JP2007296839A - Cylindrical core body and method for manufacturing endless belt using cylindrical core body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce an endless belt in which belt quality defects such as the swelling and thickness nonuniformity of the belt is suppressed. <P>SOLUTION: In the cylindrical core body 20 for manufacturing the endless belt by coating the surface with a resin solution, the middle in the axial direction of the cylindrical core body 20 is made thinner than the end parts in the axial direction. The thickness of the cylindrical core body 20 is reduced continuously from the end parts in the axial direction toward the middle in the axial direction which occupies at least 33% of the length in the axial direction of the cylindrical core body 20. The core body thickness of the cylindrical core body 20 in particular is increased gradually from the middle toward the end parts, and the core body thickness has the relationship of T<SB>2</SB><T<SB>4</SB>. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a manufacturing method of an endless belt using a polyimide resin molded using an outer peripheral surface of a mold or other resin having a property of shrinking by heating. The endless belt is preferably used as a transfer member or a fixing member in an image forming apparatus such as an electrophotographic copying machine or a laser printer.

  The image forming apparatus often uses a rotating body made of rubber or the like. However, in order to reduce the size and increase the performance of the apparatus, the rotating body may be preferably deformable. A thin resin belt is used. In this case, an endless belt that is seamless to the belt is preferable for improving image quality, and the material is preferably a polyimide resin from the viewpoint of strength, dimensional stability, and heat resistance. Several fixing devices using an endless belt are known (for example, Patent Document 1).

  In addition, for a transfer device using an endless belt, for example, a transfer belt made of a polyimide resin in which conductive powder such as carbon black or graphite is dispersed to be semiconductive is stretched around a plurality of rolls, and rotated. An apparatus for transferring an image from a photosensitive member to a sheet is mentioned (for example, Patent Document 2).

  For example, a polyimide resin endless belt is manufactured by applying a polyimide precursor to the inner surface of a cylindrical body and drying it while rotating (for example, Patent Document 3). Since it was necessary to dry the solvent of a precursor solution, there existed a problem that drying took time.

As another endless belt manufacturing method, for example, there is a method in which a polyimide precursor solution is applied to the surface of a core body by a dip coating method, dried, heated, and then peeled off (for example, Patent Document 4). ). In this method, since the solvent is dried from the outer surface of the core, the drying time can be shortened, and the shape of the outer surface of the core is molded on the inner surface of the endless belt.
Here, as a solvent for the polyimide precursor solution, an aprotic polar solvent is used, which has a property of having a high boiling point and very slow drying. In addition, since the polyimide resin film has low gas permeability, a part of the polyimide resin film tends to remain even if the solvent is dried.

  In the method of peeling after forming a polyimide resin film on the surface of the core body, residual solvent and water generated at the stage where the imidization reaction proceeds in the process of heating the film, between the inside of the film and between the core body and the film. If it stays in the film, it expands by heat and becomes a high-pressure gas, and the polyimide resin film may swell and deform. This is remarkable in the case of a thick film having a film thickness exceeding 50 μm.

  On the other hand, since the polyimide resin has a large shrinkage force during the heating reaction, the coating containing the polyimide resin formed on the outer peripheral surface of the core body shrinks when the endless belt is formed. Such shrinkage occurs non-uniformly and causes film thickness unevenness of the endless belt. In addition, the semiconductive endless belt in which the conductive powder is dispersed has a problem of causing uneven resistance. When used as a transfer belt, the resistance unevenness causes uneven toner density to be transferred. For this reason, when manufacturing conventional endless belts, it is particularly required to reduce resistance unevenness as much as possible in a semiconductive endless belt, and it is also required to reliably obtain an endless belt having no film thickness unevenness. It was.

  In view of the above technical problem, in Patent Document 5, a core having a roughened outer peripheral surface is disclosed in regard to a manufacturing method in which a polyimide precursor solution is applied to the surface of a core, dried and heated to form an endless belt. By using the body, a measure has been taken to release the generated high-pressure gas in the axial direction of the core body. However, the shape of the inner surface of the belt is also roughened, and there are cases where sliding noise with a sliding member such as a roll becomes a problem.

  In general, in order to improve the releasability between the film containing the polyimide resin and the core, a release agent is applied to the core in advance, but by limiting the application area of the release agent application, Patent Document 6 proposes a method for achieving non-uniform shrinkage in the core axis direction during heating and allowing the high-pressure gas to escape from the core axis direction. Specifically, the gap between the polyimide film and the core is created by providing a part where the release agent layer does not partially exist at both ends of the core and by partially attaching the film to the cylindrical core. The high-pressure gas was actively released. However, there has been a problem that workability is greatly deteriorated by introducing an operation for limiting the application area of the release agent, for example, a masking process, and productivity of an endless belt is remarkably lowered.

Japanese Patent Laid-Open No. 5-150679 Japanese Patent Laid-Open No. 10-218850 JP-A-57-74131 Japanese Patent Laid-Open No. 61-273919 JP 2000-271946 A JP 2000-255708 A

  In the production of an endless belt containing polyimide resin or the like and having shrinkability at the time of production, the present invention stays between the film containing polyimide and the cylindrical core when a film is formed on the outer peripheral surface of the cylindrical core. Residual solvent and high-pressure gas generated from the water generated at the stage of imidization reaction, without limiting the use conditions of the endless belt, and without sacrificing the productivity of the endless belt, Endless belt manufacturing method and cylindrical shape capable of suppressing belt quality defects such as belt bulge and film thickness unevenness of the endless belt by positively discharging in the axial direction of the cylindrical core between the outer periphery of the cylindrical core A core body is provided.

  The cylindrical core of the present invention and the method for producing an endless belt using the cylindrical core have the following characteristics.

  (1) A cylindrical core for producing an endless belt by applying a resin solution to the surface, and the thickness of the cylindrical core is a cylinder whose axial center is thinner than the axial end It is a core.

  (2) A cylindrical core for producing an endless belt by applying a resin solution to the surface, wherein the cylindrical core is characterized in that the heat capacity at both ends is larger than the central portion in the axial direction. .

  (3) The thickness of the cylindrical core body is gradually reduced from the axial end portion toward an axial central portion corresponding to at least 33% of the axial length of the cylindrical core body. It is a cylindrical core.

  (4) The thickness of the cylindrical core is gradually increased from the axial end toward the axial central portion corresponding to at least 33% of the cylindrical core axial length. It is a cylindrical core as described in said (3) which becomes thin to 50% equivalent.

  (5) The cylindrical core body according to (1), wherein the thickness of the cylindrical core body decreases continuously from the axial end portion toward the axial central portion.

  (6) The thickness of the cylindrical core body is continuously reduced from the axial end portion toward the axial central portion, and is reduced to a maximum corresponding to 50% of the axial end thickness. It is a cylindrical core body.

  (7) The cylindrical shape as described in (1) above, wherein attachment members made of the same material as the cylindrical core body or a material having a larger heat capacity than the cylindrical core body are attached to both ends in the axial direction. It is a core.

  (8) A release agent layer forming step for forming a release agent layer on the outer peripheral surface of the cylindrical core, and a resin solution is applied to the outer peripheral surface of the cylindrical core after the release agent layer forming step. A coating film forming step for forming a coating film, a coating film forming step for forming a coating film by drying and heating and firing the coating film, and peeling the coating film from the outer peripheral surface and extracting the coating film from the cylindrical core. In the endless belt manufacturing method having a peeling and extracting step, the endless belt manufacturing method using the cylindrical core body according to any one of (1) to (7) above for the cylindrical core body. .

  According to the present invention, in the production of an endless belt using a shrinkable film such as a polyimide resin, when a film is formed on the outer peripheral surface of the cylindrical core, the film stays between the film containing polyimide and the cylindrical core. Actively discharging the residual solvent and the high-pressure gas generated from the water generated when the imidization reaction proceeds in the axial direction of the cylindrical core between the coating and the outer periphery of the cylindrical core. Can do. Thereby, an endless belt in which belt quality defects such as belt bulge and film thickness unevenness of the endless belt are suppressed can be manufactured.

  Hereinafter, the present invention will be described in detail.

  The contents of the present invention, the endless belt manufacturing method, and the cylindrical core will be described below.

  The present invention provides an endless belt manufacturing method for producing an endless belt including a heat-shrinkable resin layer such as polyimide resin through at least a release agent layer forming step, a coating film forming step, a film forming step, and a peeling / extracting step. It is.

  The present invention uses a cylindrical core having a large heat capacity at both ends relative to the center, and gradually expels the gas generated at the time of heating from the center of the cylindrical core toward the end. An endless belt without unevenness is obtained. The belt material is preferably a polyimide resin from the viewpoint of strength, dimensional stability, and heat resistance. Hereinafter, a case where the polyimide resin is handled will be described in detail.

  In addition, as an endless belt manufacturing method, there are a case where a heat-shrinkable resin is applied to the outside of a cylindrical core body and a case where it is molded inside a cylindrical core body. It can be applied to a case where a heat-shrinkable resin is applied to the outside of the core body and molded. Hereinafter, a method for producing an endless belt on the outer side of the cylindrical core will be described.

  FIG. 1 is a schematic perspective view when a polyimide resin film 14 is applied and formed on a cylindrical core body 10.

In the axial direction of the cylindrical core body 10, a polyimide resin film 14 is coated and formed with a width of a length L _1. From the viewpoint of handling in belt production, generally, the polyimide resin film 14 is not applied and formed on both ends of the cylindrical core body 10.

Next, a process for causing belt swelling when the conventional cylindrical core shown in FIG. 7 is used will be described. As shown in FIG. 7, the cylindrical core body 50 is a general core shape having a uniform thickness T ₁ in the axial direction. After the polyimide resin film 54 is applied and formed on the outer peripheral surface of the cylindrical core body 50, a dry polyimide endless belt is formed through a drying process and a baking process. In the drying process and the baking process, as described above, Further, since the polyimide resin film 54 is not applied to both ends of the cylindrical core body 50, the cylindrical core body 50 starts to rise in temperature from both ends thereof. 50 starts to shrink in the circumferential direction, and both ends begin to shrink by hardening before the center of the cylindrical core 50. As a result, both end portions of the polyimide resin film 54 are pressed against both end portions of the cylindrical core body 50, and the space between the outer peripheral surface of the cylindrical core body 50 and the inner surface of the polyimide resin film 54 is It becomes a so-called sealed state. Therefore, in the heating process of the polyimide resin film 54, the residual solvent and water generated at the stage where the imidization reaction proceeds expands by heat to become the high-pressure gas 56. As described above, the high-pressure gas 56 Stays in a sealed space between the outer peripheral surface of the cylindrical core body 50 and the inner surface of the polyimide resin film 54 and cannot be removed outside. As a result, the polyimide resin film 54 may be swollen and the belt may be deformed. Here, a thick arrow shown in FIG. 7 indicates a moving direction of the high-pressure gas 56.

  As a way for the high pressure gas 56 to escape, the surface of the polyimide resin film 54 (when it becomes a film) can be used in addition to the way through the gap between the polyimide resin film 54 and the cylindrical core body 50 at both ends of the cylindrical core 50 described above. There is a way for the high-pressure gas 56 to escape toward the outermost surface. However, in heat treatment in a general drying furnace or oven, heat is transmitted from the outermost surface of the polyimide resin film 54, and thus the polyimide resin film 54 starts to solidify from the outermost surface. That is, while the high pressure gas 56 can permeate from the outermost surface of the polyimide resin film 54, the high pressure gas 56 escapes from the surface of the polyimide resin film 54, but when the outermost surface of the polyimide resin film 54 begins to solidify, The gas 56 cannot escape and stays between the cylindrical core body 50 and the polyimide resin film 54. In general, a polyimide resin has a characteristic that it is difficult to dry a solvent because of low gas permeability. Accordingly, it is understood that the high-pressure gas 56 is mainly removed from the end portion of the cylindrical core body 50, and the cylindrical core body of the present invention described below is very effective.

  In addition, with respect to the above problem, conventionally, by avoiding rapid heating in a drying process or the like and gradually heating over time, the surface of the polyimide resin film 54 can be obtained from both ends of the cylindrical core body 50. It is conceivable that the high-pressure gas 56 is extracted from the belt, but this is not a good measure in consideration of belt productivity. Further, by inserting a heating source into the cylindrical core body 50 and heating from the inside of the cylindrical core body 50, the side in contact with the cylindrical core body 50 in the polyimide resin film 54 is moved outward. The method of gradually leaking the high-pressure gas 56 is also effective, but it is not a good measure in consideration of the problem of equipment load, compatibility with design changes such as belt diameter changes, belt costs, and the like.

  Hereinafter, the structure of the cylindrical core will be described with reference to side views along the longitudinal direction of FIGS. 2 to 5 in order to explain the present invention.

  The feature of the present invention is that the heat capacity (degree of easiness of warming) of the cylindrical core itself is changed between the central portion and the end portion of the cylindrical core. This is to increase the heat capacity of both ends with respect to the part so that the heating order of the cylindrical core is changed from the center to the both ends. By forming a cylindrical core body with this configuration, even when using a general drying furnace or oven, the drying of the polyimide resin film starts from the center and proceeds toward the end, so the generated high-pressure gas Can be positively discharged from the end of the cylindrical core. Below, an example of the cylindrical core in this invention is demonstrated.

  An example of the cylindrical core body in the present embodiment has a thickness that gradually decreases from the axial end portion toward the axial center portion corresponding to at least 33% of the axial length of the cylindrical core body. Further, preferably, the thickness of the cylindrical core is gradually increased from the axial end to the axial central portion corresponding to at least 33% of the axial length of the cylindrical core in a stepwise manner. It is as thin as 50%.

