JP2019070771A - Fixing belt, fixing device, and image forming apparatus - Google Patents

Abstract

To provide a fixing belt that has high separability.SOLUTION: A fixing belt has a base layer made of a heat-resistant resin, an intermediate layer arranged on the base layer and made of a heat-resistant elastic material, and a surface layer arranged on the intermediate layer and made of a fluororesin. A plurality of projections are periodically arranged on the surface of the surface layer, and when the peak-to-peak distance of the adjacent two projections is a μm, and the height of the peak is b μm, 0.3≤a≤5.0 and 1.5≤b/a≤5.0 are satisfied.SELECTED DRAWING: Figure 1

Description

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

  Conventionally, in an electrophotographic image forming apparatus including a copying machine and a laser beam printer, a heated fixing belt is brought into contact with a transfer material carrying an unfixed toner image to transfer the toner image. A fixing device for fixing to a material is employed. As such a fixing device, one having a fixing belt and two or more rollers including a heating roller and pivotally supporting the fixing belt is known. Since the fixing belt has a relatively small heat capacity, it is excellent in fixing a toner image on a transfer material, and contributes to speeding up of image formation.

  In such a fixing device, the exit curvature of the nip formed by the fixing belt on the upper pressure member (roller) and the lower pressure member (roller) is increased or the releasability of the recording medium from the surface of the fixing belt is improved. As a result, the separation between the fixing belt and the recording medium is improved (see, for example, Patent Document 1).

  Patent Document 1 describes a fixing belt having a three-layer structure including a base material layer, an elastic layer, and a surface layer. In addition, as a material of the surface layer, it is described that a fluorine resin is most preferable from the viewpoint of releasability.

JP 2012-108545 A

  However, in order to increase the printing speed in the image forming apparatus, it is necessary to enlarge the upper pressing member and the lower pressing member to increase the heat capacity in order to compensate for the heat loss due to the continuous printing. The enlargement of the upper pressure member and the lower pressure member means a decrease in the curvature on the outlet side. Further, since the proportion of impurities in the fluorocarbon resin material promoting the mold release effect used in the surface layer of the fixing belt is very small, it is considered difficult to improve the mold release property by further reducing the impurities.

  Moreover, when a fluororesin is used for the material of a surface layer like patent document 1, the non-adhesiveness of a surface layer is decided by the number of the fluoro groups arrange | positioned on the surface of a surface layer. However, as described above, it is considered that non-adhesiveness by modification of the fluorocarbon resin is difficult because the fluorocarbon resin contains almost no impurities other than the fluoro group.

  An object of the present invention is to provide a fixing belt having high separability, and a fixing device and an image forming apparatus provided with the fixing belt.

The present invention provides a fixing belt as one means for solving the above problems, comprising: a base layer made of a heat resistant resin; an intermediate layer made of a heat resistant elastic material disposed on the base layer; A fixing belt having a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer surface layer disposed on the
A plurality of periodically formed convex portions are disposed on the surface of the surface layer,
The plurality of convex portions satisfy the following formulas (1) and (2).
0.3 ≦ a ≦ 5.0 (1)
1.5 ≦ b / aB ≦ 5.0 (2)
(In the equation (1), a is the distance between the two adjacent vertices (μm), b is the height of the vertex (μm).)

  Further, according to another aspect of the present invention, there is provided a fixing device as another means for solving the above problems, which heats an endless fixing belt, two or more rollers pivotally supporting the fixing belt, and the fixing belt. And a pressure roller arranged to be urged relative to one of the two or more rollers via the fixing belt, the pressure roller being The outer diameter of the roller to be biased is 50 mm or more, and the fixing belt is the fixing belt according to the present invention.

  Further, according to the present invention, an image forming apparatus as another means for solving the above-mentioned problems is characterized in that the unfixed toner image formed by electrophotography on the recording medium is heated and pressed onto the recording medium. It is an image forming apparatus having a fixing device for fixing, and the fixing device is a fixing device according to the present invention.

  According to the present invention, it is possible to provide a fixing belt having high separation property, and a fixing device and an image forming apparatus provided with the fixing belt.

