JP2009175700A - Cleaning roller for cleaning photoreceptor and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cleaning roller for cleaning a photoreceptor capable of efficiently collecting developer attached to an outer peripheral surface of the photoreceptor while preventing wear and damage of the outer peripheral surface of the photoreceptor, and capable of excellently maintaining its collecting performance for a long period, and also to provide an image forming apparatus including the same. <P>SOLUTION: The cleaning roller 54 for cleaning a photoreceptor is disposed in contact with the outer peripheral surface of the photoreceptor 12 to remove the developer attached to the outer peripheral surface of the photoreceptor 12. The cleaning roller 54 is constituted of a metal core 56 and a polyurethane foam layer 58 covering an outer peripheral surface of the metal core 56. The number of cells of the polyurethane foam layer 58 per inch is 40 or more and 80 or less, and an open ratio of a wall surface of cells of the polyurethane foam layer 58 is 10% or more and 50% or less. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus and a photoconductor cleaning roller used in the image forming apparatus.

  An electrophotographic image forming apparatus has a photoreceptor that carries an electrostatic latent image. When forming an image, first, the outer peripheral surface of the photoconductor is uniformly charged to a predetermined potential by a charging device, and then an electrostatic latent image is formed on the photoconductor by exposure by an exposure device. The electrostatic latent image formed on the photoconductor is visualized by toner supplied from the developing device, whereby a toner image is formed on the photoconductor. The toner image formed on the photosensitive member is transferred to a recording sheet such as paper directly or via an intermediate transfer member. The recording sheet to which the toner image has been transferred is heated and pressurized by a fixing device, whereby the toner image is fixed on the recording sheet.

  The toner image formed on the photosensitive member is transferred to a recording sheet or an intermediate transfer member. At the time of this transfer, a part of the developer (toner and toner external additive, etc.) is not transferred and the photosensitive member is transferred. Remains on top. The developer remaining on the photoreceptor is scraped off by a cleaning member disposed in contact with the photoreceptor.

  A cleaning blade is widely used as a cleaning member for a photoconductor (see Patent Document 1 and Patent Document 2). The cleaning blade has an excellent cleaning performance while having a simple structure.

  On the other hand, in recent years, the particle size of toner has been reduced in response to the demand for higher image quality. Since toner with a small particle diameter is more difficult to remove from the outer peripheral surface of the photoreceptor than conventional toners, there is an increasing demand for cleaning members with better cleaning performance.

  As a cleaning member having a cleaning performance superior to that of a cleaning blade, a technique using a cleaning roller has been proposed. The cleaning roller has a cored bar and a resin foam layer that covers the outer periphery of the cored bar, and polyurethane foam is generally used as the material of the resin foam layer. The resin foam layer (polyurethane foam layer) made of polyurethane foam increases the frequency of contact with the toner on the photoreceptor as the number of cells increases, so that the toner recovery performance can be improved. Since the pressing force to the body is small, it is possible to prevent abrasion and filming (a phenomenon in which a film such as an external additive is generated on the surface of the photoreceptor). When the polyurethane foam layer is made conductive and a predetermined voltage is applied to the cleaning roller, the toner on the photoconductor is electrostatically cleaned by the electric field formed between the photoconductor and the cleaning roller. Can be aspirated.

JP 2004-78113 A JP 2004-133269 A

  However, even if the number of cells in the polyurethane foam layer of the cleaning roller is increased, if the cells on the surface of the roller are filled with toner or external additives, the wall surfaces of the cells are difficult to come into contact with the outer peripheral surface of the photoreceptor. There is a possibility that the collection performance cannot be improved sufficiently. In particular, when the polyurethane foam layer has a closed cell structure, it is easy for the external additive and toner to agglomerate and adhere to the cell wall in the cell on the surface of the roller. In some cases, the outer peripheral surface of the photoconductor may be worn or damaged by the contact.

  Conventionally, a polyurethane foam having an open cell structure has been used as a low-hardness polyurethane foam. However, when a polyurethane foam having an open-cell structure is used, there is a problem that external additives and the like can easily pass through the polyurethane foam layer, and when used for a long period of time, the external additives and the like aggregate inside the polyurethane foam layer.

  Furthermore, when a predetermined electric field is formed between the photoconductor and the cleaning roller to electrostatically attract the toner on the photoconductor to the cleaning roller, the toner accumulates inside the polyurethane foam layer with long-term use. Then, there is a problem that the electric resistance of the polyurethane foam layer is increased, and the strength of the electric field for attracting the toner to the cleaning roller is gradually reduced.

  Accordingly, the present invention provides a photoconductor capable of efficiently recovering the developer attached to the outer peripheral surface while maintaining the recovery performance well over a long period of time while preventing the outer peripheral surface of the photoconductor from being worn or damaged. An object of the present invention is to provide a cleaning roller and an image forming apparatus including the same.

In order to solve the above-described problems, a cleaning roller for a photoreceptor according to the present invention includes:
A photoconductor cleaning roller that is disposed in contact with the outer peripheral surface of the photoconductor and removes foreign matter adhering to the outer peripheral surface of the photoconductor,
A metal core and a polyurethane foam layer covering the outer peripheral surface of the metal core;
The polyurethane foam layer has 40 to 80 cells per inch,
The opening ratio of the wall surface of the cell of the polyurethane foam layer is 10% or more and 50% or less.

An image forming apparatus according to the present invention is
The photosensitive member cleaning roller,
A photosensitive member carrying an electrostatic latent image,
The photoconductor cleaning roller is disposed in contact with the outer peripheral surface of the photoconductor.

  According to the present invention, since the number of cells of the polyurethane foam layer of the cleaning roller for the photoconductor is 40 / inch or more, a large number of cells are brought into contact with the toner and external additives at the contact portion between the photoconductor and the cleaning roller. Can be made. In addition, the number of cells of the polyurethane foam layer is 80 / inch or less, and each cell has a certain size. Furthermore, the opening ratio of the cell wall surface of the polyurethane foam layer is set to 10% or more and 50% or less, whereby the structure of the polyurethane foam layer becomes an open cell structure close to the closed cell structure. Therefore, it is possible to take in more external additives and the like than a general closed-cell structure polyurethane foam layer, and the internal additives are less likely to aggregate inside compared to a general open-cell structure. . Therefore, it is possible to efficiently recover the external additive and the like on the photoconductor and maintain the recovery performance well over a long period of time.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings. In the following description, terms indicating a specific direction (for example, “up”, “down”, “left”, “right”, and other terms including them, “clockwise direction”, “counterclockwise” ”) Is used to facilitate understanding of the invention with reference to the drawings, and the present invention should not be construed as being limited by the meaning of these terms.

[1. Image forming apparatus]
FIG. 1 shows a portion related to image formation of an electrophotographic image forming apparatus according to the present invention. The image forming apparatus may be any of a copier, a printer, a facsimile machine, and a multi-function machine having a combination of these functions. The image forming apparatus 1 includes a photoreceptor 12 that is an electrostatic latent image carrier. A specific configuration of the photoreceptor 12 will be described later. The photoreceptor 12 is drivingly connected to a motor (not shown), and is rotated in the direction of arrow 14 based on the driving of the motor. A charging station 16, an exposure station 18, a developing station 20, a transfer station 22, and cleaning stations 24 and 25 are disposed around the photoconductor 12 along the rotation direction of the photoconductor 12. In the embodiment, the first cleaning station 24 and the second cleaning station 25 are provided. However, a plurality of cleaning stations are not necessarily provided.

