Electromagnetic wave shielding film, shielded printed wiring board, and method for manufacturing electromagnetic wave shielding film

Abstract

To provide an electromagnetic wave shielding film that prevents a printed circuit of a flexible printed wiring board from being easily broken even when the film is placed on the flexible printed wiring board that is repeatedly bent at sharp angles.SOLUTION: An electromagnetic wave shielding film includes a shielding layer having a plurality of openings formed therein and an adhesive layer laminated together, and, when the shielding layer is viewed in a plan view, the openings arranged at at least a portion of the edge of the shielding layer are notched openings that expose the inner periphery.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an electromagnetic wave shielding film, a shielded printed wiring board, and a method for producing an electromagnetic wave shielding film. [Background technology]

[0002] Conventionally, an electromagnetic wave shielding film has been attached to a printed wiring board such as a flexible printed wiring board (FPC) to form a shielded printed wiring board, thereby blocking electromagnetic waves generated from within or entering from the outside.

[0003] Flexible printed wiring boards are placed in locations where they are repeatedly bent, so the electromagnetic wave shielding film used in flexible printed wiring boards is required to have bending resistance (the ability to prevent the shielding layer from breaking even when bent).

[0004] As an example of such a coverlay film (electromagnetic shielding film) having a shielding layer with improved bending resistance, Patent Document 1 discloses a coverlay film having an electromagnetic shielding layer made of a conductive material, a resistor layer having a surface resistance higher than that of the electromagnetic shielding layer, and an insulating resin layer provided between the electromagnetic shielding layer and the resistor layer, and the electromagnetic shielding layer has a plurality of openings that penetrate through the electromagnetic shielding layer in the thickness direction. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-090162 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, foldable displays have been developed. Foldable displays have a structure in which the movable parts can bend nearly 180 degrees. Flexible printed circuit boards with electromagnetic wave shielding films attached are placed on these movable parts as well.

[0007] FIG. 7 is a plan view of the shielding layer in the electromagnetic wave shielding film described in Patent Document 1. 7 has openings 531 formed therein, but does not have openings 531 formed at its end portions 530a, so that the rigidity of the shield layer 530 can be said to be high. When an electromagnetic wave shielding film such as that described in Patent Document 1 is folded, stress (a force that causes the shielding layer 530 to return to its original shape) is generated in the shielding layer 530. This stress also affects the printed circuit of the flexible printed wiring board to which the electromagnetic wave shielding film is attached. If the shield layer 530 is bent at a steep angle, this stress becomes strong, causing a problem of breakage of the printed circuit of the flexible printed wiring board. In other words, there is room for improvement in the bendability of the entire flexible printed wiring board to which the electromagnetic wave shielding film is attached.

[0008] The present invention has been made to solve the above problems, and an object of the present invention is to provide an electromagnetic wave shielding film that is less likely to cause breakage of the printed circuit of a flexible printed wiring board, even when the film is placed on a flexible printed wiring board that is repeatedly bent at sharp angles. [Means for solving the problem]

[0009] The electromagnetic wave shielding film of the present invention is an electromagnetic wave shielding film comprising a shielding layer having a plurality of openings formed therein and an adhesive layer laminated together, and is characterized in that, when the shielding layer is viewed in a plane, the openings located at at least a portion of the end of the shielding layer are notched openings that expose the inner periphery.

[0010] In the electromagnetic wave shielding film of the present invention, a cutout opening is provided at the end of the shielding layer, through which the inner periphery is exposed. The end of the shield layer where such a notch opening is formed is easily deformed, and the stress generated in the shield layer is dispersed. Therefore, even if the electromagnetic wave shielding film of the present invention is disposed on a flexible printed wiring board and is repeatedly bent at sharp angles, the printed circuit of the flexible printed wiring board can be prevented from breaking.

[0011] The electromagnetic wave shielding film of the present invention preferably has a folding portion that can be folded along a linear folding line, and when the electromagnetic wave shielding film is viewed in a plan view, the folding line intersects with the end of the shielding layer where the cutout opening is formed. When the shield layer is bent, stress is likely to be applied to the end of the shield layer located at the bent portion. However, if a notch opening is formed at the end of such a shield layer (that is, the end intersecting with the bending line), the generated stress can be alleviated.

