Electric wire and multicore cable

Abstract

An electric wire according to the present invention comprises a conductor and a coating that covers the conductor, wherein: the coating includes a first layer and a second layer that is disposed so as to be in contact with the outer side of the first layer; the first layer contains, as a main component, at least one resin selected from the group consisting of polyphenylene sulfide resins, polyurethane resins, polyester resins, and polyether ether ketone resins; the second layer contains silsesquioxane as a main component; the silsesquioxane is a polymer containing a structural unit derived from (RSiO3 / 2); the R is a polymerizable group; and the thickness of the second layer is 0.1-100 μm.

Description

Electric wires and multi-core cables

[0001] This disclosure relates to electric wires and multi-core cables.

[0002] Conventionally, electric wires comprising a conductor and a coating covering the conductor, or multi-core cables comprising electric wires, have been used in various applications such as automobiles, aircraft, rockets, satellites, industrial robots, electrical equipment, and thermal equipment (Patent Documents 1 to 7).

[0003] Japanese Patent No. 7540619 Japanese Patent No. 7540620 Japanese Unexamined Patent Publication No. 9-288914 No. 4-61808 Utility Model Publication No. 2000-30535 Japanese Patent No. 8-255513 No. 2016-192374

[0004] The electric wire of the present disclosure comprises a conductor and a coating covering the conductor, wherein the coating includes a first layer and a second layer disposed in contact with the outside of the first layer, the first layer mainly comprising at least one resin selected from the group consisting of polyphenylene sulfide resin, polyurethane resin, polyester resin, and polyetheretherketone resin, and the second layer mainly comprising silsesquioxane, the silsesquioxane being (RSio ３／２ The polymer contains constituent units derived from ), where R is a polymerizable group, and the thickness of the second layer is 0.1 μm or more and 100 μm or less.

[0005] Figure 1 is a schematic perspective view of an electric wire according to one embodiment of the present disclosure. Figure 2 is a schematic cross-sectional view along line II-II in Figure 1. Figure 3 is a schematic perspective view of another electric wire according to one embodiment of the present disclosure. Figure 4 is a schematic cross-sectional view along line IV-IV in Figure 3. Figure 5 is a schematic perspective view of a multi-core cable according to one embodiment of the present disclosure. Figure 6 is a schematic cross-sectional view along line VI-VI in Figure 5. Figure 7 is a schematic diagram illustrating part of the evaluation methods for heat resistance evaluation tests 1 to 3.

[0006] [Problems this disclosure aims to solve] When electric wires are used in various applications such as automobiles, aircraft, rockets, satellites, industrial robots, electrical equipment, and thermal equipment, the operating conditions for the electric wires can be severe. In particular, when the temperature conditions are severe, there is a need to prevent oxidative degradation caused by oxygen, ozone, atomic oxygen, etc., and to impart excellent heat resistance to the electric wires. Oxidative degradation proceeds as oxygen in the air reacts with the polymer. Oxidative degradation tends to be accelerated at higher temperatures. This is because at higher temperatures, oxygen molecules diffuse more easily within the polymer, and the polymer and oxygen react more easily. By suppressing oxidative degradation when the temperature conditions are severe, the deterioration of electric wires due to heating can be suppressed (in other words, the heat resistance of electric wires can be improved).

[0007] One method for improving the heat resistance of electric wires is to form a coating comprising a lower layer mainly composed of fluororesin or crosslinked polyolefin, and an upper layer formed on the lower layer and mainly composed of silsesquioxane (Patent Documents 1-2). In such cases, it is necessary to improve the adhesion between the "layer mainly composed of silsesquioxane" and the layer directly below the "layer mainly composed of silsesquioxane" in order to make it difficult for the "upper layer formed on the lower layer and mainly composed of silsesquioxane" to peel off from the conductor-side interface of the upper layer, without impairing the heat resistance of the electric wire. In this disclosure, when simply referred to as "adhesion," it means the adhesion between the "layer mainly composed of silsesquioxane" (in other words, the "second layer" in this disclosure) and the layer directly below the "layer mainly composed of silsesquioxane" (in other words, the "first layer" in this disclosure).

[0008] Therefore, the purpose of this disclosure is to provide an electric wire that combines excellent heat resistance and excellent adhesion, and a multi-core cable equipped with said electric wire.

[0009] [Effects of this disclosure] According to this disclosure, it is possible to provide an electric wire that has excellent heat resistance and excellent adhesion, and a multi-core cable equipped with said electric wire.

[0010] [Description of Embodiments of the Disclosure] Embodiments of the Disclosure will be described first by listing them. (1) A wire of the Disclosure comprising a conductor and a coating covering the conductor, wherein the coating comprises a first layer and a second layer disposed in contact with the outside of the first layer, the first layer mainly comprising at least one resin selected from the group consisting of polyphenylene sulfide resin, polyurethane resin, polyester resin, and polyetheretherketone resin, and the second layer mainly comprising silsesquioxane, the silsesquioxane being (RSio ３／２ The polymer contains constituent units derived from ), where R is a polymerizable group, and the thickness of the second layer is 0.1 μm or more and 100 μm or less.

[0011] According to this disclosure, it is possible to provide an electric wire that combines excellent heat resistance and excellent adhesion, and a multi-core cable equipped with said electric wire.

[0012] (2) In (1) above, the resin of the first layer is a resin modified with a first functional group, and the first functional group may have a carboxyl group or an ether group. This makes it possible to provide an electric wire and a multi-core cable equipped with the electric wire that have both better heat resistance and better adhesion.

[0013] (3) In (2) above, the first functional group may be at least one functional group selected from the group consisting of a carboxyl group, a maleic anhydride group, and an epoxy group. This makes it possible to provide an electric wire and a multi-core cable equipped with the electric wire that have both better heat resistance and better adhesion.

[0014] (4) In (1) above, the interface of the first layer near the surface of the coating may be in a hydrophilic state. This makes it possible to provide an electric wire and a multi-core cable equipped with the electric wire that have both better heat resistance and better adhesion.

[0015] (5) In (4) above, the hydrophilization treatment may be at least one selected from the group consisting of corona treatment, plasma treatment, ozone treatment, and etching treatment with activated sodium. This makes it possible to provide an electric wire and a multi-core cable equipped with the electric wire that have both superior heat resistance and superior adhesion.

[0016] (6) In any of (1) to (5) above, the coating further includes a third layer formed between the interface of the first layer near the conductor and the interface of the conductor and the coating, the third layer may mainly contain at least one resin selected from the group consisting of polyolefin resin, polyester resin, and fluororesin. This makes it possible to provide an electric wire with better heat resistance and a multi-core cable equipped with the electric wire.

[0017] (7) In (6) above, the resin of the third layer is a resin modified with a second functional group, and the second functional group may have a carboxyl group or an ether group. This makes it possible to provide an electric wire with better heat resistance and a multi-core cable equipped with the electric wire.

[0018] (8) In (7) above, the second functional group may be at least one functional group selected from the group consisting of a carboxyl group, a maleic anhydride group, and an epoxy group. This makes it possible to provide an electric wire with better heat resistance and a multi-core cable equipped with the electric wire.

[0019] (9) In any of (1) to (8) above, the polymerizable group may be a radical polymerizable group or a cationic polymerizable group. This makes it possible to provide an electric wire and a multi-core cable equipped with the electric wire that have both superior heat resistance and superior adhesion.

[0020] (10) In any of (1) to (8) above, the polymerizable group may be one polymerizable group selected from the group consisting of an acryloyl group, a methacryloyl group, and an oxetanyl group. This makes it possible to provide an electric wire and a multi-core cable equipped with the electric wire that have both superior heat resistance and superior adhesion.

