Electric wire manufacturing method

Abstract

To provide a wire production method that includes coating a surface of a core wire with a fluororesin layer, designed to enhance both workability and productivity.SOLUTION: A method for producing a wire includes the steps of: applying a dispersion containing fluororesin particles and an infrared absorber onto an outer peripheral surface of a core wire; and using a heating source that radiates infrared rays, to heat the core wire whose surface has been coated with the dispersion, thereby forming a fluororesin layer on the outer peripheral surface of the core wire.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a manufacturing technique for electric wires, and more particularly, to a technique effective when applied to a manufacturing technique for an electric wire having a core wire coated with a fluororesin.

Background Art

[0002] Japanese Patent Laid-Open No. 6-309972 (Patent Document 1) describes a technique for manufacturing a fluororesin-coated electric wire by applying a fluororesin dispersion in which fine powder of a fluororesin is dispersed in a liquid while a conductor is being run, followed by heat treatment at 150°C to 250°C under a reduced pressure of 10 Torr or less, and then baking. -1 Torr or less and then baking to produce a fluororesin-coated electric wire.

[0003] Japanese Patent Laid-Open No. 2017-203152 (Patent Document 2) describes a technique for providing a mixed dispersion (sol) liquid of fluororesin fine particles and metal oxide fine particles that is excellent in operability and workability in a coating process.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] For example, electric wires with a diameter of 50 μm or less are often used in medical devices used for medical or in-body applications. Generally, an electric wire has a core wire and an insulating layer that coats the core wire. However, for medical applications, for example, in consideration of workability during the manufacture of catheters or endoscopes and operability during use, it is desired that the insulating layer that coats the core wire has good slipperiness.

[0006] Therefore, the use of fluororesin with good slipperiness as the insulating layer covering the core wire is being considered. In this regard, the insulating layer covering the core wire is generally formed by the melt extrusion method. However, because fluororesin has high resin pressure and poor fluidity, it is difficult to use the melt extrusion method. In particular, for thin core wires with a diameter of 50 μm or less, the breaking tension of the conductor is small, so if a fluororesin that does not flow well is used to coat the core wire by the melt extrusion method, there is a risk that the thin core wire will break.

[0007] Therefore, a coating method using a dispersion is being considered as a way to cover the surface of the core wire with a fluororesin layer. In this coating method, a dispersion of fluororesin particles is applied to the surface of the core wire, and then the fluororesin particles are fired by heat treatment to form a fluororesin layer that covers the surface of the core wire.

[0008] During firing, the fluororesin particles melt and fuse together, but because fluororesin has high viscosity, firing requires high temperatures and long periods of time. Therefore, there is room for improvement in the coating method from the standpoint of workability and productivity. In other words, when applying a coating method using a dispersion liquid to cover the surface of a core wire with a fluororesin layer, improvements in workability and productivity are desired.

[0009] The object of the present invention is to provide a technology that can improve workability and productivity in a method for manufacturing electric wires in which the surface of the core wire is coated with a fluororesin layer. [Means for solving the problem]

[0010] A method for manufacturing an electric wire in one embodiment comprises the steps of applying a dispersion containing fluororesin particles and an infrared absorbent to the outer surface of a core wire, and forming a fluororesin layer on the outer surface of the core wire by heating the core wire coated with the dispersion using a heating source that emits infrared rays.

[0011] A method for manufacturing an electric wire in one embodiment includes the steps of: applying a first dispersion containing fluororesin particles and an infrared absorbent to the first surface of a core wire; forming a first fluororesin layer on the first surface of the core wire by heating the core wire coated with the first dispersion using a heating source that emits infrared rays; applying a second dispersion containing fluororesin particles and not containing an infrared absorbent to the second surface of the first fluororesin layer of the core wire; and forming a second fluororesin layer on the second surface of the first fluororesin layer by heating the core wire coated with the second dispersion using a heating source. [Effects of the Invention]

[0012] According to one embodiment, in a method for manufacturing electric wires in which the outer surface of the core wire is covered with a fluororesin layer, workability and productivity can be improved. [Brief explanation of the drawing]

[0013] [Figure 1] This is a cross-sectional view showing one cross-section of the electric wire in Embodiment 1. [Figure 2] This is a cross-sectional view showing a cross-section of an electric wire in a modified example. [Figure 3] This is a flowchart outlining the manufacturing process of electric wires. [Figure 4] This diagram schematically shows the method for manufacturing electric wires in Embodiment 1. [Figure 5] This is a cross-sectional view showing one cross-section of the electric wire in Embodiment 2. [Figure 6] This figure schematically illustrates the method for manufacturing electric wires in Embodiment 2. [Modes for carrying out the invention]

[0014] In all the drawings illustrating the embodiments, the same reference numeral is used for identical components, and repeated explanations of them are omitted. Hatching may be used even in plan views to improve clarity.

