|
(11) | EP 1 814 191 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
|
|
|
|
|||||||||||||||||||||||
| (54) | Antenna apparatus |
| (57) An antenna apparatus includes a magnetic sheet and an antenna that is provided in
the magnetic sheet and has a looped conductor and terminal electrode parts arranged
at both ends of the conductor, and a matching circuit that is provided in the magnetic
sheet, includes a first capacitor and a second capacitor each of which has a pair
of electrodes, and sets a resonant frequency by the antenna and the first and second
capacitors. One electrode of the pair of electrodes of the first capacitor is connected
to one of the terminal electrode parts, and the other electrode of the pair of electrodes
of the first capacitor is connected to the looped conductor. One electrode of the
pair of electrodes of the second capacitor is connected to the other one of the terminal
electrode parts, and the other electrode of the pair of electrodes of the second capacitor
is connected to the looped conductor.
|
BACKGROUND
[0001] The present invention relates to a radio communication medium processor that performs communication with radio communication media, such as RFIDs, i.e., IC cards, and IC tags, or an antenna apparatus used for the radio communication media themselves.
[0002] In a related art, since a radio communication processor that performs communication with radio communication media by an electromagnetic induction method, etc., or an antenna apparatus used for the radio communication media themselves has a weakened magnetic field under the influence of its surrounding metal, the mutual inductance required for communication is inadequate. Therefore, there are hindrances that a communication distance becomes short or communication becomes impossible. Thus, in order to make the processor or antenna apparatus hardly affected by a metal, a method of making the antenna and the metal spaced apart from each other by a resin spacer, etc., or making a magnetic material, such as ferrite, installed in contiguity with or in abutment with the antenna, thereby strengthening a magnetic field emitted from the antenna, has been contrived. As such, as a technique of strengthening the magnetic field of an antenna and giving durability against breakage to the antenna, a patent document (JP-A-2002-298095) suggests, for example, that a magnetic body having flexibility is installed in a bottom face or side face of the antenna.
[0003] Further, combining a matching circuit with an antenna is also considered. Fig. 13 is an exploded perspective view of an antenna apparatus related to a related art. Fig. 14 is an enlarged view of a matching circuit related to the related art. Fig. 15 is an equivalent circuit diagram of the antenna apparatus related to the related art. As shown in Figs. 13 and 14, a method of making a magnetic sheet 102 made of ferrite, etc. installed in contiguity with or in abutment with an antenna 103, thereby strengthening the magnetic field emitted from the antenna 103 emits has been contrived in a conventional antenna apparatus. Moreover, in order to mount a chip capacitor 110 used for the matching circuit 104, a through hole 109 is formed in the magnetic sheet 102. However, there is a case where the magnetic sheet 102 is largely hollowed out depending on the above configuration, and consequently the magnetic field cannot be sufficiently strengthened. Since the inductance value of an equivalent circuit shown in Fig. 15 becomes 1.6 µH when a coil of four turns is used and the magnetic sheet 102 is used, the resultant capacitance from C1 to C4 becomes about 100 pF. In this case, in order to adjust a resonant frequency within a desired range, it is necessary to adjust the resultant capacitance of the capacitors with a predetermined degree of accuracy. For example, when the range of the resonant frequency is set to 13.56 ± 50 kHz, about ± 0.5 pF is required as the degree of accuracy of the resultant capacitance. In order to realize this, it is necessary to use capacitors having a small capacitance tolerance. This causes a problem in that the operation of sorting out capacitors so that the degree of accuracy of the resultant capacitance of the capacitors may be set within a predetermined range (about ± 0.5 pF), which may increase the cost of an antenna apparatus, is needed. This results in a situation where the productivity of antenna apparatuses cannot be improved.
[0004] In order to ensure communicative stability in the radio communication processor that performs communication with various radio communication media, and the radio communication media themselves, it is necessary to adjust the resonant frequency of an antenna apparatus to a desired frequency (for example, 13.56 MHz). Since the resonant frequency of the antenna apparatus may be apt to deviate depending on the shape of an antenna, the size of a magnetic material, or the magnetic permeability of the magnetic material, it is necessary to carefully select chip capacitors of a matching circuit to adjust the resonant frequency of the antenna apparatus precisely. However, for the purpose of an improvement in the communication distance in the conventional antenna apparatus, the inductance value of an antenna is increased, or the thickness of a magnetic sheet is made large. Therefore, the capacitance of capacitors that adjust the resonant frequency of the antenna is made low. Therefore, high-precision capacitors having a small capacitance tolerance should be mounted on the matching circuit. Moreover, a process of sorting out the capacitors is needed. The process of sorting out the capacitors is very complicated. Mounting high-precision capacitors on an antenna apparatus, and necessitating the process of sorting out capacitors in the manufacture of an antenna apparatus poses a very big problem about cost reduction of the antenna apparatus.
SUMMARY
[0005] The present invention have been made in view of the aforementioned problems, and aim at providing an antenna apparatus that is low in cost, simple in structure, high in productivity, and capable of easily performing adjustment of a resonant frequency, in an antenna that communicates using an electromagnetic induction method or a microwave method.
[0006] According to the present invention, an antenna apparatus includes: an antenna (3) that has a looped conductor, and a matching circuit (4) that includes a first capacitor (10) and a second capacitor (10) each of which has a pair of electrodes, and that sets a resonant frequency by the antenna (3) and the first and second capacitors (10), wherein one electrode of the pair of electrodes of the first capacitor (10) is connected to one end of the looped conductor, and the other electrode of the pair of electrodes of the first capacitor (10) is connected to the looped conductor, and wherein one electrode of the pair of electrodes of the second capacitor (10) is connected to the other end (5) one of the looped conductor, and the other electrode of the pair of electrodes of the second capacitor (10) is connected to the looped conductor.
[0007] Since the above configuration makes it possible to form a resonant circuit with each of the first and second capacitors, the capacitance per capacitor can be set greatly compared with a case where terminal electrodes are connected to each other by a capacitor to form a resonant circuit. For example, even in a case where high precision is required for setting of a resonant frequency, the productivity of an antenna apparatus can be improved because the allowable range of the capacitance per capacitor can be extended.
[0008] Further, an embodiment related to a magnetic sheet of the antenna apparatus to be described below has a configuration in which a magnetic sheet includes a magnetic layer in which a magnetic material is continuously arranged and formed, and a sheet base (53) with flexibility, and the sheet base (53) holds the magnetic layer.
[0009] According to the above configuration, since the magnetic sheet has a magnetic layer in which a magnetic material is continuously arranged and formed, the magnetic function of the magnetic sheet can be improved and therefore variations in magnetic properties can be suppressed. Further, since the sheet base holds the magnetic layer, it is possible to provide a magnetic sheet that satisfies physical performances, such as flexibility.
[0010] Further, an embodiment related to an antenna apparatus to be described below has a configuration in which an antenna apparatus includes a magnetic sheet (2) and an antenna (3) consisting of looped antenna elements arranged in proximity to the magnetic sheet (2), and the outside dimension of the magnetic sheet (2) is larger than the outside dimension of the antenna (3).
[0011] Since the above configuration is a simple configuration in which the outside dimension of the magnetic sheet is made larger than the outside dimension of the antenna, fluctuation of a resonant frequency can be suppressed. Accordingly, generation of defective art icles caused by deviation of a resonant frequency in a manufacturing process can be reduced, and the productivity can be improved. Accordingly, the cost-reducing effect of an antenna apparatus can be expected. Also, since high precision is not required for alignment of the magnetic sheet with the antenna, and an inexpensive measure that only one side of the base may be used can be taken, the cost of an antenna apparatus can also be reduced from this point of view. In addition, since the stability of communication improves, the communication range of an antenna apparatus can be ensured, and a communication distance can be extended.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012]
Fig. 1 is a perspective view of an antenna apparatus according to Embodiment 1.
Fig. 2 is a sectional view showing the structure of the antenna apparatus according to Embodiment 1.
Fig. 3 is an enlarged view of a matching circuit according to Embodiment 1.
Fig. 4 is an equivalent circuit diagram according to Embodiment 1.
Fig. 5 is an enlarged view of the matching circuit according to Embodiment 1.
Fig. 6 is an enlarged view of the matching circuit according to Embodiment 1.
Fig. 7 is an enlarged view of the matching circuit according to Embodiment 1.
Fig. 8 is an enlarged view of the matching circuit according to Embodiment 1.
Fig. 9 is a sectional view of a magnetic sheet according to Embodiment 1.
Fig. 10 is a sectional view of a matching circuit according to Embodiment 1.
Fig. 11 is a sectional view of a matching circuit according to Embodiment 1.
Fig. 12 is a sectional view when a roller according to Embodiment 1 is used.
Fig. 13 is an exploded perspective view of an antenna apparatus in a related art.
Fig. 14 is an enlarged view of a matching circuit in the related art.
Fig. 15 is an equivalent circuit diagram of the antenna apparatus in the related art.
Fig. 16 shows comparison between the communication performance of the antenna apparatus according to Embodiment 1 and the communication performance of a conventional antenna apparatus.
Fig. 17 is an exploded perspective view illustrating an antenna apparatus according to Embodiment 2.
Fig. 18 is a sectional view, taken along an A-A line, of a matching circuit portion shown in Fig. 17.
Fig. 19 is an enlarged view showing an exemplary configuration of a matching circuit in a case where a looped antenna element that constitutes the antenna shown in Fig. 17 makes four turns.
Fig. 20 is an equivalent circuit diagram of an antenna in a case where a looped antenna element that constitutes the antenna shown in Fig. 17 makes four turns.
Fig. 21 shows the change characteristics of a resonant frequency when the outside dimension of the magnetic sheet shown in Fig. 17 is changed to a dimension around the outside dimension of the antenna.
Fig. 22 is a sectional view showing the configuration of an antenna apparatus according to Embodiment 3.
Fig. 23 shows comparison between the change characteristics of a resonant frequency when the outside dimension of the magnetic sheet is changed to a dimension around the outside dimension of an antenna, in a case where the low magnetic-permeability layer is provided between the antenna and the magnetic sheet shown in Fig. 22, and in a case where the antenna and the magnetic sheet are brought into close contact with each other.
Fig. 24 is a sectional view showing the configuration of an antenna apparatus according to Embodiment 4.
Fig. 25 shows comparison between the change characteristics of a resonant frequency when the outside dimension of the magnetic sheet is changed to a dimension around the outside dimension of an antenna, in a case where the low magnetic-permeability layer is provided between the magnetic sheet and the metal member shown in Fig. 24, and in a case where the magnetic sheet and the metal member are brought into close contact with each other.
Fig. 26 is a sectional view showing the configuration of an antenna apparatus according to Embodiment 5.
Fig. 27 shows comparison between the change characteristics of a resonant frequency when the outside dimension of the magnetic sheet is changed to a dimension around the outside dimension of an antenna, in a case where the low magnetic-permeability layers are provided between the antenna and the magnetic sheet and between the magnetic sheet and the metal member, respectively, shown in Fig. 24, and in a case where the antenna and the magnetic sheet are brought into close contact with each other and the magnetic sheet and the metal member are brought into close contact with each other, without providing the low magnetic-permeability layers therebetween.
Fig. 28 is an exploded perspective view of a magnetic sheet according to Embodiment 6.
Fig. 29 is a sectional view of the magnetic sheet according to Embodiment 6.
