JP4150754B2 - Latent image carrier - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a latent image carrier (photosensitive member) used in an image forming apparatus having an electrophotographic process, an image forming apparatus, and a vibration damping member disposed in the latent image carrier, and in particular, noise prevention in the latent image carrier. Regarding technology.

JP-A-7-72641 JP 11-184308 A

  One of the image forming processes executed in image forming apparatuses such as copying machines, facsimile machines, printers, and printing machines is a charging process. This process is a process in which a uniform charge is charged to the photosensitive member, which is a latent image carrier, and there are charging by corona discharge or contact charging.

  The corona discharge method is a method in which a corona charger is disposed with a predetermined interval between the photoconductor and a corona discharge is performed by applying a high voltage to the charger wire.

  In this method, discharge products such as ozone and nitrogen oxides are generated at the time of discharge, and this product causes environmental deterioration. Therefore, in recent years, there is a contact charging method in which a low voltage can be applied and the above-described problems do not occur. It has been adopted.

  In the contact charging method, a conductive roller, brush, or blade is brought into contact with a photoconductor, and a voltage is applied between the two to inject charge into the photoconductor. In the case of the contact charging method, a low voltage can be applied and no discharge product is generated. .

  In addition, if left standing for a long time, a part of the charging member that is in contact with the photosensitive member is deformed due to permanent distortion, and when the charging process is performed again, the contact state with the photosensitive member is May change. As a result, the uniform contact with the photoreceptor may be impaired, resulting in charging unevenness.

  For this reason, a technique has been proposed in which a minute predetermined interval is maintained between the photoconductor and the contact member to form a so-called non-contact charging range between the photoconductor and the charging member. Yes. That is, as an intermediate charging method between non-contact charging and contact charging, between the photosensitive member and a charging member (a member such as a brush, a roller brush, a roller, a blade, or a belt having appropriate conductivity and elasticity). In recent years, a method in which a minute gap is provided and charging is performed by applying a DC voltage on which DC or AC is superimposed (proximity charging) has begun to be adopted. As an example of the configuration of the proximity charging method, for example, when a charging member is a roller, a film having a predetermined thickness is provided on both circumferential surfaces of the charging roller in the axial direction, and a gap having a minute interval is provided depending on the thickness of the film. There is.

  In order not to change the charging characteristics, it is important that the gaps of the minute intervals are maintained at a predetermined size. In other words, assuming that the gap is maintained, it can be uniformly charged by applying a DC voltage that is relatively easy to set, but if the gap changes to be larger than a predetermined interval, The charging potential changes according to the increase.

For this reason, conventionally, even when an AC voltage is superimposed on a DC voltage and a gap change occurs, uniform charging characteristics are obtained.
The photosensitive member is a relatively lightweight material and a conductive metal core, specifically, a cylinder having a thin structure made of aluminum. The photoconductor having such a configuration may generate noise during operation. In other words, a device for performing each process of charging, writing, developing, transferring, and cleaning is disposed on the photoconductor oppositely. Of these devices, in particular, the charging device and the cleaning device often serve as noise generation sources of the photosensitive member.

  As is apparent from the charging conditions described above, the charging device applies an AC voltage superimposed on a DC voltage, so that the thin cylindrical portion easily resonates when the AC voltage is applied. Propagates noise to the surrounding area.

  Some cleaning devices are equipped with a blade that contacts the photoconductor, and the blade vibrates in the thin cylindrical part by repeatedly dragging and returning to the original position as the photoconductor moves, causing the photoconductor to resonate. As a result, noise is generated.

  Conventionally, in order to solve the above-described problems, in Japanese Patent Application Laid-Open No. H10-228707, the photoconductor is constituted by a solid, that is, cylindrical, rigid support. In Patent Document 2, two or more elastic bodies and a cylindrical member are installed inside the photoconductor.

  However, the technique disclosed in Patent Document 1 uses a solid metallic substrate, which increases the cost and increases the weight significantly. Problems such as scratching the surface are likely to occur.

  Moreover, in the technique shown by patent document 2, since a complicated damping member is used, it will raise a cost.

  An object of the present invention is to provide a latent image carrier capable of preventing the occurrence of noise when a thin cylindrical body is used as a latent image carrier in view of the problems in the conventional latent image carrier and an image forming apparatus using the same. It is to provide.

According to the present invention, there is provided a latent image carrier that has a photosensitive layer on the surface of a thin cylindrical substrate and can form an electrostatic latent image corresponding to an image by optical writing after the photosensitive layer is uniformly charged. A cylindrical damping member formed of an elastic body is disposed inside the cylindrical base body, and has an opening at one end of the damping member, and the opposite end of the damping member is This is solved by having an end face for pushing the vibration damping member into the cylindrical base, and the outer peripheral portion of the opposite end portion being a small diameter portion .

  According to the latent image carrier of the present invention, since the vibration damping member formed of an elastic body having a loss tangent tan δ of 0.5 or more is disposed inside the cylindrical base of the latent image carrier, the DC voltage is applied to the charging device. In addition, when the AC voltage is applied, the latent image carrier does not resonate, and further, the vibration of the cleaning blade does not propagate, so that the generation of noise can be suppressed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 is a configuration diagram of a full-color image forming apparatus, FIG. 2 is an enlarged view of an image forming apparatus in the image forming apparatus shown in FIG. 1, and FIG. 3 is a side view of a charging device in the image forming apparatus shown in FIG.

