Electromagnetic wave shielding film

Abstract

The present invention provides an electromagnetic wave shielding film having superior gas permeability and superior shielding performance for high-frequency electromagnetic waves. An electromagnetic wave shielding film 1 of the present invention includes an electromagnetic wave shielding layer 12 and a conductive adhesive layer 11, the electromagnetic wave shielding layer 12 including a first shielding layer 12a and a second shielding layer 12b, the first shielding layer 12a including an opening portion 121, and the second shielding layer 12b covering the opening portion 121 of the first shielding layer 12a. The ratio of the thickness of the first shielding layer 12a to the thickness of the second shielding layer 12b, i.e., the thickness of the first shielding layer / thickness of the second shielding layer, is preferably 3.0 to 300.

Description

Technical Field

[0001] The present invention relates to an electromagnetic wave shielding film. Background Art

[0002] Traditionally, portable devices such as smartphones and tablets have used flexible printed circuits (FPCs) with electromagnetic shielding films applied to them to block internally generated electromagnetic waves and external electromagnetic waves. Because the frequency bands of the circuits used in these devices are relatively low, the shielding layer used in these films, even if it was a thin metal layer formed by vapor deposition or sputtering, or a conductive paste layer heavily filled with conductive fillers, provided sufficient electromagnetic shielding performance.

[0003] However, in recent years, portable devices have become increasingly multifunctional. For example, network connectivity is becoming increasingly important, and achieving high definition, high image quality, 3D, and high speeds requires high-capacity signal processing. Consequently, the need to process these high-capacity signals has driven further speed increases, requiring suppression of noise received by signal lines and improving signal transmission performance. Consequently, there is a growing demand for flexible printed circuit boards (PCBs) that offer both superior shielding and transmission characteristics, and are suitable for high frequencies.

[0004] As described above, an electromagnetic wave shielding film used for a high-frequency flexible printed wiring board is known that includes a metal layer having a thickness of 0.5 μm to 12 μm and an anisotropic conductive adhesive layer in a laminated state (see Patent Document 1).

[0005] An electromagnetic wave shielding film, for example, comprises a sequentially laminated structure consisting of an adhesive layer, a metal film serving as a shielding layer, and an insulating layer. This electromagnetic wave shielding film is then laminated onto a flexible printed circuit board and heated and pressed, thereby bonding the electromagnetic wave shielding film to the printed circuit board via the adhesive layer, thereby producing a shielded printed circuit board. Components are then mounted on the shielded printed circuit board using solder reflow.

[0006] Here, when the shielded printed circuit board including the electromagnetic wave shielding film is heated during the hot pressing process and the solder reflow process, gas will be generated from the adhesive layer of the electromagnetic wave shielding film and the insulating film of the printed circuit board. In addition, when the base film of the printed circuit board is formed of a highly hygroscopic resin such as polyimide, water vapor may be generated from the base film by heating. These volatile components (gases) generated from the adhesive layer, insulating film, or base film cannot pass through the metal film and are therefore retained between the metal film and the adhesive layer. Therefore, if rapid heating is performed during the solder reflow process, the gas retained between the metal film and the adhesive layer may destroy the interlayer tight adhesion between the metal film and the adhesive layer.

[0007] A known method for preventing expansion caused by generated water vapor or other gases is to use a shielding layer having a plurality of openings (see Patent Document 2). By using this shielding layer, the gas can pass through the openings and be released to the outside, thereby preventing expansion.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: International Publication No. 2013 / 077108;

[0011] Patent Document 2: Japanese Patent Application Laid-Open No. 2004-095566. Summary of the Invention

[0012] Technical problem to be solved by the invention

[0013] However, when a plurality of openings are formed in a conventional shielding film for high frequencies, there is a problem that high-frequency electromagnetic waves, for example, 1 GHz or higher, leak from the openings.

[0014] The present invention has been made in view of the above, and an object of the present invention is to provide an electromagnetic wave shielding film having excellent gas permeability and excellent shielding performance against high-frequency electromagnetic waves.

[0015] Technical means to solve technical problems

[0016] The present inventors have conducted intensive research to achieve the above-mentioned objectives and have discovered that an electromagnetic wave shielding film comprising an electromagnetic wave shielding layer and a conductive adhesive layer, wherein the electromagnetic wave shielding layer is designed as a two-layer structure, with an opening formed in one shielding layer and the opening covered by the other shielding layer, exhibits excellent gas permeability and high-frequency electromagnetic wave shielding performance. Based on these findings, the present invention has been completed.

[0017] That is, the present invention provides an electromagnetic wave shielding film comprising an electromagnetic wave shielding layer and a conductive adhesive layer, wherein the electromagnetic wave shielding layer comprises a first shielding layer and a second shielding layer, the first shielding layer comprises an opening, and the second shielding layer covers the opening of the first shielding layer.

[0018] In the electromagnetic wave shielding film of the present invention, as described above, a plurality of openings are formed in the first shielding layer. By including such a structure, when a component is mounted on a shielded printed circuit board using the electromagnetic wave shielding film of the present invention, even if gas is generated between the electromagnetic wave shielding layer and the conductive adhesive layer during the heating and pressing process and the solder reflow process, the gas can pass through the openings in the first shielding layer. Therefore, it is difficult for gas to be trapped between the first shielding layer and the conductive adhesive layer. Therefore, it is possible to prevent the interlayer adhesion from being damaged.

[0019] Furthermore, in the electromagnetic shielding film of the present invention, as described above, the opening is covered by the second shielding layer. By having such a structure, the electromagnetic shielding film of the present invention can suppress leakage of high-frequency electromagnetic waves from the opening and has excellent high-frequency electromagnetic wave shielding performance.

[0020] In the electromagnetic wave shielding film of the present invention, it is preferred that the ratio of the thickness of the first shielding layer to the thickness of the second shielding layer, i.e., the thickness of the first shielding layer / the thickness of the second shielding layer, is 3.0 to 300. If the ratio is 3.0 or greater, the thickness of the first shielding layer is sufficiently thick relative to the thickness of the second shielding layer, and the shielding performance of high-frequency electromagnetic waves is more excellent. In addition, the thickness of the second shielding layer is sufficiently thin relative to the thickness of the first shielding layer, and the gas permeability is more excellent. If the ratio is 300 or less, the second shielding layer has a certain thickness relative to the first shielding layer, thereby further suppressing the leakage of high-frequency electromagnetic waves from the opening.

