JP2970297B2 - High resistance magnetic shield material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic shielding material which is excellent in magnetic shielding effect and workability and hardly generates heat even in a strong magnetic field. 2. Description of the Related Art In recent years, with the rapid spread of electronic devices, malfunctions and mutual interference of devices caused by magnetism have increased, and magnetic shields have been required in a wide range of fields. For example, bottom members of electromagnetic cookers, wall materials of buildings near high-voltage lines, walls and floor materials of magnetic tomography rooms in hospitals, electronic circuit boxes of automobiles, casing materials of small motors, wall materials of linear motors It is necessary to shield magnetic noise so as not to be affected by magnetism or floor material, etc., or to be not affected by magnetism from the outside. The present invention relates to a magnetic shield material optimal for these members.

[0002]

2. Description of the Related Art Conventionally, permalloy alloy plates, silicon steel plates, ferrites, and the like have been used as magnetic shielding materials for blocking unnecessary magnetism generated from a magnetic field, and soft magnetic amorphous materials have been used as composite materials. There is known an alloy powder in which an alloy powder is sandwiched between two resin films and bonded together. However, when a permalloy alloy plate or a silicon steel plate is installed in a strong AC magnetic field such as an electromagnetic cooker or an electromagnetic pot, there is a problem that the plate material generates heat due to hysteresis loss and eddy current flowing inside the plate. Further, when a permalloy alloy plate is subjected to bending, drawing, cutting, or the like, the alloy structure of the processed portion is distorted, and the magnetic shielding characteristics are extremely reduced. To restore this, the processed product must be 1000 ° C
As described above, after annealing, it is necessary to gradually cool in a non-oxidizing atmosphere, which is troublesome in manufacturing and causes a significant increase in cost. Further, the ferrite sintered body does not generate heat in a strong magnetic field, but is hard and brittle, and thus has poor workability. The magnetic shielding material in which the soft magnetic amorphous alloy powder is sandwiched between the resin films, the resin film is stuck by the binder, and the amount of the soft magnetic powder is limited because the soft magnetic powder is interposed between them. Low.

[0003] In addition to the above magnetic shield material, a magnetic shield material in which a metal soft magnetic powder such as a permalloy alloy powder or a sendust alloy powder is mixed with a resin, or an oxide soft magnetic powder such as a ferrite powder is mixed with a resin. Magnetic shielding materials are known. However, when a resin containing a metal soft magnetic powder such as an alloy powder is mixed with a resin at a high density, the powders come into contact with each other to reduce the insulating property, and generate heat due to the generation of eddy current. Inevitably, when the filling amount is reduced, the insulating property is improved, but the magnetic resistance is also increased, and there is a problem that the magnetic shielding effect is reduced. Further, those using an oxide soft magnetic powder such as ferrite do not generate heat, but have poor magnetic performance. A magnetic material in which a sendust alloy powder is blended in a resin is also known (JP-A-4-94502), which aims to enhance the workability of a sendust alloy material used as a magnetic core material. Therefore, unlike the magnetic shield material, the alloy powder is used in the form of a flake to increase the magnetic flux density, but the problem of heat generation has not been solved.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic shield material which solves the above-mentioned problems in the conventional magnetic shield material. One of the main reasons why the magnetic shielding material generates heat when the magnetic shielding material is placed in a strong magnetic field in a magnetic shielding material in which a soft magnetic powder is blended with a resin is that the magnetic flux generates a magnetic shielding layer inside the magnetic shielding material. As it flows,
This is because an eddy current is generated in the magnetic shield layer. This eddy current flows perpendicular to the direction of the magnetic flux. In view of the above, according to the present invention, by stacking an insulating layer on the magnetic shield layer, the eddy current induced in the magnetic shield layer is divided by the insulating layer, and the generation of heat is prevented by substantially preventing the eddy current from flowing. Things.