In FIG. 1, an image forming apparatus 20 includes the following apparatuses.
Image forming devices 21C, 21Y, 21M, and 21BK that form images of respective colors according to the original image, transfer devices 22 that are arranged to face the image forming devices 21C, 21Y, 21M, and 21BK, and the respective image forming devices A manual feed tray 23 serving as a sheet-like medium supply means for supplying various sheet-like media to a transfer area where the devices 21C, 21Y, 21M, 21BK and the transfer device 22 face each other, a paper feed cassette 24, a manual feed tray 23, or a paper feed A registration roller 30 that supplies the sheet-like medium conveyed from the cassette 24 in accordance with the timing of image formation by the image forming devices 21C, 21Y, 21M, and 21BK, and fixing that fixes the sheet-like medium after transfer in the transfer region. Device 40.

The image forming apparatus 20 generally includes plain paper (hereinafter simply referred to as plain paper) used for copying and the like, OHP sheets, 90K paper such as cards and postcards, thick paper having a basis weight of about 100 g / m ² or more, envelopes, and the like. Any so-called special sheet (hereinafter simply referred to as a special sheet) having a heat capacity larger than that of the paper can be used as the sheet-like medium.

  Each of the image forming devices 21C, 21Y, 21M, and 21BK develops each color of cyan, yellow, magenta, and black, and uses different toner colors, but the configuration thereof is the same. The configuration of 21C will be described as a representative of the image forming devices 21C, 21Y, 21M, and 21BK.

  The image forming device 21C serves as an electrostatic latent image carrier in the rotation direction A of a photosensitive drum 25C composed of a thin cylindrical substrate having an outer diameter of 30 mm, an inner diameter of 28.5 mm, and a peripheral wall thickness of 0.75 mm. A well-known configuration is used that includes a charging device 27C, a developing device 26C, and a cleaning device 28C that are sequentially arranged along the line, and that receives exposure light 29C between the charging device 27C and the developing device 26C. The same applies to the other image forming devices 21Y, 21M, and 21BK shown in FIG. In the image forming apparatus 20 shown in FIG. 1, since the transfer device 22 extends obliquely, the space occupied by the transfer device 22 in the horizontal direction can be reduced.

  The image forming devices 21C, 21Y, 21M, and 21BK are equipped in the image forming apparatus 20 with the unit configuration shown in FIG. In FIG. 2, the image forming device includes a photosensitive drum 25C (for convenience, the image forming device 21C will be described, and the reference numeral is indicated by 25C related to the image forming device 21C), a charging device 27C, a cleaning device 28C, and the like. Has been placed. This image forming apparatus is configured to be removable as a process cartridge. In addition, the image forming apparatuses for four colors are configured to be able to be pulled out from the apparatus main body toward the front side.

  As shown in FIG. 3, the charging device 27 </ b> C uses a roller-shaped cored bar, and has a thickness for providing a predetermined minute gap between the circumferential surface near both ends in the axial direction and the photosensitive drum 25 </ b> C. A film 27C1 having a The charging device 27C is pressed and urged toward the photosensitive drum 25C by a spring 27C3 provided on the rotating shaft 27C2, and the film 27C1 contacts the peripheral surface of the photosensitive drum 25C, thereby causing a contact with the photosensitive drum 25C. A gap G is set to face the peripheral surface.

  In the charging device 27C, for example, DC-700V is applied to the core metal by constant voltage control, and an AC voltage is applied by constant current control, so that the gap G is formed with respect to the photosensitive drum 25C. In this way, uniform charging by air discharge is performed.

  In FIG. 2, the cleaning device 28C includes a cleaning blade 28C1 that contacts the photosensitive drum 25C and scrapes off residual toner, a brush 28C2 that collects toner scraped off by the cleaning blade 28C1, and a toner that is recovered by the brush 28C. And waste toner conveying means 28C3 composed of a screw auger for conveying the toner toward the waste toner container.

  The cleaning mechanism is also provided in the charging device 27C, and the cleaning mechanism of the charging device 27C uses a pad member 27C4 that comes into contact with the film 27C1 mounted on both ends in the axial direction of the cored bar.

  Cleaning by the charging device 27C is performed to prevent the toner adhering to the photosensitive drum 25C from reversely transferring to the film because the film 27C1 is always in contact with the photosensitive drum 25C. Thus, the contact state between the film 27C1 and the photosensitive drum 25C is prevented from changing due to the reversely transferred toner or dust, and the facing distance between the photosensitive drum 25C and the charging device 27C is always kept constant. Yes.

FIG. 4 is a cross-sectional view of the photosensitive drum according to the first embodiment of the present invention.
In the present invention, measures are taken to prevent noise from occurring on the photosensitive drum 25 (collectively referring to 25C, 25Y, 25M, and 25BK).

  In FIG. 4, the photosensitive drum 25 is configured by providing a photosensitive layer on a thin cylindrical substrate 25-1 having a peripheral wall thickness of 0.75 mm, and in the space portion inside the cylindrical substrate 25-1. A cylindrical damping member 31 is loaded.

FIG. 5 is a sectional view of a photosensitive drum according to the second embodiment of the present invention.
Although the vibration damping member 31 of the first embodiment shown in FIG. 4 has a columnar shape, the vibration damping member 32 of the second embodiment shown in FIG. 5 has a hollow cylindrical shape.

