres to the developing roller, the toner at the fixed portion is charged, and the surface potential of the developing roller at the fixed portion changes. In a developing device comprising a non-magnetic toner and a magnetic carrier, a latent image on the photosensitive member is visualized as a toner image using an electrostatic field between the developing roller photosensitive member (the toner carried on the developing roller by electrostatic force). To the latent image portion of the photoconductor). For this reason, when the developing roller surface potential partially changes, the electrostatic field between the developing roller photoreceptors changes, which affects the output image. As a result, the image quality is degraded.

  The toner adhering to the developing roller is generated when the toner adhering to the developing roller is subjected to pressure or friction by the developing doctor or the photosensitive member and fused to the developing roller surface. As the speed of the developing device increases (development speed increases), the pressure and friction force increase, and the toner is more likely to adhere to the developing roller.

  Patent Document 1 describes a one-component developing device that reduces toner adhesion and sleeve ghost by forming a coating layer containing molybdenum sulfide on the surface of a developing roller.

  Patent Document 2 includes a developer storage chamber for storing a developer and a developer carrier for contacting the developer stored in the developer storage chamber and supporting the developer on the surface. In the developing device, the developer carrying member conveys the developer carried on the surface to a developing region formed between the surface of the electrostatic latent image carrying member and the surface of the developer carrying member. The developer carrying member is characterized in that a surface for carrying and transporting the developer is formed of a film containing at least a film-forming polymer material and molybdenum disulfide. Is described.

  However, in the inventions described in Patent Document 1 and Patent Document 2, since the molybdenum compound has a high electric resistance, the molybdenum compound itself is charged up due to friction with the developer, etc. There is a problem of having an influence.

  Accordingly, it is an object of the present invention to provide a developing device that can prevent toner from sticking to a developing carrier and prevent the occurrence of abnormal images due to toner sticking, and an image forming apparatus including the developing device.

  The invention of claim 1 includes a two-component developer comprising toner and a carrier, and a plurality of developer carriers that transport the developer and form a toner image on an electrostatic latent image formed on the latent image carrier. In the developing device, a coating layer of molybdenum disulfide is provided on the surface of at least one developer carrier among the plurality of developer carriers.

  According to a second aspect of the present invention, in the developing device according to the first aspect, at least one developer carrier of a developer carrier other than the developer carrier that develops a toner image at the end of the plurality of latent image carriers. The coating layer is provided on the body.

According to a third aspect of the present invention, in the developing device according to the first or second aspect, the coating layer is provided on the developer carrying member that does not include a developer regulating member that adjusts the amount of the developer on the developer carrying member. It is characterized by providing.
According to a fourth aspect of the present invention, in the developing device according to any one of the first to third aspects, the coating layer has a thickness of 10 μm or less.

  According to a fifth aspect of the present invention, in the developing device according to any one of the first to fourth aspects, the surface of the developer carrying member is formed of Al (aluminum).

  According to a sixth aspect of the present invention, there is provided a process cartridge including the developing device according to any one of the first to sixth aspects.

  A seventh aspect of the present invention is an image forming unit comprising the developing device according to any one of the first to sixth aspects or the process cartridge according to the seventh aspect.

  According to the developing device, the process cartridge, and the image forming apparatus according to the present invention, since the coating layer of molybdenum disulfide is provided on the surface of at least one developer carrying body among the developer carrying bodies, Since the adhesion of the developer can be suppressed, the occurrence of an abnormal image due to toner fixation can be prevented, and the image quality can be improved by suppressing the occurrence of the abnormal image.

1 is a schematic cross-sectional view of an image forming apparatus according to an embodiment. It is sectional drawing which shows the structure of a developing device. It is a perspective view which shows the separator of a developing device. It is a top view which shows the separator of a developing device. The developer stirring member is shown, (a) is a perspective view, and (b) is a front view. It is a perspective view which shows a developing agent conveyance member. It is a table | surface which shows the abnormality margin of a developing roller provided with the film layer by various materials. It is a schematic diagram which shows a developing device provided with a some developing roller. It is a schematic diagram which shows the case where a film | membrane is formed in a different developing roller.

