Manufacturing method of electric wire

Abstract

To provide a manufacturing method of an electric wire, capable of detecting defects inside a resin film.SOLUTION: A manufacturing method of an electric wire having a conductor, and a resin film for coating the conductor includes: applying a plurality of times a resin dispersion obtained by dispersing resin impalpable powder in liquid to the surface of the conductor; heating the product to form the resin film; and performing defect detection processing for detecting defects inside the resin film by using a laser confocal microscope. When an amount of the defects detected by the defect detection processing exceeds a threshold value, for example, the resin film is re-heated.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a method for manufacturing an electrical wire. [Background technology]

[0002] Patent Document 1 discloses a method for manufacturing an electric wire. In the disclosed method, a resin dispersion in which fine powder of fluororesin is dispersed in a liquid is applied to the surface of a conductor, and then the fluororesin film is formed by heating. The manufactured electric wire includes a conductor and a fluororesin film that covers the conductor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-309972 Summary of the Invention [Problem to be solved by the invention]

[0004] Defects may exist inside the resin film. Examples of defects include grain boundaries and interfaces. When forming a resin film, the resin dispersion may be applied multiple times. In this case, grain boundaries and interfaces are likely to occur inside the resin film.

[0005] If there is a defect inside the resin film, the mechanical strength and electrical strength of the electric wire are reduced. Therefore, in the manufacturing method of the electric wire, it is preferable to carry out a process for detecting defects inside the resin film. However, it has been difficult to detect defects inside the resin film. For medical devices such as catheters, thin electric wires with a resin film thickness of about 10 μm are used. When the resin film thickness is thin, it is even more difficult to detect defects inside the resin film.

[0006] In one aspect of the present disclosure, it is preferable to provide a method for producing an electric wire capable of detecting defects inside a resin film. [Means for solving the problem]

[0007] One aspect of the present disclosure is a method for manufacturing an electric wire including a conductor and a resin film covering the conductor, the method including applying a resin dispersion, in which fine resin powder is dispersed in a liquid, to a surface of the conductor multiple times, heating the surface to form the resin film, and performing a defect detection process to detect internal defects in the resin film using a laser confocal microscope.

[0008] According to the electric wire manufacturing method which is one aspect of the present disclosure, defects inside the resin film can be detected. [Brief description of the drawings]

[0009] [Figure 1] Fig. 1A is a plan view showing the configuration of the electric wire, and Fig. 1B is a cross-sectional view taken along line IB-IB in Fig. 1A. [Diagram 2] FIG. 2 is an explanatory diagram illustrating a configuration of an apparatus used for forming a resin film. [Diagram 3] 1 is an explanatory diagram showing a laser confocal microscope and an electric wire as viewed from the longitudinal direction of the electric wire. FIG. [Figure 4] Fig. 4A is an explanatory diagram showing the focal position on the surface of the resin film, and Fig. 4B is an explanatory diagram showing the focal position on the interface between the resin film and a conductor in a portion where no defects exist. [Diagram 5] Fig. 5A is an explanatory diagram showing a state where a defect inside a resin film, not the interface between the resin film and a conductor, is the focal position, and Fig. 5B is an explanatory diagram showing a state where the focal position is abnormally deeper than the interface between the resin film and a conductor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Exemplary embodiments of the present disclosure will now be described with reference to the drawings. First Embodiment 1. Manufacturing method of electric wire (1-1) Formation of resin film 5 As shown in Fig. 1A, an electric wire 1 manufactured by the electric wire manufacturing method of the present disclosure is a linear member. As shown in Fig. 1B, the electric wire 1 includes a conductor 3 and a resin film 5. The resin film 5 covers the conductor 3.

[0011] The conductor 3 may be a single wire or a plurality of wires twisted together. Examples of the conductor 3 include metal wires and clad wires. Examples of metals constituting the metal wire include gold, silver, copper, aluminum, tin, and alloys of two or more of these. Examples of the clad wire include platinum clad wires in which an iron-nickel core is covered with platinum, and copper-clad steel wires in which a low-carbon steel core is covered with copper.

[0012] The conductor 3 may or may not have a plating layer on its surface. For example, the conductor 3 may be a linear base material that is an insulator and has a metal plating layer formed on the surface of the base material. For example, the base material may be aramid fiber. The diameter of the conductor 3 is, for example, 10 μm or more and 50 μm or less. Examples of the material of the resin film 5 include fluororesin, propylene, polypropylene, etc. Examples of the fluororesin include perfluoroalkoxy resin (PFA), fluorinated ethylene-propylene copolymer (FEP), polytetrafluoroethylene (PTFE), etc. The thickness of the resin film 5 is, for example, 0.1 μm or more and 10 μm or less.

