JP7537155B2 - Fixing member and its manufacturing method, fixing device, image forming device, and image forming method - Google Patents

Description

The present invention relates to a fixing member and its manufacturing method, a fixing device, an image forming device, and an image forming method.

The fixing device used in image forming devices such as copiers and laser beam printers usually brings a heated fixing belt (fixing member) into contact with a recording medium carrying an unfixed toner image, fixing the toner image to the recording medium. In such fixing devices, for example, one of two or more rollers supporting the endless fixing belt is a heating roller for heating the fixing belt.

The fixing member is required to have the ability to be easily separated from the toner image after the toner image is fixed to the recording medium. If the toner image is not easily separated from the fixing member after fixing, the recording medium with the fixed toner image will wrap around the fixing member, making it difficult to eject the recording medium and more likely to cause paper jams in the image forming device.

To improve the separation between the toner image and the fixing member after fixing, a fixing member is known that has a minute uneven shape formed on the outermost surface that comes into contact with the toner image.

For example, Patent Document 1 describes a method for manufacturing a fixing member in which, when a fluororesin is heated and baked to form a release layer, the fluororesin is pressed with a surface transfer member having a micro-irregular shape, and the micro-irregular shape is transferred to the release layer. Patent Document 1 describes that forming a micro-irregular structure in the release layer in this manner improves the transportability of paper.

Japanese Patent Application Publication No. 09-277378

As described in Patent Document 1, by forming a micro-uneven structure on the surface of the fixing member, it is possible to improve the separation between the toner image and the fixing member after fixing.

However, according to the inventors' findings, even with the fixing member described in Patent Document 1, the recording medium with the fixed toner image still sometimes wound around the fixing member.

The present invention has been made in consideration of the above problems, and aims to provide a fixing member that can improve the separability between the toner image and the fixing member after fixing, a manufacturing method for the fixing member, a fixing device and an image forming device that have the fixing member, and an image forming method that uses the fixing member.

To solve the above problem, the present invention relates to a fixing member having a base layer, an elastic layer, and a release layer in this order. The fixing member has a development area ratio Sdr of 4.5 or more of the outermost surface of the fixing member, which is constituted by the release layer.

The present invention, which aims to solve the above problem, also relates to a method for manufacturing a fixing member, comprising the steps of: preparing a laminate for manufacturing a fixing member, the laminate having a base layer, an elastic layer, and a release layer in this order; and projecting a polygonal projection material onto the release layer of the laminate, so that the development area ratio Sdr of the outermost surface of the fixing member, which is constituted by the release layer, is 4.5 or more.

The present invention, which aims to solve the above problem, also relates to a fixing device used in an electrophotographic image forming apparatus, which has the above fixing member for fixing a toner image carried on a recording medium to the recording medium by applying pressure.

The present invention, which aims to solve the above problem, also relates to an electrophotographic image forming apparatus having the fixing member described above for fixing a toner image carried on a recording medium to the recording medium by applying pressure.

The present invention, which aims to solve the above problem, also relates to an image forming method that includes a step of carrying a toner image on the surface of a recording medium, and a step of fixing the carried toner image to the recording medium, the fixing step being a step of pressing the toner image onto the recording medium by the fixing member.

The present invention provides a fixing member that can improve the separation between the toner image and the fixing member after fixing, a manufacturing method for the fixing member, a fixing device and an image forming device that have the fixing member, and an image forming method that uses the fixing member.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2A is a diagram showing a schematic configuration of a fixing belt according to an embodiment of the present invention, and FIG. 2B is an enlarged view of a portion B in FIG. 2A.

The following describes an embodiment of the present invention. The fixing member according to this embodiment is an endless belt-shaped fixing belt, and has a base layer made of a heat-resistant resin, an elastic layer made of an elastic material disposed on the base layer, and a release layer made of a fluororesin disposed on the elastic layer. The fixing belt can be configured in the same manner as a known fixing belt in which a base layer, an elastic layer, and a release layer are disposed in this order, except that the release layer has a specific surface shape described below.

The base layer is made of a heat-resistant resin. "Made of heat-resistant resin" means that the main material constituting the base layer is a heat-resistant resin, and "heat-resistant" means that the base layer is sufficiently stable and exhibits the desired physical properties at the temperature (e.g., 150 to 220°C) when the fixing belt is used to fix a toner image to a recording medium in electrophotographic image formation.

The heat-resistant resin is appropriately selected from resins that do not substantially denature or deform at the above-mentioned operating temperature of the fixing belt, and may be one or more types. Examples of the heat-resistant resin include polyphenylene sulfide, polyarylate, polysulfone, polyethersulfone, polyetherimide, polyimide, polyamideimide, and polyetheretherketone. Among them, polyimide is preferred from the viewpoint of heat resistance.

Polyimide can be obtained by heating its precursor polyamic acid to 200°C or higher or by using a catalyst to promote dehydration and cyclization (imidization) reactions. Polyamic acid can be produced by dissolving a tetracarboxylic dianhydride and a diamine compound in a solvent, mixing and heating to cause a polycondensation reaction, or a commercially available product can be used. Examples of the diamine compound and tetracarboxylic dianhydride include the compounds described in paragraphs 0123 to 0130 of JP 2013-25120 A.

