Fixing Belt, Fixing Device, and Image Forming Apparatus

Abstract

To provide a fixing belt that can reduce slide resistance torque and can perform stable sliding over time.SOLUTION: A fixing belt 101 is supported by a nip forming member 103 from an inner face side and rotates while sliding over the nip forming member to fix a toner image on a recording medium to the recording medium. The fixing belt has a base material made of metal, and a slide layer that is on an inner peripheral side of the base material and slides over the nip forming member. The slide layer includes polyimide resin, and the elastic power of the slide layer is 70% or more and 85% or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a fixing belt, a fixing device, and an image forming apparatus.

Background Art

[0002] Conventionally, in the fixing process of the electrophotographic method, cost reduction by energy saving and compactification has become mainstream, and sliding fixing technology has been widely used. In the sliding fixing technology, mainly the inner peripheral surface of the fixing belt and the member facing it are slid.

[0003] In many cases, a sliding layer is provided on the inner peripheral surface of the fixing belt, and a lubricant is mainly used for the sliding portion. Conventionally, technical development has been underway on how to reduce sliding resistance and improve durability.

[0004] Patent Document 1 discloses that the rubbing layer of the fixing belt is a polyimide resin layer formed by mixing a first polyimide precursor and a second polyimide precursor having a loss elastic modulus larger than that of the first polyimide precursor. According to Patent Document 1, by adopting the above configuration, a configuration having excellent flexibility and high wear resistance can be realized.

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the conventional technology, the sliding resistance torque is high, and further improvement is required for durability and the like when used over a long period. When the sliding resistance torque is high, the fixing belt may break due to use over time.

[0006] Therefore, an object of the present invention is to provide a fixing belt capable of reducing the sliding resistance torque and performing stable sliding over time.

Means for Solving the Problems

[0007] In order to solve the above problems, the fixing belt of the present invention is a fixing belt that is supported from the inner surface side by a nip forming member, rotates while sliding on the nip forming member, and fixes the toner image on the recording medium to the recording medium. It has a base material made of metal and a sliding layer that is on the inner peripheral side of the base material and slides on the nip forming member. The sliding layer contains a polyimide-based resin, and the elastic work rate of the sliding layer is 70% or more and 85% or less.

Effects of the Invention

[0008] According to the present invention, it is possible to provide a fixing belt that can reduce the sliding resistance torque and perform stable sliding even over time.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0010] Hereinafter, the fixing belt, fixing device, and image forming apparatus according to the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments shown below, and can be changed within the scope that those skilled in the art can conceive, such as other embodiments, additions, modifications, deletions, etc. As long as the functions and effects of the present invention are achieved in any aspect, it is included in the scope of the present invention.

[0011] (Fixing Belt and Fixing Device) The fixing belt of the present invention is a fixing belt that is supported from the inner surface side by a nip forming member and rotates while sliding on the nip forming member to fix a toner image on a recording medium to the recording medium. The fixing belt has a base material made of metal and a sliding layer that is on the inner circumferential side of the base material and slides on the nip forming member. The sliding layer contains a polyimide-based resin, and the elastic work rate of the sliding layer is 70% or more and 85% or less.

[0012] The fixing device of the present invention includes the fixing belt of the present invention, a pressing member disposed at a position facing the fixing belt, and a nip forming member that supports the fixing belt from the inner surface side and forms a fixing nip.

[0013] An example of the fixing device of the present invention will be described with reference to FIG. 1. FIG. 1 is a schematic cross-sectional view of the fixing device according to the present embodiment.

[0014] First, an overview of the fixing device 100 of the present embodiment will be described. The fixing device of the present embodiment includes a fixing belt 101, a pressure roller 102 disposed at a position facing the fixing belt 101, and a nip forming member 103 that supports the fixing belt 101 from the inner surface side and forms a fixing nip. Other members are provided as necessary.

[0015] The fixing belt 101 is supported from the inner surface side by the nip forming member 103 and rotates while sliding on the nip forming member 103 to fix the toner image 106 on the recording medium 107 to the recording medium 107. The fixing belt 101 is, for example, a surface endless moving body with a hollow interior.

[0016] The pressure roller 102 is an example of a pressing member provided facing the fixing belt 101 and is a rotatable rotating body.

[0017] Inside the fixing belt 101, a nip forming member 103 for forming a fixing nip portion N (also referred to as a fixing nip, nip portion, nip, etc.) is disposed. The nip forming member 103 heats the fixing belt 101. Further, a fixing member 104 for fixing the nip forming member 102 is disposed, and as the fixing member 104, for example, a fixing pad is used.

[0018] A lubricant may be applied to the sliding surfaces of the inner side of the fixing belt 101 and the nip forming member 103 in order to ensure lubricity.

