Electromagnetic noise suppression sheet, manufacturing method for same, and communication cable and electronic device using said electromagnetic noise suppression sheet

Abstract

An electromagnetic noise suppression sheet according to the present application is configured by laminating a magnetic layer and a base material. The base material includes a resin layer and a metal layer. The magnetic layer is disposed on the resin layer side of the base material. The magnetic layer includes a soft magnetic material and a resin. The surface electric resistance value of the magnetic layer is larger than 1.0 × 108 Ω / square. When the electromagnetic noise suppression sheet is cut into a strip-shaped sheet of 10 mm × 100 mm, one short side of the strip-shaped sheet is fixed, the other short side is suspended facing downward, the strip-shaped sheet is allowed to stand for 30 minutes under an environment having a temperature of 25°C and a relative humidity of 50%, and then a distance L (mm) from the fixed side of the strip-shaped sheet to the lowest point of the suspended strip-shaped sheet is measured, a curl amount calculated by the following formula (1) is 40 mm to 80 mm, inclusive.　(1): Curl amount (mm) = 100 - L

Description

Electromagnetic noise suppression sheet, method for manufacturing the same, and communication cable and electronic device using the electromagnetic noise suppression sheet.

[0001] This application relates to an electromagnetic noise suppression sheet that absorbs magnetic field noise and 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. Furthermore, in the medical field, cordless devices are becoming more common from an infection prevention perspective, 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 equipment and communications due to electromagnetic noise generated by the devices themselves, interference with the electromagnetic waves being used, etc., is also increasing. Moreover, in recent years, millimeter-wave radar has begun to be installed in automobiles to prevent 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—so-called EMC (Electromagnetic Compatibility) countermeasures—to circuit elements and transmission lines that emit and receive electromagnetic waves in the MHz to GHz band. Recently, the use of electromagnetic noise suppression sheets wrapped around cables and connectors is also being considered.

[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 6 A film for electromagnetic shielding with a coefficient of Ω / □ or less has been proposed.

[0005] The electromagnetic shielding film described in Patent Document 1 takes into consideration the ability to conform to the shape when attached to the uneven surface of an electronic device where the effects of electromagnetic noise are to be prevented. However, when the electromagnetic shielding film of Patent Document 1 is used by wrapping it around a cable or connector, creases or scratches may form in the electromagnetic shielding film, damaging the film and potentially causing conductive material or magnetic absorbing material to detach (fall off as powder) from the edges of the electromagnetic shielding layer.

[0006] Furthermore, Patent Document 1 states that the surface resistance value of the electromagnetic wave shielding layer is 1 × 10 -3 Ω / □ or more, 1×10 6 Although the surface electrical resistance is set to a relatively small value, such as Ω / □ or less, if the surface electrical resistance becomes too small, the reflection of electromagnetic waves at the surface of the electromagnetic shielding layer increases, which degrades the signal transmission characteristics and reduces the electromagnetic noise suppression effect.

[0007] Japanese Patent Publication No. 2018-195854

[0008] This invention solves the above-mentioned problems and provides an electromagnetic noise suppression sheet that prevents damage to the sheet and shedding of powder from the magnetic layer even when the electromagnetic noise suppression sheet is wrapped around cables and connectors, and that has a great electromagnetic noise suppression effect by suppressing the reflection of electromagnetic waves on the surface of the magnetic layer and improving magnetic loss.

[0009] The electromagnetic noise suppression sheet of the present invention comprises a magnetic layer and a substrate, the substrate includes a resin layer and a metal layer, the magnetic layer is disposed on the resin layer side of the substrate, the magnetic layer includes a soft magnetic material and a resin, and the surface electrical resistance of the magnetic layer is 1.0 × 10 8The electromagnetic noise suppression sheet is larger than Ω / square, and when the sheet is cut into strips measuring 10 mm x 100 mm, one short side of the strip is fixed, and the other short side is suspended downwards, and the sheet is left standing for 30 minutes in an environment of 25°C and 50% relative humidity, the distance L (mm) from the fixed side of the strip to the lowest point of the suspended strip is measured, and the amount of curl calculated by the following formula (1) is 40 mm or more and 80 mm or less. Amount of curl (mm) = 100 - L (1)

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

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

[0012] The method for manufacturing the electromagnetic noise suppression sheet of the present invention is a method for manufacturing the electromagnetic noise suppression sheet of the present invention, comprising the steps of: mixing a soft magnetic material, a resin, and a solvent to produce a coating for forming a magnetic layer; laminating a resin layer and a metal layer to produce a substrate; applying the coating for forming the magnetic layer to the resin layer side of the substrate and drying it to produce a magnetic layer / substrate laminated sheet; and pressurizing and heating the magnetic layer / substrate laminated sheet from the magnetic layer side.

[0013] According to this invention, even when used wrapped around cables or connectors, damage to the sheet and shedding of powder from the magnetic layer can be prevented. Furthermore, the electromagnetic noise suppression effect can be greatly enhanced by suppressing the reflection of electromagnetic waves on the surface of the magnetic layer and improving the magnetic loss of the magnetic layer. In addition, an electromagnetic noise suppression sheet with excellent sliding durability of the magnetic layer can be provided.

[0014] Figure 1 is a schematic cross-sectional view showing an example of an electromagnetic noise suppression sheet according to the embodiment. Figure 2 is a schematic cross-sectional view showing an example of a coaxial cable according to the embodiment.

