Electromagnetic shielding material, electronic component, and electronic device

Abstract

Provided is an electromagnetic shielding material comprising a magnetic layer that includes magnetic particles, wherein: the electromagnetic shielding material has at least one adjacent layer in direct contact with the magnetic layer; a maximum indentation depth dmax of the magnetic layer is 100-900 nm; and the maximum indentation depth dmax is determined by nanoindentation measurement using a Berkovich diamond indenter at a maximum load of 1500 μN, a loading time of 10 seconds, and an unloading time of 10 seconds.

Description

Electromagnetic wave shielding material, electronic component and electronic device

[0001] The present invention relates to an electromagnetic wave shielding material, an electronic component and an electronic device.

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

[0003] WO2024 / 004697

[0004] An electromagnetic wave shielding material can exhibit the performance of shielding electromagnetic waves (hereinafter also referred to as "electromagnetic wave shielding performance" or "shielding performance") by reflecting electromagnetic waves incident on the electromagnetic wave shielding material at the electromagnetic wave shielding material and / or attenuating the electromagnetic waves inside the electromagnetic wave shielding material.

[0005] As a usage form of the electromagnetic wave shielding material, there may be a usage form in which it is subjected to vibration after being incorporated into an electronic component or an electronic device. Therefore, an electromagnetic wave shielding material with little decrease in shielding performance after being subjected to vibration is desirable.

[0006] In view of the above, an object of one aspect of the present invention is to provide an electromagnetic wave shielding material in which a decrease in electromagnetic wave shielding performance after being subjected 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 there is at least one adjacent layer in direct contact with the magnetic layer, and the maximum indentation depth dmax of the magnetic layer is 100 nm or more and 900 nm or less, and the maximum indentation depth dmax is the maximum indentation depth determined by nanoindentation measurement using a diamond Berkovich indenter with a maximum load of 1500 μN, a loading time of 10 seconds and an unloading time of 10 seconds. [2] The electromagnetic wave shielding material according to [1], wherein the adjacent layer is on one surface side and the other surface side of the magnetic layer. [3] The electromagnetic wave shielding material according to [1] or [2], wherein the adjacent layer is a layer containing resin. [4] The electromagnetic wave shielding material according to any one of [1] to [3], wherein the magnetic layer is between two metal layers. [5] The electromagnetic wave shielding material according to [4], wherein the adjacent layer is located on one surface side and the other surface side of the magnetic layer, and the adjacent layer is located between each of the two metal layers and the magnetic layer. [6] The electromagnetic wave shielding material according to any one of [1] to [5], wherein the magnetic layer further comprises resin. [7] The electromagnetic wave shielding material according to any one of [1] to [6], wherein the adjacent layer is a resin-containing layer, the magnetic layer is located between the two metal layers, the adjacent layer is located on one surface side and the other surface side of the magnetic layer, the adjacent layer is located between each of the two metal layers and the magnetic layer, and the magnetic layer further comprises resin. [8] An electronic component comprising the electromagnetic wave shielding material according to any one of [1] to [7]. [9] An electronic device comprising the electromagnetic wave shielding material according to any one of [1] to [7].

[0008] According to one aspect of the present invention, it is possible to provide an electromagnetic shielding material in which the deterioration of electromagnetic shielding performance after being subjected to vibration is suppressed. Furthermore, according to one aspect of the present invention, it is possible to provide electronic components and electronic devices that include this electromagnetic shielding material.

[0009] Figure 1 shows an explanatory diagram of the indentation conditions for nanoindentation measurement (left) and an example of a load-displacement curve (right). Figure 2 is a schematic cross-sectional view of the electromagnetic shielding material of Example 1. Figure 3 shows a schematic diagram of the measurement point for the maximum indentation depth.

[0010] 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.

[0011] [Electromagnetic wave shielding material] One aspect of the present invention relates to an electromagnetic wave shielding material having a magnetic layer containing magnetic particles, wherein the material has at least one adjacent layer in direct contact with the magnetic layer, and the maximum indentation depth dmax of the magnetic layer is 100 nm or more and 900 nm or less. The maximum indentation depth dmax is the maximum indentation depth determined by nanoindentation measurement using a diamond Berkovich indenter with a maximum load of 1500 μN, a loading time of 10 seconds, and an unloading time of 10 seconds.

[0012] In recent years, electromagnetic shielding materials having a multilayer structure including a magnetic layer have been proposed (see, for example, WO2024 / 004697 (Patent Document 1)). However, in a multilayer structure, if air bubbles exist around foreign matter between the magnetic layer and adjacent layers, delamination may occur starting from the air bubbles while the electromagnetic shielding material is subjected to vibration. Also, if voids exist between the magnetic layer and adjacent layers, delamination may occur starting from the voids while the electromagnetic shielding material is subjected to vibration. In contrast, it is presumed that if the magnetic layer included in the multilayer structure is a magnetic layer with a maximum indentation depth dmax of 100 nm or more and 900 nm or less, the generation of air bubbles and voids can be suppressed. The inventors believe that this makes it possible to suppress the deterioration of the shielding performance of the electromagnetic shielding material after it is subjected to vibration. However, the present invention is not limited to the presumptions described herein.

[0013] <Maximum indentation depth dmax of the magnetic layer> In the present invention and this specification, the maximum indentation depth dmax of the magnetic layer is measured in the cross-section in the thickness direction of the magnetic layer. An electromagnetic shielding material cut to a size of 3 mm x 3 mm is embedded in resin, and a cross-sectional exposed sample is prepared by cutting the cross-section of the electromagnetic shielding material, including the cross-section in the thickness direction of the magnetic layer, using an ion milling device. As the ion milling device, Hitachi High-Tech Corporation's IM4000PLUS can be used. The maximum indentation depth dmax is the maximum indentation depth determined by nanoindentation measurement using a diamond Berkovich indenter with a maximum load of 1500 μN, a loading time of 10 seconds, and an unloading time of 10 seconds. Figure 1 shows an explanatory diagram of the indentation conditions for nanoindentation measurement (left figure) and an example of a load-displacement curve (right figure). "Maximum indentation depth" is the maximum value of the displacement. The measurement conditions are as follows in detail. As a measuring device, for example, a Bruker TI-950 nanoindenter can be used. A total of 100 measurement points will be used. The method for determining the measurement points will be described in the Examples section below. The arithmetic mean of the maximum indentation depth at the 80 measurement points (excluding the top 10 and bottom 10 points) will be defined as the maximum indentation depth dmax of the magnetic layer being measured. "d" is used as an abbreviation for "depth" and "max" is used as an abbreviation for "maximum". (Measurement conditions) Measurement environment: Temperature 23°C / Relative humidity 50% Load range: 0 to 1500 μN (during measurement) Maximum load: 1500 μN (set value in the measuring device) Indentation direction: Normal to the cross-section Loading speed: 150 μN / sec Unloading speed: 150 μN / sec