[0005]

According to the present invention, there is provided (1) a magnetic shield layer having a thickness of 0.1 to 5 mm in which soft magnetic powder is oriented in layers and a non-conductive insulating layer containing insulating soft magnetic powder. The present invention relates to a high-resistance magnetic shield material characterized by being alternately laminated in a resin. The high-resistance magnetic shield material of the present invention is preferably (2) a soft magnetic powder forming a magnetic shield is a scaly powder having an average particle diameter of 5 to 300 μm made of a permalloy alloy, a sendust alloy or an amorphous alloy thereof, The insulating powder contained in the insulating layer has an average particle size of 5 to 50.
μm Mn—Zn ferrite powder or Ni—Zn ferrite powder, wherein the thickness of the insulating layer is 0.05 μm to 1 mm
belongs to.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic sectional view of a reference example showing an arrangement of magnetic shield layers used in a magnetic shield material according to the present invention, and FIG. 2 is a schematic sectional view showing an example of a laminated structure of the magnetic shield material of the present invention. is there. In FIG. 1, a magnetic shield material 10 is formed by alternately laminating a resin 11, a plurality of magnetic shield layers 20 formed by uniformly dispersing and mixing a soft magnetic powder 12 in the resin 11, and a non-conductive insulating layer 30. Is formed. As the type of the resin, a thermoplastic resin, a thermosetting resin, or the like is appropriately used according to use conditions. Specifically, when the molded body requires rigidity, a hard resin is used,
Further, when rigidity is not required, for example, when a magnetic shield material is used by being attached to a support member, a soft resin is used.

The soft magnetic powder 12 forming the magnetic shield layer 20 is preferably in the form of a scale. The scaly soft magnetic powder may be a powder obtained by flattening a general soft magnetic material into a flaky shape, and preferably has a high magnetic permeability and a low coercive force.
Specifically, a permalloy, a sendust alloy, or an amorphous alloy containing iron and cobalt as main components is suitable. The soft magnetic powder has an average particle size of 5 μm to 300 μm.
μm and an aspect ratio (major axis / thickness ratio) of 10 or more are preferred. If the average particle size is smaller than 5 μm, the number of contact points between particles that becomes a magnetic resistance when the powder is mixed with the resin is not preferred. When the average particle size is larger than 300 μm, it becomes difficult to uniformly disperse the powder when kneading the resin. If the aspect ratio is smaller than 10, the contact area between the powders decreases, and the magnetic resistance increases, which is not preferable. If the aspect ratio is larger than 10, the contact area between the powders is large and the magnetic resistance is small. For the same reason, it is preferable that the flaky soft magnetic powder is oriented in a layered manner in the resin.

The ratio of the mixed powder in the shielding material is 50
~ 90% by weight is preferred. If the amount of the mixed powder is less than 50% by weight, the resin is interposed between the powders and the magnetic resistance increases. On the other hand, if the amount is more than 90% by weight, the powder cannot be contained in the resin, so that the resin is extremely brittle and cannot be molded. Although the thickness of the magnetic shield layer 20 depends on the strength of the magnetic field and the type of powder under the use environment, it is usually 0.
1-5 mm is preferred. If the magnetic shield layer is thinner than 0.1 mm, a sufficient magnetic shield effect cannot be obtained. On the other hand, if the magnetic shield layer is thicker than 5 mm, an eddy current is easily generated, which is not preferable. In addition,
When a plurality of magnetic shield layers and insulating layers are alternately laminated, the thickness of each magnetic shield layer may be within the above range.

The insulating layer 30 is preferably made of a resin mixed with an insulating soft magnetic powder such as a Mn-Zn ferrite powder. By using such an insulating layer, a magnetic shield material having a high magnetic shield effect and a high electric resistance can be obtained. The insulating soft magnetic powder may be any oxide soft magnetic powder, and preferably has high magnetic permeability and low coercive force. Specifically, Mn-Zn ferrite powder,
Ni-Zn ferrite powder or the like is generally used. The size of the insulating powder is preferably one having an average particle size of 5 to 50 μm. If the average particle size is larger than 50 μm, it becomes difficult to disperse between the flaky powder in the resin. The particle size is 5μ
When the particle size is smaller than m, agglomeration of the powder occurs, and similarly, dispersion between the flaky powder becomes difficult. The thickness of the insulating layer 30 is preferably 0.05 μm to 1 mm. The insulating layer 30 is 0.05 μm
If it is thinner, a stable insulation effect cannot be expected, and 1m
If the thickness is larger than m, the entire thickness of the next shield material is increased, and the workability is deteriorated.

The magnetic shield material of the present invention is provided with the magnetic shield layer 20 and the insulating layer 30 inside the resin as described above. Specifically, as shown in the drawing, the magnetic shield layer 20 and the insulating layer 30 are insulated from each other. The layers 30 are alternately stacked a plurality of times (FIG. 2). In the magnetic shield material of the present invention, an insulating layer is provided along the magnetic shield layer inside the magnetic shield material, so that when a magnetic flux flows through the magnetic shield layer, an eddy current induced in a direction perpendicular to the direction of the magnetic flux is generated. Since the flow is interrupted by the insulating layer, substantially no eddy current is generated. Therefore, heat generation due to the eddy current is prevented.

