JP2008123196A - Rfid tag and method for installing rfid tag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an RFID tag attached to a metallic plate of an electronic device unit or the like, whose communication range can be controlled if necessary. <P>SOLUTION: A metallic tag is placed on a metallic plate 16 via a dielectric sheet 15 having a desired dielectric constant, wherein the metallic tag has a layered structure comprising a main antenna 3, a resin 13, and an auxiliary antenna 11. The main antenna 3 provides wave-amplifying action by the wavelength-reducing effect of the dielectric sheet 15 in a first area 17 located immediately below and increases the field intensity of the auxiliary antenna 11. Also, wave-attenuating action is provided by the dielectric sheet 15 in a second area 18 that protrudes from immediately below the main antenna 3, so that a reflected wave passing from the main antenna 3 to the auxiliary antenna 11 through the metallic plate 16 is attenuated. Thus, since the attenuation of the reflected wave is varied by varying the size of the second area 18, the communication range can be varied by varying the field intensity of the auxiliary antenna 11. <P>COPYRIGHT: (C)2008,JPO&INPIT

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 particularly to an RFID (Radio Frequency Identification) tag attached to a metal plate. The present invention relates to an RFID tag that is suitable and capable of controlling a communication distance with a reader / writer, and an RFID tag mounting method.

  An RFID tag includes a small IC chip and a small antenna, and information such as an ID recorded on the IC chip can be transmitted wirelessly (RF) from the small antenna. As a result, when the RFID tag is held by a reader / writer, information recorded on the IC chip is read in a non-contact manner. Therefore, by attaching such an RFID tag to an article, it is possible to identify each article and manage information about the article. For example, if an attribute of each part is recorded on an RFID tag attached to an assembly part at a production site or the like, the manufacturing history of the product can be managed (for example, see Patent Document 1).

Further, the RFID tag is configured as an inlet having a laminated structure including a main antenna (first antenna) on which an IC chip is mounted and an auxiliary antenna (second antenna) arranged in parallel with a resinous spacer interposed therebetween. Thus, the communication distance can be further increased by the radio wave amplification effect of the second antenna. By adopting such an RFID tag structure, a relatively long communication distance (for example, about 140 mm) is ensured even when the RFID tag is attached to a metal surface such as a housing of an electronic device via an insulating spacer. (For example, see Patent Document 2).
JP-A-2005-149004 (paragraphs 0011 to 0013, FIGS. 1 and 2) Japanese Patent Laying-Open No. 2005-210676 (paragraphs 0015 to 0020, FIGS. 1 and 2)

  However, when an RFID tag-attached part moves on the line at an assembly site of an industrial product, etc., there are processes in which the part that the reader / writer wants to read flows near the worker's position, or far away from the worker's position. There is also a flowing process. In such a case, in the RFID tag described in the above-mentioned Patent Document 2, the communication distance is determined to be within 140 mm, for example. In the case where the part is a line that flows near the worker's position, the corresponding part is placed by the reader / writer. Although it can be easily read, if the part is a line that flows farther than the worker's position, the RFID tag information cannot be read unless the worker reaches out and approaches the reader / writer to the part. Therefore, it becomes a cause of reducing work efficiency. Further, even when the information of the RFID tag attached to the component flowing in the line is automatically read by the reader / writer, the component passing through the line within 140 mm from the reader / writer that is fixedly installed can be read. A part passing through a position farther than 140 mm from the reader / writer on the line cannot be read.

  The present invention has been made in view of the above problems, and when an RFID tag is attached to a metal case such as an electronic device unit, an RFID tag that can control a communication distance as necessary, And an RFID tag mounting method.

  In order to achieve the above object, the RFID tag of the present invention is formed by mounting an IC chip on a main antenna (first antenna), and the first surface and the first surface are in a relationship of front and back. An auxiliary antenna (second antenna) that has an inlet having a second surface and an opposing surface that is disposed close to the inlet and faces the first surface of the inlet and that amplifies radio waves radiated from the first antenna. Antenna), a metal plate arranged to face the second surface of the inlet, and a dielectric having a desired dielectric constant interposed between the metal plate and the second surface of the inlet. ing.

  At this time, the dielectric is formed into a sheet shape including a first area (for example, the first area 17) facing the inlet and a second area (for example, the second area 18) protruding from the facing surface of the inlet. Since it is formed, by changing the area of the second area, the electric field intensity of the auxiliary antenna is changed to vary the radio wave distance of the metallic tag (tag body). As a preferred embodiment, when the area of the first area is fixed, as the area of the second area is reduced, the electric field strength of the auxiliary antenna increases and the radio wave distance of the metallic tag increases. .

