Fixing belt and fixing device

Abstract

To provide a fixing belt including an inner face slide layer that can inhibit an increase in torque and stick slip through the duration life.SOLUTION: A fixing belt has at least a cylindrical substrate formed of metal, a slide layer formed on an inner peripheral surface side of the cylindrical substrate, sliding with a backup member, and formed of heat-resistant resin, and a mold release layer formed on an outer peripheral surface side of the cylindrical substrate, and the fixing belt rotates while sliding on its inner surface side with the backup member with the interposition of lubricant and is used for heating and fixing a toner image on a recording material. The slide layer has filler. When a cross section with a thickness direction of the slide layer as a vertical axis is cut out, sections each of which having a length the same as the thickness are provided in an orthogonal direction to the thickness direction, and the area ratio of the filler in each section is converted into a number, and with the average area ratio of the filler in all the sections as Ave%, and the minimum area ratio as Min%, a cycle coefficient A calculated with (Ave%-Min%)÷Ave% satisfies 0.6 or more.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a fixing belt and a fixing device used in an electrophotographic image forming apparatus. [Background technology]

[0002] In the past, fixing devices for electrophotographic devices generally used a fixing roller system, but because the fixing roller has a large heat capacity, it takes a long time to heat up, there is a long waiting time at start-up, and power consumption is high. Therefore, in recent years, belt heating type fixing devices have been adopted as an on-demand system with high heat transfer efficiency and quick start-up of the device, in which the toner on the transfer paper is heated by the heat of a heater via a fixing belt with a small heat capacity.

[0003] As described in Patent Documents 1 and 2, a belt fixing device has a fixedly supported heating body, such as a ceramic heater, a fixing belt as a heat transfer member that slides against the heating body, and an elastic pressure roller as a pressure member that presses against the heating body via the fixing belt to form a fixing nip portion, and a recording material carrying an unfixed toner image is sandwiched and transported between the fixing belt and the elastic pressure roller in the fixing nip portion, and the unfixed toner image is heated, melted, and fixed onto the recording material by heat from the heating body via the fixing belt.

[0004] The fixing belt is basically configured to include at least a thin cylindrical substrate with a small heat capacity, a silicone rubber elastic layer for applying uniform pressure to the toner image and the unevenness of the paper during fixing, and a fluororesin release layer for maintaining releasability from the toner. When the cylindrical substrate is made of a heat-resistant resin, the inner surface of the cylindrical substrate itself serves as a sliding layer for contact with the heater, but when the cylindrical substrate is made of metal, an inner sliding layer made of a heat-resistant resin for maintaining sliding ability with the heater is often provided, and the configuration from inner layer to outer layer is as follows: inner sliding layer, cylindrical substrate, silicone rubber elastic layer, fluororesin release layer.

[0005] In a belt fixing device, a fixedly supported heating element is provided inside the fixing belt, and the fixing belt and recording material are sandwiched and conveyed between the heating element and an elastic pressure roller to fix the image, so friction wear occurs between the inner surface of the fixing belt and the fixedly supported heating element. As a result, problems such as self-excited vibration called stick-slip and torque increase can occur as the device wears out.

[0006] As a countermeasure to these problems, Patent Document 3 proposes that needle-shaped (whisker-shaped, fibrous) fillers are blended into the inner sliding layer of the belt, and the orientation rate of the fillers in the longitudinal direction (direction of the rotation axis) of the fixing belt is increased, thereby improving the sliding properties, wear resistance, and lubricant retention, thereby extending the belt's lifespan. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 63-313182 [Patent Document 2] Japanese Patent Application Publication No. 2-157878 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-228729 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the method of orienting needle-shaped (whisker-shaped, fibrous) shape-anisotropic fillers in the longitudinal direction described in Patent Document 3 makes it difficult to obtain abrasion resistance in the belt rotation direction (circumferential direction), which is the main sliding direction.

[0009] Furthermore, it is difficult to effectively impart surface roughness with a small amount of filler to reduce the actual contact area with the mating sliding material (backup member) and to retain the lubricant between the mating sliding material and the back-up member. If the amount of filler is increased in order to obtain the desired surface roughness, the wear resistance of the sliding layer will be impaired.

