JP7688200B2 - Carbon nanotube coated wire - Google Patents

Description

The present invention relates to a carbon nanotube coated electric wire in which a carbon nanotube wire made of multiple carbon nanotubes is coated with an insulating material.

Carbon nanotubes (hereafter sometimes referred to as "CNTs") are a material with a variety of properties and are expected to be applied in many fields.

For example, CNTs are three-dimensional mesh structures consisting of a single layer of cylindrical bodies with a hexagonal lattice mesh structure, or multiple layers arranged approximately coaxially, and are lightweight and have excellent properties such as electrical conductivity, thermal conductivity, and mechanical strength. However, it is not easy to make CNTs into wires, and there are few technologies that use CNTs as wires.

For example, in order to further improve the electrical conductivity of CNT materials, a carbon nanotube material has been proposed in which conductive deposits made of metals or the like are formed at the electrical junctions of adjacent CNT wires, and it has been disclosed that such carbon nanotube materials can be used in a wide range of applications (Patent Document 1).

On the other hand, electric wires consisting of a core wire made of one or more wire materials and an insulating coating covering the core wire are used as power lines and signal lines in various fields such as automobiles and industrial equipment. Copper or copper alloys are usually used as the material of the wire material constituting the core wire from the viewpoint of electrical properties, but in recent years, aluminum or aluminum alloys have been proposed from the viewpoint of weight reduction. For example, the specific gravity of aluminum is about 1/3 of the specific gravity of copper, and the conductivity of aluminum is about 2/3 of the conductivity of copper (when pure copper is based on 100% IACS, pure aluminum is about 66% IACS). In order to pass the same current through aluminum wire as through copper wire, the cross-sectional area of the aluminum wire needs to be about 1.5 times larger than that of copper wire. However, even if an aluminum wire with such a large cross-sectional area is used, the mass of the aluminum wire is about half the mass of a pure copper wire, so using aluminum wire is advantageous from the viewpoint of weight reduction.

In addition, as automobiles, industrial equipment, and the like continue to improve in both performance and functionality, the number of electrical devices and control devices installed is increasing, and the number of wires in the electrical wiring used in these devices and the amount of heat generated from the core wires also tend to increase. This has created a demand for improving the heat dissipation characteristics of electric wires without compromising the insulation provided by the insulating coating. At the same time, there is also a demand for lighter wires to improve the fuel efficiency of moving objects such as automobiles in order to be environmentally friendly.

Furthermore, in the past, identification marks have been applied to the outer surface of electric wires to identify the type and use of the wires. For example, automobiles are equipped with a wide variety of electrical components and electronic devices, and wire harnesses are installed to transmit power and control signals between the electrical components (electronic devices). Identification marks are applied to these various types of electric wires to identify the corresponding electric wires for each electrical circuit. If such identification marks are applied to the outer surface, their identifiability will decrease due to wear and tear. On the other hand, if an identification mark is applied to the inside of the outer surface, it is not easy to process it like metal wires or to maintain conductivity after processing, and it is difficult to process it on carbon nanotubes themselves.

Special Publication No. 2015-523944

The present invention aims to improve the identification of carbon nanotube-coated electric wires that use carbon nanotube wires.

The present invention has the following embodiments:

[1] A carbon nanotube wire having one or more carbon nanotube aggregates composed of a plurality of carbon nanotubes, and an insulating coating layer coating the carbon nanotube wire;
Equipped with
The carbon nanotube wire has an identification mark.
[2] A carbon nanotube wire formed by twisting together a plurality of carbon nanotube aggregates each composed of a plurality of carbon nanotubes, and an insulating coating layer that coats the carbon nanotube wire;
Equipped with
The carbon nanotube covered electric wire has an identification mark in a plurality of gaps of the carbon nanotube aggregate or the carbon nanotube wire.
[3] The carbon nanotube covered electric wire according to the above [1] or [2], wherein the carbon nanotube wire has another line having a different color from the carbon nanotube aggregate as the identification mark.
[4] The carbon nanotube covered electric wire according to the above [1] or [2], wherein the identification mark includes a capsule.
[5] The carbon nanotube covered electric wire according to the above [4], wherein the capsule contains a fluorescent material.
[6] The carbon nanotube covered electric wire according to the above [1] or [2], wherein the identification mark comprises a core portion containing a fluorescent substance and a shell portion containing silica.
[7] The carbon nanotube covered electric wire according to the above [1] or [2], wherein the identification mark includes a material that changes color in response to a change in temperature or stress of the carbon nanotube covered electric wire.
[8] The carbon nanotube covered electric wire according to the above [1] or [2], wherein the identification mark includes a magnetic material.
[9] The carbon nanotube covered electric wire according to the above [1] or [2], wherein the identification mark is a barcode or a QR code (registered trademark) consisting of three or more types of barcode lines each having a different line width.
[10] The carbon nanotube covered electric wire according to any one of [4] to [9] above, wherein the identification marks are positioned at regular intervals in the longitudinal direction of the carbon nanotube covered electric wire.
[11] The carbon nanotube covered electric wire according to any one of [4] to [9] above, wherein the identification mark is located at least at one end of the carbon nanotube covered electric wire in the longitudinal direction.
[12] The carbon nanotube covered electric wire according to any one of [1] to [11] above, wherein the identification mark is provided with specific information.
[13] The carbon nanotube-coated electric wire according to any one of [1] to [12] above, wherein the refractive index _nD of the material constituting the insulating coating layer is less than 1.5, and the film thickness of the insulating coating layer/diameter of the carbon nanotube wire is less than 0.2.
[14] The carbon nanotube-coated electric wire according to any one of [1] to [12] above, wherein the material constituting the insulating coating layer has a total light transmittance, as defined in JIS 7375:2008, of 75% or more, and the film thickness of the insulating coating layer/diameter of the carbon nanotube wire is less than 0.2.
[15] The carbon nanotube coated electric wire according to any one of [1] to [14] above, wherein the carbon nanotube wire is composed of a plurality of the carbon nanotube aggregates, and a half-width Δθ of the azimuth angle in an azimuth plot by small-angle X-ray scattering showing the orientation of the plurality of carbon nanotube aggregates is 60° or less.
[16] The carbon nanotube-coated electric wire according to any one of the above [1] to [15 ^] , wherein the q value of the peak top in the (10) peak of the scattering intensity by X-ray scattering showing the density of the plurality of carbon nanotubes is 2.0 nm ^-1 or more and 5.0 nm ^-1 or less, and the half-value width Δq is 0.1 nm ^-1 or more and 2.0 nm -1 or less.

