Electromagnetic noise suppression sheet, and communication cable and electronic device using same

Abstract

An electromagnetic noise suppression sheet of the present application is configured by stacking a magnetic layer and a substrate. The magnetic layer contains a soft magnetic material, a fibrous carbon material, and a resin. The volume content of the soft magnetic material contained in the magnetic layer is 30-70 vol%. The surface electrical resistance of the magnetic layer is 103-107 Ω / square.

Description

Electromagnetic noise suppression sheet, and communication cable and electronic device using the same.

[0001] This application relates to an electromagnetic noise suppression sheet that absorbs electromagnetic waves in the MHz to GHz band.

[0002] With the development of wireless communication technology, exemplified by mobile phones, various devices and sensors are increasingly being connected to networks wirelessly. In the medical field, too, cordless devices are becoming more common from the perspective of infection prevention, and medical equipment is beginning to connect wirelessly. These communications require high speed and large capacity over relatively short distances, and therefore utilize high frequencies. As the number of devices using such high frequencies increases, the risk of malfunctions in electronic devices and communications due to electromagnetic noise generated by the devices or interference with the electromagnetic waves being used is also increasing. Furthermore, in recent years, millimeter-wave radar has begun to be installed in automobiles for the purpose of preventing collision accidents. Malfunctions in these medical and automotive devices can affect human lives, so they must not be allowed to operate. Therefore, there is a growing need to apply electromagnetic noise suppression sheets, as a measure to prevent malfunctions caused by electromagnetic noise and the resulting interference, also known as EMC (Electromagnetic Compatibility), to circuit elements and transmission lines that emit and receive electromagnetic waves in the MHz to GHz band.

[0003] By providing electromagnetic noise suppression sheets to society, we can contribute to achieving three of the 17 Sustainable Development Goals (SDGs) established by the United Nations: Goal 3 (Ensure healthy lives and promote well-being for all at all ages), Goal 9 (Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation), and Goal 12 (Ensure sustainable consumption and production patterns).

[0004] In this context, Patent Document 1 describes an electromagnetic shielding film comprising a base layer and an electromagnetic shielding layer laminated on the base layer, wherein the electromagnetic shielding layer comprises at least one of a conductive material and a magnetic absorbing material, and the surface resistance of the electromagnetic shielding layer is 1 × 10⁻¹⁰ －３ Ω / □ or more, 1×10 ６It is stated that the value should be set to Ω / □ or less. Furthermore, Patent Document 1 states that carbon nanotubes can be used as the conductive material and soft magnetic metals can be used as the magnetic absorbing material.

[0005] Many of the soft magnetic metals described in Patent Document 1 exhibit excellent electromagnetic noise suppression effects at high frequencies exceeding 10 GHz, but typically have little electromagnetic noise suppression effect at low frequencies of around 1 to 10 GHz. Furthermore, Patent Document 1 specifies a surface resistance value of 1 × 10⁻⁶ for the electromagnetic wave shielding layer. －３ Ω / □ or more, 1×10 ６ Although it is broadly stated as Ω / □ or less, the surface electrical resistance value can be expressed as, for example, 1 × 10⁻⁶ ３ If the value is set below Ω / □, the surface electrical resistance becomes too small, leading to increased reflection of electromagnetic waves at the surface of the electromagnetic shielding layer, which degrades the signal transmission characteristics and reduces the electromagnetic noise suppression effect.

[0006] While it is possible to shift the peak of the transmission attenuation rate to a lower frequency range by increasing the thickness of the magnetic layer of the electromagnetic noise suppression sheet, increasing the thickness of the magnetic layer reduces the flexibility of the electromagnetic noise suppression sheet, making it difficult to wrap around cables and connectors.

[0007] Japanese Patent Publication No. 2018-195854

[0008] This invention solves the above problem and provides an electromagnetic noise suppression sheet that can simultaneously improve the electromagnetic noise suppression effect in the low-frequency range and the electromagnetic noise suppression effect by suppressing the reflection of electromagnetic waves on the surface of the magnetic layer, by setting the surface electrical resistance value of the magnetic layer within an appropriate range.

[0009] The electromagnetic noise suppression sheet of the present invention is an electromagnetic noise suppression sheet comprising a magnetic layer and a substrate laminated together, wherein the magnetic layer comprises a soft magnetic material, a fibrous carbon material, and a resin, the volume content of the soft magnetic material contained in the magnetic layer is 30% by volume or more and 70% by volume or less, and the surface electrical resistance value of the magnetic layer is 10 ３ Ω / Square or higher 10 ７ It is characterized by being less than or equal to Ω / square.

[0010] The communication cable of the present application is characterized by including the electromagnetic noise suppression sheet of the present application.

[0011] The electronic device of the present application is characterized by including the electromagnetic noise suppression sheet of the present application.

[0012] According to the present application, it is possible to provide an electromagnetic noise suppression sheet that can exhibit an electromagnetic noise suppression effect in a wide frequency band while suppressing the reflection of electromagnetic waves, and that also has excellent sliding durability of the electromagnetic noise suppression sheet.

[0013] FIG. 1 is a schematic cross-sectional view showing an example of the electromagnetic noise suppression sheet of the embodiment. FIG. 2 is a schematic cross-sectional view showing another example of the electromagnetic noise suppression sheet of the embodiment. FIG. 3 is a schematic cross-sectional view showing an example of the coaxial cable of the embodiment.

[0014] (Electromagnetic Noise Suppression Sheet) An embodiment of the electromagnetic noise suppression sheet of the present application will be described. The electromagnetic noise suppression sheet of the present embodiment is configured by laminating a magnetic layer and a base material. The magnetic layer includes a soft magnetic material, a fibrous carbon material, and a resin. The volume content ratio of the soft magnetic material contained in the magnetic layer is 30% by volume or more and 70% by volume or less, and the surface electrical resistance value of the magnetic layer is 10 ３ Ω / square or more and 10 ７ Ω / square or less.

[0015] In the electromagnetic noise suppression sheet of the present embodiment, since the fibrous carbon material is contained in the magnetic layer, the surface electrical resistance value of the magnetic layer is slightly reduced compared to the surface electrical resistance value of the magnetic layer that does not contain the fibrous carbon material, and eddy current loss occurs, so the electromagnetic noise suppression effect in the low frequency region near 10 GHz is improved. As a result, in the distribution curve of the transmission attenuation rate (Rtp) by the microstrip line method, the lower limit value of the frequency at which Rtp becomes 6 dB or more can be made to exist in the range of 7 to 12 GHz.