Fig. 30 is a sectional view of the magnetic sheet according to Embodiment 6.
Fig. 31 is a sectional view of the magnetic sheet according to Embodiment 6.
Fig. 32 is a sectional view of the magnetic sheet according to Embodiment 6.
Fig. 33 is a sectional view of the magnetic sheet according to Embodiment 6.
Fig. 34 is a view showing a manufacturing process of the magnetic sheet according to Embodiment 6.
Fig. 35 is a sectional view of a magnetic sheet according to Embodiment 7.
Fig. 36 is a view showing a manufacturing process of the magnetic sheet according to Embodiment 7.
Fig. 37 is a sectional view of a magnetic sheet according to Embodiment 8.
Fig. 38 is a view showing a manufacturing process of the magnetic sheet according to Embodiment 8.
Fig. 39 is a sectional view of a magnetic sheet according to Embodiments 9 and 10.
Fig. 40 is a view showing a manufacturing process of the magnetic sheet according to Embodiment 9.
Fig. 41 is a view showing a manufacturing process of the magnetic sheet according to Embodiment 10.
Fig. 42 is a sectional view of a magnetic sheet according to Embodiment 11.
Fig. 43 is a view showing a manufacturing process of the magnetic sheet according to Embodiment 11.
Fig. 44 is a view showing a manufacturing process of the magnetic sheet according to Embodiment 11.
Fig. 45 is a sectional view of a magnetic sheet according to Embodiment 12.
Fig. 46 is a view showing a manufacturing process of the magnetic sheet according to Embodiment 12.
Fig. 47 is a view showing a manufacturing process of the magnetic sheet according to Embodiment 12.
DETAILED DESCRIPTION
[0013] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
(Embodiment 1)
[0014] First, the shape and structure of an antenna apparatus of the present invention and structure will be described.
[0015] As shown in Fig. 1, an antenna apparatus 1 is comprised of a magnetic sheet 2 mainly composed of a ferrite-based magnetic substance, protective members 7 and 8 arranged so as to sandwich the magnetic sheet 2 therebetween, an antenna 3, a matching circuit 4, terminal connecting parts 5, a base 6, and chip capacitors 10a and 10b for matching. The antenna apparatus 1 may be contained in a radio communication medium, such as an IC card or an IC tag, and may be contained in a radio communication medium processor, such as a reader or a writer.
[0016] First, each of the parts that constitute the antenna apparatus 1 will be described in detail.
[0017] The magnetic sheet 2 has a form that constitutes an element of the antenna apparatus 1, and is made of a metallic material, such as ferrite, permalloy, sendust, or silicon alloy sheet. It is preferable to use a soft magnetic ferrite as a material that constitutes the magnetic sheet 2, and it is possible to dry-press and bake ferrite powder, thereby obtaining a high-density ferrite baked body. It is preferable that the density of the soft magnetic ferrite be 3.5 g/cm3 or more. Moreover, it is preferable that the size of a magnetic substance composed of the soft magnetic ferrite be more than a crystal grain boundary. Further, the magnetic sheet 2 is formed in the shape of a sheet (or a plate, a film, or a layer) having a thickness of about 0.05 mm to 3 mm.
[0018] The soft magnetic ferrite may be composed of Ni-ZnO3, ZnO, NiO, CuO, Fe2O3, ZnO, MnO, or CuO. Moreover, the soft magnetic ferrite may be a monolayer made of any one of magnetic substances including an amorphous alloy, a permalloy, electromagnetic copper, ferrosilicon, an Fe-Al alloy, and a sendust alloy. Further, the soft magnetic ferrite may be a laminated body of ferrite, an amorphous foil, a permalloy, electromagnetic copper, and a sendust. Further, the soft magnetic ferrite may be a laminated body obtained by combining various magnetic substances. Further, the soft magnetic ferrite may be obtained by coating a simple body of ferrite, an amorphous alloy, a permalloy, electromagnetic copper, ferrosilicon, an Fe-A1 alloy, or a sendust alloy, as shown in Fig. 9, or a laminated body as shown in Fig. 10, with at least one means of resin, an ultraviolet curable resin, a visible light curable resin, a thermoplastic resin, a thermosetting resin, a heat-resistant resin, a synthetic rubber, a double-sided tape, an adhesion layer, or a film. Further, a simple body and a laminated body of ferrite, an amorphous foil, a permalloy, electromagnetic copper, or a sendust may be an aggregate of magnetic blocks 18, as shown in fig. 11. By arranging the blocks, a magnetic substance can be efficiently formed with respect to the total thickness of the magnetic sheet 2. Moreover, by arranging all the magnetic blocks 18 so that their upper and lower sides may become almost the same plane, the maximum volume of a magnetic substance can be utilized in a range of the thickness dimension, mechanical strength, other physical performances that are required for the magnetic sheet 2, and consequently a high magnetic performance can be obtained.
[0019] The magnetic sheet 2 is made up of a single magnetic layer, multiple magnetic layers, or magnetic blocks as shown in Figs. 9 to11. As shown in Fig. 9 to 11, the magnetic sheet 2 is coated by the protective members 7 and 8 (for example, resin, an ultraviolet curable resin, a visible light curable resin, a thermoplastic resin, a thermosetting resin, a heat-resistant resin, a synthetic rubber, a double-sided tape, an adhesion layer, or a film, etc.), so that the flexibility, durability, and surface resistance thereof can be improved. Further, it is possible to form a circuit by performing pattern printing, plating, etc. on the surfaces of the protective members 7 and 8.
[0020] Further, since the magnetic sheet 2 coated by the protective members 7 and 8 has excellent flexibility, it can be easily blanked and formed by punching, etc. Accordingly, the magnetic sheet also has features that working of a complicated shape can also be performed at low cost, and in large amounts. By punching the magnetic sheet 2, as shown in Figs. 2 and 3, the matching circuit 4 and the terminal connecting parts 5 can be provided in an opening 7a of the magnetic sheet 2.
[0021] The matching circuit 4 is configured by mounting a conductor of the looped antenna 3 and the chip capacitors 10a and 10b, which are formed in the base 6, as shown in Fig. 3. This allows the matching circuit 4 to be formed on the antenna 3. Although the matching circuit 4 is conventionally formed in a space separate from the antenna 3, the antenna apparatus 1 can be miniaturized by forming the matching circuit 4 on the antenna 3. Therefore, since the opening 7a of the magnetic sheet 2 can be made small, the antenna apparatus 1 having excellent magnetic properties can be realized.
[0022] Further, since a baked body of the magnetic sheet 2 is ordinarily very brittle, the antenna 3, the matching circuit 4, and the terminal connecting parts 5 cannot be formed on the baked body. However, by coating the magnetic sheet 2 in advance with resin, an ultraviolet curable resin, a visible light curable resin, a thermoplastic resin, a thermosetting resin, a heat-resistant resin, a synthetic rubber, a double-sided tape, an adhesion layer, or a film, the antenna 3, the matching circuit 4, and the terminal connecting parts 5 can be formed on the magnetic sheet 2, so that the antenna apparatus 1 can be made small and thin. In addition, the magnetic sheet 2 may be formed in the shape of a substantially triangular prism, a substantially quadrangular prism, a substantial cylinder, a substantial sphere, etc.
[0023] The magnetic sheet 2 of the present invention, as shown in Fig. 12, is fixed to a double-sided tape or a fine adhesive tape, and crushed by the roller 19, so that flexibility can be given to the magnetic sheet 2. Further, since crushing of the sheet by the roller 19 improves the workability of the magnetic sheet 2 and reduces a load at the time of working, cost reduction of products can also be realized. Moreover, as the magnetic sheet 2 is crushed by the roller 19, voids are formed in the magnetic sheet 2. Then, when resin is printed on the magnetic sheet 2, the resin permeates into the magnetic sheet 2, serving as a binder. As a result, flexibility can be further given to the magnetic sheet 2. Further, the magnetic sheet 2 is provided with slits, so that the magnetic sheet 2 can be easily divided. Accordingly, the magnetic sheet 2 having excellent flexibility and workability can be realized. The chip capacitors 10a correspond to first and second capacitors, and connect the terminal connecting parts 5 with the conductor of the antenna 3. The chip capacitor 10b corresponds to a third capacitor, and connects adjoining conductors of the antenna 3 with each other. In the following description, if the chip capacitors 10a and 10b are not distinguished from each other, these are simply called "chip capacitor 10."
[0025] The antenna 3 is an antenna pattern and is formed from a looped conductor. As the structure of the looped conductor, the conductor has only to be formed in a surrounding shape, and their shape is not limited to a spiral shape. Further, the shape of the loop may be any of a circular shape, a substantially rectangular shape, or a polygonal shape. The loop structure of the antenna causes a sufficient magnetic field to be generated, thereby allowing communication between a radio communication medium and a radio communication medium processor by generation of induced powder and mutual inductance.
[0026] Further, since the surface resistance of the magnetic sheet 2 is large, a circuit can be directly formed on the surface of or inside the magnetic sheet 2. Thus, it is possible to directly form the antenna 3, the matching circuit 4, and the terminal connecting parts 5 in the magnetic sheet 2.
[0027] Moreover, a material for the antenna can be appropriately selected from a conductive metal wire, a metallic plate material, a metallic foil material, and a metallic cylinder material, such as gold, silver, copper, aluminum, and nickel, and the antenna can be formed by a metal wire, a metallic foil, conductive paste, plating transfer, sputtering, vapor deposition, or screen printing. Thereby, it is conventionally necessary to form the antenna 3 and the magnetic sheet 2 separately, whereas the antenna 3, the matching circuit 4, or the terminal connecting parts 5 can be formed integrally with the magnetic sheet 2. Thus, a very thin antenna apparatus 1 can also be formed.
[0028] Further, the base 6 provided with the antenna 3 can be formed from polyimide, PET, a glass epoxy substrate, etc. By forming the base from polyimide, PET, etc., it is possible to form a thin flexible antenna 3. Further, since the cost of films of polyimide, PET, etc. is low, a low-cost antenna apparatus 1 can be manufactured.
[0030] The matching circuit 4 is connected to the antenna 3, whereby the resonant frequency of an antenna is adjusted to a desired frequency, generation of a stationary wave caused by mismatching is suppressed. Thereby, it is possible to obtain an antenna apparatus 1 with stable operation and little loss. As shown in Fig. 3, the chip capacitors 10a and 10b used as matching elements are mounted so that they may serve as an intermediary between the conductors of the looped antenna 3. Examples of the mounting position of the chip capacitor 10 are shown in Figs. 3A and 3B. The chip capacitors 10a and 10b are arranged linearly in one straight line or in a zigzag pattern between the two terminal connecting parts 5. This can reduce the opening of the magnetic sheet 2, and can improve the magnetic properties of the antenna apparatus 1. As for the arrangement of the chip capacitors 10a and 10b, they may be mounted in arbitrary places of the antenna 3. In that case, a terminal connecting part of the antenna 3 becomes a connecting part between one terminal part of a chip capacitor and the antenna 3. If formation of the opening of the magnetic sheet 2 is considered, it is preferable that the chip capacitors 10a and 10b are arranged as shown in Figs. 3A and 3B. A case where a loop makes four turns will be described as an example. An equivalent circuit of Fig. 3A takes a form as shown in Fig. 4A, and can adjust its capacitance to about 4 times the capacitance of a conventional capacitor. The values of L1 to L4 are inductance values in every round of a loop, and become about 0.4 µH as values calculated experimentally. When chip capacitors having the same capacitance value are mounted, the capacitors C1 to C4 have a capacitance of about 400 pF, whereby adjustment to a desired frequency can be made. An equivalent circuit of Fig. 3B takes a form as shown in Fig. 4B, and can adjust its capacitance to about twice the capacitance of a conventional capacitor. The values of L5 and L6 are inductance values for two rounds of a loop, and become about 0.8 µH that is twice the values of L1 to L4. When chip capacitors having the same capacitance value are mounted, the capacitors C5 to C6 have a capacitance of about 200 pF, whereby adjustment to a desired frequency can be made. When both ends of a looped conductor are connected with each other by a capacitor as in the related art, the capacitance of the capacitor required to make adjustment to a desired frequency becomes about 100 pF, and almost coincides with the resultant capacitance of C1 to C4 or C5 to C6. In this case, if the resultant capacitance of a capacitor is adjusted with a predetermined degree of precision, for example, if the range of a resonant frequency is set to 13.56 ± 50 kHz, the degree of precision of the resultant capacitance is about ± 2 pF (4 x ±0.5 pF), which is enough.
