JPH0210147A - Humidity sensor - Google Patents

Abstract

PURPOSE:To obtain the title sensor whose structure is simple, whose humidity sensing function is also excellent, and which can be miniaturized by constituting the sensor so that an opposed electrode wire is brought into contact with that which has covered a linear metallic electrode with a phosphate film as a humidity sensing body by chemical conversion coating. CONSTITUTION:As for a metallic electrode 11 which becomes a first electrode, for instance, a stainless steel wire 9 is used, and the surface is covered with a Zn3(PO4)2 . 4H2O(Hopeite) humidity sensing body film 10 by electrolytic chemical conversion coating. On the film 10, a humidity sensing film layer 12 is formed, and a counter electrode 13 which becomes a second electrode is provided in a state brought into contact with the surface of the film layer. As for the counter electrode, a stainless steel wire where gold plating is performed is wound like a coil, and locking 14 is provided on both ends. In accordance with the quantity of the moisture contents of the humidity sensing body 10 and the humidity sensing film layer 12 which have adsorbed the moisture content, an electric resistance is varied, therefore, by connecting a lead wire 4 to a resistance measuring circuit 8 of the outside and reading the electric resistance between both the electrodes 11, 13, the variation of humidity can be measured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvements in humidity sensors (in a broad sense) used as humidity sensors, moisture condensation sensors, raindrop sensors, and the like.

[-Conventional technology] Conventional humidity sensors that detect humidity, etc. include those that utilize elasticity associated with absorption and desorption sources, such as hair hygrometers, and those that detect moisture evaporation due to humidity differences, such as moisture-sensing hygrometers. It has been generalized because it takes advantage of the difference between

These devices are used in a fixed position, have a large shape, are inconvenient to carry, and are difficult to set up an electronic control system to adjust the environmental humidity based on the obtained humidity information. I was not satisfied sexually.

Therefore, recently, as shown in FIG. 13(a), electrodes 2.2' are arranged on a sintered semiconductor ceramic moisture sensitive body 1, and as shown in FIG. 13(b), an electrically insulating substrate 7 is used. A humidity sensor was developed in which a humidity sensing element 1 was covered with electrodes 2 and 2', and an electronic circuit read changes in the electrical resistance of the humidity sensing element due to changes in humidity, and displayed the humidity. Some are used for practical purposes such as environmental control. In addition, 3 is a terminal electrode, 4 is a lead wire, 5 is an electrode terminal processing part, 6 is soldering, 7 is a board, and 8 is electric welding.

[Problems to be Solved by the Invention] Incidentally, the semiconductor ceramic moisture sensitive body 1 is made into a sintered body by press-molding a raw material oxide mixed powder under high pressure and then firing it at high humidity. For this reason, processes such as raw material preparation, press molding, and high-temperature firing are required. On the other hand, a moisture-sensitive sensor coated on a substrate requires raw material preparation, thermal spraying, or printing and baking steps. These steps require experience and a high degree of skill, and require the use of expensive manufacturing equipment such as a press machine, a firing furnace, a thermal spray machine, and a printing machine. Note that an alumina substrate or a heat-resistant glass substrate is used as the electrically insulating substrate that covers the moisture sensitive element.

In this way, the manufacturing cost of the humidity sensing element is high, as it uses mixed oxide powder as the raw material for the humidity sensing element, and is manufactured through complicated processes using expensive manufacturing equipment using ceramic or heat-resistant glass substrates. This is one of the reasons for delaying the spread of humidity sensors.

The humidity sensing element 1 of the sensor used in this way has a large electrical resistance corresponding to humidity, so in order to be able to connect it to an external electronic circuit and measure the resistance value, the opposite electrode 2 must be connected as shown in the figure. The comb-shaped structure is designed to lengthen the opposing portions of the electrodes and lower the resistance value between the electrodes. This comb-shaped electrode is connected to a terminal electrode 3, and is bonded to a 4-wire lead connected to an external electronic circuit by soldering 6 or electric welding 8 in an electrode terminal processing section 5.

The counter electrode 2 having a comb-shaped structure is formed by printing gold paste or ruthenium oxide paste on the moisture sensitive element 1 or the substrate 7 and firing it. It was difficult to set the distance to a desired value, and if it was less than 0.3 mm, there was a risk that the opposing electrodes would be short-circuited. For this reason, if the resistance value between the electrodes required for electronic circuit design cannot be obtained even with the use of expensive paste and skilled printing technology, it is necessary to increase the number of electrodes or lengthen the electrodes. Since the value had to be small, there were restrictions on the shape and miniaturization of the sensor.

In addition, in order to bond the lid frame or lead wire 4 that connects the sensor and an external electronic circuit to the electrode terminal 3, an electrode terminal portion 5 is provided in which silver or gold paste 1 is printed and fired in advance. When soldering, the flux used will scatter and enter the moisture sensitive element 1, adversely affecting the performance of the moisture sensitive element 1. Therefore, it is necessary to take measures to protect the moisture sensitive element 1 from contamination in advance, or to avoid soldering. It was then necessary to take steps to remove the contamination. In either case, a troublesome process is involved, which causes a decrease in productivity and product yield. On the other hand, when bonding is performed by welding 8, although the flux does not have an adverse effect, it is difficult to judge whether or not the bonding is complete, so there is a risk of problems such as poor conductivity after shipping as a product. Therefore, in any case, the process of bonding the lead frame or lead wire 4 to the electrode terminal 3 of the sensor degrades the performance of the sensor, and can be said to be an important process that affects productivity and product yield.