More specifically, as shown in FIG. 2, in the cylindrical core body 10, the core body thickness of the cylindrical core body 10 is adjusted in stages, and becomes thicker from the center toward the end. . In other words, in FIG. 2, the core thickness T ₂ <T ₃ <T ₄ is satisfied. For example, in the cylindrical core body 10 having an outer diameter of 30 mm, T ₂ may be 3 mm, T ₃ may be ₄ mm, and T ₄ may be 5 mm. In the figure, a thick line arrow indicates the moving direction of the high-pressure gas. As a result, the cylindrical core 10 has a heat capacity at both ends larger than that at the center, and the drying of the polyimide resin film 134 starts from the center and proceeds toward the end. It can be positively discharged from the end of the core 10.

Here, if the heat capacity (degree of ease of warming) of the core itself is different between the center portion and the end portion of the cylindrical core body 10 and T ₂ <T ₃ <T ₄ , the above T ₂ , The dimensions of T ₃ and T ₄ are not limited, but preferably T ₂ is 1.0 to 1.5 times, T ₃ is 1.3 to 1.8 times, and T ₄ is T ₁ . 1.6 to 2.2 times.

  In another example of the cylindrical core body in the present embodiment, the thickness of the cylindrical core body is continuously reduced from the axial end portion toward the axial central portion. More preferably, the thickness of the cylindrical core is continuously reduced from the axial end portion toward the axial central portion, and is reduced to a maximum of 50% of the axial end portion thickness.

More specifically, as shown in FIG. 3, the core member thickness of the cylindrical core body 20 is gradually thicker Shina' toward the end from the central portion, in FIG. 3, the core member thickness T ₂ <T ₄ relationship. In Example 1 to be described later, an experiment was performed on a cylindrical core body 20 having an outer diameter of 30 mm with T ₂ of 3 mm and T ₄ of 5 mm. Note that the relationship between T ₂ and T ₄ is not particularly limited as long as T ₂ <T ₄ , but preferably T _{2 with} respect to T ₁ is T ₂ and T _4. 1.0 to 1.5 times, _{T 4} is 1.6 to 2.2 times. Thus, as described above, the cylindrical core 20 has a heat capacity at both ends larger than that at the center, and the drying of the polyimide resin film 24 starts from the center and proceeds toward the end. Can be positively discharged from the end of the cylindrical core body 20.

  Another example of the cylindrical core body according to the present embodiment is an attachment made of the same material as the cylindrical core body or a material having a larger heat capacity than the cylindrical core body at both axial ends of the cylindrical core body. A member is mounted.

  More specifically, as shown in FIG. 5, the thickness of the core of the cylindrical core 30 is the same at the center and the end, but the same material as that of the cylindrical core 30 only at both ends. Alternatively, mounting members 36a and 36b made of a material having a larger heat capacity than the same material are mounted. In the present embodiment, for example, the cylindrical core 30 is made of SUS steel having a specific heat of 0.5 KJ / (Kg · ° C.) with an outer diameter of 30 mm, a length of 600 mm, and a thickness of 3 mm. The mounting members 36a and 36b to be attached to the section are made of aluminum material having a specific heat of 0.9 KJ / (Kg · ° C.) with an outer diameter of 24 mm, a length of 100 mm, and a thickness of 5 mm, and press-fitted in the direction of the white arrow in FIG. . Thus, as described above, the cylindrical core 30 has a larger heat capacity at both ends than the center, and the drying of the polyimide resin film 34 starts from the center and proceeds toward the end. Can be positively discharged from the end of the cylindrical core 30.

  The materials and dimensions of the mounting members 36a and 36b shown in FIGS. 4 and 5 can be optimized as appropriate depending on the specifications of the polyimide resin to be handled, the set film thickness, the shrinkage ratio of the polyimide resin due to heating, etc. A cylindrical member stored inside the inner diameter of the cylindrical core 30 is generally used, and the material is suitably 1.5 times or more, preferably 1.8 times or more the specific heat of the cylindrical core 30 material. Is appropriate. Further, the inner diameter of the cylindrical attachment members 36 a and 36 b is preferably 6 to 12 mm smaller than the inner diameter of the cylindrical core 30, and the length is preferably 10% or more of the cylindrical core 30.

  As described above, the structure of the cylindrical core body when the film is formed on the outer periphery of the cylindrical core body has been described. However, the present invention is not limited to this. Similarly to the above, the outer periphery of the body may be formed with a different thickness, or the same or a high heat capacity metal material may be attached to the outer periphery of the cylindrical core. Thereby, heating advances in order from the center part of a cylindrical core body, and both ends, The gas generated from a polyimide resin film at the time of heat processing can be extracted from an edge part.

  The material of the cylindrical cores 10, 20, and 30 is not particularly limited, but metals such as aluminum, zinc, copper, stainless steel, and nickel are preferable. When the material of the core is aluminum, zinc, or copper, it may be plated with chromium or nickel so that the outer peripheral surface is hardly damaged.

  As shown in FIG. 8, the other cylindrical core body of the present embodiment is formed by thinning the outer diameters at both ends by swaging, and then processing the entire core body to have a substantially uniform outer diameter. The cylindrical core body 40 is constant and has a thick wall at both ends.

  As shown in FIG. 9, the cylindrical core body 40 uses a core body base material 42 having a thickness larger than that required for an endless belt core mold. After swaging both ends of the core base material 42, the outer diameters of both ends are reduced, and then heat annealing is performed, and then the surface is cut until the entire outer surface of the core body 44 has a desired outer diameter. The cylindrical core body 40 is obtained by processing. The material of the core body base material 40 is not particularly limited as described above, but metals such as aluminum, zinc, copper, stainless steel, and nickel are preferable. When the material of the core is aluminum, zinc, or copper, it may be plated with chromium or nickel so that the outer peripheral surface is hardly damaged.

  In the swaging process, the outer diameter may be continuously pressed from the central portion of the core base material 42, or may be pressed intermittently. For example, the cylindrical core body 20 as shown in FIG. 3 can be obtained by continuously reducing the diameter from the center by swaging, and the diameter can be reduced by intermittently pressing from the center. Thus, a cylindrical core body 10 as shown in FIG. 2 can be obtained.

  Moreover, although the temperature in the said annealing process changes with materials, in order to correct | amend distortion of the core base | substrate 42 by a swaging process, in the case of aluminum, it heats at 350 to 450 degreeC for 0.5 to 2 hours. It is annealed by placing it vertically in a furnace.

  Further, the outer diameter cutting is performed by a known cutting method in which a cutting tool is brought into contact with the surface of the core body 44 while rotating the core body 44 in the circumferential direction, similarly to the formation of the processing marks described later.

  In addition, when the roughness is formed on the surface of the above-described cylindrical core body, the cylindrical core body can be formed by any one of blasting, etching, cutting, or a combination thereof. In the present embodiment, in the case of “performing cutting in the circumferential direction”, the direction of the machining line formed on the surface of the core body by cutting is formed substantially parallel to the circumferential direction of the core body. This means not only the state of being bent, but also the case of being formed slightly oblique to the circumferential direction. Further, the processing marks formed on the surface of the core body may be only those having a substantially constant angle with respect to the circumferential direction, or those having a plurality of angles may be mixed.

  FIG. 10 shows a cylindrical core body (hereinafter, also simply referred to as “core body”) 101 that is a core body mold in the case where a cut line is formed on any surface of the cylindrical core bodies 10 to 40. FIG. 10A is a schematic diagram showing an example of a cutting pattern formed in the circumferential direction of the surface, and FIG. 10A shows an example of a machining pattern formed substantially parallel to the circumferential direction. FIG. 10B shows an example of a processing eye formed in a slightly oblique direction with respect to the circumferential direction, and FIG. 10C shows a processing eye formed in a slightly oblique direction at two types of angles with respect to the circumferential direction. An example is shown. And the dashed-dotted line in the figure has shown the axial direction of the core 101. FIG. 10A to 10C are drawn with emphasis for explanation, and do not necessarily correspond to the actually formed processing eyes.

  The cutting is performed by a known processing method in which a cutting tool is brought into contact with the surface of the core body 101 while rotating the core body 101 in the circumferential direction, and the surface roughness Ra of the surface of the core body 101 is determined by the shape and feed rate of the cutting tool. These processing conditions can be controlled according to the outer diameter of the core body 101. The surface roughness Ra in the axial direction of the surface of the core body 101 is in the range of 0.3 to 3.0 μm, and the surface roughness Ra in the circumferential direction of the surface of the core body 101 is the surface in the axial direction of the surface of the core body 101. Cutting is preferably performed in the circumferential direction of the surface of the core body 101 so as to be smaller than the roughness Ra.

  However, as described above, in order to simultaneously improve the lubricant retaining ability and reduce the sliding noise, the circumferential surface roughness Ra of the inner circumferential surface is equal to the surface roughness Ra in the inner circumferential surface axial direction. When the core body 101 having a smaller shape is used, the conventional endless belt manufacturing method using the core body mold makes it difficult for gas to escape due to large irregularities on the surface of the core body 101 in the axial direction. In some cases, the swelling phenomenon that occurs in the polyimide precursor coating film in the body drying process may deteriorate.

  The relationship between the surface roughness Ra of the surface of the core body 101 and the surface roughness Ra of the inner peripheral surface of the produced endless belt 62 is substantially linear. As the surface roughness Ra of the surface of the core body 101 increases, The surface roughness Ra of the inner peripheral surface of the endless belt 62 is also increased. Therefore, the surface roughness Ra of the inner peripheral surface of the endless belt 62 can be set to a desired value by adjusting the surface roughness Ra of the surface of the core body 101.

  The surface roughness Ra here is an arithmetic average roughness which is one of the measures of roughness, and is a known stylus type surface roughness Ra measuring machine (for example, Surfcom 1400A: manufactured by Tokyo Seimitsu Co., Ltd.). Can be measured using.

  Next, a method for producing an endless belt using a cylindrical core will be described below.

  The present invention uses a cylindrical core body 10, 20, 30, 40 and a cylindrical core body 101 having a cutting line formed on the surface thereof, and uses a release agent layer forming process, a coating film forming process, and a film forming process. The endless belt is manufactured through at least four steps of the step and the peeling / extraction step, and may have other steps as necessary. Further, the endless belt produced using the present invention is an endless belt based on a film that thermally contracts, such as at least a polyimide resin layer, and is composed of two or more layers including the film base even in a single layer. May be. In the latter case, an endless belt is produced so that a film to be the film layer is always formed on the outer periphery of the cylindrical core. In the following description, each process will be described on the assumption of a single layer. Hereinafter, the cylindrical core 101 will be described by way of example.

― Mold release agent layer formation process ―
The release agent layer only needs to be formed on the outer peripheral surface or the inner peripheral surface of at least the central portion of the cylindrical core body according to the cylindrical core outer peripheral surface formation or the cylindrical core inner peripheral surface formation of the endless belt. However, in order to facilitate the peeling of the polyimide resin film at the end portion, it is desirable that it is formed at either one end portion or both ends. For forming the release agent layer, a known fluororesin or silicone resin can be used as the release agent. For example, a release agent made of silicone oil or the like is applied to the outer and inner peripheral surfaces of the cylindrical core, A release layer is formed. As the release agent, a baking type silicone release agent (for example, “KS-700” manufactured by Shin-Etsu Chemical Co., Ltd.) is most desirable.

-Coating film formation process (polyimide precursor coating process)-
After the release agent layer forming step, a coating film forming step of forming a coating film is performed by applying at least the polyimide precursor solution to the outer peripheral surfaces of the central portion and both end portions of the cylindrical core body. A conventionally well-known thing can be used as a polyimide precursor.

  The polyimide precursor solution is prepared as follows. First, a polyamic acid solution is obtained by polymerizing a tetracarboxylic dianhydride and a diamine compound in an organic polar solvent.

[Tetracarboxylic dianhydride]
There is no restriction | limiting in particular as tetracarboxylic dianhydride which can be used for manufacture of a polyamic acid, Either an aromatic type or an aliphatic type compound can be used.

  Examples of the aromatic tetracarboxylic acid include pyromellitic dianhydride, 3,3 ′, 4,4′-benzoenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyl sulfone. Tetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyl Ether tetracarboxylic dianhydride, 3,3 ′, 4,4′-dimethyldiphenylsilane tetracarboxylic dianhydride, 3,3 ′, 4,4′-tetraphenylsilane tetracarboxylic dianhydride, 1, 2,3,4-furantetracarboxylic dianhydride, 4,4′-bis (3,4-dicarboxyphenoxy) diphenyl sulfide dianhydride, 4,4′-bis (3,4-dicarboxyphenoxy) Phenylsulfone dianhydride, 4,4′-bis (3,4-dicarboxyphenoxy) diphenylpropane dianhydride, 3,3 ′, 4,4′-perfluoroisopropylidenediphthalic dianhydride, 3, 3 ′, 4,4′-biphenyltetracarboxylic dianhydride, bis (phthalic acid) phenylphosphine oxide dianhydride, p-phenylene-bis (triphenylphthalic acid) dianhydride, m-phenylene-bis (tri Phenylphthalic acid) dianhydride, bis (triphenylphthalic acid) -4,4′-diphenyl ether dianhydride, bis (triphenylphthalic acid) -4,4′-diphenylmethane dianhydride, and the like.

