Electromagnetic wave shielding materials, electronic components and electronic equipment

Abstract

To provide an electromagnetic wave shielding material having excellent formability. [Solution] An electromagnetic wave shielding material having one or more magnetic layers containing magnetic particles and a resin, the magnetic layers having a degree of cross-linking of 20% or more, and a storage modulus E' of 1.00 GPa or less at 23°C as measured by dynamic viscoelasticity at 1 Hz. Electronic components and electronic devices that include this electromagnetic wave shielding material.

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a soft magnetic film that can be used for applications such as position detection devices (see paragraphs 0096, 0122, etc. of Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] WO2014 / 132880A1 Summary of the Invention [Problem to be solved by the invention]

[0004] 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. Electromagnetic wave shielding materials can exhibit electromagnetic wave shielding performance (hereinafter also referred to as "electromagnetic wave shielding ability" or "shielding ability") by reflecting and / or attenuating electromagnetic waves incident on the electromagnetic wave shielding material. For example, the soft magnetic film described in Patent Document 1 is thought to be able to function as an electromagnetic wave shielding material.

[0005] A desirable property of an electromagnetic wave shielding material is excellent moldability. The electromagnetic wave shielding material can be processed into various shapes for incorporation into electronic components or electronic devices. Excellent moldability means that defects such as shape defects and breakage are unlikely to occur during molding. An electromagnetic wave shielding material with excellent moldability is desirable in that it is unlikely to break in a molded product during three-dimensional molding (in other words, three-dimensional molding), for example.

[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 excellent in formability. [Means for solving the problem]

[0007] One aspect of the present invention is as follows. [1] Having one or more magnetic layers containing magnetic particles and resin, The magnetic layer has a cross-linking degree of 20% or more, and The electromagnetic wave shielding material has a storage modulus E' of 1.00 GPa (gigapascals) or less at 23°C in dynamic viscoelasticity measurement of the magnetic layer at 1 Hz (hertz). [2] The electromagnetic wave shielding material according to [1], wherein the content of the resin in the magnetic layer is 5.00 parts by mass or more and 35.00 parts by mass or less, relative to a total mass of 100.00 parts by mass of the magnetic layer. [3] The electromagnetic wave shielding material according to [1] or [2], wherein the content of the resin in the magnetic layer is 15.00 parts by mass or more and 25.00 parts by mass or less, relative to 100.00 parts by mass of the total mass of the magnetic layer. [4] The electromagnetic wave shielding material according to any one of [1] to [3], wherein the magnetic layer contains an acrylic resin having an alkyl(meth)acrylate structure in which the alkyl group has 2 to 8 carbon atoms. [5] The electromagnetic shielding material according to any one of [1] to [4], wherein the glass transition temperature Tg of the magnetic layer is −80° C. or higher and lower than 5° C. [6] The electromagnetic shielding material according to any one of [1] to [5], wherein the glass transition temperature Tg of the magnetic layer is −40° C. or higher and lower than −5° C. [7] Further having two or more metal layers, and The electromagnetic wave shielding material according to any one of [1] to [6], which comprises one or more of the magnetic layers sandwiched between two metal layers. [8] The electromagnetic wave shielding material according to [7], 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. [9] The electromagnetic shielding material according to any one of [1] to [8], wherein the degree of cross-linking of the magnetic layer is 20% or more and 98% or less.

[10] The electromagnetic wave shielding material according to any one of [1] to [9], wherein the magnetic layer has a storage modulus E' of 0.05 GPa or more and 1.00 GPa or less at 23°C in dynamic viscoelasticity measurement at 1 Hz.

[11] The content of the resin in the magnetic layer is 15.00 parts by mass or more and 25.00 parts by mass or less, relative to 100.00 parts by mass of the total mass of the magnetic layer; the magnetic layer contains an acrylic resin having an alkyl (meth)acrylate structure in which the alkyl group has 2 to 8 carbon atoms, the glass transition temperature Tg of the magnetic layer is −40° C. or higher and lower than −5° C., Further having two or more metal layers, The magnetic layer is sandwiched between two metal layers. The degree of cross-linking of the magnetic layer is 20% or more and 98% or less, and The electromagnetic wave shielding material according to any one of [1] to

[10] , wherein the magnetic layer has a storage modulus E' of 0.05 GPa or more and 1.00 GPa or less at 23° C. in dynamic viscoelasticity measurement at 1 Hz.

[12] The electromagnetic wave shielding material according to

[11] , 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.

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

[12] .

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

[12] . [Effects of the Invention]

[0008] According to one aspect of the present invention, it is possible to provide an electromagnetic wave shielding material having excellent moldability. Also, according to another aspect of the present invention, it is possible to provide an electronic component and an electronic device including the electromagnetic wave shielding material. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Electromagnetic wave shielding material] One aspect of the present invention relates to an electromagnetic wave shielding material having one or more magnetic layers containing magnetic particles and a resin, the magnetic layers having a degree of cross-linking of 20% or more, and the magnetic layers having a storage modulus E' of 1.00 GPa or less at 23°C as measured by dynamic viscoelasticity at 1 Hz. Hereinafter, the storage modulus E' of the magnetic layer at 23°C as measured by dynamic viscoelasticity at 1 Hz will also be referred to as "E'(23°C)."

[0010] In the present invention and this specification, the term "electromagnetic wave shielding material" refers to a material that can exhibit shielding ability 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 ability 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] In the present invention and this specification, the term "magnetic" means ferromagnetic property. The magnetic layer will be described in detail later.

[0012] The electromagnetic wave shielding material includes at least one magnetic layer containing magnetic particles and a resin, the magnetic layer having a degree of crosslinking of 20% or more and a storage modulus E' of 1.00 GPa or less at 23°C as measured by dynamic viscoelasticity at 1 Hz. The present inventors speculate that the presence of the magnetic layer included in the electromagnetic wave shielding material may contribute to the electromagnetic wave shielding material exhibiting excellent moldability. The electromagnetic wave shielding material will be described in more detail below.

[0013] <Magnetic layer> (Degree of cross-linking of magnetic layer) In the present invention and this specification, the degree of cross-linking of the magnetic layer is a value determined by the following method. The proportion of the binder component in the magnetic layer is determined using TG / DTA (Thermogravimetry / Differential Thermal Analysis). "TG / DTA" is commonly referred to as thermogravimetric differential thermal analysis. Specifically, a measurement sample taken from the magnetic layer to be measured is measured using a TG / DTA (thermogravimetric differential thermal analysis) device at a temperature range of 23°C to 600°C with a heating rate of 10°C / min, and the percentage mass loss at 600°C is taken as the proportion of the binder component (unit: mass%). A measurement sample (70 mg) taken from the magnetic layer to be measured and 7 ml of tetrahydrofuran (THF) are added to a container whose empty mass has been measured, and the entire measurement sample is immersed in the THF at room temperature for 12 hours. In this invention and this specification, "room temperature" refers to 20 to 25°C. Thereafter, the contents of the container are stirred for 30 minutes at room temperature using a mix rotor, and then the supernatant is removed while the THF-insoluble components in the container are attracted to the bottom of the container with a magnet. Then, 7 ml of acetone is added to the container, and the contents of the container are stirred for 30 minutes at room temperature using a mix rotor. After that, the acetone-insoluble components in the container are attracted to the bottom of the container with a magnet, and the supernatant is removed. The container is then vacuum dried for 1 hour in a vacuum dryer with an internal atmosphere temperature of 80°C, and the mass of the container is then measured. The value obtained by subtracting the mass of the empty container from the measured mass is taken as the mass of the solvent-insoluble components. The degree of crosslinking is calculated from the following formula using the mass of the solvent-insoluble component thus obtained and the proportion (unit: mass %) of the binder component in the magnetic layer obtained by TG / DTA measurement. Degree of crosslinking (%) = [1 - {(mass of measurement sample (70 mg) - mass of solvent-insoluble component) / mass of binder component of measurement sample}] x 100

[0014] From the viewpoint of improving the formability of the electromagnetic wave shielding material, the degree of cross-linking of the magnetic layer is 20% or more, preferably 30% or more, and more preferably 40% or more, 50% or more, and 60% or more. Also from the viewpoint of heat resistance, which will be described later, it is preferable that the degree of cross-linking of the magnetic layer be within the above range. The degree of cross-linking can be, for example, 100% or less, less than 100%, 98% or less, 96% or less, 93% or less, or 90% or less.

