JP2011018663A - Flat soft magnetic powder and magnetic body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flat soft magnetic powder capable of exhibiting a high magnetic permeability μ' of an real number part and a low magnetic permeability μ" of an imaginary number part which are the same as those of a ferrite sintered compact when applied to a magnetic body and imparting sufficient bendability; and to provide a magnetic body using the flat soft magnetic powder.SOLUTION: This flat soft magnetic powder includes Fe-Si-Cr-based alloy, has an aspect ratio in a range of 100-150, and a thickness of ≤1 μm. The flat soft magnetic powder is preferably applied at a frequency of 13.56 MHz. Also, in the magnetic body including the flat soft magnetic powder, preferably, the magnetic permeability μ' of an actual number part is ≥80 at a frequency of 13.56 MHz and the magnetic permeability μ" of an imaginary number part is ≤10.

Description

  The present invention relates to a flat soft magnetic powder, a method for producing the same, and a magnetic material.

  In recent years, an automatic recognition system (RFID: Radio Frequency Identification) that performs electronic information communication in a non-contact manner has been rapidly spread. Various RFID communications have been put into practical use, and among them, a clearing system using a frequency of 13.56 MHz, a prepaid system, and the like are widely used.

  In an RFID using a frequency of 13.56 MHz, in order to increase the communication distance between a data carrier such as a non-contact IC card and a reader / writer for reading and writing data, for example, a magnetic permeability is provided on the back surface of an antenna provided in the reader / writer. A sheet-like magnetic body having a high height is disposed.

  This type of magnetic body desirably has a high real part permeability μ ′ and a low imaginary part permeability μ ″, and conventionally a thin plate-like ferrite sintered body has been applied.

  Also, as shown in Patent Document 1, in order to improve flexibility, a magnetic sheet formed by combining a flat soft magnetic powder and a polymer, an elastomer, or the like into a sheet shape has been applied. Patent Document 1 discloses a flat soft magnetic powder made of an Fe—Si—Al alloy and having an aspect ratio in the range of 10 to 80 as the flat soft magnetic powder in the magnetic sheet.

  Patent Document 2 discloses a flat soft magnetic powder having an alloy component of Fe group and containing at least Si and Cr as additive elements and an aspect ratio of 15 or more, and a magnetic sheet containing the soft magnetic powder. Has been.

JP 2006-39947 A JP 2007-27687 A

  However, the prior art has room for improvement in the following points. That is, the ferrite sintered body has high magnetic permeability (real part permeability μ ′ is 80 or more) and low magnetic loss (imaginary part permeability μ ″ is 10 or less), and is excellent in magnetic characteristics.

  However, the ferrite sintered body is difficult to process into a thin plate and has poor bendability. For this reason, there is a drawback in that it is easily broken when assembled to the apparatus or dropped, resulting in poor handling. Furthermore, it is necessary to affix a PET film or the like to prevent cracking, and the volume of the magnetic material is reduced by the volume increase. Therefore, there is a limit to increasing the communication distance. Recently, attempts have been made to secure bendability by arranging chip-shaped ferrite sintered bodies, but sufficient bendability is achieved compared to magnetic sheets containing flat soft magnetic powder. It is hard to say that it has.

  On the other hand, the above-described conventional magnetic sheet is excellent in handleability and the like because it is rich in flexibility, does not worry about breakage, and does not require a PET film. However, the real part permeability μ ′ is low (Patent Document 1: μ ′ <74, Patent Document 2: μ ′ <68), and the effect of improving the communication distance is not sufficient.

  The present invention has been made in view of the above circumstances, and the problem to be solved by the present invention is that when applied to a magnetic body, the high real part permeability μ ′ equivalent to that of a ferrite sintered body, the low imaginary part It is to provide a flat soft magnetic powder that can exhibit a magnetic permeability μ ″ and can impart sufficient bendability. Also, to provide a magnetic body using this flat soft magnetic powder. .

  In order to solve the above problems, the flat soft magnetic powder according to the present invention is made of an Fe—Si—Cr alloy, has an aspect ratio in the range of 100 to 150, and has a thickness of 1 μm or less. To do.

