JPH06252587A - High resistance magnetic shield material - Google Patents

Abstract

(57) [Summary] [Structure] A high resistance magnetic shield material comprising a mixed powder of flaky soft magnetic powder and insulating soft magnetic powder in a resin, preferably an average of flaky soft magnetic powder. Particle size is 5
The average particle size of the insulating soft magnetic powder is 1 to 1 mm.
A magnetic shield material having a thickness of 100 μm and a ratio of the mixed powder in the magnetic shield material of 90 to 50% by weight and a ratio of the insulating soft magnetic powder in the mixed powder of 80 to 10% by weight. [Effect] It is a highly practical magnetic shield material that has a significantly greater magnetic shield effect than conventional shield materials and does not generate heat even in a strong magnetic field. Moreover, by using the type of resin according to the purpose of use, the workability is improved. It is an excellent magnetic shield material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic shield material which has an excellent magnetic shield effect and workability and which 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 due to magnetism have increased, and magnetic shields are required in a wide range of fields. For example, bottom members of electromagnetic cookers, wall materials for buildings near high-voltage lines, wall materials and floor materials for magnetic tomography rooms in hospitals, electronic circuit boxes for automobiles, casing materials for small motors, wall materials for linear motors. It is necessary to shield magnetic noise so that floors and floor materials are not affected by magnetism or are not affected by magnetism from the outside. The present invention relates to a magnetic shield material most suitable for these members.

[0002]

2. Description of the Related Art Conventionally, permalloy alloy plate, silicon steel plate and ferrite have been used as a magnetic shield material for blocking unnecessary magnetism generated from a magnetic field, and as a composite material, a soft magnetic amorphous material has been used. It is known that an alloy powder is sandwiched between two resin films and bonded together. However, when the permalloy alloy plate or the silicon steel plate is installed in a strong alternating magnetic field such as an electromagnetic cooker or an electromagnetic cooker, there is a problem that the plate material generates heat due to hysteresis loss and eddy current flowing inside the plate. Further, when the permalloy alloy plate is subjected to bending, drawing or cutting, the alloy structure of the processed portion is distorted and the magnetic shield characteristics are extremely deteriorated. To restore this, put the processed product at 1000 ℃
After annealing as described above, it has to be annealed in a non-oxidizing atmosphere, which causes a problem in workability such as time-consuming production and a large cost increase. 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 shield material in which soft magnetic amorphous alloy powder is sandwiched between resin films has a limited amount of soft magnetic powder because the resin film is stuck with a binder and the soft magnetic powder is interposed between them, resulting in a magnetic shield effect. Low.

In addition to the above magnetic shield material, a magnetic shield material in which a metal soft magnetic powder such as permalloy alloy powder or sendust alloy powder is mixed with a resin, or an oxide soft magnetic powder such as ferrite powder is mixed in a resin. Magnetic shield materials are known. However, when a resin is mixed with a metal-based soft magnetic powder such as an alloy powder, when the magnetic powder is filled in the resin at a high density, the powders come into contact with each other to lower the insulating property and generate heat due to eddy current generation. Inevitable, if the filling amount is reduced, the insulating property is improved, but the magnetic resistance is also increased, and the magnetic shield effect is reduced. Further, the one using the oxide type soft magnetic powder such as ferrite does not generate heat but the magnetic performance is inferior. A magnetic material in which sendust alloy powder is mixed in a resin is also known (Japanese Patent Laid-Open No. 4-94502), but this is intended to enhance the workability of the sendust alloy material used as a magnetic core material. However, unlike the magnetic shield material, the alloy powder is used in the form of flakes to increase the magnetic flux density, but the problem of heat generation has not been solved.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic shield material that solves the above problems of the conventional magnetic shield material. In the magnetic shield material in which the soft magnetic powder is mixed with the resin, the voids between the magnetic powders have a magnetic resistance, so that it is preferable that the powders exist in the resin in a state of being in contact with each other as much as possible. The scale-like powders are likely to come into contact with each other and the voids between the powders are reduced, which has the advantage of reducing the magnetic resistance. On the other hand, the insulating magnetic powder has a large electric resistance and does not generate an eddy current, so that heat generation can be prevented. Therefore,
If you mix the scale-like and insulating magnetic powder into the resin,
It is possible to obtain a magnetic shield material having a low magnetic resistance and preventing heat generation. However, a typical insulating soft magnetic powder is oxide-based ferrite and the like, and since it is difficult to process ferrite into a flaky shape, it is difficult to obtain a flaky insulating soft magnetic powder. Therefore, the present invention, the insulating ferrite soft magnetic powder hard to be processed into a scale-like, is used by mixing a scale-like soft magnetic powder made of an alloy-based processable soft magnetic powder is used as a resin. By compounding, a magnetic shield material having a small magnetic resistance and an excellent magnetic shielding effect, and having a high electric resistance, the generation of an eddy current is prevented, and the magnetic shield material hardly generates heat even in a strong magnetic field.