[0021] In the electromagnetic wave shielding film of the present invention, the first shielding layer preferably has a thickness of 0.5 to 10 μm. A thickness of 0.5 μm or greater provides openings and improved shielding performance against high-frequency electromagnetic waves. However, even if the thickness exceeds 10 μm, electromagnetic wave shielding performance is barely improved. Therefore, a thickness of 10 μm or less maximizes shielding performance while minimizing costs and enabling the design of products including the electromagnetic wave shielding film of the present invention to be very compact.

[0022] In the electromagnetic wave shielding film of the present invention, the conductive adhesive layer preferably has a thickness of 3 to 20 μm. A thickness of 3 μm or greater allows the film to exhibit more adequate shielding performance against internally generated high-frequency electromagnetic waves. Furthermore, even when the thickness of the electromagnetic wave shielding film of the present invention is reduced to 20 μm or less, the film can still exhibit adequate shielding performance against internally generated high-frequency electromagnetic waves.

[0023] The electromagnetic shielding film of the present invention preferably includes the conductive adhesive layer, the first shielding layer, and the second shielding layer in the following order. The electromagnetic shielding film of the present invention having the above structure is easy to manufacture.

[0024] In the electromagnetic wave shielding film of the present invention, the openings preferably have an aperture ratio of 2.0% to 30%. An aperture ratio of 2.0% or greater provides excellent gas permeability. Furthermore, even with an aperture ratio as high as 2.0% or greater, the inclusion of the second shielding layer maintains sufficient shielding performance against high-frequency electromagnetic waves. An aperture ratio of 30% or less further maintains sufficient shielding performance against high-frequency electromagnetic waves.

[0025] In the electromagnetic wave shielding film of the present invention, the second shielding layer is preferably provided adjacent to the first shielding layer. In the electromagnetic wave shielding film of the present invention having the above structure, the first shielding layer and the second shielding layer can function together as a single shielding layer to provide shielding performance, thereby providing excellent gas permeability and further excellent shielding performance against high-frequency electromagnetic waves.

[0026] Effects of the Invention

[0027] The electromagnetic wave shielding film of the present invention has excellent gas permeability and excellent shielding performance against high-frequency electromagnetic waves. Therefore, the electromagnetic wave shielding film of the present invention has excellent shielding performance against not only low-frequency electromagnetic waves but also high-frequency electromagnetic waves, and can also suppress expansion caused by heating. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] [ Figure 1 ] A schematic cross-sectional view of an embodiment of the electromagnetic wave shielding film of the present invention;

[0029] [ Figure 2 ] A schematic cross-sectional view of another embodiment of the electromagnetic wave shielding film of the present invention;

[0030] [ Figure 3 ] A schematic cross-sectional view of yet another embodiment of the electromagnetic wave shielding film of the present invention;

[0031] [ Figure 4 ] A schematic cross-sectional view of an embodiment of a shielded printed wiring board using the electromagnetic wave shielding film of the present invention;

[0032] [ Figure 5 ]Schematic diagram of the structure of the system used in the KEC method. DETAILED DESCRIPTION

[0033] [Electromagnetic wave shielding film]

[0034] The electromagnetic wave shielding film of the present invention comprises an electromagnetic wave shielding layer and a conductive adhesive layer. The electromagnetic wave shielding layer comprises a first shielding layer and a second shielding layer, wherein the first shielding layer has an opening and the second shielding layer covers the opening of the first shielding layer.

[0035] Next, one embodiment of the electromagnetic wave shielding film of the present invention will be described. Figures 1 to 3 Each is a schematic cross-sectional view of one embodiment of the electromagnetic shielding film of the present invention.

[0036] Figure 1The electromagnetic wave shielding film 1 of the present invention includes a conductive adhesive layer 11 and an electromagnetic wave shielding layer 12 composed of a first shielding layer 12a and a second shielding layer 12b. More specifically, the electromagnetic wave shielding film 1 of the present invention includes the conductive adhesive layer 11, the first shielding layer 12a, and the second shielding layer 12b in the following order. The electromagnetic wave shielding film of the present invention having the above structure is easy to manufacture.

[0037] Figure 2 The electromagnetic wave shielding film 1 of the present invention includes a conductive adhesive layer 11, a second shielding layer 12b, and a first shielding layer 12a in the following order.

[0038] Figure 3 In the electromagnetic shielding film 1 of the present invention shown in FIG. 1 , in the electromagnetic shielding layer 12 , the second shielding layer 12 b is formed on both surfaces of the first shielding layer 12 a .

[0039] The electromagnetic wave shielding film of the present invention is as follows Figures 1 to 3 As shown, it is preferred that the second shielding layer is provided adjacent to the first shielding layer in the electromagnetic wave shielding layer. When such a structure is included, the first shielding layer and the second shielding layer can work together as a single shielding layer to exert shielding performance, thereby achieving excellent gas permeability and further excellent shielding performance against high-frequency electromagnetic waves.

[0040] The electromagnetic wave shielding film of the present invention is as follows Figures 1 to 3 As shown, the electromagnetic wave shielding layer 12 may include an insulating layer 13 on the side opposite to the conductive adhesive layer 11 .

[0041] In the electromagnetic wave shielding film of the present invention, a portion of a layer adjacent to the first shielding layer, such as the second shielding layer, the conductive adhesive layer, or the insulating layer, may be immersed in the above-mentioned opening together with a portion of a layer further laminated on the adjacent layer, for example, when the adjacent layer is a thin layer. Figures 1 to 3 In the electromagnetic wave shielding film 1 of the present invention shown in FIG. 1 , the second shielding layer 12 b is immersed in the opening 121 . Figures 1 to 3 The intrusion of the second shield layer 12b into the opening 121 may occur due to, for example, the manufacturing method. The opening may have a cavity regardless of whether or not the adjacent layer adjacent to the first shield layer infiltrates into the opening.

[0042] (1st shield layer)

[0043] A plurality of openings 121 are formed in the first shielding layer 12a. Thus, when components are mounted on a shielded printed wiring board using the electromagnetic shielding film 1 of the present invention, even if gas is generated between the electromagnetic shielding layer 12 and the conductive adhesive layer 11 during the hot pressing process or solder reflow process, the gas can pass through the openings 121 of the first shielding layer 12a. Consequently, gas is less likely to remain between the first shielding layer 12a and the conductive adhesive layer 11, thereby preventing the interlayer adhesion from being compromised.

