JPH04258750A - Manufacture of resistance-variable humidity-sensitive element - Google Patents

Abstract

PURPOSE:To manufacture a resistance-variable humidity-sensitive element having an excellent basic characteristic and environment resistance, little aging changes, and little dispersion of characteristics among elements with good reproducibility. CONSTITUTION:An acrylic polymer and a multi-functional isocyanate compound having a cationic dissociation group and a hydroxyl group are dissolved in a polar non-proton solvent serving as a good solvent for them to manufacture a humidity-sensitive base liquid. The humidity-sensitive base liquid is coated on an insulating substrate 1 formed with mating electrodes 2, heat treatment is applied to remove the solvent, and polymer chains are three-dimensionally cross-linked by the reaction between the hydroxyl group and the isocyanate group to form a polymer humidity-sensitive film 3.

Description

[Detailed description of the invention]

[Object of the invention]

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a variable resistance humidity sensing element using a polymer membrane having an ionic dissociative group as a humidity sensing element.

0003

2. Description of the Related Art A well-known method for detecting humidity in an atmosphere is to use a moisture-sensitive material whose electrical characteristics change due to adsorption and desorption of moisture. Moisture-sensitive elements using moisture-sensitive materials are designed to measure changes in the electrical conductivity and dielectric constant of the moisture-sensitive material due to adsorption and desorption of moisture by adjusting the impedance between electrodes formed in advance to sandwich the moisture-sensitive material. It is generally detected as a change in electrical resistance or capacitance. Additionally, known moisture-sensitive materials include ceramic materials, electrolytes such as lithium chloride, hygroscopic (hydrophilic) polymer materials, polymer electrolytes, and polymer composite materials containing conductive fillers. ,
Each has been put into practical use. Among these, moisture-sensitive elements using hygroscopic polymers or polymer electrolytes have a wide moisture-sensing range and excellent responsiveness, and their structure is relatively simple and easy to manufacture, so they have excellent moisture-sensing characteristics. There is also interest not only in terms of mass productivity and cost.

[0004] In moisture-sensitive elements using moisture-sensitive materials such as hygroscopic polymers and polymer electrolytes, these polymeric materials are
It is used as a self-supporting film or as a thin film on a suitable substrate. In particular, the method of using a thin film of moisture-sensitive material (moisture-sensitive film) on a substrate has many advantages when considering responsiveness, mechanical strength, manufacturing process, etc. Moisture-sensing elements with such a configuration can be roughly divided into types that detect the resistance or capacitance between the opposing electrodes by providing opposing electrodes on an insulating substrate and stacking a moisture-sensitive film to cover this (surface type). There are two types (sandwich type or capacitor type) in which a lower electrode is provided on an insulating substrate, a moisture-sensitive film and an upper electrode are sequentially laminated on top of the lower electrode, and the resistance or capacitance between the two electrodes is detected. . In addition, the polymeric material used as the moisture-sensitive membrane is required to have different electrical properties depending on the detection method, with the resistance detection type requiring the conductivity of the polymer moisture-sensitive membrane, and the capacitance detection type requiring the dielectric property ( insulation) is important.

By the way, in a capacitive detection type humidity sensing element, in order to obtain a large capacitance value in as small a space as possible, the humidity sensitive film is generally made as thin as possible, and the element is of the above-mentioned capacitor type. At this time, it is essential to improve the film formability of the moisture-sensitive film material, and the surface properties of the substrate surface and electrode surface are particularly important. Therefore, in order to obtain a smooth substrate surface, polishing processing is required, the material of the substrate is limited, and electrodes must be formed by physical vapor deposition or plating, so the element structure There are many restrictions on the manufacturing method. On the other hand, the resistance value of a resistance detection-type moisture-sensitive element is almost determined by the resistivity of the moisture-sensitive film, the distance between opposing electrodes, and its effective cross-sectional area, and a surface-type element with a relatively simple structure is sufficient. Since detection can be performed with high accuracy, it has the advantage of having fewer restrictions on device structure and manufacturing method.