  Aliphatic tetracarboxylic dianhydrides include butanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutane. Tetracarboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentylacetic acid dianhydride, 3,5,6-tricarboxynorbonane-2-acetic acid dianhydride Anhydride, 2,3,4,5-tetrahydrofurantetracarboxylic dianhydride, 5- (2,5-dioxotetrahydrofural) -3-methyl-3-cyclohexene-1,2-dicarboxylic dianhydride, Aliphatic or alicyclic tetracarboxylic dianhydrides such as bicyclo [2,2,2] -oct-7-ene-2,3,5,6-tetracarboxylic dianhydride; 4 5,9b-Hexahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] furan-1,3-dione, 1,3,3a, 4,5,9b-hexahydro-5-methyl -5- (Tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] furan-1,3-dione, 1,3,3a, 4,5,9b-hexahydro-8-methyl Examples include aliphatic tetracarboxylic dianhydrides having an aromatic ring such as -5- (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] furan-1,3-dione. Can do.

  As tetracarboxylic dianhydride, aromatic tetracarboxylic dianhydride is preferable, and pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 3, 3 ', 4,4'-biphenylsulfone tetracarboxylic dianhydride is optimally used.

[Diamine compound]
Next, the diamine compound that can be used for producing the polyamic acid is not particularly limited as long as it is a diamine compound having two amino groups in the molecular structure.

  For example, p-phenylenediamine, m-phenylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylethane, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl sulfide, 4,4 ′ -Diaminodiphenylsulfone, 1,5-diaminonaphthalene, 3,3-dimethyl-4,4'-diaminobiphenyl, 5-amino-1- (4'-aminophenyl) -1,3,3-trimethylindane, 6 -Amino-1- (4'-aminophenyl) -1,3,3-trimethylindane, 4,4'-diaminobenzanilide, 3,5-diamino-3'-trifluoromethylbenzanilide, 3,5- Diamino-4′-trifluoromethylbenzanilide, 3,4′-diaminodiphenyl ether, 2,7- Aminofluorene, 2,2-bis (4-aminophenyl) hexafluoropropane, 4,4'-methylene-bis (2-chloroaniline), 2,2 ', 5,5'-tetrachloro-4,4' -Diaminobiphenyl, 2,2'-dichloro-4,4'-diamino-5,5'-dimethoxybiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 4,4'-diamino-2, 2′-bis (trifluoromethyl) biphenyl, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, 1 , 4-bis (4-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) -biphenyl, 1,3′-bis (4-aminophenoxy) benzene, , 9-bis (4-aminophenyl) fluorene, 4,4 ′-(p-phenyleneisopropylidene) bisaniline, 4,4 ′-(m-phenyleneisopropylidene) bisaniline, 2,2′-bis [4- ( Aromatic aminodiamines such as 4-amino-2-trifluoromethylphenoxy) phenyl] hexafluoropropane, 4,4′-bis [4- (4-amino-2-trifluoromethyl) phenoxy] -octafluorobiphenyl; An aromatic diamine having two amino groups bonded to an aromatic ring such as tetraphenylthiophene and a hetero atom other than the nitrogen atom of the amino group; 1,1-metaxylylenediamine, 1,3-propanediamine, tetra Methylenediamine, pentamethylenediamine, octamethylenediamine, nonamethylenediamine, 4, 4-diaminoheptamethylenediamine, 1,4-diaminocyclohexane, isophoronediamine, tetrahydrodicyclopentadienylenediamine, hexahydro-4,7-methanoindanylene methylenediamine, tricyclo [6,2,1,02. 7] -undecylenedimethyldiamine, aliphatic diamines such as 4,4′-methylenebis (cyclohexylamine), and alicyclic diamines.

  As the diamine compound, p-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, and 4,4'-diaminodiphenyl sulfone are preferable.

  These diamine compounds can be used alone or in combination of two or more.

[Combination of tetracarboxylic dianhydride and diamine compound]
As a polyamic acid, Preferably, what consists of aromatic tetracarboxylic dianhydride and aromatic diamine from a viewpoint of the intensity | strength of a molded object is preferable.

[Organic polar solvent]
Examples of the organic polar solvent used in this polyamic acid production reaction include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, formamide solvents such as N, N-dimethylformamide and N, N-diethylformamide, acetamide, Acetamide solvents such as N, N-dimethylacetamide and N, N-diethylacetamide, pyrrolidone solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone, phenol, o-, m-, or p -Phenol solvents such as cresol, xylenol, halogenated phenol and catechol; ether solvents such as tetrahydrofuran, dioxane and dioxolane; alcohol solvents such as methanol, ethanol and butanol; cellosolve solvents such as butyl cellosolve There can be exemplified hexamethylphosphoramide, .gamma.-butyrolactone and the like, it is desirable to use them alone or as a mixture, further xylene, aromatic hydrocarbons such as toluene can be used. The solvent is not particularly limited as long as it dissolves the polyamic acid and the polyamic acid-polyimide copolymer. A conventionally known aprotic polar solvent is used, and the concentration, viscosity and the like of the polyamic acid solution are appropriately selected.

  Conductive fine particles are further added to and dispersed in the polyamic acid solution prepared by the above-described method to prepare a dispersion.

[Conductive fine particles]
As the conductive fine particles, conductive or semiconductive fine powder can be used, and there is no particular limitation as long as a desired electric resistance can be stably obtained. However, carbon black such as Ketchen Black and Acetylene Black, aluminum Examples thereof include metals such as nickel and metal, metal oxide compounds such as tin oxide, and potassium titanate. These may be used alone or in combination. In the present invention, in consideration of dispersibility in the resin, dispersion stability, resistance variation of the semiconductive polyimide endless belt, electric field dependency, and stability of electrical resistance over time, an oxidized carbon black having a pH of 5 or less is used. Preferably it is good to add.

  As a dispersion method, a known method can be applied, and examples thereof include a pole mill, a sand mill, a basket mill, and ultrasonic dispersion.

[Oxidized carbon black]
Oxidized carbon black can be produced by oxidizing carbon black to give a carboxyl group, a quinone group, a lactone group, a hydroxyl group or the like to the surface. This oxidation treatment is an air oxidation method in which contact is made with air in a high temperature atmosphere to react, a method of reacting with nitrogen oxides or ozone at room temperature, and air oxidation at high temperature, followed by ozone oxidation at a low temperature. It can be performed by a method or the like. Specifically, the oxidized carbon black can be produced by a contact method. Examples of the contact method include a channel method and a gas black method. Oxidized carbon black can also be produced by a furnace black method using gas or oil as a raw material. If necessary, after these treatments, a liquid phase oxidation treatment with nitric acid or the like may be performed. Acidic carbon black can be produced by a contact method, but is usually produced by a closed furnace method. In the furnace method, only carbon black having a high pH and a low volatile content is usually produced. For this reason, the carbon black obtained by the furnace method manufacturing and adjusted to have a pH of 5 or less by the post-treatment is also considered to be included in the present invention.

  The pH value of the oxidation-treated carbon black is pH 5.0 or less, preferably pH 4.5 or less, more preferably pH 4.0 or less. Oxidized carbon having a pH of 5.0 or less has an oxygen-containing functional group such as a carboxyl group, a hydroxyl group, a quinone group, and a lactone group on the surface, so that it has good dispersibility in the resin, and thus good dispersion stability is obtained. In addition, the resistance variation of the semiconductive polyimide endless belt can be reduced, and the electric field dependency is also reduced, so that electric field concentration due to the transfer voltage is difficult to occur.

  Here, pH is calculated | required by adjusting the aqueous suspension of carbon black and measuring with a glass electrode. Moreover, pH of acidic carbon black can be adjusted with conditions, such as processing temperature in an oxidation treatment process, and processing time.

  The oxidized carbon black preferably contains 1 to 25% by weight, preferably 2 to 20% by weight, more preferably 3.5 to 15% by weight of the volatile component. When the volatile content is less than 1% by weight, the effect of the oxygen-containing functional group attached to the surface is lost, and the dispersibility in the binder resin may be reduced. On the other hand, if it is higher than 25% by weight, it will decompose when dispersed in the binder resin, or the amount of water adsorbed on the oxygen-containing functional group on the surface will increase, resulting in Problems such as poor appearance may occur. Therefore, the dispersion | distribution in binder resin can be made more favorable by making a volatile content into the said range. This volatile content can be determined from the ratio of organic volatile components (carboxyl group, hydroxyl group, quinone group, lactone group, etc.) that come out when carbon black is heated at 950 ° C. for 7 minutes.

  Specific examples of the oxidation-treated carbon black include “Printex 150T” (pH 4.5, volatile content 10.0% by weight) and “Special Black 350” (pH 3.5, volatile content 2.2) manufactured by Degussa. %), “Special Black 100” (pH 3.3, volatile content 2.2% by weight), “Special Black 250” (pH 3.1, volatile content 2.0% by weight), “Special Black 5”. (PH 3.0, volatile matter 15.0% by weight), “Special Black 4” (pH 3.0, volatile matter 14.0% by weight), “Special Black 4A” (pH 3.0, volatile matter 14.0) %), “Special Black 550” (pH 2.8, volatile content 2.5% by weight), “Special Black 6” (pH 2.5, volatile content 18.0% by weight), “Color Black FW2”. 0 ”(pH 2.5, volatile content 20.0% by weight),“ Color Black FW2 ”(pH 2.5, volatile content 16.5% by weight),“ Color Black FW2V ”(pH 2.5, volatile content 16) .5 wt%), “MONARCH 1000” manufactured by Cabot (pH 2.5, volatile content 9.5 wt%), “MONARCH 1300” manufactured by Cabot (pH 2.5, 9.5 wt% volatile content), “ “MONARCH1400” (pH 2.5, volatile matter 9.0 wt%), “MOGUL-L” (pH 2.5, volatile matter 5.0 wt%), “REGAL400R” (pH 4.0, volatile content 3.5) Weight%) and the like.

  Conductive fine particle-dispersed polyamic, which is a polyimide precursor solution, is synthesized by reacting 100 parts by weight of an organic polar solvent with 5 to 40 parts by weight of polyamic acid and 2 to 16 parts by weight of carbon black to synthesize polyamic acid. An acid composition was obtained.

  Next, as a method of applying the polyimide precursor solution to the outer peripheral surface of the cylindrical core, a dip coating method in which the cylindrical core is dipped in the polyimide precursor solvent and pulled up, while rotating the core in the horizontal direction, A flow coating method in which a solvent is discharged onto the surface, a blade coating method in which a coating film is metalized with a blade, and other known methods can be employed.

  In the precursor coating film forming step, a polyimide precursor solution is applied to the surface of the cylindrical core body to form a polyimide precursor coating film. The coating method depends on the shape of the core body. A dip coating method in which the body is immersed in the polyimide precursor solution and pulled up, a dip coating method in which the core body is immersed in the polyimide precursor solution and pulled up, and the axial direction is set so that it is substantially parallel to the horizontal direction, rotating in the circumferential direction In the flow coating method and the flow coating method, the core body or nozzle is translated in the axial direction while discharging the polyimide precursor solution from a nozzle or the like installed almost directly on the surface of the core body. A known method such as a blade coating method in which the coating film formed on the surface of the core is metalized with a blade can be used.

  In the flow coating method and the blade coating method, the coating film formed on the surface of the core is formed in a spiral shape in the axial direction of the core, so that a seam can be formed, but the solvent contained in the polyimide precursor solution is room temperature. The seam is naturally smoothed due to the leveling properties of the liquid because of the slow drying.

  Here, “applying onto a cylindrical core” includes the case of applying onto a cylindrical core. “Apply” means to apply on the surface of the side surface of the cylindrical core, and in the case of having a layer on the side surface, it also means to apply on the surface of the layer.

  First, of the various coating methods described above, the dip coating method and the blade coating method will be described in detail. In the manufacturing method of the endless belt according to the present embodiment, the polyimide precursor coating film forming method is It is not limited to.

  In the precursor coating film forming step, when the polyimide precursor solution is applied by a dip coating method, the polyimide precursor solution has a very high viscosity, and thus the film thickness may be too thick. In that case, for example, a dip coating method in which the film thickness is controlled by an annular body as shown below can be applied.

  A dip coating method in which the film thickness is controlled by an annular body will be described with reference to FIGS. FIG. 11 is a schematic configuration diagram illustrating an example of an apparatus used for a dip coating method in which a film thickness is controlled by an annular body. However, in FIGS. 11-13, only the application | coating main part is shown and the other apparatus is abbreviate | omitted. As shown in FIG. 11, this dip coating method applies a polyimide precursor solution 102 filled in a coating tank 103 to an outer diameter of a cylindrical core body (hereinafter also simply referred to as “core body”) 101. In this coating method, the annular body 105 provided with the holes 106 is floated, the cylindrical core body 101 is immersed in the polyimide precursor solution 102 through the holes 106, and then pulled up.

  FIG. 12 is an enlarged perspective view of a main part for explaining an installation state of the annular body 105 shown in FIG. As shown in FIG. 12, an annular body 105 having a hole 106 having a diameter larger than the outer diameter of the cylindrical core body 101 by a certain gap is floated on the liquid surface of the polyimide precursor solution 102.

  The annular body 105 floats on the liquid surface of the polyimide precursor solution 102, and the material thereof is preferably not affected by the polyimide precursor solution 102. Examples thereof include various metals and various plastics. Further, the structure of the annular body 105 may be, for example, a hollow structure so as to easily float on the liquid surface of the polyimide precursor solution 102.

  The annular body 105 can freely move on the liquid surface of the polyimide precursor solution 102. Therefore, the annular body 105 is supported by a roll or a bearing in addition to a method of floating the annular body 105 on the polyimide precursor solution 102 so that the annular body 105 can move on the polyimide precursor solution 102 with a slight force. There are methods such as a method, a method of supporting the annular body 105 with an air pressure, and a method of installing it in a freely movable state. Further, a fixing means for temporarily fixing the annular body 105 may be provided so that the annular body 105 is positioned at the center of the coating tank 103. As such fixing means, there are means for providing a foot on the annular body 105, means for fixing the coating tank 103 and the annular body 105, and the like. However, when these fixing means are used, as will be described later, the fixing means is detachably disposed so that the annular body 105 can freely move when the cylindrical core body 101 is immersed and then pulled up. .

