JP5328239B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer using an electrophotographic system or an electrostatic recording system. More specifically, the present invention relates to an image forming apparatus including a transfer unit that transfers a toner image formed on an image carrier onto a recording material.

  In a conventional electrophotographic image forming apparatus, a toner image formed on an image carrier such as an electrophotographic photosensitive drum or an intermediate transfer member is electrostatically transferred onto a recording material by a transfer unit. A guide member for guiding the recording material to the transfer portion in a predetermined posture is disposed upstream of the transfer portion in the recording material conveyance direction.

  Since the recording material is preferably transported along the image carrier without forming a gap between the recording material and the recording material before entering the transfer electric field region, the image carrier is used from the front of the transfer electric field region. The recording material needs to be conveyed along the body. Therefore, the guide member has a configuration close to the image carrier and the transfer electric field region in order to increase the positional accuracy of the recording material entering the transfer portion (Patent Document 1).

  However, in such an image forming apparatus, if the guide member is close to the image carrier and the transfer electric field region, the guide member is contaminated with toner, and as a result, the recording material to be conveyed becomes dirty. . Therefore, contamination with toner can be prevented by using a guide member or a material having a frictional charging characteristic that is the same as the charging polarity of the toner on the surface of the guide member.

  However, since the guide member guides the recording material to the transfer portion, the friction between the guide member and the recording material is large. In particular, when the area where the guide member and the recording material come into contact with each other increases, the charge amount of the guide member increases. As a result, a partial discharge occurs from the guide member toward the recording material, resulting in an image defect.

  In order to prevent this, a configuration in which the guide member is made conductive and a voltage is applied to the guide member, and a configuration in which the guide member is grounded through a resistor can be cited (Patent Document 2 to Patent Document 5). However, with such a configuration, when the recording material straddles the transfer portion and the guide member, depending on the environment, there is a problem that current flows from the transfer member to which the voltage is applied to the guide member. It is not a measure.

In order to solve these problems, it is desirable to increase the surface roughness of the guide member to reduce the sliding area between the guide member and the recording material.
JP-A-2005-003907 JP 09-080931 A JP 11-338276 A Japanese Patent Laid-Open No. 08-272223 Japanese Patent Laid-Open No. 2001-154500

  However, if the surface roughness of the guide member is excessively increased, the level difference between the convex portion and the concave portion on the surface of the guide member becomes large. For this reason, there is a problem that foreign matter easily enters the recess and the charging characteristics of the guide member become unstable.

  On the other hand, it is also necessary to maintain the charging characteristics of the guide member while preventing current from flowing from the transfer member to the guide member caused by the environment.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that stabilizes charging characteristics of a guide member while reducing a sliding area between the guide member and a recording material.

Accordingly, the invention of the present application forms an image having an image carrier, a transfer member that forms a transfer portion that transfers a toner image on the image carrier onto a recording material, and a guide member that guides the recording material to the transfer portion. In the apparatus, the contact portion of the guide member that contacts the recording material is made of a porous polymer material having a porosity of 20 to 40%, and the charging series due to friction with the recording material is the same as the normal polarity of the toner. The center line average roughness Ra is 10 μm or more and 50 μm or less, and the volume resistivity is 1 × 10 12 Ωcm or more and 1 × 10 14 Ωcm or less.

  As described above, according to the present invention, the charging characteristics of the guide member can be stabilized while reducing the sliding area between the guide member and the recording material.

(Example)
FIG. 1 shows an image forming apparatus according to Embodiment 1 as an example of an image forming apparatus according to the present invention. The image forming apparatus shown in the figure is an electrophotographic four-color full-color printer, and the figure is a longitudinal sectional view schematically showing the schematic configuration.

  The image forming apparatus shown in the figure includes a drum-type electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) as a first image carrier. The photosensitive drum 1 is rotatably supported by the image forming apparatus main body, and is driven to rotate at a predetermined process speed (circumferential speed) in the direction of arrow R1 by a motor.

  The image forming process will be briefly described.

  The surface of the photosensitive drum 1 is uniformly charged to a predetermined potential and polarity by the primary charger 2 during the rotation process. The charged photosensitive drum 1 is exposed with a laser beam from an exposure device, whereby an electrostatic latent image corresponding to a first color component image (for example, a yellow color component image) of a target color image is formed.