  That is, according to the RFID tag of the present invention, when the metallic tag is placed on the metal plate with the dielectric sheet interposed, the wavelength in the area of the dielectric sheet located directly under the inlet in the metallic tag. Since it exhibits a radio wave amplification effect due to the shortening effect, the electric field strength of the auxiliary antenna of the metallic tag is further increased. As a result, the distance of radio waves from the metallic tag is extended. On the other hand, in the area of the dielectric sheet that protrudes from directly under the inlet, the radio wave from the main antenna to the metal plate is attenuated by the radio wave attenuation action, reflected by the metal plate, and irradiated to the auxiliary antenna. Therefore, the smaller the area of the dielectric sheet that protrudes from directly under the inlet, the smaller the radio wave attenuation effect, so that the amount of attenuation of the reflected wave is reduced and the electric field strength of the auxiliary antenna is increased. The distance of radio waves can be further extended. That is, the communication distance between the metallic tag and the reader / writer can be changed by changing the shape and size of the dielectric sheet.

  According to the RFID tag of the present invention, the communication distance can be controlled as necessary when the RFID tag is attached to a metal case such as an electronic device unit.

<< Summary of Invention >>
Hereinafter, an 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. First, an outline of the RFID tag in the present invention will be described.

  The RFID tag according to the present invention includes an inlet including a main antenna (first antenna) on which an IC chip is mounted, and an auxiliary antenna (second antenna) that receives a radio wave from the main antenna and performs a radio wave amplifying function. A metallic tag (tag body) is mounted on a metal plate via a dielectric sheet having a predetermined dielectric constant. At this time, the dielectric sheet exhibits a radio wave amplification effect due to the wavelength shortening effect due to the dielectric constant of the dielectric in the area facing the inlet, but the dielectric tangent of the dielectric (in the area protruding from the inlet facing position ( The electric wave attenuation effect is exhibited by the polarization effect by tan δ). Therefore, the radio wave intensity radiated from the metallic tag can be varied by appropriately changing the degree of contribution of the radio wave amplification action and the degree of contribution of the radio wave attenuation action depending on the shape of the dielectric sheet. As a result, the communication distance between the metallic tag and the reader / writer can be controlled by changing the shape of the dielectric sheet.

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

<< Preferred Embodiment >>
First, an inlet for realizing the RFID tag of the present invention will be described. 1A and 1B are structural views of an inlet used in an RFID tag according to an embodiment of the present invention, in which FIG. 1A is a perspective view showing a state in which the inlet is disassembled, and FIG. In the inlet 1 shown in FIG. 1, a main antenna 3 made of copper foil, which is plated with tin or the like, is formed on the upper surface of a film 2 made of a resin material such as polyimide resin and having a thickness of about 0.1 mm. 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 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. Then, when the electrodes of the IC chip 4 are connected so as to straddle the slit 3a, the stub surrounded by the slit 3a is connected in series between the main antenna 3 and the IC chip 4, A stub acts as a serial inductive component between the main antenna 3 and the IC chip 4. 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. Therefore, the size of the inlet 1 including the film 2, the main antenna 3, and the IC chip 4 is, for example, about 3 mm in width, 35 mm in length, and about 0.6 mm in thickness.

  Next, a metallic tag containing the inlet having the structure shown in FIG. 1 will be described. In the inlet 1 as shown in FIG. 1 described above, a communication distance of only about 40 mm can be secured. Therefore, by providing an auxiliary antenna with respect to the main antenna 3 formed in the inlet 1, the communication distance can be increased to several tens of centimeters. (For example, 140 mm) can be extended. Therefore, a configuration in which a metallic tag is formed by providing an auxiliary antenna in parallel with the main antenna 3 of the inlet 1 will be described.

  FIG. 2 is an exploded view of a metallic tag used in the RFID tag of the present invention. As shown in FIG. 2, the inlet 1 is housed in the vicinity of the center covered with the auxiliary antenna 11 formed of a thin metal material such as an aluminum alloy, and a resin material such as polyimide resin is poured into the auxiliary antenna 11. And the inlet 1 are integrated. The notch 11a formed in the auxiliary antenna 11 is formed so as to effectively radiate radio waves corresponding to the slit 3a of the inlet 1 and the IC chip 4. Also, attachment holes 12 for attaching to a metal plate (not shown) are provided near both ends of the auxiliary antenna 11.

  3A and 3B are external perspective views of a metallic tag in which the auxiliary antenna and the inlet shown in FIG. 2 are integrally formed of polyimide resin, and FIG. 3A is a front view and FIG. 3B is a rear view. As shown in FIG. 3 (b), the metallic tag 14 has a configuration in which the inlet 1 is housed near the central portion on the back side of the auxiliary antenna 11 and molded with a resin 13. As shown in FIG. 3A, the metallic tag 14 configured in this way is directly attached to a housing made of resin, for example, with the front side facing up, and a screw or the like is inserted into the mounting hole 12. Can be fixed. The metal tag 14 attached in this way can secure a communication distance of, for example, about 140 mm by the radio wave amplification action of the inlet (not shown) and the auxiliary antenna 11.

