JPH09159635A - Humidity sensor and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an inexpensive and small sensor by coating the surface of moisture-sensitive surface of humidity sensor with a protective film composed of an ester acrylate monomer and an ester acrylate monomer having siloxane skeleton. SOLUTION: An alumina substrate 1, on which integrdigital carbon electrodes 2, 3 are formed, is coated with a humidity sensitive resin film 4 to produce a humidity sensor. It is then coated with 10wt.% aqueous solution of copolymer of ester acrylate and ester acrylate having siloxane skeleton and dried at about 60 deg.C for about 1 hour to form a protective film 7. The siloxane skeleton in protective film 7 has water repellency and prevents adhesion of alcohol or tar of cigarette thus sustaining high response of humidity sensitive film 4. Consequently, a humidity sensor having performance substantially equivalent to that employing a tetrafluoro ethylene polymer protective film having a large number of micropores can be obtained inexpensively while reducing the size.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a humidity detecting sensor mounted on an electronic device or an air conditioner, and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, air conditioners for satisfying the comfort of the living environment have become widespread.

Among them, a sensor for detecting humidity, that is, a humidity and condensation sensor is being improved.

In a small space such as an indoor space or a car, a tar of a cigarette, a surfactant in a glass cleaning agent or the like adheres to the surface of the moisture-sensitive film of the sensor, which often causes a decrease in sensitivity of the humidity sensor. On the other hand, it has been proposed to install a moisture-permeable sheet having a large number of minute holes in a water-repellent polymer of tetrafluoroethylene on the surface of the humidity sensor.

[0005]

However, the moisture permeable sheet made of the above materials is expensive, and a case for holding the moisture permeable sheet is also required, so that the shape of the sensor is large. Therefore, it is small and cheap with the same performance,
There has been a strong demand for the development of a low-cost protective film having moisture permeability that can be directly formed on the moisture-sensitive film of the humidity sensor.

An object of the present invention is to downsize a humidity detecting sensor having a moisture permeable protective film.

[0007]

In order to solve this problem, in the humidity sensor of the present invention, an acrylic acid ester monomer and an acrylic acid ester monomer having a siloxane skeleton are applied to the surface of the humidity sensitive film of the humidity sensor. It is a protective film.

Since the protective film of the humidity detection sensor obtained by this structure has water repellency, the adhesion of alcohol or cigarette tar is reduced, and a small humidity detection sensor having no deterioration in the humidity-sensitive property with respect to the ambient atmosphere can be obtained. To be

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention is a humidity sensor mainly composed of a combination of an insulating substrate, a moisture sensitive film and an electrode, wherein a protective film is formed on the surface of the moisture sensitive film. It has the effect of reducing the decrease in the responsiveness of the moisture-sensitive film due to the adhesion of alcohol or tar of cigarettes.

According to a second aspect of the present invention, the protective film comprises an emulsion of a copolymer of an acrylic acid ester monomer and an acrylic acid ester monomer containing a siloxane skeleton, and the moisture sensitive film is a polar solvent. It has the effect that it can be used even if it is easily damaged.

A third aspect of the present invention is a manufacturing method in which the emulsion is applied on a humidity sensor and then heat-treated, and has a function of forming a protective film by removing water.

According to a fourth aspect of the present invention, the protective film is formed on a moisture-sensitive film formed by containing a conductive powder in a hygroscopic resin, and the resin swells by absorbing moisture, Therefore, the humidity detecting function of decreasing the contact area between the conductive powders and increasing the resistance value has an effect of improving the deterioration of the humidity detecting function due to alcohol or cigarette tar.

According to a fifth aspect of the present invention, the protective film is formed on a hygroscopic film using a polymer electrolyte,
It has an effect of improving that the function of detecting humidity due to a change in ionic conductivity due to moisture absorption is deteriorated by alcohol or cigarette tar.

Hereinafter, embodiments of the present invention will be described. The present invention forms a protective film on the surface of a humidity sensitive film of a humidity sensor, and the siloxane skeleton in the protective film has water repellency and reduces the adhesion of alcohol, cigarette tar, etc. It is based on the finding that sex deterioration can be improved. The humidity detection sensor described here includes all sensors that detect humidity and dew condensation.
As a moisture sensitive film, a film utilizing a conventionally used mechanism of electron conduction and ion conduction is known, but the protective film of the present invention can be applied to any moisture sensitive film. For example, an organic moisture-sensitive film in which conductive particles are dispersed in a hygroscopic resin, one using a polymer electrolyte, and a mixed system thereof have been proposed, but any of the moisture-sensitive films can protect the present invention. The membrane can perform its function.