[0013] The electric wire 1 is used, for example, in medical equipment, etc. Examples of the medical equipment include catheters, etc. In the method of manufacturing an electric wire disclosed herein, a resin dispersion (hereinafter referred to as resin dispersion 27) in which fine resin powder is dispersed in a liquid (dispersion medium) is applied to the surface of a conductor 3 multiple times, and then heated to form a resin film 5.

[0014] The resin film 5 can be formed, for example, by using an apparatus 11 shown in Fig. 2. The apparatus 11 includes a delivery roll 13 and a take-up roll 15. The conductor 3 is taken up around the delivery roll 13. The conductor 3 is delivered from the delivery roll 13 at a constant speed and taken up around the take-up roll 15.

[0015] The device 11 includes a first coating section 17, a second coating section 19, and a baking furnace 21. The conductor 3 sent out from the delivery roll 13 passes through the first coating section 17, the second coating section 19, and the baking furnace 21 in this order, and is then wound up around the take-up roll 15.

[0016] The first coating section 17 includes a roll coater 23 and a drying oven 25. In the first coating section 17, the conductor 3 first passes through the roll coater 23 and then passes through the drying oven 25. The roll coater 23 applies a resin dispersion 27 to the surface of the conductor 3. The drying oven 25 vaporizes the solvent contained in the resin dispersion 27 applied to the surface of the conductor 3. A layer of fine resin powder is formed on the surface of the conductor 3 that has passed through the first coating section 17.

[0017] The second coating unit 19 has the same configuration and function as the first coating unit 17. On the surface of the conductor 3 that has passed through the second coating unit 19, a layer of resin fine powder by the second coating unit 19 is formed on top of the layer of resin fine powder formed by the first coating unit 17.

[0018] In the baking furnace 21, the layer of fine powder formed on the surface of the conductor 3 is baked to become a resin film 5. Thus, the conductor 3 that has passed through the baking furnace 21 becomes an electric wire 1. The baking environment is, for example, atmospheric pressure. The baking temperature is set to a temperature equal to or higher than the melting point of the resin used in the fine powder layer. When PTFE is used, the baking temperature is, for example, 330°C or higher. In order to avoid decomposition of PTFE, the baking temperature is preferably 450°C or lower.

[0019] 2 performs the process of applying the resin dispersion 27 twice by the first application unit 17 and the second application unit 19, but the process of applying the resin dispersion 27 may be performed three or more times. The number of times the process of applying the resin dispersion 27 is performed is, for example, three, four, five, six, etc.

[0020] It is preferable that the resin film 5 has a degree of transparency sufficient to enable detection of the interface 4 between the resin film 5 and the conductor 3 by a laser confocal microscope 31 described later. The transmittance is a value that indicates the degree to which the laser light 43 irradiated by the laser confocal microscope 31 passes through the resin film 5. The smaller the thickness of the resin film 5, the higher the transmittance. The more easily the material of the resin film 5 transmits the laser light 43, the higher the transmittance. The higher the output of the laser light 43, the higher the transmittance. (1-2) Defect detection processing In the method for producing an electric wire according to the present disclosure, after the resin film 5 is formed, a defect detection process is performed to detect defects 53 inside the resin film 5 using a laser confocal microscope 31.

[0021] Examples of the defects 53 include grain boundaries, interfaces, and the like. When the process of applying the resin dispersion 27 is performed multiple times, grain boundaries and interfaces are likely to occur inside the resin film 5. The defects 53 are, for example, portions inside the resin film 5 where the refractive index of the laser light 43 changes. At the grain boundaries and interfaces, the refractive index of the laser light 43 changes.

[0022] For example, in the defect detection process, a portion of the resin film 5 where the apparent film thickness d of the resin film 5 measured using the laser confocal microscope 31 is abnormal is detected as a defect 53. The laser confocal microscope 31 has a known configuration. The configuration of the laser confocal microscope 31 is described on the website of Keyence Corporation (https: / / www.keyence.co.jp / ss / products / microscope / beginner / microscope / confocal-laser-scanning.jsp) etc. The basic configuration of the laser confocal microscope 31 will be described with reference to FIG. 3.

[0023] The laser confocal microscope 31 includes a point light source 33, a half mirror 35, an objective lens 37, a pinhole 39, and a photodetector 41. When a defect detection process is performed using the laser confocal microscope 31, a laser light 43 emitted by the point light source 33 is reflected by the half mirror 35 and travels toward the electric wire 1. The laser light 43 is focused at a focal point 47 by the action of the objective lens 37. If a substance that reflects and scatters the laser light 43 is present at the focal point 47, a part of the reflected and scattered light 49 generated at the focal point 47 is focused by the objective lens 37, passes through the half mirror 35, forms an image on the pinhole 39, and is detected by the photodetector 41. The position of the focal point 47 when the reflected and scattered light 49 is detected by the photodetector 41 is defined as a focal position 51.

