JP2005345988A - Conductive member, process cartridge and image forming apparatus provided with the conductive member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain a gap between an electroconductive member and an image carrier with high accuracy and constant over a long period of time.
[Solution]
The long conductive support 10 that forms the shaft member, the electrical resistance adjustment layer 11 formed on the outer peripheral surface 10a of the conductive support 10, and the electrical resistance adjustment layer 11 are made of different materials, and the conductive support The outer peripheral surface 10 a of the body 10 is provided on both ends of the electric resistance adjusting layer 11, protrudes in the radial direction from the outer peripheral surface 11 a of the electric resistance adjusting layer 11, and is disposed opposite the electric resistance adjusting layer 11. In the charging roller 2 (conductive member) having a pair of gap holding members 12 having an outer peripheral surface 12a in contact with the photosensitive drum 4 (image carrier), the gap holding member 12 has a dynamic friction coefficient due to the contact. It is formed to be 0.06 or less.
[Selection] Figure 1

Description

  The present invention relates to a proximity charging type conductive member, a process cartridge and an image forming apparatus provided with the conductive material, and more specifically, a gap holding member provided at an end of an electric resistance adjusting layer of the conductive member. Regarding improvement.

  Conventionally, in an electrophotographic image forming apparatus such as a copying machine, a laser beam printer, and a facsimile, a charging member that performs a charging process on a photosensitive drum (image carrier) and a toner on the photosensitive drum. A transfer member or the like that performs a transfer process is used as the conductive member.

  FIG. 7 shows an image forming apparatus 1 as an example in which a charging member is used as a conductive member, and a charging roller 2 in the image forming apparatus 1 is used as a charging member, that is, a conductive member.

  The image forming apparatus 1 includes a photosensitive drum 4 on which an electrostatic latent image is formed, a charging roller 2 that uniformly charges the photosensitive drum 4, and a power pack that applies a voltage to the charging roller 2. (Voltage application power source) 3, surface potential meter 5 for measuring the surface potential of the photosensitive drum 4, developing roller 6 for attaching toner to the electrostatic latent image on the photosensitive drum 4 formed by the laser light L, and A transfer roller 7 for transferring the toner image formed by the toner adhesion onto the recording paper S and a cleaning device 8 for cleaning the photosensitive drum 4 after the transfer processing are provided.

  In some image forming apparatuses 1, the photosensitive drum 4, the charging roller 2, the surface potential meter 5, the developing roller 6, and the cleaning device 8 are integrated as a process cartridge 9 as shown in FIG. 8.

  Here, the photosensitive drum 4 obtains a driving force from a driving mechanism (not shown) and rotates in the direction of arrow A around an axis extending in the depth direction in the drawing, and the charging roller 2 supplies power from the power pack 3. Receive and become charged.

  The charging roller 2 uniformly charges the surface 4 a of the photosensitive drum 4 facing the charging roller 2 with a desired potential. At this time, since the photosensitive drum 4 rotates in the direction of arrow A, the surface portion of the surface 4a of the photosensitive drum 4 on the downstream side in the rotational direction from the portion facing the charging roller 2 is rotated. Therefore, it will be uniformly charged sequentially.

  Subsequently, on the uniformly charged surface of the photosensitive drum 4, laser light (or the original document) that is controlled to emit light corresponding to image information such as images and characters obtained by reading from the original document or image information stored in advance. (Reflected light or transmitted light) L.

  At this time, the potential (negative potential) of the surface 4a of the photosensitive drum 4 is decreased by the irradiation of the laser light L (the absolute potential increases in a direction approaching 0 “zero”). Then, the width of the decreasing potential increases as the amount of light irradiated by the laser light L increases. Therefore, an electrostatic latent image having a potential distribution corresponding to the image information and the like is formed on the surface 4a of the photosensitive drum 4 by the irradiation of the laser light L carrying the image information and the like.

  The surface potential meter 5 detects the potential (potential distribution) of the electrostatic latent image formed on the surface 4 a of the photosensitive drum 4, and the detection result of this potential is the charge control of the charging roller 2 by the power pack 3. And used for exposure control of the laser beam L.

  When a portion of the surface 4 a on which the electrostatic latent image of the photosensitive drum 4 is formed passes through the developing roller 6, an amount of toner corresponding to the potential distribution of the electrostatic latent image adheres, and the surface 4 a of the photosensitive drum 4. In this case, a toner image having a density distribution corresponding to the electrostatic latent image appears visually (visualized image).

  This toner image is pressed against the recording paper S when the recording paper S fed toward the photosensitive drum 4 at a predetermined timing passes while being sandwiched between the photosensitive drum 4 and the transfer roller 7. Transcribed. The recording sheet S to which the toner image is transferred is conveyed in the direction of arrow B toward a fixing unit (not shown).

  On the other hand, the photosensitive drum 4 after the toner image is transferred to the recording paper S is cleaned by removing the toner remaining on the surface 4a by the cleaning device 8, and the residual charge is removed by a quenching lamp (not shown). Then, the state returns to the state before the charging process and waits for the next charging process.

  Incidentally, as a general charging method in the above-described image forming apparatus, a contact charging method in which a charging roller is brought into contact with a photosensitive drum is known (Patent Document 1).

However, when the charging roller 2 of the contact charging system is used, there are the following problems.
(1) The constituent material of the charging roller oozes out from the charging roller and adheres to the surface of the photosensitive drum, and when this adhesion proceeds, a trace of the charging roller remains on the surface of the photosensitive drum.
(2) When an AC voltage is applied to the charging roller, the charging roller in contact with the photosensitive drum vibrates and a charging sound is generated.
(3) The toner on the surface of the photosensitive drum adheres to the charging roller and the charging performance is degraded. In particular, when the dyeing of (1) occurs in the charging roller, the toner becomes more easily adhered.
(4) Substances constituting the charging roller are likely to adhere to the photoreceptor.
(5) If the photosensitive drum is not driven for a long time, permanent deformation occurs in the charging roller.

  In order to deal with such a problem, a proximity charging method has been devised in which the charging roller 2 is not brought into contact with the photosensitive drum 4 but is brought into proximity without contact (Patent Document 2).

  In this proximity charging method, the closest distance (hereinafter referred to as a gap) between the charging roller 2 and the photosensitive drum 4 is 50 μm to 300 μm so that they are opposed to each other and a voltage is applied to the charging roller 2. The photosensitive drum 4 is charged. In the proximity charging method, the charging roller 2 and the photosensitive drum 4 do not come into contact with each other. Therefore, charging caused by adhesion of the constituent material of the charging roller to the photosensitive drum and long-term non-use, which is a problem in the contact charging method. There is no problem with the permanent set of the roller. Further, regarding the reduction in charging performance of the charging roller due to toner adhesion, the toner that adheres to the charging roller is reduced, and therefore the proximity charging method is superior to the contact charging method.

As a method for realizing the proximity charging method, a tape-shaped gap holding means having a predetermined thickness is wound around both ends of the charging roller to secure a gap at a constant interval between the charging roller and the photosensitive drum ( Patent Document 3), a method in which spacer rings are provided at both ends of the charging roller to ensure a gap at a constant interval between the charging roller and the photosensitive drum (Patent Documents 2 and 4) has been proposed.
JP-A 63-149668 Japanese Patent Laid-Open No. 3-240076 JP 2002-139893 A JP-A-4-358175

  However, in the technique disclosed in Patent Document 3, the toner enters between the charging roller and the tape-shaped gap holding member, and the toner adheres or the like, or the tape-shaped gap holding member wears over time. It is difficult to keep the gap between the photosensitive drum and the charging roller at regular intervals over time.

  In addition, in order to prevent wear of the tape-shaped gap holding member, a technique of using a metal ring instead of the tape-shaped member is conceivable, but such a metal ring is in contact with the other party. If the surface layer of the photoconductor drum is worn and the base metal is exposed, a short current is generated between the base metal and the metal ring, and the power that is the power source is increased. There is a risk of damaging the pack.

  In addition, the techniques disclosed in Patent Documents 2 and 4 in which such a ring is used as a spacer ring makes the gap between the charging roller (conductive member) and the photosensitive drum (image carrier) uniform with high accuracy. Since no specific technique for maintaining is disclosed, the dimensional accuracy of the charging roller and the spacer ring varies, and the gap width (distance between the charging roller and the photosensitive drum) fluctuates. There is a problem that the charged potential of the body drum cannot be kept constant.

