Contactless information medium

A contactless communication medium includes a film base, an antenna coil disposed on a top surface of the film base and formed in a rectangular spiral shape, an IC chip performing wireless communication processing via the antenna coil, first plate electrodes connected to an inner end and an outer end of the antenna coil, and second plate electrodes disposed on a rear surface of the film base so as to be opposite to the first plate electrodes in the thickness direction of the film base. The first plate electrodes and the second plate electrodes have a first electrode portion and a second electrode portion respectively extending along a long side direction and a short side direction of the antenna coil so as to be adjacent to an inner periphery or an outer periphery of the antenna coil when viewed perpendicular to the film base.

TECHNICAL FIELD

The present invention relates to a contactless information medium.

BACKGROUND

Patent Document 1 discloses an example of an RFID medium (a contactless information medium) such as a contactless IC card which performs wireless communication using signals in an HF band (for example, 13.56 MHz). An antenna pattern of an antenna coil of such an RFID medium can be designed in any shape as long as the functional requirements for performing wireless communications with external devices are met.

Certain restrictions may be imposed on the antenna pattern in order to meet the requirements of a shape or a specific standard of an object to which the RFID medium is to be installed. For example, in the standard specified as ISO/IEC 14443-1, Class 1, an area where an antenna pattern can be arranged is set in order to provide an opening (a region having no wiring pattern) formed inside an antenna coil. Specifically, in the above standard, the area where the antenna pattern can be arranged is set to be an annular area obtained by removing, from a rectangular region having a length of 49 mm and a width of 81 mm, a substantially rectangular region having a length of 34 mm and a width of 64 mm (this rectangular region having corners rounded with R3 mm) and centered in the rectangular region.

CITATION LIST

Patent Literature

Patent Document 1: JP 2004-355442 A

SUMMARY OF THE INVENTION

Technical Problem

In such an RFID medium, a capacitance portion capable of propagating high-frequency signals using parallel plate electrodes may be provided in a circuit. In that case, a wiring pattern to connect the parallel plate electrodes to an antenna coil is necessary, and therefore it may be difficult to meet the requirements of the above standard. For example, when parallel plate electrodes are disposed substantially centrally in an opening formed inside an antenna coil as with the examples disclosed in Patent Document 1, the requirements of the above standard cannot be met. Further, when the requirements of the above standard are not met and the area of the opening of the antenna coil is insufficient, the radiation efficiency of the antenna may decrease, and therefore it is recommended that the wiring pattern be preferably accommodated within the annular area as set according to the above standard to provide the opening of the antenna coil.

To solve the problem above, an object of the present invention is to provide a contactless information medium having parallel plate electrodes and designed to have an opening of an antenna coil.

Solution to Problem

According to an aspect of the present invention, the contactless information medium includes a film base, an antenna coil, an IC chip, a first plate electrode, and a second plate electrode. The antenna coil is disposed on a first surface of the film base, and formed in a spiral shape to perform wireless communication with an external device. The IC chip is disposed on the first surface of the film base, connected to the antenna coil via an IC chip-mounted portion, and performs wireless communication processing via the antenna coil. The first plate electrode is disposed on the first surface of the film base, and connected to at least one of an inner end and an outer end of the antenna coil. The second plate electrode is disposed on a second surface of the film base so as to be opposite to the first plate electrode in the thickness direction of the film base. Further, in the contactless information medium, each of the first plate electrode and the second plate electrode has a first electrode portion and a second electrode portion. The first electrode portion and the second electrode portion respectively extend along a first side direction of the antenna coil and a second side direction intersecting with the first side direction so that the first and second electrode portions are adjacent to an inner periphery or an outer periphery of the antenna coil when viewed perpendicular to the film base. Alternatively, the first and second plate electrodes are disposed along greater than or equal to one-third of the entire length of the inner periphery or the outer periphery of the antenna coil so as to be adjacent to the inner periphery or the outer periphery of the antenna coil when viewed perpendicular to the film base.

In the contactless information medium according to another aspect of the present invention, a capacitance portion capable of propagating high frequency signals is formed of the first and second plate electrodes disposed on opposite sides of the film base. Further, the first plate electrode and the second plate electrode have a first electrode portion and a second electrode portion. The first electrode portion extends along a first side direction (for example, a long side direction) of the antenna coil so as to be adjacent to an inner periphery or an outer periphery of the antenna coil formed, for example, in a rectangular spiral shape when viewed perpendicular to the film base. The second electrode portion extends along a second side direction (for example, a short side direction) of the antenna coil. This arrangement allows the provision of plate electrodes while providing an opening of the antenna coil (a region having no wiring pattern), under the constraints imposed by the limited outer dimensions of the contactless information medium.

In the contactless information medium according to another aspect of the present invention, a capacitance portion capable of propagating high frequency signals is formed with the first plate electrode and the second plate electrode disposed on opposite sides of the film base. Further, the first and second plate electrodes are disposed along greater than or equal to one-third of the entire length of the inner periphery or the outer periphery of the antenna coil so as to be adjacent to the inner periphery or the outer periphery of the antenna coil formed in a spiral shape when viewed perpendicular to the film base. This arrangement allows having plate electrodes while providing an opening of the antenna coil, under the constraints imposed by the limited outer dimensions of the contactless information medium.

In the contactless information medium, the first plate electrode may have a first inner plate electrode connected to the inner end of the antenna coil, and a first outer plate electrode connected to the outer end of the antenna coil. The second plate electrode may have a second inner plate electrode opposite to the first inner plate electrode in the thickness direction of the film base, and a second outer plate electrode opposite to the first outer plate electrode in the thickness direction of the film base. The first outer plate electrode may be disposed on the opposite side of the first inner plate electrode with respect to a center point or center line on the plane of the film base. In that case, the first plate electrode and the like are arranged well-balanced on the surface of the film base, enabling the contactless information medium to have parallel plate electrodes and an opening of the antenna coil under the constraints imposed by the limited outer dimensions of the contactless information medium.

In the contactless information medium, the first plate electrode may have a first inner plate electrode connected to the inner end of the antenna coil, and a first outer plate electrode connected to the outer end of the antenna coil. The second plate electrode may have a second inner plate electrode opposite to the first inner plate electrode in the thickness direction of the film base, and a second outer plate electrode opposite to the first outer plate electrode in the thickness direction of the film base. Each of the first inner plate electrode and the first outer plate electrode may have the first electrode portion and the second electrode portion. In this case, the first plate electrode and the like are arranged well-balanced on the surface of the film base, thus enabling the contactless information medium to have parallel plate electrodes and an opening of the antenna coil, under the constraints imposed by the limited outer dimensions of the contactless information medium.

The contactless information medium may further include a jumper portion connecting the second inner plate electrode to the second outer plate electrode on the second surface of the film base. With the second inner plate electrode connected to the second outer plate electrode with the jumper portion, the second inner plate electrode and the second outer plate electrode are disposed on opposite sides of the film base without the plate electrodes directly connecting to each other, and a capacitance portion capable of propagating high-frequency signals can be provided in a circuit. This enables an electrical connection between electrodes to be made with greater reliability because propagation of signals by the capacitance portion will not be disturbed even if the film base expands when heated.

In the contactless information medium, the pair of inner plate electrodes consisting of the first inner plate electrode and the second inner plate electrode, and the pair of outer plate electrodes consisting of the first outer plate electrode and the second outer plate electrode may be arranged such that, when viewed perpendicular to the film base, a portion of the antenna coil along which the pair of the inner plate electrodes are disposed is different from a portion of the antenna coil along which the pair of the outer plate electrodes are disposed. In that case, the pair of the inner plate electrodes inside the antenna coil, and the pair of the outer plate electrodes outside the antenna coil are arranged such that they do not share the same portions of the antenna coil. In other words, the pair of the inner plate electrodes and the pair of the inner plate electrodes are arranged so that the two pairs do not adjoin each other and do not sandwich the same portion of the antenna coil therebetween. Thus, the antenna coil, the pair of the inner plate electrodes, and the pair of the outer plate electrodes are disposed on the film base in a balanced manner. Specifically, the antenna coil and the plate electrodes can be adequately arranged in an equally spaced and annular antenna pattern arranging area defined in a standard (for example, ISO/IEC 14443-1, class 1) and the like.

In the contactless information medium, at least one of the pair of inner plate electrodes consisting of the first inner plate electrode and the second inner plate electrode, and the pair of outer plate electrodes consisting of the first outer plate electrode and the second outer plate electrode may be arranged such that an electric current flows in the same direction as an electric current passing through the antenna coil. The number of coil turns can be effectively increased by enabling at least one of the pair of inner plate electrodes and the pair of outer plate electrodes to function as a radiating element that passes an electric current in the same direction as an electric current passing through the antenna coil. Thus, it is possible to reduce the number of turns (that is, the area of the antenna pattern) required of the antenna coil due to the number of coil turns effectively increased, thereby increasing the area of the opening of the antenna coil.

In the contactless information medium, the antenna coil has any one of a circular shape, an elliptic shape, and a polygonal shape including a rectangular shape, as examples.

In the contactless information medium, the IC chip mounting portion may be disposed outside the antenna coil when viewed perpendicular to the film base. When relatively large parts such as the IC chip mounting portion and the IC chip mounted on the IC chip mounting portion are disposed outside the antenna coil, the area of the opening of the antenna coil can be increased.

In the contactless information medium, the IC chip mounting portion may be disposed outside the antenna coil when viewed perpendicular to the film base, and the pair of outer plate electrodes consisting of the first outer plate electrode and the second outer plate electrode may be disposed, when viewed perpendicular to the film base, along the outer periphery of the antenna coil and the IC chip mounting portion. In that case, the plate electrodes can be disposed by effectively using an empty space outside the antenna coil on the film base.

In the contactless information medium, the first and second plate electrodes may be disposed on the film base such that one of the plate electrodes entirely covers the other plate electrode when viewed perpendicular to the film base. Further, in the contactless information medium, the first and second plate electrodes may be disposed on the film base such that, when viewed perpendicular to the film base, one of the plate electrodes entirely covers the other plate electrode in the first direction parallel to the surface of the film base, and the latter plate electrode entirely covers the former plate electrode in the second direction parallel to the surface of the film base and perpendicular to the first direction. With this arrangement of the plate electrodes, even if the second plate electrode is misaligned from the first plate electrode due to manufacturing tolerances and the like, capacitance of the parallel plates formed by the electrodes will not change, which reduces variations in electric characteristics of products.

In the contactless information medium, an antenna arranging region having a frame shape, where the antenna coil is disposed, is defined on the periphery of the first surface of the film base. The antenna arranging region may be located between the outer periphery of the film base and an antenna non-arranging region that covers about more than half of the entire area of the first surface and that is defined in the center of the first surface. Defining such an antenna arranging region enables the contactless information medium to have parallel plate electrodes and a required opening of the antenna coil (an antenna non-arranging region), under the constraints imposed by the limited outer dimensions of the contactless information medium.

