Electromagnetic wave shielding laminate, coating material or exterior material, electric and electronic equipment, and method for manufacturing electromagnetic wave shielding laminate

Abstract

To provide an electromagnetic wave shielding laminate with good shielding properties, a covering material or exterior material for electrical / electronic equipment equipped with the electromagnetic wave shielding laminate, and electrical / electronic equipment equipped with the covering material or exterior material.SOLUTION: An electromagnetic wave shielding laminate 100 including at least two metal layers (copper foils 110, 112) and insulating layers (PET films 120, 122, 124), and obtained by alternately laminating the metal layers and the insulating layers includes a tapered portion 115 in which a thickness T of the end portion of the electromagnetic wave shielding laminate changes. A distance A between adjacent metal layers with the insulating layer 122 interposed therebetween at the tip of each tapered portion in the thickness direction is shorter than a distance B between adjacent metal layers with the insulating layer 124 interposed therebetween at the central portion of a flat portion 116 other than the tapered portion, and the metal layers are not in contact with each other.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to an electromagnetic shielding laminate, a coating material or an exterior material, an electric / electronic device, and a method for manufacturing an electromagnetic shielding laminate.

Background Art

[0002] In environment-friendly vehicles equipped with secondary batteries such as electric vehicles and hybrid vehicles, a method is often adopted in which the DC current generated from the mounted secondary battery is converted into an AC current via an inverter, and then the necessary power is supplied to an AC motor to obtain driving force. Electromagnetic waves are generated due to the switching operation of the inverter or the like. Since electromagnetic waves cause reception interference with in-vehicle audio devices, wireless devices, etc., measures are taken to shield electromagnetic waves by housing an inverter or the like in a metal housing.

[0003] However, although a metal housing has good electromagnetic shielding characteristics, it is heavy, which reduces fuel efficiency and increases costs. Therefore, the development of an electromagnetic shielding housing to replace the metal housing is desired.

[0004] Moreover, electromagnetic waves are radiated from many electric / electronic devices including communication devices, displays, and medical devices, not only in automobiles. Electromagnetic waves may cause malfunction of precision devices, and furthermore, there are concerns about their effects on the human body. For this reason, various technologies for reducing the influence of electromagnetic waves using electromagnetic shielding materials have been developed. For example, Patent Document 1 describes using a copper foil composite formed by laminating a copper foil and a resin film as an electromagnetic shielding material. Also, Patent Document 2 describes an electromagnetic shielding material having a structure in which at least two metal foils are laminated via a solid insulating layer, and at least two of the two or more metal foils laminated via the insulating layer are electrically connected.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 7-290449 [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2017-45810 [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] However, in Patent Document 1, it is necessary to considerably increase the thickness of the electromagnetic shielding material required to obtain excellent shielding characteristics, and sufficient weight reduction cannot be achieved from the viewpoint of improving fuel efficiency in automobiles.

[0007] Further, in Patent Document 2, as a form of electrical connection, for example, it is described that the length of the metal foil is made longer than the length of the insulating layer between the metal foils, and the metal foils are brought into contact with each other (see paragraph 0073 and FIG. 4 of Patent Document 2). Thereby, not only the weight of the electromagnetic shielding material itself is reduced, but also the shielding characteristics are improved well. However, in the manufacture of the electromagnetic shielding material, since it is necessary to make the length of the metal foil longer than the length of the insulating layer between the metal foils, it is not suitable for mass-producing electromagnetic shielding materials of a desired size by slitting an electromagnetic shielding material in which a roll-shaped metal foil and an insulating layer are laminated by laminating or the like. Such is the actual situation. Therefore, there is still room for improvement in the electromagnetic shielding materials described in Patent Documents 1 and 2.

[0008] Therefore, in one embodiment of the present invention, an object is to provide an electromagnetic shielding laminate having good shielding characteristics. Further, in a further embodiment of the present invention, an object is to provide a method for manufacturing an electromagnetic shielding laminate that can be manufactured relatively easily. [Means for Solving the Problems]

[0009] That is, in one aspect, the present invention is an electromagnetic shielding laminate including at least two metal layers and insulating layers, in which the metal layers and the insulating layers are alternately laminated, and having a tapered portion where the thickness at the end of the electromagnetic shielding laminate changes, and the distance A between adjacent metal layers via the insulating layer at the tip of each tapered portion in the thickness direction is shorter than the distance B between adjacent metal layers via the insulating layer at the central portion of the flat portion other than the tapered portion, and the metal layers are not in contact with each other, which is an electromagnetic shielding laminate.

[0010] In one embodiment of the electromagnetic shielding laminate according to the present invention, the ratio L1 / T of the length L1 of each tapered portion to the thickness T of the flat portion of the electromagnetic shielding laminate is 2000% or less.

[0011] In one embodiment of the electromagnetic shielding laminate according to the present invention, the ratio A / B of the distance A to the distance B is 75% or less.

[0012] In one embodiment of the electromagnetic shielding laminate according to the present invention, the uppermost layer and the lowermost layer of the electromagnetic shielding laminate are metal layers.