The content of the heat-resistant resin in the base layer may be an amount sufficient to form the base layer, and is preferably 50% by mass or more, more preferably 60 to 75% by mass, and even more preferably 76 to 90% by mass.

The base layer may further contain components other than the heat-resistant resin, as long as the effects of this embodiment are obtained. For example, the base layer may further contain the above-mentioned filler. The filler is, for example, a component that contributes to improving at least one of the hardness, heat conductivity, and electrical conductivity of the base layer. The filler may be one or more types, and examples of the material include carbon black, ketjen black, nanocarbon, and graphite.

If the content of the filler in the base layer is too high, the toughness of the base layer may decrease, resulting in poor fixability and separation properties of the fixing belt. If the content is too low, the expected effect of the filler, such as imparting appropriate electrical conductivity, may be insufficient. From this viewpoint, the content of the filler in the base layer is preferably 3% by mass or more, more preferably 4% by mass or more, and even more preferably 5% by mass or more. From the above viewpoint, the content of the filler in the base layer is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less.

The elastic layer is made of an elastic material and has elasticity that contributes to improving the contact between the surface of the fixing belt in the fixing nip and the recording medium carrying an unfixed toner image. "Made of an elastic material" means that the main material constituting the elastic layer is an elastic material, and "elasticity" means that the fixing belt is given a deformation that allows it to come into sufficient contact with the surface of the recording medium carrying the unfixed toner image when fixing a toner image to the recording medium in electrophotographic image formation.

The elastic material may be one or more kinds, for example, a material having a loss tangent tan δ (ratio of loss modulus to storage modulus) of 0.1 or less at 20 Hz. Examples of the elastic material include elastic resin materials, examples of which include silicone rubber, thermoplastic elastomers, and rubber materials. Of these, it is preferable that the elastic material is silicone rubber, from the viewpoint of heat resistance in addition to the desired elasticity.

The silicone rubber may be one or more types. Examples of the silicone rubber include polyorganosiloxane or its heat cured product, and the addition reaction type silicone rubber described in JP 2009-122317 A. Examples of the polyorganosiloxane include dimethylpolysiloxane with both ends blocked with trimethylsiloxane groups and vinyl groups on the side chains described in JP 2008-255283 A.

The thickness of the elastic layer is preferably 5 to 300 μm, more preferably 50 to 250 μm, and even more preferably 100 to 200 μm, from the viewpoint of fully exhibiting heat conductivity and elasticity.

The elastic layer may further contain components other than the elastic resin material as long as the effect of this embodiment can be obtained. For example, the elastic material may further contain a heat-conductive filler to enhance the heat conductivity of the elastic layer. Examples of the filler material include silica, metallic silica, alumina, zinc, aluminum nitride, boron nitride, silicon nitride, silicon carbide, carbon, and graphite. The form of the filler is not limited, and may be, for example, a spherical powder, an irregular powder, a flat powder, or a fiber.

From the viewpoint of achieving both thermal conductivity and elasticity, the content of the elastic resin material in the elastic material is, for example, preferably 60 to 100% by volume, more preferably 75 to 100% by volume, and even more preferably 80 to 100% by volume.

The release layer is a layer having releasability that contributes to improving the separation of the molten toner layer on the recording medium from the surface of the fixing belt in the fixing nip, and has appropriate releasability for toner components. The release layer constitutes the outer surface of the fixing belt that contacts the recording medium during fixing. The release layer is made of a fluororesin. "Made of a fluororesin" means that the main material constituting the release layer is a fluororesin.

Examples of the above fluororesin include perfluoroalkoxy fluororesin (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP) and tetrafluoroethylene-ethylene copolymer (ETFE).

The thickness of the release layer is preferably 5 to 40 μm, more preferably 10 to 35 μm, and even more preferably 20 to 30 μm, from the viewpoints of heat transfer, conformity to deformation of the elastic layer, and release properties.

The release layer may further contain components other than the fluororesin as long as the effects of this embodiment are achieved. For example, the release layer may further contain lubricant particles. Examples of the lubricant particles include fluororesin particles, silicone resin particles, and silica particles.

From the viewpoints of heat conductivity and flexibility that sufficiently follows the deformation of the elastic layer, it is preferable that the content of the fluororesin in the material of the release layer is 70 to 100% by volume.

The release layer has a surface shape in which fine and irregular projections and recesses are formed by blasting on at least a portion of its surface. The release layer heats the toner image carried on a recording medium such as paper and simultaneously presses it against the recording medium, fixing the toner image to the recording medium. The release layer also serves to separate the fixed toner image from the fixing belt.

When the adhesive force (F1) of the heated (thermally softened) toner image to the surface of the fixing belt (surface of the release layer) is smaller than the restoring force (F2) of the recording medium to its original shape after being pressed and deformed, the release layer satisfactorily separates the fixed toner image from the fixing belt. On the other hand, with the recent expansion in the types of recording media available, many recording media with smaller restoring forces (F2) have been put on the market. Even when forming an image on these recording media with a small F2, the fixing belt is required to have a smaller adhesive force (F1) in order to separate the fixed toner image from the fixing belt satisfactorily.

