RFID tag and temperature management method

Abstract

To provide an RFID tag which enables easy temperature control of articles with good accuracy while reducing costs.SOLUTION: An RFID tag having an IC chip and an antenna for generating power through electromagnetic induction arranged on a substrate is provided, the RFID tag comprising a capacitor and a variable conductivity member having temperature-dependent conductivity mounted to be in contact with the capacitor, where capacitance of the capacitor changes depending on whether the variable conductivity member has transitioned to a conductive state due to temperature or not.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an RFID tag and a temperature control method. [Background technology]

[0002] To prevent deterioration of the quality of products such as food, high-quality alcohol, high-quality tea, cosmetics, and pharmaceuticals, it is necessary to control the temperature of the products during transportation and storage. Product temperature control during transportation and storage is usually achieved by including a temperature logger on the pallet that transports the product. Patent Document 1 also discloses an RFID (Radio Frequency Identifier) tag that can detect temperature. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-191613 Summary of the Invention [Problem to be solved by the invention]

[0004] However, since the temperature logger is equipped with a battery, it cannot be transported by air, etc. Furthermore, the RFID tag disclosed in Patent Document 1 also requires a battery.

[0005] Furthermore, when temperature management is performed using a temperature logger, a manager must constantly check the data stored in the temperature logger. Furthermore, a temperature logger can only check the temperature within a specific area around the temperature logger, and reliability cannot be guaranteed for products placed far from the temperature logger. For example, when transporting products on a pallet, the temperature at the top of the pallet, which is exposed to direct sunlight, may differ from the temperature at the bottom of the pallet, which is not exposed to direct sunlight.

[0006] In view of the above-mentioned problems, an object of the present invention is to provide an RFID tag and a temperature control method that can reduce costs and easily control the temperature of an item with good accuracy. [Means for solving the problem]

[0007] One aspect of the present invention is an RFID tag that has an IC chip and an antenna that generates power by electromagnetic induction arranged on a substrate, and that also includes a capacitor and a conductive change member that changes conductivity depending on temperature and is attached so as to be in contact with the capacitor, and the capacitance of the capacitor changes depending on whether the conductive change member has transitioned to a conductive state depending on temperature.

[0008] One aspect of the present invention is a temperature management method in which an RFID tag is arranged on a substrate and includes an IC chip, an antenna that generates power through electromagnetic induction, and a capacitor, and a conductive change member that changes conductivity depending on temperature and is attached so as to be in contact with the capacitor, the capacitance of the capacitor changing depending on whether the conductive change member has transitioned to a conductive state depending on temperature, and the RFID tag is attached to an item to be managed, and a measured value of the capacitance of the capacitor is obtained from the RFID tag. [Effects of the Invention]

[0009] According to the present invention, the temperature at which an item has been placed can be easily obtained by measuring the capacitance of the capacitor in the RFID tag. Furthermore, according to the present invention, by attaching an RFID tag to each item and managing the temperature of the item, it is possible to perform temperature management of the item inexpensively and accurately. Furthermore, according to the present invention, since a battery is not required, it does not become an obstacle when transporting the item by air. [Brief explanation of the drawings]

[0010] [Figure 1]1 is a plan view showing the configuration of an RFID tag according to a first embodiment of the present invention. [Figure 2] 1 is a cross-sectional view showing the configuration of an RFID tag according to a first embodiment of the present invention. [Figure 3] FIG. 1 is an explanatory diagram of an RFID tag according to a first embodiment of the present invention. [Figure 4] FIG. 1 is an explanatory diagram of an RFID tag according to a first embodiment of the present invention. [Figure 5] FIG. 10 is a plan view showing the configuration of an RFID tag according to a second embodiment of the present invention. [Figure 6] FIG. 10 is an enlarged view showing a portion where a conductivity change member is arranged in an RFID tag according to a second embodiment of the present invention. [Figure 7] FIG. 10 is an explanatory diagram of an RFID tag according to a second embodiment of the present invention. [Figure 8] FIG. 10 is an explanatory diagram of an RFID tag according to a second embodiment of the present invention. [Figure 9] FIG. 10 is a plan view showing the configuration of an RFID tag according to a third embodiment of the present invention. [Figure 10] FIG. 10 is an explanatory diagram of an RFID tag according to a third embodiment of the present invention. [Figure 11] FIG. 10 is an explanatory diagram of an RFID tag according to a third embodiment of the present invention. [Figure 12] FIG. 10 is an explanatory diagram of an RFID tag according to a third embodiment of the present invention. [Figure 13] FIG. 10 is an explanatory diagram of an RFID tag according to a third embodiment of the present invention. [Figure 14] FIG. 10 is a plan view showing the configuration of an RFID tag according to a fourth embodiment of the present invention. [Figure 15] FIG. 10 is a plan view showing the configuration of an RFID tag according to a fifth embodiment of the present invention. [Figure 16] FIG. 10 is a plan view showing the configuration of a modified example of the present invention. [Figure 17] FIG. 10 is an explanatory diagram of a modified example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First Embodiment 1 and 2 are a plan view and a cross-sectional view showing the configuration of an RFID tag 1 according to a first embodiment of the present invention.

