JPH11177277A - Electromagnetic wave shielding laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic wave shielding laminate which is excellent in transparency, and shields electromagnetic waves, infrared rays and near- infrared rays released from a display screen of a display device such as an electronic apparatus or a liquid crystal display(LCD) or a plasma display panel(PDP) in a transparent opening part, and prevents external electromagnetic waves from entering the electronic apparatus, etc., and is excellent in noise reduction effect. SOLUTION: In a laminate, a layer A comprising a metal and a dielectric is provided on one face of a transparent thermoplastic resin film, and a metal layer B is provided on the opposite face. In this case, a coating ratio of a metal portion for a film area on a surface of the metal layer B is 20% to 80%, and a ratio (Tnir/Tvis) of visible light transmissivity (Tvis) of a laminate to near-infrared rays transmissivity (Tnir) is 0.75 or less, and electromagnetic wave shield characteristic in a frequency band of 80 to 1000 MHz is 30 dB or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminate for shielding electromagnetic waves, and more particularly to a display device such as an electronic device and a display screen of a liquid crystal display (LCD) or a plasma display panel (PDP) in a transparent opening. The present invention relates to a laminated body for an electromagnetic wave shield that is excellent in an effect of shielding an emitted electric wave, infrared light and near infrared light, and also preventing an external electric wave from entering an electronic device and reducing noise.

[0002]

2. Description of the Related Art At present, various electric and electronic devices are used to greatly improve work efficiency. However, these electronic devices generate electromagnetic waves, albeit weakly.

Conversely, the entry of external electromagnetic waves may adversely affect electronic equipment and cause malfunctions or malfunctions. Therefore, the necessity of an electromagnetic wave shield has been emphasized.

[0004] As a conventional electromagnetic shielding material for electronic equipment, a highly conductive metal plate or metal foil such as copper or iron is used to cover the inside of a case of the equipment or to wrap around the electromagnetic wave generating source to shield the electromagnetic wave. Had gone.

In recent years, electronic devices such as computers have become smaller and more sophisticated, and at the same time, transparent display windows and liquid crystal display windows have been attached to the electronic devices.

However, since these transparent display windows and liquid crystal display windows are not shielded from electromagnetic waves, there is a problem that external electromagnetic waves enter through these transparent windows and cause malfunctions in computers and the like.

Recently, display devices such as LCDs and PDPs have been increasing. In particular, PDP display screens emit electromagnetic waves when plasma is generated, which may affect surrounding electronic devices and may cause a health problem for viewers. There is a problem that cannot be denied.

With respect to the electromagnetic wave shielding in the transparent portion, it is impossible to apply a conventional thick metal plate, and therefore, a transparent electromagnetic wave shielding material is required.

As a transparent electromagnetic wave shielding material, a shielding material having a mesh structure in which polyester fiber is coated with a conductive metal and woven in a lattice has been proposed. Such a mesh has a light transmittance. It was not satisfactory enough because of low visibility.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a liquid crystal display (LCD) or a plasma display panel (PDP) which is excellent in transparency and is provided in a display device such as an electronic device or a transparent opening. It is an object of the present invention to provide an electromagnetic wave shielding laminate excellent in an effect of shielding an electric wave, an infrared ray and a near-infrared ray, and blocking an electric field wave from the outside from entering an electronic device or the like and reducing noise.

[0011]

According to the present invention, there is provided a laminate comprising a transparent thermoplastic resin film having a layer (A) made of a metal and a dielectric on one surface and a metal layer (B) on the other surface. Wherein the coverage of the metal portion with respect to the film area on the metal layer (B) surface is 20% or more and 80% or less;
The ratio (Tnir / Tvis) between the visible light transmittance Tvis and the near infrared transmittance Tnir of the laminate is 0.75 or less, and 80 to 1
An electromagnetic wave shielding laminate having an electromagnetic wave shielding characteristic of 30 dB or more in a frequency band of 000 MHz.

As the base film used in the present invention, a thermoplastic resin film which is transparent, has flexibility, and has heat resistance capable of forming an evaporation layer by a sputtering method, a vacuum evaporation method or the like is used. preferable.