[0012] In the electromagnetic wave shielding film of the present invention, when the shielding layer is viewed in a plane, the opening has an axisymmetric shape having at least one axis of symmetry, and the opening has a first length X in a first direction along the axis of symmetry and a second length Y in a second direction perpendicular to the first direction, and the first length X may be longer than the second length Y. Furthermore, it is preferable that the electromagnetic wave shielding film of the present invention has a folding portion that can be folded along a linear folding line, and that when the electromagnetic wave shielding film is viewed in a plane, the folding line intersects with the second direction. When the openings have the above shape and are arranged as described above, stress is easily dispersed. Therefore, even if the electromagnetic wave shielding film of the present invention is disposed on a flexible printed wiring board and is repeatedly bent at sharp angles, the printed circuit of the flexible printed wiring board can be prevented from breaking.

[0013] In the electromagnetic wave shielding film of the present invention, when the shielding layer is viewed from above, the openings are preferably arranged regularly, and more preferably arranged in a staggered pattern. When the openings are arranged in a regular pattern, the shielding layer becomes flexible and stress is easily dispersed. In particular, when the openings are arranged in a staggered pattern, stress is more easily dispersed. Therefore, even if the electromagnetic wave shielding film of the present invention is disposed on a flexible printed wiring board and is repeatedly bent at sharp angles, the printed circuit of the flexible printed wiring board can be prevented from breaking.

[0014] The shielded printed wiring board of the present invention is a shielded printed wiring board including a flexible printed wiring board having a base film, a printed circuit arranged on the base film, and a coverlay arranged to cover the printed circuit, and an electromagnetic wave shielding film arranged on the coverlay side of the flexible printed wiring board, characterized in that the electromagnetic wave shielding film is the electromagnetic wave shielding film of the present invention.

[0015] As described above, in the electromagnetic wave shielding film of the present invention, even when the film is bent at a steep angle, the stress generated in the shielding layer is dispersed. Therefore, even if the shielded printed wiring board of the present invention having the electromagnetic wave shielding film of the present invention is bent at a sharp angle, the printed circuit of the flexible printed wiring board can be prevented from breaking.

[0016] The method for producing an electromagnetic wave shielding film of the present invention is characterized by comprising the steps of: preparing a shielding layer; forming an opening in the shielding layer; cutting the shielding layer through the opening to form a notch opening in at least one end of the shielding layer; and forming an adhesive layer on one main surface of the shielding layer.

[0017] By such a method, the electromagnetic wave shielding film of the present invention can be produced. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide an electromagnetic wave shielding film that is less likely to break the printed circuit of a flexible printed wiring board even when the film is placed on the flexible printed wiring board that is repeatedly bent at sharp angles. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a cross-sectional view schematically showing an example of the electromagnetic wave shielding film of the present invention. [Figure 2] FIG. 2 is a cross-sectional view schematically showing an example of a flexible printed wiring board provided with the electromagnetic wave shielding film of the present invention. [Figure 3] FIG. 3 is a cross-sectional view showing an example of a state in which the shielded printed wiring board shown in FIG. 2 is disposed in an electronic device having a movable part and bent. [Figure 4] FIG. 4 is a plan view of the electromagnetic wave shielding film of the present invention shown in FIG. 1, depicting only the shielding layer. [Figure 5A] FIG. 5A is a plan view schematically showing another example of the shielding layer in the electromagnetic wave shielding film of the present invention. [Figure 5B] FIG. 5B is a plan view schematically showing another example of the shielding layer in the electromagnetic wave shielding film of the present invention. [Figure 5C] FIG. 5C is a plan view schematically showing another example of the shielding layer in the electromagnetic wave shielding film of the present invention. [Figure 6A] FIG. 6A is a plan view schematically showing an example of the shielding layer preparation step in the method for producing an electromagnetic wave shielding film of the present invention. [Figure 6B] FIG. 6B is a plan view schematically showing an example of the opening formation step in the method for producing an electromagnetic wave shielding film of the present invention. [Figure 6C]FIG. 6C is a plan view schematically showing an example of the cutting step in the method for producing an electromagnetic wave shielding film of the present invention. [Figure 6D] FIG. 6D is a cross-sectional view that schematically shows an example of the adhesive layer forming step in the method for producing an electromagnetic wave shielding film of the present invention. [Figure 6E] FIG. 6E is a cross-sectional view that schematically illustrates an example of the protective layer forming step in the method for producing an electromagnetic wave shielding film of the present invention. [Figure 7] FIG. 7 is a plan view of the shielding layer in the electromagnetic wave shielding film described in Patent Document 1. DETAILED DESCRIPTION OF THE INVENTION

[0020] The electromagnetic wave shielding film of the present invention will be specifically described below. However, the present invention is not limited to the following embodiments, and can be appropriately modified and applied within the scope of the present invention.