[0013] In one embodiment of the electromagnetic shielding laminate according to the present invention, the insulating layer interposed between adjacent metal layers has an overhanging portion that protrudes outside the tip of the metal layer.

[0014] In one embodiment of the electromagnetic shielding laminate according to the present invention, the metal layers are not electrically connected to each other.

[0015] Further, in another aspect, the present invention is a coating material or an exterior material for an electric / electronic device including the electromagnetic shielding laminate described in any of the above.

[0016] Further, in another aspect, the present invention is an electric / electronic device including the above coating material or exterior material.

[0017] Furthermore, in another aspect, the present invention provides a method for manufacturing an electromagnetic wave shield laminate according to any one of the above, comprising using at least two metal layers and insulating layers, and forming notches in the intermediate laminate by a notch processing punch having convex portions from the outermost layer side of the intermediate laminate in which the metal layers and the insulating layers are alternately laminated; and after forming the notches, obtaining an electromagnetic wave shield laminate by punching the intermediate laminate in the thickness direction so as to cut a part of the notches.

Advantages of the Invention

[0018] According to one embodiment of the present invention, an electromagnetic wave shield laminate with good shielding characteristics can be provided. Further, according to a further embodiment of the present invention, a method for manufacturing an electromagnetic wave shield laminate that can be manufactured relatively easily can be provided.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0020] Hereinafter, the present invention is not limited to each embodiment, and components can be modified and embodied without departing from the gist thereof. Also, various inventions can be formed by appropriately combining a plurality of components disclosed in each embodiment. In the present specification, the "tapered portion" means that the ratio L1 / L0 of the horizontal length L1 of each tapered portion to the horizontal length L0 from the tip e to the centroid c of the metal layer is within 20% (see Fig. 4). Also, the "portion other than the tapered portion" is a flat portion where the thickness of the electromagnetic shielding laminate does not substantially change.

[0021] [1. Electromagnetic shielding laminate] In one embodiment of the electromagnetic shielding laminate according to the present invention, it includes at least two metal layers and insulating layers, and the metal layers and the insulating layers are alternately laminated. And in one embodiment, it has a tapered portion where the thickness at the end of the electromagnetic shielding laminate changes, and the distance A between adjacent metal layers via the insulating layer at the tip (tip surface) of each tapered portion is shorter than the distance B between adjacent metal layers via the insulating layer at the central portion of the flat portion other than the tapered portion, and it is important that the metal layers are not in contact with each other. In one embodiment, the shielding characteristics are good. In the present invention, since the metal layers are not in contact with each other, the metal layers are not electrically connected to each other.

[0022] Conventionally, as in the laminate described in Patent Document 1, a metal foil and an insulating layer were alternately laminated as an electromagnetic shielding material. In order to improve the shielding characteristics, in order to narrow the distance between adjacent metal foils through one insulating layer, it was considered to reduce the overall thickness of the insulating layer. However, the shielding characteristics at 1 MHz did not improve and sometimes deteriorated. The reason for this is presumably that the attenuation effect of electromagnetic waves decreased due to the reduction of the overall thickness of the insulating layer.

[0023] Therefore, the present inventors have earnestly considered the above circumstances and conducted extensive studies. As a result, they have found that an electromagnetic wave shielding laminate having at least two metal layers and an insulating layer, wherein the metal layers and the insulating layer are alternately laminated, and having a tapered portion where the thickness at the end of the laminate changes, and the distance A between adjacent metal layers through the insulating layer at the tip of the tapered portion in the thickness direction is shorter than the distance B between adjacent metal layers through the insulating layer at the central portion of the flat portion in the thickness direction, and the metal layers are not in contact with each other, exhibits good electromagnetic wave shielding characteristics. Further, unlike the electromagnetic wave shielding laminate described in Patent Document 2, such an electromagnetic wave shielding laminate can be manufactured relatively easily without making the length of the metal layer longer than the length of the insulating layer in the direction perpendicular to the thickness direction. Hereinafter, preferred embodiments of the present invention will be described.

[0024] In one embodiment, it can be manufactured by alternately laminating a metal layer and an insulating layer, and has a structure in which at least two metal layers are laminated via an insulating layer. From the viewpoint of electromagnetic wave shielding characteristics, the electromagnetic wave shielding laminate according to the present invention includes, for example, the following. The layers represented in parentheses may be added as appropriate. From the viewpoint of electromagnetic wave shielding characteristics, as the outermost layer of the electromagnetic wave shielding laminate, at least one of the uppermost layer and the lowermost layer is preferably a metal layer, and both the uppermost layer and the lowermost layer of the electromagnetic wave shielding laminate are preferably metal layers. (1) (Insulating layer) / Metal layer / Insulating layer / Metal layer / (Insulating layer) (2) (Insulating layer) / Metal layer / Insulating layer / Metal layer / Insulating layer / Metal layer / (Insulating layer) (3) (Insulating layer) / Metal layer / Insulating layer / Metal layer / Insulating layer / Metal layer / Insulating layer / Metal layer / (Insulating layer) In (1) to (3), one "metal layer" can be formed by laminating a plurality of metal layers without an intervening insulating layer, and one "insulating layer" can also be formed by laminating a plurality of insulating layers without an intervening metal layer. That is, a plurality of metal layers laminated without an intervening insulating layer can be regarded as one metal layer, and a plurality of insulating layers laminated without an intervening metal layer can be regarded as one insulating layer. Further, layers other than the insulating layer and the metal layer can also be provided.