FIG. 1 is a diagram showing the configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a view showing the configuration of the fixing device in the embodiment of the present invention. FIGS. 3A and 3B are diagrams showing the configuration of the fixing belt in the embodiment of the present invention. 4A and 4B are schematic views showing an example of the arrangement of the protrusions.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the attached drawings.

(Configuration of image forming apparatus)
FIG. 1 is a diagram showing the configuration of the image forming apparatus 10. As shown in FIG. FIG. 2 is a view showing the configuration of the fixing device 60. As shown in FIG.

  As shown in FIG. 1, the image forming apparatus 10 includes an image reading unit 20, an image forming unit 30, an intermediate transfer unit 40, a fixing device 60, and a recording medium conveyance unit 80.

  The image reading unit 20 reads an image from the document D and obtains image data for forming an electrostatic latent image. The image reading unit 20 includes a sheet feeding device 21, a scanner 22, a CCD sensor 23, and an image processing unit 24.

  The image forming unit 30 includes, for example, four image forming units 31 corresponding to the respective colors of yellow, magenta, cyan and black. The image forming unit 31 includes a photosensitive drum 32, a charging device 33, an exposure device 34, a developing device 35, and a cleaning device 36.

  The photosensitive drum 32 is, for example, a negatively charged organic photosensitive member having photoconductivity. The charging device 33 charges the photosensitive drum 32. The charging device 33 is, for example, a corona charger. The charging device 33 may be a contact charging device in which a contact charging member such as a charging roller, a charging brush, or a charging blade is brought into contact with the photosensitive drum 32 for charging. The exposure device 34 irradiates light to the charged photosensitive drum 32 to form an electrostatic latent image. The exposure device 34 is, for example, a semiconductor laser. The developing device 35 supplies toner to the photosensitive drum 32 on which the electrostatic latent image is formed, and forms a toner image corresponding to the electrostatic latent image. The developing device 35 is, for example, a known developing device in an electrophotographic image forming apparatus. The cleaning device 36 removes the residual toner on the photosensitive drum 32. Here, the term "toner image" refers to a state in which toner is gathered in the form of an image.

  A known toner can be used as the toner. The toner may be a one-component developer or a two-component developer. The one-component developer is composed of toner particles. The two-component developer is also composed of toner particles and carrier particles. The toner particles are composed of toner base particles and an external additive such as silica attached to the surface thereof. The toner base particles are composed of, for example, a binder resin, a colorant and a wax.

  The intermediate transfer unit 40 includes a primary transfer unit 41 and a secondary transfer unit 42.

  The primary transfer unit 41 includes an intermediate transfer belt 43, a primary transfer roller 44, a backup roller 45, a plurality of first support rollers 46, and a cleaning device 47. The intermediate transfer belt 43 is an endless belt. The intermediate transfer belt 43 is stretched by a backup roller 45 and a first support roller 46. The intermediate transfer belt 43 travels at a constant speed in one direction on the endless track by rotationally driving at least one of the backup roller 45 and the first support roller 46.

  The secondary transfer unit 42 includes a secondary transfer belt 48, a secondary transfer roller 49, and a plurality of second support rollers 50. The secondary transfer belt 48 is an endless belt. The secondary transfer belt 48 is stretched by a secondary transfer roller 49 and a second support roller 50.

  As shown in FIG. 2, the fixing device 60 includes a fixing belt 61, a roller (a heating roller 62 and a first pressure roller 63), a second pressure roller (a pressure roller) 64, and a heater (a heating device). 65, 66, a first temperature sensor 67, a second temperature sensor 68, an air flow separating device 69, a guide plate 70, and a guide roller 71.

  In the fixing belt 61, a base layer 61a, an elastic layer 61b, and a surface layer 61c are laminated in this order (see FIG. 3). The fixing belt 61 is axially supported by two or more rollers in a state in which the base layer 61a is on the inside and the surface layer 61c is on the outside. In the present embodiment, the fixing belt 61 is pivotally supported by the heating roller 62 and the first pressure roller 63. The tension of the fixing belt 61 is preferably 45 N or less. If the tension of the fixing belt 61 is more than 45 N, the first pressure roller 63 may be damaged. The tension of the fixing belt 61 is, for example, 43N. Since one of the features of the present embodiment is the fixing belt 61, the detailed description of the fixing belt 61 will be described later.

