JPH0820394B2 - Humidity sensor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a humidity sensor (in a broad sense) used as a humidity sensor, a moisture condensation sensor, a raindrop sensor, and the like.

[Prior Art] Conventionally, as a humidity sensor for detecting humidity, there are a hair hygrometer, a moisture-sensitive bulb thermometer, a lithium chloride sensor, etc., and an anti-fog control for anti-fog glass used in automobiles, aircrafts, etc. It is widely used as a sensor for performing.

However, conventional ones are not satisfactory in terms of practicability because they require maintenance and require reliability.

Therefore, recently, as shown in FIG. 15 (a), the moisture sensitive body 1 made of sintered semiconductor ceramics is provided with the electrodes 2, 2 ', and as shown in (b), the electrically insulating substrate 7 is used. There is also a humidity sensor in which the humidity sensor 1 is covered with the electrodes 2 and 2 ', which have been developed and put into practical use. In addition, 3 is a terminal electrode, 4 is a lead wire, 5 is an electrode terminal processing part, 6 is soldering, and 8 is electric welding.

[Problems to be Solved by the Invention] By the way, the semiconductor ceramic moisture sensitive body 1 is formed into a sintered body by press-molding raw material oxide mixed powder under high pressure and firing at high temperature. For this reason, steps such as raw material mixing, press molding, and high temperature firing are required, while a sensor for a moisture-sensitive material coated on a substrate requires raw material mixing, thermal spraying, printing, and baking steps. These processes require experience and a high degree of skill, and must use expensive manufacturing equipment such as a press machine, a firing furnace, or a thermal spraying machine or a printing machine. An alumina substrate or a heat-resistant glass substrate is used as the electrically insulating substrate for covering the moisture sensitive body.

As described above, because the oxide mixed powder is used as the raw material of the humidity sensitive material, or the ceramic or heat-resistant glass substrate is used, the humidity sensitive material manufactured through complicated steps by the expensive manufacturing equipment has high manufacturing cost. , It is one of the factors that delay the spread of humidity sensors.

Since the humidity sensitive body 1 of the sensor thus manufactured has a large electric resistance with respect to humidity, in order to be able to measure the resistance value by connecting it to an external electronic circuit, the counter electrode 2 should be as shown in the figure. As a comb structure, the opposing portions of the electrodes are lengthened to reduce the resistance value between the electrodes. This comb-shaped electrode is connected to the terminal electrode 3, and is bonded to a lead wire 4 for connecting to an external electrode circuit by soldering 6 or electric welding 8 in the electrode terminal processing section 5. The counter electrode 2 having a comb structure is formed by printing and applying a gold paste or a ruthenium oxide paste on the moisture sensitive body 1 or the substrate 7 and firing it. However, the counter electrode 2 is restricted between the electrodes due to the printing technique and the bleeding of the paste. It is difficult to set the distance to the desired value, and there is a risk that the counter electrode will short-circuit when the distance becomes 0.3 mm or less. For this reason, if expensive paste is used and the resistance value between electrodes required for designing an electronic circuit cannot be obtained even by a skilled printing technique, the number of electrodes may be increased or the electrodes may be lengthened to increase resistance. Since the value must be small, there were restrictions on the shape and miniaturization of the sensor.

Further, in order to bond the lead frame or the lead wire 4 for connecting the sensor to the external electronic circuit to the terminal electrode 3, an electrode terminal processing unit 5 in which a silver or gold paste is printed and fired in advance is provided. When the soldering is performed, the flux used scatters and enters the moisture sensitive body and adversely affects the performance of the moisture sensitive body 1. Therefore, take a method of protecting the moisture sensitive body 1 from contamination in advance, or remove the contamination after soldering. It was necessary to take action to remove it. In either case, a complicated process is required, which is a cause of lowering productivity and product yield. On the other hand, when the bonding is performed by the electric welding 8, the flux is not adversely affected, but it is difficult to determine whether or not the bonding is complete, which may cause a problem such as poor continuity after shipment as a product. Therefore, in any case, it can be said that the step of adhering the lead frame or the lead wire 4 to the terminal electrode 3 of the sensor is an important step that deteriorates the performance of the sensor and affects productivity and product yield.

As described above, the conventional humidity sensor has a high manufacturing cost of the humidity sensitive body, and since the electric resistance value thereof is large, the counter electrode having a comb-shaped structure is used to reduce the resistance value, and this electrode structure is also expensive. Since it requires various materials and advanced technology, it has been an obstacle to increasing the manufacturing cost of sensors and miniaturization. Further, the electrode terminal treatment required for connecting the sensor and the external electronic circuit deteriorates the performance of the sensor, lowers the productivity and the yield of the product, and causes the increase of the manufacturing cost.

