JP2011197397A - Image forming unit and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming unit and an image forming apparatus, capable of reducing the phenomenon that the mark of a blade appears as a line in an image, at start of usage.SOLUTION: The image forming unit 220 includes a photoreceptor unit 200 having a photoreceptor 210; a cleaning part 220 having a cleaning blade 221 to be in contact with the photoreceptor 210; and a charger 230 for charging the charge transport layer of the photoreceptor 210. A lubricant is applied to a part where the cleaning blade 221 contacts the photoreceptor 210; and the lubricant contains a material to be charged to a potential on the polarity side opposite to the polarity rather than the potential of the polarity, when the charge transport layer of the photoreceptor 210 is charged by the charger 230.

Description

  The present invention relates to an image forming unit and an image forming apparatus that are mounted as replacement parts on an image forming apparatus.

  In photocopiers, printers, facsimiles, or their combined machines, photoconductor units that use a photoconductor and its cleaning mechanism as a unit are used, and the photoconductor unit reaches the end of its life. When it is done, it is exchanged for a new product. A process cartridge in which a developing device is added to the constituent parts of the photosensitive unit is also used.

  In the photoreceptor unit or the like, a lubricant is applied between the photoreceptor and the cleaning blade of the cleaning mechanism, and lubrication is performed at the start of printing. For example, in Patent Document 1, diamond-like carbon or amorphous carbon fine particles are applied to the surface of a cleaning blade, and the fine particles are held between the cleaning blade and the photosensitive member for a long period of time to maintain lubrication performance. Such a technique is disclosed.

JP 2007-193306 A

  An object of the present invention is to provide an image forming unit and an image forming apparatus capable of suppressing a phenomenon in which blade marks appear as streaks in an image at the start of use.

  The invention according to claim 1 includes an image forming unit having an image holding member, and a cleaning unit having a cleaning blade in contact with the image holding member, and a lubricant in a portion where the cleaning blade contacts the image holding member. In the image forming unit coated with the image forming apparatus, the lubricant includes a material that is charged to a potential on the polarity opposite to the polarity when the charge transport layer of the image carrier is charged. It is a unit.

  The invention according to claim 2 is the invention according to claim 1, wherein the charge transport layer of the image carrier is charged to a negative potential, and the lubricant contains a melamine-formaldehyde condensate and / or melamine annulate. It is characterized by that.

  According to a third aspect of the present invention, there is provided the image forming unit according to the first or second aspect, a transfer unit that transfers the toner image formed by the image forming unit of the image forming unit to a recording sheet, and the recording sheet. The image forming apparatus includes: a fixing unit that fixes the transferred toner image; and a conveyance unit that conveys the recording sheet.

  According to the first aspect of the present invention, it is possible to suppress a phenomenon in which blade marks appear as streaks in an image at the start of use.

  According to the second aspect of the invention, it is possible to effectively reduce the phenomenon in which the blade marks appear as streaks in the image at the start of use.

  According to the third aspect of the present invention, there is provided an image forming apparatus capable of reducing a phenomenon in which blade marks appear as streaks in an image at the start of printing.

1 is a conceptual diagram of an image forming apparatus according to an embodiment. (A) is a conceptual diagram of the photoconductor unit of the embodiment, and (B) is a diagram for explaining the charging potential of the photoconductor and the lubricant. It is a graph which shows the kind of lubricant in the Example of this invention, and the grade of streak generation.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
(1) Basic Configuration and Operation of Image Forming Apparatus FIG. 1 shows an image forming apparatus 100 according to an embodiment. The image forming apparatus 100 includes four photoconductor units (image forming units) 200, 300, 400, and 500. These four photoconductor units 200 to 500 transfer the YMCK toner images onto the transfer belt 101. These toner images are superimposed on the transfer belt 101, so that a color toner image is formed on the transfer belt 101.

  The photoconductor units 200 to 500 are replaced with new products when the built-in parts reach the end of their lives. At that time, the upper cover (not shown) of the image forming apparatus 100 is opened upward, and the transfer belt 101 rises together with the upper cover to open the lower side, so that the new photoconductor units 200 to 500 are installed in the image forming apparatus. It is set so as to be detachable with respect to 100 from above.

  The four photoconductor units 200 to 500 have the same configuration except that different toners are used. Hereinafter, the photoreceptor unit 200 will be described as a representative. FIG. 2 shows the photosensitive unit 200 and its peripheral components. The photoconductor unit 200 includes a photoconductor (image holder) 210 that has a cylindrical shape and can be rotated counterclockwise in the drawing. The photoreceptor 210 is an example of a rotatable image carrier. A cleaning unit 220 and a charger 230 are disposed around the photoconductor 210. In addition, a developing device 240 fixed to the image forming apparatus 100 is disposed around the photosensitive member 210.