  However, in the present invention, an RFID tag capable of varying the communication distance using the metallic tag 14 is realized, and the embodiment will be described in detail.

  FIG. 4 is a conceptual diagram showing a state in which a metallic tag is attached to a metal plate via a dielectric sheet. Since the metallic part of the auxiliary tag 11 is covered from the front surface side to a part of the back surface side of the metallic tag 14, a dielectric sheet 15 such as polypropylene or glass epoxy is interposed as an insulator and then attached to the metal plate 16. Installing.

  When the metallic tag 14 is directly attached to the metal plate 16 without interposing the dielectric sheet 15, the inlet main antenna not shown in FIG. 4 inside the metallic tag 14 is connected to the auxiliary antenna 11 and the metallic plate. 16 is shielded by being surrounded by 16, it is difficult to radiate the radio wave having the main antenna with the IC chip as a source. Therefore, when the metallic tag 14 is directly attached to the metal plate 16, the communication distance of about 140 mm with the metallic tag 14 alone is reduced to about 20 mm.

  Next, the mounting configuration of the metallic tag 14, the dielectric sheet 15, and the metal plate 16 as shown in FIG. 4 will be described with an equivalent configuration.

  FIG. 5 is an equivalent configuration diagram when a metallic tag is mounted on a metal plate via a dielectric sheet as shown in FIG. 4, (a) is a state in which each element is disassembled, (b) ) Shows a state in which each element is laminated. That is, the RFID tag 20 shown in FIG. 5 has a slit 3a for impedance matching formed near the center of the main antenna 3, and the IC chip 4 is mounted so as to straddle the slit 3a. A resin 13 having a desired dielectric constant, a thickness of about 1 mm, and a width and length larger than that of the main antenna 3 is disposed on the upper surface of the main antenna 3. An auxiliary antenna 11 having a width and length larger than that of the main antenna 3 is disposed on the upper surface of the resin 13. Further, a metal plate 16 serving as a tag attachment member is disposed on the lower surface of the main antenna 3 via a dielectric sheet 15 having a thickness of about 2 mm. Thus, the thickness of the RFID tag 20 laminated as shown in FIG. 5B is such that it protrudes about 4 mm above the metal plate 16 including the adhesive for bonding the elements.

  In the RFID tag 20 of the present invention, the communication distance between the reader / writer can be changed by changing the size and shape of the dielectric sheet 15 shown in FIG. explain. When the main antenna 3 having the IC chip 4 mounted thereon is mounted on the dielectric sheet 15, the wavelength shortening effect is exhibited by the dielectric constant of the dielectric sheet 15, so that the physical length of the main antenna 3 (that is, The actual length is shorter than the electrical length λ / 4, but the electrical length is maintained at λ / 4.

  For example, when the radio frequency is 2.45 GHz and the dielectric sheet 15 is not on the lower 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 15 is arranged on the lower surface of the main antenna 3 and the wavelength λ is shortened to ½ due to the wavelength shortening effect due to the dielectric constant of the dielectric sheet 15, Even if the target length is kept at λ / 4, the physical length is 15 mm. That is, in order to secure a communication distance of 140 mm, the electrical length of the main antenna 3 needs to be λ / 4, but the physical length is 30 mm when the dielectric sheet 15 is not on the lower surface of the main antenna 3. On the other hand, when the dielectric sheet 15 is on the lower surface of the main antenna 3, it may be 15 mm.

  In other words, by disposing the dielectric sheet 15 on the lower surface of the main antenna 3 as shown in FIG. 5, the physical length of the main antenna 3 is 15 mm and the electrical length λ / 4 is maintained and the communication is 140 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. Accordingly, since the electrical length of the main antenna 3 extends from λ / 4 to λ / 2, the communication distance further extends beyond 140 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.

  However, when viewed from the other side, a dielectric loss tangent (tan δ) is generated in the dielectric sheet 15 due to the polarization action of the dielectric. When this tan δ increases, the dielectric loss increases and the resonance energy of the radio wave is lost. That is, the radio wave intensity passing through the dielectric sheet 15 is attenuated due to loss of resonance energy due to tan δ. In general, tan δ shows a larger value as the dielectric constant of the dielectric increases.

  That is, when the dielectric sheet 15 is disposed on the lower surface of the metallic tag 14, a phenomenon that acts in a direction of extending the communication distance by exhibiting a larger wavelength shortening effect as the dielectric constant of the dielectric sheet 15 increases. The trade-off relationship is a phenomenon in which tan δ increases as the dielectric constant of the dielectric sheet 15 increases and the radio wave intensity is attenuated to reduce the communication distance (that is, the radio wave attenuating action). appear.

