Electromagnetic wave shielding material, electronic component, and electronic device

Abstract

Provided is an electromagnetic wave shielding material having a magnetic layer containing magnetic particles, wherein, in the cross section of the magnetic layer, when the angle of the surface of the magnetic layer is 0º, the abundance ratio of magnetic particles inclined by at least 30º is 5-50% in terms of the number of particles.

Description

Electromagnetic shielding materials, electronic components, and electronic equipment

[0001] This invention relates to electromagnetic shielding materials, electronic components, and electronic equipment.

[0002] In recent years, electromagnetic shielding materials have attracted attention as materials for reducing the effects of electromagnetic waves in various electronic components and electronic devices (see, for example, Patent Document 1).

[0003] Japanese Patent Publication No. 2024-068539

[0004] Electromagnetic shielding materials can exhibit the ability to shield electromagnetic waves (hereinafter also referred to as "shielding performance") by reflecting electromagnetic waves incident on the electromagnetic shielding material and / or attenuating them within the electromagnetic shielding material.

[0005] Electromagnetic shielding materials may be used in applications where they are incorporated into electronic components or electronic devices and are then subjected to vibration. Therefore, electromagnetic shielding materials that exhibit minimal degradation in shielding performance due to vibration are desirable.

[0006] In view of the foregoing, one aspect of the present invention aims to provide an electromagnetic wave shielding material in which the deterioration of shielding performance due to vibration is suppressed.

[0007] One aspect of the present invention is as follows: [1] An electromagnetic wave shielding material having a magnetic layer containing magnetic particles, wherein, in the cross-section of the magnetic layer, when the angle of the surface of the magnetic layer is set to 0°, the abundance of magnetic particles tilted at 30° or more (hereinafter also referred to as "abundance of magnetic particles tilted at 30° or more") is 5% or more and 50% or less on a particle number basis. [2] The electromagnetic wave shielding material according to [1], wherein the storage modulus E' of the electromagnetic wave shielding material in a dynamic viscoelasticity measurement at 1 Hz is 0.010 GPa or more and less than 10.000 GPa at 50°C (hereinafter, the storage modulus E' will also be referred to as "E' at 50°C"). [3] The electromagnetic wave shielding material according to [1] or [2], wherein the magnetic layer further comprises a resin. [4] The electromagnetic wave shielding material according to [3], wherein the resin is a urethane bond-containing resin. [5] The electromagnetic wave shielding material according to [4], wherein the magnetic layer contains 13 to less than 30 parts by mass of urethane bond-containing resin, with the total mass of the magnetic layer being 100 parts by mass. [6] The electromagnetic wave shielding material according to any one of [1] to [5], wherein the magnetic layer is located between two metal layers. [7] The electromagnetic wave shielding material according to any one of [1] to [6], comprising two or more multilayer structures, each having the magnetic layer between two metal layers, wherein in each multilayer structure, the magnetic layer is in direct contact with each of the two metal layers. [8] The electromagnetic wave shielding material according to any one of [1] to [7], wherein the storage modulus E' of the electromagnetic wave shielding material in a dynamic viscoelasticity measurement at 1 Hz is 0.010 GPa or more and less than 10.000 GPa at 50°C, the magnetic layer contains 13 to less than 30 parts by mass of urethane bond-containing resin, with the total mass of the magnetic layer being 100 parts by mass, and the magnetic layer is located between two metal layers. [9] An electromagnetic wave shielding material according to [8], comprising two or more multilayer structures having the magnetic layer between two metal layers, wherein in each multilayer structure, the magnetic layer is in direct contact with each of the two metal layers.

[10] An electronic component comprising the electromagnetic wave shielding material according to any one of [1] to [9].

[11] An electronic device comprising the electromagnetic wave shielding material according to any one of [1] to [9].

[0008] According to one aspect of the present invention, an electromagnetic wave shielding material can be provided in which the deterioration of shielding performance due to vibration is suppressed. Furthermore, according to one aspect of the present invention, an electronic component and electronic device containing this electromagnetic wave shielding material can be provided.

[0009] [Electromagnetic wave shielding material] One aspect of the present invention relates to an electromagnetic wave shielding material having a magnetic layer containing magnetic particles. In the cross-section of the magnetic layer, when the angle of the surface of the magnetic layer is set to 0°, the abundance of magnetic particles tilted at 30° or more (abundance of magnetic particles tilted at 30° or more) is 5% or more and 50% or less on a particle number basis.

[0010] Through diligent research, the inventors concluded that the reason the shielding performance of an electromagnetic wave shielding material having a magnetic layer containing magnetic particles deteriorates with vibration is that vibration causes intralayer delamination in the magnetic layer. Further diligent research by the inventors revealed that by setting the percentage of magnetic particles with a 30° or greater angle in the magnetic layer to 5% or more and 50% or less, it is possible to suppress the deterioration of the shielding performance of the electromagnetic wave shielding material with vibration. This is presumed to be because setting the percentage of magnetic particles with a 30° or greater angle in the magnetic layer to 5% or more and 50% or less suppresses the occurrence of the above-mentioned intralayer delamination. However, the present invention is not limited to the presumption described herein.

[0011] In the present invention and this specification, "electromagnetic wave shielding material" means a material capable of exhibiting shielding performance against electromagnetic waves in at least one frequency or at least a portion of a frequency band. "Electromagnetic waves" include magnetic field waves and electric field waves. An "electromagnetic wave shielding material" can be a material capable of exhibiting shielding performance against one or both of the following: magnetic field waves in at least one frequency or at least a portion of a frequency band, and electric field waves in at least one frequency or at least a portion of a frequency band.

[0012] In the present invention and this specification, "magnetic" means ferromagnetic property. Details regarding the magnetic layer will be described later.

[0013] In the present invention and this specification, "metal layer" means a layer containing a metal. A metal layer may be a layer containing one or more metals, such as a pure metal consisting of a single metal element, an alloy of two or more metal elements, or an alloy of one or more metal elements and one or more nonmetal elements. Details regarding the metal layer will be described later.

[0014] In the present invention and this specification, "direct contact" between the magnetic layer and the metal layer means that they are directly adjacent to each other without any other layers in between.

[0015] <Ability of magnetic particles with an angle of 30° or more in the magnetic layer> In the present invention and this specification, the abundance of magnetic particles with an angle of 30° or more in the magnetic layer is a value obtained by the following method. The cross section in the thickness direction of the electromagnetic wave shielding material is exposed by a known method. The cross section can be exposed, for example, with a cross-section polisher (JEOL SM-09010, acceleration voltage: 5kV). For a randomly selected region of the magnetic layer portion of the exposed cross section, a cross-sectional image is acquired as a scanning electron microscope (SEM) image such that one of the two surfaces of the magnetic layer (randomly selected) is parallel to the X-axis. The imaging conditions are acceleration voltage: 5kV, magnification: 1000x, and an SEM image is obtained as a secondary electron image. The surface that is made parallel to the X-axis may be the interface between the magnetic layer and an adjacent layer. The cross-sectional image is subjected to density conversion (input 80-255, output 0-255) using the image processing software WinROOF (manufactured by Mitsubishi Corporation), and binarization is performed with a brightness threshold of 45 to distinguish between magnetic particles and other components (e.g., resin, as described later). For the resulting binarized image, objects or backgrounds consisting of a single pixel are removed (isolated point removal) to remove noise, and the angle (azimuth angle) with the X-axis when the absolute maximum length of the object is taken is determined. The angle (azimuth angle) is defined within the range of 0° to 90°. This angle measurement is performed for all magnetic particles included in the binarized image. When determining the total number of magnetic particles included in the binarized image, magnetic particles in which only a portion of the particle is included in the binarized image are also included. For magnetic particles in which only a portion of the particle is included in the binarized image, the angle (azimuth angle) is determined for the portion included in the binarized image. From the total number of magnetic particles and the number of magnetic particles with an angle (azimuth angle) of 30° or more obtained in this way, the abundance of magnetic particles with an angle (azimuth angle) of 30° or more is calculated as follows: Abundance of magnetic particles with an angle (azimuth angle) of 30° or more = 100 × Number of magnetic particles with an angle (azimuth angle) of 30° or more / Total number of magnetic particles.