  This electrostatic latent image is developed by a developing device (developing means) 4. The developing device 4 includes a rotatable rotary 4a and four developing devices mounted thereon, that is, a yellow (first) developing device 4Y, a magenta (second) developing device 4M, and a cyan (third). ) Developing device 4C and black (fourth) developing device 4K. The above-described electrostatic latent image formed on the photosensitive drum 1 is developed by a developing device. In other words, the rotation of the rotary 4a causes the yellow developing device 4Y to be disposed at the developing position facing the photosensitive drum 1, and a developing bias is applied to the developing sleeve. Then, yellow toner is attached and developed as a yellow toner image. At this time, the second to fourth developing devices 4M, 4C, and 4K are turned off and do not act on the photosensitive drum 1, and the yellow toner image developed by the second developing device 4Y is the above. The second to fourth developing devices 4M, 4C and 4K are not affected. In this embodiment, the regular charging characteristic of the toner is negative.

  Below the photosensitive drum 1, an intermediate transfer belt 5 as a second image carrier is disposed. The intermediate transfer belt 5 is formed in an endless shape (endless), and is stretched over a driving roller 6, a driven roller 7, and a secondary transfer counter roller 8. The intermediate transfer belt 5 is pressed against the surface of the photosensitive drum 1 by a primary transfer roller 9 disposed inside, thereby forming a primary transfer portion T1 between the intermediate transfer belt 5 and the photosensitive drum 1. The intermediate transfer belt 5 rotates in the direction of arrow R5 at the same speed as the process speed of the photosensitive drum 1 as the driving roller 6 rotates counterclockwise in FIG. A transfer bias is applied to the primary transfer roller 9 by a primary transfer bias application power source (not shown) at the timing when the yellow toner image formed on the photosensitive drum 1 reaches the primary transfer nip portion. As a result, the yellow toner image on the photosensitive drum 1 is primarily transferred onto the intermediate transfer belt 5.

  After the yellow toner image has been transferred, the transfer residual toner is removed by the drum cleaner 10 on the surface of the photosensitive drum 1 and is used for the next image formation.

  The above-described image forming process for the yellow toner image, that is, the charging, exposure, development, primary transfer, and cleaning processes are similarly repeated for the other three colors (magenta, cyan, and black). As a result, the four color toner images are superimposed on the intermediate transfer belt 5.

  The primary transfer bias for sequentially transferring the yellow, magenta, cyan, and black toner images from the photosensitive drum 1 to the intermediate transfer belt 5 sequentially has a polarity opposite to that of the toner (positive polarity). Applied. The applied voltage is, for example, in the range of +100 to + 2000V.

  A belt cleaner 11 is disposed in contact with the driven roller 7 across the intermediate transfer belt 5. The belt cleaner 11 removes the toner remaining on the intermediate transfer belt 5 after the secondary transfer, and is separated from the surface of the intermediate transfer belt 5 until the secondary transfer of the toner image is completed.

  A secondary transfer roller (transfer member) 12 is disposed at a position facing the secondary transfer roller 8 with the intermediate transfer belt 5 interposed therebetween. The secondary transfer roller 12 is disposed so as to be able to come into contact with and separate from the intermediate transfer belt 5, and is separated from the intermediate transfer belt 5 until the primary transfer of the yellow, magenta, and cyan toner images is completed. Has been. The secondary transfer roller 12 forms a secondary transfer portion T2 when being in contact with the intermediate transfer belt 5.

  The four-color toner image primarily transferred in such a manner as to be superimposed on the surface of the intermediate transfer belt 5 in this way is applied with a voltage to the secondary transfer roller 12 so that the recording material P such as paper, resin film, etc. Is transcribed. The recording material P stored in the paper feed cassette 13 is fed by a paper feed roller 14, transported by a transport roller (not shown), and subjected to secondary transfer at a predetermined timing by a registration roller (not shown). It is supplied to the part T2. The secondary transfer bias is applied to the secondary transfer roller 12 by a secondary transfer bias application power source (not shown).

  The recording material P supplied to the secondary transfer portion T2 is guided to the guide members 15 and 16 and supplied to the transfer nip portion T2. That is, there is an upper guide member 15 that guides the front side (the surface on which the toner image is transferred) and a lower guide member 16 that guides the back side (the side opposite to the surface on which the toner image is transferred). The recording material P is supplied to the secondary transfer portion T2 while being regulated by the guide members 15 and 16. The guide member 16 will be described in detail later.