  The present invention provides a development comprising a two-component developer comprising toner and a carrier, and a plurality of developer carriers that transport the developer and form a toner image on an electrostatic latent image formed on the latent image carrier. In the apparatus, a coating layer of molybdenum disulfide is provided on the surface of at least one developer carrier among the plurality of developer carriers. According to this example, since the adhesion of the developer to the developer carrying member can be suppressed, the occurrence of an abnormal image due to toner fixation can be prevented, the generation of the abnormal image can be suppressed, and the image quality can be improved.

  In the developing device of the present invention, the coating layer may be provided on at least one developer carrier of a developer carrier other than the developer carrier that develops a toner image at the end of the plurality of latent image carriers. Can be. According to this example, since the coating layer is provided on any of the developer carriers other than the developer carrier that develops the toner image last on the latent image carrier, the abnormal image due to the charge-up of the coating layer is Corrected by development by the downstream developing roller, the image quality can be improved.

  In the developing device of the present invention, the coating layer can be provided on a developer carrying member that does not include a developer regulating member that adjusts the amount of developer on the developer carrying member. In the developer restricting section, the developer and the developing roller surface rub against each other strongly, so that the coating layer on the developing roller surface is easily triboelectrically charged. By forming the coating layer on the developing roller that does not have a developing doctor, friction at the developer regulating portion is suppressed, the amount of charge-up of the molybdenum disulfide coating is suppressed, and the image quality is improved.

  In the developing device of the present invention, the coating layer may have a thickness of 10 μm or less. The thinner the coating layer of molybdenum disulfide, which is an insulator, the easier it is to remove charges and reduce the amount of charge-up, and the generation of abnormal images due to charge-up of the coating can be suppressed, and the image quality can be improved. .

  In the developing device of the present invention, the surface of the developer carrying member can be formed of Al (aluminum). Al or SUS (stainless steel) is generally used as the material of the developing roller surface, but SUS is harder than Al and has poor workability, and therefore the manufacturing cost is increased. On the other hand, since Al has good workability and can be manufactured at low cost, the cost can be reduced.

  The present invention also provides a process cartridge on which the developing device is mounted. Here, the process cartridge refers to a cartridge in which at least one of a charging unit, a developing unit, and a cleaning unit and a latent image carrier are integrally formed and detachable from the apparatus main body. Even when all the units are not integrated, if the charging unit, the developing unit, and the cleaning unit are detachable from the apparatus main body, the detachable portion is used. A process cartridge is formed.

  The present invention is an image forming apparatus including the developing device or the process cartridge.

  The image forming apparatus according to the present invention will be described below. FIG. 1 is a schematic cross-sectional view of an image forming apparatus according to an embodiment. The image forming apparatus includes a sheet conveying unit 100 that conveys the sheet S, an image forming unit 200 that forms an image on the sheet conveying unit 100 that is arranged and conveyed above the sheet conveying unit 100, and an image forming unit 200 that is above the image forming unit 200. An image reading unit 300 is provided that reads the image of the document that is placed. The paper transport unit 100 includes a paper tray 101 on which the paper S is stacked, a pickup roller 101a that feeds the paper S on the paper tray 101, a paper feed unit such as a feed roller 101b and a reverse roller 101c that separates the paper S, a transport roller 103, A registration roller 102 is provided.

  When the paper feed signal is turned on, the sheet S on the paper tray 101 is separated, transported by the transport roller 103, abutted against the nip portion of the registration roller 102, skew corrected, and from the drum-shaped photoconductor. The toner image is sent out at a timely timing associated with the toner image on the latent image carrier 6.

  The image forming unit 200 includes a latent image carrier 6 as a photosensitive member, a charging unit 500 arranged around the latent image carrier 6, a developing device 1, a transfer unit 700, a cleaning unit 800, and a sheet after image transfer. A paper belt supplied from the paper transport unit 100, and a writing unit 1000 that partially exposes the uniformly charged latent image carrier 6 to form a latent image. An image is formed on S, and is discharged to a discharge tray 350 via a discharge roller 250.

