WO2006036012A1

WO2006036012A1 - Magnetic sheet, antenna apparatus using the same, and method of producing magnetic sheet

Info

Publication number: WO2006036012A1
Application number: PCT/JP2005/018494
Authority: WO
Inventors: Hidetsugu Fujimoto; Kouji Nishimura; Hatsuhiro Yano; Kouichi Watanabe; Koji Yasumura; Keisuke Maruyama
Original assignee: Matsushita Electric Industrial Co., Ltd.
Priority date: 2004-09-29
Filing date: 2005-09-29
Publication date: 2006-04-06
Also published as: EP1815558A1; EP1815558B1

Abstract

A magnetic sheet is formed by a single magnetic layer and all the solid magnetic pieces constituting the magnetic layer are arranged to form the upper and lower surfaces of the magnetic layer at the same time, the volume of the solid magnetic pieces can be maximized within the range of constitution of the magnetic sheet, allowing the maximum use of the solid properties of the magnetic material.

Description

DESCRIPTION

Magnetic Sheet, Antenna Apparatus Using the Same, And

Method of Producing Magnetic Sheet

Technical Field

The present invention relates to a magnetic sheet which can be preferably used for magnetic shield such as RF-ID antenna, etc., and an antenna apparatus comprising same, and a method of producing a magnetic sheet.

Background Art

In order to attain the reduction of cost and size of wireless communications apparatus such as cellular phone, it has been desired to reduce the size of parts and raise the mounting density thereof. Further, more portable mobile electronic apparatus such as notebook personal computer have employed data communications using wireless LAN, etc., and it has been desired to reduce the size of these parts to be incorporated in these electronic apparatus and raise the mounting density thereof.

Further, even wireless communications antennas for use in these electronic apparatus are required to be provided in a narrow space, and a magnetic sheet has been inevitably used for preventing the effect of electromagnetic wave received or transmitted on electronic parts, substrates or housings disposed close thereto or the effect of these electronic parts, substrates or housings.

In the related art, this magnetic has been often cut into a proper size or shape and stuck to necessary positions on these antennas or other electronic apparatus or otherwise used. This is disclosed in JP-A-2000-349493 and JP-A-2000-244171.

Fig. 10 and 11 each are a sectional view of a magnetic sheet according to the conventional technique and Fig. 12 is a plan view of a magnetic layer according to the conventional technique.

However, the conventional magnetic sheets were disadvantageous in that workability or mountability is focused for convenience of post mounting and the constitution of the magnetic sheet is almost entirely occupied by a sheet substrate 3 which is desired to have physical properties such as flexibility as shown in Figs. 10 and 11, making it impossible to sufficiently exhibit magnetic properties.

The magnetic sheet 6 shown in section in Fig. 10 comprises regularly shaped or amorphous magnetic particles Ia dispersed in a sheet substrate 3. The enhancement of magnetic properties by this arrangement can be realized by increasing the content of the magnetic particles Ia in the magnetic sheet substrate 6. However, this method was disadvantageous in that the rise of the content of the magnetic particles Ia causes the impairment of physical properties such as flexibility of the sheet substrate 3 or makes it difficult for the magnetic particles Ia to disperse and hence causes the deviation of condensed density of the magnetic particles Ia, raising problems of damages such as formation of pores and cracking, deterioration of mechanical strength or weathering resistance, etc. and hence making it impossible to sufficiently raise the content of the magnetic particles Ia and hence the magnetic properties.

In accordance with the magnetic sheet 6 shown in section in Fig. 11 and in plan in Fig. 12, the magnetic material in the sheet substrate 3 is in the form of leaf Ib, and these magnetic leaves Ib are superimposed on each other or disposed in close contact with each other so that they are spread in the planar direction with little gap to raise the surface density of the magnetic layer 2b and enhance the magnetic function. Further, since this thin magnetic layer 2b is provided interposed between the sheet substrate 3, the physical properties of the sheet substrate 3 can be little impaired while enhancing the magnetic function.

As compared with the magnetic sheet 6 shown in section in Fig. 10, the magnetic sheet 6 shown in section in Fig. 11 comprises magnetic leaves Ib assembled in lamellar form, making it possible to exhibit high magnetic properties with a reduced content of magnetic material in the sheet substrate 3. However, the magnetic sheet 6 of Fig. 10 was disadvantageous in that in order to enhance the magnetic properties, the amount of the magnetic layer 2b formed by the magnetic leaves Ib must be raised, impairing physical properties such as flexibility of the sheet substrate 3 or deteriorating mechanical strength or weathering resistance. Therefore, the content of magnetic leaves Ib cannot be sufficiently raised, making it impossible to enhance the magnetic properties. These related art magnetic sheets were also disadvantageous in that they are obtained by mixing magnetic particles or magnetic leaves with a sheet substrate material, and then molding the mixture and thus exhibit extremely deteriorated magnetic properties as compared with the magnetic material itself.

Disclosure of Invention

An object of the present invention is to provide a magnetic sheet arranged to exhibit the maximum magnetic properties while maintaining the least required physical properties as magnetic sheet.

The present invention comprises a plurality of magnetic blocks obtained by molding a baked magnetic powder in block form and a flexible sheet substrate, wherein the plurality of magnetic blocks are arranged planarly to form a magnetic layer and the sheet material retains the magnetic layer.

In the present invention, since the magnetic sheet is formed by a single magnetic layer and all the solid magnetic pieces constituting the magnetic layer are arranged to form the upper and lower surfaces of the magnetic layer at the same time, the volume of the solid magnetic pieces can be maximized within the range of constitution of the magnetic sheet, allowing the maximum use of the solid properties of the magnetic material.

Further, by arbitrarily designing the size and shape of this magnetic material, the density of the magnetic layer can be further enhanced, making it possible to enhance the magnetic function.

Moreover, since a clearance between the solid magnetic pieces is continuously formed over the both upper and lower surfaces of the single magnetic layer, the size, shape and joint of this magnetic material can be arbitrarily designed to render the magnetic sheet more flexible to bending and deflection or more workable in cutting or the like.