  Therefore, in the RFID tag 20 of the present invention, the method of changing the size and shape of the dielectric sheet 15 shown in FIG. 5 is devised, and the radio wave amplification effect due to the wavelength shortening effect caused by the dielectric constant and the radio wave attenuation caused by tan δ. By taking advantage of the trade-off relationship of action, measures are taken to increase the communication distance accordingly.

  In the shapes of the main antenna 3 and the dielectric sheet 15 shown in FIG. 5, the width and length of the dielectric sheet 15 are larger than those of the main antenna 3. With such a shape of the dielectric sheet 15, the area of the dielectric sheet 15 (first area 17) located directly below the main antenna 3 acts in the direction of extending the communication distance by the radio wave amplification action due to the wavelength shortening effect. However, in the area (second area 18) of the dielectric sheet 15 that protrudes from directly below the main antenna 3, it acts in the direction of shortening the communication distance by the radio wave attenuation effect by tan δ. Accordingly, the RFID tag 20 having the shape shown in FIG. In FIG. 1B, the inlet 1 and the main antenna 3 are shown to have different sizes, but they are approximately the same size.

  More specifically, in the area of the dielectric sheet 15 located directly below the main antenna 3, the main antenna 3 acts as an antenna having a physical length longer than λ / 4 due to the wavelength shortening effect, and assists with strong electric field strength. The antenna 11 is excited. As a result, the electric field intensity of the radio wave radiated from the auxiliary antenna 11 is increased, so that the communication distance is extended. However, the radio wave attenuated by tan δ irradiates the metal plate 16 in the area of the dielectric sheet 15 protruding from directly below the main antenna 3. Therefore, since the attenuated radio wave is reflected from the metal plate 16 and applied to the auxiliary antenna 11, the electric field strength of the auxiliary antenna 11 is not so much added by the radio wave generated by the reflected wave from the metal plate 16. Therefore, the communication distance cannot be further extended by the reflected wave from the metal plate 16.

  Therefore, if the dielectric sheet 15 is made to have the same width and the same length as the main antenna 3 and are overlapped with each other, the area of the dielectric sheet 15 does not protrude from directly below the main antenna 3. Only the wavelength shortening effect in the area of the dielectric sheet 15 located directly below the main antenna 3 does not occur.

  That is, in the area of the dielectric sheet 15 located directly below the main antenna 3, the main antenna 3 acts as an antenna having a physical length longer than λ / 4 due to the wavelength shortening effect, and the auxiliary antenna 11 has a strong electric field strength. Since excitation is performed, the electric field strength is increased and the communication distance is extended. Furthermore, since the area of the dielectric sheet 15 does not exist in the portion that protrudes from directly below the main antenna 3, the metal plate 16 can reflect the strong radio wave received from the main antenna 3 and irradiate the auxiliary antenna 11. it can. As a result, a stronger electric field is added to the auxiliary antenna 11 by the reflected wave from the metal plate 16. Therefore, the auxiliary antenna 11 can further extend the communication distance by the action of increasing the electric field strength due to the reflected wave from the metal plate 16.

  For this reason, theoretically, if the main antenna 3 and the dielectric sheet 15 have the same size and are arranged opposite to each other and placed on the metal plate 16, the radio wave amplification effect due to the wavelength shortening effect is maximized, and There is no radio wave attenuation effect due to tan δ. Therefore, the auxiliary antenna 11 can maximize the electric field strength and maximize the communication distance by the maximum radio wave amplification effect due to the wavelength shortening effect and the radio wave enhancement effect due to the non-attenuated reflected wave from the metal plate 16. Become.

《Experimental Verification》
Next, actual measurement data of the communication distance when the shape of the dielectric sheet 15 is variously changed will be described. FIG. 6 is an outline view showing the size of the metallic tag used in the experiment for verifying the present invention and the inlet built in the metallic tag. As shown in FIG. 6, the metal tag 14 has a length of 52 mm and a width of 13 mm (that is, the size of the auxiliary antenna 11). The inlet 1 has a length of 27 mm and a width of 3 mm.

  FIG. 7 is a diagram showing measured data on the relationship between the shape of the dielectric sheet used in the experiment for verifying the present invention and the communication distance. Experiment No. 1, when the metallic tag 14 is directly attached to the metal plate 16, the inlet 1 forming the main antenna 3 is surrounded by the auxiliary antenna 11 and the metal plate 16 of the metallic tag 14 and shielded. Only leaked radio waves reach the auxiliary antenna 11 of the metallic tag 14 from the inlet 1. Therefore, the communication distance by the radio wave radiated from the auxiliary antenna 11 of the metallic tag 14 extends only about 20 mm.

