Metal laminates and electromagnetic shields

Abstract

The present invention provides a lightweight metal laminate that, when applied as an electromagnetic shield, exhibits excellent magnetic field shielding characteristics in the low-frequency range of 1 to 100 MHz. [Solution] The metal laminate according to this disclosure comprises a ferromagnetic metal foil and n (n is a natural number) conductive metal foils arranged laminated with the ferromagnetic metal foil in the thickness direction of the metal laminate, wherein the conductive metal foils satisfy the electrical resistivity, mass per unit area, density, and thickness of formula (1) described in the specification.

Description

[Technical Field]

[0001] This disclosure relates to a metal laminate and an electromagnetic shield using a metal laminate. [Background technology]

[0002] The electrification of power sources has expanded the range of applications for motors and inverters. However, motors and inverters generate electromagnetic waves during operation. Furthermore, these electromagnetic waves can become noise for electronic devices used in the vicinity, potentially causing unintended behavior in those devices. Therefore, there is a growing need for technologies that shield against such electromagnetic waves and reduce their impact on electronic devices.

[0003] To date, electromagnetic shielding bodies that block electromagnetic waves have been proposed in Japanese Patent Publication No. 2005-150130 (Patent Document 1), Japanese Patent Publication No. 2008-300801 (Patent Document 2), and Japanese Patent Publication No. 2013-214567 (Patent Document 3).

[0004] The electromagnetic wave shield disclosed in Patent Document 1 is an electromagnetic steel sheet having an electromagnetic wave absorbing effect, wherein the maximum DC relative permeability in at least one direction within the plane is 3000 or more, and a coating containing ferromagnetic powder at a volume ratio of 30% or more is formed on one or both sides thereof. Patent Document 1 discloses that this electromagnetic wave shield allows for easy magnetic shielding and electromagnetic wave shielding.

[0005] Patent Document 2 discloses an electromagnetic wave shielding body, which is a surface-treated metal material having a coating on at least a part of the surface of a metal or plated metal in which linear continuum containing fibrous magnetic metal with a diameter of 20 μm or less, or particulate magnetic metal with a diameter of 20 μm or less, is arranged in a row, with a density of 3 to 20 linear continuum containing fibrous magnetic metal or particulate magnetic metal per 10 mm width. Patent Document 2 discloses that this electromagnetic wave shielding body can provide a metal plate with excellent electromagnetic wave shielding properties at joints, gaps, and openings, and that by using it in an electronic equipment housing, it can effectively shield not only from radiated noise of 30 MHz to 1 GHz required by the international standard (CISPR), but also from radiated noise up to 10 GHz that is expected to occur in the future as the operating frequency increases.

[0006] Patent Document 3 discloses an electromagnetic wave shielding body, which is a resin-coated metal plate whose surface is covered with a resin film. The resin film contains flattened metal powder having an average particle length of 5 μm or more in its major axis and an average aspect ratio of 5 or more, as well as barium titanate. Patent Document 3 discloses that this electromagnetic wave shielding body exhibits excellent electromagnetic wave absorption, and also possesses good processability and conductivity as needed, making it particularly useful as a component material in electronic devices. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2005-150130 [Patent Document 2] Japanese Patent Publication No. 2008-300801 [Patent Document 3] Japanese Patent Publication No. 2013-214567 [Overview of the project] [Problems that the invention aims to solve]

[0008] Here, motors, inverters and the like generate electromagnetic waves with a frequency of about 1 to 100 MHz. In addition, it may be difficult to effectively shield magnetic fields in the low frequency range of 1 to 100 MHz. Hereinafter, in this specification, being able to effectively shield a magnetic field in the low frequency range of 1 to 100 MHz is referred to as "excellent magnetic field shielding properties in the low frequency range". That is, an electromagnetic wave shielding body having such excellent magnetic field shielding properties in the low frequency range has been demanded. However, the above Patent Documents 1 to 3 do not discuss the magnetic field shielding properties in the low frequency range.

[0009] Incidentally, in transport equipment represented by drones equipped with motors, inverters and the like in particular, weight reduction is strongly demanded. Therefore, further weight reduction has been required for metal laminates that are expected to be applied to electromagnetic wave shielding bodies with enhanced magnetic field shielding properties in the low frequency range. However, the above Patent Documents 1 to 3 do not discuss weight reduction of metal laminates applicable to electromagnetic wave shielding bodies.

[0010] An object of the present disclosure is to provide a metal laminate that is lightweight and has excellent magnetic field shielding properties in the low frequency range of 1 to 100 MHz when applied as an electromagnetic wave shielding body, and an electromagnetic wave shielding body using the metal laminate. [Means for Solving the Problems]

[0011] A metal laminate according to the present disclosure is comprising a ferromagnetic metal foil body, and n (n is a natural number) conductive metal foil bodies arranged to be laminated with the ferromagnetic metal foil body in the thickness direction of the metal laminate, the conductive metal foil body satisfies formula (1) in terms of electrical resistivity, mass per unit area, density, and thickness. [Mathematical Formula] Here, k in formula (1) is a natural number equal to or less than n, and ρ in formula (1) kThe electrical resistivity of the k-th conductive metal foil is substituted into the following value in units of Ω·m: k The mass per unit area of ​​the k-th conductive metal foil is in units of g / m 2 It is substituted, d k The density of the k-th conductive metal foil is in units of g / m³. 3 Substituted with, t k The thickness of the k-th conductive metal foil is substituted into the variable t in units of m, and the total thickness of the conductive metal foil is substituted into the variable t in units of m.

[0012] The electromagnetic shielding body described herein is Includes the above-mentioned metal laminate. [Effects of the Invention]

[0013] The metal laminate according to this disclosure is lightweight, yet when applied as an electromagnetic shield, it has excellent magnetic field shielding characteristics in the low-frequency range of 1 to 100 MHz. The electromagnetic shield according to this disclosure has excellent magnetic field shielding characteristics in the low-frequency range of 1 to 100 MHz and is lightweight. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a schematic diagram showing an example of a metal laminate according to this embodiment. [Figure 2] Figure 2 is a schematic diagram showing another example of the metal laminate according to this embodiment, as shown in Figure 1. [Figure 3] Figure 3 is a schematic diagram showing another example of the metal laminate according to this embodiment, as shown in Figures 1 and 2. [Figure 4] Figure 4 is a schematic diagram showing another example of the metal laminate according to this embodiment, as shown in Figures 1 to 3. [Figure 5] Figure 5 is a schematic diagram showing another example of the metal laminate according to this embodiment, as shown in Figures 1 to 4. [Figure 6] Figure 6 is a schematic diagram showing another example of the metal laminate according to this embodiment, as shown in Figures 1 to 5. [Figure 7]Figure 7 is a schematic diagram showing another example of the metal laminate according to this embodiment, as shown in Figures 1 to 6. [Figure 8] Figure 8 is a schematic diagram showing another example of the metal laminate according to this embodiment, as shown in Figures 1 to 7. [Modes for carrying out the invention]

[0015] The inventors conducted various studies on a metal laminate that is lightweight yet possesses excellent magnetic field shielding characteristics in the low-frequency range of 1 to 100 MHz when applied as an electromagnetic wave shield. As a result, the following findings were obtained.

[0016] The inventors initially investigated metal laminates having excellent magnetic field shielding characteristics in the low-frequency range of 1 to 100 MHz, focusing on the type of metal used. When attempting to shield electromagnetic waves in the low-frequency range, a method of laminating a ferromagnetic material with high magnetic permeability and a good conductor with low electrical resistivity is effective. Therefore, the inventors formed a metal laminate by laminating a ferromagnetic metal foil made of a ferromagnetic material and a conductive metal foil made of a good conductor, and evaluated the magnetic field shielding characteristics of this metal laminate. As a result, it was found that simply laminating a ferromagnetic metal foil and a conductive metal foil sometimes did not yield excellent magnetic field shielding characteristics in the low-frequency range of 1 to 100 MHz. Therefore, the inventors investigated various methods to improve the magnetic field shielding characteristics in the low-frequency range of 1 to 100 MHz in a metal laminate made by laminating a ferromagnetic metal foil and a conductive metal foil. As a result, the inventors obtained the following findings.

