JP6780239B2 - RFID tags and diapers for moisture detection - Google Patents

Description

The present invention relates to an RFID tag for detecting moisture that can detect the presence of moisture and a diaper using the RFID tag.

Conventionally, in order to detect the presence of moisture, it has been necessary to use expensive parts such as a semiconductor sensor for humidity detection.

On the other hand, a wireless IC device that more easily detects the presence or absence of water has been proposed (see, for example, Patent Document 1). In this wireless IC device, an insulating material is interposed between the feeding circuit board and the antenna, and when the humidity rises, it is detected that the degree of coupling between the feeding circuit board and the antenna changes and the communicable distance changes. Humidity is detected.

Japanese Patent No. 5182431

Examples of the insulating material include an epoxy resin in which cellulose is dispersed and an epoxy resin in which polyvinyl alcohol is dispersed. However, since these materials have a small volume change with respect to the amount of water and the area where the insulating material is used is limited, the detection sensitivity to the presence or absence of water is not sufficient.

An object of the present invention is to provide an RFID tag for moisture detection capable of detecting moisture with high sensitivity.

The RFID tag for moisture detection according to the present invention includes an RFIC element having a first input / output terminal and a second input / output terminal.
An antenna element having a first radiation electrode connected to the first input / output terminal and a second radiation electrode connected to the second input / output terminal,
A capacitor element connected in series between the first radiation electrode and the second radiation electrode and connected in parallel to the RFIC element.
With
The capacitor element is
A pair of capacitor electrodes and
A water absorbing material sandwiched between the pair of capacitor electrodes
Have,
It is configured to output the change in the dielectric constant due to the water absorption of the water absorbing material as a change in the communication distance or the signal strength.

According to the RFID tag for moisture detection according to the present invention, moisture can be detected with high sensitivity.

(A) is a side sectional view of the RFID tag for moisture detection according to the first embodiment, and (b) is a bottom view. (A) is a schematic cross-sectional view showing a cross-sectional structure of an RFIC element used for the RFID tag for moisture detection according to the first embodiment, and (b) is an equivalent circuit diagram of (a). It is an equivalent circuit diagram as a whole of the RFID tag for moisture detection which concerns on Embodiment 1. FIG. Frequency and transmission of the RFID tag for moisture detection according to the first embodiment (A) before the condenser element is provided, after the condenser element is provided (B), and after the moisture is absorbed by the water absorbing material (C). It is a graph which shows an example of the relationship with an output. It is a schematic diagram which shows the outline of communication with the moisture detection RFID tag included in the diaper with the moisture detection RFID tag which concerns on Embodiment 1. FIG. It is schematic cross-sectional view which shows the structural example of the RFID tag for moisture detection included in the diaper with the RFID tag for moisture detection which concerns on Embodiment 1. FIG. It is a flowchart of the diaper changing method using the diaper with the RFID tag for moisture detection which concerns on Embodiment 1. (A) is a side sectional view of the RFID tag for moisture detection according to the second embodiment, and (b) is a bottom view. (A) is a side sectional view of the RFID tag for moisture detection according to the third embodiment, and (b) is a bottom view. (A) is a side sectional view of the RFID tag for moisture detection according to the fourth embodiment, and (b) is a bottom view. (A) is a side sectional view of the RFID tag for moisture detection according to the fifth embodiment, and (b) is a bottom view. (A) is a side sectional view of the RFID tag for moisture detection according to the sixth embodiment, and (b) is a bottom view. It is a bottom view of the RFID tag for moisture detection which concerns on the modification of Embodiment 6. It is sectional drawing which shows the structural example of the RFID tag for moisture detection included in the diaper with the RFID tag for moisture detection which concerns on Embodiment 7. FIG. (A) is a view seen from the outer surface side of the waterproof material of the diaper with the position mark for attaching the RFID tag for use in the diaper with the RFID tag for moisture detection of FIG. 14, and (a) is (a). ) Is a view from the inner surface side of the waterproof material of the diaper.

The RFID tag for moisture detection according to the first aspect includes an RFIC element having a first input / output terminal and a second input / output terminal, and
An antenna element having a first radiation electrode connected to the first input / output terminal and a second radiation electrode connected to the second input / output terminal,
A capacitor element connected in series between the first radiation electrode and the second radiation electrode and connected in parallel to the RFIC element.
With
The capacitor element is
A pair of capacitor electrodes and
A water absorbing material sandwiched between the pair of capacitor electrodes
Have,
It is configured to output the change in the dielectric constant due to the water absorption of the water absorbing material as a change in the communication distance or the signal strength.

According to the above configuration, the change in the dielectric constant due to the water absorption of the capacitor element into the water absorbing material can be output as the change in the communication distance or the signal strength. Therefore, the water absorption state of the moisture detection RFID tag can be known by detecting the change in the communication distance or the signal strength corresponding to the reading distance.

The RFID tag for moisture detection according to the second aspect further includes, in the first aspect, the first radiation electrode and the counter electrode arranged to face at least a part of the second radiation electrode.
The pair of capacitor electrodes may be formed by the first radiation electrode, the at least a part of the second radiation electrode, and the counter electrode.

In the second aspect of the RFID tag for moisture detection according to the third aspect, even if the water absorbing material has an exposed portion not covered by the counter electrode when viewed from the stacking direction with the counter electrode. Good.