In the contactless information medium, the first plate electrode may be disposed adjacent to the closest antenna coil such that the space between the first plate electrode and the inner periphery or the outer periphery of the antenna coil is 0.5 mm or less. This allows the first plate electrode and the antenna coil to be arranged with greater efficiency.

In the contactless information medium, the film base may include an intermediate base formed of a dielectric, a first dielectric layer for adjustment formed of a dielectric and formed on a first surface of the intermediate base, and a second dielectric layer for adjustment formed of a dielectric and formed on a second surface of the intermediate base. With such a three-layer structure, the thickness of the film base formed of dielectric material, namely the distance between the first and second plate electrodes, can be more easily adjusted, for example, by changing the thickness of the first or second dielectric layer. This allows easier adjustment of the capacitance of a capacitor formed by the first and second plate electrodes without changing the shape and the like of an electrode pattern of the plate electrodes constituting the capacitor. Further, in the contactless information medium, an electrical connection is made by a capacitor formed by the first plate electrode connected to the antenna coil and the second plate electrode disposed on the rear surface. This configuration enables more simpler production and inspection processes than if the start end and the finish end of the antenna coil were directly connected to the conductor pattern on the rear surface, and a more reliable electrical connection.

In the contactless information medium, the dielectric constants of the dielectrics constituting the first and second dielectric layers may be greater than or equal to the dielectric constant of the dielectric constituting the intermediate base. This configuration enables easier adjustment of the capacitance of the capacitor formed by the first and second plate electrodes even if the first and second dielectric layers are thin.

In the contactless information medium, the first and second dielectric layers may be thinner than the intermediate base. In that case, the dielectric layers for adjusting the capacitance of the capacitor made of the first and second plate electrodes are thin, which decreases or minimizes variations in total thickness of the film base in products.

In the contactless information medium, a dielectric material constituting the first and second dielectric layers may be the same as or different from a dielectric material constituting the intermediate base.

In the contactless information medium, the first and second dielectric layers may be formed by applying the dielectric material to the intermediate base followed by curing. This configuration enables easier adjustment of the thickness and the like of the first and second dielectric layers, thus allowing the capacitance of the capacitor made of the first and second plate electrodes to be more easily adjusted.

In the contactless information medium, the metal foil constituting the antenna coil may be thicker than the metal foil constituting the second plate electrode. In that case, the electrical resistance of the antenna coil is reduced, increasing the radiation efficiency of the antenna of the contactless information medium.

Advantageous Effects of the Invention

The present invention provides a contactless information medium designed to have an opening of an antenna coil and parallel plate electrodes.

DESCRIPTION OF THE REPRESENTATIVE EMBODIMENTS

Embodiments of the present invention will be hereinafter described in detail with reference to the accompanying drawings. In the description of the drawings, like or equivalent elements are designated by like reference characters and will not be redundantly described. Also, it is to be understood that the embodiments described below are intended to be representative of the present invention. The present invention is not necessarily limited to the representative embodiments. One of skill in the art may be able to modify the embodiments below to nonetheless achieve the results of the present invention.

First Embodiment

With reference toFIG. 1AtoFIG. 3, a contactless communication medium of a first embodiment of the present invention will be described.FIG. 1Ais a top view of the contactless communication medium, showing its internal structure, whileFIG. 1Bis a rear view thereof, according to the first embodiment of the present invention.FIG. 2Ais a cross-sectional view of the contactless communication medium shown inFIG. 1AandFIG. 1B, taken along the line IIa-IIa, whileFIG. 2Bis a cross-sectional view of the contactless communication medium shown inFIG. 1AandFIG. 1B, taken along the line IIb-IIb.FIG. 3is a circuit diagram showing an equivalent circuit of the contactless communication medium shown inFIG. 1AandFIG. 1B.FIG. 1Bshows a rear side view of the contactless communication medium reversed with respect to its central longitudinal axis in the top view shown inFIG. 1A. The contactless communication medium is a contactless information medium capable of performing contactless communication with an external read/write device, such as a reader/writer, using signals primarily in the HF band, by applying RFID technology.

As shown inFIG. 1AtoFIG. 2B, a contactless communication medium10has a rectangular film base11. On a top surface (a first surface)11aof the film base11are an IC chip12, an IC chip mounting portion13, an antenna coil14, a first inner plate electrode15, and a first outer plate electrode16. On a rear surface (a second surface)11bof the film base11are a second inner plate electrode17, a second outer plate electrode18, and a jumper wire (a jumper portion)19.

The film base11is formed of materials having insulating properties and durability, for example, polyethylene naphthalate (PEN), polyethylene terephthalate copolymer (PET-G) and the like. Before machining, such as etching, a metal foil is laminated to both the front and rear surfaces11aand11bof the film base11. These metal foils are etched, for example, to form the IC chip mounting portion13, the antenna coil14, the first plate electrodes15and16, the second plate electrodes17and18, and the jumper wire19.

The antenna coil14is a planar spiral antenna and is electromagnetically coupled to an antenna of an external read/write device such as a reader/writer in order to perform wireless communication. The number of turns of the antenna coil14is, for example, about 2 to 6.FIG. 1AandFIG. 1Bshow an example with 4 turns, but the present invention is not limited to this. The width of each antenna wire constituting the antenna coil14is, for example, about 0.01 mm to 0.7 mm, more preferably about 0.02 mm to 0.6 mm. Further, the distance between the antenna wires constituting the antenna coil14is about 0.01 mm to 0.4 mm, more preferably about 0.02 mm to 0.3 mm. With this configuration, the antenna coil14sends and receives signals and receives power via wireless communication in a contactless manner. The antenna coil14is formed from a conductor disposed on the top surface11aof the film base11. Specifically, the antenna coil14is formed into a rectangular pattern by etching a copper foil or an aluminum foil having a thickness of 5 μm to 50 μm laminated on the top surface11aside of the film base11having insulating properties which is made of, for example, polyethylene terephthalate (PET) or polyethylene naphthalate (PEN) having a thickness of 15 μm to 50 μm. This antenna coil14is connected to the first outer plate electrode16at the outer end14b. The antenna coil14is connected to the first inner plate electrode15at the inner end14avia the IC chip mounting portion13and the IC chip12.

A first inner plate electrode15is a planar electrode formed inside the antenna coil14on the top surface11aof the film base11. The first inner plate electrode15has a first electrode portion15aextending along a long side direction (a first side direction) of the antenna coil14, and a second electrode portion15bextending along a short side direction (a second side direction) perpendicular to (intersecting) the long side direction of the antenna coil14. The first electrode portion15aand the second electrode portion15bare each disposed adjacent to the inner periphery of the antenna coil14when viewed perpendicular to the film base11.

A first outer plate electrode16is a planar electrode formed outside the antenna coil14on the top surface11aof the film base11. The first outer plate electrode16has a first electrode portion16aextending along the long side direction of the antenna coil14, and a second electrode portion16bextending along the short side direction of the antenna coil14, thus forming an L-shape as a whole. The first electrode portion16aand the second electrode portion16bare each disposed adjacent to the outer periphery of the antenna coil14when viewed perpendicular to the film base11. It is preferred that the first electrode portion16aand the second electrode portion16bbe disposed adjacent to the antenna coil14such that a spacing S defined by the outer periphery of the antenna coil14is 0.5 mm or less as shown inFIG. 12B. Similarly, it is preferred that other plate electrodes15,17,18and the like be disposed such that the spacing S defined by the inner periphery or the outer periphery of the antenna coil14is 0.5 mm or less. This close arrangement provides the required number of turns of the antenna coil14and realizes suitable arrangements of the plate electrodes15to18while providing the opening located at the center of the contactless communication medium10.

As shown inFIG. 1A, the portion of the antenna coil14along which the first inner plate electrode15is disposed (i.e., in the example ofFIG. 1A, the upper edge and the right edge of the antenna coil14) is different from the portion of the antenna coil14along which the first outer plate electrode16is disposed (i.e., in the example ofFIG. 1A, the left edge and the lower edge of the antenna coil14). That is, the first inner plate electrode15and the first outer plate electrode16are disposed such that they do not share the same portions (edges) of the antenna coil14. In other words, the first outer plate electrode16is disposed on the opposite side (i.e., point symmetrically) of the first inner plate electrode15with respect to a center point or a center line on the plane (surface11a) of the film base11. Such a symmetric arrangement also applies to the arrangement of a second inner electrode17and a second outer electrode18described later.

The distance between the first inner plate electrode15and the inner periphery of the antenna coil14, and the distance between the first outer plate electrode16and the outer periphery of the antenna coil14, are, for example, substantially the same as the separation width at the same circumferential position within the antenna coil14, and as described above, it is, for example, preferably 0.5 mm or less. However, the distance mentioned above may be greater than the separation width within the antenna coil14, or may be less than the separation width. Further, the first plate electrodes15and16are formed into a pattern by etching the metal foil laminated on the top surface11aof the film base11similarly to the antenna coil14. Second plate electrodes17and18and a jumper wire19described later are also similarly patterned by etching the metal foil laminated on the rear surface11bof the film base11.

The second inner plate electrode17is a planar electrode paired with the first inner plate electrode15, and is disposed on the rear surface11bof the film base11so that it is opposite to the first inner plate electrode15in the thickness direction of the film base11. Similarly to the first inner plate electrode15, the second inner plate electrode17has a first electrode portion17aextending along the long side direction of the antenna coil14, and a second electrode portion17bextending along the short side direction of the antenna coil14, thus forming an L-shape as a whole. As shown inFIG. 2AandFIG. 2B, the first and second electrode portions17aand17bare disposed opposite to the first and second electrode portions15aand15bof the first inner plate electrode15in the thickness direction of the film base11. The first and second electrode portions17aand17bare disposed adjacent to the inner periphery of the antenna coil14when viewed perpendicular to the film base11, similarly to the first and second electrode portions15aand15bof the first inner plate electrode15.

The second outer plate electrode18is a planar electrode paired with the first outer plate electrode16, and is disposed on the rear surface11bof the film base11so that it is opposite to the first outer plate electrode16in the thickness direction of the film base11. Similarly to the first outer plate electrode16, the second outer plate electrode18has a first electrode portion18aextending along the long side direction of the antenna coil14, and a second electrode portion18bextending along the short side direction of the antenna coil14, to form an L-shape as a whole. As shown inFIG. 2AandFIG. 2B, the first and second electrode portions18aand18bare disposed opposite to the first and second electrode portions16aand16bof the first outer plate electrode16in the thickness direction of the film base11. Therefore, the first and second electrode portions18aand18bare each disposed adjacent to the outer periphery of the antenna coil14when viewed perpendicular to the film base11, similarly to the first and second electrode portions16aand16bof the first outer plate electrode16.