  Here, the flat soft magnetic powder is preferably used at a frequency of 13.56 MHz.

  The gist of the magnetic body according to the present invention includes the flat soft magnetic powder.

  Here, the magnetic body preferably has a real part permeability μ ′ of 80 or more and an imaginary part permeability μ ″ of 10 or less at a frequency of 13.56 MHz.

  Moreover, it is preferable that the said magnetic body is for RFID.

  The method for producing a flat soft magnetic powder according to the present invention includes a preparation step of preparing an unflat soft magnetic powder and a flattening treatment step of flattening the prepared non-flat soft magnetic powder using a medium. Then, the gist of the flattening process is to include a procedure in which the flattening process is performed with a relatively large medium, then the medium is changed to a relatively small medium, and the flattening process is further performed.

  The flat soft magnetic powder according to the present invention is made of an Fe—Si—Cr alloy, has an aspect ratio in the range of 100 to 150, and has a thickness of 1 μm or less. Therefore, when applied to a magnetic material such as a magnetic sheet, a high real part permeability μ ′ and a low imaginary part permeability μ ″ equivalent to those of a ferrite sintered body can be expressed. This is due to the following reason. It is guessed.

  That is, by making the alloy component of the powder an Fe—Si—Cr alloy, it is easy to prevent a decrease in the real part permeability μ ′ and an increase in the imaginary part permeability μ ″ due to domain wall resonance and natural resonance. The real part permeability μ ′ can be greatly improved by setting the aspect ratio of the powder within the range of 100 to 150. Furthermore, by setting the thickness of the powder to 1 μm or less, the vortex near the frequency of 13.56 MHz. As a result, the flat soft magnetic powder according to the present invention, when applied to a magnetic material such as a magnetic sheet, has a high real part permeability μ ′, which is the same as that of a ferrite sintered body, and is low. It is considered that the imaginary part permeability μ ″ can be expressed.

  In addition, the flat soft magnetic powder according to the present invention is flat and has excellent toughness as compared with a ferrite sintered body. Therefore, the flat soft magnetic powder has resistance to bending, and the matrix material itself for bonding the powder is also bent such as rubber. Therefore, it is possible to select a material that is strong against bending, so that sufficient bendability can be imparted to the magnetic material.

  In this case, when used at a frequency of 13.56 MHz, for example, the communication distance in RFID can be increased, which is useful.

  The magnetic body according to the present invention includes the flat soft magnetic powder. Therefore, a high real part permeability μ ′ and a low imaginary part permeability μ ″ equivalent to the ferrite sintered body can be exhibited, and sufficient bendability can be imparted.

  Here, when the real part permeability μ ′ at a frequency of 13.56 MHz is 80 or more and the imaginary part permeability μ ″ is 10 or less, the present invention can be suitably applied to an RFID or the like.

  In the method for producing a flat soft magnetic powder according to the present invention, after the flattening process proceeds with the flattening process using a relatively large medium, the medium is changed to a relatively small medium, and the flattening process is further performed. Includes procedures.

  In general, in the flattening treatment with media, if the media is large (for example, the diameter of the ball as the media is large), the impact force applied to the powder is large, so that flattening is promoted. Are more likely to occur simultaneously. On the other hand, when the medium is small (for example, the diameter of the ball as the medium is small), the impact force applied to the powder is small, so that high flattening is difficult.

  However, according to the manufacturing method of the flat soft magnetic powder according to the present invention, after the grinding process was preferentially performed by a relatively large medium, the cracking of the powder was suppressed by the relatively small medium. Thinning processing (thickness reduction processing) is preferentially performed in the state. Therefore, it is possible to relatively easily obtain a flat soft magnetic powder having an aspect ratio and thickness in the above-described ranges.