As shown in Kitaki, conventional temperature sensors require high manufacturing costs for the humidity sensing element, and their electrical resistance is high, so a comb-shaped counter electrode is used to reduce the resistance. Because they require expensive materials and advanced technology, they have increased sensor manufacturing costs and hindered miniaturization. Furthermore, the electrode terminal treatment required to connect the sensor to an external electronic circuit degrades the performance of the sensor, reduces productivity and product yield, and causes an increase in manufacturing costs.

In order to solve the above-mentioned problems of conventional humidity sensors, the applicant invented a humidity sensor in which the metal electrode, the counter electrode, the method of coating the moisture sensitive body, etc. were devised, and the applicant filed a patent application. A patent application has been filed under Sho 62-261857.

The humidity sensor related to this patent application has a first electrode formed by coating a linear metal electrode with a phosphate film as a humidity sensitive body through chemical conversion treatment, and a counter electrode wire, which is a second electrode, formed into an ellipse so as to be in contact with the first electrode. It has excellent advantages such as easy construction, low manufacturing cost, excellent moisture-sensing function, and the ability to be miniaturized as required.

Although it is not clear why due to variations in the chemical conversion treatment conditions when applying the chemical conversion film to the metal electrode, the electrical resistance value of the film shows conduction regardless of humidity, and the function as a moisture sensitive body of the first electrode. may not be fulfilled. Also,
Even if there is no problem with the chemical conversion coating, the coating may be damaged in the process of bringing it into contact with the counter electrode wire that will become the second electrode, resulting in a conductive state and loss of moisture sensing function.

An object of the present invention is to provide a humidity sensor that solves the problems of conventional humidity sensors as described above.

[Means for Solving the Problems] The present invention provides a humidity sensor in which the metal electrode, the counter electrode, and the method of coating the humidity sensing part are devised, and the contact state between the second electrode and the humidity sensing element is improved. , it is possible to solve the above problem.

[Example] Example 1 FIG. 1 shows a first embodiment of the humidity sensor of the present invention.

Figures (a) and (b) are diagrams showing the configuration, and (a) is a perspective view showing the external appearance of the sensor, and (b) is an enlarged longitudinal sectional view of the electrode terminal portion.

For example, the metal electrode which becomes the first electrode is 0.9 n
+mφ stainless steel wire (SUS304>9 is used,
Zinc-based Z n 3 (P O 4) 24 is on the electrode surface.
H2O (Hopeite) moisture sensitive body coating] 0 is coated by electrolytic chemical conversion treatment. A moisture-sensitive coating layer 12 is formed on the coating 10, and a counter electrode 3 serving as a second electrode is provided in contact with the surface of the coating layer.

The counter electrode is a 0.13In gold-plated stainless steel wire.
Inφ is wound into a coil at a pitch of 0.5 m+n, and loosening preventers 14 are provided at both ends to prevent the electrode from loosening. Note that the second electrode is not limited to a metal electrode, but may be a linear one having conductivity, for example,
The electrode may be made of carbon fiber or a conductive polymer material.

One end of each of the metal electrode and the counter electrode is an electrode terminal lead 4 for connection to an external port (not shown).

The metal electrode is coated with the moisture sensitive film in the following manner. First, the stainless steel wire was immersed for 3 minutes in a 60°C aqueous solution of 2O g/I of the degreaser Fine Cleaner 4306 (manufactured by Nippon Paru Ising, hereinafter referred to as our company).
After washing with running water, it is immersed in a mixed aqueous solution of 15 g/I of hydrofluoric acid and 20 g/I of nitric acid at room temperature for 3 minutes. next.

After cleaning the surface by elution and washing again with water, Z n ”
6.15g/l, PO4-35, 6g/l, N
Os-' 9.9g/I, NaNOslOg
The electrochemical conversion treatment was carried out in a 55° C. hot water bath with a liquid composition of /l.

The electrolytic chemical conversion treatment was carried out by using a stainless steel wire as an anode and a carbon plate as a cathode, applying current at 1 ampere for 3 minutes, and then reversely applying current at 0.2 ampere for 3 minutes with the anode reversed. Rinse thoroughly with water after treatment.

It was dried in a drying oven at 100° C. for 5 minutes to obtain a chemically treated moisture-sensitive film having a thickness of 13 μm. As shown in Fig. 5, the electrical resistance of the moisture-sensitive film is determined by using a metal electrode 11 at a measuring terminal 15 that contacts the film on one side to avoid damaging the film.
The film resistance between the measurement terminal and the electrode was measured at each point on the film using the AC resistance measuring device 16.
A value of 200Ω was obtained, indicating that the film was in a conductive state and had lost its moisture sensing function.