As described above, with the first plate electrodes15and16and the second plate electrodes17and18disposed opposite to each other, the first plate electrodes15and16and the second plate electrodes17and18each form a capacitance portion (seeFIG. 3). As shown inFIG. 2AandFIG. 2B, in the present embodiment, the first plate electrodes15and16and the second plate electrodes17and18are disposed on the film base11such that the first plate electrodes15and16entirely cover the second plate electrodes17and18when viewed perpendicular to the film base11. With this arrangement of the plate electrodes, even if the second plate electrodes17and18are slightly misaligned from the first plate electrodes15and16due to manufacturing tolerances and the like, electrostatic capacitance of the parallel plates formed by both electrodes will not change, which reduces variations in electric characteristics of products.

The jumper wire19is a wire that connects the second inner plate electrode17to the second outer plate electrode18on the rear surface11bof the film base11. The jumper wire19connects a tip portion of the second electrode portion17bof the second inner plate electrode17to a side portion at the tip portion side of the first electrode portion18aof the second outer plate electrode18. It is preferred that the electrostatic capacitance between the jumper wire19and a portion of the antenna coil14opposite to the jumper wire18is low, and therefore it is preferred that the width is as small as possible (for example, about 1 to 3 mm). Further, the jumper wire19, disposed opposite to a portion of the antenna coil14in the thickness direction of the film base11, is preferably formed perpendicular to the antenna coil14. This further reduces the electrostatic capacitance generated. As used herein, the term “perpendicular” does not only include the case where the antenna coil14and the jumper wire19intersect each other at right angles when viewed perpendicular to the film base11(or when viewed through the antenna forming surface of the film base11), but also includes the case where they intersect each other at 90° plus or minus 10° (from 80° to 100°), which is a range permissible from a design perspective of. Further, “disposed perpendicular to” mentioned above means that the antenna coil14and the jumper wire19are “perpendicular to each other” at least at a portion where they are intersecting each other, but it is not necessarily required that the entire jumper wire19be “perpendicular” to the antenna coil14. Further, with the perpendicular arrangement, the jumper wire19connects the second plate electrodes17and18so that the distance therebetween is the shortest. This in turn reduces resistance losses of the jumper wire19. Such a jumper wire19allows an electrical connection between the second inner plate electrode17and the second outer plate electrode18.

The contactless communication medium10having such a configuration can be expressed as an equivalent circuit shown inFIG. 3. As shown inFIG. 3, the contactless communication medium10constitutes a circuit having the IC chip12, the antenna coil14, the first capacitance portion16and18, the jumper wire19, and the second capacitance portion15and17connected in series in that order.

The pair of inner plate electrodes15and17consisting of the first inner plate electrode15and the second inner plate electrode17(namely, the pair of plate electrodes forming the second capacitance portion15and17), and the pair of the outer plate electrodes16and18consisting of the first outer plate electrode16and the second outer plate electrode18(namely, the pair of plate electrodes forming the first capacitance portion16and18) are arranged such that an electric current flows in the same direction as an electric current passing through the antenna coil14. Such an arrangement is realized by providing the jumper wire19such that the electric current passing through the pair of outer plate electrodes16and18, the jumper wire19, and the pair of inner plate electrodes15and17flows in the same direction as the electric current passing through the antenna coil14when viewed perpendicular to the film base11(for example, clockwise or counterclockwise when viewed in the top surface11aside of the film base11).

The flow of an electric current passing through the antenna coil14at a given instant will now be described by providing an example case where the electric current passing through the antenna coil14flows from its outer end14btoward its inner end14a. As shown inFIG. 1Athe electric current passing through the antenna coil14flows from its outer end14bin a clockwise direction, circles along the antenna coil14in a rectangular shape several times, (for example, 4 times in the present embodiment), and flows into the electrode portion15aof the first inner plate electrode15via the inner end14a, the IC chip mounting portion13, and the IC chip12. Further, the electric current having flowed into the electrode portion15areturns to the outer end14bof the antenna coil14via the pair of inner plate electrodes15and17, the jumper wire19, and the pair of outer plate electrodes16and18. The direction of the electric current flowing in that order is a clockwise direction as shown in the figure ofFIG. 1A, and therefore conforms to the direction of the electric current passing through the antenna coil14.

As described above, in the contactless communication medium10of the present embodiment, capacitance portions capable of propagating high-frequency signals are formed by the first plate electrodes15and16, and the second plate electrodes17and18, which are respectively disposed on the surfaces11aand11bof the film base11so that they are opposite to each other. Further, the first plate electrodes15and16, and the second plate electrodes17and18have the first electrode portions15a,16a,17a, and18aextending along the long side direction of the antenna coil14, and the second electrode portions15b,16b,17b, and18bextending along the short side direction of the antenna coil14so that they are adjacent to the inner periphery or the outer periphery of the antenna coil14formed in a rectangular spiral shape when viewed perpendicular to the film base11. This arrangement of the plate electrodes enables the contactless communication medium to have parallel plate electrodes and an opening of the antenna coil14(a region having no wiring pattern) under the constraints imposed by the limited outer dimensions of the contactless communication medium. More specifically, for example, as shown inFIG. 12A, an opening11chaving no antenna coil14(an antenna non-arranging region) is disposed in a central portion of the top surface11aof the film base11, and on the periphery, an antenna arranging region11d, where the antenna coil14is to be arranged, is defined. In the contactless communication medium10of the present embodiment, the antenna coil14and the first plate electrodes15and16(the second plate electrodes17and18) are disposed in the antenna arranging region11d, and the region of the opening11ccovers about more than half of the entire area of the top surface11a, which provides a sufficiently large opening. In the contactless communication medium10, the IC chip mounting portion13and the IC chip12may be disposed in the opening11c; however, unlike the antenna coil14, these members are unlikely to pose problems when disposed in this position.

Further, in the contactless communication medium10of the present embodiment, the pair of inner plate electrodes15and17, and the pair of outer plate electrodes16and18are arranged such that, when viewed perpendicular to the film base11, the portion (edge) of the antenna coil14along which the pair of the inner plate electrodes15and17are disposed is different from the portion (edge) of the antenna coil14along which the pair of the outer plate electrodes16and18are disposed. In this case, the pair of inner plate electrodes15and17inside the antenna coil14and the pair of outer plate electrodes16and18outside the antenna coil14are arranged such that they do not share the same portions of the antenna coil14. That is, the pair of inner plate electrodes15and17and the pair of outer plate electrodes16and18are arranged such that they are not adjacent to each other and do not sandwich the same portion of the antenna coil14therebetween. With this arrangement, the antenna coil14, the pair of inner plate electrodes15and17, and the pair of outer plate electrodes16and18are disposed on the film base11in a balanced manner. Specifically, the antenna coil14, and the plate electrodes15,16,17, and18are appropriately arranged in an equally spaced and annular antenna pattern arrangement area as set according to a standard (for example, ISO/IEC 14443-1, Class 1) and the like.

In the contactless communication medium10of the present embodiment, the pair of inner plate electrodes15and17, and the pair of outer plate electrodes16and18are arranged so that an electric current flows in the same direction as an electric current passing through the antenna coil14as described above. The number of coil turns can be effectively increased by enabling the pair of inner plate electrodes15and17, and the pair of outer plate electrodes16and18to function as a radiating element that passes an electric current in the same direction as an electric current passing through the antenna coil14. In the example ofFIG. 1AandFIG. 1B, the number of turns of the antenna coil14is 4. However, the effective number of coil turns has been increased by 1 due to the plate electrodes15,16,17, and18, and the jumper wire19, and thus, the antenna coil14has an antenna function equivalent to that of the antenna coil14with 5 turns. Consequently, the number of turns (i.e., a region of an antenna pattern) required of the antenna coil14is reduced due to the effectively increased number of coil turns, thus increasing the area of the opening of the antenna coil14.

Further, in the present embodiment, both the pair of inner plate electrodes15and17, and the pair of outer plate electrodes16and18are disposed along two sides of the rectangular antenna coil14. However, for example, the pair of inner plate electrodes may be disposed along one side of the antenna coil14and the pair of outer plate electrodes may be disposed along the remaining three sides in a U-shape. Conversely, the pair of outer plate electrodes may be disposed along one side of the antenna coil14and the pair of inner plate electrodes may be disposed along the remaining three sides of the antenna coil14. These arrangements also produces the effects mentioned above.

Second Embodiment

With reference toFIG. 4AandFIG. 4B, a contactless communication medium of a second embodiment of the present invention will now be described.FIG. 4Ais a top view of a contactless communication medium, showing its internal structure, according to the second embodiment of the present invention, whileFIG. 4Bis a rear view thereof.FIG. 4Bis a rear view thereof, where the top view shown inFIG. 4Ais reversed about its central longitudinal axis. A contactless communication medium20of the present embodiment differs from the contactless communication medium10of the first embodiment in that a jumper wire21, connecting the second inner plate electrode17to the second outer plate electrode18, connects a tip portion of the first electrode portion17aof the second inner plate electrode17to a side portion near a tip portion of the second electrode portion18bof the second outer plate electrode18. Thus, in the contactless communication medium20, the pair of inner plate electrodes15and17, and the pair of outer plate electrodes16and18do not pass an electric current in the same direction as an electric current passing through the antenna coil14.

The flow of an electric current passing through the antenna coil14of the contactless communication medium20at a given instant will be described by providing an example case where the electric current passing through the antenna coil14flows from its outer end14btoward its inner end14a. As shown inFIG. 1A, the electric current passing through the antenna coil14flows from its outer end14bin a clockwise direction, circles around several times (for example, 4 times in the present embodiment) along the antenna coil14in a rectangular shape, and flows into the electrode portion15aof the first inner plate electrode15via the inner end14a, the IC chip mounting portion13, and the IC chip12. The electric current flowing into the electrode portion15areturns to the outer end14bof the antenna coil14via the pair of inner plate electrodes15and17, the jumper wire19, and the pair of outer plate electrodes16and18. The direction of the electric current flowing in this order is a counterclockwise direction as shown inFIG. 4A, and therefore does not conform to the direction of the electric current passing through the antenna coil14.

Thus, in the contactless communication medium20of the second embodiment, the pair of inner plate electrodes15and17and the pair of outer plate electrodes16and18do not function as radiating elements, but as capacitance portions. The contactless communication medium20has a structure similar to the contactless communication medium10of the first embodiment regarding points other than the above, and therefore produces effects similar to those of the contactless communication medium10.

Third Embodiment

With reference toFIGS. 5A and 5B, a contactless communication medium of a third embodiment of the present invention will now be described.FIG. 5Ais a top view of a contactless communication medium, showing its internal structure, according to the third embodiment of the present invention, whileFIG. 5Bis a rear view thereof.FIG. 5Bis a rear view thereof, where the top view shown inFIG. 5Ais reversed about its central longitudinal axis. A contactless communication medium30of the present embodiment differs from the contactless communication medium10of the first embodiment in that, instead of not having the pair of outer plate electrodes16and18, and the jumper wire19, it has a conduction portion31for electrically connecting the outer end14bof the antenna coil14and the second inner plate electrode17.