In any one of the first to third aspects, the RFID tag for moisture detection according to the fourth aspect has a communication distance after water absorption of the water absorbing material rather than a communication distance or signal strength of the water absorbing material before water absorption. Alternatively, the signal strength may be reduced.

The diaper with an RFID tag for moisture detection according to the fifth aspect is
With the waterproof material provided on the outer surface,
The water absorbing material provided on the inner surface side of the waterproof material and
An RFID tag for moisture detection provided adjacent to the water absorbing material,
With
The RFID tag for moisture detection is
An RFIC element having a first input / output terminal and a second input / output terminal,
An antenna element having a first radiation electrode connected to the first input / output terminal and a second radiation electrode connected to the second input / output terminal,
A capacitor element connected in series between the first radiation electrode and the second radiation electrode and connected in parallel to the RFIC element.
With
The capacitor element is
A pair of capacitor electrodes and
A water absorbing material sandwiched between the pair of capacitor electrodes
Have,
It is configured to output the change in the dielectric constant due to the water absorption of the water absorbing material as a change in the communication distance or the signal strength.

The diaper with an RFID tag for moisture detection according to the sixth aspect further includes, in the fifth aspect, a counter electrode arranged to face at least a part of the first radiation electrode and the second radiation electrode.
The pair of capacitor electrodes may be formed by the first radiation electrode, the at least a part of the second radiation electrode, and the counter electrode.

In the diaper with an RFID tag for moisture detection according to the seventh aspect, in the sixth aspect, the counter electrode is arranged on the inner surface side of the waterproof material of the diaper.
The second water-absorbing material is common to the first water-absorbing material.
The RFIC element and the antenna element may be arranged on the outer surface side of the waterproof material of the diaper.

The diaper for diapers with an RFID tag for moisture detection according to the eighth aspect is a waterproof material provided on the outer surface and having a mark indicating a place where an antenna element of the RFID tag for moisture detection is arranged.
The water absorbing material provided on the inner surface side of the waterproof material and
On the inner surface side of the water absorbing material, a counter electrode arranged to face the mark of the waterproof material,
With
By arranging the antenna element of the RFID tag on the mark on the outer surface side of the waterproof material, the water absorbing material sandwiched between the antenna element, the counter electrode, and the antenna element and the counter electrode. And, to form a capacitor element.

Hereinafter, the RFID tag for moisture detection and the diaper with the RFID tag for moisture detection according to the embodiment will be described with reference to the attached drawings. In the drawings, substantially the same members are designated by the same reference numerals.

(Embodiment 1)
FIG. 1A is a side sectional view of the RFID tag 10 for moisture detection according to the first embodiment, and FIG. 1B is a bottom view.
The moisture detection RFID tag 10 according to the first embodiment includes an RFIC element 1, an antenna element, and a capacitor element 16. The RFIC element 1 has a first input / output terminal 26a and a second input / output terminal 26b. The antenna element has a first radiation electrode 11 connected to the first input / output terminal 26a and a second radiation electrode 12 connected to the second input / output terminal 26b. That is, each radiation electrode constitutes an electric field type antenna having one end having a feeding end and the other end having an open end. The capacitor element is connected in series between the feeding end of the first radiation electrode 11 and the feeding end of the second radiation electrode 12, and is connected in parallel to the RFIC element 1. Further, the capacitor element 16 includes a pair of capacitor electrodes (first radiation electrode 11 and counter electrode 13, second radiation electrode 12 and counter electrode 13) and a pair of capacitor electrodes (first radiation electrode 11 and counter electrode 13). , And a water absorbing material 14 sandwiched between the second radiation electrode 12 and the counter electrode 13). The moisture detection RFID tag 10 is configured to output a change in the dielectric constant of the water absorbing material 14 due to water absorption as a change in communication distance or signal strength.

According to the moisture detection RFID tag 10, the change in the dielectric constant due to the water absorption of the capacitor element 16 into the water absorbing material 14 can be output as a change in the communication distance or the signal strength. Therefore, the water absorption state of the moisture detection RFID tag 10 can be known by detecting the change in the communication distance or the signal strength corresponding to the reading distance. That is, the tag 10 in the first embodiment does not separately provide an expensive sensor element such as a humidity sensor, but utilizes a change in the capacitance between the radiation electrodes constituting the impedance matching circuit between the antenna element and the RFIC element. Then, the tag can detect the change in the amount of water between the radiation electrodes as the change in the communication distance or the signal strength of the tag.

The components of the moisture detection RFID tag 10 will be described below.

<RFIC element>
FIG. 2A is a schematic cross-sectional view showing a cross-sectional structure of the RFIC element 1, and FIG. 2B is an equivalent circuit diagram of FIG. 2A.
The RFIC element 1 is configured as an RFIC package including an RFIC chip 21 for processing an RFID signal and a multilayer substrate 25 on which the RFIC chip 21 is mounted. The RFIC chip 21 may have a built-in memory circuit and signal processing circuit, and may be sealed with an epoxy resin sealing resin 24 or the like. The RFIC chip 21 is mounted on a multilayer board 25 that constitutes a power feeding circuit via a conductive bonding material 22 and a terminal electrode 23. The power feeding circuit may be formed in the form of a multilayer board.
Further, the multilayer substrate 25 is a ceramic multilayer substrate made of ceramic such as LTCC, and is an element constituting a power feeding circuit such as an L pattern constituting the inductors L1 and L2 and a C pattern constituting the capacitors C1 and C2. Is built-in. The inductor L1 and the inductor L2 have different inductance values from each other, and are magnetically coupled via the mutual inductance M. In terms of equivalent circuit, the feeding circuit further includes a capacitor C _IC . The capacitor C _IC is the stray capacitance of the RFIC chip 21 itself. The feeding circuit includes a resonance circuit mainly composed of inductors L1 and L2 and a capacitor C _IC . The resonant frequency of this resonant circuit corresponds to the carrier frequency. By providing the power feeding circuit in this way, it is possible to prevent the center frequency of the carrier frequency from changing significantly even if the electrical length of the antenna element having the first radiation electrode 11 and the second radiation electrode 12 changes. The multilayer substrate 25 is connected to the first radiation electrode 11 and the second radiation electrode 12 via the terminal electrodes 26a and 26b, respectively.