[0010] Therefore, an object of the present invention is to provide a fixing belt and fixing device equipped with an inner sliding layer that can effectively impart roughness to the sliding surface (inner peripheral surface) by optimally arranging fillers in the sliding layer and improve wear resistance in the belt rotation direction, thereby preventing torque increase and stick-slip throughout the belt's service life. [Means for solving the problem]

[0011] In order to achieve the above object, the fixing belt according to the present invention has at least a cylindrical substrate made of metal, a sliding layer made of a heat-resistant resin formed on the inner peripheral surface of the cylindrical substrate and sliding against the backup member, and a release layer formed on the outer peripheral surface of the cylindrical substrate, The sliding layer contains a filler, and the distribution of the filler in the sliding layer is configured so that dense and coarse fillers are periodically repeated in the circumferential direction of the belt. In a cross section of the sliding layer including the thickness direction of the belt and the circumferential direction of the belt, When 20 or more sections are provided, each having a length equal to the thickness, and the area ratio of the filler is quantified for each section, the average area ratio of the filler in all sections is defined as Ave%, and the minimum area ratio is defined as Min%, the periodicity coefficient calculated by (Ave% - Min%) / Ave% satisfies 0.6 or more. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a cylindrical fixing belt comprising at least three layers from the inside: an inner sliding layer, a metal substrate, and a release layer, the fixing belt having a sliding layer that has slidability, abrasion resistance, and lubricant retention properties and that prevents torque increase and stick-slip. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic cross-sectional view of an image forming apparatus used in this embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view of a fixing device used in the present embodiment. [Figure 3] FIG. 2 is a schematic diagram of a fixing belt used in the present embodiment. [Figure 4] FIG. 2 is a schematic diagram of a coating device used when coating the inner sliding layer in this example. [Figure 5]FIG. 2 is a schematic diagram of a drying device used in drying the inner surface sliding layer in this example. [Figure 6] FIG. 2 is a cross-sectional view of an inner surface sliding layer in this embodiment. [Figure 7] 1A is a diagram showing a cross section of a divided sliding layer of a fixing belt in an example, FIG. 1B is a diagram showing an area ratio of a filler, and FIG. 1C is a diagram showing a graph of the area ratio. [Figure 8] 1A is a diagram showing a cross section of a divided sliding layer of a fixing belt in a comparative example, FIG. 1B is a diagram showing the area ratio of a filler, and FIG. 1C is a diagram showing the area ratio in a graph. [Figure 9] 1 is a table showing a comparison of film thickness, periodic coefficient, and inner peripheral surface roughness between Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings, but the scope of the present invention is not limited to this embodiment, and modifications that do not detract from the spirit of the present invention are also included in the present invention.

[0015] (1) Overview of the configuration of the image forming device; 1 is a schematic cross-sectional view of the image forming apparatus used in this embodiment. Reference numeral 101 denotes a photosensitive drum serving as an image carrier, which is rotated counterclockwise as indicated by the arrow at a predetermined process speed (peripheral speed). During its rotation, the photosensitive drum 101 is charged to a predetermined polarity by a charging device 102 such as a charging roller.

[0016] Next, the charged surface is exposed based on the input image information by a laser beam 103 output from a laser optical system 110. The laser optical system 110 outputs the laser beam 103 modulated (on / off) in response to a time-series electric digital pixel signal of the target image information from an image signal generating device such as an image reading device (not shown), and scans and exposes the surface of the photosensitive drum 101.

[0017] As a result, an electrostatic latent image corresponding to the image information is formed on the surface of the photosensitive drum 101 by this scanning exposure. Reference numeral 109 denotes a mirror that deflects the output laser beam 103 from the laser optical system 110 to the exposure position on the photosensitive drum 101. The electrostatic latent image formed on the photosensitive drum is then visualized with yellow toner by a yellow developing device 104Y in the developing device 104. This yellow toner image is transferred to the surface of the intermediate transfer drum 105 at a primary transfer portion T1, which is the contact portion between the photosensitive drum 101 and the intermediate transfer drum 105.