[0019] In the present embodiment, the nip forming member 103 also functions as a backup member of the fixing nip portion N. The nip forming member 103 in the present embodiment forms the fixing nip portion N and also functions as a heat source for heating the fixing belt 101.

[0020] In addition to the above, the fixing device of the present embodiment may have a temperature sensor as temperature detecting means for detecting the temperature of the fixing belt 101. Further, the fixing device of the present embodiment may have a separating member as recording medium separating means for separating the recording medium 107 from the fixing belt 101. Further, the fixing device of the present embodiment may have a pressing means for pressing the pressing roller 102 against the fixing belt 101.

[0021] <Fixing Belt> As the fixing belt 101 in the present embodiment, an endless belt member that is thin and flexible can be used.

[0022] An example of the fixing belt will be described with reference to FIG. 2. FIG. 2 shows a cross-sectional view of the fixing belt 101. The fixing belt 101 in this example has a base material 202 made of metal and a sliding layer 201 that is on the inner peripheral side of the base material 202 and slides on the nip forming member 103, and has other layers as necessary.

[0023] <<Base Material>> As the metal in the base material 202, it can be appropriately selected, and examples thereof include metal materials such as nickel, copper, and stainless steel. Further, the base material 202 may be a single layer or a plurality of layers.

[0024] <<Sliding layer>> A sliding layer 201 containing a polyimide-based resin is provided on the inner peripheral surface of the base material 202. As the polyimide-based resin used for the sliding layer 201, for example, polyimide (BPDA / PDA) having a chemical structural formula as shown in the following structural formula (1) can be used.

[0025]

Chemical formula

[0026] The polyimide-based resin used for the sliding layer 201 preferably does not contain an ether bond as shown in the above structural formula (1). By not including an ether bond in the sliding layer, the affinity with the lubricant is ensured, and a stable driving torque can be obtained, so that the device can have a long life.

[0027] In addition to the above, as the polyimide-based resin used for the sliding layer 201, for example, polyimide (BPDA / ODA) having a chemical structural formula as shown in the following structural formula (2) may be used. By using the polyimide-based resin shown in the following structural formula (2), flexibility such as flexibility and elongation can be imparted.

[0028]

Chemical formula

[0029] Also, the polyimide shown in structural formula (1) and the polyimide shown in structural formula (2) may be mixed and used. By mixing, a function that can achieve both heat resistance and flexibility can be imparted.

[0030] The general chemical formula of an ether bond is shown in the following general formula (1). In general formula (1), R and R’ may be the same or different.

[0031]

Chemical formula

[0032] In addition to the above, examples of polyimide resins include polyamideimide (PAI). PAI has a high melting point and can be used at high temperatures.

[0033] As the polyimide resin used for the sliding layer 201, for example, a resin dissolved in a solvent such as varnish can be used. For example, a mixed solution obtained by mixing a polyimide resin or a polyimide resin precursor dissolved in varnish and a solvent is applied to the base material 202 by, for example, spray coating. Note that a filler or the like may be added to the mixed solution for the purpose of imparting abrasion resistance or the like.

[0034] As a method for forming the sliding layer 201, it can be appropriately selected. For example, the above mixed solution is applied to the base material 202 by spray coating or the like and dried. Next, coating and drying are repeated until a predetermined thickness is reached. Further, secondary drying is performed and firing is carried out. The firing can be performed using, for example, a vertical continuous far-infrared heating furnace.

[0035] In the present embodiment, the elastic work rate of the sliding layer 201 is 70% or more and 85% or less. By setting the elastic work rate of the sliding layer in the fixing belt to 70% or more and 85% or less, stable low torque can be maintained and breakage of the fixing belt can be suppressed. Therefore, according to the present invention, the sliding resistance torque can be reduced and stable sliding can be performed over time. Thereby, the life of the device can be extended. Further, according to the present invention, abrasion due to rubbing with the sliding partner can be prevented, and the driving torque can be stabilized in a process that does not generate abrasion powder.

[0036] In the present invention, it is necessary that the sliding layer 201 contains a polyimide-based resin and the elastic work ratio of the sliding layer 201 is 70% or more and 85% or less. Even if the elastic work ratio of the sliding layer 201 is 70% or more and 85% or less, when the sliding layer 201 does not contain a polyimide-based resin, the heat resistance is insufficient, and elongation or breakage occurs due to softening by heat, resulting in the inability to maintain the shape.

[0037] As a method for setting the elastic work ratio of the sliding layer 201 within the above range, it can be appropriately selected. For example, a method of appropriately adjusting the temperature (firing temperature) at which the above firing is performed can be mentioned. There is a difference in the elastic work ratio of the sliding layer 201 after firing depending on the firing temperature. The higher the firing temperature, the higher the elastic work ratio, and the lower the firing temperature, the lower the elastic work ratio.

