JP2000059081A - Manufacture of electromagnetic wave shielding material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase electromagnetic wave shielding effect, visible light transmittivity, adhesion between a substrate and a metal thin film, and the uniformity of the metal thin film by depositing a metal thin film having a conductivity on at least one face of a substrate and thereafter polishing the metal thin-film layer. SOLUTION: On at least one face of a substrate, a metal thin film having a conductivity is deposited. Silver is preferably used as metal to be deposited. Electroless plating is preferably used as a means for deposition. Next, the thin film is polished, preferably by chemical mechanical polishing, until a desired visible light transmittivity is obtained, that is, the thin film becomes 0.5 μm or below in thickness. The minimum thickness after polishing is 0.01 μm or above. Thereby, an electromagnetic wave shielding effect, a visible light transmittivity, adhesion between a substrate and a metal thin film, and the uniformity of the metal thin film can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an electromagnetic wave shielding material, and more particularly, to a cathode ray tube (hereinafter abbreviated as CRT), a liquid crystal (hereinafter abbreviated as an LCD), a plasma display (hereinafter abbreviated as a PDP), and an electro-luminescence device. (Hereinafter abbreviated as EL), light emitting diode (hereinafter L)
The present invention relates to a method for producing an electromagnetic wave shielding material having visible light transmittance used for a display such as an ED) and a filter installed on the front surface thereof.

[0002]

2. Description of the Related Art With the recent development of telecommunications information-related technology, electromagnetic environment problems such as malfunction of electronic devices and influence on human bodies due to electromagnetic waves emitted from electronic devices have been highlighted, and countermeasures have become necessary. I have.

Conventionally, various conductive surface treatments have been devised and put into practical use as means for imparting an electromagnetic wave shielding effect to a material having poor conductivity such as resin or glass. Examples of conductive surface treatment include electroless plating of copper, nickel, silver, etc., metal spraying of zinc, copper, aluminum, etc., metal foil sticking, vacuum evaporation, sputtering, ion plating, conductive paint, etc. There is a method of laminating thin films, which is applied to housings of electronic devices such as personal computers and mobile phones.

On the other hand, an electromagnetic wave shield for a display monitor such as a CRT, an LCD, a PDP, and an EL needs not only a shielding effect but also a visible light transmittance in order to ensure the transparency of a displayed image. As a conventional technique relating to an electromagnetic wave shielding material for a display monitor and a front filter thereof using a resin or glass as a substrate, there is known a method of laminating a mesh made of conductive fibers by coating a metal or the like on a substrate (for example, Japanese Patent Laid-Open Publication No. 9-1
45918, JP-A-9-247581, JP-A-9-247581, JP-A-9-247585
JP-A-9-247584), a technique using sputtering (JP-A-9-306366), and a technique using a conductive paint (JP-A-9-330666 and JP-A-9-330667). A method is disclosed in which a metal thin film thinner than the visible light range (400 to 700 nm) is provided on a substrate to achieve both a shielding effect and visible light transmittance.

[0005] However, in the method using a conductive mesh, since the metal or the fiber portion provided with conductivity does not have visible light transmittance, the visible pitch is increased by increasing the mesh pitch so as to reduce the area of the portion as much as possible. Although some measures have been taken to increase the light transmission, there is a problem in that the electromagnetic wave shielding effect is lowered, and it is difficult to satisfy both the visible light transmission and the electromagnetic wave shielding effect at a high level. However, there is a problem that moire interference fringes occur depending on the pitch width.

The technique of forming a metal thin film by sputtering is capable of obtaining a metal thin film that transmits visible light, and has excellent features such as excellent conductivity, adhesion to a substrate, and uniformity of film thickness. However, it is not suitable for a large molded product corresponding to a large area such as a PDP, and there is a problem that the apparatus is very expensive.

Further, the technique of forming a metal thin film using a conductive paint has a problem that the thin metal thin film having visible light transmittance has poor conductivity, and it is difficult to obtain a good electromagnetic wave shielding effect. However, it is difficult to achieve both visible light transmission and electromagnetic wave shielding.

Other conductive surface treatments such as electroless plating of copper, nickel, silver, etc., metal spraying of zinc, copper, aluminum, etc., and metal foil sticking are inexpensive, but have low visible light transmittance. That is, it is difficult to obtain a uniform thin film thinner than the wavelength of visible light. Separately from the surface treatment, conductive transparent substrates molded by mixing conductive filler into resin or glass have been studied as an attempt to impart an electromagnetic wave shielding effect to the resin or glass substrate itself. The method has not yet reached a level to obtain a sufficient electromagnetic wave shielding effect.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a CR
Applicable as displays such as T, LCD, PDP, EL and filters installed on the front of them.
An electromagnetic shielding material with a metal thin film laminated on a glass or resin substrate, an electromagnetic shielding material that excels in electromagnetic wave shielding effect, visible light transmission, adhesion between the substrate and the metal thin film, and uniformity of the metal thin film at a low cost. It is to provide a method for manufacturing.

