Stacked sheet

Abstract

An object of the present invention is to provide a laminated sheet having excellent electromagnetic wave shielding properties. The laminated sheet includes an alternating lamination unit formed by alternately laminating a total of 5 or more layers of an A layer and a B layer. The main content is that in the frequency-reflection attenuation curve of the laminated sheet, the laminated sheet in which the reflection attenuation amount at the peak of the reflection attenuation peak with the largest reflection attenuation amount at the peak is 5.0 dB or more.

Description

Technical Field

[0001] The present invention relates to a laminated sheet having excellent electromagnetic wave shielding properties. Background Art

[0002] With the progress of communication technology, meter waves in the frequency band of several hundred MHz to several GHz are mainly used in mobile phones and wireless communications, centimeter waves in the frequency band of several GHz to several tens of GHz are mainly used in mobile phone communications such as 4G and 5G, and wireless LAN (Wi-fi) communications, and millimeter waves in the frequency band of several tens of GHz to several hundred GHz are mainly used in automotive collision avoidance radars. Thus, electromagnetic waves in various frequency bands are transmitted alternately in the atmosphere. The frequency band of electromagnetic waves is selected according to the information capacity, transmission distance, and use, but since electromagnetic waves in adjacent frequency bands are used in various devices and applications, there is a risk of malfunction of devices, communication obstacles, and information leakage. In addition, it has also been pointed out that it has an impact on the human body that is sensitive to electromagnetic waves. In order to cope with such risks and points, the demand for electromagnetic wave shielding materials that shield electromagnetic waves has increased. In particular, in recent years, in order to achieve high-speed and large-capacity communication, communication technologies using electromagnetic waves in the GHz frequency band have been accelerated, and electromagnetic wave shielding materials that can shield electromagnetic waves in this frequency band are sought.

[0003] Electromagnetic waves propagate in space in the form of waves composed of two components, an electric field and a magnetic field. An electromagnetic wave shielding material that shields electromagnetic waves refers to a material that reflects electromagnetic waves on the surface or inside of the material or absorbs electromagnetic waves inside the material, causing the energy carried by the electromagnetic waves to be dissipated or attenuated. The effect can be further improved by combining reflection and absorption. For example, the conductive reflection technique caused by reflection on the material surface can improve the effect due to the difference in the resistance value (impedance calculated from the relative dielectric constant) between the air interface and the electromagnetic wave shielding material interface. Generally, by coating or laminating a material with a very low resistance value such as metal (copper) on the surface of the substrate, electromagnetic wave shielding properties can be obtained over a wide range of frequency bands. (Patent Document 1) On the other hand, the electromagnetic wave absorption technique that utilizes absorption inside the material makes the inside of the material contain a conductive material and / or a magnetic material, and converts the electromagnetic waves that enter the inside into induced current, causing the energy carried by the electromagnetic waves to be dissipated. It exhibits absorption performance by making a dielectric polymer such as rubber contain a carbon material or a metal material such as ferrite. (Patent Documents 2 to 4) In addition, it is also possible to stack layers with different impedances to interfere / cancel out the electromagnetic waves reflected on the front and back of the electromagnetic wave shielding material, causing them to be dissipated. (Patent Document 5)

[0004] In particular, with respect to the electromagnetic wave shielding property caused by absorption, its characteristics vary depending on the combination of a base material exhibiting dielectric properties (insulating properties) and a conductive material present inside, the thickness of the base material, and the formulation of the conductive material (type of material, combination method, content), etc. However, the arrangement state of the conductive material within the base material is also an important factor. To improve conductivity, a form is adopted in which the conductive material is arranged in a fixed direction and laminated side by side, whereby the overall effect of the shielding material can be improved. This can be referred to as the Maxwell-Wagner effect. (Non-Patent Document 1)

[0005] [Prior Art Documents]

[0006] [Patent Documents]

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2011-502285

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2003-158395

[0009] Patent Document 3: Japanese Patent Application Laid-Open No. 2017-118073

[0010] Patent Document 4: Japanese Patent Application Laid-Open No. 2019-057730

[0011] Patent Document 5: Japanese Patent Application Laid-Open No. 2019-102665

[0012] [Non-Patent Documents]

[0013] [Non-Patent Document 1]Z.M.Dang, Prog.Matter.Sci., 2012, 57, 660-723 Summary of the Invention

[0014] [Problems to be Solved by the Invention]

[0015] Regarding an electromagnetic wave shielding material using the conductive reflection technology described in Patent Document 1, techniques such as metal sputtering, vacuum evaporation, or coating a paste material containing a conductive material and / or a magnetic material on the outermost layer can be used. However, short circuits in electronic devices / communication devices may occur due to peeling, or problems may arise from the perspective of durability. On the other hand, regarding electromagnetic wave shielding materials using magnetic absorption or dielectric absorption as described in Patent Documents 2 to 5, in the existing technology where the base material contains a conductive material, in order to increase the absolute value of the electromagnetic wave attenuation amount (improve electromagnetic wave shielding performance), it is necessary to thicken the base material or increase the content of the conductive material. That is, if the materials used are determined, the electromagnetic wave shielding performance can be obtained in proportion to the product of the amount of the conductive material contained in the base material per unit volume and the thickness of the base material (such a relationship is called the "volume rule"). However, when the thickness of the base material is thickened, the toughness of the electromagnetic wave shielding material becomes stronger, so it becomes difficult to apply it to uses that require formability, such as winding it around a cable or combining a shielding material along a frame with a complex uneven shape.

[0016] On the other hand, considering the formability or production efficiency of the shielding material, compared with a stamped product using a thermoplastic resin, it is preferable to use a continuous sheet formed by melt extrusion of a thermoplastic resin. However, when forming a sheet with a high concentration of a conductive material, there are the following problems: the viscosity increasing effect (thixotropy) of the resin composition becomes stronger during extrusion, uneven discharge occurs during extrusion molding into a sheet shape, making it difficult to form a sheet with a uniform thickness, or the sheet becomes brittle and easily breaks.

[0017] [Means for Solving the Problem]

[0018] To solve the above problems, the present invention includes the following technical features. That is, a laminated sheet includes an alternating lamination unit formed by alternately laminating a total of 5 or more layers of 2 layers with different conductivities. For convenience, the layer with lower conductivity among the 2 layers with different conductivities is called layer A, and the layer with higher conductivity is called layer B. The reflection attenuation amount RL of the laminated sheet is 5.0 dB or more. The reflection attenuation amount RL is the reflection attenuation amount at the peak of the reflection attenuation peak with the maximum reflection attenuation amount when a frequency-reflection attenuation amount curve is obtained by plotting the laminated sheet with the reflection attenuation amount as the vertical axis and the frequency as the horizontal axis.

[0019] [Effects of the Invention]

[0020] The laminated sheet of the present invention exhibits high electromagnetic wave shielding properties. Therefore, it can be well used as an electromagnetic wave shielding material. In a more preferred aspect, by forming a laminated structure in which layers with high conductivity and layers with low conductivity are alternately laminated, it will have a steep and high electromagnetic wave shielding property in a specific frequency band. In addition, even if the content of the conductive material is small or it is a thin film, compared with the prior art, the same level of electromagnetic wave shielding property can be obtained. Therefore, an improvement in the formability following for the application product and the stable production of the sheet are expected. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the frequency-reflection attenuation curve of the laminated sheet of one embodiment of the present invention, and is used to explain the half-value width of the reflection attenuation peak where the reflection attenuation at the peak is the largest, and the reflection attenuation at the peak.

[0022] Figure 2 is with Figure 1 It is a schematic diagram of the frequency-reflection attenuation curve of the laminated sheet of a different embodiment, and is used to explain the half-value width of the reflection attenuation peak where the reflection attenuation at the peak is the largest, and the reflection attenuation at the peak.

[0023] Figure 3 is with Figure 1 , 2 It is a schematic diagram of the frequency-reflection attenuation curve of the laminated sheet of a different embodiment, and is used to explain the half-value width of the reflection attenuation peak where the reflection attenuation at the peak is the largest, and the reflection attenuation at the peak.

[0024] Figure 4 is with Figures 1 to 3 It is a schematic diagram of the frequency-reflection attenuation curve of the laminated sheet of a different embodiment, and is used to explain the half-value width of the reflection attenuation peak where the reflection attenuation at the peak is the largest, and the reflection attenuation at the peak. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, the laminated sheet of the present invention will be described in detail.

[0026] The laminated sheet of the present invention is a laminated sheet including an alternating lamination unit in which a total of 5 or more layers of A layers and B layers having different conductivities are alternately laminated. For the aforementioned laminated sheet, when a frequency-reflection attenuation curve is obtained by plotting the reflection attenuation on the vertical axis and the frequency on the horizontal axis, the reflection attenuation at the peak of the reflection attenuation peak where the reflection attenuation at the peak is the largest (reflection attenuation RL) must be 5 dB or more. In addition, the frequency-reflection attenuation curve can be obtained by the measurement method described later.

[0027] The laminated sheet of the present invention includes different layers such as layer A and layer B having different conductivities. The materials constituting layer A and layer B are not particularly limited, such as transparent / opaque, flexible / rigid, flat / non-flat, organic (polymer) material / inorganic (metal) material, etc. However, considering processability, a substrate made of an organic polymer material showing flexibility is preferred. Particularly preferably, a thermoplastic resin is used as the main component. Here, the so-called main component means that the layer is composed only of a thermoplastic resin, or a state in which a thermoplastic resin is used as the matrix resin and other materials such as a conductive material and a magnetic material are dispersed in the resin.

[0028] In addition, in the laminated sheet of the present invention, a hard coat using a thermosetting resin or a photocurable resin may also be used.

[0029] Layers A and B in the laminated sheet of the present invention must be layers having different conductivities. Furthermore, for convenience and considering the preferred form of the laminated sheet described later, the layer with lower conductivity is referred to as layer A and the layer with higher conductivity is referred to as layer B. The different conductivities of layers A and B mean that the conductivity / insulation index in the layer direction (plane direction of the sheet) of each of layers A and B, that is, the surface resistance value, is different. Specifically, the different conductivities of layers A and B mean that when the higher surface resistance value among the surface resistance values of layers A and B is set as α [Ω / sq] and the lower surface resistance value is set as β [Ω / sq], α / β is 1.1 or more. α / β is preferably 10 2 or more, more preferably 10 5 or more, and further preferably 10 9 or more. If the conductivity / insulation index, that is, the surface resistance value, is lower than 1.0×10 5 [Ω / sq], the electromagnetic wave shielding property will be exhibited well. Therefore, it is more preferably that the surface resistance value of layer A is 1.0×10 5 [Ω / sq] or more and the surface resistance value of layer B is lower than 1.0×10 5[Ω / □], and display the ratio of the aforementioned surface resistance values. The method of making the A layer and the B layer have different conductivities is not particularly limited. For the material design to make the A layer and the B layer have different conductivities, it is relatively simple that the A layer and the B layer are composed of a composition in which a matrix contains a conductive material, but materials with different relative dielectric constants can also be used as the matrix material to make the conductivity different thereby, or the types and / or contents of the conductive materials contained can be made different to make the conductivity different thereby. Although it will be specifically described later, in order to obtain a high amount of electromagnetic wave attenuation in a specific frequency band, it is important to control the value of the relative dielectric constant within a specific numerical range. At this time, in order to maintain the amount of electromagnetic wave attenuation while adjusting the frequency of the reflection attenuation peak to the target frequency band, it is preferable to be able to finely adjust the conductivity composition of the A layer and the B layer. In order to make the relative dielectric constants of the A layer and the B layer different, it is most preferable that the A layer and / or the B layer contains a conductive material and / or a magnetic material in a certain form. The relative dielectric constant mentioned here when describing is a dimensionless quantity representing the magnitude of the dielectric constant with the dielectric constant (electrical constant) in a vacuum as a reference. Hereinafter, the relative dielectric constant will be abbreviated as the dielectric constant.

[0030] Furthermore, the surface resistance value means the resistance value of the specimen obtained on the surface of the specimen. It can be obtained by exposing the interface by peeling off the interface where the A layer and the B layer are laminated, but by slicing each layer to expose the surface of the specimen and measuring it, it can be obtained simply and with good reproducibility.

[0031] In the laminated sheet of the present invention, in order to make the attenuation amount at the peak show a high value for the attenuation amount of the reflection attenuation peak with the maximum attenuation amount, it is important to design the layer showing a high dielectric constant among the A layer and the B layer constituting the alternating lamination unit. Generally, in the technology of conventional single-layer sheets, it is usually achieved by highly containing a conductive material and / or a magnetic material existing in the resin for increasing the dielectric constant, or by increasing the sheet thickness. However, in the laminated sheet of the present invention, a difference in dielectric constant is set by increasing the dielectric constant of one side layer and decreasing the dielectric constant of the other side layer, and together with the effect of dielectric polarization (generation of dipole moment) generated at the layer interface between the high-dielectric-constant layer and the low-dielectric-constant layer, thus, compared with a single-layer sheet containing a conductive material and / or a magnetic material with the same weight concentration, a dielectric constant improvement effect above the volume law can be obtained. In order to strongly cause such dielectric polarization contributing to the improvement of the dielectric constant, how to increase the difference in dielectric constant between the alternately arranged A layer and B layer becomes one of the important design points. Methods for making the difference in dielectric constant different are as described above, and examples include the types of resins used for the A layer and B layer, and the difference in the content of the conductive material and / or magnetic material contained in the A layer and / or B layer. However, in a preferred form: among the A layer or B layer, only one side layer contains a conductive material, and the resin on the other side is composed only of a resin without a conductive material. A further preferred form is: the layer without a conductive material is composed of a resin with a low dielectric constant, and the layer containing a conductive material is composed of a resin showing a high dielectric constant as the resin, and at the same time, the conductive material is contained at a further high concentration. In addition, as described later, increasing the number of layers will increase the number of interfaces causing dielectric polarization, so it is preferred. In addition, reducing the layer thickness can increase the number of interfaces per unit thickness, so it is preferred. That is, regarding the number of interfaces between the A layer and the B layer per unit thickness of the alternating lamination unit, it is preferably set to 2 interfaces / 100 μm or more, more preferably set to 5 interfaces / 100 μm or more, and further preferably set to 10 interfaces / 100 μm or more. As long as the manufacture of the laminate can be stably achieved, there is no particular limitation on the upper limit, but generally, based on the productivity point, it is set to 150 interfaces / 100 μm or less. In addition, at this time, the ratio of the surface resistance values of the A layer and the B layer (A layer / B layer) is set to 1×10 10 or more, preferably set to 1×10 12 .

