TW202313328A - Electromagnetic wave shield film - Google Patents

Abstract

Provided is an electromagnetic wave shield film having excellent blackness regardless of the constitutive composition of a black layer. An electromagnetic wave shield film 1 is provided on a surface thereof with a protective layer 2. The protective layer 2 has a black protective layer 21. The minimum autocorrelation length Sal of the surface of the protective layer 2 is 10 [mu]m or less. The developed area ratio Sdr of the interface is 200% or more. The ratio [Sdr/Sal] of the Sdr to the Sal is at least 50. The brightness L* on the protective layer 2 side is preferably 24 or less.

Description

Electromagnetic wave shielding film

field of invention The disclosed invention relates to an electromagnetic wave shielding film.

Background technique Until now, mobile devices such as smartphones and tablet terminals have used flexible printed circuit boards (FPCs) with electromagnetic shielding films attached to them to block electromagnetic waves generated from inside or from outside.

An electromagnetic wave shielding film (hereinafter, sometimes simply referred to as "shielding film") is used for shielding printed wiring boards. For example, the shielding film used next to the printed wiring board has: a shielding layer such as a metal layer; a conductive adhesive sheet provided on the surface of the shielding layer; and a protective layer for protecting the shielding layer.

For example, an image display device equipped with a plasma display panel (PDP), a liquid crystal display (LCD), an organic EL display, etc. requires light-shielding properties for the electromagnetic wave shielding film used therein.

In recent years, from the viewpoints of visibility and the like, there is a tendency to demand an electromagnetic wave shielding film more excellent in light-shielding properties. Patent Documents 1 and 2 disclose an electromagnetic wave shield having a black layer and improving the blackness.

prior art literature patent documents Patent Document 1: Japanese Patent Laid-Open No. 2009-76824 Patent Document 2: Japanese Patent Laid-Open No. 2004-288972

Summary of the invention The problem to be solved by the invention However, in the electromagnetic wave shields disclosed in Patent Documents 1 and 2, the blackness is increased by making the colorant in the black layer a specific type. In such a method of restricting the composition of the black layer, such as specifying the type of colorant, even if the blackness is improved, the masking film or each layer constituting the masking film may deteriorate in other performances, such as performance degradation that should have conventionally.

Therefore, an object of the disclosed invention is to provide an electromagnetic wave shielding film having excellent blackness regardless of the structural composition of the black layer.

means to solve problems The inventors of the presently disclosed invention have conducted intensive research to achieve the above object, and found that, by providing a protective layer containing a black layer on the surface of the electromagnetic wave shielding film, and making the surface of the protective layer a specific shape, regardless of the structural composition of the black layer It can have excellent blackness in any case. This disclosure invention was completed based on these knowledge.

The disclosed invention provides an electromagnetic wave shielding film, which has a protective layer on the surface, and the protective layer has a black protective layer, the minimum autocorrelation length Sal on the surface of the protective layer is 10 μm or less, and the interface expansion area ratio Sdr is 200% or more, and The ratio [Sdr/Sal] of the above-mentioned Sdr to the above-mentioned Sal is 50 or more.

The protective layer may include: a black protective layer located inside the electromagnetic wave shielding film; and a transparent protective layer or a black protective layer located on the surface of the electromagnetic wave shielding film.

The above-mentioned black protective layer may be located on the surface of the above-mentioned electromagnetic wave shielding film.

The lightness L ^* on the protective layer side is preferably 24 or less.

The root mean square slope Sdq of the surface of the protective layer is preferably 2.0 or more.

The 85° glossiness on the protective layer side is preferably 25 or less.

Invention effect The electromagnetic wave shielding film of the disclosed invention has excellent blackness regardless of the structure and composition of the black layer. Therefore, the performance of the shielding film can be maintained without changing the structural composition of the black layer, and the blackness is excellent. In addition, since the blackness is excellent, the light-shielding property is excellent. In the state where the shielding film has been bonded to the printed wiring board, the appearance of the printed wiring board or the visibility of the printed characters when printing on the surface of the protective layer of the shielding film and the printed wiring The concealment of the circuit pattern of the board is excellent.

form for carrying out the invention [Electromagnetic wave shielding film] The electromagnetic shielding film of the disclosed invention has at least a protective layer. The above-mentioned protective layer is provided on the surface of the above-mentioned electromagnetic wave shielding film. The said electromagnetic wave shielding film may be equipped with another layer other than the said protective layer. Examples of the above-mentioned other layers include an electromagnetic wave shielding layer exhibiting electromagnetic wave shielding properties, a conductive adhesive layer, and the like. Each layer constituting the above-mentioned electromagnetic wave shielding film may be a single layer or a multi-layer.

