KR102567422B1 - Electromagnetic wave shield film - Google Patents

Abstract

An object of the present invention is to realize an electromagnetic shield film that does not easily discolor due to wiping of fingerprints.
In order to solve the above problems, the electromagnetic shielding film according to the present invention includes an insulating layer 110 and a conductive layer 120, and the insulating layer 110 has a three-dimensional arithmetic average surface roughness Sa of 0.8 on the surface. Characterized in that it is ㎛ or more.

Description

Electromagnetic wave shield film {ELECTROMAGNETIC WAVE SHIELD FILM}

The present invention relates to an electromagnetic shielding film.

BACKGROUND ART [0002] In recent years, in smart phones and tablet type information terminals, etc., performance for transmitting large amounts of data at high speed is required. In order to transmit large amounts of data at high speed, it is necessary to use high-frequency signals. However, when a high-frequency signal is used, electromagnetic noise is generated from a signal circuit provided on a printed wiring board, and peripheral devices tend to malfunction. In order to prevent such a malfunction, it becomes important to shield the printed wiring board from electromagnetic waves.

In order to shield the printed wiring board, a method of obtaining a shield print wiring board by heating and pressing an electromagnetic wave shielding film having an insulating layer and a shield layer to the printed wiring board and bonding them has been studied (for example, See Patent Literature 1).

A protective film made of polyethylene terephthalate (PET) resin or the like is bonded to the surface of the insulating layer of the electromagnetic shielding film to prevent damage to the insulating layer or to protect it from foreign substances. The protective film is peeled off after bonding the electromagnetic wave shielding film to the printed wiring board. Until the protective film is peeled off, the surface of the insulating layer is protected, and the shielded printed wiring board can be handled with bare hands.

Japanese Unexamined Patent Publication No. 2004-095566

However, if the shielded printed wiring board after removing the protective film is handled with bare hands, fingerprints may adhere to the insulating layer from which the protective film has been removed. The location where the fingerprint adhered is discolored and the appearance is damaged, so there is a problem that the yield is lowered.

Even if a fingerprint is attached to the insulating layer, the electromagnetic wave shielding property is hardly affected. Therefore, discoloration of the insulating layer due to adhered fingerprints can be suppressed, and yield reduction of the shielded printed wiring board can be suppressed. As a method of suppressing discoloration of the insulating layer due to attached fingerprints, removing fingerprints can be considered. Detergents or solvents are generally used to remove fingerprints. However, in the case of the insulating layer of the electromagnetic shielding film, there is a concern that the electrical characteristics of the shielded printed wiring board may be affected, and detergents or solvents cannot be used.

In addition, in the case of a conventional electromagnetic shielding film, when the surface is rubbed with a non-woven fabric or the like to wipe off fingerprints, the surface state is locally changed, and the degree of discoloration is rather increased. Further, if the surface is rubbed with a large force, the insulating layer may be peeled off from the shielding layer and the electromagnetic shielding film may be damaged.

An object of the present invention is to realize an electromagnetic wave shielding film that is not easily discolored by wiping off fingerprints.

A first aspect of the electromagnetic shielding film of the present invention includes an insulating layer and a conductive layer, and the three-dimensional arithmetic average surface roughness Sa of the insulating layer on the surface is 0.8 μm or more.

In the first aspect of the electromagnetic shielding film, the 85° gloss on the surface of the insulating layer can be 20 or less.

A second aspect of the electromagnetic shielding film of the present invention includes an insulating layer and a conductive layer, and the insulating layer has a root mean square slope Sdq of 0.8 or more on the surface and an 85° glossiness of 10 or less.

A third aspect of the electromagnetic shielding film of the present invention includes an insulating layer and a conductive layer, and the insulating layer has a surface skewness Ssk of 0.1 or more and an 85° glossiness of 10 or less.

In each aspect of the electromagnetic shielding film, the insulating layer can have an L* value of 25 or less.

According to the electromagnetic shielding film of the present invention, discoloration due to wiping of fingerprints can be prevented from easily occurring.

1 is a cross-sectional view showing an electromagnetic wave shielding film according to an embodiment.
2 is a cross-sectional view showing an electromagnetic wave shielding film according to a modified example.
3 is a plot showing the relationship between the root mean square slope of the insulating layer and the glossiness.
4 is a plot showing the relationship between skewness and glossiness of an insulating layer.

Hereinafter, the electromagnetic wave shielding film of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be appropriately changed and applied within a range that does not change the gist of the present invention.

(electromagnetic wave shielding film)

1 is a schematic cross-sectional view schematically showing an electromagnetic wave shielding film of the present embodiment. As shown in FIG. 1 , the electromagnetic shielding film has an insulating layer 110 and a shielding layer 120 that is a conductive layer. An adhesive layer 130 may be provided on the surface opposite to the insulating layer 110 of the shielding layer 120, if necessary. By providing the adhesive layer 130, the electromagnetic wave shielding film can be easily bonded to the printed wiring board.

-Insulation layer-

The insulating layer 110 is provided to protect the shielding layer. In the electromagnetic shielding film of the present embodiment, the insulating layer 110 has a three-dimensional arithmetic mean surface roughness Sa, which is a parameter representing surface properties, of 0.8 μm or more, preferably 1.0 μm or more. When Sa is set to 0.8 µm or more, an insulating layer having a surface hardly discolored due to fingerprint wiping can be made. Here, the surface on which discoloration hardly occurs due to wiping off fingerprints is a surface on which fingerprints are attached by wiping with a wiping cloth or the like, and it is difficult to visually distinguish a surface on which fingerprints are not attached. It is a surface that becomes a state.