[0038] As a method for measuring the elastic work ratio of the sliding layer 201, measurement is performed using a Fischer microhardness tester under the conditions of a penetration depth of 1.5 μm and 23°C. As a measurement sample, a fixing belt having the sliding layer 201 is cut into strips of a predetermined size, and one such strip is taken as one sample. Five measurements are made at five locations for each such sample, and the average value can be obtained to determine the elastic work ratio of the sliding layer 201.

[0039] It is preferable that the hardness of the sliding layer 201 is smaller than the hardness of the nip forming member 103. In this case, wear and damage on the side of the nip forming member 103 with a small sliding area can be suppressed, and a stable driving torque can be obtained, so that the life of the device can be extended.

[0040] In the present embodiment, examples of the hardness include martensite hardness. The martensite hardness of the sliding layer 201 and the nip forming member 103 is measured in the same manner as the method for measuring the elastic work ratio. The martensite hardness of the sliding layer 201 can be measured simultaneously with the measurement of the elastic work ratio of the sliding layer 201.

[0041] The sliding layer 201 may contain other resins. Examples of other resins include polyphenylene sulfide (PPS), etc. PPS has a high melting point and can be used at high temperatures. Other resins include fluorine resins such as PFA and PTFE, etc. PFA and PTFE improve the sliding property. When other resins are contained in the sliding layer 201, it is preferable to contain 40% by mass or more of the polyimide-based resin in the sliding layer 201.

[0042] <<Other Layers>> -Release Layer- The fixing belt 101 may have other layers in addition to the above. For example, a release layer 204 may be provided on the outer peripheral side of the fixing belt 101. The release layer 204 is in contact with the pressure roller 102. The release layer 204 is formed of, for example, tetrafluoroethylene perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), etc.

[0043] As a method for forming the release layer 204, it can be appropriately selected. For example, a method of forming a coating film using spray coating or dipping coating, etc. can be mentioned.

[0044] -Elastic Layer- Also, an elastic layer 203 may be provided between the base material 202 and the release layer 204. The elastic layer 203 is formed of a rubber material such as silicone rubber, foamed silicone rubber, fluorine rubber, etc. Silicone rubber is often filled with a filler for imparting heat resistance and a filler for enhancing thermal conductivity.

[0045] As a method for forming the elastic layer 203, it can be appropriately selected. For example, a method of forming a coating film using dipping coating or die coating, etc. can be mentioned.

[0046] <<Thickness of Each Layer and Diameter of the Fixing Belt>> The thickness of each layer in the fixing belt 101 is not particularly limited and can be appropriately selected. In this embodiment, it is preferably thin and has a small diameter. In this case, the heat capacity can be reduced.

[0047] The thickness of the base material 202 is preferably 20 μm or more and 50 μm or less. The thickness of the sliding layer 201 is preferably 5 μm or more and 20 μm or less. The thickness of the elastic layer 203 is preferably 50 μm or more and 300 μm or less. The thickness of the release layer 204 is preferably 5 μm or more and 30 μm or less.

[0048] The thickness of the entire fixing belt 101 is preferably 1 mm or less, more preferably 0.2 mm or less, and even more preferably 0.18 mm or less. By being 0.2 mm or less, a further reduction in heat capacity can be achieved.

[0049] The diameter of the fixing belt 101 is preferably 20 mm or more and 50 mm or less, and more preferably 30 mm or less. Here, the diameter refers to the outer diameter.

[0050] Note that the diameter of the pressure roller 102 described later is preferably 20 mm or more and 50 mm or less, and is often set such that the diameters of the fixing belt 101 and the pressure roller 102 are equal. However, this embodiment is not limited to this configuration. For example, the diameter of the fixing belt 101 may be configured to be smaller than the diameter of the pressure roller 102. In this case, since the curvature of the fixing belt 101 in the fixing nip portion N is smaller than the curvature of the pressure roller 102, the recording medium 107 discharged from the fixing nip portion N is more likely to be separated from the fixing belt 101.

[0051] <Pressing member> The pressure roller 102 in this embodiment can be appropriately selected. Although not shown in FIG. 1, the pressure roller 102 in this embodiment is composed of a core metal, an elastic layer, and a release layer.

[0052] As the core metal, any metal material can be used. The elastic layer is disposed on the surface of the core metal, and for the elastic layer, for example, foamed silicone rubber, silicone rubber, fluororubber, etc. can be used. The release layer is provided on the surface of the elastic layer, and for the release layer, for example, PFA, PTFE, etc. can be used.

[0053] The pressure roller 102 is pressed, for example, by a pressing means toward the fixing belt 101. Thereby, the fixing nip portion N is formed by the fixing belt 101, the nip forming member 103, and the pressure roller 102. At the location where the pressure roller 102 and the fixing belt 101 are in pressure contact, for example, a nip portion of a predetermined width is formed by the elastic layer of the pressure roller 102 being crushed.

