JPS63305599A - Electromagnetic shield material - Google Patents

Abstract

PURPOSE:To enable the effective shielding of electromagnetic waves over a wide range of wavelength regions, by specifying soft magnetic amorphous alloy pieces of specific scale or flake shapes and laminating them to form amorphous alloy layers and next by laminating one of conductive metallic layers and one of said amorphous alloy layers at a specific interval in between. CONSTITUTION:Soft magnetic amorphous alloy pieces of scale or flake shapes, each of which is 5-100mum in its thickness and 10-15000 in its aspect ratio (a ratio of maximum length to maximum thickness), are laminated 100-500g/m<2> in weight per unit area so as to form amorphous alloy layers 2. Next one of conductive metallic layers 3 and one of said amorphous alloy layers 2 are laminated at an interval of 5-500mum in between. Electromagnetic waves, including magnetic field components on a low-frequency region and electric field components on a high-frequency region, over a wide range of wavelength regions, can be effectively shielded accordingly.

Description

[Detailed description of the invention] B. Industrial application field The present invention relates to an electromagnetic shielding material.

In recent years, with the spread of electrical and electronic devices, the weight of these devices has been reduced,
In order to lower prices, plastics are increasingly used as materials, and as a result, electromagnetic interference due to leakage of electromagnetic waves from these electrical and electronic devices has become a major problem.

Precision electrical and electronic devices such as computers and precision measuring instruments often malfunction or produce errors in measured values when exposed to external electromagnetic waves. For this reason, electromagnetic wave regulations have been enacted in the United States and West Germany, and it is planned that an electromagnetic wave regulation system will soon be established in Japan as well.

However, although various methods have been studied to shield electromagnetic waves, none of them are sufficient.

For example, methods for covering the surface of a plastic casing of electrical or electronic equipment with a shielding material include painting with conductive paint, zinc spraying, plating, vapor deposition, and sputtering. Although these methods are quite effective in shielding the electric field component, they are less effective against the magnetic field component in the low frequency range, and there is also the problem of peeling, which can cause trouble, so it is important to take adequate countermeasures. It's hard to say.

In addition, as a method of shielding electric and electronic equipment by mixing metal fillers into the plastics mentioned above, stainless steel fibers are used, taking into consideration the shielding of magnetic field components, but this also has a sufficient shielding effect. not, i.e.
In order to have a sufficient shielding effect, it is necessary to add a large amount of titanium to the metal filler, which results in a decrease in the strength of the plastic, and also causes the metal filler to appear on the surface, making it difficult to apply further coating. The cost will be high.

Furthermore, iron foil is also being considered as a shielding material with consideration given to shielding the magnetic field component, but it has low magnetic permeability for magnetic field components in the low frequency range and cannot provide a sufficient shielding effect. Compared to copper, aluminum, etc., it has a higher electrical resistance with respect to electric field components, and its shielding properties are not sufficient.

C0 Purpose of the Invention The present invention has been made in view of the above circumstances, and includes:
The object of the present invention is to provide an electromagnetic shielding material that can effectively shield electromagnetic waves over a wide frequency range, including magnetic field components in the low frequency range and electric field components in the high frequency range.

21 Structure of the Invention The present invention comprises at least one amorphous alloy layer and at least one conductive metal layer, one layer of the amorphous alloy 1 and one layer of the conductive metal layer. The layers are laminated with an interval of 5 to 500 μm, and the amorphous alloy layer has a thickness of 5 to 100 μm and an aspect ratio (however, the aspect ratio is the ratio of the maximum length to the maximum thickness). .) 10-150
00 scale-like or flake-like soft magnetic amorphous alloy pieces with a weight per unit area of 100 to 500 g/rr? The present invention relates to an electromagnetic shielding material having a laminated structure.

E1 Functions and Effects of the Invention Amorphous alloys are attracting attention as various functional materials because they exhibit unique chemical and mechanical properties that are not found in ordinary crystalline alloys. Among them, amorphous alloys such as iron-based and cobalt-based alloys do not exhibit crystal anisotropy, so they exhibit extremely good soft magnetic properties such as very small coercive force and high magnetic permeability. is expected to be put into practical use.