  Therefore, the inventors of the present invention are made of a different material from the elongated conductive support forming the shaft member, the electrical resistance adjustment layer formed on the outer peripheral surface of the conductive support, and the electrical resistance adjustment layer, An image carrier that is provided on the outer peripheral surface side of the conductive support and on both ends of the electric resistance adjusting layer, protrudes in the radial direction from the outer peripheral surface of the electric resistance adjusting layer, and is opposed to the electric resistance adjusting layer. A conductive member provided with a pair of gap holding members having an outer peripheral surface in contact with the gap, and at least the gap holding member in a state where the gap holding member, the conductive support and the electric resistance adjusting layer are integrally combined. By removing the outer peripheral surface, a conductive member is proposed in which the protrusion amount in the radial direction of the outer peripheral surface of the gap holding member with respect to the outer peripheral surface of the electrical resistance adjusting layer is set to a desired specified amount ( Japanese Patent Application No. 2003-306026 Unpublished).

  According to this proposed technique, the width of contact between the outer peripheral surface of the gap holding member and the photosensitive member can be reduced. Further, the contact area between the gap holding member and the photosensitive member is reduced, and the fluctuation of the gap distance due to the change of the contact point is reduced. Therefore, the gap distance is maintained accurately and stably over a long period of time. It becomes easy.

  However, even after the above-mentioned proposal, it is required to maintain the accuracy of the gap over a long period of time.

  The present invention has been made in view of the above circumstances, and uses a conductive member that can maintain the accuracy of the gap between the image carrier and the image carrier over a long period of time, and this conductive member. It is an object of the present invention to provide a process cartridge and an image forming apparatus.

  The conductive member according to the present invention, the process cartridge including the conductive member, and the image forming apparatus are provided with gap holding members respectively provided on both end sides of the electric resistance adjusting layer formed on the outer peripheral surface of the conductive support. By setting the dynamic friction coefficient to 0.06 or less, wear due to aging of the gap holding member is reduced, and the accuracy of the gap between the image carrier and the image carrier is stably maintained.

  That is, the conductive member according to the present invention includes a long conductive support that forms a shaft member, an electrical resistance adjustment layer formed on the outer peripheral surface of the conductive support, and a material different from the electrical resistance adjustment layer. And is provided on both the outer peripheral surface side of the conductive support and on both ends of the electric resistance adjusting layer, and protrudes in the radial direction from the outer peripheral surface of the electric resistance adjusting layer, and is disposed opposite to the electric resistance adjusting layer. A conductive member including a pair of gap holding members having an outer peripheral surface in contact with an image carrier, wherein the gap holding member is formed so that a dynamic friction coefficient thereof is 0.06 or less. .

  Here, the dynamic friction coefficient is quantitatively specified by, for example, the following test. That is, an alumina ball is pressed vertically against a test piece formed of the same material as that of the gap holding member while applying a predetermined load W, and the alumina ball is pressed within a plane of the test piece. The dynamic friction force F during the reciprocating motion is measured with a load cell.

  At this time, if the dynamic friction coefficient is μ ′, the equation F = μ′W is established, so the dynamic friction coefficient μ ′ can be calculated by μ ′ = F / W.

  According to the conductive member configured in this way, the gap holding member in contact with the image carrier has a very small value of a coefficient of dynamic friction of 0.06 or less. Even with this contact, wear of the outer peripheral surface of the gap holding member of the conductive member can be maintained at an extremely low level.

  Therefore, the amount of radial step between the outer peripheral surface of the gap holding member and the outer peripheral surface of the electric resistance adjusting layer (the protruding amount of the outer peripheral surface of the gap holding member with respect to the outer peripheral surface of the electric resistance adjusting layer), that is, the outer peripheral surface of the electric resistance adjusting layer And the surface of the image bearing member can be kept constant over a long period of time.

  According to a second aspect of the present invention, there is provided a conductive member according to the first aspect, wherein the gap holding member, the conductive support, and the electric resistance adjusting layer are integrally combined in the conductive member according to the first aspect. By removing the outer peripheral surface of the holding member, the protruding amount in the radial direction of the outer peripheral surface of the gap holding member with respect to the outer peripheral surface of the electric resistance adjusting layer is formed to be a desired specified amount. Features.

  Here, the removal processing is specifically, for example, cutting processing, grinding processing, or the like.

  Moreover, the outer peripheral surface of the gap holding member may be simply removed, or the outer peripheral surface of the electric resistance adjusting layer may be removed together with the outer peripheral surface of the gap holding member.

  According to the conductive member configured as described above, the outer peripheral surface of the gap holding member is removed in a state where the gap holding member, the conductive support, and the electric resistance adjusting layer are integrally combined, and the electric resistance Since the projecting amount in the radial direction of the outer peripheral surface of the gap holding member with respect to the outer peripheral surface of the adjustment layer is set to a desired specified amount, the gap holding member is processed alone and formed on the outer peripheral surface of the conductive support. No integration error occurs as in the case of a conductive member obtained by processing the outer peripheral surface of the formed electric resistance adjusting layer alone and then combining the two integrally, and therefore the outer peripheral surface of the gap holding member and the electric resistance The level difference between the outer peripheral surface of the adjustment layer can be made more accurate.

The conductive member according to claim 3 of the present invention is the conductive member according to claim 1 or 2, wherein the gap holding member has a wear coefficient of 5.1 × 10 ⁻⁴ mm / gf or less. It is characterized by.

  Here, the wear coefficient is specified quantitatively by, for example, the following test. That is, an alumina ball is pressed vertically against a test piece formed of the same material as that of the gap holding member while applying a predetermined load W, and the alumina ball is pressed within a plane of the test piece. The width d of the sliding flaw due to the alumina ball formed on the test piece is measured after the reciprocating motion for a predetermined number of times (for example, 150 times). The reciprocating movement and the measurement operation for the width d of the sliding flaw are performed in the same manner with the load W being different.

  When graphs are drawn with the width d of sliding flaws obtained by the above tests corresponding to the vertical axis and the load W corresponding to the horizontal axis, both have linearity, and d = mW (m; constant). Correlation is observed. The constant m (= d / W) is calculated as the above-described wear coefficient.

According to the conductive member configured in this way, the wear coefficient of the gap holding member is 5.1 × 10 ⁻⁴ mm / gf or less, so that the wear of the gap holding member with time is small, and therefore, due to wear. It is possible to prevent the transition to the image carrier and to improve the durability of the parts.

  The conductive member according to claim 4 of the present invention is the conductive member according to any one of claims 1 to 3, wherein the gap holding member has a durometer hardness HDD of 60 or more and 70 or less. It is characterized by that.

  According to the conductive member configured in this manner, since the durometer hardness HDD of the gap holding member is 60 or more, the gap holding member is not easily damaged by the load from the abutting image carrier. (Preventing damage) Therefore, it is possible to prevent the step amount between the outer peripheral surface of the gap holding member and the outer peripheral surface of the electric resistance adjusting layer from fluctuating, and the gap amount can be precisely controlled.

  In addition, since the durometer hardness HDD of the gap holding member is 70 or less, the gap holding member can also be prevented (damaged) from damaging the image carrier.

The conductive member according to claim 5 of the present invention is the conductive member according to any one of claims 1 to 4, wherein the gap holding member has a molecular weight of 1 million or more and a density of 0.1. It is formed of a polyethylene resin that is 96 g / cm ³ or more.

According to the conductive member configured as described above, the toner is fixed to the gap holding member because the gap holding member is formed of polyethylene resin having a molecular weight of 1 million or more and a density of 0.96 g / cm ³ or more. Can be prevented.

  A conductive member according to a sixth aspect of the present invention is the conductive member according to any one of the first to fifth aspects, wherein at least a surface of the outer peripheral surface of the gap holding member that contacts the image carrier. The portion has an insulating property.

  According to the conductive member configured as described above, when a high voltage is applied to the conductive member, the gap holding member that is in contact with the image carrier is separated from the image carrier (or the photosensitive substrate of the image carrier). Current leakage to the (conductive portion) and the base metal can be reliably prevented.

  The conductive member according to claim 7 of the present invention is the conductive member according to any one of claims 1 to 6, wherein the outer peripheral surface of the electric resistance adjusting layer is a surface that prevents adhesion of toner. It is characterized by being covered with a layer.

