JPH0658337B2 - Moisture-sensitive element and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial application> The present invention relates to a humidity-sensitive element whose electric resistance changes with a change in relative humidity, and more particularly to a humidity-sensitive element formed of an organic ionic polymer. It relates to a manufacturing method.

<Prior Art> As a humidity sensitive element that senses relative humidity based on a change in electric resistance or capacitance, there is the following.

a) A moisture sensitive element manufactured by impregnating a porous material with an electrolyte such as lithium chloride.

b) A moisture-sensitive element manufactured by dispersing a conductive solid in a hygroscopic polymer.

c) A moisture sensitive element manufactured by forming a metal oxide film on a substrate.

d) A moisture-sensitive element manufactured by forming a film of an organic ionic polymer on a substrate.

<Problems to be Solved by the Present Invention> The conventional techniques for manufacturing a moisture-sensitive element described above have the following problems.

In the humidity-sensitive element of a), the electrolyte is eluted when used in a high humidity environment.

In the moisture sensitive element of b), the sensitive humidity range is narrow,
Moreover, the linearity of the moisture sensitivity characteristic is poor.

In the humidity sensitive element of c), since the humidity sensitive element is contaminated by gas and fine dust in the air, the humidity sensitive property is likely to change and the reliability is low. Further, in terms of manufacturing, a post-treatment step and a cleaning step due to high temperature are required, which is complicated.

The moisture-sensitive element of d) has a wider application range than the moisture-sensitive elements of a) to c) described above, can obtain relatively stable and reliable moisture sensitive characteristics, and is excellent in durability. However, the manufacturing process is complicated and it is difficult to obtain a product having uniform characteristics.

<Object of the present invention> The present invention has been made to solve the above problems, and an object of the present invention is to provide a moisture-sensitive element that is easy to manufacture and has excellent durability and moisture-sensitive characteristics. And

<Means for Solving the Present Invention> Next, the configuration of the present invention will be described, and the means for solving the problems according to the present invention will be specified.

<A> Constituent Polymer The moisture-sensitive element according to the present invention is characterized by utilizing the excellent characteristics of the organic ionic polymer, and the polymer is constituted by the following combinations.

A polymer of the compound (A) having a sulfonic acid group and / or a carboxyl group in the side chain and a polymer of the compound (B) having a hydroxyl group in the side chain.

A polymer of a compound (A) having a sulfonic acid group and / or a carboxyl group in its side chain, and a polyhydric alcohol (C).

A copolymer comprising a compound (A) having a sulfonic acid group and / or a carboxyl group in a side chain and a compound (B) having a hydroxyl group, and a strong acid (D).

A copolymer comprising a compound (A) having a sulfonic acid group and / or a carboxyl group in a side chain and a compound (B) having a hydroxyl group, and a polyvalent strong acid (E).

However, as the above A, B, C, D and E, those selected from the compounds consisting of the following groups are used.

A: Styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, allyl sulfonic acid, vinyl sulfonic acid, acrylic acid, methacrylic acid and the like.

B: Vinyl alcohol, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate and the like.

C: ethylene glycol, glycerin, trimethylolpropane, etc.

D: Sulfuric acid, etc.

E: Pyrophosphoric acid and the like.

<B> Polymer thin film forming step A solution of the polymer having the above-mentioned constitution is applied on a substrate having an electrode, and the solvent is removed, and at the same time, a crosslinking treatment is performed by heating.

As a method for forming the electrodes, a known printing or etching method can be used.

As a method for applying the polymer solution, a known knife coater or roll coater method may be used.

Instead of coating, a method of immersing the substrate in the polymer solution or a method of using a spinner may be adopted.

<C> Ratio of Strong Acid Group to Hydroxyl Group in Polymer Thin Film According to the present invention, the ratio of strong acid group to hydroxyl group can be changed according to the target resistance value.

The ratio of strong acid groups to hydroxyl groups is generally 30: 1 to 55 :.
A range of 45 is desirable.

<D> Neutralization Step In the above-mentioned ratio area of the strong acid group and the hydroxyl group, since the strong acid group is excessive, it is necessary to neutralize it.

As a neutralization method, a method of impregnating a polymer thin film in an alkaline solution or a method of exposing it to an alkaline gas is adopted.

<Operation> The moisture-sensitive element manufactured in the above process is stable because there is no variation in moisture-sensitive characteristics because swelling and shrinkage due to moisture absorption / desorption is suppressed by crosslinking.

Further, this moisture-sensitive element is excellent in durability because it is less likely to swell and shrink and has good adhesiveness to the substrate and the electrode.

In particular, even if it is left in a high humidity environment for a long period of time, the change in moisture sensitivity characteristics is extremely small, and the moisture absorption rate and the moisture rate are fast and the response is excellent. The thinness of the film also provides excellent responsiveness.

In addition, the moisture-sensitive property can be easily controlled by adjusting the ratio of the strong acid group and the hydroxyl group.

Furthermore, since the crosslinking can be easily performed, the production process can be simplified.

<Example> Example 1 A solution composed of 8 parts of polystyrenesulfonic acid, 2 parts of glycerin and 90 parts of water is applied to a substrate in which a comb-shaped electrode is printed on an alumina plate. After the substrate is dried and heat-treated at 120 ° C., it is neutralized with a lithium hydroxide (LiOH) aqueous solution. The treated substrate was washed and dried to obtain a moisture sensitive element.