[0015] (E' of magnetic layer (23°C)) In the present invention, the storage modulus E' (E'(23°C)) at 23°C in dynamic viscoelasticity measurement at 1 Hz of the magnetic layer is determined by the dynamic viscoelasticity measurement described below. The dynamic viscoelasticity measurement is carried out using a dynamic viscoelasticity measuring device, such as the Hitachi High-Tech Science Dynamic Viscoelasticity Measuring Device DMS6100. The measurement procedure is as follows: A measurement sample measuring 28 mm in length and 10 mm in width is cut out from the magnetic layer to be measured. The viscoelasticity of the measurement sample is measured using a dynamic viscoelasticity measuring device under the following measurement conditions. From this measurement, the storage modulus E' at 23°C (E'(23°C)) is determined. Measurement conditions Chuck distance: 10mm Measurement temperature range: -50℃ to 100℃ Heating rate: 2°C / min Sampling rate: 3 seconds Measurement frequency: 1Hz

[0016] From the viewpoint of improving the formability of the electromagnetic wave shielding material, the E'(23°C) of the magnetic layer is 1.00 GPa or less, preferably 0.95 GPa or less, and more preferably 0.90 GPa or less, 0.85 GPa or less, 0.80 GPa or less, 0.75 GPa or less, 0.70 GPa or less, 0.65 GPa or less, 0.60 GPa or less, 0.50 GPa or less, 0.45 GPa or less, 0.40 GPa or less, 0.35 GPa or less, 0.30 GPa or less, and 0.25 GPa or less in this order. The E'(23°C) of the magnetic layer can be, for example, more than 0.00 GPa, or can be 0.05 GPa or more, or 0.10 GPa or more.

[0017] (glass transition temperature Tg of the magnetic layer) In the present invention and this specification, the glass transition temperature Tg of the magnetic layer is determined as the midpoint between the start and end points of the decline in a DSC (Differential Scanning Calorimetry) chart from the results of heat flow measurement using a differential scanning calorimeter. Specific examples of the measurement method include the method described in the Examples section below.

[0018] Electromagnetic wave shielding materials may be exposed to high temperatures when incorporated into electronic components or electronic devices. Therefore, it is also desirable for electromagnetic wave shielding materials to be able to exhibit high shielding ability even after being exposed to high temperatures. Electromagnetic wave shielding materials that exhibit high shielding ability after being exposed to high temperatures can contribute to significantly reducing the effects of electromagnetic waves in electronic components and electronic devices even after being exposed to high temperatures. Hereinafter, exhibiting high shielding ability after being exposed to high temperatures is also referred to as having excellent heat resistance. From the viewpoint of enabling the electromagnetic wave shielding material to exhibit excellent heat resistance, the glass transition temperature of the magnetic layer is preferably −80°C or higher, more preferably −70°C or higher, and more preferably −60°C or higher, −50°C or higher, −40°C or higher, −30°C or higher, and −20°C or higher in that order. On the other hand, from the viewpoint of further improving moldability, the glass transition temperature of the magnetic layer is preferably less than 5°C, more preferably 0°C or less, even more preferably -5°C or less, even more preferably less than -5°C, and even more preferably -10°C or less.

[0019] (magnetic particles) The magnetic particles contained in the magnetic layer can be one type selected from the group consisting of magnetic particles generally called soft magnetic particles, such as metal particles and ferrite particles, or a combination of two or more types. Metal particles generally have a saturation magnetic flux density about two to three times that of ferrite particles, and therefore can maintain relative permeability and exhibit shielding ability without magnetic saturation even under strong magnetic fields. 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."

[0020] metal particles Examples of metal particles serving as magnetic 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 alloys generally referred to as iron-based amorphous alloys, Co-containing alloys generally referred to as cobalt-based amorphous alloys, alloys generally referred to as nanocrystalline alloys, iron, permendur (Fe-Co alloy), and the like. Among these, sendust is preferred because it exhibits high saturation magnetic flux density and relative permeability. In addition to the constituent elements of the metal (including alloys), the metal particles may contain, at any content, 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. 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.

[0021] In one embodiment, the electromagnetic wave shielding ability of an electromagnetic wave shielding material against electromagnetic waves can be evaluated using the magnetic permeability (more specifically, the real part of the complex relative magnetic permeability) of the magnetic layer included in the electromagnetic wave shielding material as an index. An electromagnetic wave shielding material having a magnetic layer exhibiting high magnetic permeability (more specifically, the real part of the complex relative magnetic permeability) is preferred because it can exhibit high shielding ability against electromagnetic waves.

[0022] When complex relative permeability is measured using a permeability measuring device, the real part μ' and imaginary part μ" are usually displayed. In the present invention and this specification, the real part of complex relative permeability refers to this real part μ'. Hereinafter, the real part of complex relative permeability at a frequency of 3 MHz (megahertz) will also be referred to simply as "permeability" or "permeability μ'". Permeability can be measured using a commercially available permeability measuring device or a permeability measuring device with a known configuration. The measurement temperature is 25°C. By setting the ambient temperature surrounding the measurement sample to the measurement temperature, temperature equilibrium is achieved, and the temperature of the measurement sample can be set to the measurement temperature. From the perspective of exhibiting even better electromagnetic wave shielding ability, the permeability (real part of complex relative permeability at a frequency of 3 MHz) of the magnetic layer contained in the electromagnetic wave shielding material is preferably 40 or more, and more preferably 100 or more, both before and after thermal aging at 120°C, as determined by the method described in the Examples section below. The magnetic permeability can be, for example, 500 or less, 300 or less, or 200 or less, and can even exceed the values ​​exemplified here. Electromagnetic shielding materials with high magnetic permeability are preferred because they can exhibit excellent electromagnetic shielding ability.

[0023] From the viewpoint of forming a magnetic layer exhibiting high magnetic permeability, the magnetic particles are preferably flat-shaped particles (flat-shaped particles), and more preferably flat-shaped metal particles. By arranging the long side direction of the flat-shaped particles so that they are more 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 with an aspect ratio of 0.200 or less. The aspect ratio of flat-shaped particles is preferably 0.150 or less, more preferably 0.100 or less. The aspect ratio of flat-shaped particles can be, for example, 0.010 or more, 0.020 or more, or 0.030 or more. For example, the particle shape can be made flat by flattening using a known method. For details about the flattening process, see, for example, the description in JP 2018-131640 A, including paragraphs 0016 and 0017 and the Examples therein. An example of a magnetic layer exhibiting high magnetic permeability is a magnetic layer containing flat particles of sendust.

[0024] As described above, from the viewpoint of forming a magnetic layer exhibiting high magnetic permeability, it is preferable to arrange the long side direction of the flat particles so that it is closer to parallel to the in-plane direction of the magnetic layer. From this point of view, the degree of orientation, which is the sum of the absolute value of the average orientation angle of the flat 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 degree of orientation can be, for example, 3° or more, 5° or more, or 10° or more, and can also be less than the values ​​exemplified here. Methods for controlling the degree of orientation will be described later.

[0025] 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 using a known method. A randomly selected region of this cross section is then imaged using a scanning electron microscope (SEM). 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 image processing library OpenCV4 (Intel) uses the cv2.imread() function to read the image in grayscale with the second argument set to 0, and a binarized image is obtained using the cv2.threshold() function, with the midpoint between high and low brightness areas as the boundary. The white areas (high brightness areas) in the binarized image are identified as magnetic particles. The cv2.minAreaRect() function is used to calculate a rotated circumscribing rectangle corresponding to each magnetic particle in the resulting binarized image, 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 that are only partially included in the binarized image are also included. For particles that are only partially 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 (short side length / long side length) thus calculated 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 0.200 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 obtained above, the "orientation angle" is obtained as the rotation angle relative to the horizontal plane (surface of the magnetic layer). Particles with an aspect ratio of 0.200 or less in the binarized image are identified as flat particles. The absolute value of the average (arithmetic mean) and the variance of the orientation angles of all flat particles contained in the binarized image are calculated. This sum is defined as the "degree of orientation." The coordinates of the circumscribing rectangle are calculated using the cv2.boxPoints() function, and an image is created by overlaying the rotated circumscribing rectangle on the original image using the cv2.drawContours() function. Any rotated circumscribing rectangles that are clearly misdetected are excluded from the calculation of the aspect ratio and degree of orientation. The average (arithmetic mean) of the aspect ratios of particles identified as flat particles is defined as the aspect ratio of the flat particles contained in the magnetic layer being measured. The aspect ratio is 0.200 or less, preferably 0.150 or less, and more preferably 0.100 or less. The aspect ratio can be, for example, 0.010 or more, 0.020 or more, or 0.030 or more.

[0026] The content of magnetic particles in the magnetic layer can be, for example, 50.00 parts by weight or more, 60.00 parts by weight or more, 70.00 parts by weight or more, or 80.00 parts by weight or more, and can be, for example, 87.00 parts by weight or less, 85.00 parts by weight or less, 80.00 parts by weight or less, or 75.00 parts by weight or less, based on 100.00 parts by weight of the total weight of the magnetic layer. The magnetic layer can contain only one type of magnetic particle, or two or more types of magnetic particles in any ratio. In the present invention and this specification, when two or more types of a component are contained, the "content" refers to the total content of those components. The content of various components in the magnetic layer can be determined by known methods, such as TG / DTA (Thermogravimetry / Differential Thermal Analysis) or extraction of various components using a solvent. If the composition of the magnetic layer-forming composition used to form the magnetic layer is known, the content of various components in the magnetic layer can also be determined from this known composition.

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

[0028] 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 ability. 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 1.0×10 -10 It can be S / m or more.

[0029] (resin) In the present invention and this specification, a layer containing both magnetic particles and a resin is considered to be a "magnetic layer." The resin can function as a binder in the magnetic layer. Furthermore, at least a portion of the resin can be included in the magnetic layer in a state where it forms a crosslinked structure with a crosslinking agent, which will be described in detail later. The magnetic layer contains magnetic particles and a resin.