Examples of the polymer constituting such a thermoplastic resin film include polyester represented by polyethylene terephthalate and polyethylene naphthalate, aliphatic polyamide, aromatic polyamide, polyethylene, polypropylene, polycarbonate and the like. Of these, polyester is more preferred. Further, among the thermoplastic resin films, a biaxially stretched polyethylene terephthalate film having excellent heat resistance and mechanical strength is particularly preferable.

Such a thermoplastic resin film can be manufactured by a conventionally known method. For example, a biaxially stretched polyester film is obtained by drying a polyester, melting it at an temperature of Tm to (Tm + 70) ° C. (where Tm is the melting point of the polyester) with an extruder, and forming a die (for example, Tm).
-Die, I-die, etc.) onto a rotating cooling drum,
It is quenched at 40 to 90 ° C. to produce an unstretched film, and then the unstretched film is (Tg-10) to (Tg + 70)
At a temperature of 2.5 ° C. (Tg: glass transition temperature of polyester) at a magnification of 2.5 to 8.0 times,
Stretch at a magnification of ~ 8.0 times, and if necessary, 180 ~ 25
It can be manufactured by heat setting at a temperature of 0 ° C. for 1 to 60 seconds. The thickness of the film is preferably in the range of 5 to 250 μm.

The metal constituting the layer (A) in the present invention is preferably Au, Ag or Cu.
Among them, Ag, which hardly absorbs visible light, is particularly preferable. In addition, you may use 2 or more types of metal substances together as needed.

In the present invention, the dielectric constituting the layer (A) is TiO ₂ , ZrO ₂ , SnO ₂ , In ₂ O
_{3 and the} like are preferably exemplified. In particular, TiO ₂ or ZrO ₂ derived from an organic compound obtained by hydrolysis of alkyl titanate or alkyl zirconium is preferable because of its excellent workability. As a method for forming layer (A) from such a metal and a dielectric, vapor phase growth is preferable. , Vacuum deposition, sputtering, or plasma CVD is more preferred.

The layer (A) in the present invention is preferably formed by alternately laminating the metal layer and the dielectric layer, since the effect of preventing the reflection of visible light is improved.

The thickness of the metal layer is preferably in the range of 5 nm to 1000 nm. If the thickness is less than 5 nm, sufficient surface resistance is not exhibited, and the electromagnetic wave shielding property is deteriorated.
If it exceeds 00 nm, the visible light transmittance is reduced and the transparency is deteriorated.

It is necessary to set the thickness of the dielectric layer together with the metal layer so as to satisfy the transparency of the laminate of the present invention. The thickness of the dielectric layer is preferably in the range of 0 nm to 750 nm.

The metal constituting the metal layer (B) in the present invention is preferably at least one metal or alloy selected from Au, Ag, Cu, Al, Cr, Mg and Ni.

Further, it is preferable that the metal constituting the metal layer (B) is laminated in a mesh or linear form, since transparency is maintained and electromagnetic wave shielding characteristics are improved.

As a method of laminating the metal layer (B) in a mesh or linear shape, the metal layer (B) can be laminated on a film by transferring the metal layer. That is, a transfer film in which a release layer, a metal layer, and an adhesive layer are sequentially laminated on a base material is attached to one surface of the transparent thermoplastic resin film of the present invention, and the metal layer is transferred by thermocompression bonding. Can be.

The release layer of the transfer film is provided for easily separating the base material and the metal layer, and may be formed of a known release material, for example, wax, synthetic drying oil, cellulose dielectric, and the like. It can be formed by dissolving a resin (for example, cellulose nitrate cellulose acetate / butyrate) or a silicone resin in a solvent, applying the solution, and evaporating the solvent.

As a method for forming the metal layer of the transfer film, a vapor phase growth method is preferable, and a vacuum deposition method, a sputtering method or a plasma CVD method is particularly preferable.

The adhesive layer of the transfer film is preferably preliminarily coated with a mesh or linear adhesive (using gravure printing or the like) so that only the portion coated with the adhesive is transferred during the transfer. . As such an adhesive, a heat-sensitive adhesive is preferable, and for example, an adhesive such as vinyl acetate, vinyl chloride, and acrylic is more preferable.

