Electromagnetic noise suppression film, as well as electromagnetic noise suppression sheets using the electromagnetic noise suppression film, communication cables and electronic devices.

Abstract

The electromagnetic noise suppression film of this application includes a magnetic layer comprising a spherical soft magnetic material and an adhesive. If a magnetic field of 10 kOe is applied from the outside inwards towards the in-plane direction of the magnetic layer, the magnetization per unit area in the in-plane direction of the magnetic layer is set as M. 10 t, then relative to the magnetization M 10 The transmission attenuation rate of t, measured by the microstrip line method at 28 GHz, is 3 dB·cm². 2 / emu and above. Furthermore, the electromagnetic noise suppression sheet of this application comprises a substrate and the electromagnetic noise suppression film of this application.

Description

Technical Field

[0001] This application relates to an electromagnetic noise suppression film that absorbs electromagnetic waves in the GHz band. Background Technology

[0002] With the development of wireless communication technologies, exemplified by mobile phones, various devices and sensors are connecting to networks wirelessly. Furthermore, in the medical field, from the perspective of infection prevention, the trend towards cordless devices is increasing, and medical equipment is beginning to connect wirelessly. These communications require high speed and high capacity over short distances, utilizing high frequencies. With the increase in such high-frequency devices, the risks of malfunctions caused by electromagnetic noise generated by the devices and interference from electromagnetic waves in electronic devices and communications are increasing. Moreover, in recent years, millimeter-wave radar, intended to prevent car collisions, has also begun to be incorporated. Malfunctions in these medical and automotive devices can have life-threatening consequences, therefore, they cannot be allowed to malfunction. Therefore, the necessity of applying electromagnetic noise suppression films—so-called EMC (Electromagnetic Compatibility) countermeasures—to circuit components and transmission paths that transmit and receive electromagnetic waves in the GHz band is increasing.

[0003] Generally, the larger the imaginary part of the permeability of an electromagnetic noise suppression film, the higher the transmission attenuation rate in the microstrip line method, which is an indicator of the electromagnetic noise suppression performance of the film using magnetic materials, and the better the electromagnetic noise suppression performance. However, for the permeability of conventional iron oxide magnetic materials used as electromagnetic wave absorbing materials in electromagnetic noise suppression films, as the frequency gradually increases, it reaches a roughly constant value at a certain frequency. Afterward, the permeability increases with increasing frequency, reaching its maximum value at a specific frequency of several GHz. Thereafter, the permeability decreases approximately inversely proportional to the frequency, eventually resulting in a real part of 1 and an imaginary part of 0. This frequency at which the permeability decreases is the limit frequency at which the magnetic material can be used practically (the limiting frequency), known as the Snoek limit.

[0004] In terms of the threshold frequency, the greater the anisotropic magnetic field, the higher the frequency. Therefore, in the past, by making the shape of the magnetic body close to a sphere, the shape magnetic anisotropy of the magnetic body was eliminated, the anisotropic magnetic field of the magnetic body particles was increased, the threshold frequency was shifted to the high-frequency side, and the frequency range in which the magnetic body can be used was expanded to the high-frequency band side.

[0005] However, reducing the magnetic anisotropy by making the magnetic material nearly spherical leads to a decrease in the imaginary part of the magnetic permeability. Therefore, while using spherical magnetic materials as electromagnetic noise absorption materials in electromagnetic noise suppression films can expand the practical frequency range, it also results in a decrease in the imaginary part of the permeability of the electromagnetic noise suppression film, thus reducing its electromagnetic noise suppression performance.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2000-138492

[0009] Patent Document 2: Japanese Patent Application Publication No. 2005-340318 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] This application solves the above-mentioned problems and provides a magnetic noise suppression film in which the electromagnetic noise suppression layer (magnetic layer) has a high electromagnetic wave absorption relative to the magnetization per unit area, even when using a spherical soft magnetic body.

[0012] In addition, as prior art documents related to the electromagnetic noise suppression sheet of this application, there are Patent Document 1 and Patent Document 2. Patent Document 1 discloses an electromagnetic wave absorber containing spherical carbonyl iron with a particle size of less than 4 μm and a thickness of 1 mm after calendering. Patent Document 2 discloses an electromagnetic wave absorber containing approximately spherical carbonyl iron with an average particle size of 1 μm to 10 μm and a thickness of 1 mm to 3 mm after calendering.

[0013] Methods for solving problems

[0014] The electromagnetic noise suppression film of this application comprises a magnetic layer, characterized in that the magnetic layer comprises a spherical soft magnetic material and an adhesive, wherein if a magnetic field of 10 kOe is applied from the outside in the in-plane direction of the magnetic layer, the magnetization per unit area in the in-plane direction of the magnetic layer is set as M. 10 t, then relative to the magnetization M 10 The transmission attenuation rate of t, measured by the microstrip line method at 28 GHz, is 3 dB·cm². 2 / emu and above.

[0015] The electromagnetic noise suppression sheet of this application is characterized in that it comprises a substrate and the electromagnetic noise suppression film of this application.

[0016] The communication cable of this application is characterized in that it includes the electromagnetic noise suppression film or the electromagnetic noise suppression sheet of this application.

[0017] The electronic device of this application is characterized in that it includes the electromagnetic noise suppression film or the electromagnetic noise suppression sheet of this application.

[0018] The effects of the invention

[0019] According to this application, a magnetic noise suppression film can be provided in which the electromagnetic wave absorption of the magnetic noise suppression layer (magnetic layer) is high relative to the magnetization per unit area, even when using a spherical soft magnetic body. Attached Figure Description

[0020] Figure 1 This is a schematic side view showing a cylindrical sample used to determine magnetic properties.

[0021] Figure 2 This is a diagram showing an example of a hysteresis curve obtained by measuring magnetic properties.

[0022] Figure 3 This is a schematic cross-sectional view illustrating an example of an electromagnetic noise suppression sheet according to an embodiment.

[0023] Figure 4 This is a schematic cross-sectional view illustrating another example of an electromagnetic noise suppression sheet according to an embodiment.

