JP6500670B2 - Flat soft magnetic metal powder for magnetic sheet, magnetic sheet, and antenna coil - Google Patents

Description

The present invention relates to a flat soft magnetic metal powder used as a magnetic sheet with high magnetic permeability and low loss, which is suitable as a magnetic sheet for noncontact communication terminals.

A non-contact communication terminal, in particular, a magnetic sheet obtained by processing a soft magnetic material into a sheet shape is used for the purpose of improving the communication performance between terminals and cards using a non-contact communication terminal and the like.
Materials for the magnetic sheet include a sheet using a ferrite sheet, a polymer sheet using a flat soft magnetic metal powder, etc. These materials according to the prior art sufficiently satisfy the performance and cost required for the member. It was not a thing.

Patent Document 1 discloses a ferrite sheet and a polymer sheet using metal powder as a means for improving the communication distance. However, since the ferrite sheet is excellent in magnetic properties but lacks flexibility, it is preferable to use a member such as a protective film. There is a disadvantage that it is necessary to use in combination and it is difficult to save members and reduce costs. Further, although the polymer sheet using the metal powder is expected to simplify the structure of the entire member and reduce the cost because the flexibility of the member is excellent, the magnetic properties are not sufficient.

JP 2005-340759 A

To improve communication performance, the real part μ 'of μ' × Q (complex permeability (μ = μ'-i · μ '', i is an imaginary unit)
It is important that the characteristics such as the reciprocal of the loss coefficient (tan δ = μ ′ ′ / μ ′) represented by the imaginary part μ ′ ′ be Q (μ ′ / μ ′ ′) be excellent and the magnetic material It is required that the real part (μ ′) of the complex permeability is large and the imaginary part (μ ′ ′) is small.

In order to solve the problems described above and to achieve the object, the present invention obtains a magnetic sheet having a magnetic material with improved magnetic properties by forming a metal powder having a specific metal material composition into a flattened shape and mixing it with a predetermined resin or the like. Thus, the communication performance is improved.
As an alloy component, the object of the present invention can be achieved by containing at least 14 to 22% of Si, 0.1 to 5% of Cr, 0.1 to 2% of Mn, and Fe at atm%.
Further, by making the metal powder into a flattened shape, the demagnetizing field becomes smaller and the μ ′ characteristic is improved.

The flat soft magnetic metal powder (hereinafter sometimes referred to as “flat powder”) is more highly transparent when the flat powder has a weight average particle diameter D ₅₀ of 10 to 100 μm and an average thickness of 0.5 to ₅ μm. A magnetic susceptibility sheet is easily obtained, and the density of the sheet is also improved. If D ₅₀ is less than 10 [mu] m, hard coercive force Hc small flat powder is obtained, the number of gaps flat powders each other even when the sheets of the high-permeability magnetic sheet to become more difficult to obtain. On the other hand, if D ₅₀ exceeds 100 [mu] m, the density of the sheet calculated from the sheet surface becomes rough thickness tends to decrease.
Further, if the average thickness of the flat powder is less than 0.5 μm, flattening and sheeting become difficult in manufacture, and if it exceeds 5 μm, the demagnetizing field becomes large and the μ ′ characteristics deteriorate.

The present invention exhibits an effect that magnetic characteristics can be improved and communication performance can be improved by forming flat soft magnetic metal powder for a magnetic sheet into a specific metal material composition and particle shape.

<Flat-shaped soft magnetic metal powder>
The flat soft magnetic metal powder of the present embodiment contains at least 14% to 22% of Si, 0.1% to 5% of Cr, 0.1% to 2% of Mn, and at least Fe in the FeSiCrMn-based alloy. A magnetic sheet of high permeability (μ ') and low loss (μ') is obtained. When Mn is added as an alloy component in the above range, the coercivity Hc is lowered by selection of the heat treatment temperature, and it is considered that good characteristics can be obtained.
The weight average particle diameter _{D 50} of the flat powder is 10μm or 100μm or less, the magnetic sheet of the average thickness is 0.5~5μm high permeability can be obtained. An example of the production method is described below.

The soft magnetic alloy powder is conveniently prepared by an atomizing method such as a water atomizing method, a gas atomizing method or a gas spray water atomizing method. In the present invention, although the soft magnetic alloy powder manufactured by the water atomization method which can obtain an alloy powder at low cost is used, the present invention is not limited to this.

