JP5780408B2 - Soft magnetic resin composition and electromagnetic wave absorber - Google Patents

Description

The present invention relates to a soft magnetic resin composition and an electromagnetic wave absorber capable of arbitrarily adjusting an electromagnetic wave absorption frequency in a high frequency band of 1 GHz or more and having a thin wall and excellent electromagnetic wave absorption performance.

Conventionally, as a method to prevent malfunctions and communication failures of electronic devices, it is known to use tiles, sheets, and paints that are mixed with soft magnetic powder such as soft magnetic metal powder and spinel ferrite powder. Widely used for countermeasures against radio interference, prevention of radar false images, and other unwanted radiation of electromagnetic waves.

In recent years, with the increase in speed and capacity of information communication, use of frequencies in the GHz band is expanding in electronic devices such as personal computers and mobile phones, and information communication such as wireless LAN, Bluetooth, and DSRC. In this case, there are cases where it is difficult to effectively absorb electromagnetic waves with soft magnetic metals and spinel ferrites that have been used conventionally, and development of materials effective for electromagnetic waves in the GHz band is desired.

Electromagnetic wave absorption by magnetic wave absorbers using magnetic material uses the magnetic loss due to μ ”, which is the imaginary part of complex permeability. Therefore, in order to improve electromagnetic wave absorption performance, it is necessary to increase μ” of the material. There is. Electronic devices are becoming smaller and thinner, and in order to use them, it is necessary to reduce the thickness of the radio wave absorber. However, since the thickness and performance of the wave absorber are in a proportional relationship, it is necessary to further improve μ ”in order to maintain the performance of the wave absorber. There are a wide variety of frequencies, and it is desired to develop a radio wave absorber capable of widening the radio wave absorption effect and arbitrarily adjusting the frequency characteristics.

Hexagonal ferrite is promising as a material that exhibits excellent radio wave absorption performance in a high frequency band of GHz or higher. One of them is Y-type hexagonal ferrite. However, the Y-type hexagonal ferrite alone has a limit in improving the imaginary part μ ″ of the complex permeability, and further improvement in characteristics is desired in order to absorb unnecessary electromagnetic waves with a thinner thickness.

JP 2006-332693 A

As disclosed in Patent Document 1 described above, a composite magnetic body having at least two magnetic resonances is obtained by mixing at least two types of soft magnetic metal flat powders having different magnetic anisotropies. However, soft magnetic metal flat powders can only handle frequencies up to about 2 GHz, and the bandwidth is not sufficient. Moreover, when carbonyl iron powder is used, it can respond | correspond to about 6 GHz, However, It becomes -10 dB or less by 1 mm thickness, and absorption performance is low. In addition, the bandwidth cannot be increased. In addition, there are problems with chemical stability and weight.

The present invention has been made to solve the above-described problems, and can arbitrarily adjust an electromagnetic wave absorption frequency in a high frequency band of GHz or higher, and can obtain an excellent electromagnetic wave absorption performance with a wide band and a thin wall. It is intended to provide a soft magnetic resin composition and an electromagnetic wave absorber using the material.

An object of the present invention is to solve the problems of the above-described conventional soft magnetic resin composition and an electromagnetic wave absorber using the material.

  In order to achieve the above-mentioned object, the present invention provides a soft magnetic resin composition comprising a soft magnetic metal flat powder, a Y-type hexagonal ferrite powder, and a polymer resin. A soft magnetic resin composition having a volume ratio of type hexagonal ferrite powder of 0.2 to 5.0 is formed.

Secondly, Fe-Al-Si-based, Fe-Si-Cr-based, Fe-Si-based, Fe-Cr-based, Fe-Ni-based, Fe nanocrystal-based, Fe-based amorphous group as soft magnetic metal flat powder. The soft magnetic resin composition according to claim 1, wherein at least one soft magnetic metal flat powder having a bulk density / true density ratio of 0.02 to 0.14 is used. It is.

Third, in the Y-type ferrite powder represented by the composition Ba ₂ M ₂ Fe ₁₂ O ₂₂ , Zn, Ni, Co, Mg, Mn, Fe, Cu, Be, Ca, Sr, Ra are contained in the M portion. 3. The soft magnetic resin composition according to claim 1, wherein at least one kind of divalent metal element selected from the group is used.