[0017] To improve magnetic field shielding characteristics, increasing the thickness of the metal foil itself is an effective method. Increasing the thickness of the metal foil enhances its ability to absorb and / or attenuate magnetic fields, resulting in superior magnetic field shielding characteristics. However, in metal laminates using thick metal foil, the weight of the laminate increases as the weight of the metal foil increases. Therefore, when seeking a metal laminate that achieves both excellent magnetic field shielding characteristics in the low-frequency range and lightweight construction, increasing the thickness of the metal foil is undesirable.

[0018] On the other hand, detailed studies by the present inventors have revealed that by forming irregularities on a metal foil, particularly a conductive metal foil, and increasing its apparent thickness, it is possible to improve the magnetic field shielding characteristics in the low-frequency range while suppressing an increase in weight. First, the formation of irregularities on a conductive metal foil will be explained in detail using the drawings.

[0019] Figure 1 is a schematic diagram showing an example of a metal laminate according to this embodiment. Referring to Figure 1, the metal laminate 1 according to this embodiment comprises a ferromagnetic metal foil 10 and a conductive metal foil 20 that is laminated with the ferromagnetic metal foil 10 in the thickness direction of the metal laminate 1. Here, the conductive metal foil 20 deforms in the left-right direction of Figure 1 to form irregularities. In other words, in the metal laminate 1 according to this embodiment, the apparent thickness increases while the thickness of the conductive metal foil 20 remains thin. As a result, in the example of the metal laminate 1 according to this embodiment shown in Figure 1, a void is formed around the conductive metal foil 20.

[0020] Figures 2 and 3 are schematic diagrams showing another example of the metal laminate 1 according to this embodiment as shown in Figure 1. Referring to Figures 2 and 3, the metal laminate 1 according to this embodiment may comprise a ferromagnetic metal foil 10 and a plurality of conductive metal foils 20 arranged laminated with the ferromagnetic metal foil 10 in the thickness direction of the metal laminate 1. As shown in Figures 2 and 3, the conductive metal foils 20 deform in the same way as in Figure 1 to form irregularities. On the other hand, as shown in Figures 2 and 3, the metal laminate 1 may comprise a plurality of conductive metal foils 20.

[0021] When the metal laminate 1 includes a plurality of conductive metal foil bodies 20, as shown in Figure 2, all of the plurality of conductive metal foil bodies 20 may be formed with irregularities. Further, when the metal laminate 1 includes a plurality of conductive metal foil bodies 20, as shown in Figure 3, only some of the plurality of conductive metal foil bodies 20 may be formed with irregularities. In these cases, further, all of the plurality of conductive metal foil bodies 20 may be constituted by metal foil bodies made of the same good conductor, or may include a plurality of metal foil bodies made of different good conductors.

[0022] As described above, when irregularities are formed in the conductive metal foil body 20, various embodiments are conceivable. As a result of detailed studies by the present inventors based on the above findings, when the number of the conductive metal foil bodies 20 is n (n is a natural number), it has been clarified that if the electrical resistivity, the mass per unit area, the density, and the thickness of the conductive metal foil bodies 20 satisfy the formula (1), the metal laminate 1 that achieves both excellent magnetic field shielding properties in the low frequency region and weight reduction can be obtained. [Formula] Here, k in the formula (1) is a natural number equal to or less than n, and ρ in the formula (1) k is assigned the electrical resistivity of the k-th conductive metal foil body in the unit of Ω·m, m k is assigned the mass per unit area of the k-th conductive metal foil body in the unit of g / m 2 and is substituted, d k is assigned the density of the k-th conductive metal foil body in the unit of g / m 3 and is substituted, t k is assigned the thickness of the k-th conductive metal foil body in the unit of m, and t is assigned the total thickness of the conductive metal foil bodies in the unit of m.

[0023] The left-hand side of equation (1) is defined as LL, and the middle side of equation (1) is defined as Fn1. Fn1 is an index indicating the degree of weight increase due to deformation of the conductive metal foil 20. Furthermore, if the metal laminate 1 includes multiple conductive metal foils 20, Fn1 is the arithmetic mean of the degree of weight increase due to deformation of the multiple conductive metal foils 20. On the other hand, LL indicates the lower limit of Fn1 at which excellent magnetic field shielding characteristics in the low-frequency region can be obtained. That is, in the metal laminate 1 according to this embodiment, Fn1 is adjusted according to the electrical resistivity of the conductive metal foil 20. As a result, the metal laminate 1 according to this embodiment can improve magnetic field shielding characteristics in the low-frequency region. On the other hand, if Fn1 is too high, the above effect saturates. In this case, the weight of the conductive metal foil 20 becomes too high, and a lightweight metal laminate 1 cannot be obtained.

[0024] Therefore, the metal laminate 1 according to this embodiment comprises a ferromagnetic metal foil 10 and n (n is a natural number) conductive metal foils 20 arranged in the thickness direction of the metal laminate 1, laminated with the ferromagnetic metal foil 10, wherein the conductive metal foils 20 satisfy an Fn1 of LL ~ 1.450. As a result, the metal laminate 1 according to this embodiment can achieve both excellent magnetic field shielding characteristics in the low-frequency range and lightweight construction.

[0025] Furthermore, the reason why the metal laminate 1, which includes a conductive metal foil 20 satisfying Fn1 less than LL~1.450, can achieve both excellent magnetic field shielding characteristics in the low-frequency region and lightweight construction is not yet clear. However, the inventors speculate as follows: As described above, the conductive metal foil 20 according to this embodiment has an increased apparent thickness due to the formation of irregularities. In this case, it is speculated that as the apparent thickness of the conductive metal foil 20 satisfying Fn1 less than LL~1.450 increases, the path length of the magnetic field lines passing through the interior of the conductive metal foil 20 increases, and the effect of absorbing magnetic force becomes greater. In addition, when the conductive metal foil 20 is laminated with the ferromagnetic metal foil 10, the magnetic field lines may be bent in the in-plane direction. In this case, it is thought that the path length of the magnetic field lines passing through the interior of the conductive metal foil 20 becomes even longer. In this way, the inventors speculate that by setting the Fn1 of the conductive metal foil 20 to LL ~ 1.450, the magnetic field shielding characteristics in the low-frequency region are improved more effectively than simply increasing the thickness of the metal foil.

[0026] The inventors surmise that, through the mechanism described above, the metal laminate 1 according to this embodiment can achieve both excellent magnetic field shielding characteristics in the low-frequency range and lightweight construction. It should be noted that, through mechanisms other than those described above, the metal laminate 1 including the conductive metal foil 20 satisfying Fn1 to LL ~ 1.450 may also achieve both excellent magnetic field shielding characteristics in the low-frequency range and lightweight construction. However, the fact that the metal laminate 1 including the conductive metal foil 20 satisfying Fn1 to LL ~ 1.450 can achieve both excellent magnetic field shielding characteristics in the low-frequency range and lightweight construction has been demonstrated by the embodiments described later.

[0027] Based on the above findings, the gist of the metal laminate and electromagnetic shield according to this embodiment is as follows.

[0028] [1] A metal laminate, A ferromagnetic metal foil, The metal laminate comprises n (n is a natural number) conductive metal foils arranged in a laminated manner with the ferromagnetic metal foil in the thickness direction of the metal laminate, The conductive metal foil body is The electrical resistivity, mass per unit area, density, and thickness satisfy equation (1). Metal laminate.

number

[0029] [2] [1] The metal laminate described above, The above n is a natural number greater than or equal to 2. Metal laminate.

[0030] [3] A metal laminate as described in [1] or [2], The aforementioned metal laminate is The metal laminate includes a plurality of ferromagnetic metal foils arranged in a stacked manner in the thickness direction of the metal laminate, Metal laminate.

[0031] [4] A metal laminate according to any one of items [1] to [3], The conductive metal foil is either a copper foil or an aluminum foil. Metal laminate.

