JP2021050422A - Insulation coated carbon nano-tube wire - Google Patents

Abstract

To provide an insulation coated carbon nano-tube wire having a small diameter and light weight, with high insulation and flexibility.SOLUTION: A carbon nano-tube fiber bundle 10 made of a plurality of carbon nano-tube fibers 11 has a diameter φ of 5 μm to 150 μm. The surface of the carbon nano-tube fiber bundle 10 is coated with an insulation coating 12 having a thickness of 0.25 μ to 2.5 μm.SELECTED DRAWING: Figure 1

Description

The present invention relates to carbon nanotube wires having an insulating coating.

Conventionally, copper has been used as a material for a general conductive wire. Copper is sufficient for a conductive wire having a diameter of more than 200 μm, but it has been difficult to produce a conductive wire having a small diameter with copper. On the other hand, in the case of a fiber aggregate, a light conductive wire having a small diameter of 5 to 200 μm can be produced.

As an aggregate of such fibers, a technique for producing a CNT fiber bundle, which is a bundle of fibrous carbon nanotubes (hereinafter, also referred to as “CNT”), has been proposed (see, for example, Patent Document 1).

One of the applications of such a small diameter and light conductive wire is a flexible electric wire for a wearable device. Flexible electric wires for wearable devices are required to have wiring insulation and flexibility. As a flexible conductive wire, there is one in which the surface of the resin thread is silver-plated. However, if the silver-plated resin thread is bent with a small radius of curvature, the plating will crack and the conductivity will decrease.

In the case of a CNT fiber bundle, it is necessary to cover the surface with an insulating layer because electric leakage occurs in the exposed wiring, but if the insulating coating is thick, the flexibility is impaired.

JP-A-2017-7919

An object of the present invention is to solve the above problems, and to provide an insulating coated carbon nanotube wire having a small diameter, light weight, and high insulation and flexibility.

The present invention for solving the above problems is an insulating coated carbon nanotube wire provided with a carbon nanotube fiber bundle composed of a plurality of carbon nanotube fibers and an insulating coating for coating the surface of the carbon nanotube fiber bundle.
The diameter of the carbon nanotube fiber bundle is φ5 μm to 150 μm.
The insulating coated carbon nanotube wire is characterized in that the thickness of the insulating coating is 0.25 μm to 2.5 μm.

In the present invention, an insulating coated carbon nanotube wire is provided by a carbon nanotube fiber bundle having a diameter of φ5 μm to 150 μm and an insulating coating having a thickness of 0.25 μm to 2.5 μm covering the surface of the carbon nanotube fiber bundle. Consists of. If the wire diameter is large, it is necessary to thicken the insulating coating in order to ensure the insulating property, but as a result, the flexibility is impaired. In this respect, by setting the wire diameter of the carbon nanotube fiber bundle to 150 μm or less, it is possible to secure the flexibility while ensuring the insulating property. The smaller the wire diameter, the more flexible it is, but if it is thinner than 5 μm, it becomes difficult to manufacture. Even if the wire diameter of the carbon nanotube fiber bundle is small, if the insulating coating is thick, the flexibility is impaired, so that the thickness of the insulating coating needs to be suppressed to 2.5 μm or less. Therefore, if it is configured as described above, it is possible to produce an insulating coated carbon nanotube wire having a small diameter, light weight, and high insulation and flexibility.

Further, the present invention is an insulating coated carbon nanotube wire provided with a carbon nanotube fiber bundle composed of a plurality of carbon nanotube fibers and an insulating coating for coating the surface of the carbon nanotube fiber bundle.
The insulation-coated carbon nanotube wire is characterized in that the ratio of the thickness of the insulation coating to the diameter of the carbon nanotube fiber bundle is 1.6 to 5%.

As described above, by setting the ratio of the thickness of the insulating coating to the diameter of the carbon nanotubes to 1.6 to 5%, a thin-diameter and lightweight insulating-coated carbon nanotube wire can be produced.

Further, in the present invention, the carbon nanotube fiber bundle may be a stranded wire of the plurality of carbon nanotube fibers.

By making the carbon nanotube fiber bundle a stranded wire of a plurality of carbon nanotube fibers in this way, it is possible to produce a carbon nanotube wire having high flexibility, and the strength is also improved. Further, by coating the surface of the stranded carbon nanotube yarn with an insulating coating, there is no untwisting, so that the occurrence of wire diameter unevenness can be prevented, and stable strength characteristics and electrical characteristics can be obtained.