[0054] The pressure roller 102 is rotationally driven by a drive source such as a motor provided in the printer main body, for example. When the pressure roller 102 is rotationally driven, the driving force is transmitted to the fixing belt 101 at the fixing nip portion N, and the fixing belt 101 is driven to rotate accordingly.

[0055] In addition to the above, the rotation drive source may be on the fixing belt 101 side. In this case, the driving force transmitted by the fixing nip portion N may be transmitted to the pressure roller 102 so that the pressure roller 102 is driven to rotate accordingly.

[0056] Also, in this embodiment, the pressure roller 102 is a solid roller, but a hollow roller may be used as the pressure roller. In that case, a heating source such as a halogen heater may be disposed inside the pressure roller.

[0057] Also, in this embodiment, the pressure roller 102 has an elastic layer, but it may not have an elastic layer. When there is no elastic layer, the heat capacity is reduced and the fixing property is improved. However, when fixing unfixed toner by pressing it in the fixing nip portion N, minute irregularities on the surface of the fixing belt 101 may be transferred to the image, and gloss unevenness may occur in the solid portions of the image.

[0058] In order to prevent such gloss unevenness, it is preferable that the pressure roller 102 has an elastic layer with a thickness of 100 μm or more. In this case, minute irregularities can be absorbed by the elastic deformation of the elastic layer, so the occurrence of gloss unevenness can be prevented.

[0059] The elastic layer may be solid rubber, but when there is no heating source inside the pressure roller 102, foamed sponge rubber may also be used. Sponge rubber is preferable because its heat insulation property is enhanced, making it difficult for the heat of the fixing belt 101 to be transferred through the fixing nip portion N and taken away.

[0060] The diameter of the pressure roller 102 is not particularly limited, but it is preferably 20 mm or more and 50 mm or less.

[0061] In this embodiment, it is described as a pressure member, but it is not limited to the case where the fixing belt and the pressure member are in pressure contact with each other. It is also possible to adopt a configuration in which the pressure member does not apply pressure but simply makes contact.

[0062] <Nip forming member> The nip forming member 103 supports the fixing belt 101 from the inner surface side and forms the fixing nip portion N. The nip forming member 103 is fixed by a fixing member 104 such as a fixing pad.

[0063] In this embodiment, the nip forming member 103 also functions as a heat source and heats the fixing belt 101. The nip forming member 103 generates heat under output control from, for example, a power supply unit arranged in the printer main body. The output control can be performed, for example, by detecting the surface temperature of the fixing belt 101 using a temperature sensor and based on the detection result of the temperature sensor. In this embodiment, by controlling the output of the nip forming member 103 as such a heat source, the temperature (fixing temperature) of the fixing belt 101 can be maintained at a desired temperature.

[0064] The nip forming member 103 can be appropriately selected. For example, it can be a planar heating element. In this embodiment, a planar heating element is used as the nip forming member 103. Examples of the planar heating element include a planar heater and the like. As the heat source of the nip forming member 103, for example, a halogen heater, IH (electromagnetic induction heating), a carbon heater, or the like can be used.

[0065] When the fixing belt 101 rotates, the nip forming member 103 slides on the surface of the fixing belt 101. A lubricant may be applied between the fixing belt 101 and the nip forming member 103. When the lubricant is applied, the driving torque generated on the fixing belt 101 can be reduced, and the load due to the frictional force on the fixing belt 101 can be alleviated.

[0066] Also, as in this embodiment, by directly heating the fixing nip portion N where the nip forming member 103 is between the fixing belt 101 and the pressure roller 102, improvements such as further energy saving and shortening of the first print time can be achieved.

[0067] <lubricant> Examples of the lubricant include silicone oil. Silicone oil is preferable from the viewpoints of heat resistance, durability, and lubricating ability, and it is also preferable because various viscosities can be selected depending on the use conditions. Examples of other lubricants include fluorine oil, fluorine grease, silicone-based grease, etc. Fluorine grease mixed with a thickener can have its consistency adjusted by the thickener. Therefore, in order to prevent it from flowing out from the inner circumference to the outside of the fixing belt, measures such as adjusting the consistency become possible.

[0068] The lubricant used in this embodiment is not limited to impregnating the entire nip forming member 103 with one type. In addition to this, for example, it is also possible to use a plurality of lubricants with different viscosities and materials at the central part and both end parts of the nip forming member 103 in the axial direction of the fixing belt or the pressure roller.

[0069] The lubricant is applied, for example, to the surface of the nip forming member 103. The lubricant is applied, for example, between the sliding layer 201 formed on the inner peripheral surface of the fixing belt 101 and the nip forming member 103, and as the fixing belt 101 rotates, the lubricant wets and spreads on the inner peripheral surface of the fixing belt 101.

