TWI829647B - Electromagnetic wave shielding film - Google Patents

Abstract

An object of the present invention is to realize an electromagnetic wave shielding film that reduces the glossiness of an insulating protective layer and improves the peelability of a release film. As a solution, the electromagnetic wave shielding film of the present invention includes: an insulating protective layer; a conductive adhesive layer; and a peeling film, which is provided in the middle of the insulating protective layer on the opposite side to the conductive adhesive layer with a release agent layer interposed therebetween. surface; and the 85° glossiness of the insulating protective layer is less than 15, the 85° glossiness of the surface of the peeling film on the insulating protective layer side is less than 3, and the thickness of the release agent layer is less than 10 μm.

Description

Electromagnetic wave shielding film

The present invention relates to an electromagnetic wave shielding film and a shielding wiring board.

Background technology We conduct research on the design of a circuit pattern of a printed wiring board that cannot be seen from the outside. On the other hand, an electromagnetic wave shielding film for shielding electromagnetic noise is adhered to the surface of the printed wiring board. A black colorant is added to the insulating protective layer of the electromagnetic wave shielding film for the purpose of improving appearance and improving the visibility of printed characters (for example, see Patent Document 1). By attaching an electromagnetic wave shielding film to a printed wiring board, the circuit pattern of the printed wiring board cannot be directly recognized.

Advanced technical documents patent documents [Patent Document 1] Japanese Patent Application Publication No. 2016-143751

Summary of the invention The problem to be solved by the invention However, there is a height difference caused by the circuit pattern on the surface of the printed wiring board. Therefore, even if an electromagnetic wave shielding film in which the insulating protective layer is blackened is adhered to a printed wiring board for the purpose of improving the appearance, improving the visibility of printed characters, etc., there is still a case where the circuit pattern floats out of the electromagnetic wave due to light reflection, etc. The surface of the shielding film cannot achieve sufficient concealment. Therefore, there is a need for an electromagnetic wave shielding film that further improves concealment properties.

As a method of reducing light reflection on the surface of the insulating protective layer, it is considered to form fine irregularities on the surface of the insulating protective layer. The insulating protective layer can be formed by coating the surface of the release film with a resin composition and drying it. In this case, the unevenness on the surface of the release film will be transferred to the surface of the insulating protective layer. By using a release film with unevenness and low gloss to form the insulating protective layer, it is expected that the glossiness of the insulating protective layer will be reduced. However, if the glossiness of the release film is reduced, it may become difficult to peel off the release film, resulting in reduced productivity or damage to the surface of the insulating protective layer.

An object of the present invention is to realize an electromagnetic wave shielding film that reduces the glossiness of an insulating protective layer and improves the peelability of a release film.

means to solve problems One aspect of the electromagnetic wave shielding film of the present invention includes: an insulating protective layer; a conductive adhesive layer; and a peeling film, which is disposed in the middle of the insulating protective layer on the opposite side to the conductive adhesive layer with a release agent layer interposed therebetween. surface; and, the 85° glossiness of the insulating protective layer is less than 15, the 85° glossiness of the surface of the peeling film on the insulating protective layer side is less than 3, and the thickness of the release agent layer is less than 10 μm.

In one aspect of the electromagnetic wave shielding film, the insulating protective layer may contain a black colorant.

An aspect of the shielded wiring board of the present invention includes: a wiring board and the electromagnetic wave shielding film of the present invention, wherein the wiring board has a base layer, a circuit pattern provided on the base layer, and is connected to the base layer in a manner to cover the circuit pattern The insulating film; the electromagnetic wave shielding film is attached to the insulating film and the peeling film has been removed.

Invention effect According to the electromagnetic wave shielding film of the present invention, the glossiness of the insulating protective layer can be reduced and the peelability of the release film can be improved.

