Laminated sheets, electromagnetic wave suppressors, electrical products, communication devices, and transportation facilities

Abstract

To provide a laminated sheet of a thin film capable of shielding an electromagnetic wave of a specified frequency and having flexibility.SOLUTION: There is provided a laminated sheet which is a sheet having a structure in which five or more layers of A layer and B layer having different compositions are alternately laminated, wherein at least one of A layer and B layer contains an electromagnetic wave suppression material, when the total components constituting the sheet is defined as 100 mass%, the content of the electromagnetic wave suppression material is 1 mass% or more and 15 mass% or less and the product of the real part ε'(F / m) of the complex dielectric constant of the whole sheet and the real part μ'(H / m) of the complex dielectric constant is 4.0 FH / m2 or more and 50 FH / m2 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a laminate sheet that is thin and has excellent electromagnetic wave shielding properties despite having a low concentration of an electromagnetic wave suppressing material, and to an electromagnetic wave suppressor, electrical product, communication device, and transportation system that uses the same. [Background technology]

[0002] With recent advances in communication technology, electromagnetic waves of various frequency bands are now flying through the atmosphere, including meter waves in the hundreds of MHz to several GHz band, quasi-millimeter waves in the several GHz to several tens of GHz band, and millimeter waves in the tens to several hundred GHz band. Meter waves are primarily used for mobile phones and wireless communications, quasi-millimeter waves are primarily used for mobile communications such as 4G and 5G and wireless LAN (Wi-Fi) communications, and millimeter waves are primarily used for automobile collision prevention radar.

[0003] Electromagnetic waves are used in a frequency band that is appropriate for the amount of information, the distance to be transmitted, and the application, but electromagnetic waves of similar frequency bands are also used simultaneously in various devices and applications. As a result, there is a growing need for electromagnetic wave shielding materials that can block electromagnetic waves to prevent device malfunctions, communication disruptions, information leaks, and the effects on the human body, which is sensitive to electromagnetic waves. In particular, in recent years, the development of communication technologies that use electromagnetic waves in the high-frequency (GHz) band has accelerated in order to achieve high-speed, large-capacity communications, and electromagnetic wave shielding materials that can block electromagnetic waves in this frequency band are in demand.

[0004] Electromagnetic waves are composite waves of two different components, the electric field and the magnetic field, which propagate through space while vibrating against each other. Electromagnetic wave shielding materials are materials that lose or attenuate electromagnetic wave energy by reflecting electromagnetic waves on their surface or inside the material (reflection loss), absorbing electromagnetic waves inside the material (absorption loss), or by causing mutually reflected electromagnetic waves to interfere with each other and cancel each other out.

[0005] For example, the surface reflection of electromagnetic waves can be enhanced by the difference in electrical resistance (impedance) between the air interface and the interface of the electromagnetic wave-shielding material. As an electromagnetic wave-shielding material that uses reflection loss, a material with a very low resistance (for example, a metal such as copper) is generally coated and laminated on the surface of the substrate, thereby realizing reflection of electromagnetic waves over a wide frequency band (Patent Document 1).

[0006] Electromagnetic wave shielding materials that use absorption loss have a substrate containing a conductive material and / or a magnetic material, which absorbs the electromagnetic waves that enter the substrate as an induced current, thereby causing electromagnetic wave energy loss. Such electromagnetic wave shielding materials achieve their absorption performance by incorporating a carbon material or a metal material such as ferrite (collectively referred to as an electromagnetic wave suppressing material) into a dielectric polymer such as rubber (Patent Documents 2 to 4).

[0007] In addition, electromagnetic wave shielding materials that cancel interference invert the phase and amplitude of the electromagnetic waves reflected from the surface and the reflective layer placed on the backside, canceling out and losing the electromagnetic waves. By appropriately arranging layers with different impedances within the sheet, dielectric polarization occurs at the interface between the different impedances, resulting in dielectric loss due to the material being unable to follow the time-varying changes in the applied electric field (Patent Document 5). These three types of electromagnetic wave loss methods can be used appropriately depending on the frequency band of the electromagnetic waves to be shielded and the application. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Special Publication No. 2011-502285 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-158395 [Patent Document 3] Japanese Patent Application Laid-Open No. 2017-118073 [Patent Document 4] Japanese Patent Application Publication No. 2019-057730 [Patent Document 5] Japanese Patent Application Publication No. 2019-102665 Summary of the Invention [Problem to be solved by the invention]

[0009] However, to selectively shield electromagnetic waves in a specific frequency band, a reflection loss design that simultaneously shields a wide frequency band is inappropriate, and electromagnetic wave shielding materials based on absorption loss are more suitable. However, electromagnetic wave shielding materials based on absorption loss require the addition of a high concentration of electromagnetic wave suppression material to increase the dielectric constant of the electromagnetic wave shielding material itself. However, when a thermoplastic resin is used as the substrate for moldability, high concentrations of the electromagnetic wave suppression material can make the sheet brittle, or the effect of reflection loss rather than absorption loss can become dominant, making it difficult to shield only a specific frequency band. Furthermore, when a thermosetting or thermoplastic rubber material is used as the substrate, it is possible to add a high concentration of electromagnetic wave suppression material, but the thickness of the electromagnetic wave shielding material increases, making it difficult to apply to applications requiring flexibility. In consideration of the above-mentioned problems, the present invention aims to provide a thin-film laminate sheet that is capable of shielding electromagnetic waves of a specific frequency and is flexible. [Means for solving the problem]

[0010] To solve the above problems, the present invention has the following configuration: A laminate sheet having a configuration in which A layers and B layers having different compositions are alternately stacked in five or more layers, at least one of the A layers and B layers contains an electromagnetic wave suppressing material, the content of the electromagnetic wave suppressing material is 1% by mass to 15% by mass when all components constituting the laminate sheet are taken as 100% by mass, and the product of the real part ε' (F / m) of the complex permittivity and the real part μ' (H / m) of the complex magnetic permeability of the entire laminate sheet is 4.0 F·H / m 2 More than 50F H / m 2 A laminated sheet characterized by the following: [Effects of the Invention]

[0011] The present invention can provide a laminate sheet that has excellent frequency selectivity for the electromagnetic waves to be shielded, excellent flexibility, and a small thickness. Specifically, by increasing the difference in complex dielectric constant between alternating layers with different complex dielectric constants and increasing the number of layers, the effect of dielectric polarization at each interface between layers with different complex dielectric constants can be enhanced, thereby increasing the complex dielectric constant of the entire sheet. Therefore, a laminate sheet for an electromagnetic wave shielding material that is thinner and has molding conformability can be provided. The laminate sheet of the present invention can be suitably used as an electromagnetic wave shielding material for devices or components with complex shapes that require molding conformability. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing the half-width and electromagnetic wave attenuation of the return loss peak with the largest peak-top return loss among the peaks obtained by measuring the return loss peaks of a laminate sheet according to one embodiment of the present invention. [Figure 2] FIG. 1 is a schematic diagram showing the half-width and electromagnetic wave attenuation of the return loss peak with the largest peak-top return loss among the peaks obtained by measuring the return loss peaks of a laminate sheet according to one embodiment of the present invention. [Figure 3] FIG. 1 is a schematic diagram showing the half-width and electromagnetic wave attenuation of the return loss peak with the largest peak-top return loss among the peaks obtained by measuring the return loss peaks of a laminate sheet according to one embodiment of the present invention. [Figure 4] FIG. 1 is a schematic diagram showing the half-width and electromagnetic wave attenuation of the return loss peak with the largest peak-top return loss among the peaks obtained by measuring the return loss peaks of a laminate sheet according to one embodiment of the present invention. [Figure 5] 1 is a schematic diagram of a layer containing carbon material X and carbon black particles. [Figure 6] The vertical axis is the degree and the horizontal axis is the logarithm of the aspect ratio. [Figure 7] FIG. 2 is a schematic diagram showing an elevation angle of a carbon material. DETAILED DESCRIPTION OF THE INVENTION

[0013] The laminate sheet of the present invention will be described in detail below.

[0014] The laminate sheet of the present invention is a laminate sheet having a configuration in which five or more layers A and B, each having a different composition, are alternately laminated, and at least one of the layers A and B contains an EMI suppression material, and the content of the EMI suppression material is 1% by mass to 15% by mass when all components constituting the laminate sheet are taken as 100% by mass, and the product of the real part ε' (F / m) of the complex permittivity and the real part μ' (H / m) of the complex magnetic permeability of the entire laminate sheet is 4.0 F·H / m 2 More than 50F H / m 2 The present invention is characterized by the following:

[0015] Here, "a structure in which five or more layers of A and B are alternately laminated" refers to a structure in which A and B layers are alternately arranged in succession, for a total of five or more layers. That is, it refers to a state in which resins are laminated in a regular arrangement of A(BA)n or B(AB)n (n is a natural number greater than or equal to two). For example, a laminate sheet having a structure of A layer / B layer / A layer / B layer / A layer or a structure of B layer / A layer / B layer / A layer / B layer (hereinafter, these two laminate structures may be referred to as a laminate unit of A and B layers) all fall under the category of "a laminate sheet having a structure in which five or more layers of A and B are alternately laminated." As long as the laminate sheet of the present invention has a laminate unit of A and B layers, the outermost layer may be an A layer, a B layer, or a layer other than A and B layers. The outermost layers on both sides may be the same layer or different layers. Furthermore, the laminate sheet may have one or more laminate units of A and B layers.

[0016] As a means for obtaining a laminate sheet having a laminate unit of A layers and B layers, as described below, a method of laminating layers having different compositions in stages by pressure bonding and laminating them, or a method of laminating them all at once using a lamination device can be used. Furthermore, a functional layer different from the alternating laminate unit of A layers and B layers, such as another electromagnetic wave reflecting layer or electromagnetic wave absorbing layer, may be formed on the alternating laminate unit of A layers and B layers. When an embodiment has multiple laminate units of A layers and B layers, the multiple laminate units can be laminated via an adhesive layer or directly by thermocompression bonding. Furthermore, when an embodiment has multiple laminate units of A layers and B layers, alternating laminate units having peak tops in different frequency bands can be laminated together to form a material that simultaneously blocks multiple desired frequency bands.

[0017] The laminate sheet of the present invention, which includes a laminate unit of layers A and B, can improve electromagnetic wave shielding performance targeting a specific frequency band while reducing the overall thickness of the laminate sheet. Typically, improving electromagnetic wave shielding performance targeting a specific frequency band requires increasing the complex permittivity of the entire sheet. Conventional single-layer sheets require the addition of a high concentration of conductive material or an increased sheet thickness to achieve this. In contrast, a laminate sheet including a laminate unit of layers A and B generates dielectric polarization at the interface between layers with different permittivities, facilitating the passage of current within the sheet. Furthermore, the dense confinement of the EMI suppression material within each layer not only increases the conductivity within the layer but also reduces resistance losses due to the conductive material added within, achieving higher shielding performance than conventional products. As a result, an electromagnetic wave shielding material with excellent shielding performance can be obtained, even when the sheet is thin.

[0018] Furthermore, such a laminate sheet typically has a thinner layer thickness than a single-film sheet, which increases the packing density of the EMI suppression material within the layer and reduces the distance between the EMI suppression materials, improving the electron transfer efficiency between the EMI suppression materials and improving the EMI suppression performance of the entire laminate sheet.

[0019] Furthermore, in such a laminate sheet, the electromagnetism suppressing material is more likely to align in a direction parallel to the surface of the laminate sheet, and so by using a material that forms a linearly linked higher-order structure or an electromagnetism suppressing material that exhibits a high aspect ratio, the conductivity in the plane direction is improved and incident electromagnetic waves are more likely to be resisted by the electromagnetism suppressing material. Due to the mechanism described above, such a laminate sheet can achieve a complex permittivity value with a smaller amount of electromagnetism suppressing material, which would generally be achieved with a single-film sheet that required the inclusion of a large amount of electromagnetism suppressing material.

[0020] The number of layers in the laminate unit of layers A and B included in the laminate sheet is preferably 13 or more in total, more preferably 31 or more in total, and even more preferably 101 or more in total, because the greater the number of interface layers between layers exhibiting a high complex dielectric constant and layers exhibiting a low complex dielectric constant, the more easily the above-mentioned effects can be achieved. From the viewpoints of production cost, film formability, and electromagnetic wave shielding performance, the upper limit of the number of layers is preferably 1001. Limiting the number of layers in the laminate unit of layers A and B to 1001 or less prevents increases in production costs due to the increased size of equipment such as a feed block with fine slits. At the same time, depending on the dispersion state, shape, and size of the EMI suppression material, an increase in the number of layers reduces the thickness of each layer, which can lead to problems with thixotropy, resulting in reduced layer thickness, and the inherent shielding performance and shielding steepness can be maintained.