[0015] (Electromagnetic Noise Suppression Sheet) An embodiment of the electromagnetic noise suppression sheet of the present invention will be described. The electromagnetic noise suppression sheet of this embodiment is constructed by laminating a magnetic layer and a substrate, the substrate includes a resin layer and a metal layer, the magnetic layer is arranged on the resin layer side of the substrate, the magnetic layer includes a soft magnetic material and a resin, and the surface electrical resistance value of the magnetic layer is 1.0 × 10 8 The electromagnetic noise suppression sheet is larger than Ω / square, and when the sheet is cut into strips measuring 10 mm x 100 mm, one short side of the strip is fixed, and the other short side is suspended downwards, and the sheet is left standing for 30 minutes in an environment of 25°C and 50% relative humidity, the distance L (mm) from the fixed side of the strip to the lowest point of the suspended strip is measured, and the amount of curl calculated by the following formula (1) is 40 mm or more and 80 mm or less. Amount of curl (mm) = 100 - L (1)

[0016] In this embodiment of the electromagnetic noise suppression sheet, the curl amount is set to a range of 40 mm to 80 mm, so even when the electromagnetic noise suppression sheet is wrapped around a cable, damage to the sheet and shedding of powder from the magnetic layer can be prevented.

[0017] More specifically, in order to attach the electromagnetic noise suppression sheet of this embodiment to, for example, a coaxial cable used for communication, it is necessary to wrap the tape-shaped slit electromagnetic noise suppression sheet vertically or spirally along the longitudinal direction of the cable, on a cable that has signal wires with a diameter of approximately 1.8 mm covered with an insulator. In this wrapping process, if the electromagnetic noise suppression sheet is moderately curved (curled), it becomes easier to wrap the electromagnetic noise suppression sheet vertically or spirally around the cable.

[0018] If the curl amount is less than 40 mm, the electromagnetic noise suppression sheet will become closer to a flat sheet. When the electromagnetic noise suppression sheet is wrapped around the cable, it may be creased or scratched, damaging the sheet and potentially causing magnetic material to detach (fall out) from the edges of the magnetic layer. This detachment of magnetic material from the magnetic layer can lead to a short circuit in the cable and must be avoided at all costs.

[0019] On the other hand, if the amount of curl is greater than 80 mm, the electromagnetic noise suppression sheet will bend too much, requiring the sheet to be stretched while wrapping it around the cable. This makes the wrapping process complicated and difficult, and there is a risk of wrinkles or damage to the electromagnetic noise suppression sheet.

[0020] Furthermore, in the electromagnetic noise suppression sheet of this embodiment, the surface electrical resistance value of the magnetic layer is 1.0 × 10 8 Because it is set to be larger than Ω / square, the reflection of electromagnetic waves incident on the magnetic layer at the surface of the magnetic layer is suppressed, and the amount of electromagnetic waves incident on the magnetic layer increases, thereby improving the electromagnetic noise suppression performance of the electromagnetic noise suppression sheet. The surface electrical resistance value of the magnetic layer can be controlled by the volume content of the magnetic material in the magnetic layer, as well as the conditions of the pressurized heating treatment, such as temperature and pressure. For example, by lowering the volume content of the magnetic material and relatively increasing the amount of resin in the magnetic layer, or by increasing the conditions of the pressurized heating treatment (temperature and pressure), the magnetic material with a higher specific gravity tends to accumulate on the substrate side, and as a result, more resin is present on the surface of the magnetic layer, so the surface electrical resistance value of the magnetic layer increases.

[0021] Furthermore, the electromagnetic noise suppression sheet of this embodiment is constructed by laminating a magnetic layer and a substrate, and the substrate includes a resin layer and a metal layer. By placing the magnetic layer on the surface of the resin layer of the substrate, the adhesion between the magnetic layer and the substrate can be improved, and because the substrate includes a metal layer, not only electromagnetic noise but also electrical noise can be suppressed.

[0022] The electromagnetic noise suppression sheet of this embodiment will now be described based on 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. The base material 11 is composed of a metal layer 11a and a resin layer 11b. 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.

[0023] As described above, in the electromagnetic noise suppression sheet of this embodiment, the electromagnetic noise suppression sheet is cut into strips measuring 10 mm x 100 mm, one short side of the strip is fixed, and the other short side is suspended downwards. After being left undisturbed for 30 minutes in an environment of 25°C and 50% relative humidity, the distance L (mm) from the fixed side of the strip to the lowest point of the suspended strip is measured. The curl amount calculated by the following formula (1) is set to be in the range of 40 mm to 80 mm, but in Figure 1, the actual representation of the curl amount is omitted from the diagram. Curl amount (mm) = 100 - L (1)

[0024] The overall thickness of the electromagnetic noise suppression sheet in this embodiment is preferably 10 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 curl and making it difficult to wrap around cables and connectors.

[0025] Next, we will describe each component of the electromagnetic noise suppression sheet of this embodiment shown in Figure 1.

[0026] <Substrate> The substrate used in the electromagnetic noise suppression sheet of this embodiment is a base for forming a magnetic layer, and the substrate is composed of a laminate of a metal layer and a resin layer.

[0027] The electromagnetic noise suppression sheet of this embodiment includes a metal layer, which provides electric field shielding performance, allowing it to suppress not only magnetic noise but also electrical noise. The constituent members of the above-mentioned substrate will be described below.

[0028] [Metal Layer] The type of metal constituting the above metal layer is not particularly limited as long as it has some degree of flexibility, but aluminum, copper, permalloy, etc. are preferred. Among aluminum, soft aluminum and among copper, rolled copper are more preferred because they have high conductivity, are inexpensive, are easy to process into thin films, and have excellent flexibility. In addition, permalloy has high magnetic collection effect in the kHz range in addition to conductivity, and can also be used as a magnetic shield.

[0029] The thickness of the metal layer is preferably between 5 μm and 50 μm. If the thickness of the metal layer is less than 5 μm, the shielding performance against electrical noise decreases, and if the thickness exceeds 50 μm, the thickness of the metal layer becomes too large, reducing the processability of the electromagnetic noise suppression sheet and making it difficult to wrap the electromagnetic noise suppression sheet around cables and connectors. Also, if the thickness of the metal layer is too thick, the diameter of the cable after the electromagnetic noise suppression sheet has been wrapped around it becomes large.

[0030] The above-mentioned metal layer can be used alone as a metal foil, but it can also be formed as a thin metal film on the resin layer that constitutes the substrate, as described later, using vapor deposition or sputtering methods.