[0021] (11) The multi-core cable of the present disclosure comprises the wires described in any of (1) to (10) above.

[0022] According to this disclosure, it is possible to provide a multi-core cable having wires that possess both excellent heat resistance and excellent adhesion.

[0023] [Details of Embodiments of the Disclosure] Specific examples of electric wires and multi-core cables of one embodiment of the Disclosure (hereinafter also referred to as "this embodiment") will be described below with reference to the drawings. In the drawings of the Disclosure, the same reference numerals represent the same or corresponding parts. In addition, dimensional relationships such as length, width, thickness, and depth have been appropriately modified for clarity and simplification of the drawings and do not necessarily represent actual dimensional relationships.

[0024] In this disclosure, the notation "A to B" means an upper and lower limit of the range (i.e., A or greater and B or less), and if no unit is specified for A, but a unit is specified only for B, then the unit for A and the unit for B are the same.

[0025] In this disclosure, when compounds and the like are represented by chemical formulas, unless otherwise specified, the atomic ratios should include all conventionally known atomic ratios and should not necessarily be limited to those within the stoichiometric range.

[0026] [Embodiment 1: Electric Wire] An electric wire according to one embodiment of the present disclosure will be described with reference to Figures 1 to 4. Figure 1 is a schematic perspective view of an electric wire according to one embodiment of the present disclosure. Figure 2 is a schematic cross-sectional view along line II-II in Figure 1. Figure 3 is a schematic perspective view of another electric wire according to one embodiment of the present disclosure. Figure 4 is a schematic cross-sectional view along line IV-IV in Figure 3. One embodiment of the present disclosure (hereinafter also referred to as "this embodiment") is an electric wire 1 comprising a conductor 2 and a coating 6 covering the conductor 2, wherein the coating 6 includes a first layer 3 and a second layer 4 arranged in contact with the outside of the first layer 3, the first layer 3 mainly comprising at least one resin selected from the group consisting of polyphenylene sulfide resin, polyurethane resin, polyester resin, and polyetheretherketone resin, and the second layer 4 mainly comprising silsesquioxane, the silsesquioxane being (RSio ３／２ The polymer contains constituent units derived from ), where R is a polymerizable group, and the thickness of the second layer 4 is 0.1 μm or more and 100 μm or less.

[0027] According to this disclosure, it is possible to provide an electric wire 1 that combines excellent heat resistance and excellent adhesion, and a multi-core cable equipped with the electric wire 1. The reason for this is presumed to be as follows.

[0028] (a) In the electric wire 1 of this embodiment, the second layer 4 mainly contains silsesquioxane, and the silsesquioxane is (RSio ３／２ The polymer contains constituent units derived from ), where R is a polymerizable group, and the thickness of the second layer 4 is 0.1 μm or more and 100 μm or less. As a result, the second layer 4 forms a dense protective film, which prevents oxidative degradation due to oxygen in the air, thereby improving the heat resistance of the electric wire 1.

[0029] (b) In the electric wire 1 of this embodiment, the first layer 3 mainly contains at least one resin selected from the group consisting of polyphenylene sulfide resin, polyurethane resin, polyester resin, and polyetheretherketone resin. This increases the polarity and wettability of the first layer, thereby improving adhesion.

[0030] As described above, it is possible to provide the electric wire 1 having excellent heat resistance and excellent adhesion, and the multi-core cable including the electric wire 1.

[0031] ≪Electric wire≫ The equivalent circle diameter of the cross section perpendicular to the longitudinal direction of the electric wire 1 may be 0.1 mm or more and 50 mm or less, may be 0.2 mm or more and 20 mm or less, or may be 0.5 mm or more and 10 mm or less. Here, the longitudinal direction can be rephrased as the "first direction" described later.

[0032] The equivalent circle diameter of the cross section perpendicular to the longitudinal direction of the electric wire 1 can be specified by the following method. First, except for the point where the measurement target is the electric wire 1, the average cross-sectional area of the electric wire 1 is obtained in the same manner as the average cross-sectional area of the conductor 2. Next, based on the "average cross-sectional area of the electric wire 1", the equivalent circle diameter (that is, the number obtained by multiplying the square root of "(average cross-sectional area of the electric wire 1) / π" by 2) is calculated, whereby the equivalent circle diameter of the cross section perpendicular to the longitudinal direction of the electric wire 1 can be specified.

[0033] Note that it has been confirmed that there is no variation in the measurement results even if the measurement location is arbitrarily changed as long as the measurement is performed on the same electric wire 1 by the above method.

[0034] ≪Conductor≫ The electric wire 1 includes a conductor 2. The material of the conductor 2 can be a metal material having high conductivity and high mechanical strength. Examples of such metal materials include copper, copper alloy, aluminum, aluminum alloy, nickel, silver, soft iron, steel, and stainless steel. The conductor 2 can be a wire formed by linearly forming one kind of metal material. Further, the conductor 2 can also be a multi-layer structure in which the wire is coated with another metal by a technique such as plating. Examples of the conductor 2 having a multi-layer structure include a tin-plated copper wire, a nickel-plated copper wire, a silver-plated copper wire, a copper-plated aluminum wire, and a copper-plated steel wire.

[0035] The shape of the conductor 2 is not particularly limited, and conventionally known shapes can be used. Examples of the shape of the conductor 2 include a round wire with a circular cross-section, a square wire with a square cross-section, a flat wire with a rectangular cross-section, and a stranded wire formed by twisting a plurality of strands.

[0036] The equivalent circle diameter of the cross-section perpendicular to the longitudinal direction of the conductor 2 may be 0.05 mm or more and 30 mm or less, may be 0.1 mm or more and 15 mm or less, or may be 0.3 mm or more and 8 mm or less. Here, the longitudinal direction can be rephrased as the "first direction" described later.

[0037] The equivalent circle diameter of the cross-section perpendicular to the longitudinal direction of the conductor 2 can be specified in the same manner as the equivalent circle diameter of the cross-section perpendicular to the longitudinal direction of the electric wire 1, except for the point where the measurement object is the conductor 2.

[0038] It has been confirmed that as long as it is measured by the above method in the same conductor 2, even if the measurement location is arbitrarily changed, there is no variation in the measurement results.

[0039] The average cross-sectional area of the conductor 2 is not particularly limited and can be appropriately selected according to the application. The average cross-sectional area of the conductor 2 may be 0.0015 mm ２ or more and 550 mm ２ or less, may be 0.006 mm ２ or more and 140 mm ２ or less, or may be 0.05 mm ２ or more and 40 mm ２ or less. In the present disclosure, the method for measuring the average cross-sectional area of the conductor 2 is as follows. Stretch one conductor 2 linearly, cut the conductor 2 with a plane having the first direction connecting one end to the other end as the normal line to expose the cross-section and measure the cross-sectional area. For one conductor 2, cut the conductor 2 with a plane having the first direction as the normal line at five arbitrary locations and measure the cross-sectional area, and calculate the average value (arithmetic mean). This average value corresponds to the average cross-sectional area of the conductor 2.

[0040] <Coating> The electric wire 1 is provided with a coating 6 that covers the conductor 2. The coating 6 includes a first layer 3 and a second layer 4 that is positioned in contact with the outside of the first layer 3. The coating 6 may consist only of the first layer 3 and the second layer 4, or it may include other layers described later in addition to the first layer 3 and the second layer 4. The second layer 4 may be located on the surface of the coating 6.

[0041] The thickness of the coating 6 may be between 0.025 mm and 10 mm. If the thickness of the coating 6 is less than 0.025 mm, the coating 6 tends to be more prone to damage. If the thickness of the coating 6 is greater than 10 mm, the electric wire 1 becomes stiff and difficult to bend, and the cost tends to increase. The thickness of the coating 6 may be between 0.050 mm and 2.5 mm, or between 0.150 mm and 1 mm.