Form used to implement the invention As shown in FIG. 1 , the electromagnetic wave shielding film 101 of this embodiment includes: a conductive adhesive layer 111; an insulating protective layer 112; and a release film 115, which is provided in the middle of the insulating protective layer 112 with a release agent layer 114 interposed therebetween. The conductive adhesive layer 111 is the opposite surface. The 85° glossiness of the insulating protective layer 112 is less than 15, the 85° glossiness of the surface of the release film 115 on the side of the insulating protective layer 112 is less than 3, and the thickness of the release agent layer 114 is less than 10 μm.

In FIG. 1 , although the conductive shielding layer 113 is provided between the conductive adhesive layer 111 and the insulating protective layer 112 , when the conductive adhesive layer 111 functions as a shield, it may also be formed without the shielding layer 113 . structure.

As shown in FIG. 2 , the electromagnetic wave shielding film 101 of this embodiment can be adhered to the printed wiring board 102 to form a shielding wiring board. The printed wiring board 102 has, for example, a base layer 121, a circuit pattern 122 provided on the surface of the base layer 121, and an insulating film 124 adhered to the base layer 121 through an adhesive layer 123 so as to cover the circuit pattern 122.

If the insulating protective layer 112 is colored to make it opaque, the circuit pattern 122 cannot be directly viewed. However, due to the circuit pattern 122, unevenness may be formed on the surface of the insulating protective layer 112. The general circuit pattern 122 is formed using copper wires, and its height is several μm to more than ten μm. Since the height difference between the portion where the line exists and the portion where the line does not exist becomes smaller due to filling of the adhesive layer 123 and the conductive adhesive layer 111, the height of the unevenness generated on the surface of the insulating protective layer 112 is several μm. However, even with such slight unevenness, the existence of unevenness can be seen on a glossy surface that easily reflects light, and the circuit pattern 122 cannot be hidden.

The inventors of this case discovered that by making the 85° glossiness of the insulating protective layer 112 less than 15, preferably less than 13, and more preferably less than 10, the concealability of the circuit pattern can be greatly improved. Furthermore, the 85° glossiness of the insulating protective layer 112 can be measured by the method according to JIS Z 8741.

The insulating protective layer 112 can be formed by applying a resin composition for an insulating protective layer to the surface of the release film 115 and forming it into a sheet shape. At this time, the unevenness on the surface of the release film 115 will be transferred to the surface of the insulating protective layer 112 . Therefore, if the release film 117 with relatively large surface roughness, that is, low gloss, is used to form the insulating protective layer 112, it is expected to obtain the insulating protective layer 112 with low gloss. However, if the glossiness of the release film 115 is lowered, the adhesion between the release film 115 and the insulating protective layer 112 becomes higher, and a large force is required to peel off the release film 115 . If the force required for peeling increases, not only the productivity decreases, but also the insulating protective layer 112 may be damaged and damaged. Since the release film 115 is peeled off after the electromagnetic wave shielding film 101 is adhered to the printed wiring board 102, if the release film 115 cannot be peeled off cleanly, the final product may become a defective product.

If the release agent layer 114 provided on the surface of the release film 115 is thickened, the release film 115 can be easily peeled off. However, at this time, since the unevenness existing on the surface of the release film 115 will be filled by the release agent, the surface of the insulating protective layer 112 becomes smooth, resulting in an increase in gloss.

After research by the inventors of this case, it was found that a release agent layer 114 with a thickness of 0.1 μm or more, preferably 0.4 μm or more and less than 10 μm, and preferably less than 4 μm is provided on the surface of the release film 115 with an 85° glossiness of less than 3. , the 85° glossiness of the formed insulating protective layer 112 can be made less than 15, and the peelability of the peeling film 115 can be made good. In addition, the 85° glossiness and peelability of the release film 115 can be measured by the method described in the Example.

The material of the release film 115 is not particularly limited as long as the glossiness satisfies a predetermined value. For example, a polyolefin-based, polyester-based, polyimide-based or polyphenylene sulfide-based film may be used. The thickness of the release film is not particularly limited, but from the viewpoint of releasability, it is preferably 25 μm or more and 100 μm or less.

