Antenna sheet, RF tag, and method for manufacturing antenna sheet

Abstract

An antenna sheet comprising a dielectric substrate and an antenna portion formed from conductor strands on the dielectric substrate, wherein: the antenna portion is a closed circuit formed using at least two conductor strands including a first conductor strand and a second conductor strand that are in a physically unconnected state; a part of the first conductor strand and a part of the second conductor strand are arranged close to each other; and the first conductor strand and the second conductor strand are electrically connected by parasitic capacitance generated therebetween.

Description

Antenna sheet, RF tag, and method for manufacturing an antenna sheet

[0001] The present invention relates to an antenna sheet, more particularly to an antenna sheet having a coil antenna made of metal wires and used in IC cards and the like that capable of contactless communication, an RF tag, and a method for manufacturing an antenna sheet. This application claims priority based on Japanese Patent Application No. 2024-200600 filed in Japan on November 18, 2024, Japanese Patent Application No. 2025-088559 filed in Japan on May 28, 2025, Japanese Patent Application No. 2025-094625 filed in Japan on June 6, 2025, and Japanese Patent Application No. 2025-094816 filed in Japan on June 6, 2025, the contents of which are incorporated herein by reference.

[0002] IC cards capable of contactless communication are known. Such IC cards have a configuration in which an IC chip with contactless communication functionality is electrically connected to a booster antenna located within the card. If the IC chip is an IC module with contact terminals, the IC card can be made into a dual IC card capable of both contact and contactless communication. In such cases, the connection between the IC module and the booster antenna is generally made by electromagnetic coupling using a coupling coil.

[0003] When connecting a booster antenna to an IC via electromagnetic coupling, it is necessary to form a resonant capacitor at the end of the booster antenna or coupling coil. While it is possible to separately provide a capacitor using a metal plate, from a cost perspective, a method has been devised in which the entire antenna section, including the booster antenna, coupling coil, and capacitor, is formed from metal windings. Patent Document 1 discloses an example of such a method. In Patent Document 1, the windings at both ends of the coil that will become the booster antenna are arranged adjacent to each other, and adjacent wires are wired in a meander pattern with equal lengths, thereby forming a capacitor by utilizing the stray capacitance generated between adjacent coils. Patent Document 2 discloses another example of a method for forming the antenna section. In Patent Document 2, the resonant capacitance of the antenna is formed by arranging two windings spirally inside the coil that will become the main antenna.

[0004] Japanese Patent Publication No. 4615695, US Patent Specification No. 9275324

[0005] At present, it is difficult to say that an antenna sheet having a wound antenna has sufficient rigidity. Therefore, when the base material on which the antenna is formed is bent, the winding may be disconnected, or the gap between adjacent windings may change, resulting in a change in the capacitance for resonance.

[0006] In view of the above circumstances, an object of the present invention is to provide an antenna sheet, an RF tag, and a method for manufacturing an antenna sheet that have a wound antenna and maintain a certain rigidity.

[0007] To achieve the above object, the present invention provides the following means. [1] An antenna sheet in which an antenna portion is formed of a conductive wire on a substrate made of a dielectric, wherein the antenna portion is a closed circuit formed using at least two wire elements including a first wire element and a second wire element that are physically non-connected, and a part of the first wire element and a part of the second wire element are arranged close to each other, and the first wire element and the second wire element are electrically connected by the parasitic capacitance generated therebetween.

[0008] [2] The antenna portion has a coil-shaped booster antenna and a resonance capacitance forming portion that adjusts the resonance frequency in communication using the booster antenna, and the first wire element and the second wire element are connected by the parasitic capacitance in the resonance capacitance forming portion. The antenna sheet according to [1].

[0009] [3] The first wire element has a coil-shaped first region that constitutes a part of the booster antenna, the second wire element has a coil-shaped No. 1 region that constitutes a part of the booster antenna, and in at least a part of the booster antenna, the first region and the No. 1 region are an interleaved wiring arranged alternately in the width direction of the wire element, and the resonance capacitance forming portion includes the interleaved capacitance portion formed by the interleaved wiring. The antenna sheet according to [2].

[0010] [4] The antenna sheet according to [2] or [3], wherein the resonant capacitance forming portion includes a capacitance portion formed in a meander shape or a coil shape.

[0011] [5] The antenna sheet according to [4], wherein the first strand and the second strand intersect in a three-dimensional manner in the capacitance section.

[0012] [6] The antenna sheet according to [4] or [5], wherein the antenna portion further comprises a coupling coil connected to the booster antenna and having a smaller loop diameter than the booster antenna, and the capacitance portion and the coupling coil are located within the loop of the booster antenna.

[0013] [7] The antenna sheet according to any one of [1] to [6], wherein the antenna section comprises a spiral booster antenna, a spiral coupling coil connected to the booster antenna and smaller than the booster antenna, a capacitance section formed by capacitive coupling of the first and second strands by being placed in close proximity, and a crossover section where the conductors intersect in three dimensions, wherein one of the coupling coil and the capacitance section is located outside the spiral of the booster antenna and the other is located inside the spiral of the booster antenna, and the crossover section is provided in only one location so as to intersect in three dimensions with the coupling coil and the booster antenna.

[0014] [8] The antenna sheet according to any one of [1] to [7], wherein at least one of the first strand and the second strand is insulated.

[0015] [9] The crossover portion is the antenna sheet according to [7] or [8], located between the coupling coil and the capacitance portion.

[0016]

[10] An antenna sheet according to any one of [1] to [9], comprising: a booster antenna in which a portion of the conductors is arranged spirally along the periphery of the substrate; and a capacitance portion located inside the booster antenna and formed by a pair of conductors including the conductors arranged in close proximity to each other, wherein the capacitance portion comprises a main capacitance portion formed by the pair of conductors in which a portion of the conductors is folded back and arranged in close proximity to each other, and an extended capacitance portion formed by extending a portion of the pair of conductors in a manner continuous with the main capacitance portion, wherein the extended capacitance portion is spaced apart from the periphery of the main capacitance portion.

[0017]

[11] The antenna sheet according to

[10] , wherein the extended capacitance portion is formed by extending the pair of conductors to both ends of the conductors.

[0018]

[12] The antenna sheet according to

[10] or

[11] , wherein the length of the pair of conductors forming the extended capacitance portion is adjusted to match the resonant frequency in communication using the booster antenna.

[0019]

[13] The antenna sheet according to any one of

[10] to

[12] , wherein the extended capacity section has an extended wiring section in which a part of the pair of conductors is arranged in a linear or spiral shape, and the ends of the pair of conductors forming the extended wiring section are formed by the folded portion of the conductors.

[0020]

[14] The antenna sheet according to

[10] to

[13] , wherein the main capacitance section has a main wiring section in which a part of the pair of conductors is arranged in a spiral shape, and the ends of the pair of conductors forming the main wiring section are formed by the folded portion of the conductors.

[0021]

[15] The antenna sheet according to

[10] to

[14] , wherein at least one part of the main capacity section and the extended capacity section is arranged in the lower 1 / 3 region of the antenna sheet for a length of 1 / 5 or more of the longitudinal direction of the antenna sheet.

[0022]

[16] An antenna sheet according to any one of [1] to

[15] , comprising: a booster antenna in which a portion of the conductor is arranged spirally along the periphery of the substrate; and a capacitance portion located inside the booster antenna and formed by a pair of conductors in close proximity to each other, wherein the capacitance portion has a first wiring portion in which a portion of the pair of conductors is arranged to be folded sequentially in opposite directions, and a second wiring portion in which a portion of the pair of conductors is arranged to be folded sequentially in the same direction, and the first wiring portion and the second wiring portion are arranged to overlap in the plane of the substrate.

[0023]

[17] The antenna sheet according to

[16] , wherein a portion of the wire pair forming the first wiring section and a portion of the wire pair forming the second wiring section form a partially overlapping portion.

[0024]

[18] The antenna sheet according to

[17] , wherein the ends of the pair of conductors forming the second wiring portion are located inside the overlap portion.

[0025]

[19] The antenna sheet according to

[18] , wherein the ends of the pair of conductors forming the second wiring section are formed by the folded portion of the conductors.

[0026]

[20] The antenna sheet according to any one of

[16] to

[19] , wherein the capacitance section has a third wiring section in which the pair of conductors is extended to both ends of the conductors, continuous with the first wiring section.

[0027]

[21] The antenna sheet according to

[10] or

[20] , wherein, when the substrate has a shape corresponding to an IC card, at least a part of the extended capacitance portion or at least a part of the third wiring portion is arranged in the lower region sandwiching the central part of the IC card.

[0028]

[22] The antenna sheet according to any one of [2] to

[21] , wherein the number of loops of the first strand in the booster antenna is different from the number of loops of the second strand, and the booster antenna has a single strand antenna section in which only one of the first strand and the second strand is wired in a coil shape, and an interleaved capacitance section in which the first strand and the second strand are interleaved and wired alternately in the width direction of the strand.

[0029]

[23] The antenna sheet according to

[22] , wherein a gap is provided between the single-strand antenna section and the interleaved capacitance section, the first end of the second strand is positioned therein, and the loop of the conductor of the booster antenna formed by the second strand, extending from the first end of the second strand, is sandwiched between the first strand in the width direction of the conductor.

[0030]

[24] The antenna sheet according to

[22] or

[23] , wherein the first end of the first strand is provided on the outer circumference of the booster antenna, and the loop of the conductor of the booster antenna formed by the first strand, extending from the first end of the first strand, is sandwiched by the second strand in the width direction of the conductor.

[0031]

[25] The antenna sheet according to [1] or [2], wherein the antenna section comprises a coil-shaped booster antenna, a coupling coil formed of the second strand, and a resonant capacitance forming section for adjusting the resonant frequency in communication using the booster antenna and the coupling coil, the resonant capacitance forming section comprising a first extension wiring capacitance section formed by the first strand and a first extension wiring of the second strand extending from the coupling coil, and a second extension wiring capacitance section formed by the first strand and a second extension wiring of the second strand extending from the coupling coil.

[0032]

[26] An RF tag comprising an antenna sheet as described in any one of [1] to

[25] and an IC chip connected to the antenna sheet.

[0033]

[27] A method for manufacturing an antenna sheet, comprising: a first wire pattern forming step of forming a wiring pattern on a dielectric substrate using a conductor from a first end to a second end which will be the end of a first wire; an inter-wire pattern forming step of forming an inter-wire pattern on the substrate using the conductor from the second end to the first end which will be the end of a second wire; a second wire pattern forming step of forming a wiring pattern on the substrate using the conductor from the first end to a second end which will be a second wire; and an inter-wire pattern processing step of removing or cutting the conductor from the inter-wire pattern, wherein an antenna section is formed which is a closed circuit using the first wire and the second wire that are physically disconnected, a part of the first wire and a part of the second wire are placed in close proximity to each other, and the first wire and the second wire are electrically connected by a stray capacitance that occurs between them.

[0034] To achieve the above objectives, the present invention provides the following additional means. [A1] The present invention is an antenna sheet in which an antenna portion is formed of conductive strands on a dielectric substrate. The antenna portion is a closed circuit formed using a first strand and a second strand that are physically disconnected, and a part of the first strand and a part of the second strand are arranged in close proximity, and the first strand and the second strand are electrically connected by a stray capacitance that occurs between them. [A2] The antenna sheet according to [A1], wherein the antenna portion comprises a coil-shaped booster antenna and a resonant capacitance forming portion that adjusts the resonant frequency in communication using the booster antenna, and the first strand and the second strand are connected by the stray capacitance in the booster antenna and the resonant capacitance forming portion. [A3] The antenna sheet according to [A2], wherein the first strand has a coil-shaped first region that constitutes a part of the booster antenna, and the second strand has a coil-shaped No. 1 region that constitutes a part of the booster antenna, and in at least a part of the booster antenna, the first region and the No. 1 region are arranged alternately in the width direction of the strand. [A4] The antenna sheet according to [A2] or [A3], wherein the resonant capacitance forming portion is formed in a meander shape. [A5] The antenna sheet according to [A2] or [A3], wherein the resonant capacitance forming portion is formed in a coil shape. [A6] The antenna sheet according to any one of [A2] to [A5], wherein the first strand and the second strand intersect in three dimensions in the resonant capacitance forming portion. [A7] The antenna sheet according to any one of [A2] to [A6], wherein the antenna portion further comprises a coupling coil connected to the booster antenna and having a loop diameter smaller than that of the booster antenna, and the resonant capacitance forming portion and the coupling coil are located within the loop of the booster antenna. [A8] The antenna sheet according to any one of [A1] to [A7], further comprising a contactless communication-capable IC chip connected to the antenna portion.

[0035] To achieve the above objectives, the present invention provides the following additional means. [B1] The present invention is an antenna sheet in which an antenna portion is formed on a dielectric substrate using a first wire and a second wire made of conductors. The antenna portion has a spiral booster antenna, a spiral coupling coil connected to the booster antenna and smaller than the booster antenna, a capacitance portion formed by capacitive coupling due to the close arrangement of the first wire and the second wire, and a crossover portion where the wires intersect in three dimensions. One of the coupling coil and the capacitance portion is located outside the spiral of the booster antenna, and the other is located inside the spiral of the booster antenna. Only one crossover portion is provided so as to intersect in three dimensions with the coupling coil and the booster antenna. [B2] The antenna sheet according to [B1], wherein at least one of the first wire and the second wire is insulated. [B3] The antenna sheet according to [B1] or [B2], wherein the crossover portion is located between the coupling coil and the capacitance portion.

