Insulated wires and cables for information transmission

Abstract

An insulated wire according to one embodiment of the present disclosure is provided with: one or more linear conductors; and one or more insulating layers that are superposed on the outer circumferential surfaces of the insulators. With respect to this insulated wire, the insulating layers contain an olefin resin and an antioxidant; the content of the antioxidant is more than 1.0 part by mass but not more than 5.0 parts by mass relative to 100 parts by mass of the olefin resin; and the antioxidant is composed of a phenolic antioxidant and a sulfur-based antioxidant other than a sulfur-containing phenolic antioxidant.

Description

[Technical Field]

[0001] This disclosure relates to an insulated electric wire and a cable for information transmission. This application claims priority to Japanese Patent Application No. 2020-194761, filed on November 24, 2020. The entire contents of this Japanese patent application are incorporated herein by reference. [Background technology]

[0002] With the rise of autonomous driving technology and driver assistance functions in automobiles, there is a demand for ever greater capacity and speed in information transmission in automotive information cables.Since transmission loss is positively correlated with the signal frequency and the dielectric loss tangent of the insulating layer of the signal transmission cable, in order to increase the speed of signal transmission, it is necessary to reduce the dielectric loss tangent of the insulating layer, further reducing transmission loss and ensuring stable signal transmission.

[0003] In the prior art, a communication cable has been disclosed in which the dielectric loss of the insulating layer in the high frequency band is small and the cable has a long life even when used in a high temperature environment by using an electrical insulating material containing a phenolic antioxidant that does not have a hindered phenol structure in the insulating layer (see JP 2009-81132 A). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-81132 Summary of the Invention

[0005] An insulated wire according to one embodiment of the present disclosure includes one or more linear conductors and one or more insulating layers laminated on an outer peripheral surface of the conductors, wherein the insulating layers contain an olefin-based resin and an antioxidant, the antioxidant content being more than 1.0 part by mass and not more than 5.0 parts by mass per 100 parts by mass of the olefin-based resin, and the antioxidant is composed of a phenol-based antioxidant and a sulfur-based antioxidant excluding a sulfur-containing phenol-based antioxidant. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic cross-sectional view of an insulated wire according to one embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic cross-sectional view of a twin-ax cable according to one embodiment of the present disclosure. [Figure 3] FIG. 3 is a schematic perspective view of a coaxial cable according to an embodiment of the present disclosure. [Figure 4] FIG. 4 is a schematic cross-sectional view of the coaxial cable of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0007] [Problem to be solved by this disclosure] In the above-mentioned conventional technology, if the insulating layer contains an additive such as an antioxidant, the dielectric loss tangent may increase. In the above-mentioned in-vehicle information cable, the dielectric loss tangent has a large effect on signal attenuation as a transmission line. Meanwhile, insulating materials used in in-vehicle information cables and the like are desired to have improved heat resistance while maintaining their electrical properties.

[0008] The present disclosure has been made in light of the above circumstances, and an object of the present disclosure is to provide an insulated wire that suppresses an increase in the dielectric loss tangent of an insulating layer and has excellent heat resistance.

[0009] [Effects of this disclosure] According to the present disclosure, it is possible to provide an insulated wire that suppresses an increase in the dielectric loss tangent of an insulating layer and has excellent heat resistance.

[0010] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0011] An insulated wire according to one embodiment of the present disclosure includes one or more linear conductors and one or more insulating layers laminated on an outer peripheral surface of the conductors, wherein the insulating layers contain an olefin-based resin and an antioxidant, the antioxidant content being more than 1.0 part by mass and not more than 5.0 parts by mass per 100 parts by mass of the olefin-based resin, and the antioxidant is composed of a phenol-based antioxidant and a sulfur-based antioxidant excluding a sulfur-containing phenol-based antioxidant.

[0012] The insulating layer of the insulated wire contains an olefin-based resin having low polarity, thereby effectively reducing the dielectric loss tangent. Furthermore, the insulating layer contains an antioxidant composed of a phenol-based antioxidant and a sulfur-based antioxidant excluding sulfur-containing phenol-based antioxidants, and the antioxidant content is within the above range. This suppresses thermal degradation of the olefin-based resin and an increase in the dielectric loss tangent, while improving the heat resistance, or durability of the insulating layer in high-temperature environments. Therefore, the insulated wire suppresses an increase in the dielectric loss tangent of the insulating layer and has excellent heat resistance.

[0013] The mass ratio of the phenolic antioxidant to the sulfur-based antioxidant may be 4: 1 to 1: 4. When the mass ratio of the phenolic antioxidant to the sulfur-based antioxidant is within the above range, heat resistance can be further improved.