[0025] In this way, by alternately laminating a metal layer and an insulating layer, a remarkable improvement in electromagnetic shielding characteristics can be observed. However, the electromagnetic shielding laminate has a tapered portion where the thickness at the end changes, and at the tip (tip surface) of each tapered portion in the thickness direction, the distance A between adjacent metal layers via the insulating layer is shorter than the distance B between adjacent metal layers via the insulating layer at the central portion of the flat portion other than the tapered portion, and since the metal layers are not in contact with each other, a further improvement in electromagnetic shielding characteristics can be achieved. Although the present invention is not intended to be limited by theory, this is considered to be due to the following reasons. That is, when the distance between the metal layers becomes shorter, the amount of electromagnetic waves leaking from the insulating layer to the outside decreases, and it is considered that the shielding effect increases because the intensity of the electromagnetic waves circulating around the receiving antenna weakens.

[0026] (Distance A, Distance B) In one embodiment, from the viewpoint of shortening the distance between adjacent metal layers via the insulating layer, the ratio A / B of distance A to distance B is preferably 75% or less, more preferably 50% or less, and even more preferably 40% or less as the upper limit side. On the other hand, the above ratio A / B is typically 8% or more, more typically 10% or more as the lower limit side. More specifically, distance A is, for example, 250 μm or less, and for example, 150 μm or less as the upper limit side, while it is, for example, 1.5 μm or more, and for example, 2.0 μm or more as the lower limit side. Also, distance B is, for example, 20 μm or more, and for example, 25 μm or more as the lower limit side, while it is, for example, 300 μm or less, and for example, 250 μm or less as the upper limit side. An example of the method for measuring distance A and distance B will be described below. The electromagnetic shielding laminate can be measured by cutting it in the thickness direction and observing the cut surface with a microscope (optical microscope) or the like. That is, distance A and distance B each mean the vertical distance between the metal layers in the thickness direction.

[0027] (Tapered portion length) From the viewpoint of workability, it is preferable that the ratio L1 / T of the horizontal length L1 of each tapered portion to the thickness T of the flat portion of the electromagnetic wave shielding laminate is 2000% or less (see Fig. 4). When the above ratio is exceeded, it is necessary to add a tapering process after punching. On the other hand, the ratio L1 / T is typically 30% or more, more typically 50% or more, as the lower limit. Note that the length of the tapered portion can be measured with a microscope in the same manner as the measurement methods of the distance A and the distance B described above.

[0028] (Metal layer) In one embodiment, the material of the metal layer to be used is not particularly limited, but from the viewpoint of enhancing the shielding characteristics against an alternating magnetic field and an alternating electric field, it is preferably a metal material having excellent conductivity. Specifically, it is preferably formed of a metal having a conductivity of 1.0×10 6 S / m (value at 20°C; the same applies hereinafter) or more, more preferably the conductivity of the metal is 10.0×10 6 S / m or more, still more preferably 30.0×10 6 S / m or more, and most preferably 50.0×10 6 S / m or more. Such metals include Fe with a conductivity of about 9.9×10 6 S / m, Ni with a conductivity of about 14.5×10 6 S / m, Al with a conductivity of about 39.6×10 6 S / m, Cu with a conductivity of about 58.0×10 6 S / m, and Ag with a conductivity of about 61.4×10 6 S / m. Considering both conductivity and cost, it is preferably practical to employ Al or Cu. All the metal layers used in the electromagnetic wave shielding laminate according to the present invention may be the same metal, or different metals may be used for each layer. Also, alloys of the above-described metals can be used. Various surface treatment layers for the purpose of adhesion promotion, environmental resistance, heat resistance, and rust prevention may be formed on the surface of the metal layer.

[0029] For example, for the purpose of enhancing the environmental resistance and heat resistance required when the metal layer is the outermost layer, Au plating, Ag plating, Sn plating, Ni plating, Zn plating, Sn alloy plating (such as Sn-Ag, Sn-Ni, Sn-Cu, etc.), chromate treatment, etc. can be performed. These treatments may be combined. From the perspective of cost, Sn plating or Sn alloy plating is preferred.

[0030] Also, for the purpose of enhancing the adhesion between the metal layer and the insulating layer, chromate treatment, roughening treatment, Ni plating, etc. can be performed. These treatments may be combined. The roughening treatment is preferred as it can easily obtain good adhesion.