Further, in the present invention, the standard deviation obtained by measuring the thickness of the insulating coating at eight points may be 6% or less.

By making the thickness of the insulating coating uniform in this way, uneven insulation can be prevented, so that local destruction of the insulating coated carbon nanotube wire can be prevented.

Further, in the present invention, the insulating coating may be formed of polyimide.

In this way, dielectric breakdown can be prevented even in a high temperature environment of 200 to 220 ° C.

Further, in the present invention, the tensile strength may be 200 Mpa or more.

In the insulating coated carbon nanotube wire according to the present invention, by reducing the thickness of the insulating coating, the proportion of the coating having a lower strength than that of the carbon nanotube can be reduced, so that the tensile strength is as high as 200 MPa. Insulation coated carbon nanotube wire can be obtained.

In the present invention, the above-mentioned means for solving the problem can be used in combination as much as possible.

According to the present invention, it is possible to provide an insulating coated carbon nanotube wire having a small diameter, light weight, and high insulation and flexibility.

It is a figure which shows the structure of the insulation coating carbon nanotube wire which concerns on Embodiment 1 of this invention. It is an electron micrograph which shows the state before and after coating of the insulation coated carbon nanotube wire which concerns on Embodiment 1 of this invention. It is a figure which shows the schematic structure of the flexibility degree measuring apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the schematic structure of the manufacturing apparatus which concerns on Embodiment 1 of this invention. It is a perspective view which shows the schematic structure of the air nozzle which concerns on Embodiment 1 of this invention. It is a figure which shows the structure of the insulation coating carbon nanotube wire which concerns on Embodiment 2 of this invention. It is a figure which shows the schematic structure of the manufacturing apparatus which concerns on Embodiment 2 of this invention. It is a table explaining the Example of this invention. It is a figure which shows the schematic structure of the main part of the dielectric breakdown voltage measuring apparatus in the Example of this invention. It is a circuit diagram of the dielectric breakdown voltage measuring apparatus (FIG. 10 (A)) in the Example of this invention, and the graph (FIG. 10 (B)) which shows the voltage change at the time of measurement.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. However, the embodiments described below are examples for carrying out the present invention, and the present invention is not limited to the embodiments described below.

<Embodiment 1>
As shown in FIG. 1, the insulating coated carbon nanotube wire 1 according to the first embodiment has a structure in which the outer peripheral surface of the carbon nanotube fiber bundle 10 is coated with the insulating coating 12. In the insulating coated carbon nanotube wire 1, the entire outer peripheral surface of the carbon nanotube fiber bundle 10 which is a bundle of a plurality of fibrous carbon nanotubes (carbon nanotube fibers) 11 is covered with an insulating coating.

The diameter of the carbon nanotube fiber bundle 10 constituting the insulating coated carbon nanotube wire 1 is, for example, φ5 μm to 150 μm.
The thickness of the insulating coating 12 constituting the insulating coated carbon nanotube wire 1 is preferably 0.25 μm to 2.5 μm. By reducing the thickness of the insulating coating 12 to 0.25 μm to 2.5 μm, a lightweight insulating coated carbon nanotube wire 1 having a small diameter can be obtained. By using such an insulating coated carbon nanotube wire 1, the assembly can be made smaller and lighter. If the thickness of the insulating coating 12 is smaller than 0.25 μm, it becomes difficult to manufacture and it becomes difficult to obtain a sufficient insulating effect. On the other hand, if the thickness of the insulating coating 12 is made larger than 2.5 μm, the flexibility is impaired and the insulating coated carbon nanotube wire becomes heavier, and the conductivity is lowered when compared with the same conductive wire diameter.

The wire diameter of the carbon nanotube fiber bundle 10 of the insulating coated carbon nanotube wire 1 and the thickness of the insulating coating 12 were measured by the following measuring methods.
Any point of the insulation-coated carbon nanotube wire 1 is embedded in resin and treated with polishing ion milling (using IM4000 manufactured by Hitachi High-Technologies Corporation) so that the radial cross section can be confirmed, and then subjected to an electron microscope (manufactured by Hitachi High-Technologies Corporation). The diameter of the carbon nanotube fiber bundle 10 and the thickness of the insulating coating 12 were measured by (using SU-70). The thickness of the insulating coating 12 is the average value of the measured values of the thicknesses of eight points obtained by dividing the radial cross section of the insulating coated carbon nanotube wire by 45 degrees.

