JP6520688B2 - Magnetic sheet - Google Patents

Description

  The present invention relates to a magnetic sheet used, for example, as a magnetic shield.

  A magnetic shield material is used to prevent a magnetic field source such as a magnetized object from affecting other objects, electric circuits, and the like. As a magnetic shielding material, a metal plate of high permeability is desirable from the viewpoint of shielding characteristics, but the metal plate is extremely limited in applications in terms of properties and cost.

  On the other hand, a magnetic powder material is dispersed in an organic binder and applied in the form of a paint to a required portion of a shield to form a magnetic sheet, or applied to an appropriate flexible support or the like for a magnetic shield. It can be made into a magnetic sheet and various uses are possible.

  Such a magnetic sheet is required to have a high surface resistance. Therefore, for example, Patent Document 1 below proposes that an inorganic insulator be attached to the surface of a flat magnetic particle.

  However, in the prior art, the magnetic properties may be degraded because the inorganic insulator is attached to the surface of the flat magnetic particles. Also, conventionally, the process for attaching the inorganic insulator to the surface of the flat magnetic particles is complicated, and since glass (amorphous) is used as the inorganic insulator, it takes a long time for flat treatment and equipment And wear of the device.

Patent No. 5384711 gazette

  The present invention has been made in view of such circumstances, and an object thereof is to provide a magnetic sheet which is excellent in magnetic properties and high in sheet surface resistance while being easy to manufacture.

In order to achieve the above object, the magnetic sheet according to the present invention is
A magnetic sheet in which flat magnetic particles are dispersed in a synthetic resin,
The flat magnetic particles are at least one of an Fe-Si-Cr alloy magnetic material, an Fe-Si-Al-Cr alloy magnetic material, and an Fe-Al-Cr alloy magnetic material,
On the surface of the flat magnetic particles, a segregated substance of Cr having a length in the longitudinal direction of 0.4 μm or more is contained in the surface of the magnetic particles,
In the surface or cross section of the magnetic material sheet, five or more of the Cr segregants are observed within an arbitrary 10 μm × 10 μm field of view.

  In the magnetic sheet according to the present invention, Cr originally contained in the magnetic particles is segregated on the surface of the magnetic particles for a predetermined length or more, and the segregation of Cr is controlled to be 5 or more. Therefore, it is not necessary to prepare and attach the inorganic insulator separately from the magnetic particles, and it is possible to provide a magnetic sheet which is excellent in magnetic properties and high in sheet surface resistance while being easy to manufacture.

  Preferably, an aspect ratio obtained by dividing the length in the short direction of the Cr segregated material by the length in the longitudinal direction is 0.3 or less. By being a segregant having an aspect ratio of a predetermined value or less, it is possible to provide a magnetic sheet having excellent magnetic properties and high sheet surface resistance.

  Preferably, an aspect ratio obtained by dividing the length in the short direction of the flat magnetic particles by the length in the longitudinal direction is 0.3 or less. By using magnetic particles having an aspect ratio of a predetermined value or less, it is possible to provide a magnetic sheet having excellent magnetic properties and high sheet surface resistance even if the thickness of the sheet is reduced.

FIG. 1 is an enlarged cross-sectional view of a magnetic sheet according to an embodiment of the present invention. FIG. 2 is an enlarged sectional view of an essential part of a part II of FIG.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings.

  As shown in FIGS. 1 and 2, the magnetic sheet 2 according to an embodiment of the present invention is a magnetic sheet in which flat magnetic particles 4 are dispersed in a synthetic resin 8. The flat magnetic particles 4 are oriented in the sheet 2 so that the longitudinal direction of the particles 4 substantially coincides with the surface direction of the sheet 2.

  The synthetic resin 8 is not particularly limited, but urethane resin, polyester resin, polyethylene resin, cellulose resin, epoxy resin, phenol resin, thermoplastic resin such as amide resin, thermosetting resin, radiation curable resin, etc. are exemplified. Ru.

  The flat magnetic particles 4 are at least one of an Fe-Si-Cr alloy magnetic material, an Fe-Si-Al-Cr alloy magnetic material, and an Fe-Al-Cr alloy magnetic material. The filling ratio of the magnetic particles 4 in the magnetic sheet 2 is preferably 60 to 95 wt%.