[0042] In this disclosure, the thickness of the coating 6 can be determined by the following method: The electric wire 1 is straightened, and the electric wire 1 is cut in a plane normal to the first direction connecting one end of the electric wire 1 to the other, exposing the cross-section. The thickness of the coating 6 is measured at any three locations on the cross-section, and the average value (arithmetic mean) of these measurements is calculated. The electric wire 1 is cut at any five locations in a plane normal to the first direction, and the average value (arithmetic mean) is obtained for each of these measurements. The thickness of the coating 6 is determined by calculating the average value (arithmetic mean) of these measurements.

[0043] Furthermore, it has been confirmed that, as long as the measurement is performed on the same wire 1 using the above method, there is no variation in the measurement results even if the measurement location is arbitrarily changed.

[0044] <First Layer> The first layer 3 mainly contains at least one resin selected from the group consisting of polyphenylene sulfide resin, polyurethane resin, polyester resin, and polyetheretherketone resin. This improves the adhesion in the electric wire 1. Here, "mainly contains at least one resin selected from the group consisting of polyphenylene sulfide resin, polyurethane resin, polyester resin, and polyetheretherketone resin" means that the resin is contained in an amount of 50% by mass or more. The first layer 3 may consist of at least one resin selected from the group consisting of polyphenylene sulfide resin, polyurethane resin, polyester resin, and polyetheretherketone resin. "The first layer 3 may consist of at least one resin selected from the group consisting of polyphenylene sulfide resin, polyurethane resin, polyester resin, and polyetheretherketone resin" means that the first layer 3 may consist only of the resin, or it may contain other components (such as first unavoidable impurities) in addition to the resin, to the extent that it does not impair the effects of the present disclosure. Examples of first unavoidable impurities include crosslinking aids (such as triallyl isocyanurate and trimethylpententrimethacrylate), fillers (such as silica, talc, calcium carbonate, clay, and zinc oxide), lubricants (such as oleamide, erucamide, stearic acid, and zinc stearate), coloring pigments (such as inorganic pigments like titanium dioxide, organic pigments, and carbon), and flame retardants (such as brominated flame retardants, antimony trioxide, melamine cyanurate, magnesium hydroxide, and aluminum hydroxide). In this disclosure, polyphenylene sulfide resin can be replaced with PPS resin, polyurethane resin can be replaced with PU resin, polyester resin can be replaced with PEs resin, and polyetheretherketone resin can be replaced with PEEK resin. In this disclosure, polyphenylene sulfide resin is a concept that encompasses both uncrosslinked polyphenylene sulfide resin and crosslinked polyphenylene sulfide resin. Polyphenylene sulfide resin may be uncrosslinked polyphenylene sulfide resin.In this disclosure, polyurethane resin is a concept that encompasses both uncrosslinked polyurethane resin and crosslinked polyurethane resin. In this disclosure, polyester resin is a concept that encompasses both uncrosslinked polyester resin and crosslinked polyester resin. In this disclosure, polyetheretherketone resin is a concept that encompasses both uncrosslinked polyetheretherketone resin and crosslinked polyetheretherketone resin. Polyetheretherketone resin may be an uncrosslinked polyetheretherketone resin.

[0045] The weight-average molecular weight of the polyphenylene sulfide resin is not particularly limited, but may be, for example, 10,000 to 200,000, 20,000 to 150,000, or 30,000 to 100,000.

[0046] The polyurethane resin is not particularly limited as long as it is a polymer resin having urethane bonds, but for example, the polymer may be a copolymer having an aliphatic diol and a diisocyanate as constituent units. The lower limit of the number of carbon atoms in the aliphatic diol may be 3 or more, 4 or more, or 5 or more. The upper limit of the number of carbon atoms in the aliphatic diol may be 20 or less, 19 or less, or 18 or less. The number of carbon atoms in the aliphatic diol may be 3 or more and 20 or less, 4 or more and 19 or less, or 5 or more and 18 or less. The lower limit of the number of carbon atoms in the diisocyanate may be 5 or more, 6 or more, 7 or more, or 8 or more. The upper limit of the number of carbon atoms in the diisocyanate may be 15 or less, 14 or less, 13 or less, or 12 or less. The number of carbon atoms in the diisocyanate may be 5 or more and 15 or less, 6 or more and 14 or less, 7 or more and 13 or less, or 8 or more and 12 or less. The weight-average molecular weight of the polyurethane resin is not particularly limited, but may be, for example, 2,000 to 1,000,000, 3,000 to 500,000, or 10,000 to 300,000.

[0047] Examples of polyester resins include polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, and thermoplastic polyester elastomers.

[0048] The weight-average molecular weight of the polyether ether ketone resin is not particularly limited, but may be, for example, 5,000 to 50,000, 10,000 to 30,000, or 20,000 to 25,000.

[0049] The resin of the first layer 3 is a resin modified with a first functional group, and this first functional group may have a carboxyl group or an ether group. This makes it possible to provide an electric wire 1 and a multi-core cable equipped with the electric wire 1 that have both superior heat resistance and superior adhesion. The state of being "modified with a first functional group" means a state in which the first functional group is graft-bonded to the end or non-end of the polymer molecular chain, or a state in which the first functional group is copolymerized into the polymer molecular chain.

[0050] The first functional group may be at least one functional group selected from the group consisting of carboxyl groups, maleic anhydride groups, and epoxy groups. This increases the polarity and improves wettability in the first layer 3, making it possible to provide a wire 1 and a multi-core cable equipped with the wire 1 that have both superior heat resistance and superior adhesion.

[0051] The interface of the first layer 3 near the surface of the coating 6 may be treated to be hydrophilic. This increases the polarity and improves wettability in the first layer 3, making it possible to provide a wire and a multi-core cable equipped with such a wire that have both superior heat resistance and superior adhesion. Note that the state in which hydrophilic treatment has been applied means a state in which the chemical composition has changed and hydrophilic functional groups have been introduced.

[0052] The above hydrophilization treatment may be at least one selected from the group consisting of corona treatment, plasma treatment, ozone treatment, and etching treatment with activated sodium. This makes it possible to provide electric wires and multi-core cables equipped with such electric wires that have both superior heat resistance and superior adhesion.

[0053] The composition of the first layer 3 can be determined by combining the analysis of the chemical bonding state based on the measurement of nuclear magnetic resonance (NMR) spectra and infrared absorption spectra by Fourier transform infrared spectroscopy (FT-IR), with the measurement of the crystal melting temperature and heat of fusion using a differential scanning calorimeter.

[0054] The weight-average molecular weight of the resin in the first layer 3 may be between 10,000 and 5,000,000, between 50,000 and 2,000,000, or between 100,000 and 1,000,000. In the first layer 3, the weight-average molecular weight of the resin can be determined by measuring it using gel permeation chromatography (GPC) in accordance with JIS-K7252-1:2008 "Plastics - Method for determining the average molecular weight and molecular weight distribution of polymers by size exclusion chromatography - Part 1: General rules".

[0055] The thickness of the first layer 3 may be 0.025 mm or more and 10 mm or less. This provides better adhesion to the electric wire 1. It also makes the electric wire 1 easier to bend. The lower limit of the thickness of the first layer 3 may be 0.025 mm or more, 0.050 mm or more, 0.100 mm or more, or 0.200 mm or more. The upper limit of the thickness of the first layer 3 may be 10 mm or less, 2.5 mm or less, 1 mm or less, or 0.500 mm or less. The thickness of the first layer 3 may be 0.050 mm or more and 2.5 mm or less, or 0.100 mm or more and 1 mm or less.