  According to the conductive member configured as described above, the problem (the image carrier and the toner caused by the adhesion of the toner (or toner additive) attached to the surface of the image carrier (photosensitive member) to the surface of the electric resistance adjusting layer). Change in the amount of voids, change in electrical characteristics, etc.) can be reliably prevented, and the durability of the conductive member can be improved.

  The conductive member according to claim 8 of the present invention is characterized in that, in the conductive member according to claim 7, the electric resistance of the surface layer is larger than the electric resistance inside the electric resistance adjusting layer.

  According to the conductive member configured as described above, even when the image carrier has a defect such as a scratch, voltage is concentrated from the conductive member to the defective portion or abnormal discharge occurs. Can be prevented.

  The conductive member according to claim 9 of the present invention is the conductive member according to any one of claims 1 to 8, wherein the electric resistance adjusting layer and the gap holding member are centered on the conductive support. It is characterized by exhibiting a cylindrical shape.

  According to the conductive member configured as described above, the outer peripheral surface of the electric resistance adjusting layer is rotationally symmetric about the axis of the conductive support, and therefore the conductive member is rotated around the conductive support as a rotation axis. The discharge site from the electric resistance adjusting layer can be equalized by using the rotating material. Therefore, it is possible to prevent a specific local portion of the electrical resistance adjusting layer from being continuously discharged, and to improve the durability of the electrical resistance adjusting layer.

  According to a tenth aspect of the present invention, in the conductive member according to any one of the first to ninth aspects, the conductive member is used as a charging member in an image forming apparatus or a process cartridge. To do.

  According to the conductive member configured as described above, the image carrier can be uniformly (uniformly) charged.

  Moreover, the electroconductive member which concerns on Claim 11 of this invention is an electroconductive member which concerns on any one of Claims 1-10, and adjoins an electrical resistance adjustment layer among the both ends of each space | gap holding member. Each end of the side is cut out.

  According to the conductive member configured as described above, the length of the outer peripheral surface of the gap holding member along the axial direction of the conductive support is shortened, so that the gap holding member and the image carrier are in contact with each other. Even if the outer peripheral surface of the gap holding member is inclined with respect to the axis of the conductive support or the surface accuracy of this outer peripheral surface is insufficient, the inclination and surface accuracy of this surface are shortened. It is possible to suppress the fluctuation of the contact portion during one rotation due to the above, and to suppress the fluctuation of the gap.

  Further, the end portion of the gap holding member adjacent to the electric resistance adjusting layer is notched so that the end portion does not contact the image carrier, and the gap holding member and the electric resistance adjusting layer are In the combined state, the outer peripheral surfaces of both are continuously removed to prevent leakage of current due to the electrical resistance adjustment layer contacting the image carrier even when there is a variation in processing accuracy. can do.

  Furthermore, when performing removal processing, in the case where the outer peripheral surface of both is continuously removed after combining the electrical resistance adjusting layer and the gap holding member, this notched portion is used for removal processing. The removal allowance (machining relief) of the tool (cutting blade etc.) to be obtained can be facilitated.

  A process cartridge for an image forming apparatus according to the present invention includes at least the conductive member according to the present invention and an image carrier.

  According to the process cartridge for an image forming apparatus configured as described above, the gap holding member that comes into contact with the image carrier has a very small dynamic friction coefficient of 0.06 or less. Even with long-term contact with the body, the wear of the outer peripheral surface of the gap holding member of the conductive member can be maintained at an extremely low level.

  Therefore, the amount of radial step between the outer peripheral surface of the gap holding member and the outer peripheral surface of the electric resistance adjusting layer (the protruding amount of the outer peripheral surface of the gap holding member with respect to the outer peripheral surface of the electric resistance adjusting layer), that is, the outer peripheral surface of the electric resistance adjusting layer And the surface of the image bearing member can be kept constant over a long period of time. Moreover, the effect by the electroconductive member corresponding to each claim mentioned above can be acquired.

  Further, since at least the image carrier and the conductive member are integrally formed in the process cartridge, it can be easily replaced (highly maintainable) with respect to an apparatus such as an image forming apparatus in which the process cartridge is used. The above-described excellent conductive member can be provided.

  The image forming apparatus according to the present invention further includes at least a conductive member according to the present invention, an image carrier, and a transport unit that transports a recording medium on which an image carried on the image carrier is recorded. It is characterized by that.

  According to the image forming apparatus configured as described above, the gap holding member that is in contact with the image carrier has a very small coefficient of dynamic friction of 0.06 or less. Even with this contact, wear of the outer peripheral surface of the gap holding member of the conductive member can be maintained at a very low level.

  Therefore, the amount of radial step between the outer peripheral surface of the gap holding member and the outer peripheral surface of the electric resistance adjusting layer (the protruding amount of the outer peripheral surface of the gap holding member with respect to the outer peripheral surface of the electric resistance adjusting layer), that is, the outer peripheral surface of the electric resistance adjusting layer And the surface of the image bearing member can be kept constant over a long period of time. Moreover, the effect by the electroconductive member corresponding to each claim mentioned above can be acquired.

  Furthermore, since the above-described excellent conductive member is used, the visible image formed (recorded) on the recording medium conveyed by the conveying unit can be stabilized over a long period of time.

  According to the conductive member, the process cartridge including the conductive member, and the image forming apparatus according to the present invention, the gap holding provided respectively on both end sides of the electric resistance adjusting layer formed on the outer peripheral surface of the conductive support. By setting the coefficient of dynamic friction of the member to 0.06 or less, wear due to aging of the gap holding member can be reduced, and the accuracy of the gap between the member and the image carrier can be stably maintained.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of a conductive member, a process cartridge, and an image forming apparatus according to the invention will be described with reference to the drawings.

  FIG. 1 is a partially broken sectional view showing a configuration of a conductive member according to an embodiment of the present invention used as the charging roller 2 (charging member) of the image forming apparatus 1 shown in FIG. 7 or FIG. .

  Here, the image forming apparatus 1 shown in FIGS. 7 and 8 is a photosensitive drum 4 (image carrier) on which an electrostatic latent image is formed, and charging that performs uniform charging processing on the photosensitive drum 4. A roller 2, a power pack (voltage applying power source) 3 for applying a voltage to the charging roller 2, a surface potential meter 5 for measuring the surface potential of the photosensitive drum 4, and laser light (or reflected light or transmitted light from a document) The light carrying the image information of the original document, etc. (hereinafter the same)) The developing roller 6 for attaching toner to the electrostatic latent image formed on the photosensitive drum 4 formed by L, and the toner image formed by the adhesion of this toner Is provided with a transfer roller 7 for transferring the toner to the recording paper S, and a cleaning device 8 for removing the toner remaining on the photosensitive drum 4 after the transfer processing and erasing the residual charge.

  FIG. 8 shows an example of the image forming apparatus 1 in which the photosensitive drum 4, the charging roller 2, the surface potential meter 5, the developing roller 6, and the cleaning device 8 are integrated as a process cartridge 9.

  Here, the photosensitive drum 4 obtains a driving force from a driving mechanism (not shown) and rotates in the direction of arrow A around an axis extending in the depth direction in the drawing, and the charging roller 2 supplies power from the power pack 3. Receive and become charged.

  The charging roller 2 uniformly charges the surface 4 a of the photosensitive drum 4 facing the charging roller 2 with a desired potential. At this time, since the photosensitive drum 4 rotates in the direction of arrow A, the surface portion of the surface 4a of the photosensitive drum 4 on the downstream side in the rotational direction from the portion facing the charging roller 2 is rotated. Therefore, it is uniformly charged sequentially.

  Subsequently, the uniformly charged surface of the photosensitive drum 4 is irradiated with a laser beam L controlled to have a light output amount corresponding to image information such as an image or a character obtained by reading from a document or image information stored in advance. Is done.

  At this time, the potential (negative potential) of the surface 4a of the photosensitive drum 4 is decreased by the irradiation of the laser light L (the absolute potential increases in a direction approaching 0 (zero)). Then, the width of the decreasing potential increases as the amount of light irradiated by the laser light L increases. Therefore, an electrostatic latent image having a potential distribution corresponding to the image information and the like is formed on the surface 4a of the photosensitive drum 4 by the irradiation of the laser light L carrying the image information and the like.

