KR20180113500A - EMI shielding film - Google Patents

Abstract

The electromagnetic wave shielding film includes an insulating protective layer 110 and a shielding layer 120. The insulating protective layer 110 has an arithmetic mean slope of 30 DEG or more on the surface.

Description

EMI shielding film

The present invention relates to an electromagnetic wave shielding film.

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

In order to shield the printed wiring board, a method of attaching an electromagnetic wave shielding film having an insulating layer and a shielding layer to a printed wiring board has been studied (see, for example, Patent Document 1).

Further, an electromagnetic wave shielding film colored with an insulating protective layer in black has been studied for the purpose of concealing circuit patterns (see, for example, Patent Document 2).

It has also been studied to adjust the color tone of the insulating protective layer of the electromagnetic wave shielding film for the purpose of improving the recognizability of the white factor printed on the surface of the electromagnetic wave shielding film (see, for example, Patent Document 3 ).

Japanese Patent Application Laid-Open No. 2004-095566 Japanese Patent Application Laid-Open No. 2014-078574 Japanese Patent No. 5796690

The surface of the electromagnetic wave shielding film attached to the printed wiring board is printed with a white ink for the purpose of managing the printed wiring board in the process of assembling the electronic equipment. However, in the conventional electromagnetic wave shielding film, there is a drawback that the factor of the white ink tends to spread and the productivity of the step of printing using the white ink is low.

In addition, information terminals and the like, in which an electromagnetic wave shielding film is used, are required to be reduced in weight and size, and as a result, the size of the electromagnetic wave shielding film is reduced, and characters printed on the electromagnetic wave shielding film are also reduced.

It becomes difficult to recognize characters printed on the conventional electromagnetic wave shielding film because the size of the factor becomes smaller. Especially in a room with high illuminance, the influence becomes large.

In addition, in the conventional electromagnetic wave shielding film, when characters or symbols are printed by screen printing, ink is spread between the screen plate and the electromagnetic wave shielding film, printing accuracy is lowered, and recognition of small size characters and the like becomes difficult . Even if contrast is improved by adjusting the color tone of the insulating protective layer, there is no fundamental improvement in reduction in visibility due to blurring.

An object of the present invention is to realize an electromagnetic wave shielding film capable of easily recognizing small size characters or the like and printing with good precision.

One aspect of the electromagnetic wave shielding film includes an insulating protective layer and a shielding layer, and the insulating protective layer has an arithmetic mean slope of 30 DEG or more at the surface.

According to the electromagnetic wave shielding film of the present disclosure, small size characters and the like can be easily recognized and printed with good accuracy.

1 is a cross-sectional view showing an electromagnetic wave shielding film according to one embodiment.
2 is a cross-sectional view showing an electromagnetic wave shielding film according to a modification.

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 suitably modified and applied within the scope 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 wave shielding film has an insulating protective layer 110 and a shielding layer 120. The adhesive layer 130 may be provided on the surface of the shielding layer 120 opposite to the insulating protective layer 110 as needed. By providing an adhesive layer, the electromagnetic wave shielding film can be easily bonded to the printed wiring board.

(Insulating protective layer)

The insulating protective layer 110 is provided to protect the shielding layer. In the electromagnetic shielding film of the present embodiment, the insulating protective layer 110 has an arithmetic mean slope of 30 DEG or more.

By setting the arithmetic mean slope of the insulating protective layer 110 to 30 deg. Or more, preferably 35 deg. Or more, more preferably 40 deg. Or more, the surface area of the insulating protective layer 110 is increased, It is possible to suppress the spread of ink during screen printing. Thus, the efficiency of the printing operation can be improved.

From the viewpoint of reducing diffusion, it is preferable that the value of the arithmetic mean slope is large. However, from the viewpoint of the productivity of the insulating protective layer 110, the arithmetic mean slope is preferably 80 degrees or less, more preferably 70 degrees or less.

The arithmetic mean slope in the present disclosure can be measured in accordance with JIS B 0601 (2001).

The insulating protective layer may have a root mean square gradient of 35 占 or more, more preferably 40 占 or more, and still more preferably 45 占 or more. When the root mean square gradient of the root mean square is 35 degrees or more, the surface area of the insulating protective layer 110 is increased, and the absorbability of the ink is improved, thereby suppressing the spread of the ink during screen printing. Thus, the efficiency of the printing operation can be improved.