[0030] In this invention and this specification, "resin" means a polymer, and includes rubber and elastomer. Polymers include homopolymers and copolymers. Rubber includes natural rubber and synthetic rubber. Elastomers are polymers that exhibit elastic deformation. 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.

[0031] From the viewpoint of lowering the E'(23°C) of the magnetic layer, the resin content in the magnetic layer (if two or more resins are contained, the total content of the two or more resins; the same applies below) is preferably 5.00 parts by mass or more, more preferably 10.00 parts by mass or more, and more preferably 15.00 parts by mass or more, relative to a total mass of 100.00 parts by mass of the magnetic layer. On the other hand, from the viewpoint of increasing the magnetic permeability of the magnetic layer, the resin content in the magnetic layer is preferably 35.00 parts by mass or less, more preferably 30.00 parts by mass or less, and more preferably 25.00 parts by mass or less, relative to a total mass of 100.00 parts by mass of the magnetic layer.

[0032] Acrylic resins are preferred resins from the viewpoint of lowering the E' (23°C) of the magnetic layer. Furthermore, acrylic resins are thought to be less susceptible to thermal decomposition due to the carbon-carbon saturated bonds in the main chain. The present inventors believe that the inclusion of an acrylic resin in the magnetic layer can contribute to the electromagnetic wave shielding material being able to exhibit its high shielding ability without a significant decrease even after being exposed to high temperatures.

[0033] In the present invention and this specification, the term "acrylic resin" refers to a polymer of a (meth)acrylate compound. Polymers include homopolymers and copolymers. In the present invention and this specification, the term "(meth)acrylate compound" refers to a compound containing one or more (meth)acryloyl groups in one molecule, and the term "(meth)acryloyl group" is used to indicate either or both of an acryloyl group and a methacryloyl group. In addition, a (meth)acryloyl group may be contained in a (meth)acrylate compound in the form of a (meth)acryloyloxy group. The term "(meth)acryloyloxy group" is used to indicate either or both of an acryloyloxy group and a methacryloyloxy group.

[0034] Examples of (meth)acrylate compounds include butyl acrylates such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, and tert-butyl acrylate; cyclohexyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, and benzyl acrylate; and methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, hexyl methacrylate, and benzyl methacrylate. These compounds may be used alone or in combination of two or more. The present inventors believe that polymers of acrylic acid esters (including homopolymers and copolymers) can contribute to a higher degree of crosslinking in the magnetic layer compared to polymers of methacrylic acid esters (including homopolymers and copolymers). The inventors also believe that polymers of acrylic acid esters (including homopolymers and copolymers) tend to lower the glass transition temperature Tg of the magnetic layer compared to polymers of methacrylic acid esters (including homopolymers and copolymers).

[0035] In one embodiment, the acrylic resin can have an alkyl(meth)acrylate structure. In the present invention and this specification, the term "alkyl(meth)acrylate structure" refers to a partial structure represented by the following formula A:

[0036] [ka]

[0037] In formula A, R 10 represents a hydrogen atom or a methyl group. 10 When R is a hydrogen atom, the partial structure represented by formula A is called an alkyl acrylate structure, and R 10When is a methyl group, the partial structure represented by formula A is called an alkyl methacrylate structure, and the term "alkyl (meth)acrylate structure" is used to encompass such structures. In the present invention and this specification, an "*" in a partial structure indicates the bonding position where that partial structure is bonded to another partial structure. The acrylic resin can be a homopolymer or copolymer containing one or more types of alkyl (meth)acrylate structures as repeating units.

[0038] In formula A, R 11 represents an alkyl group. In the present invention and this specification, the number of carbon atoms in the alkyl (meth)acrylate structure is determined by the number of carbon atoms in the alkyl group R in formula A. 11 R refers to the number of carbon atoms in the alkyl group represented by 11 The alkyl group represented by R may be an unsubstituted alkyl group or an alkyl group having a substituent, and is preferably an unsubstituted alkyl group. 11 The number of carbon atoms in the alkyl group represented by R 11 In the case where the alkyl group represented by the formula (I) has a substituent, the number of carbon atoms refers to the portion other than the substituent. Examples of the substituent include alkyl groups (e.g., alkyl groups having 1 to 6 carbon atoms), hydroxy groups, alkoxy groups (e.g., alkoxy groups having 1 to 6 carbon atoms), and halogen atoms (e.g., fluorine atoms, chlorine atoms, bromine atoms, etc.). The glass transition temperature Tg of the magnetic layer can be affected by the structure of the acrylic resin contained in the magnetic layer. From the viewpoint of controlling the glass transition temperature Tg of the magnetic layer within the range described above, it is preferable to use R 11 The number of carbon atoms in the alkyl group represented by R is preferably 2 or more. 11 The number of carbon atoms in the alkyl group represented by the formula (I) is preferably 8 or less, more preferably 7 or less, and further preferably 6 or less, 5 or less, and 4 or less in that order.

[0039] An example of the acrylic resin is a copolymer of one or more compounds selected from a hydroxy group-containing compound, an unsaturated carboxylic acid, and a compound represented by the following formula 3 with a (meth)acrylate compound.

[0040] formula 3 CH2=C(X)R 1

[0041] In formula 3, R 1 represents a hydrogen atom or a methyl group, and X represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group, a -CN group, or a -CO-R 2 group, -O-CO-R 3 group, -OR 4 group or -(CH2) n -OR 5 R represents a group. 2 , R 3 , R 4 and R 5 each independently represents a hydrogen atom or an organic group having 1 to 20 carbon atoms, and the organic group may contain a halogen atom, a glycidyl group, etc. n represents an integer of 1 or more and 6 or less.

[0042] Examples of the hydroxy group-containing compound include 2-(hydroxyalkyl)acrylic acid esters such as α-hydroxymethylstyrene, α-hydroxyethylstyrene, and methyl 2-(hydroxyethyl)acrylate; and 2-(hydroxyalkyl)acrylic acids such as 2-(hydroxyethyl)acrylic acid; and these may be used alone or in combination of two or more.

[0043] Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, crotonic acid, α-substituted acrylic acid, and α-substituted methacrylic acid, and these may be used alone or in combination of two or more.

[0044] Examples of the compound represented by formula 3 include styrene, vinyl toluene, α-methyl styrene, acrylonitrile, methyl vinyl ketone, ethylene, propylene, vinyl acetate, 2-chloroethyl vinyl ether, chlorovinyl acetate, allyl glycidyl ether, glycidyl methacrylate, and glycidyl acrylate, and these may be used alone or in combination of two or more.

[0045] The acrylic resin contained in the magnetic layer may be a commercially available acrylic resin or an acrylic resin synthesized by a known method. For details on the synthesis method of the acrylic resin, see, for example, paragraphs 0016 to 0038 of JP-A No. 2002-140567 and the examples therein.

[0046] The magnetic layer may or may not contain a urethane resin. In the present invention and this specification, the term "urethane resin" refers to a resin having a structure containing one or more urethane bonds (-NH-C(=O)O-).

[0047] The acrylic resin content in the resin (100% by mass) of the magnetic layer can be 0% by mass or more, 30% by mass or more, 40% by mass or more, or 50% by mass or more, and from the viewpoint of lowering the E'(23°C) of the magnetic layer, it is preferably more than 50% by mass, more preferably 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more, in that order, and even more preferably 100% by mass. When the magnetic layer contains a resin other than acrylic resin as the resin, one example of such a resin is urethane resin.

[0048] In addition to the above components, the magnetic layer may also contain any amount of one or more of known additives such as crosslinkers, dispersants, stabilizers (e.g., antioxidants, light stabilizers such as HALS (Hindered Amine Light Stabilizer)), antifoaming agents, adhesion improvers for metals, and adhesion improvers for resins.

[0049] A crosslinking agent is a compound capable of forming a crosslinked structure, and can be included in the magnetic layer in a state in which a crosslinked structure is formed. The degree of crosslinking of the magnetic layer can also be controlled by the amount of crosslinking agent used. From the viewpoint of controlling the degree of crosslinking of the magnetic layer within the range described above, the content of the crosslinking agent in the magnetic layer is preferably 0.05 parts by mass or more and 2.00 parts by mass or less, more preferably 0.05 parts by mass or more and 0.50 parts by mass or less, and even more preferably 0.10 parts by mass or more and 0.50 parts by mass or less, based on a total mass of the magnetic layer of 100.00 parts by mass.

[0050] Specific examples of crosslinking agents include silane coupling agents, polyfunctional amine compounds, polyisocyanate compounds, etc. With regard to crosslinking agents, preferred crosslinking agents for controlling the degree of crosslinking of the magnetic layer within the range described above include one or more crosslinking agents selected from the group consisting of silane coupling agents and polyfunctional amine compounds.

[0051] A silane coupling agent is an organosilicon compound having an organic group and a hydrolyzable group, such as an alkoxy group, an acyloxy group, or a halogeno group.