As another laminating method, it is possible to laminate the metal layers in a mesh or linear shape by etching the metal layers. That is, a water-soluble adhesive (for example, polyvinyl alcohol adhesive) is applied on the base material by using gravure printing or the like in a shape to be etched, and a metal layer is laminated thereon. As a method for forming the metal layer, a vapor phase growth method is preferable. This laminate is etched with water to dissolve the metal in the water-soluble adhesive portion to obtain a mesh-like or linear metal shape. The thickness of the metal layer is 50
μm or less is preferred. An increase in the thickness of the laminate causes a decrease in the visible light transmission performance of the laminate for electromagnetic wave shielding produced from the transfer film.

In the present invention, the coverage of the metal portion with respect to the film area on the metal layer (B) surface is 20% or more and 8% or more.
It needs to be 0% or less. If the coverage is less than 20%, the electromagnetic wave shielding properties deteriorate, which is not preferable. If it exceeds 80%, the transmittance of visible light is insufficient, which is not preferable.

In the metal layer (B) according to the present invention in which the metal is laminated in a mesh or linear form, the metal has a line width (W; unit μm) of 50 μm or less and a metal line width (W). ) And the thickness (T; unit μm) of the metal layer (B) preferably satisfy the following expression (1).

[0029]

[Equation 2] W / 100 ≦ T ≦ W (1)

When the metal line width exceeds 50 μm, the transparency of the laminate of the present invention is reduced. In the relationship between the line width (W) of the metal and the thickness (T) of the metal layer (B), T <(W / 10
0), the electromagnetic wave shielding performance decreases, while W <T
, The transparency of the laminate decreases.

The laminate for shielding electromagnetic waves of the present invention has a ratio (Tnir / Tvi) between the visible light transmittance Tvis and the near infrared transmittance Tnir.
s) must be 0.75 or less. If the ratio (Tnir / Tvis) is exceeded, the selective transmittance of visible light and near-infrared light decreases, and the heat-shielding property deteriorates.

The electromagnetic wave shielding laminate according to the present invention is required to have an electric wave shielding characteristic of 30 dB or more in a frequency band of 80 to 1000 MHz. When the electric field wave shielding property is less than 30 dB, the electric field wave shielding property is insufficient, which is not preferable.

Further, in order to make the most of the electric field wave shielding characteristics of the laminate of the present invention, it is preferable to perform a hard coat treatment on the surface of the metal layer (B) or to provide a protective layer.

As such a protective layer, polyester resin,
A layer made of an acrylic resin or a silicone resin is preferable.

The hard coating method can be carried out by applying a hard coating agent used for a known polyester resin or acrylic resin. As a coating method, a known coating method such as a bar coating method, a doctor blade method, a reverse roll coating method, and a gravure roll coating method can be used. The thickness of the coating is 0.1 to
10 μm is preferred. As a hard coat treatment other than the coating method, a film obtained by hard coat treatment of a polyester film or the like may be laminated on the laminate of the present invention.

[0036]

The present invention will be described below in detail with reference to examples. In addition, the measurement of the characteristic of the laminated film for electromagnetic wave shielding was implemented according to the following method.

(1) Coverage Defined by the following formula (unit:%).

[0038]

## EQU3 ## Coverage = (area of mesh or linear metal part) / (film area) × 100

(2) Ratio of visible light transmittance (Tvis) to near-infrared transmittance (Tnir) (Tnir / Tvis) Both characteristics are described below for a heat ray shielding film laminate using Shimadzu Corporation UV-3101PC type. , The integrated visible transmittance and the integrated near-infrared reflectance were calculated according to JIS-A 5759, and the ratio (Tnir / Tvis) was determined. Visible light region 400-750 nm Near infrared light region 750-2100 nm

(3) Electric Wave Shielding Effect The electric wave shielding effect is defined by the following equation. If this value is large, the shielding effect is high.

[0041]

## EQU4 ## where SE is Shield effectiveness (dB), Ei is incident electric field strength (V / m), and Et is transmission electric field strength (V / m). Then, evaluation was performed based on the following criteria from the measured values obtained at a frequency of 80 to 1000 MHz. SE = 50 dB or more: ○ SE = 30 to 50 dB: Δ SE = less than 30 dB: × The measurement of the electric field wave shielding characteristic was performed at KEC (Kansai Electronic Industry Promotion Center).

