Electromagnetic noise suppression sheet, method for manufacturing same, and cable using electromagnetic noise suppression sheet

Abstract

An electromagnetic noise suppression sheet according to the present application comprises a base material and a magnetic layer. The magnetic layer contains a magnetic material and a binder. The binder contains an amorphous resin (A) that has a glass transition temperature of -50°C to 0° C, and an amorphous resin (B) that has a glass transition temperature of 10°C or higher. It is preferable that the amorphous resin (A) is an amorphous polyester (a) that has a glass transition temperature of -50°C to 0° C, and it is also preferable that the amorphous resin (B) is an amorphous polyester (b) that has a glass transition temperature of 10°C or higher.

Description

Electromagnetic noise suppression sheet, manufacturing method thereof, and cable using the electromagnetic noise suppression sheet

[0001] The present application relates to an electromagnetic noise suppression sheet that absorbs electromagnetic waves in the kHz to GHz band.

[0002] With the advancement of wireless communication technology, typified by mobile phones, various devices and sensors are now wirelessly connected to networks. Furthermore, in the medical field, cordless devices are becoming increasingly common to prevent infection, and medical devices are beginning to connect wirelessly. These communications require high speed and large capacity over relatively short distances, and therefore use high frequencies. With the increase in devices using such high frequencies, there is an increasing risk of malfunctions in electronic devices and communications due to malfunctions caused by electromagnetic noise generated by the devices and interference with the electromagnetic waves used. Furthermore, in recent years, millimeter-wave radar has begun to be installed in vehicles to prevent automobile collisions. Since malfunctions in these medical and automotive devices could affect human lives, malfunctions must be avoided. Therefore, there is a growing need to apply electromagnetic noise suppression sheets to circuit elements and transmission lines that emit and receive electromagnetic waves in the kHz to GHz band to prevent malfunctions caused by electromagnetic noise and the resulting interference, a so-called EMC (Electromagnetic Compatibility) measure.

[0003] In light of this situation, Patent Document 1 proposes using a laminate comprising a magnetic layer containing a magnetic powder and a binder resin and a polymer film layer as a magnetic sheet for suppressing electromagnetic wave transmission. The binder resin used in the magnetic layer of the laminate of Patent Document 1 contains a crystalline polyester resin, thereby enabling the realization of a tack-free laminate with excellent strength. On the other hand, if the magnetic layer contains a crystalline polyester resin, the crystallinity of the binder resin increases during the drying process during the manufacturing of the magnetic layer, causing the magnetic layer to harden. Therefore, when the laminate is used as a magnetic sheet wrapped around a cable or connector, cracks may occur in the magnetic layer. Furthermore, if the magnetic layer contains a crystalline polyester resin, the adhesion between the magnetic layer and the polymer film layer decreases, potentially leading to peeling between the magnetic layer and the polymer film layer.

[0004] Furthermore, prior art related to the use of the electromagnetic noise suppression sheet of the present application is Patent Document 2. Patent Document 2 discloses a communication cable in which a magnetic sheath layer in which particulate magnetic material is dispersed in a polymer material is formed as an extrusion molded body.

[0005] JP 2016-36965 A (Patent No. 6428033 A) JP 2022-108557 A

[0006] The present application solves the above problems by providing an electromagnetic noise suppression sheet that can be attached to uneven or curved surfaces of electronic devices that require protection from the effects of electromagnetic noise, or that can be wrapped around cables or connectors in particular, and that has electromagnetic wave absorption performance in the kHz to GHz band.

[0007] The electromagnetic noise suppression sheet of the present application includes a substrate and a magnetic layer, the magnetic layer including a magnetic material and a binder, and the binder including an amorphous resin (A) having a glass transition temperature of −50° C. to 0° C. and an amorphous resin (B) having a glass transition temperature of 10° C. or higher.

[0008] The method for producing an electromagnetic noise suppression sheet of the present application is a method for producing the electromagnetic noise suppression sheet of the present application, and includes the steps of mixing, together with a solvent, a magnetic material, an amorphous resin (A) having a glass transition temperature of −50° C. to 0° C., and an amorphous resin (B) having a glass transition temperature of 10° C. or higher to prepare a magnetic layer-forming paint, and applying the magnetic layer-forming paint to a substrate and drying it.

[0009] The cable of the present application includes the electromagnetic noise suppression sheet of the present application.

[0010] According to the present invention, an electromagnetic noise suppression sheet that can be attached to uneven or curved surfaces of electronic devices or wrapped around cables or connectors and has electromagnetic wave absorption performance in the kHz to GHz band can be provided.

[0011] Fig. 1 is a schematic cross-sectional view showing an example of an electromagnetic noise suppression sheet according to an embodiment. Fig. 2 is a schematic cross-sectional view showing another example of an electromagnetic noise suppression sheet according to an embodiment. Fig. 3 is a schematic cross-sectional view showing an example of a conventional coaxial cable. Fig. 4 is a schematic cross-sectional view showing an example of a coaxial cable according to an embodiment.

[0012] (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 this embodiment includes a substrate and a magnetic layer, the magnetic layer containing a magnetic material and a binder, and the binder containing an amorphous resin (A) having a glass transition temperature of −50° C. to 0° C. and an amorphous resin (B) having a glass transition temperature of 10° C. or higher.

[0013] In the electromagnetic noise suppression sheet of the present application, the magnetic layer contains, as binders, an amorphous resin (A) having a glass transition temperature of −50° C. to 0° C. and an amorphous resin (B) having a glass transition temperature of 10° C. or higher. This gives the magnetic layer excellent flexibility and adhesion, and even when the electromagnetic noise suppression sheet of the present application is used by wrapping it around a cable or connector, the magnetic layer does not crack or peel off from the substrate.

[0014] The amorphous resin (A) is particularly preferably an amorphous polyester (a) having a glass transition temperature of −50° C. to 0° C., and the amorphous resin (B) is particularly preferably an amorphous polyester (b) having a glass transition temperature of 10° C. or higher. By using an amorphous polyester (a) having a glass transition temperature of −50° C. to 0° C. and an amorphous polyester (b) having a glass transition temperature of 10° C. or higher as the binder for the magnetic layer, the flexibility and adhesion of the magnetic layer can be further improved.

[0015] Generally, when the glass transition temperature of an amorphous polyester is low, adhesion and flexibility are improved but tackiness (adhesiveness) increases, whereas when the glass transition temperature of an amorphous polyester is high, tackiness decreases but the surface becomes hard and flexibility decreases. For this reason, in the binder of this embodiment, it is preferable to use a combination of an amorphous polyester (a) having a glass transition temperature of -50°C to 0°C and an amorphous polyester (b) having a glass transition temperature of 10°C or higher. This makes it possible to realize an electromagnetic noise suppression sheet that can ensure sufficient adhesion and flexibility while suppressing tackiness.

[0016] The electromagnetic noise suppression sheet of this embodiment will be described below with reference to the drawings. Fig. 1 is a schematic cross-sectional view showing an example of the electromagnetic noise suppression sheet of this embodiment. In Fig. 1, the electromagnetic noise suppression sheet 10 includes a substrate 11 and a magnetic layer 12 disposed on the substrate 11. In Fig. 1, the electromagnetic noise suppression sheet 10 has a two-layer structure consisting of the substrate 11 and the magnetic layer 12, but it may also have a three-layer structure by further disposing an adhesive layer on the magnetic layer 12 side.

[0017] 2 is a schematic cross-sectional view showing another example of an electromagnetic noise suppression sheet according to this embodiment. In Fig. 2, an electromagnetic noise suppression sheet 10' includes a substrate 11, a metal layer 13 disposed on the substrate 11, and a magnetic layer 12 disposed on the metal layer 13. In Fig. 2, the electromagnetic noise suppression sheet 10' has a three-layer structure consisting of the substrate 11, the magnetic layer 12, and the metal layer 13, but it may also have a four-layer structure by further disposing an adhesive layer on the magnetic layer 12 side.