[0015] (Embodiment 1) <Configuration of Electric Wire> FIG. 1 is a cross-sectional view showing a cross-section of an electric wire 10 in Embodiment 1 of the present invention.

[0016] The electric wire 10 in Embodiment 1 of the present invention is, for example, an electric wire used in medical devices used for medical applications or in-body applications, and it is assumed that the diameter of this electric wire 10 is, for example, 50 μm or less. However, the technical idea in Embodiment 1 of the present invention is not limited to the electric wire used in the above-described medical device, and the diameter is not limited to 50 μm or less, and it can be applied to a wide range of electric wires.

[0017] In FIG. 1, the electric wire 10 has a core wire 1 capable of transmitting a high-frequency signal, and a fluororesin layer 2 formed so as to cover the outer peripheral surface of the core wire 1. The core wire 1 is composed of, for example, a conducting wire containing any one of copper, silver, and aluminum as a single substance or an alloy. This conducting wire can be a single wire or a stranded wire. At this time, a plating film may be formed on the surface of the conducting wire. Examples of the plating film include tin plating and silver plating. The diameter of the core wire 1 is, for example, 10 μm or more and 50 μm or less.

[0018] Note that the core wire 1 is not limited to a conducting wire, and may be composed of, for example, a non-conducting wire whose surface is covered with a conductor film. In particular, when the signal transmitted by the electric wire 10 is a high-frequency signal, due to the skin effect, the high-frequency signal flows only in the vicinity of the surface of the core wire 1. Therefore, even if the core wire 1 is composed of a non-conducting wire whose surface is covered with a conductor film, the high-frequency signal can be transmitted by this core wire 1.

[0019] Examples of the non-conducting wire whose surface is covered with a conductor film include conductive fibers obtained by applying silver plating to the outer peripheral surface of resin fibers such as nylon and polyester. This resin fiber can be a single wire or a stranded wire.

[0020] One advantage of constructing the core wire 1 from a non-conducting wire whose surface is covered with a conductive film is that, by constructing the non-conducting wire from resin, the weight of the electric wire 10 can be reduced compared to when the core wire 1 is constructed from a conductor.

[0021] The fluororesin layer 2 contains a fluororesin and an infrared absorbent. Examples of fluororesins include polytetrafluoroethylene (hereinafter sometimes referred to as "PTFE") and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (hereinafter sometimes referred to as "PFA"). On the other hand, the infrared absorbent is a substance that absorbs infrared rays and includes carbon and insulating infrared absorbents. Examples of insulating infrared absorbents include silica (nanosilica), titanium dioxide, or iron oxide (ferric oxide, triiron tetroxide).

[0022] For example, the fluororesin layer 2 contains an infrared absorbent in a proportion of 0.1% by mass or more and 5% by mass or less. Here, mass% means mass of infrared absorbent / (mass of fluororesin + mass of infrared absorbent) × 100.

[0023] Furthermore, the fluororesin layer 2 may contain a binder resin. As the binder resin, for example, polyamide-imide, polyimide, and polyethersulfone can be used individually or in combination. However, from the viewpoint of exhibiting performance such as the lubricity of the fluororesin, for example, if the fluororesin is composed of "PTFE", it is desirable that the "PTFE" content in the fluororesin layer 2 be 75% by mass or more.

[0024] The thickness of the fluororesin layer 2 is, for example, 3 μm to 10 μm.

[0025] The electric wire 10 in this embodiment is configured as described above.

[0026] <Variation> In the electric wire 10 shown in Figure 1, an example in which the core wire 1 is made of a single wire was described, but the technical concept in this embodiment 1 is not limited to this and can also be applied to electric wires in which the core wire is made of stranded wire, for example. Specifically, Figure 2 is a cross-sectional view showing one cross-section of the electric wire 10A in this modified example. In Figure 2, the electric wire 10A has a core wire 1A made of stranded wire and a fluororesin layer 2 covering the core wire 1A. In the electric wire 10A configured in this way, the core wire 1A can be made of the same material as the core wire 1 of the electric wire 10 shown in Figure 1.