[0018] Any toner remaining on the surface of the photosensitive drum 101 is cleaned by a cleaner 107. The above-described process cycle of charging, exposing, developing, primary transfer, and cleaning is repeated in the same manner to form a magenta toner image (developer 104M operates), a cyan toner image (developer 104C operates), and a black toner image (developer 104K operates). The toner images of each color formed in succession on the intermediate transfer drum 105 in this manner are secondarily transferred together onto the recording material P at a secondary transfer portion T2, which is the contact portion with the transfer roller 106. Any toner remaining on the intermediate transfer drum 105 is cleaned by a toner cleaner 108.

[0019] The cleaner 108 is capable of being brought into contact with the intermediate transfer drum 105 and is configured to be in contact with the intermediate transfer drum 105 only when cleaning the intermediate transfer drum 105. The transfer roller 106 is also capable of being brought into contact with the intermediate transfer drum 105 and is configured to be in contact with the intermediate transfer drum 105 only during secondary transfer. The recording material P that has passed through the secondary transfer portion T2 is introduced into the fixing device 100, which serves as an image heating device, and undergoes a fixing process (image heating process) for the unfixed toner image carried thereon. The recording material P that has undergone the fixing process is then discharged outside the apparatus, completing the series of image forming operations.

[0020] (2) Outline of the fixing device configuration; 2 is a schematic cross-sectional view of fixing device 100. Reference numeral 1 denotes a cylindrical fixing belt (endless belt) equipped with an elastic layer. Reference numeral 6 denotes a pressure roller serving as a pressure member that forms a fixing nip 14 between the fixing belt and the pressure roller. Reference numeral 2 denotes a fixing heater serving as a heating element, and 4 denotes a heat-resistant film guide / heater holder. Fixing heater 2 is fixed to the underside of film guide / heater holder 4 along the length of film guide / heater holder 4, allowing the fixing belt 1 and its heating surface to slide.

[0021] The fixing belt 1 is fitted onto the film guide / heater holder 4 with some degree of freedom. The film guide / heater holder 4 is made of a highly heat-resistant liquid crystal polymer resin and serves to support the fixing heater 2 and to shape the fixing belt 1 to separate it from the recording material P. The pressure roller 6 has a multi-layer structure in which a stainless steel core is layered with a silicone rubber layer approximately 3 mm thick and a PFA resin tube approximately 40 μm thick. Both ends of the core of the pressure roller 6 are rotatably supported by bearings between the rear and front side plates (not shown) of the device frame 13. A fixing unit including the fixing heater 2, film guide / heater holder 4, fixing belt stay 5, and fixing belt 1 is installed above the pressure roller 6.

[0022] This fixing unit is installed with the fixing heater 2 side facing downward and parallel to the pressure roller 6. Both ends of the fixing belt stay 5 are urged toward the pressure roller 6 by a pressure mechanism (not shown) with a force of 156.8 N (16 kgf) at one end and a total pressure of 313.6 N (32 kgf). As a result, the lower surface (heating surface) of the fixing heater 2 is pressed against the elastic layer of the pressure roller 6 with a predetermined pressure via the fixing belt 1, forming a fixing nip portion 14 of a predetermined width required for fixing.

[0023] Reference numeral 3 denotes a thermistor serving as a temperature detection means. Thermistor 3 (heater temperature sensor) is installed on the back surface (the surface opposite the heating surface) of fixing heater 2, which is the heat source, and functions to detect the temperature of fixing heater 2. Pressure roller 6 is driven to rotate at a predetermined peripheral speed in the direction of the arrow. Fixing belt 1, which is in pressure contact with this, is driven by pressure roller 6 and rotates at a predetermined speed. At this time, the inner surface of fixing belt 1 slides in close contact with the underside of fixing heater 2, and is driven to rotate around the outside of film guide / heater holder 4 in the direction of the arrow.

[0024] A semi-solid lubricant, described later, is applied to the inner surface of the fixing belt 1 to ensure sliding between the film guide / heater holder 4 and the inner surface of the fixing belt 1. The thermistor 3 is arranged so as to contact the rear surface of the fixing heater 2 and is connected to a control circuit unit (CPU) 10 (which serves as control means) via an A / D converter 9. This control circuit unit (CPU) 10 samples the output from each thermistor at a predetermined interval and reflects the temperature information thus obtained in temperature control. In other words, the control circuit unit (CPU) 10 determines the temperature control content of the fixing heater 2 based on the output of the thermistor 3, and controls the supply of electricity to the fixing heater 2 via a heater drive circuit unit 11, which is a power supply unit, so that the temperature of the fixing heater 2 reaches the target temperature (set temperature).

