Fixing belt, fixing device, and image forming apparatus

Abstract

To fully reduce abrasions caused by the sliding contact with a slide member.SOLUTION: In a fixation belt 21 (a belt member), the Martens hardness H1 (N / mm2) is 20≤H1≤70 and the pencil hardness H2 is in the range of HB to 2H, both inclusive, in an inner circumferential surface 21a (a slide surface) in sliding contact with a nip part formation member 26 (a sliding contact member). This can fully reduce the abrasion of the fixation belt 21 and the nip part formation member 26 by the sliding contact with the formation member 26 (a sliding member).SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to Fixing belt The present invention relates to a fixing device including the fixing roller, and an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a combination machine thereof. [Background technology]

[0002] 2. Description of the Related Art Conventionally, in image forming apparatuses such as copiers and printers, there has been known a technique of using a belt member such as a fixing belt that is in sliding contact with a sliding contact member (see, for example, Patent Document 1).

[0003] On the other hand, Patent Document 1 discloses a technology for reducing wear due to sliding contact between the fixing film (belt member) and the supporting member (sliding member), in which the relationship between the Vickers hardness Hv1 of the inner surface of the fixing film and the Vickers hardness Hv2 of the contact portion with the supporting member is set to |Hv1-Hv2|≦200. Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional belt members have been unable to sufficiently reduce wear between the belt member and the sliding contact member due to sliding contact with the sliding contact member.

[0005] The present invention has been made to solve the above-mentioned problems, and provides a method for sufficiently reducing wear caused by sliding contact with a sliding member. Fixing belt The present invention aims to provide a fixing device and an image forming apparatus. [Means for solving the problem]

[0006] In this invention Fixing belt is a sliding contact member Nip forming member as The sliding surface that comes into contact with A fixing belt having an inner peripheral surface which is a sliding contact surface Martens hardness H1 [N / mm 2 ] is 20≦H1≦70, and the pencil hardness H2 is HB or more and 2H or less. Effect of the Invention

[0007] According to the present invention, wear caused by sliding contact with the sliding member is sufficiently reduced. Fixing belt It is possible to provide a fixing device and an image forming apparatus. [Brief description of the drawings]

[0008] [Figure 1] 1 is an overall configuration diagram showing an image forming apparatus according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a diagram illustrating a configuration of a fixing device. [Diagram 3] FIG. 2 is a side view of the fixing device as viewed in the width direction. [Figure 4] FIG. 4 is an enlarged view showing the vicinity of a nip portion. [Diagram 5] 4 is a cross-sectional side view showing a state in which the fixing belt is held by a holding member. FIG. [Figure 6] 4 is an enlarged view showing the vicinity of a sliding contact surface between a fixing belt and a nip portion forming member; [Figure 7] 10 is an enlarged view showing the vicinity of a sliding contact surface between a fixing belt and a nip portion forming member over time as a comparative example. [Figure 8] FIG. 13 is a table showing the conditions and results of the experiment. [Figure 9] FIG. 11 is a configuration diagram showing a fixing device as a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and the duplicated description will be appropriately simplified or omitted.

[0010] First, the overall configuration and operation of the image forming apparatus will be described with reference to FIG. 1, the image forming apparatus 1 in this embodiment is a tandem type color printer. In the bottle storage section 101 located at the top of the image forming apparatus main body 1, four toner bottles 102Y, 102M, 102C, and 102K corresponding to each color (yellow, magenta, cyan, and black) are detachably (replaceably) installed. An intermediate transfer unit 85 is disposed below the bottle storage unit 101. Opposite to the intermediate transfer belt 78 of the intermediate transfer unit 85, image forming units 4Y, 4M, 4C, and 4K corresponding to each color (yellow, magenta, cyan, and black) are arranged side by side.

[0011] Photoconductor drums 5Y, 5M, 5C, and 5K are disposed in the image forming units 4Y, 4M, 4C, and 4K, respectively. A charging unit 75, a developing unit 76, a cleaning unit 77, a discharging unit (not shown), and the like are disposed around each of the photoconductor drums 5Y, 5M, 5C, and 5K. An image forming process (charging process, exposure process, developing process, transfer process, cleaning process, and discharging process) is performed on each of the photoconductor drums 5Y, 5M, 5C, and 5K, and an image of each color is formed on each of the photoconductor drums 5Y, 5M, 5C, and 5K.

[0012] The photoconductor drums 5Y, 5M, 5C, and 5K are rotated clockwise in Fig. 1 by a drive motor (not shown). Then, at the position of the charging unit 75, the surfaces of the photoconductor drums 5Y, 5M, 5C, and 5K are uniformly charged (charging process). Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach the irradiation position of the laser light L emitted from the exposure unit 3, and an electrostatic latent image corresponding to each color is formed by exposure scanning at this position (this is the exposure process).

[0013] Thereafter, the surfaces of the photoconductor drums 5Y, 5M, 5C, and 5K reach positions facing the developing unit 76, where the electrostatic latent images are developed to form toner images of the respective colors (developing process). Thereafter, the surfaces of the photoconductor drums 5Y, 5M, 5C, and 5K reach positions facing the intermediate transfer belt 78 and the first transfer bias rollers 79Y, 79M, 79C, and 79K, and at these positions the toner images on the photoconductor drums 5Y, 5M, 5C, and 5K are transferred onto the intermediate transfer belt 78 (this is the first transfer step). At this time, a small amount of untransferred toner remains on the photoconductor drums 5Y, 5M, 5C, and 5K.

[0014] Thereafter, the surfaces of the photoconductor drums 5Y, 5M, 5C, and 5K reach a position facing the cleaning unit 77, at which point the untransferred toner remaining on the photoconductor drums 5Y, 5M, 5C, and 5K is mechanically collected by the cleaning blade of the cleaning unit 77 (this is the cleaning process). Finally, the surfaces of the photoconductor drums 5Y, 5M, 5C, and 5K reach a position facing a charge removing unit (not shown), where the residual potential on the photoconductor drums 5Y, 5M, 5C, and 5K is removed. Thus, a series of image forming processes carried out on the photoconductor drums 5Y, 5M, 5C, and 5K is completed.

[0015] Thereafter, the toner images of the respective colors formed on the respective photosensitive drums through a developing process are transferred in a superimposed manner onto the intermediate transfer belt 78. In this way, a color image is formed on the intermediate transfer belt 78. Here, the intermediate transfer unit 85 is composed of the intermediate transfer belt 78, four primary transfer bias rollers 79Y, 79M, 79C, 79K, a secondary transfer backup roller 82, a cleaning backup roller 83, a tension roller 84, an intermediate transfer cleaning section 80, etc. The intermediate transfer belt 78 is stretched and supported by three rollers 82 to 84, and is moved endlessly in the direction of the arrow in FIG.