[0014] The maximum indentation depth dmax of the magnetic layer of the electromagnetic shielding material described above is 100 nm or more and 900 nm or less. As previously mentioned, it is presumed that the presence of air bubbles around foreign matter between the magnetic layer and the adjacent layer, and the presence of voids between the magnetic layer and the adjacent layer, can lead to a decrease in the shielding performance of the electromagnetic shielding material after it has been subjected to vibration. In contrast, a magnetic layer with a maximum indentation depth dmax of 100 nm or more is thought to be able to sufficiently embed foreign matter that has been mixed between the two layers when they are bonded together during the manufacturing process of the electromagnetic shielding material. As a result, the inventors presum that it is possible to suppress the generation of air bubbles around foreign matter between the magnetic layer and the adjacent layer. From the viewpoint of further suppressing the decrease in the shielding performance of the electromagnetic shielding material after it has been subjected to vibration by further suppressing the generation of air bubbles, the maximum indentation depth dmax of the magnetic layer is preferably 120 nm or more, and more preferably in the order of 140 nm or more, 160 nm or more, 180 nm or more, 200 nm or more, 250 nm or more, and 300 nm or more. On the other hand, a magnetic layer with a maximum indentation depth dmax of 900 nm or less can compress the air between the two layers when bonded with an adjacent layer during the manufacturing process of the electromagnetic shielding material, thus suppressing the formation of a gap between the magnetic layer and the adjacent layer. From the viewpoint of further suppressing the deterioration of the shielding performance of the electromagnetic shielding material after vibration by further suppressing the formation of a gap, the maximum indentation depth dmax of the magnetic layer is preferably 880 nm or less, and more preferably in the order of 860 nm or less, 840 nm or less, 820 nm or less, 800 nm or less, 780 nm or less, and 760 nm or less. The maximum indentation depth dmax of the magnetic layer can be controlled, for example, by the manufacturing conditions of the magnetic layer. Details on this will be described later.

[0015] The electromagnetic shielding material described above will be explained in more detail below.

[0016] <Magnetic Layer> The magnetic layer described above 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 a combination of two or more types can be used. 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".

[0017] (Metal Particles) In the present invention and this specification, "metal particles" include particles of pure metals consisting of a single metal element, and particles of alloys of one or more metal elements with one or more other metal elements and / or nonmetal elements. The metal particles may or may not be crystalline. That is, metal particles may be crystalline particles or amorphous particles. Examples of metal or nonmetal elements contained in metal particles include Ni, Fe, Co, Mo, Cr, Al, Si, B, P, etc. Metal particles may or may not contain components other than the constituent elements of the metal (including alloys). In addition to the constituent elements of the metal (including alloys), metal particles may contain in any proportion elements contained in additives that may be optionally added and / or elements contained in impurities that may be unintentionally mixed in during the manufacturing process of the metal particles. 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.

[0018] Examples of metal 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, and Permendur (Fe-Co alloy). Among these, Sendust is preferred because it exhibits high saturation magnetic flux density and relative permeability.

[0019] In one embodiment, a magnetic layer exhibiting high permeability (more specifically, the real part of the complex relative permeability) is preferred. 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'. Hereafter, the real part of the complex relative permeability at a frequency of 100 kHz will also be simply referred to as "permeability". Permeability can be measured using a commercially available permeability measuring device or a permeability measuring device with a known configuration. From the viewpoint of exhibiting even better electromagnetic wave shielding performance, it is preferable that the magnetic layer contained in the electromagnetic wave shielding material is a magnetic layer with a permeability (real part of the complex relative permeability at a frequency of 100 kHz) of 30 or more. The above permeability is more preferably 40 or higher, even more preferably 50 or higher, even more preferably 60 or higher, even more preferably 70 or higher, even more preferably 80 or higher, even more preferably 90 or higher, and even more preferably 100 or higher. Furthermore, the above permeability can be, for example, 200 or less, 190 or less, 180 or less, 170 or less, or 160 or less, and can exceed the values ​​exemplified herein.

[0020] From the viewpoint of forming a magnetic layer exhibiting high magnetic permeability, it is preferable that the magnetic particles are flattened 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.

[0021] As mentioned earlier, from the viewpoint of forming a magnetic layer that exhibits high magnetic permeability, it is preferable to arrange the flattened particles so that the direction of the long side is closer to parallel with the in-plane direction of the magnetic layer. From this point of view, the degree of orientation, which is the sum of the absolute value of the average orientation angle of the flattened particles with respect to the surface of the magnetic layer and the variance of the orientation angle, is preferably 30° or less, more preferably 25° or less, even more preferably 20° or less, and most preferably 15° or less. The degree of orientation can be, for example, 3° or more, 5° or more, or 10° or more, and can also be lower than the values ​​exemplified here. The method for controlling the degree of orientation will be described later.