The Fe-Si-Cr alloy magnetic body is not particularly limited, but when the composition of the Fe-Si-Cr alloy magnetic body is represented as Fe _a1 Si _b1 Cr _c1 X _d1 , the following equation holds. It is a1 = 53-85, b1 = 15-35, c1 = 0.1-6, d1 = 0.1-6.

  However, X is one or more other elements other than Fe, Si and Cr, and a1, b1, c1 and d1 are atomic% ratios of these elements, and a1 + b1 + c1 + d1 = 100. The other element X is not particularly limited, but can be selected from, for example, various metal elements such as transition metal elements and metalloid elements as needed. The other elements X may contain unavoidable impurities such as N, O, and S as long as the magnetic properties are not adversely affected.

The Fe-Si-Al-Cr alloy magnetic body is not particularly limited, but when the composition of the Fe-Si-Al-Cr alloy magnetic body is represented as Fe _a2 Si _b2 Al _e2 Cr _c2 X _d2 , The following equation holds. It is a2 = 53-85, b2 = 15-35, e2 = 15-35, c2 = 0.1-6, d2 = 0.1-6.

  However, X is one or more other elements other than Fe, Si, Cr, and Al, and a2, b2, e2, c2, d2 are atomic% ratios of those elements, and a2 + b2 + e2 + c2 + d2 = 100. The other element X is not particularly limited, but can be selected from, for example, various metal elements such as transition metal elements and metalloid elements as needed. The other elements X may contain unavoidable impurities such as N, O, and S as long as the magnetic properties are not adversely affected.

The Fe-Al-Cr alloy magnetic body is not particularly limited, but when the composition of the Fe-Al-Cr alloy magnetic body is represented as Fe _a3 Al _e3 Cr _c3 X _d3 , the following equation holds. It is a3 = 53-85, e3 = 15-35, c3 = 0.1-6, d3 = 0.1-6.

  However, X is one or more other elements other than Fe, Si and Cr, and a3, e3, c3 and d3 are atomic% ratios of those elements, and a3 + e3 + c3 + d3 = 100. The other element X is not particularly limited, but can be selected from, for example, various metal elements such as transition metal elements and metalloid elements as needed. The other elements X may contain unavoidable impurities such as N, O, and S as long as the magnetic properties are not adversely affected.

  On the surface of the flat magnetic particles 4, segregated substances 8 of Cr having a length of 0.4 μm or more in the longitudinal direction are contained in the surface of the magnetic particles 4. The aspect ratio of the magnetic particles 4 is a value obtained by dividing the length L1 in the short direction of the magnetic particles 4 by the length L0 in the longitudinal direction, and in the present embodiment, the aspect ratio is 0.3 or less. The lower limit of the aspect ratio of the magnetic particles 4 is not particularly limited, but is preferably 0.002 or more. The length L0 of the magnetic particles 4 in the longitudinal direction is preferably 5 to 60 μm.

  The aspect of the segregation 8 of Cr is defined in the same manner as the magnetic particles 4 and is the value obtained by dividing the length in the short direction by the length in the longitudinal direction, and the aspect ratio is 0.3 or less Is preferred. The lower limit of the aspect of the segregation 8 of Cr is not particularly limited, but is preferably 0.002 or more. The length in the longitudinal direction of the Cr segregation 8 is preferably 0.4 to 20 μm, and is 1/200 to 1/2 of the length L0 in the longitudinal direction of the magnetic particles 4.

  It is considered that Cr contained in the magnetic particles 4 is deposited on the surface of the particles 4 and segregated on the surface of the particles 4. For example, heat treatment conditions after flattening the magnetic particles 4 are selected as specific conditions It is obtained by doing. In the present embodiment, it is preferable that, in the surface or the cross section of the magnetic sheet 2, five or more segregated substances of Cr are observed within an arbitrary 10 μm × 10 μm field of view. In the magnetic sheet in which the segregated matter is observed in such a range, the manufacture is easy, the magnetic properties are excellent, and the sheet surface resistance is improved. The upper limit of the number of Cr segregated substances to be observed is not particularly limited, but is preferably 100 or less.

In the magnetic sheet 2 according to the present embodiment, Cr originally contained in the magnetic particles 4 is deposited on the surface of the magnetic particles 4 with a predetermined length or more. Therefore, it is not necessary to prepare and attach an inorganic insulator separately from the magnetic particles, and it is possible to provide the magnetic sheet 2 which is excellent in magnetic characteristics and high in sheet surface resistance while being easy to manufacture. A magnetic sheet 2 having a sheet surface resistance of 1.0E + 06 (1 × 10 ⁶ ) Ω or more can be easily obtained.

