JP2022018105A - Laminated sheet, electromagnetic wave inhibitor, electric product, communication equipment, and transport facility - Google Patents

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

The present invention relates to a laminated sheet which is a thin film and has an excellent electromagnetic wave shielding property while having a low concentration of an electromagnetic wave suppressing material, and an electromagnetic wave suppressing body, an electric product, a communication device, and a transportation facility using the same.

With the progress of communication technology in recent years, various types represented by metric waves in the band of several hundred MHz to several GHz, quasi-millimeter waves in the band of several GHz to several tens of GHz, and millimeter waves in the band of several tens of GHz to several hundred GHz. Electromagnetic waves in the frequency band are flying around in the atmosphere. Metric waves are mainly used in mobile phones and wireless communications, quasi-millimeter waves are mainly used in mobile communications such as 4G and 5G, and wireless LAN (Wi-fi) communications, and millimeter waves are used for automobile collision prevention radar, etc. Mainly used in.

As the electromagnetic wave, an electromagnetic wave having a frequency band suitable for the capacity of information, a transmission distance, an application, etc. is selected and used, but an electromagnetic wave having a similar frequency band is simultaneously used in various devices and applications. Therefore, there is an increasing need for an electromagnetic wave shielding material that shields electromagnetic waves in order to prevent malfunction of the device, communication failure, information leakage, and influence on the human body sensitive to electromagnetic waves. In particular, in recent years, in order to realize high-speed and large-capacity communication, the development of communication technology using electromagnetic waves in the high frequency (GHz) band is accelerating, and an electromagnetic wave shielding material capable of shielding electromagnetic waves in the frequency band is required. ing.

An electromagnetic wave is a composite wave of two components having different electric and magnetic fields, and these propagate in space while vibrating with each other. Electromagnetic wave shielding material is to reflect electromagnetic waves on the surface / inside of the material (reflection loss), absorb electromagnetic waves inside the material (absorption loss), or interfere with each other's reflected electromagnetic waves to cancel them. Refers to materials that lose or attenuate.

For example, the surface reflection of electromagnetic waves can be enhanced by the difference in electrical resistance (impedance) between the air interface and the electromagnetic wave shielding material interface. As an electromagnetic wave shielding material due to reflection loss, a material having a very low resistance value (for example, a metal such as copper) is generally applied to the surface of a base material and laminated to realize reflection of electromagnetic waves over a wide frequency band. Is known (Patent Document 1).

The electromagnetic wave shielding material due to absorption loss contains a conductive material and / or a magnetic material in the base material, and absorbs the electromagnetic wave that has entered the inside as an induced current, thereby losing the electromagnetic wave energy. Such an electromagnetic wave shielding material exhibits absorption performance by containing a metal material such as a carbon material or ferrite (generally referred to as an electromagnetic wave suppressing material) in a dielectric polymer such as rubber (generally referred to as an electromagnetic wave suppressing material). Patent Documents 2 to 4).

In addition, the electromagnetic wave shielding material by canceling the interference reverses the phase and amplitude of each other's electromagnetic waves with respect to the electromagnetic waves reflected on the surface and the electromagnetic waves reflected by the reflective layer arranged on the back surface, and cancels each other's electromagnetic waves. It is a loss. At this time, by appropriately arranging layers having different impedances inside the sheet, dielectric polarization occurs at the interfaces having different impedances, and it becomes possible to obtain a dielectric loss due to the inability to follow the time change of the applied electric field (Patent Document). 5). These three types of electromagnetic wave loss methods can be appropriately used depending on the frequency band of the electromagnetic wave to be shielded and the application.

Japanese Patent Publication No. 2011-502285 Japanese Patent Application Laid-Open No. 2003-158395 Japanese Unexamined Patent Publication No. 2017-118073 Japanese Unexamined Patent Publication No. 2019-057730 Japanese Unexamined Patent Publication No. 2019-102665

However, in order to selectively shield electromagnetic waves in a specific frequency band, a reflection loss design that simultaneously shields a wide frequency band is unsuitable, and an electromagnetic wave shielding material due to absorption loss is suitable. On the other hand, in the case of electromagnetic wave shielding materials due to absorption loss, it is necessary to increase the concentration of the electromagnetic wave shielding material to be added to increase the dielectric constant of the electromagnetic wave shielding material itself. There are problems that the sheet becomes brittle due to the high-concentration electromagnetic wave suppression material, and that the effect of reflection loss rather than absorption loss is strongly generated, making it difficult to shield only a specific frequency band. Further, when a thermosetting / thermoplastic rubber material is used as the base material, the electromagnetic wave suppressing material can be added at a high concentration, but the thickness of the electromagnetic wave shielding material becomes large and flexibility is required. It was difficult to deploy to. In view of the above problems, it is an object of the present invention to provide a thin film laminated sheet capable of shielding electromagnetic waves of a specific frequency and having flexibility.

In order to solve the above problems, the present invention has the following configurations. That is, it is a laminated sheet having a structure in which five or more layers A and B having different compositions are alternately laminated, and at least one of the A layer and the B layer contains an electromagnetic wave suppressing material to form a laminated sheet. When the total component is 100% by mass, the content of the electromagnetic wave suppressing material is 1% by mass or more and 15% by mass or less, and the real part ε'(F / m) of the complex permittivity of the entire laminated sheet and the complex permeability. It is a laminated sheet characterized in that the product of the real part μ'(H / m) of the magnetic coefficient is 4.0 F · H / m ² or more and 50 F · H / m ² or less.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a laminated sheet having excellent frequency selectivity and flexibility of electromagnetic waves to be shielded and having a small thickness. Specifically, by increasing the difference in the complex permittivity of the layers having different complex permittivity arranged alternately and forming a configuration with a large number of layers, the effect of dielectric polarization at each interface having a different complex permittivity can be obtained. It can be increased to increase the complex permittivity of the entire sheet. Therefore, it is possible to provide a laminated sheet for an electromagnetic wave shielding material, which is thinner and has molding followability. The laminated sheet of the present invention can be suitably used as an electromagnetic wave shielding material for devices and members having complicated shapes that require molding followability.

Among the peaks obtained by measuring the reflection attenuation peak of the laminated sheet according to the embodiment of the present invention, the schematic diagram showing the half-value width of the reflection attenuation peak having the largest reflection attenuation at the peak top and the electromagnetic wave attenuation. Is. Among the peaks obtained by measuring the reflection attenuation peak of the laminated sheet according to the embodiment of the present invention, the schematic diagram showing the half-value width of the reflection attenuation peak having the largest reflection attenuation at the peak top and the electromagnetic wave attenuation. Is. Among the peaks obtained by measuring the reflection attenuation peak of the laminated sheet according to the embodiment of the present invention, the schematic diagram showing the half-value width of the reflection attenuation peak having the largest reflection attenuation at the peak top and the electromagnetic wave attenuation. Is. Among the peaks obtained by measuring the reflection attenuation peak of the laminated sheet according to the embodiment of the present invention, the schematic diagram showing the half-value width of the reflection attenuation peak having the largest reflection attenuation at the peak top and the electromagnetic wave attenuation. Is. It is a schematic diagram of the layer containing carbon material X and carbon black particles. It is a curve plotted with the vertical axis as the frequency and the horizontal axis as the logarithm of the aspect ratio. It is a schematic diagram which shows the elevation angle of a carbon material.

Hereinafter, the laminated sheet of the present invention will be described in detail.

The laminated sheet of the present invention is a laminated sheet having a structure in which five or more layers A and B having different compositions are alternately laminated, and at least one of the A layer and the B layer contains an electromagnetic wave suppressing material. When the total components constituting the laminated sheet are 100% by mass, the content of the electromagnetic wave suppressing material is 1% by mass or more and 15% by mass or less, and the real part ε'(F / F /) of the complex dielectric constant of the entire laminated sheet. It is characterized in that the product of m) and the real part μ'(H / m) of the complex magnetic permeability is 4.0 F · H / m ² or more and 50 F · H / m ² or less.

Here, the "configuration in which five or more layers A and B are alternately laminated" means a configuration in which layers A and B are alternately continuous and have a total of five or more layers. That is, it refers to a state in which resins are laminated according to a regular arrangement of A (BA) n or B (AB) n (n is a natural number of 2 or more). For example, the configuration of A layer / B layer / A layer / B layer / A layer, or the configuration of B layer / A layer / B layer / A layer / B layer (hereinafter, these two laminated configurations are A layer and B layer. The laminated sheet having (sometimes referred to as a laminated unit) has a structure in which five or more layers of A layer and B layer are alternately laminated regardless of the presence or absence of layers other than A layer and B layer. Corresponds to "Sheet". As long as the laminated sheet of the present invention has a laminated unit of A layer and B layer, the outermost layer may be any of layers A and B, and layers other than A layer and B layer, and the outermost layers on both sides are the same. It may be a layer or a layer different from each other. Further, the number of laminated units of the A layer and the B layer of the laminated sheet may be one or a plurality.

As a means for obtaining a laminated sheet having a laminated unit of A layer and B layer, as described later, a method of stepwise crimping and laminating layers having different compositions to each other, or laminating at once via a laminating device. And the like can be used. Further, on the alternating laminated unit of the A layer and the B layer, a functional layer different from the alternating laminated unit such as another electromagnetic wave reflecting layer or an electromagnetic wave absorbing layer may be formed. In the case of having a plurality of laminated units of the A layer and the B layer, the plurality of laminated units can be directly laminated via the adhesive layer or by thermocompression bonding. Further, in the case of having a plurality of laminated units of the A layer and the B layer, the alternating laminated units having peak tops in different frequency bands are used in an overlapping manner, and as a material for simultaneously shielding a plurality of desired frequency bands. May be good.

By having the laminated unit of the A layer and the B layer, the laminated sheet of the present invention can improve the electromagnetic wave shielding performance targeting a specific frequency band while suppressing the thickness of the entire laminated sheet. Normally, in order to improve the electromagnetic wave shielding performance by targeting a specific frequency band, it is necessary to improve the complex dielectric constant of the entire sheet. In the conventional single film sheet, it is necessary to add a conductive material at a high concentration and to increase the thickness of the sheet for that purpose. On the other hand, in the case of a laminated sheet having a laminated unit of A layer and B layer, dielectric polarization occurs at the interface between layers having different dielectric constants, and current easily passes through the inside of the sheet. In addition, the electromagnetic wave suppression material can be tightly confined in each layer, which enhances the conductivity in the layer and is susceptible to loss due to the resistance of the conductive material added inside, resulting in higher shielding than conventional products. Performance can be achieved. As a result, it is possible to obtain an electromagnetic wave shielding material having excellent shielding performance even if the sheet is thin.

Further, in such a laminated sheet, the layer thickness per layer is usually thin even if the sheet thickness is the same as that of the single film sheet, so that the packing density of the electromagnetic wave suppressing material in the layer becomes high and the distance between the electromagnetic wave suppressing materials increases. It narrows. As a result, the electron transfer efficiency between the electromagnetic wave suppressing materials is improved, and the electromagnetic wave suppressing performance of the entire laminated sheet is improved.

Further, in such a laminated sheet, since the electromagnetic wave suppressing material is easily arranged in the direction parallel to the laminated sheet surface, the material forming a high-order structure connected in a linear manner or the electromagnetic wave suppressing showing a high aspect ratio. By using the material, the conductivity in the plane direction is improved, and the incident electromagnetic wave is easily subjected to the resistance from the electromagnetic wave suppressing material. By the above mechanism, such a laminated sheet can realize a value of complex permittivity which could not be achieved only by containing a large amount of electromagnetic wave suppressing material in a single film sheet, even with a smaller amount of electromagnetic wave suppressing material.

The number of laminated units of the A layer and the B layer contained in the laminated sheet is preferable because the more the layer interface between the layer showing a high complex dielectric constant and the layer showing a low complex dielectric constant, the easier it is to obtain the above effect. Is 13 layers or more in total, more preferably 31 layers or more in total, and more preferably 101 layers or more in total. The upper limit of the number of layers is preferably 1001 layers from the viewpoint of manufacturing cost, film forming property, and electromagnetic wave shielding performance. By setting the number of laminated units of the A layer and the B layer to 1001 layers or less, it is possible to suppress an increase in manufacturing cost due to an increase in the size of a device such as a feed block having fine slits. At the same time, depending on the dispersed state, shape, and size of the electromagnetic wave suppression material, the disturbance of the layer thickness due to the development of thixotropy, which is a problem due to the increase in the number of layers and the thinning of the thickness of each layer, is reduced, and the original shielding is achieved. It is also possible to maintain the steepness of performance and shielding.