[0024] Figure 5 This is a schematic cross-sectional view showing an example of a coaxial cable, which is one of the communication cables used in the implementation. Detailed Implementation

[0025] (Electromagnetic noise suppression film)

[0026] An embodiment of the electromagnetic noise suppression film of this application will be described. The electromagnetic noise suppression film of this embodiment is characterized by having a magnetic layer comprising a spherical soft magnetic material and a binder. When a magnetic field of 10 kOe is applied from the outside in the in-plane direction of the magnetic layer, the magnetization per unit area in the in-plane direction of the magnetic layer is set to M. 10 t, then relative to the magnetization M 10 The transmission attenuation rate of t, measured by the microstrip line method at 28 GHz, is 3 dB·cm². 2 / t or more.

[0027] In the electromagnetic noise suppression film of this application, a spherical soft magnetic material is used as the electromagnetic wave absorbing material. As described above, this increases the anisotropic magnetic field of the magnetic material, shifting the threshold frequency towards higher frequencies and expanding the frequency range in which the soft magnetic material is applicable to higher frequencies. On the other hand, making the soft magnetic material nearly spherical reduces its shape magnetic anisotropy, leading to a decrease in the imaginary part of the magnetic permeability. Therefore, if a spherical soft magnetic material is used as the electromagnetic wave absorbing material in the electromagnetic noise suppression film, there is a problem that the decrease in the imaginary part of the permeability of the electromagnetic noise suppression film leads to a reduction in electromagnetic noise suppression performance.

[0028] In the electromagnetic noise suppression film of this application, the magnetic layer is thinned to solve the above-mentioned problems. Therefore, even if a soft magnetic material with reduced permeability due to being spherical is used as the electromagnetic wave absorbing material, the electromagnetic wave absorption of the electromagnetic noise suppression film can be increased. The reasons are explained below.

[0029] That is, it is known that in the manufacturing process of magnetic layers, if a thin film of magnetic material is formed using particulate magnetic material and then subjected to calendering to achieve high filling of the magnetic material particles, the permeability of the magnetic layer increases. This is believed to be because, by achieving high filling of the magnetic material particles through calendering, the spacing between the magnetic material particles in the magnetic layer becomes closer, increasing the magnetic interaction between the particles. If a magnetic field is applied from the outside under these conditions, part of the counter-magnetic field generated in each magnetic material particle is canceled out by the magnetic interaction, while the other part of the counter-magnetic field acts in the direction of the applied magnetic field. As a whole, the magnetic layer acts in the positive direction of the applied magnetic field, thus increasing the permeability of the magnetic layer. The increase in permeability due to this counter-magnetic field is particularly significant when using soft magnetic materials.

[0030] Therefore, the inventors believed that even when using a soft magnetic material that reduces permeability by spherizing the magnetic material to form a magnetic layer, if the magnetic layer is rolled, the spherical magnetic particles are more densely packed than those of conventional non-spherical magnetic particles, and the spacing between the spherical magnetic particles in the magnetic layer is closer, which can further improve the permeability of the magnetic layer. Further research was conducted on this. The results showed that by setting the transmission attenuation rate, measured at a specific frequency using the microstrip line method, to the magnetization per unit area in the in-plane direction of the magnetic layer relative to the degree of filling of magnetic particles in the magnetic layer, 3 dB·cm, further improvement was achieved. 2 By setting the transmission attenuation rate relative to the magnetization per unit area within a specific range, a good electromagnetic wave absorption can be obtained. That is, the characteristic of this application is that, instead of simply setting a range for the transmission attenuation rate of the electromagnetic noise suppression film, a specific range is set for the transmission attenuation rate relative to the magnetization per unit area related to the filling properties of the spherical magnetic body.

[0031] Furthermore, it is known that by setting the thickness of the magnetic layer to be 5 μm or more and less than 60 μm, the in-plane magnetic anisotropy of the magnetic layer can be increased. Here, for example, in order to set the thickness of the magnetic layer to be 5 μm or more and less than 60 μm, the particle size of the spherical soft magnetic material is preferably less than 60 μm and less than the thickness of the magnetic layer. This is believed to be because: if spherical soft magnetic material particles of such a particle size are used to form the magnetic layer, the spherical soft magnetic material particles are more densely packed during the rolling process, the magnetic interaction of the spherical soft magnetic material particles plays a greater role, and the permeability of the magnetic layer is further improved.

[0032] Based on the above research, it has been confirmed that in the electromagnetic noise suppression film of this embodiment, when a magnetic field of 10 kOe is applied from the outside in the in-plane direction of the magnetic layer, the magnetization per unit area in the in-plane direction of the magnetic layer is set to M. 10 t, then it is possible to make relative to the above magnetization M 10 The transmission attenuation rate of t, measured by the microstrip line method at 28 GHz, is 3 dB·cm². 2 / emu and above.

[0033] Next, the inventors investigated whether the electromagnetic noise suppression film of this embodiment could be determined from other viewpoints. The electromagnetic noise suppression film of this embodiment, when a magnetic field of 10 kOe is applied from the outside in the in-plane direction of the magnetic layer, has a magnetization per unit area in the in-plane direction of the magnetic layer set as M. 10 t, then relative to the above magnetization M 10 The transmission attenuation rate of t, measured by the microstrip line method at 28 GHz, is 3 dB·cm². 2 / emu or above. This is because, in this embodiment, in order to achieve a transmission attenuation rate of 3dB·cm relative to the magnetization per unit area. 2 The electromagnetic noise suppression film with a density of / emu or higher has a complex relationship with factors such as the type, particle size, filling ratio, and filling amount of the spherical magnetic material used. For example, the particle size varies depending on the type of spherical magnetic material, which can sometimes affect the filling ratio and filling amount. Furthermore, when the particle size of the spherical magnetic material is small, the particles tend to aggregate, thus the filling ratio and filling amount may not necessarily improve. Therefore, it is considered simpler to determine the electromagnetic noise suppression film of this embodiment using other more specific characteristics than to use these factors.