FIG. 3 is a diagram illustrating a frequency-permeability relationship of a magnetic sheet according to Example 1. It is a figure for demonstrating the measuring method of communication distance. It is the figure which showed the relationship between the aspect-ratio of flat soft magnetic powder (Fe-8% Si-2% Cr alloy, thickness = 1 micrometer), and the real part magnetic permeability micro '(frequency 13.56MHz) of a magnetic sheet. It is the figure which showed the relationship between the thickness of flat soft magnetic powder (Fe-8% Si-2% Cr alloy, aspect-ratio = 100), and the imaginary part permeability (mu) "(frequency 13.56MHz) of a magnetic sheet.

  Hereinafter, a flat soft magnetic powder according to an embodiment of the present invention (hereinafter sometimes referred to as “the present powder”), a manufacturing method thereof (hereinafter also referred to as “the present manufacturing method”), and an implementation of the present invention. The magnetic body according to the embodiment (hereinafter sometimes referred to as “the present magnetic body”) will be described in detail.

1. This powder is a powder formed in a flat shape, and has the following alloy composition, aspect ratio, and thickness.

  This powder is composed of an Fe—Si—Cr alloy. Here, the Fe—Si—Cr-based alloy refers to an Fe-based alloy mainly containing Si and Cr. By making the alloy component of the present powder an Fe—Si—Cr alloy, it is easy to prevent a decrease in the real part permeability μ ′ and an increase in the imaginary part permeability μ ″ due to domain wall resonance and natural resonance.

  As a specific Fe—Si—Cr-based alloy, an Fe-based alloy containing Si: 1% to 15% and Cr: 1% to 5% by mass% is preferable. In this case, the lower limit of the Si content is preferably 3% or more, more preferably 5% or more, and even more preferably 7% or more, from the viewpoints of improving magnetic permeability and ensuring corrosion resistance. On the other hand, the upper limit of the Si content is preferably 10% or less, more preferably 8% or less, from the viewpoints of preventing increase in magnetostriction, flattenability, and prevention of deterioration.

  Further, the lower limit of the Cr content is preferably 2% or more from the viewpoint of ensuring corrosion resistance and the like. On the other hand, the upper limit of the Cr content is preferably 3% or less from the viewpoint of preventing a decrease in magnetic properties. The Fe—Si—Cr-based alloy may contain additive elements such as Al in addition to Si and Cr, but preferably, the domain wall resonance and the natural resonance frequency are increased at 13.56 MHz. From the standpoints of high μ ′, low μ ″, etc., it is preferable that Si and Cr are contained at the above-mentioned contents, and the balance is made of Fe and inevitable impurities.

  In addition, this powder may be comprised from 1 type of Fe-Si-Cr type | system | group alloy, and may be comprised from 2 or more types of Fe-Si-Cr type | system | group alloys.

  This powder has an aspect ratio in the range of 100 to 150. By setting the aspect ratio within the range of 100 to 150, the real part permeability μ ′ can be greatly improved. The upper limit of the aspect ratio is preferably 140 or less, and more preferably 130 or less, from the viewpoint of easily suppressing the bending of the powder in the manufacturing process. On the other hand, the lower limit of the aspect ratio is preferably 110 or more from the viewpoint of increasing the shape anisotropy of the powder and easily suppressing the influence of the demagnetizing field.

  This powder has a thickness of 1 μm or less. By setting the thickness to 1 μm or less, eddy currents near the frequency of 13.56 MHz can be easily suppressed. The upper limit of the thickness is preferably 0.9 μm or less, and more preferably 0.8 μm or less, from the viewpoint of easily suppressing the influence of eddy current. In addition, the minimum of the said thickness is not specifically limited.

  The aspect ratio of the present powder and the thickness of the present powder can be measured as follows.

That is, first, for the powder to measure the average particle diameter _{D 50.} Incidentally, the average particle diameter D ₅₀ is that the particle size at which a 50 percent cumulative volume distribution measured by laser diffraction scattering method particle size distribution measuring apparatus. Next, the powder is embedded in a resin and polished, and the thickness direction of the powder is observed with an optical microscope to determine the maximum thickness t _max and the minimum thickness t _min, and the average value (t _max + t _min ) / 2 is averaged. and the thickness _{t a.} the value of t _a calculated for 100 arbitrary particles to determine the average value thereof. This average thickness t _ave is the thickness of the powder in the present invention. Then, the aspect ratio of the present powder can be calculated by dividing the average particle diameter D ₅₀ by the average thickness t _ave (that is, average particle diameter D ₅₀ / t _ave ).