[0014] The phenolic antioxidant may have a less hindered phenol structure represented by the following formula (2) or a semi-hindered phenol structure represented by the following formula (1).

[0015] [ka] (In formulas (1) and (2), R 1 ~R 4 is a methyl group.5 is a substituent.)

[0016] When the phenol-based antioxidant has the less hindered phenol structure represented by the formula (2) or the semi-hindered phenol structure represented by the formula (1), the effect of reducing the dielectric tangent of the insulating layer and the heat resistance can be further improved.

[0017] The sulfur-based antioxidant may be one represented by the following formula (3) or (4): [ka] (In formulas (3) and (4), X 1 is -S- or -NH-, R 6 is an alkyl group. When the insulated wire contains the sulfur-based antioxidant represented by the formula (3) or (4), the heat resistance can be further improved.

[0018] The olefin-based resin may be polypropylene. When the olefin-based resin is polypropylene, the effect of reducing the dielectric loss tangent of the insulating layer can be further improved.

[0019] The insulating layer may further contain a metal damage inhibitor. By further containing the metal damage inhibitor in the insulating layer, metal damage can be suppressed, and oxidative degradation of the olefin-based resin can be suppressed. Therefore, the dielectric loss tangent of the insulating layer can be further reduced. Here, "metal damage" generally refers to the promotion of oxidative degradation of a material due to the catalytic action of a metal in contact with the material.

[0020] When a high frequency electric field of 10 GHz is applied, the dielectric loss tangent of the insulating layer is 4.2 × 10 -4 If the dielectric loss tangent of the insulating layer is within the above range when a high frequency electric field of 10 GHz is applied, the effect of reducing transmission loss can be sufficiently improved.

[0021] Another aspect of the present disclosure is an information transmission cable including one or more of the insulated wires.

[0022] The information transmission cable includes the insulated wire, which prevents an increase in the dielectric loss tangent of the insulating layer and has excellent heat resistance, thereby improving durability and reducing transmission loss in high-temperature environments.

[0023] [Details of the embodiments of the present disclosure] Hereinafter, an insulated wire and an information transmission cable according to an embodiment of the present disclosure will be described in detail with reference to the drawings as appropriate.

[0024] <Insulated wire> The insulated wire includes one or more linear conductors and one or more insulating layers laminated on the outer peripheral surface of the conductors. Fig. 1 is a schematic cross-sectional view of an insulated wire according to one embodiment of the present disclosure. As shown in Fig. 1, the insulated wire 1 includes a linear conductor 2 and one insulating layer 3 laminated on the outer peripheral surface of the conductor 2.

[0025] [conductor] The conductor 2 is, for example, a round wire having a circular cross section, but may also be a rectangular wire having a square cross section or a flat wire having a rectangular cross section, or a twisted wire made by twisting together a plurality of wires.

[0026] A metal having high electrical conductivity and high mechanical strength is preferred as the material for the conductor 2. Examples of such metals include copper, copper alloys, aluminum, aluminum alloys, nickel, silver, mild steel, steel, and stainless steel. The conductor 2 can be made of a wire-shaped material made of any of these metals, or a multilayer structure in which such a wire-shaped material is further coated with another metal, such as a nickel-coated copper wire, a silver-coated copper wire, a copper-coated aluminum wire, or a copper-coated steel wire.

[0027] The lower limit of the average cross-sectional area of ​​the conductor 2 is 0.01 mm 2 is preferable, and 0.1 mm 2 On the other hand, the upper limit of the average cross-sectional area of ​​the conductor 2 is 10 mm 2is preferable, and 5 mm 2 It is more preferable that the average cross-sectional area of ​​the conductor 2 is 0.01 mm 2 If the average cross-sectional area of ​​the conductor 2 is less than 10 mm, the volume of the insulating layer 3 relative to the conductor 2 becomes large, which may reduce the volume efficiency of a coil or the like formed using the insulated wire. 2 If the dielectric constant exceeds this value, the insulating layer 3 must be made thicker to sufficiently reduce the dielectric constant, which may result in the insulated wire having an unnecessarily large diameter. Note that the "average cross-sectional area" of a conductor refers to the average value obtained by measuring the cross-sectional areas of 10 conductors at any given point.

[0028] [Insulating layer] The insulating layer 3 is formed on the outer peripheral surface of the conductor 2 .

[0029] The insulating layer 3 contains an olefin resin and an antioxidant.

