JPS63305600A - Electromagnetic shield material - Google Patents

Abstract

PURPOSE:To enable the effective shielding of electromagnetic waves over a wide range of wavelength regions, by laminating soft magnetic amorphous alloy pieces of specific scale or flake shapes so as to compose first and second amorphous alloy layers and next laminating both the 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 end 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 compose a plurality of amorphous alloy layers 2a, that is, first and second amorphous alloy layers 2a. Next the first and second amorphous alloy layers 2a are laminated at an interval of 5-500mum in between. Accordingly, electromagnetic shield performance can be obtained for electromagnetic waves ranging from magnetic field components on a low-frequency region to electric field components on a high-frequency region.

Description

[Detailed description of the invention] B6 Industrial application fields 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. That's harsh.

In addition, as a method of shielding electric and electronic equipment by mixing metal fillers into the above-mentioned plastics, stainless steel m fibers, etc. are used, considering the shielding of magnetic field components, but this also has a sufficient shielding effect. isn't it. That is,
In order to have a sufficient shielding effect, it is necessary to add a considerable amount of the metal filler mentioned above, which results in a decrease in the strength of the plastic, and also increases the cost due to the appearance of the metal filler on the surface and further painting. Becomes 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.

C1 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.

D6 Structure of the Invention The present invention provides that the plurality of amorphous alloy layers, the first amorphous alloy layer and the second amorphous alloy layer, each have a thickness of 5 to 100 μm,
Aspect ratio (However, aspect ratio is the ratio of maximum length to maximum thickness.) 10 to 15,000 scale-like or flake-like soft magnetic amorphous alloy pieces are laminated at a weight of 100 to 500 g/unit area. The present invention relates to an electromagnetic shielding material having a structure in which the first amorphous alloy layer and the second amorphous alloy layer are stacked at an interval of 5 to 500 μm.

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 are usually supplied in the form of ribbons with a thickness of several tens of micrometers and a width of about 100 fins, and there are problems with damage due to cutting and adhesion when stacking them together to make them into plates of the specified dimensions. However, it is very difficult to handle, and in addition, it is necessary to laminate many layers to obtain a predetermined thickness, which requires a large number 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. It has been discovered that an excellent magnetic shielding material can be obtained. The present invention has been 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~
The amorphous alloy layer is formed by stacking the amorphous alloy flakes at a density of 500 g/m2, but if the amount of the amorphous alloy flakes is less than 100 g/m2, the stacking of the amorphous alloy flakes and the contact between them (
(conductivity) becomes strong and the magnetic shielding performance deteriorates. If this exceeds 500 g/m2, it becomes difficult to stack and adhere the amorphous alloy pieces, creating voids in the amorphous alloy layer, resulting in an increase in the amount of amorphous alloy pieces per unit area. Despite this, magnetic shielding properties deteriorate. A particularly preferable range of the above amount of amorphous alloy flakes is 200 to 350 g.
/I am.

The amorphous alloy layer with the above structure is made of amorphous alloy pieces that exhibit good soft magnetic properties, 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,
Electrical resistance is high compared to conductive materials with low electrical resistance such as copper and aluminum (100 to 150 μΩ・CI
I+), the thickness must be increased, which is disadvantageous.

Therefore, in order to effectively shield the magnetic field and electric field components over a wide frequency range, a plurality of the above-mentioned amorphous alloy layers are formed and each layer is laminated at intervals. When the distance between the amorphous alloy layers is less than 5 μm, it is difficult to make close contact between the amorphous alloy layers and the intermediate layer located between them, and this
If it exceeds .mu.m, the shielding material becomes thick, making handling inconvenient and industrially disadvantageous. Therefore, the above interval is 5~
The intermediate layer for forming the above-mentioned distance, which is preferably within the range of 500 μm, is preferably a dielectric material such as a plastic film (for example, a polyester film), and the dielectric loss caused by this dielectric material improves the electric field shielding property in the high frequency range. It will improve.

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

Ru.

This example is an example of a strong plate-shaped electromagnetic shielding material.
Two amorphous alloy layers 2 are formed by laminating amorphous alloy pieces 2a, sandwiching a polyester film dielectric 3, and these are made of glass, acrylic resin, vinyl chloride, epoxy resin, phenol resin, etc. In the example, epoxy resin) 2
The electromagnetic shielding material 1 is constituted by a laminate sandwiched between two plates 4. However, in FIG. 1, the above-mentioned plate 4 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 and crystalline alloy ribbons requires repeated cutting and gluing, and gluing in different cross directions and angles to make them non-directional. The work is extremely troublesome. In the present invention, if a slight magnetic field along a predetermined direction is applied during dispersion, the amorphous alloy pieces can be aligned in the longitudinal direction and given directionality.

Note that a resin film may be used instead of the resin plate 4 (
(Fig. 3), flexibility is imparted to the magnetic shielding material, making it convenient to use depending on the purpose.