[0034] The research results show that if a magnetic field of 10 kOe is applied from the outside into the in-plane direction of the magnetic layer, and then the magnetic field from the outside is changed to 8 kOe, and the magnetization per unit area in the in-plane direction is set to M8t1, and a magnetic field of 10 kOe is applied from the outside into the perpendicular direction of the magnetic layer, and then the magnetic field from the outside is changed to 8 kOe, and the magnetization per unit area in the perpendicular direction is set to M8t2, then when the ratio M8t1 / M8t2 is 1.35 or higher, in the electromagnetic noise suppression film of this embodiment, if a magnetic field of 10 kOe is applied from the outside into the in-plane direction of the magnetic layer, and the magnetization per unit area in the in-plane direction of the magnetic layer is set to M8t2, then... 10 t, then it is possible to make relative to the above magnetization M 10 The transmission attenuation rate of t, measured by the microstrip line method at 28 GHz, is 3 dB·cm². 2 / emu and above.

[0035] In the electromagnetic noise suppression film of this embodiment, a ratio of M8t1 / M8t2 of 1.35 or higher indicates that the in-plane magnetic anisotropy of the magnetic layer is greater than that in the perpendicular direction. Therefore, it can be seen that the transmission attenuation rate relative to magnetization per unit area in the microstrip line method, which is an indicator of the electromagnetic noise suppression performance of the electromagnetic noise suppression film, is related to the magnitude of the in-plane magnetic anisotropy of the magnetic layer. This is believed to be because even if a spherical magnetic material with reduced permeability is used to form the magnetic layer, increasing the in-plane magnetic anisotropy of the magnetic layer relatively increases the permeability of the magnetic layer, thereby increasing the electromagnetic wave absorption of the electromagnetic noise suppression film.

[0036] <Magnetic Layer>

[0037] The magnetic layer used in the electromagnetic noise suppression film of this embodiment will be described below. The magnetic layer of the electromagnetic noise suppression film of this embodiment functions as an electromagnetic noise suppression layer and includes a spherical soft magnetic material and an adhesive. The thickness of the magnetic layer can be set to less than 60 μm as described above, but if it is too thin, the electromagnetic wave absorption performance decreases; therefore, it is preferably set to 5 μm or more. That is, the thickness of the magnetic layer is preferably set to 5 μm or more and less than 60 μm, more preferably 10 μm or more and less than 30 μm.

[0038] Next, the constituent materials of the aforementioned magnetic layer will be explained.

[0039] [Magnetic Materials]

[0040] As the aforementioned magnetic material, a spherical soft magnetic material is used. Here, a spherical soft magnetic material is defined in this application as a soft magnetic material in which the ratio of the maximum particle size to the minimum particle size (minimum particle size / maximum particle size) is 0.8 or more and 1 or less.

[0041] The aforementioned soft magnetic material has high initial permeability, and even a small amount contained in the magnetic layer can exert electromagnetic wave absorption performance. Therefore, even if the magnetic layer is made into a thin film, it can still exert electromagnetic noise suppression effect.

[0042] Examples of soft magnetic materials include iron, iron carbonyl, ferrosilicon, permalloy, iron-silicon-aluminum magnetic alloys, Permendur alloys, soft magnetic ferrites, ferritic stainless steels, electromagnetic stainless steels, amorphous magnetic alloys, and nanocrystalline magnetic alloys. Iron carbonyl containing 97.5% by mass or more of iron (Fe) is particularly preferred as a soft magnetic material. This is because iron carbonyl can exhibit electromagnetic wave absorption properties (electromagnetic noise suppression effects) even in higher frequency regions such as the GHz band.

[0043] The average particle size of the aforementioned spherical soft magnetic material is preferably 0.1 to 50 μm, more preferably 1 to 20 μm. If the particle size of the magnetic material is too small, the particles are prone to secondary agglomeration, which tends to make it difficult to obtain a uniform coating (magnetic layer). On the other hand, if the particle size is too large, the soft magnetic material is prone to sedimentation during coating preparation, making it difficult to obtain a uniform coating. The aforementioned average particle size can be measured using a laser diffraction scattering particle size distribution measuring device.

[0044] The volume content of the spherical soft magnetic material contained in the magnetic layer is preferably 30% to 80%, 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 tends to decrease, and the strength of the magnetic layer tends to decrease.

[0045] [Adhesive]

[0046] As the aforementioned adhesive, an amorphous resin (A) with a glass transition temperature of -50°C to 0°C and an amorphous resin (B) with a glass transition temperature of 10°C or higher are preferred. Amorphous resins have high solubility in water and other solvents and excellent dispersibility of magnetic materials (magnetic powder). Therefore, by dispersing the magnetic powder in a resin dissolved in water or other solvents, and then coating and drying it on a substrate at any thickness, a magnetic layer can be formed.

[0047] 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 the adhesion of the magnetic layer to the substrate can also be improved. However, when using only amorphous resin (A), the magnetic layer is prone to stickiness, which may cause adjacent magnetic layers to adhere to each other or to the substrate when the magnetic film is overlapped or rolled into a roll. On the other hand, when using only an amorphous resin (B) with a glass transition temperature of 10°C or higher, the surface of the magnetic layer becomes hard and difficult to adhere, which may reduce the adhesion to the substrate when the magnetic layer is laminated with the substrate; and cracks may occur in the magnetic layer when it is rolled. Therefore, as the adhesive of this embodiment, it is preferable to use both the above-mentioned amorphous resins (A) and (B).

[0048] The upper limit of the glass transition temperature of the amorphous resin (B) with 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 if an amorphous resin (A) with a glass transition temperature of -50°C to 0°C is used, the surface of the magnetic layer is prone to hardening, the adhesion between the magnetic layer and the substrate may be reduced, or the magnetic layer may easily crack when attached to uneven or curved surfaces or when bent during winding.