[0031] For this reason, by mounting capacitors having different capacitances as well as capacitors having the same capacitance, the four chip capacitors can adjust a resultant capacitance and can adjust a resonant frequency. Therefore, by changing the combination of the capacitances of C1 to C4 or C5 to C6, fine adjustment of a frequency can be made, thereby improving productivity. Figs. 5 to 8 are enlarged views of the matching circuit in Embodiment 1. Referring to these figures, fine adjustment after the chip capacitors 10a and 10b are mounted can be made by adjusting a distributed constant circuit. Fig. 5 shows an example where a capacitor 12 is arranged between a terminal connecting part 5 and an antenna adjacent thereto. An equivalent circuit takes a form where capacitors are connected in parallel with C1 and C4. As a result, adjustment of C1 and C4 can be made. Although Fig. 5 shows that the capacitors 12 are formed in both the terminal connecting parts 5, respectively, a configuration where a capacitor 12 is formed only in one terminal connecting part 5 may be adopted. Fig. 6 shows an example where patterns 13 that can adjust inductance are arranged in the terminal connecting parts 5, and portions of the patterns 13 as distributed constant circuits can be trimmed so as to finely adjust an inductance value. An equivalent circuit takes such a form that L1 and L4 can be adjusted. Although Fig. 6 shows that the patterns 13 that can adjust inductance are formed in both the terminal connecting parts 5, a configuration where a pattern is formed only in one terminal connecting part may be adopted. Fig. 7 shows an example where one of the patterns 13 shown in Fig. 6 is replaced with a chip capacitor for frequency adjustment. An equivalent circuit has capacitance L that can adjust L1, and has a configuration in which capacitors 15 for fine adjustment are connected in parallel with C4. Although three capacitors 15 for fine adjustment are mounted in the example shown in Fig. 7, one or plural capacitors may be mounted. The capacitors 15 for fine adjustment can be finely adjusted by performing trimming 14. Fig. 8 shows a configuration in which a stub 16 is connected to a terminal connecting part 5. An equivalent circuit takes such a form that a capacitor is added to grounding from a terminal part. By trimming this stub 16, grounding capacitance can be adjusted, and resonant frequency can be finely adjusted. Fine adjustment may be performed by combinations of the adjusting methods shown in Figs. 5 to 8.
[0033] Since the surface resistance of the magnetic sheet 2 is large, the terminal connecting parts 5 can be directly formed in the surface of the magnetic sheet 2. The terminal connecting parts 5 may be formed on both sides of a loop, and may be formed so that they may face each other at the ends of a loop.
[0034] Further, a material for the terminal connecting parts 5 can be appropriately selected from a conductive metal wire, a metallic plate material, a metallic foil material, and a metallic cylinder material, such as gold, silver, copper, aluminum, and nickel, and the terminal connecting parts can be formed by a metal wire, a metallic foil, conductive paste, plating transfer, sputtering, vapor deposition, or screen printing.
[0036] The base 6 can be formed from polyimide, PET, a glass epoxy substrate, etc. A thin flexible antenna 3 can be formed by forming the base 6 from polyimide, PET, etc. Further, since the cost of films of polyimide, PET, etc. is low, a low-cost antenna apparatus 1 can be manufactured.
[0037] Further, wiring can be made only on one side of the base 6 by mounting a capacitor between conductors of an antenna like the matching circuit 4. As a result, since a through hole, etc. becomes unnecessary, an inexpensive base can be used and low cost can be realized.
[0039] As a material for the protective members 7 and 8, at least one means of resin, an ultraviolet curable resin, a visible light curable resin, a thermoplastic resin, a thermosetting resin, a heat-resistant resin, a synthetic rubber, a double-sided tape, an adhesion layer, or a film can be used. Selection of the material used for the protective members 7 and 8 may be performed in consideration of not only flexibility against bending, deflection, etc. of the antenna apparatus 1 and each component that constitutes the antenna apparatus 1 but also weather resistances, such as thermal resistance and moisture resistance. Further, one surface, both surfaces, one side surface, both side surfaces, or whole surface of the antenna apparatus 1 or each component that constitutes the antenna apparatus 1 may be coated by the protective members 7 and 8.
[0040] Although the baked body of the magnetic sheet 2 is usually broken due to its bending, deflection, etc., the baked body will have flexibility by coating one surface, both surfaces, one side surface, both side surfaces, or whole surface of the baked body of the magnetic sheet 2 with the protective members 7 and 8, such as resin, an ultraviolet curable resin, a visible light curable resin, a thermoplastic resin, a thermosetting resin, a heat-resistant resin, a synthetic rubber, a double-sided tape, an adhesion layer, or a film. Moreover, when the surface resistance of the protective members 7 and 8 is high, it becomes easy to form a circuit by performing pattern printing, plating, etc. on the surfaces of the protective members.
[0041] Further, since the magnetic sheet 2 coated by the protective members 7 and 8 has moderate flexibility, the magnetic sheet can be blanked and formed easily by punching, etc. Thus, the magnetic sheet also has features that working of a complicated shape can also be performed at low cost, and in large amounts.
[0042] The baked body of the magnetic sheet 2 is made ofNi-Zn-based ferrite or Mn-Zn-based ferrite. Specifically, a baked body made ofNi-Zn-based ferrite is obtained by mixing 48.5 mol% of Fe2O3 , 20.55 mol% of ZnO, 20.55 mol% of NiO, and 10.40 mol% of CuO, and by baking the resulting mixture at a temperature ranging from 750 to 900 °C for 4 hours.
[0044] First, 3000 grams of a magnetic temporarily-baked powder having the above composition, 135 grams of Metalose 60SH4000 (made by Shin-Etsu Chemical Co., Ltd.) as a water-soluble binder, 270 grams of Cerami-Sol C-08 (made by Nippon Oil & Fats) as an oily plasticizer, and 340 grams of distilled water are mixed together by a mixer for 20 minutes, and the resulting mixture is passed through three rolls three times, and is made into a green body. After this green body is kept and aged at 5 °C for 96 hours, a sheet having a thickness of about 3 mm is manufactured by a vacuum extrusion molding apparatus.
[0045] Next, this sheet is dried by causing the surface of a drum drier having a temperature 95 °C to be passed over the sheet, and is cut with a predetermined dimension, thereby manufacturing a sheet having a thickness of 0.9 mm. Then, the resulting sheet is baked at 900 °C for 3 hours, thereby manufacturing a baked body having a thickness of 0.8 mm.
[0046] This baked body is adhered to a double-sided tape, and thereafter, a protective tape is adhered onto the baked body. Then, a roller 19 is passed on the baked body, crushing the baked body. Since the baked body is crushed so that flexibility is given to the magnetic sheet 2, making the magnetic sheet 2 soft, workability becomes good and the load at the time of working also decreases.
[0047] This crushed magnetic sheet 2 is punched by a press machine, etc. An opening is formed in the magnetic sheet 2 by performing punching.
[0048] Next, the sheet on the side of the double-sided tape of the magnetic sheet 2 is peeled off, and an antenna element in which the antenna 3 and chip capacitor 10 formed on the base 6 are integrated into one with solder is adhered to the double-sided tape of the magnetic sheet 2.
[0049] Finally, the resonant frequency of the antenna apparatus 1 is adjusted by performing trimming 14 on a distributed constant circuit that is a portion of the matching circuit 4 by a laser beam machining apparatus, if needed.
[0051] Further, when the antenna apparatus 1 is mounted on a small-sized terminal, such as a cellular phone, the antenna apparatus is adhered to a required place of a small portable terminal by coating the base 6 formed with a loop antenna with a double-sided tape, an adhesive, an adhesion layer, or resin.
[0052] Next, the result obtained by performing comparison between the communication performance of the antenna apparatus 1 according to Embodiment 1 and the communication performance of a conventional antenna apparatus 101 will be described with reference to Fig. 16. In an implementation, a substrate of the conventional antenna apparatus is used, a coil of four regular turns is used as a loop pattern of an antenna, and a communication distance is obtained by measuring the distance that can be recognized from the reader side using an RFID reader.
[0053] As a result, similarly to the conventional antenna apparatus 1, the antenna apparatus 1 of the present invention can strengthen its magnetic field intensity and can lengthen a communication distance and consequently ensure sufficient communication performance.
[0054] In addition, the antenna apparatus 1 of the present invention has chip capacitors having a higher capacitance as compared with the conventional antenna apparatus 101. Therefore, the effect to the frequency related to each capacitor falls, and high-precision capacitors or a sorting process becomes unnecessary. Thus, it is possible to form a low-cost antenna apparatus 1 having high productivity. Moreover, since the antenna 3 and the matching circuit 4 can be configured in the same plane, a single-sided substrate can be used in manufacturing a base. Thus, an inexpensive base can be used, and therefore a low-cost antenna apparatus can be realized.
[0055] In addition, by providing a metal member outside (a position where the magnetic sheet 2 along with an antenna is sandwiched) the antenna apparatus 1, there is a merit that the metal member has a role of shielding and can prevent leaking of a magnetic field emitted from the antenna to the outside. This is suitable to, for example, a case where communication is performed only with a radio communication medium that exists only inside the antenna.
[0056] The present invention can also be applied to radio communication medium processors that supply electric power and transmission data to radio communication media, such as non-contact IC cards or an IC tags, that are stored in a commodity rack, etc., and that acquire received data from the radio communication media depending on load fluctuation, and particularly to applications that are required to extend a communication range, such as a medicine management system, a hazardous material management system, and a valuables management system, other than a storage rack and an exhibition rack that allow automatic merchandise management, automatic book management, etc.
(Embodiment 2)
[0057] Fig. 17 is an exploded perspective view illustrating an antenna apparatus 1A according to Embodiment 2. Fig. 18 is a sectional view, taken along an A-A line, of a matching circuit portion shown in Fig. 17.
[0058] As shown in Fig. 17, an antenna apparatus 1A used for a radio communication medium or a radio communication medium processor has a configuration in which a protective member 7, a magnetic sheet 2 made of ferrite, etc., and a protective member 8 are laminated in order on a base 6. That is, the antenna apparatus 1A has a configuration in which the magnetic sheet 2 whose both sides are coated with the protective members 7 and 8 is arranged on the top face of the base 6.