[0016] From the viewpoint of suppressing intralayer delamination in the width direction of the magnetic layer of the electromagnetic shielding material described above, the presence rate of magnetic particles with an angle of 30° or more in the magnetic layer of the magnetic layer described above is 5% or more, preferably 10% or more, and more preferably 15% or more, 20% or more, 25% or more, and 30% or more. On the other hand, from the viewpoint of suppressing intralayer delamination in the thickness direction of the magnetic layer of the magnetic shielding material described above, the presence rate of magnetic particles with an angle of 30° or more in the magnetic layer of the magnetic layer of the electromagnetic shielding material described above is 50% or less, and more preferably 48% or less.

[0017] When the electromagnetic shielding material has only one magnetic layer, the abundance of magnetic particles with a 30° or greater angle in this single magnetic layer is 5% or more and 50% or less. When the electromagnetic shielding material has two or more magnetic layers, it is preferable that the abundance of magnetic particles with a 30° or greater angle in at least one magnetic layer is 5% or more and 50% or less, and that the abundance of magnetic particles with a 30° or greater angle in more magnetic layers is 5% or more and 50% or less, and it is even more preferable that the abundance of magnetic particles with a 30° or greater angle in all magnetic layers is 5% or more and 50% or less.

[0018] The method for controlling the abundance of magnetic particles with a magnetic field of 30° or higher in the magnetic layer will be described later.

[0019] The electromagnetic shielding material described above will be explained in more detail below.

[0020] <Magnetic Layer> (Magnetic Particles) The above-mentioned magnetic layer is a layer containing magnetic particles. As magnetic particles, one type selected from the group consisting of magnetic particles generally called soft magnetic particles, such as metal particles and ferrite particles, or two or more types can be used in combination. Since metal particles generally have a saturation magnetic flux density about 2 to 3 times that of ferrite particles, they can maintain relative permeability without magnetic saturation even under a strong magnetic field and exhibit shielding performance. Therefore, it is preferable that the magnetic particles contained in the magnetic layer are metal particles. In the present invention and this specification, a layer containing metal particles as magnetic particles corresponds to a "magnetic layer".

[0021] Examples of metal particles used as magnetic particles include Sendust (Fe-Si-Al alloy), Permalloy (Fe-Ni alloy), Molybdenum Permalloy (Fe-Ni-Mo alloy), Fe-Si alloy, Fe-Cr alloy, Fe-containing alloys generally called iron-based amorphous alloys, Co-containing alloys generally called cobalt-based amorphous alloys, alloys generally called nanocrystalline alloys, iron, Permendur (Fe-Co alloy), and other particles. Among these, Sendust is preferred because it exhibits high saturation magnetic flux density and relative permeability. In addition to the constituent elements of the metal (including alloys), the metal particles may contain elements contained in additives that can be added as desired and / or elements contained in impurities that may be unintentionally introduced during the manufacturing process of the metal particles, in any desired proportion. In metal particles, the content of constituent elements of the metal (including alloys) is preferably 90.0% by mass or more, more preferably 95.0% by mass or more, and may also be 100% by mass, less than 100% by mass, 99.9% by mass or less, or 99.0% by mass or less.

[0022] In one embodiment, the shielding performance of an electromagnetic shielding material against electromagnetic waves can be evaluated using the permeability (more specifically, the real part of the complex relative permeability) of the magnetic layer contained in the electromagnetic shielding material as an indicator. Electromagnetic shielding materials having a magnetic layer exhibiting high permeability (more specifically, the real part of the complex relative permeability) are preferable because they can exhibit high shielding performance against electromagnetic waves.

[0023] When the complex relative permeability is measured using a permeability measuring device, the real part μ' and the imaginary part μ'' are usually displayed. In this invention and specification, the real part of the complex relative permeability refers to this real part μ'. Hereinafter, the real part of the complex relative permeability at a frequency of 3 MHz (megahertz) will also be simply referred to as "permeability" or "permeability μ'". Permeability can be measured using a commercially available permeability measuring device or a permeability measuring device with a known configuration. The measurement temperature is 25°C. By setting the ambient temperature around the measurement sample to the measurement temperature, temperature equilibrium can be achieved, thereby setting the temperature of the measurement sample to the measurement temperature. From the viewpoint of exhibiting even better shielding performance, the permeability of the magnetic layer contained in the electromagnetic wave shielding material (real part of the complex relative permeability at a frequency of 3 MHz) is preferably 40 or more, more preferably 100 or more, and even more preferably 120 or more. Furthermore, the magnetic permeability can be, for example, 500 or less, 300 or less, or 200 or less, and can exceed the values ​​exemplified herein. Electromagnetic shielding materials with high magnetic permeability are preferable because they exhibit excellent shielding performance.

[0024] From the viewpoint of forming a magnetic layer exhibiting high magnetic permeability, the magnetic particles are preferably flattened particles, and more preferably flattened metallic particles. By arranging the long side direction of the flattened particles to be closer to parallel with the in-plane direction of the magnetic layer, the long side direction of the particles is more aligned with the vibration direction of electromagnetic waves incident perpendicular to the electromagnetic wave shielding material, thereby reducing the demagnetizing field, and allowing the magnetic layer to exhibit higher magnetic permeability. In the present invention and this specification, "flattened particles" refers to particles with an aspect ratio of 0.20 or less. The aspect ratio of the flattened particles is preferably 0.15 or less, and more preferably 0.10 or less. The aspect ratio of the flattened particles can be, for example, 0.01 or more, 0.02 or more, or 0.03 or more. For example, the shape of the particles can be made flattened by flattening by a known method. For information on flattening, see, for example, Japanese Patent Publication No. 2018-131640, specifically paragraphs 0016, 0017, and the section on embodiments. An example of a magnetic layer exhibiting high magnetic permeability is a magnetic layer containing flattened particles of Sendust.

[0025] In the present invention and this specification, the aspect ratio of magnetic particles shall be determined by the following method. The cross-section of the magnetic layer is exposed by a known method. A cross-sectional image is obtained as a scanning electron microscope (SEM) image of a randomly selected region of this cross-section. The imaging conditions are acceleration voltage: 2kV, magnification: 1000x, and an SEM image is obtained as a backscattered electron image. The image is read out in grayscale using the cv2.imread() function of the image processing library OpenCV4 (Intel Corporation) with the second argument set to 0, and a binarized image is obtained using the cv2.threhold() function with the brightness midway between the high-brightness and low-brightness regions as the boundary. The white areas (high-brightness regions) in the binarized image are identified as magnetic particles. The rotational circumscribed rectangle corresponding to each magnetic particle portion is obtained from the obtained binarized image using the cv2.minAreaRect() function, and cv2. The minAreaRect() function returns the long side length, short side length, and rotation angle. When determining the total number of magnetic particles included in the binarized image, particles in which only a portion is included in the binarized image are also included. For particles in which only a portion is included in the binarized image, the long side length and short side length are determined for the portion included in the binarized image. The ratio of the short side length to the long side length (short side length / long side length) obtained in this way is taken as the aspect ratio of each magnetic particle. In this invention and specification, if the number of magnetic particles identified as flattened particles with an aspect ratio of 0.20 or less is 10% or more of the total number of magnetic particles included in the binarized image on a numerical basis, the magnetic layer is determined to be a "magnetic layer containing flattened particles as magnetic particles". Note that the coordinates of the bounding rectangle are calculated using the cv2.boxPoints() function and cv2. The drawContours() function is used to create an image by overlaying the rotated bounding rectangle onto the original image, and rotated bounding rectangles that are clearly misdetected are excluded from the aspect ratio calculation. Furthermore, the average value (arithmetic mean) of the aspect ratios of particles identified as flattened particles is used as the aspect ratio of flattened particles contained in the magnetic layer being measured. This aspect ratio is 0.20 or less, preferably 0.15 or less, and more preferably 0.10 or less. In addition, the above aspect ratio can be, for example, 0.01 or more, 0.02 or more, or 0.03 or more.

[0026] The content of magnetic particles in the above magnetic layer can be, for example, 50 parts by mass or more, 60 parts by mass or more, 70 parts by mass or more, or 80 parts by mass or more, based on 100 parts by mass of the total mass of the magnetic layer, or for example, 87 parts by mass or less, 85 parts by mass or less, 80 parts by mass or less, or 75 parts by mass or less. The above magnetic layer may contain only one type of magnetic particle, or it may contain two or more types of magnetic particles in any proportion. In the present invention and this specification, when two or more types of a component are included, the content refers to the total content of those components. The content of various components in the magnetic layer can be determined by known methods such as TG / DTA (Thermogravimetric Analysis) or extraction of various components using a solvent. Note that "TG / DTA" is generally called thermogravimetric differential thermal analysis. If the composition of the magnetic layer-forming composition used to form the magnetic layer is known, the content of various components in the magnetic layer can also be determined from this known composition.