[0021] It is important that the laminate sheet of the present invention includes layer A and layer B, each having a different composition. The constituent components of layer A and layer B are not particularly limited, and may be transparent / opaque, flexible / rigid, flat / non-flat, or organic (polymer) material / inorganic (metal) material. However, from the viewpoint of improving the processability of the resulting laminate sheet, it is preferable that layer A and layer B be primarily composed of an organic polymer material exhibiting flexibility. A hard coat using a thermosetting resin or photocurable resin can also be used. Here, the term "major component" refers to a component that is greater than 50% by mass but not greater than 100% by mass, preferably 70% by mass or more and not greater than 100% by mass, when the total components constituting the layer are taken as 100% by mass.

[0022] It is important that the A layer and the B layer in the laminate sheet of the present invention have different compositions. The A layer and the B layer have different compositions means that a component is present in only one of the A layer and the B layer, or that the A layer and the B layer have the same components but in different amounts. From the viewpoint of processability and electromagnetic wave shielding property design when the laminate sheet is formed, it is preferable that the A layer and the B layer in the laminate sheet of the present invention are both primarily composed of an organic polymer material, with at least one containing an organic material or an inorganic material as an electromagnetic wave suppression material.

[0023] The compositions of the A layer and the B layer are not particularly limited as long as they are different from each other. However, a composition that can reduce peeling between the A layer and the B layer is preferred to reduce the reduction in effectiveness due to peeling between the A layer and the B layer. From this perspective, it is preferable that the organic polymer material in the A layer and the organic polymer material in the B layer have the same molecular skeleton. Here, the molecular skeleton refers to the repeating unit most abundant in the molecular chain of the organic polymer material. For example, if the organic polymer material is polyethylene terephthalate, the ethylene terephthalate unit corresponds to the basic skeleton. A specific example of an embodiment in which the organic polymer materials in the A layer and the B layer have the same molecular skeleton is an embodiment in which the A layer is primarily composed of a polyester resin, and the B layer is also primarily composed of a polyester resin having the same basic skeleton as the polyester resin that is the primary component of the A layer.

[0024] The compatibility parameter can be used as an index of the adhesion between layers A and B. The compatibility parameter can be estimated using calculation methods such as those of Hansen, Hoy, and Fedors. However, the compatibility parameter of thermoplastic resins, which are components that can be suitably used as organic polymer materials, is calculated using the Fedors calculation method, which can be calculated based on the repeating structural units of the molecular chain. By using this method, the compatibility parameter of thermoplastic resins containing structural units derived from copolymerization components can be easily calculated in proportion according to the ratio of each structural unit. In the Fedors calculation method, the compatibility parameter is determined by the cohesive energy density and molar molecular volume of the molecule, which depend on the type and number of substituents, and is estimated according to formula (1). Here, Ecoh (cal / mol) is the cohesive energy, V is the molar molecular volume (cm 3 / mol).

[0025]

number

[0026] The compatibility parameter of the laminate sheet of the present invention is a value obtained by rounding off the estimated value calculated based on Fedor's formula to one decimal place. The compatibility parameters of representative thermoplastic resins include cellulose acetate: 11.0, cellulose: 15.6, polyacrylonitrile: 14.8, polyamide: 13.6, polyisobutylene: 7.7, polyethylene: 8.0, polyethylene terephthalate: 10.7, polyvinyl chloride: 10.1, polyvinyl acetate: 9.5, polycarbonate: 9.9, polystyrene: 9.4, polyvinyl alcohol: 12.6, polyphenylene sulfide: 12.5, polybutadiene: 8.3, polypropylene: 8.1, and polymethyl methacrylate: 9.3.

[0027] In order for the A layer and the B layer of the laminate sheet of the present invention to maintain interlayer adhesion after lamination, the difference in the compatibility parameter between the A layer and the B layer is preferably 2.0 or less, more preferably 1.0 or less. The A layer and the B layer may be composed of the exact same organic polymer material, with the lower limit being 0.0. However, when the compatibility parameter is 0.0, it is preferable to use different types and concentrations of electromagnetic wave suppression materials added to the A layer and the B layer to differentiate their complex dielectric constants. The complex dielectric constant is a numerical value that indicates the molecular response (degree of dielectric polarization) when an external electric field is applied. It is a dimensionless quantity specific to a substance and based on the dielectric constant (electric constant) in vacuum.

[0028] When Layer A or Layer B contains multiple organic polymer materials, the compatibility parameter of each organic polymer material is calculated by multiplying the compatibility parameter of each organic polymer material by the content ratio of the organic polymer materials and adding the resulting total. For example, if a 50:50 ratio of polyethylene terephthalate (compatibility parameter: 10.7) and polymethyl methacrylate (compatibility parameter: 9.3) is used, the compatibility parameter of the layer is 10.0, the intermediate value between the two compatibility parameters. When laminating layers primarily composed of different organic polymer materials, it is also preferable to add the organic polymer material that is the primary component of one layer to the other layer to bring the compatibility parameters of the two layers closer together and thereby improve adhesion between the two. The organic polymer material that is the primary component of the other layer can be added in the form of copolymerization or by alloying the resin and kneading it in an extruder. A cross-linked modifier containing the basic skeleton of the organic polymer material that is the primary component of the other layer can also be used.

[0029] As the organic polymer material for the A layer and B layer, it is preferable to use a thermoplastic resin, which is an organic polymer material that exhibits flexibility, from the viewpoint of the processability and film-forming properties of the laminate sheet.Examples of thermoplastic resins include polyolefin resins typified by polyethylene, polypropylene, poly(1-butene), poly(4-methylpentene), polyisobutylene, polyisoprene, polybutadiene, polyvinylcyclohexane, polystyrene, poly(α-methylstyrene), poly(p-methylstyrene), polynorbornene, and polycyclopentene; polyamide resins typified by nylon 6, nylon 11, nylon 12, and nylon 66; copolymer resins of vinyl monomers typified by ethylene / propylene copolymer, ethylene / vinylcyclohexane copolymer, ethylene / vinylcyclohexene copolymer, ethylene / alkyl acrylate copolymer, ethylene / acrylic methacrylate copolymer, ethylene / norbornene copolymer, ethylene / vinyl acetate copolymer, propylene / butadiene copolymer, isobutylene / isoprene copolymer, and vinyl chloride / vinyl acetate copolymer; acrylic resins typified by polyacrylate, polymethacrylate, polymethyl methacrylate, polyacrylamide, and polyacrylonitrile; Polyester resins typified by polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, etc., polyether resins typified by polyethylene oxide, polypropylene oxide, polyacrylene glycol, cellulose ester resins typified by diacetyl cellulose, triacetyl cellulose, propionyl cellulose, butyryl cellulose, acetylpropionyl cellulose, nitrocellulose, biodegradable polymers typified by polylactic acid, polybutyl succinate, etc., as well as polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl butyral, polyacetal, polyglycolic acid, polycarbonate, polyketone, polyether sulfone, polyether ether ketone, modified polyphenylene ether, polyphenylene sulfide, polyetherimide, polyimide, polysiloxane, tetrafluoroethylene resin, trifluoroethylene resin, trifluorochloroethylene resin, tetrafluoroethylene-hexafluoropropylene copolymer, polyvinylidene fluoride, etc. can be used.These thermoplastic resins may be used alone in each layer, or as a blend or alloy of two or more polymers. Blends and alloys can provide heat resistance, viscosity characteristics, and adhesion at the interlayer interface that cannot be achieved with a single thermoplastic resin.

[0030] The present invention is based on a laminate sheet including an alternating laminate unit in which layers of different compositions are alternately laminated. In such a laminate sheet, dielectric polarization occurs at the interface between the A and B layers, which have different compositions. The greater the number of layers and the greater the magnitude of polarization, the higher the complex permittivity of the entire laminate sheet. Therefore, selecting a material with a low complex permittivity as the thermoplastic resin constituting the A and B layers of the laminate sheet of the present invention facilitates the production of a laminate sheet that exhibits high shielding performance across a relatively wide frequency range. A thermoplastic resin with a low complex permittivity is preferably one with a permittivity of 3.0 or less. Considering versatility, processability, and lamination properties, it is preferable to select such a thermoplastic resin from among thermoplastic resins such as polyolefin resins (complex permittivity: 2.0-2.3), polyester resins (complex permittivity: 2.8-3.0), polycarbonate (complex permittivity: 2.9-3.0), and polystyrene (complex permittivity: 2.4-2.6).

[0031] Conversely, in order to achieve sharper shielding performance over a narrower band, it is preferable that the organic polymer material used has a high dielectric constant, and it is preferable to select acrylic resin (3.0 to 4.5), nylon resin (3.5 to 5.0), cellulose-based resin (complex dielectric constant: 6.7 to 8.0), vinyl monomer copolymer resin (complex dielectric constant: 3.0 to 8.0), fluororesin (complex dielectric constant: 4.0 to 8.0), polyphenylene sulfide (complex dielectric constant: 3.5 to 4.0), etc.

[0032] To achieve electromagnetic wave shielding performance, it is important that at least one of the A layer and the B layer of the laminate sheet of the present invention contains an EMI suppression material. Here, the EMI suppression material is a general term for conductive materials that exhibit the property of imparting conductivity in response to an electric field when irradiated with electromagnetic waves, and magnetic materials that absorb magnetic flux generated by a magnetic field. Since the laminate sheet of the present invention achieves electromagnetic wave shielding properties by dissipating the energy of incident electromagnetic waves through resistance from the conductive or magnetic EMI suppression material, it is necessary to include an EMI suppression material within the laminate sheet. The EMI suppression material may be contained in either the A layer or the B layer, or in both. Furthermore, only one type of EMI suppression material may be used, or multiple types of EMI suppression materials may be used in combination.

[0033] The electromagnetic wave suppression material in the laminate sheet of the present invention can be, for example, an organic carbon material as a conductive material that primarily dissipates radio waves, or an inorganic metal material as a magnetic material that primarily dissipates magnetic waves. Either the organic carbon material or the inorganic metal material can be used alone, or both can be used in combination. Furthermore, the conductive material and the magnetic material can be simultaneously contained in the same layer, or an embodiment in which the conductive material and the magnetic material are separately contained in Layer A or Layer B, respectively, can also be used.

[0034] The conductive material used in the laminate sheet of the present invention is preferably selected from carbon materials with small primary particle sizes and suitable for melt extrusion. Examples of such carbon materials include carbon black (spherical carbon) such as acetylene black, channel black, lamp black, thermal black, ketjen black, and furnace black; carbon nanotubes (cylindrical carbons such as single-walled nanotubes, multi-walled nanotubes, and cup-stacked nanotubes); flat carbons such as graphite, graphene, and others; spherical graphite, cylindrical graphite, carbon microcoils, fullerenes, and carbon fibers (long fibers and short fibers). Among these, carbon black, which easily develops a primary structure (linear structure), is preferred from the perspective of utilizing the effect of particle alignment in the plane direction of the laminated / thin film structure. Furthermore, to form a stronger conductive path in the layer direction, it is also preferable to use carbon black, which develops a structure in any direction, in combination with carbon nanotubes or flat carbon, which have a uniform structure and a high aspect ratio. By combining conductive materials with different skeletons and structures, it is possible to adjust the ratio of the content of each conductive material and to variously adjust the values ​​of the real part ε' and imaginary part ε'' of the complex permittivity to suit the frequency band that is the target of shielding.

[0035] Carbon black that readily develops a primary structure includes carbon black with a dibutyl phthalate (DBP) oil absorption (mL / 100g) of 150 or more. DBP oil absorption is an index showing the degree of development of the carbon black structure. Materials with a high DBP value indicate that carbon black particles are more likely to be connected in a linear chain, resulting in many voids between the structures. Therefore, even a small content of such a material facilitates the formation of conductive paths, making it easy to impart conductivity to layers containing such a material, making it preferable. From this perspective, the dibutyl phthalate (DBP) oil absorption is more preferably 200 mL / 100g or more, and even more preferably 350 mL / 100g or more.

[0036] When the carbon black structure develops and a conductive path is formed, the conductive material, which acts as an electromagnetic wave resistor, converts electromagnetic wave energy into thermal energy more efficiently when an electric field is generated due to electromagnetic wave irradiation, and a high electromagnetic wave suppression effect is expected. While there is no particular upper limit for DBP oil absorption, considering the possibility of structure destruction when dispersing the conductive material in a polymeric material, a value of 800 mL / 100 g is appropriate. DBP oil absorption can be measured in accordance with ASTM D 2414 (2019). Examples of such conductive spherical carbons that can be used include commercially available products such as acetylene black, furnace black, and ketjen black.