Brief Description of Drawings Figs. 1, 2, 3, 4, 5 and 6 each are a sectional view of a magnetic sheet according to an embodiment of implementation of the present invention;

Figs. 7, 8 and 9 each are a perspective view of a magnetic layer according to an embodiment of implementation of the present invention;

Fig. 10 and 11 each are a sectional view of a magnetic sheet according to the conventional technique;

Fig. 12 is a plan view of a magnetic layer according to the conventional technique. Fig. 13 is a perspective view illustrating an antenna apparatus according to Embodiment 2 of implementation of the present invention.;

Fig. 14 is a perspective view illustrating the magnetic layer of the magnetic block;

Fig. 15 is an exploded perspective view illustrating an antenna apparatus;

Fig. 16 is a sectional view illustrating a magnetic sheet according to Embodiment 2 of implementation of the present invention;

Figs. 17 to 23 each are a sectional view illustrating other examples of the magnetic sheet according to Embodiment 2 of implementation of the present invention;

Fig. 24 is an exploded perspective view illustrating an antenna apparatus;

Fig. 25 is a sectional view illustrating an antenna portion and a magnetic portion; Fig. 26 is a sectional view of a magnetic sheet;

Fig. 27 is a plan view of a magnetic layer;

Fig. 28(a) depicts an exploded perspective view of an antenna apparatus;

Fig. 28(b) depicts a plan view of the soft magnetic material;

Fig. 28(c) depicts a side view of the soft magnetic material; Fig. 28(d) depicts a perspective view of the soft magnetic material;

Fig. 29(a) is a plan view of the soft magnetic material;

Fig. 29(b) depicts a side view of the soft magnetic material;

Fig. 29(c) depicts a perspective view of the soft magnetic material;

Fig. 30(a) is a plan view of the soft magnetic material; Fig. 30(b) depicts a side view of the soft magnetic material;

Fig. 30(c) depicts a perspective view of the soft magnetic material;

Fig. 31 (a) is a plan view of the soft magnetic material;

Fig. 31(b) depicts a side view of the soft magnetic material;

Fig. 31(c) depicts a perspective view of the soft magnetic material; Fig. 32(a) is a plan view of the soft magnetic material;

Fig. 32(b) depicts a side view of the soft magnetic material;

Fig. 32(c) depicts a perspective view of the soft magnetic material;

Fig. 33 (a) is a plan view of the soft magnetic material;

Fig. 33(b) depicts a side view of the soft magnetic material; Fig. 33(c) depicts a perspective view of the soft magnetic material;

Fig. 34(a) depicts an exploded perspective view of an antenna apparatus;

Fig. 34(b) depicts a plan view of the soft magnetic material; Fig. 34(c) depicts a side view of the soft magnetic material;

Fig. 34(d) depicts a perspective view of the soft magnetic material;

Fig. 35 (a) depicts a plan view of the soft magnetic material;

Fig. 35(b) depicts a side view of the soft magnetic material; Fig. 35(c) depicts a perspective view of the soft magnetic material;

Fig. 36(a) depicts a plan view of the soft magnetic material;

Fig. 36(b) depicts a side view of the soft magnetic material;

Fig. 36(c) depicts a perspective view of the soft magnetic material;

Fig. 37(a) depicts a plan view of the soft magnetic material; Fig. 37(b) depicts a side view of the soft magnetic material;

Fig. 37(c) depicts a perspective view of the soft magnetic material;

Fig. 38(a) depicts a plan view of the soft magnetic material;

Fig. 38(b) indicates a side view of the soft magnetic material;

Fig. 38(c) indicates a perspective view of the soft magnetic material; Fig. 39(a) indicates a plan view of the soft magnetic material;

Fig. 39(b) indicates a side view of the soft magnetic material;

Fig. 39(c) indicates a perspective view of the soft magnetic material;

Fig. 40(a) depicts a sectional view of a related art antenna apparatus; and Fig. 40(b) depicts a sectional view of the antenna apparatus according to the present embodiment of implementation of the present invention

Best Mode for Carrying Out the Invention

The present invention will be further described in connection with the drawings. (Embodiment 1) Figs. 1, 2, 3, 4, 5 and 6 each are a sectional view of a magnetic sheet according to an embodiment of implementation of the present invention. Figs. 7, 8 and 9 each are a perspective view of a magnetic layer according to an embodiment of implementation of the present invention.

Fig. 1 depicts a magnetic sheet 6, and in Fig. 1, the reference numeral 1 indicates a magnetic block, the reference numeral 2 indicates a magnetic layer, and the reference numeral 3 indicates a sheet substrate. Further, the reference numerals 4a, 4b indicate the upper and lower surfaces of the magnetic layer 2, respectively. Moreover, in the present embodiment of implementation of the present invention, the magnetic layer 2 itself is not lamellar but is expressed as a magnetic layer to indicate the magnetic range between the upper and lower surfaces 7a, 7b of the magnetic sheet 6.

The magnetic block 1 is a single solid piece formed by any one of magnetic powders such as ferrite, permaloy, sendust and silicon plywood. Since all these magnetic blocks 1 are arranged to form the upper and lower surfaces 4a, 4b of the magnetic layer 2 at the same time, the maximum volume of the magnetic block 1 can be used within the range of thickness dimension, mechanical strength and other physical properties required for a magnetic sheet 6 and the specific surface area of the magnetic block 1 in the entire magnetic layer 2 can be reduced to reduce the amount of the sheet substrate 3, making it possible to obtain high magnetic properties.

Further, as shown in Figs. 7 and 8, the magnetic blocks 1 are arranged to have substantially the same shape so that the various magnetic blocks 1 and the clearances 5 between the magnetic blocks can be orderly arranged, making it easy to design properties such as magnetic properties and insulation properties, physical properties such as bending and deflection and workability in cutting, etc.

Moreover, in Fig. 9, a part or a plurality of parts of the magnetic layer 2 are formed by an assembly of magnetic blocks Ic having substantially the same shape with which an assembly of magnetic blocks Id, Ie having different shapes is combined, making it possible to enhance the degree of freedom of the standard shape, type of dimension, etc. of the magnetic sheet 6.