[0021] The electromagnetic wave shielding film of the present invention is an electromagnetic wave shielding film comprising a shielding layer having a plurality of openings formed therein and an adhesive layer laminated together, and is characterized in that, when the shielding layer is viewed in a plane, the openings located at at least a portion of the end of the shielding layer are notched openings that expose the inner periphery. As long as the electromagnetic wave shielding film of the present invention has the above characteristics, it may include various configurations within the scope of the effects of the present invention.

[0022] FIG. 1 is a cross-sectional view schematically showing an example of the electromagnetic wave shielding film of the present invention. FIG. 2 is a cross-sectional view schematically showing an example of a flexible printed wiring board provided with the electromagnetic wave shielding film of the present invention.

[0023] The electromagnetic wave shielding film 10 shown in FIG. 1 is formed by laminating a protective layer 40, a shielding layer 30 having a plurality of openings 31 formed therein, and an adhesive layer 20 in this order.

[0024] The shielded printed wiring board 1 shown in FIG. 2 includes a flexible printed wiring board 50 and an electromagnetic wave shielding film 10.

[0025] The flexible printed wiring board 50 includes a base film 51 , a printed circuit 52 disposed on the base film 51 , and a coverlay 53 disposed to cover the printed circuit 52 . The printed circuit 52 includes a ground circuit 52a. The coverlay 53 also has an exposure hole 53a formed therein to expose the ground circuit 52a.

[0026] In the shielded printed wiring board 1, the adhesive layer 20 is disposed so as to be in contact with the coverlay 53. The adhesive layer 20 fills the exposure hole 53a and is in contact with the ground circuit 52a. If the adhesive layer 20 is a conductive adhesive layer, the ground circuit 52a and the shielding layer 30 are electrically connected, which improves the shielding performance of the electromagnetic wave shielding film 10. The exposure hole 53a does not have to be formed, but if the adhesive layer 20 is a conductive adhesive layer, the adhesive layer 20 can fill the exposure hole 53a and come into contact with the ground circuit 52a, thereby improving the shielding properties.

[0027] FIG. 3 is a cross-sectional view showing an example of a state in which the shielded printed wiring board shown in FIG. 2 is disposed in an electronic device having a movable part and bent.

[0028] 3, electronic device 60 having a movable part has two plate-like members 61 connected at movable part 62. Movable part 62 allows member 61 to be opened and closed at an angle of 0 to 180°. The shielded printed wiring board 1 is disposed so as to be continuous with the two plate-like members 61 and the movable part 62. Examples of electronic devices 60 having such a movable part 62 include foldable phones, tablets, and notebook computers.

[0029] As shown in Fig. 3, when electronic device 60 having a movable part is bent, shielded printed wiring board 1 is bent along a linear bending line (in Fig. 3, the bending line is indicated by point α because it is perpendicular to the drawing). Similarly, electromagnetic wave shielding film 10 is also bent along bending line α. This folded portion is the folded portion 10 a of the electromagnetic wave shielding film 10 . The bent portion 10a may be bent so that the radius of curvature is 0.3 to 5 mm.

[0030] Each component of the electromagnetic wave shielding film 10 will be described below.

[0031] <Shield layer> FIG. 4 is a plan view of the electromagnetic wave shielding film of the present invention shown in FIG. 1, depicting only the shielding layer. As shown in FIG. 4, in the electromagnetic wave shielding film 10, the openings 31 are regularly arranged when the shielding layer 30 is viewed from above. That is, as shown in FIG. 4, the openings 31 are substantially square, and are arranged so as to line up vertically and horizontally in the shield layer 30. When the plurality of openings 31 are arranged regularly in the shield layer 30 in this way, the shield layer 30 becomes flexible and stress is easily dispersed. Therefore, even if the electromagnetic wave shielding film 10 is disposed on the flexible printed wiring board 50 and is repeatedly bent at sharp angles, the printed circuit 52 of the flexible printed wiring board 50 can be prevented from breaking.

