Electromagnetic wave shielding film, its manufacturing method, and printed wiring board with electromagnetic wave shielding film

Abstract

To provide an electromagnetic wave shield film which can improve the transmission characteristics of an FPC and satisfy all of the reduction in the thickness of the electromagnetic wave shield film, the improvement of the adhesion, the peeling prevention and the excellent heat resistance.SOLUTION: An electromagnetic wave shield film includes an insulation resin layer, an electromagnetic wave shielding layer and an adhesive layer that are laminated in this order. The electromagnetic wave shielding layer is a metal layer which has thickness between 1 μm and 5 μm and includes copper. Arithmetic mean roughness (Ra) of a surface on the adhesive layer side of the electromagnetic wave shielding layer is between 0.01 μm and 0.25 μm. The adhesive layer includes resin. Weight average molecular weight (Mw) of the resin is between 50,000 and 400,000. An acid value of the resin is between 2 mgKOH / g and 50 mgKOH / g.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] In order to shield electromagnetic noise generated from a flexible printed circuit board (hereinafter also referred to as FPC) or from external electromagnetic noise, it has been proposed to provide an electromagnetic shielding film consisting of an insulating resin layer, a metal thin film layer (hereinafter also referred to as electromagnetic wave shielding layer) adjacent to the insulating resin layer, and a conductive layer consisting of a conductive adhesive layer, on the surface of the flexible printed circuit board via an insulating film (hereinafter also referred to as coverlay film) (see, for example, Patent Document 1).

[0003] When the electromagnetic shielding layer of the electromagnetic shielding film and the transmission line of the FPC are electrically coupled, the electromagnetic shielding film affects the transmission characteristics of the FPC. As the FPC itself becomes thinner, the coverlay film also becomes thinner, shortening the distance between the FPC transmission line and the electromagnetic shielding layer of the electromagnetic shielding film, and the stronger the electrical coupling, the greater the impact that the electromagnetic shielding film has on the transmission characteristics of the FPC. In recent years, the electrical signals used in FPCs have been shifting to higher frequencies, requiring improvements in the transmission characteristics of the FPC itself, which in turn requires designs that improve the transmission characteristics of the electromagnetic wave shielding film as well. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-86120 A Summary of the Invention [Problem to be solved by the invention]

[0005] In order to improve the transmission characteristics of FPCs, it is believed to be effective to reduce transmission loss in the FPC by increasing the thickness of the electromagnetic wave shielding layer in the electromagnetic wave shielding film or by smoothing the surface of the electromagnetic wave shielding layer on the FPC side. However, thickening the electromagnetic shielding layer is an obstacle to making the FPC with electromagnetic shielding film thinner. Furthermore, thickening the electromagnetic shielding layer reduces the flexibility of the electromagnetic shielding film, which reduces its ability to conform to the steps of the FPC and makes it difficult to make electrical connections from small diameters in the coverlay film. Furthermore, smoothing the electromagnetic shielding layer reduces the adhesion between the electromagnetic shielding layer and the adhesive layer. Reduced adhesion between the electromagnetic shielding layer and the adhesive layer can lead to peeling of the electromagnetic shielding film and reduced heat resistance.

[0006] Therefore, the present invention aims to provide an electromagnetic wave shielding film that can improve the transmission characteristics of an FPC, prevents the electromagnetic wave shielding film from becoming thicker and the associated decrease in small diameter connectivity, and further prevents a decrease in adhesion between the electromagnetic wave shielding layer and the adhesive layer in the electromagnetic wave shielding film, thereby preventing peeling of the electromagnetic wave shielding film and providing an electromagnetic wave shielding film with excellent heat resistance. In other words, the present invention aims to provide an electromagnetic wave shielding film that can improve the transmission characteristics of an FPC and also satisfies all of the requirements for thinner electromagnetic wave shielding film, improved adhesion, prevention of peeling, and good heat resistance. [Means for solving the problem]

[0007] As a result of extensive research into solving the above-mentioned problems, the inventors discovered that the above-mentioned problems can be solved by making the electromagnetic wave shielding layer in the electromagnetic wave shielding film an electromagnetic wave shielding layer having a specific film thickness and specific surface roughness, and by making the adhesive layer in the electromagnetic wave shielding film an adhesive layer made of a specific resin, which combine to solve the above-mentioned problems, and thus completed the present invention.

[0008] The present invention encompasses the following aspects. [1] An electromagnetic wave shielding film comprising an insulating resin layer, an electromagnetic wave shielding layer, and an adhesive layer laminated in this order, The electromagnetic wave shielding layer is a metal layer having a thickness of 1 μm or more and 5 μm or less and containing copper, the arithmetic mean roughness (Ra) of the surface of the electromagnetic wave shielding layer on the adhesive layer side is 0.01 μm or more and 0.25 μm or less; An electromagnetic wave shielding film, characterized in that the adhesive layer contains a resin, the weight average molecular weight (Mw) of the resin is 50,000 or more and 400,000 or less, and the acid value of the resin is 2 mgKOH / g or more and 50 mgKOH / g or less. Effect of the Invention

[0009] According to the present invention, it is possible to provide an electromagnetic wave shielding film which can improve the transmission characteristics of an FPC and which satisfies all of the requirements for thinner electromagnetic wave shielding film, improved adhesion, prevention of peeling, and good heat resistance. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view showing one embodiment of an electromagnetic wave shielding film. [Diagram 2] FIG. 2 is a cross-sectional view showing another embodiment of the electromagnetic wave shielding film. [Diagram 3] FIG. 3 is a cross-sectional view showing another embodiment of the electromagnetic wave shielding film. [Figure 4] FIG. 4 is a cross-sectional view showing another embodiment of the electromagnetic wave shielding film. [Diagram 5] FIG. 5 is a cross-sectional view showing steps (A1-1) to (A1-4) of the production process as one embodiment of the production process for the electromagnetic wave shielding film of FIG. [Figure 6] FIG. 6 is a cross-sectional view showing steps (A2-1) and (A2-2) of the production process of the electromagnetic wave shielding film of FIG. 1 according to another embodiment. [Figure 7]FIG. 7 is a cross-sectional view showing a production process of step (A2-3) as another embodiment of the production process for the electromagnetic wave shielding film of FIG. [Figure 8] FIG. 8 is a cross-sectional view showing a production process of step (A2-4) as another embodiment of the production process for the electromagnetic wave shielding film of FIG. [Figure 9] FIG. 9 is a cross-sectional view showing steps (B1-1) and (B1-2) of manufacturing the electromagnetic wave shielding film of FIG. 1 according to another embodiment of the present invention, which uses a manufacturing method different from the steps shown in FIG. 5 and FIG. [Figure 10] FIG. 10 is a cross-sectional view showing another embodiment of the manufacturing process for the electromagnetic wave shielding film of FIG. 1, in which manufacturing steps (C1-1) to (C1-3) are added between steps (A1-1) to (A1-2) shown in FIG. 5. [Figure 11] FIG. 11 is a cross-sectional view illustrating one embodiment of a process for producing the electromagnetic wave shielding film of FIG. 3, in which steps (D1-1) to (D1-3) are performed after step (A1-2). [Figure 12] FIG. 12 is a cross-sectional view showing one embodiment of a printed wiring board with an electromagnetic wave shielding film. [Figure 13] 13A to 13C are cross-sectional views showing a manufacturing process for the printed wiring board with the electromagnetic shielding film of FIG. [Figure 14] FIG. 14 is a schematic diagram seen from above showing the structure of a printed wiring board with an electromagnetic shielding film used for evaluating small-diameter connectivity in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The electromagnetic wave shielding film of the present invention will be described in detail below, but the explanation of the constituent elements described below is one example of one embodiment of the present invention, and the present invention is not limited to these contents. The following definitions of terms apply throughout the specification and claims. The term "isotropically conductive adhesive layer" refers to a conductive adhesive layer that has conductivity in the thickness direction and the surface direction. The term "anisotropically conductive adhesive layer" refers to a conductive adhesive layer that has conductivity in the thickness direction but not in the surface direction. "Conductive adhesive layer with no conductivity in the surface direction" means a layer with a surface resistance of 1×10 4 This means a conductive adhesive layer having a resistance of Ω or more. The average particle diameter of the conductive particles is determined by randomly selecting 30 conductive particles from a microscopic image of the conductive particles, measuring the minimum and maximum diameters of each conductive particle, defining the median of the minimum and maximum diameters as the particle diameter of one particle, and calculating the arithmetic mean of the measured particle diameters of the 30 conductive particles. The thickness of films (e.g. release films, insulating films), coatings (e.g. insulating resin layers, adhesive layers, conductive adhesive layers), electromagnetic wave shielding layers, etc., is measured by observing the cross section of the object under a microscope, measuring the thickness at five points, and averaging the measured value. Surface resistance is measured using two thin-film metal electrodes (length 10 mm, width 5 mm, distance between electrodes 10 mm) formed by evaporating gold onto quartz glass, placing the object to be measured on these electrodes, and pressing a 10 mm x 20 mm area of ​​the object to be measured with a load of 0.049 N from above, and measuring the resistance between the electrodes with a measurement current of 1 mA or less. The arithmetic mean roughness Ra is a value obtained by measuring a roughness curve of a test piece using a laser microscope and determining the roughness curve based on JIS B 0601:2013 (ISO 4287:1997 Amd.1:2009). The weight average molecular weight (Mw) of the resin is measured by gel permeation chromatography (GPC). The acid value of the resin is determined in accordance with the measurement method described in JIS K0070-1992. The mass ratio of N atoms in the adhesive layer is determined using a trace nitrogen analyzer ND-100 (manufactured by Mitsubishi Chemical Corporation) in accordance with JIS-K2609.

[0012] (Electromagnetic wave shielding film) The electromagnetic wave shielding film of the present invention is formed by laminating an insulating resin layer, an electromagnetic wave shielding layer, and an adhesive layer in this order. The electromagnetic wave shielding layer is a metal layer containing copper and has a thickness of 1 μm or more and 5 μm or less. The arithmetic mean roughness (Ra) of the surface of the electromagnetic wave shielding layer on the adhesive layer side is 0.01 μm or more and 0.25 μm or less. The adhesive layer contains a resin, and the weight average molecular weight (Mw) of the resin is 50,000 or more and 400,000 or less, and the acid value of the resin is 2 mgKOH / g or more and 50 mgKOH / g or less.

[0013] FIG. 1 is a cross-sectional view showing a first embodiment of the electromagnetic wave shielding film of the present invention, FIG. 2 is a cross-sectional view showing a second embodiment of the electromagnetic wave shielding film of the present invention, FIG. 3 is a cross-sectional view showing a third embodiment of the electromagnetic wave shielding film of the present invention, and FIG. 4 is a cross-sectional view showing a fourth embodiment of the electromagnetic wave shielding film of the present invention. The electromagnetic wave shielding film 1 in each embodiment has an insulating resin layer 10; an electromagnetic wave shielding layer 20 adjacent to the insulating resin layer 10; an adhesive layer 22 adjacent to the electromagnetic wave shielding layer 20 on the side opposite the insulating resin layer 10; a first release film 30 adjacent to the insulating resin layer 10 on the side opposite the electromagnetic wave shielding layer 20; and a second release film 40 adjacent to the adhesive layer 22 on the side opposite the electromagnetic wave shielding layer 20.