Fourth, a soft magnetic resin composition is used as a radio wave absorber.

In the present invention, a Y-type hexagonal ferrite powder and a soft magnetic metal flat powder are mixed and mixed with a resin, so that the electromagnetic wave absorption frequency can be arbitrarily adjusted in a high frequency band of GHz or higher, and has a wide band and a thin wall. It is intended to provide a soft magnetic resin composition capable of obtaining absorption performance and an electromagnetic wave absorber using the material.

It is the figure which showed the value of the return loss in thickness of 1 mm when using Fe-Si-Cr type metal flat powder and Zn type Y-type ferrite powder, respectively, when mixing independently and mixing by 1/1. It is the figure which showed the value of the return loss in the matching thickness at the time of using the Fe-Si-Cr type metal flat powder and Zn type Y-type ferrite powder, respectively when it mixes independently and is mixed by 1/1.

  Hereinafter, specific best modes of the present invention will be described.

  The soft magnetic metal flat powder used in the present invention is an alloy powder having an average particle diameter of 20 to 30 μm produced by a gas atomizing method, and is in a hydrocarbon organic solvent so as to obtain a predetermined bulk density / true density with an attritor. And processed into a flat shape. Next, the flat powder was subjected to strain removal treatment at a predetermined temperature to obtain a soft magnetic metal flat powder.

The Y-type hexagonal ferrite powder used in the present invention has a composition of Ba ₂ M ₂ Fe ₁₂ O ₂₂ and may slightly deviate from this composition as long as the Y-type hexagonal ferrite is formed. The crystal structure of the Y-type hexagonal ferrite can be known from the X-ray diffraction peak. Further, at least one divalent metal selected from the group consisting of Zn, Ni, Co, Mg, Mn, Fe, Cu, Be, Ca, Sr, and Ra is used for the M portion.

  The Y-type hexagonal ferrite powder can be produced according to a conventional general method for producing ferrite. That is, a metal oxide or metal salt (for example, carbonate) is mixed so that Ba, M, and Fe are contained in a predetermined ratio, mixed, granulated, and then fired to form a solid solution Y-type hexagon. Crystalline ferrite can be synthesized. The firing temperature is about 1100 to 1300 ° C., the firing atmosphere is air, and the firing time is about 1 to 4 hours. Moreover, you may use a metal chloride as the flux for the raw material.

  After firing, Y-type hexagonal ferrite powder is obtained by crushing using a ball mill, vibration mill, pin mill or the like. When the average particle diameter D50 exceeds 6 μm, aggregated particles remain, and therefore it is preferably about 3 μm.

  The mixing ratio of the soft magnetic metal flat powder and the Y-type hexagonal ferrite powder is preferably 0.2 to 5.0 in terms of the volume ratio of the soft magnetic metal flat powder / Y-type hexagonal ferrite powder. When the ratio is less than 0.2, the frequency is almost the same as when the Y-type hexagonal ferrite powder is used alone, and the absorption performance is equivalent. Further, when the volume ratio of the soft magnetic metal flat powder / Y-type hexagonal ferrite powder exceeds 5.0, the frequency and the absorption performance when the soft magnetic metal flat powder is used alone are substantially the same.

  As the soft magnetic metal flat powder, Fe-Al-Si, Fe-Si-Cr, Fe-Si, Fe-Cr, Fe-Ni, Fe nanocrystal, and Fe amorphous are preferable. At least one kind of soft magnetic metal flat powder selected from among them is used. The bulk density / true density, which is an index of flatness, is preferably 0.02 to 0.14. When it is less than 0.02, the specific surface area increases, mixing with the resin becomes difficult, and the productivity is significantly reduced. Further, since the flattening process proceeds excessively, it is difficult to remove the processing distortion by the distortion removing process, and a lot of fine powder is generated, so that the magnetic characteristics are deteriorated. On the other hand, if it exceeds 0.14, since the flattening is insufficient, the demagnetizing factor is large, and the magnetic characteristics are deteriorated due to the skin effect.

  When a mixed powder of Y-type hexagonal ferrite powder and soft magnetic metal flat powder (hereinafter referred to as soft magnetic mixed powder) is mixed with a polymer resin, the content of the soft magnetic mixed powder is 10% by volume or more. Is preferred. If it is less than 10% by volume, the magnetic properties are lowered and the radio wave absorption performance is inferior. The molding method is not particularly limited, such as injection molding, extrusion molding, hot press molding, press molding, calendar roll molding, coating, spray coating and the like.

