JP7775692B2 - Absorbent article, method of manufacturing same, and moisture detection system including same - Google Patents

Description

The present invention relates to an absorbent article, a method for manufacturing the same, and a moisture detection system including the same.

Conventionally, systems using RFID (Radio Frequency Identification) have been known as a technology for detecting the presence of moisture in absorbent articles. In particular, for nursing care applications, a technology is known in which a wireless communication device such as an IC tag is embedded in a diaper to detect moisture generated by the care recipient's urination, etc.

For example, Non-Patent Document 1 discloses a technology in which a reader transmits a radio wave signal with a frequency of 950 MHz (UHF band) to an IC tag and uses the reflected signal to detect moisture. This technology detects the presence of moisture by utilizing the change in the reflection coefficient when the antenna gets wet.

Patent Document 1 also discloses a technology in which an IC tag equipped with a wetness detection terminal is attached to a diaper, and the presence or absence of moisture is detected based on fluctuations in the voltage value of the wetness detection terminal. With this technology, when the wetness detection terminal detects wetness, the IC tag emits a signal different from that in a dry state, or does not emit a signal at all. Therefore, a reader that communicates with the IC tag detects the wetness of the IC tag based on the type of signal received or the presence or absence of a signal.

Patent Document 2 also discloses a diaper that detects urination using an attached sensor device, and has a structure that includes a guide section for attaching the sensor device to the crotch area of the diaper in order to accurately detect urination while reducing discomfort to the wearer.

Japanese Patent Application Laid-Open No. 2006-349418 Japanese Patent Application Laid-Open No. 2019-130244

Hiromasa Nakajima and three others, "Development of a urination detection system using RFID technology," IEICE Transactions on Electronics, Information and Communication Engineers, Vol. J96-B, No. 12, pp. 1378-1385, December 1, 2013.

However, with the technology described in Non-Patent Document 1, the generation of moisture causes radio waves to be absorbed and the antenna impedance to change significantly, significantly reducing the receiving sensitivity of the IC tag and making it impossible to communicate with the reader, which means that the reader cannot determine whether the IC tag has malfunctioned.

Furthermore, the technology described in Patent Document 1 changes the state or function of the IC chip depending on the detection results of the wetness detection terminal, but this requires a relatively expensive IC chip and technology to mount the IC chip with high precision, posing many cost issues. Furthermore, mounting an IC chip also poses the issue of weak mechanical strength as an IC tag.

Furthermore, with the technology described in Patent Document 2, although the sensor device is positioned in a predetermined position by providing a guide section, the thickness of the sensor device is typically 1 to 30 mm, preferably 1 to 20 mm, and more preferably 1 to 15 mm, and this does not sufficiently reduce the discomfort felt by the wearer.

The present invention was made in consideration of the above, and aims to provide an absorbent article that can accurately detect the generation of moisture with a simple configuration and that causes little discomfort to the wearer.

In order to solve the above-mentioned problems and achieve the objectives, the absorbent article of the present invention is an absorbent article comprising at least a top sheet, an absorbent body, a back sheet, and a sensor having a moisture detection unit, wherein the absorbent body comprises a core that absorbs moisture and a wrap sheet that covers the core, and the sensor is disposed between the wrap sheet and the back sheet of the absorbent body, and the thickness of the sensor is 1 mm or less.

In addition, in the absorbent article according to the present invention, the moisture detection unit includes a conductor, and at least a portion of the conductor contacts the wrap sheet.

Furthermore, in the absorbent article according to the present invention, the thickness of the moisture detection part is 200 μm or less.

Furthermore, in the absorbent article according to the present invention, the moisture detection unit includes a conductor, and the thickness of the conductor is 100 μm or less.

Furthermore, in the absorbent article according to the present invention, the sensor is configured so that no part other than the moisture detection unit comes into contact with moisture.

Furthermore, in the absorbent article according to the present invention, the sensor has an antenna portion.

In addition, in the absorbent article according to the present invention, at least a portion of the antenna section is disposed in the area where the top sheet and the back sheet face each other without sandwiching the absorbent body therebetween.

Furthermore, in the absorbent article according to the present invention, in the above invention, the conductor of the moisture detection unit comprises one or more pairs of opposing patterns that are not directly connected to each other and contain at least a metal element and an organic component.

Furthermore, in the absorbent article according to the present invention, the resistance between one or more pairs of opposing patterns of the moisture detection unit that are not directly connected to each other becomes 10 MΩ or less upon contact with moisture.

Furthermore, in the absorbent article according to the present invention, the sensor has a circuit unit.

In addition, in the absorbent article according to the present invention, the sensor has a circuit section and an antenna section, and the conductive section of the circuit section and the antenna section are not in contact with each other.

The absorbent article according to the present invention is the above invention, in which the moisture detection unit and the circuit unit are formed on the same surface of the same substrate.

Furthermore, in the absorbent article according to the present invention, the circuit section includes a thin-film transistor containing carbon nanotubes.