[0056] The thickness of the first layer 3 can be determined in the same way as the thickness of the coating 6, except that the object of measurement is the first layer 3.

[0057] Furthermore, it has been confirmed that, as long as the measurement is performed on the same wire 1 using the above method, there is no variation in the measurement results even if the measurement location is arbitrarily changed.

[0058] <Layer 2> Layer 2, Layer 4, contains silsesquioxane as its main component. Here, "contains silsesquioxane as its main component" means that it contains silsesquioxane in an amount of, for example, 50% by mass or more. Silsesquioxane is (RSio ３／２ The polymer contains constituent units derived from (RSio), where R is a polymerizable group. These allow for excellent heat resistance to be imparted to the electric wire 1. The second layer 4 may consist of silsesquioxane. "The second layer 4 may consist of silsesquioxane" means that the second layer 4 may consist only of silsesquioxane, or may contain other components (such as second unavoidable impurities) in addition to silsesquioxane to the extent that it does not impair the effects of the present disclosure. Examples of second unavoidable impurities include photoradical polymerization initiators, thermal polymerization initiators, acrylic monomers, organic solvents, lubricants, and pigments. Silsesquioxane is (RSio ３／２ It may consist of constituent units derived from (RSIO). ３／２ The term "polymer containing constituent units derived from )" means that in the polymer, bonding between R and other R units may or may not occur.

[0059] Silsesquioxane may include at least one structure selected from the group consisting of random structures, ladder structures, perfect cage structures, and incomplete cage structures. Here, "random structure" means the structure represented by formula 1, "ladder structure" means the structure represented by formula 2, "perfect cage structure" means the structure represented by formula 3 or formula 4, and "incomplete cage structure" means the structure represented by formula 5 or formula 6. Note that the structure represented by formula 3 is "T ８ This can be rephrased as "T １０ This can be rephrased as:

[0060]

[0061]

[0062]

[0063] The polymerizable group may be a radical polymerizable group or a cationic polymerizable group. Because these polymerizable groups exhibit excellent polymerization reactivity, particularly photopolymerization reactivity, it is possible to provide a wire 1 and a multi-core cable equipped with the wire 1 that have superior heat resistance.

[0064] The polymerizable group may be one polymerizable group selected from the group consisting of acryloyl group, methacryloyl group, and oxetanyl group. These polymerizable groups have excellent polymerization reactivity, particularly photopolymerization reactivity, which makes it possible to provide a wire 1 and a multi-core cable equipped with the wire 1 that have superior heat resistance.

[0065] The composition of the second layer 4 can be determined by combining the analysis of the chemical bonding state based on the measurement of nuclear magnetic resonance (NMR) spectra and infrared absorption spectra by Fourier transform infrared spectroscopy (FT-IR), with the measurement of ash content by thermogravimetric analysis (TG).

[0066] The thickness of the second layer 4 is 0.1 μm or more and 100 μm or less. This allows the second layer 4 to fully exhibit its heat resistance effect, thereby improving the heat resistance of the electric wire 1. The lower limit of the thickness of the second layer 4 may be 0.1 μm or more, 0.5 μm or more, 1 μm or more, or 2 μm or more. The upper limit of the thickness of the second layer 4 may be 100 μm or less, 50 μm or less, 20 μm or less, or 10 μm or less. The thickness of the second layer 4 may be 0.5 μm or more and 50 μm or less, or 1 μm or more and 20 μm or less.

[0067] The thickness of the second layer 4 can be determined in the same way as the thickness of the coating 6, except that the object of measurement is the second layer 4.

[0068] Furthermore, it has been confirmed that, as long as measurements are taken using the above method within the same second layer 4, there is no variation in the measurement results even if the measurement location is arbitrarily changed.

[0069] <Third Layer> The coating 6 further includes a third layer 5 formed between the interface of the first layer 3 near the conductor 2 and the interface between the conductor 2 and the coating 6. The third layer 5 may contain at least one resin selected from the group consisting of polyolefin resin, polyester resin, and fluororesin as its main component. This results in excellent "interface adhesion" at the conductor-side interface of the third layer 5, making it possible to provide an electric wire and a multi-core cable equipped with such an electric wire with superior heat resistance. Here, "contains at least one resin selected from the group consisting of polyolefin resin, polyester resin, and fluororesin as its main component" means containing the resin in an amount of 50% by mass or more. The third layer 5 may consist of at least one resin selected from the group consisting of polyolefin resin, polyester resin, and fluororesin. The phrase "The third layer 5 may consist of at least one resin selected from the group consisting of polyolefin resin, polyester resin, and fluororesin" means that the third layer 5 may consist of only the resin, or may contain other components (such as second unavoidable impurities) in addition to the resin, to the extent that it does not impair the effects of the present disclosure. Examples of second unavoidable impurities include crosslinking aids (such as triallyl isocyanurate and trimethylpententrimethacrylate), fillers (such as silica, talc, calcium carbonate, clay, and zinc oxide), lubricants (such as oleamide, erucamide, stearic acid, and zinc stearate), coloring pigments (such as inorganic pigments such as titanium dioxide, organic pigments, and carbon), and flame retardants (such as brominated flame retardants, antimony trioxide, melamine cyanurate, magnesium hydroxide, and aluminum hydroxide). In this disclosure, polyolefin resin can be replaced with PO resin, and fluororesin can be replaced with Fl resin.

[0070] The above polyolefin resin is not particularly limited, but may be, for example, at least one polyolefin resin selected from the group consisting of ultra-low density polyethylene, low density polyethylene, linear low density polyethylene, high density polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-hexene copolymer, ethylene-octene copolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, and ethylene-butyl acrylate copolymer. The above polyester resin is not particularly limited, but may be, for example, at least one polyester resin selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycaprolactone, polylactic acid, polyglycolic acid, aromatic polyester, and thermoplastic polyester elastomer. The above fluororesin is not particularly limited, but may be, for example, at least one fluororesin selected from the group consisting of perfluoroalkoxyalkane resin, fluorinated ethylene propylene resin, ethylene tetrafluoroethylene copolymer resin, and crosslinked ethylene tetrafluoroethylene copolymer resin.

[0071] The resin of the third layer 5 is a resin modified with a second functional group, and this second functional group may have a carboxyl group or an ether group. This results in better "interface adhesion" at the conductor-side interface of the third layer 5, making it possible to provide an electric wire 1 and a multi-core cable equipped with this electric wire 1 with better heat resistance. The state of being "modified with a second functional group" means a state in which the second functional group is graft-bonded to the end or non-end of the polymer molecular chain, or a state in which the second functional group is copolymerized into the polymer molecular chain.

[0072] The second functional group may be at least one functional group selected from the group consisting of carboxyl groups, maleic anhydride groups, and epoxy groups. This results in better "interface adhesion" at the conductor-side interface of the third layer 5, making it possible to provide a wire 1 and a multi-core cable equipped with the wire 1 that have better heat resistance.

[0073] The interface of the third layer 5, which is close to the coating 6, may be treated to be hydrophilic. This results in better "interface adhesion" at the conductor-side interface of the third layer 5, making it possible to provide a wire and a multi-core cable equipped with such a wire that have superior heat resistance.

[0074] The above hydrophilization treatment may be at least one selected from the group consisting of corona treatment, plasma treatment, ozone treatment, and etching treatment with activated sodium. This makes it possible to provide electric wires with superior heat resistance and multi-core cables equipped with such electric wires.

[0075] The composition of the third layer 5 can be determined by combining the analysis of the chemical bonding state based on the measurement of nuclear magnetic resonance (NMR) spectra and infrared absorption spectra by Fourier transform infrared spectroscopy (FT-IR), with the measurement of the crystal melting temperature and heat of fusion using differential scanning calorimeter.