(4) Metal layer thickness The thickness was measured using a stylus type surface roughness meter. In the case of a multilayer film composed of a metal and a dielectric layer, surface etching was performed in the depth direction by Auger electron spectroscopy to determine the thickness of each layer.

Example 1 An indium oxide layer (dielectric layer: first layer) having a thickness of 10 nm was provided on one surface of a polyethylene terephthalate film having a thickness of 50 μm. A silver thin film layer having a thickness of 12 nm was provided as a second layer on the surface of the first layer, and an indium oxide layer having a thickness of 15 nm was provided as a third layer on the surface. The formation of the first to third layers is as follows.
All were performed by a sputtering method under vacuum (5 × 10 ⁻⁵ Torr).

Further, as a surface protection of the sputtered layer, a polyfunctional acrylic resin was applied on the sputtered layer so that the coating thickness after drying became 50 nm, thereby forming a laminate.

Next, cellulose acetate butyrate was applied as a release layer on polyethylene terephthalate having a thickness of 12 μm so that the film thickness after drying became 3 μm. Then, a 0.5 μm-thick film was applied on the release layer of the film. The Ag layer was laminated by a sputtering method to prepare a transfer film.

Then, a vinyl acetate-based heat-sensitive adhesive having a thickness of 1 μm after drying was applied to the surface of the laminate opposite to the sputtering layer.
m, after gravure printing in a mesh shape (line width of 20 μm) with a coverage of 30%, heat-pressing the Ag layer side of the transfer film, peeling the base film of the transfer film, and providing a mesh-like metal layer Was. Table 1 shows the characteristics of the laminate.

Comparative Example 1 A laminate was obtained in the same manner as in Example 1 except that no mesh-like metal layer was provided. Table 1 shows the characteristics of the laminate.

[Comparative Example 2] The coverage of the metal layer was 85
%, A laminate was obtained in the same manner as in Example 1 except for changing to%. Table 1 shows the characteristics of the laminate.

[0049]

[Table 1]

[0050]

According to the present invention, it is possible to provide a film having excellent light selectivity and electromagnetic wave shielding properties.

Claims (7)

[Claims] 1. One side of a transparent thermoplastic resin film,
A laminate comprising a layer (A) made of a metal and a dielectric, and a metal layer (B) provided on the opposite surface, wherein the metal layer (B)
The coverage of the metal part to the film area on the surface is 2
0% or more and 80% or less, and the visible light transmittance (T
vis) and near-infrared transmittance (Tnir) (Tnir / Tvis) is 0.75 or less, and the electric wave shielding characteristic in the frequency band of 80 to 1000 MHz is 30 dB or more. For laminate. 2. The electromagnetic wave shielding laminate according to claim 1, wherein the transparent thermoplastic resin film is a polyethylene terephthalate film or a polyethylene naphthalate film. 3. A layer (A) comprising a metal and a dielectric,
The electromagnetic wave shielding laminate according to claim 1, wherein the laminate is a layer in which metal layers and dielectric layers are alternately laminated, and the metal is at least one metal or alloy selected from gold, silver, and copper. 4. The method according to claim 1, wherein the dielectric is TiO ₂ , ZrO ₂ , SnO ₂ ,
Electromagnetic shielding laminate according to claim 1, wherein a transparent high refractive index dielectric mainly composed of In ₂ O _3. 5. The metal constituting the metal layer (B) is laminated in a mesh or linear form, and the metal line width (W; unit μ)
m) is 50 μm or less, and the relationship between the line width (W) of the metal and the thickness (T; unit: μm) of the metal layer (B) satisfies the following expression (1). Laminate. [Equation 1] W / 100 ≦ T ≦ W (1) 6. The metal constituting the metal layer (B) is Au, A
g, 1 selected from Cu, Al, Cr, Mg and Ni
The laminate for electromagnetic wave shielding according to claim 1, wherein the laminate is at least one kind of metal or alloy. 7. An electromagnetic shielding laminate comprising a protective layer made of a polyester resin or an acrylic resin provided on a metal layer (B).