[0070] <Basic operation example of the fixing device> Hereinafter, a basic operation example of the fixing device according to this embodiment will be described with reference to FIG. 1. Note that an image forming apparatus equipped with the fixing device of this embodiment is referred to as a printer or the like.

[0071] First, in this example, when the power of the printer main body is turned on, power is supplied to the nip forming member 103, and at the same time, the pressure roller 102 starts to rotate in the direction of arrow a in the figure. As a result, the fixing belt 101 is driven to rotate passively in the direction of arrow b in the figure by the frictional force with the pressure roller 102.

[0072] Here, the nip forming member 103 is in contact with the inner peripheral surface of the fixing belt 101, and since the nip forming member 103 is fixed by the fixing member 104, the sliding layer 201 formed on the inner peripheral surface of the fixing belt 101 and the nip forming member 103 slide.

[0073] Note that, as the nip forming member 103 in this example, a planar heater is used. The nip forming member 103 heats the fixing belt 101.

[0074] Also in this example, a lubricant is applied to the sliding surface between the nip forming member 103 and the fixing belt 101, and as the fixing belt 101 rotates, the lubricant spreads over the inner peripheral surface of the fixing belt 101.

[0075] Thereafter, the recording medium 107 having the unfixed toner image 106 (also referred to as a toner image or the like) is conveyed in the direction of arrow c in the figure while being guided by the guide plate, and is fed into the fixing nip portion N. In this example, the fixing nip portion N is in a pressed contact state.

[0076] Then, due to the heat of the fixing belt 101 and the pressing force between the fixing belt 101 and the pressure roller 102, the toner image 106 is fixed to the recording medium 107. The recording medium 107 on which fixing has been performed is carried out from the fixing nip portion N to the opposite side.

[0077] At this time, when the leading end of the recording medium 107 comes into contact with the leading end of the separating member, the recording medium 107 is guided in a direction to be separated from the fixing belt 101. Thereby, the recording medium 107 is separated from the fixing belt 101.

[0078] Thereafter, the separated recording medium 107 is carried out of the apparatus and stocked in the paper discharge tray.

[0079] (Image forming apparatus) As an embodiment of the image forming apparatus according to the present invention, there is provided an electrostatic latent image carrier, an electrostatic latent image forming means for forming an electrostatic latent image on the electrostatic latent image carrier, a developing means for developing the electrostatic latent image with toner to form a toner image, a transfer means for transferring the toner image to a recording medium, and a fixing device for fixing the toner image on the recording medium to the recording medium. The fixing device uses the fixing device of the present invention. Other means are provided as necessary.

[0080] An embodiment of the image forming apparatus according to the present invention will be described with reference to FIG. 3. The image forming apparatus 500 of the present embodiment uses an electrophotographic method and can include the fixing device 100 described above.

[0081] FIG. 3 is a schematic configuration diagram showing an example of the entire image forming apparatus including a fixing roller according to an embodiment of the present invention. In the present embodiment, the image forming apparatus 500 is shown as including an image forming unit for a tandem color printer. However, the image forming apparatus of the present invention is not limited to this, and may be a rotary color printer or a monochrome printer. Further, the image forming apparatus is not limited to a printer, and may be various image forming apparatuses such as a copier, a facsimile machine, or a multifunction machine combining these.

[0082] In a bottle storage portion 601 installed above the main body of the image forming apparatus 500, four toner bottles 602Y, 602M, 602C, and 602K corresponding to respective colors (yellow, magenta, cyan, black) are detachably (replaceably) installed.

[0083] Below the bottle storage portion 601, an intermediate transfer unit 85 as a part of the transfer means is disposed. Image forming units 4Y, 4M, 4C, and 4K corresponding to respective colors (yellow, magenta, cyan, black) are arranged in parallel so as to face an intermediate transfer belt 78 installed in the intermediate transfer unit 85. In the image forming units 4Y, 4M, 4C, and 4K, photosensitive drums 5Y, 5M, 5C, and 5K are respectively disposed as electrostatic latent image carriers.

[0084] Further, around the photosensitive drums 5Y, 5M, 5C, and 5K, a charging portion 75, a developing device 76, a cleaning portion 77, a charge removing portion, and the like are respectively disposed. These may be respectively referred to as charging means, developing means, cleaning means, charge removing means, and the like.

[0085] Then, each of the photoreceptor drums 5Y, 5M, 5C, and 5K rotates, and the following image forming process is performed on each of the photoreceptor drums 5Y, 5M, 5C, and 5K, and images of each color are formed on each of the photoreceptor drums 5Y, 5M, 5C, and 5K. Here, the image forming process refers to a charging process, an exposure process, a developing process, a transfer process, and a cleaning process.