The conduction portion31is a wire extending from the tip portion of the first electrode portion17aof the second inner plate electrode17to the position overlapping the outer end14bof the antenna coil14in the thickness direction of the film base11. The tip of the conduction portion31and the outer end14bare connected to each other by caulking, welding and the like via a through hole disposed in the film base11. With the outer end14bof the antenna coil14connected to the second inner plate electrode17via the conduction portion31, the contactless communication medium30constitutes an equivalent circuit of a structure where the first capacitance portion16and18, and the jumper wire19are replaced by the conduction portion31in the equivalent circuit shown inFIG. 3.

In the contactless communication medium30of the present embodiment, a capacitance portion capable of propagating high-frequency signals is formed of the first inner plate electrode15and the second inner plate electrode17respectively disposed on surfaces11aand11bof the film base11so as to be opposite to each other. Further, the first inner plate electrode15and the second inner plate electrode17respectively have the first electrode portions15aand17aextending along the long side direction of the antenna coil14, and the second electrode portions16band18bextending along the short side direction of the antenna coil14so as to be adjacent to the inner periphery of the antenna coil14formed in a rectangular spiral shape when viewed perpendicular to the film base11. This arrangement of the plate electrodes enables the contactless communication medium to have parallel plate electrodes and an opening of the antenna coil14under the constraints imposed by the limited outer dimensions of the contactless communication medium.

In the present embodiment, the pair of outer plate electrodes16and18, which are formed outside the antenna coil14, are omitted among the plate electrodes constituting the contactless communication medium10of the first embodiment. Alternatively, the pair of inner plate electrodes15and17may be omitted instead of the pair of outer plate electrodes16and18. In that case, for example, the IC chip mounting portion13is disposed anywhere between the inner end14aand the outer end14bof the antenna coil14, and a conduction portion is provided for electrically connecting the inner end14aof the antenna coil14and the second outer plate electrode18. Such a configuration enables the contactless communication medium to have parallel plate electrodes and an opening of the antenna coil14under the constraints imposed by the limited outer dimensions of the contactless communication medium, similarly to the above-described contactless communication medium30.

Fourth Embodiment

With reference toFIG. 6AandFIG. 6B, a contactless communication medium of a fourth embodiment of the present invention will now be described.FIG. 6Ais a top view of a contactless communication medium, showing its inner structure, according to the fourth embodiment of the present invention, whileFIG. 6Bis a rear view thereof. Further,FIG. 6Bis a rear view thereof, where the top view shown inFIG. 6Ais reversed about its central longitudinal axis. Regarding a contactless communication medium40of the present embodiment, a configuration that is primarily different from that of the contactless communication medium10of the first embodiment is hereinafter described.

The contactless communication medium40has a first inner plate electrode41and a first outer plate electrode42formed inside and outside the rectangular antenna coil14on the top surface11aof the film base11. The first inner plate electrode41is disposed along the four sides of the antenna coil14so as to be adjacent to the inner periphery of the antenna coil14. That is, the first inner plate electrode41is formed such that portions along each of the four sides of the antenna coil14are coupled to one another, and almost make a circle around the inner periphery of the antenna coil14. Thus, the first inner plate electrode41has an electrode portion extending along each of the long side direction and the short side direction of the antenna coil14when viewed perpendicular to the film base11. The first outer plate electrode42is disposed along the short side portion of the antenna coil14outside the antenna coil14. The first outer plate electrode42consists of a rectangular first portion42acovering more than half of the entire area, and 14 rectangular second portions42bconnected to a wiring pattern branched off from the central portion of the short side portion of the first portion42a. The second portion42bis smaller than the first portion42a, and the portions are arranged in 2 rows, 7 pieces each.

Further, the contactless communication medium40has a second inner plate electrode43and a second outer plate electrode44formed on the inside and the outside of a rectangular shaped region (i.e., a region showing the antenna coil14by dashed lines inFIG. 6Bcorresponding to the antenna coil14on the rear surface11bof the film base11. The second inner plate electrode43is formed so as to be opposite to the first inner plate electrode41in the thickness direction of the film base11. The second inner plate electrode43is arranged along the 4 sides of the rectangular shaped region so as to be adjacent to the inner periphery of the rectangular shaped region corresponding to the antenna coil14, similarly to the first inner plate electrode41. Namely, the second inner plate electrode43has an electrode portion extending along each of the long side direction and the short side direction of the antenna coil14when viewed perpendicular to the film base11. On the other hand, the second outer plate electrode44is formed so as to be opposite to the first outer plate electrode42in the thickness direction of the film base11. The second outer plate electrode44consists of a rectangular shaped first portion44acovering half or more of the entire area, and 2 rectangular shaped second portions44bconnected to wiring patterns extending from both edges of a short side portion of the first portion44a. The first portion44ais arranged so as to be opposite to the first portion42aof the first outer plate electrode42in the thickness direction of the film base11. The second portion44bis arranged so as to be opposite to 1 column (i.e., 7 pieces) of the second portions42bof the first outer plate electrode42in the thickness direction of the film base11. On the rear surface11bof the film base11, a terminal of the second inner plate electrode43and the first portion44aof the second outer plate electrode44are connected with a jumper wire45.

A flow of an electric current passing through the antenna coil14of the contactless communication medium40at a given instant is hereinafter described by providing an example of the case where the electric current passing through the antenna coil14flows from its outer end14btoward its inner end14a. As shown inFIG. 6A, the electric current passing through the antenna coil14flows from its outer end14bin a clockwise direction as shown in the figure, circles around the antenna coil14in a rectangular shape several times, (for example, 5 times in the present embodiment), and flows into the first inner plate electrode41via the inner end14a, the IC chip mounting portion13, and the IC chip12. Further, the electric current flowing into the first inner plate electrode41returns to the outer end14bof the antenna coil14via the pair of the inner plate electrodes41and43consisting of the first inner plate electrode41and the second inner plate electrode43, the jumper wire45, and the pair of outer plate electrodes42and44consisting of the first outer plate electrode42and the second outer plate electrode44. As described above, the pair of inner plate electrodes41and43are formed in a shape almost making a circle clockwise as shown inFIG. 6Ain the inner circumference side of the antenna coil14along the 4 sides of the antenna coil14when viewed perpendicular to the film base11. Therefore, the direction of the electric current passing through the pair of inner plate electrodes41and43conforms to the direction of the electric current passing through the antenna coil14.

As such, in the contactless communication medium40, the pair of inner plate electrodes41and43are arranged so as to pass the electric current along the same direction as the direction of the electric current passing through the antenna coil14. The effective number of coil turns can be increased by having the pair of inner plate electrodes41and43function as a radiating element that passes the electric current in the same direction as the direction of the electric current passing through the antenna coil14. Thus, it is possible to reduce the number of turns required of the antenna coil14due to the effectively increased number of coil turns, and the area of the opening of the antenna coil14can be increased. Further, in this example, the pair of outer plate electrodes42and44do not function as a radiating element, but purely function as a capacitance portion.

Further, as shown inFIG. 6AandFIG. 6B, in the contactless communication medium40, the first inner plate electrode41and the second inner plate electrode43are arranged on the film base11such that the first inner plate electrode41entirely covers the second inner plate electrode43when viewed perpendicular to the film base11. Further, the first electrode portion42aof the first outer plate electrode42, and the first electrode portion44aof the second outer plate electrode44are arranged on the film base11such that the first electrode portion42aentirely covers the first electrode portion44awhen viewed perpendicular to the film base11. Further, the second electrode portion42bof the first outer plate electrode42, and the second electrode portion44bof the corresponding second outer plate electrode44are arranged on the film base11such that the second electrode portion42bentirely covers the second electrode portion44bin the longitudinal direction of the film base11(a first direction parallel to the surface of the film base), and the second electrode portion44bentirely covers the second electrode portion42bin the transverse direction of the film base11(a second direction parallel to the surface of the film base and perpendicular to the first direction), when viewed perpendicular to the film base11. By arranging the plate electrodes as such, even when a slight misalignment in formation positions of the second plate electrodes43and44develops relative to formation positions of the first plate electrodes41and42due to manufacturing tolerance and the like, electrostatic capacitance of the parallel plates formed by the electrodes will not change, and an effect of reducing variance in electric properties of products can be expected.

Further, in the contactless communication medium40, the first inner plate electrode41and the second inner plate electrode43are arranged so as to be adjacent to the antenna coil14along the 4 sides of the antenna coil14when viewed perpendicular to the film base11. This arrangement of the plate electrodes enables the contactless communication medium to have parallel plate electrodes and an opening of the antenna coil14under the constraints imposed by the limited outer dimensions of the contactless communication medium.

Fifth Embodiment

Next, a contactless communication medium of a fifth embodiment of the present invention will be described with reference toFIG. 7AandFIG. 7B.FIG. 7Ais a top view showing an internal structure of a contactless communication medium of the fifth embodiment of the present invention, andFIG. 7Bis a rear view thereof. Further,FIG. 7Bshows a rear side view thereof, where the top view shown inFIG. 7Ais reversed about its central longitudinal axis. A contactless communication medium50of the present embodiment is primarily different from the contactless communication medium10of the first embodiment in that the IC chip mounting portion13is arranged on the outside of the antenna coil14when viewed perpendicular to the film base11, but is similar to the structure of the contactless communication medium10of the first embodiment regarding other aspects. Namely, although there are a few differences in size and position, the contactless communication medium50has first plate electrodes51and52, and second plate electrodes53and54which is a structure similar to the first plate electrodes15and16, and the second plate electrodes17and18in the contactless communication medium10. Further, the contactless communication medium50has a jumper wire55connecting a second inner plate electrode53and a second outer plate electrode54, similarly to the jumper wire19in the contactless communication medium10.

In the contactless communication medium50, the IC chip mounting portion13is arranged along a corner of the top surface11aof the film base11. On the other hand, the antenna coil14and the first plate electrodes51and52are arranged along a corner facing, in a diagonal direction, a corner where the IC chip mounting portion13is arranged on the top surface11aof the film base11. In an example ofFIG. 7AandFIG. 7B, one supporting portion13aof the IC chip mounting portion13is connected to a second electrode portion52bof the first outer plate electrode52via a predetermined wiring pattern. Further, the other supporting portion13bof the IC chip mounting portion13is connected to the outer end14bof the antenna coil14.

According to the contactless communication medium50of the fifth embodiment, it is possible to obtain effects similar to those produced by the contactless communication medium10of the first embodiment described above, and concurrently the area of the opening of the antenna coil14can be increased by arranging relatively large parts such as the IC chip mounting portion13and the IC chip12mounted on the IC chip mounting portion13not in the inside, but on the outside of the antenna coil14.