Also, from the viewpoint of the actual removability of fingerprint components, Sa is preferably 10 μm or less, more preferably 5 μm or less, and still more preferably 3 μm or less. The smaller Sa is to a certain extent, the advantage of being easy to peel the insulating layer from the peeling film described later can also be obtained. In addition, when Sa exceeds the above-mentioned value, it becomes difficult to wipe off the adhering fingerprint.

The degree of discoloration due to wiping of fingerprints can be evaluated qualitatively by sensory evaluation by visually observing the surface of the insulating layer 110 after wiping off fingerprints. In addition, it can be quantitatively evaluated according to the change in glossiness of the surface. As a quantitative evaluation method, a method of measuring 85° gloss on the surface of the insulating layer 110 after fingerprints are attached and wiped can be used. In this case, if the 85 degree glossiness after wiping after applying the fingerprint is preferably 20 or less, more preferably 10 or less, it becomes difficult to visually identify the traces of wiping the fingerprint. In addition, as another quantitative evaluation method, a method of measuring a difference between glossiness on the surface of the insulating layer 110 after fingerprints are attached and wiped and glossiness before fingerprints are attached may be used. That is, the smaller the difference between the glossiness of the surface of the insulating layer 110 after wiping after fingerprints are attached and the glossiness before fingerprints, the smaller the degree of discoloration due to fingerprint wiping. For example, in the case of 85 ° glossiness, if the difference in gloss between the glossiness after wiping and wiping with fingerprints and the glossiness before fingerprints is preferably 4 or less, more preferably 3 or less, fingerprints are not adhered. It is difficult to distinguish between the part and the part where fingerprints have been wiped by the naked eye.

In the electromagnetic shielding film of the present embodiment, parameters of the surface property other than Sa on the surface of the insulating layer 110 can be set as follows from the viewpoint of preventing discoloration due to wiping of fingerprints from easily occurring. The root mean square inclination Sdq is preferably 0.8 or more, more preferably 0.95 or more. The location where the fingerprint is attached tends to reflect light compared to the location where the fingerprint is not attached, and the area where the fingerprint is attached is greatly conspicuous. In addition, as the color tone of the surface of the insulating layer 110 is black and the L* value is small, the fingerprint attached portion tends to be conspicuous. On the other hand, if Sdq is to some extent large, it is possible to make the surface easy to scatter light to an appropriate degree, and it is possible to suppress the increase in reflection due to adhesion of fingerprints. In particular, when the L* value is 25 or less, increasing Sdq is effective for making the fingerprint attached portion inconspicuous.

From the standpoint of easy separation of the insulating layer from the release film described later, Sdq is preferably 10 or less, more preferably 7.0 or less, and still more preferably 3.0 or less.

The skewness Ssk is preferably 0.1 or more, more preferably 0.5 or more, still more preferably 1.0 or more. Ssk represents the symmetry of convex portions and concave portions based on the average surface on the uneven surface, and as Ssk increases, the component of the convex portions based on the average surface decreases, and parts other than the convex portions (valves) and flat portion) are relatively increased. For this reason, fingerprints can be easily wiped off by increasing Ssk to some extent.

In addition, Ssk is preferably 10 or less, more preferably 5.0 or less, and still more preferably 3.0 or less. By making Ssk into such a range, the effect of easy peeling of an insulating layer from the peeling film mentioned later is also expectable.

In addition, the maximum peak height Sp is preferably 8.0 μm or more. The root mean square deviation Sq is preferably 1.0 μm or more, more preferably 1.2 μm or more, still more preferably 1.3 μm or more. The protrusion height Spk is preferably 1.0 μm or more, more preferably 1.5 μm or more, still more preferably 1.7 μm or more. The void volume Vvc of the core portion is preferably 1.1 ml/m ² or more, more preferably 1.3 ml/m ² or more. The substantial volume Vmp of the peak part is preferably 0.07 ml/m ² or more, more preferably 0.08 ml/m ² or more, and even more preferably 0.1 ml/m ² or more.

Sp is preferably 20 μm or less, more preferably 18 μm or less, and still more preferably 15 μm or less. Sq is preferably 10 μm or less, more preferably 5.0 μm or less, and still more preferably 3.0 μm or less. Spk is preferably 10 μm or less, more preferably 5.0 μm or less, and still more preferably 3.0 μm or less. Vvc is preferably 10 ml/m ² or less, more preferably 5.0 ml/m ² or less, and still more preferably 3.0 ml/m ² or less. Vmp is preferably 1.0 ml/m ² or less, more preferably 0.5 ml/m ² or less, and still more preferably 0.3 ml/m ² or less. When Sp, Spk, Vvc, and Vmp are within the above-mentioned numerical ranges, respectively, the effect of easily peeling the insulating layer from the release film described later can be expected.

Further, a surface that is not easily discolored by wiping of a fingerprint may be defined by another parameter, not defined by Sa. For example, in order to make the surface resistant to discoloration due to wiping of fingerprints, a surface with a small proportion of the convexities relative to the average surface and a high height of the convexities is considered desirable. Therefore, Sp can be 7.0 μm or more, preferably 8.0 μm or more, and Ssk can be 0 or more, preferably 0.1 or more. In addition, Sp is 7.0 μm or more, preferably 8.0 μm or more, and Sdq can be 0.8 or more, preferably 0.9 or more. In addition, Sq can be 1.0 μm or more and Ssk can be 0 or more, preferably 0.1 or more. Further, Sq may be 1.0 μm or more, preferably 1.2 μm or more, and Sdq may be 0.8 or more, preferably 0.9 or more. In addition, Spk can be 1.0 μm or more and Ssk can be 0 or more, preferably 0.1 or more. In addition, Spk can be 1.0 μm or more, preferably 1.5 μm or more, and Sdq can be 0.8 or more, preferably 0.9 or more.