[0036] To achieve the above objectives, the present invention provides the following additional means: [C1] An antenna sheet comprising: a dielectric sheet; a conductor provided in the plane of the dielectric sheet; a booster antenna in which a part of the conductor is arranged spirally along the periphery of the dielectric sheet; a main capacitance portion located inside the booster antenna and formed by a pair of conductors in which a part of the conductor is folded back and arranged in close proximity to each other; and an extended capacitance portion located inside the booster antenna and formed by extending a part of the pair of conductors continuously with respect to the main capacitance portion, wherein the extended capacitance portion is spaced apart from the periphery of the main capacitance portion. [C2] The antenna sheet according to [C1], wherein the extended capacitance portion is formed by extending the pair of conductors to both ends of the conductor. [C3] The antenna sheet according to [C1] or [C2], wherein the length of the pair of conductors forming the extended capacitance portion is adjusted to match the resonant frequency in communication using the booster antenna. [C4] The antenna sheet according to any one of [C1] to [C3], wherein the extension capacitance section has an extension wiring section in which a part of the pair of conductors is arranged in a linear or spiral shape, and the ends of the pair of conductors forming the extension wiring section are formed by the folded-back portion of the conductors. [C5] The antenna sheet according to any one of [C1] to [C4], wherein the main capacitance section has a main wiring section in which a part of the pair of conductors is arranged in a spiral shape, and the ends of the pair of conductors forming the main wiring section are formed by the folded-back portion of the conductors. [C6] The antenna sheet according to any one of [C1] to [C5], wherein the main capacitance section and the extension capacitance section are formed by at least one or more of the conductors. [C7] The antenna sheet according to any one of [C1] to [C6], wherein the extension capacitance section is located inside the booster antenna and comprises a coupling coil in which a part of the conductor is arranged in a spiral shape with a loop diameter smaller than that of the booster antenna. [C8] The antenna sheet according to any one of [C1] to [C7], wherein, when the dielectric sheet has a shape corresponding to an IC card, at least a part of the main capacitance portion and the extended capacitance portion is arranged in the lower region sandwiching the central portion of the IC card.[C9] The antenna sheet according to [C8], wherein at least a portion of the main capacity section and the extended capacity section is arranged in the lower 1 / 3 area of ​​the IC card with a length of 1 / 5 or more of the longitudinal direction of the IC card. [C10] An RF tag comprising the antenna sheet according to any one of [C1] to [C9] and an IC chip connected to the antenna sheet.

[0037] To achieve the above objectives, the present invention provides the following additional means: [D1] An antenna sheet comprising: a dielectric sheet; a conductor provided in the plane of the dielectric sheet; a booster antenna in which a part of the conductor is arranged spirally along the periphery of the dielectric sheet; and a capacitance portion located inside the booster antenna and formed by a pair of conductors in close proximity to each other, wherein the capacitance portion has a first wiring portion in which a part of the pair of conductors is arranged to be folded sequentially in opposite directions, and a second wiring portion in which a part of the pair of conductors is arranged to be folded sequentially in the same direction, and the first wiring portion and the second wiring portion are arranged to overlap in the plane of the dielectric sheet. [D2] The antenna sheet according to [D1], wherein a part of the pair of conductors forming the first wiring portion and a part of the pair of conductors forming the second wiring portion form a partially coincidental overlapping portion. [D3] The antenna sheet according to [D1] or [D2], wherein the ends of the wire pair forming the second wiring section are located inside the overlap section. [D4] The antenna sheet according to any one of [D1] to [D3], wherein the ends of the wire pair forming the second wiring section are formed by the folded portion of the wire. [D5] The antenna sheet according to any one of [D1] to [D4], wherein the capacitance section has a third wiring section that extends the wire pair to both ends of the wire, continuous with the first wiring section. [D6] The antenna sheet according to [D5], wherein, when the dielectric sheet has a shape corresponding to an IC card, at least a part of the third wiring section is located in the lower region sandwiching the central part of the IC card. [D7] The antenna sheet according to any one of [D1] to [D6], wherein the capacitance section is formed by at least one or more wires. [D8] An antenna sheet according to any one of [D1] to [D7], which is located inside the booster antenna and comprises a coupling coil having a loop diameter smaller than that of the booster antenna and having a portion of the conductor arranged in a spiral shape. [D9] An RF tag comprising an antenna sheet according to any one of [D1] to [D8] and an IC chip connected to the antenna sheet.

[0038] According to the present invention, it is possible to provide an antenna sheet, an RF tag, and a method for manufacturing the antenna sheet, which have a wound antenna while maintaining a certain degree of rigidity.

[0039] This is a schematic plan view showing an antenna sheet according to the first embodiment of the present invention. This is an equivalent circuit diagram showing an RF tag equipped with the antenna sheet. This is another example of an equivalent circuit diagram of the antenna sheet. This is a diagram showing the arrangement of the first strands constituting the antenna portion of the antenna sheet. This is a diagram showing the arrangement of the second strands constituting the antenna portion of the antenna sheet. This is an enlarged view of section A in Figure 1. This is an enlarged view showing the capacitance portion of the antenna sheet. This is a schematic plan view showing an antenna sheet according to the second embodiment of the present invention. This is a diagram showing the arrangement of the first strands constituting the antenna portion of the antenna sheet. This is a diagram showing the arrangement of the second strands constituting the antenna portion of the antenna sheet. This is an enlarged view of section B in Figure 7. This is an enlarged view showing the capacitance portion of the antenna sheet. This is a schematic plan view showing an antenna sheet according to the third embodiment of the present invention. This is a diagram showing the arrangement of the first strands related to the antenna sheet. This is a diagram showing the arrangement of the second strands related to the antenna sheet. This is a schematic plan view showing an antenna sheet according to the fourth embodiment of the present invention. This is a diagram showing the arrangement of the first strands related to the antenna sheet. This is a diagram showing the arrangement of the second strands related to the antenna sheet. This is a plan view showing an RF tag equipped with an antenna sheet according to the fifth embodiment of the present invention. This is a plan view showing a first modified example in which the arrangement of the wire pairs forming the extended capacitance portion of the antenna sheet has been changed. This is a plan view showing a second modified example in which the arrangement of the wire pairs forming the extended capacitance portion of the antenna sheet has been changed. This is a plan view showing an RF tag equipped with an antenna sheet according to the sixth embodiment of the present invention. This is a plan view showing a first modified example in which the arrangement of the wire pairs forming the capacitance portion of the antenna sheet has been changed. This is a plan view showing a second modified example in which the arrangement of the wire pairs forming the capacitance portion of the antenna sheet has been changed. This is a schematic plan view showing an antenna sheet according to the seventh embodiment of the present invention. This is a diagram showing the arrangement of the first strands constituting the antenna portion of the antenna sheet. This is a diagram showing the arrangement of the second strands constituting the antenna portion of the antenna sheet. This is an enlarged view of section A in Figure 24. This is a schematic plan view showing an antenna sheet according to the eighth embodiment of the present invention. This is an equivalent circuit diagram of the antenna sheet shown in Figure 28A. This is a diagram showing the arrangement of the first strands constituting the antenna portion of the antenna sheet. This is an equivalent circuit diagram of the first strand of the antenna sheet shown in Figure 29A.This figure shows the arrangement of the second strands that constitute the antenna portion of the antenna sheet. This is an equivalent circuit diagram of the second strands of the antenna sheet shown in Figure 30A.

[0040] The first embodiment of the present invention will be described below with reference to Figures 1 to 6. Figure 1 is a schematic plan view showing an antenna sheet 1 according to this embodiment. The antenna sheet 1 has a substrate 10 made of a dielectric material and an antenna portion 20 formed on the substrate 10. Each part of the antenna portion 20, which will be described later, is formed of individual wires (hereinafter also referred to as conductors 12) made of conductors. Copper is a typical conductor material for the individual wires, but silver, gold, aluminum, and copper alloys can also be exemplified.

[0041] The substrate 10 is formed in a rectangular shape in plan view using an insulating material such as PET (polyethylene terephthalate), polyethylene naphthalate (PEN), PVC (polyvinyl chloride), or various types of paper. The thickness of the substrate 10 can be, for example, about 50 to 400 μm. Depending on how the antenna sheet 1 is incorporated into an IC card or the like, through holes may be formed in a part of the substrate 10.

[0042] The antenna section 20 according to this embodiment is an electrical circuit having three regions: a booster antenna 21, a coupling coil 22, and a resonant capacitance forming section C. The booster antenna 21 is a coil-shaped antenna used for contactless communication with an external reader / writer, and is formed by winding strands of wire at least once. In this embodiment, the loop of the booster antenna 21 is substantially rectangular along the periphery of the substrate 10.

[0043] The coupling coil 22 has contact terminals and is a part used for electromagnetic coupling with an IC module capable of non-contact communication. The IC module has contact terminals 3 and an IC chip 50 electrically connected thereto (see FIG. 2A). The coupling coil 22 is necessary when the antenna sheet 1 is applied to a dual IC card or the like, but can be omitted otherwise. The coupling coil 22 is formed by winding a wire around inside the loop of the booster antenna 21 so as to form a loop with a diameter smaller than that of the booster antenna 21. The three-dimensional intersection at the connection part between the coupling coil 22 and the booster antenna 21 can be configured by using, for example, covering the lower wire with a thin-film insulator or caulking connection with a jumper wire provided on the opposite surface of the substrate 10. When the antenna part 20 is formed using insulated wires, short circuits do not occur even at three-dimensional intersection points or closely arranged points (described later), so these processes can be omitted.

[0044] In this embodiment, the resonance capacitance forming part C has a capacitance part 23 and an interleaved capacitance part 24. The capacitance part 23 is arranged inside the loop of the booster antenna 21, similar to the coupling coil 22. The capacitance part 23 in this embodiment is meander-shaped and forms a capacitor by using the stray capacitance generated between adjacent wires. Details of the interleaved capacitance part 24 will be described later.

[0045] FIG. 2A is an equivalent circuit diagram showing an RF tag 100 provided with the antenna sheet 1. As shown in FIGS. 1 and 2A, the antenna sheet 1 of this embodiment forms a closed loop in which one end of the booster antenna 21 and the coupling coil 22 are electrically connected, and the other ends of the booster antenna 21 and the coupling coil 22 are electrically connected via the capacitance part 23.

[0046] In the RF tag 100 provided with the antenna sheet 1 of this embodiment having the above configuration, as shown in FIG. 2A, a high-frequency magnetic field is induced in the transceiver coil 201 by the high-frequency signal generated by the transceiver circuit 202 of the reader / writer 200. This high-frequency magnetic field is radiated into space as magnetic energy.

[0047] At this time, since the RF tag 100 is positioned in the high-frequency magnetic field, the transmission / reception coil 201 and the booster antenna 21 are electromagnetically coupled, and a current flows through the booster antenna 21. Also, the signal received by the booster antenna 21 is transmitted to the coupling coil 22, and a current flows through the coupling coil 22. As a result, the signal received by the booster antenna 21 is transmitted to the IC chip 50 by the electromagnetic coupling between the coupling coil 22 and the antenna coil 51 of the IC chip 50.

[0048] On the other hand, in the RF tag 100, when performing power supply and communication with a contact-type external device such as an automated teller machine, for example, the contact terminal on the device side is brought into contact with the contact terminal 3 of the RF tag 100. Thereby, power supply and communication are performed between the contact-type external device and the RF tag 100.

[0049] As shown in FIG. 1, the antenna unit 20 according to the present embodiment is formed of at least two element wires (two conductive wires 12) that are not physically connected. FIG. 3 shows the arrangement of the first element wire 30, which is one of the two element wires. The first element wire 30 starts from the first end portion 30a, is wound two times along the periphery of the substrate 10 to form the first region 32. The first element wire 30 then moves into the loop of the first region 32 and is wound a plurality of times with a smaller diameter than the first region 32 to form the second region 33. The first element wire 30 then moves out of the loop of the second region 33 by the three-dimensional intersection 34, forms a meander-shaped third region 35 within the loop of the first region 32, and then reaches the second end portion 30b, which is the end point.

[0050] FIG. 4 shows the arrangement of the second element wire 40, which is the other of the two element wires. The second element wire 40 starts from the second end portion 40b, forms a meander-shaped fourth region 42, and then moves near the periphery of the substrate 10. Thereafter, while making a three-dimensional intersection with the already arranged portion, it is wound five times along the periphery of the substrate 10 to form a fifth region (region No. 1) 43, and reaches the first end portion 40a, which is the end point.