[0016] The four primary transfer bias rollers 79Y, 79M, 79C, and 79K form primary transfer nips by sandwiching the intermediate transfer belt 78 between the photoconductor drums 5Y, 5M, 5C, and 5K, respectively. A transfer bias opposite to the polarity of the toner is applied to the primary transfer bias rollers 79Y, 79M, 79C, and 79K. Then, the intermediate transfer belt 78 travels in the direction of the arrow and passes sequentially through the primary transfer nips of the primary transfer bias rollers 79Y, 79M, 79C, and 79K. In this way, the toner images of each color on the photoconductor drums 5Y, 5M, 5C, and 5K are primarily transferred onto the intermediate transfer belt 78 in a superimposed manner.

[0017] Thereafter, the intermediate transfer belt 78 onto which the toner images of each color are transferred and superimposed reaches a position facing the secondary transfer roller 89. At this position, the secondary transfer backup roller 82 pinches the intermediate transfer belt 78 between itself and the secondary transfer roller 89 to form a secondary transfer nip. The four-color toner images formed on the intermediate transfer belt 78 are then transferred onto the sheet P conveyed to the position of this secondary transfer nip. At this time, untransferred toner that has not been transferred to the sheet P remains on the intermediate transfer belt 78. Thereafter, the intermediate transfer belt 78 reaches the position of the intermediate transfer cleaning unit 80. At this position, the untransferred toner on the intermediate transfer belt 78 is collected. Thus, a series of transfer processes carried out on the intermediate transfer belt 78 is completed.

[0018] Here, the sheet P transported to the position of the secondary transfer nip is transported from the paper feed section 12 arranged below the device main body 1 via a paper feed roller 97, a pair of registration rollers 98 (a pair of timing rollers), etc. More specifically, a plurality of sheets P such as transfer paper are stored in a stack in the paper feed section 12. When the paper feed roller 97 is rotated counterclockwise in FIG.

[0019] The sheet P conveyed to the registration roller pair 98 stops temporarily at the roller nip of the registration roller pair 98 that has stopped rotating. Then, the registration roller pair 98 is rotated in synchronization with the color image on the intermediate transfer belt 78, and the sheet P is conveyed toward the secondary transfer nip. In this way, the desired color image is transferred onto the sheet P.

[0020] Thereafter, the sheet P onto which the color image has been transferred at the secondary transfer nip position is conveyed to the position of the fixing device 20. Then, at this position, the color image transferred onto the surface is fixed onto the sheet P by heat and pressure from the fixing belt 21 and the pressure roller 31. Thereafter, the sheet P is discharged to the outside of the apparatus through a pair of discharge rollers 99. The sheets P discharged to the outside of the apparatus by the pair of discharge rollers 99 are sequentially stacked on a stack unit 100 as output images. In this manner, a series of image forming processes in the image forming apparatus is completed.

[0021] Next, the configuration and operation of the fixing device 20 installed in the image forming apparatus main body 1 will be described in detail with reference to FIGS. 2 to 4, the fixing device 20 is composed of a fixing belt 21 as a belt member, a nip portion forming member 26 as a sliding contact member, a reinforcing member 23, a heater 25 (heat source) as a heating means, a pressure roller 31 as a pressure member, a temperature sensor 40, a reflecting member 27, etc.

[0022] Here, the fixing belt 21 as a belt member is a thin, flexible endless belt that rotates (runs) in the direction of the arrow (counterclockwise) in Fig. 2. The fixing belt 21 has a base layer, an elastic layer, and a release layer laminated in this order from the inner peripheral surface 21a (the surface that slides against the nip portion forming member 26) side, and the overall thickness is set to 1 mm or less. The base material layer 21A of the fixing belt 21 (see FIG. 6) has a layer thickness of about 30 to 70 μm, and is made of a metal material such as nickel or stainless steel, or a resin material such as polyimide. The elastic layer of the fixing belt 21 has a thickness of about 100 to 300 μm and is made of a rubber material such as silicone rubber, foamed silicone rubber, fluororubber, etc. By providing the elastic layer, minute irregularities are not formed on the surface of the fixing belt 21 at the nip portion, and heat is uniformly transferred to the toner image T on the sheet P, preventing the occurrence of an orange peel image. The release layer of the fixing belt 21 has a layer thickness of about 10 to 50 μm, and is made of materials such as PFA (tetrafluoroethylene-perfluoroalkylvinylether copolymer), PTFE (polytetrafluoroethylene), polyimide, polyetherimide, PES (polyether sulfide), etc. By providing the release layer, releasability (peelability) for the toner T (toner image) is ensured. In this embodiment, the base material layer 21A of the fixing belt 21 is provided with a surface layer 21Aa on the inner surface 21a side (the sliding surface with the nip portion forming member 26 and the flange 29) having a thickness of about 9 to 15 μm and an adjusted Martens hardness and pencil hardness, which will be described in detail later.

[0023] The diameter of the fixing belt 21 is set to be about 15 to 120 mm. Inside (on the inner circumferential surface side) of the fixing belt 21, a nip portion forming member 26, a heater (heating means), a reinforcing member 23, a reflecting member 27, and the like are fixedly provided. Here, the nip portion forming member 26 is fixed so as to be in sliding contact with the inner peripheral surface 21a (sliding surface) of the fixing belt 21. Then, the nip portion forming member 26 is pressed against the pressure roller 31 via the fixing belt 21, thereby forming a nip portion (fixing nip portion) through which the sheet P is conveyed. With reference to Figs. 3 and 5, both ends of the nip portion forming member 26 in the width direction are held by flanges 29 (holding members) fixedly supported by the side plates 43 of the fixing device 20. Also, both ends of the fixing belt 21 in the width direction are rotatably held by the flanges 29. The nip portion forming member 26 and the flanges 29 will be described in detail later. The fixing belt 21 is directly heated by radiant heat from a heater 25 (heating means) installed inside the fixing belt 21.