[0032] Regarding the flexible organic polymer materials that can be well used in the present invention, they are particularly good from the viewpoints of processability and film-forming property of sheet materials, and thus are preferably thermoplastic resins. Examples of thermoplastic resins include polyolefin resins represented by polyethylene, polypropylene, poly(1-butene), poly(4-methylpentene), polyisobutene, polyisoprene, polybutadiene, polyvinylcyclohexane, polystyrene, poly(α-methylstyrene), poly(p-methylstyrene), polynorbornene, polycyclopentene, etc.; polyamide resins represented by nylon 6, nylon 11, nylon 12, nylon 66, etc.; copolymer resins of vinyl monomers represented by ethylene / propylene copolymer, ethylene / vinylcyclohexane copolymer, ethylene / vinylcyclohexene copolymer, ethylene / alkyl acrylate copolymer, ethylene / alkyl methacrylate copolymer, ethylene / norbornene copolymer, ethylene / vinyl acetate copolymer, propylene / butadiene copolymer, isobutene / isoprene copolymer, vinyl chloride / vinyl acetate copolymer, etc.; acrylic resins represented by polyacrylate, polymethacrylate, polymethyl methacrylate, polyacrylamide, polyacrylonitrile, etc.; polyester resins represented by polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, poly(ethylene 2,6-naphthalate), etc.; polyether resins represented by polyethylene oxide, polypropylene oxide, polyalkylene glycol, etc.; cellulose ester resins represented by diacetyl cellulose, triacetyl cellulose, propionyl cellulose, butyryl cellulose, acetyl propionyl cellulose, nitrocellulose, etc.; biodegradable polymers represented by polylactic acid, poly(butylene succinate), etc. In addition, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl butyral, polyacetal, polyglycolic acid, polycarbonate, polyketone, polyethersulfone, polyetheretherketone, modified polyphenylene ether, polyphenylene sulfide, polyetherimide, polyimide, polysiloxane, tetrafluoroethylene resin, trifluoroethylene resin, chlorotrifluoroethylene resin, tetrafluoroethylene-hexafluoropropylene copolymer, polyvinylidene fluoride, etc. can be used. These thermoplastic resins can be used alone, or as a mixture or alloy of two or more polymers. By forming a mixture or alloy, heat resistance, viscosity characteristics, adhesion at the interlayer interface, etc. that cannot be obtained from a single thermoplastic resin can be obtained.

[0033] As described above, in the laminated sheet of the present invention, by forming a laminated sheet including an alternating lamination unit in which layers having different conductivities are alternately laminated, interfacial polarization occurs at the interface between the A layer and the B layer having different conductivities, and an effect of further improving the electromagnetic wave shielding property can be obtained. Therefore, the dielectric constant of the thermoplastic resin constituting each layer is an important factor. Accordingly, the resin constituting the A layer and the resin constituting the B layer are preferably different in dielectric constant. Specifically, among the resins having a low dielectric constant, resins having a dielectric constant of 3.0 or less are preferably selected. Considering versatility, processability, laminability, etc., thermoplastic resins such as polyolefin resins (dielectric constant: 2.0 to 2.3), polyester resins (dielectric constant: 2.8 to 3.0), polycarbonate (dielectric constant: 2.9 to 3.0), and polystyrene (dielectric constant: 2.4 to 2.6) are preferably selected. These resins are particularly preferably used for the layer not containing a conductive material.

[0034] On the other hand, as the thermoplastic resin that can preferably be used for the layer containing a conductive material, a resin having a high dielectric constant is preferred, and preferably selected from: acrylic resins (dielectric constant: 3.0 to 4.5), nylon resins (dielectric constant: 3.5 to 5.0), cellulose-based resins (dielectric constant: 6.7 to 8.0), copolymer resins of vinyl monomers (dielectric constant: 3.0 to 8.0), fluororesins (dielectric constant: 4.0 to 8.0), polyphenylene sulfide (dielectric constant: 3.5 to 4.0), and the like.

[0035] In addition, a method of making the dielectric constants of layer A and layer B different can be achieved by using materials with different dielectric constants as the resin, but it can also be achieved by making the resins constituting layer A and layer B the same and adding a conductive material that imparts conductivity to set the difference in dielectric constant. As described above and below, the laminated sheet of the present invention is characterized in that layer A and layer B with different conductivities are alternately laminated, and the difference in dielectric constant between layer A and layer B is set, whereby the electromagnetic wave shielding performance can be improved by using the dielectric polarization generated at the layer interface. In order to improve the effect of dielectric polarization, the greater the difference in dielectric constant between layer A and layer B, the more effective it is. On the other hand, in order to increase the reflection attenuation amount, it is preferable that the layer with a higher dielectric constant (layer B) is designed within a specific dielectric constant range described below, and it is preferably configured such that it is easy to design the material according to the target dielectric constant. This fine adjustment of the dielectric constant is adjusted by the content of the added conductive material, which is simpler than adjusting by the resin constituting the layer. Therefore, the preferred form of the laminated sheet that satisfies these is that the layer with a lower dielectric constant (layer A) is composed of a layer without a conductive material, and the layer with a higher dielectric constant (layer B) is composed of a layer containing a conductive material. A further preferred form is that the resin constituting layer A is composed of the resin having a dielectric constant of 3.0 or less shown above, and the resin constituting layer B is composed of the resin having a dielectric constant of 3.0 or more shown above and contains a conductive material.

[0036] The laminated sheet of the present invention must include an alternating lamination unit in which 5 or more layers of layer A and layer B are alternately laminated. The so-called alternating lamination, in the case where the outermost layer has a structure of layer A, refers to a laminated state arranged according to the rule of A(BA)n or A(BA)nB (n is an integer of 2 or more). For example, a laminated sheet having a structure of layer A / layer B / layer A / layer B / layer A or layer B / layer A / layer B / layer A / layer B, regardless of whether there are layers other than layer A and layer B, all conform to the structure including an alternating lamination unit in which a total of 5 or more layers of layer A and layer B are alternately laminated. As long as the laminated sheet of the present invention has an alternating lamination unit in which layer A and layer B are laminated, the outermost layer can be any one of layer A, layer B, and layers other than layer A and layer B, and the outermost layers on both sides can be the same layer or different layers from each other. In addition, the number of alternating lamination units contained in the laminated sheet can be 1 or more. When there are multiple units, each alternating lamination unit can have the same structure or a different structure. When using multiple alternating lamination units, it is easy to achieve electromagnetic wave shielding corresponding to multiple wavelength regions. That is, when multiple alternating lamination units are laminated and used, the alternating lamination units having peaks in different frequency bands are laminated with each other, so that it is easy to simultaneously shield a desired multiple frequency bands.

[0037] Regarding the method of alternately laminating elastomeric resins such as rubber, examples include: producing sheets by rolling and stamping two types of elastomeric resins having different compositions, and obtaining a laminated sheet by alternately laminating different sheets and performing hot press bonding.

[0038] On the other hand, regarding the method of alternately laminating thermoplastic resins, examples include: separately preparing masterbatch pellets by distributing / dispersing and mixing the thermoplastic resins corresponding to each layer and appropriate additives, feeding the masterbatch pellets from different flow paths using two or more extruders, and performing lamination using a multi-manifold type feed block and a static mixer of a known lamination device. In particular, for the laminated sheet of the present invention, as described later, in order to exhibit high electromagnetic wave attenuation performance at a specific frequency, it is preferable that the dispersion of the layer thickness is small and the thickness is uniform. Therefore, in order to achieve high-precision lamination, it is preferable to use a feed block having fine slits to form the laminated sheet. In addition, by using a slit type feed block, the conductive material and / or the magnetic material are oriented / dispersed according to the laminar flow of the resin, and it becomes easy to increase the dielectric constant of the laminated sheet. When using a slit type feed block to form a laminate, it becomes possible to adjust the pressure balance by changing the length and width of the slit to achieve the thickness and its distribution of each layer. Here, the length of the slit refers to the length of the comb-shaped portion formed in the slit plate to form a flow path for alternately flowing the A layer and the B layer.

[0039] When producing a laminated sheet using the latter thermoplastic resin, the melt viscosities of two different thermoplastic resins (for convenience, these thermoplastic resins are respectively referred to as resin A and resin B) are preferably of the same grade. When the melt viscosities are greatly different, resin lamination disorder (flow marks) may occur at the lamination interface, and a uniform sheet cannot be produced. As a result, the layer thickness of each layer may become uneven, and the conductivity of each layer may become uneven accordingly, and the electromagnetic wave shielding property may vary depending on the position of the laminated sheet. In order to form a uniform laminated sheet by melt extrusion, it is preferable to fix the temperature (the melting point of the resin with the higher melting point among resin A or resin B + 10 °C) and the shear rate (100 sec -1)In the case where the melt viscosity of the resin with a higher melt viscosity is set to X [poise] and the melt viscosity of the resin with a lower melt viscosity is set to Y [poise], the ratio (X / Y) of these is 1.0 ≤ X / Y ≤ 5.0, more preferably 1.0 ≤ X / Y ≤ 2.0. In addition, when the thermoplastic resin contains a conductive material as a filler, a change in melt viscosity depending on the shear rate (thixotropy) occurs due to the high concentration of the filler, and it becomes easier to generate stronger flow marks in the resin lamination step. Further, even when only a thermoplastic resin is used, depending on the type such as an olefin resin, shear dependence of the melt viscosity of the resin sometimes occurs, so flow marks are likely to be generated during lamination, and if a resin prone to thixotropy is combined with a filler, stronger flow marks will be generated. Therefore, from the viewpoint of thermoplastic resins, it is preferable to use a resin that is not prone to thixotropy. Specifically, considering the kneadability of the conductive material, etc., it is preferably selected from: copolymerized resins of olefin series, nylon resins, polyester resins, etc. Or: according to the shear dependence of the melt viscosity generated by adding a conductive material to a layer showing high conductivity, particles different from the conductive material are added to a layer with low conductivity that does not contain a conductive material accordingly; a resin material showing non-Newtonian properties such as olefin is used, and by such methods, a method of making the shear dependence of the melt viscosity similar in characteristics is also effective in suppressing flow marks of the laminated sheet.

[0040] The number of stacked layers of the laminated sheet of the present invention must be 5 or more. In order to obtain multiple interfaces capable of generating dielectric polarization and to contain a high dielectric constant layer surrounded by two or more low dielectric constant layers, a structure of 5 or more layers is also necessary in any of the above regular arrangements. In conventional single films or low stacked number articles, it is impossible to achieve the target electromagnetic wave shielding performance unless a conductive material is added at a high concentration or the thickness of the sheet is increased. In contrast, by stacking 5 or more layers alternately, it becomes easier to obtain the effect of dielectric polarization at the interfaces of layers with different conductivities. That is, due to dielectric polarization, current becomes easier to flow inside the sheet (especially in the region near the layer interface), and the energy of the electromagnetic wave is dissipated due to the blocking of the conductive material, enabling the acquisition of an electromagnetic wave shielding material with high shielding performance. Furthermore, increasing the number of layers in a laminated sheet with a fixed thickness makes the thickness of each layer of the laminated sheet thinner, and the conductive material and / or magnetic material become easier to disperse / align in the direction parallel to the plane. Therefore, it is easy to increase the conductivity / dielectric constant of the laminated sheet, and the conductivity / dielectric constant that cannot be achieved for a single layer material unless the conductive material and / or magnetic material is contained at a high concentration can be obtained at a low concentration with the same effect. The total number of stacked layers of layer A and layer B in the alternately stacked unit contained in the laminated sheet is preferably 11 or more, more preferably 31 or more, and further preferably 101 or more. When the number of stacked layers is large, in addition to the above effects, in the case of a laminated sheet with the same thickness, by increasing the number of layers, the distance between the conductive materials becomes narrower due to the increased filling density of the conductive materials in the layer, and the electron movement efficiency between the added conductive materials also increases. Therefore, the effect as an electromagnetic wave absorption material is improved, which is preferable. In addition, since the number of layers is large and the thickness of each layer is thinner, the number of layers per unit thickness increases, so the effect of dielectric polarization is improved, and further the dielectric constant of the laminated sheet can be increased. Although there is no particular upper limit to the number of layers of the laminated sheet, when using a feeding module with fine slits, it will cause an increase in manufacturing cost due to the increase in the size of the device caused by the increase in the number of layers. Furthermore, depending on the dispersion state, shape, and size of the filler, when the number of layers increases and the thickness of each layer becomes thinner, there may sometimes be the following situation: it becomes easy to generate thixotropy due to particle addition, and the layer thickness becomes greatly uneven due to resin flow disorder, resulting in damage to the original high shielding and steep electromagnetic wave shielding performance. From the above, in terms of the upper limit of the number of layers, realistically it is 2000 layers or less.

[0041] The laminated sheet of the present invention, in addition to alternately stacking 5 or more of the above alternately stacked units of layer A and layer B with different conductivities, can also contain an electromagnetic wave reflection layer, an electromagnetic wave absorption layer, etc. in the form of layers with different functions.

[0042] The laminated sheet of the present invention is preferably an electromagnetic wave absorbing sheet containing a conductive material and / or a magnetic material, but it can also be combined with an electromagnetic wave reflecting layer that can shield a wide frequency band, and become a laminated sheet that can more strongly shield only a specific frequency when widely shielding electromagnetic waves. It can also be provided on the outermost surface of the laminated sheet to further reduce the electromagnetic wave reflection on the surface and show a new layer of low dielectric constant, so as to further improve the electromagnetic wave absorption effect. In the latter case, the dielectric constant of the layer located on the outermost surface of the laminated sheet is preferably less than 4.0, and more preferably less than 3.0. In addition, it is also preferred to provide a resistance layer showing the same impedance as the impedance of the air layer as a layer for suppressing surface reflection. The impedance of air is 377Ω, and the well-known resistance layers that meet this resistance value can be listed as: ITO, etc.

[0043] When the laminated sheet of the present invention is plotted with reflection attenuation as the vertical axis and frequency as the horizontal axis to obtain a frequency-reflection attenuation curve, the reflection attenuation at the peak where the attenuation at the peak is the largest must be 5.0 dB or more. The so-called reflection attenuation is: an electromagnetic wave is incident on the laminated sheet, a detector is placed on the electromagnetic wave incident side, and a material that can make the electromagnetic wave fully reflected to the incident side is placed on the surface opposite to the electromagnetic wave incident side, and the intensity of the electromagnetic wave returned from the laminated sheet is measured, and the reflection attenuation Γ shown in formula (1) and the ratio of the intensity of the electromagnetic wave returned to the intensity of the incident electromagnetic wave are obtained from the intensity of the incident electromagnetic wave and the intensity of the electromagnetic wave detected by the detector, and the reflection attenuation Γ is expressed in decibels (dB). In addition, the measurement of the reflection attenuation and the determination of the peak are obtained by the method described in the "Reflection Attenuation Measurement" described later. However, as long as the same result can be obtained, it is not a problem to use different apparatus systems and procedures / methods. If it is recorded briefly as an example: using the coaxial waveguide method or the free space method, electromagnetic waves are irradiated on the laminated sheets with a metal reflector made of aluminum or the like on the back, and the intensity of the electromagnetic waves returned from the laminated sheets is measured and calculated. The reflection attenuation of each frequency is measured by scanning the frequency. In the frequency-reflection attenuation curve obtained by plotting the reflection attenuation as the vertical axis and the frequency as the horizontal axis, multiple peaks are sometimes obtained, among which the attenuation of the reflection attenuation peak with the largest peak intensity (attenuation) is focused. The peak top referred to here refers to the position where the sign (slope) reverses from positive to negative, or from negative to positive when considering the slope of the tangent of the reflection attenuation spectrum, that is, the point connected to the straight line parallel to the X-axis. The reflection attenuation at the reflection attenuation peak is as follows: Figure 1 , 2As shown, when there is one peak top, a baseline is drawn for this peak, and it is represented by the difference between the reflection attenuation at the peak top at the frequency showing the peak top and the reflection attenuation between the baseline. Hereinafter, the reflection attenuation at the peak top of the reflection attenuation peak will be expressed as the reflection attenuation RL [dB]. In addition, as Figure 3 shown, even for a peak with a high attenuation of the baseline, when there is a specific peak top, the difference between the baseline of this peak top and the attenuation of the peak top is read. On the other hand, when obtaining a spectrum such as Figure 4 that has multiple peak tops including shoulder peaks, it is represented by the difference between the attenuation corresponding to the peak top and the attenuation between the baseline of the whole peak including multiple peak tops with respect to the frequency of the peak top with the highest peak among the multiple peak tops.