<Antenna element>
The antenna element is a dipole type antenna including the first radiation electrode 11 and the second radiation electrode 12. The first radiation electrode 11 and the second radiation electrode 12 are each connected to the RFIC element at the feeding end on one end side, and each other side forms an open end, extending in opposite directions from the RFIC element 1. Exists. A capacitor element 16 is connected in series between the first radiation electrode 11 and the second radiation electrode 12.
Although the RFIC element 1, the first radiation electrode 11 and the second radiation electrode 12 are directly connected to the first input / output terminal 26a and the second input terminal 26b, respectively, in FIG. 1A, for example. , Not limited to this. For example, the RFIC element 1 and the first radiation electrode 11 and the second radiation electrode 12 may have any coupling such as capacitive coupling and magnetic field coupling instead of direct connection.

<Capacitor element>
FIG. 3 is an equivalent circuit diagram of the moisture detection RFID tag 10 according to the first embodiment as a whole.
As shown in the equivalent circuit diagram of FIG. 3, the condenser element 16 is connected in series between the first radiation electrode 11 and the second radiation electrode 12, and is connected in parallel to the RFIC element 1. Further, the capacitor element 16 has a pair of capacitor electrodes and a water absorbing material sandwiched between the pair of capacitor electrodes. That is, the capacitor element 16 is a moisture-sensitive capacitor whose capacity value changes depending on the degree of water absorption of the water-absorbing material. The capacitor element 16 may be provided separately from the antenna element, or the capacitor element 16 is configured by providing a counter electrode 13 which is arranged to face at least a part of the first radiation electrode 11 and the second radiation electrode 12. You may. In this case, the pair of capacitor electrodes is composed of a feeding end portion of the first radiation electrode 11, a feeding end portion of the second radiation electrode 12, and a counter electrode 13 facing the feeding end portion of each radiation electrode. Can be done. Specifically, the first capacitor element can be configured by a pair of electrodes of the first radiation electrode 11 and the counter electrode 13. Further, the second capacitor element can be formed by a pair of electrodes of the second radiation electrode 12 and the counter electrode 13. At least one capacitor element 16 is sufficient.
The capacitor element 16 together with the power feeding circuit constitutes a matching circuit for matching the impedances of the RFIC element 1 with the first radiation electrode 11 and the second radiation electrode 12.

<Counter electrode>
The counter electrode 13 is provided so as to face at least a part of the first radiation electrode 11 and the second radiation electrode 12. The counter electrode 13 includes copper foil, copper plate, copper plating film, gold foil, gold plate, gold plating film, aluminum foil, aluminum plate, aluminum film, silver foil, silver plate, silver plating film, etc., which are used as ordinary electrodes. Materials can be used. The material is not limited to the above example, and any commonly used material can be used. Further, the formation of the thin film or the like is not limited to plating, and printing, vapor deposition or the like may be used. Further, the electrode may be formed by using conductive fibers. For example, as shown in Examples described later, aluminum may be vapor-deposited on a resin sheet or resin film such as polyethylene terephthalate (PET) to form a counter electrode.

<Water absorbing material>
A continuous water absorbing material 14 is sandwiched between the first radiating electrode 11 and the counter electrode 13 and between the second radiating electrode 12 and the counter electrode 13. As the water absorbing material 14, for example, a polymer water absorbing material (polymer-based water absorbing material) or the like can be used. Further, an inorganic water absorbing material can also be used. As the water absorbing material, it is preferable that the degree of water absorption is large. Here, the water absorbing material 14 is continuously provided between the first radiation electrode 11 and the counter electrode 13 and between the second radiation electrode 12 and the counter electrode 13, but the present invention is not limited to this. A water absorbing material may be provided separately.