[0024] Heater 25 as a heating means is a halogen heater (or a carbon heater), and both ends thereof are fixed to side plates 43 of fixing device 20 (see FIG. 3). Then, the fixing belt 21 is heated mainly except for the nip portion by radiant heat from heater 25 (heating means) whose output is controlled by a power supply unit of the apparatus main body 1. Furthermore, heat is applied to the toner image T on sheet P from the heated surface of fixing belt 21. Note that output control of heater 25 is performed based on the detection result of the belt surface temperature by temperature sensor 40 such as a thermistor facing the surface of fixing belt 21. Also, by such output control of heater 25, the temperature of fixing belt 21 (fixing temperature) can be set to a desired temperature. In the present embodiment, one heater 25 is provided on the inner circumferential surface side of the fixing belt 21, but a plurality of heaters may be provided on the inner circumferential surface side of the fixing belt 21.

[0025] In this manner, in the fixing device 20 of the present embodiment, since the fixing belt 21 is heated over a relatively wide range in the circumferential direction rather than only a portion of the fixing belt 21 locally, the fixing belt 21 can be heated sufficiently to prevent the occurrence of fixing defects even when the device is operated at high speed. In other words, since the fixing belt 21 can be heated efficiently with a relatively simple configuration, the warm-up time and the first print time can be shortened, and the device can be made more compact. In particular, in the present embodiment, the fixing device 20 is configured such that the fixing belt 21 is directly heated by the heater 25 (heating means), thereby further improving the heating efficiency of the fixing belt 21 and enabling the fixing device 20 to be further reduced in cost and size.

[0026] 5, the two flanges 29 serving as holding members are made of a heat-resistant resin material or the like, and are fitted into the side plates 43 at both widthwise ends of the fixing device 20. The flanges 29 are provided with a guide portion 29a for holding the fixing belt 21 while maintaining the circular posture of the fixing belt 21, a stopper portion 29b for restricting the movement of the fixing belt 21 in the widthwise direction (toward the belt), and the like. In this embodiment, the only members that come into contact with the inner surface 21a of the fixing belt 21 are the flanges 29 at both ends in the width direction and the nip portion forming member 26, and there are no other members (belt guides) that come into contact with the inner surface 21a and guide the rotation of the fixing belt 21.

[0027] In this embodiment, reinforcing member 23 for reinforcing the strength of nip portion forming member 26 that forms the nip portion is fixed to the inner peripheral surface side of fixing belt 21. With reference to Fig. 3, reinforcing member 23 is formed so that its widthwise length is equal to that of nip portion forming member 26, and both ends in the widthwise direction are held by flanges 29 (holding members) of fixing device 20. In detail, reinforcing member 23 is positioned so that it is sandwiched between flange 29 and nip portion forming member 26. Reinforcing member 23 abuts against pressure roller 31 via nip portion forming member 26 and fixing belt 21, thereby preventing the nip portion forming member 26 from being significantly deformed by the pressure of pressure roller 31 at the nip portion. In this embodiment, reinforcing member 23 is a plate-like member having a substantially U-shape with a recess facing the side where heater 25 is located. In order to satisfy the above-mentioned functions, reinforcing member 23 is preferably made of a metal material with high mechanical strength, such as stainless steel or iron.

[0028] In the present embodiment, a reflecting member 27 (reflecting plate) is fixed to the side of the reinforcing member 23 that faces the heater 25. This allows the heat (heat that heats the reinforcing member 23) from the heater 25 to be reflected by the reflecting member 27 and used to heat the fixing belt 21, thereby further improving the heating efficiency of the fixing belt 21. The same effect can be obtained even if a part or the whole of the surface of the reinforcing member 23 facing the heater 25 is subjected to a mirror finish or provided with a heat insulating material.

[0029] 2, the pressure roller 31 as a pressure member that contacts the outer peripheral surface of the fixing belt 21 at the position of the nip portion (fixing nip portion) has a diameter of about 30 mm, and is formed by forming an elastic layer 33 on a hollow core metal 32. The elastic layer 33 of the pressure roller 31 (pressure member) is made of a material such as foamed silicone rubber, silicone rubber, or fluororubber. A thin release layer made of PFA, PTFE, or the like may be provided on the surface of the elastic layer 33. The pressure roller 31 is pressed against the fixing belt 21 to form a desired nip portion between the two members. Also, referring to FIG. 3, the pressure roller 31 is provided with a gear 45 that meshes with a drive gear of a drive mechanism (not shown), and the pressure roller 31 is driven to rotate in the direction of the arrow (clockwise direction) in FIG. 2. Also, both ends of the pressure roller 31 in the width direction are rotatably supported by side plates 43 of the fixing device 20 via bearings 42. A heat source such as a halogen heater may be provided inside the pressure roller 31.

[0030] When the elastic layer 33 of the pressure roller 31 is made of a sponge-like material such as foamed silicone rubber, the pressure acting on the nip portion can be reduced, thereby reducing the load on the fixed member 16. Furthermore, the heat insulation of the pressure roller 31 is improved, and the heat of the fixing belt 21 is less likely to transfer to the pressure roller 31 side, thereby improving the heating efficiency of the fixing belt 21. In the present embodiment, the diameter of the fixing belt 21 is approximately equal to the diameter of the pressure roller 31, but the diameter of the fixing belt 21 can also be smaller than the diameter of the pressure roller 31. In that case, the curvature of the fixing belt 21 at the nip portion is smaller than the curvature of the pressure roller 31, so that the sheet P sent out from the nip portion is easily separated from the fixing belt 21.

[0031] 4, nip portion forming member 26 as a sliding member that slides against inner circumferential surface 21a (sliding surface) of fixing belt 21 has opposing surface 26a (surface that slides against fixing belt 21, see FIG. 6) with pressure roller 31 formed in a concave shape so as to conform to the curvature of pressure roller 31. As a result, sheet P is sent out from the nip portion so as to conform to the curvature of pressure roller 31, and it is possible to prevent a problem that sheet P after the fixing process is attracted to fixing belt 21 and is not separated. In this embodiment, the nip forming member 26 that forms the nip is formed in a concave shape, but the nip forming member 26 that forms the nip can also be formed in a flat shape. That is, the opposing surface 26a (the surface that slides against the fixing belt 21) of the nip forming member 26 can be formed in a flat shape. This makes the shape of the nip approximately parallel to the image surface of the sheet P, and the adhesion between the fixing belt 21 and the sheet P is increased, thereby improving the fixing performance. Furthermore, the curvature of the fixing belt 21 at the exit side of the nip is large, so that the sheet P sent out from the nip can be easily separated from the fixing belt 21.