The thickness of the insulating coating 12 of the insulating coated carbon nanotube wire 1 according to the present embodiment can be expressed by the ratio to the diameter of the carbon nanotube fiber bundle 10, and the ratio of the insulating coating 12 to the diameter of the carbon nanotube fiber bundle 10 is , 1.6% to 5% is preferable.

FIG. 2A is an electron micrograph showing the surface state of the carbon nanotube fiber bundle 10, and FIG. 2B is an electron micrograph showing the surface state of the insulating coated carbon nanotube wire 1.
As shown in FIG. 2A, carbon nanotube fibers are present on the surface of the carbon nanotube fiber bundle 10 in a fluffy state, but as shown in FIG. 2B, they are insulated on the surface of the carbon nanotube fiber bundle 10. By applying the coating 12, it is possible to prevent the carbon nanotube fibers 11 from fluffing. Therefore, the strength of the insulating coated carbon nanotube wire 1 is stable, and the insulating coating 12 can ensure the insulating property.

Further, since the insulating coating 12 is applied to the surface of the carbon nanotube fiber bundle 10, the cross-sectional shape can be kept circular even when the insulating coated carbon nanotube wire 1 is bent, so that the disconnection due to the deformation of the cross-sectional shape can be prevented. Can be prevented.

Further, the insulating coated carbon nanotube wire 1 according to the present embodiment has a standard deviation of 6% or less obtained by measuring the thickness of the insulating coating 12 at 8 points. The method for measuring the thickness of the insulating coating 12 is as described above. By making the thickness of the insulating coating 12 uniform in this way, uneven insulation can be prevented, so that local destruction of the insulating coated carbon nanotube wire 1 can be prevented. Here, the percentage of standard deviation is shown as the so-called coefficient of variation, which is the value obtained by dividing the standard deviation by the average value and multiplying it by 100.

As the material of the insulating coating 12, a thermosetting resin or a thermoplastic resin, which is a material generally used when the insulating coating is applied with a metal as a core wire, can be used. For example, examples of the thermosetting resin include polyimide, phenol resin, and enamel. Examples of the thermoplastic resin include polyamide, polytetrafluoroethylene, polyethylene, polypropylene, polyacetal, polystyrene, polycarbonate, polyvinyl chloride, polymethylcrylate, and polyurethane.

Polyimide is used as the material of the insulating coating 12 of the insulating coated carbon nanotube wire 1 according to the present embodiment. By forming the insulating coating 12 with polyimide, it is possible to prevent dielectric breakdown from occurring even in a high temperature environment of 200 to 220 ° C.

The tensile strength of the insulating coated carbon nanotube wire 1 according to the present embodiment is 200 MPa or more. As described above, by setting the tensile strength to 200 Mpa or more, it is possible to prevent breakage when assembling the insulating coated carbon nanotube wire 1. Materials such as resins used for insulation coating have lower strength than carbon nanotubes, so if the insulation coating is thick, the proportion of low-strength insulation coating will increase, and the tensile strength of the insulation-coated carbon nanotube wire 1 will increase. descend. However, in the present embodiment, by thinning the insulating coating 12, it is possible to obtain an insulating coated carbon nanotube wire 1 having a high tensile strength.

The measurement of the tensile strength of the insulating coated carbon nanotube wire 1 according to the present embodiment is performed by JIS Z.
This was done in accordance with the provisions of 2241 (2011). The measurement conditions for the tensile strength are temperature: 23 ° C., tensile speed: 3 mm / min, scoring distance: 100 mm, and tensile tester: STA-1150 manufactured by Orientec Co., Ltd.

(Degree of suppleness)
The “degree of suppleness”, which is one of the features of the insulating coated carbon nanotube wire 1 according to the present embodiment, will be described.
This degree of suppleness represents the ratio between the wire diameter of the insulating coated carbon nanotube wire 1 and the size of R measured by the suppleness measuring method described later. The suppleness measured in this way is represented by F. By setting F = 0.0070 to 0.180, an insulating coated carbon nanotube wire having both suppleness and strength can be obtained. It is preferable that F = 0.100 to 0.150.