[0030] The insulating layer 3 contains an olefin-based resin with low polarity, which can effectively reduce the dielectric loss tangent. Examples of the olefin-based resin include polypropylene, polypropylene-based thermoplastic elastomer, reactor-type polypropylene-based thermoplastic elastomer, dynamically crosslinked polypropylene-based thermoplastic elastomer, polyethylene (high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), and very low-density polyethylene (VLDPE)), ethylene-propylene copolymer, polymethylpentene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl methacrylate copolymer, ethylene-butyl acrylate copolymer, ethylene-propylene rubber, ethylene-acrylic rubber, ethylene-glycidyl methacrylate copolymer, and polyethylene resins such as ethylene-methacrylic acid copolymer, and ionomer resins in which ethylene-acrylic acid copolymer molecules are intermolecularly bonded by metal ions such as sodium and zinc. Other examples include those resins modified with maleic anhydride, etc., and those containing epoxy groups, amino groups, or imide groups. "High-density polyethylene (HDPE)" refers to a material with a density of 0.942 g / cm 3 "Linear low-density polyethylene (LLDPE)" refers to polyethylene with a density of 0.910 g / cm or more. 3 More than 0.930g / cm 3 "Low-density polyethylene (LDPE)" refers to polyethylene obtained by copolymerizing ethylene with an α-olefin, with a density of less than 0.910 g / cm. 3 More than 0.930g / cm 3 "Very low density polyethylene (VLDPE)" means polyethylene with a density of less than 0.870 g / cm and obtained by polymerizing ethylene by high-pressure polymerization. 3 More than 0.910g / cm 3"Polymethylpentene" refers to polyethylene of less than 100% by mass. Examples of "polymethylpentene" include homopolymers of 4-methyl-1-pentene, and copolymers of 4-methyl-1-pentene with 3-methyl-1-pentene or other α-olefins. Examples of such α-olefins include propylene, butene, pentene, hexene, heptene, octene, vinyl acetate, methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate.

[0031] Among these, polypropylene is preferred as the olefin-based resin, and polypropylene having a melting point of 140°C or higher is more preferred. Examples of polypropylene include homopolypropylene, random polypropylene, and block polypropylene. Homopolypropylene is a homopolymer of propylene. Examples of random polypropylene include copolymers of propylene with ethylene or an α-olefin having 4 to 20 carbon atoms. Block polypropylene is a resin composed of homopolypropylene as the main component, a random copolymer elastomer as a copolymer component, and an ethylene polymer as an optional component. Among these, block polypropylene or homopolypropylene is more preferred in terms of mechanical strength. When the olefin-based resin is such a polypropylene, the dielectric tangent reduction effect and heat resistance of the insulating layer can be further improved. Note that the "main component" refers to the component with the largest content.

[0032] The lower limit of the content of the olefin-based resin in the insulating layer 3 is preferably 95.0 mass %, more preferably 98.0 mass %. If the content of the olefin-based resin is less than 95.0 mass %, it may be difficult to satisfactorily reduce the dielectric tangent of the insulating layer. On the other hand, the upper limit of the content of the olefin-based resin is preferably 99.9 mass %, more preferably 99.5 mass %. If the content of the olefin-based resin exceeds 99.9 mass %, the content of antioxidants and the like in the insulating layer may be insufficient, and the effect of improving the heat resistance of the insulating layer may not be sufficiently high.

[0033] The insulating layer 3 may contain a resin other than the olefin-based resin, such as polytetrafluoroethylene, acrylic resin, or fluororubber, as a processability improver in an amount of 0.1% by mass to 5.0% by mass.

[0034] (antioxidant) The antioxidant prevents oxidation of the insulating layer 3. The antioxidant is composed of a phenol-based antioxidant and a sulfur-based antioxidant excluding sulfur-containing phenol-based antioxidants. The insulated wire contains an olefin-based resin that is prone to oxidative degradation, but by using the antioxidant composed of a phenol-based antioxidant and a sulfur-based antioxidant excluding sulfur-containing phenol-based antioxidants, the heat resistance of the insulating layer 3 can be further improved.

[0035] The mass ratio of the phenolic antioxidant to the sulfur-based antioxidant is preferably 4: 1 to 1: 4. When the mass ratio of the phenolic antioxidant to the sulfur-based antioxidant is within the above range, heat resistance can be further improved.

[0036] The phenolic antioxidant preferably has a less-hindered phenol structure represented by the following formula (2) or a semi-hindered phenol structure represented by the following formula (1): When the phenolic antioxidant has a less-hindered phenol structure represented by the following formula (2) or a semi-hindered phenol structure represented by the following formula (1), the effect of reducing the dielectric tangent of the insulating layer and the heat resistance can be further improved.