  In the present embodiment, the aspect ratio of the magnetic particles 4 is 0.3 or less. By providing magnetic particles 4 having an aspect ratio of a predetermined value or less, it is possible to easily form a sheet even if the thickness of magnetic sheet 2 is reduced, and to provide magnetic sheet 2 having excellent magnetic properties and high sheet surface resistance. it can. The thickness of the magnetic sheet 2 is not particularly limited, but preferably 50 to 100 μm.

  The magnetic sheet 2 of the present embodiment is used, for example, for the use of a magnetic shield, but as other uses, a noise filter, a radio wave absorber, and the like are exemplified.

  The magnetic sheet 2 of the present embodiment is manufactured, for example, as follows. First, the alloy particles having the above-described composition are flattened to obtain flat magnetic particles 4. The production of the alloy particles may be performed by quenching the molten alloy or crushing of the alloy ingot, and the method is not particularly limited. The method for quenching the molten alloy is not particularly limited, but it is preferable to use the water atomization method because alloy particles having a desired particle diameter can be obtained without the grinding step and the productivity is high.

  In the water atomizing method, high-pressure water is injected into a molten alloy to solidify and pulverize it, and then it is cooled in water, the details of which are described in, for example, Japanese Patent Application No. 1-12267.

  Instead of the water atomization method, a method may be used in which a molten metal is made to collide with a cooling substrate to obtain a thin strip, flake, or granular alloy. Such methods include a single roll method, a double roll method, or an atomization method. In these methods, the obtained quenched alloy may be crushed as needed to obtain alloy particles of a desired particle size.

  In the case of producing alloy particles by crushing of an alloy ingot, it is preferable that the ingot be subjected to a solution treatment and then crushed.

  The average particle size of the alloy particles may be suitably determined in accordance with the particle size and aspect ratio of the intended flat soft magnetic particles, but usually, the weight average particle size D50 is 5 to 30 μm, preferably 7 to 20 μm. do it.

  The alloy particles are preferably subjected to a heat treatment for adjusting the crystal structure. The holding temperature and temperature holding time at the time of heat treatment applied to the alloy particles before flattening are preferably 10 minutes to 10 hours at 100 to 600 ° C. More preferable heat treatment conditions are at 300 to 500 ° C. for 30 minutes to 2 hours.

  There are no particular limitations on the means for flattening the alloy particles, and any means may be used as long as the desired flattening is possible.

  However, in the present embodiment, since flattening of the alloy particles proceeds mainly by cleavage, it is preferable to use a means capable of efficiently performing cleavage.

  As such means, a medium stirring mill, a rolling ball mill, etc. may be mentioned, and among these, it is particularly preferable to use a medium stirring mill.

  The medium stirring mill is a stirrer also referred to as a pin type mill, a bead mill or an agitator ball mill, and is described, for example, in JP-A-61-259739, JP-A-1-12267, and the like.

  The flat soft magnetic particles thus obtained are preferably subjected to a heat treatment. It is preferable to make holding temperature in the case of this heat processing into 390 to 550 degreeC for 20 minutes-4 hours. Moreover, the holding | maintenance temperature of more preferable heat processing is 390-500 degreeC. The holding time is not particularly limited, but preferably 30 minutes to 3 hours.

  In the present embodiment, the temperature rise rate and the temperature drop rate are particularly important as well as the above temperature range, and the temperature rise rate from 100 ° C. is preferably 5 to 50 ° C./min, more preferably 10 50 ° C / min. In addition, the temperature lowering rate up to 100 ° C. is preferably 2 to 20 ° C./min, more preferably 5 to 20 ° C./min.

Furthermore, in the present embodiment, once the degree of vacuum is less than 0.1 Pa, an inert gas is introduced to set the oxygen concentration to 1 × 10 ^{−8 to} 0.01 Pa, and heat treatment (temperature rise, retention and temperature decrease It is preferable to do the whole process). Examples of the inert gas include nitrogen, argon, helium and carbon dioxide.

  Under such heat treatment conditions, that is, heat treatment close to quenching by quenching, the segregated state of Cr formed during heat treatment holding time is kept close to that during heat treatment holding even at room temperature, and predetermined on the surface of flat magnetic particles 4. It is believed that several or more Cr can be deposited. The heat treatment may be performed in a magnetic field.