[0031] [Resin layer] The resin layer constituting the above 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 constituting the above-mentioned resin layer 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.

[0032] The surface of the resin layer 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 resin layer may be subjected to coating treatments with undercoating agents (such as silicone treatment), primer treatment, matting treatment, crosslinking treatment, etc.

[0033] The resin layer may be a single layer or a laminate of two or more layers. Furthermore, known additives such as fillers, flame retardants, degradation inhibitors, antistatic agents, softeners, and plasticizers may be added to the resin layer as needed.

[0034] The thickness of the resin layer is not particularly limited, but is preferably 5 to 20 μm, more preferably 10 to 15 μm. If the thickness of the resin layer is within the above range, both the strength and flexibility of the electromagnetic noise suppression sheet of the present embodiment can be achieved.

[0035] The base material can also be used as a metal / resin composite film by laminating the metal layer and the resin layer.

[0036] When the ratio R / S of the thickness R of the resin layer to the thickness S of the metal layer is considered, it is preferably 0.5 or more and 6.0 or less. More preferably, the ratio R / S is 0.5 or more and 2.0 or less. As described in the manufacturing method of the electromagnetic noise suppression sheet described later, the ratio R / S is one of the requirements for controlling the amount of curl of the electromagnetic noise suppression sheet of the present embodiment within an appropriate range.

[0037] <Magnetic layer> The magnetic layer used in the electromagnetic noise suppression sheet of the present embodiment functions as an electromagnetic noise suppression layer, contains a soft magnetic material and a resin, and the magnetic layer is disposed on the resin layer side of the base material. 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 magnetic noise suppression effect is reduced. If the thickness exceeds 60 μm, the flexibility of the magnetic layer is reduced, and it tends to be difficult to wind the electromagnetic noise suppression sheet around a cable or connector.

[0038] Also, the arithmetic mean roughness Ra of the surface of the magnetic layer is preferably 0.5 μm or more and 3.0 μm or less. If Ra is within the above range, the surface of the magnetic layer has an appropriate roughness, the sliding effect of the surface of the magnetic layer is improved, and the sliding durability of the magnetic layer is improved when winding around a cable.

[0039] Hereinafter, the constituent materials of the magnetic layer will be described.

[0040] [Soft magnetic material] Generally, magnetic materials include soft magnetic materials and hard magnetic materials. In the present embodiment, a soft magnetic material is used. This is because the soft magnetic material has a high initial magnetic permeability and can exhibit the shielding performance of magnetic noise even when a small amount is contained in the magnetic layer, so that the electromagnetic noise suppression effect can be exhibited even if the magnetic layer is made into a thin film.

[0041] As the above soft magnetic material, for example, iron, carbonyl iron powder, silicon iron, permalloy, Fe-Si-Al alloy, permendur, soft ferrite, ferrite-based stainless steel, electromagnetic stainless steel, amorphous magnetic alloy, nanocrystalline magnetic alloy, etc. can be mentioned. As the soft magnetic material, particularly, carbonyl iron powder represented by Fe(CO)5 is preferable. This is because carbonyl iron powder can exhibit electromagnetic wave absorption performance (electromagnetic noise suppression effect) even in a relatively high frequency region such as the GHz band.

[0042] The above soft magnetic material is usually provided as spherical or flat powder, but the powder of the above magnetic material may be granular (amorphous), needle-shaped, etc. Its average particle diameter is preferably 3 μm or more and 50 μm or less, and more preferably 3 μm or more and 20 μm or less. If the average particle diameter of the above soft magnetic material is too small, the particles tend to aggregate secondarily, and as a result, it is difficult to obtain a uniform coating film (magnetic layer). On the other hand, if the above average particle diameter is too large, the particles protrude from the magnetic layer as protrusions, so when the electromagnetic noise suppression sheet is attached to or wound around an uneven surface or a curved surface, the magnetic layer tends to be easily peeled off from the base material. The above average particle diameter can be measured with a laser diffraction scattering type particle size distribution measuring device.

[0043] However, in order to further improve the sliding durability of the above magnetic layer, the above soft magnetic material is preferably flat powder. This is because it is easier to adjust the arithmetic mean roughness Ra of the surface of the magnetic layer to 0.5 μm or more and 3.0 μm or less by pressure heat treatment with flat powder.

[0044] The volume content of the above soft magnetic material contained in the above magnetic layer is preferably 30% by volume or more and 70% by volume or less. If the above volume content is less than 30% by volume, the amount of the soft magnetic material decreases, so the magnetic noise suppression effect decreases. If the above volume content exceeds 70% by volume, the flexibility of the magnetic layer decreases, and it tends to be difficult to wind the electromagnetic noise suppression sheet around a cable or a connector. Also, if the amount of the magnetic material becomes too large, conversely, the amount of the resin decreases, so there is a risk that the magnetic material will fall off (powder drop) to the outside from the end of the magnetic layer.

[0045] The magnetic loss tanδ of the above magnetic layer is preferably 0.50 or higher. Since tanδ = μ'' / μ', setting tanδ to 0.50 or higher increases the imaginary part (μ'') of the permeability, thus increasing the magnetic loss and improving the electromagnetic wave shielding performance. Generally, the imaginary part of the permeability becomes larger when the voids in the magnetic layer are reduced and the packing density of the magnetic powder increases. Therefore, as described in the manufacturing method of the electromagnetic noise suppression sheet later, the magnetic loss tanδ can be controlled to an appropriate value by improving the packing density of the magnetic powder by pressurizing and heating the electromagnetic noise suppression sheet.

[0046] [Resin] The resin used in the magnetic layer functions as a binder that holds and fixes the soft magnetic material and adheres it to the substrate. At least one of thermoplastic resins, thermosetting resins, and rubber can be used as the resin. When a magnetic layer is formed by applying a coating for a magnetic layer containing the soft magnetic powder of this application onto a substrate, thermosetting resins or rubber are preferred. Furthermore, when the soft magnetic powder of this application is mixed with a resin, melted, and extruded, and a substrate is provided thereon, a thermoplastic resin is preferred. Furthermore, when the soft magnetic powder of this application is mixed with a resin, the mixture is molded into a sheet by pressurizing and heating, and a substrate is provided thereon, rubber can be used.