[0032] As shown in FIG. 4, the shield layer 30 has a first end 30a and a second end 30b opposite to the first end 30a. The openings 31 located at the first end 30a and the second end 30b are cut by a boundary line β between the ends (first end 30a and second end 30b) and the outside, and are notched openings 32 that expose the inner periphery 33.

[0033] The ends (first end 30a and second end 30b) of the shield layer 30 where the cutout openings 32 are formed are easily deformed, and stress generated in the shield layer 30 is dispersed. Therefore, even if the electromagnetic wave shielding film 10 is disposed on the flexible printed wiring board 50 and is repeatedly bent at sharp angles, the printed circuit 52 of the flexible printed wiring board 50 can be prevented from breaking.

[0034] As shown in FIG. 4, the bending line α intersects with the boundary line β. The angle formed by the bending line α and the boundary line β is not particularly limited, but is preferably 90°. When the shield layer is bent, stress is likely to be applied to the end of the shield layer located at the bent portion. However, if the notched opening 32 is formed at the end of the shield layer 30 (that is, the end intersecting with the bending line α), the stress can be alleviated.

[0035] In the electromagnetic wave shielding film 10, the shielding layer is preferably made of a metal layer having a Young's modulus of 50 GPa or more. Such a shield layer 30 has sufficient strength and therefore high bending resistance. Furthermore, if the shield layer 30 is made of a metal layer, the electrical conductivity will be high, and therefore the shielding performance will be improved.

[0036] When the shield layer 30 is made of a metal layer, the metal layer preferably contains at least one metal selected from the group consisting of copper, silver, gold, aluminum, nickel, tin, palladium, chromium, titanium, and zinc. The metal layer may also be made of an alloy of at least two metals selected from this group. These metals are suitable as the shielding layer of the electromagnetic wave shielding film.

[0037] In the electromagnetic wave shielding film 10, the thickness of the shielding layer 30 is preferably 0.1 to 50 μm, more preferably 0.5 to 10 μm, and even more preferably 1.0 to 6 μm. If the thickness of the shielding layer is less than 0.1 μm, the shielding layer will be too thin and have low strength, resulting in reduced bending resistance. Also, it will be difficult to sufficiently reflect and absorb electromagnetic waves, resulting in reduced electromagnetic wave shielding properties. If the thickness of the shielding layer exceeds 50 μm, the entire electromagnetic wave shielding film becomes thick and difficult to handle.

[0038] In the electromagnetic wave shielding film of the present invention, the shape of the openings in plan view is not limited to a square, and may be a polygon such as a triangle, rectangle, rhombus, pentagon, hexagon, or octagon, or may be a circle or an ellipse. Furthermore, the openings may have a single shape or a mixture of multiple shapes.

[0039] From the viewpoint of facilitating stress dispersion, the shape of the opening in plan view is preferably a line-symmetric shape having at least one axis of symmetry. In the electromagnetic wave shielding film of the present invention, the opening preferably has a first length X in a first direction D1 along the symmetry axis and a second length Y in a second direction D2 perpendicular to the first direction D1, the first length X being longer than the second length Y, and the bending line α intersects with the second direction D2. More preferably, the bending line α intersects with the second direction D2 at an angle of 90°. When the openings have the above shape and are arranged as described above, stress is easily dispersed. Therefore, even if the electromagnetic wave shielding film 10 is disposed on the flexible printed wiring board 50 and is repeatedly bent at sharp angles, the printed circuit 52 of the flexible printed wiring board 50 can be prevented from breaking.

[0040] In the electromagnetic wave shielding film of the present invention, when the shielding layer is viewed from above, the openings are preferably arranged regularly, and particularly preferably arranged in a staggered pattern. A staggered arrangement of the openings helps distribute stress. Therefore, even if the electromagnetic wave shielding film 10 is disposed on the flexible printed wiring board 50 and is repeatedly bent at sharp angles, the printed circuit 52 of the flexible printed wiring board 50 can be prevented from breaking. In the electromagnetic wave shielding film of the present invention, the openings do not need to be arranged regularly when the shielding layer is viewed in plan view.

[0041] The shielding layer having such characteristics will be described below with reference to the drawings. 5A to 5C are plan views each showing a schematic view of another example of the shielding layer in the electromagnetic wave shielding film of the present invention.