[0032] [5] A metal laminate according to any one of items [1] to [4], The chemical composition of the ferromagnetic metal foil contains one or more elements selected from the group consisting of iron and nickel. Metal laminate.

[0033] [6] [5] The metal laminate described above, The ferromagnetic metal foil is one or more selected from the group consisting of crystalline pure iron or Fe-Ni alloy. Metal laminate.

[0034] [7] A metal laminate according to any one of items [1] to [6], further, Disposed between the ferromagnetic metal foil and the ferromagnetic metal foil, between the conductive metal foil and the conductive metal foil, and at least one of the above, The ferromagnetic metal foil and / or the conductive metal foil are bonded to the ferromagnetic metal foil and / or the conductive metal foil, comprising a bonding layer. Metal laminate.

[0035] [8] A metal laminate including any one of items [1] to [7], Electromagnetic wave shielding device.

[0036] The metal laminate and electromagnetic shield according to this embodiment will be described in detail below. In the drawings used for explanation, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.

[0037] [Metal laminate] The metal laminate 1 according to this embodiment comprises a ferromagnetic metal foil 10 and n conductive metal foils 20 arranged laminated with the ferromagnetic metal foil 10 in the thickness direction of the metal laminate 1. Here, the number n of conductive metal foils 20 is a natural number (an integer greater than or equal to 1). As described above, Figures 1 to 3 are schematic diagrams showing an example of the metal laminate 1 according to this embodiment. Referring to Figure 1, the metal laminate 1 according to this embodiment may comprise a ferromagnetic metal foil 10 and one conductive metal foil 20 arranged laminated with the ferromagnetic metal foil 10 in the thickness direction of the metal laminate 1. Referring to Figures 2 and 3, the metal laminate 1 according to this embodiment may comprise a ferromagnetic metal foil 10 and two or more conductive metal foils 20 arranged laminated with the ferromagnetic metal foil 10 in the thickness direction of the metal laminate 1. Here, the metal laminate 1 according to this embodiment may include components other than the ferromagnetic metal foil 10 and the conductive metal foils 20. The following describes in detail the ferromagnetic metal foil 10, the conductive metal foil 20, and the other components.

[0038] [Ferromagnetic metal foil] In this embodiment, the ferromagnetic metal foil 10 is laminated with the conductive metal foil 20 to form a metal laminate 1. Here, the ferromagnetic metal foil 10 can be any metal foil made of a ferromagnetic material, and the type of metal is not particularly limited. In this specification, a ferromagnetic material means a metal having high magnetic permeability. In this specification, "high magnetic permeability" means, for example, a maximum relative permeability of 10,000 or more. A higher maximum relative permeability is preferable because it can improve the magnetic field shielding characteristics when applied as an electromagnetic wave shielding body.

[0039] Specifically, the metals used in the ferromagnetic metal foil 10 according to this embodiment are, for example, iron (Fe), nickel (Ni), cobalt (Co), and metal materials containing these. Preferably, the chemical composition of the ferromagnetic metal foil 10 contains one or more elements selected from the group consisting of Fe and Ni. In other words, the ferromagnetic metal foil 10 may be a metal foil made of electromagnetic soft iron as defined by JIS C2504:2000, a metal foil made of an Fe-based alloy containing Ni, a metal foil made of a Ni-based alloy, or a metal foil with a Ni plating layer formed on its surface. Furthermore, in the case of Fe-based alloys containing Ni, Ni-based alloys, and metal foils with a Ni plating layer formed on them, elements other than Fe and Ni may also be contained.

[0040] More preferably, the ferromagnetic metal foil 10 is one selected from the group consisting of a metal foil made of pure iron as defined by JIS G0203:2009, a metal foil made of an iron-nickel soft magnetic material described in JIS C2531:1999, and a metal foil with a Ni plating layer formed on its surface. Thus, it is preferable to use a metal foil of a steel type having high magnetic permeability as the ferromagnetic metal foil 10. In particular, crystalline high-purity iron is suitable for application to the ferromagnetic metal foil 10 because it combines lightness and magnetic permeability. Generally, the higher the purity of crystalline high-purity iron, the higher the magnetic permeability. Therefore, when using crystalline pure iron, it is preferable to have a purity of about 4N, i.e., a purity of 99.99% or higher.

[0041] Furthermore, the recrystallization temperature of pure iron is lower than the melting point of aluminum. Also, as will be described later, in this embodiment, an aluminum foil can be used as the conductive metal foil 20 in the metal laminate 1. In other words, the metal laminate 1 can be manufactured by performing a molten aluminum plating treatment on rolled pure iron. In this case, the effect of removing the distortion of the pure iron due to the heat of the molten aluminum is also obtained. In this case, additional annealing heat treatment is unnecessary, and the manufacturing cost of the metal laminate 1 can be reduced, which is preferable.

[0042] Furthermore, the Fe-Ni alloy referred to as permalloy, as described in JIS C2531:1999, has extremely high magnetic permeability, making it suitable for application to ferromagnetic metal foil 10. Permalloy also has a low coefficient of thermal expansion. Therefore, when the electromagnetic shielding body is used in combination with a resin with a low coefficient of thermal expansion, such as fiber-reinforced plastic (FRP), the thermal stress caused by heat pressing during joining is reduced. As a result, the deterioration of the electromagnetic shielding body's properties due to processing can be suppressed.

[0043] The metal laminate 1 according to this embodiment may include a plurality of ferromagnetic metal foils 10. Specifically, Figure 4 is a schematic diagram showing another example of the metal laminate 1 according to this embodiment, as shown in Figures 1 to 3. Referring to Figure 4, the metal laminate 1 may comprise a conductive metal foil 20 and a plurality of ferromagnetic metal foils 10 arranged laminated with the conductive metal foil 20 in the thickness direction of the metal laminate 1. In the example shown in Figure 4, the plurality of ferromagnetic metal foils 10 are arranged so as to sandwich the conductive metal foil 20. However, in the metal laminate 1 according to this embodiment, one ferromagnetic metal foil 10 may be in contact with the conductive metal foil 20, while the other ferromagnetic metal foil 10 is in contact only with the ferromagnetic metal foil 10. The metal laminate 1 according to this embodiment may further include three or more ferromagnetic metal foils 10. In other words, the ferromagnetic metal foils 10 are not particularly limited in this embodiment.

[0044] Preferably, the total thickness of the ferromagnetic metal foil 10 is 5 to 150 μm. If the total thickness of the ferromagnetic metal foil 10 is too thick, the weight of the metal laminate 1 may become too heavy. Therefore, the preferred upper limit of the total thickness of the ferromagnetic metal foil 10 is 150 μm, more preferably 120 μm, even more preferably 100 μm, even more preferably 80 μm, and even more preferably 50 μm. The lower limit of the total thickness of the ferromagnetic metal foil 10 is not particularly limited, but may be 5 μm or 10 μm. As described above, the metal laminate 1 according to this embodiment may include a plurality of ferromagnetic metal foils 10. In this case, the total thickness of the ferromagnetic metal foil 10 means the sum of the thicknesses of the plurality of ferromagnetic metal foils 10.

[0045] As described above, the conductive metal foil 20 of the metal laminate 1 in this embodiment has irregularities formed on it. On the other hand, it is preferable that the ferromagnetic metal foil 10 of the metal laminate 1 in this embodiment be smoother than the conductive metal foil 20. If the ferromagnetic metal foil 10 has irregularities similar to those of the conductive metal foil 20, there is a concern that its magnetic properties will deteriorate. Therefore, it is preferable that the metal laminate 1 in this embodiment comprises a relatively smooth ferromagnetic metal foil 10 and a conductive metal foil 20 with irregularities formed on it.

[0046] If the ferromagnetic metal foil 10 is smoother than the conductive metal foil 20, the apparent thickness of the ferromagnetic metal foil 10 is, for example, less than 300 μm. Here, the apparent thickness of the ferromagnetic metal foil 10 refers to the distance between the highest point of the ferromagnetic metal foil 10 and the table when the ferromagnetic metal foil 10 is placed on a smooth table.

