Electromagnetic noise suppression sheet and cable including same

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) having a glass transition temperature of -50°C to 10°C and an amorphous resin (B) having a glass transition temperature of 50°C to 100°C. A DSC curve of the magnetic layer obtained by differential scanning calorimetry exhibits a plurality of baseline shifts A and B in the range of -20°C to 80°C in the DSC curve.

Description

Electromagnetic Noise Suppression Sheet and Cable Using the Same

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

[0002] With the development of wireless communication technologies represented by mobile phones, various devices and sensors are being wirelessly connected to the network. Also, in the medical field, from the perspective of infection prevention, equipment is becoming cordless, and medical devices are starting to be wirelessly connected. These communications require high-speed, large-capacity transmission over relatively short distances and use high frequencies. With the increasing number of devices that use such high frequencies, the risk of malfunctions and interference with the electromagnetic waves used due to electromagnetic noise generated by the devices is increasing. Furthermore, in recent years, millimeter-wave radars for preventing automobile collision accidents have also started to be installed. Malfunctions in devices in these medical and automotive fields can affect human lives, so there must be no malfunctions. Therefore, there is an increasing need to apply an electromagnetic noise suppression sheet, as a countermeasure against electromagnetic noise generated by devices and the malfunctions caused by the resulting interference, i.e., so-called EMC (Electromagnetic Compatibility), to circuit elements and transmission lines that transmit and receive electromagnetic waves in the kHz to GHz band.

[0003] By providing electromagnetic noise suppression sheets to society, it is possible to contribute to the achievement of three of the 17 Sustainable Development Goals (SDGs) established by the United Nations: Goal 3 (Ensure healthy lives and promote well-being for all people of 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 proposes using a laminate comprising a magnetic layer containing magnetic powder and a binder resin, and a polymer compound film layer, as a magnetic sheet that suppresses the transmission of electromagnetic waves. Here, the binder resin used in the magnetic layer of the laminate in Patent Document 1 contains a crystalline polyester resin, making it possible to realize a tackless 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 in the manufacture of the magnetic layer, causing the magnetic layer to harden. If the laminate is used as a magnetic sheet wrapped around cables or connectors, 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 compound film layer decreases, and the magnetic layer and the polymer compound film layer may peel off.

[0005] Furthermore, Patent Document 2 is a prior art document related to the application of the electromagnetic noise suppression sheet of the present invention. Patent Document 2 discloses a communication wire in which a magnetic sheath layer, in which particulate magnetic material is dispersed in a polymer material, is formed as an extruded molded body.

[0006] Japanese Patent Publication No. 2016-36965 (Japanese Patent Publication No. 6428033) Japanese Patent Publication No. 2022-108557

[0007] This invention solves the above problem and provides an electromagnetic noise suppression sheet that can be attached to uneven or curved surfaces of electronic devices where the effects of electromagnetic noise are to be prevented, or in particular wrapped around cables and connectors, and has electromagnetic wave absorption performance in the kHz to GHz band.

[0008] The electromagnetic noise suppression sheet of the present invention comprises a substrate and a magnetic layer, the magnetic layer comprises a magnetic material and a binder, the binder comprises an amorphous resin (A) having a glass transition temperature of -50°C to 10°C and an amorphous resin (B) having a glass transition temperature of 50°C to 100°C, and is characterized in that when the DSC curve of the magnetic layer is obtained by differential scanning calorimetry, the DSC curve has a plurality of baseline shifts in the range of -20°C to 80°C.

[0009] The cable of the present invention is characterized by including the electromagnetic noise suppression sheet of the present invention.

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

[0011] Figure 1 is a schematic diagram showing an example of the DSC curve of the magnetic layer of an electromagnetic noise suppression sheet. Figure 2 is a schematic diagram showing the differential curve (DDSC curve) obtained by taking the first derivative of the DSC curve in Figure 1. Figure 3 is a schematic cross-sectional view showing an example of an electromagnetic noise suppression sheet according to an embodiment. Figure 4 is a schematic cross-sectional view showing another example of an electromagnetic noise suppression sheet according to an embodiment. Figure 5 is a schematic cross-sectional view showing an example of a conventional coaxial cable. Figure 6 is a schematic cross-sectional view showing an example of a coaxial cable according to an embodiment. Figure 7 is the DSC curve of the magnetic layer of the electromagnetic noise suppression sheet of Example 3. Figure 8 is the DDSC curve of the magnetic layer of the electromagnetic noise suppression sheet of Example 3.

[0012] (Electromagnetic Noise Suppression Sheet) An embodiment of the electromagnetic noise suppression sheet of the present invention will now be described. The electromagnetic noise suppression sheet of this embodiment includes a substrate and a magnetic layer, the magnetic layer includes a magnetic material and a binder, the binder includes an amorphous resin (A) having a glass transition temperature of -50°C to 10°C and an amorphous resin (B) having a glass transition temperature of 50°C to 100°C, and is characterized in that when the DSC curve of the magnetic layer is obtained by differential scanning calorimetry, the DSC curve has a plurality of baseline shifts in the range of -20°C to 80°C.

[0013] Generally, when multiple resins are mixed and used in a magnetic layer, if the compatibility of the multiple resins is high, the multiple resins will integrate and become one, exhibiting resin properties similar to those of a single resin. When the DSC curve of the magnetic layer is obtained by differential scanning calorimetry in this state, a baseline shift caused by the glass transition of the compatible resins is observed in the DSC curve.

[0014] On the other hand, when multiple resins are mixed and used in a magnetic layer, if the compatibility of the multiple resins is low, the multiple resins will not be compatible and will exist as multiple separate resin phases, resulting in the resin properties of each resin phase being exhibited individually. If the DSC curve of the magnetic layer is obtained by differential scanning calorimetry in this state, multiple baseline shifts caused by the glass transitions of the multiple resins that exist individually will be observed in the DSC curve.

[0015] In the electromagnetic noise suppression sheet of the present invention, the magnetic layer includes an amorphous resin (A) with a glass transition temperature of -50°C to 10°C and an amorphous resin (B) with a glass transition temperature of 50°C to 100°C as a binder, and when the DSC curve of the magnetic layer is obtained by differential scanning calorimetry, the DSC curve has multiple baseline shifts in the range of -20°C to 80°C. Therefore, it is considered that amorphous resin (A) and amorphous resin (B) are immiscible and exist as separate resin phases within the magnetic layer.

[0016] Therefore, in the magnetic layer of the electromagnetic noise suppression sheet of the present invention, the properties of the amorphous resin (A) with a glass transition temperature of -50°C to 10°C are individually exhibited, resulting in excellent flexibility and adhesion of the magnetic layer. Even when the electromagnetic noise suppression sheet of the present invention is used by wrapping it around cables or connectors, cracks will not occur in the magnetic layer, and the magnetic layer will not peel off from the substrate.

[0017] On the other hand, if the magnetic layer contains only amorphous resin (A) with a glass transition temperature of -50°C to 10°C, the blocking properties of the magnetic layer surface increase, and when the electromagnetic noise suppression sheet is wound onto the core, a problem occurs where the sheets stick together, making it difficult to unwind the sheet (blocking phenomenon). Furthermore, it is not possible to impart thermal fusion properties to the magnetic layer.