It is an object of the present invention to provide a humidity sensor that solves the above problems of the conventional humidity sensor.

[Means for Solving Problems] The present invention is to solve the above problems by a humidity sensor configured by devising a method of coating a metal electrode, a counter electrode, and a moisture sensitive body.

[Embodiment] Reference Example 1: FIG. 1 shows a reference example of the humidity sensor of the present invention. FIGS. 9A to 9D are views for showing the manufacturing process. The size shown in (a) of the figure is, for example, 10 mm ×
A 10 mm × 0.6 mm galvanized steel plate 9 is punched out and molded to form a first metal electrode 11 coated on the surface as a moisture sensitive body 10. The moisture sensitive material 10 is calcium and zinc based Zn ₂ Ca (PO ₄ ) ₂ 2H ₂ O (Scholzite), and the metal electrode is coated with the degreasing agent Parculin N364S (manufactured by Nihon Parkerizing Co., Ltd. ) In a 60 ° C hot bath for 10 minutes, washed with running water, then immersed in a 10% hydrochloric acid aqueous solution to elute and clean the surface of the galvanized layer. After washing with water again, the chemical conversion treatment agent Fericoat (made by our company) 95- It was dipped in a 98 ° C chemical bath for 10 minutes for chemical conversion treatment. After the treatment, it was thoroughly washed with water, drained and dried at 100 ° C. for 5 minutes in a drying oven to manufacture a metal electrode 11 coated with a moisture-sensitive film having a thickness of 15 μm. Counter electrode 13
As shown in (b) of the figure, the phosphor bronze for springs with a thickness of 0.3 mm is punched into a size of 11 mm × 7 mm and molded, and on both sides, for example, a diameter of 0.4 mmφ, a plurality of 84 pieces. Vent holes 12 are formed. The humidity sensor of the reference example is constructed by mounting the metal electrode 11 inside the counter electrode 13 so as to sandwich the metal electrode 11 and fixing the metal electrode 11 by the fixing metal fitting 14 shown in FIG. .

In addition, 4 is an electrode terminal lead wire, for example, 0.3 mm × 0.5 mm
A size of × 10mm is used. As the counter electrode 13 ,
The elastic material is selected as described above, and as shown in FIG.
When the electrode 11 is sandwiched and fixed in the electrode 13 , the moisture sensitive body 10 and the counter electrode 13 are brought into contact with each other with an appropriate pressure.

The ventilation holes 12 provided in the counter electrode 13 are for allowing moisture to easily reach the moisture sensitive body 10. Instead of or in addition to this, the counter electrode 13 is provided. May be formed in a zigzag shape so that the length of the contact side becomes long.

The counter electrode 13 is a structure in which folded a single electrode as shown in FIG. (B), the counter electrode 13 has been described for the case of mounting the metal electrode to the inward, instead of this 1 It may be constituted by a single sheet, and may be simply superposed on the metal electrode 11 and fixed to each other.

Since the electric resistance of the moisture-sensing body 10 that has adsorbed moisture changes depending on the amount of moisture, the lead wire 4 is connected to an external resistance measuring circuit (omitted) and the humidity-sensing body between the electrodes 11 and 13 is connected. By reading the electric resistance in the thickness direction of 10, the change in humidity can be measured. The moisture sensitive body 10 made of this phosphate film is
Since it is a very thin film of the order of 10μ, its resistance value is much smaller than the sheet resistance value obtained by measuring with a conventional comb-shaped electrode.

In FIG. 1, the reason why the zinc-plated iron molded body is used for the electrode 11 is that it is suitable for coating the phosphate coating used for the moisture sensitive body by chemical conversion treatment. Besides this,
Iron, copper, nickel and stainless steel can also be used as metal electrodes because they can form a phosphate film.

On the other hand, the reason why the phosphor bronze is used as the counter electrode 13 is that the contact resistance between the humidity sensing element and the counter electrode can be low and the fluctuation can be carried with a small amount. It is not limited to this. In environments where corrosion is a concern, nickel plating, gold plating or other precious metal plating is also effective. If the counter electrode is coated with a phosphate film, the short circuit between electrodes, which is rarely seen when the moisture sensitive body of the metal electrode is thin or when a part of the film is removed, can be completely prevented. Not only can it be done, but it can be said that it is the best means for rust prevention. In addition, the phosphate coating is iron,
It can be said that it is an inexpensive material as a moisture sensitive material for coating the counter electrode, because a film easily deposited from an aqueous solution can be formed on the surface of copper, nickel and galvanized iron materials.