The moisture-sensitive coating layer 12 formed on the moisture-sensitive body film 10 is made of 10 g of zinc phosphate powder Zrz (POt>z・4H2O).
Heat-reactive water-soluble urethane resin Elastron H・3
8 (hereinafter abbreviated as H.38 manufactured by Daiichi Kogyo Seiyaku) 8 m
The pesto paste was added at a ratio of 1.5 liters and water was added while kneading, and the viscosity of the pesto was adjusted so as to draw strings.

As shown in FIG. 6, the paste reservoir 18
Insert the metal electrode 11 coated with the moisture-sensitive film 10 onto the upper surface of the bases 1 to 17 housed in the housing, pass it through the nozzle hole 2O of one nozzle, and pull out the line in the direction of the arrow.The metal electrode will remove the paste pool. During the passage, the surface of the moisture-sensitive body film is wetted with the paste, and the amount of adhesion is regulated by the nozzle hole to form a coating layer 12 of uniform thickness. One nozzle has a structure that allows it to be removed from the paste reservoir so that the size of the metal electrode cylinder can be changed, so the thickness of the coating layer can be varied. In this example, the nostle hole diameter is 9.05 mm. The electrode wire coated with the coating layer was left in the atmosphere for 10 hours, and then heated in an oven at 160°C for 5 minutes to solidify Pase I, forming a moisture-sensitive coating layer with a thickness of 11μ. The finished metal electrode was formed.

Of course, drying after applying the paste can be done in a heating oven instead of leaving it in the air, but rapid heating will sometimes generate a large amount of water vapor and destroy the coating, so drying at temperatures below 100℃ is possible. Heating is recommended.

After drying, the coating layer is solidified by heating at 160°C.
Since it is applied on top of the moisture-sensitive film coated with a chemical conversion treatment, the countless micropores distributed in the film act as an anchor effect for the paste to adhere, and the hardened coating layer peels off from the underlying HopeiLe film. There will be no fear of doing so. In addition, the main component of the coating layer is phosphoric acid substratum Z n 3
(P 04) 2.4 H2O, phosphate dissolves in water to a very small extent and dissociates into ions, and in the absence of water it has the property of losing conductivity and has a moisture-sensitive function, so the coating layer is made of 2O.
When the thickness is less than μ, the resistance value changes greatly depending on the level of humidity, and exhibits excellent moisture sensitivity characteristics. However, if the coating thickness exceeds 20μ, the electrical insulation effect of the resin component in the coating becomes stronger, and it takes time for moisture to penetrate, so the electrical resistance value decreases even in high humidity. The decrease is small and the moisture sensing function tends to be impaired.

In the metal electrode of this example in which a coating layer with a thickness of 11 nm was formed, the one covered with the moisture-sensitive film and in the conductive state as described above had a relative humidity (hereinafter abbreviated as RH). 5
It now showed a resistance value of 1 MΩ or more in a 0% atmosphere, the continuity was repaired, and the moisture sensing function was restored.

The reason why the stainless steel wire of the counter electrode wrapped around the moisture-sensitive coating III layer is plated with gold is to keep the contact resistance between the coating layer and the electrode small and unchanged, and any material that meets this purpose may be used. However, it is not limited to this. Nickel plating and platinum plating are also effective in environments where corrosion is a concern. The loosening preventers 14 at both ends of the electrode are made using epoxy adhesive Honto E (manufactured by Konishi Co., Ltd.) to prevent the coiled counter electrode from springing back and damaging the contact between the moisture-sensitive coating and the electrode. (hereinafter referred to as adhesive)
The helix is used to surround several pitches of the helix and is adhesively fixed to the metal electrode. It is also possible to bind this part of the helix with nylon thread or thin metal wire and then fix it with resin.

Since the electrical resistance changes depending on the amount of moisture in the moisture sensitive body 10 and the moisture sensitive coating layer 12 that have absorbed moisture, the lid wire 4 is connected to an external resistance measuring circuit 8 (not shown) and the picture electrode is By reading the electrical resistance between Y and 11, the change in tA degree can be measured.

The moisture sensitive body 10 made of this phosphate film and the moisture sensitive coating layer 12 mainly composed of phosphate are each very thin films of the order of 10 μm, so their resistance values are lower than those using conventional comb-shaped electrodes. This value is much smaller than the sheet resistance value obtained by measuring the object.

In FIG. 1, the reason why 5t JS304 stainless steel wire is used for electrodes -1 and -V is that it is suitable for coating the phosphate film used in the moisture sensitive element by electrochemical conversion treatment. In addition, iron, copper, nickel, and titanium can also be used as metal electrodes because they can form phosphate films.

The humidity characteristics of this example are IKHz.

The results measured using a 5V power supply are shown in the 7th semi-logarithmic curve.
As shown in the figure. As shown in the figure, a sensor in which a moisture-sensitive coating layer 12 is formed on a moisture-sensitive element 10 exhibits a high resistance value in a low humidity range of 75% or less relative humidity, and does not show a large change in response to changes in humidity. However, the resistance value changes rapidly in high humidity areas. Moreover, there is almost no difference in resistance value at the same humidity during humidification and dehumidification. Therefore, it can be said that this humidity sensor has excellent performance as a dew condensation sensor.