[0012] The RFID tag 1 has an IC chip 20, an antenna 30, and a capacitor 40 arranged on one main surface (mounting surface) of a base material 10 made of PET (polyethylene terephthalate) resin or the like. The upper surface of the mounting surface of the RFID tag 1 is covered by being laminated with a surface material 50. The surface material 50 can be made of a resin-based material such as PET or transparent PET, or paper. An adhesive layer 60 is provided on the opposite main surface of the RFID tag 1. The adhesive layer 60 is a layer to which an adhesive is applied, and may be, for example, double-sided tape. The RFID tag 1 can be attached to an article such as a commodity by means of the adhesive layer 50. This adhesive layer 50 may be an adhesive layer that uses a hot melt instead of an adhesive.

[0013] The IC chip 20 is an integrated circuit of semiconductor electronic components. Various information about an item is stored in the IC chip 20. For example, the IC chip 20 stores information about the item to which the RFID tag 1 is attached. The IC chip 20 also has the function of executing various controls and data processing in the RFID tag 1. The IC chip 20 also has the function of executing a process to detect the capacitance of the capacitor 40.

[0014] The antenna 30 inputs and outputs data to and from an external reader / writer, and generates power through electromagnetic induction. A loop antenna, in which wiring is wound in a spiral shape (which may be a polygonal spiral) on a plane, is used as the antenna 30. The antenna 30 is formed by vapor deposition or etching of a metal such as aluminum or copper. Alternatively, the antenna 30 may be formed from conductive ink or conductive paste.

[0015] The capacitor 40 is a capacitor whose capacitance changes depending on whether heat is applied until the conductivity change member 70 reaches a certain temperature. The capacitor 40 has wirings 41 and 42. One end of the wirings 41 and 42 is electrically connected to the IC chip 20 as a detection end 43, and the other end is an open end 44 arranged close to each other, forming a pair of electrodes. The wirings 41 and 42 are arranged so that a portion between one end and the other end is spaced apart from each other. In this embodiment, the conductivity change member 70 is provided at the open end 44 so as to straddle the wirings 41 and 42. That is, on one main surface of the RFID tag 1, the conductivity change member 70 is provided at a position facing (overlapping) the wiring 41 and the wiring 42 at the open end 44 when viewed vertically to the main surface.

[0016] The conductivity change member 70 is a member that transitions to a conductive state when heat is applied until the temperature reaches or exceeds a certain reference temperature. That is, the conductivity change member 70 has a large resistance value (for example, infinity) below the reference temperature and is in a non-conductive state. When heat is applied from the outside until the temperature reaches or exceeds the reference temperature, the conductivity change member 70 transitions to a conductive state (for example, several hundred Ω or less). Furthermore, the conductivity of the conductivity change member 70 is irreversible, and once it becomes conductive, it maintains its conductivity and exhibits almost no change in conductivity even when the temperature drops below the reference temperature. Such a conductivity change member 70 is, for example, a material in which a conductive material is encapsulated in an insulating capsule that melts when heated. When heat is applied from the outside to a temperature above the reference temperature, the capsule melts and the conductive material seeps out from within the capsule. Furthermore, such a conductivity change member may be formed in a planar shape by including multiple capsules containing a conductive material in an insulating substrate.

[0017] As described above, in the first embodiment of the present invention, the conductivity change member 70 is provided on the open end 44 side of the wirings 41 and 42 so as to straddle the wirings 41 and 42. The IC chip 20 measures the capacitance value of the capacitor 40, and by referring to the measurement result, the temperature environment in which the item is placed can be determined. This will be described below.

