JP7316761B2 - CARBON NANOTUBE WIRE AND MANUFACTURING METHOD THEREOF, WIRE HARNESS - Google Patents

Description

TECHNICAL FIELD The present invention relates to a carbon nanotube wire, a method for producing the same, and a wire harness.

Carbon nanotubes (hereinafter sometimes referred to as “CNT”) are materials having various properties and are expected to be applied to many fields.

CNT is a three-dimensional network structure composed of a single layer of cylindrical bodies having a hexagonal lattice network structure or multiple layers arranged substantially coaxially, and is lightweight and has electrical conductivity, thermal conductivity, It has excellent properties such as mechanical strength and current density. Therefore, it is desired to use CNT in the form of a wire, and to use a carbon nanotube wire having a wire diameter increased according to current or a carbon nanotube wire having a plurality of carbon nanotube wires.

However, since CNTs have high rigidity, it is sometimes difficult to process them into strands or wires. For example, when manufacturing a carbon nanotube wire, it has sometimes been difficult to obtain a high-density wire structure that does not cause gaps between carbon nanotube wires. If there is such a gap between the carbon nanotube wires, the adhesive strength between the carbon nanotube wires is small, so that when an external force is applied to the carbon nanotube wire, the carbon nanotube wires tend to loosen. Further, when a voltage is applied to the carbon nanotube wire and current is passed, the gaps between the carbon nanotube wires hinder the flow of electrons, which may lead to a decrease in conductivity. As a result, the carbon nanotube wire sometimes has low mechanical strength and low electrical conductivity.

Patent Document 1 (Japanese Patent Application Laid-Open No. 2013-76198) discloses a CNT/carbon fiber composite material having a structure in which a plurality of carbon nanotubes are entangled on the surface of a carbon fiber to form a carbon nanotube network thin film ( Claim 1). According to Patent Document 1, it is possible to obtain a fiber-reinforced molded article in which the base material is firmly adhered to the surface of the carbon fiber so as not to be peeled off, by having the configuration as described above.
Patent Document 2 (Japanese Patent Application Laid-Open No. 2006-261084) discloses a heater wire including two or more insulated wires having a circular cross-sectional shape and one or more bare wires (FIGS. 1, 3, and 5). .
Patent Document 3 (Japanese Patent No. 5819888) discloses a method of aggregating CNT fibrils to form a fibrous aggregate by a dry method (claim 6).
Patent Document 4 (Japanese Patent No. 5990202) discloses a method for producing a carbon nanotube fiber, comprising the steps of aggregating multi-walled carbon nanotubes to form a fiber thread and doping the multi-walled carbon nanotubes with a dopant by a dry method. Disclose (claim 15).
Patent Document 5 (Japanese Patent No. 5350635) discloses a method for producing a yarn containing CNT fibers by a dry method (claim 19).
Patent Document 6 (Japanese Patent No. 5135620) discloses a method for producing an aggregated spinning structure containing carbon nanotubes by a wet method ([0037] to [0040]).

JP 2013-76198 A JP 2006-261084 A Japanese Patent No. 5819888 Japanese Patent No. 5990202 Japanese Patent No. 5350635 Japanese Patent No. 5135620

However, in the CNT/carbon fiber composite material of Patent Document 1, carbon nanotubes are used simply as network thin films, and are not related to carbon nanotube wires or the like. In addition, in the CNT/carbon fiber composite material of Patent Document 1, although a plurality of carbon nanotubes are entwined, the basic carbon fiber conductor itself has a circular cross section, so the mechanical strength and conductivity decrease as described above. could not adequately respond to
Since the electric wire constituting the heater wire of Patent Document 2 has a circular cross-sectional shape, the contact ratio between the electric wires is small, and the characteristics required for the electric wire may not be sufficiently satisfied.
Single CNTs are rigid linear molecules, but aggregates of CNTs are agglomerated by intermolecular forces. Therefore, a CNT wire made of a CNT aggregate does not have the rigidity of a copper wire made of metal-bonded crystals, and hangs down under its own weight.
In addition, in the case of spinning CNT strands by a dry method as in Patent Documents 3 to 5, it is difficult to control the state of agglomeration between individual CNTs when pulling out the CNT strands from a furnace, substrate, or the like. When the CNT wire is spun by a wet method as in Patent Document 6, it is difficult to control the state of aggregation of single CNTs when the CNT wire is pulled out from the dispersion. For this reason, it has been difficult to produce a CNT strand having a uniform diameter and a perfectly circular cross-sectional shape.
Therefore, in the case of twisting CNT wires manufactured by the conventional dry method or wet method, a plurality of CNT wires having non-uniform cross-sectional shapes and lacking rigidity are twisted together, resulting in a perfect circle. It has been difficult to produce a CNT wire having a cross-sectional shape. In addition, there is also a problem that a CNT wire made of such a CNT element wire is crushed during winding, resulting in a flattened shape.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a carbon nanotube wire having excellent electrical conductivity and mechanical strength and a method for producing the same.

