JP4978769B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that forms a toner image by selectively attaching toner to a latent image due to a difference in electrostatic potential, transfers the toner image onto a recording medium, and then heats and pressurizes to form a fixed image. .

  In an electrophotographic image forming apparatus, an electrostatic latent image is formed by irradiating the surface of a uniformly charged photosensitive drum with image light, and toner is electrostatically transferred to the electrostatic latent image. As a result, a toner image is formed on the photosensitive drum. The toner image is transferred to a recording medium directly or via an intermediate transfer member, and fixed on the recording medium.

  As a transfer device for transferring a toner image on a photosensitive drum to a recording medium, a transfer bias voltage is applied to a transfer roller pressed against the photosensitive drum, and the toner image is transferred to the recording medium passing through these pressure contact portions. Is known that electrostatically transfers the image. Also, in an image forming apparatus that transfers a toner image to a recording medium after the toner image is once transferred to the intermediate transfer body, the toner image is transferred from the photosensitive drum to the intermediate transfer body, or from the intermediate transfer body to the recording medium. A similar transfer device is used for transfer.

  Further, as a fixing device for fixing an unfixed toner image on a recording medium, a heating rotator having an endless peripheral surface that circulates, and a pressure roller as a pressure member that presses the toner image against the peripheral surface Is widely used. In this fixing device, the heating rotator and the pressure member are brought into pressure contact with each other, and a recording medium carrying a toner image is inserted into these pressure contact portions (fixing nip portions). As a result, the recording medium passes through the fixing nip as the heating rotator rotates, and the unfixed toner image on the recording medium is heated and pressed.

  The heating rotator used in such a fixing device has an endless shape that is rotated by a heating roller, a heater, or an electromagnetic induction heating device having a hollow metal core such as aluminum and a heater supported therein. Belts and the like are known. These peripheral surfaces are coated with a fluorine resin or the like in order to prevent adhesion of toner or the like. On the other hand, as the pressure member, a pressure roller having a heat-resistant elastic layer such as silicone rubber on a metal core is widely used. To prevent the toner transferred to the heating rotator, that is, the offset toner, from transferring to the surface of the pressure roller and contaminating the back surface of the recording medium, the fluororesin is less likely to adhere to the pressure roller. It has been proposed to provide a surface layer of the system. For example, the peripheral surface of the pressure roller is covered with a thin tubular PFA resin layer.

  In such a fixing device in which the surface of the pressure roller is coated with a fluororesin-based material, since the surface has high insulation, the pressure roller is caused by friction when the recording medium passes through the fixing nip portion. The surface of is charged. In general, fluororesin is negatively charged by friction with paper, and when the negative potential on the surface of the pressure roller increases, the negatively charged toner on the recording medium is electrically connected to the surface of the pressure roller. Repulsion tends to cause so-called electrostatic offset that transfers to the surface of the heating rotator.

Patent Document 1 discloses a technique for preventing the offset as described above, and it is proposed that the surface of the pressure roller is made conductive by being coated with a fluororesin containing a filler such as carbon. Yes. That is, in the fixing device described in Patent Document 1, the surface resistance value of the pressure roller is set to 10 ¹⁰ Ω or less, whereby charging of the surface of the pressure roller is prevented and the toner is electrostatically heated on the surface of the rotating body. It is intended to prevent the offset that shifts to.
Japanese Patent Laid-Open No. 9-222816

  However, if the resistance of the surface layer of the pressure roller is reduced as in Patent Document 1, charging of the surface of the pressure roller can be suppressed and electrostatic offset of the toner can be prevented, but the following problems are encountered. Occurs.

  Due to the downsizing of the image forming apparatus, the distance between the transfer pressure contact portion and the fixing nip portion is shortened. Depending on the size of the recording medium to be conveyed, the recording medium is simultaneously spread over both the transfer pressure contact portion and the fixing nip portion. May be retained. That is, while the rear portion of the same recording medium is sandwiched between the transfer pressure contact portions, the front portion is simultaneously inserted into the fixing nip portion. In such a case, in the fixing device in which the resistance of the surface layer of the pressure roller is set to be small, the transfer current leaks from the transfer pressure contact portion to which the transfer bias voltage is applied to the pressure roller through the recording medium, May cause poor transfer. In particular, in a high humidity environment, the electrical resistance of the recording medium decreases, and this phenomenon becomes remarkable.

