TW201930513A - Electromagnetic wave shielding film capable of reducing the glossiness of an insulating protective layer and the peelability of a release film - Google Patents

Abstract

An electromagnetic wave shielding film is disclosed, which the glossiness of an insulating protective layer is reduced and the peelability of a release film is improved. The disclosed electromagnetic wave shielding film includes an insulating protective layer; a conductive adhesive layer; and a release film which is interposed between a release agent layer and the insulating protective layer and on a surface opposite to the conductive adhesive layer. In addition, the insulating protective layer has an 85 DEG C glossiness of less than 15, the surface of the release film on the insulating protective layer side has an 85 DEG C glossiness of less than 3, and the thickness of the release agent layer is less than 10 [mu]m.

Description

Electromagnetic wave shielding film

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

BACKGROUND ART We have studied 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 stuck on the surface of the printed wiring board. A black-based colorant is added to the insulating protective layer of the electromagnetic wave shielding film for the purpose of improving the appearance and visibility of printed characters (for example, refer to Patent Document 1). Since the electromagnetic wave shielding film is stuck on the printed wiring board, the circuit pattern of the printed wiring board cannot be viewed directly.

Prior technical literature Patent literature
[Patent Document 1] Japanese Patent Laid-Open No. 2016-143751

SUMMARY OF THE INVENTION Problems to be Solved by the Invention However, there is a step difference caused by a circuit pattern on the surface of a printed wiring board. Therefore, even if the insulating protective layer is pasted with a blackened electromagnetic wave shielding film on the printed wiring board for the purpose of beautiful appearance and improved visibility of printed fonts, there are still cases in which a circuit pattern floats out of electromagnetic waves due to light reflection or the like. The surface of the shielding film cannot be sufficiently concealed. Therefore, it is necessary to further improve the concealment of the electromagnetic wave shielding film.

As a method of reducing light reflection on the surface of the insulating protective layer, it is considered that fine unevenness is formed on the surface of the insulating protective layer. The insulating protective layer can be formed by coating and drying a resin composition on the surface of the release film. At this time, the unevenness on the surface of the release film is transferred to the surface of the insulating protective layer. By forming the insulating protective layer using a release film provided with uneven unevenness, the gloss of the insulating protective layer can be expected to decrease. However, if the gloss of the release film is lowered, the release of the release film may become difficult, so that productivity may be reduced or the surface of the insulating protective layer may be damaged.

An object of the present invention is to realize an electromagnetic wave shielding film that can reduce the gloss of an insulating protective layer and improve the releasability of a release film.

Means for Solving the Problems One aspect of the electromagnetic wave shielding film of the present invention includes: an insulating protective layer; a conductive adhesive layer; and a release film disposed in the insulating protective layer through the release agent layer to be in contact with the conductive adhesive layer. The agent layer is the surface on the opposite side; and the 85 ° gloss of the insulating protective layer is less than 15, the 85 ° gloss of the surface of the insulating protective layer side of the release film 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.

One aspect of the shielded wiring substrate of the present invention includes a wiring substrate and the electromagnetic wave shielding film of the present invention, wherein the wiring substrate has a base layer, a circuit pattern provided on the base layer, and a base layer is attached to the base layer to cover the circuit pattern The insulating film; the electromagnetic wave shielding film is attached to the insulating film and the release film has been removed.

ADVANTAGE OF THE INVENTION According to the electromagnetic wave shielding film of this invention, the glossiness of an insulation protective layer can be reduced and the peelability of a peeling film can be improved.

The form for implementing the invention is shown in FIG. 1. The electromagnetic wave shielding film 101 according to this embodiment includes: a conductive adhesive layer 111; an insulating protective layer 112; and a release film 115 provided on the insulating protection through the release agent layer 114. The layer 112 is positioned on the surface opposite to the conductive adhesive layer 111. The 85 ° gloss of the insulating protection layer 112 is less than 15, the 85 ° gloss of the surface on the side of the insulation protection layer 112 of the release film 115 is less than 3, and the thickness of the release agent layer 114 is less than 10 μm.

In FIG. 1, although a 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, a non-shielding layer 113 may be formed. The construction.

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

If the insulating protective layer 112 is colored to be opaque, the circuit pattern 122 cannot be directly viewed. However, due to the relationship of the circuit pattern 122, unevenness is formed on the surface of the insulating protection layer 112. A general circuit pattern 122 is formed using a copper wire, and its height is several μm to more than ten μm. Since the height difference between the portion where the line is present and the portion where the line does not exist is reduced by filling 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 presence of unevenness can be visually recognized on a glossy surface that easily reflects light, and the circuit pattern 122 cannot be hidden.