[0047] Examples of thermosetting resins that can be used include phenolic resins, urea resins, melamine resins, epoxy resins, polyester resins, alkyd resins, silicone resins, polyurethane resins, acrylic resins, and the like. These resins are preferably crosslinked in the magnetic layer by adding a crosslinking agent. As the crosslinking agent, isocyanates and epoxy group-containing compounds can be used.

[0048] Examples of the thermoplastic resins that can be used include polyethylene, polypropylene, polystyrene, ABS resin, methyl methacrylate resin, polyvinyl chloride, polyamide, polyethylene terephthalate, polybutylene terephthalate, and polycarbonate.

[0049] Examples of the above-mentioned rubbers include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), butyl rubber (IIR), nitrile rubber (NBR), ethylene-propylene rubber (EPDM), chloroprene rubber (CR), acrylic rubber (ACM), chlorosulfonated polyethylene rubber (CSR), urethane rubber (PUR), silicone rubber (Q), fluororubber (FKM), ethylene-vinyl acetate rubber (EVA), epichlorohydrin rubber (CO), polysulfide rubber (T), urethane rubber (U), and the like.

[0050] Furthermore, from another perspective, it is preferable that the above 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 powders). Therefore, by dispersing magnetic powder in a resin dissolved in water or other solvents, and then coating and drying it on a substrate to an arbitrary thickness, it is possible to form a magnetic layer into a sheet.

[0051] 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.

[0052] 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).

[0053] 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.

[0054] 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.

[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 is a method for manufacturing the electromagnetic noise suppression sheet described above, and is characterized by comprising the steps of: mixing a soft magnetic material, a resin, and a solvent to produce a coating for forming a magnetic layer; laminating a resin layer and a metal layer to produce a substrate; applying the coating for forming a magnetic layer to the resin layer side of the substrate and drying it to produce a magnetic layer / substrate laminated sheet; and pressurizing and heating the magnetic layer / substrate laminated sheet from the magnetic layer side.

[0056] By applying pressure and heat treatment to the above-mentioned magnetic layer-substrate laminated sheet from the magnetic layer side, the voids in the magnetic layer are compressed, reducing the thickness of the magnetic layer, and the magnetic layer itself shrinks due to the shrinkage of the resin in the magnetic layer. Furthermore, the resin layer constituting the substrate shrinks due to the above-mentioned pressure and heat treatment. On the other hand, the metal layer constituting the substrate expands slightly due to the above-mentioned pressure and heat treatment, but does not shrink. Therefore, the electromagnetic noise suppression sheet manufactured by applying pressure and heat treatment to the above-mentioned magnetic layer-substrate laminated sheet from the magnetic layer side will bend (curl) with the magnetic layer side facing inward and the metal layer side facing outward. This bending (curling) occurs more significantly when the substrate contains a metal layer than when only resin is used as the substrate.

[0057] The degree of curvature (curl amount) can be controlled by appropriately adjusting the thickness of the resin layer, metal layer, and magnetic layer of the substrate used, as well as the pressure and temperature of the pressurized heat treatment. For example, it can also be controlled by changing the thickness of the magnetic layer or the resin layer. Specifically, increasing the thickness of the magnetic layer to between 10 μm and 60 μm makes it easier for the material to curl towards the magnetic layer. Also, increasing the thickness of the resin layer to between 5 μm and 20 μm, or increasing the thickness of the metal layer to between 5 μm and 50 μm, makes it easier for the material to curl towards the substrate.

[0058] Using the above control means, the manufactured electromagnetic noise suppression sheet is cut into 10 mm x 100 mm strips, one short side of each strip is fixed, and the other short side is suspended downwards. After being left undisturbed for 30 minutes in an environment of 25°C and 50% relative humidity, the distance L (mm) from the fixed side of the strip to the lowest point of the suspended strip is measured. The amount of curl calculated by the following formula (1) can be controlled to be between 40 mm and 80 mm. Curl amount (mm) = 100 - L (1)

[0059] More specifically, the amount of curl can be controlled by changing the ratio R / S of the thickness R of the resin layer and the thickness S of the metal layer that constitute the base material, thereby adjusting the degree of shrinkage of the base material. For example, by setting the ratio R / S of the thickness R of the resin layer and the thickness S of the metal layer in the range of 0.5 to 6.0, an appropriate range of curl can be achieved.

[0060] If the above ratio R / S is less than 0.5, the thickness of the resin layer after pressurized heat treatment is thin, resulting in less shrinkage of the resin layer and too little curl in the magnetic noise suppression sheet. As a result, the sheet approaches a flat shape, and when the electromagnetic noise suppression sheet is wrapped around a cable, creases and scratches may form on the sheet, damaging it and potentially causing magnetic material to detach (fall out as powder) from the edges of the magnetic layer. On the other hand, if the above ratio R / S is greater than 6.0, the thickness of the resin layer after pressurized heat treatment is thick, resulting in greater shrinkage of the resin layer and excessive curvature of the sheet. When wrapping the electromagnetic noise suppression sheet around a cable, it is necessary to stretch the sheet while wrapping it, making the wrapping process complicated and difficult, and potentially causing wrinkles and scratches on the electromagnetic noise suppression sheet.

[0061] Thus, one effective means of controlling the amount of curl is to utilize the difference in shrinkage between the resin layer and the metal layer constituting the base material, specifically by using the shrinkage of the resin layer due to pressurized heat treatment. To achieve this, the amount of curl can be controlled by changing the ratio R / S of the thickness R of the resin layer and the thickness S of the metal layer constituting the base material, as described above. Furthermore, by controlling the temperature, time, and pressure of the pressurized heat treatment, the amount of curl required for an electromagnetic noise suppression sheet can also be imparted.

