JP4847849B2 - RFID tag - Google Patents

Description

  The present invention relates to an RFID (Radio Frequency Identification) tag that transmits information such as ID (Identification) recorded on an IC chip by RF (Radio Frequency: radio frequency), and more particularly to an RFID (Radio Frequency Identification) tag attached to a metal surface. The present invention relates to a flexible RFID tag that secures a desired communication distance.

A general-purpose RFID tag has a thin and flexible structure in which a small antenna on which an IC chip is mounted is laminated with a skin film. Therefore, since such a flexible RFID tag can be easily attached to parts of various shapes, the RFID tag is recorded on the IC chip by holding the RFID tag within, for example, 40 mm by a reader / writer. Component information can be read without contact. For example, at the production site or the like, if the attribute of each part is recorded on the RFID tag attached to the form corresponding to the assembly part, the manufacturing history of the product can be managed (for example, Patent Document 1). reference).
JP-A-2005-149004 (paragraphs 0011 to 0013, FIGS. 1 and 2)

  However, in production sites, there is also a demand for attaching a flexible RFID tag directly to an assembly part rather than attaching it to a form. However, parts assembled at production sites include non-metallic parts and metallic parts. When a flexible RFID tag as described above is directly attached to a metal part, the radio wave radiated from the reader / writer to the small antenna in the RFID tag is almost absorbed by the metal part, and the RFID tag Radio waves radiated to the outside from the small antenna will be significantly reduced. Accordingly, the electric field strength of the RFID tag is significantly weakened to reduce the communication distance. Therefore, even if the reader / writer is brought into contact with the RFID tag, the information on the IC chip cannot be read.

  There is also known an RFID tag in which a metal foil of approximately the same size is mounted on the surface of the RFID tag, and the metal foil is configured as an auxiliary antenna. However, an RFID tag provided with such an auxiliary antenna is not a metal. When affixed to a component, the communication distance between the RFID tag and the reader / writer is remarkably increased to, for example, about 140 mm by the radio wave amplification effect of the auxiliary antenna. However, when an RFID tag having an auxiliary antenna on its surface is attached to a metal part, the small antenna in the RFID tag is covered and shielded by the metal surface of the metal part and the auxiliary antenna. Most of the radio waves do not reach the small antenna in the RFID tag. As a result, since almost no radio waves are radiated from the small antenna to the auxiliary antenna, the radio amplification function of the auxiliary antenna is hardly performed and the communication distance of the RFID tag is remarkably reduced. Similarly to the above, even if the reader / writer is brought into contact with the auxiliary antenna, the information on the IC chip cannot be read.

  Note that although there are parts with curved surfaces in the assembled parts, if the flexibility of the RFID tag is used, the parts can be easily attached to curved parts. However, even when a flexible RFID tag is directly attached to a metal part having a curved surface, the communication distance of the RFID tag is significantly reduced regardless of whether there is an auxiliary antenna.

  The present invention has been made in view of the above-described problems, and an RFID tag that can secure a desired communication distance even when a surface is directly attached to a flat or curved metal part. The purpose is to provide.

  In order to achieve the above object, an RFID tag of the present invention includes an inlet on which a main antenna (first antenna) on which an IC chip is mounted is laminated with a film and mounted on a planar metal surface, and the inlet An auxiliary antenna (second antenna) that is disposed to face each other and is curved in a direction away from the surface of the inlet as it goes to at least one tip in the longitudinal direction. It is constituted by.

  In a preferred embodiment, the auxiliary antenna is formed in a curved shape in a direction away from the surface of the inlet as it goes to the tip portions on both sides in the longitudinal direction. As will be described later, by changing the curved shape of the auxiliary antenna, the communication distance between the reader / writer can be varied. Note that a dielectric sheet having a desired dielectric constant and approximately the same size as the inlet may be interposed between the inlet and the auxiliary antenna. By interposing such a dielectric sheet, the communication distance can be further extended by the wavelength shortening effect.