[0042] The shield layer 30A shown in FIG. 5A has rectangular openings 31A arranged in a staggered pattern. The opening 31A has a first length X in a first direction D1 along the symmetry axis AS and a second length Y in a second direction D2 perpendicular to the first direction D1, the first length X being longer than the second length Y, and the bending line α intersects with the second direction D2 at 90°. Furthermore, the shield layer 30A has cutout openings 32A at the first end 30Aa and the second end 30Ab, through which the inner circumferential portion 33A is exposed.

[0043] The shield layer 30B shown in FIG. 5B has diamond-shaped openings 31B arranged in a staggered pattern. The opening 31A has a first length X in a first direction D1 along the symmetry axis AS and a second length Y in a second direction D2 perpendicular to the first direction D1, the first length X being longer than the second length Y, and the bending line α intersects with the second direction D2 at 90°. Furthermore, the shield layer 30B has cutout openings 32B at the first end 30Ba and the second end 30Bb, through which the inner circumferential portion 33B is exposed.

[0044] Shield layer 30C shown in FIG. 5C has elliptical openings 31C arranged in a staggered pattern. The opening 31C has a first length X in a first direction D1 along the symmetry axis AS and a second length Y in a second direction D2 perpendicular to the first direction D1, the first length X being longer than the second length Y, and the bending line α intersects with the second direction D2 at 90°. Furthermore, the shield layer 30C has cutout openings 32C at the first end 30Ca and the second end 30Cb, through which the inner circumferential portion 33C is exposed.

[0045] The cutout openings (32, 32A, 32B, 32C) described so far have a shape obtained by cutting the opening in a straight line, but in the electromagnetic wave shielding film of the present invention, the cutout openings may also have a shape obtained by cutting the opening in a curved line.

[0046] In the electromagnetic wave shielding film 10, the density of the openings 31 in the shielding layer 30 is not particularly limited, but is preferably 10 to 200,000 pieces / mm 2 It is preferable that the number of particles is 20 to 500 / mm 2 More preferably, the number of particles is 50 to 200 / mm 2 It is more preferable that: The density of the openings in the shield layer is 10 / mm 2 If it is less than this, the stress is difficult to relax. The density of the openings in the shield layer is 200,000 / mm 2 If the applied current exceeds this value, the strength of the shielding layer will decrease and the shielding layer will be easily destroyed.

[0047] In the electromagnetic wave shielding film 10, the opening area of ​​the opening 31 in the shielding layer 30 is 0.5 to 5000 μm 2 It is preferable that the thickness is 10 to 3000 μm. 2 It is more preferable that: The aperture ratio of the openings 31 is preferably 0.01 to 90%, and more preferably 0.1 to 50%.

[0048] <Adhesive layer> The adhesive layer 20 in the electromagnetic wave shielding film 10 is not particularly limited to any material as long as it has the function of adhering the electromagnetic wave shielding film 10 to a flexible printed wiring board, but it is preferable that it contains an adhesive resin as an adhesive component.

[0049] Examples of adhesive resins that can be used include thermoplastic resins such as styrene-based resins, vinyl acetate-based resins, polyester-based resins, polyethylene-based resins, polypropylene-based resins, imide-based resins, amide-based resins, and acrylic-based resins, and thermosetting resins such as phenol-based resins, epoxy-based resins, urethane-based resins, melamine-based resins, and alkyd-based resins. The adhesive layer 20 may contain one of these resins alone, or may contain two or more of these resins.

[0050] In the electromagnetic wave shielding film 10, the adhesive layer 20 may be a conductive adhesive layer. When the adhesive layer 20 is a conductive adhesive layer, the shielding layer 30 of the electromagnetic wave shielding film 10 and the ground circuit 52a of the flexible printed wiring board 50 can be electrically connected. In this case, the electromagnetic wave shielding film 10 has good shielding performance.

[0051] In the electromagnetic wave shielding film 10, the conductive adhesive layer may be an isotropically conductive adhesive layer or an anisotropically conductive adhesive layer, but is preferably an anisotropically conductive adhesive layer. When the conductive adhesive layer has anisotropic conductivity, the transmission characteristics of high frequency signals transmitted through the signal circuit of the flexible printed wiring board are improved compared to when the conductive adhesive layer has isotropic conductivity.

