JPH05142182A - Moisture sensor - Google Patents

Abstract

PURPOSE:To obtain a sensor that is superior in aging characteristics and linearlity in the atmosphere of high temperature an high moisture and has a low moisture hysterisis by providing a moisture sensitive layer comprising monomer polymer or copolymer that is synthesized through quarternary chlarination of dimethylaminopropylmethacrylamide by the use of benzyl halide between a pair of electrodes provided on an insulation substrate. CONSTITUTION:An inorganic insulation substrate 3 on which a pair of comb type electrodes 1 and 2 composed of platinum, gold, etc. are formed on the surface thereof is immersed in a moisture sensitive agent solution, and then is dried at 100 deg.C for 20 min to from a moisture sensitive layer 4 between a pair of the electrodes 1 and 2 and on the surfaces of the electrodes 1 and 2. The layer 4 comprises a monomer polymer or copolymer that is synthesized through quaternary chlorination of a dimethylaminopropylmethacrylamide by the use of benzylhalide. Thus, the layer is superior in aging characteristics and linearlity necessary for a moisture sensor not only at room temperature but also in a high-temperature and high-moisture atmosphere, and can work at a low moisture hysterisis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a humidity sensor which uses an organic polymer material as a moisture sensitive layer to detect a change in humidity as a change in electric resistance or capacitance.

[0002]

2. Description of the Related Art Generally, it is known that an organic polymer material can be used as a moisture-sensitive layer because it is excellent in adsorption and desorption of water molecules.

Conventionally, a humidity sensor using these organic polymer materials as a moisture sensitive layer is disclosed in, for example, JP-A-59-13345.
It is proposed by the gazette No. 3.

[0004] The technical content is that a polymer or copolymer of methacrylamidopropyltrimethylammonium halide as an organic polymer material is formed between a pair of electrodes formed on a known insulating substrate made of, for example, alumina or glass. The moisture sensitive agent is applied to form a moisture sensitive layer, and a change in electric resistance of the moisture sensitive layer with respect to humidity is utilized.

However, the moisture-sensitive layer made of the organic polymer material as described above is inferior in stability over time in a high temperature atmosphere from the results of studies by the present inventors. It has been confirmed that there is a problem that the relationship between the electric resistance value and the electric resistance value is not logarithmically linear (lack of linearity), and that it is not necessarily preferable for practical use in order to obtain higher reliability.

Therefore, for example, an attempt was made to solve the above-mentioned problems by adopting a method of applying ethyl cellulose or the like on the moisture-sensitive layer and applying an overcoat, but this attempt temporarily solves the above-mentioned problems. However, in addition to the complicated structure, increased man-hours and high cost, there is characteristic deterioration due to aging over long-term use. It didn't come.

This is due to the above organic polymer material itself, and it has been necessary to improve the organic polymer material which can contribute to the basic elimination of the above problems.

[0008]

As described above, the humidity sensor using a moisture-sensitive layer made of an organic polymer material, which has been conventionally proposed, is not reliable because of the organic polymer material itself constituting the moisture-sensitive layer. It was chipped and the desired performance could not be obtained.

The present invention has been made to solve the above problems, and lacks linearity which is a problem in the prior art and lacks stability with time under high temperature and high humidity. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above drawbacks, to provide a humidity sensor having excellent characteristics over time in a high temperature and high humidity atmosphere, excellent linearity, and small humidity hysteresis.

[0010]

SUMMARY OF THE INVENTION A humidity sensor according to the present invention has a structure in which dimethylaminopropylmethacrylamide is formed between a pair of electrodes formed on an insulating substrate with benzyl halide.
It is characterized in that a moisture sensitive layer made of a polymer or a copolymer of a monomer which is chlorinated and synthesized is provided.

[0011]

According to the humidity sensor thus constructed, the moisture sensitive layer is composed of a polymer or copolymer of monomers synthesized by quaternary chlorination of dimethylaminopropylmethacrylamide with benzyl halide. The humidity-sensitive layer has excellent stability over time not only at room temperature, which is required for a humidity sensor, but also at high temperature and high humidity, has good linearity, and has a small humidity hysteresis, which greatly contributes to high reliability. To do.

[0012]

EXAMPLES Examples of the present invention will be described below.

As shown in FIG. 1, an inorganic insulating substrate 3 made of, for example, alumina or glass, on the surface of which a pair of comb-shaped electrodes 1 and 2 made of platinum, gold or the like is formed by printing or the like, will be described below. It is dipped in a moisture sensitive agent solution and then dried at 100 ° C. for 20 minutes, and the moisture sensitive layer 4 is formed between the pair of comb-shaped electrodes 1 and 2 and on the surfaces of the comb-shaped electrodes 1 and 2.
To form.