  The gap between the outer diameter of the cylindrical core body 101 and the minimum hole diameter of the hole 106 is adjusted according to the coating film thickness. The desired coating thickness, that is, the dry film thickness, is the product of the wet film thickness and the non-volatile concentration of the polyimide precursor solution 102. Thus, a desired wet film thickness is obtained. In addition, the gap between the outer diameter of the cylindrical core body 101 and the minimum hole diameter of the hole 106 is preferably 1 to 2 times the desired wet film thickness. The reason why the distance is 1 to 2 times is that the gap distance does not always become a wet film thickness due to the viscosity and / or surface tension of the polyimide precursor solution 102. Thus, the minimum hole diameter of the desired hole 106 is obtained from the desired dry film thickness and the desired wet film thickness.

  The wall surface of the hole 106 provided in the annular body 105 may be configured to be substantially perpendicular to the liquid level of the floating polyimide precursor solution 102. For example, it may be a straight line in the cross-sectional view shown in FIG. 12, and the straight line may be perpendicular to the liquid surface of the polyimide precursor solution 102, or may be configured in another form. For example, as shown in FIG. 13 (a), the lower part immersed in the polyimide precursor solution 102 is wide, and the upper part is narrow, and is an oblique linear wall surface 107, or as shown in FIG. 13 (b), polyimide Examples thereof include a curved wall 108 having a wide lower part immersed in the precursor solution 102 and a narrow upper part. In particular, as shown in FIG. 13 (a) or FIG. 13 (b), a shape in which the lower part immersed in the polyimide precursor solution 102 is wide is preferable. Here, FIG. 5 shows the shape of the wall surface of the hole 106 provided in the annular body 105, FIG. 13 (a) is a schematic wall surface 107, and FIG. 13 (b) is a schematic cross section showing a curved wall surface 108. FIG.

  When performing dip coating, the cylindrical core body 101 is immersed in the polyimide precursor solution 102 through the hole 106 so that the cylindrical core body 101 does not contact the annular body 105. Next, the cylindrical core body 101 is pulled up through the hole 106. At that time, the coating film 104 is formed by the gap between the cylindrical core body 101 and the hole 106. The pulling speed is preferably about 100 to 1500 mm / min. The polyimide precursor solution 102 preferable for this coating method has a solid content concentration of 10 to 40% by mass and a viscosity of 1 to 200 Pa · s. Here, “raising” means a relative rise of the polyimide precursor solution 102 with respect to the liquid surface.

  When pulling up the cylindrical core body 101 through the hole 106, the annular body 105 is in a freely movable state, the hole 106 of the annular body 105 is circular, and the outer periphery of the cylindrical core body 101 is also circular. Therefore, the annular body 105 can move so that the frictional resistance between the cylindrical core body 101 and the annular body 105 is constant. That is, when the cylindrical core body 101 is pulled up, if the gap between the annular body 105 and the cylindrical core body 101 is to be narrowed at a certain position, the frictional resistance is increased in the portion where the cylindrical core body 101 is to be narrowed. On the other hand, the frictional resistance becomes small on the opposite side, and a state in which the frictional resistance is temporarily non-uniform can occur. However, since the annular body 105 moves freely, the outer periphery of the cylindrical core body 101 is circular, and the hole 106 of the annular body 105 is circular, the frictional resistance is not uniform. The annular body 105 moves so as to be in a uniform state. Therefore, the annular body 105 does not come into contact with the cylindrical core body 101.

  Further, the position where the frictional resistance is uniform is a position where the circular shape of the outer periphery of the cylindrical core body 101 and the circular shape of the hole 106 of the annular body 105 are substantially concentric. Therefore, even if the center of the circle of the cross section of the cylindrical core body 101 is deviated within the allowable range in the axial direction, the annular body 105 moves so as to follow it. Therefore, a polyimide precursor coating 104 having a certain wet film thickness can be formed on the surface of the cylindrical core 101.

  Furthermore, the coating apparatus used for the dip coating method includes a cylindrical core body holding means for holding the cylindrical core body 101, and a first moving means and / or a polyimide precursor for moving the holding means in the vertical direction as required. You may have the 2nd moving means to move the coating tank 103 into which the solution 102 is put up and down. In some cases, the holding means, the first moving means, and / or the second moving means have a flare in a plane crossing the pulling direction when moving. Even in such a case, the annular body 105 can move following the deflection.

  By applying such a dip coating method in which the film thickness is controlled by the annular body 105, the sagging at the upper end portion of the cylindrical core body 101 due to the use of the polyimide precursor solution 102 having a high viscosity is reduced and simplified. The film thickness can be made uniform.

  Next, the blade coating method will be described.

  In the blade coating method, the polyimide precursor solution is flattened with a spatula while allowing the polyimide precursor solution to flow down to the outer surface of the cylindrical core, and the flow point and spatula of the polyimide precursor solution are moved from one end of the cylindrical core to the other end. The polyimide precursor solution is applied to the outer surface of the cylindrical core body by moving it horizontally.

  The blade coating method will be described with reference to FIG. FIG. 14 is a schematic configuration diagram showing an example of an apparatus used for the blade coating method. However, in FIG. 14, only the coating main part is shown, and other devices are omitted. In FIG. 14, the polyimide precursor solution is caused to flow down from the container 202 through the nozzle 204 while rotating the cylindrical core body 201 in the arrow direction. The nozzle 204 may be attached to the container 202, but may be separated from each other and connected by a pipe to fix the container 202 separately.

  The flow-down polyimide precursor solution is flattened by the spatula 203. Immediately after passing the spatula 203, streaks may remain, but the streaks disappear with time due to the fluidity of the polyimide precursor solution. The nozzle 204 and the spatula 203 are interlocked and moved from one end of the cylindrical core body 201 to the other end in the horizontal direction, whereby the entire surface of the cylindrical core body 201 can be applied. The moving speed is the coating speed.

  The conditions at the time of application are that the rotational speed of the cylindrical core 201 is 20 to 200 rpm, and the application speed V is the outer diameter k of the cylindrical core 201, the flow-down amount f of the polyimide precursor solution, and the desired wet film thickness. It is related to t, and is represented by the equation V = f / (t · k · π). Here, π represents the circumference ratio.

  When the polyimide precursor solution is caused to flow down, the polyimide precursor solution having a high viscosity is difficult to flow down naturally by gravity alone, so that it is also effective to extrude it with air pressure or a pump. The distance between the nozzle 204 and the cylindrical core 201 may be arbitrary, but is preferably about 10 to 100 mm so that the falling liquid is not interrupted. This is because if liquid breaks off, bubbles may be involved.

  The spatula 203 is made of a material that is not affected by the polyimide precursor solution, for example, a plastic such as polyethylene or fluorine resin, or a thin plate of metal such as brass or stainless steel, and is made of an elastic material. This is formed into a width of 10 to 50 mm and lightly pressed against the cylindrical core body 201. If the polyimide precursor solution passes, the spatula 203 is separated from the cylindrical core body 201 with a certain gap, and at that time, the polyimide precursor solution is pushed out. The concentration of the polyimide precursor solution preferable for this coating method is 10 to 25% by weight, and the viscosity is about 10 to 1000 Pa · s. When the spatula 203 is not present, the polyimide precursor solution that has flowed down adheres to the cylindrical core 201 in a streak shape and does not become flat.

  The coating surface is not formed over the entire surface of the cylindrical core 201, and some uncoated portions are left at both ends. If a cylindrical body having the same outer diameter as that of the cylindrical core body 201 is attached to both ends of the cylindrical core body 201 and applied to the cylindrical body, the entire surface of the cylindrical core body 201 is applied. A coating film can also be formed. In that case, the cylindrical body may be removed after application and the coating film may be washed.

― Film formation process ―
The film forming process includes a drying process for drying the polyimide precursor solution and a heating process for heating and baking. The polyimide precursor coating film formed on the outer peripheral surface of the core is preferably dried at a drying temperature of 50 to 100 ° C. and a drying time of 30 to 200 minutes. When dripping occurs in the polyimide precursor coating film due to the influence of gravity before drying, it is preferable to rotate the core in the axial direction at 10 to 500 rpm.

  At the time after drying, the polyimide precursor coating film contains about 10-40% of the initial content of the solvent, and the coating film still has flexibility. Therefore, the coating film cannot be removed from the core and does not retain the strength as a tubular object.

  Subsequently, it is preferable that the heating conditions for forming the polyimide precursor film by heating and baking the polyimide precursor coating film are performed at 350 to 450 ° C. for 20 to 60 minutes. At that time, it is preferable to increase the temperature stepwise or gradually at a constant rate, rather than immediately increasing the temperature until the temperature is reached so that the film does not easily swell.

  The polyimide resin contracts with a strong force when it undergoes a condensation reaction by heating. The present invention is characterized in that a gas escape passage for gas generated during heating is secured by using the contraction. Therefore, abnormal outer diameters such as belt bulge and film thickness unevenness of the endless belt can be suppressed.

― Peeling / extraction process ―
After cooling the core, either remove the film from the core and then cut both ends of the film, or cut both ends of the film on the core and then remove the film from the core to obtain an endless belt be able to. Alternatively, the endless belt obtained by removing the resin from the mold may be further subjected to slit processing, punching drilling processing, tape winding processing, or the like as necessary.

― Endless belt layer structure and application ―
When using an endless belt produced by utilizing the present invention as a transfer body, conductive particles are dispersed in a polyimide material. Examples of the conductive particles include carbon black, carbon fiber, and graphite.

  When an endless belt is used as a fixing member, it is effective to form a non-adhesive resin layer on the belt surface in order to prevent fusion of toner adhering to the surface (outer peripheral surface). Examples of the material include fluorine resins such as polytetrafluoroethylene (PTFE) and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA). The non-adhesive layer may contain materials such as carbon powder, inorganic compound powders such as titanium oxide and barium sulfate for the purpose of improving wear resistance, electrostatic offset, and compatibility with toner adhesion preventing oil. Good. A preferable polyimide resin layer for the fixing belt has a thickness of 25 to 200 μm, and a non-adhesive layer has a thickness of 5 to 50 μm.

  Further, when a release layer is formed as the above-mentioned adhesive resin layer, in the release layer forming step, the polyimide precursor coating dried to such an extent that the coating film does not deform even if left standing in the precursor drying step. For example, a release resin such as a fluororesin is applied to the film to form a release layer.

  Here, as the fluororesin, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-per Fluoromethyl vinyl ether copolymer (MFA), tetrafluoroethylene-perfluoroethyl vinyl ether copolymer (EFA), polyethylene-tetrafluoroethylene (ETFE), polyvinylidene fluoride (PVDF), polychlorotrifluoride ethylene (PCTFE), Examples include vinyl fluoride (PVF). Polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, especially from the viewpoint of heat resistance and mechanical properties. (PFA), tetrafluoroethylene - perfluoro methyl vinyl ether copolymer (MFA), tetrafluoroethylene - perfluoro ethyl vinyl ether copolymer (EFA) is preferably used.

  In addition, a filler may be added to the fluororesin layer as a release layer in order to improve wear resistance and electrostatic offset. As such a filler, an inorganic material is preferable, and specifically, at least one of barium sulfate, synthetic mica, graphite, carbon black and the like is preferably dispersed.

  In order to form such a fluororesin layer, the aqueous dispersion is applied to the surface of the polyimide precursor coating film using the dip coating method described above. Moreover, when the adhesiveness of a polyimide precursor coating film and a fluorine-type resin layer is insufficient, there exists the method of apply | coating and forming in advance a primer layer on the polyimide precursor coating film surface as needed. Examples of the material for the primer layer include polyphenylene sulfide, polyethersulfone, polysulfone, polyamideimide, polyimide, and derivatives thereof, and it is preferable that the primer layer further includes at least one compound selected from fluorine resins. Moreover, as thickness of a primer layer, the range of 0.5-10 micrometers is preferable.

  In forming the primer layer and the fluororesin layer, after the endless belt is obtained using the manufacturing method of the present embodiment, the primer layer and the fluororesin film are applied to the outer peripheral surface of the endless belt or It is also possible to use a known method of coating a fluororesin tube.

  A release agent may be applied to the surface of the core body mold so that it is not difficult to peel the film that becomes a seamless tubular body from the core body mold.

  Then, the unevenness | corrugation of the inner peripheral surface of the endless belt using the core metal mold | die in this Embodiment is demonstrated.

  As described above, when the polyimide precursor coating formed on the core surface is heated and dried, the polyimide resin coating is swollen by the gas generated by evaporation of the solvent remaining in the coating. It may occur. Therefore, conventionally, the surface of the core is roughened by uniformly blasting the surface of the core so that the gas generated in the coating film can be effectively released during the heat treatment. The roughness Ra (arithmetic mean roughness) is about 0.6 to 1.0 μm, and a rough surface having uniform roughness in the circumferential direction and the axial direction of the core body is formed. Hereinafter, the endless belt is also referred to as an “endless belt”.

  On the other hand, in the fixing device 60 shown in FIG. 15, the endless belt 62 is rubbed against the pressure pad 64 disposed inside the endless belt 62 while relative to the fixed pressure pad 64. Therefore, the belt inner peripheral surface is worn by friction with the pressure pad 64, and the endless belt 62 is damaged, or the wear powder causes the pressure pad 64 and the belt inner peripheral surface to be worn. There was a possibility that the sliding resistance of the endless belt 62 would be increased, resulting in a rotation failure of the endless belt 62.