The results of humidity characteristics of this reference example measured using a 1 KHz, 5 V power supply are shown in FIG. 6 as a semi-logarithmic curve.
As shown in the figure, the humidity sensitive element 10 has a high resistance value in a low temperature range of 75% or less of relative humidity and does not show a large change with respect to humidity change, but the resistance value changes rapidly in the high humidity range. ing. In addition, there is almost no difference in resistance between humidification and dehumidification at the same humidity. Therefore, it can be said that this humidity sensor has excellent performance as a dew condensation sensor. Fig. 7 shows the resistance curve after the humidity test of this humidity sensor was repeated 1,000 times under the condition of RH70% RH100%. As can be seen by comparing Fig. 6 and Fig. 6, the resistance values are in the initial and final stages. In the experiment, there is almost no change, and it is clear that the stability is excellent.

In this reference example, both the metal electrode 11 and the counter electrode 13 coated with the moisture sensitive body 10 are flat plates, and the counter electrode 13 is in close contact with substantially the entire area of the moisture sensitive body 10 to press the film. Although it has a structure, if the metal electrode has a curved cross section such that it protrudes outward like a circle or an ellipse, a linear counter electrode can be wound around the metal electrode and brought into contact with the moisture sensitive film. . In this case, the end of the wound counter electrode can be used as it is as an electrode terminal lead wire, so that the structure of the sensor is further simplified. Each embodiment of the present invention thus configured will be described below.

Example 1: Fig. 2, the surface zinc phosphate Zn ₃ (especially side) of a cylindrical metal electrode 11 (PO ₄₎ a ₂ · 4H ₂ O (Hopeite) film coated as sensitive wet product 10 ， This metal electrode is a linear counter electrode to 11
A humidity sensor is formed by winding 13 together. In this case, for example, a copper wire having a diameter of 0.6 mm is used as the wire forming the counter electrode, and a cylindrical iron material having a diameter of 6 mm and a height of 12 mm is used as the metal electrode 11 , and the wire spacing is 0.8 mm. In the figure, 15a and 15b are, for example, 2 mmmφ plastic stakes, which are used to prevent the wires that will be the counter electrodes from loosening.

In this case, the metal electrode 11 may not be covered with the moisture sensitive body, but instead may be a linear counter electrode that serves as the moisture sensitive body and is coated with a phosphate film.

FIG. 8 and FIG. 9 are the measured values in the case of Example 1 where the moisture sensitivity characteristics and humidification / dehumidification were repeated 1,000 times, and the same effects as in Reference Example 1 were observed.

Example 2: FIG. 3 shows that both the metal electrode 11 and the counter electrode 13 are linear electrodes, and one of them is coated with a phosphate film to serve as the moisture sensitive body 10. This is a sensor configuration.

As a specific example, as the metal electrode 11 , 0.4 mmmφ
For the counter electrode 13 , the iron wire coated with nickel plating of 1 μ and gold plating of 0.5 μ was used as the counter electrode 13 , and manganese phosphate (Mn, Fe) ₅ was used as the humidity sensor.
Chemical conversion treatment may be carried out according to Reference Example 1 so as to form a film of H ₂ (PO ₄ ) ₄ / 4H ₂ O (Hureaulite).

FIG. 10 and FIG. 11 are the moisture sensitivity characteristic diagram and the actual measurement value after 1,000 times of humidification and dehumidification for Example 2 respectively.

Example 3: FIG. 4 shows an example in which one of the electrodes 11 and 13 is a plurality of stranded wires, and the wire-shaped opposite electrodes are iron wire, copper wire, nickel wire, nickel chrome wire, and stainless wire. It is possible to reduce the contact resistance with the moisture sensitive body 10 by using any one of these wires or a wire plated with gold or platinum to reduce the contact resistance of the moisture sensitive body 10 with a stranded wire. Since it is pressed, there is little change in the contact resistance and it is suitable for this configuration. The moisture sensitivity characteristics in this case are as shown in FIG.

In this case, it goes without saying that the metal wire coated with the phosphate film can be used as the counter electrode.