[0037] Carbon black, a preferred EMI suppression material, tends to have a low real part ε' of the complex dielectric constant (described below), which is an important parameter for the laminate sheet of the present invention. Therefore, it is preferable to use a cylindrical carbon material, such as carbon nanotubes, or a flat material, such as graphite, graphene, etc., in combination with the carbon material suitable for increasing the real part ε' of the complex dielectric constant. This configuration improves the dielectric constant and enhances the EMI shielding performance by dispersing a conductive material with a high aspect ratio in the thickness direction, which is known as the Maxwell-Wagner effect. Specifically, by forming a large number of microscopic dielectric polarizations at the interface between a thermoplastic resin exhibiting dielectric properties (for example, polyolefin resins, polyester resins, acrylic resins, vinyl monomer copolymer resins, etc., which were previously exemplified as resins with a low complex dielectric constant) and a conductive material, and aligning cylindrical or flat conductive materials parallel to the film thickness direction so that these polarizations are parallel and facing each other like parallel plate capacitors, when electromagnetic waves are irradiated and an electric field is applied, a large number of charges are likely to accumulate at the interface between the low dielectric resin and the conductive material, thereby increasing the conductivity within the laminate sheet.

[0038] Due to this effect, when electromagnetic waves are incident, they are resisted by the conductive material, making it easier for the electromagnetic wave energy to be converted into thermal energy, which is expected to result in improved electromagnetic wave shielding performance. Based on this concept, in addition to the formation of layer interfaces between Layers A and B in this laminate sheet, it is preferable that the conductive material be aligned in the plane direction of the laminate sheet, and that the dielectric polarization formed at the interface between the resin constituting the layer and the conductive material also occur in parallel in the plane direction of each layer of the laminate sheet. In other words, the higher the aspect ratio of the conductive material, the more likely it is that the laminate sheet will have this type of configuration after undergoing a stretching process or the like during film production, so it is preferable to use a cylindrical or flat material in combination.

[0039] In relation to the preferred cylindrical and flat materials, when the laminate sheet of the present invention contains a carbon material, it is preferable that the carbon material contains a material exhibiting an aspect ratio of 40 to 5000 (hereinafter referred to as carbon material X). By containing carbon material X, carbon material X is more likely to remain within the layers of the laminate sheet without breaking through the layer interfaces, and carbon material X is more likely to be oriented in the plane direction of the laminate sheet due to the resin flow and stretching process in the lamination process. Furthermore, by using carbon material X, the area ratio covered by the carbon material when viewed from a direction perpendicular to the sheet is increased, thereby reducing the effect of electromagnetic waves penetrating perpendicular to the laminate sheet and leaking through gaps between particles.

[0040] By including a carbon material with an aspect ratio of 40 or more, the above effects can be fully achieved. On the other hand, by limiting the aspect ratio of the carbon material to 5000 or less, the interaction between the thermoplastic resin and the carbon material is suppressed, and deterioration of the formability of the laminate sheet during the stretching process and molding is alleviated. Furthermore, by limiting the aspect ratio of the carbon material to 5000 or less, clogging of the foreign matter removal filter with the carbon material during the extrusion process is also reduced, thereby reducing the occurrence of equipment problems due to lower than expected carbon material concentration and sudden pressure increases. From the above perspectives, the aspect ratio of carbon material X is more preferably 100 or more and 3000 or less.

[0041] Furthermore, it is particularly preferable to use carbon material X in combination with carbon black particles in order to further strengthen the bonds between carbon material X particles and further suppress electromagnetic wave leakage. The carbon black particles referred to here refer to particles or the higher-order structure formed by the particles with an aspect ratio of less than 40. When carbon material X and carbon black particles are used in combination, the bonds between the particles in contact with each other expand in the plane direction of the laminate sheet, as shown in Figure 5, for example, thereby improving the electrical conductivity and, ultimately, the complex dielectric constant. Figure 5 shows a schematic diagram of a layer containing carbon material X and carbon black particles, where reference numeral 4 denotes resin, reference numeral 5 denotes carbon material X, and reference numeral 6 denotes carbon black particles.

[0042] The aspect ratio of an EMI suppression material can be measured using the following procedure. First, a cross-section sample obtained by ion milling a laminate sheet is observed using a scanning electron microscope (SEM) or a transmission electron microscope (TEM) to obtain a cross-sectional image. When cutting the cross section, freezing or resin embedding may be performed as appropriate, depending on the flexibility of the resin that makes up the laminate sheet, to minimize damage to the particles. Furthermore, during observation, sputtering may be performed as appropriate to suppress charge buildup. The obtained cross-sectional image is then binarized and brightness adjusted using image analysis software such as "ImageJ" (NIH) or "Mac-View" (Mountec), and the EMI suppression material portion is then extracted. Each extracted EMI suppression material is then subjected to ellipse approximation, and the major and minor axes are measured and their ratios are calculated to calculate the aspect ratio. Note that the manufacturing process can cause anisotropy in the particle arrangement of the EMI suppression material in the longitudinal and transverse directions within the laminate sheet. Furthermore, not all EMI suppression materials are necessarily oriented in either the longitudinal or transverse direction. For example, if the EMI suppression material is oriented with a tilt toward the depth direction in a cross-sectional image, the aspect ratio obtained by elliptical approximation will not match the actual situation. Taking these issues into consideration, the aspect ratio was calculated by performing the above-described measurements and analysis on the cross sections of the EMI suppression material in both longitudinal and transverse directions. The aspect ratio obtained by elliptical approximation for the EMI suppression material in both images was then plotted as a curve (reference numeral 7) in Figure 6, with the vertical axis representing degrees and the horizontal axis representing the logarithm of the aspect ratio. The maximum value of this curve is defined as the aspect ratio of the EMI suppression material. Carbon materials with a maximum value between 40 and 5000 are designated as carbon material X.

[0043] In the laminate sheet of the present invention, the average elevation angle between the carbon material X and the sheet surface direction is preferably 0° or more and 15° or less. The elevation angle between the carbon material X and the sheet surface direction refers to the elevation angle between the long axis direction of the carbon material X and the sheet surface direction (reference numeral 8), as shown by reference numeral 9 in FIG. 7 . This elevation angle can be analyzed using image analysis software. Specifically, the orientation of the layer interface in the cross-sectional image of the laminate sheet obtained by the above-described method is defined as the sheet surface direction (0°), and the smaller angle between the long axis of the carbon material X and the sheet surface direction can be defined. In other words, regardless of whether the carbon material X is oriented clockwise or counterclockwise with respect to the interface, the magnitude of this elevation angle is in the range of 0° or more and 90° or less. The average elevation angle in the laminate sheet is determined by extracting 100 particles of carbon material X with high aspect ratios contained in the image in order of increasing aspect ratio, and then averaging the elevation angles of these particles.

[0044] The smaller the average elevation angle between the carbon material X and the sheet surface direction, the more oriented the carbon material X is in the surface direction. By reducing the average elevation angle, the carbon material X is more bonded to itself compared to a laminate sheet in which the carbon material X is dispersed in all directions within the layer. Therefore, improvements in conductivity and, ultimately, complex dielectric constant can be expected. Furthermore, if the carbon material X is a flat carbon material, the particle area when observed from the surface of the laminate sheet is large, which is preferable because it allows for more efficient absorption of electromagnetic waves. From the above perspective, the average elevation angle between the carbon material X and the sheet surface direction is more preferably 0° or more and 10° or less, and even more preferably 0° or more and 5° or less.

[0045] Examples of methods for keeping the average elevation angle between the major axis of carbon material X and the sheet surface direction within this range include increasing the number of layers in the laminate sheet, reducing the overall thickness of the laminate sheet, or increasing the number of layers without changing the overall thickness of the laminate sheet to reduce the thickness of each layer relative to the major axis of carbon material X, orienting carbon material X in the stretching direction by a stretching process, or increasing the particle concentration to strengthen the interaction between conductive particles, and the like, and these may be used in appropriate combinations.

[0046] Magnetic materials that can be used in the laminate sheet of the present invention include materials containing metal components, such as elemental metals such as silver, copper, iron, cobalt, nickel, chromium, aluminum, zinc, and tin, as well as their metal oxides, metal nitrides, metal carbides, metal borides, metal oxynitrides, metal hydroxides, metal oxyborides, organometallic complexes, and compounds and mixtures thereof. Particularly preferred components include indium tin oxide (ITO) and indium zinc oxide (IZO), which are commonly used as transparent conductive metal oxides to increase magnetic permeability, as well as stainless steel materials and organometallic complexes such as carbonyl iron, hexacyanoiron, and aminoiron. It is also preferable to use flat, expanded inorganic metal materials for these materials, as this can further enhance the electromagnetic wave shielding performance of the laminate sheet of the present invention.

[0047] The electromagnetism suppressing material of the present invention can be appropriately selected from the conductive materials and magnetic materials described above. However, when a large amount of a magnetic material composed of a metal is added and a film is produced by melt extrusion, friction between the device and the magnetic material can cause problems such as material crushing and device damage. Furthermore, due to the material-specific Snoek limit, magnetic materials tend to be unable to shield electromagnetic waves below a certain frequency (approximately 10 GHz). This makes them unsuitable as shielding materials for applications that utilize electromagnetic waves in high-frequency bands, such as 5G communications. For this reason, it is preferable to use at least one carbon material as the electromagnetism suppressing material for the present invention from the perspective of suppressing electromagnetic waves in high-frequency bands. Furthermore, in order to increase the return loss, in order to control the real and imaginary parts of the complex permittivity of the layer with a relatively high complex permittivity within the range of formula (A) described below, it is preferable to include carbon black, a carbon material that can increase the value of the imaginary part of the complex permittivity. Furthermore, in order to control the value within the range of formula (B), it is preferable to use a carbon material with a high aspect ratio or a material with a high permittivity, such as ferrite, as a carbon material that reduces the value of the imaginary part of the complex permittivity.

[0048] Furthermore, a dielectric material with excellent charge storage ability can also be added as an electromagnetic wave suppression material used in the laminate sheet of the present invention. Dielectric materials do not have the effect of providing resistance to irradiated electromagnetic waves and directly causing loss. However, as described below, in order to shield electromagnetic waves in a specific frequency band, it is preferable to control the real term ε' and imaginary term ε'' of the complex permittivity of the laminate sheet within a specific range. In this case, adding not only a conductive material in which the real term ε' and imaginary term ε'' of the complex permittivity tend to both fluctuate, but also a dielectric material that can selectively improve the real term ε' of the complex permittivity is preferable, as this allows for more precise control of the complex permittivity and reduces tan δ, as described below. Examples of dielectric materials that can be used here include magnesium oxide, titanium oxide, barium titanate, strontium titanate, calcium titanate, lead zirconate titanate, titanium oxide, iron oxide (ferrite), bismuth ferrite, and the like, which have a perovskite structure or a rutile structure. Titanium oxide, ferrite, barium titanate, and the like are preferred because they are versatile and exhibit a high dielectric constant.

[0049] From the viewpoint of achieving both electromagnetic wave shielding performance and the strength of the laminate sheet itself, it is important that the content of the electromagnetic wave suppression material in the laminate sheet of the present invention is 1% by mass or more and 15% by mass or less, where the total mass of all components constituting the laminate sheet is 100% by mass. If the content of the electromagnetic wave suppression material exceeds 15% by mass, high electromagnetic wave shielding performance is likely to be achieved, but problems such as deterioration of laminate film formability due to thixotropy and weakening of the sheet may occur. Furthermore, surface reflection may occur, preventing electromagnetic waves from reaching the interior of the sheet, and the desired dielectric polarization effect may not be achieved. On the other hand, if the content of the electromagnetic wave suppression material is less than 1% by mass, sufficient electromagnetic wave shielding performance cannot be achieved. From the above viewpoints, the content of the electromagnetic wave suppression material is more preferably 3% by mass or more and 9% by mass or less.

[0050] When a laminate sheet contains multiple types of electromagnetic wave suppressing materials, the content of the electromagnetic wave suppressing materials is calculated by adding together all of the electromagnetic wave suppressing materials. Furthermore, in the laminate sheet of the present invention, the content of the electromagnetic wave suppressing material in each layer (Layer A, Layer B) can be any amount, as long as the content of the electromagnetic wave suppressing material is between 1% and 15% by mass, where the total mass of all components constituting the laminate sheet is taken as 100% by mass.