  Experiment No. 2, when the size of the dielectric sheet 15 is the same as that of the metallic tag 14 (length 52 mm, width 13 mm), the inlet of the dielectric sheet 15 laid under the metallic tag 14 The wavelength shortening effect acts only on the area of the dielectric sheet 15 facing directly below 1. On the other hand, in the area of the dielectric sheet 15 that protrudes from directly below the inlet 1, the radio wave attenuating action acts greatly, and the electric field strength enhancing action by the reflected wave from the metal plate 16 hardly occurs.

  That is, in the area of the dielectric sheet 15 that protrudes from directly below the inlet 1, the radio wave radiated from the main antenna 3 of the inlet 1 is attenuated by the radio wave attenuating action and irradiated to the metal plate 16. The reflected radio wave is again attenuated by the radio wave attenuating action and is applied to the auxiliary antenna 11. Therefore, the electric field strength of the auxiliary antenna 11 is hardly enhanced by the reflected wave from the metal plate 16.

  Therefore, the communication distance is about 120 mm corresponding to the electric field strength realized by the wavelength shortening effect, and is almost the same as the communication distance when the metallic tag 14 is used alone. However, in Experiment No. 1 in which the metallic tag 14 was directly attached to the metal plate 16. Compared to the case of 1, the communication distance is extended about 6 times.

  Experiment No. 3, when the length of the dielectric sheet 15 is slightly shorter than the length of the metallic tag 14 and the width of both is the same (that is, the length of the dielectric sheet 15 is 40 mm and the width is 13 mm). In this case, in addition to the effect of the wavelength shortening effect in the area of the dielectric sheet 15 that is directly below the inlet 1, the area of the dielectric sheet 15 that protrudes from directly below the inlet 1 is slightly reduced. Since the action is slightly reduced and the electric field strength is slightly increased, the communication distance is increased to about 290 mm. In this case, the communication distance is extended by about 14.5 times compared to the case where the metallic tag 14 is directly attached to the metal plate 16.

  Experiment No. 4, the width (13 mm) of the dielectric sheet 15 is made the same as the width of the metallic tag 14 in the regions located at the central portion and both end portions of the metallic tag 14 as shown in FIG. The width (3 mm) of the dielectric sheet 15 was made the same as the width of the inlet 1. As a result, the wavelength shortening effect in the area of the dielectric sheet 15 facing directly below the inlet 1 is ensured, and the area of the dielectric sheet 15 that protrudes from directly below the inlet 1 is further reduced. Since the effect of increasing the electric field strength is slightly increased, the communication distance is extended to about 320 mm. In this case, the communication distance is extended about 16 times compared to the case where the metallic tag 14 is directly attached to the metal plate 16.

  Experiment No. 5, the width (13 mm) of the dielectric sheet 15 is made the same as the width of the metallic tag 14 only in the region located in the central portion of the metallic tag 14 as shown in the figure, and the dielectric is formed in the other portions. The width (3 mm) of the sheet 15 was made the same as the width of the inlet 1. As a result, the wavelength shortening effect in the area of the dielectric sheet 15 facing directly below the inlet 1 is ensured, and the area of the dielectric sheet 15 that protrudes from directly below the inlet 1 is almost eliminated. Since the effect of enhancing the electric field strength is greatly increased with almost no loss, the communication distance is greatly increased to about 430 mm. In this case, compared with the case where the metallic tag 14 is directly attached to the metal plate 16, the communication distance is extended by about 21.5 times.

  The dielectric sheet 15 is set to Experiment No. By making the shape as shown in FIG. The reason why the communication distance is greatly increased as compared with the case of the shape 4 is as follows. Since the main antenna 3 that forms the inlet 1 has a feeding point at the center, the voltage at the center of the main antenna 3 is low, so the electric field strength is weak. However, since both ends of the main antenna 3 have a high voltage, the electric field strength is also strong. Therefore, Experiment No. 5, the area occupied by the dielectric sheet 15 is reduced outside the both end portions of the main antenna 3 (in the example of the figure, the dielectric sheet is disposed outside the both end portions of the main antenna 3). If the area occupied by 15 is reduced to zero), the effect of eliminating the radio wave attenuating effect is greatly affected. That is, the dielectric sheet 15 is set to Experiment No. From the shape like FIG. By changing to a shape such as 5, the radio wave attenuating action is almost eliminated at both end portions of the main antenna 3 having a high electric field strength.

  Experiment No. 6, when the shape of the dielectric sheet 15 is the same as the width (3 mm) and length (27 mm) of the inlet 1 as shown in the figure, the wavelength shortening effect is theoretically ensured, The radio wave attenuating action is completely eliminated, the radio wave enhancing action by the reflected wave from the metal plate 16 is added to the maximum, and the communication distance is extended to the maximum. However, the communication distance in this case is 390 mm in actual measurement. The communication distance is shorter than the communication distance 430 mm in the case of shape 5.