However, amorphous alloys usually have a thickness of several tens of μm and a width of 100 f.
It is supplied in the form of a ribbon of about 1.5 lbs., and it is very difficult to handle it because it is difficult to cut into sheets of the specified size and has problems with adhesion when stacking them together. In order to do this, it is necessary to stack many layers,
It requires a lot of man-hours and is problematic in terms of productivity.

As a result of intensive research, the present inventor has found that by forming a magnetic amorphous alloy into scales and laminating them, the above-mentioned excellent properties of the magnetic amorphous alloy can be retained, and productivity can also be improved. The present invention, which has found that an excellent magnetic shielding material can be obtained, was made based on the above findings.

Soft magnetic amorphous alloy flakes (hereinafter simply referred to as amorphous alloy flakes)
) If the thickness is less than 5 μm, it will be difficult to produce an amorphous alloy piece, and if it becomes thicker than 100 μm, it will be difficult to make it amorphous, so the thickness should be 5 to 100 μm. A particularly preferred thickness is 20 to 60 μm.

If the aspect ratio of the amorphous alloy flakes is less than 10, the magnetic permeability of the amorphous alloy flakes decreases, the magnetic properties of the amorphous alloy flakes change, and lamination becomes difficult, resulting in deterioration of magnetic shielding properties. It becomes like this. On the other hand, if the aspect ratio is 15000
If it exceeds this, handling of the amorphous alloy pieces becomes troublesome and productivity decreases. A particularly preferred range of aspect ratio is 50 to 10,000.

The weight of the above amorphous alloy piece per unit area is 100~
However, if the amount of amorphous alloy flakes is less than 100 g/nr, the lamination of amorphous alloy flakes and the space between them will be reduced. contact(
conduction) becomes difficult and magnetic shielding performance deteriorates. If this exceeds 500 g/rrr, it becomes difficult to stack and adhere the amorphous alloy pieces, creating voids in the amorphous alloy layer, and the amount of amorphous alloy pieces per unit area increases. Despite this, magnetic shielding properties deteriorate. A particularly preferable range of the above amount of amorphous alloy flakes is 200 to 350
g/d.

The amorphous alloy layer with the above structure is made of amorphous alloy pieces that exhibit good soft magnetism, so it is effective in shielding magnetic field components in the low frequency range, but it is effective in shielding magnetic field components in the high frequency range. Since the electric field component is the main component of electromagnetic waves,
It has a high electrical resistance (100 to 150 μΩ・co
+), the thickness must be increased, which is disadvantageous.

On the other hand, conductive materials with low electrical resistance are used for electromagnetic shielding materials used in high frequency regions, but since these are non-magnetic materials or magnetic materials with low magnetic permeability, they are susceptible to magnetic field components in low frequency regions. Against them, they are almost powerless.

Therefore, in the present invention, a layer made of laminated amorphous alloy pieces is used as a layer effective in shielding magnetic field components in a low frequency region, and a shield is effective in shielding electric field components in a high frequency region. Layers of conductive materials are laminated to effectively shield electromagnetic waves in a wide frequency range.

If the structure is such that the amorphous alloy layer and the conductive material layer are directly adhered to each other, the two layers will interfere with each other and the properties cannot be expected, and lamination using adhesive is industrially advantageous. , provide a gap between both layers using an insulating material such as plastic film. This interval, that is, the thickness of the insulating layer is 5μ
If it is less than 500 μm, it will be difficult to make close contact between the amorphous alloy layer and the insulating layer, and if it exceeds 500 μm, the shielding material will become thick and difficult to handle, which is also disadvantageous from an industrial perspective. Therefore, the above-mentioned interval (thickness of the insulating layer) is preferably within the range of 5 to 500 μm.

Further, when a plurality of amorphous alloy layers and a plurality of conductive material layers are provided, it is desirable that the two layers be arranged alternately at intervals (with an insulating layer in between).

As the conductive material, metal plates such as copper, aluminum, nickel, and iron can be used.