  Therefore, in order to lower the sliding resistance between the pressure pad 64 and the endless belt 62, a sheet-like low friction sheet 68 is disposed, and further, silicone oil or the like is used to lower the sliding resistance on the low friction sheet 68. A heat-resistant lubricant is applied.

  In such a fixing device 60, the endless belt 62 having an inner peripheral surface made of a rough surface uniformly processed by blasting has an inner peripheral surface that is smoother than a belt whose inner peripheral surface is smoothed. Since the retention capability of the lubricant is improved and the decrease in the lubricant due to use over time can be suppressed, the durability performance of the endless belt 62 is improved.

  However, in the endless belt 62 having a uniform rough inner peripheral surface, a sliding sound generated when the endless belt 62 rotates may be a problem. This sliding sound is generated when the unevenness of the uniformly roughened inner peripheral surface slides with the low friction sheet 68, and the larger the surface roughness of the inner peripheral surface of the belt, the larger the sliding noise. For this reason, it has been considered that it is difficult to achieve both the holding ability of the lubricant.

  Therefore, when various studies were made on the surface roughness of the inner peripheral surface of the endless belt 62, the surface roughness Ra in the circumferential direction of the inner peripheral surface was determined by processing such as cutting in the circumferential direction of the endless belt 62. If the shape is smaller than the surface roughness Ra in the axial direction of the inner peripheral surface, it is possible to ensure the retention capability of the lubricant, and at the same time, the unevenness of the inner peripheral surface in the direction along the rotational direction of the endless belt 62 is increased. Since it became small, it turned out that a sliding noise can also be suppressed.

  The relationship between the surface roughness Ra of the surfaces of the cores 10 to 40 and 101 shown in FIGS. 1 to 5 and 10 and the surface roughness Ra of the inner peripheral surface of the produced endless belt 62 is substantially linear. As the surface roughness Ra of the surface of the core body 101 increases, the surface roughness Ra of the inner peripheral surface of the endless belt 62 also increases. Therefore, the surface roughness Ra of the inner peripheral surface of the endless belt 62 can be set to a desired value by adjusting the surface roughness Ra of the surface of the core body 101. On the other hand, the surface roughness Ra of the outer peripheral surface of the endless belt 62 also depends on the film thickness of the endless belt 62 (hereinafter abbreviated as “belt film thickness”). Here, Ra mentioned later is the meaning also including Ra1-Ra4 mentioned above.

  At that time, the surface roughness Ra in the circumferential direction of the surface of the core body 101 is not particularly limited as long as it is smaller than the surface roughness Ra in the axial direction of the surface of the core body 101, but the surface roughness Ra in the circumferential direction is degassed. Since it does not depend on performance, it is preferably 0.5 μm or less, more preferably 0.4 μm or less, and particularly preferably 0.3 μm or less, regardless of the belt film thickness. When the surface roughness Ra in the circumferential direction of the endless belt 62 is 0.5 μm or more, the load torque when the endless belt 62 is rotated increases or the sliding noise increases. There is. On the other hand, the surface roughness Ra of the outer peripheral surface of the endless belt 62 varies depending on the purpose of use. However, when the surface roughness Ra of the outer peripheral surface is 1.5 μm or more as a whole, problems such as image defects may easily occur. The surface roughness Ra of the outer peripheral surface of the endless belt 62 is preferably 1.5 μm or less.

  Further, the belt film thickness of the endless belt 62 is preferably in the range of 20 to 200 μm, more preferably in the range of 30 to 140 μm, and particularly preferably in the range of 50 to 120 μm.

  When the endless belt 62 manufactured using such a core body 101 is used in the fixing device 60, it is possible to reduce the sliding noise while reducing the load torque when the endless belt 62 rotates. It becomes.

  The surface roughness Ra here is an arithmetic average roughness which is one of the measures of roughness, and is a known stylus type surface roughness Ra measuring machine (for example, Surfcom 1400A: manufactured by Tokyo Seimitsu Co., Ltd.). Can be measured using.

  The measurement of the surface roughness Ra in the endless belt 62 of the present embodiment is based on JIS B0601-1994 using the Surfcom 1400A, the evaluation length Ln = 4 mm, the reference length L = 0.8 mm, and the cutoff value. The measurement was performed under the measurement condition of 0.8 mm. Although it is possible to measure under other conditions, it is preferable to measure under conditions that can be correlated with the above-mentioned measurement conditions, and the measured values are converted to values evaluated under the above-described measurement conditions. It is evaluated by.

  As described above, in the fixing device 60 of the present embodiment shown in FIG. 15, the surface roughness Ra in the circumferential direction of the inner circumferential surface of the endless belt 62 is smaller than the surface roughness Ra in the inner circumferential axis direction. Thus, it is possible to suppress the sliding noise when the endless belt 62 is rotated while reducing the load torque when the endless belt 62 rotates. “Small” means that it is clearly smaller than the range of measurement error when measuring the surface roughness Ra and the range of variation when the endless belt 62 is manufactured. Specifically, the inner peripheral surface It means that the ratio of the surface roughness Ra in the circumferential direction of the inner circumferential surface to the surface roughness Ra in the axial direction (circumferential surface roughness Ra / axial surface roughness Ra) is 0.95 or less.

  Further, when the core mold of the present embodiment described above is used, the swelling phenomenon at the center portion in the width direction of the obtained endless belt 62 is suppressed. The diameter difference ratio can be formed to 0.3% or less. Therefore, the rotation speed of the endless belt 62 is set to be substantially constant in the width direction so that a substantially uniform frictional force acts on the paper P passing through the nip portion N from the endless belt 62 in the width direction. Therefore, it is possible to set the conveyance speed of the paper P to be faster at both ends, and to effectively apply a force in the width direction from the center to both ends of the paper P. Therefore, the occurrence of paper wrinkles on the paper P and the occurrence of image defects such as image gloss unevenness can be suppressed.

  The endless belt 62 of the present embodiment is not particularly limited as long as it is an endless belt containing at least a polyimide resin. However, in the present embodiment, the “endless belt containing at least polyimide resin” means a single-layer endless belt composed of a polyimide resin layer or a layer mainly composed of polyimide resin (hereinafter referred to as “single-layer endless belt”). The endless belt having a structure of two or more layers in which other layers are laminated on the inner peripheral surface and / or outer peripheral surface of the single-layer endless belt (hereinafter referred to as “multilayer endless belt”). Also means).

  Moreover, a main component means that content of the polyimide resin in a single layer endless belt is 50 mass% or more.

[Image forming apparatus]
Next, two types of fixing devices used for the fixing means of the image forming apparatus of the present invention will be described by way of example.

[Embodiment 1]
FIG. 15 is a schematic configuration diagram illustrating a fixing device to which the exemplary embodiment is applied. A fixing device 60 shown in FIG. 15 has a function of fixing a toner image transferred to a paper P as a recording material (recording paper) to the paper P in an electrophotographic image forming apparatus such as a copying machine or a printer. is doing. As shown in FIG. 15, the fixing device 60 includes a fixing roll 61 as an example of a rotating member, an endless belt 62 as an example of a belt member, and a pressure pressed from the fixing roll 61 via the endless belt 62. A main part is constituted by a pressure pad 64 as an example of a member.

  The fixing roll 61 is a cylindrical roll configured by laminating a heat-resistant elastic body layer 612 and a release layer 613 around a metal core (cylindrical cored bar) 611, and is rotatably supported. Rotates at a predetermined surface speed.

  Inside the fixing roll 61, for example, a halogen heater 66 having a rating of 600 W is disposed as a heat source. On the other hand, a temperature sensor 69 is disposed in contact with the surface of the fixing roll 61. A control unit (not shown) of the image forming apparatus controls the lighting of the halogen heater 66 based on the temperature measurement value by the temperature sensor 69, and the surface temperature of the fixing roll 61 becomes a predetermined set temperature (for example, 175 ° C.). It is adjusted to maintain.

  The endless belt 62 is a seamless endless belt, the pressure pad 64 disposed inside the endless belt 62, the upstream belt guide member 63a and the downstream belt guide member 63b, and both ends of the endless belt 62. It is rotatably supported by an edge guide member 80 (see FIG. 15 in the subsequent stage) as an example of a belt regulating member disposed in the section. Then, it is disposed so as to be pressed against the fixing roll 61 at the nip portion N, and rotates following the fixing roll 61.

  Here, FIG. 16 is a diagram illustrating a configuration in which the endless belt 62 is supported, and shows one end region of the fixing device 60 as viewed from the downstream side in the conveyance direction of the paper P.

  As shown in FIG. 16, both end portions in the width direction of the endless belt 62 are supported by edge guide members 80 fixed to both end portions of a holder 65 disposed inside the endless belt 62. The edge guide member 80 is provided on the outer side of the belt traveling guide portion 801 having a cylindrical shape in which a notch is formed in a portion corresponding to the nip portion N and the vicinity thereof, that is, a C-shaped cross section, A flange portion 802 formed with an outer diameter larger than the outer diameter of the endless belt 62 and a holding portion for positioning and fixing the edge guide member 80 to the fixing device 60 main body provided on the outer surface of the edge guide member 80. 803.

  The endless belt 62 rotates at the both ends in the width direction of the endless belt 62 following the fixing roll 61 while the inner peripheral surfaces of both ends are supported by the edge guide member 80. Further, the endless belt 62 is restricted from moving in the width direction of the endless belt 62 (belt walk) by the flange portion 802, so that the endless belt 62 is prevented from being displaced.

  On the other hand, in the region excluding both ends in the width direction of the endless belt 62, the endless belt 62 is supported by the pressure pad 64, the upstream belt guide member 63a, and the downstream belt guide member 63b (see also FIG. 3). And in the area | region except the both ends of the endless belt 62, the low friction sheet | seat 68 arrange | positioned so that the internal peripheral surface of the endless belt 62 may cover the pressure pad 64 and the upstream belt guide member 63a, and a downstream belt guide It rotates while rubbing against the member 63b.

  The upstream belt guide member 63 a and the downstream belt guide member 63 b are attached to a holder 65 disposed inside the endless belt 62 along the longitudinal direction. The downstream belt guide member 63b that directly rubs against the inner peripheral surface of the endless belt 62 is made of a material having a low friction coefficient so that the endless belt 62 can smoothly rotate, and the endless belt 62 It is made of a material with low thermal conductivity so that it is difficult to take heat away from it. Specifically, a heat resistant resin such as tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) or polyphenylene sulfide (PPS) is used.

  On the other hand, the upstream belt guide member 63a that slides on the inner peripheral surface of the endless belt 62 via the low friction sheet 68 is also formed of a material having low thermal conductivity.

  Next, the pressure pad 64 is supported by a metal holder 65 inside the endless belt 62. Then, it is arranged in a state of being pressed against the fixing roll 61 via the endless belt 62, and forms a nip portion N with the fixing roll 61. In the pressure pad 64, a pre-nip member 64 a for securing a wide nip portion N is disposed on the inlet side (upstream side) of the nip portion N. Further, on the outlet side (downstream side) of the nip portion N, the surface of the fixing roll 61 is locally pressed to smooth the surface of the toner image and impart image gloss, and the surface of the fixing roll 61 is distorted (dented). ) To form a down curl on the sheet P, and a separation nip member 64b for separating the sheet P from the surface of the fixing roll 61 is disposed.

  The pressure pad 64 is provided with a low friction sheet 68 as an example of a low friction member on the surface in contact with the endless belt 62 in order to reduce the sliding resistance between the inner peripheral surface of the endless belt 62 and the pressure pad 64. It has been.

  The low friction sheet 68 has an upstream end of the nip portion N fixed to the bottom surface of the holder 65 by a downstream belt guide member 63b. The upstream belt guide member 63a is covered and disposed in a state of being sandwiched between the pressure pad 64 and the inner peripheral surface of the endless belt 62 in the entire nip portion N. The downstream side of the nip portion N of the low friction sheet 68 is not fixed and is set to a free end (free) state so that the low friction sheet 68 is not distorted. The low friction sheet 68 has a sliding resistance between the inner peripheral surface of the endless belt 62 and the pressure pad 64 under a state in which a pressing force is applied between the pressure pad 64 and the fixing roll 61 at the nip portion N. (Friction resistance) is reduced.

  In such a configuration, the fixing roll 61 is connected to a drive motor (not shown) and rotates in the direction of arrow C, and the endless belt 62 rotates in the same direction as the fixing roll 61 following this rotation. The sheet P on which the toner image is electrostatically transferred in the image forming apparatus is guided by the fixing inlet guide 56 and conveyed to the nip portion N. When the paper P passes through the nip portion N, the toner image on the paper P is fixed by the pressure acting on the nip portion N and the heat supplied from the fixing roll 61. In the fixing device 60 of the present embodiment, since the nip portion N can be configured widely by the concave pre-nip member 64a that substantially follows the outer peripheral surface of the fixing roll 61, stable fixing performance can be ensured.

  In the vicinity of the downstream side of the nip portion N, the paper P peeled off from the fixing roll 61 by the peeling nip member 64b is completely separated from the fixing roll 61 and guided to the paper discharge path toward the discharge portion of the image forming apparatus. A peeling assisting member 70 is provided for this purpose. The peeling auxiliary member 70 is held by a baffle holder 72 in a state in which the peeling baffle 71 is close to the fixing roll 61 in a direction (counter direction) opposite to the rotation direction of the fixing roll 61.

