Electromagnetic wave shield material, electronic component, and electronic apparatus

Abstract

Provided are: an electromagnetic wave shield material that has a magnetic layer containing magnetic particles, the magnetic layer having a scratch mark cross-sectional area of not less than 0.08 μm2 and not more than 1.25 μm2; and an electronic component and an electronic apparatus that include the electromagnetic wave shield material.

Description

Electromagnetic wave shielding materials, electronic components and electronic equipment

[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 been attracting attention as materials for reducing the effects of electromagnetic waves in various electronic components and electronic devices. For example, Patent Document 1 discloses a component mounting substrate covered with an electromagnetic wave shielding material containing magnetic particles (referred to as an "electromagnetic wave shielding layer" in Patent Document 1) (see paragraph 0109, Table 1, etc. of Patent Document 1).

[0003] JP 2018-129498 A

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

[0005] Incidentally, electromagnetic wave shielding materials may be used in a manner in which they are exposed to vibrations after being incorporated into electronic components or electronic devices, and therefore it is desirable for the electromagnetic wave shielding material to exhibit minimal deterioration in shielding performance after being exposed to vibrations.

[0006] In view of the above, an object of one aspect of the present invention is to provide an electromagnetic wave shielding material that is suppressed from deteriorating in electromagnetic wave shielding performance after being subjected to vibration.

[0007] One aspect of the present invention is as follows: [1] An electromagnetic wave shielding material having a magnetic layer containing magnetic particles, wherein the scratch cross-sectional area of ​​the magnetic layer is 0.08 μm ２ 1.25 μm or more ２An electromagnetic wave shielding material that is the following: [2] The electromagnetic wave shielding material according to [1], which has the magnetic layer between two metal layers. [3] The electromagnetic wave shielding material according to [2], which has one or more layers containing a resin between the magnetic layer sandwiched between the two metal layers and one or both of the two metal layers. [4] The electromagnetic wave shielding material according to any one of [1] to [3], wherein the magnetic layer further contains a resin. [5] The scratch cross-sectional area of ​​the magnetic layer is 0.10 μm ２ 1.00 μm or more ２ [6] The electromagnetic wave shielding material according to any one of [1] to [4], wherein the magnetic layer is disposed between two metal layers, the magnetic layer further contains a resin, and the scratch cross-sectional area of ​​the magnetic layer is 0.10 μm ２ 1.00 μm or more ２ The electromagnetic shielding material according to any one of [1] to [5], which is the following: [7] The electromagnetic shielding material according to [6], which has one or more layers containing a resin between the magnetic layer sandwiched between the two metal layers and one or both of the two metal layers. [8] An electronic component comprising the electromagnetic shielding material according to any one of [1] to [7]. [9] An electronic device comprising the electromagnetic 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 wave shielding material that suppresses deterioration of electromagnetic wave shielding performance after being subjected to vibration, and also to provide electronic components and electronic devices that include this electromagnetic wave shielding material.

[0009] FIG. 1 is an explanatory diagram of measuring the cross-sectional shape of a magnetic layer. FIG. 2 is a schematic diagram showing a change in load during a scratching operation. FIG. 3 is a schematic diagram of a cross-section of a magnetic layer on which scratches have been formed by a scratching operation. FIG. 4 is a schematic diagram of a differential image. FIG. 5 is a schematic diagram for explaining test conditions. FIG. 6 is an example of a cross-sectional curve. FIG. 7 is a schematic cross-sectional diagram of a multilayer laminate included in the electromagnetic wave shielding material of Example 1. FIG. 8 is a schematic cross-sectional diagram of the electromagnetic wave shielding material of Example 1. FIG. 9 is an explanatory diagram of a method for measuring thermal conductivity.

[0010] In the present invention and this specification, the term "electromagnetic wave shielding material" refers to a material that can exhibit shielding performance against electromagnetic waves of at least one frequency or at least a part of a frequency band. "Electromagnetic waves" include magnetic waves and electric waves. An "electromagnetic wave shielding material" can be a material that can exhibit shielding performance against one or both of magnetic waves of at least one frequency or at least a part of a frequency band, and electric waves of at least one frequency or at least a part of a frequency band.

[0011] The thickness of each layer included in the electromagnetic shielding material and the thickness of the covering material can be determined by taking an image of a cross section exposed by a known method using a scanning electron microscope (SEM) and then calculating the arithmetic mean of the thicknesses at five randomly selected points in the resulting SEM image.

[0012] [Electromagnetic Wave Shielding Material] One aspect of the present invention is an electromagnetic wave shielding material having a magnetic layer containing magnetic particles, wherein the scratch cross-sectional area of ​​the magnetic layer is 0.08 μm ２ 1.25 μm or more ２ The present invention relates to the following electromagnetic wave shielding material.

[0013] The inventors believe that by suppressing the occurrence of minute localized damage in the magnetic layer while the electromagnetic shielding material is subjected to vibration, it is possible to suppress the deterioration of the shielding performance of the electromagnetic shielding material after it is subjected to vibration. In this regard, it is presumed that if large voids exist in the magnetic layer, these voids may become the starting point for minute localized damage within the magnetic layer. In contrast, if the scratch cross-sectional area is 1.25 μm ２ The inventors believe that the magnetic layers described below contain few or no such coarse voids. Furthermore, even in magnetic layers in which minute localized damage originating from coarse voids is unlikely to occur, if there are areas in the magnetic layer where magnetic particles are too close to each other, it is presumed that minute localized damage may occur in the magnetic layer due to interference between the magnetic particles while being subjected to vibration. In contrast, in magnetic layers with a scratch cross-sectional area of ​​0.08 μm ２The present inventors believe that in the magnetic layer described above, the magnetic particles are spaced apart to an appropriate degree, making interference between the magnetic particles unlikely to occur, although the present invention is not limited to the speculations described in this specification.

[0014] <Scratch Cross-Sectional Area of ​​Magnetic Layer> The "scratch cross-sectional area" of the magnetic layer in the present invention and this specification is determined by the following method.

[0015] (1) Preparation of cross-section exposed samples: A piece of electromagnetic shielding material cut into a size of 3 mm x 3 mm is embedded in resin, and a cross section of the electromagnetic shielding material, including a cross section in the thickness direction of the magnetic layer, is cut using an ion milling device. An IM4000PLUS manufactured by Hitachi High-Tech Corporation can be used as the ion milling device. In this way, three cross-section exposed samples are prepared from the electromagnetic shielding material to be measured.

[0016] (2) Measuring the Shape of the Magnetic Layer Cross Section Before Scratching For each of the three cross-section exposed samples prepared in (1) above, the shape of the magnetic layer cross section exposed on the sample before scratching is measured using nanoindentation. A Bruker Triboindenter TI-950 can be used as the measuring device for nanoindentation measurements. The same diamond Berkovich indenter is used for measuring the magnetic layer cross-section shape and for the scratching operation described below. The position at which the indenter contacts the exposed magnetic layer cross section is any position within the range of the cross section exposed by the ion milling device in the width direction of the magnetic layer, and near the center of the magnetic layer in the thickness direction of the magnetic layer. The indenter is brought into contact with the magnetic layer cross section with a vertical load of 1 μN, and the indenter is scanned over an area of ​​15.0 μm × 15.0 μm to measure the shape of the magnetic layer cross section. The number of measurement lines is 256, the number of data points per line is 256, and the scanning frequency per line is 0.5 Hz. Hereinafter, the direction of each measurement line will be referred to as the "left-right direction," and the direction perpendicular to the measurement line will be referred to as the "up-down direction." FIG. 1 is an explanatory diagram of the shape measurement of the magnetic layer cross section. In the above-described shape measurement of the magnetic layer cross section, both a height image (hereinafter referred to as the "right scan image") obtained by scanning the measurement line to the right (right scan) and a height image (hereinafter referred to as the "left scan image") obtained by scanning the measurement line to the left (left scan) are obtained, as shown in FIG. 1(a), for example. FIG. 1(a) shows the magnetic layer cross section viewed from a direction perpendicular to the cross section, and the left and right views of FIG. 1(a) show the same region scanned to the right and left, respectively. Using image analysis software, the height values ​​of the right scan image and the left scan image at each point in the height image are compared, and an image (hereinafter referred to as the "corrected image") using the smaller height value is calculated (e.g., FIG. 1(b)). As the image analysis software, ImageJ, which is published by the National Institutes of Health (NIH), can be used. In this way, a corrected image of the cross-sectional shape of the magnetic layer before the scratching operation is obtained.

[0017] (3) Scratching of Magnetic Layer Cross Section After measuring the cross-sectional shape of the magnetic layer as described in (2) above, the cross section of the magnetic layer was scratched at room temperature of 20 to 25°C for each of the three exposed cross-section samples. Figure 2 is a schematic diagram showing the load change during the scratching operation. In Figure 2, the vertical load is represented as a negative load. Figure 3 is a schematic diagram of the cross section of the magnetic layer on which scratches were formed by the scratching operation. The scratching start point was defined as a position 2.5 μm below the topmost point in the vertical direction near the center of the area (15.0 μm × 15.0 μm) where the cross-sectional shape before the scratching operation was measured, and the scratching end point was defined as a position 10.0 μm below the scratching start point. The scratching operation was performed by contacting the indenter with a vertical load of 2 μN at a position 3.0 μm above the scratching start point, applying a load to the cross section of the magnetic layer. Specifically, a vertical load of 2 μN was applied at a scanning speed of 1.5 μm / s to the scratch start point, followed by a linear downward scan of 3.0 μm. The horizontal movement was stopped at the scratch start point, and the vertical load was increased to 1000 μN at a rate of 200 μN / s. Once the load reached 1000 μN, the vertical load was increased to 1000 μN at a scanning speed of 0.67 μm / s for a distance of 10.0 μm from the scratch start point to the scratch end point (corresponding to "constant load scratch" in FIG. 2). Upon reaching the scratch end point, the horizontal movement was stopped, and the vertical load was reduced to 2 μN at a rate of 200 μN / s. The vertical load was then reduced to 2 μN at a scanning speed of 1.5 μm / s for a distance of 3.0 μm from the scratch end point. By the above scratching operation, scratches are formed on the cross section of the magnetic layer, for example as shown in FIG.

