WO2006008866A1

WO2006008866A1 - Moisture sensor

Info

Publication number: WO2006008866A1
Application number: PCT/JP2005/008604
Authority: WO
Inventors: Mitsuru Fujiwara; Keizo Sakamoto
Original assignee: Kabushiki Kaisha Awajitec
Priority date: 2004-07-16
Filing date: 2005-05-11
Publication date: 2006-01-26
Also published as: KR20070043692A

Abstract

A moisture sensor (1) comprising an electrode sheet (3) having a base sheet and a pair of electrodes (11) arranged on the base sheet. The electrode sheet (3) is dielectric when it is dry but conductive when it is moist. A filter sheet (5) is laid on top of the electrode sheet (3). The filter sheet (5) exhibits water repellency and has a large number of small holes (31). An electrical resistive element (27) is arranged for electrically connecting the electrodes (11). The filter sheet (5) is composed of an ethylene-vinyl acetate copolymer film. The electrodes (11) are composed of conductive ink.

Description

Specification

Moisture sensor

Technical field

[0001] The present invention relates to a sensor for detecting moisture. More specifically, the present invention relates to a sensor structure for detecting blood leakage in an artificial dialysis treatment.

Background art

[0002] There is known a technique in which an electrode is detected when a diaper is replaced by detecting a relatively large amount of moisture. For example, a conventional forceuria detection device has been proposed (see, for example, Patent Document 1). The operating state of this urine detector is being checked under a low voltage. This urine detection device includes a salt-containing adhesive. This salt-containing adhesive exhibits insulating properties in a dry state. This salt-containing adhesive has high electrical conductivity when it absorbs moisture contained in urine. Therefore, this salt-containing adhesive functions as a urine detection switch that conducts by moisture contained in urine. When this switch is turned on, a buzzer or other reporting means notifies the presence of urine (water).

[0003] By the way, for example, when leakage of blood in a medical field or leakage of a drug in an infusion or the like is detected, detection of moisture with higher accuracy is required. Specifically, human perspiration and other disturbance factors as false positives must be eliminated. A typical example is hemodialysis treatment. In this treatment, a dialysis monitoring device is used. This dialysis monitoring device has a function of detecting an abnormality in the concentration of dialysate. However, in this treatment, bleeding from needle removal must be checked by medical personnel. There are various causes of this needle pull-out accident, which may be caused by a patient's consciousness disorder, body movements due to itching and shoulder and back pain, etc., and coma during treatment.

[0004] Therefore, in order to prevent a needle pulling accident, a patrol by a nurse needs to be performed, for example, every 15 minutes. However, there are times when nurses are busy and there are limits to human checks. Therefore, the withdrawal of needles that relied on human attention There is a risk in checking. Therefore, conventionally, a moisture detection device has been proposed for more accurately detecting leakage of a liquid to be detected such as blood during artificial dialysis (see, for example, Patent Document 2).

FIG. 9 shows a conventional moisture detection device 41. FIG. 10 is a partial enlarged cross-sectional view of the moisture sensor 43 provided in the moisture detection device 41.

The moisture sensor 43 has a water absorbing material 45. The water absorbing material 45 has an overlay U and an underlay L having water absorption. Overlay U and underlay L show electrical insulation in the dry state. An electrode 49 is sandwiched between the underlay L and the overlay U. The electrode 49 has an electric resistance element 47. A conductive adhesive 51 is interposed between the underlay L and the overlay U. The electrode 49 is sandwiched between the underlay L and the overlay U via the conductive adhesive 51. The conductive adhesive 51 is configured to have a high conductivity upon water absorption (an electrical resistance value of about several kilo ohms). In the moisture sensor 43, the resistance value of the electric resistance element 47 is set to, for example, about 20Ω. As a result, the conventional moisture detection device 41 can self-check for contact failure of the moisture detection device 41 at all times. In addition, the moisture detecting device 41 does not detect normal sweat and does not detect normal sweat because the electrical resistance value decreases when the conductive adhesive 51 contains sufficient moisture. Can be reliably detected.

[0007] However, the human constitution is extremely diverse, and the salt concentration in sweat varies from 0.3 mass% to 1.

There is a variation of about 7% by mass. Furthermore, the amount of sweating varies from person to person. Therefore, when the moisture sensor 43 of the moisture detection device 41 is used, for example, wrapped around a person's arm, the absorbent material 45 may absorb a large amount of sweat after a long period of time. In such a case, the moisture detection device 41 may erroneously detect the perspiration as a liquid to be detected such as blood.