[0027] Similarly, the fluororesin layer 2 of the electric wire 10A is made of the same material as the fluororesin layer 2 of the electric wire 10. For example, the fluororesin layer 2 of the electric wire 10A also contains an infrared absorber.

[0028] <Overview of Electric Wire Manufacturing Method> Next, we will explain the general method of manufacturing the electric wire 10 shown in Figure 1, for example.

[0029] Figure 3 is a flowchart illustrating the overview of the manufacturing method for electric wires.

[0030] In Figure 3, first, a dispersion containing fluororesin particles and an infrared absorber is prepared (S101). For example, the prepared dispersion contains water as a solvent (liquid), fluororesin particles, an infrared absorber, a surfactant, a thickener, and a pH adjuster.

[0031] Next, the dispersion is applied to the outer surface of the core wire (S102). Methods for applying the dispersion to the outer surface of the core wire include, for example, spray coating or dip coating.

[0032] Next, the core wire coated with the dispersion is heated (S103). Specifically, a heating source that emits infrared rays is used to heat the core wire coated with the dispersion on its outer surface at a heating temperature of, for example, 380°C to 600°C. Here, as a heating source that emits infrared rays, examples include an infrared lamp in addition to a normal electric furnace. If the heating temperature falls below the lower limit of 380°C, the fluororesin particles cannot be fired. On the other hand, if the heating temperature exceeds the upper limit of 600°C, the fluororesin will decompose. For this reason, it is desirable to perform the heating at a temperature of 380°C to 600°C. Through this heating process, the dispersion is dried and the fluororesin particles are fired (melted and fused together).

[0033] To summarize the above, the method for manufacturing an electric wire can be said to include the steps of: applying a dispersion containing fluororesin particles and an infrared absorbent to the outer surface of a core wire; and forming a fluororesin layer on the outer surface of the core wire by heating the core wire coated with the dispersion using a heating source that emits infrared rays.

[0034] As described above, for example, the electric wire 10 shown in Figure 1 can be manufactured.

[0035] <Specific manufacturing methods for electric wires> Next, we will explain the specific manufacturing method of electric wires, referring to the diagrams.

[0036] Figure 4 is a schematic diagram showing the manufacturing method of the electric wire 10 in this embodiment 1.

[0037] In Figure 4, first, the core wire 1 is fed out from the feed roller 100. For example, the core wire 1 is fed out from the feed roller 100 at a speed of, for example, 1 m / min to 1.6 m / min. The core wire 1 fed out from the feed roller 100 then passes through the dispersion 200. By making the direction of passage of the core wire 1 vertical, dripping of the dispersion 200 can be prevented, and the film thickness of the fluororesin layer 2 can be made uniform. The dispersion 200 contains fluororesin particles and an infrared absorber dispersed in water, which is the solvent. As the core wire 1 passes through the dispersion 200, the dispersion 200 is applied to the outer surface of the core wire 1. After that, the core wire 1 with the dispersion 200 applied to its outer surface passes through the heating furnace (firing furnace) 300. At this time, the heating furnace 300 is equipped with, for example, a heating source 310A and a heating source 310B that emit infrared rays, and the core wire 1, on which the dispersion liquid 200 is coated on its outer surface, is heated by these heating sources 310A and 310B. For example, the core wire 1 on which the dispersion liquid 200 is coated on its outer surface is heated under heating conditions of a heating temperature of approximately 540°C to 580°C and a heating time of 40 to 60 seconds.

[0038] As a result, the dispersion 200 applied to the outer surface of the core wire 1 dries, and the fluororesin particles are fired (melted and fused together). This forms a fluororesin layer 2 on the outer surface of the core wire 1. In other words, the core wire 1, with the dispersion 200 applied to its outer surface, passes through the heating furnace 300 to become an electric wire 10 with a fluororesin layer 2 formed on its outer surface. In the heating furnace 300, the fluororesin particles are fired, and the gas generated during firing is exhausted from the exhaust port 320 by an exhaust blower. The electric wire 10 sent out of the heating furnace 300 is then wound up by a winding roller 400.

[0039] As described above, the electric wire 10 in this embodiment 1 can be manufactured.

[0040] <Features of Embodiment 1> Next, we will describe the features of this first embodiment.