[0049] As the aforementioned amorphous resin (A), amorphous polyesters, amorphous polyurethanes, and amorphous acrylic resins with a glass transition temperature of -50°C to 0°C can be used. As the aforementioned amorphous resin (B), amorphous polyesters, amorphous polyurethanes, and amorphous acrylic resins with a glass transition temperature of 10°C or higher can be used. Among these, amorphous polyesters (a) with a glass transition temperature of -50°C to 0°C are particularly preferred as amorphous resin (A), and amorphous polyesters (b) with a glass transition temperature of 10°C or higher are particularly preferred as amorphous resin (B). Amorphous polyesters, in particular, exhibit excellent solubility and flexibility, making them suitable for manufacturing film-like magnetic layers.

[0050] Based on the above viewpoint, the preferred mass ratio of the amorphous polyester (a) and the amorphous polyester (b) is (a):(b) = 95:5 to 35:65. The mass ratio of the amorphous polyester (a) and (b) can be estimated to some extent by measuring the glass transition temperature of the magnetic layer and the intensity of the two detected glass transition temperature peaks. The glass transition temperature can be measured using a differential scanning calorimeter (DSC).

[0051] Examples of the aforementioned amorphous polyesters (a) and (b) include, for instance, "VYLON" (registered trademark) manufactured by Toyobo Co., Ltd., "PLASCOAT" (registered trademark) manufactured by Moyo Chemical Co., Ltd., "NichigoPOLYESTER" (registered trademark) manufactured by Mitsubishi Chemical Co., Ltd., and "ALMATEX" (registered trademark) manufactured by Mitsui Chemicals Co., Ltd. They exhibit excellent solubility in water and organic solvents, and therefore can be used in any proportion dissolved in water or organic solvents.

[0052] Furthermore, at least one of the aforementioned amorphous polyester (a) and amorphous polyester (b) preferably includes a cross-linked portion cross-linked via amide bonds. This further improves the adhesion of the magnetic layer to the substrate. Typically, the aforementioned amorphous polyesters (a) and (b) have carboxyl groups at at least at their molecular ends; additionally, carboxyl groups can be arbitrarily assigned to their molecular chains. Therefore, by using a cross-linking agent, a cross-linked portion cross-linked via amide bonds can be formed.

[0053] Next, further characteristics of the electromagnetic noise suppression film of this embodiment will be described.

[0054] <Reflection attenuation>

[0055] When the reflection attenuation of the electromagnetic noise suppression film of this embodiment is measured using the microstrip line method within a measurement frequency range of 10 GHz to 30 GHz, the average value of the aforementioned reflection attenuation can be -20 dB or less. That is, the reflection attenuation, as the absolute value of - dB, can be increased, and reflection can be reduced. This is because, in the magnetic layer of the electromagnetic noise suppression film of this embodiment, a spherical magnetic material is used as the electromagnetic wave absorbing material, and the reflection characteristics of a spherical magnetic material are smaller than those of a non-spherical magnetic material. Therefore, the transmission attenuation rate of the electromagnetic noise suppression film of this embodiment can be improved.

[0056] <Methods for Determining the Properties of Electromagnetic Noise Suppression Films>

[0057] [Transmission attenuation rate relative to magnetization per unit area]

[0058] The transmission attenuation rate of the electromagnetic noise suppression film was measured using the microstrip line method (according to IEC62333-1, IEC62333-2). Specifically, the transmission attenuation rate was measured by connecting a vector network analyzer "MS46122B-043" manufactured by Anritsu Corporation and a microstrip line "TF-30A test tool" manufactured by KEYCOM Corporation with a coaxial cable "MWX051-03000KFSKMS / B" (3m) manufactured by Junko Co., Ltd.

[0059] The vector network analyzer was first calibrated using SOLT (Short-Open-Load-Thru) and measured using the analysis software "DMP-002041020-09 Measurement Program" manufactured by KEYCOM. The frequency range was set to 0.1 GHz to 30 GHz, and the measurement points were set using a linear scale of 401 points. A 30 mm × 30 mm electromagnetic noise suppression film was placed on the microstrip line. The electromagnetic wave reflection attenuation (S11M) and electromagnetic wave transmission attenuation (S21M) were measured under a load applied to a 150 g PTFE block. The transmission attenuation rate (Rtp) was calculated using the following formula (1). Then, the calculated Rtp was divided by the magnetization per unit area (unit: emu / cm²). 2 From this, the transmission attenuation rate (Rtp-S) relative to the magnetization per unit area is calculated. In addition, the average value of the reflection attenuation from 10 GHz to 30 GHz is the average value from 10 GHz to 30 GHz at point 134 with 0.1 GHz as the first point.

[0060] Equation (1):

[0061] [Mathematical Expression 1]

[0062]

[0063] [Magnetic properties]

[0064] The hysteresis curve of the electromagnetic noise suppression film was determined using a vibration-test type magnetometer "VSM-P7" manufactured by Toei Kogyo Co., Ltd. Specifically, a cut sample was prepared by cutting the electromagnetic noise suppression film into a circle with a diameter of 8 mm. This cut sample was then... Figure 1 The sample is prepared by stacking 10 sheets to form a cylindrical shape.

[0065] As a plotting mode for data from a vibrating specimen magnetometer, the applied magnetic field is set to -10kOe to 10kOe, such as... Figure 2 As shown, after applying a maximum positive magnetic field of 10 kOe to the magnetic layer to achieve positive magnetization (point A), the opposite direction (as opposed to the positive direction) is considered. Figure 2 A magnetic field of 10 kOe to -10 kOe is applied in the direction of 1a until magnetization (point B) occurs in the opposite direction. The magnetization (unit: emu) under a linear scale of 316 points is calculated using the "VSM-P7 analytical software" manufactured by Toei Industrial Co., Ltd.

[0066] For cylindrical samples, such as Figure 1As shown, the case where an external magnetic field is applied along the stacking direction is defined as the perpendicular direction, and the case where an external magnetic field is applied perpendicularly to the stacking direction (in-plane direction of the cylindrical sample) is defined as the in-plane direction. The magnetization was measured for both in-plane and perpendicular magnetic field application directions. Then, the magnetization at each measurement point was divided by the in-plane area of ​​the sample, i.e., 0.16πcm². 2 Calculate the magnetization per unit area.