[0005]

According to the present invention, the following magnetic shield material is provided. (1) A high resistance magnetic shield material comprising a resin containing mixed powder of flaky soft magnetic powder and insulating soft magnetic powder. (2) The average particle size of the flaky soft magnetic powder is 5 μm to 1 mm, and the average particle size of the insulating soft magnetic powder is 1 to 100 μm.
(1) High resistance magnetic shield material. (3) The ratio of the mixed powder in the magnetic shield material is 90 to
50% by weight of the magnetic shield material according to the above (1) or (2). (4) The magnetic shield material according to (1), (2) or (3) above, wherein the ratio of the insulating soft magnetic powder in the mixed powder is 80 to 10% by weight. (5) The magnetic shield material according to the above (1), wherein the flaky soft magnetic powder is oriented in layers in the resin through the insulating soft magnetic powder.

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic sectional view of a magnetic shield material according to the present invention. As shown in the figure, in the magnetic shield material 10 of the present invention, scale-like soft magnetic powder 12 and insulating soft magnetic powder 13 are mixed in resin 11. As the type of resin, a thermoplastic resin, a thermosetting resin, or the like is appropriately used according to the use conditions. Specifically, a hard resin is used when the molded body requires rigidity, and a soft resin is used when rigidity is not required, such as when the molded body is attached to a support member.

The flaky soft magnetic powder may be a powder obtained by flattening a general soft magnetic material into flakes, and preferably has a high magnetic permeability and a low coercive force. Specifically, a permalloy alloy, a sendust alloy, or an amorphous alloy containing iron and cobalt as main components is suitable. The soft magnetic powder preferably has an average particle size of 5 μm to 1 mm (1000 μm) and an aspect ratio (major axis / thickness ratio) of 10 or more. If the average particle size is smaller than 5 μm, the contact resistance between the particles, which becomes the magnetic resistance when the powder is mixed in the resin, increases, which is not preferable. If the average particle size is larger than 1 mm, it becomes difficult to uniformly disperse the powder in the resin when kneading. If the aspect ratio is smaller than 10, the contact area between the powders is reduced and the magnetic resistance is increased, which is not preferable. Aspect ratio is 1
If it is larger than 0, 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 be oriented in a layer in the resin.

As the insulating soft magnetic powder, any oxide soft magnetic powder may be used, and one having a high magnetic permeability and a low coercive force is desirable. Specifically, Mn-Zn ferrite powder, Ni
-Zn ferrite powder is generally used. The insulating powder has a particle size of 1 to 100 μm (average particle size of 5 to 50 μm).
Those of () are preferable. If the particle size is larger than 100 μm, it becomes difficult to disperse the flaky powder in the resin. Also, when the particle size is smaller than 1 μm, the powder agglomerates and similarly it becomes difficult to disperse it between the flaky powders.

In the magnetic shield material of the present invention, the insulating soft magnetic powder intervenes between the flaky soft magnetic powder particles in the resin, so that the electric resistance becomes large, and the induced current due to the passage of the magnetic flux hardly flows. Since it prevents the generation of eddy currents,
It is possible to prevent heat generation of the magnetic shield material. on the other hand,
With respect to the magnetic flux, since all the powders are soft magnetic powders, the magnetic flux flows through these powders and exhibits a high magnetic shield effect. The ratio of insulating soft magnetic powder in the mixed powder is 1
0 to 80% by weight is desirable. If the amount of the insulating powder is less than 10% by weight, the effect is insufficient, and if it is more than 80% by weight, the mutual contact of the powders becomes insufficient and voids are easily generated. However, the magnetic permeability of the entire magnetic shield material decreases, which is not preferable.

The ratio of the mixed powder in the shield material is 50.
~ 90 wt% is preferred. If the amount of the mixed powder added is less than 50% by weight, the resin is present between the powders to increase the magnetic resistance. On the other hand, if the amount added is more than 90% by weight, the powder cannot be contained in the resin and it becomes extremely brittle and cannot be molded. When the mixed powder is added to the resin and kneaded, a magnetic shield material in which the powder is uniformly dispersed in the resin is obtained. In this molding process, it is possible to orient the flaky soft magnetic powder contained in the resin into a layer by press-pressing a mixture of the resin and the powder, or by applying magnetism,
A magnetic shield material having a high magnetic shield effect can be obtained.

