JPH10173392A - Electromagnetic wave shielding sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide both the shield and radiation characteristic by using an insulation sheet having surface layers, contg. flattened soft-magnetic metal powders buried, so that their major axes extend along the surface of the sheet layers and inner layer adjacent the surface layers, the inner layer having buried spherical and/or granular metallic powders. SOLUTION: A sheet 1 has a flexible sheet main body 2, surface layers 4 at both sides of the sheet 2 and inner layer 8 disposed between the layers 4, contg. flattened soft-magnetic metal powders 6 buried so that their major axes extend along the surface of the sheet 2 and the layer 8 contg. spherical or granular metal powders 9 uniformly dispersed and buried in every section of the sheet 2. The metal power layers 4 shield the infiltrating electromagnetic waves, and the heat of the metal powders 6 due to eddy currents at shielding is transferred to the same or opposite layer 4 through the layer 8 and radiated from its surface, thus providing both the shielding and radiation characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic wave shielding sheet used to shield radio waves and magnetism, and more particularly to a sheet having both excellent shielding characteristics and heat radiation characteristics.

[0002]

2. Description of the Related Art In recent years, digital circuits forming an information network have rapidly spread with the progress of computerization. In the manufacturing industry, various control devices, measuring devices, sensors, and the like are systematized by computer control, and are used in large numbers. However, radio waves of various wavelengths, such as leakage from a conductive cable or a motor to the surroundings of a computer or the like due to illegal radio, etc., become noise and cause malfunction of the computer or the like, impede communication, and also affect the human body. Have been watched. On the other hand, there is also a problem that magnetism leaks from a power supply cable, a motor, or the like to the surroundings, causing a malfunction of a computer or the like or a stop of a device. In order to prevent such radio waves and magnetism (hereinafter referred to as electromagnetic waves) from leaking or to prevent the effects thereof, various shielding sheets wound around a cable or the like have been proposed.

[0003] For example, a shielding sheet 70 whose partial cross section is shown in FIG. 6A is a sheet body 7 made of a soft synthetic rubber or the like.
2, metal powder 74 made of a spherical or granular soft magnetic material is substantially uniformly dispersed and embedded. The shielding sheet 80 shown in FIG. 6B has a flat metal powder 84 made of a soft magnetic material in a sheet body 82 made of a soft synthetic rubber or the like. It is buried in a substantially uniform distribution so as to be substantially along the direction. Since the shielding sheet 80 can reduce the influence of the demagnetizing field by the flat metal powder 84 as compared with the shielding sheet 70,
An excellent shielding effect can be obtained. Further, the shielding sheet 90 shown in FIG. 6 (C) has a flat-shaped metal powder 94 made of a soft magnetic material along a surface on both sides inside a sheet body 92 made of a soft synthetic rubber or the like. To the seat body 9
2 is buried substantially along the surface direction. Although the shielding sheet 90 has a slightly lower shielding effect than the shielding sheet 80, the amount of the metal powder 94 used is reduced and the weight of the entire sheet 90 is reduced.

By the way, these shielding sheets 70 to 9
Many objects to be shielded such as cables, wiring, boards, components, and devices that are used with 0 generate a large amount of heat. Covering the shielded object with the shielding sheet 70 or the like hinders heat radiation, and there is a problem in that the shielded object must be used with a reduced rating. In addition, the shielding sheet 7
The metal powders 74, 84, 94 of 0 to 90 also generate heat because an eddy current is generated by a magnetic field passing through them. These heats are transmitted between the metal powders 74, 84, and 94 and radiated to the outside. With respect to such heat radiation characteristics, the shielding sheet 70 in which the granular metal powder 74 is substantially uniformly dispersed and embedded is the most excellent, and conversely, the shielding sheet 70 in which the metal powder 94 is not embedded at an intermediate position of the sheet body 92. Sheet 90 is lowest. Such heat generation has the problems of further deteriorating the sheet bodies 72, 82, and 92, and weakening the state of winding around a cable or the like or the state of sticking in a shield room due to cracking or peeling.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art described above and to provide an electromagnetic shielding sheet having both excellent shielding characteristics and heat radiation characteristics. .

