JPH11198274A - Electromagnetic wave shielding laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic wave shielding laminate of superior transparency for sealing electromagnetic waves, infrared rays and near infrared rays transmitted from a display device such as an electromagnetic equipment and the display screens of a liquid crystal display(LCD) and a plasma display panel(PDP), shutting off external electromagnetic waves infiltrated into the electromagnetic equipment or the like and providing the superior noise reducing effect. SOLUTION: A laminate is constituted of a layer A formed of a transparent thermoplastic resin film, a layer B formed of a metal and a dielectric body C, and the laminate is a laminate I formed of layers laminated in the order of A/B/C or a laminate II formed of layers laminated in the order of A/C/B, and the visible beam transmittance is 50% or more, and the electric field shielding characteristics on 80-1000 MHz frequency zones are 50 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]

The present invention is a laminate comprising a layer (A) composed of a transparent thermoplastic resin film, a layer (B) composed of a metal and a dielectric, and a metal layer (C). The laminate is the laminate (I) laminated in the order of A / B / C or the laminate (II) laminated in the order of A / C / B, the visible light transmittance is 50% or more, and 8
An electromagnetic wave shielding laminate having an electric wave shielding characteristic in a frequency band of 0 to 1000 MHz of 50 dB or more.

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 oriented polyethylene terephthalate film or a biaxially oriented polyethylene naphthalate film which is excellent in 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.

Electromagnetic waves are shielded by absorbing and reflecting electric field waves and electromagnetic waves on a shield. In particular, in order to improve the shielding properties of electric field waves, the electric field waves are reflected by a uniform metal surface having a low resistance (low resistance effect), and the electric field waves are absorbed by a grid-like metal layer (thickness effect) to improve the shielding effect. Can be enhanced.

The layer of metal in layer (B) serves as such a low resistance uniform metal surface. The metal constituting the layer (B) in the present invention is Au, Ag or C
u is preferably exemplified. 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 addition, a layer made of a dielectric material is provided to suppress reflection of visible light and increase transmittance.

As the dielectric constituting the layer (B) in the present invention, 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 (B) from such a metal and a dielectric, a vapor phase growth method is preferable. , Vacuum deposition, sputtering, or plasma CVD is more preferred.

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

The thickness of the metal layer in the layer (B) is from 1 nm to
A range of 1000 nm is preferred. When the thickness is less than 1 nm, a sufficient surface resistance value is not exhibited, and the electromagnetic wave shielding property is deteriorated. When the thickness exceeds 1000 nm, the visible light transmittance is reduced and the transparency is deteriorated.

The thickness of the dielectric layer in the layer (B) needs to be set 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 0 nm
The range of -750 nm is preferred.

The metal constituting the metal layer (C) in the present invention is preferably at least one metal or alloy selected from metals having a volume resistivity of 20 [Ω · m] or less. It is preferably at least one metal or alloy selected from Ag, Cu, Al, Cr, Mg and Ni.

It is preferable that the metal constituting the metal layer (C) 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 (C) in a mesh or linear shape, the film layer (A) is transferred by transferring the metal layer.
Can be laminated. That is, a transfer film in which a release layer, a metal layer, and an adhesive layer are sequentially laminated on a substrate,
The metal layer (C) can be transferred by affixing to one surface of the transparent thermoplastic resin film (A) in the present invention, and by applying heat and pressure.

The release layer of the transfer film is provided for easily separating the base material and the metal layer, and may be formed using a known release material, for example, wax, synthetic drying oil, and fibrous dielectric material. 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, a metal layer can be laminated in a mesh or linear shape by etching the metal layer. 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 (C) in the laminate of the present invention is preferably 50 μm or less, that is, the thickness of the metal layer of the transfer film is preferably 50 μm or less. Further, the thickness of the metal layer (C) is preferably 0.01 to 30 μm. 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.

The laminate for shielding electromagnetic waves of the present invention comprises the above-mentioned film layer (A) and a layer (B) comprising a metal and a dielectric.
And the metal layer (C) can be manufactured by laminating in the order of A / B / C or A / C / B.

The laminate of the present invention has a visible light transmittance of 50.
%. If it is less than 50%, transparency deteriorates, which is not preferable.

The laminate of the present invention has a thickness of 80 to 100.
The electric field wave shielding characteristic in the 0 MHz frequency band is 50
It is necessary to be at least dB. When the electric field wave shielding property is less than 50 dB, the electric field wave shielding property is insufficient, which is not preferable.