In addition, the absorbent articles of the present invention are manufactured using a method that uses printing technology in one of the manufacturing processes.

The moisture detection system according to the present invention also includes an absorbent article according to any of the above inventions and a transceiver device equipped with means for wirelessly communicating with the absorbent article.

The present invention provides an absorbent article that accurately detects moisture generation with a simple configuration and causes minimal discomfort to the wearer, as well as a moisture detection system using the same.

FIG. 1 is a plan view showing an absorbent article according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing the absorbent article according to the first embodiment of the present invention. FIG. 3 is a schematic diagram showing a moisture detection unit in a sensor in an absorbent article according to an embodiment of the present invention. FIG. 4 is a plan view showing an absorbent article according to a modified example of the first embodiment of the present invention. FIG. 5 is a schematic diagram showing a first modified example of a sensor in an absorbent article according to an embodiment of the present invention. FIG. 6 is a schematic diagram showing a second modified example of the sensor according to the embodiment of the present invention. FIG. 7 is a schematic cross-sectional view showing a thin film transistor according to an embodiment of the present invention. FIG. 8 is a plan view showing an absorbent article according to a second modification of the first embodiment of the present invention. FIG. 9 is a schematic diagram showing a third modification of the sensor according to the embodiment of the present invention. FIG. 10 is a schematic diagram showing a fourth modified example of the sensor according to the embodiment of the present invention. FIG. 11 is a schematic diagram showing a moisture detection system according to an embodiment of the present invention.

The following describes an embodiment of the present invention (hereinafter referred to as "embodiment") with reference to the accompanying drawings.

(Embodiment 1)
FIG. 1 is a plan view schematically showing an absorbent article according to a first embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along the line XX' in FIG.

The absorbent article 10 according to this first embodiment includes a top sheet 12 on the body side and a back sheet 11 on the clothing side, with an absorbent body 20 sandwiched between the top sheet 12 and the back sheet 11. The absorbent body 20 has a core 21 covered by a wrap sheet 22. A sensor 30 is disposed between the back sheet 11 and the wrap sheet 22 that covers the absorbent body 20.

The absorbent article 10 is not particularly limited in its use or shape, as long as it is an absorbent article designed and manufactured to absorb moisture excreted from the human body. Specific examples of the absorbent article 10 include disposable diapers, feminine hygiene products, and incontinence products. The absorbent article 10 may also be a pad that absorbs moisture. Pants-type diapers, reusable pants, etc. can be worn over such a pad.

The top sheet 12 is not particularly limited in terms of material or configuration, as long as it is permeable to moisture absorbed by the absorbent article 10. Specific examples of the top sheet 12 include liquid-permeable nonwoven fabrics, three-dimensional perforated films, and laminates thereof. It may also be a sheet made by combining various materials, with different properties in terms of moisture permeability and surface condition in different parts. Because the top sheet 12 comes into direct contact with the human body, it is preferable that it be made of a nonwoven fabric that feels pleasant against the skin.

The backsheet 11 is not particularly limited in terms of material or configuration, as long as it is configured to be impermeable to moisture absorbed by the absorbent article 10. Specific examples of the backsheet 11 include nonwoven fabric, non-porous film, porous film, and laminates thereof. It may also be a composite of various materials, resulting in a sheet that is partially moisture-impermeable or has different surface properties. While the backsheet 11 is configured to be moisture-impermeable, it is desirable for it to be vapor-permeable to improve comfort for the wearer.

The core 21 may be made of any material or configuration, as long as it is capable of absorbing and retaining moisture. Specific examples of the core 21 include absorbent materials made of cellulose fibers or water-absorbent polymers.

The wrap sheet 22 is made of a moisture-permeable material, and there are no particular restrictions on its material or configuration, as long as it is capable of holding the core 21. Specific examples of the wrap sheet 22 include paper, nonwoven fabric, perforated film, and laminates and composites thereof.

The top sheet 12, absorbent body 20, and back sheet 11 are bonded together to form the absorbent article 10, but there are no particular restrictions on the bonding method, materials used for bonding, bonding area, bonding range, etc., and any suitable method or configuration can be used for each as long as it can achieve the function of the absorbent article.

In this embodiment 1, the top sheet 12 may have three-dimensional gathers near the long side edges to prevent moisture leakage. Furthermore, tape may be placed near the short side edges of the back sheet 11 to form a pants-type diaper.

Furthermore, to improve the wearing comfort of the wearer, the outer shape of the absorbent article 10 according to this embodiment 1 may be shaped to fit the human body.

In addition, a nonwoven fabric or the like may be placed on the side of the backsheet 11 opposite the topsheet 12 (the side that comes into contact with clothing) to improve the feel.

The sensor 30, although not shown, has a moisture detection section formed on a substrate, which detects moisture excreted from the human body. Moisture excreted from the human body passes through the top sheet 12 and is absorbed by the absorbent body 20. By placing the sensor 30 between the absorbent body 20 and the back sheet 11, moisture absorbed by the absorbent body 20 comes into contact with the moisture detection section of the sensor 30, making it possible to detect moisture excreted from the human body. Furthermore, because the sensor 30 is placed on the back sheet 11 side of the absorbent body 20 rather than the top sheet 12 side, this reduces any discomfort felt by the wearer when wearing the absorbent article 10 and does not impair comfort.