Example 4: As shown in FIG. 5 (a)-(b)-(c)-(d), the manufacturing process is shown as follows.
Fold two metal wires, twist them into contact with each other, cut the bent parts, and use one wire as the metal electrode 11 , the other electrode as the counter electrode 13 , and the wire end as the electrode terminal lead wire 4. did. It can be said that this embodiment is the simplest humidity sensor in the embodiments.

Even in this configuration, the number of wires coated with the moisture sensitive body 10 does not have to be one, and two or more moisture sensitive body coated wires are bent and twisted together to form one or more wires at the end. ，
The humidity sensor can be constructed by dividing the remaining plural lines into groups and using one group as a metal electrode and the other group as a counter electrode and cutting the bent portion.

FIG. 13 shows the moisture sensitivity characteristic in this case. In this case, as shown in the figure, there is no change in the resistance value between humidification and dehumidification, so there is a practical advantage as a sensor with extremely good performance as a dew condensation element that does not cause hysteresis.

The moisture sensitive body 10 of each of the above-mentioned embodiments is constituted by a phosphate coating, and the entire surface of the mild steel plate electrode 11 is coated by the chemical conversion treatment method. According to this method, a film having a uniform thickness can be coated by a simple process of immersing the mild steel sheet in the aqueous solution phosphate mixed bath. The phosphate coating produced by the chemical conversion treatment method is firmly adhered to the steel sheet, and because the coating has a myriad of extremely fine pores, it is highly hygroscopic and hydrophilic. It can be said that it is the most suitable method for coating the phosphate film of.

The following are examples of those that can produce a phosphate film that can be coated by a chemical conversion treatment method.

_{That, Zn 3 (PO 4) 2} · 4H 2 O (Hopeite), Zn 2 Fe (PO 4) 2 · 4
_{H 2 O (Phosphophyllite), Zn} 2 Ca (PO 4) 2 · 2H 2 O (Scholzi
te), Zn ₃ (PO ₄ ) ₂・ 2H ₂ O, AlPO ₄・ 2H ₂ O, AlPO ₄ ,, Fe ₃ (PO ₄ ) ₂
・ 8H ₂ O (Vivianite), (Mn, Fe) ₅ H ₂ (PO ₄ ) ₄・ 4H ₂ O (Hurea
_{ulite), FePO 4 · 2H 2} O (Strengite), Fe 5 H 2 (PO 4) 4 · 4H
₂ O (Fe-Hureaulite), Mn ₅ H ₂ (PO ₄ ) ₄・ 4H ₂ O (Mn-Hureaul
ite), CaHPO ₄・ 2H ₂ O (Brushite), CaHPO ₄ (Monetit
Although a phosphate coating containing at least one of the above e) as a main component is used as a moisture sensitive material and is suitable for coating the metal electrode 11 or the counter electrode 13 , the phosphate coating of the present invention is a chemical conversion coating. It is not limited to the treatment method.

For example, phosphate powder or phosphate glass powder may be spray-coated, or they may be adjusted to paste ink for printing / application. Also, conventionally,
You may make it coat | cover the oxide semiconductor film currently used as a moisture sensitive body.

It is desirable that the thickness of the phosphate film be 0.5 to 120μ, and if the metal electrode or the counter electrode is linear and twisted or wound, it should be 0.5 to 3μ.
A thickness of 0μ is desirable. The reason for this is that if the film thickness is 0.5 μm or less, short-circuiting between electrodes is likely to occur when the electrodes are contacted by causing a part where the film is cut off and the electrode is exposed, while a film thickness of 120 μm or more In this case, the unevenness of the surface of the film increases and the contact between the moisture sensitive body and the counter electrode deteriorates, resulting in an increase in the electrical resistance between the electrodes. Also, the film thickness is 30μ
When twisting the above items, the film peels off the wire.
It becomes easy to fall off.

In addition, the humidity sensitivity of the phosphate film obtained by the chemical conversion treatment varies greatly on a semi-logarithmic graph in the high humidity dew condensation environment as shown in Figs. 6 and 7, but in the low humidity region. Since the ions have the property of not easily dissociating, the change in electric resistance corresponding to the change in humidity is small
We succeeded in improving the humidity sensor suitable for the humidity sensor by the method described below.