Further, since the flexibility of the magnetic sheet can be maintained while inhibiting the deterioration of the magnetic properties, the working frequency band is 13.56 MHz. When used in RFID (Radio Frequency Identification) system, the magnetic sheet can be mounted even in an uneven place while assuring the desired wireless range. The magnetic sheet is suitable particularly for the case where the mounting space is limited as in cellular phone.

In Figs. 7, 8 and 9, the individual magnetic block 1 is shown in the form of prism or column by way of representative example for ease of molding but may be in the form of trigonal prism, polygonal prism, pyramid, cone, sphere or needle. Alternatively, amorphous magnetic blocks 1 may be provided to reduce the number of steps of working the magnetic block 1. In Figs. 1 to 5, examples of the configuration of the magnetic block 1 and the sheet substrate 3 are depicted.

In Fig. 1, the magnetic block 1 is shown embedded in the sheet substrate 3. Herein too, the magnetic layer 2 is formed by a single layer and the thickness of the magnetic block 1 is maximized, making it possible to drastically reduce the amount of the sheet substrate 3, and further, in Fig. 2, the magnetic block 1 is shown retained by the sheet substrate 3 on the upper and lower surfaces 4a, 4b of the magnetic layer 2. In the configuration of Fig. 2, the clearance 5 is formed on the side of the magnetic block 1, making it possible to not only further reduce the amount of the sheet substrate 3 but also cause the clearance 5 to act as a buffer layer and thus exhibit stable properties without giving any stress-strain to the magnetic block 1 even if a load such as bending and deflection is applied to the magnetic sheet substrate 6.

Further, in Fig. 3, the sheet substrate 3 is shown excluded on the upper and lower surfaces 4a, 4b of the magnetic layer 2 and provided only on the side of the magnetic block 1. In this case, the upper and lower surfaces 4a, 4b of the magnetic layer 2 are disposed flush with the upper and lower surfaces 7a, 7b of the magnetic sheet 6, respectively. Accordingly, the magnetic block 1 is exposed at the upper and lower surfaces 7a, 7b of the magnetic sheet substrate 6, and it is thus effective in the case where the magnetic properties of the magnetic block 1 axe directly utilized. Similarly, Fig. 4 depicts a configuration that one surface 7a of the magnetic sheet substrate 6 is flush with one surface 4a of the magnetic layer 2.

Further, in Fig. 5, a configuration is depicted that the magnetic block 1 is retained by the sheet substrate 3 only on one surface 4b of the magnetic layer 2.

In the present embodiment of implementation of the present invention, a single magnetic layer 2 is provided between the upper and lower surfaces 7a, 7b of the magnetic sheet, the magnetic sheet layer 2 is formed by a plurality of magnetic blocks 1 having different shapes and all the solid pieces of magnetic block 1 are arranged to form the upper and lower surfaces 4a, 4b of the magnetic layer 2 at the same time, making it possible to retain the magnetic block 1 by the sheet substrate 3 only on one surface 4b of the magnetic layer 2.

In this configuration, even when the sheet substrate 3 is processed such that it is bent in a direction such that the clearance 5 between the magnetic blocks 1 is opened or it is deflected, the magnetic properties characteristic to the magnetic block 1 can be exhibited without applying a great stress to the magnetic block 1. For example, an embodiment that can cope with a bent form shown in Fig. 6 can be easily realized.

As the sheet substrate 3 there is preferably used a resin or rubber, but selection may be conducted taking into account not only flexibility to bending or deflection but also weathering resistance such as heat resistance and moisture resistance.

(Embodiment 2)

Fig. 13 is a perspective view illustrating an antenna apparatus according to Embodiment 2 of implementation of the present invention. In Fig. 13, an antenna apparatus 30A comprises an antenna pattern 2, a matching circuit 3, a sheet substrate 4 and a magnetic block 10. The plurality of magnetic blocks 10 are arranged planarly to form a magnetic layer 9 and the sheet substrate retains the magnetic layer 9.

As shown in Fig. 13, the magnetic sheet substrate 1 incorporated in the antenna apparatus 30A is an antenna-integrated magnetic sheet substrate, and the magnetic layer of the magnetic block 10 and the antenna pattern 2 are retained covered by the sheet substrate 4 to form an integrated structure.

When the antenna apparatus 30A is thus arranged, the antenna apparatus 30A can be reduced in its thickness and weight and can be provided with high magnetic properties, making it possible to enhance the wireless properties of RFID. Further, since the antenna pattern 2 is covered by the sheet substrate 4, the denaturatiion or corrosion of the surface of the antenna pattern can be prevented. Moreover, troubles such as deformation or separation of antenna pattern 2 due to external stress can be prevented.

Next, the magnetic layer of the magnetic block 10 as a magnetic material in Embodiment 2 of implementation of the present invention will be described. Fig. 14 is a perspective view illustrating the magnetic layer of the magnetic block 10 in Embodiment 2 of implementation of the present invention, and in Fig. 14, the reference numeral 9 indicates a magnetic layer.

As shown in Fig. 14, when the plurality of magnetic blocks 10 are assembled to form the magnetic layer 9, magnetic materials can be formed at a high density in the antenna apparatus 30A, making it possible to obtain high magnetic properties and easily design the bending, deflection, etc. of the antenna apparatus 30A and facilitate cutting at the subsequent step.

Next, an antenna apparatus comprising a magnetic sheet according to Embodiment 2 of implementation of the present invention will be described. Fig. 15 is an exploded perspective view illustrating an antenna apparatus according to Embodiment 2 of implementation of the present invention. In Fig. 15, the reference numeral 5 indicates an upper housing, the reference numeral 6 indicates a metal sheet, and the reference numeral 7 indicates a lower housing.

As shown in Fig. 15, the antenna apparatus 3OB according to Embodiment 2 of implementation of the present invention comprises a magnetic sheet and a metal sheet 6 provided interposed between the upper housing 5 and the lower housing 7.

Thus, the antenna apparatus 30A has an integrated structure comprising the magnetic layer 9 of the magnetic block 10 and the antenna pattern 2 retained covered by the sheet substrate 4, making it possible to maximize the magnetic properties thereof while maintaining the least required physical properties of the antenna apparatus 30A and hence enhance the wireless properties of the antenna apparatus 40. Further, when the impedance of the antenna is adjusted with the metal sheet 6 attached thereto, the effect of metal around the installation place can be eliminated. In some detail, no change of impedance of antenna or deviation (change) of resonance frequency due to the effect of metal around the installation place can occur, eliminating the necessity of adjusting resonance frequency.