  The damping members 31 and 32 can be formed of a material such as butyl rubber or nitrile rubber, for example. In addition to rubber, various resins or metals can be used. In the rubber damping member, the damping effect is obtained by the elasticity of the rubber material. In the case of other materials, the damping effect can be obtained by the elasticity of the material. In addition, by attaching the vibration damping member, the weight of the photosensitive drum 25 is increased, the resonance frequency of the photosensitive drum itself is changed to the low frequency side, and an unpleasant high frequency noise is effectively reduced.

Here, the loss tangent tan δ related to the damping effect of the damping members 31 and 32 will be described.
A tangent of a stress and strain phase angle: δ (loss angle) in a material is called a loss tangent (tan δ). This loss tangent tan δ is a value unique to the material and indicates the vibration damping effect of the material. That is, if the value of the loss tangent tan δ is large, it can be said that the material exhibits a greater vibration damping effect.

  The loss tangent tan δ of the damping member material used in the experiment described below was measured according to the non-resonant vibration method defined in JIS K 7244-4. A sample having a thickness of 2 mm, a width of 5 mm, and a length of 30 mm was used as a test piece, and measurement was performed at an applied frequency of 30 Hz.

  Now, in the configuration shown in FIG. 2, the inventor of the present application mounts a cylindrical or cylindrical damping member made of a material whose loss tangent tan δ is changed inside the photosensitive drum 25, and the charging roller An experiment was conducted to measure the acoustic power when a charging bias (a direct current superimposed with an alternating current) was applied to the power supply 27. FIG. 6 is a graph showing the experimental results, in which the vertical axis represents the sound power and the horizontal axis represents the loss tangent tan δ.

  As can be seen from the graph of FIG. 6, tan δ is 0.5 or more for the cylindrical vibration damping member, and tan δ is 0.6 or more for the cylindrical vibration damping member. The vibration was suppressed to the level. If tan δ is 0.8 or more, a higher vibration damping effect can be obtained.

  The reason why the cylindrical damping member can be silenced with a loss tangent tanδ smaller than that of the cylindrical damping member is because of the weight of the damping member itself (because the cylindrical shape is heavier than the cylindrical shape) This is because the resonance frequency of the photosensitive drum itself can be changed to the low frequency side, and harsh high frequency noise can be effectively reduced.

  As described above, when the loss tangent tan δ is 0.5 or more with a cylindrical damping member and the loss tangent tan δ is 0.6 or more with a cylindrical damping member, a practically sufficient damping effect is obtained. If the loss tangent tan δ is 0.8 or more, a higher vibration damping effect can be obtained. Thereby, the vibration (noise) generated by the charging device 27 or the cleaning blade 28C1 can be suppressed. Of course, the same applies to other photosensitive drums as well as the cyan photosensitive drum 25C described above.

  In addition, by setting it as the structure which inserted and arrange | positioned the rigid body, for example, metal rod etc., in the cylinder of the cylindrical-shaped damping member 32, the weight of a damping member can be increased and the noise reduction effect can be heightened. This configuration can also be referred to as a configuration in which a rigid body is disposed inside the photosensitive drum 25 via an elastic body (vibration control member 32).

  It is also possible to round the sheet-like elastic body into a cylindrical vibration damping member. According to this configuration, since the cylindrical vibration damping member can be obtained with an inexpensive sheet-like elastic body, the cost of the vibration damping member can be reduced. Further, the vibration damping member can be easily mounted on the photosensitive drum. In addition, when the sheet-like elastic body is formed in a cylindrical shape, the joint or overlap of the sheet end portions is prevented from being parallel (non-parallel) to the axis of the cylinder to prevent deformation of the photoreceptor. Can do. When the seam or overlap of the sheet end is parallel to the cylindrical axis, the thin photosensitive member may be deformed by pressing in the vertical direction (by opening) by the sheet end.

  Next, the measurement result of the acoustic power when the axial length L2 of the damping member 31 or 32 is changed with respect to the charging region L1 shown in FIG. 3 is shown in the graph of FIG. As can be seen from this graph, the vibration was suppressed to a level where there was no problem in hearing when the axial length L2 of the damping member was 60% or more of the charged region L1.

  The effect of suppressing vibration (noise) varies depending on the loss tangent tan δ and weight of the damping member. As a result of experiments conducted by the inventors of the present invention with various loss tangent tan δ and weight damping members, the graph of FIG. As shown, the change in the damping effect is large when L2 / L1 is between 50% and 60% (the slope of the graph is large), and the fluctuation of the effect is small (the slope of the graph is small) when it is 60% or more. Therefore, it is proposed that L2 is 60% or more of L1.

  Next, the measurement result of the acoustic power when the thickness (t) of the cylindrical damping member 32 is changed is shown in the graph of FIG. As can be seen from this graph, the vibration was suppressed to a level where there was no problem in hearing when the thickness t of the damping member 32 was 4 mm or more.

  In this case as well, the suppression effect of vibration (noise) varies depending on the loss tangent tan δ and weight of the damping member. However, as shown in the graph of FIG. 8, the damping effect changes when the wall thickness t is between 3 mm and 4 mm. The thickness t of the cylindrical damping member should be 4 mm or more, since a good value can be obtained with a large (large slope of the graph) and little effect fluctuation (small slope of the graph) at 4 mm or more. This is a proposal.

  In the case of a cylindrical vibration damping member, the amount of material can be reduced as compared with a columnar shape, and the cost can be reduced. Of course, it goes without saying that the loss tangent tan δ of the material, the weight as the damping member, the length in the axial direction, the thickness, etc. are appropriately selected and set so as to obtain the necessary damping effect.