Patent Document 1: Japanese Patent Application Laid-Open No. 2002-55074

Patent Document 2: Japanese Unexamined Patent Application Publication No. 2004-177120

Disclosure of the invention

[0009] The present invention has been made with a strong background, and an object of the present invention is to provide a moisture sensor that is less prone to erroneous detection due to sweat or the like other than the liquid to be detected. In order to achieve the above object, a moisture sensor according to the present invention includes a base sheet and an electrode sheet having a pair of electrodes arranged on the base sheet. This electrode sheet exhibits insulation in a dry state and conductivity in a state containing moisture. The moisture sensor includes a water-repellent filter sheet superimposed on the electrode sheet, and a water-permeable and water-retaining sheet superimposed on the filter sheet. The filter sheet has a large number of small holes.

[0011] An adhesive layer for adhering the electrode sheet and the sheet having water permeability and water retention may also serve as the filter sheet.

[0012] It is preferable that an electrical resistance element for electrically connecting the pair of electrodes is disposed.

[0013] More preferably, the filter sheet has an ethylene acetate vinyl copolymer film strength having a wall thickness of 10 μm to 100 μm.

[0014] It is preferable that the small holes are uniformly arranged as a whole in the effective area of the moisture sensor, and the inner diameter of the small holes is set to an lmm force of 4 mm. The density of the small holes is preferably set to 50 to 500 per 100 cm ² .

[0015] The electrode is preferably printed on the base sheet using a conductive ink.

[0016] Preferably, the base sheet includes a hydrophilic sheet and a reinforcing film made of polyester sandwiched therebetween.

[0017] The electrode is preferably in contact with a conductive adhesive that absorbs moisture and enhances conductivity.

[0018] The conductive adhesive is preferably a paste containing starch as a hydrophilic polymer and 10% or more and 21% or less saline as an aqueous electrolyte solution.

[0019] The conductive adhesive is preferably applied to a hydrophilic sheet or penetrated into the hydrophilic sheet.

[0020] The moisture sensor according to the present invention does not react to human sweat and reliably detects a large amount of water contained in blood, urine or the like locally. Therefore, this moisture sensor is used when blood or other liquid to be detected leaks at the site of artificial dialysis treatment. Is reliably detected.

Brief Description of Drawings

FIG. 1 is a perspective view of a moisture sensor according to a first embodiment of the present invention.

[FIG. 2] FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is an exploded perspective view of the moisture sensor according to the first embodiment of the present invention.

FIG. 4 is a wiring diagram of the detection device according to the first embodiment of the present invention.

FIG. 5 is a perspective view showing a usage state of the moisture sensor according to the first embodiment of the present invention.

FIG. 6 is a diagram schematically showing an electric circuit between the moisture sensor and the patient's arm according to the first embodiment of the present invention in artificial dialysis.

FIG. 7 is an exploded perspective view of a moisture sensor according to a second embodiment of the present invention.

FIG. 8 is a diagram schematically showing an apparatus for forming an adhesive layer of a moisture sensor according to a second embodiment of the present invention.

FIG. 9 is a conceptual diagram showing a conventional moisture detection device.

FIG. 10 is a partial enlarged cross-sectional view of a moisture sensor that is a detection unit of the moisture detection device. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

[0023] <First embodiment>

As shown in FIG. 1, the moisture detection device A includes a moisture sensor 1 as a detection unit and a display unit D. The moisture sensor 1 and the display unit D are connected via a connector C. The structure of the moisture sensor 1 will be described with reference to FIGS. In FIG. 3, the upper side is the side where the liquid to be detected comes into contact with the moisture sensor 1 in use.

The moisture sensor 1 includes an electrode sheet 3, a filter sheet 5, and a sheet 7 having water permeability and water retention. The electrode sheet 3 exhibits insulation in a dry state and conductivity in a state containing moisture. The electrode sheet 3 includes a base sheet 9 and a pair of electrodes 11 (1 la, ib) disposed on the base sheet 9. Electrode sheet 3 is electrolytic It contains a toxic substance and is highly hydrophilic. Therefore, when the electrode sheet 3 contains moisture, the conductivity of the electrode sheet 3 increases. That is, the electrical resistance value becomes small.

[0026] The material of the base sheet 9 of the electrode sheet 3 is not particularly limited as long as the electrode 11 is stably supported. In other words, the base sheet 9 only needs to have mechanical strength that cannot be easily broken with a small force and water resistance that does not swell or dissolve by self-absorbing moisture in the air. As shown in FIG. 2, in this electrode sheet 3, the base sheet 9 has an overlaid base sheet 13 and an underlaid base sheet 15. The overlaid base sheet 13 is in a position where the liquid to be detected comes into contact with the underlaid base sheet 15 in advance. The underlay base sheet 15 is in a position to support the electrode 11 with a downward force.