[0014] The electromagnetic wave shielding film 1 of the first embodiment is an example in which the adhesive layer 22 is an anisotropic conductive adhesive layer 24. The electromagnetic wave shielding film 1 of the second embodiment is an example in which the adhesive layer 22 is an isotropically conductive adhesive layer . The electromagnetic wave shielding film 1 of the third embodiment is an example in which the electromagnetic wave shielding film 1 of the first embodiment further includes a silane coupling agent layer 80 between the electromagnetic wave shielding layer and the adhesive layer. The electromagnetic wave shielding film 1 of the fourth embodiment is an example in which a silane coupling agent layer 80 is further included between the electromagnetic wave shielding layer and the adhesive layer in the electromagnetic wave shielding film 1 of the second embodiment.

[0015] <Insulating resin layer> The insulating resin layer 10 becomes a protective layer for the electromagnetic wave shielding layer 20 after the electromagnetic wave shielding film 1 is attached to the surface of an insulating film provided on the surface of a flexible printed wiring board and the first release film 30 is peeled off.

[0016] Examples of the insulating resin layer 10 include a coating film formed by applying a composition containing a thermosetting resin and a curing agent, semi-curing or curing the composition, drying the coating liquid containing a thermosetting resin, a curing agent, and a solvent, semi-curing or curing the coating liquid, coating the coating liquid containing a thermoplastic resin and a solvent, drying the coating liquid, and a layer made of a film obtained by melt molding a composition containing a thermoplastic resin. The insulating resin layer 10 is preferably a coating film formed by applying a coating liquid containing a resin material (a combination of a thermosetting resin and a curing agent, or a thermoplastic resin) and a solvent, drying the coating liquid, and semi-curing or curing the coating liquid as necessary, in order to further improve the adhesion between the insulating resin layer 10 and the electromagnetic wave shielding layer 20.

[0017] Examples of the thermosetting resin include polyester, amide resin, epoxy resin, phenol resin, amino resin, alkyd resin, urethane resin, synthetic rubber, ultraviolet-curable acrylate resin, etc. As the thermosetting resin, epoxy resin is preferable because it has excellent heat resistance and can be cured at the temperature when the electromagnetic wave shielding film is mounted on the FPC. The curing agent may be any known curing agent suitable for the type of thermosetting resin. Examples of the thermoplastic resin include aromatic polyether ketone, polyimide, polyamide imide, polyether imide, polyamide, polysulfone, polyether sulfone, polyphenylene sulfone, polyphenylene sulfide, polyphenylene sulfide sulfone, and polyphenylene sulfide ketone.

[0018] The insulating resin layer 10 may contain either or both of a colorant (pigment, dye, etc.) and a filler in order to conceal the printed circuit of the printed wiring board with the electromagnetic shielding film or to impart design features to the printed wiring board with the electromagnetic shielding film. As either or both of the colorant and the filler, from the viewpoints of weather resistance, heat resistance, and hiding power, a pigment or a filler is preferred, and from the viewpoints of hiding power and design of the printed circuit, a black pigment or a combination of a black pigment with another pigment or a filler is more preferred. The insulating resin layer 10 may contain a flame retardant. The insulating resin layer 10 may contain other components as necessary within the range that does not impair the effects of the present invention.

[0019] The surface resistance of the insulating resin layer 10 is 1×10 6 From a practical standpoint, the surface resistance of the insulating resin layer 10 is preferably 1×10 19 Ω or less is preferable. The thickness of the insulating resin layer 10 is preferably 0.1 μm to 30 μm, more preferably 0.5 μm to 20 μm, and even more preferably 3 μm to 15 μm. If the thickness of the insulating resin layer 10 is equal to or greater than the lower limit of the above range, the insulating resin layer 10 can fully function as a protective layer. If the thickness of the insulating resin layer 10 is equal to or less than the upper limit of the above range, the electromagnetic wave shielding film 1 can be made thin.

[0020] The arithmetic mean roughness (Ra) of the surface of the insulating resin layer 10 on the electromagnetic wave shielding layer side is preferably 0.01 μm or more and 0.3 μm or less. This is because, when the electromagnetic wave shielding layer 20 is formed on the insulating resin layer 10, it is possible to obtain an electromagnetic wave shielding layer 20 having a smooth surface by forming the electromagnetic wave shielding layer 20 on the insulating resin layer 10 having a smooth surface, although this depends on the formation method.

[0021] <Electromagnetic wave shielding layer> The electromagnetic wave shielding layer 20 is a layer made of a thin metal film containing copper. Since the electromagnetic wave shielding layer 20 is formed so as to extend in the planar direction, it has conductivity in the planar direction and functions as an electromagnetic wave shielding layer or the like.

[0022] Examples of the electromagnetic wave shielding layer 20 include a deposition film formed by physical vapor deposition (vacuum deposition, sputtering, ion beam deposition, electron beam deposition, etc.) or chemical vapor deposition, a plating film formed by plating, a metal foil, etc. Among them, a vacuum deposition film or sputtering film formed by a vacuum film formation method (vacuum deposition method, sputtering method, etc.), or a plating film formed by an electrolytic plating method is preferred because of its excellent conductivity in the surface direction. A deposition film formed by a vacuum deposition method is more preferred because it can be easily formed. In addition, a deposition film formed by a vacuum deposition method also has excellent adhesion to an insulating resin layer. Furthermore, the electromagnetic wave shielding layer 20 is preferably a rolled copper foil, since it is possible to obtain an electromagnetic wave shielding layer having a desired surface smoothness and thickness.

[0023] The metal constituting the electromagnetic wave shielding layer 20 is not limited to copper, and may also contain other metals such as aluminum, silver, gold, conductive ceramics, and the like.

[0024] The thickness of the electromagnetic wave shielding layer 20 is 1 μm or more and 5 μm or less, preferably 1 μm or more and 3 μm or less, and more preferably 1.5 μm or more and 3 μm or less. If the thickness of the electromagnetic wave shielding layer 20 is 1 μm or more, the transmission characteristics of the FPC can be improved. If the thickness of the electromagnetic wave shielding layer 20 is 1.5 μm or more, the transmission characteristics of the FPC become even better. If the thickness of the electromagnetic wave shielding layer 20 is 5 μm or less, the electromagnetic wave shielding film 1 can be made thinner. If the thickness of the electromagnetic wave shielding layer 20 is 3 μm or less, the productivity and flexibility of the electromagnetic wave shielding film 1 become good.

[0025] The arithmetic mean roughness (Ra) of the surface on the adhesive layer side of the electromagnetic wave shielding layer 20 is 0.01 μm or more and 0.25 μm or less. If the electromagnetic wave shielding layer 20 has an arithmetic mean roughness (Ra) in the range of 0.01 μm or more and 0.25 μm or less, it is possible to improve the transmission characteristics of the FPC while ensuring good adhesion with the adhesive layer.

[0026] The surface resistance of the electromagnetic wave shielding layer 20 is preferably 0.001Ω or more and 1Ω or less, and more preferably 0.001Ω or more and 0.1Ω or less. If the surface resistance of the electromagnetic wave shielding layer 20 is equal to or more than the lower limit of the above range, the electromagnetic wave shielding layer 20 can be made sufficiently thin. If the surface resistance of the electromagnetic wave shielding layer 20 is equal to or less than the upper limit of the above range, the electromagnetic wave shielding layer 20 can function sufficiently as an electromagnetic wave shielding layer.

[0027] <Adhesive layer> The adhesive layer 22 is a layer for attaching the electromagnetic wave shielding film 1 to a printed wiring board with an insulating film. The adhesive layer 22 may be a simple adhesive layer having no electrical conductivity, or may be a conductive adhesive layer having electrical conductivity for electrically connecting the electromagnetic wave shielding film 1 and a printed wiring board. The adhesive layer 22 is preferably a conductive adhesive layer from the viewpoint of allowing the electromagnetic wave shielding layer 20 to function sufficiently as an electromagnetic wave shielding layer.

[0028] The adhesive layer 22 is a layer made of an adhesive containing a resin. The resin contained in the adhesive layer 22 has a weight average molecular weight (Mw) of 50,000 or more and 400,000 or less, and an acid value of 2 mgKOH / g or more and 50 mgKOH / g or less. The adhesive layer 22 containing a resin with such physical properties can ensure good adhesion between the electromagnetic wave shielding layer 20 and the adhesive layer 22. The weight average molecular weight (Mw) of the resin is 50,000 or more and 400,000 or less, and more preferably 65,000 or more and 250,000 or less. If the weight average molecular weight (Mw) of the resin is equal to or more than the lower limit of the above range, resin flow during thermocompression bonding can be suppressed. If the weight average molecular weight (Mw) of the resin is equal to or less than the upper limit of the above range, the resin softens in a short time during thermocompression bonding, and the thermocompression bonding time can be shortened. Here, the weight average molecular weight (Mw) of the resin is a value obtained by converting the molecular weight measured by gel permeation chromatography (GPC) into polystyrene equivalent.

[0029] The acid value of the resin is preferably 1 mgKOH / g or more and 50 mgKOH / g or less, more preferably 10 mgKOH / g or more and 50 mgKOH / g or less. If the acid value of the resin is 1 mgKOH / g or more, the adhesion between the adhesive layer and the electromagnetic wave shielding layer is improved. If the acid value of the resin is 10 mgKOH / g or more, the reaction can be sufficiently promoted during thermocompression bonding, and disconnection of the electrical connection between the electromagnetic wave shielding layer and the FPC can be prevented when the pressure is released. If the acid value of the resin is equal to or less than the upper limit of the above range, the storage period of the adhesive layer can be extended. The acid value is the amount of potassium hydroxide required to neutralize the acid contained in 1 g of a resin sample in mg. The measurement is performed under the following conditions in accordance with the measurement method described in JIS K0070-1992.

[0030] [Method for measuring the acid value of resin] (1) Accurately weigh the ground resin sample (0.5 g) to (2.0 g), and define the weight of the resin component as Wg. (2) Place the sample in a beaker (300 mL) and add a mixture of toluene / ethanol (volume ratio 4 / 1) (150 mL) to dissolve. (3) Titrate using a potentiometric titrator with a 0.1 mol / L ethanol solution of KOH. (4) The amount of KOH solution used at this time is designated as S (mL), a blank is measured at the same time, and the amount of KOH solution used at this time is designated as B (mL), and the amount is calculated using the following formula (i), where f is the KOH factor. Acid number (mgKOH / g) = [(SB) × f × 5.61] / W Equation (i)

[0031] The resin contained in the adhesive layer 22 is not particularly limited in type as long as it satisfies the above-mentioned conditions of weight average molecular weight (Mw) and acid value, and can be appropriately selected depending on the purpose. The types of adhesives include, for example, solvent-vaporizing adhesives, thermosetting adhesives, and mixtures thereof. An example of a solvent-evaporating adhesive is one that contains a thermoplastic resin and a solvent. The thermosetting adhesive may include an adhesive containing a thermosetting resin and a curing agent.

[0032] Among them, from the viewpoint of improving the adhesion between the electromagnetic wave shielding layer 20 and the adhesive layer 22, it is preferable that the resin contained in the adhesive layer 22 is a resin having at least one of an amine structure, an amide structure, a urea structure, a urethane structure, and an imide structure. For example, examples of the thermosetting resin include amino resin, imide resin, and urethane resin. For example, examples of the thermoplastic resin include polyurea and polyamide. The resin contained in the adhesive layer may be a thermoplastic resin such as a styrene resin or a thermosetting resin such as an epoxy resin. Furthermore, a rubber component such as a nitrile rubber may be used.