In addition, Sp can be 20 μm or less, preferably 18 μm or less, and Ssk can be 10 or less, preferably 5 or less. In addition, Sp can be 20 μm or less, preferably 18 μm or less, and Sdq can be 10 or less, preferably 3.0 or less. In addition, Sq can be 10 μm or less, preferably 5 μm or less, and Ssk can be 10 or less, preferably 5.0 or less. In addition, Sq can be 10 μm or less, preferably 5.0 μm or less, and Sdq can be 10 or less, preferably 3.0 or less. In addition, Spk can be 10 μm or less, preferably 5.0 μm or less, and Ssk can be 10 or less, preferably 5.0 or less. In addition, Spk can be 10 μm or less, preferably 5.0 μm or less, and Sdq can be 10 or less, preferably 3.0 or less. By setting it as such a range, the effect of peeling an insulating layer easily from a peeling film is also expectable.

In addition, the surface properties in the present invention are values measured based on ISO 25178-6:2010, and specific measurement methods are described in Examples.

The insulating layer 110 has a 60° glossiness before fingerprints are preferably 3 or less, more preferably 2 or less, still more preferably 1 or less. Further, the 85° glossiness is preferably 20 or less, more preferably 15 or less, even more preferably 10 or less, still more preferably 5 or less, and still more preferably 3 or less.

By setting the glossiness before fingerprint adhesion to such a value, scattering of light occurs to an appropriate degree on the surface of the insulating layer 110, and the glossiness is suppressed to an appropriate degree. In this way, discoloration due to wiping of fingerprints can be prevented from occurring more easily.

In particular, the 60° glossiness of the insulating layer 110 before fingerprints are attached is preferably 3 or less, more preferably 2 or less, still more preferably 1 or less, and the 85° glossiness is preferably 20 or less. , more preferably 15 or less, still more preferably 10 or less, even more preferably 5 or less, and even more preferably 3 or less, so that discoloration due to wiping of fingerprints is very difficult to occur on the surface. can do.

In addition, 60 degree glossiness and 85 degree glossiness in this indication can be measured by the method shown in an Example.

In particular, when Sdq is 0.8 or more, preferably 0.9 or more, and the 85° gloss is 10 or less, preferably 5 or less, and more preferably 3 or less, discoloration due to wiping of fingerprints can be easily prevented. there is.

Further, Ssk is greater than 0, preferably 0.1 or more, more preferably 0.5 or more, and the 85° gloss is 10 or less, preferably 5 or less, and more preferably 3 or less, so that fingerprint wiping can be performed. discoloration can be easily prevented.

In the present disclosure, a method for obtaining the insulating layer 110 is not particularly limited, and a known method may be used. For example, the concavo-convex shape of the release film is transferred to the insulating layer 110 by applying a resin composition for forming the insulating layer 110 to the surface of the release film having the concavo-convex shape imparted by embossing and drying it. method can be used. A method of forming the insulating layer 110 having a concavo-convex shape by coating and drying a resin composition containing particles for concavo-convex formation on the surface of the shielding layer 120 may be used. A method of spraying dry ice or the like on the surface of the insulating layer 110 may be used. After the active energy ray-curable composition is applied to the surface of the shielding layer 120, a mold having a concave-convex shape is pressed to cure the curable composition layer, and then the mold is peeled off. Other well-known methods can also be used.

Among these, from the viewpoint of productivity, a method of applying and drying a resin composition containing particles for concavo-convex formation to obtain the insulating layer 110 having a concavo-convex shape is preferable. In this case, the particles for forming irregularities are not particularly limited, but, for example, resin fine particles or inorganic fine particles can be used. Resin microparticles can be made into acrylic resin microparticles, polyacrylonitrile microparticles, polyurethane microparticles, polyamide microparticles, and polyimide microparticles. Further, the inorganic fine particles include calcium carbonate fine particles, calcium silicate fine particles, clay, kaolin, talc, silica fine particles, glass fine particles, diatomaceous earth, mica powder, alumina fine particles, magnesium oxide fine particles, zinc oxide fine particles, barium sulfate fine particles, aluminum sulfate fine particles, Calcium sulfate microparticles, magnesium carbonate microparticles, etc. can be used. These resin fine particles and inorganic fine particles may be used alone or in combination of a plurality thereof. From the viewpoint of enhancing the friction resistance of the insulating layer, inorganic fine particles are preferable.

The grains for forming irregularities have a 50% average particle diameter of preferably 2 µm or more, more preferably 4 µm or more, from the viewpoint of generating appropriate irregularities on the surface of the insulating layer 110 and obtaining a predetermined surface property. It is more preferable that it is ㎛ or more. Further, in order to suppress the whitening of the insulating layer, the 50% average particle size is preferably 30 μm or less, more preferably 20 μm or less.

The addition amount of the grains for forming irregularities to the insulating layer 110 is preferably 3% by mass or more, more preferably 5% by mass or more, from the viewpoint of obtaining a predetermined surface property. Further, from the viewpoint of suppressing whitening of the insulating layer, it is preferably 30% by mass or less, more preferably 20% by mass or less, and still more preferably 17% by mass or less.