Thus, in the antenna apparatus 30A according to Embodiment 1 of implementation of the present invention, the wireless properties of RFID can be fully satisfied without deteriorating the antenna properties.

It goes without saying that the antenna apparatus 30B according to Embodiment 2 of implementation of the present invention can be used as antenna apparatus according to Embodiment 2 of implementation of the present invention, as shown in Fig. 15 but also as antenna apparatus shown in Fig. 24 and can provide high magnetic properties.

Further, as compared with the antenna apparatus shown in Fig. 24, the antenna apparatus according to Embodiment 2 of implementation of the present invention can be reduced in its dimension in the thickness direction and thickness to reduce the number of parts and the weight thereof.

Herein, Fig. 16 is a sectional view illustrating a magnetic sheet according to Embodiment 2 of implementation of the present invention. As shown in Fig. 16, a sheet substrate 4 is packed in the adjacent magnetic blocks 10, making it possible to enhance the retaining strength of the magnetic block 10 and provide a flexible antenna apparatus 30A and hence arbitrarily cope with bending or deflection and facilitate cutting. The antenna apparatus 30A can be subjected to various deformations. Figs. 17 to 23 each are a sectional view illustrating other examples of the magnetic sheet according to Embodiment 2 of implementation of the present invention.

As shown in Fig. 17, in the antenna apparatus 30A, a clearance 8 is formed between the adjacent magnetic blocks 10, making it possible to provide a flexible antenna apparatus 30A and hence arbitrarily cope with bending or deflection and facilitate cutting.

Further, as shown in Fig. 18 the adjacent magnetic blocks 10 are arranged to come in contact with each other, making it possible to raise the volume of the magnetic block 10 with respect to the entire antenna apparatus 30A and hence obtain high magnetic properties. Further, as shown in Fig. 19, the magnetic block 10 is formed by a number of magnetic layers 9 and the magnetic layers 9 are bonded to each other with a sheet substrate 4, making it easy to predetermine optimum magnetic properties by predetermining the number of magnetic layers 9 to be laminated.

Further, as shown in Fig. 20, a sheet substrate 4 is formed on the side of the magnetic layer 9 of the plurality of magnetic blocks 10, rendering the side of the magnetic block 10 (magnetic layer 9) resistant to the external stress or impact and hence making it possible to prevent the occurrence of cracking or breaking of the magnetic block 10 and prevent the exfoliation of the magnetic block 10 and the sheet substrate 4 from each other. Moreover, the penetration of water content, etc. from side can be prevented to enhance reliability.

In the case shown in Fig. 21, an adhesive sheet 12 such as double-bonded tape, for example, is provided on the sheet substrate 4 of the magnetic block 10 retained by the sheet substrate 4, an antenna pattern 2 is formed on this adhesive sheet 12 and the sheet substrate 4 is disposed on the antenna pattern 2, making it possible to efficiently connect the antenna apparatus 30A comprising the magnetic blocks 10 and the antenna pattern 2 to each other.

Further, as shown in Fig. 22, the adhesive sheet 12 is formed on the sheet substrate 4 of the plurality of magnetic blocks 10 retained by the sheet substrate 4 and the antenna pattern 2 embedded in the sheet substrate 4 is fixed by the adhesive sheet 12, making it possible to efficiently connect the antenna apparatus 30A comprising the magnetic blocks 10 and the sheet substrate 4 comprising the antenna pattern 2 to each other. Moreover, since the antenna pattern 2 is fixed by embedding, no damage, deformation or positional deviation of the antenna pattern 2 during assembly can occur, making it possible to form the antenna pattern 2 with a good precision and hence obtain stable wireless properties in RFID system.

As shown in Fig. 23, the antenna pattern 2 is formed on the upper part of the magnetic blocks 10, making it possible to reduce the total thickness of the antenna apparatus 30A.

Next, the details of the various parts will be described. The magnetic sheet comprises at least an assembly of a plurality of magnetic blocks 10, a sheet substrate 4 retaining or supporting the assembly 9 and an antenna pattern 2. In the case where the magnetic sheet is used as a member separate of antenna, that is, the magnetic sheet is not integrated with the antenna and is installed on the back surface of the antenna or other sites, or in the case where the magnetic sheet is used for purposes other than antenna such as inhibition of electromagnetic interference with electronic apparatus, the magnetic sheet may be provided free of antenna pattern 2, and, in this case, this magnetic sheet comprises at least an assembly 9 of a plurality of magnetic blocks 10 and a sheet substrate 4 retaining or supporting the assembly 9. Further, the magnetic blocks 10 of this magnetic sheet may be made of a ferrite- based material and other metallic magnetic sheets may be laminated on this ferrite magnetic sheet.

The antenna pattern 2 has a loop antenna structure. Referring to the structure of the loop antenna, the loop antenna may be a loop having an opening provided in the center thereof and may be in the form of circle, substantial circle or polygon. Further, the material of the loop antenna may be properly selected from the group consisting of electrically-conductive metal wire, metallic sheet, metallic foil, metallic cylinder, etc. The loop antenna may be formed by metal wire, metal foil, electrically-conductive paste, transfer of deposit, sputtering, vacuum deposition or screen printing.

In accordance with the matching circuit 3, the antenna properties can be difficultly affected by metal present around the installation place or other factors and the occurrence of stationary wave due to nonmatching can be inhibited, making it possible to provide an antenna having stable operation and reduced loss.

As the sheet substrate 4 there is preferably used, e.g., resin or rubber. Selection may be conducted taking into account not only flexibility to bending or deflection but also weathering resistance such as heat resistance and moisture resistance. The sheet substrate 4 according to the present invention may retain the plurality of magnetic blocks 10 with a resin sheet or include the plurality of magnetic blocks 10 with a resin material to form a sheet, and its form is not limited. In some detail, the sheet substrate 4 may be a laminate or molded material. The upper housing 5 and the lower housing 7 may be made of a resin material, making it possible to reduce the weight of the antenna apparatus.