[0018] (4) Measurement of the Shape of the Magnetic Layer Cross Section After Scratching For each of the three exposed cross-section samples, after the scratching operation described in (3) above, the shape of the magnetic layer cross section after scratching was measured under the same conditions in the same area as the area where the shape of the magnetic layer cross section before scratching was measured. In this case, as described above, both a height image obtained by scanning to the right (right scan image) and a height image obtained by scanning to the left (left scan image) were acquired, and the height values ​​of the right scan image and the left scan image were compared at each point of the height image, and an image (corrected image) using the smaller height value was calculated. The corrected images obtained before and after scratching were compared, and if the relative position shift caused by sample drift was less than 10 px (pixels), the relative position shift was manually corrected, and an image (hereinafter referred to as a "difference image") was calculated by subtracting the corrected image before scratching from the corrected image after scratching (hereinafter referred to as the "height change amount"). Figure 4 is a schematic diagram of a difference image. If the deviation in relative position caused by sample drift is 10 px or more, the measurement results for that region are excluded from the measurement results for calculating the scratch cross-sectional area of ​​the magnetic layer of the electromagnetic shielding material being measured (5) described below. Figure 5 is a schematic diagram for explaining test conditions. Figure 5(a) is a schematic diagram showing the scratch location during the scratching operation. Figure 5(b) is a schematic diagram showing the "base height calculation region" described below. Figure 5(c) is a schematic diagram showing the "cross-sectional curve acquisition region" described below. The region within 2.2 μm from the top edge (the edge on the scratch start side in the scratching direction), within 1.7 μm from the bottom edge, within 4.1 μm from the left edge, and within 4.1 μm from the right edge of the region where the cross-sectional shape was measured is defined as the "base height calculation region" (see Figure 5(b)). The arithmetic mean of the height change within the base height calculation region of the differential image is calculated as the "base height," and an image is calculated by subtracting the base height value from the entire differential image (hereinafter referred to as the "base height-corrected differential image"). The region from 3.25 μm to 8.88 μm from the top edge of the base height-corrected differential image is defined as the "primary profile curve acquisition region" (see FIG. 5C). A primary profile is acquired by calculating the arithmetic mean of the height change in the vertical direction (width 5.63 μm) at each horizontal position for the primary profile curve acquisition region of the base height-corrected differential image. FIG. 6 shows an example of a primary profile curve.The sum of values ​​obtained by multiplying the absolute value of the height change amount for the cross-sectional curve by the distance in the left-right direction between adjacent data points is calculated as the "cross-sectional area of ​​the scratch."

[0019] (5) Calculation of the Scratch Cross-Section Area of ​​the Magnetic Layer of the Electromagnetic Shielding Material to be Measured The above measurements are performed in six measurement regions for each of the three exposed-section samples, and measurement results are obtained for each measurement region. The distance between different measurement regions is set to 150 μm or more. However, if the measurement results for regions where the relative position shift caused by sample drift during differential image calculation is 10 px or more are excluded as described above, measurement results for a total of six measurement regions other than those regions are obtained to calculate the scratch cross-section area. In this way, a total of 18 scratch cross-section areas are calculated for the three exposed-section samples, and their arithmetic average is used as the scratch cross-section area of ​​the magnetic layer of the electromagnetic shielding material to be measured.

[0020] The scratch cross-sectional area of ​​the magnetic layer of the electromagnetic wave shielding material is set to 0.08 μm from the viewpoint of suppressing a decrease in the electromagnetic wave shielding performance of the electromagnetic wave shielding material after being subjected to vibration. ２ 1.25 μm or more ２ From this viewpoint, the scratch cross-sectional area of ​​the magnetic layer of the electromagnetic wave shielding material is 0.09 μm or less. ２ It is preferable that the thickness is 0.10 μm or more. ２ More preferably, it is 0.15 μm or more. ２ or more, 0.20μm ２ From the above viewpoint, the scratch cross-sectional area of ​​the magnetic layer of the electromagnetic wave shielding material is more preferable in the above order. ２ Preferably, it is 1.15 μm or less. ２ Below, 1.10 μm ２ Below, 1.05μm ２ Below, 1.00μm ２ Below, 0.90μm ２ Below, 0.85μm ２ Below, 0.80μm ２ Below, 0.75μm ２ Below, 0.70μm ２ Below, 0.65 μm ２ Below, 0.60μm ２Below, 0.55 μm ２ Below, 0.50 μm ２ Below, 0.45μm ２ The scratch cross-sectional area of ​​the magnetic layer can be controlled, for example, by the method for preparing the magnetic layer-forming composition, as will be described in detail below.

[0021] The electromagnetic wave shielding material will be described in more detail below.

[0022] <Magnetic Layer> The magnetic layer is a layer containing magnetic particles. The magnetic particles can be one 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. Metal particles generally have a saturation magnetic flux density about two to three times that of ferrite particles, and therefore can maintain relative permeability without magnetic saturation even under strong magnetic fields, thereby demonstrating 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 is considered to be a "magnetic layer."

[0023] (Metal Particles) In the present invention and this specification, the term "metal particles" includes 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 non-metal elements. Metal particles may or may not be crystalline. That is, metal particles may be crystalline particles or amorphous particles. Examples of metal or non-metal 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 elements contained in optional additives and / or elements contained in impurities that may be unintentionally mixed in during the manufacturing process of the metal particles, at any content. In the metal particles, the content of the 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.

[0024] Examples of metal particles include particles of sendust (Fe—Si—Al alloy), permalloy (Fe—Ni alloy), molybdenum permalloy (Fe—Ni—Mo alloy), Fe—Si alloy, Fe—Cr alloy, Fe-containing alloy generally called iron-based amorphous alloy, Co-containing alloy generally called cobalt-based amorphous alloy, alloy generally called nanocrystalline alloy, iron, permendur (Fe—Co alloy), etc. Among these, sendust is preferred because it exhibits high saturation magnetic flux density and relative permeability.

[0025] In one embodiment, a magnetic layer exhibiting high magnetic permeability (more specifically, the real part of complex relative magnetic permeability) is preferred. When complex relative magnetic permeability is measured using a magnetic permeability measuring device, the real part μ' and the imaginary part μ" are usually displayed. In this invention and this specification, the real part of complex relative magnetic permeability refers to this real part μ'. Hereinafter, the real part of complex relative magnetic permeability at a frequency of 100 kHz will also be simply referred to as "magnetic permeability". Magnetic permeability can be measured using a commercially available magnetic permeability measuring device or a magnetic permeability measuring device with a known configuration. From the perspective of being able to exhibit even better electromagnetic wave shielding performance, it is preferred that the magnetic layer included in the electromagnetic wave shielding material be a magnetic layer with a magnetic permeability (real part of complex relative magnetic permeability at a frequency of 100 kHz) of 30 or more. The magnetic permeability is more preferably 40 or more, even more preferably 50 or more, even more preferably 60 or more, even more preferably 70 or more, even more preferably 80 or more, even more preferably 90 or more, and even more preferably 100 or more. The magnetic permeability can be, for example, 200 or less, 190 or less, 180 or less, 170 or less, or 160 or less, and can also exceed the values ​​exemplified here.

[0026] From the viewpoint of forming a magnetic layer exhibiting high magnetic permeability, the magnetic particles are preferably particles having a flat shape (flat-shaped particles). By arranging the long side direction of the flat-shaped particles so that they are more nearly parallel to the in-plane direction of the magnetic layer, the long side direction of the particles is more aligned with the vibration direction of the electromagnetic waves incident perpendicular to the electromagnetic wave shielding material, thereby reducing the demagnetizing field, and the magnetic layer can exhibit higher magnetic permeability. In the present invention and this specification, "flat-shaped particles" refers to particles having an aspect ratio of 0.20 or less. The aspect ratio of flat-shaped particles is preferably 0.15 or less, more preferably 0.10 or less. The aspect ratio of flat-shaped 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 flat by flattening using a known method. For details on the flattening process, see, for example, the description in JP 2018-131640 A, including the descriptions in paragraphs 0016 and 0017 and Examples of the same publication. An example of a magnetic layer exhibiting high magnetic permeability is a magnetic layer containing flat particles of sendust.

[0027] As described above, from the viewpoint of forming a layer exhibiting high magnetic permeability as a magnetic layer, it is preferable to arrange the long side direction of the flat-shaped particles so that it is closer to parallel to the in-plane direction of the magnetic layer.From this point of view, the orientation degree, which is the sum of the absolute value of the average orientation angle of the flat-shaped particles relative 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 even more preferably 15° or less.The orientation degree 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 orientation degree will be described later.