[0018] The overall thickness of the electromagnetic noise suppression sheet of 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, resulting in reduced electromagnetic wave absorption and a reduced strength of the entire sheet. On the other hand, if the overall thickness of the electromagnetic noise suppression sheet is too thick, the flexibility will be reduced, making it difficult to wrap around a cable or connector for use.

[0019] Next, each of the components of the electromagnetic noise suppression sheet of this embodiment will be described.

[0020] <Substrate> The substrate used in the electromagnetic noise suppression sheet of this embodiment serves as a base on which the magnetic layer is formed.

[0021] The substrate may be any flexible material capable of ensuring adhesion to the magnetic layer, and typically a resin film is used. Examples of resins constituting the substrate 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, polyether ketone 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, fluorine-based resins, silicone resins, cellulose resins, and substrates made of crosslinked materials of these resins. Among these, polyethylene terephthalate (PET) is more preferable in terms of mechanical properties and cost. These resin materials can be used alone or in combination. The resin material may have a functional group, if necessary. A functional monomer or a modifying monomer may be grafted onto the resin material.

[0022] The surface of the substrate may be subjected to a known surface treatment to improve adhesion to the adjacent magnetic layer. Specific examples of such surface treatments include corona discharge treatment, ozone exposure treatment, high-voltage shock exposure treatment, and ionizing radiation treatment. The substrate may also be subjected to a coating treatment with an undercoat agent (such as silicone treatment), a primer treatment, a matte treatment, a crosslinking treatment, or the like.

[0023] The substrate may be in the form of a single layer or a laminate of two or more layers. If necessary, known auxiliary agents such as fillers, flame retardants, antidegradants, antistatic agents, softeners, and plasticizers may be added to the substrate.

[0024] The thickness of the substrate is not particularly limited, but is preferably 5 to 20 μm, and more preferably 10 to 15 μm. If the thickness of the substrate is within this range, the electromagnetic noise suppression sheet of this embodiment can achieve both strength and flexibility.

[0025] The substrate may be any material that is flexible and can ensure adhesion to the magnetic layer, and therefore a metal layer such as a metal foil, which will be described later, may be used as the substrate instead of the resin film. That is, a metal layer may be used as the substrate 11 in FIG. 1.

[0026] <Magnetic Layer> The magnetic layer used in the electromagnetic noise suppression sheet of this embodiment contains a magnetic material and a binder. There are no particular limitations on the thickness of the magnetic layer, but if it is too thin, electromagnetic wave absorption decreases, and if it is too thick, flexibility decreases, so it is usually set in the range of 5 to 70 μm. The constituent materials of the magnetic layer are described below.

[0027] [Binder] The binder may contain an amorphous resin (A) having a glass transition temperature of −50° C. to 0° C. and an amorphous resin (B) having a glass transition temperature of 10° C. or higher. Amorphous resins have high solubility in water and other solvents and excellent dispersibility for magnetic materials (magnetic powder). Therefore, by dispersing magnetic powder in a resin dissolved in water or other solvent, applying the resin to a substrate at a desired thickness, and drying it, it is possible to form a magnetic layer into a sheet.

[0028] By using an amorphous resin (A) with a glass transition temperature of -50°C to 0°C, the magnetic layer can be made more flexible and its adhesion to the substrate can be improved. However, if only the amorphous resin (A) is used, the magnetic layer is likely to become tacky (sticky), and when the magnetic sheets are stacked or wound into a roll, the magnetic layers may stick to each other. On the other hand, if only the amorphous resin (B) with a glass transition temperature of 10°C or higher is used, the surface of the magnetic layer will be hard and less likely to stick, but there is a possibility that the adhesion between the magnetic layer and the substrate will decrease and the magnetic layer will crack when wound and used. For this reason, the binder of this embodiment uses a combination of the above amorphous resins (A) and (B).

[0029] The upper limit of the glass transition temperature of the amorphous resin (B) having a glass transition temperature of 10° C. or higher is preferably 100° C., and more preferably 80° C. If the glass transition temperature is higher than this upper limit, even when used in combination with an amorphous resin (A) having a glass transition temperature of −50° C. to 0° C., the surface of the magnetic layer is likely to become hard, which may reduce adhesion between the magnetic layer and the substrate, or make the magnetic layer more susceptible to cracking when attached to an uneven or curved surface or when folded during wrapping.

[0030] 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. Of these, amorphous resin (A) is preferably amorphous polyester (a) having a glass transition temperature of -50°C to 0°C, and amorphous resin (B) is preferably amorphous polyester (b) having a glass transition temperature of 10°C or higher. Of the amorphous resins, amorphous polyester has excellent solubility and flexibility and is suitable for producing a sheet-shaped magnetic layer.

[0031] From the above viewpoints, the content ratio of the amorphous polyester (a) to the amorphous polyester (b) is preferably (a):(b)=95:5 to 35:65 by mass, and more preferably (a):(b)=90:10 to 50:50. The content ratio of the amorphous polyesters (a) and (b) can be estimated to some extent from the intensities 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 using a differential scanning calorimeter (DSC).

[0032] Examples of the amorphous polyesters (a) and (b) include "Vylon" (registered trademark) manufactured by Toyobo Co., Ltd., "Pluscoat" (registered trademark) manufactured by Goo Chemical Co., Ltd., "Nichigo Polyester" (registered trademark) manufactured by Mitsubishi Chemical Corporation, and "Alumatex" (registered trademark) manufactured by Mitsui Chemicals, Inc. These have excellent solubility in water and organic solvents and can be used by dissolving them in water or organic solvents at any ratio.

[0033] Furthermore, at least one of the amorphous polyester (a) and the amorphous polyester (b) preferably contains a crosslinked portion crosslinked by an amide bond. 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 the molecular terminals, and carboxyl groups can be optionally added to the molecular chains. Therefore, by using a crosslinking agent having an oxazoline group or a carbodiimide group, as described below, a crosslinked portion crosslinked by an amide bond can be formed.

[0034] In addition to the amorphous resin (A) and the amorphous resin (B), the binder may contain at least one of a crystalline resin and an amorphous resin having a glass transition temperature greater than 0° C. and less than 10° C., to the extent that the effects of the invention are not impaired. In this case, the total amount of the amorphous resin (A) and the amorphous resin (B) is preferably 90% by mass or more, and more preferably 95% by mass or more, of the total amount of the binder.

[0035] [Magnetic Material] As the magnetic material, soft magnetic materials and hard magnetic materials can be used, but it is preferable to use soft magnetic materials. Soft magnetic materials have high initial magnetic permeability and can exhibit electromagnetic wave absorption performance even when contained in a small amount in the magnetic layer, so that electromagnetic noise suppression effects can be exhibited even when the magnetic layer is thin.

[0036] Examples of the soft magnetic material include iron, silicon iron, permalloy, sendust, permendur, soft ferrite, electromagnetic stainless steel, amorphous magnetic alloys, and nanocrystalline magnetic alloys, but carbonyl iron, represented by Fe(CO)5, is particularly preferred as the soft magnetic material because carbonyl iron can exhibit electromagnetic wave absorption performance (electromagnetic noise suppression effect) even in relatively high frequency ranges such as the GHz band.

[0037] Examples of the hard magnetic material include hard ferrite (ferrite magnet), alnico magnet, samarium-cobalt magnet, neodymium magnet, samarium-iron-nitrogen magnet, and the like.