  The heating roller 62 has a rotatable aluminum sleeve and a heater 65 disposed therein. The first pressure roller 63 has, for example, a rotatable core metal and an elastic layer disposed on the outer peripheral surface thereof.

  The second pressure roller 64 is disposed to face the first pressure roller 63 with the fixing belt 61 interposed therebetween. The second pressure roller 64 has, for example, a rotatable aluminum sleeve and a heater 66 disposed in the sleeve. The second pressure roller 64 is disposed close to and away from the first pressure roller 63. When the second pressure roller 64 approaches the first pressure roller 63, the first pressure roller 64 receives the first pressure roller 64 via the fixing belt 61. The elastic layer of the pressure roller 63 is pressed to form a fixing nip portion which is a contact portion with the fixing belt 61. The outer diameter of the second pressure roller 64 is preferably 50 mm or more. If the outer diameter of the second pressure roller 64 is less than 50 mm, the heat capacity of the roller can not be secured, and the printing speed of the image forming apparatus 10 can not be increased.

  The first temperature sensor 67 is a device for detecting the temperature of the fixing belt 61 heated by the heating roller 62. The second temperature sensor 68 is a device for detecting the temperature of the outer peripheral surface of the second pressure roller 64.

  The air flow separation device 69 is a device for generating an air flow from the downstream side in the moving direction of the fixing belt 61 to the fixing nip portion to promote separation of the recording medium S from the fixing belt 61.

  The guide plate 70 is a member for guiding the recording medium S having the unfixed toner image to the fixing nip portion. The guide roller 71 is a member for guiding the recording medium on which the toner image is fixed to the outside of the image forming apparatus 10 from the fixing nip portion.

  It returns to the explanation of FIG. The recording medium conveyance unit 80 includes three sheet feeding tray units 81 and a plurality of registration roller pairs 82. In the paper feed tray unit 81, recording media (standard paper, special paper, and the like in the present embodiment) identified based on basis weight, size, and the like are accommodated for each preset type. The registration roller pair 82 is arranged to form a desired conveyance path.

  In such an image forming apparatus 10, the toner image is transferred onto the recording medium S by the intermediate transfer unit 40 based on the image data acquired by the image reading unit 20 on the recording medium S sent by the recording medium transport unit 80. It is formed. The recording medium S on which the toner image is formed at the intermediate transfer unit 40 is sent to the fixing device 60.

  The fixing belt 61 in the fixing device 60 is rotationally driven at a predetermined speed, and is heated to a desired temperature (for example, 190 ° C.) by the heater 65 by feedback control by the first temperature sensor 67, for example. The second pressure roller 64 is heated to a desired temperature (for example, 180 ° C.) by the heater 66 by feedback control by the second temperature sensor 68, for example. Then, in accordance with the arrival of the recording medium S, the second pressure roller 64 biases the outer peripheral surface of the first pressure roller 63 via the fixing belt 61 to form a fixing nip portion.

  On the other hand, the recording medium S carrying an unfixed toner image is guided to the nip portion while being guided by the guide plate 70. Then, the fixing belt 61 is in close contact with the recording medium S, whereby the unfixed toner image is quickly fixed to the recording medium S. In addition, the recording medium S receives the air flow from the air flow separating device 69 at the downstream end of the fixing nip portion. Therefore, separation of the recording medium S from the fixing belt 61 is promoted. The recording medium separated from the fixing belt 61 is guided by the guide roller 71 to the outside of the image forming apparatus 10.

(Structure of fixing belt)
Next, the fixing belt 61 will be described in detail. FIG. 3A is a perspective view of the fixing belt 61, and FIG. 3B is an enlarged view of a region A shown in FIG. 3A.

  As shown in FIGS. 3A and 3B, the fixing belt 61 includes a base layer 61a, an elastic layer 61b, and a surface layer 61c. Further, in the fixing belt 61, the base layer 61a is positioned inside, and the surface layer 61c is positioned outside.

  The base layer 61a is made of a heat resistant resin. The heat resistant resin can be appropriately selected from resins which do not cause modification and deformation within the range of the use temperature of the fixing belt 61. Examples of heat resistant resins include polyphenylene sulfide, polyarylate, polysulfone, polyether sulfone, polyether imide, polyimide, polyamide imide and polyether ether ketone. The heat resistant resin is preferably polyimide in terms of heat resistance. The heat resistant resin may be used alone or in combination of two or more.