The electrode 11 is disposed on the base sheet 9. This base sheet 9 has electrical insulation in a dry state. The base sheet 9 is preferably hydrophilic and flexible. As the material of the base sheet 9, polyethylene, polypropylene, nylon, polyethylene terephthalate, polycarbonate, polychlorinated bule, polysalt butadiene, polyimide, silicone rubber, silicone resin, cloth, paper and the like can be employed. In particular, as a material constituting the base sheet 9, paper, cloth, non-woven fabric and the like which are hydrophilic cellulose fibers are preferably used. Of these, Japanese paper is preferred. This is because Japanese paper is thin, environmentally friendly and strong, and has hydrophilic properties.

As shown in FIGS. 2 and 3, the underlay base sheet 15 includes a reinforcing sheet 17, an upper sheet 19, and a lower sheet 21. An upper sheet 19 is disposed on the front surface side of the base sheet 9 with the reinforcing sheet 17 interposed therebetween, and a lower sheet 21 is disposed on the back surface side of the base sheet 9 with the reinforcing sheet 17 interposed therebetween. The reinforcing sheet 17, the upper sheet 19, and the lower sheet 21 are integrally formed. As will be described later, the underlying base sheet 15 does not wrinkle while maintaining flexibility even when the electrode 11 is printed. There are no particular restrictions on the material and thickness of the reinforcing sheet 17. However, the material constituting the reinforcing sheet 17 has a relatively high rigidity and a certain degree of flexibility (typically, a resin film such as polyester, polypropylene, polyethylene, polysalt cellulose). Can be adopted.

[0029] Since the underlay base sheet 15 has the laminated structure as described above, the electrode 11 is removed. Attaching work becomes easy. When Japanese paper is used as the material constituting the upper sheet 19 and the lower sheet 21, it is preferable that an adhesive is used on both the upper and lower surfaces of the reinforcing sheet 17. Thereby, the adhesiveness of the upper sheet 19 and the lower sheet 21 is ensured. The size of the base sheet 9 is appropriately determined according to the application of the moisture sensor 1. For example, when the moisture sensor 1 is used to monitor blood leakage during artificial dialysis, the base sheet 9 is typically about the A4 size of paper. The thickness dimension of the base sheet 9 varies depending on the electrode 11, the material of the base sheet 9, and the laminated structure of the base sheet 9. However, the thickness dimension of the base sheet 9 is preferably about 0.5 mm to 3 mm. Thereby, the base sheet 9 has a certain flexibility and is easy to handle.

[0030] This base sheet 9 is usually made of a hydrophilic material. The base sheet 9 is infiltrated with a predetermined electrolyte solution and then dried. The electrode sheet 3 is configured by arranging the pair of electrodes lla and ib on the base sheet 9 in parallel. In addition, after the pair of electrodes lla and lib are arranged in parallel to the base sheet 9, a predetermined electrolyte solution is infiltrated into the base sheet 9 and dried to form the electrode sheet 3. Also good. The electrolyte solution preferably contains a hydrophilic polymer as will be described later. Examples of the electrolyte of the electrolyte solution include inorganic salts such as sodium chloride, potassium chloride, and sodium nitrate, ammonium salts, alkali metal salts of fatty acids, and alkali metal salts of glutamic acid. These salts are electrically conductive because they dissolve in water and ionize. Among these electrolytes, sodium chloride is particularly preferable. Because salt is a strong electrolyte, it has a stable conductivity with little difference in solubility depending on temperature, and has the power of being inexpensive. It is preferable that the salt is a water-soluble liquid of 10% by mass to 21% by mass.

[0031] In the case where the electrode 11 is electrically connected because the electrode sheet 3 locally contains moisture, the probability of erroneous detection is high. In order to realize accurate detection, it is important that a certain amount of moisture (for example, about 5 cc to 10 cc) is detected when the moisture is diffused into the electrode sheet 3. In order to achieve a relatively uniform diffusion of moisture, an electrolyte solution containing a hydrophilic polymer is preferably used.

[0032] Furthermore, when an electrolyte solution containing a hydrophilic polymer is employed, moisture is removed from the electrode case. When the moisture is dried, the electrical insulation of the electrode sheet 3 is stably maintained. This hydrophilic polymer is preferably water-soluble. Examples of the hydrophilic polymer include cellulose, starch, and pectin. In particular, starch such as rice starch, wheat starch, potato starch and corn starch is preferred. These have the advantage of also functioning as an adhesive. Further, among the above starches, potato starch is more preferably used because of its high degree of adhesion.

[0033] Specific examples of the water-soluble adhesive 24 containing an electrolyte include, for example, potato 1 mass% to 5 mass%, sodium chloride 15 mass% to 21 mass%, and water 74 mass% to 84 mass%. Can be employed. The amount of the salt may be an amount in the vicinity of saturation solubility that can be dissolved in water at room temperature. This glue is produced by mixing water, salt and potato starch and stirring with heating. And if this stirring product exhibits a uniform consistency, conductive paste will be manufactured by cooling this.

