JP2002014560A - Polyimide tubular object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyimide tubular object which can sufficiently prevent the generation of wrinkles of a sheet to be transferred, such as transfer paper. SOLUTION: This polyimide tubular object contains a polyimide resin and is molded to a tubular form and is respectively formed with large-diameter straight parts of the maximum outer diameter and approximately uniform in the outer diameter in an axial direction on both end sides in the axial direction. The lengths in the axial direction of the large-diameter straight parts are respectively >=0.03 to <=0.3 L with respect to the length L over the entire part of the tubular object. Even more, the smallest-diameter part is formed in the central part in the axial direction and tapered parts continuously reduced in the diameter toward the smallest-diameter part are respectively formed between the smallest-diameter part and the large-diameter straight parts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyimide tubular article used for an electrophotographic copying machine or a laser beam printer.

[0002]

2. Description of the Related Art Polyimide resin has excellent mechanical properties,
It has heat resistance and chemical properties.Conventionally, polyimide tubular products in which a polyimide resin is formed into a tubular shape are often used as intermediate transfer belts for toner images such as electrophotographic copiers and laser beam printers, and heat fixing belts. Used in industrial fields. Here, these polyimide tubular articles will be described by taking as an example those used as heat fixing members such as copying machines and laser beam printers.

Conventionally, a color laser printer or a color copying machine using an electrophotographic technique has a heating roller system, that is, a heating mechanism as a device for fixing a toner image formed on copy paper or transfer paper. Commonly used is to fuse the toner image on the copy paper by heating and melting the toner while sequentially feeding the copy paper on which the toner image is formed between the fixing roller and the pressure roller pressed against it. It had been.

In recent years, an apparatus using a tubular member made of polyimide has been widely used in place of the heat fixing roller. As a fixing mechanism of this apparatus, for example, a drive roll, a tension roll, and a heater are provided inside a thin-film polyimide tubular article, a backup roll is provided outside, and a toner is interposed between the polyimide tubular article and the backup roll via a heater. Supply the copy paper on which the image was formed,
A mechanism for sequentially fixing toner images is employed. Also, using a tubular material having a relatively small outer diameter, a ceramic heater and a tubular material support are inserted inside the tubular material, the ceramic heater surface is pressed with a pressure roller through the tubular material, and the toner is contacted with the narrow contact surface. The copy paper on which the image was formed is sent sequentially,
A mechanism for heat fixing is also employed.

Conventionally, a polyimide tubular article used in this fixing device has a substantially constant outer diameter and circumference at a central portion, an end portion, and an arbitrary position in an axial direction. As a result, there is a problem that wrinkles are likely to occur on the copy paper when passing through the heating section of the fixing device. The occurrence of the wrinkles often occurs when the peripheral speed of the polyimide tubular article traveling between the drive roll and the backup roll is slightly different depending on different places in the axial direction, and therefore, it travels in contact with the tubular article. This is probably because the passing speed of the copy paper differs depending on the location. Also, wrinkles are likely to occur on the copy paper due to the influence of the moisture of the copy paper, the pressure of the pressure roll, the difference in the nip width between the pressure roll and the tubular member, and the like. The occurrence of wrinkles on this copy paper
In particular, with the speeding up of the fixing device and the spread of the double-sided printing device, it has become a major problem.

To solve such a problem, Japanese Patent Publication No. 7-216
Japanese Patent Publication No. 80 proposes a method for preventing the occurrence of wrinkles on copy paper as described above. In this method, a tubular material (endless film) having a circumferential length that increases from one point other than the end in the axial direction toward the end (that is, a tapered flared shape) is used as the tubular material (endless film), and the tubular material is pressed tightly to the tubular material. The moving speed of the copy paper is greater at the end than at the center, so that both ends of the copy paper are stretched, and the generation of wrinkles on the copy paper is suppressed.

[0007]

However, the present inventors have conducted tests on a polyimide tubular article having the shape proposed in Japanese Patent Publication No. Hei 7-21680.
It has been found that wrinkling of the copy paper cannot be sufficiently prevented by using such a tubular material.

[0008] The reason for this is not completely clear,
In the case of a tubular article having the above shape, the moving speed of the copy paper is certainly higher at both ends than at the center, but one of the reasons is that it is difficult to make the moving speeds of both ends completely the same. Guessed.

Further, such a problem may occur in a sheet to be conveyed such as copying paper, even when a polyimide tubular article is used as a heat fixing member of a copying machine or a laser printer as described above. Conceivable.