[0031] Also, for the purpose of enhancing the shielding characteristics against a DC magnetic field, a metal layer with a high relative permeability can be provided. Examples of the metal layer with a high relative permeability include Fe-Ni alloy plating, Ni plating, etc.

[0032] When using a copper foil as the metal layer, since the shielding characteristics are improved, a high-purity one is preferred, and the purity is preferably 99.5 mass% or more, more preferably 99.8 mass% or more. As the copper foil, rolled copper foil, electrolytic copper foil, copper foil by metallization, etc. can be used, but a rolled copper foil with excellent flexibility and formability is preferred. When adding alloy elements to the copper foil to form a copper alloy foil, the total content of these elements and inevitable impurities may be less than 0.5 mass%. In particular, when the copper foil contains at least one selected from Sn, Mn, Cr, Zn, Zr, Mg, Ni, Si, and Ag in a total of 50 to 2000 mass ppm, and / or P in 10 to 50 mass ppm, the elongation is improved compared to a pure copper foil of the same thickness, which is preferred.

[0033] In one embodiment, the thickness of the metal layer used is preferably 4 μm or more per layer. If it is less than 4 μm, the ductility of the metal layer will be significantly reduced, and the formability of the electromagnetic shielding laminate may be insufficient. Also, if the thickness of each layer is less than 4 μm, a large number of metal layers need to be laminated to obtain excellent electromagnetic shielding characteristics, which also causes a problem of increased manufacturing cost. From such a perspective, the thickness of the metal layer is more preferably 10 μm or more per layer, still more preferably 15 μm or more, still more preferably 20 μm or more, still more preferably 25 μm or more, and still more preferably 30 μm or more. On the other hand, if the thickness of the metal layer per layer exceeds 100 μm, the formability will be deteriorated. Therefore, the thickness of the metal layer is preferably 100 μm or less per layer, more preferably 50 μm or less, still more preferably 45 μm or less, and particularly preferably 40 μm or less.

[0034] Since an insulating layer is interposed between the metal layers, if there are at least two metal layers, the effects of the present invention can be achieved. However, although the shielding characteristics improve as the number of laminated metal layers increases, increasing the number of laminated layers increases the lamination process, leading to an increase in manufacturing cost. Also, the improvement effect of the shielding characteristics tends to saturate. Therefore, the number of metal layers in the electromagnetic shielding laminate may be 5 layers or less, or 4 layers or less. When there are 3 or more metal layers, the ratio A / B of the distance A to the distance B between at least one outermost metal layer or the metal layer adjacent to the outermost layer and the metal layer adjacent to it via the insulating layer may be 75% or less.

[0035] That is, in one embodiment, the total thickness of the metal layer can be 15 to 150 μm, can also be 100 μm or less, can also be 80 μm or less, and can also be 60 μm or less.

[0036] (Insulating layer) A remarkable improvement in electromagnetic shielding characteristics by laminating a plurality of metal layers can be obtained by interposing an insulating layer between the metal layers. Even if the metal layers are directly stacked on top of each other, although the shielding characteristics are improved by increasing the total thickness of the metal layers, a remarkable improvement effect cannot be obtained. This is presumably because the number of reflections of electromagnetic waves increases due to the presence of an insulating layer between the metal layers, and the electromagnetic waves are attenuated.

[0037] As the insulating layer, it is preferable that the difference in impedance from the metal layer is large in terms of obtaining excellent electromagnetic shielding characteristics. In order to cause a large impedance difference, it is necessary that the relative permittivity of the insulating layer is small. Specifically, it is preferably 10 (the value at 20 °C. The same applies hereinafter) or less, more preferably 5.0 or less, and even more preferably 3.5 or less. In principle, the relative permittivity does not become smaller than 1.0. Generally, even for readily available materials, the lowest value is about 2.0. Even if it is made lower to approach 1.0, the increase in shielding characteristics is limited, while the material itself becomes special and expensive. Considering the balance between cost and effect, the relative permittivity is preferably 2.0 or more, and more preferably 2.2 or more.

[0038] Specifically, examples of materials constituting the insulating layer include glass, metal oxides, paper, natural resins, and synthetic resins, with synthetic resins being preferred from the perspective of processability. It is also possible to mix fiber reinforcements such as carbon fibers, glass fibers, and aramid fibers into these materials. From the perspectives of availability and processability, synthetic resins include 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, phenol resins, melamine resins, ABS resins, polyvinyl alcohol, urea resins, polyvinyl chloride, PC (polycarbonate), polystyrene, styrene-butadiene rubber, etc. Among these, PET, PEN, polyamide, and polyimide are preferred due to processability and cost reasons. Synthetic resins can also be made into elastomers such as urethane rubber, chloroprene rubber, silicone rubber, fluororubber, styrene-based, olefin-based, vinyl chloride-based, urethane-based, and amide-based. Furthermore, the synthetic resin itself may serve as an adhesive, and in this case, the structure is such that the metal layer is laminated via the adhesive. There are no particular restrictions on the adhesive, but examples include acrylic resin-based, epoxy resin-based, urethane-based, polyester-based, silicone resin-based, vinyl acetate-based, styrene-butadiene rubber-based, nitrile rubber-based, phenol resin-based, cyanoacrylate-based, etc. Due to ease of manufacturing and cost reasons, urethane-based, polyester-based, and vinyl acetate-based are preferred.