[0022] In the present invention and this specification, the aspect ratio and orientation of the 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 an SEM (Scanning Electron Microscope) image of a randomly selected region of this cross-section. The imaging conditions are an acceleration voltage of 2 kV and a magnification of 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 parts as the boundary. The white parts (high-brightness parts) in the binarized image are identified as magnetic particles. For the obtained binarized image, cv2. The rotational circumscribed rectangle corresponding to the portion of each magnetic particle is obtained using the minAreaRect() function, and the long side length, short side length, and rotation angle are obtained as the return value of the cv2.minAreaRect() function. When determining the total number of magnetic particles included in the above binarized image, particles in which only a portion is included in the binarized image shall be included. For particles in which only a portion is included in the binarized image, the long side length, short side length, and rotation angle 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 shall be taken as the aspect ratio of each magnetic particle. In the present invention and this 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 above binarized image on a numerical basis, then the magnetic layer shall be determined to be a "magnetic layer containing flattened particles as magnetic particles". Furthermore, the "orientation angle" is determined from the rotation angle obtained above, as the rotation angle with respect to the horizontal plane (the surface of the magnetic layer). Particles with an aspect ratio of 0.20 or less obtained in the binarized image are identified as flattened particles. For the orientation angles of all flattened particles included in the binarized image, the sum of the absolute value of the mean (arithmetic mean) and the variance is calculated. This sum is defined as the "degree of orientation".Furthermore, the coordinates of the bounding rectangle are calculated using the cv2.boxPoints() function, and an image is created by superimposing the rotated bounding rectangle onto the original image using the cv2.drawContours() function. Rotated bounding rectangles that are clearly misdetected are excluded from the calculation of aspect ratio and orientation. In addition, 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. Such an aspect ratio is 0.20 or less, preferably 0.15 or less, and more preferably 0.10 or less. The above aspect ratio can also be, for example, 0.01 or more, 0.02 or more, or 0.03 or more.

[0023] The content of magnetic particles in the above magnetic layer can be, for example, 50% by mass or more, 60% by mass or more, 70% by mass or more, or 80% by mass or more, with respect to the total mass of the magnetic layer, and can also be, for example, 100% by mass or less, 98% by mass or less, or 95% by mass or less.

[0024] (Resin) The magnetic layer may contain magnetic particles and a resin. In the present invention and this specification, "resin" may be a homopolymer or copolymer. In a magnetic layer containing magnetic particles and a resin, the resin content may be, for example, 1 part by mass or more, 3 parts by mass or more, or 5 parts by mass or more per 100 parts by mass of magnetic particles, or 20 parts by mass or less, or 15 parts by mass or less.

[0025] Resins can act as binders in the magnetic layer. Examples of resins included in the magnetic layer include conventionally known thermoplastic resins, thermosetting resins, UV-curable resins, radiation-curable resins, rubber-based materials, and elastomers. Specific examples include polyester resins, polyethylene resins, polyvinyl chloride resins, polyvinyl butyral resins, polyurethane resins, cellulose resins, ABS (acrylonitrile-butadiene-styrene) resins, nitrile-butadiene rubbers, styrene-butadiene rubbers, epoxy resins, phenolic resins, amide resins, styrene elastomers, olefin elastomers, vinyl chloride elastomers, polyester elastomers, polyamide elastomers, polyurethane elastomers, and acrylic elastomers.

[0026] In addition to the above components, the magnetic layer may also contain one or more known additives such as curing agents, dispersants, stabilizers, and coupling agents in any amount.

[0027] The electromagnetic shielding material described above may contain only one magnetic layer, or two or more magnetic layers, with a maximum indentation depth dmax of 100 nm to 900 nm.

[0028] When the electromagnetic shielding material contains only one magnetic layer, the thickness of this single magnetic layer can be, for example, 5 μm or more, and from the viewpoint of further improving the shielding performance of the electromagnetic shielding material, it is preferable to have a thickness of 10 μm or more, and more preferably 20 μm or more. On the other hand, the thickness of this single magnetic layer can be, for example, 100 μm or less or 90 μm or less, and from the viewpoint of improving the moldability of the electromagnetic shielding material, it is preferable to have a thickness of less than 90 μm, more preferably 80 μm or less, and even more preferably 70 μm or less. When the electromagnetic shielding material contains two or more magnetic layers, the thickness of each of these two or more magnetic layers (i.e., the thickness per layer) can be, for example, 5 μm or more, and from the viewpoint of further improving the shielding performance of the electromagnetic shielding material, it is preferable to have a thickness of 10 μm or more, and more preferably 20 μm or more. On the other hand, the thickness of this single magnetic layer can be, for example, 100 μm or less or 90 μm or less, and it is preferable to have a thickness of less than 90 μm, and more preferably 80 μm or less. The thicknesses of two or more magnetic layers can be the same or different. The thickness of each layer in the electromagnetic shielding material can be determined by imaging a cross-section exposed by a known method using a scanning electron microscope (SEM), and taking the arithmetic mean of the thicknesses of five randomly selected points in the resulting SEM image.

[0029] <Adjacent Layers> The magnetic layer included in the electromagnetic wave shielding material, having a maximum indentation depth dmax of 100 nm to 900 nm, is in direct contact with the adjacent layer on one surface side and / or the other surface side. In the present invention and this specification, "direct contact" of two layers means that the two layers are adjacent to each other without any other layers in between. As described above, the inventors surmise that a magnetic layer with a maximum indentation depth dmax of 100 nm to 900 nm can suppress the generation of bubbles and voids between the magnetic layer and the adjacent layer.

[0030] One form of the adjacent layer is a resin-containing layer. A "resin-containing layer" is a layer containing one or more types of resin. Another form of the adjacent layer is a metal layer. The resin-containing layer and the metal layer will be explained in detail below.

[0031] <Resin-containing layer> (Adhesive layer) An adhesive layer can be considered as one form of a resin-containing layer. In the present invention and this specification, "adhesive layer" refers to a layer that has tackiness on its surface at room temperature. With respect to tackiness, "room temperature" 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 layer 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 layer on either surface can be peeled off.

[0032] As the adhesive layer, a film can be used which has been processed into shape by coating it with an adhesive-forming composition containing an adhesive such as an acrylic adhesive, a rubber adhesive, a silicone adhesive, or a urethane adhesive. The adhesive-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-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-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 release-treated resin films can be used as the support material. By using a support whose surface to be coated has been subjected to a release treatment, the adhesive layer and the support can be easily separated after film formation. The adhesive layer can be formed by coating the surface to be coated with an adhesive layer-forming composition in which the adhesive is dissolved and / or dispersed in a solvent and drying it. Alternatively, an adhesive tape containing an adhesive layer can be used. As an adhesive tape, for example, double-sided tape can be used. Double-sided tape has adhesive layers on both sides of the support. In addition, an adhesive tape having an adhesive layer on one side of the support can also be used. Examples of supports include films, nonwoven fabrics, and paper made of 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.As adhesive tapes having an adhesive layer on one or both sides of the support, commercially available products can be used, and adhesive tapes manufactured by known methods can also be used.