[0006]

In order to solve the above-mentioned problems, the present invention comprises a flat metal powder layer having excellent shielding characteristics and a spherical / granular metal powder layer having excellent heat transfer characteristics. This is based on the idea of providing adjacent to each other in the seat body so as to obtain each characteristic. That is, the electromagnetic wave shielding sheet of the present invention has a flexible sheet body made of an insulating material and a soft shape having a flat shape in which the major axis is embedded substantially along the surface direction in a part of the sheet body. It is characterized by having a layer of magnetic metal powder and a layer of spherical and / or granular metal powder embedded in the sheet body adjacent to the flat metal powder layer.
The plane direction indicates a direction perpendicular to the thickness direction of the sheet.

According to this configuration, the shielding of the electromagnetic wave is mainly performed by the flat metal powder layer, and the heat generated mainly by the flat metal powder and the heat generated by the object to be shielded are reduced. Then, the heat is radiated to the outside through the adjacent spherical or granular metal powder layer. In addition, the soft magnetic metal powder includes iron, nickel, or cobalt, or an alloy based on any of them, such as silicon steel, or an alloy composed of the above combination, such as permalloy, sendust, and ferrite-based oxide. Things shall be included. In addition, the spherical and / or granular metal powder is not particularly limited as long as it is a metal or an alloy having a high thermal conductivity, but by using the soft magnetic metal,
The shielding characteristics can be further enhanced.

[0008] In the present invention, the flat metal powder layer may include:
An electromagnetic wave shielding sheet embedded along at least one surface in the sheet body and having a layer of spherical and / or granular metal powder embedded in the sheet body adjacent to the flat metal powder layer is also provided. Including. Further, the flat metal powder layer is buried at a substantially middle position in the thickness direction in the sheet body, and is adjacent to the flat metal powder layer and between at least one surface of the sheet body. Spherical and / or
Alternatively, an electromagnetic wave shielding sheet in which a layer of granular metal powder is embedded is also included. According to these configurations, the flat metal powder layer and the spherical and / or granular metal powder layer are buried along the entire cross section of the sheet body or along the surface to be radiated. Both characteristics can be reliably obtained.

[0009] The flat metal powder embedded in the electromagnetic wave shielding sheet may have an average major axis of 100 µm or less, an average minor axis of 50 µm or less, and an average thickness of 10 µm or less. This makes it possible to obtain excellent shielding characteristics with little influence of the demagnetizing field. It is desirable from the viewpoint of maintaining the flexibility of the shielding sheet and using the spherical and granular metal powder having an average particle diameter of 100 μm or less from the viewpoint of production. The shielding properties can be obtained by embedding at least 20% or more by volume of the flat metal powder and 40% by weight of the sheet as a layer.

Further, the present invention also includes an electromagnetic wave shielding sheet in which the insulating material constituting the sheet body is any one of rubber, resin, and a composite material in which a reinforcing material is mixed.
The rubber is a synthetic rubber or a natural rubber such as chloroloprene, and the resin is a high-density polyethylene, a polypropylene, a polyamide, a cellulose acetate, a phenolfural, or a polyethylbenten (T.
PX) or the like, and any of talc, mica, glass fiber, metal fiber, or asbestos having excellent heat transfer properties is used as the reinforcing material.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a partial cross-sectional view of an electromagnetic wave shielding sheet 1 of the present invention. This shielding sheet 1
Is made of a flexible sheet body 2 made of chloroprene rubber and a flat soft magnetic metal powder 6 along each surface on both sides of the body 2 so that the major axis thereof is substantially along the surface direction of the body 2. Layers 4 and 4 composed of many metal powders 6 buried in
And a layer 8 made of a spherical or granular metal powder 9 buried in the cross section of the main body 2 in a substantially uniform manner between the layers 4.