[0038] The magnetic material is typically provided as a spherical or flat powder, with an average particle size of preferably 0.1 to 100 μm, more preferably 1 to 20 μm. If the particle size of the magnetic material is too small, the particles are prone to secondary aggregation, making it difficult to obtain a uniform coating film (magnetic layer). On the other hand, if the particle size is too large, the particles protrude from the magnetic layer as protrusions, which tends to cause the magnetic layer to peel off from the substrate when attached to an uneven or curved surface or when wrapped around it. Furthermore, if the particle size is large, the particles tend to settle when used as a coating material, making it difficult to obtain a uniform coating film. The average particle size can be measured using a laser diffraction / scattering particle size distribution analyzer.

[0039] The volume content of the soft magnetic material contained in the magnetic layer is preferably 30 to 80%, and more preferably 40 to 70%. If the volume content is below 30%, the electromagnetic wave absorption performance (electromagnetic noise suppression effect) of the magnetic layer tends to be insufficient, while if it exceeds 80%, the proportion of binder in the magnetic layer decreases, reducing the adhesion of the magnetic layer to the substrate and making the magnetic layer more susceptible to cracking and powder falling when bent.

[0040] <Metal Layer> As shown in Fig. 2, by disposing a metal layer on the electromagnetic noise suppression sheet of this embodiment, the electromagnetic noise suppression sheet can be endowed with electric field shielding performance, and can suppress not only magnetic noise but also electrical noise. In Fig. 2, the metal layer is disposed between the substrate and the magnetic layer, but it may also be disposed on the outer surface of the magnetic layer.

[0041] The type of metal constituting the metal layer is not particularly limited as long as it has flexibility and adhesion to the magnetic layer, but aluminum, copper, etc. are preferred because they are inexpensive, can be easily processed into a thin film, and have excellent flexibility.

[0042] The thickness of the metal layer is not particularly limited, but if it is too thick, flexibility decreases, so it is usually set in the range of 0.1 to 30 μm.

[0043] The metal layer can be used alone as a metal foil, but can also be used by forming a metal thin film on the above-mentioned substrate (resin film) by vapor deposition or sputtering.

[0044] As mentioned above, the metal layer can also be used as the substrate 11 in FIG.

[0045] <Adhesive Layer> When an adhesive layer is disposed on the electromagnetic noise suppression sheet of this embodiment, the thickness of the adhesive layer is preferably 10 to 50 μm, more preferably 15 to 35 μm. If the thickness is less than 10 μm, sufficient adhesive strength may not be obtained. If the thickness exceeds 50 μm, the adhesive effect of the adhesive layer saturates and the overall thickness of the electromagnetic noise suppression sheet increases, reducing the flexibility of the electromagnetic noise suppression sheet, reducing its ability to conform when attached to electronic components, and making it difficult to wrap around wiring, etc.

[0046] (Method for manufacturing an electromagnetic noise suppression sheet) An embodiment of a method for manufacturing an electromagnetic noise suppression sheet according to the present invention will be described. The method for manufacturing an electromagnetic noise suppression sheet according to the present invention is the same as the method for manufacturing the electromagnetic noise suppression sheet according to the present invention, and includes the steps of mixing a magnetic material, an amorphous resin (A) having a glass transition temperature of −50° C. to 0° C., and an amorphous resin (B) having a glass transition temperature of 10° C. or higher together with a solvent to prepare a coating material for forming a magnetic layer, and applying the coating material for forming a magnetic layer to a substrate and drying it.

[0047] <Magnetic Layer-Forming Paint> The magnetic layer-forming paint can be prepared by mixing a magnetic material, an amorphous resin (A) having a glass transition temperature of −50° C. to 0° C., an amorphous resin (B) having a glass transition temperature of 10° C. or higher, and a solvent. Generally, amorphous resins have excellent paint properties, so by using the magnetic layer-forming paint, a magnetic layer can be easily formed on a substrate using a normal coating process.

[0048] The magnetic material can be the same as the magnetic material that constitutes the magnetic layer of the electromagnetic noise suppression sheet of the present application.

[0049] The amorphous resin (A) having a glass transition temperature of −50° C. to 0° C. and the amorphous resin (B) having a glass transition temperature of 10° C. or higher can be the same as the resin materials constituting the magnetic layer of the aforementioned electromagnetic noise suppression sheet.

[0050] Furthermore, at least one resin selected from the amorphous resin (A) having a glass transition temperature of −50° C. to 0° C. and the amorphous resin (B) having a glass transition temperature of 10° C. or higher preferably contains a carboxyl group, which allows crosslinking moieties to be formed in the amorphous resins (A) and (B) by using a crosslinking agent.

[0051] As described above, amorphous polyesters have carboxyl groups at least at the molecular terminals and can optionally have carboxyl groups added to their molecular chains, so that the amorphous resin (A) is particularly preferably an amorphous polyester (a) having a glass transition temperature of −50° C. to 0° C., and the amorphous resin (B) is particularly preferably an amorphous polyester (b) having a glass transition temperature of 10° C. or higher. Furthermore, many amorphous polyesters are water-soluble, and the magnetic material also has good wettability to aqueous solvents, so the amorphous polyester can be easily dispersed in an aqueous solvent together with the magnetic material.

[0052] The crosslinking agent contained in the magnetic layer-forming coating material is preferably a resin having at least one selected from an oxazoline group and a carbodiimide group. Oxazoline groups and carbodiimide groups react with carboxyl groups to form amide bonds, allowing the amorphous polyester resins (a) and (b) to be crosslinked by amide bonds. This can further improve the adhesion of the formed magnetic layer and prevent magnetic powder from falling off during magnetic layer formation.

[0053] The crosslinking agent reacts quickly with the carboxyl groups of the amorphous polyester due to the heat of the drying step after the magnetic layer-forming coating material is applied to the substrate, forming crosslinked portions through amide bonds. Alternatively, crosslinked portions can be formed using epoxy bonds, urethane bonds, etc., but because the reaction rate for forming crosslinks with epoxy bonds, urethane bonds, etc. is slow, the crosslinking reaction may not be completed by the time of the drying step and winding step after the coating material is applied to the substrate, and there is a possibility that the magnetic layers may stick together during the winding step and the subsequent aging step.

[0054] Examples of resins having the oxazoline group include "Epocross" (registered trademark) manufactured by Nippon Shokubai Co., Ltd., and examples of resins having the carbodiimide group include "Carbodilite" (registered trademark) manufactured by Nisshinbo Chemical Inc.

[0055] It is desirable to use water as the solvent. The magnetic material has excellent wettability with water and can be easily dispersed in water, which allows for homogenization of the coating film containing the magnetic material and improves the filling of the magnetic material in the coating film. In addition to water, water-soluble solvents such as ethyl alcohol, methyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, ethylene glycol, and propylene glycol can also be used. These water-soluble solvents can be used alone, in combination, or further mixed with water to obtain the desired coating material.

[0056] The content of the solvent is not particularly limited, but may be 50.0% by mass or more and 99.5% by mass or less relative to the total mass of the coating material for forming the magnetic layer.

[0057] The coating material for forming the magnetic layer may further contain a surface conditioner, an antifoaming agent, a thickener, and the like.

[0058] <Formation of Magnetic Layer> Examples of a method for applying the magnetic layer-forming coating material onto a substrate include bar coating, reverse coating, gravure coating, microgravure (registered trademark) coating, die coating, dipping, spin coating, slit coating, and spray coating.

[0059] The drying after application is preferably carried out at 100 to 150°C for 3 to 30 minutes under conditions that allow the solvent component of the magnetic layer-forming coating material to evaporate. If the solvent remains in the magnetic layer, the strength tends to decrease. Drying methods include, for example, hot air drying, heat drying, vacuum drying, and natural drying.

