JP6863908B2 - Electromagnetic wave shield film - Google Patents

Description

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

It is being studied to make the circuit pattern of the printed wiring board invisible from the outside. On the other hand, an electromagnetic wave shielding film for shielding electromagnetic noise is attached 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 aesthetics and visibility of printing (see, for example, Patent Document 1). By attaching the electromagnetic wave shield film to the printed wiring board, the circuit pattern of the printed wiring board can be made invisible directly.

Japanese Unexamined Patent Publication No. 2016-143751

However, there is a step on the surface of the printed wiring board due to the circuit pattern. Therefore, even if an electromagnetic wave shield film having a blackened insulating protective layer is attached to the printed wiring board for the purpose of improving aesthetics and visibility of printing, the circuit pattern is formed on the surface of the electromagnetic wave shield film due to light reflection or the like. It may be raised and sufficient concealment may not be obtained. Therefore, there is a demand for an electromagnetic wave shielding film having further improved concealment.

As a method of reducing the reflection of light on the surface of the insulating protective layer, it is conceivable to form fine irregularities on the surface of the insulating protective layer. The insulating protective layer can be formed by applying a resin composition to the surface of the release film and drying it. In this case, since the unevenness on the surface of the release film is transferred to the surface of the insulation protective layer, the glossiness of the insulation protection layer is increased by forming the insulation protection layer using the release film provided with the unevenness and having a low glossiness. Expected to be smaller. However, if the glossiness of the release film is reduced, it becomes difficult to remove the release film, which may reduce productivity or damage the surface of the insulating protective layer.

An object of the present disclosure is to make it possible to realize an electromagnetic wave shielding film in which the glossiness of the insulating protective layer is reduced and the peelability of the release film is improved.

One aspect of the electromagnetic wave shielding film of the present disclosure is peeling provided on the surface of the insulating protective layer, the conductive adhesive layer, and the surface of the insulating protective layer on the opposite side of the conductive adhesive layer via the release agent layer. The insulating protective layer includes a film, the 85 ° glossiness is less than 15, the 85 ° glossiness on the surface of the release film on the insulating protective layer side is less than 3, and the thickness of the release agent layer is less than 10 μm. Is.

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

One aspect of the shielded wiring board of the present disclosure is a wiring board having a base layer, a circuit pattern provided on the base layer, and an insulating film adhered to the base layer so as to cover the circuit pattern, and an insulating film. It is provided with the electromagnetic shielding film of the present disclosure which is adhered onto the surface and the release film is removed.

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

It is sectional drawing which shows the electromagnetic wave shielding film which concerns on one Embodiment. It is sectional drawing which shows the shield wiring board which concerns on one Embodiment. It is a top view which shows the circuit pattern for hiding property evaluation.

As shown in FIG. 1, the electromagnetic wave shielding film 101 of the present embodiment is separated from the conductive adhesive layer 111, the insulating protective layer 112, and the surface of the insulating protective layer 112 on the opposite side of the conductive adhesive layer 111. It has a release film 115 provided via a mold layer 114. The insulation protective layer 112 has an 85 ° glossiness of less than 15, the surface of the release film 115 on the insulation protection layer 112 side has an 85 ° glossiness of less than 3, and the release agent layer 114 has a thickness of less than 10 μm. Is.

In FIG. 1, a conductive shield layer 113 is provided between the conductive adhesive layer 111 and the insulating protective layer 112, but when the conductive adhesive layer 111 functions as a shield, the shield layer 113 Can be configured without the provision of.

As shown in FIG. 2, the electromagnetic wave shield film 101 of the present embodiment can be adhered to the printed wiring board 102 to form a shielded wiring board. The printed wiring board 102 includes, for example, a circuit pattern 122 provided on the surfaces of the base layer 121 and the base layer 121, and an insulating film 124 bonded to the base layer 121 via an adhesive layer 123 so as to cover the circuit pattern 122. have.