[0006] Such a resistance detection type moisture-sensitive element is generally constructed by forming a pair of opposing electrodes on an insulating substrate such as alumina, and forming a polymer moisture-sensitive film to cover these electrodes. Used as a surface type element. In addition, the moisture-sensitive membrane materials for the resistance detection type mentioned above include polymers having ionic dissociative groups in their molecules (polymer electrolytes in a broad sense) and polymers having hydrophilic functional groups. Polymers with conductivity are commonly used. The counter electrode has a comb-like shape in order to have a sufficient opposing length, and is made of a noble metal such as gold or platinum because corrosion resistance is required. In addition, physical vapor deposition and printing methods are used to form the counter electrode, but vapor deposition requires expensive equipment and complicated processes such as patterning, so thick-film conductor paste made of precious metals is used. , printing, and baking are common methods.

[0007] Furthermore, in order to form the above-mentioned moisture-sensitive film on the counter electrode, a moisture-sensitive mother liquor is prepared by dissolving a polymer having an ionic dissociative group serving as a humidity-sensitive element in a solvent, and then this moisture-sensitive mother liquor is This is generally done by casting onto a counter electrode. In addition, in order to improve film-forming properties at this time, using hydrophobic segments as the basic skeleton, ionic dissociative groups are introduced by copolymerization with ionic comonomers or polymer reactions, or hydrophobic polymers and polymers are introduced. Efforts have been made such as blending molecular electrolytes. In addition, it is water resistant, solvent resistant, moisture resistant,
In order to improve environmental resistance properties such as heat resistance, methods for three-dimensionally crosslinking polymer chains have been devised and applied. This crosslinking method includes, for example, a method in which a polyfunctional monomer is added and copolymerized, a method in which a reactive functional group such as an epoxy group or an isocyanate group is introduced into a polymer chain and reacted with a crosslinking component, and a method in which a radical generator is used. Alternatively, a method of adding an oxidizing agent and irradiating with radiation is exemplified.

[0008]

[Problem to be Solved by the Invention] As a method for improving the solvent resistance, humidity resistance, heat resistance, etc. of a polymeric moisture-sensitive material having an ionic dissociative group and obtaining a highly reliable moisture-sensitive element, the above-mentioned methods are as follows. Although such a method of crosslinking the polymer chains of moisture-sensitive materials is particularly useful, it has the following problems.

First, there are physical changes caused by crosslinking. Although it depends on the molecular structure and composition of polymers having ionic dissociative groups, they generally have a relatively small molecular weight, a low glass transition point (Tg), and often have poor film-forming properties. In particular, the higher the concentration of ionic dissociative groups, the greater this tendency. When such a polymer is crosslinked, if the crosslinking density is too high, the film becomes hard and may crack under various environments or peel off from the substrate or electrode. On the other hand, if the crosslinking density is too low, solvent resistance will be insufficient, making it difficult to cast a protective film, which will not only impose major restrictions on the manufacturing process, but also cause the film to flow and deform. occurs, and as a result, sufficient environmental resistance and stability over time cannot be obtained.

Second, there is a change in the resistance value and the linearity of resistance change due to crosslinking. In detection methods that utilize the ionic conductivity of polymer membranes, it is necessary that the concentration of dissociated ions (carriers) be sufficient according to moisture absorption, and that their mobility be sufficiently large. The concentration and type of sexually dissociable groups, the latter of which are considered to mainly depend on the molecular structure of the polymer chain and its molecular mobility. When polymer chains are cross-linked, the molecular mobility of the polymer chains decreases, resulting in a decrease in ionic conductivity and an increase in the resistivity of the moisture-sensitive membrane itself. In some cases, it becomes difficult to measure the resistance value. Also, depending on the crosslink density,
Hysteresis may increase or responsiveness may decrease.

The third factor is the influence of remaining unreacted crosslinking agents and active substances. In crosslinking treatment, it is necessary that various reactions proceed quantitatively, and if unreacted substances or active substances remain, chemical reactions will gradually occur, causing changes over time.

Furthermore, as a method for forming a moisture-sensitive film, after preparing a moisture-sensitive mother liquor containing moisture-sensitive components and additive components as described above, this is applied onto a substrate on which electrodes are formed, and a solvent is removed. The most common method is to remove the moisture-sensitive film, but in order to minimize the variation in characteristics between devices and improve stability over time, it is necessary to ensure that the moisture-sensitive film is a homogeneous and dense film, that is, has good film formability. Good things are necessary. To this end, it is important to optimize not only the composition of the moisture-sensitive film, but also the selection of the solvent, and the film-forming method and conditions.