[0033] The thickness of the adhesive layer is not particularly limited; the thickness of each layer can be, for example, 1 μm or more and 30 μm or less.

[0034] (Adhesive Layer) An adhesive layer can also be considered as one form of a layer containing resin. In the present invention and this specification, "adhesive layer" refers to a layer in which a liquid or gel-like adhesive solidifies after contact with an adherend through a change in state such as drying and curing, and at that time exhibits adhesion to the adherend through an anchoring effect, physical interaction, or the formation of chemical bonds. In one form, the adhesive layer may be a layer that does not have tackiness on its surface at room temperature. The adhesive contains a resin that solidifies after drying or curing. Examples of such resins include vinyl acetate resin, ethylene vinyl acetate resin, epoxy resin, cyanoacrylate resin, acrylic resin, polyurethane resin, chloroprene rubber, styrene butadiene rubber, etc. These resins may be liquid or gel-like in nature, or a solid resin may dissolve in a solvent to become liquid or gel-like. Examples of solvents contained in adhesives include water, ketone-based solvents such as acetone, methyl ethyl ketone, and cyclohexanone; acetic acid ester-based solvents such as ethyl acetate, butyl acetate, cellosolve acetate, propylene glycol monomethyl ether acetate, and carbitol acetate; carbitols such as cellosolve and butyl carbitol; aromatic hydrocarbon-based solvents such as toluene and xylene; amide-based solvents such as dimethylformamide, dimethylacetamide, and N-methylpyrrolidone; alcohol-based solvents such as ethanol, methanol, and propanol; and halogen-based solvents such as dichloromethane, trichloroethylene, and dichlorofluoroethane.

[0035] The thickness of the adhesive layer is not particularly limited; the thickness of each layer can be, for example, 1 μm or more and 30 μm or less.

[0036] (Resin Layer) As one form of a layer containing resin, a resin layer can also be mentioned. In the present invention and this specification, "resin layer" means a resin film formed from a thermoplastic resin such as a synthetic resin, wherein the resin film has a film-like structure on its own and does not tack at room temperature. Examples of thermoplastic resins contained in the resin film include polyethylene (PE) resin, polypropylene (PP) resin, polyvinyl chloride (PVC) resin, polystyrene (PS) resin, vinyl acetate resin, polyurethane resin, polyvinyl alcohol resin, ethylene vinyl acetate resin, styrene-butadiene rubber, acrylonitrile butadiene rubber, silicone rubber, olefin-based elastomer (PP), styrene-based elastomer, ABS (acrylonitrile-butadiene-styrene) resin, polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polycarbonate (PC) resin, acrylic resins such as polymethyl methacrylate (PMMA), cyclic polyolefins, triacetylcellulose (TAC), and various other resins.

[0037] The resin layer can be bonded to a metal layer or a magnetic layer via an adhesive or bonding layer. Furthermore, since the resin layer contains a thermoplastic resin, it has the property of softening when heated. When pressed against an object while heated, it flows and conforms to minute irregularities on the surface of the object, exhibiting adhesive force through an anchoring effect. The bonded state can then be maintained upon cooling. Therefore, in one embodiment, the resin layer can be bonded to other layers without the need for an adhesive or bonding layer.

[0038] The thickness of the resin layer is preferably 10 μm or more, and more preferably 12 μm or more, as a thickness per resin layer. The thickness of the resin layer is preferably 250 μm or less, more preferably 230 μm or less, even more preferably 210 μm or less, and even more preferably 190 μm or less, as a thickness per resin layer.

[0039] <Metal Layer> The electromagnetic shielding material described above may include one or more metal layers. In one embodiment, the electromagnetic shielding material may have a magnetic layer between two metal layers, the magnetic layer having a maximum indentation depth dmax of 100 nm to 900 nm. It is presumed that having a multilayer structure in which a magnetic layer is sandwiched between two metal layers is preferable for improving the electromagnetic shielding performance of the electromagnetic shielding material, particularly its shielding performance against magnetic fields. In one embodiment, in a multilayer structure in which a magnetic layer is sandwiched between two metal layers, one or more other layers, including at least an adjacent layer, may be interposed between one or both of the two metal layers and the magnetic layer. For example, an adjacent layer (or one or more other layers) may be located between each of the two metal layers and the magnetic layer. In another embodiment, in a multilayer structure in which a magnetic layer is sandwiched between two metal layers, one or both of the two metal layers may be an adjacent layer (i.e., a layer in direct contact with the magnetic layer).

[0040] In the present invention and this specification, "metal layer" means a layer containing a metal. The 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.

[0041] If the electromagnetic shielding material has a multilayer structure in which a magnetic layer is sandwiched between two metal layers, the electromagnetic shielding material may contain one or more such multilayer structures, or two or more. That is, the electromagnetic shielding material may contain at least two metal layers, three or more metal layers, at least one magnetic layer, or two or more magnetic layers. In one embodiment, the two or more metal layers included in the electromagnetic shielding material may have the same composition and thickness, and in another embodiment, they may have different compositions and / or thicknesses. This is also true when the electromagnetic shielding material includes two or more magnetic layers, and when the electromagnetic shielding material includes two or more other layers, such as the resin layer described above.

[0042] The metal layer contained in the electromagnetic shielding material described above may be a layer containing one or more metals selected from the group consisting of various pure metals and various alloys. The metal layer can exert an attenuation effect in the electromagnetic shielding material. This is preferable from the viewpoint of improving the shielding performance of the electromagnetic shielding material. The attenuation effect is greater the larger the propagation constant, and the propagation constant is greater the higher the electrical conductivity, so it is preferable that the metal layer contains a metal element with high electrical conductivity. From this viewpoint, it is preferable that the metal layer contains a pure metal of Ag, Cu, Au, or Al, or an alloy containing any of these as 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, 99.8% by mass or less) in the 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.

[0043] The purity of the metal in the metal layer, that is, the content of the metal in the metal layer, in one embodiment, may be 99.0% by mass or more, 99.5% by mass or more, or 99.8% by mass or more relative to 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, a pure metal or alloy processed into a sheet shape can be used as the metal layer. For example, a commercially available metal foil or a metal foil produced by a known method can be used as the metal layer. For pure Cu metal, sheets of various thicknesses (so-called copper foils) are commercially available. For example, such copper foil can be used as the metal layer. Based on the production method, copper foils include electrolytic copper foil obtained by depositing copper foil on a cathode through electroplating, and rolled copper foil 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 Al, sheets of various thicknesses (so-called aluminum foil) are commercially available. For example, such aluminum foil can be used as the metal layer.