Table 1 shows the dry-humidity test of this humidity sensor from R870% to 98
It shows the resistance value when repeated 1,000 times under the condition of %.

As shown in the same table, there was almost no change in the resistance value between the initial and final stages of the experiment, indicating that it has excellent stability.

K in the table indicates a dry-wet cycle.

Table 1 In this example, the shape of the metal electrode was cylindrical, but it is of course possible to make the shape of the metal electrode plate-like. By forming a coating layer, the moisture-sensitive resistance can be set low.

Embodiment 2 FIG. 2 shows a second embodiment of the temperature sensor of the present invention. A humidity sensor is shown in which a two-layer moisture-sensitive coating layer 12.12" is coated on a moisture-sensitive film 10 coated on a metal electrode 11. Figures (a) and (b) show the structure. (A) is an external perspective view thereof, and (B) is an enlarged vertical cross-sectional view of a part of the moisture sensing part.A metal electrode 1 serving as a first electrode.
1, a 0.6 mmφ copper wire is used, and the surface of the electrode is coated with Zn5(PO,)2-4H2O(Hopeit
e) The film of the moisture sensitive element 10 is coated by chemical conversion treatment. A moisture-sensitive coating layer 12 is formed on the second side of the coating, and a counter electrode 13 that is in contact with the coating layer and serves as a second electrode is gold-plated.
0.3 with a 5μ thick nickel wire (50μφ)
It is wound into a coil with a pitch of mm.

After the counter electrode is provided, on top of the coating layer 12.

Furthermore, a moisture-sensitive coating layer 12° is formed. The wires at the beginning and end of the winding of the counter electrode wound in a coil shape are brought together to form the electrode terminal 4 as shown in the electrode collection line 15, and when measuring humidity, the metal electrode ] 1 and the counter electrode 13 so that the current density is uniform over the entire length of the electrode.

For chemical conversion treatment of copper wire, use degreasing material (FC-4360: manufactured by our company)
After washing with water, pickling with a mixture of chromic acid and sulfuric acid for 3 minutes to clean the surface, washing with water again, and immersing in the electrolytic chemical treatment hot bath for 10 minutes. Then, the film was coated without applying electricity. After the treatment, the film was thoroughly washed with water and dried in a drying oven at 100°C for 5 minutes.The thickness of the moisture sensitive film was 8μ.

The result of measuring the electrical resistance of this film using the method described above is IMΩ
There was no problem with the above, but because the thickness of the No. 7 coating was thin, it was damaged when the counter electrode was wrapped around it, resulting in a conductive state and loss of moisture sensing function.

The moisture-sensitive coating layer 12 on the moisture-sensitive body coating 10 was prepared by applying and solidifying a paste having the same composition as in Example 1 in the same manner as in Example 1 to form a coating layer with a thickness of 9 μm. By forming this coating layer, the underlying moisture-sensitive film was strengthened, and there was no need to worry about conduction when wrapping the counter electrode. To wrap the electrode on top of the coating layer, fix the beginning and end of the electrode to the coating using adhesive (Aron α, manufactured by Toagosei Chemical Co., Ltd.), so that the electrode that has been wrapped once will spring back. This prevents loosening. After fixing the electrodes, the moisture-sensitive coating layer 12' formed on the moisture-sensitive coating 12 is made of Zn, (Pot) 2 and 4.
H2O4, 5g, KIP2O70.9, , Sodium metaphosphate aqueous solution 3.1. ml, H383, Oml
A coating layer was formed by the above coating method using the paste prepared by kneading, and after drying in an oven at 80°C for 20 minutes, it was heated at 160°C for 5 minutes to solidify for 20 minutes. It is desirable to apply this moisture sensitive coating layer to a thickness that does not allow the counter electrode to be buried in the coating. If the coating layer is so thick that the lines are completely buried, the humidity detection speed will be slow. Become.

The thickness of the coating layer could be regulated by increasing or decreasing the amount of water in the paste by changing the ratio of the aqueous sodium metaphosphate solution and Z n (P O,) 2 .4 H2O during paste preparation. The coating film thickness of this example was 21 μm, and FIG. 8 shows the change in resistance value when this was kept in an RH 98% atmosphere for 24 hours and then transferred to an R8 30% atmosphere.

The resistance value increases from approximately IKΩ at R898% to IMΩ within 20 seconds, indicating good moisture sensitivity characteristics. 9th
The figure shows the relationship between humidity and resistance value in this example.

At RH30 and 098%, the resistance value corresponding to one humidity change changes on a gentle curve, and the humidity sensitivity characteristics change from the dew condensation sensor type in the first embodiment to the humidity sensor type. There is. Furthermore, the curves during humidification and dehumidification coincide, and no hysteresis occurs at all.

Table 2 shows the resistance values when R, I (30° → 98%) is repeated 1,000 times. In the same table, indicates the dry/wet cycle.

As shown in Table 2, it can be seen that the resistance value remains stable with almost no change between the initial and final stages of the experiment.