[0076] The weight-average molecular weight of the resin in the third layer 5 may be between 10,000 and 5,000,000, between 50,000 and 2,000,000, or between 100,000 and 1,000,000. In the third layer 5, the weight-average molecular weight of the resin can be determined by measuring it using gel permeation chromatography (GPC) in accordance with JIS-K7252-1:2008 "Plastics - Method for determining the average molecular weight and molecular weight distribution of polymers by size exclusion chromatography - Part 1: General rules".

[0077] The thickness of the third layer 5 may be 0.025 mm or more and 10 mm or less. This makes it less likely for gaps to form at the conductor-side interface of the third layer 5, and thus better "adhesion of the interface" can be achieved at the conductor-side interface of the third layer 5. It also makes it easier to bend the electric wire 1. The lower limit of the thickness of the third layer 5 may be 0.025 mm or more, 0.030 mm or more, 0.050 mm or more, 0.075 mm or more, or 0.1 mm or more. The upper limit of the thickness of the third layer 5 may be 5 mm or less, 3 mm or less, 2.5 mm or less, or 1 mm or less. The thickness of the third layer 5 may be 0.050 mm or more and 2.5 mm or less, or 0.150 mm or more and 1 mm or less.

[0078] The thickness of the third layer 5 can be determined in the same way as the thickness of the coating 6, except that the object of measurement is the third layer 5.

[0079] Furthermore, it has been confirmed that, as long as the measurement is performed on the same wire 1 using the above method, there is no variation in the measurement results even if the measurement location is arbitrarily changed.

[0080] <Other Layers> The coating 6 described above may further include other layers. Examples of these other layers include a base layer located between the conductor 2 and the third layer 5 when the third layer 5 is present, a base layer located between the conductor 2 and the first layer 3 when the third layer 5 is not present, and an intermediate layer located between the third layer 5 and the first layer 3 when the third layer 5 is present.

[0081] ≪Method for Manufacturing Electric Wires≫ The method for manufacturing the electric wire 1 of this embodiment includes, for example, a first step of preparing a conductor 2, a compound for forming the first layer 3, and a varnish for forming the second layer 4, in this order; a second step of forming the first layer 3 on the outer surface of the conductor 2; and a third step of forming the second layer 4 on the surface of the first layer 3. The first step includes a first A step of preparing the conductor 2, a first B step of preparing the compound for forming the first layer 3, and a first C step of preparing the varnish for forming the second layer 4. The method for manufacturing the electric wire 1 of this embodiment may further include a "step of forming other layers." The "step of forming other layers" can be carried out by conventionally known methods.

[0082] <First Step> <First A Step: Step to prepare the conductor> In the first A step, the conductor 2 is prepared. The conductor 2 may be prepared by manufacturing it using a conventionally known method, or by purchasing a commercially available product.

[0083] <Step 1B: Step to prepare the compound for forming the first layer> In Step 1B, the compound for forming the first layer 3 is prepared. For example, the compound for forming the first layer 3 can be prepared by the following method. First, at least one resin selected from the group consisting of polyphenylene sulfide resin, polyurethane resin, polyester resin, and polyetheretherketone resin is prepared as a raw material. In addition to the resin, for example, a crosslinking aid, lubricant, filler, etc. may be prepared as a raw material. Next, the compound for forming the first layer 3 can be prepared by kneading the raw materials.

[0084] The weight-average molecular weight of the resin may be 10,000 or more and 5,000,000 or less, 50,000 or more and 2,000,000 or less, or 100,000 or more and 1,000,000 or less.

[0085] The mixing process can be carried out, for example, using a roller heated to between 280°C and 350°C. The mixing time can be between 5 minutes and 30 minutes.

[0086] <Step 1C: Step to prepare varnish for forming the second layer> In Step 1C, the varnish for forming the second layer 4 is prepared. For example, the varnish for forming the second layer 4 can be prepared by the following method. First, a silsesquioxane derivative is prepared as a raw material. The silsesquioxane derivative may be prepared by manufacturing it using a conventionally known method, or it may be prepared by purchasing a commercially available product. In addition to the silsesquioxane derivative, for example, a photoradical polymerization initiator, an acrylic monomer, a solvent, etc., may be prepared as raw materials. Next, the varnish for forming the second layer 4 can be prepared by adding the photoradical polymerization initiator, etc., to the silsesquioxane derivative and stirring.

[0087] The stirring speed may be, for example, 10 rpm to 1000 rpm. The stirring temperature may be 10°C to 40°C. The stirring temperature may also be room temperature. The stirring time may be 5 minutes to 30 minutes.

[0088] <Step 1D: Step to prepare the compound for forming the third layer> In Step 1D, the compound for forming the third layer 5 is prepared. For example, the compound for forming the third layer 5 can be prepared by the following method. First, at least one resin selected from the group consisting of polyolefin resin, polyester resin, and fluororesin is prepared as a raw material. In addition to the resin, for example, a crosslinking aid, lubricant, filler, etc. may be prepared as a raw material. Next, the compound for forming the third layer 5 can be prepared by kneading the raw materials.

[0089] The weight-average molecular weight of the resin may be 10,000 or more and 5,000,000 or less, 50,000 or more and 2,000,000 or less, or 100,000 or more and 1,000,000 or less.

[0090] <Second Step> In the second step, a first layer 3 is formed on the outer surface of the conductor 2. For example, the first layer 3 can be formed by the following method. First, the compound for forming the first layer 3 is injected under pressure into an extruder set to a head temperature of 300°C to 350°C and a cylinder temperature of 280°C to 320°C. Next, the compound for forming the first layer 3 is extruded onto the outer surface of the conductor 2. In this way, the first layer 3 can be formed on the outer surface of the conductor 2.

[0091] In the second step, a third layer 5 may be formed on the outer surface of the conductor 2 before forming the first layer 3 on the outer surface of the conductor 2. For example, the third layer 5 can be formed by the following method. First, the compound for forming the third layer 5 is injected under pressure into an extruder set to a head temperature of 210°C to 300°C and a cylinder temperature of 190°C to 280°C. Next, the compound for forming the third layer 5 is extruded and coated onto the outer surface of the conductor 2. In this way, the third layer 5 can be formed on the outer surface of the conductor 2.

[0092] <Third Step> In the third step, the second layer 4 is formed on the surface of the first layer 3. For example, the second layer 4 can be formed by the following method. First, a varnish for forming the second layer 4 is applied to the surface of the first layer 3. Next, the second layer 4 can be formed on the surface of the first layer 3 by performing a light curing treatment on the varnish for forming the second layer 4 applied to the surface of the first layer 3 under the following conditions. Note that the third step may be repeated until the thickness of the second layer 4 reaches a predetermined thickness. (Conditions for light curing treatment) Light source: High-pressure mercury lamp (Input power: 10 W / cm or more and 300 W / cm or less) Lamp height: 1 cm or more and 50 cm or less Conveyor speed: 1 m / min or more and 10 m / min or less Cumulative light amount per pass: 1,000 mJ / cm ２ 30,000mJ / cm or more ２ Number of passes: 1 to 10 Atmosphere:

[0093] [Embodiment 2: Multi-core cable] The multi-core cable of this embodiment will be described with reference to Figures 5 and 6. Figure 5 is a schematic perspective view of a multi-core cable according to one embodiment of the present disclosure. Figure 6 is a schematic cross-sectional view along line VI-VI in Figure 5. The multi-core cable 100 of this embodiment comprises the electric wire 1 described in Embodiment 1.

[0094] According to this disclosure, it is possible to provide a multi-core cable having wires that possess both excellent heat resistance and excellent adhesion.