[0086] The image forming process for the photoreceptor drums 5Y, 5M, 5C, and 5K will be described below. The photoreceptor drums 5Y, 5M, 5C, and 5K are rotationally driven clockwise in the figure by a drive motor. Then, in the charging unit 75 (only the one corresponding to the photoreceptor drum 5K is shown in the figure), the surfaces of the photoreceptor drums 5Y, 5M, 5C, and 5K are uniformly charged (charging process).

[0087] After being charged, the surfaces of the photoreceptor drums 5Y, 5M, 5C, and 5K are irradiated and exposed by the laser light emitted from the exposure unit 40 as an example of the exposure means, and an electrostatic latent image corresponding to each color is formed (exposure process). The photoreceptor drums 5Y, 5M, 5C, and 5K on which the latent image is formed are toner-developed by the developing device 76 (only the one corresponding to the photoreceptor drum 5K is labeled in the figure), and toner images of each color are formed (developing process).

[0088] Furthermore, the toner images on the photoreceptor drums 5Y, 5M, 5C, and 5K are transferred onto the intermediate transfer belt 78 by the intermediate transfer belt 78 and the primary transfer bias rollers 79Y, 79M, 79C, and 79K (primary transfer process). In this way, by transferring the toner images onto the intermediate transfer belt 78 in an overlapping manner, a color image is formed on the intermediate transfer belt 78.

[0089] After the transfer, the photoreceptor drums 5Y, 5M, 5C, and 5K reach the cleaning unit 77, and the untransferred toner remaining on the surfaces of the photoreceptor drums 5Y, 5M, 5C, and 5K is mechanically recovered by the cleaning blade of the cleaning unit 77 (cleaning process). Note that only the one corresponding to the photoreceptor drum 5K is labeled in the figure.

[0090] After that, the charging unit removes the residual potential on the surfaces of the photoreceptor drums 5Y, 5M, 5C, and 5K. In this way, a series of image forming processes for the photoreceptor drums 5Y, 5M, 5C, and 5K is completed.

[0091] Next, a series of transfer processes performed on the intermediate transfer belt 78 will be described.

[0092] The intermediate transfer unit 85 is composed of an endless 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 unit 80, and the like.

[0093] The intermediate transfer belt 78 is stretched and supported by the secondary transfer backup roller 82, the cleaning backup roller 83, and the tension roller 84, and is moved in the direction of the arrow in the figure by the rotational drive of the secondary transfer backup roller 82.

[0094] The primary transfer bias rollers 79Y, 79M, 79C, 79K form primary transfer nips by sandwiching the intermediate transfer belt 78 between the photoreceptor drums 5Y, 5M, 5C, 5K, respectively. A transfer bias opposite to the polarity of the toner is applied to the primary transfer bias rollers 79Y, 79M, 79C, 79K.

[0095] The intermediate transfer belt 78 runs in the direction of the arrow and sequentially passes through the primary transfer nips between the intermediate transfer belt 78 and the photoreceptor drums 5Y, 5M, 5C, 5K. In this way, the toner images of each color on the photoreceptor drums 5Y, 5M, 5C, 5K are superposed on the intermediate transfer belt 78 and primary transfer is performed.

[0096] After the first transfer, the intermediate transfer belt 78 reaches the position facing the secondary transfer roller 89. At this position, the secondary transfer backup roller 82 forms a secondary transfer nip by sandwiching the intermediate transfer belt 78 with the secondary transfer roller 89. In the secondary transfer nip, the four-color toner image formed on the intermediate transfer belt 78 is transferred onto the conveyed recording medium P. Note that these secondary transfer roller 89 and secondary transfer backup roller 82 are considered as part of the transfer means.

[0097] After the transfer, the intermediate transfer belt 78 reaches the intermediate transfer cleaning unit 80, and the untransferred toner on the intermediate transfer belt 78 is recovered. Thus, a series of transfer processes performed on the intermediate transfer belt 78 is completed.

[0098] Here, the recording medium 107 conveyed to the position of the secondary transfer nip is conveyed from the paper feeding unit 50 disposed below the main body of the image forming apparatus 500 via the paper feeding roller 97 and the registration roller 98. That is, a plurality of recording media 107 such as transfer paper are stacked and stored in the paper feeding unit 50.

[0099] When the paper feeding roller 97 is rotationally driven counterclockwise in the figure, it is fed to the registration roller 98 in order from the uppermost recording medium 107. The recording medium 107 conveyed to the registration roller 98 temporarily stops at the position of the roller nip of the registration roller 98 where the rotational drive is stopped.

[0100] Then, in synchronization with the toner image on the intermediate transfer belt 78, the registration roller 98 is rotationally driven, whereby the recording medium 107 is conveyed toward the secondary transfer nip. In this way, the toner image is transferred onto the recording medium 107.

