JP2008151580A - Wireless tag - Google Patents

Abstract

To provide an apparatus capable of detecting the presence of a specific gas with high accuracy while adopting a simpler configuration than before.
In wireless tags 10 and 10A each having an antenna 30 for wireless communication, a changing substance that causes the communication function to disappear or change due to a specific physical phenomenon caused by a specific gas is disposed at least in part. A wireless tag 10, 10A characterized by the above. By adopting such a configuration, a specific gas in a space can be used without using a large-scale device equipped with a device for applying a voltage to a substance that reacts with a specific gas or detecting its electrical resistance. It is possible to accurately detect the presence or absence.
[Selection] Figure 1

Description

  The present invention relates to a wireless tag.

Conventionally, various sensors for detecting the presence of a specific gas have been proposed. For example, Patent Document 1 discloses a hydrogen sensor that can detect hydrogen with relatively high accuracy. The hydrogen sensor disclosed in Patent Document 1 is formed by laminating a NiZr alloy thin film and a palladium film on an electrically insulating substrate, and the resistance value between electrodes provided on the surface of the NiZr alloy thin film is an absorption amount of hydrogen gas. Hydrogen detection is performed by utilizing the fact that it changes according to the conditions.
JP 2002-328108 A

  However, the hydrogen sensor of the kind disclosed in Patent Document 1 needs to incorporate a device for applying a voltage between the electrodes, a device for measuring the resistance between the electrodes, and the like, and the apparatus becomes a large-scale configuration. There is a problem.

  The present invention has been devised under such a background, and an object thereof is to provide an apparatus capable of accurately detecting the presence of a specific gas while taking a simpler configuration than the conventional one. To do.

  In order to solve the above-described problem, a wireless tag having an antenna for wireless communication, which is a preferred embodiment of the present invention, has a changing substance that extinguishes or changes a communication function when a predetermined physical phenomenon is caused by a specific gas. It is arranged at least partially.

  In this aspect, the change substance is a substance whose impedance changes when it contacts a specific gas, and at least a part of the antenna may be covered with the substance.

  The variable substance may be a substance in which a solid electrolyte is sandwiched between a pair of electrodes that generate an electromotive force when contacted with a specific gas, and a communication function may be generated by the electromotive force generated by the substance.

  According to another preferred aspect of the present invention, a wireless tag includes a coil and another element for transmitting a radio signal from the coil when the coil receives a radio signal having a specific frequency. The coil or the other element is covered with a changing material whose impedance changes only while in contact with a specific gas.

  According to another preferred aspect of the present invention, a wireless tag includes a coil and another element for transmitting a radio signal from the coil when the coil receives a radio signal having a specific frequency. All or part of the coil or the other element is covered with tungsten oxide, which is a variable substance whose impedance changes only while in contact with hydrogen, or a member mixed with the tungsten oxide.

  In this aspect, the other elements include a memory for storing data, a rectifier that rectifies an alternating current induced by the coil receiving a radio signal having a specific frequency, and obtains a direct current, and A power storage unit that stores the acquired direct current; a control unit that reads data from the memory under the action of the stored direct current, and transmits a radio signal obtained by converting the read data from the coil; You may have.

  In addition, the stability of the element may be improved by wrapping at least the change substance, and may be wrapped by a substance having appropriate gas permeability.

  According to the present invention, it is possible to accurately detect the presence of a specific gas while taking a simple configuration.

(First embodiment)
A first embodiment of the present invention will be described. FIG. 1 is a top view showing an appearance of a wireless tag 10 according to the present embodiment. FIG. 2 is a top view showing an internal configuration of the passive type wireless tag 10 according to the present embodiment, and FIG. 3 is a bottom view thereof. 4 is a cross-sectional view taken along line AA in FIG.

  The wireless tag 10 includes an antenna coil 30 serving as an antenna, an IC (Integrated Circuit) 40, and jumper wires 52 and 53 on an upper surface or a lower surface of a substrate 20, and the antenna coil 30 is covered with a resin material 31 mixed with tungsten. In addition, all of them are wrapped with Japanese paper 50 and sealed. The IC 40 and the jumper wires 52 and 53 correspond to “other elements” in the claims.