  In addition, the RFID tag of the present invention is arranged in a substantially tangential direction at the apex of the curved portion of the inlet and the inlet mounted on the curved metal member with the main antenna on which the IC chip is mounted laminated with a film. It can also be constituted by an auxiliary antenna that amplifies the radio wave radiated from the main antenna.

  That is, the auxiliary antenna is not curved in the longitudinal direction with respect to the inlet arranged on the planar metal plate, but the inlet is arranged on the surface of the curved metal member with respect to the planar arranged auxiliary antenna. Even if it arrange | positions, a desired clearance gap can be formed in the front-end | tip part of an inlet. Therefore, since the front end portion of the inlet can receive the radio wave from the reader / writer and radiate it to the auxiliary antenna, the communication distance of the RFID tag can be extended by the radio wave amplification effect of the auxiliary antenna.

  According to the RFID tag of the present invention, a desired communication distance can be secured even if the surface is directly attached to a flat or curved metal part.

<< Summary of Invention >>
Hereinafter, a communication distance variable type RFID tag according to the best mode for carrying out the present invention (hereinafter referred to as “embodiment”) will be described with reference to the drawings with a suitable example, but easy to understand. First, an outline of the RFID tag in the present invention will be described.

  In the RFID tag of the present invention, a thin and flexible inlet in which a main antenna (first antenna) on which an IC chip is mounted is laminated with a skin film is attached to a flat metal plate, and the surface of the inlet ( That is, an auxiliary antenna (second antenna) having the same size as the inlet is mounted on the radio wave radiation surface. At this time, the auxiliary antenna is brought into close contact with the surface of the inlet in the vicinity of the center of the inlet, and is curved in a direction away from the surface of the inlet as it goes to both ends in the longitudinal direction of the inlet.

  By forming the auxiliary antenna in a curved shape in this way, a desired gap is formed at both ends of the inlet having a high electric field strength so that the inlet is not shielded by the metal plate and the auxiliary antenna. The emitted radio wave reaches both ends of the inlet. Therefore, radio waves with strong electric field intensity radiated from both end portions of the inlet reach the auxiliary antenna. Accordingly, since the auxiliary antenna exhibits a radio wave amplification action, the electric field intensity of the radio wave radiated from the auxiliary antenna is further increased, and as a result, the communication distance between the RFID tag and the reader / writer is extended.

  When the inlet is attached to a metal pipe having a curved surface, an auxiliary antenna is mounted in a substantially tangential direction at the apex of the inlet. This forms a desired gap so that the inlet is not shielded by the metal pipe and the auxiliary antenna at both ends of the inlet having high electric field strength. Therefore, since the radio waves radiated from the reader / writer reach both end portions of the inlet, the radio waves radiated from both end portions of the inlet reach the auxiliary antenna, and the RFID tag and the reader / writer are The communication distance between can be extended.

  Hereinafter, some embodiments of the RFID tag according to the present invention will be described in detail with reference to the drawings.

<< First Embodiment >>
First, in order to facilitate understanding of the RFID tag in the present invention, the configuration of an inlet for realizing the RFID tag of the present invention will be described. In addition, although the inlet said here is a thing of the same structure as the flexible RFID tag described by the above-mentioned prior art, in this invention, the metal plate (metal surface) and the inlet which mount an inlet and its inlet Since the RFID tag that can secure a desired communication distance can be realized by the auxiliary antenna (second antenna) arranged on the upper surface of the substrate, the flexible RFID tag described in the prior art is called an inlet. I will decide.

  FIG. 1 is an internal structure diagram of an inlet used in an embodiment of an RFID tag according to the present invention, (a) is a perspective view showing a state in which the inlet is disassembled, and (b) is a top view of the inlet. FIG. 2 is a completed view of the inlet showing a state in which the surface is laminated with a skin film in the AA sectional view of FIG.