[0011]

EXAMPLES Examples of the present invention will be shown below. The present embodiment is an example, and the present invention is not limited to the following embodiments. Example 1 Scale-like Fe-based soft magnetic alloy powder (average major axis 15 μm, average minor axis 7 μm, average thickness 0.5 μm) and insulating Mn-Zn
Ferrite powder (average particle size 9.3 μm) in a weight ratio of 80:
Mixed in a proportion of 20. This mixed powder was added to vinyl chloride resin (75% by weight of powder-25% by weight of resin), and the mixture was kneaded using a two-roll mill, and then the kneaded product was injected into a sheet. This sheet was pressed to a thickness of 2 mm to obtain a magnetic shield material (Sample 1). The magnetic shield characteristics of this magnetic shield material were measured by the measuring device 30 shown in FIG. The device 30 includes a base 31, a support column 32,
A stand including an arm 33 is provided, and an elevating means 41 and a mounting table 42 are provided on the stand.
A magnet 44 of known strength is placed in a box 43 placed on top of the second box. Further, the detection end 51 of the magnetic intensity detector 50 is supported by the arm 33 so as to be vertically movable, and the tip thereof is installed so as to face the magnet 44. The sample 60 is placed on the box 43, and the height of the detection end 51 is changed to adjust the distance between the magnet 44 and the detection end 51 so that the detector 50 shows an appropriate value. 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 strength is 100 gauss,
The detection end 51 was installed at the positions of 80 gauss, 60 gauss, 40 gauss, and 20 gauss, and the magnetic intensity shielded by the sample 1 was measured. For comparison, the same magnetic shield material as that of Sample 1 (Sample 2) except that the insulating Mn-Zn ferrite powder was not mixed with the Fe-based flaky soft magnetic alloy powder.
Was manufactured, and its magnetic shield effect was measured by the same method as in Sample 1. The results are shown in Table 1 (unit is Gauss).
As shown in Table 1, sample 1 is sample 2 using flaky powder.
It has achieved a shielding effect that is not much different from.

[0012]

[Table 1] Magnetic field strength (G) 100 80.0 60.0 40.0 20.0 Sample 1 (G) 31.1 27.2 21.6 15.2 8.4 Sample 2 (G) 28.4 25.6 21.0 14.8 8.1

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 heated every heating time. Was measured with a surface thermometer. The results are shown in Table 2. As is clear from these results, the heat generation amount of Sample 1 according to this example is half that of Sample 2 containing only the conventional flaky powder, and a remarkable heat generation prevention effect is achieved.

[0014]

[Table 2] Heating time (min) 0 2 4 6 8 10 Sample 1 (° C) 22.0 28.2 33.1 37.0 42.3 44.0 Sample 2 (° C) 22.0 51.4 65.3 73.1 77.6 84.1

Example 3 The mixing ratio of the scaly powder to the insulating powder was 60.
Example 1 except that the weight% and the insulating powder 40% were changed.
A magnetic shield material was manufactured in the same manner as in (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).

[0016]

[Table 3] Magnetic field strength (G) 100 80.0 60.0 40.0 20.0 Sample 3 (G) 33.0 28.7 22.9 16.3 8.6

Example 4 With respect to the magnetic shield material (Sample 3) obtained in Example 3, the calorific value in the magnetic field was measured by the same method 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 also has a magnetic shield effect which is not so different from the conventional one, but the amount of heat generation is reduced by half, and an excellent heat generation prevention effect is achieved.

[0018]

[Table 4] Heating time (min) 0 2 4 6 8 10 Sample 3 (° C) 22.0 28.0 31.9 35.0 38.8 40.1

[0019]

The magnetic shield material of the present invention is a highly practical magnetic shield material that has a markedly greater magnetic shield effect than conventional shield materials and does not generate heat even in a strong magnetic field. Further, by using the kind of resin according to the purpose of use, a magnetic shield material having excellent workability can be obtained. As an example, by using a thermoplastic resin, it can be bent into a fixed shape, and the powder in the processed portion does not cause magnetic strain, 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. Further, even when a thermosetting resin is used, it can be processed in a similar manner depending on the construction site.

[Brief description of drawings]

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

FIG. 2 is a schematic diagram of a magnetic intensity measuring device used in Examples.

[Explanation of symbols]

 10-Magnetic Shielding Material 11-Resin 12-Scale Soft Magnetic Powder 13-Insulating Soft Magnetic Powder

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical indication location H01F 1/34 B 15/04 8123-5E (72) Inventor Yoshihiko Chikita Kitabukuro-cho, Omiya-shi, Saitama Prefecture 1-chome 297, New Material Development Center, Mitsubishi Materials Corporation

Claims (5)

[Claims] 1. A high resistance magnetic shield material comprising a resin containing mixed powder of flaky soft magnetic powder and insulating soft magnetic powder. 2. The average particle size of the flaky soft magnetic powder is from 5 μm to
The high resistance magnetic shield material according to claim 1, wherein the insulating soft magnetic powder has an average particle diameter of 1 mm and 1 to 100 µm. 3. The magnetic shield material according to claim 1, wherein the ratio of the mixed powder in the magnetic shield material is 90 to 50% by weight. 4. The ratio of the insulating soft magnetic powder in the mixed powder is 80 to 10% by weight.
Magnetic shield material. 5. The magnetic shield material according to claim 1, wherein the scale-like soft magnetic powder is oriented in layers in the resin through the insulating soft magnetic powder.