[0039] The resin material can be laminated in the form of a film or fibers. Also, a resin layer may be formed by applying an uncured resin composition to the metal layer and then curing it, but a resin film that can be attached to the metal layer is preferred for ease of manufacturing. In particular, a PET film can be preferably used. In particular, using a biaxially stretched film as the PET film can enhance the strength of the shielding material.

[0040] The thickness of the insulating layer is not particularly limited, but it is preferable that the thickness of one insulating layer in the tapered portion is thinner than the thickness of one insulating layer at the central portion of the flat portion. The thickness of one insulating layer in the tapered portion is, for example, 250 μm or less, and for example, 150 μm or less on the upper limit side. On the other hand, the thickness of one insulating layer in the tapered portion is, for example, 1.5 μm or more, and for example, 2.0 μm or more on the lower limit side. Also, the thickness of one insulating layer at the central portion of the flat portion is, for example, 20 μm or more, and for example, 25 μm or more on the lower limit side. On the other hand, the thickness of one insulating layer at the central portion of the flat portion is, for example, 300 μm or less, and for example, 250 μm or less on the upper limit side. In the electromagnetic wave shielding laminate in which the outermost layer is an insulating layer, the thickness of the insulating layer of the outermost layer may be equal to the thickness of one insulating layer at the central portion of the flat portion.

[0041] (Overhang portion) In one embodiment, the insulating layer interposed between adjacent metal layers may have an overhang portion that protrudes outside the tip of the metal layer.

[0042] As a lamination method for laminating the insulating layer and the metal layer, an adhesive may be used between the insulating layer and the metal layer, or the insulating layer may be thermocompression bonded to the metal layer without using an adhesive. A method of simply overlapping without using an adhesive may also be used, but in consideration of the integrity of the electromagnetic wave shielding laminate, at least the ends (for example, each side when the shielding material is square) are preferably joined by an adhesive or by thermocompression bonding. However, from the viewpoint of not applying excessive heat to the insulating layer, it is preferable to use an adhesive. The adhesive is the same as those described above and is not particularly limited, but examples include acrylic resin-based, epoxy resin-based, urethane-based, polyester-based, silicone resin-based, vinyl acetate-based, styrene-butadiene rubber-based, nitrile rubber-based, phenol resin-based, cyanoacrylate-based, etc. For reasons of ease of manufacture and cost, urethane-based, polyester-based, and vinyl acetate-based are preferable.

[0043] The thickness of the adhesive layer is preferably 6 μm or less. If the thickness of the adhesive layer exceeds 6 μm, only the metal layer is likely to break after laminating the insulating layer on the metal layer. However, this does not apply when the adhesive layer as described above also serves as the insulating layer, and the thickness can be the same as that described in the explanation of the insulating layer.

[0044] In one embodiment, the thickness of the electromagnetic shield laminate at the tip of the tapered portion is, for example, 400 μm or less, for example, 300 μm or less as the upper limit. On the other hand, the thickness of the electromagnetic shield laminate at the tip of the tapered portion is, for example, 8 μm or more, for example, 10 μm or more as the lower limit. Note that the thickness of the electromagnetic shield laminate at the central portion of the flat portion is, for example, 500 μm or less, for example, 400 μm or less as the upper limit. On the other hand, the thickness of the electromagnetic shield laminate is, for example, 100 μm or more, for example, 150 μm or more as the lower limit.

[0045] According to one embodiment, it can have magnetic field shielding characteristics (how much the signal is attenuated on the receiving side) of 36 dB or more at 1 MHz, preferably 40 dB or more, more preferably 50 dB or more, even more preferably 60 dB or more, and particularly preferably 70 dB or more, and can have magnetic field shielding characteristics of, for example, 36 to 90 dB. In the present invention, the magnetic field shielding characteristics shall be measured by the KEC method. The KEC method refers to the "Electromagnetic Wave Shielding Characteristics Measurement Method" at the Kansai Electronic Industry Promotion Center.

[0046] (Use) In one embodiment, the electromagnetic wave shielding laminate can be used as a coating material or exterior material for electrical and electronic devices (e.g., inverters, communication devices, resonators, electron tubes / discharge lamps, electric heating devices, electric motors, generators, electronic components, printed circuits, medical devices, etc.), a coating material for harnesses and communication cables connected to electrical and electronic devices, an electromagnetic wave shielding sheet, an electromagnetic wave shielding panel, an electromagnetic wave shielding bag, an electromagnetic wave shielding box, an electromagnetic wave shielding chamber, etc., for various electromagnetic wave shielding applications.