  The charging station 16 includes a charging device 26 that charges the photosensitive layer, which is the outer peripheral surface of the photoreceptor 12, to a predetermined potential. In the embodiment, the charging device 26 is represented as a cylindrical roller. However, instead of this, other types of charging devices (for example, a rotary or fixed brush-type charging device or a wire-discharge-type charging device) may be used. Can be used.

  In the exposure station 18, the image light 30 emitted from the exposure device 28 disposed in the vicinity of the photosensitive member 12 or away from the photosensitive member 12 travels toward the outer peripheral surface of the charged photosensitive member 12. A passage 32 is provided. On the outer peripheral surface of the photoconductor 12 that has passed through the exposure station 18, an electrostatic latent image is formed that includes a portion where the image light is projected and the potential is attenuated and a portion where the charged potential is substantially maintained. In the embodiment, the portion where the potential is attenuated is the electrostatic latent image portion, and the portion where the charged potential is substantially maintained is the electrostatic latent image non-image portion.

  The developing station 20 includes a developing device 34 that visualizes the electrostatic latent image using a powder developer. The developing device 34 includes a developing roller 44 that is disposed to face the outer peripheral surface of the photoconductor 12, and a housing 42 that stores a developer. For example, a one-component developer is used as the developer. As the toner constituting the developer, it is preferable to use a toner having a small particle diameter, which can improve the image quality. Specifically, the average particle diameter of the toner is preferably 4.5 μm or more and 7.0 μm or less. In addition, the average particle diameter as used in this specification shall point out the volume average particle diameter obtained by the measurement using the flow type particle image analyzer FPIA-2100 made by Sysmex Corporation. Here, the volume average particle diameter means a particle diameter obtained by the following method. First, a projected area is calculated for each particle, and assuming a sphere having the same projected area as the calculated projected particle area, the diameter and volume of the sphere are set as the particle diameter and the volume of the particle, respectively. After obtaining the particle diameter and volume for a predetermined number of particles by this method, it represents a volume-based distribution with the particle diameter as the horizontal axis and the integrated value of the volume as the vertical axis. The particle size at 50% is defined as the volume average particle size.

  The transfer station 22 includes a transfer device 36 that transfers a visible image formed on the outer peripheral surface of the photoreceptor 12 to a sheet 38 such as paper or film. In the embodiment, the transfer device 36 is represented as a cylindrical roller, but other types of transfer devices (for example, wire discharge transfer devices) can also be used.

  The first cleaning station 24 includes a cleaning device 40 that collects untransferred toner remaining on the outer peripheral surface of the photoconductor 12 without being transferred to the sheet 38 at the transfer station 22 from the outer peripheral surface of the photoconductor 12. In the embodiment, the cleaning device 40 is shown as a plate-like blade, but other types of cleaning devices (for example, a rotary type or a fixed type brush type cleaning device) may be used instead.

  The second cleaning station 25 includes a cleaning roller 54 that removes toner on the photoconductor 12 that has not been removed by the first cleaning station 24. A specific configuration of the cleaning roller 54 will be described later.

  In the embodiment, the cleaning device 40 is provided in the first cleaning station 24, and the cleaning roller 54 is provided in the second cleaning station 25. However, the cleaning roller 54 is provided in the first cleaning station 24, A cleaning device 40 may be provided in the second cleaning station 25.

  When the image forming apparatus 1 having such a configuration forms an image, the photoconductor 12 rotates clockwise based on the driving of a motor (not shown). At this time, the outer peripheral portion of the photoreceptor passing through the charging station 16 is charged to a predetermined potential by the charging roller 26. The charged outer periphery of the photoconductor is exposed to image light 30 at an exposure station 18 to form an electrostatic latent image. The electrostatic latent image is conveyed to the developing station 20 along with the rotation of the photosensitive member 12, where it is visualized as a developer image by the developing device 34. The visualized developer image is conveyed to the transfer station 22 along with the rotation of the photosensitive member 12, and is transferred to the sheet 38 by the transfer device 36 there. The sheet 38 to which the developer image has been transferred is conveyed to a fixing station (not shown), where the developer image is fixed to the sheet 38. The outer peripheral portion of the photosensitive member that has passed through the transfer station 22 is conveyed to the first cleaning station 24 where the developer remaining on the outer peripheral surface of the photosensitive member 12 without being transferred to the sheet 38 is recovered. The outer peripheral portion of the photosensitive member that has passed through the first cleaning station 24 is conveyed to the second cleaning station 25 where the developer remaining on the outer peripheral surface of the photosensitive member 12 is recovered.

[2. Photoconductor]
The photoconductor 12 includes, for example, a cylindrical conductive support and a photosensitive layer formed outside the conductive support. An intermediate layer is provided between the conductive support and the photosensitive layer to improve the adhesion between the conductive support and the photosensitive layer and to prevent charge injection from the conductive support to the photosensitive layer. It may be.

(Conductive support)
As a material for the conductive support, for example, aluminum is used, but a metal other than aluminum (for example, nickel) can also be used. In addition, a material other than metal may be used as the conductive support. For example, a material in which a conductive member such as aluminum is vapor-deposited on the surface of plastic or a material in which a conductive material is applied on the surface of paper or plastic is used. It can also be used.

(Photosensitive layer)
The photosensitive layer has a charge generation layer containing a charge generation material and a binder resin, and a charge transport layer formed outside the charge generation layer and containing a charge transport material and a binder resin. For example, X-type phthalocyanine is used as the charge generation material, and butyral resin is used as the binder resin of the charge generation layer. As the charge transport material, for example, a styryl compound is used, and as the binder resin for the charge transport layer, for example, a polycarbonate resin is used.

[3. Photoconductor cleaning roller)
The photoconductor cleaning roller 54 includes a cored bar 56 and a polyurethane foam layer 58 that covers the outer periphery of the cored bar 56. The specific configuration of the polyurethane foam layer 58 will be described in detail later. The cleaning roller 54 is arranged in parallel with the photoconductor 12 and rotatably. The cleaning roller 54 is drivingly connected to a motor (not shown), and rotates in the counterclockwise direction in the drawing based on the driving of the motor. As a result, the photosensitive member 12 and the cleaning roller 54 rotate in a direction (the so-called width direction) in which they move in the same direction at their contact portion (nip portion) 66. As shown in FIG. 2, the developer on the photoreceptor 12 is scraped off by the cleaning roller 54 at the nip portion 66.

The peripheral speed of the cleaning roller 54 is determined according to the peripheral speed of the photoconductor 12. Specifically, the ratio R (V _B / V _A ) of the peripheral speed V _B of the cleaning roller 54 to the peripheral speed V _A of the photoconductor 12 is set to be 0.5 or more and 3 or less, for example. If the peripheral speed ratio R (V _B / V _A ) is set to be smaller than 0.5, it is not possible to ensure a sufficient scraping force of the developer on the photosensitive member 12 by the cleaning roller 54. On the other hand, if the peripheral speed ratio R (V _B / V _A ) is set to be larger than 3, an excessive load is applied to the polyurethane foam layer 58 of the cleaning roller 54. The cleaning roller 54 may be driven by the photosensitive member 12 without drivingly connecting the motor to the cleaning roller 54. In that case, the peripheral speed ratio R (V _B / V _A ) is 1.0.