According to the findings of the inventors, the adhesion force (F1) of the heat-softened toner image to the surface of the release layer is expressed as the product of the intermolecular force between the recording medium and the toner image and the real contact area where the recording medium and the toner image come into contact. In this embodiment, the real contact area is made smaller to reduce the adhesion force (F1), thereby allowing the fixed toner image to be separated from the fixing belt well even on a recording medium with a smaller restoring force (F2). In addition, by making the real contact area smaller, air can easily enter the recesses on the surface of the release layer, reducing the surface energy of the release layer (lotus effect), which is also thought to allow the fixed toner image to be separated from the fixing belt well.

From the above viewpoint, in the present embodiment, the release layer has an interface development area ratio Sdr of 4.5 or more as specified in ISO 25178:2012. By making the Sdr 4.5 or more, the real contact area of the surface of the release layer can be made smaller, and the surface energy can be made smaller, so that the fixed toner image and the fixing belt can be separated well. The Sdr of the release layer may be 4.5 or more, but is more preferably 5.0 or more, even more preferably 7.0 or more, even more preferably 9.5 or more, and particularly preferably 10.0 or more. There is no particular upper limit for Sdr, but it can be 20 or less in terms of ease of processing the surface of the release layer, etc.

The Sdr of the surface of the release layer can be a value obtained by observation using a shape analysis laser microscope "VK-X250" (manufactured by Keyence Corporation). For example, a 50x objective lens is used for observation, double scan is always set, the measurement size (number of pixels) is standard (1024 x 768), the measurement quality is high precision, the Z-axis pitch is the smaller of the RPD (Real Peak Detection), the image processing includes surface inclination correction, reference surface correction, and end correction, and the quantification region (ROI) is the entire area. In order to eliminate the variation in measurement value due to the measurement position, it is desirable to obtain the development area ratio Sdr for four locations and calculate the average value of these to be used as the development area ratio Sdr of the surface of the release layer.

The above uneven shape can be appropriately formed on the surface of the release layer by a known method for roughening the surface of a resin film, but from the viewpoint of realizing the desired surface roughness regardless of the manufacturing method of the release layer, it is preferable to form it by blasting using polygonal projection material. Note that polygonal projection material means a projection material having a polygonal polyhedral shape with multiple parts and multiple faces.

According to the knowledge of the present inventors, when transferring from a surface transfer member having a minute uneven shape as described in Patent Document 1, it is difficult to achieve a developed surface area ratio Sdr of 4.5 or more on the release layer surface.

For example, as described in Patent Document 1, when an uneven shape is formed by transfer from a surface transfer member having a fine uneven shape, a regular uneven shape is usually formed on the surface of the release layer. However, such a regular uneven shape may cause interference with the toner image, causing unevenness in the transferability of the toner image. If a portion of the toner image that was difficult to transfer adheres to the fixing belt (release layer), the recording medium after fixing may wrap around the fixing belt, causing a transport failure of the recording medium. In response to this, by forming a fine and irregular uneven shape by blasting using a polygonal projection material, the development area ratio Sdr of the surface of the release layer is set to 4.5 or more, and the occurrence of the above-mentioned interference is also suppressed, allowing the fixed toner image to be separated from the fixing belt satisfactorily.

In addition, according to the findings of the present inventors, it is difficult to achieve an expanded surface area ratio Sdr of 4.5 or more on the release layer surface by blasting using projection material that is not polygonal, such as spherical. This is believed to be because when spherical projection material is projected, only depressions caused by the projection material itself are formed. In contrast, polygonal projection material has corners on its surface. When the projection material is projected onto the release layer, in addition to depressions caused by the projection material itself, fine irregularities caused by the corners are imparted to the surface of the release agent, which is believed to enable the expanded surface area ratio Sdr of the release layer surface to be 4.5 or more.

The fixing belt can be manufactured by a method including the steps of preparing a laminate for manufacturing the fixing belt, the laminate having a base layer, an elastic layer, and a release layer in this order, and projecting polygonal projection material onto the surface of the release layer.

The laminate for manufacturing the fixing belt can be a known fixing belt whose surface does not have an uneven shape with a development area ratio Sdr of 4.5 or more. The base layer, elastic layer, and release layer are as described above.

The laminate can be produced by forming a base layer made of a heat-resistant resin, applying a material containing an elastic resin material in the form of a film and heat-curing it to form an elastic layer, and applying a material containing a fluororesin in the form of a film and heat-baking it to form a release layer. Alternatively, the laminate can be produced by forming a base layer made of a heat-resistant resin, covering it with a fluororesin film to form the release layer, injecting a material containing an elastic resin material between the base layer and the release layer, and heat-curing it to form the elastic layer. According to the findings of the present inventors, when a release layer is formed by applying a material containing a fluororesin, the release layer is likely to be finely processed by blast processing because the molecular weight (weight average molecular weight) of the fluororesin is small, and the development area ratio Sdr of the surface of the release layer can be increased.

The projection of the above-mentioned projection material may be carried out in the same manner as normal blasting, except that polygonal projection material is used. Examples of the above-mentioned polygonal projection material include boron carbide, silicon carbide, alumina such as white fused alumina and brown fused alumina, white pig iron, zircon, steel, stainless steel, iron such as iron powder, ceramics, glass powder, and plant-based projection materials such as peach seeds, apricot seeds, and walnuts.

