Metal resin composite electromagnetic wave shielding material

Abstract

Provided is a metal-resin composite electromagnetic wave shielding material having high moldability. The metal-resin composite electromagnetic wave shielding material is obtained by laminating N (where N is an integer of 1 or more) metal layers and M (where M is an integer of 1 or more) resin layers, and is characterized in that VFL (Value of Forming Limit) satisfies VFL > 0.24, and the metal-resin composite electromagnetic wave shielding material is obtained by laminating N (where N is an integer of 1 or more) metal layers and M (where M is an integer of 1 or more) resin layers.

Description

Technical Field

[0001] The present invention relates to a metal-resin composite electromagnetic wave shielding material, and in particular to a metal-resin composite electromagnetic wave shielding material that can be used as a covering material or an exterior material of an electrical device or an electronic device. Background Art

[0002] In recent years, the world has paid more and more attention to the global environmental issues, and the popularity of environmentally friendly cars equipped with secondary batteries, such as electric cars and hybrid cars, has also been progressing. In these cars, the DC current generated by the installed secondary battery is often converted into AC current through an inverter, and the required power is supplied to the AC motor to obtain driving force. The conversion operation of the inverter will cause the generation of electromagnetic waves. Electromagnetic waves will interfere with the reception of signals from vehicle-mounted audio equipment, wireless devices, etc. Therefore, in the past, measures have been taken to shield electromagnetic waves by housing the inverter or the battery, motor, etc. together with the inverter in a metal casing.

[0003] However, metal electromagnetic wave shielding materials have low molding processability, and there is also a weight problem because they are metal. Therefore, the following have been designed: a resin composition for press molding containing a resin and an electromagnetic wave shielding filler (Patent Document 1: Japanese Patent Publication No. 2021-55113); a method for press molding a mesh-like electromagnetic wave shielding body in a mold, the mesh-like electromagnetic wave shielding body is formed by a mesh metal body and has a flat box-shaped unfolded shape with a central part of the box and a bent edge around it formed by bending (Patent Document 2: Japanese Patent Publication No. 4811245); an electromagnetic wave shielding fabric, characterized in that it is woven from a mixed yarn, which is formed by Z-twisting and / or S-twisting metal wires on one or more conventional spinnable fibers (Patent Document 3: Japanese Patent Publication No. 2011-179162).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2021-55113

[0007] Patent Document 2: Japanese Patent No. 4811245

[0008] Patent Document 3: Japanese Patent Application Publication No. 2011-179162 Summary of the invention

[0009] Technical problem to be solved by the invention

[0010] However, when using a resin mixed with a conductive filler, the shielding property per unit thickness is insufficient, and a greater thickness is required to obtain a higher shielding effect in the shielding of the magnetic field. In addition, when using a mesh shielding body and an electromagnetic wave shielding fabric for press molding, there is a problem of reduced shielding effect at the four corners due to gaps formed in the molded body, and a disadvantage of poor effect in the shielding of the magnetic field. Therefore, a method for improving molding processability by an improved method different from the prior art is required.

[0011] Metal foils (metal layers) such as copper foil used in electromagnetic shielding materials are usually several to several tens of μm thick, so they are prone to cracking when laminated with resin films and molded. Therefore, it is important to suppress cracking and improve moldability.

[0012] Although metal-resin composite materials with high molding processability can be molded into complex shapes, when the molding volume is large, the internal metal layer may be cracked during molding. The cracking of a large metal layer may be related to the reduction of shielding properties, so it is necessary to prevent the cracking.

[0013] The present invention is proposed in view of the above situation. In one embodiment, the technical problem to be solved is to provide a metal-resin composite electromagnetic wave shielding material with high molding processability, that is, capable of conforming to unevenness of 5 mm or more.