Since the carbon nanotube wire has an identification mark, the carbon nanotube coated electric wire can have excellent identification properties.

1 is an explanatory diagram of a carbon nanotube covered electric wire according to an embodiment; 1 is an explanatory diagram of a carbon nanotube wire used in a carbon nanotube covered electric wire according to an embodiment. FIG. 1A is a diagram showing an example of a two-dimensional scattering image of a scattering vector q of an aggregate of multiple carbon nanotubes by SAXS, and FIG. 1B is a graph showing an example of the azimuth angle vs. scattering intensity of an arbitrary scattering vector q, with the position of the transmitted X-ray as the origin, in the two-dimensional scattering image. 1 is a graph showing the relationship between the q value and strength by WAXS of a plurality of carbon nanotubes constituting a carbon nanotube aggregate. 1 is an explanatory diagram of a carbon nanotube covered electric wire having an identification mark according to one embodiment. 1 is an explanatory diagram of a carbon nanotube covered electric wire having an identification mark according to one embodiment. 1 is an explanatory diagram of a carbon nanotube covered electric wire having an identification mark according to one embodiment.

1. Carbon Nanotube Covered Electric Wire Hereinafter, a carbon nanotube covered electric wire according to an embodiment will be described with reference to the drawings.

As shown in FIG. 1, a carbon nanotube coated electric wire (hereinafter, sometimes referred to as a "CNT coated electric wire") 1 according to one embodiment is configured such that an insulating coating layer 21 is coated on the outer peripheral surface of a carbon nanotube wire (hereinafter, sometimes referred to as a "CNT wire") 10. That is, the insulating coating layer 21 is coated along the longitudinal direction of the CNT wire 10. In the CNT coated electric wire 1, the entire outer peripheral surface of the CNT wire 10 is coated with the insulating coating layer 21. In the CNT coated electric wire 1, the insulating coating layer 21 is in direct contact with the outer peripheral surface of the CNT wire 10. In this case, the CNT coated electric wire 1 includes a carbon nanotube wire having one or more carbon nanotube aggregates composed of a plurality of carbon nanotubes, and an insulating coating layer that coats the carbon nanotube wire. Although not shown in FIG. 1, the CNT wire 10 has an identification mark. In FIG. 1, the CNT wire 10 is a single wire (single wire) made of a single CNT wire 10, but the CNT wire 10 may be a twisted wire made of multiple CNT wires 10 twisted together. By twisting the CNT wire 10 into a twisted wire, the circle equivalent diameter and cross-sectional area of the CNT wire 10 can be adjusted as appropriate. In this case, the CNT coated electric wire 1 includes a carbon nanotube wire made of multiple twisted carbon nanotube aggregates made of multiple carbon nanotubes, and an insulating coating layer that coats the carbon nanotube wire. The CNT coated electric wire 1 also has an identification mark in the gaps between the carbon nanotube aggregates or the carbon nanotube wire.

As shown in FIG. 2, the CNT wire 10 is formed by bundling together a single carbon nanotube aggregate (hereinafter sometimes referred to as "CNT aggregate") 11, which is composed of a plurality of CNTs 11a, 11a, ... each having one or more layered structures. Here, the CNT wire means a CNT wire having a CNT ratio of 90 mass% or more. Note that the calculation of the CNT ratio in the CNT wire does not include plating and dopants. In FIG. 2, the CNT wire 10 is configured by bundling together a plurality of CNT aggregates 11. The longitudinal direction of the CNT aggregate 11 forms the longitudinal direction of the CNT wire 10. Therefore, the CNT aggregate 11 is linear. The plurality of CNT aggregates 11, 11, ... in the CNT wire 10 are arranged with their major axis directions almost aligned. Therefore, the multiple CNT aggregates 11, 11, ... in the CNT wire 10 are aligned. The equivalent circle diameter of the CNT wire 10, which is a single wire, is not particularly limited, but is, for example, 0.01 mm or more and 4.0 mm or less. The equivalent circle diameter of the CNT wire 10, which is a twisted wire, is not particularly limited, but is, for example, 0.1 mm or more and 15 mm or less.

The CNT aggregate 11 is a bundle of CNTs 11a having a layer structure of one or more layers. The longitudinal direction of the CNTs 11a forms the longitudinal direction of the CNT aggregate 11. The multiple CNTs 11a, 11a, ... in the CNT aggregate 11 are arranged with their major axis directions almost aligned. Therefore, the multiple CNTs 11a, 11a, ... in the CNT aggregate 11 are aligned. The circle equivalent diameter of the CNT aggregate 11 is, for example, 20 nm or more and 1000 nm or less, and 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. For convenience, only CNTs 11a having a two-layer structure are shown in FIG. 2, but the CNT aggregate 11 may also include CNTs having a three-layer structure or more or a single-layer structure, and may be formed from CNTs having a three-layer structure or more or a single-layer structure.

CNT11a, which has a two-layer structure, has two cylindrical bodies T1 and T2, each having a hexagonal lattice mesh structure, arranged approximately coaxially to form a three-dimensional mesh structure, and is called a DWNT (double-walled nanotube). The hexagonal lattice, which is the structural unit, is a six-membered ring with carbon atoms at its vertices, and these are adjacent to other six-membered rings and are continuously bonded to each other.

The properties of the CNT11a depend on the chirality of the cylindrical body. Chirality is broadly classified into armchair type, zigzag type, and chiral type, with the armchair type exhibiting metallic behavior, the zigzag type exhibiting semiconducting and semimetallic behavior, and the chiral type exhibiting semiconducting and semimetallic behavior. Therefore, the conductivity of the CNT11a varies greatly depending on the chirality of the cylindrical body. In the CNT aggregate 11 constituting the CNT wire 10 of the CNT coated electric wire 1, it is preferable to increase the proportion of armchair type CNT11a exhibiting metallic behavior in order to further improve the conductivity.