Sixth Embodiment

Next, a contactless communication medium of a sixth embodiment of the present invention will be described with reference toFIG. 8AandFIG. 8B.FIG. 8Ais a top view showing an internal structure of a contactless communication medium of the sixth embodiment of the present invention, andFIG. 8Bis a rear view thereof. Further,FIG. 8Bshows a rear side view thereof, where the top view shown inFIG. 8Ais reversed about its central longitudinal axis. A contactless communication medium60of the present embodiment is primarily different from the contactless communication medium40of the fourth embodiment in that the IC chip mounting portion13is arranged on the outside of the antenna coil14when viewed perpendicular to the film base11, but is similar to the structure of the contactless communication medium40of the fourth embodiment regarding other details. Namely, although there are a few differences in size and position, the contactless communication medium60has first plate electrodes61and62, and second plate electrodes63and64which is a structure similar to the first plate electrodes41and42, and the second plate electrodes43and44in the contactless communication medium40. Further, the contactless communication medium60has a jumper wire65connecting a second inner plate electrode63and a second outer plate electrode64, similarly to the jumper wire45in the contactless communication medium40.

In the contactless communication medium60, the IC chip mounting portion13is arranged along a corner of the top surface11aof the film base11, similarly to the contactless communication medium50of the fifth embodiment. On the other hand, the antenna coil14and the first inner plate electrode61are arranged along a corner facing, in a diagonal direction, a corner where the IC chip mounting portion13is arranged on the top surface11aof the film base11. In the example ofFIG. 8AandFIG. 8B, one supporting portion13aof the IC chip mounting portion13is connected to a first electrode portion62bof the first outer plate electrode62via a predetermined wiring pattern. Further, the other supporting portion13bof the IC chip mounting portion13is connected to the outer end14bof the antenna coil14.

According to the contactless communication medium60of the sixth embodiment, it is possible to obtain effects similar to those produced by the contactless communication medium40of the fourth embodiment described above, and concurrently the area of the opening of the antenna coil14can be increased by arranging relatively large parts such as the IC chip mounting portion13and the IC chip12mounted on the IC chip mounting portion13not in the inside, but on the outside of the antenna coil14.

Further, in the contactless communication medium60, the pair of outer plate electrodes62and64consisting of the first outer plate electrode62and the second outer plate electrode64are arranged along the outer periphery and the IC chip mounting portion13in the short side portion of the antenna coil14when viewed perpendicular to the film base11. A space on the film base11where the first outer plate electrode62and the second outer plate electrode64are arranged is a space necessarily formed when the IC chip mounting portion13is arranged on the outside of the antenna coil14. By arranging the first outer plate electrode62and the second outer plate electrode64on the space necessarily formed as such, plate electrodes can be arranged by effectively using an empty space on the outside of the antenna coil14on the film base11. Thereby, the area of plate electrodes functioning as a capacitance portion can be increased, and performance as a capacitance portion can be stabilized.

Seventh Embodiment

Next, a contactless communication medium of a seventh embodiment of the present invention will be described with reference toFIG. 9AandFIG. 9B.FIG. 9Ais a top view showing an internal structure of a contactless communication medium of the seventh embodiment of the present invention, andFIG. 9Bis a rear view thereof. Further,FIG. 9Bshows a rear side view thereof, where the top view shown inFIG. 9Ais reversed about its central longitudinal axis. A contactless communication medium70of the present embodiment is different from the contactless communication medium60of the sixth embodiment in that it further has a first outer plate electrode71, a second outer plate electrode72, and a jumper wire73, but is similar to the contactless communication medium60regarding other details. The first outer plate electrode71and the second outer plate electrode72are arranged along the outer periphery and the IC chip mounting portion13in the short side portion of the antenna coil14when viewed perpendicular to the film base11. Further, the jumper wire73is branched off from the jumper wire65, and connects the second outer plate electrode72and the second plate electrodes63and64.

In the contactless communication medium70of the seventh embodiment, in addition to the contactless communication medium60of the sixth embodiment, the area of plate electrodes functioning as a capacitance portion can be further increased by arranging the plate electrodes (the first outer plate electrode71and the second outer plate electrode72) while effectively using also a space necessarily formed on the outside of the long side portion of the antenna coil14, and performance as a capacitance portion can be stabilized. Further, in the contactless communication medium70, a structure omitting the first outer plate electrode62and the second outer plate electrode64, namely, a structure of arranging the plate electrodes while effectively using only a space necessarily formed in the outside of the long side portion of the antenna coil14, may be employed.

Eighth Embodiment

Next, a contactless communication medium of an eighth embodiment of the present invention will be described with reference toFIG. 10AandFIG. 10B.FIG. 10Ais a top view showing an internal structure of a contactless communication medium of the eighth embodiment of the present invention, andFIG. 10Bis a rear view thereof. Further,FIG. 10Bshows a rear side view thereof, where the top view shown inFIG. 10Ais reversed about its central longitudinal axis. A contactless communication medium80of the present embodiment is different in shape from the contactless communication medium10of the first embodiment in that first plate electrodes82and83, and second plate electrodes84and85are formed not in an “L” shape, but in a crescent shape, but is equivalent to the contactless communication medium10regarding its function as a circuit (which is to be described later in detail).

The first inner plate electrode82is a crescent shaped planar electrode formed in the inside of an antenna coil81which is a pattern formed in a circle on the top surface11aof the film base11. The first inner plate electrode82is arranged along substantially half of the inner periphery of the antenna coil81(i.e., at least a third or more of the entire length of the inner circumference of the antenna coil81), so as to be adjacent to the inner periphery of the antenna coil81when viewed perpendicular to the film base11. The first outer plate electrode83is a crescent shaped planar electrode formed on the outside of the antenna coil81which is a pattern formed in a circle on the top surface11aof the film base11. The first outer plate electrode83is arranged along substantially half of the outer periphery of the antenna coil81(i.e., at least a third or more of the entire length of the outer circumference of the antenna coil81), so as to be adjacent to the outer periphery of the antenna coil81when viewed perpendicular to the film base11.

As shown inFIG. 10A, a portion of the antenna coil81along which the first inner plate electrode82is arranged (i.e., the left half of an arc portion of the antenna coil81) is different from a portion of the antenna coil81along which the first inner plate electrode82is arranged (i.e., the right half of the arc portion of the antenna coil81in an example ofFIG. 10A). Namely, the first inner plate electrode82and the first outer plate electrode83are arranged such that they do not share the same portions of the antenna coil81(the arc portion). In other words, the first outer plate electrode83is arranged on the opposite side (i.e., point symmetrically) to the first inner plate electrode82with respect to a center point or a center line on the plane (surface11a) of the film base11, similarly to the first embodiment and the like. Further, this holds true for the arrangement relation between the second inner plate electrode84and the second outer plate electrode85as described later.

The second inner plate electrode84is a crescent-shaped planar electrode forming a pair with the first inner plate electrode82, and is arranged on the rear surface11bof the film base11so as to be opposite to the first inner plate electrode82in the thickness direction of the film base11. The second inner plate electrode84extends along substantially half of the inner periphery of the antenna coil81(i.e., at least a third or more of the entire length of the inner circumference of the antenna coil81) when viewed perpendicular to the film base11, similarly to the first inner plate electrode82. The second outer plate electrode85is a crescent-shaped planar electrode forming a pair with the first outer plate electrode83, and is arranged on the rear surface11bof the film base11so as to be opposite to the first outer plate electrode83in the thickness direction of the film base11. The second outer plate electrode85extends along substantially half of the outer periphery of the antenna coil81(i.e., at least a third or more of the entire length of the outer circumference of the antenna coil81) when viewed perpendicular to the film base11, similarly to the first outer plate electrode83. The second inner plate electrode84and the second outer plate electrode85are connected with a jumper wire86.

The first plate electrodes82and83and the second plate electrodes84and85form each of the 2 capacitance portions by arranging the first plate electrodes82and83and the second plate electrodes84and85to be opposite to each other. In the present embodiment, as an example, the first plate electrodes82and83, and the second plate electrodes84and85are arranged on the film base11such that the first plate electrodes82and83entirely cover the second plate electrodes84and85when viewed perpendicular to the film base11. By arranging the plate electrodes as such, even when a slight misalignment in formation positions of the second plate electrodes84and85develops relative to formation positions of the first plate electrodes82and83due to manufacturing tolerance and the like, electrostatic capacitance of the parallel plates formed by both electrodes will not change, and an effect of reducing variance in electric properties of products can be expected.

The contactless communication medium80having such a structure constitutes an equivalent circuit of the contactless communication medium10shown inFIG. 3, where the antenna coil14is replaced by the antenna coil81, the first capacitance portions15and17are replaced by the capacitance portions82and84formed by the first inner plate electrode82and the second inner plate electrode84, the jumper wire19is replaced by the jumper wire86, and the second capacitance portions16and18is replaced by the capacitance portions83and85formed by the first outer plate electrode83and the second outer plate electrode85. As such, the contactless communication medium80is different from the contactless communication medium10of the first embodiment regarding the shape of each portion, but is equivalent thereto in the function as a circuit.

The pair of inner plate electrodes82and84consisting of the first inner plate electrode82and the second inner plate electrode84(namely, the pair of plate electrodes forming the capacitance portions82and84), and the pair of outer plate electrodes83and85consisting of the first outer plate electrode83and the second outer plate electrodes85(namely, the pair of plate electrodes forming the capacitance portion83and85) are arranged so as to pass an electric current along the same direction as the direction of an electric current passing through the antenna coil81. Such an arrangement is realized by setting up the jumper wire86such that the electric current passing through the pair of inner plate electrodes82and84, the jumper wire86, and the pair of outer plate electrodes83and85passes in the same direction as the direction of the electric current passing through the antenna coil81when viewed perpendicular to the film base11(for example, a clockwise or counterclockwise direction when viewed in the top surface11aside of the film base11).

A flow of an electric current passing through the antenna coil81at a given instant is hereinafter described by providing an example of the case where the electric current passing through the antenna coil81flows from its outer end81btoward its inner end81a. As shown in ofFIG. 10A, the electric current passing through the antenna coil81flows from its outer end81bin a counterclockwise direction as shown in the figure, circles around the antenna coil81in a circular shape several times, (for example, 4 times in the present embodiment), and flows into the first inner plate electrode82via the inner end81a, the IC chip mounting portion13, and the IC chip12. Further, the electric current flowing into the first inner plate electrode82returns to the outer end81bof the antenna coil81via the pair of inner plate electrodes82and84, the jumper wire86, and the pair of outer plate electrodes83and85. The direction of such electric current is a counterclockwise direction as shown inFIG. 10A, and therefore conforms to the direction of the electric current passing through the antenna coil81.

As such, in the contactless communication medium80of the eighth embodiment, capacitance portions capable of propagating high-frequency signals are formed on both surfaces11aand11bof the film base11such that the first plate electrodes82and83and the second plate electrodes84and85are arranged disposed to each other. Further, the first plate electrodes82and83and the second plate electrodes84and85are arranged along roughly half or more of the inner periphery or the outer periphery of the antenna coil81so as to be adjacent to the inner periphery or the outer periphery of the antenna coil81formed in a circular spiral shape when viewed perpendicular to the film base11. This arrangement of the plate electrodes enables the contactless communication medium to have parallel plate electrodes and an opening of the antenna coil81under the constraints imposed by the limited outer dimensions of the contactless communication medium.