The moisture detection unit changes state depending on the presence or absence of moisture and has the function of detecting the presence of moisture, so there are no particular limitations on its structure, the materials that make it up, or the method of detecting moisture using it. Specific moisture detection unit configurations include, for example, (1) a configuration in which a pair of conductors are arranged with a certain spatial distance between them, and moisture is detected by detecting a change in the conductivity between the conductors when moisture adheres between them; (2) a configuration in which multiple independent conductor patterns are arranged, and moisture is detected by detecting a change in the conductivity between the conductors when moisture adheres between the conductors; (3) a configuration in which multiple independent conductor patterns are arranged, and moisture adheres to a moisture-impermeable insulating material placed on the conductors, and the capacitance between the conductors changes when moisture adheres to the conductor; and (4) a configuration that includes a conductor pattern formed in a loop to obtain a specific inductance, and utilizes the change in capacitance generated in the conductor when moisture approaches the conductor.

There are no particular restrictions on the material or composition of the conductor, as long as it is electrically conductive, but it is preferable that it has low corrosion resistance due to moisture and high conductivity. Specific examples of conductors include inorganic substances containing at least one element selected from the group consisting of gold, copper, silver, nickel, tin, bismuth, lead, zinc, palladium, platinum, aluminum, tungsten, molybdenum, and carbon, mixtures or laminates of the above inorganic substances with organic substances, and conductive organic substances.

Figure 3 shows a schematic diagram of a preferred shape of the moisture detection unit. The moisture detection unit 60 shown in the figure has a pattern of a first electrode 61 and a second electrode 62 on an electrically insulating substrate 63. These electrodes may be connected to an external power source or the like via wiring (not shown).

In the moisture detection unit 60 shown in Figure 3, the first electrode 61 and the second electrode 62 consist of a pair of opposing patterns that contain at least a metal element and an organic component and are not directly connected to each other. Here, when moisture adheres to any part between the first electrode 61 and the second electrode 62, the first electrode 61 and the second electrode 62 become electrically connected via the moisture, and the resistance value between the first electrode 61 and the second electrode 62 decreases. Moisture can be detected by reading this change in resistance value.

Preferably, the metal element is one that has high conductivity and excellent workability, and examples include gold, silver, copper, nickel, tin, bismuth, lead, zinc, palladium, platinum, aluminum, tungsten, molybdenum, and carbon. These metals may be used alone or as alloys. Furthermore, the metal element is preferably contained in particulate form, and may be a mixture of particles of two or more types of metal.

Organic components are not particularly limited, but include monomers, oligomers, polymers, photopolymerization initiators, compounds with carboxyl groups, polymerization inhibitors, plasticizers, leveling agents, surfactants, silane coupling agents, antifoaming agents, pigments, etc.

When the first electrode 61 and the second electrode 62 contain a mixture or laminate of a metal element and an organic component, the electrodes have excellent adhesion to the substrate and are easy to process.

In Figure 3, a comb-shaped pattern is shown as the shape of the opposing pattern, but the shape of the opposing pattern is not limited to this as long as the first electrode and second electrode are opposed to each other.

The opposing patterns formed by the first electrode 61 and the second electrode 62 determine the presence or absence of moisture by detecting a decrease in resistance between the opposing patterns due to the adhesion of moisture. However, from the perspective of ease of determining the presence or absence of moisture using a circuit, it is preferable that the resistance between the opposing patterns be 10 MΩ or less due to contact with moisture.

The thickness of the sensor 30 is 1 mm or less. This is thin enough so as not to reduce the comfort of the wearer. From the viewpoint of achieving both ease of handling during manufacturing of the sensor 30 and improved comfort of the absorbent article for the wearer, the sensor thickness preferably has a lower limit of 10 μm or more, more preferably 50 μm or more, and an upper limit of 500 μm or less.

By adjusting the moisture absorption characteristics of the absorbent body 20, it is possible to control the time it takes for moisture excreted from the human body to reach the sensor 30, and the amount of moisture that reaches the sensor 30. This makes it possible to create an absorbent article in which the sensor 30 detects moisture at the desired time or absorption amount. Methods for adjusting the moisture absorption characteristics of the absorbent body 20 include adjusting the thickness of the core 21, or adjusting the material and composition of the core 21 (for example, changing the composition of the core 21 in the thickness direction).

After the sensor 30 detects moisture, the method for communicating the moisture detection to the wearer or the person changing the absorbent article is not particularly limited. Examples of such methods include a method in which the sensor 30 changes color, a method in which the sensor 30 emits light and/or sound, or a method in which communication is carried out between the sensor 30 and a reading device using a magnetic field, electric field, radio waves, ultrasonic waves, or the like.