[0016] Furthermore, in the electromagnetic noise suppression sheet of this embodiment, the inclusion of fibrous carbon material in the magnetic layer improves the sliding durability of the magnetic layer. Specifically, the magnetic layer is usually formed by mixing a soft magnetic material, a fibrous carbon material, a resin, and a solvent to create a magnetic layer-forming coating, applying the coating to a substrate, and drying it. During this application process, the soft magnetic material, which has a higher specific gravity, settles into the coating film, while the fibrous carbon material, which has a lower specific gravity, does not settle and remains near the surface of the coating film. As a result, the fibrous carbon material content near the surface of the magnetic layer after drying is relatively high. Therefore, it is thought that the long axes of the fibrous carbon material are aligned in the application direction (MD direction) of the coating near the surface of the magnetic layer, improving the sliding effect in the MD direction of the magnetic layer surface and improving the sliding durability of the magnetic layer.

[0017] Furthermore, in the electromagnetic noise suppression sheet of this embodiment, the surface electrical resistance value of the magnetic layer is 10 ３ Ω / Square or higher 10 ７ Since it is set to Ω / square or less, the surface electrical resistance of the magnetic layer does not become too small, which suppresses the reflection of electromagnetic waves on the surface of the magnetic layer, improves the transmission attenuation rate (Rtp) without impairing the transmission characteristics, and greatly enhances the electromagnetic noise suppression effect. On the other hand, if the above surface electrical resistance value is 10 ７ When the Ω / square value exceeds a certain limit, it is thought that the amount of fibrous carbon material in the magnetic layer decreases, resulting in a reduction in the electromagnetic noise suppression effect in the low-frequency range, as well as a decrease in the sliding durability of the magnetic layer.

[0018] The fibrous carbon material is preferably carbon nanotubes. By adding carbon nanotubes to the magnetic layer, the surface electrical resistance of the magnetic layer is slightly reduced, and eddy current loss occurs, thereby improving the electromagnetic noise suppression effect in the low-frequency region around 10 GHz. As a result, even without increasing the thickness of the magnetic layer, the peak of the transmission attenuation rate can be shifted to a lower frequency region, enabling electromagnetic noise suppression across a wide frequency band. Furthermore, as mentioned above, the sliding effect in the MD direction of the magnetic layer surface can be improved, thereby improving the sliding durability of the magnetic layer. The improved sliding durability of the magnetic layer prevents damage to the magnetic layer and powder shedding (separation and fall of magnetic powder from the magnetic layer) when attaching the electromagnetic noise suppression sheet to cables, etc.

[0019] The volume content of fibrous carbon material, such as carbon nanotubes, contained in the magnetic layer is preferably 0.05% by volume or more and 5.0% by volume or less. If the amount of fibrous carbon material added exceeds the upper limit of the volume content, the surface electrical resistance of the magnetic layer may become too low, leading to increased reflection of electromagnetic waves at the surface of the magnetic layer, which may degrade the signal transmission characteristics and reduce the noise suppression effect. Conversely, if the volume content falls below the lower limit, the transmission attenuation rate and sliding durability may decrease.

[0020] The presence of fibrous carbon material near the surface of the magnetic layer was confirmed by Raman spectral analysis of the magnetic layer, with a value of 1580 cm⁻¹ in the Raman spectrum. －１ ~1600cm －１ This can be determined by whether or not a G-band peak originating from fibrous carbon exists within that range.

[0021] Furthermore, in the electromagnetic noise suppression sheet of this embodiment, the volume content of the soft magnetic material contained in the magnetic layer is set to 30% by volume or more and 70% by volume or less, so that an electromagnetic noise suppression effect can be achieved in the high-frequency range. On the other hand, if the volume content of the soft magnetic material exceeds 70% by volume, the amount of soft magnetic material relative to the resin in the magnetic layer becomes too large, which may make it difficult to form the magnetic layer. Also, if the volume content falls below 30% by volume, there is a risk that the transmission attenuation rate will decrease.

[0022] The soft magnetic material is preferably carbonyl iron powder. This is because carbonyl iron powder has excellent electromagnetic noise suppression effects at high frequencies exceeding several tens of GHz, and its transmission attenuation rate peaks around 30 GHz.

[0023] The electromagnetic noise suppression sheet of this embodiment will be described below with reference to the drawings. The electromagnetic noise suppression sheet of this embodiment is constructed by laminating a magnetic layer and a base material. Figure 1 is a schematic cross-sectional view showing an example of the electromagnetic noise suppression sheet of this embodiment. In Figure 1, the electromagnetic noise suppression sheet 10 comprises a base material 11 and a magnetic layer 12 laminated on the base material 11. In Figure 1, the electromagnetic noise suppression sheet 10 is composed of a base material 11 and a magnetic layer 12, but an adhesive layer may also be placed on either of the outer surfaces.

[0024] Figure 2 is a schematic cross-sectional view showing another example of the electromagnetic noise suppression sheet of this embodiment. In Figure 2, the electromagnetic noise suppression sheet 20 comprises a base material 21 and a magnetic layer 22 laminated on the base material 21. The base material 21 is composed of a metal layer 21a and a resin layer 21b. In Figure 2, the electromagnetic noise suppression sheet 20 is composed of a base material 21 and a magnetic layer 22, but an adhesive layer may also be placed on either of the outer surfaces.

[0025] The overall thickness of the electromagnetic noise suppression sheet in this embodiment is preferably 15 to 85 μm, and more preferably 20 to 60 μm. If the overall thickness of the electromagnetic noise suppression sheet is too thin, the thickness of the magnetic layer will also be thin, reducing the electromagnetic noise suppression effect and the overall strength of the sheet. On the other hand, if the overall thickness of the electromagnetic noise suppression sheet is too thick, its flexibility will decrease, making it difficult to wrap around cables and connectors.

[0026] Next, each component of the electromagnetic noise suppression sheet of this embodiment will be described.

[0027] <Substrate> The substrate used in the electromagnetic noise suppression sheet of this embodiment is a base material for forming the magnetic layer. The substrate can be any material that is flexible and can ensure adhesion with the magnetic layer, and a resin film is usually used. Examples of resins that make up the above-mentioned resin film include polyolefin resins (polyethylene, polypropylene, etc.), polyester resins (polyethylene terephthalate: PET, polyethylene naphthalate: PEN, polybutylene terephthalate: PBT, polybutylene naphthalate: PBN, etc.), polyimide resins, polyamide resins, ethylene-vinyl acetate copolymers, ionomer resins, ethylene-(meth)acrylic acid copolymers, ethylene-(meth)acrylic acid ester copolymers, ethylene-butene copolymers, ethylene-hexene copolymers, polyurethane resins, polyetherketone resins, polyether resins, polyethersulfone resins, polystyrene resins (polystyrene, etc.), polyvinyl chloride resins, polyvinylidene chloride resins, polyvinyl alcohol resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate copolymers, polycarbonate resins, fluoropolymers, silicone resins, cellulose resins, and crosslinked products of these resins. Among these, polyethylene terephthalate (PET) is more preferred in terms of mechanical properties and cost. These resins can be used individually or in combination of two or more types. Furthermore, the resins may have functional groups as needed. Functional monomers or modifier monomers may also be grafted onto the resin material.