  The cleaning roller 54 is arranged so that the contact pressure to the photosensitive member 12 is 5N or more and 30N or less. If the contact pressure on the photoconductor 12 is less than 5N, the cleaning roller 54 cannot sufficiently secure the developer scraping force on the photoconductor 12. On the other hand, if the contact force to the photoconductor 12 is larger than 30N, an excessive load is applied to the photoconductor 12.

  The cleaning roller 54 is preferably arranged so that the contact nip width between the cleaning roller 54 and the photoconductor 12 is 3 mm or more and 8 mm or less in the circumferential direction. By setting the contact nip width to 3 mm or more, it is possible to sufficiently secure the scraping force of the developer on the photoconductor 12 by the cleaning roller 54, and by setting the contact nip width to 8 mm or less, the load applied to the photoconductor 12 is reduced. Can be suppressed.

  The amount of the polyurethane foam layer 58 biting into the photoreceptor 12 is preferably 5% to 40% of the thickness of the polyurethane foam layer 58. By setting the biting amount to 5% or more, it is possible to sufficiently secure the scraping power of the developer on the photoreceptor 12 by the cleaning roller 54, and by setting the biting amount to 40% or less, the polyurethane foam layer of the cleaning roller 54 The load on 58 can be suppressed.

  A scraping member 70 is disposed in contact with the outer peripheral surface of the cleaning roller 54. At the contact portion between the cleaning roller 54 and the scraping member 70, a part of the developer contained in the polyurethane foam layer 58 of the cleaning roller 54 is scraped off by the scraping member 70. As a result, excessive toner and external additives can be prevented from accumulating inside the polyurethane foam layer 58 and aggregation of the toner and external additives inside the polyurethane foam layer 58 can be prevented. However, in the present invention, the scraping member is not necessarily provided. A specific example of the configuration of the scraping member will be described later.

  A power supply 68 is connected to the cleaning roller 54. When a predetermined voltage is applied to the cleaning roller 54 by turning on the power supply 68, the photosensitive member 12 is interposed between the photosensitive member 12 and the cleaning roller 54. An electric field for electrostatically attracting the upper toner to the cleaning roller 54 is formed. Thereby, the toner remaining on the photoreceptor 12 can be removed more efficiently. However, in the present invention, the power source 68 is not necessarily provided, and the toner on the photoconductor 12 may be removed only by a mechanical operation.

[4. (Polyurethane foam layer of cleaning roller)
As shown in FIG. 3, the polyurethane foam layer 58 has a large number of cells (bubbles) 80. A cell 80 having an opening 82 on the wall surface is connected to another cell 80 through the opening 82. When the ratio of the area S ₁ of the opening 82 to the area S of the entire wall surface of the cell 80 (S ₁ / S × 100) is defined as the opening ratio, the opening ratio of the cell wall surface of the polyurethane foam layer 58 is 10% or more and 50%. It is as follows. The opening ratio is higher than the opening ratio (about 1%) of a polyurethane foam having a general closed cell structure manufactured by a known mechanical floss method or the like, and is generally manufactured by a known chemical foaming method or the like. It is lower than the open area ratio (about 60%) of polyurethane foam having an open cell structure. That is, the polyurethane foam layer 58 has an open cell structure close to a closed cell structure. Therefore, a larger amount of developer can be taken into the interior than a polyurethane foam layer having a general closed-cell structure, and the developer is less likely to aggregate inside than a general open-cell structure. Therefore, the developer recovery performance can be sufficiently secured, and the recovery performance can be favorably maintained over a long period of time.

  In addition, the polyurethane foam layer 58 has 40 to 80 cells per inch. This number of cells is smaller than the number of cells of a general closed-cell structure polyurethane foam (about 100 cells / inch) and larger than the number of cells of a general open-cell structure polyurethane foam (about 25 cells / inch). . That is, the polyurethane foam layer 58 can bring a larger number of cells into contact with the developer at the nip portion 66 between the cleaning roller 54 and the photosensitive member 12 than a general polyurethane foam having an open cell structure. Further, since each cell of the polyurethane foam layer 58 is larger than a polyurethane foam having a general closed cell structure, it is difficult for the developer to be clogged in each cell. Therefore, developer agglomerates or adherents hardly occur in the cells on the surface of the polyurethane foam layer 58, and damage to the photoreceptor 12 due to contact with the agglomerates or adherents can be suppressed. Therefore, even when the relatively low hardness photoconductor 12 whose surface layer is made of polycarbonate resin is used, damage to the photoconductor 12 can be suppressed.

  The polyurethane foam layer 58 has a hardness as low as that of a general open cell structure. In the present specification, the hardness of the polyurethane foam layer 58 is determined so that the polyurethane foam layer 58 is pressed to a depth corresponding to 30% of the surface side of the thickness (until the thickness of the polyurethane foam layer 58 becomes 70% of the original). It is represented by the magnitude of the load per unit length that the pressing surface receives when it is pushed into the contacting surface. Specifically, the hardness of the polyurethane foam layer 58 is preferably 1 gf / mm or more and 5 gf / mm or less. This hardness is smaller than the hardness when the polyurethane foam layer has a general closed cell structure (about 8.5 gf / mm), and the hardness when the polyurethane foam layer has a general open cell structure (0.8 gf). / Mm). By setting the hardness of the polyurethane foam layer 58 to 1 gf / m or more, it is possible to sufficiently ensure the scraping power of the developer by the polyurethane foam layer 58, so that the developer on the photoconductor 12 can be used as the photoconductor 12 and the polyurethane It is possible to prevent slipping through the nip 66 with the foam layer 58. By setting the hardness of the polyurethane foam layer 58 to 8 gf / m or less, it is possible to prevent the polyurethane foam layer 58 from pressing the outer peripheral surface of the photoconductor 12 with an excessive force, thereby developing the developer on the photoconductor 12. Can be prevented from being crushed by the polyurethane foam layer 58 and causing filming on the surface of the photoreceptor 12.

  Furthermore, the average value of the cell diameter of the polyurethane foam layer 58 is preferably 100 μm or more and 500 μm or less. The average value of the cell diameter is smaller than the cell diameter (about 700 μm) of a general open-cell structure polyurethane foam layer, and larger than the cell diameter (about 80 μm) of a general closed-cell structure polyurethane foam layer. . That is, since the polyurethane foam layer 58 has finer cells than a general polyurethane foam layer having an open cell structure, the polyurethane foam layer 58 is more frequently contacted with the developer on the photoreceptor 12 and scrapes off the developer more reliably. Can do.

Furthermore, the polyurethane foam layer 58 has a lower density than a polyurethane foam layer having a general closed cell structure. Specifically, the density of the polyurethane foam layer 58 is preferably 0.03 g / cm ³ or more and 0.2 g / cm ³ or less. Thereby, the flexibility of the polyurethane foam layer 58 can be sufficiently secured, and the photoreceptor 12 can be prevented from being pressed by the polyurethane foam layer 58 with an excessive force.