  More specifically, each substrate 20 is a member obtained by forming a dielectric material in which tungsten oxide is contained in a predetermined ratio in a resin such as polyethylene, polypropylene, or polyester into a plate shape. The tungsten oxide has a property of being electrically conductive while being in contact with hydrogen and having an insulating property when not in contact with hydrogen. In other words, this tungsten oxide is a changing substance whose impedance changes only while in contact with hydrogen.

  As shown in FIG. 2, an antenna coil 30 is disposed around a rectangular region 21 at the substantially center of the upper surface of the substrate 20. The antenna coil 30 is made of a conductive material such as aluminum, copper, or silver, and has a pentagonal shape in which one of four corners of a rectangle is cut out in a five-fold spiral. The shape of the antenna coil 30 is obtained by etching a thin film of a conductive material applied to the upper surface of the substrate 20 to form a conductive line. An IC 40 is disposed in the rectangular region 21 of the substrate 20. The IC 40 is electrically connected to a conductive wire that forms one side of the innermost circumference of the antenna coil 30.

  In addition, a through-hole 51 penetrates in a vertical direction in a right-angled triangular gap 22 formed between one of the four corners of the upper surface of the substrate 20 and an obliquely connected portion of the antenna coil 30. The jumper wires 52 and 53 extend from the through hole 51 toward substantially the center of the upper and lower surfaces of the substrate 20, respectively. Among these jumper wires 52 and 53, the jumper wire 52 on the upper surface of the substrate 20 is the innermost part of the antenna coil 30 so as to straddle each notched portion of the five-fold pentagon forming the antenna coil 30. It is arranged between the peripheral end and the through hole 51.

And between the jumper wire 52 and the antenna coil 30, the insulating layer (not shown) for insulating both is provided. On the other hand, as shown in FIG. 3, the jumper wire 53 on the lower surface is disposed so as to face the jumper wire 52 on the upper surface across the substrate 20. Further, the end of the jumper wire 53 is electrically connected to the auxiliary electric wire 55. The auxiliary electric wire 55 is electrically connected to the end portion of the conductive wire forming one side of the outermost periphery of the antenna coil 30 through the through hole 54. Therefore, a capacitor is formed by each of the antenna coil 30 and the jumper wire 52 facing each other with the insulating layer (not shown) interposed therebetween, and the antenna coil 30 and the jumper wire 53 facing each other with the substrate 20 interposed therebetween. That is, the wireless tag 10 according to the present embodiment includes an LC resonance circuit in which a coil and a capacitor are connected in parallel.

FIG. 5 is an equivalent circuit of the wireless tag 10 according to the present embodiment. As shown in FIG. 5, the wireless tag 10 includes an antenna coil 30, an antenna coil 30 and an upper jumper wire 52, a capacitor 54 including the antenna coil 30 and a lower jumper wire 53, and an IC 40 connected in parallel. Can be expressed as Therefore, when the antenna coil 30 receives a radio signal of a specific frequency (hereinafter simply referred to as “resonance frequency”) that causes the LC resonance circuit to resonate, an AC signal corresponding to the waveform of the radio signal is induced and supplied to the IC 40. Is done. There is a relationship represented by the following formula among the inductance of the coil, the capacitance of the capacitor, and the resonance frequency.

  In the relational expression (1), F is the resonance frequency of the LC resonance circuit. L is the inductance of the coil. C is the capacitance of the capacitor. As described above, the wireless tag 10 according to the present embodiment includes two capacitors in which the antenna coil 30 and the upper jumper wire 52 are opposed to each other, and the antenna coil 30 and the lower jumper wire 53 are opposed to each other. Therefore, the value C to be input to the relational expression (1) is the combined capacitance of both capacitors.

  The capacitance of each capacitor is inversely proportional to the distance between the antenna coil 30 and the jumper wires 52 and 53, and is proportional to the area of the overlapping portion of the antenna coil 30 and the jumper wires 52 and 53. The jumper wire 52 is arranged so as to straddle each notched portion of the five-fold pentagon forming the antenna coil 30. Therefore, as shown in FIG. 4, the overlapping portion of the antenna coil 30 and the jumper wires 52 and 53 is intermittently formed in a skewer shape at the same interval as the width of each of the conductive wires 30 a to 30 f forming each side of the antenna coil 30. Will do.