It is an object of the present invention, in view of the above-mentioned conventional problems, to provide a polyimide tubular article which can sufficiently prevent wrinkles of a conveyed sheet such as copy paper.

[0011]

Means for Solving the Problems The inventors of the present invention have studied to solve the above problems, and as a result, by using a polyimide tubular article having a specific shape, the generation of wrinkles on a sheet to be conveyed is sufficiently reduced. And found that the present invention was completed.

That is, the present invention relates to a polyimide tubular article which contains a polyimide resin and is formed into a tubular shape, and has a maximum outer diameter and a substantially constant outer diameter in the axial direction at both ends in the axial direction. The large-diameter straight portions are respectively formed, and the axial length of the large-diameter straight portion is set to 0.03 L or more and 0.3 L or less with respect to the entire length L of the tubular object. A minimum diameter portion is formed at the central portion in the axial direction, and between the minimum diameter portion and the large-diameter straight portion, tapered portions that continuously reduce in diameter toward the minimum diameter portion are formed. The present invention relates to a polyimide tubular article characterized by the following (claim 1).

In the polyimide tubular article of the present invention, the large diameter straight portions at both ends have the same outer diameter, that is, the same outer diameter over a predetermined length in the axial direction (hereinafter sometimes referred to as L1 and L2, respectively). Because of the perimeter, when a copy paper or the like is tightly pressure-fed using this tubular material, it is easy to ensure the same and stable movement speed of both ends, and the length of each of L1 and L2 is 0.03L (0.03 × L) or more and 0.3L (0.3 × L)
L) Since it is the following, the generation of wrinkles on copy paper or the like can be sufficiently prevented. That is, when the lengths of L1 and L2 are less than 0.03L, it is difficult to stably maintain the moving speed at both ends of the conveyed sheet such as copy paper, and it is possible to sufficiently suppress the generation of wrinkles. Can not. If this length exceeds 0.3 L, it is difficult to always make the moving speed of both ends greater than the central part, especially the minimum diameter part having the smallest outer diameter, and it is not possible to sufficiently prevent the occurrence of wrinkles. .

In addition, since tapered portions are formed between the large-diameter straight portion and the minimum-diameter portion so as to continuously decrease in diameter toward the minimum-diameter portion, the occurrence of wrinkles on the conveyed sheet can be more sufficiently prevented. can do. The effect is considered to be due to the fact that in the tapered portion, the moving speed continuously increases as moving away from the minimum diameter portion, and a rapid change in speed is prevented. In other words, the large-diameter straight portions on both end sides receive a driving force smoothly by a pressure roll or the like which is in pressure contact with the outside and transmitting the drive, thereby stabilizing the moving speed of the copy paper or the like. Thus, the driving force transmitted to the minimum diameter portion having a small outer diameter is smaller than that of the large diameter straight portion. As a result, in the tapered portion, a sudden change in the driving force generated at the step portion (the portion where the surface forms an angle of 90 degrees and is recessed toward the shaft center and the diameter reduction is discontinuous) occurs. It is considered that since the driving force is prevented from changing and the driving force changes continuously, the speed change that can occur due to the difference in the driving force also becomes continuous, and the transported sheet can move smoothly.

In the present invention, the central portion is intended to mean the central point in the axial direction between the two large-diameter straight portions and the vicinity thereof. Is also included.

In the present invention, it is preferable that the large-diameter straight portion has a uniform thickness. The large-diameter straight portion has an outer diameter that is substantially constant over a predetermined length in the axial direction, so that it is easy to produce a uniform thickness, and by adopting such a configuration, the tubular material itself can be used for a long time. It has excellent mechanical strength to withstand. That is, when the thickness of the tubular material used in the fixing device or the like is not uniform, the tubular material is likely to be damaged from the end by being used for a long period of time. Since the thickness is uniform, it is difficult to break from the end.

Further, in the present invention, the tapered portion is formed in the entire region between the large-diameter straight portion and the minimum-diameter portion so as to continuously reduce the diameter from the large-diameter straight portion to the minimum-diameter portion. What is obtained is preferable. By adopting such a configuration, like a tubular article having a stepped portion, there is no concentration of stress on the driving force generated in the stepped portion,
The risk of breakage such as tearing of the tube itself is also reduced.