  Further, the recording medium at the transfer pressure contact portion is strongly charged to the positive polarity when the toner has a polarity opposite to that of the toner, that is, the toner has a negative polarity due to the action of the transfer bias voltage. When a recording medium that is positively charged in this manner is brought into contact with the pressure roller, if the resistance of the pressure roller is set to a small value and grounded, electrostatic induction occurs and the surface of the pressure roller is An induced charge is generated. Due to this negative charge, electrostatic attraction acts on the paper powder having a positive charge adhering to the back surface of the recording medium, particularly calcium carbonate contained in the neutral paper, and the paper powder adheres to the surface of the pressure roller. Then, after the recording medium passes through the pressure contact portion between the heating roller and the pressure roller, the paper dust attached to the pressure roller is pressed against the heating roller and transferred to the surface of the heating roller. If the paper powder transferred to the surface of the heating roller is accumulated without being removed, the surface of the heating roller is charged to the positive polarity, and the toner charged to the negative polarity is attracted to attract the offset.

  The present invention has been made in order to solve the above-described problems, and its object is to prevent a transfer bias current from leaking through a recording medium sandwiched between fixing nips, and to improve the situation. In addition to realizing the transfer, it is possible to prevent an offset in which the toner is transferred to the heating roller.

In order to solve the above-mentioned problem, the invention according to claim 1 forms a toner image by selectively adhering powdery toner to a latent image due to a difference in electrostatic potential formed on an image carrier. An image forming unit, the image carrier, or an intermediate transfer member to which a toner image is temporarily transferred from the image carrier, and the recording medium passing between the image carrier or the intermediate transfer person A transfer member that transfers the toner image; and a fixing device that heat-fixes the toner image by sandwiching the recording medium onto which the toner image is transferred in a fixing nip portion where the heating rotator and the pressure member are pressed against each other. The distance between the transfer pressure contact portion where the transfer member is pressed against the image carrier or the intermediate transfer member and the fixing nip portion is long in the conveyance direction of the recording medium. The pressure member is set shorter than A plurality of layers are laminated on a substrate and immediately below layer is formed just below the surface layer forming the surface, the straight and the lower layer is grounded, the fixing nip portion of the heating rotating body and said pressure member resistance values of the plurality of layers when the current flows to ground, the resistance value of the surface layer forming the surface, is set to be higher than the resistance value immediately below layer formed immediately below the surface layer from the , the resistance value of the immediately below layer removes the charge of the surface layer due to friction between said surface layer and the recording medium, small from the recording medium of about inhibit toner offset to the heating rotator The resistance value of the surface layer is set to a value large enough to suppress the generation of an induced charge that causes the offset in the immediate lower layer due to the charge of the charged recording medium, the total resistance value of the layer immediately below layer The image forming a transfer bias current applied to the transfer nip portion via the recording medium that is interposed in the fixing nip portion is set to a large value in order to suppress the leaking to the pressure member Providing the device.

According to a second aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein the surface layer and the immediate lower layer when an electric current flows from a fixing nip portion between the heating rotator and the pressure member to the ground. The total resistance value is 10 ⁸ Ω or more and 10 ¹⁴ Ω or less.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, when the current flows from the fixing nip portion between the heating rotator and the pressure member to the ground, The resistance value shall be less than 10 ⁸ Ω.

  In this image forming apparatus, since the resistance value of the surface layer of the pressure member is set large, the transfer bias acting on the transfer pressure contact portion through the recording medium inserted in the fixing nip portion does not leak. . Even if the surface layer is charged by friction with the recording medium, the resistance value of the immediate lower layer is small, so that the electric charge is removed from the immediate lower layer by grounding. Furthermore, since the resistance value of the surface layer is large, no induced charge is generated on the surface of the pressure roll by the charge of the recording medium even if the immediate lower layer is grounded.