  The magnetic sheet 2 is obtained by dispersing the magnetic particles 4 composed of the soft magnetic powder thus obtained in a binder containing a synthetic resin to form a sheet. The method for forming a sheet is not particularly limited, and an example is a coating method.

  In addition to the magnetic particles 4 and the synthetic resin 6 made of soft magnetic powder, the paste for magnetic sheet before sheeting may contain a curing agent, a dispersing agent, a stabilizer, a coupling agent, etc. . Such a paste is usually formed into a desired shape or applied after being made into a composition for application using a necessary solvent, and then heat-cured as necessary to form a sheet. Curing may be generally carried out by heating in a heating oven at 50 to 80 ° C. for about 6 to 100 hours.

  The present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the present invention.

  Hereinafter, the present invention will be described based on further detailed examples, but the present invention is not limited to these examples.

Example 1
In this example, alloy particles are produced by a water atomizing method, then the alloy particles are flattened by a medium stirring mill, and heat treatment is further performed to obtain soft magnetic powder (magnetic particles) comprising flat soft magnetic particles. The

The composition of the flat soft magnetic particles is an Fe-Si-Cr alloy magnetic material, and when expressed as Fe _a1 Si _b1 Cr _c1 X _d1 , a1 = 70, b1 = 28, c1 = 2, d1 = It was 0.

At the time of heat treatment, after the degree of vacuum is once made less than 0.1 Pa, nitrogen gas as an inert gas is introduced to set the oxygen concentration to 1 × 10 ^{−8 to} 0.01 Pa, and heat treatment (heating and holding And the entire process of temperature decrease.

  The heat treatment conditions were as follows. The temperature rising rate from 100 ° C. is 20 ° C./min, the temperature falling rate to 100 ° C. is 10 ° C./min, the holding temperature is 390 ° C., and the holding time is 60 minutes. there were.

  The heat-treated flat soft magnetic particles were mixed with a binder solution containing polyurethane as a main component to prepare a magnetic paste. The filling rate of the magnetic particles in the paste was 80 wt%.

  The magnetic paste was applied to a long PET substrate having a thickness of 75 μm to a thickness of 25 μm, wound into a roll, and then cured by heating at 60 ° C. for 60 minutes. This was cut into a sheet to obtain a magnetic sheet sample. The coercivity (Hc) when converted to 100% of the material is shown in Table 1 as the magnetic properties of the sample of the magnetic sheet. About 100 mg of flat powder was put into a plastic container and the holding power was measured using Hc meter K-HC1000 manufactured by Tohoku Special Steel Co., Ltd. in a shape in which flat powder was fixed with a lid.

  Furthermore, the surface resistance of the magnetic sheet was measured by a method in which two terminals were brought into contact with the front and back surfaces of a sheet with a thickness of 100 μm or less using HIGH RESISTANCE METER 4339B manufactured by Agilent Technology. The results are shown in Table 1.

  Furthermore, the Q value of the sample of the magnetic sheet was determined by the method described below. That is, it carried out using HP16454A as a fixture, using Agilent E4991A RF impedance / material analyzer by Agilent Technologies. The results are shown in Table 1. In Table 1, the Q value of Example 1 is shown converted to 100, and the other Examples and Comparative Examples are shown at a ratio compared to the Q value of Example 1.

  In addition, when a sample of the magnetic sheet was cut at a cross section perpendicular to the sheet surface and the cut surface was observed by EPMA, flat magnetic particles 4 were dispersed in the synthetic resin 6 as shown in FIG. It was confirmed that there is. In addition, it has been confirmed that the segregated substance 8 of Cr having a length in the longitudinal direction of 0.4 μm or more is contained inside the surface of the magnetic particles 4 and is present.

  In addition, six of five or more segregated substances 8 of Cr are observed in a 10 μm × 10 μm field of view, and the average aspect ratio of all the segregated elements 8 of Cr observed in the field of view is 0.3 or less And was confirmed to be 0.2. In addition, it was confirmed that the average of the aspect ratio of the flat magnetic particles 4 observed in the field of view was 0.3 or less, and was 0.01.

Example 2
A magnetic sheet was produced in the same manner as in Example 1 except that the holding temperature at the heat treatment was changed to 420 ° C., and the same measurement was performed. The results are shown in Table 1.