In the polyimide tubular article of the present invention, the difference in outer diameter between the large-diameter straight portion and the minimum-diameter portion is preferably 10 μm or more and 70 μm or less, more preferably 20 μm or less.
It is more preferable that the thickness be at least 50 μm. Within such a range, there is almost no risk of the tubular article itself being torn, and the generation of wrinkles on the conveyed sheet can be more sufficiently prevented. On the other hand, when the outer diameter difference is less than 10 μm, it is difficult to stably move the conveyed sheet at both end portions to be sufficiently larger than the minimum diameter portion at the center portion. In the case of a polyimide tubular article exceeding 70 μm, there is a problem that the tubular article itself is easily torn because the peripheral speed difference between the end portion and the minimum diameter portion is too large.

In the polyimide tubular article of the present invention, it is preferable that the minimum diameter part is formed as a small diameter straight part whose outer diameter is substantially constant in the axial direction. The generation of wrinkles on the conveyed sheet is likely to occur particularly when thin copy paper (thin paper) or the like is used. However, according to the above configuration, the use of such a conveyed sheet having a small thickness is particularly difficult. It is effective and can sufficiently prevent the generation of wrinkles even for a transported sheet having a very small thickness. In such a configuration, it is more effective if the length of the small diameter straight portion is 0.03 L or more and 0.3 L or less with respect to the length L of the entire tubular object.

In the polyimide tubular article of the present invention,
It is preferable that the outer surface be covered with a fluororesin layer via a conductive primer layer, and that the conductive primer layer be exposed at least partially, particularly at one end. According to such a configuration, the surface of the polyimide layer (the outer surface of the tubular article main body) is covered with the conductive primer layer, and the surface of the polyimide layer is covered with the fluorine-based resin layer in a partially exposed state. From the portion (exposed portion of the primer layer), the charge charged to the tubular article can be discharged. Further, since the outer surface is covered with the fluorine-based resin layer, it is possible to prevent the molten toner from sticking to the tubular material when fixing the toner. That is, the releasability of the toner is good. Furthermore, it is possible to prevent a situation in which the adhesiveness of the surface is suppressed and the sheet to be conveyed adheres to the surface of the polyimide tubular material more than necessary and the sheet to be conveyed cannot be smoothly conveyed. In the case of a tubular article having such a three-layer structure, the outer diameter of the polyimide tubular article of the present invention means the outer diameter of the outermost layer.

Here, as the conductive primer layer, for example, a mixture of a powder having excellent conductivity such as carbon black, gold powder, and silver powder mixed with a primer for fluororesin can be used. The fluorine-based resin layer is a layer made of a fluorine-based resin, and examples of the fluorine-based resin include polytetrafluoroethylene (PTFE) and tetrafluoroethylene-perfluoroalkylvinyl ether resin (PF).
A) and a fluororesin such as a tetrafluoroethylene-hexafluoropropylene resin (FEP) can be used.

The polyimide tubular article of the present invention usually has an overall length of 50 to 500 mm and an overall thickness of 30 to 1 mm.
It is manufactured so as to have a diameter of 50 μm and an average outer diameter of 10 to 100 mm.

The polyimide tubular article of the present invention can be produced using a polyimide precursor solution. The polyimide precursor solution can be obtained, for example, by reacting an aromatic tetracarboxylic dianhydride with an aromatic diamine component in an organic polar solvent. Representative examples of such aromatic tetracarboxylic anhydrides include pyromellitic dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 3,3', 4,4 ' -Benzophenone tetracarboxylic dianhydride, a tetracarboxylic acid ester thereof, or a mixture of the above tetracarboxylic acids. On the other hand, there is no particular limitation on the aromatic diamine component, and paraphenylenediamine, metaphenylenediamine, 4,4′-diaminodiphenyl ether, 4,4 ′
-Diaminodiphenylmethane and the like. Examples of the organic polar solvent include dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone, phenols and the like. These organic polar solvents may be used by mixing hydrocarbons such as xylene, hexane, and toluene.

The polyimide tubular article of the present invention can be produced from the above polyimide precursor solution, for example, as follows. First, a cylindrical mold is prepared. An outer surface of this mold is processed into a shape required for forming a tubular article having a difference in outer diameter as described above. Further, it is preferable to cover the surface of the cylindrical mold with an inorganic coating layer in order to facilitate the separation of the polyimide product from the mold as the final product.