[0051] In the antenna sheet 1 shown in Figure 1, two strands, a first strand 30 and a second strand 40, are arranged to form an antenna section 20 on the substrate 10. Figure 5 is an enlarged view of section A in Figure 1. The booster antenna 21 is composed of a first region 32 of the first strand 30 and a fifth region 43 of the second strand 40. Within the inner part of the loop of the booster antenna 21, the first strand 30 and the second strand 40 are arranged in close proximity so as to alternate in the width direction of the strands. More specifically, as shown in Figures 1 to 5, except for a part, the second strand 40 is wound five times along the periphery of the substrate 10, and the first strand 30 is wound two times along the periphery of the substrate 10. In the loop formed by the strands at the periphery of the substrate 10, the second strand 40 (1st winding from the inner circumference), the first strand 30 (1st winding from the inner circumference), the second strand 40 (2nd winding from the inner circumference), and the first strand 30 (2nd winding from the inner circumference) are arranged from the inside outwards. In this specification, the arrangement of the first strand 30 and the second strand 40 alternately at the periphery of the substrate 10 is referred to as interleaved wiring.

[0052] The coupling coil 22 consists of the second region 33 of the first wire 30. Figure 6 is an enlarged view of the capacitance section 23. The capacitance section 23 consists of the third region 35 of the first wire 30 and the fourth region 42 of the second wire 40, with the first wire 30 and the second wire 40 arranged in a meander shape and positioned close together. In the capacitance section 23, a three-dimensional intersection 232 occurs between the first wire 30 and the second wire 40 at the folded portion 231 furthest from the second end 40b of the second wire.

[0053] In the booster antenna 21, the first strand 30 and the second strand 40 are capacitively coupled at the interleaved wiring locations. Thus, the first strand 30 and the second strand 40, which form a loop at the periphery of the substrate 10, are placed in close proximity, and the resonant capacitance forming section C created by the stray capacitance between them is called the interleaved capacitance section 24. The interleaved capacitance section 24 is provided within the booster antenna 21 and functions as both a transmitting and receiving antenna and a resonant capacitance forming section C used for contactless communication. Thus, in this embodiment, the booster antenna 21 includes a single-strand antenna section 21a formed from either the first strand 30 or the second strand 40, and an interleaved capacitance section 24 formed from the first strand 30 and the second strand 40.

[0054] Figure 2B shows an equivalent circuit diagram of the antenna sheet 1 when the interleaved capacitance section 24 is included. By providing the capacitance section 23, which becomes the resonant capacitance forming section C (capacitance), and the interleaved capacitance section 24 in the antenna section 20, a closed loop of the LC resonant circuit as shown in Figure 2B is formed. In the example shown in Figure 1 of this embodiment, the interleaved capacitance section 24 is provided on the inner circumference side of the booster antenna 21, but the embodiment is not limited to this example, and the interleaved capacitance section 24 may be provided on the outer circumference side of the booster antenna 21, or the entire booster antenna 21 may be an interleaved capacitance section 24 (see the seventh embodiment and the second embodiment for details). Furthermore, the interleaved capacitance section 24 may not be provided.

[0055] In this embodiment, in the antenna section 20, the first strand 30 and the second strand 40, which are located in close proximity in the resonant capacitance forming section C including the capacitance section 23 and the interleaved capacitance section 24, are capacitively coupled. In the resonant capacitance forming section C, the first strand 30 and the second strand 40 may also be capacitively coupled with the substrate 10, which acts as a dielectric, located between them. Thus, the antenna section 20 forms a closed circuit including the booster antenna 21, the coupling coil 22, and the resonant capacitance forming section C, using two strands that are physically disconnected. The resonant capacitance forming section C contributes to adjusting the resonant frequency when the IC module connected to the antenna sheet 1 performs contactless communication using the booster antenna 21.

[0056] ・Method for manufacturing the antenna sheet The method for manufacturing the antenna sheet 1 will be described below. Note that the following manufacturing method is merely an example, and other manufacturing methods may be used. The antenna portion 20 according to this embodiment can be formed by arranging the first strand 30 and the second strand 40 on the substrate 10 using a known winding drawing device. In this case, the arrangement of each strand may begin from either end. For example, the arrangement of the first strand 30 may begin from the second end 30b, or the arrangement of the second strand 40 may begin from the first end 40a.

[0057] Alternatively, the entire antenna section 20 may be formed by drawing a single strand, and then the strand may be cut to form an antenna section 20 consisting of two strands. In the antenna section 20 shown in Figure 1, the second end 30b of the first strand 30 and the first end 40a of the second strand 40 are close together. For example, drawing can be started from the first end 30a of the first strand 30, drawn up to the second end 30b, then the region of the second strand 40 is drawn from the first end 40a, and after drawing up to the second end 40b, the boundary between the second end 30b and the first end 40a can be cut.

[0058] More specifically, a wiring pattern is formed from the first end 30a, which is the end of the first wire 30, to the second end 30b using conductive strands (conductor wires 12) covered with an insulator (first wire pattern formation step). The method for forming the wiring pattern may be a known method. For example, the strands are fed out from the tip of a drawing head capable of emitting ultrasonic vibrations, and the surface of the substrate 10 is melted by the pressure of the drawing head and the energy from the ultrasonic waves, thereby bonding the strands to the substrate 10. The strands and the substrate 10 may be bonded by embedding the strands in the substrate 10, or by heat-fusing the insulator on the surface of the strands to the substrate 10. Alternatively, the strands and the substrate 10 may be bonded with a known adhesive.

[0059] After the first strand pattern formation step, a strand pattern P is formed with the strands from the second end 30b to the first end 40a, which is the end of the second strand 40 (strand pattern formation step). Figure 5 shows the locations where the strand pattern P was provided when manufacturing the antenna sheet 1 of this embodiment with dotted lines. In this specification, imaginary lines connecting the ends of the strands on which such a strand pattern P was provided are also referred to as the strand pattern P. In the strand pattern P, the strands may be bonded to the substrate 10 in the same way as in the first strand pattern formation step. In particular, if the second end 30b and the first end 40a are close together (for example, if the distance between the ends 30b and 40a is shorter than the distance between the other ends), the strands may be bonded to the substrate 10. Also, if the strand pattern formed in the first strand pattern formation step is not formed between the ends 30b and 40a, the strands may be bonded to the substrate 10.

[0060] Further details will be explained in the seventh embodiment, but in the inter-wire pattern formation process, after the first wire pattern formation process, the wires may be wired without adhering them to the substrate 10 from the second end 30b to the first end 40a, which is the end of the second wire 40 (jumper section formation process). In particular, if there is a certain distance between the second end 30b of the first wire 30 and the first end 40a of the second wire 40, or if the wire pattern formed in the first wire pattern formation process is formed between the ends 30b and 40a, it is preferable to wire the wires without adhering them to the substrate 10. In the jumper section formation process, for example, at the second end 30b, the drawing head is raised from the surface of the substrate 10 and the wires are wired without adhering them to the substrate 10 up to the first end 40a, and then the wires are adhering to the substrate 10 again at the first end 40a. The region of the inter-wire pattern P in which the wires are wired without adhering them to the substrate 10 will hereafter be called the jumper section Jm. Figure 27 shows the locations where jumper sections Jm were provided when manufacturing the antenna sheet 1 of the seventh embodiment, indicated by dotted lines. In this specification, imaginary lines connecting the ends of the wires on which such jumper sections Jm were provided are also referred to as jumper sections Jm.

[0061] Next, a wiring pattern is formed from the first end 40a to the second end 40b, which will become the second strand 40 (second strand pattern formation step). The method for forming the wiring pattern is the same as the method described in the first strand pattern formation step. Then, both ends of the strand pattern P are cut to remove the strands of the strand pattern P, or the strands of the strand pattern P are cut (strand pattern processing step). As a result, the strands wired on the substrate 10 in one stroke become the first strand 30 and the second strand 40, which are physically disconnected. In the strand pattern P, the strands may be adhered to the substrate 10, but even if they are adhered, the adhesive distance between the strands and the substrate 10 in the strand pattern P is short, so the force required to separate the strands is small. Therefore, the strand pattern P can be removed easily. In the jumper section Jm, the strands are not adhered to the substrate 10, so the jumper section Jm can be removed easily by cutting the strands at both ends of the jumper section Jm.

[0062] The above-described formation method can also be described as a method of forming the antenna section 20 using only one strand, a so-called "one-stroke" method. However, in this case, the above-described crossover will inevitably occur at the folded portion 231 of the capacitance section 23. When two or more strands are used to arrange the strands in a manner generally similar to that of the antenna section 20, it is possible to omit the crossover in the capacitance section 23. Therefore, the presence of a crossover in the capacitance section 23 is a strong indication that the first strand 30 and the second strand 40 were originally the same strand, and were cut after the formation of the antenna section to become multiple strands. The crossover is not limited to the example of being provided in the capacitance section 23, but may also be provided in the coupling coil 22, or in the booster antenna 21 as in the embodiment described later. In this specification, the location of the crossover is also called the crossover section CO (see the third embodiment, etc.).

[0063] Based on the above, the most likely evidence that the first strand 30 and the second strand 40 were originally the same strand, and that the inter-strand pattern P was cut after the formation of the antenna section 20 to become multiple strands, is that both of the following conditions (1) and (2) are met. Condition (1) There is an overpass at some point in the antenna section 20. Note that the overpass in condition (1) refers to the intersection of the first strand 30 and the second strand 40. The intersection of two first strands 30 is not included in the overpass in condition (1), nor is the intersection of two second strands 40. Condition (2) The inter-strand pattern P, which is a virtual line connecting the end of the first strand 30 and the end of the second strand 40, includes inter-strand patterns P that do not intersect with strands, and / or inter-strand patterns P that intersect with only one of the two strands and not with the other strand. In this embodiment, condition (1) is satisfied because there is a grade separation in at least the capacitance section 23, and condition (2) is satisfied because there is an inter-wire pattern P that does not intersect with the individual wires. The inter-wire pattern P (jumper section Jm) that intersects with only one of the two wires and not with the other wire in condition (2) will be explained in the seventh embodiment.

[0064] On the other hand, if the first strand 30 and the second strand 40 are drawn and arranged separately, it is not necessary to provide a three-dimensional intersection in the antenna section 20. By placing the ends of each strand in appropriate positions, a closed circuit can be formed simply by arranging the first strand and the second strand in close proximity in the antenna section 20.

[0065] In this embodiment, the antenna sheet 1 is configured such that at least two strands, including the first strand 30 and the second strand 40 constituting the antenna portion 20, are electrically connected by stray capacitance between the strands, even though they are physically disconnected, thereby forming a closed circuit. This allows the substrate 10 to be given a certain degree of rigidity while still having the antenna portion 20. Furthermore, the resonant capacitance forming portion C, formed by the connection of the first strand 30 and the second strand 40 by stray capacitance, prevents fluctuations in inter-strand capacitance.

[0066] Furthermore, in the booster antenna 21, the number of loops of the first strand 30 differs from the number of loops of the second strand 40. The booster antenna 21 has a single-strand antenna section 21a in which only one of the first strand 30 or the second strand 40 is wired in a coil shape, and an interleaved capacitance section 24 in which the first strand 30 and the second strand 40 are interleaved and alternately arranged in the width direction of the strands. As a result, in addition to the capacitance section 23 which is originally intended to function as a capacitor, the first strand 30 and the second strand 40 are also arranged in close proximity with a small inter-center axis distance (pitch) in a part of the booster antenna 21 (i.e., the interleaved capacitance section 24). As a result, compared to conventional antenna sheets, more strands are arranged in both the peripheral part and the central part surrounded by the peripheral part, making it possible to create an antenna sheet with superior rigidity. In particular, by forming the booster antenna 21 and interleaved capacitance section 24 with conductive wires on the periphery of the substrate 10, it is possible to more effectively prevent wire breakage and fluctuations in inter-wire capacitance due to bending of the antenna sheet 1.

[0067] In this embodiment, the pitch between the first wire 30 and the second wire 40, which are electrically connected by stray capacitance, that is, the pitch in the adjacent arrangement, can be appropriately set within the range that generates stray capacitance. For example, it can be 1.5 times or more and 4 times or less the diameter of the wire, and preferably 2 times or more and 3 times or less.

[0068] The manufacturing method of the antenna sheet 1 according to this embodiment includes: a first strand pattern forming step of forming a wiring pattern on a dielectric substrate 10 using a conductor 12 from a first end 30a, which will be the end of the first strand 30, to a second end 30b; an inter-strand pattern forming step of forming an inter-strand pattern P on the substrate 10 using a conductor 12 from the second end 30b to the first end 40a, which will be the end of the second strand 40; a second strand pattern forming step of forming a wiring pattern on the substrate 10 using a conductor 12 from a first end 40a, which will become the second strand 40, to a second end 40b; and an inter-strand pattern processing step of removing or cutting the conductor 12 of the inter-strand pattern P. An antenna section 20, which is a closed circuit formed using the first strand 30 and the second strand 40 that are physically disconnected, is formed, with a part of the first strand 30 and a part of the second strand 40 placed in close proximity, and the first strand 30 and the second strand 40 are electrically connected by the stray capacitance that occurs between them. This makes it possible to manufacture an antenna sheet 1 that has a certain rigidity and prevents fluctuations in inter-wire capacitance in a so-called single-stroke drawing. Furthermore, the inter-wire pattern formation step may include a jumper section formation step in which the conductor 12 is wired from the second end 30b of the first wire 30 to the first end 40a of the second wire 40 without being bonded to the substrate 10, thereby forming a jumper section Jm.

[0069] <Second Embodiment> A second embodiment of the present invention will be described with reference to Figures 7 to 11. In the following description, components that are common to those already described will be denoted by the same reference numerals, and redundant descriptions will be omitted.