  The present powder can be suitably used at a frequency of 13.56 MHz. In this case, specifically, there is an advantage that, for example, the communication distance can be increased when applied to RFID.

1. This manufacturing method This manufacturing method is a method which can manufacture suitably this powder mentioned above. This manufacturing method basically includes a powder preparation process and a flattening process. Hereinafter, it demonstrates in order of each process.

(1) Powder preparation step The powder preparation step is a step of preparing an unflattened soft magnetic powder that has not yet been flattened. The material which comprises the said soft-magnetic powder is various Fe-Si-Cr type alloys mentioned above. The soft magnetic powder prepared in the powder preparation step may be composed of one type of Fe—Si—Cr based alloy, or may be composed of two or more types of Fe—Si—Cr based alloy.

  In the present powder preparation step, the soft magnetic powder may be milled by itself or supplied from other sources. The powder milling method is not particularly limited, but preferably, the molten metal spraying method can be exemplified as a suitable method from the viewpoint of homogenization of the alloy composition and the like. In the molten metal spraying method, from the viewpoint of reducing the oxygen content and keeping the coercive force low, it is better to spray using a gas that does not contain oxygen, such as nitrogen and argon, and also shut off the air after milling. It is desirable to keep it.

In addition, the upper limit of the average particle diameter D ₅₀ (according to the measurement method) of the unflattened soft magnetic powder as a raw material is preferably 40 μm or less, more preferably from the viewpoint of preventing the powder from being flattened. In the range of 30 μm or less. On the other hand, the lower limit of the average particle diameter D ₅₀ (according to the measurement method) of the non-flat soft magnetic powder used as a raw material is preferably 1 μm or more, more preferably 10 μm or more, from the viewpoints of ease of handling, mass productivity, and the like. Good to be.

(2) Flattening treatment step The flattening treatment step is a step of flattening the unflattened soft magnetic powder prepared in the powder preparation step using a medium.

  Here, the flattening process in the present manufacturing method is changed to a relatively small medium after the flattening process is advanced with a relatively large medium (hereinafter, referred to as “first half process”), and It includes a procedure for performing a flattening process (hereinafter also referred to as “second half process”). Thus, after the grinding process is preferentially performed with a relatively large medium, the thinning process (thickness reduction process) is preferentially performed in a state where cracking of the powder is suppressed with a relatively small medium. As a result, it is possible to relatively easily obtain the present powder having the aspect ratio and thickness within the above-described ranges.

  Examples of the flattening means include an attritor and a ball mill. In the case of an attritor or a ball mill, specifically, a stainless steel ball such as SUJ2 can be suitably used as the medium.

  The media form is preferably a ball from the viewpoint of processability and the like. In this case, the media diameter at the time of the first half treatment is preferably within a range of 3.5 to 6 mm, more preferably within a range of 4 to 5 mm, from the viewpoint of preferentially causing the grinding treatment. Good to have. On the other hand, the media diameter at the time of the second half treatment is preferably from the viewpoint of easy thinning treatment (thickness reduction treatment) preferentially in a state where cracking of the powder is suppressed, from the viewpoint of good thickness reduction efficiency, etc. It is good to be in the range of 3 mm, more preferably in the range of 2 to 3 mm.

  For the time of the first half treatment and the second half treatment, an optimum range can be selected in consideration of the type of flattening means, the alloy composition, and the like.

  When an attritor is used as the flattening means, the first half processing time is preferably 5 to 30 hours, more preferably 10 from the viewpoint that the flattening can be performed efficiently within a range where the powder does not cause crushing. ~ 20 hours, more preferably 13-17 hours. On the other hand, the second half treatment time is preferably 1 to 10 hours, more preferably 1 to 5 hours, and still more preferably 2 from the viewpoint of reducing only the thickness and easily suppressing the influence on the powder diameter. It should be ~ 3 hours.