[0044]

[0045] The reflection attenuation amount RL of the reflection attenuation peak represented in this way must be shown as a value of 5.0 dB or more. When the reflection attenuation amount of the baseline is 0 dB, according to Equation (1), it is synonymous with the reflection attenuation amount Γ. Therefore, when the reflection attenuation amount RL is less than 5.0 dB, it means that the penetration rate of electromagnetic waves is higher than 30%. Therefore, a laminated sheet with a reflection attenuation amount RL of the reflection attenuation peak less than 5.0 dB cannot be said to have sufficient electromagnetic wave shielding properties. In the laminated sheet of the present invention, the reflection attenuation amount RL at the reflection attenuation peak where the reflection attenuation amount is the largest is preferably 15.0 dB or more, more preferably 20.0 dB or more, and further preferably 30.0 dB or more. When the reflection attenuation amount RL at the peak where the reflection attenuation amount is the largest shows around 30.0 dB, it means that compared with the electromagnetic wave shielding properties in the frequency bands before and after the peak, 99.9% of the incident electromagnetic waves are shielded, and it can be said to have very high electromagnetic wave shielding properties. The upper limit is not particularly limited, but it is preferably 100 dB or less. Furthermore, the width of the frequency band where the reflection attenuation amount RL of the reflection attenuation peak with the largest reflection attenuation amount at the peak exceeds 5.0 dB, although showing steep and high electromagnetic wave shielding properties, is preferably as wide as possible across a wide frequency band. This can reduce the variation in the frequency band caused by the thickness unevenness of the laminated sheet. Specifically, the width of the frequency band where the reflection attenuation amount RL of the reflection attenuation peak with the largest reflection attenuation amount at the peak exceeds 5.0 dB preferably spans a frequency band of 1.0 GHz or more, more preferably 3.0 GHz or more, and further preferably 5.0 GHz or more. As for the upper limit, it is preferably 20.0 GHz or less. In order for the reflection attenuation amount RL of the reflection attenuation peak with the largest reflection attenuation amount at the peak to show a high value of 5.0 dB or more, from the perspective of the composition of the laminated sheet, it can be achieved by the following: a large number of laminations, small thickness unevenness of the layer thickness, increasing the overall thickness of the thickened sheet, etc.; from the perspective of additives, it can be achieved by the following: conductive materials and / or showing high conductivity / magnetism, increasing the content concentration of these, etc.

[0046] In the laminated sheet of the present invention, when the reflection attenuation amount RL [dB] of the reflection attenuation peak having the maximum reflection attenuation amount at the reflection attenuation peak is set, the frequency showing this reflection attenuation amount is set to f [GHz], and the overall thickness of the laminated sheet is set to t [mm], RL / (t×f) is preferably 0.2 or more and 15 or less. Compared with the prior art, the laminated sheet of the present invention is characterized in that by adopting a form of alternately laminating a layer with a low dielectric constant and a layer with a high dielectric constant, compared with the conventional single film or a sheet with a low number of laminations, the sheet thickness can be made thinner and formability can be imparted. This feature is applicable to sheets targeting any frequency band. However, since the thickness and the frequency show a trade-off relationship, from the constitution of the laminated sheet showing the same dielectric constant, when the frequency band is shifted to the high-frequency side, the theoretical thickness tends to become thinner. Therefore, the effect of the thin film exceeding the volume rule of the laminated sheet of the present invention cannot be discussed only by the relationship between the reflection attenuation amount RL and the thickness t (for example, RL / t, etc.), and it is important that the aforementioned relationship among the three elements of the frequency f, the laminated sheet thickness t, and the reflection attenuation amount RL of the reflection attenuation peak is more excellent than the prior art. RL / (t×f) is more preferably 0.45 or more and 12 or less, and most preferably 0.75 or more and 10 or less. When RL / (t×f) is less than 0.2, the reflection attenuation amount RL is low, and sometimes sufficient electromagnetic wave shielding performance to be used as an electromagnetic wave shielding application cannot be obtained, or although there is electromagnetic wave shielding property, the thickness is thick and the sufficient performance exceeding the volume rule cannot be shown. When RL / (t×f) is higher than 15, although the reflection attenuation amount is high, since the thickness is too thin, sometimes the lamination accuracy / film forming property of the laminated sheet deteriorates due to the high-concentration addition of the conductive material and / or the magnetic material. In order to make RL / (t×f) satisfy the preferred range, the effect is further improved by combining the following elements: the number of laminations of the laminated sheet is large and in a state where many dielectric polarizations are generated, the layer thickness unevenness is small, the conductive material and / or shows high conductivity / magnetism, and even a constitution in which the dielectric constant can be freely designed by using a plurality of conductive materials, and the real part and the imaginary part of the dielectric constant of the layer showing a high dielectric constant satisfy the dielectric constant relationship described later. The preferred conditions for each element are as described in this specification.

[0047] Among the reflection attenuation peaks of the laminated sheet of the present invention, the reflection attenuation peak with the largest reflection attenuation amount preferably exists in the frequency band of 1 to 100 GHz. When the laminated sheet of the present invention is used for electromagnetic wave shielding applications in high-frequency applications where it is difficult to target with conventional conductive reflection technologies or magnetic absorption technologies, it preferably has the largest attenuation peak in the GHz frequency band. For this reason, it is most preferable to use the conductive material or dielectric material described later as the material contained in the laminated sheet to form a dielectric absorption type laminated sheet. Generally, in order to shield the near field corresponding to a frequency band less than several GHz, a sheet containing a magnetic material such as a metal represented by silver or copper or a metal oxide such as ferrite in a dielectric substrate can be used. However, when targeting the high-frequency band of the GHz frequency band, it becomes impossible to obtain the magnetic loss in the frequency band higher than a specific frequency, which is called the Snoek limit, peculiar to magnetic materials. Due to such characteristics, it is usually necessary to cover with a high concentration of magnetic materials. There are also conventional technologies that use special materials such as ε-iron oxide, but in addition to the high cost of the materials, a high concentration of addition is also required. Therefore, it is inferior in terms of cost / film formability compared to the case of using conductive materials. In the case of producing a laminated sheet by melt extrusion, thixotropy caused by a high concentration of fillers is inevitable, and in addition, the metal part of the extruder may be damaged due to the added magnetic material. Therefore, when producing a laminated sheet by a melt extrusion step with a low concentration of fillers, in order to obtain electromagnetic wave shielding properties in the above-mentioned GHz frequency band, it is preferable to obtain electromagnetic wave shielding properties in the high-frequency band by absorbing electromagnetic waves by containing a conductive material or a conductive / magnetic composite material. In the case of targeting a frequency band of several GHz by using a magnetic material in combination, it is preferable to use a metal material with a high aspect ratio that causes electromagnetic wave energy loss through a high magnetic permeability. By adding a material with a high aspect ratio to the laminated sheet, it is possible to achieve the alignment of the material along the plane direction, which is difficult for a conventional single-layer film, and a material with shielding properties can be formed even in the GHz frequency band. The aspect ratio can be expressed as the ratio of the length in the thickness direction of the material to the length of the major axis in the plane direction. When the former is set to t1 and the latter is set to t2, it is preferably 0.001 or more and 0.95 or less, more preferably 0.01 or more and 0.1 or less. If the aspect ratio becomes less than 0.001, since the magnetic material becomes too thin, the material may deform or break during the compounding and film-forming processes, and the effect of the magnetic material may not be obtained.

[0048] The laminated sheet of the present invention preferably has a surface resistance value [Ω / □] of 1.0×10 5As described above, when using the laminated sheet as an electromagnetic wave absorbing sheet, in order to allow the electromagnetic wave efficiency to propagate well within the laminated sheet and cause the energy of the electromagnetic wave to be dissipated within the laminated sheet, it is preferable to suppress the reflection of the electromagnetic wave at the interface between the air layer and the outermost layer of the laminated sheet. When the electromagnetic wave is perpendicularly incident, the reflectivity R of the electromagnetic wave at the interface between two regions X and Y having different dielectric constants (ε) and magnetic permeabilities (μ) is expressed by Equation (2). When focusing on the interface reflection between the air layer and the outermost surface of the laminated sheet, it is particularly affected by the difference in the ratio of the dielectric constant (ε) and the magnetic permeability (μ) of the air layer and the outermost layer of the laminated sheet. However, since the dielectric constant (ε) and the magnetic permeability (μ) of the air layer are 1, in order to suppress the electromagnetic wave reflection, it is effective to make the ratio of the dielectric constant ε and the magnetic permeability μ of the outermost layer of the laminated sheet close to 1. Specifically, it is preferable to use a resin as a material with a low dielectric constant / low magnetic permeability to make the conductivity and magnetic permeability close to those of the air layer, and to change to a form that does not contain both a conductive material and a magnetic material. The dielectric constant / magnetic permeability is used as an index of insulation / conductivity because in the case of the laminated sheet of the present invention, it is difficult to measure each layer one by one. Therefore, in order to express the insulation / conductivity of each layer, it is preferable to use a surface resistance value that roughly represents the correlation. In the present invention, it is expressed by the values measured using a high resistivity meter and a low resistivity meter manufactured by Mitsubishi Chemical Corporation according to JIS standards. The index of conductivity that does not easily cause surface reflection of electromagnetic waves, that is, the surface resistance value [Ω / □], preferably shows 1.0×10 5 [Ω / □] or more, more preferably 1.0×10 9 [Ω / □] or more, and even more preferably 1.0×10 13 [Ω / □] or more. The method of making the surface resistance value of the outermost surface fall within the above range is not particularly limited, and examples include: a method of reducing or not containing the conductive / magnetic material and the conductive polymer component contained in the layer having the outermost surface. The layer with a surface resistance value showing 1.0×10 5 [Ω / □] or more only needs to be the layer on the electromagnetic wave incident side during installation, and it is sufficient to be arranged on at least one side, but it is more preferably arranged on the outermost surfaces on both sides. In order to make the surface resistance value show 1.0×10 5 [Ω / □] or more, it can be achieved by the following: designing the layer located on the surface layer to have a low addition concentration of the conductive material and / or magnetic material, or designing it not to contain a conductive polymer or additive that shows conductivity as a resin.

[0049]

[0050] Furthermore, μ X and ε X respectively represent the dielectric constant and magnetic permeability of region X, μ Yand ε Y respectively represent the permittivity and magnetic permeability of region Y.

[0051] The laminated sheet of the present invention preferably contains a conductive material in layer A or layer B. The conductive material may contain only one type or may use a plurality of conductive materials in combination.

[0052] The conductive material can be appropriately selected from organic carbon systems with small primary particle sizes and suitable for melt extrusion. Of course, the conductive material is not limited to organic carbon-based materials. In addition, it can also be used in combination with an electromagnetic wave shielding material and a dielectric material mainly composed of inorganic components other than the organic carbon system described later. If only the electromagnetic wave shielding material and the dielectric material mainly composed of inorganic components are used to form a laminated sheet film with an extruder, in order to obtain the electromagnetic wave shielding performance brought by conductivity / magnetism, it is necessary to add the electromagnetic wave shielding material at a high concentration, and there may be problems such as material crushing and device damage due to friction between the device and the metal of the conductive material. Therefore, it is preferred that at least one of the conductive materials is an organic carbon-based material containing carbon as the main component. By the so-called carbon as the main component, among all the elements constituting the conductive material, the molar ratio of carbon is 50 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more, and particularly preferably 95 mol% or more.

[0053] As the organic carbon-based conductive material, for example, carbon blacks (spherical carbon) such as acetylene black, channel black, lamp black, thermal black, Ketjen black, furnace black, etc.; carbon nanotubes such as single-walled nanotubes, multi-walled nanotubes, and stacked cup nanotubes which are cylindrical carbon; flat carbon such as graphite, graphene, etc. In addition, there are also spherical graphite, cylindrical graphite, carbon microcoils, fullerenes, carbon fibers (long fibers, short fibers), etc. Among them, in order to utilize the effect of particle alignment in the plane direction brought by the laminated structure and improve the conductivity of the layer containing the conductive material, it is preferred to use conductive carbon black with an easily developed primary structure (linear structure). In addition, in order not to disrupt the laminated structure and more strongly form a conductive path in the layer direction, it is preferred to use, in addition to carbon black with a structure that can develop in any direction, a combination of a carbon nanotube or flat carbon with a uniform structure and a high aspect ratio. In particular, materials with their size and thickness controlled at the nanoscale are preferred, and it is more preferred to use carbon black, carbon nanotubes, graphene, graphite, etc.

[0054] This is because the following effect of improving the electromagnetic wave shielding property known as the Maxwell-Wagner effect can be obtained: arranging a conductive material with a high aspect ratio (including the formed higher-order structure) in a direction where the long axis of the material is slightly parallel to the surface of the laminated sheet and including it in a resin substrate (especially a thermoplastic resin substrate such as a polyolefin resin, a polyester resin, an acrylic resin, a copolymer resin of vinyl monomers, etc. which is a resin with a low dielectric constant), and in the layer composed of the resin substrate containing the conductive material, sandwiching the resin substrate between the conductive materials. By changing to this form, many microscopic dielectric polarizations are formed at the interface between the layer of the conductive material and the layer of the resin substrate, improving the electromagnetic wave shielding property. Specifically, by utilizing the laminar flow or stretching step brought about by the lamination step, the conductive material contained in the resin substrate showing dielectricity is changed to the following form: arranging these polarizations in a neat and substantially parallel direction to the sheet plane direction and in a form where they are juxtaposed and opposed like a parallel plate capacitor. Thus, when an electromagnetic wave is irradiated and an electric field is applied, many charges are likely to accumulate at the interface between the substrate as a dielectric and the conductive material, and the conductivity within the laminated sheet can be improved. As a result, when an electromagnetic wave is incident, it is blocked by the conductive material, and the electromagnetic wave energy is easily converted into thermal energy. As a result, the shielding property brought about by electromagnetic wave absorption can be improved. As the conductive material used to achieve such a form through processes such as the lamination step and the stretching step, among the materials described previously, it is preferable to use a cylindrical material, a flat material, a carbon nanotube, and carbon black with a high DBP oil absorption amount as materials with a high aspect ratio.