The present invention solves the problems of cross-linked ion conductive polymer membranes as described above, has excellent basic characteristics and environmental resistance, has little change over time, and has small variations in characteristics between devices. It is an object of the present invention to provide a method for manufacturing a variable resistance humidity sensing element, which makes it possible to manufacture the variable resistance humidity sensing element with good reproducibility.

[Configuration of the invention]

[0015]

[Means and Effects for Solving the Problems] The method for manufacturing a variable resistance humidity sensing element of the present invention includes a counter electrode provided on an insulating substrate, and an ionic electrode formed across the counter electrode. In manufacturing a resistance change type moisture sensitive element comprising a moisture sensitive film made of a crosslinked polymer having a dissociative group, an acrylic polymer having a cationic dissociative group and a hydroxyl group and a polyfunctional isocyanate compound are used. By dissolving these in a polar aprotic solvent which is a good solvent to prepare a moisture-sensitive mother liquor, and applying this moisture-sensitive mother liquor on the insulating substrate on which the counter electrode is formed, heat treatment is performed. The method is characterized in that the moisture-sensitive film is formed.

That is, in the present invention, a solution (moisture-sensitive mother liquor) in which the above-mentioned acrylic polymer having a cationic dissociative group and a hydroxyl group and a polyfunctional isocyanate compound are dissolved in a polar aprotic solvent is applied to the counter electrode. The polymer moisture-sensitive film is formed by coating the substrate on which the film has been formed, removing the solvent by heat treatment, and three-dimensionally crosslinking the polymer chains through the reaction between hydroxyl groups and isocyanate groups. Form a film. The above-mentioned polymeric moisture-sensitive membrane is a reaction product of an acrylic polymer having a cationic dissociative group and a hydroxyl group and a polyfunctional isocyanate compound, and the main moisture-sensitive component is a cationic dissociable component in the acrylic polymer. It is the basis. Furthermore, the hydroxyl groups in the acrylic polymer and the isocyanate groups in the polyfunctional isocyanate compound contribute to crosslinking of the polymer chains. Note that the compositions of both components involved in the above reaction, that is, the acrylic polymer and the isocyanate compound, are not limited to a specific composition, but appropriate combinations and crosslinking conditions are selected depending on the molecular structure.

Here, the solvent of the moisture-sensitive mother liquor must be a good solvent for the above-mentioned acrylic polymer and polyfunctional isocyanate compound, and must be homogeneous and smooth in the process of evaporating the solvent and forming a polymer film. A polymer film can be obtained (good film formability)
In addition, it is necessary that there is no reactivity with isocyanate groups.

Although the solubility of the above-mentioned acrylic polymer varies depending on the composition, it is generally soluble in highly polar organic solvents, and is soluble in alcohols such as methanol and ethanol, cellosolves, mixed solvents containing alcohols, or chlorine. The system solvent is a good solvent. However, it does not dissolve in ester solvents such as ethyl acetate and ketones such as acetone, which are good solvents for polyfunctional isocyanate compounds. In terms of solubility, alcohols, cellosolves, and chlorinated solvents are considered as solvents for this system, but solvents containing alcohols and cellosolves have hydroxyl groups, so they are less reactive with polyfunctional isocyanates. This makes it unsuitable as a solvent for this system because it interferes with the desired crosslinking reaction between the hydroxyl groups in the acrylic polymer chain and the polyfunctional isocyanate. On the other hand, chlorinated solvents such as methylene chloride and chloroform have no problems with respect to solubility and reactivity with isocyanates, but the solvent has high volatility and a high evaporation rate, resulting in poor film-forming properties. On the other hand, some polar aprotic solvents that dissolve both the acrylic polymer and the polyfunctional isocyanate compound have relatively low volatility, so that film-forming properties can be improved. Furthermore, since it has no reactivity with isocyanate groups and does not interfere with crosslinking reactions, it is possible to improve film-forming properties and to obtain a moisture-sensitive film with excellent basic properties and stability over time.

[0019] The polar aprotic solvent used in the present invention is a solvent that has a large dipole moment among solvents that do not have the ability to provide protons and do not self-dissociate. Specifically, Examples include N,N-dimethylformamide (DMF), N,N-dimethylacetamide, dimethylsulfoxide (DMSO), and N-methylpyrrolidone (NMP). Although ketones such as acetone, methyl ethyl ketone (MEK), and tetrahydrofuran are also in the class of polar aprotic solvents, they cannot be used in the present invention because they do not dissolve the above-mentioned acrylic polymer. As a method for applying the above-mentioned moisture-sensitive mother liquid onto the substrate, commonly used spin coating methods, dip coating methods, etc. can be applied, as long as the conditions do not impair film-forming properties.