It is important that the laminated sheet of the present invention contains layers A and B having different compositions from each other. The components of the A layer and the B layer are not particularly limited, such as transparent / opaque, flexible / rigid, flat / non-flat, organic (polymer) material / inorganic (metal) material. However, from the viewpoint of improving the processability of the obtained laminated sheet, it is preferable that the A layer and the B layer are mainly composed of an organic polymer material exhibiting flexibility. Further, a hard coat using a thermosetting resin or a photocurable resin can also be used. Here, the main component means that it contains more than 50% by mass and 100% by mass or less, preferably 70% by mass or more and 100% by mass or less, when all the components constituting the layer are 100% by mass. be.

It is important that the A layer and the B layer in the laminated sheet of the present invention are layers having different compositions from each other. The composition of the A layer and the B layer is different from each other because there is a component contained in only one of the A layer and the B layer, or the components of the A layer and the B layer are the same but their contents are different from each other. Say that. The A layer and the B layer in the laminated sheet of the present invention both contain an organic polymer material as a main component from the viewpoint of designability and electromagnetic wave shielding characteristics when the laminated sheet is used, and at least one of them is an organic material as an electromagnetic wave suppression material. It is preferable that the embodiment contains an inorganic material or an inorganic material.

The composition of the A layer and the B layer is not particularly limited as long as the compositions are different from each other. A possible composition is preferred. From this viewpoint, 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 means a repeating unit contained most 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. As a specific example of the embodiment in which the organic polymer materials in the A layer and the B layer have the same molecular skeleton, the A layer contains a polyester resin as a main component, and the B layer also has the same basic skeleton as the polyester resin which is the main component of the A layer. An embodiment in which a polyester resin having a above-mentioned material is used as a main component can be mentioned.

A compatibility parameter can be used as an index showing the adhesion between the A layer and the B layer. The compatibility parameter can be estimated by a calculation method such as Hansen, Hoy, and Fedors, but the compatibility parameter of the thermoplastic resin, which is a component that can be suitably used as an organic polymer material, is a repetition of the molecular chain. A Fedors calculation method that can be calculated based on structural units is used. By using this method, the compatibility parameter of the thermoplastic resin containing the structural unit derived from the copolymerization component can be easily calculated according to the ratio of each structural unit. In the Fedors calculation method, the cohesive energy density of the molecule and the molar molecular volume, which depend on the type and number of substituents, determine the compatibility parameter, and the compatibility parameter is estimated according to the formula (1). Here, _Ecoh (cal / mol) represents the aggregation energy, and V represents the molar molecular volume (cm ³ / mol).

The compatibility parameter in the laminated sheet of the present invention is a value rounded off to the second decimal place of the estimated value calculated based on the Fedor formula. As compatibility parameters of typical thermoplastic resins, 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, Polymethylmethacrylate: 9.3 and the like.

The difference in the compatibility parameters between the A layer and the B layer for the A layer and the B layer of the laminated sheet of the present invention to show interlayer adhesion even after the lamination is preferably 2.0 or less, more preferably 1. It is 0 or less. The A layer and the B layer may be made of exactly the same organic polymer material, and the lower limit is 0.0. However, when the compatibility parameter shows 0.0, the type and content concentration of the electromagnetic wave suppressing material added to the A layer and the B layer are different in order to make the complex permittivity of the A layer and the B layer different. Is preferable. The complex permittivity is a numerical value indicating the response (degree of dielectric polarization) of a molecule when an electric field is applied from the outside, is unique to a substance, and is based on the permittivity in vacuum (electric constant). It is a dimensionless quantity.

When the A layer or the B layer contains a plurality of organic polymer materials, the sum of the values of the compatibility parameters of each organic polymer material alone multiplied by the content ratio of the organic polymer materials is the phase of the layer. Use as a solubility parameter. For example, when the polyethylene terephthalate component (compatibility parameter: 10.7) and polymethyl methacrylate (compatibility parameter: 9.3) are contained in a ratio of 50:50, it corresponds to an intermediate value of both compatibility parameters. 10.0 is the compatibility parameter of the layer. When laminating layers containing different organic polymer materials as main components, add the organic polymer materials that are the main components of the other layer to one layer, and the numerical value of the compatibility parameter of both layers. It is also preferable to improve the adhesion between the two by bringing them closer to each other. The method of adding the organic polymer material which is the main component of the other layer may be a copolymerization method or a method of alloying the resin and kneading it in an extruder. Further, a method of adding a cross-linking type modifier having a basic skeleton of an organic polymer material which is a main component of the other layer can also be adopted.

As the organic polymer material in the A layer and the B layer, it is preferable to use a thermoplastic resin which is an organic polymer material exhibiting flexibility from the viewpoint of processability and film forming property of the laminated sheet. Examples of the thermoplastic resin include polyethylene, polypropylene, poly (1-butene), poly (4-methylpentene), polyisobutylene, polyisoprene, polybutadiene, polyvinylcyclohexane, polystyrene, poly (α-methylstyrene), and poly (poly (α-methylstyrene)). P-methylstyrene), polynorbornene, polyolefin-based resins such as polycyclopentene, polyamide-based resins such as nylon 6, nylon 11, nylon 12, and nylon 66, ethylene / propylene copolymers, and ethylene / vinylcyclohexane copolymers. , Ethylene / vinyl cyclohexene copolymer, ethylene / alkyl acrylate copolymer, ethylene / acrylic methacrylate copolymer, ethylene / norbornen copolymer, ethylene / vinyl acetate copolymer, propylene / butadiene copolymer, isobutylene / isoprene copolymer, vinyl chloride / vinyl acetate copolymer, etc. Vinyl monomer copolymer resins, polyacrylates, polymethacrylates, polymethylmethacrylates, polyacrylamides, acrylic resins typified by polyacrylonitrile, polyethylene terephthalates, polypropylene terephthalates, polybutylene terephthalates, polyethylene-2,6-naphthalates, etc. Represented by polyester resin represented by, polyethylene oxide, polypropylene oxide, polyether resin represented by polyacrylene glycol, diacetyl cellulose, triacetyl cellulose, propionyl cellulose, butyryl cellulose, acetyl propionyl cellulose, nitro cellulose. Cellulose ester-based resins, polylactic acid, biodegradable polymers typified by polybutyl succinate, etc. In addition, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl butyral, polyacetal, polyglucoric acid, polycarbonate, polyketone, poly Ethersulphon, polyether ether ketone, modified polyphenylene ether, polyphenylene sulfide, polyetherimide, polyimide, polysiloxane, tetrafluoroethylene resin, trifluoroethylene resin, trifluorochloride ethylene resin, tetrafluoroethylene-6 foot A propylene copolymer, polyvinylidene fluoride, or the like can be used. These thermoplastic resins may be used alone in each layer, or may be used as two or more kinds of polymer blends or polymer alloys. By performing blending and alloying, it is possible to obtain heat resistance, viscosity characteristics, adhesion at the interface between layers, etc., which cannot be obtained from one type of thermoplastic resin.

The present invention is based on a laminated sheet including an alternating laminated unit in which layers having different compositions are alternately laminated. In the laminated sheet of such an embodiment, dielectric polarization is caused at the interface between the A layer and the B layer having different compositions, and the larger the number of layers and the larger the scale of polarization, the higher the complex dielectric constant of the entire laminated sheet can be. Therefore, if a material having a low complex dielectric constant is selected as the thermoplastic resin constituting the A layer and the B layer of the laminated sheet of the present invention, it becomes easy to obtain a laminated sheet exhibiting high shielding performance over a relatively wide frequency band. As the thermoplastic resin having a low complex dielectric constant, it is preferable to select a thermoplastic resin having a dielectric constant of 3.0 or less, and in consideration of versatility, processability, and stackability, a polyolefin resin (complex dielectric constant:: 2.0 to 2.3), polyester resin (complex dielectric constant: 2.8 to 3.0), polycarbonate (complex dielectric constant: 2.9 to 3.0), polystyrene (complex dielectric constant: 2.4) It is preferable to select from thermoplastic resins such as ~ 2.6).

On the contrary, in order to achieve steep shielding performance in a narrower band, the material used as the organic polymer material preferably has a high dielectric constant, and acrylic resin (3.0 to 4.5) and nylon resin (3). .5 to 5.0), cellulose 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) It is preferable to select a rate: 4.0 to 8.0), polyphenylene sulfide (complex dielectric constant: 3.5 to 4.0), or the like.

From the viewpoint of realizing electromagnetic wave shielding performance, it is important that at least one of the A layer and the B layer contains an electromagnetic wave suppressing material in the laminated sheet of the present invention. Here, the electromagnetic wave suppressing material is a general term for a conductive material having a property of imparting conductivity in response to an electric field when irradiated with an electromagnetic wave, and a magnetic material that absorbs a magnetic flux generated by a magnetic field. Since the laminated sheet of the present invention realizes electromagnetic wave shielding characteristics by losing the energy of the incident electromagnetic wave by receiving the resistance of the electromagnetic wave by the electromagnetic wave suppressing material having conductivity or magnetism, the inside thereof It is necessary to include electromagnetic wave suppression material. The electromagnetic wave suppressing material may be contained in one of the A layer and the B layer, or may be contained in both of them. Further, as the electromagnetic wave suppressing material, only one kind may be used, or a plurality of kinds of electromagnetic wave suppressing materials may be used in combination.

As the electromagnetic wave suppressing material in the laminated sheet of the present invention, for example, an organic carbon-based carbon material can be selected as a conductive material capable of mainly losing radio waves, and an inorganic metal material can be selected mainly as a magnetic material capable of losing magnetic waves. Either one of the organic carbon-based carbon material and the inorganic metal material can be used, or both can be used in combination. Further, the same layer may contain the conductive material and the magnetic material at the same time, or the A layer or the B layer may contain the conductive material and the magnetic material separately, respectively.

The conductive material used for the laminated sheet of the present invention is preferably appropriately selected from carbon materials having a small size of primary particles 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, single-layer nanotubes, multilayer nanotubes, and cup-stacked nanotubes. Carbon nanotubes, which are cylindrical carbons, flat carbons such as graphite, graphite, and graphene, spherical graphite, cylindrical graphite, carbon microcoils, fullerene, carbon fibers (long fibers, short fibers), and the like can be used. Above all, from the viewpoint of utilizing the effect of particle arrangement in the plane direction due to the laminated / thin film structure, it is preferable to use carbon black in which a primary structure (linear structure) is easily developed. In addition to carbon black, which develops a structure in any direction, carbon nanotubes with a uniform structure and a high aspect ratio, flat carbon, etc. should be used in combination to form a stronger conductive path in the layer direction. Is also preferable. By using conductive materials with different skeletons and structures together, the ratio of the content of each conductive material is distributed, and the real part ε'and the imaginary part ε of the complex permittivity are matched to the frequency band targeted for shielding. The numerical value of'' can be adjusted in various ways.

Examples of carbon black in which the primary structure is likely to develop include carbon black having a dibutyl phthalate (DBP) oil absorption (mL / 100 g) of 150 or more. The amount of DBP oil absorbed is an index showing the degree of development of the structure of carbon black. A material having a large numerical value means that carbon black particles are easily connected to each other in a straight line, which means that there are many voids between structures, so that a conductive path is easily formed even with a small content, which is included. It is preferable because conductivity can be easily imparted to the layer. From the above viewpoint, the amount of dibutyl phthalate (DBP) oil absorbed is more preferably 200 mL / 100 g or more, still more preferably 350 mL / 100 g or more.

When the structure of carbon black develops and a conductive path is formed, the conversion of electromagnetic wave energy into thermal energy by the conductive material, which is an electromagnetic wave resistor, is more efficient when an electric field is generated by being irradiated by electromagnetic waves. It is carried out and a high electromagnetic wave suppression effect is expected. The upper limit of the DBP oil absorption amount is not particularly limited, but considering that there is a concern that the structure may be destroyed when the conductive material is dispersed in the polymer material, 800 mL / 100 g is appropriate. be. The amount of DBP oil absorbed can be measured according to ASTM D 2414 (2019). As the conductive spherical carbon, for example, commercially available ones such as acetylene black, furnace black, and ketjen black can be used.

Among carbon materials, carbon black, which is a preferable electromagnetic wave suppressing material, tends to have a low real part ε'(described later) of complex dielectric constant, which is an important parameter in the laminated sheet of the present invention. Therefore, it is preferable to use carbon nanotubes, which are cylindrical materials, and flat materials such as graphite, graphite, and graphene, as suitable carbon materials for increasing the complex permittivity real part ε'. With such an aspect, the dielectric constant is improved and the electromagnetic wave shielding performance can be obtained by dispersing the conductive material having a high aspect ratio in the thickness direction, which is known as the Maxwell-Wagner effect. .. Specifically, a thermoplastic resin exhibiting dielectric property (for example, a polyolefin-based resin, a polyester-based resin, an acrylic resin, a copolymer-based resin of a vinyl monomer, etc. exemplified above as a resin having a low complex dielectric constant) and a conductive material. A lot of micro-dielectric polarization is formed at the interface with, and cylindrical and flat materials are aligned parallel to each other in the film thickness direction as conductive materials, and these polarizations are arranged in parallel like a parallel plate condenser and face each other. By making this aspect, when an electric field is applied by irradiating an electromagnetic wave, a large amount of electric charge is likely to be accumulated at the interface between the resin which is a low dielectric and the conductive material, and the conductivity in the laminated sheet can be enhanced. ..