The substrate on which the moisture detection unit of the sensor 30 is formed is not particularly limited in material or configuration, as long as it is electrically insulating and can be processed to a thickness of 1 mm or less. To ensure that the absorbent article conforms to the human body when worn, the substrate is preferably flexible. It is also preferable that the substrate is moisture-impermeable. Specific examples of substrates include PET (polyethylene terephthalate) film, PP (polypropylene) film, PVC (polyvinyl chloride) film, and laminates thereof.

From the viewpoint of industrial processability, the thickness of the substrate is preferably 5 μm or more, and more preferably 10 μm or more. On the other hand, from the viewpoint of not reducing the comfort of the absorbent article worn by the wearer, the thickness is preferably 1 mm or less, and more preferably 500 μm or less.

Furthermore, the moisture detection unit detects moisture when, for example, moisture adheres to any part between the first electrode 61 and the second electrode 62, the first electrode 61 and the second electrode 62 become electrically connected via the moisture, reducing the resistance between the first electrode 61 and the second electrode 62. To properly allow moisture to adhere between the first electrode 61 and the second electrode 62, it is desirable for at least one of the first electrode 61 and the second electrode 62, and preferably both, to be in contact with the wrap sheet. In other words, it is preferable for at least a portion of the conductor of the moisture detection unit to be in contact with the wrap sheet.

In addition, to ensure that moisture adheres more appropriately between the first electrode 61 and the second electrode 62, it is preferable that when the absorbent article is worn on the body and the wrap sheet deforms, the moisture detection section also deforms along with the shape of the wrap sheet. To achieve this, it is desirable that the moisture detection section be no thicker than a certain thickness. The thickness of the moisture detection section is preferably no thicker than 200 μm, and more preferably no thicker than 100 μm.

Furthermore, the thickness of the first electrode 61 and the second electrode 62 is preferably thin, preferably 100 μm or less. This is because if the first electrode 61 and/or the second electrode 62 are thick, the aspect ratio of the space formed by the distance between the first electrode 61 and the second electrode 62 and the thickness of the first electrode 61 and the second electrode 62 becomes large, which may make it difficult for moisture to penetrate between the first electrode 61 and the second electrode 62. Having the thickness of the first electrode 61 and the second electrode 62 be 100 μm or less has the effect of making it easier for moisture to adhere between the first electrode 61 and the second electrode 62.

In the first embodiment, the sensor 30 is attached at approximately the center of the absorbent article 10 on a flat surface. This position corresponds to the crotch area of the wearer. However, the attachment position of the sensor 30 is not particularly limited as long as the objective of the present invention can be achieved. From the perspective of increasing the reliability of the sensor and minimizing discomfort felt by the wearer of the absorbent article, it is preferable that the sensor be placed in a location other than approximately the center of the absorbent article.

For example, in a modified version of embodiment 1 shown in Figure 4, the sensor 30, which is disposed between the back sheet 11 and absorber 20 of the absorbent article 15, is positioned not approximately in the center of the plane of the absorbent article 15, but at a position offset in the direction of the long side. In this embodiment, the stress on the sensor 30 is smaller than when the sensor 30 is positioned approximately in the center. This makes it possible to provide an absorbent article equipped with a more reliable sensor.

As described above, embodiment 1 of the present invention provides an absorbent article that accurately detects moisture generation with a simple configuration and causes minimal discomfort to the wearer.

(Variation 1)
Next, modified examples of the sensor used in the absorbent article according to the embodiment of the present invention will be described. Fig. 5 is a diagram schematically illustrating sensor modification 1. The sensor 32 shown in the figure includes an antenna unit 70 in addition to a moisture detection unit 60 on a substrate 40, but otherwise has the same configuration as the sensor 30 included in the absorbent article shown in embodiment 1.

The antenna unit 70 has the function of communicating the status of the moisture detector 60 to a reading device external to the absorbent article 10 without being directly connected to the reading device via a wire. As long as this function is possible, there are no particular limitations on the material, shape, or method of the antenna unit 70.

Regarding the shape of the antenna unit 70, Figure 5 shows a so-called dipole antenna, which is intended for communication with the outside world via radio waves, but this is not limited to this. The antenna unit 70 can have an antenna shape suitable for various communication methods, such as using a loop antenna when communicating with the outside world via a magnetic field, as described below.

As for the method of communication with the outside, for example, if radio waves are used as a method of communication with the outside of the absorbent article 10, the following method can be used as an example. A reading device is placed outside the absorbent article 10, and the reading device irradiates the sensor with radio waves of a specific frequency, which are then received by the antenna unit 70. The state of the moisture detection unit 60 can be recognized by utilizing the fact that the state of the radio waves output from the antenna unit 70 changes depending on the state of the moisture detection unit 60.