In particular, since the total resistance value of the surface layer and the immediate lower layer is 10 ⁸ Ω or more, the transfer bias current is efficiently prevented from leaking from the pressure member via the recording medium sandwiched between the fixing nip portions. it can. In addition, the total resistance value of the surface layer and the immediately lower layer is set to 10 ¹⁴ Ω or less, and the resistance value of the immediately lower layer is set to less than 10 ⁸ Ω. Even if it occurs, it is easily removed from the immediate lower layer to the ground. Accordingly, in an image forming apparatus in which the distance between the transfer pressure contact portion and the fixing nip portion is short, transfer failure can be prevented even when the toner image is transferred and fixed simultaneously on the same recording medium, and the toner is heated by the heating rotator. It will not be transferred to.
The resistance value of the surface layer refers to the resistance value of the surface layer when a current flows from the fixing nip portion between the heating rotator and the pressure member to the ground. The resistance value of the immediately lower layer refers to the resistance value of the immediately lower layer when a current flows from the fixing nip portion to the ground, and the same applies to the inventions according to the present application.

  As described above, in the image forming apparatus according to the present invention, the transfer bias current is prevented from leaking from the pressure member of the fixing device via the recording medium sandwiched between the transfer pressure contact portion and the fixing nip portion. Transfer defects can be avoided. In addition, it is possible to prevent the generation of induced powder on the surface of the pressure member and transfer of paper dust, and even if the surface of the pressure member is charged due to friction with the recording medium, the charge is efficiently grounded. Can be removed. Therefore, toner offset is also prevented.

Hereinafter, embodiments of the invention according to the present application will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing an image forming apparatus which is an embodiment of the invention according to the present application.
The image forming apparatus includes a cylindrical photosensitive drum 1 (image carrier) on which a latent image is formed by irradiating image light after uniform charging, and around the photosensitive drum 1. A charging device 2 that uniformly charges the surface of the photosensitive drum 1, an exposure device 3 that irradiates the photosensitive drum 1 with image light to form a latent image on the surface, and an electrostatic latent image on the photosensitive drum 1. Transfer in which a transfer bias voltage is applied between the photosensitive drum 1 and the developing device 4 for visualizing the image by selective adhesion of toner, and the toner image on the photosensitive drum is transferred to a recording medium by an electric field formed. A roller 5 and a cleaning device 6 for removing toner remaining on the photosensitive drum 1 after the toner image is transferred are provided.

Further, a paper feed tray 7 that stores a recording medium to which a toner image is transferred, and a recording medium fed one by one from the paper feed tray 7 are transferred to a pressure contact portion 5a where the photosensitive drum 1 and the transfer roller 5 face each other. A conveying path 8 for conveying the recording medium, a registration roller 9 for feeding the conveyed recording medium to the transfer pressure contact portion 5a at a predetermined timing, and a heating roller 21 and a pressure roller 22 for pressing the toner image transferred to the recording medium. A fixing device 10 that is sandwiched between the fixing nip portion 10a and that is heated and pressed, and a paper discharge roller 11 that feeds a recording medium to a paper discharge tray 12.
In this embodiment, the distance between the transfer pressure contact portion 5a and the fixing nip portion 10a is 80 mm. When a recording medium of A4 size or B5 size is passed, the transfer pressure contact portion 5a and the fixing nip portion are fixed. It will be clamped simultaneously by both parts 10a.

  The photosensitive drum 1 is a photosensitive material composed of various inorganic photosensitive materials such as Se, a-Si, a-SiC, and Cds, organic photosensitive materials, amorphous selenium photosensitive materials, and amorphous silicon photosensitive materials on the surface of a metal drum. What formed the body layer can be used.

  The charging device 2 is a roller made of a conductive metal such as stainless steel or aluminum and coated with a high resistance material. The charging device 2 is in contact with the photosensitive drum 1 and is driven to rotate. When a predetermined voltage is applied, a continuous discharge is generated in a minute gap near the contact portion between the roller and the photosensitive drum 1, and the surface of the photosensitive drum 1 is charged almost uniformly. It is.

  The exposure apparatus 3 outputs a laser that blinks for each pixel based on an image signal, and exposes and scans the peripheral surface of the photosensitive drum 1 with a polygon mirror. As a result, the potential of the exposed portion is attenuated on the peripheral surface of the photosensitive drum 1, and a latent image is formed due to the difference in electrostatic potential.

The developing device 4 has a developing roller 4 a at a position close to and facing the photosensitive drum 1, and a developing bias voltage is applied between the developing roller 4 a and the photosensitive drum 1.
Then, the toner is carried on the peripheral surface of the developing roller 4a and conveyed to a portion facing the photosensitive drum 1, and the toner carried on the peripheral surface is transferred to a latent image in an electric field to form a visible image. Is.