As long as the release agent layer 114 meets a predetermined thickness, its material is not particularly limited. For example, melamine resin, polyolefin resin, epoxy resin, alkyd resin, fluorine resin, acrylic resin, paraffin resin, Urea resin, etc. The thickness of the release agent layer can be adjusted using various coating methods. Taking direct gravure printing as an example, it can be controlled by adjusting the number of lines and depth of the plate, or adjusting the solid content of the coating agent. . In addition, the thickness of the release agent layer can be measured by the method shown in the embodiment.

The insulating protective layer 112 may be formed of thermoplastic resin, thermosetting resin, active energy ray curable resin, or the like. The thermoplastic resin is not particularly limited, and styrene-based resin, vinyl acetate-based resin, polyester-based resin, polyethylene-based resin, polypropylene-based resin, imide-based resin, acrylic resin, etc. can be used. The thermosetting resin is not particularly limited, and phenolic resins, epoxy resins, urethane resins having an isocyanate group at the terminal, urea resins having an isocyanate group at the terminal, and urea resins having an isocyanate group at the terminal can be used. Based on urethane urea resin, melamine resin or alkyd resin, etc. In addition, the active energy ray curable resin is not particularly limited, and for example, a polymerizable compound having at least two (meth)acryloxy groups in the molecule can be used. These resins can be used alone, or two or more types can be used in combination.

From the viewpoint of reducing gloss, the insulating protective layer 112 preferably contains a black colorant. The black colorant may be a black pigment or a mixed pigment obtained by subtractively mixing a plurality of pigments to make the mixture black. The black pigment may be, for example, any one of carbon black, Ketjen black, carbon nanotube (CNT), perylene black, titanium black, iron black and aniline black or a combination thereof. The mixed pigment can be used by mixing red, green, blue, yellow, purple, cyan, magenta and other pigments, for example. From the viewpoint of reducing the glossiness, the amount of the black colorant added is preferably 0.5% by mass or more, preferably 1% by mass or more, based on 100 parts by mass of the resin.

The insulating protective layer 112 may optionally contain at least one of the following: hardening accelerator, tackifier, antioxidant, plasticizer, ultraviolet absorber, defoaming agent, leveling agent, filler, flame retardant, viscosity regulator and anti-caking agents, etc.

In addition, the thickness of the insulating protective layer 112 is not particularly limited and can be appropriately set as needed. It can be 1 μm or more, preferably 4 μm or more, and can be 20 μm or less, preferably 10 μm or less, and more preferably 5 μm or less. By setting the thickness of the insulating protective layer 112 to 1 μm or more, the conductive adhesive layer 111 and the shielding layer 113 can be fully protected. By setting the thickness of the insulating protective layer 112 to 20 μm or less, the flexibility of the electromagnetic wave shielding film 101 can be ensured, and the electromagnetic wave shielding film 101 can be easily applied to members requiring flexibility.

When the shielding layer 113 is provided, the shielding layer 113 can be formed of metal foil, evaporated film, conductive filler, etc.

The metal foil is not particularly limited, and may be made of any one of nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, zinc, or the like, or a foil containing two or more alloys.

The vapor deposition film is not particularly limited, and can be formed by vapor deposition of nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, zinc, etc. For evaporation, electrolytic plating, electroless plating, sputtering, electron beam evaporation, vacuum evaporation, chemical vapor deposition (CVD) or metal organic chemical vapor deposition (MOCVD) can be used. .

When the shielding layer 113 is formed by a conductive filler, the shielding layer 113 can be formed by applying a solvent mixed with the conductive filler on the surface of the insulating protective layer 112 and then drying it. As the conductive filler, metal fillers, metal-coated resin fillers, carbon fillers, and mixtures thereof can be used. Regarding metal fillers, you can use: copper powder, silver powder, nickel powder, silver-coated copper powder, gold-coated copper powder, silver-coated nickel powder, gold-coated nickel powder, etc. These metal powders can be produced by electrolysis, atomization, and reduction. The shapes of metal powder include spherical, flake, fibrous, dendritic, etc.