Furthermore, for example, when a magnetic field is used as a method of communicating with the outside of the absorbent article 10, the following method can be used as an example. A reading device equipped with a loop-shaped antenna is placed outside the absorbent article 10, and a periodically changing magnetic field is applied from the loop-shaped antenna, generating an electromotive force in the antenna unit 70 through electromagnetic induction. The state of the current caused by this electromotive force changes depending on the presence or absence of moisture in the moisture detection unit 60, and the mutual inductance between the loop-shaped antenna of the reading device and the antenna unit 70 changes. By reading this change, the presence or absence of moisture in the moisture detection unit 60 can be recognized.

In order for the absorbent article 10 to communicate efficiently with an external reading device, it is preferable to use a material with high conductivity for the antenna portion 70. Specific examples of materials that can be used to form the antenna portion 70 include the same materials that can be used to form the conductors described above.

(Variation 2)
6 is a schematic diagram showing sensor variation 2. The sensor 34 shown in the figure includes a circuit section 80 in addition to a moisture detection section 60 and an antenna section 70, but otherwise has the same configuration as the sensor 32 shown in variation 1.

The circuit unit 80 is disposed between the moisture detection unit 60 and the antenna unit 70, and controls the moisture detection unit 60 as well as the antenna unit 70, efficiently communicating between the absorbent article 10 and an external reading device. More specifically, the circuit unit 80 detects moisture by applying a DC voltage, an AC voltage, or a specific electrical signal to the moisture detection unit 60.

When a DC voltage is applied from the circuit unit 80 to the moisture detection unit 60, the current of the applied DC voltage source changes depending on whether or not moisture is present in the moisture detection unit 60. By utilizing this phenomenon, the presence or absence of moisture can be recognized by the circuit unit 80. Furthermore, when a specific electrical signal is applied from the circuit unit 80 to the moisture detection unit 60, the amount of change in that signal changes depending on whether or not moisture is present in the moisture detection unit 60. By utilizing this phenomenon, the presence or absence of moisture can be recognized by the circuit unit 80.

An example of applying a specific electrical signal from the circuit unit 80 to the moisture detection unit 60 is to output a square wave of a specific frequency from the circuit unit 80 to the moisture detection unit 60. By utilizing the phenomenon in which the square wave signal changes depending on the presence or absence of moisture in the moisture detection unit 60, the circuit unit 80 can recognize the presence or absence of moisture.

Furthermore, the circuit unit 80 rectifies the voltage generated by the antenna unit 70 and changes the electrical characteristics of the antenna unit 70, such as impedance, thereby enabling efficient communication between the antenna unit 70 and an external reading device.

The circuit unit 80 is preferably arranged on a substrate and is a collection of functional elements designed to achieve the desired operation. Examples of functional elements include transistors, resistors, capacitors, and diodes, and the circuit unit 80 includes at least one of these.

The circuit unit 80 preferably includes a thin-film transistor containing carbon nanotubes, which allows for the realization of a thin, inexpensive sensor. Figure 7 shows a schematic cross-sectional view of a thin-film transistor containing carbon nanotubes in the semiconductor layer. The thin-film transistor shown in Figure 7 comprises a gate electrode 81, a gate insulating film 82, a semiconductor layer 85, a source electrode 83, and a drain electrode 84 formed on a substrate 43.

The substrate 43 may be separate from the substrate on which the sensor is formed, but it is preferable that it is common to (integrated with) the substrate on which the sensor is formed.

The material constituting the gate electrode 81 is preferably an inorganic substance containing at least one element selected from the group consisting of gold, copper, silver, nickel, tin, bismuth, lead, zinc, palladium, platinum, aluminum, tungsten, molybdenum, and carbon, but the material and formation method are not particularly limited as long as the desired electrical characteristics are obtained.

The material that makes up the gate insulating film 82 is not particularly limited, as long as it provides the desired insulating properties. Examples include silicon oxide, siloxane, alumina, and polyimide. From the perspective of reducing manufacturing costs, it is preferable that the material that makes up the gate insulating film 82 be a material that can be formed using printing technology.

The semiconductor layer 85 contains at least semiconducting carbon nanotubes, and controls the current between the source electrode 83 and the drain electrode 84 using an electric field from the gate electrode 81 via the gate insulating film 82. In order to control the current between the source and drain electrodes with high precision using the electric field from the gate electrode 81, a high proportion of semiconducting carbon nanotubes is preferable. Specifically, it is preferable that 80% or more of the carbon nanotubes are semiconducting, and it is even more preferable that 90% or more are semiconducting.

More preferably, the semiconductor layer 85 includes a carbon nanotube composite having a conjugated polymer attached to at least a portion of its surface. Examples of such carbon nanotube composites include those disclosed in WO 2009/139339.

The material that constitutes the source electrode 83 and the drain electrode 84 may be any conductive material that can be commonly used as an electrode. Examples include indium tin oxide (ITO), gold, silver, copper, aluminum, polysilicon, conductive polymers, and carbon materials. These electrode materials may be used alone, or multiple materials may be layered or mixed for use. From the perspective of reducing manufacturing costs, it is preferable that the material that constitutes the source electrode 83 and the drain electrode 84 be a material that can be formed using printing technology.

