JP2022035698A - Liquid detection sensor and manufacturing method therefor - Google Patents

Abstract

To provide a liquid detection sensor that excels in detection accuracy and highly reliable, and which is easy to be manufactured.SOLUTION: Provided is a liquid detection sensor for constituting a primary cell by giving a liquid between a pair of positive and negative electrodes and detecting the liquid by an electromotive force generated thereby. A positive electrode and a negative electrode composed of powder based on cathode and anode active materials are provided on a substrate adjoining a border so as to cover the surfaces of a pair of current collectors composed of a given conductor, respectively. Each of the cathode and anode resistivities is adjusted so as to give an electromotive force between the electrodes without shorting these when the liquid is given to the border.SELECTED DRAWING: Figure 1

Description

The present invention relates to a liquid detection sensor for detecting the presence of an aqueous solution such as water and a method for manufacturing the same, and more particularly to a liquid detection sensor for detecting by an electromotive force generated by forming a primary battery due to the presence of the aqueous solution and a method for manufacturing the same. ..

As a liquid detection sensor that detects the presence of a liquid such as water, there is one that utilizes the conductivity of the liquid. Generally, by measuring the change in resistance value between electrodes due to the intervention of liquid such as water, the presence or absence of liquid between the electrodes can be easily detected, but on the other hand, a circuit. A power supply is required to configure. Therefore, among such liquid sensors, a liquid detection sensor that can operate without a power source has been proposed.

For example, Patent Document 1 discloses a liquid sensor in which a probe (detection unit) also serves as a battery as a liquid detection sensor for detecting the presence or absence of an aqueous solution such as water or urine. It is not necessary to separately prepare a power supply such as a battery for operation, it does not depend on the installation environment, and it is said to be excellent in maintainability. Here, a Ni electrode as a negative electrode and a carbon electrode as a positive electrode are printed on a substrate made of a ceramic plate such as alumina in a comb-tooth shape with a gap so as not to come into contact with each other, and a substrate including this electrode is printed. Above, a water-absorbing agent made of PVA (polyvinyl alcohol) powder containing an electrolyte such as ammonium chloride, starch, or the like is provided in the form of a film in a naturally dried state. When water or the like is supplied and absorbed by the water-absorbing agent, ammonium chloride decomposes into ions, functions as a primary battery, and generates an electromotive force to drive a detection circuit to detect a liquid. A depolarizer such as manganese dioxide is mixed with the water absorbing agent to promote the ionization reaction.

Further, in Patent Document 2, a liquid detection sensor is provided in which a flat plate-shaped separator made of an insulator capable of sucking up an electrolyte solution by a capillary phenomenon is arranged between both flat plate-shaped electrodes, and a primary battery is made to function with a small amount of liquid. It has been disclosed.

Japanese Unexamined Patent Publication No. 61-167854 International Publication No. 2018/092773 Pamphlet

As described above, in the liquid detection sensor in which a liquid is given so as to fill the gap between the electrodes to form a primary battery and a circuit is formed by this electromotive force, it is better to reduce the distance between the electrodes with a smaller amount of liquid. Can be filled in and the detection accuracy can be improved. However, there has been a problem of lack of reliability, such as a malfunction due to an electric short circuit between the electrodes even when no liquid is applied. Further, in order to manufacture such an electrode by printing, it becomes a factor to increase the manufacturing cost such as selection of a material and control of a highly accurate printing process.

The present invention has been made in view of the above circumstances, and an object of the present invention is to detect an electromotive force generated by constituting a primary battery due to the presence of an aqueous solution such as water. It is an object of the present invention to provide a liquid detection sensor which is excellent in accuracy, has high reliability, and is easy to manufacture, and a method for manufacturing the same.

The liquid detection sensor according to the present invention is a liquid detection sensor that constitutes a primary battery by applying a liquid between a pair of electrodes of a positive electrode and a negative electrode, and detects the liquid by the electromotive force generated by the liquid, and is on a substrate. The positive electrode and the negative electrode made of powder made of a positive electrode active material and a negative electrode active material are provided so as to cover the surfaces of a pair of current collectors made of a given conductor so as to be in contact with the boundary between the positive electrode and the negative electrode. Each of the resistors of the negative electrode is adjusted so as to apply an electromotive force between the electrodes without short-circuiting when a liquid is applied on the boundary.

According to these characteristics, it is possible to obtain a highly reliable and easy-to-manufacture liquid detection sensor having excellent detection accuracy of an aqueous solution such as water.

In the above invention, the resistivity may be adjusted by a conductive auxiliary agent given together with the powder. Further, the resistivity may be adjusted by the diameter and density of the powder. According to these characteristics, the resistivity can be easily adjusted, the detection accuracy of an aqueous solution such as water is excellent, and a highly reliable liquid detection sensor can be obtained, which is easy to manufacture.

In the above invention, the positive electrode active material may be silver oxide and the negative electrode active material may be zinc. According to such a feature, a high electromotive force can be obtained, and a liquid detection sensor having particularly excellent detection accuracy of an aqueous solution such as water can be obtained.

