CN-122029950-A - Electromagnetic wave absorbing member for sub-terahertz frequency band of 100GHz or more

Abstract

The electromagnetic wave absorbing member for the sub-terahertz frequency band of the present invention is characterized by comprising a polymer material and carbon nanotubes, wherein the carbon nanotubes comprise single-walled carbon nanotubes as a main component, the electromagnetic wave absorbing member has an electrical conductivity of 0.1 (S/cm) or more and 2.0 (S/cm) or less, and an attenuation ratio at a frequency of 300 (GHz) of 5 (dB) or more.

Inventors

• YATSUZUKA TAICHI
• Yamagishi Chiko

Assignees

• 日本瑞翁株式会社

Dates

Publication Date

20260512

Application Date

20241021

Priority Date

20231025

Claims (11)

1. 1. An electromagnetic wave absorbing member for sub-terahertz frequency band of 100GHz or more, The electromagnetic wave absorbing member comprises a polymer material and carbon nanotubes, The carbon nanotubes comprise single-walled carbon nanotubes as a main component, The electromagnetic wave absorbing member has a conductivity of 0.1 (S/cm) or more and 2.0 (S/cm) or less, and a decay rate of 5 (dB) or more at a frequency of 300 (GHz).
2. 2. The electromagnetic wave absorbing member according to claim 1, wherein, The attached amount of the carbon nanotubes is A (mg), The conductivity of the carbon nanotubes is C (S/cm), the index I obtained according to the following formula (1) is more than 40 and less than 500, 。
3. 3. The electromagnetic wave absorbing member according to claim 1 or 2, wherein, The electromagnetic wave absorbing member is formed in a single-layer sheet shape.
4. 4. The electromagnetic wave absorbing member according to claim 3, wherein, The electromagnetic wave absorbing member has a thickness of 300 [ mu ] m or less.
5. 5. The electromagnetic wave absorbing member according to claim 3, wherein, The electromagnetic wave absorbing member is configured to include a polymer sheet containing the polymer material, and the carbon nanotubes attached to the polymer sheet.
6. 6. The electromagnetic wave absorbing member according to claim 3, wherein, The electromagnetic wave absorbing member is a sheet formed from a composition including the polymer material and the carbon nanotubes.
7. 7. The electromagnetic wave absorbing member of claim 5, wherein, The polymer sheet is a nonwoven fabric formed using polymer fibers made of the polymer material.
8. 8. The electromagnetic wave absorbing member according to claim 1 or 2, wherein, The G/D ratio of the carbon nanotubes is 4.0 or less.
9. 9. The electromagnetic wave absorbing member according to claim 1 or 2, wherein, The BET specific surface area of the carbon nanotubes is 600 (m 2/g) or more.
10. 10. The electromagnetic wave absorbing member according to claim 1 or 2, wherein, The effective length of the carbon nanotubes is 40 (nm) to 1000 (nm).
11. 11. The electromagnetic wave absorbing member according to claim 1 or 2, wherein, The electromagnetic wave absorbing member has an attenuation rate of 5 (dB) or more in a frequency band of 200 (GHz) or more and 300 (GHz) or less.

Description

Electromagnetic wave absorbing member for sub-terahertz frequency band of 100GHz or more Technical Field The invention relates to an electromagnetic wave absorbing member for a sub-terahertz frequency band of more than 100 GHz. Background Conventionally, in the electric field, the communication field, and the like, it has been known that a composite material in which a conductive material such as a carbon nanotube (hereinafter, also referred to as "CNT") is mixed with an insulating material such as a resin is used as an electromagnetic wave absorbing material. In these fields, although the frequency of use varies depending on the application, electromagnetic waves in a frequency range other than the desired frequency range may be generated as noise in an actual use environment. Accordingly, there is a need for an electromagnetic wave absorbing material that can attenuate electromagnetic waves of unwanted frequencies without attenuating the electromagnetic waves of the desired frequencies. For example, patent document 1 discloses an electromagnetic wave absorbing sheet comprising a sheet-like fibrous substrate and single-wall CNTs located within the sheet-like substrate, and having an electrical conductivity of 0.7 to 20 (S/cm). The electromagnetic wave absorption sheet is disclosed to have a transmission attenuation rate of 20dB or more in at least a part of the range of 1GHz to 10 GHz. Prior art literature Patent literature Patent document 1 International publication No. 2020/067203. Disclosure of Invention Problems to be solved by the invention In recent years, electromagnetic wave absorption performance in the 6G band (sub-terahertz band of 100GHz or more) has been demanded. However, the CNT-containing electromagnetic wave absorbing sheet capable of exhibiting electromagnetic wave absorbing performance in the sub-terahertz frequency band has not been studied sufficiently so far, including the above-mentioned patent document 1. The purpose of the present invention is to provide an electromagnetic wave absorbing member that has excellent electromagnetic wave absorbing performance in the sub-terahertz frequency band of 100GHz or more. Solution for solving the problem The present inventors have conducted intensive studies in order to solve the above-mentioned problems. Then, the present inventors have newly found that, in an electromagnetic wave absorbing member comprising a polymer material and carbon nanotubes, the attenuation ratio in the sub-terahertz frequency band of 100GHz or more can be improved by the carbon nanotubes comprising single-walled carbon nanotubes as a main component and having the conductivity of the electromagnetic wave absorbing member within a predetermined range, and completed the present invention. That is, an object of the present invention is to advantageously solve the above-described problems, and an electromagnetic wave absorbing member for the sub-terahertz frequency band of the present invention is as follows. [1] An electromagnetic wave absorbing member comprising a polymer material and carbon nanotubes, wherein the carbon nanotubes comprise single-walled carbon nanotubes as a main component, and wherein the electromagnetic wave absorbing member has an electrical conductivity of 0.1 (S/cm) or more and 2.0 (S/cm) or less and an attenuation ratio of 5 (dB) or more at a frequency of 300 (GHz). By using a single-walled carbon nanotube as a main component and having conductivity in the above range, electromagnetic wave absorption performance can be exhibited in the sub-terahertz frequency band of 100GHz or more. The conductivity and the decay rate were measured by the methods described in examples. [2] In the electromagnetic wave absorbing member of the above item [1], the amount of the carbon nanotubes attached is preferably A (mg), the conductivity of the carbon nanotubes is preferably C (S/cm), and the index I obtained according to the following formula (1) is preferably 40 to 500. If the index I is within the above range, electromagnetic wave absorption performance in the sub-terahertz frequency band is more excellent. In the present specification, "conductivity of carbon nanotubes" refers to conductivity measured using bucky paper formed using a predetermined amount of CNTs as described in the examples. [3] In the electromagnetic wave absorbing member of the above [1] or [2], the electromagnetic wave absorbing member is preferably formed as a single-layered sheet. By making the electromagnetic wave absorbing member a single-layer sheet, the electromagnetic wave absorbing member can be made thin and lightweight. [4] In the electromagnetic wave absorbing member of the above-mentioned [1] to [3], the thickness of the electromagnetic wave absorbing member is preferably 300 (μm) or less. If the thickness of the electromagnetic wave absorbing member is less than the upper limit, the electromagnetic wave absorbing member can be suitably used for mobile terminals such as smart phon