[0018] 3 and 4 are explanatory diagrams of the RFID tag 1 according to the first embodiment of the present invention. Fig. 3 shows a state when the temperature is low, and Fig. 4 shows a state when the temperature is equal to or higher than a reference temperature.

[0019] As described above, the conductivity change member 70 has a high resistance when the temperature is lower than the reference temperature (when it has never exceeded the reference temperature), and transitions to a conductive state when the temperature exceeds the reference temperature. Therefore, the conductivity change member 70 can be regarded as a switch that switches between the wiring 41 and the wiring 42 from off to on depending on the temperature. When the temperature is below the reference temperature, the resistance of the conductivity change member 70 is high. Therefore, as shown in FIG. 3 , the switch formed by the conductivity change member 70 is off, and the open end 44 is in an open state. In this state, the wirings 41 and 42 function as electrodes for the area of the capacitor 40, and the measured capacitance of the capacitor 40 increases.

[0020] 4, when the temperature is heated to a reference temperature or higher, the conductivity change member 70 transitions to a conductive state, and the switch formed by the conductivity change member 70 turns on the line between the wiring 41 and the wiring 42. When the switch formed by the conductivity change member 70 is turned on, the wirings 41 and 42 are electrically connected (short-circuited) at the open end 44 via the conductivity change member 70. In this state, the electrodes are short-circuited, so the capacitor 40 loses its function as a capacitor, and the measured capacitance of the capacitor 40 becomes smaller.

[0021] As described above, in the first embodiment of the present invention, the conductivity change member 70 is provided on the open end 44 side of the wirings 41 and 42 so as to straddle the wirings 41 and 42. When the temperature is below a reference temperature, the switch formed by the conductivity change member 70 is off, and the measured value of the capacitance of the capacitor 40 is large. When the temperature is equal to or higher than the reference temperature, the conductivity change member 70 becomes conductive, and the switch formed by the conductivity change member 70 is turned on. As a result, the wirings 41 and 42 are short-circuited at the open end 44, and the measured value of the capacitance of the capacitor 40 is reduced. Therefore, when such an RFID tag 1 is attached to an item for management, the temperature of the item can be managed by communicating with the RFID tag 1 using an external reader / writer and obtaining the measured value of the capacitance of the capacitor 40 from the RFID tag 1. For example, it is possible to determine whether an item to which the RFID tag 1 is attached has been placed in an environment exceeding a reference temperature based on the measured value of the capacitance of the capacitor 40. Furthermore, in this embodiment, power can be supplied by the antenna 30 in the RFID tag 1, so there is no need to install a battery in the RFID tag 1 itself. Furthermore, by attaching the RFID tag 1 to each individual item, the temperature of each item can be managed with high precision. For example, even if multiple items are stored in a single container or the like and it is desired to know the temperature of each item, by providing the RFID tag 1, there is no need to provide a temperature sensor for each individual item, which allows for cost reduction compared to attaching individual temperature sensors. Furthermore, even if the RFID tag 1 is cooled to a temperature below the reference temperature, the conductivity of the conductivity changing member 70 is not lost, so it is possible to determine whether the item has been placed in an environment at a temperature above the reference temperature even after the RFID tag 1 has been cooled to a temperature below the reference temperature.

[0022] <Second embodiment> Next, a second embodiment of the present invention will be described. Fig. 5 is a plan view showing the configuration of an RFID tag 101 according to the second embodiment of the present invention. In this embodiment, conductivity change members 71 and 72 are arranged midway between the detection end 43 and the open end 44 of the wirings 41 and 42. The conductivity change members 71 and 72 are arranged so as to straddle the notched portions of the wirings 41 and 42. Therefore, the conductivity change members 71 and 72 can be regarded as switches that switch parts of the wirings 41 and 42 from an OFF state to an ON state depending on the temperature.

[0023] That is, FIG. 6 is an enlarged view of the portion of the wiring 41 where the conductivity change member 71 is disposed. As shown in FIG. 6, a notch 45 is formed in the wiring 41 midway between the detection end 43 and the open end 44, and the conductivity change member 71 is disposed so as to straddle this notch 45. At low temperatures, the resistance value of the conductivity change member 71 is high, and even if the conductivity change member 71 is in contact with each end of the wiring 41, the wiring 41 is electrically disconnected at the notch 45. When the temperature rises above a reference temperature, the conductivity change member 71 transitions to a conductive state, and the notch 45 of the wiring 41 becomes electrically connected via the conductivity change member 70. Similarly, for the portion of the conductivity change member 72, when the temperature is raised above the reference temperature, the notch of the wiring portion 42 transitions to a conductive state.