[0034] The electrode 11 is prepared separately. The electrode 11 is sandwiched between the base sheets 9. The electrode 11 is configured by arranging flexible and fine conductive wires in parallel at a predetermined interval. The thickness dimension of this conductive wire is set to 0.3 mm or less. The electrode 11 is preferably formed in a film shape and has flexibility. The electrode 11 may be formed of a conductive thread or a fine metal wire. For example, when the base sheet 9 is woven or non-woven, the electrode 11 may be sewn directly to the base sheet 9. The conductive yarn may be a twisted metal fiber. The electrode 11 may be formed of a tape-like conductive plate (for example, aluminum foil) that is thinly extended.

Specifically, the electrode sheet 3 is manufactured by covering the underlying base sheet 15 with the underlying base sheet 13 after the electrodes 11 are wired on the underlying base sheet 15. The electrode 11 is in close contact with the underlying base sheet 15 and the underlying base sheet 13. Thereby, the moisture sensor 1 can perform a stable detection operation. Further, the use of the conductive adhesive 24 containing the electrolyte solution makes the detection operation of the moisture sensor 1 more stable. As described above, since the conductive adhesive 24 includes a polymer component, the gap between the pair of electrodes l la and l ib is wet in proportion to the amount of absorbed water. Therefore, when the amount of absorbed water reaches a predetermined amount, the electrodes 11 are electrically connected. In other words, The difference between the conductivity between the electrodes 11 when the moisture sensor 1 is in a dry state and the conductivity between the electrodes 11 when water is contained becomes clear.

[0036] The conductive adhesive 24 is applied or infiltrated into the hydrophilic sheet. It is preferable that the lower surface (the surface facing the electrode 11) of the overlay base sheet 13 is covered with the conductive adhesive 24. As a result, the electrode 11 and the underlying base sheet 15 are integrated together. Further, the conductive adhesive 24 is provided on the entire lower surface of the overlay base sheet 13, and the overlay base sheet 13 is bonded to the underlay base sheet 15, whereby the electrode 11 and the base sheet 9 are integrated. Specifically, the starch paste is sprayed on the lower surface of the overlay base sheet 13. This starch paste contains a nearly saturated amount of sodium chloride as described above. Then, this overlay base sheet 13 is affixed to the underlying base sheet 15. However, the electrode 11 may be sandwiched in the base sheet 9 in a state of being embedded in the water-soluble paste, and then the water-soluble paste may be dried.

[0037] The electrode 11 is preferably printed on the base sheet 9. In this case, the conductive ink 25 is employed as a material constituting the electrode 11. This facilitates the production of a homogeneous electrode sheet 3. As the conductive ink 25 used for the electrode 11, a conductive metal paste is suitable. As the conductive metal paste, a paste obtained by dispersing fine particles of gold, silver, platinum, palladium, copper or the like in a binder resin is used. The conductive metal paste is printed on a heat-resistant base sheet 9 such as Japanese paper or polyimide, whereby the electrode 11 is formed. In the present embodiment, the electrode 11 is made of a pair of conductive metal pastes of the same type. As shown in FIG. 1 and FIG. 3, each conductive metal paste is arranged in parallel at equal intervals from the pair of electrode terminals T, and is disposed on almost the entire surface of the base sheet 9. The pair of electrode terminals T are provided at two force points on one end of the base sheet 9. The electrode 11 meanders uniformly to cover the entire surface of the base sheet 9!

[0038] The metal particles contained in the conductive metal paste are ultrafine particles and are uniformly dispersed. The electrode 11 is fired at a low temperature of about 120 ° C to 240 ° C. Thereby, the electrode 11 is printed on the base sheet 9 without damaging the base sheet 9. As shown in FIG. 3, in the present embodiment, an electrode 11 made of silver paste is printed on the base sheet 9. In this embodiment, the width dimension of the electrode 11 to be printed is about 2 mm. [0039] Between the pair of electrodes 11, an electric resistance element 27 for electrically connecting the pair of electrodes 11 is disposed. By providing the electric resistance element 27, the electrode sheet 3 does not contain moisture, and even between the electrodes 11 is energized. By providing the electric resistance element 27, the moisture sensor 1 can operate without using a high voltage. In addition, the moisture sensor 1 can distinguish whether the moisture present is the liquid to be detected or other moisture to be detected. The resistance value of the electric resistance element 27 is normally set to about 20 kΩ force and 50 μΩ. The effect of the electric resistance element 27 will be described in detail later.