[0014] Solutions to technical problems

[0015] The inventors have conducted in-depth research and found that metal-resin composite electromagnetic wave shielding materials that meet certain conditions for VFL (Value of Forming Limit) calculated based on specific parameters have high molding processability and can be molded into a continuous body, especially capable of adapting to bumps and depressions of 5 mm or more. The present invention is completed based on the above knowledge and is exemplified below. [1]

[0017] A metal-resin composite electromagnetic wave shielding material is obtained by laminating N (where N is an integer greater than 1) metal layers and M (where M is an integer greater than 1) resin layers, characterized in that:

[0018] The VFL (Value of Forming Limit) calculated according to the following formula satisfies VFL>0.24: [2]

[0020]

[0021] The metal-resin composite electromagnetic wave shielding material as described in [1], wherein when the conductivity of the metal layer is denoted as σ (S / m) and the total thickness of the metal layer is denoted as d (m), the apparent conductivity C satisfies C = σ × d > 1.0 × 10 -11 (S). [3]

[0023] The metal-resin composite electromagnetic wave shielding material as described in [1] or [2], wherein the thickness of each metal layer is 4 to 100 μm. [4]

[0025] The metal-resin composite electromagnetic wave shielding material according to any one of [1] to [3], wherein the thickness of each resin layer is 4 to 600 μm. [5]

[0027] The metal-resin composite electromagnetic wave shielding material as described in any one of [1] to [4], wherein the total thickness of each metal layer is 15 to 150 μm. [6]

[0029] A covering material or exterior material for an electric device or an electronic device comprising the metal-resin composite electromagnetic wave shielding material as described in any one of [1] to [5]. [7]

[0031] An electrical device or electronic device having the covering material or exterior material as described in [6].

[0032] Effects of the Invention

[0033] According to one embodiment of the present invention, a metal-resin composite electromagnetic wave shielding material having high moldability can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a diagram for explaining a method for evaluating the forming limit in accordance with ISO-12004-2-2008.

[0035] Figure 2 It is a diagram showing the deformation angle and the distance between marks after deformation.

[0036] Figure 3 It is a diagram showing a method of calculating the maximum strain ε1 and the minimum strain ε2 required for calculating the VFL.

[0037] FIG. 4 is a diagram schematically showing a pattern of cracks penetrating a metal layer. DETAILED DESCRIPTION

[0038] Next, the embodiments of the present invention will be described in detail. The present invention is not limited to the following embodiments, and it should be understood that appropriate design changes and improvements can be made based on the common knowledge of those skilled in the art without departing from the scope of the present invention.

[0039] (1.Metal layer)

[0040] The material of the metal layer of the metal-resin composite electromagnetic wave shielding material of one embodiment of the present invention is not particularly limited. When the conductivity of the metal layer of the metal-resin composite electromagnetic wave shielding material is denoted by σ (S / m) and the total thickness of the metal layer is denoted by d (m), the apparent conductivity C preferably satisfies C = σ × d > 1.0 × 10 -11 (S). In the case of multiple metal layers, the conductivity of each layer is denoted by σ N (S / m), and the thickness of each layer is recorded as d N The total apparent conductivity C of the metal layer at (m) preferably satisfies C = Σσ N ×d N >1.0×10 -11 (S). By satisfying this condition, a high shielding effect can be ensured as a metal-resin composite electromagnetic wave shielding material.

[0041] In this specification, the electrical conductivity is measured based on the four-probe method defined in JIS K7194.

[0042] On the surface of the metal layer, various surface treatment layers can be formed for the purpose of promoting bonding, environmental resistance, heat resistance and rust prevention. For example, in order to improve the environmental resistance and heat resistance required when the metal surface is the outermost layer, Au plating, Ag plating, Sn plating, Ni plating, Zn plating, Sn alloy plating (Sn-Ag, Sn-Ni, Sn-Cu, etc.), chromate treatment, etc. can be performed. These treatments can also be combined. From a cost point of view, Sn plating or Sn alloy plating is preferred. In addition, in order to improve the adhesion between the metal layer and the resin layer, or between the metal layers, chromate treatment, roughening treatment, Ni plating, etc. can be performed. These treatments can also be combined. Roughening treatment is easy to obtain adhesion and is preferred. In addition, in order to improve the shielding effect against the DC magnetic field, a metal plating with high relative magnetic permeability can be provided. As metal platings with relatively high relative magnetic permeability, Fe-Ni alloy plating, Ni plating, etc. can be listed.