[0052] The silane coupling agent may have a hydrophobic group. Examples of the silane coupling agent having a hydrophobic group as a functional group include alkoxysilanes such as methyltrimethoxysilane (MTMS), dimethyldimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, and decyltrimethoxysilane; chlorosilanes such as methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, and phenyltrichlorosilane; and hexamethyldisilazane (HMDS).

[0053] The silane coupling agent may also have a vinyl group. Examples of the silane coupling agent having a vinyl group include alkoxysilanes such as methacryloxypropyltriethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropylmethyldiethoxysilane, methacryloxypropylmethyldimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, and vinylmethyldimethoxysilane; chlorosilanes such as vinyltrichlorosilane and vinylmethyldichlorosilane; and divinyltetramethyldisilazane.

[0054] The silane coupling agent may also have an amino group. Examples of the silane coupling agent having an amino group include aminopropyltriethoxysilane, aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-8-aminooctyltrimethoxysilane, aminoalkoxysilanes having amines at both ends (for example, FM-3311, FM-3321, and FM-3325 manufactured by JNC Corporation), and polyfunctional amine aminoalkoxysilanes (for example, X-12-972F manufactured by Shin-Etsu Chemical Co., Ltd.).

[0055] Examples of crosslinked structures that can be formed by a silane coupling agent include a crosslinked structure formed by hydrolysis and condensation of the alkoxysilane portion of the silane coupling agent, and a crosslinked structure formed by the reaction of a functional group (e.g., an amino group) of the silane coupling agent with a functional group (e.g., a halogen atom) of the acrylic resin and condensation of the alkoxysilane portion.

[0056] A polyfunctional amine compound is a compound having two or more amino groups (-NH2) per molecule. A preferred polyfunctional amine compound is a diamine compound having two amino groups per molecule. Specific examples of diamine compounds include those listed in Tokyo Chemical Industry Co., Ltd.'s diamine monomer catalog (URL: https: / / www.tcichemicals.com / assets / brochure-pdfs / Brochure_FF046_J.pdf). Diamine compounds that are more suitable for controlling the degree of crosslinking of the magnetic layer within the aforementioned range include 1,8-octanediamine, 1,10-decanediamine, 1,12-dodecanediamine, 1,8-diamino-3,6-dioxaoctane, 1,4-bis(3-aminopropoxy)butane, bis[2-(3-aminopropoxy)]ethyl ether, triethylenetetramine, and N,N'-bis(2-aminoethyl)-1,3-propanediamine.

[0057] An example of a crosslinked structure that can be formed by a polyfunctional amine compound is a crosslinked structure formed by a reaction between an amino group of the polyfunctional amine compound and a functional group (for example, a glycidyl group) of an acrylic resin.

[0058] When the electromagnetic shielding material includes only one magnetic layer, the thickness of this magnetic layer can be, for example, 5 μm or more, and from the viewpoint of further improving the shielding ability 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 further improving moldability, it is preferably less than 90 μm, more preferably 80 μm or less, and even more preferably 70 μm or less. When the electromagnetic wave shielding material includes two or more magnetic layers, the thickness of each of these two or more magnetic layers (i.e., the thickness per layer) can be, for example, 5 μm or more, and from the viewpoint of further improving the shielding ability 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 this single 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.

[0059] The thickness of each layer included in the electromagnetic wave shielding material is determined by photographing a cross section exposed by a known method with a scanning electron microscope (SEM) and calculating the arithmetic mean of the thicknesses at five randomly selected points in the resulting SEM image.

[0060] In one embodiment, the electromagnetic shielding material can consist of only one magnetic layer, or can consist of only two or more magnetic layers. In another embodiment, the electromagnetic shielding material can further include two or more metal layers, with one or more of the magnetic layers sandwiched between the two metal layers. That is, in one embodiment, the electromagnetic shielding material can have a multilayer structure in which the 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. The inventors speculate that the multilayer structure can contribute to the electromagnetic shielding material being able to exhibit high shielding ability against electromagnetic waves. More details are as follows. To achieve high electromagnetic wave shielding performance in an electromagnetic wave shielding material, it is desirable to enhance the electromagnetic wave attenuation capacity and increase reflection at the interface. That is, it is desirable for electromagnetic waves to be significantly attenuated by repeatedly reflecting at the interface and passing through the electromagnetic wave shielding material multiple times. However, in terms of the behavior of metal layers and magnetic layers with respect to electromagnetic waves, metal layers tend to have high electromagnetic wave attenuation capacity but low magnetic wave reflection at the interface, while magnetic layers tend to have lower electromagnetic wave attenuation capacity than metal layers but high magnetic wave reflection at the interface. Therefore, it is difficult for a metal layer or a magnetic layer alone to achieve both high reflection and attenuation of electromagnetic waves, especially magnetic waves. In contrast, when an electromagnetic wave shielding material has a multilayer structure in which a magnetic layer is sandwiched between two metal layers, it is possible to achieve both the above-mentioned interface reflection and attenuation within the layers. The inventors believe that this allows the electromagnetic wave shielding material to exhibit high shielding performance against electromagnetic waves, specifically against magnetic waves.

[0061] When the electromagnetic shielding material includes two or more metal layers, the two or more metal layers have the same composition and thickness in one embodiment, and different compositions and / or thicknesses in another embodiment. This also applies to cases where the electromagnetic shielding material includes two or more magnetic layers, and to cases where the electromagnetic shielding material includes two or more other layers, such as resin layers (described below).

[0062] <Metal layer> 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.

[0063] 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 electromagnetic wave shielding material. This is preferable from the perspective of improving the shielding ability 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 contains a metal element with high electrical conductivity. From this perspective, it is preferable that the metal layer contains 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 and having a purity of 99.0% or higher is called a pure metal. Purity is measured by mass. An alloy is generally a pure metal with a composition adjusted by adding one or more metal or non-metal elements to a pure metal for corrosion prevention, strength improvement, etc. 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) of the alloy. From the viewpoint of economy, pure metal Cu or Al or an alloy containing Cu or Al as a main component is preferable, and from the viewpoint of high electrical conductivity, pure metal Cu or an alloy containing Cu as a main component is more preferable.

[0064] 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, based on the total mass of the metal layer. The metal content in the metal layer refers to the content by mass unless otherwise specified. For example, the metal layer can be a pure metal or alloy processed into a sheet. For example, a commercially available metal foil or a metal foil prepared by a known method can be used as the metal layer. Pure copper (Cu) sheets (so-called copper foil) of various thicknesses are commercially available. For example, such copper foil can be used as the metal layer. Copper foils include electrolytic copper foils obtained by depositing copper foil on a cathode by electroplating, 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, aluminum sheets (so-called aluminum foils) of various thicknesses are commercially available. For example, such aluminum foils can be used as the metal layer.

[0065] From the viewpoint of reducing the weight 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 and Mg, and more preferably a layer containing a metal selected from the group consisting of Al and Mg as its main component. The main component of a metal layer is the component with the highest proportion by mass. In a layer containing a metal selected from the group consisting of Al and Mg as its main component, Al or Mg is the component with the highest proportion by mass in this layer. Such a layer may contain only Al or Mg, or may contain both Al and Mg. Both Al and Mg have a small value obtained by dividing the specific gravity by the electrical conductivity (specific gravity / electrical conductivity). The smaller this value, the lighter the electromagnetic wave shielding material can be while exhibiting high shielding performance. For example, the value obtained by dividing the specific gravity by the electrical conductivity of Cu, Al, and Mg (specific gravity / electrical conductivity) calculated from literature values ​​is as follows: Cu: 1.5×10 -7 m / S, Al: 7.6 × 10 -8 m / S, Mg: 7.6 × 10-8 m / S. From the above values, Al and Mg can be said to be preferred metals from the viewpoint of reducing the weight of the electromagnetic shielding material. In one embodiment, the metal layer containing a metal selected from the group consisting of Al and Mg can contain only one of Al and Mg, and in another embodiment, it can contain both. From the viewpoint of reducing the weight of the electromagnetic shielding material, it is more preferable that one or both (preferably both) of the two metal layers sandwiching the magnetic layer is a metal layer containing 80.0 mass% or more of a metal selected from the group consisting of Al and Mg, and it is even more preferable that the metal layer contains 90.0 mass% or more of a metal selected from the group consisting of Al and Mg. Of Al and Mg, the metal layer containing at least Al can be a metal layer with an Al content of 80.0 mass% or more, or can also be a metal layer with an Al content of 90.0 mass% or more. Of Al and Mg, the metal layer containing at least Mg can be a metal layer with an Mg content of 80.0 mass% or more, or can also be a metal layer with an Mg content of 90.0 mass% or more. The content of the metal selected from the group consisting of Al and Mg, the Al content, and the Mg content can each be, for example, 99.9 mass% or less. The content of the metal selected from the group consisting of Al and Mg, the Al content, and the Mg content are each expressed as a percentage relative to the total mass of the metal layer.