[0060] (Cable) An embodiment of a cable according to the present invention will be described. The cable according to the present invention is characterized by including the electromagnetic noise suppression sheet according to the embodiment of the present invention described above. The cable according to the present invention includes communication cables such as coaxial cables, twisted pair cables, and multi-core cables. In particular, coaxial cables are used for high-frequency transmission and are used as video cables.

[0061] A coaxial cable, which is an example of a cable according to this embodiment, will now be described. In this coaxial cable, the electromagnetic noise suppression sheet of the present application described above is used as the magnetic sheath layer of the coaxial cable. By using the electromagnetic noise suppression sheet of the present application as the magnetic sheath layer of the coaxial cable, the electromagnetic noise suppression sheet of the present application can function as the electromagnetic noise suppression layer of the coaxial cable. Furthermore, by using the electromagnetic noise suppression sheet of the present application as the magnetic sheath layer of the coaxial cable, it is possible to prevent cracks from occurring in the magnetic sheath layer and to prevent magnetic powder from falling off from the cut surface when the coaxial cable is cut.

[0062] Next, the coaxial cable of this embodiment will be described with reference to the drawings in comparison with a conventional coaxial cable.

[0063] Fig. 3 is a schematic cross-sectional view showing an example of a conventional coaxial cable. In Fig. 3, the conventional coaxial cable 20 includes an inner conductor 21, an insulating layer 22, a metal foil 23, a metal braid 24, a magnetic sheath layer 25, and an outer coating layer 26. Details of each component of the coaxial cable 20 are described in detail in Patent Document 2 (JP 2022-108557 A).

[0064] The magnetic sheath layer 25 of the conventional coaxial cable 20 is formed as an extrusion molded body by extruding a magnetic sheath layer-forming material, which is formed by dispersing magnetic powder in a matrix material made of a polymeric material, onto the outer surface of a linear conductor made of an inner conductor 21, an insulating layer 22, a metal foil 23, and a metal braid 24. This has caused problems such as an increased thickness of the magnetic sheath layer 25 and a longer processing time. Furthermore, when the coaxial cable is cut, magnetic powder is likely to fall off from the cut surface.

[0065] 4 is a schematic cross-sectional view showing an example of a coaxial cable according to the present embodiment. A coaxial cable 30 according to the present embodiment includes an inner conductor 31, an insulating layer 32, a metal foil 33, a metal braid 34, a magnetic sheath layer 35, and an outer coating layer 36. The magnetic sheath layer 35 uses the electromagnetic noise suppression sheet of the present application and is composed of a base layer 35a and a magnetic layer 35b disposed on one side of the base layer 35a.

[0066] In FIG. 4, the magnetic layer 35b of the magnetic sheath layer 35 is disposed on the axial center side, but the base layer 35a may also be disposed on the axial center side.

[0067] The magnetic sheath layer 35 of the coaxial cable 30 of this embodiment can be formed by wrapping the electromagnetic noise suppression sheet of the present application around the outer surface of a linear conductor consisting of the inner conductor 31, the insulating layer 32, the metal foil 33, and the metal braid 34. This allows the thickness of the magnetic sheath layer to be thin, and also shortens the processing time. Furthermore, this also prevents magnetic powder from falling off from the cut surface when the coaxial cable is cut.

[0068] In addition to the coaxial cables, the electromagnetic noise suppression sheet of the present invention can be used on uneven surfaces or corners of electronic devices that emit electromagnetic noise or that require electromagnetic noise prevention. The electromagnetic noise suppression sheet of the present invention can also be used as a substitute for ferrite cores used in cables for electronic devices.

[0069] 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" in the following means "parts by mass."

[0070] Example 1 Preparation of Magnetic Layer Coating The following components were mixed and dispersed to prepare Magnetic Layer Coating A. (1) Soft magnetic material (Tenichi Corporation's spherical carbonyl iron powder, trade name "YW-3"): 53.43 parts (2) Amorphous polyester (a) (water-soluble polyester resin solution, GOO Chemical Co., Ltd., trade name "PLASCOAT Z-3310", Tg: -20°C, solids concentration: 25.0% by mass, solvent: water): 15.77 parts (3) Amorphous polyester (b) (water-soluble polyester resin solution, GOO Chemical Co., Ltd., trade name "PLASCOAT Z-730", Tg: 43°C, solids concentration: 25.0% by mass, solvent: water): 10.51 parts (4) Solvent (n-propyl alcohol): 10.00 parts (5) Pure water: 10.29 parts

[0071] In the magnetic layer forming paint A, the content ratio of the amorphous polyesters (a) and (b) was (a):(b) = 60:40 by mass, and the volume content of the soft magnetic material relative to the total solid content of the magnetic layer forming paint A was 60%.

[0072] <Formation of Magnetic Layer> Next, a 12 μm thick PET film (manufactured by Toyobo Co., Ltd., product name "Ester Film E5100") was used as a substrate, and the magnetic layer forming paint A was applied to one main surface of the substrate using an applicator, and then dried for 3 minutes at 120° C. This was cut into a 150 mm square and pressed in a press at 50° C. and 210 kg / cm. 2 The sheet was pressed at 100° C. for 30 seconds to form a magnetic layer on one of its main surfaces, producing an electromagnetic noise suppression sheet of Example 1. The magnetic layer had a thickness of 38 μm, and the electromagnetic noise suppression sheet had a total thickness of 50 μm.

[0073] Example 2 Preparation of Magnetic Layer Coating The following components were mixed and dispersed to prepare Magnetic Layer Coating B. (1) Soft magnetic material (flat carbonyl iron powder manufactured by Tenichi Co., Ltd., trade name "YP"): 50.43 parts (2) Amorphous polyester (a) (water-soluble polyester resin solution, manufactured by GOO Chemical Co., Ltd., trade name "PLASCOAT Z-3310", Tg: -20°C, solid content: 25.0% by mass, solvent: water): 30.63 parts (3) Amorphous polyester (b) (water-soluble polyester resin solution, manufactured by GOO Chemical Co., Ltd., trade name "PLASCOAT Z-730", Tg: 43°C, solid content: 25.0% by mass, solvent: water): 7.66 parts (4) Solvent (n-propyl alcohol): 10.00 parts (5) Pure water: 1.28 parts

[0074] In the magnetic layer forming paint B, the content ratio of the amorphous polyesters (a) and (b) was (a):(b) = 80:20 by mass, and the volume content of the soft magnetic material relative to the total solid content of the magnetic layer forming paint B was 50%.

[0075] <Formation of Magnetic Layer> Next, an electromagnetic noise suppression sheet of Example 2 having a magnetic layer formed thereon was produced in the same manner as in Example 1, except that magnetic layer-forming paint B was used instead of magnetic layer-forming paint A of Example 1. The thickness of the magnetic layer was 28 μm, and the total thickness of the electromagnetic noise suppression sheet was 40 μm.

[0076] Example 3 Preparation of Magnetic Layer-Forming Paint The following components were mixed and dispersed to prepare Magnetic Layer-Forming Paint C. (1) Soft magnetic material (Tenichi Co., Ltd. spherical carbonyl iron powder, trade name "YW-5"): 53.01 parts (2) Amorphous polyester (a) (water-soluble polyester resin solution, GOO Chemical Co., Ltd., trade name "Plus Coat Z-3310", Tg: -20 ° C., solid content: 25.0% by mass, solvent: water): 19.56 parts (3) Amorphous polyester (b) (water-soluble polyester resin solution, GOO Chemical Co., Ltd., trade name "Plus Coat Z-730", Tg: 43 ° C., solid content: 25.0% by mass, solvent: water): 8.38 parts (4) Oxazoline group-containing polymer (Nippon Shokubai Co., Ltd., trade name "Epocross WS500", solid content: 40.0% by mass, solvent: water): 2.00 parts (5) Solvent (n-propyl alcohol): 10.00 parts (6) Pure water: 7.04 parts

[0077] In the magnetic layer forming paint C, the content ratio of the amorphous polyesters (a) and (b) was (a):(b) = 70:30 by mass, and the volume content of the soft magnetic material relative to the total solid content of the magnetic layer forming paint C was 60%.