[0032] In addition, the material for forming the nip portion forming member 26 as the sliding contact member may be a resin material or a metal material, but a resin material (such as a liquid crystal polymer, polyamideimide, polyimide, etc.) that has sufficient rigidity so as not to bend significantly even when subjected to the pressure from the pressure roller 31 and has heat resistance and heat insulation properties is preferable. Furthermore, the opposing surface 26a of the nip portion forming member 26 (including the case where the surface is coated) may have grooves or a convex pattern formed thereon.

[0033] It is preferable that the opposing surface 26a (the surface that comes into sliding contact with the fixing belt 21) of the nip portion forming member 26 is coated with a low-friction material (such as diamond-like carbon, PTFE, molybdenum disulfide, graphite, etc.) in order to reduce the sliding resistance with the fixing belt 21. In this case, a coating layer can be formed by forming a film on the opposing surface 26a of the nip portion forming member 26 made of a resin material by a method such as spray painting with paint having the above-mentioned low-friction material dispersed therein, and then baking the film. In addition, the opposing surface 26a of the nip portion forming member 26 (including the case where the surface is coated) may be coated with a lubricant (for example, silicone oil, silicone grease whose base oil is silicone oil, fluorosilicone oil, fluorosilicone grease whose base oil is fluorosilicone oil, fluorine oil, fluorine grease whose base oil is fluorine oil, or a combination of any two or more of these) in order to reduce sliding resistance with the fixing belt 21. In the present embodiment, heater 25 is used as a heating means for heating fixing belt 21. However, by using a ceramic heater or the like as nip portion forming member 26, nip portion forming member 26 functioning as a sliding contact member can also function as a heating means. In this case, facing surface 26a of nip portion forming member 26 may be made of an inorganic material such as glass or ceramics, or may have a resin coating formed on the outermost surface.

[0034] In this embodiment, the reinforcing member 23 (and the reflecting member 27) is disposed so as to isolate the space between the nip portion forming member 26 and the heater 25 (heating means). In this embodiment, the heater 25 is installed so as to face a relatively wide range of the circumferential direction of the fixing belt 21 (inner peripheral surface 21a), so that the fixing belt 21 can be heated without temperature unevenness in the circumferential direction even during heating standby (print operation standby). Therefore, after receiving a print request, the print operation can be performed promptly. In this case, in a conventional on-demand fixing device (see, for example, Japanese Patent No. 2884714), if the pressure roller is deformed and heat is applied during heating standby at the nip portion, depending on the material of the rubber of the pressure roller, thermal deterioration may occur, shortening the life of the pressure roller, or compression set may occur in the pressure roller (compression set of rubber increases when heat is applied to the deformation of the rubber). If compression set occurs in the pressure roller, a part of the pressure roller becomes concave, and the desired nip width cannot be obtained, causing poor fixing or abnormal noise during rotation. In contrast, in the present embodiment, reinforcing member 23 (and reflecting member 27) is provided between nip portion forming member 26 and heater 25 to block the heat of heater 25, so that heat is less likely to reach nip portion forming member 26 during heating standby. This reduces the inconvenience of pressure roller 31 being heated to a high temperature in a deformed state during heating standby, and makes it possible to prevent the above-mentioned problems from occurring.

[0035] Furthermore, when a lubricant is applied between the nip portion-forming member 26 and the fixing belt 21 to reduce frictional resistance between the two members, the lubricant may deteriorate when used under high-temperature conditions in addition to the high-pressure conditions at the nip portion, which may result in malfunctions such as slippage of the fixing belt 21. In contrast, in the present embodiment, reinforcing member 23 (and reflecting member 27) is provided between nip portion forming member 26 and heater 25 to block the heat of heater 25, making it difficult for the heat of heater 25 to reach the lubricant in the nip portion. This reduces deterioration of the lubricant due to high temperatures, and makes it possible to prevent the above-mentioned problems from occurring.

[0036] In addition, in this embodiment, since the reinforcing member 23 (and the reflecting member 27) is installed between the nip forming member 26 and the heater 25 so as to block the heat of the heater 25, the nip forming member 26 is insulated, and the fixing belt 21 is not actively heated in the nip. Therefore, the temperature of the sheet P fed into the nip is lowered when it is sent out of the nip. That is, at the exit of the nip, the temperature of the toner image fixed on the sheet P is lowered, the viscosity of the toner is reduced, and the toner adhesive force to the fixing belt 21 is reduced, and the sheet P is separated from the fixing belt 21 in this state. Therefore, the sheet P immediately after the fixing process is prevented from wrapping around the fixing belt 21 and causing a jam, and the toner is prevented from sticking to the fixing belt 21.

[0037] Hereinafter, a brief description will be given of the normal operation of the fixing device 20 configured as above. When the power switch of the device main body 1 is turned on, power is supplied to the heater 25, and the pressure roller 31 starts to rotate in the direction of the arrow in Fig. 2. As a result, the fixing belt 21 also rotates in the direction of the arrow in Fig. 2 due to the frictional force with the pressure roller 31 at the nip portion. Thereafter, the sheet P is fed from the paper feed unit 12, and an unfixed color image is carried (transferred) onto the sheet P at the position of the secondary transfer roller 89. The sheet P carrying the unfixed image T (toner image) is transported in the direction of the arrow Y10 in FIG. 2 while being guided by a guide plate (not shown), and is sent into the nip portion between the fixing belt 21 and the pressure roller 31, which are in a pressure-contact state. Then, the toner image T is fixed onto the surface of the sheet P by the heating of the fixing belt 21 heated by the heater 25 and the pressing force of the nip portion forming member 26 reinforced by the reinforcing member 23 and the pressure roller 31. Thereafter, the sheet P sent out from the nip portion is transported in the direction of the arrow Y11.

[0038] The fixing belt 21, which is a characteristic feature of the fixing device 20 (image forming apparatus 1) in this embodiment, will be described in detail below. As previously explained using Figures 2 to 4, etc., the fixing device 20 is provided with a fixing belt 21 as a belt member, a nip portion forming member 26 as a sliding contact member, a pressure roller 31 as a pressure member that is pressed against the nip portion forming member 26 (sliding contact member) via the fixing belt 21 to form a nip portion (fixing nip portion) through which the sheet P is transported, a flange 29, etc. The inner peripheral surface 21a of the fixing belt 21 (belt member) serves as a sliding contact surface that comes into sliding contact with the nip portion forming member 26 and the flange 29, which serve as sliding contact members.