[0047] [2. Method for manufacturing electromagnetic wave shielding laminate] In one embodiment of the method for manufacturing the electromagnetic wave shielding laminate according to the present invention, it is the method for manufacturing the electromagnetic wave shielding laminate described above, and as an example, notch formation and punching are performed in this order. Note that descriptions overlapping with the above description are omitted.

[0048] (Notch formation) As shown in FIGS. 1(A) and (B), using at least two metal layers and insulating layers, a notch is formed in the intermediate laminate (the laminate before the following notch processing is referred to as the intermediate laminate) in which the metal layers and the insulating layers are alternately laminated, from the outermost layer side (e.g., the lowermost layer side) with a notch processing punch having a convex portion. Each metal layer may be made of the same or different materials and may have the same or different thicknesses. Also, each insulating layer may be made of the same or different materials and may have the same or different thicknesses. The angle and radius of curvature R of the tip of the notch, the pressing load (or the amount of pushing in) of the notch, etc. can be variously set according to the thickness and material of each metal layer and each insulating layer. Note that the outermost layer of the intermediate laminate in which the notch is formed is preferably a metal layer because the amount of deformation after processing is small and the springback is also small.

[0049] When the outer surface of the uppermost layer of the intermediate laminate is pressed with a notch processing die and pushed so that the convex portion of the notch processing punch abuts on the outer surface of the lowermost layer of the intermediate laminate, a notch is formed on the outer surface of the lowermost layer of the intermediate laminate.

[0050] (Punching) After forming the notch, as shown in FIG. 1(C), an electromagnetic shielding laminate is obtained by punching the intermediate laminate in the thickness direction so as to cut a part of the notch. More specifically, the intermediate laminate is placed on a die, and the intermediate laminate is punched with the punch in the thickness direction so that the punch hits the apex of the notch. As a result, tapered portions are formed at the ends of the metal layers adjacent to each other via the insulating layer, with the width becoming narrower toward the tip. The distance A between the metal layers adjacent to each other via the insulating layer at the tip of each tapered portion is shorter than the distance B between the metal layers adjacent to each other via the insulating layer at the central portion of the flat portion other than the tapered portion, and an electromagnetic shielding laminate in which the metal layers are not in contact with each other is obtained. Also, no sag or the like occurs on the entire fractured surface (tip) after punching. If, in the above-described embedding step, as shown in FIGS. 2(A) and (B), the laminate is punched with a punch without forming a notch in the intermediate laminate, the metal layers are not in contact with each other in the intermediate laminate after cutting, but sag may occur on the entire fractured surface due to the metal layer and the insulating layer being pulled during punching. Such sag is presumed to deteriorate the shielding characteristics of the electromagnetic shielding laminate.

[0051] Note that the clearance between the punch and the die is appropriately, for example, 2 to 8% of the total thickness of the electromagnetic shielding laminate from the viewpoint of suppressing the occurrence of sag on the fractured surface.

[0052] In addition, in one embodiment of the method for manufacturing an electromagnetic shielding laminate according to the present invention, when the metal layer and the insulating layer are not joined by an adhesive or thermocompression bonding or the like during the production of the intermediate laminate, in order to prevent misalignment, a step of fixing the end portion of the electromagnetic shielding laminate after punching (for example, if it is rectangular in top view, the four side end portions) with tape may be included.

Example

[0053] The present invention will be specifically described based on test examples, examples, and comparative examples. The following descriptions of the examples and comparative examples are merely specific examples for facilitating the understanding of the technical content of the present invention, and the technical scope of the present invention is not limited by these specific examples.

[0054] [Study on the Fabrication of Electromagnetic Wave Shielding Laminates] (Test Examples 1 - 2) As shown in Table 1, as Test Example 1, a copper foil (width: 50 mm, depth: 40 mm, thickness: 18 - 21 μm) and a PET film (width: 50 mm, depth: 40 mm, thickness: 99 - 100 μm) were prepared. As Test Example 2, a copper foil (width: 50 mm, depth: 40 mm, thickness: 35 - 36 μm) and a PC film (width: 50 mm, depth: 40 mm, thickness: 100 μm) were prepared. According to the configuration shown in Table 1, the PET film or PC film and the copper foil were joined with an adhesive to fabricate an intermediate laminate (see Fig. 1(A)). Next, a notch was formed in the intermediate laminate using a notch - processing punch having a convex portion from the lowermost layer side of the intermediate laminate (see Fig. 1(B)). Next, the intermediate laminate was placed on the die, and the intermediate laminate was punched in the thickness direction with the punch so that the punch hit the apex of the notch, thereby obtaining an electromagnetic wave shielding laminate in which a tapered portion and a flat portion other than the tapered portion were formed (see Fig. 1(C)). At this time, the clearance between the die and the punch was set to 0.01 mm.