  Next, the developing device mounted on the image forming apparatus according to the embodiment will be described. FIG. 2 is a cross-sectional view showing the configuration of the developing device. The developing device 1 forms a toner image on the latent image on the latent image carrier 6 with a two-component developer having a non-magnetic toner and a magnetic carrier. The developing device 1 includes a toner hopper 2 that replenishes toner, a toner replenishing roller 3, developing rollers 4 and 5 that are developer carriers, a developer conveying member 7, a developer stirring member 8, a developing doctor 9, and a separator 10. . In the figure, reference numeral 17 denotes a case, and reference numeral 18 denotes a toner concentration detector. Here, in this embodiment, the developing device 1 is configured as a process cartridge that is integrally configured with a latent image carrier 6 on which a toner image is formed on the outer peripheral surface and is detachable from the image forming apparatus main body.

  In the developing device 1, the toner hopper 2 stores toner, and when the toner concentration detector 18 detects a decrease in the toner concentration in the developer, the toner in the toner hopper 2 is removed by the rotation of the toner supply roller 3. Replenished in the developer. The developer conveying member 7 conveys the developer toward the developing roller 4, and the developer agitating member 8 laterally agitates the developer in the axial direction of the developing roller 4.

  The developer conveying member 7 is driven to rotate counterclockwise in FIG. 1, and the developer agitating member 8 is driven to rotate clockwise in FIG. The developer conveying member 7 (see FIG. 6) supplies the developer to the developing roller 4. The supplied developer is conveyed while being carried on the peripheral surface of the developing roller 4 rotating in the counterclockwise direction, and an image is formed on the photoreceptor 6 rotating in the clockwise direction by the developer carried and carried. The electrostatic latent image is visualized as a toner image. Further, the developer carried on the peripheral surface of the developing roller 4 is carried and conveyed on the circumferential surface of the developing roller 5, and the electrostatic latent image formed on the photosensitive member 6 is also transferred to the toner by this carried and conveyed developer. Visualized as an image.

  The developer supplied to the developing roller 4 is scraped off by the developing doctor 9, and the scraped developer is guided to the separator 10. FIG. 3 is a perspective view showing a separator of the developing device, and FIG. 4 is a plan view showing the separator of the developing device. As shown in FIGS. 3 and 4, the separator 10 includes fins 11 that are arranged at a certain angle a and a developer transport screw member 12 that is rotationally driven, and the developer passing through the fins 11 is In the developing device shown in FIG. 2, the developer is conveyed from the near side to the far side (see the arrow in FIG. 4) and dropped toward the developer stirring member 8.

  On the other hand, a part of the developer falls on the developer conveying screw member 12 through the separator opening 13, and the dropped developer is broken by the broken arrow as shown in FIG. 4 by the developer conveying screw member 12. While being carried in the direction, it is dropped toward the developer stirring member 8. FIG. 5 shows a developer stirring member, where (a) is a perspective view and (b) is a front view. As shown in FIG. 5, the developer agitating member 8 is configured such that, for example, a large number of ellipsoidal plates 15 are fixedly mounted on a single shaft 14 with a constant angle P and a constant angle b. The developer is laterally stirred (reciprocating in the direction of the rotation axis) while the developer stirring member 8 is driven to rotate. FIG. 6 is a perspective view showing the developer conveying member. The developer conveying member 7 is a member in which fins 7b are radially formed on the shaft 7a.

  Next, the developing rollers 4 and 5 will be described. In this example, the surface of the developing rollers 4 and 5 is made of aluminum (Al). Further, a coating layer of molybdenum disulfide (MoS2) having a thickness of 4 to 8 μm is formed on the surfaces of the developing roller 4 and the developing roller 5.

  Hereinafter, the margin for occurrence of abnormal images due to toner adhesion to the developing roller when various coating layers are formed on Al of the developing roller will be described. FIG. 7 is a table showing an abnormality occurrence margin of a developing roller having a film layer made of various materials. Note that the abnormal image occurrence margin means that the larger the margin is, the less an abnormal image is generated (the image quality is better). In Ni, Cr coating and alumite treatment, the margin for occurrence of abnormal images due to toner adhesion to the developing roller was equivalent to that on the Al surface, and no improvement effect was observed. In contrast, the MoS2 (molybdenum disulfide) coating greatly improved the margin for abnormal image generation. Ni, Cr, anodized and MoS2 have different surface slidability. MoS2 has a small coefficient of friction and excellent slidability compared to other materials (see FIG. 7). If the slidability is excellent, it is difficult for toner to adhere to the surface, and the sticking of the sleeve can be suppressed.