[0039] Here, the fixing belt 21 (belt member) in this embodiment has a Martens hardness H1 [N / mm 2 ] is 20≦H1≦70, and the pencil hardness H2 is HB or more and 2H or less. More specifically, in this embodiment, the base layer 21A (the innermost layer in the laminated structure) of the fixing belt 21 has a surface layer 21Aa having a thickness of about 9 to 15 μm on the inner surface 21a (the surface that comes into contact with the nip portion forming member 26). This surface layer 21Aa (the inner surface 21a of the base layer 21A (fixing belt 21)) is a blend of polyimide varnish (or polyamide resin), PTFE, and carbon black, and has a Martens hardness H1 [N / mm 2 ] is adjusted to be 20≦H1≦70, and the pencil hardness H2 is adjusted to be HB or more and 2H or less.

[0040] The "Martens hardness" is an index that indicates the degree of hardness based on the load required to scratch a measurement object with an indenter and form a depression of a certain depth. Furthermore, "pencil hardness" refers to the hardest pencil scale value that does not leave a mark on the object being measured.

[0041] With this configuration, even if the nip portion forming member 26 or the flange 29 slides against the fixing belt 21, the wear of the fixing belt 21, the nip portion forming member 26, and the flange 29 can be reduced.

[0042] The reasons for this are explained in detail below. Conventionally, in the fixing nip of the fixing device 20, the sliding resistance between the inner circumferential surface 21a of the fixing belt 21 and the nip portion forming member 26 as a sliding contact member was large, and a lot of wear powder of these members was generated. In particular, even if a lubricant was applied to the sliding surfaces of these members to reduce the sliding resistance in the fixing nip, the viscosity of the lubricant increased due to mixing of the lubricant with the wear powder, and the driving torque of the device increased instead. To solve this problem, if the Martens hardness or pencil hardness of the fixing belt 21 is simply set to be large, the wear of the fixing belt 21 can be reduced, but the wear of the nip portion forming member 26 (sliding contact member) will be accelerated. This is because hardness is generally a characteristic that indicates hardness, that is, which of two different substances will be damaged when they are brought into sliding contact with each other. For this reason, in the past, attempts were made to solve the problem using two broad approaches: The first approach is to adjust the relationship between the hardness of the fixing belt and the hardness of the sliding contact member to a certain relationship, thereby minimizing the total amount of wear debris generated by both members. Although this approach has a certain effect, it is not possible to sufficiently reduce the wear of both members. In other words, this approach merely sets the point at which both members gradually wear out, thereby satisfying the lifespan of the fixing device, and does not sufficiently reduce the wear itself. The second approach is to use a lubricant to reduce contact between the two components. In this approach, it is important to control the oil film formed by the lubricant, and it is theoretically possible to completely prevent wear by controlling the material and surface properties. However, due to the limitations of mechanical precision, such as slight unevenness and undulations in organic materials, it was difficult to completely lubricate both components without contact. In addition, when a fixing device is designed to perform at its best at high temperatures, the driving torque increases at low temperatures, making it difficult to set the temperature range that can be handled. In addition, it was very difficult to practically realize an ideal oil film due to the absorption of lubricant by organic materials, volatilization, and wear caused by exogenous impurities.

[0043] In order to solve such problems, the inventors of the present application made extensive efforts through analysis, experiments, etc., and as a result, they focused on two types of hardness, Martens hardness H1 and pencil hardness H2, and discovered that by manufacturing a fixing belt 21 having an inner surface 21a (sliding surface) with opposing properties, namely, setting the Martens hardness H1 low and setting the pencil hardness H2 high, it is possible to reduce wear on the inner surface 21a of the fixing belt 21 and also reduce wear on the sliding member (nip portion forming member 26). The inner circumferential surface 21a of the fixing belt 21, which has a low Martens hardness and a high pencil hardness, exhibits a suspension effect by softening and deforming the surface layer 21Aa having the inner circumferential surface 21a, even if the sliding pressure increases locally and temporarily due to the influence of slight roughness, undulations, vibrations, etc. present in the sliding contact member (nip portion forming member 26). Therefore, a highly robust sliding state can be realized, and it becomes possible to prevent wear of the sliding contact member (nip portion forming member 26) while preventing wear of the inner circumferential surface 21a of the fixing belt 21. The Martens hardness contains a relatively large amount of hardness information in the vicinity of the outermost surface. In contrast, the pencil hardness contains a relatively large amount of information about the adhesive strength between the surface layer 21Aa and its underlying layer. In other words, the surface layer 21Aa, which is soft on the surface but hard inside and firmly adheres to the underlying layer, does not wear out the sliding member and does not wear out itself.

[0044] FIG. 6 is an enlarged view of a portion where the inner circumferential surface 21a (surface layer 21Aa) of the fixing belt 21 and the opposing surface 26a of the nip portion forming member 26 make sliding contact with each other. As shown in FIG. 6(A), when at least one of the inner circumferential surface 21a (surface layer 21Aa) and the opposing surface 26a is made of an organic material, the inner circumferential surface 21a and the opposing surface 26a are not mirror surfaces but have a certain degree of roughness. However, in this embodiment, the Martens hardness of the inner circumferential surface 21a (surface layer 21Aa) is set low and the pencil hardness is set high, so that the surface layer 21Aa is very soft and has a high ability to deform. Therefore, even if the inner circumferential surface 21a and the opposing surface 26a are in sliding contact with each other for a long time and are affected by the roughness, waviness, vibration, contamination, etc. of both, the displacement is buffered, and the inner circumferential surface 21a and the opposing surface 26a slide in contact with each other while maintaining the roughness as it is, without being worn down, as shown in Fig. 6 (B). In other words, the sliding resistance between the inner circumferential surface 21a and the opposing surface 26a is prevented from increasing locally and temporarily, and wear debris is less likely to be generated on the inner circumferential surface 21a and the opposing surface 26a. In other words, since the surface layer 21Aa is very soft, wear particles are unlikely to be generated not only from the fixing belt 21 (surface layer 21Aa) but also from the nip portion forming member 26 (opposing surface 26a). In contrast, when the conventional fixing belt 121 (see FIG. 7) is used, if the inner circumferential surface 121a (base material layer 121A) of the fixing belt 121 and the opposing surface 26a of the nip portion forming member 26 are in sliding contact with each other for a long time, wear progresses from a portion where the sliding pressure is locally and temporarily increased due to the influence of the roughness, undulation, vibration, contamination, etc. of both. Therefore, wear debris generated by such wear further generates a local pressure increase, and even if the inner circumferential surface 121a and the opposing surface 26a initially have roughness, the inner circumferential surface 121a and the opposing surface 26a eventually become almost mirror-like, as shown in FIG. 7. Then, if the wear between the inner circumferential surface 121a and the opposing surface 26a becomes large in this way, problems such as an increase in the driving torque of the device and a decrease in the original functions of the fixing belt 1 and the nip portion forming member 26 occur.