[0047] [Conductive metal foil] In this embodiment, the conductive metal foil 20 is laminated with the ferromagnetic metal foil 10 in the thickness direction of the metal laminate 1 to form the metal laminate 1. Here, the conductive metal foil 20 is a metal foil made of a good conductor, and the type of metal is not particularly limited. In this specification, a good conductor means a metal having a low electrical resistivity. Specifically, the electrical resistivity of a good conductor is, for example, 3.00 × 10⁻¹⁰. -8 It is less than or equal to Ω·m.

[0048] Specifically, the metals used in the conductive metal foil 20 according to this embodiment are, for example, aluminum (Al), copper (Cu), and metal materials containing these. Preferably, the conductive metal foil 20 is an Al foil or a Cu foil. Both Al and Cu are metals with low electrical resistivity and are suitable metals to be used in the conductive metal foil 20.

[0049] As described above, the metal laminate 1 according to this embodiment comprises n conductive metal foils 20 arranged in a laminate with a ferromagnetic metal foil 10. Here, n is a natural number. Therefore, as shown in Figure 1, the metal laminate 1 according to this embodiment may include one conductive metal foil 20. As shown in Figures 2 and 3, the metal laminate 1 according to this embodiment may include two conductive metal foils 20. Figure 5 is a schematic diagram showing another example of the metal laminate 1 according to this embodiment as shown in Figures 1 to 4. As shown in Figure 5, the metal laminate 1 according to this embodiment may include four conductive metal foils 20. Furthermore, although not shown, the metal laminate 1 according to this embodiment may include three conductive metal foils 20, or five or more conductive metal foils 20. In other words, in this embodiment, the number of conductive metal foils 20 is not particularly limited, and can be one or more.

[0050] The conductive metal foil 20 according to this embodiment has irregularities formed by deformation. Here, the irregularities formed by the conductive metal foil 20 only need to have height differences in the thickness direction of the conductive metal foil 20, and their shape is not particularly limited. Specifically, as shown in Figures 1 to 5, the conductive metal foil 20 may be bent and have a shape in which convex and concave portions are repeated with regularity in the left-right direction of the drawing. In this case, the shape of the convex and concave portions is also not limited. Figure 6 is a schematic diagram showing another example of the metal laminate 1 according to this embodiment as shown in Figures 1 to 5. As shown in Figure 6, the shape of the irregularities may form a smooth curve. In other words, the conductive metal foil 20 according to this embodiment may be processed into an irregular shape by a process such as corrugation.

[0051] The conductive metal foil 20 according to this embodiment may also have irregularities formed by embossing (raising) or debossing (debossing). Specifically, Figure 7 is a schematic diagram showing another example of the metal laminate 1 according to this embodiment, as shown in Figures 1 to 6. As shown in Figure 7, the conductive metal foil 20 may have partially formed convex portions (and concave portions), and the convex portions and concave portions may be repeated in a regular pattern in the left-right direction of the drawing. In this case, the shape of the convex portions and concave portions is not particularly limited. Furthermore, the conductive metal foil 20 according to this embodiment may have a shape with convex portions and concave portions without any regularity. In other words, in the metal laminate 1 according to this embodiment, the shape of the irregularities formed by the conductive metal foil 20 is not particularly limited, as long as the n conductive metal foils 20 satisfy formula (1).

[0052] In this embodiment, when the number of conductive metal foils 20 is n (where n is a natural number), if the electrical resistivity, mass per unit area, density, and thickness of the conductive metal foils 20 satisfy equation (1), it has become clear that a metal laminate 1 can be obtained that achieves both excellent magnetic field shielding characteristics in the low-frequency range and lightweight construction.

number

[0053] As described above, the left side of equation (1) is defined as LL, and the middle side of equation (1) is defined as Fn1. Fn1 is an index that shows the degree of weight increase due to deformation of the conductive metal foil 20, and when the metal laminate 1 contains multiple conductive metal foils 20, it is the arithmetic mean of the degree of weight increase due to deformation of the multiple conductive metal foils 20. In other words, when the metal laminate 1 contains one conductive metal foil 20, 1 is substituted for n. In this case, Fn1 is transformed as shown in equation (A) below. Fn1=(m-dt) / dt (A) Here, in equation (A), m represents the mass per unit area of ​​the conductive metal foil in units of g / m². 2 The value is substituted, and d is the density of the conductive metal foil in units of g / m³. 3 The value is substituted, and the thickness of the conductive metal foil is substituted for t in units of m.

[0054] Furthermore, if the metal laminate 1 contains two conductive metal foils 20, then n is substituted with 2. In this case, Fn1 is transformed as shown in equation (B) below. Fn1={(m1-d1t1) / d1t1+(m2-d2t2) / d2t2} / 2 (B) Here, in equation (B), m1 represents the mass per unit area of ​​the first conductive metal foil in units of g / m². 2 The values ​​are substituted, and d1 is the density of the first conductive metal foil in units of g / m³. 3 The values ​​are substituted as follows: t1 is the thickness of the first conductive metal foil in units of m, and m2 is the mass per unit area of ​​the second conductive metal foil in units of g / m 2 The value is substituted, and d2 is the density of the second conductive metal foil in units of g / m³. 3 The value is substituted, and the thickness of the second conductive metal foil is substituted for t2 in units of m.

[0055] On the other hand, LL indicates the lower limit of Fn1 at which excellent magnetic field shielding characteristics can be obtained in the low-frequency region. As described above, when there is one conductive metal foil 20 in the metal laminate 1, n is substituted with 1. In this case, LL is transformed as shown in equation (C) below. LL = 0.228ρ × 10 8-0.338 (C) Here, the electrical resistivity of the conductive metal foil in Ω·m is substituted for ρ in equation (C).

[0056] Furthermore, if the metal laminate 1 contains two conductive metal foils 20, then n is substituted with 2. In this case, LL is transformed as shown in equation (D) below. LL=(0.228ρ1×10 8 -0.338) × t1 / t + (0.228ρ2 × 10 8 -0.338) × t² / t (D) Here, in equation (D), the electrical resistivity of the first conductive metal foil is substituted for ρ1 in units of Ω·m, the thickness of the first conductive metal foil is substituted for t1 in units of m, the total thickness of the two conductive metal foils (=t1+t2) is substituted for t in units of m, the electrical resistivity of the second conductive metal foil is substituted for ρ2 in units of Ω·m, and the thickness of the second conductive metal foil is substituted for t2 in units of m.

[0057] Thus, in the metal laminate 1 according to this embodiment, the lower limit of Fn1 is adjusted according to the electrical resistivity of the conductive metal foil 20. As a result, the metal laminate 1 according to this embodiment can improve the magnetic field shielding characteristics in the low-frequency region. On the other hand, if Fn1 is too high, the above effect saturates. In this case, the weight of the conductive metal foil 20 becomes too high, and a lightweight metal laminate 1 cannot be obtained.

[0058] Therefore, the metal laminate 1 according to this embodiment comprises a ferromagnetic metal foil 10 and n (n is a natural number) conductive metal foils 20 arranged in the thickness direction of the metal laminate 1, laminated with the ferromagnetic metal foil 10, wherein the conductive metal foils 20 satisfy an Fn1 of LL ~ 1.450. As a result, the metal laminate 1 according to this embodiment can achieve both excellent magnetic field shielding characteristics in the low-frequency range and lightweight construction.

[0059] In the metal laminate 1 according to this embodiment, the thickness of the conductive metal foil 20 is 5 to 300 μm. Therefore, the total thickness t of the n conductive metal foils 20 is also 5 to 300 μm. Here, the total thickness t of the conductive metal foils 20 means the sum of the thicknesses of the multiple conductive metal foils 20. If the total thickness t of the conductive metal foils 20 is too thick, the weight of the metal laminate 1 may become too heavy. Therefore, the preferred upper limit of the total thickness t of the conductive metal foils 20 is 250 μm, more preferably 200 μm, more preferably 150 μm, more preferably 120 μm, and still more preferably 100 μm. The lower limit of the total thickness t of the conductive metal foils 20 is not particularly limited, but may be 5 μm or 10 μm.