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

The insulating protective layer 112 can be formed by coating the surface of the release film 115 with a resin composition for an insulating protective layer and making it into a sheet form. At this time, the unevenness of the release film surface 115 is transferred to the surface of the insulating protective layer 112. Therefore, if the insulating protective layer 112 is formed using a release film 117 having a large surface roughness, that is, a low gloss, it is expected that an insulating protective layer 112 having a low gloss may be obtained. However, if the gloss of the release film 115 is reduced, the adhesion between the release film 115 and the insulating protective layer 112 becomes high, and a large force is required to peel the release film 115. When the force required for peeling becomes large, not only productivity decreases, but the insulating protective layer 112 may be damaged to cause a defect. Since the peeling film 115 is peeled after the electromagnetic wave shielding film 101 is adhered to the printed wiring board 102, if the peeling film 115 cannot be peeled cleanly, the final product becomes a defective product.

When the release agent layer 114 provided on the surface of the release film 115 is thickened, peeling of the release film 115 becomes easy. However, at this time, since the unevenness existing on the surface of the release film 115 is filled with 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 the present case, it was found that a release agent layer 114 having 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 having a gloss of less than 3 at 85 ° In this case, the 85 ° glossiness of the formed insulating protective layer 112 can be made less than 15 and the peelability of the release film 115 can be made good. The 85 ° gloss and peelability of the release film 115 can be measured by the method described in the examples.

The material of the release film 115 is not particularly limited as long as the gloss satisfies a predetermined value, and for example, a polyolefin-based, polyester-based, polyimide-based, or polyphenylene sulfide-based film can 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.

The material of the release agent layer 114 is not particularly limited as long as it satisfies a predetermined thickness. 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 by various coating methods. Taking direct gravure printing as an example, it can be controlled by adjusting the number of lines, the depth of the plate, or the solid content of the coating agent. . The thickness of the release agent layer can be measured by the method shown in the examples.

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

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

The insulating protective layer 112 may optionally include at least one of the following: hardening accelerator, tackifier, antioxidant, plasticizer, ultraviolet absorber, defoamer, leveling agent, filler, flame retardant, viscosity modifier And anti-caking agents.

In addition, the thickness of the insulating protective layer 112 is not particularly limited, and may be appropriately set as necessary, and may be 1 μm or more, preferably 4 μm or more, and may 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 sufficiently 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 a member requiring flexibility.

When the shielding layer 113 is provided, the shielding layer 113 can be formed by a metal foil, a vapor-deposited film, a conductive filler, or the like.

The metal foil is not particularly limited, and can be made of any one of nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, and zinc, or an alloy containing two or more kinds.

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

When the shielding layer 113 is formed of a conductive filler, the shielding layer 113 can be formed by coating a solvent prepared with a conductive filler on the surface of the insulating protective layer 112 and drying it. As the conductive filler, a metal filler, a metal-coated resin filler, a carbon filler, and a mixture thereof can be used. As for the metal filler, copper powder, silver powder, nickel powder, silver-coated copper powder, gold-coated copper powder, silver-coated nickel powder, and gold-coated nickel powder can be used. These metal powders can be produced by electrolytic method, atomization method, and reduction method. Examples of the shape of the metal powder include a spherical shape, a small plate shape, a fibrous shape, and a dendritic shape.

In this embodiment, the thickness of the shielding layer 113 may 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, it is considered from the viewpoint of ensuring the elongation at break. In other words, the thickness of the shielding layer 113 is preferably 12 μm or less.

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

When the conductive adhesive layer 111 contains a thermoplastic resin, the thermoplastic resin may be, for example, a styrene resin, a vinyl acetate resin, a polyester resin, a polyethylene resin, a polypropylene resin, a fluorene resin, or Acrylic resin, etc. These resins may be used singly or in combination of two or more kinds.

When the conductive adhesive layer 111 contains a thermosetting resin, the thermosetting resin can be, for example, a phenol-based resin, an epoxy-based resin, a urethane-based resin, a melamine-based resin, a polyamide-based resin, and an alcohol. Acid-based resins, etc. The active energy ray-curable resin is not particularly limited, and for example, a polymerizable compound having at least two (meth) acrylic fluorenyloxy groups in a molecule can be used. These resins may be used singly or in combination of two or more kinds.