On the other hand, it has been found that doping chiral CNT11a, which exhibits semiconducting behavior, with a substance (heterogeneous element) that has electron donating or electron accepting properties causes the chiral CNT11a to exhibit metallic behavior. In addition, in general metals, doping with a heterogeneous element causes scattering of conduction electrons inside the metal, reducing the conductivity. Similarly, doping CNT11a, which exhibits metallic behavior, with a heterogeneous element causes a reduction in conductivity.

In this way, the doping effect on the CNT11a exhibiting metallic behavior and the CNT11a exhibiting semiconducting behavior is in a trade-off relationship from the viewpoint of electrical conductivity, so theoretically it is desirable to separately produce the CNT11a exhibiting metallic behavior and the CNT11a exhibiting semiconducting behavior, perform a doping process only on the CNT11a exhibiting semiconducting behavior, and then combine them. However, with the current manufacturing technology, it is difficult to selectively produce the CNT11a exhibiting metallic behavior and the CNT11a exhibiting semiconducting behavior, and the CNT11a exhibiting metallic behavior and the CNT11a exhibiting semiconducting behavior are produced in a mixed state. For this reason, in order to further improve the electrical conductivity of the CNT wire 10 consisting of a mixture of the CNT11a exhibiting metallic behavior and the CNT11a exhibiting semiconducting behavior, it is preferable to select a layer structure of the CNT11a in which doping with a different element/molecule is effective.

For example, CNTs with fewer layers, such as a two-layered or three-layered structure, are relatively more conductive than CNTs with more layers, and when doped, the doping effect is greatest in CNTs with a two-layered or three-layered structure. Therefore, in order to further improve the conductivity of the CNT wire 10, it is preferable to increase the proportion of CNTs with a two-layered or three-layered structure. Specifically, the proportion of CNTs with a two-layered or three-layered structure relative to the total CNTs is preferably 50% by number or more, and more preferably 75% by number or more. The proportion of CNTs with a two-layered or three-layered structure can be calculated by observing and analyzing the cross section of the CNT aggregate 11 with a transmission electron microscope (TEM) and measuring the number of layers for each of 100 CNTs.

In one embodiment, the CNT wire 10 has one or more CNT aggregates 11. As described above, the CNT aggregate 11 is an aggregate of CNTs 11a. For this reason, compared to wires made of other materials such as copper wire, identification mark materials such as pigments, dyes, fluorescent substances, and color-changing materials can easily penetrate into the CNT aggregate 11, and due to the high specific surface area of the CNTs themselves, the adsorption of the identification mark material to the CNT aggregate 11 is high. As a result, the identification mark material penetrates into the interior of the CNT wire 10 and is stably retained.

The identification mark also has excellent durability and weather resistance, allowing the CNT wire 10 to maintain stable visibility of the identification mark for a longer period of time. In conventional metal-based wires, the identification mark is simply attached to the surface, so the identification mark is easily detached from the wire when the wire is coated or cleaned after the identification mark is applied. In contrast, the identification mark is firmly attached to the CNT wire of one embodiment, so the identification mark does not detach from the CNT wire, and the CNT wire can maintain a higher level of visibility than conventional metal-based wires.

Next, we will explain the orientation of CNTs 11a and CNT aggregates 11 in the CNT wire 10.

Figure 3(a) shows an example of a two-dimensional scattering image of scattering vector q of multiple CNT aggregates 11, 11, ... by small angle X-ray scattering (SAXS), and Figure 3(b) is a graph showing an example of an azimuth plot showing the relationship between the azimuth angle of an arbitrary scattering vector q, with the position of the transmitted X-ray as the origin, and the scattering intensity in the two-dimensional scattering image.

SAXS is suitable for evaluating structures with a size of several nm to several tens of nm. For example, by analyzing information of an X-ray scattering image using SAXS in the following manner, it is possible to evaluate the orientation of CNT 11a with an outer diameter of several nm and the orientation of CNT aggregate 11 with an outer diameter of several tens of nm. For example, when an X-ray scattering image of CNT wire 10 is analyzed, as shown in FIG. 3(a), the y component q _y is distributed more narrowly than the x component q _x of the scattering vector q (q=2π/d, d is the lattice spacing) of the CNT aggregate 11. In addition, as a result of analyzing the azimuth plot of SAXS for the same CNT wire 10 as in FIG. 3(a), the half-width Δθ of the azimuth angle in the azimuth plot shown in FIG. 3(b) is 48°. From these analysis results, it can be said that the CNTs 11a, 11a... and the CNT aggregates 11, 11,... have good orientation in the CNT wire 10. In this way, since the CNTs 11a, 11a... and the CNT aggregates 11, 11,... have good orientation, the heat of the CNT wire 10 is easily dissipated while being smoothly transferred along the longitudinal direction of the CNTs 11a and the CNT aggregates 11. Therefore, the CNT wire 10 exhibits superior heat dissipation characteristics compared to a metal core wire, since the heat dissipation route can be adjusted in the longitudinal direction and the cross-sectional direction of the diameter by adjusting the orientation of the CNTs 11a and the CNT aggregates 11. The orientation refers to the angle difference between the vectors of the internal CNTs and CNT aggregates with respect to the vector V in the longitudinal direction of the twisted wire produced by twisting and gathering the CNTs.

In order to obtain a certain level of orientation indicated by the half-width Δθ of the azimuth angle in the azimuth plot of small-angle X-ray scattering (SAXS), which shows the orientation of multiple CNT aggregates 11, 11, ..., and to further improve the heat dissipation characteristics of the CNT wire 10, the half-width Δθ of the azimuth angle is preferably 60° or less, and particularly preferably 50° or less.

Next, we will explain the arrangement structure and density of the multiple CNTs 11a that make up the CNT aggregate 11.

Figure 4 is a graph showing the relationship between the q value and intensity by WAXS (wide-angle X-ray scattering) of multiple CNTs 11a, 11a, ... that make up the CNT aggregate 11.