If the insulating protective layer 112 is colored to make it opaque, the circuit pattern 122 cannot be directly visually recognized. However, the circuit pattern 122 forms irregularities on the surface of the insulating protective layer 112. The general circuit pattern 122 is formed of copper lines and has a height of several μm to ten and several μm. Since the difference in height between the portion where the line exists and the portion where the line does not exist is reduced by embedding 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 a few μm. However, even with such a slight unevenness, the presence of the unevenness can be visually recognized on a glossy surface that easily reflects light, and the circuit pattern 122 cannot be concealed.

The inventors of the present application have found that the hiding property of the circuit pattern can be greatly improved by setting the 85 ° glossiness of the insulating protective layer 112 to less than 15, preferably less than 13, and more preferably less than 10. The 85 ° glossiness of the insulating protective layer 112 can be measured by a method conforming 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 to form a sheet. In this case, 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 by using the release film 117 having a large surface roughness, that is, a low glossiness, it is expected that the insulating protective layer 112 having a low glossiness can be obtained. However, when the glossiness 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 when the release film 115 is peeled off. If the force required for peeling is increased, not only the productivity is lowered, but also the insulating protective layer 112 may be destroyed and a defect may occur. Since the release film 115 is peeled off after the electromagnetic wave shield film 101 is adhered to the printed wiring substrate 102, if the release film 115 cannot be peeled off cleanly, the final product will be defective.

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, in this case, 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 and the glossiness increases.

As examined by the inventors of the present application, a release agent having a thickness of 0.1 μm or more, preferably 0.4 μm or more and less than 10 μm, preferably less than 4 μm on the surface of the release film 115 having an 85 ° glossiness of less than 3. It has been found that when the layer 114 is provided, 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 improved. The 85 ° glossiness and peelability of the release film 115 can be measured by the method described in Examples.

The material of the release film 115 is not particularly limited as long as the glossiness 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 is preferably 25 μm or more and 100 μm or less from the viewpoint of peelability.

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 Resins, urea resins, etc. can be used. The thickness of the release agent layer can be adjusted by adjusting the thickness of various coating methods. For example, in the case of the direct gravure method, the thickness is controlled by adjusting the number of lines of the plate, the plate depth, and the solid content of the coating agent. it can. Further, the thickness of the release agent layer can be measured by the method shown in 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 styrene resin, vinyl acetate resin, polyester resin, polyethylene resin, polypropylene resin, imide resin, acrylic resin and the like can be used. The thermosetting resin is not particularly limited, but is 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 a urethane urea-based resin having an isocyanate group at the terminal. , Melamine-based resin, Alkid-based resin, or the like can be used. The active energy ray-curable resin is not particularly limited, and for example, a polymerizable compound having at least two (meth) acryloyloxy groups in the molecule can be used. These resins may be used alone or in combination of two or more.

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

The insulating protective layer 112 includes a curing accelerator, a tackifier, an antioxidant, a plasticizer, an ultraviolet absorber, a defoaming agent, a leveling agent, a filler, a flame retardant, a viscosity modifier, and a viscosity modifier, if necessary. At least one such as an antiblocking agent may be contained.

The thickness of the insulating protective layer 112 is not particularly limited and can be appropriately set as needed, but is 1 μm or more, preferably 4 μm or more, and 20 μm or less, preferably 10 μm or less, more preferably 5 μm or less. Can be. By setting the thickness of the insulating protective layer 112 to 1 μm or more, the conductive adhesive layer 111 and the shield 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 it becomes easy to apply the electromagnetic wave shielding film 101 to a member requiring flexibility. ..

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

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

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

When the shield layer 113 is formed by the conductive filler, the shield layer 113 can be formed by applying a solvent containing the conductive filler to 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, or a mixture thereof can be used. As the metal filler, copper powder, silver powder, nickel powder, silver coat copper powder, gold-coated copper powder, silver-coated nickel powder, gold-coated nickel powder and the like can be used. These metal powders can be produced by an electrolytic method, an atomizing method, or a reducing method. Examples of the shape of the metal powder include a spherical shape, a flake shape, a fibrous shape, and a dendritic shape.

In the present embodiment, the thickness of the shield layer 113 may be appropriately selected according to the required electromagnetic shielding effect and repeated bending / sliding resistance, but in the case of a metal foil, it is 12 μm from the viewpoint of ensuring breaking elongation. The following is preferable.