Next, a method for measuring suppleness (F) will be described. FIG. 3 shows a schematic configuration of the flexibility measuring device 20. FIG. 3A shows a top view of the measuring device 20. The right side of the paper surface is the front side of the measuring device 20, the upper side of the paper surface is the right side surface of the measuring device 20, and the lower side of the paper surface is the left side. In the measuring device 20, a rectangular plate-shaped fixing table 22 is arranged on the rectangular plate-shaped measuring table 21. The area of the upper surface of the fixing table 22 is formed to be smaller than the upper surface of the measuring table 21, and the fixing table is arranged on the left side of the back surface side of the measuring table 21. A fixing jig 23 for fixing the insulating coated carbon nanotube wire 1 to be measured is provided on the front side of the right side surface 22b of the fixing base 22.

Then, the insulation-coated carbon nanotube wire 1 having a length of 250 mm is fixed to the fixing base 22 by using the fixing jig 23. The insulating coated carbon nanotube wire 1 fixed by the fixing jig 23 is routed from the back side to the front side along the right side surface 22b of the fixing table 22 and parallel to the upper surface 21d of the measuring table 21. It is bent to the left around the corner where the right side surface 22b and the front surface 22a intersect. The insulating coated carbon nanotube wire 1 to which the weight 24 of 0.5 g is attached to the end is further along the front surface 22a of the fixing table 22 parallel to the upper surface 21d of the measuring table 21 and to the left on the left side of the measuring table 21. It is routed toward the surface 21c. The end of the insulating coated carbon nanotube wire 1 is bent vertically downward along the left side surface 21c of the measuring table 21 due to the weight of the weight 24.

At the corner between the right side surface 22b and the front surface 22a of the fixed base 22, the R measuring unit 201 shown by the broken line circle in FIG. 3A is formed. It is an enlarged view of the R measurement part 201 of the figure on the right side of FIG. 3 (A). The radius of curvature of the insulating coated carbon nanotube wire 1 bent along the corners of the right side surface 22b and the front surface 22a of the fixing base 22 is indicated by R.
Here, the distance L1 from the right side surface 22b of the fixing table 22 to the left side surface 21c of the measuring table 21 is 150 mm.

FIG. 3B is a right side view of the measuring device 20. Here, the distance L2 from the front surface of the fixing jig 23 to the front surface 22a of the fixing table 22 is 30 mm, and the height L3 from the upper surface 21d of the measuring table 21 to the insulating coated carbon nanotube wire 1 is 3 mm.
FIG. 3C is a left side view of the measuring device. As described above, the insulating coated carbon nanotube wire 1 drawn from the fixing jig 23 is routed along the front surface 22a of the fixing base 22, and is vertically aligned with the left side surface 21c of the measuring base 21 due to the weight of the weight 24. It hangs down.

The radius of curvature R of the insulating coated carbon nanotube wire 1 in the measuring unit 201 of the measuring device 20 described above is measured with a field of view of 50 times using a microscope VHX-5000 manufactured by KEYENCE CORPORATION. Then, the ratio of the wire diameter of the insulating coated carbon nanotube wire 1 to R is measured as the value of the suppleness F.

(Manufacturing equipment and manufacturing method)
FIG. 3 shows a schematic configuration of the insulating coated carbon nanotube wire 1 manufacturing apparatus 100 according to the present embodiment. The manufacturing apparatus 100 and the manufacturing method of the insulating coated carbon nanotube wire 1 will be described with reference to FIG.

In the manufacturing apparatus 100, fibrous carbon nanotubes (hereinafter, referred to as “carbon nanotube fibers”) 11, ..., 11 which are linearly connected in a plurality of rows from the end of the carbon nanotube array 30 including a plurality of carbon nanotubes are constant. Pulled out at speed. The plurality of rows of carbon nanotube fibers 11, ..., 11 thus drawn out are guided by the collecting die 31 and converged to form the carbon nanotube fiber bundle 10. The collecting die 31 has, for example, circular pores, and a plurality of rows of carbon nanotube fibers 11, ..., 11 are compressed in the radial direction and converged.