[0033] In order to improve the adhesion between the electromagnetic wave shielding layer 20 and the adhesive layer 22, it is preferable that the adhesive layer 22 contains a component having a structure containing an N atom, such as an amino group or an amide group. Therefore, the ratio of the mass of N atoms in the adhesive layer 22 (the mass ratio of N atoms in the adhesive layer) is preferably 0.5% or more and 10% or less, and more preferably 0.5% or more and 5% or less. If the mass ratio of N atoms in the adhesive layer is 0.5 or more, the adhesion between the electromagnetic wave shielding layer and the adhesive layer is improved. If the mass ratio of N atoms in the adhesive layer is 10 or less, the ratio of rigid molecular skeletons containing N atoms in the resin can be suppressed, and the flexibility of the electromagnetic wave shield is improved. If the mass ratio of N atoms in the adhesive layer is 5 or less, the dielectric properties of the adhesive layer are improved, and the transmission properties are further improved. The proportion of the mass of N atoms in the adhesive layer 22 is the proportion of the mass of N atoms to the total mass of the adhesive that forms the adhesive layer 22, and can be determined, for example, by the following method.

[0034] [Method for measuring the mass ratio of N atoms in adhesive layer] The mass ratio of N atoms in the adhesive layer is measured in accordance with JIS-K2609.

[0035] In addition, from the viewpoint of improving the adhesion between the electromagnetic wave shielding layer 20 and the adhesive layer 22, it is preferable that the adhesive layer 22 contains an adhesion improver having at least one of a melamine structure, a triazine structure, a phosphoric acid structure, an alkoxysilane structure, and a mercapto group. For example, examples of the adhesion improver include a silane coupling agent having a melamine skeleton, a silane coupling agent having a mercapto group, and an imidazole having a triazine skeleton.

[0036] The thickness of the adhesive layer 22 is preferably 2 μm or more and 25 μm or less, and more preferably 2 μm or more and 10 μm or less. When the thickness of the adhesive layer 22 is equal to or more than the lower limit of the above range, the adhesiveness can be ensured. When the thickness of the adhesive layer 22 is equal to or less than the upper limit of the above range, the electromagnetic wave shielding film can be made thin.

[0037] The adhesive may optionally contain a flame retardant. The adhesive may contain cellulose resin and microfibrils (eg, glass fibers) to increase the strength of the adhesive layer and improve punching properties. The adhesive may contain other components as necessary within the range that does not impair the effects of the present invention.

[0038] <<Conductive adhesive layer>> The case where the adhesive layer 22 is a conductive adhesive layer will be described below. The conductive adhesive layer has electrical conductivity at least in the thickness direction and has adhesiveness. The conductive adhesive layer may be an anisotropic conductive adhesive layer 24 that has conductivity in the thickness direction but not in the surface direction, or an isotropic conductive adhesive layer 26 that has conductivity in the thickness direction and the surface direction. The conductive adhesive layer is preferably anisotropic conductive adhesive layer 24 in that it has good transmission characteristics due to its lack of conductivity in the surface direction and improves the flexibility of the electromagnetic wave shielding film 1. The conductive adhesive layer is preferably isotropic conductive adhesive layer 26 in that it can function sufficiently as an electromagnetic wave shielding layer.

[0039] The conductive adhesive layer contains conductive particles in a layer of adhesive containing the above-mentioned resin. The anisotropic conductive adhesive layer 24 includes, for example, an adhesive 24a containing the above-mentioned resin and conductive particles 24b. The isotropically conductive adhesive layer 26 includes, for example, an adhesive 26a containing the above-mentioned resin and conductive particles 26b.

[0040] Examples of conductive particles include metal (silver, platinum, gold, copper, nickel, palladium, aluminum, solder, etc.) particles, graphite powder, baked carbon particles, plated baked carbon particles, metal-coated core-shell type resin particles, etc. Metal particles are preferred in terms of high conductivity, and copper particles are more preferred in terms of low cost.

[0041] The average particle diameter of the conductive particles 24b in the anisotropic conductive adhesive layer 24 is preferably 2 μm or more and 26 μm or less, more preferably 4 μm or more and 16 μm or less. If the average particle diameter of the conductive particles 24b is equal to or more than the lower limit of the above range, the stability of the electrical connection is improved, and the conductive particles 24b are less likely to impair the fluidity of the resin of the anisotropic conductive adhesive layer 24, so that the conformability of the anisotropic conductive adhesive layer 24 to the shape of the through-holes of the insulating film can be ensured. If the average particle diameter of the conductive particles 24b is equal to or less than the upper limit of the above range, the conductive particles 24b do not hinder the contact between the resin of the anisotropic conductive adhesive layer 24 and the surface of the adherend, and sufficient adhesion can be ensured.

[0042] The average particle diameter of the conductive particles 26b in the isotropic conductive adhesive layer 26 is preferably 0.1 μm or more and 10 μm or less, and more preferably 0.2 μm or more and 1 μm or less. If the average particle diameter of the conductive particles 26b is equal to or more than the lower limit of the above range, the contact frequency of the conductive particles 26b increases, and the conductivity in the three-dimensional direction can be stably improved. If the average particle diameter of the conductive particles 26b is equal to or less than the upper limit of the above range, the conductive particles 26b do not hinder the contact between the resin of the isotropic conductive adhesive layer 26 and the surface of the adherend, and sufficient adhesion can be ensured.

[0043] The proportion of the conductive particles 24b in the anisotropic conductive adhesive layer 24 is preferably 1% by volume or more and 30% by volume or less, and more preferably 2% by volume or more and 10% by volume or less, of 100% by volume of the anisotropic conductive adhesive layer 24. If the proportion of the conductive particles 24b is equal to or more than the lower limit of the above range, the conductivity of the anisotropic conductive adhesive layer 24 is good. If the proportion of the conductive particles 24b is equal to or less than the upper limit of the above range, the adhesion and fluidity (ability to conform to the shape of the through holes in the insulating film) of the anisotropic conductive adhesive layer 24 are good. In addition, the flexibility of the electromagnetic wave shielding film 1 is improved.

[0044] The proportion of the conductive particles 26b in the isotropic conductive adhesive layer 26 is preferably 50% by volume or more and 80% by volume or less, and more preferably 60% by volume or more and 70% by volume or less, of 100% by volume of the isotropic conductive adhesive layer 26. If the proportion of the conductive particles 26b is equal to or more than the lower limit of the above range, the conductivity of the isotropic conductive adhesive layer 26 is good. If the proportion of the conductive particles 26b is equal to or less than the upper limit of the above range, the adhesion and fluidity (ability to conform to the shape of the through holes in the insulating film) of the isotropic conductive adhesive layer 26 are good. In addition, the flexibility of the electromagnetic wave shielding film 1 is improved.

[0045] The surface resistance of the anisotropic conductive adhesive layer 24 is 1×10 4 Ω or more 1×10 16 Ω or less is preferable, 1×10 6 Ω or more 1×10 14 Ω or less is more preferable. If the surface resistance of the anisotropic conductive adhesive layer 24 is equal to or greater than the lower limit of the above range, the content of the conductive particles 24b can be kept low. If the surface resistance of the anisotropic conductive adhesive layer 24 is equal to or less than the upper limit of the above range, there is no practical problem with anisotropy.

[0046] The surface resistance of the isotropic conductive adhesive layer 26 is preferably 0.05Ω or more and 2.0Ω or less, and more preferably 0.1Ω or more and 1.0Ω or less. If the surface resistance of the isotropic conductive adhesive layer 26 is equal to or more than the lower limit of the above range, the content of the conductive particles 26b is kept low, the viscosity of the conductive adhesive does not become too high, and the applicability is further improved. In addition, the fluidity of the isotropic conductive adhesive layer 26 (the ability to conform to the shape of the through holes of the insulating film) can be further ensured. If the surface resistance of the isotropic conductive adhesive layer 26 is equal to or less than the upper limit of the above range, the entire surface of the isotropic conductive adhesive layer 26 has uniform conductivity.

[0047] The thickness of the anisotropic conductive adhesive layer 24 is preferably 2 μm or more and 25 μm or less, and more preferably 5 μm or more and 20 μm or less. If the thickness of the anisotropic conductive adhesive layer 24 is equal to or more than the lower limit of the above range, the fluidity (ability to conform to the shape of the through-holes of the insulating film) of the anisotropic conductive adhesive layer 24 can be ensured, and the through-holes of the insulating film can be sufficiently filled with the conductive adhesive. In addition, the distance between the electromagnetic wave shielding layer 20 and the printed circuit can be increased, improving the transmission characteristics. If the thickness of the anisotropic conductive adhesive layer 24 is equal to or less than the upper limit of the above range, the electromagnetic wave shielding film 1 can be made thinner. In addition, the flexibility of the electromagnetic wave shielding film 1 is improved.

[0048] The thickness of the isotropic conductive adhesive layer 26 is preferably 2 μm or more and 20 μm or less, more preferably 3 μm or more and 10 μm or less. If the thickness of the isotropic conductive adhesive layer 26 is equal to or more than the lower limit of the above range, the adhesion is improved. In addition, the fluidity (ability to conform to the shape of the through-holes of the insulating film) of the isotropic conductive adhesive layer 26 can be ensured, the through-holes of the insulating film can be sufficiently filled with the conductive adhesive, and the folding resistance is also ensured, so that the isotropic conductive adhesive layer 26 will not break even if repeatedly folded. If the thickness of the isotropic conductive adhesive layer 26 is equal to or less than the upper limit of the above range, the electromagnetic wave shielding film 1 can be made thinner. In addition, the flexibility of the electromagnetic wave shielding film 1 is improved. In addition, the transmission characteristics are improved by making the film thickness of the isotropic conductive adhesive layer 26, which has a higher surface resistance than the electromagnetic wave shielding layer 20, thinner.

[0049] When the adhesive layer 22 is a conductive adhesive layer, the "mass ratio of N atoms in the adhesive layer" refers to the proportion of the mass of N atoms to the total mass of the adhesive excluding the conductive particles from the conductive adhesive layer. The mass ratio of N atoms in the conductive adhesive layer can be determined, for example, by the following method.

[0050] [Method for measuring the mass ratio of N atoms in adhesive layer] The mass ratio of N atoms in the adhesive layer is measured in accordance with JIS-K2609.

[0051] <First release film> The first release film 30 serves as a protective film for the insulating resin layer 10 and improves the handleability of the electromagnetic wave shielding film 1. The first release film 30 is peeled off from the insulating resin layer 10 after the electromagnetic wave shielding film 1 is attached to the printed wiring board with an insulating film.

[0052] The first release film 30 has, for example, a base layer 32 and an adhesive layer or release agent layer 34 provided on the surface of the base layer 32 facing the insulating resin layer 10. In this specification, the adhesive layer or release agent layer 34 is also referred to as an adhesive layer / release agent layer 34. The first release film 30 may be one in which an adhesive layer / release agent layer 34 is provided directly on the surface of the base material layer 32; or it may be one in which an adhesive layer / release agent layer 34 is provided on the surface of the insulating resin layer 10, and then the base material layer 32 is attached to the surface of the adhesive layer / release agent layer 34, thereby providing an adhesive layer / release agent layer 34 on the surface of the base material layer 32.