[0028] In the present invention and this specification, the aspect ratio of the magnetic particles and the degree of orientation are determined by the following method. A cross section of the magnetic layer is exposed by a known method. A cross section image of a randomly selected region of this cross section is obtained as an SEM (Scanning Electron Microscope) image. The imaging conditions are an acceleration voltage of 2 kV and a magnification of 1000x, and the SEM image is obtained as a backscattered electron image. The second argument is set to 0 using the cv2.imread() function of the image processing library OpenCV4 (manufactured by Intel Corporation) to read in grayscale, and a binarized image is obtained using the cv2.threshold() function, with the intermediate brightness between the high-brightness and low-brightness areas as the boundary. White areas (high-brightness areas) in the binarized image are identified as magnetic particles. The obtained binarized image is subjected to cv2.imread(). A rotated circumscribed rectangle corresponding to each magnetic particle portion is calculated using the minAreaRect() function, and the long side length, short side length, and rotation angle are calculated as the return values ​​of the cv2.minAreaRect() function. When calculating the total number of magnetic particles contained in the binarized image, particles in which only a portion of the particle is included in the binarized image are also included. For particles in which only a portion of the particle is included in the binarized image, the long side length, short side length, and rotation angle are calculated for the portion included in the binarized image. The ratio of the short side length to the long side length calculated in this manner (short side length / long side length) is used as the aspect ratio of each magnetic particle. In the present invention and this specification, if the number of magnetic particles identified as flat-shaped particles with an aspect ratio of 0.20 or less is 10% or more by number of the total number of magnetic particles contained in the binarized image, the magnetic layer is determined to be a "magnetic layer containing flat-shaped particles as magnetic particles." Furthermore, from the rotation angle determined above, the "orientation angle" is determined as the rotation angle relative to the horizontal plane (surface of the magnetic layer). Particles with an aspect ratio of 0.20 or less determined in the binarized image are identified as flat-shaped particles. The sum of the absolute value of the average value (arithmetic mean) and the variance of the orientation angles of all flat-shaped particles contained in the binarized image is determined. The sum thus determined is the "degree of orientation."The coordinates of the circumscribed rectangle are calculated using the cv2.boxPoints() function, and an image is created by overlaying the rotated circumscribed rectangle on the original image using the cv2.drawContours() function. Any rotated circumscribed rectangles that are clearly misdetected are excluded from the calculation of the aspect ratio and degree of orientation. The average value (arithmetic mean) of the aspect ratios of particles identified as flat-shaped particles is used as the aspect ratio of the flat-shaped particles contained in the magnetic layer to be measured. This aspect ratio is 0.20 or less, preferably 0.15 or less, and more preferably 0.10 or less. The aspect ratio can be, for example, 0.01 or more, 0.02 or more, or 0.03 or more.

[0029] The content of magnetic particles in the magnetic layer can be, for example, 50% by weight or more, 60% by weight or more, 70% by weight or more, or 80% by weight or more, relative to the total weight of the magnetic layer, and can be, for example, 100% by weight or less, 98% by weight or less, or 95% by weight or less.

[0030] In one embodiment, the magnetic layer can be an insulating layer. In the present invention and this specification, "insulating" in relation to a magnetic layer means that the electrical conductivity is less than 1 S (Siemens) / m. The electrical conductivity of a certain layer is calculated from the surface electrical resistivity of the layer and the thickness of the layer using the following formula. Electrical conductivity can be measured by a known method. Electrical conductivity [S / m] = 1 / (surface electrical resistivity [Ω] × thickness [m])

[0031] The present inventors believe that the magnetic layer being an insulating layer is preferable for the electromagnetic wave shielding material to exhibit even higher electromagnetic wave shielding performance. From this point of view, the electrical conductivity of the 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 magnetic layer is, for example, 1.0×10 －１２ S / m or more or 1.0 x 10 －１０ It can be S / m or more.

[0032] (Resin) The magnetic layer can contain magnetic particles and a resin. In a magnetic layer containing magnetic particles and a resin, the content of the resin can be, for example, 1 part by mass or more, 3 parts by mass or more, or 5 parts by mass or more, and 20 parts by mass or less, or 15 parts by mass or less, per 100 parts by mass of the magnetic particles.

[0033] Resins can serve as binders in the magnetic layer. Examples of resins contained in the magnetic layer include conventionally known thermoplastic resins, thermosetting resins, ultraviolet-curable resins, radiation-curable resins, rubber-based materials, elastomers, etc. 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-based elastomers, olefin-based elastomers, vinyl chloride-based elastomers, polyester-based elastomers, polyamide-based elastomers, polyurethane-based elastomers, and acrylic elastomers.

[0034] In addition to the above components, the magnetic layer may also contain any amount of one or more known additives such as a hardener, dispersant, stabilizer, coupling agent, etc.

[0035] The electromagnetic wave shielding material has a scratch cross-sectional area of ​​0.08 μm ２ 1.25 μm or more ２ The electromagnetic wave shielding material may include only one magnetic layer having a scratch cross-sectional area of ​​0.08 μm or less, or may include two or more magnetic layers having a scratch cross-sectional area of ​​0.08 μm or less. ２ 1.25 μm or more ２ The magnetic layer may include one or more of the following magnetic layers, and may also include one or more other layers in addition to the magnetic layer: One form of the other layer may be a metal layer.

[0036] The electromagnetic wave shielding material has a scratch cross-sectional area of ​​0.08 μm ２ 1.25 μm or more ２When the electromagnetic shielding material includes only one magnetic layer having a scratch cross-sectional area of ​​0.08 μm or less, the thickness of this 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 preferably 10 μm or more, and more preferably 20 μm or more. On the other hand, the thickness of this magnetic layer can be, for example, 100 μm or less or 90 μm or less, and from the viewpoint of improving the molding processability of the electromagnetic shielding material, it is preferably less than 90 μm, more preferably 80 μm or less, and even more preferably 70 μm or less. When the electromagnetic shielding material has a scratch cross-sectional area of ​​0.08 μm or less, the thickness of this magnetic layer can be, for example, 100 μm or less or 90 μm or less, and from the viewpoint of improving the molding processability of the electromagnetic shielding material, it is preferably less than 90 μm, more preferably 80 μm or less, and even more preferably 70 μm or less. ２ 1.25 μm or more ２ When the electromagnetic wave shielding material includes two or more magnetic layers each having a thickness of 10 μm or more, 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 wave shielding material, it is preferably 10 μm or more, and more preferably 20 μm or more. On the other hand, the thickness of one magnetic layer can be, for example, 100 μm or less or 90 μm or less, preferably less than 90 μm, and more preferably 80 μm or less. The thicknesses of the two or more magnetic layers can be the same or different.

[0037] <Metal Layer> In one embodiment, the electromagnetic wave shielding material has a scratch cross-sectional area of ​​0.08 μm ２ 1.25 μm or more ２ The following magnetic layer can be present between two metal layers: It is presumed that having an electromagnetic wave shielding material with a multilayer structure in which a magnetic layer is sandwiched between two metal layers is preferable in terms of improving the electromagnetic wave shielding performance of the electromagnetic wave shielding material, in particular its shielding performance against magnetic field waves.

[0038] In the present invention and this specification, the term "metal layer" refers to a layer containing a metal. The metal layer may be a layer containing one or more metals as a pure metal consisting of a single metal element, as an alloy of two or more metal elements, or as an alloy of one or more metal elements and one or more non-metal elements.

[0039] When the electromagnetic shielding material has a multilayer structure in which a magnetic layer is sandwiched between two metal layers, the electromagnetic shielding material can include one or more such multilayer structures, or can include two or more. That is, the electromagnetic shielding material can include at least two metal layers, or can include three or more metal layers, or can include at least one magnetic layer, or can include two or more magnetic 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, the compositions and / or thicknesses are different. This point 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 a layer containing a resin, as described below.

[0040] The metal layer included in the electromagnetic wave shielding material can be a layer containing one or more metals selected from the group consisting of various pure metals and various alloys. The metal layer can exhibit an attenuation effect in the shielding material. This is preferable from the perspective of improving the shielding performance of the electromagnetic wave shielding material. The attenuation effect is greater with a larger propagation constant, and the propagation constant is greater with a higher electrical conductivity. Therefore, it is preferable that the metal layer contain a metal element with high electrical conductivity. From this perspective, it is preferable that the metal layer contain a pure metal such as Ag, Cu, Au, or Al, or an alloy containing any of these as a 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 measured by mass. An alloy is generally a pure metal whose composition is adjusted by adding one or more metal or non-metal elements to a pure metal for purposes such as corrosion prevention and strength improvement. The main component of 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 (e.g., 99.8% by mass or less) in the alloy. From the viewpoint of economy, pure metal Cu or Al or an alloy containing Cu or Al as a main component is preferred, and from the viewpoint of high electrical conductivity, pure metal Cu or an alloy containing Cu as a main component is more preferred.

[0041] In one embodiment, the purity of the metal in the metal layer, i.e., the metal content in the metal layer, can 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. The metal content in the metal layer refers to the content based on mass, unless otherwise specified. For example, the metal layer can be a pure metal or alloy processed into a sheet shape. For example, a commercially available metal foil or a metal foil prepared by a known method can be used as the metal layer. Pure Cu metal sheets (so-called copper foils) of various thicknesses are commercially available. For example, such copper foils can be used as the metal layer. Copper foils include electrolytic copper foils obtained by electroplating copper foils on a cathode, and rolled copper foils obtained by thinly rolling an ingot under heat and pressure. Both copper foils can be used as the metal layer of the electromagnetic wave shielding material. Furthermore, Al sheets (so-called aluminum foils) of various thicknesses are commercially available. For example, such aluminum foils can be used as the metal layer.