[0037] [ka]

[0038] In the above formulas (1) and (2), R 1 ~R 4 is a methyl group. 5 is a substituent.

[0039] Specific examples of antioxidants having a semi-hindered phenol structure include 3,9-bis[2-{3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy}-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5,5]undecane (e.g., Sumilizer GA-80 manufactured by Sumitomo Chemical Co., Ltd., Adeka STAB AO-80 manufactured by Adeka Corporation), ethylene bis(oxyethylene) bis[3-(5-tert-butyl-hydroxy-m-tolyl)propionate] (e.g., Irganox 245 manufactured by BASF Japan Ltd.), and triethylene glycol bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate] (e.g., Adeka STAB AO-70 manufactured by Adeka Corporation).

[0040] Specific examples of antioxidants having a resembling phenol structure include 4,4'-thiobis(6-tert-butyl-m-cresol) (e.g., Sumilizer WX-R manufactured by Sumitomo Chemical Co., Ltd.), 4,4'-butylidenebis(3-methyl-6-tert-butylphenol) (e.g., Nocrac NS-30 manufactured by Ouchi Shinko Chemical Industry Co., Ltd., and Adeka STAB AO-40 manufactured by Adeka Corporation), 4,4'-thiobis(3-methyl-6-tert-butyl)phenol (e.g., Nocrac 300 manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), 1,1,3-tris-(2-methyl-4-hydroxy-5-tert-butylphenyl)butane (e.g., Adeka STAB AO-30 manufactured by Adeka Corporation), and bis[3,3-bis(3-tert-butyl-4-hydroxyphenyl)butyrate]ethylene (e.g., HOSTANOX O3 manufactured by Clariant Chemicals).

[0041] The sulfur-based antioxidant is preferably represented by the following formula (3) or (4): When the insulated wire contains the sulfur-based antioxidant represented by the following formula (3) or (4), the heat resistance can be further improved.

[0042] [ka]

[0043] In the above formulas (3) and (4), X 1 is -S- or -NH-, R 6 is an alkyl group.

[0044] Examples of the sulfur-based antioxidant represented by the above formula (3) include 2-mercaptobenzothiazole (for example, Sancerer M manufactured by Sanshin Chemical Industry Co., Ltd.) and 2-mercaptobenzimidazole (for example, Sumilizer MB manufactured by Sumitomo Chemical Co., Ltd.).

[0045] Examples of the sulfur-based antioxidant represented by the above formula (4) include distearyl thiodipropionate (Irganox PS802FL manufactured by BASF), pentaerythritol tetrakis-(3-dodecylthiopropionate) (Seenox 412s manufactured by Shipro Chemicals), didodecylthiodipropionate (Seenox DL manufactured by Shipro Chemicals), ditetradecylthiodipropionate (Seenox DM manufactured by Shipro Chemicals), and dioctadecylthiodipropionate (Seenox DS manufactured by Shipro Chemicals).

[0046] Of these, 2-mercaptobenzothiazole and pentaerythritol tetrakis-(3-dodecylthiopropionate) are preferred as the sulfur-based antioxidant, from the viewpoint of further improving the effect of reducing the dielectric tangent of the insulating layer and the heat resistance.

[0047] The lower limit of the antioxidant content in the insulating layer is more than 1.0 part by mass, preferably 2.0 parts by mass, and more preferably 4.0 parts by mass, per 100 parts by mass of the olefin-based resin. If the antioxidant content is 1.0 part by mass or less, it may be difficult to improve the effect of suppressing thermal degradation of the olefin-based resin and an increase in the dielectric loss tangent. On the other hand, the upper limit of the antioxidant content is 5.0 parts by mass, preferably 4.9 parts by mass, and more preferably 4.8 parts by mass, per 100 parts by mass of the olefin-based resin. If the antioxidant content exceeds 5.0 parts by mass, the effect of suppressing an increase in the dielectric loss tangent may be reduced, which may impair the electrical properties of the insulated wire.

[0048] (Metal Deterioration Inhibitor) It is preferable that the insulating layer further contains a metal damage inhibitor. The metal damage inhibitor stabilizes metal ions by chelate formation and suppresses deterioration of the coating resin caused by metal ions, so-called metal damage. By further containing a metal damage inhibitor in the insulating layer, metal damage can be suppressed and oxidative deterioration of the olefin-based resin can be suppressed. Therefore, the dielectric loss tangent of the insulating layer can be further reduced. The metal damage inhibitor in this embodiment is preferably a copper damage inhibitor.