[0027] In one embodiment, the magnetic layer described above can be an insulating layer. In the present invention and this specification, "insulating" means that the electrical conductivity is less than 1 S (siemens) / m. The electrical conductivity of a layer is calculated from the surface electrical resistivity of the layer and the thickness of the layer by the following formula. Electrical conductivity can be measured by known methods. Electrical conductivity [S / m] = 1 / (Surface electrical resistivity [Ω] × Thickness [m])

[0028] The inventors surmise that it is preferable for the above-mentioned magnetic layer to be an insulating layer in order for the above-mentioned electromagnetic wave shielding material to exhibit even higher shielding performance. From this point of view, the electrical conductivity of the above-mentioned magnetic layer is preferably less than 1 S / m, more preferably 0.5 S / m or less, even more preferably 0.1 S / m or less, and even more preferably 0.05 S / m or less. The electrical conductivity of the above-mentioned magnetic layer is, for example, 1.0 × 10 －１２ S / m or more or 1.0 × 10 －１０ It can be S / m or higher.

[0029] (Resin) The above magnetic layer may be a layer containing magnetic particles and resin. The resin can act as a binder in the magnetic layer. In the present invention and this specification, a layer containing both magnetic particles and resin is referred to as a "magnetic layer". In the present invention and this specification, "resin" means polymer and also includes rubber and elastomer. Polymers include homopolymers and copolymers. Rubber includes natural rubber and synthetic rubber. Elastomers are polymers that exhibit elastic deformation.

[0030] The magnetic layer may contain a urethane bond-containing resin. In the present invention and this specification, "urethane bond-containing resin" means a resin containing one or more urethane bonds (-NH-C(=O)O-) in one molecule. The urethane bond-containing resin includes various urethane bond-containing resins such as polyurethane resins, polyester urethane resins, and polyurethane elastomers. In the magnetic layer, polyurethane resin may be used alone or in combination of two or more types. The type of resin contained in the magnetic layer can be determined by organic analysis such as pyrolysis GC / MS (Gas Chromatography / Mass Spectrometry) or Fourier transform infrared spectroscopy. For example, if isocyanate component residue and / or polyol component residue are observed by pyrolysis GC / MS, it can be determined that it is a urethane bond-containing resin.

[0031] From the viewpoint of further suppressing the decrease in shielding performance due to vibration, the content of the urethane bond-containing resin in the above magnetic layer is preferably 13 parts by mass or more, more preferably 14 parts by mass or more, even more preferably 15 parts by mass or more, and even more preferably 16 parts by mass or more, based on 100 parts by mass of the total mass of the magnetic layer. Furthermore, from the viewpoint of improving the shielding performance of the electromagnetic wave shielding material, the content of the urethane bond-containing resin in the above magnetic layer is preferably less than 30 parts by mass, more preferably 29 parts by mass or less, and even more preferably 28 parts by mass or less, 27 parts by mass or less, 26 parts by mass or less, 25 parts by mass or less, 24 parts by mass or less, and 23 parts by mass or less, in that order.

[0032] The resin contained in the magnetic layer may consist solely of a urethane-bonded resin, or it may contain one or more other resins in any amount in addition to the urethane-bonded resin. The amount of urethane-bonded resin per 100 parts by mass of the total amount of resin in the magnetic layer may be, for example, 80 parts by mass or more, 85 parts by mass or more, 90 parts by mass or more, or 95 parts by mass or more, or it may be 100 parts by mass or less, 100 parts by mass or less, less than 100 parts by mass, 99 parts by mass or less, or 98 parts by mass or less.

[0033] In addition to the above components, the magnetic layer may also contain one or more known additives such as curing agents, curing catalysts, dispersants, stabilizers, and coupling agents in any amount.

[0034] For example, a compound having a crosslinking group can be used as a curing agent. When the curing agent is a compound having a crosslinking group, in a magnetic layer containing such a curing agent, the curing agent may be included in a form in which at least a portion of the crosslinking group has undergone a crosslinking reaction. In the present invention and this specification, "crosslinking group" means a group that can undergo a crosslinking reaction, and a specific example thereof is an isocyanate group. As a curing agent, a compound having two or more crosslinking groups (for example, two to four) in one molecule is preferred, and a specific example thereof is a polyfunctional isocyanate. A polyfunctional isocyanate is a compound having two or more isocyanate groups in one molecule, for example, a compound having two to four isocyanate groups in one molecule. In one embodiment, with 100 parts by mass of resin contained in the magnetic layer, the magnetic layer may contain 2.5 parts by mass or more or 10 parts by mass or more of polyfunctional isocyanate. Furthermore, in one embodiment, the magnetic layer may contain 100 parts by mass or less, or 40 parts by mass or less, of a polyfunctional isocyanate, with 100 parts by mass or less of a resin contained in the magnetic layer. Furthermore, in one embodiment, the magnetic layer may contain 2.5 parts by mass or more, or 10 parts by mass or more, of a polyfunctional isocyanate, with 100 parts by mass or less of a urethane bond-containing resin contained in the magnetic layer. Furthermore, in one embodiment, the magnetic layer may contain 100 parts by mass or less, or 40 parts by mass or less, of a polyfunctional isocyanate, with 100 parts by mass or less of a urethane bond-containing resin contained in the magnetic layer.

[0035] <Metal Layer> The electromagnetic wave shielding material described above may consist only of the magnetic layer described above, or it may have one or more layers other than the magnetic layer described above. A specific example of such a layer is a metal layer. For example, the electromagnetic wave shielding material may have a multilayer structure that includes a magnetic layer between two metal layers. Having such a multilayer structure is preferable from the viewpoint of improving the shielding performance of the electromagnetic wave shielding material. When the electromagnetic wave shielding material has only one multilayer structure that includes a magnetic layer between two metal layers, the abundance of magnetic particles with an angle of 30° or more in the magnetic layer included in this multilayer structure is 5% or more and 50% or less. When the electromagnetic wave shielding material has two or more multilayer structures that include a magnetic layer between two metal layers, it is preferable that the abundance of magnetic particles with an angle of 30° or more in the magnetic layer included in at least one multilayer structure is 5% or more and 50% or less, and it is preferable that the abundance of magnetic particles with an angle of 30° or more in more magnetic layers is 5% or more and 50% or less, and it is even more preferable that the abundance of magnetic particles with an angle of 30° or more in all magnetic layers is 5% or more and 50% or less.

[0036] If the electromagnetic shielding material has one or more multilayer structures in which a magnetic layer is placed between two metal layers, the electromagnetic shielding material includes at least two metal layers and may also include three or more metal layers. In one embodiment, the two or more metal layers included in the electromagnetic shielding material have the same composition and thickness, and in another embodiment, they have different compositions and / or thicknesses. Furthermore, if the electromagnetic shielding material includes two or more magnetic layers, in one embodiment, the two or more magnetic layers have the same composition and thickness, and in another embodiment, they have different compositions and / or thicknesses.

[0037] In one embodiment, in the above multilayer structure, one or both of the two metal layers may be layers that are in direct contact with the magnetic layer located between the two metal layers. In another embodiment, one or more other layers may exist between one or both of the two metal layers and the magnetic layer located between the two metal layers. Specific examples of the layer configuration of the electromagnetic shielding material will be described later.

[0038] As the metal layer, a layer containing one or more metals selected from the group consisting of various pure metals and various alloys can be used. The metal layer can exert an attenuation effect in electromagnetic wave shielding material. The attenuation effect is greater the larger the propagation constant, and the propagation constant is greater the larger the electrical conductivity; therefore, it is preferable that the metal layer contains a metal element with high electrical conductivity. From this point of view, it is preferable that the metal layer contains a pure metal of Ag, Cu, Au, or Al, or an alloy in which any of these is the main component. A pure metal is a metal consisting of a single metal element and may contain trace amounts of impurities. Generally, a metal consisting of a single metal element with a purity of 99.0% or more is called a pure metal. Purity is based on mass. An alloy is generally a pure metal with one or more metal elements or non-metal elements added to adjust its composition for purposes such as corrosion prevention and strength improvement. The main component in an alloy is the component with the highest proportion by mass, and can be, for example, a component that accounts for 80.0% by mass or more (for example, less than 100% by mass or 99.8% by mass or less) in an alloy. From an economic standpoint, pure metals of Cu or Al, or alloys mainly composed of Cu or Al, are preferred, and from the standpoint of high electrical conductivity, pure metals of Cu or alloys mainly composed of Cu are more preferred.