In this case, from the viewpoint of increasing the developed area ratio Sdr of the surface of the release layer, it is preferable that the projection material is harder. From this viewpoint, the projection material preferably has a new Mohs hardness of 4 or more, more preferably 5.5 or more, even more preferably 7 or more, and particularly preferably 10 or more. There is no particular upper limit on the new Mohs hardness of the projection material, but it is usually 15 or less, and preferably 13 or less.

In addition, from the viewpoint of increasing the developed surface area ratio Sdr of the release layer, it is preferable that the projection material has a larger specific gravity. From this viewpoint, it is preferable that the projection material has a specific gravity of 1.0 or more and 8.0 or less, and more preferably 2.0 or more and 8.0 or less.

In addition, from the viewpoint of increasing the development area ratio Sdr of the surface of the release layer, it is preferable that the projection material is smaller in size. From this viewpoint, the projection material preferably has a median particle size (particle size at which the integrated value is 50 volume % in the volume-based particle size distribution curve) of 40 μm or more and 200 μm or less, more preferably 40 μm or more and 150 μm or less, and even more preferably 40 μm or more and 100 μm or less.

The projection pressure of the above projection material is not particularly limited, but can be, for example, 0.05 MPa or more and 0.5 MPa or less, and preferably 0.1 MPa or more and 0.3 MPa or less.

The fixing belt is applied to a fixing device in an electrophotographic image forming apparatus. An image forming apparatus having the fixing belt can be configured in the same manner as a known image forming apparatus having a fixing device for fixing an unfixed toner image on a recording medium to the recording medium by heating and pressurizing the recording medium using the fixing belt, except for having the fixing belt. The fixing belt can be used for high-speed image formation using the electrophotographic method, and can also be used for image formation at lower speeds. "High speed" in high-speed image formation means, for example, a printing speed of 60 sheets/minute or more on an A4 recording medium, and more specifically, a printing speed of 60 to 80 sheets/minute on an A4 recording medium.

The fixing device has an endless fixing belt, two or more rollers for endlessly supporting the fixing belt, a heating device for heating the fixing belt supported by the rollers, and a pressure roller arranged so as to be relatively urged toward one of the two or more rollers. The fixing device can be configured in the same manner as a known so-called biaxial belt fixing device, except that the fixing belt of this embodiment is used as the endless fixing belt.

At least one of the two or more rollers may incorporate the heating device, and may include, for example, a heating roller for heating the fixing belt. The heating roller has, for example, a heat-conductive sleeve made of aluminum or the like, and a heat source such as a halogen heater disposed inside the sleeve. The outer circumferential surface of the sleeve may be covered with a layer made of a fluororesin such as polytetrafluoroethylene (PTFE).

The heating device may be a heating device arranged outside the roller, i.e., a heating device arranged on the inner or outer side of the endless track formed by the supported fixing belt, facing the endless track, or may include both a heating device built into the roller and a heating device arranged outside the roller.

Of the two or more rollers, there may be one or more rollers other than the heating roller, and they may be configured appropriately according to other desired functions.

The roller diameter of the roller that is urged by the pressure roller through the fixing belt is preferably large from the viewpoint of being able to handle high-speed image formation, for example, 50 mm or more. If the roller diameter is large, the recording medium tends to be difficult to separate from the fixing belt at the fixing nip during fixing, making such separation difficult during high-speed image formation. In the fixing device, the roller diameter can be appropriately set according to the excellent separation and fixability of the fixing belt and the desired image formation speed. For example, it is more preferable that the roller diameter is 60 mm or more from the viewpoint of high-speed image formation and improved fixability of the fixing belt to the recording medium during fixing.

The fixing belt is supported by the two or more rollers in a stretched state, i.e., under a predetermined tension. If the tension is too large, the physical properties that contribute to the adhesion of the fixing belt to the recording medium, such as the elasticity of the elastic layer, may not be fully expressed in the fixing nip. From the viewpoint of adhesion, the tension is preferably 45 N or less, and more preferably 50 N or less. The tension may be large enough to maintain the shape of the endless track formed by the fixing belt being supported by the rollers, for example, 20 N or more. The tension can be adjusted, for example, by the distance between the two or more rollers.

The image forming apparatus having the fixing belt can be configured in the same manner as a known image forming apparatus having a fixing device for fixing an unfixed toner image on a recording medium to the recording medium by applying heat and pressure using the fixing belt, except that it has the fixing belt.

Hereinafter, the embodiments of the present invention will be further described with reference to the drawings.
1, the image forming apparatus 1 includes an image reading unit 10, an operation display unit 20, an image processing unit 30, an image forming unit 40, a paper conveying unit 50, a fixing unit 60, and a control unit 100. The image forming apparatus 1 can implement an image forming method similar to a known method, except that the fixing unit 60 uses the fixing belt.

The control unit 100 is a device that cooperates with the deployed program to centrally control the operation of each block of the image forming device 1, and includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory).

The image reading unit 10 is configured with an automatic document feeder 11, also known as an ADF (Auto Document Feeder), and an original image scanning device 12 (scanner). The operation display unit 20 is configured, for example, with a liquid crystal display (LCD: Liquid Crystal Display) with a touch panel, and functions as a display unit and an operation unit. The image processing unit 30 is equipped with a circuit that performs digital image processing on input image data according to initial settings or user settings.