The flat soft magnetic metal powders 6 are buried with each other substantially along the surface direction of the main body 2 to form a layer 4.
The shielding characteristics are obtained. As the metal powder 6, for example, a PC Permalloy-1 (80% Ni-Fe) alloy is formed into a powder having an average particle diameter of 100 μm or less by an atomizing method, and further, the powder is put into a ball mill called a so-called attritor. Crushed flat, the average major axis is 100 μm or less, the average minor axis is 50 μm or less, and the average thickness is 10 μm or less,
For example, it is a flat, substantially strip-shaped one of 1 μm. The spherical and granular metal powders 9 used were powders of the same alloy having an average particle diameter of 100 μm or less by an atomizing method.

Since the shielding sheet 1 has the layers 4 of the metal powder 6 on both surfaces of the main body 2, no matter from which surface electromagnetic waves are to enter, it is shielded by the layer 4 located on the surface side. In addition, the metal powder 6 due to the eddy current at the time of shielding is used.
And the heat generated from the object to be shielded are also transferred to the same surface side or to the opposite layer 4 via the inner layer 8 of the metal powder 9 and also radiated from the surface side. Although the metal powder 9 also generates a small amount of heat, the heat is similarly transferred and radiated on any one of the surface sides, so that the heat hardly stays in the sheet body 2.

FIG. 1B is a partial sectional view of an electromagnetic wave shielding sheet 10 of a different form. The shielding sheet 10 includes a large number of metal sheets in which flat soft magnetic metal powders 14 are embedded along one surface of the same sheet body 11 as described above so that the major axis thereof is substantially along the surface direction of the body 11. It has a layer 12 made of powder 14 and a layer 16 made of spherical or granular metal powder 18 buried and substantially uniformly dispersed throughout the remaining main body 11. These metal powders 14 and 18 are also the same alloy as described above and have similar dimensions. The layer 12 made of the metal powder 14 is provided on a surface side on which electromagnetic waves are to enter from the outside or leakage to the outside is to be shielded. And layer 1
Even if the metal powder 14 or the like generates heat due to the shielding of 2, heat is radiated from the surface side or the metal powder 18 in the layer 16 and is radiated from the opposite surface. Become.

FIG. 1C is a partial cross-sectional view of an electromagnetic wave shielding sheet 20 having a further different form. Shielding sheet 20
A flat soft magnetic metal powder 24 along one surface of the same sheet body 21 as described above,
1, a layer 22 made of a large number of metal powders 24 buried substantially along the surface direction, and a spherical or metal sphere buried adjacent to this layer 22 and substantially uniformly dispersed to an intermediate position in the thickness direction of the sheet body 21. It has a layer 26 made of granular metal powder 28. The metal powders 24 and 28 are also the same alloy as described above, and have similar dimensions. The layer 22 made of the metal powder 24 is also provided on the surface side on which electromagnetic waves are to enter from the outside or leakage to the outside is to be shielded. Then, the metal powder 24 is shielded by the layer 22.
When the heat is generated, it is possible to radiate heat to the surface side close to them and to radiate the same surface side from the separated position via each metal powder 28 of the inner layer 26.

FIG. 2A is a partial sectional view of another form of the electromagnetic wave shielding sheet 30. The shielding sheet 30 embeds a flat soft magnetic metal powder 34 at a substantially central position in the thickness direction in the same sheet body 31 as described above so that the major axis thereof is substantially along the surface direction of the body 31. Many metal powders 3
4 and a layer 36 made of spherical or granular metal powder 38 that is substantially uniformly dispersed and embedded between the layer 32 and one surface of the main body 31. This sheet 30
The difference in the shielding properties of the layer 32 is small on both surfaces. The metal powders 34 and 38 have the same alloy and dimensions as those described above. Even if the metal powder 34 and the like in the central portion generate heat due to the shielding of the layer 32, the heat is radiated from the surface side of the layer 36 via the metal powder 38 in the layer 36 adjacent to the central portion. Heat is less likely to be trapped.