  The internal structure of the inlet 1 shown in FIG. 1 is that a main antenna 3 made of copper foil with tin plating or the like is formed on the upper surface of a substrate film 2 made of a resin material such as polyimide resin and having a thickness of about 0.1 mm. ing. Since the main antenna 3 has a thickness of about several tens of microns, it is possible to form the main antenna 3 by performing metal vapor deposition on the upper surface of the substrate film 2. A slit 3a for impedance matching is formed near the center of the main antenna 3, and the IC chip 4 is mounted so as to straddle the slit 3a.

  That is, a hook-like (L-shaped) slit 3a for impedance matching between the IC chip 4 and the main antenna 3 is formed in the feeding portion at the center of the main antenna 3, and the key is formed by the slit 3a. A portion surrounded by a shape is formed as a stub. The IC chip 4 is formed with a plurality of electrodes at intervals so as to straddle the slit 3a. When the electrodes of the IC chip 4 are connected so as to straddle the slit 3a, the stub surrounded by the slit 3a in a hook shape is connected in series between the main antenna 3 and the IC chip 4. Between the main antenna 3 and the IC chip 4, a stub acts as a serial inductive component. Therefore, the capacitive component in the IC chip 4 is canceled by the inductive component, and the impedances of the main antenna 3 and the IC chip 4 are matched.

  When the main antenna 3 is formed of a dipole antenna by forming the impedance matching slit 3a in the main antenna 3 as described above, the length of the main antenna 3 when the wavelength of the radio frequency is λ is Even if the target length is about λ / 4, a communication distance of several centimeters or more can be secured. For example, when a radio wave having a frequency of 2.45 GHz is used, a communication distance of about 40 mm can be realized even if the length of the main antenna 3 is about 30 mm. The width of the main antenna 3 is not particularly limited, but is about 2 mm, for example.

  The elements laminated with the substrate film 2, the main antenna 3, and the IC chip 4 as shown in FIG. 1 are laminated with the outer film 5 as shown in FIG. Therefore, as shown in FIG. 2, the size of the inlet 1 in which the substrate film 2, the main antenna 3, and the IC chip 4 are laminated with the outer skin film 5 is, for example, 3 mm in width, 35 mm in length, and 0 in thickness. It is about 6mm.

  When the inlet 1 configured as shown in FIG. 2 is directly mounted on a metal plate, radio waves radiated from the reader / writer (not shown) to the inlet 1 are almost absorbed by the metal plate or diffusely reflected by the metal plate. Therefore, the main antenna 3 in the inlet 1 is not reached. Therefore, almost no radio wave travels from the main antenna 3 of the inlet 1 to the outside. For this reason, the communication distance between the inlet 1 and the reader / writer is almost zero.

  Also, when the inlet 1 is directly mounted on a metal plate and an auxiliary antenna having the same size as that of the inlet is mounted on the surface opposite to the inlet 1, the main antenna 3 inside the inlet 1 is connected to the metal plate. And the auxiliary antenna, the radio wave hardly reaches the inlet 1 from a reader / writer (not shown). Accordingly, since almost no radio wave travels from the main antenna 3 of the inlet 1 to the outside, the communication distance between the inlet 1 and the reader / writer is almost zero. Therefore, in the RFID tag according to the first embodiment of the present invention, when the auxiliary antenna is mounted on the upper surface of the inlet 1, the shape of the auxiliary antenna is devised to extend the communication distance of the inlet 1.

  FIG. 3 is a cross-sectional view of the RFID tag according to the first embodiment of the present invention. That is, this figure is a cross-sectional view when the flexible inlet 1 shown in FIG. 2 is attached to the surface of the metal plate 6 and the auxiliary antenna 7 made of a metal foil such as an aluminum foil is mounted on the surface of the inlet 1. Therefore, in FIG. 3, the structure of the substrate film 2, the main antenna 3 on which the IC chip 4 is mounted, and the outer film 5 is an inlet 1 as shown in FIG.