Next, after a polyimide precursor solution is applied to the outer surface of the mold, the solution is placed in a heating furnace and subjected to heat drying treatment, and is converted to imide by an intramolecular condensation reaction of polyamic acid. After the heat treatment at the specified temperature and time,
The mold is removed from the heating furnace, and after cooling, the polyimide tube is removed from the mold. The tubular article having a conductive primer layer and a fluorine-based resin layer is produced by coating the surface of the above-mentioned polyimide tubular article with a primer layer and a fluorine-based resin layer by a conventional method.

Further, it can be produced, for example, by the following method. That is, after applying a polyimide precursor solution to the outer surface of a cylindrical mold having a uniform outer diameter, a heat treatment is performed at a relatively low temperature to obtain a polyimide (polyimide intermediate) in which the imide conversion reaction has not sufficiently progressed. A columnar tubular article is formed. Cutting dies having different outer diameters in the axial direction as described above are inserted into the polyimide intermediate, and heated at a high temperature to complete the imidization reaction. By this second-stage heat treatment, the polyimide intermediate shrinks along the outer diameter of the inserted mold, and a polyimide tubular article having the shape of the present invention can be manufactured.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described more specifically with reference to the drawings.

FIGS. 1 (a), 1 (b) and 1 (c) are schematic views showing embodiments of a polyimide tubular article according to the present invention. The polyimide tubular article shown in FIG. 1A has a large-diameter straight portion 2 having a maximum outer diameter and a substantially constant outer diameter formed in the axial direction at both ends. That is, between the both ends in the axial direction of the large-diameter straight portion 2, that is, A, B
The outer diameters of the two large-diameter straight portions 2 are substantially constant, that is, they are formed to have the same diameter.

From the edges B and D on the center point C side of the large-diameter straight portion 2, the outer diameter continuously decreases from the edges B and D and becomes a minimum value at the center point C. That is, between the large diameter straight portion 2 and the center point C, a tapered portion 4 that continuously reduces in diameter is formed in the entire area.
Is formed as a minimum diameter portion.

The large-diameter straight portion 2 has lengths L1 and L2 in the axial direction, respectively, and L1 and L2 are each 0.03 L to the total length L of the tubular body.
It is necessary that the length is not less than 0.3 L and preferably not less than 0.1 L and less than 0.2 L. In addition, this L1
Preferably, L2 and L2 have the same length, that is, both large-diameter straight portions 2 have the same length, but may have different lengths as long as the effects of the present invention are not impaired.

The polyimide tubular article according to the present invention is not limited to the embodiment shown in FIG. 1 (a), and can be appropriately designed and changed. For example, as shown in FIG.
It is also possible to adopt a form in which the outer diameter of the polyimide tubular material continuously decreases in a curve from the edges B and D of the large diameter straight portion 2 toward the minimum diameter portion C.

Further, as shown in FIG. 1 (c), the outer diameter of the polyimide tubular article continuously increases from the edges B and D of the large-diameter straight portion toward the edges C1 and C2 of the minimum-diameter portion, respectively. It is also possible to adopt a mode in which the outer diameter between C1 and C2 is substantially equal, that is, a mode in which the small-diameter straight section 3 in which the outer diameter of the minimum diameter section is substantially constant in the axial direction is formed. According to the polyimide tubular article having the forms shown in FIGS. 1A, 1B, and 1C, it is possible to sufficiently prevent the occurrence of wrinkles such as copy paper.

[0033]

Hereinafter, embodiments of the present invention will be described.
The present invention is not limited to these examples.

Example 1 An aluminum cylindrical mold having an outer diameter of 30 mm and a length of 500 mm was prepared. The outer diameter of this mold was cut so that a tubular article having the form shown in FIG. 1A could be formed. That is, starting from a position 130 mm from both ends of the mold, the cutting was performed so that the cutting depth was linearly increased toward the center point in the axial direction, and the center point was cut so as to have a depth of 40 μm. .
Next, the surface of the mold was polished to a surface roughness Rzl μm. The surface of this mold was coated with a silicon oxide-based coating agent, heated and baked, and covered with silicon oxide.