  As a method of mounting the cylindrical / cylindrical damping member in the photosensitive drum, a method of press-fitting with the outer diameter of the damping member set slightly larger than the inner diameter of the photosensitive drum, and a slightly smaller diameter than the inner diameter of the drum Then, a method of bonding with an adhesive can be employed. With either mounting method, it is possible to obtain a sufficient damping effect.

  However, in the press-fitting, when the inner diameter of the photosensitive drum is D and the outer diameter of the damping member is d, if d is smaller than D, the vibration damping / silent effect cannot be obtained due to poor contact with the inner surface of the photosensitive member. If d is significantly larger than D, an excessive force is required when mounting the damping member inside the photosensitive member, and the assembling property is not good, and the photosensitive member is deformed during assembly. Sometimes it ends up. Therefore, it is preferable to be in the range of D ≦ d ≦ D + 1 mm.

  FIG. 9 shows a different embodiment of the cylindrical damping member, and is a schematic diagram for explaining the operation of inserting the damping member 33 of this embodiment into the photosensitive drum 25. The outer diameter of the damping member 33 is slightly larger (within 1 mm) than the inner diameter of the photosensitive drum 25.

As shown in FIG. 9, the damping member 33 of the present embodiment has a shape in which one end of a cylinder is closed and an end surface 33a is provided. The opposite cylindrical end is open. In order to mount the vibration damping member 33 in the photosensitive drum 25, first, as shown in FIG. 9A, the photosensitive drum 25 is set up on an appropriate base, and the end of the photosensitive drum 25 is set. The damping member 33 is placed on the top. Then, the assembly jig 41 is inserted into the cylinder of the vibration damping member 33, the end surface 33a of the vibration damping member 33 is pushed by the jig 41 , and the vibration damping member 33 is moved to the photosensitive drum as shown in FIG. 9B. Push into 25. At this time, the outer diameter of the damping member 33 becomes smaller due to friction with the inner surface of the photosensitive drum, and the damping member 33 can be easily press-fitted into the photosensitive drum 25. The action / effect of the damping member 33 is the same as that of the cylindrical damping member 32 described with reference to FIG. 5, and it is preferable that the axial length L2 of the damping member 33 is 60% or more of the charging region L1. It is preferable that t is 4 mm or more, as in the case of the vibration damping member 32 of FIG.

  It should be noted that a hole may be provided in the end surface 33a that closes one end of the cylinder at a size and a position that does not hinder the operation of inserting the cylindrical damping member into the photosensitive drum. That is, it is not necessary to completely close one end of the cylinder. The reason for making a hole in the end face 33a is to prevent the thickness of the hollow portion from becoming uneven due to the inclination of the mold of the hollow portion when the damping member is molded.

  Moreover, as shown in FIG. 9, the damping member 33 of the present embodiment is provided with a small-diameter portion 33b on the outer side of the tip portion where the end surface 33a is present. The small-diameter portion 33b may have a tapered (linear) cross section as shown in the figure or a small-diameter portion having a curved cross section. By providing such a small diameter portion 33b, when the vibration damping member 33 is placed on the end of the photosensitive drum 25, positioning of the cylindrical vibration damping member 33 with the center of the photosensitive drum 25 can be easily performed. .

  Such a small-diameter portion of the damping member is not limited to the damping member of the present embodiment, but is also effective for a cylindrical damping member. That is, in FIG. 4, by providing small diameter portions 31 a at both ends of the cylindrical vibration damping member 31, positioning is performed to align the center of the vibration damping member and the drum when the vibration damping member 31 is inserted into the photosensitive drum 25. Becomes easy. Further, the small diameter portion may be provided only on one side or both sides of the damping member. Needless to say, when it is provided only on one side, it is inserted into the photoreceptor from the side having the small diameter portion.

  By the way, as for the damping member, the contact surface with the inner surface of the photoreceptor may not be a continuous surface. FIG. 10 shows an example of such a damping member. 10, (I) is a cylindrical damping member, (II) is a columnar damping member, and (a) and (b) are a sectional view and a side view, respectively.

  As shown in this figure, the cylindrical damping member 34 and the columnar damping member 35 are provided with recesses 34c and 35c that make one round of the outer peripheral surface thereof. By providing the recess 34c or 35c, the contact surface with the inner surface of the photoconductor does not become a continuous surface, the resistance when inserting the damping members 34 and 35 into the photoconductor is small, and the insertion work is easy. become. In addition, the amount of material forming the vibration damping member can be reduced, leading to cost reduction. In addition, the recessed part provided in the outer peripheral surface of a damping member may be continuous in a helical shape, or may be provided with a plurality of helical recessed parts.

Next, an embodiment in which the present invention is applied to an image forming apparatus including a contact charging device will be described.
Each of the embodiments shown in FIGS. 11, 12, and 13 includes a charging roller 37, a brush roller 47, and a magnetic brush charging device 47 as a contact charging device. Each example is the same except that the configuration of the charging device is different, and is basically the same as the above-described embodiment (using a non-contact charging device) described with reference to FIGS.