  The present powder can be produced basically through the above steps, but a heat treatment step for heat treating the powder after the flattening treatment can be arbitrarily added. When the heat treatment step is added, it is possible to mainly remove the processing strain generated in the powder by the flattening treatment and improve the magnetic permeability characteristics.

  Specifically, the lower limit of the heat treatment temperature in the heat treatment step is preferably 200 ° C. or more, more preferably 300 ° C., from the viewpoint of easily removing the strain introduced in the flattening treatment step and improving the magnetic permeability. As described above, more preferably, it is 350 ° C. or higher. On the other hand, the upper limit of the heat treatment temperature in the heat treatment step is preferably 850 ° C. or less, more preferably 800 ° C. or less, and further preferably 600 ° C. or less, from the viewpoint of suppressing fusion between powders. . Therefore, from the viewpoint of improving the overall magnetic characteristics (real part permeability μ ′, imaginary part permeability μ ″), 380 to 430 ° C. is most preferable.

  The lower limit of the heat treatment time in the heat treatment step is preferably 30 minutes or longer, more preferably 1 hour or longer, and further preferably 2 hours or longer from the viewpoint of uniform thermal diffusion to the powder. On the other hand, the upper limit of the heat treatment time in the heat treatment step is preferably 5 hours or less, more preferably 3 hours or less, from the viewpoint of improving productivity.

  The heat treatment in the heat treatment step is preferably performed in an inert atmosphere such as argon or nitrogen from the viewpoints of preventing powder oxidation and preventing fusion.

  In addition, as a heat processing method in a heat processing process, a vacuum baking furnace, a rotary kiln, etc. can be illustrated.

2. This magnetic body This magnetic body contains this powder. Specifically, the present magnetic body has a structure in which the present powder is dispersed in a matrix material such as rubber, elastomer or resin.

  Examples of the matrix material include chlorinated polyethylene, acrylic rubber, and ethylene acrylic rubber as suitable materials. The matrix material can be used alone or in combination of two or more materials.

  The content of the present powder contained in the present magnetic body can be selected in consideration of the required magnetic permeability characteristics, the thickness of the present magnetic body, and the like. From the viewpoint of permeability characteristics, balance of thickness and the like, it is preferably 20 to 60% by volume, more preferably 40 to 55% by volume.

  The magnetic material may have an applicable frequency range of 13.56 MHz. This is because the usefulness of the present invention is enhanced, such as being able to be suitably used for RFID and increasing the communication distance.

  The real part permeability μ ′ of the present magnetic body is preferably 80 or more, and more preferably 100 or more. Further, the imaginary part permeability μ ″ of the present magnetic body is preferably 10 or less, more preferably 6 or less, and still more preferably 4 or less, because it can be suitably used for RFID.

  The shape of the magnetic body can be appropriately selected according to the application. From the viewpoint of widening the range of application to various uses, a planar shape such as a sheet shape is preferable.

Hereinafter, the present invention will be described more specifically with reference to examples.
1. Production of flat soft magnetic powder and magnetic material according to Examples and Comparative Examples (Example 1 and Example 2)
As shown in Table 1, a molten alloy (Example 1) having a chemical composition (mass%) of Fe-8% Si-2% Cr, and a chemical composition (mass%) of Fe-10% Si-2% Cr. The molten alloy (Example 2) was sprayed in an argon gas atmosphere, and each soft magnetic powder as a raw material was milled.