[0055] <Evaluation Method> (Observation after Punching) The electromagnetic wave shielding laminate was observed under the following observation conditions and evaluated based on the following criteria. The results are shown in Table 1, Fig. 3A (Test Example 1), and Fig. 3B (Test Example 2). · Observation Conditions Measuring instrument: Microscope (Keyence VHX - 6000) Measurement location: Cross - sectional shape of the end of the laminate (the laminate was cut, embedded in resin, and then polished to obtain the cross - sectional shape after cutting the laminate). Observation magnification: 20 times ·Judgment criterion: In the obtained electromagnetic wave shielding laminate, when the ratio A / B of the distance A between the metal layers adjacent to each other via the insulating layer at the tip of the tapered portion to the distance B between the metal layers adjacent to each other via the insulating layer at the central portion of the flat portion other than each tapered portion is 75% or less, it is indicated as "〇". Note that the distance A and the distance B in Test Example 1 mean the vertical distance in the thickness direction between the lowermost metal layer formed with the notch and the metal layer adjacent to each other via the insulating layer.

[0056]

Table 1

[0057] (Consideration 1) In Test Examples 1 to 2, using copper foils as at least two metal layers and an insulating layer, after forming a notch in the intermediate laminate with a notch processing punch having a convex portion from the lowermost layer side of the intermediate laminate in which the metal layer and the insulating layer are alternately laminated, the intermediate laminate was punched in the thickness direction so as to cut a part of the notch. As a result, an electromagnetic wave shielding laminate having a tapered portion whose end thickness changes, and at the tip of each tapered portion in the thickness direction, the distance A between the metal layers adjacent to each other via the insulating layer is shorter than the distance B between the metal layers adjacent to each other via the insulating layer at the central portion of the flat portion other than the tapered portion, and the metal layers are not in contact with each other was obtained (see FIGS. 3A and B).

[0058] [Electromagnetic Wave Shielding Laminate] <Example 1> In Example 1, the electromagnetic wave shielding laminate 100 shown in FIG. 4 was manufactured as follows. First, two copper foils 110 and 112 (width: 60 mm, depth: 60 mm, thickness: 17 μm) as metal layers, two PET films 120 and 124 (width: 50 mm, depth: 50 mm, thickness: 100 μm) as insulating layers, and one PET film 122 (width: 70 mm, depth: 70 mm, thickness: 25 μm) were prepared respectively. The PET film 120, the PET film 122, the PET film 124, and the copper foil 112 were laminated in this order on the copper foil 110, and an intermediate laminate was obtained without using an adhesive.

[0059] Regarding the intermediate laminate, in order to form a tapered portion and a flat portion other than the tapered portion, at the step between the end edges of the PET films 120 and 124 and the PET film 122, the copper foils 110 and 112 were bent along the step. Next, the four sides of the laminate were taped to fix the positions of the respective members, and an electromagnetic shield laminate 100 shown in FIG. 4 was obtained. Since both the width and the depth of the PET film 122 were longer than those of the copper foils 110 and 112, the obtained electromagnetic shield laminate 100 had an overhanging portion 123.

[0060] (Electromagnetic Shielding Property Evaluation) While the copper foils 110 and 112 and the PET films 120, 122, and 124 constituting the electromagnetic shield laminate 100 were being measured, the outer peripheral portion of the electromagnetic shield laminate 100 was fixed with tape so that no displacement occurred, and the electromagnetic shield laminate 100 was installed in a magnetic field shielding property evaluation apparatus (manufactured by Techno Science Japan, model T SES-KEC), and the magnetic field shielding property was evaluated by the KEC method under room temperature (25°C) conditions. Then, the frequency was changed from 0.1 MHz to 10 MHz, and the transition of the magnetic field shielding property with respect to the change in frequency was investigated. Table 2 shows the magnetic field shielding property at 1 MHz.

[0061] (Distance A, Distance B, Tapered Portion Length) Regarding the distance A between the copper foils 110 and 112 adjacent to each other via the PET film 122 at the tip of the tapered portion 115, the thickness of the PET film 122 measured with a height gauge (manufactured by Toyo Seiki Seisakusho) corresponded to this, and this is shown in Table 2. Also, regarding the distance B between the copper foils 110 and 112 adjacent to each other via the PET films 120, 122, and 124 at the central portion of the flat portion 116, the total value of the thicknesses of the PET films 120, 122, and 124 measured with a height gauge corresponded to this, and this is shown in Table 2. The horizontal length L1 of each tapered portion is approximately 5 mm, and the ratio L1 / L0 of the horizontal length L1 of the tapered portion to the horizontal length L0 from the tip e to the center of gravity c of the copper foils 110 and 112 is 20% or less respectively, and the ratio L1 / T of the horizontal length L1 of each tapered portion to the thickness T of the central portion of the flat portion of the electromagnetic shielding laminate 100 is surely within 2000% or less respectively.

