Electromagnetic wave shielding film and shielded printed wiring board

Abstract

To provide an electromagnetic wave shielding film that can achieve both volatile component permeability and shielding properties and has sufficiently high bending resistance.SOLUTION: An electromagnetic wave shielding film according to the present invention includes an adhesive layer, a metal layer made of metal laminated on the adhesive layer, and an insulating layer laminated on the metal layer, and a plurality of openings are formed in the metal layer, the openings including island-shaped metal layer-forming openings (A) in which one or more island-shaped metal layers are formed inside the openings, and the island-shaped metal layer-forming openings (A) including island-shaped metal layer-forming openings (A1) in which the total area of the island-shaped metal layers in one island-shaped metal layer-forming opening (A) is 40 to 80% of the area inside the outline of the one island-shaped metal layer-forming opening (A).SELECTED DRAWING: Figure 1B

Description

[Technical Field]

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

[0002] BACKGROUND ART Conventionally, an electromagnetic wave shielding film has been attached to a printed wiring board such as a flexible printed wiring board (FPC) to shield it from external electromagnetic waves.

[0003] An electromagnetic wave shielding film typically has a structure in which a conductive adhesive layer, a shielding layer made of a metal thin film or the like, and an insulating layer are laminated in this order. This electromagnetic wave shielding film is superimposed on a printed wiring board and then hot-pressed, whereby the electromagnetic wave shielding film is adhered to the printed wiring board by the adhesive layer, producing a shielded printed wiring board. After this adhesion, components are mounted on the shielded printed wiring board by solder reflow. The printed wiring board also has a structure in which the printed pattern on the base film is covered with an insulating film.

[0004] When manufacturing a shielded printed wiring board, heating the board by hot pressing or solder reflow generates gas from the adhesive layer of the electromagnetic wave shielding film and the insulating film of the printed wiring board. Furthermore, if the base film of the printed wiring board is made of a highly hygroscopic resin such as polyimide, water vapor may be generated from the base film upon heating. These volatile components generated from the adhesive layer, insulating film, and base film cannot pass through the shielding layer and instead accumulate between the shielding layer and the adhesive layer. Therefore, if rapid heating is performed during the solder reflow process, the volatile components accumulated between the shielding layer and the adhesive layer may destroy the interlayer adhesion between the shielding layer and the adhesive layer, resulting in a decrease in shielding properties.

[0005] To solve this problem, a number of openings are provided in the shielding layer (metal thin film) to improve air permeability. By providing multiple openings in the shielding layer, even if volatile components are generated, they can pass through the shielding layer through the openings, preventing the volatile components from accumulating between the shielding layer and the conductive adhesive layer and preventing a deterioration in shielding properties due to a breakdown in interlayer adhesion.

[0006] As an electromagnetic wave shielding film having openings in such a shielding layer (metal layer), Patent Document 1 describes an electromagnetic wave shielding film comprising a conductive adhesive layer, a shielding layer laminated on the conductive adhesive layer, and an insulating layer laminated on the shielding layer, in which a plurality of openings are formed in the shielding layer, and the opening areas of the openings are 70 to 71,000 μm. 2 and the aperture ratio of the openings is 0.05 to 3.6%.

[0007] Patent Document 2 also describes a substrate that is composed of an insulating layer, a metal layer, and a conductive adhesive layer, and the metal layer has an area of ​​0.7 to 5000 μm 2 The openings are 100 to 200,000 pieces / cm 2 The electromagnetic wave shielding sheet has the openings in the metal layer, and the distance from the center point of the opening to the center point of the nearest opening and the number of openings in the area of ​​the metal layer are adjusted to be within a predetermined range. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2018 / 147298 [Patent Document 2] Japanese Patent Application Publication No. 2018-60987 Summary of the Invention [Problem to be solved by the invention]

[0009] The electromagnetic wave shielding films (electromagnetic wave shielding sheets) described in Patent Documents 1 and 2 can prevent volatile components from accumulating between the shielding layer (metal layer) and the conductive adhesive layer, thereby preventing the breakdown of interlayer adhesion. However, these electromagnetic wave shielding films (electromagnetic wave shielding sheets) have the problem of not having sufficiently high bending resistance. Furthermore, because the shielding layer (metal layer) has openings, electromagnetic waves can easily pass through the electromagnetic wave shielding film through these openings. In particular, the shielding properties in the high frequency range above 10 GHz were insufficient.

[0010] 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 can achieve both volatile component permeability and shielding properties, and has sufficiently high bending resistance. [Means for solving the problem]

[0011] The electromagnetic wave shielding film of a first aspect of the present invention is an electromagnetic wave shielding film comprising an adhesive layer, a metal layer made of metal laminated on the adhesive layer, and an insulating layer laminated on the metal layer, wherein a plurality of openings are formed in the metal layer, the openings including island-shaped metal layer-forming openings (A) in which one or more island-shaped metal layers are formed inside the openings, and the island-shaped metal layer-forming openings (A) include island-shaped metal layer-forming openings (A1) in which the total area of ​​the island-shaped metal layers in one island-shaped metal layer-forming opening (A) is 40 to 80% of the area inside the outline of one island-shaped metal layer-forming opening (A).

[0012] In the electromagnetic wave shielding film of the first aspect of the present invention, the opening includes an island-shaped metal layer-forming opening (A) in which one or more island-shaped metal layers are formed inside the opening. In this specification, the term "island-shaped metal layer" refers to a metal layer that is located inside the region surrounded by the outline of the opening and does not contact the outline of the opening. In the electromagnetic wave shielding film of the first embodiment of the present invention, the opening may have a peninsula-shaped metal layer formed therein that is in contact with the outline of the opening, but such a peninsula-shaped metal layer is not included in the "island-shaped metal layer."

[0013] The island-shaped metal layer is not connected to the outline of the opening and is independent from the metal layer that forms the opening, so even if the island-shaped metal layer is subjected to a force such as pressure or stress, the force is unlikely to be transmitted to the metal layer that forms the opening. Therefore, even if a volatile component is generated between the metal layer and the adhesive layer and the volatile component exerts pressure on the island-shaped metal layer, the pressure is unlikely to be transmitted to the metal layer forming the opening. Additionally, volatile components can pass through the metal layer through the openings. Therefore, in the electromagnetic wave shielding film of the first aspect of the present invention, it is possible to prevent the interlayer adhesion between the metal layer and the adhesive layer from being destroyed due to the generation of volatile components.

[0014] Generally, when electromagnetic waves reach an electromagnetic wave shielding film, the electromagnetic waves are reflected and absorbed by the metal layer of the electromagnetic wave shielding film, and as a result, the electromagnetic waves are shielded by the electromagnetic wave shielding film. When openings are formed in the metal layer of an electromagnetic wave shielding film, electromagnetic waves may pass through the electromagnetic wave shielding film through the openings. The ease of transmission of electromagnetic waves depends on the size and number of the openings.

[0015] When an island-shaped metal layer is formed inside the opening, as in the electromagnetic wave shielding film of the first aspect of the present invention, such an island-shaped metal layer also functions as a shielding layer that reflects and absorbs electromagnetic waves. In other words, when the opening in the metal layer includes an island-shaped metal layer-forming opening (A), the electromagnetic wave shielding film has higher shielding properties than when the inside of the opening in the metal layer is entirely empty.

[0016] Furthermore, when an island-shaped metal layer is present in the openings, as in the electromagnetic wave shielding film of the first aspect of the present invention, the metal layer is less likely to bend. This can be explained as follows. If no island-shaped metal layer is formed in the opening and the inside of the opening is entirely empty, there is nothing in the opening that exhibits deformation resistance when the electromagnetic wave shielding film is folded. However, if there is an island-shaped metal layer inside the opening, as in the electromagnetic wave shielding film of the first embodiment of the present invention, stress is also applied to the island-shaped metal layer when the electromagnetic wave shielding film is folded. Since the island-shaped metal layer is made of metal and exhibits deformation resistance, it exhibits deformation resistance to the stress that attempts to fold the electromagnetic wave shielding film. As a result, the metal layer is also less likely to bend and break. For these reasons, the bending resistance of the electromagnetic wave shielding film according to the first aspect of the present invention, which has island-shaped metal layers, is sufficiently high.