[0044] The shape of the above-mentioned opening is not particularly limited, and its plane shape (i.e., the shape seen from the upper side of the electromagnetic wave shielding film) can be circular, elliptical, racetrack, polygonal (e.g., triangle, quadrilateral, pentagon, hexagon, octagon, etc.), star-shaped, etc. Among them, a circle is preferred from the perspective of the ease of forming the opening. In addition, the cross-sectional shape (i.e., the shape seen from the front of the cross section of the electromagnetic wave shielding film) can be rectangular (square or rectangular, Figures 1 to 3 The plurality of openings may be in the same shape or in two or more different shapes.

[0045] The arrangement pattern of the openings is not particularly limited, and examples thereof include a lattice pattern, a houndstooth pattern, and a honeycomb structure.

[0046] The opening area of ​​the openings (area of ​​each opening) is not particularly limited, but is preferably 50 to 75,000 μm. 2 , more preferably 60 to 35000 μm 2 , more preferably 70 to 10000 μm 2 The above opening area is 50μm 2 The above opening area is 75000μm 2 The following shows that the shielding performance of high-frequency electromagnetic waves is further improved.

[0047] The aperture ratio of the opening is not particularly limited, but is preferably 2.0 to 30%, more preferably 3.6 to 15%, and even more preferably 3.6 to 8%. An aperture ratio of 2.0% or greater provides even better gas permeability. Furthermore, even when the aperture ratio is relatively high, at 2.0% or greater, the inclusion of the second shielding layer allows for sufficient shielding performance against high-frequency electromagnetic waves. An aperture ratio of 30% or less allows for even further sufficient shielding performance against high-frequency electromagnetic waves.

[0048] From the perspective of superior shielding performance against high-frequency electromagnetic waves, the first shielding layer is preferably a metal layer. Examples of metals constituting the metal layer include gold, silver, copper, aluminum, nickel, tin, palladium, chromium, titanium, zinc, or alloys thereof. Of these, copper and silver layers are preferred from the perspective of superior shielding performance against high-frequency electromagnetic waves, while copper is preferred from the perspective of economic efficiency.

[0049] From the viewpoint of excellent shielding performance against high-frequency electromagnetic waves, the first shielding layer is preferably a metal plate or a metal foil. Specifically, the layer constituting the first shielding layer is preferably a copper plate (copper foil) or a silver plate (silver foil).

[0050] The first shielding layer may be a single layer or multiple layers (for example, a layer coated with metal plating). However, if it is a multi-layered layer, the opening is provided at the same position so as to penetrate the multi-layered first shielding layer.

[0051] The thickness of the first shielding layer is preferably 0.5 to 10 μm, more preferably 1 to 6 μm. A thickness of 0.5 μm or greater provides improved shielding performance against high-frequency electromagnetic waves, including openings. However, even if the thickness exceeds 10 μm, electromagnetic shielding performance is barely improved. Therefore, a thickness of 10 μm or less maximizes shielding performance, reduces costs, and allows for compact designs of products including the electromagnetic shielding film of the present invention.

[0052] (Second shield layer)

[0053] The second shielding layer 12b covers the plurality of openings 121 included in the first shielding layer 12a. This prevents electromagnetic waves from leaking through the openings 121. The first shielding layer 12a includes the openings 121 and exhibits superior shielding performance against high-frequency electromagnetic waves. The second shielding layer can be a single layer or multiple layers.

[0054] From the perspective of suppressing the leakage of high-frequency electromagnetic waves, the second shielding layer is preferably a metal layer. Examples of metals constituting the metal layer include gold, silver, copper, aluminum, nickel, tin, palladium, chromium, titanium, and zinc. These metals may be used alone or in combination of two or more.

[0055] The second shielding layer may be a single metal layer, an alloy layer, or a metal-plated layer. Of these, copper layers and silver layers are preferred, and silver layers are more preferred, from the perspective of excellent shielding performance against high-frequency electromagnetic waves.

[0056] The second barrier layer is preferably a metal vapor-deposited layer or a metal sputtered layer from the perspective of easier thinning and better gas permeability. A metal vapor-deposited layer is more preferred from the perspective of superior economic efficiency. Specifically, the layer constituting the second barrier layer is preferably a copper vapor-deposited layer or a silver vapor-deposited layer.

[0057] The thickness of the second shielding layer is preferably 0.05 to 1 μm, more preferably 0.1 to 0.5 μm. A thickness of 0.1 μm or greater provides better shielding performance against high-frequency electromagnetic waves. A thickness of 0.5 μm or less provides better gas permeability.

[0058] The ratio of the thickness of the first shielding layer to the thickness of the second shielding layer, i.e., the thickness of the first shielding layer / the thickness of the second shielding layer, is preferably 3.0 to 300, more preferably 3.5 to 200, further preferably 4.0 to 30, and further preferably 6.5 to 30. If the above ratio is 3.0 or greater, the thickness of the first shielding layer is sufficiently thick relative to the thickness of the second shielding layer, and the shielding performance of high-frequency electromagnetic waves is more superior. In addition, the thickness of the second shielding layer is sufficiently thin relative to the thickness of the first shielding layer, and the gas permeability is more superior. If the above ratio is 300 or less, the second shielding layer has a certain degree of thickness relative to the first shielding layer, thereby further suppressing the leakage of high-frequency electromagnetic waves from the opening.

[0059] (Conductive adhesive layer)

[0060] The conductive adhesive layer 11 has bonding and conductivity sufficient to bond the electromagnetic wave shielding film of the present invention to a printed wiring board, for example. The conductive adhesive layer is preferably formed adjacent to the electromagnetic wave shielding layer. The conductive adhesive layer may be a single layer or multiple layers.

[0061] The conductive adhesive layer preferably contains a binder component and conductive particles.

[0062] Examples of the binder component include thermoplastic resins, thermosetting resins, active energy ray-curable compounds, etc. The binder component may be used alone or in combination of two or more.

[0063] Examples of the thermoplastic resin include polystyrene resins, vinyl acetate resins, polyester resins, polyolefin resins (e.g., polyethylene resins, polypropylene resin compositions, etc.), polyimide resins, acrylic resins, etc. The thermoplastic resins may be used alone or in combination of two or more.

[0064] Examples of the thermosetting resin include phenolic resins, epoxy resins, polyurethane resins, melamine resins, and alkyd resins. The thermosetting resins may be used alone or in combination of two or more.

[0065] Examples of the epoxy resin include bisphenol epoxy resins, spirocycle epoxy resins, naphthalene epoxy resins, biphenyl epoxy resins, terpene epoxy resins, glycidyl ether epoxy resins, glycidyl amine epoxy resins, and novolac epoxy resins.