Further, in the contactless communication medium80of the eighth embodiment, the pair of inner plate electrodes82and84and the pair of outer plate electrodes83and85are arranged such that, when viewed perpendicular to the film base11, the portion (an arc portion) of the antenna coil81along which the pair of inner plate electrodes82and84are arranged is different from the portion (an arc portion) of the antenna coil81along which the pair of outer plate electrodes83and85are arranged. In this case, the pair of inner plate electrodes82and84in the inside of the antenna coil81, and the pair of outer plate electrodes83and85of the antenna coil81are arranged such that they do not share the same portions of the antenna coil81. Namely, the pair of inner plate electrodes82and84and the pair of outer plate electrodes83and85are arranged such that they are not adjacent to each other and do not sandwich the same portion of the antenna coil14therebetween. Thereby, the antenna coil81, the pair of inner plate electrodes82and84, and the pair of outer plate electrodes83and85can be arranged on the film base11with balance. Specifically, the antenna coil81, and the plate electrodes82,83,84, and85can be appropriately arranged in an equally spaced and annular antenna pattern arrangement area as set in a standard (for example, ISO/IEC 14443-1, Class 1) and the like.

Further, in the contactless communication medium80of the eighth embodiment, the pair of inner plate electrodes82and84, and the pair of outer plate electrodes83and85are arranged so as to pass an electric current along the same direction as the electric current passing through the antenna coil81as described above. The effective number of coil turns can be increased by having the pair of inner plate electrodes82and84and the pair of outer plate electrodes83and85function as radiating elements that pass an electric current along the same direction as the direction of an electric current passing through the antenna coil81. In the example ofFIG. 10AandFIG. 10B, the number of turns of the antenna coil81is 4. However, the effective number of coil turns is increased by 1 due to the plate electrodes82,83,84, and85, and the jumper wire86, and an antenna function equivalent to that of the antenna coil81but having 5 turns can be provided. Thus, it is possible to reduce the number of turns (namely, the area of an antenna pattern) required of the antenna coil81due to the effectively increased number of coil turns, and the area of the opening of the antenna coil81can be increased.

Accordingly, as in the case of the contactless communication medium80of the eighth embodiment, where the antenna coil81is patterned in a circular shape, and the plate electrodes82,83,84, and85are tailored to the circular shaped antenna coil81, it is possible to produce similar effects to those produced in the contactless communication medium10of the first embodiment. Further, in the contactless communication medium80, by pattern forming the antenna coil81in a circular shape, the film base11in the contactless communication medium80is closer in shape to a square than the film base11in the contactless communication medium10where the antenna coil14is formed in a rectangular shape. Thereby, the contactless communication medium80can be appropriately used as a contactless communication medium incorporated into a circular object in a planar view of, for example, of a token (coin) of a casino and the like.

Further, present embodiment is illustrated by an example where the pair of inner plate electrodes82and84are arranged along substantially half of the inner periphery of the antenna coil81when viewed perpendicular to the film base11, and the pair of outer plate electrodes83and85are arranged along substantially half of the outer periphery of the antenna coil81when viewed perpendicular to the film base11. However, the pair of inner plate electrodes may be arranged along about more than half of the inner periphery of the antenna coil81when viewed perpendicular to the film base11, while the pair of outer plate electrodes83and85may not be arranged along substantially half of the outer periphery of the antenna coil81when viewed perpendicular to the film base11. Further, the pair of outer plate electrodes83and85may be arranged along about more than half of the outer periphery of the antenna coil81when viewed perpendicular to the film base11, while the pair of inner plate electrodes may not be arranged along about more than half of the inner periphery of the antenna coil81when viewed perpendicular to the film base11. Namely, it is only necessary that at least one of the pair of inner plate electrodes and the pair of outer plate electrodes are arranged along about more than half of the inner periphery or the outer periphery of the antenna coil81. Further, the shape of the antenna coil81may not be a circular shape, but an elliptic shape, or it may have a polygonal shape. In the case of using an antenna coil having such a shape other than a circular shape, a structure of a contactless communication medium based on the idea similar to the content described in the present embodiment may be adopted.

Ninth Embodiment

Next, a contactless communication medium of a ninth embodiment of the present invention will be described with reference toFIG. 11AandFIG. 11B.FIG. 11Ais a top view showing an internal structure of a contactless communication medium of a ninth embodiment of the present invention, andFIG. 11Bis a rear view thereof. Further,FIG. 11Bshows a rear side view thereof, where the top view shown inFIG. 11Ais reversed about its central longitudinal axis. A contactless communication medium90of the present embodiment is primarily different from the contactless communication medium80of the eighth embodiment in that the IC chip mounting portion13is arranged on the outside of the antenna coil81when viewed perpendicular to the film base11. Further, the contactless communication medium90is primarily different from the contactless communication medium80of the eighth embodiment in that the pair of crescent-shaped inner plate electrodes82and84are replaced by a pair of inner plate electrodes92and94formed along nearly the entire inner circumference of the antenna coil81when viewed perpendicular to the film base11

The first inner plate electrode92is arranged along nearly the entire inner periphery of the antenna coil81so as to be adjacent to the inner periphery of the antenna coil81when viewed perpendicular to the film base11. On the other hand, the first outer plate electrode93is arranged along substantially half of the outer periphery of the antenna coil81so as to be adjacent to the outer periphery of the antenna coil81when viewed perpendicular to the film base11, similarly to the first outer plate electrode83in the contactless communication medium80of the eighth embodiment. The second plate electrodes94and95are formed on the rear surface11bof the film base11so as to be opposite to the first plate electrodes92and93in the thickness direction of the film base11. The second inner plate electrode94and the second outer plate electrode95are connected with a jumper wire96.

A flow of an electric current passing through the antenna coil81of the contactless communication medium90at a given instant is hereinafter described by providing an example of the case where the electric current passing through the antenna coil81flows from its outer end81btoward its inner end81a. As shown inFIG. 11A, the electric current passing through the antenna coil81flows from its outer end81bin a counterclockwise direction as shown in the figure, circles around the antenna coil81in a circular shape several times, (for example, 4 times in the present embodiment), and flows into the first inner plate electrode92from the inner end81a. Further, the electric current flowing into the first inner plate electrode92returns to the outer end14bof the antenna coil14via the pair of inner plate electrodes92and94, the jumper wire96, and the pair of outer plate electrodes93and95. As described above, the pair of inner plate electrodes92and94are formed in a shape almost making a circle counterclockwise, as shown inFIG. 11A, along the inner periphery of the antenna coil81when viewed perpendicular to the film base11. Therefore, the direction of the electric current passing through the pair of inner plate electrodes92and94conforms to the direction of the electric current passing through the antenna coil81.

As such, in the contactless communication medium90, the pair of inner plate electrodes92and94are arranged so as to pass the electric current in the same direction as the direction of the electric current passing through the antenna coil81. The effective number of coil turns can be increased by having the pair of inner plate electrodes92and94function as a radiating element that passes an electric current along the same direction as the direction of an electric current passing through the antenna coil81. Thus, it is possible to reduce the number of turns required of the antenna coil81due to the effectively increased number of coil turns, and the area of the opening of the antenna coil81can be increased. On the other hand, in this example, the pair of outer plate electrodes93and95do not function as a radiating element, but purely function as a capacitance portion.

According to the contactless communication medium90of the ninth embodiment, it is possible to increase the area of the opening of the antenna coil81by arranging relatively large parts such as the IC chip mounting portion13and the IC chip12mounted on the IC chip mounting portion13not in the inside, but on the outside of the antenna coil81.

The contactless communication medium of the present embodiment may be as described above, but the contactless communication medium of the present invention is not limited to the embodiment described above, and various modifications can be applied. For example, the structure of each portion described in the first to ninth embodiments described above can be adequately combined in aspects other than the combinations adopted in the embodiments described above. Further, the contactless communication media described above may include not only a contactless IC card, but also, for example, contactless communication media such as an electronic passport and the like, and are not particularly limited. The same holds true for the following modifications.

Contactless communication mediums (contactless information mediums) according to further embodiments of the present invention will be described with reference to the drawings. In the description, the same sign may be assigned for an element having the same element or the same function, and repeated description will be omitted.

First, a contactless communication medium (contactless information medium) of a first modification will be described with reference toFIG. 13AtoFIG. 15.FIG. 13Ais a top view showing an internal structure of a contactless communication medium of the first modification, andFIG. 13Bis a rear view thereof.FIG. 14Ais a cross sectional view of the contactless communication medium shown inFIG. 13AandFIG. 13Balong the line XIVa-XIVa, andFIG. 14Bis a cross sectional view of the contactless communication medium shown inFIG. 13AandFIG. 13Balong the line XIVb-XIVb.FIG. 15is a circuit diagram showing an equivalent circuit of the contactless communication medium shown inFIG. 13AandFIG. 13B. Further,FIG. 13Bshows a rear side view of the view shown inFIG. 13Awhere the view is reversed about its central longitudinal axis.

A contactless communication medium110is a wireless communication medium with RFID capable of performing contactless communication with an external read/write device such as a reader/writer while applying RFID technology and using signals primarily in the HF band. The contactless communication medium110has a rectangular shaped film base111as shown inFIG. 13AthroughFIG. 14B. An IC chip112, an antenna coil113, and first plate electrodes114aand114bare arranged on a top surface111aof the film base111, and second plate electrodes116aand116b, and a jumper wire117are arranged on a rear surface111bof the film base111.

The film base111is a base made up of dielectric and having, for example, a triple-layer structure, and has a structure having an intermediate base111cas the main base having insulating properties and durability such as polyethylene naphthalate (PEN), polyethylene terephthalate copolymer (PET-G) and the like. On both the front and rear surfaces of the intermediate base111c, first and second dielectric layers111dand111e, having a smaller thickness than that of the intermediate base111c, are provided for adjustment. Further, details of the first and second dielectric layers111dand111ewill be described later.

A metal foil is laminated on both the front and rear surfaces111aand111bof the film base111prior to processing by etching and the like, and the antenna coil113, the first plate electrodes114aand114b, the second plate electrodes116aand116b, and the jumper wire117are formed by processing the metal foil such as by etching. The metal foil arranged on each of the front and rear surfaces111aand111bof the film base111may have the same thickness, or the thickness of the metal foil on the top surface111aside where the antenna coil113is arranged may be made larger than the thickness of the metal foil on the rear surface111bside where the second plate electrodes116aand116bare arranged, since the antenna coil113is arranged with a small pitch and the electrical resistance of the antenna coil113needs to be reduced. Further, such a three-layer structure may obviously be applied to the contactless communication medium10and the like of the first embodiment to the ninth embodiment described above.