A black colorant can be added to the insulating layer 110 . By adding a black colorant, the L* value of the insulating layer 110 can be reduced, and the visibility of markings (letters, figures, etc.) printed on the surface of the insulating layer can be improved. When the marking printed on the insulating layer 110 is white, the L* value is preferably 25 or less, more preferably 20 or less, and still more preferably 18 or less. And the L* value in this indication can be measured based on JIS Z 8781-4 (2013).

The black colorant can be a black pigment or a mixed pigment obtained by mixing a plurality of pigments in a reduced color to black. The black pigment may be any one or combination of carbon black, ketjen black, carbon nanotube (CNT), perylene black, titanium black, iron black, and aniline black, for example. As the mixed pigment, for example, pigments such as red, green, blue, yellow, purple, cyan, and magenta may be mixed and used.

The particle size of the black colorant should be as long as the required L* value can be realized, but from the viewpoint of dispersibility and reduction of the L* value, the average primary particle diameter is preferably 20 nm or more, and 100 nm or less it is desirable The average primary particle diameter of the black colorant can be obtained from the average value of about 20 primary particles observed from an image magnified by a transmission electron microscope (TEM) by about 50,000 to 1,000,000 times.

From the viewpoint of reducing the L* value, the amount of the black colorant added to the insulating layer 110 is preferably 0.5% by mass or more, and more preferably 1% by mass or more. However, the black colorant may be added as needed, and may not be added.

In addition, glossiness also affects the visibility of printing. Also from the viewpoint of the visibility of printing, the 60° glossiness of the insulating layer 110 is preferably 3 or less, more preferably 2 or less, still more preferably 1 or less. The 85° gloss is preferably 20 or less, more preferably 15 or less, even more preferably 10 or less, still more preferably 5 or less, and still more preferably 3 or less.

The insulating layer 110 preferably has required insulating properties and also satisfies predetermined mechanical strength, chemical resistance and heat resistance.

The resin material constituting the insulating layer is not particularly limited as long as it has sufficient insulating properties. For example, a thermoplastic resin composition, a thermosetting resin composition, an active energy ray curable composition, or the like can be used.

The thermoplastic resin composition is not particularly limited, but styrene-based resin compositions, vinyl acetate-based resin compositions, polyester-based resin compositions, polyethylene-based resin compositions, polypropylene-based resin compositions, imide-based resin compositions, acrylic resin compositions, and the like can be used. can Although it does not specifically limit as a thermosetting resin composition, A phenol type resin composition, an epoxy type resin composition, a urethane type resin composition, a melamine type resin composition, an alkyd type resin composition, etc. can be used. Although it does not specifically limit as an active energy ray-curable composition, For example, the polymeric compound etc. which have 2 or more (meth)acryloyloxy groups in a molecule can be used. These compositions may be used individually by 1 type, and may use 2 or more types together.

Further, in the insulating layer 110, in addition to the above-described fine particles and colorants, a curing accelerator, a tackifier, an antioxidant, a pigment, a dye, a plasticizer, a UV absorber, an antifoaming agent, A leveling agent, a filler, a flame retardant, a viscosity modifier, and an antiblocking agent may be contained.

The thickness of the insulating layer 110 is not particularly limited and can be appropriately set as needed, but from the viewpoint of sufficiently protecting the shielding layer, it is preferably 1 μm or more, and more preferably 4 μm or more. Further, from the viewpoint of ensuring the flexibility of the electromagnetic wave shielding film, it is preferably 20 μm or less, and more preferably 10 μm or less.

-shielding layer-

The shielding layer 120 of this embodiment can be made into a metal layer. For the shielding layer 120, a metal layer made of any one of nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, and zinc, or an alloy containing two or more thereof can be used. In addition, the material and thickness of the metal layer may be appropriately selected according to the required electromagnetic shielding effect and resistance to repeated bending and sliding. From the viewpoint of obtaining a sufficient electromagnetic shielding effect, the thickness of the metal layer is preferably 0.1 μm or more. Further, from the viewpoints of productivity, flexibility, etc., it is preferable to set it as 8 micrometers or less. And, the metal layer can be formed by an electrolytic plating method, an electroless plating method, a sputtering method, an electron beam evaporation method, a vacuum evaporation method, a CVD method, a metal organic method, or the like. In addition, the metal layer can also be formed of metal foil, metal nanoparticles, scaly metal particles, or the like.

-Adhesive layer-

The electromagnetic shielding film of this embodiment may include the adhesive layer 130 on the side opposite to the insulating layer 110 of the shielding layer 120 . The adhesive layer 130 can be formed of an adhesive resin composition. The adhesive resin composition is not particularly limited, but includes a styrenic resin composition, a vinyl acetate resin composition, a polyester resin composition, a polyethylene resin composition, a polypropylene resin composition, an imide resin composition, an amide resin composition, and an acrylic resin composition. Thermoplastic resin compositions such as resin compositions, and thermosetting resin compositions such as phenolic resin compositions, epoxy resin compositions, urethane resin compositions, melamine resin compositions, and alkyd resin compositions can be used. These may be used individually by 1 type, and may use 2 or more types together.

The adhesive layer 130 can be a layer having isotropic conductivity or anisotropic conductivity, if necessary. When the adhesive layer 130 is a layer having isotropic or anisotropic conductivity, conductive fine particles may be added to the adhesive resin composition.