[0062] Furthermore, when determining the ratio R / S of the resin layer thickness R to the metal layer thickness S, the thicknesses R of the resin layer and S of the metal layer do not change to a degree that would affect the value of the R / S ratio before and after the pressurized heat treatment. Therefore, either the thickness of R or S before or after the pressurized heat treatment may be used.

[0063] Furthermore, the above pressurized heating treatment reduces the voids in the magnetic layer and increases the density of the soft magnetic material in the magnetic layer, thereby increasing the imaginary part of the magnetic permeability and thus enhancing the electromagnetic noise suppression effect.

[0064] <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 resin, and a solvent.

[0065] The soft magnetic material and resin described above are the same as those that constitute the magnetic layer of the electromagnetic noise suppression sheet of this embodiment.

[0066] 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.

[0067] 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.

[0068] The above-mentioned coating for forming a magnetic layer may further contain surface modifiers, defoamers, thickeners, etc.

[0069] <Formation of Magnetic Layer> As a method for applying the above-mentioned magnetic layer forming coating onto the substrate, for example, the comma method (comma direct method, comma reverse method, etc.), bar coating method, reverse method, gravure coating method, microgravure® coating method, die coating method, dipping method, spin coating method, slit coating method, spray coating method, etc. can be used.

[0070] 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.

[0071] The above-mentioned pressure heating treatment can be carried out by a calendar treatment using a metal roll or a resin roll. Also, when the formation of the magnetic layer is carried out sheet by sheet, the above-mentioned pressure heating treatment can be carried out by a pressing treatment. In the above-mentioned pressure heating treatment, it is preferably carried out at a temperature not lower than the glass transition temperature (Tg) of the resin used for the formed magnetic layer, and more preferably at a temperature 20 °C or higher than Tg. Thereby, bubbles (voids) contained in the resin of the magnetic layer can be reduced, and the density of the soft magnetic material in the magnetic layer increases, so that particularly the imaginary part (μ") of the magnetic permeability of the magnetic layer can be increased. As a result, tanδ (= imaginary part of magnetic permeability μ" / real part of magnetic permeability μ') is improved and the magnetic loss increases, so that the electromagnetic noise suppression effect is improved.

[0072] Also, in the case of the above-mentioned calendar treatment, the pressure of the above-mentioned pressure heating treatment preferably has a linear pressure of 100 kg / cm or more, and in the case of the above-mentioned pressing treatment, a surface pressure of 200 kg / cm 2 or more is preferable. It is preferable to carry out the pressure heating treatment by a calendar treatment in that a large pressure can be applied per unit area. The number of times of the above-mentioned calendar treatment and pressing treatment may be a plurality of times.

[0073] By the above-mentioned drying and pressure heating treatment, since the magnetic material in the magnetic layer has a large specific gravity, it tends to gather inside (substrate side), and therefore it is considered that the vicinity of the surface of the magnetic layer becomes resin material rich. Thereby, the surface electrical resistance value of the magnetic layer can be made larger than 8 1.0 × 10 8 Ω / square, and the arithmetic mean roughness Ra of the surface of the magnetic layer can be controlled to be 0.5 μm or more and 3.0 μm or less. Furthermore, since the vicinity of the surface of the magnetic layer becomes resin material rich, powder falling from the magnetic layer is suppressed and the sliding durability of the magnetic layer is also improved.

[0074] (Communication cable) An embodiment of the communication cable of the present application will be described. The communication cable of this embodiment is characterized by including the electromagnetic noise suppression sheet of the above-mentioned embodiment of the present application. The communication cable of this embodiment includes a coaxial cable, a twisted pair cable, a multi-core cable, etc. In particular, a coaxial cable is used for high-frequency transmission and is used for video cable applications.

[0075] 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.

[0076] Figure 2 is a schematic cross-sectional view showing an example of a coaxial cable. The coaxial cable 20 comprises an internal conductor 21, an insulating layer 22, a metal foil 23, a metal braid 24, an electromagnetic noise suppression layer 25, and an outer covering layer 26. The electromagnetic noise suppression layer 25 uses the electromagnetic noise suppression sheet of the present invention described above, and is composed of a base layer 25a and a magnetic layer 25b arranged on one side of the base layer 25a.

[0077] In Figure 2, the magnetic layer 25b of the electromagnetic noise suppression layer 25 is positioned on the axial side, but the base material layer 25a may also be positioned on the axial side.

[0078] The electromagnetic noise suppression layer 25 of the coaxial cable 20 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 21, an insulating layer 22, a metal foil 23, and a metal braid 24. This allows for a thinner electromagnetic noise suppression layer and shorter processing time.

[0079] (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.

[0080] 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".

[0081] (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): 37.0 parts (2) Amorphous polyester (a) (water-soluble polyester resin solution, manufactured by Go-o Chemical Co., Ltd., product name "Pluscoat Z-3310", resin Tg: -20℃, solids concentration: 25.0% by mass, solvent: water): 29.9 parts (3) Amorphous polyester (b) (water-soluble polyester resin solution, manufactured by Go-o Chemical Co., Ltd., product name "Pluscoat Z-730", resin Tg: 43℃, solids concentration: 25.0% by mass, solvent: water): 12.8 parts (4) Crosslinking agent (oxazoline group-containing polymer, manufactured by Nippon Shokubai Co., Ltd., product name "Epocross WS500", solids concentration: 40.0% by mass, solvent: water): 4.0 parts (5) Solvent (n-propyl alcohol): 10.0 parts (6) Pure water: 6.3 parts

[0082] <Formation of Magnetic Layer> Next, an aluminum foil / PET composite film (manufactured by Daido Chemical Co., Ltd., product name "Alpet #1012"), which was made by laminating a 10 μm thick aluminum foil and a 12 μm thick PET film, was used as a base material. The above-mentioned magnetic layer forming coating was applied to the PET surface of the base material using a comma direct application method so that the thickness of the magnetic layer after calendering would be 25.3 μm, and it was dried at 100°C. Subsequently, the electromagnetic noise suppression sheet of Example 1 was produced by calendering the raw material roll with a metal roll in a calendering device at a temperature of 60°C and a linear pressure of 100 kg / cm, thereby forming a magnetic layer on the PET surface. The volume content of the magnetic material contained in the above magnetic layer was 34.2 volume%.