[0066] The above-mentioned bisphenol type epoxy resin can be exemplified by bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, tetrabromobisphenol A type epoxy resin, and the like. The above-mentioned glycidyl ether type epoxy resin can be exemplified by tris(glycidyloxyphenyl)methane, tetra(glycidyloxyphenyl)ethane, and the like. The above-mentioned glycidyl amine type epoxy resin can be exemplified by tetraglycidyl diaminodiphenylmethane, and the like. The above-mentioned novolak type epoxy resin can be exemplified by cresol (novolak) type epoxy resin, phenol (novolak) type epoxy resin, α-naphthol (novolak) type epoxy resin, brominated phenol (novolak) type epoxy resin, and the like.

[0067] The active energy ray-curable compound is not particularly limited, and can be exemplified by a polymerizable compound having at least two free reactive groups (e.g., (meth)acryloyl groups) in the molecule, and the like. The above-mentioned active energy ray-curable compound can be used singly or two or more kinds can be used.

[0068] The above-mentioned adhesive component preferably comprises a thermosetting resin. In this case, after the electromagnetic wave shielding film of the present application is arranged on a printed wiring board for bonding to the printed wiring board, the adhesive component can be cured by pressure and heat, and the bonding to the printed wiring board is excellent.

[0069] When the above-mentioned adhesive component comprises a thermosetting resin, the components constituting the above-mentioned adhesive component can comprise a curing agent for promoting the thermal curing reaction. The above-mentioned curing agent can be appropriately selected depending on the kind of the above-mentioned thermosetting resin. The above-mentioned curing agent can be used singly or two or more kinds can be used.

[0070] The content ratio of the adhesive component in the above-mentioned conductive adhesive layer is not particularly limited, and is preferably 5 to 60 mass%, more preferably 10 to 50 mass%, and further preferably 20 to 40 mass% with respect to 100 mass% of the total amount of the conductive adhesive layer. When the above-mentioned content ratio is 5 mass% or more, the close bonding to the printed wiring board is more excellent. When the above-mentioned content ratio is 60 mass% or less, the conductive particles can be sufficiently contained.

[0071] The above-mentioned conductive particles can be exemplified by metal particles, metal-coated resin particles, metal fibers, carbon fillers, carbon nanotubes, and the like. The above-mentioned conductive particles can be used singly or two or more kinds can be used.

[0072] The above-mentioned metal particles and the metal constituting the coating portion of the above-mentioned metal-coated resin particles can be exemplified by gold, silver, copper, nickel, zinc, and the like. The above-mentioned metal can be used singly or two or more kinds can be used.

[0073] Specifically, examples of the metal particles include copper particles, silver particles, nickel particles, silver-coated copper particles, gold-coated copper particles, silver-coated nickel particles, gold-coated nickel particles, and silver-coated alloy particles. Examples of the silver-coated alloy particles include silver-coated copper alloy particles in which alloy particles containing copper (e.g., copper alloy particles composed of an alloy of copper, nickel, and zinc) are coated with silver. The metal particles can be produced by electrolysis, atomization, reduction, and the like.

[0074] Among them, the metal particles are preferably silver particles, silver-coated copper particles, and silver-coated copper alloy particles. Silver-coated copper particles and silver-coated copper alloy particles are particularly preferred from the viewpoints of excellent conductivity, suppression of oxidation and aggregation of the metal particles, and reduction in metal particle costs.

[0075] Examples of the shape of the conductive particles include spherical, flake (scale), dendritic, fibrous, and irregular (polyhedral) shapes.

[0076] The conductive particles preferably have a median diameter (D50) of 1 to 50 μm, more preferably 3 to 40 μm. A median diameter of 1 μm or greater improves dispersibility, inhibits aggregation, and resists oxidation. A mean particle diameter of 50 μm or less improves conductivity.

[0077] The conductive adhesive layer may have isotropic conductivity or anisotropic conductivity as required, but preferably has anisotropic conductivity from the perspective of improving the transmission characteristics of high-frequency signals transmitted by the signal circuit of the printed wiring board.

[0078] The content of the conductive particles in the conductive adhesive layer is not particularly limited, but is preferably 2 to 95% by mass, more preferably 5 to 80% by mass, and even more preferably 10 to 70% by mass, relative to the total weight of the conductive adhesive layer (100% by mass). A content of 2% by mass or greater improves conductivity. A content of 95% by mass or less provides sufficient binder content, resulting in improved adhesion to the printed wiring board.

[0079] The conductive adhesive layer may contain other ingredients in addition to the above-mentioned components, within the scope that does not impair the effects of the present invention. Examples of such other ingredients include well-known and commonly used ingredients in adhesive layers. Examples of such other ingredients include defoamers, viscosity modifiers, antioxidants, diluents, anti-settling agents, fillers, colorants, leveling agents, coupling agents, ultraviolet absorbers, and tackifying resins. Such other ingredients may be used alone or in combination of two or more.

[0080] The thickness of the conductive adhesive layer is preferably 3 to 20 μm, more preferably 5 to 15 μm. A thickness of 3 μm or greater allows the film to exhibit more adequate shielding performance against internally generated high-frequency electromagnetic waves. Furthermore, even when the thickness of the electromagnetic wave shielding film of the present invention is as thin as 20 μm or less, it can still exhibit adequate shielding performance against internally generated high-frequency electromagnetic waves.

[0081] (Insulation layer)

[0082] The insulating layer 13 is formed on the surface of the electromagnetic shielding layer 12. The insulating layer 13 has insulating properties and has the function of protecting the conductive adhesive layer 11 and the electromagnetic shielding layer 12 in the electromagnetic shielding film 1 of the present invention. The insulating layer may be a single layer or multiple layers.

[0083] The insulating layer preferably includes a binder component. Examples of the binder component include thermoplastic resins, thermosetting resins, and active energy ray-curable compounds. The thermoplastic resins, thermosetting resins, and active energy ray-curable compounds may be the same as those listed above as binder components that may be included in the conductive adhesive layer. A single binder component may be used, or two or more may be used.

[0084] The insulating layer may contain other components besides the binder component, as long as the effects of the present invention are not impaired. Examples of such other components include defoamers, viscosity modifiers, antioxidants, diluents, anti-settling agents, fillers, colorants, leveling agents, coupling agents, UV absorbers, and tackifying resins. These other components may be used alone or in combination of two or more.