(The protective layer) The said protective layer has the function of protecting each internal layer, such as the said electromagnetic wave shielding layer, in the said electromagnetic wave shielding film. The above-mentioned protective layer has at least a black protective layer (black protective layer). The above protective layer may also be an insulating layer (insulating protective layer).

The above-mentioned protective layer may be a single layer or multiple layers. When the protective layer is a multilayer, for example, it may be a laminate of two or more layers having different physical properties such as material, hardness, or modulus of elasticity. For example, a laminate of a low-hardness outer layer and a high-hardness inner layer has a cushioning effect on the outer layer, so that electromagnetic waves applied to the metal layer, etc. Shielding pressure. Therefore, damage to the electromagnetic wave shielding layer due to the level difference provided on the printed wiring board can be suppressed.

When the protective layer is a single layer, the protective layer of the single layer is the black protective layer, and the black protective layer is located on the surface of the electromagnetic wave shielding film. When the protective layer is a multiple layer, at least one of the protective layers is the black protective layer. Also, when the above-mentioned protective layer is a multilayer, it is preferable to have at least one black protective layer inside (that is, outside the surface) of the above-mentioned electromagnetic wave shielding film. Also, when the protective layer is a multiple layer, it is more preferable that the protective layer located on the surface of the electromagnetic wave shielding film is a transparent protective layer or a black protective layer. In this case, the protective layer located on the surface can be made to exhibit a function different from that of the black protective layer located inside, such as excellent surface hardness. In addition, when the above-mentioned protective layer is a multi-layer, when there are multiple layers of black protective layers, the multiple black protective layers may be layers with the same composition (content of coloring agent, etc.) or thickness, or different layers. layers.

One embodiment of the electromagnetic wave shielding film described above will be described with reference to FIGS. 1 to 3 . 1 to 3 are schematic cross-sectional views showing one embodiment of the above-mentioned electromagnetic wave shielding film.

The electromagnetic wave shielding film 1 shown in FIG. 1 has: a conductive adhesive layer 4; an electromagnetic wave shielding layer 3, which is adjacent to one side of the conductive adhesive layer 4; and a protective layer 2, which is arranged on the surface of the electromagnetic wave shielding layer 3. (The surface opposite to the conductive adhesive layer 4). The protective layer 2 is composed of a single layer of the black protective layer 21 . In other words, the electromagnetic wave shielding film 1 includes the conductive adhesive layer 4 , the electromagnetic wave shielding layer 3 and the black protective layer 21 in this order. In addition, the electromagnetic wave shielding layer 3 may not be provided.

The electromagnetic wave shielding film 1 shown in FIG. 2 , its protective layer 2 is composed of two layers, a black protective layer 21 and a transparent protective layer 22 , which is different from the electromagnetic wave shielding film 1 shown in FIG. 1 . The transparent protective layer 22 is located on the surface of the electromagnetic wave shielding film 1 . The electromagnetic wave shielding film 1 shown in FIG. 3 is not the transparent protective layer 22 but a black protective layer 23 on the protective layer on its surface, which is different from the electromagnetic wave shielding film 1 shown in FIG. 2 .

The minimum autocorrelation length Sal of the surface of the protective layer (such as 2a shown in Fig. 1 to Fig. 3 ) is less than 10 μm, preferably less than 9.7 μm, preferably less than 6.0 μm. The smaller the above-mentioned Sal, the smaller the height of each unevenness on the surface. Said Sal is, for example, 1 μm or more, preferably 2 μm or more.

The interface development area ratio Sdr of the surface of the protective layer is at least 200%, preferably at least 250%, and preferably at least 300%. The above Sdr indicates how much the expanded area (surface area) of the defined area increases relative to the area of the defined area, and the Sdr of a completely flat surface is 0%.

The ratio [Sdr/Sal] of the above-mentioned Sdr (%) to the above-mentioned Sal (μm) on the surface of the protective layer is 50 or more, preferably 53 or more, preferably 60 or more.

In the above electromagnetic wave shielding film, since the above-mentioned Sal, the above-mentioned Sdr, and the above-mentioned ratio [Sdr/Sal] are respectively within the above-mentioned ranges, each unevenness on the surface of the protective layer is small and the developed surface area is large. Thereby, the reflectance of visible light incident on the surface of the protective layer can be reduced. Therefore, as long as the shape of the surface of the protective layer is set within the above range, no matter what the structural composition of the black protective layer is, compared to the case where the shape of the surface of the protective layer is not set within the above range, it will have a more excellent black color. Spend. In addition, the above-mentioned electromagnetic wave shielding film sets the Sal and Sdr on the surface of the protective layer within a specific range, and does not intend to increase the height of the concave-convex shape on the surface of the protective layer. An embedding layer such as a release treatment layer for embedding particles. Therefore, compared with the conventional electromagnetic wave shielding film, the productivity, curling resistance, particle drop-off resistance, etc. of the electromagnetic wave shielding film will not be reduced.