The square-root-mean-square slope in the present disclosure can be measured in accordance with JIS B 0601 (2001).

A method of obtaining an insulating protective layer having an arithmetic mean slope and a root mean square slope within a predetermined range is not particularly limited, and a known method can be used. As such a method, there are a method of applying the resin composition for forming the insulating protective layer on the surface of the release film imparted with the concavo-convex shape by embossing and then drying and transferring the relief shape of the release film to the insulating protective layer, A method in which a resin composition containing fine particles is coated on a surface of a protective layer and dried to form an insulating protective layer having a concavo-convex shape, a method of spraying dry ice on the surface of an insulating protective layer, a method of applying an active energy ray- And a method of pressing the mold having the concavo-convex shape to cure the curable composition layer and peeling the mold.

Among these methods, from the viewpoint of productivity, a method of applying an insulating resin composition containing fine particles and drying the resin composition to obtain an insulating protective layer having an irregular shape is preferable. In this case, the fine particles to be added to the insulating protective layer 110 are not particularly limited. For example, resin fine particles or inorganic fine particles can be used. The resin fine particles may be acrylic resin fine particles, polyacrylonitrile fine particles, polyurethane fine particles, polyamide fine particles, and polyimide fine particles. The inorganic fine particles may be fine particles such as 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, Calcium sulfate fine particles, and magnesium carbonate fine particles. These resin fine particles and inorganic fine particles may be used alone or in combination of a plurality of them. From the viewpoint of enhancing the scratch resistance of the insulating protective layer, inorganic fine particles are preferable.

The fine particles preferably have a 50% average particle diameter of 2 占 퐉 or more, more preferably 4 占 퐉 or more from the viewpoint of causing appropriate irregularities on the surface of the insulating protective layer and increasing the arithmetic mean slope and the root mean square slope, More preferably 10 mu m or more. In order to suppress the whitening of the insulating protective layer, the 50% average particle diameter is preferably 30 占 퐉 or less, more preferably 20 占 퐉 or less.

The amount of the fine particles added to the insulating protective layer 110 is preferably 3% by mass or more, more preferably 5% or more from the viewpoint of increasing the arithmetic mean slope and the root mean square slope. From the viewpoint of suppressing the whitening of the insulating protective layer, it is preferably 30 mass% or less, more preferably 20 mass% or less, and further preferably 17 mass% or less.

To the insulating protective layer 110, a black coloring agent may be added. By adding the black coloring agent, the L * value of the insulating protective layer 110 can be made smaller, and the visibility of characters can be further improved. When the characters to be printed on the insulating protective layer 110 are white, the L * value is preferably 20 or less, and more preferably 18 or less. The L * value in the present disclosure can be measured in accordance with JIS Z 8781-4 (2013).

The black colorant may be a black pigment or a mixed pigment obtained by blackening a plurality of pigments by mixing them with each other. The black pigment can be, for example, any one of carbon black, ketjen black, carbon nanotube (CNT), perylene black, titanium black, iron black and aniline black, or a combination thereof. The mixed pigments can be used by mixing pigments such as red, green, blue, yellow, purple, cyan and magenta.

The particle diameter of the black coloring agent is not limited so long as it can realize the required L * value. However, it is preferable that the average primary particle diameter is 20 nm or more in view of reduction of dispersibility and L * value, desirable. The average primary particle diameter of the black colorant can be obtained from an average value of about 20 primary particles that can be observed from an image enlarged by about 50,000 to 100,000 times by a transmission electron microscope (TEM).

From the viewpoint of decreasing the L * value, the addition amount of the black coloring agent to the insulating protective 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 the black colorant may not be added.

By setting the 60 ° gloss of the insulating protective layer 110 to 3% or less, preferably 2% or less, and more preferably 1% or less, appropriate light scattering occurs on the surface of the insulating protective layer 110, Is adequately suppressed. This makes it possible to improve the visibility of the factor. The 85 degree gloss of the insulating protective layer 110 is preferably 10% or less, more preferably 3% or less, and further preferably 1% or less.

The 60 占 glossiness and 85 占 glossiness in the present disclosure can be measured by the method shown in Examples.

