JP2006039947A - Composite magnetic sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite magnetic sheet which secures high transmission and reception characteristics in frequency bands 1 to 20 MHz, is easy to treat, and is less expensive. <P>SOLUTION: The composite magnetic sheet 10 is formed by mixing a bonding agent with soft magnetic powers in a flat shape and has specified plasticity. The composite magnetic sheet 10 has a real number part μ' of complex permeability equal to or over 30 and an imaginary number part μ" equal to or below 10 in 1-20 MHz. Q value to be a ratio between the real number part μ' and the imaginary number part μ" of the composite magnetic sheet 10 is equal to 5 or larger. An aspect ratio of the soft magnetic powers in the flat shape ranges from 10 to 80. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a flexible composite magnetic sheet formed by blending a flat soft magnetic powder and a binder.

  Data exchange between a data carrier such as an RF tag or a non-contact IC card including a microchip configured with an IC memory and a communication circuit and a small antenna and a reader / writer for reading and writing data is performed without contact (using electromagnetic waves). In RFID (Radio Frcqucncy Identification) performed by wireless communication), a settlement system or a prepaid system using a frequency band of 1 to 20 MHz, particularly a 13.56 MHz band, is known. (For example, refer to Patent Document 1).

In the RFID, in order to increase the communication distance of electromagnetic waves between the data carrier and the reader / writer, for example, on the back surface of an antenna provided in the reader / writer, a magnetic material having a high magnetic permeability to improve electromagnetic wave transmission / reception characteristics It has been implemented. As this magnetic material, it is preferable that the real part μ ′ of the complex permeability is high and the imaginary part (damage) μ ″ is small, and a sintered ferrite powder is applied.
Japanese Patent Laid-Open No. 2003-224677

  However, in the magnetic body obtained by sintering ferrite powder, it takes time to make a thin plate, and it is difficult to make it into a different shape. Therefore, it is difficult to increase the cost and the usable parts are limited. In addition, since it is a sintered body, it is not flexible, and may be broken when assembled or dropped into the apparatus, so that it must be handled with care. In particular, as a data carrier used in the 13.56 MHz band, a card type that requires a reduction in thickness is the mainstream, and when a non-flexible magnetic material is used for this card, sufficient strength must be ensured. Furthermore, the problem that the cost increases further is caused.

  That is, the present invention has been proposed to solve this problem in view of the above-described problems related to the prior art, and ensures high transmission / reception characteristics in the frequency band of 1 to 20 MHz, is easy to handle, and is low. It aims at providing the composite magnetic sheet which can be manufactured at cost.

In order to overcome the above-mentioned problems and achieve the desired purpose suitably, the composite magnetic sheet according to the present invention is:
In an automatic recognition apparatus for transmitting and receiving data by electromagnetic waves between a non-contact data carrier and a reader / writer, a composite magnetic sheet disposed on the back surface of an antenna in the data carrier and / or reader / writer. And
The composite magnetic sheet is a flexible sheet formed by blending a flat soft magnetic powder and a binder,
The real part μ ′ of the complex permeability at 1 to 20 MHz is 30 or more and the imaginary part μ ″ is 10 or less.

  According to the composite magnetic sheet according to the present invention, high transmission / reception characteristics can be secured in a frequency band of 1 to 20 MHz. In addition, since the sheet has flexibility, it can be prevented from cracking when assembled to the apparatus or handled. Furthermore, since it can be easily reduced in thickness and can be easily formed into various shapes, the arrangement site is not limited and can be provided at low cost.

  By using an Fe-Si-Al-based alloy component of the soft magnetic powder, the real part μ ′ of the complex permeability can be increased. Further, by setting the aspect ratio of the soft magnetic powder in the range of 10 to 80, the imaginary part μ ″ of the complex magnetic permeability can be reduced.

  Next, the composite magnetic sheet according to the present invention will be described below with reference to the accompanying drawings by way of preferred examples.