In the embodiment shown in FIG. 11, the photosensitive drum 25 as an image carrier is driven to rotate at a predetermined speed (process speed) in the clockwise direction in the drawing as shown by an arrow. A charging roller 37 is provided in contact with the photosensitive drum 25. The charging roller 37 is provided with a conductive rubber layer 37b on the outer periphery of the cored bar 37a, and supports both ends of the cored bar 37a freely by a bearing member (not shown) and the like and a predetermined pressure on the photosensitive drum 25 by a pressing unit (not shown). It is pressed with the applied pressure. In the case of this example, the charging roller 37 rotates following the photosensitive drum 25. Further, in this example, a medium resistance rubber layer of about 1 × 10 ⁵ Ω · cm is coated on a core metal 37a having a diameter of 9 mm so as to have a diameter of 16 mm.

  The core metal 37 a is connected to the power source 50, and a predetermined bias is applied from the power source 50 to the charging roller 37. As a result, the peripheral surface of the photosensitive drum 25 is uniformly charged to a predetermined polarity and potential.

  Damping members 31, 32, 33 or 34, 35 as shown in FIGS. 4, 5, 9 or 10 are mounted on the photosensitive drum 25. Due to the action of the vibration damping member, even when a contact-type charging device such as the charging roller 37 of this example is used and a charging bias in which an AC voltage is superimposed in addition to a DC voltage is applied, the resonance of the photosensitive drum 25 is performed. Further, the generation of noise is suppressed without propagating the vibration of the cleaning blade.

  In the embodiment of FIG. 12, a brush roller 47 constituted by a fur brush is provided in contact with the photosensitive drum 25 with a predetermined pressing force against the elasticity of the brush portion 47b, thereby forming a charging nip having a predetermined width. is doing.

  As a material for the fur brush, for example, a fur treated with carbon, copper sulfide, metal, and metal oxide is used, and the fur brush is charged by winding or pasting it on a metal or other conductive core metal. Use a vessel.

  In this example, a metal cored bar 47a also serving as an electrode is wound spirally on a tape made of conductive rayon fiber REC-B manufactured by Unitika Co., Ltd. as a brush portion 47b, and spirally wound. The roll brush has a length of 14 mm and an axial length of 250 mm. The brush of the brush part has a density of 300 denier / 50 filaments and 155 per square millimeter. This roll brush was inserted into a pipe having an inner diameter of 12 mm while rotating in one direction, and the brush and the pipe were set to be concentric, and left in a high-temperature and high-humidity atmosphere to bend and bevel.

The resistance value of the fur brush roller is 1 × 10 ⁵ Ω at an applied voltage of 100V. This resistance value was converted from the current that flows when a fur brush roller is brought into contact with a metal drum having a diameter of φ30 mm with a nip width of 3 mm and a voltage of 100 V is applied.

The resistance value of the fur brush charger is such that, even when a low-voltage defective part such as a pinhole occurs on the photosensitive member that is the object to be charged, an excessive leakage current flows into this part and the charging nip part becomes poorly charged. In order to prevent image defects, it is necessary to be 10 ⁴ Ω or more, and in order to sufficiently inject charges onto the surface of the photoreceptor, it is necessary to be 10 ⁷ Ω or less.

  In addition to REC-B manufactured by Unitika Ltd., the brush material is REC-C, REC-M1, REC-M10, SA-7 manufactured by Toray Industries, Inc., Nippon Kashiwa Co., Ltd. It is possible to use Sanderlon manufactured by Kanebo, Beltron manufactured by Kanebo, Kuraray Co., Ltd., Krabobo, carbon dispersed in rayon, Mitsubishi Rayon Co., Ltd. global, etc. One brush is 3 to 10 denier, and preferably has a density of 10 to 100 filaments / bundle and 80 to 600 brushes / mm. The hair foot is preferably 1 to 10 mm.

  The fur brush roller 47 of this example is rotationally driven at a predetermined peripheral speed (surface speed) in the direction opposite to the rotation direction (counter) of the photoconductor 25 and contacts the photoconductor surface with a speed difference. By applying a predetermined charging voltage from the power source 50 to the fur brush roller 47, the surface of the rotating photoconductor is uniformly contact-charged to a predetermined polarity and potential. In this example, the contact charging of the photosensitive member by the fur brush roller 47 is performed by direct injection charging, and the surface of the rotating photosensitive member is charged to a potential substantially equal to the charging voltage applied to the fur brush roller.

  Damping members 31, 32, 33 or 34, 35 as shown in FIGS. 4, 5, 9 or 10 are also mounted on the photosensitive drum 25 in this example. Even if a contact-type charging device such as the fur brush roller 47 of this example is used to apply a charging bias in which an AC voltage is superimposed in addition to a DC voltage, the vibration damping member functions as described above. Resonance is prevented, and further, generation of noise is suppressed without propagating the vibration of the cleaning blade.

  In the embodiment shown in FIG. 13, a charging device 57 of a magnetic brush type is provided adjacent to the photosensitive drum 25, and is configured to bring the magnetic brush MB into contact with the circumferential surface of the photosensitive drum with a predetermined nip width. The charging device 57 of this example includes a non-magnetic sleeve 57a for supporting the magnetic brush MB and a magnet roller body 57b (not shown) built in the non-magnetic sleeve 57a. Various ferrite particles can be used as the charging member.

  The magnetic brush MB as a contact charging member in this example is prepared by mixing Zn—Cu ferrite particles having an average particle diameter of 25 μm and Zn—Cu ferrite particles having an average particle diameter of 10 μm at a weight ratio of 1: 0.05. Using magnetic particles obtained by coating ferrite particles having an average particle diameter of 25 μm having a peak at the position of each average particle diameter with a medium resistance resin layer, the coated magnetic particles are coated on the sleeve 57a with a thickness of 1 mm. It is a magnetic brush. The magnetic particles are carried on the sleeve by the magnetic force of the magnet roller body 57b built in the sleeve 57a.