Further, in order to maximize the electric wave shielding characteristics of the laminate of the present invention, it is preferable to perform a hard coat treatment on the metal layer (C) surface or 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 coat treatment method can be carried out by applying a hard coat 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.

[0034]

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) Visible light transmittance Shimadzu Corporation UV-3101PC model was used to calculate the product of the solar energy intensity and the transmittance for every 50 nm in the wavelength range of 450 to 750 nm for the heat ray shielding film laminate. The sum was obtained by dividing the sum by the sum of the solar energy intensities, and evaluated according to the following criteria. 60% or more: 50% or more and less than 60%: ○ Less than 50%: ×

(2) 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.

[0037]

## EQU1 ## where SE is Shield effectiveness (dB), Ei is incident electric field strength (V / m), and Et is transmission electric field strength (V / m).

Then, the following criteria were evaluated from the measured values obtained at the 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).

(3) 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 A polyethylene terephthalate film (A ₁ ) having a thickness of 50 μm was coated on one surface with a thickness of 10 nm.
(Dielectric layer: first layer). On the surface of the first layer, a silver thin film layer (containing 10% of copper) having a thickness of 12 nm was provided as a second layer, and then a titanium oxide layer having a thickness of 15 nm was provided as a third layer on the surface thereof. A layer (B ₁ ) made of a dielectric was laminated. The first to third layers
Each of the layers was formed by a sputtering method under a vacuum (5 × 10 ⁻⁵ Torr).

Next, cellulose acetate butyrate was applied as a release layer on a 12 μm-thick polyethylene terephthalate so that the film thickness after drying was 3 μm, and then 0.5 μm-thick was applied on the release layer of the film. A silver layer (containing 10% of copper) is laminated by a sputtering method, and a vinyl acetate-based heat-sensitive adhesive having a dry thickness of 0.5 μm is further formed thereon.
Gravure printing was performed so as to form a grid with a line width of 20 μm and 100 mesh to prepare a transfer film.

The Ag layer side of this transfer film was heated and pressed to the layer (B ₁ ) side of the above-mentioned laminate, and the base film of the transfer film was peeled off to provide a mesh-like metal layer (C ₁ ). A laminate was made. This laminate has a configuration in which the layers are laminated in the order of A ₁ / B ₁ / C ₁ . Table 1 shows the characteristics of the laminate.

Example 2 The structure of the laminate was A ₁ / C ₁ / B
_A laminate was prepared in the same manner as in Example 1 except that the number was changed to ₁ . 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 A vinyl acetate-based heat-sensitive adhesive in a transfer film was dried at a thickness of 0.5 μm and a line width of 50 μm.
A laminate was obtained in the same manner as in Example 1, except that gravure printing was performed so as to form a grid of m and 100 mesh. Table 1 shows the characteristics of the laminate.

[0046]

[Table 1]

[0047]

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

Claims (8)

[Claims] 1. A laminate comprising a layer (A) made of a transparent thermoplastic resin film, a layer (B) made of a metal and a dielectric, and a metal layer (C), wherein the laminate is made of A
Laminate (I) or A / C /
A laminate (II) laminated in the order of B, wherein the visible light transmittance is 50% or more, and the electric wave shielding property in the frequency band of 80 to 1000 MHz is 50 dB or more, wherein . 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 (B) comprising a metal and a dielectric,
2. The electromagnetic wave shielding laminate according to claim 1, wherein the laminate is formed by alternately laminating metal layers and dielectric layers, and the metal is at least one metal or alloy selected from Au, Ag, and Cu. 4. The method according to claim 1, wherein the dielectric is TiO ₂ , ZrO ₂ , SnO ₂ ,
Electromagnetic shielding laminate according to claim 2, wherein the transparent high refractive index dielectric mainly composed of an In ₂ O _3. 5. The electromagnetic wave shielding laminate according to claim 1, wherein the metal constituting the metal layer (C) is at least one metal or alloy selected from metals having a volume resistivity of 20 [Ω · m] or less. body. 6. The laminated body for electromagnetic wave shielding according to claim 5, wherein the metal constituting the metal layer (C) is laminated in a mesh or linear form, and the thickness of the metal layer (C) is 50 μm or less. 7. The metal constituting the metal layer (C) is Au, A
g, 1 selected from Cu, Al, Cr, Mg and Ni
7. The laminate for shielding electromagnetic waves according to claim 6, wherein the laminate is at least one kind of metal or alloy. 8. An electromagnetic wave shielding laminate in which a protective layer made of a polyester resin or an acrylic resin is provided on the outermost layer on the side where the metal layer (C) is laminated.