[0060] In this embodiment, the order in which the ferromagnetic metal foil 10 and the conductive metal foil 20 are laminated is not particularly limited, and they can be laminated in any desired order. It is preferable that the ferromagnetic metal foil 10 be positioned near the center in the thickness direction of the metal laminate 1. In this case, the metal laminate 1 may also have a plurality of conductive metal foils 20 arranged symmetrically in the thickness direction of the metal laminate 1, with the ferromagnetic metal foil 10 in between. When the metal laminate 1 is processed into an electromagnetic wave shield, bending stress may be applied. In this case, if the ferromagnetic metal foil 10 is positioned near the center in the thickness direction of the metal laminate 1, the ferromagnetic metal foil 10 will be positioned on the neutral plane of the bending stress. As a result, when used as an electromagnetic wave shield, the decrease in the magnetic permeability of the ferromagnetic metal foil 10 due to bending stress is suppressed, which is preferable.

[0061] In this embodiment, the electrical resistivity ρ of the conductive metal foil 20 can be measured by the following method. Specifically, a test piece is prepared from the conductive metal foil 20 according to this embodiment, and the volume resistivity is determined by the DC four-terminal method. When measuring the volume resistivity by the DC four-terminal method, the length, width, and thickness of the test piece between the voltage terminals, the current value applied, and the measured voltage are all given three significant figures. The volume resistivity obtained in this way is defined as the electrical resistivity.

[0062] In this embodiment, the total mass m per unit area of ​​the conductive metal foil 20 can be measured by the following method. In this embodiment, the mass per unit area of ​​the conductive metal foil 20 is the mass per unit area when the conductive metal foil 20 is placed on a horizontal surface and viewed from above. 2 This refers to the mass per unit area. Specifically, a test specimen is prepared from the conductive metal foil 20 according to this embodiment. The size of the test specimen does not need to be more than 1.0 mm × 1.0 mm, and can be set as appropriate. The mass per unit area is determined from the mass of the test specimen and the area of ​​the test specimen.

[0063] In this embodiment, the density of the conductive metal foil 20 can be measured by the Archimedes method. Specifically, a test specimen is prepared from the conductive metal foil 20 according to this embodiment. The size of the test specimen is preferably, for example, 5 mm x 5 mm or larger. The thickness of the conductive metal foil 20 is measured in advance. The mass is measured in air and in pure water, and the density of the test specimen can be determined from the buoyancy it experiences.

[0064] Furthermore, as described above, the conductive metal foil 20 in this embodiment is preferably an Al foil or a Cu foil. When an Al foil is used as the conductive metal foil 20, if the Al foil has a purity of 99.30% or higher, the density is 2.70 g / m³. 3 It can be used. Similarly, when using a Cu foil as the conductive metal foil 20, if the Cu foil has a purity of 99.96% or higher, the density will be 8.94 g / m³. 3 You can use it.

[0065] As described above, the conductive metal foil 20 according to this embodiment has an uneven surface to increase its apparent thickness. As a result, excellent magnetic field shielding characteristics in the low-frequency range can be obtained while reducing the increase in weight. In this case, it is preferable that the apparent thickness of the conductive metal foil 20 according to this embodiment be 15 times or more the total thickness of the conductive metal foil 20. If the apparent thickness is 15 times or more the total thickness of the conductive metal foil 20, the Fn1 of the conductive metal foil 20 can be stably made LL or higher. As a result, the metal laminate 1 according to this embodiment can stably achieve both excellent magnetic field shielding characteristics in the low-frequency range and weight reduction.

[0066] [Other configurations] The metal laminate 1 according to this embodiment may have components other than the ferromagnetic metal foil 10 and the conductive metal foil 20. Specifically, the metal laminate 1 may have a bonding layer. Figure 8 is a schematic diagram showing another example of the metal laminate 1 as shown in Figures 1 to 7. Referring to Figure 8, the metal laminate 1 may include a bonding layer 30 between the ferromagnetic metal foil 10 and the conductive metal foil 20 that bonds the conductive metal foil 20 to the ferromagnetic metal foil 10. In this embodiment, the metal laminate 1 may further include a bonding layer 30 (not shown) between a plurality of conductive metal foils 20 that bonds the conductive metal foils 20 to each other. In other words, the metal laminate 1 according to this embodiment may include a bonding layer 30 that is disposed between ferromagnetic metal foils 10 and ferromagnetic metal foils 10, between conductive metal foils 20 and conductive metal foils 20, and between ferromagnetic metal foils 10 and conductive metal foils 20, and bonds the ferromagnetic metal foils 10 and / or conductive metal foils 20 to each other.

[0067] Here, the material of the bonding layer 30 is not particularly limited and may be a metal or a resin. If the bonding layer 30 is a metal, the metal may be a single metal, an alloy, or an intermetallic compound. If the bonding layer 30 is a resin, the resin is not particularly limited and examples include polyethylene terephthalate resin (PET resin), polyethylene resin, polypropylene resin, polyurethane resin, polyvinyl chloride resin, polyimide resin, etc. The resin referred to here may be a resin made from a single raw material, a resin containing multiple raw materials, or a composite resin containing glass fibers or carbon fibers, etc. Among resins, fiber-reinforced plastic (FRP) is particularly preferred from the viewpoint of moldability. Furthermore, from the viewpoint of moldability, thermosetting and / or thermoplastic resins may be used as the resin.

[0068] [Magnetic field shielding characteristics in the low-frequency range] The metal laminate 1 according to this embodiment, when applied as an electromagnetic wave shield, has excellent magnetic field shielding characteristics in the low-frequency range of 1 to 100 MHz. The metal laminate 1 according to this embodiment also has stable and excellent magnetic field shielding characteristics in the extremely low-frequency range of 1 to 10 MHz, and has extremely excellent magnetic field shielding characteristics in the low-frequency range of 10 to 100 MHz. Specifically, the magnetic field shielding characteristics in the low-frequency range can be evaluated by the following method.

[0069] In this embodiment, the magnetic field shielding characteristics are evaluated using the KEC method developed by the Kansai Electronics Industry Promotion Center (KEC). Specifically, a test specimen is prepared from the metal laminate 1 according to this embodiment. Electromagnetic waves having a predetermined frequency are transmitted perpendicularly to the surface of the test specimen from a transmitting antenna, and the electromagnetic waves that have passed through the test specimen are received by a receiving antenna. In this way, the degree to which the electromagnetic waves that have passed through the test specimen have been attenuated is measured. More specifically, the measurement test machine used is the MA8602B electromagnetic shielding characteristic tester manufactured by Anritsu Corporation, and the E5071 from Agient Technologies can be used as the network analyzer used for generating and measuring electromagnetic waves.

[0070] [Electromagnetic wave shielding] The electromagnetic shielding body according to this embodiment includes the metal laminate 1 according to this embodiment. That is, the electromagnetic shielding body only needs to include the metal laminate 1, and may also include components other than the metal laminate 1. For example, the electromagnetic shielding body may have the metal laminate 1 bonded to a resin substrate molded into a housing shape. For example, the electromagnetic shielding body may consist only of the metal laminate 1.

[0071] If the electromagnetic shield consists only of a metal laminate 1, it may be installed as a partition between a source of low-frequency electromagnetic waves, such as a motor or inverter, and electronic equipment that needs to be protected from the effects of electromagnetic noise. If the electromagnetic shield has a hollow housing shape, it may house a source of low-frequency electromagnetic waves inside, or it may house electronic equipment that needs to be protected from the effects of electromagnetic noise inside.