[0052] When the adhesive layer 20 is a conductive adhesive layer, the adhesive layer 20 contains a conductive filler. The conductive filler is not particularly limited, but may be silver powder, copper powder, nickel powder, solder powder, aluminum powder, silver-coated copper powder obtained by silver-plating copper powder, fine particles of polymer fine particles or glass beads coated with metal, carbon fiber, graphite, or the like. Among these, copper powder or silver-coated copper powder, which is inexpensively available, is preferable from the viewpoint of economy.

[0053] The shape of the conductive filler is not particularly limited, and can be appropriately selected from spherical, flake, scale, dendrite, rod, fiber, etc. Among these, the flake shape is preferred. If the conductive filler is a flake-shaped conductive filler, the conductive filler also bends when the electromagnetic wave shielding film 10 is bent, making it easier for the conductive filler particles to maintain contact with each other, and as a result, the conductivity of the conductive adhesive layer is less likely to decrease.

[0054] The average particle size of the conductive filler is not particularly limited, but is preferably 0.5 to 15.0 μm, and more preferably 5 to 13 μm. When the average particle size of the conductive filler is 0.5 μm or more, the conductive adhesive layer has good conductivity. When the average particle size of the conductive filler is 15.0 μm or less, the conductive adhesive layer can be made thin.

[0055] The weight ratio of the conductive filler contained in the conductive adhesive layer is preferably 10 to 80% by weight. When the conductive adhesive layer has anisotropic conductivity, the weight ratio of the conductive filler contained in the conductive adhesive layer is preferably 5 to 40% by weight, and more preferably 10 to 35% by weight.

[0056] The thickness of the adhesive layer 20 is not particularly limited and can be set appropriately as needed, but is preferably 0.5 to 30.0 μm. If the thickness of the adhesive layer is less than 0.5 μm, it becomes difficult to obtain good adhesion. If the thickness of the adhesive layer exceeds 30.0 μm, the entire electromagnetic wave shielding film becomes thick and difficult to handle.

[0057] <Protective layer> In the electromagnetic wave shielding film 10, the protective layer 40 is not particularly limited as long as it has sufficient insulating properties and can protect the shielding layer 30 and the adhesive layer 20, but it is preferable that it is composed of, for example, a thermoplastic resin composition, a thermosetting resin composition, an active energy ray-curable composition, etc. The thermoplastic resin composition is not particularly limited, but examples thereof include a styrene-based resin composition, a vinyl acetate-based resin composition, a polyester-based resin composition, a polyethylene-based resin composition, a polypropylene-based resin composition, an imide-based resin composition, and an acrylic-based resin composition.

[0058] The thermosetting resin composition is not particularly limited, but examples thereof include phenolic resin compositions, epoxy resin compositions, urethane resin compositions, melamine resin compositions, and alkyd resin compositions.

[0059] The active energy ray-curable composition is not particularly limited, but examples thereof include polymerizable compounds having at least two (meth)acryloyloxy groups in the molecule.

[0060] The protective layer 40 may be made of a single material, or may be made of two or more materials.

[0061] The protective layer 40 may contain, as needed, a curing accelerator, a tackifier, an antioxidant, a pigment, a dye, a plasticizer, an ultraviolet absorber, an antifoaming agent, a leveling agent, a filler, a flame retardant, a flame retardant assistant, a viscosity adjuster, an antiblocking agent, and the like.

[0062] The thickness of the protective layer 40 is not particularly limited and can be set appropriately as needed, but is preferably 1 to 15 μm, and more preferably 3 to 10 μm. If the thickness of the protective layer 40 is less than 1 μm, it is too thin and it is difficult to sufficiently protect the shield layer 30 and the adhesive layer 20 . If the thickness of the protective layer 40 exceeds 15 μm, the electromagnetic wave shielding film 10 will be difficult to bend due to the excessive thickness, and the toughness of the protective layer 40 will decrease, making it difficult to apply to components that require bending resistance.

[0063] Although the protective layer 40 is formed in the electromagnetic wave shielding film 10, the protective layer may not be formed in the electromagnetic wave shielding film of the present invention.

[0064] The flexible printed wiring board 50 will now be described.

[0065] In flexible printed wiring board 50, base film 51 and coverlay 53 are preferably both made of engineering plastics, such as polypropylene, cross-linked polyethylene, polyester, polybenzimidazole, polyimide, polyimideamide, polyetherimide, and polyphenylene sulfide (PPS).

[0066] In the flexible printed wiring board 50, the printed circuit 52 can be made of a common circuit material such as copper.