[0024] On the other hand, when the laser light 43 is reflected and scattered at a position away from the focal point 47, or when the laser light 43 is not reflected and scattered, the photodetector 41 does not detect the reflected and scattered light 49. The position of the focal point 47 when the photodetector 41 does not detect the reflected and scattered light 49 is not the focal position 51.

[0025] The laser light 43 irradiated to the electric wire 1 is basically reflected and scattered at the interface 4 and the surface 5A of the resin film 5. Therefore, basically, the position at the interface 4 and the position at the surface 5A become the focal position 51.

[0026] Basically, the laser light 43 irradiated to the electric wire 1 is hardly reflected or scattered in the part inside the resin film 5 other than the interface 4 and the surface 5A. Therefore, basically, the position inside the resin film 5 other than the interface 4 and the surface 5A does not become the focal position 51.

[0027] The laser confocal microscope 31 can change the position of the focal point 47 in the z direction. The z direction is the radial direction of the electric wire 1. The laser confocal microscope 31 can scan the laser light 43 in the x direction and the y direction. As shown in FIG. 1, the x direction is the longitudinal direction of the electric wire 1. The y direction is the width direction of the electric wire 1. The x direction and the y direction are each perpendicular to the z direction. The x direction is perpendicular to the y direction.

[0028] Therefore, the laser confocal microscope 31 can move the position of the focal point 47 to any position in a three-dimensional space consisting of the x, y, and z directions, and detect whether or not there is a substance that reflects and scatters the laser light 43 at that position (i.e., whether or not the position is the focal position 51).

[0029] As described above, basically, the position at the interface 4 and the position at the surface 5A become the focal position 51, and the positions inside the resin film 5 that are not at the interface 4 or the surface 5A do not become the focal position 51, so the laser confocal microscope 31 can detect the positions at the interface 4 and the positions at the surface 5A as the focal position 51.

[0030] When performing defect detection processing, at any coordinate (x, y) in the x and y directions, a focal position 51_1 on the surface 5A is detected by the laser confocal microscope 31 as shown in FIG. 4A. At the same coordinate (x, y), a focal position 51_2 on the interface 4 is detected as shown in FIG. 4B. Next, at the same coordinate (x, y), the distance in the z direction between the focal positions 51_1 and 51_2 is calculated. If no defect 53 exists at the coordinate (x, y), the calculated distance is the film thickness d of the resin film 5 at the coordinate (x, y).

[0031] The thickness d of the resin film 5 is calculated by the above method at each of a plurality of coordinates (x, y) within the thickness measurement range, whose length in the x direction is Lx shown in Fig. 1 and whose length in the y direction is Ly shown in Fig. 1 and Fig. 3. Lx is, for example, 0.14 mm. Ly is a length that can cover the entire electric wire 1 in the y direction.

[0032] Next, within the film thickness measurement range, a portion where the film thickness d is abnormal is detected as a defect 53. A portion where the film thickness d is abnormal is a portion where the film thickness d changes rapidly compared to the surrounding area. The reason why the film thickness d becomes abnormal in the defect 53 is as follows.

[0033] In the example shown in FIG. 5A, there is a defect 53 inside the resin film 5. The refractive index of the defect 53 is different from the refractive index of the surroundings. In the example shown in FIG. 5A, the defect 53, not the interface 4, becomes the focal position 51-2. The focal position 51-2 is closer to the focal position 51-1 than the interface 4. Therefore, the film thickness d of the defect 53 is abnormally thinner than the film thickness d of the surroundings.

[0034] In the example shown in FIG. 5B, there is a defect 53 inside the resin film 5. The refractive index of the defect 53 is different from the refractive index of the surroundings. In the example shown in FIG. 5B, due to the difference in the refractive index of the defect 53, the focal position 51-2 is abnormally deep or abnormally shallow compared to the interface 4. Therefore, the film thickness d of the defect 53 is abnormally thick or thin compared to the film thickness d of the surroundings.

[0035] In another case, the focal position 51-2 may not be detected due to the presence of a defect 53. In this case, the film thickness d at the defect 53 is also abnormally thicker or thinner than the surrounding film thickness d. (1-3) Reheating In the electric wire manufacturing method of the present disclosure, for example, when the amount of defects 53 detected by the defect detection process exceeds a threshold, the resin film 5 is heated again. The amount of defects 53 is, for example, the ratio of the number of positions where defects 53 are detected to the total number of positions where the film thickness d is measured in the film thickness measurement range.