[0040] Like the electrode 11, the electric resistance element 27 is preferably printed with the conductive ink 25. As the conductive ink 25 constituting the electric resistance element 27, carbon ink can be adopted. As the carbon used in the carbon ink, non-graphitizable materials such as phenol resin, furfuryl alcohol, salt vinylidene, cellulose, and wood are preferably used. This ink is a paste obtained by kneading carbon powder and a binder made of a resin such as phenol or epoxy. The conductive ink 25 constituting the electric resistance element 27 is printed on the surface of the upper sheet 19 of the underlay base sheet 15. In the present embodiment, as shown in FIG. 3, the electric resistance element 27 is printed on the upper sheet 19 on the left side in the drawing. That is, the electric resistance element 27 is printed on the edge opposite to the side where the electrode terminal T is disposed. The electric resistance element 27 is printed in a strip shape over the entire width direction of the upper sheet 19. The width of the electric resistance element 27 is set to about 3 mm to 5 mm. As shown in FIG. 2, the electrodes 11 are printed so as to cross over the printed electric resistance elements 27.

As shown in FIG. 3, a filter sheet 5 is disposed on the electrode sheet 3 created as described above. The filter sheet 5 has water repellency and a large number of small holes 31. The filter sheet 5 allows moisture to pass only through the small holes 31. When an amount of moisture that wets a certain area of the filter sheet 5 is present, the moisture passes through the small holes 31 of the filter sheet 5. The filter sheet 5 is formed so as to cover the entire electrode sheet 11. That is, the filter sheet 5 is disposed so as to cover the entire effective area of the electrode sheet 3. Here, the “effective area” means that the electrode sheet 3 is to be examined. This is an area where the intelligent liquid can be detected. Therefore, a marginal end region that does not have conductivity is excluded from the effective region.

[0042] The filter sheet 5 may be simply sandwiched between the electrode sheet 3 and a sheet 7 having water permeability and water retention. However, the filter sheet 5 is preferably integrated with the electrode sheet 3 and the sheet 7 having water permeability and water retention. This makes it easy to handle the filter sheet 5. The filter sheet 5 may be bonded between the electrode sheet 3 and the sheet 7 using an adhesive. The filter sheet 5 is preferably flexible. Thereby, even when the filter sheet 5 is integrated with the electrode sheet 3, it is possible to follow the deformation of the electrode sheet 3 and the like.

[0043] As a material constituting the filter sheet 5, for example, an ethylene vinyl acetate copolymer film is preferably employed. This ethylene acetate butyl copolymer film has high flexibility and can be heat-bonded to the base sheet 9 or the like. The filter sheet 5 is reliably integrated with the electrode sheet 3 by heat-adhering the ethylene acetate butyl copolymer film. As a material constituting the filter sheet 5, a polytetrafluoroethylene film can also be adopted. This polytetrafluoroethylene film can also be heat-bonded to the electrode sheet 3. The wall thickness of the filter sheet 5 is preferably 10 m or more because it is easily damaged when it is too thin. More preferably, the thickness of the filter sheet 5 is 20 μm or more, and more preferably 30 μm or more. If the filter sheet 5 is too thick, the flexibility becomes poor, and therefore it is preferably about 100 m or less. For this reason, the thickness of the filter sheet 5 is more preferably 80 m or less. More preferably, the thickness of the filter sheet 5 is 60 μm or less.

[0044] The shape and size of the small holes 31 of the filter sheet 5 are not particularly limited. In short, as described above, the shape and size of the small holes 31 may be determined so that the moisture passes through the small holes 31 when a certain amount of water is present. The small holes 31 of the filter sheet 5 may be meshes formed as a result of the filter sheet 5 being knitted in a lattice shape. In the present embodiment, this mesh is also included in the small holes provided in the filter sheet 5. The large number of small holes 31 are distributed at equal intervals. If the small holes 31 are too small, they are likely to be filled with foreign substances and other objects. Therefore, the inner diameter of the small hole 31 is 1. Omm or more. It is preferable. More preferably, the inner diameter of the small hole 31 is 1.2 mm or more, and more preferably 1.5 mm or more.

[0045] If the small hole 31 is too large, the probability of passing moisture other than the liquid to be detected increases. Therefore, the inner diameter of the small hole 31 is preferably 4. Omm or less. More preferably, the small hole 31 has an inner diameter of 3.5 mm or less, and more preferably 3. Omm or less. The interval between adjacent small holes 31 is set to about 10 mm in the case of a small hole 31 with an inner diameter of 2. Omm. However, the interval between the small holes 31 can be set as appropriate. If the density of the small holes 31 is too small, detection that the liquid to be detected is difficult to pass through is delayed. Therefore, the number of small holes 31 per 100 cm ² area of the filter sheet 5 is preferably set to about 50 or more and 500 or less.