  A friction force is applied to the carrier and the developing roller made of a magnetic material such as magnetite or ferrite by rubbing with the developer at the developing doctor or the photosensitive member. When such contact with the developer is repeated, the toner is fused to the surface of the developing roller and fixed. In general, in a developing device composed of a two-component developer composed of a toner and a carrier, a latent image on the photoreceptor is visualized as a toner image using an electrostatic field between the developing roller photoreceptors (by electrostatic force, The toner carried on the developing roller is conveyed to the latent image portion of the photoreceptor). The toner is charged by frictional charging with the carrier (mainly performed by a developing doctor), and moves the electrostatic field. For this reason, the toner is given a charging ability by giving a certain amount of resistance. When this toner adheres to the surface of the developing roller, an electric charge is applied to the fixing portion (charge up), and the surface potential of the developing roller 4 partially changes. As a result, the electrostatic field between the developing roller photoconductors partially changes, and abnormal images such as background smudges and image density unevenness occur, resulting in degradation of image quality.

  Since the developing roller on which the MoS2 coating layer is formed is excellent in slidability, the developer slips on the surface, the toner hardly adheres to the surface of the developing roller, and the friction between the developer and the developing roller is reduced. Therefore, toner adhesion to the developing roller can be reduced. As a result, it is possible to suppress the occurrence of an abnormal image due to toner sticking to the developing roller, leading to an improvement in image quality. However, MoS2 is an insulator and charges itself up. As a result, an abnormal image similar to toner fixation occurs.

  Next, a developing device including a plurality of developing rollers will be described. FIG. 8 is a schematic diagram showing a developing device including a plurality of developing rollers. This developing device includes four developing rollers 4a, 4b, and 4c, all of which rotate in the same direction. In addition, the arrow in a figure represents the rotation direction of a developing roller and a photoreceptor. In this case, the amount of the developer is regulated by the developing doctor 9 installed on the developing roller 4a, and the developer is carried from the developing roller 4a to the developing roller 4b to the developing roller 4c, and the electrostatic latent image on the photosensitive member 6 is transferred. The toner is attached to the image and developed. At this time, the developing roller 4a having the developing doctor 9 is more rubbed with the developer than the developing rollers 4b and 4c having no developing doctor 9 which is a developer regulating member, so that the toner is easily fixed. When toner adheres to the developing roller 4a, the adhered portion is charged up.

  When the toner fixing amount is small and the charge-up amount is small, the background contamination and image density unevenness generated in the developing roller 4a are small and corrected by the development of the downstream developing rollers 4b and 4c. However, when the charge-up amount increases, correction cannot be made by developing the downstream developing rollers 4a and 4c. Furthermore, since the fixed toner is charged up to the same polarity as the toner, when the developing roller 4a is charged up, a potential difference is generated between the developing rollers 4a and 4b. When the potential difference becomes large, the toner is developed from the developing roller 4a to 4b, so that the toner easily adheres to the surface of the developing roller 4b. As a result, toner sticking occurs. Similarly, when the developing roller 4b is fixed with toner, the developing roller 4c is also fixed with toner. As a result, an abnormal image due to toner fixation occurs over time.

  FIG. 9 is a schematic view showing a case where a film is formed on different developing rollers. FIG. 9A shows a case where the developing roller 4a shown in FIG. 8 is coated with a MoS2 film. At this time, the toner sticking of the developing roller 4a can be prevented by the MoS2 film. Then, since no potential difference due to the fixed toner is generated between the developing roller 4a and the developing roller 4b, the toner is not developed from the developing roller 4a to 4b. That is, since it is possible to suppress the toner from adhering to the surface of the developing roller 4b, the progress of the toner fixing can be suppressed. Then, the progress of fixing of the developing roller 4c can be suppressed. As a result, the occurrence of abnormal images due to toner fixation can be suppressed, and the image quality can be improved.