[0051] In addition to the EMI suppression material, the laminate sheet of the present invention may contain, as necessary, dispersants, surface modifiers, lubricants, crosslinking agents, vulcanization accelerators, antioxidants, crystal nucleating agents, flame retardants, flow modifiers (plasticizers, thickeners), antiblocking agents, etc., to the extent that the inherent properties of the laminate sheet are not impaired. These components may be contained in layer A, layer B, or any layer other than layer A and layer B, as long as the inherent properties of the laminate sheet are not impaired.

[0052] In order to achieve high electromagnetic wave shielding performance while keeping the thickness low, the laminate sheet of the present invention has a product of the real part ε' (F / m) of the complex permittivity of the entire laminate sheet and the real part μ' (H / m) of the complex magnetic permeability of 4.0 F H / m 2 More than 50F H / m 2 It is important that the impedance Z is an essential parameter for determining the electromagnetic wave shielding performance of the laminated sheet and the frequency band that can be shielded. in、 The return loss Γ calculated from this depends on the complex permittivity, complex permeability, and thickness of the entire sheet, as shown in equations (2) and (3), respectively. Therefore, in order to achieve high electromagnetic wave shielding performance with a thin film, the product of the real part of the complex permittivity, ε', and the real part of the complex permeability, μ', must be a high value. In equations (2) and (3), Z0 is the characteristic impedance in air, d is the thickness, λ is the wavelength, μ is the magnetic permeability, and ε is the permittivity, and the value of Z0 is 377Ω.

[0053]

number

[0054]

number

[0055] The product of the real part of the complex permittivity ε' and the real part of the complex permeability μ' is 4.0 F·H / m 2 A lower value means that the material does not contain enough electromagnetic wave suppressing material to provide sufficient resistance when electromagnetic waves are incident. In order to improve electromagnetic wave shielding performance, the higher the product of the real part of the complex permittivity ε' and the real part of the complex magnetic permeability μ', the thinner the sheet itself can be, which is preferable. However, if the amount of electromagnetic wave suppressing material is excessive, thixotropy occurs, causing an increase in melt viscosity, which can lead to lamination disorder, making the laminate sheet brittle and difficult to handle. Therefore, in reality, the product of the real part of the complex permittivity ε' and the real part of the complex magnetic permeability μ' of the laminate sheet should be 50 F·H / m 2 In terms of thin film thickness, electromagnetic wave shielding performance, and ease of handling, the product of the real part ε' of the complex permittivity and the real part μ' of the complex magnetic permeability is preferably 5.0 F·H / m 2 More than 25F H / m 2 or less, and more preferably 6.0 F·H / m 2 More than 25F H / m 2 The reasons for this are as follows. To improve the dielectric constant of the entire sheet, it is effective to include an electromagnetic wave suppression material with a high dielectric constant, or to increase the number of layers and reduce the thickness of each layer. Furthermore, when an electromagnetic wave suppression material with a high aspect ratio is used, it is also effective to orient the electromagnetic wave suppression material in the plane direction of the sheet through a stretching process.

[0056] The real part ε' of the complex permittivity, the imaginary part ε'' described below, and the real part μ' of the complex magnetic permeability of the laminate sheet of the present invention can be measured by the method described in the section "Complex permittivity measurement" in the Examples. The real part and imaginary part (ε h ', ε h '', ε A ', ε B The complex dielectric constant of each layer can be measured by the above method or the method described in "Calculation of the complex dielectric constant of each layer" in the Examples.

[0057] The product of the real part of the complex permittivity ε' and the real part of the complex permeability μ' is 4.0 F·H / m 2 More than 50F H / m 2 Examples of methods for achieving the above or below preferred ranges include adding a conductive material to only one layer to increase the difference in dielectric constant between Layer A and Layer B, or increasing the number of layers to reduce the thickness per layer and increase the density of the EMI suppression material. Other methods include using carbon black with a DBP oil absorption within the range described below as the EMI suppression material, using a dielectric material such as barium titanate, ferrite, or titanium oxide as a material with a high dielectric constant, or using graphite or graphene, an EMI suppression material with a high aspect ratio, to improve the dielectric constant. Furthermore, to increase the dielectric constant of a thin laminate sheet, the laminate sheet can be stretched, as described below, to reduce the thickness per layer and orient the EMI suppression material in the plane of the sheet.

[0058] The laminate sheet of the present invention preferably has a dielectric loss tangent tanδ (=ε″ / ε′) of 0.10 or more and 0.50 or less, where ε″ is the imaginary part of the complex dielectric constant of the entire laminate sheet. Tanδ, which indicates the relationship between the real and imaginary parts of the complex dielectric constant, is an important parameter related to the shielding properties of electromagnetic waves that penetrate into the laminate sheet. More specifically, a tanδ of 0.50 or less indicates that the real part, which represents the ease with which electricity passes through the laminate sheet, is sufficient. That is, a tanδ of 0.50 or less is advantageous for shielding low-frequency electromagnetic waves, which are high-energy electromagnetic waves. Furthermore, a tanδ of 0.10 or more generally indicates that the imaginary part, which represents the absorption / loss effect, is high. That is, a tanδ of 0.10 or more provides sufficient electromagnetic wave shielding effect through dielectric absorption. In particular, for shielding electromagnetic waves in relatively low frequency bands, such as quasi-millimeter waves, a tanδ of 0.20 or more and 0.40 or less is more preferable. Here, quasi-millimeter waves refer to electromagnetic waves with frequencies between 3 GHz and 30 GHz, and millimeter waves refer to electromagnetic waves with frequencies above 30 GHz up to 300 GHz.

[0059] Furthermore, the electromagnetic wave shielding performance and frequency band of the laminate sheet of the present invention are affected not only by the overall thickness of the laminate sheet, but also by the difference in the complex permittivity of the A layer and the B layer, which are alternately arranged to cause dielectric polarization. Specifically, the difference in the complex permittivity between the A layer and the B layer must be sufficiently large, and the real part ε of the complex permittivity of the layer that exhibits a relatively high complex permittivity must be h ' and the imaginary part ε h Controlling ε'' is extremely effective in adjusting the electromagnetic wave shielding performance. The region where a specific sheet thickness exhibits high electromagnetic wave shielding performance for a specific frequency band can be calculated based on formula (2). Furthermore, in order for a laminated sheet to exhibit high electromagnetic wave shielding performance, it is necessary to control the real part of the complex permittivity ε of the layer with a relatively high complex permittivity between layer A and layer B. h '(F / m) and the imaginary part ε h It is preferable that (F / m) satisfies the relational expression (A) or (B). (A)ε h ''≧1 and 0.15ε h '+2≦ε h ''≦0.23ε h '+7.7 (B) 5 ≥ ε h ''≧1 and 0.01ε h '+1≦ε h ''≦0.09ε h '+2 The real part of the complex permittivity ε of a layer with a relatively high complex permittivity h ' and the imaginary part ε h By controlling '' within this range, it is possible to achieve high electromagnetic wave shielding performance at a specific frequency even if the sheet thickness is thin.

[0060] The real part of the complex permittivity ε of a layer with a relatively high complex permittivity h ' and the imaginary part ε hMethods for controlling the complex dielectric constant ε′′ to satisfy the above relational expression (A) or (B) include, for example, using carbon black as an EMI suppression material whose DBP oil absorption falls within the range described below, using barium titanate, carbonyl iron, or ferrite oxide as a material with a high dielectric constant, or using graphite, graphene, or other EMI suppression materials with a high aspect ratio to improve the dielectric constant. In particular, to satisfy expression (A), the real part ε of the complex dielectric constant h ' and the imaginary part ε h Since it is required to increase both ε and ε′, it is preferable to use carbon black, and in order to satisfy the formula (B), the imaginary part of the complex dielectric constant, ε h A low .DELTA.' value is required, and this can be achieved by using at least one dielectric material, such as barium titanate, ferrite, or titanium oxide, or at least one conductive material with a high aspect ratio, such as graphite or graphene, either alone or in combination. This can also be achieved by increasing the number of layers, or by using the stretching method described below to reduce the thickness of each layer while orienting the electromagnetism suppressing material in the plane direction of the sheet. These methods may also be combined as appropriate.

[0061] In the laminated sheet of the present invention, in order to obtain the effect of dielectric polarization, the real parts of the complex dielectric constants of the A layer and the B layer are set to ε A ', ε B ', then |ε A '-ε B is preferably 1 or more and 100 or less, and more preferably 5 or more and 50 or less. As described above, in the laminate sheet of the present invention, it is important to generate dielectric polarization by utilizing the difference in the complex dielectric constant between the A layer and the B layer. A '-ε B When |'| is 1 or more, dielectric polarization occurs between layers, and the effect of dielectric polarization can be fully obtained. A '-ε BBy keeping '| 100 or less, stable film formation can be achieved without excessively increasing the particle concentration and without layer disturbance. Even with a thin film, it is possible to obtain an electromagnetic wave shielding effect of dielectric absorption with a peak top in a specific frequency band in the GHz frequency band. The magnitude of the real part of the complex permittivity of each layer varies depending on the content of the electromagnetic wave suppressing material and the thickness of the layer containing the electromagnetic wave suppressing material. More specifically, the greater the content of the electromagnetic wave suppressing material and the thinner the layer containing the electromagnetic wave suppressing material, the larger the real part of the complex permittivity of that layer.

[0062] Furthermore, the laminate sheet of the present invention has ε A ' and ε B ', but 2.0≦ε A ' / ε B ' ≦ 25 or 2.0 ≦ ε B ' / ε A It is preferable that ε′≦25. A ' / ε B ' or ε B ' / ε A If ε' exceeds 25, it means that the difference in the permittivity between layer A and layer B is too large (the content of the EMI suppression material between the two layers is significantly different). In this state, layer disturbance is likely to occur, making it difficult to form a laminated sheet. A ' / ε B ' or ε B ' / ε A When ε' is 25 or less, film-forming properties are stable. A ' / ε B ' or ε B ' / ε A When ε' is 2.0 or more, the difference in complex permittivity between the A layer and the B layer is at a level sufficient to achieve electromagnetic wave shielding properties. A ' / ε B ' ≦ 25 or 2.0 ≦ ε B ' / ε AOne way to satisfy ε′≦25 is to adjust the amount of EMI suppression material in each layer. More specifically, if the layer with a higher dielectric constant is Layer A, for example, reducing the amount of EMI suppression material in Layer A, increasing the amount of EMI suppression material in Layer B, or using both of these methods together can reduce ε′≦25. A ' / ε B From the above viewpoint, ε A ' and ε B ', but 3.0≦ε A ' / ε B ' ≦ 20 or 3.0 ≦ ε B ' / ε A It is more preferable that '≦20 is satisfied.

[0063] From the viewpoint of film formation stability, the laminate sheet of the present invention preferably has a total thickness of 0.1 mm or more and 1.5 mm or less. A total thickness of 1.5 mm or less prevents excessive stiffness and provides sufficient moldability for the laminate sheet. Therefore, even when continuously forming the sheet into a film, the torque during roll stretching is reduced, stabilizing film formation and preventing increases in production costs. On the other hand, a total thickness of 0.1 mm or more reduces sheet tearing during stretching due to the electromagnetism suppressing material. From the above viewpoints, the total thickness of the laminate sheet is more preferably 0.2 mm or more and 1.0 mm or less, and even more preferably 0.3 mm or more and 0.75 mm or less. The total thickness of the laminate sheet can be measured by taking a cross-sectional photograph of the laminate sheet cut perpendicular to the sheet surface using a microscope and measuring the length of the photograph.

[0064] There are various ways to adjust the total thickness of the laminate sheet, such as adjusting the total output from the extruder, the lip width of the die used to form the sheet, and the conveying speed of the film-forming device. Among these, uniformly doubling the speed of the film-forming device is the simplest way to adjust the total thickness of the laminate sheet without affecting layer disturbance. Furthermore, in order to achieve in-plane orientation of the EMI suppression material and reduce the thickness while increasing the dielectric constant of the high-dielectric-constant layer, this can be achieved by stretching the laminate sheet in both the longitudinal and transverse directions using the stretching method described below, in addition to adjusting the conveying speed of the film-forming device.