In this embodiment, the thickness of the shielding layer 113 can be appropriately selected according to the required electromagnetic shielding effect and repeated bending and sliding resistance. When the shielding layer 113 is a metal foil, the thickness is selected from the perspective of ensuring the breaking elongation. In other words, the thickness of the shielding layer 113 is preferably less than 12 μm.

In this embodiment, the conductive adhesive layer 111 includes at least one of a thermoplastic resin, a thermosetting resin, an active energy ray curable resin, and a conductive filler.

When the conductive adhesive layer 111 contains a thermoplastic resin, examples of the thermoplastic resin that can be used include: styrene-based resin, vinyl acetate-based resin, polyester-based resin, polyethylene-based resin, polypropylene-based resin, imide-based resin, and Acrylic resin, etc. One type of these resins may be used alone, or two or more types may be used in combination.

When the conductive adhesive layer 111 contains a thermosetting resin, for example, the thermosetting resin can use: phenol resin, epoxy resin, urethane resin, melamine resin, polyamide resin, and alcohol. Acid resin, etc. The active energy ray-curable resin is not particularly limited, and for example, a polymerizable compound having at least two (meth)acryloxy groups in the molecule can be used. One type of these resins may be used alone, or two or more types may be used in combination.

The thermosetting resin includes, for example, a first resin component having a reactive first functional group and a second resin component that reacts with the first functional group. The first functional group can be, for example, an epoxy group, a amide group, a hydroxyl group, or the like. The second functional group may be selected based on the first functional group. For example, when the first functional group is an epoxy group, the second functional group may be a hydroxyl group, a carboxyl group, an epoxy group, an amine group, or the like. Specifically, for example, when the first resin component is an epoxy resin, as the second resin component, epoxy-modified polyester resin, epoxy-modified polyamide resin, and epoxy-modified acrylic resin can be used. Resin, epoxy modified polyurethane polyurea resin, carboxyl modified polyester resin, carboxyl modified polyamide resin, carboxyl modified acrylic resin, carboxyl modified polyurethane polyurea resin And urethane modified polyester resin, etc. Among these, carboxyl-modified polyester resin, carboxyl-modified polyamide resin, carboxyl-modified polyurethane polyurea resin, and urethane-modified polyester resin are preferred. In addition, when the first resin component is a hydroxyl group, as the second resin component, the following can be used: epoxy-modified polyester resin, epoxy-modified polyamide resin, epoxy-modified acrylic resin, epoxy-modified Polyurethane polyurea resin, carboxyl modified polyester resin, carboxyl modified polyamide resin, carboxyl modified acrylic resin, carboxyl modified polyurethane polyurea resin and urethane modified Quality polyester resin, etc. Among these, carboxyl-modified polyester resin, carboxyl-modified polyamide resin, carboxyl-modified polyurethane polyurea resin, and urethane-modified polyester resin are preferred.

The thermosetting resin may also contain a hardener for accelerating the thermosetting reaction. When the thermosetting resin has a first functional group and a second functional group, the curing agent can be appropriately selected according to the types of the first functional group and the second functional group. When the first functional group is an epoxy group and the second functional group is a hydroxyl group, imidazole-based hardeners, phenol-based hardeners, cationic hardeners, etc. can be used as the hardener. One type of these hardeners may be used alone, or two or more types may be used in combination. In addition, any ingredients may also include defoaming agents, antioxidants, viscosity adjusters, diluents, anti-settling agents, leveling agents, coupling agents, colorants, flame retardants, etc.

The conductive filler is not particularly limited, and for example, metal fillers, metal-coated resin fillers, carbon fillers, and mixtures thereof can be used. Regarding metal fillers, examples include: copper powder, silver powder, nickel powder, silver-coated copper powder, gold-coated copper powder, silver-coated nickel powder, gold-coated nickel powder, etc. These metal powders can be produced by electrolysis, atomization or reduction. Among them, any one of silver powder, silver-coated copper powder and copper powder is preferred.

From the viewpoint of fillers being in contact with each other, the average particle size of the conductive filler is preferably 1 μm or more, more preferably 3 μm or more, and is preferably 50 μm or less, more preferably 40 μm or less. The shape of the conductive filler is not particularly limited and may be spherical, flake-like, dendritic, fibrous, etc.