[0018] In contrast, the magnetic layer of the electromagnetic noise suppression sheet of the present invention contains an amorphous resin (B) with a glass transition temperature of 50°C to 100°C, and the properties of the amorphous resin (B) can be individually exhibited, thereby suppressing excessive blocking and providing heat-sealability to PVC (polyvinyl chloride) resin. By suppressing excessive blocking of the electromagnetic noise suppression sheet, blocking can be prevented when the electromagnetic noise suppression sheet is wound up and stored after manufacturing. In particular, blocking can be prevented when storing in high-temperature or high-temperature and high-humidity environments, thus reducing the burden of temperature and humidity control during storage of the electromagnetic noise suppression sheet. Furthermore, the heat-sealability of the electromagnetic noise suppression sheet is an important characteristic for securely fixing the electromagnetic noise suppression sheet in a predetermined position by heat fusion when the electromagnetic noise suppression sheet is wrapped around cables or connectors.

[0019] As described above, in the electromagnetic noise suppression sheet of the present invention, the magnetic layer includes an amorphous resin (A) with a glass transition temperature of -50°C to 10°C and an amorphous resin (B) with a glass transition temperature of 50°C to 100°C as a binder, and when the DSC curve of the magnetic layer is obtained by differential scanning calorimetry, there are multiple baseline shifts in the range of -20°C to 80°C of the DSC curve, so that adhesion and flexibility can be sufficiently ensured, blocking can be suppressed, and an electromagnetic noise suppression sheet with heat fusion properties can be realized.

[0020] On the other hand, if the baseline shift is in the range below -20°C, the influence of the resin with the lower glass transition temperature becomes greater, increasing blocking properties and raising the risk of blocking phenomena. Also, if the baseline shift is in the range above 80°C, the influence of the resin with the higher glass transition temperature becomes greater, reducing the flexibility and adhesion of the magnetic layer. When the electromagnetic noise suppression sheet is wrapped around cables or connectors, there is a risk of cracks forming in the magnetic layer, and the magnetic layer peeling off from the substrate.

[0021] The electromagnetic noise suppression sheet of this embodiment will be described below. First, the relationship between the DSC curve obtained by differential scanning calorimetry of the magnetic layer of the electromagnetic noise suppression sheet and the differential curve (DDSC curve) obtained by taking the first derivative of the DSC curve will be explained.

[0022] Figure 1 is a schematic diagram showing an example of a DSC curve of the magnetic layer of the electromagnetic noise suppression sheet of this embodiment. The magnetic layer of the electromagnetic noise suppression sheet of this embodiment contains an amorphous resin (A) with a glass transition temperature of -50°C to 10°C and an amorphous resin (B) with a glass transition temperature of 50°C to 100°C. The amorphous resins (A) and (B) are incompatible and exist as two separate resin phases. Therefore, in the DSC curve of Figure 1, two baseline shifts A and B, caused by the glass transitions of the two separately existing amorphous resins (A) and (B), are observed in the range of -20°C to 80°C. Here, the baseline refers to the DSC curve in the temperature range in which no transition or reaction occurs in the magnetic layer, and in Figure 1, it refers to the DSC curve in the region other than baseline shifts A and B (a straight line with a constant slope in Figure 1). Also in Figure 1, the inflection points a and b of the two baseline shifts A and B are observed.

[0023] Figure 2 is a schematic diagram showing the differential curve (DDSC curve) obtained by taking the first derivative of the DSC curve in Figure 1. The temperatures corresponding to the inflection points a and b of the DSC curve in Figure 1 coincide with the temperatures corresponding to the local minimums a and b of the two negative peaks A and B in the range of -20°C to 80°C in the DDSC curve in Figure 2.

[0024] Here, the temperatures corresponding to the inflection points a and b of the DSC curve in Figure 1, and the temperatures corresponding to the local minimums a and b at the negative peaks A and B of the DDSC curve in Figure 2, are usually different from the intrinsic glass transition temperatures of amorphous resin (A) and amorphous resin (B), which will be discussed later. This is because, even though amorphous resin (A) and amorphous resin (B) are incompatible and exist as two separate resin phases, some interaction occurs between them, and this interaction is thought to change the intrinsic glass transition temperatures of each.

[0025] In Figure 1, an example where a baseline shift is clearly observed is shown to simplify the explanation of the DSC curve. However, in the actual magnetic layer's DSC curve, although a baseline shift exists, it may be small and not clearly visible from the DSC curve. Even in such cases, when the DDSC curve is determined from the obtained DSC curve, negative peaks A and B can be clearly observed at the positions of the DDSC curve corresponding to baseline shifts A and B of the DSC curve. Therefore, even if the baseline shift of the DSC curve is small, the existence of a baseline shift can be reliably confirmed from that DDSC curve.

[0026] Here, the temperature difference corresponding to the minimum values ​​of the multiple negative peaks (two negative peaks in Figure 2) is preferably between 20°C and 40°C (40°C in Figure 2). This allows the electromagnetic noise suppression sheet of this embodiment to further improve adhesion and flexibility, as well as further suppress blocking. If the above temperature difference falls below 20°C, the influence of the resin with the lower glass transition temperature becomes greater, increasing blocking and reducing the blocking phenomenon prevention effect. Also, if the above temperature difference exceeds 40°C, the influence of the resin with the higher glass transition temperature becomes greater, reducing the flexibility and adhesion of the magnetic layer.

[0027] Next, the electromagnetic noise suppression sheet of this embodiment will be described with reference to the drawings. Figure 3 is a schematic cross-sectional view showing an example of the electromagnetic noise suppression sheet of this embodiment. In Figure 3, the electromagnetic noise suppression sheet 10 comprises a base material 11 and a magnetic layer 12 placed on the base material 11. In Figure 3, the electromagnetic noise suppression sheet 10 has a two-layer structure consisting of a base material 11 and a magnetic layer 12, but a three-layer structure may also be made by placing an adhesive layer on the magnetic layer 12 side.

[0028] Figure 4 is a schematic cross-sectional view showing another example of the electromagnetic noise suppression sheet of this embodiment. In Figure 4, the electromagnetic noise suppression sheet 10' comprises a base material 11, a metal layer 13 placed on the base material 11, and a magnetic layer 12 placed on the metal layer 13. In Figure 4, the electromagnetic noise suppression sheet 10' has a three-layer structure consisting of a base material 11, a magnetic layer 12, and a metal layer 13, but it may also have a four-layer structure by placing an adhesive layer on the magnetic layer 12 side. Also, in Figure 4, an example is shown where the layers are arranged in the order of magnetic layer 12 / metal layer 13 / base material 11, but they may also be arranged in the order of magnetic layer 12 / base material 11 / metal layer 13.

[0029] The overall thickness of the electromagnetic noise suppression sheet in this embodiment is preferably 15 to 150 μm, and more preferably 30 to 120 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 wave absorption capacity and the overall strength of the sheet. On the other hand, if the overall thickness of the electromagnetic noise suppression sheet is too thick, its flexibility will decrease, making it difficult to wrap around cables and connectors.