[0017] In addition, in the electromagnetic wave shielding film of the first embodiment of the present invention, the island-shaped metal layer forming openings (A) include island-shaped metal layer forming openings (A1) in which the total area of ​​the island-shaped metal layers in one of the island-shaped metal layer forming openings (A) is 40 to 80% of the area inside the outline of one of the island-shaped metal layer forming openings (A). When the total area of ​​the island-shaped metal layers is 40 to 80% of the area inside the outline of one of the island-shaped metal layer forming openings (A), bending resistance and shielding properties become good. If the total area of ​​the island-shaped metal layers is less than 40% of the area inside the outline of one of the island-shaped metal layer-forming openings (A), the island-shaped metal layers will be small, resulting in low deformation resistance and a tendency for the bending resistance of the electromagnetic wave shielding film to decrease, as well as for the shielding properties to decrease. If the total area of ​​the island-shaped metal layers exceeds 80% of the area inside the outline of one of the island-shaped metal layer forming openings (A), the passageway for volatile components becomes narrow, making it more likely that the adhesion between the layers will be destroyed.

[0018] In the electromagnetic wave shielding film of the first aspect of the present invention, the proportion of the number of the island-shaped metal layer forming openings (A) to the total number of the openings is preferably 25% or more. When the number of island-shaped metal layer forming openings (A) is large, the effects of preventing the destruction of interlayer adhesion due to the formation of the above-mentioned island-shaped metal layer, the effects of improving shielding properties, and the effects of improving bending resistance are more easily achieved.

[0019] In the electromagnetic wave shielding film of the first aspect of the present invention, the proportion of the number of the island-shaped metal layer forming openings (A1) to the total number of the openings is preferably 5% or more. When the number of island-shaped metal layer forming openings (A1) is large, the effect of including island-shaped metal layer forming openings (A1) in which the total area of ​​the island-shaped metal layer in one island-shaped metal layer forming opening (A) is 40 to 80% of the area inside the outline of one island-shaped metal layer forming opening (A) is more easily achieved. In other words, the bending resistance and shielding properties of the electromagnetic wave shielding film according to the first aspect of the present invention become even better.

[0020] The electromagnetic wave shielding film of the second aspect of the present invention is an electromagnetic wave shielding film comprising an adhesive layer, a metal layer made of metal laminated on the adhesive layer, and an insulating layer laminated on the metal layer, wherein a plurality of openings are formed in the metal layer, and the openings include island-shaped metal layer-forming openings (A) in which one or more island-shaped metal layers are formed inside the openings, and the total area of ​​the island-shaped metal layers in the entire metal layer is 1 to 90% of the total area inside the outlines of the openings in the entire metal layer.

[0021] In the electromagnetic wave shielding film of the second aspect of the present invention, the opening includes an island-shaped metal layer-forming opening (A) in which one or more island-shaped metal layers are formed inside the opening, and therefore the electromagnetic wave shielding film exhibits the effects of preventing the destruction of interlayer adhesion due to the formation of the island-shaped metal layers, improving shielding properties, and improving bending resistance. In the electromagnetic wave shielding film of the second embodiment of the present invention, the opening may have a peninsula-shaped metal layer formed therein that is in contact with the outline of the opening, but such a peninsula-shaped metal layer is not included in the "island-shaped metal layer."

[0022] In the electromagnetic wave shielding film of the second aspect of the present invention, the total area of ​​the island-shaped metal layers in the entire metal layer is 1 to 90% of the total area inside the outlines of the openings in the entire metal layer. When the total area of ​​the island-shaped metal layers in the entire metal layer is 1 to 90% of the total area inside the contours of the openings in the entire metal layer, bending resistance and shielding properties are improved. If the total area of ​​the island-shaped metal layers in the entire metal layer is less than 1% of the total area inside the outline of the opening in the entire metal layer, this means that the number of island-shaped metal layers in the entire metal layer is small. In other words, this means that the number of island-shaped metal layers that exhibit deformation resistance is small. As a result, the bending resistance of the electromagnetic wave shielding film is likely to decrease. In addition, the shielding properties are also likely to decrease. If the total area of ​​the island-shaped metal layers in the entire metal layer exceeds 90% of the total area inside the outline of the opening in the entire metal layer, the path for volatile components becomes narrow, making it more likely that the adhesion between the layers will be destroyed.

[0023] In the electromagnetic wave shielding film of the second aspect of the present invention, the island-shaped metal layer forming openings (A) preferably include island-shaped metal layer forming openings (A1) in which the total area of ​​the island-shaped metal layers in one island-shaped metal layer forming opening (A) is 40 to 80% of the area inside the outline of one island-shaped metal layer forming opening (A). When the electromagnetic wave shielding film includes the island-shaped metal layer forming openings (A1), the bending resistance and shielding properties become good. If the total area of ​​the island-shaped metal layers is less than 40% of the area inside the outline of one of the island-shaped metal layer-forming openings (A), the island-shaped metal layers will be small, resulting in low deformation resistance and a tendency for the bending resistance of the electromagnetic wave shielding film to decrease, as well as for the shielding properties to decrease. If the total area of ​​the island-shaped metal layers exceeds 80% of the area inside the outline of one of the island-shaped metal layer forming openings (A), the passageway for volatile components becomes narrow, making it more likely that the adhesion between the layers will be destroyed.

[0024] In the electromagnetic wave shielding film of the second aspect of the present invention, the proportion of the number of the island-shaped metal layer forming openings (A1) to the total number of the openings is preferably 5% or more. When the number of island-shaped metal layer forming openings (A1) is large, the effect of including island-shaped metal layer forming openings (A1) in which the total area of ​​the island-shaped metal layer in one island-shaped metal layer forming opening (A) is 40 to 80% of the area inside the outline of one island-shaped metal layer forming opening (A) is more easily achieved. That is, the bending resistance and shielding properties of the electromagnetic wave shielding film are further improved.

[0025] In the electromagnetic wave shielding film of the second aspect of the present invention, the proportion of the number of the island-shaped metal layer forming openings (A) to the total number of the openings is preferably 25% or more. When the number of island-shaped metal layer forming openings (A) is large, the effects of preventing the destruction of interlayer adhesion due to the formation of the above-mentioned island-shaped metal layer, the effects of improving shielding properties, and the effects of improving bending resistance are more easily achieved.

[0026] In the electromagnetic wave shielding film of the first embodiment of the present invention and the electromagnetic wave shielding film of the second embodiment of the present invention (hereinafter, when simply referred to as "electromagnetic wave shielding film of the present invention", both embodiments are included), the aperture ratio of the metal layer is preferably 5 to 90%. If the opening ratio of the openings is less than 5%, the proportion of openings is too small, making it difficult for volatile components to pass through the metal layer. As a result, volatile components tend to accumulate between the metal layer and the adhesive layer. Therefore, the interlayer adhesion between the metal layer and the adhesive layer is easily destroyed by the volatile components. If the opening ratio of the openings exceeds 90%, the ratio of the openings is too large, and the strength of the metal layer decreases, resulting in a decrease in bending resistance. In this specification, the term "aperture ratio" refers to the ratio of the total aperture area of ​​a plurality of apertures to the area of ​​the entire main surface of the metal layer. Note that, when calculating the "aperture ratio," the island-shaped metal layer portions are not included in the aperture area.

[0027] In the electromagnetic wave shielding film of the present invention, the average value of the area inside the outline of one of the openings is 5 to 2000 μm 2 It is preferable that: The average area inside the contour of one opening is 5 μm 2 If the opening is less than 1 / 2 mm, the opening will be too narrow, making it difficult for the volatile components to pass through the metal layer, which will result in the volatile components easily accumulating between the metal layer and the adhesive layer, which will easily destroy the interlayer adhesion between the metal layer and the adhesive layer. The average area inside the contour of one opening is 2000 μm 2 If it exceeds this value, the opening will be too wide, reducing the strength of the metal layer and making it more likely that bending resistance will decrease.

