JPS6258631B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a paint, and an object of the present invention is to provide a paint that provides a magnetic shielding effect just by application.

Hitherto, shielding of magnetic fields has been carried out in various ways. Recently, there has been a demand for reliable and inexpensive means for shielding magnetic field disturbances caused by trains and automobiles, fluctuations in terrestrial magnetism, and low-frequency magnetic fields generated from commercial power sources.

Conventionally, methods are known to shield high-frequency magnetic fields to some extent by using radio wave absorbers made of carbon powder or ferrite sintered bodies, radio wave reflectors made of zinc-plated iron plates, and the like. However, the only way to shield in the low frequency range is to cover it with an expensive plate with high magnetic permeability.

An object of the present invention is to provide a means for easily performing magnetic shielding at low cost.

The object of the present invention is to achieve the above object by providing a coating material that can impart a magnetic shielding effect simply by coating it on a substrate.

The present invention uses fine powder of high magnetic permeability alloys such as Fe-Ni alloy, Fe-Ni-Co alloy, Fe-Si-Al alloy, and Fe-Ni-Mo alloy in a polymer compound binder. This is a magnetic shielding paint made by mixing .

The magnetic shielding paint of the present invention is manufactured as follows.

Fe-Ni alloy, Fe-Ni-Co alloy, Fe-Ni-
Raw materials for high-permeability materials such as Mo-based alloys and Fe-Si-Al-based alloys are melted in a vacuum high-frequency melting furnace, etc., cast into ingots, the outer shell is shaved, and solution treatment is performed, followed by magnetic annealing. to obtain a high magnetic permeability material. After that, this is processed using a crusher to a particle size of 0.01 to 100μ.
Repeat the grinding and grinding process until In order to prevent oxidation during this time, it is preferable to carry out the process in an inert gas atmosphere. Further, annealing may be additionally performed in a hydrogen atmosphere to enhance magnetism. The thus obtained powder particles have an irregular flat shape and a thickness of 0.01 to 50 μm, as shown by 1 in FIG. The powder particles obtained above are mixed into a synthetic resin binder such as synthetic rubber, epoxy, polyester, acrylic, silicone, melamine, phenol, etc. to obtain a paint.

FIG. 2 shows an example of three coats of this paint. In order to make the flat direction of the fine powder parallel to the coated substrate, it is desirable that the thickness t of one coat is less than the maximum diameter of the fine powder, usually 50 to 80 μ. When brushing or spraying, apply multiple coats several times or several dozen times. If the thickness of one coat is too large, the flat direction of the fine powder will not be parallel to the coated substrate and the shielding effect will be impaired. The base material 3 may be a material such as metal, wood, plastic, or asbestos concrete, and may be a molded product, a fitted product, or a laminated product.

If the magnetic shielding paint according to the present invention is used outdoors for a long period of time, the fine powder may be exposed and oxidized, or the binder may age. Therefore, materials 4 such as unsaturated polyester resin, epoxy resin, polymethyl methacrylate, polystyrene, polycarbonate, urea resin, acrylic copolymer, etc.
It does not matter if it covers the surface of the coating layer.

The volume ratio of magnetic shielding fine powder and polymer compound is
The hours are 10:90-90:10. Preferably volume ratio 20:80
~80:20. This is because if there is less fine powder that shields magnetism, there will be a lot of magnetic leakage and there will be no magnetic shielding effect. Furthermore, if the amount of fine powder increases, the coating properties will deteriorate significantly.

Next, the present invention will be explained in more detail by giving experimental examples. Measurements were carried out in a plastic box measuring 800 mm x 800 mm x 800 mm. A fluxgate type magnetometer was used to measure the low frequency magnetic field. High-frequency magnetic field measurements were performed using a loop antenna in accordance with MIL-STD-285. In the experiment, the magnetic shielding paint of the present invention was applied to the surface of a plastic box 20 times at a coating thickness of approximately 50 μm each time, and the total coating thickness was approximately 1 mm, and the capacitance of the magnetic shielding fine powder was increased. Attenuation was measured by varying the frequency. In addition, in order to particularly compare the case where the flat direction of the fine powder and the substrate direction are parallel and the case where they are different,
Similar measurements were also carried out on a sample coated seven times (total coating thickness approximately 1 mm) with a coating thickness t of approximately 150 μm. FIG. 3 shows the relationship between the ratio of the amount of magnetic shielding fine powder, that is, the volume ratio, and the shielding effect, that is, the amount of attenuation. When the volume ratio is about 10%, the effect is less than 2 dB. However, when the thickness t of one coating is 50μ20
When applied twice, an attenuation of 20 dB was obtained at 60% or more.
Further, even if the volume ratio was increased, the damping effect did not improve. On the other hand, in 7 coats with a single coat thickness t of 150μ, at most 6 dB even if the volume ratio is 60% or more.
It was moderately hot. That is, the shielding effect can be improved by about 14 dB by applying a coating method in which the thickness of each coating is small and the coating is repeated until the required coating thickness is made so that the flat direction of the magnetic shielding fine powder 1 is parallel to the direction of the coated substrate. FIG. 4 shows the relationship between the shielding effect and the frequency.
20 coats with a thickness of 50μ has a shielding effect of 20dB from 50Hz, and can shield up to 50dB at 1MHz. However, with a thickness of 150 μ and 7 coats, the effect is only about 5 dB at frequencies below 1 kHz, and at 1 MHz.
The shielding effect is poor at 15dB.

As described above, the present invention is based on the high magnetic permeability material Fe-
Uses fine powder of Ni alloy, Fe-Ni-Co alloy, Fe-Si-Al alloy, Fe-Ni-Mo alloy, and the shape of the fine powder is flattened into irregular shapes including disk shapes. A better shielding effect was obtained in the low frequency range (50 Hz to 1 MHz) by creating and applying the coating method so that the flat direction of the fine powder was parallel to the direction of the substrate to be coated. This is at most conventional shielding materials.
This is an excellent feature compared to the shielding effect that appears above 500kHz.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the shape of fine powder of a high magnetic permeability material. FIG. 2 is a sectional view showing the painted state.
FIG. 3 is a diagram showing the relationship between the volume ratio of the amount of magnetic shielding fine powder and the amount of attenuation. FIG. 4 is a diagram showing the relationship between frequency and attenuation amount. 1... Powder particles, 2... Binder, 3... Base material.

Claims (1)

[Claims] 1 Fe-Ni alloy, Fe-Ni-Co alloy, Fe-Si
-Magnetic shielding paint made by mixing fine powder of high magnetic permeability alloys such as Al alloys and Fe-Ni-Mo alloys into a polymer binder. 2. The magnetic shielding paint according to claim 1, wherein the fine powder is flat irregularly shaped particles. 3. In the magnetic shielding paint according to claim 2, the flat particles have a thickness of 0.01 to 50 μm and a particle size of 0.01 μm.
A magnetic shielding paint characterized by ~100μ. 4. In the magnetic shielding paint according to claim 1, the ratio of the fine powder to the polymeric compound binder is
A magnetic shielding paint characterized by a ratio of 10:90 to 90:10.