[0024] 7 and 8 are explanatory diagrams of an RFID tag 101 according to a second embodiment of the present invention. Fig. 7 shows a state when the temperature is low, and Fig. 8 shows a state when the temperature is equal to or higher than a reference temperature.

[0025] 7, when the temperature is lower than the reference temperature, the resistance values of the conductivity change members 71 and 72 are large, and the switch formed by the conductivity change members 71 and 72 is turned off. When the switch formed by the conductivity change members 71 and 72 is turned off, the electrodes of the capacitor 40 are the portions of the wirings 41 and 42 between the detection end 43 and the conductivity change members 71 and 72. Therefore, the portion of the capacitor 40 that functions as a capacitor is the region S1, and since this region has a small area, the measured capacitance of the capacitor 40 is small.

[0026] 8, when the temperature reaches or exceeds the reference temperature, the conductivity change members 71 and 72 become conductive, and the switch formed by the conductivity change members 71 and 72 is turned on. In this state, the wirings 41 and 42 become electrodes for the region S2 of the capacitor 40, so the area of the electrodes increases and the measured capacitance of the capacitor 40 increases.

[0027] As described above, in this embodiment, when the temperature is below the reference temperature, the resistance values of the conductivity change members 71 and 72 are high, and therefore the wirings 41 and 42 are disconnected at the portions of the conductivity change members 71 and 72. As a result, the area of the portion of the capacitor 40 that functions as a capacitor decreases, and the detected value of the capacitance decreases. In contrast, when the temperature is above the reference temperature, the wirings 41 and 42 are connected at the portions of the conductivity change members 71 and 72. As a result, the area of the portion of the capacitor 40 that functions as a capacitor increases, and the measured value of the capacitance of the capacitor 40 increases. Therefore, the temperature of an item can be managed by obtaining the measured value of the capacitance of the capacitor 40 using an external reader / writer.

[0028] <Third embodiment> Next, a third embodiment of the present invention will be described below. Fig. 9 is a plan view showing the configuration of an RFID tag 201 according to the third embodiment of the present invention.

[0029] 5, in the second embodiment described above, one conductivity change member 71 and one conductivity change member 72 are disposed between the detection end 43 and the open end 44 of the wirings 41 and 42, respectively. In contrast, in this embodiment, a plurality of conductivity change members 71a-71c and 72a-72 are disposed between the detection end 43 and the open end 44 of the wirings 41 and 42. With this configuration, the temperature can be controlled in multiple stages.

[0030] 9, three conductivity change members 71a, 71b, and 71c are arranged midway from the detection end 43 to the open end 44 of the wiring 41. Furthermore, three conductivity change members 72a, 72b, and 72c are arranged midway from the detection end 43 to the open end 44 of the wiring 42. Cutouts are provided in the wirings 41 and 42 at the portions where the conductivity change members 71a and 72a, 71b and 72b, and 71c and 72c are arranged.

[0031] The conductivity change members 71a and 72a, 71b and 72b, and 71c and 72c are arranged so that the temperatures at which they become conductive increase from the detection end 43 to the open end 44. That is, the conductivity change members 71a and 72a become conductive at temperatures T11 or higher. The conductivity change members 71b and 72b become conductive at temperatures T12 or higher (T12>T11). The conductivity change members 71c and 72c become conductive at temperatures T13 or higher (T13>T12>T11).

[0032] 10 to 13 are explanatory diagrams of an RFID tag 201 according to the third embodiment of the present invention. Fig. 10 shows the state when the temperature is below T11. Fig. 11 shows the state when the temperature is equal to or higher than T11 but lower than T12. Fig. 12 shows the state when the temperature is equal to or higher than T12 but lower than T13. Fig. 13 shows the state when the temperature is equal to or higher than T13.