  The surface potential meter 5 detects the potential (potential distribution) of the electrostatic latent image formed on the surface 4 a of the photosensitive drum 4, and the detection result of this potential is the charge control of the charging roller 2 by the power pack 3. And used for exposure control of the laser beam L.

  When a portion of the surface 4 a on which the electrostatic latent image of the photosensitive drum 4 is formed passes through the developing roller 6, an amount of toner corresponding to the potential distribution of the electrostatic latent image adheres, and the surface 4 a of the photosensitive drum 4. The toner image having a density distribution corresponding to the electrostatic latent image is visually developed (developed).

  This toner image is pressed against the recording paper S when the recording paper S fed toward the photosensitive drum 4 at a predetermined timing passes while being sandwiched between the photosensitive drum 4 and the transfer roller 7. Transcribed. The recording sheet S on which the toner image is transferred is conveyed in the direction of arrow B toward a fixing unit (not shown).

  On the other hand, the photosensitive drum 4 after the toner image is transferred to the recording paper S is cleaned by removing the toner remaining on the surface 4a by the cleaning device 8, and the residual charge is removed by a quenching lamp (not shown). Then, the state returns to the state of the charging process and waits for the next charging process.

  In these image forming apparatuses 1, an electric resistance adjusting layer 11 (surface layer 11 b) to be described later of the charging roller 2 and an outer peripheral surface 4 a (see FIG. 1) of the photosensitive drum 4 are interposed via a predetermined gap M. It is of the proximity charging system that is facing.

  The charging roller 2 shown in FIG. 1 includes a long, substantially cylindrical conductive support 10 that forms a shaft member, an electric resistance adjustment layer 11 formed on the outer peripheral surface 10a of the conductive support 10, and an electric resistance adjustment. It is made of a material different from that of the layer 11, provided on the outer peripheral surface 10 a side of the conductive support 10 and on both ends of the electric resistance adjusting layer 11, and protrudes in the radial direction from the outer peripheral surface 11 a of the electric resistance adjusting layer 11. And a pair of gap holding members 12 having an outer peripheral surface 12 a that abuts against the photosensitive drum 4 disposed to face the electric resistance adjusting layer 11. Further, the outer peripheral surface 11a of the electric resistance adjusting layer 11 is covered with a surface layer 11b that prevents adhesion of toner.

Here, the gap retaining member 12 has a kinetic friction coefficient of 0.06 or less and a wear coefficient of 5.1 × 10 5 from the viewpoint of the above-described wear resistance performance while ensuring smooth slidability with the photosensitive drum 4. ^-4 mm / gf or less, durometer hardness HDD (according to JIS) of 60 or more and 70 or less, molecular weight of 1 million or more and density of 0.96 g / from the viewpoint of preventing sticking of toner and toner additive It is formed of a polyethylene resin that is cm ³ or more.

  The electrical resistance adjusting layer 11 has a cylindrical shape centered on the conductive support 10, and each gap holding member 12 also has a cylindrical shape centered on the conductive support 10.

  FIG. 2 is a schematic diagram showing a state where the charging roller 2 shown in FIG. 1 is installed adjacent to the photosensitive drum 4. The charging roller 2 is disposed in contact with the photosensitive drum 4 at an arbitrary pressure. At this time, the outer peripheral surface 12a of the gap holding member 12 contacts the outer peripheral surface 4a of the photosensitive drum 4, but the electric resistance A gap M is formed between the outer surface 11 a of the adjustment layer 11 and the outer peripheral surface 4 a of the photosensitive drum 4.

  Further, in the charging roller 2, the outer peripheral surfaces 12a of both the gap holding members 12 are regions other than the image forming region K2 in the region K1 in which the photosensitive layer formed on the outer peripheral surface 4a of the photosensitive drum 4 is formed. (Non-image forming area) It is installed so as to abut on K3. In this state, the photosensitive drum 4 can be charged by applying a voltage from the power pack 3 to the conductive support 10 of the charging roller 2.

  Further, since the photosensitive drum 4 also has a cylindrical shape, the charging roller 2 and the photosensitive drum 4 are rotated in opposite directions by a rotation driving unit (not shown), so that the portions of the surfaces facing each other are circumferential. Can be changed. Therefore, chemical degradation of the surface due to energization stress is unlikely to occur, and the product life can be increased (durability can be improved).

  In order to prevent slippage between the charging roller 2 and the photosensitive drum 4, it is preferable that the charging roller 2 is also driven to rotate independently by a drive gear or the like, similarly to the photosensitive drum 4.

  Further, the photosensitive drum 4 and the charging roller 2 do not necessarily have a cylindrical shape, and may have an elliptical cylindrical shape.

  Here, a measurement method for quantitatively specifying the dynamic friction coefficient of the gap holding member 12 and a measurement method for quantitatively specifying the wear coefficient will be described with reference to FIG.

  First, as shown in FIG. 3A, an alumina ball (a member formed in a spherical shape by an alumina material) is placed on a flat test piece TP with the same material as the gap holding member 12 with a predetermined vertical load W ( For example, the alumina ball is pressed vertically with a load of 0.3 kgf, and the alumina ball is reciprocated a predetermined number of times (for example, 10 times) with a predetermined amplitude X in the plane of the test piece TP. Is measured with a load cell. This measurement result is shown in FIG.

  At this time, if the dynamic friction coefficient is μ ′, the equation F = μ′W is established, so the dynamic friction coefficient μ ′ can be calculated by μ ′ = F / W.

  In the gap holding member 12 in this embodiment, the dynamic friction coefficient μ ′ quantitatively measured in this way is set to 0.06 or less.

  Further, the wear coefficient is quantitatively specified by the following test. That is, with the test apparatus shown in FIG. 3A, an alumina ball and a predetermined vertical load W (for example, 0.15 kgf) are applied to the flat test piece TP using the same material as the gap holding member 12. The alumina ball is pressed vertically while the alumina ball is reciprocated a predetermined number of times (for example, 150 times) with a predetermined amplitude X in the plane of the test piece TP. The width d (see FIG. 4 (a)) of the wound is measured.

  Then, the measurement operation of the reciprocating motion and the width d of the sliding flaw is performed in the same manner after setting the load W to different values (for example, 0.3 kgf and 0.45 kgf).

  When a graph is drawn with the width d of the sliding scratches obtained by the above tests corresponding to the vertical axis and the load W corresponding to the horizontal axis, for example, the graph shown in FIG. It has a linearity with respect to the width d, and a correlation d = mW (m; constant) is recognized. Then, a constant m (= d / W) calculated by the load W and the scratch width d is specified as the above-described wear coefficient.

In the gap holding member 12 in the present embodiment, the wear coefficient m quantitatively measured in this way is set to 5.1 × 10 ⁻⁴ mm / gf or less.

  According to the charging roller 2 according to the present embodiment configured as described above, the gap holding member 12 in contact with the photosensitive drum 4 has a very small value such that the coefficient of dynamic friction μ ′ is 0.06 or less. Therefore, the wear of the outer peripheral surface 12a of the gap holding member 12 can be maintained at an extremely low level even by long-term contact with the photosensitive drum 4.

  Therefore, the step difference in the radial direction between the outer peripheral surface 12 a of the gap holding member 12 and the outer peripheral surface 11 a of the electric resistance adjusting layer 11, that is, between the outer peripheral surface 11 a of the electric resistance adjusting layer 11 and the outer peripheral surface 4 a of the photosensitive drum 4. The length of the gap M can be maintained constant over a long period of time.

Further, according to the charging roller 2 according to the present embodiment, since the wear coefficient m of the gap holding member 12 is 5.1 × 10 ⁻⁴ mm / gf or less, the wear of the gap holding member 12 with time is small, Therefore, it is possible to prevent transition to the photosensitive drum 4 due to wear and to increase the durability of the parts.

  Furthermore, according to the charging roller 2 according to the present embodiment, since the durometer hardness HDD of the gap holding member 12 is 60 or more, the gap holding member 12 is easily damaged by the load received from the photosensitive drum 4 that abuts. Accordingly, it is possible to prevent the step amount between the outer peripheral surface 12a of the gap holding member 12 and the outer peripheral surface 11a of the electric resistance adjusting layer 11 from fluctuating, and to precisely control the length of the gap M. be able to.