The present invention has the following embodiments.
[1] A carbon nanotube wire having a plurality of carbon nanotube strands composed of a carbon nanotube aggregate composed of a plurality of carbon nanotubes,
A carbon nanotube wire, wherein the contact ratio between the carbon nanotube wires is 5% or more.
[2] The carbon nanotube wire according to [1] above, wherein the contact rate between the carbon nanotube wires is 10% or more.
[3] The carbon nanotube wire according to [2] above, wherein the contact ratio is 15% or more.
[4] The carbon nanotube wire according to any one of [1] to [3] above, wherein the cross-sectional shape of the carbon nanotube wire is polygonal.
[5] A wire harness having a plurality of the carbon nanotube wires according to any one of [1] to [4] above.
[6] A step of forming a plurality of carbon nanotube strands each composed of a carbon nanotube aggregate composed of a plurality of carbon nanotubes;
forming a carbon nanotube wire having a plurality of the carbon nanotube wires;
a step of applying a stress to the carbon nanotube wire so that the contact ratio between the carbon nanotube wires is 5% or more;
A method for producing a carbon nanotube wire.

A carbon nanotube wire having excellent electrical conductivity and mechanical strength and a method for producing the same can be provided.

1 is an explanatory diagram of a carbon nanotube wire according to a first embodiment; FIG. FIG. 2 is a schematic diagram of a carbon nanotube wire used for the carbon nanotube wire according to the first to second embodiments. FIG. 5 is an explanatory diagram of a modified example of the carbon nanotube wire according to the first to second embodiments; FIG. 4 is a schematic diagram of a carbon nanotube wire according to a third embodiment; It is a schematic diagram showing a measuring method of "hardness to unravel" in an example.

1. Carbon Nanotube Wire The carbon nanotube wire according to each embodiment will be described below with reference to the drawings.

FIG. 1(a) is a perspective view of the carbon nanotube wire 1 of the first embodiment, and FIG. 1(b) is a cross-sectional view of the CNT wire 1. As shown in FIG. A CNT wire 1 according to the first embodiment has a plurality of carbon nanotube strands 2 each composed of a carbon nanotube aggregate composed of a plurality of carbon nanotubes. The cross-sectional shape of the CNT wire 2 is hexagonal, and the contact ratio between the CNT wires 2 is 5% or more. The contact ratio is determined by counting the ratio of the contact portion to the outer peripheral portion of the CNT wire 2 using image analysis software from the obtained cross-sectional image of the CNT wire 1 . Whether or not the cross-sectional shape of the CNT wire 2 is polygonal can be determined by converting the outer peripheral portion of the CNT wire 2 into coordinate data using image analysis software for the obtained cross-sectional image of the CNT wire 1, and by linear approximation. Determined by the method of counting straight sections. In FIG. 1, a plurality of CNT strands 2 are twisted together to form a twisted wire conductor 3. As shown in FIG. The plurality of CNT wires 2 may or may not be in the form of a twisted wire conductor in which the CNT wires 2 are twisted. Although the cross-sectional shape of the CNT wire 2 is hexagonal in FIG. 1, it may have a cross-sectional shape other than this as long as the contact ratio between the CNT wires is 5% or more. Moreover, the CNT wire 1 has an insulating coating layer 4 forming the outer peripheral portion of the CNT wire 1 so as to cover the CNT wire 2 . Note that the insulating coating layer 4 is not an essential component, and the CNT wire 1 may not have the insulating coating layer 4 depending on the case. The contact ratio of the CNT wires in the first embodiment is preferably 10% or more (10 to 100%), more preferably 15% or more (15 to 100%).

In general, CNT wires have a non-uniform cross section, resulting in a low contact ratio, and even when twisted, there are fine gaps between the CNT wires, which reduces the mechanical strength of the CNT wire. It is one of the reasons for the decrease. In addition, since the voids between the CNT strands have low electrical conductivity, the electrical conductivity of the entire CNT wire is reduced. On the other hand, in the CNT wire 1 of the first embodiment, the contact ratio between the CNT wires 2 is 5% or more. Voids can be made smaller. Therefore, the mechanical strength of the entire CNT wire 1 can be improved to make it less likely to bend and improve durability against external force. Moreover, the electrical conductivity of the entire CNT wire 1 can be made excellent.