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

When the conductive adhesive layer 111 contains a thermoplastic resin, for example, a styrene resin, a vinyl acetate resin, a polyester resin, a polyethylene resin, a polypropylene resin, an imide resin, an acrylic resin, or the like can be used as the thermoplastic resin. Can be used. These resins may be used alone or in combination of two or more.

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

The thermosetting resin contains, 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, an amide group, a hydroxyl group, or the like. The second functional group may be selected according to the first functional group. For example, when the first functional group is an epoxy group, it may be a hydroxyl group, a carboxyl group, an epoxy group, an amino group or the like. Specifically, for example, when the first resin component is an epoxy resin, the second resin component is an epoxy group-modified polyester resin, an epoxy group-modified polyamide resin, an epoxy group-modified acrylic resin, an epoxy group-modified polyurethane polyurea resin, or a carboxyl. A group-modified polyester resin, a carboxyl group-modified polyamide resin, a carboxyl group-modified acrylic resin, a carboxyl group-modified polyurethane polyurea resin, a urethane-modified polyester resin, or the like can be used. Among these, a carboxyl group-modified polyester resin, a carboxyl group-modified polyamide resin, a carboxyl group-modified polyurethane polyurea resin, and a urethane-modified polyester resin are preferable. When the first resin component is a hydroxyl group, the second resin component includes an epoxy group-modified polyester resin, an epoxy group-modified polyamide resin, an epoxy group-modified acrylic resin, an epoxy group-modified polyurethane polyurea resin, and a carboxyl group-modified polyester resin. A carboxyl group-modified polyamide resin, a carboxyl group-modified acrylic resin, a carboxyl group-modified polyurethane polyurea resin, a urethane-modified polyester resin, and the like can be used. Among these, a carboxyl group-modified polyester resin, a carboxyl group-modified polyamide resin, a carboxyl group-modified polyurethane polyurea resin, and a urethane-modified polyester resin are preferable.

The thermosetting resin may contain a curing agent that accelerates the 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 curing agent, a phenol-based curing agent, a cationic curing agent, or the like can be used. These can be used alone or in combination of two or more. In addition, an antifoaming agent, an antioxidant, a viscosity modifier, a diluent, an antioxidant, a leveling agent, a coupling agent, a coloring agent, a flame retardant and the like may be included as optional components.

The conductive filler is not particularly limited, and for example, a metal filler, a metal-coated resin filler, a carbon filler, and a mixture thereof can be used. Examples of the metal filler include copper powder, silver powder, nickel powder, silver coat 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 atomizing method, a reducing method, or the like. Of these, any of silver powder, silver-coated copper powder and copper powder is preferable.

From the viewpoint of contact between the fillers, the conductive filler has an average particle size of preferably 1 μm or more, more preferably 3 μm or more, 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, flaky, dendritic, fibrous, or the like.

The content of the conductive filler can be appropriately selected depending on the intended use, but is preferably 5% by mass or more, more preferably 10% by mass or more, preferably 95% by mass or less, more preferably 95% by mass or less in the total solid content. It is 90% by mass or less. From the viewpoint of embedding property, it is preferably 70% by mass or less, more preferably 60% by mass or less. Further, when anisotropic conductivity is realized, it is preferably 40% by mass or less, more preferably 35% by mass or less.

The thickness of the conductive adhesive layer 111 is preferably 1 μm to 50 μm from the viewpoint of embedding property.

Hereinafter, the electromagnetic wave shielding film of the present disclosure will be described in more detail with reference to Examples. The following examples are exemplary and are not intended to limit the invention.

<Manufacturing of electromagnetic wave shield film>
A release agent was applied to the surface of the release film made of polyethylene terephthalate (PET) having a predetermined gloss on the insulating layer side using a wire bar to form a release agent layer having a predetermined thickness. The thickness of the release agent layer was measured by an optical interference type film thickness meter (ST-2000-DLXn manufactured by K-MAC). A composition for an insulating protective layer is applied to the surface of the release film on which the release agent layer is formed, using a wire bar, and heat-dried to insulate the film to a thickness of 5 μm. A protective layer was formed. Next, a 0.1 μm Ag-deposited film was formed as a shield layer on the insulating protective layer. The composition for a conductive adhesive layer was applied onto the shield layer with a wire bar, and then dried at 100 ° C. for 3 minutes to form a conductive adhesive layer having a thickness of 15 μm.