  Next, each member constituting the fixing device 60 will be described in detail. First, in the fixing roll 61, the core 611 is formed of a cylindrical body made of a metal having high thermal conductivity such as iron, aluminum, or SUS, for example, an outer diameter of 30 mm, a wall thickness of 1.8 mm, and a length of 360 mm. .

  The heat-resistant elastic body layer 612 is composed of an elastic body having high heat resistance, and it is particularly preferable to use an elastic body such as rubber or elastomer having a rubber hardness of about 15 to 45 ° (JIS-A). Specifically, silicone rubber, fluorine rubber, or the like can be used. In the fixing device 60 of the present embodiment, the core 611 is coated with a silicone HTV rubber having a rubber hardness of 35 ° (JIS-A) with a thickness of 600 μm.

  For the release layer 613, for example, a heat-resistant resin such as a silicone resin or a fluororesin is used, but a fluororesin is suitable from the viewpoint of the releasability to the toner and the wear resistance. As the fluororesin, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP) and the like can be used. The thickness of the release layer 613 is preferably 5 to 50 μm. In fixing device 60 of the present embodiment, PFA having a thickness of 30 μm is coated.

  The endless belt 62 is a seamless endless belt formed in a cylindrical shape with an outer diameter of 30 mm and a length of 340 mm so that defects caused by the seam do not occur in the output image. The base layer and the base layer The fixing roller 61 side surface (outer peripheral surface) or a release layer coated on both surfaces. For the base layer, a polymer such as a thermosetting polyimide resin, a thermoplastic polyimide resin, a polyamideimide resin, or a polybenzimidazole resin is preferably used from the viewpoint of heat resistance, mechanical properties, and the like. The thickness is set to about 30 to 200 μm, preferably 50 to 125 μm, more preferably about 70 to 100 μm.

  As the release layer to be coated on the surface of the base layer, a fluororesin is used. Here, as the fluororesin, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-perfluoromethyl vinyl ether, particularly from the viewpoint of heat resistance, mechanical properties and the like. A copolymer (MFA), a tetrafluoroethylene-perfluoroethyl vinyl ether copolymer (EFA), a tetrafluoroethylene-hexafluoropropylene copolymer (FEP) and a mixture thereof are preferably used. The thickness is set to about 5 to 100 μm, preferably about 10 to 50 μm.

  In the fixing device 60 of the present embodiment, the seamless tubular body described above is used as an endless belt, and the endless belt 62 has a base layer made of thermosetting polyimide having a circumferential length of 94 mm, a thickness of 70 μm, and a width of 320 mm, and a thickness of 30 μm. A structure in which a release layer made of PFA is laminated is used.

  Here, in the endless belt 62 having an outer diameter of 30 mm according to the present embodiment, the difference in outer diameter between the central portion and both end portions in the width direction is 100 μm or less, more preferably, by comparison between an example and a comparative example described later. It is set to 50 μm or less. Thus, in the endless belt 62 having an outer diameter of 30 mm, the rotational speed of the endless belt 62 driven by the fixing roll 61 is increased by forming the outer diameter difference between the central portion and both ends of the endless belt 62 to be 100 μm or less. The nip portion N can be set at a substantially constant speed in the width direction. Accordingly, it is possible to suppress the non-uniform frictional force from the endless belt 62 in the width direction from acting on the paper P passing through the nip portion N. Therefore, the occurrence of paper wrinkles on the paper P and the occurrence of image defects such as image gloss unevenness are suppressed.

  That is, the sheet P on which the toner image has been electrostatically transferred passes through the nip portion N of the fixing device 60 to fix the toner image on the sheet P. However, the conveyance force when the sheet P passes through the nip portion N is The sheet P is received from the driving-side fixing roll 61 and is conveyed by receiving frictional force from the fixing roll 61 as the fixing roll 61 rotates.

  On the other hand, in a state where the paper P is not conveyed to the nip portion N, the driven endless belt 62 is also rotated by receiving the frictional force from the fixing roll 61, but the paper P is conveyed to the nip portion N, In a state where the paper P is nipped by the nip portion N, the endless belt 62 receives a conveying force from the fixing roll 61 via the paper P. Accordingly, when viewed from the sheet P side, when the sheet P passes through the nip portion N, the sheet P is subjected to the conveying force from the fixing roll 61 and at the same time, the direction opposite to the conveying direction from the endless belt 62 side. The frictional force (reverse conveying force) acts.

  Therefore, if the outer diameter of the endless belt 62 is larger at the center than at both ends in the width direction, the rotational speed of the endless belt 62 at the nip N is slower at both ends than at the center, and the paper P is As it goes to both ends, a larger reverse conveying force is received from the endless belt 62. In that case, the conveyance of the paper P cannot follow the rotation of the fixing roll 61 toward the both ends.

  In particular, the fixing roll 61 is formed in a so-called flare shape in which the outer diameter is increased from the center to both ends, or the pressing force between the peeling nip member 64b and the fixing roll 61 is increased from the center to both ends. By setting, in the nip portion N, the conveyance speed of the paper P is configured to increase toward both ends so that a force in the width direction is always applied to the paper P from the center to both ends. ing. Then, by pulling the paper in the direction of both ends by the force in the width direction, the occurrence of paper wrinkles on the paper P is suppressed. However, when the paper P receives a large sliding resistance from the endless belt 62 toward both ends, such a force in the width direction of the paper P does not act, and the paper P is caused to have paper wrinkles and image gloss unevenness. It will be.

  Specifically, in the endless belt 62 having an outer diameter of 30 mm, when the difference between the outer diameters of both end portions and the central portion exceeds 100 μm, the rotational speed of the endless belt 62 at the nip portion N increases at the central portion in the width direction. The variation in speed, such as slowness at both ends, becomes large, and therefore, a non-uniform frictional force from the endless belt 62 in the width direction acts on the paper P passing through the nip portion N. That is, since the rotational speed of the endless belt 62 is proportional to the outer diameter of the endless belt 62, when (the outer diameter difference between the both ends and the center) / outer diameter (= outer diameter difference ratio) exceeds a predetermined value. The variation in the rotational speed of the endless belt 62 between the central portion and both ends in the width direction becomes large, and a non-uniform frictional force from the endless belt 62 in the width direction acts on the paper P passing through the nip portion N. . In order to suppress the variation in the rotational speed of the endless belt 62 to such an extent that a substantially uniform frictional force acts on the paper P in the width direction, the difference is obtained by comparing the embodiment described later and the comparative example. On the basis of the result, it is necessary to set the outer diameter difference ratio within 100 μm / 30 mm≈0.3%.

  Therefore, in the fixing device 60 of the present embodiment, the outer diameter difference ratio between the center portion and both end portions of the endless belt 62 is formed to be 0.3% or less. As described above, the endless belt 62 formed in this way effectively increases the conveyance speed of the paper P toward both ends, and effectively applies the force in the width direction from the center to both ends of the paper P. It becomes possible to make it. Therefore, the occurrence of paper wrinkles on the paper P and the occurrence of image defects such as image gloss unevenness can be suppressed.

  Next, the pressure pad 64 disposed inside the endless belt 62 is composed of the pre-nip member 64a and the peeling nip member 64b as described above. The prenip member 64a is supported by the holder 65 so as to press the fixing roll 61 with a load of, for example, 35 kgf by a spring or an elastic body. An elastic body such as silicone rubber or fluororubber, a leaf spring, or the like can be used for the prenip member 64 a, and the surface on the fixing roll 61 side is formed with a concave curved surface that substantially follows the outer peripheral surface of the fixing roll 61. In the fixing device 60 of the present embodiment, silicone rubber having a width of 10 mm, a thickness of 5 mm, and a length of 320 mm is used.

  The peeling nip member 64 b is directly supported by the holder 65, and the holder 65 is set at a predetermined position with respect to the fixing roll 61, thereby coming into contact with the fixing roll 61 with a predetermined pressing force. Further, the peeling nip member 64b is formed of a heat-resistant resin such as PPS, polyimide, polyester, or polyamide, or a metal such as iron, aluminum, or SUS. As the shape of the peeling nip member 64b, the outer surface shape in the nip portion N is formed as a convex curved surface having a constant radius of curvature.

  In the fixing device 60 of the present embodiment, the endless belt 62 is wrapped around the fixing roll 61 by the pressure pad 64 (the pre-nip member 64a and the peeling nip member 64b) at a winding angle of about 40 ° and has a width of about 10 mm. A nip portion N is formed.

  Further, a lubricant application member 67 is disposed on the bottom surface of the downstream side belt guide member 63b along the longitudinal direction of the fixing device 60. The lubricant application member 67 is disposed so as to contact the inner peripheral surface of the endless belt 62 and supplies an appropriate amount of lubricant. As a result, the lubricant is supplied to the sliding portion between the endless belt 62 and the low friction sheet 68, and the sliding resistance between the endless belt 62 and the pressure pad 64 via the low friction sheet 68 is further reduced. 62 is smoothly rotated. Further, it has an effect of suppressing wear on the inner peripheral surface of the endless belt 62 and the surface of the low friction sheet 68.

  As the lubricant, a lubricant that has durability against long-term use under a fixing temperature environment and can maintain wettability with the inner peripheral surface of the endless belt 62 is suitable. For example, liquid oil such as silicone oil or fluorine oil, synthetic lubricating oil grease in which a solid substance and a liquid are mixed, or a combination thereof can be used. Silicone oils include dimethyl silicone oil, dimethyl silicone oil with organometallic salt addition, dimethyl silicone oil with hindered amine addition, dimethyl silicone oil with organometallic salt and hindered amine addition, methylphenyl silicone oil, amino-modified silicone oil, amino-modified silicone-added amino-modified silicone. Oil, hindered amine-added amino-modified silicone oil, carboxy-modified silicone oil, silanol-modified silicone oil, sulfonic acid-modified silicone oil, and the like can also be used. Moreover, as fluoro oil, perfluoropolyether oil and modified perfluoropolyether oil can be used. In the fixing device 60 of the present embodiment, amino-modified silicone oil is used.

[Embodiment 2]
In the first embodiment, the fixing device 60 is described in which the endless belt 62 in which the pressure pad 64 is pressed as the pressing unit is used for the fixing roll 61 having the heat source. In the second embodiment, a fixing device using a fixing belt with a heat generation source pressed as a heating unit will be described. In addition, about the structure similar to Embodiment 1, the same code | symbol is used and the detailed description is abbreviate | omitted here.

  FIG. 17 is a side sectional view showing the configuration of the fixing device 90 in the present embodiment. As shown in FIG. 17, in the fixing device 90 of the present embodiment, a seamless tubular body is used as the fixing belt 92, and the fixing belt 92 is disposed on the toner image carrying surface side of the paper P. A ceramic heater 82 which is a resistance heating element as an example of a heat source is disposed inside the fixing belt 92, and heat is supplied from the ceramic heater 82 to the nip portion N.

  The ceramic heater 82 has a substantially flat surface on the pressure roll 91 side. Then, it is arranged in a state of being pressed against the pressure roll 91 via the fixing belt 92 and forms a nip portion N. Therefore, the ceramic heater 82 also functions as a pressure member. The sheet P that has passed through the nip portion N is peeled off from the fixing belt 92 by the change in the curvature of the fixing belt 92 in the exit region (peeling nip portion) of the nip portion N.

  Further, in order to reduce the sliding resistance between the inner peripheral surface of the fixing belt 92 and the ceramic heater 82 between the inner peripheral surface of the fixing belt 92 and the ceramic heater 82, a low friction sheet 68 as an example of a rubbing member. Is arranged. The low friction sheet 68 may be configured separately from the ceramic heater 82 or may be configured integrally with the ceramic heater 82.

  On the other hand, a pressure roll 91 as an example of a rotating member is disposed so as to face the fixing belt 92 and is rotated in the direction of arrow D by a drive motor (not shown), and the fixing belt 92 is driven to rotate by this rotation. Has been. The pressure roll 91 includes a core (cylindrical core) 911, a heat-resistant elastic body layer 912 coated on the outer peripheral surface of the core 911, and a release layer 913 made of a heat-resistant resin coating or a heat-resistant rubber coating. Has been configured.

  The fixing belt 92 is an endless belt whose original shape is formed in a cylindrical shape, and includes a base layer 921 made of a thermosetting polyimide resin, a thermoplastic polyimide resin, a polyamideimide resin, a polybenzimidazole resin, and the like, and the base layer. It is comprised with the release layer 922 which consists of a fluororesin etc. coat | covered on the surface (outer peripheral surface) or both surfaces of the 921 side of the pressure roll 91.

  Here, the fixing belt 92 includes a ceramic heater 82 disposed inside the fixing belt 92, an upstream belt guide member 93 a and a downstream belt guide member 93 b, and belt regulation disposed at both ends of the fixing belt 92. It is rotatably supported by an edge guide member (not shown) as an example of the member. In the fixing device 90 of the present embodiment, since the low friction sheet 68 is configured to cover only the ceramic heater 82, the upstream belt guide member 93 a and the downstream belt guide member 93 b are both included in the fixing belt 92. The fixing belt 92 is supported while directly rubbing against the peripheral surface.

  Then, the sheet P on which the toner image is electrostatically transferred in the image forming apparatus is guided to the nip portion N of the fixing device 90 by the fixing inlet guide 56. When the paper P passes through the nip portion N, the toner image on the paper P is fixed by the pressure acting on the nip portion N and the heat supplied from the ceramic heater 82 on the fixing belt 92 side. Also in the fixing device 90 of the present embodiment, since the nip portion N can be configured widely between the pressure roll 91 and the ceramic heater 82, stable fixing performance can be ensured.