The transfer roller 5 is formed by forming a semiconductive rubber layer 5c having a thickness of about several millimeters on the outer periphery of the metal shaft 5b. The transfer roller 5 is in contact with the peripheral surface of the photosensitive drum 1 and is driven to rotate. It has become. As shown in FIG. 2, a transfer bias voltage is applied to the metal shaft 5b from the power supply device 13, and a transfer electric field is formed between the metal shaft 5b and the grounded photosensitive drum 1.
The recording medium fed between the transfer roller 5 and the photoconductive drum 1 is brought into contact with the toner image on the photoconductive drum 1, and an electric field formed between the transfer roller 5 and the photoconductive drum 1. The charged toner is electrostatically transferred onto the recording medium by the action.

  The fixing device 10 is provided on the downstream side of the transfer pressure contact portion 5a in the conveyance direction of the recording medium. As shown in FIG. 2, the fixing device 10 is in pressure contact with the heating roller 21 incorporating a halogen lamp 23 as a heat source. And a pressure roller 22. The heating roller 21 is rotationally driven through a drive transmission means (not shown) such as a gear, and the pressure roller 22 is rotated by the rotational driving of the heating roller 21. The heating roller 21 and the pressure roller 22 are pressed against each other with a pressure of 300 N, and a nip portion having a width of about 6 mm is formed in the circumferential direction. The nip portion 10a is located 80 mm away from the transfer pressure contact portion 5a.

  A separation claw 24 for preventing the recording medium P from being wound around the heating roller 21 is disposed on the downstream side of the fixing nip portion 8a where the heating roller 21 and the pressure roller 22 are pressed against each other. A thermistor 25 as temperature detecting means is disposed on the peripheral surface of the heating roller 21, and the blinking of the halogen lamp 23 is controlled based on the detected temperature of the thermistor. Thereby, the surface temperature of the heating roller 21 is controlled to be about 180 °.

  The heating roller 21 is formed of aluminum having a thickness of 1 mm and a hollow cylindrical core metal 21 a having an outer diameter of 25 mm, and PFA resin is baked on the outer peripheral surface of the core metal 21 a so as to have a thickness of 30 μm. And the surface release layer 21b.

The pressure roller 22 has an iron cylindrical member as a core metal 22a, and an elastic layer 22b (immediate lower layer) such as sponge or rubber is provided on the surface of the core metal 22a, and a surface layer made of PFA resin thereon. 22c is laminated. In the present embodiment, the cored bar 22a is an iron member having an outer diameter of 10 mm. The elastic layer 22b (immediately lower layer) is a porous silicone rubber having a thickness of 7.5 mm. The conductive filler is dispersed and mixed, and a current flows from the fixing nip portion between the heating roller 21 and the pressure roller 22 to the ground. The resistance is adjusted to 10 ⁶ Ω when flowing . The cored bar 22a is electrically grounded.

The surface layer 22c is obtained by coating the elastic layer 22b (immediate lower layer) with a tube-shaped PFA resin having a thickness of 50 μm. Conductive fillers such as carbon particles are dispersed, and the heating roller 21 and the pressure roller 22 are dispersed. The resistance when the current flows from the fixing nip to the ground is adjusted to 10 ¹⁰ Ω.
In the present embodiment, the resistance value is adjusted as described above. However, the total resistance values of the surface layer 22c and the immediately lower layer 22b are adjusted to 10 ⁸ Ω or more and 10 ¹⁴ Ω or less. The resistance value may be appropriately set within a range of less than 10 ⁸ Ω.

  In the present embodiment, the thickness of the surface layer 22c made of PFA resin is 50 μm, but it is sufficient that the surface layer 22c has a thickness of about 10 μm or more. The thickness can be appropriately set as long as the resistance value when the current flows to the core metal 22c is the above value.

The image forming apparatus as described above operates as follows.
The photosensitive drum 1 is charged to a substantially uniform negative polarity by the charging device 2, and the exposure device 3 irradiates the peripheral surface of the charged photosensitive drum 1 with image light based on the image data. The charged potential of the exposed portion of the surface of the photosensitive drum 1 is attenuated, and a latent image is formed due to a potential difference from the non-exposed portion. The developing device 4 carries a negatively charged toner on the peripheral surface of the developing roller 4 a in a thin layer, and transports the toner to a position facing the peripheral surface of the photosensitive drum 1. An electric field is generated between the photosensitive drum 1 and the developing roller 4a by a developing bias voltage applied between the two, and the toner having a negative charge is transferred to the exposed portion. The toner image formed in this way is conveyed to the transfer pressure contact portion 5a to which the transfer roller 5 is pressed by the rotation of the photosensitive drum 1.