  As shown in FIG. 4, the antenna coil 30 on the upper surface of the substrate 20 is covered with a resin material 31 mixed with tungsten oxide. The Japanese paper 50 shown in FIG. 1 is a substance that wraps tungsten oxide to improve the stability of the element and has appropriate gas permeability. This Japanese paper 50 is intended to prevent damage caused by water adhering to each element on the substrate 20, such as the IC 40, the antenna coil 30, and the jumper wires 52 and 53, and to allow hydrogen to permeate inside.

  FIG. 6 is a diagram illustrating an internal configuration of the IC 40. As shown in FIG. 6, the IC 40 includes an EEPROM (Electronically Erasable and Programmable Read Only Memory) 41, a rectification unit 42, a power storage unit 43, a CPU (Central Processing Unit: equivalent to a control unit) 44, and a modulation unit 45. ing. The rectifying unit 42 and the CPU 44 are electrically connected to a conductive wire that forms one side of the innermost circumference of the antenna coil 30.

  The EEPROM 41 stores 32-bit data representing a unique ID (Identification) code. The rectifying unit 42 supplies a direct current obtained by rectifying the AC signal induced by the antenna coil 30 to the power storage unit 43. The power storage unit 43 stores the direct current supplied from the rectification unit 42. The CPU 44 reads the data stored in the EEPROM 41 using the direct current stored in the power storage unit 43 as drive power and supplies the data to the modulation unit 45. The modulation unit 45 transmits a radio signal obtained by modulating data supplied to the modulation unit 45 from the antenna coil 30.

  Next, the characteristic operation of this embodiment will be described. The characteristic operation of the present embodiment is caused when the wireless tag 10 is carried in a space where hydrogen exists and a wireless signal having a frequency corresponding to the resonance frequency of the wireless tag 10 is transmitted toward the space. As described above, when the LC resonance circuit of the wireless tag 10 receives a wireless signal having its own resonance frequency, it induces an alternating current, and the alternating current is stored in the power storage unit 43 and becomes the starting power of the CPU 44. However, when the wireless tag 10 is carried into a space where hydrogen is present, the hydrogen passes through the Japanese paper 50 and comes into contact with the tungsten oxide contained in the resin material 31. Then, the tungsten oxide becomes conductive. That is, even the gaps between the conductive wires 30a to 30f, which are portions where the antenna coil 30 and the jumper wires 52 and 53 overlap, are made conductive. In some cases, the inductance L also fluctuates due to a short circuit of the antenna coil 30. As a result, the values of L and C in the above calculation formula (1) vary, and the resonance frequency itself of the LC resonance circuit also varies. Therefore, an alternating current is not induced by the radio signal transmitted so far toward the space, and the data stored in the EEPROM 41 is not transmitted.

  According to the embodiment described above, the presence / absence of hydrogen in the space where the wireless tag 10 is carried can be determined by the presence / absence of a reply from the wireless tag 10 to the wireless signal transmitted toward the space. That is, no response is made even if a reader or reader / writer that transmits a radio signal having a frequency corresponding to the resonance frequency of the wireless tag 10 is brought close. Therefore, it is possible to accurately detect the presence or absence of hydrogen in the space without using a large-scale apparatus equipped with a device for applying a voltage to a substance that reacts with hydrogen and detecting its electrical resistance.

(Second Embodiment)
A second embodiment of the present invention will be described.
The wireless tag 10A according to the present embodiment is a so-called reflective wireless tag that does not include the IC 40. Since the external appearance of the wireless tag 10A according to the present embodiment is the same as that of the first embodiment, the description thereof will be omitted. FIG. 7 is a top view showing an internal configuration of the wireless tag 10A according to the present embodiment, and FIG. 8 is a bottom view thereof. FIG. 9 is a sectional view taken along line BB in FIG. In addition, the same code | symbol is attached | subjected to the same member as 1st Embodiment, and those re-explanations are abbreviate | omitted or simplified.

  As shown in FIG. 7, a rectangular thin film electrode 71 is disposed instead of the IC 40 in the rectangular region 21 at the substantially center of the upper surface of the substrate 20 of the wireless tag 10 </ b> A. The thin film electrode 71 is electrically connected to the innermost end of the antenna coil 30. The antenna coil 30 has a shape in which a rectangle is wound five times. The outermost end of the antenna coil 30 is connected to a through hole 51 penetrating in the vertical direction. As shown in FIG. 8, a lead wire 73 extends from the lower surface side of the through hole 51 toward the thin film electrode 72. That is, in the wireless tag 10A, a capacitor is formed by the thin film electrodes 71 and 72 respectively disposed on the upper and lower surfaces of the substrate 20 and includes an LC resonance circuit. As shown in FIG. 9, the upper surface of the substrate 20 of the wireless tag 10A is covered with a resin material 31 mixed with tungsten. In the first embodiment, only the portion where the antenna coil 30 is disposed on the upper surface of the substrate 20 is covered with the resin material 31. On the other hand, in this embodiment, almost the entire upper surface of the substrate 20 is covered with the covering material 31.