[0053] Examples of the resin material for the base layer 32 include polyethylene terephthalate (hereinafter also referred to as PET), polyethylene naphthalate, polyethylene isophthalate, polybutylene terephthalate, polyolefin, polyacetate, polycarbonate, polyphenylene sulfide, polyamide, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, synthetic rubber, liquid crystal polymer, etc. As the resin material, PET is preferable from the viewpoints of heat resistance (dimensional stability) during production of the electromagnetic wave shielding film 1 and cost. The substrate layer 32 may include a colorant or a filler.

[0054] The thickness of the base layer 32 is preferably 5 μm or more and 500 μm or less, more preferably 10 μm or more and 150 μm or less, and even more preferably 25 μm or more and 100 μm or less. When the thickness of the base layer 32 is equal to or more than the lower limit of the above range, the electromagnetic wave shielding film 1 has good handleability. When the thickness of the base layer 32 is equal to or less than the upper limit of the above range, heat is easily transferred to the adhesive layer 22 when the electromagnetic wave shielding film 1 is heat-pressed onto a printed wiring board with an insulating film.

[0055] An adhesive layer 34 or a release agent layer 34 is disposed between the base layer and the insulating resin layer. Because the first release film 30 has an adhesive layer or release agent layer 34, the first release film 30 is prevented from peeling off from the insulating resin layer 10 when the second release film 40 is peeled off from the adhesive layer 22 or when the electromagnetic wave shielding film 1 is attached to a printed wiring board or the like by heat pressing, and the first release film 30 can fully fulfill its role as a protective film. As the adhesive, a known adhesive may be used. The release agent layer 34 is formed by performing a release treatment with a release agent on the surface of the base layer 32. Since the first release film 30 has the release agent layer 34, when the first release film 30 is peeled off from the insulating resin layer 10, the first release film 30 is easily peeled off and the insulating resin layer 10 is less likely to break. As the release agent, a known release agent may be used.

[0056] The thickness of the adhesive layer 34 is preferably 0.05 μm or more and 50.0 μm or less, and more preferably 0.1 μm or more and 25.0 μm or less. If the thickness of the adhesive layer 34 is within the above range, the surface of the first release film 30 has appropriate adhesiveness. The thickness of the release agent layer 34 is preferably 0.005 μm or more and 2.0 μm or less, and more preferably 0.01 μm or more and 1.5 μm or less. If the thickness of the release agent layer 34 is within the above range, the first release film can be peeled off even more easily.

[0057] <Second release film> The second release film 40 protects the adhesive layer 22 and improves the handleability of the electromagnetic wave shielding film 1. The second release film 40 is peeled off from the adhesive layer 22 before the electromagnetic wave shielding film 1 is attached to a printed wiring board with an insulating film.

[0058] The second release film 40 has, for example, a base layer 42 and a release agent layer or adhesive layer 44 provided on the surface of the base layer 42 on the conductive adhesive layer side. In this specification, the release agent layer or the adhesive layer 44 is also referred to as a release agent layer / adhesive layer 44.

[0059] The resin material of the base material layer 42 may be similar to the resin material of the base material layer 32 of the first release film 30 . The substrate layer 42 may include a colorant or a filler. The thickness of the base layer 42 is preferably 5 μm or more and 500 μm or less, more preferably 10 μm or more and 150 μm or less, and even more preferably 25 μm or more and 100 μm or less.

[0060] Between the base layer 42 and the adhesive layer 22, a release agent layer 44 or a pressure-sensitive adhesive layer 44 is disposed. The release agent layer 44 is formed by performing a release treatment with a release agent on the surface of the base layer 42. Since the second release film 40 has the release agent layer 44, when the second release film 40 is peeled off from the adhesive layer 22, the second release film 40 is easily peeled off and the adhesive layer 22 is less likely to break. As the release agent, a known release agent may be used.

[0061] The thickness of the release agent layer 44 is preferably 0.05 μm or more and 2.0 μm or less, and more preferably 0.1 μm or more and 1.5 μm or less. If the thickness of the release agent layer 44 is within the above range, the second release film 40 can be peeled off even more easily.

[0062] As the adhesive layer 44, the same adhesive layer as that described in the section <First release film> above can be used.

[0063] <Silane coupling agent layer> A further preferred embodiment of the electromagnetic wave shielding film according to the present invention is an electromagnetic wave shielding film having a silane coupling agent layer 80 between the electromagnetic wave shielding layer 20 and the adhesive layer 22, as shown in FIG. 3 or FIG. By providing the silane coupling agent layer, the adhesion between the electromagnetic wave shielding layer 20 and the adhesive layer 22 can be improved. To form the silane coupling agent layer on the electromagnetic wave shielding layer 20, a conventionally known method can be used. For example, the silane coupling agent can be dissolved in water or an organic solvent, and the liquid can be applied to the surface of the electromagnetic wave shielding layer 20 and then dried to form the silane coupling agent layer. Examples of the silane coupling agent include vinyltrimethoxysilane, vinyltriethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, tris-(trimethoxysilylpropyl)isocyanurate, 3-ureidopropyltrialkoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis(triethoxysilylpropyl)tetrasulfide, and 3-isocyanatepropyltriethoxysilane.

[0064] <Composition of electromagnetic wave shielding film> In the present invention, the electromagnetic wave shielding film has at least an insulating resin layer, an electromagnetic wave shielding layer, and an adhesive layer. The electromagnetic wave shielding film may or may not include a first release film and a second release film. Therefore, in this specification, the term "electromagnetic wave shielding film" may refer to the insulating resin layer, the electromagnetic wave shielding layer, and the adhesive layer, as well as the first release film and / or the second release film, and may also refer to the electromagnetic wave shielding film without including these release films.

[0065] <Thickness of electromagnetic shielding film> The thickness of the electromagnetic wave shielding film 1 (excluding the release film) is preferably 5 μm to 45 μm, more preferably 5 μm to 30 μm. If the thickness of the electromagnetic wave shielding film 1 (excluding the release film) is equal to or greater than the lower limit of the above range, the film is less likely to break when the first release film 30 is peeled off. If the thickness of the electromagnetic wave shielding film 1 (excluding the release film) is equal to or less than the upper limit of the above range, the printed wiring board with the electromagnetic wave shielding film can be made thinner.

[0066] (Manufacturing method of electromagnetic wave shielding film) An example of a first embodiment of the method for producing an electromagnetic shielding film of the present invention is a production method by the following method (A1). Note that in the following method (A1), an electromagnetic shielding film in which the adhesive layer is an anisotropic conductive adhesive layer 24 shown in Fig. 1 is used as an example of the electromagnetic shielding film, but the adhesive layer is not limited to this. The production method described below is similarly applicable whether the adhesive layer is an isotropic conductive adhesive layer 27 or an adhesive layer 22 that does not contain conductive particles. Specifically, the method (A1) is a method comprising the following steps (A1-1) to (A1-4). Hereinafter, the method (A1) will be described with reference to FIG. Step (A1-1): A step of forming an insulating resin layer 10 on one surface of a first release film 30. Step (A1-2): A step of forming an electromagnetic wave shielding layer 20 on the surface of the insulating resin layer 10 opposite to the first release film 30. Step (A1-3): A step of forming an anisotropic conductive adhesive layer 24 on the surface of the electromagnetic wave shielding layer 20 opposite to the insulating resin layer 10. Step (A1-4): A step of laminating a second release film 40 on the surface of the anisotropic conductive adhesive layer 24 opposite to the electromagnetic wave shielding layer 20. Each step of the method (A1) will be described in detail below.

[0067] The method for forming the insulating resin layer 10 in the step (A1-1) may be, for example, the following method. A method in which a coating material containing a thermosetting resin and a curing agent is applied to the surface of the first release film 30 on the adhesive layer / release agent layer 34 side, and then semi-cured or cured. A method in which a paint containing a thermoplastic resin is applied to the surface of the first release film 30 on the pressure-sensitive adhesive layer / release agent layer 34 side, and then dried. A method in which a film formed by extrusion molding of a composition containing a thermoplastic resin is directly laminated on the surface of the first release film 30 on the pressure-sensitive adhesive layer / release agent layer 34 side. Among the above methods, from the viewpoint of heat resistance during soldering, etc., a method in which a paint containing a thermosetting resin and a curing agent is applied to the surface of the first release film 30 on the adhesive layer / release agent layer 34 side, and then semi-cured or cured is preferred. Examples of a method for applying the coating material include methods using various coaters such as a die coater, a gravure coater, a roll coater, a curtain flow coater, a spin coater, a bar coater, a reverse coater, a kiss coater, a fountain coater, a rod coater, an air doctor coater, a knife coater, a blade coater, a cast coater, and a screen coater. When semi-curing or curing the thermosetting resin, it is sufficient to heat it using a heater such as a heater or an infrared lamp.

[0068] In the step (A1-2), the electromagnetic wave shielding layer 20 is formed on the surface of the insulating resin layer 10 opposite to the first release film 30 side. The electromagnetic wave shielding layer 20 can be formed by a vacuum film forming method (vacuum deposition, sputtering), an electrolytic plating method, or a method of attaching a metal foil (copper foil). When the thickness of the electromagnetic wave shielding layer 20 is less than 3 um, the method of forming a vapor deposition film by vacuum deposition or the method of forming a plated film by electrolytic plating is preferred from the viewpoint of forming an electromagnetic wave shielding layer 20 having a desired thickness and surface shape. The method of forming a vapor deposition film by vacuum deposition is more preferred from the viewpoint of forming an electromagnetic wave shielding layer 20 that has high gas permeability, can easily release gas generated inside under high temperature conditions to the outside, and can easily form the electromagnetic wave shielding layer 20 by a dry process. When the thickness of the electromagnetic wave shielding layer 20 is 3 um or more, a method of performing a lamination process by applying pressure and / or heat so that the insulating resin layer 10 and the metal foil (copper foil) come into contact is preferable, since deterioration of the insulating resin layer 10 due to the thermal history of the vacuum deposition does not occur and the electromagnetic wave shielding layer 20 having the desired thickness can be easily formed. Here, the pressure in the pressurizing treatment is preferably from 0.1 kPa to 100 kPa, more preferably from 0.1 kPa to 20 kPa, and even more preferably from 1 kPa to 10 kPa. The heating temperature may be -30°C to +50°C above the glass transition temperature of the semi-cured or cured insulating resin layer, and preferably 50°C to 150°C.

[0069] In the step (A1-3), a conductive adhesive paint containing adhesive 24a, conductive particles 24b, and a solvent is applied to the surface of electromagnetic wave shielding layer 20 opposite insulating resin layer 10. The solvent is evaporated from the applied conductive adhesive paint to form an anisotropic conductive adhesive layer 24 . Examples of solvents contained in the conductive adhesive paint include esters (butyl acetate, ethyl acetate, methyl acetate, isopropyl acetate, ethylene glycol monoacetate, etc.), ketones (methyl ethyl ketone, methyl isobutyl ketone, acetone, amyl ethyl ketone, cyclohexanone, etc.), alcohols (methanol, ethanol, isopropanol, butanol, propylene glycol monomethyl ether, propylene glycol, etc.), toluene, etc. The method for applying the conductive adhesive is the same as the method for applying the paint in the step (A1-1). By applying a conductive adhesive paint to the surface of the electromagnetic wave shielding layer 20 opposite the insulating resin layer 10, the anisotropic conductive adhesive layer 24 is formed so that components and molecular skeletons contained in the anisotropic conductive adhesive layer 24 that have strong interactions with the electromagnetic wave shielding layer 20 are oriented in the electromagnetic wave shielding layer 20, thereby improving the adhesion between the electromagnetic wave shielding layer 20 and the anisotropic conductive adhesive layer 24.