[0055] As the carbon black that can be suitably used in the present invention, the following can be cited: carbon black having a dibutyl phthalate (DBP) oil absorption [mL / 100 g] of 150 or more. The DBP oil absorption [mL / 100 g] is an index indicating the degree of development of the carbon black structure. A material with a large value of this indicates that carbon black particles are easily connected in a straight chain to each other, and thus there are many voids between the structures. Therefore, even with a smaller content, a conductive path can be formed and conductivity can be imparted, so it is preferred. The DBP oil absorption [mL / 100 g] of the carbon black is more preferably 250 or more, and further preferably 350 or more. If the structure of the carbon black is developed and a conductive path is formed, when an electric field is generated by the irradiation of electromagnetic waves, charges will accumulate at the interface between the base material as a dielectric and the conductive material. By converting the electromagnetic wave energy into heat energy using the electromagnetic wave blocker, i.e., the conductive material, a high shielding property brought by electromagnetic wave absorption is exhibited. The upper limit of the DBP oil absorption is not particularly limited. If it is considered that the structure may be damaged when dispersed in the polymer material constituting the conductive material, it is preferably 800 [mL / 100 g] or less. Furthermore, the DBP oil absorption can be measured in accordance with ASTM D 2414-79. As such a conductive spherical carbon, commercially available ones such as acetylene carbon black, furnace black, and Ketjen black can be used.

[0056] Furthermore, as an electromagnetic wave shielding material mainly composed of an inorganic component different from the aforementioned conductive material that can be used in the laminated sheet of the present invention, the following can be used: elemental metals such as silver, copper, iron, nickel, chromium, aluminum, zinc, and tin, and metal oxides, metal nitrides, metal carbides, metal borides, metal oxynitrides, metal hydroxides, metal oxyborides, metal carbonyls, and organometallic coordination compounds of these. In particular, as preferred components, the following can also be used: indium tin oxide (ITO) and indium zinc oxide (IZO) known as transparent conductive metal oxides, and as stainless steel materials and organometallic coordination compounds, iron carbonyl, iron hexacyano, and iron amide can also be used. These inorganic metal-based magnetic materials also follow the same idea as the aforementioned carbon materials, and flat-shaped materials that have been extended are preferably used because the electromagnetic wave shielding property can be further improved in the laminated sheet of the present invention.

[0057] Furthermore, regarding the additives used in the laminated sheet of the present invention, a dielectric material having excellent charge storage ability can also be added. The dielectric material is not a material having the following effect: the effect of blocking the irradiated electromagnetic waves and directly dissipating the energy possessed by the electromagnetic waves. However, as will be described later, in order to shield electromagnetic waves in a specific frequency band, it is preferred to make the real part ε h ’ and the imaginary part ε h”controlled within a specific range. At this time, by using not only the real part ε h ’ of the dielectric constant and the imaginary part ε h ” of the dielectric constant, for a conductive material whose numerical value tends to change together with the added concentration, and also by using a dielectric material that can selectively increase the real part ε h ’ of the dielectric constant, it is possible to control the value of the complex permittivity more highly, and thus it is preferred. Examples of the dielectric material that can be used here include: magnesium oxide, titanium oxide, barium titanate, strontium titanate, calcium titanate, lead zirconate titanate, titanium oxide, iron oxide (ferrite), bismuth ferrite, etc., which have a perovskite structure or a rutile structure. However, titanium oxide, ferrite, barium titanate, etc. are common and exhibit a high dielectric constant, so they are preferred.

[0058] As the electromagnetic wave suppression material used in the laminated sheet of the present invention, it is preferred to use two or more types of materials among the aforementioned organic carbon-based conductive material, the electromagnetic wave shielding material mainly composed of inorganic components, and the dielectric material. This is because when controlling the dielectric constant of the layer showing a high dielectric constant described later to a preferred range where a high electromagnetic wave attenuation amount is shown, by changing the content concentration with a single material alone, the relationship between the real part and the imaginary part of the dielectric constant only shows a linear behavior in the dielectric constant plane, and it becomes difficult to control it within a specific range. Therefore, by using materials showing a linear relationship between the real part and the imaginary part of the dielectric constant different from the above, it becomes possible to two-dimensionally control the real part and the imaginary part of the dielectric constant in the dielectric constant plane, and thus it becomes easier to design a laminated sheet with a higher attenuation amount. At this time, materials with different conductive materials can be used in combination, or an electromagnetic wave shielding material mainly composed of inorganic components or a dielectric material can be used in combination in addition to the conductive materials. In particular, iron oxide, barium titanate, titanium oxide, carbonyl iron, etc. with a high complex dielectric constant can increase the real part without increasing the value of the imaginary part of the complex dielectric constant, and can adjust the dielectric constant more drastically by using it in combination with a carbon material, so it can be preferably used as the second material.

[0059] From the viewpoint of balancing the electromagnetic wave shielding performance and the strength of the laminated sheet itself, when the total components constituting the laminated sheet are set to 100% by mass, the content of these electromagnetic wave shielding materials is preferably 1% by weight or more and less than 15% by weight. Generally speaking, when high conductivity is to be obtained, the content of the conductive material must be increased. If the content of the conductive material is high, high conductivity can be obtained, but on the other hand, the film-forming property / processability will be significantly impaired, and the sheet itself may become fragile. On the contrary, if the content of the conductive material is too small, the effect of electromagnetic wave shielding may sometimes not be obtained sufficiently. Therefore, regarding the content of the conductive material, it is preferably 1% by weight or more and less than 15% by weight. More preferably, it is 1.5% by weight or more and less than 10% by weight, and still more preferably, it is 2% by weight or more and less than 5% by weight. Furthermore, when the laminated sheet contains a plurality of electromagnetic wave suppressing materials, the content of the electromagnetic wave suppressing materials is calculated by adding up all the electromagnetic wave suppressing materials.

[0060] As described above, the conductive material contained in the laminated sheet of the present invention may exist only in either the A layer or the B layer, or may exist in both the A layer and the B layer. When both the A layer and the B layer contain the conductive material and become highly conductive layers, the effect of dielectric polarization cannot be obtained sufficiently at the interface of each layer of the laminated sheet, and the entire laminated sheet will exhibit an effect similar to that of the electromagnetic wave shielding material of a single film, and sometimes a steep electromagnetic wave shielding property at only the desired frequency cannot be obtained. In addition, since the conductivity / dielectric constant of the layer located on the surface layer increases, surface reflection of electromagnetic waves occurs. If the laminated sheet contains the conductive material uniformly throughout, compared with a laminated sheet obtained by making the B layer contain more conductive material, there may be a case where the effect of electromagnetic wave absorption brought about by the conductive material is reduced. Therefore, when the laminated sheet has a repeating unit of A(BA)n, it is preferable that the amount of the conductive material contained in the A layer corresponding to the surface layer is less than the amount of the conductive material contained in the B layer not corresponding to the surface layer. More specifically, it is preferably that the total content of the conductive material contained in the A layer is 1% by weight or less relative to the weight of the entire laminated sheet, and the content of the conductive material contained in the B layer is 1% by weight or more relative to the weight of the entire laminated sheet. Still more preferably, the difference in the content of the conductive material between the A layer and the B layer is large, especially in a form where the A layer does not contain the conductive material and only the B layer contains the conductive material.

[0061] In the laminated sheet of the present invention, in addition to the aforementioned conductive material / magnetic material / dielectric material, dispersants, surface modifiers, lubricants, crosslinking agents, vulcanization accelerators, antioxidants, crystal nucleating agents, flame retardants, light absorbers (ultraviolet absorbers, pigments, heat ray absorbers, etc.), flow modifiers (plasticizers, tackifiers), anti-caking agents, etc. may be contained as needed within the range that does not impair the original characteristics of the laminated sheet. Furthermore, as long as the original characteristics of the laminated sheet are not impaired, these components may be present in any one of the A layer, the B layer, and the layers other than the A layer and the B layer.

[0062] The laminated sheet of the present invention preferably has the aforementioned A layer on at least one of its surfaces. By providing the A layer with low conductivity on the surface layer, it is possible to suppress the reflection effect caused by the B layer with a high dielectric constant, and to enable the electromagnetic wave irradiated onto the laminated sheet to penetrate well into the laminated sheet, and the effect of the laminated sheet as an electromagnetic wave absorbing sheet can be fully exerted. Whether to dispose the A layer only on one side of the surface layer or on both sides can be appropriately selected with reference to the practicality when using the laminated sheet as an electromagnetic wave absorbing material.

[0063] The electromagnetic wave shielding property and frequency band of the laminated sheet of the present invention can be obtained by using the impedance Z shown in Formula (3) and Formula (4). in And the reflection attenuation amount Γ calculated therefrom. In addition, as can be understood from the formula, Z in And Γ depend on the dielectric constant, magnetic permeability, and thickness of the entire sheet. Therefore, in order to achieve high electromagnetic wave shielding performance with a thin film, the product of the real part ε’ of the dielectric constant and the real part μ’ of the magnetic permeability must show a high value. Furthermore, in Formula (3) and Formula (4), Z0 represents the characteristic impedance of the atmosphere, d represents the thickness of the laminated sheet, λ represents the wavelength, μ represents the magnetic permeability of the entire laminated sheet, ε represents the dielectric constant of the entire laminated sheet, and the value of Z0 is 377Ω.

[0064]

[0065]

[0066] The dielectric constant and magnetic permeability of the entire laminated sheet affect the design of the dielectric constants of the A layer and the B layer that are alternately arranged to cause dielectric polarization. Specifically, the difference in the dielectric constants of the A layer and the B layer is large enough, and the real part ε h ’ and the imaginary part ε h”Controlling this is extremely effective for adjusting the electromagnetic wave shielding property. In a region where a high electromagnetic wave shielding property is exhibited for a specific frequency band at a specific sheet thickness, it can be calculated based on Equation (3) and Equation (4). Furthermore, in order for the laminated sheet to exhibit a high electromagnetic wave shielding property, among the A layer and the B layer, the real part ε h ’ and the imaginary part ε h ” preferably satisfy the relational expression of Equation (A) or Equation (B).

[0067] (A) εh” ≥ 1, and 0.17εh’ + 2.3 ≤ εh” ≤ 0.27εh’ + 3.3

[0068] (B) 5 ≥ εh” ≥ 1, and 0.02εh’ + 1 ≤ εh” ≤ 0.07εh’ + 1.9

[0069] By controlling the real part ε h ’ and the imaginary part ε h ” of the dielectric constant of the layer with a relatively high dielectric constant within this range, high electromagnetic wave shielding property can be achieved at a specific frequency even in the case of a thin sheet thickness.

[0070] The real part ε’ of the dielectric constant, the imaginary part ε” described later, and the real part μ’ of the magnetic permeability of the laminated sheet of the present invention can be measured by the method described in the item of “Dielectric Constant Measurement” in the examples. Furthermore, the real part and the imaginary part (ε h ’, ε h ”) of the dielectric constant of each layer can be measured by the above method and the method described in “Calculation of Dielectric Constant of Each Layer” in the examples. Briefly explained, a jig of a waveguide or a lens antenna is used in accordance with the frequency to be measured, and the reflection / transmission characteristics of the electromagnetic wave when the electromagnetic wave emitted from the electromagnetic wave generating device is incident on the specimen provided in the waveguide or between the lens antennas can be calculated according to the known S-parameter method. Furthermore, as the measuring device and the calculation software, there is no particular limitation as long as they can measure and calculate. For example, the devices described in the examples and the calculation software attached to these devices can be used. In this case, the real term ε’ and the imaginary term ε” of the dielectric constant can be obtained by reading the values automatically calculated by the calculation software.

[0071] Controlling the real part ε h ’ and the imaginary part ε hExamples of methods for satisfying the relational expressions of the above formula (A) or the above formula (B) include: using carbon black with a DBP oil absorption value within the following range as a conductive material, or using barium titanate, iron oxide ferrite, or titanium oxide as a dielectric material, or using iron carbonyl as a magnetic material, and increasing the dielectric constant using graphite, graphene, etc., which are conductive materials with a high aspect ratio. In particular, in order to satisfy formula (A), it is required to increase the real part ε h of the dielectric constant together with the imaginary part ε h ". Therefore, it is preferable to use carbon black. In order to satisfy formula (B), the imaginary part ε h of the dielectric constant is required to be low. Therefore, it can be achieved by using at least one of dielectric materials such as barium titanate, ferrite, and titanium oxide, and conductive materials with a high aspect ratio such as graphite and graphene, either alone or in combination. Further, it can also be achieved by changing to the following forms: using the stretching method described below to reduce the layer thickness of each layer, or increasing the number of layers of the multilayer laminate through a feed module with slits, and dispersing / orienting the conductive material and / or magnetic material in the plane direction of the sheet.

[0072] In the laminated sheet of the present invention, preferably, the ratio RL / fΔ of the half-value width fΔ [GHz] of the reflection attenuation peak having the maximum reflection attenuation amount at the peak to the reflection attenuation amount RL [dB] at the peak of the reflection attenuation peak having the maximum reflection attenuation amount is 5.0 or more. RL / fΔ is an index indicating the steepness of the reflection attenuation peak. By setting RL / fΔ within such a range, when it is installed in electronic devices, communication devices, etc., it can become a material that only shields the desired electromagnetic wave region. RL / fΔ can be increased by reducing the unevenness of the layer thickness of layer A and / or layer B, or the combination of resins, using a material with a high DBP oil absorption or a high aspect ratio as the conductive material, increasing the number of laminations, etc., thereby increasing the difference in dielectric constants between the highly conductive layer and the lowly conductive layer. These ratios RL / fΔ are more preferably 10.0 or more, and further preferably 20.0 or more. When RL / fΔ at the maximum reflection attenuation peak is less than 5, it means that, like conventional materials, it is a material that shields electromagnetic waves in a wide frequency band, and in the case of attenuating only electromagnetic waves of a specific frequency, there may be electromagnetic wave shielding in an undesired frequency band. The upper limit value of RL / fΔ at the maximum reflection attenuation peak is not particularly limited, but when the steepness is very high, sometimes a slight change in the laminated sheet thickness and a change in the concentration of the conductive material may cause the peak position to shift sensitively, and there is a possibility of not obtaining the desired electromagnetic wave shielding property. Therefore, RL / fΔ at the maximum reflection attenuation peak preferably shows less than 200. The half-value width also depends on the frequency of the reflection attenuation peak having the maximum reflection attenuation amount at the peak, but a laminated sheet of the present invention with a smaller half-value width is preferred as it can cut only a specific frequency. Specifically, the half-value width fΔ [GHz] is preferably 10.0 or less, more preferably 5.0 or less, and further preferably 2.0 or less.

[0073] Furthermore, in the laminated sheet of the present invention, the frequency of the peak of the reflection attenuation peak having the maximum reflection attenuation amount at the peak is determined by the dielectric constant / permeability of the layer showing conductivity. Therefore, it can be controlled not only by the type and content of the conductive material, but also by the thicknesses of the alternately laminated A layers and B layers having different conductivities. Electronic devices, communication devices, and transportation vehicles have different frequencies to be attenuated and frequencies not to be attenuated depending on their uses. Since the laminated sheet of the present invention can easily control the frequency to be electromagnetically shielded, it can be suitably used in electronic devices, communication devices, and transportation vehicles.