In order to form a predetermined electric field between the photoreceptor 12 and the cleaning roller 54, the polyurethane foam layer 58 is provided with conductivity. The volume resistivity of the polyurethane foam layer 58 is preferably 10 ² Ωcm or more and 10 ⁷ Ωcm or less. Thereby, the polyurethane foam layer 58 has appropriate conductivity, and an appropriate electric field can be formed between the photoconductor 12 and the cleaning roller 54.

[5. (Polyurethane foam production method)
With respect to the polyurethane foam layer 58 having the above configuration, a method for producing a polyurethane foam as a material thereof will be described.

  The polyurethane foam used in the present invention is produced by a method combining a known mechanical flossing method and a known chemical foaming method.

  The mechanical flossing method and the chemical foaming method are common in that foaming is performed by mixing a polyol and an isocyanate. However, in the mechanical froth method, a foaming agent is not used as a raw material, and physical foaming is performed by mixing a gas for forming bubbles such as an inert gas, whereas in a chemical foaming method, a raw material is used. The difference is that a foaming agent is used and chemical foaming is performed by a chemical reaction between the isocyanate and the foaming agent. When the mechanical floss method is employed, a polyurethane foam having a homogeneous closed cell structure can be produced, but it is difficult to produce a polyurethane foam having an open cell structure having a low density. On the other hand, when the chemical foaming method is employed, a low-density open-cell structure polyurethane foam can be easily produced, but it is difficult to produce a homogeneous closed-cell structure polyurethane foam.

  In contrast to these conventional manufacturing methods, the polyurethane foam manufacturing method used in the present invention is used in the chemical foaming method in addition to the polyol, isocyanate and gas for forming bubbles used in the mechanical floss method. A foaming agent is used as a raw material, which combines physical foaming due to the incorporation of gas for forming bubbles and chemical foaming associated with the chemical reaction of the isocyanate and the foaming agent. Therefore, homogeneous cells formed by physical foaming are joined together by chemical foaming, and a homogeneous and low density polyurethane foam, that is, a polyurethane foam having an open cell structure close to a closed cell structure can be produced. Hereinafter, a specific manufacturing method will be described.

  The polyurethane foam used in the present invention is produced from the beginning through a raw material adjustment step, a mixing step, and a heating step.

  In the raw material adjusting step, each raw material used for manufacturing the polyurethane foam is adjusted. As raw materials, secondary materials such as polyol, isocyanate, gas for forming bubbles such as inert gas, foaming agent, and catalyst are used.

  As a polyol, the well-known polyol which has an active hydrogen group is used individually or in combination of 2 or more types, for example. Specifically, examples of the polyol used include polyether polyol, polyester polyol, polycarbonate polyol, and polydiene-based polyol. As the isocyanate, for example, a well-known aromatic system such as toluene diphenyl diisocyanate (TDI), TDI prepolymer, methylene diphenyl diisocyanate (MDI), crude MDI, polymeric MDI, uretdione-modified MDI, or carbodiimide-modified MDI, aliphatic or aliphatic Various polyisocyanates such as ring systems are used. For example, nitrogen is used as the gas for forming bubbles. As the foaming agent, a raw material that generates a gas by a chemical reaction with isocyanate is used, and specifically, water or the like is used. The blowing agent is mixed with the polyol in advance before the mixing step. As the catalyst, for example, an amine catalyst and an organic acid salt catalyst are used. Amine-based catalysts are mainly used to promote rapid chemical foaming, and organic acid salt-based catalysts are mainly used to cure the polyurethane foam backbone. As the organic acid salt catalyst, it is preferable to use a heat-sensitive catalyst that exhibits a catalytic effect by required heating. Thereby, the hardening of the skeleton of the polyurethane foam can be delayed more than the chemical foaming carried by the amine-based catalyst, and chemical foaming can surely occur.

  Factors that determine the hardness of the polyurethane foam include, for example, the type of polyol and the isocyanate index. In the present specification, the isocyanate index refers to a percentage of the ratio N / M of the number of moles of isocyanate groups in isocyanate to the total number of moles M of hydroxyl groups of the blowing agent and hydroxyl groups of the polyol. In order to form the polyurethane foam to have the above-mentioned desired hardness, for example, a polyether polyol or a polyester polyol having a molecular weight of 1000 to 6000 and a functional group number of 2 to 5 is preferably used as the polyol. It is preferable to adjust the isocyanate index to 90 to 110.

  When water is used as a foaming agent, carbon dioxide is generated by a chemical reaction between water and isocyanate when the raw materials are mixed, thereby forming bubbles (cells). In order to form a low-density polyurethane foam having fine cells, carbon dioxide generated by a chemical reaction between water and isocyanate is placed inside the bubbles (cells) physically generated by the gas for forming bubbles. Need to get in. In order to achieve this object, it is preferable to adjust the mixing amount of water to 0.3 to 1.5 parts by mass with respect to 100 parts by mass of the polyol.

  In the mixing step, a polyol, an isocyanate, a gas for forming bubbles, a catalyst, and the like mixed with a foaming agent such as water are mixed. As a result, first, physical foaming occurs, and homogeneous bubbles (cells) having a bubble-forming gas as a nucleus are formed. Then, a gas such as carbon dioxide is generated by causing a chemical reaction between the blowing agent contained in the polyol and the isocyanate, and this gas enters the cell formed by physical foaming, and the cell diameter as a whole. Increases and the cells are connected. Thereby, a cell having a large diameter is formed while being homogeneous.

  In the heating step, the mixed raw material is heated to accelerate the resinification reaction and cure the polyurethane foam skeleton. The heating temperature and heating time in the heating step are appropriately determined according to the raw material of the polyurethane foam in accordance with a known mechanical flossing method.

  According to the manufacturing method demonstrated above, the polyurethane foam with a high opening rate of a cell wall surface is formed compared with the polyurethane foam manufactured by the mechanical floss method. For this reason, when the polyurethane foam is impregnated with a solution containing a conductive substance or the like, the solution easily penetrates into the polyurethane foam, so that a function such as conductivity can be easily imparted.

  The polyurethane foam manufactured in this way is processed into a desired shape and fixed to a cored bar, whereby the cleaning roller 54 is manufactured.

  Then, the method to provide electroconductivity to a polyurethane foam is demonstrated. As a method for imparting conductivity to the polyurethane foam, for example, a foam molding method using a raw material mixed with a conductive material such as carbon black, polypyrrole or an ionic conductive material, or a conductive material as described above is used. Examples include a method in which a polyurethane foam is impregnated with a solution to be contained and then the polyurethane foam is heated and dried.

  More preferably, a method of impregnating polyurethane foam into a solution containing carbon black is employed. According to this method, even after the conductivity is imparted, the properties of the polyurethane foam are not impaired, and it is possible to avoid as much as possible that the electrical resistance value and hardness of the polyurethane foam vary depending on the environment. The above carbon black refers to carbon black in a broad sense. Examples of carbon black that can be used include carbon black in a narrow sense such as furnace black, thermal black, channel black, acetylene black, ketjen black, and color black, and graphite. In addition, a polymer material obtained by polymerizing vinyl monomers in a branched manner on the surface of carbon black or graphite in a narrow sense can be used as the carbon black in a broad sense.