  Moreover, since the durometer hardness HDD of the gap holding member 12 is 70 or less, it is possible to prevent the gap holding member 12 from damaging the photosensitive drum 4.

Furthermore, according to the charging roller 2 according to the present embodiment, the gap holding member 12 is formed of polyethylene resin having a molecular weight of 1 million or more and a density of 0.96 g / cm ³ or more. It is possible to prevent the toner from adhering to the toner.

  Further, the charging roller 2 according to the present embodiment prevents the toner from adhering to the outer peripheral surface 11a of the electric resistance adjusting layer 11 because the outer peripheral surface 11a of the electric resistance adjusting layer 11 is covered with the surface layer 11b. be able to.

  The gap holding member 12 in the charging roller 2 is formed by molding, for example, and the characteristics required for the gap holding member 12 are the outer peripheral surface 4a of the photosensitive drum 4 and the electric resistance adjusting layer 11. The gap M between the outer peripheral surface 11a (the outer peripheral surface of the surface layer 11b when the outer peripheral surface 11b is provided on the outer peripheral surface 11a of the electrical resistance adjusting layer 11 as in this embodiment) In order to achieve this, it is desirable that the material be formed of a material having low hygroscopicity and high wear resistance.

  That is, a material having high hygroscopicity has a large volume expansion coefficient due to moisture absorption. Therefore, the step amount between the outer peripheral surface of the gap holding member 12 and the outer peripheral surface 11a of the electric resistance adjusting layer 11 (the outer peripheral surface of the surface layer 11b) is hygroscopic. It is easy to change depending on the degree, and the gap between the photosensitive drum 4 and the electric resistance adjusting layer 11 corresponding to the step amount is likely to change. Therefore, a thing with a small hygroscopic property is preferable.

  On the other hand, those with low wear resistance have a large amount of wear due to friction with the photosensitive drum 4, and therefore the outer peripheral surface of the gap holding member 12 and the outer peripheral surface 11a of the electric resistance adjusting layer 11 (the outer peripheral surface of the surface layer 11b). ), And the gap between the photosensitive drum 4 and the electrical resistance adjusting layer 11 corresponding to the step amount is likely to be reduced. Accordingly, those having high wear resistance, that is, those having a small wear coefficient m are preferred.

  It is also important that the toner and the toner additive are difficult to adhere (adhere) and that the photosensitive drum 4 is not worn because it slides in contact with the photosensitive drum 4.

  Specifically, general-purpose resins such as polyethylene (PE), polypropylene (PP), polyacetal (POM), polymethyl methacrylate (PMMA), polystyrene (PS) and copolymers thereof (AS, ABS), PC, urethane And fluorine. In order to securely support and fix the gap holding member 12, an adhesive can be applied and bonded.

Moreover, it is preferable that the space | gap holding member 12 is formed with the insulating material, and it is preferable that a volume specific resistance is 10 < ¹³ > ohm-cm or more as this insulating parameter | index. Here, the reason why the insulating property is necessary is to prevent a leak current from being generated with respect to the photosensitive substrate of the photosensitive drum 4.

  Note that the entire gap holding member 12 is not limited to the insulating one, and at least the surface portion of the outer peripheral surface 12a of the gap holding member 12 that contacts the photosensitive drum 4 has an insulating property. There may be. This is because the occurrence of the leakage current described above can be prevented if the surface portion has insulating properties.

The electric resistance adjusting layer 11 is formed of a thermoplastic resin composition in which a polymer type ion conductive material is dispersed. The volume resistivity of the electric resistance adjusting layer 11 is preferably 10 ⁶ Ωcm or more and 10 ⁹ Ωcm or less. This is because if it exceeds 10 ⁹ Ωcm, charging ability and transfer ability are insufficient, and if it is less than 10 ⁶ Ωcm, leakage due to voltage concentration on the entire photosensitive drum 4 may occur.

  The thermoplastic resin used for the electrical resistance adjusting layer 11 is not particularly limited, but polyethylene (PE), polypropylene (PP), polymethyl methacrylate (PMMA), polystyrene (PS) and copolymers thereof ( A general-purpose resin such as AS or ABS is preferable because it can be easily molded.

  Further, as the polymer type ion conductive material dispersed in the thermoplastic resin, a polymer compound containing a polyether ester amide component is preferable. Polyether ester amide is an ion conductive polymer material, and is uniformly dispersed and immobilized at a molecular level in a matrix polymer. Therefore, there is no variation in resistance value due to poor dispersion as seen in a composition in which an electron conductive conductive agent such as metal oxide or carbon black is dispersed. In addition, since it is a polymer material, bleed-out hardly occurs.

  In addition, about a compounding quantity, in order to make an electrical resistance value into a desired value, it is necessary to make a thermoplastic resin into 30 to 70 weight% and a polymeric ion conductive agent to 70 to 30 weight%.

  There is no restriction | limiting in particular regarding the manufacturing method of a resin composition, It can manufacture easily by melt-kneading the mixture of each material with a biaxial kneader, a kneader, etc.

  The formation of the electric resistance adjusting layer 11 on the conductive support 10 is performed by applying the semiconductive resin composition to the conductive support by a method such as extrusion molding as well as the injection molding described in the present embodiment. By covering the outer peripheral surface 10a of 10, it can be performed easily.

  If only the electric resistance adjusting layer 11 is formed on the conductive support 10 to constitute the charging roller 2, toner or a toner additive may adhere to the electric resistance adjusting layer 11 and the performance may deteriorate. Such a problem can be avoided by forming the above-described surface layer 11 b on the outer peripheral surface 11 a of the electric resistance adjusting layer 11.

  The electric resistance value of the surface layer 11b is preferably set to be larger than the electric resistance value of the electric resistance adjusting layer 11, and in this setting, the photosensitive drum 4 has a defect. Even in this case, it is possible to avoid the concentration of the charging voltage on the defective portion and the abnormal discharge (leakage).

However, even if the electric resistance value of the surface layer 11b is simply increased, the charging ability and the transfer ability are insufficient, so that the difference in electric resistance value between the surface layer 11b and the electric resistance adjusting layer 11 is 10 ³ Ωcm or less. It is preferable to limit.

  As a material for forming the surface layer 11b, a fluorine resin, a silicone resin, a polyamide resin, a polyester resin, or the like is preferable. This is because they are excellent in non-adhesiveness and can effectively prevent the toner from sticking. In addition, since the resin material is electrically insulative, the electrical resistance value of the surface layer 11b can be appropriately adjusted by dispersing various conductive materials in the resin.

  As a method of forming the surface layer 11b on the electric resistance adjusting layer 11, for example, the constituent material of the surface layer 11b described above is dissolved in an organic solvent to generate a paint, and this paint is spray-coated, dipped, or roll-coated. What is necessary is just to apply | coat on the electrical resistance adjustment layer 11 by various coating methods, such as. In addition, as for the layer thickness of the surface layer 11b, about 10-30 micrometers is desirable.

  Further, the material of the surface layer 11b may be one-component or two-component, but when a two-component paint that uses a curing agent is used, it is environmentally resistant and non-adhesive. It is possible to improve the properties, which is preferable. However, the two-component paint is generally a method in which the resin is crosslinked and cured by heating the coating film, and since the electric resistance adjusting layer 11 is a thermoplastic resin, it is difficult to heat at a high temperature. .

  As the two-component paint, it is desirable to use a main agent having a hydroxyl group in the molecule and an isocyanate resin that causes a crosslinking reaction with the hydroxyl group. By using an isocyanate-based resin, a crosslinking / curing reaction can be caused in a relatively low temperature environment of 100 ° C. or lower.

  The inventors of the present application have investigated from the non-adhesiveness of the toner, and as a result, confirmed that the resin is a silicone-based resin having a high non-adhesive property of the toner, and in particular, an acrylic silicone resin having an acrylic skeleton in the molecule. It was found to be good.

  Since the charging roller 2 has important electrical characteristics (especially resistance value), it is necessary to make the surface layer 11b conductive. A method of providing the surface layer 11b with conductivity can be realized by dispersing a conductive agent in the resin material.

  The conductive agent is not particularly limited, and various types can be applied. For example, conductive carbon such as ketjen black EC or acetylene black, SAF, ISAF, HAF, FEF, GPF, SRF, Metals such as FT or MT rubber carbon, oxidized color carbon, pyrolytic carbon, indium-doped tin oxide (ITO), tin oxide, titanium oxide, zinc oxide, copper, silver, or germanium Alternatively, a metal oxide, a conductive polymer such as polyaniline, polypyrrole, or polyacetylene can be used.