The carbon nanotube fiber bundle 10 is alternately routed around the peripheral surfaces of the guide rollers 32a, 32b, and 32c arranged in order on the downstream side of the collecting die 31, and is introduced into the coating resin tank 33. That is, the carbon nanotube fiber bundle 10 drawn out from the collecting die 31 is from the peripheral surface of one of the rotating shafts of the guide roller 32a (upper in the figure) to the peripheral surface of the other (lower in the figure) of the rotating shaft of the guide roller 32b. After being routed to the peripheral surface of one of the rotating shafts of the guide roller 32c (upper in the figure), the guide roller 32c is introduced into the coated resin tank 33. Magnetic fluid bearings are used for the bearings of the rotating shafts of the guide rollers 32a, 32b, and 32c. Since the carbon nanotube fiber bundle 10 of the present embodiment is very thin and has a low tension level, it is difficult to stabilize the tension. In the manufacturing process according to the present embodiment, the feed rate of the carbon nanotube fiber bundle 10 affects the amount of adhesion of the resin 34, so that the thickness of the insulating coating 12 varies if the feed rate changes. In this respect, since the magnetic fluid bearing acts as an appropriate brake, the tension and the delivery speed can be kept constant. Therefore, the guide rollers 32a, 32b, and 32c using the magnetic fluid bearing can stably deliver the carbon nanotube fiber bundle 10 to the coated resin tank 33 with low tension. The carbon nanotube fiber bundle 10 is introduced from the upper side of the coated resin tank 33. The coating resin tank 33 is filled with, for example, a resin having a solid content concentration diluted to 5 to 25 wt% with a solvent as the resin 34 for forming the insulating coating. The carbon nanotube fiber bundle 10 introduced into the coated resin tank 33 is guided to the outside of the coated resin tank 33 by being routed around the peripheral surface of the roller 35 provided in the coated resin tank. The carbon nanotube fiber bundle 10 adheres the resin 34 to the surface by passing through the resin 34 filled in the coated resin tank 33.

The carbon nanotube fiber bundle 10 having the resin 34 adhered to the surface passes through the draining die 36 after being guided to the outside of the coated resin tank 33, and the excess resin adhering to the surface is removed. The draining die 46 has, for example, circular pores, and removes excess resin 34 adhering to the surface of the carbon nanotube fiber bundle 10 passing through the pores.

The carbon nanotube fiber bundle 10 that has passed through the draining die 36 passes through the hollow portion 37a of the annular air nozzle 37. As shown in FIG. 5, the shape of the air nozzle 37 is such that a plurality of nozzles 38, ..., 38 are provided along the annular inner surface 37b facing the hollow portion 37a, and the nozzles 38, ..., 38 are provided in the central direction from the nozzles 38, ..., 38. Air is discharged toward. ^{Air of 10 to 50 m 3} / min is discharged in the central direction from the nozzles 38, ..., 38 arranged along the circumferential direction with respect to the carbon nanotube fiber bundle 10 passing through the hollow portion 37a of the air nozzle 37 in the axial direction. By doing so, the thickness of the resin 34 adhering to the surface of the carbon nanotube fiber bundle 10 can be made uniform in the circumferential direction.

The carbon nanotube fiber bundle 10 that has passed through the air nozzle 37 is passed through the coated resin baking furnace 39 held at 200 to 600 ° C. to bake the resin 34 adhering to the surface.

In this way, the resin 34 adheres to the coated resin tank 33, the excess resin 34 is removed by the draining die 36, the thickness of the coated resin is made uniform by the air nozzle 37, and the resin 34 is baked by the coated resin baking furnace 39. An insulating coated carbon nanotube wire 1 is produced, and after being routed around the peripheral surface of the roller 40, it is wound around the peripheral surface of the take-up reel 41 by the rotation of the take-up reel 41.

The number of nozzles 38 provided in the air nozzle 37 is not particularly limited. The flow rate of air from each nozzle 38 is set according to the number of nozzles 38 so that the flow rate of the air discharged from the nozzles 38, ..., 38 is 10 to 50 m ^{3 / min.}

The thickness of the insulating coating 12 of the insulating coated carbon nanotube wire 1 is adjusted by adjusting the speed at which the carbon nanotube fiber bundle 10 to which the resin 34 is attached passes through the coating resin baking furnace 39. When obtaining a thick insulating coating, the resin 34 adheres to the coating resin tank 33, the excess resin 34 is removed by the draining die 36, the thickness of the coating resin is made uniform by the air nozzle 37, and the coating resin is baked. The process of baking the resin 34 in the furnace 39 may be repeated a plurality of times.