On the other hand, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and paraphenylenediamine are converted to N
By reacting in a -methyl-2-pyrrolidone solvent, a polyimide precursor solution having a solid content concentration of 17% by weight and a viscosity of 1500 poise was prepared. The mold was immersed in the polyimide precursor solution to a length of 430 mm and pulled up. Thereafter, a ring-shaped outer mold having an inner diameter of 41 mm was dropped from the uppermost part of the mold by its own weight and externally fitted. Then, a film of a polyimide precursor solution having a thickness of about 500 μm was formed on the outer surface of the mold. Next, the cylindrical mold was placed in a high-temperature constant temperature bath, and was heated at 120 ° C. for 1 hour for 200 hours.
The mixture was heated at 1 ° C. for 1 hour to remove the solvent and allow the imide conversion to proceed. Then, at 250 ° C. for 1 hour, 400 ° C.
For 1 hour to complete the imide conversion reaction. After cooling, it was separated from the cylindrical mold to obtain a polyimide tube having an average film thickness of 50 μm. From both ends of this tubular material, it was cut at a position of 100 mm, and both ends were cut off to obtain a 300 mm long polyimide tubular material. As a result of measuring the outer diameter of the tubular object, 30 mm from both ends toward the center point.
The outer diameter of the large diameter straight portion up to the position (0.1 times the total length of 300 mm) is 30.10 mm, the outer diameter gradually decreases from this position toward the center point, and the minimum diameter at the center point. And its outer diameter was 30.06 mm. That is, the difference between the maximum value (outside diameter of the large-diameter straight portion) and the minimum value (outside diameter of the minimum diameter portion) of the outer diameter of the tubular object is 40 μm, and the outer diameter of the used mold is faithfully reflected. It was of the form that was.

Example 2 An aluminum cylindrical mold having an outer diameter of 24 mm and a length of 500 mm was prepared. The outer diameter of this mold was cut so that a tubular article having the form shown in FIG. 1A could be formed. That is, starting from a position 120 mm from both ends of the mold, the cutting was performed so that the cutting depth was increased linearly toward the center point in the axial direction, and the center point was cut so as to have a depth of 30 μm. .
Next, the surface of the mold was processed in the same manner as in Example 1.

The above mold was immersed in the same polyimide precursor solution as in Example 1 to a length of 430 mm and pulled up.
Thereafter, a ring-shaped outer die having an inner diameter of 31 mm was dropped from the uppermost part of the die by its own weight, and a coating of a polyimide precursor solution having a thickness of about 500 μm was formed on the outer surface of the die. Next, the cylindrical mold was placed in a high-temperature constant temperature bath and heated at 120 ° C. for 1 hour and at 200 ° C. for 1 hour to remove the solvent and proceed the imide conversion reaction. The thickness of the polyimide film in this state (polyimide intermediate) was about 70 μm.

Next, a composition solution was prepared by adding about 12% by weight of carbon black powder to a fluororesin primer ("Teflon 855-001" manufactured by DuPont). The polyimide intermediate adhered to a mold was dip-coated on this solution. After this immersion, it is pulled out of the solution and
Drying treatment was performed at 1 ° C. for 1 hour. The thickness of the conductive primer layer was 4 μm. Next, on this primer layer, a composition in which 0.6% by weight of Ketjen black (carbon black manufactured by Ketjen Black International) was added to a water dispersion of a fluororesin composition comprising 70% by weight of PTFE and 30% by weight of PFA. The liquid was applied by a dipping method so that the thickness after drying was about 10 μm.

Next, the polyimide intermediate covered with the primer layer and the fluororesin layer was heat-treated at 250 ° C. for 1 hour and at 400 ° C. for 1 hour. After cooling, it is separated from the cylindrical mold and the polyimide layer (average thickness 50μ)
m) to obtain a tubular article (average total thickness: 64 μm) in which the conductive primer layer and the fluororesin layer were laminated. The tube was cut at both ends at 100 mm from both ends, and both ends were cut off to obtain a 300 mm-length polyimide tube. As a result of measuring the outer diameter of the tubular object, 20 mm from the both ends toward the center point (0.0 mm of the total length of 300 mm).
The outer diameter (ie, the outer diameter of the large-diameter straight portion) up to the position of (67 times) is 24.128 mm, and the outer diameter gradually decreases from this position toward the center point, and the minimum diameter portion at the center point. And its outer diameter was 24.098 mm. That is, the difference between the maximum value (outside diameter of the large diameter straight portion) and the minimum value (outside diameter of the minimum diameter portion) of the outer diameter of the tubular article was 30 μm.

This polyimide tubular article was mounted on an electrophotographic fixing device, and a double-sided printing test was performed on A4 size copy paper. As a result, no wrinkles were generated.

Comparative Example 1 An aluminum cylindrical mold having an outer diameter of 24 mm and a length of 500 mm was prepared. The outer diameter of this mold was cut so that a tubular article having the form shown in FIG. 2 could be formed. That is, the cutting was performed so that the cutting depth was linearly increased toward the center point in the axial direction, starting from a position 100 mm from both ends of the mold, and the depth of the center point was set to 30 μm.