WAXS is suitable for evaluating the structure of a substance having a size of a few nm or less. For example, by using WAXS to analyze information on an X-ray scattering image by the following method, the density of CNT11a having an outer diameter of a few nm or less can be evaluated. As a result of analyzing the relationship between the scattering vector q and the intensity for any one CNT aggregate 11, as shown in FIG. 4, the value of the lattice constant estimated from the q value of the peak top of the (10) peak observed in the vicinity of q=3.0 nm ^-1 to 4.0 nm ^-1 is measured. Based on the measured value of this lattice constant and the diameter of the CNT aggregate observed by Raman spectroscopy, TEM, or the like, it can be confirmed that the CNT11a, 11a, ... form a hexagonal close-packed structure in a planar view. Therefore, it can be said that the diameter distribution of the multiple CNT aggregates in the CNT wire 10 is narrow, and the multiple CNT11a, 11a, ... are regularly arranged, that is, have a high density, forming a hexagonal close-packed structure and existing at a high density.
In this way, the multiple CNT aggregates 11, 11... have good orientation, and furthermore, the multiple CNTs 11a, 11a,... that make up the CNT aggregate 11 are regularly arranged and densely packed, so heat from the CNT wire 10 is easily dissipated while being smoothly transferred along the longitudinal direction of the CNT aggregate 11. Therefore, the CNT wire 10 exhibits superior heat dissipation characteristics compared to a metal core wire, because the heat dissipation route can be adjusted in the longitudinal direction and in the radial cross-sectional direction by adjusting the arrangement structure and density of the CNT aggregates 11 and CNTs 11a.

From the viewpoint of further improving the heat dissipation characteristics by obtaining a high density, it is preferable that the q value of the peak top in the (10) peak of the scattering intensity by X-ray scattering, which indicates the density of the multiple CNTs 11 a, 11 a, ..., is 2.0 nm ^-1 or more and 5.0 nm ^-1 or less, and the half width Δq (FWHM) is 0.1 nm ^-1 or more and 2.0 nm ^-1 or less.

The orientation of the CNT aggregate 11 and CNT 11, as well as the arrangement structure and density of the CNT 11a, can be adjusted by appropriately selecting a spinning method such as dry spinning or wet spinning and the spinning conditions of the spinning method, as described below.

Next, we will explain the insulating coating layer 21 that covers the outer surface of the CNT wire 10.

The insulating coating layer 21 may be opaque or transparent. If the insulating coating layer 21 is opaque, the carbon nanotube coated electric wire 1 is used in which the identification mark located on the CNT wire 10 cannot be seen through the insulating coating layer 21 when the CNT coated electric wire 1 is viewed from the outside. In this case, when the insulating coating layer 21 becomes thin due to wear or the like, or when a part of the insulating coating layer 21 peels off to expose the outer surface of the CNT wire 10, the thinning or peeling of the insulating coating layer 21 can be confirmed by visually checking the identification mark on the outer surface of the CNT wire 10. Since this identification mark has high identifiability, the identification mark can be confirmed even from a distance, and deterioration of the CNT coated electric wire 1 can be detected early with ease and low cost.

Furthermore, when a transparent or semi-transparent insulating coating layer 21 is used, the CNT-coated electric wire 1 is one in which the identification mark located on the CNT wire 10 can be seen through the insulating coating layer 21 when the CNT-coated electric wire 1 is viewed from the outside. Examples of the CNT-coated electric wire 1 having a transparent insulating coating layer 21 include the following CNT-coated electric wires.
(a) A CNT-coated electric wire 1 in which the refractive index _nD of the material constituting the insulating coating layer 21 is less than 1.5, and the film thickness of the insulating coating layer 21/the wire diameter of the CNT wire 10 is less than 0.2;
(b) The CNT-coated electric wire 1, in which the material constituting the insulating coating layer 21 has a total light transmittance, as defined in JIS 7375:2008, of 75% or more, and the film thickness of the insulating coating layer 21/diameter of the CNT wire 10 is less than 0.2.

In the above cases (a) or (b), the insulating coating layer 21 has high transparency, and the identification mark located on the CNT wire 10 can be effectively viewed. In the above case of (b), the total light transmittance defined in JIS 7375:2008 is preferably 90% or more. By having the refractive index _nD and total light transmittance of the material constituting the insulating coating layer 21 within the above ranges, the identification mark can be more easily identified.

In addition, since the ratio of the thickness of the insulating coating layer 21 to the diameter of the CNT wire 10 is less than 0.2, the identification mark can be made easily identifiable. The thickness of the insulating coating layer 21 and the diameter of the CNT wire 10 can be calculated by averaging information obtained from images of the cross section of the CNT coated electric wire 1 observed with an SEM or optical microscope for the same radial cross section every 10 cm in the longitudinal direction of the 1.0 m CNT coated electric wire 1.

The material for the insulating coating layer 21 can be a material used for the insulating coating layer of a coated electric wire using a metal core, such as a thermoplastic resin. Examples of thermoplastic resins include polytetrafluoroethylene (PTFE), polyethylene, polypropylene, polyacetal, polystyrene, polycarbonate, polyamide, polyvinyl chloride, polyvinyl acetate, polyurethane, polymethyl methacrylate, acrylonitrile butadiene styrene resin, and acrylic resin. These may be used alone or in a suitable mixture of two or more types.

The insulating coating layer 21 may be a single layer as shown in FIG. 1, or may alternatively be two or more layers. If necessary, a layer of thermosetting resin may be provided between the outer surface of the CNT wire 10 and the insulating coating layer 21.

Next, an example of a method for manufacturing the CNT-coated electric wire 1 according to an embodiment of the present invention will be described. The CNT-coated electric wire 1 can be manufactured by first manufacturing CNTs 11a, forming a CNT wire 10 having an identification mark from the resulting multiple CNTs 11a, and then coating the outer peripheral surface of the CNT wire 10 with an insulating coating layer 21.

CNT11a can be produced by a floating catalyst method (Japanese Patent No. 5819888) or a substrate method (Japanese Patent No. 5590603). The strand of CNT wire 10 can be produced by dry spinning (Japanese Patent No. 5819888, Japanese Patent No. 5990202, Japanese Patent No. 5350635), wet spinning (Japanese Patent No. 5135620, Japanese Patent No. 5131571, Japanese Patent No. 5288359), liquid crystal spinning (Japanese Translation of PCT International Publication No. 2014-530964), etc.

The method for coating the insulating coating layer 21 on the outer surface of the CNT wire 10 obtained as described above can be a method for coating an insulating coating layer on an aluminum or copper core wire, for example, a method in which the thermoplastic resin that is the raw material for the insulating coating layer 21 is melted and extruded around the CNT wire 10 to coat it.

The CNT-coated electric wire 1 according to the embodiment of the present invention can be used as a general electric wire such as a wire harness, and a cable may be made from the general electric wire using the CNT-coated electric wire 1.