[0041] A key feature of this embodiment 1 is that the dispersion applied to the outer surface of the core wire contains an infrared absorbent. This allows the infrared absorbent in the dispersion to efficiently absorb infrared radiation emitted from the heat source when the core wire coated with the dispersion is heated using an infrared-emitting heat source. As a result, the core wire coated with the dispersion heats up rapidly. Therefore, the fluororesin particles in the dispersion are quickly fired. In other words, according to the features of this embodiment 1, the heating time required for firing the fluororesin particles can be shortened. This means that the core wire's travel speed can be increased. For example, the speed can be increased from 1 m / min to 1.6 m / min to 2 m / min to 2.5 m / min. Therefore, according to these features, the productivity of the electric wire can be improved, as can the workability. Specifically, according to these features, the productivity and workability of manufacturing electric wires coated with a fluororesin layer can be improved.

[0042] In particular, as shown in Figure 4, the heating furnace 300 is provided with an exhaust port 320, in which case the heating effect due to the feature points in this embodiment 1 is effective. This is because, when the heating furnace 300 is provided with an exhaust port 320, the heat generated in the heating furnace 300 escapes through the exhaust port 320, which increases the time required to heat the core wire coated with the dispersion. In this regard, according to the feature points in this embodiment 1, even if the heat generated in the heating furnace 300 escapes through the exhaust port 320, the heating effect of the infrared absorber compensates for this, thus shortening the heating time required for firing the fluororesin particles.

[0043] Here, the infrared absorber can be any substance that efficiently absorbs infrared rays. However, since it will ultimately be contained in the fluororesin layer, which is the insulating layer covering the core wire, it is desirable that the infrared absorber be an insulating material. For example, nanosilica, titanium dioxide, or iron oxide can be given as insulating infrared absorbers.

[0044] Furthermore, it is desirable that the amount of infrared absorbent contained in the fluororesin layer be between 0.1% by mass and 5% by mass. This is because, for example, if the amount of infrared absorbent is less than 0.1% by mass, the heating effect due to infrared absorption by the infrared absorbent will be diminished. On the other hand, if the amount of infrared absorbent exceeds 5% by mass, it will affect the properties of the fluororesin layer itself. Specifically, in order to maximize the slipperiness of the fluororesin layer itself, it is desirable that the fluororesin layer does not contain any impurities other than fluororesin.

[0045] In this regard, since infrared absorbers are also impurities, it is desirable to reduce the amount of infrared absorber as much as possible while still allowing the heating effect to be fully realized in order to maximize the slipperiness of the fluororesin layer. Taking this into consideration, in this embodiment 1, it is desirable that the amount of infrared absorber contained in the fluororesin layer be 5% by mass or less.

[0046] Furthermore, the fluororesin layer may contain a binder resin, and in this case, the binder resin becomes an impurity in the fluororesin layer, so it is desirable that the binder resin content be below a predetermined value. For example, if the fluororesin constituting the fluororesin layer is made of "PTFE", it is desirable that the "PTFE" content in the fluororesin layer be 75% by mass or more. In other words, it is desirable that the binder resin content in the fluororesin layer be less than 25% by mass.

[0047] From the above, it can be concluded that the fluororesin layer contains infrared absorbers, which are impurities. However, from the perspective of ensuring the inherent slipperiness of the fluororesin, it is desirable to include as few impurities as possible. On the other hand, since infrared absorbers can shorten the heating time required for firing the fluororesin particles, from this perspective, including infrared absorbers is useful. In other words, a configuration that includes infrared absorbers has the advantage of shortening the heating time required for firing the fluororesin particles, but it also has the disadvantage of making it difficult to maximize the inherent slipperiness of the fluororesin.

[0048] Therefore, the following describes a technical concept that aims to shorten the heating time required for firing fluororesin particles using infrared absorbers while maximizing the inherent slipperiness of the fluororesin. In other words, it describes a technical concept that achieves both a reduction in the heating time required for firing fluororesin particles and maximizing the inherent slipperiness of the fluororesin.

[0049] (Embodiment 2) <Wiring configuration> Figure 5 is a cross-sectional view showing one cross-section of the electric wire 20 in this second embodiment.