[0028] In the electromagnetic wave shielding film of the present invention, the thickness of the metal layer is preferably 0.4 to 1.9 μm. If the thickness of the metal layer is less than 0.4 μm, the metal layer will be too thin and have low strength, resulting in reduced bending resistance. Furthermore, it will be difficult to sufficiently reflect and absorb electromagnetic waves, resulting in reduced shielding properties. If the thickness of the metal layer exceeds 1.9 μm, the entire electromagnetic wave shielding film becomes thick and difficult to handle.

[0029] In the electromagnetic wave shielding film of the present invention, 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. A metal layer containing these metals functions favorably as a shielding layer that blocks electromagnetic waves.

[0030] The electromagnetic wave shielding film of the present invention has a water vapor permeability of 40 g / m2 in accordance with JIS K7129 at a temperature of 80°C, a humidity of 95% RH, and a differential pressure of 1 atm. 2 Preferably 24 hours or more. When the water vapor permeability is within this range, volatile components are less likely to accumulate between the metal layer and the adhesive layer, and therefore the interlayer adhesion between the metal layer and the adhesive layer is less likely to be destroyed by volatile components.

[0031] The shielded printed wiring board of the present invention is a shielded printed wiring board having a base member on which a printed circuit is formed, an insulating film provided on the base member so as to cover the printed circuit, and an electromagnetic wave shielding film provided on the printed wiring board, characterized in that the electromagnetic wave shielding film is the electromagnetic wave shielding film of the first aspect of the present invention or the electromagnetic wave shielding film of the second aspect of the present invention. The shielded printed wiring board of the present invention comprises the electromagnetic wave shielding film of the present invention. Therefore, delamination between the metal layer and the adhesive layer of the electromagnetic wave shielding film is unlikely to occur, resulting in good shielding properties. Furthermore, even if the electromagnetic wave shielding film is bent as the shielded printed wiring board is bent, the electromagnetic wave shielding film is unlikely to be damaged. [Effects of the Invention]

[0032] According to the present invention, it is possible to provide an electromagnetic wave shielding film that can achieve both volatile component permeability and shielding properties, and also has sufficiently high bending resistance. [Brief explanation of the drawings]

[0033] [Figure 1A] FIG. 1A is a cross-sectional view schematically showing an example of an electromagnetic wave shielding film according to a first embodiment of the present invention. [Figure 1B] FIG. 1B is a cross-sectional view taken along line AA in FIG. 1A. [Figure 1C] FIG. 1C is an enlarged view of the portion indicated by the dashed line in FIG. 1B. [Figure 2] FIG. 2 is a cross-sectional view schematically showing an example of a shielded printed wiring board of the present invention. [Figure 3] FIG. 3 is a schematic diagram showing the configuration of a system used in the KEC method. DETAILED DESCRIPTION OF THE INVENTION

[0034] 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.

[0035] (First embodiment) Fig. 1A is a cross-sectional view schematically showing an example of an electromagnetic wave shielding film according to a first embodiment of the present invention, and Fig. 1B is a cross-sectional view taken along line AA in Fig. 1A. 1A, the electromagnetic wave shielding film 10 is an electromagnetic wave shielding film in which an insulating layer 20, a metal layer 30, and an adhesive layer 40 are laminated in this order. An opening 50 is formed in the metal layer 30. As shown in FIG. 1B, the opening 50 includes an island-shaped metal layer forming opening (A) 51 in which an island-shaped metal layer 31 is formed inside the opening 50.

[0036] Each component of the electromagnetic wave shielding film 10 will be described in detail below.

[0037] (metal layer) In the electromagnetic wave shielding film 10, the metal layer 30 functions as a shielding layer that blocks electromagnetic waves.

[0038] The island-shaped metal layer 31 is not connected to the outline of the opening 50 and is independent from the metal layer 30 that forms the opening 50. Therefore, even if the island-shaped metal layer 31 is subjected to a force such as pressure or stress, the force is unlikely to be transmitted to the metal layer 30 that forms the opening 50. Therefore, even if volatile components are generated between the metal layer 30 and the adhesive layer 40 and pressure is applied to the island-shaped metal layer 31 by the volatile components, the pressure is unlikely to be transmitted to the metal layer 30 forming the opening 50. Additionally, volatile components can pass through the metal layer 30 through the openings 50 . Therefore, in the electromagnetic wave shielding film 10, it is possible to prevent the interlayer adhesion between the metal layer 30 and the adhesive layer 40 from being destroyed due to the generation of volatile components.

[0039] Generally, when electromagnetic waves reach an electromagnetic wave shielding film, the electromagnetic waves are reflected and absorbed by the metal layer of the electromagnetic wave shielding film, and as a result, the electromagnetic waves are shielded by the electromagnetic wave shielding film. Furthermore, when openings are formed in the metal layer of the electromagnetic wave shielding film, electromagnetic waves may pass through the electromagnetic wave shielding film through the openings. The ease of transmission of electromagnetic waves depends on the size and number of the openings.

[0040] When island-shaped metal layers 31 are formed inside the openings 50, as in the electromagnetic wave shielding film 10, such island-shaped metal layers 31 also function as a shielding layer that reflects and absorbs electromagnetic waves. In other words, when the openings 50 in the metal layer 30 include island-shaped metal layer-forming openings (A) 51, the electromagnetic wave shielding film has higher shielding properties than when the inside of the openings in the metal layer are entirely empty spaces.

[0041] Furthermore, when the metal layer 31 has island shapes in the openings 50 as in the electromagnetic wave shielding film 10, the metal layer 30 is less likely to bend. This can be explained as follows. If no island-shaped metal layer is formed in the opening and the inside of the opening is entirely empty, there is nothing in the opening that exhibits deformation resistance when the electromagnetic wave shielding film is folded. However, if there is an island-shaped metal layer 31 inside the opening 50, as in the electromagnetic wave shielding film 10, stress is also applied to the island-shaped metal layer 31 when the electromagnetic wave shielding film 10 is folded. Since the island-shaped metal layer 31 is made of metal and exhibits deformation resistance, the island-shaped metal layer 31 exhibits deformation resistance to the stress that attempts to fold the electromagnetic wave shielding film 10. As a result, the metal layer 30 is also less likely to bend and is less likely to break. For this reason, the bending resistance of the electromagnetic wave shielding film 10 having the island-shaped metal layers 31 is sufficiently high.

[0042] As shown in Figure 1B, the island-shaped metal layer formation opening (A) 51 includes an island-shaped metal layer formation opening (A1) 51a in which the total area of ​​the island-shaped metal layer 31 in one island-shaped metal layer formation opening (A) 51 is 40 to 80% of the area inside the outline of one island-shaped metal layer formation opening (A) 51.

[0043] The area of ​​the island-shaped metal layer 31 and the area inside the outline of one island-shaped metal layer forming opening (A) 51 will be described in more detail with reference to the drawings. FIG. 1C is an enlarged view of the portion indicated by the dashed line in FIG. 1B. As shown in FIG. 1C, the area of ​​the island-shaped metal layer 31 means the area of ​​the region indicated by the symbol S1 in FIG. 1C. As shown in FIG. 1C, the area inside the outline of one island-shaped metal layer forming opening (A) 51 is the area indicated by the symbol S T This refers to the area of ​​the region indicated by .

[0044] In addition, the total value of the area S1 of the island-shaped metal layer 31 in one island-shaped metal layer forming opening (A) 51 means the area of ​​that one island-shaped metal layer 31 if there is only one island-shaped metal layer 31 in one island-shaped metal layer forming opening (A) 51, and if there are multiple island-shaped metal layers 31, it means the total value of the areas of the multiple island-shaped metal layers 31.

[0045] In the island-shaped metal layer forming opening (A1) 51a, the total value of the area S1 is T It is preferably 45 to 75%, and more preferably 50 to 60% of the total.

[0046] In the island-shaped metal layer forming opening (A1) 51a, the total value of the area S1 is equal to the area S T When the thickness is 40 to 80%, the bending resistance and shielding properties are improved. The sum of the areas S1 and S2 is the area S T If the area is less than 40%, the island-shaped metal layers are small, which reduces deformation resistance and tends to reduce the bending resistance of the electromagnetic wave shielding film, as well as the shielding properties. The sum of the areas S1 and S2 is the area S T If the ratio exceeds 80%, the passageway for volatile components becomes narrow, which makes the adhesion between layers more likely to be broken.