[0025] The control circuit unit (CPU) 10 also controls the fixing belt life estimation sequence (described later), and is connected to the drive motor of the pressure roller 6 via an A / D converter 9. The fixing heater has an alumina substrate and a resistance heating element on top of which a conductive paste containing a silver-palladium alloy is applied in the form of a uniform film about 10 μm thick by screen printing. Furthermore, a pressure-resistant glass coating is applied on top of this, making it a ceramic heater.

[0026] (3) Outline of the fixing belt structure; FIG. 3 is a schematic diagram of the fixing belt 1 obtained in this example. 1c is a cylindrical substrate, 1b is an inner sliding layer disposed on the inner peripheral surface of the cylindrical substrate 1c, and 1a is a filler blended into the inner sliding layer. 1d is a silicone rubber elastic layer covering the outer peripheral surface of the cylindrical substrate 1c, and is disposed via a primer layer. 1e is a fluororesin release layer serving as a surface layer covering the outer peripheral surface of the silicone rubber elastic layer 1d, and is disposed between the silicone rubber elastic layer 1d and the silicone rubber elastic layer 1d via a silicone rubber adhesive layer.

[0027] This will be explained in detail below.

[0028] (3-1) Cylindrical substrate 1c; Considering the need for heat resistance and bending resistance, metals such as stainless steel (SUS), nickel, and nickel alloys are preferably used for the cylindrical substrate 1c. Since the cylindrical substrate 1c needs to have a low heat capacity while having high mechanical strength, it is desirable for the thickness to be 20 to 50 μm, preferably 25 to 45 μm. In this example, a SUS substrate with an inner diameter of 24 mm and a thickness of 30 μm is used as the substrate.

[0029] (3-2) Inner sliding layer 1b; A resin having both high durability and high heat resistance, such as a polyimide resin, is suitable for the inner surface sliding layer 1b. In this embodiment, a polyimide precursor solution obtained by reacting an aromatic tetracarboxylic dianhydride or its derivative with an aromatic diamine in a substantially equimolar organic polar solvent is applied to the inner circumferential surface of the substrate 21, and after the solvent is dried, the inner surface sliding layer 1b is formed by a dehydration ring-closing reaction (imidization reaction) caused by heating.

[0030] The thickness of the inner sliding layer 1b is preferably about 5 to 25 μm. In particular, if it is about 7 to 20 μm, it is easy to achieve both wear resistance in the fixing nip and heat conductivity for transmitting heat from the heater to the cylindrical substrate 1c.

[0031] (3-2-1) Polyimide precursor solution Representative examples of aromatic tetracarboxylic dianhydrides include pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, etc. These aromatic tetracarboxylic dianhydrides can be used alone or in combination of two or more.

[0032] Representative examples of aromatic diamines include 4,4'-oxydianiline (4,4'-ODA), paraphenylenediamine (PPDA), metaphenylenediamine (MPDA), etc. These aromatic diamines can be used alone or in combination of two or more.

[0033] Examples of the organic polar solvent include N,N-dimethylacetamide (DMAc), dimethylformamide (DMF), and N-methyl-2-pyrrolidone (NMP).

[0034] (3-2-2) Filler 1a A filler can be blended into the inner sliding layer to improve wear resistance. To improve wear resistance, fillers such as fluororesins such as polytetrafluoroethylene, molybdenum disulfide, and graphite can be blended. It is best to select the appropriate filler depending on the sliding combination. In the present invention, a lubricant is used in combination with a ceramic material, so the filler to be blended must have cleavage properties and appropriate hardness, and mica materials are preferred.

[0035] Fluorphlogopite (KMg3(AlSi3)O), a non-swelling synthetic mica, 10 F2) and potassium tetrasilicic mica (KMg 2.5 SiO 10 F2), sodium tetrasilicic mica (NaMg 2.5 SiO 10 F2) and sodium hectorite (Na 0.33 Mg 2.67 Li 0.33 SiO 10F2), as well as silica (SiO2), hexagonal boron nitride (BN), graphite, graphene, etc. can be used.