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
Cavitation method proposed in Publication No. 6907 (molten metal is supplied to the surface of a roll that has a surface layer with low wettability to the molten metal and is rotating at high speed, and the molten metal is turned into fine molten metal droplets) It is desirable to apply a method of rapidly solidifying the molten metal droplets by colliding them with a metal rotating body that rotates at high speed after dividing the molten metal droplets.

Specific examples of the present invention will be described below.

straight! LL An amorphous alloy piece of Cott, eFeq Si ity B 7 (the number attached to the element symbol indicates the atomic % of the elemental component; the same shall apply hereinafter) was produced by the cavitation method described above.

This amorphous alloy piece has an average thickness of 30 μm and an aspect ratio of 400 to 600.

This amorphous alloy piece was used to prepare an electromagnetic shielding material 11 having two amorphous alloy layers 2 as shown in FIGS. 1 and 3. That is, the amorphous alloy piece 2a was sandwiched between a polyester film 3 having a thickness of 50 μm at a weight of 250 g/rd, and these were further sandwiched between two polyester films 3 having the same thickness to form an electromagnetic shielding material 11. . The amorphous alloy layer and the polyester film 3 are fixed to each other with an adhesive (not shown). In the electromagnetic shielding material shown in FIG. 3, the same polyester film as the intermediate layer 3 is used in place of the outer layer plate 4 of the electromagnetic shielding material shown in FIG.

The electromagnetic shielding properties of this electromagnetic shielding material 11 were measured using a spectrum analyzer TR-4172 manufactured by Atopan Test Co., Ltd. The measurement procedure is schematically shown in FIG. 7 for the magnetic field component and in FIG. 8 for the electric field component, respectively. 200 n x 200 m electromagnetic shielding material 11y; (a magnetic wave transmitting loop antenna 5 with a diameter of 10 mm or a length of 1 at a position 10 fins away from the tll on one side)
A magnetic wave receiving loop antenna 6 with a diameter of 10 nm or a radio wave receiving probe antenna 16 with a length of 10 fl is placed at a position 10 mm away from the other side of the zero dragon radio wave transmitting probe antenna 15, and these are tracked. Connect to spectrum analyzer TR41727 with generator. Attenuation of the magnetic waves or radio waves from the transmitting antenna 5 or 15 due to the electromagnetic shielding material 111fZ, It is detected by the receiving antenna 6 or 16, and measured by the spectrum analyzer TR41727.

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

In addition, in FIG. 5 and FIG. 6, the shielding effect is expressed as an absolute value in dB. For comparison, FIGS. 5 and 6 also show the results of similar measurements on a 100 μm thick copper plate (893glrd, comparative example).

11 Example 1 Co with an average thickness of 40 μm and an aspect ratio of 400 to 600
(y, IF e e, as itt B f amorphous alloy pieces 2a were made to have a weight of 250 g/rrf, and four amorphous alloy layers 2 were provided to form an electromagnetic shielding material 21 shown in FIG. 4.

A polyester film 3 having a thickness of 25 μm is arranged between each amorphous alloy layer 2 and on the outermost layer. The rest is the same as in the first embodiment.

The electromagnetic shielding properties of this electromagnetic shielding material 21 were measured in the same manner as in the above-mentioned Example. 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.
When compared with a comparative copper plate at 00kHz, it shows a very good shielding effect. 1 to 100 as electric field component
In the high frequency range of MHz, the shielding effect is equivalent to or better than that of the comparative copper plate, which shows a good shielding effect.

As described above, both Examples 1 and 2 exhibit 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.

[Brief explanation of drawings]

The drawings all show examples of the present invention, and FIG. 1 is a plan view of the electromagnetic shielding material, and FIG. 2, FIG. 3, and FIG. 4 each schematically show the structure of the electromagnetic shielding material. An enlarged sectional view, FIGS. 5 and 6 are graphs showing the relationship between frequency and shielding effect, and FIGS. 7 and 8 are schematic diagrams showing the procedure for measuring the shielding effect, respectively. In addition, in the symbols shown in the drawings, 1.11.21...... Electromagnetic shielding material 2.
......Amorphous alloy layer 2a...Soft magnetic amorphous alloy piece 3...
・・・・・・Polyester film 4・・・・・・・・・
Epoxy resin 5.15...... Transmission antenna 6.16.
...Old...Receiving antenna 7...It is a measuring instrument (spectrum analyzer).

Claims (1)

[Claims] 1. The plurality of amorphous alloy layers, the first amorphous alloy layer and the second amorphous alloy layer, each have a thickness of 5 to 100 μm and an aspect ratio (however, the aspect ratio is (maximum length ratio) 10 to 15,000 scale-like or flake-like soft magnetic amorphous alloy pieces with a weight of 10 to 15,000 pieces per unit area.
It has a structure formed by laminating 0 to 500 g/m^2, and
An electromagnetic shielding material in which the first amorphous alloy layer and the second amorphous alloy layer are laminated with an interval of 5 to 500 μm.