2. Identification Mark In the carbon nanotube covered electric wire according to one embodiment, the carbon nanotube wire has an identification mark. The identification mark is provided on at least a part of the exposed outer surface of the carbon nanotube wire or inside the carbon nanotube wire. The identification mark may be for identifying the type, use, and state (for example, normal state, abnormal state) of the carbon nanotube covered electric wire. In addition, the identification mark may be provided with specific information such as information on the electric wire itself or information related to the electric wire. The material of the identification mark is not particularly limited as long as it can be identified by visual inspection, binoculars, electromagnetic waves of a specific wavelength such as visible light or other light, magnetism, or the like. The carbon nanotube wire may have another line having a color different from that of the carbon nanotube aggregate as the identification mark. The identification mark may include a capsule. The size of the capsule is not particularly limited, and examples of the capsule include a microcapsule and a nanocapsule. The capsule may include a fluorescent material. In addition, the identification mark may be composed of a core portion containing a fluorescent material and a shell portion containing silica. The identification mark may include a pigment, a dye, or a material whose color changes in response to a temperature change or a stress change of the carbon nanotube coated electric wire. When the identification mark includes a pigment or a dye, the identification mark is located on the outer surface of the carbon nanotube wire, and the identification mark can be visually recognized by making the color of the identification mark different from the color of the portion other than the identification mark on the outer surface of the carbon nanotube wire. The identification mark may also include a resin or a magnetic material. When the identification mark includes a magnetic material, the identification mark can be identified by magnetism. Furthermore, the identification mark may be a barcode, particularly a barcode (multi-binary code) consisting of three or more types of barcode lines having different line widths. The identification mark may be a QR code (registered trademark). When the identification mark is a barcode (particularly a multi-binary code) or a QR code (registered trademark), specific information can be added to these codes. When a barcode or the like consisting of a thin line pattern is added as an identification mark to a conventional wire mainly made of metal, the size of the identification mark itself is small and its adhesion is low, so that the identification mark has low identifiability and a clear identification mark cannot be added. In addition, since the conventional identification mark attached to the wire mainly made of metal is inferior in durability and weather resistance, the identification mark peels off in a short time, and the visibility is deteriorated. In contrast, in the present embodiment, since the identification mark has high adsorption to the CNT wire as described above, even if a barcode or the like composed of a fine line pattern is attached as the identification mark, the identification mark has high identification property and can be made into an identification mark with excellent visibility. Furthermore, since the identification mark attached to the CNT wire has excellent durability and weather resistance, the identification mark does not peel off even when used for a long period of time, and excellent visibility can be maintained. The above effect is more remarkable when a barcode (multibinary code) and a QR code (registered trademark) consisting of three or more barcode lines with different line widths are used as the identification mark. That is, the multibinary code and the QR code (registered trademark) are composed of even finer lines and image patterns than normal barcodes, but since these codes have high adsorption to the CNT wire, they can be made into an identification mark with excellent identification property and visibility. Furthermore, the identification marks made of these codes attached to the CNT wire are highly durable and weather resistant, so even when used for long periods of time, the identification marks will not peel off and will maintain excellent visibility.
Each material constituting the identification mark will be described in detail below.

(Other wires)
The other wire as the identification mark is not particularly limited, and may be a conductive wire or an insulating wire. By using a conductive wire as the identification mark, it is possible to achieve both conductivity and identification of the carbon nanotube covered electric wire. As the conductive wire, an aluminum wire, an aluminum alloy wire, a copper wire, a copper alloy wire, or a combination of these wires can be used. These conductive wires have a color different from that of the carbon nanotubes themselves, so they can be used as an identification mark. Since the insulating wire can easily control the color and can have a color that is significantly different from that of the carbon nanotube wire, it is possible to improve the identification of the carbon nanotube covered electric wire. As the insulating wire, a wire made of a thermoplastic resin, a thermosetting resin, or the like can be used. The other wire may be a single wire (single wire) or a twisted wire. It is preferable that the other wire is a single wire, and a twisted wire in which the carbon nanotube aggregate and the other wire are twisted can be obtained to obtain a carbon nanotube covered electric wire with high mechanical strength.

(capsule)
The capsules are, for example, microcapsules or nanocapsules having a particle size ranging from several tens of nanometers to several hundreds of micrometers. The shape of the capsule is not particularly limited, and for example, a spherical shape, an elliptical shape, etc. can be used. For example, the encapsulation method can be an in situ polymerization method, an interfacial polymerization method, a coacervation method, a spray drying method, a dry mixing method, an orifice method, etc.

(Identification mark having a core portion and a shell portion)
The core of the identification mark is filled with a liquid material, and the liquid material is held in the core by being covered by the shell. Therefore, when the liquid material is held in the core, the identification mark does not have identification, and when the liquid material in the core is released, the identification can be expressed by the liquid material. For example, when a microcapsule is used as the identification mark, when high stress or high temperature is applied to the microcapsule, the liquid material is instantly released from the microcapsule, and the identification can be expressed in a short time. In addition, when the liquid material is released little by little from the core over a long period of time (slow release), the identification can be gradually expressed.

The liquid material filled in the core portion is not particularly limited as long as it has excellent identifiability, and may be an insulating gel, a pigment, a dye, a fluorescent material, a magnetic material, or the like, which will be described later. Of these liquid materials, it is preferable to use a fluorescent material as the liquid material, since it has excellent identifiability, especially in dark places. It is also preferable that the identification mark is composed of a core portion containing a fluorescent material and a shell portion containing silica. For example, fluorescent silica particles may be used.

The material of the shell is not particularly limited, and thermoplastic resin, thermosetting resin, etc. can be used, but it is preferable to use a thermoplastic resin.

(Pigment)
The pigment is not particularly limited, and examples thereof include red pigments, blue pigments, green pigments, yellow pigments, orange pigments, purple pigments, and combinations of these pigments. In addition, inorganic pigments and organic pigments can also be used.

Examples of inorganic pigments include titanium oxide, barium sulfate, calcium carbonate, zinc oxide, lead sulfate, yellow lead, zinc yellow, red iron oxide (red iron (III) oxide), cadmium red, ultramarine, Prussian blue, chromium oxide green, cobalt green, and amber.