The image forming section 40 includes an image forming unit 41, an intermediate transfer unit 42, and a secondary transfer unit 43 for forming images using the color toners of the Y, M, C, and K components based on input image data.

Image forming unit 41 is composed of four image forming units 41Y, 41M, 41C, and 41K for the Y, M, C, and K components. Image forming units 41Y, 41M, 41C, and 41K have similar configurations, so for ease of illustration and explanation, common components are indicated with the same reference numerals, and when distinguishing between them, the reference numerals are followed by Y, M, C, or K. In FIG. 1, reference numerals are only assigned to the components of image forming unit 41Y for the Y component, and reference numerals are omitted for the components of the other image forming units 41M, 41C, and 41K.

The image forming unit 41 includes an exposure device 411, a developing device 412, a photosensitive drum 413, a charging device 414, and a drum cleaning device 415.

The photoconductor drum 413 is a negatively charged organic photoconductor (OPC: Organic Photo-conductor) in which an undercoat layer (UCL), a charge generation layer (CGL), and a charge transport layer (CTL) are sequentially laminated on the circumferential surface of an aluminum conductive cylinder (aluminum tube), for example.

The charging device 414 is a non-contact charging device that uses, for example, corona discharge. The charging device 414 may also be a contact charging device that contacts the photosensitive drum 413 to charge it. The exposure device 411 is composed of, for example, a semiconductor laser. The developing device 412 is a developing device for a two-component developer, and contains the developer of each color component (for example, a two-component developer consisting of a small particle size toner and a magnetic material). The drum cleaning device 415 has a drum cleaning blade, such as an elastic blade, that is arranged so as to be in sliding contact with the surface of the photosensitive drum 413.

The intermediate transfer unit 42 includes an intermediate transfer belt 421, a primary transfer roller 422, a number of support rollers 423 including a backup roller 423A, and a belt cleaning device 426.

The intermediate transfer belt 421 is an endless belt that is stretched in a loop around a number of support rollers 423. At least one of the support rollers 423 is a drive roller, and the others are driven rollers. The belt cleaning device 426 has a belt cleaning blade, such as an elastic blade, that is arranged so as to be in sliding contact with the surface of the intermediate transfer belt 421.

The secondary transfer unit 43 includes, for example, a secondary transfer roller 431. The secondary transfer unit 43 may be configured in such a way that a secondary transfer belt is stretched in a loop shape around a plurality of support rollers including the secondary transfer roller.

The fixing section 60 is disposed as a unit within the fixing device F. The fixing section 60 has an endless fixing belt 61, two rollers 64, 65 for supporting the fixing belt 61 in an endless manner, a heating device 63 for heating the fixing belt 61 supported by the rollers 64, 65, and a pressure roller 62 disposed so as to be biased relative to the roller 64.

The roller 64 is disposed opposite the pressure roller 62 via the fixing belt 61, and the roller diameter is 50 mm or more. The rollers 64 and 65 support the fixing belt 61 on an endless track with a tension of 45 N. For example, the roller 64 is a drive roller, and the roller 65 is a driven roller. The heating device 63 is, for example, composed of a halogen lamp or a resistance heating element, and is built into the roller 65. The pressure roller 62 is disposed so as to be freely approachable and detachable from the roller 64. The pressure roller 62 presses against the fixing belt 61 supported by the roller 64, forming a fixing nip portion that holds and transports the paper S. The paper S corresponds to a recording medium, and is, for example, standard paper, special paper, etc.

The heating device 63 may be an induction heating (IH) type heating device. An air separation unit may be further disposed within the fixing device F, which separates the paper S from the fixing belt 61 or the pressure roller 62 by blowing air. The fixing section 60 corresponds to the fixing device described above.

As shown in FIG. 2A, the fixing belt 61 is an endless belt, and as shown in FIG. 2B, it is configured by stacking a base layer 611, an elastic layer 612, and a release layer 613 in this order. The base layer 611 is a polyimide belt, and carbon black is dispersed in the base layer 611. The elastic layer 612 is an elastic layer made of, for example, silicone rubber, and the release layer 613 is a layer of, for example, perfluoroalkoxy fluorine resin (PFA).

The release layer 613 has an uneven surface formed by blasting. The uneven surface is such that the development area ratio Sdr of the outermost surface of the fixing belt 61, which is formed by the release layer 613, is 4.5 or more.

The paper transport section 50 includes a paper feed section 51, a paper discharge section 52, a first transport section 53, and a second transport section 57. The three paper feed tray units 51a to 51c that make up the paper feed section 51 store paper S, identified based on basis weight, size, and the like, in predetermined types. The first transport section 53 includes multiple transport roller sections including an intermediate transport roller section 54, a loop roller section 55, and a registration roller section 56. The second transport section 57 includes a switchback path 58 in which multiple transport roller sections are arranged, and a back transport path 59.