  A polyimide can be obtained by heating the polyamic acid which is its precursor at 200 degreeC or more temperature, or advancing a dehydration and cyclization (imidization) reaction of a polyamic acid using a catalyst. The polyamic acid may be produced by dissolving a tetracarboxylic acid dianhydride and a diamine compound in a solvent and carrying out a polycondensation reaction by mixing and heating, or a commercially available product may be used. The compound as described in stage 0123-0130 of Unexamined-Japanese-Patent No. 2013-25120 is contained in the example of a diamine compound and tetracarboxylic dianhydride.

  The base layer 61a may further include components other than the heat resistant resin as long as the effects of the present embodiment can be obtained. For example, the material of the base layer 61a may further include other resin components. The content of the heat resistant resin in the material of the base layer 61a is preferably 40 to 100% by volume from the viewpoint of formability and the like.

  The elastic layer 61 b is made of an elastic material. Examples of the material (elastic material) of the elastic layer 61 b include elastic resin materials such as silicone rubber, thermoplastic elastomer, and rubber material. The elastic material is preferably silicone rubber.

  Examples of silicone rubber include polyorganosiloxane or its heat-cured product, and addition reaction type silicone rubber described in JP-A-2009-122317. Examples of polyorganosiloxanes include dimethylpolysiloxanes described in paragraph 0029 of JP-A-2008-255283, which are blocked at both ends with a trimethylsiloxane group and have a vinyl group in the side chain. The silicone rubber may be used alone or in combination of two or more.

  The thickness of the elastic layer 61 b is, for example, preferably 30 to 400 μm, more preferably 50 to 300 μm, and still more preferably 100 to 250 μm from the viewpoint of sufficiently expressing heat conductivity and elasticity. .

  The elastic layer 61 b may further include components other than the elastic resin material as long as the effects of the present embodiment can be obtained. For example, the elastic material may further include a thermally conductive filler to increase the thermal conductivity of the elastic layer. Examples of filler materials include silica, metal silica, alumina, zinc, aluminum nitride, boron nitride, silicon nitride, silicon carbide, carbon and graphite. The form of the filler is not limited, and is, for example, spherical powder, amorphous powder, flat powder or fiber.

  The content of the elastic resin material in the elastic material is preferably 60 to 100% by volume, more preferably 75 to 100% by volume, and still more preferably 80 to 100% by volume.

  The surface layer 61c has an appropriate releasability with respect to the toner. The surface layer 61 c is located on the outer surface of the fixing belt 61 that contacts the recording medium S at the time of fixing. The material of the surface layer 61c is a fluorine resin. More specifically, the material of the surface layer 61c is preferably a perfluoroalkoxy fluorine resin (PFA).

  A plurality of convex portions are periodically arranged on the surface of the surface layer 61c. The fixing belt 61 according to the present embodiment achieves high separation from the recording medium S by the plurality of convex portions disposed on the surface of the surface layer 61 c. The shape of the convex portion can be appropriately designed as long as the surface layer 61c can be provided with releasability. The shape of the convex portion may be a quadrangular pyramid, a triangular pyramid, or a cone. In the present embodiment, the shape of the convex portion is preferably a quadrangular pyramid from the viewpoint of productivity.

When a distance between the two adjacent convex portions (μm) is a and a height of the apex (μm) is b, the plurality of convex portions satisfy the following expressions (1) and (2) .
0.3 ≦ a ≦ 5.0 (1)
1.5 ≦ b / a ≦ 5.0 (2)

  Here, when the distance (μm) a between the apexes of two adjacent convex portions is less than 0.3 μm, the contact area between the recording medium S and the surface layer 61c becomes large, and high separability can not be obtained. On the other hand, if the distance (μm) a between the apexes of two adjacent projections is more than 5.0 μm, the recording medium S gets in between the adjacent projections, and high separability can not be obtained.