[0085] The thickness of the insulating layer is preferably 1 to 15 μm, more preferably 3 to 10 μm. A thickness of 1 μm or greater provides more adequate protection for the electromagnetic shielding layer and the conductive adhesive layer. A thickness of 15 μm or less provides superior flexibility and is economically advantageous.

[0086] The electromagnetic wave shielding film of the present invention may have a separator (peel-off film) on the insulating layer side and / or the conductive adhesive layer side. The separator is laminated and can be peeled off from the electromagnetic wave shielding film of the present invention. The separator is an element that covers the insulating layer and the conductive adhesive layer for protection and is peeled off when the electromagnetic wave shielding film of the present invention is used.

[0087] Examples of the separator include polyethylene terephthalate (PET) film, polyethylene film, polypropylene film, plastic film coated with a release agent such as a fluorine-based release agent or a long-chain alkyl acrylate-based release agent, and paper.

[0088] The thickness of the above separation member is preferably 10 to 200 μm, more preferably 15 to 150 μm. When the thickness is 10 μm or more, the protection performance is more excellent. When the thickness is 200 μm or less, the separation member is easily peeled off during use.

[0089] The electromagnetic wave shielding film of the present application can have an adhesion-improving coating layer between the insulating layer and the electromagnetic wave shielding layer. When this structure is included, the close adhesion of the electromagnetic wave shielding layer to the insulating layer is more excellent.

[0090] The material forming the above adhesion-improving coating layer can be exemplified by polyurethane-based resins, acrylic-based resins, core-shell composite resins having a polyurethane-based resin as a shell and an acrylic-based resin as a core, epoxy-based resins, polyimide-based resins, polyamide-based resins, melamine-based resins, phenol-based resins, urea-formaldehyde-based resins, blocked isocyanates obtained by reacting a blocking agent such as phenol with a polyisocyanate, polyvinyl alcohol, polyvinylpyrrolidone, and the like. The above material can be used singly or two or more kinds can be used.

[0091] The electromagnetic wave shielding film of the present application is excellent in gas permeability and in shielding performance of high-frequency electromagnetic waves. Therefore, the electromagnetic wave shielding film of the present application is excellent in shielding performance of electromagnetic waves in a low frequency range, and in a high frequency range (for example, 1 GHz or more, particularly 5 GHz or more), and can suppress expansion due to heating.

[0092] The electromagnetic wave shielding film of the present application preferably has an electromagnetic wave shielding property of 85 dB or more, more preferably 90 dB or more, at 0.1 GHz measured by the KEC method. The upper limit of the electromagnetic wave shielding property at 0.1 GHz is, for example, 100 dB.

[0093] The electromagnetic wave shielding film of the present application preferably has an electromagnetic wave shielding property of 80 dB or more, more preferably 82 dB or more, at 1 GHz measured by the KEC method. The upper limit of the electromagnetic wave shielding property at 1 GHz is, for example, 100 dB.

[0094] The electromagnetic wave shielding film of the present application preferably has an electromagnetic wave shielding property of 68 dB or more, more preferably 70 dB or more, further preferably 75 dB or more, still further preferably 80 dB or more, particularly preferably 90 dB or more, at 15 GHz measured by the coaxial pipe method based on ASTM D4935 (temperature 25°C, relative humidity 30 to 50%). The upper limit of the electromagnetic wave shielding property at 15 GHz is, for example, 100 dB.

[0095] The electromagnetic wave shielding film of the present invention is preferably used for printed circuit boards, and is particularly preferably used for flexible printed circuit boards (FPCs). The electromagnetic wave shielding film of the present invention has excellent shielding performance against not only low-frequency electromagnetic waves but also high-frequency electromagnetic waves. Furthermore, its excellent gas permeability can suppress expansion caused by heating. Therefore, the electromagnetic wave shielding film of the present invention is well suited for use as an electromagnetic wave shielding film for flexible printed circuit boards.

[0096] (Method for producing the electromagnetic wave shielding film of the present invention)

[0097] The method for producing the electromagnetic shielding film of the present invention will be described.

[0098] exist Figure 1 In the manufacturing process of the electromagnetic wave shielding film 1 of the present invention, the conductive adhesive layer 11, the first laminate including the first shielding layer 12a and the second shielding layer 12b, and the insulating layer 13 are first separately manufactured. Then, the separately manufactured first laminate and the insulating layer 13 are laminated (lamination method).

[0099] When preparing the first laminate, the conductive adhesive layer 11 can be formed by, for example, applying (spreading) the adhesive composition for forming the conductive adhesive layer 11 on a temporary substrate such as a release film or a substrate, and then removing the solvent and / or partially curing the adhesive composition as needed.

[0100] The adhesive composition may include, in addition to the components of the conductive adhesive layer, a solvent. Examples of the solvent include toluene, acetone, methyl ethyl ketone, methanol, ethanol, propanol, and dimethylformamide. The solids concentration of the adhesive composition may be appropriately determined based on the thickness of the conductive adhesive layer to be formed.

[0101] The adhesive composition can be applied by a well-known coating method. For example, a coating machine such as a gravure roll coater, a reverse roll coater, an oil roll coater, a lip coater, a dip roll coater, a rod coater, a knife coater, a spray coater, a comma coater, a direct coater, or a slot coater can be used.

[0102] Next, the first shielding layer 12a, which is pre-formed with an opening 121, is laminated on the surface of the conductive adhesive layer 11 formed on the separator. The opening 121 can be formed by well-known or commonly used methods such as punching or laser irradiation of a metal plate (or metal layer). In addition, when the above-mentioned metal plate is made of an etchable material such as copper, a resist having a pattern that forms the opening 121 can be arranged on the surface of the above-mentioned metal plate, and the opening 121 is formed by etching. In addition, a conductive paste or a paste that functions as a plating catalyst can also be printed on the surface of the above-mentioned metal plate. In this printing process, the opening 121 can be formed by printing in a certain pattern. When printing the above-mentioned paste that functions as a plating catalyst, after the opening 121 is formed by printing the paste, it is preferably formed by forming a metal film by an electroless plating method or an electrolytic plating method to form the first shielding layer 12a.

[0103] Next, the second shielding layer 12b is formed on the side of the first shielding layer 12a disposed on the conductive adhesive layer 11. The second shielding layer 12b is preferably formed by vapor deposition or sputtering. Well-known and commonly used methods can be employed for the vapor deposition and sputtering methods. By forming the second shielding layer 12b on the surface of the first shielding layer 12a by vapor deposition or sputtering, a structure can be formed in which the second shielding layer 12b partially penetrates the opening 121, thereby covering the opening 121.