Due to such an effect, when an electromagnetic wave is incident, it receives resistance from a conductive material, and the electromagnetic wave energy is easily converted into heat energy, and as a result, it can be expected that the electromagnetic wave shielding performance is improved. Based on this idea, in addition to forming the layer interface between the A layer and the B layer in this laminated sheet, the conductive materials are aligned in the plane direction of the laminated sheet and formed at the interface between the resin constituting the layer and the conductive material. It is preferable that the dielectric polarization to be generated is also generated so as to be parallel to the surface direction of each layer of the laminated sheet. That is, the more the conductive material has a structure having a high aspect ratio, the more likely it is that a laminated sheet having such an aspect can be obtained by undergoing a stretching step during film formation. It is preferable to use the same material in combination.

In relation to the cylindrical material and the flat material which are the preferable materials, when the laminated sheet of the present invention contains a carbon material, the carbon material exhibits an aspect ratio of 40 or more and 5000 or less (hereinafter, carbon material X). It is preferable to include (referred to as). By including the carbon material X, the carbon material X can easily stay in the layer without breaking through the layer interface in the laminated sheet, and the carbon material X is oriented in the direction of the laminated sheet surface due to the resin flow or the stretching process in the laminating process. It will be easier. In addition, by using the carbon material X, the area ratio covered by the carbon material when confirmed from the direction perpendicular to the sheet also increases, and electromagnetic waves that enter in the direction perpendicular to the laminated sheet pass through the gaps between the particles. The effect of leakage can be reduced.

By including a carbon material having an aspect ratio of 40 or more, the above effect can be sufficiently obtained. On the other hand, by suppressing the aspect ratio of the carbon material to 5000 or less, the interaction between the thermoplastic resin and the carbon material is suppressed, and the deterioration of the formability of the laminated sheet during the stretching process and molding is reduced. Furthermore, by suppressing the aspect ratio of the carbon material to 5000 or less, it is possible to reduce the clogging of the carbon material in the foreign matter removal filter during the extrusion process, so that the carbon material concentration becomes lower than expected and the pressure is suddenly increased. It is also possible to reduce the occurrence of equipment troubles due to. From the above viewpoint, the aspect ratio of the carbon material X is more preferably 100 or more and 3000 or less.

Further, it is particularly preferable to use the carbon material X in combination with the carbon black particles for the purpose of making the connection between the carbon materials X closer and further suppressing the leakage of electromagnetic waves. The carbon black particles referred to here refer to the particles or those having a higher-order structure formed by the particles having an aspect ratio of less than 40. When the carbon material X and the carbon black particles are used in combination, for example, as shown in FIG. 5, the connection of the particles in contact with each other spreads in the plane direction of the laminated sheet, so that the conductivity can be improved and the complex dielectric constant can be improved. Note that FIG. 5 shows a schematic diagram of a layer containing carbon material X and carbon black particles, in which reference numeral 4 is a resin, reference numeral 5 is carbon material X, and reference numeral 6 is carbon black particles.

The aspect ratio of the electromagnetic wave suppression material can be measured by the following procedure. First, a cross-sectional section sample obtained by performing ion milling processing on a laminated sheet is observed with a scanning electron microscope (SEM) or a transmission electron microscope (TEM) to obtain a cross-sectional image. At the time of cross-section cutting, a method may be used in which damage to the particles is suppressed by appropriately performing a freezing treatment or a resin embedding treatment according to the flexibility of the resin constituting the laminated sheet. Further, at the time of observation, a sputtering treatment may be appropriately performed to suppress charge-up. Electromagnetic wave suppression material part after binarizing and adjusting the brightness of the obtained cross-sectional image using image analysis software such as "ImageJ" (manufactured by NIH) and "Mac-View" (manufactured by Mountech). Is extracted. After that, an elliptical approximation process is applied to each of the extracted electromagnetic wave suppression materials, and the major axis and the minor axis are measured to obtain the ratio, thereby calculating the aspect ratio. The electromagnetic wave suppression material in the laminated sheet may have anisotropy in the particle arrangement in the longitudinal direction and the width direction depending on the manufacturing process, and all the electromagnetic wave suppression materials are oriented in the longitudinal direction and the width direction. For example, when the electromagnetic wave suppressing material is inclined and oriented in the depth direction of the cross-sectional image, the aspect ratio obtained by approximating the ellipse does not match the actual situation. In consideration of the above problems, the aspect ratio is approximately elliptical with respect to the electromagnetic wave suppression materials of both images after performing the above measurements and analyzes for each cross section in the longitudinal direction and the width direction. As shown in FIG. 6, the obtained aspect ratio is represented by a curve (reference numeral 7) plotted with the vertical axis as the frequency and the horizontal axis as the logarithmic aspect ratio, and the maximum value thereof is taken as the aspect ratio of the electromagnetic wave suppression material. The carbon material whose maximum value is in the range of 40 or more and 5000 or less is the carbon material X.

In the laminated sheet of the present invention, it is preferable that the average value of the elevation angles formed by the carbon material X and the sheet surface direction is 0 ° or more and 15 ° or less. The elevation angle formed by the carbon material X and the sheet surface direction means the elevation angle formed by 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. This elevation angle can be analyzed by image analysis software. Specifically, in the cross-sectional image of the laminated sheet obtained by the above method, the direction indicated by the layer interface is set to the sheet surface direction (0 °) on the cross-sectional image. It can be defined by the smaller angle of the angle formed by the major axis of the carbon material X. That is, 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. For the average value of the elevation angle in the laminated sheet, 100 particles of the carbon material X having a high aspect ratio contained in the image are extracted in the order of showing the numerical value having the high aspect ratio, and the average value of the elevation angle of each particle is used.

The smaller the average value of the elevation angles formed by the carbon material X and the sheet surface direction, the more the carbon material X is oriented in the surface direction. By reducing the average value of the elevation angles, the carbon in the layer is concerned. The carbon materials X are more connected to each other as compared to the laminated sheet in which the material X is dispersed in all directions. Therefore, it is expected that the conductivity and the complex permittivity will be improved. Further, when the carbon material X is a flat carbon material, the area of the particles when observed from the surface of the laminated sheet becomes large, and electromagnetic waves can be absorbed more efficiently, which is preferable. From the above viewpoint, the average value of the elevation angles formed by the carbon material X and the sheet surface direction is more preferably 0 ° or more and 10 ° or less, and further preferably 0 ° or more and 5 ° or less.

As a method of keeping the average value of the elevation angle formed by the long axis of the carbon material X and the sheet surface direction within the range, for example, the number of layers of the laminated sheet is increased, the thickness of the entire laminated sheet is reduced, or the entire laminated sheet is thinned. A method of reducing the thickness of each layer with respect to the long axis of the carbon material X by increasing the number of layers without changing the thickness of the carbon material X, a method of orienting the carbon material X in the stretching direction by a stretching step, and increasing the particle concentration. Examples thereof include a method of strengthening the interaction between the conductive particles, and these can be used in combination as appropriate.

Examples of the magnetic material that can be used for the laminated sheet of the present invention include materials containing a metal component, for example, a single metal such as silver, copper, iron, cobalt, nickel, chromium, aluminum, zinc, and tin, and , These metal oxides, metal nitrides, metal carbides, metal boroides, metal oxide nitrides, metal hydroxides, metal oxide hydrides, organic metal complexes, and their compounds and mixtures can be used. can. In particular, as a preferable component, indium tin oxide (ITO) and indium zinc oxide (IZO), which are generally used as transparent conductive metal oxides in order to increase magnetic permeability, as well as stainless steel materials and organic metal complexes. Carbonyl iron, hexacyano iron, amino iron and the like can be used. As for these inorganic metal materials, it is preferable to use a spread flat material because the laminated sheet of the present invention can further enhance the electromagnetic wave shielding performance.

The electromagnetic wave suppression material of the present invention can be appropriately selected from the above-mentioned conductive material and magnetic material and used. However, when a large amount of a magnetic material composed of a metal is contained and a film is formed by melt extrusion, the film is formed. The friction between the device and the magnetic material may cause problems such as material crushing and chipping of the device. Further, the magnetic material tends to be unable to shield electromagnetic waves of a certain frequency (about 10 GHz) or less due to the Snoke limit peculiar to the material, and may not be suitable as a shielding material for applications using electromagnetic waves in a high frequency band such as 5G communication. .. From this, it is preferable to use at least one carbon material as the electromagnetic wave suppression material used in the present invention from the viewpoint of electromagnetic wave suppression in the high frequency band. Further, in order to increase the amount of reflection attenuation, in order to control the real part and the imaginary part of the complex permittivity of the layer having a relatively high complex permittivity within the range of the formula (A) described later, the imaginary number of the complex permittivity It is preferable to contain carbon black, which is a carbon material capable of increasing the numerical value of the portion. Further, in order to control within the range of the formula (B), it is possible to use a carbon material having a high aspect ratio or a material such as ferrite having a high dielectric constant as the carbon material having a low value of the imaginary part of the complex permittivity. preferable.

Further, as an electromagnetic wave suppressing material used for the laminated sheet of the present invention, a dielectric material having an excellent ability to store electric charges can be added. The dielectric material is not a material that has the effect of giving resistance to the irradiated electromagnetic wave and causing a direct loss. However, as will be described later, in order to shield the electromagnetic waves in a specific frequency band, it is preferable to control the real term ε'and the imaginary term ε'' of the complex permittivity of the laminated sheet to a specific range. Not only conductive materials whose complex permittivity real term ε'and imaginary term ε'' tend to fluctuate, but also dielectric materials which can selectively improve the complex permittivity real term ε'are added. This is preferable because the value of the complex permittivity can be controlled more highly and the tan δ described later can be reduced. The dielectric materials that can be used here include magnesium oxide, titanium oxide, barium titanate, strontium titanate, calcium titanate, lead zirconate titanate, titanium oxide, and iron oxide (ferrite) that have a perovskite structure or a rutile structure. ), Bismus ferrite, etc., but titanium oxide, ferrite, barium titanate and the like are preferable because they are versatile and exhibit a high dielectric constant.

From the viewpoint of achieving both the electromagnetic wave shielding performance and the strength of the laminated sheet itself, the laminated sheet of the present invention has an electromagnetic wave suppressing material content of 1% by mass or more and 15% by mass when all the components constituting the laminated sheet are 100% by mass. It is important that it is less than or equal to%. When the content of the electromagnetic wave suppressing material exceeds 15% by mass, high electromagnetic wave shielding performance can be easily obtained, but problems such as deterioration of laminated film forming property and weakening of the sheet due to thixotropy occur. In addition, due to surface reflection, electromagnetic waves may not reach the inside of the sheet, and the desired effect of dielectric polarization may not be obtained. On the other hand, if the content of the electromagnetic wave suppressing material is less than 1% by mass, the electromagnetic wave shielding performance cannot be sufficiently obtained. From the above viewpoint, the content of the electromagnetic wave suppressing material is more preferably 3% by mass or more and 9% by mass or less.

When the laminated sheet contains a plurality of types of electromagnetic wave suppressing materials, the content of the electromagnetic wave suppressing material shall be calculated by adding up all the electromagnetic wave suppressing materials. Further, in the laminated sheet of the present invention, if the content of the electromagnetic wave suppressing material is 1% by mass or more and 15% by mass or less when all the components constituting the laminated sheet are 100% by mass, each layer (A layer). , B layer), the content of the electromagnetic wave suppressing material can be arbitrary.

In addition to the electromagnetic wave suppressing material, the laminated sheet of the present invention contains, if necessary, a dispersant, a surface modifier, a lubricant, a cross-linking agent, a vulcanization accelerator, an antioxidant, a crystal nucleating agent, a flame retardant, and the like. A flow modifier (plasticizer, thickener), an anti-blocking agent, and the like may be contained within a range in which the original characteristics of the laminated sheet are not impaired. As long as the original characteristics of the laminated sheet are not impaired, these components may be contained in any of the layers other than the A layer, the B layer, the A layer and the B layer.