[0095] The multi-core cable 100 according to this embodiment is not particularly limited as long as it includes the electric wire 1 described in Embodiment 1, but examples include the multi-core cable 100 shown in Figures 5 and 6. In Figure 6, the multi-core cable 100 includes the electric wire 1 described in Embodiment 1 and a sheath layer 20 disposed around the electric wire 1. The sheath layer 20 may have an inner sheath layer 20a and an outer sheath layer 20b (outer covering). In this disclosure, the multi-core cable 100 means a cable comprising multiple electric wires. "The multi-core cable of this embodiment includes the electric wire 1 described in Embodiment 1" means that at least one of the multiple electric wires comprising the multi-core cable 100 described in this embodiment is the electric wire 1 described in Embodiment 1.

[0096] ≪Manufacturing Method for Multi-Core Cables≫ The manufacturing method for multi-core cables according to this embodiment can be carried out by the same method as conventionally known methods, except that the electric wire described in Embodiment 1 is used.

[0097] This embodiment will be described in more detail by reference to examples. However, this embodiment is not limited by these examples.

[0098] <<Preparation of Electric Wires>> Electric wires for samples 1-80 and 101-108 were prepared as follows.

[0099] <Step 1> Conductors listed in Tables 4-1 to 4-5 were prepared by purchasing commercially available products (Step 1A). In addition, the raw materials listed in Tables 1-1 to 1-5 were mixed with the composition listed in Tables 1-1 to 1-5 using rolls heated to the temperatures listed in Tables 1-1 to 1-5 for the time listed in Tables 1-1 to 1-5 to prepare the compound for forming the first layer (Step 1B). For the polyphenylene sulfide resin (PPS), Toray Industries' "Torelina A670R63" (product name) was used. For the polyurethane resin (PU), BASF's "Elastoran 1154D" (product name) was used. For the polyester resin (PEs), Mitsubishi Chemical's "Nichigo Polyester SP160" (product name) was used. For the polyetheretherketone resin (PEEK), Evonik's "VESTAKEP 1000G" (product name) was used. As a crosslinking agent, "Triallyl Isocyanurate (TAIC)" (trade name) manufactured by Mitsubishi Chemical Corporation was used. As the "unsaturated monomer having a maleic anhydride group" (hereinafter also referred to as the "first unsaturated monomer"), maleic anhydride manufactured by Tokyo Chemical Industry Co., Ltd. was used. As the "unsaturated monomer having a carboxyl group" (hereinafter also referred to as the "second unsaturated monomer"), acrylic acid manufactured by Tokyo Chemical Industry Co., Ltd. was used. As the "unsaturated monomer having an epoxy group" (hereinafter also referred to as the "third unsaturated monomer"), allyl glycidyl ether manufactured by Tokyo Chemical Industry Co., Ltd. was used.

[0100] Furthermore, a varnish for forming the second layer was prepared by adding raw materials other than the SQ derivatives listed in the "Step 1C" column of Tables 2-1 to 2-5 to the silsesquioxane (SQ) derivative in a composition described in the "Step 1C" column of Tables 2-1 to 2-5, and stirring under the conditions described in the "Step 1C" column of Tables 2-1 to 2-5 (Step 1C). Note that if "-" is written in all columns of the "Step 1C" column of Tables 2-1 to 2-5, it means that "Step 1C" was not performed. Note that the silsesquioxane derivatives listed in Tables 5-1 to 5-5 were used as the "SQ derivatives". As the silsesquioxane derivative in which R (polymerizable group) is an acryloyl group (radical polymerizable group), "AC-SQ TA-100" (trademark) manufactured by Toagosei Co., Ltd. was used. As a silsesquioxane derivative in which R (polymerizable group) is a methacryloyl group (radical polymerizable group), "MAC-SQ TM-100" (trademark) manufactured by Toagosei Co., Ltd. was used. As a silsesquioxane derivative in which R (polymerizable group) is an oxetanyl group (cationic polymerizable group), "QX-SQ SI-20" (trademark) manufactured by Toagosei Co., Ltd. was used. As a photoradical polymerization initiator, "BLUESIL PI 2074" (trademark) manufactured by ELKEM was used.

[0101] Furthermore, the compound for forming the third layer was prepared by kneading the raw materials listed in the "First D Process" column of Tables 2-1 to 2-5 with the composition listed in the "First D Process" column of Tables 2-1 to 2-5, using a roll heated to the temperature listed in the "First D Process" column of Tables 2-1 to 2-5, for the time listed in the "First D Process" column of Tables 2-1 to 2-5 (First D Process). The polyolefin resin (PO) listed in the "First D Process" column of Tables 2-1 to 2-5 was "Modic P512VB" (product name) manufactured by Mitsubishi Chemical Corporation. The polyester resin (PEs) listed in the "First D Process" column of Tables 2-1 to 2-5 was "Nichigo Polyester SP160" (product name) manufactured by Mitsubishi Chemical Corporation. The fluororesin (Fl) used in the "First D Process" column of Tables 2-1 to 2-5 was "Fluon LH8000" (product name) manufactured by AGC Corporation. If "-" is written in any of the "First D Process" columns of Tables 2-1 to 2-5, it means that "First D Process" was not performed.

[0102] <Second Step> First, the compound for forming the third layer was pressurized into an extruder, with the head set to the temperature described in the "Third Layer Formation Step" column of Tables 3-1 to 3-5, and the cylinder set to the temperature described in the "Third Layer Formation Step" column of Tables 3-1 to 3-5. Next, the compound for forming the third layer was extruded onto the outer circumference of the conductor so that the thickness of the third layer was as described in Tables 4-1 to 4-5. In this way, the third layer was formed on the outer surface of the conductor. Note that if "-" is written in all columns of the "Third Layer Formation Step" column of Tables 3-1 to 3-5, it means that the formation of the third layer was not performed.

[0103] Next, the compound for forming the first layer was pressurized into an extruder, with the head set to the temperature specified in the "First Layer Formation Process" column of Tables 3-1 to 3-5, and the cylinder set to the temperature specified in the "First Layer Formation Process" column of Tables 3-1 to 3-5. Next, if a third layer was present, the compound for forming the first layer was extruded onto the surface of the third layer so that the thickness of the first layer was as specified in Tables 4-1 to 4-5. If a third layer was not present, the compound for forming the first layer was extruded onto the outer surface of the conductor so that the thickness of the first layer was as specified in Tables 4-1 to 4-5. Next, unless "0" was entered in the "Electron Beam [kGy]" column of the "First Layer Formation Process" column in the "Second Process" column of Tables 3-1 to 3-5, the extruded compound for forming the first layer was irradiated with an electron beam of the dose specified in Tables 3-1 to 3-5. As described above, the first layer was formed on the outer surface of the conductor.

[0104] <Step 3> First, a varnish for forming the second layer was applied to the surface of the first layer. Next, the varnish for forming the second layer applied to the surface of the first layer was subjected to a light curing treatment under the following conditions to form the second layer on the surface of the first layer. The application of the varnish for forming the second layer and the light curing treatment were repeated until the thickness of the second layer was as shown in Tables 5-1 to 5-5. Note that if "-" is written in all the columns of the "Step 3" column in Tables 3-1 to 3-5, it means that "Step 3" was not performed. (Conditions for photocuring treatment) Light source: High-pressure mercury lamp (Input power [W / cm] is as described in the "Third Process" column of Tables 3-1 to 3-5) Lamp height: As described in the "Third Process" column of Tables 3-1 to 3-5 Conveyor speed: As described in the "Third Process" column of Tables 3-1 to 3-5 Cumulative light amount per pass: As described in the "Third Process" column of Tables 3-1 to 3-5 Number of passes: As described in the "Third Process" column of Tables 3-1 to 3-5 Atmosphere: Air

[0105] Based on the above, electric wires corresponding to samples 1-80 and 101-108 were manufactured. Furthermore, the electric wire corresponding to sample 109 was manufactured using the same method as the electric wire corresponding to sample 1 in Patent Document 1. The electric wire corresponding to sample 110 was manufactured using the same method as the electric wire corresponding to sample 1 in Patent Document 2.