  As the polymer resin, thermoplastic resins such as polyamide, polyester, polycarbonate, polyether sulfone, polyphenylene sulfide, urethane, and ethylene ethyl acrylate can be used. Further, thermoplastic elastomers such as chlorinated polyethylene, SBS, and SEBS, synthetic rubbers such as neoprene-based and chloroprene-based rubbers, and natural rubbers can be used. Furthermore, as the thermosetting resin, an epoxy resin, an acrylic resin, a urea resin, or the like can be used, but is not limited thereto. In addition, various surface treatments with a coupling agent, a dispersing agent, a rust preventive agent, an antioxidant, a heat stabilizer, a pigment, a nonmagnetic filler, a plasticizer, as long as the object of the present invention is not impaired. Various additives such as a reinforcing agent, a heat conductive filler, and an adhesive can be added alone or in combination. The coupling agent may be surface-treated with a silane coupling agent, titanate coupling agent, zircoaluminate coupling agent, aluminum coupling agent or the like in order to improve miscibility with other components.

  The method for producing a soft magnetic resin composition comprising the soft magnetic powder and the polymer resin of the present invention is not particularly limited, and can be performed by various known methods. For example, after the raw materials are dispersed with a universal mixer, they may be kneaded using a single kneading or biaxial extrusion kneading method or a pressure kneader.

  The soft magnetic metal flat powder used in Examples 1 to 3 and Comparative Examples 1 and 2 was an Fe—Si—Cr alloy (Si = 9 wt%, Cr = 1.5 wt%) produced by a gas atomization method and having an average particle size of 30 μm. ) Was obtained by performing a flattening treatment using an attritor so as to obtain a predetermined bulk density / true density. The bulk density was measured based on JISZ2504. The true density was measured using AccuPyc1330 manufactured by Shimadzu Corporation.

The Y-type hexagonal ferrite powder used in Examples 1 to 3 and Comparative Examples 3 and 4 were mixed with raw materials so as to have a composition of Ba ₂ Zn ₂ Fe ₁₂ O ₂₂ , and fired at 1200 ° C. for 4 hours. A Y-type hexagonal ferrite sintered body was produced. This Y-type hexagonal ferrite sintered body was pulverized using a ball mill to obtain a Y-type hexagonal ferrite powder having an average particle diameter D50 of 3 μm.

  Example 1 was mixed so that the volume ratio of soft magnetic metal flat powder / Y-type hexagonal ferrite powder was 5.0 to obtain a soft magnetic mixed powder. This soft magnetic mixed powder and chlorinated polyethylene resin were mixed and kneaded at 1: 1 (mass%), rolled to a thickness of 1 mm with a rolling roll, and then hot-pressed at 140 ° C. to form a sheet. The obtained sheet is punched into a shape having an outer diameter of 7 mm, an inner diameter of 3 mm, and a thickness of 1 mm. The complex permeability and complex permittivity were calculated. The return loss is the result of simulation based on the values of the complex permeability and complex permittivity calculated from the S parameter. The larger the return loss, the higher the radio wave absorption performance. When the sheet is 1 mm thick, the frequency width of the return loss of -10 dB or more and the peak value of the return loss are shown in Table 1.

  In Example 2, a sheet was formed in the same manner as in Example 1, except that the volume ratio of the soft magnetic metal flat powder / Y-type hexagonal ferrite powder was 1.0. The evaluation method is the same as in Example 1, and the results are shown in Table 1.

  In Example 3, a sheet was formed in the same manner as in Example 1 except that the volume ratio of the soft magnetic metal flat powder / Y-type hexagonal ferrite powder was 0.2. The evaluation method is the same as in Example 1, and the results are shown in Table 1.

  In Comparative Example 1, a sheet was formed in the same manner as in Example 1 except that only the soft magnetic metal flat powder was used. The evaluation method is the same as in Example 1, and the results are shown in Table 1.

  In Comparative Example 2, a sheet was formed in the same manner as in Example 1 except that the volume ratio of the soft magnetic metal flat powder / Y-type hexagonal ferrite powder was 6.0. The evaluation method is the same as in Example 1, and the results are shown in Table 1.