[0042] From the viewpoint of one or more of economy, high electrical conductivity, and weight reduction of the electromagnetic wave shielding material, it is preferable that one or both (preferably both) of the two metal layers sandwiching the magnetic layer be a metal layer containing a metal selected from the group consisting of Al, Mg, and Cu, and it is more preferable that the layer be a layer containing a metal selected from the group consisting of Al, Mg, and Cu as a 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 a main component, Al, Mg, or Cu is the component with the highest proportion by mass in this layer. Such a layer can contain only one, two, or three metals selected from Al, Mg, and Cu. From one or more of the above viewpoints, it is more preferable that one or both (preferably both) of the two metal layers sandwiching the magnetic layer be a metal layer having a metal content selected from the group consisting of Al, Mg, and Cu of 80.0% by mass or more, and even more preferable that the metal content selected from the group consisting of Al, Mg, and Cu be a metal layer having a metal content of 90.0% by mass or more. A metal layer containing at least Al among Al, Mg, and Cu can be a metal layer having an Al content of 80.0% by mass or more, or can be a metal layer having an Al content of 90.0% by mass or more. A metal layer containing at least Mg among Al, Mg, and Cu can be a metal layer having an Mg content of 80.0% by mass or more, or can be a metal layer having an Mg content of 90.0% by mass or more. A metal layer containing at least Cu among Al, Mg, and Cu can be a metal layer having a Cu content of 80.0% by mass or more, or can be a metal layer having 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 be, for example, 100 mass % or less or 99.9 mass % or less, respectively. 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 expressed as a percentage relative to the total mass of the metal layer.

[0043] With regard to the thickness of the metal layer, from the viewpoint of further improving the processability 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 even more preferably 10 μm or more. On the other hand, from the viewpoint of the processability of the metal layer, the thickness per layer is preferably 200 μm or less, more preferably 100 μm or less, and even more preferably 50 μm or less. In the electromagnetic wave shielding material, the thicknesses of the multiple metal layers can be the same or different.

[0044] In one embodiment, the electromagnetic shielding material may have one or both outermost layers made of a metal layer. This feature contributes to the electromagnetic shielding material being able to exhibit high shielding performance against magnetic fields in the low-frequency range of approximately 100 kHz to 1 MHz. Furthermore, having at least one outermost layer of the electromagnetic shielding material made of a metal layer may also contribute to suppressing edge peeling in molded articles obtained by molding. In one embodiment, one or both outermost layers of the electromagnetic shielding material may be a metal layer that sandwiches a magnetic layer with another metal layer.

[0045] In one embodiment, in the electromagnetic wave shielding material, the magnetic layer and the metal layer can be arranged as layers that are in direct contact with each other. That is, the magnetic layer and the metal layer can be adjacent to each other without any other layer interposed therebetween. For example, in a multilayer structure in which the magnetic layer is sandwiched between two metal layers, one or both of the two metal layers can be arranged as layers that are in direct contact with the magnetic layer. That is, one or both of the two metal layers can be adjacent to the magnetic layer without any other layer interposed therebetween.

[0046] In another embodiment, the electromagnetic wave shielding material can have one or more layers containing a resin between the magnetic layer and the metal layer. For example, a multilayer structure in which the magnetic layer is sandwiched between two metal layers can have one or more layers containing a resin between one or both of the two metal layers and the magnetic layer. A "layer containing a resin" is a layer containing one or more types of resin.

[0047] <Layer Containing Resin> (Adhesive Layer) One example of a resin-containing layer is an adhesive layer. In the present invention and this specification, the term "adhesive layer" refers to a layer having tackiness on its surface at room temperature. With regard to tackiness, "room temperature" refers to 23°C. Such a layer adheres to an adherend due to its adhesive force when it comes into contact with the adherend. Tackiness generally refers to the property of exhibiting adhesive strength in a short time after contact with the adherend with very little force. In the present invention and this specification, the term "having tackiness" refers to a result of No. 1 to No. 32 in the inclined ball tack test (measurement environment: temperature 23°C, relative humidity 50%) specified in JIS Z 0237:2009. When another layer is laminated on the surface of the adhesive layer, for example, the other layer can be peeled off to expose the adhesive layer surface, and the above test can be performed. When another layer is laminated on both one surface and the other surface of the adhesive layer, the other layer on either surface may be peeled off.

[0048] The adhesive layer can be formed 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, and then processing it into a film shape. The adhesive layer-forming composition can be applied, for example, to a support. Coating can be performed using a known coating device such as a blade coater or a die coater. Coating can be performed using a so-called roll-to-roll method or a batch method. Examples of supports to which the adhesive layer-forming composition is applied include films made of various resins such as polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), acrylics such as polycarbonate (PC) and polymethyl methacrylate (PMMA), cyclic polyolefins, triacetyl cellulose (TAC), polyether sulfide (PES), polyether ketone, and polyimides. Supports whose surfaces (coated surfaces) to which the adhesive layer-forming composition is applied (the surfaces to be coated) have been subjected to a release treatment by a known method can be used. 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. 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. An adhesive layer can be formed by applying an adhesive layer-forming composition, in which an adhesive is dissolved and / or dispersed in a solvent, to the surface to be coated and drying the composition. Alternatively, an adhesive tape including an adhesive layer can also be used. Examples of the adhesive tape include double-sided tape. Double-sided tape has adhesive layers on both sides of the support. Alternatively, an adhesive tape having an adhesive layer on one side of the support can also be used. Examples of the support include films, nonwoven fabrics, and paper made of various resins such as polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polycarbonate (PC), acrylics such as polymethyl methacrylate (PMMA), cyclic polyolefins, triacetyl cellulose (TAC), polyether sulfide (PES), polyether ketone, and polyimide.As the adhesive tape having an adhesive layer on one or both sides of a support, a commercially available product can be used, and an adhesive tape produced by a known method can also be used.

[0049] The thickness of the adhesive layer is not particularly limited, and the thickness per layer can be, for example, 1 μm or more and 30 μm or less.

[0050] (Adhesive Layer) One form of a resin-containing layer is an adhesive layer. In the present invention and this specification, an "adhesive layer" refers to a layer in which a liquid or gel adhesive contacts an adherend and solidifies through a state change such as drying or curing, thereby exerting adhesion to the adherend through an anchoring effect, physical interaction, or the formation of a chemical bond. In one form, the adhesive layer may be a layer that has no tackiness on the surface at room temperature. The adhesive includes 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 themselves be liquid or gel-like. Alternatively, a solid resin may dissolve in a solvent to become liquid or gel-like. Examples of solvents contained in the adhesive include ketone-based solvents such as water, acetone, methyl ethyl ketone, and cyclohexanone; acetate 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.

[0051] The thickness of the adhesive layer is not particularly limited, and the thickness per layer can be, for example, 1 μm or more and 30 μm or less.

[0052] (Resin Layer) One form of a layer containing a resin can be a resin layer. In the present invention and this specification, the term "resin layer" refers to a resin film formed from a thermoplastic resin such as a synthetic resin in a film-like shape, and the resin film has a film-like structure by itself and is not tacky 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, triacetyl cellulose (TAC), and other various resins.

[0053] The resin layer can be bonded to a metal layer or a magnetic layer via an adhesive layer or pressure-sensitive adhesive layer. Since the resin layer contains a thermoplastic resin, it softens when heated. When pressed against an adherend in a heated state, it flows and conforms to minute irregularities on the adherend surface, exerting adhesive strength through an anchoring effect. The adhesive state can then be maintained by cooling. Therefore, in one embodiment, the resin layer can be bonded to another layer without an adhesive layer or pressure-sensitive adhesive layer.

[0054] The thickness of the resin layer, as measured per resin layer, is preferably 10 μm or more, and more preferably 12 μm or more. The thickness of the resin layer, as measured per 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. In one embodiment, the electromagnetic wave shielding material has a multilayer structure in which a magnetic layer is sandwiched between two metal layers, and can include one or more resin layers having a thickness within the above range between one or both of the two metal layers and the magnetic layer. For example, the multilayer structure can include one resin layer having a thickness within the above range between one of the two metal layers and the magnetic layer, and / or between the other metal layer and the magnetic layer.

[0055] <Specific Example of Layer Configuration> The total number of magnetic layers included in the electromagnetic wave shielding material is one or more, and can be one layer, or two or more layers, or can be, for example, four or less. When the electromagnetic wave shielding material includes two or more magnetic layers, it is preferable that the scratch cross-sectional area of ​​some or all of the two or more magnetic layers is within the range described above, and that the scratch cross-sectional area of ​​all layers is within the range described above. Meanwhile, the total number of metal layers included in the electromagnetic wave shielding material is zero or one or more, and can be two or more layers, for example, two to five layers.

[0056] In one embodiment, in a multilayer structure in which a magnetic layer is sandwiched between two metal layers, the magnetic layer can be in direct contact with both metal layers. In this case, specific examples of the layer configuration of the electromagnetic shielding material include the following: 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" In an electromagnetic shielding material including two or more multilayer structures each having a magnetic layer between two metal layers, as in Examples A2 and A3, the metal layers sandwiching the magnetic layer in one multilayer structure can also be the metal layers sandwiching the magnetic layer in another multilayer structure. In the electromagnetic shielding material, the total number of multilayer structures each having the magnetic layer between two metal layers can be, for example, one to four. The total number of multilayer structures is one in Example A1, two in Example A2, and three in Example A3. It is preferable that the total number of layers in the multilayer structure is two or more (e.g., 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 written to the left of the symbol and the layer written to the right of the symbol are in direct contact with each other without any other layer in between. This point also applies to the following description unless otherwise specified.