[0044] From the viewpoint of economic efficiency, high electrical conductivity, and weight reduction of electromagnetic wave shielding material, the metal layer is preferably a metal layer containing a metal selected from the group consisting of Al, Mg, and Cu, and more preferably a layer containing a metal selected from the group consisting of Al, Mg, and Cu as its main component. The main component of a metal layer is the component with the highest proportion by mass. In a layer containing a metal selected from the group consisting of Al, Mg, and Cu as its main component, Al, Mg, or Cu is the component with the highest proportion by mass in this layer. Such a layer may contain only one, two, or three metals from Al, Mg, and Cu. From one or more of the above viewpoints, the metal layer is more preferably a metal layer with a metal content of 80.0% by mass or more of the metal selected from the group consisting of Al, Mg, and Cu, and even more preferably a metal layer with a metal content of 90.0% by mass or more of the metal selected from the group consisting of Al, Mg, and Cu. A metal layer containing at least Al from among Al, Mg, and Cu may have an Al content of 80.0% by mass or more, or an Al content of 90.0% by mass or more. A metal layer containing at least Mg from among Al, Mg, and Cu may have an Mg content of 80.0% by mass or more, or an Mg content of 90.0% by mass or more. A metal layer containing at least Cu from among Al, Mg, and Cu may have a Cu content of 80.0% by mass or more, or a Cu content of 90.0% by mass or more. The content of the metal selected from the group consisting of Al, Mg, and Cu, the Al content, the Mg content, and the Cu content can each be, for example, 100% by mass or less, or 99.9% by mass or less. The content of the metal selected from the group consisting of Al, Mg, and Cu, the Al content, the Mg content, and the Cu content are each percentages of the total mass of the metal layer.

[0045] Regarding the thickness of the metal layer, from the viewpoint of further improving the workability of the metal layer and the shielding performance of the electromagnetic wave shielding material, the thickness per layer is preferably 4 µm or more, more preferably 5 µm or more, and still more preferably 10 µm or more. On the other hand, from the viewpoint of workability of the metal layer, the thickness per layer is preferably 200 µm or less, more preferably 100 µm or less, and still more preferably 50 µm or less. In the above electromagnetic wave shielding material, the plurality of metal layers may have the same thickness or different thicknesses.

[0046] In one embodiment, in the electromagnetic wave shielding material, one of the outermost layers or both of the outermost layers may be a metal layer. This point can contribute to the fact that the electromagnetic wave shielding material can exhibit high shielding performance against magnetic field waves in a low frequency region around 100 kHz to 1 MHz. Further, having at least one outermost layer of the electromagnetic wave shielding material being a metal layer can also contribute to suppressing the occurrence of edge peeling in a molded product obtained by molding processing. In one embodiment, one or both outermost layers of the electromagnetic wave shielding material may be a metal layer that sandwiches a magnetic layer together with another metal layer.

[0047] <Specific Examples of Layer Configuration> The total number of magnetic layers included in the electromagnetic shielding material is one or more, and may be one, two or more, or for example, four or fewer. When the electromagnetic shielding material includes two or more magnetic layers, it is preferable that the maximum indentation depth dmax of some or all of the two or more magnetic layers is 100 nm or more and 900 nm or less, and the maximum indentation depth dmax of all layers is 100 nm or more and 900 nm or less. The electromagnetic shielding material may include, for example, a total of 1 to 12 layers containing resin. The total number of resin layers included in the electromagnetic shielding material (preferably resin layers having the thickness described above) may be, for example, one to four layers. The total number of layers selected from the group consisting of adhesive layers and bonding layers included in the electromagnetic shielding material may be, for example, one to four layers or one to eight layers. The total number of metal layers included in the electromagnetic shielding material is zero or one or more, and may be two or more, for example, two to five layers.

[0048] In one embodiment, a multilayer structure in which a magnetic layer is sandwiched between two metal layers allows the magnetic layer to be in direct contact with both metal layers. In this case, specific examples of the layer configuration of the electromagnetic shielding material can be given below. Example A1: "metal layer / magnetic layer / metal layer" Example A2: "metal layer / magnetic layer / metal layer / magnetic layer / metal layer" Example A3: "metal layer / magnetic layer / metal layer / magnetic layer / metal layer / magnetic layer / metal layer / metal layer" In an electromagnetic shielding material that includes two or more multilayer structures having a magnetic layer between two metal layers, for example, as in Example A2 and Example A3, the metal layer sandwiching the magnetic layer in one multilayer structure can also be the metal layer sandwiching the magnetic layer in another multilayer structure. In the electromagnetic shielding material, the total number of multilayer structures having a magnetic layer between two metal layers can be, for example, one to four. The total number of the above multilayer structures is one in Example A1, two in Example A2, and three in Example A3. It is preferable that the total number of the above-mentioned multilayer structures be two or more (for example, two, three, or four) from the viewpoint of further improving the shielding performance of the electromagnetic wave shielding material. In the above, the symbol " / " means that the layer described to the left of this symbol and the layer described to the right are in direct contact without any other layers in between. This point is also the same in the following description unless otherwise specified.

[0049] In another embodiment, a multilayer structure having a magnetic layer between two metal layers may have one or more layers containing resin between one or both of the two metal layers and the magnetic layer. In the above multilayer structure, one of the two metal layers may be adjacent to the magnetic layer without any other layers in between, and there may be one or more layers containing resin between the other metal layer and the magnetic layer. Alternatively, the above multilayer structure may also have one or more layers containing resin between each of the two metal layers and the magnetic layer.

[0050] The above multilayer structure may include an adhesive layer and / or bonding layer between the resin layer and the metal layer. In one embodiment, the adhesive layer and / or bonding layer may be included between the resin layer and the magnetic layer in the above multilayer structure. In another embodiment, the resin layer and the magnetic layer may be in direct contact with each other in the above multilayer structure. That is, the resin layer and the magnetic layer may be adjacent to each other without any other layers in between.

