JPH1070393A - Manufacture of electromagnetic shielding material and electromagnetic shielding technique - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an electromagnetic shielding material which is thin enough, high in electromagnetic shielding properties, lightweight, and manufactured at a low cost by a method wherein a conductive metal spraying film is formed on a material by spraying conductive metal through a normal temperature metal spraying method. SOLUTION: Conductive metal is sprayed on a material such as a veneer as thick as a few μm or above through a normal temperature metal spraying method for the formation of an electromagnetic shielding material. This electromagnetic shielding property imparting method is applicable to all materials such as wood, plastic, metal and so on. Therefore, when a space is demarcated by walls, all the walls are enhanced in electromagnetical shielding properties, whereby the space can be easily and electromagnetically shielded. A conductive metal spraying film formed as above is porous, so that the porous parts of the film are sealed up with sealing material so as to enable the film to be improved in stability and strength. Base coating material is previously applied onto the surface of a material so as to enhance adhesion of the sprayed film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an electromagnetic shield material and a method of shielding electromagnetic waves for preventing troubles in medical equipment, music halls and the like caused by electromagnetic waves emitted from a portable telephone or the like. Things.

[0002]

2. Description of the Related Art Recently, portable telephones, PHSs, wireless LANs, and the like have rapidly spread. Along with this, troubles caused by electromagnetic waves generated by these have become a problem. Examples of such troubles include problems such as malfunctions of medical equipment in hospitals and generation of telephone call sounds during music concerts. Therefore, the need for shielding electromagnetic waves in space is increasing.

At present, the electromagnetic wave in space is
The following method has been proposed as a rule method. (1) Cover the space with a conductive material made of metal. (2) The space is covered with a carbon fiber nonwoven fabric or a composite material using the same as a base material. (3) Although not yet implemented, a driving form method using a wood fiber cement board and aluminum expanded metal has been devised.

[0004]

When an electromagnetic wave shield is applied by the above-mentioned conventional method, existing walls, doors and the like are demolished.
A wall material, a door, and the like having a shield must be attached, and a joint between members must be shielded. In addition, it was very difficult to obtain a high shielding performance of about 100 db by a shielding method other than using a metal material.

[0005] Also, in the production of a material subjected to shielding, the thickness as a shield material is required, and when a metal material is used, an increase in weight becomes a problem. was there. Therefore, there is a problem that these methods cannot be used. In addition, there was a problem that the production of the shield material was troublesome and the cost was increased.

[0006] The invention according to claim 1 of the present invention is:
It is an object of the present invention to provide a method of manufacturing an electromagnetic shield material that can provide electromagnetic wave shielding performance with a small thickness that does not cause a problem and is light and can be manufactured at low cost. Another object of the present invention is to provide, in addition to the above object, an electromagnetic shielding method which can be directly applied to existing walls, doors, floors and the like.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on a method capable of imparting conductivity with a small thickness, and as a result, have found that a method for forming a conductive film can be used.
According to the present invention, it has been found that a conductive metal sprayed film formed on a material to be shielded by spraying a conductive metal by a room temperature metal spraying method exhibits extremely effective electromagnetic wave shielding characteristics. Reached.

Although other methods such as the use of a conductive paint and a conductive polymer which can provide an electromagnetic wave shielding ability with a small thickness have been studied, these methods are not suitable for industrial use. No shielding ability was obtained.

According to the first aspect of the present invention, a conductive metal is sprayed on a material to be shielded by electromagnetic waves by a cold metal spraying method, and a conductive metal spray coating is formed on the material. It is characterized by having been formed. In addition, the invention according to claim 4 is a method for forming a wall material surrounding a space for shielding electromagnetic waves,
The method is characterized in that a conductive metal is sprayed by a room temperature metal spraying method to form a conductive metal spray coating on a wall material or the like, and the space is shielded by electromagnetic waves.

Room temperature metal spraying method (hereinafter referred to as MS method)
Is a thermal spraying method that can be applied to all kinds of materials including wood, because the thermal spraying is performed at room temperature, unlike the conventional metal spraying method. At present, this MS method is mainly used for rust prevention and corrosion prevention of metal products, but is not used for electromagnetic wave shielding at all.

[0011]

Next, an embodiment of the present invention will be described. According to the present invention, a conductive metal is sprayed onto a material such as veneer to a thickness of several μm or more by the MS method, and is used for electromagnetic wave shielding. As a material for imparting the electromagnetic wave shielding ability, any material such as wood, plastic, and metal can be applied. Therefore, if the electromagnetic wave shielding ability is given to all of the wall materials and the like forming the space in which the electromagnetic wave is to be shielded, the space can be easily shielded.