Example 3
A magnetic sheet was produced in the same manner as in Example 1 except that the holding temperature at the heat treatment was changed to 450 ° C., and the same measurement was performed. The results are shown in Table 1.

Example 4
A magnetic sheet was produced in the same manner as in Example 1 except that the holding temperature at the heat treatment was changed to 500 ° C., and the same measurement was performed. The results are shown in Table 1.

Example 5
A magnetic sheet was produced in the same manner as in Example 1 except that the holding temperature at the heat treatment was changed to 550 ° C., and the same measurement was performed. The results are shown in Table 1.

Comparative Example 1
A magnetic sheet was produced in the same manner as in Example 1 except that the holding temperature at the heat treatment was changed to 370 ° C., and the same measurement was performed. The results are shown in Table 1.

Comparative example 2
A magnetic sheet was produced in the same manner as in Example 1 except that the holding temperature at the heat treatment was set to 450 ° C., and the temperature rising rate and the temperature lowering rate were set to values shown in Table 1, and similar measurements were performed. The results are shown in Table 1.

Comparative example 3
A magnetic sheet was produced in the same manner as in Example 1 except that the holding temperature at the heat treatment was changed to 600 ° C., and the same measurement was performed. The results are shown in Table 1.

According to Evaluation Examples 1 to 5, it is possible to realize a structure in which five or more Cr segregates having a length of 0.4 μm or more in the longitudinal direction are present in a field of 10 μm × 10 μm, As a result, it was confirmed that the magnetic properties were equal to or higher than Comparative Examples 1 to 3 and that the sheet surface resistance was improved. Furthermore, according to Examples 1-5, it has confirmed that Q value was also improved compared with Comparative Examples 1-3.

  As shown in Table 1, from the viewpoint of improving sheet surface resistance, the number of segregated substances of Cr is preferably 6 to 12, and more preferably 8 to 12. Further, from the viewpoint of improving both the coercivity (or Q value) and the sheet resistance, the number of segregated substances of Cr is preferably 6 to 12, and more preferably 8 to 12.

Example 6
Magnetic sheets are prepared in the same manner as in Examples 1 to 6 and Comparative Examples 1 to 3 except that Fe-Si-Al-Cr alloy magnetic bodies are used as the flat soft magnetic particles, and similar measurements are carried out. went. Similar results to those of Examples 1 to 6 and Comparative Examples 1 to 3 were obtained.

Incidentally, the composition of Fe-Si-Al-Cr-based alloy magnetic Fe _a2 Si _b2 Al _e2 Cr _c2 when expressed as _{X d2, a2 = 64, b2} = 16, e2 = 16, c2 = 2, d2 = It was 2. However, X was Co.

Example 7
Magnetic sheets were produced in the same manner as in Examples 1 to 6 and Comparative Examples 1 to 3 except that Fe-Al-Cr alloy magnetic bodies were used as the flat soft magnetic particles, and similar measurements were performed. . Similar results to those of Examples 1 to 6 and Comparative Examples 1 to 3 were obtained.

In the case where the composition of the Fe-Al-Cr-based alloy magnetic represented as _{Fe a3 Al e3 Cr c3 X d3} , were a3 = 64, e3 = 32, c3 = 2, d3 = 2. However, X was Ti.

2 Magnetic sheet 4 Magnetic material particle 6 Synthetic resin 8 Cr segregation product

Claims (3)

A magnetic sheet in which flat magnetic particles are dispersed in a synthetic resin,
The flat magnetic particles are at least one of an Fe-Si-Cr alloy magnetic material, an Fe-Si-Al-Cr alloy magnetic material, and an Fe-Al-Cr alloy magnetic material,
On the surface of the flat magnetic particles, a segregated substance of Cr having a length in the longitudinal direction of 0.4 μm or more is contained in the surface of the magnetic particles,
5. A magnetic sheet characterized in that five or more segregated substances of Cr are observed within an arbitrary 10 μm × 10 μm field of view on the surface or cross section of the magnetic sheet.   The magnetic sheet according to claim 1, wherein an aspect ratio obtained by dividing the length in the short direction of the Cr segregated material by the length in the longitudinal direction is 0.3 or less.   The magnetic sheet according to claim 1 or 2, wherein an aspect ratio obtained by dividing the length in the short direction of the flat magnetic particles by the length in the longitudinal direction is 0.3 or less.

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