[0011] The magnetic shield material is obtained by uniformly kneading and dispersing flaky soft magnetic powder in a resin, and then processing it into a sheet by press molding to form a resin sheet for a magnetic shield layer. Can be formed by laminating and integrating with a non-conductive resin sheet to be formed. Further, a mixture of a flaky soft magnetic powder and a resin may be applied to the surface of the insulating layer resin sheet to form a magnetic shield layer, and a resin sheet may be provided on the surface of the magnetic shield layer. When the insulating layer is prepared by mixing the insulating soft magnetic powder, the insulating soft magnetic powder is uniformly kneaded and dispersed in a resin, and then processed into a sheet to form the resin sheet for the magnetic shield layer. Or the kneaded material may be applied to the surface of the magnetic shield layer to form an insulating layer. In this molding process, the mixture of the resin and the powder is press-pressed, or by applying magnetism, the flaky soft magnetic powder contained in the resin can be oriented in a layered manner. Material can be obtained.

[0012]

Examples of the present invention will be described below. Examples 1 and 2 are reference examples showing a laminated structure of a magnetic shield layer and an insulating layer, which are the basic structures of the present invention. Examples 3 and 4 are based on this laminated structure and are based on the magnetic shield layer and the insulating powder. This is an example showing a high-resistance magnetic shield material of the present invention in which an insulating layer containing is laminated. Example 1 (Reference Example) A flaky Fe-based soft magnetic alloy powder (average major axis: 15 μm, average minor axis: 7 μm, average thickness: 0.5 μm) and a vinyl chloride resin were mixed at a weight ratio of 75:25. After kneading using this roll, the kneaded material was injection molded into a sheet. This sheet was formed into a thickness of 0.5 mm by a press to obtain a magnetic shield sheet. On the other hand, the vinyl chloride resin containing no soft magnetic powder was formed into a sheet having a thickness of 0.3 mm to obtain an insulating sheet. The three insulating sheets and the four magnetic shield sheets were alternately stacked and pressure-bonded by a roll mill to obtain a magnetic shield laminate having a thickness of 2.9 mm (Sample 1). The magnetic shield characteristics of the magnetic shield material were measured by the measuring device 30 shown in FIG. The device 30 includes a base 31, a support 3
2, a stand including an arm 33, on which a lifting means 41 and a mounting table 42 are provided, and a magnet 44 of known strength is loaded into a box 43 mounted on the mounting table 42. Have been. Also, the detection end 51 of the magnetic intensity detector 50
Is supported by the arm 33 so as to be able to move up and down, and is installed so that the tip thereof faces the magnet 44. The sample 60 is placed on the box 43, and the height of the detection end 51 is changed so that the detector 44 shows an appropriate value.
And adjust the distance. A magnetic shield material (sample 1) is placed on the upper surface of the box 43, and the magnetic intensity is measured by the detector 50. In this embodiment, the initial magnetic intensity is 100 gauss,
The detection end 51 was set at a position of 80 Gauss, 60 Gauss, 40 Gauss, or 20 Gauss, and the magnetic intensity shielded by the sample 1 was measured. For comparison, a magnetic shield sheet (sample 2) having a thickness of 2 mm made of a magnetic shield sheet was manufactured without laminating the insulating sheets, and the magnetic shield effect was measured by the same method as that of sample 1. Table 1 shows the result (unit is Gauss). As shown in Table 1, Sample 1 and Sample 2
Achieves almost the same shielding effect.

[0013]

[Table 1] Magnetic field strength (G) 100 80.0 60.0 40.0 20.0 Sample 1 (G) 29.0 25.9 21.2 15.1 8.3 Sample 2 (G) 28.6 25.2 20.8 14.9 8.0

Example 2 Using a commercially available electromagnetic cooker, the above-mentioned magnetic shield materials (samples 1 and 2) were mounted on the back side at a position 2 mm away from the induction heating coil, and each magnetic shield material was changed for each heating time. Was measured with a surface thermometer. The results are shown in Table 2. As is clear from this result, the heat generation amount of Sample 1 having the insulating layer according to the present example was reduced by half compared to Sample 2 in which only the conventional flaky powder was blended, and a remarkable heat generation preventing effect was achieved. .