[0066] From one or more of the viewpoints 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 more preferably a layer containing a metal selected from the group consisting of Al, Mg, and Cu as a primary component. In a layer containing a metal selected from the group consisting of Al, Mg, and Cu as a primary component, Al, Mg, or Cu is the component with the highest proportion by mass in this layer. Such a layer may contain only one, two, or three metals 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 containing 80.0 mass% or more of a metal selected from the group consisting of Al, Mg, and Cu, and even more preferably a metal layer containing 90.0 mass% or more of a metal selected from the group consisting of Al, Mg, and Cu. A metal layer containing at least Al among Al, Mg, and Cu can be a metal layer with an Al content of 80.0 mass% or more, or can be a metal layer with an Al content of 90.0 mass% or more. A metal layer containing at least Mg among Al, Mg, and Cu can be a metal layer with an Mg content of 80.0 mass% or more, or can be a metal layer with an Mg content of 90.0 mass% or more. A metal layer containing at least Cu among Al, Mg, and Cu can be a metal layer with a Cu content of 80.0 mass% or more, or can be a metal layer with a Cu content of 90.0 mass% or more. The content of the metal selected from the group consisting of Al, Mg, and Cu, the Al content, the Mg content, and the Cu content can each be, for example, 99.9 mass% or less. The content of the metal selected from the group consisting of Al, Mg, and Cu, the Al content, the Mg content, and the Cu content are each expressed as a percentage relative to the total mass of the metal layer.

[0067] Regarding the thickness of the metal layer, from the viewpoint of further improving the processability of the metal layer and the shielding ability 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.

[0068] In one embodiment, one or both outermost layers of the electromagnetic shielding material can be a metal layer. This can contribute to the electromagnetic shielding material being able to exhibit high shielding ability against magnetic fields in the low-frequency range of around 100 kHz to 1 MHz. Furthermore, having at least one outermost layer of the electromagnetic shielding material be a metal layer can also contribute to suppressing edge peeling in a molded product obtained by molding. In one embodiment, one or both outermost layers of the electromagnetic shielding material can be a metal layer that sandwiches a magnetic layer with another metal layer.

[0069] In one embodiment, when the electromagnetic wave shielding material has the multilayer structure, one or both of the two metal layers and the magnetic layer can be arranged as layers that directly contact each other. That is, one or both of the two metal layers and the magnetic layer can be adjacent to each other without any other layer interposed therebetween. In another embodiment, the multilayer structure can also have one or more layers containing a resin between one or both of the two metal layers and the magnetic layer. The resin-containing layer is a layer containing one or more types of resin. Specific embodiments of the resin-containing layer are described below.

[0070] <Layer containing resin> (Adhesive layer) An 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 that has tackiness on its surface at room temperature. Regarding 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 within 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, which can then be subjected to the above test. When another layer is laminated on both sides of the adhesive layer, the other layer on either side can be peeled off.

[0071] 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 processing it into a film. The adhesive layer-forming composition can be applied onto a support, for example. 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. Examples of the substrate onto which the adhesive 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. The substrate may be one whose surface (the surface to be coated) onto which the adhesive layer-forming composition is applied has been subjected to a release treatment by a known method. One form of release treatment is the formation of a release layer. Alternatively, a commercially available release-treated resin film may be used as the substrate. By using a substrate whose surface to be coated has been subjected to a release treatment, the adhesive layer and the substrate 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 a surface to be coated and drying the composition. Alternatively, an adhesive tape containing an adhesive layer can be used. Examples of the adhesive tape include double-sided tape. Double-sided tape has adhesive layers on both sides of a support. Alternatively, an adhesive tape having an adhesive layer on one side of a support can be used. Examples of the support include films of various resins such as polyesters (e.g., polyethylene terephthalate (PET) and polyethylene naphthalate (PEN)), polycarbonate (PC), acrylics (e.g., polymethyl methacrylate (PMMA)), cyclic polyolefins, triacetyl cellulose (TAC), polyether sulfide (PES), polyether ketone, and polyimide, nonwoven fabrics, and paper. Commercially available adhesive tapes having adhesive layers on one or both sides of a support can also be used.

[0072] 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.

[0073] (adhesive layer) An 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 in which a liquid or gel adhesive solidifies after contacting an adherend through a state change such as drying or curing, and at that time exerts adhesion to the adherend through an anchoring effect, physical interaction, or the formation of a chemical bond. In one embodiment, the adhesive layer may be a layer that does not have tackiness on the surface at room temperature. The adhesive contains a resin that solidifies after drying or curing. Examples of such resins include vinyl acetate resin, ethylene vinyl acetate resin, epoxy resin, cyanoacrylate resin, acrylic resin, polyurethane resin, chloroprene rubber, and styrene butadiene rubber. These resins may be liquid or gel-like themselves. Alternatively, a solid resin may be dissolved 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.

[0074] 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.

[0075] (resin layer) One example of a layer containing a resin is a resin layer. In the present invention and this specification, the term "resin layer" refers to a resin film formed by molding a thermoplastic resin such as a synthetic resin into a film 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 elastomers (PP), styrene-based elastomers, 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, and various resins such as triacetyl cellulose (TAC).

[0076] The resin layer can be bonded to a metal layer or a magnetic layer via an adhesive layer or a 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 a pressure-sensitive adhesive layer.

[0077] The thickness of the resin layer, expressed as the thickness of each resin layer, is preferably 10 μm or more, and more preferably 12 μm or more. The thickness of the resin layer, expressed as the thickness of each 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.

[0078] <Examples of layer configuration> The total number of magnetic layers contained in the electromagnetic wave shielding material is one or more, and can be two or more, or can be, for example, four or less. When the electromagnetic wave shielding material contains only one magnetic layer, this magnetic layer has a degree of crosslinking and an E' (23°C) within the above ranges. When the electromagnetic wave shielding material contains two or more magnetic layers, at least one magnetic layer has a degree of crosslinking and an E' (23°C) within the above ranges. In other words, when the electromagnetic wave shielding material contains two or more magnetic layers, some or all of the magnetic layers can be magnetic layers having a degree of crosslinking and an E' (23°C) within the above ranges. When the electromagnetic wave shielding material has the multilayer structure, the total number of metal layers included in the electromagnetic wave shielding material is two or more, and can be, for example, two to five layers.

[0079] In one embodiment, in a multilayer structure in which the 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 structure of the electromagnetic wave 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 wave shielding material including two or more multilayer structures each including the magnetic layer between two metal layers, 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, as in Examples A2 and A3, for example. In the electromagnetic wave shielding material, the total number of multilayer structures each including 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. A total of two or more (e.g., two, three, or four) multilayer structures is preferred from the viewpoint of further improving the shielding ability of the electromagnetic wave shielding material. In the above, the symbol " / " means that the layer on the left of the symbol and the layer on the right of the symbol are in direct contact with each other without any intervening layer. This also applies to the following description unless otherwise specified.

[0080] In another embodiment, the multilayer structure of the electromagnetic shielding material, in which the magnetic layer is sandwiched between two metal layers, can include one or more resin-containing layers 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 intervening layer, and one or more resin-containing layers can be included between the other metal layer and the magnetic layer. Alternatively, the multilayer structure can have one or more resin-containing layers between each of the two metal layers and the magnetic layer. As the resin-containing layer located between the metal layer and the magnetic layer, at least a resin layer is preferred. In one embodiment, the electromagnetic shielding material can include one or more polyester resin-containing layers between one or both of the two metal layers and the magnetic layer, and the polyester resin-containing layer is preferably a resin layer.

[0081] 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.

[0082] 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.

[0083] 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 with an adhesive layer on one or both sides of the support. For example, as in Example B3, the metal layer sandwiching one magnetic layer may also be the metal layer sandwiching another magnetic layer. For example, in Example B3, metal layer 2 is one of the two metal layers sandwiching magnetic layer 1 and is also one of the 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 glue layer 1 / resin layer 1 / magnetic layer 1 / resin layer 2 / adhesive layer 2 or glue layer 2 / metal layer 2" Example B2: "Metal layer 1 / adhesive layer 1 or glue layer 1 / resin layer 1 / magnetic layer 1 / metal layer 2 / adhesive layer 2 or glue 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 glue layer 1 / resin layer 1 / magnetic layer 1 / metal layer 2 / magnetic layer 2 / resin layer 2 / adhesive layer 2 or glue layer 2 / metal layer 3" Example B7: "Metal layer 1 / adhesive layer 1 or bonding layer 1 / resin layer 1 / magnetic layer 1 / metal layer 2 / magnetic layer 2 / metal layer 3 / adhesive layer 2 or bonding layer 2 / resin layer 2" Example B8: "Metal layer 1 / adhesive layer 1 or glue layer 1 / resin layer 1 / magnetic layer 1 / resin layer 2 / adhesive layer 2 or glue layer 2 / metal layer 2 / magnetic layer 2 / resin layer 3 / adhesive layer 3 or glue layer 3 / metal layer 3"

[0084] In another embodiment, the multilayer structure of the electromagnetic shielding material in which the magnetic layer is sandwiched between two metal layers can be a multilayer structure in which two or more magnetic layers are sandwiched between the two metal layers. Such a multilayer structure can also include one or more layers containing a resin between two adjacent magnetic layers. For example, the multilayer structure of the electromagnetic shielding material in which the magnetic layer is sandwiched between two metal layers can include two magnetic layers between the two metal layers and one layer containing a resin between the two magnetic layers. A specific example of the layer configuration of an electromagnetic shielding material having such a multilayer structure can be Example B9 below. Example B9: "Metal layer 1 / Magnetic layer 1 / Resin layer 1 / Magnetic layer 2 / Metal layer 2"

[0085] <Method of manufacturing electromagnetic wave 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 in any ratio, can be selected based on the solubility of the components used in preparing the magnetic layer-forming composition. 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.