[0020] Next, the polymer moisture-sensitive membrane material, element configuration, etc. used in the present invention will be explained. The acrylic polymer used in the present invention has a cationic dissociative group and a hydroxyl group in the same molecule. Such acrylic polymers can be synthesized by copolymerizing monomers having each functional group as starting materials, or by introducing corresponding functional groups into a backbone polymer through a polymer reaction. It can be synthesized by various known methods.

[0021] Examples of the acrylic polymer include (
Copolymers of hydrophobic monomers such as meth)acrylic acid alkyl esters and styrene, comonomers having a cationic dissociative group, and comonomers having hydroxyl groups, or copolymers of the latter two are particularly preferred. Compared to the method of introducing various functional groups through polymer reactions, the copolymerization method makes it relatively easy to create polymers with the desired molecular structure by changing the type and concentration of monomers. This is because it can be synthesized. Moreover, it can also be synthesized stepwise by the macromer method. From this point of view, an acrylic polymer obtained using an acrylic monomer having a (meth)acryloyl group as a main raw material is desirable in the present invention from the viewpoint of ease of obtaining raw materials and synthesis.

[0022] As the above-mentioned monomer having a cationic dissociative group, quaternary ammonium salts such as 2-(meth)acryloxyalkyl-N-trialkylammonium halide and (meth)acrylamidoalkyltrialkylammonium halide are used. It will be done. Also,
Examples of monomers having a hydroxyl group include 2-hydroxyalkyl (meth)acrylate and N-hydroxyalkyl acrylamide, and examples of monomers having both a cationic functional group and a hydroxyl group include 2-hydroxy-3-( Examples include meth)acryloxyalkylammonium halide. In addition, as an example of introducing by polymer reaction, a method of chloromethylating styrene units in a copolymer and treating with trialkylamine to exchange halogen, etc. can be mentioned.

Examples of the polyfunctional isocyanate compound used in the present invention include diisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate; Examples include polyfunctional isocyanates which are addition reaction products of these diisocyanates to polyhydric alcohols, and polymers of diisocyanates. Examples of polyfunctional isocyanates include addition reaction products (adducts) of the above-mentioned diisocyanates to trimethylolpropane,
It includes those in which the hydroxyl groups of polyhydric alcohols are completely substituted and those in which the hydroxyl groups are partially substituted. Examples of the diisocyanate polymer include a tolylene diisocyanate trimer and a polymer of tolylene diisocyanate trimer and hexamethylene diisocyanate.

As the polyfunctional isocyanate used in the present invention, it is desirable to use an addition reaction product (adduct) to a polyhydric alcohol having a relatively large molecular weight or a polymer of diisocyanate. This can be achieved by using a polyfunctional isocyanate with a relatively large molecular weight.
Not only can a moisture-sensitive element with sufficient solvent resistance and heat resistance and excellent stability over time be obtained, but also the formability of the moisture-sensitive film is improved, and the variation in characteristics between elements is significantly reduced. It's for a reason. In addition, by using a high molecular weight polyfunctional isocyanate, toxicity, which is a problem when using isocyanates, is also reduced. The above effects are exhibited when the molecular weight of the polyfunctional isocyanate is greater than about 400, and in the present invention, it is possible to use such a polyfunctional isocyanate with a large molecular weight as a crosslinking component. desirable.

Furthermore, the reaction between the hydroxyl group and the isocyanate group in the acrylic polymer is highly reactive, and the reaction may proceed simply by mixing, but in order to quantitatively react, heating is required. It is desirable to do so.