[0039] The purity of the metal in the metal layer, that is, the content of the metal, can be 99.0% by mass or more, preferably 99.5% by mass or more, and more preferably 99.8% by mass or more, based on the total mass of the metal layer. Unless otherwise specified, the content of the metal in the metal layer refers to the content based on mass. For example, as the metal layer, a pure metal or alloy processed into a sheet shape can be used. For example, as the metal layer, a commercially available metal foil or a metal foil produced by a known method can be used. For pure Cu metal, sheets of various thicknesses (so-called copper foils) are commercially available. For example, such a copper foil can be used as the metal layer. According to their production methods, copper foils include electrolytic copper foils obtained by depositing copper foil on a cathode through electroplating, and rolled copper foils obtained by applying heat and pressure to an ingot to roll it into a thin sheet. Any of these copper foils can be used as the metal layer of the electromagnetic wave shielding material. Also, for example, for Al, sheets of various thicknesses (so-called aluminum foils) are commercially available. For example, such an aluminum foil can be used as the metal layer.

[0040] From the viewpoint of reducing the weight of the electromagnetic wave shielding material, it is preferable that at least one of the metal layers contained in the electromagnetic wave shielding material is a metal layer containing a metal selected from the group consisting of Al and Mg. This is because both Al and Mg have a small value obtained by dividing specific gravity by electrical conductivity (specific gravity / electrical conductivity). When a metal with a smaller value is used, an electromagnetic wave shielding material that exhibits high shielding performance can be made lighter. As values calculated from literature values, for example, the values obtained by dividing specific gravity by electrical conductivity (specific gravity / electrical conductivity) of Cu, Al, and Mg are as follows. Cu: 1.5×10 －７ m / S, Al: 7.6×10 －８ m / S, Mg: 7.6×10 －８m / S. From the above values, Al and Mg can be said to be preferred metals from the viewpoint of reducing the weight of the electromagnetic shielding material. A metal layer containing a metal selected from the group consisting of Al and Mg may, in one form, contain only Al or Mg, and in another form, contain both. From the viewpoint of reducing the weight of the electromagnetic shielding material, it is more preferable that one or more metal layers included in the above electromagnetic shielding material have a content of 80.0 mass% or more of a metal selected from the group consisting of Al and Mg, and even more preferable that have a content of 90.0 mass% or more of a metal selected from the group consisting of Al and Mg. A metal layer containing at least Al among Al and Mg may have an Al content of 80.0 mass% or more, and may also have an Al content of 90.0 mass% or more. A metal layer containing at least Mg among Al and Mg may have an Mg content of 80.0 mass% or more, and may also have an Mg content of 90.0 mass% or more. The content of the metal selected from the group consisting of Al and Mg, the Al content, and the Mg content can each be, for example, less than 100% by mass or 99.9% by mass or less. The content of the metal selected from the group consisting of Al and Mg, the Al content, and the Mg content are each the content relative to the total mass of the metal layer.

[0041] In one embodiment, one or more metal layers included in the electromagnetic shielding material may be metal layers with a Cu content of 80.0% by mass or more. The Cu content of such layers may be 90.0% by mass or more, and may be 99.9% by mass or less. In another embodiment, one or more metal layers may be metal layers with an Al content of 80.0% by mass or more. The Al content of such layers may be 90.0% by mass or more, and may be less than 100% by mass or 99.9% by mass or less. The Cu content and Al content are, respectively, the content relative to the total mass of the metal layer. In one embodiment, all metal layers included in the electromagnetic shielding material may be metal layers with a Cu or Al content within the above range.

[0042] <Specific Example of Layer Structure> Specific examples of the layer structure of the electromagnetic wave shielding material described above include, for example, the following examples. Example 1: "Metal layer / Magnetic layer / Metal layer" Example 2: "Metal layer / Magnetic layer / Metal layer / Magnetic layer / Metal layer" Example 3: "Metal layer / Magnetic layer / Metal layer / Magnetic layer / Metal layer / Magnetic layer / Metal layer" In an electromagnetic wave shielding material comprising two or more multilayer structures each containing a magnetic layer between two metal layers, as shown in Examples 2 and 3, for example, a metal layer that sandwiches a magnetic layer in one multilayer structure can also be a metal layer that sandwiches a magnetic layer in another multilayer structure. In the electromagnetic wave shielding material described above, the total number of multilayer structures each including the magnetic layer between two metal layers can be, for example, 1 to 4. The total number of the above-mentioned multilayer structures is 1 in Example 1, 2 in Example 2, and 3 in Example 3. Having a total number of the above-mentioned multilayer structures of 2 or more (e.g., 2, 3 or 4) is preferable from the viewpoint of further improving the shielding performance of the electromagnetic wave shielding material. In the above description, the symbol " / " is used to mean both that the layer described on the left of the symbol and the layer described on the right of the symbol are in direct contact with no other layer interposed therebetween, and that they are laminated indirectly with one or more other layers interposed therebetween. Specific examples of the above-mentioned other layers include a layer for bonding described later. The total number of magnetic layers contained in the electromagnetic wave shielding material is 1 or more, may be 2 or more, and may be 4 or less, for example. On the other hand, the total number of metal layers contained in the electromagnetic wave shielding material is only 1 or 2 or more, and may be, for example, 2 to 5 layers.

[0043] <Various Thicknesses> From the viewpoints of processability of the metal layer and the shielding performance of the electromagnetic wave shielding material, the thickness of the metal layer per layer is preferably 4 µm or more, more preferably 5 µm or more, still more preferably 10 µm or more, even more preferably 15 µm or more, even still more preferably 20 µm or more, and yet even more preferably 25 µm or more. On the other hand, from the viewpoint of processability of the metal layer, the thickness per layer of the metal layer is preferably 100 µm or less, more preferably 50 µm or less, still more preferably 45 µm or less, and even more preferably 40 µm or less.

[0044] If the thickness of one of the two metal layers located on either side of the magnetic layer is T1, and the thickness of the other metal layer is T2, and T1 is greater than or equal to T2 (i.e., T1 = T2 or T1 > T2), then the ratio of the thicknesses of the two metal layers (T2 / T1) can be, for example, 0.10 or more. From the viewpoint of being able to exhibit higher shielding performance against magnetic field waves, it is preferable that it be 0.15 or more, more preferably 0.30 or more, even more preferably 0.50 or more, even more preferably 0.70 or more, and even more preferably 0.80 or more. From the viewpoint of being able to exhibit even higher shielding performance against magnetic field waves, it is preferable that the difference between T1 and T2 is smaller. The ratio of the thicknesses (T2 / T1) can be 1.00 or less, and can also be 1.00 (i.e., T1 = T2). If the electromagnetic shielding material described above includes two or more multilayer structures having a magnetic layer between two metal layers, the above description regarding the thickness ratio (T2 / T1) can be applied to at least one of the multilayer structures included in the electromagnetic shielding material, or it can be applied to two or more, or it can be applied to all of them.

[0045] Electromagnetic shielding material can be bent and processed into any shape according to its application. When the electromagnetic shielding material is bent, if the width of the bent portion (hereinafter referred to as "bending width") is wide, the shape of the bent portion becomes a gentle curve, which may make it difficult to process into the desired shape. From this point of view, a narrower bending width is preferable. The thicker the total thickness of the metal layers contained in the electromagnetic shielding material, the wider the bending width tends to be. From the viewpoint of narrowing the bending width of the electromagnetic shielding material, the total thickness of the metal layers contained in the electromagnetic shielding material is preferably 100 μm or less, more preferably 90 μm or less, even more preferably 80 μm or less, even more preferably 70 μm or less, even more preferably 60 μm or less, even more preferably 50 μm or less, and still even more preferably 40 μm or less. The total thickness of the metal layers contained in the electromagnetic shielding material can be, for example, 8 μm or more or 10 μm or more.

[0046] Regarding the thickness of the magnetic layer, from the viewpoint of the shielding performance of the electromagnetic wave shielding material, the thickness per layer can be, for example, 3 μm or more, preferably 10 μm or more, and more preferably 20 μm or more. Furthermore, from the viewpoint of the processability of the electromagnetic wave shielding material, the thickness per layer of the magnetic layer can be, for example, 90 μm or less, preferably 70 μm or less, and more preferably 50 μm or less. When the electromagnetic wave shielding material includes two or more layers of the magnetic layer, the total thickness of the magnetic layers included in the electromagnetic wave shielding material can be, for example, 6 μm or more, and can also be, for example, 180 μm or less.