<Detection of water absorption state>
FIG. 4 shows before (A) the condenser element 16 of the moisture detection RFID tag 10 according to the first embodiment is provided, after the condenser element 16 is provided (B), and after the water absorbing material 14 absorbs moisture ((A)). It is a graph which shows an example of the relationship between the frequency of C) and a transmission output. The detection of the water absorption state by the water absorption RFID tag 10 will be described with reference to FIG.
First, the RFID tag 10 for moisture detection forms a matching circuit between the RFIC element 1, the first radiation electrode 11 and the antenna element provided with the second radiation electrode 12 even when the capacitor element 16 is not provided. , Adjusted to obtain the maximum transmission output at a predetermined frequency (Fig. 4: A). Further, when the capacitor element 16 is provided, the capacitor element 16 constitutes a matching circuit between the antenna element including the first radiation electrode 11 and the second radiation electrode 12. Also in this case, when the water absorbing material 14 is before water absorption, there is no significant change in the relationship between the frequency and the transmission output as compared with before the condenser element 16 is provided (FIG. 4: B).
On the other hand, the water absorbing material 14 of the capacitor element 16 absorbs water, so that the capacitance between the first radiation electrode 11 and the counter electrode 13 and the capacitance between the second radiation electrode 12 and the counter electrode 13 are respectively. Change. As a result, the relationship between the frequency and the transmission output changes significantly after the water absorption material 14 as compared with the case before the water absorption, and the transmission output at the predetermined frequency is greatly reduced (FIG. 4: C). For example, in Example 1 described later, the change is 20 dBm or more. In this case, communication between the moisture detection RFID tag 10 and the reader / writer (R / W) becomes impossible. By detecting a change in the transmission output at a predetermined frequency, the water absorption state of the water absorption material 14 of the moisture detection RFID tag 10 can be detected. The relationship between the frequency and the transmission output (A, B, C) in FIG. 4 is an example, and is not limited to this.

In this case, a matching circuit is formed between the RFIC element 1 and the antenna element including the first radiation electrode 11 and the second radiation electrode 12. Therefore, regarding the configuration of the condenser element 16, the material, size, and the like of the water absorbing material 14 can be freely selected as long as the relationship between the frequency and the transmission output is not significantly changed before the water absorbing material 14 absorbs water. Alternatively, the capacitor element 16 may be provided to cause a slight frequency shift. If the frequency shift amount before water absorption by the capacitor element 16 is large and the transmission output before water absorption is significantly deteriorated, the optimum center frequency when the capacitor element 16 is added by changing the circuit constant in the RFID element or the like. so that can be obtained, but it may also be made design changes. Therefore, a material having good water absorption can be used as the water absorbing material 14, and good detection performance can be obtained. Further, the counter electrode 13 may have a large area regardless of the sizes of the first radiation electrode 11, the second radiation electrode 12, and the RFIC element 1. As a result, the allowable range for the positions facing the first radiation electrode 11, the second radiation electrode 12, and the water absorbing material 14 is increased, so that the alignment can be easily performed. Further, the water absorbing material 14 may have a large area regardless of the sizes of the first radiation electrode 11, the second radiation electrode 12, and the RFIC element 1. This makes it easier to absorb the moisture around the RFID tag 10 for moisture detection, and the moisture can be detected with higher sensitivity.
As described above, according to the moisture detection RFID tag 10, the water absorption state can be detected by detecting the change in the transmission output at a predetermined frequency.

Here, the case where the transmission output is maximum at a predetermined frequency before the water absorption material 14 absorbs water and the transmission output decreases at a predetermined frequency after the water absorption material 14 absorbs water has been described, but the present invention is not limited to this. .. For example, the transmission output may be low at a predetermined frequency before the water absorbing material 14 absorbs water, and may increase at a predetermined frequency after the water absorbing material 14 absorbs water. In the latter case, the water absorption state can be detected by detecting that the transmission output increases at a predetermined frequency after the water absorption material 14 absorbs water.

Next, the diaper 30 with the RFID tag for moisture detection using the RFID tag 10 for moisture detection will be described.
FIG. 5 is a schematic view showing an outline of communication with the moisture detection RFID tag 10 included in the moisture detection RFID tagged diaper 30 according to the first embodiment. FIG. 6 is a schematic view showing the configuration of the diaper 30 with the RFID tag for moisture detection according to the first embodiment.
In the detection of the water absorption state in the diaper 30 with the RFID tag for moisture detection, the RFID tag 10 for moisture detection is attached to the diaper 30. As a result, it is possible to know the water absorption state in the diaper by communicating between the reader / writer 40 and the moisture detection RFID tag 10 and detecting a change in the communication distance or the signal strength.

<Diapers with RFID tags for moisture detection>
The diaper 30 with an RFID tag for moisture detection has a waterproof material 32 provided on the outer surface, water absorbing materials 34a and 34b provided on the inner surface side of the waterproof material 32, and moisture detection provided adjacent to the water absorbing material 34a. The RFID tag 10 for use is provided. The moisture detection RFID tag 10 is the same as the moisture detection RFID tag 10, and is connected to the RFIC element 1 having the first input / output terminal 26a and the second input / output terminal 26b and the first input / output terminal 26a. An antenna element having a second radiation electrode 12 connected to the first radiation electrode 11 and the second input / output terminal 26b, and the first radiation electrode 11 and the second radiation electrode 12 are connected in series and A capacitor element 16 connected in parallel to the RFID element 1 is provided. The capacitor element 16 has a pair of capacitor electrodes (first radiation electrode 11 and counter electrode 13, second radiation electrode 12 and counter electrode 13), and a water absorbing material 14 sandwiched between the pair of capacitor electrodes. The moisture detection RFID tag 10 is configured to output a change in the dielectric constant of the water absorbing material 14 due to water absorption as a change in communication distance or signal strength.
The diaper 30 may constitute the whole or a part of the diaper. Further, the diaper 30 may be used as a part of the diaper, that is, as an inner or a pad. In this case, the inner diaper 30 can be replaced without replacing the outer.

The components of the diaper 30 will be described below.