[0059] An antenna 3 that is an antenna pattern having a predetermined shape is provided on the top face of the base 6. Further, terminal connecting parts 5 are provided on the top face of the base 6 so as to intersect a side face of the antenna 3. A region where the terminal connecting parts 5 are formed is a matching circuit 4, and chip capacitors 12 are provided in a fashion shown in Fig. 18. Cutout parts are provided in the protective member 7, the magnetic sheet 2, and the protective member 8 in regions corresponding to the matching circuit 4.
[0060] In the antenna apparatus 1A shown in Fig. 17, the outside dimension of the magnetic sheet 2 is made larger than the outside dimension of the antenna 3. Specifically, the outside dimension of the magnetic sheet 2 is 1 mm larger than the outside dimension of the antenna 3. This can stabilize the resonant frequency of the antenna apparatus 1, even if the position of adhesion between the magnetic sheet 2 and the antenna 3 somewhat deviates on the surface of the magnetic sheet 2 (refer to Fig. 21). That is, since the operation of adhering the magnetic sheet 2 to the antenna 3 becomes easy, an antenna apparatus having high productivity can be realized.
[0061] Hereinafter, the feature of each component will be described first, and then, the manufacturing procedure of the component will be described. The magnetic sheet 2 is obtained by forming a metallic material, such as ferrite, a permalloy, a sendust, or a silicon alloy sheet, in a form that constitutes an element of the antenna apparatus 1, and the magnetic sheet is formed in the shape of a sheet (or in the shape of a plate, a film or a layer) having a thickness of 0.05 mm to about 3 mm.
[0062] As a material used for this magnetic sheet 2, a soft magnetic ferrite is preferable. A ferrite powder can be dry-pressed and baked and thereby made into a high-density ferrite baked body. It is preferable that the density of the ferrite baked body be 3.5 g/cm3 or more, and the size thereof be more than a crystal grain boundary.
[0063] The soft magnetic ferrite may be composed of Ni-ZnO3, ZnO, NiO, CuO, Fe2O3, ZnO, MnO, or CuO. Further, the soft magnetic ferrite may be a monolayer of any one magnetic substance of an amorphous alloy, a permalloy, electromagnetic copper, ferrosilicon, an Fe-Al alloy, and a sendust alloy, may be a laminated body of ferrite, an amorphous foil, a permalloy, electromagnetic copper, and a sendust, or may be a laminated body obtained by combining various magnetic substances.
[0064] Moreover, the soft magnetic ferrite may be obtained by coating a simple body or a laminated body of ferrite, an amorphous alloy, a permalloy, electromagnetic copper, ferrosilicon, an Fe-Al alloy, or a sendust alloy, with at least one means of resin, an ultraviolet curable resin, a visible light curable resin, a thermoplastic resin, a thermosetting resin, a heat-resistant resin, a synthetic rubber, a double-sided tape, an adhesion layer, or a film. In addition, a simple body or a laminated body of ferrite, an amorphous foil, a permalloy, electromagnetic copper, and a sendust may be an aggregate of magnetic blocks.
[0065] By arranging the blocks, a magnetic substance can be efficiently formed with respect to the total thickness of the magnetic sheet 2. Further, by arranging all the magnetic blocks so that their upper and lower sides may become almost the same plane, the maximum volume of a magnetic substance can be utilized in a range of the thickness dimension, mechanical strength, other physical performances that are required for the magnetic sheet 2, and consequently a high magnetic performance can be obtained.
[0066] As described above, the magnetic sheet 2 is composed of a monolayer, multilayer structure, or magnetic blocks. In this case, the magnetic sheet is fixed to a double-sided tape or a fine adhesive tape, and is crushed by the roller 19, so that flexibility can be given to the magnetic sheet. Also, since the workability of the magnetic sheet 2 and a load at the time of working is reduced, cost reduction of products can also be realized. Further, as the magnetic sheet 2 is crushed by the roller, voids are formed in the magnetic sheet 2. Then, when resin is printed on the magnetic sheet 2, the resin permeates into the magnetic sheet 2, serving as a binder. As a result, flexibility can be further given to the magnetic sheet 2.
[0067] Further, by coating the magnetic sheet 2 with at least one means of resin, an ultraviolet curable resin, a visible light curable resin, a thermoplastic resin, a thermosetting resin, a heat-resistant resin, a synthetic rubber, a double-sided tape, an adhesion layer, or a film, flexibility becomes high and excellent durability can be ensured. In addition, since the surface resistance of the magnetic sheet 2 becomes high, it becomes easy to form a circuit on the surface of the magnetic sheet by pattern printing, plating, etc.
[0068] Further, the magnetic sheet 2 is coated with by the protective members 7 and 8. In this case, since the magnetic sheet 2 has excellent flexibility as described above, it can be easily blanked and formed by punching, etc. Accordingly, working of a complicated shape can also be performed at low cost, and in large amounts. By punching the magnetic sheet 2, as shown in Fig. 17, the matching circuit 4 and the terminal connecting parts 5 can be provided in an opening of the magnetic sheet 2.
[0069] Further, since a baked body of the magnetic sheet 2 is ordinarily very brittle, the antenna 3, the matching circuit 4, and the terminal connecting parts 5 cannot be formed on the baked body. However, by coating the magnetic sheet 2 in advance with resin, an ultraviolet curable resin, a visible light curable resin, a thermoplastic resin, a thermosetting resin, a heat-resistant resin, a synthetic rubber, a double-sided tape, an adhesion layer, or a film, the antenna 3, the matching circuit 4, and the terminal connecting parts 5 that are brought into close contact with the magnetic sheet 2 can be formed on the magnetic sheet 2, so that the antenna apparatus 1 can be made small and thin. Further, the magnetic sheet 2 is provided with slits, so that the magnetic sheet 2 can be easily divided. Thus, the magnetic sheet 2 having more excellent flexibility and workability can be realized.
[0070] Next, an antenna element that constitutes the antenna 3 is obtained by forming conductors in the shape of a loop. As the structure of the looped conductors, the conductors have only to be formed in a surrounding shape, and the shape of the loop may be any of a circular shape, a substantially rectangular shape, or a polygonal shape. Since the loop structure can generate a sufficient magnetic field to be generated, communication between a radio communication medium and a radio communication medium processor by mutual inductance is allowed.
[0071] A material for an antenna element can be appropriately selected from a conductive metal wire, a metallic plate material, a metallic foil material, and a metallic cylinder material, such as gold, silver, copper, aluminum, and nickel, and the antenna can be formed by a metal wire, a metallic foil, conductive paste, plating transfer, sputtering, vapor deposition, or screen printing.
[0072] Since the matching circuit 4 is composed of the chip capacitor 12 mounted so that the capacitor may serve as an intermediary between conductors of a looped antenna element of the antenna 3 formed in the base 6, and a distributed constant line that takes impedance matching, the matching circuit 4 can be formed on the looped antenna element, and the antenna apparatus 1 can be made small. Therefore, by forming a cutout part having a minimum size corresponding to the matching circuit 4 in the magnetic sheet 2 can be made small, the antenna apparatus 1 having excellent magnetic properties can be realized.
[0073] Further, since the surface resistance of the magnetic sheet 2 is large, a circuit can be directly formed on the surface of or inside the magnetic sheet 2. Thus, it is possible to form the antenna 3, the matching circuit 4, and the terminal connecting parts 5, which need to be separately formed in the related art, integrally with the magnetic sheet 2. This allows a very thin antenna apparatus 1 to be formed.
[0074] Next, the base 6 can be formed from polyimide, PET, a glass epoxy substrate, etc. By forming the base from polyimide, PET, etc., it is possible to form a thin flexible antenna 3. Further, since the cost of films of polyimide, PET, etc. is low, a low-cost antenna apparatus 1 can be manufactured.
[0075] Wiring can be made only on one side of the base 6 even if the antenna 3 is formed and a matching circuit is provided. As a result, since a through hole, etc. becomes unnecessary, a base can be formed inexpensively and low cost can be realized.
[0076] Since the matching circuit 4 is configured such that the chip capacitor 12 used as a matching element serves as an intermediary between conductors of a looped antenna element, and such that matching of impedance can be achieved according to the number of chip capacitors 12 to be mounted as shown in Fig. 19, generation of a stationary wave caused by mismatching can be suppressed, thereby realizing an antenna apparatus 1 whose operation is stabilized.
[0077] Fig. 19 is an enlarged view showing an exemplary configuration of a matching circuit in a case where a looped antenna element that constitutes the antenna shown in Fig. 17 makes four turns. As shown in Fig.19, since the matching circuit 4 is configured as a distributed constant line and the looped antenna element makes four turns, four stubs 13 that establish matching of impedance are provided. The resonant frequency of the antenna apparatus 1 can be adjusted by performing trimming on each distributed constant line by machining using a laser, a router, etc. Further, it is also possible to adjust the resonant frequency of the antenna apparatus 1 by mounting the chip capacitor 12 or a chip inductor on a terminal formed on the matching circuit 4.
[0078] Fig. 20 is an equivalent circuit diagram of an antenna in a case where a looped antenna element that constitutes the antenna shown in Fig. 17 makes four turns. Since four chip capacitors are mounted when the looped antenna element makes four turns, an equivalent circuit of the antenna 3, as shown in Fig. 20, will have a configuration in which four parallel circuits, each of which consists of the inductance L and capacitor C shown in the conventional example (Fig. 16), are connected in series. The four capacitors C that are connected in series correspond to the chip capacitor 12, respectively. By adjusting the capacitance of each of the four chip capacitors 12 in the matching circuit 4, fine adjustment of the resonant frequency of the capacitor can be made, and the productivity improves.
[0079] Next, the terminal connecting parts 5 can be appropriately selected from a conductive metal wire, a metallic plate material, a metallic foil material, and a metallic cylinder material, such as gold, silver, copper, aluminum, and nickel, and the terminal connecting parts can be formed by a metal wire, a metallic foil, conductive paste, plating transfer, sputtering, vapor deposition, or screen printing.
[0080] The terminal connecting parts 5 may be formed so that they bridge across a pattern of the looped antenna element. Further, the terminal connecting parts may be formed so that they may face each other at an end of the pattern without bridging over the pattern. In addition, since the surface resistance of the magnetic sheet 2 is large as mentioned above, the terminal connecting parts 5 can be directly formed in the surface of the magnetic sheet 2.
[0081] Finally, as a material for the protective members 7 and 8, at least one means of resin, an ultraviolet curable resin, a visible light curable resin, a thermoplastic resin, a thermosetting resin, a heat-resistant resin, a synthetic rubber, a double-sided tape, an adhesion layer, or a film can be used. Selection of the material for the protective members is performed in consideration of not only flexibility against bending, deflection, etc. of the antenna apparatus 1 and each component that constitutes the antenna apparatus 1 but also weather resistances, such as thermal resistance and moisture resistance. Further, one surface, both surfaces, one side surface, both side surfaces, or whole surface of the antenna apparatus 1 or each component that constitutes the antenna apparatus 1 may be coated by the protective members 7 and 8.