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

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

The thermoplastic resin composition is not particularly limited, but a styrene resin composition, a vinyl acetate resin composition, a polyester resin composition, a polyethylene resin composition, a polypropylene resin composition, an imide resin composition, and an acrylic resin composition may be used . The thermosetting resin composition is not particularly limited, but a phenol resin composition, an epoxy resin composition, a urethane resin composition, a melamine resin composition, and an alkyd resin composition can be used. The active energy ray curable composition is not particularly limited, and for example, a polymerizable compound having at least two (meth) acryloyloxy groups in the molecule can be used. These compositions may be used alone, or two or more of them may be used in combination.

In addition to the fine particles and the colorant, the insulating protective layer 110 may contain a curing accelerator, a tackifier, an antioxidant, a pigment, a dye, a plasticizer, an ultraviolet absorber, a defoaming agent, a leveling agent, A stabilizer, a blocking agent, and the like.

The thickness of the insulating protective layer 110 is not particularly limited and may be appropriately set as necessary. However, from the viewpoint of sufficiently protecting the shielding layer, the thickness is preferably 1 占 퐉 or more, more preferably 4 占 퐉 or more. From the viewpoint of ensuring the flexibility of the electromagnetic wave shielding film, the thickness is preferably 10 占 퐉 or less, more preferably 5 占 퐉 or less.

(Shielding layer)

The shielding layer 120 of the present embodiment may be a metal layer. The shielding layer 120 may be 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 of them. The material and thickness of the metal layer may be appropriately selected in accordance with the required electromagnetic shielding effect and repeated bending and sliding resistance. From the viewpoint of obtaining a sufficient electromagnetic shielding effect, the thickness of the metal layer is preferably 0.1 mu m or more. Further, from the viewpoints of productivity and flexibility, it is preferable that the thickness is 8 占 퐉 or less. 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 or the like. The metal layer may be formed of a metal foil, metal nanoparticles, scaly metal particles, or the like.

(Adhesive layer)

The electromagnetic wave shielding film of the present embodiment may have the adhesive layer 130 on the side opposite to the insulating protective 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, and examples thereof include a styrene 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, A thermosetting resin composition such as a phenol resin composition, an epoxy resin composition, a urethane resin composition, a melamine resin composition and an alkyd resin composition can be used. These may be used alone, or two or more of them may be used in combination.

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

The conductive fine particles are not particularly limited, but fine metal 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. It is also possible to use a silver-coated copper alloy powder coated with a copper powder and metal-coated fine particles coated with a metal fine particle, glass beads or the like. Of these, from the viewpoint of economical efficiency, a copper powder or a silver-coated copper that can be obtained at low cost is preferable.

The 50% average particle diameter of the conductive particles is not particularly limited, but is preferably 0.5 占 퐉 or more from the viewpoint of obtaining good conductivity. Further, from the viewpoint of thinning the conductive adhesive layer, it is preferable that the thickness is 15 mu m or less.

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

The thickness of the adhesive layer 130 can be adjusted as needed, but is preferably 0.5 占 퐉 or more from the viewpoint of obtaining good adhesion. Further, from the viewpoint of thinning the electromagnetic wave shielding film, it is preferable that the thickness is 20 mu m or less.

The electromagnetic wave shielding film has the insulating protective layer 110, the shielding layer 120 and the adhesive layer 130. However, as shown in FIG. 2, the insulating protective layer 110 and the isotropic conductive adhesive Layer 140 may be provided.

The insulating protective layer 110 may have the same structure as the electromagnetic wave shielding film shown in Fig. 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 for producing shielding film)

The electromagnetic wave shielding film can be produced by a known manufacturing method. An example is shown below.

First, a conductive adhesive layer 130 is formed on a support film having a surface subjected to releasing treatment. Specifically, a solution of an adhesive layer composition containing a material constituting the adhesive layer 130 is coated on the surface of the support film and dried to form the adhesive layer 130. [

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

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

Thereafter, the support film is peeled off to obtain an electromagnetic wave shielding film.

The insulating protective layer 110 may be formed on the surface of the isotropic conductive adhesive layer 140 by using the adhesive layer 130 as the isotropic conductive adhesive layer 140.

The surface of the insulating protection layer 110 may be subjected to a treatment such as sandblasting in order to adjust the arithmetic average inclination and the root mean square inclination of the surface of the insulating protection layer 110. [

Is formed from the side of the adhesive layer 130, but it may also be formed sequentially from the side of the insulating protective layer 110. [ In this case, it is also possible to adjust the arithmetic mean slope and the root mean square slope on the surface of the adhesive layer 130 by transferring the fine pattern onto the surface of the adhesive layer 130 using a support film having a fine pattern.