<Embodiment 2>
FIG. 6 shows the structure of the insulating coated carbon nanotube wire 2 according to the second embodiment of the present invention. Regarding the configuration common to the first embodiment, the same reference numerals will be used and detailed description thereof will be omitted. In FIG. 6, the insulating coated carbon nanotube wire 2 is viewed with a part of the insulating coating 12 removed, but the entire outer peripheral surface of the carbon nanotube fiber bundle 13 is insulated and coated as in the first embodiment. 12 covers.

The carbon nanotube fiber bundle 13 of the insulating coated carbon nanotube wire 2 according to the present embodiment is produced by twisting a bundle of a plurality of carbon nanotube fibers 11.
Like carbon nanotubes, carbon fiber is a conductive and lightweight material, but carbon fiber has strength but poor toughness, and when bent, it easily breaks even with a large radius of curvature. On the other hand, by applying the insulating coating to the untwisted carbon nanotube fiber bundle 10 as in the insulating coated carbon nanotube wire 1 of the first embodiment, the disconnection due to bending is less likely to occur than the carbon fiber, but it is smaller. With the radius of curvature, the cross-sectional shape is not a circle but a crushed shape, so it is easily broken. By twisting the bundle of carbon nanotube fibers 11 to form the carbon nanotube fiber bundle 13 as a twisted wire body as in the case of the insulating coated carbon nanotube wire 2 according to the present embodiment, the flexibility and strength are improved. ..

Further, if the carbon nanotube fiber bundle 13 is simply twisted, the twist is returned and uneven wire diameter occurs, and it is difficult to obtain stable strength and electrical characteristics. On the other hand, in the insulating coated carbon nanotube, by applying the insulating coating to the carbon nanotube fiber bundle 13 which is a stranded wire, there is no untwisting, so that the occurrence of wire diameter unevenness can be prevented, and stable strength and electrical characteristics can be obtained. Obtainable.

Even when the carbon nanotube fiber bundle 13 according to the present embodiment is bent in the longitudinal direction with a radius of curvature of 3 times or less, the cross-sectional shape of the carbon nanotube fiber bundle 13 is maintained in a circular shape, so that disconnection due to bending is unlikely to occur.

(Manufacturing equipment and manufacturing method)
As the insulating coated carbon nanotube wire 2 according to the present embodiment, the same apparatus as the manufacturing apparatus 100 according to the first embodiment can be used except that the bundles of the plurality of carbon nanotube fibers 11 are twisted. Therefore, the same reference numerals are used for the same configurations as in the first embodiment, and detailed description thereof will be omitted.

FIG. 7A is a manufacturing apparatus 200-1 for manufacturing a stranded wire of the carbon nanotube fiber bundle 10 according to the second embodiment. FIG. 7B is a manufacturing apparatus 200-2 for producing the insulating coated carbon nanotube wire 2 from the stranded wire of the carbon nanotube fiber bundle 10.

In the manufacturing apparatus 200-1, the carbon nanotube fiber bundle 10 drawn out from the collecting die 31 is wound around the peripheral surfaces of the take-up capstans 51a and 51b arranged on the downstream side of the collecting die 31. It is wound on the take reel 53. The take-up reel 53 rotates around the rotation axis indicated by the arrow Rd1 to take up the carbon nanotube fiber bundle 10. At this time, the carbon nanotube fiber bundles 10 drawn out from the take-up capstans 51a and 51b are fixed by the fixed chuck 52, the take-up reel 52 is orthogonal to the rotation axis of the take-up reel 53, and the carbon nanotube fiber bundle 10 is wound. The carbon nanotube fiber bundle 10 is twisted by rotating in the direction indicated by the arrow Rd2 (clockwise when the fixed chuck 52 is viewed from the take-up reel 53) with the taking direction as the rotation axis, and the carbon nanotubes are twisted. The fiber bundle 13 is produced. While the take-up reel 53 is rotating in the Rd2 direction, the take-up capstans 51a and 51b are separated from each other to increase the length of the carbon nanotube fiber bundle 10 orbiting the peripheral surfaces of the take-up capstans 51a and 51b. Let me. As a result, the carbon nanotube fiber bundle 10 is pulled out from the collecting die 31 at a constant speed regardless of the fixing by the fixing chuck 52 on the downstream side. When the twisting by the rotation of the take-up reel 53 in the Rd2 direction is completed, the fixation by the fixed chuck 52 is released, and the carbon nanotube fiber bundle 10 is pulled out from the take-up capstans 51a and 51b by the rotation of the take-up reel 53 in the Rd1 direction. The carbon nanotube fiber bundle 10 is wound around the winding reel 53. At this time, the take-up capstans 51a and 51b approach each other to unwind the carbon nanotube fiber bundle 10 to be taken up by the take-up reel 53. In this way, the approach and separation of the take-up capstans 51a and 51b synchronized with the rotation of the take-up reel 53 in the Rd1 and Rd2 directions are intermittently repeated.