With the above configuration, thin-film transistors can be formed inexpensively by using methods such as screen printing, gravure printing, offset printing, inkjet printing, dispenser coating, nozzle coating, and drop-cast coating in the thin-film transistor manufacturing process, which includes forming at least the semiconductor layer 85. This makes it possible to create a thin, highly functional circuit unit 80 at low cost.

In addition to thin-film transistors, the circuit section 80 may also include functional elements such as diodes, resistors, and capacitors. There are no particular restrictions on the type of functional element required, but from the standpoint of manufacturing costs and from the standpoint of not impairing the wearing comfort of the absorbent article for the wearer, it is preferable that the functional element be formed on a substrate using printing technology.

From the perspective of detecting moisture with higher sensitivity, the sensor 34 is preferably a sensor that detects moisture by having the moisture detection unit 60 come into direct contact with moisture. On the other hand, direct contact with moisture can cause deterioration of the circuit unit 80 and antenna unit 70 due to changes in characteristics and corrosion. Therefore, it is preferable to provide a protective layer on these components to prevent them from coming into direct contact with moisture.

In other words, it is preferable that the sensor 34 be configured so that no parts other than the moisture detection unit 60 come into contact with moisture. Specific examples of such configurations include providing the circuit unit 80 and antenna unit 70 with a moisture-impermeable protective layer, while providing the moisture detection unit 60 with a moisture-permeable protective layer or no protective layer at all. This configuration makes it possible to provide a sensor with superior durability. This point is preferably applicable not only to the sensor 34 according to Variation 2, but also to sensors generally applicable to the present invention.

Furthermore, since the proximity of moisture, which is a dielectric, can cause fluctuations in the characteristics of the antenna unit 70, it is preferable that the antenna unit 70 be located as far away from moisture as possible. Therefore, the antenna unit 70 is preferably located in a portion where the top sheet and back sheet face each other without the absorbent body sandwiched between them. Such a portion is, for example, the peripheral edge of the absorbent article 10 according to embodiment 1 of the present invention, an example of which is shown in Figure 8. In the absorbent article 18 shown in Figure 8, the sensor 34 is located across both the portion where the top sheet and back sheet face each other without the absorbent body 20 sandwiched between them, and the portion where the absorbent body 20 is sandwiched between them, and the antenna unit is located in the portion where the absorbent body 20 is not sandwiched between them. This arrangement prevents the antenna unit from coming into contact with the absorbent body 20, which absorbs and retains moisture, making it possible to suppress fluctuations in the antenna unit's characteristics due to moisture.

It is not necessary for the entire antenna to be positioned in a facing area between the top sheet and back sheet without the absorbent body 20 sandwiched between them; as long as the effect of moisture on the antenna can be reduced, it is acceptable for only a portion of the antenna to be positioned in a facing area between the top sheet and back sheet without the absorbent body 20 sandwiched between them.

In Figure 6, there is only one wire between the moisture detection unit 60 and the circuit unit 80, but this is for the sake of schematic illustration, and the number of wires in an actual sensor is not particularly limited. Similarly, in subsequent diagrams showing sensors schematically, the number of wires between the moisture detection unit 60 and the circuit unit 80 is not limited to the number shown.

(Variation 3)
9 is a schematic diagram showing sensor variation 3. The sensor 36 shown in the figure has a moisture detection unit 60, an antenna unit 70, and a circuit unit 80 formed on the same surface of a substrate 40. The configuration of sensor 36 according to variation 3 is the same as that of sensors 32 and 34 shown in variations 1 and 2, except for the points described below.

In the sensor 36 according to this third variation, the moisture detection unit 60, antenna unit 70, and circuit unit 80 are formed on the same surface of the substrate 40, which reduces the thickness of the sensor compared to, for example, mounting a circuit made of an IC chip on the substrate or attaching a separately formed moisture detection sensor to the substrate. This makes it possible to provide a thin absorbent article that causes less discomfort to the wearer.

Here, for example, the moisture detection unit 60 being formed on the surface of the substrate 40 means that the moisture detection unit 60 is formed directly on the surface of the substrate 40, such as by printing at least one of the elements necessary to form the moisture detection unit using printing technology.

Printing technology refers to a technique for forming at least one of the materials that make up each part by printing it directly onto the substrate 40. Examples of printing methods include screen printing, gravure printing, offset printing, inkjet printing, dispenser coating, nozzle coating, and drop-cast coating.

As such, in the method for manufacturing absorbent articles according to an embodiment of the present invention, it is preferable that printing technology be included in the sensor manufacturing process.