  A specific method for imparting conductivity to the polyurethane foam by impregnation will be described.

  First, carbon black is mixed with water or an organic solvent together with a binder to prepare an impregnating liquid having a predetermined viscosity. The binder is used to adhere and fix carbon black in the polyurethane foam. As the binder, a material having elasticity even after being fixed to the polyurethane foam is suitably used. Specifically, for example, rubber latex or the like is used. The viscosity of the impregnating liquid is not particularly limited, but is preferably about 8 to 15 cps under a temperature condition of 25 degrees from the viewpoint of allowing the impregnating liquid to easily penetrate into the polyurethane foam. The viscosity of the impregnating liquid can be adjusted, for example, by adjusting the blending ratio of water or an organic solvent and carbon black, or by adding a surfactant.

  When the polyurethane foam is impregnated with the impregnation liquid, the impregnation liquid penetrates from the surface of the polyurethane foam to the inside. Examples of the impregnation method include a method of applying an impregnation liquid on the surface of the polyurethane foam, a method of immersing the polyurethane foam in the impregnation liquid, and the like. It is preferable that the impregnating liquid penetrates from the surface of the polyurethane foam into a thickness portion of about 0.02 mm to 0.1 mm. Adjustment of the degree of impregnation with the impregnating liquid is performed by adjusting the conditions for squeezing the impregnating liquid from the container for the impregnating liquid, the polyurethane foam cell size, the concentration of the impregnating liquid, or the viscosity of the impregnating liquid. By doing.

By using the above impregnation liquid preparation method and impregnation method, it is possible to impart appropriate conductivity to the polyurethane foam layer 58 while suppressing an increase in the hardness of the polyurethane foam layer 58. The volume resistivity of the polyurethane foam layer 58 is preferably 10 ² Ωcm or more and 10 ⁷ Ωcm or less. Further, from the viewpoint of reducing the influence on the hardness of the polyurethane foam layer 58, the volume resistivity of the polyurethane foam layer 58 is more preferably 10 ⁴ Ωcm or more and 10 ⁷ Ωcm or less, and more preferably 10 ⁵ Ωcm or more and 10 ⁷ Ωcm or less. Even more preferably.

  After the above impregnation is completed, the polyurethane foam is dried by heating. As a result, the water or organic solvent in the impregnating liquid that has penetrated into the polyurethane foam evaporates and the binder in the impregnating liquid is cured. When the binder is cured, the conductive material contained in the impregnating solution together with the binder is fixed to the cell wall surface of the polyurethane foam, thereby imparting conductivity to the polyurethane foam. The polyurethane foam is dried by heating, for example, at a temperature of 120 ° C. or more and 130 ° C. or less for a time of 20 minutes or more and 30 minutes or less. The conditions for the heat drying are the material and size of the polyurethane foam before drying, In addition, it is appropriately determined depending on the type of binder in the impregnating liquid.

  When conductivity is imparted to the polyurethane foam layer 58 of the cleaning roller 54, a predetermined electric field is formed between the photosensitive member 12 and the cleaning roller 54, so that not only the mechanical action but also the cleaning of the photosensitive member 12 is performed. Electrical action can also be used.

  More specifically, when most of the deposits (for example, toner or external additives) on the outer peripheral surface of the photoconductor 12 are negatively charged, there is a gap between the photoconductor 12 and the cleaning roller 54. For example, a direct current electric field (for example, a potential difference of 100 volts or more and 1000 volts or less) is formed such that a positive current (for example, 10 μA or more and 30 μA or less) flows from the cleaning roller 54 toward the photosensitive member 12. In this case, the negatively charged deposit on the photoconductor 12 is easily transferred to the cleaning roller 54 by the action of an electric field, and the outer peripheral surface of the photoconductor 12 can be efficiently cleaned. However, the configuration of the electric field formed between the photoconductor 12 and the cleaning roller 54 is not particularly limited. For example, by forming an AC electric field, not only the negatively charged deposit but also the positive polarity. It is also possible to make it possible to efficiently collect deposits that are electrically charged.

[6. Scraping member)
Next, the configuration of the scraping member that scrapes off the foreign matter in the polyurethane foam layer 58 of the cleaning roller 54 will be specifically described. The shape of the scraping member is not particularly limited, and for example, a blade-like, rod-like, or roller-like scraping member is used.

  In the embodiment shown in FIG. 1, a blade-shaped scraping member 70 is used. Thus, when using the blade-shaped scraping member 70, the material of the scraping member 70 is not specifically limited, For example, rubbers, such as urethane rubber, or metals, such as stainless steel or iron, are used. Even when a bar-shaped scraping member is used, the material of the scraping member is not particularly limited, and for example, rubber or metal can be used.

  In the embodiment shown in FIG. 4, a roller-shaped scraping member 72 is used. For example, iron is used as the material of the scraping member 72, but the material is not necessarily limited thereto. As a material other than iron used for the roller-shaped scraping member 72, for example, a metal such as aluminum, stainless steel, or an alloy, or a rubber such as urethane, EPDM, or NBR is used. Further, a roller having a plurality of layers such as a roller in which the surface of a metal roller or a rubber roller is covered with a coat layer may be used as the scraping member 72. Furthermore, a roller having a brush-like surface layer can also be used as the scraping member 72.

  The scraping member 72 is disposed parallel to the cleaning roller 54 and rotatably. The scraping member 72 is drivingly connected to a motor (not shown), and is rotated in the clockwise direction in the drawing by driving the motor. As a result, the cleaning roller 54 and the scraping member 72 rotate in the same direction (so-called with direction) at their contact portions.

  A scraper 74 made of metal, for example, is disposed in contact with the outer peripheral surface of the scraping member 72. Thereby, the foreign matter on the scraping member 72 scraped off from the cleaning roller 54 is scraped off by the scraper 74. Therefore, the scraping performance of the scraping member 72 can be satisfactorily maintained over a long period of time, and accordingly, the cleaning performance of the cleaning roller 54 can be maintained.

  In the embodiment shown in FIG. 4, not only an electric field (for example, a potential difference of 100 volts) is formed between the photosensitive member 12 and the cleaning roller 54, but also a predetermined electric field is generated between the cleaning roller 54 and the scraping member 72. It is preferable to configure so as to form a potential difference (for example, a potential difference of 100 volts). Thereby, the scraping performance of the scraping member 72 can be enhanced.

[7. (Pre-charging member)
As shown in FIG. 5, a pre-charging member 76 is provided on the upstream side of the cleaning roller 54 in the rotation direction of the photoconductor 12 to make the charging polarity of the adhering material such as toner on the outer peripheral surface of the photoconductor 12 uniform. Also good. In this case, by applying a predetermined negative or positive polarity voltage to the pre-charging member 76, the charged polarity of the deposit on the photoconductor 12 is made negative or positive, thereby cleaning the deposit. It becomes easy to collect by the roller 54.