_{The twist angle θ L} of the carbon nanotube fiber bundle 13 is preferably 5 to 30 °, more preferably 5 to 25 °. When the twist angle θ _L is smaller than 5 °, it is almost the same as when there is no twist. Therefore, no increase in strength is observed, and the change in cross-sectional area shape when the insulating coated carbon nanotube wire 2 is bent is improved. Not seen. On the other hand, if the twist angle θ _L is larger than 30 °, cracks occur along the twists and the strength is greatly reduced when tension is applied or bent. When the twist angle θ _L is 25 ° or less, such a decrease in strength does not occur, and when it is 25 to 30 °, only a slight decrease in strength occurs.

As described above, the reel 53 on which the carbon nanotube fiber bundle 13 formed as a stranded wire is wound is used as a feeding reel 53 for feeding out the carbon nanotube fiber bundle 13 toward the coated resin tank 33 in the manufacturing apparatus 200-2. It is attached. A magnetic fluid bearing 54 is used for the rotating shaft of the feeding reel 53. Since the carbon nanotube fiber bundle 13 of the present embodiment is very thin and has a low tension level, it is difficult to stabilize the tension. In the manufacturing process according to the present embodiment, the feed rate of the carbon nanotube fiber bundle 13 affects the amount of adhesion of the resin 34. Therefore, if the feed rate changes, the thickness of the insulating coating 12 varies. In this respect, since the magnetic fluid bearing acts as an appropriate brake, the tension and the delivery speed can be kept constant. Therefore, the feeding reel 53 using the magnetic fluid bearing can stably feed the carbon nanotube fiber bundle 13 to the coated resin tank 33 with low tension.
The resin 34 is applied to the entire surface of the carbon nanotube fiber bundle 13 fed from the feeding reel 53 and introduced into the coated resin tank 33 from the upper side through the upper peripheral surface of the guide roller 55 supported by the magnetic fluid bearing. Since the step of producing the insulating coated carbon nanotube wire 2 is the same as that of the first embodiment, the description thereof will be omitted.

<Example>
An embodiment of the present invention will be described below in comparison with a comparative example.
FIG. 8 shows the carbon nanotube fiber bundle diameter (μm), coating thickness (μm), standard deviation of coating thickness, coating material, and type of carbon nanotube wire for Examples 1 to 5 and Comparative Examples 1 to 5 of the present invention. “Fiber bundle” indicates non-stranded wire), tensile strength (MPa), breakdown voltage (V), and degree of suppleness. R in the breakdown voltage represents the fluctuation range which is the difference between the maximum value and the minimum value. The standard deviation of the coating thickness here is not the coefficient of variation.

The method of measuring the dielectric breakdown voltage will be described below.
FIG. 9 is a side view (FIG. 9 (A)) and a plan view (FIG. 9 (B)) schematically showing the configuration of the main part of the dielectric breakdown voltage measuring device 60. FIG. 10A is a circuit diagram of the dielectric breakdown voltage measuring device, and FIG. 10B is a graph showing the relationship between the voltage applied to the sample and time.
A copper foil electrode 62 is arranged on one side of the insulating substrate 61. A lead wire 621 is connected to the electrode 62. One end of the insulating coated carbon nanotube wire 1 as a sample is fixed on the electrode 62 via a conductive tape 63 in a state of being covered with the insulating coating 12. On the other side of the insulating substrate 61, an electrode 64 is arranged so as to sandwich and fix the insulating coated carbon nanotube wire 1 from which the insulating coating 12 is peeled off and the carbon nanotube fiber bundle 10 is exposed to the insulating substrate 61. A lead wire 641 is connected to the electrode 64. Here, the insulating coated carbon nanotube wire 1 is peeled off by 10 mm from the insulating coating 12 at a portion 50 mm away from the end portion of the electrode 62. The same applies to the case where the dielectric breakdown voltage is measured using the insulation-coated carbon nanotube wire 2 as a sample.