The CNT wire of the second embodiment has a twisted wire conductor of CNT strands composed of a carbon nanotube aggregate composed of a plurality of carbon nanotubes. That is, in the second embodiment, the stranded conductor is formed by twisting a plurality of CNT strands. The contact rate of this CNT wire is 5% or more (5 to 100%). In the second embodiment, since the contact ratio of the CNT wires is 5% or more, the contact area between the adjacent CNT wires can be increased and the gap between the CNT wires can be reduced. Therefore, the electrical conductivity of the entire CNT wire can be made excellent. The contact ratio of the CNT wires in the second embodiment is preferably 10% or more (10 to 100%), more preferably 15% or more (15 to 100%). Moreover, the CNT wire may have an insulating coating layer forming the outer peripheral portion of the CNT wire so as to cover the stranded conductor.

Below, each part constituting the CNT wire according to the first to second embodiments will be described in detail.

(Carbon nanotube wire)
FIG. 2 is a schematic diagram of carbon nanotube wires used for the carbon nanotube wires according to the first and second embodiments. As shown in FIG. 2, the CNT wire 2 is a carbon nanotube aggregate (hereinafter referred to as "CNT aggregate") composed of a plurality of CNTs 11a, 11a, ... having a layer structure of one or more layers. ) is formed from eleven singular or plural bundled together. Here, the CNT aggregate and the CNT wire mean those having a CNT ratio of 90% by mass or more. Plating and dopants are excluded from the calculation of the CNT ratio in the CNT wire. In FIG. 2, the CNT wire 2 has a configuration in which a plurality of CNT aggregates 11 are bundled. The equivalent circle diameter of the CNT wire 2 is not particularly limited, but is, for example, 0.01 mm or more and 4.0 mm or less.

The CNT aggregate 11 is a bundle of CNTs 11a having a layered structure of one or more layers. The longitudinal direction of the CNTs 11 a forms the longitudinal direction of the CNT aggregate 11 . A plurality of CNTs 11a, 11a, . Therefore, the plurality of CNTs 11a, 11a, . . . in the CNT aggregate 11 are oriented. The equivalent circle diameter of the CNT aggregate 11 is, for example, 20 nm or more and 1000 nm or less, more typically 20 nm or more and 80 nm or less. The width dimension of the outermost layer of the CNTs 11a is, for example, 1.0 nm or more and 5.0 nm or less.

The CNTs 11a constituting the CNT aggregate 11 are cylindrical bodies having a single-layer structure or a multi-layer structure, and are called SWNTs (single-walled nanotubes) and MWNTs (multi-walled nanotubes), respectively. In FIG. 2, for the sake of convenience, only the CNT 11a having a two-layer structure is shown, but the CNT assembly 11 also includes CNTs having a layer structure of three or more layers and CNTs having a single-layer structure. It may be formed from CNTs having a layer structure of three or more layers or from CNTs having a single-layer structure. Note that the cross-sectional shape of the CNT aggregate 11 constituting the CNT wire 2 of the first to second embodiments may be polygonal, as in the third embodiment described later.

The orientation of the CNT aggregate 11 and the orientation of the CNTs 11a can be adjusted by appropriately selecting a spinning method such as wet spinning or liquid crystal spinning and the spinning conditions of the spinning method, which will be described later.

In the first and second embodiments, the cross-sectional shape of the CNT wire 2 in the CNT wire 1 may be polygonal. In this case, the cross-sectional shape of the CNT wire 2 in the first and second embodiments is not particularly limited as long as it is polygonal. Examples of the cross-sectional shape of the CNT wire 2 include a triangle, a quadrangle, a pentagon, a hexagon, an octagon, a decagon, and a dodecagon. In the case of a polygonal shape, when a CNT wire is created from multiple CNT strands, surface contact is formed between the CNT strands when molded by applying an external force such as pressure, unlike CNT strands with a circular cross-sectional shape. and the contact area between the CNT strands is greatly increased. Moreover, the cross-sectional shape of the CNT wire 2 may be a regular polygon or an irregular polygon. Furthermore, the cross-sectional size and shape of each CNT wire 2 may be different. Preferably, the cross-sectional shape of each CNT wire 2 should be a regular polygon of the same size, since the contact ratio between adjacent CNT wires can be increased and the CNT wires 2 can be packed at a high density. Further, when viewed in cross section of the CNT wire 1, each CNT element wire 2 may be arranged regularly or irregularly. Preferably, the CNT strands 2 are arranged regularly because the contact ratio between adjacent CNT strands can be increased. FIG. 3 is an example of a cross-sectional view of the CNT wire 1 of the first to second embodiments. FIGS. 3(a), (b), and (c) respectively show a CNT wire 1 in which CNT wires 2 having the same size regular square, regular octagon, and regular decagonal cross-sectional shapes are regularly arranged. It is a figure representing. FIG. 3(d) is a diagram showing a CNT wire 1 in which CNT wires 2 having the same square cross-sectional shape are arranged irregularly. As shown in FIG. 3, the CNT wires of the first and second embodiments can be regularly or irregularly arranged with various polygonal cross-sectional shapes when viewed in cross section.