[0070] Figure 7 shows a schematic plan view of the antenna sheet 1 according to this embodiment, and Figures 8 and 9 show the arrangement of the first strand 130 and the second strand 140 related to the antenna sheet 1, respectively. The antenna section 120 related to the antenna sheet 1 is the same as in the first embodiment in that it has three regions: a booster antenna, a coupling coil, and a resonant capacitance forming section, but differs in that the capacitance section 123 is loop-shaped like the booster antenna 121, rather than meander-shaped. The arrangement of the first strand 130 and the second strand 140 is also generally the same as the first strand 30 and the second strand 40 according to the first embodiment in that they each have a first region 132 to a third region 135 and a fourth region 142 to a fifth region 143.

[0071] Figure 10 is an enlarged view showing part B of Figure 7. The booster antenna 121 of this embodiment differs from the first embodiment in that the first strand 130 of the first region 132 and the second strand 140 of the fifth region 143 are arranged alternately in close proximity in the width direction of the strands throughout the entire structure. That is, in this embodiment, the first strand 130 and the second strand 140 are electrically connected throughout the booster antenna 121 to form an interleaved capacitance section 124. In other words, the booster antenna 121 functions as both a transmitting and receiving antenna and a resonant capacitance forming section C used for contactless communication.

[0072] Figure 11 shows an enlarged view of the capacitance section 123 according to this embodiment. In the capacitance section 123, similar to the booster antenna 121, the first strand 130 of the third region 135 and the second strand 140 of the fourth region 142 are arranged alternately in close proximity in the width direction of the strands throughout the entire structure. Both the first strand 130 and the second strand 140 are wound to the inside of the loop, then folded back and wound again to the outside. This arrangement is made possible by providing a three-dimensional intersection 123A of the first strand 130 and the second strand 140 within the loop of the capacitance section 123. Although the capacitance section 123 differs in appearance from the capacitance section 23 according to the first embodiment, it is similar in that it forms a capacitor by utilizing the stray capacitance generated between adjacent first strands 130 and second strands 140, and also has the same function of adjusting the resonant frequency when the connected IC module performs contactless communication.

[0073] The antenna sheet 1 according to this embodiment, like the first embodiment, has excellent rigidity because many strands are arranged on the substrate 10. The configuration according to this embodiment has the advantage that the windings forming the capacitance portion 123 can be arranged more densely than in the first embodiment, and the capacitance portion 123 can be made smaller.

[0074] The antenna sheet 1 according to this embodiment can be manufactured using a procedure that is generally the same as that of the antenna sheet 1 according to the first embodiment. That is, the first strand 130 and the second strand 140 may be formed by arranging them using a winding drawing device, or the entire antenna portion 120 may be formed with a single strand, and then the first and second strands may be formed by cutting at a desired location. The cutting location can be determined as appropriate in either embodiment, but the first strand after cutting must have at least a part of the first region, the second region, and at least a part of the third region in a continuous manner. Similarly, the second strand after cutting must have at least a part of the fourth region and at least a part of the fifth region in a continuous manner, so the cutting location should be determined while keeping these points in mind.

[0075] It should be noted that the first and second embodiments, and the embodiments described later, are not necessarily limited to the above-described forms, and various modifications can be made without departing from the spirit of the present invention. For example, the following modifications may be made: The position of the coupling coil and capacitance section is not limited to those shown in the embodiments, and can be freely set within the loop of the booster antenna. However, in IC cards to which the antenna sheet is applied, the user's name, etc., may be embossed on the lower side in a plan view, so by arranging the coupling coil and capacitance section towards the upper side in a plan view of the antenna sheet, corresponding to one of the short sides of the rectangular loop of the booster antenna 21, as shown in Figure 1, damage to the strands due to such printing can be avoided or mitigated.

[0076] The antenna section according to the present invention may be composed of three or more strands. Furthermore, there are no particular restrictions on the order in which the multiple strands constituting the antenna section are arranged, and can be freely determined. For example, the second strand may be arranged first, followed by the first strand. Thus, the names "first strand" and "second strand" have no purpose other than to allow for mutual identification and are completely unrelated to the order in which they are manufactured. Similarly, the names "first end" and "second end" of each strand have no purpose other than to allow for mutual identification and are completely unrelated to the order in which they are manufactured.

[0077] - In cases where the antenna sheet according to the present invention is configured specifically for contactless communication, a contactless communication-capable IC chip may be directly connected to the antenna portion without providing a coupling coil. In this case, the connected IC chip may be a bare chip, a module, or any other, and the timing of connecting the antenna portion and the IC chip may be after arranging one of the first and second strands, or after forming the entire antenna portion.

[0078] <Third Embodiment> A third embodiment of the present invention will be described below with reference to Figures 12 to 14. In the following description, components that are common to those already described will be denoted by the same reference numerals, and redundant explanations will be omitted.

[0079] When an electromagnetically coupled booster antenna (antenna section) is formed with a single winding, typically, as described in Patent Document 1, a crossover occurs at least two points between the antenna and the coupling coil. The winding is generally arranged using a known winding drawing device, but at crossover points, it is necessary to lift the head of the winding drawing device upwards, pass it over the already arranged windings, and then lower the head. Since the time required to draw the winding tends to increase as the number of crossover points increases, and the thickness of the antenna increases at crossover points compared to other parts, it is desirable to have as few crossover points as possible.

[0080] In view of the above circumstances, the objective of the third embodiment is to provide an antenna sheet that has an electromagnetic coupling coil and a resonant capacitance while having a small number of crossover sections.

[0081] Figure 12 is a schematic plan view showing the antenna sheet 1 according to this embodiment. The antenna sheet 1 has a substrate 10 made of a dielectric material and an antenna portion 20 formed on the substrate 10. Each part of the antenna portion 20, which will be described later, is made up of strands made of conductors. Copper is a typical conductor material for the strands, but silver, gold, aluminum, and copper alloys can also be used as examples.

[0082] The substrate 10 is formed in a rectangular shape in plan view using an insulating material such as PET (polyethylene terephthalate), polyethylene naphthalate (PEN), PVC (polyvinyl chloride), or various types of paper. The thickness of the substrate 10 can be, for example, about 50 to 400 μm. Depending on how the antenna sheet 1 is incorporated into an IC card or the like, through holes may be formed in a part of the substrate 10.

[0083] The antenna section 20 according to this embodiment has three regions: a booster antenna 21, a coupling coil 22, and a resonant capacitance forming section C. The booster antenna 21 is a coil-shaped antenna used for contactless communication with an external reader / writer, and is formed by winding strands of wire in a spiral shape at least once.

[0084] The coupling coil 22 is the part used for electromagnetic coupling with the IC module, which has contact terminals. In Figure 12, the location of the IC module is shown by a dashed line. The IC module has contact terminals and an electrically connected IC chip, and its basic structure is well known. When the IC module is electromagnetically coupled with the booster antenna 21 via the coupling coil 22, the IC chip becomes capable of two types of communication: contact communication using the contact terminals and contactless communication using the booster antenna 21. The coupling coil 22 is formed by winding strands of wire in a spiral manner multiple times to form a loop with a diameter smaller than that of the booster antenna 21.

[0085] In this embodiment, the capacitance section 23 is formed by arranging in close proximity an upstream region 31 connected to the booster antenna 21 and a downstream region 41 connected to the coupling coil 22, with adjacent upstream and downstream regions 31 and 41 capacitively coupled. Furthermore, as shown in Figure 12, an interleaved capacitance section 24 is provided on the periphery of the substrate 10 with interleaved wiring. Thus, a circuit including the booster antenna 21, the coupling coil 22, and the resonant capacitance forming section C is configured. The upstream region 31 and the downstream region 41 run parallel to each other, extending in a spiral shape from the outside to the inside, folding back at the innermost point and extending in a spiral shape from the inside to the outside, returning to the starting position of the winding. The upstream region 31 and the downstream region 41 are formed such that the downstream region 41 has an "outbound side" that goes from the outside to the inside and an "return side" that goes from the inside to the outside, and the "outbound side" and "return side" of the upstream region 31 are positioned to sandwich it, thereby preventing the creation of a crossover area where the upstream region 31 and the downstream region 41 intersect in three dimensions.

[0086] In this embodiment, the loop of the booster antenna 21 is generally a roughly rectangular shape along the periphery of the substrate 10, but in the area where the coupling coil 22 is provided, it curves inward away from the periphery of the substrate 10, passes around the coupling coil 22, and returns to the periphery of the substrate 10. Due to this winding configuration, the coupling coil 22 is located on the outside of the loop of the booster antenna 21. On the other hand, the capacitance section 23 is located on the inside of the loop of the booster antenna 21.

[0087] In this embodiment, the antenna section 20 consists of a booster antenna 21, a coupling coil 22, and a resonant capacitance forming section C, all formed from two strands. Figure 13 shows the arrangement of the first strand 30, which is one of the two strands. The first strand 30 forms a part of the booster antenna 21 and the upstream region 31 of the capacitance section 23. Figure 14 shows the arrangement of the second strand 40, which is the other of the two strands. The second strand 40 forms the coupling coil 22, the downstream region 41 of the capacitance section 23, and the remaining part of the booster antenna 21.

[0088] ・Method for manufacturing the antenna sheet 1 The method for manufacturing the antenna sheet 1 is generally the same as the method described in the first embodiment, but the differences will be explained below. The antenna portion 20 can be formed on the substrate 10 using a known winding drawing device. A winding drawing device generally softens the substrate 10 while arranging the strands, so that a portion of the strands can be embedded into the substrate 10 and fixedly arranged on the substrate 10. The procedure for forming the antenna portion in this embodiment will be described below. First, the first strand 30 is drawn starting from the first end 30a and wound in a spiral shape of a predetermined shape from the outside to the inside to form a part of the booster antenna 21. In the booster antenna 21, a second strand 40 will be placed between adjacent first strands later, so the strands are wound while ensuring a distance of at least the diameter of the second strand 40.

[0089] Next, the upstream region 31 is formed within the loop of the booster antenna 21. At this time, a spacing of at least twice the diameter of the second strand 40 is ensured between the first strands 30 so that the downstream region 41 can be arranged back and forth between the first strands 30. After forming the upstream region 31, the drawing is terminated at the desired second end 30b, and the first strand 30 is cut. This completes the arrangement of the first strand 30. Since there are no crossover sections in the first strand 30, the head of the winding drawing device does not need to be raised or lowered during drawing, and drawing can be performed without interruption from the first end 30a to the second end 30b.

[0090] Next, the second strand 40 is placed. Drawing begins from the first end 40a, and the second strand 40 is placed between the first strands 30 that form part of the booster antenna 21, while being wound in a spiral shape from the inside outwards to form the rest of the booster antenna 21. In the completed booster antenna 21, the outermost and innermost circumferences are formed by the first strands. After that, at the part where the loop of the booster antenna 21 is displaced inwards, a coupling coil 22 is formed on the outside of the loop. The coupling coil 22 is formed in a spiral shape from the outside inwards.

[0091] Once the coupling coil 22 has been formed up to the innermost circumference, drawing is temporarily stopped and the head is raised. The substrate 10 and the head are moved relative to each other, and after the head is moved to a predetermined position within the loop of the booster antenna 21, the head is lowered. Due to the above movement of the head, a crossover area CO is created in the second strand 40. The crossover area CO intersects not only the loop of the coupling coil 22 that was formed immediately before, but also the loop of the booster antenna 21, which includes the first strand 30 and the second strand 40. In other words, by intersecting both the coupling coil 22 and the booster antenna 21, the second strand 40 is moved into the loop of the booster antenna 21 with only one crossover area CO.

[0092] Finally, the capacitance section 23 is completed when the second strand 40 is arranged back and forth along the upstream region 31 between the first strands 30 in the upstream region 31 to form the downstream region 41. When drawing is stopped at the desired position (the second end 40b of the second strand 40) and the second strand 40 is cut, the antenna sheet 1 of this embodiment, with the antenna section 20 formed on the substrate 10, is completed. The antenna section 20 is formed of two strands that are physically disconnected, but the two strands are capacitively coupled in the resonant capacitance forming section C, which includes the capacitance section 23 and the interleaved capacitance section 24, so that the whole functions as a closed circuit. Note that a jumper section Jm may be formed when moving the head from the second end 30b of the first strand 30 to the first end 40a of the second strand 40. The antenna section 20 may then be formed by removing the jumper section Jm.

[0093] As described above, in this embodiment, the antenna sheet 1 has one crossover portion CO that intersects with both the coupling coil 22 and the booster antenna 21 in three dimensions, and the capacitance portion 23 is formed so that no crossover portion occurs. This makes it possible to provide an antenna sheet with an electromagnetic coupling coil and resonant capacitance, while having a small number of crossover portions. Specifically, although it has a configuration that includes a coil for electromagnetic coupling and a capacitor for resonance, the drawing of the strands can be completed with only one three-dimensional intersection. As a result, the effort and time required to raise and lower the head of the drawing device can be reduced, and manufacturing can be done efficiently.

[0094] At crossover points, it is necessary to arrange the intersecting wires so that they do not cause an electrical short circuit. There are several specific methods, but the simplest is to use insulated wires for at least one of the first wire 30 and the second wire 40.