  Experiment No. The reason why the communication distance is shortened against the theory in the shape of the dielectric sheet 15 of 6 is as follows. That is, Experiment No. With the shape of the dielectric sheet 15 of 5, the width of the metallic tag 14 is the same as that of the metallic tag 14 in the central portion of the dielectric sheet 15, so that the width of the metallic tag 14 and the dielectric sheet 15 can be easily adjusted. For this reason, the width and alignment of the inlet 1 are necessarily performed even in the narrow portion of the dielectric sheet 15. Thereby, the wavelength shortening effect of the main antenna 3 formed in the inlet 1 is reliably performed.

  However, experiment no. In the shape of the dielectric sheet 15 of 6, there is no positioning for aligning the width with the metallic tag 14, and as a result, the position of the narrow portion of the dielectric sheet 15 and the width direction of the inlet may be slightly shifted. is there. At this time, since the width of the dielectric sheet 15 and the inlet is 3 mm, the width is shifted by 3% even if the width alignment of both is shifted by 0.1 mm, for example. As a result, the wavelength shortening effect of the main antenna 3 is not completely performed, so that the electric field strength cannot be maximized and the communication distance cannot be extended as theoretically.

  Furthermore, as described above, since the electric field strength is weak in the central portion of the inlet 1, even if the width of the dielectric sheet 15 is wider than the width of the inlet 1 in the central portion, the radio wave attenuation action hardly occurs. Therefore, Experiment No. As shown in FIG. 5, even if the width of the center portion of the dielectric sheet 15 is increased, the electric wave attenuation effect hardly occurs. Therefore, the electric field strength due to the wavelength shortening effect and the electric field strength enhancement effect due to the reflected wave that is almost the maximum. With this, the maximum communication distance is obtained.

  That is, Experiment No. As in the shape of the dielectric sheet 15 shown in FIG. 5, increasing the width of the central portion of the dielectric sheet 15 to the width of the metallic tag 14 makes it easy to align the width of the metallic tag 14 and the dielectric sheet 15. In addition, since the metallic tag 14 can be stably placed on the dielectric sheet 15, it is extremely useful to increase the width of the central portion of the dielectric sheet 15.

  Experiment No. 7, as shown in the figure, the shape of the dielectric sheet 15 was 5 mm wide and 30 mm long, which was slightly larger than the shape of the inlet 1 (width 3 mm × length 27 mm). As a result, a margin is generated in the positional relationship between the dielectric sheet 15 and the inlet 1, so that the dielectric sheet 15 exists immediately below the inlet 1 even if the opposing position of the dielectric sheet 15 and the inlet 1 is slightly shifted. Therefore, the wavelength shortening effect of the inlet 1 is completely performed. In addition, since the area where the dielectric sheet 15 protrudes from the inlet 1 is very small, the radio wave attenuation effect hardly occurs. As a result, the communication distance is 450 mm, and the dielectric sheet 15 is set to Experiment No. The communication distance is somewhat longer than in the case of the shape as shown in FIG. Further, the communication distance is extended by about 22.5 times compared to the case where the metallic tag 14 is directly attached to the metal plate 16.

  However, Experiment No. 7, the width of the dielectric sheet 15 facing the inlet 1 is slightly wider. However, it is still difficult to align the dielectric sheet 15 and the inlet 1, and the dielectric sheet 15 The stability when the metallic tag 14 is placed on the surface is deteriorated. For this purpose, Experiment No. Although the communication distance is slightly smaller than the shape of the dielectric sheet 15 of FIG. The shape of the dielectric sheet 15 shown in FIG.

  FIG. 8 is an actual measurement characteristic diagram showing a change characteristic of the communication distance when the shape of the dielectric sheet is changed. In FIG. 8, as a dielectric sheet, (a) a foamed polypropylene plate (thickness = 2.0 mm (2 t), relative dielectric constant (ε) = 2.0, tan δ = 0.015), (b) glass epoxy plate (Thickness = 1.6 mm (1.6 t), relative permittivity = 3.7, tan δ = 0.01), and (c) acrylic plate (thickness = 2.0 mm (2 t), relative permittivity = 2) .6, tan δ = 0.005) shows a change in communication distance depending on the shape of the dielectric sheet.

  When a foamed polypropylene (PP) plate is used as the dielectric sheet 15, the communication distance varies significantly depending on the shape of the dielectric sheet 15 as shown in the characteristic (a). That is, Experiment No. As shown in FIG. 2, when the area of the dielectric sheet 15 is increased so that the influence of the radio wave attenuation effect on the wavelength shortening effect appears greatly, the radio wave enhancement effect due to the reflected wave from the metal plate 16 is small, and therefore the communication distance. Does not extend that much. On the other hand, Experiment No. 4 and Experiment No. As shown in FIG. 5, as the area of the dielectric sheet 15 is reduced to reduce the influence of the electric wave attenuation action and the ratio of the wavelength shortening effect is increased, the electric wave enhancement action by the reflected wave from the metal plate 16 increases. Effectively, the communication distance has greatly increased.