Next, each obtained soft magnetic powder was flattened using an attritor. At this time, for the first 15 hours, the flattening treatment was performed with the following formulation 1. During the subsequent 2 hours, a flattening treatment was performed with the following formulation 2.
<Formulation 1>
Milled soft magnetic powder: 1.0 kg
Medium: 2.0 L (naphthethol)
Media: Ball (SUJ2, diameter 4.8mm), usage 18kg
Lubricant: 10 g (zinc stearate)
<Formulation 2>
Soft magnetic powder obtained by the flattening treatment of Formulation 1: 1.0 kg
Medium: 2.0 L (naphthethol)
Media: Ball (SUJ2, 2.4mm diameter), 18kg usage
Lubricant: 10 g (zinc stearate)

  Subsequently, the soft magnetic powder subjected to the flattening treatment was subjected to a heat treatment temperature of 2 hours at 400 ° C. in an argon gas atmosphere. Thus, flat soft magnetic powders according to Example 1 and Example 2 were obtained.

  Next, the magnetic sheet which concerns on Example 1 and Example 2 was produced using the obtained flat soft magnetic powder which concerns on Example 1 and Example 2. FIG. That is, 15 parts by weight of chlorinated polyethylene was dissolved in 300 parts by weight of toluene to prepare a rubber solution, and 85 parts by weight of each flat soft magnetic powder was added to the solution and mixed to obtain a dispersion.

  Subsequently, the obtained dispersion liquid was apply | coated by the doctor blade method on the polyester resin film (base material). In coating, the blade gap was adjusted so that the thickness of the sheet obtained after drying was 0.1 mm.

  Next, the applied solution was naturally dried and then pressed under conditions of a temperature of 130 ° C., a pressure of 15 MPa, and a time of 3 minutes. Thereby, the magnetic sheet which concerns on Example 1 and Example 2 was produced.

(Comparative Example 1)
A magnetic sheet according to Comparative Example 1 was prepared by burying commercially available chip-like ferrite sintered bodies side by side.

(Comparative Example 2)
In the production of the flat soft magnetic powder according to the example described above, the soft magnetic powder as a raw material was milled using a molten alloy having a chemical composition (mass%) of Fe-8% Si-2% Cr, and this A flat soft magnetic powder according to Comparative Example 2 was obtained in the same manner except that the raw material powder was subjected to a flattening treatment in which only the flattening treatment of Formulation 1 was performed for 15 hours.

  In addition, in the production of the magnetic sheet according to the above-described example, the flat soft magnetic powder according to Comparative Example 2 was used in place of the flat soft magnetic powder according to Example. A magnetic sheet was prepared.

2. Evaluation (average particle diameter D ₅₀ , average thickness t _ave , aspect ratio)
Each flat soft magnetic powder prepared by the above measurement method, the average particle diameter D _50, the average thickness t _ave, was determined aspect ratio.

(Bending test)
Each produced magnetic sheet was subjected to a 90 ° bending test. “○” indicates that the material that can be bent at 90 ° has sufficient bendability, but it cannot be bent at 90 °, but it cannot be bent at all. “△”, and those that could not be bent at all were evaluated as “x” as being inferior in bendability.

(Cracking test)
Each produced magnetic sheet was wound around a cylindrical body having a diameter of 10 mm, and the presence or absence of cracks was confirmed. The case where no crack occurred was evaluated as “◯”, and the case where a crack occurred was evaluated as “×”.

(Permeability characteristics)
For each magnetic sheet, the real part permeability μ ′ and the imaginary part permeability μ ″ were measured as follows.

  That is, each sample was produced by punching the produced magnetic sheets (Example 1, Example 2, Comparative Example 2) into a ring shape having an outer diameter of 7 mm and an inner diameter of 3 mm, and the magnetic sheet of Comparative Example 1 was cut. A sample was made. For each of these samples, the impedance characteristic of each sample was measured over a range of 1 MHz to 100 MHz using an impedance analyzer HP4294A (manufactured by Agilent Technologies), and the real part permeability μ ′ and the imaginary part permeability at a frequency of 13.56 MHz. μ ″ was calculated. The relationship between the frequency and the magnetic permeability of the magnetic sheet according to Example 1 is shown in FIG. 1. As shown in FIG. 1, according to the magnetic sheet according to Example 1, the frequency range is 1 MHz to 20 MHz. It can be seen that the magnetic permeability is good.