The IC chip112is constituted by an IC tag storing, for example, ID information. The IC chip112is arranged along a length of the antenna coil antenna coil113on the top surface111aof the film base111, and both its terminals are connected to the antenna coil113. The IC chip112performs wireless communication processing via the conducted antenna coil113, and sends and receives predetermined signals to and from an external read/write device.

The antenna coil113is a plane spiral shaped antenna for performing contactless wireless communication by electromagnetically coupling with an antenna of an external read/write device such as a reader/writer. The antenna coil113sends and receives signals and receives power by wireless communication in a contactless state. The antenna coil113is formed from a conductor (metal foil) arranged on the top surface111aof the film base111. Specifically, the antenna coil113is patterned, for example, by etching a copper foil or an aluminum foil having a thickness of 5 μm to 50 μm laminated on the top surface111aside of the film base111having a thickness of 15 μm to 50 μm. Such an antenna coil113is connected to the plate electrode114aat its outer end, and is connected to the plate electrode114bat its inner end.

The first plate electrodes114aand114bare each a rectangular shaped plate electrode, and are arranged in parallel at one side of the top surface111aof the film base111sandwiching a portion of the antenna coil113therebetween. The plate electrode114bis formed in the inside of the antenna coil113, and therefore its electrode area is smaller than that of the plate electrode114a. However, the electrode areas of plate electrodes114aand114bmay be the same, or the electrode area of the plate electrode114bmay be larger than that of the plate electrode114a. Further, the plate electrode114ais connected to the outer end of the antenna coil113as described above, and the plate electrode114bis connected to the inner end of the antenna coil113. Further, the first plate electrodes114aand114bare patterned by etching the metal foil laminated on the top surface111aside of the film base111similarly to the antenna coil113. The second plate electrodes116aand116b, and the jumper wire117to be described later are also similarly formed.

The second plate electrodes116aand116bare each a rectangular plate electrode, and are arranged in parallel at one side of the rear surface111bof the film base111, with a portion of the region corresponding to the antenna coil113located therebetween. The plate electrode116bis formed in the inside of the region corresponding to the antenna coil113(region of the antenna coil113shown by dotted lines inFIG. 13B), and therefore its electrode area is smaller than that of the plate electrode116a, which is, however, not limited, similarly to the first plate electrodes114aand114b. Further, as shown inFIG. 14AandFIG. 14B, the second plate electrodes116aand116bare formed so as to be opposite to the first plate electrodes114aand114bin the thickness direction of the film base111. More specifically, the plate electrode114aand the plate electrode116aare opposite to each other, and the plate electrode114band the plate electrode116bare opposite to each other. With such an arrangement, the first plate electrodes114aand114b, and the second plate electrodes116aand116beach form 2 capacitance portions (seeFIG. 15).

Further, plate electrodes114aand116aopposite to each other have the same shape and the same size (area), and plate electrodes114band116bopposite to each other similarly have the same shape and the same size. Further, each plate electrode of these first plate electrodes114aand114b, and the second plate electrodes116aand116bare in conformity when viewed perpendicular to the film base111. Further, the second plate electrodes116aand116b, unlike the first plate electrodes114aand114b, are not connected to the antenna coil113.

The jumper wire117is a wire which connects the second plate electrodes116aand116bon the rear surface11bof the film base111. The jumper wire117preferably has a small electrostatic capacitance between it and a portion of the antenna coil113opposite to the jumper wire117, and therefore its width is preferably as small as possible, for example, in the order of 1 to 3 mm. By such a jumper wire117, conduction between the plate electrode116aand the plate electrode116bis achieved. Further, in the example shown inFIG. 13B, the jumper wire117is connected to the plate electrodes116aand116bin the long side direction of the plate electrodes116aand116bshown in the upper portion of the figure, but it may be connected at other portions such as a central portion.

The contactless communication medium110having such a structure can be expressed as an equivalent circuit as shown inFIG. 15. Namely, as shown inFIG. 15, the contactless communication medium110is constituted by a circuit having the IC chip112, the antenna coil113, the first capacitance portion114aand116a, the jumper wire117, and the second capacitance portion114band116barranged in this order.

Here, a layer structure of the film base111of the contactless communication medium110having such a structure, and effects and functions produced thereby will be further described in detail with reference toFIG. 14AandFIG. 14B.

As shown inFIG. 14AandFIG. 14B, the film base111constituting the contactless communication medium110has a three-layer structure having, in addition to the intermediate base111cwhich is the primary base, a first dielectric layer for adjustment111dcomprising dielectric and formed on a surface of the intermediate base111cshown in the upper portion of the figure, and a second dielectric layer for adjustment111ecomprising dielectric and formed on a surface of the intermediate base111cshown in the lower portion of the figure. The reason that the film base111has such a three-layer structure in the contactless communication medium110of the present modification is to enable adjustment by simple means of the electrostatic capacitance values of the capacitance portion (capacitor) formed by the first and second plate electrodes114aand116a, and the capacitance portion (capacitor) formed by the first and second plate electrodes114band116b, by adjusting the thickness, dielectric constant and the like of the first and second dielectric layers111dand111e. The first and second dielectric layers111dand111eare layers for adjusting the electrostatic capacitance value, and from the perspective of making the contactless communication medium110thinner, it is preferable that it is thinner than the thickness of the intermediate base111c, which is not limited.

In order to enable adjustment of such an electrostatic capacitance value, the dielectric material constituting the first and second dielectric layers111dand111emay be constituted by a different material from a dielectric material of the intermediate base111c, for example, comprising PET and the like, but may be constituted by the same material. A material constituting the first and second dielectric layers111dand111eincludes, for example, polyester-based resin, polyether-based resin, polyethylene, polypropylene, EVA resin and the like. The first and second dielectric layers111dand111emay be formed by coating such dielectric material on both the front and rear surfaces of the intermediate base111c, followed by curing. In the case of adopting such a production method, the thicknesses and the materials used (i.e., dielectric constant) of the first and second dielectric layers111dand111ecan be adequately adjusted. Further, the film base111of such a three-layer structure may obviously be adopted in the structure of the film base111used in the first embodiment to the ninth embodiment described above, and by adopting the structure of the film base111in the film base11, it is possible to similarly produce the same functions, effects and the like to be described later in the contactless communication medium and the like of the first embodiment to the ninth embodiment.

Thus, in the contactless communication medium110of the present embodiment, the film base111sandwiched between the first plate electrodes114aand114band the second plate electrodes116aand116bhas a three-layer structure having the intermediate base111c, and the first and second dielectric layers111dand111e. Therefore, the thickness of the film base111comprising the dielectric, namely the separation distances between the first and second plate electrodes114aand116a, and between114band116bcan be easily adjusted, for example, by changing the thickness of the first and second dielectric layers111dand111e, and it is possible to easily adjust the capacitances of the capacitors made of the first and second plate electrodes114a,114b,116a, and116bwithout changing the shapes (areas) and the like of the electrode pattern of the plate electrodes114a,114b,116a, and116bconstituting the capacitors. Further, in the contactless communication medium110, the structure is such that conduction is achieved with capacitors formed between the first plate electrodes114aand114bconnected to the antenna coil113, and the second plate electrodes116aand116barranged on the rear surface side, and therefore production and inspection processes can be simplified and connection reliability can be improved compared to the case where the start end and the finish end of the antenna coil113are directly connected to a conductor pattern on the rear surface side.

Further, in the contactless communication medium110, the dielectric constants of the dielectrics constituting the first and second dielectric layers111dand111eare equivalent to or more than the dielectric constant of the dielectric constituting the intermediate base111c. Therefore, even when the layer thicknesses of the first and second dielectric layers for adjustment111dand111eare small, the capacitances of the capacitors made of the first and second plate electrodes114a,114b,116a, and116bcan be easily adjusted.

Further, in the contactless communication medium110, the thicknesses of the first and second dielectric layers111dand111eare smaller than the thickness of the intermediate base111c. As such, the dielectric layers for adjustment for adjusting the capacitances of the capacitors made of the first and second plate electrodes114a,114b,116a, and116bcan be made thin, and therefore it is possible to control the variance in total thickness of the film base111in each product. Further, the whole contactless communication medium110can be made thinner.

Further, in the contactless communication medium110, for example, the first and second dielectric layers111dand111eare formed by coating a predetermined dielectric material on the intermediate base111c, followed by curing. As such, the thicknesses, dielectric constants and the like of the first and second dielectric layers111dand111ecan be easily adjusted, and therefore it is possible to easily adjust the capacitances of the capacitors made of the first and second dielectric layers114a,114b,116a, and116b.

Further, in the contactless communication medium110, the thickness of the metal foil constituting the antenna coil113is larger than the thickness of the metal foil constituting the second plate electrode116aand116b. As such, electrical resistance in the antenna coil113can be reduced, and it is possible to improve the radiation efficiency of the antenna of the contactless communication medium110. Further, this structure may be adopted in the structure of the contactless communication medium used in the first embodiment to the ninth embodiment of the present invention described above.

Further, in the example described above, an example where the areas in the plane of the plate electrodes114aand116aconstituting a capacitor of the contactless communication medium110conform to each other, and concurrently the areas in the plane of the plate electrodes114band116bconstituting another capacitor conform to each other is shown. However, the present invention is not limited to this. For example, as shown inFIG. 16AandFIG. 16B, the area in the plane of the second plate electrode116aarranged on the rear surface111bside may be larger than the area in the plane of the first plate electrode114a, and that, when viewed in a direction perpendicular to the plane of the first and second plate electrodes114aand116a, the first plate electrode114amay be surrounded by the second plate electrode116a. When forming each of the first and second plate electrodes114aand116aon either surface, a position and the like of both plate electrodes114aand116amay be somewhat misaligned from designed values due to production errors and the like. By adopting the structure described above, even in the case where the arrangement positions of the first and second plate electrodes are somewhat misaligned from the designed values, it is possible to have a capacitor with a predetermined capacitance value.

Further, to the contrary, as shown inFIG. 17AandFIG. 17B, the area in the plane of the first plate electrode114amay be larger than the area in the plane of the second plate electrode116a, and that, when viewed perpendicular to the plane of the first and second plate electrodes114aand116a, the second plate electrode116amay be surrounded by the first plate electrode114a. However, the antenna coil113is also formed on the same side as the first plate electrode114a, and therefore, by making the size of the second plate electrode116alarger, the contactless information medium110as a whole is likely to be downsized. Further, a relation between areas of the first and second plate electrodes114aand116awas described above, but the same holds true for a relation between areas of the first and second plate electrodes114band116b.

Next, a contactless communication medium of a second modification will be described with reference toFIG. 18AtoFIG. 20.FIG. 19is a cross sectional view schematically showing a flow of an electric current between plate electrodes of the contactless communication medium shown inFIG. 18AandFIG. 18B.FIG. 20is a circuit diagram showing an equivalent circuit of the contactless communication medium shown inFIG. 18AandFIG. 18B. As shown inFIG. 18AandFIG. 18B, the contactless communication medium110ahas the film base111, the IC chip112, the antenna coil113, the first plate electrodes114aand114b, the second plate electrodes116aand116b, and the jumper wire117, similarly to the first modification.