Examples of organic pigments include anthraquinone pigments, aminoanthraquinone pigments, quinacridone pigments, quinacridonequinone pigments, diketopyrrolopyrrole pigments, perylene pigments, perinone pigments, anthanthrone pigments, benzimidazolone pigments, disazo condensate pigments, azo pigments, thioindigo pigments, pyranthrone pigments, dioxazine pigments, quinophthalone pigments, isoindoline pigments, and phthalocyanine pigments.

By using a pigment as the material for the identification mark, the visibility of the identification mark can be improved.

(dye)
The dye is not particularly limited, but may be, for example, a red dye, a blue dye, a green dye, a yellow dye, or a combination of these dyes. Examples of the dye include azo dyes, anthraquinone dyes, phthalocyanine dyes, quinoneimine dyes, quinoline dyes, nitro dyes, carbonyl dyes, methine dyes, etc. By using a dye as the material of the identification mark, the visibility of the identification mark can be improved.

(Fluorescent material)
The identification mark may also contain a fluorescent substance. By using a fluorescent substance as the material of the identification mark, the carbon nanotube coated electric wire can be recognized even in a dark place. There is no particular limitation on the fluorescent substance, and it may be an organic compound, an inorganic compound, a semiconductor particle, or the like. The material of the fluorescent substance is not particularly limited, but examples thereof include C.I. Basic Red 1, 2, 9, 12, 13, 14, 17, C.I. Basic Violet 1, 3, 7, 10, 11:1, 14, C.I. Acid Yellow 73, 184, 250, C.I. Acid Red 51, 52, 92, 94, C.I. Direct Yellow 11, 24, 26, 87, 100, 147, C.I. Direct Orange 26, 29, 29:1, 46, C.I. Direct Red 1, 13, 17, 239, 240, 242, 254, etc.

When a fluorescent substance is used, the insulating coating layer is preferably translucent or transparent, and more preferably transparent. When the insulating coating layer is transparent, the identification mark can be recognized even in a dark place. When the insulating coating layer is translucent, when the insulating coating layer becomes thin due to wear or the like, only the thinned portion can be easily recognized. In particular, in a dark place, only this portion emits fluorescence, so that the deteriorated portion of the carbon nanotube coated electric wire can be effectively identified. Also, a light-absorbing substance may be used instead of a fluorescent substance.

(Color changing material)
The identification mark may include a material that changes color differently from the normal state when a specific characteristic value or physical value of the carbon nanotube covered electric wire changes and the carbon nanotube covered electric wire becomes in an abnormal state that makes it impossible to use. For example, the identification mark may include a color-changing material that changes color in response to a temperature change or a stress change of the carbon nanotube covered electric wire. The color-changing material may change color reversibly or irreversibly. That is, when the color-changing material changes color reversibly, the color changes when the carbon nanotube covered electric wire becomes in an abnormal state, but the original color returns when the carbon nanotube covered electric wire returns to a normal state. On the other hand, when the color-changing material changes color irreversibly, the color changes when the carbon nanotube covered electric wire becomes in an abnormal state, and the color does not change even when the carbon nanotube covered electric wire returns to a normal state.

By using an identification mark containing a color-changing material that changes color in response to temperature changes, when the carbon nanotube covered electric wire is placed in a low or high temperature environment and reaches an unusable temperature, the color change of the identification mark can be visually recognized to recognize such an abnormal state. Therefore, there is no need to directly measure the temperature of the carbon nanotube covered electric wire, and the color change can be confirmed from a distance, making it possible to easily and inexpensively confirm the abnormal state of the carbon nanotube covered electric wire and to detect deterioration of the carbon nanotube covered electric wire at an early stage.

Examples of color-changing materials that change color in response to temperature changes include pigments containing leuco dyes, color-developing substances, and color-changing temperature regulators, and encapsulated pigments that are coated with resin. Examples of leuco dyes include diphenylmethane phthalides, indolyl phthalides, diphenylmethane azaphthalides, phenyl indolyl azaphthalides, fluorans, styrinquinolines, and diaza rhodamine lactones. It is also possible to adjust the type of color that changes and the color-changing temperature range by changing the composition of the leuco dyes, color-developing substances, and color-changing temperature regulators.

By using an identification mark containing a color-changing material that changes color in response to stress changes, when the carbon nanotube covered electric wire is bent or heavy objects such as snow are placed on the carbon nanotube covered electric wire, such abnormal conditions can be confirmed by visually checking the color change of the identification mark when the carbon nanotube covered electric wire is subjected to high stress. Therefore, there is no need to directly measure the stress applied to the carbon nanotube covered electric wire, and the color change can be confirmed from a distance, making it possible to simply and inexpensively check for abnormal conditions in the carbon nanotube covered electric wire and detect deterioration of the carbon nanotube covered electric wire at an early stage. Furthermore, CNTs are extremely strong compared to metal wires, and deterioration may occur preferentially around the connecting members. Such changes in condition can also be recognized by the color change of the identification mark. Therefore, it is also preferable to use the identification mark around the connecting members.

(resin)
The identification mark may also contain a resin. In this case, since the resin constituting the identification mark on the outer surface of the carbon nanotube wire is made of a material different from the CNT, the surface properties, color, texture, etc. of these materials are different, and the identification mark can be visually recognized. The resin constituting the identification mark may be either a thermoplastic resin or a thermosetting resin.

Thermoplastic resins include, but are not limited to, vinyl polymers such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, (meth)acrylic resins, ethylene-vinyl acetate copolymers, and ethylene-vinyl alcohol copolymers, polylactic acid resins, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyamides such as nylon and polyamidoamines, polyvinyl acetal resins such as polyvinyl acetoacetal, polyvinyl benzal, and polyvinyl butyral resins, ionomer resins, polyphenylene ether, polyphenylene sulfide, polycarbonate, polyether ether ketone, polyacetal, ABS resins, LCPs (liquid crystal polymers), fluororesins, urethane resins, elastomers, and modified versions of these resins.

Thermosetting resins are not particularly limited, but examples include phenolic resins, urea resins, melamine resins, epoxy resins, unsaturated polyester resins, polyimides, polyurethanes, and silicone resins.