[0047] As shown in FIG. 1B, the electromagnetic wave shielding film 10 may include island-shaped metal layer-free openings 55 in which no island-shaped metal layer is formed inside the openings 50. In addition, the island-shaped metal layer forming opening (A) 51 of the electromagnetic wave shielding film 10 has a structure in which the total area S1 of the island-shaped metal layer 31 in one island-shaped metal layer forming opening (A) 51 is smaller than the inner area S of the outline of one island-shaped metal layer forming opening (A) 51. T The island-shaped metal layer forming openings (A2) 51b may be less than 40% of the area of ​​the island-shaped metal layer forming openings (A2). Furthermore, the island-shaped metal layer forming opening (A) 51 of the electromagnetic wave shielding film 10 is such that the total area S1 of the island-shaped metal layer 31 in one island-shaped metal layer forming opening (A) 51 is smaller than the inner area S of the outline of one island-shaped metal layer forming opening (A) 51. T The island-shaped metal layer forming openings (A3) 51c may account for more than 80% of the total area.

[0048] In the electromagnetic wave shielding film 10, the density of the openings 50 in the metal layer 30 is not particularly limited, but is preferably 10 to 5000 openings / mm 2It is preferable that the number of particles is 10 to 2000 / mm 2 It is more preferable that: The density of the openings in the metal layer is 10 / mm 2 If the thickness is less than 1000 nm, the passageway for the volatile components becomes narrow, and the adhesion between the layers is likely to be destroyed. The density of the openings in the metal layer is 5000 / mm 2 If the temperature exceeds this value, the strength of the metal layer decreases and the metal layer becomes more susceptible to breakage.

[0049] In the electromagnetic wave shielding film 10, the ratio of the number of island-shaped metal layer forming openings (A) 51 to the number of openings 50 is preferably 25% or more, more preferably 30% or more, and even more preferably 50% or more. When the number of island-shaped metal layer forming openings (A) 51 is large, the effects of preventing the destruction of interlayer adhesion due to the formation of the above-mentioned island-shaped metal layers 31, the effects of improving shielding properties, and the effects of improving bending resistance are more easily achieved.

[0050] In the electromagnetic wave shielding film 10, the proportion of the number of island-shaped metal layer forming openings (A1) 51a to the number of openings 50 is preferably 5% or more, and more preferably 8% or more. When the number of the island-shaped metal layer forming openings (A1) 51a is large, the total value of the area S1 in the island-shaped metal layer forming openings (A1) 51a is smaller than the area S T The effect is more easily exhibited when the island-shaped metal layer forming openings (A1) 51a, which account for 40 to 80% of the total area, are included. That is, the bending resistance and shielding properties of the electromagnetic wave shielding film 10 become even better.

[0051] In the electromagnetic wave shielding film 10, the total area S1 of the island-shaped metal layers 31 in the entire metal layer 30 is smaller than the area S inside the outline of the opening 50 in the entire metal layer 30. T The total value is preferably 1 to 90%, more preferably 10 to 75%, further preferably 45 to 75%, and particularly preferably 50 to 60%. The sum of the area S1 of the island-shaped metal layers 31 in the entire metal layer 30 is smaller than the area S T When the total value is 1 to 90%, the bending resistance and shielding properties of the electromagnetic wave shielding film 10 become good. The sum of the area S1 of the island-shaped metal layers 31 in the entire metal layer 30 is smaller than the area S T If the total value is less than 1%, it means that the number of island-shaped metal layers in the entire metal layer is small. In other words, it means that the number of island-shaped metal layers that exhibit deformation resistance is small. As a result, the bending resistance of the electromagnetic wave shielding film is likely to decrease. In addition, the shielding properties are also likely to decrease. The sum of the area S1 of the island-shaped metal layers 31 in the entire metal layer 30 is smaller than the area S T If the total value exceeds 90%, the passage of the volatile components becomes narrow, which makes the adhesion between the layers more likely to be broken.

[0052] In this specification, the area S1 of the island-shaped metal layer 31 and the area S inside the contour of the opening 50 are T means a value measured by the following method. First, an image of the metal layer is obtained using a scanning electron microscope (SEM). Next, the obtained image is binarized into black and white for the island-shaped metal layer 31 portion and the gap portion of the opening 50 using image analysis software "GIMP 2.10.6". Next, the area S1 of the island-shaped metal layer 31 and the area S inside the outline of the opening 50 are calculated from the number of pixels of the island-shaped metal layer 31 portion and the gap portion of the opening 50. T Calculate.

[0053] In the electromagnetic wave shielding film 10, the aperture ratio of the metal layer 30 is preferably 5 to 90%, more preferably 30 to 90%, even more preferably 40 to 80%, and even more preferably 40 to 60%. If the opening ratio of the openings is less than 5%, the proportion of openings is too small, making it difficult for volatile components to pass through the metal layer. As a result, volatile components tend to accumulate between the metal layer and the adhesive layer. Therefore, the interlayer adhesion between the metal layer and the adhesive layer is easily destroyed by the volatile components. If the opening ratio of the openings exceeds 90%, the ratio of the openings is too large, and the strength of the metal layer decreases, resulting in a decrease in bending resistance. In this specification, the term "aperture ratio" refers to the ratio of the total aperture area of ​​the plurality of openings 50 to the area of ​​the entire main surface of the metal layer 30. In calculating the "aperture ratio," the island-shaped metal layer 31 portions are not included in the aperture area.

[0054] In the electromagnetic wave shielding film of the present invention, the average value of the inner area of ​​the outline of one of the openings is 5 to 2000 μm 2 It is preferable that the thickness is 50 to 1800 μm. 2 It is more preferable that: The average area inside the contour of one opening is 5 μm 2 If the opening is less than 1 / 2 mm, the opening will be too narrow, making it difficult for the volatile components to pass through the metal layer, which will result in the volatile components easily accumulating between the metal layer and the adhesive layer, which will easily destroy the interlayer adhesion between the metal layer and the adhesive layer. The average area inside the contour of one opening is 2000 μm 2 If the opening exceeds this value, the strength of the metal layer decreases because the opening is too wide, and bending resistance tends to decrease.

[0055] In the electromagnetic wave shielding film of the present invention, the shape of the openings is not particularly limited, and may be circular, elliptical, racetrack, triangular, rectangular, pentagonal, hexagonal, octagonal, star-shaped, or the like. In the electromagnetic wave shielding film of the present invention, the opening may have a shape in which a peninsula-shaped metal layer is formed in contact with the outline of the opening. Note that in the electromagnetic wave shielding film of the present invention, such a peninsula-shaped metal layer is not included in the "island-shaped metal layer." The shape of the plurality of openings may be of one type alone, or a combination of multiple types.

[0056] In the electromagnetic wave shielding film 10, the thickness of the metal layer 30 is preferably 0.4 to 1.9 μm, more preferably 0.5 to 1.8 μm, and even more preferably 0.8 to 1.5 μm. Furthermore, when the thickness of the metal layer 30 is 0.4 to 1.9 μm, the transmission characteristics become good in a signal transmission system that transmits high-frequency signals with frequencies of 0.01 to 10 GHz. If the thickness of the metal layer is less than 0.4 μm, the metal layer will be too thin and have low strength, resulting in reduced bending resistance. Furthermore, it will be difficult to sufficiently reflect and absorb electromagnetic waves, resulting in reduced shielding properties. If the thickness of the metal layer exceeds 1.9 μm, the entire electromagnetic wave shielding film becomes thick and difficult to handle.

[0057] In the electromagnetic wave shielding film 10, the metal layer 30 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 contain an alloy of these metals. Of these metals, copper is more preferable. The metal layer 30 containing these metals functions favorably as a shielding layer that blocks electromagnetic waves.

[0058] (adhesive layer) In the electromagnetic wave shielding film 10, the adhesive layer 40 may or may not be conductive, but is preferably conductive.