[0028] The surface of the above-mentioned substrate may be subjected to known surface treatments to improve adhesion with adjacent magnetic layers. Specific examples of such surface treatments include corona discharge treatment, ozone exposure treatment, high-voltage electric shock exposure treatment, and ionization radiation treatment. Furthermore, the substrate may be subjected to coating treatments with undercoating agents (such as silicone treatment), primer treatment, matting treatment, crosslinking treatment, etc.

[0029] The form of the above-mentioned base material may be a single layer or a laminate of two or more layers. Further, known auxiliaries such as fillers, flame retardants, deterioration inhibitors, antistatic agents, softeners, plasticizers, etc. may be added to the above resin layer as necessary.

[0030] The thickness of the above-mentioned base material is not particularly limited, but is preferably 5 to 20 μm, more preferably 10 to 15 μm. If the thickness of the above-mentioned base material is within the above range, both the strength and flexibility of the electromagnetic noise suppression sheet of the present embodiment can be achieved.

[0031] The above-mentioned base material can also be used as a metal / resin composite film by laminating the above resin film (resin layer) and metal foil (metal layer). By providing the above-mentioned base material with a metal layer, electric field shielding performance can be imparted to the electromagnetic noise suppression sheet, and not only magnetic noise but also electric noise can be suppressed.

[0032] The type of metal constituting the above metal layer is not particularly limited as long as it has a certain degree of flexibility, but aluminum, copper, permalloy, etc. are preferable. This is because aluminum and copper have high conductivity, are inexpensive, are easy to process into thin films, and have excellent flexibility. In addition to conductivity, permalloy has a high magnetic flux concentration effect in the kHz region and can also obtain the effect as a magnetic shield.

[0033] The thickness of the above metal layer is preferably 5 μm or more and 15 μm or less. If the thickness of the above metal layer is less than 5 μm, the shielding performance of electric noise will decrease. If the thickness exceeds 15 μm, the thickness of the metal layer will become too large, the processability of the electromagnetic noise suppression sheet will decrease, and it will be difficult to wind up the sheet.

[0034] As the above metal layer, it can be used alone as a metal foil, or it can also be formed as a metal thin film on the above resin film (resin layer) by vapor deposition or sputtering and used.

[0035] <Magnetic layer> The magnetic layer used in the electromagnetic noise suppression sheet of the present embodiment functions as an electromagnetic noise suppression layer and contains a soft magnetic material, a fibrous carbon material, and a resin.

[0036] The thickness of the magnetic layer is preferably 10 μm or more and 60 μm or less. If the thickness of the magnetic layer is less than 10 μm, the shielding performance against magnetic noise will decrease, and if the thickness exceeds 60 μm, the flexibility of the magnetic layer will decrease, making it difficult to wrap around cables and connectors. The constituent materials of the magnetic layer will be described below.

[0037] [Soft Magnetic Materials] Generally, magnetic materials include soft magnetic materials and hard magnetic materials, but in this embodiment, soft magnetic materials are used. Soft magnetic materials have high initial magnetic permeability and can exhibit magnetic noise shielding performance even when included in small amounts in the magnetic layer, so they can exhibit electromagnetic noise suppression effects even when the magnetic layer is made into a thin film.

[0038] Examples of the above soft magnetic materials include iron, carbonyl iron powder, silicon iron, permalloy, Fe-Si-Al alloy, permendur, soft ferrite, ferritic stainless steel, electromagnetic stainless steel, amorphous magnetic alloy, nanocrystal magnetic alloy, etc., but in particular, Fe(CO) ５ Carbonyl iron powder represented by [formula] is preferred. This is because carbonyl iron powder can exhibit electromagnetic wave absorption performance (electromagnetic noise suppression effect) even in high frequency ranges of several tens of GHz or higher.

[0039] The above-mentioned soft magnetic material is usually provided as a spherical or flattened powder, and its average particle size is preferably 3 μm to 50 μm, and more preferably 3 μm to 20 μm. If the average particle size of the soft magnetic material is too small, the particles tend to aggregate secondarily, making it difficult to obtain a uniform coating (magnetic layer). On the other hand, if the average particle size is too large, the particles protrude from the magnetic layer as protrusions, making it difficult to attach or wrap the electromagnetic noise suppression sheet to uneven or curved surfaces, as the magnetic layer tends to peel off from the substrate. The above-mentioned average particle size can be measured using a laser diffraction scattering particle size distribution analyzer.

[0040] As previously stated, the volume content of the soft magnetic material contained in the magnetic layer is between 30% and 70% by volume. If the volume content of the soft magnetic material falls below 30% by volume, the shielding performance against magnetic noise decreases. If the volume content exceeds 70% by volume, the flexibility of the magnetic layer decreases, making it difficult to wrap around cables and connectors. Furthermore, the sliding durability decreases due to the relatively smaller amount of resin.

[0041] [Fibrous Carbon Materials] As the above-mentioned fibrous carbon materials, pitch-based carbon fibers, PAN (polyacrylonitrile)-based carbon fibers, rayon-based carbon fibers, and carbon nanotubes can be used, but as mentioned above, carbon nanotubes are the most preferred.

[0042] As the carbon nanotubes mentioned above, single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), branched carbon nanotubes, branched multi-walled carbon nanotubes, etc., can be used. Among these, SWCNTs are preferred because they can control the surface electrical resistance of the magnetic layer with only a small amount.