[0083] (Example 2) An electromagnetic noise suppression sheet for Example 2 was prepared in the same manner as in Example 1, except that the magnetic layer forming coating was applied in a comma-direct manner so that the thickness of the magnetic layer after calendering was 20.4 μm, and the linear pressure of the calendering was changed to 200 kg / cm.

[0084] (Example 3) An electromagnetic noise suppression sheet of Example 3 was prepared in the same manner as in Example 1, except that the magnetic layer forming coating was applied in a comma-direct manner so that the thickness of the magnetic layer after calendering was 19.9 μm, and the linear pressure of the calendering was changed to 300 kg / cm.

[0085] (Example 4) An electromagnetic noise suppression sheet for Example 4 was prepared in the same manner as in Example 1, except that the calendar temperature was changed to 20°C.

[0086] (Example 5) An electromagnetic noise suppression sheet of Example 5 was prepared in the same manner as in Example 1, except that the magnetic layer forming coating was applied in a comma-direct manner so that the thickness of the magnetic layer after calendering was 58.0 μm, and the linear pressure of the calendering was changed to 200 kg / cm.

[0087] (Example 6) An aluminum foil / PET composite film, formed by laminating a 5 μm thick aluminum foil and a 29 μm thick PET film, was used as the base material. A magnetic layer forming coating was applied using a comma direct method so that the thickness of the magnetic layer after calendering was 23.1 μm, and the linear pressure of the calendering was changed to 200 kg / cm. In addition, the electromagnetic noise suppression sheet of Example 6 was prepared in the same manner as in Example 1.

[0088] (Example 7) An electromagnetic noise suppression sheet of Example 7 was prepared in the same manner as in Example 1, except that the magnetic layer forming coating was applied in a comma-direct manner so that the thickness of the magnetic layer after calendering was 27.2 μm, and the linear pressure of the calendering was changed to 200 kg / cm.

[0089] (Example 8) An electromagnetic noise suppression sheet of Example 8 was prepared in the same manner as in Example 1, except that the magnetic layer forming coating was applied in a comma-direct manner so that the thickness of the magnetic layer after calendering was 21.0 μm, and the calendering temperature was changed to 80°C.

[0090] (Example 9) An electromagnetic noise suppression sheet of Example 9 was prepared in the same manner as in Example 1, except that the magnetic layer forming coating was applied in a comma-direct manner so that the thickness of the magnetic layer after calendering was 20.2 μm, the calendering temperature was changed to 80°C, and the linear pressure of the calendering was changed to 300 kg / cm.

[0091] (Example 10) An electromagnetic noise suppression sheet of Example 10 was prepared in the same manner as in Example 1, except that the magnetic layer forming coating was applied in comma direct so that the thickness of the magnetic layer after calendering was 21.5 μm, the volume content of the magnetic material contained in the magnetic layer was changed to 68.0 volume%, and the linear pressure of the calendering was changed to 200 kg / cm.

[0092] (Comparative Example 1) A magnetic layer forming coating was applied in comma direct so that the thickness of the magnetic layer after calendering was 35.9 μm, and the calendering process was not performed in the magnetic layer formation step. In addition, an electromagnetic noise suppression sheet of Comparative Example 1 was prepared in the same manner as in Example 1.

[0093] (Comparative Example 2) An electromagnetic noise suppression sheet for Comparative Example 2 was prepared in the same manner as in Example 1, except that the magnetic layer forming coating was applied in a comma-direct manner so that the thickness of the magnetic layer after calendering was 25.9 μm, and the linear pressure of the calendering was changed to 50 kg / cm.

[0094] (Comparative Example 3) An electromagnetic noise suppression sheet for Comparative Example 3 was prepared in the same manner as in Example 1, except that an aluminum foil / PET composite film, which was made by laminating an aluminum foil with a thickness of 5 μm and a PET film with a thickness of 32 μm, was used as the base material, a magnetic layer forming coating was applied comma-directly so that the thickness of the magnetic layer after calendering was 20.8 μm, the calendering temperature was changed to 90°C and the linear pressure of the calendering was changed to 300 kg / cm.

[0095] (Comparative Example 4) An electromagnetic noise suppression sheet for Comparative Example 4 was prepared in the same manner as in Example 1, except that an aluminum foil / PET composite film, which was made by laminating an aluminum foil with a thickness of 15 μm and a PET film with a thickness of 5 μm, was used as the base material, a magnetic layer forming coating was applied comma-directly so that the thickness of the magnetic layer after calendering was 23.5 μm, and the linear pressure of the calendering treatment was changed to 200 kg / cm.

[0096] The following measurements were performed on the electromagnetic noise suppression sheets of Examples 1 to 10 and Comparative Examples 1 to 4 described above.

[0097] <Curl Amount> The fabricated electromagnetic noise suppression sheet was cut into 10 mm x 100 mm strips. One short side of each strip was fixed, and the other short side was suspended downwards. After being left undisturbed for 30 minutes in an environment of 25°C and 50% relative humidity, the distance L (mm) from the fixed side of the strip to the lowest point of the suspended strip was measured, and the curl amount was calculated using the following formula (1): Curl Amount (mm) = 100 - L (1)

[0098] <Surface Electrical Resistivity> The surface electrical resistance of the magnetic layer of the fabricated electromagnetic noise suppression sheet was measured using a high-frequency eddy current non-destructive resistivity measuring device (product name "EC-80P") manufactured by Napson Corporation.

[0099] <Arithmetic Mean Roughness Ra> The arithmetic mean roughness Ra of the magnetic layer surface of the fabricated electromagnetic noise suppression sheet was measured using a digital microscope manufactured by Keyence Corporation (product name "VHX-X1").