  In addition, as a conductivity imparting material for imparting conductivity, there is also an ionic conductive material. As the ionic conductive material, inorganic materials such as sodium perchlorate, lithium perchlorate, calcium perchlorate, or lithium chloride are used. An ionic conductive material, or an organic ionic conductive material such as modified fatty acid dimethyl ammonium ethosulphate, ammonium stearate acetate, or lauryl ammonium acetate can be used.

  As an example of the manufacturing method of the charging roller 2, as shown in FIG. 5A, an electric resistance adjusting layer 11 is formed on the conductive support 10 by injection molding, and then the electric resistance adjusting layer 11 is formed. Adhesive is applied to the outer peripheral surface 10a of the conductive support 10 on both end surfaces, and the gap holding member 12 is fitted to the portion where the adhesive is applied, and the gap holding member 12 is attached to the conductive support 10. Adhesion is fixed ((b) in the figure).

  Thus, in the state where the gap holding member 12, the conductive support 10 and the electric resistance adjusting layer 11 are integrally combined, as shown in FIG. While rotating, the outer peripheral surface 12a of the gap holding member 12 and the outer peripheral surface 11a of the electric resistance adjusting layer 11 are continuously cut (removed) by the cutting blade T, so that the outer peripheral surface 11a of the electric resistance adjusting layer 11 is obtained. The protrusion amount in the radial direction of the outer peripheral surface 12a of the gap holding member 12 is formed to a desired specified amount M1, and the outer diameters of both outer peripheral surfaces 11a and 12a are finished.

  Then, in a state where the gap holding member 12, the conductive support 10 and the electric resistance adjusting layer 11 are integrally combined, the gap holding member 12 and the electric resistance adjusting layer 11 are continuously cut, By forming the outer peripheral surfaces 12a and 11a, the gap holding member 12 is processed alone, and the outer peripheral surface 11a of the electric resistance adjusting layer 11 formed on the outer peripheral surface 10a of the conductive support 10 is processed alone, Thereafter, there is no accumulation error as in the case of a charging roller in which the two are integrally combined. Therefore, the protrusion amount in the radial direction of the outer peripheral surface 12a of the gap holding member 12 with respect to the outer peripheral surface 11a of the electric resistance adjusting layer 11 Can be accurately set to the desired amount M1.

  Therefore, the length of the gap M between the outer peripheral surface 11a of the electric resistance adjusting layer 11 and the outer peripheral surface 4a of the photosensitive drum 4 can be accurately formed to the specified amount M1.

  The surface layer 11b is formed on the outer peripheral surface 11a of the electrical resistance adjusting layer 11 by, for example, the above-described application after the gap cutting member 12 is protected (masked) after the above-described cutting process (same as above). (D).

  Furthermore, when continuously cutting the gap holding member 12 and the electric resistance adjusting layer 11 described above, as shown in FIG. 1B, the electric resistance adjusting layer among the both ends of each gap holding member 12. 11 is preferably removed so as to be cut out.

  By notching the end portions 12b, 12b of the gap members 12, 12, the length of the outer peripheral surface 12a of the gap holding member 12 along the axial direction of the charging roller 2 is shortened. The contact length between the member 12 and the photosensitive drum 4 is shortened. For example, the outer peripheral surface 12a of the gap holding member 12 is inclined with respect to the axis C of the conductive support 10, or the surface of the outer peripheral surface 12a. Even if the accuracy is insufficient, the variation of the contact portion during one rotation of the charging roller 2 due to the inclination of the surface 12a and the surface accuracy can be suppressed, and the variation of the gap M can be suppressed.

  Further, by cutting out these end portions 12b, the end portions 12b can be prevented from coming into contact with the photosensitive drum 4, and the gap holding member 12 and the electric resistance adjusting layer 11 are combined. Even when the outer peripheral surfaces 12a and 11a of both are continuously cut and there is a variation in processing accuracy, the electric resistance adjusting layer 11 contacts the photosensitive drum 4 and current leakage occurs. Can be prevented.

  Furthermore, when performing the cutting process, the end 12b is notched, so that a cutting allowance (processing escape) of the cutting blade T is obtained, and the cutting process can be facilitated. In addition, the shape of the notch as a clearance allowance may be any shape.

Hereinafter, by using a plurality of specific examples 1 to 3 of the charging roller 2 of the above-described embodiment and comparative examples 1 and 2, charging unevenness (the gap between the charging roller and the photosensitive drum) is determined. The change state was evaluated as the image quality of the obtained image), the wear of the gap holding member 12 was compared, and the presence or absence of toner adhering to the gap holding member 12 was evaluated.
(Example 1)
ABS resin (Denka ABS GR-0500; manufactured by Denki Kagaku Kogyo Co., Ltd.) 50 weights as the electric resistance adjusting layer 11 with respect to the outer peripheral surface of a cylindrical core shaft (conductive support 10) having an outer shape of 8 mm made of stainless steel. %, Polyether ester amide (IRGASTAT P18; manufactured by Ciba Specialty Chemicals Co., Ltd.) 50% by weight was molded into a cylindrical shape by injection molding.

  Next, a cylindrical member made of high-density polyethylene resin (Novatech HY540; manufactured by Nippon Polychem Co., Ltd.) is inserted and bonded to both ends of the molded product as the gap holding member 12, and the outside of the gap holding member 12 is removed by cutting. Simultaneous finishing (continuous cutting shown in FIG. 5C) was performed so that the diameter (maximum diameter) was 12.12 mm and the outer diameter of the electric resistance adjusting layer 11 was 12.00 mm.

Next, a mixture comprising an acrylic silicone resin (3000 VH-P; manufactured by Kawakami Paint Co., Ltd.), an isocyanate curing agent, and carbon black (35% by weight based on the total solid content) is formed on the outer peripheral surface 11a of the electrical resistance adjusting layer 11. Thus, the surface layer 11b having a layer thickness of about 10 μm was formed, and the charging roller 2 (conductive member) shown in FIG. 5D was obtained.
(Example 2)
ABS resin (Denka ABS GR-0500; manufactured by Denki Kagaku Kogyo Co., Ltd.) 50 weights as the electric resistance adjusting layer 11 with respect to the outer peripheral surface of a cylindrical core shaft (conductive support 10) having an outer shape of 8 mm made of stainless steel. %, Polyether ester amide (IRGASTAT P18; manufactured by Ciba Specialty Chemicals Co., Ltd.) 50% by weight was molded into a cylindrical shape by injection molding.

  Next, a cylindrical member made of high-density polyethylene resin (Jyrex KM780K; manufactured by Nippon Polyolefin Co., Ltd.) is inserted and bonded to both ends of the molded product as the gap holding member 12, and the outside of the gap holding member 12 is removed by cutting. Simultaneous finishing (continuous cutting shown in FIG. 5C) was performed so that the diameter (maximum diameter) was 12.12 mm and the outer diameter of the electric resistance adjusting layer 11 was 12.00 mm.

Subsequently, a silicone resin (slip coating agent HS-3; manufactured by Toshiba Silicone Co., Ltd.), a curing agent (XC9603; manufactured by GE Toshiba Silicone Co., Ltd.), a catalyst (YC6831; A surface layer 11b having a layer thickness of about 10 μm is formed by a mixture (surface resistance: 8.3 × 10 ⁹ Ω) composed of Silicone Co., Ltd.) and carbon black (30% by weight with respect to the total solid content). The charging roller 2 (conductive member) shown in (d) was obtained.
(Example 3)
ABS resin (Denka ABS GR-0500; manufactured by Denki Kagaku Kogyo Co., Ltd.) 50 weights as the electric resistance adjusting layer 11 with respect to the outer peripheral surface of a cylindrical core shaft (conductive support 10) having an outer shape of 8 mm made of stainless steel. %, Polyether ester amide (IRGASTAT P18; manufactured by Ciba Specialty Chemicals Co., Ltd.) 50% by weight was molded into a cylindrical shape by injection molding.