[0036] Methods for dispersing the filler in the polyimide precursor solution include a method in which the filler is directly added to the polyimide precursor solution, pre-stirred with a mixer or other mixing machine, and then dispersed with a three-roll mill or the like; a method in which the filler is added in advance to a polar solvent (e.g., NMP) similar to the polyimide precursor solution, a filler dispersion solvent is prepared using a sand mill or a bead mill, and then the filler is mixed with a separately obtained polyimide precursor solution in a mixing machine such as a mixer.

[0037] The optimum amount of the filler to be blended varies depending on the type of polyimide precursor solution and filler. However, in order to adjust the surface roughness of the sliding layer within an appropriate range and to maintain the range in which the abrasion resistance of the sliding layer is not impaired, the amount of the filler to be blended is preferably 7% by volume or more and 15% by volume or less relative to the volume of the sliding layer.

[0038] If the filler content is less than 7% by volume, the actual contact area with the mating sliding material is reduced, and it is difficult to obtain the surface roughness required to retain the intervening lubricant.

[0039] Furthermore, if the filler content is more than 15% by volume, the filler makes the polyimide hard and brittle, impairing the abrasion resistance strength, making it difficult to maintain an appropriate surface roughness, i.e., sliding properties and lubricant retention, throughout durability.

[0040] (3-2-3) Formation of inner sliding layer 1b To make the thickness of the inner sliding layer 1b about 12 μm, the polyimide precursor solution 23 containing the filler is applied to the inner surface of the cylindrical substrate 1c by ring coating or the like so as to have a thickness of about 70 to 80 μm.

[0041] 4 is a schematic diagram of a coating device for the ring coating method. Support columns 201 and 202 are formed on a base 21. A coating head 22 is fixed onto the support column 201, and is connected to a coating liquid supply device (not shown).

[0042] A work hand 25 that holds the cylindrical base body 1c is formed on the support 202 as a work moving device 26. The work moving device 26 can be moved up and down by a motor provided on the support 202, and the work hand 25 formed on the work moving device can also be moved up and down by the movement of the work moving device 26.

[0043] A slit (not shown) perpendicular to the axis of the cylinder is formed around the outer periphery of the coating head 22, and a polyimide precursor solution 23 containing a filler is uniformly supplied from the slit, and the cylindrical substrate 1c is moved along the outer periphery of the coating head 22 to coat the inner surface of the cylindrical substrate 1c. In this device, the thickness of the sliding layer is determined by the amount of coating, and any amount of coating can be obtained by changing the clearance, the supply speed of the polyimide precursor solution 23, and the movement speed of the workpiece moving device 26.

[0044] After applying a polyimide precursor solution 23 containing a filler to the inner surface of the cylindrical substrate 1c, the solution is heated to evaporate the organic polar solvent contained in the polyimide precursor solution 23, thereby increasing the viscosity of the polyimide precursor solution 23 and allowing it to maintain its shape.

[0045] The polyimide precursor solution 23 coated on the inner surface of the cylindrical substrate 1c is placed for approximately 300 seconds in a heating and drying furnace 30, as shown in Figure 5, in which high-temperature oil at 160°C is fed from an oil inlet 31 through a heating cylinder 32 and discharged from an oil outlet 33. This reduces the organic polar solvent contained in the polyimide precursor solution 23 from approximately 90% by volume to less than approximately 30% by volume, thereby increasing the viscosity of the polyimide precursor solution 23 and preventing it from flowing out of the inner surface of the cylindrical substrate 1c.

[0046] When evaporating the organic polar solvent, ventilation is required to keep the organic polar solvent below its lower explosion limit. For ventilation, air is sent through an intake port 34 in Figure 5, passes through the cylindrical substrate 1c, and is exhausted from an exhaust port 35.

[0047] After reducing the organic polar solvent to less than about 30% by volume, the cylindrical substrate 1c is dried, for example, in a hot air circulation oven at 200°C for 30 minutes, and then baked for 20 to 120 minutes in a hot air circulation oven at 300°C to 400°C, a temperature range that does not reduce the fatigue strength of the cylindrical substrate 1c, thereby forming an inner sliding layer 1b of polyimide resin in which a filler is dispersed by a dehydration ring-closing reaction.