[0059] First, the case where the adhesive layer 40 is conductive will be described. When the adhesive layer 40 is conductive, the adhesive layer 40 is preferably composed of conductive particles and an adhesive resin composition.

[0060] The conductive particles are not particularly limited, but may be metal fine particles, carbon nanotubes, carbon fibers, metal fibers, or the like.

[0061] When the conductive particles are metal microparticles, the metal microparticles are 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 microparticles or glass beads coated with metal, etc. Among these, copper powder or silver-coated copper powder, which is inexpensively available, is preferable from the viewpoint of economy.

[0062] The average particle size of the conductive particles is not particularly limited, but is preferably 0.5 to 15.0 μm. When the average particle size of the conductive particles is 0.5 μm or more, the adhesive layer has good conductivity. When the average particle size of the conductive particles is 15.0 μm or less, the adhesive layer can be made thin.

[0063] The shape of the conductive particles is not particularly limited, but can be appropriately selected from spherical, flat, scale-like, dendritic, rod-like, fibrous, and other shapes.

[0064] The material for the adhesive resin composition is not particularly limited, but examples thereof include thermoplastic resin compositions such as styrene-based resin compositions, vinyl acetate-based resin compositions, polyester-based resin compositions, polyethylene-based resin compositions, polypropylene-based resin compositions, imide-based resin compositions, amide-based resin compositions, and acrylic-based resin compositions; and thermosetting resin compositions such as phenol-based resin compositions, epoxy-based resin compositions, urethane-based resin compositions, melamine-based resin compositions, and alkyd-based resin compositions. The adhesive resin composition may contain one of these materials alone or a combination of two or more of them.

[0065] The amount of conductive particles contained in the adhesive layer 40 is not particularly limited, but is preferably 15 to 80% by weight, and more preferably 15 to 60% by weight. Within the above range, the adhesiveness of the adhesive layer 40 to the printed wiring board is improved.

[0066] The thickness of the adhesive layer 40 is not particularly limited and can be set appropriately as needed, but is preferably 0.5 to 20.0 μm. If the thickness of the adhesive layer is less than 0.5 μm, it becomes difficult to obtain good electrical conductivity. If the thickness of the adhesive layer exceeds 20.0 μm, the overall thickness of the electromagnetic wave shielding film will be too large and difficult to handle.

[0067] Furthermore, the adhesive layer 40 may have anisotropic conductivity or may have isotropic conductivity, but preferably has anisotropic conductivity. When the adhesive layer 40 has anisotropic conductivity, the transmission characteristics of high frequency signals transmitted through the signal circuits of the printed wiring board are improved compared to when the adhesive layer 40 has isotropic conductivity.

[0068] By setting the proportion of the conductive particles in the adhesive layer 40 to 2 to 40% by weight, the adhesive layer 40 can be given anisotropic conductivity. Furthermore, by setting the proportion of conductive particles in the adhesive layer 40 to be more than 40% by weight and not more than 80% by weight, it is possible to impart isotropic conductivity to the adhesive layer 40.

[0069] Next, a case where the adhesive layer 40 does not have electrical conductivity will be described. When the adhesive layer 40 does not have electrical conductivity, the adhesive layer 40 is preferably made of an adhesive resin composition. The preferred materials for the adhesive resin composition are the same as the preferred materials for the adhesive resin composition when the adhesive layer 40 is electrically conductive.

[0070] Whether the adhesive layer 40 is conductive or not, the adhesive 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 viscosity adjuster, and the like.

[0071] (insulating layer) In the electromagnetic wave shielding film 10, the insulating layer 20 is not particularly limited as long as it has sufficient insulating properties and can protect the metal layer 30 and the adhesive layer 40, 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.

[0072] 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.

[0073] 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.

[0074] The insulating layer 20 may be made of a single material, or may be made of two or more materials.

[0075] The insulating layer 20 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 viscosity adjuster, an antiblocking agent, and the like.

[0076] The thickness of the insulating layer 20 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 insulating layer 20 is less than 1 μm, it is too thin and it is difficult to sufficiently protect the metal layer 30 and the adhesive layer 40 . If the thickness of the insulating layer 20 exceeds 15 μm, the electromagnetic wave shielding film 10 becomes difficult to bend due to the excessive thickness, and the insulating layer 20 itself becomes more susceptible to breakage, making it difficult to apply to components that require resistance to bending.

[0077] (Other configurations) In the electromagnetic wave shielding film 10, an anchor coat layer may be formed between the insulating layer 20 and the metal layer 30. Materials for the anchor coat layer include urethane resin, acrylic resin, core-shell composite resin with urethane resin as the shell and acrylic resin as the core, epoxy resin, imide resin, amide resin, melamine resin, phenol resin, urea-formaldehyde resin, blocked isocyanate obtained by reacting polyisocyanate with a blocking agent such as phenol, polyvinyl alcohol, and polyvinylpyrrolidone.

[0078] The electromagnetic wave shielding film 10 may also have a support film on the insulating layer 20 side, and may have a peelable film on the adhesive layer 40 side. When the electromagnetic wave shielding film 10 has a support film or a peelable film, the electromagnetic wave shielding film 10 becomes easier to handle when transporting the electromagnetic wave shielding film 10 or when manufacturing a shielded printed wiring board or the like using the electromagnetic wave shielding film 10. Such a support film and peelable film are to be peeled off when the electromagnetic wave shielding film 10 is placed on a printed wiring board or the like.

[0079] The electromagnetic wave shielding film 10 has a water vapor permeability of 40 g / m2 in accordance with JIS K7129 at a temperature of 80°C, a humidity of 95% RH, and a differential pressure of 1 atm. 2 24 hours or more is preferable, and 200 g / m 2 24 hours or more is preferable. When the electromagnetic wave shielding film 10 has these parameters, volatile components can easily pass through the metal layer. As a result, volatile components are less likely to accumulate between the metal layer and the adhesive layer. Therefore, the interlayer adhesion between the metal layer and the adhesive layer is less likely to be destroyed by volatile components.

[0080] The electromagnetic wave shielding film of the present invention may be used for any purpose as long as it is intended to block electromagnetic waves. In particular, the electromagnetic wave shielding film of the present invention is preferably used for a printed wiring board, particularly a flexible printed wiring board. As described above, the electromagnetic wave shielding film of the present invention is less likely to trap volatile components between the shielding layer and the adhesive layer during the production of a shielded printed wiring board. Furthermore, the electromagnetic wave shielding film of the present invention has sufficient bending resistance. Therefore, the electromagnetic wave shielding film of the present invention is less likely to break even when used in a flexible printed wiring board and repeatedly bent. Therefore, the electromagnetic wave shielding film of the present invention can be suitably used as an electromagnetic wave shielding film for flexible printed wiring boards. In this case, the electromagnetic wave shielding film 10 is preferably used in a signal transmission system that transmits signals with frequencies of 0.01 to 10 GHz.

[0081] Next, an example of a method for producing the electromagnetic wave shielding film of the present invention will be described. In the method for producing an electromagnetic wave shielding film of the present invention, an insulating layer is first prepared, and a metal layer is formed on one surface of the insulating layer.

[0082] The metal layer may be formed by disposing a metal foil, by plating such as electrolytic plating or non-electrolytic plating, by vapor deposition, or by printing. These methods can be carried out by conventionally known methods.

[0083] Next, an opening is formed in the metal layer, and at this time, an island-shaped metal layer forming opening (A) is formed inside the opening, in which one or more island-shaped metal layers are formed. Furthermore, at least one of the island-shaped metal layer formation openings (A) is an island-shaped metal layer formation opening (A1) in which the total area of ​​the island-shaped metal layer in one island-shaped metal layer formation opening (A) is 40 to 80% of the area inside the outline of one island-shaped metal layer formation opening (A).

[0084] The method for providing the openings is not particularly limited, and examples thereof include a method of forming a resist on the metal layer and then etching the resist, and a method of irradiating the metal layer with a laser.