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[0136] ≪Evaluation of Electric Wire Characteristics≫ <Composition of the First Layer> For each electric wire sample, the composition of the first layer was determined by the method described in Embodiment 1. The results obtained are recorded in the "Composition" column of the "First Layer" column in Tables 4-1 to 4-5. When a component name is listed in the "Composition" column of the "First Layer" column in Tables 4-1 to 4-5, it means that the first layer mainly contains the component listed in the "Composition" column of the "First Layer" column in Tables 4-1 to 4-5. For example, when "PPS" is listed in the "Composition" column of the "First Layer" column in Tables 4-1 to 4-5, it means that the first layer mainly contains polyphenylene sulfide resin.

[0137] <Composition of the Second Layer> For each sample of electric wire, the composition of the second layer was determined by the method described in Embodiment 1. The results obtained are recorded in the "Composition" column of the "Second Layer" column in Tables 5-1 to 5-5. When a component name is listed in the "Composition" column of the "Second Layer" column in Tables 5-1 to 5-5, it means that the second layer mainly contains the component listed in the "Composition" column of the "Second Layer" column in Tables 5-1 to 5-5. For example, if "SQ" is written in the "Composition" column of the "Second Layer" column in Tables 5-1 to 5-5, and "Acryloyl group (radical polymerizable group)" is written in the "R" column of the "Second Layer" column in Tables 5-1 to 5-5, the second layer mainly contains silsesquioxane, and the silsesquioxane is (RSio ３／２ The polymer contains constituent units derived from ), where R is a polymerizable group, and the polymerizable group is a radical polymerizable group and is an acryloyl group.

[0138] <Composition of the Third Layer> For each sample of electric wire, the composition of the third layer was determined by the method described in Embodiment 1. The results obtained are recorded in the "Composition" column of the "Third Layer" column in Tables 4-1 to 4-5. When a component name is listed in the "Composition" column of the "Third Layer" column in Tables 4-1 to 4-5, it means that the third layer mainly contains the component listed in the "Composition" column of the "Third Layer" column in Tables 4-1 to 4-5. For example, when "PO" is written in the "Composition" column of the "Third Layer" column in Tables 4-1 to 4-5, it means that the third layer mainly contains polyolefin resin.

[0139] <Thickness of the coating, thickness of the first layer, thickness of the second layer, and thickness of the third layer> For each wire sample, the thickness of the coating was determined by the method described in Embodiment 1. The results obtained are recorded in the "Thickness [mm]" column of the "Coating" column in Tables 5-1 to 5-5. For each wire sample, the thickness of the first layer was determined by the method described in Embodiment 1. The results obtained are recorded in the "Thickness [mm]" column of the "First Layer" column in Tables 4-1 to 4-5. For each wire sample, the thickness of the second layer was determined by the method described in Embodiment 1. The results obtained are recorded in the "Thickness [μm]" column of the "Second Layer" column in Tables 5-1 to 5-5. For each wire sample, the thickness of the third layer was determined by the method described in Embodiment 1. The results obtained are recorded in the "Thickness [μm]" column of the "Third Layer" column in Tables 4-1 to 4-5.

[0140] <Equivalent diameter of the cross-section perpendicular to the longitudinal direction of the electric wire> For each electric wire sample, the equivalent diameter of the cross-section perpendicular to the longitudinal direction of the electric wire was determined by the method described in Embodiment 1. The results obtained are recorded in the "Equivalent diameter of the cross-section [mm]" column of the "Electric Wire" column in Tables 5-1 to 5-5.

[0141] <Heat Resistance Evaluation Test 1> First, eight wires (length: 350 mm) for each sample were prepared. Next, the coating was removed from both ends of the wires, specifically from the end and from the area between the end and a point 25 mm away from the end in the longitudinal direction of the wire. Next, each of the eight wires (length: 350 mm) for each sample was left for 3000 hours in a constant temperature bath at 85±2°C, 100±2°C, 125±3°C, 150±3°C, 175±3°C, 200±3°C, 225±4°C, and 250±4°C, respectively. Next, after removing the wires from the constant temperature bath, they were left at room temperature for 16 hours. Next, a mandrel 11 having a diameter 1.5 times the equivalent circular diameter of the cross-section perpendicular to the longitudinal direction of the wire 12 was placed on a weight 13 with a mass of 5 kg and a winding speed of 1 s. －１ The wire was wrapped twice in two locations at room temperature (Figure 7). Next, after visually confirming that no conductors were exposed on each wire, the wire was immersed in salt water (3% by mass) for 10 minutes. Next, the wire was energized at 1 kV for 1 minute. Next, the presence or absence of coating damage was determined by visual inspection of the wire. Next, the heat resistance of the wire was evaluated based on the following evaluation criteria. The results obtained are recorded in the "Heat Resistance Evaluation Test 1" column of Tables 6-1 to 6-5. The closer the evaluation result is to H, the better the heat resistance of the wire. (Evaluation Criteria) A: No damage to the coating when the temperature of the constant temperature bath is 85±2℃ or lower B: No damage to the coating when the temperature of the constant temperature bath is 100±2℃ or lower C: No damage to the coating when the temperature of the constant temperature bath is 125±3℃ or lower D: No damage to the coating when the temperature of the constant temperature bath is 150±3℃ or lower E: No damage to the coating when the temperature of the constant temperature bath is 175±3℃ or lower F: No damage to the coating when the temperature of the constant temperature bath is 200±3℃ or lower G: No damage to the coating when the temperature of the constant temperature bath is 225±4℃ or lower H: No damage to the coating when the temperature of the constant temperature bath is 250±4℃ or lower

[0142] ≪Heat Resistance Evaluation Test 2≫ First, eight wires (length: 350 mm) for each sample were prepared. Next, the coating was removed from both ends of the wires, specifically from the end and from the area between the end and a point 25 mm away in the longitudinal direction of the wire. Next, each of the eight wires (length: 350 mm) for each sample was left for 240 hours in a constant temperature bath at 110±2°C, 125±3°C, 150±3°C, 175±3°C, 200±3°C, 225±4°C, 250±4°C, and 275±4°C, respectively. Next, after removing the wires from the constant temperature bath, they were left at room temperature for 16 hours. Next, a mandrel 11 having a diameter five times the equivalent circle diameter of the cross-section perpendicular to the longitudinal direction of the wire 12 was placed on a weight 13 with a mass of 5 kg and a winding speed of 1 s. －１ The wire was wrapped twice in two locations at room temperature (Figure 7). Next, after visually confirming that no conductors were exposed on each wire, the wire was immersed in salt water (3% by mass) for 10 minutes. Next, the wire was energized at 1 kV for 1 minute. Next, the presence or absence of coating damage was determined by visual inspection of the wire. Next, the heat resistance of the wire was evaluated based on the following evaluation criteria. The results obtained are recorded in the "Heat Resistance Evaluation Test 2" column of Tables 6-1 to 6-5. The closer the evaluation result is to H', the better the heat resistance of the wire. (Evaluation Criteria) A': No damage to the coating when the temperature of the constant temperature bath is 110±2℃ or lower B': No damage to the coating when the temperature of the constant temperature bath is 125±3℃ or lower C': No damage to the coating when the temperature of the constant temperature bath is 150±3℃ or lower D': No damage to the coating when the temperature of the constant temperature bath is 175±3℃ or lower E': No damage to the coating when the temperature of the constant temperature bath is 200±3℃ or lower F': No damage to the coating when the temperature of the constant temperature bath is 225±4℃ or lower G': No damage to the coating when the temperature of the constant temperature bath is 250±4℃ or lower H': No damage to the coating when the temperature of the constant temperature bath is 275±4℃ or lower