The conductive fine particles are not particularly limited, but metal fine particles, carbon nanotubes, carbon fibers, metal fibers and the like can be used. For example, metal fine particles such as silver powder, copper powder, nickel powder, solder powder, and aluminum powder can be used. Further, silver-coated copper powder obtained by plating the copper powder with silver, and metal-coated fine particles obtained by coating polymer fine particles, glass beads, or the like with metal can also be used. Especially, from a viewpoint of economical efficiency, a copper powder or silver coated copper powder which can be obtained cheaply is preferable.

Although the 50% average particle diameter of electroconductive particle is not specifically limited, 0.5 micrometer or more is preferable from a viewpoint of obtaining favorable electroconductivity. Moreover, it is preferable to set it as 15 micrometers or less from a viewpoint of making a conductive adhesive layer thin.

The shape of the conductive particles is not particularly limited, but can be appropriately selected from a spherical shape, a flat shape, a scale shape, and a dendrite shape.

Although the thickness of the adhesive layer 130 can be adjusted as needed, it is preferable to set it as 0.5 micrometer or more from a viewpoint of obtaining good adhesiveness. Further, from the viewpoint of thinning the electromagnetic wave shielding film, it is preferable to set it to 20 μm or less.

Although the configuration in which the electromagnetic shielding film has the insulating layer 110, the shielding layer 120, and the adhesive layer 130 has been described, as shown in FIG. 2, the insulating layer 110 and the isotropic conductive adhesive layer ( 140) may be configured.

The insulating layer 110 can have the same configuration as the electromagnetic wave shielding film shown in FIG. 1 . The isotropically conductive adhesive layer 140 can be formed of the same adhesive resin composition and conductive fine particles as the adhesive layer 130 . The isotropic conductive adhesive layer 140 functions as a shielding layer.

-Method of manufacturing shield film-

The electromagnetic shielding film of this embodiment can be manufactured by a known manufacturing method. An example thereof is shown below.

First, an adhesive layer 130 having conductivity is formed on a support film having a surface subjected to release treatment. Specifically, the adhesive layer 130 is formed by coating and drying a solution of the adhesive layer composition containing the material constituting the adhesive layer 130 on the surface of the support film.

Next, a shielding layer 120 is formed on the surface of the adhesive layer 130 . Specifically, a method of bonding a metal foil formed to a predetermined thickness in advance to the adhesive layer 130 or a method of forming a metal layer on the surface of the adhesive layer 130 by vapor deposition or plating can be used.

Next, the insulating layer 110 is formed on the surface of the shielding layer 120 . Specifically, a method of coating and drying a solution of an insulating layer composition containing a material constituting the insulating layer 110 on the surface of the shielding layer 120 may be used.

Then, by peeling off the support film, an electromagnetic wave shielding film can be obtained.

In addition, the adhesive layer 130 may be the isotropic conductive adhesive layer 140 and the insulating layer 110 may be formed on the surface of the isotropic conductive adhesive layer 140 .

In order to set the surface properties on the surface of the insulating layer 110 to a predetermined state, the surface of the insulating layer 110 may be subjected to a treatment such as sand blasting.

Although an example of forming from the adhesive layer 130 side has been shown, it may be formed sequentially from the insulating layer 110 side. In this case, the surface properties of the insulating layer 110 may be set to a predetermined state by transferring the fine pattern to the surface of the insulating layer 110 using a support film having a fine pattern.

[Example]

Hereinafter, the present invention will be described in detail by examples. Incidentally, the following examples are illustrative and do not particularly limit the present invention.

<Production of electromagnetic shielding film>

-Production of adhesive layer-

100 parts by mass of bisphenol A type epoxy resin (jER1256, manufactured by Mitsubishi Chemical), 0.1 part by mass of curing agent (ST14, manufactured by Mitsubishi Chemical), and dendrite-like silver coat copper powder in toluene so that the amount of solid content is 20% by mass (Average particle diameter of 13 micrometers) 25 mass parts were added and stirred-mixed, and the conductive adhesive layer composition was prepared. An adhesive layer was formed on the surface of the support film by applying the obtained adhesive layer composition to a PET film having a release treatment on the surface and drying it by heat.

-Production of shielding layer-

A rolled copper foil having a thickness of 2 μm was bonded to the surface of the obtained adhesive layer.

-Production of Insulation Layer-

100 parts by mass of bisphenol A type epoxy resin (jER1256, manufactured by Mitsubishi Chemical Corporation) in toluene so that the amount of solid content is 20% by mass, 0.1 parts by mass of (ST14, manufactured by Mitsubishi Chemical Corporation) as a curing agent, carbon as a black colorant 15 parts by mass of particles (made by Tokai Carbon, Toka Black #8300/F) and a predetermined amount of particles for forming irregularities were blended to prepare an insulating layer composition. This composition was applied to the resulting shielding layer and dried by heating to obtain an electromagnetic shielding film.

<Characteristic evaluation method>

[Measurement of Surface Properties of Insulating Layer]

Using a confocal microscope (Optelics HYBRID, manufactured by Lasertec, objective lens 20x), after measuring 5 random points on the surface of the insulating layer of the electromagnetic shielding film, using data analysis software (LMeye7), the slope of the surface was measured. Correction was performed, surface properties were measured based on ISO 25178-6:2010, and the arithmetic average was obtained. And, the cut-off wavelength of the S-filter was 0.0025 mm, and the cut-off wavelength of the L-filter was 0.8 mm.

[Measurement of L* value]

The L* value was measured using an integrating sphere spectrophotometer (manufactured by X-Rite, Ci64, tungsten light source). And, the a* value and the b* value were also measured.