[0074] In the laminated sheet of the present invention, when the average value of the layer thickness of layer B is set to tB [mm] and the standard deviation is set to tBσ [mm], the coefficient of variation tBσ / tB is preferably 0.3 or less. As described above, layer A is a constituent located on the surface layer. When it is a layer with a surface resistance value higher than that of layer B, layer B showing conductivity will become the main layer responsible for electromagnetic wave shielding brought about by electromagnetic wave absorption. However, when the thicknesses of these layers vary among the layers, the dielectric constant of each layer is different, resulting in a variation in the frequency of electromagnetic waves for which shielding can be obtained. If the thickness of layer B showing conductivity is made uniform and the coefficient of variation tBσ / tB falls within the above range, since layers with a fixed dielectric constant value are laminated, the electromagnetic wave shielding property can exhibit steepness, and frequency selectivity can be obtained at a high electromagnetic wave attenuation amount, so it is preferable. The coefficient of variation tBσ / tB showing the variation in layer thickness is preferably 0.2 or less, more preferably 0.1 or less. When it is a laminated sheet made of a thermoplastic resin, instead of using a mixer to increase the number of laminations, the coefficient of variation can be reduced by using a slit-type feeding module. There is no particular limitation on the lower limit of the coefficient of variation tBσ / tB, but in view of the productivity of the laminated sheet, it is practical to be 0.01 or more.

[0075] In addition, although there is no limitation on the layer thickness of layer A of the laminated sheet of the present invention, if it becomes a layer thinner than the distance where the conductive material contained in layer B exists, the effect of macroscopic dielectric polarization between layer A showing dielectricity and layer B showing conductivity cannot be obtained, and there may be a case where the electromagnetic wave loss is reduced. Therefore, when the average thickness of layer A is set to tA [mm], it is designed that tA ≥ tB, which is preferable as it can surely separate the adjacent layer Bs sufficiently.

[0076] Regarding a preferred form of the present invention, an electromagnetic wave shield having the aforementioned laminated sheet and a reflector can be cited. The reflector is a plate-like material having a function of reflecting electromagnetic waves. By combining it with the surface opposite to the electromagnetic wave incident surface of the laminated sheet, it will form a form in which electromagnetic waves travel back and forth in the laminated sheet, so the electromagnetic wave absorption efficiency can be improved. On the other hand, when the reflector is arranged in the front, the following form is also possible: a form in which a certain degree of electromagnetic waves are reflected on the surface of the reflector and a part of the penetrated electromagnetic waves are steeply shielded in the laminated sheet. In order to make full use of the electromagnetic wave absorption characteristics of the laminated sheet of the present invention, the former configuration is more preferable.

[0077] The reflector only needs to be able to reflect electromagnetic waves, and there is no particular limitation on the constituent material. Examples of the constituent material include metals such as aluminum, copper, iron, and gold, alloys such as stainless steel, and carbon films. The reflector only needs to contain a metal or an alloy, or contain carbon, and there is no limitation on the shape and thickness. The shape should be adapted to the material to be applied and can be a plate shape such as a plane, a curved surface, or a hemisphere.

[0078] Examples of the reflector include: a plate-shaped reflector containing metal, alloy, or carbon; a laminated reflector having a film made of metal, alloy, or carbon formed on the surface of a polymer film, sheet, plate, etc.; a composite reflector in which metal, alloy, or carbon is dispersed inside a polymer film, sheet, plate, etc.; a composite reflector containing a network made of metal or alloy inside a polymer film, sheet, plate, etc. In addition, for the present invention, when the support, frame, etc. in each application contain metal, alloy, carbon, etc., they can also be used as they are as a reflector.

[0079] In a preferred embodiment of the present invention, examples of electronic devices and communication devices having the aforementioned laminated sheet or the aforementioned electromagnetic wave shield include: preventing virtual images caused by electromagnetic waves used in 4G / 5G communication, wireless LAN, anti-collision (ITS) radar, etc., reducing the radiation of unnecessary electromagnetic waves from electronic devices provided inside the frames of computers, mobile phones, radios, medical devices, vehicle bumpers, etc., and preventing malfunction of devices caused by radiation from adjacent devices. In addition, as long as it is an electronic device or a communication device that uses frequencies in the GHz band, the laminated sheet of the present invention can be mounted and used without being limited to the above.

[0080] Furthermore, in a preferred embodiment of the present invention, examples include: vehicles, aircraft, ships, and other mobile mechanisms, buildings, tunnels, guardrails, highways, bridges, towers, and other structures, as well as communication facilities such as telecommunications and telephones, which have the aforementioned laminated sheet or the aforementioned electromagnetic wave shield. Regarding the method of applying the laminated sheet of the present invention, methods such as directly attaching it via an adhesive or attaching it to structures such as floors, ceilings, walls, and columns via other sheets, shielding plates, panels, etc. can be used. In addition, it can also be used as a wall material and window material for a shielding room to prevent the influence of electromagnetic wave blockage / noise from the outside.

[0081] Next, a preferred manufacturing method of the alternating lamination unit of the laminated sheet of the present invention will be described below. It goes without saying that the present invention is not to be construed as being limited to the examples described below.

[0082] An example of the manufacturing method of the alternating laminate unit will be described below, in the case where a base polymer such as rubber or thermoplastic elastomer is used. A predetermined amount of a conductive material is blended in the base polymer, and it is kneaded using a known device such as a kneader, Banbury mixer, mill mixer, rolling mill, jet mill, ball mill, etc. and contained therein to produce a polymer containing the conductive material. A single base polymer or the produced polymer containing the conductive material is respectively rolled and melt-extruded by batch press to form a sheet having a desired thickness. Thereafter, the sheet corresponding to the A layer and the sheet corresponding to the B layer produced are laminated, and the desired laminated alternating laminate unit is obtained by stamping or laminating. The welding temperature also depends on the resin used, but is preferably in the temperature range of 150°C to 400°C, more preferably 250 to 380°C.

[0083] An example of the manufacturing method of the alternating laminate unit will be described below in the case where a thermoplastic resin showing flexibility that can be preferably used in the present invention is used. After kneading a thermoplastic resin prepared in the form of pellets and a predetermined amount of a conductive material using a twin-screw extruder, it is extruded in a sausage shape, cooled in a water tank, and then cut by a chip cutter to form a master pellet containing the conductive material. At this time, the conductive material can be dry-mixed with the resin and then metered and fed through a feed hopper, or can be side-fed into the molten resin from an arbitrary position of the extruder using a side feeder. It can be appropriately selected according to the specific gravity and shape of the conductive material that can be used.

[0084] Each thermoplastic resin constituting the A layer and the B layer is dried in hot air or under vacuum and then supplied to its respective extruder. Each resin heated and melted above the melting point in the extruder is discharged with a uniform discharge amount using a gear pump or the like, and foreign matters and modified resins are removed through a filter or the like. These resins pass through a multi-layer lamination device capable of laminating to a desired number of laminations, are formed into a target shape by a die head, and are discharged in a sheet shape. The sheet discharged from the die head is extruded onto a cooling body such as a casting drum, and a cast sheet is obtained by being cooled and solidified. At this time, since the cast sheet itself shows conductivity, a method of blowing air from a slit-shaped, dot-shaped, or surface-shaped device to closely contact the cooling body such as a casting drum and rapidly cool and solidify, or a method of using a pinch roll to closely contact the cooling body and rapidly cool and solidify is preferably used.

[0085] As a multi-layer laminating device, as described above, a multi-manifold die, a feed module, a static mixer, etc. can be used. However, especially in order to efficiently obtain the multi-layer laminated structure of the present invention, a feed module having fine slits is preferably used. If such a feed module is used, since the device will not be extremely enlarged, the amount of foreign matter generated due to thermal deterioration is small, and when the number of laminated layers is extremely large, high-precision lamination becomes possible. In addition, compared with the prior art, the lamination accuracy in the width direction is also remarkably improved. In addition, for this device, since the thickness of each layer can be adjusted in the shape (length, width) of the slit, it becomes possible to achieve an arbitrary layer thickness. In addition, the following method can also be suitably used: after a laminate is formed by a feed module, the number of laminated layers is doubled by laminating via a static mixer to increase the number of laminated layers. In this case, since the layer thicknesses of the laminated laminates will be exactly the same, it is suitable for the idea of the present invention that preferably has a uniform layer thickness.

[0086] The obtained cast sheet can be subsequently biaxially stretched in the longitudinal direction and the width direction as needed. The stretching can be carried out by successive biaxial stretching or simultaneous biaxial stretching. In addition, it can be further re-stretched in the longitudinal direction and / or the width direction.

[0087] First, the case of successive biaxial stretching will be described. Here, the stretching in the longitudinal direction means stretching to give molecular orientation in the longitudinal direction to the sheet, which is usually carried out by the circumferential speed difference of rollers, and can be carried out in one stage or in multiple stages using multiple pairs of rollers. The stretching ratio varies depending on the type of resin, but is usually preferably 1.1 to 15 times, and particularly preferably 1.5 to 4 times. In addition, as the stretching temperature, it is preferably set in the range of the glass transition temperature of the resin constituting the alternating lamination unit to the glass transition temperature + 100°C.

[0088] For the alternating lamination unit stretched in the longitudinal direction obtained in this way, after surface treatment such as corona treatment, flame treatment, plasma treatment, etc. as needed, a primer layer can be formed to improve the adhesion to the film laminated on the upper part. In the in-line coating step, the primer layer can be coated on one side, or can be coated on both sides simultaneously, or can be coated on the two sides one by one in sequence.

[0089] The so-called stretching in the width direction is used to give the sheet a orientation in the width direction. Usually, a tenter is used to transfer the sheet while clamping both ends of the sheet with clips, so as to elongate it in the width direction. As the stretching ratio, it varies depending on the type of resin, but usually it is preferably 1.1 to 15 times, and particularly preferably 1.5 to 6 times. In addition, as the stretching temperature, it is preferably the glass transition temperature of the resin constituting the alternating laminate unit to the glass transition temperature + 120 °C. After the biaxially stretched alternating laminate unit is heat-treated at a temperature above the stretching temperature and below the melting point in the tenter and slowly cooled uniformly, it is cooled to room temperature and wound up. In addition, if necessary, in order to impart a low orientation angle and thermal dimensional stability to the sheet, relaxation treatment or the like may be used in combination in the longitudinal direction and / or the width direction during slow cooling from the heat treatment.

[0090] Next, the case of simultaneous biaxial stretching will be described. In the case of simultaneous biaxial stretching, for the obtained cast sheet, after surface treatment such as corona treatment, flame treatment, or plasma treatment is applied as needed, functions such as slipperiness, adhesiveness, and antistatic property can also be imparted by on-line coating. In the step of on-line coating, the adhesive layer can be coated on one side of the alternating laminate unit, or can be coated on both sides of the alternating laminate unit simultaneously or one by one in sequence.

[0091] Then, the cast sheet is guided to a simultaneous biaxial tenter, and while clamping both ends of the sheet with clips and transferring it, stretching is performed simultaneously in the longitudinal direction and the width direction. For simultaneous biaxial stretching machines, there are pantograph methods, screw methods, drive motor methods, and linear motor methods, but preferably the drive motor method or the linear motor method that can arbitrarily change the stretching ratio and can perform relaxation treatment at any place. The stretching ratio varies depending on the type of resin. Usually, the area ratio is preferably 2 to 50 times, and particularly preferably 4 to 20 times. The stretching speed can be the same speed, or stretching can be performed at different speeds in the longitudinal direction and the width direction. In addition, in terms of the stretching temperature, it is preferably the glass transition temperature of the resin constituting the alternating laminate unit to the glass transition temperature + 120 °C.

[0092] The simultaneously biaxially stretched alternating laminated unit thus obtained is preferably heat-treated at a temperature above the stretching temperature and below the melting point in a tenter in order to impart planarity and dimensional stability. During this heat treatment, in order to suppress the distribution of the main orientation axis in the width direction, it is preferable to perform a relaxation treatment in the longitudinal direction instantaneously before and / or immediately after entering the heat treatment zone. After being heat-treated in this way, it is slowly cooled uniformly and then 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 during slow cooling from the heat treatment. A relaxation treatment is performed in the longitudinal direction instantaneously before and / or immediately after entering the heat treatment zone.

[0093] In order to obtain the desired electromagnetic wave shielding property, the produced alternating laminated units may be bonded to each other via a bonding sheet, an adhesive sheet, a double-sided tape, etc., either the same alternating laminated units or alternating laminated units having different thicknesses and compositions.

[0094] Furthermore, for the purpose of improving electromagnetic wave penetrability or causing electromagnetic wave reflection, etc., layers having different dielectric constants may be laminated on the outermost surface of the alternating laminated unit. At this time, a coating layer containing a material showing suitable conductivity / magnetism may be coated, or different resin layers / mesh layers, etc. may be laminated via an adhesive sheet, etc., and it is also possible to laminate a resin / metal layer by the following methods: sputtering (plane or rotary magnetron sputtering, etc.), evaporation (electron beam evaporation, etc.), chemical vapor deposition, metalorganic chemical vapor deposition, plasma-enhanced / supported / activated chemical vapor deposition, ion sputtering, etc., which are used as thin film metal coating techniques.

[0095] Hereinafter, the present invention will be described according to examples, but the present invention is not construed as being limited to these examples. Each characteristic is measured by the following methods.

[0096] (Measurement method of characteristics and evaluation method of effects)

[0097] The measurement method of characteristics and the evaluation method of effects in the present invention are as follows.

[0098] (1) Layer thickness, number of laminations, lamination structure

[0099] The layer composition of the laminated sheet is obtained by observing a sample of the cross-section cut using a microtome through differential interference microscopy or transmission electron microscopy (TEM), in accordance with the layer thickness of each layer constituting the laminated sheet. In the former case, more specifically, when the thickness of each layer constituting the laminated sheet is 1 μm or more, a differential interference microscope "DMLBHC" manufactured by Leica is used to observe the cross-section of the laminated sheet under the condition of a magnification of 1000 times (eyepiece 10 times, objective lens 100 times), a cross-section photograph is taken, and the layer composition and the thickness of each layer are measured. The length measurement is performed using particle size analysis software "Macview" (manufactured by MOUNTECH), and the measurement of the layer thickness is to measure the vertical distance between layer interfaces where the contrast can be clearly distinguished. Data at five arbitrary points are measured, and the average value of the thickness of each layer is used as the measured data. The major axis length of the particles is to measure a total of 100 points of the longest distance of the higher-order structure formed by the particles confirmed in the image, and the average data is used. For the latter transmission electron microscopy (TEM) observation, a transmission electron microscope model H-7100FA (manufactured by Hitachi, Ltd.) is used to observe the cross-section of the laminated sheet under the condition of an acceleration voltage of 75 kV, a cross-section photograph is taken, and the layer composition and the thickness of each layer are measured. Furthermore, in some cases, a staining technique using RuO4 or OsO4, etc. is used to obtain high contrast. In addition, according to the thickness of the thinnest layer (thin film layer) among all the layers introduced into one image, when the thickness of the thin film layer is less than 50 nm, the observation is carried out at a magnification of 100,000 times, when the thickness of the thin film layer is 50 nm or more and less than 500 nm, the observation is carried out at a magnification of 40,000 times, and when it is 500 nm or more, the observation is carried out at a magnification of 10,000 times, and the layer thickness, the number of laminations, and the lamination structure are determined. In addition, among the obtained images, the thickness of each layer of the B layer in a specific cross-section is read, and the average value and the standard deviation of the layer thickness are calculated. The average value and the standard deviation of the layer thickness of the B layer in five different cross-sections are calculated, and the average of the five calculated values is adopted as the average value tB [mm] and the standard deviation tBσ [mm].