(Measurement of limit communication distance)
FIG. 2 is a diagram for explaining a method for measuring a communication distance. As shown in FIG. 2, each magnetic sheet 3 is affixed to the antenna 2 of the actual mobile phone 1 and the reader 4 close to the actual mobile phone 1 is separated so that the bit error first occurs and the actual mobile phone. The distance to 1 was determined as the limit communication distance. Table 1 summarizes the test results.

3. Aspect ratio-permeability characteristics The flat soft magnetic powder has a chemical composition (mass%) of Fe-8% Si-2% Cr, a thickness of 1 μm, and a real part permeability of the magnetic sheet when the aspect ratio is changed. The change of magnetic susceptibility μ ′ (frequency 13.56 MHz) was determined. The result is shown in FIG.

4). Thickness-permeability characteristics The imaginary number of the magnetic sheet when the chemical composition (mass%) of the flat soft magnetic powder is fixed to Fe-8% Si-2% Cr, the aspect ratio is 100, and the thickness of the powder is changed. The change in the partial permeability μ ″ (frequency 13.56 MHz) was determined. The result is shown in FIG.

5. Discussion From the above results, the following can be understood. That is, according to FIG. 3, when the alloy constituting the flat soft magnetic powder is an Fe—Si—Cr alloy, when the aspect ratio is less than 100 and the aspect ratio exceeds 150, the real part permeability μ ′ is It turns out that there exists a tendency to become small with less than 100. This is presumably because when the aspect ratio is less than 100, the shape anisotropy decreases and the demagnetizing field increases. On the other hand, when the aspect ratio exceeds 150, it is presumed that the flat soft magnetic powder is bent by stress during kneading with the matrix polymer during sheet production. From this result, it can be seen that the aspect ratio is preferably in the range of 100 to 150.

  Next, according to FIG. 4, it can be seen that when the thickness of the flat soft magnetic powder exceeds 1 μm, the imaginary part permeability μ ”tends to increase rapidly. The thickness of the flat soft magnetic powder is 1 μm. If the thickness is too high, the influence of eddy current is presumed to be large, which shows that the thickness of the flat soft magnetic powder is preferably 1 μm or less.

  And according to Table 1 and FIG. 1, although the magnetic sheet which concerns on the comparative example 1 has favorable magnetic permeability property, since chip-shaped ferrite sintered compact is arranged and embedded in the base material, chip-shaped ferrite sintering It turns out that it is a grade to bend a little along the arrangement | sequence of a body, and it turns out that it is easy to produce a crack.

  Further, Comparative Example 2 has a structure in which the flat soft magnetic powder is dispersed in the matrix polymer, so that it has excellent bendability and does not generate cracks, but does not satisfy the conditions defined in this application. It can be seen that the real part permeability μ ′ is low and the limit communication distance is short.

  In contrast, the magnetic sheets according to Examples 1 and 2 use the flat soft magnetic powder according to Examples 1 and 2. Therefore, it was confirmed that it was possible to express a high real part permeability μ ′ and a low imaginary part permeability μ ″, which were rich in flexibility and without fear of breakage.

  Heretofore, the embodiments and examples of the present invention have been described. The present invention is not particularly limited to these embodiments and examples, and various modifications can be made.

Claims (6)

  A flat soft magnetic powder comprising an Fe—Si—Cr alloy, having an aspect ratio in the range of 100 to 150, and a thickness of 1 μm or less.   The flat soft magnetic powder according to claim 1, which is used at a frequency of 13.56 MHz.   A magnetic material comprising the flat soft magnetic powder according to claim 1.   4. The magnetic body according to claim 3, wherein a real part permeability μ ′ at a frequency of 13.56 MHz is 80 or more and an imaginary part permeability μ ″ is 10 or less.   The magnetic body according to claim 3 or 4, wherein the magnetic body is for RFID. A preparation step of preparing an unflattened soft magnetic powder;
A flattening treatment step of flattening the prepared non-flat soft magnetic powder using a medium,
The flattening process step includes
A method for producing a flat soft magnetic powder, comprising the steps of performing a flattening process with a relatively large medium, then changing to a relatively small medium, and further performing the flattening process.

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