[0010]

In order to achieve the above object, the present invention basically has the following arrangement.

That is, a method of manufacturing a visible light transmitting electromagnetic wave shielding material, comprising laminating a conductive metal thin film on at least one surface of a substrate, and then polishing the metal thin film layer. ".

[0012]

Embodiments of the present invention will be described below.

First, the visible light transmittance as referred to in the present invention is indispensable for satisfying the visibility and color tone of a displayed image on a practical level.
It is represented by a transmittance of visible light in the range of 00 nm, and preferably has at least 40% or more over the entire wavelength range. In addition, the electromagnetic wave shielding effect referred to in the present invention is:
It refers to how much the electromagnetic wave energy can be attenuated by absorbing or reflecting the energy (frequency) of the electromagnetic wave by the shielding material, and the attenuation of the electric field strength at a certain measurement distance (3 m, 10 m, or 30 m) (decibel; d
B (μV / m)) from 30 MHz to 1000 M
Preferably, the quasi-peak value of the electric field intensity attenuation in the frequency range of Hz has at least 30 dB or more.

The substrate used in the present invention includes CRT, LC
A transparent substrate used for flat panel displays such as D, PDP, EL, LED, etc. and a filter installed on the front thereof, including a glass substrate such as non-alkali glass, soda lime glass, borosilicate glass, and polymethyl meta A transparent resin substrate such as create and polycarbonate is exemplified.

In the present invention, first, a metal thin film having conductivity is laminated on at least one surface of the substrate. The metal to be laminated is not particularly limited as long as it is a conductive metal, but gold, platinum, palladium, silver, copper, brass,
A metal or alloy containing at least one selected from cobalt, iron, tin, nickel, zinc, and aluminum is preferable, and the volume specific resistivity (Ω · cm) is low;
Considering that it is inexpensive and easy to form a thin film, silver is more preferably used.

Means for laminating the metal thin film is not particularly limited as long as it is a method capable of forming the metal thin film. Electroless plating, metal spraying, metal foil sticking, vacuum evaporation, sputtering, ion Various conductive surface treatments conventionally used as means for imparting an electromagnetic wave shielding effect to poorly conductive materials such as resin and glass, such as plating and conductive paint, are preferably used. Uniformity, adhesion to substrate, easy thin film formation,
Considering that it can be manufactured at low cost, electroless plating is more preferable.

The method of electroless plating on resin or glass is as follows.
Degreasing process-Etching process-Activation process (Sensitizing / Activating)-Like electroless plating,
A generally known method is used. In the case of silver plating, a silver mirror reaction is suitably used in the last electroless plating step. In addition, recently, the mainstream method of applying electromagnetic wave shielding to the housing of notebook PCs, etc., is to apply a primer containing a catalyst on the surface to be laminated, and apply electroless plating directly on it. "SST
(Single Side Technology) Method (Industrial Materials Vol.44 N
o.9 p.56) are also preferably used in the present invention.

Furthermore, electrolytic plating may be performed after electroless plating.

The thickness of the metal thin film to be laminated is not particularly limited, but is preferably 10 μm or less in order to reduce the time required for the subsequent polishing.

After laminating the metal thin film, the thin film is polished until a desired visible light transmittance is obtained, that is, until the thickness of the thin film becomes 0.5 μm or less, preferably 0.4 μm or less. On the other hand, the lower value of the film thickness after polishing is preferably 0.01 μm or more. Examples of the polishing means include mechanical polishing for polishing using abrasive grains, chemical polishing using a chemical action such as dissolving metal, electrolytic polishing, and the like.In the present invention, recently, in the semiconductor manufacturing field as ultra-precision polishing, Chemical mechanical polishing method (Chem
Ical Mechanical Polish
g; hereinafter abbreviated as CMP).

CMP is a process in which a slurry (abrasive) in which hard ultrafine abrasive grains are dispersed in a working fluid having a chemical effect such as formation of an oxide film or a hydrated film or etching has a polishing surface. In this method, the workpiece surface is super-precisely polished by moving the polishing surface relative to the workpiece surface. In the field of semiconductor manufacturing, it has been applied as a polishing technique for polishing a bare silicon wafer or a flattening technique for a compound semiconductor or metal wiring formed on silicon.

The hard ultrafine abrasive used in the present invention is not particularly limited as long as it is a polishing agent for CMP, but preferably has a particle size of 1 μm or less, and further improves the surface flatness. Considering this, those having a diameter of 0.3 μm or less are more preferable. The material of the abrasive grains is colloidal silica, iron oxide powder, barium carbonate powder, zirconia oxide powder, alumina powder,
At least one of cerium oxide powder and manganese dioxide powder is preferable, and more preferably, colloidal silica or alumina powder having a particle size of 0.2 μm or less is suitably used.

As the working fluid used in the present invention, a solution having an action of forming an oxide film or a hydrated film on the worked surface of the metal thin film and a solution having an etching action are preferably used. Examples thereof include aqueous hydrogen peroxide and aqueous ammonia.