In the image forming apparatus 1, the automatic document feeder 11 transports the document D placed on the document tray by a transport mechanism and sends it to the document image scanning device 12. The automatic document feeder 11 can continuously read the images (including both sides) of multiple documents D placed on the document tray at once. The document image scanning device 12 optically scans the document transported from the automatic document feeder 11 onto the contact glass or the document placed on the contact glass, and forms an image of the reflected light from the document on the light receiving surface of a CCD (Charge Coupled Device) sensor 12a to read the document image. The image reading unit 10 generates input image data based on the reading result by the document image scanning device 12. This input image data is subjected to predetermined image processing in the image processing unit 30 as necessary.

The control unit 100 controls the drive current supplied to a drive motor (not shown) that rotates the photoconductor drum 413. As a result, the photoconductor drum 413 rotates at a constant peripheral speed. The charging device 414 uniformly charges the photoconductive surface of the photoconductor drum 413 to a negative polarity. The exposure device 411 irradiates the photoconductor drum 413 with laser light corresponding to an image of each color component, and an electrostatic latent image of each color component is formed on the surface of the photoconductor drum 413 due to the potential difference with the surroundings. The developing device 412 visualizes the electrostatic latent image by attaching toner of each color component to the surface of the photoconductor drum 413 to form a toner image.

Meanwhile, the intermediate transfer belt 421 runs at a constant speed in the direction of arrow A by the rotation of the support roller 423, which serves as a drive roller. The primary transfer roller 422 presses the intermediate transfer belt 421 against the photosensitive drum 413 to form a primary transfer nip, and the toner images of each color on the photosensitive drum 413 are primarily transferred onto the intermediate transfer belt 421 so that the toner images of each color are sequentially superimposed. Residual toner remaining on the surface of the photosensitive drum 413 is removed from the surface after the primary transfer by the elastic blade of the drum cleaning device 415, which contacts the surface of the photosensitive drum 413.

On the other hand, the secondary transfer roller 431 is pressed against the backup roller 423A via the intermediate transfer belt 421 to form a secondary transfer nip. Paper S fed from the paper feed unit 51 or the second transport unit 57 is transported to the secondary nip transfer unit. The inclination and widthwise position (offset) of the paper S are corrected during the process of transport by the first transport unit 53.

When the paper S passes through the secondary transfer nip, the toner image carried on the intermediate transfer belt 421 is secondarily transferred to the paper S (a process for carrying a toner image on the surface of a recording medium). The paper S onto which the toner image has been transferred is transported toward the fixing unit 60. Residual toner remaining on the surface of the intermediate transfer belt 421 after the secondary transfer is removed from the surface by the above-mentioned elastic blade in the belt cleaning device 426, which contacts the surface of the intermediate transfer belt 421.

The fixing unit 60 heats and presses the conveyed paper S in the fixing nip, fixing the toner image onto the paper S (the process of fixing the carried toner image onto the recording medium). The drive control of the fixing belt 61, pressure roller 62, heating device 63, etc. is performed by the control unit 100.

The fixing belt 61 is heated by the heating device 63, and as a result, the fixing belt 61 becomes uniform at a predetermined fixing temperature (e.g., 170°C) across the width. The fixing temperature is a temperature that can supply the thermal energy required to melt the toner on the paper S, and differs depending on factors such as the type of paper S on which the image is formed.

In the case of double-sided printing, the second transport section 57 transports the paper S to the switchback path 58, then switches back and transports it to the back-side transport path 59, thereby inverting the paper S and supplying it to the first transport section 53 (upstream of the loop roller section 55). The paper S is then again supplied to the secondary transfer nip section to transfer the desired toner image onto the paper S, and the toner image is then fixed onto the paper S in the fixing section 60.

The paper S on which the desired image has been formed is then discharged outside the image forming device 1 by the paper discharge section 52 equipped with paper discharge rollers 52a.

The fixing belt 61 has excellent fixing properties for the toner image on the paper S and excellent separation properties for the paper S at the fixing nip, even during high-speed image formation.

The present invention thus configured provides a fixing member that can enhance the separation between the toner image and the fixing member after fixing, a manufacturing method for the fixing member, a fixing device and an image forming device that have the fixing member, and an image forming method that uses the fixing member.

The present invention will be described in more detail using the following examples and comparative examples. Note that the present invention is not limited to the following examples.

[Test 1]
A varnish containing polyamic acid and 8% by mass of carbon black was spin-coated on the outside of a cylindrical mold, then dried at 300 to 450° C. and imidized to produce a cylindrical polyimide tubular product (substrate belt) with an inner diameter of 99 mm, a length of 360 mm, and a thickness of 70 μm. The polyamic acid was a polymer obtained by dehydration condensation of 3,3′,4,4′-biphenyltetracarboxylic dianhydride and p-phenylenediamine.

Next, a silicone rubber material was applied to the surface of the base belt and cured by heating to create an elastic layer of silicone rubber 200 μm thick.

Furthermore, a PFA resin dispersion was applied to the surface of the elastic layer, dried, and then heated and baked to create a release layer with a thickness of 30 μm.

A support was inserted into the resulting laminated belt and rotated, and while the nozzle of the blasting device was moved relative to the rotation axis, a projection material was fired from the nozzle of the blasting device toward the PFA layer, forming an uneven shape on the surface of the PFA layer. Polygonal white fused alumina (hardness: 12, manufacturer's published median particle size: 63-75 μm) was used as the projection material (media), the projection pressure of the projection material was 0.3 MPa, the movement length was 100 mm, the angle between the projection direction and the PFA layer was 90°, and the nozzle was moved in only one direction.