[0046] It is preferable that the sheet 7 having water permeability and water retention disposed on the filter sheet 5 is formed in a mesh shape or has a structure having micropores or the like. As a result, water can pass through the sheet 7. This sheet 7 can store a certain amount of moisture. And the sheet | seat 7 allows the water | moisture content of the amount exceeding the water retention amount to pass through. As a material constituting the sheet 7, for example, synthetic fibers such as polyvinyl alcohol and polyester, or natural fibers such as cellulose, cotton, hemp, and wool can be employed. And the said sheet | seat 7 is comprised by the woven fabric, nonwoven fabric, or paper which consist of these materials. As a material having water retention or hygroscopicity, cotton or a nonwoven fabric having cellulose fiber strength is more preferable.

[0047] The sheet 7 having water permeability and water retention exhibits a nother effect for holding or dispersing a part of the liquid to be detected. In sweating and the like, water has a large area power. Moisture generated in such a wide area force is absorbed and held in the sheet 7 having water permeability and water retention, and at the same time, is emitted as a gas. As a result, moisture emitted from a wide area such as sweat cannot enter the filter sheet 5 side.

[0048] In the moisture sensor 1 according to this embodiment, for example, even when a person emits moisture due to a large amount of sweat, this is not detected as a liquid to be detected, and the detection accuracy is greatly improved.

As shown in FIG. 4, the display unit D of the detection apparatus A having the moisture sensor 1 includes divided resistance circuits Cl, C2, and C3. The output values of these resistance circuits are compared. This comparison Depending on the result, one of the five types of signals is selected. In Fig. 4, the resistance R0 of the moisture sensor 1 is set to 20kΩ. The resistance circuit C1 is composed of a power source and a resistance 1: 1 (= 201 ^). Resistor circuit C2 also has resistance 2 (= 1001 ^) and variable resistance Rl (= 10kΩ to 20kΩ). Resistor circuit C3 consists of resistor r3 (= 20kΩ) and variable resistor R2 (= 50kΩ force to 100kΩ) force.

[0050] When the wiring of the detection device A is normally connected, the power supply voltage V0 is distributed to the variable resistance R1 and the resistance rl. The voltage added to the variable resistor R1 and the voltage added to the resistor rl are input to the negative signal input terminal of the comparator HI and the positive signal input terminal of the comparator H2, respectively. In addition, when the moisture sensor 1 is not connected or has a poor contact, the voltage V0 of the power supply drops due to the presence of the resistor rl. The value of this dropped voltage is input to comparator HI and comparator H2.

[0051] In the resistor circuit C2, a predetermined voltage is applied to the negative signal input terminal of the comparator H2.

Specifically, for example, when the variable resistor R1 is set to 20 kQ, the voltage V0 XR1Z (r2 + Rl) = V0Z6 is applied to the negative signal input terminal of the comparator H2. In the resistor circuit C3, a predetermined voltage is applied to the positive signal input terminal of the comparator HI. Specifically, when the variable resistor R2 is set to lOOkQ, the voltage V0 XR2 / (r3 + R2) = V0 X5Z6 is applied to the positive signal input terminal of the comparator HI.

[0052] The power supply is connected to the output terminal of the comparator HI through a resistor r4 (= 470 kQ), a red light emitting diode LR1, and a buzzer BZ1. The power supply is connected to the output terminal of the comparator H2 through a resistor r 4 (= 470 kΩ), a red light emitting diode LR2 and a buzzer 2. The power source is grounded via a resistor r4 and a resistor r5 (= 470 kΩ). The output terminals of the comparator HI and the comparator H2 are connected to the signal input terminals of the 2-input AND gate AG. The output terminal of 2-input AND gate AG is connected to blue light emitting diode LB.

[0053] When the moisture sensor 1 is not connected, the output of the comparator HI is at a low level. The low level output of this comparator HI causes the red diode LR1 to emit light and the buzzer BZ1 to sound. When moisture sensor 1 is connected, the two outputs of comparator HI and comparator H2 will be at high level. These two signals are input to the 2-input AND gate AG. The output switches to a high level. As a result, the blue light emitting diode LB emits light. When the moisture sensor 1 absorbs a liquid to be detected (for example, blood) and the resistance value between the electrodes 11 is reduced to several tens of Ω, the output of the comparator H2 becomes a low level. As a result, the red light emitting diode LR2 and the buzzer BZ2 are activated.