[0048] (3-3) Silicone rubber elastic layer 1d; The silicone rubber elastic layer 1d functions as an elastic layer supported by the fixing member to apply uniform pressure to the unevenness of the toner image and paper during fixing. To achieve this function, it is preferable to use an addition-reaction crosslinking liquid silicone rubber as the material for the silicone rubber elastic layer 1d, as it is easy to process, can be processed with high dimensional accuracy, and does not produce reaction by-products during heat curing. Furthermore, the elasticity can be adjusted by adjusting the degree of crosslinking depending on the type and amount of filler (described below).

[0049] In general, addition reaction crosslinking liquid silicone rubber contains an organopolysiloxane having an unsaturated aliphatic group, an organopolysiloxane having silicon-bonded active hydrogen, and a platinum compound as a crosslinking catalyst.

[0050] The organopolysiloxane having silicon-bonded active hydrogen reacts with the alkenyl groups of the organopolysiloxane component having unsaturated aliphatic groups under the catalytic action of the platinum compound to form a crosslinked structure.

[0051] The silicone rubber elastic layer 1d may contain a filler to improve the thermal conductivity, reinforcement, and heat resistance of the fixing belt.

[0052] In particular, for the purpose of improving thermal conductivity, it is preferable that the filler has high thermal conductivity, and specific examples thereof include inorganic substances, particularly metals and metal compounds.

[0053] Specific examples of high thermal conductivity fillers include silicon carbide (SiC), silicon nitride (Si3N4), boron nitride (BN), aluminum nitride (AlN), alumina (Al2O3), zinc oxide (ZnO), magnesium oxide (MgO), silica (SiO2), copper (Cu), aluminum (Al), silver (Ag), iron (Fe), and nickel (Ni).

[0054] These can be used alone or in combination of two or more. The average particle size of the highly thermally conductive filler is preferably 1 μm or more and 50 μm or less from the viewpoints of handling and dispersibility. The shape can be spherical, pulverized, plate-like, whisker-like, etc., but spherical is preferred from the viewpoint of dispersibility.

[0055] In terms of contribution to the surface hardness of the fixing belt and efficiency of heat conduction to unfixed toner during fixing, the thickness of the silicone rubber elastic layer is preferably in the range of 100 μm to 500 μm, particularly 200 μm to 400 μm.

[0056] In this embodiment, alumina was used as the highly thermally conductive filler, and the thermal conductivity of the elastic layer 1d was set to 1.0 W / mK and the thickness was set to 300 μm.

[0057] (3-4) Fluorine resin release layer; The fluororesin release layer may be, for example, a tubular resin such as tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer (PFA), polytetrafluoroethylene (PTFE), or tetrafluoroethylene-hexafluoropropylene copolymer (FEP). Among the materials listed above, PFA is preferred from the viewpoints of moldability and toner releasability.

[0058] The thickness of the fluororesin release layer is preferably 50 μm or less, because this maintains the elasticity of the silicone rubber elastic layer underneath when laminated, and prevents the surface hardness as a fixing member from becoming too high.

[0059] The adhesiveness of the inner surface of the fluororesin tube can be improved by previously subjecting it to sodium treatment, excimer laser treatment, ammonia treatment, or the like.

[0060] In this example, a PFA tube having a thickness of 20 μm obtained by extrusion molding was used. The inner surface of the tube was treated with ammonia to improve wettability with the adhesive described below.

[0061] The silicone rubber adhesive layer that fixes the PFA tube 1e as a fluororesin release layer to the silicone rubber elastic layer 1d is made of a cured product of an addition-curing type silicone rubber adhesive that is applied to the surface of the silicone rubber elastic layer 1d. The addition-curing type silicone rubber adhesive contains addition-curing type silicone rubber blended with a self-adhesive component, typically a silane having a functional group such as an acryloxy group, a hydrosilyl group (SiH group), an epoxy group, or an alkoxysilyl group.

[0062] Next, the addition-curing silicone rubber adhesive is cured and bonded by heating for a predetermined time using a heating means such as an electric furnace, and both ends are cut to the desired length to obtain the fixing belt as the fixing member of this embodiment.

