Fixing belt and fixing device

Abstract

To solve the problem in which: non-uniform surface roughness of the entire inner face slide layer of a fixing belt causes problems such as an increase in torque due to small roughness in part of the fixing belt and chipping of the slide layer due to large roughness.SOLUTION: An endless fixing member is composed of at least three layers comprising a surface layer, a base layer, and a slide layer formed of resin from the outside. The thickness of the slide layer is 8-20 μm. The slide layer has a Benard convection type cell structure on a surface not in contact with the base layer. The slide layer has an additive having a D50 of 4.5 μm or less and an aspect ratio of less than 50.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a fixing belt and a fixing device used in a heat fixing device of 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 installed inside the fixing belt, and the fixing belt and the material to be fixed are sandwiched and conveyed between the heating element and an elastic pressure roller to fix the image. Therefore, friction wear occurs between the inner surface of the fixing belt and the fixedly supported heating element. As a result, as the device wears out, problems such as self-excited vibration called stick-slip (hereafter referred to as film squeal) and torque increase occur.

[0006] As a countermeasure to these problems, Patent Document 3 discloses that a sliding filler is added to the sliding layer on the inner surface of the fixing belt to roughen the inner surface, thereby solving the problems.

[0007] In addition, a method has been proposed in which fillers are added to generate surface roughness on the inner surface, and during the process of forming the resin for the sliding layer, Benard-Marangoni convection is generated to create cells on the inner surface, thereby creating surface roughness. [Prior art documents] [Patent documents]

[0008] [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]

[0009] However, cells created by Bénard-Marangoni convection using additives have the problem that if the additive's aspect ratio is large, the surface roughness changes depending on the film thickness when applied, and the thickness fluctuates during manufacturing, resulting in an unstable roughness.In addition, if the thickness becomes uneven during manufacturing, the entire inner sliding layer of the fixing belt will have uneven surface roughness, which can cause problems such as increased torque due to small roughness in some parts of the fixing belt, or abrasion of the sliding layer due to large roughness.

[0010] An object of the present invention is to provide a fixing device that can prevent torque increase in a part of the fixing belt and abrasion of the sliding layer in a part of the fixing belt. [Means for solving the problem]

[0011] As a result of extensive research, the authors have found that it is possible to achieve a constant surface roughness that is independent of film thickness by doing the following:

[0012] That is, the fixing member of the present invention is an endless fixing member consisting of at least three layers, from the outside, a surface layer, a base layer, and a sliding layer made of resin, the sliding layer having a thickness of 8 to 20 μm, the sliding layer having a Benard convection type cell structure on the side not in contact with the base layer, and the sliding layer Nia It is characterized by having an additive with an aspect ratio of less than 50. [Effects of the Invention]

[0013] According to the present invention, by forming a sliding layer with uniform roughness regardless of thickness, the uniform surface roughness can prevent torque increase and wear of the sliding layer in parts of the fixing belt. [Brief explanation of the drawings]

[0014] [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 ring coating device used in the present example. [Figure 5] FIG. 2 is a diagram summarizing the specifications of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] Next, a description will be given of a form for carrying out the present invention, but the scope of the present invention is not limited to this form alone, and modifications that do not detract from the spirit of the present invention are also included in the present invention.

[0016] (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.

[0017] Next, the charged surface is exposed to a laser beam 103 output from a laser optical system 110 based on input image information. The laser optical system 110 outputs the laser beam 103 modulated (on / off) in response to time-series electric digital pixel signals of target image information from an image signal generating device such as an image reader (not shown), and scans and exposes the surface of the photosensitive drum 101. As a result of this scanning and exposure, an electrostatic latent image corresponding to the image information is formed on the surface of the photosensitive drum 101. Reference numeral 109 denotes a mirror that deflects the laser beam 103 output from the laser optical system 110 to an exposure position on the photosensitive drum 101.