<RFID tag for moisture detection>
Since the moisture detection RFID tag 10 is the same as the moisture detection RFID tag 10, description of the details of its configuration will be omitted.
The Moisture Detecting RFID Tag 10 is provided between the water absorbing material 34a and the water absorbing material 34b in FIG. 6, but is not limited to this. The moisture detection RFID tag 10 may be provided, for example, between the waterproof material 32 and the water absorbing material 34a. Since the diaper 30 may damage the human buttock 50 when it comes into direct contact with the human buttock 50, it is preferable to place the diaper 30 between the diaper 30 and the diaper 50 via a water absorbing material 34b.

<Diapers>
The diaper 30 may be either an integrated diaper or a water-absorbing material for diapers, which is an inner (or pad) in the case of a diaper separated into an outer and an inner. The diaper 30 may be any of infant diapers, adult urine leak pants, urine leak pads, nursing pants, nursing diapers and the like. Further, it may be a diaper for pets. Alternatively, it may be a water absorbing material for diapers which is an inner of these. The age and gender of the user and pet are not limited.

<Water absorbing material>
The water absorbing materials 34a and 34b are components of the diaper 30, and a water absorbing material in which a polymer water absorbing material or the like is arranged can be used. As described above, the moisture detection RFID tag 10 used here may be arranged between the water absorbing material 34a and the water absorbing material 34b, or between the waterproof material 32 and the water absorbing material 34a.

<Waterproof material>
The waterproof material 32 can be used as long as it is provided so as not to wet the outer surface of the diaper 30. For example, a polyolefin-based film, a polyolefin-based non-woven fabric, a polyester-based non-woven fabric, or the like can be used.

<How to change diapers>
FIG. 7 is a flowchart of diaper change when the diaper 30 with the RFID tag for moisture detection of FIG. 6 is used.
(1) The care-requiring person wears the diaper 30 with an RFID tag for moisture detection, or the care-requiring person wears it (S11).
(2) At the time of regular patrol of diaper change, the caregiver reads the moisture detection RFID tag 10 on the diaper 30 of the care recipient, for example, by a smartphone-combined reader 40 arranged at a certain distance (S12). ). The reader 40 is not limited to a smartphone-combined reader, and may be a stationary reader. It may be a handy type reader that is not a smartphone combination type. Stationary readers include those that are laid under the body of a lying caregiver, such as sheets and futons.
(3) It is determined whether or not the specified time has passed after wearing the diaper (S13), and if the specified time or more has passed, the caregiver removes the diaper 30 of the care recipient (S14). , The person requiring long-term care wears or has the new diaper 30 attached with the moisture detection RFID tag 10 attached (S15). After that, the process returns to reading (S12) of the RFID tag 10 for moisture detection.
If the specified time has not passed, the process proceeds to the next step S16.
By changing the diaper according to the time after wearing the diaper in this way, diaper rash, pressure ulcer, etc. can be prevented. For example, when using a diaper that can be absorbed multiple times, if the amount of urination is small, the urine attached to the diaper may come into contact with the body for a long period of time and cause pressure ulcers. Also, in the case of "when urine is not guided to the tag part due to posture" or "when the tag comes off", setting a "specified time" encourages diaper change. It is possible to prevent urine from leaking to the bed or the like.
(4) It is determined whether the signal strength in communication with the moisture detection RFID tag 10 is equal to or higher than the threshold value (S16), and if the signal strength is equal to or higher than the threshold value (YES), the water absorbing material of the moisture detection RFID tag 10 14 indicates that water is not absorbed. That is, there is no water in the diaper 30 yet, and the diaper is not changed (S17), and the reading of the RFID tag 10 during the regular patrol is returned (S12).
On the other hand, when the signal strength in communication with the moisture detection RFID tag 10 is less than the threshold value (NO), it is considered that the water absorbing material 14 is absorbing water. In this case, a considerable amount of water, that is, urine, stool, or the like is present in the diaper 30. Therefore, it can be determined that the allowable amount is full or exceeds the allowable amount, and the process proceeds to the next step S18.

(5) The caregiver removes the diaper 30 of the care recipient (S18), and the care recipient puts on or puts on a new diaper 30 with the moisture detection RFID tag 10 attached (S19).
(6) Immediately after changing the diaper, the moisture detection RFID tag 10 is read by the reader 40 arranged at a fixed distance from the diaper 30 (S20). After that, the process proceeds to step S16 for determining whether the signal strength in communication with the moisture detection RFID tag 10 is equal to or higher than the threshold value. By reading the moisture detection RFID tag 10 immediately after changing the diaper in this way, the initial failure of the moisture detection RFID tag 10 can be detected. In this case, the flow does not end even if the diaper is changed.
It should be noted that the reading of the RFID tag 10 for moisture detection (S20) immediately after the diaper change may not be performed, and the reading of the RFID tag 10 during the regular patrol may be returned (S12). That is, the reading of the moisture detection RFID tag 10 immediately after changing the diaper may be omitted.
As described above, it is possible to change diapers by regular patrols using the smartphone-combined reader 40. Further, in this flowchart, the diaper can be changed repeatedly as many times as necessary according to the actual state.

Here, it is determined whether the signal strength from the moisture detection RFID tag 10 is equal to or higher than the threshold value, and the change in the wireless communication state is detected. As a result, the water absorption state is detected. A threshold value corresponding to the signal strength at the allowable amount may be set so that the diaper is changed when the allowable amount is reached. Therefore, the wet state of the diaper 30 can be grasped more appropriately, and the necessity of changing the diaper can be determined more reliably. For example, when displaying the moisture state in the diaper 30, the wet state of the diaper 30 may be quantified or visualized and displayed. For example, the wet state of the diaper 30 may be displayed by a plurality of colors such as yellow and red to make it easier to understand the necessity of changing the diaper.