  Next, a cylindrical member made of high-density polyethylene resin (Jyrex KM780K; manufactured by Nippon Polyolefin Co., Ltd.) is inserted and bonded to both ends of the molded product as the gap holding member 12, and the outside of the gap holding member 12 is removed by cutting. Simultaneous finishing (continuous cutting shown in FIG. 5C) was performed so that the diameter (maximum diameter) was 12.12 mm and the outer diameter of the electric resistance adjusting layer 11 was 12.00 mm.

Next, the outer peripheral surface 11a of the electric resistance adjusting layer 11 is made of an acrylic silicone resin (3000VH-P, manufactured by Kawakami Paint Co., Ltd.), an isocyanate-based curing agent, and carbon black (35% by weight with respect to the total solid content). A surface layer 11b having a layer thickness of about 10 μm was formed from the mixture, and the charging roller 2 (conductive member) shown in FIG. 5D was obtained.
(Comparative Example 1)
ABS resin (Denka ABS GR-0500; manufactured by Denki Kagaku Kogyo Co., Ltd.) 50 weights as the electric resistance adjusting layer 11 with respect to the outer peripheral surface of a cylindrical core shaft (conductive support 10) having an outer shape of 8 mm made of stainless steel. %, Polyether ester amide (IRGASTAT P18; manufactured by Ciba Specialty Chemicals Co., Ltd.) 50% by weight was molded into an outer diameter of 12.0 mm in a cylindrical shape by injection molding.

  Next, the outer peripheral surface 11a of the electrical resistance adjusting layer 11 is made of urethane resin (Adekabon titer AM36; manufactured by Asahi Denka Kogyo Co., Ltd.), an isocyanate curing agent, and carbon black (30% by weight with respect to the total solid content). A surface layer 11b having a layer thickness of about 10 μm was formed by the mixture.

Next, a cylindrical member made of a low density polyethylene resin (NC524A; manufactured by Nippon Polyolefin Co., Ltd.) is inserted and bonded to both ends of the molded product as the gap holding member 12, and the outer diameter of the gap holding member 12 is obtained by cutting. Simultaneous finishing (continuous cutting shown in FIG. 5C) is performed so that the maximum diameter is 12.12 mm and the outer diameter of the electric resistance adjusting layer 11 is 12.00 mm. FIG. The charging roller 2 (conductive member) shown in FIG.
(Comparative Example 2)
Perchloric acid is added to 100 parts by weight of epichlorohydrin rubber (Epichromer CG; manufactured by Daiso Corporation) as the electric resistance adjusting layer 11 with respect to the outer peripheral surface of a cylindrical core shaft (conductive support 10) made of stainless steel having an outer diameter of 8 mm. A rubber composition containing 3 parts by weight of ammonium was coated through an extrusion molding and vulcanization process, and finished to an outer diameter of 12 mm by grinding.

  Next, a layer thickness is formed on the surface by a mixture of a polyvinyl butyral resin (Denka Butyral 3000-K; manufactured by Denki Kagaku Kogyo Co., Ltd.), an isocyanate curing agent, and tin oxide (25% by weight based on the total solid content) A 10 μm surface layer was formed.

After that, a ring-shaped gap holding member made of low-density polyethylene resin (NC544A; manufactured by Nippon Polyolefin Co., Ltd.) is inserted and bonded to both ends as a gap holding member, and the outer diameter (maximum diameter) of the gap holding member is obtained by cutting. Were simultaneously finished to 12.12 mm and the outer diameter of the electric resistance adjusting layer was 12.00 mm to obtain a charging roller 2 (conductive member) shown in FIG.
(test)
Each charging roller 2 of each of the above Experimental Examples 1 to 3 and Comparative Examples 1 and 2 is mounted on the image forming apparatus 1 shown in FIG. 7, and charging unevenness (change state of the gap between the charging roller and the photosensitive drum) Was evaluated as the image quality of the obtained image), the wear of the gap holding member was compared, and the presence or absence of toner adhering to the gap holding member was evaluated.

  The test conditions were evaluated after the voltage applied to the charging roller was DC = −800 V and AC = 2400 Vpp (frequency = 2 kHz) and 600,000 sheets of recording paper were passed. The test environment is a temperature of 23 ° C. and a humidity of 60% RH. The above evaluation results are shown in Table 1.

表１より明らかなように、実施例１〜実施例３の帯電ローラはいずれも、比較例１，２に対して、帯電ムラの発生は無く、空隙保持部材の摩耗は良好（摩耗量が少ない）であり、かつ空隙保持部材へのトナーの固着も良好（固着量は少ない）であることが確認された。

As is clear from Table 1, the charging rollers of Examples 1 to 3 are free from uneven charging and the wear of the gap holding member is good compared to Comparative Examples 1 and 2 (the amount of wear is small). In addition, it was confirmed that the toner is firmly fixed to the gap holding member (the fixing amount is small).

  As described above, the embodiment and examples in which the conductive member according to the present invention is used as the charging roller have been described. However, the conductive member according to the present invention is not limited to the charging roller, and the transfer roller, the development The present invention can also be applied as a roller, a photosensitive drum, and the like, and even when applied as such, it is possible to achieve the same operations and effects as the above-described embodiment.

  Further, as shown in FIG. 8, the charging roller 2, the photosensitive drum 4, the surface potential meter 5, the developing roller 6, and the cleaning device 8 of the above-described embodiment are integrated by a connecting member (not shown). The process cartridge 9 is an embodiment of the process cartridge according to the present invention, and this process cartridge 9 can also exhibit the same operations and effects as those provided by the charging roller 2 of the present embodiment. Is possible.

  Furthermore, the process cartridge 9 of such an embodiment can be easily replaced (highly maintainable) with respect to the apparatus in which the process cartridge 9 is used, such as the image forming apparatus 1, and the excellent charging roller 2 described above can be used. It can also be provided by a simple desorption operation.

  FIG. 6 is a schematic configuration diagram showing an embodiment of the image forming apparatus of the present invention, which is an image forming apparatus 1 (for example, a digital copying machine) including the charging roller 2 of the above-described embodiment.

  The illustrated image forming apparatus 1 is provided at the uppermost part of the apparatus main body, and is provided at a lower part of the apparatus main body, a document reading unit 20 that optically reads a document placed on a predetermined reading table as image information, A paper feeding unit 30 in which a large number of recording papers S are stored, an image recording unit 40 that records on the recording paper S the image information of the original read by the original reading unit 20 on the recording paper S as a visible image, A paper discharge unit 50 on which the recording paper S on which a visible image (image) has been recorded is placed, and a conveyance unit 60 that conveys the recording paper from the paper supply unit 30 through the image recording unit 40 to the paper discharge unit 50. And a fixing unit 70 that is provided on the conveyance path of the conveyance unit 60 from the image recording unit 40 to the paper discharge unit 50 and fixes the image on the recording sheet S conveyed from the image recording unit 40. is there.

  Here, the document reading unit 20 includes, for example, a light source that emits light for reading the document, a scanning unit that reads a reflected light image from the document while irradiating the document with light emitted from the light source, a line sensor, and the like. The reflected light image read by the line sensor is transmitted to the image recording unit 40 as image information.

  The paper feeding unit 30 includes two types of paper feeding trays 31 and 32 corresponding to the size difference of the recording paper S arranged in two upper and lower stages, and feeds the recording paper S of an arbitrary size. The manual paper feed unit 33 is provided. In addition, as for the paper feed trays 31 and 32, for example, a large paper feed tray 31 corresponding to a large recording paper S is arranged on the lower side, and a small paper feed tray 32 corresponding to a small recording paper S is provided. Is arranged on the upper side.

  Each of the paper feed trays 31 and 32 and the manual paper feed unit 33 feeds recording paper S one by one and feeds paper onto the transport path of the transport unit 60. 34, 35, and 36 are provided.

  The image recording unit 40 corresponds to the process cartridge 9 shown in FIG. 8 in which the charging roller 2 and the photosensitive drum 4 of the above-described embodiment are integrally configured, and the image information transmitted from the document reading unit 20. Laser light L carrying image information is emitted by controlling the amount of light, and electrostatic latent images corresponding to this image information are formed on the outer peripheral surface of the photosensitive drum 4 uniformly charged by the charging roller 2. And a writing unit 41 for recording an image.

  The paper discharge unit 50 includes a bin tray 51 provided on the lower side and a paper discharge tray 52 provided on the upper side. Whether the paper is discharged to the bin tray 51 or to the paper discharge tray 52. This sorting is performed by the paper discharge rollers 64 and 65 provided on the transport path of the transport unit 60 in accordance with an instruction input on an operation panel (not shown).