  The cleaning unit 220 includes a blade 221, an auger 222, a film seal 223, and a static elimination device 224. The blade 221 is a plate-like member made of a urethane material and is in contact with the photoreceptor 210. As the photoconductor 210 rotates counterclockwise in the figure, the residue on the photoconductor 210 is removed at the edge portion of the blade 221. That is, as shown in the figure, the photoconductor 210 rotates counterclockwise in the drawing, and the tip of the blade 221 contacts the surface portion of the photoconductor 210 moving from above from below. At this time, the developer residue on the surface of the photoreceptor 210 is scraped off by the blade 221. Further, the blade 221 has a function of uniformly adhering the lubricant supplied by being included in the developer to the photoreceptor 210 by rubbing the surface of the photoreceptor 210.

  The auger 222 has a function of conveying powder in the axial direction by a rotating spiral structure, and the blade 221 conveys the residue scraped off from the photoreceptor 210 toward a discharge container (not shown). The static eliminator 224 neutralizes the charge collected by the film seal 223.

  The charger 230 generates a charge by discharging, gives a charge to the surface portion of the photoreceptor 210 cleaned and discharged by the cleaning unit 220, and charges it to a negative potential.

  Scanning light from an exposure device (not shown) is applied to the rotating photoreceptor 210 from a portion between the charger 230 and the developer 240. By irradiating the surface of the photoreceptor 210 charged by the charger 230 with light from the exposure device, the photoreceptor 210 is partially exposed to form an electrostatic latent image on the surface of the photoreceptor 210. .

  A developing device 240 is arranged on the downstream side of the portion where this exposure is performed. The developing device 240 includes augers 241 and 242 and a developing roll 243. The augers 241 and 242 convey the developer containing toner and lubricant from the storage container storing the developer to the developing roll 243. The developing roll 243 supplies toner to a portion of the photoreceptor 210 where the electrostatic latent image is formed, and develops the electrostatic latent image. By this development, a toner image is formed on the photoreceptor 210.

  The developer contains a lubricant to be supplied to the surface of the photoreceptor 210, and the developing device 240 also functions as a lubricant supply unit. Specifically, the lubricant is supplied to the surface of the photoconductor 210 together with the toner by using toner particles made by adhering the powder of the lubricant aid. As the lubricating aid, fluorine-based resin powder is preferable, and among them, polytetrafluoroethylene powder is particularly preferable because it is difficult for the toner to be released from the toner and the lubricant can be supplied to the photoreceptor 210 with good uniformity. The lubricating aid is preferably contained in a proportion of 0.05 to 1% by weight with respect to the toner.

  The toner image developed by the developing device 240 reaches the portion of the transfer position 201 as the photoconductor 210 rotates in the counterclockwise direction in the drawing. At the transfer position 201, a transfer roll 202 is disposed opposite the photoconductor 210, and the transfer belt 101 is sandwiched between the photoconductor 210 and the transfer roll 202. A bias voltage is applied between the photoconductor 210 and the transfer roll 202, and the toner image on the photoconductor 210 is primarily transferred onto the transfer belt 101 by the action of the pressure caused by the pinching and the bias voltage. Transcribed.

  Returning to FIG. 1, the image forming apparatus 100 includes a paper storage device 102 that stores paper as a sheet-like recording medium. The paper stored in the paper storage device 102 is transported along the transport path 103 toward the secondary transfer unit 104. The secondary transfer unit 104 includes a pressure roll 105 and a counter roll 106, and a transfer belt 101 is sandwiched between both rolls. A bias voltage is applied between the pressure roll 105 and the opposing roll 106. When the sheet conveyed through the conveying path 103 is sandwiched between the transfer belt 101 and the pressure roll 105, the toner image formed on the transfer belt 101 is secondarily applied to the sheet by the action of pressure and bias voltage. Transcribed.

  A fixing unit 107 is disposed on the downstream side of the secondary transfer unit 104 on the sheet conveyance path 103. The fixing unit 107 includes a heating roll 108 and a pressure roll 109. A sheet on which a toner image is formed is sandwiched between the heating roll 108 and the pressure roll 109. At that time, heat and pressure are applied to the sheet, whereby the toner image is fixed on the sheet. The sheet on which the image is thus formed is discharged onto the sheet discharge surface 110.

(2) Composition of Lubricant The photoconductor unit 200 of this embodiment is a consumable item, and is replaced with a new product when the photoconductor 210 or the like reaches the end of its life. Before the photoreceptor unit 200 is packaged, a lubricant is applied to the contact portion between the cleaning blade 221 of the cleaning unit 220 and the surface of the photoreceptor 210. The lubricant is obtained by dispersing a powder of a lubricating substance in a solvent, and is applied with a brush or the like. By applying the lubricant, it is possible to reduce wear on the surface of the photoconductor 210 from the beginning when the photoconductor unit 200 is mounted on the image forming apparatus 100 and printing is started. When printing is started, lubrication is performed with a lubricant contained in the toner.