Table 2 Also, the reason why the moisture sensitivity changed from a dew sensor type to a humidity sensor type is because potassium pyrophosphate, a water-soluble alkali phosphate with strong hygroscopicity, is included in the composition of the moisture-sensitive coating layer. This is based on the effect of using sodium metaphosphate and sodium metaphosphate, and even in low humidity ranges such as R030%, the results shown in Figures 7 and 9 are
As seen in the comparison in the figure, the resistance value can be kept low.

Furthermore, due to the formation of this coating layer, the counter electrode is tightly fixed to the underlying moisture-sensitive coating layer 12, and there is no misalignment between the electrode and the dry/wet coating, so that the resistance value does not change even with repeated moisture sensing. It is thought that it is no longer possible.

In addition, in seven experiments, water-soluble potassium pyrophosphate and metaphosphoric acid sorter were mixed to form a paste component.

May be used alone. The same effect can also be obtained by impregnating a chemical conversion film with a moisture absorbent in water before forming a moisture-sensitive coating layer, allowing it to be supported, and then drying to form a moisture-sensitive coating. It is also possible to carry out impregnation and support after forming.

Embodiment 3 FIG. 3 shows a humidity sensor having a structure in which a counter electrode 13 is wound around a chemical conversion film moisture sensitive element 10 on a metal electrode 11, and then a moisture sensitive coating layer 12 is formed.

The chemical conversion film moisture sensitive body improves the defects observed in Examples 1 and 2. As a specific example, metal electrode] 1 is a 0.6 mmφ iron wire, and for the counter electrode 13, a 0.14 mmφ piano wire is nickel-plated 1μ,
The one coated with gold plating with a thickness of 0.5 μm was also coated with manganese phosphate (Mn, Fe) 2H2 (P
O4) 4.4H2O (Hureaulite) was chemically treated according to Example 2 to form a film,
In addition, as for the moisture-sensitive coating layer formed on the moisture-sensitive body, Hureaulite powder, a water-soluble epoxy resin COL EX313 as a binder, and a hardening agent Evomin (manufactured by Nakase Kasei Kogyo) were used as in Example 1. The prepared paste was applied and allowed to dry and harden. FIG. 10 and Table 3 show the moisture sensitivity characteristics of this example and 1000 humidifications.

This is the actual measured resistance value during dehumidification.

Table 3 Example 4: FIG. 4 is an example of a humidity sensor of the present invention made from a single wire coated with a chemical conversion coated moisture sensitive element and then coated with a moisture sensitive coating layer. In the same figure, (a) is a stainless steel wire on which no moisture-sensitive film or moisture-sensitive coating layer is formed, and (b) is a stainless steel wire.
1 is an enlarged longitudinal sectional view thereof, in which a moisture-sensitive coating J112 is formed on the moisture-sensitive coating 10 coated based on the recipe of Example 1 in the manner described below. That is, a stainless steel wire of 0.3 mmφ on which a moisture-sensitive film was formed was coated with an acrylic emulsion (product name: VAN) containing colloidal silica force.
COAT DV759 (manufactured by Dainippon Ink & Chemicals) (hereinafter referred to as coloital silica/acrylic composite particle emulsion) was immersed for 1 minute and then dried at 100°C for 15 minutes to form a thin coating film that is permeable to water vapor. ing. (C), (D), and (E) are external perspective views showing the steps for manufacturing the sensor. The stainless steel wire is bent in two to maintain contact with each other as shown in (c), and the bent part is cut as shown in (e). The wire becomes a counter electrode, and the electrode terminal lead 4 is formed by removing the underlying moisture-sensitive film from the humidity-sensitive coating layer at the terminal end of the electrode.

In the case of the humidity sensor finished in the shape shown in FIG. 4 (e), the relationship between humidity and impedance also has a humidity sensing function as shown in Table 4.

<Note> Conditions of this experiment: I K11z, 0.5VX
If we show the relationship between impedance and RH in Table 4, which shows Ω, on a semi-logarithmic graph, we can see that the impedance changes linearly as the humidity changes, as shown in Figure 11.1 From this point, The structure shown in FIG. 4 (e) can be said to be of a humidity sensor type. According to this method, the sensor structure is extremely easy and can be manufactured at low cost, so it is suitable for disposable products such as diaper covers.

As the heat-shrinkable tube that maintains contact between the wires, a tube with a window as shown in (f) can also be used. Furthermore, instead of using one wire by bending it, it is of course possible to use two wires with a film and a coating formed thereon in contact with each other.

The moisture sensitive element 10 in each of the above embodiments is composed of a phosphate film, which is coated over the entire surface of the metal electrode 1 by electroless or electrolytic chemical conversion treatment.

According to this method, a film of uniform thickness can be coated by simply penetrating the metal electrode material into an aqueous phosphate mixed bath. The phosphate produced by the chemical conversion treatment adheres strongly to the metal electrode, and the film has countless extremely fine pores. FIG. 12 shows this state. The phosphate film 10 coated on the metal electrode 11 in FIG. Micropores 21 are formed, which serve as a foothold for adhesion of the moisture-sensitive coating layer applied on top of the film, and play the role of an anchor effect.
It is highly hygroscopic and hydrophilic, and has an excellent moisture-sensing function.