  The recording material P after the secondary transfer of the toner image is transported to the fixing device 17 via the transport unit 18, where it is heated and pressurized to fix the toner image on the surface. As a result, a four-color full-color image is formed on the recording material.

  On the other hand, the toner remaining on the surface of the intermediate transfer belt 5 after the secondary transfer of the toner image is removed by a belt cleaner in contact with the surface of the intermediate transfer belt 5 and used for the transfer of the next toner image. .

  Next, features of the present invention will be described in detail. The recording material P is first transported from the registration rollers, and the front side hits the upper guide member 15 and proceeds accordingly. Then, no gap is formed between the photosensitive drum 1 and the sheet is conveyed along the intermediate transfer belt 5 before entering the transfer electric field region. When the recording material P reaches the transfer portion T2, thereafter, the recording material P is always in contact with the lower guide member 16 and is guided to the lower guide member 16, and the positional accuracy of the entry into the photosensitive drum 1 is maintained. It has a configuration that droops.

  In the present embodiment, the upper guide member 10 that guides the surface side of the recording material P is made of stainless steel that is a nonmagnetic conductive member, and the surface thereof is covered with an insulating sheet member. . This is to prevent the magnetic field of the developing magnet from being obstructed by shortening the distance between the developing device and the upper guide member 15 by downsizing the apparatus. Further, since it is close to the intermediate transfer belt 5, it is made conductive and has the same polarity as the toner for the purpose of preventing disturbance of the visible toner image formed on the intermediate transfer belt 5 by giving an electrostatic effect. Is applied. Further, under a high temperature and high humidity environment (temperature 30 ° C./humidity 80%), the impedance of the recording material is lowered by humidity, and there arises a problem that the transfer voltage interferes with the voltage applied to the upper guide member 15. Therefore, in order to prevent this problem, the structure is covered with an insulating sheet member. On the other hand, as shown in FIG. 2, in the lower guide member 16 that guides the back side of the recording material P, the base material 16a is formed of an insulating material. A sheet member 16b is bonded to a portion (contact portion) that is strongly rubbed against the recording material P. In the present embodiment, the sheet member 16b is attached to the base material 16a as the contact portion, but may be configured to be coated. The entire lower guide member 16 is in a float state.

  In this embodiment, the sheet member 16b is made of a high molecular polyethylene having a negative charge series due to friction with the recording material P and a surface roughness Ra of 10 μm or more and 50 μm or less. The thickness of the sheet member 16b is 2 mm. The length of the sheet member 16b in the direction orthogonal to the conveyance direction of the recording material P is the same as the length of the base material.

  The reason is as follows. First, the charging series by friction with the recording material P was made the same polarity as the toner. Accordingly, the rubbing portion of the sheet member 16b with the recording material P acts to repel the toner, and toner contamination of the lower guide member 16 can be prevented.

  In the surface roughness (centerline average roughness), if the surface roughness Ra of the sheet member 16b is less than 10 μm, the contact area with the recording material P increases and friction increases, so that the sheet member 16b Overcharged. As a result, an abnormal image is generated due to excessive discharge of charges. On the other hand, when the surface roughness Ra exceeds 50 μm, the surface roughness increases, and the powder scraped by the friction of the recording material may clog the valleys of the sheet member, and the required charged state can be obtained. Because it becomes impossible.

  Here, for the surface roughness, a contact type surface roughness measuring device (Surfcom 570A, manufactured by Tokyo Seimitsu Co., Ltd.) was used in an environment of 23 ° C. and 55 RH%. When measuring the sheet member, a measurement distance is set to 2.5 mm, and a contact needle having a diamond tip (5 μmR, 90 ° cone) is used. And the average value at the time of measuring repeatedly 3 times by changing a measurement location is calculated | required as centerline average roughness Ra of a sheet | seat member.

  The volume resistivity of the sheet material is 1 × 10 12 Ωcm or more, and preferably 1 × 10 14 Ωcm or less.