FIG. 2B is a partial sectional view of an electromagnetic wave shielding sheet 40 of still another embodiment. The shielding sheet 40 is
A flat soft magnetic metal powder 44 is buried at a substantially central position in the thickness direction in the same sheet main body 41 as described above, from a large number of metal powders 44 buried such that the major axis thereof is substantially along the surface direction of the main body 41. And layers 46 and 46 of spherical or granular metal powder 48 buried and substantially uniformly dispersed and embedded between the layer 42 and both surfaces of the main body 41. The sheet 40 has a cross-sectional structure symmetrical in the thickness direction, and there is no difference in the shielding characteristics between the layers 42 and 46 on both surfaces. The above metal powders 44 and 48 have the same alloy and dimensions as those described above. Even if the metal powder 44 and the like in the central part generate heat due to the shielding of the layer 42, the metal powder 48 in each layer 46 adjacent to both sides of the metal powder 44 and the like.
The heat is also radiated from both front sides through the sheet, so that heat is hardly trapped in the sheet body 42. Note that the spherical and granular metal powders 9, 18, 28, 38, and 48 in each embodiment are also soft magnetic and therefore have an electromagnetic wave shielding effect. The thickness of these sheets 10 to 40 is at least about 0.2 mm or more.

Next, a method of manufacturing the shielding sheet 1 will be outlined with reference to FIG. FIG. 3 (A) shows that a spherical or granular metal powder 9 is kneaded with chloroprene rubber 2a having fluidity,
The step of obtaining the powder mixed insulator 2b will be described. As shown in FIG. 3 (B), the powder mixed insulator 2b is inserted substantially vertically between a pair of flat rolls 50 whose peripheral surfaces are close to each other and opposed to each other. Powder 6 is added to the surface of powder mixed insulator 2b by spraying or the like. The powder mixed insulator 2b pressed between the rolls 50 is shown in FIG.
As shown in (C), the layer 4 of the metal powder 6 is formed along both surfaces.
And it becomes the flat shielding sheet 1 which has the layer 8 of the metal powder 9 between them.

In order to obtain the shielding sheet 10, the flat metal powder 6 may be sprayed from only one side in the step shown in FIG. In addition, the shielding sheet 20
Is obtained by further contacting the chloroprene rubber 2a on the surface of the shielding sheet 10 on the layer 16 side and pressing the sheet through a pair of flat rolls 50.
Further, the shielding sheet 30 can be obtained by further adhering the chloroprene rubber 2a to the surface of the shielding sheet 10 on the layer 12 side, and passing between the pair of flat rolls 50. In order to obtain the shielding sheet 40, the powder-mixed insulator 2b is further attached to the surface of the shielding sheet 10 on the layer 12 side, and a pair of flat rolls 50 is formed.
Can be obtained by passing through. Each of the shielding sheets 1 to 40 is pressed by a press or the like, in addition to the above-described rolling method, by adhering and laminating the powder-mixed insulator 2b and the flat metal powder 6 or the chloroprene rubber 2a in the order described above. It is also possible to manufacture by performing.

Next, the shielding sheet 1 (inventive example), the conventional shielding sheet 70 (comparative example 1), and the shielding sheet
The shielding characteristics and the heat radiation characteristics of (Comparative Example 2) are compared. The shielding sheet 1 embeds (in a volume ratio of about 60%) metal powders 6 and 9 having the above-mentioned shape made of PC Permalloy-1 alloy, and the shielding sheets 70 and 90 are also made of PC Permalloy-1 alloy. Metal powders 74 and 94 of the same shape as
2 and 92 (by volume ratio, the sheet 70 is about 60% and the sheet 90 is about 20%). Then, as shown in FIG. 4, two copper wires 60 having a diameter of 3 mm are wired in parallel with a distance of 10 mm between centers, and a shielding sheet 1, 70, 90 having a thickness of 1 mm is provided around these. Elliptical cylinder 6 directly wound
The elliptic cylinder 62 was covered with a Gauss meter outside. An alternating current of 0.1 V, 100 A, and 50 Hz was applied to the copper wire 60, and a magnetic field of 1 G (Gauss) was applied around the copper wire 60, and the attenuation rate of the magnetic field outside each elliptic cylinder 62 was measured.