  In addition, when the height (μm) b of the apex with respect to the distance (μm) a between the two adjacent projections is less than 1.5, the recording medium S gets in between the adjacent projections, resulting in high separability. Can not be obtained. On the other hand, if the height (μm) b of the apex with respect to the distance (μm) a between two adjacent projections is more than 5.0 b, the shape of the projections becomes difficult to hold, and high separability is obtained. Absent.

Further, it is preferable that the plurality of convex portions further satisfy the following expressions (3) and (4).
0.5 ≦ a ≦ 2.0 (3)
2.0 ≦ b / a ≦ 3.5 (4)

  When the plurality of convex portions satisfy the expressions (3) and (4), the separation between the surface layer 61 c and the recording medium S can be further enhanced.

The distance (μm) a between the two adjacent convex portions and the height (μm) b of the apex should satisfy the above (1) to (4) at a rate of 50% per 1 mm ^{2 of} the surface layer 61c. It is more preferable if the above (1) to (4) are satisfied at a rate of 80% per 1 mm ^{2 of} the surface layer 61c. As for the distance (μm) a between the apexes of two adjacent convex portions, first, SEM image data of 10000 × is prepared by SEM. Next, a plurality of convex portions included in 1 mm ² of the surface layer 61c are detected. Next, the distance between the apexes of two adjacent convex portions was determined. In addition, for the height (μm) b of the apex, first, SEM image data of 10000 × is prepared by SEM. Next, a plurality of convex portions included in 1 mm ² of the surface layer 61c are detected. Next, for each convex portion, the surface of the surface layer 61c and the apex of the convex portion were sandwiched by two parallel lines, and the distance between the two parallel lines was determined.

  The plurality of projections are preferably formed in an area of 50% or more, more preferably 80% or more, with respect to the surface of the surface layer 61c, and preferably 100% of the area (surface layer 61c). Preferably, it is formed on the entire surface).

  FIGS. 4A and 4B show examples of the arrangement of the plurality of convex portions in the surface layer 61c when the fixing belt 61 is viewed in plan. The shaded portions in FIGS. 4A and 4B indicate regions in which the convex portions are formed.

  As shown in FIG. 4A, the plurality of convex portions may be arranged in a plurality of lines in the direction along the rotation direction of the fixing belt 61. In this case, the width of the region in which the plurality of projections are disposed is equal to or greater than the width of the region in which the projections are not disposed. Thereby, the area of the plurality of convex portions is 50% or more with respect to the surface of the surface layer 61c.

  As shown in FIG. 4B, even if the plurality of convex portions are arranged in a plurality of lines in a direction along the direction orthogonal to the direction along the rotation direction of the fixing belt 61 (the width direction of the fixing belt 61). Good. Also in this case, the width of the region in which the plurality of projections are disposed is equal to or greater than the width of the region in which the projections are not disposed. Thereby, the area of the plurality of convex portions is 50% or more with respect to the surface of the surface layer 61c.

  The method of forming the plurality of convex portions can be appropriately selected by known techniques. For example, the plurality of convex portions can be formed by using a laser marker on the surface of the formed surface layer 61c. The method of forming a plurality of projections by a laser marker is preferable from the viewpoint of productivity. In addition, even if the surface layer 61c is processed by blasting or the like, the convex portions become random, and therefore, the convex portions can not be formed as in the present embodiment.

  The thickness of the surface layer 61c is, for example, preferably 5 to 40 μm, more preferably 10 to 35 μm, from the viewpoint of heat transfer, tracking of deformation of the elastic layer, and expression of releasability. More preferably, it is -30 μm.

  The surface layer 61 c may further include other components other than the fluorine resin as long as the effects of the present embodiment can be obtained. For example, the surface layer 61c may further include lubricant particles. Examples of lubricant particles include silicone resin particles and silica particles.

  The content of the fluorine resin in the material of the surface layer 61c is preferably 70 to 100% by volume from the viewpoint of heat conductivity and flexibility sufficiently to follow deformation of the elastic layer.

  The fixing belt 61 may further include other layers than the base layer 61a, the elastic layer 61b, and the surface layer 61c in the range where the effects of the present embodiment can be obtained. Examples of other layers include reinforcing layers.

  The reinforcing layer is a layer for enhancing the mechanical strength of the fixing belt 61. For example, the reinforcing layer is disposed on the surface (inner peripheral surface of the base layer 61a) of the fixing belt 61 opposite to the elastic layer 61b and the surface layer 61c. The said reinforcement layer can be comprised with the heat resistant resin mentioned above, and the thickness can be decided suitably.