  In this example, a charging nip having a width of about 5 mm (width in the rotation direction) was formed between the magnetic brush MB and the photosensitive drum 25. The gap between the sleeve 57a for holding the magnetic particles and the photosensitive member 25 was about 500 μm. The nonmagnetic sleeve 57a is rotated so that the sleeve surface rubs in the opposite direction (with a magnetic brush) at twice as fast as the peripheral speed of the surface of the photosensitive member. Was in uniform contact. A predetermined charging bias is applied to the sleeve 57a from the power supply 50, and the surface of the photosensitive member is uniformly charged to a predetermined polarity and potential via the magnetic brush MB.

  Damping members 31, 32, 33 or 34, 35 as shown in FIGS. 4, 5, 9 or 10 are also mounted on the photosensitive drum 25 in this example. Due to the action of the vibration damping member, even when a contact-type charging device such as the magnetic brush charging device 57 of this example is used and a charging bias in which an AC voltage is superimposed in addition to a DC voltage is applied, the photosensitive drum 25 Is prevented, and further, the vibration of the cleaning blade is not propagated and the generation of noise is suppressed.

  By the way, when the weight of the damping member is too light compared with the weight of the charging member, the vibration of the photosensitive drum cannot be suppressed. Therefore, it is preferable that each vibration damping member has a weight of 70% or more of the weight of the charging member (for example, the charging roller). Even in a non-contact charging device, for example, a charging device in which a charging member is arranged at a small interval on a photosensitive drum, it is preferable that the charging member has a weight of 70% or more of the charging member weight.

  Further, since the vibration damping effect is not sufficient when the volume of the damping member occupying the inside of the photosensitive drum is small, each of the above damping members preferably has a volume of 30% or more of the photosensitive drum volume.

  In addition, if each of the damping members has a high hardness, there is a risk that the photoreceptor is deformed by mounting the damping member on the photoreceptor drum. Therefore, it is preferable that each vibration damping member has a JIS hardness of 30 to 70 degrees.

Finally, a latent image carrier to which the vibration damping member of each of the above embodiments is attached will be described.
There are various known photoreceptors used in electrophotography, such as those using inorganic semiconductor materials such as selenium and amorphous silicon, those using organic semiconductor materials, or combinations thereof. In recent years, organic photoconductors have been widely used because of their low cost, high degree of freedom in photoconductor design, and non-pollution. However, the vibration damping member of each embodiment described above can be mounted on any type of photoreceptor.

  Organic electrophotographic photoreceptors include photoconductive resins represented by polyvinylcarbazole (PVK), charge transfer complex types represented by PVK-TNF (2,4,7-trinitrofluorenone), phthalocyanine-binders Are known, such as a pigment dispersion type, a function separation type photoreceptor using a combination of a charge generation material and a charge transport material, and the function separation type photoreceptor is attracting attention.

  The mechanism of electrostatic latent image formation in this function-separated type photoreceptor is that when the photoreceptor is charged and irradiated with light, the light passes through the transparent charge transport layer and is absorbed by the charge generation material in the charge generation layer, The charge-generating substance that has absorbed the light generates charge carriers, which are injected into the charge transport layer, move in the charge transport layer according to the electric field generated by the charge, and neutralize the charge on the surface of the photoreceptor. Thus, an electrostatic latent image is formed. In the function-separated type photoreceptor, it is known and useful to use a combination of a charge transport material having absorption mainly in the ultraviolet region and a charge generation material having absorption mainly in the visible region.

  On the other hand, as a weak point of an organic electrophotographic photosensitive member, it is known that mechanical and chemical durability is poor. That is, many charge transport materials have been developed as low molecular weight compounds, but low molecular weight compounds alone are not film-forming, so they are usually dispersed and mixed in an inert polymer. However, the charge transport layer composed of a low-molecular charge transport material and an inert polymer is generally soft and poor in mechanical durability. In the electrophotographic process, various contact members (development / transfer paper / cleaning brush / cleaning blade) are used repeatedly. Etc.) The film is likely to be scraped by the mechanical load received from the above.

Therefore, a protective layer containing a filler may be provided as a surface layer on the photosensitive layer for the purpose of protecting the photosensitive layer and improving durability.
Materials used for this protective layer include ABS resin, ACS resin, olefin-vinyl monomer copolymer, chlorinated polyether resin, allyl resin, phenol resin, polyacetal resin, polyamide resin, polyamideimide resin, polyacrylate resin , Polyallylsulfone resin, polybutylene resin, polybutylene terephthalate resin, polycarbonate resin, polyethersulfone resin, polyether resin, polyethylene terephthalate resin, polyimide resin, acrylic resin, polymethylpentene resin, polypropylene resin, polyphenylene oxide resin, polysulfone resin, Examples of the resin include AS resin, AB resin, BS resin, polyurethane resin, polyvinyl chloride resin, polyvinylidene chloride resin, and epoxy resin.