[0082] In particular, the baked body itself of the magnetic sheet 2 is usually broken due to its bending, deflection, etc., whereas the baked body will have flexibility by coating one surface, both surfaces, one side surface, both side surfaces, or whole surface of the baked body of the magnetic sheet 2 with the protective members 7 and 8, such as resin, an ultraviolet curable resin, a visible light curable resin, a thermoplastic resin, a thermosetting resin, a heat-resistant resin, a synthetic rubber, a double-sided tape, an adhesion layer, or a film. Moreover, since the surface resistance becomes high, it becomes easy to form a circuit by performing pattern printing, plating, etc. on the surfaces of the protective members.
[0083] Next, the manufacturing procedure of the antenna apparatus 1 will be described. First, a baked body for the magnetic sheet 2 is made of either Ni-Zn-based ferrite or Mn-Zn-based ferrite. Here, the baked body of the magnetic sheet 2 is made of Ni-Zn-based ferrite. In this case, a baked body made of Ni-Zn-based ferrite is obtained by mixing 48.5 mol% of Fe2O3 , 20.5 5 mol% of ZnO, 20.55 mol% of NiO, and 10.40 mol% of CuO, and by baking the resulting mixture at a temperature ranging from 750 to 900 °C for 4 hours.
[0084] First, 3000 grams of a magnetic temporarily-baked powder having the above composition, 135 grams of Metalose 60SH4000 (made by Shin-Etsu Chemical Co., Ltd.) as a water-soluble binder, 270 grams of Cerami-Sol C-08 (made by Nippon Oil & Fats) as an oily plasticizer, and 340 grams of distilled water are mixed together by a mixer for 20 minutes, and the resulting mixture is passed through three rolls three times, and is made into a green body. After this green body is kept and aged at 5 °C for 96 hours, a sheet having a thickness of about 3 mm is manufactured by a vacuum extrusion molding apparatus.
[0085] Then, this sheet is dried by causing the surface of a drum drier having a temperature 95 °C to be passed over the sheet, and is cut with a predetermined dimension, thereby manufacturing a sheet having a thickness of 0.9 mm. Then, the resulting sheet is baked at 900 °C for 3 hours, thereby manufacturing a baked body having a thickness of 0.8 mm.
[0086] Thereafter, this baked body is adhered to a double-sided tape, and then a protective tape is pasted on the baked body. Then, a roller is passed on the baked body, crushing the baked body. Since the baked body is crushed so that flexibility is given to the magnetic sheet 2, making the magnetic sheet 2 soft, workability becomes good and the load at the time of working also decreases.
[0087] Then, by performing punching on the crushed magnetic sheet 2 by a press machine, etc., the outside dimension of the magnetic sheet 2 is made 1 mm larger than the outside dimension of the antenna 3, and simultaneously a cutout part is formed. Then, a protective sheet (protective member 7) on the side of the double-sided tape of the magnetic sheet 2 is peeled off, and an antenna element in which a looped antenna element of the antenna 3 and chip capacitor 12 formed in advance on the base 6 are integrated into one by soldering is adhered to the double-sided tape of the magnetic sheet 2. Since the outside dimension of the magnetic sheet 2 is made larger, high-precision alignment is required for this adhering operation, a desired resonant frequency can be obtained stably (refer to Fig. 2 1), and the productivity improves thanks to a decrease in the number of defective articles with deviation of a resonant frequency.
[0088] Finally, the resonant frequency of the antenna apparatus 1 is adjusted by performing trimming on a distributed constant circuit that is a portion of the matching circuit 4 by a laser beam machining apparatus, if needed. The antenna apparatus 1 is completed through such processes. When the antenna apparatus 1 is mounted on a small-sized terminal, such as a cellular phone, the antenna apparatus is adhered to a required place of a small portable terminal by coating the base 6 formed with a looped antenna element with a double-sided tape, an adhesive, an adhesion layer, or resin.
[0089] Here, the characteristics of a resonant frequency realized by the antenna apparatus 1 according to the present embodiment will be described with reference to Fig. 21. Fig. 2 1 shows the change characteristics of a resonant frequency when the outside dimension of the magnetic sheet shown in Fig. 17 is changed to a dimension around the outside dimension of the antenna. In Fig. 21, the axis of abscissa represents a dimension (mm) of the magnetic sheet 2 that is expressed by a difference to the outside dimension of the antenna 3, and the axis of ordinate represents the coefficient of variation of a resonant frequency (1 kHz/µm).
[0090] It can be understood from the test result shown in Fig. 21 that, if the outside dimension of the magnetic sheet 2 is 1 mm larger than that of the antenna 3, the coefficient of variation of a resonant frequency of the antenna apparatus 1 becomes small, and consequently the resonant frequency is stabilized. Since this can reduce generation of defective articles caused by deviation of a resonant frequency and can improve workability as mentioned above, the productivity of the antenna apparatus can be improved and thereby a cost-reducing effect can be expected. In addition, stability of communication improves.
(Embodiment 3)
[0091] Fig. 22 is a sectional view showing the configuration of an antenna apparatus 1B according to Embodiment 3. In addition, in Fig. 22, the same reference numerals are given to the same components as or equivalent to the components shown in Fig. 18 (Embodiment 2).
[0092] In the antenna apparatus 1B shown in Fig. 22, a low magnetic-permeability layer 20 is provided between the base 6 and the magnetic sheet 2 with the protective member 7 between the layer and the magnetic sheet in the configuration shown in Fig. 18 (Embodiment 1).
[0093] The low magnetic-permeability layer 20 is made of one means of resin, an ultraviolet curable resin, a visible light curable resin, a thermoplastic resin, a thermosetting resin, a heat-resistant resin, a synthetic rubber, a double-sided tape, an adhesion layer, or a film.
[0094] This low magnetic-permeability layer 20 is provided according to the following procedure. That, in the manufacturing procedure described in Embodiment 2, a protective sheet (protective member 7) on the side of the double-sided tape of the magnetic sheet 2 that define the dimension and a cutout part of the magnetic sheet 2 is peeled off. Thereafter, the low magnetic-permeability layer 20 is formed by adhering a double-sided tape having a thickness of 30 mm onto an antenna element in which a looped antenna element of the antenna 3 and chip capacitor 12 formed in advance on the base 6 are integrated into one by soldering. Then, by adhering the peeled-off sheet on the side of the double-sided tape of the magnetic sheet 2 onto the low magnetic-permeability layer, the low magnetic-permeability layer 20 is interposed between the antenna 3 and the magnetic sheet 2.
[0095] As such, fluctuation of the resonant frequency of an antenna apparatus can be suppressed low by maintaining low magnetic permeability between the antenna 3 and the magnetic sheet 2 (refer to Fig. 23). Fig. 23 shows comparison between the change characteristics of a resonant frequency when the outside dimension of the magnetic sheet 2 is changed to a dimension around the outside dimension of an antenna 3, in a case where the low magnetic-permeability layer 20 is provided between the antenna 3 and the magnetic sheet 2, and in a case where the antenna 3 and the magnetic sheet 2 are brought into close contact with each other.
[0096] In Fig. 23, the axis of abscissa represents a dimension (mm) of the magnetic sheet 2 that is expressed by a difference to the outside dimension of the antenna 3, and the axis of ordinate represents a resonant frequency (MHz). Reference numeral 30 denotes a characteristic curve when the antenna 3 and the magnetic sheet 2 are brought into close contact with each other, and reference numeral 31 denotes a characteristic curve when the low magnetic-permeability layer 20 is provided between the antenna 3 and the magnetic sheet 2. It can be understood from the test result shown in Fig. 23 that providing the low magnetic-permeability layer 20 between the antenna 3 and the magnetic sheet 2 leads to a smaller resonant frequency fluctuation than brining the antenna 3 and the magnetic sheet 2 into close contact with each other.
[0097] Accordingly, in the antenna apparatus 1B, the magnetic permeability between the antenna 3 and the magnetic sheets 2 is made low. Thereby, since the stability of the resonant frequency of the antenna apparatus 1B can be further improved than that of the antenna apparatus 1A, generation of defective articles caused by a resonant frequency deviation can be further reduced, and therefore the productivity of an antenna apparatus can be improved. The stability of a communication distance of the antenna apparatus 1B can also be further enhanced than that of the antenna apparatus 1A.
(Embodiment 4)
[0098] Fig. 24 is a sectional view showing the configuration of an antenna apparatus 1C according to Embodiment 4. In addition, in Fig. 24, the same reference numerals are given to the same components as or equivalent to the components shown in Fig. 18 (Embodiment 2).
[0099] As shown in Fig. 24, in the antenna apparatus 1C according to this embodiment 4, a low magnetic-permeability layer 21 and a metal member 22 are laminated in this order on the protective member 8 that covers the top face (in the drawing) of the magnetic sheet 2 in the configuration shown in Fig. 18 (Embodiment 1).
[0100] Similarly to the low magnetic-permeability layer 20, the low magnetic-permeability layer 21 is made of one means of resin, an ultraviolet curable resin, a visible light curable resin, a thermoplastic resin, a thermosetting resin, a heat-resistant resin, a synthetic rubber, a double-sided tape, an adhesion layer, or a film.
[0101] The low magnetic-permeability layer 21 and the metal member 22 are provided according to the following procedure. That, in the manufacturing procedure described in Embodiment 2, a protective sheet (protective member 7) on the side of the double-sided tape of the magnetic sheet 2 that define the dimension and a cutout part of the magnetic sheet 2 is peeled off. Thereafter, the peeled-off sheet on the side of the double-sided tape of the magnetic sheet 2 is adhered onto an antenna element in which a looped antenna element of the antenna 3 and chip capacitor 12 formed in advance on the base 6 are integrated into one by soldering. Then, the low magnetic-permeability layer 21 is formed by adhering a double-sided tape having a thickness of 30 mm onto the magnetic sheet 2 (specifically, the protective member 8). Then, the metal member 22 is adhered onto the low magnetic-permeability layer. Thereby, the low magnetic-permeability layer 21 and the metal member 22 are laminated in this order.
[0102] By adopting such a configuration, the metal member 22 has a role of shielding. Thus, leakage of a magnetic field emitted from the antenna 3 to the outside can be prevented. Also, since low magnetic permeability is maintained between the magnetic sheet 2 and the metal member 22, fluctuation of the resonant frequency of an antenna apparatus can be suppressed low (refer to Fig. 25).
[0103] Fig. 25 shows comparison between the change characteristics of a resonant frequency when the outside dimension of the magnetic sheet 2 is changed to a dimension around the outside dimension of an antenna 3, in a case where the low magnetic-permeability layer 21 is provided between the magnetic sheet 2 and the metal member 22 shown in Fig. 24, and in a case where the magnetic sheet 2 and the metal member 22 are brought into close contact with each other.
[0104] In Fig. 25, the axis of abscissa represents a dimension (mm) of the magnetic sheet 2 that is expressed by a difference to the outside dimension of the antenna 3, and the axis of ordinate represents a resonant frequency (MHz). Reference numeral 33 denotes a characteristic curve when the magnetic sheet 2 and the metal member 22 are brought into close contact with each other, and reference numeral 34 denotes a characteristic curve when the low magnetic-permeability layer 21 is provided between the magnetic sheet 2 and the metal member 22. It can be understood from the test result shown in Fig. 25 that providing the low magnetic-permeability layer 21 between the magnetic sheet 2 and metal member 22 leads to a smaller resonant frequency fluctuation than brining the magnetic sheet 2 and the metal member 22 into close contact with each other.