[0018] The electrostatic latent image formed on the photosensitive drum is visualized with yellow toner by the yellow developing device 104Y of the developing device 104. This yellow toner image is transferred to the surface of the intermediate transfer drum 105 at a primary transfer station T1, which is the contact point between the photosensitive drum 101 and the intermediate transfer drum 105. Any toner remaining on the surface of the photosensitive drum 101 is cleaned by a cleaner 107. The above-described process cycle of charging, exposure, development, primary transfer, and cleaning is repeated in the same manner to form a magenta toner image (developing device 104M operates), a cyan toner image (developing device 104C operates), and a black toner image (developing device 104K operates). The toner images of each color formed in succession on the intermediate transfer drum 105 in this manner are then secondarily transferred together onto the recording material P at a secondary transfer station T2, which is the contact point 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 parallel to the pressure roller 6 with the fixing heater 2 facing downward. 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 via the fixing belt 1 with a predetermined pressure, forming a fixing nip 14 of the predetermined width required for fixing. Reference numeral 3 denotes a thermistor serving as a temperature detection means. The thermistor 3 (heater temperature sensor) is installed on the back surface (the surface opposite the heating surface) of the fixing heater 2, which is the heat source, and functions to detect the temperature of the fixing heater 2. The pressure roller 6 is driven to rotate at a predetermined peripheral speed in the direction indicated by the arrow. The fixing belt 1, which is in pressure contact with the pressure roller 6, rotates at a predetermined speed driven by the pressure roller 6. At this time, the inner surface of the fixing belt 1 slides in close contact with the lower surface of the fixing heater 2 and rotates around the outer periphery of the film guide / heater holder 4 in the direction of the arrow.

[0023] 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).

[0024] 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.

[0025] (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 is disposed with an adhesive layer interposed therebetween. 1a is a needle-shaped anisotropic filler compounded in the inner sliding layer, and is disposed along the longitudinal direction of the fixing belt. 1d is a silicone rubber elastic layer covering the outer peripheral surface of the cylindrical substrate 1c, and is disposed with a primer layer interposed therebetween. 1e is a fluororesin tube serving as a fluororesin surface layer, and is disposed on the silicone rubber elastic layer 1d with a silicone rubber adhesive layer interposed therebetween.

[0026] This will be explained in detail below.

[0027] (4) Cylindrical substrate; Since the fixing belt is required to have heat resistance, it is preferable to use a cylindrical substrate 1c that is heat-resistant and flex-resistant. For example, as a metal substrate, metal materials such as nickel electroforming or stainless steel can be used, as described in JP 2002-258648, JP 05 / 054960, and JP 2005-121825. In this embodiment, stainless steel 304 was used.

[0028] (5) inner sliding layer; Resins with high durability and high heat resistance, such as polyimide resin, polyamide-imide resin, and polyether ether ketone resin, are suitable for the inner surface sliding layer 1b. In particular, polyimide resin is preferred in terms of ease of manufacture, heat resistance, elastic modulus, strength, etc., and polyimide resin was used for the inner surface sliding layer in this example.

[0029] To improve sliding performance, it is desirable to add particles of graphite, molybdenum disulfide, fluororesin, etc. Mica is preferred from the standpoints of ease of production, heat resistance, lubricity, etc., and mica was used as an additive in this example as well.

[0030] (5-1) Polyimide precursor solution The polyimide inner sliding layer is formed by applying a polyimide precursor solution obtained by reacting approximately equimolar amounts of an aromatic tetracarboxylic dianhydride or a derivative thereof with an aromatic diamine in an organic polar solvent to the inner surface of the cylindrical substrate, drying, and heating the solution, followed by a dehydration ring-closing reaction.

[0031] Representative examples of aromatic tetracarboxylic acids 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 acids can be used alone or in combination of two or more.

[0032] Typical examples of aromatic diamines include 4,4'-diaminodiphenyl ether, paraphenylenediamine, benzidine, etc. These aromatic diamines can be used alone or in combination of two or more.

[0033] Examples of the organic polar solvent include dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone, phenol, O-, M-, and P-cresol.

[0034] (5-2) Additives The particle size of the additive must be selected to create irregularities in the sliding layer. From the viewpoint of cell formation, a particle size of less than 4.5 μm is desirable for a sliding layer thickness of 8 to 20 μm.

[0035] In order to create lubricity in the sliding layer, it is necessary to select a material with lubricity. Furthermore, since it is also required to be wear-resistant and not induce wear on the sliding components when it is detached from the sliding layer, it is necessary to select a material with an appropriate hardness. Considering these conditions, suitable additives include tetrafluoroethylene (PTFE), graphite, molybdenum disulfide, and mica.