The laminated sheet of the present invention has a real part ε'(F / m) of the complex permittivity of the entire laminated sheet and a real part μ'(H /) of the complex magnetic permeability from the viewpoint of realizing high electromagnetic wave shielding performance while suppressing the thickness. It is important that the product of m) is 4.0 F · H / m ² or more and 50 F · H / m ² or less. The impedance Z _in, which is an important parameter for determining the electromagnetic wave shielding performance and the frequency band that can be shielded, and the reflection attenuation amount Γ calculated by the impedance are expressed in the equations (2) and (3), respectively. As shown, it depends on the complex dielectric constant, complex magnetic permeability and thickness of the entire sheet. Therefore, in order to achieve high electromagnetic wave shielding performance with a thin film, it is necessary to show a value in which the product of the real part ε'of the complex permittivity and the real part μ'of the complex magnetic permeability is high. In equations (2) and (3), Z ₀ indicates the characteristic impedance in the atmosphere, d indicates the thickness, λ indicates the wavelength, μ indicates the magnetic permeability, and ε indicates the dielectric constant, and the value of Z ₀ is 377Ω. be.

The fact that the product of the real part ε'of the complex permittivity and the real part μ'of the complex magnetic permeability is lower than 4.0 F · H / m ² means that the electromagnetic wave suppression material is sufficient to receive sufficient resistance when an electromagnetic wave is incident. It means that it is not contained. In order to improve the electromagnetic wave shielding performance, the higher the product of the real part ε'of the complex permittivity and the real part μ'of the complex magnetic permeability, the thinner the sheet itself can be made, which is preferable. If it becomes excessive, the molten viscosity increases due to thixotropy, which causes stacking disorder, and the laminated sheet becomes brittle, which may cause a problem that it cannot be handled. Therefore, in reality, the product of the real part ε'of the complex permittivity of the laminated sheet and the real part μ'of the complex magnetic permeability is 50 F · H / m ² or less. In terms of thinning, electromagnetic shielding performance, and handleability, 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 or more and 25 F · H / m. It is ² or less, more preferably 6.0 F · H / m ² or more and 25 F · H / m ² or less. In order to improve the dielectric constant of the entire sheet, it is effective to include an electromagnetic wave suppressing material having a high dielectric constant, or to increase the number of layers to reduce the layer thickness per layer. Further, when an electromagnetic wave suppressing material having a high aspect ratio is used, it is also an effective means to orient the electromagnetic wave suppressing material in the plane direction of the sheet through a stretching step.

The real part ε'of the complex permittivity of the laminated sheet of the present invention, the imaginary part ε'' described later, and the real part μ'of the complex magnetic permeability are measured by the method described in the section of "Measurement of complex permittivity" in the examples. can do. The real and imaginary parts (ε _h ', ε _h '', ε _A ', ε _B ') of the complex permittivity of each layer are described in "Calculation of the complex permittivity of each layer" in the above method and Examples. It can be measured by the method of.

As a method of setting the product of the real part ε'of the complex permittivity and the real part μ'of the complex magnetic permeability to 4.0 F · H / m ² or more and 50 F · H / m ² or less or the above-mentioned preferable range, for example, A. A method of adding a conductive material to only one layer in order to increase the difference in dielectric constant between the layer and the B layer, and increasing the number of layers to reduce the thickness of each layer to reduce the density of the electromagnetic wave suppression material. There are ways to raise it. In addition, carbon black, which indicates the range of DBP oil absorption to be described later, is used as the electromagnetic wave suppression material, and a dielectric material such as barium titanate, ferrite, or titanium oxide is used as the material having a high dielectric constant, and electromagnetic wave suppression having a high aspect ratio is used. It is possible to improve the dielectric constant by using materials such as graphite and graphene. Further, in order to increase the dielectric constant with respect to the thin-film laminated sheet, the electromagnetic wave suppressing material is applied in the surface direction of the sheet while reducing the layer thickness per layer through the stretching step described later. A method of orienting to can be used.

In the laminated sheet of the present invention, when the imaginary part of the complex permittivity of the entire laminated sheet is the imaginary part ε'', the dielectric loss tangent tan δ (= ε'' / ε') of the entire laminated sheet is 0.10 or more and 0. It is preferably .50 or less. Tan δ, which shows the relationship between the real and imaginary parts of the complex permittivity, is an important parameter related to the shielding characteristics of electromagnetic waves that have entered the laminated sheet. More specifically, the fact that tan δ is 0.50 or less means that the numerical value of the real part indicating the ease of passing electricity into the laminated sheet is sufficient. That is, setting tan δ to 0.50 or less is advantageous when shielding low-frequency electromagnetic waves, which are high-energy electromagnetic waves. Further, when tan δ is 0.10 or more, it means that the numerical value of the imaginary part indicating the effect of absorption / loss is generally high. That is, by setting tan δ to 0.10 or more, the effect of electromagnetic wave shielding by dielectric absorption can be sufficiently obtained. In particular, it is more preferable that tan δ is 0.20 or more and 0.40 or less in order to aim at electromagnetic wave shielding having a relatively low frequency band such as quasi-millimeter waves. Here, the quasi-millimeter wave means an electromagnetic wave having a frequency of 3 GHz or more and 30 GHz or less, and the millimeter wave means an electromagnetic wave having a frequency exceeding 30 GHz and 300 GHz.

Further, for the electromagnetic wave shielding performance and frequency band of the laminated sheet of the present invention, it is important to design the thickness of the entire laminated sheet, the complex dielectric constant, and the complex magnetic permeability. The difference between the complex permittivity of the B layer and the B layer also has an effect. Specifically, the real part ε _{h'and the imaginary part ε h '} ' of the complex permittivity of the layer showing a relatively high complex permittivity and the difference between the complex permittivity of the A layer and the B layer is sufficiently large. Control is extremely effective in adjusting the electromagnetic wave shielding performance. The region showing high electromagnetic wave shielding performance for a specific frequency band with a specific sheet thickness can be calculated based on the equation (2). Further, in order for the laminated sheet to exhibit high electromagnetic wave shielding performance, the real part ε _h '(F / m) and the imaginary part of the complex permittivity of the layer having a relatively high complex permittivity among the A layer and the B layer. It is preferable that ε _h '''' (F / m) satisfies the relational expression of (A) or (B).
(A) ε _h '' ≧ 1 and 0.15 ε _h '+ 2 ≦ ε _h '' ≦ 0.23 ε _h '+7.7
(B) 5 ≧ ε _h '' ≧ 1 and 0.01 ε _h '+1 ≦ ε _h '' ≦ 0.09 ε _h '+2
By controlling the real part ε _{h'and the imaginary part ε h '} ' of the complex permittivity of the layer with a relatively high complex permittivity within this range, high electromagnetic wave shielding performance at a specific frequency even when the sheet thickness is thin. Can be realized.

The method of controlling the real part ε _{h'and the imaginary part ε h '} ' of the complex permittivity of the layer having a relatively high complex permittivity so as to satisfy the relational expression of the above (A) or the above (B) is For example, carbon black having a DBP oil absorption amount in the range described later is used as an electromagnetic wave suppressing material, barium titanate, carbonyl iron, and ferrite oxide are used as a material having a high dielectric constant, and graphite is an electromagnetic wave suppressing material having a high aspect ratio. It is possible to improve the dielectric constant by using graphene or the like. In particular, in order to satisfy the equation (A), it is required to increase both the real part ε _{h'and the imaginary part ε h '} ' of the complex permittivity, so it is preferable to use carbon black, and it is preferable to use carbon black. In order to satisfy the equation, the imaginary part ε _h '' of the complex permittivity is required to be low, so that the dielectric materials such as barium titanate, ferrite and titanium oxide, and the aspect ratio such as graphite and graphene This can be achieved by using at least one type of highly conductive material, alone or in combination. Further, it can be achieved by increasing the number of layers or by using the stretching method described later to reduce the layer thickness per layer and to orient the electromagnetic wave suppressing material in the plane direction of the sheet. In addition, these methods may be combined appropriately.

The _{laminated sheet} of the present _{invention |} | Is preferably 1 or more and 100 or less, and more preferably 5 or more and 50 or less. In the laminated sheet of the present invention, as described above, it is important to generate dielectric polarization by utilizing the difference in complex dielectric constant between the A layer and the B layer. When | ε _A' -ε _B '| is 1 or more, dielectric polarization between layers is generated, and the effect of dielectric polarization can be sufficiently obtained. On the other hand, when | ε _A' -ε _B '| is 100 or less, stable film formation can be achieved without extremely increasing the particle concentration, and the GHz frequency band can be specified even for a thin film. It is possible to obtain an electromagnetic wave shielding effect of dielectric absorption having a peak top in the frequency band of. The size of the real part of the complex permittivity of each layer varies depending on the content of the electromagnetic wave suppressing material and the layer thickness of the layer containing the electromagnetic wave suppressing material. More specifically, the larger the content of the electromagnetic wave suppressing material and the smaller the layer thickness of the layer containing the electromagnetic wave suppressing material, the larger the real part of the complex permittivity in the layer.

Further, in the laminated sheet of the present invention, it is preferable that ε _{A'and ε B'satisfy 2.0 ≤ ε A'/ ε B'≤ 25 or 2.0 ≤ ε B ' / ε A'≤ 25} . .. If ε _A '/ ε B'or ε _B '/ ε _A'exceeds 25, the difference in permittivity between the _A layer and the B layer is too large (the content of the electromagnetic wave suppression material between the two layers is significantly different). Means. In such a state, the stacking disorder is likely to occur and it becomes difficult to form the laminated sheet. That is, when ε _A '/ ε _B'or ε _B '/ ε _A'is 25 or less, the film forming property is stable. On the other hand, when ε _A '/ ε _B'or ε _B '/ ε _A'is 2.0 or more, the complex permittivity difference between the A layer and the B layer is at a level sufficient to realize the electromagnetic wave shielding characteristics. Become. As a means for satisfying 2.0 ≤ ε _A '/ ε _B'≤ 25 or 2.0 ≤ ε _B '/ ε _A'≤ 25, a method of adjusting the amount of the electromagnetic wave suppressing material in each layer can be mentioned. More specifically, for example, when the layer having a higher dielectric constant is the A layer, by reducing the electromagnetic wave suppressing material of the A layer, increasing the electromagnetic wave suppressing material of the B layer, and using these in combination, ε _A '/ ε _B'can be made smaller. From the above viewpoint, it is more preferable that ε _{A'and ε B'satisfy 3.0 ≤ ε A'/ ε B'≤ 20 or 3.0 ≤ ε B ' / ε A'≤ 20} .

From the viewpoint of film forming stability, the laminated sheet of the present invention preferably has a total thickness of 0.1 mm or more and 1.5 mm or less. When the total thickness is 1.5 mm or less, the stiffness is not excessive and the laminated sheet has sufficient molding processability. Therefore, even when the film is continuously formed as a sheet, the torque at the time of rolling the roll is suppressed, so that the film formation is stable and the increase in the manufacturing cost can be suppressed. On the other hand, when the total thickness is 0.1 mm or more, the sheet tearing during stretching due to the electromagnetic wave suppressing material can be suppressed. From the above viewpoint, the total thickness of the laminated sheet is more preferably 0.2 mm or more and 1.0 mm or less, still more preferably 0.3 mm or more and 0.75 mm or less. The total thickness of the laminated sheet can be measured by taking a cross-sectional photograph of the laminated sheet perpendicular to the sheet surface with a microscope and measuring the length thereof.

There are various methods for adjusting the total thickness of the laminated sheet, such as the total discharge amount from the extruder, the lip width of the die for forming the sheet, and the transport speed of the film forming apparatus. Above all, by uniformly inserting the film-forming apparatus at double speed, the total thickness of the laminated sheet can be adjusted most easily and without affecting the lamination disorder. Further, in order to realize the in-plane orientation of the electromagnetic wave suppressing material and to make the thin film while increasing the dielectric constant of the layer having a high dielectric constant, in addition to adjusting the transport speed of the film forming apparatus, the laminated sheet is stretched as described later. This can be achieved by stretching in the longitudinal direction and the width direction.

The electromagnetic wave suppressing material contained in the laminated sheet of the present invention has a higher-order structure formed by the component contained most in the laminated sheet among the electromagnetic wave suppressing materials from the viewpoint of reducing the amount of the electromagnetic wave suppressing material and reducing the stacking disorder. When the major axis is X (nm) and the average layer thickness of the layers A and B containing a large amount of the component is Y (nm), the X / Y is 0.01 or more and 10.0 or less. Is more preferable, 0.01 or more and 5.0 or less is more preferable, and 0.05 or more and 5.0 or less is further preferable. Here, the higher-order structure of the electromagnetic wave suppressing material means an aggregate formed by connecting the electromagnetic wave suppressing materials. Further, the said component means a component contained most in the sheet among the electromagnetic wave suppressing materials. Note that X and Y can be measured by measuring the length of an image taken by a differential interference microscope, and for the length measurement, for example, particle size analysis software "Macview" (manufactured by Mountech) can be used.