[0043] When using copper foil, based on the improvement of shielding performance, high-purity copper foil is preferred, and the purity is preferably 99.5% by mass or more, and more preferably 99.8% by mass or more. As copper foil, rolled copper foil, electrolytic copper foil, metallized copper foil, etc. can be used, preferably rolled copper foil with excellent bending and forming properties (forming properties include drawing properties. The same applies below). In the case of adding alloy elements to copper foil to form copper alloy foil, the total content of these elements and unavoidable impurities is preferably less than 0.5% by mass. In addition, if the copper foil contains a total of 50 to 2000 mass ppm of at least one selected from the group of Sn, Mn, Cr, Zn, Zr, Mg, Ni, Si and Ag, and / or contains 10 to 50 mass ppm of P, the elongation is improved compared with the pure copper foil of the same thickness, so it is preferred.

[0044] The thickness of the metal layer of the metal-resin composite electromagnetic wave shielding material constituting one embodiment of the present invention is preferably 4 μm or more for each sheet. If it is 4 μm or more, it can avoid the difficulty of handling, and can prevent the ductility of the metal layer from being significantly reduced, the molding processability of the laminate from being insufficient, etc. In addition, when the thickness of each layer is less than 4 μm, multiple metal layers must be stacked in order to obtain an excellent electromagnetic wave shielding effect, which leads to the problem of increased manufacturing costs. Based on this viewpoint, the thickness of the metal layer is more preferably 10 μm or more for each sheet, more preferably 12 μm or more, and further preferably 15 μm or more. On the other hand, when the thickness of each layer exceeds 100 μm, the molding processability may be deteriorated, so the thickness of each layer is preferably 100 μm or less, more preferably 50 μm or less, further preferably 45 μm or less, and further preferably 40 μm or less. As a method for measuring the thickness of the metal layer, for example, a constant pressure thickness tester (THICKNESS METERB-1, manufactured by Toyo Seiki Seisaku-sho) can be used according to JIS K 6250: Method A in 2019 to average the measured values ​​of 4 points in the sheet sample surface to obtain the thickness. It should be noted that the diameter of the indenter can be selected to be 5 mm and the pressure on the indenter can be selected to be 1.22 N for measurement. It is assumed that when measuring the thickness of the metal layer in the laminate, the thickness section can be observed by SEM or the like for measurement.

[0045] The metal layer constituting the metal resin composite electromagnetic wave shielding material can be a single sheet. Based on the viewpoint of improving molding processability and shielding performance, the metal layer constituting the metal resin composite electromagnetic wave shielding material is preferably stacked with a plurality of sheets separated by a resin layer. Based on the viewpoint that the total thickness of the metal resin composite electromagnetic wave shielding material can be timely reduced to ensure excellent electromagnetic wave shielding properties, the metal layer is more preferably stacked with a resin layer to more than two sheets. By stacking more than two metal layers separated by a resin layer, even if the total thickness of the metal layer is the same, the shielding effect is significantly improved compared with the case where the metal layer is a single layer or two metal layers are stacked without a resin layer. Although the total thickness of the metal layers increases when the metal layers are directly overlapped with each other, the shielding effect is also improved, but in order to obtain a significant improvement effect, it is preferred to stack the metal layers separated by a resin layer. That is, by stacking a plurality of metal layers constituting a laminated body separated by a resin layer, the total thickness of the metal layers required to obtain the same electromagnetic wave shielding effect can be reduced, and both lightweight and electromagnetic wave shielding effects of the laminated body can be achieved. It should be noted that in this case, as long as the metal layers are not directly stacked on each other, a structure in which a part or all of the resin layers are stacked can be adopted. Of course, a structure in which the metal layers and the resin layers are alternately stacked can also be adopted.

[0046] It is believed that this is because the resin layer exists between the metal layers, so the number of reflections of the electromagnetic wave increases and the electromagnetic wave is attenuated. However, although the more the number of metal layers is stacked, the more the electromagnetic wave shielding properties are improved, when the number of stacked layers increases, the number of stacking steps will also increase, which will lead to an increase in manufacturing costs and the shielding improvement effect will tend to be saturated. Therefore, the metal layers constituting the metal-resin composite electromagnetic wave shielding material are preferably 5 or less, more preferably 4 or less, and even more preferably 3 or less.

[0047] In one embodiment of the present invention, when forming multiple metal layers, all metal layers may be made of the same material, or different materials may be used for each layer. In addition, all metal layers may have the same thickness, or the thickness of each layer may be different.