  However, when a glass epoxy plate having a large relative dielectric constant and tan δ is used as the dielectric sheet 15, the influence of the radio wave attenuating action acts more than the influence of the wavelength shortening effect, and the reflected wave from the metal plate 16 is less. Therefore, the radio wave enhancement effect of the auxiliary antenna 11 is suppressed, and as shown in the characteristic (b), the experiment No. Even if the area of the dielectric sheet 15 that protrudes from the inlet 1 is reduced as in the shape of the dielectric sheet 15 shown in FIG. However, Experiment No. As shown in the shape of the dielectric sheet 15 shown in FIG. 5, the communication distance increases rapidly if the influence of the wavelength shortening effect appears greatly by minimizing the portion where the dielectric sheet 15 protrudes from the inlet 1.

  However, even if the shape of the dielectric sheet 15 in which the influence of the wavelength shortening effect appears most (that is, the shape of Experiment No. 5), the glass epoxy plate having a larger relative dielectric constant (for example, ε = 3.7) is better. The reason why the communication distance is shorter than that of foamed polypropylene is that the relative dielectric constant is small (for example, ε = 2.0), because tan δ increases as the relative dielectric constant increases. This is because the radio wave attenuating action is greatly exerted in the entire area of the dielectric sheet 15 in the shape of 5, and the reflected wave from the metal plate 16 is weakened. Therefore, in the case of a glass epoxy plate having a large relative dielectric constant, it is considered that the communication distance does not extend as much as a foamed polypropylene (PP) plate having a small relative dielectric constant.

  Further, in the case of an acrylic plate, since the relative permittivity is smaller than that of a glass epoxy plate, the degree of influence of the radio wave attenuation action is reduced. Therefore, as shown in the characteristic (c), the area of the dielectric sheet 15 is reduced, As the ratio of the wavelength shortening effect is increased by reducing the influence of the radio wave attenuation effect, the communication distance is relatively increased. However, the communication distance does not extend as much as the foamed polypropylene (PP) plate having a relative dielectric constant of 2.0 because the tan δ of the acrylic plate is large and the influence of the electric wave attenuation effect is larger than that of the foamed polypropylene (PP) plate. It seems to be because.

  From the above, since the dielectric having a large relative dielectric constant has a large tan δ, the dielectric sheet 15 having a desired relative dielectric constant is used (for example, the relative dielectric constant is 2.0). By using the dielectric sheet 15 only in the area facing the inlet 1, the communication distance can be maximized. Furthermore, the communication distance can be shortened as the area of the dielectric sheet 15 protruding from the area facing the inlet 1 is increased.

  For this reason, the communication distance of the metallic tag 14 can be controlled by changing the area of the dielectric sheet 15 facing the metallic tag 14 in a desired shape. However, since it is practically difficult to dispose the dielectric sheet 15 only in the area facing the inlet 1, the width of the dielectric sheet 15 is set to the width of the metallic tag 14 in the central portion of the inlet 1 having the weakest electric field strength. It is desirable to secure the maximum communication distance by performing alignment in the same manner as in FIG.

  According to the RFID tag of the present invention, when a metallic tag is placed on a metal plate of a housing such as an electronic device unit via a dielectric sheet, the shape and size of the dielectric sheet are changed. Thus, the degree to which the radio wave amplification action contributes by the wavelength shortening effect of the dielectric and the degree to which the radio wave attenuation action by the dielectric loss tangent contributes can be changed. Thereby, the communication distance between the metallic tag and the reader / writer can be controlled. Therefore, in an assembly line of a factory or the like, if RFID tags having different communication distances are used according to the perspective position of the parts flowing through the line, information on the RFID tags attached to the parts can be read efficiently and reliably. Work efficiency is further improved.

It is a structural view of the inlet used for the RFID tag which concerns on embodiment of this invention, (a) is a perspective view which shows the state which decomposed | disassembled the inlet, (b) is a top view of an inlet. It is an exploded view of the metallic tag used for the RFID tag of this invention. It is an external appearance perspective view of the metallic tag which integrally molded the auxiliary antenna and inlet shown in FIG. 2 with a polyimide resin etc., (a) is a front view, (b) is a back view. It is a conceptual diagram which shows the state which attaches a metallic tag to a metal plate through a dielectric material sheet. FIG. 5 is an equivalent configuration diagram when a metallic tag is mounted on a metal plate via a dielectric sheet as shown in FIG. 4, (a) is a state in which each element is disassembled, and (b) is each element. The state which laminated | stacked is shown. It is an external view which shows the magnitude | size of the metallic tag used for the experiment for demonstrating this invention, and the inlet incorporated in the metallic tag. It is a figure which shows the actual measurement data of the relationship between the shape of the dielectric material sheet used for the experiment for demonstrating this invention, and communication distance. It is an actual measurement characteristic figure which shows the change characteristic of communication distance when the shape of a dielectric material sheet is changed.