[0078] <Formation of Magnetic Layer> Next, an electromagnetic noise suppression sheet of Example 3 having a magnetic layer formed thereon was produced in the same manner as in Example 1, except that magnetic layer-forming paint C was used instead of magnetic layer-forming paint A of Example 1. The thickness of the magnetic layer was 36 μm, and the total thickness of the electromagnetic noise suppression sheet was 48 μm.

[0079] Example 4 Preparation of Magnetic Layer-Forming Paint The following components were mixed and dispersed to prepare Magnetic Layer-Forming Paint D. (1) Soft magnetic material (Tenichi Co., Ltd. spherical carbonyl iron powder, trade name "YW-3"): 53.43 parts (2) Amorphous polyester (a) (water-soluble polyester resin solution, GOO Chemical Co., Ltd., trade name "Plus Coat Z-3310", Tg: -20 ° C., solid content: 25.0% by mass, solvent: water): 14.46 parts (3) Amorphous polyester (b) (water-soluble polyester resin solution, GOO Chemical Co., Ltd., trade name "Plus Coat Z-730", Tg: 43 ° C., solid content: 25.0% by mass, solvent: water): 11.83 parts (4) Carbodiimide group-containing polymer (Nisshinbo Chemical Co., Ltd., trade name "Carbodilite SV-02", solid content: 40.0% by mass, solvent: water): 2.00 parts (5) Solvent (n-propyl alcohol): 10.00 parts (6) Pure water: 8.29 parts

[0080] In the magnetic layer forming paint D, the content ratio of the amorphous polyesters (a) and (b) was (a):(b) = 55:45 by mass, and the volume content of the soft magnetic material relative to the total solid content of the magnetic layer forming paint D was 60%.

[0081] <Formation of Magnetic Layer> Next, an electromagnetic noise suppression sheet of Example 4, in which a magnetic layer was formed, was produced in the same manner as in Example 1, except that magnetic layer-forming paint D was used instead of magnetic layer-forming paint A of Example 1. The thickness of the magnetic layer was 38 μm, and the total thickness of the electromagnetic noise suppression sheet was 50 μm.

[0082] Example 5 Preparation of Magnetic Layer-Forming Coating The following components were mixed and dispersed to prepare Magnetic Layer-Forming Coating E. (1) Soft magnetic material (spherical Mn-Zn ferrite powder manufactured by Toda Kogyo Co., Ltd., product name "BSF-547"): 53.62 parts (2) Amorphous polyester (a) (water-soluble polyester resin solution manufactured by GOO Chemical Co., Ltd., product name "PLASCOAT Z-3310", Tg: -20°C, solid content: 25.0% by mass, solvent: water): 22.97 parts (3) Amorphous polyester (b) (water-soluble polyester resin solution manufactured by GOO Chemical Co., Ltd., product name "PLASCOAT Z-730", Tg: 43°C, solid content: 25.0% by mass, solvent: water): 2.55 parts (4) Solvent (n-propyl alcohol): 10.00 parts (5) Pure water: 10.86 parts

[0083] In the magnetic layer forming paint E, the content ratio of the amorphous polyesters (a) and (b) was (a):(b) = 90:10 by mass, and the volume content of the soft magnetic material relative to the total solid content of the magnetic layer forming paint E was 70%.

[0084] <Formation of Magnetic Layer> Next, an electromagnetic noise suppression sheet of Example 5, in which a magnetic layer was formed, was produced in the same manner as in Example 1, except that magnetic layer-forming paint E was used instead of magnetic layer-forming paint A of Example 1. The thickness of the magnetic layer was 40 μm, and the total thickness of the electromagnetic noise suppression sheet was 52 μm.

[0085] Example 6 An electromagnetic noise suppression sheet of Example 6 was produced in the same manner as in Example 3, except that the thickness of the magnetic layer was changed to 5 μm and the total thickness of the electromagnetic noise suppression sheet was changed to 17 μm.

[0086] Example 7 An electromagnetic noise suppression sheet of Example 7 was produced in the same manner as in Example 3, except that the thickness of the magnetic layer was changed to 70 μm and the total thickness of the electromagnetic noise suppression sheet was changed to 82 μm.

[0087] Example 8 Preparation of Magnetic Layer-Forming Paint The following components were mixed and dispersed to prepare Magnetic Layer-Forming Paint F. (1) Soft magnetic material (Tenichi Co., Ltd. spherical carbonyl iron powder, trade name "YW-5"): 53.01 parts (2) Amorphous polyester (a) (water-soluble polyester resin solution, GOO Chemical Co., Ltd., trade name "Plus Coat Z-3310", Tg: -20 ° C., solid content: 25.0% by mass, solvent: water): 27.39 parts (3) Amorphous polyester (b) (water-soluble polyester resin solution, GOO Chemical Co., Ltd., trade name "Plus Coat Z-730", Tg: 43 ° C., solid content: 25.0% by mass, solvent: water): 0.56 parts (4) Oxazoline group-containing polymer (Nippon Shokubai Co., Ltd., trade name "Epocross WS500", solid content: 40.0% by mass, solvent: water): 0.75 parts (5) Solvent (n-propyl alcohol): 10.00 parts (6) Pure water: 8.29 parts

[0088] In the magnetic layer forming paint F, the content ratio of the amorphous polyesters (a) and (b) was (a):(b) = 98:2 by mass, and the volume content of the soft magnetic material relative to the total solid content of the magnetic layer forming paint F was 60%.

[0089] <Formation of Magnetic Layer> Next, an electromagnetic noise suppression sheet of Example 8 having a magnetic layer formed thereon was produced in the same manner as in Example 1, except that magnetic layer-forming paint F was used instead of magnetic layer-forming paint A of Example 1. The thickness of the magnetic layer was 38 μm, and the total thickness of the electromagnetic noise suppression sheet was 50 μm.

[0090] Example 9 Preparation of Magnetic Layer Forming Paint Magnetic layer forming paint G was prepared by mixing and dispersing the following components. (1) Soft magnetic material (Tenichi Co., Ltd. spherical carbonyl iron powder, trade name "YW-5"): 53.01 parts (2) Amorphous polyester (a) (water-soluble polyester resin solution, GOO Chemical Co., Ltd., trade name "Plus Coat Z-3310", Tg: -20 ° C., solid content: 25.0% by mass, solvent: water): 8.38 parts (3) Amorphous polyester (b) (water-soluble polyester resin solution, GOO Chemical Co., Ltd., trade name "Plus Coat Z-730", Tg: 43 ° C., solid content: 25.0% by mass, solvent: water): 19.56 parts (4) Oxazoline group-containing polymer (Nippon Shokubai Co., Ltd., trade name "Epocross WS500", solid content: 40.0% by mass, solvent: water): 0.75 parts (5) Solvent (n-propyl alcohol): 10.00 parts (6) Pure water: 8.30 parts

[0091] In the magnetic layer forming paint G, the content ratio of the amorphous polyesters (a) and (b) was (a):(b) = 30:70 by mass, and the volume content of the soft magnetic material relative to the total solid content of the magnetic layer forming paint G was 60%.