[0033] 10, when the temperature is below T11, the resistance values of the conductivity change members 71a-71c and 72a-72c all increase. Therefore, the switches formed by the conductivity change members 71a-71c and 72a-72c are all turned off. At this time, the electrodes of the capacitor 40 are the portions of the wirings 41 and 42 between the detection end 43 and the conductivity change members 71a and 72a. Therefore, the portion of the capacitor 40 that functions as a capacitor is the region S11, and the measured value C11 of the capacitance of the capacitor 40 becomes small.

[0034] As shown in FIG. 11, when the temperature rises above T11, the conductivity change members 71a and 72a become conductive. Furthermore, until the temperature reaches T12, the resistance values of the conductivity change members 71b and 72b and the conductivity change members 71c and 72c are high. Therefore, the switch formed by the conductivity change members 71a and 72a is in the ON state, and the switch formed by the conductivity change members 71b and 72b and the conductivity change members 71c and 72c is in the OFF state. At this time, the electrodes of the capacitor 40 are the portions of the wirings 41 and 42 between the detection end 43 and the conductivity change members 71b and 72b. Therefore, the area of the portion of the capacitor 40 that functions as a capacitor extends to region S12. Therefore, the measured capacitance C12 of the capacitor 40 is larger than the measured capacitance C11 when the temperature is below T11 (C12 > C11).

[0035] As shown in FIG. 12, when the temperature rises above T12, the conductivity change members 71a and 72a and the conductivity change members 71b and 72b become conductive. Furthermore, the resistance values of the conductivity change members 71c and 72c are high until the temperature reaches T13. Therefore, the switch formed by the conductivity change members 71a and 72a and the conductivity change members 71b and 72b is in the ON state, and the switch formed by the conductivity change members 71c and 72c is in the OFF state. At this time, the electrodes of the capacitor 40 are the portions of the wirings 41 and 42 between the detection end 43 and the conductivity change members 71c and 72c. Therefore, the area of the portion of the capacitor 40 that functions as a capacitor extends to region S13. Therefore, the measured capacitance C13 of the capacitor 40 is larger than the measured capacitance C12 at temperatures below T12 (C13 > C12 > C11).

[0036] 13, when the temperature rises above T13, the conductivity change members 71a and 72a, 71b and 72b, and 71c and 72c all become conductive. At this time, the entire wiring 41 and 42 from the detection end 43 to the open end 44 becomes an electrode of the capacitor 40. Therefore, the area of the portion of the capacitor 40 that functions as a capacitor expands to a region S14. As a result, the measured capacitance C14 of the capacitor 40 is even larger than the measured value C13 when the temperature is lower than T12 (C14>C13>C12>C11).

[0037] As described above, in this embodiment, the temperature can be determined in multiple stages from the measured value of the capacitance of capacitor 40. That is, when the temperature is less than T11, the measured value of the capacitance of capacitor 40 is C11, when the temperature is less than T11 and equal to or less than T12, the measured value of the capacitance of capacitor 40 is C12, when the temperature is less than T12 and equal to or less than T13, the measured value of the capacitance of capacitor 40 is C13, and when the temperature is equal to or greater than T13, the measured value of the capacitance of capacitor 40 is C14, where the relationship is (C14>C13>C12>C11).

[0038] <Fourth embodiment> Next, a fourth embodiment of the present invention will be described below. Fig. 14 is a plan view showing the configuration of an RFID tag 301 according to the fourth embodiment of the present invention.

[0039] In this embodiment, the conductivity change members 71a-71c and 72a-72c are used, each of which changes color depending on temperature. For example, the conductivity change members 71a-72a, 71b-72b, and 71c-72c are white at normal temperatures. The conductivity change members 71a-72a become conductive and change color to red when the temperature reaches a predetermined temperature T11 or higher. The conductivity change members 71b-72b become conductive and change color to green when the temperature reaches a predetermined temperature T12 or higher. The conductivity change members 71c-72c become conductive and change color to blue when the temperature reaches a predetermined temperature T13 or higher. Such a substance can be realized, for example, by encapsulating a conductive material and ink in an insulating material, which are encapsulated in heat and melt, so that the conductive material and ink ooze out of the molten capsules when the temperature reaches a predetermined temperature or higher. The color that changes depending on temperature can be changed by changing the color of the ink encapsulated in the capsules. The other configurations are the same as those of the third embodiment. In this embodiment, temperature control can be performed by measuring the capacitance of the capacitor 40, and temperature control can also be performed visually by observing the colors of the conductivity change members 71a and 72a, 71b and 72b, and 71c and 72c.