  When the volume resistivity exceeds 1 × 10 14 Ωcm, an abnormal image is generated due to the discharge of the above-described excessive charge even if the surface roughness is increased as described above. Further, when the resistance of the sheet material falls below 1 × 10 12 Ωcm, there arises a problem that a current flows from the transfer member to which the voltage is applied to the recording material.

Here, a method for measuring volume resistivity will be described. The volume resistivity can be measured in accordance with JIS K6991 using a circular electrode (for example, HR probe of Hirester IP manufactured by Mitsubishi Yuka Co., Ltd.). A method for measuring the volume resistivity will be described with reference to the drawings. FIG. 3 is a schematic plan view (a) and a schematic cross-sectional view (b) showing an example of a circular electrode. The circular electrode shown in FIG. 3 includes a first voltage application electrode A ′ and a second voltage application electrode B ′. The first voltage application electrode A ′ has a cylindrical electrode part C ′ and a cylindrical shape having an inner diameter larger than the outer diameter of the cylindrical electrode part C ′ and surrounding the cylindrical electrode part C ′ at a constant interval. Ring-shaped electrode portion D ′. A sheet electrode is sandwiched between the second voltage application electrode B ′ and the cylindrical electrode part C ′ and the ring electrode part D ′ in the first voltage application electrode A ′, and the cylindrical electrode part in the first voltage application electrode A ′. A current I (A) that flows when a voltage V (V) is applied between the part C ′ and the second voltage application electrode B ′;
ρv = 19.6 × (V / I) × t (1)
Thus, the volume resistivity ρv (Ωcm) of the sheet member can be calculated. Here, in Formula (1), t shows the thickness of a measuring object.

  The sheet member 16b in which the surface roughness of the sheet member 16b and the volume resistance value of the sheet member 16b are within the above-described range is adhered to the lower guide member 16, and the recording material P and the lower guide member 16 are rubbed together. Will do. With this configuration, it is possible to achieve an appropriate charge sufficient to prevent toner contamination and to prevent excessive charging due to friction with the recording material P.

  The upper guide member 10 and the lower guide member 16 are configured as described above. Under a normal temperature and low humidity environment (temperature 23 ° C./humidity 5%), the recording material P is allowed to stand in the same environment for one week. It was used and examined in the same environment. The recording material conveyance speed at the time of this examination was examined at a speed at which 30 sheets of A4 size recording material were passed per minute.

  In this study, sheet members having different surface roughness and volume resistivity were attached to the guide member, and the images in each case were determined. The recording material P is first transported from the registration rollers, and the front side hits the upper guide member 15 and proceeds accordingly. Then, no gap is formed between the photosensitive drum 1 and the photosensitive drum 1 is conveyed along the photosensitive drum 1 before entering the transfer electric field region. When the recording material P reaches the transfer nip T, the recording material P is always rubbed against the lower guide member 16 and conveyed in a guided state.

  The examination result is shown in FIG. ○ indicates that the image is good, × indicates that there is an abnormality, XX indicates that the abnormality level is severe, and Δ indicates that there are other defects. Further, Δ and X of Ra of 50 μm or more are because the powder scraped by the friction of the recording material clogs the gap of the sheet material for a long period of use, which increases the charged state by the rubbing.

  At this time, the lower guide member 16 and the recording material P are rubbed strongly. When an insulating member is used for the lower guide member 16, the lower guide member 16 and the recording material P are on the recording material due to frictional charging between the recording material P and the lower guide member 16. Excess charged charge cannot be removed. For this reason, a horizontal streak-like abnormal image was seen in the image after transfer.

  Here, the influence on the image with respect to the surface roughness and the volume resistance value will be examined with reference to FIG. It can be seen that when the surface roughness is 10 μm or more and 50 μm or less, the rank of the image defect is increased even outside the region. That is, when the volume resistivity is less than 10 12 Ωcm, the surface roughness is outside the range of 10 μm or more and 50 μm or less. On the other hand, when the surface roughness is in the range of 10 μm or more and 50 μm or less, it can be seen that the rank is increased like Δ to ○. The reason is that the contact area between the recording material and the sheet member is reduced. X and Δ of Ra of 50 μm or more are because the powder scraped by the friction of the recording material clogs the gap of the sheet material for a long period of use, and this increases the charged state by the rubbing.