  A filler may be added to the protective layer for the purpose of further improving the wear resistance. Examples of the filler include fluorine resins such as polytetrafluoroethylene, silicone resins, and those in which inorganic materials such as titanium oxide, tin oxide, potassium titanate, silica, and alumina are dispersed. The amount of filler added to the protective layer is usually 10 to 40%, preferably 20 to 30% on a weight basis. If the amount of the filler is less than 10%, the wear is large and the durability is inferior, and if it exceeds 40%, the increase in the bright part potential at the time of exposure becomes remarkable, and the decrease in sensitivity cannot be ignored.

  Furthermore, a dispersion aid can be added to the protective layer in order to improve the dispersibility of the filler. As the added dispersion aid, those used in paints and the like can be used as appropriate, and the amount thereof is usually 0.5 to 4%, preferably 1 to 2% based on the amount of filler contained on a weight basis. .

  In addition, it is also effective to add a charge transport material to the protective layer, and an antioxidant can be added as necessary. As a method for forming the protective layer, a normal coating method such as a spray method is employed. The thickness of the protective layer is suitably about 0.5 to 10 μm, preferably about 4 to 6 μm.

  In the photoreceptor to which the present invention is applied, an intermediate layer can be provided between the photosensitive layer and the protective layer. In the intermediate layer, a binder resin is generally used as a main component. Examples of these resins include polyamide, alcohol-soluble nylon, water-soluble polyvinyl butyral, polyvinyl butyral, and polyvinyl alcohol. As a method for forming the intermediate layer, a normal coating method is employed as described above. In addition, about 0.05-2 micrometers is suitable for the thickness of an intermediate | middle layer.

  Next, specific examples of the photoreceptor will be described. However, the photoreceptor to which the present invention is applied is not limited to the following examples. Note that “parts” used in the following description all represent parts by weight.

[Production of Photosensitive Member 1 for Example Evaluation]
By coating and drying an undercoat layer coating solution, a charge generation layer coating solution, and a charge transport layer coating solution in the following order on a φ30 mm aluminum drum in sequence, an undercoat layer of 3.5 μm, A 0.2 μm charge generation layer and a 25 μm charge transport layer were formed to obtain an electrophotographic photoreceptor for evaluation (photoreceptor No. 1).

[Coating liquid for undercoat layer]
6 parts alkyd resin (Beckosol 1307-60-EL, manufactured by Dainippon Ink & Chemicals, Inc.)
4 parts of melamine resin (Super Becamine G-821-60, manufactured by Dainippon Ink & Chemicals, Inc.)
Titanium oxide 40 parts Methyl ethyl ketone 200 parts

[Coating liquid for charge generation layer]
2.5 parts of trisazo pigment having the following structure

ポリビニルブチラール（ＵＣＣ：ＸＹＨＬ）０．２５部
シクロヘキサノン２００部
メチルエチルケトン８０部

Polyvinyl butyral (UCC: XYHL) 0.25 parts cyclohexanone 200 parts methyl ethyl ketone 80 parts

[Coating liquid for charge transport layer]
10 parts of bisphenol A type polycarbonate (Teijin: Panlite K1300)
10 parts of low molecular charge transport material with the following structure

塩化メチレン１００部

100 parts of methylene chloride

[Production of Photosensitive Member 3 for Example Evaluation]
An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that a protective layer coating solution having the following composition was used on the charge transport layer of the photosensitive member 1 for evaluation of the example and a protective layer of 2 μm was laminated. Electrophotographic photosensitive member (photosensitive member No. 3) was obtained.
[Protective layer coating solution]
2 parts of charge transport material with the following structure

Ａ型ポリカーボネート４部
塩化メチレン１００部

Type A polycarbonate 4 parts Methylene chloride 100 parts

[Preparation of Photosensitive Member 4 for Example Evaluation]
An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that a protective layer coating solution having the following composition was used on the charge transport layer of the photosensitive member 1 for evaluation of the example and a protective layer of 2 μm was laminated. Electrophotographic photosensitive member (photosensitive member No. 4) was obtained.
[Protective layer coating solution]
4 parts of charge transport material having the structure described in chemical formula 2 4 parts of A type polycarbonate 1 part of titanium oxide 1 part of methylene chloride 100 parts

[Preparation of Photosensitive Member 5 for Example Evaluation]
An electrophotographic photosensitive member was prepared in the same manner except that the titanium oxide of the filler dispersed in the protective layer was changed to aluminum oxide in the photosensitive member 4 for evaluation, and an electrophotographic photosensitive member for evaluation (photosensitive member No. 5). Got.

  The following Table 1 shows the above No.1. Results of performing a continuous paper feeding test using a digital copying machine Imagio MF200 (trade name) manufactured by Ricoh Co., Ltd., using evaluation photoconductors 1 to 5 (however, explanation of photoconductor No. 2 is omitted) Is shown. The description of the structure of the comparative photoconductor is omitted.

  The “F / C ratio” in the table is the ratio of fluorine and carbon atoms on the surface of the photoreceptor, and serves as an index of the amount of fluorine-based material deposited on the surface of the photoreceptor. Further, “Δd” is a reduction amount from the initial value of the photosensitive layer thickness due to actual machine running. “◎” indicating image quality is very good (overall evaluation of image density / resolution, etc.), “◯” is good (overall evaluation of image density / resolution, etc.), “Δ1” is slightly “△ 2” indicates a slight streak-like image / stain, “Δ3” indicates a slight image flow, “× 1” indicates an obvious image density decrease, and “× 2” indicates A streak-like image / stain occurrence, “× 3” is an image flow occurrence.