[0063] Example 1 A polyimide precursor solution (U-Varnish S; manufactured by Ube Industries, Ltd.) using 3,3',4,4'-biphenyltetracarboxylic dianhydride as the aromatic tetracarboxylic dianhydride and paraphenylenediamine as the aromatic diamine was blended with fluorine phlogopite mica with an aspect ratio of 50 (average particle diameter 6 μm, particle thickness 100 nm) as the flake filler 1a, at a volume of 7% of the total solid content to be formed as the inner sliding layer 1b. The filler dispersion solution was prepared by adding the flake filler (fluorine phlogopite mica) directly to the polyimide precursor solution (U-Varnish S), pre-stirring with a mixer, and then dispersing with a three-roll mill.

[0064] The polyimide precursor solution 23 in which this filler was dispersed was applied to the inner surface of the cylindrical substrate 1c by ring coating so as to have a coating thickness of 77 μm.

[0065] After coating, the coating film was heated and dried for 300 seconds in a heating and drying oven 30 in which the temperature of the hot oil was set to 160°C.

[0066] Thereafter, the cylindrical substrate 1c was left to dry in a hot air circulating oven at 200°C for 30 minutes, and then left to bake in another hot air circulating oven at 400°C for 30 minutes to form the inner sliding layer 1b.

[0067] The thickness of the inner surface sliding layer 1b formed on the inner surface of the cylindrical substrate 1c was 12 μm.

[0068] The surface of this cylindrical substrate 1c was coated with a hydrosilyl silicone primer (DY39-051 A / B; manufactured by Dow Corning Toray Co., Ltd.) and cured by heating at 200°C for 5 minutes. A 300 μm thick addition-reaction crosslinkable liquid silicone rubber was coated on the outer surface and cured by heating at 200°C for 30 minutes to form a silicone rubber elastic layer 1d. The outer surface was then covered with a 20 μm thick PFA tube as a fluororesin release layer 1e via silicone adhesive (SE1819 CV A / B; manufactured by Dow Corning Toray Co., Ltd.) and cured by heating at 200°C for 2 minutes.

[0069] (Comparative Example) A fixing belt was produced in the same manner as in Example 1, except that the scaly filler 1a was changed to fluorine phlogopite having an aspect ratio of 80 (average particle diameter 8 μm, particle thickness 100 nm).

[0070] [Filler distribution in the inner sliding layer 1b] The distribution of the scaly filler 1a blended in the inner sliding layer 1b was determined by cutting out a cross section of the inner sliding layer 1b with the thickness direction as the vertical axis, and providing 20 or more sections in a direction perpendicular to the thickness direction, each section having the same length as the thickness.The area ratio of the filler 1a was quantified for each section, and the average area ratio of the filler 1a over all sections was defined as Ave%, and the minimum area ratio was defined as Min%, and the periodicity coefficient was calculated by (Ave% - Min%) ÷ Ave%.

[0071] In this example, the fixing belt was cut in the rotation direction (circumferential direction), and the inner sliding layer 1b of the cut surface was cross-sectionally milled using an ion milling device (IM4000PLUS; manufactured by Hitachi High-Technologies Corporation). The cross section was then observed with a scanning electron microscope (SEM) and image-processed to be quantified. Figure 6 shows cross-sectional views of the sliding layer, with (a) being that of the example and (b) being that of the comparative example. The upper row is an optical observation image, and the lower row is an image obtained by binarizing the optical observation image.

[0072] Fig. 7 shows the cross section of the sliding layer of the Example, where the binarized image was divided into sections with the same width as the thickness in the plane direction using the image analysis software "ImageJ" (Fig. 7a), and the results of calculating the filler area ratio for each section and the periodic coefficient calculated from (Ave% - Min%) ÷ Ave% (Fig. 7b), and a graph of the area ratio for each section (Fig. 7c). Fig. 8 shows the cross section of the sliding layer of the Comparative Example, where the sliding layer was similarly divided into sections with the same width as the thickness (Fig. 7a), and the results of calculating the filler area ratio for each section and the periodic coefficient calculated from (Ave% - Min%) ÷ Ave% (Fig. 7b), and a graph of the area ratio for each section (Fig. 7c).

[0073] [Inner surface (surface) roughness of inner sliding layer 1b] Figure 9 shows a summary of the film thickness, periodic coefficient, and roughness of the example and comparative example. The surface roughness of the inner circumferential surface of the inner sliding layer 1b was measured as the arithmetic mean roughness Ra (μm, JIS B0601) using a surface roughness measuring device (Surfcorder, manufactured by Kosaka Laboratory Co., Ltd.). The measurement conditions were an evaluation length of 4 mm, a cutoff value of 0.8 mm, and a feed rate of 0.1 mm / s.