[0101] The recording medium 107 onto which the color image has been transferred by the secondary transfer nip is conveyed to the fixing device 100. Then, the recording medium 107 is heated and pressed by the fixing belt 101 and the pressure roller 102 in the fixing device 100, and the toner image transferred onto the surface is fixed onto the recording medium 107. Thereafter, the recording medium 107 is discharged outside the main body of the image forming apparatus 500 via the paper discharge roller 99 and sequentially stacked on the stack unit 60.

[0102] As described above, the image formation on the recording medium 107 by the image forming apparatus 500 is completed.

Example

[0103] Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

[0104] (Example 1) The fixing device used in this example has the configuration shown in FIG. 1, and the fixing belt used in this example has the configuration shown in FIG. 2. Details will be described below.

[0105] As the material of the base material 202 in the fixing belt 101, nickel (Ni) and copper (Cu) were used, and the Ni layer and the Cu layer were laminated. The thickness of the Ni layer was 30 μm, the thickness of the Cu layer was 10 μm, and the laminated base material 202 had a thickness of 40 μm.

[0106] A sliding layer 201 is provided on the inner peripheral surface of the base material 202. A polyimide-based resin with high heat resistance was used for the sliding layer 201, and a coating film was formed by spray coating. In this example, U-Varnish-S manufactured by Ube Industries, Ltd. having the chemical structural formula shown in the above structural formula (1) was used for the sliding layer 201. The thickness of the sliding layer 201 was 10 μm.

[0107] Here, details of the formation of the sliding layer 201 will be described. First, NMP (N-methyl-2-pyrrolidinone) manufactured by Kanto Chemical Co., Inc. was prepared for U-Varnish-S at a ratio of 1:0.8 to obtain a mixed solution. Although it is possible to add a filler or the like to the prepared mixed solution for reasons such as imparting abrasion resistance, it was decided not to add it in this example. This mixed solution was applied to the inner peripheral surface of the base material 202 of the fixing belt 101 by spray coating. Next, drying was performed, and further, coating and drying were repeatedly performed until a predetermined film thickness was obtained. When the thickness reached 10 μm, drying was performed at 150 °C for 20 minutes, and then secondary drying was performed at 230 °C for 120 minutes.

[0108] Furthermore, firing was carried out, but there is a difference in the elastic work rate of the sliding layer 201 after firing depending on the firing temperature. The higher the temperature, the higher the elastic work rate, and vice versa. In this example, using a vertical continuous far-infrared heating furnace, the temperature was set so that the fixing belt reached a physical temperature of 340 °C, and firing was carried out for 30 minutes. The physical temperature of the fixing belt was measured wirelessly by inserting a fixing belt equipped with a thermocouple into the firing furnace while rotating it.

[0109] An elastic layer 203 is provided on the surface side (outer peripheral side) of the base material 202. As the material of the elastic layer 203, silicone rubber was used, and a coating film was formed by dipping coating. The thickness of the elastic layer 203 was set to 120 μm.

[0110] A release layer 204 is provided on the elastic layer 203. PFA was used as the material of the release layer 204, and a coating film was formed by dipping coating. The thickness of the release layer 204 was set to 7 μm.

[0111] The fixing belt 101 was formed in this way. The outer diameter of the obtained fixing belt 101 was 30 mm.

[0112] Regarding the obtained fixing belt 101, the elastic work rate of the sliding layer was measured as follows. The elastic work rate of the sliding layer was measured using a Fischer microhardness tester. As the measurement conditions, the indentation depth was set to 1.5 μm and the measurement temperature was set to 23°C. The measurement sample was prepared by cutting the fixing belt into strips of 30 mm × 90 mm. Five measurements were performed on one sample, and the average value was used. As a result of the measurement as described above, the elastic work rate of the sliding layer 201 was 81%.

[0113] Also, it is possible to measure the martensite hardness simultaneously with the measurement of the elastic work rate, and the martensite hardness of the sliding layer 201 was measured under the same conditions.

[0114] Next, the fixing device in this embodiment will be described. In the fixing device used in this embodiment, a pressure roller 102 is provided at a position facing the fixing belt 101. The pressure roller 102 used in this embodiment has a three-layer structure of a core metal, an elastic layer, and a release layer. As the pressure roller 102 used in this embodiment, the configuration described in the above embodiment was appropriately selected.

[0115] A planar heater was used as the nip forming member 103, and a fixing pad was used as the fixing member 104. The martensite hardness of the surface of the nip forming member 103, that is, the portion that slides with the fixing belt 101, was also measured in the same manner as above. When the martensite hardness of the nip forming member 103 was compared with the martensite hardness of the sliding layer 201, the relationship between the two was such that the sliding layer <became a planar heater.