If the plate thickness is 5 μm, the shielding effect against electric fields in the high frequency range is not significant, and if it exceeds 500 μm, the shielding material becomes heavy and difficult to handle. Therefore, the thickness of this conductive metal layer is preferably within the range of 5 to 500 μm.

To, Example The present invention will be explained in detail below.

Figure 1 is a plan view of the electromagnetic shielding material based on the present invention, Figure 2 is a plan view of the electromagnetic shielding material based on the present invention;
The figure is also an enlarged sectional view schematically showing the structure.

In this example, a polyester film 4 is sandwiched between an amorphous alloy layer 2 formed by laminating amorphous alloy pieces 2a and N3 made of a conductive metal such as copper, and the same polyester film This is an example in which the electromagnetic shielding material 1 is configured as a 4N laminated structure with the film 4 adhered thereto. However, in FIG. 1, the outermost polyester film is not shown.

As can be seen from FIG. 1, the amorphous alloy pieces 2a are uniformly dispersed and stacked in random directions, so that they are naturally non-directional. On the other hand, laminating amorphous alloy ribbons or crystalline alloy ribbons requires repeated cutting and gluing, bonding in cross directions and different angles to make them non-directional, and requires dispersion. Sometimes, by applying a slight magnetic field along a predetermined direction, the amorphous alloy pieces can be aligned in the longitudinal direction and given directionality.

If the composition of the amorphous alloy piece exhibits soft magnetism, it exhibits magnetic shielding properties.

Amorphous alloy flakes can be made by cutting from a ribbon or by a known melt extraction method, but from the viewpoint of productivity and because the peripheral edge of the amorphous alloy flake can be made thinner and flake-like. , the present applicant first published JP-A-58
Cavity silane method proposed in Publication No. 6907 (molten metal is supplied to the surface of a roll rotating at high speed, which has a surface layer with low wettability to the molten metal, and the molten metal is pulverized into fine particles). It is desirable to apply a method in which the molten metal droplets are divided into molten metal droplets and then rapidly solidified by colliding with a metal rotating body rotating at high speed.

Specific examples of the present invention will be described below.

Co(HFey, JS
lifB! (The number attached to the element symbol represents the atomic percent of the elemental component; the same shall apply hereinafter.) An amorphous alloy piece was produced.

This amorphous alloy piece has an average thickness of 40 μm and an aspect ratio of 200 to 500.

This amorphous alloy piece was used to prepare an electromagnetic shielding material 1 having one amorphous alloy layer 2 and one metal layer 3 as shown in FIGS. 1 and 2. That is, a polyester film 4 with a thickness of 25 μm is placed on a copper plate 3 with a thickness of 100 μm,
Amorphous alloy pieces 2a are laminated thereon at a rate of 250 g/rrf, and a polyester film 4 with a thickness of 25 μm is further covered as the outermost layer, and these are bonded with an adhesive (not shown) to form an electromagnetic shielding material. It was set to 1.

The electromagnetic shielding properties of this electromagnetic shielding material 1 were measured using a spectrum analyzer TR-4172 manufactured by Atopan Test Co., Ltd. The measurement procedure is schematically shown in FIG. 9 for the magnetic field component and in FIG. 10 for the electric field component. 200m x 200B electromagnetic shielding material 11'; Ig) jl,, 10 days away from one side from dll' is a loop antenna 5 for magnetic wave transmission with a diameter of 10 cranes.
Alternatively, a radio wave transmitting probe antenna 15 with a length of 10 fl is placed on the other side at a distance R of 1 (hm) from a magnetic wave receiving loop antenna 6 with a diameter of 10 m or a radio wave receiving probe antenna 16 with a length of 10 cm, respectively. , these are measured using spectrum analyzer TR4172 with tracking generator.
Connect to 7. Attenuation of the magnetic waves or radio waves from the transmitting antenna 5 or 15 due to the electromagnetic shielding material 1t/l is detected by the receiving antenna 6 or 16, and measured by the spectrum analyzer TR41727.

The measurement results are shown in FIGS. 4 and 5.