  In FIG. 3, the auxiliary antenna 7 mounted on the surface of the inlet 1 is formed of a metal foil having substantially the same length and width as the main antenna 3. Moreover, the auxiliary antenna 7 is not arranged in parallel with the main antenna 3 but is formed in a curved shape in a direction away from the surface of the main antenna 3 as it goes to both ends in the longitudinal direction of the main antenna 3. . At this time, the gap a generated between the auxiliary antenna 7 and the outer skin film 5 on the upper side of the main antenna 3 may be air having a relative dielectric constant of 1, but the auxiliary antenna 7 is curved. In order to hold it stably, for example, an epoxy resin having a relative dielectric constant of about 2 may be interposed.

  Here, the reason why the auxiliary antenna 7 is curved will be described. Since the main antenna 3 that forms the inlet 1 has a feeding point at the center, the electric field strength is weak at the center of the main antenna 3 because the voltage is low. However, both ends of the main antenna 3 have high electric field strength because of the high voltage. Therefore, if the main antenna 3 is curved at both end portions of the main antenna 3 having high electric field strength so as not to be shielded by the metal plate 6 and the auxiliary antenna 7 (that is, a desired gap between the main antenna 3 and the auxiliary antenna 7). a), radio waves radiated from a reader / writer (not shown) reach both end portions of the main antenna 3. Therefore, radio waves with strong electric field intensity radiated from both ends of the main antenna 3 reach the auxiliary antenna 7. Accordingly, since the auxiliary antenna 7 exhibits a radio wave amplification function, the electric field intensity of the radio wave radiated from the auxiliary antenna 7 is further increased. As a result, the communication distance between the RFID tag 10 and the reader / writer is extended.

  That is, in the vicinity of the central portion of the main antenna 3, the auxiliary antenna 7 is disposed in close contact with the main antenna 3 and the skin film 5, so that the vicinity of the central portion of the main antenna 3 is shielded. However, since the electric field strength is weak in the vicinity of the center of the main antenna 3, even if the radio wave radiated from that portion is shielded and does not reach the auxiliary antenna 7, it hardly affects the radio wave amplification effect of the auxiliary antenna 7. .

  However, in the vicinity of both ends of the main antenna 3 having a strong electric field strength, the main antenna 3 and the auxiliary antenna 7 are relatively separated by a gap a made of a dielectric material such as air or epoxy resin. Strong radio waves radiated from the vicinity of both ends of the radiated light are radiated to the auxiliary antenna 7 without being shielded. Furthermore, the radio wave reflected from the metal plate 6 from the main antenna 3 is also radiated to the auxiliary antenna 7. As a result, the auxiliary antenna 7 has a strong electric field strength by performing a radio wave amplifying action between the radio wave directly radiated from the main antenna 3 and the radio wave reflected from the metal plate 6, so that the communication distance can be extended.

  Furthermore, since the auxiliary antenna 7 is curved, the radio waves radiated from the auxiliary antenna 7 are converged in the direction of the center line of the auxiliary antenna 7, so that the electric field strength is obtained at a predetermined distance. Becomes even stronger. Therefore, if the reader / writer is placed near the position where the radio wave converges, the reader / writer can receive a relatively strong radio wave, so that information on the RFID tag can be read more accurately.

《Experimental Verification》
Next, a description will be given of the results of experiments on how much the communication distance of the RFID tag extends when the auxiliary antenna 7 mounted on the inlet 1 is curved as described above. FIG. 4 is a configuration diagram of Example 1 of communication distance measurement by the RFID tag of the present invention using the curved auxiliary antenna 7. FIG. 5 is a configuration diagram of a second embodiment of communication distance measurement using the RFID tag of the present invention using the curved auxiliary antenna 7. Furthermore, FIG. 6 is a block diagram of Example 3 of communication distance measurement by the RFID tag of the present invention using the curved auxiliary antenna 7.