The metal sheet 6 is preferably made of a nonmagnetic material such as aluminum sheet.

The magnetic layer 9 is an assembly of magnetic blocks 10 which can be orderly arranged to form a magnetic material efficiently with respect to the total thickness of the magnetic sheet 30.

The magnetic block 10 is formed by a metallic magnetic material such as ferrite-based material, permaloy, sendust and silicon plywood. When all the magnetic blocks 10 are arranged such that the upper and lower surfaces thereof are flush with each other, the maximum volume of the magnetic material can be used within the range of thickness dimension, mechanical strength and other physical properties required for the magnetic sheet and the specific surface area of the magnetic blocks 10 in the entire magnetic layer 9 can be reduced, making it possible to reduce the amount of the sheet substrate 4 and hence obtain high magnetic properties. The material constituting the magnetic block 10 (magnetic powder constituting the magnetic block 10) may be made of a soft magnetic ferrite, even a high density baked ferrite obtained by dry-pressing a ferrite-based magnetic powder which is a soft magnetic ferrite and then baking the ferrite-based magnetic powder thus pressed, and the density of the soft magnetic ferrite is preferably 3.5 g/cm³ or more. Further, the size of the soft magnetic ferrite-based magnetic powder is preferably not smaller than the grain boundary. Examples of the soft magnetic ferrite include Ni-Zn-based ferrites and Mn-Zn-based ferrites, and the soft magnetic ferrite may be made OfFe₂O₃, ZnO, MO and CuO or Fe₂O₃, ZnO, MnO and CuO. Moreover, the magnetic block 10 may be a magnetic block made of any of amorphous alloy, permaloy, magnetic steel, silicon steel, Fe-Al alloy and sendust alloy or may be a laminate of amorphous foil, permaloy, electromagnetic steel, silicon steel or sendust. Further, the magnetic block 10 may be in the form of substantially trigonal column, substantially rectangular column, substantially polygonal column, substantially circular column, substantial sphere or the like.

As the adhesive sheet 12 there may be used a double-sided tape or the like. A sticking agent or adhesive may be used instead of the adhesive sheet 12.

In this arrangement, a magnetic sheet 30 having excellent properties can be provided, and the antenna apparatus 40 can exhibit stable properties of RFID system to assure desired wireless range. While the aforementioned embodiment has bee described with reference to the magnetic sheet shown in Fig. 15 as an example of magnetic sheet, the magnetic sheet is not limited to the magnetic sheet shown in Fig. 15.

Next, a method of producing the magnetic sheet will be described. The magnetic material (ferrite) was composed of from 46.0 to 50.0 mol-% OfFe₂O₃, from 18.0 to 22.5 mol-% of MO, from 18.0 to 22.5 mol-% of ZnO and from 8.5 to 12.0 mol-% of CuO.

Subsequently, the magnetic material thus compounded was subjected to mixing/grinding (5 to 20 hours), dried, ground, and then calcinated in a baking furnace (600⁰C to I₃OOO⁰C). The magnetic powder thus calcinated was granulated with a polyvinyl-based binder, molded into a block form to prepare predetermined solid pieces (magnetic block 10), and then baked in a baking furnace (800⁰C to 1,200⁰C).

The thickness of the magnetic block 10 thus prepared is 0.25 mm, but an optimum dimension of 0.03 m or more can be arbitrarily selected depending on the requirements for installation form. The shape of the magnetic block 10 was a 2 mm square. The baked density of the magnetic block 10 was 5.1 g/cm³.

The magnetic block 10 thus completed was laid on the sheet substrate, bonded and fixed to the sheet substrate, and then laminated with other sheet substrates and antenna patterns on the top thereof to obtain a magnetic sheet 30. Since the magnetic block 10 which has been baked to a high density is laid on the sheet substrate, a magnetic material having a high permeability can be prepared, making it possible to enhance the wireless range of RFID. Examples of the method of forming the magnetic block 10 include a method which comprises cutting the magnetic block baked into a magnetic block 10, and a method which comprises cutting a baked material prepared by doctor blade into solid pieces, and any of these methods may be selected.

(Embodiment 3)

The reference numeral 1 indicates an antenna apparatus shown illustrating the internal structure of RFID system, the reference numeral 2 indicates a resin case (main body), the reference numeral 3 indicates an antenna pattern formed on the antenna substrate, the reference numeral 4 indicates a matching circuit, the reference numeral 5 indicates a soft magnetic material, the reference numeral 6 indicates a resin spacer, the reference numeral 7 indicates a metal sheet, and the reference numeral 8 indicates a resin case (back cover).

Firstly, in the structure of the antenna apparatus 1, the characteristics and , advantage of the structures shown in the various drawings will be briefly described.

Fig. 28(a) depicts an exploded perspective view of an antenna apparatus according to the present embodiment of implementation of the present invention. Disposed under the antenna substrate having the antenna pattern 3 and the matching circuit 4 formed thereon is the soft magnetic material 5. Disposed under the soft magnetic material 5 are the resin spacer 6 and the metal sheet 7. The aforementioned parts are received in the resin case (main body) 2 and the resin case (back cover) 8. The soft magnetic material 5 is formed by an assembly of a plurality of magnetic blocks, making it possible to enhance productivity and prepare a soft magnetic material having an excellent quality and little dispersion of properties. Further, by disposing the soft magnetic material 5 under the antenna pattern 3, an effect can be exerted of assuring desired wireless range while inhibiting the change of resonance frequency or the rise of loss due to eddy current generated in the metal present on the back of RIFD system. Fig. 28(b) depicts a plan view of the soft magnetic material according to the present embodiment of implementation of the present invention. Fig. 28(c) depicts a side view of the soft magnetic material according to the present embodiment of implementation of the present invention. Fig. 28(d) depicts a perspective view of the soft magnetic material according to the present embodiment of implementation of the present invention. The reference numeral 9 indicates a magnetic block in the soft magnetic material 5.