[0070] In step (A1-4), a second release film 40 is laminated on the side of the anisotropic conductive adhesive layer 24 opposite the electromagnetic wave shielding layer 20 so that the release agent layer / adhesive layer 44 is in contact with the anisotropic conductive adhesive layer 24. After laminating the second release film 40 onto the anisotropic conductive adhesive layer 24, the laminate consisting of the first release film 30, the insulating resin layer 10, the electromagnetic wave shielding layer 20, the anisotropic conductive adhesive layer 24, and the second release film 40 may be subjected to a lamination process using pressure and / or heat in order to increase the adhesion between the layers. The pressure conditions are the same as those in the pressure treatment in the step (A1-2). Also in the step (A1-4), a heat treatment may be carried out in the same manner as in the step (A1-2). In the method (A1), the lamination is performed in steps (A1-2) and (A1-4) by way of example, but the stage at which the lamination is performed is not limited to this.

[0071] As a second embodiment of the method for producing an electromagnetic wave shielding film of the present invention, for example, the following production method (A2) can be mentioned. Specifically, the method (A2) comprises the following steps (A2-1) to (A2-4). Hereinafter, the method (A2) will be described with reference to Figures 6 to 8. Steps (A2-1) and (A2-2) are shown in Figure 6, step (A2-3) in Figure 7, and step (A2-4) in Figure 8. Step (A2-1): A step of forming an insulating resin layer 10 on one surface of a first release film 30. Step (A2-2): A step of forming an electromagnetic wave shielding layer 20 on the surface of the insulating resin layer 10 opposite to the first release film 30 to form a laminate (p1). Step (A2-3): A step of forming an anisotropic conductive adhesive layer 24 on a second release film 40 to form a laminate (p2). Step (A2-4): A step of bonding the laminate (p1) and the laminate (p2) together so that the electromagnetic wave shielding layer 20 of the laminate (p1) and the anisotropic conductive adhesive layer 24 of the laminate (p2) are in contact with each other.

[0072] Step (A2-1) and step (A2-2) are the same as the above-mentioned step (A1-1) and step (A1-2), respectively. Step (A2-3) is similar to the above-described step (A1-3) except that a conductive adhesive paint containing a thermosetting adhesive 24a and conductive particles 24b is applied to the surface of the second release film 40 on which the release agent layer / adhesive layer 44 is provided, rather than to the electromagnetic wave shielding layer 20, to form an anisotropic conductive adhesive layer 24. In the step (A2-4) of bonding the laminate (p1) and the laminate (p2), a lamination treatment by applying pressure may be performed to enhance the adhesion between the laminate (p1) and the laminate (p2). The pressure conditions are the same as those in the pressure treatment in the step (A1-2). Also in the step (A2-4), a heat treatment may be performed as in the step (A1-2). By bonding the electromagnetic wave shielding layer 20 and the anisotropic conductive adhesive layer 24 together by lamination processing, the electromagnetic wave shielding layer 20 and the anisotropic conductive adhesive layer 24 can be laminated even when the insulating resin layer 10 is sensitive to solvents or when a conductive adhesive paint containing a component such as a water-based solvent that oxidizes the electromagnetic wave shielding layer 20 is used.

[0073] As a third embodiment of the method for producing an electromagnetic wave shielding film of the present invention, for example, the following production method (B1) can be mentioned. The laminate obtained in step (A1-2) of FIG. 5 or the laminate obtained in step (A2-2) of FIG. 6 can be produced not only by the above-mentioned methods (A1) and (A2), but also by the following method (B1). The following method (B1) differs, for example, in that, whereas the above methods (A1) and (A2) form an electromagnetic wave shielding layer 20 on an insulating resin layer 10, the following method (B1) forms an insulating resin layer 10 on an electromagnetic wave shielding layer 20. Specifically, the method (B1) is a method comprising the following steps (B1-1) to (B1-4). Hereinafter, the method (B1) will be described with reference to FIG. Step (B1-1): A step of forming an insulating resin layer 10 on the surface of the electromagnetic wave shielding layer 20 opposite to the carrier film 100 side. Step (B1-2): A step of forming a first release film 30 on the surface of the insulating resin layer 10 opposite to the electromagnetic wave shielding layer 20.

[0074] In step (B1-1), the electromagnetic wave shielding layer 20 is desirably in the form of a single layer of metal foil (copper foil) or a laminate formed on a carrier film 100 having a base layer 102 with a release agent layer 104 provided on the surface thereof. Examples of the single layer of metal foil (copper foil) include rolled copper foil, electrolytic copper foil, etc. Rolled copper foil is preferred because it allows the surface of the electromagnetic wave shielding layer 20 to be smooth. Examples of the carrier film 100 include a film similar to the first release film 30, a metal foil (copper foil), etc. A film similar to the first release film 30 is preferred since it allows the formation of a smoother electromagnetic wave shielding layer 20. Methods for forming the electromagnetic wave shielding layer 20 on the carrier film 100 include a method using a vacuum film formation method (vacuum deposition, sputtering), a method using an electrolytic plating method, etc. The method of forming a deposition film by vacuum deposition is preferred because it is possible to form an electromagnetic wave shielding layer 20 that has high gas permeability and can easily release gas generated inside under high temperature conditions to the outside, and the electromagnetic wave shielding layer 20 can be easily formed by a dry process. The insulating resin layer 10 may be formed on the electromagnetic wave shielding layer 20 by the same method as in the above step (A1-1). That is, the insulating resin layer 10 can be formed by applying a paint for forming an insulating resin layer to the electromagnetic wave shielding layer 20, or the like. In the step (B1-2), the first release film 30 is laminated on the surface of the insulating resin layer 10 opposite the electromagnetic wave shielding layer 20 such that the adhesive layer / release agent layer 34 is in contact with the insulating resin layer 10. The carrier film 100 is peeled off between steps (B1-1) and (B1-2), or after step (B1-2), at a stage when the laminate including the insulating resin layer 10 and the electromagnetic wave shielding layer 20 can be handled even if the carrier film 100 is peeled off. By steps (B1-1) and (B1-2), a laminate similar to the laminate obtained in step (A1-2) of FIG. 5 or the laminate obtained in step (A2-2) of FIG. 6 is obtained. Therefore, the obtained laminate can be subjected to steps (A1-3) to (A1-4) shown in FIG. 5, or steps (A2-3) to (A2-4) shown in FIGS.

[0075] As a fourth embodiment of the method for producing an electromagnetic wave shielding film of the present invention, for example, the following production method (C1) can be mentioned. Specifically, the method (C1) is a method comprising the following steps (C1-1) and (C1-2). 10 may be added between steps (A1-1) and (A1-2) in FIG. 5, or between steps (A2-1) and (A2-2) in FIG. Step (C1-1): A step of forming a separate film 90 on the side of the insulating resin layer 10 opposite the first release film 30, and subjecting the laminate consisting of the first release film 30, the insulating resin layer 10, and the separate film 90 to a lamination process using pressure and / or heat to bond the insulating resin layer 10 and the separate film 90 together. Step (C1-2): A step of heating the laminate consisting of the first release film 30, the insulating resin layer 10, and the separate film 90 to harden the insulating resin layer 10. Step (C1-3): A step of peeling off the separate film 90 from the surface of the insulating resin layer 10.

[0076] In the step (C1-1), a lamination process is performed on the electromagnetic wave shielding layer 20 side of the insulating resin layer 10 using a separate film 90 to bond the insulating resin layer 10 and the separate film 90. This smoothes the surface of the insulating resin layer 10 on the electromagnetic wave shielding layer 20 side. The lamination conditions may be the same as those described in the above step (A1-2). Here, the type of the separate film is not particularly limited as long as it can smooth the surface of the insulating resin layer 10 when laminated, and can be appropriately selected depending on the purpose. For example, a film similar to the first release film 30 can be mentioned. After peeling off the separate film 90 from the insulating resin layer 10 in step (C1-3), the electromagnetic wave shielding layer 20 is formed on the insulating resin layer 10 in a manner similar to that shown in step (A1-2) of FIG. 5 and step (A2-2) of FIG. 6. After a laminate consisting of a first release film 30, an insulating resin layer 10, and an electromagnetic wave shielding layer 20 is obtained by the step (A1-2) described in FIG. 10, it can be subjected to the steps (A1-3) to (A1-4) shown in FIG. 5, or the steps (A2-3) to (A2-4) shown in FIGS. 7 and 8.

[0077] 10, an insulating resin layer 10 having a smoother surface can be formed even if the leveling of the paint that forms the insulating resin layer 10 is poor. Then, by forming the electromagnetic wave shielding layer 20 on the insulating resin layer 10 having a smoother surface, an electromagnetic wave shielding layer 20 having a smoother surface can be obtained. By making the surface of the electromagnetic wave shielding layer 20 on the FPC side even smoother, an electromagnetic wave shielding film with better FPC transmission characteristics can be obtained.

[0078] As a fifth embodiment of the method for producing an electromagnetic wave shielding film of the present invention, for example, the following production method (D1) can be mentioned. The following method (D1) corresponds to a method for producing the electromagnetic wave shielding film of Fig. 3. The following method (D1) differs from the above methods (A1) and (A2), for example, in that a silane coupling agent layer 80 is formed between the electromagnetic wave shielding layer 20 and the adhesive layer 22. Specifically, the method (D1) comprises the following steps (D1-1) to (D1-3). Hereinafter, the method (D1) will be described with reference to Fig. 11. In Fig. 11, for example, a laminate consisting of a first release film 30, an insulating resin layer 10, and an electromagnetic wave shielding layer 20 obtained in step (A1-2) in Fig. 5 or step (A2-2) in Fig. 6 is used to carry out the manufacturing steps (D1-1) to (D1-3) described below. Step (D1-1): A step of forming a silane coupling layer 80 on the surface of the electromagnetic wave shielding layer 20 opposite to the insulating resin layer 10. Step (D1-2): A step of forming an anisotropic conductive adhesive layer 24 on the surface of the silane coupling layer 80 opposite to the electromagnetic wave shielding layer 20. Step (D1-3): A step of laminating a second release film 40 on the surface of the anisotropic conductive adhesive layer 24 opposite to the electromagnetic wave shielding layer 20. Each step of the method (D1) will be described in detail below.

[0079] In the step (D1-1), a coating material for forming a silane coupling agent layer, in which a silane coupling agent is dissolved in a solvent, is applied to the surface of the electromagnetic wave shielding layer 20 opposite the insulating resin layer 10. The silane coupling layer 80 is formed by volatilizing the solvent from the applied paint for forming the silane coupling agent layer. In step (D1-2), similarly to the above-mentioned step (A1-3), a conductive adhesive paint containing an adhesive 24a, conductive particles 24b, and a solvent is applied to the surface of the silane coupling layer 80 opposite the electromagnetic wave shielding layer 20. The solvent is evaporated from the applied conductive adhesive paint to form an anisotropic conductive adhesive layer 24 . In step (D1-3), similarly to step (A1-4) above, a second release film 40 is laminated on the side of the anisotropic conductive adhesive layer 24 opposite the electromagnetic wave shielding layer 20, so that the release agent layer / adhesive layer 44 is in contact with the anisotropic conductive adhesive layer 24.