[0100] <Magnetic Loss tanδ> The magnetic loss tanδ of the magnetic layer of the fabricated electromagnetic noise suppression film was measured in accordance with IEC 60556-2006. Specifically, the magnetic loss was measured using an Anritsu Corporation vector network analyzer "MS46122B-043" and a Keycom Corporation high-frequency magnetic material measurement system "PER01," connected by a Junko Co., Ltd. coaxial cable "MWX051-03000KFSKMS / B" (3m). The measurement sample was processed into an 8mm diameter toroidal shape and used by setting it in the measurement jig of the "PER01" measurement system.

[0101] The vector network analyzer underwent a SOLT (Short-Open-Load-Thru) calibration beforehand, and measurements were taken using Keycom's analysis software, "DMP-PWR01-03A Measurement Software."

[0102] The frequency range was set to 0.01 GHz to 10 GHz. Measurement points were established using a logarithmic scaling of 401 points, and μr' (real part of relative permeability) and μr'' (imaginary part of relative permeability) were measured. The magnetic loss (tanδ) values ​​for each of the 11 points, including the point at 3.04 GHz and five points before and after 3.04 GHz, were calculated using the following formula (2). The average of these 11 magnetic loss values ​​was taken as the magnetic loss (tanδ) for each sample. tanδ = μr'' / μr' (2)

[0103] <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.

[0104] 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 sample was extracted. Let A be the average brightness of the part where the carbide blade was not sliding, and B be the average brightness of the part where the carbide blade was sliding. The brightness reduction amount C (%) of the sliding part was calculated using the following formula (3): C (%) = (A - B) / A × 100 (3)

[0105] This decrease in brightness corresponds to the amount of magnetic layer scraped off by the edge of the carbide blade, which is then smoothed out and reattached on the flat part of the blade. A greater decrease in brightness indicates lower sliding durability of the magnetic layer and more powder shedding. Here, a brightness decrease of 20% or less in the sliding part was evaluated as high sliding durability (rating A). On the other hand, a brightness decrease exceeding 20% ​​in the sliding part was evaluated as low sliding durability (rating B).

[0106] <Ease of wrapping around cables> The ease of wrapping around cables was evaluated by wrapping the electromagnetic noise suppression sheet around a cable using TapeFormers' "MODEL A" tape former, and visually inspecting the condition of the electromagnetic noise suppression sheet. Specifically, the electromagnetic noise suppression sheet was slit into a 10 mm wide tape, and wrapped around a 3 mm outer diameter IV wire using TapeFormer "MODEL A" at a tape speed of 10 m / sec and tape tension of 2 N. As a result, the condition of the electromagnetic noise suppression sheet was visually checked and evaluated according to the following criteria: Evaluation A: No particular problems in appearance Evaluation B: Wrinkles or folds were observed on the edges of the sheet Evaluation C: Powder was observed falling off the sheet

[0107] The results described above, along with the configuration of the fabricated electromagnetic noise suppression sheet, are shown in Tables 1 and 2.

[0108]

[0109]

[0110] From Tables 1 and 2, the electromagnetic noise suppression sheets of Examples 1 to 10 have a curl amount in the range of 40 to 80 mm, and have an appropriate curl, resulting in good wrapping properties around cables, making it easy to wrap the electromagnetic noise suppression sheets around cables vertically or spirally. In addition, the surface electrical resistance value of the magnetic layer is 1.0 × 10⁻⁶. 8 Because it is greater than Ω / square, the reflection of electromagnetic waves incident on the magnetic layer at the magnetic layer surface is suppressed, resulting in a higher magnetic noise suppression effect. Furthermore, because the calendering treatment is carried out under appropriate conditions, the packing of magnetic powder is improved, and the magnetic loss of the magnetic layer increases, thus further enhancing the magnetic noise suppression effect. In addition, by carrying out the calendering treatment under appropriate conditions, the packing of magnetic powder is improved, and the resin inside the magnetic layer comes to the surface of the magnetic layer, resulting in improved sliding durability.

[0111] On the other hand, in the electromagnetic noise suppression sheets of Comparative Examples 1 to 4, the curl amount was less than 40 mm or greater than 80 mm, so when the electromagnetic noise suppression sheets were wrapped around the cable, wrinkles or folds occurred at the edges, or powder fell off. In addition, in Comparative Example 1, the surface electrical resistance value of the magnetic layer was 1.0 × 10⁻⁶. 8Because it is smaller than Ω / square, the magnetic noise suppression effect is low, and furthermore, because calendar treatment is not performed, the magnetic loss of the magnetic layer is small, and the sliding durability of the magnetic layer is also poor.

[0112] Furthermore, the electromagnetic noise suppression sheets of Examples 1 to 10, each with a curl amount controlled to be between 40 mm and 80 mm, were wound and laminated on the surface of a 5-inch diameter core member to form a pancake shape. After being stored in this state for one week, the electromagnetic noise suppression sheets were unwound from the core member and the curl amount was measured again. It was found that all of the electromagnetic noise suppression sheets were able to maintain a curl amount of between 40 mm and 80 mm.