By forming the moisture detection unit 60, antenna unit 70, and circuit unit 80 on the same surface, the sensor can be manufactured using a simpler process than if they were formed on both sides. Furthermore, by using the surface on which the moisture detection unit 60, antenna unit 70, and circuit unit 80 are not formed as the attachment section to the absorbent article, the overall area of the sensor can be reduced. Furthermore, by forming the moisture detection unit 60 and circuit unit 80 on the same surface, the moisture detection unit 60 and circuit unit 80 can be integrally formed, enabling more cost-effective manufacturing than if they were fabricated separately. Furthermore, by using the same conductive material for at least one of the circuit unit 80 and the moisture detection unit 60, it is possible to form the moisture detection unit 60 using one of the processes for forming the circuit unit 80. This is advantageous from the perspectives of simplifying the manufacturing process and reducing costs, and also has the advantage of eliminating the need for processes or materials to connect the circuit unit 80 and the moisture detection unit 60.

(Variation 4)
10 is a diagram schematically illustrating a fourth variation of the sensor. The sensor 38 shown in the figure comprises a moisture detection unit 60 and a circuit unit 80 on a first substrate 41, and an antenna unit 70 on a second substrate 42. Other than that, the sensor 38 has the same configuration as the sensor 36 shown in the third variation.

The first substrate 41 and the second substrate 42 are bonded at the area indicated by the double-headed arrow between them. In other words, this sensor 38 has a structure in which the substrate 41 on which the circuit section 80 is formed and the substrate 42 on which the antenna section 70 is formed are bonded together. The bonding area and bonding method are not particularly limited, as long as electrical connection is established between the first substrate 41 and the second substrate 42 at the necessary locations. For example, the substrate with the smaller area of the first substrate 41 or the second substrate 42 may be bonded to the other substrate over its entire surface. Alternatively, only a portion of the substrate with the smaller area may be bonded to the other substrate. Bonding methods include, but are not limited to, adhesive bonding and thermocompression bonding.

Figure 10 shows a sensor in which the first substrate 41 is larger than the second substrate 42, but there is no particular limitation on the size relationship between them. Furthermore, there is no particular limitation on the relationship between the thicknesses of the first substrate 41 and the second substrate 42, but it is preferable for the second substrate 42 to be thinner than the first substrate 41.

The configuration shown in Variation 4 makes it possible to fabricate some of the elements required for the sensor -- the moisture detection unit, circuit unit, and antenna unit -- on separate substrates, enabling manufacturing with only the minimum manufacturing steps required for each element. For example, with the configuration shown in Figure 10, only the antenna unit needs to be manufactured on the second substrate 42, eliminating the need to go through the processes of manufacturing functional elements required for the circuit unit 80, such as transistors, resistors, capacitors, and diodes. This eliminates the use of unnecessary materials during manufacturing and also reduces the amount of electricity and industrial water used in manufacturing, thereby reducing the environmental impact of sensor manufacturing.

Furthermore, by allowing the thicknesses of the first substrate 41 and the second substrate 42 to be freely selected depending on the respective functions, manufacturing process, and other conditions, it is possible to provide an absorbent article that is inexpensive and provides an improved wearing comfort for the wearer. Specifically, for example, the first substrate 41 includes the moisture detection unit 60 and the circuit unit 80, and therefore requires a relatively complex manufacturing process. To ensure smooth execution of this process and enhance controllability during the process, it is preferable to use a relatively thick substrate. On the other hand, the second substrate 42 includes only the antenna unit 70 and can be manufactured by simply forming a conductor pattern for the antenna. This reduces the number of manufacturing processes and heat treatment steps, making it possible to use a relatively thin substrate. In other words, compared to when all elements are constructed from the same substrate, although the thickness of the adhesive portion increases, the portion of the second substrate 42 alone can be made thinner. As a result, it is possible to provide a sensor that provides an improved wearing comfort as a whole.

It is desirable to manufacture the antenna unit 70 in a large size from the perspective of improving its characteristics, such as communication distance and communication speed. On the other hand, from the perspective of cost and comfort for the wearer, it is desirable to manufacture the antenna unit 70 in a small size. When determining the size of the antenna unit 70, it is desirable to take these trade-off relationships into consideration and design it with the required characteristics in mind.

In this case, as shown in Variation 4, a first substrate 41 is used to form the circuit section 80 and moisture detection section 60, and a second substrate 42 is used to form the antenna section. By thinning the second substrate 42, material costs can be reduced and the thickness can be made such that it does not cause discomfort to the wearer. This reduces the constraints on increasing the size of the antenna section 70, making it possible to improve the communication characteristics with the outside of the absorbent article.

When bonding at least two substrates together, as in Variation 4, electrical connection is required between each substrate. Therefore, it is generally preferable to achieve electrical connection by bonding the substrates together so that the conductive portions of each substrate are in physical contact. Hereinafter, achieving electrical connection in this manner will be referred to as "making a physical connection."

On the other hand, when making a physical connection, the relative positions of the substrates must be strictly controlled before they are bonded together, which is likely to increase costs. If such concerns arise, it is preferable to bond the substrates together so that the conductive parts of each substrate do not come into contact with each other. Hereinafter, making an electrical connection using this method will be referred to as "making a contactless connection." Making a contactless connection eliminates the need to precisely align the substrates, making it possible to manufacture sensors more inexpensively.