On the other hand, the recording medium sent one by one from the paper tray 7 is temporarily held by the registration roller 9 and sent to the transfer pressure contact portion 5a at a timing when it comes into contact with the toner image on the photosensitive drum 1. The recording medium contacts the surface of the photosensitive drum 1 on the upstream side of the transfer pressure contact portion 5a, and passes through the transfer pressure contact portion 5a in a close contact state.
An electric field is formed around the transfer pressure contact portion 5a and its periphery by a transfer bias voltage, and the toner image is transferred to the recording medium within the electric field.

  Thereafter, a positive charge is applied to the recording medium by discharge when the recording medium carrying the toner image T is peeled off from the transfer roller 5, and the toner image T is held on the recording medium and sent to the fixing device 10. It is done.

  In the fixing device 10, the recording medium P carrying a toner image is sandwiched in the fixing nip portion 10 a between the heating roller 21 and the pressure roller 22, and the toner pressed against the heating roller 21 is heated and melted to record the recording medium P. Crimped on top. The recording medium P that has passed through the fixing nip 10 a is peeled off from the heating roller 21 or the pressure roller 22 and sent to the paper discharge roller 11.

  In the image forming apparatus, the distance between the transfer pressure contact portion 5a and the fixing nip portion 10a is as short as 80 mm, and the front portion P1 of the recording medium that has passed through the transfer pressure contact portion 5a is inserted into the fixing nip portion 10a. Further, the rear portion P2 is still sandwiched between the transfer pressure contact portions 5a. Even in such a state, the surface layer of the pressure roller 22 is formed of a material having a large electric resistance, and the resistance value from the fixing nip portion 10a to the ground is large, so that it is sandwiched between the fixing nip portion 10a. The transfer bias current does not leak through the recording medium P. Therefore, good transfer can be maintained.

In the process of fixing the toner image, the negatively charged toner passes through the fixing nip portion 10a while being attracted to the recording medium P having a positive charge. Since the resistance value of the surface layer 22c of the pressure roller 22 is adjusted to 10 ¹⁰ Ω and the resistance value of the immediate lower layer 22b is adjusted to 10 ⁶ Ω, the surface layer 22c is hardly charged due to friction with the recording medium P. Even if an electric charge is generated, it is removed by grounding via the directly conductive lower layer 22b. Therefore, the pressure roller 22 does not have a strong charge, and electrostatic offset due to charging of the pressure roller 22 does not occur.

Further, the surface layer of the pressure roller 22 has a resistance value set to a slightly high value of 10 ¹⁰ Ω and a thickness of 10 μm or more. Therefore, the surface layer of the pressure roller 22 is guided to the surface of the pressure roller 22 by the charge of the recording medium P. There is no charge. Accordingly, it is also possible to prevent paper dust having positive charges that are separably present on the back surface of the recording medium from being transferred to the surface of the heating roller 21 by induced charges generated on the surface of the pressure roller 22. As a result, toner offset induced by the transfer of paper dust to the heating roller 21 and accumulation is also prevented.

  As described above, the problem that the transfer bias current leaks from the fixing device 10 via the recording medium can be solved by setting the pressure roller 22 to a high resistance. By making the resistance high, toner offset tends to occur during fixing. On the other hand, the pressure roller 22 has a plurality of layers, and by appropriately setting these resistance values, both prevention of transfer bias current leakage and prevention of offset can be realized. .

Next, an experiment for confirming the effect of the invention according to the present application will be described.
In this experiment, the state of occurrence of transfer failure when a toner image is fixed while changing the distance between the transfer pressure contact portion and the fixing nip portion using the conventional fixing device and the fixing device 10 according to the present invention is described. It is a comparison.
The conventional fixing device used in this experiment is replaced with the pressure roller 22 in the fixing device of the present embodiment, and has an additional layer having a high resistance elastic layer and a release layer whose resistance value is adjusted to 10 ⁵ Ω. A release roller is grounded using a pressure roller. The elastic layer is formed of silicone rubber that does not contain a conductive filler around the core metal, and the release layer is made of a PFA tube having a resistance value adjusted to 10 ⁵ Ω by containing a conductive filler. It is formed by wrapping around the outer peripheral surface. The heating roller and other parts are the same as those of the fixing device of this embodiment. The recording medium was P paper manufactured by Fuji Xerox Office Supply Co., which was left to stand for about 12 hours in an environment at 28 ° C. and a relative humidity of 85% to contain water.