[0104] Meanwhile, when producing the insulating layer 13 , the insulating layer 13 can be formed by, for example, applying (spreading) the resin composition for forming the insulating layer 13 on a temporary substrate such as a release film or a substrate, and performing solvent removal and / or partial curing as needed.

[0105] The resin composition may further include a solvent (solvent) in addition to the components contained in the insulating layer. The solvent may include any of the substances exemplified as solvents that may be contained in the adhesive composition. The solid content concentration of the resin composition may be appropriately set depending on the thickness of the insulating layer to be formed, etc.

[0106] The resin composition can be applied using a known coating method, for example, a coater used for applying the adhesive composition can be used.

[0107] Next, the exposed surface of the separately produced first laminate (on the side facing the second shielding layer 12b) and the insulating layer 13 are laminated to produce the electromagnetic wave shielding film 1 of the present invention. After the above lamination, in addition to the second shielding layer 12b, the conductive adhesive layer 11 and the insulating layer 13 may also penetrate the opening 121 in the first shielding layer 12a due to the pressure during lamination.

[0108] While the manufacturing method of separately manufacturing the first laminate and the insulating layer and subsequently laminating them has been described, the present invention is not limited to this manufacturing method. For example, another embodiment may include separately manufacturing the conductive adhesive layer 11, the second laminate including the first shielding layer 12a, the second shielding layer 12b, and the insulating layer 13, and subsequently laminating them together.

[0109] When producing the second laminate, the insulating layer 13 is formed as described above, and then the second shielding layer 12b and the first shielding layer 12a are formed on the insulating layer 13. The methods for forming the first shielding layer 12a and the second shielding layer 12b are described above. Here, by forming the second shielding layer 12b by vapor deposition or sputtering, and then placing the first shielding layer 12a on the second shielding layer 12b, a structure can be formed in which the opening 121 is covered while a portion of the second shielding layer 12b does not penetrate the opening 121. The exposed surface of the resulting second laminate (the first shielding layer 12a side) is then bonded to the conductive adhesive layer 11, which is similarly formed as for the first laminate, to produce the electromagnetic wave shielding film 1 of the present invention. In the electromagnetic wave shielding film of the present invention produced in this manner, one or more of the second shielding layer, the conductive adhesive layer, and the insulating layer may penetrate into the opening in the first shielding layer due to the pressure during bonding.

[0110] in addition, Figure 2 The electromagnetic wave shielding film 1 of the present invention shown in FIG. 1 can be similar to the above-mentioned electromagnetic wave shielding film except that the positional relationship between the first shielding layer 12a and the second shielding layer 12b is reversed. Figure 1 The electromagnetic wave shielding film 1 of the present invention is produced in the same manner as shown in the manufacturing method.

[0111] For example, in Figure 2 In the manufacturing process of the electromagnetic wave shielding film 1 of the present invention, the conductive adhesive layer 11 and the third laminate including the second shielding layer 12b, the first shielding layer 12a, and the insulating layer 13 are first separately manufactured. The separately manufactured conductive adhesive layer 11 and the third laminate are then laminated together (lamination method). The method for manufacturing the conductive adhesive layer 11 is as described above.

[0112] When producing the third laminate, the insulating layer 13 is formed as described above. Subsequently, the first shielding layer 12a is formed on the insulating layer 13, followed by the second shielding layer 12b. The methods for forming the first shielding layer 12a and the second shielding layer 12b are described above. Here, by forming the second shielding layer 12b on the surface of the first shielding layer 12a by vapor deposition or sputtering, a structure can be formed in which the openings 121 are covered while a portion of the second shielding layer 12b penetrates the openings 121. The exposed surface (the second shielding layer 12b side) of the resulting third laminate is then laminated to the conductive adhesive layer 11 to produce the electromagnetic wave shielding film 1 of the present invention. In the electromagnetic wave shielding film of the present invention produced in this manner, after lamination, in addition to the second shielding layer 12b, the conductive adhesive layer 11 and the insulating layer 13 may also penetrate the openings 121 in the first shielding layer 12a due to the pressure during lamination.

[0113] in addition, Figure 2 Another embodiment of the method for producing the electromagnetic wave shielding film 1 of the present invention is to separately produce a fourth laminate including the conductive adhesive layer 11, the second shielding layer 12b, and the first shielding layer 12a, and the insulating layer 13, and then laminate them together. The method for producing the insulating layer 13 is as described above.

[0114] When producing the fourth laminate, the conductive adhesive layer 11 is formed as described above. The second shielding layer 12b is then formed on the conductive adhesive layer 11, followed by the first shielding layer 12a. The methods for forming the first and second shielding layers 12a and 12b are described above. Here, by forming the second shielding layer 12b by vapor deposition or sputtering, and then placing the first shielding layer 12a on the second shielding layer 12b, a structure can be achieved where the openings 121 are covered while a portion of the second shielding layer 12b does not penetrate the openings 121. The exposed surface (the first shielding layer 12a side) of the resulting fourth laminate is then laminated to the insulating layer 13 to produce the electromagnetic wave shielding film 1 of the present invention. In the electromagnetic wave shielding film of the present invention produced in this manner, after lamination, in addition to the second shielding layer 12b, the conductive adhesive layer 11 and the insulating layer 13 may also penetrate the openings 121 in the first shielding layer 12a due to the pressure during lamination.

[0115] As another form other than the above-mentioned lamination method, the electromagnetic wave shielding film of the present invention can also be manufactured by a method of sequentially laminating each layer (direct coating method). Figure 1 The electromagnetic shielding film 1 of the present invention can be produced by applying (spreading) the resin composition for forming the insulating layer 13 on the surface of the second shielding layer 12b of the first laminate, and performing desolvation and / or partial curing as needed to form the insulating layer 13. Figure 2 and Figure 3The electromagnetic wave shielding film 1 of the present invention shown above can also be produced in the same manner.

[0116] [Printed circuit board]

[0117] Figure 4 One embodiment of a printed wiring board including the electromagnetic wave shielding film of the present invention is shown in the figure. Figure 4 The shielded printed circuit board 2 shown includes: a printed circuit board 20, an electromagnetic wave shielding laminate 1' stacked on the printed circuit board 20, a conductive adhesive layer 30 filled in the through hole 14 of the electromagnetic wave shielding laminate 1', and a reinforcing plate 40 joined by the conductive adhesive layer 30. The reinforcing plate 40 can be replaced by an external grounding member. The electromagnetic wave shielding laminate 1' is formed by the electromagnetic wave shielding film 1 of the present invention. Specifically, for example, the electromagnetic wave shielding laminate 1' is formed by hot pressing the printed circuit board stacked with the electromagnetic wave shielding film 1 of the present invention, and the conductive adhesive layer 11 is thermally cured or melted and cooled to solidify.