  The presence or absence of hydrogen can be detected by using the wireless tag 10A having such a configuration in combination with a so-called gate-type radio wave transmitter and radio wave receiver. FIG. 10 is a diagram showing a mechanism of hydrogen detection using the wireless tag 10A according to the present embodiment. The radio wave transmitter 81 and the radio wave receiver 82 shown in FIG. 10 are installed so as to face each other across a space to be detected. The radio wave transmitter 81 transmits a radio signal having a frequency corresponding to the resonance frequency of the radio tag 10A toward the space, and the radio wave receiver 82 determines the intensity of the radio signal that has reached itself through the space. measure. In this state, the wireless tag 10A according to the present embodiment is carried in the space. When hydrogen is not present in the space, the LC resonance circuit of the wireless tag 10A resonates and an alternating current is induced, so that the intensity of the wireless signal reaching the radio wave receiver 82 is reduced. On the other hand, when hydrogen is present in the space, the resonance frequency itself of the LC resonance circuit of the wireless tag 10A fluctuates, so that resonance does not occur, and the strength of the wireless signal reaching the radio wave receiver 82 does not decrease.

  Therefore, the presence or absence of hydrogen in the space can be easily detected by referring to the change in the intensity of the wireless signal reaching the radio wave receiver 82 after carrying the wireless tag 10A in the space.

(Other embodiments)
The present invention can be modified in various ways.
In both the above embodiments, the substrate 20 and all the elements on the substrate 20 are wrapped and sealed with Japanese paper 50. On the other hand, even if the substrate 20 and all the elements on the substrate 20 are wrapped and sealed with another material that does not transmit a substance that causes damage to the internal circuit, such as water, but allows hydrogen molecules to pass therethrough, Good.

  In the first embodiment, the modulation unit 45 is built in the IC 40, and the data read from the EEPROM 41 by the CPU 44 is modulated by the modulation unit 45 into a radio signal. On the other hand, a configuration may be adopted in which the modulation unit 45 is not incorporated by causing the CPU 44 to perform data modulation.

  In the first embodiment, the resin material 31 containing tungsten oxide is coated on the antenna coil 30 on the substrate 20 of the wireless tag 10. On the other hand, not the antenna coil 30 but the resin material 31 containing tungsten oxide may be covered between each part in the IC 40. In such a configuration, when hydrogen enters the IC 40 and comes into contact with the tungsten oxide, a short-circuit state is established in which these parts are electrically connected, and normal signal processing cannot be performed. Therefore, it becomes impossible to respond to a radio signal transmitted in the space, and the presence or absence of hydrogen in the space can be detected.

  Further, not only the antenna coil 30 but also the resin material 31 containing tungsten oxide may be covered so as to straddle the jumper wire 52. In such a configuration, when hydrogen touches the resin material 31 containing tungsten oxide, the jumper wire 52 and the antenna coil 30 that should have been electrically isolated by an insulating layer are electrically connected. A short circuit occurs. Therefore, it becomes impossible to respond to the radio signal transmitted in the space, and the existence of hydrogen in the space can be understood.

  In the above embodiment, tungsten oxide is used as a substance that changes from an insulator to a conductor under the action of hydrogen. On the other hand, another changing substance whose impedance changes under the action of a gas other than hydrogen, such as oxygen or nitrogen, may be used instead of tungsten oxide. For example, instead of using a substance with a solid electrolyte sandwiched between a pair of electrodes that generate an electromotive force when it comes in contact with carbon dioxide, the communication function of the wireless tag is generated by the electromotive force generated by the substance due to the contact with carbon dioxide. May be. Alternatively, a substance containing a tin oxide semiconductor may be used instead to detect carbon monoxide, methane, ammonia, or the like.