[0030] Next, each component of the electromagnetic noise suppression sheet of this embodiment will be described.

[0031] <Substrate> The substrate used in the electromagnetic noise suppression sheet of this embodiment is a base material for forming the magnetic layer.

[0032] The above-mentioned substrate can be any material that is flexible and can ensure adhesion to the magnetic layer, and is usually a resin film. Examples of resins that make up the above-mentioned 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, 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, fluororesins, 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. One or more of these resin materials can be used. Furthermore, the above resin materials may have functional groups as needed. Functional monomers or modifier monomers may also be grafted onto the resin material.

[0033] The surface of the above-mentioned substrate may be subjected to known surface treatments to improve adhesion with adjacent magnetic layers. Specific examples of such surface treatments include corona discharge treatment, ozone exposure treatment, high-voltage electric shock exposure treatment, and ionization radiation treatment. Furthermore, the substrate may be subjected to coating treatments with undercoating agents (such as silicone treatment), primer treatment, matting treatment, crosslinking treatment, etc.

[0034] The above-mentioned substrate may be a single layer or a laminate of two or more layers. Furthermore, known auxiliary agents such as fillers, flame retardants, degradation inhibitors, antistatic agents, softeners, and plasticizers may be added to the substrate as needed.

[0035] The thickness of the above-mentioned substrate is not particularly limited, but is preferably 5 to 20 μm, and more preferably 10 to 15 μm. If the thickness of the above-mentioned substrate is within the above range, both strength and flexibility can be achieved in the electromagnetic noise suppression sheet of this embodiment.

[0036] Since the above-mentioned substrate can be flexible and capable of ensuring adhesion with the magnetic layer, a metal layer such as a metal foil, as described later, can be used as the substrate instead of the resin film. That is, a metal layer can be used as the substrate 11 in Figure 3.

[0037] <Magnetic Layer> The magnetic layer used in the electromagnetic noise suppression sheet of this embodiment includes a magnetic material and a binder. The thickness of the magnetic layer is not particularly limited, but if it is too thin, the electromagnetic wave absorption performance decreases, and if it is too thick, the flexibility decreases, so it is usually set in the range of 10 to 100 μm. The constituent materials of the magnetic layer described above will be explained below.

[0038] [Binder] The above binder may contain an amorphous resin (A) with a glass transition temperature of -50°C to 10°C and an amorphous resin (B) with a glass transition temperature of 50°C to 100°C. 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.

[0039] By using amorphous resin (A) with a glass transition temperature of -50°C to 10°C, flexibility can be imparted to the magnetic layer, and the adhesion of the magnetic layer to the substrate can also be improved. However, using amorphous resin (A) alone can easily cause blocking in the magnetic layer, and when magnetic sheets are stacked or wound into a roll, the magnetic layers may stick to each other. On the other hand, using amorphous resin (B) alone with a glass transition temperature of 50°C to 100°C makes the surface of the magnetic layer hard and less likely to stick, but there is a possibility that the adhesion between the magnetic layer and the substrate will decrease, or that the magnetic layer may crack when used in a wound manner. For this reason, amorphous resins (A) and (B) are used in combination as the binder in this embodiment. Furthermore, it is preferable that the glass transition temperature of amorphous resin (A) is in the range of -18°C to 7°C from the viewpoint of compatibility with amorphous resin (B).

[0040] In particular, by using amorphous resin (B) with a glass transition temperature of 50°C to 100°C, excessive blocking properties can be suppressed and the blocking phenomenon can be prevented, as well as providing heat-sealability to PVC (polyvinyl chloride) resin. On the other hand, if the glass transition temperature of amorphous resin (B) is higher than 100°C, even if used in combination with amorphous resin (A) with a glass transition temperature of -50°C to 10°C, the surface of the magnetic layer tends to harden, which can reduce the adhesion between the magnetic layer and the substrate, and the magnetic layer may crack easily when attached to uneven or curved surfaces, or when bent during wrapping. Furthermore, it is preferable that the glass transition temperature of amorphous resin (B) be in the range of 53°C to 84°C, and more preferably in the range of 53°C to 67°C. Specifically, it is preferable that the glass transition temperature of amorphous resin (A) is in the range of -18°C to 7°C, and the glass transition temperature of amorphous resin (B) is in the range of 53°C to 84°C, and more preferably that the glass transition temperature of amorphous resin (A) is in the range of -18°C to 7°C, and the glass transition temperature of amorphous resin (B) is in the range of 53°C to 67°C.

[0041] As described above, by using the amorphous resin (B) having a glass transition temperature of 50°C to 100°C, the magnetic layer can be imparted with heat fusion properties with respect to a PVC (polyvinyl chloride) resin. Specifically, the 180° peel adhesion force to the PVC resin plate, measured in accordance with JIS Z0237 (2022) after thermally fusing the magnetic layer to the PVC resin plate, is preferably 2.0 N / 25 mm or more. When the 180° peel adhesion force is within this range, the heat fusion properties of the magnetic layer with respect to the PVC (polyvinyl chloride) resin can be sufficiently ensured.

[0042] Here, even when the amorphous resins (A) and (B) are used in combination, the glass transition temperature (Tg) means the respective inherent glass transition temperatures of the amorphous resins (A) and (B), and the glass transition temperatures of the respective resins are the temperatures measured separately by differential scanning calorimetry (DSC) defined in JIS K 7121-1987.

[0043] Further, when the magnetic layer used in the electromagnetic noise suppression sheet of the present embodiment uses a combination of an amorphous resin (A) having a glass transition temperature of -50°C to 10°C and an amorphous resin (B) having a glass transition temperature of 50°C to 100°C, when obtaining the DSC curve of the magnetic layer by differential scanning calorimetry, it is necessary to have a plurality of baseline shifts in the range of -20°C to 80°C of the DSC curve. For this purpose, as described above, the amorphous resin (A) having a glass transition temperature of -50°C to 10°C and the amorphous resin (B) having a glass transition temperature of 50°C to 100°C need to have low compatibility.

[0044] To reduce the compatibility between the amorphous resin (A) having a glass transition temperature of -50°C to 10°C and the amorphous resin (B) having a glass transition temperature of 50°C to 100°C, it is preferable that the Tg difference between the combined amorphous resin (A) and amorphous resin (B) is large. Specifically, the Tg difference is preferably 50°C or more. Further, when using an amorphous resin (C) having another Tg in addition to the amorphous resins (A) and (B), among the amorphous resins (A), (B), and (C), the Tg difference between the resin having the largest volume% content and the resin having the second largest volume% content is preferably 65°C or more.