[0048] Therefore, in the metal-resin composite electromagnetic shielding material according to one embodiment of the present invention, the total thickness of all metal layers can be 15 to 150 μm, 100 μm or less, 80 μm or less, or 60 μm or less.

[0049] (2. Resin layer)

[0050] In the metal-resin composite electromagnetic wave shielding material of one embodiment of the present invention, by sandwiching a resin layer between metal layers, an effective improvement in the electromagnetic wave shielding effect produced by stacking multiple metal layers can be obtained. Although the total thickness of the metal layers increases and the shielding effect is improved by directly stacking the metal layers, in order to obtain a significant improvement effect, it is preferred to stack the metal layers through the resin layer. It can be considered that this is because the resin layer exists between the metal layers, so the number of reflections of the electromagnetic waves increases and the electromagnetic waves are attenuated.

[0051] As the resin layer, based on the fact that a better electromagnetic wave shielding effect can be obtained, a resin layer with a larger difference in resistance with the metal layer is more preferred. In order to produce a larger difference in resistance, the relative dielectric constant of the resin layer needs to be smaller, specifically, preferably 10.0 (value at 20°C. The same below.) or less, more preferably 5.0 or less, and even more preferably 3.5 or less. In principle, the relative dielectric constant will not be less than 1.0. Among the materials commonly purchased, the lowest is about 2.0. Even if it is lower than this and close to 1.0, the increase in the shielding effect has a limit. On the other hand, the material itself becomes special and expensive. Taking into account the balance between cost and effect, the relative dielectric constant is preferably above 2.0, and more preferably above 2.2.

[0052] Specifically, based on the viewpoint of molding processability, synthetic resins are particularly preferred as materials constituting the resin layer. The resin layer can be mixed with fiber-reinforced materials such as carbon fiber, glass fiber and aramid fiber. In addition, based on the viewpoint of improving shielding properties, magnetic materials can be mixed into the resin layer within the scope of the present invention. As synthetic resins, based on the viewpoints of easy purchase and molding processability, polyesters such as PET (polyethylene terephthalate), PEN (polyethylene naphthalate) and PBT (polybutylene terephthalate), olefin resins such as polyethylene and polypropylene, polyamides, polyimides, liquid crystal polymers, polyacetals, fluororesins, polyurethanes, acrylic resins, epoxy resins, silicone resins, phenolic resins, melamine resins, ABS resins, polyvinyl alcohol, urea resins, polyvinyl chloride, polycarbonate, polystyrene, styrene butadiene rubber, etc., among which PET, PEN, polyamides and polyimides are preferred based on the viewpoints of molding processability and cost. Synthetic resins may also be selected from: polyurethane rubber, chloroprene rubber, silicone rubber, fluororubber, styrene-based, olefin-based, vinyl chloride-based, urethane-based, amide-based and other elastomers. The resin layers used in the metal-resin composite electromagnetic wave shielding material of one embodiment of the present invention may all be composed of the same resin material, or different resin materials may be used for each layer. Based on the viewpoint of formability, preferably, part or all of the resin layer is an insulating layer.

[0053] The resin material can be laminated in the form of a film or a fiber. In addition, the resin layer can be formed by coating an uncured resin composition on the metal layer and then curing it, but for the sake of ease of manufacturing, it is preferred to use a resin film that can be attached to the metal layer. In particular, a PET film can be preferably used. In particular, by using a biaxially stretched corrugated film as the PET film, the strength of the shielding material can be improved.

[0054] There is no particular restriction on the thickness of the resin layer. When the thickness of each sheet is less than 4 μm, there is a tendency for the (elongation) fracture strain of the shielding material to decrease. Therefore, the thickness of each sheet of the resin layer is preferably 4 μm or more, more preferably 7 μm or more, even more preferably 9 μm or more, even more preferably 10 μm or more, further preferably 20 μm or more, even more preferably 40 μm or more, even more preferably 80 μm or more, and even more preferably 100 μm or more. On the other hand, when the thickness of each sheet exceeds 600 μm, there is a tendency for the (elongation) fracture strain of the shielding material to decrease. Therefore, the thickness of each sheet of the resin layer is preferably 600 μm or less, more preferably 500 μm or less, even more preferably 400 μm or less, even more preferably 250 μm or less, and even more preferably 200 μm or less. In one embodiment of the present invention, all resin layers may be of the same thickness, or the thickness of each layer may be different. Here, a resin layer refers to a continuous portion of the resin without a metal layer sandwiched therebetween. For example, even when multiple resin films are continuously stacked during the manufacturing process of electromagnetic wave shielding materials, since there is no metal layer sandwiched between these films, they appear to be one continuous body and are therefore considered as one resin layer. The thickness of the resin layer can be measured by the same method as the thickness of the metal layer described above.