  As in the configuration of the RFID tag according to the first embodiment shown in FIG. 4, the upper surface of the inlet 1 attached to the surface of the metal plate 6 (that is, the radio wave radiation surface) is curved in the radio wave radiation direction. The auxiliary antenna 7 is mounted. At this time, the auxiliary antenna 7 is curved symmetrically with respect to the center, and the distance between the metal plate 6 and the auxiliary antenna 7 near the tip of the auxiliary antenna 7 is set to about 5 mm. That is, if the thickness of the inlet 1 is about 0.6 mm, the gap between the surface of the inlet 1 and the tip of the auxiliary antenna 7 is about 4.4 mm.

  In this way, by providing a gap between the auxiliary antenna 7 and the inlet 1 at both end portions of the inlet 1, radio waves from a reader / writer (not shown) reach near both end portions of the inlet 1. Therefore, strong radio waves radiated from the vicinity of both end portions of the inlet 1 having high electric field strength are radiated to the auxiliary antenna 7. In addition, radio waves reflected from the metal plate 6 from the inlet 1 are also radiated to the auxiliary antenna 7. As a result, the auxiliary antenna 7 has a strong electric field strength due to the radio wave amplification effect of the radio wave directly radiated from the inlet 1 and the radio wave reflected from the metal plate 6, and thus the communication distance in the actual measurement result extends to about 80 mm. . In the case of the embodiment of FIG. 4, the gap between the curved portion of the auxiliary antenna 7 and the surface of the inlet 1 is air having a relative dielectric constant of 1, but an epoxy resin or the like having a relative dielectric constant of about 2 is used. Such a dielectric may be interposed.

  Further, as shown in the second embodiment of FIG. 5, the gap between the metal plate 6 and the auxiliary antenna 7 is set to about 6 mm in the vicinity of one end portion of the auxiliary antenna 7, and the vicinity of the other end portion of the auxiliary antenna 7 is the inlet 1. When the so-called auxiliary antenna 7 is slightly bent from the side, the communication distance in the measurement result is about 40 mm. In this case, since the vicinity of one end of the auxiliary antenna 7 is shielded by the metal plate 6 and the auxiliary antenna 7, the communication distance is shorter than that of the RFID tag having the configuration of the first embodiment shown in FIG. That is, in the RFID tag according to the first embodiment, the communication distance can be changed by changing the curved shape of the auxiliary antenna 7.

  Further, as shown in the configuration diagram of the RFID tag of Example 3 shown in FIG. 6, a dielectric sheet 8 having a desired dielectric constant of about 2 mm in thickness is formed on the upper surface of the inlet 1 attached to the surface of the metal plate 6. Further, an auxiliary antenna 7 that is curved in the radio wave radiation direction is mounted thereon. At this time, the auxiliary antenna 7 is curved symmetrically with respect to the center so that the gap between the metal plate 6 and the auxiliary antenna 7 near the tip of the auxiliary antenna 7 is about 7 mm. The communication distance in the actual measurement result in this case greatly increases to about 150 mm to 280 mm, although there are differences depending on the type and thickness of the dielectric sheet 8.

  Thus, the reason why the communication distance of the RFID tag is dramatically increased by interposing the dielectric sheet 8 having the same size as the inlet 1 between the inlet 1 and the auxiliary antenna 7 is as follows. That is, when the dielectric sheet 8 is mounted on the surface of the inlet 1, a wavelength shortening effect is exhibited by the dielectric constant of the dielectric sheet 8, so that the physical length of the main antenna 3 (see FIG. 1) built in the inlet 1 (That is, the actual length) is shorter than the electrical length λ / 4, but the electrical length is maintained at λ / 4. Note that λ is the wavelength of the used radio wave.

  For example, when the radio frequency is 2.45 GHz and the dielectric sheet 8 is not on one surface of the main antenna 3, the physical length when the electrical length of the main antenna 3 is λ / 4 is 30 mm. When the dielectric sheet 8 is arranged on one surface of the main antenna 3, and the wavelength λ is shortened to ½ due to the wavelength shortening effect by the dielectric constant of the dielectric sheet 8, Even if the target length is kept at λ / 4, the physical length is 15 mm. That is, for example, as shown in FIG. 4, in order to secure a communication distance of 80 mm, the electrical length of the main antenna 3 needs to be λ / 4, but the physical length of the dielectric sheet 15 is that of the main antenna 3. When it is not on one side, 30 mm is required, whereas when the dielectric sheet 15 is on one side of the main antenna 3, 15 mm is sufficient.