Next, after performing polishing in the same manner as in Example 1, it was covered with a silicon oxide film. On the surface of this mold,
In the same manner as in Example 2, a polyimide precursor solution, a conductive primer and a fluororesin were applied and heat-treated to obtain a three-layered tubular article. The tube was cut at both ends at 100 mm from both ends, and both ends were cut off to obtain a 300 mm-length polyimide tube. As a result of measuring the outer diameter of the tubular object, the outer diameter of both ends was 24.128 mm,
The outer diameter decreases linearly from both ends toward the center point,
The minimum diameter portion was at the center, and the outer diameter was 24.098 mm. That is, the difference in the outer diameter of the tubular article was 30 μm as in the tubular article produced in Example 2. This polyimide tubular article, that is, a polyimide tubular article having no large-diameter straight portion at both ends, was attached to an electrophotographic fixing device, and A4
As a result of performing a double-sided printing test on the plate copy paper, wrinkles were observed.

The outer diameter of 24mm in the same manner as in Comparative Example 2 Example 2, using a cylindrical aluminum mold length 500 mm, cutting as tubing in the form of FIG. 1 (a) can be formed did. However, starting from a position 200 mm from both ends of the mold as a starting point, cutting was performed so as to linearly increase the cutting depth toward the center point in the axial direction, and cutting was performed so that the depth of the center point became 20 μm. Next, after polishing was performed in the same manner as in Example 1, a silicon oxide film was coated.

Using this cylindrical mold, a tubular product having a three-layer structure was produced in the same manner as in Example 2, and both ends of the tubular product were cut at 100 mm to obtain a 300 mm long polyimide tubular product. I got The large-diameter straight portions at both ends of the tubular article were each 100 mm (0.33 times the total length), and the portion having a smaller outer diameter than the large-diameter straight portion (the portion other than the large-diameter straight portion) was also 100 mm. As a result of the same test as in Example 2 using this polyimide tube,
There were wrinkles on the copy paper.

[0045]

As described above, according to the polyimide tubular article of the present invention, the generation of wrinkles on a conveyed sheet such as copy paper can be sufficiently prevented.

[Brief description of the drawings]

FIGS. 1A, 1B, and 1C are perspective views showing polyimide tubular articles according to different embodiments.

FIG. 2 is a perspective view showing a polyimide tubular article of a comparative example.

[Explanation of symbols]

2 ... Large diameter straight section, 3 ... Small diameter straight section, 4, ...
・ Tapered part, C ・ ・ ・ Minimum diameter part

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/16 G03G 15/16 // C08L 79:08 C08L 79:08 (72) Inventor Takayuki Arata Shiga 5-13-13 Ichisatoyama, Otsu-shi, Ltd. In-STI Co., Ltd. (72) Inventor Seisuke Nagaoka 5-13-13, Ichiriyama, Otsu-shi, Shiga F.S. ) 2H032 AA05 2H033 AA15 BA11 BA12 BB03 BB13 BB26 BE03 4F006 AA39 AB19 AB72 AB73 BA07 BA11 BA12 CA00 CA08 EA01 4F071 AA60 AH12 AH17 BA02 BB01 BC05 4F100 AK17C AK49A BA03 BA07 BA10 BA01 BA10 JBA BAC

Claims (4)

[Claims] 1. A large-diameter straight tube having a maximum outer diameter and a substantially constant outer diameter in the axial direction at both ends in the axial direction, comprising a polyimide tubular article containing a polyimide resin and formed into a tubular shape. The length of the large diameter straight portion in the axial direction is set to 0.03 L or more and 0.3 L or less with respect to the length L of the entire tubular object. A minimum diameter portion is formed in the center portion, and between the minimum diameter portion and the large diameter straight portion,
A polyimide tubular article, characterized in that a tapered portion that continuously reduces in diameter toward the minimum diameter portion is formed. 2. The polyimide tubular article according to claim 1, wherein an outer diameter difference between the large diameter straight portion and the minimum diameter portion is 10 μm or more and 70 μm or less. 3. The polyimide tubular article according to claim 1, wherein the minimum diameter portion is formed as a small diameter straight portion whose outer diameter is substantially constant in the axial direction. 4. An outer surface is coated with a fluororesin layer via a conductive primer layer, and the conductive primer layer is exposed at least in part.
4. The polyimide tubular article according to any one of claims 1 to 3.