[0072] As described above, when applied as an electromagnetic wave shield, the metal laminate 1 may be subjected to bending stress. In this case, the metal laminate 1 may be bent after being bonded to other components (for example, a resin sheet). In such cases, it is preferable that the ferromagnetic metal foil 10 be positioned on the neutral plane of the bending stress. Specifically, for example, when a resin sheet is bonded to the metal laminate 1, it is often preferable to position the ferromagnetic metal foil 10 near the center in the thickness direction of the electromagnetic wave shield including the resin sheet on the metal laminate 1. In this case, the decrease in the magnetic permeability of the ferromagnetic metal foil 10 due to bending stress is suppressed.

[0073] [Method for manufacturing metal laminates] The method for manufacturing the metal laminate 1 according to this embodiment is not particularly limited, as long as it can laminate a ferromagnetic metal foil 10 and a conductive metal foil 20 that satisfy the above requirements. The method for laminating the ferromagnetic metal foil 10 and the conductive metal foil 20 is not particularly limited, but for example, the ferromagnetic metal foil 10 and the conductive metal foil 20 may be heated and then pressed together. For example, the conductive metal foil 20 may be formed by further plating the ferromagnetic metal foil 10. Specifically, when an aluminum foil is formed as the conductive metal foil 20, it is preferable to perform a molten aluminum plating treatment. In this case, an alloy of iron and aluminum and / or an intermetallic compound may be formed between the ferromagnetic metal foil 10 and the conductive metal foil 20. In this case, fine irregularities are further formed at the interface between the ferromagnetic metal foil 10 and the conductive metal foil 20. Specifically, when a copper foil is formed as the conductive metal foil 20, it is preferable to perform an electroplating treatment.

[0074] As a method for laminating the ferromagnetic metal foil 10 and the conductive metal foil 20, a bonding layer 30 may be formed between the ferromagnetic metal foil 10 and the conductive metal foil 20 to bond them. In this case, fine irregularities may be formed on the surfaces of the ferromagnetic metal foil 10 and / or the conductive metal foil 20 before forming the bonding layer 30 and bonding them. Alternatively, a plating layer may be formed on the surfaces of the ferromagnetic metal foil 10 and / or the conductive metal foil 20 before forming the bonding layer 30. By forming a plating layer, the corrosion resistance of the ferromagnetic metal foil 10 and / or the conductive metal foil 20 can be improved. In this case, the thickness of the plating layer is preferably 1 μm or less. Thus, as a method for laminating the ferromagnetic metal foil 10 and the conductive metal foil 20, any known method can be used as appropriate.

[0075] Preferably, the ferromagnetic metal foil 10 is annealed before laminating the ferromagnetic metal foil 10 and the conductive metal foil 20. Annealing removes strain from the ferromagnetic metal foil 10, thereby increasing its permeability. The annealing conditions can be appropriately set according to the composition of the ferromagnetic metal foil 10. The metal laminate 1 can be manufactured by the above method. Note that the metal laminate 1 according to this embodiment may be manufactured by methods other than the manufacturing method described above.

[0076] The effects of the metal laminate according to this embodiment will be further explained in detail below with reference to examples. The conditions in the following examples are just one example of conditions adopted to confirm the feasibility and effects of the metal laminate according to this embodiment. In other words, the metal laminate according to this embodiment is not limited to this one example of conditions. [Examples]

[0077] Ferromagnetic metal foils of each material code listed in Table 1 were prepared.

[0078] [Table 1]

[0079] The material codes A1 to A4 listed in Table 1 refer to the material of the ferromagnetic metal foil. The electromagnetic soft iron listed in Table 1 corresponds to SUY as defined in JIS C2504:2000 and contained impurities of C: 0.004%, Mn: 0.36%, P: 0.011%, and S: 0.008% by mass (material code "A1" in Table 1). The 42 alloy listed in Table 1 had a chemical composition of Ni: 40.67% by mass, with the remainder being Fe and impurities (material code "A2" in Table 1). The PC permalloy listed in Table 1 had a chemical composition of Ni: 77.8%, Cu: 3.48%, Mo: 4.49% by mass, with the remainder being Fe and impurities (material code "A3" in Table 1). The high-purity iron listed in Table 1 used Fe foil with a purity of 99.99% or higher (material code "A4" in Table 1).

[0080] The ferromagnetic metal foils with material codes A1 to A4 were annealed under the conditions shown in Table 1 in a non-oxidizing atmosphere. The values ​​in parentheses in the "Heat Treatment Conditions" column refer to the furnace atmosphere. Using the above method, ferromagnetic metal foils of each material code were prepared.

[0081] The material codes B1 and B2 listed in Table 1 refer to the material of the conductive metal foil. The aluminum listed in Table 1 is 99.31% pure aluminum foil (material code "B1" in Table 1). The electrical resistivity of this aluminum foil, determined by the four-terminal method, is 2.73 × 10⁻⁶. -8 The resistivity was Ω / m. The copper listed in Table 1 was 99.99% pure copper foil (material code "B2" in Table 1). The electrical resistivity of this copper foil, determined by the four-terminal method, was 1.73 × 10⁻⁶. -8 The value was Ω / m. The electrical resistivity was determined using the measurement method described above, and the room temperature at the time of measurement was 22°C.

[0082] In Example 1, material code A1 (electromagnetic soft iron) was used as the ferromagnetic metal foil, and material code B1 (aluminum) was used as the conductive metal foil. Table 2A shows the material code and total thickness (μm) of the ferromagnetic metal foil used in the metal laminate for each test number. Furthermore, for each test number, the composition of the ferromagnetic metal foil and the conductive metal foil is shown in the "Metal Laminate Composition" column of Table 2B. The underlined text in the "Metal Laminate Composition" column indicates the thickness of the ferromagnetic metal foil. That is, the metal laminate for test number 1 has a two-layer structure consisting of a 20 μm conductive metal foil and a 10 μm ferromagnetic metal foil from top to bottom in the thickness direction of the metal laminate.

[0083] [Table 2A]

[0084] [Table 2B]

[0085] Furthermore, Table 2A shows the material code of the conductive metal foil used, the total thickness t (μm), the mass per unit area m, LL, and Fn1 for each test number of the metal laminate.

[0086] For each test number of metal laminate, the magnetic field shielding characteristics were evaluated using the KEC method as described above. The measurement tester used was the MA8602B electromagnetic shielding characteristics tester manufactured by Anritsu Corporation, and the network analyzer used for generating and measuring electromagnetic waves was the E5071 from Agient Technologies. Measurements were taken by varying the frequency from 1 to 100 MHz, and evaluating the magnetic field shielding characteristics in each frequency band. The frequency sweep speed was set to 19.3 seconds for each interval. The room temperature during measurement was 23°C. In this example, the magnetic field shielding effect of PC permalloy alone with a thickness of 50 μm was used as the evaluation criterion. The obtained magnetic field shielding effects from 1 to 10 MHz and from 10 to 100 MHz are shown in Table 2B, respectively.

[0087] [Evaluation Results] Referring to Tables 2A and 2B, the Fn1 of the conductive metal foils for test numbers 1-3 and 5 was less than LL. On the other hand, the Fn1 of the conductive metal foil for test number 4 was LL or greater. As a result, the magnetic field shielding effect of the metal laminate for test number 4 was 3.0 dB or more higher than that of test numbers 1-3 and 5 in the 1-10 MHz range. Furthermore, the magnetic field shielding effect of the metal laminate for test number 4 was significantly higher in the 10-100 MHz range.

[0088] In particular, comparing test number 4 and test number 5, test number 4 had a lighter mass m per unit area and superior magnetic field shielding effect in the 1-100 MHz range. In other words, the metal laminate of test number 4 was lightweight yet possessed excellent magnetic field shielding characteristics in the low-frequency range of 1-100 MHz. [Examples]

[0089] In Example 2, material code A1 (electromagnetic soft iron) was used as the ferromagnetic metal foil, and material code B1 (aluminum) was used as the conductive metal foil. Table 3A shows the material code and total thickness (μm) of the ferromagnetic metal foil used in the metal laminate for each test number. Furthermore, for each test number, the composition of the ferromagnetic metal foil and conductive metal foil is shown in the "Metal Laminate Composition" column of Table 3B. The underlined text in the "Metal Laminate Composition" column indicates the thickness of the ferromagnetic metal foil. That is, the metal laminate for test number 6 has a three-layer structure from top to bottom in the thickness direction of the metal laminate: a 20 μm conductive metal foil, a 10 μm ferromagnetic metal foil, and a 20 μm conductive metal foil.