  The wireless tags 10 and 10A according to both the above embodiments are passive types that do not have a power source inside. On the other hand, you may make it coat | cover the antenna coil 30 on the board | substrate 20 of the active type radio | wireless tag 10 which has a power supply inside with the resin material 31 containing a tungsten oxide. When the active type wireless tag 10 is used, the reader side only needs to maintain the reception state of the radio wave from the wireless tag 10 and needs to transmit a wireless signal having a frequency corresponding to the resonance frequency of the wireless tag 10 by itself. Disappear.

  The wireless tags 10 and 10A according to both the above embodiments cover the resin material 31 containing tungsten oxide from above the antenna coil 30 on the substrate 20. On the other hand, not only the antenna coil 30 but also the entire element including the antenna coil 30 on the substrate 20 may be covered with the resin material 31.

  In both the above embodiments, the antenna coil 30 on the upper surface of the substrate 20 is covered with the resin material 31 mixed with tungsten oxide. On the other hand, the antenna coil 30 on the upper surface of the substrate 20 may be covered with tungsten oxide itself.

  In the first embodiment, the EEPROM 41 is employed as a storage element (memory) built in the IC 40 of the wireless tag 10. On the other hand, other storage elements (memory) such as S-RAM (Static Random Access Memory) and FeRAM (Ferroelectric Random Access Memory) may be adopted.

It is a top view which shows the external appearance of the wireless tag concerning 1st Embodiment of this invention. It is a top view which shows the internal structure of the radio | wireless tag shown in FIG. It is a bottom view which shows the internal structure of the radio | wireless tag shown in FIG. FIG. 3 is a cross-sectional view of the wireless tag shown in FIG. 1 taken along line AA in FIG. 2 is an equivalent circuit of the wireless tag shown in FIG. 1. It is an internal block diagram of IC of the wireless tag shown in FIG. It is a top view which shows the internal structure of the wireless tag concerning 2nd Embodiment of this invention. FIG. 8 is a bottom view showing an internal configuration of the wireless tag shown in FIG. 7. FIG. 8 is a cross-sectional view of the wireless tag shown in FIG. 7 taken along line BB. It is a figure which shows the mechanism of the hydrogen detection using the radio | wireless tag shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10,10A ... Wireless tag, 20 ... Board | substrate, 30 ... Antenna coil (antenna), 31 ... Resin material containing tungsten oxide, 40 ... IC, 41 ... EEPROM, 42 ... Rectification part, 43 ... Power storage part, 44 ... CPU, 45 ... Modulation unit, 50 ... Japanese paper, 51,54 ... Through hole, 52,53 ... Jumper wire, 55 ... Auxiliary wire, 71 ... Thin electrode, 73 ... Lead wire, 81 ... Radio wave transmitter, 82 ... Radio wave receiver

Claims (7)

In a wireless tag having an antenna for wireless communication,
A change substance that causes the communication function to disappear or change due to a specific physical phenomenon caused by a specific gas is disposed at least in part.
A wireless tag characterized by that. The change substance is
A substance whose impedance changes when it comes into contact with a specific gas, and at least a part of the antenna is covered with the substance.
The wireless tag according to claim 1, wherein: The change substance is a substance in which a solid electrolyte is sandwiched between a pair of electrodes that generate an electromotive force when contacted with a specific gas, and a communication function is generated by the electromotive force generated by the substance.
The wireless tag according to claim 1, wherein: A coil and other elements for transmitting a radio signal from the coil when the coil receives a radio signal of a specific frequency are provided on the substrate,
All or part of the coil or the other element is covered with a variable substance whose impedance changes only while in contact with a specific gas.
A wireless tag characterized by that. A coil and other elements for transmitting a radio signal from the coil when the coil receives a radio signal of a specific frequency are provided on the substrate,
All or part of the coil or the other element is covered with tungsten oxide or a member mixed with tungsten oxide, which is a change substance whose impedance changes only while in contact with hydrogen,
A wireless tag characterized by that. The other elements are
A memory for storing data;
A rectifier that rectifies an alternating current induced by the coil receiving a radio signal of a specific frequency, and acquires a direct current;
A power storage unit for storing the acquired direct current; and
A controller that reads data from the memory under the action of the stored direct current, and transmits a radio signal obtained by converting the read data from the coil;
The wireless tag according to claim 5, further comprising: Enveloping at least the changing substance and improving the stability of the element and enclosing the substance with appropriate gas permeability;
The wireless tag according to any one of claims 1 to 6, wherein:

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