[0067] In this application specification, the magnetization per unit area in the in-plane direction when an external magnetic field of 10 kOe is applied is expressed as M. 10 Additionally, the magnetization per unit area in the in-plane direction when the external magnetic field is changed from 10 kOe to 8 kOe is denoted as M8t1, and the magnetization per unit area in the perpendicular direction when the external magnetic field is changed from 10 kOe to 8 kOe is denoted as M8t2.

[0068] (Electromagnetic noise suppression sheet)

[0069] An embodiment of the electromagnetic noise suppression sheet of this application will be described. The electromagnetic noise suppression sheet of this embodiment is characterized by having a substrate and the electromagnetic noise suppression film (magnetic layer) of the embodiment described above.

[0070] The electromagnetic noise suppression sheet of this embodiment includes a substrate, thus improving the overall strength of the sheet. Furthermore, the electromagnetic noise suppression sheet of this embodiment includes the electromagnetic noise suppression film (magnetic layer) of the embodiments of this application. Therefore, when a magnetic field of 10 kOe is applied from the outside in the in-plane direction of the magnetic layer, the magnetization per unit area in the in-plane direction of the magnetic layer is set to M. 10 t, then it is possible to make relative to the magnetization M 10 The transmission attenuation rate of t, measured by the microstrip line method at 28 GHz, is 3 dB·cm². 2 / emu and above.

[0071] <Substrate>

[0072] The aforementioned substrate is the base for forming the magnetic layer. As long as the substrate is flexible and can ensure adhesion to the magnetic layer, a resin film is typically used. Examples of resins constituting the aforementioned 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 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, fluorine resins, silicone resins, cellulose resins, and substrates formed from crosslinks of these resins. Among these, polyethylene terephthalate (PET) is preferred in terms of mechanical properties and price. One or more of these resin materials can be used. Furthermore, the aforementioned resin materials can have functional groups as needed. Additionally, functional monomers and modified monomers can also be grafted onto the resin materials.

[0073] To improve adhesion to adjacent magnetic layers, the surface of the substrate can be subjected to known surface treatments. Examples of such surface treatments include corona discharge treatment, ozone exposure treatment, high-voltage electric shock exposure treatment, and ionization radiation treatment. Additionally, the substrate can be subjected to coating treatments using primers (such as silicone treatment), primer treatment, matte treatment, and crosslinking treatment.

[0074] The aforementioned substrate can be a single layer or a laminate consisting of two or more layers. Furthermore, known additives such as fillers, flame retardants, deterioration inhibitors, antistatic agents, softeners, and plasticizers can be added to the substrate as needed.

[0075] The thickness of the substrate is not particularly limited, but is preferably 5μm to 20μm, and more preferably 10μm to 15μm. If the thickness of the substrate is within the above range, the strength and flexibility of the electromagnetic noise suppression sheet of this embodiment can be balanced.

[0076] The aforementioned substrate only needs to be flexible and able to ensure adhesion to the magnetic layer. Therefore, a metal layer such as a metal foil (described later) can be used as the substrate instead of the resin film. Alternatively, a composite film formed by laminating a resin film with a metal foil can also be used as the substrate.

[0077] <Metallic Layer>

[0078] When the substrate described above is made of resin film, the electromagnetic noise suppression sheet of the embodiment may further include a metal layer. If the electromagnetic noise suppression sheet of this embodiment is provided with a metal layer, it can be endowed with electric field shielding properties, and can suppress not only magnetic noise but also electrical noise.

[0079] The type of metal constituting the aforementioned metal layer is not particularly limited as long as it possesses flexibility and good adhesion to the magnetic layer; aluminum, copper, and permalloy are preferred. This is because aluminum and copper have high conductivity, are inexpensive, are easily processed into thin films, and have excellent flexibility. In addition, permalloy, besides being conductive, also has a high magnetic focusing effect in the kHz region, thus providing a magnetic shielding effect.

[0080] The thickness of the aforementioned metal layer is not particularly limited, but if it is too thick, the flexibility will be reduced, so it is usually set to a range of 0.1~30μm.

[0081] As the aforementioned metal layer, metal foil can be used alone, or a metal film can be formed on the aforementioned substrate (resin film) by vapor deposition or sputtering.

[0082] <Adhesive layer>

[0083] The electromagnetic noise suppression sheet of this embodiment may further include an adhesive layer. When an adhesive layer is provided on the electromagnetic noise suppression sheet of this embodiment, the thickness of the adhesive layer is preferably 10 μm to 50 μm, more preferably 15 μm to 35 μm. If the thickness is less than 10 μm, sufficient adhesion may not be achieved. Furthermore, if the thickness exceeds 50 μm, the adhesive effect of the adhesive layer becomes saturated, and the total thickness of the electromagnetic noise suppression sheet increases. Therefore, the flexibility of the electromagnetic noise suppression sheet decreases, its conformability when attached to electronic components decreases, and it becomes difficult to wind it into wiring, etc.

[0084] Next, the electromagnetic noise suppression sheet of this embodiment will be described with reference to the accompanying drawings. Figure 3 This is a schematic cross-sectional view illustrating an example of the electromagnetic noise suppression sheet of this embodiment. Figure 3 In the electromagnetic noise suppression sheet 10, there is a substrate 11 and a magnetic layer 12 disposed on the substrate 11. Figure 3 In this embodiment, the electromagnetic noise suppression sheet 10 is configured as a two-layer structure consisting of a substrate 11 and a magnetic layer 12, but it can also be further configured with an adhesive layer on either the substrate 11 side or the magnetic layer 12 side to form a three-layer structure.

[0085] in addition, Figure 4 This is a schematic cross-sectional view illustrating other examples of the electromagnetic noise suppression sheet of this embodiment. Figure 4In this process, the electromagnetic noise suppression sheet 20 includes a substrate 11, a metal layer 13 disposed on the substrate 11, and a magnetic layer 12 disposed on the metal layer 13. Figure 4 In this design, the electromagnetic noise suppression sheet 20 is configured as a three-layer structure consisting of a substrate 11, a magnetic layer 12, and a metal layer 13. However, it can also be further configured as a four-layer structure by adding an adhesive layer on either the substrate 11 side or the magnetic layer 12 side. Figure 4 In this case, the metal layer 13 is disposed between the substrate 11 and the magnetic layer 12, but it can also be disposed on the outer surface of the magnetic layer 12.