[0065] From the viewpoint of reducing stacking disorder while minimizing the amount of EMI suppression material contained in the laminate sheet of the present invention, the EMI suppression material preferably has a ratio X / Y of 0.01 to 10.0, more preferably 0.01 to 5.0, and even more preferably 0.05 to 5.0, where X (nm) is the long axis of the higher-order structure formed by the component of the EMI suppression material that is most abundant in the laminate sheet, and Y (nm) is the average thickness of the layer A or B containing that component in large amounts. Here, the higher-order structure of the EMI suppression material refers to an aggregate formed by continuous segments of the EMI suppression material. Furthermore, the component refers to the component of the EMI suppression material that is most abundant in the sheet. Note that X and Y can be measured by measuring the length of an image captured with a differential interference microscope. Measurements can be performed using, for example, particle size analysis software "Macview" (manufactured by Mountech Co., Ltd.).

[0066] A high X / Y ratio means that the EMI material is more likely to be aligned parallel to the planar direction of the sheet within the layer. A high X / Y ratio makes it easier for regions to form between dielectric components such as resin and the EMI material, and when electromagnetic waves are incident, microscopic dielectric polarization occurs at the interface between the EMI material and dielectric components such as resin. This tends to improve the complex permittivity of the entire laminated sheet. However, if the X / Y ratio is excessively high, the EMI material may clog filters during the film-forming process, or the EMI material may break through the layer interface without following the lamination flow, causing lamination disruption.

[0067] More specifically, by ensuring that X / Y is 0.01 or greater, it becomes easier to obtain sufficient electromagnetic wave shielding effect while suppressing the amount of EMI suppression material, and layer disturbance and defects in the formed film sheet are reduced. On the other hand, by ensuring that X / Y is 10.0 or less, clogging of filters and the like by the EMI suppression material and layer disturbance resulting from the EMI suppression material not following the flow of the layers can be reduced. From the above perspectives, it is preferable that X / Y is 0.1 or greater and 10.0 or less.

[0068] X / Y can be increased by making the EMI suppression material a material that is easily linked in a flat or linear chain, or by reducing the number of laminated sheets or the laminate ratio of layers containing the EMI suppression material, thereby reducing the thickness of each layer.

[0069] The electrical properties of each of the A and B layers constituting the laminate sheet of the present invention can also be expressed using the surface resistivity in the layer direction (plane direction of the sheet) of each layer. The surface resistivity can be measured in accordance with JIS standards using a high resistivity meter (JIS K6911 (1995)) and a low resistivity meter (JIS K7194 (1994)) manufactured by Mitsubishi Chemical Corporation. In the laminate sheet of the present invention, when the larger of the surface resistivity values ​​of the A layer and the B layer is designated as α (Ω / □) and the smaller of the surface resistivity values ​​is designated as β (Ω / □), α is 1.0 × 10 5 Ω / □ or more 1.0×10 16 Ω / □ or less, and β is 1.0Ω / □ or more and 1.0×10 5 It is preferable that α is less than Ω / □. More preferably, α is 1.0×10 11 Ω / □ or more 1.0×10 16 Ω / □ or less, and β is 1.0Ω / □ or more and 5.0×10 3 More preferably, α is 1.0×10 13 Ω / □ or more 1.0×10 16 Ω / □ or less, and β is 1.0Ω / □ or more and 2.0×10 3 The surface resistivity, which indicates electrical conductivity, is generally 1.0×10 5 Since the above relationship is satisfied, it is preferable from the viewpoint of the electromagnetic wave shielding performance of the laminate sheet in order to increase the conductivity in the high-dielectric layer of the laminate sheet and to fully express the dielectric polarization at each resin interface. The fact that both α and β are within the above ranges means that the electrical properties of Layer A and Layer B are different from each other, and by adopting such an embodiment, the complex dielectric constant of the laminate sheet is increased, thereby improving the electromagnetic wave shielding performance of the laminate sheet. The surface resistivity can be measured by the method described in the "Surface Resistivity Measurement" section of the Examples.

[0070] The method for differentiating the complex permittivity and surface resistivity of layer A and layer B is not particularly limited. For example, organic polymer materials with different complex permittivities may be used as the resins used in layer A and layer B, or the same type of organic polymer material may be used in layer A and layer B, but the type and / or content of the electromagnetic wave suppressing material contained in layer A and layer B may be different. In particular, in order to adjust the frequency band showing the return loss peak, a configuration that allows fine adjustment of the complex permittivity and surface resistivity of layer A and layer B is preferred. A configuration in which layer A and layer B have different complex permittivities and contain at least one type of electromagnetic wave suppressing material to vary the difference in surface resistivity between layer A and layer B is most preferred.

[0071] The layer having a surface resistivity value of α is preferably located on the side where electromagnetic waves are incident during mounting, from the viewpoint of suppressing surface reflection of electromagnetic waves and transmitting the electromagnetic waves through the laminate sheet to fully exhibit the electromagnetic wave shielding effect due to dielectric polarization. This layer may be located on at least one side, but if it is necessary to shield unwanted electromagnetic waves from both the outside and the inside of the item to be mounted, it is more preferable that it be located on the outermost surface on both sides.

[0072] Furthermore, although there are no particular limitations on α / β, if α / β is 1.1 or more, the electrical properties will be different enough to realize electromagnetic wave shielding performance when the laminated sheet is made. In order to increase the complex dielectric constant of the laminated sheet, which is a feature of the present invention, the larger α / β is, the better, and α / β is preferably 10 2 More than 10, more preferably 5 More preferably, 10 9 That's all.

[0073] It is important that the laminate sheet of the present invention generates dielectric polarization by utilizing the difference in complex dielectric constant between Layer A and Layer B. Therefore, even when an EMI suppression material is contained in both Layer A and Layer B, the content w of the EMI suppression material in Layer A is set to 0.05 to 0.05 to 0.05 in order to generate a difference in the dielectric constant between the two layers. A and the content of electromagnetic wave suppression material in layer B, w BMore specifically, the content of the electromagnetic wave suppressing material in layer A is preferably w A (mass %), the content of the electromagnetic wave suppressing material in the B layer is w B (mass%), w B >w A By adopting such an embodiment, even if the components of the A layer and the B layer are the same, a difference in the dielectric constant between the two layers can be generated.

[0074] It is possible to select whether the content of layer A or layer B is greater, but in order to weaken the effect of surface reflection of electromagnetic waves, allow electromagnetic waves to penetrate into the interior of the laminated sheet, and realize a state in which the incident electromagnetic waves are resisted by the electromagnetic wave suppression material inside the sheet and lost as heat energy, layer A should be located on the outermost surface on both sides, and w A <w B It is preferable that the following relational expression is satisfied.

[0075] In the laminate sheet of the present invention, in a return loss spectrum plotted with return loss on the vertical axis and frequency on the horizontal axis, the peak with the largest return loss is preferably located in the frequency band of 1 to 100 GHz. Return loss is a value that represents the amount of loss of an electromagnetic wave during a round trip within the laminate sheet when the intensity of the electromagnetic wave, which is reflected by the laminate sheet after being incident on the laminate sheet at a specific frequency, is measured. The return loss can be measured and the peak top identified using the method described in "Return Loss Measurement."

[0076] Return loss can be calculated using the coaxial waveguide method or the free-space method by irradiating electromagnetic waves from the non-reflective side of a laminated sheet with a metal such as aluminum vapor-deposited on the back side or with an existing reflector, and measuring the intensity of the electromagnetic waves that reflect off the metal plate and travel back and forth within the laminated sheet. During measurement, return loss is measured by sweeping the frequency, and a return loss spectrum, plotted with return loss on the vertical axis and frequency on the horizontal axis, may yield multiple peaks. The peak with the highest return loss is the one we focus on. The "peak top" here refers to the point where the slope of the tangent to the return loss spectrum changes sign (slope) from positive to negative or from negative to positive.

[0077] Next, the return loss of the return loss peak will be described with reference to the drawings, citing specific examples. Figures 1 to 4 are schematic diagrams showing the half-width and electromagnetic wave attenuation of the return loss peak with the largest peak-top return loss among the peaks obtained by measuring the return loss peaks of a laminate sheet according to one embodiment of the present invention. In Figures 1 to 4, the reference numerals 1 to 3 respectively represent the return loss spectrum, the electromagnetic wave attenuation I at the peak top of the return loss peak with the largest peak-top attenuation, and the half-width R of the return loss peak with the largest peak-top attenuation.

[0078] When a spectrum has a single peak top, as in the embodiments of Figures 1 and 2, the baseline of the peak is used as a reference, and the difference in return loss between the peak top and the baseline at the frequency where the peak top is located is taken as the return loss at the peak top. Even if a peak has a high baseline return loss, as in the embodiment of Figure 3, when it has a unique peak top, the return loss at the peak top can be determined by reading the difference in dB between the baseline and the peak top. On the other hand, when a spectrum like that of Figure 4, which has multiple peak tops including shoulder peaks, is obtained, the return loss at the peak top can be determined by the difference between the return loss corresponding to the peak top at the frequency of the highest peak among the multiple peak tops and the return loss at the baseline of all peaks including the multiple peak tops.

[0079] Generally, sheets containing magnetic materials are used to shield near-field frequencies below a few GHz. However, when targeting high-frequency bands in the GHz range, due to the characteristic of magnetic materials, known as the Snoek limit, where magnetic loss drops sharply at a certain frequency, a common method is to incorporate a high concentration of magnetic material to increase attenuation. When a laminate sheet is produced by melt extrusion, the viscosity increases due to the high filler content, resulting in poor lamination accuracy. Furthermore, the magnetic material may be added at a high concentration, resulting in loss of the extruder metal parts. Furthermore, while the reflection loss due to the magnetic material is achieved, electromagnetic waves do not penetrate into the sheet, making it difficult to achieve the dielectric polarization effect inherent to the laminate sheet of the present invention. Therefore, when the laminate sheet of the present invention is produced by a melt extrusion process with a low content of EMI suppression material, in order to easily obtain electromagnetic wave shielding performance due to dielectric polarization, it is preferable to use a conductive material or a composite of a conductive material and a dielectric material to achieve electromagnetic wave shielding performance in the high-frequency band. It is preferable to have a return loss peak with the largest peak-top return loss between 1 and 100 GHz.

[0080] In the laminate sheet of the present invention, in a return loss spectrum plotted with return loss on the vertical axis and frequency on the horizontal axis, where RL (dB) is the return loss at the peak top of the return loss peak with the largest return loss, f (GHz) is the frequency at which this return loss occurs, and t (mm) is the thickness of the laminate sheet, it is preferable that RL / (t×f) be 0.40 or more and 5.00 or less. Compared to conventional techniques, the laminate sheet of the present invention is characterized by having layers with low dielectric constants and layers with high dielectric constants alternately laminated, thereby increasing the dielectric constant compared to conventional single-film or low-layer sheets, thereby increasing electromagnetic wave attenuation, or by reducing the sheet thickness to impart flexibility and formability, or by achieving both of these effects.

[0081] This characteristic applies to sheets targeting any frequency band. However, because thickness and frequency exhibit a trade-off relationship, the theoretical thickness of laminated sheets with the same dielectric constant tends to decrease as the frequency band is shifted to a higher frequency. Therefore, the thin-film effect of the laminated sheet of the present invention that exceeds the volume law cannot be expressed solely by the relationship between the return loss RL and the thickness t (e.g., RL / t). The relationship between the three factors of frequency f, the laminated sheet thickness t, and the return loss RL at the return loss peak is crucial. From this perspective, RL / (t×f) is preferably 0.60 to 3.50, and even more preferably 0.80 to 3.00. An RL / (t×f) ratio of 0.40 or greater indicates that electromagnetic wave shielding performance exceeding the volume law is obtained, sufficient for electromagnetic wave shielding applications. An RL / (t×f) ratio of 5.00 or less indicates that a certain thickness is ensured, the amount of electromagnetic wave suppression material is kept to an appropriate level, and the melt viscosity balance of the resins constituting each layer is appropriate. Therefore, by making RL / (t×f) 5.00 or less, layer disturbance is suppressed, and deterioration of the lamination precision and film-forming properties of the laminated sheet is alleviated.

[0082] To achieve the above-mentioned preferred range of RL / (t×f), it is effective to increase the number of layers in the laminate sheet to enhance the dielectric polarization effect, to use a carbon material X with a high aspect ratio to increase the dielectric constant, or to use carbon material X in combination with carbon black, or to adjust the electromagnetic wave suppression material or the laminate configuration so that the real part εh' and imaginary part εh'' of the dielectric constant of the layer with a relatively high complex dielectric constant satisfy the above-mentioned preferred dielectric constant relationship, and these can be combined as appropriate. The preferred conditions for each element are as described above.