The root-mean-square slope Sdq of the surface of the protective layer is preferably 2.0 or higher, preferably 3.0 or higher, more preferably 3.5 or higher. When said Sdq is 2.0 or more, there exists a tendency for the blackness of the surface of a protective layer to improve.

The arithmetic average height Sa of the surface of the protective layer is preferably 0.4-2.0 μm, more preferably 0.5-1.5 μm. If the arithmetic mean height Sa is within the above range, it is preferable from the viewpoint of the balance between glossiness and productivity. The maximum peak height Sp on the surface of the protective layer is preferably 2.5-9.0 μm, preferably 3.0-7.0 μm. If the maximum peak height Sp is within the above range, it is preferable from the viewpoint of the balance between glossiness and productivity. The maximum trough depth Sv on the surface of the protective layer is preferably 2.0-7.0 μm, more preferably 3.0-7.0 μm. When the maximum trough depth Sv is within the above range, it is preferable from the viewpoint of the balance between glossiness and productivity. The maximum height Sz of the surface of the protective layer is preferably 6.0-20.0 μm, more preferably 6.5-15.0 μm. If the maximum height Sz is within the above range, it is preferable from the viewpoint of the balance between glossiness and productivity.

Each layer constituting the above-mentioned protective layer preferably contains a binder component. Examples of the above-mentioned binder components include thermoplastic resins, thermosetting resins, active energy ray-curing compounds, and the like. The said binder component may use only 1 type, and may use 2 or more types.

The aforementioned thermoplastic resins include, for example: polystyrene resins, vinyl acetate resins, polyester resins, polyolefin resins (such as polyethylene resins, polypropylene resin compositions, etc.), polyimide resins , Acrylic resin, etc. The above-mentioned thermoplastic resins may be used alone, or two or more kinds may be used.

Examples of the thermosetting resin include both thermosetting resins (thermosetting resins) and resins obtained by curing the thermosetting resins. Examples of the thermosetting resin include phenolic resins, epoxy resins, urethane resins, melamine resins, and alkyd resins. The above-mentioned thermosetting resins may be used alone, or two or more kinds may be used.

The above-mentioned epoxy resins include, for example: bisphenol-type epoxy resins, spiro-ring epoxy resins, naphthalene-type epoxy resins, biphenyl-type epoxy resins, terpene-type epoxy resins, epoxy Propyl ether type epoxy resin, glycidylamine type epoxy resin, novolac type epoxy resin, etc.

Examples of the bisphenol epoxy resin include bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, and tetrabromobisphenol A epoxy resin. The above-mentioned glycidyl ether type epoxy resin may, for example, be ginseng(glycidoxyphenyl)methane, tetrakis(glycidoxyphenyl)ethane or the like. As the said glycidylamine type epoxy resin, tetraglycidyl diamino diphenyl methane etc. are mentioned, for example. Examples of the novolak-type epoxy resin include cresol novolac-type epoxy resins, phenol novolac-type epoxy resins, α-naphthol novolac-type epoxy resins, and brominated phenol novolac-type epoxy resins.

Examples of the active energy ray-curable compound include both compounds curable by irradiation with active energy ray (active energy ray-curable compound) and compounds obtained by curing the above-mentioned active energy ray-curable compound. The active energy ray-curing compound is not particularly limited, and examples thereof include polymerizable compounds having one or more (preferably two or more) radical reactive groups (such as (meth)acryl groups) in the molecule. The above-mentioned active energy ray-curable compound may be used alone, or two or more kinds may be used.

The above-mentioned black protective layer preferably contains a colorant. The above-mentioned colorant is preferably a black-based colorant. The above-mentioned black coloring agent can use known or customary coloring agents (pigments, dyes, etc.) for presenting black, for example: carbon black (furnace black, channel black, acetylene black, thermal carbon black, lamp black, pine smoke etc.), graphite, copper oxide, manganese dioxide, aniline black, perylene black, titanium black, cyan black, activated carbon, ferrite (non-magnetic ferrite, magnetic ferrite, etc.), magnetite, oxide Chromium, iron oxide, molybdenum disulfide, chromium complexes, anthraquinone colorants, zirconium nitride, etc. One type of black coloring agent may be used, or two or more types may be used. Moreover, the coloring agent which has the function of a black coloring agent by combining and blending the coloring agent which expresses the color other than black can also be used.

The above-mentioned protective layer may also contain other components other than the above-mentioned components within the scope of not impairing the effects of the presently disclosed invention. Examples of other ingredients mentioned above include hardeners, hardening accelerators, plasticizers, flame retardants, defoamers, viscosity modifiers, antioxidants, diluents, anti-settling agents, fillers, other colorants, leveling agents , coupling agent, ultraviolet absorber, tackifying resin, anti-caking agent, etc. The above-mentioned other components may be used alone or in combination of two or more.