In this way, an endless fixing belt 1 was obtained, which has a polyimide base layer, a silicone rubber elastic layer, and a PFA release layer stacked in this order, and has a surface shape that includes an uneven shape.

The surface shape of the fixing belt 1 was observed with a shape analysis laser microscope "VK-X250" (manufactured by Keyence Corporation). For the observation, a 50x objective lens was used, double scan was always set, the measurement size (number of pixels) was standard (1024 x 768), the measurement quality was high precision, the Z-axis pitch was the smaller of the RPD (Real Peak Detection), the image processing included surface inclination correction, reference surface correction, and end correction, and the quantification region (ROI) was the entire area. In this way, the developed area ratio Sdr of the outermost surface was obtained for four locations, and the average of these was calculated to obtain the developed area ratio Sdr of the outermost surface of the fixing belt 1.

The developed area ratio Sdr of the outermost surface of the fixing belt 1 measured in this way was 11.6.

[Test 2]
A varnish containing polyamic acid and 8% by mass of carbon black was spin-coated on the outside of a cylindrical mold, then dried at 300 to 450° C. and imidized to produce a cylindrical polyimide tubular product (substrate belt) with an inner diameter of 99 mm, a length of 360 mm, and a thickness of 70 μm. The polyamic acid was a polymer obtained by dehydration condensation of 3,3′,4,4′-biphenyltetracarboxylic dianhydride and p-phenylenediamine.

Next, a cylindrical stainless steel core with an outer diameter of 99 mm was attached to the inside of the base belt, and a cylindrical mold that holds a 30 μm-thick PFA tube on its inner surface was placed on the outside of the base belt, thus holding the core and the cylindrical mold coaxially and forming a cavity between them. Next, a silicone rubber material was injected into the cavity and heated to harden, creating an elastic layer of silicone rubber with a thickness of 200 μm.

A polygonal projection material was projected onto the laminated belt thus obtained in the same manner as in Test 1, to obtain an endless fixing belt 2 having a polyimide base layer, a silicone rubber elastic layer, and a PFA release layer stacked in this order, and a surface shape including a concave-convex shape.

The developed area ratio Sdr of the outermost surface of the fixing belt 2, measured in the same manner as in Test 1, was 9.9.

[Test 3]
A fixing belt 3 was obtained in the same manner as in Test 2, except that the projection pressure of the projection material was set to 0.2 MPa.

The developed area ratio Sdr of the outermost surface of the fixing belt 3, measured in the same manner as in Test 1, was 7.8.

[Test 4]
A fixing belt 4 was obtained in the same manner as in Test 2, except that the projection pressure of the projection material was set to 0.1 MPa.

The developed area ratio Sdr of the outermost surface of the fixing belt 4, measured in the same manner as in Test 1, was 6.7.

[Test 5]
A fixing belt 5 was obtained in the same manner as in Test 3, except that polygonal white fused alumina (hardness: 12, median particle size published by the manufacturer: 53 to 63 μm) was used as the blast material.

The developed area ratio Sdr of the outermost surface of the fixing belt 5, measured in the same manner as in Test 1, was 5.7.

[Test 6]
A fixing belt 6 was obtained in the same manner as in Test 2, except that polygonal glass powder (hardness: 5.5, median particle size published by the manufacturer: 106 μm or less) was used as the blast material.

The developed area ratio Sdr of the outermost surface of the fixing belt 6, measured in the same manner as in Test 1, was 5.4.

[Test 7]
A fixing belt 7 was obtained in the same manner as in Test 2, except that a polygonal peach material (hardness: 4, median particle size published by the manufacturer: 154 μm or less) was used as the blast material.

The developed area ratio Sdr of the outermost surface of the fixing belt 7, measured in the same manner as in Test 1, was 4.5.

[Test 8]
A fixing belt 8 was obtained in the same manner as in Test 2, except that spherical glass beads (hardness: 5.5, median particle size published by the manufacturer: 106 to 125 μm or less) were used as the blast material.

The developed area ratio Sdr of the outermost surface of the fixing belt 8, measured in the same manner as in Test 1, was 2.1.

[Test 9]
A #600 wrapping film was brought into contact with the laminated belt obtained in the same manner as in Test 2, a support was inserted into the laminated belt, and the laminated belt was rotated, and the wrapping film was reciprocated while applying a load of 100 kp. In this manner, an endless fixing belt 9 was obtained, which had a polyimide base layer, a silicone rubber elastic layer, and a PFA release layer stacked in this order, and had a surface shape including a concave-convex shape.

The developed area ratio Sdr of the outermost surface of the fixing belt 9, measured in the same manner as in Test 1, was 3.9.

[Test 10]
A fixing belt 10 was obtained in the same manner as in Test 9, except that a #240 wrapping film was used.

The developed area ratio Sdr of the outermost surface of the fixing belt 10, measured in the same manner as in Test 1, was 1.7.