[Evaluation of Discoloration by Fingerprints]

The surface of a rubber stopper with a diameter of 2.5 cm was damaged with #240 abrasive paper. Next, 5 μL of artificial sap (JIS C9606: manufactured by Isekyu) was dropped on the surface of the PET film, and the damaged surface of the rubber stopper was pressed against the artificial sputum (500 g load, 10 seconds). Subsequently, the rubber stopper to which the artificial sputum was adhered was pressed against the surface of the insulating layer (500 g load, for 10 seconds) to adhere the artificial sputum. Next, a nonwoven fabric (Wipe All X70, manufactured by Nippon Paper Cresia) was cut to a size of about 3 cm × 3 cm, placed on an artificial sap, and reciprocated 20 times with a load of 500 g (one-way distance = 10 cm) to wipe. The value obtained by subtracting the value of the 85 ° gloss before attaching the artificial sphere solution from the value of the 85 ° gloss after wiping was used as the 85 ° gloss difference. 60° gloss and 85° gloss were measured using a BYK Gardner micro-gloss (portable gloss meter).

(Example 1)

As the particles for forming irregularities applied to the insulating layer, silica particles having an average particle diameter of 7 μm were used, and the blending amount was 40 parts by mass. Sa of the surface of the insulating layer of the obtained electromagnetic shielding film was 1.02 μm, Sdq was 1.26, and Ssk was 2.22. The 60° gloss before the artificial saliva was attached was 1.1, and the 60° gloss after wiping off the fingerprint was 5.2. The 85° gloss before the artificial saliva was attached was 1.5, the 85° gloss after fingerprints were wiped off was 1.9, and the 85° gloss difference was 0.4. The L* value was 21.3.

(Example 2)

An electromagnetic shielding film was obtained in the same manner as in Example 1, except that the blending amount of the particles for forming irregularities was 50 parts by mass. Sa of the surface of the insulating layer of the obtained electromagnetic shielding film was 1.18 µm, Sdq was 1.26, and Ssk was 2.21. The 60° gloss before the artificial saliva was attached was 0.5, and the 60° gloss after wiping off the fingerprint was 6.7. The 85° gloss before the artificial saliva was attached was 1.8, the 85° gloss after fingerprints were wiped off was 2.4, and the 85° gloss difference was 0.6. The L* value was 20.1.

(Example 3)

An electromagnetic shielding film was obtained in the same manner as in Example 1, except that the blending amount of the particles for forming irregularities was 35 parts by mass. Sa of the surface of the insulating layer of the obtained electromagnetic shielding film was 1.31 µm, Sdq was 0.95, and Ssk was 1.47. The 60° gloss before the artificial saliva was attached was 0.5, and the 60° gloss after wiping off the fingerprint was 1.8. The 85° gloss before the artificial saliva was attached was 1.7, the 85° gloss after fingerprints were wiped off was 2.5, and the 85° gloss difference was 0.8. The L* value was 20.1.

(Example 4)

An electromagnetic shielding film was obtained in the same manner as in Example 1, except that silica particles having an average particle diameter of 9 µm were used as the particles for forming irregularities, and the blending amount was 40 parts by mass. Sa of the surface of the insulating layer of the obtained electromagnetic shielding film was 0.92 µm, Sdq was 1.38, and Ssk was 3.10. The 60° gloss before the artificial saliva was attached was 2.1, and the 60° gloss after wiping off the fingerprint was 6.1. The 85° gloss before the artificial saliva was attached was 2.1, the 85° gloss after fingerprints were wiped off was 2.6, and the 85° gloss difference was 0.5. The L* value was 23.5.

(Example 5)

An electromagnetic shielding film was obtained in the same manner as in Example 4, except that the blending amount of the particles for forming irregularities was 50 parts by mass. Sa of the surface of the insulating layer of the obtained electromagnetic shielding film was 0.92 µm, Sdq was 1.02, and Ssk was 2.53. The 60° gloss before the artificial saliva was attached was 1.5, and the 60° gloss after wiping off the fingerprint was 4.9. The 85° gloss before the artificial saliva was attached was 1.7, the 85° gloss after fingerprints were wiped off was 3.2, and the 85° gloss difference was 1.5. The L* value was 24.3.

(Example 6)

An electromagnetic shielding film was obtained in the same manner as in Example 1, except that silica particles having an average particle diameter of 5 µm were used as the particles for forming irregularities, and the blending amount was 70 parts by mass. Sa of the surface of the insulating layer of the obtained electromagnetic shielding film was 1.05 µm, Sdq was 0.92, and Ssk was 0.80. The 60° gloss before the artificial saliva was attached was 0.5, and the 60° gloss after wiping off the fingerprint was 2.4. The 85° gloss before the artificial saliva was attached was 4.6, the 85° gloss after fingerprints were wiped off was 6.3, and the 85° gloss difference was 1.7. The L* value was 23.6.

(Example 7)

An electromagnetic shielding film was obtained in the same manner as in Example 1, except that silica particles having an average particle diameter of 7 µm were used as the particles for forming irregularities and the blending amount was 60 parts by mass. Sa of the surface of the insulating layer of the obtained electromagnetic shielding film was 1.11 μm, Sdq was 1.12, and Ssk was 1.46. The 60° gloss before the artificial saliva was attached was 0.4, and the 60° gloss after wiping off the fingerprint was 1.9. The 85° gloss before the artificial saliva was attached was 3.8, the 85° gloss after fingerprints were wiped off was 6.5, and the 85° gloss difference was 2.7. The L* value was 21.9.