That is, focusing on the fact that the chemical conversion coating contains countless ultrafine pores as described above, potassium phosphate, sodium metaphosphate, sodium pyrophosphate, sodium pyrophosphate, or pyrophosphate, which are phosphates soluble in water, are noted. Immerse a metal electrode or counter electrode coated with a phosphate film in an aqueous or alcoholic solution of one or more of potassium, a mixture thereof, or a salt belonging to an alkaline salt or an alkaline earth ortho dihydrate, or a counter electrode. Then, after impregnating the ultrafine pores of the film, water or alcohol was evaporated to obtain a water-soluble phosphate. Soluble phosphate supported on ultra-fine pores dissociates into ions to lower the resistance between the electrodes even at low temperatures, and changes in resistance corresponding to changes in humidity are increased to improve the sensitivity for humidity sensors. Sufficiently functions as a wet body. Since the pores in which water-soluble phosphate is supported are minute, the phosphate solution that has been made into an aqueous solution does not flow out, and there is no problem in durability.

FIG. 14 shows that the soluble phosphate is supported on the micropores. As shown in FIG. 2A, an enlarged view of the moisture sensitive body 10 made of a phosphate film covering the metal electrode 1 ′ in FIG. 2B is oriented in innumerable and disordered directions. The fine holes 16 that have been formed are formed.
As shown in the enlarged cross-sectional view of FIG. 3C, the soluble phosphate 17 is carried therein. The micropores 16 in which the phosphate 17 is present can be filled with a sesame (Fe ₂ O ₃ ) or colloidal magnetic iron oxide (Fe ₃ O ₄ ) or semiconductor oxide fine powder. That is, if the valve stem is suspended in an alcohol liquid in which sodium metaphosphate is dissolved and the liquid is applied to the phosphate film surface with a feather or a brush, the valve stem powder is carried into the alcohol and enters into the fine pores, and the alcohol When the powder is vaporized, the rouge powder is supported in the fine pores by sodium metaphosphate. The same applies to semiconductor oxides and magnetic iron oxides.
The oxides carried in the micropores in this way are also effective in lowering the resistance value of the humidity sensor and the condensation sensor and adjusting the sensitivity.

(Operation) In the humidity sensor of the present invention, the metal electrode is coated with the moisture sensitive body, and the counter electrode is brought into contact with the metal electrode. It can be detected.

Also, when the present invention is applied to a wire-shaped metal electrode and a counter electrode, and a humidity sensor is configured by twisting both electrodes, the moisture-sensing body and the electrode come into contact with each other at the twisted portion, so that the humidity sensor can be properly connected. This is to detect humidity.

Any known moisture sensitive material may be used as the moisture sensitive material in the above-mentioned configuration, but in particular, if a phosphate coating obtained by chemical conversion treatment is adopted as the moisture sensitive material, it is included in the phosphate sensitive coating. Due to the excellent hygroscopicity and hydrophilicity of the large number of micropores, it is possible to manufacture highly accurate humidity sensors with extremely high sensitivity.

Furthermore, the water resistance of the sensor can be adjusted by impregnating and supporting water-soluble phosphate or iron oxide in the micropores, so it is possible to use the dew condensation sensor instead of the humidity sensor. Became.

Since the micropores are micropores, the substance carried in the micropores does not flow out, and a long life is guaranteed.

(Effect of the Invention) The humidity sensor of the present invention has the following excellent effects as compared with the conventional one.

There is no need for comb-shaped electrodes like the conventional one,
As a result, it is excellent in that the electric contact between the counter electrode and the moisture sensitive body can be made over the entire surface of the electrode.

Since the electrode terminal lead wire can be formed integrally with the electrode, there is no need for a terminal treatment for adhering the lead frame or the lead wire to the electrode end. (Since this terminal treatment is usually performed by soldering or welding, it is a troublesome process such as contamination of the moisture-sensitive material by the flux for soldering and difficulty in judging the quality of welding. It can be said that the effect that can be omitted is a remarkable effect from the viewpoint of improving productivity and quality.) When a phosphate film coated on a metal electrode by a chemical conversion treatment method is used as a moisture sensitive material, this phosphate is a liquid. Although it dissolves only slightly in water and dissociates into ions to show conductivity, it reversibly returns to phosphate with the disappearance of water and loses conductivity, so it is possible to detect the presence or absence of condensation in a high humidity environment. It can be said that it is an excellent material as a moisture sensitive body. Also, as can be seen from the results of coating a metal surface with a phosphate film for many years as an anticorrosive agent, this film has a strong resistance to the environment, so if this film is used as a moisture sensitive material, the response will be high. , It is possible to build a durable condensation sensor.

As in each case of Examples 1 to 4, in the structure in which the metal electrode and the counter electrode are linearly twisted and twisted, the twisted portion serves as a moisture sensitive portion, and the end of the electrode also serves as a terminal lead wire as it is. It can be manufactured, is extremely easy to manufacture, and can be manufactured at low cost.