[0047] Furthermore, the total thickness of the electromagnetic shielding material can be, for example, 250 μm or less. From the viewpoint of narrowing the bending width, a thinner total thickness of the electromagnetic shielding material is also preferable. From this point of view, the total thickness of the electromagnetic shielding material is preferably 200 μm or less, more preferably 190 μm or less, and even more preferably 170 μm or less. The total thickness of the electromagnetic shielding material can be, for example, 30 μm or more or 40 μm or more.

[0048] The thickness of each layer in the electromagnetic shielding material is determined by imaging a cross-section exposed by a known method using a scanning electron microscope (SEM), and then taking the arithmetic mean of the thicknesses of five randomly selected points in the resulting SEM image.

[0049] <Storage modulus E' of electromagnetic shielding material (E' at 50°C)> The E' at 50°C of the electromagnetic shielding material can be, for example, 0.010 GPa or more and 15.000 GPa or less, and from the viewpoint of further suppressing the decrease in shielding performance due to vibration, it is preferable that it be 0.010 GPa or more and less than 10.000 GPa. From the viewpoint of the above, it is more preferable that the E' at 50°C of the electromagnetic shielding material be 0.100 or more, and even more preferable that it be 0.200 or more. Also from the viewpoint of the above, it is more preferable that the E' at 50°C of the electromagnetic shielding material be 9.000 GPa or less, and even more preferable in the order of 5.000 GPa or less, 3.000 GPa or less, 1.000 GPa or less, and 0.800 or less. The E' at 50°C of the electromagnetic shielding material can be controlled by the type and content of resin contained in the magnetic layer. When the magnetic layer contains a urethane bond-containing resin, the E' at 50°C can be controlled by the amount of urethane bond-containing resin in the magnetic layer.

[0050] In the present invention and this specification, the E' at 50°C of the electromagnetic shielding material is a value obtained by the dynamic viscoelasticity measurement described below. The dynamic viscoelasticity measurement is performed using a dynamic viscoelasticity measuring device. For example, the DMS6100 dynamic viscoelasticity measuring device manufactured by Hitachi High-Tech Science Corporation can be used as the dynamic viscoelasticity measuring device. The measurement procedure is as follows: A measurement sample measuring 28 mm in length and 10 mm in width is cut from the electromagnetic shielding material to be measured. The viscoelasticity of the measurement sample is measured in the dynamic viscoelasticity measuring device under the following measurement conditions. The storage modulus E' at 50°C (E' at 50°C) is obtained by this measurement. (Measurement conditions) Chuck distance: 10 mm Measurement temperature range: -50°C to 100°C Heating rate: 2°C / min Sampling rate: 3 seconds Measurement frequency: 1 Hz

[0051] <Method for Manufacturing Electromagnetic Wave Shielding Material> (Method for Forming a Magnetic Layer) The magnetic layer described above can be produced, for example, by applying a magnetic layer-forming composition and drying the resulting coating layer. The magnetic layer-forming composition may contain the components described above and may further optionally contain one or more solvents. Examples of solvents include various organic solvents, such as ketone solvents like acetone, methyl ethyl ketone, and cyclohexanone; acetic acid ester solvents like ethyl acetate, butyl acetate, cellosolve acetate, propylene glycol monomethyl ether acetate, and carbitol acetate; carbitols like cellosolve and butyl carbitol; aromatic hydrocarbon solvents like toluene and xylene; and amide solvents like dimethylformamide, dimethylacetamide, and N-methylpyrrolidone. One solvent selected considering the solubility of the components used in preparing the magnetic layer-forming composition, or two or more solvents mixed in any proportion, can be used. The solvent content of the magnetic layer-forming composition is not particularly limited and should be determined considering the coatability of the magnetic layer-forming composition.

[0052] A composition for forming a magnetic layer can be prepared by mixing various components sequentially or simultaneously in any order. Furthermore, if necessary, dispersion can be performed using known dispersers such as ball mills, bead mills, sand mills, and roll mills, and / or stirring can be performed using known stirrers such as shaking stirrers.

[0053] The prevalence of magnetic particles with a 30° or greater angle in the magnetic layer formed by applying the magnetic layer-forming composition can be controlled by the shear rate during application. Increasing the shear rate tends to decrease the prevalence of magnetic particles with a 30° or greater angle in the formed magnetic layer. Conversely, decreasing the shear rate tends to increase the prevalence of magnetic particles with a 30° or greater angle in the formed magnetic layer.

[0054] The magnetic layer-forming composition can be applied, for example, to a support. The application can be carried out using known coating equipment such as a blade coater or die coater. The application can be performed using a so-called roll-to-roll method or a batch method.

[0055] Examples of supports to which the magnetic layer-forming composition is applied include films of various resins such as polyester (PET), polyethylene terephthalate (PEN), polycarbonate (PC), acrylic (PMMA), cyclic polyolefins, triacetylcellulose (TAC), polyether sulfide (PES), polyether ketone, and polyimide. For these resin films, refer to paragraphs 0081 to 0086 of Japanese Patent Application Publication No. 2015-187260. As the support, a support that has been subjected to a release treatment by a known method on the surface to which the magnetic layer-forming composition is applied (the surface to be coated) can be used. One form of the release treatment is the formation of a release layer. For the release layer, refer to paragraph 0084 of Japanese Patent Application Publication No. 2015-187260. Alternatively, a commercially available pre-released resin film can be used as the support. By using a support with a release treatment on the surface to be coated, the magnetic layer and the support can be easily separated after film formation.

[0056] In one embodiment, a metal layer is used as a support, and the magnetic layer-forming composition is directly applied onto the metal layer. By directly applying the magnetic layer-forming composition onto the metal layer, the magnetic layer can be formed directly on the metal layer without the need for other layers.

[0057] The coated layer formed by applying the magnetic layer-forming composition can be dried by known methods such as heating or blowing hot air. The drying process can be carried out under conditions that allow the solvent contained in the magnetic layer-forming composition to volatilize. For example, the drying process can be carried out in a heated atmosphere with an ambient temperature of 80 to 150°C for 1 minute to 2 hours.

[0058] Regarding a composition for forming a magnetic layer, which includes magnetic particles and a resin in addition to a curing agent, the curing agent can be described in the preceding text. The magnetic layer formed using such a composition can be cured with a curing agent at any stage. Depending on the type of curing agent, the curing treatment can be heat treatment or light irradiation treatment. For example, if the curing treatment is heat treatment, in one embodiment it can be performed before the pressurization treatment described later, and in another embodiment it can be performed after the pressurization treatment described later. According to the inventors' studies, when the heat treatment is performed after the pressurization treatment, there is a tendency for the permeability of the formed magnetic layer to increase. The heat treatment can be performed, for example, by holding the magnetic layer before or after the pressurization treatment in an environment with an ambient temperature of 35°C or higher (for example, 35°C to 150°C). The holding time can be, for example, 3 to 72 hours.

[0059] (Pressurization of magnetic layers) Magnetic layers can also be subjected to pressure treatment after film formation. By subjecting a magnetic layer containing magnetic particles to pressure treatment, the density of magnetic particles within the magnetic layer can be increased, resulting in higher magnetic permeability. Furthermore, magnetic layers containing flattened particles can achieve higher magnetic permeability through pressure treatment.

[0060] Pressurization can be performed by applying pressure in the thickness direction of the magnetic layer using a plate press, roll press, etc. A plate press places the object to be pressed between two flat press plates positioned vertically, and applies pressure to the object by bringing the two press plates together using mechanical or hydraulic pressure. A roll press passes the object to be pressed between rotating pressure rolls positioned vertically, and applies pressure by applying mechanical or hydraulic pressure to the pressure rolls during this process, or by making the distance between the pressure rolls smaller than the thickness of the object to be pressed.