The thickness of the protective layer is not particularly limited, and can be appropriately set as required, preferably 1-20 μm, preferably 2-15 μm, more preferably 3-10 μm. When the said thickness is 1 micrometer or more, the internal layer body can be protected more fully. When the said thickness is 20 micrometers or less, it will be excellent in softness and flexibility, and it is also economically advantageous.

When the protective layer is a multiple layer, the thickness of the protective layer (such as a transparent protective layer) located on the surface of the electromagnetic wave shielding film is preferably 0.1-10 μm, preferably 0.5-5 μm. Also, the thickness of the black protective layer located inside the electromagnetic wave shielding film is preferably 0.5-15 μm, preferably 1-10 μm.

(Electromagnetic wave shielding layer) As the above-mentioned electromagnetic wave shielding layer, known or commonly used shielding layers having electromagnetic wave shielding properties can be used. The above-mentioned electromagnetic wave shielding layer preferably contains a metal layer therein. The above-mentioned electromagnetic wave shielding layer may be any one of a single layer and a multi-layer.

The metal constituting the above metal layer can be, for example, gold, silver, copper, aluminum, nickel, tin, palladium, chromium, titanium, zinc or alloys thereof. The aforementioned metal layer is preferably a metal plate or metal foil. That is, the metal layer is preferably a copper plate (copper foil) or a silver plate (silver foil).

The thickness of the electromagnetic wave shielding layer is preferably 0.01-10 μm. If the above-mentioned thickness is more than 0.01 μm, more sufficient shielding performance can be obtained. Flexibility will become more favorable as the said thickness is 10 micrometers or less.

(conductive adhesive layer) The said conductive adhesive layer has adhesiveness and electroconductivity for bonding the said electromagnetic wave shielding film to a printed wiring board, for example. The conductive adhesive layer is preferably formed adjacent to the electromagnetic wave shielding layer. The conductive adhesive layer may be either a single layer or a multilayer.

The conductive adhesive layer preferably contains a binder component and conductive particles that can function as an adhesive. Examples of the above-mentioned binder components include thermoplastic resins, thermosetting resins, active energy ray-curing compounds, and the like. The above-mentioned thermoplastic resin, thermosetting resin, and active energy ray-curable compound can be exemplified by the above-mentioned binder components that may be contained in the protective layer, respectively. The said binder component may use only 1 type, and may use 2 or more types.

Wherein, the above-mentioned binder component is preferably a thermosetting resin. In this case, after arranging the electromagnetic wave shielding film on the printed wiring board, the adhesive component can be hardened by pressurization and heating, and adhesiveness becomes more favorable.

When the above-mentioned binder component contains a thermosetting resin, the components constituting the above-mentioned binder component may also contain a curing agent for promoting a thermosetting reaction. The above-mentioned curing agent can be appropriately selected according to the type of the above-mentioned thermosetting resin. The above curing agents may be used alone or in combination of two or more.

The content ratio of the adhesive component in the conductive adhesive layer is not particularly limited, but it is preferably 40-98% by mass, more preferably 50-97% by mass, and more preferably 100% by mass of the total amount of the conductive adhesive layer. It is preferably 60-96% by mass, more preferably 70-95.5% by mass, especially preferably 75-95% by mass. When the said content rate is 40 mass % or more, the adhesiveness to a printed wiring board will become more excellent. Electroconductive particle can be contained in sufficient amount as the said content rate is 98 mass % or less.

Examples of the above-mentioned conductive particles include metal particles, metal-coated resin particles, metal fibers, carbon fillers, carbon nanotubes, and the like. The said electroconductive particle may use only 1 type, and may use 2 or more types.

The said metal particle and the metal which comprise the coating part of the said metal clad resin particle include gold, silver, copper, nickel, zinc, etc., for example. One of the above metals may be used alone, or two or more of them may be used.

Specifically, examples of the metal particles include copper particles, silver particles, nickel particles, silver-coated copper particles, gold-coated copper particles, silver-coated nickel particles, gold-coated nickel particles, and silver-coated alloy particles. The above-mentioned silver-clad alloy particles include, for example, silver-clad copper alloy particles in which copper-containing alloy particles (for example, copper alloy particles composed of an alloy of copper, nickel, and zinc) are coated with silver. The above-mentioned metal particles can be produced by an electrolysis method, an atomization method, a reduction method, or the like.

Among them, the above-mentioned metal particles are preferably silver particles, silver-coated copper particles, and silver-coated copper alloy particles. Silver-coated copper particles and silver-coated copper alloy particles are particularly preferable in view of excellent electrical conductivity, suppression of oxidation and aggregation of metal particles, and reduction in cost of metal particles.