[0143] ≪Heat Resistance Evaluation Test 3≫ First, eight wires (length: 350 mm) for each sample were prepared. Next, the coating was removed from both ends of the wires, specifically from the end and from the area between the end and a point 25 mm away in the longitudinal direction of the wire. Next, each of the eight wires (length: 350 mm) for each sample was left for 6 hours in a constant temperature bath at 135±3°C, 150±3°C, 175±3°C, 200±3°C, 225±4°C, 250±4°C, 275±4°C, and 300±4°C, respectively. Next, after removing the wires from the constant temperature bath, they were left at room temperature for 16 hours. Next, a mandrel 11 having a diameter 1.5 times the equivalent circular diameter of the cross-section perpendicular to the longitudinal direction of the wire 12 was placed on a weight 13 with a mass of 5 kg and a winding speed of 1 s. －１ The wire was wrapped twice in two locations at room temperature (Figure 7). Next, after visually confirming that no conductors were exposed on each wire, the wire was immersed in salt water (3% by mass) for 10 minutes. Next, the wire was energized at 1 kV for 1 minute. Next, the presence or absence of coating damage was determined by visual inspection of the wire. Next, the heat resistance of the wire was evaluated based on the following evaluation criteria. The results obtained are recorded in the "Heat Resistance Evaluation Test 3" column of Tables 6-1 to 6-5. The closer the evaluation result is to H'', the better the heat resistance of the wire. (Evaluation Criteria) A'': No damage to the coating when the temperature of the constant temperature bath is 135±3℃ or lower B'': No damage to the coating when the temperature of the constant temperature bath is 150±3℃ or lower C'': No damage to the coating when the temperature of the constant temperature bath is 175±3℃ or lower D'': No damage to the coating when the temperature of the constant temperature bath is 200±3℃ or lower E'': No damage to the coating when the temperature of the constant temperature bath is 225±4℃ or lower F'': No damage to the coating when the temperature of the constant temperature bath is 250±4℃ or lower G'': No damage to the coating when the temperature of the constant temperature bath is 275±4℃ or lower H'': No damage to the coating when the temperature of the constant temperature bath is 300±4℃ or lower

[0144] <Adhesion Evaluation Test> For each sample of electric wire, adhesion evaluation was performed using the cross-cut method in accordance with JIS K5600-5-6 (ISO 2409). Specifically, first, six parallel cuts were made on the surface of the coating, and then six more parallel cuts were made perpendicular to these six parallel cuts, thereby forming a grid-like pattern of cuts on the surface of the coating. The depth of these cuts was limited to the interface between the first and second layers. Next, a tape approximately 75 mm long was applied to the surface of the coating so as to cover the grid-like pattern of cuts. Then, the tape was peeled off from one end within one second. The angle between the direction from one end of the tape to the other and the direction of peeling was 60°. The evaluation criteria were as follows. The results obtained are recorded in the "Adhesion Evaluation Test" column of Tables 6-1 to 6-5. A result of 0, 1, or 2 indicates excellent adhesion. If "-" is written in the "Adhesion Evaluation Test" column of Tables 6-1 to 6-5, it means that the second layer is not present and therefore evaluation was not possible (in other words, it means that excellent adhesion is not present). (Evaluation Criteria) 0: The edges of the cuts are perfectly smooth and there is no peeling at any of the grid lines (in other words, the area of ​​peeling is 0%). 1: Small peeling of the coating occurs at the intersections of the cuts (in other words, the area of ​​peeling is more than 0% but 5% or less). 2: The coating peels along the edges of the cuts, at the intersections, or both (in other words, the area of ​​peeling is more than 5% but 15% or less). 3: The paint film is partially or completely peeling along the edges of the cut, or various parts of the groove are partially or completely peeling, or both (in other words, the area of ​​peeling is more than 15% but not more than 35%). 4: The paint film is partially or completely peeling along the edges of the cut, or several grooves are partially or completely peeling, or both (in other words, the area of ​​peeling is 35% or less).5. Any degree of peeling that cannot be classified under evaluation criterion 4 (in other words, the area of ​​the peeled portion exceeds 35%).

[0145] The wires corresponding to samples 1 to 80 are examples. The wires corresponding to samples 101 to 110 are comparative examples. From the results in Tables 6-1 to 6-5, it was found that the wires corresponding to samples 1 to 80 possess both superior heat resistance and superior adhesion compared to the wires corresponding to samples 101 to 110.

[0146] Based on the above, it was found that the electric wires related to samples 1 to 80 possess both excellent heat resistance and excellent adhesion.

[0147] As described above, embodiments and examples of this disclosure have been explained, but it is also intended from the outset that the configurations of each of the above embodiments and examples may be combined as appropriate or modified in various ways.

[0148] The embodiments and examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the embodiments and examples described above, and all modifications within the scope of the claims are intended to be included in the meaning of equivalents and within the scope.

[0149] 1. Electric wire, 2. Conductor, 3. First layer, 4. Second layer, 5. Third layer, 6. Sheath, 11. Mandrel, 12. Electric wire, 13. Weight, 100. Multi-core cable

Claims

1. An electric wire comprising a conductor and a coating covering the conductor, wherein the coating includes a first layer and a second layer disposed in contact with the outside of the first layer, the first layer mainly comprises at least one resin selected from the group consisting of polyphenylene sulfide resin, polyurethane resin, polyester resin, and polyether ether ketone resin, and the second layer mainly comprises silsesquioxane, the silsesquioxane being (RSio ３／２ A wire comprising a polymer containing constituent units derived from ), wherein R is a polymerizable group, and the thickness of the second layer is 0.1 μm or more and 100 μm or less.

2. The electric wire according to claim 1, wherein the resin of the first layer is a resin modified with a first functional group, and the first functional group has a carboxyl group or an ether group.

3. The electric wire according to claim 2, wherein the first functional group is at least one functional group selected from the group consisting of a carboxyl group, a maleic anhydride group, and an epoxy group.

4. The electric wire according to claim 1, wherein the interface of the first layer near the surface of the coating is in a hydrophilic state.

5. The electric wire according to claim 4, wherein the hydrophilization treatment is at least one selected from the group consisting of corona treatment, plasma treatment, ozone treatment, and etching treatment with activated sodium.

6. The electric wire according to any one of claims 1 to 5, wherein the coating further comprises a third layer formed between the interface of the first layer near the conductor and the interface of the conductor and the coating, and the third layer mainly comprises at least one resin selected from the group consisting of polyolefin resin, polyester resin, and fluororesin.

7. The electric wire according to claim 6, wherein the resin of the third layer is a resin modified with a second functional group, and the second functional group has a carboxyl group or an ether group.

8. The electric wire according to claim 7, wherein the second functional group is at least one functional group selected from the group consisting of a carboxyl group, a maleic anhydride group, and an epoxy group.

9. The electric wire according to any one of claims 1 to 8, wherein the polymerizable group is a radical polymerizable group or a cationic polymerizable group.

10. The electric wire according to any one of claims 1 to 8, wherein the polymerizable group is one polymerizable group selected from the group consisting of an acryloyl group, a methacryloyl group, and an oxetanyl group.

11. A multi-core cable comprising the electric wire described in any one of claims 1 to 10.

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