[0055] Generally, the resin layer has higher ductility than the metal layer. Therefore, by using the resin layer to support the two surfaces of each metal layer, the ductility of the shielding metal layer is significantly improved, and the molding processability of the laminate is inevitably improved. From the perspective of improving the molding processability, it is preferred to overlap the metal layers through the resin layer rather than directly overlapping the metal layers.

[0056] The resin layer surface may be subjected to various surface treatments for the purpose of improving adhesion to the metal layer, etc. For example, by applying a primer coating or corona treatment to the bonding surface of the resin layer with the shielding metal layer, adhesion to the shielding metal layer can be improved.

[0057] (3. Electromagnetic wave shielding materials)

[0058] In one embodiment of the present invention, a metal-resin composite electromagnetic wave shielding material is provided, which is obtained by laminating N (wherein N is an integer greater than 1) metal layers and M (wherein M is an integer greater than 1) resin layers, and is characterized in that the VFL (Value of Forming Limit) calculated by the following formula satisfies VFL>0.24.

[0059]

[0060] N is not limited as long as it is an integer greater than 1, and a higher electromagnetic wave shielding effect can be obtained by increasing N. Typically, N is 1, 2, 3, 4 or 5 as described above.

[0061] M is not limited as long as it is an integer greater than 1. In order to sandwich a resin layer between metal layers and improve the electromagnetic shielding effect, typically, M=N+1 or M=N-1 or M=N. From the viewpoint of grounding, at least one of the outermost layers is preferably a metal layer.

[0062] The method for calculating VFL will be described in detail below. The present inventors have found that the larger the VFL calculated according to the above formula, the higher the moldability.

[0063] Evaluate the forming limit using the mold for FLD (forming limit diagram) Figure 1 The die is designed by reducing the dimensions listed in ISO-12004-2-2008 by 25%. The dimensions of the stamped parts are: D = 22.5 mm, R part R f =2mm, 4mm or 6mm. The R part of the mold is set to R d=2mm. The gap between the stamping part and the die is set to 2.25mm. By making the blank holder have a W-shaped cut, the extrusion pressure of the die is set to an initial pressure of 4000N, thereby preventing the test piece from being pulled in during molding. When setting the test piece, in order to reduce the influence of material or friction, the drive plate is clamped between the test piece and the push plate. As a drive plate, NITOFLON No.900UL (thickness 0.05mm) manufactured by Nitto Denko Corporation can be used. In addition, the drive plate is selected to have an outer shape of φ60mm and a φ2mm hole in the center. A circular test piece of φ60mm is cut out, and a grid-like mark with a spacing of 1mm is marked near the center. The test piece is molded by increasing the extrusion depth of the stamping part by 0.5mm each time. For a test piece with n=3 prepared at one depth, observe any four sides of the grid near the center of each test piece with a microscope, and record the extrusion depth of the stamping when the crack through the metal layer is observed to be more than 50% (that is, more than 6 of the 12 observation positions in total). Then, the size (L1, L2, L3, L4) and deformation angle (θ1, θ2) of each side at the extrusion depth of the stamping are measured using a microscope ( Figure 2 ).

[0064] Next, for the above four sides of each test piece, the average length of the deformed side and the average deformation angle were calculated according to the following formula:

[0065]

[0066]

[0067]

[0068] Next, refer to Figure 3 Based on the above average length and average deformation angle, the true strains ε1 and ε2 equivalent to the maximum strain and minimum strain in the edge are calculated.

[0069] The calculation order of ε1 and ε2 is as follows.

[0070] first,

[0071] Set as When , the ellipse inscribed in the deformed parallelogram is as shown below.