  In addition to the paper discharge rollers 64 and 65 described above, the transport unit 60 includes a registration roller pair 61 that controls the paper feed position of the recording paper S on the transport path before the image recording unit 40, and the recording paper in the image recording unit 40. S is provided with a transfer conveyance belt 62 and the like for transferring the toner image formed on the photosensitive drum 4. The transfer conveyance belt 62 is circulated by the rotation of the drive roller 63.

  In the image forming apparatus 1 of the present embodiment configured as described above, first, the image information written on the document is read by the document reading unit 20, and the image information obtained by the reading is sent to the writing unit 41. .

  Next, the image recording unit 40 rotates the photosensitive drum 4 in the direction of the arrow, and its outer peripheral surface is neutralized by the neutralizing lamp of the process cartridge 9 and averaged to the reference potential, and then uniformly and uniformly by the charging roller 2. Charged.

  Then, the writing unit 41 irradiates the photosensitive drum 4 with the laser light L whose light amount is controlled in accordance with the transmitted image information, and accordingly, on the outer peripheral surface of the photosensitive drum 4, the image information corresponds to the image information. An electrostatic latent image of potential distribution is formed.

  When the photosensitive drum 4 further rotates and passes the developing roller 6, an amount of toner corresponding to the potential distribution of the electrostatic latent image adheres to the outer peripheral surface of the photosensitive drum 4, and the potential of the electrostatic latent image. A toner image having a density distribution corresponding to the distribution is developed.

  On the other hand, a paper feed tray 31 or 32 containing a recording sheet S of a size designated by an operation panel (not shown), or a paper feed roller 34 or 35 or 36 of the manual feed tray 33 is fed from the corresponding tray 31, 32 or 33. Then, the recording sheets S are pulled out one by one and fed onto the transport path of the transport unit 60.

  Here, the registration roller pair 61 skews the recording sheet S so that the leading end of the recording sheet S fed on the transporting path accurately coincides with the leading end of the toner image on the photosensitive drum 4. (Skew; arrival time difference) is corrected to accurately adjust the conveyance timing of the recording paper S.

  Then, the recording sheet S whose transport timing is adjusted is transported to the image recording unit 40 by the transfer transport belt 62 so that the toner image on the photosensitive drum 4 is transferred, and the toner image is transferred.

  The recording sheet S on which the toner image has been transferred is further conveyed by the transfer conveyance belt 62, separated from the transfer conveyance belt 62 at a portion where the transfer conveyance belt 62 is wound around the driving roller 63, and then to the fixing unit 70. Be transported.

  Here, due to the rigidity (roughness) of the recording paper S, the radius of curvature of the recording paper S itself formed when the recording paper S bends is larger than the radius of curvature of the driving roller 63, so that the recording paper S is driven. The recording paper S is separated from the transfer conveyance belt 62 in the portion that has passed the roller 63.

  The fixing unit 70 fixes the toner by transferring the toner transferred onto the recording paper S to the recording paper S by applying a clamping pressure while heating the recording paper S.

  Then, the recording sheet S on which the toner image is fixed is discharged by the discharge rollers 64 and 65 to the discharge tray 52 or the bin tray 51 corresponding to the instruction input to the operation panel.

  On the other hand, the toner remaining on the photosensitive drum 4 of the image recording unit 40 rotates to the cleaning position which is the next process, is scraped off by the cleaning blade of the cleaning device 8, and proceeds to the next image recording process again.

  As described above in detail, according to the image forming apparatus 1 of the present embodiment, it is possible to achieve the same operations and effects as the operations and effects achieved by the charging roller 2 of the present embodiment.

  Furthermore, since the above-described excellent charging roller 2 is used, the visible image recorded on the recording paper S (recording medium) conveyed by the conveying unit 60 should be stable over a long period of time. Can do.

  Note that the image forming apparatus according to the present invention is not limited to the form of the image forming apparatus 1 shown in FIG. 6, and includes other forms of copying machines and laser printers that do not include the document reading unit 20. Various types of printers and facsimile machines may be used, and any type of apparatus may be used as long as an image (including characters) is formed based on a signal (information) by an electrophotographic method.

It is a figure which shows the charging roller which is an example of the electroconductive member which concerns on this invention, (a) is schematic, (b) is a fragmentary broken sectional view which shows the detail of the A section in (a). FIG. 2 is a diagram showing a positional relationship between a charging roller and a photosensitive drum shown in FIG. 1 (the charging roller is a cross-sectional view). It is a figure explaining the test apparatus for expressing a dynamic friction coefficient and a wear coefficient quantitatively, (a) shows the structure, (b) represents the dynamic friction force F during a test. (A) is the figure which shows the width | variety of the abrasion flaw formed in the test piece for the detection of a wear coefficient, (b) represents the graph which shows the relationship between a vertical load and the width | variety of an abrasion flaw, respectively. FIG. 2 is a cross-sectional view schematically illustrating a method for forming the charging roller illustrated in FIG. 1. FIG. 2 is a diagram illustrating a main part of an example of an image forming apparatus including the charging roller illustrated in FIG. 1. 1 is a diagram illustrating a main configuration of an image forming apparatus. FIG. 3 is a diagram illustrating a main configuration of an image forming apparatus including a process cartridge.

Explanation of symbols

1 Image forming apparatus 2 Charging roller (conductive member)
4 Photosensitive drum (image carrier)
4a outer peripheral surface 9 process cartridge 10 conductive support 10a outer peripheral surface 11 electrical resistance adjusting layer 11a outer peripheral surface 11b surface layer 12 gap holding means 12a outer peripheral face 12b end M gap

Claims (13)

The elongated conductive support constituting the shaft member, the electrical resistance adjustment layer formed on the outer peripheral surface of the conductive support, and the electrical resistance adjustment layer are made of different materials, and the conductive support The outer peripheral surface side is provided on both ends of the electric resistance adjusting layer, protrudes in the radial direction from the outer peripheral surface of the electric resistance adjusting layer, and contacts the image carrier disposed opposite to the electric resistance adjusting layer. In a conductive member provided with a pair of gap holding members having an outer peripheral surface in contact with each other,
The conductive member, wherein the gap holding member is formed so that a dynamic friction coefficient thereof is 0.06 or less.   In a state where the gap holding member, the conductive support, and the electric resistance adjusting layer are integrally combined, at least the outer peripheral face of the gap holding member is removed and processed with respect to the outer peripheral face of the electric resistance adjusting layer. The conductive member according to claim 1, wherein an amount of protrusion of the outer peripheral surface of the gap holding member in the radial direction is a desired specified amount. The conductive member according to claim 1, wherein the gap holding member has a wear coefficient of 5.1 × 10 ⁻⁴ mm / gf or less.   The conductive member according to any one of claims 1 to 3, wherein the gap holding member has a durometer hardness HDD of 60 or more and 70 or less. The said space | gap holding member is formed with the polyethylene resin whose molecular weight is 1 million or more and whose density is 0.96 g / cm < ³ > or more, The any one of Claim 1 to 4 characterized by the above-mentioned. Conductive member.   6. The conductive member according to claim 1, wherein at least a portion of the outer peripheral surface of the gap holding member that is in contact with the image carrier has an insulating property.   The conductive member according to claim 1, wherein an outer peripheral surface of the electric resistance adjusting layer is covered with a surface layer that prevents adhesion of toner.   The conductive member according to claim 7, wherein an electric resistance of the surface layer is larger than an electric resistance inside the electric resistance adjusting layer.   The conductive member according to any one of claims 1 to 8, wherein the electrical resistance adjusting layer and the gap holding member have a cylindrical shape centered on the conductive support. .   The conductive member according to claim 1, wherein the conductive member is used as a charging member in an image forming apparatus or a process cartridge.   11. The device according to claim 1, wherein, of both end portions of each gap holding member, each end portion on the side adjacent to the electric resistance adjusting layer is cut out. 11. Conductive member.   12. A process cartridge for an image forming apparatus, comprising at least the conductive member according to claim 1 and the image carrier. The electroconductive member according to claim 1, the image carrier, and a conveyance unit that conveys a recording medium on which an image carried on the image carrier is recorded. An image forming apparatus.

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