With such a structure, if the thickness of the wire is reduced, the overall shape can be remarkably downsized, and it can be applied to various applications.

Since it is possible to manufacture a small and inexpensive humidity sensor in this way, it can also be used as a humidity sensor for disposable items such as diapers for infants and bedridden elderly.

[Brief description of drawings]

FIG. 1 is a drawing showing a reference example, and FIGS. 2 to 5 are drawings showing the respective cases of embodiments 1 to 4 of the present invention.
FIG. 2 and FIG. 2 are perspective views, and FIGS. 3 to 5 are plan views. Further, FIGS. 6 to 13 are characteristic diagrams showing experimental results for the above-mentioned respective examples, and FIG.
The figure shows the state of soluble phosphate supported on the micropores. (A) is a partially enlarged view of (b), (b) is a front view,
(C) is a vertical enlarged view of (a). FIG. 15 is a perspective view showing a conventional example. 10 …… Moisture sensor, 11 …… Metal electrode 12 …… Vent hole, 13 …… Counter electrode 14 …… Fixing bracket

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Kazuhiro Ishikura 1-15-1 Nihonbashi, Chuo-ku, Tokyo Japan Parkerizing Co., Ltd. (72) Inventor Yasuo Imai 1-1-15 Nihonbashi, Chuo-ku, Tokyo Japan Parkerizing Incorporated (56) Reference JP 54-58897 (JP, A) JP 57-17101 (JP, A) JP 59-47703 (JP, A) Actual development 57-41157 (JP, A) U) Actual development Sho 55-118155 (JP, U) Actual public Sho 54-37355 (JP, Y2)

Claims (8)

[Claims] 1. A metal electrode serving as a first electrode and a counter electrode serving as a second electrode, wherein one or both of the metal electrode and the counter electrode is coated with a moisture sensitive film. , Second
A linear counter electrode serving as an electrode is wound around a metal electrode so as to be in electrical contact with the film of the moisture sensitive body, and the first electrode and the second electrode each include one or a plurality of wires. , A humidity sensor characterized in that each of these electrodes is twisted together. 2. The humidity sensor according to claim 1, wherein the second electrode is made of metal. 3. The first electrode according to claim 1, wherein the metal electrode is integrally formed with the electrode terminal lead thereof, and the second electrode is integrally formed with the counter electrode and the electrode terminal lead thereof. The humidity sensor described. 4. The first electrode and the second electrode are each formed by bending one or more wires, cutting a stranded wire obtained by twisting these wires at a bent portion, and one of the stranded wires at one end of the stranded wire. Alternatively, it is divided into two groups of a plurality of line portions and the remaining one or a plurality of line portions, one group is a metal electrode that serves as the first electrode, and the other group is a counter electrode that serves as a second electrode. The humidity sensor according to claim 1, wherein the humidity sensor is a wire terminal. 5. The humidity sensor according to any one of claims 1 to 4, wherein the film of the moisture sensitive body is a phosphate film. 6. The phosphate coating is Zn ₃ (PO ₄ ) ₂ .4H ₂ O, Zn _{2
Fe (PO 4) 2 · 4H} 2 O, Zn 2 Ca (PO 4) 2 · 2H 2 O, Zn 3 (PO 4) 2 · 2H
₂ O, AlPO ₄・ 2H ₂ O, AlPO ₄ , Fe ₃ (PO ₄ ) ₂・ 8H ₂ O, (Mn, F
_{e) 5 H 2 (PO 4} ) 4 · 4H 2 O, FePO 4 · 2H 2 O, Fe 5 H 2 (PO 4) 4 · 4H
_{1 out of 2} O, Mn ₅ H ₂ (PO ₄ ) ₄ / 4H ₂ O, CaHPO ₄ 2H ₂ O, CaHPO ₄
The humidity sensor according to claim 5, wherein the humidity sensor is a chemical conversion treatment film containing two or more species as a main component. 7. A salt or a mixture of a plurality of salts selected from water-soluble alkali phosphate or alkaline earth ortho dihydrogen phosphate having fine pores in the phosphate coating, or metaline. The humidity sensor according to claim 5, which carries one or a mixture of a plurality of moisture sensitive agents such as potassium acid and lithium chloride. 8. The micropores in the phosphate coating are valve stems (Fe ₂ O
₃ ) or a magnetic sensor according to claim 5, which carries magnetic iron oxide or semiconductor oxide.