The polymer moisture-sensitive membrane of the present invention obtained in this manner has urethane bonds formed by the reaction between the hydroxyl group introduced into the acrylic polymer having a cationic dissociative group and the polyfunctional isocyanate compound. Because the polymer chains are three-dimensionally cross-linked, the urethane cross-linking treatment provides excellent environmental resistance such as water resistance, solvent resistance, and moisture resistance, and it also has excellent environmental resistance such as water resistance, solvent resistance, moisture resistance, etc. There is almost no change over time. Moreover, since the cationic dissociative group is maintained as it is by crosslinking the polymer chains, the resistance value increases little due to the crosslinking process, the hysteresis is small, and the responsiveness is also excellent. and,
In the film-forming process, polar aprotic solvents such as DMF, DMSO, and NMP are used, making it possible to significantly improve film-forming properties and stabilizing the polymer moisture-sensitive film with the above-mentioned characteristics. In addition, it is possible to reduce the variation between elements. Especially a few μm
It is preferable that these properties are sufficiently exhibited when the film is made into a thin film of about 100%.

[0027] For the configuration of the variable resistance type moisture sensing element of the present invention, various known element configurations can be applied, which include a counter electrode provided so as to be able to detect a change in resistivity of a polymeric moisture sensitive film. be. An example of a general element configuration is shown in FIGS. 1 and 2. In these figures, 1 is alumina,
It is an insulating substrate such as glass. A comb-shaped counter electrode 2 made of a noble metal such as gold or platinum is provided on the surface of the insulating substrate 1.
is provided, and a polymer moisture-sensitive film 3 is formed to cover the comb-shaped counter electrode 2. Furthermore, a moisture-permeable protective film 4 is further formed on the surface of the polymer moisture-sensitive film 3. Although this protective film 4 is not necessarily required, it has water resistance,
In order to improve dew condensation resistance, it is desirable to form this. Further, as the material for forming the protective film 4, cellulose derivatives such as ethyl cellulose and cellulose acetate butyrate, which have relatively low hygroscopicity and sufficient moisture permeability, are preferable. The reason why cellulose derivatives are used here is that they have good film formability and can provide relatively flexible films, and are particularly effective in improving water resistance and dew condensation resistance. Note that, like the moisture-sensitive film, this cellulose-based protective film is formed by dissolving it in an organic solvent, applying it by spin coating or dip coating, and drying it by heating. Since the polymeric moisture-sensitive membrane is crosslinked, it has a certain degree of resistance to organic solvents, and even if a polar solvent is used, the moisture-sensitive membrane that has already been formed will not dissolve.

[0028]

[Examples] Examples of the present invention will be described below.

Example 1 As a moisture-sensitive material, methacrylamide propyldimethylbutylammonium bromide having a cationic dissociative group,
A ternary copolymer consisting of 2-hydroxyethyl methacrylate having a hydroxyl group and n-butyl methacrylate was synthesized by a radical polymerization method and purified. Next, the above terpolymer was treated with N, which is a polar aprotic solvent.
-Methylpyrrolidone to obtain a solution having a hydroxyl group content of 0.60% by weight (based on the solution). Further, to this solution, a polyfunctional isocyanate compound (1 mol:3 mol adduct of trimethylolpropane and tolylene diisocyanate) was added in an amount equal to the hydroxyl group.
was added to prepare a moisture-sensitive mother liquor.

Next, using the above moisture-sensitive mother liquor, a moisture-sensitive element as shown in FIGS. 1 and 2 was manufactured. That is, a homogeneous paste containing gold mercaptide as a main component is printed and fired on the alkali-free glass substrate 1 to a film thickness of about 0.5 mm.
.mu.m, and a comb-shaped counter electrode 2 with a distance of about 200 .mu.m between the electrodes was formed. The above-mentioned moisture-sensitive mother liquid was spin-coated onto the electrode-attached substrate, and then heat-treated at 100° C. for 30 minutes to form a polymer moisture-sensitive film 3 having a thickness of 4 μm to 5 μm. Further, a lead wire was attached to obtain a resistance variable moisture sensing element A.

Example 2 Commercially available ion conductive resin solution Elecondo B-149 (trade name, Soken Kagaku Co., Ltd.) having hydroxyl groups (0.73% by weight, based on solution) and quaternary ammonium base
) and a polyfunctional isocyanate compound (1 mol: 3 mol of trimethylolpropane and hexamethylene diisocyanate) in an equimolar amount relative to the above hydroxyl group content.
1 adduct) was dissolved in dimethyl sulfoxide (DMSO) to prepare a moisture-sensitive mother liquor. Then, this moisture-sensitive mother liquid was applied onto the electrode-attached substrate by the same method as in Example 1, and heat-treated in the same manner to obtain a moisture-sensitive element B.