[0061] The pressure during pressurization can be set arbitrarily. For example, in the case of a plate press, it can be set to, for example, 1 to 50 N (Newtons) / mm ２In the case of a roll press, for example, the linear pressure is 20 to 400 N / mm. The pressurization time can be set arbitrarily. When using a plate press, for example, it is 5 seconds to 4 hours. When using a roll press, the pressurization time can be controlled by the conveying speed of the object to be pressed, for example, the conveying speed is 10 cm / min to 200 m / min. The material of the press plate and pressurization roll can be arbitrarily selected from metal, ceramics, plastic, rubber, etc. During the pressurization process, it is also possible to perform a heating and pressurizing process by, for example, applying heat to both or one side of the press plate in a plate press or to one side of the rolls in a roll press. In the heating and pressurizing process, the magnetic layer can be softened by heating, thereby obtaining a high compression effect when pressure is applied. The heating temperature can be set arbitrarily, for example, between 50°C and 200°C. The above heating temperature can be the internal temperature of the press plate or roll. This temperature can be measured by a thermometer installed inside the press plate or roll. In one embodiment, heat treatment can be performed as a curing treatment for the curing agent before or after the heating and pressurizing treatment. Such heat treatment is as described above. After heating and pressurizing treatment in a plate press, for example, the magnetic layer can be removed by separating the press plates while the press plate is still hot. Alternatively, the press plates can be cooled by methods such as water cooling or air cooling while maintaining pressure, and then the press plates can be separated to remove the magnetic layer. In a roll press, the magnetic layer can be cooled by methods such as water cooling or air cooling immediately after pressing. It is also possible to repeat the pressurizing treatment two or more times. If the magnetic layer is formed on a release film, for example, the pressurizing treatment can be performed while the magnetic layer is laminated on the release film. Alternatively, the magnetic layer can be peeled off the release film and the pressurizing treatment can be performed on the magnetic layer alone.

[0062] (Bonding of metal and magnetic layers) Adjacent metal and magnetic layers can be directly bonded together, for example, by applying pressure and heat. A plate press, roll press, etc., can be used for bonding. During the bonding process, the magnetic layer softens, promoting contact with the surface of the metal layer, thereby bonding the two adjacent layers together. The pressure during bonding can be set arbitrarily. In the case of a plate press, for example, 1 to 50 N / mm ２ In the case of a roll press, for example, the linear pressure is 20 to 400 N / mm. The pressing time during crimping can be set arbitrarily. When using a plate press, for example, it is 5 seconds to 30 minutes. When using a roll press, it can be controlled by the conveying speed of the object to be pressed, for example, the conveying speed is 10 cm / min to 200 m / min. The temperature during crimping can be selected arbitrarily, for example, 50°C to 200°C. The above temperature during crimping can be, for example, the internal temperature of the press plate or roll.

[0063] The metal layer and the magnetic layer can also be bonded together by interposing an adhesive layer and / or bonding layer between them.

[0064] In the present invention and this specification, "adhesive layer" refers to a layer that has tackiness on its surface at room temperature. Here, "room temperature" refers to 23°C, and the room temperature described later with respect to the adhesive layer also refers to 23°C. Such a layer adheres to an object by its adhesive force when it comes into contact with the object. Tackiness generally refers to the property of exhibiting adhesive force in a short time after contact with an object with very light force. In the present invention and this specification, "having tackiness" means that the result in the inclined ball tack test specified in JIS Z 0237:2009 (measurement environment: temperature 23°C, relative humidity 50%) is No. 1 to No. 32. If other layers are laminated on the surface of the adhesive layer, for example, the surface of the adhesive layer exposed by peeling off the other layers can be subjected to the above test. If other layers are laminated on one surface and the other surface of the adhesive layer, the other layers on either surface can be peeled off.

[0065] As the adhesive layer, a film can be made by coating an adhesive layer-forming composition containing an adhesive such as an acrylic adhesive, a rubber adhesive, a silicone adhesive, or a urethane adhesive. The adhesive layer-forming composition can be applied, for example, to a support. The application can be carried out using known application equipment such as a blade coater or a die coater. The application can be carried out in a so-called roll-to-roll manner or in a batch manner. Examples of support materials to which the adhesive layer-forming composition is applied include films of various resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN) and other polyesters, polycarbonate (PC), polymethyl methacrylate (PMMA) and other acrylics, cyclic polyolefins, triacetylcellulose (TAC), polyether sulfide (PES), polyether ketone, and polyimide. As the support material, a support material can be used in which the surface to which the adhesive layer-forming composition is applied (the surface to be coated) has been subjected to a release treatment by a known method. One form of release treatment is the formation of a release layer. Alternatively, commercially available pre-released resin films can be used as the support material. By using a support with a release treatment applied to the surface to be coated, the adhesive layer and the support can be easily separated after film formation. An adhesive layer can be laminated onto the surface of a metal layer or magnetic layer by coating an adhesive layer-forming composition, in which the adhesive is dissolved and / or dispersed in a solvent, onto the metal layer or magnetic layer and drying it.

[0066] Furthermore, by overlapping a film-like adhesive layer with a metal layer or magnetic layer and applying pressure, the adhesive layer can be laminated onto the surface of the metal layer or magnetic layer.

[0067] To manufacture electromagnetic shielding materials having an adhesive layer, adhesive tape containing the adhesive layer can also be used. Double-sided tape can be used as the adhesive tape. Double-sided tape has adhesive layers on both sides of a support, and both adhesive layers may have tackiness at room temperature. Alternatively, adhesive tape with an adhesive layer on one side of the support can also be used. Examples of support materials include films, nonwoven fabrics, and paper made from various resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), acrylics such as polymethyl methacrylate (PMMA), cyclic polyolefins, triacetylcellulose (TAC), polyether sulfide (PES), polyether ketone, and polyimide. Commercially available adhesive tapes with adhesive layers on one or both sides of the support can be used, as can double-sided tapes manufactured by known methods.

[0068] In the present invention and this specification, "adhesive layer" means a layer that does not have tackiness on its surface at room temperature, and which, when heated and pressed against an adherend, flows and follows minute irregularities on the adherend surface, exhibiting adhesive force through an anchoring effect, or, when heated and pressed against an adherend, forms a chemical bond with the adherend surface through a chemical reaction, thereby exhibiting adhesive force. The adhesive layer can soften and / or undergo a chemical reaction upon heating. The above-mentioned "no tackiness" means that in the inclined ball tack test specified in JIS Z 0237:2009 (measurement environment: temperature 23°C, relative humidity 50%), ball No. 1 does not stop. If other layers are laminated on the surface of the adhesive layer, for example, the adhesive layer surface exposed by peeling off the other layers can be subjected to the above test. If other layers are laminated on one surface and the other surface of the adhesive layer, the other layers on either surface can be peeled off.

[0069] A film-like resin material can be used as the adhesive layer. Thermoplastic resins and / or thermosetting resins can be used as the resin material. Thermoplastic resins have the property of softening when heated, and when pressed against the adherend while heated, they flow and conform to minute irregularities on the adherend surface, exhibiting adhesive strength through an anchoring effect. The adhesive state can then be maintained by cooling. Thermosetting resins can undergo a chemical reaction when heated, and when heated in contact with the adherend, a chemical reaction occurs, forming a chemical bond with the adherend surface and exhibiting adhesive strength.

[0070] Examples of thermoplastic resins include polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polyvinyl acetate, polyurethane, polyvinyl alcohol, ethylene vinyl acetate copolymer, styrene-butadiene rubber, acrylonitrile-butadiene rubber, silicone rubber, olefin-based elastomers (PP), styrene-based elastomers, ABS resin, polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polycarbonate (PC), acrylics such as polymethyl methacrylate (PMMA), cyclic polyolefins, and triacetylcellulose (TAC). Examples of thermosetting resins include epoxy resins, phenolic resins, melamine resins, thermosetting urethane resins, xylene resins, and thermosetting silicone resins. It is preferable in terms of adhesion between the magnetic layer and the adhesive layer because the adhesive layer contains a resin whose main polymer skeleton is similar to that of the resin contained in the magnetic layer, thus increasing the compatibility between the resin in the magnetic layer and the resin contained in the adhesive layer. For example, it is preferable that the magnetic layer contains a urethane-bonded resin and the adhesive layer also contains a urethane-bonded resin.

[0071] The film-like resin material used as the adhesive layer may be a commercially available product or a film-like resin material prepared by a known method.

[0072] In one embodiment, an adhesive layer made of a film-like resin material can be laminated onto the surface of a metal layer or magnetic layer by coating a resin or resin precursor dissolved and / or dispersed in a solvent onto a metal layer or magnetic layer, and curing it by drying or polymerization. Alternatively, an adhesive layer can be formed by coating a support with a resin or resin precursor dissolved and / or dispersed in a solvent, curing it by drying or polymerization, and then peeling it off the support.

[0073] By overlapping a film-like adhesive layer with a metal layer or magnetic layer and applying pressure under heating, the adhesive layer can be laminated onto the surface of the metal layer or magnetic layer. Alternatively, by overlapping the magnetic layer (the object to be adhered) with the adhesive layer of a metal layer (which has an adhesive layer laminated on its surface) and applying pressure under heating, the metal layer and magnetic layer can be bonded together via the adhesive layer. Alternatively, by overlapping the metal layer (the object to be adhered) with the adhesive layer of a magnetic layer (which has an adhesive layer laminated on its surface) and applying pressure under heating, the metal layer and magnetic layer can be bonded together via the adhesive layer. The application of pressure under heating can be performed using a plate press, roll press, or the like, which have a heating mechanism.