The humectant solution is prepared by the following means.
That is, dimethylaminopropyl methacrylamide 8
5.2 g of benzyl bromide and 85.5 g of benzyl bromide were dissolved in acetone and reacted at 50 ° C. for 30 hours to synthesize a monomer, which was put into ether, filtered and vacuum dried to obtain a white solid monomer. Then, this monomer was dissolved in benzene together with benzoyl peroxide, and this was reacted under vacuum at 30 ° C. for 20 hours to obtain a polymer, which was then purified with methanol, ethyl acetate, etc.
After drying, it is dissolved in methanol again to prepare.

Next, lead terminals 8 and 9 are attached to the terminal lead-out portions 5 and 6 of the pair of comb-shaped electrodes 1 and 2, for example, via solder 7, to complete the humidity sensor.

According to the humidity sensor having the above structure, the moisture sensitive layer 4 is composed of a polymer or copolymer of monomers synthesized by quaternary chlorination of dimethylaminopropylmethacrylamide with benzyl bromide. , It has excellent stability over time not only at room temperature but also at high temperature and high humidity, and can maintain stable characteristics for a long time. At the same time, it exhibits good linearity and small humidity hysteresis. There is an advantage that an excellent effect that can greatly contribute to the high reliability of the humidity sensor can be obtained.

This has been proved by the results of experiments in which the characteristics of the present invention and the conventional example are compared as described below.

That is, the resistance to relative humidity between the present invention A manufactured according to the above-described embodiment and the conventional example A manufactured using the polymer of methacrylamidopropyltrimethylammonium bromide exemplified in the above-mentioned prior art as the moisture sensitive layer. As a result of the value characteristic comparison, the result is as shown in FIG.

Also, dimethylaminopropyl methacrylamide was reacted with benzyl chloride in the same manner as in the case of the present invention A to prepare a monomer, to obtain methacrylamidopropyl dimethyl benzyl ammonium chloride, and methacryl amide propyl dimethyl benzyl ammonium chloride A high temperature (85 ° C. dry atmosphere) of the present invention B manufactured using a polymer as a moisture-sensitive layer and the conventional example B using a polymer of methacrylamidopropyltrimethylammonium chloride exemplified in the above-mentioned prior art as a moisture-sensitive layer. ) Aging characteristics and high humidity (50 ℃, 90
% RH atmosphere) As a result of comparison of characteristics over time under standing, the results are as shown in FIGS. 3 and 4.

As is apparent from FIG. 2, the invention A has excellent linearity as compared with the conventional example A,
Further, as is clear from FIGS. 3 and 4, the conventional example B has a large change in relative humidity with time in a high temperature and high humidity atmosphere, whereas the invention B has a high relative humidity in both a high temperature and high humidity atmosphere. Even after 1000 hours, the rate of change was within ± 3% RH, indicating that the deterioration over time was small.

In the above examples, benzyl bromide was used as an example of the benzyl halide to be reacted with dimethylaminopropyl methacrylamide, but benzyl chloride was used instead of benzyl bromide, or dimethylaminopropyl methacrylamide and benzyl were used. It goes without saying that a synthetic bromide monomer and a synthetic monomer of dimethylaminopropyl methacrylamide and benzyl chloride may be copolymerized.

[0022]

According to the present invention, since the relationship between the relative humidity and the resistance value is excellent in logarithmic linearity, it is highly utilized in a circuit and has little deterioration with time even in a high temperature and high humidity atmosphere and has an initial characteristic. It is possible to obtain a highly reliable humidity sensor which can maintain the above-mentioned value and has a small humidity hysteresis.

[Brief description of drawings]

FIG. 1 is a front view showing a humidity sensor according to an embodiment of the present invention.

FIG. 2 is a characteristic curve diagram showing resistance values with respect to relative humidity.

FIG. 3 is a characteristic curve diagram showing aging characteristics when left at high temperature.

FIG. 4 is a characteristic curve diagram showing a time-dependent characteristic when left at high humidity.

[Explanation of symbols]

 1, 2 Comb-shaped electrodes 3 Insulating substrate 4 Moisture-sensitive layer 5, 6 Terminal lead-out portion 7 Solder 8, 9 Lead terminal

Claims (1)

[Claims] 1. A pair of electrodes formed on an insulating substrate,
A humidity sensor comprising a moisture sensitive layer made of a polymer or copolymer of monomers synthesized by quaternary chlorination of dimethylaminopropyl methacrylamide with benzyl halide.