[0043] The volume content of the fibrous carbon material contained in the magnetic layer is preferably 0.05 vol% to 5.0 vol%, more preferably 0.05 vol% to 0.2 vol%, and even more preferably 0.06 vol% to 0.18 vol%. If the volume content of the fibrous carbon material contained in the magnetic layer is less than 0.05 vol%, the sliding effect on the surface of the magnetic layer cannot be obtained, and the sliding durability of the magnetic layer decreases. On the other hand, if the volume content is greater than 5.0 vol%, the surface electrical resistance of the magnetic layer decreases, and the reflection of electromagnetic waves at the surface of the magnetic layer increases, so the average value of the return loss (S11) increases, and the signal transmission characteristics deteriorate when used for noise suppression in cables, circuits, etc. In addition, if the volume content is greater than 5.0 vol%, the amount of soft magnetic material contained in the magnetic layer decreases, so the transmission attenuation rate (Rtp) tends to decrease, which is undesirable. Furthermore, when MWCNTs are used, the electrical resistance value increases due to the scattering of electrons caused by interactions between the multilayer layers and defects in the multilayer structure. Therefore, when using MWCNTs, the content can be increased compared to SWCNTs. When using MWCNTs, from the viewpoint of the sliding durability of the magnetic layer, the suppression of reflection on the surface, and the transmission characteristics which are the effects of using SWCNTs, the volume content of MWCNTs is preferably 1.5 volume% to 5.0 volume%.

[0044] However, when using MWCNTs, from the viewpoint of reducing the impact on the human body, it is preferable that at least one of the following conditions be met: the geometric tube diameter range is less than 30 nm or 3 μm or more, the length is less than 5 μm, or the aspect ratio is less than 3:1. Here, the geometric tube diameter range is the diameter of the outermost layer. The aspect ratio is the ratio of the geometric tube diameter range to the length, i.e., the value of length / geometric tube diameter range.

[0045] [Resin] The resin used in the magnetic layer functions as a binder that holds and fixes the soft magnetic material. Preferably, the resin includes an amorphous resin (A) with a glass transition temperature of -50°C to 0°C and an amorphous resin (B) with a glass transition temperature of 10°C or higher. Amorphous resins have high solubility in water and other solvents and excellent dispersibility of magnetic materials (magnetic powder). Therefore, by dispersing magnetic powder in a resin dissolved in water or other solvents, and coating and drying it on a substrate to an arbitrary thickness, it is possible to form a magnetic layer into a sheet.

[0046] As the amorphous resin (A), amorphous polyester, amorphous polyurethane, amorphous acrylic, etc., having a glass transition temperature of -50°C to 0°C can be used, and as the amorphous resin (B), amorphous polyester, amorphous polyurethane, amorphous acrylic, etc., having a glass transition temperature of 10°C or higher can be used. Among these, amorphous polyester (a) with a glass transition temperature of -50°C to 0°C is particularly preferred as amorphous resin (A), and amorphous polyester (b) with a glass transition temperature of 10°C or higher is particularly preferred as amorphous resin (B). Among amorphous resins, amorphous polyester has excellent solubility and flexibility and is suitable for manufacturing sheet-like magnetic layers.

[0047] From the above viewpoint, the content ratio of amorphous polyester (a) and amorphous polyester (b) is preferably (a):(b) = 95:5 to 35:65 by mass ratio, and more preferably (a):(b) = 90:10 to 50:50. The content ratio of amorphous polyester (a) and (b) can be estimated to some extent from the intensity of the two glass transition temperature peaks detected by measuring the glass transition temperature of the magnetic layer. The glass transition temperature can be measured by differential scanning calorimeter (DSC).

[0048] Examples of the amorphous polyesters (a) and (b) mentioned above include "Byron" (registered trademark) manufactured by Toyobo Co., Ltd., "Pluscoat" (registered trademark) manufactured by Go-O Chemical Co., Ltd., "Nichigo Polyester" (registered trademark) manufactured by Mitsubishi Chemical Corporation, and "Almatex" (registered trademark) manufactured by Mitsui Chemicals, Inc. Because these have excellent solubility in water and organic solvents, they can be used by dissolving them in water or organic solvents in any proportion.

[0049] Furthermore, it is preferable that at least one of the amorphous polyester (a) and the amorphous polyester (b) includes a crosslinked portion formed by amide bonds. This further improves the adhesion of the magnetic layer to the substrate. Typically, the amorphous polyesters (a) and (b) have carboxyl groups at least at their molecular ends, and carboxyl groups can be optionally added to their molecular chains. Therefore, by using a crosslinking agent, a crosslinked portion formed by amide bonds can be formed.

[0050] Next, further characteristics of the electromagnetic noise suppression film of this embodiment will be described.

[0051] <Return Loss> When the return loss (S11) of the electromagnetic noise suppression film of this embodiment is measured by the microstrip line method in the measurement frequency range of 0 to 30 GHz, the average value of the return loss can be reduced to -18 dB or less. That is, the return loss, which is the absolute value of the - dB value, can be increased, and reflection can be reduced. In the electromagnetic noise suppression sheet of this embodiment, the surface electrical resistance value of the magnetic layer is set to 10 ３ Ω / Square or higher 10 ７ Because it is set to Ω / square or less, the surface electrical resistance of the magnetic layer does not become too low, and the reflection of electromagnetic waves at the surface of the magnetic layer can be suppressed. As a result, the transmission attenuation rate of the electromagnetic noise suppression sheet of this embodiment can be increased.

[0052] <Transmission Attenuation Rate (Rtp)> The transmission attenuation rate (Rtp) of the electromagnetic noise suppression sheet was measured using the microstrip line method (compliant with IEC 62333-1 and IEC 62333-2). Specifically, the transmission attenuation rate was measured by connecting an Anritsu Corporation vector network analyzer "MS46122B-043" and a Keycom Corporation microstrip line "TF-30A test fixture" with a 3m coaxial cable "MWX051-03000KFSKMS / B" manufactured by Junko Co., Ltd.

[0053] The vector network analyzer was pre-calibrated using SOLT (Short-Open-Load-Thru) and measured using Keycom's analysis software "DMP-002041020-09 measurement program". The frequency range was 0.1 GHz to 30 GHz, and measurement points were set using 401-point linear scaling. A 30 mm x 30 mm electromagnetic noise suppression film was placed on the microstrip line, and the electromagnetic wave reflection attenuation (S11M) and electromagnetic wave transmission attenuation (S21M) were measured with a load of a 150 g PTFE block applied. The transmission attenuation rate (Rtp) was calculated using the following formula (1).

[0054] Formula (1):

[0055] (Method for Manufacturing an Electromagnetic Noise Suppression Sheet) An embodiment of the method for manufacturing the electromagnetic noise suppression sheet of the present invention will be described. The method for manufacturing the electromagnetic noise suppression sheet of the present invention of this embodiment is a method for manufacturing the electromagnetic noise suppression sheet of the present invention as described above, and includes a first step of mixing a soft magnetic material, a fibrous carbon material, a resin, and a solvent to produce a coating for forming a magnetic layer; a second step of applying the coating for forming a magnetic layer to a substrate and drying it to produce a magnetic layer / substrate laminated sheet; and a third step of calendering the magnetic layer / substrate laminated sheet.