  Here, since vibration is applied to the photoconductor unit 200 during carrying and transportation, the lubricating material is frictionally charged between the cleaning blade 221 and the surface of the photoconductor 210, and an electrostatic memory remains on the photoconductor 210 and the image is left. Defects may occur. That is, when the lubricating material is charged, the portion of the photoreceptor 210 that comes into contact with the lubricating material is charged with a polarity opposite to that of the lubricating material. For this reason, when the photosensitive member 210 (charge transport layer) is charged by the charger 230, streaks occur in the image due to the potential difference between the charged potential and the portion charged to the opposite polarity.

  In the present embodiment, the lubricating substance is a material that is charged to a potential on the opposite polarity side of the potential of the polarity when the photosensitive member 210 is charged by the charger 230. For example, as shown in FIG. 2B, if the lubricating substance is charged to a potential of -A, the portion of the tourist body 210 that contacts the lubricating substance is charged to a potential of + A. Here, if the charge transport layer of the photoreceptor 210 is charged to a potential of −B by the charger 230, a potential difference of (A + B) is generated from the portion charged by the lubricant.

  On the other hand, if the lubricating material is charged to a potential of + A, the portion of the tourist body 210 that contacts the lubricating material is charged to a potential of -A. If the photosensitive member 210 is charged to a potential of −B by the charger 230, a potential difference of (A−B) is generated from the portion charged by the lubricant, and the potential difference in the photosensitive member 210 is compared with the above case. Is shortened by 2B. Therefore, the occurrence of streaks in the image is suppressed.

  Here, when the photosensitive member 210 is charged to a negative potential by the charger 230, the lubricating substance is a substance that is easily positively charged and has good lubricating characteristics, such as melamine / formaldehyde condensate, melamine cyanurate, etc. Melamine-based resin fine particles and nylon fine particles can be used. In particular, melamine is preferable because it has a high positive chargeability, is easy to be finely divided, and has excellent lubricating properties. By the way, melamine / formaldehyde condensate can be micronized to 0.2 μm and melamine cyanurate can be micronized to 0.5 μm. Nylon has the same ease of positive charging as the melamine type, but has a drawback in that there is a limit to micronization (about 1.0 μm). Carbon particles should not be used because they are difficult to be charged and have insufficient lubrication properties.

  A fine powder of polytetrafluoroethylene (PTFE), polymethyl methacrylate (PMMA), and a melamine / formaldehyde condensate was prepared as a lubricating substance, and the fine powder was dispersed in a solvent to prepare a lubricant. Then, the lubricant was applied to the portion where the photosensitive unit and the cleaning blade were in contact, the image was printed, and the presence or absence of streaks was observed. The result is shown in FIG. The photosensitive member was negatively charged for printing.

  FIG. 3 shows the ease of charging of each fine powder. Melamine / formaldehyde condensate is easily charged to a positive potential, and PMMA is easily charged to a negative potential. PTFE is more likely to be charged to a negative potential. As shown in FIG. 3, in the example using the fine powder of melamine / formaldehyde condensate, no streak was observed in the image and the image grade was G0. On the other hand, slight or obvious streaks were observed in the examples using the fine powder of PMMA (grade G2 to G4), and clear streaks were recognized in the examples using the fine powder of PTFE (grade G3.5 to G5). ). That is, as the fine powder is easily charged to the positive potential, the generation of streaks can be suppressed.

  The present invention can be applied not only to charging the photoreceptor to a negative potential but also to charging to a positive potential. In that case, fine particles of PMMA can be used as the lubricating substance. Further, the present invention is not limited to the photoconductor unit but can be applied to a process cartridge. Further, in the above embodiment, the charger 230 is included in the photosensitive unit 220, but the charger 230 may be fixed to the image forming apparatus 100 and not included in the photosensitive unit 220.

  The present invention can be used for an image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multifunction machine of these, and a photosensitive unit and a process cartridge mounted on the image forming apparatus.

101 Transfer belt (transfer section)
103 Transport path (transport section)
104 Secondary transfer part (transfer part)
107 Fixing unit 200 Photosensitive unit (image forming unit)
202 Transfer roller (transfer section)
210 Photoconductor (image carrier)
220 Cleaning unit 221 Cleaning blade

Claims (3)

In an image forming unit comprising: an image forming unit having an image holding member; and a cleaning unit having a cleaning blade in contact with the image holding member, wherein a lubricant is applied to a portion where the cleaning blade comes into contact with the image holding member.
The image forming unit, wherein the lubricant includes a material that is charged to a potential on a polarity side opposite to the polarity when the charge transport layer of the image carrier is charged.   2. The image forming unit according to claim 1, wherein the charge transport layer of the image carrier is charged to a negative potential, and the lubricant contains melamine / formaldehyde condensate and / or melamine annulate.   The image forming unit according to claim 1, a transfer unit that transfers a toner image formed by the image forming unit of the image forming unit to a recording sheet, and the toner image transferred to the recording sheet is fixed. An image forming apparatus comprising: a fixing unit that causes the recording sheet to be conveyed; and a conveyance unit that conveys the recording sheet.

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