  Here, the result of charging characteristics when the sheet member and the recording material in FIG. In this measurement, the distance between the surface potential member and the measurement object is set to 3 mm, and the surface potential of the measurement object is measured (hereinafter, the same measurement method). FIG. 5 shows that when the sheet member 16b has a volume resistivity of 10 13 Ωcm and a surface roughness of 1 μm and 10 μm passes through the A4 size recording material continuously at the above-described conveyance speed. This shows how the surface potential increases. In addition, the size is the same for all the sheet members. Since the sheet member of the present embodiment has a surface roughness of 10 μm, it tends to be saturated with a small amount of charge even if the number of sheets passed is increased. As a result, the occurrence of excessive charging on the recording material P due to frictional charging with the recording material P can be suppressed, and a normal transfer image can be obtained even when images are continuously formed. On the other hand, when the surface roughness that increases the contact area is 1 μm, the surface is saturated with a high charge amount, and in this case, an image defect occurs (rank XX). Moreover, since the sheet member 16b is affixed to the base material 16a formed of an insulating member, the entire guide member is in a float state. For this reason, the transfer bias applied at the time of image formation causes a current to flow into the lower guide member 16, and a defective image due to insufficient transfer current does not occur.

  Thus, image defects can be reduced by setting the surface roughness within the range of 10 μm or more and 50 μm or less.

  Further, the volume resistivity of the sheet member 16b will be examined. When the volume resistivity exceeds 1 × 10 14 Ωcm, an abnormal image is generated due to the discharge of the above-described excessive charge even if the surface roughness is increased as described above. That is, at 10 ^ 14 Ωcm, the level at which no image defect occurs (◯), but at 10 ^ 14 Ωcm, the level at which image defect occurs (Δ). Further, when the resistance of the sheet material falls below 1 × 10 12 Ωcm, the transfer voltage is transmitted through the recording material and interferes with the lower guide member as described in the explanation of the configuration of the upper guide member 10 described above. This is because problems will occur. That is, at 10 ^ 12 Ωcm, the level at which no image defect occurs (◯), but below 10 ^ 12 Ωcm, the level at which image defect occurs (Δ).

  Thus, the volume resistivity of the sheet material is desirably 1 × 10 12 Ωcm to 1 × 10 14 Ωcm.

  Further, regarding the toner contamination of the entire guide member, since the charging series of the sheet member 16b that is slightly charged by friction with the recording material P has the same polarity as the toner, a force repelling the toner acts, and the guide member Can prevent toner stains. Therefore, it was possible to prevent toner contamination of the recording material.

  In addition, since the lower guide member 16 has a simple configuration in which the sheet member 16b is attached and is electrically floated, a higher effect can be obtained with a configuration that is less expensive than the conventional configuration.

  Thus, according to the present invention, it is possible to stabilize the charging characteristics of the guide member while reducing the sliding area between the guide member and the recording material.

(Second embodiment)
Next, a second embodiment of the present invention will be described.

  FIG. 1 is a schematic cross-sectional view of an image forming apparatus showing an embodiment of the present invention. In the present embodiment, as the material of the sheet member 16b, a porous polymer material having a charging property having the same polarity as that of the toner and an infinite number of porous structures with a small contact area is used. The center line average roughness Ra is 10 μm or more and 50 μm or less, and the volume resistivity of the contact portion is 1 × 10 12 Ωcm or more and 1 × 10 14 Ωcm or less.

  As shown in FIG. 6, this porous polymer material has a continuous pore structure having innumerable minute pores therein and has air permeability. In addition, it has excellent wear resistance and extremely low dynamic sliding resistance. The average pore diameter of the porous polymer material in this example is 10 μm to 20 μm. Moreover, the porosity which represents the filling degree of material is 20 to 40%.

  As an advantage of using this material, first, when rubbing against the recording material for a long period of use, even if the surface of the porous material is slightly scraped, the next pore structure appears from the lower layer as the surface. Therefore, the surface roughness is hardly lowered. That is, the center line average roughness Ra can be maintained at 10 μm to 50 μm for a long period of time. FIG. 7 shows a change state of the surface roughness of the sheet member with respect to the number of image formations. As can be seen from FIG. 7, the contact area with the recording material can always be kept small, and the charging of the recording material does not increase and does not affect the image. The length and thickness of the sheet member 16b in the direction orthogonal to the recording material conveyance direction are the same as those in the first embodiment. The conveyance speed of the recording material of the image forming apparatus is a speed at which 30 A4-sized recording materials are conveyed per minute.