The content of the conductive filler can be appropriately selected according to the use, but it is preferably 5 mass% or more, more preferably 10 mass% or more, and more preferably 95 mass% or less, more preferably 90 mass% or less in the total solid content. From the viewpoint of landfillability, the content is preferably 70 mass% or less, and more preferably 60 mass% or less. In addition, when achieving anisotropic conductivity, the content is preferably 40 mass% or less, and more preferably 35 mass% or less.

From the viewpoint of embedding properties, the thickness of the conductive adhesive layer 111 is preferably 1 μm to 50 μm.

[Example] Hereinafter, the electromagnetic wave shielding film of the present invention will be described in further detail using examples. The following examples are examples and are not intended to limit the present invention.

＜Production of electromagnetic wave shielding film＞ A release agent is applied to the surface of the release film made of polyethylene terephthalate (PET) that has a predetermined glossiness and is on the insulating layer side using a wire bar to form a release agent layer with a predetermined thickness. The thickness of the release agent layer was measured using an optical interference type film thickness meter (ST-2000-DLXn, manufactured by K-MAC Corporation). The composition for an insulating protective layer was applied using a wire bar on the surface of the release film on which the release agent layer was formed, and the composition was heated and dried to form an insulating protective layer with a thickness of 5 μm. Next, a 0.1 μm Ag evaporated film was formed on the insulating protective layer as a shielding layer. After applying the composition for the conductive adhesive layer on the shielding layer with a wire bar, it was dried at 100° C. for 3 minutes to form a conductive adhesive layer with a thickness of 15 μm.

Use alkyd resin as a release agent. The insulating protective layer has a two-layer structure, which is a hard coat layer of polyester transparent resin with a thickness of 2 μm and a soft layer of epoxy black resin containing carbon black with a thickness of 3 μm. The composition for the conductive adhesive layer is set to use conductive particles of silver-coated copper powder in an epoxy resin containing a phosphorus-based flame retardant.

＜Preparation of shielded wiring board＞ The obtained electromagnetic wave shielding film and the printed wiring board were bonded using a press machine under conditions of temperature: 170°C, time: 3 minutes, and pressure: 2 to 3 MPa to prepare a shielding wiring board.

The printed wiring board is one in which a circuit pattern 122 as shown in FIG. 3 is formed on a base layer 121 made of a polyimide film. The circuit pattern 122 is formed of copper foil with a line width of 0.1 mm and a height of 12 μm. On the base layer 121, an adhesive layer with a thickness of 25 μm and a covering layer (insulating film) composed of a polyimide film with a thickness of 12.5 μm are provided to cover the circuit pattern.

＜Evaluation of peelability＞ After the electromagnetic wave shielding film was adhered to the printed wiring board, a peel strength tester (PFT50S manufactured by PALMEC Co., Ltd.) was used to evaluate the peelability of the surface peeling film at a sample width of 10 mm, a peeling angle of 170°, and a peeling speed of 1000mm/min. When the release film can be peeled off without material damage during peeling, the peelability is considered to be good, and when the release film material is damaged during peeling, the peelability is considered to be poor.

＜Measurement of Glossiness＞ The 85° glossiness was measured in accordance with JIS Z 8741 using a portable gloss meter (BYK Gardner Microgloss Meter, Toyo Seiki Co., Ltd.).

The glossiness of the release film is measured on the side of the release film that becomes the insulating layer protective layer before applying the release agent.

The glossiness of the insulating protective layer is measured after the electromagnetic wave shielding film is adhered to the printed wiring board and the release film is peeled off.

＜Evaluation Hiddenness＞ Place the shielded wiring board with the electromagnetic wave shielding film attached on a flat tabletop, and evaluate whether the circuit pattern is visible from the side of the electromagnetic wave shielding film in an environment where the illumination on the surface of the shielding wiring board is 800-1000 lux. The viewing angle is set in the range of 0 to 180 degrees relative to the electromagnetic wave shielding film surface. When the circuit pattern cannot be visually recognized, it is regarded as good concealment (○), and when the circuit pattern is visible, it is regarded as poor concealment (×).