  As an auxiliary means for completely separating the fixed sheet P from the fixing belt 92, a peeling assisting member 70 can be disposed on the downstream side of the nip portion N of the fixing belt 92. The peeling auxiliary member 70 is held by a baffle holder 72 in a state where the peeling baffle 71 is close to the fixing belt 92 in a direction (counter direction) opposite to the rotation direction of the fixing belt 92.

  In the fixing device 90 of the present embodiment, the fixing belt 92 is manufactured by the manufacturing method described in the first embodiment. Thereby, the outer diameter in the width direction of the fixing belt 92 is formed to be substantially uniform. Therefore, the rotation speed of the fixing belt 92 driven by the pressure roll 91 can be set to a substantially constant speed at the nip portion N. As a result, the non-uniform frictional force from the fixing belt 92 in the width direction acts on the paper P passing through the nip portion N, so that an image such as paper wrinkles on the paper P or image gloss unevenness is generated. The occurrence of defects is suppressed. In particular, by using the fixing belt 92 having an outer diameter difference ratio of 0.3% or less manufactured by such a manufacturing method, there is an effect of suppressing generation of paper wrinkles in the paper P and image defects such as image gloss unevenness. Become prominent.

  Further, according to such a manufacturing method, when the fixing belt 92 having a shape in which the circumferential surface roughness Ra of the inner peripheral surface of the fixing belt 92 is smaller than the surface roughness Ra in the inner peripheral surface axial direction is manufactured. Further, the outer diameter difference in the width direction of the fixing belt 92 can be substantially uniform, and the outer diameter difference ratio can be 0.3% or less. For this reason, in the fixing device 90 using the fixing belt 92, the holding ability of the lubricant on the inner peripheral surface of the fixing belt 92 can be improved, so that the load torque during rotation is reduced and at the same time when the fixing belt 92 is rotated. It is possible to suppress the sliding sound to an allowable level.

  In the first and second embodiments, the endless belt used in the fixing devices 60 and 90 has been described. However, the present invention is not limited to such a form. That is, for example, it can be applied to an intermediate transfer belt used in an image forming apparatus. It can also be applied to a photoreceptor belt or a contact charging film.

  At that time, when used as a charged body such as an intermediate transfer belt or a contact charging film, the conductive particles can be dispersed in the endless belt, and the endless belt manufacturing method of the present embodiment is used. When producing an endless belt, it is preferable to add these conductive particles to the polyimide precursor solution.

Examples of the conductive particles include carbon black, carbon beads obtained by granulating carbon black, carbon fibers, carbon-based materials such as graphite, metals or alloys such as copper, silver, and aluminum, tin oxide, indium oxide, antimony oxide, A conductive metal oxide such as SnO ₂ —In ₂ O ₃ composite oxide, a conductive whisker such as potassium titanate, or the like can be used.

  As mentioned above, although the manufacturing method of the endless belt of this invention was demonstrated, this invention is not limited only to these embodiment, In the range which does not deviate from the meaning, it is various based on the knowledge of those skilled in the art. The present invention can be implemented with improvements, changes and modifications.

<Appendix>
(Supplementary note 1) After the cylindrical core body is thinned by swaging, the entire core body is processed to have a substantially uniform outer diameter, and the outer diameter is constant and the wall thickness is increased at both ends. It is a finished core.

  (Appendix 2) A liquid heat-resistant resin composition is applied to the outer surface of a cylindrical core body to form a coating film of the composition by coating with a predetermined film thickness, and then subjected to a heating step to thereby form a heat-resistant resin composition In the manufacturing method of an endless belt having a step of removing the molded heat-resistant resin composition from the core body, the cylindrical core body is formed by thinning the outer diameter at both ends by swaging, and then the entire core body Is a core having a constant outer diameter and a thick wall at both ends.

  (Supplementary note 3) A liquid heat-resistant resin composition is applied to the outer surface of the cylindrical core body with a predetermined film thickness to form a coating film of the composition. In the method of manufacturing an endless belt having a step of removing the molded heat-resistant resin composition from the core, the surface roughness Ra of the outer surface of the cylindrical core is defined by JIS B601-1994. A core having a thickness Ra (arithmetic mean roughness) of 2.5 μm or less is used.

  (Appendix 4) A liquid heat-resistant resin composition is applied to the outer surface of the cylindrical core body to form a coating film of the composition by coating with a predetermined film thickness, and then a heat-resistant resin composition is obtained through a heating step. In the method of manufacturing an endless belt having the step of removing the molded heat-resistant resin composition from the core, the outer surface of the central portion of the cylindrical core has an axial roughness Ra4 rather than a circumferential roughness Ra3. Use a core with a larger surface.

  (Additional remark 5) It is a manufacturing method of the endless belt whose outer peripheral surface of a cylindrical core body is coat | covered with a mold release agent, and the contact angle of water is 70 degrees-115 degrees.

  (Additional remark 6) The said heating process is divided into the drying process which volatilizes a fixed amount of solvent, and the baking process which substantially volatilizes a solvent after that, on the surface of the heat resistant resin composition coating film after the drying process, predetermined | prescribed film thickness It is a manufacturing method of an endless belt further including the heat-resistant release layer application | coating process which apply | coats the heat-resistant release material of this.

  (Additional remark 7) It is a manufacturing method of an endless belt which further includes the rubber layer formation process which forms a heat resistant rubber layer on the surface of the said heat resistant resin composition.

  (Additional remark 8) It is a manufacturing method of an endless belt in which the solution which has an aromatic polyimide precursor as a main component is used as said heat resistant resin composition.

  (Supplementary Note 9) A liquid heat-resistant resin composition is applied to the outer surface of the cylindrical core at a predetermined film thickness to form a coating film of the composition, followed by a heating step, whereby the heat-resistant resin composition It is a seamless belt made of heat resistant resin produced by a production method having a step of removing the molded heat resistant resin composition from the core.

  (Appendix 10) A heat-resistant resin composition is formed by coating a liquid heat-resistant resin composition with a predetermined film thickness on the outer surface of a cylindrical core body to form a coating film of the composition, followed by a heating step. A seamless belt produced by a production method having a step of removing the molded heat-resistant resin composition from the core, and the surface roughness Ra5 in the circumferential direction of the inner circumferential surface of the belt is the surface in the axial direction of the inner circumferential surface. The endless belt is smaller than the roughness Ra6.

  (Additional remark 11) The said heat resistant resin seamless belt is a seamless belt in which the outer diameter difference of the longitudinal direction both ends and the center part was formed to 0.3% or less of the outer diameter.

  (Appendix 12) Charging means for charging the surface of the image carrier, electrostatic latent image forming means for forming an electrostatic latent image corresponding to image information on the charged surface of the image carrier, and on the surface of the image carrier Developing means for developing the formed electrostatic latent image with toner to obtain a toner image; transfer means for transferring the toner image formed on the surface of the image carrier to the surface of the recording medium; and An image forming apparatus including at least a fixing unit configured to fix the transferred toner image. The image carrier, an intermediate transfer belt used in the transfer unit, a paper transport belt, a fixing belt used in the fixing unit, At least one of the pressure belts is an image forming apparatus using the seamless belt or the endless belt described in the claims or the above.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

Example 1
N-methylpyrrolidone solution containing polyimide precursor (trade name: U varnish, Ube Industries, Ltd., solid content concentration 18% by weight, viscosity 5 Pa · s) and silicone leveling agent (trade name: DC3PA) to solid content On the other hand, it was added and mixed well so as to be 200 ppm to obtain a coating solution.

Next, as the cylindrical core body 20 shown in FIG. 3, an aluminum cylinder having an outer diameter of 30 mm and a length of 600 mm is prepared, and after roughening the outer peripheral surface end, a silicone-based mold release agent (trade name) : KS-700, manufactured by Shin-Etsu Chemical Co., Ltd.), and a baking treatment was performed at 300 ° C. for 1 hour to form a release agent layer. Incidentally, 3 mm the core thickness _{T 2} of the cylindrical core body 20, the core thickness _{T 4} was 5 mm.

  The coating was performed by a blade coating method (flow coating method) in which the coating solution was discharged while rotating the cylindrical core in the horizontal direction, and the coating film was metalized with a blade. The rotation speed of the core was 450 rpm, the flow rate of the coating solution was 80 g / min, and the moving speed of the blade was 1500 mm / min.

  After coating, the axial direction of the cylindrical core was horizontal, placed in a drying furnace at 110 ° C., and the coating was dried for 40 minutes while rotating at 18 rpm. Then, the coating film was heated at 350 degreeC for 2 hours, and the polyimide resin film 14 was formed. The heated polyimide resin film 14 was extracted from the cylindrical core body 10 by hand, and both ends 30 mm were cut with a uniform width to obtain an endless belt having a width of 400 mm.

  In the endless belt manufacturing process described above, the belt bulge is evaluated when the cylindrical core 20 used in the present embodiment shown in FIG. 3 is used and when the conventional cylindrical core shown in FIG. 7 is used. And compared. The belt swelling was confirmed by measuring the belt outer diameter in the axial direction at a pitch of 20 mm from one end. The results are shown in Table 1 and FIG. When the conventional cylindrical core body is used, there is a bulge of about 40 μm at the center of the belt, but when the cylindrical core body 20 used in this embodiment is used, the bulge is about 10 μm. The effectiveness of the invention can be confirmed.

なお、全て、単位は「ｍｍ」である。

In all cases, the unit is “mm”.

(Example 2)
Application of a solution containing a polyimide precursor (hereinafter abbreviated as “PI precursor solution”) to the surface of the core was performed as follows using a coating apparatus having the configuration shown in FIG.

  As the PI precursor solution, an N-methylpyrrolidone solution (trade name: U varnish, manufactured by Ube Industries, solid content concentration: 18%, viscosity: about 5 Pa · s) is used as the PI precursor solution. An application tank consisting of a cylindrical container having an inner diameter of 80 mm and a height of 600 mm was filled.

  Further, as the core, a 5000 series aluminum alloy cylinder having an outer diameter of 34 mm, a length of 500 mm, and a thickness of 3 mm was used. As described above, the diameter of the cylinder was reduced to 30.6 mm by swaging. Then, after heat annealing once, the surface is cut until the entire outer surface of the core body has an outer diameter of 30 mm, and the surface roughness Ra of the core body (an example of the cylindrical core body 40 shown in FIG. 8) is In addition, an axial direction of 2.4 μm and a circumferential direction of 0.4 μm were prepared. Further, a silicone mold release agent (trade name: KS700, manufactured by Shin-Etsu Chemical Co., Ltd.) was applied to the surface and baked at 330 ° C. for 1 hour.

  On the other hand, an annular body 105 shown in FIG. 11 is made of Teflon (registered trademark) having an outer diameter of 40 mm and a triangular cross section inside a stainless steel hollow ring having an outer diameter of 65 mm, an inner diameter of 40 mm, and a height of 30 mm. A ring was used. The minimum hole diameter of this Teflon (registered trademark) ring was 31.3 mm.

  Next, after the annular body 105 was floated on the coating solution, the annular body 105 was fixed so as not to move, and the core was axially perpendicularly inserted into the hole of the annular body at a speed of 500 mm / min and immersed. . Next, the fixing of the annular body was released, and the core body was pulled up at a speed of 150 mm / min. During the pulling, the annular body did not contact the core body, and a PI precursor coating film having a wet film thickness of about 650 μm was formed on the surface of the core body.

  Subsequently, the core body on which the PI precursor coating film was formed was placed in a drying furnace. The set temperature was initially 30 ° C., and the temperature was gradually increased so as to reach 120 ° C. after 1 hour. Thereafter, a PFA dispersion water-based paint (trade name: AD-2CR, manufactured by Daikin Industries, Ltd.) is dip-coated on the surface of the PI precursor coating film formed on the surface of the core after the drying treatment cooled to room temperature. did.

  That is, the core body on which the PI precursor coating film after drying was formed was immersed in a dispersion water-based paint with its longitudinal direction vertical, and then pulled up at a speed of 300 mm / min. A PFA coating film having a thickness of 20 μm was formed on the film surface.

  Subsequently, after drying at room temperature for 5 minutes, water was removed from the PFA coating film by heating and drying at 60 ° C. for 10 minutes. Then, it heated at 380 degreeC for 30 minute (s), and while forming the PI resin film, the PFA coating film was baked. After cooling to room temperature, the PI resin film is peeled off from the surface of the core, so that there is no swelling (the difference in the outer diameter was 31 μm with respect to the total length of the belt of 450 mm excluding both ends). An endless belt (an electrophotographic fixing endless belt) of Example 2 in which a PFA layer having a film thickness of 20 μm was formed on the outer peripheral surface of the resin layer could be obtained. Adhesion between the PI resin layer and the PFA layer of this endless belt was sufficient. Further, since the release agent was previously applied to the surface of the core body, the inner peripheral surface of the endless belt did not adhere to the core body at the time of peeling.

(Example 3)
As the core, an aluminum cylinder having an outer diameter of 34 mm, a length of 500 mm, and a thickness of 3 mm was used. As described above, this cylinder was reduced in diameter by swaging so that both ends were 30.6 mm, and then heated and annealed once. After the treatment, the surface is cut until the entire outer surface of the core body has an outer diameter of 30 mm, and this surface is disposed in the circumferential direction at both ends of the core body (an example of the cylindrical core body 40 shown in FIG. 8). The PI film thickness was 70 μm and PFA was the same as in Example 1 except that the surface roughness Ra in the axial direction was 1.0 μm and the surface roughness Ra in the circumferential direction was 0.2 μm by cutting. The endless belt of Example 3 was obtained with a uniform film thickness of 20 μm and no blistering defect (the difference in outer diameter was 21 μm with respect to the total belt length of 450 mm excluding both ends).