[0086] The magnetic layer-forming composition can be prepared by mixing the various components sequentially in any order or simultaneously. If necessary, dispersion treatment can be carried out using a known dispersing machine such as a ball mill, bead mill, sand mill, or roll mill, and / or stirring treatment can be carried out using a known stirring machine such as a vibration stirring machine.

[0087] 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.

[0088] Examples of substrates onto which the magnetic layer-forming composition is applied include films of various resins, such as polyesters (e.g., polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), acrylics (e.g., 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. The substrate may have a surface (coating surface) onto which the magnetic layer-forming composition is applied (a surface to be coated) that has been subjected to a release treatment by a known method. 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 may be used as the substrate. Using a substrate with a release-treated coating surface allows for easy separation of the magnetic layer from the substrate after film formation.

[0089] The magnetic layer-forming composition can also be applied to the surface of the previously described layers, such as a metal layer or a resin layer. For example, by applying the magnetic layer-forming composition to the surface of a metal layer or a resin layer and, if necessary, applying pressure to the magnetic layer described below, it is possible to produce a multilayer partial structure ("magnetic layer / metal layer" or "magnetic layer / resin layer") in which a magnetic layer is sandwiched between two metal layers of an electromagnetic shielding material. As an example, an electromagnetic shielding material having the layer structure of Example A1, "metal layer / magnetic layer / metal layer," described above, can be produced by applying pressure and heat to two "magnetic layer / metal layer" partial structures with the magnetic layers facing each other and bonding them together.

[0090] The coating layer formed by applying the magnetic layer-forming composition can be dried by known methods such as heating or hot air blowing. The drying can be carried out under conditions that allow the solvent contained in the magnetic layer-forming composition to volatilize. For 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.

[0091] 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.

[0092] (Pressure treatment of magnetic layer) The magnetic layer can also be subjected to pressure treatment after deposition. By applying pressure to a magnetic layer containing magnetic particles, the magnetic particle density in the magnetic layer can be increased, resulting in a higher magnetic permeability. Furthermore, for a magnetic layer containing flat-shaped particles, the degree of orientation can be reduced by applying pressure, resulting in a higher magnetic permeability.

[0093] The pressure treatment can be carried out by applying pressure in the thickness direction of the magnetic layer using a plate press, roll press, or the like. A plate press places the object to be pressed between two flat press plates arranged one above the other, and applies pressure to the object by bringing the two press plates together using mechanical or hydraulic pressure. A roll press passes the object to be pressed between rotating pressure rolls arranged one above the other, and applies pressure 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.

[0094] The pressure during the pressure treatment can be set arbitrarily. For example, in the case of a plate-type press, the pressure is set to, for example, 1 to 50 N (Newton) / mm 2 In 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 plate press is used, it 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 object to be pressed, and the conveying speed is, for example, 10 cm / min to 200 m / min. The material of the press plate and pressure roll can be selected arbitrarily from metal, ceramic, plastic, rubber, and the like. During pressure treatment, it is also possible to apply heat to both the upper and lower press plates or one of the press plates of a plate-shaped press, or to one of the upper and lower rolls of a roll press. Heating can soften the magnetic layer, thereby achieving a high compression effect when pressure is applied. The temperature during heating can be set as desired, for example, between 50°C and 200°C. The temperature during heating 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 plates while they are still at a high temperature. Alternatively, the press plates can be cooled by water cooling, air cooling, or the like while maintaining the pressure, and then the press plates can be separated to remove the magnetic layer. In the case of a roll press, the magnetic layer can be cooled immediately after pressing by water cooling, air cooling or the like. The pressure treatment can be repeated two or more times. When the magnetic layer is formed on a release film, for example, it can be subjected to pressure treatment while laminated on the release film, or it can be peeled off from the release film and subjected to pressure treatment as a single magnetic layer.

[0095] (Laminating various layers) The various layers can be bonded together using a pressure-sensitive adhesive layer or adhesive layer, as described above. Furthermore, in the electromagnetic wave shielding material, two adjacent layers can also be bonded by, for example, applying pressure and heat to them. For the bonding, a plate-type press, a roll press, or the like can be used. 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, promoting contact with the surface of the adjacent layer, 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.

[0096] 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-like electromagnetic shielding material, or a sheet-like 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, molding performed without heating the object and / or mold, or by heating at a low temperature, is generally referred to as cold forming. In one embodiment, the electromagnetic shielding material exhibits excellent formability in cold forming and is suitable for cold forming such as drawing and stretch forming. Drawing is a molding method in which a sheet-like object is pressed using a pair of dies, one female and one male, to form a container with a bottom of various shapes, such as a cylinder, a rectangular tube, or a cone. In contrast, bulging is a method of forming a molded product with a curved surface bulging out from a flat surface from a sheet-like object. bulging 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 produces a shallow molded product, while deep drawing produces 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). The electromagnetic shielding material can be an electromagnetic shielding material that is difficult to break when formed by such a three-dimensional forming method. Publicly known techniques can be applied to the three-dimensional forming method.

[0097] [Electronic Components] One aspect of the present invention relates to an electronic component including 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 according to 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, the electromagnetic wave shielding material can be three-dimensionally molded into a cylindrical shape and placed as a cover material that covers the outside of a cable.

[0098] [Electronic equipment] 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 as a cover material covering 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 covering the outside of a cable.

[0099] One example of how the electromagnetic shielding material can be used is to cover a semiconductor package on a printed circuit board with the electromagnetic shielding material. For example, "Electromagnetic Shielding Technology for Semiconductor Packages" (Toshiba Review Vol. 67 No. 2 (2012) p. 8) discloses a method for achieving high shielding effectiveness by electrically connecting a side via at the edge of the package substrate to the inner surface of the electromagnetic shielding material when covering a semiconductor package with the electromagnetic shielding material, 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. [Example]

[0100] 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. "Parts" in the following descriptions are "parts by mass."

[0101] [Magnetic layer resin] Regarding the resins for the magnetic layer shown in Table 1, "acrylic resin 1" is an acrylic rubber product name Nipol model number AR71 manufactured by Zeon Corporation. Acrylic resin 1 is an acrylic resin (solid concentration 100% by mass) synthesized using ethyl acrylate as the (meth)acrylate compound and vinyl chloroacetate as the compound represented by formula 3.

[0102] "Acrylic resin 2" is an acrylic resin synthesized by the following method. Emulsion polymerization and slurry formation were carried out according to the synthesis example described in paragraph 0097 of JP 2022-140567 A, except that "15 parts of ethyl acrylate, 55 parts of n-butyl acrylate, 28 parts of methoxyethyl acrylate, and 2 parts of mono-n-butyl fumarate" described in the same paragraph was changed to "97 parts of octyl acrylate and 3 parts of vinyl chloroacetate." The obtained slurry was dried under reduced pressure in a vacuum dryer at an internal atmospheric temperature of 80 ° C. to obtain an acrylic resin (solid content concentration 100% by mass).

[0103] The number of carbon atoms in the alkyl group of the alkyl(meth)acrylate structure of each of the acrylic resins 1 and 2 is shown in Table 1.

[0104] The "urethane resin" is UR-6100 (solid content concentration: 45% by mass) manufactured by Toyobo Co., Ltd.

[0105] [Cross-linking agent for magnetic layer] Regarding the crosslinking agents for the magnetic layer shown in Table 1, "KBM-903" is a silane coupling agent manufactured by Shin-Etsu Silicones Co., Ltd. (product name: KBM-903). "Coronate L" is a polyisocyanate compound manufactured by Tosoh Corporation (trade name: Coronate L).

[0106] Each of the electromagnetic shielding materials in Examples 1 to 8 and Comparative Examples 1 and 2 described below is an electromagnetic shielding material consisting of only one magnetic layer.

[0107] [Example 1] <Preparation of Magnetic Layer-Forming Composition (Coating Liquid)> In a plastic bottle Fe-Si-Al flat magnetic particles (MKT Sendust MFS-SUH): 9.88g Resin (see Table 1): 2.42g Crosslinker (see Table 1): 0.0495 g Methyl ethyl ketone: 29g The mixture was mixed for 96 hours using a shaking stirrer to prepare a coating liquid (magnetic layer-forming composition). In the magnetic layer formed from the prepared coating liquid, the resin content and crosslinker content relative to the total mass of the magnetic layer (100.00 parts by mass) are the values ​​shown in Table 1.

[0108] <Magnetic Layer Preparation> (Magnetic layer formation) The coating liquid was applied to the release surface of a release-treated PET film (PET75-LS2 manufactured by Nippa Corporation) using a blade coater with a coating gap of 650 μm, and the film was dried for 8 minutes in a drying device with an internal atmospheric temperature of 90°C, forming a film-like magnetic layer on the release-treated PET film.