As for the shape of the said electroconductive particle, spherical shape, flake shape (scale shape), dendritic shape, fibrous shape, amorphous shape (polyhedron) etc. are mentioned.

The median diameter (D50) of the above-mentioned conductive particles is preferably 1-50 μm, more preferably 3-40 μm. When the said median diameter is 1 micrometer or more, the dispersibility of electroconductive particle will be favorable and aggregation will be suppressed, and it will be hard to oxidize. Electroconductivity will become favorable as the said average particle diameter is 50 micrometers or less. The above-mentioned median diameter can be measured from the volume-based particle size distribution.

The content ratio of the conductive particles in the conductive adhesive layer is not particularly limited, but it is preferably 2-80% by mass, more preferably 5-60% by mass, and more preferably 100% by mass of the total amount of the conductive adhesive layer. Preferably, it is 10 to 40% by mass. When the said content ratio is 2 mass % or more, electroconductivity will become more favorable. If the said content ratio is 80 mass % or less, a sufficient amount of adhesive components can be contained, and the adhesiveness to a printed wiring board will become more favorable.

The said conductive adhesive layer can be set as the layer body which has isotropic conductivity or anisotropic conductivity as needed. When the conductive adhesive layer has anisotropic conductivity, the electromagnetic wave shielding film preferably has the structure of the electromagnetic wave shielding layer (for example, [protective layer/electromagnetic wave shielding layer/conductive adhesive layer]). When the conductive adhesive layer has isotropic conductivity, the electromagnetic shielding film may have a structure without the electromagnetic shielding layer (for example, [protective layer/conductive adhesive layer]).

In the range which does not impair the effect of this disclosure, the said electroconductive adhesive agent layer may contain other components other than the said each component. The above-mentioned other components can be exemplified as the components contained in the known or customary adhesive layer. The other ingredients mentioned above can be for example: hardening accelerators, plasticizers, flame retardants, defoamers, viscosity regulators, antioxidants, diluents, anti-settling agents, fillers, colorants, leveling agents, coupling agents, UV absorbers, tackifying resins, anti-caking agents, etc. The above-mentioned other components may be used alone or in combination of two or more.

The thickness of the conductive adhesive layer is preferably 1-40 μm, preferably 5-30 μm. When the said thickness is 1 micrometer or more, the adhesive strength with respect to an adherend becomes more favorable. When the said thickness is 40 micrometers or less, cost can be suppressed, and the product provided with the said electroconductive adhesive layer can be designed lightly and thinly. In addition, when the adhesive component (binder component) constituting the conductive adhesive layer begins to flow due to heating or the like and penetrates into the opening formed in the adherend, the thickness of the conductive adhesive layer at this time is The thickness of the adhesive layer in the area that does not penetrate into the opening.

The above-mentioned electromagnetic wave shielding film may have a separator (peeling film) on the protective layer side and/or the conductive adhesive layer side. The separator is laminated so that it can be peeled off from the electromagnetic wave shielding film. The separator is an element to be protected by covering with a protective layer or a conductive adhesive layer, and it will be peeled off when using the electromagnetic wave shielding film.

Examples of the separator include: polyethylene terephthalate (PET) film, polyethylene film, polypropylene film, and one whose surface is coated with a release agent such as a fluorine-based release agent or a long-chain alkyl acrylate-based release agent. Plastic film or paper etc.

The thickness of the above separator is preferably 10-200 μm, preferably 15-150 μm. When the above-mentioned thickness is 10 μm or more, the protection performance will be more excellent. When the said thickness is 200 micrometers or less, it becomes easy to peel off a separator at the time of use.

The above electromagnetic wave shielding film may further have an anchor coating layer formed between the protective layer and the electromagnetic wave shielding layer. With such a structure, the adhesion between the electromagnetic wave shielding layer and the protective layer becomes better.

Examples of materials for forming the above-mentioned anchor coating layer include: urethane-based resins, acrylic resins, core-shell composite resins with urethane-based resins as shells and acrylic resins as cores, and epoxy-based resins. , polyimide resin, polyamide resin, melamine resin, phenol resin, urea-formaldehyde resin, blocked isocyanate obtained by reacting a blocking agent such as phenol with polyisocyanate, polyvinyl alcohol, polyethylene pyrrolidone etc. One of the above materials may be used alone, or two or more of them may be used.