[0085] Furthermore, when a metal foil is disposed as the metal layer, the metal foil may be composed of a sparingly soluble component that is less soluble in the etching solution and a readily soluble component that is more soluble in the etching solution than the sparingly soluble component. In this case, the metal foil is immersed in an etching solution to dissolve the easily soluble component, thereby forming openings in the areas where the easily soluble component was previously present. By adjusting the proportion of the easily soluble component, the composition of the etching solution, the etching conditions, etc., it is possible to form an island-shaped metal layer formation opening (A1) in which the total area of ​​the island-shaped metal layer in one island-shaped metal layer formation opening (A) is 40 to 80% of the area inside the outline of one island-shaped metal layer formation opening (A).

[0086] In this case, examples of the combination of the slightly soluble component and the easily soluble component include a combination of copper and copper oxide. Such metal foils are preferably rolled tough pitch copper foils, which are composed of copper oxide (I) and pure copper with a copper purity of 99.9% by weight or higher, with the copper oxide corresponding to the readily soluble component and the pure copper corresponding to the sparingly soluble component. In addition to tough pitch copper, HA foil (manufactured by JX Nippon Oil & Gas Exploration & Metals) and other foils containing copper oxide can also be used. Furthermore, because copper foils of the desired thickness can be obtained by etching the rolled copper foil, the thickness of the metal thin film can be precisely controlled, making them suitable for use in electromagnetic wave shielding films.

[0087] When the metal layer is formed by plating or printing, the metal layer may be formed in advance so that openings and island-shaped metal layers are formed, thereby making it possible to omit the step of separately providing openings.

[0088] Thereafter, an adhesive layer is formed on the metal layer in which the island-shaped metal layer forming openings (A1) have been formed.

[0089] The electromagnetic wave shielding film of the present invention can be produced through the above steps. In the above process, instead of an insulating layer, a metal layer may be formed on one side of the conductive adhesive layer, and an insulating layer may be formed on the metal layer in which the island-shaped metal layer forming openings (A1) are formed in the same manner as above, thereby producing an electromagnetic wave shielding film. Alternatively, an electromagnetic wave shielding film may be produced by forming island-shaped metal layer forming openings (A1) in the same manner as described above on copper foil laminated on a carrier copper foil instead of an insulating layer, laminating an insulating layer or a conductive adhesive layer, and then peeling off the carrier copper foil.

[0090] The electromagnetic wave shielding film of the present invention is disposed on a printed wiring board and becomes a part of the shielded printed wiring board. Such a shielded printed wiring board will now be described. A shielded printed wiring board including the electromagnetic wave shielding film of the present invention is also one embodiment of the present invention.

[0091] FIG. 2 is a cross-sectional view schematically showing an example of a shielded printed wiring board of the present invention. The shielded printed wiring board 1 shown in Figure 2 has a printed wiring board 60 having a base member 61 on which a printed circuit 62 is formed, an insulating film 63 provided on the base member 61 so as to cover the printed circuit 62, and an electromagnetic wave shielding film 10 provided on the printed wiring board 60. In the shielded printed wiring board 1, the adhesive layer 40 of the electromagnetic wave shielding film 10 is in contact with the insulating film 63 of the printed wiring board.

[0092] The shielded printed wiring board 1 includes an electromagnetic wave shielding film 10. Therefore, delamination between the metal layer 30 and the adhesive layer 40 of the electromagnetic wave shielding film 10 is unlikely to occur, resulting in good shielding properties. Furthermore, even when the electromagnetic wave shielding film 10 is bent as the shielded printed wiring board 1 is bent, the electromagnetic wave shielding film 10 is unlikely to be damaged.

[0093] In addition, if the adhesive layer 40 of the electromagnetic wave shielding film 10 is conductive and the printed circuit 62 includes a ground circuit, a hole may be formed in the insulating film 63 to expose the ground circuit, and the adhesive layer 40 may be brought into contact with the ground circuit. With this configuration, the metal layer 30, which is a shielding layer, can be electrically connected to the ground circuit, improving the shielding characteristics.

[0094] Furthermore, both the base member 61 and the insulating film 63 are preferably made of engineering plastics, such as polypropylene, cross-linked polyethylene, polyester, polybenzimidazole, polyimide, polyimideamide, polyetherimide, and polyphenylene sulfide (PPS).

[0095] The printed circuit 62 can be made of conventional circuit materials such as copper.

[0096] The base member 61 and the printed circuit 62 may be bonded with an adhesive, or may be bonded without adhesive, similar to a so-called adhesiveless copper-clad laminate. The insulating film 63 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.

[0097] (Second embodiment) The electromagnetic wave shielding film according to the second embodiment of the present invention is an electromagnetic wave shielding film comprising an adhesive layer, a metal layer made of a metal laminated on the adhesive layer, and an insulating layer laminated on the metal layer, wherein a plurality of openings are formed in the metal layer, and the openings include island-shaped metal layer-forming openings (A) in which one or more island-shaped metal layers are formed inside the openings, and the total area of ​​the island-shaped metal layers in the entire metal layer is 1 to 90% of the total area inside the outlines of the openings in the entire metal layer.

[0098] In the electromagnetic wave shielding film according to the first embodiment of the present invention, it was an essential constituent requirement that the film include an island-shaped metal layer forming opening (A1) in which the total area of ​​the island-shaped metal layer in one island-shaped metal layer forming opening (A) is 40 to 80% of the area inside the outline of one island-shaped metal layer forming opening (A). However, in the electromagnetic wave shielding film according to the second embodiment of the present invention, this constituent requirement is not essential, and the essential constituent requirement is that the total area of ​​the island-shaped metal layers in the entire metal layer is 1 to 90% of the total area inside the outlines of the openings in the entire metal layer. Also, in the electromagnetic wave shielding film according to the second embodiment of the present invention, the total area of ​​the island-shaped metal layers in the entire metal layer is more preferably 10 to 75%, even more preferably 45 to 75%, and particularly preferably 50 to 60% of the total area inside the outlines of the openings in the entire metal layer.

[0099] When the total area of ​​the island-shaped metal layers in the entire metal layer is 1 to 90% of the total area inside the contours of the openings in the entire metal layer, bending resistance and shielding properties are improved. If the total area of ​​the island-shaped metal layers in the entire metal layer is less than 1% of the total area inside the outline of the opening in the entire metal layer, this means that the number of island-shaped metal layers in the entire metal layer is small. In other words, this means that the number of island-shaped metal layers that exhibit deformation resistance is small. As a result, the bending resistance of the electromagnetic wave shielding film is likely to decrease. In addition, the shielding properties are also likely to decrease. If the total area of ​​the island-shaped metal layers in the entire metal layer exceeds 90% of the total area inside the outline of the opening in the entire metal layer, the path for volatile components becomes narrow, making it more likely that the adhesion between the layers will be destroyed.

[0100] In addition, the electromagnetic wave shielding film according to the second embodiment of the present invention preferably includes island-shaped metal layer forming openings (A1) in which the total area of ​​the island-shaped metal layers in one of the island-shaped metal layer forming openings (A) is 40 to 80% of the area inside the outline of one of the island-shaped metal layer forming openings (A). When the electromagnetic wave shielding film according to the second embodiment of the present invention includes the island-shaped metal layer forming openings (A1), the bending resistance and shielding properties become good.

[0101] In the electromagnetic wave shielding film of the present invention, the proportion of the number of the island-shaped metal layer forming openings (A) in the total number of the openings is preferably 25% or more. When the number of island-shaped metal layer forming openings (A) is large, the effects of preventing the destruction of interlayer adhesion due to the formation of the above-mentioned island-shaped metal layer, the effects of improving shielding properties, and the effects of improving bending resistance are more easily achieved.

[0102] In the electromagnetic wave shielding film according to the second embodiment of the present invention, the proportion of the number of island-shaped metal layer forming openings (A1) in the total number of openings is preferably 5% or more, and more preferably 8% or more. When the number of island-shaped metal layer forming openings (A1) is large, the effect of including island-shaped metal layer forming openings (A1) in which the total area of ​​the island-shaped metal layer in one island-shaped metal layer forming opening (A) is 40 to 80% of the area inside the outline of one island-shaped metal layer forming opening (A) is more easily achieved. That is, the bending resistance and shielding properties of the electromagnetic wave shielding film according to the second embodiment of the present invention are further improved.