[0105] Accordingly, in the antenna apparatus 1C, when the metal member 22 having a shielding effect is arranged on the side of the magnetic sheet 2 opposite to the antenna 3, the magnetic permeability between the magnetic sheet 2 and the metal members 22 is made low and thereby the stability of a resonant frequency is ensured. Thus, generation of defective articles caused by a resonant frequency deviation can be reduced, and the productivity of an antenna apparatus can be improved. Further, the stability of a communication distance can be enhanced.
[0106] Also, since leakage of a magnetic field emitted from the antenna 3 to the outside can be prevented by providing the metal member 22, an antenna apparatus that is suitable, for example, when information exchange is performed only with a radio communication medium that exists only inside the antenna apparatus can be realized.
(Embodiment 5)
[0107] Fig. 26 is a sectional view showing the configuration of an antenna apparatus 1D according to Embodiment 5. In addition, in Fig. 26, the same reference numerals are given to the same components as or equivalent to the components shown in Fig. 18 (Embodiment 2).
[0108] As shown in Fig. 26, a low magnetic-permeability layer 23 is provided between the base 6 and the magnetic sheet 2 with the protective member 7 between the layer and the magnetic sheet. Further, a low magnetic-permeability layer 24 and a metal member 25 are laminated in this order on the protective member 8.
[0109] The features of the low magnetic-permeability layers 23 and 24 are as described in Embodiments 3 and 4. That, in the manufacturing procedure described in Embodiment 2, a protective sheet (protective member 7) on the side of the double-sided tape of the magnetic sheet 2 that define the dimension and a cutout part of the magnetic sheet 2 is peeled off Thereafter, the low magnetic-permeability layer 23 is formed by adhering a double-sided tape having a thickness of 30 mm onto an antenna element in which a looped antenna element of the antenna 3 and chip capacitor 12 formed in advance on the base 6 are integrated into one by soldering. Then, by adhering the peeled-off sheet on the side of the double-sided tape of the magnetic sheet 2 onto the low magnetic-permeability layer, the low magnetic-permeability layer 23 is interposed between the antenna 3 and the magnetic sheet 2.
[0110] Then, a double-sided tape having a thickness of 30 µm is adhered onto the magnetic sheet 2 (specifically onto the protective member 8) to form a low magnetic-permeability layer 24, and the metal member 25 is adhered onto the double-sided tape, whereby the low magnetic-permeability layer 24 and the metal member 25 are laminated in this order.
[0111] By adopting such a configuration, the metal member 25 has a role of shielding. Thus, leakage of a magnetic field emitted from the antenna 3 to the outside can be prevented. Also, since low magnetic permeability is maintained between the antenna 3 and the magnetic sheet 2 and the magnetic sheet 2 and the metal member 25, fluctuation of the resonant frequency of an antenna apparatus can be suppressed low (refer to Fig. 27).
[0112] Fig. 27 shows comparison between the change characteristics of a resonant frequency when the outside dimension of the magnetic sheet 2 is changed to a dimension around the outside dimension of an antenna 3, in a case where the low magnetic-permeability layers 21 and 24 are provided between the antenna 3 and the magnetic sheet 2 and between the magnetic sheet 2 and the metal member 25, respectively, shown in Fig. 24, and in a case where the antenna and the magnetic sheet are brought into close contact with each other and the magnetic sheet and the metal member are brought into close contact with each other, without providing the low magnetic-permeability layers therebetween.
[0113] In Fig. 27, the axis of abscissa represents a dimension (mm) of the magnetic sheet 2 that is expressed by a difference to the outside dimension of the antenna 3, and the axis of ordinate represents a resonant frequency (MHz). Reference numeral 35 denotes a characteristic curve when the antenna 3 and the magnetic sheet 2 are brought into close contact with each other and the magnetic sheet 2 and the metal member 25 are brought into close contact with each other, and reference numeral 36 denotes a characteristic curve when the low magnetic-permeability layers 23 and 24 are provided between the antenna 3 and the magnetic sheet 2 and between the magnetic sheet 2 and the metal member 25, respectively. It can be understood from the test result shown in Fig. 27 that maintaining low magnetic permeability between the antenna 3 and the magnetic sheet 2 and between the magnetic sheet 2 and the metal member 25 leads to a smaller resonant frequency fluctuation than bringing the magnetic sheet 2 and the metal member 25 into close contact with each other and bringing the magnetic sheet 2 and the metal member 25 into close contact with each other.
[0114] Accordingly, in the antenna apparatus ID, when the metal member 25 having a shielding effect is arranged on the side of the magnetic sheet 2 opposite to the antenna 3, the magnetic permeability between the magnetic sheet 2 and the metal members 25 and the magnetic permeability between the magnetic sheet 2 and the metal member 25 are made low and thereby the stability of a resonant frequency is ensured. Thus, generation of defective articles caused by a resonant frequency deviation can be reduced, and the productivity of an antenna apparatus can be improved. Further, the stability of a communication distance can be enhanced.
[0115] Also, since leakage of a magnetic field emitted from the antenna to the outside can be prevented by providing the metal member 25 having a shielding effect, an antenna apparatus that is suitable, for example, when communication is performed only with a radio communication medium that exists only inside the antenna apparatus can be realized.
[0116] Further, in Embodiments 2 to 5 described above, the effect to the frequency given by each chip capacitor falls by providing a plurality of chip capacitors for matching. Thus, high-precision capacitors, a sorting process, etc. become unnecessary. As a result, improvement of productivity and cost reduction can be made. Moreover, since the antenna and the matching circuit 4 can be configured in the same plane, a single-sided substrate can be used for a base. From this point, a low-cost antenna apparatus can be realized.
[0117] As mentioned above, the antenna apparatus according to the present invention is useful to suppress fluctuation of a resonant frequency to improve productivity and realize cost reduction, and particularly, suitable to ensure a predetermined communication distance and extend a communication range, when it is used for an RFID system that performs communication in a non-contact manner.
(Embodiment 6)
[0118] In Embodiment 6, a magnetic sheet 2A that can be used suitably for Embodiments 1 to 5 will be described. Fig. 28 is an exploded perspective view of the magnetic sheet 2A according to Embodiment 6, and Figs. 29 to 33 are sectional views of the magnetic sheet 2A according to Embodiment 6. Fig. 34 is a view showing a manufacturing process of the magnetic sheet 2A.
[0119] The magnetic sheet 2A includes a magnetic member 52 mainly composed of a ferrite-based magnetic substance, a double-sided adhesive tape 53 as an adhesive sheet, and a protective tape 54 as a protective member.
[0120] Although a metallic material, such as ferrite, a permalloy, a sendust, or a silicon alloy sheet, can be used as the magnetic member 52, it is preferable to use, in particular, a soft magnetic ferrite. A soft magnetic ferrite can be made into a high-density ferrite baked body by dry-pressing and baking a ferrite powder. It is preferable that the density of the soft magnetic ferrite be set to 3.5 g/cm3 or more.
[0121] Since insulating resistance becomes high by using a baked body for a magnetic member, an antenna apparatus is hardly influenced by a leakage current or an electric field from the outside. Accordingly, communication of an antenna or a radio communication medium processor can be ensured. Since insulating resistance becomes high by using a baked body for a magnetic member, an antenna, and a circuit, such as a matching circuit, can be incorporated onto a magnetic sheet, and thus an antenna apparatus can be miniaturized.
[0122] Although the soft magnetic ferrite may contain Ni-ZnO3, ZnO, NiO, and CuO as its components, it may contain Fe2O3, ZnO, MnO, or CuO. Moreover, the soft magnetic ferrite may be any one of magnetic substances including an amorphous alloy, a permalloy, electromagnetic copper, ferrosilicon, an Fe-A1 alloy, and a sendust alloy.
[0123] Further, in the magnetic sheet 2A, the magnetic member 52 is coated with at least one means of resin, an ultraviolet curable resin, a visible light curable resin, a thermoplastic resin, a thermosetting resin, a heat-resistant resin, a synthetic rubber, a double-sided tape, an adhesion layer, or a film. Thus, flexibility is high, durability is excellent, and surface resistance is high. In addition, it is easy to form a circuit on the surface of the magnetic sheet by pattern printing, plating, etc., and it is also easy to form a through hole extending through layers.
[0124] Further, since the magnetic member 52 coated by the above material has excellent flexibility, the magnetic sheet can be blanked and formed easily by punching, etc. Thus, the magnetic sheet has features that working of a complicated shape can also be performed at low cost, and in large amounts.
[0125] Since the magnetic member 52 of the present invention, as shown in Fig. 34, is fixed to a double-sided tape 53 or a fine adhesive tape, is rolled and crushed by the roller 19, and is boned to the double-sided adhesive tape 53 or a fine adhesive tape, the magnetic member has high flexibility.
[0126] Next, the double-sided adhesive tape 53 as an adhesive sheet will be described. The double-sided adhesive tape 53 is bonded to the bottom face of the magnetic member 52, and the magnetic member 52 is fixed at the time of manufacture of the magnetic sheet 2A. Also, a film of the surface of the double-sided tape opposite to its surface to which the magnetic member 52 is bonded is peeled off, so that a loop antenna, a matching circuit, etc. can be bonded to the adhesive tape, or the adhesive tape can be adhered to on an RFID device. Although the double-sided adhesive tape 53 is used in Embodiment 6, a fine adhesive tape, etc. may be used in addition to the double-sided adhesive tape 53.
[0127] Next, a protective tape 54 as a protective member will be described. The protective tape 54 is bonded to the top face of the magnetic member 52 to protect the magnetic member 52 and to prevent the magnetic member 52 crushed by the roller 19 from dropping out.
[0128] In addition, it is also preferable to use sheet-like resin as the protective member. As a material of the sheet-like resin, at least one of resin, an ultraviolet curable resin, a visible light curable resin, a thermoplastic resin, a thermosetting resin, and a heat-resistant resin is used ordinarily. The material used for the sheet-like resin is selected not only in consideration of the flexibility corresponding to the bending, deflection, etc. of the magnetic sheet 1, etc. but also in consideration of weather resistance, such as thermal resistance and moisture resistance.
[0129] The magnetic member 52 that is a baked body is usually broken due to its bending, etc., whereas the magnetic member will have excellent flexibility and have high surface resistance by coating one surface, both surfaces, one side surface, both side surfaces, or whole surface of the magnetic member 52 that is a baked body with the above resin 55. As a result, it is easy to form a circuit on the surface of the magnetic member by pattern printing, plating, etc.
[0130] Further, since the magnetic member 52 coated with the resin 55 has moderate flexibility, it can be easily blanked and formed by punching, etc. Accordingly, the magnetic member has features that working of a complicated shape can also be performed at low cost and in larger amounts. Moreover, magnetic powder may be mixed into the resin 55 so as to form the resin having magnetic properties.
[0131] Next, the manufacturing process of the magnetic sheet 2A of Embodiment 6 will be described. The baked body of the magnetic member 52 is made ofNi-Zn-based ferrite or Mn-Zn-based ferrite. Specifically, a baked body made ofNi-Zn-based ferrite is obtained by mixing 48.5 mol% of Fe2O3, 20.55 mol% of ZnO, 20.55 mol% of NiO, and 10.40 mol% of CuO, and by baking the resulting mixture at a temperature ranging from 750 to 9000 °C for 4 hours.