[0116] Also, in this embodiment, a lubricant was used. Fluorine oil was used as the lubricant. The lubricant was applied to the surface of the nip forming member 103 so that it spread and wet the inner peripheral surface as the fixing belt 101 rotated.

[0117] The following evaluations were performed in this embodiment. In this evaluation, 400,000 sheets were passed through in the running test, and the fixing belt 101 and the pressure roller 102 in the fixing device were rotationally driven. Regarding the dynamic torque (sliding resistance torque) of the motor for rotational drive, the initial torque and the torque when 400,000 sheets were passed (torque at 400k) were measured and evaluated. The case where both the initial torque and the torque at 400k were 0.77 N·m or less was regarded as passing. The evaluation results are shown in Table 1 below. Also, the same evaluation was carried out for the examples and comparative examples described later, and the results are shown in Table 1.

[0118] (Example 2) In the production of the fixing belt of Example 1, the fixing belt was produced in the same manner as in Example 1, except that the temperature was set so that the fixing belt reached a physical temperature of 360 °C using a vertical continuous far-infrared heating furnace. The relationship between the martensite hardness of the sliding layer and the martensite hardness of the planar heater was that the sliding layer > planar heater.

[0119] (Example 3) In Example 1, as the polyimide-based resin used for the sliding layer 201, the one shown in the above structural formula (1) and the one shown in the above structural formula (2) were used in a changed manner, and these were mixed to obtain a mixed solution. Actually, U-Varnish-S and U-Varnish-A manufactured by Ube Industries, Ltd. were used, and a mixed polyimide resin was produced such that U-Varnish-S was 80% and U-Varnish-A was 20%. Otherwise, the fixing belt was produced in the same manner as in Example 1.

[0120] (Example 4) In Example 2, a mixed polyimide resin was used for the sliding layer 201 in the same manner as in Example 3. Otherwise, the fixing belt was produced in the same manner as in Example 2.

[0121] (Comparative Example 1) In Example 1, when firing the sliding layer 201, the firing was carried out with the temperature set so that the physical temperature became 280 °C. Otherwise, the fixing belt was produced in the same manner as in Example 1. The elastic work rate of the sliding layer 201 in the obtained fixing belt was 65%.

[0122] (Comparative Example 2) In Example 1, when firing the sliding layer 201, the firing was carried out with the temperature set so that the actual temperature became 390°C. Other than that, a fixing belt was produced in the same manner as in Example 1. The elastic work rate of the sliding layer 201 in the obtained fixing belt was 89%.

[0123] (Comparative Example 3) In Example 1, when firing the sliding layer 201, the firing was carried out with the temperature set so that the actual temperature became 280°C. Also, a mixed polyimide resin was used in the same manner as in Example 3. Other than that, a fixing belt was produced in the same manner as in Example 1. The relationship between the martensitic hardness of the sliding layer and the martensitic hardness of the surface heater was such that the sliding layer > the surface heater.

[0124]

Table 1

Explanation of Signs

[0125] 101 Fixing belt 102 Pressing roller 103 Nip forming member 104 Fixing member 106 Toner image 107 Recording medium 201 Sliding layer 202 Base material 203 Elastic layer 204 Release layer

Prior Art Documents

Patent Documents

[0126]

Patent Document 1

Claims

1. A fixing belt that is supported from the inner surface side by a nip forming member and rotates while sliding on the nip forming member to fix a toner image on a recording medium to the recording medium, having a base material made of metal and a sliding layer that is on the inner peripheral side of the base material and slides on the nip forming member, wherein the sliding layer contains a polyimide-based resin, and the elastic work rate of the sliding layer is 70% or more and 85% or less. A fixing belt characterized by this.

2. The polyimide-based resin is a mixed polyimide resin containing a polyimide having a chemical structural formula shown in the following structural formula (1) and a polyimide having a chemical structural formula shown in the following structural formula (2). The fixing belt according to claim 1, characterized by this. 【Chemical Formula 1】 【Chemical 2】

3. The fixing belt according to claim 1 or 2, characterized in that the hardness of the sliding layer is smaller than the hardness of the nip forming member.

4. The fixing belt according to any one of claims 1 to 3, a pressing member disposed at a position facing the fixing belt, and a nip forming member that supports the fixing belt from the inner surface side and forms a fixing nip. A fixing device characterized by this.

5. The fixing device according to claim 4, characterized in that the nip forming member is a planar heating element that heats the fixing belt.

6. An electrostatic latent image carrier, electrostatic latent image forming means for forming an electrostatic latent image on the electrostatic latent image carrier, developing means for developing the electrostatic latent image with toner to form a toner image, transfer means for transferring the toner image to a recording medium, and a fixing device for fixing the toner image on the recording medium to the recording medium. The image forming apparatus is provided with, wherein the fixing device is the fixing device according to claim 4 or 5.

Images