In addition, in FIGS. 4 and 5, the shielding effect is expressed in absolute value in dB. Figures 4 and 5 show a copper plate with a thickness of 100 μm (893 g/m, Comparative Example 1) for comparison.
) and the same amorphous alloy layer as in the above example, and a metal layer (
The results of similar measurements on an electromagnetic shielding material (Comparative Example 2) that does not have a copper plate (copper plate) are also shown (Comparative Example 1 only in Fig. 5).

The same measurements were carried out under the same conditions as in Example 1 except that the copper plate 3 of Example 1 was replaced with an aluminum foil having a thickness of 15 μm.

The measurement results are shown in FIGS. 5 and 6.

In both Examples 1 and 2, the magnetic field component is 10 to 1 in the low frequency region.
At 00 kHz, the shielding material of the amorphous alloy layer (
Even compared to Comparative Example 2), it shows a very good shielding effect. In the high frequency range of 1 to 100 MHz as an electric field component, the shielding effect is equivalent to or higher than that of the comparative copper plate, which shows a good shielding effect.

As described above, both Examples 1 and 2 showed good electromagnetic shielding properties from the magnetic field component in the low frequency range to the electric field component in the high frequency range, and these electromagnetic shielding materials are excellent electromagnetic shielding materials that have never existed before. It is.

Imperial plate 1 As shown in FIG. 3, this example has three amorphous alloy layers 2 and two metal layers 3, with a polyester film 4 interposed between each amorphous alloy layer 2. This is an example in which the electromagnetic shielding material 11 has a multilayer laminated structure with the metal layer 3 sandwiched therebetween, and the upper and lower surface layers are polyester films 4.

The amorphous alloy layer 2 has an average thickness of 40 μm and an aspect ratio of 2.
00-500 Cotl, I Fe #J Siσ
Bt amorphous alloy piece 2. A is laminated at 250g/rrf.

Further, the metal N3 is a copper plate with a thickness of 100 μm, and the thickness of the polyester film 4 is 25 μm.

Regarding the shielding properties of this electromagnetic shielding material against magnetic field components in the low frequency range, the same measurements as in Example 1.2 were performed.

The measurement results are shown in FIG. For comparison, FIG. 8 shows the same two copper plates as above (Comparative Example 4), and a layer of 2.5 mm thick between three amorphous alloy layers without any copper plate layer.
Electromagnetic shielding material sandwiching μm polyester films and using the same polyester film as the upper and lower surface layers (Comparative Example 5)
) The results of similar measurements are also shown.

As can be seen from FIG. 8, this electromagnetic shielding material has significantly improved shielding performance in the low frequency range compared to Comparative Example 4.5, and Example 1.2 shown in FIGS. 4 and 6. The shielding properties are further improved.

In Comparative Example i, the shielding performance in the low frequency range was good, but the shielding performance in the high frequency range was poor because it did not have a fully bent layer.

[Brief explanation of drawings]

The drawings all show embodiments of the present invention; FIG. 1 is a plan view of the electromagnetic shielding material, FIGS. 2 and 3 are enlarged cross-sectional views schematically showing the structure of the electromagnetic shielding material, respectively; Figures 4, 5, 6, 7, and 8 are graphs showing the relationship between frequency and shielding effect, respectively. Figures 9 and 10 are schematic diagrams showing how to measure shielding effect, respectively. It is. In addition, in the symbols shown in the drawings, 1.11...... Electromagnetic shielding material 2...
...Amorphous alloy layer 2a...Soft magnetic amorphous alloy piece 3...
・・・・・・Copper or aluminum layer 4・・・・・・・・・
・Polyester film 5.15...Transmission antenna 6.16...Reception antenna (7...Measuring instrument (spectrum analyzer) It is.

Claims (1)

[Claims] 1. Comprising at least one amorphous alloy layer and at least one conductive metal layer, the distance between one of the amorphous alloy layers and one of the conductive metal layers is 5 to 500 μm. and the amorphous alloy layer has a thickness of 5 to 10
0 μm, aspect ratio (however, the aspect ratio is the ratio of the maximum length to the maximum thickness) 10 to 15,000 scale-like or flaky soft magnetic amorphous alloy pieces with a weight per unit area of 100 to 500 g/ Electromagnetic shielding material with m^2 laminated structure.