[0080] <Action and effect> In the electromagnetic wave shielding film 1 of this embodiment, the electromagnetic wave shielding layer has a specific film thickness and surface roughness, and the adhesive layer contains a specific resin, so that it is possible to improve the transmission characteristics of the FPC and also to satisfactorily reduce the thickness of the electromagnetic wave shielding film and improve its adhesion.

[0081] <Other embodiments> The electromagnetic wave shielding film of the present invention is not limited to the embodiment shown in the figures as long as it has an insulating resin layer, an electromagnetic wave shielding layer adjacent to the insulating resin layer, and an adhesive layer adjacent to the electromagnetic wave shielding layer on the side opposite the insulating resin layer. For example, in the first embodiment, the anisotropic conductive adhesive layer 24 may be changed to an isotropic conductive adhesive layer 26 . For example, the insulating resin layer may be two or more layers. The first release film may have a release agent layer instead of the pressure-sensitive adhesive layer. The second release film may have a pressure-sensitive adhesive layer instead of the release agent layer. The first release film or the second release film may not have an adhesive layer or a release agent layer, and may be composed of only a base layer. When the insulating resin layer has sufficient flexibility and strength, the first release film may be omitted. If the surface of the adhesive layer has little tack, the second release film may be omitted.

[0082] (Printed wiring board with electromagnetic shielding film) The printed wiring board with electromagnetic wave shielding film of the present invention comprises a printed wiring board having a printed circuit provided on at least one side of a substrate, an insulating film adjacent to the side of the printed wiring board on which the printed circuit is provided, and the electromagnetic wave shielding film of the present invention described above, with an adhesive layer provided adjacent to the insulating film.

[0083] FIG. 12 is a cross-sectional view showing a first embodiment of a printed wiring board with an electromagnetic shielding film obtained by the production method of the present invention. A flexible printed wiring board 2 with an electromagnetic wave shielding film includes a flexible printed wiring board 50, an insulating film 60, and the electromagnetic wave shielding film 1 of the first embodiment. The flexible printed wiring board 50 has a printed circuit 54 provided on at least one surface of a base film 52 . The insulating film 60 is provided on the surface of the flexible printed wiring board 50 on which the printed circuit 54 is provided. The anisotropic conductive adhesive layer 24 of the electromagnetic wave shielding film 1 is adhered to the surface of the insulating film 60. In addition, the anisotropic conductive adhesive layer 24 is electrically connected to the printed circuit 54 through a through hole (not shown) formed in the insulating film 60. In the flexible printed wiring board 2 with an electromagnetic wave shielding film, the second release film 40 is peeled off from the anisotropic conductive adhesive layer 24. When the first release film 30 becomes unnecessary in the flexible printed wiring board 2 with an electromagnetic wave shielding film, the first release film 30 is peeled off from the insulating resin layer 10.

[0084] In the vicinity of the printed circuit 54 (signal circuit, ground circuit, ground layer, etc.) excluding the portion with the through hole, the electromagnetic wave shielding layer 20 of the electromagnetic wave shielding film 1 is positioned opposite and spaced apart via the insulating film 60 and the anisotropic conductive adhesive layer 24. The distance between the printed circuit 54 and the electromagnetic wave shielding layer 20, excluding the portion with the through holes, is approximately equal to the sum of the thickness of the insulating film 60 and the thickness of the anisotropic conductive adhesive layer 24. The distance is preferably 15 μm or more and 200 μm or less, and more preferably 30 μm or more and 200 μm or less. If the distance is less than 15 μm, the line width of the signal circuit must be reduced to adjust the characteristic impedance of the signal circuit, making it technically difficult to manufacture a stable printed circuit 54. If the distance is more than 200 μm, the flexible printed wiring board 2 with the electromagnetic wave shielding film becomes thick and the flexibility is insufficient.

[0085] <Flexible printed wiring board> The flexible printed wiring board 50 is formed by processing the copper foil of a copper-clad laminate into a desired pattern by a known etching method to form a printed circuit (power supply circuit, ground circuit, ground layer, etc.). Examples of copper-clad laminates include those in which copper foil is attached to one or both sides of a base film 52 via an adhesive layer (not shown); and those in which a resin solution or the like that forms a base film 52 is cast onto the surface of the copper foil. Examples of materials for the adhesive layer include epoxy resins, polyesters, polyimides, polyamideimides, polyamides, phenolic resins, urethane resins, acrylic resins, and melamine resins. The thickness of the adhesive layer is preferably 0.5 μm or more and 30 μm or less.

[0086] <<Base film>> The base film 52 is preferably a film having heat resistance, more preferably a polyimide film or a liquid crystal polymer film, and even more preferably a polyimide film. The surface resistance of the base film 52 is set to 1×10 6 From a practical standpoint, the surface resistance of the base film 52 is preferably 1×10 19 Ω or less is preferable. The thickness of the base film 52 is preferably 5 μm or more and 200 μm or less, and from the viewpoint of flexibility, is more preferably 6 μm or more and 100 μm or less, and even more preferably 10 μm or more and 50 μm or less.

[0087] <<Printed Circuit>> Examples of the copper foil constituting the printed circuit 54 (signal circuit, ground circuit, ground layer, etc.) include rolled copper foil and electrolytic copper foil, with rolled copper foil being preferred from the standpoint of flexibility. The thickness of the copper foil is preferably from 1 μm to 50 μm, and more preferably from 7 μm to 35 μm. The ends (terminals) of the printed circuit 54 in the longitudinal direction are not covered by the insulating film 60 or the electromagnetic shielding film 1 because they are used for soldering, connector connection, component mounting, and the like.

[0088] <Insulating film> The insulating film 60 is formed by forming an adhesive layer (not shown) on one side of an insulating film body (not shown) by applying an adhesive, attaching an adhesive sheet, or the like. The surface resistance of the insulating film itself is 1×10 6 The surface resistance of the insulating film itself should be less than 1×10 19 Ω or less is preferable. The insulating film body is preferably a film having heat resistance, more preferably a polyimide film or a liquid crystal polymer film, and even more preferably a polyimide film. The thickness of the insulating film body is preferably 1 μm or more and 100 μm or less, and from the viewpoint of flexibility, more preferably 3 μm or more and 25 μm or less. Examples of materials for the adhesive layer include epoxy resin, polyester, polyimide, polyamideimide, polyamide, phenol resin, urethane resin, acrylic resin, melamine resin, polystyrene, polyolefin, etc. The epoxy resin may contain a rubber component (such as carboxy-modified nitrile rubber) to impart flexibility. The thickness of the adhesive layer is preferably from 1 μm to 100 μm, and more preferably from 1.5 μm to 60 μm.

[0089] The shape of the opening of the through hole is not particularly limited, and examples of the shape of the opening of the through hole 62 include a circle, an ellipse, and a rectangle.

[0090] (Method of manufacturing a printed wiring board with electromagnetic shielding film) The method for producing a printed wiring board with an electromagnetic wave shielding film of the present invention includes a step of bonding a printed wiring board having a printed circuit on at least one side of a substrate to the above-mentioned electromagnetic wave shielding film of the present invention via an insulating film, and during the bonding, the insulating film is adhered to the side of the printed wiring board on which the printed circuit is provided and also to the adhesive layer of the electromagnetic wave shielding film. The method for producing a printed wiring board with an electromagnetic wave shielding film of the present invention includes producing an electromagnetic wave shielding film by the above-mentioned method for producing an electromagnetic wave shielding film of the present invention, and then carrying out the following steps (a) and (b). Step (a): A step of providing an insulating film on the surface of the printed wiring board on which the printed circuit is provided, to obtain a printed wiring board with an insulating film. Step (b): When the electromagnetic wave shielding film has a second release film, a step of peeling the second release film from the electromagnetic wave shielding film, then overlapping the printed wiring board with the insulating film and the electromagnetic wave shielding film so that the adhesive layer is in contact with the surface of the insulating film, and pressing them together to adhere the adhesive layer to the surface of the insulating film, thereby obtaining a printed wiring board with the electromagnetic wave shielding film.

[0091] As a more preferred embodiment, the method for producing a printed wiring board with an electromagnetic wave shielding film of the present invention comprises the following steps (a) to (d). Step (a): A step of providing an insulating film on the surface of the printed wiring board on which the printed circuit is provided, to obtain a printed wiring board with an insulating film. Step (b): When the electromagnetic wave shielding film has a second release film, a step of peeling the second release film from the electromagnetic wave shielding film, then overlapping the printed wiring board with the insulating film and the electromagnetic wave shielding film so that the adhesive layer is in contact with the surface of the insulating film, and pressing them together to press the adhesive layer onto the surface of the insulating film, thereby obtaining a printed wiring board with the electromagnetic wave shielding film. Step (c): In the case where the electromagnetic wave shielding film has a first release film, after step (b), a step of peeling the first release film from the electromagnetic wave shielding film when the first release film is no longer needed. Step (d): If the adhesive contained in the adhesive layer is a thermosetting adhesive, a step of fully curing the adhesive layer between steps (a) and (b) or after step (c), as necessary.

[0092] Hereinafter, a method for producing a flexible printed wiring board with an electromagnetic wave shielding film will be described with reference to FIG.

[0093] <Process (a)> 13, an insulating film 60 having through holes 62 formed in positions corresponding to the printed circuits 54 is overlaid on the flexible printed wiring board 50, an adhesive layer (not shown) of the insulating film 60 is bonded to the surface of the flexible printed wiring board 50, and the adhesive layer is cured to obtain a flexible printed wiring board 3 with an insulating film. The adhesive layer of the insulating film 60 may be temporarily bonded to the surface of the flexible printed wiring board 50, and the adhesive layer may be fully cured in step (d). The adhesive layer is bonded and cured, for example, by hot pressing using a press (not shown) or the like.

[0094] <Process (b)> As shown in FIG. 13, the electromagnetic wave shielding film 1 from which the second release film 40 has been peeled off is placed on top of a flexible printed wiring board 3 with an insulating film, and pressed (preferably hot pressed) to obtain a flexible printed wiring board 2 with an electromagnetic wave shielding film in which the anisotropic conductive adhesive layer 24 is pressure-bonded to the surface of the insulating film 60 and the anisotropic conductive adhesive layer 24 is electrically connected to the printed circuit 54 through the through hole 62.

[0095] The anisotropic conductive adhesive layer 24 is bonded by, for example, heat pressing using a press (not shown) or the like. The time for the heat press is preferably from 20 seconds to 60 minutes, and more preferably from 30 seconds to 30 minutes. The temperature of the heat press (the temperature of the hot platens of the press) is preferably 140°C or higher and 210°C or lower, and more preferably 150°C or higher and 190°C or lower. The pressure of the heat press is preferably 0.5 MPa or more and 20 MPa or less, and more preferably 1 MPa or more and 16 MPa or less.

[0096] <Process (c)> As shown in FIG. 13, when the first release film 30 is no longer needed, the first release film 30 is peeled off from the insulating resin layer 10.

[0097] <Action and effect> The printed wiring board 2 with electromagnetic wave shielding film of this embodiment has the characteristics of the electromagnetic wave shielding film of the present invention described above, and is a printed wiring board having an electromagnetic wave shielding film with good FPC transmission characteristics, thin film properties, and excellent adhesion.