[0090] [Table 3A]

[0091] [Table 3B]

[0092] Table 3A shows the material code of the conductive metal foil used, the total thickness t (μm), the mass per unit area m, LL, and Fn1 for each test number of the metal laminate. Here, the mass per unit area m (g / m 2 ) is the mass m per unit area of ​​multiple conductive metal foils. k (g / m 2 This represents the sum of ( ). Furthermore, the magnetic field shielding characteristics of the metal laminate for each test number were evaluated in the same manner as in Example 1. The obtained magnetic field shielding effects for 1 to 10 MHz and 10 to 100 MHz are shown in Table 3B, respectively.

[0093] [Evaluation Results] Referring to Tables 3A and 3B, the Fn1 of the conductive metal foils in test numbers 6 and 8 was less than LL. On the other hand, the Fn1 of the conductive metal foil in test number 7 was LL or greater. As a result, the magnetic field shielding effect of the metal laminate in test number 7 was 3.0 dB or more higher than that of test numbers 6 and 8 in the 1-10 MHz range. Furthermore, the magnetic field shielding effect of the metal laminate in test number 7 was significantly higher in the 10-100 MHz range.

[0094] In particular, comparing test number 7 and test number 8, test number 7 had a lighter mass m per unit area and superior magnetic field shielding effect in the 1-100 MHz range. In other words, the metal laminate of test number 7 was lightweight yet possessed excellent magnetic field shielding characteristics in the low-frequency range of 1-100 MHz. [Examples]

[0095] In Example 3, material code A1 (electromagnetic soft iron) was used as the ferromagnetic metal foil, and material code B1 (aluminum) was used as the conductive metal foil. Table 4A shows the material code and total thickness (μm) of the ferromagnetic metal foil used in the metal laminate for each test number. Furthermore, for each test number, the composition of the ferromagnetic metal foil and the conductive metal foil is shown in the "Metal Laminate Composition" column of Table 4B. The underlined text in the "Metal Laminate Composition" column indicates the thickness of the ferromagnetic metal foil. That is, the metal laminate for test number 9 has a two-layer structure consisting of a 50 μm conductive metal foil and a 10 μm ferromagnetic metal foil from top to bottom in the thickness direction of the metal laminate.

[0096] [Table 4A]

[0097] [Table 4B]

[0098] Table 4A shows the material code of the conductive metal foil used, the total thickness t (μm), the mass per unit area m, LL, and Fn1 for each metal laminate with a given test number. Furthermore, the magnetic field shielding characteristics of each metal laminate with a given test number were evaluated using the same method as in Example 1. The obtained magnetic field shielding effects for 1-10 MHz and 10-100 MHz are shown in Table 4B, respectively.

[0099] [Evaluation Results] Referring to Tables 4A and 4B, the Fn1 of the conductive metal foils for test numbers 9 and 13 was less than LL. On the other hand, the Fn1 of the conductive metal foils for test numbers 10 to 12 was LL or greater. As a result, the magnetic field shielding effect of the metal laminates for test numbers 10 to 12 was 3.0 dB or more higher than that of test numbers 9 and 13 in the 1 to 10 MHz range. Furthermore, the magnetic field shielding effect of the metal laminates for test numbers 10 to 12 was extremely high in the 10 to 100 MHz range. In other words, the metal laminates for test numbers 10 to 12, while being lightweight, possessed excellent magnetic field shielding characteristics in the low-frequency range of 1 to 100 MHz. [Examples]

[0100] In Example 4, material code A1 (electromagnetic soft iron) was used as the ferromagnetic metal foil, and material code B2 (copper) was used as the conductive metal foil. Table 5A shows the material code and total thickness (μm) of the ferromagnetic metal foil used in the metal laminate for each test number. Furthermore, for each test number, the composition of the ferromagnetic metal foil and the conductive metal foil is shown in the "Metal Laminate Composition" column of Table 5B. The underlined text in the "Metal Laminate Composition" column indicates the thickness of the ferromagnetic metal foil. That is, the metal laminate for test number 14 has a two-layer structure consisting of a 10 μm conductive metal foil and a 10 μm ferromagnetic metal foil from top to bottom in the thickness direction of the metal laminate.

[0101] [Table 5A]

[0102] [Table 5B]

[0103] Table 5A shows the material code of the conductive metal foil used, the total thickness t (μm), the mass per unit area m, LL, and Fn1 for each metal laminate with a given test number. Furthermore, the magnetic field shielding characteristics of each metal laminate with a given test number were evaluated using the same method as in Example 1. The obtained magnetic field shielding effects for 1-10 MHz and 10-100 MHz are shown in Table 5B, respectively.

[0104] [Evaluation Results] Referring to Tables 5A and 5B, the Fn1 of the conductive metal foils for test numbers 14-17 was less than LL. On the other hand, the Fn1 of the conductive metal foil for test number 18 was LL or greater. As a result, the magnetic field shielding effect of the metal laminate for test number 18 was more than 3.0 dB higher than that of test numbers 14-17 in the 1-10 MHz range. Furthermore, the magnetic field shielding effect of the metal laminate for test number 18 was extremely high in the 10-100 MHz range. In other words, the metal laminate for test number 18, while being lightweight, possessed excellent magnetic field shielding characteristics in the low-frequency range of 1-100 MHz. [Examples]

[0105] In Example 5, material code A1 (electromagnetic soft iron) was used as the ferromagnetic metal foil, and material code B2 (copper) was used as the conductive metal foil. Table 6A shows the material code and total thickness (μm) of the ferromagnetic metal foil used in the metal laminate for each test number. Furthermore, for each test number, the composition of the ferromagnetic metal foil and the conductive metal foil is shown in the "Metal Laminate Composition" column of Table 6B. The underlined text in the "Metal Laminate Composition" column indicates the thickness of the ferromagnetic metal foil. That is, the metal laminate for test number 19 has a two-layer structure consisting of a 20 μm conductive metal foil and a 10 μm ferromagnetic metal foil from top to bottom in the thickness direction of the metal laminate.

[0106] [Table 6A]

[0107] [Table 6B]

[0108] Table 6A shows the material code of the conductive metal foil used, the total thickness t (μm), the mass per unit area m, LL, and Fn1 for each metal laminate with a given test number. Furthermore, the magnetic field shielding characteristics of each metal laminate with a given test number were evaluated using the same method as in Example 1. The obtained magnetic field shielding effects for 1-10 MHz and 10-100 MHz are shown in Table 6B, respectively.

[0109] [Evaluation Results] Referring to Tables 6A and 6B, the Fn1 of the conductive metal foils for test numbers 19 and 20 was less than LL. On the other hand, the Fn1 of the conductive metal foils for test numbers 21 and 22 was LL or greater. As a result, the magnetic field shielding effect of the metal laminates for test numbers 21 and 22 was 3.0 dB or more higher than that of test numbers 19 and 20 in the 1-10 MHz range. Furthermore, the magnetic field shielding effect of the metal laminates for test numbers 21 and 22 was extremely high in the 10-100 MHz range. In other words, the metal laminates for test numbers 21 and 22, while being lightweight, possessed excellent magnetic field shielding characteristics in the low-frequency range of 1-100 MHz. [Examples]

[0110] In Example 6, material code A1 (electromagnetic soft iron) was used as the ferromagnetic metal foil, and material code B2 (copper) was used as the conductive metal foil. Table 7A shows the material code and total thickness (μm) of the ferromagnetic metal foil used in the metal laminate for each test number. Furthermore, for each test number, the composition of the ferromagnetic metal foil and conductive metal foil is shown in the "Metal Laminate Composition" column of Table 7B. The underlined text in the "Metal Laminate Composition" column indicates the thickness of the ferromagnetic metal foil. That is, the metal laminate for test number 23 has a three-layer structure from top to bottom in the thickness direction of the metal laminate: a 20 μm conductive metal foil, a 20 μm conductive metal foil, and a 10 μm ferromagnetic metal foil.