[0132] The magnetic sheet 1 composed of the above members is manufactured as follows. First, 3000 grams of a magnetic temporarily-baked powder having the above composition, 135 grams of Metalose 60SH4000 (made by Shin-Etsu Chemical Co., Ltd.) as a water-soluble binder, 270 grams of Cerami-Sol C-08 (made by Nippon Oil & Fats) as an oily plasticizer, and 340 grams of distilled water are mixed together by a mixer for 20 minutes, and the resulting mixture is passed through three rolls three times, and is made into a green body.
After this green body is kept and aged at a temperature of 5 °C for 96 hours, it is molded into a plate having a thickness of about 3 mm by a vacuum extrusion molding apparatus.
[0133] Next, this plate is dried by passing the surface of a drum drier having a temperature 95 °C over the plate, and is cut with a predetermined dimension, thereby manufacturing plates having a thickness of 0.9 mm. Then, the resulting plates are baked at 900 °C for 3 hours, thereby manufacturing plate-like magnetic members 52 having a thickness of 0.8 mm.
[0134] As shown in Figs. 29 to 33, in Embodiment 6, a plurality of the plate-like magnetic members 52 are arranged on the double-sided adhesive tape 53 such that their portions overlap each other. Specifically, plate-like magnetic members 52 having a rectangular cross section, as shown in Fig. 29, can be arranged such that their portions overlap each other, plate-like magnetic members 52 having a hooked cross section, as shown in Fig. 30, can be arranged such that a hooked portion of one plate-like magnetic member overlaps a flat plate portion of the adjacent magnetic member 52, portions of a plate-like magnetic member having a T-shaped cross section, as shown in Fig. 31, can be arranged so as to overlap portions of magnetic plate-like members 52 having a rectangular cross section, plate-like magnetic members 52 having a parallelogram cross section, as shown in Fig. 32, can be arranged such that their inclined planes overlap each other, or plate-like magnetic members 52 having a trapezoidal cross section, as shown in Fig. 33, can be arranged such that their inclined planes overlap each other.
[0135] By arranging the plate-like magnetic members 52 such that their portions overlap each other, a gap between the plate-like magnetic members 52 in their arranging direction can be eliminated. By eliminating a gap between the plate-like magnetic members 52 in their arranging direction, variations in magnetic properties caused in the magnetic sheet 1 can be reduced, and a magnetic sheet 2A having uniform magnetic properties can be manufactured.
[0136] Next, the manufacturing process of the magnetic sheet 2A will be described. As shown in Figs. 29 to 33, a plurality of magnetic plate-like members 52 are arranged on the double-sided adhesive tape 53 such that their portions overlap each other. Then, as shown in Fig. 34, a rolling machine, such as a roller 19, is passed over the double-sided adhesive tape 53 to press and then roll and crush the plurality of plate-like magnetic members 52, thereby bonding the magnetic member to the double-sided adhesive sheet 53 with no gap.
[0137] Then, as shown in Fig. 34, an excessive magnetic powder (magnetic member) that has remained on the magnetic member 52 without being bonded to the double-sided adhesive tape 53 is removed, with the magnetic sheet 2A turned upside down. Next, the protective tape 54 as a protective member is bonded to the magnetic member 52 crushed by a rolling machine, such as the roller 19.
[0138] As another example of the manufacturing process of the magnetic sheet 2A, the protective tape 54 is not bonded, but a thermosetting resin 55 as a protective member may be applied (bonded) with a thickness of 10 µm by a screen printing method, and then may be dried and cured at a temperature of 150 °C for 1 hour in a constant temperature bath. Then, the magnetic sheet 2A is punched by a press machine, etc. The magnetic sheet 2A is completed through the above steps.
(Embodiment 7)
[0139] In Embodiment 7, a magnetic sheet 2B that can be suitably used in Embodiments 1 to 5 similarly to the magnetic sheet 2A according to Embodiment 6 will be described. The shape and structure of the magnetic sheet the 2B in Embodiment 7 will be described. Fig. 35 is a sectional view of the magnetic sheet 2B in Embodiment 7, and Fig. 36 is a view showing a manufacturing process of the magnetic sheet 2B in Embodiment 7.
[0140] The plate-like magnetic members 52, the double-sided adhesive tape 53, the protective tape 54, and the resin 55 are equivalent to those of Embodiment 6. As shown in Fig. 35, in Embodiment 7, a magnetic member piece 57 as a filling magnetic member is arranged above (in the vicinity of) a gap between a plurality of plate-like magnetic members 52 arranged on the double-sided adhesive tape 53.
[0141] By arranging the magnetic member piece 57 above the gap between the plate-like magnetic members 52, when the plate-like magnetic members 52 and the magnetic member piece 57 is rolled and crushed by the roller 19, the crushed magnetic member piece 57 can enter the gap between the plate-like magnetic members 52 to eliminate the gap between the plate-like magnetic members 52. By eliminating the gap between the plate-like magnetic members 52, variations in magnetic properties caused in the magnetic sheet 2B can be reduced, and a magnetic sheet 2B having uniform magnetic properties can be manufactured.
[0142] Next, the manufacturing process of the magnetic sheet 2B according to Embodiment 7 will be described. The plate-like magnetic members 52 are manufactured similarly to the magnetic sheet 2A of Embodiment 6 as described above. The plate-like magnetic member 52, as shown in Fig. 36, is adhered to the double-sided adhesive tape 53. Then, the magnetic member piece 57 is arranged above the gap between a plurality of the plate-like magnetic members 52. Then, an apparatus such as the roller 19 is passed over the double-sided adhesive tape 53 to roll and crush the plate-like magnetic members 52 and the magnetic member piece 57, thereby bonding them to the double-sided adhesive tape 53 without a gap.
[0143] Next, an excessive magnetic powder (magnetic member) that has remained on the magnetic members 52 without being bonded to the double-sided adhesive tape 53 is removed, with the magnetic sheet 1 turned upside down. Next, the protective tape 54 is bonded onto the magnetic members 52 bonded to the double-sided adhesive tape 53.
[0144] As another example of the manufacturing process of the magnetic sheet 2B according to Embodiment 7, the protective tape 54 is not bonded, but a thermosetting resin 5 as a protective member may be applied (bonded) with a thickness of 10 µm by a screen printing method, and then may be dried and cured at a temperature of 150 °C for 1 hour in a constant temperature bath. Then, the magnetic sheet 2B is punched by a press machine, etc. The magnetic sheet 2B is completed through the manufacturing process.
(Embodiment 8)
[0145] In Embodiment 8, a magnetic sheet 2C that can be suitably used in Embodiments 1 to 5 similarly to the magnetic sheet 2A according to Embodiment 6 will be described. The shape and structure of the magnetic sheet 2C according to Embodiment 8 will be described. Fig. 37 is a sectional view of the magnetic sheet 2C according to Embodiment 8, and Fig. 38 is a view showing a manufacturing process of the magnetic sheet 2C in Embodiment 8.
[0146] The plate-like magnetic members 52, the double-sided adhesive tape 53, the protective tape 54, and the resin 55 are equivalent to those of the magnetic sheet 2A of Embodiment 6. As shown in Fig. 37, in Embodiment 8, a magnetic powder 58 as a filling magnetic member is filled into a gap between a plurality of plate-like magnetic members 52 arranged on the double-sided adhesive tape 53.
[0147] By filling the magnetic powder 58 into the gap between the plate-like magnetic members 52, variations in magnetic properties caused in the magnetic sheet 2C can be reduced, and a magnetic sheet 2C having uniform magnetic properties can be manufactured.
[0148] Next, a manufacturing process of the magnetic sheet 2C of Embodiment 8 will be described with reference to Fig. 38. The plate-like magnetic members 52 are manufactured similarly to Embodiment 6. The plate-like magnetic members 52 are arranged on the double-sided adhesive tape 53, and the magnetic powder 58 as a filling magnetic member is filled (disposed) into a gap between the plate-like magnetic members 52.
[0149] Next, an excessive magnetic powder (magnetic member) 58 that has remained on the magnetic members 52 without being bonded to the double-sided adhesive tape 53 is removed, with the magnetic sheet 2C turned upside down. Next, the protective tape 54 is bonded onto the plate-like magnetic members 52 and the filling magnetic powder 58.
[0150] As another example of the manufacturing process of the magnetic sheet 2C according to Embodiment 8, the protective tape 54 is not bonded, but a thermosetting resin 55 as a protective member may be applied (bonded) with a thickness of 10 µm by a screen printing method, and then may be dried and cured at a temperature of 150 °C for 1 hour in a constant temperature bath.
[0151] Thereafter, an apparatus such as the roller 19 is passed to roll and crush the plate-like magnetic members 52 and the magnetic powder 58, thereby bonding them to the double-sided adhesive tape 53 without a gap. Then, the magnetic sheet 2C is punched by a press machine, etc. The magnetic sheet 2C of Embodiment 8 is completed through the above manufacturing process.
(Embodiment 9)
[0152] In Embodiment 9, a magnetic sheet 2D that can be suitably used in Embodiments 1 to 5 similarly to the magnetic sheet 2A according to Embodiment 6 will be described. The shape and structure of the magnetic sheet 2D according to Embodiment 9 will be described. Fig. 39 is a sectional view of the magnetic sheet 2D in Embodiment 9, and Embodiment 10 as described later, and Fig. 40 is a view showing a manufacturing process of the magnetic sheet 2D in Embodiment 9.
[0153] The plate-like magnetic members 52, the double-sided adhesive tape 53, the protective tape 54, and the resin 55 are equivalent to those of the magnetic sheet 2A of Embodiment 6.
[0154] The manufacturing process of the magnetic sheet 2D according to Embodiment 9 will be described. The plate-like magnetic members 52 are manufactured similarly to Embodiment 6. A plate-like magnetic member 52 as a first layer is arranged on the double-sided adhesive tape 53, a thermosetting resin 55 is applied on the plate-like magnetic member, and a plate-like magnetic member 52 as a second layer that is a filling magnetic member is bonded onto the thermosetting resin 55. As shown in Fig. 39, a plurality of plate-like magnetic members 52 as the second member are arranged on a plurality of plate-like magnetic members 52 as the first layer arranged on the double-sided adhesive tape 53 such that a central portion of each of the plate-like magnetic members as the first layer is located above each gap.
[0155] Next, the magnetic sheet 2D is left in a constant temperature bath having a temperature of 150 °C for 1 hour, thereby curing the thermosetting resin 55. In this case, the plate-like magnetic members 52 as the first and second layers may be bonded together by the double-sided adhesive tape 53 or an adhesive material, without using the thermosetting resin 5.
[0156] Next, an apparatus such as the roller 19 is passed to roll and crush the plate-like magnetic members 52 as the first and second layers. Then, the crushed plate-like magnetic members 52 as the second layer that is a filling magnetic member is filled into the gaps between the plate-like magnetic members 52 as the first layer, thereby bonding them to the double-sided adhesive tape 53 without a gap. Then, an excessive magnetic powder (magnetic member) that has remained on the magnetic members 52 without being bonded to the double-sided adhesive tape 53 is removed.
[0157] Thereafter, the protective tape 54 is bonded onto the magnetic members 52 bonded to the double-sided adhesive tape 53. Then, the magnetic sheet 2D is punched by a press machine, etc. The magnetic sheet 2D of Embodiment 9 is completed through the above manufacturing process.