[0040] <Fifth embodiment> Next, a fourth embodiment of the present invention will be described. Fig. 15 is a plan view showing the configuration of an RFID tag 401 according to a fifth embodiment of the present invention.

[0041] As shown in FIG. 5, in the RFID tag 101 according to the second embodiment of the present invention, the conductivity change members 71 and 72 are disposed on both the wiring 41 and the wiring 42. In contrast, in this embodiment, the conductivity change member 71 or 72 is disposed on only one of the wiring 41 and the wiring 42. In the example of FIG. 15, the conductivity change member 71 is provided on the wiring 41, and the wiring 42 serves as a common electrode of the capacitor 40. In the second embodiment described above, the conductivity change members 71 and 72 turn on / off the wirings 41 and 42 of both poles of the capacitor 40 in accordance with the temperature. In contrast, in this embodiment, one wiring 42 of the capacitor 40 serves as a common electrode, and the conductivity change member 71 turns on / off one wiring 41 in accordance with the temperature. Other configurations are basically the same as those of the second embodiment.

[0042] <Modifications and application examples> The present invention allows for various modifications and applications. For example, as shown in Fig. 1, in a first embodiment, a conductivity change member 70 is disposed at the open end 44 of the wirings 41 and 42. As shown in Fig. 5, in a second embodiment, conductivity change members 71 and 72 are disposed between the detection end 43 and the open end 44 of the wirings 41 and 42. By combining these embodiments, it is possible to detect temperature changes at multiple stages.

[0043] 16, a conductivity change member 70 is disposed at the open ends 44 of the wirings 41 and 42, and conductivity change members 71 and 72 are disposed midway between the detection ends 43 and the open ends 44 of the wirings 41 and 42. By differentiating the temperature at which the conductivity change member 70 becomes conductive from the temperature at which the conductivity change members 71 and 72 become conductive, it is possible to detect temperature in two stages. Furthermore, by combining the first embodiment with the third and fourth embodiments, it is possible to detect temperature in more stages.

[0044] Furthermore, as shown in FIG. 9, in the third embodiment, the length of the electrodes for the capacitor 40 is changed by turning on / off the conductivity change members 71a to 71c and 72a to 72c depending on the temperature, but as shown in FIG. 17, conductivity change members 73a to 73d may be disposed between the wirings of the capacitors 40a to 40e, and the area of the capacitor may be changed by turning on / off the conductivity change members 73a to 73d depending on the temperature.

[0045] Although an embodiment of the present invention has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the gist of the present invention. [Explanation of symbols]

[0046] 10...substrate, 20...IC chip, 30...antenna, 40...capacitor, 41, 42... Wiring, 50... Surface material, 70, 71, 72, 73... Conductive change members

Claims

1. An RFID tag having an IC chip and an antenna that generates power by electromagnetic induction arranged on a substrate, A capacitor; a conductivity change member whose conductivity changes depending on temperature and attached to the capacitor so as to be in contact with the capacitor; The capacitance of the capacitor changes depending on whether the conductivity change member has transitioned to a conductive state in response to temperature. RFID tags like this.

2. The RFID tag according to claim 1 , wherein the conductivity change member is disposed at an open end of a wiring that serves as an electrode of the capacitor.

3. 3. The RFID tag according to claim 1, wherein the conductive change member is disposed midway between the detection end and the open end of a wiring that serves as an electrode of the capacitor.

4. 4. The RFID tag according to claim 3, wherein a plurality of the conductivity change members are arranged midway between the detection end and the open end of the wiring that serves as the electrode of the capacitor.

5. The RFID tag according to claim 4 , wherein the conductivity-changing member is disposed so that the temperature at which the conductivity changes increases from the detection end toward the open end.

6. 2. The RFID tag according to claim 1, wherein the conductivity-changing member changes its conductivity and color in response to temperature.

7. An RFID tag is an RFID tag that includes an IC chip, an antenna that generates power by electromagnetic induction, and a substrate, and is arranged on the substrate, the RFID tag comprising: a capacitor; and a conductivity change member that changes conductivity depending on temperature and is attached so as to be in contact with the capacitor; the capacitance of the capacitor changes depending on whether the conductivity change member has transitioned to a conductive state in response to temperature, The RFID tag is attached to an item to be managed, and a measurement value of the capacitance of the capacitor is obtained from the RFID tag. This is a temperature control method.

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