A high X / Y means that the electromagnetic wave suppressing materials are likely to be arranged in parallel to the plane direction of the sheet inside the layer. When the X / Y is high, a region sandwiched between the dielectric component such as resin and the electromagnetic wave suppressing material is likely to be formed, and when an electromagnetic wave is incident, the interface between the electromagnetic wave suppressing material and the dielectric component such as resin is microscopic. Dielectric polarization occurs. Therefore, the complex permittivity of the entire laminated sheet is likely to be improved. However, if the X / Y becomes excessively high, the filter may be clogged with the electromagnetic wave suppressing material in the film forming process, or the electromagnetic wave suppressing material may not follow the flow of the lamination and break through the layer interface, resulting in stacking disorder.

More specifically, when the X / Y is 0.01 or more, it becomes easy to obtain a sufficient electromagnetic wave shielding effect while suppressing the electromagnetic wave suppressing material, and the stacking disorder and the defect of the film-forming sheet are alleviated. On the other hand, when the X / Y is 10.0 or less, it is possible to reduce clogging of the filter or the like due to the electromagnetic wave suppressing material and stacking disorder caused by the electromagnetic wave suppressing material not following the flow of the stacking. From the above viewpoint, X / Y is preferably 0.1 or more and 10.0 or less.

For X / Y, the X is increased by making the electromagnetic wave suppressing material a material that can be easily connected in a flat or linear manner, or the number of sheets laminated and the stacking ratio of the layer containing the electromagnetic wave suppressing material are reduced. It can be increased by reducing the layer thickness per layer.

Further, the electrical properties of each of the A layer and the B layer constituting the laminated sheet of the present invention can also be expressed by using the surface resistivity value in the layer direction (planar direction of the sheet) of each layer. The surface resistivity value conforms to the JIS standard and can be measured using a high resistivity meter (JIS K6911 (1995)) and a low resistivity meter (JIS K7194 (1994)) manufactured by Mitsubishi Chemical Corporation. .. In the laminated sheet of the present invention, of the surface specific resistance value of the A layer and the surface specific resistance value of the B layer, the larger value is α (Ω / □) and the smaller value is β (Ω / □). ), Α is 1.0 × 10 ⁵ Ω / □ or more and 1.0 × 10 ¹⁶ Ω / □ or less, and β is 1.0 Ω / □ or more and less than 1.0 × 10 ⁵ Ω / □. Is preferable. More preferably, α is 1.0 × 10 ¹¹ Ω / □ or more and 1.0 × 10 ¹⁶ Ω / □ or less, and β is 1.0 Ω / □ or more and 5.0 × 10 ³ Ω / □ or less. That is. More preferably, α is 1.0 × 10 ¹³ Ω / □ or more and 1.0 × 10 ¹⁶ Ω / □ or less, and β is 1.0 Ω / □ or more and 2.0 × 10 ³ Ω / □ or less. That is. Since the surface resistivity value indicating that there is conductivity is generally 1.0 × ¹⁰⁵ or less, in order to increase the conductivity in the high dielectric layer of the laminated sheet, and also to increase the dielectric at each resin interface. In order to sufficiently develop the polarization, it is preferable to satisfy the above relational expression from the viewpoint of the electromagnetic wave shielding performance of the laminated sheet. The fact that both α and β are in the above range means that the electrical properties of the A layer and the B layer are different from each other. Electromagnetic wave shielding performance is improved. The surface resistivity value can be measured by the method described in the section "Measurement of surface resistivity value" in Examples.

The method of making the complex permittivity and the surface resistivity value of the A layer and the B layer different is not particularly limited. For example, organic polymer materials having different complex dielectric constants may be used as the resin used for the A layer and the B layer, and the types of the organic polymer materials used for the A layer and the B layer are the same, and the A layer and the B layer are used. The type and / or content of the electromagnetic wave suppressing material contained in the layer A and / or the content may be different between the layer A and the layer B. In particular, in order to adjust the frequency band showing the reflection attenuation peak, a configuration in which the complex dielectric constant and surface resistivity value of the A layer and the B layer can be finely adjusted is preferable, and the complex dielectric constant of the A layer and the B layer is preferable. Most preferably, the resistivity is different, and at least one kind of electromagnetic wave suppressing material is contained, and the difference in surface resistivity between the A layer and the B layer is different.

The layer having a surface specific resistance value of α suppresses the surface reflection of electromagnetic waves and allows the electromagnetic waves to pass through the laminated sheet to fully exert the electromagnetic wave shielding effect due to the dielectric polarization. It is preferably located in a layer. This layer may be placed on at least one side, but it is located on the outermost surface of both sides when blocking unnecessary electromagnetic waves from both the outside and the inside for the item to be mounted. Is more preferable.

Further, the α / β is not particularly limited, but if α / β is 1.1 or more, the electrical characteristics are different to the extent that the electromagnetic wave shielding performance can be realized when the laminated sheet is used. 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 102 or ^more , more preferably ¹⁰⁵ or more, and further preferably ¹⁰⁹ or more. ..

It is important that the laminated sheet of the present invention generates dielectric polarization using the difference in complex dielectric constant between the A layer and the B layer. Therefore, even when the electromagnetic wave suppressing material is contained in both the A layer and the B layer, in order to cause a dielectric constant difference between the two layers, the content of the electromagnetic wave suppressing material in the A layer w _A and the B layer. It is preferable that the content w _B of the electromagnetic wave suppressing material is different. More specifically, when the content of the electromagnetic wave suppressing material in the A layer is w _A (mass%) and the content of the electromagnetic wave suppressing material in the B layer is w _B (mass%), w _B > It is preferable to satisfy w _A. With such an embodiment, even if the components of the A layer and the B layer are the same, a difference in dielectric constant between the two layers can be generated.

Which of the A layer and the B layer has a higher content can be appropriately selected, but the effect of the surface reflection of the electromagnetic wave is weakened and the electromagnetic wave penetrates into the laminated sheet, and the incident electromagnetic wave is the resistance of the electromagnetic wave suppressing material inside the sheet. In order to realize the mode of losing heat energy in response to the above, it is preferable that the layer A is located on the outermost surfaces on both sides and the relational expression of w _A <w _B is satisfied.

In the laminated sheet of the present invention, in the reflection attenuation spectrum plotted with the vertical axis as the reflection attenuation amount and the horizontal axis as the frequency, the peak top of the reflection attenuation amount peak having the largest reflection attenuation amount is the frequency band of 1 to 100 GHz. It is preferable to be present in. The amount of reflection attenuation is the amount of electromagnetic wave loss when reciprocating in the laminated sheet when measuring the intensity of the electromagnetic wave reflected and returned by the laminated sheet with respect to the electromagnetic wave of a specific frequency incident on the laminated sheet. It is a expressed value and is expressed in units of decibels (dB). The reflection attenuation amount can be measured and the peak top can be specified by the method described in "Reflection attenuation amount measurement".

The amount of reflection attenuation uses the coaxial waveguide method or the free space method, and a metal such as aluminum is vapor-deposited on the back surface, or electromagnetic waves are applied to the laminated sheet combined with the existing reflection plate from the side without the reflection layer. , It is possible to measure and calculate the intensity of electromagnetic waves that reflect the metal plate and reciprocate in the laminated sheet. In the measurement, the frequency is swept to measure the reflection attenuation, and multiple peaks may be obtained in the reflection attenuation spectrum plotted with the vertical axis as the reflection attenuation and the horizontal axis as the frequency. Among them, the reflection attenuation is the most. Focus on peaks with large volumes. The peak top here refers to a position where the sign (slope) is inverted from positive to negative or negative to positive when considering the slope of the tangent line of the reflection attenuation spectrum.

Subsequently, the reflection attenuation amount of the reflection attenuation amount peak will be described with reference to the drawings with specific examples. FIGS. 1 to 4 show half-value width and electromagnetic wave attenuation of the reflection attenuation peak having the largest reflection attenuation at the peak top among the peaks obtained by measuring the reflection attenuation peak of the laminated sheet according to the embodiment of the present invention. A schematic diagram showing the amount is shown. In addition, in FIGS. The half price width R of the reflection attenuation peak is shown.

When a single peak top is provided as in the embodiments of FIGS. 1 and 2, the difference in the amount of reflection attenuation between the peak top and the baseline at the frequency located at the peak top is set as a reference with respect to the baseline of the peak. The amount of reflection attenuation at the top. Further, even if the peak has a high reflection attenuation of the baseline as in the embodiment of FIG. 3, if it has a specific peak top, the numerical difference between the baseline of the peak top and the dB of the peak top is read. Therefore, the amount of reflection attenuation at the peak top can be determined. On the other hand, when a spectrum as shown in FIG. 4 having a plurality of peak tops including a shoulder peak is obtained, it corresponds to the peak top with respect to the frequency of the peak top of the highest peak among the plurality of peak tops. The reflection attenuation at the peak top can be determined by the difference between the reflection attenuation and the reflection attenuation at the baseline of the entire peak including the plurality of peak tops.

Generally, a sheet containing a magnetic material is used to shield the near field corresponding to a frequency band of less than several GHz, but when aiming at a high frequency band in the GHz band, it is called the Snoke limit peculiar to the magnetic material. Since the magnetic loss in a certain frequency band is sharply reduced, a method of containing a high concentration of a magnetic material to increase the amount of attenuation is generally used. At this time, when a laminated sheet is produced by melt extrusion, the viscosity increases due to the high concentration of the filler, which deteriorates the lamination accuracy, and the contained magnetic material may cause a defect in the metal part of the extruder. Further, since the high concentration is added, the reflection loss due to the magnetic material can be obtained, but the electromagnetic wave does not pass through the inside of the sheet, and it becomes difficult to obtain the effect due to the original dielectric polarization of the laminated sheet of the present invention. Therefore, in the laminated sheet of the present invention, when the laminated sheet is produced by the melt extrusion step with a low content of the electromagnetic wave suppressing material, in order to easily obtain the electromagnetic wave shielding performance by dielectric polarization, a conductive material or a conductive material is used. It is preferable to obtain electromagnetic wave shielding performance in a high frequency band by using a composite system of a dielectric material, and it is preferable that there is a reflection attenuation peak having the largest reflection attenuation at the peak top at 1 to 100 GHz.

In the laminated sheet of the present invention, in the reflection attenuation spectrum plotted with the vertical axis as the reflection attenuation amount and the horizontal axis as the frequency, the reflection attenuation amount at the peak top of the reflection attenuation amount peak having the largest reflection attenuation amount at the peak top is RL ( When dB), the frequency indicating the reflection attenuation amount is f (GHz), and the thickness of the laminated sheet is t (mm), RL / (t × f) is preferably 0.40 or more and 5.00 or less. .. The laminated sheet of the present invention has a higher dielectric constant than the conventional single film or a sheet having a low number of laminated layers by alternately laminating layers having a low dielectric constant and layers having a high dielectric constant, as compared with the prior art. By increasing the amount, it is possible to increase the amount of electromagnetic wave attenuation, or to reduce the thickness of the sheet to impart flexibility and moldability, or both.

This feature is applied to sheets targeting any frequency band, but since the thickness and frequency magnitude show a trade-off relationship, in a laminated sheet configuration showing the same dielectric constant, When shifting the frequency band to the high frequency side, the theoretical thickness tends to be thin. For this reason, the effect of the thin film exceeding the volume rule of the laminated sheet of the present invention cannot be expressed only by the relationship between the reflection attenuation amount RL and the thickness t (for example, RL / t), and the frequency f and the laminated sheet thickness cannot be expressed. The relationship between t and the reflection attenuation amount RL of the reflection attenuation peak is important. From the above viewpoint, RL / (t × f) is more preferably 0.60 or more and 3.50 or less, and further preferably 0.80 or more and 3.00 or less. The fact that RL / (t × f) is 0.40 or more means that electromagnetic wave shielding performance exceeding the volume rule, which is sufficient for use in electromagnetic wave shielding applications, can be obtained. The fact that RL / (t × f) is 5.00 or less means that a certain thickness is secured, the amount of electromagnetic wave suppressing material is suppressed to an appropriate amount, and the melt viscosity balance of the resin constituting each layer is appropriate. It means that there is. Therefore, when RL / (t × f) is 5.00 or less, the stacking disorder is suppressed, and the deterioration of the stacking accuracy and the film forming property of the laminated sheet is reduced.