Here, when the moisture detection RFID tag 10 is configured so that the communication distance or signal strength after water absorption of the water absorbing material 14 is smaller than the communication distance or signal strength of the water absorbing material 14 before water absorption. Was explained. However, the present invention is not limited to this case, and conversely, for example, in the moisture detection RFID tag 10, the communication distance or signal strength after water absorption of the water absorbing material 14 is larger than the communication distance or signal strength before water absorption of the water absorbing material 14. It may be configured as such.
It should be noted that the series of steps S13 to S15 for determining whether or not a specified time has passed after wearing the diaper is not essential and may be performed as needed.

As described above, since the moisture detection RFID tag 10 according to the first embodiment can be attached to the diaper 30 to detect moisture, it is possible to detect a wet state due to urine, stool, sweat or the like. Further, since the RFID tag 10 for moisture detection is used, it is not necessary to use expensive parts such as a semiconductor sensor for humidity detection, and the configuration can be inexpensive. Moreover, since the configuration itself is simple, it is highly reliable. It is preferable that each water absorbing material 14 of the moisture detection RFID tag 10 has a water absorption equal to or higher than that of the water absorbing materials 34a and 34b of the diaper 30. If the water absorption of the water absorbing material 14 is lower than the water absorption of the water absorbing materials 34a and 34b of the diaper 30, the water absorption performance deteriorates. However, in the case of an application for detecting the upper limit of use of a diaper, the water absorbing material in the diaper absorbs water up to the absorption limit, so that the water absorption of the water absorbing material 14 absorbs water of the water absorbing materials 34a and 34b of the diaper 30. be lower than the sex, the applications that detects the diaper use upper limit, Ru can be used effectively.

(Example 1)
A more specific RFID tag 10 for moisture detection according to the first embodiment will be described. In this RFID tag 10 for moisture detection, a back electrode 13 using aluminum vapor deposition on polyethylene terephthalate (PET) having a size of 5 mm × 5 mm was used. Further, as the water absorbing material 14, a non-woven fabric made of cellulose / acrylic resin (pulp / acrylic ester copolymer) (Trix HV30: manufactured by Hashimoto Cloth Co., Ltd.) was used.
According to the moisture detection RFID tag 10 according to the first embodiment, the transmission output after the water absorbing material 14 absorbs water is reduced by about 20 dBm or more at the center frequency of the communication as compared with the water absorbing material 14 before the water absorption. By absorbing the water in the water absorbing material 14 in this way, a large change in the received power can be detected, so that the water absorption state can be detected with high sensitivity.

(Embodiment 2)
FIG. 8A is a side sectional view of the RFID tag 10a for moisture detection according to the second embodiment, and FIG. 8B is a bottom view.
In comparison with the moisture detection RFID tag according to the first embodiment, the moisture detection RFID tag 10a has the capacitor element 16 on the same side as the RFIC element 1 with respect to the first radiation electrode 11 and the second radiation electrode 12. It differs in that it is provided. That is, the counter electrode 13 and the water absorbing material 14 may be provided on the same side as the RFIC element 1 with respect to the first radiation electrode 11 and the second radiation electrode 12. Further, the counter electrode 13 is provided above the RFIC element 1 and covers the RFIC element 1. Thereby, the RFIC element 1 can be protected. Further, instead of the hard RFIC element 1, for example, a soft PET resin sheet or the like that functions as a counter electrode 13 can be arranged on the outer surface, so that the tactile sensation to human skin can be softened.

(Embodiment 3)
9 (a) is a side sectional view of the RFID tag 10b for moisture detection according to the third embodiment, and FIG. 9 (b) is a bottom view.
Compared with the RFID tag for moisture detection according to the first embodiment, the RFID tag 10b for moisture detection is provided with the counter electrode 13 and the water absorbing material 14 so as to overlap the entire surfaces of the first radiation electrode 11 and the second radiation electrode 12. It differs in that it is. As a result, the first radiation electrode 11 and the second radiation electrode 12 can be stably supported. Further, since the area of the water absorbing material 14 is maximized, the change in the dielectric constant due to the absorption of water into the water absorbing material 14 becomes large, and the water can be detected with higher sensitivity.
Here, the counter electrode 13 and the water absorbing material 14 are provided so as to overlap the entire surfaces of the first radiation electrode 11 and the second radiation electrode 12, but the present invention is not limited to this. For example, the counter electrode and the water absorbing material may be provided so as not to straddle the centers of the first radiation electrode 11 and the second radiation electrode 12 and to overlap only one of the first radiation electrode 11 and the second radiation electrode 12. (Not shown).

(Embodiment 4)
10 (a) is a side sectional view of the RFID tag 10c for moisture detection according to the fourth embodiment, and FIG. 10 (b) is a bottom view. The side sectional view of FIG. 10A is a sectional view seen from the direction AA of FIG. 10B, and shows a sectional view of the hole 17.
The moisture detection RFID tag 10c is different from the moisture detection RFID tag according to the first embodiment in that at least one pore 17 is provided in the counter electrode 13. Since the pores 17 provided in the counter electrode 13 make it easier for the water absorbing material 14 to absorb water, it is possible to detect the water more sensitively.