[0098] <Other embodiments> Incidentally, the printed wiring board with an electromagnetic wave shielding film in the present invention is not limited to the embodiment shown in the figures as long as it has a printed wiring board, an insulating film adjacent to the surface of the printed wiring board on which the printed circuit is provided, and an electromagnetic wave shielding film having an adhesive layer adjacent to the insulating film. For example, the flexible printed wiring board may have a ground layer on the back side. Also, the flexible printed wiring board may have printed circuits on both sides, and an insulating film and an electromagnetic wave shielding film may be attached to both sides. Instead of the flexible printed wiring board, a rigid printed circuit board that has no flexibility may be used. Instead of the electromagnetic shielding film 1 of the first embodiment, the electromagnetic shielding films 1 of the second to fourth embodiments may be used. EXAMPLES

[0099] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0100] (Conductive adhesive paint formulation) As conductive adhesives, adhesives A to H were obtained according to the following formulations. <Adhesive A> As resin 1 to be contained in the adhesive layer, acid-modified SEBS (hydrogenated styrene-based thermoplastic block copolymer of styrene-ethylene / butylene-styrene; Asahi Kasei Corporation, M1943) having a weight average molecular weight of 94,000 and an acid value of 10 mgKOH / g was used. As the resin 2 contained in the adhesive layer, an epoxy resin (manufactured by Mitsubishi Chemical Corporation, jER 1001) was used. 60 parts by mass of resin 1, 40 parts by mass of resin 2, 3 parts by mass of a curing agent (UDH-J, manufactured by Ajinomoto Fine-Techno Co., Ltd.), 3 parts by mass of an adhesion improver (VD-5, a melamine-based silane coupling agent, manufactured by Shikoku Chemical Industry Co., Ltd.), and 20 parts by mass of conductive particles (Culox3050, manufactured by Culox Corporation) were mixed to produce adhesive A, which is a conductive adhesive paint, as shown in Table 1 below. The mass ratio of N atoms in adhesive A was 1.2%.

[0101] <Adhesive B~Adhesive H> Adhesives B to H were prepared in the same manner as adhesive A, except that the type of resin 1 in adhesive A was changed as shown in Table 1 below. In Table 1, NBR indicates nitrile rubber made of a copolymer of butadiene and acrylonitrile, and HNBR indicates hydrogenated nitrile rubber. In Table 1, resin 1 of adhesive B was M1911 manufactured by Asahi Kasei Corporation, resin 1 of adhesive C was UR3500 manufactured by Toyobo Corporation, resin 1 of adhesive D was NX775 manufactured by Zeon Corporation, resin 1 of adhesive E was 3610 manufactured by Zeon Corporation, resin 1 of adhesive F was H1041 manufactured by Asahi Kasei Corporation, resin 1 of adhesive G was UR1700 manufactured by Toyobo Corporation, and resin 1 of adhesive H was 2010H manufactured by Zeon Corporation. The measurement results of the mass ratios of N atoms in adhesives B to H are shown in Table 1.

[0102] [Table 1]

[0103] Example 1 A first release film was prepared in which an adhesive layer made of an acrylic adhesive was provided on the side opposite to the side on which a release layer of a release PET film (manufactured by Toyobo Co., Ltd., CN200, film thickness 50 μm) was formed. An epoxy resin (manufactured by Mitsubishi Chemical Corporation, jER 1001), a curing agent (2-methyl-4-ethylimidazole), and carbon black were mixed in a mass ratio of 100:2:4 to prepare a coating material for the insulating resin layer. A coating material for an insulating resin layer was applied to the surface of the adhesive layer of the first release film using a die coater and dried. Thereafter, a polypropylene film (P2002, manufactured by Toyobo Co., Ltd.) was placed and laminated at 120°C. The insulating resin layer was cured at 120° C. for 48 hours, and the polypropylene film (P2002, manufactured by Toyobo Co., Ltd.) was peeled off. The insulating resin layer after curing had a thickness of 10 μm. Next, copper was physically deposited by electron beam deposition on the surface of the insulating resin layer opposite the first release film to form an electromagnetic wave shielding layer (thickness 1 μm) made of a copper deposition film. Next, the coating material of the adhesive A was applied to the surface of the electromagnetic wave shielding layer opposite the insulating resin layer using a die coater, and then dried to form a conductive adhesive layer (film thickness 4 μm). A second release film was prepared in which a release agent layer made of a non-silicone release agent was provided on one side of a PET film (manufactured by Toyobo Co., Ltd., CN200, film thickness 50 μm). The second release film was laminated to the side of the conductive adhesive layer opposite the electromagnetic wave shielding layer so that the release agent layer was in contact with the conductive adhesive layer, thereby obtaining the electromagnetic wave shielding film of Example 1. The measurement results of the arithmetic mean roughness (Ra) of the surface of the electromagnetic wave shielding layer on the adhesive layer side in the electromagnetic wave shielding film of Example 1, and the measurement results of the arithmetic mean roughness (Ra) of the surface of the insulating resin layer on the electromagnetic wave shielding layer side in the electromagnetic wave shielding film of Example 1 are shown in Table 2 below.

[0104] (Evaluation of electromagnetic wave shielding film) <Evaluation of transmission characteristics> The electromagnetic wave shielding film of Example 1 was evaluated for transmission characteristics by the following method. In a printed wiring board with electromagnetic shielding film, in which the electromagnetic shielding film obtained in Example 1 was attached to a printed wiring board for transmission characteristic measurement, a network analyzer E5071C (manufactured by Agilent Japan) was connected to the exposed signal wiring of the wiring board (corresponding to the above-mentioned printed circuit 54), a 10 GHz sine wave was input, the transmission loss was measured, and the transmission characteristics were evaluated from the difference with the transmission characteristics of a printed wiring board for transmission characteristic measurement to which no electromagnetic shielding film was attached. The FPC cable used as the printed wiring board for measuring the transmission characteristics was configured as follows: L2 coverlay: polyimide (thickness 12.5μm), adhesive layer (thickness 25μm), L2 rolled copper foil (thickness 18μm), base: LCP (thickness 50μm), L1 rolled copper foil (thickness 18μm), adhesive layer (thickness 25μm), L1 coverlay: polyimide (thickness 12.5μm). The total length of the FPC cable was 144mm, the total length of the signal line was 140mm, and 2mm on each end was exposed (connector connection part). The laminated portion of L2 rolled copper foil (thickness 18 μm), base: LCP (thickness 50 μm), and L1 rolled copper foil (thickness 18 μm) has exposed portions at both ends that are 2 mm longer than the adhesive layer (thickness 25 μm) and the L2 or L1 cover layer: polyimide (thickness 12.5 μm), and these exposed portions have been treated with a surface treatment to prevent oxidation, consisting of electroless nickel plating (1 μm) and electroless gold plating (0.05 μm). The transmission characteristics were evaluated according to the following criteria. [Evaluation Criteria] ◎ The difference in transmission loss is less than 2.0 dB / 140 mm. Extremely good. The difference in transmission loss is 2.0 dB / 140 mm or more and less than 10.0 dB / 140 mm. This is good. × The difference in transmission loss is 10.0 dB / 140 mm or more. Not practical.

[0105] <Evaluation of heat resistance> The heat resistance of the electromagnetic wave shielding film of Example 1 was evaluated by the following method. The electromagnetic shielding film was pressed onto a 125 um polyimide film at 2 MPa, 180°C, and 120 seconds so that the conductive adhesive layer and polyimide film were in contact, and then the first release film was peeled off and the conductive adhesive layer was cured by heating in an oven at 150°C for 1 hour to obtain a laminate for evaluation. The laminate for evaluation was floated in a solder bath at 288°C for 10 seconds so that the solder and insulating resin layer were in contact. The heat resistance was evaluated from the appearance of the electromagnetic shielding film after the laminate for evaluation was removed from the solder bath. The heat resistance was evaluated according to the following criteria. [Evaluation Criteria] No abnormalities × Air bubbles or other abnormalities have occurred

[0106] <Evaluation of Adhesion> For the electromagnetic wave shielding film of Example 1, the adhesion (adhesion) between the electromagnetic wave shielding layer and the adhesive layer was evaluated by the following method. The above-mentioned evaluation laminate was subjected to an adhesion test (cross-cut method) in accordance with JIS K 5600-5-6:1999 (ISO 2409:1992). The cut was made from the insulating resin layer side. The adhesion was evaluated based on the number of remaining squares out of 5 x 5 = 25 squares. The adhesion was evaluated according to the following criteria. [Evaluation Criteria] ○ No abnormalities for 24 or more squares × 2 or more squares are abnormal

[0107] <Evaluation of minimum connection diameter> The following method was used to confirm whether it was possible to minimize electrical coupling between the electromagnetic shielding layer of the electromagnetic shielding film and the transmission lines of the FPC and to suppress the effects of the electromagnetic shielding film on the transmission characteristics of the FPC. In a printed wiring board with an electromagnetic wave shielding film, the minimum diameter of a through hole (also called a connection hole) was measured when electrical connection was made between wiring, electromagnetic wave shielding layer, and wiring via the electromagnetic wave shielding film present in the through hole (also called a connection hole). A printed wiring board with an electromagnetic shielding film having the configuration shown in FIG. 14 was used. In FIG. 14, a printed wiring 111 (corresponding to the above-mentioned printed circuit 54) is provided on a substrate 110 (corresponding to the above-mentioned base film 52), and on the printed wiring 111, an insulating film is provided. The insulating film on the printed wiring 111 is provided with through holes 112 and 113 (also called connection holes, corresponding to the through hole 62 in FIG. 13) which are circular openings. Several types of printed wiring boards were prepared in which the diameters of the through holes 113 were changed to a pair of 113a and 113b. An electromagnetic wave shielding film 114 was provided on each printed wiring board as shown in FIG. A tester was applied to each printed wiring board with an electromagnetic wave shielding film to measure the resistance between the wiring, the electromagnetic wave shielding layer and the wiring. The diameters of the through holes in the printed wiring boards with the electromagnetic shielding film that showed a resistance value of 1Ω or less were measured, and the smallest diameter among the measured diameters was taken as the minimum connection diameter.

[0108] The evaluation results of the above-mentioned transmission characteristics, heat resistance, adhesion, and minimum connection diameter for the electromagnetic wave shielding film of Example 1 are shown in Table 3 below.