[0103] The preferred materials and configurations of the adhesive layer and metal layer of the electromagnetic wave shielding film according to the second embodiment of the present invention are the same as the preferred materials and configurations of the adhesive layer and metal layer of the electromagnetic wave shielding film according to the first embodiment of the present invention. [Example]

[0104] Examples will be given below to explain the present invention more specifically, but the present invention is not limited to these examples.

[0105] Example 1 An insulating layer made of epoxy resin with a thickness of 5 μm was prepared. Next, a copper foil having a thickness of 3 μm and containing copper(I) oxide particles was placed on the insulating layer. The rolled copper foil was then etched to a thickness of 1 μm, which dissolved the copper (I) oxide in the copper foil and created openings.

[0106] The rolled copper foil after etching was photographed using an SEM, and the image was analyzed. It was observed that the island-shaped metal layer forming openings (A) included island-shaped metal layer forming openings (A1) in which one or more island-shaped metal layers were formed inside the openings, and the total area of ​​the island-shaped metal layers in one island-shaped metal layer forming opening (A) was 40 to 80% of the area inside the outline of one island-shaped metal layer forming opening (A). The proportion of the number of island-shaped metal layer forming openings (A1) to the total number of openings was 5%, and the opening ratio of the openings was 7.5%. In addition, in this rolled copper foil, the ratio of the total area of ​​the island-shaped metal layer in one island-shaped metal layer forming opening (A) to the area inside the outline of one island-shaped metal layer forming opening (A) was calculated, and the overall average value was calculated to be 51%.

[0107] The etched rolled copper foil was then coated with a conductive adhesive layer of 15 μm thick, which was made of a phosphorus-containing epoxy resin and 20 wt% Ag-coated Cu powder added. The coating method used was lip coating. Through the above steps, the electromagnetic wave shielding film according to Example 1 was produced.

[0108] (Example 2) and (Example 3) The electromagnetic wave shielding films of Examples 2 and 3 were produced in the same manner as in Example 1, except that the etching time was adjusted so that the ratio of the number of island-shaped metal layer forming openings (A1) to the total number of openings and the opening rate of the openings were as shown in Table 1. In addition, in the electromagnetic wave shielding film of Example 2, the ratio of the total area of ​​the island-shaped metal layer in one island-shaped metal layer forming opening (A) to the area inside the outline of one island-shaped metal layer forming opening (A) was calculated, and the overall average value was calculated to be 54%. Furthermore, in the electromagnetic wave shielding film of Example 3, the ratio of the total area of ​​the island-shaped metal layer in one island-shaped metal layer forming opening (A) to the area inside the outline of one island-shaped metal layer forming opening (A) was calculated, and the overall average value was calculated to be 41%.

[0109] (Comparative Example 1) An insulating layer made of epoxy resin with a thickness of 5 μm was prepared. Next, a 75 μm opening was formed on one main surface of the insulating layer. 2 A 50 nm silver layer was formed by printing silver paste so that multiple openings with an opening ratio of 0.14% and an opening pitch of 250 μm were formed. The silver paste was prepared by dispersing silver particles with an average particle size of 30 nm in a mixed solvent of 35 parts by mass of ethanol and 65 parts by mass of ion-exchanged water using a polyethyleneimine compound as a dispersant to give a silver concentration of 15 wt %. Next, after printing the silver paste, the insulating layer was immersed in an electroless copper plating solution ("ARG Copper" manufactured by Okuno Pharmaceutical Co., Ltd., pH 12.5) at 55°C for 20 minutes to form an electroless copper plating film (thickness 0.5 μm) on the silver layer. Next, the surface of the electroless copper plating film obtained above was placed on the cathode, phosphorous copper was placed on the anode, and electroplating was carried out at a current density of 2.5 A / dm using an electroplating solution containing copper sulfate. 2For 30 minutes, electroplating was performed at 1000 K for 30 minutes to deposit a copper plating layer with a total thickness of 1 μm on the silver layer. The electroplating solution used was a solution containing 70 g / L of copper sulfate, 200 g / L of sulfuric acid, 50 mg / L of chloride ions, and 5 g / L of Top Lucina SF (a brightener manufactured by Okuno Chemical Industries Co., Ltd.). The copper plating layer was coated with a conductive adhesive layer made of phosphorus-containing epoxy resin with 20% by weight of Ag-coated Cu powder added, to a thickness of 15 μm, using a lip coating method. Through the above steps, an electromagnetic wave shielding film according to Comparative Example 1 was produced.

[0110] (Comparative Example 2) A rolled copper foil made of tough pitch copper (manufactured by JX Nippon Mining & Metals Corporation) with a thickness of 6 μm was etched to reduce the thickness to 2 μm. The etching solution used was 25.0 g / L CuSO4·5H2O, with 8.5 vol% concentrated sulfuric acid (98%) and 4.5 vol% hydrogen peroxide (35%) added. This dissolved the copper oxide (I) in the rolled copper foil, creating openings, and the rolled copper foil was then washed. The washed rolled copper foil was photographed by SEM and the image was analyzed, and no island-shaped metal layer-forming openings (A) where one or more island-shaped metal layers were formed inside the openings were observed. The aperture ratio of the opening was 1.4%.

[0111] The rolled copper foil with the openings was then placed on an insulating layer made of epoxy resin with a thickness of 5 μm. The rolled copper foil was then coated with a conductive adhesive layer of 15 μm thick, which was made of a phosphorus-containing epoxy resin and 20 wt% Ag-coated Cu powder added, using a lip coating method. Through the above steps, an electromagnetic wave shielding film according to Comparative Example 2 was produced.

[0112] (Comparative Example 3) to (Comparative Example 5) Electromagnetic wave shielding films according to Comparative Examples 3 to 5 were produced in the same manner as in Example 1, except that the etching time was adjusted and the proportion of the area of ​​the island-shaped metal layer in the island-shaped metal layer-forming opening (A) was adjusted so that island-shaped metal layer-forming openings (A1) were not formed, and the aperture ratio of the openings was set as shown in Table 1. In Comparative Examples 3 and 4, although island-shaped metal layer forming openings (A) were observed, the maximum ratio of the total area of ​​the island-shaped metal layers in one island-shaped metal layer forming opening (A) to the area inside the outline of one island-shaped metal layer forming opening (A) was less than 10%. In addition, in Comparative Example 5, although island-shaped metal layer formation openings (A) were observed, the minimum value of the ratio of the total area of ​​the island-shaped metal layers in one island-shaped metal layer formation opening (A) to the area inside the outline of one island-shaped metal layer formation opening (A) exceeded 80%.

[0113] [Table 1]

[0114] (Measurement of water vapor permeability) The water vapor permeability of the electromagnetic wave shielding films of each Example and Comparative Example was measured by a differential pressure method (in accordance with JIS K7129). The measurement conditions were a temperature of 80°C, a humidity of 95% RH, and a differential pressure of 1 atm. The results are shown in Table 1.

[0115] (Evaluation of the presence or absence of delamination) The electromagnetic wave shielding films of each example and comparative example were placed on a printed wiring board using a heat press. The printed wiring board was then left in a clean room at 23°C and 63% RH for 7 days, after which it was subjected to the reflow temperature conditions and evaluated for the presence or absence of delamination. The reflow temperature profile was set to a maximum of 265°C, assuming lead-free solder. The presence or absence of delamination was evaluated by passing the printed wiring board with the shielding film attached through IR reflow five times and visually inspecting for the presence or absence of blistering. Here, a "◎" was given for a shielding film that showed no blistering at all, a "◯" for a shielding film that showed only partial blistering, and an "×" for a shielding film that showed significant blistering over the entire surface. The results are shown in Table 1.

[0116] (Evaluation of electromagnetic wave shielding properties) Regarding the electromagnetic wave shielding properties of the electromagnetic wave shielding films of each example and each comparative example, the shielding properties at 1 GHz were evaluated by the KEC method using an electromagnetic wave shielding effectiveness measuring device developed by the KEC Kansai Electronics Industry Development Center, a general incorporated association, and the shielding properties at 10 GHz were measured by the coaxial tube method.