[0045] As the amorphous resin (A), amorphous polyester, amorphous polyurethane, amorphous acrylic, etc., having a glass transition temperature of -50°C to 10°C can be used, and as the amorphous resin (B), amorphous polyester, amorphous polyurethane, amorphous acrylic, etc., having a glass transition temperature of 50°C to 100°C can be used. Among these, amorphous polyester (a) with a glass transition temperature of -50°C to 10°C is particularly preferred as amorphous resin (A), and amorphous polyester (a) with a glass transition temperature of -18°C to 7°C is more preferred. Furthermore, as amorphous resin (B), amorphous polyester (b) with a glass transition temperature of 50°C to 100°C is preferred, amorphous polyester (b) with a glass transition temperature of 53°C to 84°C is more preferred, and amorphous polyester (b) with a glass transition temperature of 53°C to 67°C is even more preferred. Specifically, it is preferable that amorphous resin (A) includes amorphous polyester (a) with a glass transition temperature of -50°C to 10°C, and amorphous resin (B) includes amorphous polyester (b) with a glass transition temperature of 50°C to 100°C; more preferably that amorphous resin (A) includes amorphous polyester (a) with a glass transition temperature of -18°C to 7°C, and amorphous resin (B) includes amorphous polyester (b) with a glass transition temperature of 53°C to 84°C; and even more preferably that amorphous resin (A) includes amorphous polyester (a) with a glass transition temperature of -18°C to 7°C, and amorphous resin (B) includes amorphous polyester (b) with a glass transition temperature of 53°C to 67°C. Among amorphous resins, amorphous polyester is excellent in solubility and flexibility, and is suitable for manufacturing sheet-like magnetic layers.

[0046] 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 magnitude of two baseline shifts detected by measuring the DSC curve and DDSC curve of the magnetic layer, or from the magnitude of two peaks in the DDSC curve.

[0047] As the above amorphous polyesters (a) and (b), for example, "Vylon" (registered trademark) manufactured by Toyobo Co., Ltd., "Plascote" (registered trademark) manufactured by Gohsei Chemical Industry Co., Ltd., "Nichigo Polyester" (registered trademark) manufactured by Mitsubishi Chemical Corporation, "Armatex" (registered trademark) manufactured by Mitsui Chemicals, Inc., etc. can be mentioned. Since these are excellent in solubility in water and organic solvents, they can be dissolved in water or organic solvents at an arbitrary ratio and used.

[0048] As the above binder, in addition to the above amorphous resin (A) and the above amorphous resin (B), at least one of a crystalline resin and an amorphous resin having a glass transition temperature greater than 10°C and less than 50°C may be included as long as the effects of the present application are not impaired. In that case, the total amount of the above amorphous resin (A) and the above amorphous resin (B) is preferably 90% by mass or more, and more preferably 95% by mass or more, based on the total amount of the above binder.

[0049] [Magnetic Material] As the above magnetic material, a soft magnetic material and a hard magnetic material can be used, but it is preferable to use a soft magnetic material. Since the soft magnetic material has a high initial permeability and can exhibit electromagnetic wave absorption performance even when a small amount is contained in the magnetic layer, an electromagnetic noise suppression effect can be exhibited even when the magnetic layer is made into a thin film.

[0050] As the above soft magnetic material, for example, iron, silicon iron, permalloy, sendust, permendur, soft ferrite, electromagnetic stainless steel, amorphous magnetic alloy, nanocrystalline magnetic alloy, etc. can be mentioned. As the soft magnetic material, in particular, 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.

[0051] As the above hard magnetic material, hard ferrite (ferrite magnet), alnico magnet, samarium cobalt magnet, neodymium magnet, samarium iron nitride magnet, etc. can be mentioned.

[0052] The magnetic material described above is usually provided as a spherical or flattened powder, with an average particle size of preferably 0.1 to 100 μm, and more preferably 1 to 20 μm. If the particle size of the magnetic material is too small, the particles tend to aggregate secondarily, making it difficult to obtain a uniform coating (magnetic layer). On the other hand, if the particle size is too large, the particles protrude from the magnetic layer as protrusions, making it easy for the magnetic layer to peel off the substrate when applied to uneven or curved surfaces or wrapped around them. Also, if the particle size is large, it tends to settle when used as a coating, making it difficult to obtain a uniform coating. The average particle size can be measured using a laser diffraction scattering particle size distribution analyzer.

[0053] 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 less than 30%, the electromagnetic wave absorption performance (electromagnetic noise suppression effect) of the magnetic layer tends to be insufficient, and 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 it more prone to cracks and powder shedding when the magnetic layer is bent.

[0054] <Metal Layer> As shown in Figure 4, by placing a metal layer on the electromagnetic noise suppression sheet of this embodiment, the electromagnetic noise suppression sheet can be given electric field shielding performance, and not only magnetic noise but also electrical noise can be suppressed. In Figure 4, the metal layer is placed between the substrate and the magnetic layer, but it may also be placed on the outer surface of the magnetic layer or on the outer surface of the substrate.

[0055] The type of metal constituting the above metal layer is not particularly limited as long as it has flexibility and adhesion to the magnetic layer, but aluminum, copper, etc. are preferred. This is because aluminum, copper, etc. are inexpensive, easy to process into thin films, and have excellent flexibility.

[0056] The thickness of the above-mentioned metal layer is not particularly limited, but if it is too thick, the flexibility will decrease, so it is usually set in the range of 0.1 to 30 μm.

[0057] 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 aforementioned substrate (resin film) by vapor deposition or sputtering. Furthermore, a composite sheet in which the substrate and metal foil are pre-bonded can also be used as the above-mentioned metal layer.

[0058] Furthermore, as mentioned above, the above-mentioned metal layer can also be used as the base material 11 in Figure 3.

[0059] <Adhesive Layer> When an adhesive layer is placed on the electromagnetic noise suppression sheet of this embodiment, the thickness of the adhesive layer is preferably 10 to 50 μm, and 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 will saturate, and the total thickness of the electromagnetic noise suppression sheet will increase, which will reduce the flexibility of the electromagnetic noise suppression sheet, making it difficult to follow when attaching it to electronic components or to wrap it around wiring, etc.

[0060] (Cable) Embodiments of the cable of this application will now be described. The cable of this embodiment is characterized by comprising the electromagnetic noise suppression sheet of the embodiment of this application described above. The cable of this embodiment 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 for video cable applications.

[0061] The following describes a coaxial cable, which is an example of the cable of this embodiment. In this coaxial cable, the electromagnetic noise suppression sheet of the present invention is used as the magnetic sheath layer of the coaxial cable. By using the electromagnetic noise suppression sheet of the present invention as the magnetic sheath layer of the coaxial cable, the electromagnetic noise suppression sheet of the present invention can function as the electromagnetic noise suppression layer of the coaxial cable. Furthermore, by using the electromagnetic noise suppression sheet of the present invention 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 from the cut surface when the coaxial cable is cut. Moreover, by using the electromagnetic noise suppression sheet of the present invention as the magnetic sheath layer of the coaxial cable, the magnetic sheath layer can be directly heat-fused to the outer coating layer of the coaxial cable, eliminating the need to provide an adhesive layer between the magnetic sheath layer and the outer coating layer.