[0100] (2) Measurement of reflection attenuation

[0101] In accordance with the measurement frequency band, the measurement unit is changed as described below for measurement. In addition, based on the obtained results, a frequency-reflection attenuation curve is plotted with the reflection attenuation on the vertical axis and the frequency on the horizontal axis.

[0102] (2-1) Frequency band from 1 GHz to 40 GHz

[0103] Using a vector network analyzer (E8361A) manufactured by Agilent Technologies, Inc., the reflection attenuation of the laminated sheet was measured. In the frequency band of 0.5 GHz to 18 GHz, measurement was performed using a circular coaxial waveguide with an outer diameter of φ7 mm and an inner diameter of φ3.04 mm. In the frequency band of 18 to 26.5 GHz, measurement was performed using a rectangular waveguide of 4.32 mm × 10.67 mm. In the frequency band of 26.5 to 40 GHz, measurement was performed using a rectangular waveguide with an internal shape of 3.56 mm × 7.11 mm. The frequency stride during measurement was set so that 200 frequencies could be measured in each frequency band. A 3-mm aluminum metal plate was placed on the back of the laminated sheet used as the specimen, resulting in the following state: the electromagnetic wave incident in the state without the electromagnetic wave absorption caused by the laminated sheet was in a state of total reflection. The S 11 parameter value of 11 was used to analyze the reflection attenuation peak. This S

[0104] (2-2) Frequency band of 40 to 110 GHz

[0105] For a laminated sheet with a side length of 150 mm, an aluminum metal plate was attached to the back to produce a measurement sample. Using a lens antenna type oblique incidence type electromagnetic wave absorber (electromagnetic wave absorbing material) / reflection attenuation measurement device LAF-26.5B manufactured by KEYCOM Co., Ltd., electromagnetic waves were irradiated at an oblique incidence of 15° in accordance with JIS R 1679, and the reflection attenuation 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). Furthermore, although the value in the frequency band of 33 to 40 GHz can also be obtained by this measurement method, the reflection attenuation in the frequency band above 33 GHz and below 40 GHz was measured using the measurement data in (2-1).

[0106] (3) Dielectric constant measurement

[0107] For the laminated sheet, the measurement unit / measurement method was changed as follows for each measurement frequency for analysis.

[0108] (3-1) Frequency band of 1 GHz to 40 GHz

[0109] An Agilent Technologies, Inc. vector network analyzer (E8361A) was used. Separately, for the frequency band from 0.5 GHz to 18 GHz, a circular coaxial waveguide with an outer diameter of φ7 mm and an inner diameter of φ3.04 mm was used; for the frequency band from 18 to 26.5 GHz, a rectangular waveguide with dimensions of 4.32 mm × 10.67 mm was used; and for the frequency band from 26.5 to 40 GHz, a rectangular waveguide with an inner shape of 3.56 mm × 7.11 mm was used. The laminated sheet sample was punched and vertically inserted into the interior of each of the aforementioned waveguides for measurement. The frequency step width during measurement was set to enable 200 frequency measurements in each frequency band. The complex permittivity was analyzed using the attached analysis software N1500A - 001 of the device.

[0110] (3 - 2) 40 - 110 GHz Frequency Band

[0111] A laminated sheet of 150 mm square was used. Using a relative permittivity / attenuation measurement device LAF - 26.5A of the lens antenna method that uses the frequency variation method manufactured by KEYCOM Co., Ltd., the complex permittivity was measured for each frequency band of 33 - 50 GHz (WR - 22), 50 - 75 GHz (WR - 15), and 75 - 110 GHz (WR - 10). Furthermore, although the values for 33 - 40 GHz were also measured by this measurement method, the complex permittivity in the frequency band above 33 GHz and below 40 GHz was obtained using the measurement data in (3 - 1).

[0112] (4) Surface Resistance Value Measurement

[0113] (4 - 1) High Resistance Value Measurement

[0114] For regions with high resistance values (1.0×10 6 ~1.0×10 13 [Ω / □]), a high resistivity meter Hiresta - UP (MCP - HT450) manufactured by Mitsubishi Chemical Corporation was used for measurement. For the surface of the laminated sheet cut into a 10 cm square, the URS probe (MCP - HTP14) was pressed, and the resistance value was measured in accordance with JIS K6911 (1995). The measurement was carried out 5 times while changing the measurement position, and the arithmetic mean of the 5 obtained measurement values was used.

[0115] In addition, when measuring the surface resistance value of the inner layer, the thickness of the outermost layer confirmed by transmission electron microscopy was utilized, and after grinding the surface using a grinding device, the probe was pressed for measurement.

[0116] (4 - 2) Low Resistance Value Measurement

[0117] For the region with a low resistance value (1.0×10 6 ~1.0×10 -1 [Ω / □]), measurement is performed using the low resistivity meter Loresta-EP (MCP-T360) manufactured by Mitsubishi Chemical Corporation. Press the ASP probe (MCP-TP03P) against the surface of the laminated sheet that has been cut into a 10 cm square, and measure the resistance value according to JIS K 7194. While changing the measurement position, measurements are made with a sample number of 5, and the arithmetic mean of the 5 obtained measurement values is used.

[0118] (5) DBP oil absorption

[0119] The laminated sheet is dissolved in a solvent that can dissolve the resin of the substrate. For the carbon-based conductive particles extracted / separated, measurement is performed using the absorptometer C type manufactured by Brabender Corporation according to ASTM D2414-79. While kneading the carbon-based conductive particles put into the mixer at a rotation speed of 125 [min -1 , DBP is added dropwise at a dropping rate of 4 [mL / min], and the DBP oil absorption analyzed from the obtained viscosity curve is read.

[0120] (6) Calculation of the dielectric constant of each layer

[0121] A macro software is made and used to calculate the impedance in the case where the structure of the laminated sheet is replaced with an equivalent circuit by substituting the values of the dielectric constant, magnetic permeability, and layer thickness of the A layer and the B layer. By substituting the obtained impedance Z in into the non-reflection condition formula and formula (4) based on the reflection attenuation amount, and making the calculation of the reflection attenuation amount Γ a macro that is continuously calculated across a fixed frequency band. Then, in such a way that it is consistent with the reflection attenuation spectrum measured by the method described in item (2), the dielectric constant and magnetic permeability of each layer are set, and the dielectric constant / magnetic permeability when the reflection attenuation spectrum is the most approximate is read to determine the dielectric constant / magnetic permeability of each layer. Furthermore, when it is difficult to calculate the dielectric constant, a single-layer sheet is made with the same composition as the layer showing a relatively high dielectric constant in the examples, and by using the frequency change method of the aforementioned vector network analyzer, the frequency showing the minimum value of the penetration attenuation amount is determined. Since this minimum value is an integer multiple of 1 / 2 of the effective wavelength penetrating the sheet thickness, the dielectric constant is obtained. Even with the auxiliary software (SFW05) of the dielectric constant measurement system (Model No. DPS10) using the frequency change method of KEYCOM Company for free space measurement, the same value can be determined.

[0122] [Example]

[0123] (Example 1)

[0124] Stamping was carried out using 100 parts by weight of an ethylene - propylene - terpolymer rubber manufactured by Mitsui Chemicals, Inc. to produce a sheet A with a thickness of 0.5 mm and a size of 200 mm square. On the other hand, to 90 parts by weight of an ethylene - propylene - terpolymer rubber manufactured by Mitsui Chemicals, 10 parts by weight of a carbon black (spherical carbon) conductive material with a primary particle size of 40 nm and a DBP oil absorption of 360 was blended, and it was kneaded using a two - roll mill. After preparing a rubber containing the conductive material, the rubber containing the conductive material was stamped to produce a sheet B with a thickness of 0.5 mm and a size of 200 mm square. By thermocompression - bonding these rubber - formed sheets in the order of sheet A, sheet B, sheet A, sheet B, sheet A at 250 °C to form 5 - layer overlap, a laminated sheet with a thickness of 2.5 mm laminated in 5 layers was obtained. Using this laminated sheet for reflection attenuation measurement, as a result, the reflection attenuation peak with the largest attenuation at the peak frequency of 30 GHz was obtained, and the reflection attenuation at this peak was 12 dB, and its half - value width was 2 GHz.

[0125] (Comparative Example 1)

[0126] To 96 parts by weight of an ethylene - propylene - terpolymer rubber manufactured by Mitsui Chemicals, Inc., 4 parts by weight of the spherical carbon conductive material with a primary particle size of 39.5 nm and a DBP oil absorption of 360 used in Example 1 was blended, and it was kneaded using a two - roll mill. After preparing a rubber containing the conductive material, the rubber containing the conductive material was stamped and formed into a sheet - like shape with a thickness of 2.5 mm and a size of 200 mm square to produce a single - film sheet.

[0127] Reflection attenuation measurement was carried out. As a result, compared with Example 1, the frequency band of the peak of the reflection attenuation peak with the largest attenuation at the peak was the same as that of Example 1, but the reflection attenuation at the reflection attenuation peak was 7 dB, and its half - value width reached 5 GHz and the frequency band was wide, which was a weak reflection attenuation peak.

[0128] (Example 2)

[0129] For 90 parts by weight of a homopolypropylene resin showing a melt flow rate of 30, 10 parts by weight of the spherical carbon - based conductive material used in Example 1 was blended, and it was kneaded using a twin - screw extruder with the conductive material fed from the side to produce conductive masterbatch pellets.

[0130] A homopolypropylene resin with a melt flow rate of 30 was used as the resin for the A-layer side, and the aforementioned conductive masterbatch pellets were used as the resin for the B-layer side. The prepared polypropylene resin and conductive masterbatch pellets were respectively fed into a twin-screw extruder and melt-kneaded at 270 °C in their respective twin-screw extruders. The kneading condition in each twin-screw extruder was to set the screw rotation speed relative to the discharge amount to 0.7. Then, the extruded resins were merged in 9 multi-manifold type feed modules to form an alternating laminate unit with a thickness of 1 mm, which was alternately laminated in 9 layers in the thickness direction with a lamination ratio of 1.0. The obtained alternating laminate unit was composed of a total of 5 A-layers and a total of 4 B-layers containing conductive materials, and it was confirmed by transmission electron microscopy that they were alternately laminated in the thickness direction. In addition, the layer thickness became larger as it approached the center in the thickness direction, and the difference in the thickness of each layer was large.

[0131] Two produced alternating laminate units were adhered via an adhesive sheet with a thickness of 25 μm to form a laminated sheet with a total of 19 layers including the adhesive layer. Reflection attenuation measurement was carried out, and as a result, there was a reflection attenuation peak with the largest attenuation amount at the peak frequency of 26 GHz, and the reflection attenuation amount at this peak was 16 dB, and the half-value width was 2 GHz.

[0132] (Comparative Example 2)

[0133] Relative to 95 parts by weight of the homopolypropylene resin with a melt flow rate of 30 used in Example 2, 5 parts by weight of the spherical carbon conductive material used in Example 2 was contained to produce conductive masterbatch pellets, and these conductive masterbatch pellets were respectively fed into the twin-screw extruder used in Example 2 as the resins for the A-layer and B-layer, and an alternating laminate unit of the A-layer and B-layer was produced under the same conditions as in Example 2 to produce a pseudo single film sheet with a thickness of 1 mm in which the A-layer and B-layer were composed of the same material (denoted as composed only of the A-layer in the table). Reflection attenuation measurement was carried out, and as a result, there was a reflection attenuation peak with the largest attenuation amount at the peak frequency of 65 GHz, and the reflection attenuation amount at this peak was 11 dB, and the half-value width was 10 GHz.

[0134] (Comparative Example 3)

[0135] Two pseudo single film sheets produced in Comparative Example 2 (denoted as composed only of the A-layer in the table) were adhered via an adhesive sheet with a thickness of 25 μm, thereby forming a laminated sheet with a total of 3 layers including 2 pseudo single film sheets and 1 adhesive layer. Reflection attenuation measurement was carried out, and as a result, there was a reflection attenuation peak with the largest attenuation amount at the peak frequency of 36 GHz, and the reflection attenuation amount at this peak was 13 dB, and the half-value width was 5 GHz.

[0136] (Example 3)

[0137] In Example 2, except that a feed module having 31 slits was used as the feed module and 31 layers were alternately laminated in the thickness direction with a lamination ratio of 1.0, the same procedure as in Example 2 was carried out to obtain an alternately laminated unit with a thickness of 1 mm. The obtained alternately laminated unit was confirmed by a transmission electron microscope to be alternately laminated in the thickness direction to form 16 layers of A layer and 15 layers of B layer containing a conductive material. In addition, with respect to the laminated thickness, compared with the case where the manifold type feed module of Example 2 was used, the coefficient of variation of the layer thickness of the B layer became smaller, but due to the influence of the thixotropy of the resin, it became an alternately laminated unit with slightly disordered lamination.

[0138] Two produced alternately laminated units were bonded via an adhesive sheet with a thickness of 25 μm to obtain a laminated sheet having a total of 63 layers including the adhesive layer. Reflection attenuation measurement was carried out, and as a result, due to the effect of the increased number of layers, the attenuation amount at the peak was 20 dB, which was the reflection attenuation amount at the peak of the maximum reflection attenuation peak, and the half-value width was 2.1 GHz.

[0139] (Example 4)

[0140] In Example 3, after the confluence of the feed module having 31 layers of slits, the number of laminated layers was increased to 61 layers by means of a static mixer that doubled the number of laminations in one thickness direction layer. Except for this, the same procedure as in Example 3 was carried out to obtain an alternately laminated unit with a thickness of 1 mm. The obtained alternately laminated unit was confirmed by a transmission electron microscope to be a unit alternately laminated in the thickness direction with 31 layers of A layer and 30 layers of B layer. At the confluence part of the 31-layer laminates, the thickness of the A layer became twice as thick. The coefficient of variation of the laminated thickness of the B layer was at the same level as that of Example 3, and it became an alternately laminated unit with more disordered lamination than Example 3.

[0141] Two produced alternately laminated units were bonded via an adhesive sheet with a thickness of 25 μm, whereby a laminated sheet having a total of 123 layers including the adhesive layer was obtained. When reflection attenuation measurement was carried out, the attenuation amount at the peak became 24 dB higher than that of Example 3, which was the reflection attenuation amount at the peak of the maximum reflection attenuation peak.