The lightness L ^* of the protective layer side of the electromagnetic shielding film is preferably 24 or less. The above-mentioned lightness L ^* is the lightness specified in the L ^* a ^* b ^* color system. The above-mentioned lightness L ^* is a value measured from the protective layer side with respect to the above-mentioned electromagnetic wave shielding film on the outermost surface of the above-mentioned protective layer, and when a separator is provided, the separator is peeled off and then measured. In addition, in the laminated structure composed of the above-mentioned protective layer and the above-mentioned conductive adhesive layer, it is particularly preferable that the lightness L ^* measured from the protective layer side is within the above-mentioned range. When the above-mentioned lightness L ^* is 24 or less, the blackness is high and the concealability is further excellent. The said lightness L ^* can be measured based on JISZ8722 (2009).

The 85° glossiness of the protective layer side of the electromagnetic shielding film is preferably 25 or less, preferably 22 or less. If the said 85 degree glossiness is 25 or less, the concealment|concealment of the circuit pattern of a printed wiring board will become more excellent in the state which bonded the shielding film to a printed wiring board. In addition, in the laminated structure composed of the above-mentioned protective layer and the above-mentioned conductive adhesive layer, it is particularly preferable that the 85° gloss measured from the protective layer side is within the above-mentioned range.

The 60° glossiness of the protective layer side of the electromagnetic shielding film is preferably 2.0 or less, preferably 1.5 or less. If the above-mentioned 60° gloss is less than 2.0, the aesthetics of the printed wiring board or the visibility of printed characters when printing on the surface of the protective layer of the shielding film will be more excellent when the shielding film is bonded to the printed wiring board. In addition, in the laminated structure composed of the above-mentioned protective layer and the above-mentioned conductive adhesive layer, it is particularly preferable that the 60° gloss measured from the protective layer side is within the above-mentioned range.

The above-mentioned glossiness is a value measured from the protective layer side with respect to the above-mentioned electromagnetic wave shielding film on the outermost surface of the above-mentioned protective layer, and when there is a separator, the separator is peeled off and then measured. The said glossiness can be measured by the method based on JISZ8741.

The reflectance of light at a wavelength of 450 nm on the protective layer side of the electromagnetic shielding film is preferably 5.0% or less, preferably 4.0% or less. If the above-mentioned reflectance is below 5.0%, the blackness will be further improved. In addition, in the laminated structure composed of the above-mentioned protective layer and the above-mentioned conductive adhesive layer, it is particularly preferable that the above-mentioned reflectance measured from the protective layer side is within the above-mentioned range.

The reflectance of light at a wavelength of 550 nm on the protective layer side of the electromagnetic shielding film is preferably 5.0% or less, preferably 4.0% or less. If the above-mentioned reflectance is below 5.0%, the blackness will be further improved. In addition, in the laminated structure composed of the above-mentioned protective layer and the above-mentioned conductive adhesive layer, it is particularly preferable that the above-mentioned reflectance measured from the protective layer side is within the above-mentioned range.

The reflectance of light at a wavelength of 650 nm on the protective layer side of the electromagnetic shielding film is preferably 5.0% or less, preferably 4.0% or less. If the above-mentioned reflectance is below 5.0%, the blackness will be further improved. In addition, in the laminated structure composed of the above-mentioned protective layer and the above-mentioned conductive adhesive layer, it is particularly preferable that the above-mentioned reflectance measured from the protective layer side is within the above-mentioned range.

The above-mentioned reflectance is a value measured from the protective layer side with respect to the above-mentioned electromagnetic wave shielding film on the outermost surface of the above-mentioned protective layer, and when there is a separator, the separator is peeled off and then measured. The said reflectance can be measured by the method based on JISZ8722.

The above-mentioned electromagnetic wave shielding film is preferably used for printed wiring boards, and is particularly preferably used for flexible printed wiring boards (FPC).

(Manufacturing method of electromagnetic wave shielding film) One embodiment of the manufacturing method of the above-mentioned electromagnetic shielding film will be described. When producing the electromagnetic wave shielding film 1 shown in FIG. 1, first, the laminated body of the protective layer 2 and the electromagnetic wave shielding layer 3, and the conductive adhesive layer 4 are produced individually. Then, the individually produced laminate and the conductive adhesive layer 4 are bonded together (lamination method). In addition, for the electromagnetic wave shielding film without the electromagnetic wave shielding layer 3 , the protective layer 2 and the conductive adhesive layer 4 are produced separately, and then the protective layer 2 and the conductive adhesive layer 4 are bonded together.

The protective layer 2 can be formed, for example, by coating (coating) a resin composition for forming the protective layer 2 on a transfer film such as a separator, and removing the solvent and/or partially hardening as necessary. Concavo-convex shapes are formed on the surface of the above-mentioned transfer film for coating the above-mentioned resin composition. By forming the above-mentioned protective layer in this way, the shape derived from the above-mentioned concavo-convex shape can be transferred to the surface of the protective layer. The concave-convex shape on the surface of the above-mentioned transfer film can be produced by known or customary methods, such as sandblasting, embedding particles in each layer constituting the transfer film so that they protrude from the surface of the transfer film, etc. In addition, by appropriately performing sandblasting conditions or adjusting the size of embedded particles to design the concave-convex shape formed on the surface of the transfer film, surface parameters such as Sal and Sdr on the surface of the protective layer can be adjusted. Then, the above-mentioned transfer film can be used as a separator in the above-mentioned electromagnetic wave shielding film.