[0049] The lower limit of the melting point of the metal damage inhibitor is 200° C., and more preferably 220° C. When the lower limit of the melting point of the metal damage inhibitor is 200° C., the effect of reducing the dielectric tangent of the insulating layer and the effect of suppressing metal damage can be improved.

[0050] The metal damage inhibitor is not particularly limited, and examples thereof include salicylic acid derivatives, phthalic acid derivatives, triazole compound complexes, and aromatic secondary amine compounds. Examples of the salicylic acid derivatives include N-N'-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyl]hydrazine (product name: Irganox MD1024, melting point 60°C to 67°C), 3-(N-salicyloyl)amino-1,2,4-triazole (product name: Adekastab CDA-1, melting point 315°C to 325°C), and decamethylenedicarboxylic acid disalicyloylhydrazide (product name: Adekastab CDA-6, melting point 209°C to 215°C). Examples of the phthalic acid derivatives include isophthalic acid bis(2-phenoxypropionylhydrazide) (product name: CUNOX, melting point 225°C). Examples of the triazole compound complex include a complex containing 2-hydroxy-N-1H-1,2,4-triazol-3-ylbenzamide as the main component (product name: Adekastab CDA-1M, melting point 214°C or higher), etc. Examples of the aromatic secondary amine compound include N,N'-di-2-naphthyl-p-phenylenediamine (product name: Nocrac White, melting point 225°C or higher).

[0051] Among these, from the viewpoint of further improving the metal damage suppression effect, salicylic acid derivatives, phthalic acid derivatives, or a combination thereof are preferred, and 3-(N-salicyloyl)amino-1,2,4-triazole and isophthalic acid bis(2-phenoxypropionylhydrazide) are more preferred. The above metal damage inhibitors can be used singly or in combination.

[0052] The lower limit of the content of the metal damage inhibitor relative to 100 parts by mass of the olefin-based resin is preferably 0.05 parts by mass, more preferably 0.2 parts by mass, and even more preferably 0.5 parts by mass. If the mass ratio of the metal damage inhibitor is less than 0.05 parts by mass, it may be difficult to improve the metal damage suppression effect. On the other hand, the upper limit of the mass ratio of the metal damage inhibitor is preferably 2.0 parts by mass, more preferably 1.0 part by mass. If the mass ratio of the metal damage inhibitor exceeds 2.0 parts by mass, additives in the insulating layer may precipitate from the resin onto the surface and crystallize, causing so-called blooming, which may impair the quality of the insulating layer.

[0053] (Other ingredients) The insulating layer may contain, in addition to the olefin resin and antioxidant, other components such as a flame retardant, a flame retardant assistant, a pigment, an antioxidant, and the like.

[0054] The flame retardant imparts flame retardancy to the insulating layer, and examples of the flame retardant include halogen-based flame retardants such as chlorine-based flame retardants and bromine-based flame retardants.

[0055] The flame retardant aid further improves the flame retardancy of the insulating layer. Examples of the flame retardant aid include antimony trioxide.

[0056] The pigment is used to color the insulating layer, and various known pigments can be used, such as titanium oxide.

[0057] The upper limit of the dielectric loss tangent of the insulating layer when a high frequency electric field of 10 GHz is applied is 4.2 × 10 -4is preferred, and 3.0 × 10 -4 is more preferable, and 2.0 × 10 -4 It is more preferable that the dielectric loss tangent of the insulating layer is 4.2×10 -4 By keeping the value of the transmission loss at 1000 W or less, the effect of reducing the transmission loss can be sufficiently improved.

[0058] The upper limit of the relative dielectric constant of the insulating layer is preferably 2.5, more preferably 2.3. If the relative dielectric constant exceeds 2.5, there is a risk that the transmission loss cannot be sufficiently reduced and a sufficient transmission speed cannot be obtained.

[0059] The above "dielectric loss tangent" and "relative dielectric constant" are values ​​measured according to a method conforming to JIS-R1641 (2007).

[0060] The lower limit of the average thickness of the insulating layer 3 is preferably 50 μm, more preferably 100 μm. On the other hand, the upper limit of the average thickness of the insulating layer 3 is preferably 1500 μm, more preferably 1000 μm. If the average thickness of the insulating layer 3 is less than 50 μm, the insulating properties may be reduced. Conversely, if the average thickness of the insulating layer 3 exceeds 1500 μm, the volume efficiency of a cable or the like formed using the insulated wire may be reduced. The "average thickness" of the insulating layer refers to the average value obtained by measuring the thickness of the insulating layer at 10 arbitrary points.