[0142] (Example 5)

[0143] As the resin constituting layer B, 10 parts by weight of the carbon-based conductive material used in Example 1 was blended with 90 parts by weight of polyethylene terephthalate resin having a melting point of 254°C and an intrinsic viscosity IV of 0.63. Using this conductive material, a conductive masterbatch pellet was produced by kneading with a twin-screw extruder fed from the side. As the resin constituting layer A, polyethylene terephthalate resin having a melting point of 254°C and an intrinsic viscosity IV of 0.8 was used, and as the resin constituting layer B, the aforementioned conductive masterbatch pellet was used. The prepared resins were respectively fed into a twin-screw extruder and melt-kneaded at 280°C in their respective twin-screw extruders. Then, the resins extruded were merged in a feed block having 31 slits, and through a single-stage static mixer, an alternating laminated unit with a thickness of 1 mm and 61 layers alternately laminated in the thickness direction with a lamination ratio of 1.0 was obtained. Compared with Example 4, by using a resin that does not easily exhibit thixotropy, an alternating laminated unit with almost no lamination disorder was obtained.

[0144] Two produced alternating laminated units were adhered via an adhesive sheet with a thickness of 25 μm, thereby obtaining a laminated sheet having a total of 123 layers including the adhesive layer. The reflection attenuation amount was measured, and as a result, there was a reflection attenuation peak with the largest attenuation amount at the peak frequency of 27 GHz, and in addition, a steeper peak than that in Example 4 was successfully confirmed.

[0145] (Example 6)

[0146] In Example 5, as the resin for layer A, a conductive masterbatch pellet obtained by blending 1 part by weight of the spherical carbon conductive material used in Example 1 with 99 parts by weight of polyethylene terephthalate resin having a melting point of 254°C and an intrinsic viscosity IV of 0.8 was used, and as the resin for layer B, a conductive masterbatch pellet obtained by blending 9 parts by weight of spherical carbon conductive material with 91 parts by weight of polyethylene terephthalate resin having a melting point of 254°C and a viscosity IV of 0.63 was used. Except for this, the same operations as in Example 5 were carried out to obtain a laminated sheet having a total of 123 layers. The reflection attenuation amount was measured, and as a result, since the conductivity of layer A was not so high, there was a reflection attenuation peak with the largest attenuation amount at the peak frequency of 26 GHz, and this peak was relatively steep.

[0147] (Example 7)

[0148] In Example 5, a conductive masterbatch pellet obtained by blending 10 parts by weight of a spherical carbon conductive material having a primary particle size of 8 nm and a DBP oil absorption of 95 mL / 100 g as a conductive material with respect to 90 parts by weight of a polyethylene terephthalate resin having a melting point of 254°C and an intrinsic viscosity IV of 0.8 was used as the resin for the A layer. And a conductive masterbatch pellet obtained by blending 5 parts by weight of the spherical carbon conductive material used in Example 1 with respect to 95 parts by weight of a polyethylene terephthalate resin having a melting point of 254°C and a viscosity IV of 0.63 was used as the resin for the B layer. Except for this, it was carried out in the same manner as in Example 5 to obtain a laminated sheet having a total of 123 layers. When the reflection attenuation amount was measured, the attenuation amount of the peak having a frequency of 25 GHz at the peak was the largest reflection attenuation peak, and this peak was a peak with a small steepness.

[0149] (Example 8)

[0150] In Example 5, except that the content of the conductive material was set to 5 parts by weight, the same resin and manufacturing method as in Example 5 were used to obtain a laminated sheet having a total of 123 layers. Due to the small content, the conductivity decreased, and the frequency band of the reflection attenuation peak having the largest attenuation amount at the peak also shifted to the high-frequency band. However, due to the laminated structure, a steep shielding property was obtained. This laminated sheet had a reflection attenuation peak having the largest attenuation amount at the peak with a frequency of 55 GHz, and the reflection attenuation amount at the peak of this reflection attenuation peak was 18 dB.

[0151] (Example 9)

[0152] In Example 5, except that a carbon-based conductive material having a primary particle size of 35 nm and a DBP oil absorption of 500 mL / 100 g was used as the conductive material and the blending amount of the conductive material was set to 5 parts by weight, the same resin and manufacturing method as in Example 5 were used to obtain a laminated sheet having a total of 123 layers. By changing to a conductive material that can form a structure more, on the one hand, the conductivity was improved, but on the other hand, the thixotropy was strong and the disorder of the laminated thickness became large. This laminated sheet had a reflection attenuation peak having the largest attenuation amount at the peak with a frequency of 11 GHz, and the reflection attenuation amount of this reflection attenuation peak showed a peak with an attenuation amount as high as 25 dB.

[0153] (Example 10)

[0154] Except that in Example 9, the blending amount of the conductive material was set to 3.6 parts by weight, the same resin and manufacturing method as in Example 9 were used to obtain a laminated sheet having a total of 123 layers. By reducing the blending amount of the conductive material, thixotropy did not occur and laminated disorder did not occur, and a laminated sheet with a more uniform layer thickness was obtained. The obtained reflection attenuation peak is as shown in Table 2.

[0155] (Example 11)

[0156] In Example 5, except that a carbon-based conductive material with a primary particle size of 44 nm and a DBP oil absorption of 220 mL / 100 g was used as the conductive material once, and the blending amount of the conductive material was set to 15 parts by weight, the same resin and manufacturing method as in Example 5 were used to obtain a laminated sheet with a total of 123 layers. It is a conductive material that is not easy to form a structure. By containing it at a high concentration, the conductivity is improved, but the thixotropy caused by the increase in particle concentration is strong, and a laminated sheet with chaotic lamination can be seen. This laminated sheet has a reflection attenuation peak with the largest attenuation amount at the peak with a frequency of 38 GHz, and the reflection attenuation amount at the peak of this reflection attenuation peak is 23 dB. It is a laminated sheet with a steep peak with a high RL / fΔ.

[0157] (Comparative Example 4)

[0158] In Example 5, except that a spherical carbon conductive material with a primary particle size of 8 nm and a DBP oil absorption of 95 mL / 100 g was used as the conductive material once, and the blending amount of the conductive material was set to 15 parts by weight, the same procedure as in Example 5 was carried out to obtain a laminated sheet with a total of 123 layers. The conductive material contained is a carbon material used to exhibit blackness, and almost no conductivity can be obtained within the layer. In addition, the reflection attenuation amount was measured. As a result, it has a reflection attenuation peak with the largest attenuation amount at the peak with a frequency of 48 GHz, and the reflection attenuation amount at this peak is 4.5 dB, and the half-value width is 15 GHz. The reflection attenuation amount is so small, and it is a material in which the attenuation of electromagnetic waves does not show steepness at all.

[0159] (Example 12)

[0160] In Example 5, except that the resin used for layer A and the resin used for layer B were reversed to obtain a 123-layer laminated sheet with a repeating structure of B(AB)n, the same manufacturing method as in Example 5 was used to obtain the laminated sheet. Since the conductive layer B is arranged on the outermost surface, the reflection of electromagnetic waves generated on the surface of the laminated sheet occurs, and the effect of absorption inside becomes weaker. The magnitude of the reflection attenuation amount of the peak of the electromagnetic wave reflection attenuation amount showing the maximum reflection attenuation amount also becomes smaller, but it is a material with a relatively steep peak. Furthermore, in this example, the layer with lower conductivity is set as layer B, and the layer with higher conductivity is set as layer A for display.

[0161] (Example 13)

[0162] In Example 5, 5 parts by weight of the carbon-based conductive material used in Example 5 and 2 parts by weight of graphene powder material with an average particle size of 5 μm were blended as the conductive materials, and these conductive materials were kneaded by a twin-screw extruder with side feeding to produce a conductive masterbatch pellet. Except for using the aforementioned masterbatch pellet as the resin for layer B, the same resin and manufacturing method as in Example 5 were used to obtain a laminated sheet with a total of 123 layers. By containing flat graphene powder, the conductivity of this laminated sheet in the layer containing graphene powder in the direction parallel to the sheet surface is extremely improved, and it has a reflection attenuation peak with the largest attenuation amount at the peak with a frequency of 8 GHz. The reflection attenuation amount at the peak of the reflection attenuation peak is 36 dB, and it is a laminated sheet with a steep reflection attenuation peak with a large RL / fΔ.

[0163] (Example 14)

[0164] 5 parts by weight of the carbon-based conductive material used in Example 5 and 3 parts by weight of carbon nanotube material with an average diameter of 1.5 nm and an average length of 500 nm were blended as the conductive materials, and these conductive materials were kneaded by a twin-screw extruder with side feeding to produce a conductive masterbatch pellet. Except for using the aforementioned masterbatch pellet as the resin for layer B, the same resin and manufacturing method as in Example 5 were used to obtain a laminated sheet with a total of 123 layers. By using a carbon nanotube material with a high aspect ratio, the conductivity of this laminated sheet in the layer containing carbon nanotubes in the direction parallel to the sheet surface is improved, and it has a reflection attenuation peak with the largest attenuation amount at the peak with a frequency of 6 GHz, and the reflection attenuation amount at the peak of this reflection attenuation peak is 26 dB, obtaining a laminated sheet with a steep reflection attenuation peak with a large RL / fΔ.

[0165] (Example 15)

[0166] In Example 13, the produced alternating laminated unit was stretched 1.4 times at 90 °C in the long side direction and 1.5 times at 100 °C in the width direction to obtain a laminated sheet with a thickness of 500 μm. Through transmission electron microscope observation, a preferred tendency was obtained that the graphene powder was more arranged in the direction parallel to the sheet surface compared with Example 13. Four pieces of the obtained laminated sheets were bonded via an adhesive, thereby becoming the target laminated sheet. Through transmission electron microscope observation, both spherical carbon and graphene powder obtained a preferred tendency of being more arranged in the direction parallel to the sheet surface. It became a design that was more likely to cause dielectric polarization, and compared with Example 13, it became a sheet with both a high attenuation amount and steepness.

[0167] (Example 16)

[0168] In Example 13, an alternating stacking unit was prepared in the same manner as in Example 13 except that a feed module with 101 slits whose pressure loss was adjusted by slit length / width was used as a stacking device and the coefficient of variation of the thickness of each layer was 0.18. The two obtained stacked sheets were bonded together via an adhesive to obtain the target stacked sheet. A stacked sheet having a peak frequency of 23 GHz with the maximum attenuation at the peak, and a peak reflection attenuation of 30 dB at the peak of the reflection attenuation peak, and having a steep reflection attenuation peak with a large RL / fΔ was obtained.

[0169] (Example 17)

[0170] In Example 13, an alternating stacking unit was produced in the same manner as in Example 13 except that a feed module having 201 slits whose pressure loss was adjusted by slit length / width was used as a stacking device. Two alternating stacking units produced were bonded together via an adhesive sheet having a thickness of 25 μm, thereby obtaining a stacking sheet having a total of 403 layers including an adhesive layer. When the thickness of each layer was observed using a transmission electron microscope, it was confirmed that the coefficient of variation of the thickness of each layer was 0.12. The stacking sheet was a stacking sheet having the characteristics described in Table 2.

[0171] (Example 18)

[0172] In Example 13, an alternating stacking unit was produced in the same manner as in Example 13 except that a feed module having 501 slits whose pressure loss was adjusted by slit length / width was used as a stacking device. Two alternating stacking units produced were bonded together via an adhesive sheet having a thickness of 25 μm, thereby obtaining a stacking sheet having a total of 1003 layers including an adhesive layer. When the thickness of each layer was observed using a transmission electron microscope, it was confirmed that the coefficient of variation of the thickness of each layer was 0.08. A stacking sheet having the characteristics described in Table 2 was obtained as a stacking sheet.

[0173] (Example 19)

[0174] As a conductive material, 10 parts by weight of the graphene powder material with an average particle size of 5 μm used in Example 13 was mixed and kneaded through a twin-screw extruder that feeds these conductive materials from the side to produce a conductive masterbatch. Except for using the aforementioned masterbatch as the resin for the B layer, a laminated sheet with a total of 123 layers was obtained using the same resin and manufacturing method as in Example 13. Due to the high conductivity of graphene, a steep peak was observed at 800 MHz, showing a high reflection attenuation.

[0175] (Example 20)

[0176] To 95 parts by weight of an isophthalic acid copolybutylene terephthalate resin with a melting point of 210 °C, 5 parts by weight of a carbon-based conductive material having a primary particle size of 40 nm and a DBP oil absorption of 400 mL / 100 g was blended, and the conductive material was kneaded using a twin-screw extruder fed from the side to produce a conductive masterbatch pellet.

[0177] A polyethylene terephthalate resin having an intrinsic viscosity IV of 0.8 at a melting point of 254 °C was used as the resin for the A layer side, and the aforementioned conductive masterbatch pellet was used as the resin for the B layer side. The prepared polyethylene terephthalate resin and conductive resin were respectively fed into a twin-screw extruder and melt-kneaded at 270 °C in their respective twin-screw extruders. The kneading conditions in their respective twin-screw extruders were such that the screw speed relative to the discharge amount was set to 0.7. Then, the extruded resins were made to converge in 11 multi-manifold type feed modules, and a molten sheet having 11 layers alternately laminated in the thickness direction with a lamination ratio of 1.0 was discharged from the die. The discharged molten sheet was cooled and solidified on a casting drum, and by adjusting the drum rotation speed, a laminated sheet with a thickness of 1 mm was obtained. The obtained laminated sheet was composed of a total of 6 layers of A layer and a total of 5 layers of B layer containing a conductive material, and it was confirmed by microscopic observation that they were alternately laminated in the thickness direction. The electromagnetic wave attenuation performance of the laminated sheet is shown in Table 4.

[0178] (Comparative Example 5)

[0179] To 97.5 parts by weight of an isophthalic acid copolybutylene terephthalate resin with a melting point of 210 °C, 2.5 parts by weight of conductive spherical carbon particles having a primary particle size of 40 nm and a DBP oil absorption of 400 mL / 100 g was blended, and the conductive material was kneaded using a twin-screw extruder fed from the side to produce a conductive masterbatch pellet. This masterbatch pellet was discharged from the die to form a sheet shape and cooled and solidified on a casting drum, and by adjusting the drum rotation speed, a single film sheet with a thickness of 1 mm was thus produced. The performance of the obtained single film sheet is shown in Table 3, and no special electromagnetic wave shielding property exceeding the volume rule level was obtained.

[0180] (Comparative Example 6)

[0181] In Comparative Example 5, the drum rotation speed was increased to obtain a single film sheet with a thickness of 0.5 mm. Two pieces of this single film sheet were adhered via an acrylic adhesive sheet with a thickness of 0.05 mm to obtain a three-layer laminated sheet having a layer containing conductive particles on the outermost layer (denoted as composed only of A layer in the table). The performance of the obtained single film sheet is shown in Table 3, and the three-layer laminate did not obtain sufficient electromagnetic wave shielding property exceeding the volume rule level.

[0182] (Example 21)

[0183] In Example 20, two resins were made to merge using a feed module having 51 slits, and a molten sheet having 51 layers alternately laminated in the thickness direction with a lamination ratio of 1.0 was discharged from the die. Other than this, it was carried out in the same manner as in Example 20, and a laminated sheet having a thickness of 1 mm was obtained. The obtained laminated sheet was configured to have a total of 26 layers of A layer and a total of 25 layers of B layer containing a conductive material, and it was confirmed by microscopic observation that they were alternately laminated in the thickness direction. As shown in Table 4, by increasing the number of laminated layers and using a slit-type feed module, a result was obtained in which the reflection attenuation amount was increased at the reflection attenuation peak.