  The fixing belt 61 can be manufactured using a known method for manufacturing a laminated fixing belt. For example, in the fixing belt 61, a process of covering a tube serving as the surface layer 61c on the outer surface of an endless molded article made of a heat resistant resin serving as the base layer 61a, an elastic material or a precursor thereof between the molded article and the tube And, optionally, heat curing the elastic material or the precursor.

  As described above, in the fixing belt according to the present embodiment, the relationship between the distance (μm) a between the apexes of two adjacent convex portions and the height (μm) b of the apex is 0.3 ≦ a. In order to satisfy ≦ 5.0 and 1.5 ≦ b / a ≦ 5.0, the surface layer 61 c contacts the recording medium S with an appropriate area. Thus, the fixing belt has high releasability.

  The present invention will be more specifically described using the following examples and comparative examples. Hereinafter, unless otherwise stated, each operation was performed at room temperature (20 ° C.). The present invention is not limited to the following examples and the like.

Example 1
A stainless steel cylindrical cored bar with an outer diameter of 60 mm was adhered to the inside of a belt base made of a thermosetting polyimide resin with an inner diameter of 99 mm, a length of 360 mm, and a thickness of 70 μm. Next, a cylindrical mold holding a PFA tube with a thickness of 30 μm on the inner circumferential surface is covered on the outer side of the belt base material, and thus the core metal and the cylindrical mold are coaxially held, and between the two Form a cavity. Then, a silicone rubber material was injected into the cavity and heat cured to form a 200 μm thick elastic layer of silicone rubber. Finally, the belt was fixed to a laser marker (MD-T1010W: Keyence Corporation), and a plurality of quadrangular pyramidal convex portions were formed on the entire surface of the surface layer at a dot interval of 5 μm and a laser power of 20% at 200 kHz. Thus, a fixing belt 1 was produced in which a belt substrate, an elastic layer of silicone rubber and a surface layer made of a fluorocarbon resin were laminated in this order. In addition, the distance between the apexes (μm) a of two adjacent convex portions and the height (μm) b of the apexes were measured using a laser microscope (Vk-X250: KEYENCE CORPORATION).

[Examples 2 to 8, Comparative Examples 1 to 8]
Similar to the fixing belt of Example 1 except that the relationship between the distance between apexes (μm) a of two adjacent convex portions and the height (μm) b of the apexes is as shown in Table 1. Examples 2-8 and comparative examples 1-8 were produced, respectively.

Comparative Example 9
Comparative Example 9 was produced in the same manner as Example 1 except that the plurality of convex portions were not formed by the laser marker. At this time, the height (μm) b of the vertex with respect to the distance (μm) a between the two adjacent protrusions is 0.

Comparative Example 10
Comparative Example 10 was produced in the same manner as in Example 1 except that the laser marker was used and blasting was performed. At this time, the height (μm) b of the vertex with respect to the distance (μm) a between the two adjacent protrusions is 0.

  Table 1 shows the ratio b / a of the height (μm) b of the vertex to the distance (μm) a between the two adjacent protrusions and the distance (μm) a between the two adjacent protrusions.

[Evaluation]
Fixing belts 1 to 18 were respectively installed as fixing belts of an electrophotographic image forming apparatus provided with a biaxial belt type fixing device as shown in FIG. The diameter of the roller (which is disposed to face the pressure roller) that supports the fixing belt, which is a roller that constitutes the fixing nip portion, is 60 mm. For each fixing belt, the surface temperature of the fixing belt is 180 ° C., and a toner image (toner adhesion amount of a magenta solid image in a width of 5 cm in a direction perpendicular to the conveyance direction of the plain paper 8 g / m ² ) was transferred, and the plain paper was passed through the fixing nip at a speed of 60 sheets / minute in the longitudinal direction to form a fixed image of the band-like image on the plain paper.