[Example]

Hereinafter, the present invention will be described in detail by way of examples. The following examples are illustrative and do not limit the invention in any way.

<Characteristic evaluation>

[Evaluation of burnout]

An alphanumeric character of 1 mm x 2 mm was printed on the surface of the insulating protective layer of the electromagnetic wave shielding film by using a screen printing plate and the shape of the alphanumeric characters was observed by a microscope to evaluate the presence or absence of spreading. When the spreading out was not recognized, the result was rated &amp; cir &amp; and when the outline was deformed or the ink was repelled, it was evaluated as &amp; cir &amp;

[Evaluation of visibility]

The visibility was measured by observing 45 ° specular reflection. In the darkroom, the LED light (manufactured by SUPRABEAM) was placed at a height of 10 cm from the table top so that the irradiation aperture was approximately 45 degrees from the vertical direction, and at a position 10 cm away from right below the irradiation aperture, Film. Next, from the position 10 cm in the horizontal direction and 10 cm in the vertical direction from the position where the electromagnetic wave shielding film was mounted, three alphanumeric characters (0.5 mm in length, 0.2 mm in width, and 0.1 mm Interval) was observed, and the ease of observation was evaluated. When the entire outline of the factor can be clearly recognized, it is rated as ○, and when the factor can not be visually recognized, it is rated as ×.

[Measurement of arithmetic mean slope and root mean square slope]

The arbitrary five visual fields on the surface of the insulating protective layer were observed using a laser microscope (VK-X200, manufactured by KEYENCE CORPORATION, VK-X200, objective lens 50 times), and an arithmetic mean slope and a root mean square slope in accordance with JIS B 0601 Were measured. The reference length was 280 mu m.

[Measurement of L * value]

The L * value was measured using an integrating sphere spectroscopic colorimeter (X64 manufactured by X-Rite, tungsten light source).

[Measurement of glossiness]

60 ° gloss and 85 ° gloss were measured by BYK Gardner micro-gloss (portable glossmeter).

(Example 1)

- Preparation of conductive adhesive layer -

100 parts by mass of a bisphenol A-type epoxy resin (jER1256, manufactured by Mitsubishi Chemical Corporation), 0.1 part by mass of a curing agent (ST14, manufactured by Mitsubishi Chemical Corporation) and a mean particle diameter 47 parts by mass of spherical silver-coated copper powder was added thereto, and the mixture was stirred and mixed to prepare a conductive adhesive layer composition. The obtained adhesive layer composition was applied to a PET film whose surface was subjected to releasing treatment and then heated and dried to form an adhesive layer on the surface of the supporting film.

- Fabrication of shielding layer -

On the surface of the obtained adhesive layer, a silver layer having a thickness of 0.1 mu m was formed by a vapor deposition method.

- Fabrication of insulation protective layer -

100 parts by mass of a bisphenol A type epoxy resin (jER1256, manufactured by Mitsubishi Chemical Corporation), 0.1 parts by mass of a curing agent (ST14, manufactured by Mitsubishi Chemical Corporation), and 0.1 part by mass of a black colorant 15 parts by mass of carbon particles (Toka Black # 8300 / F, manufactured by Tokai Carbon Co., Ltd.) as a colorant and 10 parts by mass of urethane resin particles having an average particle size of 6 占 퐉 as fine particles were blended to prepare an insulating protective layer composition. This composition was applied to the obtained shielding layer and dried by heating to obtain an electromagnetic wave shielding film of Example 1.

The arithmetic mean slope at the surface of the obtained insulating protective layer was 43 °, the root mean square slope was 50 °, the L * value was 18, the 60 ° gloss was 0.2%, and the 85 ° gloss was 0.3%. When the presence or absence of spreading was evaluated, no skipping of the ink was observed and no spreading was observed. Also, the visibility of the factor was good.

(Example 2)

The procedure of Example 1 was repeated except that 10 parts by mass of the urethane resin particles having an average particle diameter of 2 탆 was added to the insulating protective layer composition. The arithmetic mean slope at the surface of the obtained insulating protective layer was 32 °, the root mean square slope was 39 °, the L * value was 20, the 60 ° gloss was 1.1% and the 85 ° gloss was 2.3%. When the presence or absence of spreading was evaluated, no skipping of the ink was observed and no spreading was observed. Also, the visibility of the factor was good.