Further, the method for manufacturing a liquid detection sensor according to the present invention is a method for manufacturing a liquid detection sensor in which a primary battery is formed by applying a liquid between a pair of electrodes of a positive electrode and a negative electrode, and the liquid is detected by the electromotive force generated by the primary battery. The positive electrode and the negative electrode, which are made of powder of the positive electrode active material and the negative electrode active material, are in contact with each other so as to cover the surfaces of the pair of current collectors made of conductors given on the substrate. As described above, the resistances of the positive electrode and the negative electrode are adjusted so as to apply electromotive force between the electrodes without short-circuiting when the liquid is applied on the boundary.

According to these features, it is possible to easily manufacture a highly reliable liquid detection sensor having excellent detection accuracy of an aqueous solution such as water.

In the above invention, the resistivity may be adjusted by a conductive auxiliary agent given together with the powder. Further, the resistivity may be adjusted by the diameter and density of the powder. According to these characteristics, the resistivity can be easily adjusted, the detection accuracy of an aqueous solution such as water is excellent, and a highly reliable liquid detection sensor can be easily manufactured.

In the above invention, the positive electrode active material may be silver oxide and the negative electrode active material may be zinc. According to such a feature, it is possible to easily manufacture a liquid detection sensor which can obtain a high electromotive force and has particularly excellent detection accuracy of an aqueous solution such as water.

It is (a) sectional drawing and (b) enlarged side view of the main part which show an example of the liquid detection sensor of this invention. It is an external photograph of the liquid detection sensor used in the manufacturing test. It is an external photograph of the liquid detection device used in the manufacturing test. It is an external photograph which shows the manufacturing example of another liquid detection sensor.

One embodiment of the present invention will be described with reference to FIG.

As shown in FIG. 1, the liquid detection sensor 10 includes a substrate 1 and a pair of electrodes composed of a positive electrode 2a and a negative electrode 2b arranged on the substrate 1. Each of the positive electrode 2a and the negative electrode 2b is arranged so as to cover the surface of a pair of current collectors 3 provided apart from each other on the substrate 1, and is provided by printing so as to touch the boundary B with each other. The boundary B is not necessarily formed perpendicular to the substrate 1, and for example, the positive electrode 2a may ride on the negative electrode 2b. Then, the current collector 3 is made of a conductor and is electrically connected to each terminal 4, so that the electromotive force generated between the positive electrode 2a and the negative electrode 2b can be taken out to the outside. The positive electrode 2a is made of a powder made of a positive electrode active material, and is formed by firing, for example, a paste containing the powder. Similarly, the negative electrode 2b is also formed by powder made of a negative electrode active material.

Further, as described above, the positive electrode 2a and the negative electrode 2b are formed so as to be in contact with each other at the boundary B, but a gap may be formed at the boundary B. That is, it does not matter whether there is a gap or whether there is contact as long as they are close to each other as a result of formation.

Here, when a liquid L such as an aqueous solution is supplied on the boundary B, the liquid detection sensor 10 constitutes a primary battery with the positive electrode active material and the negative electrode active material, and generates an electromotive force. By detecting the electromotive force between the terminals 4, it is possible to detect that the liquid L exists on the boundary B between the electrodes.

By the way, as described above, the positive electrode 2a and the negative electrode 2b are formed so as to be in contact with each other at the boundary B, and if a short circuit occurs when the liquid L is supplied, the electromotive force is not taken out to the outside and the liquid L exists. It cannot be detected. Therefore, in the liquid detection sensor 10, the resistivityes of the positive electrode 2a and the negative electrode 2b are adjusted so as to apply an electromotive force between the electrodes without short-circuiting when the liquid L is given on the boundary B.

In order to obtain such a resistivity, an electrode can be formed from a mixture obtained by, for example, adjusting the amount of an insulating substance with respect to the powder of each active material. More specifically, a paste composed of a mixture of powders of each active material and an insulating binder can be applied onto a substrate and a current collector and fired to obtain an electrode. In this case, it is preferable to perform the coating by printing because the production can be simplified. Further, it is also preferable to select a positive electrode active material and a negative electrode active material having a large resistivity when formed as an electrode, reduce the amount of the conductive auxiliary agent added, or do not add the conductive auxiliary agent. .. In this way, the mixing ratio of the active material and the binder in the paste, the amount of the conductive auxiliary agent added, the diameter and density of the powder in the paste, the selection of the material as the active material, and the setting of the firing conditions are appropriately set. Adjust the resistance.

As described above, according to the liquid detection sensor 10, when the liquid L is applied to the boundary B between the electrodes, a short circuit does not occur even if the electrodes come into contact with each other, and the liquid can be used as a highly reliable liquid detection sensor. Further, since it is only necessary to manufacture the boundary B of the positive electrode 2a and the negative electrode 2b so as to be in contact with each other, the dimensions can be easily controlled and the manufacturing can be easily performed.

[Manufacturing test]
The results of the above-mentioned trial production of the liquid detection sensor and the liquid detection test will be described with reference to FIGS. 2 to 4.