(1) Separability The separability between each fixing belt and the plain paper at the time of fixing the above-mentioned belt-like solid image was judged according to the following criteria.
A: The paper separates without curling B: The paper curls slightly but there is no problem C: Can not separate (paper jam occurs)

(2) Fixability The belt-like solid image was visually observed, and the fixability was determined according to the following criteria. Incidentally, the image defect due to the fixing failure means an image defect due to cold offset (roughness of appearance) or an image defect due to hot offset (occurrence of sheet passing jam).
A: Solid image does not show defects due to poor fixing B: Small defects are found but there is no problem C: Solid images have defects due to poor fixing

[result]
As shown in Table 2, in the fixing belts 1 to 8 in which 0.3 ≦ a ≦ 5.0 and 1.5 ≦ b / a ≦ 5.0, the low temperature fixability and the separation property are excellent. The In particular, in the fixing belts 1 to 4 in which 0.5 ≦ a ≦ 2.0 and 2.0 ≦ b / a ≦ 3.5, the separability was further excellent.

  On the other hand, the fixing belts 9 to 18 in which a was not in the range of 0.3 to 5.0 or b / a was not in the range of 1.5 to 5.0 were particularly inferior in separability. This is considered to be because a plurality of convex portions are not formed on the surface layer.

  According to the present invention, in an electrophotographic image forming apparatus using a high speed machine having a fixing belt, it is possible to realize good fixing and to prevent the occurrence of paper jam. Therefore, according to the present invention, further speeding-up, higher performance and labor saving can be expected in the electrophotographic image forming apparatus, and further spread of the image forming apparatus is expected.

DESCRIPTION OF SYMBOLS 10 image forming apparatus 20 image reading unit 21 sheet feeding device 22 scanner 23 CCD sensor 24 image processing unit 30 image forming unit 31 image forming unit 32 photosensitive drum 33 charging device 34 exposure device 35 developing device 36 cleaning device 40 intermediate transfer portion 41 Primary transfer unit 42 Secondary transfer unit 43 Intermediate transfer belt 44 Primary transfer roller 45 Backup roller 46 First support roller 47 Cleaning device 48 Secondary transfer belt 49 Secondary transfer roller 50 Second support roller 50 Fixing roller 60 Fixing device 61 Fixing belt 62 Heating Roller 63 first pressure roller 64 second pressure roller 65, 66 heater 67 first temperature sensor 68 second temperature sensor 69 air flow separating device 70 guide plate 71 guide roller 80 recording medium conveyance portion 81 paper feed tray unit 8 A pair of registration rollers D document S paper (recording medium)

Claims (7)

A fixing belt comprising: a base layer made of a heat resistant resin; an intermediate layer made of a heat resistant elastic material disposed on the base layer; and a surface layer made of a fluorocarbon resin disposed on the intermediate layer ,
A plurality of periodically formed convex portions are disposed on the surface of the surface layer,
The plurality of convex portions satisfy the following formulas (1) and (2):
Fixing belt.
0.3 ≦ a ≦ 5.0 (1)
1.5 ≦ b / a ≦ 5.0 (2)
(In the equation (1), a is the distance between the two adjacent convex portions (μm), and b is the height of the apex (μm).) The fixing belt according to claim 1, wherein the plurality of periodically formed convex portions further satisfy the following Expression (3) and Expression (4).
0.5 ≦ a ≦ 2.0 (3)
2.0 ≦ b / a ≦ 3.5 (4) The heat resistant resin is polyimide,
The elastic material is silicone rubber,
The plurality of convex portions are disposed on the entire surface of the surface layer,
The fixing belt according to claim 1.   The fixing belt according to any one of claims 1 to 3, wherein the fluorine resin is a perfluoroalkoxy fluorine resin. Endless fixing belt,
Two or more rollers pivotally supporting the fixing belt;
A heating device for heating the fixing belt;
A pressure roller arranged to be urged relative to one of the two or more rollers via the fixing belt;
The outer diameter of the roller biased by the pressure roller is 50 mm or more.
The fixing belt is the fixing belt according to any one of claims 1 to 4.
Fixing device.   The fixing device according to claim 5, wherein the fixing belt is supported by the two or more rollers so as to have a tension of 45 N or less. An image forming apparatus having a fixing device for fixing an unfixed toner image formed on a recording medium by an electrophotographic method on the recording medium by heating and pressing,
The fixing device is the fixing device according to claim 5 or 6,
Image forming apparatus.

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