[0056] <Paint for forming a magnetic layer> The above-mentioned paint for forming a magnetic layer can be made by mixing a soft magnetic material, a fibrous carbon material, a resin, and a solvent.

[0057] The soft magnetic material, fibrous carbon material, and resin described above are the same as those that constitute the magnetic layer of the electromagnetic noise suppression sheet in the embodiment of the present invention described above.

[0058] Examples of solvents that can be used include water, ethyl alcohol, methyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, ethylene glycol, propylene glycol, methyl ethyl ketone, ethyl acetate, toluene, and the like.

[0059] The content of the above solvent is not particularly limited, but it should be 50.0% by mass or more and 99.5% by mass or less, relative to the total mass of the magnetic layer forming coating.

[0060] When carbon nanotubes are used as the fibrous carbon material described above, it is preferable to add a dispersant to the coating for forming the magnetic layer. Strong pi-pi interactions and van der Waals forces act on the surface of carbon nanotubes, causing them to form bundle structures, which often makes dispersion in the solvent difficult. For this reason, it is preferable to use a dispersant to sufficiently disperse the carbon nanotubes in the coating for forming the magnetic layer.

[0061] Examples of dispersants that can be used include surfactants, resin-type dispersants, and fluororesins. These surfactants are mainly classified into anionic, cationic, nonionic, and amphoteric types, and a suitable surfactant can be used in a suitable amount depending on the dispersion conditions.

[0062] The above-mentioned coating for forming a magnetic layer may further contain surface modifiers, defoamers, thickeners, etc.

[0063] <Formation of Magnetic Layer> As a method for applying the above-mentioned magnetic layer-forming coating onto the substrate, for example, coating methods such as bar coating, reverse coating, gravure coating, microgravure® coating, die coating, dipping, spin coating, slit coating, and spray coating can be used.

[0064] The drying after coating as described above can be carried out under conditions that allow the solvent component of the magnetic layer-forming coating to evaporate, and is preferably done at 80 to 150°C for 3 to 30 minutes. If solvent remains in the magnetic layer, the strength tends to be inferior. Drying methods include, for example, hot air drying, heating drying, vacuum drying, and natural drying.

[0065] The above calendering process can be carried out using metal or resin rolls. Furthermore, when forming the magnetic layer on a single sheet, it can be done by press working. Both the calendering process and press working are preferably carried out at a temperature above the glass transition temperature (Tg) of the resin used for the formed magnetic layer, and more preferably at a temperature 20°C or more higher than Tg. The pressure for the calendering process is preferably a linear pressure of 250 kg / cm or higher. The pressure for the press working is preferably 200 kg / cm. ２ The above pressure is preferable. Furthermore, the calendering and pressing processes may be performed multiple times.

[0066] Generally, the calendering and pressing processes described above improve the smoothness of the magnetic layer, and when the magnetic layer comes into contact with other layers, the contact area increases, reducing the sliding durability of the magnetic layer. However, as mentioned above, in the coating and drying process of this invention, the soft magnetic material with a high specific gravity mainly moves towards the substrate side of the coating film, while the fibrous carbon material with a low specific gravity tends to remain mainly near the surface of the coating film. Therefore, the content of fibrous carbon material near the surface of the magnetic layer after drying is relatively higher than in the interior of the coating film or on the substrate side. For this reason, it is thought that the long axes of the fibrous carbon material near the surface of the magnetic layer tend to align in the coating direction (MD direction), improving the sliding effect of the magnetic layer surface in the MD direction and thus improving the sliding durability of the magnetic layer.

[0067] (Communication Cable) An embodiment of the communication cable of the present invention will now be described. The communication cable of this embodiment is characterized by comprising the electromagnetic noise suppression sheet of the embodiment of the present invention described above. The communication cable of this embodiment includes coaxial cables, twisted pair cables, multi-core cables, etc. In particular, coaxial cables are used for high-frequency transmission and are used for video cable applications.

[0068] The following describes a coaxial cable, which is one of the communication cables in this embodiment, based on the drawings. In the coaxial cable described below, the electromagnetic noise suppression sheet of this application is used as the electromagnetic noise suppression layer of the coaxial cable.

[0069] Figure 3 is a schematic cross-sectional view showing an example of a coaxial cable. The coaxial cable 30 comprises an internal conductor 31, an insulating layer 32, a metal foil 33, a metal braid 34, an electromagnetic noise suppression layer 35, and an outer covering layer 36. The electromagnetic noise suppression layer 35 uses the electromagnetic noise suppression sheet of the present invention described above, and is composed of a base layer 35a and a magnetic layer 35b arranged on one side of the base layer 35a.

[0070] In Figure 3, the magnetic layer 35b of the electromagnetic noise suppression layer 35 is positioned on the axial side, but the base material layer 35a may also be positioned on the axial side.

[0071] The electromagnetic noise suppression layer 35 of the coaxial cable 30 can be formed by wrapping the electromagnetic noise suppression sheet of this invention around the outer surface of a linear conductor consisting of an internal conductor 31, an insulating layer 32, a metal foil 33, and a metal braid 34. This allows for a thinner electromagnetic noise suppression layer and shorter processing time.

[0072] Furthermore, in the winding process described above, it is necessary to wind a tape-shaped slit electromagnetic noise suppression sheet onto the outer surface of the linear conductor with a diameter of approximately 1.8 mm in a longitudinal or spiral manner. However, during this process, the electromagnetic noise suppression sheet is subjected to large tensions, bending stresses, and shear forces, which may cause damage to the magnetic layer or shedding of powder. However, as mentioned above, the electromagnetic noise suppression sheet of the present invention has high sliding durability of the magnetic layer, thus preventing damage to the magnetic layer and shedding of powder.

[0073] (Electronic Device) An embodiment of the electronic device of the present invention will now be described. The electronic device of this embodiment is characterized by comprising the electromagnetic noise suppression sheet of the embodiment of the present invention described above. This makes it possible to use the electromagnetic noise suppression sheet of the present invention as an electromagnetic noise suppression member of the electronic device. Specifically, in the electronic device of this embodiment, for example, the electromagnetic noise suppression sheet of the present invention is placed on the uneven surfaces and corners of electronic equipment that emits electromagnetic noise or electronic equipment that is to be protected from electromagnetic noise. Furthermore, the electromagnetic noise suppression sheet of the present invention can also be used as a substitute for ferrite cores used in cables for electronic equipment.