[0061] [Insulated wire manufacturing method] Next, a method for producing the insulated wire will be described. The insulating layer 3 of the insulated wire is formed by extrusion molding. The method for producing the insulated wire includes a step (extrusion step) of extruding a resin composition for forming an insulating layer onto the outer peripheral surface of the conductor 2. The structure of the resin composition for forming an insulating layer is the same as that of the insulating layer described above, and therefore a description thereof will be omitted.

[0062] <Advantages> The insulated wire suppresses an increase in the dielectric loss tangent of the insulating layer and has excellent heat resistance.

[0063] <Information transmission cable> The information transmission cable includes one or more of the insulated wires. Examples of the information transmission cable include a differential transmission cable and a coaxial cable.

[0064] [Differential transmission cable] A differential transmission cable is a cable for transmitting differential signals and is suitable for use in fields requiring high-speed communication. An example of a differential transmission cable is a twin-ax cable having a twin-ax structure.

[0065] FIG. 2 is a schematic cross-sectional view of a twin-ax cable, one embodiment of the information transmission cable. As shown in FIG. 2, twin-ax cable 10 has a twin-ax structure with a pair of insulated wires, each consisting of a first insulated wire 1a and a second insulated wire 1b. First insulated wire 1a has a linear conductor 2a and one insulating layer 3a laminated on the outer surface of conductor 2a. Second insulated wire 1b has a linear conductor 2b and one insulating layer 3b laminated on the outer surface of conductor 2b. The first insulated wire 1a and second insulated wire 1b are made of the insulated wires. Twin-ax cable 10 also has a train wire 5, which is a third conductor, and a shielding tape 30 arranged to cover insulated wires 1a, 1b, and train wire 5.

[0066] When a twin-axial cable is used as the information transmission cable, it is possible to efficiently transmit signals at high speed and with high precision. Furthermore, by grounding the train wire 5, it is possible to prevent static electricity from building up in the twin-axial cable 10. Furthermore, by including the shielding tape 30, it is possible to prevent interference from external electromagnetic noise and reduce interference between the signal lines of the signal line pair.

[0067] The shielding tape 30 is an insulating film made of a resin such as polyvinyl chloride resin or flame-retardant polyolefin resin, with a conductive layer provided on one side. For example, a tape-shaped material such as copper-coated PET tape can be used as the shielding tape 30. The inclusion of the shielding tape 30 prevents external electromagnetic noise interference and reduces interference between the signal lines of a signal line pair. In this embodiment, the shielding tape 30 is arranged to cover the outer periphery of the insulating layers 3a and 3b. The shielding tape 30 is arranged on the outer periphery of the first insulating layer 3a and the second insulating layer 3b so as to wrap the first insulated wire 1a, the second insulated wire 1b, and the train wire 5 and fix the relative positional relationship between the first insulated wire 1a and the second insulated wire 1b.

[0068] [Twinax cable manufacturing method] A method for manufacturing a twin-ax cable, which is one embodiment of the information transmission cable, is, for example, to manufacture the twin-ax cable by bundling a first insulated wire and a second insulated wire together, arranging a train wire, which is a third conductor, and wrapping a shielding tape around the outer periphery.

[0069] [Coaxial cable] A coaxial cable, which is one embodiment of the information transmission cable, includes the insulated wire described above, an outer conductor covering the circumferential surface of the insulated wire, and an outer jacket layer covering the circumferential surface of the outer conductor, and the insulated wire includes one of the conductors and one of the insulating layers covering the circumferential surface of the conductor. This embodiment of the coaxial cable will be described with reference to Figures 3 and 4.

[0070] 3 and 4 includes an insulated wire 1 having a conductor 2 and an insulating layer 3 covering the circumferential surface of the conductor 2, an outer conductor 45 covering the circumferential surface of the insulated wire 1, and an outer jacket layer 46 covering the circumferential surface of the outer conductor 45. That is, the coaxial cable 40 has a cross-sectional configuration in which the conductor 2, the insulating layer 3, the outer conductor 45, and the outer jacket layer 46 are concentrically stacked. The information transmission cable is a coaxial cable 40, which enables a reduction in diameter. The insulated wire 1, the conductor 2, and the insulating layer 3 are the same as those of the insulated wire 1 in FIG. 1, and therefore the same reference numerals are used and their description will be omitted.