(Example 3)

Except that 10 parts by mass of urethane resin particles having an average particle size of 5 占 퐉 were added to the insulating protective layer composition. The arithmetic mean slope at the surface of the obtained insulating protective layer was 46 占 and the square mean slope was 52 占 The L * value was 21, the 60 占 glossiness was 0.3%, and the 85 占 glossiness was 2.6%. When the presence or absence of spreading was evaluated, no skipping of the ink was observed and no spreading was observed. Also, the visibility of the factor was good.

(Example 4)

Except that the fine particles added to the insulating protective layer composition were 13 parts by mass of acrylic styrene resin particles having an average particle size of 5 占 퐉. The arithmetic mean slope at the surface of the obtained insulating protective layer was 35 占 and the root mean square slope was 43 占 The L * value was 18, the 60 占 glossiness was 0.8%, and the 85 占 glossiness was 2.1%. The presence or absence of spreading was evaluated, and the visibility of the factor was good.

(Comparative Example 1)

5 parts by mass of a black coloring agent to be added to the insulating protective layer composition was used, and no fine particles were added. The insulating protective layer composition is coated on the surface of the support film having the concavo-convex shape on the surface subjected to the releasing treatment, and the resultant is bonded to the shielding layer. Thereafter, the support film is peeled from the surface of the insulating protective layer, Thereby forming a protective layer. The other conditions were the same as those in Example 1. The arithmetic mean slope at the surface of the obtained insulating protective layer was 22 占 and the root mean square slope was 31 占 The L * value was 28, the 60 占 glossiness was 2.0% and the 85 占 glossiness was 43.4%. When the presence or absence of spreading was evaluated, the ink was skipped. In addition, the factor could not be visually recognized by being mixed with reflected light.

(Comparative Example 2)

Except that 5 parts by mass of a black coloring agent to be added to the insulating protective layer composition and no fine particles were added. The arithmetic mean slope at the surface of the obtained insulating protective layer was 16 °, the root mean square slope was 25 °, the L * value was 27, the 60 ° gloss was 11.1%, and the 85 ° gloss was 36.7%. When the presence or absence of spreading was evaluated, the ink was skipped. In addition, the factor could not be visually recognized by being mixed with reflected light.

(Comparative Example 3)

Except that 5 parts by mass of a black coloring agent to be added to the insulating protective layer composition and no fine particles were added. The arithmetic mean slope at the surface of the obtained insulating protective layer was 23 占 and the square mean slope was 30 占 The L * value was 25, the 60 占 glossiness was 4.2% and the 85 占 glossiness was 33.1%. When the presence or absence of spreading was evaluated, the ink was skipped. In addition, the factor could not be visually recognized by being mixed with reflected light.

(Comparative Example 4)

The support film was the same as that of Comparative Example 1 except that a surface roughness of 0.6 mu m was used. The arithmetic mean slope on the surface of the obtained insulating protective layer was 13 占, the square mean slope was 19 占, the L * value was 28, the 60 占 glossiness was 8.0%, and the 85 占 glossiness was 43.1%. The factor could not be confused with reflected light.

(Comparative Example 5)

Except that the fine particles added to the insulating protective layer composition were changed to 3 parts by mass of urethane resin particles having an average particle size of 7 占 퐉. The arithmetic mean slope at the surface of the obtained insulating protective layer was 14 °, the slope of the root mean square was 20 °, the L * value was 26, the 60 ° gloss was 6.1%, and the 85 ° gloss was 36.9%. The factor could not be confused with reflected light.

Table 1 summarizes the compositions and characteristics of the insulating protective layer in each of the examples and comparative examples.

[Table 1]

In all of the insulating protective layers of Examples 1 to 3, in which the arithmetic average inclination at the surface was not less than 30 degrees, no repulsion of the ink was recognized, and the printability was good. In addition, the insulating protective layers of Examples 1 to 3 were superior in transparency and visibility compared with the insulating protective layer of the comparative example.

[Industrial applicability]

The electromagnetic wave shielding film of the present disclosure is capable of printing small size characters and the like with good precision and is useful as an electromagnetic wave shielding film for use in electronic equipment and the like.

110: Insulation protective layer
120: shielding layer
130: adhesive layer
140: isotropic conductive adhesive layer

Claims (1)

An insulating protective layer, and a shielding layer,
Wherein the insulating protective layer has an arithmetic mean slope at the surface of 30 DEG or more.

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