[0086] The overall thickness of the electromagnetic noise suppression sheet in this embodiment is preferably 10 μm to 85 μm, more preferably 20 μm to 60 μm. This is because if the overall thickness of the electromagnetic noise suppression sheet is too thin, the thickness of the magnetic layer also becomes thinner, reducing the electromagnetic wave absorption performance, and the overall strength of the sheet also decreases. On the other hand, if the overall thickness of the electromagnetic noise suppression sheet is too thick, its flexibility decreases, making it difficult to wind onto cables or connectors for use.

[0087] The electromagnetic noise suppression film and sheet of this embodiment can be used directly in film or sheet form, or they can be further processed into strips for use. When the film and sheet are processed into strips, their width can be appropriately set according to the application. In addition, when the film and sheet are processed into strips, for example, the strip-shaped electromagnetic noise suppression film and sheet can be wound and stored.

[0088] (Manufacturing method of electromagnetic noise suppression sheet)

[0089] An embodiment of the method for manufacturing the electromagnetic noise suppression sheet of this application will be described. The method for manufacturing the electromagnetic noise suppression sheet of this embodiment is a method for manufacturing the electromagnetic noise suppression sheet of this application described above, comprising: a step of mixing a spherical soft magnetic material and an adhesive with a solvent to prepare a coating for forming a magnetic layer; a step of applying the coating for forming a magnetic layer to a substrate and drying it to form a magnetic layer; and a step of calendering the formed magnetic layer.

[0090] Coatings for forming magnetic layers

[0091] The coating for forming the magnetic layer described above can be made by mixing a spherical soft magnetic material, an adhesive, and a solvent.

[0092] For the aforementioned spherical soft magnetic material and adhesive, the same materials as those used for the magnetic layer of the electromagnetic noise suppression film constituting the aforementioned embodiment of this application can be used.

[0093] As solvents, for example, water, ethanol, methanol, n-propanol, isopropanol, n-butanol, isobutanol, ethylene glycol, propylene glycol, etc. can be used.

[0094] The content of the solvent is not particularly limited, but it can be set to 50.0% by mass or more and 99.5% by mass or less relative to the total mass of the coating for forming the magnetic layer.

[0095] Surface modifiers, defoamers, thickeners, etc., can be further added to the coatings used to form the magnetic layer.

[0096] <Formation of the Magnetic Layer>

[0097] As a method for applying the coating for forming the magnetic layer onto the substrate, coating methods such as rod coating, reverse coating, gravure coating, microgravure coating, mold coating, dip coating, spin coating, slot coating, and spray coating can be used.

[0098] The drying process after coating can be carried out under conditions that allow the solvent components of the coating used to form the magnetic layer to evaporate, preferably at 80°C to 150°C for 3 to 30 minutes. If solvent remains in the magnetic layer, there is a tendency for poor strength. Drying methods can include, for example, hot air drying, heating drying, vacuum drying, and natural drying.

[0099] The above-described calendering process can be performed using metal rollers or resin rollers. Furthermore, regarding the formation of the magnetic layer, in the case of a single sheet, calendering can be performed by pressing. During calendering, it is preferable to perform the process above the glass transition temperature of the formed magnetic layer, and the calendering process can be performed multiple times.

[0100] (Communication cable)

[0101] An embodiment of the communication cable of this application will be described. The communication cable of this embodiment is characterized by having the electromagnetic noise suppression film or electromagnetic noise suppression sheet described in the aforementioned embodiment of this application. The communication cable of this embodiment includes coaxial cable, twisted pair cable, multi-core cable, etc. In particular, coaxial cable is used for high-frequency transmission and is used as an image cable.

[0102] Hereinafter, a coaxial cable, which is one of the communication cables in this embodiment, will be described based on the accompanying drawings. In the coaxial cable described below, the electromagnetic noise suppression sheet of this application is used as the electromagnetic noise suppression layer of the coaxial cable.

[0103] Figure 5This is a schematic cross-sectional view showing an example of a coaxial cable. The coaxial cable 30 includes an inner conductor 31, an insulation 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 this application described above, and is composed of a substrate layer 35a and a magnetic layer 35b disposed on one side of the substrate layer 35a.

[0104] exist Figure 5 In this case, the magnetic layer 35b of the magnetic sheath layer 35 is disposed on the axial side, but the substrate layer 35a can also be disposed on the axial side.

[0105] The magnetic sheath layer 35 of the coaxial cable 30 can be formed by winding the electromagnetic noise suppression sheet of this application onto the outer surface of a linear conductor composed of an inner conductor 31, an insulation layer 32, a metal foil 33, and a metal braid 34. Therefore, the thickness of the magnetic sheath layer can be reduced, and the processing time can also be shortened.

[0106] (Electronic devices)

[0107] An embodiment of the electronic device of this application will be described. The electronic device of this embodiment is characterized by including the electromagnetic noise suppression film or electromagnetic noise suppression sheet of the embodiment described above. Therefore, the electromagnetic noise suppression film or electromagnetic noise suppression sheet of this application can be used as an electromagnetic noise suppression component of an electronic device. Specifically, the electronic device of this embodiment, for example, places the electromagnetic noise suppression film or electromagnetic noise suppression sheet of this application on the uneven surface or corner of an electronic device that emits electromagnetic noise or an electronic device for which electromagnetic noise is to be prevented. Alternatively, the electromagnetic noise suppression sheet of this application can be used as a replacement for the ferrite core used in cables for electronic devices.

[0108] Example

[0109] The present application will now be described in detail using examples. However, the present application is not limited to the following examples. Unless otherwise specified, "parts" in the following description refers to "parts by mass".

[0110] (Example 1)

[0111] <Preparation of Coatings for Forming Magnetic Layers>

[0112] Mix and disperse the following components to prepare a coating for forming a magnetic layer.