[0071] The outer conductor 45 serves as a ground and as a shield to prevent electrical interference from other circuits. This outer conductor 45 covers the outer surface of the insulating layer 3. Examples of the outer conductor 45 include a braided shield, a horizontally wound shield, a tape shield, a conductive plastic shield, and a metal tube shield. Among these, braided shields and tape shields are preferred from the viewpoint of high-frequency shielding. When a braided shield or a metal tube shield is used as the outer conductor 45, the number of shields can be determined appropriately depending on the shield to be used and the desired shielding properties. A single shield or a multiple shield such as a double shield or a triple shield may be used.

[0072] The outer covering layer 46 protects the conductor 2 and the outer conductor 45, and provides insulation as well as flame retardancy, weather resistance, etc. This outer covering layer 46 preferably contains a thermoplastic resin as a main component.

[0073] Examples of the thermoplastic resin include polyvinyl chloride, polyolefins such as low-density polyethylene, high-density polyethylene, foamed polyethylene, and polypropylene, polyurethane, and fluororesin. Among these, polyolefins and polyvinyl chloride are preferred from the viewpoints of cost and ease of processing. The above-listed materials may be used alone or in combination of two or more, and may be selected appropriately depending on the function to be achieved by the outer covering layer 46.

[0074] [Coaxial cable manufacturing method] The coaxial cable 40 is formed by covering the insulated wire 1 with an outer conductor 45 and an outer sheath layer 46 .

[0075] The covering with the outer conductor 45 can be performed by a known method depending on the shielding method to be applied. For example, a braided shield can be formed by inserting the insulated wire 1 into a tubular braid and then shrinking the braid. A horizontally wound shield can be formed by winding a metal wire such as a copper wire around the insulating layer 3. A tape shield can be formed by winding a conductive tape such as an aluminum-polyester laminate tape around the insulating layer 3.

[0076] The covering with the outer sheath layer 46 can be performed in the same manner as the covering of the conductor 2 with the insulating layer 3 of the insulated wire 1. Alternatively, the thermoplastic resin or the like may be applied to the peripheral surfaces of the insulated wire 1 and the outer conductor 45.

[0077] <Advantages> The information transmission cable includes the insulated wire, which prevents an increase in the dielectric loss tangent of the insulating layer and has excellent heat resistance, thereby improving durability and reducing transmission loss in high-temperature environments.

[0078] [Other embodiments] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is not limited to the configurations of the above-described embodiments, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0079] The insulating layer of the insulated wire may be foamed, which reduces the composite dielectric constant and also reduces the weight of the insulated wire.

[0080] The information transmission cable may be a multi-core cable in which a plurality of twin-axial cables are further covered with an outer sheath. By using a multi-core cable, it is possible to transmit signals with a larger capacity than with a twin-axial cable.

[0081] The conductor can also be made of a twisted wire, which is made by twisting together multiple metal wires. In this case, multiple types of metal wires may be combined. The number of twists is generally seven or more.

[0082] The insulated wire may have a primer layer laminated directly on the conductor. A suitable primer layer is a crosslinked resin, such as ethylene, that does not contain metal hydroxide. The provision of such a primer layer can prevent deterioration over time in the peelability of the insulating layer and the conductor, thereby preventing a decrease in the efficiency of the wire connection process. [Example]

[0083] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0084] [Insulating layers No. 1 to No. 11] A resin composition for an insulating layer was obtained by mixing polypropylene (Novatec EA9: a polypropylene-based homopolymer manufactured by Japan Polypropylene Corporation) as the main component olefin resin and a metal damage inhibitor so that the contents (parts by mass) were as shown in Table 1. The resin composition for an insulating layer was press-molded to produce sheet-like insulating layers No. 1 to No. 27. The press-molding conditions were that the mixture was preheated at 180°C for 5 minutes, then further pressurized at that temperature and held for 5 minutes.

[0085] As a metal damage inhibitor, N,N'-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyl]hydrazine represented by the following formula (K-3) ("Irganox MD1024" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., melting point 60°C to 67°C) was used.

[0086] [ka]

[0087] Ethylenebis(oxyethylene)bis[3-(5-tert-butyl-hydroxy-m-tolyl)propionate] (Irganox 245, manufactured by BASF Japan Ltd.) was used as a phenolic antioxidant having a semi-hindered phenol structure. In addition, 4,4'-thiobis(3-methyl-6-tert-butyl)phenol (Nocrac 300 manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) was used as a phenolic antioxidant having a less hindered phenol structure.

[0088] As sulfur-based antioxidants, 2-mercaptobenzothiazole (Suncerer M manufactured by Sanshin Chemical Industry Co., Ltd.) and didodecylthiodipropionate (Seenox DL manufactured by Shipro Chemical Industry Co., Ltd.) were used.