Explanation of symbols

1 Inlet 2 Film 3 Main antenna (first antenna)
3a slit 4 IC chip 11 auxiliary antenna (second antenna)
11a Notch 12 Mounting hole 13 Resin 14 Metallic tag 15 Dielectric sheet 16 Metal plate 17 First area 18 Second area 20 RFID tag

Claims (13)

An inlet having an IC chip mounted on a first antenna and having a first surface and a second surface that is in a front-back relationship with the first surface;
A second antenna that is disposed in proximity to the inlet and has a facing surface that faces the first surface of the inlet, and that amplifies radio waves radiated from the first antenna;
A metal plate arranged to face the second surface of the inlet;
An RFID tag comprising: a dielectric having a desired dielectric constant and interposed between the metal plate and the second surface of the inlet. An inlet having an IC chip mounted on a first antenna and having a first surface and a second surface that is in a front-back relationship with the first surface;
A second antenna that is disposed in proximity to the inlet and has a facing surface that faces the first surface of the inlet, and that amplifies radio waves radiated from the first antenna;
A dielectric having a desired dielectric constant and located on the second face side of the inlet;
An RFID tag applied to a metal surface,
The dielectric is provided between the metal surface and the second surface of the inlet, and includes a first area facing the inlet and a second area protruding from the facing surface of the inlet,
The RFID tag, wherein the second area has a predetermined shape and a predetermined area in consideration of a communication distance when applied to the metal surface. The dielectric is formed in a sheet shape including a first area facing the inlet and a second area protruding from the facing surface of the inlet,
The RFID tag according to claim 1, wherein the second area has a predetermined shape and a predetermined area in consideration of a communication distance. The relationship between the first area and the second area with respect to the communication distance is that when the area of the first area is fixed, the second antenna is reduced as the area of the second area is reduced. 4. The RFID tag according to claim 2, wherein the electric field strength of the radio wave increases and the radio wave flight distance increases. 5. When the inlet and the second antenna are used as a tag main body, the dielectric body has substantially the same width and length as the tag main body on a surface facing the tag main body. The RFID tag according to any one of claims 1 to 4. When the inlet and the second antenna are used as a tag main body, the dielectric has a width substantially the same as the tag main body and a short length on a surface facing the tag main body. The RFID tag according to any one of claims 1 to 4. When the inlet and the second antenna are used as a tag body, the dielectric body has substantially the same width as the tag body at both end portions and a center portion of the tag body on the surface facing the tag body. The RFID tag according to any one of claims 1 to 4, wherein the other portion has substantially the same width as the inlet. When the inlet and the second antenna are used as a tag main body, the dielectric is substantially the same width as the tag main body at the central portion of the tag main body on the surface facing the tag main body, and other portions. The RFID tag according to any one of claims 1 to 4, wherein the RFID tag has substantially the same width as that of the inlet. When the inlet and the second antenna are used as a tag main body, the dielectric body has substantially the same width and the same length as the inlet on the surface facing the tag main body. The RFID tag according to claim 1. The RFID tag according to any one of claims 1 to 9, wherein a relative dielectric constant of the dielectric is approximately 2.0. An inlet formed by mounting an IC chip on the first antenna;
A dielectric sheet having a desired dielectric constant, disposed on the surface of the inlet facing the radio wave radiation surface of the first antenna and having the same size as the inlet, and placed on a metal plate. An RFID tag characterized by A first step of placing a dielectric sheet of a desired shape having a desired dielectric constant on a metal plate;
A metallic tag in which a first antenna on which an IC chip is mounted and a second antenna that amplifies radio waves radiated from the first antenna are disposed on a surface of the dielectric sheet via a resin material. And a second step of placing
In the first step, by changing the shape of the dielectric sheet as necessary, the electric field intensity of the second antenna is changed to vary the radio wave distance of the metallic tag. RFID tag mounting method. A first step of placing a dielectric sheet of a desired shape having a desired dielectric constant on a metal plate;
A metallic tag in which a first antenna on which an IC chip is mounted and a second antenna that amplifies radio waves radiated from the first antenna are disposed on a surface of the dielectric sheet via a resin material. And a second step of placing
In the first step, by arranging the dielectric sheet having a shape selected as necessary, the electric field strength of the second antenna is changed to vary the radio wave distance of the metallic tag. An RFID tag mounting method characterized by the above.

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