(Comparative Example 1)

An electromagnetic shielding film was obtained in the same manner as in Example 1, except that silica particles having an average particle diameter of 2 µm were used as the particles for forming irregularities, and the blending amount was 60 parts by mass. Sa of the surface of the insulating layer of the obtained electromagnetic shielding film was 0.57 µm, Sdq was 0.80, and Ssk was 0.07. The 60° gloss before the artificial saliva was attached was 0.8, and the 60° gloss after wiping off the fingerprint was 2.2. The 85° gloss before the artificial saliva was attached was 16.8, the 85° gloss after wiping off the fingerprint was 26.7, and the 85° gloss difference was 9.9. The L* value was 24.4.

(Comparative Example 2)

An electromagnetic shielding film was obtained in the same manner as in Comparative Example 1, except that the blending amount of the particles for forming irregularities was 65 parts by mass. Sa of the surface of the insulating layer of the obtained electromagnetic shielding film was 0.66 µm, Sdq was 0.90, and Ssk was -0.22. The 60° gloss before the artificial saliva was attached was 0.5, and the 60° gloss after wiping off the fingerprint was 3.9. The 85° gloss before the artificial saliva was attached was 15.9, the 85° gloss after fingerprints were wiped off was 30.4, and the 85° gloss difference was 14.5. The L* value was 21.9.

(Comparative Example 3)

An insulating layer composition containing no particles for concavo-convex formation was prepared. This was applied to the surface of the support film and dried and cured to obtain an insulating layer. The support film was a PET film having a thickness of 20 µm and subjected to release treatment, to which a concavo-convex shape (Sa = 0.60 µm, Sdq = 0.61) was provided on the surface by embossing. Next, after bonding the insulating layer to the shielding layer produced in the same manner as in Example 1, the support film was peeled off to obtain an electromagnetic shielding film. Sa of the surface of the insulating layer of the obtained electromagnetic shielding film was 0.58 µm, Sdq was 0.65, and Ssk was -0.78. The 60° gloss before the artificial saliva was attached was 4.2, and the 60° gloss after wiping off the fingerprint was 9.1. The 85° gloss before the artificial saliva was attached was 34.0, the 85° gloss after wiping off the fingerprint was 42.8, and the 85° gloss difference was 8.8. The L* value was 25.3.

(Comparative Example 4)

As the support film, an electromagnetic shielding film was obtained in the same manner as in Comparative Example 3 except that silica fine particles were blended and a concavo-convex shape (Sa = 0.6 μm, Sdq = 0.47 μm) was used on the surface. Sa of the surface of the insulating layer of the obtained electromagnetic shielding film was 0.59 µm, Sdq was 0.49, and Ssk was -0.85. The 60° gloss before the artificial saliva was attached was 7.6, and the 60° gloss after wiping off the fingerprint was 13.3. The 85° gloss before artificial saliva was attached was 38.7, the 85° gloss after fingerprints were wiped off was 48.0, and the 85° gloss difference was 9.3. The L* value was 28.2.

(Comparative Example 5)

As the support film, an electromagnetic shielding film was obtained in the same manner as in Comparative Example 3 except that a surface having a concavo-convex shape (Sa = 0.47 μm, Sdq = 0.59 μm) was used by sand mat processing. Sa of the surface of the insulating layer of the obtained electromagnetic shielding film was 0.45 µm, Sdq was 0.58, and Ssk was -0.25. The 60° gloss before the artificial saliva was attached was 5.4, and the 60° gloss after wiping off the fingerprint was 11.9. The 85° gloss before the artificial saliva was attached was 26.1, the 85° gloss after wiping off the fingerprint was 51.0, and the 85° gloss difference was 24.9. The L* value was 27.2.

(Comparative Example 6)

An electromagnetic shielding film was obtained in the same manner as in Comparative Example 3, except that a support film having a concavo-convex shape (Sa = 0.45 µm, Sdq = 0.56 µm) was used on the surface by sand mat processing. Sa of the surface of the insulating layer of the obtained electromagnetic shielding film was 0.45 µm, Sdq was 0.54, and Ssk was -0.60. The 60° gloss before the artificial saliva was attached was 9.2, and the 60° gloss after wiping off the fingerprint was 16.6. The 85° gloss before the artificial saliva was attached was 30.4, the 85° gloss after wiping off the fingerprint was 54.7, and the 85° gloss difference was 24.3. The L* value was 27.2.

(Comparative Example 7)

An electromagnetic shielding film was obtained in the same manner as in Comparative Example 3, except that a support film having a concavo-convex shape (Sa = 0.51 μm, Sdq = 0.55 μm) was used on the surface by sand mat processing. Sa of the surface of the insulating layer of the obtained electromagnetic shielding film was 0.49 µm, Sdq was 0.55, and Ssk was -0.37. The 60° gloss before the artificial saliva was attached was 8.6, and the 60° gloss after wiping off the fingerprint was 16.7. The 85° gloss before the artificial saliva was attached was 21.6, the 85° gloss after fingerprints were wiped off was 56.7, and the 85° gloss difference was 35.1. The L* value was 27.2.

(Comparative Example 8)

As the support film, an electromagnetic shielding film was obtained in the same manner as in Comparative Example 3 except that silica fine particles were blended and a concavo-convex shape (Sa = 0.43 µm, Sdq = 0.40 µm) was used on the surface. Sa of the surface of the insulating layer of the obtained electromagnetic shielding film was 0.42 µm, Sdq was 0.38 µm, and Ssk was -1.19. The 60° gloss before the artificial saliva was attached was 11.7, and the 60° gloss after wiping off the fingerprint was 17.9. The 85° gloss before the artificial saliva was attached was 52.4, the 85° gloss after fingerprints were wiped off was 58.9, and the 85° gloss difference was 6.5. The L* value was 27.9.