[0045] In contrast, when the fixing belt 21 of the present embodiment is used, it is possible to reduce wear of the fixing belt 21 and the nip portion forming member 26 (and the flange 29) over time. Moreover, when paying attention to the process of wear debris generation from the inner circumferential surface 21a (surface layer 21Aa), the inner circumferential surface 121a of the conventional fixing belt 121 (see FIG. 7) receives a deformation force from the sliding contact member (nip portion forming member 26), and when the generated displacement reaches a limit, a part of the inner circumferential surface 121a falls off as wear debris. Therefore, in the present embodiment, when the inner circumferential surface 21a (surface layer 21Aa) of the fixing belt 21 receives a deformation force, the Martens hardness of the inner circumferential surface 21a (surface layer 21Aa) is not made hard to resist the deformation force, but rather, in order to prevent displacement from easily occurring and wear debris from falling off the film, the Martens hardness of the inner circumferential surface 21a (surface layer 21Aa) is made low and the pencil hardness is made high. In other words, the Martens hardness is an index of the susceptibility of the outermost surface (inner surface 21a) to scratches on the opposing member (nip portion forming member 26), while the pencil hardness is an index of the resistance of the surface film to falling off when subjected to an impact force (attack) from the opposing member (nip portion forming member 26). Therefore, the fixing belt 21, which has the contradictory properties of low Martens hardness and high pencil hardness, is useful in preventing wear.

[0046] Here, the fixing belt 21 (belt member) in this embodiment is formed so that the permanent deformation when measuring the Martens hardness H1 on the inner surface 21a (sliding contact surface) is 50% or more and 80% or less with respect to the indentation depth. In addition, in the fixing belt 21 (belt member) in the present embodiment, the thickness of the surface layer 21Aa having the inner circumferential surface 21a (sliding contact surface) is set to 10 μm or more. With this configuration, the effect of reducing wear on the fixing belt 21, the nip portion forming member 26, and the flange 29 described above can be further achieved.

[0047] The reasons for this are explained in detail below. When the inner circumferential surface 21a (surface layer 21Aa) of the fixing belt 21 receives a deforming force from the nip portion forming member 26, in order to cushion the load caused by the force, it is preferable that the surface layer 21Aa of the fixing belt 21 is easily deformed and has a large layer thickness. Moreover, the deformation of the inner circumferential surface 21a (surface layer 21Aa) at that time is not elastic deformation but plastic deformation, which maintains the effect of reducing the generation of wear particles for a long time. Therefore, the surface layer 21Aa, in which the permanent strain (residual strain) in the Martens hardness measurement is 50% or more relative to the indentation depth and the layer thickness is 10 μm or more, can significantly reduce the wear of both the fixing belt 21 and the nip portion forming member 26 for a long period of time. This is because, when a material with excellent elastic deformability is used as the surface layer 21Aa, it can be kept in a completely scratch-free state while the deformation is within the elastic deformation range, but if the deformation exceeds the elastic deformation range, cohesive failure, that is, the generation of wear powder, occurs. This is thought to be because, in general, materials with excellent elastic deformability have a cross-linked structure, a high molecular weight, and few grain boundaries, and therefore, when the limit of elastic deformation is exceeded, irreversible breakage of the molecular structure or fatigue failure occurs. On the other hand, when a soft material with excellent plastic deformability is used for the surface layer 21Aa, due to a low molecular weight, a large number of grain boundaries, etc., even if the deformation exceeds the range of plastic deformation, the material is unlikely to become liberated as wear debris and is thought to re-stabilize in the deformed state. For these reasons, when the deformation of the inner circumferential surface 21a (surface layer 21Aa) of the fixing belt 21 is a plastic deformation rather than an elastic deformation, even if the inner circumferential surface 21a (surface layer 21Aa) is scratched, wear debris is less likely to be generated, and this effect is maintained for a long time.

[0048] Here, the fixing belt 21 (belt member) in the present embodiment is formed so that the emissivity of the inner circumferential surface 21a (sliding surface) is 0.94 or more. Specifically, the material and color of the fixing belt 21 (particularly, the surface layer 21Aa) are selected so as to achieve such emissivity. This "emissivity" is the ease with which an object radiates heat, and is expressed as a number between 0 and 1 (the closer to "0," the less likely it is to radiate heat, and the closer to "1," the easier it is to radiate heat). Emissivity is the emissivity when the temperature of the object's surface is measured with a thermometer and the measured temperature matches the temperature of the radiation thermometer set to "1" for thermal radiation. Furthermore, "emissivity" also refers to the ease with which the thermal energy of light can be received. Therefore, if a fixing belt 21 with high emissivity is used, the thermal energy generated by the heater 25 can be efficiently received, and energy loss can be reduced, resulting in a fixing device 20 with a long life and high energy. In particular, if the emissivity of the fixing belt 21 falls below 0.94, sufficient energy saving properties and durability cannot be obtained. In the fixing device 20 of the present embodiment, the emissivity of the fixing belt 21 (the inner circumferential surface 21a) is set to 0.94 or more, so that it is possible to improve energy saving properties and durability.

[0049] Hereinafter, the conditions and results of an experiment conducted by the present inventor to confirm the effects of the present invention will be described with reference to FIG. As shown in FIG. 8, ten fixing belts 21 having different Martens hardness and pencil hardness (and permanent set) were used as Examples 1 to 5 and Comparative Examples 1 to 5 to conduct experiments to confirm the durability of the fixing belt 21 (fixing device 20).

[0050] The “Martens hardness” of the inner surface 21a of the fixing belt 21 was measured using a measuring device “Fischerscope HCU H100VP” under the following measurement conditions: a diamond indenter (face angle 136°), an indentation depth of 5 μm, and an indentation speed of 5 μm / 20 s (same for both loading and unloading). The measurement was performed 10 times in an environment of 23°C, and the average value was used. In order to reduce floating during the measurement, the measurement was performed by fixing the fixing belt 21 to a metal stage having a flat surface with a radius of about 20 mm. If there was an elastic layer made of silicone rubber or PFA on the inner peripheral surface 21a side of the fixing belt 21, it was removed, and the measurement was performed so that the base layer 21A (made of stainless steel, nickel, polyimide, etc.) of the fixing belt 21 was in direct contact with the metal stage. In addition, fixing by sticking double-sided tape on the back side was avoided. The Martens hardness was measured at a depth of 1 μm. Also, "permanent strain" in Fig. 8 is the residual strain of the inner circumferential surface 21a (surface layer 21Aa), and is expressed as a percentage of the value obtained by dividing the indentation depth of 5 [μm] by the value [μm] of the indentation depth at the moment of no load at the end of the experiment, which is read from the indentation depth vs. load curve. In other words, "permanent strain" in Fig. 8 is the ratio (%) of the permanent strain to the indentation depth when measuring the Martens hardness.