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, amidino group, or a hydroxyl group. 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, or an amine group. Specifically, for example, when the first resin component is an epoxy resin, as the second resin component, epoxy-modified polyester resin, epoxy-modified polyamine resin, and epoxy-modified acrylic can be used. Resin, epoxy-modified polyurethane polyurea resin, carboxy-modified polyester resin, carboxy-modified polyamine resin, carboxy-modified acrylic resin, carboxy-modified polyurethane polyurea resin And urethane modified polyester resin. Among these, a carboxyl modified polyester resin, a carboxyl modified polyamine resin, a carboxyl modified polyurethane polyurea resin, and a urethane modified polyester resin are preferred. When the first resin component is a hydroxyl group, epoxy resin modified polyester resin, epoxy modified polyamide resin, epoxy modified acrylic resin, and epoxy modified can be used as the second resin component. Polyurethane polyurea resin, carboxyl modified polyester resin, carboxyl modified polyamine resin, carboxyl modified acrylic resin, carboxyl modified polyurethane polyurea resin, and urethane modified High quality polyester resin. Among these, a carboxyl modified polyester resin, a carboxyl modified polyamine resin, a carboxyl modified polyurethane polyurea resin, and a urethane modified polyester resin are preferred.

The thermosetting resin may contain a curing agent for promoting a thermosetting reaction. When the thermosetting resin has a first functional group and a second functional group, the curing agent can be appropriately selected depending on 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, an imidazole-based hardener, a phenol-based hardener, or a cationic hardener can be used as the hardener. These hardeners may be used singly or in combination of two or more kinds. In addition, the optional component may include a defoamer, an antioxidant, a viscosity modifier, a diluent, an anti-settling agent, a leveling agent, a coupling agent, a colorant, a flame retardant, and the like.

The conductive filler is not particularly limited, and examples thereof include metal fillers, metal-coated resin fillers, carbon fillers, and mixtures thereof. Examples of the metal filler include copper powder, silver powder, nickel powder, silver-coated copper powder, gold-coated copper powder, silver-coated nickel powder, and gold-coated nickel powder. These metal powders can be produced by an electrolytic method, an atomization method, or a reduction method. Among them, any one of silver powder, silver-coated copper powder, and copper powder is preferred.

From the viewpoint that the fillers are in contact with each other, the average particle diameter of the conductive filler is preferably 1 μm or more, more preferably 3 μm or more, and preferably 50 μm or less, and more preferably 40 μm or less. The shape of the conductive filler is not particularly limited, and may be spherical, platelet-shaped, dendritic, or fibrous.

The content of the conductive filler can be appropriately selected according to the application, and it is preferably 5 mass% or more, more preferably 10 mass% or more, and more preferably 95 mass% or less, and more preferably 90 mass% or less in the total solid content. From the viewpoint of landfillability, it is preferably 70% by mass or less, and more preferably 60% by mass or less. When anisotropic conductivity is achieved, it is preferably 40% by mass or less, and more preferably 35% by mass or less.

From the viewpoint of landfillability, 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 more detail using examples. The following examples are illustrative 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 having a predetermined glossiness and made of polyethylene terephthalate (PET) on the side of the insulating layer to apply a release agent using a wire rod to form a release agent layer having a predetermined thickness. The thickness of the release agent layer was measured using an optical interference film thickness meter (manufactured by K-MAC, ST-2000-DLXn). On the surface on the side where the release agent layer is formed of the release film on which the release agent layer is formed, a composition for an insulating protection layer is coated with a wire rod and dried by heating to form an insulation protection layer having a thickness of 5 μm. Next, a 0.1 μm Ag vapor-deposited film was formed on the insulating protective layer as a shielding layer. The conductive adhesive layer composition was coated on the shielding layer with a wire rod, and then dried at 100 ° C for 3 minutes to form a conductive adhesive layer having a thickness of 15 µm.

Use an alkyd resin for the release agent. The insulating protective layer has a two-layer structure, a hard coating layer of a polyester transparent resin having a thickness of 2 μm, and a soft coating layer of an epoxy black resin containing carbon black having 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.

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

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

＜ Evaluation of peelability ＞
After the electromagnetic wave shielding film was adhered to the printed wiring board, the peelability of the surface peeling film was evaluated using a peel strength tester (PLM50P, manufactured by PLM50S) with a sample width of 10 mm, a peel angle of 170 °, and a peel speed of 1000 mm / min. The case where the release film can be peeled without material damage at the time of peeling is considered to be good peelability, and the case where the peel film material is broken at the time of peeling is considered to be poor peelability.