  In Comparative Example 3, a sheet was formed in the same manner as in Example 1 except that the volume ratio of the soft magnetic metal flat powder / Y-type hexagonal ferrite powder was 0.1. The evaluation method is the same as in Example 1, and the results are shown in Table 1.

  In Comparative Example 4, a sheet was formed in the same manner as in Example 1 except that only Y-type hexagonal ferrite powder was used. The evaluation method is the same as in Example 1, and the results are shown in Table 1.

  From Table 1, the example has a wider frequency range for maintaining the return loss of −10 dB or more than the comparative example, and shows the return loss equivalent to the comparative example 1 using only the soft magnetic metal flat powder.

  FIG. 1 shows the frequency characteristics of the return loss when Example 2 and Comparative Examples 1 and 4 are 1 mm thick. It can be seen that when the soft magnetic metal flat powder and the Y-type ferrite powder are mixed and used, the frequency region where the return loss is −10 dB or more is widened.

  FIG. 2 shows the frequency characteristics of the return loss when the matching thicknesses of Examples 1 to 3 and Comparative Examples 1 and 4 are used. It can be seen that the frequency can be adjusted by using a mixture of soft magnetic metal flat powder and Y-type hexagonal ferrite powder.

  The soft magnetic metal flat powder is selected from the group of Fe-Al-Si, Fe-Si-Cr, Fe-Si, Fe-Cr, Fe-Ni, Fe nanocrystal, and Fe amorphous. By using a soft magnetic metal flat powder having a bulk density / true density ratio of 0.02 to 0.14, it can be used as a material excellent in moldability and radio wave absorption performance.

  The soft magnetic metal flat powder used in Examples 4 and 5 and Comparative Examples 5 and 6 was flattened in the same manner as in Example 1, and the flattening time was adjusted so that the bulk density / true density would be a predetermined ratio. To obtain a soft magnetic metal flat powder.

  The Y-type hexagonal ferrite used in Examples 4 and 5 and Comparative Examples 5 and 6 obtained Y-type hexagonal ferrite powder in the same manner as in Example 1.

  In Example 4, a sheet was formed in the same manner as in Example 2 except that a soft magnetic metal flat powder having a bulk density / true density of 0.02 was used. The evaluation method is the same as in Example 1, and the results are shown in Table 2.

  In Example 5, a sheet was formed in the same manner as in Example 2 except that a soft magnetic metal flat powder having a bulk density / true density of 0.10 was used. The evaluation method is the same as in Example 1, and the results are shown in Table 2.

  In Comparative Example 5, a sheet was formed in the same manner as in Example 2 except that a soft magnetic metal flat powder having a bulk density / true density of 0.01 was used. This is shown in Table 2.

  In Comparative Example 6, a sheet was formed in the same manner as in Example 2 except that a soft magnetic metal flat powder having a bulk density / true density of 0.15 was used. The evaluation method is the same as in Example 1, and the results are shown in Table 2.

  From Table 2, comparing the comparative example and the example, it can be seen that the example is excellent in moldability and the return loss is -10 dB or more.

Industrial applicability

The present invention can be used for noise countermeasure devices such as electromagnetic waves, products for countermeasures against radio wave interference, and the like.

Claims (3)

The flat soft magnetic metal powder and the Y-type hexagonal ferrite powders A soft resin composition comprising a polymer resin, soft magnetic metal flat powder is Fe-Al-Si-based, Fe-Si-Cr system, Fe- One type or a mixture of two or more types selected from the group of Si-based, Fe-Cr-based, Fe-Ni-based, Fe nanocrystalline, and Fe-based amorphous, wherein the bulk density / true of the soft magnetic metal flat powder A soft magnetic resin composition having a density ratio of 0.02 to 0.10 and a soft magnetic metal flat powder / Y-type hexagonal ferrite powder volume ratio of 1.0 to 5.0 . Ba ₂ M ₂ Fe ₁₂ O ₂₂ In the Y-type hexagonal ferrite powder represented by the composition: at least one or more divalent selected from the group of Zn, Ni, Co, Mg, Mn, Fe, Cu, Be, Sr, Ra in the M part The soft magnetic resin composition according to claim 1, wherein a metal element is used. An electromagnetic wave absorber comprising the soft magnetic resin composition according to claim 1.

Images