Phosphate coatings that can be coated by chemical conversion treatment include the following.

That is, Zn, (P○-)z ・4 H2O (To1-op
eite).

Zn2F e(po4>24H2O(Phoshop
hyllite)Z n 2Ca (P 04)2 ・
2 H2O (Scholzite), Zn3 (POl
),・2H2O,AIPO,・2H2O,AIPO
.

p e3 (PO4) 2・8H2O (Vivia
nite), (MnFe>5H2(P O+)4 4
H2O (Hureaulite), FePO<・2
H2O (Strengite), Fe5H2 (P O
+)+ 4H2O(F e-Hureaulite
), M n SH2(P O+) 4H2O(Mn
-Hureaulite), CaHPO, 2+-1
2O (Brushite), CaHP Ot (M
The metal electrode 11 can be coated with a phosphate film containing one or more of the following as a moisture sensitive material.

The thickness of the phosphate film is preferably 0.5 to 100 microns. This is because if the film thickness is less than 0.5μ, the film will be interrupted midway and the electrode will be exposed.When forming the moisture-sensitive film layer, the film layer applied to the exposed part of the electrode Since it comes into contact with an electrode surface that does not have an anchor effect, adhesion is insufficient, and repeated moisture sensing causes it to peel off and change its resistance value.

On the other hand, in the case of a film thickness of 100μ or more, when a moisture-sensitive coating layer is formed, the penetration of moisture is prolonged and the resistance value becomes unstable.
Moreover, the electrical resistance increases too much and the moisture sensing function deteriorates.

In addition, the moisture-sensitive coating layers 12 and 12° formed on the moisture-sensitive body 10 of each example are coated with a resin or a powder of one or more of the phosphates that can be coated by a chemical conversion treatment method. It is formed by applying and drying a paste prepared by kneading resin and water by the coating method shown in FIG. 6, or by dipping and drying it in a colloidal silica/acrylic composite particle emulsion. According to this coating method, a coating layer of uniform thickness can be created simply by passing the metal electrode through the paste pool. The main component of the coating layer is phosphate, and the blended resin is moisture permeable and hydrophilic, so it has good moisture sensitivity. In addition, the numerous fine pores distributed in the underlying phosphate film serve as an anchor effect, so that the film and the coating layer are firmly adhered to each other. Therefore, as in the examples, the coating layer has a great effect in repairing conduction defects in the film and at the same time enhancing the moisture-sensing function. Organic solvent-based resins can be used as the resin used to prepare the paste, but thermosetting and water-soluble resins require a diluent or water, and the formed coating layer becomes hydrophilic. Suitable for preparing paste for this purpose. The phosphate used to prepare the paste 1 is usually a powder with the same composition as the phosphate film, or is limited to this if the purpose is to change or adjust the moisture sensitivity characteristics of the film. isn't it.

In addition, as shown in the second embodiment, in addition to the phosphates in the chemical formation film composition, hygroscopic alkali phosphates, alkaline earth hydrogen sulfates, lithium chloride, and other known By kneading one or more types of oxide powders such as glass powder, silica sand powder, alumina powder, tin oxide powder, and chromium oxide powder in addition to a moisture absorbent, it is possible to adjust and control the moisture sensitivity characteristics of one humidity sensor. It's even easier to do.

Furthermore, the moisture sensitive body may be constructed using a chromate chemical conversion film such as chromate phosphate 1 film or a non-chromate chemical conversion film such as a titanium-tannic acid complex salt film as the chemical conversion film.

[Function] The humidity sensor of the present invention has a structure in which a metal electrode is coated with a moisture sensitive body made of a chemical conversion film, and a counter electrode is brought into contact with this moisture sensitive body. By applying this coating layer, it is possible to repair conduction defects in the moisture sensitive body coating that occur during chemical conversion treatment, and the strength of the coating is reinforced, making it possible to connect the counter electrode to metal. It is possible to prevent conduction defects due to film breakage that occur when making contact with electrodes.

When this invention is applied to a cylindrical metal electrode and a linear counter electrode, and a humidity sensor is constructed by wrapping the counter electrode around the metal electrode, the humidity-sensitive coating layer is formed in the following order: conduct.

■After applying the coating layer, wrap the counter electrode around it.

■After wrapping the counter electrode, a coating layer is formed.

(2) Using method (1) above, a coating layer is further formed.

(2) allows repair of the moisture sensitive body, (2) fixes the counter electrode, and (2) allows repair of the moisture sensitive body and fixation of the counter electrode. These■
In (2), the counter electrode is in contact with the moisture-sensitive coating layer, and in (2), the counter electrode is in direct contact with the moisture-sensitive body to accurately detect humidity.

In the above configuration, the phosphate film was used as the moisture sensitive element. For example, Zn3 (POl
)2.4H2O (Hopeite) is slightly hydrolyzed by moisture to form the formula (4).