[0113] With respect to embodiments of the present application including the above-described embodiments 1 to 10, the following additional embodiments are further disclosed. (Additional Embodiment 1) An electromagnetic noise suppression sheet comprising a magnetic layer and a substrate, wherein the substrate includes a resin layer and a metal layer, the magnetic layer is disposed on the resin layer side of the substrate, the magnetic layer includes a soft magnetic material and a resin, and the surface electrical resistance of the magnetic layer is 1.0 × 10 8An electromagnetic noise suppression sheet characterized in that, when the electromagnetic noise suppression sheet is cut into strips of 10 mm x 100 mm, one short side of the strip is fixed, the other short side is suspended downwards, and after being left standing for 30 minutes in an environment of 25°C and 50% relative humidity, the distance L (mm) from the fixed side of the strip to the lowest point of the suspended strip is measured, and the amount of curl calculated by the following formula (1) is 40 mm or more and 80 mm or less. Amount of curl (mm) = 100 - L (1) (Appendix form 2) 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 3) An electromagnetic noise suppression sheet according to appendix form 1 or 2, wherein the volume content of the soft magnetic material contained in the magnetic layer is 30 volume% or more and 70 volume% or less. (Appendix Form 4) An electromagnetic noise suppression sheet according to any one of Appendix Forms 1 to 3, wherein the arithmetic mean roughness Ra of the surface of the magnetic layer is 0.5 μm or more and 3.0 μm or less. (Appendix Form 5) An electromagnetic noise suppression sheet according to any one of Appendix Forms 1 to 4, wherein the thickness of the metal layer is 5 μm or more and 50 μm or less. (Appendix Form 6) An electromagnetic noise suppression sheet according to any one of Appendix Forms 1 to 5, wherein the thickness of the resin layer is 5 μm or more and 20 μm or less. (Appendix Form 7) An electromagnetic noise suppression sheet according to any one of Appendix Forms 1 to 6, wherein the ratio R / S when the thickness of the resin layer is R and the thickness of the metal layer is S is 0.5 or more and 6.0 or less. (Appendix Form 8) An electromagnetic noise suppression sheet according to any one of Appendix Forms 1 to 7, wherein the soft magnetic material has a flattened shape. (Appendix Form 9) An electromagnetic noise suppression sheet according to any one of Appendix Forms 1 to 8, wherein the soft magnetic material is carbonyl iron powder. (Appendix Form 10) An electromagnetic noise suppression sheet according to any one of Appendix Forms 1 to 9, wherein the magnetic loss tanδ (μ'' / μ') of the magnetic layer is 0.50 or more. (Appendix Form 11) A communication cable characterized by including an electromagnetic noise suppression sheet according to any one of Appendix Forms 1 to 10. (Appendix Form 12) An electronic device characterized by including an electromagnetic noise suppression sheet according to any one of Appendix Forms 1 to 10.(Appendix Form 13) A method for manufacturing an electromagnetic noise suppression sheet according to any of the appendix forms 1 to 10, comprising the steps of: mixing a soft magnetic material, a resin, and a solvent to produce a coating for forming a magnetic layer; laminating a resin layer and a metal layer to produce a substrate; applying the coating for forming the magnetic layer to the resin layer side of the substrate and drying it to produce a magnetic layer / substrate laminated sheet; and pressurizing and heating the magnetic layer / substrate laminated sheet from the magnetic layer side. (Appendix Form 14) A method for manufacturing an electromagnetic noise suppression sheet according to appendix form 13, wherein the solvent contained in the coating for forming the magnetic layer is at least one selected from water and a water-soluble solvent.

[0114] 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.

[0115] 10 Electromagnetic noise suppression sheet 11 Base material 11a Metal layer 11b Resin layer 12 Magnetic layer 20 Coaxial cable 21 Internal conductor 22 Insulation layer 23 Metal foil 24 Metal braid 25 Electromagnetic noise suppression layer 25a Base material layer 25b Magnetic layer 26 Outer covering layer

Claims

1. An electromagnetic noise suppression sheet comprising a magnetic layer and a substrate laminated together, wherein the substrate includes a resin layer and a metal layer, the magnetic layer is disposed on the resin layer side of the substrate, the magnetic layer includes a soft magnetic material and a resin, and the surface electrical resistance of the magnetic layer is 1.0 × 10 8 An electromagnetic noise suppression sheet characterized in that, when the electromagnetic noise suppression sheet is cut into strips measuring 10 mm x 100 mm, one short side of the strip is fixed, the other short side is suspended downwards, and after being left standing for 30 minutes in an environment of 25°C and 50% relative humidity, the distance L (mm) from the fixed side of the strip to the lowest point of the suspended strip is measured, and the amount of curl calculated by the following formula (1) is 40 mm or more and 80 mm or less. Curl amount (mm) = 100 - L (1) 2. 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.

3. The electromagnetic noise suppression sheet according to claim 1, wherein the volume content of the soft magnetic material contained in the magnetic layer is 30 volume% or more and 70 volume% or less.

4. The electromagnetic noise suppression sheet according to claim 1, wherein the arithmetic mean roughness Ra of the surface of the magnetic layer is 0.5 μm or more and 3.0 μm or less.

5. The electromagnetic noise suppression sheet according to claim 1, wherein the thickness of the metal layer is 5 μm or more and 50 μm or less.

6. The electromagnetic noise suppression sheet according to claim 1, wherein the thickness of the resin layer is 5 μm or more and 20 μm or less.

7. The electromagnetic noise suppression sheet according to claim 1, wherein the ratio R / S, where R is the thickness of the resin layer and S is the thickness of the metal layer, is 0.5 or more and 6.0 or less.

8. The electromagnetic noise suppression sheet according to claim 1, wherein the soft magnetic material has a flattened shape.

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 magnetic loss tanδ (μ'' / μ') of the magnetic layer is 0.50 or more.

11. A communication cable characterized by including an electromagnetic noise suppression sheet according to any one of claims 1 to 10.

12. An electronic device characterized by including an electromagnetic noise suppression sheet according to any one of claims 1 to 10.

13. A method for manufacturing an electromagnetic noise suppression sheet according to any one of claims 1 to 10, comprising the steps of: mixing a soft magnetic material, a resin, and a solvent to produce a coating for forming a magnetic layer; laminating a resin layer and a metal layer to produce a substrate; applying the coating for forming a magnetic layer to the resin layer side of the substrate and drying it to produce a magnetic layer / substrate laminated sheet; and pressurizing and heating the magnetic layer / substrate laminated sheet from the magnetic layer side.

14. The method for manufacturing an electromagnetic noise suppression sheet according to claim 13, wherein the solvent contained in the magnetic layer forming paint is at least one selected from water and a water-soluble solvent.

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