[0092] <Formation of Magnetic Layer> Next, an electromagnetic noise suppression sheet of Example 9, in which a magnetic layer was formed, was produced in the same manner as in Example 1, except that magnetic layer-forming paint G was used instead of magnetic layer-forming paint A of Example 1. The thickness of the magnetic layer was 38 μm, and the total thickness of the electromagnetic noise suppression sheet was 50 μm.

[0093] Example 10 Preparation of Magnetic Layer-Forming Paint The following components were mixed and dispersed to prepare Magnetic Layer-Forming Paint H. (1) Soft magnetic material (Tenichi Co., Ltd. spherical carbonyl iron powder, trade name "YW-5"): 53.01 parts (2) Amorphous polyurethane (a) (water-soluble polyurethane resin solution, Fujikura Kasei Co., Ltd., trade name "USC-2101", Tg: -33 ° C., solid content: 35.0% by mass, solvent: water): 13.97 parts (3) Amorphous polyester (b) (water-soluble polyester resin solution, Goo Chemical Co., Ltd., trade name "Plus Coat Z-730", Tg: 43 ° C., solid content: 25.0% by mass, solvent: water): 8.38 parts (4) Oxazoline group-containing polymer (Nippon Shokubai Co., Ltd., trade name "Epocross WS500", solid content: 40.0% by mass, solvent: water): 0.75 parts (5) Solvent (n-propyl alcohol): 10.00 parts (6) Pure water: 13.89 parts

[0094] In the magnetic layer forming paint H, the content ratio of the amorphous resins (a) and (b) was (a):(b) = 70:30 by mass, and the volume content of the soft magnetic material relative to the total solid content of the magnetic layer forming paint H was 60%.

[0095] <Formation of Magnetic Layer> Next, an electromagnetic noise suppression sheet of Example 10 having a magnetic layer formed thereon was produced in the same manner as in Example 1, except that magnetic layer-forming paint H was used instead of magnetic layer-forming paint A of Example 1. The thickness of the magnetic layer was 38 μm, and the total thickness of the electromagnetic noise suppression sheet was 50 μm.

[0096] Example 11 Preparation of Magnetic Layer-Forming Paint Magnetic layer-forming paint I was prepared by mixing and dispersing the following components. (1) Soft magnetic material (Tenichi Co., Ltd. spherical carbonyl iron powder, trade name "YW-5"): 53.01 parts (2) Amorphous acrylic (a) (water-soluble acrylic resin solution, Fujikura Kasei Co., Ltd., trade name "ABH-6201", Tg: -6 ° C., solid content: 43.0% by mass, solvent: water): 13.00 parts (3) Amorphous polyester (b) (water-soluble polyester resin solution, Goo Chemical Co., Ltd., trade name "Plus Coat Z-730", Tg: 43 ° C., solid content: 25.0% by mass, solvent: water): 5.59 parts (4) Oxazoline group-containing polymer (Nippon Shokubai Co., Ltd., trade name "Epocross WS500", solid content: 40.0% by mass, solvent: water): 0.75 parts (5) Solvent (n-propyl alcohol): 10.00 parts (6) Pure water: 17.65 parts

[0097] In the magnetic layer forming paint I, the content ratio of the amorphous resins (a) and (b) was (a):(b) = 80:20 by mass, and the volume content of the soft magnetic material relative to the total solid content of the magnetic layer forming paint I was 60%.

[0098] <Formation of Magnetic Layer> Next, an electromagnetic noise suppression sheet of Example 11 having a magnetic layer formed thereon was produced in the same manner as in Example 1, except that magnetic layer-forming paint I was used instead of magnetic layer-forming paint A of Example 1. The thickness of the magnetic layer was 38 μm, and the total thickness of the electromagnetic noise suppression sheet was 50 μm.

[0099] Example 12 Preparation of Magnetic Layer-Forming Paint The following components were mixed and dispersed to prepare Magnetic Layer-Forming Paint J. (1) Soft magnetic material (Tenichi Co., Ltd. spherical carbonyl iron powder, trade name "YW-5"): 53.01 parts (2) Amorphous polyester-polyurethane (a) (polyester-polyurethane resin solution, Toyobo MC Co., Ltd., trade name "Byron UR-6100", Tg: -30 ° C., solid content: 45.0 mass%, solvent: cyclohexanone / aromatic solvent / isophorone = 40 mass% / 40 mass% / 20 mass%): 7.76 parts (3) Amorphous polyester-polyurethane (b) (polyester-polyurethane resin solution, Toyobo MC Co., Ltd., trade name "Byron UR-3600", Tg: 40 ° C., solid content: 40.0 mass%, solvent: methyl ethyl ketone / toluene = 63 mass% / 37 mass%): 8.73 parts (4) Isocyanate-based curing agent (Tosoh Corporation, trade name "Coronate HX"): 0.2 parts (5) Solvent (methyl ethyl ketone): 15.00 parts (6) Solvent (toluene): 15.30 parts

[0100] In the magnetic layer forming paint J, the content ratio of amorphous polyester-polyurethane (a) and (b) was (a):(b) = 50:50 by mass, and the volume content of the soft magnetic material relative to the total solid content of the magnetic layer forming paint J was 60%.

[0101] <Formation of Magnetic Layer> Next, an electromagnetic noise suppression sheet of Example 12 having a magnetic layer formed thereon was produced in the same manner as in Example 1, except that magnetic layer-forming paint J was used instead of magnetic layer-forming paint A of Example 1. The thickness of the magnetic layer was 38 μm, and the total thickness of the electromagnetic noise suppression sheet was 50 μm.

[0102] Comparative Example 1 Preparation of Magnetic Layer-Forming Paint Magnetic layer-forming paint K was prepared by mixing and dispersing the following components: (1) Soft magnetic material (spherical carbonyl iron powder manufactured by Tenichi Co., Ltd., product name "YW-3"): 53.43 parts (2) Amorphous polyester (b) (water-soluble polyester resin solution manufactured by GOO Chemical Co., Ltd., product name "PLASCOAT Z-730", Tg: 43°C, solid content: 25.0% by mass, solvent: water): 26.29 parts (3) Solvent (n-propyl alcohol): 10.00 parts (4) Pure water: 10.28 parts

[0103] In the magnetic layer forming coating material K, only amorphous polyester (b) was used as the amorphous resin, and the volume content of the soft magnetic material relative to the total solid content of the magnetic layer forming coating material K was 60%.

[0104] <Formation of Magnetic Layer> Next, an electromagnetic noise suppression sheet of Comparative Example 1, on which a magnetic layer was formed, was produced in the same manner as in Example 1, except that magnetic layer-forming paint K was used instead of magnetic layer-forming paint A of Example 1. The thickness of the magnetic layer was 38 μm, and the total thickness of the electromagnetic noise suppression sheet was 50 μm.

[0105] Comparative Example 2 Preparation of Magnetic Layer Coating The following components were mixed and dispersed to prepare Magnetic Layer Coating L. (1) Soft magnetic material (Tenichi Co., Ltd. spherical carbonyl iron powder, trade name "YW-3"): 53.43 parts (2) Amorphous polyester (a) (water-soluble polyester resin solution, GOO Chemical Co., Ltd., trade name "PLASCOAT Z-3310", Tg: -20°C, solid content: 25.0% by mass, solvent: water): 26.29 parts (3) Solvent (n-propyl alcohol): 10.00 parts (4) Pure water: 10.28 parts

[0106] In the magnetic layer forming coating material L, only amorphous polyester (a) was used as the amorphous resin, and the volume content of the soft magnetic material relative to the total solid content of the magnetic layer forming coating material L was 60%.