An alkyd resin-based release agent was used. The insulating protective layer has a two-layer structure consisting of a hard coat layer of a polyester-based transparent resin having a thickness of 2 μm and a soft coat layer of a carbon black-containing epoxy-based black resin having a thickness of 3 μm. The composition for the conductive adhesive layer was prepared by using conductive particles of silver-coated copper powder in a phosphorus-based flame retardant-containing epoxy resin.

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

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

<Evaluation of peelability>
After adhering the electromagnetic wave shield film to the printed wiring substrate, the peeling film on the surface is peeled off using a peeling strength tester (PFT50S manufactured by Palmec Co., Ltd.) with a sample width of 10 mm, a peeling angle of 170 °, and a peeling speed of 1000 mm / min. Was evaluated. When the release film peels off without material breakage at the time of peeling, the peelability is good, and when the release film breaks at the time of peeling, the peelability is poor.

<Measurement of glossiness>
The 85 ° glossiness was performed in accordance with JIS Z 8741 using a portable glossiness meter (BYK Gardner Micro-Gloss, Toyo Seiki Seisakusho).

The glossiness of the release film was measured with respect to the surface of the release film on the protective layer side before the release agent was applied.

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

<Evaluation of concealment>
The shielded wiring board to which the electromagnetic wave shield film was adhered was placed on a flat table surface, and it was evaluated whether the circuit pattern could be visually recognized from the electromagnetic wave shield film side in an environment where the surface illuminance of the shielded wiring board was 800-1000 lux. .. The viewing angle was in the range of 0 to 180 degrees with respect to the surface of the electromagnetic wave shield film. When the circuit pattern cannot be visually recognized, the concealment property is good (◯), and when the circuit pattern can be visually recognized, the concealment property is poor (×).

(Example 1)
As the release film, a PET film having a thickness of 50 μm and an 85 ° glossiness 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 ° glossiness of the insulating protective layer after peeling the release film was 9.2. Moreover, the concealing property was good.

(Example 2)
As the release film, a PET film having a thickness of 50 μm and an 85 ° glossiness 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 ° glossiness of the insulating protective layer after peeling the release film was 9.6. Moreover, the concealing property was good.

(Comparative Example 1)
As the release film, a PET film having a thickness of 50 μm and an 85 ° glossiness 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 ° glossiness of the insulating protective layer after peeling the release film was 35.4. Moreover, the concealment property was poor.

(Comparative Example 2)
As the release film, a PET film having a thickness of 50 μm and an 85 ° glossiness 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 ° glossiness of the insulating protective layer after peeling the release film was 15.5. Moreover, the concealment property was poor.

(Comparative Example 3)
As the release film, a PET film having a thickness of 50 μm and an 85 ° glossiness 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.

The electromagnetic wave shield film of the present disclosure has a low glossiness of the insulating protective layer and can easily peel off the release film, and is useful as an electromagnetic wave shield film or the like.

101 Electromagnetic wave shield film 102 Printed wiring board 111 Conductive adhesive layer 112 Insulation protective layer 113 Shield layer 114 Release agent layer 115 Release film 121 Base layer 122 Circuit pattern 123 Adhesive layer 124 Insulation film

Claims (3)

Insulation protective layer and
With a conductive adhesive layer,
A release film provided on the surface of the insulating protective layer opposite to the conductive adhesive layer via a release agent layer is provided.
The insulating protective layer has an 85 ° glossiness of less than 15.
The thickness of the releasing agent layer, 0.1 [mu] m or more state, and are less than 4 [mu] m,
The release film is an electromagnetic wave shielding film having an 85 ° glossiness of less than 3. The electromagnetic wave shielding film according to claim 1, wherein the insulating protective layer contains a black colorant. A wiring board having a base layer, a circuit pattern provided on the base layer, and an insulating film adhered to the base layer so as to cover the circuit pattern.
A shielded wiring board comprising the electromagnetic wave shielding film according to claim 1 or 2, which is adhered onto the insulating film and the release film is removed.

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