As shown in FIG. 2, the electrode cells arranged so that the long sides of the rectangular positive electrode 2a and the negative electrode 2b are in contact with each other are formed on the substrate 1 so as to connect three in series, and the liquid detection sensor 10'is formed. And said.

Specifically, first, a current collector with silver ink was printed on a polyimide substrate having a thickness of 125 μm at the positions of the positive electrode and the negative electrode, heated to 130 to 150 ° C., and held for 30 minutes for firing.

Next, a zinc paste in which a binder was mixed with zinc particles as a negative electrode active material was applied by printing on a current collector on the negative electrode side, heated to 200 ° C., held for 30 minutes, and fired. Further, a silver oxide paste in which a binder was mixed with silver oxide particles to be a positive electrode active material was applied by printing on a current collector on the positive electrode side, heated to 150 ° C., held for 30 minutes, and fired. In particular, since the zinc and silver oxide pastes do not have conductivity even when fired, high resistivity can be imparted to each of the positive electrode 2a and the negative electrode 2b. Since silver oxide is reduced by heating at 160 ° C. or higher, it is fired at the end. As the material of the above-mentioned paste, zinc powder obtained by crushing was used for the zinc particles, and silver oxide powder obtained by crushing was used for the silver oxide particles. In addition, polyester resin was used as the binder, SC0024 solvent (manufactured by Fujikura Kasei Co., Ltd.) was used as the diluent, and no conductive auxiliary agent was added.

Further, by wiring so as to connect the current collectors of the above-mentioned electrode cells, they are electrically connected in series and terminals are provided at both ends. From the above, the liquid detection sensor 10'was obtained. Further, an LED 6 (see FIG. 3) was connected to the terminal of the liquid detection sensor 10'.

As shown in FIG. 3, 1% saline solution was dropped as liquid L on the boundary between the positive electrode 2a and the negative electrode 2b of each of the three electrode cells of the obtained liquid detection sensor 10'. Then, it was confirmed that the LED 6 connected to the liquid detection sensor 10'lighted up and the liquid L could be detected. Similar results were obtained even when a cellulose resin was used instead of the polyester resin as the binder for the above-mentioned paste.

Further, as shown in FIG. 4, a liquid detection sensor 10 ″ was created in which comb-shaped positive electrodes and negative electrodes were alternately inserted. It was confirmed that the liquid detection sensor 10 ″ can also detect the liquid in the same manner. By combining zinc and silver oxide, a high electromotive force can be obtained, and a liquid detection sensor having particularly excellent detection accuracy of an aqueous solution such as water can be obtained.

Although typical examples according to the present invention and modifications based on the same have been described so far, the present invention is not necessarily limited to these. Those skilled in the art will be able to find various alternative examples without departing from the attached claims.

1 Substrate 2a Positive electrode 2b Negative electrode 3 Current collector 4 Terminal 10 Liquid detection sensor L Liquid B Boundary

It is sectional drawing which shows an example of the liquid detection sensor of this invention. It is an external photograph of the liquid detection sensor used in the manufacturing test. It is an external photograph of the liquid detection device used in the manufacturing test. It is an external photograph which shows the manufacturing example of another liquid detection sensor.

Claims (8)

A liquid detection sensor that constitutes a primary battery by applying a liquid between a pair of electrodes of a positive electrode and a negative electrode, and detects the liquid by the electromotive force generated by the liquid.
The positive electrode and the negative electrode made of powder made of a positive electrode active material and a negative electrode active material are provided so as to cover the surfaces of a pair of current collectors made of conductors given on the substrate, respectively, with their boundaries in contact with each other.
A liquid detection sensor characterized in that each of the resistivityes of the positive electrode and the negative electrode is adjusted so as to apply an electromotive force between the electrodes without short-circuiting when a liquid is applied on the boundary. The liquid detection sensor according to claim 1, wherein the resistivity is adjusted by a conductive auxiliary agent given together with the powder. The liquid detection sensor according to claim 2, wherein the resistivity is adjusted by the diameter and density of the powder. The liquid detection sensor according to claim 1, wherein the positive electrode active material is silver oxide and the negative electrode active material is zinc. It is a method of manufacturing a liquid detection sensor that constitutes a primary battery by applying a liquid between a pair of electrodes of a positive electrode and a negative electrode and detects the liquid by an electromotive force generated by the primary battery.
By printing so as to cover the surface of each pair of current collectors made of conductors given on the substrate, and to touch the boundary between the positive electrode and the negative electrode made of powder made of the positive electrode active material and the negative electrode active material. Manufacture of a liquid detection sensor provided, wherein the resistance of each of the positive electrode and the negative electrode is adjusted so as to apply an electromotive force between the electrodes without short-circuiting when the liquid is applied on the boundary. Method. The method for manufacturing a liquid detection sensor according to claim 5, wherein the resistivity is adjusted by a conductive auxiliary agent given together with the powder. The method for manufacturing a liquid detection sensor according to claim 5, wherein the resistivity is adjusted by the diameter and density of the powder. The method for manufacturing a liquid detection sensor according to one of claims 5 to 7, wherein the positive electrode active material is silver oxide and the negative electrode active material is zinc.

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