The conductive metal may be any metal as long as it can be made into a wire, for example, zinc,
Examples include conductive metals such as copper, copper-based alloys, tin, solder, and iron, and zinc and aluminum pseudo-alloys. Particularly, zinc, a pseudo-alloy of aluminum and zinc are preferable.

The thermal spray coating can be formed by thermal spraying using a normal temperature arc sprayer or the like. The pseudo alloy spray coating can be formed by simultaneously spraying zinc and aluminum. The thickness of the conductive metal spray coating is preferably several μm to several hundred μm. When the thickness is a few μm, the electromagnetic wave shielding performance is sufficiently exhibited. When the thickness is too large, not only is it not economical, but also the sprayed coating tends to peel off.

Since the conductive metal spray coating formed as described above is porous, in order to stabilize the spray coating and increase the strength, the porous portion is sealed with a sealing agent or paint. good. Further, in order to improve the adhesion of the thermal spray coating, a base coating may be applied in advance.

[0015]

【Example】

Example 1 An electromagnetic shield material of the present invention was manufactured, and an electromagnetic shield characteristic and a magnetic shield characteristic were measured.

(Manufacture of shield material) A sprayed coating of zinc and aluminum is applied to paper using a room-temperature arc spraying machine.
Simultaneous thermal spraying was performed so as to have a galvalume composition of 55% aluminum and 45% zinc to form sprayed pseudo-alloy films of 50 μm and 100 μm. For comparison, a paper in which a conductive polymer was applied to a thickness of 3 mm on paper and a paper in which a Ni-based conductive paint was applied to a thickness of 40 μm on paper were prepared.

(Measurement method) The difference between when a sample is mounted and when no sample is mounted between the shield boxes is measured by a receiver (spectrum analyzer).
The attenuation value (dB) was used.

The receiver (SA) is an electromagnetic wave (50 KHz)
Is measured using a Yokogawa-Hullet Packard Co., Ltd. T
Using ype / 8553B, magnetic (50-1000K
Hz) is measured by using HEWLETT PACARD T
ype / 8554B was used. As a standard signal generator (SSG), Type / MG6 manufactured by Anritsu Electric KK
45A was used.

With respect to the above-mentioned sample, by the above-mentioned measuring method,
The electromagnetic wave shield characteristics and the magnetic shield characteristics were measured.
The results are shown in FIGS. In the figure, + mark: 100 µm Zn / Al pseudo alloy sprayed paper □ mark: 50 µm Zn / Al pseudo alloy sprayed paper △ mark: 3 mm conductive polymer ○ mark: 40 µm Ni-based conductive paint

As is clear from the above results, the electromagnetic wave shielding material of the present invention exhibits remarkably excellent electromagnetic wave shielding ability. On the other hand, the conductive polymer and the Ni-based conductive paint, which similarly exhibit an electromagnetic wave shielding ability by a thin film, did not exhibit the electromagnetic shielding ability to be industrially usable.

Example 2 An electromagnetic wave shielding test of the shield material of the present invention was performed in a radio wave anechoic chamber. (Manufacture of shield material) Using a room temperature arc spraying machine, a spray coating of about 100 μm of zinc alone, a spray coating of zinc and aluminum, 55% of aluminum, zinc on an 8 mm thick plywood Thermal spraying was carried out simultaneously so as to have a galvalume composition of 45% to form a pseudo-alloy sprayed film of about 100 μm, which was subjected to a test.

(Measurement Conditions) (1) A metal box 4 having the shape shown in FIG. 3 and test equipment were arranged. In order to measure the far electromagnetic field as far as possible, the constant frequency range is set to 300 MHz or more in consideration of the distance between the transmitting and receiving antennas 1 and 2 and the ease of handling of the size of the box 4 and the like. And

(2) In order to minimize the influence of mutual induction with the image as much as possible,
The distance between the receiving antennas 1 and 2 and the types of the transmitting and receiving antennas 1 and 2 were determined as follows. (A) The frequency range to be measured is from 300 MHz to 1
In the case of GHz, a log-periodic diball array antenna (commonly called log veri) is used as the transmitting and receiving antennas 1 and 2, and the lower frequency limit is 3
At 00 MHz (wavelength 1 m), the distance between the shield material 3 to be tested is 1 m (1λ) for the transmitting antenna 1 and 0.6 m (0.6 λ for the surrounding metal box 4 at the receiving antenna 2 inside the box).
0.75λ) can be secured. Therefore, when the frequency is higher than 300 MHz, mutual induction is further reduced.

(A) The frequency range to be measured is 1 GHz
In the case of 3 GHz to 3 GHz, a double rigid guide antenna is used as the transmitting / receiving antennas 1 and 2 and the lower frequency limit is 1 GHz (wavelength 0.3
m), a distance of 0.3 m (1λ) was secured by the transmitting antenna 1 and a distance of 0.15 m (0.5λ) was secured by the receiving antenna 2. In this case, as in (a) above, the mutual induction is further reduced as the frequency increases.