[0074] The examples and comparative examples have shown that, for example, by using fillers with different aspect ratios and average particle sizes, it is possible to form sliding films with different periodic coefficients and change the roughness. Although the exact mechanism has not been clarified, it is speculated that, with regard to the convection of the coating liquid that occurs during the coating drying process during film formation, depending on the filler characteristics, there are cases where the particles ride the convection flow or change their orientation along with the convection flow.

[0075] With this configuration, it is possible to increase the surface roughness of the sliding layer even with the same amount of filler, effectively imparting roughness to the sliding surface side (inner peripheral surface side), and improving the wear resistance in the belt rotation direction, thereby providing a fixing belt with an inner sliding layer that can prevent torque increase and stick-slip throughout its durable lifespan. [Explanation of symbols]

[0076] 100 Fixing device 101 Photosensitive drum 102 Charging device 103 Laser light 104 Developing device 105 Intermediate transfer drum 106 Transfer roller 107 Toner cleaner 108 Toner cleaner 109 Deflecting Mirror 110 Laser Optical System T1 Primary transfer section T2 Secondary transfer section 1 Fuser belt 2 Fixing heater 3 Thermistor 4 Film guide and heater holder 5 Fixing belt stay 6 Pressure roller 7 Entrance Guide 8 Fixing roller 9. A / D Converter 10 Control circuit section (CPU) 11 Heater drive circuit section 12 Motor drive circuit section 13 Device frame 14 Fixing nip t Unfixed toner image P recording material 1a Shape-anisotropic filler 1b Inner sliding layer 1c Cylindrical substrate 1d Silicone rubber elastic layer 1e Fluorine resin surface layer (fluorine resin tube) 21 Foundation 22 Coating head 23 Polyimide precursor solution 24 Cylindrical substrate 25 Work Hand 26 Work moving device 27 Motor 31 Cylindrical substrate 311 Core metal holding jig 32 Coating table 33 Coating head 34 Coating head holder 35 Addition-curing silicone rubber composition layer 36 tubes 37 Cylinder Pump

Claims

1. A fixing belt used for heat-fixing a toner image on a recording material, the fixing belt rotating while sliding on a backup member with a lubricant interposed between the inner surface thereof, at least, a cylindrical substrate made of metal; a sliding layer made of a heat-resistant resin formed on the inner peripheral surface of the cylindrical base body and sliding on the backup member; a release layer formed on the outer peripheral surface of the cylindrical substrate; and the sliding layer contains a filler, and the distribution of the filler in the sliding layer is configured so that density and roughness are periodically repeated in the circumferential direction of the belt, a fixing belt, characterized in that, in a cross section of the sliding layer including the thickness direction and the circumferential direction of the belt, 20 or more sections are provided in the circumferential direction of the belt, each section having the same length as the thickness of the sliding layer, and when an area ratio of the filler is quantified for each section, a periodic coefficient calculated by (Ave% - Min%) / Ave% satisfies 0.6 or more, where Ave% is the average area ratio of the filler over all sections and Min% is the minimum area ratio.

2. The backup member is a planar heating element.

2. The fixing belt according to claim 1, wherein the fixing belt is a rotatable member.

3. The inner circumferential surface of the sliding layer rotates while sliding against the backup member.

2. The fixing belt according to claim 1, wherein the fixing belt is a rotatable member.

4. The thickness of the sliding layer is 5 to 25 μm.

2. The fixing belt according to claim 1, wherein the fixing belt is a rotatable member.

5. The fixing belt described in Claim 1, characterized in that the sliding layer is formed through a drying process in which a solvent containing the filler is applied to the base, followed by a baking process in which the solvent is heated and baked after the drying process, and is configured so that convection occurs in the solvent during the drying process.

6. A fixing belt as described in any one of claims 1 to 5, characterized in that the fixing belt is a film member.

7. A fixing belt as described in any one of claims 1 to 6, characterized in that the amount of the filler contained in the sliding layer is 7 volume % or more and 15 volume % or less with respect to the volume of the sliding layer.

8. A fixing device characterized by comprising a fixing belt described in any one of claims 1 to 7.

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