[0095] <Fourth Embodiment> A fourth embodiment of the present invention will be described with reference to Figures 15 to 17. In the following description, components that are the same as or similar to those already described will be denoted by the same reference numerals, and redundant descriptions may be omitted.

[0096] Figure 15 shows a schematic plan view of the antenna sheet 1 according to this embodiment. In the antenna portion 20 of the antenna sheet 1, the configuration of the coupling coil 22 and the capacitance portion 23 is generally the same as in the third embodiment, but the spiral shape of the booster antenna 21A is different from that of the third embodiment. Furthermore, due to the shape of the booster antenna 21A, the coupling coil 22 is located inside the loop of the booster antenna 21A, and the capacitance portion 23 is located outside the loop of the booster antenna 21A, which is different from the third embodiment.

[0097] The procedure for forming the antenna section 20 in this embodiment using a winding drawing device will now be described. In this procedure, the first strand 30 shown in Figure 16 and the second strand 40 shown in Figure 17 are formed continuously using the same strand. First, drawing begins from the first end 30a shown in Figure 16, and the wire is wound in a spiral shape from the inside out to form a part of the booster antenna 21A. Next, the upstream region 31 is formed outside the loop of the booster antenna 21A. The distance between strands of the booster antenna 21A and the upstream region 31 is the same as in the third embodiment.

[0098] When the drawing reaches the second end 30b shown in Figure 16, the placement of the portion that will become the first strand 30 on the substrate 10 is complete. However, the strand is not cut yet, and the portion that will become the second strand 40 is placed on the substrate 10. In other words, the jumper portion Jm is formed. This placement starts from the first end 40a side shown in Figure 17. First, new strands are placed between the strands that form part of the booster antenna 21A, and the remaining part of the booster antenna 21A is formed by winding them in a spiral shape from the outside to the inside. Next, a coupling coil 22 is formed in a spiral shape from the outside to the inside within the loop of the booster antenna 21A.

[0099] Once the coupling coil 22 has been formed up to the innermost circumference, drawing is temporarily stopped and the head is raised. The substrate 10 and the head are moved relative to each other, and the head is moved to a predetermined position outside the loop of the booster antenna 21A, and then the head is lowered. This forms a crossover region CO that intersects both the coupling coil 22 and the booster antenna 21A in three dimensions.

[0100] Subsequently, the downstream region 41 of the booster antenna 21A is formed in an operation largely similar to that of the third embodiment, and a capacitance section 23 is formed outside the loop of the booster antenna 21A. After the capacitance section 23 is formed, the strand is detached from the winding drawing device at a desired position (the second end 40b of the second strand 40). Finally, when the strand is cut near the second end 30b or the first end 40a, or when the jumper section Jm is removed, the single strand placed on the substrate 10 is divided into the first strand 30 and the second strand 40, completing the antenna section 20 and the antenna sheet 1.

[0101] In the antenna sheet 1 according to this embodiment, the crossover portion CO intersects with both the coupling coil 22 and the booster antenna 21 in three dimensions, and the capacitance portion 23 is formed so that no crossover portion occurs. Therefore, similar to the third embodiment, the effort and time required to raise and lower the head of the drawing device can be reduced, and it can be manufactured efficiently.

[0102] In the fourth embodiment, an example was described in which all the strands are arranged by continuous drawing using a single strand, and then this strand is cut to form the first strand 30 and the second strand 40. However, as with the third embodiment, it is naturally possible to form the antenna section 20 using two strands. Similarly, the antenna section according to the third embodiment may be formed by continuous drawing using a single strand and cutting the strand after drawing.

[0103] As described above, the antenna sheet 1 of the third and fourth embodiments is an antenna sheet 1 in which an antenna portion 20 is formed on a dielectric substrate 10 using a first strand 30 and a second strand 40 made of conductors. The antenna portion 20 includes a spiral booster antenna 21, a spiral coupling coil 22 connected to the booster antenna 21 and smaller than the booster antenna 21, a capacitance portion 23 formed by capacitive coupling of the first strand 30 and the second strand 40 by being placed in close proximity, and a crossover portion CO where the strands intersect in three dimensions. One of the coupling coil 22 and the capacitance portion 23 is located outside the spiral of the booster antenna 21, and the other is located inside the spiral of the booster antenna 21, and the crossover portion CO is provided at only one location so as to intersect in three dimensions with the coupling coil 22 and the booster antenna 21. In the third embodiment, of the coupling coil 22 and the capacitance section 23, the coupling coil 22 is located outside the spiral of the booster antenna 21, and the capacitance section 23 is located inside the spiral of the booster antenna 21. In the fourth embodiment, of the coupling coil 22 and the capacitance section 23, the capacitance section 23 is located outside the spiral of the booster antenna 21, and the coupling coil 22 is located inside the spiral of the booster antenna 21.

[0104] It should be noted that the third and fourth embodiments, and the embodiments described later, are not necessarily limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, the following modifications may be made. For example, the arrangement of the strands in the capacitance section is not limited to the spiral shape shown in the embodiments. Even with other configurations such as a meander shape, it is possible to form a capacitance section without creating a crossover area by arranging a second strand that reciprocates between a first strand that reciprocates.

[0105] <Fifth Embodiment> The fifth embodiment of the present invention will now be described in detail with reference to the drawings. In the following description, components that are common to those already described will be denoted by the same reference numerals, and redundant descriptions will be omitted.

[0106] From a manufacturing cost perspective, an antenna module has been proposed in which the booster antenna, coupling coil, and capacitor are all formed together using conductors provided within the plane of a dielectric sheet (see, for example, Patent Documents 1 and 2).

[0107] Specifically, Patent Document 1 discloses an IC module that utilizes stray capacitance between adjacent coils by arranging the conductors at both ends of a coil that serves as a booster antenna adjacent to each other and wiring adjacent conductors of equal length in a meander pattern. Patent Document 2 also discloses a capacitance section in which pairs of conductors, with a portion of the conductor folded back and placed close to each other, are arranged in a meander or spiral pattern.

[0108] Incidentally, when forming a capacitance section using pairs of wires placed in close proximity to each other as described above, variations in the capacitance of the capacitance section are likely to occur due to factors such as the positional accuracy of the wires during wiring. For this reason, in order to match the resonant frequency in communication using a booster antenna, a portion of the wires is cut after wiring to adjust the capacitance.

[0109] However, when adjusting the length of such wires, there is a risk that the wire to be cut may interfere with an adjacent wire, making the work difficult. There is also a risk of accidentally damaging other wires.

[0110] The fifth embodiment was proposed in view of the above conventional circumstances, and aims to provide an antenna sheet suitable for adjusting the length of the conductors forming the capacitance section, and an RF tag equipped with such an antenna sheet.

[0111] As a fifth embodiment, an RF tag 100 equipped with an antenna sheet 1, as shown in Figures 18 to 20, will be described. Figure 18 is a plan view showing the RF tag 100 equipped with the antenna sheet 1. Figure 19 is a plan view showing a second modified example in which the arrangement of the wire pairs 13 forming the extended capacitance portion 23b of the antenna sheet 1 is changed. Figure 20 is a plan view showing a second modified example in which the arrangement of the wire pairs 13 forming the extended capacitance portion 23b of the antenna sheet 1 is changed. As shown in the figures, in this embodiment, the resonant capacitance forming portion C includes the extended capacitance portion 23b.

[0112] As shown in Figure 18, the RF tag 100 of this embodiment is a contactless communication-enabled IC card, and has a structure in which an inlet containing an antenna sheet 1 and an IC chip (not shown) connected to the antenna sheet 1 is built into a plastic card body 2 which serves as the outer casing. The typical size of the card body 2 is 85.6 mm x 54 mm, with a corner radius (R) of 3 mm and a thickness of 0.76 mm.

[0113] Furthermore, the RF tag 100 of this embodiment is equipped with contact terminals 3 electrically connected to the IC chip 50 shown in Figure 2, and functions as a dual IC card capable of contact and contactless communication. The contact terminals 3 are provided in an exposed state from the surface of the card body 2. Generally, the contact terminals 3 are provided near the center of one side (left side) in the longitudinal direction (left-right direction) within the plane of the card body 2.

[0114] The antenna sheet 1 of this embodiment comprises a substrate 10 (dielectric sheet) made of a dielectric material and a conductor 12 provided within the plane of the substrate 10.

[0115] The substrate 10 is made of an insulating resin such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), or polyvinyl chloride (PVC), or a dielectric material such as paper. The substrate 10 has a shape corresponding to the card body 2, that is, a rectangular shape with rounded corners in a plan view. The thickness of the substrate 10 is, for example, about 50 to 400 μm.

[0116] The conductor 12 is, for example, made of copper wire or enameled wire, which is copper wire coated with an insulating film. In addition to copper wire, metal wires such as gold, silver, aluminum, and copper alloys can also be used. The thickness (diameter) of the conductor 12 is, for example, about 50 to 200 μm.

[0117] The antenna sheet 1 of this embodiment has an antenna section 20 formed of strands of conductive wire. The antenna section 20 includes a booster antenna 21 in which a portion of the conductive wire 12 is arranged spirally around the periphery of the substrate 10, a coupling coil 22 located inside the booster antenna 21 in which a portion of the conductive wire 12 is arranged spirally with a loop diameter smaller than that of the booster antenna 21, and a capacitance section 23 located inside the booster antenna 21, formed by a pair of conductive wires 13 in which a portion of the conductive wire 12 is folded back and placed close to each other.

[0118] In other words, the booster antenna 21, coupling coil 22, and capacitance unit 23 are formed collectively by routing a single wire 12 within the plane of the substrate 10.

[0119] Furthermore, the antenna section 20, which includes the booster antenna 21, coupling coil 22, and capacitance section 23, is not limited to being formed by a single conductor 12 as described above, but can also be formed using multiple conductors 12. That is, as described in the first to fourth embodiments, the conductor pair 13 may include a first strand 30 and a second strand 40 in which the conductor pair 13 is physically non-contacting. In addition, the conductors 12 can be crossed in a three-dimensional manner while being electrically insulated from each other, or routed through holes formed in the substrate 10.

[0120] As shown in Figures 18 and 2, the antenna sheet 1 of this embodiment forms a closed loop in which one end of the booster antenna 21 and the coupling coil 22 are electrically connected, and the other end of the booster antenna 21 and the coupling coil 22 are electrically connected via a capacitance section 23.

[0121] The booster antenna 21 is formed by winding a conductor 12 spirally at least once, and is electromagnetically coupled to the transmit / receive coil 201 of the reader / writer 200 shown in Figure 2. In this embodiment, the booster antenna 21 is formed by a conductor 12 that is wound spirally along the outer circumference of the substrate 10, while maintaining a constant distance between adjacent conductors 12.

[0122] The coupling coil 22 is formed by spirally winding a conductor 12, which is continuous with the booster antenna 21, at least once, to electromagnetically couple with the antenna coil 51 connected to the IC chip 50 shown in Figure 2.

[0123] In this embodiment, the coupling coil 22 is formed by spirally circulating conductors 12 around the position that overlaps with the contact terminal 3 in a plan view, while maintaining a constant spacing between adjacent conductors 12, so that in a plan view it forms a polygonal shape such as a regular octagon or a circular shape. On the other hand, the antenna coil 51 of the IC chip 50 is positioned opposite the coupling coil 22.

[0124] The coupling coil 22 is necessary when applied to the dual IC card described above, but it can be omitted when not applied to a dual IC card.

[0125] The capacitance section 23 is formed as a resonant capacitor that forms a resonant circuit with the booster antenna 21. It is formed by a pair of wires 13 that utilize the stray capacitance generated between a pair of wires 12 that are placed close together by folding back a portion of the wire 12. In other words, this pair of wires 13 forms a capacitor in which the capacitance is adjusted according to the length while keeping the distance between adjacent wires 12 constant.

[0126] The capacitance section 23 is located in the upper region (hereinafter referred to as the "upper region") E1 on one side of the central part in the short-side direction (vertical direction) within the plane of the substrate 10. On the other hand, the lower region (hereinafter referred to as the "lower region") E2 on the other side of the central part in the short-side direction (vertical direction) within the plane of the substrate 10 is a blank area where the IC card number, expiration date, name, etc., are printed by embossing, and therefore the placement of the conductive wires 12 should be avoided.

[0127] The capacitance section 23 includes a main capacitance section 23a in which a portion of the wire pair 13 is arranged in a spiral shape, and an extended capacitance section 23b in which the wire pair 13 is extended to both ends 12a of the wire 12, continuous with the main capacitance section 23a.

[0128] The main capacitance section 23a is located in the upper region E1 within the plane of the substrate 10 and consists of a main wiring section formed by spirally winding a portion of the wire pair 13 at least once.

[0129] Furthermore, the ends of the wire pairs 13 that form the main wiring section of the main capacitance section 23a are formed by the folded portions 14 of the wires 12. In this embodiment, the main capacitance section 23a is formed by four wires 12 that are arranged in close proximity to each other, by folding back two sets of wire pairs 13 at their respective folded portions 14.

[0130] As a result, in the main capacitance section 23a, the number of conductors 12 forming the conductor pair 13 can be substantially increased by increasing the number of folded sections 14. In other words, in this main capacitance section 23a, the capacitance can be adjusted according to the number of conductors 12 forming the conductor pair 13.