In order to keep RL / (t × f) in the above-mentioned preferable range, the number of laminated sheets is increased to enhance the dielectric polarization effect, and the carbon material X having a high aspect ratio is used to increase the dielectric constant. Further, the carbon material X and carbon black are used in combination, and the electromagnetic wave is used so that the real part εh ′ and the imaginary part εh ′ ′ of the permittivity of the layer having a relatively high complex permittivity satisfy the above-mentioned preferable permittivity relationship. It is effective to adjust the restraining material and the laminated structure, and these can be combined as appropriate. The preferable conditions for each element are as described above.

Since the laminated sheet of the present invention is a laminated sheet having excellent frequency selectivity and flexibility of electromagnetic waves to be shielded and having a small thickness, it has a complicated shape that requires electromagnetic wave suppression applications, for example, molding followability. It can be suitably used as an electromagnetic wave shielding material for devices and members.

Hereinafter, the electromagnetic wave suppressor of the present invention will be specifically described. The electromagnetic wave suppressor of the present invention is characterized by having the laminated sheet of the present invention and a reflector. By combining the reflector on the side opposite to the electromagnetic wave incident surface of the laminated sheet, the electromagnetic wave is reciprocated in the laminated sheet, so that the electromagnetic wave absorption efficiency can be further improved. On the other hand, when the reflector is arranged on the front surface, it is possible to reflect a certain amount of electromagnetic waves on the surface of the reflector and steeply shield a part of the transmitted electromagnetic waves in the laminated sheet. In order to fully utilize the electromagnetic wave shielding property due to the dielectric polarization of the laminated sheet of the present invention, the former configuration is more preferable.

The constituent material, shape, and thickness of the reflector are not particularly limited as long as they can reflect electromagnetic waves. Examples of the constituent material include metals such as aluminum, copper, iron and gold, alloys such as stainless steel, and carbon films. The shape is preferably matched to the material to be applied, and can be, for example, a plate shape such as a flat surface, a curved surface, or a hemisphere. Further, as a method of laminating the reflector with the laminated sheet of the present invention, for example, a method of laminating a ready-made reflector with an adhesive or the like, or a method of directly laminating the reflector on the surface of the laminated sheet by metal vapor deposition can be used.

Examples of reflectors include laminated type reflectors and polymer films in which a film made of metal, alloy, or carbon is formed on the surface of a plate reflector containing metal, alloy, or carbon, a polymer film, a sheet, or a plate. , Composite type reflectors in which metals, alloys and carbon are dispersed inside sheets and plates, and composite type reflectors containing a reticulated body made of metal and alloy inside polymer films, sheets and plates. Be done. Further, in the present invention, when the support, the housing, etc. in each application contain metal, alloy, carbon, etc., they can be used as they are as a reflector.

As a preferred embodiment of the present invention, electromagnetic wave prevention used in 4G / 5G communication, wireless LAN, collision prevention (ITS) radar, etc., computer, mobile phone, radio, measuring device, medical device, vehicle bumper, etc. The above-mentioned laminated sheet or the above-mentioned electromagnetic wave is used for the purpose of reducing unnecessary electromagnetic wave radiation from electronic devices, semiconductors, and circuits inside the housing, and preventing device malfunction due to radiation from outside or adjacent devices. Examples thereof include electronic devices and communication devices having a shield. In addition, any electronic device or communication device that uses a frequency in the GHz band is not limited to the above, and the laminated sheet of the present invention can be mounted and used.

Further, as a preferred embodiment of the present invention, the above-mentioned laminated sheet, a means of transportation such as a vehicle, an aircraft, or a ship having the above-mentioned electromagnetic wave shield, a wall surface of a structure such as a building, a tunnel, a guardrail, a highway, a bridge, or a steel tower. , Telegraph, communication facilities such as telephone, and other transportation facilities can also be mentioned. As a method of applying the laminated sheet of the present invention, it is attached to a structure such as a floor, a ceiling, a wall, a window, a pillar, etc. directly via an adhesive or the like, or via another sheet, a shielding plate, a panel, or the like. Etc. can be used. In addition, it can also be used as a wall material or window material for a shielded room to prevent the influence of electromagnetic wave jamming noise from the outside.

Next, a preferable method for producing the laminated sheet of the present invention will be described below by way of example, but the present invention is not construed as being limited to such examples.

First, a laminated sheet in the case of using rubber, a thermoplastic elastomer, or the like as a base polymer of a base material will be described as an example. First, a predetermined amount of the electromagnetic wave suppression material is mixed with the base polymer, and the mixture is kneaded and contained in a known device such as a kneader, a Banbury mixer, a mill mixer, a roll mill, a jet mill, or a ball mill to contain the electromagnetic wave suppression material-containing base polymer mixture. To get. The base polymer alone or the prepared base polymer containing an electromagnetic wave suppressing material is formed into a sheet having a desired thickness by rolling or melt extrusion by batch pressing, respectively. Then, the prepared sheet corresponding to the layer A and the sheet corresponding to the layer B (the compositions of both are different from each other) are alternately laminated in a total of 5 or more layers, and pressed or laminated to obtain a laminated sheet. The fusion temperature at this time is preferably 150 ° C. to 400 ° C., more preferably 250 to 380 ° C., although it depends on the type of resin used.

Next, a method for producing a laminated sheet when a thermoplastic resin exhibiting flexibility, which is a preferable resin in the present invention, is used will be described as an example. First, the thermoplastic resin prepared in the form of pellets and a predetermined amount of electromagnetic wave suppression material are kneaded with a twin-screw extruder and extruded into a gut shape, which is cooled in a water tank and cut with a chip cutter. Form master pellets containing electromagnetic wave suppression material. At this time, the electromagnetic wave suppressing material may be dry-blended together with the resin and then weighed and fed from the hopper, or may be side-fed into the molten resin from an arbitrary position of the extruder using a side feeder. The feeding method is not limited to the above, and can be appropriately selected according to the specific gravity and shape of the electromagnetic wave suppressing material to be used.

The respective thermoplastic resins or thermoplastic resin compositions constituting the A layer and the B layer have different compositions from each other. After drying these thermoplastic resins or thermoplastic resin compositions in hot air or under vacuum, they are supplied to separate extruders and heated and melted in the extruder to a temperature equal to or higher than the melting point of the thermoplastic resin. After that, the extrusion amount is made uniform by a gear pump or the like, the thermoplastic resin or the thermoplastic resin composition is discharged, and the foreign matter and the modified resin are removed by a filter or the like.

Subsequently, these thermoplastic resins or thermoplastic resin compositions are laminated by a multi-layer laminating device capable of laminating to a desired number of laminations, molded into a desired shape with a die, and discharged into a sheet shape. The sheet-like material discharged from the die is extruded onto a cooling body such as a casting drum and cooled and solidified to become a cast sheet. At this time, since the cast sheet itself exhibits conductivity, air is blown out from a slit-shaped, spot-shaped, or planar device to be brought into close contact with a cooling body such as a casting drum to be rapidly cooled and solidified. It is preferable to use a method of bringing them into close contact with each other for quenching and solidification.

As the multi-layer stacking device, a multi-manifold die, a feed block, a static mixer, or the like can be used, but in particular, in order to efficiently obtain the multi-layer laminated body of the present invention, it is preferable to use a feed block having fine slits. .. When such a feed block is used, the device does not become extremely large, so that the amount of foreign matter generated due to thermal deterioration is small, and high-precision stacking is possible even when the number of stacks is extremely large. In addition, the stacking accuracy in the width direction is significantly improved as compared with the conventional technique. Furthermore, since the thickness of each layer can be adjusted by the shape of the slit (length, width) in this device, it is easy to achieve an arbitrary layer thickness, and particles are laminated by the effect of the resin flow during the laminating process. There is also an advantage that it is easy to orient the particles in the direction of the sheet surface.

When a laminated sheet is produced using a slit type feed block, the thickness and distribution of each layer can be adjusted by changing the length and width of the slit to adjust the pressure balance. The length of the slit is the length of the comb tooth portion that forms a flow path for alternately flowing the A layer and the B layer in the slit plate. Further, a method of forming a laminate with a feed block and then stacking the laminates via a static mixer so as to double the number of laminates can also be preferably used. In this case, since the layer thickness of each of the laminated bodies is exactly the same, it is suitable for the idea of the present invention that it is preferable to make the laminated thickness uniform.

The obtained cast sheet can be biaxially stretched in the longitudinal direction and the width direction, if necessary. When biaxial stretching is performed, biaxial stretching may be performed sequentially or biaxial stretching may be performed at the same time. Further, if necessary, re-stretching may be performed in the longitudinal direction and / or the width direction.

First, sequential biaxial stretching, which first stretches in the longitudinal direction and then stretches in the width direction, will be described. Here, the stretching in the longitudinal direction refers to uniaxial stretching for giving the sheet a molecular orientation in the longitudinal direction, and is usually performed by the difference in peripheral speed of the rolls. This stretching may be performed in one step or in multiple steps using a plurality of roll pairs. The draw ratio varies depending on the type of resin, but is usually preferably 1.1 to 7.0 times, and particularly preferably 1.5 to 4.0 times. Further, the stretching temperature is preferably set within the range of the glass transition temperature of the resin constituting the sheet to the glass transition temperature + 100 ° C. The uniaxially stretched laminated sheet thus obtained is subjected to surface treatment such as corona treatment, frame treatment, plasma treatment, etc. as necessary, and then a primer layer for improving the adhesion with the film laminated on the upper part. Can also be formed. In the step of in-line coating, the primer layer may be applied to one side, or may be applied to both sides simultaneously or one side at a time.

Stretching in the width direction means stretching to give orientation in the width direction to the sheet, and is usually carried out by using a tenter while gripping both ends of the sheet with clips. The stretching ratio varies depending on the type of resin, but is usually preferably 1.1 to 7.0 times, and particularly preferably 1.5 to 5.0 times. The stretching temperature is preferably from the glass transition temperature of the resin constituting the sheet to the glass transition temperature + 120 ° C. The laminated sheet thus biaxially stretched is heat-treated in a tenter at a stretching temperature or higher and a melting point or lower, slowly cooled uniformly, cooled to room temperature, and wound up. Further, if necessary, a relaxation treatment or the like may be used in combination in the longitudinal direction and / or the width direction when slowly cooling from the heat treatment in order to impart a low orientation angle and thermal dimensional stability of the sheet.

Subsequently, the case of simultaneous biaxial stretching will be described. In the case of simultaneous biaxial stretching, the obtained cast sheet is subjected to surface treatment such as corona treatment, frame treatment, plasma treatment, etc. as necessary, and then slipperiness, adhesiveness, antistatic property, etc. are exhibited. The function may be imparted by in-line coating. In the step of in-line coating, the coat layer may be applied to one side of the sheet, or may be applied to both sides simultaneously or one side at a time.

Next, the cast sheet is guided to the simultaneous biaxial tenter, and the sheet is conveyed while gripping both ends of the sheet with clips, and is simultaneously and / or stepwise stretched in the longitudinal direction and the width direction. Simultaneous biaxial stretching machines (tenters) include pantograph type, screw type, drive motor type, linear motor type, etc., but the stretching ratio can be changed arbitrarily, and relaxation processing should be performed at any location. A drive motor system or a linear motor system that can be used is preferable. The stretching ratio varies depending on the type of resin, but usually, the area ratio is preferably 2.0 to 50 times, and more preferably 4.0 to 20 times. The stretching speed may be the same, or may be stretched in the longitudinal direction and the width direction at different speeds. The stretching temperature is preferably from the glass transition temperature to the glass transition temperature + 120 ° C. of the resin constituting the alternating lamination unit.

In order to impart flatness and dimensional stability to the sheet simultaneously biaxially stretched in this way, it is preferable to continuously heat-treat the sheet in the tenter to have a stretching temperature or higher and a melting point or lower. During this heat treatment, in order to suppress the distribution of the main orientation axis in the width direction, it is preferable to perform the relaxation treatment in the longitudinal direction instantly immediately before and / or immediately after entering the heat treatment zone. After being heat-treated in this manner, it is uniformly slowly cooled, cooled to room temperature, and wound up. Further, if necessary, a relaxation treatment may be performed in the longitudinal direction and / or the width direction when slowly cooling from the heat treatment. Immediately before and / or immediately after entering the heat treatment zone, the relaxation treatment can be performed in the longitudinal direction.

In the laminated sheet of the present invention thus obtained, in order to obtain the desired electromagnetic wave shielding performance, the laminated sheets having the same laminated sheets or different thicknesses and compositions are bonded to each other, such as an adhesive sheet, an adhesive sheet, and a double-sided tape. It can also be pasted together via.