After drying the alloy powder, flattening treatment is performed.
There is no restriction | limiting in particular in the flattening method, For example, it can carry out using an attritor, a ball mill, a vibration mill etc. Among them, it is preferable to use an attritor that can be processed in a short time as compared with a ball mill or a vibration mill. The flattening treatment is preferably performed wet using an organic solvent.
Even when a brittle soft magnetic alloy powder is used by adding an organic solvent, a flat powder having a large particle diameter and sufficiently flattened can be produced at a high yield.
As said organic solvent, toluene, hexane, acetone, methanol and C2-C4 monohydric alcohol can be used, for example.
It is preferable that it is 200-2000 mass parts with respect to 100 mass parts of alloy powder, and, as for the addition amount of an organic solvent, it is more preferable that it is 500-1000 mass parts. If the addition amount of the organic solvent is less than 200 parts by mass, the particle size of the flat powder tends to be small, and if it exceeds 2000 parts by mass, the treatment time becomes long and the productivity is lowered.

In order to increase the particle size of the flat powder, a flattening aid may be used together with the organic solvent. As the flattening aid, for example, a fatty acid such as stearic acid can be suitably used. The addition amount of the flattening aid is preferably 0.1 to 5 parts by mass, and more preferably 0.5 to 2 parts by mass with respect to 100 parts by mass of the heat treatment powder. Even if the addition amount of the flattening aid exceeds 5 parts by mass, the particle size of the flat powder does not increase further, the recovery utilization of the organic solvent becomes difficult, and the contamination of the heat treatment furnace becomes intense. Moreover, when a C2-C4 monohydric alcohol is used as an organic solvent, the flat powder with a large particle size is obtained, without adding a flattening aid.

The flattening time is a time to reach a predetermined average particle size and average thickness. Although depending on the apparatus and conditions of flattening, about 1 to 5 hours have a predetermined particle diameter and thickness as residence time (the actual time in which the slurry obtained by adding the organic solvent to the alloy powder passes through the inside of the processing apparatus) Suitable for obtaining As the particle size of the flat powder increases, the average thickness decreases, and the aspect ratio defined by the average particle size D ₅₀ / average thickness increases. Since the bulk density BD decreases as the aspect ratio increases, the bulk density BD of flat powder can be used as a substitute characteristic of the aspect ratio. In the present invention, the permeability characteristics are improved when the aspect ratio is 20 or more and 50 or less, but the bulk density at that time is 0.15 to 0.50 Mg / m ³ in the FeSiCrMn-based alloy described in this example. BD can be measured using a bulk density meter in accordance with JIS K-5101.

The weight average particle size D ₅₀ and the average thickness of the flat powder are values measured by the following method.
D ₅₀ is measured by a laser diffraction type particle size distribution measuring apparatus utilizing a diffraction theory of Fraunhofer, the particle size at which a 50 percent cumulative volume distribution. In this example, the measured value was obtained using “HELOS SYSTEM” manufactured by Nippon Laser Co., Ltd. having a dry dispersion unit.
The average thickness was obtained by burying the flat powder with a resin and then curing it on a magnet having a magnetic flux in the direction perpendicular to the polishing surface, and after mirror-finishing, the cross section was observed by SEM.
The aspect ratio was made the value of " _D50 / thickness" using the said average particle diameter and average thickness.

It is preferable to heat-treat the obtained flat soft magnetic metal powder in an inert atmosphere after the flattening process. As a result, the coercive force Hc is reduced, and a high magnetic permeability magnetic sheet can be easily obtained. The heat treatment temperature and holding time are selected according to the composition and loading amount of the flat soft magnetic metal powder. The coercive force Hc can be measured using a commercially available Hc meter (in this example, manufactured by Tohoku Steel Co., Ltd., trade name "K-HC1000").

<Magnetic sheet>
A magnetic sheet can be produced using the flat soft magnetic metal powder. An example of the method for producing the magnetic sheet of the present invention is as follows.
A magnetic paint containing a mixed solvent of a flat soft magnetic metal powder, a polyurethane resin as a binder, a solvent selected from toluene, xylene, butyl acetate etc. as a dilution solvent, and a solvent such as methyl ethyl ketone is kneaded. The kneading method is not particularly limited, but in this example, a planetary mixer was used. Immediately before the end of kneading, an isocyanate compound is added as a curing agent, and finally, vacuum degassing is performed to remove air bubbles contained in the paint.

The compounding ratio of the binder is preferably set in the range of 8 to 22 parts by weight, and more preferably in the range of 8 to 18 parts by weight with respect to 100 parts by weight of the flat soft magnetic metal powder. Ru.
The addition amount of the curing agent is set in the range of 5 parts by weight to 30 parts by weight with respect to 100 parts by weight of the binder, and more preferably in the range of 10 parts by weight to 20 parts by weight.
The amount of volatile solvent added is adjusted so that the paint viscosity is in a certain range. The range of the coating viscosity is preferably 400 to 1,500 mPa · s. If the coating viscosity is less than 400 mPa · s, the trace of magnetic field orientation performed immediately after coating tends to remain, and if the coating viscosity is high, unevenness tends to remain on the sheet surface after drying, and the appearance is deteriorated.