[0131] The extended capacitance portion 23b is located in the upper region E1 within the plane of the substrate 10 and is formed by extending the wire pair 13 from the boundary A with the wire pair 13 that forms the main capacitance portion 23a toward both ends 12a of the wire 12. The ends 12a of the wire 12 are ultimately bent in opposite directions.

[0132] The extended capacitance section 23b is positioned at a distance from the main capacitance section 23a. Specifically, this extended capacitance section 23b has an extended wiring section 23b1 in which a portion of the conductor pair 13 is arranged in a spiral shape.

[0133] The extension wiring section 23b1 is formed by spirally winding the pair of conductors 13 around the conductors 12 up to both ends 12a, continuous with the main capacitance section 23a. The extension wiring section 23b1 is spaced apart from the conductors 13 that form the main capacitance section 23a, and is arranged spirally to surround the main capacitance section 23a.

[0134] In other words, the extension wiring section 23b1 is spaced further apart from the conductor pairs 13 forming the main capacitance section 23a, with a spacing greater than the spacing between adjacent conductor pairs 13 forming the main capacitance section 23a.

[0135] In the RF tag 100 equipped with the antenna sheet 1 having the above configuration, as shown in Figure 2, a high-frequency magnetic field is induced in the transmitting / receiving coil 201 by the high-frequency signal generated in the transmitting / receiving circuit 202 of the reader / writer 200. This high-frequency magnetic field is radiated into space as magnetic energy.

[0136] At this time, the RF tag 100 is positioned in a high-frequency magnetic field, causing electromagnetic coupling between the transmitting / receiving coil 201 and the booster antenna 21, and current flows through the booster antenna 21. In addition, the signal received by the booster antenna 21 is transmitted to the coupling coil 22, and current flows through the coupling coil 22 as well. As a result, the signal received by the booster antenna 21 is transmitted to the IC chip 50 by electromagnetic coupling between the coupling coil 22 and the antenna coil 51.

[0137] On the other hand, when the RF tag 100 is used to supply power and communicate with a contact-type external device, such as an automated teller machine, the contact terminals of the device are brought into contact with the contact terminals 3 of the RF tag 100. This enables power supply and communication between the contact-type external device and the RF tag 100.

[0138] In the antenna sheet 1 of this embodiment, the length of the wire pair 13 forming the extended capacitance section 23b is adjusted to match the resonant frequency in communication using the booster antenna 21 described above. Specifically, a portion of the wire pair 13 forming the extended wiring section 23b1 is cut from both ends 12a of the wire 12, and the capacitance of the capacitance section 23 is adjusted.

[0139] As a result, in the antenna sheet 1 of this embodiment, variations in capacitance caused by positional accuracy during wiring of the conductor 12 can be kept to a minimum. Consequently, it is possible to optimize the capacitance of the capacitance section 23 to match the resonant frequency in communication using the booster antenna 21.

[0140] Therefore, the RF tag 100 of this embodiment, by including the antenna sheet 1 of this embodiment as described above, exhibits less fluctuation in the resonant frequency and enables stable contactless communication.

[0141] Furthermore, in the antenna sheet 1 of this embodiment, the extension wiring section 23b1 that forms the extension capacitance section 23b described above is arranged at a distance from the periphery of the main capacitance section 23a. This makes it possible to adjust the capacitance of the capacitance section 23 while preventing interference between the wires 12 to be cut and adjacent wires 12 when cutting a portion of the wire pair 13 that forms the extension wiring section 23b1. As a result, it is possible to significantly reduce the occurrence of problems such as accidentally damaging other wires 12.

[0142] The fifth embodiment is not necessarily limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0143] The following are some examples of variations, but these are not exhaustive, and other modifications are possible. Furthermore, these modifications can be freely combined in any way, as long as they do not create contradictions.

[0144] For example, the antenna sheet 1 of the fifth embodiment may have a configuration in which the arrangement of the wire pairs 13 that form the extended capacitance portion 23b is changed, as shown in Figure 19, as a first modification.

[0145] Specifically, in the extended capacitance section 23b shown in Figure 19, a portion of the pair of conductors 13 that form the extended wiring section 23b1 is positioned away from the main capacitance section 23a located in the upper region E1, and is arranged in a line shape to avoid the embossing in the lower region E2.

[0146] Furthermore, in the extended capacity section 23b shown in Figure 19, the extension wiring section 23b1 is formed by four closely spaced conductors 12, by folding back the pairs of conductors 13 that form the extension wiring section 23b1 at their respective folding sections 14.

[0147] As a result, the antenna sheet 1 of this embodiment can increase capacitance and enhance design flexibility, such as design flexibility.

[0148] Furthermore, as a second modification, the antenna sheet 1 of the fifth embodiment may have a configuration in which the arrangement of the wire pairs 13 that form the extended capacitance portion 23b is changed, as shown in Figure 20.

[0149] Specifically, in the extended capacitance section 23b shown in Figure 20, a portion of the wire pair 13 forming the extended wiring section 23b1 is arranged spirally at a position that avoids the embossing of the lower region E2, separated from the main capacitance section 23a located in the upper region E1. Furthermore, the ends of the wire pair 13 forming the extended capacitance section 23b are formed by the folded portion 14 of the wire 12.

[0150] As a result, the antenna sheet 1 of this embodiment can increase capacitance and enhance design flexibility, such as design flexibility.

[0151] Furthermore, if the substrate 10 has a shape corresponding to an IC card, it is preferable to place at least one part of the main capacity section 23a and the extended capacity section 23b in the lower region E2 of the IC card, in order to space the extended capacity section 23b away from the periphery of the main capacity section 23a. In addition, it is preferable that at least one part of the main capacity section 23a and the extended capacity section 23b is placed in the lower 1 / 3 region of the IC card with a length of 1 / 5 or more of the longitudinal direction of the IC card.

[0152] <Sixth Embodiment> A sixth embodiment of the present invention will be described in detail below with reference to the drawings. In the following description, components that are common to those already described will be denoted by the same reference numerals, and redundant descriptions will be omitted.

[0153] When the wire pairs forming the capacitance section described above are arranged in a meander or spiral pattern, there is a concern that in-phase noise may be superimposed on these wire pairs, potentially leading to malfunction or failure of the IC chip.

[0154] The sixth embodiment was proposed in view of the above conventional circumstances, and aims to provide an antenna sheet that suppresses the superposition of in-phase noise on the wire pair forming the capacitance section, and an RF tag equipped with such an antenna sheet.

[0155] As a sixth embodiment, an RF tag 100 equipped with an antenna sheet 1, as shown in Figures 21 to 23, will be described. Figure 21 is a plan view showing the RF tag 100 equipped with the antenna sheet 1. Figure 22 is a plan view showing a second modified example in which the arrangement of the wire pairs 13 forming the capacitance portion 23 of the antenna sheet 1 is changed. Figure 23 is a plan view showing a second modified example in which the arrangement of the wire pairs 13 forming the capacitance portion 23 of the antenna sheet 1 is changed.

[0156] As shown in Figure 21, the RF tag 100 of this embodiment is a contactless communication-enabled IC card, and has a structure in which an inlet containing an antenna sheet 1 and an IC chip (not shown) connected to the antenna sheet 1 is built into a plastic card body 2 which serves as the outer casing. The typical size of the card body 2 is 85.6 mm x 54 mm, with a corner radius (R) of 3 mm and a thickness of 0.76 mm.

[0157] Furthermore, the RF tag 100 of this embodiment is equipped with contact terminals 3 electrically connected to the IC chip 50 shown in Figure 2, and functions as a dual IC card capable of contact and contactless communication. The contact terminals 3 are provided in an exposed state from the surface of the card body 2. Generally, the contact terminals 3 are provided near the center of one side (left side) in the longitudinal direction (left-right direction) within the plane of the card body 2.

[0158] The antenna sheet 1 of this embodiment comprises a substrate 10 and a conductor 12 provided within the surface of the substrate 10.

[0159] The substrate 10 is made of an insulating resin such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), or polyvinyl chloride (PVC), or a dielectric material such as paper. The substrate 10 has a shape corresponding to the card body 2, that is, a rectangular shape with rounded corners in a plan view. The thickness of the substrate 10 is, for example, about 50 to 400 μm.

[0160] The conductor 12 is, for example, made of copper wire or enameled wire, which is copper wire coated with an insulating film. In addition to copper wire, metal wires such as gold, silver, aluminum, and copper alloys can also be used. The thickness (diameter) of the conductor 12 is, for example, about 50 to 200 μm.

[0161] The antenna sheet 1 of this embodiment includes a booster antenna 21 in which a portion of the conductor 12 is arranged spirally around the periphery of the substrate 10, a coupling coil 22 located inside the booster antenna 21 and in which a portion of the conductor 12 is arranged spirally with a loop diameter smaller than that of the booster antenna 21, and a capacitance portion 23 located inside the booster antenna 21 and formed by a pair of conductors 13 in which a portion of the conductor 12 is folded back and placed close to each other.

[0162] In other words, the booster antenna 21, coupling coil 22, and capacitance unit 23 are formed collectively by routing a single wire 12 within the plane of the substrate 10.

[0163] Furthermore, the antenna section 20, which includes the booster antenna 21, coupling coil 22, and capacitance section 23, is not limited to being formed by a single conductor 12 as described above, but can also be formed using multiple conductors 12. That is, as described in the first to fifth embodiments, the conductor pair 13 may include a first strand 30 and a second strand 40 in which the conductor pair 13 is physically non-contacting. In addition, the conductors 12 can be crossed in a three-dimensional manner while being electrically insulated from each other, or routed through holes formed in the substrate 10.

[0164] As shown in Figures 21 and 2, the antenna sheet 1 of this embodiment forms a closed loop in which one end of the booster antenna 21 and the coupling coil 22 are electrically connected, and the other end of the booster antenna 21 and the coupling coil 22 are electrically connected via a capacitance section 23.

[0165] The booster antenna 21 is formed by winding a conductor 12 spirally at least once, and is electromagnetically coupled to the transmit / receive coil 201 of the reader / writer 200 shown in Figure 2. In this embodiment, the booster antenna 21 is formed by a conductor 12 that is wound spirally along the outer circumference of the substrate 10, while maintaining a constant distance between adjacent conductors 12.

[0166] The coupling coil 22 is formed by spirally winding a conductor 12, which is continuous with the booster antenna 21, at least once, to electromagnetically couple with the antenna coil 51 connected to the IC chip 50 shown in Figure 2.

[0167] In this embodiment, the coupling coil 22 is formed by spirally circulating conductors 12 around the position that overlaps with the contact terminal 3 in a plan view, while maintaining a constant spacing between adjacent conductors 12, so that in a plan view it forms a polygonal shape such as a regular octagon or a circular shape. On the other hand, the antenna coil 51 of the IC chip 50 is positioned opposite the coupling coil 22.

[0168] The coupling coil 22 is necessary when applied to the dual IC card described above, but it can be omitted when not applied to a dual IC card.

[0169] The capacitance section 23 is formed as a resonant capacitor that forms a resonant circuit with the booster antenna 21. It is formed by a pair of wires 13 that utilize the stray capacitance generated between a pair of wires 12 that are placed close together by folding back a portion of the wire 12. In other words, this pair of wires 13 forms a capacitor in which the capacitance is adjusted according to the length while keeping the distance between adjacent wires 12 constant.

[0170] The capacitance section 23 is located in the upper region (hereinafter referred to as the "upper region") E1 on one side of the central part in the short-side direction (vertical direction) within the plane of the substrate 10. On the other hand, the lower region (hereinafter referred to as the "lower region") E2 on the other side of the central part in the short-side direction (vertical direction) within the plane of the substrate 10 is a blank area where the IC card number, expiration date, name, etc., are printed by embossing, and therefore the placement of the conductive wires 12 should be avoided.

[0171] The capacitance section 23 includes a first wiring section 23c in which a portion of the wire pair 13 is sequentially folded back in the opposite direction, a second wiring section 23d which is continuous with the first wiring section 23c and in which a portion of the wire pair 13 is sequentially folded back in the same direction, and a third wiring section 23e which is continuous with the first wiring section 23c and extends the wire pair 13 to both ends 12a of the wire 12.

[0172] Furthermore, the capacitance section 23 is arranged such that a portion of the first wiring section 23c and the second wiring section 23d overlap within the plane of the substrate 10. Specifically, a portion of the wire pair 13 forming the first wiring section 23c and a portion of the wire pair 13 forming the second wiring section 23d form an overlapping section 27 where they partially coincide.

[0173] Specifically, in this embodiment, the first wiring section 23c is located in the upper region E1 within the plane of the substrate 10 and is formed by sequentially folding back (U-turning) a portion of the wire pair 13 in the opposite direction at least twice. As a result, the first wiring section 23c is formed by folding back a portion of the wire pair 13 in a meandering manner. In the example shown in Figure 21, the first wiring section 23c extends from the starting end D towards the ending end A. The wire pair 13 extends to the left from the starting end D, makes two 90° turns to the right to make a U-turn, and then makes two 90° turns to the left to make another U-turn. Thus, the wires extending from the starting end D towards the ending end A include U-turns drawn by bending to the left and U-turns drawn by bending to the right. The fact that the direction of bending in the 90° bends included in the U-turns differs between the right and left directions is referred to as "sequentially folding back in the opposite direction." With this wiring, the first wiring section 23c has a wiring pattern formed in a zigzag shape that progresses in the vertical direction of the antenna sheet 1. In the example in Figure 21, the first wiring section 23c includes U-turns, including one drawn by bending to the left and another drawn by bending to the right, but the number of U-turns may be two or more. The direction in which the zigzag shape of the first wiring section 23c progresses is not limited to the vertical direction of the antenna sheet 1, but may be in any direction.