[0107] <Formation of Magnetic Layer> Next, an electromagnetic noise suppression sheet of Comparative Example 2, on which a magnetic layer was formed, was produced in the same manner as in Example 1, except that magnetic layer-forming paint L was used instead of magnetic layer-forming paint A of Example 1. The thickness of the magnetic layer was 38 μm, and the total thickness of the electromagnetic noise suppression sheet was 50 μm.

[0108] Comparative Example 3 Preparation of Magnetic Layer-Forming Paint The following components were mixed and dispersed to prepare Magnetic Layer-Forming Paint M. (1) Soft magnetic material (Tenichi Co., Ltd. spherical carbonyl iron powder, trade name "YW-5"): 53.01 parts (2) Amorphous polyester-polyurethane (a) (polyester-polyurethane resin solution, Toyobo MC Co., Ltd., trade name "Byron UR-6100", Tg: -30 ° C., solid content: 45.0 mass%, solvent: cyclohexanone / aromatic solvent / isophorone = 40 mass% / 40 mass% / 20 mass%): 7.76 parts (3) Amorphous polyester (b) (polyester resin solution, Toyobo MC Co., Ltd., trade name "Byron 500", Tg: 4 ° C., solid content: 30.0 mass%, solvent: methyl ethyl ketone): 11.65 parts (4) Isocyanate-based curing agent (Tosoh Corporation, trade name "Coronate HX"): 0.2 parts (5) Solvent (methyl ethyl ketone): 15.00 parts (6) Solvent (toluene): 12.38 parts

[0109] In the magnetic layer forming paint M, the content ratio of the amorphous resins (a) and (b) was (a):(b) = 50:50 by mass, and the volume content of the soft magnetic material relative to the total solid content of the magnetic layer forming paint M was 60%.

[0110] <Formation of Magnetic Layer> Next, an electromagnetic noise suppression sheet of Comparative Example 3, on which a magnetic layer was formed, was produced in the same manner as in Example 1, except that the magnetic layer-forming paint M was used instead of the magnetic layer-forming paint A of Example 1. The thickness of the magnetic layer was 38 μm, and the total thickness of the electromagnetic noise suppression sheet was 50 μm.

[0111] Comparative Example 4 Preparation of Magnetic Layer-Forming Paint The following components were mixed and dispersed to prepare Magnetic Layer-Forming Paint N. (1) Soft magnetic material (Tenichi Co., Ltd. spherical carbonyl iron powder, trade name "YW-5"): 53.01 parts (2) Amorphous polyester (a) (polyester resin solution, Toyobo MC Co., Ltd., trade name "Byron 500", Tg: 4 ° C., solid content: 30.0 mass%, solvent: methyl ethyl ketone): 7.76 parts (3) Amorphous polyester-polyurethane (b) (polyester-polyurethane resin solution, Toyobo MC Co., Ltd., trade name "Byron UR-3600", Tg: 40 ° C., solid content: 40.0 mass%, solvent: methyl ethyl ketone / toluene = 63 mass% / 37 mass%): 8.73 parts (4) Isocyanate-based curing agent (Tosoh Corporation, trade name "Coronate HX"): 0.2 parts (5) Solvent (methyl ethyl ketone): 15.00 parts (6) Solvent (toluene): 11.41 parts

[0112] In the magnetic layer forming paint N, the content ratio of the amorphous resins (a) and (b) was (a):(b) = 50:50 by mass, and the volume content of the soft magnetic material relative to the total solid content of the magnetic layer forming paint N was 60%.

[0113] <Formation of Magnetic Layer> Next, an electromagnetic noise suppression sheet of Comparative Example 4, in which a magnetic layer was formed, was produced in the same manner as in Example 1, except that the magnetic layer-forming paint N was used instead of the magnetic layer-forming paint A of Example 1. The thickness of the magnetic layer was 38 μm, and the total thickness of the electromagnetic noise suppression sheet was 50 μm.

[0114] The electromagnetic noise suppression sheets of Examples 1 to 12 and Comparative Examples 1 to 4 were evaluated as follows.

[0115] <Adhesion> First, 11 cuts were made vertically and horizontally at 1 mm intervals on the magnetic layer surface of the prepared electromagnetic noise suppression sheet, reaching down to the substrate, to create 100 grids. Next, cellophane tape was firmly pressed onto the grids, and the edge of the tape was quickly peeled off at a 45° angle. The state of the grids was observed, and the adhesion of the magnetic layer of the electromagnetic noise suppression sheet was evaluated as follows:

[0116] Grade A: When none of the grids have peeled off. Grade B: When peeling at the intersections of the cuts and at parts of the grid is less than 5%. Grade C: When peeling at the intersections of the cuts and at parts of the grid is 5% or more.

[0117] <Flexibility> The prepared electromagnetic noise suppression sheet was cut into a 10 mm × 100 mm tape, and the substrate surface of this tape-like sheet was wrapped around the outer periphery of a stainless steel metal rod so that it was in contact with the periphery at approximately 360°, and held in this state for 1 minute. Thereafter, the magnetic layer surface of the wrapped tape-like sheet was observed under a microscope, and the flexibility of the magnetic layer of the electromagnetic noise suppression sheet was evaluated as follows.

[0118] Evaluation A: When wrapped around a stainless steel rod with a diameter of 1 mm, no peeling or cracks occurred in the magnetic layer. Evaluation B: When wrapped around a stainless steel rod with a diameter of 2 mm, no peeling or cracks occurred in the magnetic layer. Evaluation C: When wrapped around a stainless steel rod with a diameter of 2 mm, peeling or cracks occurred in the magnetic layer.

[0119] <Tackiness> Two sheets of the produced electromagnetic noise suppression sheet were cut into 10 cm squares, and the sheets were stacked so that the magnetic layer surface of one sheet was in contact with the substrate surface of the other sheet. A weight with a diameter of 1 cm was pressed against the stacked sheets with a load of 1 kg for 30 seconds. Thereafter, the state of adhesion of the stacked sheets was observed, and the tackiness of the magnetic layer of the electromagnetic noise suppression sheet was evaluated as follows.

[0120] Evaluation A: When only the top sheet of a stack of sheets is lifted, the bottom sheet does not adhere. Evaluation B: When only the top sheet of a stack of sheets is lifted, the bottom sheet adheres, but falls off under its own weight in less than 5 seconds. Evaluation C: When only the top sheet of a stack of sheets is lifted, the bottom sheet adheres, but does not fall off for 5 seconds or more.

[0121] <Magnetic Noise Suppression Effect> The magnetic noise suppression effect of the produced electromagnetic noise suppression sheet was confirmed by evaluating the internal decoupling ratio (Rda) using an intra-decoupling ratio measurement system (compliant with IEC 62333-2) that uses a vector network analyzer and a loop antenna. Specifically, the internal decoupling ratio at 100 MHz and the frequencies at which the maximum internal decoupling ratio was achieved from 100 MHz to 10 GHz were measured.

[0122] The results are shown in Tables 1 and 2, along with the materials constituting the magnetic layers of the electromagnetic noise suppression sheets that were produced.

[0123]

[0124]

[0125] It can be seen from Tables 1 and 2 that the electromagnetic noise suppression sheets of Examples 1 to 12 exhibited a magnetic noise suppression effect, and also achieved good results in adhesion, flexibility, and tackiness. On the other hand, the electromagnetic noise suppression sheets of Comparative Examples 1 to 4 exhibited a magnetic noise suppression effect, but Comparative Examples 1 and 4, which did not contain an amorphous resin (a) with a glass transition temperature of 0°C or lower in the magnetic layer, exhibited poor adhesion and flexibility, and Comparative Examples 2 and 3, which did not contain an amorphous resin (b) with a glass transition temperature of 10°C or higher in the magnetic layer, exhibited poor tackiness.