[0109] (Pressure treatment of magnetic layer) The upper and lower press plates of a plate-type press (Mini Test Press manufactured by Toyo Seiki Co., Ltd.) were heated to 140°C (internal temperature of the press plates), and the magnetic layer from which the release-treated PET film had been removed was sandwiched between two 1mm thick Teflon (registered trademark) sheets and subjected to a pressure of 30N / mm 2 The pressure was maintained for 10 minutes with the upper and lower press plates cooled to 50°C (internal temperature of the press plates) while the pressure was maintained, and then the magnetic layer was removed from between the two Teflon (registered trademark) sheets.

[0110] Measurement samples were cut out from the magnetic layer (electromagnetic wave shielding material) obtained above and used for the following various evaluations of the magnetic layer.

[0111] [Evaluation method] <Method for measuring the degree of cross-linking of the magnetic layer> A measurement sample for TG / DTA measurement and a measurement sample for determining the mass of the solvent-insoluble component were cut out from the magnetic layer. The proportion of the binder component (unit: mass%) of the measurement sample for TG / DTA measurement was determined using the method described above. Specifically, a Hitachi High-Tech Science TG / DTA7300 was used as the TG / DTA measurement device, and 3 mg of the measurement sample cut out from the magnetic layer was placed in an alumina pan. Measurements were performed in a nitrogen atmosphere at a temperature range of 23°C to 600°C at a heating rate of 10°C / min, and the mass loss percentage at 600°C was taken as the proportion of the binder component (unit: mass%). The mass of the solvent-insoluble components was determined by the method described above using a 70 mg measurement sample cut out from the magnetic layer. Using the mass of the solvent-insoluble component and the proportion of the binder component thus determined, the degree of crosslinking was calculated according to the formula described above. For example, in Example 1, the mass loss percentage at 600°C was 20%, so the proportion of the binder component in the magnetic layer was set to 20%. Therefore, the mass of the binder component in the measurement sample was calculated to be 70 mg x 0.2 = 14 mg. The mass of the solvent-insoluble component was 68.6 mg, so the degree of crosslinking was calculated as follows: Degree of crosslinking=[1-{(70-68.6) / (70×0.2)}]×100=(1-0.1)×100=90(%)

[0112] <Method for measuring E' (23°C) of the magnetic layer> A measurement sample measuring 28 mm in length and 10 mm in width was cut out from the magnetic layer, and dynamic viscoelasticity measurements were carried out using a Hitachi High-Tech Science DMS6100 dynamic viscoelasticity measuring device according to the measurement procedure described above. E' (23°C) was calculated from the measurement results.

[0113] <Method for measuring the glass transition temperature Tg of the magnetic layer> A measurement sample was cut out from the magnetic layer. Heat flow measurements were performed on the cut-out measurement sample using a differential scanning calorimeter, DSC6200 manufactured by SII Technology, under the following conditions. The same sample was subjected to two temperature increase / decrease cycles, and the glass transition temperature Tg was determined using the measurement result from the second heating. (Measurement conditions) Atmosphere in the measurement chamber: Nitrogen (50 mL / min) Heating rate: 10°C / min Measurement start temperature: -100℃ Measurement end temperature: 200℃ Sample pan: Aluminum pan Mass of sample to be measured: 5 mg Calculation of glass transition temperature Tg: The midpoint between the start and end points of the decline on the DSC chart was taken as Tg.

[0114] <Measurement of magnetic permeability before and after heating at 120℃> A measurement sample measuring 28 mm x 10 mm was cut out from the magnetic layer, and the magnetic permeability was measured using a magnetic permeability measuring device (Per01 manufactured by Keycom Corporation) to determine the magnetic permeability as the real part of the complex relative magnetic permeability (μ') at a frequency of 3 MHz (measurement temperature: 25°C). The magnetic permeability thus determined is referred to as the "magnetic permeability before aging at 120°C." After measuring the magnetic permeability before aging at 120°C, the measurement sample was placed in a high-temperature atmosphere at 120°C for 24 hours, and then the magnetic permeability was determined by the above method (measurement temperature: 25°C). The magnetic permeability thus determined is referred to as the "magnetic permeability after aging at 120°C." Table 2 shows the evaluation results of the "magnetic permeability before aging at 120°C" and the "magnetic permeability after aging at 120°C" evaluated according to the following evaluation criteria. A: Magnetic permeability μ' is 100 or more B: Magnetic permeability μ' is 40 or more and less than 100 C: Magnetic permeability μ' is less than 40

[0115] <Measurement of electrical conductivity> 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 Kogyo Co., Ltd.), 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 on a sample piece of the magnetic layer cut to a size of 60 mm x 60 mm, and a voltage of 25 V was applied to both 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 It was S / m. The thickness of the magnetic layer was determined by the following method. Electrical conductivity [S / m] = 1 / (surface electrical resistivity [Ω] x thickness [m])

[0116] <Acquisition of cross-sectional images of magnetic layer (electromagnetic wave shielding material)> Cross-section processing was carried out to expose the cross section of the magnetic layer (electromagnetic wave shielding material) by the following method. The magnetic layer was cut into a size of 3 mm x 3 mm, embedded in resin, and the cross section of the magnetic layer was cut using an ion milling device (IM4000PLUS manufactured by Hitachi High-Technologies Corporation). The cross section of the exposed magnetic layer was observed using a scanning electron microscope (SU8220 manufactured by Hitachi High-Technologies Corporation) at an accelerating voltage of 2 kV and a magnification of 100x to obtain a backscattered electron image. The thickness of the magnetic layer was measured at five points on the obtained image using the scale bar as a reference. The arithmetic mean of the measurements at the five points was taken as the thickness of the magnetic layer. The thickness of the magnetic layer was 30 μm.

[0117] <Acquisition of cross-sectional images of the magnetic layer> The cross section of the magnetic layer exposed by cross-section processing in the same manner as above was observed with a scanning electron microscope (SU8220 manufactured by Hitachi High-Technologies Corporation) at an acceleration voltage of 2 kV and a magnification of 1000 times to obtain a backscattered electron image.

[0118] <Measurement of aspect ratio of magnetic particles and degree of orientation of flat particles> Using the backscattered electron image obtained above, the aspect ratio of the magnetic particles was determined by the method described above, and the flat-shaped particles were identified from the aspect ratio value. Whether or not the magnetic layer contained flat-shaped 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 found to be 13°. The average value (arithmetic mean) of the aspect ratios of all particles identified as flat-shaped particles was also calculated as the aspect ratio of the flat-shaped particles contained in the magnetic layer. The calculated aspect ratio was 0.071.

[0119] <Elongation at break of electromagnetic wave shielding material (magnetic layer)> A test sheet measuring 100 mm in length and 10 mm in width was cut out from the electromagnetic shielding material (magnetic layer) of Example 1. This test sheet was attached to a tensile tester, and a tensile test was performed under the following measurement conditions. A Tensilon universal testing machine (RTF-1310) manufactured by A&D Corporation was used as the tensile tester. To allow the test sheet to adapt to the measurement environment, the test sheet was left in the measurement environment for 15 minutes or more before being attached to the tensile tester and the tensile test was performed. The breaking elongation was calculated as "breaking elongation [unit: %] = 100 × L / chuck distance," where L is the maximum elongation of the test sheet stretched in the tensile test (i.e., the elongation displacement in the longitudinal direction at the time the test sheet breaks). Breakage of the test sheet can be determined by the stress reduction in the stress-strain curve, visual inspection, etc. From the viewpoint of formability of the electromagnetic shielding material (e.g., formability in cold forming), it is preferable that the breaking elongation of the magnetic layer thus determined be 10% or more, more preferably 15% or more, even more preferably 20% or more, and even more preferably 25% or more. Furthermore, the breaking elongation of the magnetic layer can be, for example, 100% or less, 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, or 40% or less. From the viewpoint of improving the formability of the electromagnetic shielding material, a larger breaking elongation of the magnetic layer is preferable. For electromagnetic shielding materials that include a magnetic layer and one or more other layers, a measurement sample for measuring the breaking elongation of the magnetic layer can be taken from the electromagnetic shielding material by a known method. (Measurement conditions) Chuck distance: 50mm Measurement environment: Temperature 23°C, relative humidity 50% Load cell: 500N (Newton) Pulling speed: 50 mm / min Tensile direction: Lengthwise

[0120] [Examples 2 to 8, Comparative Examples 1 and 2] An electromagnetic wave shielding material (magnetic layer) was produced and various evaluations were carried out in the same manner as in Example 1, except that the items shown in Table 1 were changed as described in Table 1. In Example 7, acrylic resin 1 and urethane resin were mixed in a ratio of 1:1 (based on the mass of the solid content of the resin) and used. In Example 8, Comparative Example 1, and Comparative Example 2, in the magnetic layer formed from the prepared magnetic layer-forming composition, the solid content of the urethane resin relative to the total mass of the magnetic layer (100.00 mass parts) was the value shown in the resin amount column in Table 1.

[0121] The evaluation results obtained for Examples 1 to 8 and Comparative Examples 1 and 2 are shown in Table 2.