The polishing cloth used in the present invention is not particularly limited as long as it is a polishing cloth for precision polishing. However, since the metal thin film layer is uniformly polished, the substrate is warped or undulated. As such a polishing cloth, for example, a type in which a non-woven fabric of polyester fiber is impregnated with polyurethane (for example, trade name: Suba series,
Rodel Nitta Co., Ltd.), polyurethane foam type having closed cells (for example, trade name: IC1000, M
H series, manufactured by Rodale Nitta Co., Ltd., suede type (for example, trade name: Supreme series, manufactured by Rodale Nitta Co., Ltd.), two-layer type (for example, IC
1000 and Suba, Rodale Nitta Co., Ltd.).

Further, in the present invention, it is desirable to form an antireflection film on the metal thin film layer after obtaining desired visible light transmittance by polishing. The antireflection film is preferably a silica film, and is laminated by a coating method such as spin coating, spray coating, screen printing, or coating.

[0026]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Comparative Example 1 Polycarbonate having a size of 240 × 180 mm and a thickness of 0.5 mm was used as a substrate, and a silver thin film layer was formed on one surface of the substrate by electroless plating. In the electroless plating, first, the masked substrate is immersed in an aqueous solution containing 540 mL / L of sulfuric acid and 25 g / L of chromic acid at 70 ° C. for 30 minutes to etch the substrate, and then, 20 g / L of stannous tin chloride, Sensitizing is performed by immersing in an aqueous solution of hydrochloric acid 5 mL / L for 5 minutes at 25 ° C., and then 0.2 g / L of palladium chloride,
Activating was performed by immersion in an aqueous solution of hydrochloric acid 1 mL / L at 35 ° C. for 5 minutes. Thereafter, silver nitrate 60 g / L,
It was immersed in a solution of 28% ammonia 60 g / L and 37% formaldehyde 40 mL / L at room temperature for 2 minutes to form a silver thin film. The average thickness of the obtained silver thin film layer is 1.5 μm.
No visible light transmittance in the range of 400 to 700 nm was obtained, and no transparency was obtained.

Comparative Example 2 In Comparative Example 1, the concentration and temperature of the electroless plating solution,
By changing the processing conditions such as immersion time, and trying to obtain a thickness of 0.4μm or less at which visible light transmittance is obtained as the thickness of the silver thin film layer, as the thickness of the thin film layer became thinner,
It has become difficult to stably obtain a uniform thin film over the entire surface of the substrate.

Example 1 In the same manner as in Comparative Example 1, a silver thin film layer having an average thickness of 1.5 μm was formed on one surface of a polycarbonate substrate. Thereafter, the silver thin film layer was polished by CMP. A slurry in which alumina having a particle diameter of 230 nm is suspended in a hydrogen peroxide solution is used as the slurry, and Suba40 manufactured by Rodel Nitta is used as the polishing cloth.
0 was used. Polishing was performed for 10 minutes at a rotation speed of a rotary platen of 60 rpm and a processing pressure of 200 g / cm ² .

The polished silver thin film layer has a thickness of 0.22 μm.
m, the surface roughness was 10 nm or less, and a silver thin film having a uniform thickness and a very small thickness unevenness over the entire surface of the substrate was obtained. The transmittance of visible light in the range of 400 to 700 nm was 80% on average, and a transmittance sufficiently satisfying the visibility was obtained. Further, the surface resistance value of the electromagnetic wave shielding panel thus obtained is 0.3Ω / □, and the electromagnetic wave shielding effect at a measurement distance of 10 m is approximately 45 dB in the range of 30 MHz to 230 MHz, and 230 MHz to 1000 MHz.
And a shielding effect that sufficiently satisfies the allowable value of Class A at a measuring distance of 10 m measured by the Voluntary Control Council for Interference by Information Technology Equipment (VCCI).

[0031]

According to the present invention, CRT, LCD, PD
Electromagnetic wave shielding material, visible light transmission, substrate and metal thin film, which can be applied as a display such as P, EL, LED, etc., and a metal thin film laminated on a glass or resin substrate, which can be applied as a filter installed in front of them A method for manufacturing an electromagnetic wave shielding material having excellent adhesion to a thin film and uniformity of a metal thin film at a low cost can be provided.

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Claims (4)

[Claims] A thin film of a conductive metal is laminated on at least one surface of a substrate made of glass or resin,
A method for producing a visible light transmitting electromagnetic wave shielding material, which comprises polishing the metal thin film layer thereafter. 2. The method for manufacturing a visible light transmitting electromagnetic wave shielding material according to claim 1, wherein a chemical mechanical polishing method is used for the polishing means. 3. The method for manufacturing a visible light transmitting electromagnetic wave shielding material according to claim 1, wherein an electroless plating method is used as a means for laminating a conductive metal thin film. 4. The method for producing a visible light transmitting electromagnetic wave shielding material according to claim 1, wherein the substrate is made of glass or resin.