[0057] In another embodiment, the multilayer structure of the electromagnetic wave shielding material having a magnetic layer between two metal layers can include one or more layers containing a resin between one or both of the two metal layers and the magnetic layer. In the multilayer structure, one of the two metal layers can be adjacent to the magnetic layer without any other layer in between, and one or more layers containing a resin can be included between the other metal layer and the magnetic layer. Alternatively, the multilayer structure can have one or more layers containing a resin between each of the two metal layers and the magnetic layer.

[0058] The multilayer structure may include an adhesive layer and / or a bonding layer between the resin layer and the metal layer. In one embodiment, the adhesive layer and / or the bonding layer may be included between the resin layer and the magnetic layer in the multilayer structure. In another embodiment, the resin layer and the magnetic layer may be in direct contact with each other in the multilayer structure. That is, the resin layer and the magnetic layer may be adjacent to each other without any other layer interposed therebetween.

[0059] The electromagnetic wave shielding material may include, for example, a total of 1 to 12 resin-containing layers. The total number of resin layers included in the electromagnetic wave shielding material (preferably resin layers having the thickness described above) may be, for example, 1 to 4. The total number of layers selected from the group consisting of pressure-sensitive adhesive layers and adhesive layers included in the electromagnetic wave shielding material may be, for example, 1 to 4 or 1 to 8.

[0060] The following are examples of the arrangement of the "magnetic layer," "metal layer," "resin layer," and "adhesive or bonding layer" in the electromagnetic wave shielding material. In the following examples, the "adhesive layer" may include a support, or the "adhesive layer" may be an adhesive tape having an adhesive layer on one or both sides of the support. For example, as in Example B3, a metal layer sandwiching a magnetic layer may also be a metal layer sandwiching another magnetic layer. For example, in Example B3, metal layer 2 is one of two metal layers sandwiching magnetic layer 1, and is also one of two metal layers sandwiching magnetic layer 2. Furthermore, in Example B3, the outermost layer on one side of the electromagnetic wave shielding material is metal layer 1, which sandwiches magnetic layer 1 together with metal layer 2, and the outermost layer on the other side of the electromagnetic wave shielding material is metal layer 3, which 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 / metal layer 2 / magnetic layer 2 / metal layer 3 / adhesive layer 2 or adhesive layer 2 / resin layer 2" Example B8: "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 adhesive layer 1 / metal layer 1 / magnetic layer 1 / metal layer 2 / adhesive layer 2 or adhesive layer 2 / resin layer 2"

[0061] <Method for Manufacturing Electromagnetic Shielding Material> (Method for Forming Magnetic Layer) The magnetic layer can be prepared, for example, by applying a magnetic layer-forming composition and drying the resulting coating. The magnetic layer-forming composition can contain the components described above and can further contain one or more solvents. Examples of solvents include various organic solvents, such as ketone-based solvents such as acetone, methyl ethyl ketone, and cyclohexanone; acetate 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; and amide-based solvents such as dimethylformamide, dimethylacetamide, and N-methylpyrrolidone. A single solvent or a mixture of two or more solvents selected in any ratio based on the solubility of the components used in preparing the magnetic layer-forming composition can be used. The solvent content of the magnetic layer-forming composition is not particularly limited and can be determined based on factors such as the coatability of the magnetic layer-forming composition.

[0062] The magnetic layer-forming composition can be prepared by sequentially mixing the various components in any order or by simultaneously mixing them. Furthermore, if necessary, dispersion treatment can be performed using a known dispersing machine such as a ball mill, bead mill, sand mill, or roll mill, and / or stirring treatment can be performed using a known stirrer such as a shaking stirrer. Using a magnetic layer-forming composition with less bubbles mixed in tends to result in a smaller scratch cross-sectional area of ​​the magnetic layer formed. Methods for suppressing bubbles from being mixed in the magnetic layer-forming composition include suppressing the generation of bubbles during stirring treatment and / or performing a defoaming treatment on the magnetic layer-forming composition after stirring treatment.

[0063] The magnetic layer-forming composition can be applied, for example, to a support. The application can be carried out using a known application device such as a blade coater or a die coater. The application can be carried out by a so-called roll-to-roll method or a batch method. The application speed when applying the composition is not particularly limited.

[0064] Examples of substrates onto which the magnetic layer-forming composition is applied include films of various resins, such as polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), acrylics such as polycarbonate (PC) and polymethyl methacrylate (PMMA), cyclic polyolefins, triacetyl cellulose (TAC), polyether sulfide (PES), polyether ketone, and polyimide. For details of these resin films, see paragraphs 0081 to 0086 of JP 2015-187260 A. As the substrate, a substrate whose surface (the surface to be coated) onto which the magnetic layer-forming composition is applied has been subjected to a release treatment by a known method can be used. One form of release treatment is the formation of a release layer. For details of the release layer, see paragraph 0084 of JP 2015-187260 A. Alternatively, commercially available release-treated resin films can be used as the substrate. By using a substrate whose surface to be coated has been subjected to a release treatment, the magnetic layer and the substrate can be easily separated after film formation.

[0065] In one embodiment, the magnetic layer-forming composition can be applied directly onto the metal layer, using the metal layer as a support. By applying the magnetic layer-forming composition directly onto the metal layer, a laminate structure of the metal layer and the magnetic layer can be produced in one step.

[0066] The coating layer formed by applying the magnetic layer-forming composition can be dried by known methods such as heating or blowing hot air. The drying can be carried out under conditions that allow the solvent contained in the magnetic layer-forming composition to volatilize. As an example, the drying can be carried out for 1 minute to 2 hours in a heated atmosphere at an ambient temperature of 80 to 150°C.

[0067] The degree of orientation of the flat particles described above can be controlled by the type of solvent, amount of solvent, liquid viscosity, coating thickness, etc., of the magnetic layer-forming composition. For example, if the boiling point of the solvent is low, convection occurs upon drying, which tends to increase the degree of orientation. If the amount of solvent is small, the degree of orientation tends to increase due to physical interference between adjacent flat particles. On the other hand, if the liquid viscosity is low, the flat particles are more likely to rotate, which tends to decrease the degree of orientation. If the coating thickness is made thinner, the degree of orientation tends to decrease. In addition, performing the pressure treatment described below can contribute to reducing the degree of orientation. By adjusting the various manufacturing conditions described above, the degree of orientation of the flat particles can be controlled within the range described above.

[0068] (Pressure treatment of magnetic layer) The magnetic layer after deposition can also be subjected to pressure treatment. By pressure treating a magnetic layer containing magnetic particles, the magnetic particle density in the magnetic layer can be increased, resulting in a higher magnetic permeability. Furthermore, the magnetic layer containing flat-shaped particles can have a lower degree of orientation by pressure treatment, resulting in a higher magnetic permeability.

[0069] The pressure treatment can be carried out by applying pressure in the thickness direction of the magnetic layer using a flat plate press, a roll press, or the like. A flat plate press places the object to be pressed between two flat press plates arranged above and below, and the two press plates are brought together using mechanical or hydraulic pressure to apply pressure to the object to be pressed. A roll press passes the object to be pressed between rotating pressure rolls arranged above and below, and pressure can be applied by applying mechanical or hydraulic pressure to the pressure rolls or by making the distance between the pressure rolls smaller than the thickness of the object to be pressed.

[0070] The pressure during the pressure treatment can be set arbitrarily. For example, in the case of a flat press, the pressure is set to, for example, 1 to 50 N (Newton) / mm ２In the case of a roll press, the linear pressure is, for example, 20 to 400 N / mm. The pressing time can be set as desired. When a flat plate press is used, the time is, for example, 5 seconds to 30 minutes. When a roll press is used, the pressing time can be controlled by the conveying speed of the material to be pressed, for example, 10 cm / min to 200 m / min. The materials of the press plate and pressure roll can be selected from metal, ceramic, plastic, rubber, etc. During the pressing process, heat can be applied to both the upper and lower press plates or one of the press plates on the plate press, or to one of the upper and lower rolls of the roll press. Heating can soften the magnetic layer, thereby achieving a high compression effect when pressure is applied. The heating temperature can be set as desired, for example, from 50°C to 200°C. The heating temperature can be the internal temperature of the press plate or roll. This temperature can be measured using a thermometer installed inside the press plate or roll. After heating and pressurizing treatment in a plate-type press, the magnetic layer can be removed, for example, by separating the press plate while the temperature of the press plate is still high. Alternatively, the press plate can be cooled by water cooling, air cooling, or the like while maintaining the pressure, and then the press plate can be separated and the magnetic layer can be removed. In a roll press, the magnetic layer can be cooled by water cooling, air cooling, or the like immediately after pressing. It is also possible to repeat the pressure treatment two or more times. When the magnetic layer is formed on a release film, for example, the magnetic layer can be laminated on the release film and then pressure treated. Alternatively, the magnetic layer can be peeled off from the release film and pressure treated as a single layer.

[0071] (Bonding of Various Layers) An adhesive layer or a bonding layer can be used to bond the various layers together. The adhesive layer and the bonding layer are as described above. In the electromagnetic wave shielding material, two adjacent layers can also be bonded together by, for example, applying pressure and heat to bond them together. A plate-type press, a roll press, or the like can be used for the bonding. For example, when a magnetic layer is disposed as a layer that directly contacts an adjacent layer, the magnetic layer softens in the bonding step, facilitating contact with the surface of the adjacent layer, thereby allowing the magnetic layer and the adjacent layer to be bonded together without any other layer interposed. The pressure during bonding can be set as desired. In the case of a plate-type press, for example, a pressure of 1 to 50 N / mm ２ In the case of a roll press, the linear pressure is, for example, 20 to 400 N / mm. The pressure application time during compression can be set as desired. When a plate press is used, it is, for example, 5 seconds to 30 minutes. When a roll press is used, it can be controlled by the conveying speed of the material to be pressed, and the conveying speed is, for example, 10 cm / min to 200 m / min. The temperature during compression can be selected as desired, and is, for example, 20°C or higher and 200°C or lower. The temperature during compression can be, for example, the internal temperature of the press plate or roll.