Further, layers having different dielectric constants can be laminated on the outermost surface of the laminated sheet of the present invention for the purpose of enhancing electromagnetic wave transmission or causing electromagnetic wave reflection. At this time, a coating layer containing a material exhibiting suitable conductivity / magnetism may be applied, or different resin layers / mesh layers or the like may be laminated via an adhesive sheet or the like. In addition, sputtering (plane or rotary magnetron sputtering, etc.), evaporation (electron beam evaporation, etc.), chemical vapor deposition, organic metal chemical vapor deposition, plasma strengthening / support / activation chemical vapor deposition, ion sputtering, etc., which are used as sheet metal coating technology. The resin / metal layer can be appropriately laminated according to the required function.

Further, the laminated sheet of the present invention can be made into a laminated sheet that shields only a part of a specific frequency more strongly by combining an electromagnetic wave reflecting layer capable of shielding a wide frequency band. On the other hand, it is also possible to provide a new layer having a low complex dielectric constant for lowering the reflection of electromagnetic waves on the surface on the outermost surface of the laminated sheet to obtain a laminated sheet having a higher effect of absorbing electromagnetic waves. Further, in addition to the latter, it is also preferable that the layer showing a high complex dielectric constant of the laminated sheet shows a layer thickness distribution in which the layer thickness continuously decreases from the surface to the inside of the sheet. Since it is a laminated sheet in which the concentration of the electromagnetic wave suppressing material added to the layer showing a high complex dielectric constant is constant, the thickness of the layer showing a high complex dielectric constant is continuously reduced from the surface layer to the inner layer, so that the inner layer is more electromagnetic wave. The restraining materials are in a state of being tightly connected, and the complex dielectric constant gradually increases. As a result, the electromagnetic wave can be taken into the laminated sheet without being inadvertently reflected, so that the effect of absorbing the electromagnetic wave can be enhanced.

Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited to these Examples. Each characteristic was measured by the following method.

(Characteristic measurement method and effect evaluation method)
The method for measuring the characteristics and the method for evaluating the effect in the present invention are as follows.

(1) Layer thickness, number of laminates, laminated structure, particle major axis The layer composition of the laminated sheet was determined by observing a sample obtained by cutting out a cross section parallel to the thickness direction using a microtome by differential interference contrast microscopy. More specifically, using a differential interference microscope "DMLBHC" manufactured by Leica, the cross section of the laminated sheet was observed under the condition of a magnification of 1000 times (eyepiece lens 10 times, objective lens 100 times), and a cross-sectional photograph was taken. The layer composition and the thickness of each layer were measured. The length was measured using the particle size analysis software "Macview" (manufactured by Mountech), and the layer thickness was measured by measuring the vertical distance between the layer interfaces where the contrast difference could be clearly discriminated. Data at 5 locations were randomly measured, and the average value of the thickness of each layer was used as actual measurement data. For the particle major axis, the longest distance of the higher-order structure formed by the particles confirmed in the image was measured at a total of 100 points, and the averaged data was used.

(2) Complex permittivity measurement The measurement unit and measurement method were changed for each measurement frequency of the laminated sheet and analyzed.

(2-1) 1 GHz to 40 GHz frequency band A vector network analyzer (E8631A) manufactured by Agilent Technologies, Inc. was used. The frequency band of 0.5 GHz to 18 GHz is a donut-shaped coaxial waveguide with an outer diameter of φ7 mm and an inner diameter of φ3.04 mm, and the frequency band of 18 to 26.5 GHz is a rectangular lead of 4.32 mm × 10.67 mm. A wave guide was used, and a rectangular waveguide having an internal shape of 3.56 mm × 7.11 mm was used in the frequency band of 26.5 to 40 GHz. The laminated sheet sample was punched and inserted vertically into each of the waveguides for measurement. The measurement interval was set so that 200 points could be measured for each frequency band. The complex permittivity was analyzed using the analysis software N1500A-001 attached to the apparatus.

(2-2) A laminated sheet having a frequency band of 40 to 110 GHz and a size of 150 mm square was used. 33 to 50 GHz (WR-22), 50 to 75 GHz (WR-15), 75 using a lens antenna type relative permittivity / attenuation measuring device LAF-26.5A using the frequency change method manufactured by Keycom. The complex permittivity was measured for each frequency band of ~ 110 GHz (WR-10). Although the value of 33 to 40 GHz is also measured by the measurement method, the measurement data in (2-1) was used for the complex permittivity in the frequency band of 33 GHz or more and less than 40 GHz.

(3) Reflection attenuation measurement The measurement was carried out by changing the measurement unit and measurement method as follows according to the measurement frequency band.

(3-1) 1 GHz to 40 GHz frequency band A vector network analyzer (E8631A) manufactured by Agilent Technologies Co., Ltd. was used to measure the amount of reflection attenuation (reflection attenuation spectrum) of the laminated sheet. The frequency band of 0.5 GHz to 18 GHz is a donut-shaped coaxial waveguide with an outer diameter of φ7 mm and an inner diameter of φ3.04 mm, and the frequency band of 18 to 26.5 GHz is a rectangular lead of 4.32 mm × 10.67 mm. The wave guide was measured using a rectangular waveguide having an internal shape of 3.56 mm × 7.11 mm in the frequency band of 26.5 to 40 GHz. The measurement interval was set so that 200 points could be measured for each frequency band. A 3 mm aluminum metal plate was installed on the back surface of the laminated sheet as a sample, and the incident electromagnetic wave was totally reflected when the laminated sheet did not absorb the electromagnetic wave. The reflection attenuation peak was analyzed using the S-parameter value of _S11 , which represents the intensity ratio of the reflected electromagnetic wave to the incident electromagnetic wave.

(3-2) An aluminum metal plate was attached to the back surface of a laminated sheet having a frequency band of 40 to 110 GHz and a frequency band of 150 mm square to prepare a measurement sample. Using Keycom's lens antenna type diagonally incident type electromagnetic wave absorber (electromagnetic wave absorbing material) and reflection attenuation measuring device LAF-26.5B, in accordance with JIS R 1679 (2007), at an oblique incident of 15 °. Electromagnetic waves were irradiated, and the amount of reflection attenuation (reflection attenuation spectrum) was measured for each frequency band of 33 to 50 GHz (WR-22), 50 to 75 GHz (WR-15), and 75 to 110 GHz (WR-10). Although the value of 33 to 40 GHz is also measured by the measurement method, the measurement data in (3-1) was used for the amount of reflection attenuation in the frequency band of 33 GHz or more and less than 40 GHz.

(4) Calculation of complex permittivity of each layer A macro that can calculate the impedance when the configuration of the laminated sheet is replaced with an equivalent electric circuit by substituting the variables of the permittivity, magnetic permeability, and layer thickness of the A and B layers. We built and utilized the software. By substituting the obtained impedance Z _in into the equation (3) based on the non-reflection condition equation and the reflection attenuation amount, the calculation for calculating the reflection attenuation amount Γ is a macro that continuously calculates over a certain frequency band. It was created. Then, the dielectric constant and the magnetic permeability of each layer are set so as to match the reflection attenuation spectrum measured by the method described in (3), and the dielectric constant and the magnetic permeability when the reflection attenuation spectrum is most similar are read. The permittivity and magnetic permeability of each layer were determined. When it is difficult to calculate the dielectric constant, a single-layer sheet is prepared with the same composition as the layer showing a relatively high dielectric constant in the example, and transmission is performed by the frequency change method using the vector network analyzer described above. It was decided to specify the frequency indicating the minimum value of the attenuation. Since this minimum value is an integral multiple of 1/2 of the execution wavelength transmitted through the sheet thickness, the dielectric constant was obtained. The same value can also be confirmed by the attached software (SFW05) of the permittivity measurement system (Model No. DPS10) for free space measurement by the frequency change method of Keycom.

(5) Surface resistivity measurement (5-1) High resistivity measurement For regions with high resistivity (1.0 × 10 ⁶ to 1.0 × 10 ¹³ ), Mitsubishi Chemical Corporation's high resistance It was measured using a resistivity meter Hiresta-UP (MCP-HT450). A URS probe (MCP-HTP14) was pressed against the surface of the laminated sheet cut into 10 cm squares, and the resistivity value was measured according to JIS K 6911 (1995). The measurement was performed with n number 5 while changing the measurement position, and the average value was taken as the measured value. When measuring the surface resistivity value of the inner layer, the thickness of the outermost layer confirmed by the differential interference microscope was measured by pressing the probe after polishing the surface with a polishing device.

(5-2) Measurement of low resistivity value For the region with low resistance value (1.0 × 10 ⁶ to 1.0 × 10 ^-1 ), the low resistivity meter Loresta-EP manufactured by Mitsubishi Chemical Corporation (Loresta-EP) It was measured using MCP-T360). The ASP probe (MCP-TP03P) was pressed against the surface of the laminated sheet cut into 10 cm squares, and the resistivity value was measured according to JIS K 7194 (1994). The measurement was performed with n number 5 while changing the measurement position, and the average value was taken as the measured value.

(6) DBP Oil Absorption Amount The laminated sheet is dissolved in a solvent that can dissolve the resin of the base material, and the carbon-based conductive particles extracted and separated are treated with ASTM D2414 (Absorbometer C type manufactured by Brabender). It was measured according to (2019). While kneading the carbon-based conductive particles put into the mixer at a rotation speed of 125 min ^-1 , DBP was dropped at a dropping rate of 4 mL / min, and the DBP oil absorption amount analyzed based on the obtained viscosity curve was read. rice field.

(7) Aspect ratio of electromagnetic wave suppression material, average value of elevation angle between carbon material X and seat surface direction, X / Y
The longitudinal cross section and the width cross section of the laminated sheet were embedded in an epoxy resin and polished, and then the surface was polished with Ion Milling IB-19520CCP manufactured by JEOL Ltd. At this time, the acceleration voltage was 4 kV and the processing temperature was −120 ° C. Then, Pt-Pd metal was deposited at 2 mA for 3.75 minutes using a sputtering apparatus IB-3 manufactured by Eiko Engineering. In this way, processed samples having a cross section in the thickness direction-width direction and a cross section in the thickness direction-longitudinal direction of each sample were obtained. Next, observation was performed with a scanning electron microscope JSM-6700F manufactured by JEOL Ltd., and a cross-sectional image was acquired. The light at the time of observation was irradiated in a direction parallel to the thickness direction of the processed sample, and a cross-sectional image was obtained under the following observation conditions.
<Observation conditions>
Acceleration voltage: 3kV
Objective aperture: 4
Secondary electron detection: ON
Mode: LEI
Emission: 10μA
Magnification: 10000 times Inclination: None After that, the area formed by each particle is extracted from each cross-sectional image by the AnalizeParticles (particle analysis) function of the image analysis software ImageJ manufactured by NIH, and the area of each area is determined by Fit Ellipse. The Major (major axis) and Particle (minor axis) when the ellipse was approximated were calculated. The value obtained by dividing the Major of each particle by the Minor was obtained as the aspect ratio of each particle with three significant figures. This work was performed on any approximately 200 particles present in the cross-section observation image. Draw a curve plotting the aspect ratio of each particle in the obtained observation image with the vertical axis as the frequency and the horizontal axis as the logarithmic aspect ratio (Fig. 6), and the maximum value in the range of 40 or more and 5000 or less aspect ratio. Was taken as the aspect ratio of the carbon material X. The analysis was performed with n = 7 for a rectangular range of 1.5 μm × 12 μm inside the layer in each of the longitudinal direction and the width direction, and the average value of 5 points excluding the maximum value and the minimum value of each was calculated.

The average value of the elevation angle of the particles (carbon material X) showing a high aspect ratio is obtained by binarizing each of the cross-sectional images, and then selecting 100 particles from the highest aspect ratio in descending order of the aspect ratio. The angle formed by the long axis of each particle and the film surface direction (direction of the interface) was measured, and the average value of the obtained values was calculated. At this time, when a plurality of particles overlap, the particle in the foreground is the analysis target.

Further, the Major was calculated for the higher-order structure of the particles contained most in the observed image, and the X / Y was calculated by substituting with the layer thickness average value obtained in the item (1). At this time, the particles having a Minor of 0 were excluded from the analysis target as abnormal values.

<Resin, rubber, and electromagnetic wave suppression material>
In order to obtain the sheets of each example and each comparative example, the following components were used as a resin, rubber, and an electromagnetic wave suppressing material.

<Resin, rubber>
-Ethylene-propylene-terpolymer rubber (EPDM): Ethylene-propylene-terpolymer rubber (manufactured by Mitsui Chemicals, Inc.)
Homo-polypropylene: Homo-polypropylene resin showing melt flow rate 30 (manufactured by Prime Polymer Co., Ltd.)
-Isophthalic acid copolymerized polyethylene terephthalate (isophthalic acid copolymerized PET): isophthalic acid copolymerized polyethylene terephthalate having a melting point of 210 ° C.-Polyethylene terephthalate (PET): polyethylene terephthalate having a melting point of 254 ° C. and a viscosity of IV0.8.