[0174] The second wiring section 23d is located in the upper region E1 within the plane of the substrate 10 and is formed by folding a portion of the wire pair 13 back in the same direction at least twice in sequence. As a result, the second wiring section 23d is formed by folding a portion of the wire pair 13 back in a circular fashion. In the example shown in Figure 21, the second wiring section 23d extends from the starting point B towards the end point C. The wire pair 13 extends to the right from the starting point B, bends 90° to the left four times, and arrives at the end point C. Due to the U-turns drawn by bending 90° in the same direction to the left and right toward the center of the spiral pattern, the second wiring section 23d is formed as a spiral wiring pattern with its end located inside the spiral shape of the wiring pattern. In the example shown in Figure 21, the second wiring section 23d is provided with a spiral pattern drawn by bending 90° only to the left from a predetermined starting point, but it may also be a spiral pattern drawn by bending 90° only to the right from a predetermined starting point. Furthermore, the number of U-turns may be two or more.

[0175] The overlapping portion 27 is provided between the end A of the wire pair 13 forming the first wiring portion 23c and the starting end B of the wire pair 13 forming the second wiring portion 23d. The end of the wire pair 13 forming the second wiring portion 23d is located inside this overlapping portion 27.

[0176] Furthermore, the end C of the wire pair 13 forming the second wiring section 23d is formed by the folded portion 14 of the wire 12, which is the end of the wire pair 13 forming the second wiring section 23d.

[0177] In this embodiment, a capacitance section 23 is formed by four closely spaced conductors 12 by folding back two pairs of conductors 13 at their respective folded-back portions 14. This makes it possible to substantially increase the number of conductors 12 forming the pairs of conductors 13 in the capacitance section 23 by increasing the number of folded-back portions 14. In other words, the capacitance in this capacitance section 23 can be adjusted according to the number of conductors 12 forming the pairs of conductors 13.

[0178] The third wiring section 23e is located in the upper region E1 within the plane of the substrate 10 and is formed by extending the wire pair 13 from the starting end D of the wire pair 13 that forms the first wiring section 23c toward both ends 12a of the wire 12. The ends 12a of the wire 12 are ultimately bent in opposite directions.

[0179] In the antenna sheet 1 of this embodiment, the length of the wire pair 13 forming the third wiring section 23e is adjusted to match the resonant frequency in communication using the booster antenna 21. Specifically, a portion of the wire pair 13 forming the third wiring section 23e is cut from both ends 12a of the wire 12, and the capacitance of the capacitance section 23 is adjusted.

[0180] As a result, in the antenna sheet 1 of this embodiment, variations in capacitance caused by positional accuracy during wiring of the conductor 12 can be kept to a minimum. Consequently, it is possible to optimize the capacitance of the capacitance section 23 to match the resonant frequency in communication using the booster antenna 21.

[0181] In the RF tag 100 equipped with the antenna sheet 1 having the above configuration, as shown in Figure 2, a high-frequency magnetic field is induced in the transmitting / receiving coil 201 by the high-frequency signal generated in the transmitting / receiving circuit 202 of the reader / writer 200. This high-frequency magnetic field is radiated into space as magnetic energy.

[0182] At this time, the RF tag 100 is positioned in a high-frequency magnetic field, causing electromagnetic coupling between the transmitting / receiving coil 201 and the booster antenna 21, and current flows through the booster antenna 21. In addition, the signal received by the booster antenna 21 is transmitted to the coupling coil 22, and current flows through the coupling coil 22 as well. As a result, the signal received by the booster antenna 21 is transmitted to the IC chip 50 by electromagnetic coupling between the coupling coil 22 and the antenna coil 51.

[0183] On the other hand, when the RF tag 100 is used to supply power and communicate with a contact-type external device, such as an automated teller machine, the contact terminals of the device are brought into contact with the contact terminals 3 of the RF tag 100. This enables power supply and communication between the contact-type external device and the RF tag 100.

[0184] In the antenna sheet 1 of this embodiment, the first wiring portion 23c and the second wiring portion 23d that form the capacitance portion 23 are arranged to overlap within the plane of the substrate 10 described above.

[0185] Specifically, a portion of the wire pair 13 forming the first wiring section 23c and a portion of the wire pair 13 forming the second wiring section 23d partially coincide to form an overlapping section 27. Furthermore, the ends of the wire pair 13 forming the second wiring section 23d are located inside this overlapping section 27.

[0186] In other words, the wire pairs 13 forming the capacitance section 23 are arranged irregularly overall, unlike arrangements with regularity such as meander or spiral shapes. As a result, in the antenna sheet 1 of this embodiment, it is possible to suppress the superposition of in-phase noise on the wire pairs 13 forming the capacitance section 23.

[0187] Therefore, in the RF tag 100 of this embodiment, by providing the antenna sheet 1 of this embodiment described above, it is possible to reduce the risk of in-phase noise superimposed on the wire pair 13 forming the capacitance section 23, which could cause malfunction or failure of the IC chip 50.

[0188] The sixth embodiment is not necessarily limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0189] The following are some examples of variations, but these are not exhaustive, and other modifications are possible. Furthermore, these modifications can be freely combined in any way, as long as they do not create contradictions.

[0190] For example, the antenna sheet 1 of the sixth embodiment may have a configuration in which the arrangement of the wire pairs 13 that form the capacitance portion 23 is changed, as shown in Figure 22, as a first modification.

[0191] Specifically, in the capacitance section 23 shown in Figure 22, the spacing between adjacent pairs of conductors 13 that form the first wiring section 23c and the second wiring section 23d is narrowed. That is, by arranging the two sets of conductor pairs 13 that form the first wiring section 23c and the second wiring section 23d in close proximity to each other, the first wiring section 23c and the second wiring section 23d are formed by eight conductors 12 that are arranged in close proximity to each other.

[0192] As a result, in the antenna sheet 1 of this embodiment, it is possible to adjust the capacitance of the capacitance section 23.

[0193] Furthermore, as a second modification, the antenna sheet 1 of the sixth embodiment may have a configuration in which the arrangement of the wire pairs 13 that form the capacitance portion 23 is changed, as shown in Figure 23.

[0194] Specifically, in the capacitance section 23 shown in Figure 23, a portion of the wire pair 13 forming the third wiring section 23e is arranged along the outer periphery of the lower region E2. That is, a portion of the wire pair 13 forming this capacitance section 23 is extended to a position that avoids the embossing of the lower region E2. Thus, when the substrate 10 has a shape corresponding to an IC card, it is preferable that at least a portion of the third wiring section 23e be arranged in the lower region E2 of the IC card.

[0195] As a result, the antenna sheet 1 of this embodiment can increase capacitance and enhance design flexibility, such as design flexibility.

[0196] <Seventh Embodiment> The seventh embodiment of the present invention will now be described in detail with reference to the drawings. In the following description, components that are common to those already described will be denoted by the same reference numerals, and redundant descriptions will be omitted.

[0197] Figure 24 shows a schematic plan view of the antenna sheet 1 according to this embodiment, and Figures 25 and 26 show the arrangement of the first strand 30 and the second strand 40 related to the antenna sheet 1, respectively. The antenna section 20 related to the antenna sheet 1 is the same as in the first embodiment in that it has three regions: a booster antenna 21, a coupling coil 22, and a resonant capacitance forming section C, but differs in that the interleaved capacitance section 24 is provided on the outer circumference of the booster antenna 21. The shape of the capacitance section 23 in this embodiment is formed by combining the features of the capacitance section 23 described in the first to sixth embodiments, so a detailed explanation is omitted.

[0198] In this embodiment, the loop-shaped booster antenna 21 at the periphery of the antenna sheet 1 is provided with a single-strand antenna portion 21a formed of a first strand 30 on the inside, and an interleaved capacitance portion 24 formed of the first strand 30 and a second strand 40 on the outside. Within the booster antenna 21, a gap S is provided between the single-strand antenna portion 21a and the interleaved capacitance portion 24. The width of the gap S is greater than the pitch between strands in the closely spaced portion described in the first embodiment. The first end portion 40a of the second strand 40 is provided in the gap S.

[0199] As shown in the portion labeled X1 in Figure 27, the first strand 30o1, which extends from the first end 30a of the first strand 30 and is the first turn from the outside, is positioned between the second strand 40o1, which is the first turn from the outside, and the second strand 40o2, which is the second turn from the outside. As a result, in the booster antenna 21, with some exceptions, the outermost first strand 30o1 is sandwiched between the second strand 40 (second strand 40o1 and second strand 40o2). As shown in the portion labeled X2 in Figure 27, the second strand 40i1, which extends from the first end 40a of the second strand 40 and is the first turn from the inside, is sandwiched between the first strand 30 (first strand 30inner and first strand 30outer). As a result, in the booster antenna 21, the innermost second strand 40i1 is sandwiched between the first strand 30.

[0200] ・Manufacturing Method of Antenna Sheet 1 The manufacturing method of the antenna sheet 1 of this embodiment will be described below. Note that the following manufacturing method is merely an example, and other manufacturing methods may be adopted. First, a wiring pattern is formed from the first end 30a, which is the end of the first strand 30, to the second end 30b using a conductive strand (conductor 12) covered with an insulator (first strand pattern formation step). The method for forming the wiring pattern is the same as the method described in the first embodiment. In this embodiment, a wiring pattern that will become a booster antenna 21 is formed by creating six loops in a counterclockwise direction around the periphery of the substrate 10, starting from the first end 30a provided at the upper left corner of the four corners of the substrate 10. At this time, the multiple loops are made in a spiral shape from the outside to the inside. Since the first end 30a is provided at the upper left corner of the periphery of the antenna sheet 1, the loop shape is bent inward to form a recess R. Then, inside the recess R, a gap S is provided between the second and third turns from the outer circumference of the first strand 30.

[0201] After the first strand pattern formation step, the strands are wired from the second end 30b to the first end 40a of the second strand 40 without being bonded to the substrate 10 (jumper section formation step). In this embodiment, the second end 30b of the first strand 30 is provided inside the blank section S, and the first end 40a of the second strand 40 is provided in the blank section. Therefore, the jumper section Jm intersects with the single strand antenna section 21a. This satisfies condition (2) for a trace of a single continuous line as described in the first embodiment.

[0202] Next, a wiring pattern is formed from the first end 40a to the second end 40b, which will become the second strand 40 (second strand pattern formation step). The method for forming the wiring pattern is the same as the method described in the first strand pattern formation step. In this embodiment, a wiring pattern that will become the interleaved capacitance portion 24 of the booster antenna 21 is formed by creating approximately three loops clockwise around the periphery of the substrate 10, starting from the first end 40a provided in the blank area S. At this time, the multiple loops are made in a spiral shape from the inside to the outside. In the outermost loop of the second strand 40, the second strand 40 and the booster antenna 21 intersect in three dimensions below the blank area S (see crossover area CO in Figure 27). Thus, the condition (1) for a trace of a single continuous line, as described in the first embodiment, is satisfied.

[0203] Then, both ends of the jumper section Jm are cut and the individual wires of the jumper section Jm are removed (jumper section removal process).

[0204] In this embodiment, the first strand pattern formation step, which forms the first strand 30 with a large number of loops in the booster antenna 21, is performed first. Then, the jumper section Jm is formed in the jumper section formation step, and the strands are guided into the blank section S surrounded by the first strand 30 formed in the first strand pattern formation step, and the second strand pattern formation step is performed from the blank section S. By removing the jumper section Jm, the strands wired in one stroke on the substrate 10 become the first strand 30 and second strand 40 which are physically disconnected. This makes it possible to manufacture an antenna sheet 1 that allows for more efficient single-stroke wiring patterns, provides a certain degree of rigidity, and prevents fluctuations in inter-strand capacitance. The jumper section Jm may also intersect with the single-strand antenna section 21a. This improves the freedom of wiring design and allows for more favorable variations in wiring design.

[0205] In this embodiment, the antenna sheet 1 has a gap S between the single-strand antenna section 21a and the interleaved capacitance section 24, where the first end 40a of the second strand 40 is positioned. The loop of the conductor 12 of the booster antenna 21 formed by the second strand 40, extending from the first end 40a of the second strand 40, is sandwiched between the first strand 30 (first strand 30 inner and first strand 30 outer) in the width direction of the conductor 12. In addition, the first end 30a of the first strand 30 is provided on the outer circumference of the booster antenna 21, and the loop of the conductor 12 of the booster antenna 21 formed by the first strand 30, extending from the first end 30a of the first strand 30, is sandwiched between the second strand 40 (second strand 40o1 and second strand 40o2) in the width direction of the conductor 12. As a result, the booster antenna 21 and interleaved capacitance section 24 are formed on the periphery of the substrate 10 using conductive wires, which more effectively prevents wire breakage and fluctuations in inter-wire capacitance due to bending of the antenna sheet 1. Furthermore, the interleaved capacitance section 24 is provided on the outer circumference of the booster antenna 21, allowing more current to flow through the outer circumference, and thus increasing the capacitance.