Example 4
As the core body, an aluminum cylinder having an outer diameter of 30.6 mm, an inner diameter of 28 mm, and a length of 500 mm is fitted with a cylindrical body having a thickness of 2 mm and a width of 60 mm by press-fitting to the inner diameter (the cylindrical shape shown in FIG. 4). Core body 30) By cutting this surface in the circumferential direction, the outer diameter is 30.0 mm, the axial surface roughness Ra is 0.4 μm, and the circumferential surface roughness Ra is 0.15 μm. Further, cutting is performed by moving the cutting tool in the axial direction at both end portions 60 mm on the core surface, and forming cutting grooves in the circumferential direction so that the circumferential roughness Ra is 1 μm and the axial roughness is Ra 0.1 μm. Except for the above, in the same manner as in Example 1, the PI film thickness was 70 μm, the PFA film thickness was 20 μm, uniform, and no blistering defect (the difference in the outer diameter with respect to the total belt length of 450 mm excluding both ends). The endless bell of Example 4 It was obtained.

(Example 5)
A coating film was prepared in the same manner as in Example 1 except that the surface roughness Ra in the axial direction was 0.03 μm and the surface roughness Ra in the circumferential direction was 0.005 μm by burnishing the surface of the core body. . The endless belt of Example 4 could be obtained with a uniform belt film thickness of 70 μm and no bulging defect (the difference in outer diameter was 22 μm with respect to the belt total length of 450 mm excluding both ends). . Further, since the release agent was previously applied to the surface of the core body, the inner peripheral surface of the endless belt did not adhere to the core body at the time of peeling.

(Example 6)
In the manufacturing process of the endless belt shown in Example 3, a PFA dispersion water-based paint (trade name: AD-2CR, on the surface of the PI precursor coating film formed on the core surface after the drying treatment cooled to room temperature. Daikin Industries, Ltd.) was applied by dip coating.

  That is, the core body on which the PI precursor coating film after drying is formed is dipped in a dispersion water-based paint with its longitudinal direction vertical, and then pulled up at a speed of 400 mm / min. A PFA coating film having a thickness of 28 μm was formed on the film surface.

  Subsequently, after drying at room temperature for 5 minutes, water was removed from the PFA coating film by heating and drying at 60 ° C. for 10 minutes. Then, it heated at 380 degreeC for 30 minute (s), and while forming the PI resin film, the PFA coating film was baked. After cooling to room temperature, the PI resin film is peeled off from the surface of the core, so that there is no swelling (the difference in the outer diameter was 28 μm compared to the total length of the belt of 450 mm excluding both ends). An endless belt (an electrophotographic fixing endless belt) of Example 5 in which a 29 μm thick PFA layer was formed on the outer peripheral surface of the resin layer could be obtained. Adhesion between the PI resin layer and the PFA layer of this endless belt was sufficient.

(Example 7)
In the production process of the endless belt shown in Example 3, the surface of the PI precursor coating film formed on the surface of the core after the drying process cooled to room temperature was coated with silicone rubber DY35-3030 (Toray Dow Corning Silicone Co., Ltd.) was applied by a blade coating method to a coating thickness of 100 μm, and then FEP dispersion aqueous paint (trade name: NEOFLON FEP, manufactured by Daikin Industries, Ltd.) was applied by dip coating.

  That is, the PI precursor coating film after drying and the core body on which the silicone rubber resin is formed on the outer surface are immersed in the dispersion water-based paint with the longitudinal direction vertical, and then 300 mm / min. The PFA coating film having a film thickness of 20 μm was formed on the surface of the PI precursor coating film by pulling up at a speed.

  Subsequently, after drying at room temperature for 5 minutes, water was removed from the FEP coating film by heating and drying at 60 ° C. for 10 minutes. Then, it heated at 380 degreeC for 30 minutes, and while forming the PI resin film, the FEP coating film was baked. After cooling to room temperature, the PI resin film is peeled off from the surface of the core, so that there is no swelling (the difference in the outer diameter was 31 μm with respect to the total length of the belt of 450 mm excluding both ends). It was possible to obtain an endless belt (fixing endless belt for electrophotography) of Example 6 in which a silicone rubber layer having a thickness of 70 μm was formed on the outer peripheral surface of the resin layer and an FEP layer having a thickness of 20 μm was formed thereon. Adhesion between the PI resin layer of the endless belt and each of the silicone rubber layer and the FEP layer was sufficient.

(Comparative Example 1)
In the process of manufacturing an endless belt shown in Example 2, a comparative example was made in the same manner as in Example 2 except that a core having a uniform thickness of 1 mm in the longitudinal direction and an outer diameter of 30 mm and a length of 500 mm was used as the core. 1 endless belt was obtained. As a result, a uniform belt with a PI film thickness of 70 μm and a PFA film thickness of 20 μm was obtained, but a belt with a central portion swelled with a difference in outer diameter of 105 μm was obtained with respect to a belt total length of 450 mm excluding both ends. .

  Moreover, when this mold was repeatedly used, the end portion was damaged, and the process stopped in the coating / drying process.

(Comparative Example 2)
In the process of manufacturing the endless belt shown in Example 2, the entire outer surface of the core body as a core body is burnished to have an axial surface roughness Ra of 0.03 μm and a circumferential surface roughness Ra of 0. 0.005 μm, except that the PFA dispersion water-based paint (trade name: AD-) was applied to the surface of the PI precursor coating film formed on the surface of the core after the drying treatment cooled to room temperature in the same manner as in Comparative Example 1. 2CR, manufactured by Daikin Industries, Ltd.) was applied by dip coating.

  That is, the core body on which the PI precursor coating film after drying was formed was immersed in a dispersion water-based paint with its longitudinal direction vertical, and then pulled up at a speed of 300 mm / min. A PFA coating film having a thickness of 20 μm was formed on the film surface.

  Subsequently, after drying at room temperature for 5 minutes, water was removed from the PFA coating film by heating and drying at 60 ° C. for 10 minutes. Then, it heated at 380 degreeC for 30 minute (s), and while forming the PI resin film, the PFA coating film was baked. After cooling to room temperature, the endless belt of Comparative Example 2 (for electrophotography) in which a PFA layer having a thickness of 20 μm was formed on the outer peripheral surface of a PI resin layer having a thickness of 70 μm by peeling the PI resin film from the surface of the core body A fixing endless belt) was obtained, but a belt having a bulged central portion having a difference in outer diameter of 112 μm with respect to a belt total length of 450 mm excluding both ends was obtained. The adhesion between the PI resin layer and the PFA layer of this endless belt was sufficient.

  Next, the endless belt 62 is cut to 344 mm, and the fixing device 60 shown in FIG. 15 is installed in an electrophotographic copying machine (Fuji Xerox Co., Ltd .: Docu Center Color 400). The supported paper P (manufactured by Fuji Xerox Co., Ltd .: P paper A3 size) was passed through to evaluate the occurrence rate of paper wrinkles, image gloss unevenness, and image defects. The results are also shown in Table 2.

  As shown in Table 2, when the endless belt 62 of Examples 2 to 7 is used, the paper wrinkle generation rate is 0%, whereas the endless belt 62 of Comparative Example 1 is used. Was 25%, and the occurrence rate in Comparative Example 2 was 33%.

  Further, when the endless belt 62 of Examples 2 to 7 was used, the gloss unevenness of the image did not occur, whereas when the endless belt 62 of Comparative Example 1 and Comparative Example 2 was used. The gloss unevenness corresponding to the swollen portion of the endless belt 62 occurred.

  As described above, in the endless belt 62 having the outer diameter of 30 mm as in Comparative Example 1 and Comparative Example 2, when the difference in the outer diameter between the both end portions and the central portion exceeds 100 μm, the rotation of the endless belt 62 at the nip portion N is performed. The variation in speed is such that the moving speed is fast at the center in the width direction and slow at both ends. For this reason, the sheet P passing through the nip portion N is not widened from the endless belt 62 in the width direction. Uniform frictional force acts. Therefore, in order to set the rotational speed of the endless belt 62 at a substantially constant speed in the width direction, in the endless belt 62 having an outer diameter of 30 mm, the both end portions and the central portion as in the first to sixth embodiments are arranged. It is necessary to set the outer diameter difference to 100 μm or less, that is, to set the outer diameter difference ratio within 100 μm / 30 mm≈0.3%.

  Then, the endless belt 62 formed in this way can increase the conveyance speed of the paper P toward both ends, and can effectively apply a force in the width direction from the center to both ends on the paper P. It becomes possible. Therefore, the occurrence of paper wrinkles on the paper P and the occurrence of image defects such as image gloss unevenness can be suppressed.

  As described above, according to the manufacturing method of the endless belt (endless belt 62) of the present embodiment, at least the liquid heat resistant resin composition is applied to the outer surface of the cylindrical core body with a predetermined film thickness. In the method of manufacturing an endless belt, the method includes forming a coating film of the composition, then forming a heat-resistant resin composition by passing through a heating step, and removing the molded heat-resistant resin composition from the core. Use a core having a larger heat capacity per unit width than the central part in the axial direction, or thicker at both ends than the central part. By using the core body, the endless belt can be prevented from being swollen, and the outer diameter difference in the longitudinal direction of the endless belt can be formed substantially uniformly, thereby suppressing the yield reduction of the belt. Things are possible .

  Further, by using the endless belt manufactured by the manufacturing method of the present embodiment as the endless belt 62 in the fixing device 60, the rotational speed of the endless belt 62 driven by the fixing roll 61 is changed in the width direction at the nip portion N. Can be set at substantially constant speed. As a result, non-uniform frictional force across the width direction from the endless belt 62 is suppressed from acting on the paper P passing through the nip portion N. Therefore, the generation of paper wrinkles on the paper P, image gloss unevenness, and the like The occurrence of defects is suppressed.

  In particular, by using the endless belt 62 having an outer diameter difference ratio of 0.3% or less manufactured by the manufacturing method of the present embodiment, generation of paper wrinkles in the paper P and occurrence of image defects such as image gloss unevenness. The suppressing effect becomes remarkable.

  Further, according to the manufacturing method of the endless belt of the present embodiment, the endless belt having a shape in which the circumferential surface roughness Ra of the inner circumferential surface of the endless belt 62 is smaller than the surface roughness Ra in the inner circumferential surface axial direction. Also when manufacturing 62, the outer diameter difference in the width direction of the endless belt 62 is substantially uniform, and the outer diameter difference ratio can be formed to be 0.3% or less. Therefore, in the fixing device 60 using the endless belt 62, the ability of retaining the lubricant on the inner peripheral surface of the endless belt 62 can be improved, so that the load torque during rotation is reduced and at the same time the endless belt 62 is rotated. It is possible to suppress the sliding sound to an allowable level.

  As an application example of the present invention, there is application to an image forming apparatus such as a copying machine or a printer using an electrophotographic system.

It is a schematic perspective view explaining the structure of the cylindrical core used for this invention, and the polyimide resin film apply | coated and formed on the outer peripheral surface. It is a schematic sectional drawing along the longitudinal direction explaining the structure of an example of the cylindrical core body of this invention. It is a schematic sectional drawing along the longitudinal direction explaining the structure of another example of the cylindrical core of this invention. It is a schematic sectional drawing along the longitudinal direction explaining the structure of another example of the cylindrical core of this invention. It is a figure explaining mounting | wearing of the cylindrical core body shown in FIG. 4, and the attachment member attached to the inside. It is the contrast graph which plotted each outer diameter of the endless belt manufactured using the cylindrical core used for the present Example, and the endless belt manufactured using the conventional cylindrical core. The end of the conventional cylindrical core and the end of the polyimide resin film adhere to each other during the heat treatment, and part of the gas stays between the vicinity of the center of the cylindrical core and the center of the polyimide resin film. FIG. It is a schematic sectional drawing along the longitudinal direction explaining the structure of another example of the cylindrical core of this invention. It is process drawing explaining an example of the manufacturing process of the cylindrical core shown in FIG. It is a schematic diagram which shows the example of the cutting process formed in the circumferential direction of the core surface. It is a schematic block diagram which shows an example of the apparatus used for the dip coating method which controls a film thickness with an annular body. It is a principal part expansion perspective view for demonstrating the installation state of an annular body. It is the figure which showed the shape of the wall surface of the hole provided in an annular body. It is a schematic block diagram which shows an example of the apparatus used for a blade application | coating method. 2 is a side cross-sectional view illustrating a configuration of a fixing device according to Embodiment 1. FIG. It is sectional drawing of the edge part of the fixing device explaining the state by which the endless belt was supported. FIG. 4 is a side sectional view illustrating a configuration of a fixing device according to a second embodiment.

Explanation of symbols

10, 20, 30, 40, 50 Cylindrical core, 14, 24, 34, 54 Polyimide resin film, 56 high pressure gas, L ₁ , L ₂ length, T ₁ , T ₂ , T ₃ core thickness.

Claims (3)

  A cylindrical core for producing an endless belt by applying a resin solution to the surface, wherein the cylindrical core has a thickness that is thinner in the axial center than in the axial end. A cylindrical core body.   A cylindrical core for producing an endless belt by applying a resin solution on a surface thereof, wherein the heat capacity at both ends is larger than that at an axially central portion. A mold release agent layer forming step for forming a release agent layer on the outer peripheral surface of the cylindrical core, and a resin solution is applied to the outer peripheral surface of the cylindrical core after the release agent layer forming step. A film forming process for forming a film, a film forming process for forming a film by drying and heating and firing the coating film, and a peeling / extracting process for separating the film from the outer peripheral surface and extracting it from the cylindrical core. In an endless belt manufacturing method comprising:
A method for producing an endless belt, wherein the cylindrical core body according to claim 1 or 2 is used for the cylindrical core body.

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