[0122] [Table 1]

[0123] [Table 2]

[0124] As shown in Table 2, the electromagnetic shielding materials of Examples 1 to 8 had larger breaking elongation values ​​than the electromagnetic shielding materials of Comparative Examples 1 and 2. These results confirm that the electromagnetic shielding materials of Examples 1 to 8 have excellent formability.

[0125] Each of the electromagnetic wave shielding materials of Examples 9 to 15 and Comparative Example 3 described below is an electromagnetic wave shielding material having a multilayer structure in which a magnetic layer is sandwiched between two metal layers.

[0126] [Example 9] <Production of electromagnetic wave shielding material> An electromagnetic wave shielding material was produced by cutting out a magnetic layer obtained as described above for Example 1. A 50 μm-thick aluminum foil (JIS H4160:2006 compliant, alloy number 1N30, temper (1)O, Al content of 99.3 mass% or more) was used as the metal layer, and a laminate was produced by stacking three layers of "aluminum foil (metal layer) / magnetic layer / aluminum foil (metal layer)" without any other layer between any two adjacent layers. The upper and lower press plates of a plate press (Yamamoto Iron Works large hot press TA-200-1W) were heated to 140°C (internal temperature of the press plates), the laminate was placed in the center of the press plates, and a pressure of 4.66 N / mm 2 The aluminum foil and the magnetic layer were thermocompression-bonded by maintaining this applied pressure for 15 minutes. The upper and lower press plates were cooled to 50°C (internal temperature of the press plates) while maintaining the pressure, and then the laminate was removed from the plate press. In this way, an electromagnetic wave shielding material having a layer structure of "aluminum foil (metal layer) / magnetic layer / aluminum foil (metal layer)" was obtained.

[0127] <Acquiring a cross-sectional image of an electromagnetic wave shielding material> The cross-section of the electromagnetic wave shielding material was processed to expose the cross-section in the following manner. The electromagnetic wave shielding material was cut into pieces measuring 3 mm x 3 mm and embedded in resin, and the cross section of the electromagnetic wave shielding material was cut using an ion milling device (IM4000PLUS manufactured by Hitachi High-Technologies Corporation). The cross section of the exposed electromagnetic shielding material was observed using a scanning electron microscope (SU8220, manufactured by Hitachi High-Technologies Corporation) at an accelerating voltage of 2 kV and a magnification of 100x to obtain a backscattered electron image. Using the scale bar as a reference, the thickness of the magnetic layer and the thickness of each of the two metal layers were measured at five locations on the obtained image. The arithmetic mean of each was taken as the thickness of the magnetic layer and the thickness of each metal layer. The thickness of the magnetic layer was 30 μm, and the thickness of each metal layer was 50 μm.

[0128] <Moldability> The electromagnetic wave shielding material of Example 9 was draw-molded in a mold (manufactured by Amada Co., Ltd.) consisting of a male mold and a female mold at room temperature (25°C) without heating to produce a hemispherical three-dimensional molded product. The produced three-dimensional molded product was visually inspected for the presence or absence of fractures, and the moldability was evaluated based on the inspection results according to the following evaluation criteria. (Evaluation criteria) A: Using a 4cm deep hemispherical mold, it is possible to mold a 4cm deep three-dimensional product without breaking. B: Using a hemispherical mold with a depth of 3 cm, a three-dimensional molded product with a depth of 3 cm can be molded without breaking. Furthermore, when a hemispherical mold having a depth of 4 cm was used, fractures were observed in the resulting three-dimensional molded product having a depth of 4 cm, or no three-dimensional molded product having a depth of 4 cm was obtained. C: A fracture occurred in a 2cm deep three-dimensional molded product obtained using a 2cm deep hemispherical mold.

[0129] <Evaluation of shielding ability before and after heating at 120°C (KEC method)> A 15cm x 15cm piece of electromagnetic shielding material was placed between the antennas of a KEC method evaluation device, which included a signal generator, an amplifier, a pair of magnetic field antennas, and a spectrum analyzer. The ratio of the received signal strength without the electromagnetic shielding material to the received signal strength with the electromagnetic shielding material at a frequency of 100 kHz was calculated as the shielding ability. This was performed on the magnetic field antenna to determine the electromagnetic shielding ability (magnetic field shielding ability). KEC is an abbreviation for Kansai Electronics Industry Development Center. The shielding ability evaluated from the value calculated in this way according to the following evaluation criteria is referred to as the "shielding ability before aging at 120°C." After measuring the shielding ability before aging at 120°C, the electromagnetic shielding material was placed in a high-temperature atmosphere at 120°C for 24 hours, and then the shielding ability was determined using the above method. The shielding ability evaluated from the thus determined value according to the following evaluation criteria was designated as the "shielding ability after aging at 120°C." (Evaluation criteria) A:20dB or more B: 15dB or more and less than 20dB C: Less than 15dB

[0130] [Examples 10 to 14, Comparative Example 3] For the examples or comparative examples shown in the "Magnetic Layer" column of Table 3, the magnetic layers were cut out from the magnetic layers obtained as described above, but the electromagnetic wave shielding materials were prepared and various evaluations were carried out using the methods described for Example 9.

[0131] [Example 15] An electromagnetic wave shielding material was produced and various evaluations were carried out in the same manner as in Example 9, except for the following points. Instead of aluminum foil, Panac Alpet 50-50 (a laminate consisting of a 50 μm thick aluminum foil (metal layer with an Al content of 99.0% by mass or more) and a 50 μm thick polyester film (resin layer) bonded together via a 3 μm thick adhesive layer) was used. The resulting electromagnetic wave shielding material had a layer structure of "aluminum foil (metal layer) / adhesive layer / resin layer / magnetic layer / resin layer / adhesive layer / aluminum foil (metal layer)."

[0132] The evaluation results obtained for Examples 9 to 15 and Comparative Example 3 are shown in Table 3.

[0133] [Table 3]

[0134] As shown in Table 3, the electromagnetic shielding materials of Examples 9 to 15 were superior in formability to the electromagnetic shielding material of Comparative Example 3. [Industrial Applicability]

[0135] One aspect of the present invention is useful in the technical fields of various electronic components and various electronic devices.

Claims

1. having one or more magnetic layers containing magnetic particles and resin; The degree of cross-linking of the magnetic layer is 20% or more, and The electromagnetic wave shielding material has a storage modulus E' of 1.00 GPa or less at 23° C. in dynamic viscoelasticity measurement at 1 Hz of the magnetic layer.

2. 2. The electromagnetic wave shielding material according to claim 1, wherein the content of the resin in the magnetic layer is 5.00 parts by mass or more and 35.00 parts by mass or less, relative to a total mass of 100.00 parts by mass of the magnetic layer.

3. 2. The electromagnetic wave shielding material according to claim 1, wherein the content of the resin in the magnetic layer is 15.00 parts by mass or more and 25.00 parts by mass or less, relative to a total mass of 100.00 parts by mass of the magnetic layer.

4. 2. The electromagnetic wave shielding material according to claim 1, wherein the magnetic layer contains an acrylic resin having an alkyl (meth)acrylate structure in which the alkyl group has 2 to 8 carbon atoms.

5. 2. The electromagnetic wave shielding material according to claim 1, wherein the glass transition temperature Tg of the magnetic layer is −80° C. or higher and lower than 5° C.

6. 2. The electromagnetic wave shielding material according to claim 1, wherein the glass transition temperature Tg of the magnetic layer is −40° C. or higher and lower than −5° C.

7. Further comprising two or more metal layers, and 2. The electromagnetic wave shielding material according to claim 1, comprising one or more magnetic layers sandwiched between two metal layers.

8. 8. The electromagnetic wave shielding material according to claim 7, 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.

9. 2. The electromagnetic wave shielding material according to claim 1, wherein the degree of cross-linking of the magnetic layer is 20% or more and 98% or less.

10. 2. The electromagnetic wave shielding material according to claim 1, wherein the magnetic layer has a storage modulus E' of 0.05 GPa or more and 1.00 GPa or less at 23° C. in a dynamic viscoelastic measurement at 1 Hz.

11. the content of the resin in the magnetic layer is 15.00 parts by mass or more and 25.00 parts by mass or less, with respect to a total mass of 100.00 parts by mass of the magnetic layer; the magnetic layer contains an acrylic resin having an alkyl (meth)acrylate structure in which the alkyl group has 2 to 8 carbon atoms, the glass transition temperature Tg of the magnetic layer is −40° C. or higher and lower than −5° C., Further comprising two or more metal layers, The magnetic layer is sandwiched between two metal layers. The degree of cross-linking of the magnetic layer is 20% or more and 98% or less, and 2. The electromagnetic wave shielding material according to claim 1, wherein the magnetic layer has a storage modulus E' of 0.05 GPa or more and 1.00 GPa or less at 23° C. in dynamic viscoelasticity measurement at 1 Hz.

12. 12. The electromagnetic wave shielding material according to claim 11, 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.

13. An electronic component comprising the electromagnetic wave shielding material according to any one of claims 1 to 12.

14. An electronic device comprising the electromagnetic wave shielding material according to any one of claims 1 to 12.

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