As for the transmitting antenna 1, as a condition for forming a plane wave, the relationship between the dimension D and the distance R of the antenna is formulated as follows. R ≧ 2D ² / λ In the above case (A), λ ≦ 1 m and D = 0.75 m, so that R ≧ 1.1 m, and in the above case (A), λ ≦
Since 0.3 m and D = 0.14 m, R ≧ 0.13 m
Becomes As shown above, the distance between the transmitting antenna 1 and the shield material 1 to be tested is 1 m (1.3 m from the longest element of Logberg) and 0.3 m, respectively.
The condition in this case is also satisfied.

(3) The size of the shield material 3 to be tested is
When the frequency is 300 MHz at the distance between the antennas of (2), the basic size is 1.2 m which sufficiently includes the width of the first Fresnel zone. In addition, since the resonance frequency in the primary mode in the case of a cube having a side of 1.2 m is 216 MHz, setting the above frequency range of 300 MHz or more is appropriate from this point as well.

(4) Further, in order to prevent unnecessary reflection inside, the basic mold is deformed so that the side of the deep portion which is 1.5 m on one side and 0. 85
By adopting a horn type of mx 0.65 m and installing radio wave absorbers on the rear and side surfaces, the internal Q is lowered, and the resonance of higher mode is reduced.

(5) The transmitting antenna 1 is 1.4 mm from the floor.
When the height was set to m and the frequency was from 300 MHz to 1 GHz, a radio wave absorbing material was laid on the floor to remove the influence of reflection. (6) For the contact of the mounting surface of the shielded material 3 to the box with the box under test, a mesh line (3.5 cm wide, 0.2 cm thick) is drawn with the flange portion 5 of the box and the shielded material 3 under test. Sandwiched between. The results measured as described above are shown in the following Table 1 and FIG.

[0029]

[Table 1]

[0030]

According to the first aspect of the present invention, it is possible to provide an effective electromagnetic wave shielding performance at a small thickness where the thickness does not matter, and at the same time it is light and low cost. For example, it can produce a remarkably remarkable effect as compared with a conventional method of manufacturing this kind of electromagnetic shielding material.

According to the fourth aspect of the present invention, in addition to the above-described effects, the electromagnetic wave shield space can be easily constructed on the existing wall, door, floor, or the like as it is. Can be formed.

[0032]

[Brief description of the drawings]

FIG. 1 shows a diagram of electromagnetic wave shield characteristics measured in Example 1.

FIG. 2 shows a diagram of a magnetic shield characteristic measured in Example 1.

FIG. 3 shows a diagram of electromagnetic wave shield characteristics measured in Example 2.

[Explanation of symbols]

 + Mark: 100 μm Zn / Al pseudo alloy sprayed paper □ mark: 50 μm Zn / Al pseudo alloy sprayed paper △: 3 mm conductive polymer ○: 40 μm Ni-based conductive paint

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] December 6, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Change

[Correction contents]

[Brief description of the drawings]

FIG. 1 shows a diagram of electromagnetic wave shielding characteristics measured in Example 1.

FIG. 2 shows a diagram of magnetic shield characteristics measured in Example 1.

FIG. 3 is a perspective view illustrating a configuration of a measurement system used for measurement in Example 2.

FIG. 4 shows a diagram of electromagnetic wave shielding characteristics measured in Example 2.

[Explanation of symbols] +: 100 μm Zn / Al pseudo alloy sprayed paper □: 50 μm Zn / Al pseudo alloy sprayed paper △: 3 mm conductive polymer ○: 40 μm Ni-based conductive paint

Claims (6)

[Claims] 1. A method of manufacturing an electromagnetic shield material, comprising: spraying a conductive metal onto a material to be shielded by a room temperature metal spraying method to form a conductive metal sprayed coating on the material. Method. 2. The method according to claim 1, wherein the conductive metal is zinc, a pseudo-alloy of aluminum or zinc. 3. A porous portion of the conductive metal spray coating,
3. The method for producing a shield material according to claim 1, wherein the sealing material is sealed with a sealing agent or a paint. 4. A wall material or the like surrounding a space for shielding electromagnetic waves,
An electromagnetic wave shielding method comprising spraying a conductive metal by a room temperature metal spraying method, forming a conductive metal sprayed coating on a wall material or the like, and shielding the space by electromagnetic waves. 5. The method according to claim 4, wherein said conductive metal is zinc, an aluminum pseudo-alloy or zinc. 6. A porous portion of said conductive metal spray coating,
The shielding method according to claim 4 or 5, wherein the sealing process is performed with a sealing agent or a paint.