  FIG. 1 shows a composite magnetic sheet 10 according to an embodiment disposed on a card-type RF tag 14 as a data carrier incorporating a microchip (not shown) composed of an IC memory and a communication circuit and a small antenna 12. The composite magnetic sheet 10 is formed into a flexible sheet by blending a flat soft magnetic powder and a binder at a required ratio. That is, since the composite magnetic sheet 10 has flexibility, when it is handled alone or attached to the RF tag 14 and carried, it is not broken by being dropped or deformed and is easy to handle. In addition, since it can be easily thinned and can be easily formed into an irregular shape or the like, the manufacturing cost can be kept low, and the attachment site is not limited. The data carrier is not limited to the RF tag but includes a non-contact IC card.

  As the soft magnetic powder, a material having a high real part μ ′ value of complex permeability and a low imaginary part μ ″ value, for example, an alloy component of Fe—Si—Al type is preferably used. That is, by using the Fe—Si—Al-based alloy component, the real part μ ′ of the complex permeability can be increased in the frequency band of 1 to 20 MHz. The soft magnetic powder is, for example, a flat (scalar) obtained by pulverizing a magnetic material produced by a rapid solidification method to a required size, or a spherical one obtained by a gas atomizing method or the like using an attritor. A flat shape is used. The blending ratio of the soft magnetic powder is appropriately set in the range of 30 to 60% by volume depending on the required complex magnetic permeability and flexibility.

Aspect ratio of the soft magnetic powder, that is, a value obtained by dividing the average (average particle diameter) of the major axis L ₁ and minor axis L ₂ of the flat particles by the thickness H [{(L ₁ + L ₂ ) / 2 } / H] is preferably in the range of 10 to 80, more preferably 20 to 30 in order to keep the imaginary part μ ″ of the complex permeability low in the frequency band of 1 to 20 MHz. Then, by reducing the imaginary part μ ″ of the complex permeability, the Q value as a performance coefficient which is the ratio {(μ ′) / (μ ″)} of the real part μ ′ and the imaginary part μ ″ Can be 5 or more in the region of 1 to 20 MHz. As a result, the electromagnetic wave transmission / reception characteristics of the RF tag 14 are improved, and the communication distance to the reader / writer 16 (see FIG. 2) that transmits / receives data to / from the RF tag 14 can be increased.

  As the binder, an organic binder such as a polymer or an elastomer is used. As the organic binder, for example, a chlorinated polyethylene or an acrylic binder is preferably used, but it may be a rubber or the like, as long as it can impart the required flexibility to the composite magnetic sheet 10. .

  In the illustrated example, the composite magnetic sheet 10 is attached to the RF tag 14 in the automatic recognition apparatus. However, the reader / writer 16 that transmits and receives data to and from the RF tag 14 has an antenna provided on the reader / writer 16. Alternatively, the composite magnetic sheet 10 may be attached to a position on the back side. Furthermore, the composite magnetic sheets 10 may be attached to both the RF tag 14 and the reader / writer 16, respectively.

[Experimental example]
By mixing 25 kg of Fe-Si-Al gas atomized powder produced by the gas atomizing method and 28.8 liters of chlorinated polyethylene, putting it in an attritor with 250 kg of balls (steel balls) and rotating it for a predetermined time The powder was flattened. By changing the processing time in the attritor, the aspect ratio of the obtained flat powder was changed, and comparative materials having the aspect ratio of 8 and 107 and inventive materials of 10 to 79 were produced. The thickness of the flat powder was measured by embedding the powder in a resin, polishing the powder, and observing the powder exposed on the polished surface with an optical microscope. Regarding the particle size measurement, the flat powder was observed with a scanning electron microscope, and the average particle size (major axis L ₁ and minor axis L ₂ ) was measured.

  About each obtained composite material of the comparative material and the inventive material, after annealing at 800 ° C. for 2 hours in a non-oxidizing atmosphere, kneader kneading-dispensing rolling-calender rolling, and a sheet shape having a thickness of about 1 mm It was. Here, fractional rolling refers to rolling that forms a sheet from a kneaded product using an open roll.

  Then, for the comparative material having the aspect ratio of 8 and 107 and the invention material of 10 to 79, the real part μ ′ and the imaginary part μ ′ of the complex permeability at 13.56 MHz are obtained by the impedance analyzer with one turn method. Table 1 shows values obtained by measuring 'and Q values calculated from the real part μ ′ and the imaginary part μ ″. Further, as shown in FIG. 2, comparison materials and invention materials of a size that covers the antenna 12 provided on the tag 14 are attached to the back surface of the substantially business card size RF tag 14, and the surface of the RF tag 14 is attached to a reader / writer. Table 1 shows the communication distance measured with the 16 reading surfaces (front surfaces) facing each other as a difference with respect to the communication distance measured with the composite magnetic sheet 10 not attached.