As shown in FIG. 10A, the lead wire 621 is branched into a lead wire 621a and a lead wire 621b, and an applied voltage measuring device (multimeter 3457A manufactured by Azilent Technology Co., Ltd.) 65 and a DC power supply device (Advantest Co., Ltd.) are respectively. R6145) 66 is connected. The lead wire 641 is branched into a lead wire 641a and a lead wire 641b, and is connected to an applied voltage measuring device 65 and a current measuring device (multimeter R6781E manufactured by Advantest Co., Ltd.) 67. Then, the lead wire 641b is connected to the DC power supply device 66 via the current measuring device 67.

Using the measuring device 60 configured as described above, the insulation breakdown voltage of the insulation-coated carbon nanotube wire 1 (the same applies to the insulation-coated carbon nanotube wire 3) is measured as follows.
First, as shown in FIG. 10B, a voltage is swept and applied from the DC power supply device 66 to the insulating coated carbon nanotube wire 1 at a speed of 0.1 V / sec in the range of 0 to 60 V, and the current measuring device 67 Measure the energizing current by.
Next, the horizontal axis is the voltage and the vertical axis is the current, and the measured value of the energizing current at the time of voltage sweep is plotted, and the voltage value when the measured value of the energizing current suddenly rises due to dielectric breakdown of the insulating coated carbon nanotube wire 1. Was defined as the dielectric breakdown voltage.

Examples 1 to 3 are examples of the insulating coated carbon nanotube wire 1 in which the entire surface of the untwisted wire of the carbon nanotube fiber bundle 10 is coated with an insulating coating according to the step according to the first embodiment. Examples 4 to 6 are examples of the insulating coated carbon nanotube wire 2 having an insulating coating on the entire surface of the twisted carbon nanotube fiber bundle 13 according to the step according to the second embodiment.

In Comparative Example 1, since the carbon nanotube fiber bundle diameter is large, the thickness of the insulating coating is also large, and the degree of suppleness is low. In Comparative Example 2, the thickness of the insulating coating is thin and the dielectric breakdown voltage is low. In Comparative Example 3, the thickness of the insulating coating is thick and the degree of suppleness is low. In Comparative Example 4, the thickness of the insulating coating varies widely, and the dielectric breakdown voltage varies widely. In Comparative Example 5, since the insulating coating is thick, the tensile strength is low and the degree of suppleness is also low. Further, in Comparative Example 5, since the thickness of the insulating coating varies widely, the dielectric breakdown voltage varies greatly.

As described above, the insulating coated carbon nanotube wire 1 according to Examples 1 to 3 and Examples 4 to 6
The insulating coated carbon nanotube wire 2 according to the above has a small diameter, is lightweight, and has high insulating properties and flexibility.

1,2 ... Insulation coated carbon nanotube wire 10, 13 ... Carbon nanotube fiber bundle 11 ... Carbon nanotube fiber 12 ... Insulation coating

Claims (6)

An insulating coated carbon nanotube wire comprising a carbon nanotube fiber bundle composed of a plurality of carbon nanotube fibers and an insulating coating for coating the surface of the carbon nanotube fiber bundle.
The diameter of the carbon nanotube fiber bundle is φ5 μm to 150 μm.
An insulating coated carbon nanotube wire having a thickness of the insulating coating of 0.25 μm to 2.5 μm. An insulating coated carbon nanotube wire comprising a carbon nanotube fiber bundle composed of a plurality of carbon nanotube fibers and an insulating coating for coating the surface of the carbon nanotube fiber bundle.
An insulating coated carbon nanotube wire characterized in that the ratio of the thickness of the insulating coating to the diameter of the carbon nanotube fiber bundle is 1.6 to 5%. The insulating coated carbon nanotube wire according to claim 1 or 2, wherein the carbon nanotube fiber bundle is a stranded wire of the plurality of carbon nanotube fibers. The insulating coated carbon nanotube wire according to any one of claims 1 to 3, wherein the standard deviation obtained by measuring the thickness of the insulating coating at eight points is 6% or less. The insulating coated carbon nanotube wire according to any one of claims 1 to 4, wherein the insulating coating is formed of polyimide. The insulating coated carbon nanotube wire according to any one of claims 1 to 5, wherein the tensile strength is 200 Mpa or more.

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