[0050] In Figure 5, the electric wire 20 comprises a core wire 1, a fluororesin layer 2A covering the first outer surface of the core wire 1, and a fluororesin layer 2B covering the second outer surface of the fluororesin layer 2A. Here, the fluororesin layer 2A contains an infrared absorbent, while the fluororesin layer 2B does not. That is, in this second embodiment, the electric wire 20 has a fluororesin layer covering the first outer surface of the core wire 1 that is constructed from a laminated structure of a fluororesin layer 2A containing an infrared absorbent and a fluororesin layer 2B not containing an infrared absorbent. In this case, the fluororesin layer 2B not containing an infrared absorbent constitutes the outermost layer of the electric wire 20.

[0051] The electric wire 20 in this second embodiment is constructed as described above.

[0052] <Manufacturing methods for electric wires> Next, the manufacturing method of the electric wire 20 will be explained with reference to the drawings.

[0053] Figure 6 is a schematic diagram showing the manufacturing method of the electric wire 20 in this second embodiment.

[0054] In Figure 6, first, the core wire 1 is fed out from the feed roller 100. The core wire 1 fed out from the feed roller 100 then passes through the dispersion 200A. The dispersion 200A contains fluororesin particles and an infrared absorber dispersed in water, which is the solvent. As the core wire 1 passes through the dispersion 200A, the dispersion 200A is applied to the first outer surface of the core wire 1. After that, the core wire 1 with the dispersion 200A applied to its first outer surface passes through the heating furnace (firing furnace) 300. At this time, the heating furnace 300 is equipped with, for example, a heating source 310A that emits infrared rays, and the core wire 1 with the dispersion 200A applied to its first outer surface is heated by this heating source 310A.

[0055] As a result, the dispersion 200A applied to the first outer surface of the core wire 1 dries, and the fluororesin particles are fired (melted and fused together). This forms a fluororesin layer 2A on the first outer surface of the core wire 1. In other words, the core wire 1, with the dispersion 200A applied to its first outer surface, passes through the heating furnace 300, thereby forming a fluororesin layer 2A on its first outer surface. In the heating furnace 300, the fluororesin particles are fired, and the gas generated during firing is exhausted from the exhaust port 320. The core wire 1 with the fluororesin layer 2A formed on its first outer surface is then sent out of the heating furnace 300.

[0056] Next, the core wire 1, which has a fluororesin layer 2A formed on its first outer surface, is sent out of the heating furnace 300 and passes through the dispersion 200B. Here, the dispersion 200B contains fluororesin particles dispersed in water, which is the solvent, but does not contain an infrared absorber. As the core wire 1 with the fluororesin layer 2A formed on its first outer surface passes through the dispersion 200B, the dispersion 200B is coated onto the second outer surface of the fluororesin layer 2A. After that, the core wire 1 with the dispersion 200B coated onto the second outer surface of the fluororesin layer 2A passes through the heating furnace (firing furnace) 300. At this time, a heating source 310B that emits infrared rays is provided inside the heating furnace 300, and the core wire 1 with the dispersion 200B coated onto the second outer surface of the fluororesin layer 2A is heated by this heating source 310B.

[0057] As a result, the dispersion 200B applied to the second outer surface of the fluororesin layer 2A dries, and the fluororesin particles are fired (melted and inter-particle fusion). This forms the fluororesin layer 2B on the second outer surface of the fluororesin layer 2A. In other words, the core wire 1, to which the dispersion 200B has been applied to the second outer surface of the fluororesin layer 2A, passes through the heating furnace 300 to become an electric wire 20 with the fluororesin layer 2B formed on the second outer surface of the fluororesin layer 2A. In the heating furnace 300, the fluororesin particles are fired, and the gas generated during firing is exhausted from the exhaust port 320. The electric wire 20 sent out of the heating furnace 300 is then wound up by the winding roller 400.

[0058] As described above, the electric wire 20 in this second embodiment can be manufactured.

[0059] The method for manufacturing the electric wire 20 described above can be summarized as follows: The method for manufacturing the electric wire 20 comprises the steps of: applying a first dispersion containing fluororesin particles and an infrared absorbent to the first surface of a core wire; forming a first fluororesin layer on the first surface of the core wire by heating the core wire coated with the first dispersion using a heating source that emits infrared rays; applying a second dispersion containing fluororesin particles and not containing an infrared absorbent to the second surface of the first fluororesin layer of the core wire; and forming a second fluororesin layer on the second surface of the first fluororesin layer by heating the core wire coated with the second dispersion using a heating source.

[0060] <Features of Embodiment 2> Next, we will describe the features of this second embodiment.