[0074] The present application will be described in detail below using examples. However, the present application is not limited to the following examples. Unless otherwise specified, "parts" below means "parts by mass".

[0075] (Example 1) <Preparation of magnetic layer forming paint> A magnetic layer forming paint was prepared by mixing and dispersing the following components. (1) Soft magnetic material (flattened carbonyl iron powder manufactured by Tenichi Co., Ltd., product name "RPZ", Fe content: 99.0% by mass, average particle size: 15 μm): 33.21 parts (2) Amorphous polyester (a) (water-soluble polyester resin solution, manufactured by Go-o Chemical Co., Ltd., product name "Pluscoat Z-3310", Tg: -20℃, solid content concentration: 25.0% by mass, solvent: water): 26.82 parts (3) Amorphous polyester (b) (water-soluble polyester resin solution, manufactured by Go-o Chemical Co., Ltd., product name "Pluscoat Z-730", Tg: 43℃, solid content concentration: 25.0% by mass, solvent: water): 11.49 parts (4) Crosslinking agent (oxazoline group-containing polymer, manufactured by Nippon Shokubai Co., Ltd., product name "Epocross WS500", solid content concentration: 40.0% by mass, solvent: water): 3.59 parts (5) Single-walled carbon nanotube (SWCNT) dispersion (dispersion solvent: isopropyl alcohol, SWCNT solid content concentration: 0.2% by mass): 10.30 parts (6) Solvent (n-propyl alcohol): 8.97 parts (7) Purified water: 5.63 parts

[0076] In the above-mentioned coating for forming a magnetic layer, the volume content of the soft magnetic material was 34.2% and the volume content of SWCNTs was 0.063% relative to the total solid content of the coating for forming a magnetic layer.

[0077] <Formation of Magnetic Layer> Next, a PET film with a thickness of 12 μm (manufactured by Toyobo Co., Ltd., product name "Toyobo Ester® Film E5102") was used as a substrate, and the above-mentioned magnetic layer forming coating was applied to one main surface of the substrate using an applicator, and then dried at 120°C for 3 minutes. This was cut into 150 mm squares and pressed at a temperature of 50°C and a surface pressure of 210 kg / cm² using a press machine. ２ An electromagnetic noise suppression sheet of Example 1 was fabricated by pressing it for 30 seconds, forming a magnetic layer on one of its main surfaces. The thickness of the magnetic layer was 37 μm, and the overall thickness of the electromagnetic noise suppression sheet was 49 μm.

[0078] (Example 2) An electromagnetic noise suppression sheet of Example 2 was prepared in the same manner as in Example 1, except that the volume content of SWCNTs relative to the total solid content of the magnetic layer forming coating was changed to 0.118%.

[0079] (Example 3) An electromagnetic noise suppression sheet of Example 3 was prepared in the same manner as in Example 1, except that the volume content of SWCNTs relative to the total solid content of the magnetic layer forming coating was changed to 0.175%, the thickness of the magnetic layer was changed to 30 μm, and the overall thickness of the electromagnetic noise suppression sheet was changed to 42 μm.

[0080] (Example 4) An electromagnetic noise suppression sheet of Example 4 was prepared in the same manner as in Example 1, except that the volume content of the soft magnetic material relative to the total solid content of the magnetic layer forming coating was changed to 30.5%, the volume content of SWCNTs was changed to 0.12%, the thickness of the magnetic layer was changed to 41 μm, and the overall thickness of the electromagnetic noise suppression sheet was changed to 53 μm.

[0081] (Example 5) An electromagnetic noise suppression sheet of Example 5 was prepared in the same manner as in Example 1, except that the volume content of the soft magnetic material relative to the total solid content of the magnetic layer forming coating was changed to 65%, the volume content of SWCNTs was changed to 0.13%, the thickness of the magnetic layer was changed to 23 μm, and the overall thickness of the electromagnetic noise suppression sheet was changed to 35 μm.

[0082] (Example 6) An electromagnetic noise suppression sheet of Example 6 was prepared in the same manner as in Example 1, except that the volume content of SWCNTs relative to the total solid content of the magnetic layer forming coating was changed to 0.11%, the thickness of the magnetic layer was changed to 60 μm, and the overall thickness of the electromagnetic noise suppression sheet was changed to 72 μm.

[0083] (Example 7) An electromagnetic noise suppression sheet for Example 7 was prepared in the same manner as in Example 1, except that the carbon nanotubes used were changed to multi-walled carbon nanotubes (MWCNTs), the volume content of MWCNTs relative to the total solid content of the magnetic layer forming coating was changed to 1.5%, the thickness of the magnetic layer was changed to 40 μm, and the overall thickness of the electromagnetic noise suppression sheet was changed to 52 μm.

[0084] (Example 8) An electromagnetic noise suppression sheet for Example 8 was prepared in the same manner as in Example 1, except that the carbon nanotubes used were changed to multi-walled carbon nanotubes (MWCNTs), the volume content of MWCNTs relative to the total solid content of the magnetic layer forming coating was changed to 2.8%, the thickness of the magnetic layer was changed to 40 μm, and the overall thickness of the electromagnetic noise suppression sheet was changed to 72 μm.

[0085] (Example 9) An electromagnetic noise suppression sheet for Example 9 was prepared in the same manner as in Example 1, except that the carbon nanotubes used were changed to multi-walled carbon nanotubes (MWCNTs), the volume content of MWCNTs relative to the total solid content of the magnetic layer forming coating was changed to 5.0%, the thickness of the magnetic layer was changed to 40 μm, and the overall thickness of the electromagnetic noise suppression sheet was changed to 72 μm.

[0086] (Comparative Example 1) An electromagnetic noise suppression sheet for Comparative Example 1 was prepared in the same manner as in Example 1, except that the volume content of SWCNTs relative to the total solid content of the magnetic layer forming coating was changed to 0%, the thickness of the magnetic layer was changed to 39 μm, and the overall thickness of the electromagnetic noise suppression sheet was changed to 51 μm.

[0087] (Comparative Example 2) The electromagnetic noise suppression sheet of Comparative Example 2 was prepared in the same manner as in Example 1, except that the volume content of SWCNTs relative to the total solid content of the magnetic layer forming coating was changed to 0.014%, the thickness of the magnetic layer was changed to 38 μm, and the overall thickness of the electromagnetic noise suppression sheet was changed to 50 μm.

[0088] (Comparative Example 3) The electromagnetic noise suppression sheet of Comparative Example 3 was prepared in the same manner as in Example 1, except that the volume content of SWCNTs relative to the total solid content of the magnetic layer forming coating was changed to 0.041%, the thickness of the magnetic layer was changed to 34 μm, and the overall thickness of the electromagnetic noise suppression sheet was changed to 46 μm.