Simultaneously, a thermometer was brought into contact with the inner and outer surfaces of each of the elliptical cylinders 62, and the temperature difference between the inner and outer surfaces after the alternating current was passed for 100 minutes was measured. The results are shown in the graph of FIG. From this graph, Comparative Example 1 in which spherical and granular metal powder 74 was uniformly embedded in the entire cross section
Showed a low decay rate of about 45% and a low temperature difference of about 35 ° C. Comparative Example 2 in which the flat metal powder 94 was embedded only on the surface side of the sheet body 92 showed a high attenuation rate of about 50% and a high temperature difference of about 70 ° C. In contrast, the invention examples exhibited a high decay rate of about 60% and a low temperature difference of about 40 ° C. From the above results, the invention example has a high attenuation rate of about 60% as compared with the comparative example 1, and the temperature difference is reduced by embedding the spherical and granular metal powder 9 further inside the comparative example as compared with the comparative example 2. It could be as low as 40 ° C.

From these results, when the amount of buried metal powder increases, the damping rate improves and the temperature difference between the inside and outside decreases. Conversely, when the amount of burying metal decreases, the damping rate decreases and the temperature difference between the inside and outside increases, and the damping rate increases. It is considered that the rate and the temperature difference between the inside and outside have an almost inverse relationship. Among them, in the case of the invention example, a higher damping rate and a smaller temperature difference than in the comparative example 1 could be obtained with a relatively small amount of burying metal powder. This is due to the cross-sectional structure of the shielding sheet 1 in which the layer 4 of the flat metal powder 6 having excellent shielding characteristics and the layer 8 of the spherical and granular metal powder 9 having excellent heat transfer characteristics are combined. I think that the. This also applies to other forms of shielding sheets 10 to 40. still,
It is presumed that the attenuation rate of the electric field when each of the sheets 1, 70, 90 is the cylindrical body 62 is also the same.

The sheet for shielding electromagnetic waves of the present invention is not limited to the above embodiments. The insulator constituting the sheet body includes synthetic rubbers such as polybutadiene rubber, polyisoprene rubber, ethylene isoprene rubber, butadiene acrylonitrile rubber, isobutylene isoprene rubber, styrene butadiene rubber, phenolic, epoxy,
A flexible resin such as polyester, acrylic, polyethylene, polypropylene, and polyamide can be used. It is desirable to use high-density polyethylene, polypropylene, polyamide or the like having relatively high thermal conductivity among the resins. Furthermore, when a composite material reinforced by mixing glass fiber, metal fiber, mica, talc, asbestos, or the like in the above rubber or resin is used, heat dissipation is also improved.

The soft magnetic metal powder includes PC permalloy (78% Ni-Fe) and PB permalloy (45% Ni-F).
e), PD permalloy (36% Ni-Fe), 12% Mn-9.6% Cu
Permalloy alloys such as -6% Fe-Ni, 42% Ni-Fe and 52%
Ni-Fe alloys such as Ni-Fe, Kovar (29% Ni-17% Co-F
e), so-called electromagnetic stainless steel of 10-18% Cr-Fe, 3-10%
Cr-3-10% Si-Fe, 9-22% Ni-16-26% Cr-Fe, Fe-
Cr-Al alloy, Fe-Cr-Al-Si alloy, Permendur alloy (Fe-Co-X, where X is V, Al, Si, Cr) Used. In these cases,
The material of the metal powder can be changed or the metal powder of a plurality of materials can be used together in the same layer depending on the embedding position in the sheet body. In addition, copper or aluminum having a high thermal conductivity other than a soft magnetic material, or various alloys based on these can be used for the spherical or granular metal powder mainly responsible for thermal conductivity.

Further, the use of the shielding sheet may be wrapped around various cables, pasted around or inside high-voltage equipment or equipment having a built-in transformer, or covered around the storage section of various information media. Thus, it can protect against electromagnetic waves entering from the outside. Further, it can also be used to prevent crosstalk between substrates by interposing between IC wiring substrates. Alternatively, a shield room can be easily formed by laying on a floor in a room containing a device, a computer, and the like for performing precise processing and measurement, and attaching the device to a wall surface or a ceiling surface.