＜ Measure glossiness ＞
The 85 ° gloss was measured in accordance with JIS Z 8741 using a portable gloss meter (BYK Gardner Micro Gloss Meter, Toyo Seiki Seisakusho).

The gloss of the release film was measured on the surface of the release film before the release agent was applied, which was the protective layer on the insulating layer side.

The gloss of the insulating protective layer was measured after the electromagnetic wave shielding film was attached to the printed wiring board and the release film was peeled off.

＜ Evaluation of Hiddenness ＞
The shielding wiring substrate to which the electromagnetic wave shielding film was attached was placed on a flat table, and the circuit pattern was visually recognized from the electromagnetic shielding film side in an environment where the illuminance on the surface of the shielding wiring substrate was 800-1000 lux. The viewing angle is set to a range of 0 to 180 degrees with respect to the electromagnetic wave shielding film surface. When the circuit pattern cannot be visually recognized, it is considered to have good concealability (○), and when the circuit pattern is visually recognized, it is considered to be poor in concealment (×).

(Example 1)
As a release film, a PET film having a thickness of 50 μm and an 85 ° gloss of 2.3 was used. A release agent layer having a thickness of 0.7 μm was formed on the surface of the release film on the side of the insulating protective layer. The peelability of the release film was good. The 85 ° gloss of the insulating protective layer after peeling the release film was 9.2. In addition, the hiding property was good.

(Example 2)
As a release film, a PET film having a thickness of 50 μm and an 85 ° gloss of 2.3 was used. A release agent layer having a thickness of 3.0 μm was formed on the surface of the release film on the side of the insulating protective layer. The peelability of the release film was good. The 85 ° gloss of the insulating protective layer after peeling the release film was 9.6. In addition, the hiding property was good.

(Comparative example 1)
As a release film, a PET film having a thickness of 50 μm and an 85 ° gloss of 19.3 was used. A release agent layer having a thickness of 0.4 μm was formed on the surface of the release film on the side of the insulating protective layer. The peelability of the release film was good. The 85 ° gloss of the insulating protective layer after peeling the release film was 35.4. In addition, the concealment is poor.

(Comparative example 2)
As a release film, a PET film having a thickness of 50 μm and an 85 ° gloss of 2.3 was used. A release agent layer having a thickness of 10.0 μm was formed on the surface of the release film on the side of the insulating protective layer. The peelability of the release film was poor. The 85 ° gloss of the insulating protective layer after peeling the release film was 15.5. In addition, the concealment is poor.

(Comparative example 3)
As a release film, a PET film having a thickness of 50 μm and an 85 ° gloss of 2.3 was used. A release agent layer having a thickness of 0.05 μm was formed on the surface of the release film on the side of the insulating protective layer. The peelability of the release film was poor.

Table 1 summarizes each embodiment and comparative example.

[Table 1]

INDUSTRIAL APPLICABILITY The electromagnetic wave shielding film of the present invention has a low gloss of the insulating protective layer and can easily peel off the release film, and is suitable as an electromagnetic wave shielding film or the like.

101‧‧‧ electromagnetic wave shielding film

102‧‧‧printed wiring board

111‧‧‧ conductive adhesive layer

112‧‧‧Insulation protective layer

113‧‧‧Shield

114‧‧‧ release agent layer

115‧‧‧ peeling film

121‧‧‧ basal layer

122‧‧‧Circuit Pattern

123‧‧‧Adhesive layer

124‧‧‧ insulating film

FIG. 1 is a sectional view showing an electromagnetic wave shielding film according to an embodiment.

FIG. 2 is a cross-sectional view showing a shielded wiring substrate according to an embodiment.

FIG. 3 is a plan view showing a circuit pattern for hiding evaluation.

Claims (3)

An electromagnetic wave shielding film having: Insulation protection A conductive adhesive layer; and The release film is provided on the surface of the insulating and protective layer on the side opposite to the conductive adhesive layer through the release agent layer; In addition, the 85 ° gloss of the aforementioned insulating protective layer is less than 15, The 85 ° gloss of the surface of the release protective layer side of the release film is less than 3, The thickness of the release agent layer is less than 10 μm. The electromagnetic wave shielding film according to 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 an insulating film attached to the base layer so as to cover the circuit pattern; The electromagnetic wave shielding film is attached to the insulating film and the peeling film is removed.