(stranded conductor)
Moreover, in the first embodiment, each CNT wire 2 can be twisted together to form the stranded conductor 3 . In the second embodiment, each CNT strand 2 is twisted together to form a stranded conductor 3 . In each embodiment, the average diameter, number, twisting method, etc. of the CNT wires 2 constituting the stranded conductor 3 are not particularly limited, and a desired one is appropriately selected according to the type, diameter, application, etc. of the CNT wire 1. can do. In some cases, the stranded conductor 3 may have strands made of a material other than CNT.

(insulating coating layer)
In the first and second embodiments, the insulating coating layer 4 that the CNT wire 1 may have can contain resin. The type of resin is not particularly limited, and either thermoplastic resin or thermosetting resin can be used.

Examples of thermoplastic resins include polyethylene, polypropylene, polyethylene terephthalate, polyacrylate, polymethacrylate, polyamideimide, polystyrene, polyvinyl chloride, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polylactic acid resin, poly Butylene terephthalate, polyvinyl acetoacetal, polyvinyl benzal, polyvinyl butyral, ionomer resin, polyphenylene ether, polyphenylene sulfide, polycarbonate, polyether ether ketone, polyacetal, ABS resin, fluorine resin and the like can be mentioned.
Examples of thermosetting resins include phenol resins, urea resins, melamine resins, epoxy resins, unsaturated polyester resins, polyimides, polyurethanes, and silicone resins.

2. Carbon Nanotube Wire The carbon nanotube wire of the third embodiment is composed of a plurality of carbon nanotube aggregates composed of a plurality of carbon nanotubes. Moreover, the cross-sectional shape of the aggregate of carbon nanotubes is polygonal. Whether or not the cross-sectional shape of the CNT aggregate is polygonal is determined by counting straight portions in the obtained cross-sectional image of the CNT aggregate, as in the case of the CNT wire. The cross-sectional shape of the CNT aggregate in the CNT wire is not particularly limited as long as it is polygonal. Examples of the cross-sectional shape of the CNT aggregate include triangular, quadrangular, pentagonal, hexagonal, octagonal, decagonal, and dodecagonal shapes. Moreover, the cross-sectional shape of the CNT aggregate may be a regular polygon or an irregular polygon. Furthermore, the cross-sectional size and shape of each CNT aggregate may be different. Preferably, the cross-sectional shape of each CNT aggregate should be a regular polygon of the same size, since the contact ratio between adjacent CNT aggregates can be increased and the CNT aggregates can be packed at a high density. In addition, each CNT aggregate may be arranged regularly or irregularly when viewed in cross section of the CNT wire. Preferably, the CNT aggregates are arranged regularly because the contact ratio between adjacent CNT aggregates can be increased.

FIG. 4 is a schematic diagram of a carbon nanotube wire according to the third embodiment. As shown in FIG. 4, the CNT wire 2 is formed by bundling a plurality of CNT aggregates 11 composed of a plurality of CNTs 11a, 11a, . . . having a layer structure of one or more layers. Here, the CNT aggregate means one having a CNT ratio of 90% by mass or more. In FIG. 4, each CNT aggregate 11 has a hexagonal cross-sectional shape. The CNT wire 2 has a configuration in which a plurality of CNT aggregates 11 are bundled. The equivalent circle diameter of the CNT wire 2 is not particularly limited, but is, for example, 0.01 mm or more and 4.0 mm or less.