[0089] (Comparative Example 4) The electromagnetic noise suppression sheet of Comparative Example 4 was prepared in the same manner as in Example 1, except that the volume content of SWCNTs relative to the total solid content of the magnetic layer forming coating was changed to 0.189%, the thickness of the magnetic layer was changed to 34 μm, and the overall thickness of the electromagnetic noise suppression sheet was changed to 46 μm.

[0090] (Comparative Example 5) An electromagnetic noise suppression sheet for Comparative Example 5 was prepared in the same manner as in Example 1, except that the volume content of the soft magnetic material relative to the total solid content of the magnetic layer forming coating was changed to 25%, the volume content of SWCNTs was changed to 0.13%, the thickness of the magnetic layer was changed to 36 μm, and the overall thickness of the electromagnetic noise suppression sheet was changed to 48 μm.

[0091] (Comparative Example 6) An electromagnetic noise suppression sheet for Comparative Example 6 was prepared in the same manner as in Example 1, except that the volume content of the soft magnetic material relative to the total solid content of the coating for forming the magnetic layer was changed to 73%, the volume content of SWCNTs was changed to 0.12%, the thickness of the magnetic layer was changed to 30 μm, and the overall thickness of the electromagnetic noise suppression sheet was changed to 42 μm.

[0092] (Comparative Example 7) A Comparative Example 7 electromagnetic noise suppression sheet was prepared in the same manner as in Example 1, except that the volume content of SWCNTs relative to the total solid content of the magnetic layer forming coating was changed to 0.22%, the thickness of the magnetic layer was changed to 34 μm, and the overall thickness of the electromagnetic noise suppression sheet was changed to 46 μm.

[0093] The electromagnetic noise suppression sheets of Examples 1 to 9 and Comparative Examples 1 to 7 were subjected to the following measurements, and the results are shown in Tables 1, 2, and 3.

[0094] <Surface electrical resistance value> Napson Corporation's high-frequency eddy current nondestructive resistivity measuring device (product name "EC-80P") and high surface electrical resistance value (10 ４ If the resistance was greater than or equal to Ω / square, the surface electrical resistance of the magnetic layer of the fabricated electromagnetic noise suppression sheet was measured using a high resistivity meter manufactured by Nitto Seiko Analytech Co., Ltd. (product name "High Resista UP MCP-HT450").

[0095] <Raman Spectrum> Using a micro-laser Raman spectrophotometer (product name "Lab RAM ARAMIS") manufactured by Horiba Jobin Yvon, the Raman spectrum of the magnetic layer of the fabricated electromagnetic noise suppression sheet was measured by FT-Raman spectroscopy. In the measured Raman spectrum, 1580 cm⁻¹ －１ ~1600cm －１ We checked whether a G-band peak originating from fibrous carbon was present in the range shown above. －１ ~1600cm －１ If a G-band peak originating from fibrous carbon is present in this range, it indicates that the added carbon nanotubes are present on the surface layer of the magnetic layer.

[0096] The above measurement conditions were: laser wavelength: 532 nm, exposure time: 1 second, number of integrations: 2, scan range: 40 × 40 μm, step: 2 μm. The average spectrum across the entire range was calculated and analyzed. Furthermore, the grating (resolution): 300 lines, objective lens: 50x, laser attenuation filter: D1 (reduces the original light to 1 / 10), laser intensity: 0.6 mW, spot: 1 μmφ.

[0097] <Electromagnetic Noise Suppression Effect> For the fabricated electromagnetic noise suppression sheet, the distribution curve of the transmission attenuation rate (Rtp) by the microstrip line method and the average value of the return loss (S11) at measurement frequencies from 0.1 to 30 GHz were measured using the measurement method described above.

[0098] Next, we determined the lower limit of the frequency at which the transmission attenuation rate (Rtp) is 6 dB or higher in the above-mentioned distribution curve of Rtp. When this lower limit is in the range of 7 to 12 GHz, it can be seen that the electromagnetic noise suppression effect is high in the low-frequency region around 10 GHz.

[0099] Furthermore, when Rtp at a measurement frequency of 10 GHz was determined, if Rtp at 10 GHz was 6.0 dB or higher, and the average value of the return loss (S11) was -18 dB or lower, it was found that the reflection of electromagnetic waves at the surface of the magnetic layer could be suppressed, maintaining a good transmission attenuation rate (Rtp) without impairing the signal transmission characteristics, and demonstrating a high electromagnetic noise suppression effect. This was given an evaluation of A. On the other hand, when Rtp at 10 GHz was below 6.0 dB, or when the average value of the return loss (S11) was above -18 dB, it was found that the electromagnetic noise suppression effect was low, and this was given an evaluation of B.

[0100] <Sliding Durability> A measurement sample was prepared by slitting the fabricated electromagnetic noise suppression sheet into a 10 mm wide tape. Next, using a carbide rotor wear testing machine equipped with a carbide blade that is a cylinder with a diameter of 30 mm and a width of 20 mm and has 18 grooves with a width of 3 mm on its outer surface, the magnetic layer side of the prepared measurement sample was wrapped around the carbide blade at a winding angle of 90 degrees with a tension of 1 N. With the magnetic layer of the measurement sample in contact with the carbide blade, the carbide blade was rotated at a rotation speed of 600 rpm, and a wear test was performed by sliding the magnetic layer and the carbide blade for 10 minutes.

[0101] Next, the surface of the magnetic layer of the measurement sample after the abrasion test was observed with an optical microscope, and the brightness distribution in the longitudinal direction of the measurement tape was extracted. Let A be the average brightness of the area where the carbide blade was not sliding, and B be the average brightness of the area where the carbide blade was sliding. The brightness reduction amount C (%) in the sliding area was then calculated using the following formula: C (%) = (A - B) / A × 100

[0102] This decrease in brightness indicates the amount of magnetic layer scraped off by the edge of the carbide blade, which was then smoothed out and reattached on the flat part of the blade. A greater decrease in brightness indicates weaker sliding durability of the magnetic layer and more powder shedding. Here, a brightness decrease of 18% or less in the sliding part was evaluated as high sliding durability (rating A). On the other hand, a brightness decrease exceeding 18% in the sliding part was evaluated as low sliding durability (rating B).

[0103] The results described above, along with the configuration of the fabricated electromagnetic noise suppression sheet, are shown in Tables 1, 2, and 3.