(Embodiment 5)
11 (a) is a side sectional view of the RFID tag 10d for moisture detection according to the fifth embodiment, and FIG. 11 (b) is a bottom view. The side sectional view of FIG. 11A is a sectional view seen from the BB direction of FIG. 11B, and shows the cross section of the slit 18.
The moisture detection RFID tag 10d is different from the moisture detection RFID tag according to the first embodiment in that the counter electrode 13 is provided with a slit 18. Since the slit 18 provided in the counter electrode 13 facilitates the absorption of water into the water absorbing material 14, the water can be detected with higher sensitivity. A plurality of slits 18 may be provided.

(Embodiment 6)
12 (a) is a side sectional view of the RFID tag 10e for moisture detection according to the sixth embodiment, and FIG. 12 (b) is a bottom view.
Compared with the moisture detection RFID tag according to the first embodiment, the moisture detection RFID tag 10e shows that the water absorbing material 14 covers an exposed portion that is not covered by the counter electrode 13 when viewed from the stacking direction with the counter electrode 13. Have. Specifically, the difference is that the water absorbing material 14 has a portion (exposed portion) protruding from the counter electrode 13. As a result, the water absorbing material 14 easily absorbs the moisture around the RFID tag 10e for moisture detection, so that the moisture can be detected more sensitively. The water absorbing material 14 may have a size larger than that of the counter electrode 13. Alternatively, the water absorbing material 14 may have a portion that protrudes from the counter electrode 13 at least in part. In this case, the water absorbing material 14 may have a size smaller than that of the counter electrode 13 except for the portion protruding from the counter electrode 13.

(Modification example)
FIG. 13 is a bottom view of the moisture detection RFID tag 10f according to the modified example of the sixth embodiment.
The moisture detection RFID tag 10f is wider than the width of the first radiation electrode 11 and the second radiation electrode 12 in which the counter electrode 13 is an antenna element, when compared with the moisture detection RFID tag 10e according to the sixth embodiment. It differs in that. As a result, the allowable range can be widened even when the counter electrode 13, the first radiation electrode 11, and the second radiation electrode 12 are misaligned, and fluctuations in the capacitance value of the capacitor element 16 can be suppressed. Therefore, there is an advantage that the allowable range of dimensions at the time of manufacturing can be widened and practical application can be easily performed. Further, since both the counter electrode 13 and the water absorbing material 14 are wider than the widths of the first radiation electrode 11 and the second radiation electrode 12, the allowable range for the misalignment of the counter electrode 13 and the water absorbing material 14 can be increased.

(Embodiment 7)
<Diapers with RFID tags for moisture detection>
FIG. 14 is a schematic cross-sectional view showing a configuration example of a moisture detection RFID tag 10g included in the moisture detection RFID tagged diaper 30a according to the seventh embodiment. FIG. 15A is a developed view of the waterproof material 32 of the diaper 30a with the position mark 36 for attaching the RFID tag for use in the diaper 30a with the RFID tag for moisture detection in FIG. 14 as viewed from the outer surface side. FIG. 15B is a developed view of the waterproof material 32 of the diaper 30a of FIG. 15A as viewed from the inner surface side.
Compared with the RFID tag for moisture detection according to the first embodiment, the moisture detection RFID tag 10g has a water absorbing material 34a sandwiched between the first radiation electrode 11, the second radiation electrode 12, and the counter electrode 13. It is common with the water absorbing material 34a of the diaper 30a, and differs in that it is a component of the diaper 30a. Further, the counter electrode 13 and the water absorbing material 34a are arranged on the inner surface side of the diaper 30a, and the RFID tag including the RFIC element 1 and the first radiation electrode 11 and the second radiation electrode 12 and the counter electrode 13 is waterproof to the diaper 30a. It differs in that it is arranged on the outer surface side of the material 32. The condenser element is formed by sandwiching the water absorbing material 34a between the first radiation electrode 11 and the second radiation electrode 12 on the outer surface side of the waterproof material 32 of the diaper 30a and the counter electrode 13 on the inner surface side of the diaper 30a. Since this condenser element uses the water absorbing material 34a, which is a component of the diaper 30a, as the water absorbing material, the dielectric constant changes due to the water absorption of the water absorbing material 34a. As a result, the water content inside the diaper 30a can be detected with high sensitivity. Further, since the RFID tag is arranged on the outer surface side of the waterproof material 32 of the diaper 30a, the RFID tag itself does not get wet and can be used repeatedly.

As shown in FIG. 15A, the RFID tag can be easily attached by using the diaper 30a having the position mark 36 for attaching the moisture detection RFID tag 10. In FIGS. 15A and 15B, the position mark 36 shows the shape of the counter electrode 13 as it is, but the present invention is not limited to this. The position mark 36 may be a position mark such as a round shape or a cross shape so as to roughly represent the position of the counter electrode 13 or the position where the RFID tag is attached, instead of the shape of the counter electrode 13 as it is. Alternatively, as the position mark 36, a guide line indicating the position where the RFID tag is attached may be provided.
Further, a water absorbing material 34 is arranged on the inner surface side of the diaper 30a, and a counter electrode 13 is further inserted on the inner surface side of the water absorbing material 34. As the counter electrode 13, for example, as described above, a resin sheet or a resin film printed with conductive ink, a vapor-deposited conductive material, or a fiber or woven fabric woven with conductive fibers is used. You may use it.
Further, by arranging the antenna element of the RFID tag (first radiation electrode 11, second radiation electrode 12) on the position mark 36 on the outer surface side of the waterproof material 32, the diaper 30a with the RFID tag for moisture detection can be configured. .. Specifically, the antenna element (first radiation electrode 11, second radiation electrode 12) arranged at the position mark 36, the counter electrode 13, and the water absorbing material 34 sandwiched between the antenna element and the counter electrode 13. , Can form the capacitor element 16.