[0051] Examples of the arrangement of the "magnetic layer," "metal layer," "resin layer," and "adhesive layer or bonding layer" in the electromagnetic shielding material described above include the following. In the following examples, the "adhesive layer" may include a support, and the "adhesive layer" may be an adhesive tape having adhesive layers on one or both sides of the support. For example, as in Example B3, a metal layer sandwiching one magnetic layer may also be a metal layer sandwiching another magnetic layer. For example, in Example B3, metal layer 2 is one of the two metal layers sandwiching magnetic layer 1, and is also the other of the two metal layers sandwiching magnetic layer 2. Also, in Example B3, one outermost layer of the electromagnetic shielding material is metal layer 1 that sandwiches magnetic layer 1 together with metal layer 2, and the other outermost layer of the electromagnetic shielding material is metal layer 3 that sandwiches magnetic layer 2 together with metal layer 2. Example B1: "Metal layer 1 / Adhesive layer 1 or adhesive layer 1 / Resin layer 1 / Magnetic layer 1 / Resin layer 2 / Adhesive layer 2 or adhesive layer 2 / Metal layer 2" Example B2: "Metal layer 1 / Adhesive layer 1 or adhesive layer 1 / Resin layer 1 / Magnetic layer 1 / Metal layer 2 / Adhesive layer 2 or adhesive layer 2 / Resin layer 2" Example B3: "Metal layer 1 / Adhesive layer 1 or adhesive layer 1 / Resin layer 1 / Magnetic layer 1 / Resin layer 2 / Adhesive layer 2 or adhesive layer 2 / Metal layer 2 / Adhesive layer 3 or adhesive layer 3 / Resin layer 3 / Magnetic layer 2 / Resin layer 4 / Adhesive layer 4 or adhesive layer 4 / Metal layer 3" Example B4: "Metal layer 1 / Adhesive layer 1 or adhesive layer 1 / Resin layer 1 / Magnetic layer 1 / Metal layer 2 / Adhesive layer 2 or adhesive layer 2 / Resin layer 2 / Magnetic layer 2 / Resin layer 3 / Adhesive layer 3 or adhesive layer 3 / Metal layer 3" Example B5: "Metal layer 1 / Adhesive layer 1 or adhesive layer 1 / Resin layer 1 / Magnetic layer 1 / Metal layer 2 / Adhesive layer 2 or adhesive layer 2 / Resin layer 2 / Magnetic layer 2 / Metal layer 3 / Adhesive layer 3 or adhesive layer 3 / Resin layer 3" Example B6: "Metal layer 1 / Adhesive layer 1 or adhesive layer 1 / Resin layer 1 / Magnetic layer 1 / Metal layer 2 / Magnetic layer 2 / Resin layer 2 / Adhesive layer 2 or adhesive layer 2 / Metal layer 3" Example B7: "Metal layer 1 / Adhesive layer 1 or adhesive layer 1 / Resin layer 1 / Magnetic layer 1 / Resin layer 2 / Adhesive layer 2 or adhesive layer 2 / Metal layer 2 / Magnetic layer 2 / Resin layer 3 / Adhesive layer 3 or adhesive layer 3 / Metal layer 3" Example B9: "Resin layer 1 / Adhesive layer 1 or bonding layer 1 / Metal layer 1 / Magnetic layer 1 / Metal layer 2 / Adhesive layer 2 or bonding layer 2 / Resin layer 2"

[0052] <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 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 or two or more solvents selected considering the solubility of the components used in preparing the magnetic layer-forming composition can be mixed in any ratio and 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.

[0053] 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.

[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. The application speed is not particularly limited.

[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, a laminated structure of a metal layer and a magnetic layer can be manufactured in a single step. In another embodiment, a resin-containing layer is used as a support, and the magnetic layer-forming composition is directly applied onto the resin-containing layer. By directly applying the magnetic layer-forming composition onto the resin-containing layer, a laminated structure of a resin-containing layer and a magnetic layer can be manufactured in a single step.

[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] The degree of orientation of the flattened particles described above can be controlled by the type of solvent, amount of solvent, viscosity, and coating thickness of the magnetic layer forming composition. For example, if the boiling point of the solvent is low, convection occurs due to drying, which tends to increase the degree of orientation. If the amount of solvent is low, physical interference between adjacent flattened particles tends to increase the degree of orientation. On the other hand, if the viscosity is low, rotation of the flattened particles is more likely to occur, which tends to decrease the degree of orientation. Reducing the coating thickness tends to decrease the degree of orientation. Furthermore, applying pressure, as described later, can contribute to reducing the degree of orientation. By adjusting the various manufacturing conditions described above, the degree of orientation of the flattened particles can be controlled within the range described above.

[0059] (Pressurization of magnetic layer) The magnetic layer can also be subjected to pressure treatment after film formation. By pressurizing a magnetic layer containing magnetic particles, the density of magnetic particles within the magnetic layer can be increased, resulting in higher magnetic permeability. Furthermore, in magnetic layers containing flattened particles, the degree of orientation can be reduced by pressure treatment, resulting in higher magnetic permeability. In addition, the maximum indentation depth of the magnetic layer can be controlled by the pressure treatment conditions of the magnetic layer.

[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 a plate press, for example, 1 to 50 N (Newtons) / mm ２ For example, in the case of a roll press machine, the load capacity is 3 to 100 N / mm. ２The value of the maximum indentation depth dmax of the magnetic layer tends to decrease as the pressure applied during pressurization increases. When using a plate press, the pressurization time can be set arbitrarily, for example, from 5 seconds to 60 minutes. When using a roll press, the peripheral speed of the roll can be set arbitrarily, for example, from 0.25 to 10 m / min. The material of the press plate and pressurization roll can be arbitrarily selected from metal, ceramics, plastic, rubber, etc. During pressurization, it is also possible to apply heat to both or one side of the press plates of a plate press or to one side of the rolls of a roll press. Heating can soften the magnetic layer, thereby obtaining a high compression effect when pressure is applied. The temperature during heating can be set arbitrarily, for example, from 50°C to 200°C. The above-mentioned temperature during heating can be the internal temperature of the press plate or roll. Such a temperature can be measured by a thermometer installed inside the press plate or roll. After heating and pressing in a plate press, the magnetic layer can be removed by separating the press plates while they are still hot, for example. Alternatively, the press plates can be cooled by water cooling, air cooling, or other methods while maintaining pressure, and then separated to remove the magnetic layer. In a roll press, the magnetic layer can be cooled by water cooling, air cooling, or other methods immediately after pressing. It is also possible to repeat the pressing process two or more times. The value of the maximum indentation depth dmax of the magnetic layer tends to decrease as the number of pressing processes increases. When the magnetic layer is deposited on a release film, it can be pressed while laminated on the release film, for example. Alternatively, the magnetic layer can be peeled off the release film and pressed as a single layer.