[0061] A key feature of this second embodiment is that, as shown in Figure 5, for example, the fluororesin layer covering the outer surface of the core wire 1 is assumed to be composed of a laminated structure of a fluororesin layer 2A containing an infrared absorbent and a fluororesin layer 2B not containing an infrared absorbent, and the manufacturing method for the electric wire 20 is, for example, the manufacturing method shown in Figure 6.

[0062] As a result, for example, as shown in Figure 6, the fluororesin layer 2A containing the infrared absorbent is formed by heating the first outer surface of the core wire 1 with the dispersion 200A containing the infrared absorbent using a heat source 310A provided in the heating furnace 300. Therefore, the infrared absorbent contained in the dispersion 200A rapidly raises the temperature of the core wire 1 coated with the dispersion 200A. Consequently, the fluororesin particles contained in the dispersion 200A are rapidly fired, and the heating time required for firing the fluororesin particles can be shortened.

[0063] On the other hand, the fluororesin layer 2B, which does not contain an infrared absorber, is formed by applying a dispersion 200B, which does not contain an infrared absorber, to the second outer surface of the fluororesin layer 2A, and then heating it with a heat source 310B provided in the heating furnace 300. Therefore, since the dispersion 200B does not contain an infrared absorber, it might appear that, at first glance, no heating effect due to an infrared absorber is obtained in the process of forming the fluororesin layer 2B.

[0064] However, in the process of forming the fluororesin layer 2B, the dispersion 200B is applied to the second outer surface of the fluororesin layer 2A, which contains an infrared absorbent. Therefore, when the dispersion 200B applied to the second outer surface of the fluororesin layer 2A is heated by the heat source 310B provided in the heating furnace 300, the heat generated by the absorption of infrared rays by the infrared absorbent contained in the fluororesin layer 2A is transferred to the dispersion 200B applied to the fluororesin layer 2A. In other words, although the dispersion 200B itself does not contain an infrared absorbent, the fluororesin layer 2A to which the dispersion 200B is applied contains an infrared absorbent, and as a result, the heat generated by the absorption of infrared rays by this infrared absorbent indirectly heats the dispersion 200B.

[0065] As a result, the infrared absorption by the infrared absorber contained in the fluororesin layer 2A indirectly increases the temperature of the dispersion 200B, which does not contain an infrared absorber. Therefore, according to the features of this second embodiment, the fluororesin particles contained in the dispersion 200B are quickly fired, and as a result, the heating time required for firing the fluororesin particles can be shortened when forming the fluororesin layer 2B. Note that the fluororesin layer 2A and / or the fluororesin layer 2B may each be formed multiple times.

[0066] From the above, according to the features of this second embodiment, the heating effect caused by the infrared absorber can be obtained not only when forming the fluororesin layer 2A containing the infrared absorber, but also when forming the fluororesin layer 2B that does not contain the infrared absorber. Therefore, according to the features of this second embodiment, a remarkable effect can be obtained in which the heating time required for firing the fluororesin particles can be shortened in the formation process of both the fluororesin layer 2A and the fluororesin layer 2B.

[0067] Furthermore, in this second embodiment, a fluororesin layer 2B that does not contain an infrared absorber is formed on the outermost layer of the electric wire 20. This means that a fluororesin layer 2B that does not contain an impurity such as an infrared absorber is formed on the outermost layer of the electric wire 20. Therefore, according to this second embodiment, the inherent slipperiness of the fluororesin can be maximized on the outermost surface of the electric wire 20. Thus, it can be seen that this second embodiment makes it possible to achieve both a reduction in the heating time required for firing the fluororesin particles and the maximization of the inherent slipperiness of the fluororesin.

[0068] The present invention has been described in detail above based on its embodiments, but it goes without saying that the present invention is not limited to the above embodiments and can be modified in various ways without departing from its essence.

[0069] The above-mentioned embodiment includes the following forms.

[0070] (Note 1) A step of applying a dispersion containing fluororesin particles and an infrared absorber to the outer surface of the core wire, A step of forming a fluororesin layer on the outer surface of the core wire by heating the core wire, which has the dispersion applied to its outer surface, using a heating source that emits infrared rays, A method for manufacturing electric wires, comprising the following features.

[0071] (Note 2) In the method for manufacturing electric wires described in Appendix 1, The infrared absorber is carbon, and the method for manufacturing electric wires.