(Magnetic material)
The identification mark may include a magnetic material. By including the magnetic material in the identification mark, the identification mark can be identified by a device capable of detecting magnetism. The magnetic material is not particularly limited, but may include iron oxides such as magnetite, maghemite, and ferrite, or iron oxides including other metal oxides, metals such as Fe, Co, and Ni, or alloys of these metals with metals such as Al, Co, Cu, Pb, Mg, Ni, Sn, Zn, Sb, Be, Bi, Cd, Ca, Mn, Se, Ti, W, and V, and mixtures thereof.

(Provision of information)
Specific information can also be added to the identification mark. For example, specific information can be added by directly printing a specific character, figure, number, etc. on the identification mark. Also, specific code information such as a barcode, QR code (registered trademark), etc. can be printed on the identification mark itself or on the identification mark. The barcode can be a barcode (multi-binary code) consisting of three or more types of barcode lines with different line widths. This code information can be optically read. In another example, an IC chip can be provided on the identification mark, and specific information can be read with an IC chip reader or written with an IC chip writer. In another example, the identification mark contains a magnetic material, and specific information can be added to the identification mark by the magnetic material, and the information can be read by a magnetic reader.

(Method of applying identification marks)
The method for providing the identification mark to the carbon nanotube wire is not particularly limited, but the following method can be mentioned, for example.
(a) a method for forming a carbon nanotube wire from a mixed material obtained by mixing a material for an identification mark having a predetermined size and shape with a material for a carbon nanotube wire other than the material for the identification mark;
(b) a method of printing an identification mark on the outer surface of the carbon nanotube wire;
(c) A method of chemically reacting the material of the outer surface of the carbon nanotube wire with the material of the identification mark to form a chemical bond between the material of the outer surface and the material of the identification mark.

In the above method (a), the mixing method for obtaining the mixed material is not particularly limited, but examples include ball mill mixing, bead mill mixing, container rotation type mixing methods such as V-type mixer and Bohle container mixer, mixing methods using mechanical stirring force such as ribbon mixer, and stirring and mixing methods using air currents such as fluidized bed. Carbon nanotube wire can be obtained from the obtained mixed material. For example, if the identification mark includes a core portion containing a fluorescent substance and a shell portion containing silica, carbon nanotube wire can be obtained by mixing and twisting these materials with the strands of the carbon nanotube aggregate.

The above method (b) is not particularly limited, but may include a method of printing an ink containing the material of the identification mark on the outer surface of the carbon nanotube wire. The ink printing method is not particularly limited, but may include inkjet printing, super inkjet printing, screen printing, transfer printing, offset printing, jet printing, dispenser, jet dispenser, needle dispenser, comma coater, slit coater, die coater, gravure coater, letterpress printing, intaglio printing, gravure printing, soft lithography, dip pen lithography, spray coater, spin coater, dip coater, and electrochemical painting. The ink may contain a solvent, dispersant, surfactant, etc. as necessary as a component other than the material of the identification mark.

The above method (c) is not particularly limited, but examples thereof include a method in which an organic peroxide or the like is used on the outer surface of the carbon nanotube wire to chemically react the carbon nanotube wire with the material of the identification mark. For example, organic peroxides thermally decompose at a relatively low temperature, or react with a reducing substance to easily generate free radicals. The properties of the generated free radicals can promote the addition of the identification mark material to the unsaturated double bonds in the material of the outer surface, or the abstraction of hydrogen atoms and the addition of the identification mark material. The organic peroxide is not particularly limited, but examples thereof include ketone peroxides, peroxyketals, hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxyesters, peroxydicarbonates, etc.

(Shape, size and position of identification mark)
The shape and size of the identification mark and the position of the identification mark on the carbon nanotube wire are not particularly limited. The shape, size, and position of the identification mark can be appropriately determined depending on the purpose of providing the identification mark. The shape of the identification mark can be, for example, a polygon, a circle, a shape surrounding the outer periphery of the carbon nanotube wire, a letter, a pattern consisting of multiple colors, etc. In addition, the size of the identification mark is not particularly limited.

Figures 5(a) to 5(d) are schematic diagrams showing a CNT coated electric wire 1 having an identification mark, and Figure 5(e) is an enlarged view of the barcode which is the identification mark 31 in Figure 5(b). Note that in Figures 5(a) to 5(d), the outer surface of the CNT wire 10 is shown in schematic form by a solid line, the internal structure of the CNT coated electric wire 1 is omitted, and the outer surface of the insulating coating layer is shown by a dotted line.

Figure 5(a) shows an example in which the identification mark 31 is located on the outer surface of the CNT wire 10 at least at one end 32 in the longitudinal direction 33 of the CNT coated electric wire 1. The identification mark 31 may be located at one end 32 of the CNT wire 10 or at both ends 32. In Figure 5(a), for example, if the insulating coating layer is transparent, the identification mark 31 allows the end of the electric wire for connection to a terminal to be visually identified.

Figure 5(b) shows an example in which the identification marks 31 are positioned at regular intervals on the outer surface of the CNT wire 10 in the longitudinal direction 33 of the CNT-coated electric wire 1. In Figure 5(b), for example, if the insulating coating layer is transparent, the identification marks 31 can be used as length marks for identifying the length of the CNT-coated electric wire 1.

Figure 5 (c) shows an example in which an identification mark 31 is provided on the outer surface of the CNT wire 10, extending from the first end to the second end in the longitudinal direction 33 of the CNT-coated electric wire 1. That is, the identification mark 31 is provided continuously between both ends along the longitudinal direction 33. In Figure 5 (c), for example, when the insulating coating layer is transparent, the identification mark 31 may include a material whose color changes in response to temperature or stress changes in the CNT-coated electric wire 1. In this embodiment, when a specific part of the CNT-coated electric wire 1 deteriorates in a low or high temperature environment or due to a high stress load, only the identification mark 31 located at that specific part exhibits a different color from the identification marks 31 located at other parts. Therefore, the deteriorated part of the CNT-coated electric wire 1 can be detected early and countermeasures can be taken.