[0111] [Table 7A]

[0112] [Table 7B]

[0113] Table 7A shows the material code of the conductive metal foil used, the total thickness t (μm), the mass per unit area m, LL, and Fn1 for each test number of the metal laminate. Note that, as in Example 2, the mass per unit area m (g / m 2 ) is the mass m per unit area of ​​multiple conductive metal foils. k (g / m 2 This represents the sum of ( ). Furthermore, the magnetic field shielding characteristics of the metal laminate for each test number were evaluated in the same manner as in Example 1. The obtained magnetic field shielding effects for 1 to 10 MHz and 10 to 100 MHz are shown in Table 7B, respectively.

[0114] [Evaluation Results] Referring to Tables 7A and 7B, the Fn1 of the conductive metal foils for test numbers 23, 24, and 26 was less than LL. On the other hand, the Fn1 of the conductive metal foil for test number 25 was LL or greater. As a result, the magnetic field shielding effect of the metal laminate for test number 25 was 3.0 dB or more higher than that of test numbers 23, 24, and 26 in the 1-10 MHz range. Furthermore, the magnetic field shielding effect of the metal laminate for test number 25 was extremely high in the 10-100 MHz range. In other words, the metal laminate for test number 25, while being lightweight, possessed excellent magnetic field shielding characteristics in the low-frequency range of 1-100 MHz. [Examples]

[0115] In Example 7, material codes A1 (electromagnetic soft iron) to A4 (high-purity iron) were used as the ferromagnetic metal foil, and material code B1 (aluminum) was used as the conductive metal foil. Table 8A shows the material code and total thickness (μm) of the ferromagnetic metal foil used in the metal laminate for each test number. Furthermore, for each test number, the composition of the ferromagnetic metal foil and the conductive metal foil is shown in the "Metal Laminate Composition" column of Table 8B. The underlined text in the "Metal Laminate Composition" column indicates the thickness of the ferromagnetic metal foil. That is, the metal laminate for test number 27 has a two-layer structure consisting of a 50 μm conductive metal foil and a 50 μm ferromagnetic metal foil from top to bottom in the thickness direction of the metal laminate.

[0116] [Table 8A]

[0117] [Table 8B]

[0118] Table 8A shows the material code of the conductive metal foil used, the total thickness t (μm), the mass per unit area m, LL, and Fn1 for each metal laminate with a given test number. Furthermore, the magnetic field shielding characteristics of each metal laminate with a given test number were evaluated using the same method as in Example 1. The obtained magnetic field shielding effects for 1-10 MHz and 10-100 MHz are shown in Table 8B, respectively.

[0119] [Evaluation Results] Referring to Tables 8A and 8B, the Fn1 of the conductive metal foils for test numbers 27, 29, 30, 32, 33, 35, 36, and 38 was less than LL. On the other hand, the Fn1 of the conductive metal foils for test numbers 28, 31, 34, and 37 was LL or greater. As a result, the magnetic field shielding effect of the metal laminates for test numbers 28, 31, 34, and 37 was 3.0 dB or more higher than that of test numbers 27, 29, 30, 32, 33, 35, 36, and 38 in the 1-10 MHz range. Furthermore, the magnetic field shielding effect of the metal laminates for test numbers 28, 31, 34, and 37 was extremely high in the 10-100 MHz range. In other words, the metal laminates for test numbers 28, 31, 34, and 37, while being lightweight, possessed excellent magnetic field shielding characteristics in the low-frequency range of 1-100 MHz. [Examples]

[0120] In Example 8, material code A1 (electromagnetic soft iron) was used as the ferromagnetic metal foil, and material code B1 (aluminum) was used as the conductive metal foil. Table 9A shows the material code and total thickness (μm) of the ferromagnetic metal foil used in the metal laminate for each test number. Furthermore, for each test number, the composition of the ferromagnetic metal foil and conductive metal foil is shown in the "Metal Laminate Composition" column of Table 9B. The underlined text in the "Metal Laminate Composition" column indicates the thickness of the ferromagnetic metal foil. That is, the metal laminate for test number 39 has a three-layer structure from top to bottom in the thickness direction of the metal laminate: a 50 μm conductive metal foil, a 10 μm ferromagnetic metal foil, and a 10 μm ferromagnetic metal foil.

[0121] [Table 9A]

[0122] [Table 9B]

[0123] Table 9A shows the material code of the conductive metal foil used, the total thickness t (μm), the mass per unit area m, LL, and Fn1 for each metal laminate with a given test number. Furthermore, the magnetic field shielding characteristics of each metal laminate with a given test number were evaluated using the same method as in Example 1. The obtained magnetic field shielding effects for 1-10 MHz and 10-100 MHz are shown in Table 9B, respectively.

[0124] [Evaluation Results] Referring to Tables 9A and 9B, the Fn1 of the conductive metal foils for test numbers 39 and 41 was less than LL. On the other hand, the Fn1 of the conductive metal foil for test number 40 was LL or greater. As a result, the magnetic field shielding effect of the metal laminate for test number 40 was 3.0 dB or more higher than that of test numbers 39 and 41 in the 1-10 MHz range. Furthermore, the magnetic field shielding effect of the metal laminate for test number 40 was extremely high in the 10-100 MHz range. In other words, the metal laminate for test number 40, while being lightweight, possessed excellent magnetic field shielding characteristics in the low-frequency range of 1-100 MHz.

[0125] The embodiments of this disclosure have been described above. However, the embodiments described above are merely examples for implementing this disclosure. Therefore, this disclosure is not limited to the embodiments described above, and the embodiments described above can be modified as appropriate without departing from the spirit of this disclosure. [Explanation of symbols]

[0126] 1. Metal Laminate 10 Ferromagnetic metal foil 20 Conductive metal foil 30 Bonding layer

Claims

1. A metal laminate, A ferromagnetic metal foil, The metal laminate comprises n (n is a natural number) conductive metal foils arranged in a stack with the ferromagnetic metal foil in the thickness direction of the metal laminate, The conductive metal foil body is The electrical resistivity, mass per unit area, density, and thickness satisfy equation (1). Metal laminate. [Math 1] Here, k in equation (1) is a natural number less than or equal to n, and ρ in equation (1) ｋ The electrical resistivity of the k-th conductive metal foil is substituted into the following value, with the value of m being the unit: Ω・m. ｋ The mass per unit area of ​​the k-th conductive metal foil is in units of g / m². ２ Substituted with d ｋ The density of the k-th conductive metal foil is in units of g / m³. ３ Substituted with, t ｋ The thickness of the k-th conductive metal foil is substituted into the variable t in units of m, and the total thickness of the conductive metal foil is substituted into the variable t in units of m.

2. A metal laminate according to claim 1, The aforementioned n is a natural number greater than or equal to 2. Metal laminate.

3. A metal laminate according to claim 1, The aforementioned metal laminate is The metal laminate includes a plurality of ferromagnetic metal foils arranged in a stacked manner in the thickness direction of the metal laminate, Metal laminate.

4. A metal laminate according to claim 1, The conductive metal foil is either a copper foil or an aluminum foil. Metal laminate.

5. A metal laminate according to claim 1, The chemical composition of the ferromagnetic metal foil contains one or more elements selected from the group consisting of iron and nickel. Metal laminate.

6. A metal laminate according to claim 5, The ferromagnetic metal foil is one or more selected from the group consisting of crystalline pure iron or Fe-Ni alloy. Metal laminate.

7. The metal laminate according to claim 1, further, Disposed between the ferromagnetic metal foil and the ferromagnetic metal foil, between the conductive metal foil and the conductive metal foil, and at least one of the above, The ferromagnetic metal foil and / or the conductive metal foil are bonded to the ferromagnetic metal foil and / or the conductive metal foil, comprising a bonding layer. Metal laminate.

8. A metal laminate comprising any one of claims 1 to 7, Electromagnetic wave shielding device.

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