[0015]

[Table 2] Heating time (min) 0 2 4 6 8 10 Sample 1 (° C) 22.0 27.8 32.6 36.3 41.5 43.5 Sample 2 (° C) 22.0 51.2 65.4 73.4 77.2 84.0

Example 3 A flaky Fe-based soft magnetic alloy powder (average major axis: 15 μm, average minor axis: 7 μm, average thickness: 0.5 μm) and a vinyl chloride resin were mixed at a weight ratio of 75:25. After kneading using this roll, the kneaded material was injection molded into a sheet. This sheet was formed into a thickness of 0.5 mm by a press to obtain a magnetic shield sheet. On the other hand, an insulating sheet was obtained by molding a vinyl chloride resin (powder 75 wt% -resin 25 wt%) mixed with Mn-Zn ferrite insulating soft magnetic powder (average particle size 15 μm) into a sheet having a thickness of 0.3 mm. The three insulating sheets and the four magnetic shield sheets were alternately stacked and pressure-bonded by a roll mill to obtain a magnetic shield laminate having a thickness of 2.9 mm (Sample 3).
The magnetic shield effect of this magnetic shield material was measured in the same manner as in Example 1. The results are shown in Table 3 (unit is Gauss).

[0017]

[Table 3] Magnetic field strength (G) 100 80.0 60.0 40.0 20.0 Sample 3 (G) 22.3 20.1 17.3 11.0 6.1

Example 4 The amount of heat generated in the magnetic field of the magnetic shield material (sample 3) obtained in Example 3 was measured in the same manner as in Example 2. The results are shown in Table 4. As shown in Tables 3 and 4, the magnetic shield material of this example has a high magnetic shield effect, but the heat generation is reduced by half, and achieves an excellent heat prevention effect.

[0019]

[Table 4] Heating time (min) 0 2 4 6 8 10 Sample 3 (° C) 22.0 30.2 35.1 37.9 42.2 44.0

[0020]

The magnetic shielding material of the present invention has a much higher magnetic shielding effect than conventional shielding materials, and is a highly practical magnetic shielding material that does not generate heat even in a strong magnetic field. In addition, a magnetic shield material having excellent workability can be obtained by using the type of resin according to the purpose of use. As an example, by using a thermoplastic resin, it can be bent into a certain shape, and the powder in the processed portion does not cause magnetostriction, so that the magnetic characteristics do not deteriorate. Therefore, there is an advantage that the workability is excellent such that the work can be performed on site. Also, when a thermosetting resin is used, processing can be similarly performed in accordance with the construction site.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a magnetic shield material according to the present invention.

FIG. 2 is a schematic sectional view of a magnetic shield material according to the present invention.

FIG. 3 is a schematic diagram of a magnetic intensity measuring device used in an embodiment.

[Explanation of symbols]

 Reference Signs List 10-magnetic shield material 11-resin 12-flaky soft magnetic powder 20-magnetic shield layer 30-insulating layer

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroyuki Imai 1-297 Kitabukurocho, Omiya City, Saitama Prefecture Inside the New Material Development Center, Mitsubishi Materials Corporation (72) Inventor Yoshihiko Ciudata 1 Kitabukurocho, Omiya City, Saitama Prefecture 297-chome, Mitsubishi Materials Corporation New Materials Development Center (56) References JP-A-59-119900 (JP, A) JP-A-63-305600 (JP, A) JP-A-2-42798 (JP, A A) JP-A-5-95197 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05K 9/00

Claims (2)

(57) [Claims] 1. A layer thickness of a soft magnetic powder oriented in a layered manner.
A high-resistance magnetic shield material comprising a magnetic shield layer having a thickness of 1 to 5 mm and a plurality of non-conductive insulating layers containing insulating soft magnetic powder alternately laminated in a resin. 2. The soft magnetic powder forming the magnetic shield is a flaky powder of a permalloy alloy, a sendust alloy or an amorphous alloy thereof, having an average particle size of 5 to 300 μm, and the insulating powder contained in the insulating layer is an average particle size. Diameter 5-5
0 μm Mn—Zn ferrite powder or Ni—Zn ferrite powder, wherein the thickness of the insulating layer is 0.05 μm to 1 μm.
The high-resistance magnetic shield material according to claim 1, which is mm.