  Here, the charge-up of MoS2 itself, which is an insulator, becomes a problem. According to the inventor's measurement, as time passed, the charge-up amount increased with toner fixation, and the value reached 200 V or more. Generally, since the electrostatic potential for forming a toner image is ˜400V, it can be seen how large value is 200V. However, the charge-up amount on the surface of the developing roller in which the MoS2 coating layer having a thickness of 10 μm was provided on the aluminum substrate under the same conditions was about ˜20V. The charge-up amount of MoS2 is smaller than the charge-up amount of toner fixing that proceeds. For this reason, even if an abnormal image is generated due to the MoS2 charge-up on the developing roller 4a, it is corrected by the development of the developing rollers 4b and 4c. As a result, the image quality is improved.

  As shown in FIG. 9B, when the developing roller 4b of the developing unit shown in FIG. 8 is coated with MoS2, the surface of the developing roller 4a is fixed with toner, and the developing rollers 4a and 4b In the meantime, a potential difference due to the fixed toner is generated, and the toner is developed on the developing rollers 4a to 4b. However, since there is a coating layer on the surface of the developing roller 4b, the toner can be prevented from sticking. Further, since the developing roller 4b does not adhere the toner, it is possible to suppress the progress of the toner fixing of the developing roller 4c. In this case, an abnormal image due to the fixed toner charge-up is generated by the development with the developing roller 4a due to the toner fixing, but the abnormal image at 4a is corrected by the subsequent development with the developing rollers 4b and 4c. . An abnormal image due to the charge-up of the MoS2 coating layer of the developing roller 4b is corrected by the development of the developing roller 4c. As a result, the occurrence of abnormal images due to toner fixation can be suppressed, and the image quality can be improved.

  As shown in FIG. 9C, when the developing roller 4c of the developing unit shown in FIG. 8 is coated with MoS2, the toner is fixed to the developing rollers 4a and 4b as time passes. The developing roller 4c coated with the coating can suppress toner sticking. In addition, the occurrence of an abnormal image in the development by the developing rollers 4a and 4b can be corrected by the development by the developing roller 4c. However, since the developing roller 4c finally visualizes the toner image on the photosensitive member 6, the developing roller 4c is affected by the charge-up of the MoS 2 itself. However, in a developing device having a plurality of developing rollers, the development contribution per developing roller is smaller than in the case of one developing roller. Therefore, compared to the case of one developing roller, in FIG. 9C, the degree of abnormal images due to the charge-up of MoS2 can be reduced. As a result, the image quality is improved.

In the above example, the developing device having three stages of developing rollers has been described. However, the developing roller may have two stages or four stages or more.

DESCRIPTION OF SYMBOLS 1 Developing device 2 Toner hopper 3 Toner supply roller 4 Developing roller 4a, 4b, 4c Developing roller 5 Developing roller 6 Latent image carrier 7 Developer conveying member 7a Shaft 7b Fin 8 Developer stirring member 9 Developing doctor 10 Separator 11 Fin 12 Developer conveying screw member 13 Separator opening 14 Shaft 15 Elliptical plate 18 Toner density detector 100 Paper conveying unit 101 Paper tray 101a Pickup roller 101b Feeding roller 101c Reverse roller 102 Registration roller 103 Conveying roller 200 Image forming unit 250 Paper discharging roller 300 Image Reading unit 350 Paper discharge tray 500 Charging means 700 Transfer means 800 Cleaning means 850 Conveying belt 900 Fixing device 1000 Means

JP 2006-301485 A Japanese Patent No. 2835964

Claims (7)

In a developing device comprising a two-component developer comprising a toner and a carrier, and a plurality of developer carriers that transport the developer and form a toner image on an electrostatic latent image formed on the latent image carrier.
A developing device, wherein a coating layer of molybdenum disulfide is provided on a surface of at least one developer carrier among the plurality of developer carriers.   2. The coating layer is provided on at least one developer carrier of a developer carrier other than the developer carrier that develops a toner image lastly among the plurality of latent image carriers. Development device.   The developing device according to claim 1, wherein the coating layer is provided on a developer carrier that does not include a developer regulating member that adjusts the amount of the developer on the developer carrier.   The developing device according to claim 1, wherein the coating layer has a thickness of 10 μm or less.   The developing device according to claim 1, wherein a surface of the developer carrying member is made of Al (aluminum).   A process cartridge comprising the developing device according to any one of claims 1 to 6. An image forming unit comprising the developing device according to claim 1, or the process cartridge according to claim 7.