In the above, as an example of use of the RFID tag 10 for moisture detection, an example of use of the diaper 30 which is attached to the diaper 30 and has the same is given, but the application is not limited to the above example. For example, the RFID tag 10 for water leakage can be attached to the outside of the water pipe and used as an RFID tag for detecting water leakage to detect water leakage.

The frequency band in which the moisture detection RFID tag is used may be any band such as the LF band, the HF band, the UHF band, and the SHF band. Further, the RFID tag for moisture detection is not limited to the one having a so-called tag function, and may have other functions such as the one having a reader / writer function.

It should be noted that the present disclosure includes appropriately combining any of the various embodiments and / or examples described above, and the respective embodiments and / or embodiments. The effects of the examples can be achieved.

According to the RFID tag for moisture detection according to the present invention, a change in the dielectric constant due to water absorption of the condenser element into the water absorbing material can be output as a change in communication distance or signal strength. Therefore, by detecting a change in communication distance or signal strength, it is possible to know the water absorption state of the RFID tag for moisture detection.

1 RFIC element 10, 10a, 10b, 10c, 10d, 10e, 10f, 10g RFID tag for moisture detection 11 First radiation electrode 12 Second radiation electrode 13 Opposing electrode 14 Water absorption material (second water absorption material)
16 Capacitor element 17 Hole 18 Slit 21 RFIC chip 22 Conductive bonding material 23 Terminal electrode 24 Encapsulating resin 25 Multilayer board 26a First input / output terminal (terminal electrode)
26b 2nd input / output terminal (terminal electrode)
30, 30a Diaper 32 Waterproof material 34a, 34b Water absorbing material (first water absorbing material)
36 RFID tag mounting position mark 40 Reader / writer 50 Buttocks

Claims (5)

An RFIC element having a first input / output terminal and a second input / output terminal,
An antenna element having a first radiation electrode connected to the first input / output terminal and a second radiation electrode connected to the second input / output terminal,
A capacitor element connected in series between the first radiation electrode and the second radiation electrode and connected in parallel to the RFIC element.
With
The capacitor element is
A pair of capacitor electrodes and
A water absorbing material sandwiched between the pair of capacitor electrodes
Have,
It is configured to output the change in dielectric constant due to water absorption of the water absorbing material as a change in communication distance or signal strength.
Further provided with counter electrodes arranged to face at least a part of the first radiation electrode and the second radiation electrode.
At least a part of the first radiation electrode and the second radiation electrode, and the counter electrode.
The pair of capacitor electrodes are constructed by
The water absorbing material is an RFID tag for moisture detection having an exposed portion that is not covered by the counter electrode when viewed from the stacking direction with the counter electrode.
The RFID tag for moisture detection according to claim 1, wherein the communication distance or signal strength after water absorption of the water absorbing material is configured to be smaller than the communication distance or signal strength before water absorption of the water absorbing material.
With the waterproof material provided on the outer surface,
A first water absorbing material provided on the inner surface side of the waterproof material and
An RFID tag for moisture detection provided adjacent to the water absorbing material,
With
The RFID tag for moisture detection is
An RFIC element having a first input / output terminal and a second input / output terminal,
An antenna element having a first radiation electrode connected to the first input / output terminal and a second radiation electrode connected to the second input / output terminal,
A capacitor element connected in series between the first radiation electrode and the second radiation electrode and connected in parallel to the RFIC element.
With
The capacitor element is
A pair of capacitor electrodes and
A second water absorbing material sandwiched between the pair of capacitor electrodes,
Have,
It is configured to output the change in dielectric constant due to water absorption of the second water absorbing material as a change in communication distance or signal strength.
Further provided with counter electrodes arranged to face at least a part of the first radiation electrode and the second radiation electrode.
The first radiation electrode, the at least a part of the second radiation electrode, and the counter electrode.
The pair of capacitor electrodes are constructed by
The second water absorbing material is a diaper with an RFID tag for moisture detection, which has an exposed portion that is not covered by the counter electrode when viewed from the stacking direction with the counter electrode.
The counter electrode is arranged on the inner surface side of the waterproof material of the diaper.
The second water-absorbing material is common to the first water-absorbing material.
The diaper with an RFID tag for moisture detection according to claim 3, wherein the RFIC element and the antenna element are arranged on the outer surface side of the waterproof material of the diaper.
A waterproof material provided on the outer surface side and having a mark indicating a place where the antenna element of the RFID tag is arranged,
The water absorbing material provided on the inner surface side of the waterproof material and
On the inner surface side of the water absorbing material, a counter electrode arranged to face the mark of the waterproof material,
With
By arranging the antenna element of the RFID tag on the mark on the outer surface side of the waterproof material, the water absorbing material sandwiched between the antenna element, the counter electrode, and the antenna element and the counter electrode. And, the capacitor element is composed by
The water absorbing material is a diaper to which an RFID tag for moisture detection can be attached , which has an exposed portion not covered by the counter electrode when viewed from the stacking direction with the counter electrode.

Images