[0062] (Bonding of various layers) Adhesive layers or bonding layers can be used to bond various layers. The adhesive layers and bonding layers are as described above. In addition, in the above electromagnetic wave shielding material, two layers that are in direct contact can be bonded together by applying pressure and heat, for example. A plate press, a roll press, etc. can be used for bonding. For example, when a magnetic layer is placed as a layer that is in direct contact with an adjacent layer, the magnetic layer softens during the bonding process, promoting contact with the surface of the adjacent layer, thereby bonding the magnetic layer and the adjacent layer without the need for other layers in between. 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 arbitrarily selected, for example, 20°C or higher and 200°C or lower. The above-mentioned temperature during crimping can be, for example, the internal temperature of the press plate or roll. In the crimping process of the magnetic layer described above, the magnetic layer and the adjacent layer can also be bonded by performing the crimping process after placing the adjacent layer on the magnetic layer.

[0063] The electromagnetic shielding material described above can be incorporated into electronic components or electronic devices in any shape. The electromagnetic shielding material can be in sheet form, and its size is not particularly limited. In this invention and specification, "sheet" is synonymous with "film". Furthermore, the electromagnetic shielding material can be a three-dimensional molded product obtained by three-dimensionally molding a sheet-like electromagnetic shielding material, or it can be a sheet-like electromagnetic shielding material for three-dimensional molding. Various molding methods such as die press molding, vacuum forming, and pressure forming can be used as the three-dimensional molding method. Regarding the molding method, molding performed without heating the object to be molded and / or the mold, or by heating without raising the temperature too much, is generally called cold forming. In one embodiment, the electromagnetic shielding material can exhibit excellent moldability in cold forming and is suitable for cold forming such as deep drawing and stretching. Deep drawing is a molding method in which a sheet-like object to be molded is pressed using a pair of female and male molds to form various bottomed containers of various shapes such as cylinders, rectangular tubes, and cones. In contrast, stretch molding is a method of forming a molded product from a sheet-like material in which a curved surface protrudes from a flat surface. Stretch molding can be performed using only a male mold without a female mold. Deep drawing is broadly classified into deep drawing and shallow drawing. Shallow drawing produces molded products with shallow depths, while deep drawing produces molded products with greater depths (for example, deeper than the diameter of a cylinder or cone, or the length of one side of a pyramid). The electromagnetic shielding material described above can be an electromagnetic shielding material that is resistant to breakage when formed by such three-dimensional molding methods. Known techniques can be applied to the three-dimensional molding methods.

[0064] [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, for example, be three-dimensionally molded into any shape according to the shape of the electronic component and placed inside the electronic component, or it can be three-dimensionally molded into the shape of a cover material that covers the outside of the electronic component and placed as a cover material. Alternatively, it can be three-dimensionally molded into a cylindrical shape and placed as a cover material that covers the outside of a cable.

[0065] [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, 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 formed into a cylindrical shape and used as a cover material covering the outside of a cable.

[0066] 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. If the electromagnetic shielding material has one or both outermost layers that are metal layers, it can be suitably used when performing the above-mentioned wiring.

[0067] 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. Unless otherwise specified, the following steps were carried out at room temperature of 20 to 25°C.

[0068] [Example 1] <Preparation of coating solution (composition for forming a magnetic layer)> 100 g of Fe-Si-Al flattened particles (Sendust MFS-SUH manufactured by MKT Corporation), 12 g of polystyrene polybutadiene block copolymer (manufactured by Sigma-Aldrich Japan), and 205 g of cyclohexanone were added to a plastic bottle, and the mixture was shaken in a shaking stirrer for 1 hour to prepare the coating solution.

[0069] <Fabrication of Magnetic Layer> (Deposition of Magnetic Layer) Two PET films were cut from a PET film roll with a thickness of 100 μm. A coating solution was applied to one of the two PET films using a blade coater with a coating gap of 300 μm, and dried in a drying apparatus with an internal ambient temperature of 80°C for 30 minutes to form a sheet-shaped magnetic layer.

[0070] (Pressurization of the magnetic layer) The upper and lower rolls of a roll press machine (SA-602 manufactured by Tester Industries) were heated to 110°C (internal temperature of the rolls), and the laminate, in which the other of the two PET films was placed on top of the magnetic layer on the PET film, was passed between the upper and lower rolls at a peripheral speed of 1 m / min (nip width: 1 mm) and the pressure shown in Table 1 was applied five times (this number is referred to as the "number of treatments"). In this way, a laminate in which a magnetic layer was sandwiched between two PET films was obtained.

[0071] <Fabrication of Electromagnetic Shielding Material> A sample piece for permeability measurement was cut from a portion of the above laminate. After cutting the sample piece, a laminate measuring 154 mm x 154 mm was cut from the laminate after bonding each of the PET films on the top and bottom surfaces to a 5 μm thick double-sided tape (NeoFix 5 S2 manufactured by Nichiei Shinka Co., Ltd.). A copper foil measuring 150 mm x 150 mm with a thickness of 12 μm (compliant with JIS H3100:2018 standard, alloy number C1100R, copper content of 99.90 mass% or more) was bonded to each of the double-sided tapes on the top and bottom surfaces of this laminate. In this way, an electromagnetic shielding material consisting of seven layers was obtained: a metal layer, an adhesive layer, a PET film, a magnetic layer, a PET film, an adhesive layer, and a metal layer. In the fabricated electromagnetic shielding material, each of the two PET films is an adjacent layer that is in direct contact with the magnetic layer. In the fabricated electromagnetic shielding material, as described above, the magnetic layer is larger than the copper foil, so the magnetic layer protrudes 2 mm from the copper foil on all four sides, and the two layers of copper foil do not come into contact. Figure 2 is a schematic cross-sectional view of the electromagnetic shielding material of Example 1. In the figure, "PET" refers to PET film. Note that Figure 2 and the other drawings are schematic diagrams, and the relative sizes of the various layers shown in the figures (thickness, etc.) do not differ from the actual relative sizes. Two electromagnetic shielding materials were fabricated; one was used to evaluate the electromagnetic shielding performance described later, and the other was used for other measurements.