[0072] <Coating of End Surfaces of Magnetic Layer> In one embodiment, the electromagnetic wave shielding material can be an electromagnetic wave shielding material that includes a multilayer structure having the magnetic layer between two metal layers, and in which part or all of the end surfaces of the magnetic layer are covered with a coating material.

[0073] In the multilayer structure, the magnetic layer is located between two metal layers. Therefore, if one of the pair of surfaces of the magnetic layer is called the upper surface and the other the lower surface, the surface of one of the two metal layers faces the upper surface, and the surface of the other metal layer faces the lower surface. The "end surface" of such a magnetic layer is the surface that does not face the surface of the metal layer, i.e., the side surface. The terms "upper surface" and "lower surface" are used to indicate the relative positional relationship between the pair of surfaces of the magnetic layer, and the electromagnetic wave shielding material is not limited to being used with the upper and lower surfaces arranged parallel to a horizontal plane.

[0074] The electromagnetic wave shielding material can be in any shape and size, such as a sheet (which can also be referred to as a film). For example, a sheet-shaped electromagnetic wave shielding material can be folded into any shape and incorporated into an electronic component or electronic device. In the multilayer structure included in the sheet-shaped electromagnetic wave shielding material, the magnetic layer and metal layer can also have a sheet shape. The sheet shape can be, for example, a sheet shape having an upper surface, a lower surface, and four end surfaces, and the surface shapes of the upper and lower surfaces can be, for example, rectangular. The rectangular upper surface and the rectangular lower surface can be the same size or different sizes. Note that the terms "same size" and "same" regarding surface shape used in this specification are intended to allow for normal manufacturing errors. In one embodiment, the surface of the metal layer facing the upper surface of the magnetic layer in a sheet-shaped material having an upper surface, a lower surface, and four end surfaces can have the same size and surface shape as the upper surface of the magnetic layer, and in another embodiment, the surface of the metal layer facing the upper surface of the magnetic layer can have a different size and / or surface shape from the upper surface of the magnetic layer. Regarding the surface of the metal layer facing the lower surface of the magnetic layer, the surface of the metal layer facing the lower surface of the sheet-shaped magnetic layer having an upper surface, a lower surface, and four end surfaces can have the same size and surface shape as the lower surface of the magnetic layer in one embodiment, or can have a different size and / or surface shape from the lower surface of the magnetic layer in another embodiment. For example, in the above multilayer structure, the end surfaces of the magnetic layer can protrude outward from the end surfaces of the two metal layers in one embodiment, or can be recessed inward from the end surfaces of the two metal layers in another embodiment. Furthermore, in another embodiment, the upper and lower surfaces of the two metal layers and the magnetic layer included in the multilayer structure can all have the same size and surface shape. In either case, in the above electromagnetic wave shielding material, some or all of the end surfaces of the magnetic layer are covered with a coating material.

[0075] (Coating Material) As the coating material for covering part or all of the end faces of the magnetic layer, various adhesives, liquid or solid sealants, resin films, adhesive tapes, metal foils with adhesive layers, etc. can be used. For example, in the multilayer structure produced as described above, a coating material can be attached to part or all of the end faces of the magnetic layer that are exposed and not covered by the metal layer by a known method, thereby covering part or all of the end faces of the magnetic layer with the coating material. On the other hand, the end faces of the metal layers included in the multilayer structure do not need to be covered with the coating material, and part or all of the end faces may be covered with the coating material.

[0076] In one embodiment, the coating material covering the end faces of the magnetic layer can be only one type of coating material. In another embodiment, the coating material covering a portion of the end faces of the magnetic layer can be different in thickness and / or composition from the coating material covering the other portion. For example, in a sheet-shaped magnetic layer having an upper surface, a lower surface, and four end faces, in one embodiment, all four end faces can be covered with the same coating material. In another embodiment, the coating material covering one or more of the four end faces can be different in thickness and / or composition from the coating material covering the other one or more of the four end faces. Each end face can be partially or entirely covered with a coating material. The thickness of the coating material can be, for example, 10 μm or more or 30 μm or more, and can be, for example, 300 μm or less or 200 μm or less.

[0077] In one embodiment, a portion or all of the coating material covering the end faces of the magnetic layer can be a coating material with a higher thermal conductivity than the magnetic layer. Coating a portion or all of the end faces of the magnetic layer with a coating material with a higher thermal conductivity than the magnetic layer is preferable from the viewpoint of improving the thermal conductivity of the electromagnetic wave shielding material and improving heat dissipation. The coating material with high thermal conductivity can be selected from those containing a material with high thermal conductivity. Examples of materials with high thermal conductivity include various metals, ceramics, semiconductors, etc. These high thermal conductivity materials can be used alone, as a mixture, or as a composite with a resin, etc., as the coating material with high thermal conductivity.

[0078] Methods for measuring thermal conductivity are classified into steady-state methods and unsteady-state methods. In the present invention and this specification, "thermal conductivity" refers to thermal conductivity measured by a steady-state method. Specific examples of methods for measuring thermal conductivity include the methods described in the examples below.

[0079] A coating material having a higher thermal conductivity than the magnetic layer has a thermal conductivity of more than 1.0, preferably 1.2 or more, and more preferably 1.4 or more, relative to the thermal conductivity of the magnetic layer (1.0). Furthermore, a coating material having a higher thermal conductivity than the magnetic layer can have a thermal conductivity of, for example, 3.0 or less or 2.5 or less, relative to the thermal conductivity of the magnetic layer (1.0), or can exceed the values ​​exemplified here.

[0080] For example, for a sheet-shaped magnetic layer having an upper surface, a lower surface, and four end surfaces, the coating material covering one or more end surfaces can be a coating material with a higher thermal conductivity than the magnetic layer. More specifically, the coating material covering one or more end surfaces can be a coating material with a higher thermal conductivity than the magnetic layer, and the thermal conductivity of the coating material covering one or more other end surfaces can be equal to or lower than that of the magnetic layer. Alternatively, all of the four end surfaces covered by a coating material can be covered by a coating material with a higher thermal conductivity than the magnetic layer. Alternatively, all four end surfaces can be covered by a coating material with a higher thermal conductivity than the magnetic layer. In one embodiment, only a portion of each of the end surfaces can be covered by a coating material with a higher thermal conductivity than the magnetic layer, or in another embodiment, the entire surface can be covered by a coating material with a higher thermal conductivity than the magnetic layer.

[0081] In one embodiment, a part or all of the coating material that covers the end face of the magnetic layer can be a conductive coating material. In the present invention and this specification, with regard to a coating material, "conductive" refers to a resistivity ρ of 1 Ω·m or less, and "insulating" refers to a material that does not fall under such conductive characteristics. The resistivity ρ of the conductive coating material is 1 Ω·m or less, for example, 0.1 Ω·m or less, preferably 0.01 Ω·m or less, and more preferably 0.001 Ω·m or less. The resistivity ρ of the conductive coating material can be, for example, 0.2 mΩ·m or more or 0.5 mΩ·m or more, or can be less than the values ​​exemplified here. The resistivity ρ is calculated by measuring the resistance value R (unit: Ω) of the object to be measured and multiplying the cross-sectional area S (unit: m ２ ) and the distance between the electrodes L [m], using the following formula: The resistance value R can be measured using a known measuring device capable of measuring resistance values, such as a commercially available digital multimeter. Specific examples of methods for measuring the resistivity ρ include the methods described in the examples below. Resistivity ρ (unit: Ω·m) = RS / L

[0082] Conductive coating materials can include various metal foils, metal plates, conductive tapes, conductive adhesives, etc. The use of conductive coating materials is preferable for the following reasons: In a shielding material having a multilayer structure in which a magnetic layer containing magnetic particles is sandwiched between two metal layers, if both the outermost layer and the outermost layer are metal layers, when the shielding material is attached to a metal case of an electronic circuit, one metal layer can be electrically connected to the metal case. However, the other metal layer is likely to be electrically disconnected from the metal case because it is connected via a magnetic layer, which generally tends to have high electrical resistance. In this case, the other metal layer becomes a so-called floating conductor, which can cause cavity resonance with the signal wiring of the electronic circuit, resulting in strong noise. Furthermore, the operation of the electronic circuit can charge the other metal layer, potentially causing a voltage increase or static electricity. For this reason, electrical conductivity between the metal layers of the shielding material is preferable. In this regard, to ensure electrical conductivity between the metal layers, it is preferable for the coating material covering the end faces of the magnetic layer to be conductive, and it is even more preferable for the conductive coating material to be in contact with both the one metal layer and the other metal layer. For two metal layers, if the intermetallic resistance is 100Ω or less, it can be said that there is electrical continuity between the metal layers. When there is electrical continuity between the metal layers, the intermetallic resistance can be, for example, 10Ω or less, preferably 1Ω or less, and more preferably 0.5Ω or less. The intermetallic resistance can be, for example, 20 mΩ or more or 50 mΩ or more, or can be less than the values ​​exemplified here. The intermetallic resistance can be measured using a known measuring device capable of measuring resistance, such as a commercially available digital multimeter. Specific examples of methods for measuring the intermetallic resistance include the methods described in the Examples below.