[0036] (5-3) Formation of polyimide resin sliding layer Possible coating methods include ring coating. Figure 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 on support column 201, and is connected to a coating liquid supply device (not shown).

[0037] A work hand 25 that holds the cylindrical base 24 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.

[0038] 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 an even amount of additives is supplied from the slit, and the cylindrical substrate 24 is moved along the outer periphery of the coating head 22 to coat the inner surface of the cylindrical substrate 24. In this device, the thickness of the sliding layer is determined by the amount of coating, and any amount of coating (film thickness) 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.

[0039] After coating, the cylindrical substrate with the coated inner surface is baked, for example, in a hot air circulating oven at 80°C to 150°C for 5 to 30 minutes to dry the solvent, and then baked in a hot air circulating oven at 200°C to 240°C for 5 to 60 minutes, or in a hot air circulating oven at 350°C to 400°C for 10 to 60 minutes, thereby forming a uniform polyimide inner sliding layer that prevents the varnish from bumping.

[0040] The same is true when a polyimide resin is used for the cylindrical substrate itself; it can be produced by a conventionally known manufacturing method, that is, by applying a polyimide precursor solution to the outer or inner surface of a cylindrical core, drying the coating layer of the polyimide precursor solution, and then heat-curing (imidizing) it while it is still attached to the core surface, or by removing the coating layer from the core surface once it has solidified to a strength sufficient to maintain the structure of a tubular object, and then heat-curing it in the next step. [Example]

[0041] The additives related to the present invention will be described below. In this example, MK-100 (Katakura Corp. Agri) mica was used as the additive. MK-100 has an aspect ratio of 30 to 50 and a particle size D50 of 4.5 μm. 4.5 parts of mica was added per 100 parts of polyimide precursor solution. The polyimide precursor solution used was a mixture of U-Varnish-A, U-Varnish-S301, and U-Varnish-S (Ube Industries) in a ratio of 5:3:2. After coating, the inner surface of the coated cylindrical substrate was baked, for example, in a hot air circulation oven at 150°C for 5 minutes to dry the solvent, followed by baking at 200°C for 60 minutes in a hot air circulation oven and then baking at 350°C for 60 minutes in a hot air circulation oven to form a polyimide resin sliding layer.

[0042] The evaluation results for this example are shown in Figure 5. As a comparative example, PDM-5B (Topy Industries) with an aspect ratio of 50 or more and a particle size D50 of 5 μm was used. The firing conditions for the comparative example were the same as for this example. The results show the surface roughness Ra when the thickness of the sliding layer was varied to 10, 12, and 14 μm. In the comparative example, Ra tends to increase as the thickness increases, but in this example, the roughness is constant and independent of thickness.

[0043] By producing and evaluating the fixing belts of the present example and the comparative example, it was confirmed that the inner surface roughness can be made uniform regardless of the thickness of the sliding layer. [Explanation of symbols]

[0044] 1 Fuser belt 1e Surface resin layer (fluororesin) 1d Elastic layer (silicone rubber) 1c Cylindrical substrate 1b Inner resin layer 1a Additives 22 Ring coat nozzle (coating liquid discharge part) 23 Polyimide precursor solution 24 Fixing belt substrate 27 Drive motor 100 Fixing device t Unmelted toner P recording material

Claims

1. An endless fixing member comprising at least three layers, from the outside, a surface layer, a base layer, and a sliding layer made of resin, wherein the sliding layer has a thickness of 8 to 20 μm, the sliding layer has a Benard convection type cell structure on the side not in contact with the base layer, and the sliding layer contains an additive having an aspect ratio of less than 50.

2. 2. The fuser member of claim 1, wherein the additive is mica.

3. 2. The fixing member according to claim 1, wherein the resin layer is made of a polyimide resin.

4. A fixing member described in any one of claims 1 to 3, characterized in that the additive has a D50 of 4.5 μm or less.

5. A fixing member described in any one of claims 1 to 4, characterized in that the additive is a needle-shaped anisotropic filler.

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

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