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

[0063] Figure 5 is a schematic cross-sectional view showing an example of a conventional coaxial cable. In Figure 5, the conventional coaxial cable 20 comprises an internal conductor 21, an insulating layer 22, a metal foil 23, a metal braided body 24, a magnetic sheath layer 25, and an outer covering layer 26. Details of each component of the coaxial cable 20 are described in detail in Patent Document 2 (Japanese Patent Application Publication No. 2022-108557).

[0064] The magnetic sheath layer 25 of the conventional coaxial cable 20 described above was formed by extruding a magnetic sheath layer forming material, which is made by dispersing magnetic powder in a matrix material made of polymer material, onto 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, as an extruded molded body. As a result, the thickness of the magnetic sheath layer 25 was increased, and the processing time was also increased. Furthermore, when the coaxial cable was cut, magnetic powder tended to fall off the cut surface.

[0065] In contrast, Figure 6 is a schematic cross-sectional view showing an example of a coaxial cable according to this embodiment. The coaxial cable 30 of this embodiment comprises an internal conductor 31, an insulating layer 32, a metal foil 33, a metal braid 34, a magnetic sheath layer 35, and an outer covering layer 36. The magnetic sheath layer 35 uses the electromagnetic noise suppression sheet of the present invention described above, and is composed of a base material layer 35a and a magnetic layer 35b arranged on one side of the base material layer 35a.

[0066] In Figure 6, the base layer 35a of the magnetic sheath layer 35 is positioned on the axial side, but the magnetic layer 35b may also be positioned on the axial side.

[0067] The magnetic sheath layer 35 of the coaxial cable 30 in this embodiment can be formed by wrapping the electromagnetic noise suppression sheet of this application around the outer surface of a linear conductor consisting of an internal conductor 31, an insulating layer 32, a metal foil 33, and a metal braid 34. This allows for a thinner magnetic sheath layer and shorter processing time. Furthermore, it prevents magnetic powder from falling from the cut surface when the coaxial cable is cut. Moreover, in the coaxial cable 30 of this embodiment, the magnetic sheath layer 35 and the outer covering layer 36 can be joined by heat fusion.

[0068] In addition to the coaxial cable mentioned above, the electromagnetic noise suppression sheet of this invention can be used on the uneven surfaces and corners of electronic devices that emit electromagnetic noise or electronic devices where electromagnetic noise needs to be prevented. Furthermore, the electromagnetic noise suppression sheet of this invention can 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" below means "parts by mass".

[0070] (Example 1) <Preparation of magnetic layer forming coating> Magnetic layer forming coating A was prepared by mixing and dispersing the following components. (1) Magnetic material (flattened reduced carbonyl iron powder manufactured by Tenichi Co., Ltd., trade name "RPZ"): 43.8 parts (2) Amorphous polyester resin solution (a1) (manufactured by Toyobo MC Co., Ltd., trade name "Byron® BX-10SS", resin Tg: -18°C, solids concentration: 30.0% by mass, solvent: methyl ethyl ketone, toluene): 18.3 parts (3) Amorphous polyester resin solution (b1) (manufactured by Toyobo MC Co., Ltd., trade name "Byron® 20SS", resin Tg: 67°C, solids concentration: 30.0% by mass, solvent: methyl ethyl ketone, toluene): 18.3 parts (4) Crosslinking agent (polyisocyanate for paints / non-yellowing type, manufactured by Tosoh Corporation, trade name "Coronate® Hx"): 0.2 parts (5) Solvent (methyl ethyl ketone): 19.4 parts

[0071] In the above-mentioned magnetic layer forming coating A, the content ratio of amorphous polyester resin solutions (a1) and (b1) was (a1):(b1) = 50:50 by mass ratio, and the volume content of the magnetic material relative to the total solid content of the magnetic layer forming coating A was 40%.

[0072] <Formation of Magnetic Layer> Next, an electromagnetic noise suppression sheet of Example 1 was prepared using a PET film with a thickness of 12 μm (manufactured by Toyobo Co., Ltd., product name "Toyobo Ester® Film E5100") as a substrate. The magnetic layer forming coating A was applied to one main surface of the substrate using an applicator, and then dried at 120°C for 3 minutes to form a magnetic layer on one main surface. The thickness of the magnetic layer was 100 μm.

[0073] (Example 2) <Preparation of magnetic layer forming coating> Magnetic layer forming coating B was prepared by mixing and dispersing the following components. (1) Magnetic material (flattened reduced carbonyl iron powder manufactured by Tenichi Co., Ltd., trade name "RPZ"): 43.8 parts (2) Amorphous polyester resin solution (b1) (manufactured by Toyobo MC Co., Ltd., trade name "Byron® 20SS", resin Tg: 67°C, solids concentration: 30.0% by mass, solvent: methyl ethyl ketone, toluene): 22.0 parts (3) Amorphous polyester resin solution (a2) (manufactured by Toyobo MC Co., Ltd., trade name "Byron® 63SS", resin Tg: 7°C, solids concentration: 30.0% by mass, solvent: methyl ethyl ketone, toluene): 14.6 parts (4) Crosslinking agent (polyisocyanate for paints / non-yellowing type, manufactured by Tosoh Corporation, trade name "Coronate® Hx"): 0.2 parts (5) Solvent (methyl ethyl ketone): 19.4 parts

[0074] In the above-mentioned magnetic layer forming coating B, the content ratio of amorphous polyester resin solutions (b1) and (a2) was (b1):(a2) = 60:40 by mass ratio, and the volume content of the magnetic material relative to the total solid content of the magnetic layer forming coating B was 40%.

[0075] <Formation of Magnetic Layer> Next, an electromagnetic noise suppression sheet of Example 2 was prepared in the same manner as in Example 1, except that the magnetic layer forming paint B was used instead of the magnetic layer forming paint A of Example 1. The thickness of the magnetic layer was 100 μm.

[0076] (Example 3) <Preparation of coating for forming a magnetic layer> Coating C for forming a magnetic layer was prepared by mixing and dispersing the following components. (1) Magnetic material (flattened reduced carbonyl iron powder manufactured by Tenichi Co., Ltd., trade name "RPZ"): 43.8 parts (2) Amorphous polyester resin solution (a1) (manufactured by Toyobo MC Co., Ltd., trade name "Byron® BX-10SS", resin Tg: -18°C, solids concentration: 30.0% by mass, solvent: methyl ethyl ketone, toluene): 11.0 parts (3) Amorphous polyester resin solution (b1) (manufactured by Toyobo MC Co., Ltd., trade name "Byron® 20SS", resin Tg: 67°C, solids concentration: 30.0% by mass, solvent: methyl ethyl ketone, toluene): 18.3 parts (4) Amorphous polyester resin solution (a2) (manufactured by Toyobo MC Co., Ltd., trade name "Byron® 63SS", resin Tg: 7°C, solids concentration: 30.0% by mass, solvent: methyl ethyl ketone, toluene): 7.3 parts (5) Crosslinking agent (polyisocyanate for paints / non-yellowing type, manufactured by Tosoh Corporation, trade name "Coronate® Hx"): 0.2 parts (6) Solvent (methyl ethyl ketone): 19.4 parts

[0077] In the above-mentioned magnetic layer forming coating C, the content ratio of amorphous polyester resin solutions (a1), (b1), and (a2) was (a1):(b1):(a2) = 30:50:20 by mass ratio, and the volume content of the magnetic material relative to the total solid content of the magnetic layer forming coating C was 40%.