[0083] The laminated sheet of the present invention is a laminated sheet that has excellent frequency selectivity for the electromagnetic waves to be shielded, excellent flexibility, and small thickness, and therefore can be suitably used for electromagnetic wave suppression applications, for example, as an electromagnetic wave shielding material for devices and components with complex shapes that require molding followability.

[0084] The electromagnetic wave suppressor of the present invention will be described in detail below. The electromagnetic wave suppressor of the present invention is characterized by comprising the laminate sheet of the present invention and a reflector. By combining the reflector on the side of the laminate sheet opposite the electromagnetic wave incident surface, the electromagnetic wave is directed back and forth within the laminate sheet, thereby further improving the electromagnetic wave absorption efficiency. On the other hand, when the reflector is placed on the front surface, it is possible to reflect a certain amount of electromagnetic wave from the reflector surface and sharply shield a portion of the transmitted electromagnetic wave within the laminate sheet. In order to fully utilize the electromagnetic wave shielding properties due to dielectric polarization of the laminate sheet of the present invention, the former configuration is more preferable.

[0085] The reflector may be made of any material, shape, or thickness that can reflect electromagnetic waves. Examples of materials include metals such as aluminum, copper, iron, and gold, alloys such as stainless steel, and carbon films. The shape is preferably selected to match the material to be used, and may be, for example, a flat, curved, or hemispherical plate. The reflector may be laminated with the laminate sheet of the present invention by, for example, bonding a pre-made reflector with an adhesive or by directly laminating the reflector on the surface of the laminate sheet by metal vapor deposition.

[0086] Examples of reflectors include plate reflectors containing metal, alloy, or carbon, laminated reflectors in which a film made of metal, alloy, or carbon is formed on the surface of a polymer film, sheet, plate, etc., composite reflectors in which metal, alloy, or carbon is dispersed inside a polymer film, sheet, plate, etc., and composite reflectors containing a mesh made of metal or alloy inside a polymer film, sheet, plate, etc. In addition, in the present invention, when a support, housing, etc. for each application contains a metal, alloy, carbon, etc., it can be used as a reflector as is.

[0087] Preferred embodiments of the present invention include electronic devices and communication devices that include the above-mentioned laminate sheet or the above-mentioned electromagnetic wave shielding body for purposes such as preventing false images caused by electromagnetic waves used in 4G / 5G communications, wireless LAN, and ITS radar, reducing unwanted electromagnetic wave radiation from electronic devices, semiconductors, and circuits installed inside housings such as computers, mobile phones, radios, measuring instruments, medical devices, and vehicle bumpers, and preventing malfunctions of devices due to radiation from external or adjacent devices. Other electronic devices or communication devices that use frequencies in the GHz band can be equipped with the laminate sheet of the present invention and can be used, but are not limited to the above.

[0088] Further, preferred embodiments of the present invention include transportation means such as vehicles, aircraft, and ships equipped with the laminate sheet or the electromagnetic wave shielding body described above, walls of structures such as buildings, tunnels, guardrails, highways, bridges, and steel towers, and communication facilities such as telegraph and telephone facilities. The laminate sheet of the present invention can be applied by attaching it directly to structures such as floors, ceilings, walls, windows, and pillars using an adhesive or by attaching it to other sheets, shielding plates, panels, etc. It can also be used as a wall or window material for shielded rooms to protect against external electromagnetic jamming and noise.

[0089] Next, a preferred method for producing the laminate sheet of the present invention will be explained below using examples, but the present invention should not be construed as being limited to such examples.

[0090] First, we will explain a laminate sheet using rubber, thermoplastic elastomer, or the like as the base polymer substrate. First, a predetermined amount of EMI suppression material is blended with the base polymer and kneaded using a known device such as a kneader, Banbury mixer, mill mixer, roll mill, jet mill, or ball mill to obtain a base polymer mixture containing EMI suppression material. The base polymer alone, or the prepared base polymer containing EMI suppression material, is rolled using a batch press or melt extruded to form a sheet of the desired thickness. Next, a total of five or more layers of the prepared layer A sheets and layer B sheets (each having a different composition) are alternately stacked and pressed or laminated to obtain a laminate sheet. The fusion temperature during this process varies depending on the type of resin used, but is preferably 150°C to 400°C, more preferably 250°C to 380°C.

[0091] Next, we will explain an example of a laminate sheet manufacturing method using a flexible thermoplastic resin, which is a preferred resin in this invention. First, a thermoplastic resin prepared in pellet form and a predetermined amount of EMI suppression material are mixed in a twin-screw extruder and extruded into a gut shape. This is then cooled in a water tank and cut with a chip cutter to form master pellets containing the EMI suppression material. The EMI suppression material may be dry-blended with the resin and then metered and fed from a hopper, or it may be side-fed into the molten resin using a side feeder from any position in the extruder. The feeding method is not limited to the above and can be selected appropriately depending on the specific gravity and shape of the EMI suppression material used.

[0092] The thermoplastic resins or thermoplastic resin compositions constituting Layer A and Layer B have different compositions. These thermoplastic resins or thermoplastic resin compositions are dried in hot air or under vacuum, then fed into separate extruders, where they are heated and melted to a temperature above the melting point of the thermoplastic resin. The extrusion rate is then equalized using a gear pump or the like, and the thermoplastic resin or thermoplastic resin composition is discharged, from which foreign matter, modified resins, etc. are removed using a filter or the like.

[0093] Next, these thermoplastic resins or thermoplastic resin compositions are laminated in a multi-layer lamination device capable of laminating the desired number of layers, molded into the desired shape using a die, and extruded into a sheet. The sheet-like material extruded from the die is extruded onto a cooling body such as a casting drum and cooled and solidified to form a cast sheet. In this case, since the cast sheet itself exhibits electrical conductivity, it is preferable to use a method in which air is blown from a slit-shaped, spot-shaped, or planar device to bring the cast sheet into close contact with a cooling body such as a casting drum and rapidly solidify it, or a method in which the cast sheet is brought into close contact with a cooling body using a nip roll and rapidly solidify it.

[0094] Multi-layer lamination devices such as multi-manifold dies, feed blocks, and static mixers can be used. However, to efficiently obtain the multilayer laminate of the present invention, it is particularly preferable to use a feed block with fine slits. The use of such a feed block prevents the device from becoming excessively large, reduces the amount of foreign matter generated due to thermal degradation, and enables high-precision lamination even when an extremely large number of layers are stacked. Furthermore, the lamination accuracy in the width direction is significantly improved compared to conventional technology. Furthermore, this device has the advantages of easily achieving any layer thickness by adjusting the shape (length and width) of the slits, and of easily orienting particles in the direction of the laminate sheet surface during the lamination process due to the effect of resin flow.

[0095] When producing a laminate sheet using a slit-type feedblock, the thickness and distribution of each layer can be adjusted by adjusting the length and width of the slit to achieve a pressure balance. The slit length refers to the length of the comb-like portion that forms the flow path for alternately flowing layers A and B through the slit plate. Another suitable method is to form a laminate in the feedblock, then stack the laminates in a static mixer to double the number of layers. In this case, the layer thickness of each stacked laminate is exactly the same, which is consistent with the concept of the present invention, which prefers uniform layer thickness.

[0096] The resulting cast sheet can be biaxially stretched in the longitudinal and transverse directions as needed. When biaxial stretching is performed, the stretching may be performed sequentially or simultaneously. Furthermore, if necessary, the sheet may be further stretched again in the longitudinal and / or transverse directions.

[0097] First, we will explain sequential biaxial stretching, in which the sheet is first stretched in the longitudinal direction and then in the transverse direction. Here, stretching in the longitudinal direction refers to uniaxial stretching to impart molecular orientation to the sheet in the longitudinal direction, and is usually performed by varying the peripheral speed of rolls. This stretching can be performed in a single stage or in multiple stages using multiple pairs of rolls. The stretching ratio varies depending on the type of resin, but is usually preferably 1.1 to 7.0 times, with 1.5 to 4.0 times being particularly preferred. The stretching temperature is preferably set within the range from the glass transition temperature of the resin constituting the sheet to the glass transition temperature + 100°C. The uniaxially stretched laminate sheet obtained in this manner can be subjected to surface treatment such as corona treatment, flame treatment, or plasma treatment, as necessary, and then a primer layer can be formed to improve adhesion with the film to be laminated on top. In the in-line coating process, the primer layer can be applied to one side, or to both sides simultaneously, or one side at a time.

[0098] Width-direction stretching refers to stretching to impart width-direction orientation to a sheet. This is typically performed using a tenter, with both ends of the sheet held by clips while being conveyed. The stretching ratio varies depending on the type of resin, but is typically preferably 1.1 to 7.0 times, with 1.5 to 5.0 times being particularly preferred. The stretching temperature is preferably between the glass transition temperature of the resin constituting the sheet and the glass transition temperature + 120°C. The biaxially stretched laminate sheet is then heat-treated in the tenter from the stretching temperature to the melting point, uniformly cooled slowly, and then cooled to room temperature and wound up. If necessary, relaxation treatments, such as a longitudinal and / or width-direction relaxation treatment, may be performed during the heat-treatment and slow cooling process to impart a low orientation angle and thermal dimensional stability to the sheet.

[0099] Next, simultaneous biaxial stretching will be described. In the case of simultaneous biaxial stretching, the obtained cast sheet may be subjected to a surface treatment such as corona treatment, flame treatment, or plasma treatment as necessary, and then provided with properties such as easy slippage, easy adhesion, and antistatic properties by in-line coating. In the in-line coating process, the coating layer may be applied to one side of the sheet, or to both sides simultaneously or one side at a time.

[0100] The cast sheet is then introduced into a simultaneous biaxial tenter, where it is conveyed while being held at both ends with clips and stretched simultaneously and / or stepwise in the longitudinal and transverse directions. Simultaneous biaxial stretching machines (tenters) include pantograph, screw, drive motor, and linear motor types. Drive motor or linear motor types are preferred, as they allow for variable stretching ratios and relaxation treatment at any desired location. The stretching ratio varies depending on the type of resin, but an area ratio of 2.0 to 50 times is generally preferred, with 4.0 to 20 times being particularly preferred. The stretching speeds may be the same or different in the longitudinal and transverse directions. The stretching temperature is preferably between the glass transition temperature of the resin constituting the alternating laminate unit and glass transition temperature + 120°C.

[0101] The simultaneously biaxially stretched sheet is preferably subsequently heat-treated in a tenter at a temperature equal to or higher than the stretching temperature and lower than the melting point to impart flatness and dimensional stability. During this heat treatment, it is preferable to instantaneously relax the sheet in the longitudinal direction immediately before and / or immediately after entering the heat treatment zone to suppress the distribution of the main orientation axis in the width direction. After heat treatment in this manner, the sheet is uniformly and slowly cooled, then cooled to room temperature, and wound up. If necessary, relaxation treatment may be performed in the longitudinal and / or width directions during the slow cooling from the heat treatment. It may also be instantaneously relaxed in the longitudinal direction immediately before and / or immediately after entering the heat treatment zone.

[0102] The laminated sheet of the present invention obtained in this manner can be bonded to other laminated sheets of the same type or to other laminated sheets of different thicknesses or compositions via an adhesive sheet, pressure-sensitive adhesive sheet, double-sided tape, etc., in order to obtain the desired electromagnetic wave shielding performance.

[0103] Furthermore, a layer with a different dielectric constant can be laminated on the outermost surface of the laminate sheet of the present invention to enhance electromagnetic wave transparency or to cause electromagnetic wave reflection. In this case, a coating layer containing a material exhibiting appropriate electrical conductivity / magnetic properties may be applied, or different resin layers / mesh layers may be laminated via an adhesive sheet or the like. Furthermore, resin / metal layers can be appropriately laminated according to the required function using sheet metal coating techniques such as sputtering (e.g., planar or rotary magnetron sputtering), evaporation (e.g., electron beam evaporation), chemical vapor deposition, metalorganic chemical vapor deposition, plasma-enhanced / assisted / activated chemical vapor deposition, and ion sputtering.

[0104] Furthermore, the laminate sheet of the present invention can be combined with an electromagnetic wave reflective layer capable of shielding a wide frequency band to provide stronger shielding for only certain frequencies. Alternatively, a new layer exhibiting a low complex dielectric constant can be provided on the outermost surface of the laminate sheet to further reduce electromagnetic wave reflection at the surface, resulting in a laminate sheet with enhanced electromagnetic wave absorption. In addition to the latter, it is also preferable for the layer exhibiting a high complex dielectric constant to exhibit a layer thickness distribution in which the layer thickness continuously decreases from the surface to the interior of the sheet. Because the concentration of the EMI suppression material added to the layer exhibiting a high complex dielectric constant is constant, the thickness of the layer exhibiting a high complex dielectric constant can be continuously reduced from the surface to the inner layer, resulting in a state in which the EMI suppression material is more densely connected in the inner layer, resulting in a gradual increase in complex dielectric constant. This allows EMI to be absorbed into the interior of the laminate sheet without inadvertently reflecting it, thereby enhancing the EMI absorption effect. [Example]

[0105] The present invention will be described below with reference to examples, but the present invention is not limited to these examples. Each property was measured by the following methods.