  In other words, by disposing the dielectric sheet 15 on one surface of the main antenna 3 as shown in FIG. 6, the physical length of the main antenna 3 is 15 mm and the electrical length λ / 4 is maintained and the communication is 80 mm. Where the distance can be secured, the physical length of the main antenna 3 is actually 30 mm, so the electrical length due to the wavelength shortening effect has increased to λ / 2. Therefore, since the electrical length of the main antenna 3 extends from λ / 4 to λ / 2, the communication distance further extends from 80 mm to about 150 mm to 280 mm. That is, the larger the dielectric constant of the dielectric sheet 15, the greater the wavelength shortening effect and the longer the communication distance. For example, when the width and length of the inlet 1 and the dielectric sheet 8 are the same, a glass epoxy having a relative dielectric constant of about 3.6 is used as the dielectric sheet 8 than a foamed polypropylene having a relative dielectric constant of 2. The communication distance is longer.

<< Second Embodiment >>
In the second embodiment, a case will be described in which a metal pipe 11 having a curved metal surface is used instead of bending the auxiliary antenna 7 as in the first embodiment.

  FIG. 7 is a cross-sectional view of Example 1 of the RFID tag according to the second embodiment of the present invention. As shown in FIG. 7, the inlet 1 is attached to the curved surface of the metal pipe 11, and a planar base plate (first base plate) 9 is placed in a substantially tangential direction at the apex of the curved portion of the inlet 1. The auxiliary antenna 7 is mounted thereon. Since the base plate 9 is flat, a gap a is formed between the inlet 1 and the base plate 9 except for the apex portion of the inlet 1.

  That is, by providing a gap a between the auxiliary antenna 7 and the inlet 1 at both ends of the inlet 1, radio waves from a reader / writer (not shown) reach the vicinity of both ends of the inlet 1. Accordingly, strong radio waves radiated from the vicinity of both ends of the inlet 1 having high electric field strength are radiated to the auxiliary antenna 7. As a result, the auxiliary antenna 7 has a strong electric field strength due to the radio wave amplification effect of the radio wave radiated from the inlet 1, and the communication distance in the actual measurement result extends to about 50 mm. In the case of the embodiment of FIG. 7, the space between the inlet 1 and the base plate 9 is a gap a by air except for the apex portion of the inlet 1, but in order to stably mount the base plate 9, The gap a may be filled with an epoxy resin or the like.

  FIG. 8 is a cross-sectional view of Example 2 of the RFID tag according to the second embodiment of the present invention. As shown in FIG. 8, even if the auxiliary antenna 7 is sandwiched between the base plate (first base plate) 9a and the base plate (second base plate) 9b on both sides, the measured communication distance extends to about 50 mm. . In order to protect the auxiliary antenna 7 formed of a thin metal foil, it is desirable to sandwich the auxiliary antenna 7 between the base plates 9a and 9b as shown in FIG. The base plates 9a and 9b are preferably made of an insulator having a thickness of about 1 mm. If the base plates 9a and 9b are made of a thick insulator or a dielectric having a high dielectric constant, the communication distance may be reduced.