  In addition, in the case of a hole structure, the relative permittivity is low because the structure has a large surface area and a large number of voids compared to the same material that does not have a hole structure. . FIG. 8 is a graph showing the transition of the surface potential of the sheet member with respect to the continuous recording material rubbing frequency. FIG. 8 shows the transition of the surface potential between a polymer material having a surface roughness of 1 μm, a polymer material having a surface roughness of 10 μm, and a porous polymer material having a surface roughness of 10 μm. In this examination, the volume resistivity of any sheet member is 1 × 10 13 Ωcm. In addition, the size is the same for all the sheet members. As can be seen from FIG. 8, it is understood that the surface potential of the porous polymer material is small when the recording material is rubbed with the same number of times.

  As described above, even when a high-resistance material is used for the purpose of preventing a transfer bias leak to the guide member, if a porous material is used, the recording material is excessively charged, and the image is transferred to the image during transfer. It can prevent the influence.

  This porous polymer material has a porosity of 20 to 40% representing the filling degree of the material. This is because if the porosity is less than 20%, the material portion and the void portion are likely to be unevenly distributed, and a portion that is excessively charged locally occurs due to friction with the recording material. On the other hand, if it exceeds 40%, the hole is clogged with scraped pieces of the recording material, causing deterioration in charging performance, and increasing the number of voids, the strength cannot be maintained. As a result, wear due to rubbing with the recording material becomes severe, and the product life is shortened.

  In the calculation method of the porosity, VH indicates the volume of the void between the inner surfaces of the porous sheet member, and the porosity is obtained from VH / VT × 100 (%), where VT is the total volume of the porous sheet member. .

  In the above embodiment, the guide member has a float configuration, but the same applies to a configuration in which the guide member is grounded via a resistor having a high resistance value and a configuration in which a voltage is applied to the guide member. An effect can be obtained.

  In the above embodiment, the toner image is formed on the recording material from the intermediate transfer belt. However, the same effect can be obtained even when the electrophotographic photosensitive member and the transfer member are in contact with each other and the toner image is transferred onto the recording material without the intermediate transfer belt.

  In the above embodiment, the sheet member is attached to the lower guide member. However, the same effect can be obtained even if the sheet member is attached to the upper guide member.

  As described above, according to the present invention, it is possible to stabilize the charging characteristics of the guide member while reducing the sliding area between the guide member and the recording material.

  Furthermore, by using a porous material, the above effect can be obtained over a long period of time.

1 is a diagram illustrating an image forming apparatus according to a first embodiment of the present invention. The figure which expanded the transfer guide part of 1st Example of this invention. Diagram for measuring device to calculate volume resistivity The figure which shows the state of the image with respect to volume resistivity and surface ancestry Charging characteristic diagram when the sheet member and the recording material of the first embodiment of the present invention are rubbed against each other Structural schematic diagram of the porous polymer material of the second embodiment of the present invention The number of image formations and the surface roughness of the sheet member according to the second embodiment of the present invention Charging characteristic diagram when rubbing the porous polymer material and the recording material of the second embodiment of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging apparatus 3 Exposure apparatus 4 Developing apparatus 5 Intermediate transfer belt 12 Transfer member 15 Upper guide member 16 Lower guide member 16a Base material 16b Sheet member P Recording material (recording paper)

Claims (3)

In an image forming apparatus comprising: an image carrier; a transfer member that forms a transfer portion that transfers a toner image on the image carrier onto a recording material; and a guide member that guides the recording material to the transfer portion.
The contact portion of the guide member that comes into contact with the recording material is made of a porous polymer material having a porosity of 20 to 40%, and the charging series due to friction with the recording material is the same polarity as the normal polarity of the toner. The center line average roughness Ra is 10 μm or more and 50 μm or less, and the volume resistivity is 1 × 10 12 Ωcm or more and 1 × 10 14 Ωcm or less. The image forming apparatus according to claim 1, wherein the porous polymer material has an average pore diameter of 10 μm to 20 μm. 3. The guide member according to claim 1, wherein the guide member is a guide member that guides the recording material to a transfer unit by contacting the surface of the recording material opposite to the surface facing the image carrier. Image forming apparatus.

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