[0106] (Methods for measuring characteristics and evaluating effects) The methods for measuring the properties and evaluating the effects in the present invention are as follows.

[0107] (1) Layer thickness, number of layers, layer structure, particle length The layer structure of the laminate sheet was determined by observing cross sections parallel to the thickness direction of the laminated sheet using a microtome under a differential interference microscope. Specifically, a Leica DMLBHC differential interference microscope was used to observe the cross section of the laminated sheet at 1000x magnification (10x eyepiece, 100x objective lens), and cross-sectional photographs were taken to measure the layer structure and thickness of each layer. Measurements were performed using the particle size analysis software Macview (Mountec Co., Ltd.), and layer thickness was measured by measuring the vertical distance between layer interfaces where contrast differences were clearly discernible. Data were measured at five random locations, and the average value of each layer thickness was used as the actual measurement data. The particle long diameter was determined by measuring the longest distance of the higher-order structure formed by the particles observed in the image at a total of 100 points, and the average data was used.

[0108] (2) Complex permittivity measurement The laminated sheet was analyzed by changing the measurement unit and measurement method for each measurement frequency as follows.

[0109] (2-1) 1GHz to 40GHz frequency band An Agilent Technologies Vector Network Analyzer (E8361A) was used. A donut-shaped coaxial waveguide with an outer diameter of 7 mm and an inner diameter of 3.04 mm was used for the 0.5 GHz to 18 GHz frequency band. A rectangular waveguide with a rectangular shape of 4.32 mm x 10.67 mm was used for the 18 to 26.5 GHz frequency band. A rectangular waveguide with an internal shape of 3.56 mm x 7.11 mm was used for the 26.5 to 40 GHz frequency band. A laminated sheet sample was punched and inserted vertically into each of the waveguides for measurement. The measurement interval was set so that 200 measurements could be taken for each frequency band. The complex permittivity was analyzed using the analysis software N1500A-001 provided with the instrument.

[0110] (2-2) 40 to 110 GHz frequency band A 150mm square laminated sheet was used. A Keycom LAF-26.5A lens antenna type dielectric constant and attenuation measuring device utilizing the frequency change method was used to measure the complex permittivity in the frequency bands of 33 to 50GHz (WR-22), 50 to 75GHz (WR-15), and 75 to 110GHz (WR-10). While this measurement method also measures values ​​from 33 to 40GHz, the complex permittivity in the frequency band between 33GHz and less than 40GHz was measured using the measurement data in (2-1).

[0111] (3) Return loss measurement Measurements were carried out by changing the measurement unit and measurement method as follows according to the measurement frequency band.

[0112] (3-1) 1GHz to 40GHz frequency band The return loss (reflection loss spectrum) of the laminate sheet was measured using an Agilent Technologies Vector Network Analyzer (E8361A). A donut-shaped coaxial waveguide with an outer diameter of 7 mm and an inner diameter of 3.04 mm was used for the 0.5 GHz to 18 GHz frequency band, a rectangular waveguide with a rectangular shape of 4.32 mm x 10.67 mm was used for the 18 to 26.5 GHz frequency band, and a rectangular waveguide with an internal shape of 3.56 mm x 7.11 mm was used for the 26.5 to 40 GHz frequency band. The measurement interval was set to allow 200 measurements for each frequency band. A 3 mm aluminum metal plate was placed on the back of the laminate sheet sample, so that incident electromagnetic waves would be totally reflected when there was no electromagnetic wave absorption by the laminate sheet. S, which represents the intensity ratio of the reflected electromagnetic wave to the incident electromagnetic wave, is used. 11 The S-parameter values ​​were used to analyze the reflection loss peak.

[0113] (3-2) 40 to 110 GHz frequency band A 150 mm square laminated sheet was attached to the back of an aluminum metal plate to prepare a measurement sample. A Keycom Corporation lens antenna type oblique incidence electromagnetic wave absorber (electromagnetic wave absorbing material) return loss measurement device, LAF-26.5B, was used to measure the return loss (return loss spectrum) in the frequency bands of 33 to 50 GHz (WR-22), 50 to 75 GHz (WR-15), and 75 to 110 GHz (WR-10) in accordance with JIS R 1679 (2007). While this measurement method also measures values ​​from 33 to 40 GHz, the return loss in the frequency band from 33 GHz to less than 40 GHz was measured using the data measured in (3-1).

[0114] (4) Calculation of the complex permittivity of each layer We developed and utilized macro software that can calculate the impedance when the laminated sheet configuration is replaced with an equivalent electrical circuit by substituting the variables of the permittivity, permeability, and layer thickness of layers A and B. The obtained impedance Z in A macro was created to continuously calculate the return loss Γ over a certain frequency band by substituting Γ into equation (3), which is based on the non-reflection condition and return loss. The permittivity and permeability of each layer were then set to match the return loss spectrum measured using the method described in (3). The permittivity and permeability values ​​for each layer were then read to determine the values ​​that best matched the return loss spectrum. When it was difficult to calculate the permittivity, a single-layer sheet was created with the same composition as the layer exhibiting a relatively high permittivity in the example. The frequency variation method using the vector network analyzer described above was used to identify the frequency at which the minimum transmission loss was achieved. The permittivity was calculated based on the minimum value, which is an integer multiple of 1 / 2 the effective wavelength transmitted through the sheet thickness. The same value can also be confirmed using the software (SFW05) included with Keycom's permittivity measurement system (Model No. DPS10) for free-space measurements using the frequency variation method.

[0115]

number

[0116] (5) Surface resistivity measurement (5-1) High resistance measurement High resistance region (1.0×10 6 ~1.0×10 13 ) was measured using a high resistivity meter, Hiresta-UP (MCP-HT450) manufactured by Mitsubishi Chemical Corporation. A URS probe (MCP-HTP14) was pressed against the surface of a laminated sheet cut into a 10 cm square, and the resistivity was measured in accordance with JIS K 6911 (1995). Measurements were made at five different measurement positions, and the average value was taken as the measured value. When measuring the surface resistivity of the inner layer, the surface was polished with a polishing device to the thickness of the outermost layer confirmed with a differential interference microscope, and then the probe was pressed against the surface to measure.

[0117] (5-2) Low resistance measurement Low resistance region (1.0×10 6 ~1.0×10 -1 ) was measured using a low resistivity meter Loresta-EP (MCP-T360) manufactured by Mitsubishi Chemical Corporation. An ASP probe (MCP-TP03P) was pressed against the surface of a laminated sheet cut into a 10 cm square, and the resistivity was measured in accordance with JIS K 7194 (1994). Measurements were made at different measurement positions with n=5, and the average value was taken as the measured value.

[0118] (6) DBP oil absorption The laminated sheet was dissolved in a solvent that could dissolve the base resin, and the carbon-based conductive particles extracted and separated were measured using a Brabender Absorbometer C type in accordance with ASTM D2414 (2019). The carbon-based conductive particles were placed in a mixer at a rotation speed of 125 min -1 While kneading, DBP was added dropwise at a rate of 4 mL / min, and the DBP oil absorption was analyzed based on the obtained viscosity curve.

[0119] (7) Aspect ratio of the electromagnetic wave suppression material, the average elevation angle between the carbon material X and the sheet surface direction, X / Y The longitudinal and width cross sections of the laminated sheet were embedded in epoxy resin and polished, and then the surface was polished using a JEOL IB-19520CCP ion mill. The acceleration voltage was 4 kV and the processing temperature was -120°C. Pt-Pd metal was then deposited at 2 mA for 3.75 minutes using an Eiko Engineering IB-3 sputtering machine. In this way, processed samples of the thickness-width cross section and the thickness-longitudinal cross section of each sample were obtained. Next, cross-sectional images were obtained using a JEOL JSM-6700F scanning electron microscope. Light was irradiated parallel to the thickness direction of the processed sample during observation, and cross-sectional images were obtained under the following observation conditions. <Observation conditions> Accelerating voltage: 3 kV Objective aperture: 4 Secondary electron detection: ON Mode: LEI Emission: 10μA Magnification: 10000x Inclination: None The AnalyzeParticles function of NIH's ImageJ image analysis software was then used to extract the area of ​​each particle from each cross-sectional image. The area of ​​each region was then approximated as an ellipse using Fit Ellipse, and the major and minor diameters were calculated. The aspect ratio of each particle was calculated by dividing the major by the minor, with three significant digits. This process was performed on approximately 200 randomly selected particles present in the cross-sectional observation image. The aspect ratios of each particle in the obtained observation image were plotted as a curve, with the vertical axis representing degrees and the horizontal axis representing the logarithm of the aspect ratio (Figure 6). The maximum value between 40 and 5000 was taken as the aspect ratio of carbon material X. The analysis was performed on a 1.5 μm × 12 μm rectangular area within the layer in both the longitudinal and transverse directions, with n = 7. The average of five points was calculated, excluding the maximum and minimum values.

[0120] The average elevation angle of particles (carbon material X) exhibiting a high aspect ratio was calculated by binarizing each cross-sectional image, selecting 100 particles in descending order of aspect ratio, measuring the angle between the long axis of each particle and the film surface direction (direction of the interface) using the image analysis software, and averaging the obtained values. In this case, if multiple particles overlap, the particle at the forefront was the object of analysis.

[0121] In addition, the Major was calculated for the higher-order structure of the particle most frequently found in the observed image, and X / Y was calculated by dividing it by the average layer thickness calculated in (1). Note that particles with a Minor of 0 were excluded from the analysis as outliers.

[0122] <Resin, rubber, and electromagnetic wave suppression materials> To obtain the sheets of each example and comparative example, the following components were used as the resin, rubber, and electromagnetic wave suppressing material.

[0123] <Resin, rubber> Ethylene-propylene terpolymer rubber (EPDM): Ethylene-propylene terpolymer rubber (manufactured by Mitsui Chemicals, Inc.) Homopolypropylene: Homopolypropylene resin with a melt flow rate of 30 (Prime Polymer Co., Ltd.) Isophthalic acid copolymer polyethylene terephthalate (isophthalic acid copolymer PET): Isophthalic acid copolymer polyethylene terephthalate with a melting point of 210°C · Polyethylene terephthalate (PET): Polyethylene terephthalate with a melting point of 254°C and a viscosity of IV 0.8.

[0124] <Electromagnetic wave suppression material> Carbon black A: Carbon black with a primary particle diameter of 38 nm and a DBP oil absorption of 145 mL / 100 g Carbon black B: Carbon black with a primary particle diameter of 50 nm and a DBP oil absorption of 250 mL / 100 g Carbon black C: Carbon black with a primary particle diameter of 40 nm and a DBP oil absorption of 360 mL / 100 g Carbon Black D: Carbon black with a primary particle diameter of 19 nm and a DBP oil absorption of 95 mL / 100 g (manufactured by Asahi Carbon Co., Ltd.) Carbon black E: Carbon black with DBP oil absorption of 500 mL / 100 g Graphite: Flake graphite with an average particle size (D50) of 5.3 μm and an average thickness of 100 nm Graphene: Graphene powder with an average particle size (D50) of 5.8 μm and an average thickness of 7 nm Barium titanate: Barium titanate powder with an average particle size (D50) of 0.1 μm Carbon nanotube 1: Multi-walled carbon nanotube with an average particle size (D50) of 1.5 μm and an average diameter of 10 nm Carbon nanotubes 2: Single-walled carbon nanotubes with an average particle size (D50) of 2 μm and an average diameter of 1 nm.

[0125] Example 1 EPDM was press-molded to produce Sheet A (A layer) 0.40 mm thick and 200 mm square. Separately, EPDM and carbon black B were blended in a mass ratio of 87.5:12.5 and kneaded in a two-roll mill. The resulting mixture was pressed to produce Sheet B (B layer) 0.40 mm thick and 200 mm square. Five layers were then laminated in the order of Sheet A, Sheet B, Sheet A, Sheet B, and Sheet A, and thermocompressed at 250°C to produce a 2.0 mm thick laminate sheet. The evaluation results are shown in Table 1.