[0072]

[0073] Convert the above “※” from orthogonal coordinates (x, y) to polar coordinates

[0074] becomes

[0075] Be the biggest and smallest satisfy Therefore, Solving it, we can find the following

[0076]

[0077] according to Find l1′ and l2′ as shown below.

[0078]

[0079] l1′ and l2′ represent the maximum diameter and the minimum diameter of the ellipse.

[0080] The true strain is expressed as follows using the lattice spacings l0, l1' and l2'.

[0081] ε1=ln{(l1′-l0)+1}, ε2=ln((l2′-l0)+1}

[0082] The larger value of the calculated value is recorded as the maximum strain, and the smaller value is recorded as the minimum strain.

[0083] Finally, the maximum depth d at which the crack penetrates the metal layer by less than 50% is used as the forming limit, and the VFL (Value of Forming Limit) of each side is calculated according to the following formula. In order to reduce measurement deviation, the calculated VFL of each side is averaged and used as the VFL of the test piece.

[0084]

[0085] It should be noted that the rupture that penetrates the metal layer refers to the rupture that penetrates the outermost metal layer when the metal layer is the outermost layer (FIG. 4(A)), and refers to the rupture that penetrates the metal layer when the metal layer is not the outermost layer of the metal layer but is covered by a resin layer when the resin layer is peeled off and the inner metal layer closest to the resin layer is observed (FIG. 4(B)). In the case where both the resin layer and the metal layer are ruptured, even if no rupture occurs in the metal layer in the four observed sides, it is considered that there is rupture that penetrates the metal layer in all the sides (FIG. 4(C)).

[0086] When the VFL calculated according to the above steps is greater than 0.24, it indicates that the molding limit of the metal resin composite electromagnetic wave shielding material is greater than 5.0 mm, and it can be seen that the molding processability is relatively high. Therefore, when VFL is greater than 0.24, it can be molded in a continuum manner, for example, it can conform to bumps and depressions of more than 5 mm. Based on this view, VFL is preferably greater than 0.26, more preferably greater than 0.28, even more preferably greater than 0.30, even more preferably greater than 0.32, even more preferably greater than 0.34, further preferably greater than 0.36, even more preferably greater than 0.38, and even more preferably greater than 0.40. There is no particular limit to the upper limit of VFL, for example, based on the viewpoints of production efficiency and cost, it can be set to less than 0.50.

[0087] The method of increasing the VFL is not particularly limited, and there are methods such as adjusting the thickness of the metal layer of each layer and adjusting the elongation of the resin layer.

[0088] The metal-resin composite electromagnetic wave shielding materials of various embodiments of the present invention can be used, in particular, for covering materials or exterior materials of electrical equipment or electronic equipment (for example, inverters, communication machines, resonators, electron tubes and discharge lamps, electrical heating equipment, motors, generators, electronic components, printed circuits, mechanical equipment, etc.), covering materials for wiring harnesses and communication cables connected to electrical equipment or electronic equipment, electromagnetic wave shielding sheets, electromagnetic wave shielding plates, electromagnetic wave shielding bags, electromagnetic wave shielding boxes, electromagnetic wave shielding rooms and other electromagnetic wave shielding purposes. In addition, the metal-resin composite electromagnetic wave shielding materials of various embodiments of the present invention can also be used as press-in parts for press-in molding. Furthermore, in order to improve the electromagnetic wave shielding effect, electromagnetic wave shielding sheets such as magnetic sheets can be attached to the inner and / or outer sides of the metal-resin composite electromagnetic wave shielding materials of the present invention without affecting the scope of the present invention.

[0089] [Example]

[0090] The following will show examples of the present invention together with comparative examples, but they are provided only for better understanding of the present invention and its advantages and are not intended to limit the present invention.

[0091] As the metal layer, three kinds of rolled copper foils were prepared (when measured from the surface using EBSD (crystal orientation analysis), type A: the crystal grain size is 300 μm or more; type B: the crystal grain size is 10 μm or more; type C: the crystal grain size is less than 10 μm.) and two kinds of aluminum foils (type A: A8021 material; type B: the A8021 material is annealed at 300°C for 1 hour.), and as the resin layer, three kinds of resins (PET: polyethylene terephthalate film, PE: polyethylene film, PC: polycarbonate film) were prepared. The thickness and conductivity of various copper foils, as well as the thickness of various resins are shown in Table 1. It should be noted that in Table 1, the resin marked as "×" in the "filler" column has no filler added, and the value marked as "0" has filler added.