[0083] For example, for a sheet-shaped magnetic layer having an upper surface, a lower surface, and four end surfaces, the coating material covering one or more end surfaces can be a conductive coating material. More specifically, the coating material covering one or more end surfaces can be a conductive coating material, and the coating material covering one or more other end surfaces can be an insulating coating material. Alternatively, all of the four end surfaces that are covered with a coating material can be covered with a conductive coating material. Alternatively, all four end surfaces can be covered with a conductive coating material. In one embodiment, only a portion of each of the end surfaces can be covered with a conductive coating material, and in another embodiment, the entire surface can be covered with a conductive coating material. It is preferable that all four end surfaces be covered with a conductive coating material that has a higher thermal conductivity than the magnetic layer.

[0084] The electromagnetic shielding material 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 the present invention and this specification, "sheet" is synonymous with "film." The electromagnetic shielding material can also be a three-dimensionally molded product obtained by three-dimensionally molding a sheet-shaped electromagnetic shielding material, or a sheet-shaped electromagnetic shielding material for three-dimensional molding. Various molding methods, such as mold press molding, vacuum molding, and pressure molding, can be used as three-dimensional molding methods. Regarding molding methods, for example, molding performed without heating the object and / or mold, or by heating at a low temperature, is generally called cold forming. Examples of cold forming methods include drawing molding and stretch forming. Drawing molding is a molding method in which a sheet-shaped object is pressed using a pair of molds, consisting of a female mold and a male mold, to form a container with a bottom of various shapes, such as a cylinder, a rectangular tube, or a cone. In contrast, stretch forming is a method of forming a molded product with a curved surface extending from a flat surface from a sheet-shaped object. Stretch forming can also be performed using a press with only a male mold without a female mold. Drawing is broadly divided into deep drawing and shallow drawing. Shallow drawing forms a shallow molded product, while deep drawing forms a deep molded product (for example, a depth greater than the diameter of a cylinder or cone or the length of one side of a pyramid). Publicly known techniques can be applied to three-dimensional forming methods.

[0085] [Electronic Component] One aspect of the present invention relates to an electronic component comprising the electromagnetic wave shielding material. Examples of the electronic component include various electronic components such as electronic components contained in electronic devices such as mobile phones, personal digital assistants, and medical devices, as well as semiconductor elements, capacitors, coils, and cables. The electromagnetic wave shielding material can be three-dimensionally molded into any shape depending on the shape of the electronic component and placed inside the electronic component, or 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.

[0086] [Electronic Device] One aspect of the present invention relates to an electronic device including the electromagnetic shielding material. Examples of the electronic device include electronic devices such as mobile phones, personal digital assistants, and 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 can include the electromagnetic shielding material as a component of the electronic components included in the device. Furthermore, as a component of the electronic device, the electromagnetic shielding material can be disposed inside the electronic device, or can be disposed as a cover material that covers the outside of the electronic device. Alternatively, the electromagnetic shielding material can be three-dimensionally molded into a cylindrical shape and disposed as a cover material that covers the outside of a cable.

[0087] One example of a use of the electromagnetic shielding material 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 achieving high shielding effectiveness by electrically connecting a side via at the end of the package substrate to the inner surface of the electromagnetic shielding material when covering a semiconductor package with the electromagnetic shielding material, thereby achieving ground wiring. To achieve such wiring, it is desirable for the outermost layer of the electromagnetic shielding material on the electronic component side to be a metal layer. When one or both outermost layers of the electromagnetic shielding material are metal layers, the electromagnetic shielding material can be suitably used for such wiring.

[0088] 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. The following steps were carried out at room temperature of 20 to 25°C unless otherwise specified.

[0089] Example 1 Preparation of Coating Liquid (Magnetic Layer-Forming Composition) 100 g of Fe—Si—Al flat-shaped magnetic particles (Sendust MFS-SUH manufactured by MKT Corporation), 12 g of polystyrene-polybutadiene block copolymer (manufactured by Sigma-Aldrich Japan K.K.), and 205 g of cyclohexanone were added to a plastic bottle, and the mixture was stirred by shaking in a shaking mixer for 1 hour to prepare a coating liquid. The prepared coating liquid was then degassed using ultrasonic degassing (output: 200 W, frequency: 28 kHz) for the time shown in Table 1 ("Coating liquid degassing time" in Table 1).

[0090] <Preparation of Magnetic Layer> (Magnetic Layer Formation) The degassed coating liquid was applied to the release surface of a release-treated PET film (PET75TR manufactured by Nippa Corporation) using a blade coater with a coating gap of 300 μm, and dried for 30 minutes in a drying device with an internal atmosphere temperature of 80° C. to form a sheet-shaped magnetic layer.

[0091] (Pressure treatment of magnetic layer) The upper and lower press plates of a plate press (large hot press TA-200-1W manufactured by Yamamoto Iron Works) were heated to 140°C (internal temperature of the press plate), and the magnetic layer on the release film was placed together with the release film at the center of the press plate. ２ The pressure was maintained for 10 minutes under this condition. The upper and lower press plates were cooled to 50°C (internal temperature of the press plates) while the pressure was maintained, and then the magnetic layer was removed together with the release film.

[0092] <Formation of Multilayer Structure> After peeling off the release film, a sample piece was cut from a portion of the magnetic layer for the following magnetic permeability, electrical conductivity, and thermal conductivity measurements. From the magnetic layer after the sample piece was cut out, 5 μm-thick double-sided tape (NeoFix5 S2 manufactured by Nichiei Shinka Co., Ltd.) was attached to each of the top and bottom surfaces, and a 154 mm × 154 mm rectangular magnetic layer was cut out. A 12 μm-thick, 150 mm × 150 mm rectangular copper foil (JIS H3100:2018 compliant, alloy number C1100R, copper content 99.90% by mass or more) was attached to each of the double-sided tapes on the top and bottom surfaces of this magnetic layer. In this way, a laminate was produced in which a magnetic layer was disposed between two metal layers (copper foils), and the metal layers and magnetic layers were attached together with double-sided tape. In the produced laminate, the magnetic layer is larger than the copper foil as described above, so the magnetic layer protrudes from the copper foil by 2 mm on each of the four sides, and the two layers of copper foil are not in contact. Figure 7 shows a schematic cross-sectional view of the laminate. Note that Figure 7 and other drawings are schematic diagrams, and the relative sizes (thickness, etc.) of the various layers shown in the drawings differ from the relative sizes of the actual dimensions.

[0093] <Coating of Magnetic Layer End Surfaces> FIG. 8 shows a schematic cross-sectional view of the electromagnetic shielding material of Example 1. The electromagnetic shielding material of Example 1 was produced by the following method. Four tape pieces were cut from conductive tape (CU-35C, manufactured by 3M Japan, thickness 51 μm) to form the covering material. Each tape piece was 154 mm long and 10 mm wide. These four tape pieces covered the four side surfaces of the laminate, and the tape pieces were attached to the laminate as shown in the schematic cross-sectional view of FIG. 8. In this way, the electromagnetic shielding material of Example 1 was obtained, in which all four end surfaces of the magnetic layer of the laminate were covered with a covering material. In the electromagnetic shielding material of Example 1, the covering material covering the end surfaces of the magnetic layer is in contact with each surface of the two metal layers (if the upper surface in FIG. 8 is called the upper surface and the lower surface is called the lower surface, then the upper surface of the upper metal layer and the lower surface of the lower metal layer). Furthermore, all four end surfaces of the magnetic layer are entirely covered with a covering material.

[0094] <Measurement of magnetic permeability of magnetic layer> The magnetic layer was cut into a rectangle of 28 mm × 10 mm, and the magnetic permeability was measured using a magnetic permeability measuring device (per01 manufactured by Keycom Corporation). The magnetic permeability was calculated as the real part of the complex relative magnetic permeability (μ′) at a frequency of 100 kHz. The calculated magnetic permeability was 148.

[0095] <Measurement of Electrical Conductivity of Magnetic Layer> A cylindrical main electrode with a diameter of 30 mm was connected to the negative pole of a digital 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 pole. The main electrode and the ring electrode were placed in a position surrounding it on a sample piece of the magnetic layer cut into a 60 mm x 60 mm rectangle, and a voltage of 25 V was applied to both poles 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 －２ The thickness was determined by the following method: Electrical conductivity [S / m] = 1 / (surface electrical resistivity [Ω] × thickness [m])

[0096] <Obtaining a Cross-Sectional Image of the Shielding Material> Cross-section processing was performed to expose the cross section of the shielding material of Example 1 using the following method. A 3 mm x 3 mm rectangular piece of shielding material was embedded in resin, and the cross section of the shielding material was cut using an ion milling device (IM4000PLUS, manufactured by Hitachi High-Technologies Corporation). The cross section of the exposed shielding material was observed using a scanning electron microscope (SU8220, manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 2 kV and a magnification of 100x to obtain a backscattered electron image. From the obtained image, the thickness of the magnetic layer and the two metal layers was measured at five locations using the scale bar as a reference, and the arithmetic mean of each was used as the thickness of the magnetic layer and the thickness of each of the two metal layers. The thickness of the magnetic layer was 30 μm, and the thickness of each metal layer was 10 μm. The thicknesses of the various coating materials described above were also determined in the same manner and confirmed to be the thicknesses described above.