[evaluation]
Each of the fixing belts 1 to 10 was installed as a fixing belt of a full-color copying machine "bizhubPRESS C1070" (Konica Minolta, Inc.). Then, the separation assist air blow was turned off, and a red solid image was formed on a recording medium, which was plain paper of 73.3 g/ ^m2 per square meter, OK Topcoat+ (manufactured by Oji Paper Co., Ltd.). At this time, the distance from the leading edge of the recording medium in the conveying direction to the leading edge of the solid image (leading edge margin) was set to 0 mm, 2 mm, and 4 mm, respectively, and it was observed whether the solid image could be passed without being wrapped around the fixing belt. Based on the observation results, the separability of each fixing belt was evaluated according to the following criteria.
◎ Even with a leading edge margin of 0 mm, paper could be passed without the image wrapping. 〇 With a leading edge margin of 0 mm, the image wrapped around the paper, but with a leading edge margin of 2 mm, paper could be passed without the image wrapping. △ With leading edge margins of 0 mm and 2 mm, the image wrapped around the paper, but with a leading edge margin of 4 mm, paper could be passed without the image wrapping, and it was considered that there was no practical problem.
× Image wrapping occurred even with a leading edge margin of 4 mm

The manufacturing conditions (manufacturing method of the release layer, type of projection material, and projection pressure) of each of Fixing Belts 1 to 10, the outermost surface development area ratio Sdr, and the evaluation results of separation are shown in Table 1.

As is clear from Table 1, fixing belts 1 to 10, which have an uneven surface formed on the outermost surface using polygonal projection material, have an outermost surface developed area ratio Sdr of 4.5 or more, and all of them have excellent toner image separation properties. In particular, the larger the outermost surface developed area ratio Sdr, the better the separation properties.

On the other hand, fixing belt 8, in which a concave-convex shape was formed on the outermost surface using spherical projection material, and fixing belts 9 and 10, in which a concave-convex shape was formed on the outermost surface by transferring a minute concave-convex shape from a wrapping film, did not have an outermost surface developed area ratio Sdr of 4.5 or more, and in both cases, the toner image separation ability was low.

According to the present invention, in electrophotographic image formation using a biaxial belt fixing device, it is possible to improve both the fixability of the fixing belt and the separability of the fixing belt from the recording medium, regardless of the type of recording medium. Therefore, according to the present invention, it is expected that the types of recording media that can be used in electrophotographic image forming devices will become more diverse, and that such image forming devices will become even more widespread.

1 Image forming apparatus 10 Image reading section 11 Automatic document feeder 12 Document image scanning device 12a CCD sensor 20 Operation display section 30 Image processing section 40 Image forming section 41 Image forming unit 42 Intermediate transfer unit 43 Secondary transfer unit 50 Paper transport section 51 Paper feed section 51a to 51c Paper feed tray unit 52 Paper discharge section 52a Paper discharge roller 53 First transport section 54 Intermediate transport roller section 55 Loop roller section 56 Registration roller section 57 Second transport section 58 Switchback path 59 Back transport path 60 Fixing section 61 Fixing belt 62 Pressure roller 63 Heating device 64, 65 Roller 100 Control section 411 Exposure device 412 Development device 413 Photoconductor drum 414 Charging device 415 Drum cleaning device 421 Intermediate transfer belt 422 Primary transfer roller 423 Support roller 423A Backup roller 426 Belt cleaning device 431 Secondary transfer roller 611 Base layer 612 Elastic layer 613 Release layer D Original F Fixing unit S Paper

Claims (10)

A fixing member having a base layer, an elastic layer, and a release layer in this order,
The outermost surface of the fixing member, which is constituted by the release layer , has an irregular concave-convex shape, and a developed area ratio Sdr of the outermost surface is 4.5 or more. The fixing member according to claim 1 , wherein the outermost surface is blasted. The fixing member according to claim 1 or 2 , wherein the outermost surface is subjected to blast processing with polygonal projection material. The fixing member according to any one of claims 1 to 3 , wherein the fixing member is in the form of an endless belt. providing a laminate for manufacturing a fuser member, the laminate having, in order, a base layer, an elastic layer, and a release layer;
and projecting a polygonal projection material onto the release layer of the laminate to set the development area ratio Sdr of the outermost surface of the fixing member, which is constituted by the release layer, to 4.5 or more.
A method for manufacturing a fixing member. The method for manufacturing a fixing member according to claim 5 , wherein the projection material has a new Mohs hardness of 5.5 or more. The method for manufacturing a fixing member according to claim 5 or 6 , wherein the laminate has a shape of an endless belt. A fixing device for use in an electrophotographic image forming apparatus, the fixing device having a fixing member for fixing a toner image carried on a recording medium to the recording medium by applying pressure,
A fixing device, wherein the fixing member is the fixing member according to any one of claims 1 to 4 or is a fixing member manufactured by the method according to any one of claims 5 to 7 . 1. An electrophotographic image forming apparatus having a fixing member for fixing a toner image carried on a recording medium to the recording medium by applying pressure thereto,
An image forming apparatus, wherein the fixing member is the fixing member according to any one of claims 1 to 4 or the fixing member manufactured by the method according to any one of claims 5 to 7 . carrying a toner image on a surface of a recording medium;
and fixing the carried toner image to the recording medium,
The image forming method, wherein the fixing step is a step of pressing the toner image onto the recording medium by a fixing member according to any one of claims 1 to 4 or a fixing member manufactured by the method according to any one of claims 5 to 7 .

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