Zr+:+(PO2)2・4t12O=Zn”+2Zn
PO4-+4112O (]) This equation (4) moves to the right side, liberates metal ions, and becomes ionic conductive. This is because when the water runs out, it reversibly shifts to the left side and becomes insulating. This is the reason why not only phosphate chemical conversion coatings but also chemical conversion coatings having such properties, such as chromate chemical conversion coatings or non-chromate chemical conversion coatings, can be used as the moisture sensitive body coating of the present invention.

The moisture-sensitive coating layer is formed by applying and hardening phosphate powder onto the moisture-sensitive element using a resin as a binder, and can repair and strengthen the phosphate coating containing defects as described above. Furthermore, the coating film itself can be imparted with moisture sensitivity and hygroscopicity, thereby adjusting and improving the moisture sensitivity characteristics of a humidity sensor, and transferring dew condensation type characteristics to a humidity sensor type.

Phosphate film moisture-sensitive material contains countless micropores in the film, so the moisture-sensitive coating layer adheres tightly to the film due to the anchoring effect of the micropores, so it can be repeatedly dried and wet. It also guarantees a long service life without peeling.

[Effects of the Invention] The humidity sensor of the present invention has the following superior effects compared to conventional ones.

■An electrode with a comb-shaped structure like the conventional one is not required, and as a result, it is excellent in that the opposite electrode and the moisture-sensitive body can be brought into contact over the entire length of the electrode.

■When using a chemical conversion film such as a phosphate film coated on a metal electrode by a chemical conversion process as a moisture sensitive body, for example, phosphate dissolves very slightly in liquid water and dissociates into ions, making it conductive. However, as moisture disappears, it reversibly returns to phosphate and loses its conductivity, making it an excellent material for use as a moisture-sensitive material to detect the presence or absence of dew condensation in a high-humidity environment.

In addition, as seen in the experience of coating metal surfaces with a phosphate film for many years as a rust preventive treatment agent, this film has strong resistance to the environment, so if this film is used as a moisture sensitive element, it will have a high response rate. A durable condensation sensor can be built.

■The moisture-sensitive coating layer formed on the phosphate film by applying a paste prepared with phosphate and a thermosetting water-soluble resin uses the numerous micropores distributed in the phosphate film as footholds. This improves the yield of sensor elements by contacting the moisture sensitive body and repairing conduction defects occurring in the phosphate film, and preventing damage to the film that occurs when the counter electrodes are brought into contact.

Furthermore, by imparting hygroscopicity to the coating layer, the dew condensation sensor can be transformed into a humidity sensor that responds to low humidity. In addition, the space between the coils of the opposing electrodes is filled and fixed, and W
Prevents electrode displacement due to impact or thermal changes, and prevents element deterioration over a long period of time.

■As in the first to third embodiments, in the case where a counter electrode is wound around a metal electrode, the part where the counter electrode is wound once becomes the moisture sensing part, and the end of the electrode can also serve as the terminal lead wire. This eliminates the need for terminal processing to bond the lead frame or lead wire to the electrode terminal, making production extremely easy and inexpensive. (This terminal treatment is usually done by soldering or welding, but soldering is a troublesome process that contaminates the moisture sensitive element with the flux used and makes it difficult to judge whether welding is good or bad.) (The effect of being able to omit this can be said to be a noteworthy effect from the perspective of improving productivity and quality.) With such a structure, if the wire thickness is reduced and the winding pitch of the counter electrode is shortened, the overall The shape can be significantly reduced, and by increasing or decreasing the number of turns, the resistance value corresponding to humidity can be freely adjusted, making it suitable for various uses.

■Those using a moisture-sensitive coating film formed by dipping and drying a colloidal silica/acrylic composite particle emulsion liquid have high water vapor permeability, and the moisture-sensing function of the moisture-sensitive coating film is not inhibited. It can prevent damage and contribute to the production of inexpensive humidity sensor elements. Therefore, it is suitable as a sensor for use in disposable products such as diapers for infants and bedridden elderly people.

[Brief explanation of the drawing]

Figures 1 to 4 are drawings showing the first to fourth embodiments of the present invention, in which (A) is a perspective view showing the external appearance of the sensor, and (B) is a perspective view of the sensor in (A) of each figure. A partial longitudinal enlarged view of the sensor, Figures 4 (C) to (E) are perspective views showing the sensor manufacturing procedure, Figure 5 is a perspective view showing the resistance measurement terminal, and Figure 6 is a perspective view showing the sensor manufacturing procedure.
The figure is a longitudinal sectional front view, Figures 7 to 11 are characteristic diagrams for each example, and Figure 12 is a diagram showing the micropores of the moisture sensitive element, in which (b) is a perspective view, and (a) FIG. 13 is a partially enlarged perspective view of the exit (1), (c) is an enlarged longitudinal sectional view of (a), and FIG. 13 is a perspective view showing a conventional example. 9 Ni stainless steel wire 10. Chemical conversion treatment moisture-sensitive body 1]: Metal electrode 12.12': Moisture-sensitive coating layer 13: Counter electrode 14: M stopper 15: Electrode Summary Applicant Nippon Pariki Rising Co., Ltd. Agent Patent attorney Certified copy Isou