[0097] <Measurement of the aspect ratio of magnetic particles and the degree of orientation of flat-shaped particles> In the cross section of the shielding material of Example 1, which was exposed by cross section processing in the same manner as above, the magnetic layer portion was observed with a scanning electron microscope (SU8220 manufactured by 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 by the method described above, and flat-shaped particles were identified from the aspect ratio value. Whether or not the magnetic layer contained flat-shaped particles as magnetic particles was determined as described above, and it was determined that the magnetic layer contained flat-shaped particles. Furthermore, the degree of orientation of the magnetic particles identified as flat-shaped particles was determined by the method described above, and it was 13°. In addition, the average (arithmetic mean) of the aspect ratios of all particles identified as flat-shaped particles was calculated as the aspect ratio of the flat-shaped particles contained in the magnetic layer. The calculated aspect ratio was 0.071.

[0098] <Measurement of Thermal Conductivity of Magnetic Layer and Coating Material> Figure 9 shows an explanatory diagram of the thermal conductivity measurement method. The thermal conductivity of the sample pieces of the magnetic layer obtained by the method described above and each coating material was determined using the following method. A 2 mm wide cut was made in the center of a piece of 50 mm x 50 mm, 1 mm thick EPDM (ethylene propylene diene) rubber sheet (manufactured by Akitsu Kogyo Co., Ltd.), and the sheet was placed on a hot plate (SCP-125, manufactured by AS ONE Corporation). One K-type thermocouple (referred to as "T1") attached to a thermocouple thermometer (AD-5602A, manufactured by A&D Co., Ltd.) was inserted into the cut. An aluminum plate (hereinafter referred to as "aluminum plate") (A1050P manufactured by Hikari Corporation) having a size of 50 mm x 50 mm and a thickness of 1 mm was placed on the EPDM rubber sheet, and one K-type thermocouple (referred to as "T2") attached to a thermocouple thermometer (AD-5602A manufactured by A&D Corporation) was placed at a position shifted by 5 mm from the center, and the coating portion near the junction point of the thermocouple was fixed to the aluminum plate using adhesive tape (Kapton (registered trademark) manufactured by Teraoka Seisakusho Co., Ltd.) cut into a 10 mm x 2 mm rectangle. A 50 mm x 50 mm rectangular specimen (either a sample piece of the magnetic layer obtained by the method described above or each coating material) was placed on an aluminum plate. A single K-type thermocouple (referred to as "T3") attached to a thermocouple thermometer (AD-5602A, manufactured by A&D Co., Ltd.) was placed 5 mm off-center in the opposite direction to T2. The coating near the thermocouple junction was secured to the specimen using adhesive tape (Kapton, manufactured by Teraoka Seisakusho Co., Ltd.) cut into a 10 mm x 2 mm rectangle. The specimen was then secured to a hot plate 5 mm from each of the four corners using adhesive tape (Kapton, manufactured by Teraoka Seisakusho Co., Ltd.) cut into a 20 mm x 2 mm rectangle. Room-temperature (23°C) air was blown toward the specimen at a rate of 15 liters per minute from a 4 mm inner diameter air hose placed directly above the specimen, cooling the center of the specimen. The hot plate was set to 65°C and heated. The temperature was considered to be in a steady state when the temperature change of each of the thermometers T1, T2, and T3 became 1°C or less per minute, and the thermal conductivity was calculated using the following formula from the temperatures at each point T1 [°C], T2 [°C], T3 [°C] and the thickness d [μm] of the object to be measured, with the thermal conductivity of the aluminum plate being KAl.Thermal conductivity of object to be measured = KAl × d × (T2 - T1) / (500 × (T3 - T2)) Using the above method, the thermal conductivities of the magnetic layer and coating material contained in the thermal conductivity measurement sample were each determined. The thermal conductivity of the coating material was determined as a relative value, with the thermal conductivity of the magnetic layer being 1.0, and was found to be 1.9.

[0099] <Measurement of Resistivity of Coating Material> The resistivity of the conductive tape (CU-35C manufactured by 3M Japan) used as the coating material above was measured by the following method. Two probes of a digital multimeter (KU-2608 manufactured by Kaise Co., Ltd.) were applied to the surface of the adhesive layer side of the conductive tape cut into 20 mm x 5 mm, and the resistance value R was measured. One probe was applied to a position 5 mm inside from one end in the longitudinal direction and at the center in the width direction, and the other probe was applied to a position 5 mm inside from the other end in the longitudinal direction and at the center in the width direction. The distance L between the electrodes of the digital multimeter used here was 0.01 m. The cross-sectional area S of the object to be measured, calculated from "thickness x width", was 2.55 x 10 －５ m ２ The resistivity ρ was calculated from the resistance value R, the distance between the electrodes L, and the cross-sectional area S of the object to be measured using the following formula, and was found to be 0.00051 Ω·m. Resistivity ρ (unit: Ω·m) = RS / L

[0100] <Measurement of Intermetallic Resistance Value> For the electromagnetic wave shielding material of Example 1, one probe of a digital multimeter (KU-2608 manufactured by Kaise Co., Ltd.) was placed against the center of the outer surface of one metal layer of the electromagnetic wave shielding material, and the other probe was placed against the center of the outer surface of the opposite metal layer, and the resistance value was measured to be 0.2 Ω.

[0101] Examples 2 and 3, Comparative Example 1 Electromagnetic wave shielding materials were prepared by the method described in Example 1, except that the degassing time of the coating liquid (magnetic layer-forming composition) was changed as shown in Table 1.

[0102] Comparative Example 2 An electromagnetic wave shielding material was prepared by the method described in Example 1, except that the coating liquid (magnetic layer-forming composition) was not subjected to degassing treatment.

[0103] [Example 4] In order to prevent bubbles from forming in the coating liquid during shaking stirring, 500 g of alumina balls with a diameter of 1 mm were placed in a plastic bottle, and the components of the coating liquid were then filled into the plastic bottle so that no air gaps were formed inside the bottle, and shaking stirring was carried out for 1 hour using a shaking stirrer. Except for the above points, an electromagnetic wave shielding material was produced using the method described for Example 1. The shaking stirring method for the coating liquid in Example 4 is referred to as "B." In contrast, in Examples and Comparative Examples other than Example 4, no alumina balls were placed in the plastic bottle, and shaking stirring was carried out in a state where the air and coating liquid were mixed in the bottle. The shaking stirring method for the coating liquid in Examples and Comparative Examples other than Example 4 is referred to as "A."

[0104] [Measurement of Scratch Cross-Section Area of ​​Magnetic Layer] For each of the electromagnetic wave shielding materials of the Examples and Comparative Examples, the scratch cross-section area of ​​the magnetic layer was determined by the method described above. An IM4000PLUS manufactured by Hitachi High-Technologies Corporation was used as the ion milling device, a Triboindenter TI-950 manufactured by Bruker was used as the surface shape measuring device, and ImageJ was used as the image analysis software.

[0105] [Evaluation of Electromagnetic Wave Shielding Performance (KEC Method)] Each of the electromagnetic wave shielding materials (size: 150 mm × 150 mm) in the Examples and Comparative Examples was subjected to a vibration treatment using the following method. A vibration tester and the electromagnetic wave shielding material were placed in a chamber, and a vibration treatment was performed for 72 hours, in which vibration was applied using a sine wave with a frequency of 25 Hz and an amplitude of 1.5 mm. The ambient temperature during the vibration treatment was constant at 40°C, and the vibration treatment was performed for 72 hours. The electromagnetic wave shielding performance of each electromagnetic wave shielding material was evaluated before and after the vibration treatment using the following method. The electromagnetic wave shielding material was placed between the antennas of a KEC method evaluation device including a signal generator, an amplifier, a pair of magnetic field antennas, and a spectrum analyzer, and the ratio (unit: dB (decibels)) of the received signal strength when the electromagnetic wave shielding material was not present to the received signal strength when the electromagnetic wave shielding material was present was determined at frequencies from 100 kHz to 1 GHz, and this was used to determine the shielding performance. This was performed on the magnetic field antenna to determine the magnetic wave shielding performance. KEC is an abbreviation for the Kansai Electronics Industry Development Center.

[0106] The results are shown in Table 1.

[0107]

[0108] From the results shown in Table 1, it can be confirmed that the electromagnetic wave shielding materials of Examples 1 to 4 suppress the deterioration of electromagnetic wave shielding performance after being subjected to vibration compared to the electromagnetic wave shielding materials of Comparative Examples 1 and 2.

[0109] 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, the scratch cross-sectional area of ​​the magnetic layer being 0.08 μm ２ 1.25 μm or more ２ The electromagnetic wave shielding material is as follows:

2. The electromagnetic shielding material according to claim 1, wherein the magnetic layer is disposed between two metal layers.

3. The electromagnetic shielding material according to claim 2, further comprising one or more layers containing a resin between the magnetic layer sandwiched between the two metal layers and one or both of the two metal layers.

4. The electromagnetic shielding material according to claim 1, wherein the magnetic layer further contains a resin.

5. The scratch cross-sectional area of ​​the magnetic layer is 0.10 μm ２ 1.00 μm or more ２ 2. The electromagnetic shielding material according to claim 1, wherein:

6. The magnetic layer is disposed between two metal layers, the magnetic layer further comprises a resin, and the scratch cross-sectional area of ​​the magnetic layer is 0.10 μm ２ 1.00 μm or more ２ 2. The electromagnetic shielding material according to claim 1, wherein:

7. The electromagnetic shielding material according to claim 6, further comprising one or more layers containing a resin between the magnetic layer sandwiched between the two metal layers and one or both of the two metal layers.

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

9. An electronic device comprising the electromagnetic shielding material according to any one of claims 1 to 7.

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