In the embodiment shown in FIG. 5, the precharging member 76 has a base material 77 and brush fibers 78 attached to the base material 77. For the base material 77, a conductive material is used. Specific materials used for the substrate 77 include, for example, conductive nylon resin, polyester resin, acrylic resin, or vinylon resin. The brush fiber 78 is implanted in the base material 77. As the material of the brush fiber 78, for example, nylon resin such as nylon 66 or nylon 6, polyester resin, fluorine resin, acrylic resin, or vinylon resin is used. In addition, a conductive material such as carbon black is added to the material of the brush fiber 78, thereby imparting conductivity to the brush fiber 78. The single yarn diameter (thickness) of the brush fiber 78 is preferably 10 μm or more and 50 μm or less, and more preferably 20 μm or more and 30 μm or less. The density of the brush fibers 78 is preferably 50 kF / inch ² or more and 400 kF / inch ² or less, more preferably 200 kF / inch ² or more and 300 kF / inch ² or less. The pile length (projection length from the base material 77) of the brush fiber 78 is preferably 0.5 mm or more and 10 mm or less, and more preferably 3 mm or more and 8 mm or less. The volume resistivity of the brush fiber 78 is preferably 10 ⁵ Ωcm or more and 10 ¹⁴ Ωcm or less, more preferably 10 ⁶ Ωcm or more and 10 ⁸ Ωcm or less.

When the regular charging polarity of the toner is negative, most of the toner adhering to the photoconductor 12 is negatively charged. However, due to the influence of the transfer bias or the like, not only the negatively charged deposit on the outer peripheral surface of the photoconductor 12 but also the deposit having a charge amount of zero or substantially zero and the positively charged deposit. Exists. Therefore, it is preferable to apply a negative voltage to the pre-charging member 76, whereby the charge polarity of the deposit on the photoconductor 12 can be made negative. Deposits on the photoreceptor 12 whose charging polarity is made negative by the pre-charging member 76 are efficiently collected by the cleaning roller 54 to which a positive voltage is applied. In this case, if the volume resistivity of the brush fiber 78 is 10 ⁶ Ωcm or more and 10 ⁸ Ωcm or less, the bias current applied to the pre-charging member 76 is preferably −100 μA or more and −10 μA or less, and −80 μA. It is desirable that it is -40 μA or less.

However, a positive voltage may be applied to the pre-charging member 76, and in this case, the charge polarity of the deposit on the photoconductor 12 can be made positive. Deposits on the photoreceptor 12 whose charging polarity is made positive by the pre-charging member 76 are efficiently recovered by the cleaning roller 54 to which a negative voltage is applied. In this case, if the volume resistivity of the brush fiber 78 is 10 ⁶ Ωcm or more and 10 ⁸ Ωcm or less, the bias current applied to the pre-charging member 76 is preferably 10 μA or more and 100 μA or less, and 40 μA or more and ⁸⁰ μA or less. It is desirable that

In a more specific embodiment in which the pre-charging member 76 is provided, it is made of conductive nylon resin, the single yarn diameter (thickness) is 20 μm, the density is 240 kF / inch ² , and the pile length (projection length from the base material 77) B) is used, and a brush fiber 78 having a volume resistivity of 10 ⁸ Ωcm is used. A plurality of brush fibers 78 are planted in the base material 77 in a dense state. The overall density of the brush fibers 78 is a square bar shape that extends in the length direction of the photoreceptor 12 and has a width of 10 mm. In this embodiment, a DC electric field (a potential difference of 2500 volts) is formed between the precharging member 76 and the photosensitive member 12 so that a current of −60 μA flows from the precharging member 76 toward the photosensitive member 12. The As a result, the deposit on the photoconductor 12 is uniformly charged to a negative polarity before being collected by the cleaning roller 54. Furthermore, in this embodiment, 10 μA or more is passed from the scraping member 72 via the cleaning roller 54 to the photosensitive member 12 between the scraping member 72 and the cleaning roller 54 and between the cleaning roller 54 and the photosensitive member 12. A DC electric field (potential difference of 100 volts each) is formed so that a current of 30 μA or less flows. As a result, the adhering matter whose charging polarity is made negative by the pre-charging member 76 as described above is satisfactorily removed from the photoreceptor 12 by the cleaning roller 54 and the scraping member 72.

  When the precharge member 76 is provided as described above, the bias applied to the precharge member 76 may be controlled so as to discharge foreign matters such as toner staying in the precharge member 76. For example, in a configuration in which a negative bias is applied to the precharge member 76 during cleaning of the photoconductor 12, most of the foreign matter staying inside the precharge member 76 is positively charged or has a charge amount. Zero or nearly zero. Therefore, the foreign matter staying in the precharge member 76 is controlled on the photosensitive member 12 by controlling the bias to be applied to the precharge member 76 with a polarity opposite to that in the normal state, that is, a positive polarity bias at an appropriate timing. Can be exhaled. After the discharge of the foreign matter is completed, the pre-charging member 76 may be controlled so as to apply a normal polarity, that is, a negative polarity bias again. As a result, the foreign matter discharged onto the photoconductor 12 When the sheet 12 is conveyed again to the portion facing the pre-charging member 76 as the rotation 12 rotates, the pre-charging member 76 is negatively charged and is collected from the photoreceptor 12 by the cleaning roller 54 to which a positive-polarity bias is applied. .

  The configuration of the pre-charging member does not necessarily have a brush shape as described above as long as it has a desired charging function. For example, a blade-shaped precharging member may be used, and in this case, for example, a material similar to the brush fiber 78 described above or a metal such as stainless steel or aluminum is used as the material of the precharging member. A rotary pre-charging member can also be used. In this case, for example, a rotating member having an outer peripheral surface formed in a brush shape or a rotating member made of a foam is preferably used.

  While the present invention has been described with reference to the above-described embodiments, the present invention is not limited to the above-described embodiments. For example, in the present invention, the method for producing the polyurethane foam layer is not necessarily limited to the above-described embodiment, and does not prevent the polyurethane foam layer from being produced by another method.

  A test was conducted to confirm suitable physical properties of the polyurethane foam layer of the cleaning roller for the photoconductor. Specifically, as the physical properties of the polyurethane foam layer, suitable values of the number of cells, the cell wall opening ratio, hardness, average cell diameter, density, and volume resistivity were confirmed.

  As the image forming apparatus, an image forming apparatus of Magiccolor 5570 manufactured by Konica Minolta Co., Ltd. was used, and an appropriately modified photoconductor cleaning roller was mounted on the image forming apparatus. Note that the cleaning device 40 and the scraping member 70 according to the above-described embodiment were not mounted.

  As the polyurethane foam layer of the cleaning roller for the photoconductor, one made of any one of the materials 1 to 14 shown in Table 1 was used. These materials 1 to 14 were produced by the method described in the above embodiment, using polyol, isocyanate, amine-based catalyst, organic acid salt-based catalyst, water (foaming agent) and foam stabilizer as raw materials. Specifically, polyether polyol (trade name Actol ED-37B (number average molecular weight 3000); manufactured by Mitsui Takeda Chemical Co., Ltd.) was used as the polyol. As the isocyanate, methylene diphenyl diisocyanate (MDI) (trade name Millionate MTL-S; manufactured by Nippon Polyurethane) was used. As an amine-based catalyst, Kaolyzer No. 23NP was used. EP73660A manufactured by PANTECHNOLOGY was used as the organic acid salt catalyst. As the foam stabilizer, linear dimethylpolysiloxane (trade name: Niaxsilicone L5614; manufactured by GE Silicones) was used. The amount of each raw material used is as shown in Table 1.