3. Method for producing carbon nanotube wire A method for producing a carbon nanotube wire includes a step of forming a plurality of carbon nanotube strands each composed of a carbon nanotube assembly composed of a plurality of carbon nanotubes; The method includes a step of forming a wire, and a step of applying stress to the carbon nanotube wire so that the contact ratio between the carbon nanotube wires is 5% or more. A production example of the CNT wire 1 according to the first and second embodiments will be described below.
In the first and second embodiments, first, CNT aggregates in which CNTs 11 are aggregated are produced. CNT aggregates can be produced by methods such as the floating catalyst method (Japanese Patent No. 5819888) and the substrate method (Japanese Patent No. 5590603). For example, the CNT strand 2 can be produced by wet spinning (Patent No. 5135620, Patent No. 5131571, Patent No. 5288359), liquid crystal spinning (Japanese Patent Publication No. 2014-530964), etc., but these is not limited to the method of More specifically, when the CNT wire 2 is produced from a solution in which CNTs are dissolved or dispersed, the material after passing through a nozzle having pores is immersed in a coagulation liquid and then dried to obtain a desired result. A CNT wire 2 having a polygonal cross-sectional shape can be obtained.

Next, a CNT wire 1 is obtained by bundling or twisting a plurality of CNT wires 2 obtained as described above. A twister can be used to twist the CNT wires 2 together. Next, by applying stress to the CNT wire 1, the contact ratio between the CNT wires 2 is set to 5% or more. The method of applying stress to the CNT wire 1 is not particularly limited, but for example, by applying external pressure from the side surface of the CNT wire 2, the contact ratio between adjacent CNT wires 2 can be improved. The external pressure may be gas pressure or mechanical force. The contact rate can be adjusted by adjusting the value of the external pressure.

The CNT wire 1 according to one embodiment can be used as a general electric wire such as a wire harness, and a general electric wire using the CNT wire 1 may be used to produce a cable. When the CNT wire 1 is used as a general electric wire such as a wire harness, for example, by bundling a plurality of CNT wires 1, a wire harness having a plurality of CNT wires 1 can be obtained.

(Examples 1-5 and Comparative Examples 1-2)
Using the floating catalyst vapor deposition (CCVD) method, an alumina tube with an inner diameter of 60 mm and a length of 1600 mm was heated to 1300 ° C. in an electric furnace of a CNT manufacturing apparatus. A raw material solution containing at least one aromatic hydrocarbon composition, ferrocene as a catalyst, and thiophene as a reaction accelerator was supplied by spraying. Hydrogen was supplied as carrier gas at 9.5 L/min. The produced CNTs were collected while being continuously wound up to obtain CNT aggregates. Next, an aqueous solution containing 1% by mass of CNT aggregates and 1% by mass of sodium dodecylsulfonate was prepared and treated with an ultrasonic homogenizer for 30 minutes to obtain a dispersion of CNT aggregates. This dispersion was injected into ethanol from a syringe using a nozzle having a 0.3 mm regular polygonal hole at a speed of 1 m/min. Subsequently, the CNT wire having an average diameter of 20 μm and the cross-sectional shape shown in Table 1 was obtained by transferring to a water tank, washing and drying. Next, 19 CNT wires were bundled and twisted at a rotational pitch with a wire twister to obtain a CNT wire having the contact ratio shown in Table 1. The contact rate can be improved by increasing the rotation pitch of the twisting machine, and can be decreased by decreasing the rotation pitch.

The method for determining the cross-sectional shape of the carbon nanotube wire, and the method for evaluating the contact ratio, volume resistivity, and resistance to unraveling will be described below.

(Method for Determining Cross-Sectional Shape of Carbon Nanotube Wire)
Each CNT wire was surfaced by polishing, and its cross section was observed with a scanning electron microscope (SEM) at a magnification of 100 to 2000 to obtain a cross-sectional image. The outer peripheral portion of the cross-sectional image of the CNT wire was converted into coordinate data using image analysis software. At least 5 points on each straight line part of the outer peripheral part are extracted, and when linear approximation is performed from the coordinate data using the least squares method, the square of the correlation coefficient R2 is 0.95 or more. regarded as a straight section. A polygon whose perimeter was surrounded by straight lines was judged to be a polygon. Also, when it was determined to be a polygon, it was determined to be a polygon with the number of straight lines (for example, when the number of straight lines was n, it was determined to be an n-sided polygon).

(contact rate)
In the same manner as described above, the contact ratio was defined as the ratio of the length of the portion where the sides (surfaces) were in contact with respect to the total perimeter of the CNT wire on the cross-sectional image. Ten or more arbitrary CNT strands were selected and the average contact ratio was calculated. A contact rate of 15% or more was marked as "◎", a contact rate of 10% or more and less than 15% was marked as "○", a contact rate of 5% or more and less than 10% was marked as "△", and a contact rate of less than 5% was marked as "×". .