[0062] <Comparative Example 1> In Comparative Example 1, the electromagnetic shielding laminate 200 shown in FIG. 5 was produced as follows. First, two copper foils 210 and 212 (width: 60 mm, depth: 60 mm, thickness: 17 μm) as metal layers, two PET films 220 and 224 (width: 50 mm, depth: 50 mm, thickness: 100 μm) as insulating layers, and one PET film 222 (width: 70 mm, depth: 70 mm, thickness: 25 μm) were prepared respectively. The PET film 220, the PET film 222, the PET film 224, and the copper foil 212 were laminated in this order on the copper foil 210 to obtain an intermediate laminate. The electromagnetic shielding laminate 200 was produced in the same manner as in Example 1 except that no taper processing was performed on each end of the metal layer. Regarding the distance C between the adjacent copper foils 210 and 212 through the PET films 220, 222, and 224, the total value of the thicknesses of the PET films 220, 222, and 224 is shown in Table 3. Regarding the obtained electromagnetic shielding laminate 200, the magnetic field shielding characteristics were evaluated by the KEC method. The results are shown in Table 3.

[0063] <Comparative Example 2> In Comparative Example 2, the electromagnetic wave shield laminate 300 shown in FIG. 6 was produced as follows. Two copper foils 310 and 312 (width: 60 mm, depth: 60 mm, thickness: 17 μm) were prepared as metal layers, and one PET film 322 (width: 60 mm, depth: 60 mm, thickness: 25 μm) was prepared as an insulating layer. The PET film 322 and the copper foil 312 were laminated in this order on the copper foil 310 to obtain an intermediate laminate. An electromagnetic wave shield laminate 300 was produced in the same manner as in Example 1, except that no taper processing was performed on each end of the metal layer. The distance D between the adjacent copper foils 310 and 312 through the PET film 322 is shown in Table 3 for the thickness of the PET film 322. Note that, for the obtained electromagnetic wave shield laminate 300, the magnetic field shielding characteristics were evaluated by the KEC method. The results are shown in Table 3.

[0064] [Table 2]

[0065] [Table 3]

[0066] (Consideration 2) In Example 1, there were taper portions where the thickness at the ends changed, and the distance A between the adjacent metal layers through the insulating layer at the tip of each taper portion in the thickness direction was shorter than the distance B between the adjacent metal layers through the insulating layer at the central portion of the flat portion other than the taper portions, and since none of the metal layers were in contact with each other, an electromagnetic wave shield laminate with good shielding characteristics was obtained. On the other hand, in Comparative Examples 1 and 2, since no taper processing was performed, the distances C and D between the adjacent metal layers through the insulating layer at the tip and the distances C and D between the adjacent metal layers through the insulating layer at the central portion were equal, resulting in inferior shielding characteristics compared to Example 1. In particular, in Comparative Example 2, even though the distance D was equal to the distance A, it was shorter than the distance B compared to Example 1, resulting in inferior shielding characteristics. Considering Example 1, it is presumed that electromagnetic wave shield laminates with good shielding characteristics were obtained in Test Examples 1 and 2.

Explanation of Signs

[0067] 100, 200, 300 Electromagnetic wave shield laminate 110, 112, 210, 212, 310, 312 Copper foil 115 Taper portion 120, 122, 124, 220, 222, 224, 320 PET film 123 Overhang portion A - D Distance L0, L1 Horizontal length T Thickness c Centroid e Tip

Claims

1. An electromagnetic shielding laminate comprising at least two metal layers and insulating layers, wherein the metal layers and the insulating layers are alternately laminated, having a tapered portion where the thickness of the end of the electromagnetic shielding laminate changes, in the thickness direction, the distance A between adjacent metal layers via the insulating layer at the tip of each tapered portion is shorter than the distance B between adjacent metal layers via the insulating layer at the central portion of the flat portion other than the tapered portion, An electromagnetic shielding laminate in which the metal layers are not in contact with each other.

2. The electromagnetic shielding laminate according to Claim 1, wherein the ratio L1 / T of the length L1 of each tapered portion to the thickness T of the flat portion of the electromagnetic shielding laminate is 2000% or less.

3. The electromagnetic shielding laminate according to Claim 1 or 2, wherein the ratio A / B of the distance A to the distance B is 75% or less.

4. The electromagnetic shielding laminate according to Claim 1 or 2, wherein the uppermost layer and the lowermost layer of the electromagnetic shielding laminate are metal layers.

5. The electromagnetic shielding laminate according to Claim 1 or 2, wherein the insulating layer interposed between adjacent metal layers has an overhanging portion that protrudes outside the tip of the metal layer.

6. The electromagnetic shielding laminate according to Claim 1 or 2, wherein the metal layers are not electrically connected to each other.

7. A coating material or exterior material for an electric / electronic device comprising the electromagnetic shielding laminate according to Claim 1 or 2.

8. An electric / electronic device comprising the coating material or exterior material according to Claim 7.

9. A method for manufacturing an electromagnetic shielding laminate according to Claim 1 or 2, forming a notch in the intermediate laminate with a notch processing punch having a convex portion from the outermost layer side of the intermediate laminate in which at least two metal layers and insulating layers are alternately laminated using the metal layers and the insulating layers, A method for manufacturing an electromagnetic shielding laminate, comprising the step of obtaining the electromagnetic shielding laminate by punching the intermediate laminate in the thickness direction so as to cut a part of the notch after forming the notch.

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