[0117] First, the KEC method will be described. FIG. 3 is a schematic diagram showing the configuration of a system used in the KEC method. The system used in the KEC method comprises an electromagnetic shielding effectiveness measuring device 80, a spectrum analyzer 91, an attenuator 92 that attenuates by 10 dB, an attenuator 93 that attenuates by 3 dB, and a preamplifier 94.

[0118] As shown in Fig. 3, an electromagnetic shielding effectiveness measuring device 80 is provided with two measuring jigs 83 facing each other. An electromagnetic shielding film (indicated by reference numeral 10 in Fig. 3) according to each example and comparative example is sandwiched between these measuring jigs 83. The measuring jig 83 incorporates the dimensional distribution of a TEM cell (Transverse Electromagnetic Cell) and has a structure divided symmetrically in a plane perpendicular to its transmission axis direction. However, to prevent the formation of a short circuit due to the insertion of the electromagnetic shielding film 10, a flat central conductor 84 is arranged with a gap between it and each measuring jig 83.

[0119] In the KEC method, first, a signal output from a spectrum analyzer 91 is input to a transmitting-side measuring jig 83 via an attenuator 92. The signal is then received by a receiving-side measuring jig 83 and passed through the attenuator 93, amplified by a preamplifier 94, and the signal level is then measured by the spectrum analyzer 91. The spectrum analyzer 91 outputs the amount of attenuation when the electromagnetic shielding film 10 is installed in the electromagnetic shielding effectiveness measuring device 80, using the amount of attenuation when the electromagnetic shielding film 10 is not installed in the electromagnetic shielding effectiveness measuring device 80 as a reference.

[0120] Next, the coaxial tube method will be explained. The coaxial tube method conformed to ASTM D4935, and measured the amount of attenuation of 10 GHz electromagnetic waves by the electromagnetic wave shielding films of each example and each comparative example using a coaxial tube type shielding effectiveness measurement system manufactured by Keycom Corporation under conditions of a temperature of 25°C and a relative humidity of 30 to 50%.

[0121] Using this device, the electromagnetic wave shielding films of each example and comparative example were cut into 15 cm squares under conditions of a temperature of 25°C and a relative humidity of 30 to 50%, and the electromagnetic wave shielding properties at 1 GHz or 10 GHz were measured and evaluated. The evaluation criteria were as follows: The results are shown in Table 1.

[0122] (Evaluation of bending resistance) The electromagnetic wave shielding films according to the examples and comparative examples were evaluated by the following methods. Each electromagnetic wave shielding film was attached to both sides of a 50 μm thick polyimide film using a heat press, and the film was cut to a size of 130 mm x 15 mm to prepare a test piece. The bending resistance of each test piece was measured using an MIT bending fatigue tester (manufactured by Yasuda Seiki Seisakusho Co., Ltd., No. 307 MIT type bending fatigue tester) in accordance with the method specified in JIS P8115:2001. The test conditions are as follows: Bending clamp tip R: 0.38 mm Bending angle: ±135° Bending speed: 175 cpm Load: 500gf Detection method: The built-in electrical device detects breaks in the shielding film

[0123] The evaluation criteria for bending resistance were as follows: The results are shown in Table 1. Good: No breakage occurred even after 2500 bending cycles. ×: Breakage occurred after bending less than 2500 times.

[0124] As shown in Table 1, it was found that the electromagnetic wave shielding films according to each example had both volatile component permeability and shielding properties, and further had sufficiently high bending resistance. [Explanation of symbols]

[0125] 1 Shielded printed wiring board 10 Electromagnetic wave shielding film. 20 insulating layer 30 metal layer 31 Island-shaped metal layer 40 Adhesive layer 50 Opening 51 Island metal layer formation opening (A) 51a Island metal layer forming opening (A1) 51b Island metal layer forming opening (A2) 51c Island metal layer forming opening (A3) 55 Opening without island metal layer formation 60 Printed wiring board 61 Base material 62 Printed Circuits 63 Insulating film 80 Electromagnetic wave shielding effectiveness measuring device 83 Measuring Jig 84 Center conductor 91 Spectrum Analyzer 92, 93 Attenuators 94 Preamp

Claims

1. An electromagnetic wave shielding film comprising an adhesive layer, a metal layer made of metal laminated on the adhesive layer, and an insulating layer laminated on the metal layer, The metal layer has a plurality of openings formed therein, the openings include island-shaped metal layer forming openings (A) in which one or more island-shaped metal layers are formed inside the openings, an island-shaped metal layer-forming opening (A) including an island-shaped metal layer-forming opening (A1) in which the total area of ​​the island-shaped metal layer in one island-shaped metal layer-forming opening (A) is 40 to 80% of the area inside the outline of one island-shaped metal layer-forming opening (A).

2. 2. The electromagnetic wave shielding film according to claim 1, wherein the ratio of the number of the island-shaped metal layer forming openings (A) to the total number of the openings is 25% or more.

3. 3. The electromagnetic wave shielding film according to claim 1, wherein the proportion of the number of the island-shaped metal layer forming openings (A1) to the total number of the openings is 5% or more.

4. An electromagnetic wave shielding film comprising an adhesive layer, a metal layer made of metal laminated on the adhesive layer, and an insulating layer laminated on the metal layer, The metal layer has a plurality of openings formed therein, the openings include island-shaped metal layer forming openings (A) in which one or more island-shaped metal layers are formed inside the openings, an electromagnetic wave shielding film, characterized in that the total area of ​​the island-shaped metal layers in the entire metal layer is 1 to 90% of the total area inside the outlines of the openings in the entire metal layer.

5. The electromagnetic wave shielding film according to claim 4, wherein the island-shaped metal layer forming openings (A) include island-shaped metal layer forming openings (A1) in which the total area of ​​the island-shaped metal layer in one island-shaped metal layer forming opening (A) is 40 to 80% of the area inside the outline of one island-shaped metal layer forming opening (A).

6. 6. The electromagnetic wave shielding film according to claim 5, wherein the ratio of the number of the island-shaped metal layer forming openings (A1) to the total number of the openings is 5% or more.

7. 7. The electromagnetic wave shielding film according to claim 4, wherein the proportion of the number of said island-shaped metal layer forming openings (A) in the total number of said openings is 25% or more.

8. An electromagnetic wave shielding film comprising an adhesive layer, a metal layer made of metal laminated on the adhesive layer, and an insulating layer laminated on the metal layer, The metal layer has a plurality of openings formed therein, some of the plurality of openings are island-shaped metal layer forming openings (A) in which one or more island-shaped metal layers are formed inside the openings, an island-shaped metal layer-forming opening (A) including an island-shaped metal layer-forming opening (A1) in which the total area of ​​the island-shaped metal layer in one island-shaped metal layer-forming opening (A) is 40 to 80% of the area inside the outline of one island-shaped metal layer-forming opening (A).

9. 9. The electromagnetic wave shielding film according to claim 1, wherein the metal layer has an aperture ratio of 5 to 90%.

10. The average value of the inner area of ​​the outline of one of the openings is 5 to 2000 μm ２ 10. The electromagnetic wave shielding film according to claim 1, wherein

11. 11. The electromagnetic wave shielding film according to claim 1, wherein the metal layer has a thickness of 0.4 to 1.9 μm.

12. 12. The electromagnetic wave shielding film according to claim 1, wherein the metal layer contains at least one metal selected from the group consisting of copper, silver, gold, aluminum, nickel, tin, palladium, chromium, titanium, and zinc.

13. The water vapor permeability according to JIS K7129 is 40 g / m at a temperature of 80°C, humidity of 95% RH, and a differential pressure of 1 atm. ２ The electromagnetic wave shielding film according to any one of claims 1 to 12, which has a shelf life of 24 hours or more.

14. a printed wiring board having a base member on which a printed circuit is formed and an insulating film provided on the base member so as to cover the printed circuit; A shielded printed wiring board having an electromagnetic wave shielding film provided on the printed wiring board, A shielded printed wiring board, wherein the electromagnetic wave shielding film is the electromagnetic wave shielding film according to any one of claims 1 to 13.

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