(volume resistivity)
The CNT wire was connected to a resistance measuring machine (manufactured by Keithley Co., Ltd., device name "DMM2000"), and the resistance was measured by the four-terminal method. The volume resistivity was calculated based on the formula r=RA/L (R: resistance, A: cross-sectional area of CNT wire, L: measured length). A volume resistivity of 5×10 ⁻⁴ Ωcm or less is indicated by “◎”, a volume resistivity of more than 5×10 ⁻⁴ Ωcm to 8×10 ⁻⁴ Ωcm is indicated by “○”, and a volume resistivity of more than 8×10 ⁻⁴ Ωcm to 1×. A value of 10 ⁻³ Ωcm or less was rated as “Δ”, and a value of over 1×10 ⁻³ Ωcm was rated as “x”.

(difficult to unravel)
FIG. 5 is a schematic diagram showing a method for measuring "difficulty in unraveling". As shown in FIG. 5, first, a piece of CNT wire 21 is held between jigs 20 having a bend R of 3 mm (state a). Next, after bending the CNT wire 21 by 90 degrees along the jig (state b), it is returned to the original linear state a, and after being further bent 90 degrees in the opposite direction (state c), the original linear shape to state a. A bending test of the CNT wire 1 was performed at a speed of about 20 times per minute, with the series of operations described above being one time. Then, the bending test was repeated until the CNT wire rod 21 was unraveled and the CNT wire inside was exposed. A case of 500 or more and 999 or less was rated as "Δ", and a case of less than 500 was rated as "x".
The above evaluation results are shown in Table 1 below.

As shown in Table 1, when the contact ratio is within the range of 5 to 100%, the carbon nanotube wire exhibits excellent volume resistivity and is less likely to fray. As a result, it was confirmed that a carbon nanotube wire having excellent electrical conductivity and mechanical strength can be obtained in the present invention.

Reference Signs List 1, 21 Carbon nanotube wire 2 Carbon nanotube element wire 3 Twisted wire conductor 4 Insulating coating layer 11 Carbon nanotube assembly 11a Carbon nanotube 20 Jig

Claims (6)

A carbon nanotube wire having a plurality of carbon nanotube strands composed of a carbon nanotube aggregate composed of a plurality of carbon nanotubes,
The contact ratio between the carbon nanotube wires is 5% or more,
The carbon nanotube wire is formed by twisting the carbon nanotube wire,
A carbon nanotube wire, wherein the carbon nanotube wire is bent 1000 times or more until the carbon nanotube wire is unraveled in the following test.
<Test>
One carbon nanotube wire was held in a straight state between jigs with a bend R of 3 mm, then the carbon nanotube wire was bent 90 degrees in one direction along the jig, and then returned to its original straight shape. After returning to the state, bending 90 degrees in the opposite direction, and then returning to the original straight state, the test was performed at a speed of 20 times per minute, and the carbon nanotube wire was unraveled and the inside was The number of times until the carbon nanotube wire becomes bare is measured. 2. The carbon nanotube wire according to claim 1, wherein the contact ratio between said carbon nanotube wires is 10% or more. The carbon nanotube wire according to claim 2, wherein said contact ratio is 15% or more. The carbon nanotube wire according to any one of claims 1 to 3, wherein the carbon nanotube wire has a polygonal cross-sectional shape. A wire harness comprising a plurality of the carbon nanotube wires according to any one of claims 1 to 4. a step of forming a plurality of carbon nanotube strands each composed of a carbon nanotube assembly composed of a plurality of carbon nanotubes;
forming a carbon nanotube wire having a plurality of the carbon nanotube wires that are twisted together ;
By applying stress to the carbon nanotube wire, the contact ratio between the carbon nanotube wires is 5% or more, and the number of times of bending until the carbon nanotube wire is loosened is 1000 or more in the following test. A step of forming a carbon nanotube wire such as
A method for producing a carbon nanotube wire.
<Test>
One carbon nanotube wire was held in a straight state between jigs with a bend R of 3 mm, then the carbon nanotube wire was bent 90 degrees in one direction along the jig, and then returned to its original straight shape. After returning to the state, bending 90 degrees in the opposite direction, and then returning to the original straight state, the test was performed at a speed of 20 times per minute, and the carbon nanotube wire was unraveled and the inside was The number of times until the carbon nanotube wire becomes bare is measured.