[0113] (1) Soft magnetic material (spherical carbonyl iron powder manufactured by Tianyi Company, trade name "YW-5", Fe content: 97.5% by mass): 42.2 parts

[0114] (2) Amorphous polyester (a) (water-soluble polyester resin solution, manufactured by Mutual Chemicals, trade name "PLASCOAT Z-3310", Tg: -20℃, solid content concentration: 25.0% by mass, solvent: water): 12.5 parts

[0115] (3) Amorphous polyester (b) (water-soluble polyester resin solution, manufactured by Mutual Chemicals, trade name "PLASCOAT Z-730", Tg: 43℃, solid content concentration: 25.0% by mass, solvent: water): 8.3 parts

[0116] (4) Crosslinking agent (containing oxazoline polymer, manufactured by Nippon Shokubai Co., Ltd., trade name "EPOCROS WS500", solid content concentration: 40.0% by mass, solvent: water): 3.0 parts

[0117] (5) Defoamer (silicone-free polymer, manufactured by BYK-Chemie, trade name "BKY-012", solid content concentration: 100.0% by mass): 0.2 parts

[0118] (6) Thickener (aqueous synthetic layered silicate lithium montmorillonite, manufactured by BYK-Chemie, trade name "LAPONITERD", solids concentration: 100.0% by mass): 1.2 parts

[0119] (7) Solvent (n-propanol): 10.0 parts

[0120] (8) Pure water: 22.6 parts

[0121] In the above-mentioned coating for forming a magnetic layer, the content ratio of amorphous polyester (a) and (b) is (a):(b) = 60:40 by mass ratio of solid components. The volume content of soft magnetic material is 50.0% relative to the total solid components of the above-mentioned coating for forming a magnetic layer.

[0122] <Formation of the Magnetic Layer>

[0123] Next, using a 12μm thick PET film (manufactured by Toyobo Co., Ltd., trade name "ESTERFILM E5100") as the substrate, the aforementioned magnetic layer forming coating was applied directly to one main surface of the substrate using a comma-shaped doctor blade, with the thickness of the magnetic layer after calendering being 10μm. The coating was then dried at 100°C. Subsequently, the blank roll was calendered using a calendering apparatus with metal rollers at a temperature of 50°C and a linear pressure of 50 kg / cm, thereby producing the electromagnetic noise suppression sheet of Example 1 with a magnetic layer formed on one main surface.

[0124] (Example 2)

[0125] The thickness of the magnetic layer was changed to 30 μm, and the electromagnetic noise suppression sheet of Example 2 was produced in the same manner as in Example 1.

[0126] (Example 3)

[0127] The thickness of the magnetic layer was changed to 50 μm, and the electromagnetic noise suppression sheet of Example 3 was produced in the same manner as in Example 1.

[0128] (Comparative Example 1)

[0129] The thickness of the magnetic layer was changed to 60 μm, and the electromagnetic noise suppression sheet of Comparative Example 1 was prepared in the same manner as in Example 1.

[0130] (Comparative Example 2)

[0131] As a soft magnetic material, Fe-Si-Cr spherical iron powder (Fe 88.8 Si 6.2 Cr 5.0 The electromagnetic noise suppression sheet of Comparative Example 2 was prepared by replacing spherical carbonyl iron powder (trade name "YW-5") with Fe content: 87.0% by mass, and changing the thickness of the magnetic layer to 100 μm. Otherwise, the same procedure as in Example 1 was followed.

[0132] (Comparative Example 3)

[0133] As a soft magnetic material, Fe-Si-Cr spherical iron powder (Fe 88.8 Si 6.2 Cr 5.0 The electromagnetic noise suppression sheet of Comparative Example 3 was prepared by replacing spherical carbonyl iron powder (trade name "YW-5") with Fe content: 87.0% by mass, and changing the thickness of the magnetic layer to 30 μm. Otherwise, the same procedure as in Example 1 was followed.

[0134] For the electromagnetic noise suppression sheets of Examples 1-3 and Comparative Examples 1-3 above, the measurement relative to the magnetization M was measured using the aforementioned measurement method. 10 The transmission attenuation rate (Rtp-S) relative to magnetization per unit area, measured by the microstrip line method at 28 GHz, M8t1 / M8t2, and the average value of reflection attenuation (S11) at the measurement frequency of 10 GHz to 30 GHz.

[0135] The above results, together with the magnetic material and thickness of the magnetic layer of the fabricated electromagnetic noise suppression sheet, are shown in Table 1.

[0136] [Table 1]

[0137]

[0138] As shown in Table 1, in the electromagnetic noise suppression sheets of Examples 1-3, it is possible to reduce the relative magnetization M 10 The transmission attenuation rate (Rtp-S) relative to magnetization per unit area, measured by the microstrip line method at 28 GHz, is 3 dB·cm. 2 The electromagnetic wave absorption per unit area of ​​the magnetic layer is higher than that of the electromagnetic noise suppression sheets of Comparative Examples 1-3. Furthermore, in the electromagnetic noise suppression sheets of Examples 1-3, M8t1 / M8t2 can be made to be 1.35 or higher, and compared to the electromagnetic noise suppression sheets of Comparative Examples 1-3, the in-plane magnetic anisotropy of the magnetic layer is greater than the magnetic anisotropy in the perpendicular direction. Moreover, in the electromagnetic noise suppression sheets of Examples 1-3, the average value of the reflection attenuation measured by the microstrip line method in the measurement frequency range of 10 GHz to 30 GHz is less than -20 dB, resulting in low reflection.

[0139] Regarding the embodiments of this application including the above-described embodiments 1 to 3, the following appendix is ​​further disclosed.

[0140] (Appendix 1) An electromagnetic noise suppression film, comprising a magnetic layer, characterized in that the magnetic layer comprises a spherical soft magnetic body and an adhesive, wherein when a magnetic field of 10 kOe is applied from the outside in the in-plane direction of the magnetic layer, the magnetization per unit area in the in-plane direction of the magnetic layer is set as M. 10 t, then relative to the magnetization M 10 The transmission attenuation rate of t, measured by the microstrip line method at 28 GHz, is 3 dB·cm². 2 / emu and above.