(Embodiment 10)
[0158] In Embodiment 10, a magnetic sheet 2E that can be suitably used in Embodiments 1 to 5 similarly to the magnetic sheet 2A according to Embodiment 6 will be described. First, the shape and structure of the magnetic sheet 2E in Embodiment 10 of the present invention will be described. Fig. 41 is a view showing a manufacturing process of the magnetic sheet 2E in Embodiment 10.
[0159] The plate-like magnetic members 52, the double-sided adhesive tape 53, and the resin 55 are equivalent to those used in the magnetic sheet 2A according to Embodiment 6.
[0160] The manufacturing process of the magnetic sheet 2E according to Embodiment 10 will be described. The plate-like magnetic members 52 are manufactured similarly to Embodiment 6. A plate-like magnetic member 52 as a first layer is arranged on the double-sided adhesive tape 53, a thermosetting resin 55 is applied on the plate-like magnetic member, and a plate-like magnetic member 52 as a second layer that is a filling magnetic member is bonded onto the thermosetting resin 55. As shown in Fig. 39, a plurality of plate-like magnetic members 52 as the second member are arranged on a plurality of plate-like magnetic members 52 as the first layer arranged on the double-sided adhesive tape 53 such that a central portion of each of the plate-like magnetic members as the first layer is located above each gap.
[0161] Next, the magnetic sheet 2E is left in a constant temperature bath having a temperature of 150 °C for 1 hour, thereby curing the thermosetting resin 55. In this case, the plate-like magnetic members 52 as the first and second layers may be bonded together by the double-sided adhesive tape 53 or an adhesive material, without using the thermosetting resin 55.
[0162] Next, the resin 55 is applied on the plate-like magnetic members 52 as the second layer. A thermosetting resin is used as the resin 55, and a resin having a film thickness of 20 µm is formed on the plate-like magnetic members 52 as the second layer by screen printing. Next, the magnetic sheet 2E is left in a constant temperature bath having a temperature of 150 °C for 1 hour, thereby drying and curing the thermosetting resin 55.
[0163] Thereafter, an apparatus such as the roller 19 is passed to roll and crush the plate-like magnetic members 52 as the first and second layers. Then, portions of the crushed plate-like magnetic members 52 as the second layer that is a filling magnetic member is filled into the gaps between the plate-like magnetic members 52 as the first layer, thereby bonding them to the double-sided adhesive tape 53 without a gap.
[0164] In addition, the rolling and crushing step of the plate-like magnetic members 52 by the roller 19 may be performed before the step of applying and drying the resin 55. Then, the magnetic sheet 2E is punched by a press machine, etc. The magnetic sheet 2E of Embodiment 10 is completed through the above manufacturing process.
(Embodiment 11)
[0165] In Embodiment 10, a magnetic sheet 2F that can be suitably used in Embodiments 1 to 5 similarly to the magnetic sheet 2A according to Embodiment 6 will be described. First, the shape and structure of the magnetic sheet 2F in Embodiment 11 of the present invention will be described. Fig. 42 is a sectional view of the magnetic sheet 2F in Embodiment 11, and Figs. 43 and 44 are views showing a manufacturing process of the magnetic sheet 2F in Embodiment 11.
[0166] The plate-like magnetic members 52, the double-sided adhesive tape 53, and the resin 55 are equivalent to those used in the magnetic sheet according to Embodiment 6.
[0167] Next, the manufacturing process of the magnetic sheet 2F of Embodiment 11 will be described with reference to Fig. 43. The plate-like magnetic members 52 are manufactured similarly to Embodiment 6. The thermosetting resin 55 is applied to the plate-like magnetic member 52 to bond the plate-like magnetic member 52 together. In this case, the plate-like magnetic members 52 may be bonded together by the double-sided adhesive tape 53 or an adhesive material, without using the thermosetting resin 55.
[0168] The bonded plate-like magnetic members 52 are arranged on the double-sided adhesive tape 53, and then the protective tape 54 is bonded onto the plate-like magnetic members 52 as an upper layer. In this case, as shown in Fig. 39, the thermosetting resin 55 may be applied on the plate-like magnetic members 52 as the second layer, and may be dried and cured in a constant temperature bath at a temperature of 150 °C for 1 hour, in addition to bonding the protective tape 54.
[0169] Thereafter, an apparatus such as the roller 19 is passed to roll and crush the plate-like magnetic members 52 as the lower and upper layers. Then, portions of the crushed plate-like magnetic members 52 as the upper layer that is a filling magnetic member is filled into the gaps between the plate-like magnetic members 52 as the lower layer, thereby bonding them to the double-sided adhesive tape 53 without a gap.
[0170] In addition, the rolling and crushing step of the plate-like magnetic members 52 by the roller 19 may be performed before the step of bonding the protective tape 54 or the step of applying, drying, and curing the resin 55. Then, the magnetic sheet 2F is punched by a press machine, etc. The magnetic sheet 2F of Embodiment 11 is completed through the above manufacturing process. Fig. 44 is a view showing a manufacturing process of the magnetic sheet in Embodiment 11. Like Fig. 44, a resin coating and drying step may be performed before the step by the roller 19.
(Embodiment 12)
[0171] First, the shape and structure of the magnetic sheet 2G in Embodiment 12 of the present invention will be described. Fig. 45 is a sectional view of the magnetic sheet 2G in Embodiment 12, and Figs. 46 and 47 are views showing a manufacturing process of the magnetic sheet 2G in Embodiment 12.
[0172] The double-sided adhesive tape 53, the protective tape 54, and resin 55 are equivalent to those used for the magnetic sheet 2A according to Embodiment 6, and the magnetic powder 58 is obtained by finely crushing the magnetic member 52 of Embodiment 6 until it turns into a powder of 0.1 to 100 µm.
[0173] Next, the manufacturing process of the magnetic sheet 2G of Embodiment 12 will be described with reference to Fig. 46 and Fig. 47. The magnetic member 52 of Embodiment 6 is put into a crusher, and is finely crushed into a magnetic powder 58 of 0.1 to 100 µm.
[0174] Next, as shown in Fig. 46, the magnetic powder 58 is covered on the double-sided adhesive tape 53 without any gap, and bonded thereto, and the protective tape 54 is bonded onto the covered magnetic powder 58. In this case, the protective tape 54 is not bonded, but as shown in Fig. 47, the thermosetting resin 55 may be applied (bonded) on the plate-like magnetic powder 58, and may be dried and cured in a constant temperature bath at a temperature of 150 C for 1 hour. Then, the magnetic sheet 2G is punched by a press machine, etc. The magnetic sheet 2G is completed through the manufacturing process.
[0175] The magnetic sheet of the present invention can also be used for radio communication medium processors that supply electric power and transmission data to radio communication media, such as non-contact IC cards or an IC tags, that are stored in a commodity rack, etc., and that acquire received data from the radio communication media depending on load fluctuation, and particularly to apparatuses that are required to extend a communication range, such as a medicine management system, a hazardous material management system, and a valuables management system, other than a storage rack and an exhibition rack that allow automatic merchandise management, automatic book management, etc.
[0176] This application is based upon and claims the benefit of priority of Japanese Patent Application Nos. 2006-020283 filed on January 30, 2006; 2006-030810 filed on February 8, 2006; and 2006-154279 filed on June 2, 2006, the contents of which are incorporated herein by reference in its entirety.
1. An antenna apparatus comprising:
an antenna (3) that has a looped conductor , and
a matching circuit (4) that includes a first capacitor (10) and a second capacitor (10) each of which has a pair of electrodes, and that sets a resonant frequency by the antenna (3) and the first and second capacitors (10),
wherein one electrode of the pair of electrodes of the first capacitor (10) is connected to one end of the looped conductor, and the other electrode of the pair of electrodes of the first capacitor (10) is connected to the looped conductor, and
wherein one electrode of the pair of electrodes of the second capacitor (10) is connected to the other end (5) one of the looped conductor, and the other electrode of the pair of electrodes of the second capacitor (10) is connected to the looped conductor.
2. The antenna apparatus according to Claim 1, wherein the matching circuit (4) further
includes a third capacitor (10) that has a pair of electrodes, and the resonant frequency
is set by the antenna (3) and the first, second, and third capacitors (10), and
wherein one electrode of the pair of electrodes of the third capacitor (10) is connected to the looped conductor, and the other electrode of the pair of electrodes of the third capacitor (10) is connected to the looped conductor on the inner peripheral side or outer peripheral side of the conductor to which the one electrode of the third capacitor (10) is connected.
wherein one electrode of the pair of electrodes of the third capacitor (10) is connected to the looped conductor, and the other electrode of the pair of electrodes of the third capacitor (10) is connected to the looped conductor on the inner peripheral side or outer peripheral side of the conductor to which the one electrode of the third capacitor (10) is connected.
3. The antenna apparatus according to Claim 1, further comprising:
a magnetic sheet (2) that has a magnetic substance,
wherein both the antenna (3) and the matching circuit (4) are provided wit h the magnetic sheet (2).
4. The antenna apparatus according to Claim 3, wherein the matching circuit (4) is provided
on one surface of the magnetic sheet (2).
5. The antenna apparatus according to Claim 1, wherein the matching circuit (4) consists
of a distributed constant circuit, a chip capacitor, or a chip inductor.
6. The antenna apparatus according to Claim 1, wherein a pattern for adjusting the resonant
frequency is formed in the distributed constant circuit of the matching circuit (4),
or the antenna (3).
7. The antenna apparatus according to Claim 1, wherein the matching circuit (4) has a
stub (16) that adjusts the resonant frequency in the antenna (3).
8. The antenna according to Claim 3, wherein the outside dimension of the magnetic sheet
(2) is larger than the outside dimension of the antenna (3).
9. The antenna apparatus according to Claim 8, wherein a low magnetic-permeability layer
(20) is provided between the antenna (3) and the magnetic sheet (2).
10. The antenna apparatus according to Claim 8, wherein a metal member (2 2) is provided
on the side of the magnetic sheet (2) opposite to the antenna (3), and a low magnetic-permeability
layer (20) is provided between the magnetic sheet (2) and the metal member (22).
11. The antenna apparatus according to Claim 8, wherein a metal member (2 2) is provided
on the side of the magnetic sheet (2) opposite to the antenna (3), low magnetic-permeability
layers (20) are provided between the magnetic sheet (2) and the antenna (3) and between
the magnetic sheet (2) and the metal member (22), respectively.
12. The antenna apparatus according to Claim 8, wherein the outside dimension of the magnetic
sheet (2) is 1 mm or more larger than the outside dimension of the antenna (3).
13. The antenna apparatus according to Claim 1, wherein the magnetic sheet (2) includes
a magnetic layer in which a magnetic material is continuously arranged and formed,
and a sheet base (53) with flexibility, and the sheet base (53) holds the magnetic
layer.
14. A magnetic sheet comprising:
a magnetic layer in which a magnetic material is continuously arranged and formed, and
a sheet base (53) with flexibility,
wherein the sheet base (53) holds the magnetic layer.
15. An antenna apparatus comprising:
a magnetic sheet (2), and
an antenna (3) consisting of looped antenna elements arranged in proximity to the magnetic sheet (2),
wherein the outside dimension of the magnetic sheet (2) is larger than the outside dimension of the antenna (3).
REFERENCES CITED IN THE DESCRIPTION
This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.
Patent documents cited in the description