[0051] On the other hand, the "pencil hardness" of the inner circumferential surface 21a of the fixing belt 21 was measured in accordance with JIS-K5600. However, the pencils (pencil scale) used were manufactured by MITSUBISHI. In addition, in order to evaluate the scratches, only the adhesion of the surface layer 21Aa to the base layer 21A was to be evaluated, so a state in which the surface layer 21Aa was scraped off and the main part of the base layer 21A was completely exposed was judged as "failed." For example, if the base layer 21A is stainless steel or nickel, it is judged as "failed" when no surface layer 21Aa remains in the area scratched with the pencil and the metallic luster is clearly visible. In contrast, if even a small amount of the surface layer 21Aa remained at the scratched area, the pencil scale was marked as "passed." For example, if some of the surface layer 21Aa remains, the main part of the base layer 21A may be visible through the scratched area, and in such a case, the pencil scale was marked as "passed." The remaining surface layer 21Aa was measured using a micrometer or a laser microscope, and if the remaining surface layer 21Aa was found to be 1 μm or more, it was deemed to be "passed." When it was unclear whether the test passed or failed, the pencil scale hardness was increased until it was confirmed that the main part of the base layer 21A was completely exposed, which was deemed to be a failure.

[0052] The "durability evaluation" of the fixing belt 21 was performed by installing the fixing belts 21 of Examples 1 to 5 and Comparative Examples 1 to 5 in a fixing device 2 (installed in an electrophotographic image forming apparatus manufactured by Ricoh Co., Ltd.) shown in FIG. 2, which was modified to remove unnecessary parts for the evaluation. The "durability evaluation" was performed by applying a predetermined pressure and temperature to the fixing belt 1, repeating a running sequence during printing, and using the highest value of the motor drive torque [N / m] until the total running distance calculated from the outer diameter of the fixing belt 21 reached 500 [km]. The drive torque during the evaluation was not an instantaneous value during operation or when stopped, but a value during running at the running speed to be evaluated (for example, 300 [mm / s]). The amount of lubricant applied to the fixing belt 21 was the amount specified for the product (for example, 5 g), and was not replenished after the evaluation began. In addition, because the motor drive torque [N / m] depends on the size, configuration, and linear speed of the device, the percentage normalized by the rated value of the motor drive torque (for example, 1.0 [N / m]) was used as the "durability evaluation result." If 0≦100×maximum drive torque value / rated drive torque value<100[%], the torque was deemed OK (judgment: "○"), and if 100[%]≦100×maximum drive torque value / rated drive torque value, the torque was deemed NG (judgment: "X").

[0053] The fixing belt 21 used in "Example 1" in Fig. 8 is a belt in which an elastic layer made of silicone rubber with a layer thickness of 0.2 mm is formed on a base material layer 21A made of nickel, and then a release layer made of PFA with a layer thickness of 0.03 mm is further formed on the surface of the elastic layer. The fixing belt 21 uses a surface layer 21Aa of the base material layer 21A with a layer thickness of 15 µm, which is spray-painted with 20 wt% polyimide varnish, 80 wt% PTFE particles, and carbon black, and is finally baked at 300°C. However, the polyimide varnish is mixed by weight after hardening. Then, the final baking is performed at 300°C. In contrast, the fixing belt 21 used in "Example 2" is similar to that in "Example 1" except that the surface layer 21Aa of the base layer 21A has a layer thickness of 13 μm and is finally baked at 330°C. The fixing belt 21 used in "Example 3" is similar to that in "Example 1" except that the surface layer 21Aa of the base layer 21A has a layer thickness of 21 μm and is finally baked at 280°C. The fixing belt 21 used in "Example 4" is similar to that in "Example 1" except that the surface layer 21Aa of the base material layer 21A has a thickness of 9 μm, is spray-painted with 20% by weight of polyamideimide resin, 80% by weight of PTFE particles, and carbon black, and is finally baked at 270°C. The fixing belt 21 used in "Example 5" is similar to that in "Example 4" except that the surface layer 21Aa of the base layer 21A has a layer thickness of 14 μm and is finally baked at 300°C.

[0054] The fixing belt 21 used in "Comparative Example 1" in FIG. 8 is similar to that in "Example 1" except that the surface layer 21Aa of the base layer 21A has a thickness of 10 μm, is spray-painted with 30% by weight of polyamideimide resin, 70% by weight of PTFE particles, and carbon black, and is finally baked at 300° C. The fixing belt 21 used in "Comparative Example 2" is similar to that in "Example 1" except that the surface layer 21Aa of the base layer 21A has a layer thickness of 15 μm and is finally baked at 230°C. The fixing belt 21 used in "Comparative Example 3" is similar to that in "Example 1" except that the surface layer 21Aa of the base layer 21A has a thickness of 13 μm, is spray-painted with 60% by weight of polyimide varnish, 40% by weight of PTFE particles, and carbon black, and is finally baked at 350°C. The fixing belt 21 used in "Comparative Example 4" is similar to that in "Example 1" except that the surface layer 21Aa of the base layer 21A has a thickness of 9 μm, is spray-painted with 10% by weight of polyimide varnish, 90% by weight of PTFE particles, and carbon black, and is finally baked at 280°C. The fixing belt 21 used in "Comparative Example 5" is similar to that in "Example 1" except that the surface layer 21Aa of the base layer 21A has a thickness of 9 μm, is spray-painted with 30% by weight of polyimide varnish, 70% by weight of PTFE particles, and carbon black, and is finally baked at 330°C.

[0055] The effects of the present invention described above can also be confirmed from the experimental results of Examples 1 to 5 and Comparative Examples 1 to 5 in FIG. That is, the Martens hardness H1 [N / mm 2 By using the fixing belt 21 formed so that the pencil hardness H2 is HB or more and 2H or less, the wear of the fixing belt 21 and the nip portion forming member 26 is sufficiently reduced, and the increase in the drive torque of the device (reduction in durability) is mitigated. In addition, the above-mentioned effects are further enhanced by using a fixing belt 21 in which the permanent strain when measuring the Martens hardness H1 on the inner surface 21a is 50% or more and 80% or less relative to the indentation depth, and the thickness of the surface layer 21Aa is set to 10 μm or more.