[0141] (Appendix 2) According to the electromagnetic noise suppression film described in Appendix 1, if a magnetic field of 10 kOe is applied from the outside to the in-plane direction of the magnetic layer and then the magnetic field from the outside is changed to 8 kOe, the magnetization per unit area in the in-plane direction is set to M8t1, and if a magnetic field of 10 kOe is applied from the outside to the vertical direction of the magnetic layer and then the magnetic field from the outside is changed to 8 kOe, the magnetization per unit area in the vertical direction is set to M8t2, then the ratio M8t1 / M88t2 is 1.35 or more.

[0142] (Appendix 3) The electromagnetic noise suppression film according to Appendix 1 or 2, wherein the spherical soft magnetic body is spherical carbonyl iron.

[0143] (Appendix 4) The electromagnetic noise suppression film according to Appendix 3, wherein the carbonyl iron contains more than 97.5% by mass of iron.

[0144] (Appendix 5) An electromagnetic noise suppression film according to any one of Appendix 1 to 4, wherein the volume content of the spherical soft magnetic body included in the magnetic layer is 30% to 80%.

[0145] (Appendix 6) An electromagnetic noise suppression film according to any one of appendix 1 to 5, wherein the thickness of the magnetic layer is 5 μm or more and less than 60 μm.

[0146] (Appendix 7) An electromagnetic noise suppression film according to any one of Appendix 1 to 5, wherein the thickness of the magnetic layer is 10 μm or more and 30 μm or less.

[0147] (Appendix 8) The electromagnetic noise suppression film according to any one of Appendix 1 to 7, wherein when the reflection attenuation is measured by microstrip line method in the range of measurement frequency 10 GHz to 30 GHz, the average value of the reflection attenuation is less than -20 dB.

[0148] (Appendix 9) An electromagnetic noise suppression sheet, characterized in that it comprises a substrate and an electromagnetic noise suppression film as described in any one of Appendix 1 to 8.

[0149] (Appendix 10) The electromagnetic noise suppression sheet according to Appendix 9, wherein the substrate is a resin film.

[0150] (Appendix 11) The electromagnetic noise suppression sheet according to Appendix 9 or 10 further comprises a metal layer.

[0151] (Appendix 12) A communication cable, characterized in that it comprises an electromagnetic noise suppression film as described in any one of Appendix 1 to 8 or an electromagnetic noise suppression sheet as described in any one of Appendix 9 to 11.

[0152] (Appendix 13) An electronic device, characterized in that it comprises an electromagnetic noise suppression film as described in any one of Appendix 1 to 8 or an electromagnetic noise suppression sheet as described in any one of Appendix 9 to 11.

[0153] This application can also be implemented in ways other than those described above. The embodiments disclosed in this application are examples and are not limited thereto. Regarding the scope of this application, the appended claims take precedence over the description in the foregoing specification, and all modifications within the scope equivalent to the claims are included in the claims.

[0154] Explanation of reference numerals in the attached figures

[0155] 10, 20 Electromagnetic noise suppression sheets

[0156] 11 substrates

[0157] 12 magnetic layers

[0158] 13 metal layers

[0159] 30 coaxial cable

[0160] 31 Internal wires

[0161] 32 insulation layers

[0162] 33 metal foil

[0163] 34 Metal Braided Fabric

[0164] 35 magnetic sheath layers

[0165] 35a substrate layer

[0166] 35b magnetic layer

[0167] 36. External coating.

Claims

1. An electromagnetic noise suppression film, comprising a magnetic layer, characterized in that, The magnetic layer comprises spherical soft magnetic materials and an adhesive. If a magnetic field of 10 kOe is applied from the outside in the in-plane direction of the magnetic layer, and the magnetization per unit area in the in-plane direction of the magnetic layer is set as M... 10 t, then relative to the magnetization M 10 The transmission attenuation rate of t, measured by the microstrip line method at 28 GHz, is 3 dB·cm². 2 / emu and above.

2. The electromagnetic noise suppression film according to claim 1, wherein, If a magnetic field of 10 kOe is applied from the outside into the in-plane direction of the magnetic layer and then the magnetic field from the outside is changed to 8 kOe, and the magnetization per unit area in the in-plane direction is set to M8t1, and a magnetic field of 10 kOe is applied from the outside into the vertical direction of the magnetic layer and then the magnetic field from the outside is changed to 8 kOe, and the magnetization per unit area in the vertical direction is set to M8t2, then the ratio M8t1 / M8t2 is 1.35 or higher.

3. The electromagnetic noise suppression film according to claim 1, wherein, The spherical soft magnetic material is spherical carbonyl iron.

4. The electromagnetic noise suppression film according to claim 3, wherein, The carbonyl iron contains more than 97.5% by mass of iron.

5. The electromagnetic noise suppression film according to claim 1, wherein, The volume fraction of the spherical soft magnetic material contained in the magnetic layer is 30% to 80%.

6. The electromagnetic noise suppression film according to claim 1, wherein, The thickness of the magnetic layer is greater than 5 μm and less than 60 μm.

7. The electromagnetic noise suppression film according to claim 1, wherein, The thickness of the magnetic layer is more than 10 μm and less than 30 μm.

8. The electromagnetic noise suppression film according to claim 1, wherein, When the reflection attenuation is measured using the microstrip line method within the frequency range of 10 GHz to 30 GHz, the average value of the reflection attenuation is below -20 dB.

9. An electromagnetic noise suppression sheet, characterized in that, It comprises a substrate and an electromagnetic noise suppression film according to any one of claims 1 to 8.

10. The electromagnetic noise suppression sheet according to claim 9, wherein, The substrate is a resin film.

11. The electromagnetic noise suppression sheet according to claim 9, wherein, It also contains a metal layer.

12. A communication cable, characterized in that, The electromagnetic noise suppression film comprising any one of claims 1 to 8.

13. An electronic device, characterized in that, The electromagnetic noise suppression film comprising any one of claims 1 to 8.

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