On the other hand, as shown inFIG. 18AandFIG. 18B, in the contactless communication medium110a, unlike the first modification, plate electrodes114a,114b,116a, and116bare formed on a flow path of an electric current passing through the antenna coil113and constituting a portion of a coil pattern. The plate electrodes114a,114b,116a, and116bare included in the coil pattern including the antenna coil113, and therefore, for example as shown inFIG. 19, an electric current passes from the plate electrode114bto the plate electrode116bacross the film base111. As such, the electric current passes along the travelling direction indicated by arrows in the figure, and therefore the amount of electric current passing through the first plate electrode114bis larger than the amount of electric current passing through the second plate electrode116bin region α, whereas the amount of electric current passing through the second plate electrode116bis larger than the amount of electric current passing through the first plate electrode114bin region β. The relation between the amounts of electric currents holds true between the planar electrodes114aand116a. Further, an average electric current density in an electrode cross section of each of the plate electrodes114a,114b,116a, and116bmay be used as an index in place of the amount of electric current, similarly to the case of using the amount of electric current. As such, in the case where the first and second plate electrodes114a,114b,116a, and116bare formed on a flow path of an electric current passing through the antenna coil113and constituting a portion of the coil pattern, the plate electrodes114a,114b,116a, and116bcan be used as a portion of the antenna, and under the limited antenna forming region, it is possible to increase the number of coil turns and concurrently enlarge the opening area of the antenna. Further, an equivalent circuit of such a contactless communication medium110ais shown inFIG. 20.

Further, as shown inFIG. 19, the electric current passing through the plate electrode114bdecreases from an end A toward the other end B, whereas the electric current passing through the plate electrode116bincreases from an end A′ toward the other end B′. Therefore, for example, the plate electrode114bmay be shaped such that one side is a broad portion114cand the other side is a thin portion114das shown inFIG. 21A, and the plate electrode116bmay be shaped such that one side is a thin portion116cand the other side is a broad portion116das shown inFIG. 21B. In this case, as shown inFIG. 21C, in the region α where the amount of electric current passing through the first plate electrode114bis larger than the amount of electric current passing through the second plate electrode116b, the area of the first plate electrode114b(114c) is larger than the area of the second plate electrode116b(116c). However in the region β where the amount of electric current passing through the second plate electrode116bis larger than the amount of electric current passing through the first plate electrode114b, the area of the second plate electrode116b(116d) is larger than the area of the first plate electrode114b(114d). As such, by reducing the size of a plate electrode at a position where the amount of electric current passing through is small, it is possible to enlarge the forming region of another member such as the antenna coil113while keeping the electrical resistance low.

Further, shapes of the plate electrodes114band116bare not limited to the above, and other shapes can be adequately selected. For example, as shown inFIG. 22AandFIG. 22B, the plate electrodes114band116bmay have a planar triangular shape. In this case, as shown inFIG. 22C, in the region α where the amount of electric current passing through the first plate electrode114bis larger than the amount of electric current passing through the second plate electrode116b, the area of the first plate electrode114bis larger than the area of the second plate electrode116b. However in the region β where the amount of electric current passing through the second plate electrode116bis larger than the amount of electric current passing through the first plate electrode114b, the area of the second plate electrode116bis larger than the area of the first plate electrode114b. Therefore, it is possible to enlarge the forming region of another member such as the antenna coil113and the like similarly as described above. Further, also in the case of the second modification, this structure may be adequately applied in the structures of the contactless communication medium of the first embodiment to the ninth embodiment described above similarly to the first modification.

The contactless communication medium of the modifications has been described, but the wireless communication medium having RFID of the modifications is not limited to the examples described above, and various modifications can be applied. For example, in the modification described above, the film base111is constituted by a three-layer structure. However, the present invention is not limited to a three-layer structure, and the film base111may be formed from a structure having 4 or more layers, each comprising a dielectric. In this case, it is possible to more finely adjust the capacitances of the capacitors constituted by the first and second plate electrodes114a,114b,116a, and116b. Further, in the example described above, 2 capacitors were formed with the first and second plate electrodes114a,114b,116a, and116band both terminals of the antenna coil113were conducted. However, it is only necessary that at least one of the 2 has a capacitor structure, and the other electrode may be directly conducted.

Appendices will be provided regarding the contactless communication mediums (contactless information medium) described in modifications 1 and 2 and the like described above.

A contactless information medium comprising:

a film base comprising a dielectric;

an antenna coil disposed on at least one surface of the film base;

an IC chip performing wireless communication processing via the antenna coil;

a first plate electrode disposed on the one surface of the film base; and

a second plate electrode disposed on the other surface of the film base so as to be opposite to the first plate electrode in the thickness direction with the film base therebetween,

wherein the film base has an intermediate base comprising a dielectric, a first dielectric layer for adjustment comprising a dielectric and formed on one surface of the intermediate base, and a second dielectric layer for adjustment comprising a dielectric and formed on the other surface of the intermediate base.

The contactless information medium according to Appendix 1, wherein the dielectric constants of the dielectrics constituting the first and second dielectric layers for adjustment are greater than or equal to the dielectric constant of the dielectric constituting the intermediate base.

The contactless information medium according to Appendix 1 or 2, wherein the thickness of the first and second dielectric layers for adjustment is less than the thickness of the intermediate base.

The contactless information medium according to any one of Appendices 1 to 3, wherein the dielectric material constituting the first and second dielectric layers for adjustment is different from the dielectric material constituting the intermediate base.

The contactless information medium according to any one of Appendices 1 to 4, wherein the thickness of a metal foil constituting the antenna coil is greater than the thickness of a metal foil constituting the second plate electrode.

The contactless information medium according to any one of Appendices 1 to 5, wherein the first and second dielectric layers for adjustment are formed by applying the dielectric material to the intermediate base followed by curing.

The contactless information medium according to any one of Appendices 1 to 6, wherein the area of the second plate electrode in the plane is larger than the area of the first plate electrode in the plane, and the first plate electrode is surrounded by the second plate electrode when viewed in the direction perpendicular to the plane of the first and second plate electrodes.

The contactless information medium according to any one of Appendices 1 to 6, wherein the area of the first plate electrode in the plane is larger than the area of the second plate electrode in the plane, and the second plate electrode is surrounded by the first plate electrode when viewed in the direction perpendicular to the plane of the first and second plate electrodes.

The contactless information medium according to any one of Appendices 1 to 6, wherein the first and second plate electrodes are formed on a flow path of an electric current passing through the antenna coil and constitute a portion of a coil pattern, are formed such that the area of the second plate electrode is larger than the area of the first plate electrode in a region where the amount of electric current flowing through the second plate electrode is larger than the amount of electric current flowing through the first plate electrode, and are formed such that the area of the first plate electrode is larger than the area of the second plate electrode in a region where the amount of electric current flowing through the first plate electrode is larger than the amount of electric current flowing through the second plate electrode.

The contactless information medium according to any one of Appendices 1 to 6, wherein the first and second plate electrodes are formed on a flow path of an electric current passing through the antenna coil and constitute a portion of a coil pattern, are formed such that the area of the second plate electrode is larger than the area of the first plate electrode in a region where an average electric current density in an electrode cross section of the second plate electrode is larger than an average electric current density in an electrode cross section of the first plate electrode, and are formed such that the area of the first plate electrode is larger than the area of the second plate electrode in a region where an average electric current density in an electrode cross section of the first plate electrode is larger than an average electric current density in an electrode cross section of the second plate electrode.

Effects and functions of the contactless information medium according to Appendix 1 to Appendix 10 will now be described.

In the contactless information medium of Appendix 1, the film base sandwiched between the first and second plate electrodes has at least a three-layer structure of the intermediate base and the first and second dielectric layers for adjustment. This configuration enables easier adjustment of the thickness of the film base including a dielectric, that is, the separation distance between the first and second plate electrodes by, for example, changing the thickness of the first or second dielectric layer for adjustment. Consequently, the capacitance of the capacitor made of the first and second plate electrodes can be easily adjusted without changing the shape and the like of the electrode pattern of the plate electrodes constituting the capacitor. Further, in the contactless information medium, an electrical connection is made with a capacitor formed by the first plate electrode connected to the antenna coil and the second plate electrode disposed on the rear surface. This configuration enables simpler production and inspection processes than if the start end and the finish end of the antenna coil were directly connected to the conductor pattern on the rear surface, and a more reliable electrical connection.

In the contactless information medium of Appendix 2, even when the thickness of the first and second dielectric layers for adjustment is small, the capacitance of the capacitor formed of the first and second plate electrodes can be easily adjusted.

In the contactless information medium of Appendix 3, the dielectric layer for adjustment for adjusting the capacitance of the capacitor made of the first and second plate electrodes can be made thin, and therefore it is possible to control the variance in total thickness of a film base in each product.

In the contactless information medium of Appendix 4, the dielectric material constituting the first and second dielectric layers for adjustment may be different from or the same as the dielectric material constituting the intermediate base.

In the contactless information medium of Appendix 5, electrical resistance of the antenna coil can be reduced, and therefore it is possible to improve the radiation efficiency of an antenna of the contactless information medium.

In the contactless information medium of Appendix 6, thickness and the like of the first and second dielectric layers for adjustment can be easily adjusted, and therefore it is possible to easily adjust the capacitance of the capacitor made of the first and second plate electrodes.

According to the contactless information medium of Appendix 7, when forming each of the first and second plate electrodes on either surface of a base film, a position and the like of the plate electrodes may be misaligned from designed values due to production errors and the like. By adopting the structure described above, even in the case where the arrangement positions of the first and second plate electrodes are somewhat misaligned from the designed values, it is possible to have a capacitor with a predetermined capacitance. Further, to the contrary, as in the case of Appendix 8, it is possible to have the area of the first plate electrode in the plane larger than the area of the second plate electrode in the plane, and the second plate electrode surrounded by the first plate electrode when viewed in the direction perpendicular to the plane of the first and second plate electrodes. However, the antenna coil is also formed on the same side as the first plate electrode, and therefore, by making the size of the second plate electrode larger, the contactless information medium as a whole is likely to be downsized.

In the contactless information medium of Appendices 9 and 10, when the first and second plate electrodes are formed on a flow path of an electric current passing through the antenna coil and constitute a portion of a coil pattern, the plate electrodes can be used as a portion of the antenna coil, and with a limited antenna forming region, it is possible to increase the number of coil turns and concurrently increase the opening area of the antenna. Further, by reducing the size of the plate electrodes at a position where a flow of electric current is small, it is possible to enlarge a formation region of another member such as an antenna coil and the like.

INDUSTRIAL APPLICABILITY

The present invention provides a contactless information medium having parallel plate electrodes and designed to have an opening of an antenna coil.

REFERENCE SIGNS LIST