Fig. 29(a) is a plan view of the soft magnetic material according to the present embodiment of implementation of the present invention. Fig. 29(b) depicts a side view of the soft magnetic material according to the present embodiment of implementation of the present invention. Fig. 29(c) depicts a perspective view of the soft magnetic material according to the present embodiment of implementation of the present invention. In this arrangement, an effect can be exerted of reducing the weight of the soft magnetic material and assure desired wireless range while inhibiting the change of resonance frequency or the rise of loss due to eddy current generated in the metal present on the back of RJFD system.

Fig. 30(a) is a plan view of the soft magnetic material according to the present embodiment of implementation of the present invention. Fig. 30(b) depicts a side view of the soft magnetic material according to the present embodiment of implementation of the present invention. Fig. 30(c) depicts a perspective view of the soft magnetic material according to the present embodiment of implementation of the present invention. In this arrangement, a flexible soft magnetic material resistant to impact can be prepared.

Fig. 31 (a) is a plan view of the soft magnetic material according to the present embodiment of implementation of the present invention. In this arrangement, any thickness can be coped with, making it easy to adjust the intensity of magnetic field. Fig. 32(a) depicts a plan view of the soft magnetic material according to the present embodiment of implementation of the present invention. In this arrangement, a variety of magnetic blocks can be used, making it possible to prepare a magnetic material at a high productivity and a reduced cost.

Fig. 33 (a) depicts a plan view of the soft magnetic material according to the present embodiment of implementation of the present invention. In this arrangement, the intensity of magnetic field at the end of RFED can be raised, making it possible to eliminate skip zones during communication.

The outline and point of the structure of the various drawings have been described above. Next, the detail of the various parts will be described.

The reference numeral 1 indicates an antenna apparatus shown illustrating the internal structure of RFID system which comprises a resin case (main body) 2, an antenna pattern 3 formed on the antenna substrate, a matching circuit 4, a soft magnetic material 5, resin spacer 6, a metal sheet 7 and a resin case (back cover) 8 as shown in Fig. 28.

The reference numeral 3 is an antenna pattern having a loop antenna structure. Referring to the structure of the loop antenna, the loop antenna may be a loop having an opening provided in the center thereof and may be in the form of circle, substantial circle or polygon. Further, the material of the loop antenna may be properly selected from the group consisting of electrically-conductive metal wire, metallic sheet, metallic foil, metallic cylinder, etc.

The reference numeral 4 indicates a matching circuit, and the connection of the matching circuit 4 makes it less likely that the antenna properties can be affected by metal present around the installation place and can prevent the occurrence of stationary wave due to nonmatching, making it possible to provide an antenna having stable operation and little loss.

The reference numeral 5 indicates a soft magnetic material, the soft magnetic material 5 is disposed on the back surface of the antenna pattern 3, and as the material thereof there may be used a soft magnetic ferrite, amorphous alloy, permaloy, electromagnetic steel, silicon steel, Fe-Al alloy, sendust alloy or the like. Referring to the shape of the soft magnetic material, if ferrite is used, a tabular or sheet-like soft magnetic material may be used. The sheet-like ferrite may be prepared by kneading a ferrite powder with an organic binder such as resin material, and then drying the mixture. The use of the magnetic sheet makes it possible to assure flexibility and enhance impact resistance or durability. The reference numeral 9 indicates a magnetic block which is a constituent member of the soft magnetic material 5. The constitution of the soft magnetic material 5 by an assembly of magnetic blocks 9 makes it possible to exert an effect of enhancing the productivity of the soft magnetic material 5, provide an excellent quality and reduce the dispersion of magnetic properties.

The reference numeral 10 indicates a soft magnetic material according to another embodiment of implementation of the present invention. The soft magnetic material 10 is formed by an assembly of magnetic blocks 9 and has a through-hole 11 formed in the center thereof. In this arrangement, the productivity of the soft magnetic material 10 can be enhanced, an excellent quality can be provided, the dispersion of magnetic properties can be reduced, and the reduction of weight can be realized. The reference numeral 12 indicates a soft magnetic material according to other embodiment of implementation of the present invention. The soft magnetic material 12 is formed by an assembly of magnetic blocks 14 and the magnetic block 14 is a magnetic sheet comprising a laminate of sheets. In this arrangement, a flexible soft magnetic material resistant to impact can be prepared.

The reference numeral 15 indicates a soft magnetic material according to a further embodiment of implementation of the present invention. The soft magnetic material 15 is formed by an assembly of magnetic blocks 16 and the magnetic block 16 is a vertical laminate of two layers of magnetic bulk material. In this arrangement, any thickness can be coped with, making it easy to adjust the intensity of magnetic field.

The reference numeral 17 indicates a soft magnetic material according to a further embodiment of implementation of the present invention. The soft magnetic material 17 is formed by an assembly of magnetic block pieces 18 and the magnetic block 18 is in a trigonal column. In this arrangement, a variety of magnetic blocks can be used, making it possible to prepare a magnetic material at a high productivity and a reduced cost.

The reference numeral 19 indicates a soft magnetic material according to a further embodiment of implementation of the present invention. The soft magnetic material 19 is formed by an assembly of ferrite bulk materials 21 in the center thereof and an assembly of magnetic ferrite sheets 20 in the periphery thereof. In this arrangement, the intensity of magnetic field at the end of RFID can be raised, making it possible to eliminate skip zones during communication.

The reference numeral 6 indicates a resin spacer disposed under the soft magnetic material 5 and as the material of the resin spacer there may be selected a resin or the like, making it possible to attain the reduction of weight.

The reference numeral 7 indicates a metal sheet and as the material of the metal sheet there is preferably used a nonmagnetic material such as aluminum sheet.

The reference numeral 2 indicates a resin case (main body) and the reference numeral 8 indicates a resin case (back cover). The resin case (main body) 2 and the resin case (back cover) 8 are arranged to interpose parts such as antenna substrate and magnetic material, raising the ease of assembly during preparation and the dimensional precision of positioning and assembly of various elements and hence making it possible to eliminate the dispersion of properties.

In these arrangements, the productivity of the soft magnetic material 5 can be raised to provide a soft magnetic material having an excellent quality and little dispersion of properties, making it possible to obtain stable properties of RFID system and assure desired wireless range.