As shown in FIG. 5, the moisture sensor 1 according to the present embodiment can be used to detect blood leakage in artificial dialysis. When blood leaks from the needles at the tips of the artificial dialysis tubes 39a and 39b, the moisture sensor 1 is placed at a position where the blood can be received. The moisture sensor 1 is thin and flexible. Therefore, the moisture sensor 1 can be wound around and fixed to the arm of the patient to which the two artificial dialysis tubes 39a and 39b are attached. In particular, when a conventional moisture sensor is wrapped around the arm of a patient with high sweating, the conventional moisture sensor may absorb a large amount of sweat in a short time and falsely detect that the sweat is blood. It was. However, since the moisture sensor 1 according to the present embodiment includes the filter sheet 5, erroneous detection due to detection of sweat is avoided.

[0055] FIG. 6 is a diagram schematically showing an electrical circuit between the moisture sensor 1 and the patient's arm in artificial dialysis.

As shown in the figure, when blood 50 leaks from the patient's arm 51, the arm 51, the needle 52 pierced by the arm 51, and the electrode 11 of the moisture sensor 1 pass through this blood 50. It will be electrically connected to. At this time, the electrodes l la and l ib are electrically connected to each other through the blood 50, and the electric resistance value between the electrodes l la and l ib is rapidly reduced to a few tens of Ω. On the other hand, the electrical resistance value between the electrodes l la and l ib via the arm 51 is close to the electrical resistance value of the skin (about 20 kΩ to 50 kQ), and between the electrodes l la and l ib via the blood 50 It is much larger than the electrical resistance value. Therefore, when blood 50 leaks, current flows between electrodes l la and 1 lb through blood 50, and almost no current flows through arm 51 (about 1 to 2 A). Therefore, the moisture sensor 1 is gentle to the patient.

[0058] Next, a second embodiment of the present invention will be described. In FIG. 7 as well, the liquid to be detected comes into contact with the upper force moisture sensor 40 in the same figure. [0059] The moisture sensor 40 according to the present embodiment differs from the moisture sensor 1 according to the first embodiment in that the moisture sensor 1 has water permeability and water retention as shown in FIG. Whereas the filter sheet 5 is separately disposed between the sheet 7 and the overlaid base sheet 13, the moisture sensor 40 according to the present embodiment has the above-described sheet 7 and overlaid base as shown in FIG. The adhesive layer 41 is formed between the sheet 13 and the sheet 13. In other words, the adhesive layer 41 also serves as a filter sheet having the same function as the filter sheet 5. The other configuration of the moisture sensor 40 is the same as that of the moisture sensor 1.

[0060] The adhesive layer 41 is typically made of urethane resin. However, the adhesive layer 41 may be made of various other materials as long as the material has water repellency. By using urethane resin as the adhesive layer 41, the sheet 7 and the overlying base sheet 13 are securely attached. The adhesive layer 41 has a large number of small holes 42. Since the urethane resin constituting the adhesive layer 41 has water repellency, by providing the small holes 42, the water that has penetrated the sheet 7 side force passes only through the small holes 42 and is overlaid on the base sheet 13 Move to the side. When there is an amount of moisture that wets a certain area of the adhesive layer 41, the moisture passes through the small hole 42. The adhesive layer 41 is disposed so as to cover the entire effective area of the electrode sheet 3 where the liquid to be detected is detected.

[0061] The shape and size of the small hole 42 of the adhesive layer 41 are not particularly limited. However, if the small holes 42 are too small, they are likely to be filled with foreign matters and other things. Accordingly, the inner diameter of the small hole 42 is preferably 1. Omm or more. More preferably, the inner diameter of the small hole 42 is 1.2 mm or more, and more preferably 1.5 mm or more. In addition, the large number of small holes 42 are distributed at equal intervals.

[0062] On the other hand, if the small hole 42 is too large, the probability that moisture other than the liquid to be detected will pass increases. Therefore, the inner diameter of the small hole 42 is preferably 4. Omm or less. More preferably, the inner diameter of the small hole 42 is 3.5 mm or less, and more preferably 3. Omm or less. The interval between adjacent small holes 42 is set to about 1 Omm when the inner diameter of the small holes 42 is 2. Omm. However, this interval can be set as appropriate. If the density of the small holes 42 is too small, it is difficult for the liquid to be detected to pass through and detection is delayed. Therefore, the number of small holes 42 per 100 cm ² area of the adhesive layer 41 is set to about 50 or more and 500 or less. It is preferable.

As shown in FIG. 8, the forming device 43 includes a transfer roller 44 and a pressing roller 45. The transfer roller 44 is rotated about the rotation shaft 46 by a predetermined driving device (not shown). The transfer roller 44 is made of metal or resin, and a large number of recesses 48 are provided on the peripheral surface 47 thereof. The pressing roller 45 is made of grease or rubber, and is disposed adjacent to the radial direction of the transfer roller 44. The overlay base sheet 13 is fed between the transfer roller 44 and the pressure roller 45. The distance between the axes of the transfer roller 44 and the pressure roller 45 is set so that a predetermined gap is formed between them. As a result, the overlying base sheet 13 passing between the transfer roller 44 and the pressing roller 45 is pressed with a predetermined pressing force.