A release treatment layer may also be provided on the surface of the above-mentioned transfer film having a concave-convex shape. Examples of the above-mentioned release treatment layer include layers formed by surface treatment with a release treatment agent such as silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide. In addition, when there is a release treatment layer, the thickness and shape of the release treatment layer can be appropriately set so that the unevenness of the surface does not disappear, that is, the transfer film has the above-mentioned unevenness.

The resin composition forming the above-mentioned protective layer contains, for example, a solvent (vehicle) in addition to each component contained in the above-mentioned protective layer. Examples of solvents include toluene, acetone, methyl ethyl ketone, methanol, ethanol, propanol, dimethylformamide and the like. The solid content concentration of the resin composition can be appropriately set in accordance with the thickness of the formed protective layer and the like.

A known coating method can be used for coating of the said resin composition. For example, gravure roll coater, reverse roll coater, touch roll coater, lip coater dip roll coater, rod coater, knife coater can be used Coating machine, spray coating machine, notch wheel coating machine, direct coating machine, slot die coating machine and other coating machines.

Next, the electromagnetic wave shielding layer 3 is formed on the surface of the protective layer 2 formed on the transfer film. The formation of the electromagnetic wave shielding layer 3 is preferably performed by vapor deposition or sputtering. Known or usual methods can be used for the vapor deposition method and the sputtering method described above. In this way, a laminate of the protective layer 2/electromagnetic wave shielding layer 3 was produced.

On the other hand, when producing the conductive adhesive layer 4, for example, the adhesive composition for forming the conductive adhesive layer 4 can be coated (coated) on a temporary base material or base material such as a separation membrane, and depending on It is necessary to remove the solvent and/or partially harden to form the conductive adhesive layer 4 .

The above-mentioned adhesive composition contains, for example, a solvent (vehicle) in addition to each component contained in the above-mentioned conductive adhesive layer. As a solvent, what was illustrated about the solvent which can be contained in the said resin composition is mentioned, for example. The solid content concentration of the above-mentioned adhesive composition can be appropriately set in accordance with the thickness of the conductive adhesive layer to be formed, and the like.

A known coating method can be used for coating the above-mentioned adhesive composition. For example, the above-mentioned coater used for coating the resin composition can be mentioned.

Next, the exposed surface (the side of the electromagnetic wave shielding layer 3 ) of the separately produced laminate was bonded to the conductive adhesive layer 4 to produce the electromagnetic wave shielding film 1 .

The electromagnetic wave shielding film 1 can also be manufactured by the method of laminating|stacking each layer sequentially as another aspect other than the said lamination method (direct coating method). For example, the electromagnetic wave shielding film 1 shown in FIG. 1 can be manufactured as follows: on the surface of the electromagnetic wave shielding layer 3 of the above-mentioned laminate, apply (coat) the adhesive composition for forming the conductive adhesive layer 4 material, and if necessary, remove the solvent and/or partially harden to form the conductive adhesive layer 4 .

A shielded printed wiring board can be produced using the above electromagnetic wave shielding film. For example, by bonding the conductive adhesive layer of the above electromagnetic wave shielding film to a printed wiring board (such as a cover layer), a shielded printed wiring board with the above electromagnetic wave shielding film bonded to the printed wiring board can be produced. In the above-mentioned shielded printed wiring board, the conductive adhesive layer can be thermally cured by, for example, subsequent heat and pressure treatment.

Example Hereinafter, one embodiment of the electromagnetic wave shielding film of the disclosed invention will be described in more detail based on examples, but the electromagnetic wave shielding film of the disclosed invention is not limited to these examples.

Embodiment 1~3 and comparative example 1~3 (forms a protective layer) A resin solution (solid content: 35% by mass) containing a polyester resin and an amino resin as a hardener is applied to the release-treated surface of the transfer film that has been made to protect The surface of the layer was formed into a shape having the surface parameters shown in Table 1, and the solvent was removed by heating, thereby forming a transparent protective layer.

Next, a resin solution (solid content: 20 mass %) mixed with carbon black in epoxy resin was applied to the surface of the transparent protective layer, and the solvent was removed by heating, thereby forming a black protective layer. In this manner, a protective layer in which a transparent protective layer (thickness 1 μm) and a black protective layer (thickness 3 μm) were sequentially laminated on the transfer film was produced.