(Embodiment 4)

The reference numeral 1 indicates an antenna apparatus shown illustrating the internal structure of RFID system, the reference numeral 2 indicates a resin case (main body), the reference numeral 3 indicates an antenna pattern formed on the antenna substrate, the reference numeral 4 indicates a matching circuit, the reference numeral 5 indicates a soft magnetic material, the reference numeral 6 indicates a resin spacer, the reference numeral 7 indicates a metal sheet, and the reference numeral 8 indicates a resin case (back cover) . Firstly, in the structure of the antenna apparatus 1, the characteristics and advantage of the structures shown in the various drawings will be briefly described.

Fig. 34(a) depicts an exploded perspective view of an antenna apparatus according to the present embodiment of implementation of the present invention. Disposed under the antenna substrate having the antenna pattern 3 and the matching circuit 4 formed thereon is the soft magnetic material 5. Disposed under the soft magnetic material 5 are the resin spacer 6 and the metal sheet 7. The aforementioned parts are received in the resin case (main body) 2 and the resin case (back cover) 8. The soft magnetic material 5 has a through-hole provided in the center thereof to reduce the weight of RFID system, making it possible to exert an effect of assuring desired wireless range while inhibiting the change of resonance frequency or the rise of loss due to eddy current generated in the metal present on the back of RIFD system. Fig. 34(b) depicts a plan view of the soft magnetic material according to the present embodiment of implementation of the present invention. Fig. 34(c) depicts a side view of the soft magnetic material according to the present embodiment of implementation of the present invention. Fig. 34(d) depicts a perspective view of the soft magnetic material according to the present embodiment of implementation of the present invention.

Fig. 35 (a) depicts a plan view of the soft magnetic material according to the present embodiment of implementation of the present invention. Fig. 35(b) depicts a side view of the soft magnetic material according to the present embodiment of implementation of the present invention. Fig. 35(c) depicts a perspective view of the soft magnetic material according to the present embodiment of implementation of the present invention. In this arrangement, the weight of the soft magnetic material can be reduced, and since the soft magnetic material has a fallen portion 10 formed in the center thereof, a part of the soft magnetic material is a planar continuous structure, making it possible to prevent the deterioration of strength thereof.

Fig. 36(a) depicts a plan view of the soft magnetic material according to the present embodiment of implementation of the present invention. Fig. 36(b) depicts a side view of the soft magnetic material according to the present embodiment of implementation of the present invention. Fig. 36(c) depicts a perspective view of the soft magnetic material according to the present embodiment of implementation of the present invention. In this arrangement, the weight of the soft magnetic material can be reduced, and since the soft magnetic material has a fallen portion formed on the both surfaces of the center thereof, a part of the soft magnetic material is a planar continuous structure, making it possible to prevent the deterioration of strength thereof.

Fig. 37(a) depicts a plan view of the soft magnetic material according to the present embodiment of implementation of the present invention. Fig. 37(b) depicts a side view of the soft magnetic material according to the present embodiment of implementation of the present invention. Fig. 37(c) depicts a perspective view of the soft magnetic material according to the present embodiment of implementation of the present invention. In this arrangement, the desired strength can be maintained while attaining the reduction of weight of the soft magnetic material. Fig. 38(a) depicts a plan view of the soft magnetic material according to the present embodiment of implementation of the present invention. Fig. 38(b) indicates a side view of the soft magnetic material according to the present embodiment of implementation of the present invention. Fig. 38(c) indicates a perspective view of the soft magnetic material according to the present embodiment of implementation of the present invention. In this arrangement, a variety of antenna patterns can be coped with while attaining the reduction of weight of the soft magnetic material.

Fig. 39(a) indicates a plan view of the soft magnetic material according to the present embodiment of implementation of the present invention. Fig. 39(b) indicates a side view of the soft magnetic material according to the present embodiment of implementation of the present invention. Fig. 39(c) indicates a perspective view of the soft magnetic material according to the present embodiment of implementation of the present invention. The soft magnetic material 22 comprises two or more layers of soft magnetic material 17 laminated on each other. The reference numeral 16 indicates a joint comprising a laminate of soft magnetic material layers 17. In this arrangement, the thickness can be reduced while attaining the reduction of weight of the soft magnetic material. Fig. 40(a) depicts a sectional view of a related art antenna apparatus. Fig. 40(b) depicts a sectional view of the antenna apparatus according to the present embodiment of implementation of the present invention. Even a through-hole is formed in the soft magnetic material, the intensity of magnetic field cannot be reduced, making it possible to assure the desired wireless range. Further, an effect can be maintained of inhibiting the change of resonance frequency or the rise of loss due to eddy current generated in the metal present on the back thereof.

The outline and point of the structure of the various drawings have been described above.

Next, the detail of the various parts will be described. The reference numeral 1 indicates an antenna apparatus shown illustrating the internal structure of RFID system which comprises a resin case (main body) 2, an antenna pattern 3 formed on the antenna substrate, a matching circuit 4, a soft magnetic material 5, resin spacer 6, a metal sheet 7 and a resin case (back cover) 8 as shown in Fig. 34.

The reference numeral 3 is an antenna pattern having a loop antenna structure. Referring to the structure of the loop antenna, the loop antenna may be a loop having an opening provided in the center thereof and may be in the form of circle, substantial rectangle or polygon. Further, the material of the loop antenna may be properly selected from the group consisting of electrically-conductive metal wire, metallic sheet, metallic foil, metallic cylinder, etc. The reference numeral 4 indicates a matching circuit, and the connection of the matching circuit 4 makes it less likely that the antenna properties can be affected by metal present around the installation place and can prevent the occurrence of stationary wave due to nonmatching, making it possible to provide an antenna having stable operation and little loss.

The reference numeral 5 indicates a soft magnetic material, the soft magnetic material 5 is disposed on the back surface of the antenna pattern 3, and as the material thereof there may be used a soft magnetic ferrite, amorphous alloy, permaloy, electromagnetic steel, silicon steel, Fe-Al alloy, sendust alloy or the like. Referring to the shape of the soft magnetic material, if ferrite is used, a tabular or sheet-like soft magnetic material may be used. The sheet-like ferrite may be prepared by kneading a ferrite powder with an organic binder such as resin material, and then drying the mixture. The use of the magnetic sheet makes it possible to assure flexibility and enhance impact resistance or durability. The reference numeral 9 indicates a through-hole provided in the center of the soft magnetic material 5. The provision of the through-hole makes it possible to reduce the weight of the soft magnetic material.