[0104]

[0105]

[0106]

[0107] Tables 1, 2, and 3 show that the electromagnetic noise suppression sheets of Examples 1 to 9 can simultaneously exhibit electromagnetic noise suppression effects in the low-frequency range and electromagnetic noise suppression effects by suppressing the reflection of electromagnetic waves on the magnetic layer surface, while also possessing high sliding durability. On the other hand, the electromagnetic noise suppression sheets of Comparative Examples 1 to 7 showed inferiority in at least one of the following: electromagnetic noise suppression effect or sliding durability.

[0108] With respect to embodiments of the present application including the above-described embodiments 1 to 9, the following additional embodiments are further disclosed. (Additional Embodiment 1) An electromagnetic noise suppression sheet comprising a magnetic layer and a substrate laminated together, wherein the magnetic layer comprises a soft magnetic material, a fibrous carbon material, and a resin, the volume content of the soft magnetic material contained in the magnetic layer is 30% by volume or more and 70% by volume or less, and the surface electrical resistance of the magnetic layer is 10 ３ Ω / Square or higher 10 ７An electromagnetic noise suppression sheet characterized by having a coefficient of Ω / square or less. (Appendix 2) The electromagnetic noise suppression sheet according to Appendix 1, wherein the fibrous carbon material is a carbon nanotube. (Appendix 3) The electromagnetic noise suppression sheet according to Appendix 1, wherein the volume content of the fibrous carbon material contained in the magnetic layer is 0.05 volume% or more and 5.0 volume% or less. (Appendix 4) The electromagnetic noise suppression sheet according to Appendix 1, wherein the volume content of the fibrous carbon material contained in the magnetic layer is 0.05 volume% or more and 0.2 volume% or less. (Appendix 5) The electromagnetic noise suppression sheet according to Appendix 4, wherein the fibrous carbon material contained in the magnetic layer is a SWCNT. (Appendix 6) The electromagnetic noise suppression sheet according to Appendix 1, wherein the volume content of the fibrous carbon material contained in the magnetic layer is 1.5 volume% or more and 5.0 volume% or less. (Appendix 7) The electromagnetic noise suppression sheet according to Appendix 6, wherein the fibrous carbon material contained in the magnetic layer is a MWCNT. (Appendix Form 8) In the Raman spectrum of the magnetic layer, 1580 cm⁻¹ －１ ~1600cm －１ An electromagnetic noise suppression sheet according to Appendix Form 1, wherein a G-band peak originating from fibrous carbon exists in the range. (Appendix Form 9) An electromagnetic noise suppression sheet according to Appendix Form 1, wherein the soft magnetic material is carbonyl iron powder. (Appendix Form 10) An electromagnetic noise suppression sheet according to Appendix Form 1, wherein the thickness of the magnetic layer is 10 μm or more and 60 μm or less. (Appendix Form 11) An electromagnetic noise suppression sheet according to Appendix Form 1, wherein the overall thickness is 15 μm or more and 85 μm or less. (Appendix Form 12) An electromagnetic noise suppression sheet according to Appendix Form 1, wherein the lower limit of the frequency at which Rtp is 6 dB or more in the distribution curve of the transmission attenuation rate (Rtp) by the microstrip line method is in the range of 7 to 12 GHz. (Appendix Form 13) A communication cable characterized by including an electromagnetic noise suppression sheet according to any one of Appendix Forms 1 to 12. (Appendix Form 14) An electronic device characterized by including an electromagnetic noise suppression sheet according to any one of Appendix Forms 1 to 12.

[0109] This application can also be implemented in forms other than those described above. The embodiments disclosed herein are examples and are not limiting. The scope of this application shall be interpreted in accordance with the claims attached, which take precedence over the description in the above specification, and all modifications within the scope equivalent to the claims shall be included in the claims.

[0110] 10, 20 Electromagnetic noise suppression sheet 11, 21 Base material 21a Metal layer 21b Resin layer 12, 22 Magnetic layer 30 Coaxial cable 31 Internal conductor 32 Insulation layer 33 Metal foil 34 Metal braid 35 Electromagnetic noise suppression layer 35a Base material layer 35b Magnetic layer 36 Outer covering layer

Claims

1. An electromagnetic noise suppression sheet comprising a magnetic layer and a substrate laminated together, wherein the magnetic layer comprises a soft magnetic material, a fibrous carbon material, and a resin, the volume content of the soft magnetic material contained in the magnetic layer is 30% by volume or more and 70% by volume or less, and the surface electrical resistance of the magnetic layer is 10 ３ Ω / Square or higher 10 ７ An electromagnetic noise suppression sheet characterized by having a value of Ω / square or less.

2. The electromagnetic noise suppression sheet according to claim 1, wherein the fibrous carbon material is a carbon nanotube.

3. The electromagnetic noise suppression sheet according to claim 1, wherein the volume content of the fibrous carbon material contained in the magnetic layer is 0.05 volume% or more and 5.0 volume% or less.

4. The electromagnetic noise suppression sheet according to claim 1, wherein the volume content of the fibrous carbon material contained in the magnetic layer is 0.05 volume% or more and 0.2 volume% or less.

5. The electromagnetic noise suppression sheet according to claim 4, wherein the fibrous carbon material contained in the magnetic layer is SWCNT.

6. The electromagnetic noise suppression sheet according to claim 1, wherein the volume content of the fibrous carbon material contained in the magnetic layer is 1.5 volume% or more and 5.0 volume% or less.

7. The electromagnetic noise suppression sheet according to claim 6, wherein the fibrous carbon material contained in the magnetic layer is MWCNT.

8. In the Raman spectrum of the magnetic layer, 1580 cm⁻¹ －１ ~1600cm －１ The electromagnetic noise suppression sheet according to claim 1, wherein a G-band peak originating from fibrous carbon exists within the range.

9. The electromagnetic noise suppression sheet according to claim 1, wherein the soft magnetic material is carbonyl iron powder.

10. The electromagnetic noise suppression sheet according to claim 1, wherein the thickness of the magnetic layer is 10 μm or more and 60 μm or less.

11. The electromagnetic noise suppression sheet according to claim 1, wherein the overall thickness is 15 μm or more and 85 μm or less.

12. The electromagnetic noise suppression sheet according to claim 1, wherein the lower limit of the frequency at which Rtp is 6 dB or more exists in the range of 7 to 12 GHz in the distribution curve of the transmission attenuation rate (Rtp) by the microstrip line method.

13. A communication cable characterized by including an electromagnetic noise suppression sheet according to any one of claims 1 to 12.

14. An electronic device characterized by including an electromagnetic noise suppression sheet according to any one of claims 1 to 12.

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