[0064] The adhesive layer 41 is formed by transferring urethane resin to the overlay base sheet 13. Specifically, urethane resin is applied to the peripheral surface 47 of the transfer roller 43. At this time, since the concave portion 48 is provided, the urethane resin is not applied to the portion of the peripheral surface 47 corresponding to the concave portion 48. When the transfer roller 44 is driven and the overlying base sheet 13 is fed between the transfer port roller 44 and the pressure roller 45, the urethane resin applied to the peripheral surface of the transfer port roller 44 is transferred to the overlaid base sheet 13. Is transcribed. At this time, since the concave portion 48 is provided in the transfer roller 44, urethane resin is not transferred to the portion corresponding to the concave portion 48 of the overlay base sheet 13, and the portion where the urethane resin is not transferred is The small hole 42 is formed. In this way, the adhesive layer 41 having the small holes 42 is formed on the overlay base sheet 13. Of course, the adhesive layer 41 can be formed by other methods.

[0065] In addition to the function of the filter sheet 5 according to the first embodiment, the adhesive layer 41 has a function as an adhesive that bonds the sheet 7 and the base sheet 13 to each other. In other words, the adhesive that bonds the sheet 7 and the overlying base sheet 13 has the function of the filter sheet 5. Therefore, it is not necessary to separately configure the filter sheet. As a result, the number of parts of the moisture sensor 40 is reduced, and the manufacturing cost can be reduced.

Claims

The scope of the claims

[I] an electrode sheet having a base sheet and a pair of electrodes arranged on the base sheet, exhibiting insulation in a dry state and conductivity in a state containing moisture;

A filter sheet having water repellency superimposed on the electrode sheet;

A moisture sensor having water permeability and water retention superimposed on the filter sheet, wherein the filter sheet has a large number of small holes.

[2] The adhesive layer for bonding the electrode sheet and the sheet also serves as the filter sheet

The moisture sensor according to claim 1.

[3] An electric resistance element for electrically connecting the pair of electrodes is arranged! The moisture sensor according to claim 1.

[4] An electric resistance element is provided to electrically connect the pair of electrodes! The moisture sensor according to claim 2.

[5] The moisture sensor according to claim 1, wherein the filter sheet has an ethylene acetate vinyl copolymer film strength having a wall thickness of 10 μm to 100 μm.

[6] The moisture sensor according to claim 2, wherein the filter sheet has an ethylene acetate vinyl copolymer film strength having a wall thickness of 10 μm to 100 μm.

[7] The small holes are evenly arranged in the effective area of the moisture sensor, the small hole inner diameter dimensional force is set to Slmm to 4 mm, and the small hole density is set to 50 to 500 per 100 cm ^2. The moisture sensor according to claim 1.

[8] The small holes are evenly arranged in the effective area of the moisture sensor, the small hole inner diameter dimensional force is set to Slmm to 4 mm, and the small hole density is set to 50 to 500 per 100 cm ^2. The moisture sensor according to claim 2.

[9] The moisture sensor according to claim 1, wherein the electrode is printed on the base sheet using a conductive ink.

10. The moisture sensor according to claim 2, wherein the electrode is printed on the base sheet using a conductive ink.

[II] The moisture sensor according to claim 1, wherein the base sheet has a pair of hydrophilic sheets and a reinforcing film made of polyester sandwiched between them.

12. The moisture sensor according to claim 2, wherein the base sheet has a pair of hydrophilic sheets and a reinforcing film made of polyester sandwiched between them.

13. The moisture sensor according to claim 1, wherein the electrode is disposed in contact with a conductive adhesive that absorbs moisture and increases conductivity.

14. The moisture sensor according to claim 2, wherein the electrode is disposed in contact with a conductive adhesive that absorbs moisture and increases conductivity.

15. The moisture sensor according to claim 13, wherein the conductive adhesive is a paste containing starch as a hydrophilic polymer and 10% to 21% saline as an aqueous electrolyte solution.

16. The moisture sensor according to claim 14, wherein the conductive adhesive is a paste containing starch as a hydrophilic polymer and 10% to 21% saline as an aqueous electrolyte solution.

[17] The conductive adhesive is applied to the hydrophilic sheet or penetrated into the hydrophilic sheet.

The moisture sensor according to claim 13.

18. The moisture sensor according to claim 14, wherein the conductive adhesive is applied to a hydrophilic sheet or penetrated into the hydrophilic sheet.