[0074] Furthermore, as an example of an adhesive means, we can also mention the double-sided tape described in Japanese Patent Application Publication No. 2003-20453 as a silicone-based substrate-less double-sided tape.

[0075] General adhesive and bonding layers have extremely low electrical conductivity compared to metal layers, extremely low magnetic permeability compared to magnetic layers, and a relative permittivity only a few times that of air, while their characteristic impedance and propagation constant are similar to those of air. Therefore, using general adhesive and / or bonding layers does not affect the shielding performance of electromagnetic shielding materials, or the effect is negligibly small. The thickness of each layer of adhesive and bonding layers is not particularly limited and can be, for example, between 1 μm and 30 μm.

[0076] In one embodiment, the electromagnetic shielding material described above can be manufactured by following one or more of the following steps. However, the manufacturing method of the electromagnetic shielding material is not particularly limited.

[0077] The metal layer and the magnetic layer are bonded together using an adhesive or bonding layer formed in the form of a film.

[0078] The bonding of the metal layer and the magnetic layer is performed by forming a magnetic layer with an adhesive or bonding layer on its surface, and then bonding this magnetic layer to the metal layer via the adhesive or bonding layer.

[0079] The bonding of the metal layer and the magnetic layer is performed by forming a metal layer with an adhesive or bonding layer on its surface, and then bonding this metal layer to the magnetic layer via the adhesive or bonding layer.

[0080] The adhesive layer or bonding layer is directly coated onto the surface of the metal layer or magnetic layer.

[0081] A magnetic layer having an adhesive or bonding layer on its surface is formed by coating a release film with an adhesive or bonding layer, applying pressure to bond it to the magnetic layer, or applying heat and pressure to bond it to the magnetic layer, and then peeling off the release film.

[0082] A metal layer having an adhesive or bonding layer on its surface is formed by coating a release film with an adhesive or bonding layer, applying pressure to bond it to a magnetic layer, or applying heat and pressure to bond it to a metal layer, and then peeling off the release film.

[0083] The electromagnetic shielding material described above can be in any shape and size, such as a film (or sheet). For example, a film-like electromagnetic shielding material can be bent into any shape and incorporated into electronic components or electronic equipment.

[0084] [Electronic Components] One aspect of the present invention relates to an electronic component including the above-mentioned electromagnetic shielding material. Examples of the above-mentioned electronic component include various electronic components such as electronic components included in electronic devices such as mobile phones, personal digital assistants, and medical devices, semiconductor elements, capacitors, coils, and cables. The above-mentioned electromagnetic shielding material can be bent into any shape according to the shape of the electronic component and placed inside the electronic component, or it can be placed as a cover material that covers the outside of the electronic component. Alternatively, it can be processed into a cylindrical shape and placed as a cover material that covers the outside of a cable.

[0085] [Electronic Devices] One aspect of the present invention relates to electronic devices including the electromagnetic shielding material described above. Examples of such electronic devices include mobile phones, personal digital assistants, medical devices, and other electronic devices; electronic devices including various electronic components such as semiconductor elements, capacitors, coils, and cables; and electronic devices in which electronic components are mounted on a circuit board. Such electronic devices may include the electromagnetic shielding material as a component of the electronic components contained in them. Furthermore, the electromagnetic shielding material can be placed inside the electronic device, or as a cover material covering the outside of the electronic device. Alternatively, it can be processed into a cylindrical shape and used as a cover material covering the outside of a cable.

[0086] One example of how the above-mentioned electromagnetic shielding material can be used is to cover a semiconductor package on a printed circuit board with the electromagnetic shielding material. For example, "Electromagnetic Shielding Technology for Semiconductor Packages" (Toshiba Review Vol. 67 No. 2 (2012) P. 8) discloses a method for obtaining a high shielding effect by performing ground wiring by electrically connecting the side vias at the edge of the package substrate to the inner surface of the electromagnetic shielding material when covering a semiconductor package with the electromagnetic shielding material. In order to perform such wiring, it is desirable that the outermost layer on the electronic component side of the electromagnetic shielding material be a metal layer. In one embodiment, the above-mentioned electromagnetic shielding material can have one or both of its outermost layers be metal layers, making it suitable for use when performing the above-mentioned wiring.

[0087] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the embodiments shown in the examples.

[0088] [Urethane-containing resin for magnetic layer] The urethane-containing resin for the magnetic layer shown in Table 1 is the following resin. In Table 1, polyurethane resin is referred to as "polyurethane" and polyester urethane resin as "polyester urethane". The polyurethane resin is Nipponran 5120 manufactured by Tosoh Corporation. The polyester urethane resin is UR-6100 manufactured by Toyobo Co., Ltd.

[0089] [Example 1] <Preparation of composition for forming a magnetic layer (coating solution)> The following were added to a plastic bottle: Fe-Si-Al flattened magnetic particles (Sendust MFS-SUH, manufactured by MKT): 12 g Polyester urethane resin (UR-6100, manufactured by Toyobo Co., Ltd., solid content concentration 45% by mass): 6.7 g Polyfunctional isocyanate (Takenate D101E, manufactured by Mitsui Chemicals, Ltd., solid content concentration 75% by mass): 0.1 g Cyclohexanone: 25 g The mixture was mixed in a shaking stirrer for 12 hours to prepare the coating solution. The total mass of the magnetic layer formed from the prepared composition for forming a magnetic layer was taken as 100 parts by mass, and the content of the polyester urethane resin is as shown in Table 1.

[0090] <Magnetic Layer Preparation> (Deposition of Magnetic Layer) The coating solution was applied to the peeled surface of a peeled PET film (PET75-JOL manufactured by Nipper Co., Ltd.) using a blade coater with a coating gap of 200 to 600 μm. The shear rate during coating was as shown in Table 1. After coating, the film was dried for 30 minutes in a drying apparatus with an internal ambient temperature of 80°C to form a magnetic layer on the peeled PET film.

[0091] (Pressurization and heat treatment of the magnetic layer) The upper and lower press plates of a plate press (Mini Test Press manufactured by Toyo Seiki) are heated to 140°C (internal temperature of the press plates), and the magnetic layer from which the above-mentioned peeled PET film has been removed is sandwiched between two 1 mm thick Teflon® sheets, and subjected to a pressure of 30 N / mm between the upper and lower press plates. ２was held for 10 minutes under the applied pressure. While maintaining the pressure, the upper and lower press plates were cooled to 50°C (the internal temperature of the press plates), and then the magnetic layer was taken out from between the two Teflon (registered trademark) sheets. Thereafter, in order to cause a crosslinking reaction between the polyester urethane resin contained in the magnetic layer and the polyfunctional isocyanate, the magnetic layer was held in a drying apparatus with an internal atmospheric temperature of 60°C for 48 hours to perform heat treatment. Measurement samples for various measurements described later were cut out from a part of the magnetic layer obtained by applying the pressure treatment and the heat treatment in this manner.

[0092] <Preparation of Electromagnetic Wave Shielding Material> The magnetic layer obtained above was used as the magnetic layer, and a copper foil having a thickness of 20 µm (conforming to JIS H3100:2018 standard, alloy number C1020R-H, Cu content of 99.9 mass% or more) was used as the metal layer. Five layers of "copper foil (metal layer) / magnetic layer / copper foil (metal layer) / magnetic layer / copper foil (metal layer)" were stacked without interposing any other layer between two adjacent layers to prepare a laminate. The upper and lower press plates of a plate press (large hot press TA-200-1W manufactured by Yamamoto Iron Works Co., Ltd.) were heated to 140°C (the internal temperature of the press plates), the laminate was placed in the center of the press plates, and 4.66 N / mm ２ was held for 10 minutes under the applied pressure to thermocompress the copper foils and the magnetic layer. While maintaining the pressure, the upper and lower press plates were cooled to 50°C (the internal temperature of the press plates), and then the laminate was taken out from the plate press. Thus, the electromagnetic wave shielding material of Example 1 was obtained. The electromagnetic wave shielding material of Example 1 includes two multilayer structures of "copper foil (metal layer) / magnetic layer / copper foil (metal layer)".