[0126] Example 2 First, 89% by mass of homo-polypropylene and 11% by mass of carbon black B were blended in a twin-screw extruder with a side feed of an EMI suppression material to produce master pellets. Next, the homo-polypropylene pellets (layer A raw material) and the master pellets (layer B raw material) were fed into separate twin-screw extruders, melted at 270°C, and mixed. The mixing conditions were a screw rotation speed of 0.7 relative to the output rate. These pellets were then merged in a multi-manifold feed block with 13 flow channels. The layer A raw material and the layer B raw material were laminated in alternating layers in the thickness direction at a layering ratio of 1.0, resulting in an alternating laminate. The alternating laminate was fed into a T-die and molded into a sheet. It was then pressed against a casting drum, the surface temperature of which was maintained at 25°C using a spot air system, where it was rapidly cooled and solidified into a 2.0 mm-thick laminate sheet. The evaluation results are shown in Table 1.

[0127] Example 3 Two 1 mm thick laminate sheets were prepared using the same raw materials as in Example 2, and these were bonded together via a 25 μm thick optical adhesive sheet (manufactured by Tomoegawa Paper Co., Ltd.) primarily composed of acrylic resin to form a 2.0 mm thick laminate sheet (the optical adhesive sheet is thinner than the laminate sheet, so it is not considered as part of the laminate sheet thickness). The thickness was adjusted by adjusting the rotation speed of the casting drum (the same applies to other examples and comparative examples below). The evaluation results are shown in Table 1.

[0128] (Examples 4 and 5) A laminated sheet having a thickness of 1.2 mm was obtained in the same manner as in Example 2, except that the laminating device and the number of layers were as shown in Table 1. The evaluation results are shown in Table 1.

[0129] Example 6 A laminated sheet having a thickness of 1.2 mm was obtained in the same manner as in Example 2, except that the composition of the raw materials constituting each layer, the lamination device, and the number of layers were as shown in Table 1, that each raw material was passed through seven FSS-type leaf disc filters before being fed to the feed block, and that each raw material was discharged while being metered using a gear pump. The evaluation results are shown in Table 1.

[0130] (Examples 7 to 14) A laminate sheet was obtained in the same manner as in Example 6, except that the composition of the raw materials constituting each layer, the thickness of the laminate sheet, the film-forming conditions, and the number of layers were as shown in Tables 1 and 2. The evaluation results are shown in Tables 1 and 2.

[0131] Example 15 The laminate sheet obtained in Example 8 was heated using a group of rolls set at 90°C, then stretched 1.5 times in the longitudinal direction while rapidly heating both sides of the film using a radiation heater within a 100mm stretching section, and then cooled. This uniaxially stretched laminate sheet was introduced into a tenter, preheated with hot air at 90°C, and then stretched 2.0 times in the transverse direction at 140°C to obtain a laminate sheet with a thickness of 0.33mm. The evaluation results are shown in Table 2.

[0132] Example 16 Three laminate sheets obtained in Example 15 were bonded together with a 25 μm thick optical pressure-sensitive adhesive to obtain a 1.0 mm thick laminate sheet having a total of 305 layers. The evaluation results are shown in Table 2.

[0133] Example 17 Using the laminate sheet of Example 11, a laminate sheet having a thickness of 1.0 mm and having 305 layers was obtained by the post-stretching process described in Examples 15 and 16. The evaluation results are shown in Table 2.

[0134] Example 18 96% by mass of isophthalic acid copolymerized polyethylene terephthalate resin with a melting point of 210°C was blended with 4% by mass of graphene powder with an average particle size (D50) of 5.8 μm as an EMI suppression material. The EMI suppression material was side-fed into a twin-screw extruder using a screw segment configuration that minimizes shear stress. This master pellet was used as the resin constituting Layer B to obtain a 301-layer alternating laminate. The stretching conditions were then modified to 3.0 times in the longitudinal direction and 3.0 times in the transverse direction, as described in Example 15, to obtain a 0.50 mm-thick laminate sheet. The thickness of each layer was approximately 1.6 μm, and the graphene powder was confirmed to be neatly aligned in the planar direction. The evaluation results are shown in Table 2.

[0135] (Examples 19 and 20) A laminate sheet having 301 layers was obtained in the same manner as in Example 18, except that the composition of the raw materials constituting each layer was as shown in Table 2. The evaluation results are shown in Table 2.

[0136] Example 21 A 601-layer laminate sheet was obtained in the same manner as in Example 19, except that the molten resin was joined in a feed block with 601 slits. Although the increased number of layers caused some lamination disorder, the sheet still exhibited sufficient performance for use as an electromagnetic wave shielding agent. The evaluation results are shown in Table 2.

[0137] (Comparative Example 1) A laminate sheet was obtained in the same manner as in Example 1, except that the composition of the raw material for layer B was as shown in Table 2. The evaluation results are shown in Table 2.

[0138] (Comparative Example 2) A single-layer sheet was produced by blending EPDM and carbon black A in a mass ratio of 80:20, kneading the mixture in a two-roll mill, and pressing the resulting mixture into a sheet 2.0 mm thick and 200 mm square. The evaluation results are shown in Table 2 (note that since this sheet has a single-layer structure, it is listed in Table 2 as consisting only of layer A).

[0139] (Comparative Example 3) An unstretched laminate sheet was obtained in the same manner as in Example 2, except that the raw material for layer B had the composition shown in Table 2. The evaluation results are shown in Table 2.

[0140] (Examples 22 to 27, 30) A laminate sheet was obtained in the same manner as in Example 6, except that the composition of the raw materials constituting each layer, the thickness of the laminate sheet, the film-forming conditions, and the number of layers were as shown in Table 3. The evaluation results are shown in Table 3.

[0141] Example 28 Using the laminate sheet of Example 23, a laminate sheet having a thickness of 1.0 mm and having 305 layers was obtained by the post-stretching process described in Examples 15 and 16. The evaluation results are shown in Table 3.

[0142] Example 29 A laminate sheet having 301 layers was obtained in the same manner as in Example 18, except that the composition of the raw materials constituting each layer was as shown in Table 3. The evaluation results are shown in Table 3.

[0143] [Table 1]

[0144] [Table 2]

[0145] [Table 3]

[0146] The laminated sheets of Examples 3, 16, and 17 deviated slightly from the values ​​listed in the table due to deformation of the pressure-sensitive adhesive sheet caused by lamination, but the difference was so small that it was considered to be the value listed in the table. Formulas (A) and (B) are as follows. (A)ε h ''≧1 and 0.15ε h '+2≦ε h ''≦0.23ε h'+7.7 (B) 5 ≥ ε h ''≧1 and 0.01ε h '+1≦ε h ''≦0.09ε h '+2. [Industrial Applicability]

[0147] The laminate sheet of the present invention includes a unit in which layers with a low complex dielectric constant and layers with a high complex dielectric constant are alternately laminated. This allows for a low concentration of EMI suppression material and a high electromagnetic wave attenuation despite the thin film, something that was difficult to achieve with conventional single-film or low-layer sheets. Furthermore, in a preferred embodiment, by controlling the complex dielectric constants of both layers within a specific range, it is possible to achieve sharp and strong shielding of only specific frequencies of electromagnetic waves, thereby effectively preventing malfunctions of devices that use electromagnetic waves in similar frequency bands and information leakage during high-volume data communications due to high-frequency electromagnetic waves. Specifically, the laminate sheet can be suitably used in electronic devices and communication devices that use communication technologies using electromagnetic waves in the GHz frequency band, as well as in vehicles equipped with such devices and in transportation systems, including all types of traffic control infrastructure. [Explanation of symbols]

[0148] 1: Return loss spectrum 2: The return loss peak with the largest attenuation at the peak top. 3: The half-width R of the return loss peak with the largest peak top attenuation 4: Resin 5: Carbon material 6: Carbon black particles 7: A curve plotted with the vertical axis as degrees and the horizontal axis as the logarithm of the aspect ratio. 8: Sheet surface direction 9: Elevation angle between carbon material X and the sheet surface

Claims

1. A laminate sheet having a configuration in which five or more layers A and B having different compositions are alternately stacked, at least one of the layers A and B containing an electromagnetic wave suppressing material, the content of the electromagnetic wave suppressing material being 1% by mass to 15% by mass when all components constituting the laminate sheet are taken as 100% by mass, and the product of the real part ε' (F / m) of the complex permittivity and the real part μ' (H / m) of the complex magnetic permeability of the entire laminate sheet at a frequency showing a peak top of the return loss in the frequency band of 1 GHz to 110 GHz is 4.0 F·H / m ２ More than 50F・H / m ２ A laminated sheet characterized by the following:

2. 2. The laminate sheet according to claim 1, wherein the dielectric loss tangent tanδ(ε″ / ε′) of the entire laminate sheet is 0.10 or more and 0.50 or less, when the imaginary part of the complex dielectric constant of the entire laminate sheet is ε″F / m.

3. The real part ε of the complex permittivity of the layer with a relatively high complex permittivity between layer A and layer B h '(F / m) and the imaginary part ε h 3. The laminate sheet according to claim 1, wherein the tensile strength (F / m) satisfies the relational expression (A) or (B). (1)ε h ''≧1、かつ、1015ε h '22≦ε h ''≦23ε h '747 (B) 5 ≧ ε h ''≧1 and 0.01ε h '+1≦ε h ''≦0.09ε h '+2

4. 4. The laminate sheet according to claim 1, wherein at least one of the electromagnetic wave suppressing materials is a carbon material.

5. The laminate sheet according to claim 4, wherein the carbon material comprises carbon black.

6. 6. The laminate sheet according to claim 4, wherein the carbon material comprises a carbon material X having an aspect ratio of 40 or more and 5,000 or less.

7. 7. The laminate sheet according to claim 6, wherein an average value of an elevation angle between the carbon material X and the sheet surface direction is 0° or more and 15° or less.

8. 8. The laminate sheet according to claim 1, wherein X / Y is 0.01 or more and 10.0 or less, where X (nm) is the major axis of a higher-order structure formed by a component of the electromagnetic wave suppression material that is contained in the laminate sheet in the largest amount, and Y (nm) is the average thickness of the layer A or the layer B that contains that component in the largest amount.

9. When the larger of the surface resistivity values ​​of the A layer and the B layer is defined as α (Ω / □) and the smaller of the two is defined as β (Ω / □), α is 1.0×10 ５ Ω / □ or more 1.0×10 １６ Ω / □ or less, and β is 1.0Ω / □ or more and 1.0×10 ５ The laminate sheet according to any one of claims 1 to 8, characterized in that it has a modulus of elasticity of less than Ω / □.

10. The real terms of the complex permittivity of the A layer and the B layer are respectively ε Ａ '(F / m), ε Ｂ ' (F / m), then |ε Ａ '-ε Ｂ 10. The laminate sheet according to claim 1, wherein | is 1 or more and 100 or less.

11. The ε Ａ ' and the ε Ｂ ', 2.0≦ε Ａ ' / ε Ｂ '≦25 or 2.0≦ε Ｂ ' / ε Ａ The laminated sheet according to claim 10, wherein '≦25 is satisfied.

12. The content of the electromagnetic wave suppressing material in the layer A is w Ａ (mass %), and the content of the electromagnetic wave suppressing material in Layer B is w Ｂ (mass%), w Ｂ >w Ａ The laminate sheet according to any one of claims 1 to 11, wherein the above formula (1) is satisfied.

13. 13. The laminate sheet according to claim 1, wherein in a return loss spectrum plotted with return loss on the vertical axis and frequency on the horizontal axis, a peak top of the return loss peak having the largest return loss is present in a frequency band of 1 to 100 GHz.

14. The laminate sheet according to any one of claims 1 to 13, wherein in a return loss spectrum plotted with return loss on the vertical axis and frequency on the horizontal axis, RL (dB) is the return loss at the peak top of the return loss peak having the largest return loss at the peak top, f (GHz) is the frequency corresponding to the peak top, and t (mm) is the thickness of the laminate sheet, and RL / (f x t) is 0.40 or more and 5.00 or less.

15. The laminate sheet according to any one of claims 1 to 14, which is used for suppressing electromagnetic waves.

16. An electromagnetic wave suppressor comprising the laminate sheet according to any one of claims 1 to 15 and a reflector.

17. An electrical product comprising the laminate sheet according to any one of claims 1 to 15 or the electromagnetic wave suppressor according to claim 16.

18. A communication device comprising the laminate sheet according to any one of claims 1 to 15 or the electromagnetic wave suppressor according to claim 16.

19. A means of transportation equipped with the laminate sheet according to any one of claims 1 to 15 or the electromagnetic wave suppressor according to claim 16.

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