[0078] <Formation of Magnetic Layer> Next, an electromagnetic noise suppression sheet of Example 3 was prepared in the same manner as in Example 1, except that the magnetic layer forming paint C was used instead of the magnetic layer forming paint A of Example 1. The thickness of the magnetic layer was 100 μm.

[0079] (Example 4) <Preparation of magnetic layer forming coating> Magnetic layer forming coating D was prepared by mixing and dispersing the following components. (1) Magnetic material (flattened reduced carbonyl iron powder manufactured by Tenichi Co., Ltd., trade name "RPZ"): 43.8 parts (2) Amorphous polyester resin solution (a1) (manufactured by Toyobo MC Co., Ltd., trade name "Byron® BX-10SS", resin Tg: -18°C, solids concentration: 30.0% by mass, solvent: methyl ethyl ketone, toluene): 18.3 parts (3) Amorphous polyester resin solution (b2) (manufactured by Toyobo MC Co., Ltd., trade name "Byron® 220", resin Tg: 53°C, solids concentration: 30.0% by mass, solvent: methyl ethyl ketone, toluene): 18.3 parts (4) Crosslinking agent (polyisocyanate for paints / non-yellowing type, manufactured by Tosoh Corporation, trade name "Coronate® Hx"): 0.2 parts (5) Solvent (methyl ethyl ketone): 19.4 parts

[0080] In the above-mentioned magnetic layer-forming coating D, the content ratio of amorphous polyester resin solutions (a1) and (b2) was (a1):(b2) = 50:50 by mass ratio, and the volume content of the magnetic material relative to the total solid content of the magnetic layer-forming coating D was 40%.

[0081] <Formation of Magnetic Layer> Next, an electromagnetic noise suppression sheet of Example 4 was prepared in the same manner as in Example 1, except that the magnetic layer forming paint D was used instead of the magnetic layer forming paint A of Example 1. The thickness of the magnetic layer was 100 μm.

[0082] (Example 5) <Preparation of magnetic layer forming coating> Magnetic layer forming coating E was prepared by mixing and dispersing the following components. (1) Magnetic material (flattened reduced carbonyl iron powder manufactured by Tenichi Co., Ltd., trade name "RPZ"): 43.8 parts (2) Amorphous polyester resin solution (a1) (manufactured by Toyobo MC Co., Ltd., trade name "Byron® BX-10SS", resin Tg: -18°C, solids concentration: 30.0% by mass, solvent: methyl ethyl ketone, toluene): 18.3 parts (3) Amorphous polyester resin solution (b3) (manufactured by Toyobo MC Co., Ltd., trade name "Byron® GK880", resin Tg: 84°C, solids concentration: 30.0% by mass, solvent: methyl ethyl ketone, toluene): 18.3 parts (4) Crosslinking agent (polyisocyanate for paints / non-yellowing type, manufactured by Tosoh Corporation, trade name "Coronate® Hx"): 0.2 parts (5) Solvent (methyl ethyl ketone): 19.4 parts

[0083] In the above-described magnetic layer-forming coating E, the content ratio of amorphous polyester resin solutions (a1) and (b3) was (a1):(b3) = 50:50 by mass ratio, and the volume content of the magnetic material relative to the total solid content of the magnetic layer-forming coating E was 40%.

[0084] <Formation of Magnetic Layer> Next, an electromagnetic noise suppression sheet of Example 5 was prepared in the same manner as in Example 1, except that the magnetic layer forming paint E was used instead of the magnetic layer forming paint A of Example 1. The thickness of the magnetic layer was 100 μm.

[0085] (Comparative Example 1) <Preparation of Magnetic Layer Forming Coating> Magnetic layer forming coating F was prepared by mixing and dispersing the following components: (1) Magnetic material (flattened reduced carbonyl iron powder manufactured by Tenichi Co., Ltd., trade name "RPZ"): 43.8 parts (2) Amorphous polyester resin solution (a1) (manufactured by Toyobo MC Co., Ltd., trade name "Byron® BX-10SS", resin Tg: -18℃, solid content concentration: 30.0% by mass, solvent: methyl ethyl ketone, toluene): 36.6 parts (3) Crosslinking agent (polyisocyanate for coatings / non-yellowing type, manufactured by Tosoh Corporation, trade name "Coronate® Hx"): 0.2 parts (4) Solvent (methyl ethyl ketone): 19.4 parts

[0086] The volume content of the magnetic material relative to the total solid content of the magnetic layer-forming coating F described above was 40%.

[0087] <Formation of Magnetic Layer> Next, an electromagnetic noise suppression sheet of Comparative Example 1 was prepared in the same manner as in Example 1, except that the magnetic layer forming paint F was used instead of the magnetic layer forming paint A of Example 1. The thickness of the magnetic layer was 100 μm.

[0088] (Comparative Example 2) <Preparation of Magnetic Layer Forming Coating> A magnetic layer forming coating G was prepared by mixing and dispersing the following components: (1) Magnetic material (flattened reduced carbonyl iron powder manufactured by Tenichi Co., Ltd., trade name "RPZ"): 43.8 parts (2) Amorphous polyester resin solution (a2) (manufactured by Toyobo MC Co., Ltd., trade name "Byron® 63SS", resin Tg: 7℃, solid content concentration: 30.0% by mass, solvent: methyl ethyl ketone, toluene): 36.3 parts (3) Crosslinking agent (polyisocyanate for coatings / non-yellowing type, manufactured by Tosoh Corporation, trade name "Coronate® Hx"): 0.2 parts (4) Solvent (methyl ethyl ketone): 19.4 parts

[0089] The volume content of the magnetic material relative to the total solid content of the magnetic layer-forming coating G described above was 40%.

[0090] <Formation of Magnetic Layer> Next, an electromagnetic noise suppression sheet of Comparative Example 2 was prepared in the same manner as in Example 1, except that the magnetic layer forming paint G was used instead of the magnetic layer forming paint A of Example 1. The thickness of the magnetic layer was 100 μm.

[0091] (Comparative Example 3) <Preparation of Magnetic Layer Forming Coating> Magnetic layer forming coating H was prepared by mixing and dispersing the following components. (1) Magnetic material (flattened reduced carbonyl iron powder manufactured by Tenichi Co., Ltd., trade name "RPZ"): 43.8 parts (2) Amorphous polyester resin solution (a1) (manufactured by Toyobo MC Co., Ltd., trade name "Byron® BX-10SS", resin Tg: -18°C, solids concentration: 30.0% by mass, solvent: methyl ethyl ketone, toluene): 18.3 parts (3) Amorphous polyester resin solution (a2) (manufactured by Toyobo MC Co., Ltd., trade name "Byron® 63SS", resin Tg: 7°C, solids concentration: 30.0% by mass, solvent: methyl ethyl ketone, toluene): 18.3 parts (4) Crosslinking agent (polyisocyanate for paints / non-yellowing type, manufactured by Tosoh Corporation, trade name "Coronate® Hx"): 0.2 parts (5) Solvent (methyl ethyl ketone): 19.4 parts

[0092] In the above-mentioned magnetic layer forming coating H, the content ratio of amorphous polyester resin solutions (a1) and (a2) was (a1):(a2) = 50:50 by mass ratio, and the volume content of the magnetic material relative to the total solid content of the magnetic layer forming coating H was 40%.