[0118] Printed wiring board 20 includes a base member 21, a circuit pattern 23 provided on a surface portion of base member 21, an insulating protective layer (cover film) 24 covering and insulating circuit pattern 23, and an adhesive layer 22 covering circuit pattern 23 and bonding circuit pattern 23, base member 21, and insulating protective layer 24. Circuit pattern 23 includes a plurality of signal circuits.

[0119] The electromagnetic wave shielding laminate 1' is stacked on the printed circuit board 20, specifically on the insulating protective layer 24 in the printed circuit board 20, in the order of a conductive adhesive layer 11', a first shielding layer 12a, a second shielding layer 12b, and an insulating layer 13. The electromagnetic wave shielding laminate 1' contains a through hole 14 that penetrates the thickness direction (i.e., exposed on the surface of the printed circuit board 20). Because it contains the through hole 14, the conductive adhesive layer 30 flows into the through hole 14 by pressurization and heating, and can be electrically connected to the conductive adhesive layer 11'. The bottom of the through hole 14 is the printed circuit board 20, specifically the insulating protective layer 24. That is, the through hole 14 is formed by the side of the insulating layer 13, the side of the electromagnetic wave shielding layer composed of the first shielding layer 12a and the second shielding layer 12b, the side of the conductive adhesive layer 11', and the surface of the printed circuit board 20 (especially the insulating protective layer 24).

[0120] Conductive adhesive layer 30 is disposed on electromagnetic shielding laminate 1', fills through-hole 14, and is electrically connected to conductive adhesive layer 11' in through-hole 14. Reinforcing plate 40 is fixed to printed wiring board 20 and electromagnetic shielding laminate 1' via conductive adhesive layer 30.

[0121] The conductive adhesive layer 30 does not contact the circuit pattern. In this case, the adhesive forming the conductive adhesive layer 30 flows into the through-hole at a low level, preventing air bubbles from being introduced into the through-hole due to insufficient flow. This, for example, can suppress contact surface peeling during the reflow process, achieving stable connection reliability.

[0122] The shielded printed wiring board 2 can be manufactured by a manufacturing method including the following steps: laminating the electromagnetic wave shielding film 1 of the present invention on the printed wiring board 20 (shielding film laminating step), laminating a reinforcing plate 40 including an electromagnetic wave adhesive film on the upper side of the through hole 14 so that the electromagnetic wave adhesive film contacts the electromagnetic wave shielding film 1 of the present invention (reinforcing plate laminating step), and allowing the electromagnetic wave adhesive film to flow into the through hole 14 by thermocompression bonding, thereby forming a conductive adhesive layer 30 from the electromagnetic wave adhesive film, and bringing the conductive adhesive layer 11' in the electromagnetic wave shielding laminate 1' into contact with the conductive adhesive layer 30 (thermocompression bonding step). By the thermocompression bonding, the conductive adhesive layer 11 is thermally cured or melted and cooled to solidify to form the conductive adhesive layer 11', thereby forming the electromagnetic wave shielding laminate 1' from the electromagnetic wave shielding film 1 of the present invention.

[0123] In the shielding film lamination step, the electromagnetic wave shielding film 1 of the present invention is laminated onto the printed wiring board 20 such that the insulating protective layer 24 is in contact with the conductive adhesive layer 11. The through-holes 14 may be formed before or after lamination of the electromagnetic wave shielding film 1 of the present invention. The through-holes 14 may be formed, for example, by laser processing.

[0124] In the reinforcing plate lamination step, the conductive adhesive film and reinforcing plate 40 are bonded together and cut into any size. Then, the surface of the conductive adhesive film is placed on the surface of the insulating layer 13 to close the opening of the through hole 14 .

[0125] Then, during the thermocompression bonding process, the conductive adhesive film softens and flows due to pressure and heat, and flows into the through-hole 14 due to the pressure during the pressurization. It then solidifies through subsequent cooling or thermal polymerization, thereby forming the conductive adhesive layer 30. Thus, the conductive adhesive film flows due to thermocompression bonding, thereby contacting the conductive adhesive layer 11'.

[0126] Example

[0127] The present invention will be further described in detail below based on examples, but the present invention is not limited to these examples.

[0128] Example 1

[0129] (1) Formation of insulating layer

[0130] On a release film serving as a base material, a resin composition composed of an epoxy resin was applied to a thickness of 5 μm to prepare an insulating layer.

[0131] (2) Formation of the second shielding layer

[0132] A silver layer (second shielding layer) having a thickness of 0.1 μm was formed on the insulating layer obtained above by vapor deposition.

[0133] (3) Formation of the first shielding layer

[0134] A plating catalyst layer was formed on the second shielding layer obtained above using a silver paste, and each opening area was formed to have an opening ratio of 2.0% and an opening area of ​​1970 μm. 2 The silver layer has a thickness of 30 nm. The openings are circular in shape, and the openings are arranged in a houndstooth pattern.

[0135] Next, the insulating layer including the second shield layer after printing the silver paste was immersed in an electroless copper plating solution (pH 12.5) at 55° C. for 20 minutes to form an electroless copper plating film (thickness 0.5 μm).

[0136] Next, the surface of the electroless copper plating film obtained above was placed at the cathode, and phosphorus-containing copper was placed at the anode, and an electroplating solution containing copper sulfate was used at a current density of 2.5 A / dm 2 Electroplating was performed for 30 minutes to form a copper plating layer (first shield layer) with a total thickness of 2.0 μm on the second shield layer of the insulating layer. The electroplating solution used was a solution of 70 g / L copper sulfate, 200 g / L sulfuric acid, 50 mg / L chloride ions, and 5 g / L brightener.

[0137] (4) Formation of Conductive Adhesive Layer

[0138] An adhesive composition was applied to the first shielding layer obtained above to a thickness of 15 μm. This adhesive composition, consisting of 20% by mass of Ag-coated Cu powder added to a phosphorus-containing epoxy resin, was applied using a lip coating method. The coating was then heated at 100°C for 30 seconds to volatilize the solvent component, forming a conductive adhesive layer.

[0139] As described above, an electromagnetic wave shielding film having a structure of conductive adhesive layer / first shielding layer / second shielding layer / insulating layer was produced.