[Table 1]
┏━━━┳━━━━━━━┳━━━━━━━━━┳━━━━┳━━━━━━━━┓
┃ ┃ Aspect ratio ┃ Real part ┃ Imaginary part Ｑ Q value ┃ Communication distance (cm) ┃
┣━━━╋━━━━━━━╋━━━━━━━━━╋━━━━╋━━━━━━━━┫
┃ Comparison material ┃ 8 ８ 23 ┃ 5.2 ┃ 4.4 ＋１ +1.0 ┃
┣━━━╋━━━━━━━╋━━━━━━━━━╋━━━━╋━━━━━━━━┫
┃ Invention material ┃ 10 １０ 37 ┃ 6.7 ┃ 5.5 ┃ +5.0 ５
┣━━━╋━━━━━━━╋━━━━━━━━━╋━━━━╋━━━━━━━━┫
┃ Invention Material ┃ 21 ２１ 48 ┃ 7.8 ┃ 6.2 ┃ +5.0 ┃
┣━━━╋━━━━━━━╋━━━━━━━━━╋━━━━╋━━━━━━━━┫
┃Invention Material┃ 48 ６５ 65 ┃ 8.4 ┃ 7.7 ┃ +4.5 ┃
┣━━━╋━━━━━━━╋━━━━━━━━━╋━━━━╋━━━━━━━━┫
┃ Invention Material ┃ 79 ７９ 74 ┃ 9.8 ┃ 7.6 ＋ +4.6 ４
┣━━━╋━━━━━━━╋━━━━━━━━━╋━━━━╋━━━━━━━━┫
┃ Comparative material ┃ 107 １０７ 83 ┃ 12 ┃ 6.9 ＋ +2.0 ┃
┗━━━┻━━━━━━━┻━━━━━━━━━┻━━━━┻━━━━━━━━┛

  From the above results, the aspect ratio of the real part μ ′ ≧ 30, the imaginary part μ ″ ≦ 10, and the Q value ≧ 5 among the conditions of the real part μ ′ and the Q value are not satisfied. For the comparative material of 8 and the comparative material having an aspect ratio of 107 that did not satisfy the condition of the imaginary part μ ″, the communication distance was slightly extended.

  On the other hand, for the inventive material having an aspect ratio of the flat powder of 10 to 79, all the conditions of the real part μ ′ ≧ 30, the imaginary part μ ″ ≦ 10, and the Q value ≧ 5 of the complex permeability are satisfied. Satisfying, and a significant extension of its communication distance was achieved.

It is the schematic which shows the RF tag which attached the composite magnetic sheet which concerns on an Example. It is explanatory drawing which shows the state of the experiment which measures the communication distance of RF tag using the composite magnetic sheet which concerns on an Example.

Explanation of symbols

10 composite magnetic sheet, 12 antenna, 14 RF tag (data carrier)

Claims (5)

In an automatic recognition device that transmits and receives data by electromagnetic waves between a non-contact data carrier (14) and a reader / writer (16), an antenna in the data carrier (14) and / or the reader / writer (16) A composite magnetic sheet disposed on the back surface of (12),
The composite magnetic sheet (10) is a flexible sheet formed by blending a flat soft magnetic powder and a binder,
A composite magnetic sheet, wherein the real part μ ′ of the complex permeability at 1 to 20 MHz is 30 or more and the imaginary part μ ″ is 10 or less.   The composite magnetic sheet according to claim 1, wherein a Q value that is a ratio of a real part μ ′ and an imaginary part μ ″ of the complex permeability is 5 or more.   The composite magnetic sheet according to claim 1, wherein the binder is an organic binder such as a polymer or an elastomer.   The composite magnetic sheet according to any one of claims 1 to 3, wherein an alloy component of the soft magnetic powder is Fe-Si-Al. The composite magnetic sheet according to any one of claims 1 to 4, wherein the flat soft magnetic powder has an aspect ratio in the range of 10 to 80.

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