[0093] <Formation of Magnetic Layer> Next, an electromagnetic noise suppression sheet of Comparative Example 3 was prepared in the same manner as in Example 1, except that the magnetic layer forming paint H was used instead of the magnetic layer forming paint A of Example 1. The thickness of the magnetic layer was 100 μm.

[0094] (Comparative Example 4) <Preparation of Magnetic Layer Forming Coating> Magnetic layer forming coating I was prepared by mixing and dispersing the following components. (1) Magnetic material (flattened reduced carbonyl iron powder manufactured by Tenichi Co., Ltd., trade name "RPZ"): 43.8 parts (2) Amorphous polyester resin solution (a2) (manufactured by Toyobo MC Co., Ltd., trade name "Byron® 63SS", resin Tg: 7°C, solids concentration: 30.0% by mass, solvent: methyl ethyl ketone, toluene): 18.3 parts (3) Amorphous polyester resin solution (c) (manufactured by Toyobo MC Co., Ltd., trade name "Byron® GK810", resin Tg: 46°C, solids concentration: 30.0% by mass, solvent: methyl ethyl ketone, toluene): 18.3 parts (4) Crosslinking agent (polyisocyanate for paints / non-yellowing type, manufactured by Tosoh Corporation, trade name "Coronate® Hx"): 0.2 parts (5) Solvent (methyl ethyl ketone): 19.4 parts

[0095] In the above-described magnetic layer forming coating I, the content ratio of amorphous polyester resin solutions (a2) and (c) was (a2):(c) = 50:50 by mass ratio, and the volume content of the magnetic material relative to the total solid content of the magnetic layer forming coating I was 40%.

[0096] <Formation of Magnetic Layer> Next, an electromagnetic noise suppression sheet of Comparative Example 4 was prepared in the same manner as in Example 1, except that the magnetic layer forming paint I was used instead of the magnetic layer forming paint A of Example 1. The thickness of the magnetic layer was 100 μm.

[0097] The electromagnetic noise suppression sheets of Examples 1 to 5 and Comparative Examples 1 to 4 described above were evaluated as follows.

[0098] <Differential Scanning Calorimetry Characteristics> The differential scanning calorimetry of the magnetic layer of the fabricated electromagnetic noise suppression sheet was measured using a differential scanning calorimetry meter "DSC7000X" (product name) manufactured by Hitachi High-Tech Science Corporation. Specifically, the sample was heated from -50°C to 110°C at a heating rate of 20°C / min (initial heating process), and then held at 110°C for 5 minutes. Next, the sample was cooled from 110°C to -50°C at a cooling rate of -20°C / min (cooling process), and then held at -50°C for 5 minutes. Subsequently, the sample was heated from -50°C to 110°C at a heating rate of 20°C / min (second heating process).

[0099] Next, the DSC curve and the DDSC curve obtained by taking the first derivative of the DSC curve were obtained from the second heating process described above. Figure 7 shows the DSC curve of the magnetic layer of the electromagnetic noise suppression sheet of Example 3, and Figure 8 shows the DDSC curve of the magnetic layer of the electromagnetic noise suppression sheet of Example 3. From the DDSC curve in Figure 8, two negative peaks and minimum values ​​a and b at each negative peak were observed in the range of -20°C to 80°C. From this, it was determined that the temperatures of 14°C (a) and 50°C (b) corresponding to minimum values ​​a and b are the temperatures corresponding to the inflection points in the two baseline shifts of the DSC curve, and as a result, it was confirmed that there are two baseline shifts in the range of -20°C to 80°C of the DSC curve of Example 3.

[0100] Generally, the glass transition temperature is the temperature corresponding to the minimum value at the negative peak of the DDSC curve, which is at least 50°C higher than the cooling temperature (in this case, -50°C) measured by differential scanning calorimeter, and at least 30°C lower than the heating temperature (in this case, 110°C). For this reason, although a temperature of -28°C corresponding to the minimum value c at the third negative peak is observed in the DDSC curve of Figure 8, the temperature of -28°C corresponding to the minimum value c is not included in the glass transition temperature, and the third baseline shift corresponding to the temperature of -28°C in the DSC curve of Figure 7 does not correspond to the baseline shift in the range of -20°C to 80°C of the DSC curve of the present application.

[0101] Similarly, the number of baseline shifts in the DSC curve in the range of -20°C to 80°C was determined from the DSC curves and DDSC curves of Examples 1, 2, 4, and 5 and Comparative Examples 1 to 4. Two baseline shifts were confirmed in Examples 1, 2, 4, and 5, and one baseline shift was confirmed in Comparative Examples 1 to 4.

[0102] <Blocking properties> Two 10cm square pieces of the fabricated electromagnetic noise suppression sheet are prepared. The magnetic layer surface of one sheet is placed in contact with the base material surface of the other sheet. 50g / mm² of material is then applied to the stacked sheets at a temperature of 50°C. ２The load was applied for 24 hours. After that, the adhesion state of the stacked sheets was observed, and the blocking properties of the magnetic layer of the electromagnetic noise suppression sheet were evaluated as follows.

[0103] Evaluation A: When only the upper sheet of the stacked sheets is lifted, the lower sheet does not stick. Evaluation B: When only the upper sheet of the stacked sheets is lifted, the lower sheet sticks, but falls due to its own weight in less than 3 seconds. Evaluation C: When only the upper sheet of the stacked sheets is lifted, the lower sheet sticks, but falls due to its own weight in 3 seconds or more but less than 5 seconds. Evaluation D: When only the upper sheet of the stacked sheets is lifted, the lower sheet sticks, but does not fall for 5 seconds or more.

[0104] <Adhesion after heat fusion> The 180° peel adhesion strength of the fabricated electromagnetic noise suppression sheet to a PVC resin board was measured in accordance with JIS Z0237 (2022). Specifically, first, the fabricated electromagnetic noise suppression sheet was cut into a tape shape with a width of 25 mm and a length of 120 mm. Next, excluding the 1 cm portion at the longitudinal end of this tape-shaped sheet, the magnetic layer side of the tape-shaped sheet was placed on a PVC resin board with a width of 50 mm and a length of 125 mm. The tape-shaped sheet was heated from the tape-shaped sheet side to a temperature of 160°C using a hot plate, and a roller was moved back and forth once at a speed of 5 mm / second while applying a load of 2000 g from the tape-shaped sheet side, so as to ensure that no air remained between the tape-shaped sheet and the PVC resin board, and the tape-shaped sheet and the PVC resin board were heat-fused to prepare a sample for tensile testing.