[0140] Examples 2 to 16

[0141] An electromagnetic shielding film was produced in the same manner as in Example 1 except that the aperture ratio of the first shielding layer and the material and thickness of the second shielding layer were changed to those shown in the table.

[0142] Comparative Examples 1 to 3

[0143] An electromagnetic shielding film was produced in the same manner as in Example 1, except that the second shielding layer was not used and the aperture ratio of the first shielding layer was changed to that shown in the table.

[0144] (evaluate)

[0145] The electromagnetic shielding films obtained in Examples and Comparative Examples were evaluated as follows. The evaluation results are shown in the table.

[0146] (1) Reflow expansion

[0147] The electromagnetic shielding films obtained in each of Examples and Comparative Examples were evaluated for reflow expansion by the following method.

[0148] First, each electromagnetic wave shielding film was attached to a printed circuit board by hot pressing to produce a shielded printed circuit board. Next, the film was exposed to reflow temperature conditions, followed by cooling to room temperature, and the presence of expansion was evaluated five times. The reflow temperature conditions assumed lead-free solder, a preheating temperature of 180°C, a preheating time of 60 seconds, and exposure to a maximum temperature of 265°C for 10 seconds. The curve was set. The presence of expansion was then visually observed and evaluated based on the following criteria.

[0149] ○ (good): The shielding film does not swell at all.

[0150] × (bad): The shielding film swelled.

[0151] (2) Shielding

[0152] The electromagnetic shielding properties of the electromagnetic shielding films obtained in each Example and Comparative Example were measured at 0.1 GHz and 1 GHz using the KEC method, and at 15 GHz using the coaxial tube method. The measured electromagnetic shielding properties are shown in Table 1. The unit of shielding performance shown in the table is [dB].

[0153] <KEC法>

[0154] Figure 5 Schematic diagram of the system structure used in the KEC method. The system used in the KEC method is composed of an electromagnetic wave shielding effect measuring device 51, a spectrum analyzer 52, an attenuator 53 for performing 10dB attenuation, an attenuator 54 for performing 3dB attenuation, and a preamplifier 55. Figure 5 As shown, in the electromagnetic shielding effect measuring apparatus 51, two measuring jigs 61 are provided opposite to each other. The electromagnetic shielding films ( Figure 5Indicated by reference numeral 70). The measuring fixture 61 includes a size distribution of a TEM chamber (Transverse ElectroMagnetic CeLL), and is divided into a left-right symmetrical structure in a plane perpendicular to its transmission axis direction. In order to prevent the formation of a short circuit due to the insertion of the electromagnetic wave shielding film 70, the flat center conductor 62 is arranged with a gap between each measuring fixture 61. In the KEC method, first, the signal output by the spectrum analyzer 52 is input to the measuring fixture 61 on the receiving side through the attenuator 53. Then, after the signal received by the measuring fixture 61 on the receiving side and passed through the attenuator 54 is amplified by the preamplifier 55, the signal level is measured by the spectrum analyzer 52. The spectrum analyzer 52 outputs the attenuation amount when the electromagnetic wave shielding film 70 is set in the electromagnetic wave shielding effect measuring device 51, based on the state where the electromagnetic wave shielding film 70 is not set in the electromagnetic wave shielding effect measuring device 51. Using this apparatus, the electromagnetic shielding films obtained in Examples and Comparative Examples were cut into 15 cm squares at 25°C and 30-50% relative humidity, and electromagnetic shielding properties at 0.1 GHz and 1 GHz were measured and evaluated.

[0155] <Coaxial tube method>

[0156] The attenuation of 15 GHz electromagnetic waves by the electromagnetic shielding films obtained in the Examples and Comparative Examples was measured using a coaxial tube shielding effectiveness measurement system from KEYCOM at 25°C and 30-50% relative humidity in accordance with ASTM D4935.

[0157]

[0158] The electromagnetic wave shielding film (Example) of the present invention exhibited excellent gas permeability and no reflow expansion. It also exhibited excellent electromagnetic wave shielding performance. On the other hand, the use of a first shielding layer without openings (Comparative Example 1) and the use of a second shielding layer without openings (Comparative Examples 2 and 3) resulted in either poor gas permeability, resulting in reflow expansion, or poor electromagnetic wave shielding performance.

[0159] Reference numerals

[0160] 1. Electromagnetic wave shielding film of the present invention

[0161] 11Conductive adhesive layer

[0162] 12Electromagnetic wave shielding layer

[0163] 12a 1st shielding layer

[0164] 121 opening

[0165] 12b 2nd shielding layer

[0166] 13 Insulation layer

[0167] 2 Shielded printed circuit board

[0168] 20 printed circuit boards

[0169] 21 Basic components

[0170] 22 adhesive layers

[0171] 23 Circuit Graphics

[0172] 24 Insulation protection layer (covering film)

[0173] 1'Electromagnetic wave shielding laminate

[0174] 11' conductive adhesive layer

[0175] 14 through holes

[0176] 30 conductive adhesive layer

[0177] 40 reinforcement plate

Claims

1. An electromagnetic wave shielding film, characterized in that: The electromagnetic wave shielding film comprises an electromagnetic wave shielding layer and a conductive adhesive layer. The electromagnetic wave shielding layer includes a first shielding layer and a second shielding layer, wherein the first shielding layer includes an opening, and the second shielding layer covers the opening of the first shielding layer. The ratio of the thickness of the first shielding layer to the thickness of the second shielding layer, that is, the thickness of the first shielding layer / the thickness of the second shielding layer, is 3.0 to 300. The thickness of the second shielding layer is 0.1 to 0.5 μm.

2. The electromagnetic wave shielding film according to claim 1, wherein: The ratio of the thickness of the first shield layer to the thickness of the second shield layer, ie, the thickness of the first shield layer / the thickness of the second shield layer, is 4.0-30.

3. The electromagnetic wave shielding film according to claim 1, wherein: The thickness of the first shielding layer is 0.5 to 10 μm.

4. The electromagnetic wave shielding film according to claim 1, wherein: The conductive adhesive layer has a thickness of 3 to 20 μm.

5. The electromagnetic wave shielding film according to claim 1, wherein: The conductive adhesive layer, the first shield layer, and the second shield layer are contained in the following order.

6. The electromagnetic wave shielding film according to claim 1, wherein: The opening ratio of the opening portion is 2.0 to 30%.

7. The electromagnetic wave shielding film according to any one of claims 1 to 6, characterized in that: The second shielding layer is disposed adjacent to the first shielding layer.

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