(Comparative Example 9)

An electromagnetic shielding film was obtained in the same manner as in Example 1, except that silica particles having an average particle diameter of 5 µm were used as the particles added to the insulating layer, and the blending amount was 40 parts by mass. Sa of the surface of the insulating layer of the obtained electromagnetic shielding film was 0.49 µm, Sdq was 0.74, and Ssk was -0.77. The 60° gloss before the artificial saliva was attached was 1.0, and the 60° gloss after wiping off the fingerprint was 19.8. The 85° gloss before the artificial saliva was attached was 33.2, the 85° gloss after fingerprints were wiped off was 61.0, and the 85° gloss difference was 27.8. The L* value was 22.0.

(Comparative Example 10)

As the support film, an electromagnetic shielding film was obtained in the same manner as in Comparative Example 3 except that silica fine particles were blended and a concavo-convex shape (Sa = 0.36 µm, Sdq = 0.36 µm) was used on the surface. Sa of the surface of the insulating layer of the obtained electromagnetic shielding film was 0.35 µm, Sdq was 0.36, and Ssk was -0.31. The 60° gloss before the artificial saliva was attached was 6.9, and the 60° gloss after wiping off the fingerprint was 12.1. The 85° gloss before the artificial saliva was attached was 58.6, the 85° gloss after fingerprints were wiped off was 63.0, and the 85° gloss difference was 4.4. The L* value was 26.3.

(Comparative Example 11)

As the support film, an electromagnetic shielding film was obtained in the same manner as in Comparative Example 3 except that silica fine particles were blended and a concavo-convex shape (Sa = 0.46 µm, Sdq = 0.65 µm) was used on the surface. Sa of the surface of the insulating layer of the obtained electromagnetic shielding film was 0.43 µm, Sdq was 0.62, and Ssk was -0.40. The 60° gloss before the artificial saliva was attached was 2.4, and the 60° gloss after wiping off the fingerprint was 16.6. The 85° gloss before artificial saliva was attached was 42.6, the 85° gloss after fingerprints were wiped off was 71.8, and the 85° gloss difference was 29.2. The L* value was 28.2.

(Comparative Example 12)

As the support film, an electromagnetic shielding film was obtained in the same manner as in Comparative Example 3 except that silica fine particles were blended and a concavo-convex shape (Sa = 0.31 μm, Sdq = 0.58 μm) was used on the surface. Sa of the surface of the insulating layer of the obtained electromagnetic shielding film was 0.34 µm, Sdq was 0.55, and Ssk was -0.48. The 60° gloss before the artificial saliva was attached was 4.3, and the 60° gloss after wiping off the fingerprint was 30.2. The 85° gloss before the artificial saliva was attached was 64.2, the 85° gloss after wiping off the fingerprint was 80.6, and the 85° gloss difference was 16.4. The L* value was 24.4.

(Comparative Example 13)

As the support film, an insulating layer was applied to the surface of the support film and dried in the same manner as in Comparative Example 3, except that a PET film having a concave-convex shape (Sa = 1.5 μm, Sdq = 4.89 μm) was used on the surface by embossing. hardened Next, the insulating layer was bonded to the shielding layer prepared in the same manner as in Example 1. Next, an attempt was made to peel off the support film, but the support film and the insulating layer adhered firmly, and interface destruction of the insulating layer/shielding layer occurred in a part. Sa of the surface of the insulating layer where interface failure was not observed was 1.3 μm, Sdq was 3.6, and Ssk was -1.60. And, in this comparative example, since interfacial destruction occurred, glossiness and L* value were not measured.

Table 1 shows the evaluation of surface properties and discoloration of the electromagnetic shielding films of each Example and Comparative Example. Table 1 also shows the values of Sp, Sq, Spk, Vvc, Vmp, a* and b*.

[Table 1]

3 shows the relationship between Sdq and 85 ° glossiness. At least when Sdq is 0.8 or more and the 85° glossiness is 10 or less, the gloss difference is 4 or less, and discoloration due to wiping of fingerprints does not easily occur.

4 shows the relationship between Ssk and 85° glossiness. At least when Ssk is 0.1 or more and the 85 degree glossiness is 10 or less, the gloss difference is 4 or less, and discoloration due to wiping of fingerprints does not easily occur.

The electromagnetic shielding film of the present invention can prevent easy discoloration due to wiping of fingerprints, and is useful as an electromagnetic shielding film used for printed wiring boards and the like.

110: insulating layer
120: shielding layer
130: adhesive layer
140: isotropic conductive adhesive layer

Claims (4)

Including an insulating layer and a shield layer,
The insulating layer is an electromagnetic shielding film having a maximum peak height Sp on the surface measured based on ISO 25178-6:2010 of 8.0 μm or more. Including an insulating layer and a shielding layer,
The electromagnetic shielding film according to claim 1 , wherein the insulating layer has a protruding ridge height Spk on the surface measured based on ISO 25178-6:2010 of 1.0 μm or more. Including an insulating layer and a shielding layer,
The electromagnetic shielding film according to claim 1 , wherein the insulating layer has a core volume Vvc of 1.1 ml/m ² or more, measured according to ISO 25178-6:2010. Including an insulating layer and a shielding layer,
The electromagnetic shielding film according to claim 1 , wherein the insulating layer has a substantial volume Vmp of ridges on the surface of 0.07 ml/m ² or more, measured based on ISO 25178-6:2010.