For example, when a non-contact connection is made in a sensor having a circuit unit and an antenna unit, the conductive part of the circuit unit and the antenna are not in direct contact. In other words, the conductive part of the circuit unit and the antenna are not in contact. Note that non-contact connection is possible not only in the sensor according to Variation 4, but also in the sensors according to Variations 2 and 3 described above.

When making a contactless connection, for example, in variant example 4, the electrical connection between the circuit unit 80 and the antenna unit 70 can be achieved by using electric fields and magnetic fields, either singly or in combination. One method for achieving electrical connection through electric field coupling is to arrange patterns on the circuit unit 80 and the antenna unit 70 that cause capacitive coupling between them, and then capacitively couple the two via an electrically insulating material. Another method for achieving electrical connection through magnetic field coupling via the second substrate 42 is to form loop-shaped conductor patterns on the circuit unit 80 and the antenna unit 70, respectively, and establish an electrical connection between the two patterns using electromagnetic induction.

(Moisture detection system)
Fig. 11 is a diagram schematically illustrating a moisture detection system 100 using an absorbent article 10 according to an embodiment of the present invention. The moisture detection system 100 shown in the figure is composed of the absorbent article 10 and a reading device 90 that is a means for wirelessly communicating with the absorbent article 10. The absorbent article 10 also includes the top sheet, absorbent body, back sheet, etc. shown in the embodiments so far, but these are omitted in Fig. 11.

Information about the presence or absence of moisture inside the absorbent article 10 can be communicated between the absorbent article 10 and the reading device 90 without connecting a physical wire, and the moisture status of the absorbent article 10 can be detected by the reading device 90. Although not shown in Figure 11, the reading device 90 is connected to an external network line and is equipped with a system that notifies the wearer or the worker replacing the absorbent article as necessary.

By building the system described above, it becomes possible to notify the moisture status of absorbent articles, and by replacing the absorbent articles when necessary, the wearer of the absorbent articles can continue to feel comfortable.

10 Absorbent article 11 Back sheet 12 Top sheet 15 Absorbent article 18 Absorbent article 20 Absorbent body 21 Core 22 Wrap sheets 30, 32, 34, 36, 38 Sensor 40 Substrate 41 First substrate 42 Second substrate 43 Substrate 60 Moisture detection unit 61 First electrode 62 Second electrode 63 Substrate 70 Antenna unit 80 Circuit unit 81 Gate electrode 82 Gate insulating layer 83 Source electrode 84 Drain electrode 85 Semiconductor layer 90 Reading device 100 Moisture detection system

Claims (15)

An absorbent article comprising at least a top sheet, an absorbent body, a back sheet, and a sensor having a moisture detection unit,
The absorbent body comprises a core that absorbs moisture and a wrap sheet that covers the core,
the sensor is disposed between the wrap sheet and the back sheet of the absorbent body;
The thickness of the sensor is 1 mm or less,
the sensor has a circuit portion and an antenna portion,
the circuit portion is provided on a first substrate, and the antenna portion is provided on a second substrate;
An absorbent article characterized in that the conductive portion of the circuit portion and the antenna portion are configured to be out of contact with each other . The absorbent article of claim 1, wherein the moisture detection unit includes a conductor, and at least a portion of the conductor contacts the wrap sheet. The absorbent article according to claim 1 or 2, wherein the moisture detection portion has a thickness of 200 μm or less. The absorbent article according to any one of claims 1 to 3, wherein the moisture detection unit includes a conductor, and the thickness of the conductor is 100 μm or less. The absorbent article according to any one of claims 1 to 4, wherein the sensor is configured so that no part other than the moisture detection section comes into contact with moisture. The absorbent article according to any one of claims 1 to 5, wherein the sensor has an antenna portion. The absorbent article of claim 6, wherein at least a portion of the antenna section is disposed in a portion where the top sheet and the back sheet face each other without sandwiching the absorbent body therebetween. The absorbent article of any one of claims 1 to 7, wherein the moisture detection unit includes a conductor, and the conductor is composed of one or more pairs of opposing patterns that are not directly connected to each other and contain at least a metal element and an organic component. The absorbent article of claim 8, wherein the resistance between one or more pairs of opposing patterns that are not directly connected to each other in the moisture detection unit becomes 10 MΩ or less upon contact with moisture. The absorbent article according to any one of claims 1 to 9, wherein the sensor has a circuit portion. The absorbent article according to claim 10 , wherein the sensor is configured such that the moisture detection section and the circuit section are formed on the same surface of the same substrate. The absorbent article according to claim 10 or 11 , wherein at least one type of conductive material in the circuit portion is the same as the conductive material forming the moisture detection portion. The absorbent article according to any one of claims 10 to 12 , wherein the circuit portion includes a thin film transistor containing carbon nanotubes. The method for manufacturing an absorbent article according to any one of claims 1 to 13 , characterized in that a printing technique is included in the manufacturing process of the sensor. A moisture detection system comprising the absorbent article according to any one of claims 1 to 13 and a transceiver device having means for wirelessly communicating with the absorbent article.