A method for measuring physical properties of materials 1 to 14 will be described. Regarding the number of cells, the surface of the cleaning roller (3 locations in the axial direction × 8 locations in the circumferential direction) was observed with a scanning electron microscope (SEM), and the number of cells per inch was measured at each observed location, and the average value thereof was measured. Was calculated. Regarding the aperture ratio of the cell wall, it was observed at a magnification of 100 to the outer peripheral surface by scanning electron microscopy (SEM) of the cleaning roller, the wall surfaces of the cells of the observed surface and the area S ₁ of the openings to calculate the total area S The aperture ratio (S ₁ / S × 100) was determined. Regarding the hardness, when the polyurethane foam layer is pushed into a predetermined pressing surface until its thickness reaches 70% of the original, the load per unit length that the pressing surface receives is measured. The value (gf / mm) was taken as hardness. The average cell diameter is measured with a scanning electron microscope (SEM) on the surface of the supply roller (3 in the axial direction × 8 in the circumferential direction), and the diameter of 10 cells (240 in total) is measured at each observation location. It calculated from those measured values. Regarding the density, the weight of the polyurethane foam layer was obtained by subtracting the weight of the core metal from the weight of the cleaning roller, the volume of the polyurethane foam layer was obtained based on the dimensions, and the density was calculated from the weight and the volume.

As the toner, two types of toners (toner A and toner B) having different average particle diameters are used, and Experimental Example A1 to Experimental Example A14 using the toner A having an average particle diameter of 4.5 μm, and the average particle diameter Experimental Example B1 to Experimental Example B14 using Toner B having a diameter of 7.0 μm were set. In all the experimental examples, the potential difference between the cleaning roller and the photosensitive member was set to 50 V, and the suction force was applied to the negatively charged toner on the cleaning roller side. In all the experimental examples, the rotation direction of the cleaning roller is set to a so-called width direction with respect to the photoconductor, and the ratio R (V _B / V) of the peripheral speed V _B of the cleaning roller to the peripheral speed V _A of the photoconductor. _A ) was set to 0.5. For each experimental example, the polyurethane foam layer materials used are as shown in Tables 2 and 3. The polyurethane foam layer of each experimental example was given conductivity so as to have the volume resistivity shown in Tables 2 and 3. For each experimental example, the contact pressure of the cleaning roller to the photosensitive member, the contact nip width between the photosensitive member and the cleaning roller, and the amount of biting of the cleaning roller into the photosensitive member were set as shown in Tables 2 and 3. .

  For each experimental example, 50,000 solid images were continuously printed using the above-described image forming apparatus in an environment of an ambient temperature of 28 ° C. and a relative humidity of 85%, and the initial image quality of continuous printing, image omission during continuous printing, and Then, the evaluation on the scratches on the surface of the photoreceptor after completion of continuous printing was performed. The image omission evaluated here is due to poor cleaning of the photoreceptor. In the evaluation regarding the image omission due to the cleaning failure, the case where no image omission occurred was expressed as “none”, and when the image omission occurred, it was represented by the number of prints at the time of occurrence (see Tables 2 and 3). The evaluation of the scratches on the photoreceptor is represented by “A” when no scratches occur, “B” when minor scratches occur, and “C” when scratches are significant. (See Tables 2 and 3).

  After the above continuous printing is completed, the image forming apparatus is left overnight in the same temperature and humidity environment, and 50,000 solid images are continuously printed on the next morning using the image forming apparatus. Was evaluated. The image omission evaluated here is caused by a product generated by a chemical reaction between a film such as an external additive formed on the photoreceptor and ozone. The evaluation regarding the image omission due to the chemical reaction between the coating and ozone was expressed as “none” when no image omission occurred and “present” when the image omission occurred (Tables 2 and 3). reference).

  The test results shown in Table 2 and Table 3 will be examined.

  For Experimental Example A1 to Experimental Example A10-2 and Experimental Example B1 to Experimental Example B10-2 using Materials 1 to 10, evaluation of initial image quality, evaluation of missing images due to poor cleaning, and scratches on the photoreceptor The evaluation regarding the image loss and the evaluation regarding the image omission caused by the chemical reaction between the coating film and ozone were both good. In contrast, Experimental Examples A11 to A14 and Experimental Examples B11 to B14 using the materials 11 to 14 were poor in evaluation except for the initial image quality evaluation.

  The reason why the image loss due to poor cleaning occurred in Experimental Example A11 and Experimental Example B11 using the material 11 is that the number of cells of the material 11 (35 / inch) is the number of cells of other materials (40 to 85 / This is considered to be because the frequency of the contact of the cell wall with the developer on the photosensitive member is low, and the developer on the photosensitive member cannot be sufficiently scraped off by the cleaning roller. Further, since the toner that could not be scraped was fixed by repeated contact with the member that contacts the photoconductor, it is considered that minor scratches were generated on the surface of the photoconductor. Furthermore, the film on the photoconductor and ozone undergo a chemical reaction by being left overnight with filming of an external additive or the like on the photoconductor. It is considered that image loss occurred in the initial stage of continuous printing the next morning due to adhesion to the surface. From this, it was found that the number of cells of the polyurethane foam layer is preferably 40 / inch or more.

  In Example A12 and Example B12 using the material 12, the image omission due to poor cleaning occurred because the number of cells of the material 12 (85 / inch) was different from the number of cells of other materials (35-80 / In other words, the cells on the surface of the cleaning roller are filled with the developer, and the wall surface of the cell is difficult to contact the developer on the photoconductor. It is thought that it was because it was not scraped off. In addition, it is considered that the developer aggregates or fixed matter formed in the cells on the surface of the cleaning roller contacted the outer peripheral surface of the photoconductor, thereby causing scratches on the surface of the photoconductor. Further, it is considered that image omission occurred at the initial stage of continuous printing the next morning due to a chemical reaction between a coating such as an external additive generated on the surface of the photoreceptor and ozone. From this, it was found that the number of cells of the polyurethane foam layer is preferably 80 / inch or less. Therefore, the number of cells in the polyurethane foam layer is preferably 40 cells / inch or more and 80 cells / inch or less.

  The reason why the image omission due to poor cleaning occurred in Experimental Example A13 and Experimental Example B13 using the material 13 is that the aperture ratio (60%) of the cell wall surface of the material 13 is the aperture ratio (60%) of the cell wall surface of the other material ( This is considered to be because the developer accumulated in the polyurethane foam layer as the number of printed sheets increased, and the scraping power of the cleaning roller decreased. Further, it is considered that the collected toner adheres to the surface of the roller by accumulating inside the cleaning roller, and the surface of the photoconductor is slightly damaged due to contact with the hardened roller surface. Further, it is considered that image omission occurred at the initial stage of continuous printing the next morning due to a chemical reaction between a coating such as an external additive generated on the surface of the photoreceptor and ozone. From this, it was found that the opening ratio of the cell wall surface of the polyurethane foam layer is preferably 50% or less.