[0105] Next, after the heat-sealed tensile test samples were left for 20 to 40 minutes, a tensile testing machine was used to peel the tape-shaped sheet from the PVC resin plate at a peel angle of 180° and a peeling speed of 5 mm / second, starting from a 1 cm portion of the longitudinal end of the unheat-sealed tape-shaped sheet. The adhesive strength to the PVC resin plate was measured and defined as the 180° peel adhesive strength to the PVC resin plate, as measured in accordance with JIS Z0237 (2022).

[0106] The results described above, along with the constituent materials of the magnetic layer of the fabricated electromagnetic noise suppression sheet, are shown in Tables 1 and 2. In Tables 1 and 2, carbonyl iron powder is denoted as "RPZ" and baseline shift as "BLS".

[0107]

[0108]

[0109] Table 1 shows that in Examples 1 to 5, where multiple baseline shifts in the magnetic layer were observed, good results were obtained in terms of blocking properties and adhesive strength after thermal bonding. On the other hand, Table 2 shows that in Comparative Examples 1 to 4, where only one baseline shift in the magnetic layer was observed, a decrease in blocking properties and adhesive strength after thermal bonding was seen. In all of the above examples, the transmission attenuation rate was sufficient.

[0110] With respect to embodiments of the present application including the above-described Examples 1 to 5, the following appendix embodiments are further disclosed. (Appendix Embodiment 1) An electromagnetic noise suppression sheet comprising a substrate and a magnetic layer, wherein the magnetic layer comprises a magnetic material and a binder, the binder comprises an amorphous resin (A) having a glass transition temperature of -50°C to 10°C and an amorphous resin (B) having a glass transition temperature of 50°C to 100°C, and when the DSC curve of the magnetic layer is obtained by differential scanning calorimetry, the DSC curve has a plurality of baseline shifts in the range of -20°C to 80°C. (Appendix Embodiment 2) The electromagnetic noise suppression sheet according to Appendix Embodiment 1, wherein the temperature corresponding to each inflection point in the plurality of baseline shifts of the DSC curve coincides with the temperature corresponding to each minimum value in the plurality of negative peaks in the range of -20°C to 80°C in the differential curve obtained by first differentiating the DSC curve. (Appendix form 3) An electromagnetic noise suppression sheet according to appendix form 1 or 2, wherein the amorphous resin (A) is an amorphous polyester (a) having a glass transition temperature of -50°C to 10°C, and the amorphous resin (B) is an amorphous polyester (b) having a glass transition temperature of 50°C to 100°C. (Appendix form 4) An electromagnetic noise suppression sheet according to any of appendix forms 1 to 3, wherein the amorphous resin (A) has a glass transition temperature of -18°C to 7°C. (Appendix form 5) An electromagnetic noise suppression sheet according to any of appendix forms 1 to 4, wherein the amorphous resin (B) has a glass transition temperature of 53°C to 84°C. (Appendix form 6) An electromagnetic noise suppression sheet according to any of appendix forms 1 to 5, wherein the amorphous resin (B) has a glass transition temperature of 53°C to 67°C. (Appendix form 7) An electromagnetic noise suppression sheet according to any of appendix forms 1 to 6, wherein the amorphous resin (A) has a glass transition temperature of -18°C to 7°C, and the amorphous resin (B) has a glass transition temperature of 53°C to 84°C. (Appendix form 8) An electromagnetic noise suppression sheet according to any of appendix forms 1 to 7, wherein the amorphous resin (A) has a glass transition temperature of -18°C to 7°C, and the amorphous resin (B) has a glass transition temperature of 53°C to 67°C.(Appendix Form 9) An electromagnetic noise suppression sheet according to any one of Appendix Forms 1 to 3, wherein, after heat-sealing the magnetic layer to the PVC resin plate, the 180° peel adhesive strength to the PVC resin plate, measured in accordance with JIS Z0237 (2022), is 2.0 N / 25 mm or more. (Appendix Form 10) An electromagnetic noise suppression sheet according to any one of Appendix Forms 1 to 9, wherein the magnetic material includes a soft magnetic material. (Appendix Form 11) An electromagnetic noise suppression sheet according to Appendix Form 10, wherein the soft magnetic material is carbonyl iron powder. (Appendix Form 12) An electromagnetic noise suppression sheet according to any one of Appendix Forms 1 to 11, wherein the base material is a resin film. (Appendix Form 13) An electromagnetic noise suppression sheet according to any one of Appendix Forms 1 to 12, further including a metal layer. (Appendix Form 14) A cable characterized by including an electromagnetic noise suppression sheet according to any one of Appendix Forms 1 to 13.

[0111] 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.

[0112] 10, 10' Electromagnetic noise suppression sheet 11 Base material 12 Magnetic layer 13 Metal layer 20, 30 Coaxial cable 21, 31 Internal conductor 22, 32 Insulation layer 23, 33 Metal foil 24, 34 Metal braid 25, 35 Magnetic sheath layer 35a Base material layer 35b Magnetic layer 26, 36 Outer covering layer

Claims

1. An electromagnetic noise suppression sheet comprising a substrate and a magnetic layer, wherein the magnetic layer comprises a magnetic material and a binder, the binder comprises an amorphous resin (A) having a glass transition temperature of -50°C to 10°C and an amorphous resin (B) having a glass transition temperature of 50°C to 100°C, and when the DSC curve of the magnetic layer is determined by differential scanning calorimetry, the DSC curve has a plurality of baseline shifts in the range of -20°C to 80°C.

2. The electromagnetic noise suppression sheet according to claim 1, wherein the temperature corresponding to each inflection point in a plurality of baseline shifts of the DSC curve coincides with the temperature corresponding to each minimum value in a plurality of negative peaks in the range of -20°C to 80°C in the differential curve obtained by first differentiating the DSC curve.

3. 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 10°C, and the amorphous resin (B) is an amorphous polyester (b) having a glass transition temperature of 50°C to 100°C.

4. The electromagnetic noise suppression sheet according to claim 1, wherein the amorphous resin (A) has a glass transition temperature of -18°C to 7°C.

5. The electromagnetic noise suppression sheet according to claim 1, wherein the amorphous resin (B) has a glass transition temperature of 53°C to 84°C.

6. The electromagnetic noise suppression sheet according to claim 1, wherein the amorphous resin (B) has a glass transition temperature of 53°C to 67°C.

7. The electromagnetic noise suppression sheet according to claim 1, wherein the amorphous resin (A) has a glass transition temperature of -18°C to 7°C, and the amorphous resin (B) has a glass transition temperature of 53°C to 84°C.

8. The electromagnetic noise suppression sheet according to claim 1, wherein the amorphous resin (A) has a glass transition temperature of -18°C to 7°C, and the amorphous resin (B) has a glass transition temperature of 53°C to 67°C.

9. The electromagnetic noise suppression sheet according to claim 1, wherein, after the magnetic layer is heat-fused to the PVC resin plate, the 180° peel adhesive strength to the PVC resin plate, measured in accordance with JIS Z0237 (2022), is 2.0 N / 25 mm or more.

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

11. The electromagnetic noise suppression sheet according to claim 10, wherein the soft magnetic material is carbonyl iron powder.

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

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

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

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