Moisture-sensitive characteristics of this humidity-sensitive element measured with a sine wave of 1 KHz at 25 ° C. are shown by [I] in FIG.

Example 2 To a substrate obtained by printing comb electrodes on an alumina plate, a solution of 6 parts of poly-2-acrylamido-2-methylpropanesulfonic acid, 4 parts of polyvinyl alcohol and 90 parts of water is applied. After the substrate is dried and heat-treated at 100 ° C., it is neutralized with ammonia vapor. The treated substrate was washed and dried to obtain a moisture sensitive element.

The humidity sensitive characteristics of this humidity sensitive element measured with a sine wave of 1 KHz at 25 ° C. are shown in FIG. 1 [II].

Example 3 Copolymer (sodium 2-acrylamido-2-methylpropane sulfonate and 2-hydroxyethyl acrylate were copolymerized at a monomer charge ratio of 8: 2) was used as a substrate obtained by printing comb electrodes on an alumina plate. And a solution of 2 parts altophosphoric acid and 90 parts water is impregnated. Impregnation is 4 cm / min. The treated substrate was dried and heat-treated at 100 ° C. to obtain a humidity sensitive element.

FIG. 2 [III] shows the humidity-sensitive characteristics of this humidity-sensitive element measured at 25 ° C. with a sine wave of 1 KHz.

Example 4 The moisture-sensitive element obtained in Example 3 was tested at 50 ° saturated RH and 50
℃ 10% or less 1 hour each exposure in a dry atmosphere of RH
It was subjected to a dry and wet cycle test as a cycle. Using a humidity sensitive element in each cycle number, at 25 ° C, 40%, 6
The resistance at 1 KHz sine wave was measured under 0%, 80% and 100% RH, and the results as shown in FIG. 3 were obtained.

From this test result, it is understood that the humidity sensitive element of the present invention has excellent durability.

Example 5 Copolymer (sodium acrylate and 2-hydroxyethyl acrylate copolymerized at a monomer charging ratio of 9: 1) was used as a substrate in which a comb-shaped electrode was printed on an alumina plate.
It is impregnated with a solution consisting of 4 parts, 1 part sulfuric acid and 95 parts water. Impregnation is 6 cm / min. The treated substrate was dried and heat-treated at 80 ° C. to obtain a humidity sensitive element.

Moisture-sensitive characteristics of this humidity-sensitive element measured with a sine wave of 1 KHz at 25 ° C. are shown by [IV] in FIG.

<Effects of the Present Invention> Since the present invention is as described above, the following effects can be obtained.

<B> Crosslinking of the polymer suppresses swelling and shrinkage due to moisture absorption and desorption. Therefore, the moisture-sensitive property is stable, and its fluctuation is extremely small even when left for a long time especially in a high humidity environment. It also has excellent durability.

<B> By adjusting the ratio of the strong acid group to the hydroxyl group in the polymer, the moisture sensitivity characteristics can be easily controlled.

<C> Absorption / dehumidification speed is fast and responsiveness is excellent.

<D> Since the polymer is easily cross-linked, the production process can be simplified.

[Brief description of drawings]

FIG. 1 and FIG. 2: Explanatory diagram showing characteristics (humidity-resistance change) of the humidity sensitive element according to the present invention. FIG. 3: Explanatory diagram of results of dry-wet cycle test of the moisture sensitive element according to the present invention.

Claims (6)

[Claims] 1. A moisture-sensitive element having a sulfonic acid group and / or a carboxyl group as a moisture-sensitive group, which is constituted by crosslinking a polymer containing the moisture-sensitive group and a polymer containing an alcoholic hydroxyl group. And an organic ionic polymer moisture sensitive element. 2. A moisture-sensitive element having a sulfonic acid group and / or a carboxyl group as a moisture-sensitive group, which is characterized in that a polymer containing the moisture-sensitive group and a polyhydric alcohol are crosslinked. Organic ionic polymer moisture sensitive element. 3. A moisture-sensitive element having a sulfonic acid group and / or a carboxyl group as a moisture-sensitive group, wherein a strong acid is added to a copolymer of a monomer having the moisture-sensitive group and a monomer having an alcoholic hydroxyl group to crosslink. An organic ionic polymer moisture-sensitive element, characterized by being configured as follows. 4. A moisture-sensitive element having a sulfonic acid group and / or a carboxyl group as a moisture-sensitive group, wherein a polyvalent strong acid is added to a copolymer of a monomer having the moisture-sensitive group and a monomer having an alcoholic hydroxyl group. An organic ionic polymer moisture-sensitive element, characterized in that it is formed by cross-linking. 5. A polymer having a sulfonic acid group and / or a carboxyl group as a moisture-sensitive group and a polymer having an alcoholic hydroxyl group or a polyhydric alcohol are applied to a substrate having a comb-shaped electrode, and heat-treated to crosslink. A method for manufacturing a humidity-sensitive element, comprising: 6. A strong acid or a polyvalent strong acid is added to a copolymer of a monomer containing a sulfonic acid group and / or a carboxyl group as a moisture-sensitive group and a monomer containing an alcoholic hydroxyl group, which is used as a base having a comb-shaped electrode. A method for producing a moisture-sensitive element, which comprises coating, heat-treating and crosslinking.