[0089] <Evaluation> The insulating layers No. 1 to No. 27 obtained as described above were subjected to measurement of the dielectric loss tangent and the relative dielectric constant, and to a heat aging resistance test.

[0090] (Measurement of dielectric loss tangent and relative permittivity) The dielectric loss tangent and relative permittivity of the obtained sheet-like sample were measured when a high frequency electric field of 10 GHz was applied according to the method of JIS-R1641 (2007). The measurement was carried out three times and the average value was calculated.

[0091] (Heat aging test) For the insulating layers No. 1 to No. 28, a heat aging resistance test was carried out in accordance with the JASO D611 standard using the following procedure. The sheet was punched into a dumbbell shape (JIS No. 3) and placed in thermostatic chambers set at 160°C, 180°C, and 200°C, and the time until the tensile elongation fell below 100% was determined as the lifespan. An Arrhenius plot was performed based on the results, and the temperature at which the tensile elongation reached 100% after a 10,000-hour aging test was estimated, and this was taken as the 10,000-hour heat resistance temperature, with a temperature of 125°C or higher being considered acceptable.

[0092] The results of the measurements of the dielectric loss tangent and relative dielectric constant and the heat aging resistance test are shown in Table 1.

[0093] [Table 1]

[0094] From the results in Table 1, Nos. 1 to 7, in which the insulating layer contains an antioxidant composed of a phenolic antioxidant and a sulfur-based antioxidant excluding sulfur-containing phenolic antioxidants, and the total content of the antioxidants is more than 1.0 part by mass and not more than 5.0 parts by mass per 100 parts by mass of the olefin resin, have a dielectric loss tangent of 4.20 × 10 -4 The dielectric loss tangent was suppressed to below 10,000° C., and the 10,000-hour heat resistance temperature in the heat aging test was 125° C. or higher. Furthermore, Nos. 1 to 6, in which the phenolic antioxidant had a less hindered phenol structure or a semi-hindered phenol structure, exhibited a more favorable effect of reducing the dielectric loss tangent.

[0095] On the other hand, for insulating layers Nos. 8 to 11 in which the content of the antioxidant was 1.0 part by mass or less or more than 5.0 parts by mass per 100 parts by mass of the olefin-based resin, the dielectric loss tangent was 4.20 × 10 -4 The values ​​were either higher than 10,000 hours or the 10,000-hour heat resistance temperature was poor.

[0096] From the above, it can be seen that the insulated wire suppresses an increase in the dielectric loss tangent of the insulating layer and has excellent heat resistance. [Explanation of symbols]

[0097] 1, 1a, 1b insulated wire, 2, 2a, 2b conductor, 3, 3a, 3b insulation layer, 5 train wire, 10 twinax cable, 30 shielding tape, 40 coaxial cable, 45 outer conductor, 46 outer jacket layer.

Claims

1. one or more linear conductors; one or more insulating layers laminated on the outer peripheral surface of the conductor; Equipped with the insulating layer contains an olefin-based resin and an antioxidant, the content of the antioxidant is more than 1.0 part by mass and not more than 5.0 parts by mass per 100 parts by mass of the olefin-based resin, the antioxidant is composed of a phenol-based antioxidant and a sulfur-based antioxidant excluding sulfur-containing phenol-based antioxidants, The insulated wire, wherein the phenol-based antioxidant has a less hindered phenol structure or a semi-hindered phenol structure.

2. 2. The insulated wire according to claim 1, wherein a mass ratio of the phenol-based antioxidant to the sulfur-based antioxidant is 4:1 to 1:

4.

3. 3. The insulated wire according to claim 1, wherein the phenolic antioxidant has a less hindered phenol structure represented by the following formula (2) or a semi-hindered phenol structure represented by the following formula (1): 【Chemistry 1】 (In formulas (1) and (2), R １ ~R ４ is a methyl group. ５ is a substituent.)

4. 4. The insulated wire according to claim 1, wherein the sulfur-based antioxidant is represented by the following formula (3) or (4): 【Chemistry 2】 (In formulas (3) and (4), X １ is -S- or -NH-, R ６ is an alkyl group.)

5. 5. The insulated wire according to claim 1, wherein the olefin-based resin is polypropylene.

6. 6. The insulated wire according to claim 1, wherein the insulating layer further contains a metal inhibitor.

7. When a high frequency electric field having a frequency of 10 GHz is applied, the dielectric loss tangent of the insulating layer is 4.0×10 －４ The insulated wire according to any one of claims 1 to 6, wherein:

8. An information transmission cable comprising one or more insulated electric wires according to any one of claims 1 to 7.

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