[0206] <Eighth Embodiment> The eighth embodiment of the present invention will now be described in detail with reference to the drawings. In the following description, components that are common to those already described will be denoted by the same reference numerals, and redundant descriptions will be omitted.

[0207] In the antenna sheet, for example, as shown in Figure 2A, a closed loop is formed by connecting a booster antenna, a coupling coil, and a resonant capacitance forming section in series. In this case, the amount of current flowing through the booster antenna and the coupling coil is equal, which can make fine-tuning of antenna characteristics, such as adjusting the degree of coupling with the card module, difficult. Therefore, in this embodiment, the amount of current flowing through the booster antenna and the coupling coil is adjusted by the coupling capacitance of the resonant capacitance forming section provided by the second strand in the LC resonant circuit formed by the first strand. This allows the amount of current flowing through the booster antenna and the coupling coil to be adjusted separately.

[0208] As an eighth embodiment, for example, the antenna sheet 1 shown in Figures 28A to 30B will be described. Figure 28A is a plan view of the antenna sheet 1. Figures 29A and 30A show the arrangement of the first strand 30 and the second strand 40, respectively. Figures 28B, 29B, and 30B are equivalent circuit diagrams of the antenna section 20 shown in Figures 28A, 29A, and 30A, respectively.

[0209] As shown in Figure 28A, the antenna section 20 according to this embodiment is formed of two strands (two conductors 12) that are not physically connected. As shown in Figure 29A, the first strand 30 forms the booster antenna 21 and the capacitance section 23. In the example of Figure 29A, the ends 30a and 30b of the first strand 30 are provided at the ends of the capacitance section 23 that are furthest from the booster antenna 21 along the wiring pattern formed by the conductors 12.

[0210] As shown in Figure 30A, the second strand 40 forms the coupling coil 22, the first extension wire 28a-1 extending from the inner circumference of the coupling coil 22, and the second extension wire 28b-1 extending from the outer circumference of the coupling coil 22. As shown in Figure 28A, the first extension wire 28a-1 extends between the first strand 30i1, which is the first turn from the inner circumference of the booster antenna 21, and the first strand 30i2, which is the second turn from the inner circumference. The second extension wire 28b-1 extends along one side of the pair of first strands 30 that form the capacitance section 23.

[0211] As shown in Figures 28A and 28B, the first extension wiring capacitance section 28a is formed by the first extension wiring 28a-1 and a portion of the first strand 30 of the booster antenna 21. The second extension wiring capacitance section 28b is formed by the second extension wiring 28b-1 and a portion of the first strand 30 of the capacitance section 23. As a result, a circuit in which the first extension wiring capacitance section 28a, the coupling coil 22, and the second extension wiring capacitance section 28b are arranged in series is provided in parallel with the capacitance section 23. In the circuit of Figure 28B, the current flowing through the closed loop shown in Figure 29B is branched and directed towards the coupling coil 22. In other words, the amount of current flowing through the coupling coil 22 can be adjusted by adjusting the capacitance of the first extension wiring capacitance section 28a and the second extension wiring capacitance section 28b provided at both ends of the coupling coil 22. As explained in the first embodiment, the amount of current flowing through the booster antenna 21 can be adjusted by adjusting the capacitance of the capacitance section 23.

[0212] In the antenna sheet 1 of this embodiment, the antenna section 20 includes a coil-shaped booster antenna 21, a coupling coil 22 formed of a second strand 40, and a resonant capacitance forming section C that adjusts the resonant frequency in communication using the booster antenna 21 and the coupling coil 22. The resonant capacitance forming section C includes a first extension wiring capacitance section 28a formed by a first strand 30 and a first extension wiring 28a-1 of the second strand 40 extending from the coupling coil 22, and a second extension wiring capacitance section 28b formed by the first strand 30 and a second extension wiring 28b-1 of the second strand 40 extending from the coupling coil 22. This makes it possible to adjust the amount of current flowing through the booster antenna 21 and the coupling coil 22, respectively. Therefore, it becomes possible to finely adjust the performance of the booster antenna 21.

[0213] Although each embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments, and modifications and combinations of the configuration that do not depart from the spirit of the present invention are also included. Some modifications are given below as examples, but these are not all, and other modifications are also possible. Furthermore, two or more of these modifications can be freely combined as long as they do not create contradictions.

[0214] For example, the RF tag to which the present invention is applied is not necessarily limited to the IC card described above, and the antenna sheet to which the present invention is applied can be applied to various types of RF tags.

[0215] 1...Antenna sheet 2...Card body 3...Contact terminals 10...Circuit board 12...Conductor wire 13...Conductor pair 14...Folded section 20...Antenna section 21, 21A...Booster antenna 21a...Single strand antenna section 22...Coupling coil 23, 123...Capacitance section (capacitor) 23a...Main capacitance section 23b...Extension capacitance section 23b1...Extension wiring section 23c...First wiring section 23d...Second wiring section 23e...Third wiring section 27...Overlap section 28a...First extension wiring capacitance section 28a-1...First extension wiring 28b...Second extension wiring capacitance section 28b-1...Second extension wiring 30...First strand 30a...First end 30b...Second end 32...First region 40...Second strand 40a...First end 40b...Second end 43...Fifth region (Region 1) 50...IC chip 51...Antenna coil 123A, 232...Overpass 100...RF tag (IC card) 200...Reader / writer 201...Transmit / receive coil 202...Transmit / receive circuit C...Resonant capacitance forming section CO...Crossover section E1...Upper region E2...Lower region P...Interwire pattern Jm...Jumper section S...Blank section

Claims

1. An antenna sheet having an antenna portion formed of conductive wires on a dielectric substrate, wherein the antenna portion is a closed circuit formed using at least two wires, including a first wire and a second wire that are physically disconnected, and a portion of the first wire and a portion of the second wire are placed in close proximity to each other, and the first wire and the second wire are electrically connected by the stray capacitance generated between them.

2. The antenna sheet according to claim 1, wherein the antenna section comprises a coil-shaped booster antenna and a resonant capacitance forming section for adjusting the resonant frequency in communication using the booster antenna, and the first strand and the second strand are connected in the resonant capacitance forming section by the stray capacitance.

3. The antenna sheet according to claim 2, wherein the first strand has a coil-shaped first region that constitutes a part of the booster antenna, the second strand has a coil-shaped region 1 that constitutes a part of the booster antenna, and in at least a part of the booster antenna, the first region and region 1 are arranged alternately in the width direction of the strand in an interleaved wiring configuration, and the resonant capacitance forming portion includes the interleaved wiring interleaved capacitance portion.

4. The antenna sheet according to claim 2, wherein the resonant capacitance forming portion includes a capacitance portion formed in a meander shape or a coil shape.

5. The antenna sheet according to claim 4, wherein the first strand and the second strand intersect in a three-dimensional manner in the capacitance section.

6. The antenna sheet according to claim 4 or 5, wherein the antenna portion further comprises a coupling coil connected to the booster antenna and having a smaller loop diameter than the booster antenna, and the capacitance portion and the coupling coil are located within the loop of the booster antenna.

7. The antenna sheet according to claim 1, wherein the antenna portion comprises: a spiral booster antenna; a spiral coupling coil connected to the booster antenna and smaller than the booster antenna; a capacitance portion formed by capacitive coupling of the first and second strands by being placed in close proximity; and a crossover portion where the conductors intersect in three dimensions, wherein one of the coupling coil and the capacitance portion is located outside the spiral of the booster antenna and the other is located inside the spiral of the booster antenna, and the crossover portion is provided at only one location so as to intersect in three dimensions with the coupling coil and the booster antenna.

8. The antenna sheet according to claim 1 or 2, wherein at least one of the first strand and the second strand is insulated.

9. The antenna sheet according to claim 7, wherein the crossover portion is located between the coupling coil and the capacitance portion.

10. The antenna sheet according to claim 1, comprising: a booster antenna in which a portion of the conductor is arranged spirally along the periphery of the substrate; and a capacitance portion located inside the booster antenna and formed by a pair of conductors including the conductor, which are arranged in close proximity to each other, wherein the capacitance portion comprises: a main capacitance portion formed by the pair of conductors in which a portion of the conductor is folded back and arranged in close proximity to each other; and an extended capacitance portion formed by extending a portion of the pair of conductors in a continuous manner with respect to the main capacitance portion, wherein the extended capacitance portion is arranged at a distance from the periphery of the main capacitance portion.

11. The antenna sheet according to claim 10, wherein the extended capacitance portion is formed by extending the pair of conductors to both ends of the conductors.

12. The antenna sheet according to claim 11, wherein the length of the pair of conductors forming the extended capacitance portion is adjusted to match the resonant frequency in communication using the booster antenna.

13. The antenna sheet according to claim 10, wherein the extended capacitance section has an extended wiring section in which a part of the pair of conductors is arranged in a linear or spiral shape, and the ends of the pair of conductors forming the extended wiring section are formed by the folded portion of the conductors.

14. The antenna sheet according to claim 10, wherein the main capacitance section has a main wiring section in which a part of the pair of conductors is arranged in a spiral shape, and the ends of the pair of conductors forming the main wiring section are formed by the folded portion of the conductors.

15. The antenna sheet according to claim 10, wherein at least a portion of the main capacitance section and the extended capacitance section is arranged in the lower 1 / 3 region of the antenna sheet with a length of 1 / 5 or more of the longitudinal direction of the antenna sheet.

16. The antenna sheet according to claim 1, comprising: a booster antenna in which a portion of the conductor is arranged spirally along the periphery of the substrate; and a capacitance portion located inside the booster antenna and formed by a pair of conductors in close proximity to each other, wherein the capacitance portion has a first wiring portion in which a portion of the pair of conductors is arranged to be folded sequentially in opposite directions, and a second wiring portion in which a portion of the pair of conductors is arranged to be folded sequentially in the same direction, and the first wiring portion and the second wiring portion are arranged to overlap in the plane of the substrate.

17. The antenna sheet according to claim 16, wherein a portion of the pair of conductors forming the first wiring section and a portion of the pair of conductors forming the second wiring section form a partially overlapping portion.

18. The antenna sheet according to claim 17, wherein the ends of the pair of conductors forming the second wiring portion are located inside the overlap portion.

19. The antenna sheet according to claim 18, wherein the ends of the pair of conductors forming the second wiring section are formed by the folded portion of the conductors.

20. The antenna sheet according to claim 16, wherein the capacitance section has a third wiring section that extends the pair of conductors to both ends of the conductors, continuous with the first wiring section.

21. The antenna sheet according to claim 10 or 20, wherein, when the substrate has a shape corresponding to an IC card, at least a portion of the extended capacitance portion or at least a portion of the third wiring portion is arranged in the area below the central portion of the IC card.

22. The antenna sheet according to claim 2, wherein the number of loops of the first strand in the booster antenna is different from the number of loops of the second strand, and the booster antenna comprises: a single strand antenna section in which only one of the first strand and the second strand is wired in a coil shape, and an interleaved capacitance section in which the first strand and the second strand are interleaved and alternately arranged in the width direction of the strands.

23. The antenna sheet according to claim 22, wherein a gap is provided between the single-strand antenna section and the interleaved capacitance section, the first end of the second strand being positioned therein, and the loop of the conductor of the booster antenna formed by the second strand, extending from the first end of the second strand, is sandwiched between the first strand in the width direction of the conductor.

24. The antenna sheet according to claim 22 or 23, wherein the first end of the first strand is provided on the outer circumference of the booster antenna, and the loop of the conductor of the booster antenna formed by the first strand, extending from the first end of the first strand, is sandwiched between the second strand in the width direction of the conductor.

25. The antenna sheet according to claim 1, wherein the antenna section comprises a coil-shaped booster antenna, a coupling coil formed from the second strand, and a resonant capacitance forming section for adjusting the resonant frequency in communication using the booster antenna and the coupling coil, and the resonant capacitance forming section includes a first extension wiring capacitance section formed by the first strand and a first extension wiring of the second strand extending from the coupling coil, and a second extension wiring capacitance section formed by the first strand and a second extension wiring of the second strand extending from the coupling coil.

26. An RF tag comprising an antenna sheet according to claim 1 or 2, and an IC chip connected to the antenna sheet.

27. A method for manufacturing an antenna sheet, comprising: a first wire pattern forming step of forming a wiring pattern on a dielectric substrate using a conductor from a first end to a second end which will be the end of a first wire; an inter-wire pattern forming step of forming an inter-wire pattern on the substrate using the conductor from the second end to the first end which will be the end of a second wire; a second wire pattern forming step of forming a wiring pattern on the substrate using the conductor from the first end to a second end which will be a second wire; and an inter-wire pattern processing step of removing or cutting the conductor from the inter-wire pattern, wherein an antenna section is formed which is a closed circuit using the first wire and the second wire that are physically disconnected, and a part of the first wire and a part of the second wire are placed in close proximity to each other, and the first wire and the second wire are electrically connected by the stray capacitance that occurs between them.

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