  According to the RFID tag of the present invention, when a flexible inlet is affixed to a metal surface and an auxiliary antenna is mounted on the surface of the inlet, it is desired between the inlet and the front end portion of the auxiliary antenna in the longitudinal direction. The gap is formed. Therefore, since the radio wave transmitted and received at the tip end portion of the inlet is not shielded, the radio wave from the tip end portion of the inlet is effectively radiated to the auxiliary antenna. Therefore, the communication distance can be extended by the radio wave amplification effect of the auxiliary antenna. That is, according to the RFID tag of the present invention, when the inlet is attached to a planar metal part, a desired gap is formed by making the auxiliary antenna curved, and the inlet is attached to the curved metal pipe. Since the desired gap can be formed by making the auxiliary antenna flat, the desired communication distance can be secured even if the inlet is directly attached to a metal part having a flat or curved surface. Is possible. Therefore, it can be used effectively in a power company, a gas company, etc. for managing pipes and wiring by attaching them to metal pipes and power cables.

It is an internal structure figure of an inlet used for an embodiment of an RFID tag concerning the present invention, (a) is a perspective view showing the state where an inlet was decomposed, and (b) is a top view of an inlet. It is the completion drawing of the inlet which shows the state which laminated | stacked the surface with the outer skin film in AA sectional drawing of FIG.1 (b). It is sectional drawing of the RFID tag in the 1st Embodiment of this invention. It is a block diagram of Example 1 of the communication distance measurement by the RFID tag of this invention using the curved auxiliary antenna. It is a block diagram of Example 2 of the communication distance measurement by the RFID tag of this invention using the curved auxiliary antenna. It is a block diagram of Example 3 of the communication distance measurement by the RFID tag of this invention using the auxiliary antenna 7 made curved. It is sectional drawing of Example 1 of the RFID tag in the 2nd Embodiment of this invention. It is sectional drawing of Example 2 of the RFID tag in the 2nd Embodiment of this invention.

Explanation of symbols

1 Inlet 2 Substrate film 3 Main antenna (first antenna)
3a Slit 4 IC chip 5 Outer film 6 Metal plate 7 Auxiliary antenna (second antenna)
8 Dielectric sheet 9, 9a, 9b Base plate 10 RFID tag 11 Metal pipe a Clearance

Claims (10)

An inlet on which a first antenna mounted with an IC chip is laminated with a film and mounted on a planar metal surface;
And a second antenna that is arranged to face the inlet and is formed in a curved shape in a direction away from the surface of the inlet as it goes to at least one tip portion in the longitudinal direction. . An RFID including an inlet on which a first antenna mounted with an IC chip is laminated with a film and a second antenna disposed to face the inlet, and the inlet is applied to a planar metal surface A tag,
The RFID tag, wherein the second antenna is formed in a curved shape in a direction away from the surface of the inlet as it goes to at least one tip portion in the longitudinal direction. 3. The RFID tag according to claim 1, wherein the second antenna is formed in a curved shape in a direction away from the surface of the inlet as it goes to the tip portions on both sides in the longitudinal direction. . The dielectric material which has a desired dielectric constant is interposed between the curved part of the said inlet and the said 2nd antenna. The any one of the Claims 1-3 characterized by the above-mentioned. RFID tag. 5. A dielectric sheet having a desired dielectric constant is interposed between the inlet and the second antenna. The dielectric sheet has substantially the same size as the inlet and has a desired dielectric constant. The RFID tag according to any one of the above. An inlet on which a first antenna mounted with an IC chip is laminated with a film and mounted on a curved metal surface;
An RFID tag comprising: a second antenna disposed substantially in a tangential direction at a vertex of a curved portion of the inlet. An RFID tag comprising an inlet on which a first antenna mounted with an IC chip is laminated with a film, and a second antenna arranged opposite to the inlet, the inlet being applied to a curved metal surface Because
The RFID tag, wherein the second antenna is arranged in a substantially tangential direction at a vertex of a curved portion of the inlet. The first base plate made of an insulator for holding the second antenna flat is interposed on the surface of the second antenna on the side facing the inlet. The RFID tag according to claim 6 or 7. The RFID tag according to claim 8, wherein a second base plate made of an insulating material is interposed on the radio wave radiation surface of the second antenna. The RFID tag according to claim 8 or 9, wherein a dielectric having a desired dielectric constant is interposed between the first base plate and the curved portion of the inlet.

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