[0036] By reheating the resin film 5, defects 53 inside the resin film 5 can be reduced. The environment for reheating is, for example, atmospheric pressure. The temperature for reheating is set, for example, to a temperature equal to or higher than the melting point of the resin constituting the resin film 5. When PTFE is used, the temperature for reheating is equal to or higher than 330°C and equal to or lower than 450°C. When the temperature for reheating is equal to or higher than the melting point of the resin constituting the resin film 5, the effect of reducing defects 53 is even greater.

[0037] 2. Benefits of wire manufacturing method (1A) According to the electric wire manufacturing method of the present disclosure, it is possible to detect the defect 53 inside the resin film 5. In particular, even when the thickness of the resin film 5 is 0.1 μm or more and 10 μm or less, it is possible to detect the defect 53 inside the resin film 5.

[0038] (1B) In the electric wire manufacturing method of the present disclosure, for example, when the amount of defects 53 detected by the defect detection process exceeds a threshold, the resin film 5 can be heated again. In this case, the defects 53 inside the resin film 5 can be reduced. <Other embodiments> Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and can be implemented in various modified forms.

[0039] (1) In the electric wire manufacturing method of the present disclosure, other inspections may be further performed on the electric wire 1. Examples of other inspections include measuring the outer diameter of the electric wire 1, observing the appearance of the resin film 5 with an electron microscope, peeling and recovering the resin film 5 from the electric wire 1, and performing a tensile test or a voltage resistance test.

[0040] (2) The function of one component in each of the above embodiments may be shared by multiple components, or the functions of multiple components may be performed by one component. Also, part of the configuration of each of the above embodiments may be omitted. Also, at least part of the configuration of each of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

[0041] (3) In addition to the above-described method for manufacturing an electric wire, the present disclosure can be realized in various forms, such as a method for inspecting an electric wire and a method for manufacturing a catheter. [Technical idea disclosed in this specification] [Item 1] A method for manufacturing an electric wire including a conductor and a resin film covering the conductor, A resin dispersion in which fine powder of resin is dispersed in a liquid is applied to the surface of the conductor several times, and then heated to form the resin film; performing a defect detection process for detecting defects inside the resin film using a laser confocal microscope; A method for manufacturing electric wire. [Item 2] A method for producing the electric wire according to item 1, If the amount of the defects detected by the defect detection process exceeds a threshold, the resin film is heated again. A method for manufacturing electric wire. [Item 3] A method for producing an electric wire according to item 1 or 2, In the defect detection process, a portion of the resin film where a thickness of the resin film is abnormal as measured using a laser confocal microscope is detected as the defect. A method for manufacturing electric wire. [Item 4] A method for producing an electric wire according to any one of items 1 to 3, The thickness of the resin film is 0.1 μm or more and 10 μm or less. A method for manufacturing electric wire. [Item 5] A method for producing an electric wire according to any one of items 1 to 4, The resin film has a transmittance sufficient to enable detection of an interface between the resin film and the conductor by a laser confocal microscope. A method for manufacturing electric wire. [Explanation of symbols]

[0042] Reference Signs List 1...electric wire, 3...conductor, 4...interface, 5...resin film, 5A...surface, 11...apparatus, 13...delivery roll, 15...winding roll, 17...first coating section, 19...second coating section, 21...baking furnace, 23...roll coater, 25...drying furnace, 27...resin dispersion, 31...laser confocal microscope, 33...point light source, 35...half mirror, 37...objective lens, 39...pinhole, 41...photodetector, 43...laser light, 47...focus, 49...reflected scattered light, 51, 51_1, 51_2...focus position, 53...defect

Claims

1. A method for manufacturing an electric wire including a conductor and a resin film covering the conductor, A resin dispersion in which fine powder of resin is dispersed in a liquid is applied to the surface of the conductor several times, and then heated to form the resin film; performing a defect detection process for detecting defects inside the resin film using a laser confocal microscope; A method for manufacturing electric wire.

2. A method for producing an electric wire according to claim 1, If the amount of the defects detected by the defect detection process exceeds a threshold, the resin film is heated again. A method for manufacturing electric wire.

3. A method for producing an electric wire according to claim 1 or 2, In the defect detection process, a portion of the resin film where a thickness of the resin film is abnormal as measured using a laser confocal microscope is detected as the defect. A method for manufacturing electric wire.

4. A method for producing an electric wire according to claim 1 or 2, The thickness of the resin film is 0.1 μm or more and 10 μm or less. A method for manufacturing electric wire.

5. A method for producing an electric wire according to claim 1 or 2, The resin film has a transmittance sufficient to allow an interface between the resin film and the conductor to be detected by a laser confocal microscope. A method for manufacturing electric wire.

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