[0092] In each example, stacking is performed according to the stacking structure shown in Table 1. Urethane adhesive is used as the adhesive for stacking. The order of each layer shown in the stacking structure is the order of stacking. It should be noted that "Resin" refers to a resin layer and "Metal" refers to a metal layer. Although there is an adhesive layer between each resin layer and each metal layer, its representation is omitted in Table 1.

[0093] (Evaluation of Formability)

[0094] For each embodiment and comparative example, the depth of the forming limit was evaluated using the mold for the FLD (forming limit diagram) described above, and VFL was calculated based on the strain at this time. As shown in Table 1, the depth of the forming limit in the embodiment is 5.0 mm or more, and the forming processability is excellent. At this time, the values ​​of VFL are all higher than 0.24. It should be noted that in Table 1, "Formability" marked as "◎" means that the depth of the forming limit is 8.5 mm or more, marked as "○" means that the depth of the forming limit is 5.0 mm or more and less than 8.5 mm, marked as "△" means that the depth of the forming limit is 4.0 mm or more and less than 5.0 mm, and marked as "×" means that the depth of the forming limit is less than 4.0 mm.

[0095] (Evaluation of shielding properties)

[0096] Then, for each embodiment and comparative example, the apparent conductivity C = σ × d (S) is calculated based on the conductivity σ (S / m) and the total thickness d (m) of the metal layer. The conductivity of the metal layer is obtained by the 4-probe method described above, and the thickness of the metal layer is measured using a constant pressure thickness tester (THICKNESS METER B-1, manufactured by Toyo Seiki Manufacturing Co., Ltd.) for each metal layer before lamination with the resin according to the method described above. In addition, for each embodiment and comparative example, the magnetic field shielding effect at a frequency of 500 kHz was evaluated at room temperature (25°C) using a magnetic field measuring fixture of a KEC method shielding effect measuring device (manufactured by technoscience, JSE-KEC) and a network analyzer (manufactured by Keysight Technologies, E5080). The calculation results of the apparent conductivity C and the measurement results of the shielding effect are shown in Table 1. It can be seen that the embodiments of the present invention can improve the molding processability and maintain the shielding effect. It should be noted that in Table 1, "shielding effect" marked as "0" means that the shielding effect is more than 10 dB according to the KEC method in the frequency band of 500 kHz, and "×" means that the shielding effect is less than 10 dB according to the KEC method in the frequency band of 500 kHz.

[0097]

Table 1

[0098]

[0099] As shown in Table 1, the metal-resin composite electromagnetic wave shielding material of the embodiment of the present invention has excellent molding processability because the VFL is greater than 0.24. In addition, the shielding effect is also maintained at a high level. In addition, as shown in Example 24, although multiple layers of resin films are continuously stacked as resin layers, the parts without the metal layer are combined and regarded as one resin layer.

Claims

1. A metal-resin composite electromagnetic wave shielding material, which is obtained by laminating N metal layers and M resin layers, wherein: N is an integer greater than or equal to 1, and M is an integer greater than or equal to 1, wherein: The VFL calculated according to the following formula satisfies VFL>0.24:

2. The metal-resin composite electromagnetic wave shielding material according to claim 1, wherein: When the conductivity of the metal layer is denoted as σ (S / m) and the total thickness of the metal layer is denoted as d (m), the apparent conductivity C satisfies C = σ × d > 1.0 × 10 -11 (S).

3. The metal-resin composite electromagnetic wave shielding material according to claim 1 or 2, wherein: The thickness of each metal layer is 4 to 100 μm.

4. The metal-resin composite electromagnetic wave shielding material according to any one of claims 1 to 3, wherein: The thickness of each resin layer is 4 to 600 μm.

5. The metal-resin composite electromagnetic wave shielding material according to any one of claims 1 to 4, wherein: The total thickness of each metal layer is 15 to 150 μm. 6 . A covering material or exterior material for an electric device or an electronic device, comprising the metal-resin composite electromagnetic wave shielding material according to claim 1 .

7. An electric device or an electronic device comprising the covering material or the exterior material according to claim 6.

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