[0126] The following supplementary embodiments are further disclosed in relation to the embodiments of the present application including Examples 1 to 12 described above. (Supplementary Embodiment 1) An electromagnetic noise suppression sheet including a substrate and a magnetic layer, wherein the magnetic layer includes a magnetic material and a binder, and the binder includes an amorphous resin (A) having a glass transition temperature of -50°C to 0°C and an amorphous resin (B) having a glass transition temperature of 10°C or higher. (Supplementary Embodiment 2) The electromagnetic noise suppression sheet according to Supplementary Embodiment 1, wherein the amorphous resin (A) is an amorphous polyester (a) having a glass transition temperature of -50°C to 0°C, and the amorphous resin (B) is an amorphous polyester (b) having a glass transition temperature of 10°C or higher. (Supplementary Embodiment 3) The electromagnetic noise suppression sheet according to Supplementary Embodiment 2, wherein the content ratio of the amorphous polyester (a) to the amorphous polyester (b) is (a):(b) = 95:5 to 35:65 by mass. (Additional Embodiment 4) The electromagnetic noise suppression sheet according to Additional Embodiment 2, wherein the content ratio of the amorphous polyester (a) to the amorphous polyester (b) is (a):(b)=90:10 to 50:50 by mass. (Additional Embodiment 5) The electromagnetic noise suppression sheet according to any one of Additional Embodiments 2 to 4, wherein at least one of the amorphous polyester (a) and the amorphous polyester (b) contains a crosslinked portion formed by crosslinking via an amide bond. (Additional Embodiment 6) The electromagnetic noise suppression sheet according to any one of Additional Embodiments 1 to 5, wherein the total amount of the amorphous resin (A) and the amorphous resin (B) is 90 mass % or more with respect to the total amount of the binder. (Additional Embodiment 7) The electromagnetic noise suppression sheet according to any one of Additional Embodiments 1 to 6, wherein the magnetic material contains a soft magnetic material. (Additional Embodiment 8) The electromagnetic noise suppression sheet according to Additional Embodiment 7, wherein the soft magnetic material is carbonyl iron. (Additional Form 9) The electromagnetic noise suppression sheet according to Additional Form 7 or 8, wherein the volume content of the soft magnetic material in the magnetic layer is 30 to 80%. (Additional Form 10) The electromagnetic noise suppression sheet according to any of Additional Forms 1 to 9, wherein the substrate is a resin film. (Additional Form 11) The electromagnetic noise suppression sheet according to any of Additional Forms 1 to 10, further including a metal layer. (Additional Form 12) The electromagnetic noise suppression sheet according to any of Additional Forms 1 to 11, wherein the overall thickness is 10 to 85 μm.(Addendum 13) A method for producing the electromagnetic noise suppression sheet according to any one of Addendums 1 to 12, comprising the steps of: mixing a magnetic material, an amorphous resin (A) having a glass transition temperature of -50°C to 0°C, and an amorphous resin (B) having a glass transition temperature of 10°C or higher, together with a solvent, to prepare a magnetic layer-forming paint; and applying the magnetic layer-forming paint to a substrate and drying it. (Addendum 14) A method for producing an electromagnetic noise suppression sheet according to Addendum 13, wherein at least one resin selected from the amorphous resin (A) and the amorphous resin (B) contained in the magnetic layer-forming paint contains a carboxyl group. (Addendum 15) A method for producing an electromagnetic noise suppression sheet according to Addendum 14, wherein the magnetic layer-forming paint further contains a resin having at least one selected from an oxazoline group and a carbodiimide group as a crosslinking agent. (Additional Form 16) The method for producing an electromagnetic noise suppression sheet according to any one of Additional Forms 13 to 15, wherein the solvent contained in the magnetic layer-forming paint is at least one selected from water and water-soluble solvents. (Additional Form 17) A cable comprising the electromagnetic noise suppression sheet according to any one of Additional Forms 1 to 12.

[0127] The present application may be implemented in other forms than those described above. The embodiments disclosed in the present application are merely examples and are not intended to be limiting. The scope of the present application shall be interpreted in accordance with the appended claims rather than the above description, and all modifications within the scope of the claims are intended to be embraced within the scope of the claims.

[0128] REFERENCE SIGNS LIST 10, 10' Electromagnetic noise suppression sheet 11 Substrate 12 Magnetic layer 13 Metal layer 20, 30 Coaxial cable 21, 31 Inner conductor 22, 32 Insulating layer 23, 33 Metal foil 24, 34 Metal braid 25, 35 Magnetic sheath layer 35a Substrate layer 35b Magnetic layer 26, 36 Outer coating layer

Claims

1. An electromagnetic noise suppression sheet comprising a substrate and a magnetic layer, the magnetic layer comprising a magnetic material and a binder, the binder comprising an amorphous resin (A) having a glass transition temperature of -50°C to 0°C, and an amorphous resin (B) having a glass transition temperature of 10°C or higher.

2. The electromagnetic noise suppression sheet according to claim 1, wherein the amorphous resin (A) is an amorphous polyester (a) having a glass transition temperature of -50°C to 0°C, and the amorphous resin (B) is an amorphous polyester (b) having a glass transition temperature of 10°C or higher.

3. The electromagnetic noise suppression sheet according to claim 2, wherein the content ratio of the amorphous polyester (a) and the amorphous polyester (b) is, in mass ratio, (a):(b)=95:5 to 35:

65.

4. The electromagnetic noise suppression sheet according to claim 2, wherein the content ratio of the amorphous polyester (a) and the amorphous polyester (b) is, in terms of mass ratio, (a):(b)=90:10 to 50:

50.

5. The electromagnetic noise suppression sheet according to claim 2, wherein at least one of the amorphous polyester (a) and the amorphous polyester (b) contains a crosslinked portion crosslinked by an amide bond.

6. The electromagnetic noise suppression sheet according to claim 1, wherein the combined amount of the amorphous resin (A) and the amorphous resin (B) is 90 mass % or more based on the total amount of the binder.

7. The electromagnetic noise suppression sheet according to claim 1, wherein the magnetic material includes a soft magnetic material.

8. The electromagnetic noise suppression sheet according to claim 7, wherein the soft magnetic material is carbonyl iron.

9. The electromagnetic noise suppression sheet according to claim 7, wherein the volume content of the soft magnetic material in the magnetic layer is 30 to 80%.

10. The electromagnetic noise suppression sheet according to claim 1, wherein the substrate is a resin film.

11. The electromagnetic noise suppression sheet according to claim 1, further comprising a metal layer.

12. The electromagnetic noise suppression sheet according to claim 1, which has an overall thickness of 10 to 85 μm.

13. A method for producing an electromagnetic noise suppression sheet according to any one of claims 1 to 12, comprising the steps of: mixing a magnetic material, an amorphous resin (A) having a glass transition temperature of -50°C to 0°C, and an amorphous resin (B) having a glass transition temperature of 10°C or higher, together with a solvent, to prepare a paint for forming a magnetic layer; and applying the paint for forming a magnetic layer to a substrate and drying it.

14. The method for producing an electromagnetic noise suppression sheet according to claim 13, wherein at least one resin selected from the amorphous resin (A) and the amorphous resin (B) contained in the coating material for forming the magnetic layer contains a carboxyl group.

15. The method for producing an electromagnetic noise suppression sheet according to claim 14, wherein the coating material for forming the magnetic layer further contains, as a crosslinking agent, a resin having at least one type selected from the group consisting of an oxazoline group and a carbodiimide group.

16. The method for producing an electromagnetic noise suppression sheet according to claim 13, wherein the solvent contained in the coating material for forming the magnetic layer is at least one selected from the group consisting of water and water-soluble solvents.

17. A cable comprising an electromagnetic noise suppression sheet according to any one of claims 1 to 12.

Images