The above-mentioned magnetic paint is applied on a base film to a predetermined thickness by a doctor blade method, and after magnetic orientation, it is dried. Although the base film is not particularly limited, a 75 μm thick polyethylene terephthalate (PET) film was used in this example.
Although the sheet after magnetic orientation is dried, the drying method may be natural drying or forced drying by heating.

The dried magnetic sheet is evaluated by density and magnetic properties. The density was determined from a thickness of a magnetic sheet punched into a toroidal shape six pieces at a time using a mold having an outer diameter of 18 mm and an inner diameter of 10 mm, and its weight and a spindle diameter of 6 mm. The magnetic characteristics were measured by one turn method using an impedance analyzer (trade name “E4991A” manufactured by Agilent Technologies, Inc.) and an attached test fixture (16454A) by stacking six sheets of the above-described toroidal sample.

In order to improve the communication performance of the magnetic sheet used as the magnetic core member of the noncontact communication terminal, it is important that the performance index represented by μ ′ × Q is excellent, and according to the present invention, this index is 2000 or more. Thus, good communication performance can be obtained.
The preferred embodiment of the present invention has been described above, but the present invention is not limited to this.

Hereinafter, the present invention will be specifically described based on examples.
(Examples 1 to 7)
After drying the alloy powder prepared to have the alloy composition of Table 1 by the water atomization method, add 7.3 times by mass isopropyl alcohol, and using the attritor, the bulk density BD is about 0.30 Mg / m ^It was flattened until it reached ³ . The resulting average particle size _{D 50} of the flat powder is 30～38Myuemu, average thickness was 1.1～1.3Myuemu. The flat powder was heat-treated in an Ar gas atmosphere for 2 hours to obtain a flat soft magnetic metal powder having a coercive force Hc of about 400 A / m.
A binder and an organic solvent were added to the above flat soft magnetic metal powder and kneaded, then a curing agent was added and vacuum degassing while kneading.
The obtained magnetic paint was applied on one surface of a 75 μm-thick PET base film at a coating thickness of 400 μm by a blade coating method, dried after magnetic orientation, and dried. Drying was performed at normal temperature (25 ° C.) to prepare a magnetic sheet.

(Comparative Examples 1 to 4)
Magnetic sheets were produced in the same manner as in Examples 1 to 7 except that as the alloy composition, Mn was not contained, or Mn was made to have a ratio of more than 2% of atm%.
(Comparative Examples 5 to 8)
In the same manner as in Examples 1 to 7 except that the alloy composition has a ratio of Cr exceeding 0% or 5% by atm%, or a ratio of Si less than 14% or exceeding 22% by atm%. A magnetic sheet was produced.

実施例１〜７は、Ｍｎ比率がａｔｍ％で０．１〜２％の範囲であり、μ´×Ｑの高い磁性シートが得られた。また、実施例７ではＭｎに加え、さらにＣｏを添加したが、良好な特性が得られた。一方、比較例１〜８はμ´×Ｑがいずれも低い値となった。 Table 1 shows the experimental results when the alloy composition was changed.

In Examples 1 to 7, the Mn ratio was in the range of 0.1 to 2% at atm%, and a magnetic sheet having a high μ ′ × Q was obtained. Further, in Example 7, in addition to Mn, Co was further added, but good characteristics were obtained. On the other hand, in Comparative Examples 1 to 8, the values of μ ′ × Q were all low.

As described above, by using the flat soft magnetic powder according to the present invention, a magnetic sheet with high magnetic permeability (μ ′) and low loss (μ ′ ′) can be realized, and the communication distance of the noncontact communication terminal is improved. It is useful to

Claims (4)

Flat soft magnetic metal powder for magnetic sheet, containing at least 14% to 14% of Si, 0.1 to 5% of Cr, at least 1% to 2% of Mn, and Fe as an alloy component,
The weight average particle diameter _{D 50} of 10 to 100 [mu] m, an average thickness of 0.5 to 5 [mu] m, flaky soft magnetic metal powder for magnetic sheet. A flat soft magnetic metal powder for a magnetic sheet according to claim 1;
Containing a binder,
Magnetic sheet. An antenna coil comprising the magnetic sheet according to claim 2. Flat soft magnetic metal powder for a magnetic sheet containing Si 14 to 22 atm %, Cr 0.1 to 5 atm%, Mn 0.1 to 2 atm%, and Fe as alloy components (with Si: 4 to 21 atm) %, B: 4 to 21 atm %, Cr: 5 atm % or less (not including 0 atm %), C: 5 atm % or less (not including 0 atm %), Mn: 1 atm % or less (0 atm %) S: not more than 0.1 atm % (not including 0 atm %), with the balance composition consisting of Fe and unavoidable impurities, and the average particle size: 20 to 100 μm and aspect ratio (average particle size) Diameter / average thickness): excluding amorphous flat metal soft magnetic powder having flatness of 5 to 100).