[0067] The base film 51 and the printed circuit 52 may be bonded with an adhesive, or may be bonded without adhesive, similar to a so-called adhesiveless copper-clad laminate. The coverlay 53 may be formed by bonding multiple flexible insulating films with an adhesive, or may be formed by a series of methods such as coating a photosensitive insulating resin, drying, exposing, developing, and heat treating.

[0068] The electromagnetic wave shielding film 10 can be attached to the flexible printed wiring board 50 by a conventionally known method. For example, it is preferable to place the electromagnetic wave shielding film 10 on the flexible printed wiring board 50 so that the adhesive layer 20 of the electromagnetic wave shielding film 10 contacts the coverlay 53 of the flexible printed wiring board 50, and then perform thermocompression bonding under conditions of 150 to 200°C, 2 to 5 MPa, and 1 to 60 minutes.

[0069] Next, an example of a method for producing the electromagnetic wave shielding film of the present invention will be described. The method for producing an electromagnetic wave shielding film of the present invention includes a shielding layer preparation step, an opening formation step, a cutting step, and an adhesive layer formation step. The method for producing an electromagnetic wave shielding film of the present invention may also include a protective layer formation step after the cutting step. Each step will be explained below with reference to the drawings.

[0070] (1) Shield layer preparation process FIG. 6A is a plan view schematically showing an example of the shielding layer preparation step in the method for producing an electromagnetic wave shielding film of the present invention. In this step, a shield layer 30'' without openings is prepared as shown in FIG. 6A.

[0071] (2) Opening formation process FIG. 6B is a plan view schematically showing an example of the opening formation step in the method for producing an electromagnetic wave shielding film of the present invention. Next, as shown in FIG. 6B, openings 31 are formed in a regular array in the shield layer 30'' where no openings are formed. The openings 31 shown in FIG. 6B are substantially square and are regularly arranged vertically and horizontally. The preferred shape and arrangement of the openings 31 have already been described, and therefore will not be described here.

[0072] (3) Cutting process FIG. 6C is a plan view schematically showing an example of the cutting step in the method for producing an electromagnetic wave shielding film of the present invention. Next, as shown in FIG. 6C, the shield layer 30' is cut along the straight line β so as to pass through the opening 31, thereby forming the shield layer 30. By this cutting, the ends (first end 30a and second end 30b) of the shield layer 30 are formed, and further, the cutout opening 32 through which the inner periphery 33 is exposed is formed.

[0073] (4) Adhesive layer formation process FIG. 6D is a cross-sectional view that schematically shows an example of the adhesive layer forming step in the method for producing an electromagnetic wave shielding film of the present invention. Next, as shown in FIG. 6D, adhesive layer 20 is formed on one main surface 30S1 of shield layer 30.

[0074] (5) Protective layer formation process FIG. 6E is a cross-sectional view that schematically illustrates an example of the protective layer forming step in the method for producing an electromagnetic wave shielding film of the present invention. Next, the protective layer 40 is formed on the other main surface 30S2 of the shield layer 30 as shown in FIG. 6E.

[0075] Through the above steps, the electromagnetic wave shielding film 10 can be manufactured.

[0076] In the method for producing an electromagnetic wave shielding film of the present invention, the opening is formed by cutting the opening. However, the shielding layer of the electromagnetic wave shielding film of the present invention may be formed by plating, etching, vapor deposition or the like so that cut openings are formed in advance at the edges of the shielding layer.

[0077] This specification describes the following inventions:

[0078] The present invention (1) is an electromagnetic wave shielding film comprising a shielding layer having a plurality of openings formed therein and an adhesive layer laminated together, wherein, when the shielding layer is viewed in plan, the openings arranged at at least a portion of the edge of the shielding layer are notched openings that expose the inner periphery.

[0079] The present invention (2) is the electromagnetic wave shielding film according to the present invention (1), wherein the electromagnetic wave shielding film has a folding portion that can be folded along a linear folding line, and when the electromagnetic wave shielding film is viewed in a plane, the folding line intersects with the end of the shielding layer where the cutout opening is formed.

[0080] The present invention (3) is the electromagnetic wave shielding film according to the present invention (1) or (2), wherein, when the shielding layer is viewed in plan, the opening has an axisymmetric shape having at least one axis of symmetry, and the opening has a first length X in a first direction along the axis of symmetry and a second length Y in a second direction perpendicular to the first direction, and the first length X is longer than the second length Y.