Claims (18)

[Claims] 1. A metal electrode serving as the first electrode is coated with a moisture-sensitive film,
In a humidity sensor configured such that a counter electrode serving as a second electrode is in contact with the film, the humidity sensitive body film is a chemically treated film, and a moisture sensitive coating layer is formed on the chemically treated film. A humidity sensor characterized by: 2. The humidity sensor according to claim 1, wherein the second electrode is metal. 3. 3. The humidity sensor according to claim 1, wherein the first electrode has a metal electrode and an electrode terminal lead integrally formed, and the second electrode has a counter electrode and its terminal lead integrally formed. 4. 4. The humidity sensor according to claim 1, wherein the counter electrode is linear and is wound around a metal electrode. 5. The humidity sensor according to claim 4, wherein the metal electrode is cylindrical. 6. 5. The humidity sensor according to claim 4, wherein the metal electrode is plate-shaped and has both sides coated with a chemical conversion film. 7. Claim 2 or 3, in which one wire is bent in two, the wires are brought into contact with each other, and the wires are fixed to each other at both ends of the contact portion, one of which is configured as a metal electrode and the other as a counter electrode.
Humidity sensor listed. 8. The humidity sensor according to claim 2 or 3, wherein two wires are brought into contact with each other, and the wires are fixed to each other at both ends of the contact portion, so that one of the wires serves as a metal electrode and the other as a counter electrode. 9. 9. The humidity sensor according to claim 5, wherein the metal electrode and the counter electrode are brought into contact with each other and are covered with a heat-shrinkable resin molded body. 10. Either or both of the metal electrode and counter electrode are made of steel,
Claim 2, 3, 4, 5, or 6 made of copper, aluminum, nickel, stainless steel, titanium, or alloys thereof, or zinc-plated or tin-plated metals or alloys.
Or the humidity sensor according to 7, 8 or 9. 11. Claim 9 or 10, wherein either or both of the metal electrode and the counter electrode are plated with gold or platinum.
Humidity sensor listed. 12. 12. The humidity sensor according to claim 1, wherein the chemical conversion coating is a phosphate coating, a chromate coating, or a non-chromate coating. 13. Phosphate film is Zn_3(PO_4)_2・4H
_2O (Hopeite), Zn_2Fe (PO_4)
_2・4H_2O (Phosphophyllite)
, Zn_2Ca(PO_4)_2・2H_2O(Sch
olzite), Zn_3(PO_4)_2・2H_2
O, AIPO_4, AIPO_4・2H_2O, Fe_
3(PO_4)_2・8H_2O(Vivianite
), (Mn,Fe)_5H_2(PO_4)_4・4H
_2O(Hureaulite), Mn_5H_2(P
O_4)_4・4H_2O(Mn-Hureaulit
e), Fe_5H_2(PO_4)_4・4H_2O(
Fe-Hureaullite), FePO_4・2H
_2O (Strengite), CaHPO_4・2H
_2O(Brushite), CaHPO_4(Mon
Phosphate chromate is a chemical conversion coating whose main component is one or more of the following: The humidity sensor according to claim 12, wherein the film or the non-chromate film is a titanium-tannic acid complex salt film or a zirconium-phytic acid complex salt film. 14. 14. The humidity sensor according to claim 1, wherein the moisture-sensitive coating layer is a coating layer containing phosphate and resin as main components. 15. The phosphate contained in the moisture-sensitive coating layer is Zn_3 (PO
_4)_2・4H_2O(Hopeite), Zn_2
Fe(PO_4)_2・4H_2O(Phoshop
hyllite), Zn_2Ca(PO_4)_2・2
H_2O (Scholzite), Zn_3 (PO_4
)_2・2H_2O, AlPO_4, AlPO_4・2
H_2O, Fe_3(PO_4)_2・8H_2O(V
ivianite), (Mn, Fe)_5H_2(PO
_4)_4・4H_2O (Hureaulite), M
n_5H_2(PO_4)_4・4H_2O(Mn-H
ureaulite), Fe_5H_2(PO_4)_
4・4H_2O (Fe-Hureaulite), Fe
PO_4・2H_2O (Strengite), CaH
PO_4・2H_2O (Brushite), CaHP
Claim 1: One or more types of O_4 (Monetite), and the resin is a heat-reactive water-soluble urethane resin.
Humidity sensor according to 4. 16. One or more mixtures of known moisture absorbers such as water-soluble alkali phosphates, alkaline earth orthodihydrogen phosphates, or lithium chloride are added to either or both of the chemical conversion coating and the moisture-sensitive coating layer. The humidity sensor according to claim 1, 12, 13, 14 or 15, wherein the humidity sensor is supported. 17. 17. The humidity sensor according to claim 1, wherein the moisture-sensitive coating layer is a coating layer formed by coating a colloidal silica/acrylic composite particle emulsion. 18. Claim 1 or 12 or 13 or 14 or 15, wherein the moisture-sensitive coating layer is a coating film formed from a moisture-permeable paint.
Alternatively, the humidity sensor described in 16 or 17.