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

(Example 1)
EPDM was press-molded to prepare a sheet A (layer A) having a thickness of 0.40 mm and a square size of 200 mm. On the other hand, EPDM and carbon black B were mixed at 87.5: 12.5 (mass ratio) and kneaded with a two-roll mill, and the obtained mixture was pressed to obtain a sheet B having a thickness of 0.40 mm and a square shape of 200 mm. B layer) was created. Next, five layers of sheet A, sheet B, sheet A, sheet B, and sheet A were laminated in this order and thermocompression bonded at 250 ° C. to obtain a laminated sheet having a thickness of 2.0 mm. The evaluation results are shown in Table 1.

(Example 2)
First, a master pellet was prepared by blending 11% by mass of carbon black B with 89% by mass of homopolypropylene and kneading with a twin-screw extruder in which an electromagnetic wave suppressing material was side-fed. Subsequently, the homopolypropylene pellets (raw material for layer A) and the master pellets (raw material for layer B) were charged into separate twin-screw extruders, and both were melted and kneaded at 270 ° C. At this time, the kneading condition was set to 0.7 for the screw rotation speed with respect to the discharge amount. Next, these are merged by a multi-manifold type feed block having 13 flow paths, and the raw materials for the A layer and the raw materials for the B layer are laminated at a stacking ratio of 1.0 so that the resurface layers on both sides are the A layer. Thirteen layers were alternately laminated in the thickness direction to obtain an alternating laminate. The alternating laminated body was supplied to a T-die to form a sheet, and then pressed against a casting drum whose surface temperature was maintained at 25 ° C. by a spot air method to quench and solidify the laminated sheet to a thickness of 2.0 mm. .. The evaluation results are shown in Table 1.

(Example 3)
Two laminated sheets having a thickness of 1 mm were prepared using the same raw materials as in Example 2, and these were bonded together via an optical adhesive sheet (manufactured by Tomoegawa Paper Co., Ltd.) containing an acrylic resin having a thickness of 25 μm as a main component. The thickness of the laminated sheet was 2.0 mm (the thickness of the optical adhesive sheet is thinner than that of the laminated sheet, so it is not considered as the thickness of the laminated sheet). At this time, the thickness was adjusted by adjusting the rotation speed of the cast drum (hereinafter, the same applies to other examples, comparative examples, etc.). The evaluation results are shown in Table 1.

(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 apparatus and the number of laminating were as shown in Table 1. The evaluation results are shown in Table 1.

(Example 6)
Table 1 shows the composition of the raw materials that make up each layer, the laminating device, and the number of laminating points. However, a laminated sheet having a thickness of 1.2 mm was obtained in the same manner as in Example 2 except that each raw material was discharged. The evaluation results are shown in Table 1.

(Examples 7-14)
A laminated 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 laminated sheet, the film forming conditions, and the number of laminated sheets were as shown in Tables 1 and 2. The evaluation results are shown in Tables 1 and 2.

(Example 15)
The laminated sheet obtained in Example 8 was heated in a roll group set at 90 ° C., and then stretched 1.5 times in the longitudinal direction while being rapidly heated from both sides of the film by a radiation heater between the stretched section lengths of 100 mm. After that, it was cooled once. This uniaxially stretched laminated sheet was guided to a tenter, preheated with hot air at 90 ° C., and then stretched 2.0 times in the width direction at a temperature of 140 ° C. to obtain a laminated sheet having a thickness of 0.33 mm. The results of each evaluation are shown in Table 2.

(Example 16)
Three laminated sheets obtained in Example 15 were bonded together via an optical adhesive having a thickness of 25 μm to obtain a laminated sheet having a total of 305 layers and a thickness of 1.0 mm. The results of each evaluation are shown in Table 2.

(Example 17)
Using the laminated sheet of Example 11, a laminated sheet having a thickness of 1.0 mm having 305 layers was obtained by the post-stretching step described in Examples 15 and 16. The results of each evaluation are shown in Table 2.

(Example 18)
A form in which 4% by mass of graphene powder having an average particle size (D50) of 5.8 μm is blended with 96% by mass of an isophthalic acid copolymer polyethylene terephthalate resin having a melting point of 210 ° C. as an electromagnetic wave suppressing material, and the electromagnetic wave suppressing material is side-fed. Master pellets were prepared with a screw segment configuration that is less likely to be sheared through the twin-screw extruder kneading. This master pellet is used as a resin constituting the B layer to obtain an alternating laminated body of 301 layers, and then, in the stretching steps described in Example 15, the film is 3.0 times in the longitudinal direction and 3 in the film width direction. The stretching conditions were changed to 0.0 times, and a laminated sheet having a thickness of 0.50 mm was obtained. It was confirmed that the thickness per layer was as thin as about 1.6 μm, and the graphene powder was arranged in an orderly manner so as to be arranged in the plane direction. The results of each evaluation are shown in Table 2.

(Examples 19 and 20)
A laminated 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 results of each evaluation are shown in Table 2.

(Example 21)
In Example 19, a 601 layer laminated sheet was obtained in the same manner as in Example 19 except that the molten resin was merged with a feed block having 601 slits. Although the stacking disorder occurred due to the increase in the number of layers, it showed sufficient performance to be used as an electromagnetic wave shielding agent. The results of each evaluation are shown in Table 2.

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

(Comparative Example 2)
EPDM and carbon black A are mixed at an ratio of 80:20 (mass ratio) and kneaded with a two-roll mill, and the obtained mixture is pressed and molded into a sheet having a thickness of 2.0 mm and a square of 200 mm. A single film sheet was prepared. The evaluation results are shown in Table 2 (Since this sheet has a single-layer structure, it is described in Table 2 as having only the A layer).

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

(Examples 22 to 27, 30)
A laminated 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 laminated sheet, the film forming conditions, and the number of laminated sheets were as shown in Table 3. The evaluation results are shown in Table 3.

(Example 28)
Using the laminated sheet of Example 23, a laminated sheet having a thickness of 1.0 mm having 305 layers was obtained by the post-stretching step described in Examples 15 and 16. The evaluation results are shown in Table 3.

(Example 29)
A laminated 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.

The laminated sheets of Examples 3, 16 and 17 slightly deviate from the values shown in the table due to the deformation of the adhesive sheet due to the bonding, but the difference is considered to be the values shown in the table because of a slight difference. did. The formula (A) and the formula (B) are as follows.
(A) ε _h '' ≧ 1 and 0.15 ε _h '+ 2 ≦ ε _h '' ≦ 0.23 ε _h '+7.7
(B) 5 ≧ ε _h '' ≧ 1 and 0.01 ε _h '+1 ≦ ε _h '' ≦ 0.09 ε _h '+2.

The laminated sheet of the present invention contains a unit in which layers having a low complex dielectric constant and layers having a high complex dielectric constant are alternately laminated, so that it is difficult to achieve with a conventional single film or a sheet having a low number of laminated layers. Although it contains a low concentration of and is a thin film, it can achieve a high electromagnetic wave attenuation. Further, as a preferred embodiment, by controlling the numerical values of the complex permittivity of both to a specific range, it is possible to steeply and strongly shield only the electromagnetic wave of a specific frequency, so that an apparatus using electromagnetic waves of a similar frequency band is used. It is possible to effectively prevent malfunctions and information leakage in large-capacity information communication due to high-frequency electromagnetic waves. Specifically, it is suitably used for electronic devices and communication devices using communication technology using electromagnetic waves in the GHz frequency band, vehicles equipped with them as a means of transportation, or transportation facilities including all infrastructures for traffic control. can do.

1: Reflection attenuation spectrum 2: Reflection attenuation with the largest attenuation at the peak top Electromagnetic wave attenuation at the peak of the peak I
3: Half width R of the reflection attenuation peak with the largest attenuation at the peak top
4: Resin 5: Carbon material X
6: Carbon black particles 7: Curve plotted with the vertical axis as the frequency and the horizontal axis as the logarithm of the aspect ratio 8: Sheet surface direction 9: Elevation angle between the carbon material X and the sheet surface direction

Claims (19)

A laminated sheet having a structure in which five or more layers A and B having different compositions are alternately laminated, and at least one of the A layer and the B layer contains an electromagnetic wave suppressing material, and all the components constituting the laminated sheet. The content of the electromagnetic wave suppressing material is 1% by mass or more and 15% by mass or less when the value is 100% by mass, and the real part ε'(F / m) of the complex dielectric constant of the entire laminated sheet and the complex magnetic permeability. A laminated sheet characterized in that the product of the real part μ'(H / m) is 4.0 F · H / m ² or more and 50 F · H / m ² or less. When the imaginary part of the complex permittivity of the entire laminated sheet is ε''F / m, the dielectric loss tangent tan δ (ε'' / ε') of the entire laminated sheet is 0.10 or more and 0.50 or less. The laminated sheet according to claim 1, which is a feature. Of the layers A and B, the real part ε _h '(F / m) and the imaginary part ε _h '' (F / m) of the complex permittivity of the layer having a relatively high complex permittivity are (A) or The laminated sheet according to claim 1 or 2, wherein the relational expression of (B) is satisfied.
(A) ε _h '' ≧ 1 and 0.15 ε _h '+ 2 ≦ ε _h '' ≦ 0.23 ε _h '+7.7
(B) 5 ≧ ε _h '' ≧ 1 and 0.01 ε _h '+1 ≦ ε _h '' ≦ 0.09 ε _h '+2 The laminated sheet according to any one of claims 1 to 3, wherein at least one of the electromagnetic wave suppressing materials is a carbon material. The laminated sheet according to claim 4, wherein the carbon material contains carbon black. The laminated sheet according to claim 4 or 5, wherein the carbon material contains a carbon material X exhibiting an aspect ratio of 40 or more and 5000 or less. The laminated sheet according to claim 6, wherein the average value of the elevation angles formed by the carbon material X and the sheet surface direction is 0 ° or more and 15 ° or less. The major axis of the higher-order structure formed by the component contained most in the laminated sheet among the electromagnetic wave suppressing materials is X (nm), and the average layer thickness of the layers A and B in which the component is contained in a large amount is defined. The laminated sheet according to any one of claims 1 to 7, wherein X / Y is 0.01 or more and 10.0 or less when Y (nm) is used. Of the surface specific resistance value of the A layer and the surface specific resistance value of the B layer, when the larger value is α (Ω / □) and the smaller value is β (Ω / □), α is It is characterized in that it is 1.0 × 10 ⁵ Ω / □ or more and 1.0 × 10 ¹⁶ Ω / □ or less, and β is 1.0 Ω / □ or more and less than 1.0 × 10 ⁵ Ω / □. The laminated sheet according to any one of claims 1 to 8. When the real terms of the complex permittivity of the A layer and the B layer are ε _A '(F / m) and ε _B '(F / m), respectively, | ε _A' -ε _B '| is 1 or more. The laminated sheet according to any one of claims 1 to 9, wherein the number is 100 or less. The tenth aspect of the present invention, wherein the ε _A'and the ε _{B'satisfy 2.0 ≤ ε A '} / ε _B'≤ 25 or 2.0 ≤ ε _B '/ ε _A'≤ 25. The laminated sheet described. When the content of the electromagnetic wave suppressing material in the A layer is w _A (mass%) and the content of the electromagnetic wave suppressing material in the B layer is w _B (mass%), w _B > w _A is satisfied. The laminated sheet according to any one of claims 1 to 11, wherein the laminated sheet is characterized by the above-mentioned. In the reflection attenuation spectrum plotted with the vertical axis as the reflection attenuation amount and the horizontal axis as the frequency, the peak top of the reflection attenuation amount peak having the largest reflection attenuation amount is present in the frequency band of 1 to 100 GHz. The laminated sheet according to any one of claims 1 to 12. In the reflection attenuation spectrum plotted with the vertical axis as the reflection attenuation and the horizontal axis as the frequency, the reflection attenuation at the peak top of the reflection attenuation peak with the largest reflection attenuation at the peak top is RL (dB), and the peak top is the reflection attenuation. According to any one of claims 1 to 13, where RL / (f × t) is 0.40 or more and 5.00 or less when the corresponding frequency is f (GHz) and the thickness of the laminated sheet is t (mm). The laminated sheet described. The laminated sheet according to any one of claims 1 to 14, characterized in that it is used for electromagnetic wave suppression. An electromagnetic wave suppressor comprising the laminated sheet according to any one of claims 1 to 15 and a reflector. An electric product using the laminated sheet according to any one of claims 1 to 15 or the electromagnetic wave suppressor according to claim 16. A communication device using the laminated sheet according to any one of claims 1 to 15 or the electromagnetic wave suppressor according to claim 16. A transportation system equipped with the laminated sheet according to any one of claims 1 to 15 or the electromagnetic wave suppressor according to claim 16.

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