In the above, when the shielding sheet is attached, it is desirable to apply an adhesive to a part or all of one surface of the sheet body, or to set a so-called double-sided tape in advance. Note that, in order to facilitate the application of the adhesive, it is preferable that paper is bonded to one surface of the sheet body in advance.
In the case of laying on a floor in a room, a non-slip function can also be provided by forming a large number of uneven stripes or projections on the front surface side of the sheet body which is the upper surface in advance. Further, the shielding sheet may be thinned and formed into a bag shape or a flat box shape by bending and bonding, and used as a means for transporting or storing a recording medium such as an FD.

[0027]

As described above, the electromagnetic wave shielding sheet of the present invention uses a relatively small amount of metal powder and embeds a plurality of layers of metal powder having different shapes in the sheet body. And high heat dissipation characteristics. Further, the flexibility of the shielding sheet itself is not impaired, and the weight can be reduced. Furthermore, even if the electromagnetic wave shielding sheet is used for a long period of time, deterioration such as cracking and peeling due to the deterioration are unlikely to occur, and the sheet also has excellent durability.

[Brief description of the drawings]

FIGS. 1A to 1C are partial cross-sectional views showing each embodiment of a shielding sheet of the present invention.

FIGS. 2A and 2B are partial cross-sectional views each showing another embodiment of the shielding sheet of the present invention.

3 (A) and 3 (B) are schematic views showing a manufacturing process of the shielding sheet of the present invention, and FIG. 3 (C) is an enlarged sectional view of a portion C surrounded by a dashed line in FIG. 3 (B).

FIG. 4 is a cross-sectional view showing a state in which the shielding sheet of the present invention is covered in an elliptical cylindrical shape around a copper wire.

FIG. 5 is a graph showing a magnetic field attenuation rate of the shielding sheet of the present invention and a conventional shielding sheet and a temperature difference between inside and outside of the sheet.

FIGS. 6A to 6C are partial cross-sectional views showing various forms of a conventional shielding sheet.

[Explanation of symbols]

 1, 10, 20, 30, 40 ... shielding sheet 2, 11, 21, 31, 41 ... sheet body 4, 12, 22, 32, 42 ... flat metal powder layer 6, 14,24,34,44… Flat metal powder 8,16,26,36,46… Spherical and granular metal powder layer 9,18,28,38,48… Spherical and granular Metal powder

Claims (6)

[Claims] 1. A sheet body made of an insulating material and having flexibility, and a layer of a soft magnetic metal powder having a flat shape in which a major axis is buried substantially along a surface direction in a part of the sheet body. And a spherical and / or granular metal powder layer buried adjacent to the flat metal powder layer in the sheet body. 2. The flat metal powder layer is buried along at least one surface in the sheet body, and a spherical and / or granular metal powder is adjacent to the flat metal powder layer. The electromagnetic wave shielding sheet according to claim 1, wherein a layer of the powder is embedded in the sheet body. 3. The flat metal powder layer is buried at a substantially middle position in the thickness direction in the sheet body, and is adjacent to the flat metal powder layer and has a surface of at least one sheet body. The electromagnetic wave shielding sheet according to claim 1, wherein a spherical and / or granular metal powder layer is buried between the sheet and the metal sheet. 4. An average major axis of said flat metal powder is 100.
The electromagnetic wave shielding sheet according to any one of claims 1 to 3, wherein the sheet has an average minor axis of 50 μm or less, and an average thickness of 10 μm or less. 5. The sheet material according to claim 1, wherein the insulating material constituting the sheet body is any one of rubber, resin, and a composite material in which a reinforcing material is mixed. Electromagnetic wave shielding sheet. 6. The rubber is a synthetic rubber or a natural rubber,
The resin is high-density polyethylene, polypropylene, polyamide, cellulose acetate, phenolfural,
Or polymethylbenten, and the reinforcing material is at least one of talc, mica, glass fiber, metal fiber, and asbestos.
2. The electromagnetic wave shielding sheet according to 1.