この表１から明らかなように、上記Ｎｏ．１〜５の感光体においては、高精細のハードコピーを長期間安定して得ることができた。

As apparent from Table 1, the above No. 1 was obtained. In the photoconductors 1 to 5, high-definition hard copies could be stably obtained for a long time.

  And said No .. By mounting the above-described vibration-damping member on the photoconductors 1 to 5, a non-contact type (including a proximity type) charging device or a contact-type charging device is used to charge the AC voltage in addition to the DC voltage. Even when a bias is applied, the resonance of the photosensitive drum is suppressed, and the vibration propagation of the cleaning blade is also prevented, thereby preventing the generation of noise.

  Although the present invention has been described with reference to the above embodiments, the present invention is not limited thereto. For example, the material forming the vibration damping member is not limited to the exemplified material, and any material that satisfies the necessary loss tangent tan δ may be used.

Further, the configuration of the charging device is not limited to the illustrated one, and a contact method or a non-contact method (including a proximity method) may be used.
Further, the present invention can be applied not only to a color image forming apparatus in which a plurality of photosensitive drums are arranged side by side but also to a color image forming apparatus using a single photosensitive member or a monochrome image forming apparatus. Of course, the image forming apparatus is not limited to a printer, and the present invention can also be applied to a copying machine, a facsimile, or a printing machine.

1 is a configuration diagram of a full-color image forming apparatus. FIG. 2 is an enlarged view of an image forming device in the image forming apparatus shown in FIG. 1. FIG. 3 is a front view of a charging device in the image forming apparatus shown in FIG. 2. 1 is a cross-sectional view of a photosensitive drum according to a first embodiment of the present invention. It is sectional drawing of the photoconductor drum which concerns on the 2nd Embodiment of this invention. It is a graph which shows the change of the damping effect by the loss tangent of a damping member. It is a graph which shows the change of the damping effect by the axial direction length of a damping member. It is a graph which shows the change of the damping effect by the wall thickness of a cylindrical damping member. It is a schematic diagram which shows the Example from which a cylindrical shape damping member differs. It is sectional drawing and a side view which show an example of the damping member whose contact surface with a photoreceptor inner surface is not a continuous surface. It is a side view which shows the Example provided with a charging roller as a charging device of a contact system. It is a side view which shows the Example provided with a fur brush roller as a charging device of a contact system. It is a side view which shows an Example provided with a magnetic brush charging device as a contact-type charging device.

Explanation of symbols

20 Image forming apparatus 21C, 21Y, 21M, 21BK Image forming apparatus 25 () Photosensitive drum as latent image carrier 25-1 Cylindrical substrate 27C, 27Y, 27M, 27BK Charging device 31 Cylindrical damping member 32 Cylindrical shape control Vibrating member 33 Cylindrical damping member with one end closed 37 Charging roller 47 Fur brush roller 57 Magnetic brush charging device

Claims (17)

A latent image carrier having a photosensitive layer on the surface of a thin cylindrical substrate and capable of forming an electrostatic latent image corresponding to an image by optical writing after the photosensitive layer is uniformly charged,
A cylindrical vibration damping member formed of an elastic body is disposed inside the cylindrical base body,
An opening is provided at one end of the damping member, the opposite end of the damping member has an end surface for pushing the damping member into the cylindrical base, and an outer peripheral portion of the opposite end Has a small diameter portion.   The latent image carrier according to claim 1, wherein a loss tangent tan δ of the cylindrical vibration damping member is 0.6 or more.   The latent image carrier according to claim 1, wherein the weight of the cylindrical vibration damping member is 70% or more of the weight of the charging member that charges the latent image carrier.   The latent image carrier according to any one of claims 1 to 3, wherein the volume of the cylindrical damping member is 30% or more of the volume of the latent image carrier.   The latent image carrier according to claim 1, wherein the cylindrical vibration damping member has a JIS hardness of 30 to 70 degrees.   6. The latent image carrier according to claim 1, wherein an axial length of the cylindrical vibration damping member is 60% or more of a charged region of the latent image carrier. 7. . The internal diameter of the said cylindrical base | substrate is set to D and the outer diameter of the said cylindrical shape damping member is set to d, It is D <d <= (D + 1mm), The any one of Claims 1-6 characterized by the above-mentioned. Latent image carrier.   The latent image carrier according to claim 1, wherein the cylindrical vibration damping member is made of rubber.   The latent image carrier according to claim 1, wherein the cylindrical vibration damping member is made of resin.   The latent image carrier according to any one of claims 1 to 9, wherein a thickness of the cylindrical vibration damping member is 4 mm or more.   The latent image carrier according to any one of claims 1 to 10, wherein the cylindrical vibration damping member has a recess in a contact surface with an inner surface of a cylindrical substrate. The latent image carrier according to claim 1, wherein the small-diameter portion at the opposite end portion of the vibration damping member has a curved shape . The latent image carrier according to claim 1, wherein the small-diameter portion at the opposite end of the vibration damping member is tapered . The latent image carrier according to any one of claims 1 to 13, wherein a rigid body is disposed inside the cylindrical vibration damping member . The latent image carrier according to claim 14, wherein the rigid body is a metal rod . An image is formed by integrally supporting the latent image carrier according to any one of claims 1 to 15, a charging device for charging the latent image carrier, and a cleaning device for cleaning the latent image carrier. A process cartridge that is detachable from the device. An image forming apparatus comprising the latent image carrier according to any one of claims 1 to 15 or the process cartridge according to claim 16 .

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