  A4LEF in Table 1 is a sheet that is fed with the long side of A4 size paper at the top, and the length in the transport direction is 210 mm. A4SEF is a sheet that passes through the short side of A4 size paper, and the length in the transport direction is 297 mm. A3SEF is a sheet that is fed with the short side of A3 size paper at the top, and its length in the transport direction is 420 mm.

As shown in Table 1, in the conventional fixing device, when the recording medium P carrying the toner image is held between both the transfer pressure contact portion and the fixing nip portion at the same time, transfer failure occurred. This is presumably because the transfer bias current leaked from the pressure roller through the recording medium sandwiched in the fixing nip portion.
On the other hand, when the fixing device of this embodiment is used, the distance between the transfer pressure contact portion and the fixing nip portion is shorter than the length of the recording medium to be conveyed, and the recording medium P is simultaneously applied to the fixing nip portion and the transfer pressure contact portion. Even when it was pinched, no transfer failure occurred. Even in such a case, no offset occurs in the fixing device in this embodiment.

1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic diagram illustrating a state in which a recording medium is simultaneously sandwiched between a transfer pressure contact portion and a fixing nip portion in the image forming apparatus illustrated in FIG. 1.

1: Photosensitive drum, 2: Charging device, 3: Exposure device, 4: Development device, 5: Transfer roller, 5a: Transfer pressure contact portion, 6: Cleaning device, 7: Paper tray, 8: Transport path, 9: Resist Roller, 10: fixing device, 10a: fixing nip, 11: paper discharge roller, 12: paper discharge tray,
21: heating roller, 22: pressure roller, 23: halogen lamp, 24: separation claw, 25: thermistor,

Claims (3)

Image forming means for selectively adhering powdery toner to a latent image due to a difference in electrostatic potential formed on an image carrier to form a toner image;
Transfer that transfers the toner image onto a recording medium that is pressed against the image carrier or an intermediate transfer member to which a toner image is temporarily transferred from the image carrier and passes between the image carrier and the intermediate transfer member. Members,
An image forming apparatus comprising: a fixing device that heats and fixes the toner image by sandwiching the recording medium onto which the toner image is transferred in a fixing nip portion where a heating rotator and a pressure member are pressed against each other. And
The distance between the transfer pressure contact portion where the transfer member is pressed against the image carrier or the intermediate transfer member and the fixing nip portion is set to be shorter than the length in the conveyance direction of the recording medium,
The pressure member is formed by laminating a plurality of layers on a base material, a direct lower layer is formed immediately below the surface layer forming the surface, and the direct lower layer is grounded,
Resistance values of the plurality of layers when the current flows from the fixing nip of the rotatable heating member and the pressure member to ground, the resistance value of the surface layer forming the surface, formed just below the surface layer It is set to be higher than the resistance value of the immediate lower layer ,
The resistance value of the immediately lower layer is a value that is small enough to remove the charged charge of the surface layer due to friction between the surface layer and the recording medium, and to suppress toner offset from the recording medium to the heating rotator. Set to
The resistance value of the surface layer is set to a value large enough to suppress the generation of the induced charge that causes the offset in the immediate lower layer due to the charge of the charged recording medium,
The total resistance value of the surface layer and the immediate lower layer is that the transfer bias current acting on the transfer pressure contact portion leaks to the pressure member via the recording medium inserted in the fixing nip portion. An image forming apparatus, wherein the image forming apparatus is set to a value large enough to suppress. The resistance values of the surface layer and the immediate lower layer when current flows from the fixing nip portion between the heating rotator and the pressure member to the ground are 10 ⁸ Ω or more and 10 ¹⁴ Ω or less in total. The image forming apparatus according to claim 1. 3. The resistance value of the immediately lower layer when a current flows from a fixing nip portion between the heating rotator and the pressure member to the ground is less than 10 ⁸ Ω. Image forming apparatus.

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