[0072] <Measurement of Magnetic Permeability of the Magnetic Layer> Since the influence of the PET film on the magnetic permeability is slight, a 28 mm x 10 mm rectangular sample piece was cut from a laminate consisting of two PET films with a magnetic layer sandwiched between them, and used as the sample piece for measuring the magnetic permeability of the magnetic layer. The magnetic permeability of this sample piece was measured using a magnetic permeability measuring device (per01, manufactured by Keycom Co., Ltd.), and the magnetic permeability of the magnetic layer was determined as the real part (μ') of the complex ratio magnetic permeability at a frequency of 100 kHz. The thickness of the magnetic layer obtained by the method described later was input to the magnetic permeability measuring device. The determined magnetic permeability was 151.

[0073] <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 of Example 1. The electromagnetic shielding material, cut to a size of 3 mm x 3 mm, was embedded in resin, and the cross-section of the electromagnetic shielding material was cut using an ion milling device (Hitachi High-Tech Corporation IM4000PLUS). The exposed cross-section of the electromagnetic 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. From the obtained image, the thickness of each layer was measured at five randomly selected locations using a scale bar as a reference, and the arithmetic mean of these measurements was taken as the thickness of each layer. The thickness of the magnetic layer was 28 μm, the thickness of each PET film was 99 μm, the thickness of each double-sided tape was 5 μm, and the thickness of each metal layer was 12 μm.

[0074] <Measurement of Aspect Ratio of Magnetic Particles and Orientation Degree of Flattened Particles> In the cross-section of the electromagnetic wave shielding material of Example 1, which was exposed by cross-sectional processing using the method described above, 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, and a backscattered electron image was obtained. Using the backscattered electron image obtained above, the aspect ratio of the magnetic particles was determined using the method described above, and flattened particles were identified from the value of the aspect ratio. When it was determined whether or not the magnetic layer contained flattened particles as magnetic particles, as described above, it was determined that the magnetic layer contained flattened particles. Furthermore, when the orientation degree of the magnetic particles identified as flattened particles was determined using the method described above, it was found to be 12°. In addition, 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.

[0075] <Measurement of Maximum Indentation Depth dmax of Magnetic Layer> A cross-sectional sample was prepared by performing cross-sectional processing to expose the cross-section of the electromagnetic shielding material of Example 1 using the method described above. A Bruker Nanoindenter TI-950 was used as the measuring device, and the maximum indentation depth at each of the 100 measurement points was measured according to the measurement method and conditions described above. The measurement was performed at a total of 100 points in the cross-section of the magnetic layer, with 5 points in the thickness direction at 3 μm intervals symmetrically from the center line and 20 points in the width direction at 10 μm intervals. Figure 3 shows a schematic diagram of the measurement points for the maximum indentation depth. The arithmetic mean of the maximum indentation depth at the 80 measurement points, excluding the top 10 and bottom 10 points of the measured data, was taken as the maximum indentation depth dmax of the magnetic layer being measured. If the thickness of the magnetic layer is 12 μm or less and it is not possible to take 5 measurement points in the thickness direction at 3 μm intervals, the interval of the measurement points in the thickness direction should be set to 3 μm, and the number of measurement points in the width direction should be increased to a total of 100 measurement points. For example, for a magnetic layer with a thickness of 10 μm, a total of 100 measurement points can be taken: 4 points in the thickness direction and 25 points in the width direction.

[0076] [Examples 2-5, Comparative Examples 1 and 2] Except for the pressure and number of treatment cycles shown in Table 1, the electromagnetic shielding material was fabricated and the maximum indentation depth dmax of the magnetic layer was measured using the method described for Example 1.

[0077] <Evaluation of Electromagnetic Shielding Performance (KEC Method)> The following vibration treatment was performed on each electromagnetic shielding material in the examples and comparative examples. 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 electromagnetic shielding performance of each electromagnetic shielding material was evaluated before and after the above vibration treatment using the following method. The electromagnetic shielding material was placed between the antennas of the KEC method evaluation apparatus, which includes 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 used 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 "initial shielding performance," and the shielding performance of the electromagnetic shielding material after the vibration treatment described above, as "shielding performance after vibration treatment."

[0078]

[0079] The results shown in Table 1 confirm that the electromagnetic shielding materials of Examples 1 to 5 show a suppression of the degradation of electromagnetic shielding performance after vibration compared to the electromagnetic shielding materials of Comparative Examples 1 and 2.

[0080] One aspect of the present invention is useful in the technical field of various electronic components and various electronic devices.

Claims

1. An electromagnetic wave shielding material having a magnetic layer containing magnetic particles, wherein the material has at least one adjacent layer in direct contact with the magnetic layer, and the maximum indentation depth dmax of the magnetic layer is 100 nm or more and 900 nm or less, and the maximum indentation depth dmax is the maximum indentation depth determined by nanoindentation measurement using a diamond Berkovich indenter with a maximum load of 1500 μN, a loading time of 10 seconds and an unloading time of 10 seconds.

2. The electromagnetic wave shielding material according to claim 1, wherein the adjacent layer is located on one surface side and the other surface side of the magnetic layer.

3. The electromagnetic wave shielding material according to claim 1, wherein the adjacent layer is a layer containing resin.

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

5. The electromagnetic wave shielding material according to claim 4, wherein the adjacent layer is located on one surface side and the other surface side of the magnetic layer, and the adjacent layer is located between each of the two metal layers and the magnetic layer.

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

7. The electromagnetic wave shielding material according to claim 1, wherein the adjacent layer is a layer containing resin, the magnetic layer is located between two metal layers, the adjacent layer is located on one surface side and the other surface side of the magnetic layer, the adjacent layer is located between each of the two metal layers and the magnetic layer, and the magnetic layer further contains resin.

8. An electronic component comprising an electromagnetic shielding material according to any one of claims 1 to 7.

9. Electronic device comprising an electromagnetic shielding material according to any one of claims 1 to 7.

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