(Formation of conductive adhesive layer) An adhesive composition (solid content: 30% by mass) in which copper powder is mixed with epoxy resin is applied to the release-treated surface of a PET film whose surface has been subjected to a release treatment, and the solvent is removed by heating. In this way, a conductive adhesive layer (thickness: 10 μm) was formed.

(Making electromagnetic wave shielding film) The above-mentioned conductive adhesive layer and the black protective layer of the above-mentioned protective layer were bonded together to produce an electromagnetic wave shielding film composed of a conductive adhesive layer/black protective layer/transparent protective layer.

(evaluate) About each electromagnetic wave shielding film produced in the Example and the comparative example, it evaluated as follows. The evaluation results are shown in Table 1.

(1) Surface parameters of the protective layer Using a confocal microscope (trade name "OPTELICS HYBRID", manufactured by Lasertec, objective lens 100 times), complying with ISO25178, on the surface of the transparent protective layer exposed by peeling the transfer film from the electromagnetic wave shielding film, the transparent Measure the arithmetic mean height Sa, maximum peak height Sp, maximum trough depth Sv, maximum height Sz, minimum autocorrelation length Sal, root mean square slope Sdq and interface expansion area ratio of the concave-convex shape formed on any 5 places on the surface of the protective layer Sdr. In addition, the cutoff wavelength of the S filter is set to 0.0025mm, and the cutoff wavelength of the L filter is set to 0.8mm.

(2) Gloss Using a portable glossmeter (trade name "Gardner micro gloss", manufactured by BYK), measured on the surface of the transparent protective layer exposed by peeling the transfer film from the electromagnetic wave shielding film. 60° glossiness and 85° glossiness of the concave-convex shape formed on the surface of the transparent protective layer.

(3) reflectivity Using a spectrophotometer (trade name "CM-26d", manufactured by KONICA MINOLTA Co., Ltd.), in accordance with JIS Z8722 (condition c), the exposed color of the transfer film from the electromagnetic wave shielding film was measured. On the surface of the transparent protective layer, the light reflectances at wavelengths of 450 nm, 550 nm, and 650 nm were measured.

(4) Lightness L ^* Lightness L was measured on the surface of the transparent protective layer exposed by peeling the transfer film from the electromagnetic wave shielding film using a spectrophotometer (trade name "Ci64UV", manufactured by X-rite Co., Ltd.) ^* .

[Table 1]

As can be seen from Table 1, compared with the electromagnetic wave shielding films (comparative examples 1-3) in which at least one of Sal, Sdr and [Sdr/Sal] is not in a specific range, the electromagnetic wave shielding films of the embodiments have lower lightness and blackness. excellent. Therefore, based on this example, it was confirmed that blackness can be improved by having a protective layer having a specific surface shape regardless of the composition of the black layer.

1: Electromagnetic wave shielding film 2: Protective layer 2a: Protective layer surface 3: Electromagnetic wave shielding layer 4: Conductive adhesive layer 21,23: Black protective layer 22: Transparent protective layer

FIG. 1 is a schematic cross-sectional view showing an embodiment of an electromagnetic wave shielding film disclosed in the present invention. Fig. 2 is a schematic cross-sectional view showing another embodiment of the electromagnetic wave shielding film of the disclosed invention. Fig. 3 is a schematic cross-sectional view showing yet another embodiment of the electromagnetic shielding film of the disclosed invention.

1: Electromagnetic wave shielding film

2: Protective layer

2a: Protective layer surface

3: Electromagnetic wave shielding layer

4: Conductive adhesive layer

21: Black protective layer

Claims (6)

An electromagnetic wave shielding film, which has a protective layer on the surface, and the protective layer has a black protective layer, the minimum autocorrelation length Sal on the surface of the protective layer is 10 μm or less, the interface expansion area ratio Sdr is 200% or more, and the Sdr is relative to The ratio [Sdr/Sal] of the aforementioned Sal is 50 or more. Such as the electromagnetic wave shielding film of claim 1, wherein the aforementioned protective layer has: A black protective layer located inside the aforementioned electromagnetic wave shielding film; and A transparent protective layer or a black protective layer located on the surface of the electromagnetic wave shielding film. The electromagnetic wave shielding film according to claim 1, wherein the black protective layer is located on the surface of the electromagnetic wave shielding film. The electromagnetic shielding film according to any one of claims 1 to 3, wherein the lightness L ^* on the protective layer side is 24 or less. The electromagnetic shielding film according to any one of claims 1 to 4, wherein the root mean square slope Sdq of the surface of the protective layer is 2.0 or more. The electromagnetic wave shielding film according to any one of claims 1 to 5, wherein the 85° gloss on the side of the protective layer is 25 or less.

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