[0109] (Examples 2 to 10) The electromagnetic wave shielding films of Examples 2 to 8 were produced in the same manner as in Example 1, except that in Example 1, the film thickness and surface arithmetic mean roughness (Ra) of the electromagnetic wave shielding layer, the surface arithmetic mean roughness (Ra) of the insulating resin layer, and the type of adhesive of the conductive adhesive layer were changed as shown in Table 2. However, in Example 7, the temperature was changed from 120° C. to 100° C., whereas in Example 1, a polypropylene film (P2002, manufactured by Toyobo Co., Ltd.) was provided and then lamination was performed at 120° C. In Example 8, the temperature was changed from 120° C. to 80° C., whereas in Example 1, a polypropylene film (P2002, manufactured by Toyobo Co., Ltd.) was provided and then lamination was performed at 120° C. In Example 9, a coating material for an insulating resin layer was applied onto a rolled copper foil (film thickness 3 μm), dried, and then a first release film was placed and laminated at 120° C. Next, the coating material for the adhesive A was applied onto the surface of the rolled copper foil opposite to the insulating resin layer side and dried to form a conductive adhesive layer (film thickness 4 μm). Then, a second release film was attached so that the release agent layer was in contact with the conductive adhesive layer, and laminated to obtain an electromagnetic wave shielding film of Example 9. In Example 10, an electromagnetic wave shielding film was prepared in the same manner as in Example 10, except that the thickness of the electromagnetic wave shielding layer and the arithmetic mean roughness (Ra) of the surface were changed as shown in Table 2. The electromagnetic wave shielding film thus produced was evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0110] (Comparative Example 1 to Comparative Example 10) The electromagnetic wave shielding films of Comparative Examples 1 to 4 were produced in the same manner as in Example 1, except that in Example 1, the film thickness and surface arithmetic mean roughness (Ra) of the electromagnetic wave shielding layer, the surface arithmetic mean roughness (Ra) of the insulating resin layer, and the type of adhesive of the conductive adhesive layer were changed as shown in Table 2. In Comparative Examples 5 to 7, the coating material for the insulating resin layer was applied to the surface of the pressure-sensitive adhesive layer of the first release film in Example 1, dried, and then copper was vapor-deposited on the surface of the insulating resin layer opposite to the first release film. That is, in Comparative Examples 5 to 7, lamination treatment using a polypropylene film (P2002, manufactured by Toyobo Co., Ltd.) was not performed. The film thickness and surface arithmetic mean roughness (Ra) of the electromagnetic wave shielding layer, the surface arithmetic mean roughness (Ra) of the insulating resin layer, and the type of adhesive of the conductive adhesive layer in Comparative Examples 5 to 7 are as shown in Table 2. In Comparative Examples 8 to 9, the electromagnetic wave shielding films of Comparative Examples 8 to 9 were prepared in the same manner as in Example 9, except that the film thickness of the electromagnetic wave shielding layer and the arithmetic mean roughness (Ra) of the surface, as well as the type of adhesive of the conductive adhesive layer, were changed as shown in Table 2. In Comparative Example 10, an electromagnetic wave shielding film of Comparative Example 10 was produced in the same manner as in Example 9, except that an electrolytically plated copper foil film produced by an electrolytic plating method was used instead of the rolled copper foil in Example 9. The film thickness and arithmetic mean roughness (Ra) of the electromagnetic wave shielding layer, as well as the type of adhesive for the conductive adhesive layer in Comparative Example 10, are as shown in Table 2. The electromagnetic wave shielding film thus produced was evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0111] [Table 2]

[0112] [Table 3]

[0113] The present invention includes the following aspects. [1] An electromagnetic wave shielding film comprising an insulating resin layer, an electromagnetic wave shielding layer, and an adhesive layer laminated in this order, The electromagnetic wave shielding layer is a metal layer having a thickness of 1 μm or more and 5 μm or less and containing copper, the arithmetic mean roughness (Ra) of the surface of the electromagnetic wave shielding layer on the adhesive layer side is 0.01 μm or more and 0.25 μm or less; An electromagnetic wave shielding film, characterized in that the adhesive layer contains a resin, the weight average molecular weight (Mw) of the resin is 50,000 or more and 400,000 or less, and the acid value of the resin is 2 mgKOH / g or more and 50 mgKOH / g or less. [2] The electromagnetic wave shielding film according to [1], wherein the mass ratio of N atoms in the adhesive layer is 0.5% or more and 10% or less. [3] The electromagnetic wave shielding film according to [1] or [2], wherein the resin contained in the adhesive layer is a resin having at least one of an amine structure, an amide structure, a urea structure, a urethane structure, and an imide structure. [4] The electromagnetic wave shielding film according to any one of [1] to [3], wherein the adhesive layer contains an adhesion improver having at least one of a melamine structure, a triazine structure, a phosphoric acid structure, an alkoxysilane structure, and a mercapto group. [5] The electromagnetic wave shielding film according to any one of [1] to [4] above, wherein the adhesive layer has a thickness of 2 μm or more and 25 μm or less. [6] The electromagnetic wave shielding film according to any one of the above [1] to [5], wherein the insulating resin layer has a surface facing the electromagnetic wave shielding layer with an arithmetic mean roughness (Ra) of 0.01 μm or more and 0.3 μm or less. [7] The electromagnetic wave shielding film according to any one of the above [1] to [6], wherein the electromagnetic wave shielding layer is a vapor deposition film. [8] The electromagnetic wave shielding film according to any one of the above [1] to [6], wherein the electromagnetic wave shielding layer is a rolled copper foil. [9] The electromagnetic wave shielding film according to any one of the above [1] to [8], further comprising a silane coupling agent layer between the electromagnetic wave shielding layer and the adhesive layer.

[10] A method for producing an electromagnetic wave shielding film according to any one of [1] to [7] and [9], comprising the steps of: forming the electromagnetic wave shielding layer on the surface of the insulating resin layer by a vacuum film formation method or an electrolytic plating method.

[11] The method for producing an electromagnetic wave shielding film according to

[10] above, wherein the electromagnetic wave shielding layer is formed on a surface of the insulating resin layer by a vacuum deposition method.

[12] A method for producing an electromagnetic shielding film according to any one of [1] to [9], A method for producing an electromagnetic wave shielding film, comprising bonding a surface of the electromagnetic wave shielding layer facing the insulating resin layer and a surface of the insulating resin layer facing the electromagnetic wave shielding layer by performing a lamination treatment using pressure and / or heat.

[13] A method for producing an electromagnetic shielding film according to any one of [1] to [9], The method for producing an electromagnetic wave shielding film, wherein the insulating resin layer is formed by applying a coating material for forming an insulating resin layer to the electromagnetic wave shielding layer.

[14] A method for producing an electromagnetic wave shielding film according to any one of [1] to [9], The method for producing an electromagnetic wave shielding film, wherein the insulating resin layer is formed by applying a coating material for forming an insulating resin layer to a first release film.

[15] After forming the insulating resin layer by applying a coating material for forming the insulating resin layer to a first release film, a separate film is disposed on the electromagnetic wave shielding layer side of the insulating resin layer, and a lamination process is performed by applying pressure and / or heat to bond the insulating resin layer and the separate film together; The method for producing an electromagnetic wave shielding film according to [7] above, wherein the separate film is then peeled off from the insulating resin layer.

[16] A method for producing an electromagnetic shielding film according to any one of [1] to [8], The adhesive layer is formed by applying a coating material for forming an adhesive layer to the electromagnetic wave shielding layer, in the method for producing an electromagnetic wave shielding film.

[17] A method for producing the electromagnetic shielding film according to [9] above, The silane coupling agent layer is formed by applying a coating material for forming a silane coupling agent layer to the electromagnetic wave shielding layer, The method for producing an electromagnetic wave shielding film, wherein the adhesive layer is formed by applying a coating material for forming an adhesive layer to the formed silane coupling agent layer.

[18] A printed wiring board having a printed circuit on at least one side of a substrate; an insulating film adjacent to a surface of the printed wiring board on which the printed circuit is provided; The electromagnetic wave shielding film according to any one of [1] to [9] above, in which the adhesive layer is provided adjacent to the insulating film; A printed wiring board with an electromagnetic wave shielding film.

[19] A method for manufacturing a printed wiring board, comprising: a printed circuit board having a printed circuit on at least one surface of a substrate; and the electromagnetic shielding film according to any one of [1] to [9] above, wherein the electromagnetic shielding film is pressure-bonded via an insulating film; When the insulating film is pressed against the printed wiring board, the insulating film is adhered to the surface of the printed wiring board on which the printed circuit is provided and also to the adhesive layer of the electromagnetic wave shielding film. [Industrial Applicability]

[0114] The electromagnetic wave shielding film of the present invention is useful as an electromagnetic wave shielding member in flexible printed wiring boards for electronic devices such as smartphones, mobile phones, optical modules, digital cameras, game consoles, notebook computers, and medical instruments. [Explanation of symbols]

[0115] 1. Electromagnetic wave shielding film 2. Flexible printed wiring board with electromagnetic shielding film 3. Flexible printed circuit board with insulating film 10 Insulating resin layer 20 Electromagnetic shielding layer 22 Adhesive layer 24 Anisotropic conductive adhesive layer 24a Adhesive 24b Conductive particles 26 Isotropic conductive adhesive layer 26a Adhesive 26b Conductive particles 30 First release film 32 Base material layer 34 Adhesive layer / Release layer 40 Second release film 42 Base material layer 44 Release layer / adhesive layer 50 Flexible printed wiring board 52 Base Film 54 Printed Circuits 60 Insulating Film 62 Through hole 80 Silane coupling agent layer 90 Separate Film 100 career film 102 Base material layer 104 Release agent layer

Claims

1. An electromagnetic wave shielding film comprising an insulating resin layer, an electromagnetic wave shielding layer, and an adhesive layer laminated in this order, The electromagnetic wave shielding layer is a metal layer having a thickness of 1 μm or more and 5 μm or less and containing copper, the arithmetic mean roughness (Ra) of the surface of the electromagnetic wave shielding layer on the adhesive layer side is 0.04 μm or more and 0.25 μm or less; An electromagnetic wave shielding film, characterized in that the adhesive layer contains a resin, the resin has a weight average molecular weight (Mw) of 63,000 or more and 400,000 or less, the resin has an acid value of 2 mg KOH / g or more and 50 mg KOH / g or less, and the mass ratio of N atoms is 0.5% or more and 10% or less.

2. 2 . The electromagnetic wave shielding film according to claim 1 , wherein the resin contained in the adhesive layer is a resin having at least one of an amine structure, an amide structure, a urea structure, a urethane structure, and an imide structure.

3. 3. The electromagnetic wave shielding film according to claim 1, wherein the adhesive layer contains an adhesion improver having at least one of a melamine structure, a triazine structure, a phosphoric acid structure, an alkoxysilane structure, and a mercapto group.

4. The electromagnetic wave shielding film according to any one of claims 1 to 3, wherein the adhesive layer has a thickness of 2 µm or more and 25 µm or less.

5. 5. The electromagnetic wave shielding film according to claim 1, wherein the insulating resin layer has a surface facing the electromagnetic wave shielding layer with an arithmetic mean roughness (Ra) of 0.01 μm or more and 0.3 μm or less.

6. The electromagnetic wave shielding film according to any one of claims 1 to 5, wherein the electromagnetic wave shielding layer is a vapor deposition film.

7. The electromagnetic wave shielding film according to any one of claims 1 to 5, wherein the electromagnetic wave shielding layer is a rolled copper foil.

8. A method for producing an electromagnetic wave shielding film comprising laminating an insulating resin layer, an electromagnetic wave shielding layer, and an adhesive layer in this order, comprising: The electromagnetic wave shielding layer is a metal layer having a thickness of 1 μm or more and 5 μm or less and containing copper, the arithmetic mean roughness (Ra) of the surface of the electromagnetic wave shielding layer on the adhesive layer side is 0.04 μm or more and 0.25 μm or less; the adhesive layer contains a resin, the resin has a weight average molecular weight (Mw) of 63,000 or more and 400,000 or less, and the resin has an acid value of 2 mgKOH / g or more and 50 mgKOH / g or less; A coating material for forming an insulating resin layer is applied to a first release film to form the insulating resin layer, and then a separate film is disposed on the electromagnetic wave shielding layer side of the insulating resin layer, and a lamination process is performed by applying pressure and / or heat to bond the insulating resin layer and the separate film together; Thereafter, the separate film is peeled off from the insulating resin layer.

9. A printed wiring board having a printed circuit provided on at least one surface of a substrate; an insulating film adjacent to a surface of the printed wiring board on which the printed circuit is provided; The electromagnetic wave shielding film according to any one of claims 1 to 7, wherein the adhesive layer is provided adjacent to the insulating film; A printed wiring board with an electromagnetic wave shielding film.

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