Also, FIG. 5(d) shows an example in which a barcode is provided as an identification mark 31 on the outer surface of the CNT wire 10, and specific information related to the CNT coated electric wire 1 can be given to the barcode. In one embodiment, as shown in FIG. 5(e), the identification mark 31 is a barcode (multi-binary code) consisting of three or more types of barcode lines with different line widths L. For example, when a barcode including a thin barcode line of 100 μm or less is provided as an identification mark on a conventional wire mainly made of metal, the adhesion of the identification mark is low, making it difficult to identify each line of the barcode. In addition, the identification mark attached to the conventional wire is poor in durability and weather resistance, so that the identification mark peels off in a short time. In contrast, in this embodiment, as described above, the adhesion of the identification mark to the CNT wire is high, so that even if a barcode consisting of a fine barcode line is provided as an identification mark, the identification of the barcode is high. In addition, the identification mark attached to the CNT wire is excellent in durability and weather resistance, so that the identification mark is unlikely to peel off even when used for a long period of time. Furthermore, if pigments, dyes, fluorescent substances, color-changing materials, etc. are used as barcode materials, the visibility of the barcode can be further improved.

Figure 6 is a schematic diagram showing another CNT-coated electric wire 1 having an identification mark, and is a cross-sectional view of the CNT-coated electric wire 1 taken along a line perpendicular to its longitudinal direction. In Figure 6, the CNT wire 10 is a twisted wire, but is shown in a schematic manner. As shown in Figure 6, the CNT wire 10 has an identification mark 40, and the core of the identification mark 40 is filled with a fluorescent material. When the insulating coating layer 21 becomes thin due to friction or the like, and a thin film portion 38 is generated, a large stress is also applied to the identification mark 40 located near the thin film portion 38, and the fluorescent material in the identification mark 40 is released and flows along the twist direction of the CNT wire 10. Since the thin film portion 38 has a recessed shape, the fluorescent material eventually accumulates in this thin film portion 38. As a result, the identification of the thin film portion becomes prominent, and the generation of the thin film portion 38 can be detected early.

Figure 7 is a schematic diagram showing another CNT-coated electric wire 1 having an identification mark. In Figure 7, the CNT wire 10 is a twisted wire, but its outer surface is shown in solid lines, the internal structure of the CNT-coated electric wire 1 is omitted, and the outer surface of the insulating coating layer is shown in dotted lines. In the CNT-coated electric wire 1 in Figure 7, fluorescent material 39 is distributed throughout the entire CNT wire 10. The CNT wire 10 in Figure 7 can be obtained by twisting the strands of the carbon nanotube aggregate while mixing the fluorescent material with them.

Example 1
Using the floating catalyst vapor deposition (CCVD) method, a raw material solution containing decahydronaphthalene as a carbon source, ferrocene as a catalyst, and thiophene as a reaction promoter was sprayed into an alumina tube with an inner diameter of φ60 mm and a length of 1600 mm, which was heated to 1300 ° C. by an electric furnace of a CNT manufacturing device. Hydrogen was supplied as a carrier gas at 9.5 L / min. The generated CNT was continuously wound and collected, and a CNT wire with a diameter of about 100 μm and a length of 75 m was obtained. Next, the obtained CNT wire was heated to 500 ° C. in the atmosphere and further purified by acid treatment. Then, the highly purified CNT aggregate was doped with nitric acid. Next, 100 mL of an ethanol solution (0.1 wt%) of fluorescent silica particles (Quartz dot, manufactured by Furukawa Advanced Engineering Co., Ltd.) containing rhodamine 6G and having a particle size of 0.1 μm was prepared, and the CNT wire was immersed in this solution for 1 hour. The CNT wire was then removed from the solution and dried at 60° C. for 4 hours to obtain a CNT wire labeled with an identification mark made of fluorescent silica particles. Next, a thermoplastic resin (polypropylene) was melted using an extrusion molding machine and extruded around the CNT wire to obtain a CNT-coated electric wire in which a transparent insulating coating layer having a thickness of about 50 μm was coated on the outer surface of the CNT wire. The obtained CNT-coated electric wire was irradiated with a laser diode having an emission wavelength of 532 nm at night and confirmed through an optical filter (LOPF-25C-532, manufactured by Sigma Koki Co., Ltd.), and the CNT wire was clearly visible due to the green fluorescence derived from the fluorescent silica particles (fluorescent material) that are the identification mark.

REFERENCE SIGNS LIST 1 Carbon nanotube coated electric wire 10 Carbon nanotube wire 11 Carbon nanotube aggregate 11a Carbon nanotube 21 Insulating coating layer 31, 40 Identification mark 32 End 33 Longitudinal direction 38 Thin film portion 39 Fluorescent material

Claims (6)

A carbon nanotube wire having one or more carbon nanotube aggregates each composed of a plurality of carbon nanotubes, and an insulating coating layer that coats the carbon nanotube wire;
Equipped with
The carbon nanotube wire has an identification mark,
The carbon nanotube coated electric wire, wherein the identification mark is a microcapsule having a core portion containing a fluorescent substance and a shell portion containing silica . A carbon nanotube wire formed by twisting together a plurality of carbon nanotube aggregates each composed of a plurality of carbon nanotubes, and an insulating coating layer that coats the carbon nanotube wire;
Equipped with
The carbon nanotube aggregate or the carbon nanotube wire has an identification mark in a plurality of gaps,
The carbon nanotube coated electric wire, wherein the identification mark is a microcapsule having a core portion containing a fluorescent substance and a shell portion containing silica . 3. The carbon nanotube covered electric wire according to claim 1 , wherein the refractive index _nD of the material constituting the insulating coating layer is less than 1.5, and the ratio of the thickness of the insulating coating layer to the diameter of the carbon nanotube wire is less than 0.2. 3. The carbon nanotube-coated electric wire according to claim 1, wherein the material constituting the insulating coating layer has a total light transmittance of 75% or more as defined in JIS 7375:2008, and the ratio of the thickness of the insulating coating layer to the wire diameter of the carbon nanotube wire is less than 0.2. the carbon nanotube wire is composed of a plurality of the carbon nanotube aggregates,
5. The carbon nanotube-coated electric wire according to claim 1 , wherein a half-width Δθ of an azimuth angle in an azimuth plot by small-angle X-ray scattering showing the orientation of a plurality of the carbon nanotube aggregates is 60° or less. 6. The carbon nanotube-coated electric wire according to claim ¹ , wherein the q value of the peak top in the (10) peak of the scattering intensity by X-ray scattering showing the density of the plurality of carbon nanotubes is 2.0 nm -1 or more and 5.0 nm ^-1 or less, and the half-value width Δq is 0.1 nm ^-1 or more and 2.0 nm ^-1 or less.

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