The reference numeral 18 indicates a soft magnetic material according to another embodiment of implementation of the present invention comprising a fallen portion 10 formed on one surface of the center thereof. In this arrangement, the desired strength can be maintained while attaining the reduction of weight of the soft magnetic material.

The reference numeral 19 indicates a soft magnetic material according to other embodiment of implementation of the present invention having a fallen portion 11 formed on the both surfaces of the center thereof. In this arrangement, the desired strength can be maintained while attaining the reduction of weight of the soft magnetic material.

The reference numeral 20 indicates a soft magnetic material according to a further embodiment of implementation of the present invention having a through-hole formed on one surface of the center thereof filled with a nonmagnetic resin 13 such as resin. In this arrangement, the desired strength can be maintained while attaining the reduction of weight of the soft magnetic material.

The reference numeral 21 indicates a soft magnetic material according to a further embodiment of implementation of the present invention the through-hole 14 provided in the center of which is in columnar form. The through-hole 14 is not limited to this shape and may be in any other shape. The shape of the through-hole 14 can be freely changed to cope with various antenna patterns.

The reference numeral 22 indicates a soft magnetic material according to a further embodiment of implementation of the present invention illustrating a through-hole 15 provided in the center thereof. The soft magnetic material 22 comprises a plurality of layers of soft magnetic material 17 laminated on each other. The reference numeral 16 indicates a joint comprising a laminate of soft magnetic material layers. The reference numeral 6 indicates a resin spacer disposed under ^"the soft magnetic material 5 and as the material of the resin spacer there may be selected a resin or the like, making it possible to attain the reduction of weight.

The reference numeral 7 indicates a metal sheet and as the material of the metal sheet there is preferably used a nonmagnetic material such as aluminum sheet. The reference numeral 2 indicates a resin case (main body) and the reference numeral 8 indicates a resin case (back cover). The resin case (main body) 2 and the resin case (back cover) 8 are arranged to interpose parts such as antenna substrate and magnetic material, raising the ease of assembly during preparation and the dimensional precision of positioning and assembly of various elements and hence making it possible to eliminate the dispersion of properties.

In accordance with the antenna apparatus 1 of RFID system having the aforementioned arrangement, the weight reduction can be attained and trxe desired wireless range can be assured while inhibiting the change of resonance frequency or the rise of loss due to eddy current generated in the metal present on the back of RIFD system. This application is based upon and claims the benefit of priorities of Japanese

Patent Application Nos. 2004-283886 filed on September 29, 2004; 200-4-287050 filed on September 30, 2004; 2004-365716 filed on December 17, 2004; and 2004-365726 filed on December 17, 2004, the contents of which are incorporated herein by reference in its entirety.

Industrial Applicability

According to the present invention, a magnetic sheet is arranged to exhibit the maximum magnetic properties while maintaining the least required physical properties as magnetic sheet.

Claims

1. A magnetic sheet comprising: a plurality of magnetic blocks having magnetic properties and being in block form; and a flexible sheet substrate, wherein the aforementioned plurality of magnetic blocks are arranged planarly to form a magnetic layer and the aforementioned sheet substrate retains the aforementioned magnetic layer.

2. The magnetic sheet of Claim 1, wherein the aforementioned magnetic layer is formed by the aforementioned magnetic blocks having substantially the same shape.

3. The magnetic sheet of Claim 1, wherein the aforementioned magnetic layer is formed by the aforementioned magnetic blocks having different shape.

4. The magnetic sheet of Claim 1, wherein the aforementioned sheet substrate is in sheet form and retains at least one surface of the aforementioned magnetic layer.

5. The magnetic sheet of Claim 1, wherein the plurality of magnetic blocks are obtained by forming ferrite-based magnetic powder in block.

6. The magnetic sheet of Claim 5, wherein the aforementioned plurality of magnetic blocks are obtained by forming the aforementioned soft magnetic ferrite- based magnetic powder in block.

7. The magnetic sheet of Claim 1, wherein the plurality of magnetic blocks comprise at least one aforementioned magnetic block arranged adjacent to other aforementioned magnetic block at a predetermined interval.

8. The magnetic sheet of Claim 1, wherein the plurality of magnetic blocks comprise at least one aforementioned magnetic block arranged adjacent to other aforementioned magnetic block with the aforementioned sheet substrate interposed therebetween.

9. The magnetic sheet of Claim 1, wherein the plurality of magnetic blocks comprise at least one aforementioned magnetic block arranged adjacent to and in contact with other aforementioned magnetic block.

10. The magnetic sheet of Claim 1, wherein the plurality of magnetic blocks form a laminate of a plurality of the aforementioned magnetic layers.

11. The magnetic sheet of Claim 1, wherein the aforementioned sheet substrate includes the aforementioned magnetic layer.

12. The magnetic sheet of Claim 1, wherein a through-hole is provided in tlie center of the aforementioned magnetic layer.

13. The magnetic sheet of Claim 1, wherein a fallen portion is provided on at least one surface of the aforementioned magnetic layer at the center thereof.

14. An antenna apparatus comprising: a magnetic sheet of Claim 1; and an antenna provided on at least one of the aforementioned sheet substrate and tfcie aforementioned magnetic layer of the aforementioned magnetic sheet.

15. The antenna apparatus of Claim 14, wherein the aforementioned antenna is in loop form.

16. The antenna apparatus of Claim 14, wherein the aforementioned antenna is an antenna pattern formed by any of metal foil, electrically-conductive paste, deposit transfer, sputtering, vacuum deposition and screen printing.

17. A magnetic sheet comprising: an antenna; and a soft magnetic material obtained by molding a baked magnetic powder into a planar form, wherein a through-hole is provided in the center of the aforementioned soft magnetic material.

18. A method of producing a magnetic sheet which comprises: molding a magnetic powder in a block form, baking the aforementioned magnetic powder thus molded to form a plurality of magnetic blocks, and retaining a magnetic layer, which comprises the aforementioned plurality of magnetic blocks arranged planarly, by a flexible sheet substrate.