[0056] <Modification> As shown in FIG. 9, the fixing device 20 in the modified example is of an electromagnetic induction heating type, and the fixing belt 21 is heated by electromagnetic induction. As shown in FIG. 9, the fixing device 20 in the modified example is also composed of a fixing belt 21 (belt member), a nip portion forming member 26 (sliding contact member), a reinforcing member 23, a pressure roller 31 (heating member), a temperature sensor 40, etc., similar to that in FIG. Here, in the fixing device 20 in the modified example, an induction heating section 50 is provided as a heating means instead of the heater 25. The fixing belt 21 in the modified example is heated by electromagnetic induction by the induction heating section 50. The induction heating unit 50 is composed of an excitation coil, a core, a coil guide, and the like. The excitation coil is a Litz wire made of bundled thin wires that is extended in the width direction (the direction perpendicular to the paper surface of FIG. 9) so as to cover a part of the fixing belt 21. The coil guide is made of a highly heat-resistant resin material or the like, and holds the excitation coil and the core. The core is a semi-cylindrical member made of a ferromagnetic material such as ferrite (relative magnetic permeability is about 1000 to 3000), and is provided with a center core and a side core to form an efficient magnetic flux toward the fixing belt 21. The core is disposed so as to face the excitation coil that is extended in the width direction. On the other hand, in addition to the base layer, elastic layer, and release layer described with reference to Fig. 2 and the like, a heat generating layer (for example, it can be formed between the elastic layer and the release layer, or the base layer can be used as the heat generating layer) that is electromagnetically induction heated by the induction heating unit 50 is formed in the fixing belt 21. The material of the heat generating layer can be nickel, stainless steel, iron, copper, cobalt, chromium, aluminum, gold, platinum, silver, tin, palladium, an alloy made of a plurality of these metals, or the like. 9, the fixing belt 21 is heated at a position facing the induction heating unit 50. In more detail, by passing a high-frequency alternating current through the excitation coil, magnetic lines of force are formed around the fixing belt 21 so that they alternate in both directions. At this time, eddy currents are generated on the surface of the heat generating layer of the fixing belt 21, and Joule heat is generated due to the electrical resistance of the heat generating layer itself. This Joule heat causes electromagnetic induction heating of the heat generating layer, and the fixing belt 21 is heated. In the thus configured electromagnetic induction heating type fixing device 20, the Martens hardness H1 [N / mm 2 ] is 20≦H1≦70, and the pencil hardness H2 is HB or more and 2H or less. This sufficiently reduces wear of the fixing belt 21 and the nip portion forming member 26 due to sliding contact with the nip portion forming member 26 (sliding contact member).

[0057] As described above, the fixing belt 21 (belt member) in the present embodiment has a Martens hardness H1 [N / mm 2 ] is 20≦H1≦70, and the pencil hardness H2 is HB or more and 2H or less. This sufficiently reduces wear of the fixing belt 21 and the nip portion forming member 26 due to sliding contact with the nip portion forming member 26 (sliding contact member).

[0058] In this embodiment, the present invention is applied to the fixing belt 21 as a belt member, but the belt member to which the present invention is applied is not limited to this, and the present invention can be applied to all belt members that come into sliding contact with a sliding member, for example, the intermediate transfer belt 78. In addition, in this embodiment, the fixing belt 21 is configured to be in sliding contact with both the nip portion forming member 26 and the flange 29, but is not limited to this configuration. For example, the fixing belt 21 can be configured to be in sliding contact only with the nip portion forming member 26, or the fixing belt 21 can be configured to be in sliding contact with other members. In the present embodiment, the sliding member is configured to be in sliding contact with the inner peripheral surface 21a of the fixing belt 21, but the sliding member may be configured to be in sliding contact with the outer peripheral surface (or both surfaces) of the fixing belt. In that case, the Martens hardness and pencil hardness of the outer peripheral surface (or both surfaces) of the fixing belt are optimized. In addition, in this embodiment, the base material layer 21Aa of the fixing belt 21 is provided with a surface layer 21Aa whose Martens hardness and pencil hardness are optimized. However, it is also possible to optimize the Martens hardness and pencil hardness of the base material layer 21Aa itself without providing the surface layer 21Aa. In these cases, the same effects as those of this embodiment can be obtained.

[0059] It is clear that the present invention is not limited to the present embodiment, and that the present embodiment may be modified as appropriate within the scope of the technical concept of the present invention in addition to the modifications suggested in the present embodiment. Furthermore, the number, position, shape, etc. of the components are not limited to the present embodiment, and may be any number, position, shape, etc. suitable for implementing the present invention. [Explanation of symbols]

[0060] 1 Image forming apparatus (image forming apparatus main body), 20 Fixing device, 21 Fixing belt (belt member), 21A base material layer, 21Aa surface layer, 21a Sliding surface, 25 heater (heating means), 26 Nip portion forming member (sliding contact member), 26a Opposite surface, 31 Pressure roller (pressure member). [Prior art documents]

Patent Document

[0061]

Patent Document 1

Claims

1. A fixing belt having an inner circumferential surface that serves as a sliding contact surface that comes into sliding contact with a nip portion forming member serving as a sliding contact member, Martens hardness H1 on the sliding surface [N / mm 2 and the pencil hardness H2 is in the range of HB to 2H.

2. 2. The fixing belt according to claim 1, wherein a permanent deformation in measuring a Martens hardness on the sliding contact surface is 50% or more and 80% or less with respect to a pressing depth.

3. 3. The fixing belt according to claim 1, wherein the surface layer having the sliding contact surface has a thickness of 10 [mu]m or more.

4. 4. The fixing belt according to claim 1, wherein the emissivity of the sliding contact surface is 0.94 or more.

5. The inner circumferential surface is a surface layer formed on the inner circumferential surface side of a base material layer, 5. The fixing belt according to claim 1, wherein the surface layer is a mixture of polyimide varnish or polyamide resin, polytetrafluoroethylene, and carbon black.

6. A fixing belt according to any one of claims 1 to 5, The nip portion forming member, a pressing member that is in pressure contact with the nip portion forming member via the fixing belt to form a nip portion through which a sheet is conveyed; A fixing device comprising:

7. An image forming apparatus comprising the fixing device described in claim 6.

Images