[0072] (Note 3) In the method for manufacturing electric wires described in Appendix 1, The infrared absorbent is an insulating infrared absorbent, and the method for manufacturing electric wires.

[0073] (Note 4) In the method for manufacturing electric wires described in Appendix 3, A method for manufacturing electric wires, comprising the infrared absorber containing silica, titanium oxide, or iron oxide.

[0074] (Note 5) In the method for manufacturing electric wires described in Appendix 1, A method for manufacturing electric wires, wherein the fluororesin layer contains 0.1% by mass or more and 5% by mass or less of the infrared absorber.

[0075] (Note 6) In the method for manufacturing electric wires described in Appendix 1, A method for manufacturing an electric wire, comprising the step of forming a fluororesin layer on the outer surface of the core wire, wherein the core wire coated with the dispersion is heated using a heating source that emits infrared rays while exhausting the heat.

[0076] (Note 7) In the method for manufacturing electric wires described in Appendix 1, A method for manufacturing electric wires, wherein the core wire is composed of a conductor.

[0077] (Note 8) In the method for manufacturing electric wires described in Appendix 7, A method for manufacturing an electric wire, wherein the aforementioned conductor contains copper, silver, or aluminum, either as a single element or as an alloy.

[0078] (Note 9) In the method for manufacturing electric wires described in Appendix 7, A method for manufacturing an electric wire, wherein a plating film is formed on the surface of the aforementioned conductor.

[0079] (Note 10) In the method for manufacturing electric wires described in Appendix 1, A method for manufacturing electric wires, wherein the core wire is composed of a non-conducting wire whose surface is covered with a conductive film.

[0080] (Note 11) In the method for manufacturing electric wires described in Appendix 10, The method for manufacturing an electric wire, wherein the aforementioned insulated wire is made of resin.

[0081] (Note 12) In the method for manufacturing electric wires described in Appendix 1, The fluororesin layer contains polytetrafluoroethylene, a method for manufacturing electric wires.

[0082] (Note 13) In the method for manufacturing electric wires described in Appendix 12, A method for manufacturing electric wires, wherein the polytetrafluoroethylene content in the fluororesin layer is 75% by mass or more.

[0083] (Note 14) In the method for manufacturing electric wires described in Appendix 1, The diameter of the core wire is 10 μm or more and 50 μm or less. A method for manufacturing electric wires, wherein the thickness of the fluororesin layer is 3 μm or more and 10 μm or less.

[0084] (Note 15) A step of applying a first dispersion containing fluororesin particles and an infrared absorber to the first surface of a core wire, A step of forming a first fluororesin layer on the first surface of the core wire by heating the core wire coated with the first dispersion on the first surface using a heating source that emits infrared rays, A step of applying a second dispersion containing fluororesin particles and not containing an infrared absorber to the second surface of the first fluororesin layer of the core wire on which the first fluororesin layer is formed, A step of forming a second fluororesin layer on the second surface of the first fluororesin layer by heating the core wire, on which the second dispersion liquid has been applied, using the aforementioned heating source, A method for manufacturing electric wires, comprising the following features.

[0085] (Note 16) In the method for manufacturing electric wires described in Appendix 15, The second fluororesin layer is the outermost layer, a method for manufacturing electric wires. [Explanation of symbols]

[0086] 1 core wire 1A core wire 2. Fluororesin layer 2A Fluororesin layer 2B Fluoropolymer layer 10 Electric wire 10A wire 20 Electric wire 100 Feed Rollers 200 Dispersion 200A dispersion 200B dispersion 300 Furnace 310A heating source 310B heating source 320 exhaust port 400 winding rollers

Claims

1. A step of applying a first dispersion containing fluororesin particles and an infrared absorber to the first surface of a core wire, A step of forming a first fluororesin layer on the first surface of the core wire by heating the core wire coated with the first dispersion on the first surface using a heating source that emits infrared rays, A step of applying a second dispersion containing fluororesin particles and not containing an infrared absorber to the second surface of the first fluororesin layer of the core wire on which the first fluororesin layer is formed, A step of forming a second fluororesin layer on the second surface of the first fluororesin layer by heating the core wire, on which the second dispersion liquid has been applied, using the aforementioned heating source, A method for manufacturing electric wires, comprising the following features.

2. In the method for manufacturing an electric wire according to claim 1, The second fluororesin layer is the outermost layer, a method for manufacturing electric wires.

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