[0184] (Example 22)

[0185] In Example 20, two resins were made to merge in a feed module having 101 slits, and a molten sheet having 101 layers alternately laminated in the thickness direction with a lamination ratio of 1.0 was discharged from the die. Other than this, it was carried out in the same manner as in Example 20, and a laminated sheet having a thickness of 1 mm was obtained. The obtained laminated sheet was configured to have a total of 51 layers of A layer and a total of 50 layers of B layer containing a conductive material, and it was confirmed by microscopic observation that they were alternately laminated in the thickness direction. As shown in Table 4, by further increasing the number of laminated layers, a result was obtained in which the reflection attenuation amount was further increased at the reflection attenuation peak.

[0186] (Example 23)

[0187] In Example 22, the rotation speed of the roller was increased to obtain an alternately laminated unit having a thickness of 0.33 mm. Three pieces of this alternately laminated unit were bonded via an acrylic adhesive sheet having a thickness of 0.05 mm, whereby a laminated sheet having a total of 305 layers and a thickness of approximately 1.0 mm was obtained. The properties of the obtained laminated sheet are shown in Table 4, and the effect due to the increase in the number of laminated layers was obtained.

[0188] (Example 24)

[0189] In Example 20, two resins were made to merge in a feed module having 301 slits, and a molten sheet having 301 layers alternately laminated in the thickness direction with a lamination ratio of 1.0 was discharged from the die. Other than this, it was carried out in the same manner as in Example 20, and a laminated sheet having a thickness of 1 mm was obtained. The obtained laminated sheet was configured to have a total of 151 layers of A layer and a total of 150 layers of B layer containing a conductive material, and it was confirmed by microscopic observation that they were alternately laminated in the thickness direction. Compared with Example 23, by using a slit-type feed module with a larger number of layers, a laminated sheet was obtained in which the layer thickness unevenness became less and a steeper electromagnetic wave shielding property was exhibited.

[0190] (Example 25)

[0191] In Example 22, a laminated sheet with a thickness of 0.5 mm was obtained by increasing the rotational speed of the drum. By thinning the film, as recorded in Table 4, a laminated sheet was obtained as follows: a laminated sheet in which the frequency band of the reflection attenuation peak with the largest attenuation amount at the peak was shifted to a higher frequency while maintaining the magnitude of the reflection attenuation amount, compared to the laminated sheet of Example 22.

[0192] (Example 26)

[0193] To 90 parts by weight of isophthalic acid copolyester terephthalate resin with a melting point of 210°C, 10 parts by weight of a carbon-based conductive material used in Example 11 with a primary particle size of 44 nm and a DBP oil absorption of 220 mL / 100 g was blended, and the conductive masterbatch pellets were prepared by kneading using a twin-screw extruder in which the conductive material was fed from the side.

[0194] A polyethylene terephthalate resin showing a viscosity IV of 0.8 at a melting point of 254°C was used as the resin for the A layer side, and the aforementioned conductive masterbatch pellets were used as the resin for the B layer side. The two resins were merged in the same feed module with 101 slits as in Example 22, and a molten sheet with 101 layers alternately laminated in the thickness direction with a lamination ratio of 1.0 was discharged from the die. The discharged molten sheet was cooled and solidified on a casting drum, and a laminated sheet with a thickness of 1 mm was obtained by adjusting the drum rotational speed. By adding a material with low conductivity at a high concentration, as recorded in Table 4, a laminated sheet showing good electromagnetic wave cut-off property in the high-frequency band was obtained.

[0195] (Example 27)

[0196] In Example 26, barium titanate as a dielectric material was used as a dielectric constant adjuster for the conductive masterbatch pellets. Specifically, to 80 parts by weight of isophthalic acid copolyester terephthalate resin with a melting point of 210°C, 10 parts by weight of a carbon-based conductive material with a primary particle size of 44 nm and a DBP oil absorption of 220 mL / 100 g and 20 parts by weight of barium titanate with an average particle size of 0.5 μm from Sakai Chemical Industry Co., Ltd. were blended to prepare the conductive masterbatch pellets. Except for this, the same procedure as in Example 26 was carried out, and a laminated sheet with a thickness of 1 mm was obtained. As shown in Table 4, by adjusting the dielectric constant, a laminated sheet with more excellent electromagnetic wave shielding property was obtained.

[0197] (Example 28)

[0198] 95 parts by weight of an isophthalic acid copolymerized polybutylene terephthalate resin having a melting point of 210°C was blended with 5 parts by weight of a carbon-based conductive material having a primary particle size of 35 nm and a DBP oil absorption of 500 mL / 100 g used in Example 9, and the conductive material was kneaded using a twin-screw extruder fed from the side to produce conductive masterbatch pellets.

[0199] A polyethylene terephthalate resin having a viscosity IV of 0.8 at a melting point of 254°C was used as the resin for the A-layer side, and the aforementioned conductive masterbatch pellets were used as the resin for the B-layer side. The two resins were made to converge in the same feed block with 101 slits as in Example 22, and a molten sheet having 101 layers alternately laminated in the thickness direction with a lamination ratio of 1.0 was extruded from the die. The extruded molten sheet was cooled and solidified on a casting drum, and a laminated sheet having a thickness of 1 mm was obtained by adjusting the drum rotation speed. As shown in Table 5, it is a material with a high imaginary part of the dielectric constant, but a laminated sheet showing high electromagnetic wave shielding properties was obtained.

[0200] (Example 29)

[0201] In Example 28, barium titanate, which is a dielectric material, was used as a dielectric constant adjuster for the conductive masterbatch pellets. Specifically, 85 parts by weight of an isophthalic acid copolymerized polybutylene terephthalate resin having a melting point of 210°C was blended with 5 parts by weight of a carbon-based conductive material having a primary particle size of 35 nm and a DBP oil absorption of 500 mL / 100 g, and 20 parts by weight of barium titanate with an average particle size of 0.5 μm from Sakai Chemical Industry Co., Ltd. to form conductive masterbatch pellets. Other than that, it was carried out in the same manner as in Example 28 to obtain a laminated sheet having a thickness of 1 mm. As shown in Table 5, by adjusting the dielectric constant, a laminated sheet with extremely excellent electromagnetic wave shielding properties was obtained.

[0202] (Example 30)

[0203] In Example 28, as a dielectric constant adjuster for the conductive masterbatch pellets, graphene powder material with an average particle size of 5 μm, which was used as a carbon-based conductive material in Example 13, was used. Specifically, 95 parts by weight of an isophthalic acid copolymerized polybutylene terephthalate resin having a melting point of 210°C was blended with 2 parts by weight of a carbon-based conductive material having a primary particle size of 35 nm and a DBP oil absorption of 500 mL / 100 g, and 3 parts by weight of the aforementioned graphene powder material with an average particle size of 5 μm to form conductive masterbatch pellets. Other than that, it was carried out in the same manner as in Example 28 to obtain a laminated sheet having a thickness of 1 mm. As shown in Table 5, by adjusting the dielectric constant, a laminated sheet showing excellent electromagnetic wave shielding properties compared to Example 28 was obtained.

[0204] (Example 31)

[0205] In Example 22, except that a 6-nylon resin having a melting point of 222°C was used as the resin for the A-layer side, the same procedure as in Example 22 was carried out to obtain a laminated sheet having a thickness of 1 mm. By using a resin having a high dielectric constant as the raw material for forming the A-layer, as shown in Table 5, the reflection attenuation amount decreased somewhat. It is considered that the balance of the dielectric constants of the A-layer and the B-layer did not reach the level of Example 22.

[0206] (Example 32)

[0207] In Example 22, except that a conductive masterbatch pellet obtained by blending 2 parts by weight of a carbon-based conductive material having a primary particle size of 35 nm and a DBP oil absorption of 500 mL / 100 g used in Example 9 with a polyethylene terephthalate resin having a viscosity IV of 0.65 at a melting point of 254°C was used as the resin for the A-layer side, the same procedure as in Example 22 was carried out to obtain a laminated sheet having a thickness of 1 mm. As shown in Table 5, the attenuation amount decreased in the same manner as in Example 31, and as a result, the frequency band of the reflection attenuation peak having the largest attenuation amount at the peak shifted to the high-frequency side.

[0208] (Example 33)

[0209] In Example 22, after the obtained molten sheet was cooled and solidified on a casting drum, a roll group adjusted to a temperature of 85°C was used, and the sheet was stretched 2-fold in the sheet transfer direction by the difference in the circumferential speeds of the rolls to obtain a stretched laminated sheet having a thickness of 0.5 mm. By undergoing the stretching process, the effect of dispersing / orienting the carbon-based conductive material added to the B-layer in the plane direction was obtained, and the dielectric constant increased, and a laminated sheet having the properties shown in Table 5 was obtained.

[0210] (Example 34)

[0211] In Example 22, after the obtained molten sheet was cooled and solidified on a casting drum, a roll group adjusted to a temperature of 85°C was used, and the sheet was stretched 3-fold in the sheet transfer direction by the difference in the circumferential speeds of the rolls and then rapidly cooled. Thereafter, the sheet stretched in the transfer direction was continuously guided to a tenter, and while holding both ends of the sheet with clips and transferring it, the sheet was stretched 3.3-fold in the width direction in a room controlled at 120°C to obtain an alternating laminated unit having a thickness of 0.166 mm. Three obtained alternating laminated units were laminated via an acrylic adhesive sheet having a thickness of 0.025 mm to obtain a laminated sheet having a total of 305 layers and a thickness of about 0.5 mm. The properties of the obtained laminated sheet are as described in Table 5, and a laminated sheet having excellent electromagnetic wave shielding properties exceeding the volume law was obtained.

[0212] (Example 35)

[0213] By subjecting the molten sheet obtained in Example 30 to the stretching process described in Example 34, an alternating laminated sheet with a thickness of 0.166 mm was obtained. Three pieces of the obtained alternating laminated units were bonded via an acrylic adhesive sheet with a thickness of 0.025 mm, whereby a laminated sheet with a total of 305 layers and a thickness of approximately 0.5 mm was obtained. By the effect of the dispersed arrangement within the flat carbon plane, a laminated sheet with excellent electromagnetic wave shielding properties exceeding the concept of the volume law was obtained in the same manner as in Example 34.

[0214]

[0215]

[0216]

[0217]

[0218]

[0219] Industrial Applicability

[0220] The laminated sheet of the present invention, by including a unit in which a layer with high conductivity and a layer with low conductivity are alternately laminated, can achieve a high electromagnetic wave attenuation amount even when the conductive material is contained at a low concentration and the film is thin, which is difficult to achieve for conventional single films or sheets with a low number of laminated layers. As a preferred form, since it can steeply and strongly shield only electromagnetic waves of a specific frequency, it can prevent malfunction of devices using electromagnetic waves in a similar frequency band, and prevent information leakage in large-capacity information communication caused by high-frequency electromagnetic waves. Specifically, it can be suitably used in: electronic devices, communication devices using communication technologies with electromagnetic waves in the GHz frequency band, or vehicles used as mobile mechanisms equipped with these, or transportation means including all infrastructure for traffic control.

[0221] Explanation of Reference Numerals

[0222] 1: Reflection attenuation peak

[0223] 2: Reflection attenuation amount at the peak (reflection attenuation amount RL) of the reflection attenuation peak with the maximum attenuation amount at the peak

[0224] 3: Half-value width of the reflection attenuation peak with the maximum attenuation amount at the peak.

Claims

1. A laminated sheet, characterized in that, It includes an alternating laminated unit formed by alternately laminating a total of five or more layers of two layers with different conductivities. The layer with lower conductivity among the two layers with different conductivities is called layer A, and the layer with higher conductivity is called layer B. When the higher surface resistance value among the surface resistance values of layer A and layer B is set as α and the lower surface resistance value is set as β, α / β is 1.1 or more, where the units of both α and β are Ω / □. Only layer B contains a conductive material. The reflection attenuation amount RL of the laminated sheet is 5.0 dB or more. The reflection attenuation amount RL is the reflection attenuation amount at the peak of the reflection attenuation peak with the largest reflection attenuation amount when a frequency-reflection attenuation curve is obtained by plotting the laminated sheet with the reflection attenuation amount as the vertical axis and the frequency as the horizontal axis. Moreover, the real part εh’ and the imaginary part εh” of the complex dielectric constant of layer B satisfy the following formula (A) or formula (B). (A): εh”≥1, and 0.17εh’ + 2.3 ≤ εh” ≤ 0.27εh’ + 3.3 (B): 5≥εh”≥1, and 0.02εh’ + 1 ≤ εh” ≤ 0.07εh’ + 1.9 Here, the units of both εh’ and εh” are F / m.

2. For the laminated sheet according to claim 1, when the reflection attenuation amount at the peak of the reflection attenuation peak with the largest reflection attenuation amount is set as RL, the frequency corresponding to this peak is set as f, and the thickness of the laminated sheet is set as t, RL / (t×f) is 0.2 or more and 15 or less, where the unit of RL is dB, the unit of f is GHz, and the unit of t is mm.

3. For the laminated sheet according to claim 1 or 2, the reflection attenuation peak with the largest attenuation amount exists in the frequency band of 1 to 100 GHz.

4. The laminated sheet according to claim 1 or 2, wherein the surface resistance value of the outermost surface on at least one side of the laminated sheet is 1.0×10 5 Ω / sq or more.

5. For the laminated sheet according to claim 1 or 2, when the average value of the layer thickness of layer B is set as tB and the standard deviation is set as tBσ, the coefficient of variation tBσ / tB is 0.3 or less, where the unit of tB is mm and the unit of tBσ is mm.

6. For the laminated sheet according to claim 1 or 2, the conductive material is a material with carbon as the main component.

7. For the laminated sheet according to claim 6, the material with carbon as the main component is carbon black.

8. For the laminated sheet according to claim 7, the dibutyl phthalate (DBP) oil absorption amount of the carbon black is 150 mL / 100 g or more.

9. For the laminated sheet according to claim 7 or 8, in addition to containing the carbon black, it also contains a conductive material other than spherical carbon.

10. For the laminated sheet according to claim 1 or 2, relative to the weight of the entire laminated sheet, it contains 1 wt% or more and less than 15 wt% of the conductive material.

11. For the laminated sheet according to claim 1 or 2, both layer A and layer B have a thermoplastic resin as the main component.

12. For the laminated sheet according to claim 1 or 2, the ratio RL / fΔ of the half-value width fΔ of the reflection attenuation peak with the largest electromagnetic wave attenuation amount at the peak to the maximum attenuation amount RL is 5.0 or more. The unit of the half-value width fΔ is GHz. The maximum attenuation amount RL is the electromagnetic wave attenuation amount at the peak of the reflection attenuation peak with the maximum electromagnetic wave attenuation amount at the peak, and the unit is dB.

13. An electromagnetic wave shield includes the laminated sheet and the reflector according to claims 1 to 12.

14. An electromagnetic wave related device, characterized in that, It is equivalent to any one of electronic devices, communication devices, and devices used in vehicles, and has the laminated sheet according to any one of claims 1 to 12.

15. An electromagnetic wave related device, characterized in that, It is equivalent to any one of electronic devices, communication devices, and devices used in vehicles, and has the electromagnetic wave shield according to claim 13.

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