Comparative Example 1 A moisture-sensitive element C was obtained using the same composition and method as in Example 2 except that methyl cellosolve was used as the solvent for the moisture-sensitive mother liquor.

Comparative Example 2 A moisture-sensitive element D was obtained using the same composition and method as in Example 2 except that methylene chloride was used as the solvent for the moisture-sensitive mother liquor.

The film forming properties and device characteristics of each of the variable resistance humidity sensitive devices obtained as described above were evaluated. The results are shown in Table 1 and FIGS. 3, 4, and 5. Film formability was determined by visual inspection. Regarding device characteristics, variations between devices were evaluated by measuring the range of initial resistance values. In addition, in order to compare the solvent resistance, moisture sensitive element A
, B, and C were each dip-coated with a cyclohexanone solution of ethyl cellulose and dried by heating to form a protective film, and the changes in humidity characteristics were compared. The humidity characteristics were determined by using a split flow humidity generator SRH-1 (trade name, manufactured by Shinei Co., Ltd.) and measuring the resistance value of the element at 25° C. with an LCR meter (1 kHz, 1 V). Furthermore, 60℃, 90℃
Under high temperature and high humidity conditions of %RH, changes in humidity characteristics were measured after each element was left without electricity. Figure 3 shows the measurement results of humidity sensing element A, and Figure 4 shows the measurement results of humidity sensing element B.
FIG. 5 shows the measurement results of the moisture sensitive element C.

[0035] (Hereafter the margin)
Table 1
moisture sensing element
Film formability Initial value
Moisture resistance
(exterior)
Resistance value range 60℃, 90%RH, 1
000h
(n=20)
Changes over time after being left unattended

(at50%RH) (at50%RH)
A (Example 1) Good 120kΩ to 190kΩ
-2%RH B (Example 2)
Good 58kΩ ~ 90kΩ
-1%RH C(
Comparative example 1) Good 50kΩ~
86kΩ -14%RH
D (Comparative Example 2) Surface roughness 11
0kΩ~850kΩ -17%RH

Slightly whitening
As shown in Table 1, only the surface of element D was whitened, the surface was rough, the film thickness was uneven, and it was inferior to the others. In addition, element D had a large variation in initial resistance value, and some elements had significantly large resistance values.

Regarding the solvent resistance, as is clear from FIGS. 3, 4 and 5, the moisture sensitive element A according to the example
, B show very slight changes in humidity characteristics due to the formation of the protective film, whereas the characteristics of the humidity sensing element C according to the comparative example change significantly. Furthermore, it can be seen that both the moisture sensitive elements A and B according to the example have good environmental resistance.

[0037]

Effects of the Invention As explained above, according to the method of manufacturing a variable resistance type moisture sensing element of the present invention, a moisture sensing element with excellent film formation properties, small variations between elements, and excellent environmental resistance can be produced. can be obtained stably.

[Brief explanation of the drawing]

FIG. 1 is a plan view schematically showing an example of the structure of a moisture-sensitive element of the present invention.

FIG. 2 is a cross-sectional view of the moisture-sensitive element shown in FIG. 1.

FIG. 3 is a diagram showing humidity characteristics of a humidity sensing element A according to an embodiment of the present invention.

FIG. 4 is a diagram showing humidity characteristics of a humidity sensing element B according to another embodiment of the present invention.

FIG. 5 is a diagram showing humidity characteristics of a humidity-sensitive element C according to a comparative example.

[Explanation of symbols]

1...Insulating substrate 2...Comb-shaped counter electrode 3...Polymer moisture sensitive membrane 4...Protective film

Claims (1)

[Claims] 1. A variable resistance type comprising a counter electrode provided on an insulating substrate, and a moisture sensitive film made of a crosslinked polymer having an ionic dissociative group formed across the counter electrode. In manufacturing a moisture-sensitive element, an acrylic polymer having a cationic dissociative group and a hydroxyl group and a polyfunctional isocyanate compound are dissolved in a polar aprotic solvent that is a good solvent for them, and a moisture-sensitive mother liquor is prepared. Prepare
A method for manufacturing a variable resistance type moisture-sensitive element, characterized in that the moisture-sensitive mother liquid is coated on an insulating substrate on which the counter electrode is formed, and then the moisture-sensitive film is formed by performing heat treatment.