[0093] <Measurement of Magnetic Permeability> A measurement sample with a size of 28 mm × 10 mm was cut out from the above magnetic layer, magnetic permeability measurement was performed using a magnetic permeability measuring apparatus (per01 manufactured by Keycom Corporation), and the magnetic permeability was obtained as the real part of complex relative permeability (μ') at a frequency of 3 MHz (measurement temperature: 25°C). The magnetic permeability obtained in this manner was 130.

[0094] <Measurement of Electrical Conductivity> A cylindrical main electrode with a diameter of 30 mm was connected to the negative terminal side of a digital super-insulation resistance meter (TR-811A, manufactured by Takeda Riken), and a ring electrode with an inner diameter of 40 mm and an outer diameter of 50 mm was connected to the positive terminal side. The main electrode and the ring electrode were placed on a sample piece of the magnetic layer cut to a size of 60 mm x 60 mm, and a voltage of 25 V was applied to both electrodes to measure the surface electrical resistivity of the magnetic layer alone. The electrical conductivity of the magnetic layer was calculated from the surface electrical resistivity and the following formula. The calculated electrical conductivity was 1.1 x 10⁻⁶. －２ The conductivity was S / m. The thickness used was the thickness of the magnetic layer, determined by the method described later. Electrical conductivity [S / m] = 1 / (Surface electrical resistivity [Ω] × Thickness [m])

[0095] <Measurement of the abundance of magnetic particles with a 30° or greater angle in the magnetic layer> The cross-section in the thickness direction of the electromagnetic shielding material was exposed. The cross-section was exposed using a cross-section polisher (JEOL SM-09010 model, acceleration voltage: 5kV). In the exposed cross-section, the abundance of magnetic particles with a 30° or greater angle in the magnetic layer was determined for a portion of one of the two magnetic layers contained in the electromagnetic shielding material, randomly selected, using the method described above. Since the two magnetic layers contained in the electromagnetic shielding material were manufactured using the same formulation and method, the abundance of magnetic particles with a 30° or greater angle in both magnetic layers is similar.

[0096] <Measurement of E' at 50°C for electromagnetic shielding material> A measurement sample measuring 28 mm in length and 10 mm in width was cut from the electromagnetic shielding material, and dynamic viscoelasticity measurements were performed using a Hitachi High-Tech Science Corporation DMS6100 dynamic viscoelasticity measuring device according to the measurement procedure described above. From the obtained measurement results, E' at 50°C in the 1 Hz dynamic viscoelasticity measurement was determined.

[0097] <Acquisition of Cross-Sectional Images of Electromagnetic Shielding Material> The following method was used to perform cross-sectional processing to expose the cross-section of the electromagnetic shielding material. The shielding material, cut to a size of 3 mm x 3 mm, was embedded in resin, and the cross-section of the shielding material was cut using an ion milling device (Hitachi High-Tech Corporation IM4000PLUS). The exposed cross-section of the shielding material was observed using a scanning electron microscope (Hitachi High-Tech Corporation SU8220) under conditions of an acceleration voltage of 2 kV and a magnification of 100x, and a backscattered electron image was obtained. Using the obtained image as a reference, the thickness of each of the two magnetic layers, the thickness of each of the three metal layers, and the total thickness of the shielding material were measured at five locations, with the scale bar as the reference. The arithmetic mean of each was taken as the thickness of each magnetic layer, the thickness of each metal layer, and the total thickness of the shielding material. The thickness of each magnetic layer was 30 μm, the thickness of each metal layer was 20 μm, and the total thickness of the electromagnetic shielding material was 120 μm.

[0098] <Acquisition of Cross-Sectional Image of Magnetic Layer> In the same manner as above, a cross-section of the electromagnetic wave shielding material of Example 1 was processed and exposed. A randomly selected region of the magnetic layer was observed using a scanning electron microscope (SU8220, Hitachi High-Tech Corporation) under conditions of an acceleration voltage of 2 kV and a magnification of 1000x to obtain a backscattered electron image.

[0099] <Measurement of Aspect Ratio of Magnetic Particles> Using the backscattered electron images obtained above, the aspect ratio of the magnetic particles was determined by the method described earlier, and flattened particles were identified from the aspect ratio values. When it was determined whether or not the magnetic layer contained flattened particles as magnetic particles, as described earlier, it was determined that the magnetic layer contained flattened particles. Furthermore, the average value (arithmetic mean) of the aspect ratios of all particles identified as flattened particles was calculated as the aspect ratio of the flattened particles contained in the magnetic layer. The calculated aspect ratio was 0.071.

[0100] <Evaluation of Shielding Performance (KEC Method)> The electromagnetic shielding material of Example 1 was subjected to vibration treatment by the following method. A vibration tester and the electromagnetic shielding material were placed in a chamber, and vibration treatment was performed for 72 hours using a sine wave with a frequency of 25 Hz and an amplitude of 1.5 mm. During the 72 hours of vibration treatment, the ambient temperature for vibration treatment was kept constant at 40°C. The shielding performance of the electromagnetic shielding material was evaluated before and after the above vibration treatment by the following method. The electromagnetic shielding material was placed between the antennas of a KEC method evaluation device including a signal generator, amplifier, a pair of magnetic field antennas, and a spectrum analyzer, and the ratio of the received signal strength with and without the electromagnetic shielding material (unit: dB (decibels)) was determined at frequencies from 100 kHz to 1 GHz, and this was defined as the shielding performance. This was done for the magnetic field antenna to determine the magnetic field shielding performance. KEC is an abbreviation for Kansai Electronics Industry Promotion Center. Table 1 shows the shielding performance of the electromagnetic shielding material before the vibration treatment described above, as "shielding performance before vibration treatment," and the shielding performance of the electromagnetic shielding material after the vibration treatment described above, as "shielding performance after vibration treatment."

[0101] [Examples 2-6, Comparative Examples 1-4] Electromagnetic shielding materials were manufactured and various evaluations were performed using the method described for Example 1, except that the items shown in Table 1 were changed as shown in Table 1. For the above examples and comparative examples, various thicknesses were measured using the methods described above. The thickness of each magnetic layer, the thickness of each copper foil (metal layer), and the total thickness of the shielding material were the same as those obtained for Example 1.

[0102] The results are shown in Table 1.

[0103]

[0104] The results shown in Table 1 confirm that the electromagnetic shielding materials of Examples 1 to 6 suppress the degradation of shielding performance due to vibration compared to the electromagnetic shielding materials of Comparative Examples 1 to 4.

[0105] One aspect of the present invention is useful in the technical fields of various electronic components and various electronic devices.

Claims

1. An electromagnetic wave shielding material having a magnetic layer containing magnetic particles, wherein, in the cross-section of the magnetic layer, when the angle of the surface of the magnetic layer is set to 0°, the proportion of magnetic particles tilted at 30° or more is 5% or more and 50% or less based on the number of particles.

2. The electromagnetic shielding material according to claim 1, wherein the storage modulus E' of the electromagnetic shielding material in a dynamic viscoelastic measurement at 1 Hz is 0.010 GPa or more and less than 10.000 GPa at 50°C.

3. The electromagnetic wave shielding material according to claim 1, wherein the magnetic layer further comprises a resin.

4. The electromagnetic wave shielding material according to claim 3, wherein the resin is a urethane bond-containing resin.

5. The electromagnetic wave shielding material according to claim 4, wherein the magnetic layer contains 13 to 30 parts by mass of a urethane bond-containing resin, with the total mass of the magnetic layer being 100 parts by mass.

6. The electromagnetic wave shielding material according to claim 1, wherein the magnetic layer is located between two metal layers.

7. The electromagnetic wave shielding material according to claim 1, comprising two or more multilayer structures having the magnetic layer between two metal layers, wherein in each multilayer structure, the magnetic layer is in direct contact with each of the two metal layers.

8. The electromagnetic shielding material according to claim 1, wherein the storage modulus E' of the electromagnetic shielding material in a dynamic viscoelastic measurement at 1 Hz is 0.010 GPa or more and less than 10.000 GPa at 50°C, and the magnetic layer contains 13 parts by mass or more and less than 30 parts by mass of a urethane bond-containing resin, with the total mass of the magnetic layer being 100 parts by mass, and the magnetic layer is located between two metal layers.

9. The electromagnetic wave shielding material according to claim 8, comprising two or more multilayer structures having the magnetic layer between two metal layers, wherein in each multilayer structure, the magnetic layer is in direct contact with each of the two metal layers.

10. An electronic component comprising an electromagnetic shielding material according to any one of claims 1 to 9.

11. Electronic equipment comprising an electromagnetic shielding material according to any one of claims 1 to 9.

Images