[0081] The present invention (4) is the electromagnetic wave shielding film according to the present invention (3), wherein the electromagnetic wave shielding film has a folding portion that can be folded along a linear folding line, and when the electromagnetic wave shielding film is viewed in a plane, the folding line intersects with the second direction.

[0082] The present invention (5) is the electromagnetic wave shielding film according to any one of the present inventions (1) to (4), wherein the openings are regularly arranged when the shielding layer is viewed from above.

[0083] The present invention (6) is the electromagnetic wave shielding film according to the present invention (5), wherein the openings are arranged in a staggered pattern.

[0084] The present invention (7) is a shielded printed wiring board including a flexible printed wiring board having a base film, a printed circuit arranged on the base film, and a coverlay arranged to cover the printed circuit, and an electromagnetic wave shielding film arranged on the coverlay side of the flexible printed wiring board, characterized in that the electromagnetic wave shielding film is the electromagnetic wave shielding film according to any one of the present inventions (1) to (6).

[0085] The present invention (8) is a method for producing an electromagnetic wave shielding film, comprising: a shielding layer preparation step of preparing a shielding layer having no openings formed therein; an opening formation step of forming openings in the shielding layer having no openings formed therein; a cutting step of cutting the shielding layer through the openings to form a notched opening in at least one end of the shielding layer; and an adhesive layer formation step of forming an adhesive layer on one main surface of the shielding layer. [Explanation of symbols]

[0086] 1 Shielded printed wiring board 10 Electromagnetic wave shielding film 10a Bending part 20 Adhesive layer 30, 30A, 30B, 30C, 30´, 30´´ Shield layer 30a, 30Aa, 30Ba, 30Ca 1st end 30b, 30Ab, 30Bb, 30Cb 2nd end 30S1 One main surface 30S2 other main surface 31, 31A, 31B, 31C opening 32, 32A, 32B, 32C Cutout openings 33, 33A, 33B, 33C inner circumference 40 protective layer 50 Flexible printed wiring board 51 Base film 52 Printed Circuits 52a Ground Circuit 53 Coverlay 53a Exposure hole 60 Electronic equipment 61 Components 62 Moving parts 530 Shield Layer 530a end 531 Opening α Bending line β border

Claims

1. An electromagnetic wave shielding film comprising a shielding layer having a plurality of openings formed therein and an adhesive layer laminated together, When the shielding layer is viewed in plan, An electromagnetic wave shielding film, characterized in that the opening arranged at at least a part of an end of the shielding layer is a notched opening that exposes an inner periphery.

2. the electromagnetic wave shielding film has a folding portion that can be folded along a linear folding line, The electromagnetic wave shielding film according to claim 1 , wherein, when the electromagnetic wave shielding film is viewed in plan, the folding line intersects with the end of the shielding layer where the cutout opening is formed.

3. When the shielding layer is viewed from above, the opening has an axisymmetric shape having at least one axis of symmetry, the opening has a first length X in a first direction along the axis of symmetry and a second length Y in a second direction perpendicular to the first direction; The electromagnetic wave shielding film according to claim 1 , wherein the first length X is longer than the second length Y.

4. the electromagnetic wave shielding film has a folding portion that can be folded along a linear folding line, The electromagnetic wave shielding film according to claim 3 , wherein the folding line intersects with the second direction when the electromagnetic wave shielding film is viewed in a plan view.

5. The electromagnetic wave shielding film according to claim 1 , wherein the openings are regularly arranged when the shielding layer is viewed from above.

6. The electromagnetic wave shielding film according to claim 5 , wherein the openings are arranged in a staggered pattern.

7. a flexible printed wiring board including a base film, a printed circuit disposed on the base film, and a coverlay disposed to cover the printed circuit; a shielded printed wiring board including an electromagnetic wave shielding film disposed on the coverlay side of the flexible printed wiring board, 7. A shielded printed wiring board, wherein the electromagnetic wave shielding film is the electromagnetic wave shielding film according to claim 1.

8. a shield layer preparation step of preparing a shield layer in which no openings are formed; an opening forming step of forming an opening in the shielding layer where no opening is formed; a cutting step of cutting the shielding layer through the opening to form a notched opening at least at one end of the shielding layer; and forming an adhesive layer on one main surface of the shielding layer.

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