(Example 1) A PET film with a thickness of 50 μm and an 85° glossiness of 2.3 was used as the release film. A release agent layer with a thickness of 0.7 μm was formed on the surface of the release film that becomes the insulating protective layer. The peelability of the release film was good. The 85° glossiness of the insulating protective layer after peeling off the release film is 9.2. Also, the concealability is good.

(Example 2) A PET film with a thickness of 50 μm and an 85° glossiness of 2.3 was used as the release film. A release agent layer with a thickness of 3.0 μm was formed on the surface of the release film that becomes the insulating protective layer. The peelability of the release film was good. The 85° glossiness of the insulating protective layer after peeling off the release film is 9.6. Also, the concealability is good.

(Comparative example 1) A PET film with a thickness of 50 μm and an 85° glossiness of 19.3 was used as the release film. A release agent layer with a thickness of 0.4 μm was formed on the surface of the release film that becomes the insulating protective layer. The peelability of the release film was good. The 85° glossiness of the insulating protective layer after peeling off the release film is 35.4. Also, concealment is bad.

(Comparative example 2) A PET film with a thickness of 50 μm and an 85° glossiness of 2.3 was used as the release film. A release agent layer with a thickness of 10.0 μm was formed on the surface of the release film that becomes the insulating protective layer. The peelability of the release film was poor. The 85° glossiness of the insulating protective layer after peeling off the release film is 15.5. Also, concealment is bad.

(Comparative example 3) A PET film with a thickness of 50 μm and an 85° glossiness of 2.3 was used as the release film. A release agent layer with a thickness of 0.05 μm was formed on the surface of the release film that becomes the insulating protective layer. The peelability of the release film was poor.

Table 1 summarizes each embodiment and comparative examples.

[Table 1]

industrial availability The electromagnetic wave shielding film of the present invention has a low glossiness of the insulating protective layer and the release film can be easily peeled off, so it is suitable as an electromagnetic wave shielding film and the like.

101‧‧‧Electromagnetic wave shielding film 102‧‧‧Printed wiring board 111‧‧‧Conductive adhesive layer 112‧‧‧Insulating protective layer 113‧‧‧shielding layer 114‧‧‧Release agent layer 115‧‧‧Peel-off film 121‧‧‧Basilar layer 122‧‧‧Circuit pattern 123‧‧‧Adhesive layer 124‧‧‧Insulation film

FIG. 1 is a cross-sectional view showing an electromagnetic wave shielding film according to an embodiment. FIG. 2 is a cross-sectional view of a shielded wiring board according to an embodiment. FIG. 3 is a plan view showing a circuit pattern for concealment evaluation.

101‧‧‧Electromagnetic wave shielding film

102‧‧‧Printed wiring board

111‧‧‧Conductive adhesive layer

112‧‧‧Insulating protective layer

113‧‧‧shielding layer

121‧‧‧Basilar layer

122‧‧‧Circuit pattern

123‧‧‧Adhesive layer

124‧‧‧Insulation film

Claims (3)

An electromagnetic wave shielding film comprising: an insulating protective layer; a conductive adhesive layer; and a peeling film disposed on a surface of the insulating protective layer opposite to the conductive adhesive layer with a release agent layer interposed therebetween; and , the 85° glossiness of the insulating protective layer is less than 15, the 85° glossiness of the peeling film is less than 3, and the thickness of the release agent layer is 0.1 μm or more and less than 4 μm. The electromagnetic wave shielding film of claim 1, wherein the insulating protective layer contains a black colorant. A shielded wiring substrate, comprising: a wiring substrate and the electromagnetic wave shielding film according to claim 1 or 2, wherein the wiring substrate has a base layer, a circuit pattern provided on the base layer, and is connected to the base in a manner to cover the circuit pattern layer of insulating film; the electromagnetic wave shielding film is adhered to the aforementioned insulating film and the aforementioned peeling film has been removed.