  The reason why the image omission due to poor cleaning occurred in Experimental Example A14 and Experimental Example B14 using the material 14 is that the opening ratio (5%) of the cell wall surface of the material 14 is the opening ratio of the cell wall surface of the other material ( This is considered to be because the material 14 has a structure close to a complete closed cell structure. Specifically, because of the structure of the polyurethane foam layer, the developer scraped by the cleaning roller is difficult to enter the polyurethane foam layer, and the cells on the surface of the cleaning roller are easily filled with the developer. This is probably because the wall surface is less likely to contact the outer peripheral surface of the photoreceptor. Further, it is considered that developer aggregates or adherents were generated in the cells on the surface of the polyurethane foam layer, and the outer peripheral surface of the photoreceptor was damaged by these aggregates or adherents. Further, it is considered that image omission occurred at the initial stage of continuous printing the next morning due to a chemical reaction between a coating such as an external additive generated on the surface of the photoreceptor and ozone. From this, it was found that the opening ratio of the cell wall surface of the polyurethane foam layer is preferably 10% or more. Therefore, the opening ratio of the cell wall surface of the polyurethane foam layer is preferably 10% or more and 50% or less.

  Moreover, in Experimental example A1-Experimental example A10-2 and Experimental example B1-Experimental example B10-2 which satisfy | filled the acceptance standard in any evaluation, the hardness of material is 1-5 gf / mm. From this, it was confirmed that if the hardness of the polyurethane foam layer is 1 gf / mm or more and 5 gf / mm or less, sufficient cleaning performance can be secured by satisfying other conditions.

  Furthermore, in Experimental Example A1 to Experimental Example A10-2 and Experimental Example B1 to Experimental Example B10-2 that satisfy the acceptance criteria in any evaluation, the average cell diameter is 100 to 500 μm. From this, it was confirmed that if the average cell diameter of the polyurethane foam layer is 100 μm or more and 500 μm or less, sufficient cleaning performance can be secured by satisfying other conditions.

In addition, in Experimental Example A1 to Experimental Example A10-2 and Experimental Example B1 to Experimental Example B10-2 in which all evaluations satisfied the acceptance criteria, the density of the polyurethane foam layer was 0.03 to 0.2 g / cm ³ . is there. From this, it was confirmed that if the density of the polyurethane foam layer is 0.03 g / cm ³ or more and 0.2 g / cm ³ or less, sufficient cleaning performance can be secured by satisfying other conditions.

  Further, Experimental Example A1 to Experimental Example A10-2 using the toner A having an average particle diameter of 4.5 μm, and Experimental Example B1 to Experimental Example B10-2 using the toner B having an average particle diameter of 7.0 μm. In any of the above, since all the evaluations passed the acceptance criteria, when using a toner having a small particle diameter of 4.5 μm or more and 7.0 μm or less, sufficient cleaning performance can be achieved by satisfying the above-mentioned various conditions. It was confirmed that it can be secured.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to the present invention. FIG. 4 is an enlarged cross-sectional view showing a contact portion between a photoconductor and a cleaning roller. It is a figure which shows the cell structure of a polyurethane foam layer. It is a figure which shows embodiment which uses a roller-shaped scraping member. It is a figure which shows embodiment using a pre-charging member.

Explanation of symbols

1: image forming apparatus, 12: photoconductor, 16: charging station, 18: exposure station, 20: developing station, 22: transfer station, 24: first cleaning station, 25: second cleaning station, 26: charging Apparatus: 28: exposure device, 30: image light, 32: passage, 34: developing device, 36: transfer device, 38: sheet, 40: cleaning device, 42: housing, 44: developing roller, 54: cleaning roller, 56 : Core metal, 58: Polyurethane foam layer, 66: Contact part (nip part) between the photoreceptor and the cleaning roller, 68: Power supply, 70, 72: Scraping member, 76: Pre-charging member, 80: Polyurethane foam layer Cell, 82: Opening of cell wall surface.

Claims (14)

A cleaning roller for a photoconductor that is disposed in contact with the outer peripheral surface of the photoconductor and removes the developer attached to the outer peripheral surface of the photoconductor,
A metal core and a polyurethane foam layer covering the outer peripheral surface of the metal core;
The polyurethane foam layer has 40 to 80 cells per inch,
A cleaning roller for a photoreceptor, wherein the opening ratio of the wall surface of the cell of the polyurethane foam layer is 10% or more and 50% or less.   The polyurethane foam layer has a load per unit length received by the pressing surface of 1 gf / mm or more when pressed into a predetermined pressing surface to a depth of 30% of the thickness of the polyurethane foam layer. The photoconductor cleaning roller according to claim 1, wherein the cleaning roller is 5 gf / mm or less.   3. The cleaning roller for a photoreceptor according to claim 1, wherein an average value of the cell diameter is 100 μm or more and 500 μm or less. The photosensitive roller cleaning roller according to claim 1, wherein a density of the polyurethane foam layer is 0.03 g / cm ³ or more and 0.2 g / cm ³ or less. The photosensitive roller cleaning roller according to claim 1, wherein the polyurethane foam layer has a volume resistivity of 10 ² Ωcm to 10 ⁷ Ωcm.   6. The polyurethane foam layer according to claim 1, wherein the polyurethane foam layer is produced by mixing a polyol, an isocyanate, a gas for forming bubbles, and a foaming agent that generates a gas by a chemical reaction with the isocyanate. The cleaning roller for a photoreceptor according to any one of the above. The photoconductor cleaning roller according to any one of claims 1 to 6,
A photosensitive member carrying an electrostatic latent image,
The image forming apparatus, wherein the photoconductor cleaning roller is disposed in contact with an outer peripheral surface of the photoconductor.   8. The image forming apparatus according to claim 7, wherein the contact pressure of the photoconductor cleaning roller to the photoconductor is 5 N / m or more and 30 N / m or less. The amount of penetration of the polyurethane foam layer into the photoreceptor is 5% or more and 40% or less of the thickness of the polyurethane foam layer,
9. The image forming apparatus according to claim 7, wherein a contact nip width between the charging roller cleaning roller and the charging roller in a circumferential direction of the charging roller cleaning roller is 3 mm or more and 8 mm or less.   The scraping member for scraping out the foreign matter contained in the polyurethane foam layer is disposed in contact with the outer peripheral surface of the photoconductor cleaning roller. The image forming apparatus described.   The precharging member for making the charged polarity of the deposit on the outer peripheral surface of the photosensitive member uniform is provided upstream of the cleaning roller for the photosensitive member in the rotation direction of the photosensitive member. Item 11. The image forming apparatus according to any one of Items 7 to 10.   12. The image forming apparatus according to claim 7, wherein a cleaning member different from the cleaning roller for the photosensitive member is disposed in contact with the outer peripheral surface of the photosensitive member.   The image forming apparatus according to claim 7, wherein the photosensitive member and the cleaning roller for the photosensitive member rotate in a direction in which the photosensitive member and the cleaning roller for the photosensitive member move in the same direction. Including toner used to visualize the electrostatic latent image,
The image forming apparatus according to claim 7, wherein an average particle size of the toner is 4.5 μm or more and 7.0 μm or less.

Images