The protective film used in the present invention is an emulsion composed of a copolymer of acrylic acid ester and acrylic acid ester containing a siloxane skeleton. Commercially available products such as Acryset GF-255 from Nippon Shokubai Co., Ltd. are suitable for the purpose of the present invention. Since this is an emulsion, that is, an aqueous solution, it has a feature that it can be used even when the moisture-sensitive film is easily attacked by a polar solvent.

Hereinafter, the present invention will be described more specifically. (Embodiment 1) 19.5 g of 2-hydroxyethyl methacrylate, 1.42 g of glycidyl methacrylate, and 19 mg of azobisisobutyronitillyl as a polymerization initiator are dissolved in 110 g of ethyl cellosolve, and the mixture is dissolved under nitrogen flow at 8
Copolymerization was carried out by heating at 0 ° C. for 5 hours. After the reaction was completed, the solution was poured into ether to precipitate the polymer. After purification with a methanol-ether system, it was dried under reduced pressure at room temperature to obtain a white polymer. 2 g of this resin was added to ethyl cellosolve 2
It is dissolved in 0 g, 0.5 g of acetylene black having an average particle size of 40 mμ and 7 g of benzyl alcohol are added as a conductive powder, and they are sufficiently kneaded with a three-roll mill. Then, 19.8 mg of 1,3-bis (hydrazinocarboethyl) -5-isopropylhydantoin and 37.8 mg of 1,12-diaminododecane as a curing agent were dissolved in a minimum amount of benzyl alcohol, and then added to the above kneaded product. Disperse into paste. The paste was applied onto an alumina substrate having a comb-shaped carbon electrode formed thereon, and the paste was applied and cured by heating at 150 ° C. for 30 minutes to form a solid coating. The structure of the dew condensation sensor thus created is shown in FIG. In the figure, 1 is an alumina substrate,
2, 3 are comb-shaped carbon electrodes, 4 is a moisture-sensitive resin film, and 5 and 6 are lead wires connected to the electrodes 2 and 3, respectively. A 10 wt% aqueous solution of Acrylic GF-255 is dipped in this dew condensation sensor and dried at 60 ° C. for 1 hour to form a protective film 7.

Comparative Example 1 A dew condensation sensor was prepared in the same manner as in Embodiment 1 except that the protective film was not formed.

(Comparative Example 2) In the first embodiment, a case for covering the surface of the moisture sensitive film is prepared, and a hole is formed therein.

A moisture-permeable film having a large number of minute holes formed in a water-repellent polymer of tetrafluoroethylene is attached to the inside thereof.

(Embodiment 2) 80 g of polyethylene oxide-sodium iodide complex and carbon black (Diablack manufactured by Mitsubishi Kasei Co., Ltd.) are melt-kneaded at 200 ° C. for 30 minutes to obtain a moisture-sensitive composition. This composition is press-molded into a sheet, which is then adhered onto an alumina substrate and silver paste is used to form electrodes on both ends to obtain a humidity-sensitive resistor element. This moisture-sensitive resistor element has a reset GF-
A 20 wt% aqueous solution of 255 is dipped and dried at 80 ° C. for 1 hour to form a protective film.

Comparative Example 3 A humidity sensor was prepared in the same manner as in Embodiment 2 except that the protective film was not formed.

(Comparative Example 4) In the second embodiment, a case for covering the surface of the moisture sensitive film is prepared and a hole is formed therein.

A protective film having a large number of minute holes in a water-repellent polymer of tetrafluoroethylene is attached to the inside thereof.

An environmental test using a cigarette and a detergent was carried out for the humidity detection sensor manufactured as described above, and the delay of the detection time due to the change in each moisture-sensitive property before and after the test was evaluated.

(1) Tobacco test: Put the sensor in a 12 liter container, fill it with smoke for one cigarette, and leave it for 24 hours. This is set as one cycle and repeated for 5 cycles.

(2) Detergent test: 2 for the sensor
Spray glass cleaner from 0 cm distance for 3 seconds at a time. This is repeated 10 times.

The evaluation results will be described below.

[0028]

[Table 1]

As is clear from the above results, the humidity detecting sensor provided with the protective film of the present invention is remarkably improved in the deterioration of the moisture sensitivity characteristic as compared with the original humidity sensor not provided with the protective film. . Furthermore, although the deterioration of the moisture-sensitive property is slightly worse than that of a protective film in which a polymer of tetrafluoroethylene is provided with a large number of minute pores, the degree of improvement compared with that without a protective film is insignificant. Is.

Further, it can be widely used as the dew condensation sensor as in the first embodiment and the humidity detecting sensor as in the second embodiment.

Although an alumina substrate is used as a substrate in the embodiments, other ceramic substrates and heat-resistant resin substrates may be used.

[0032]

EFFECTS OF THE INVENTION Conventionally, a protective film in which a large number of minute holes are provided in a polymer of tetrafluoroethylene has been used, but by using the inexpensive protective film of the present invention, the performance is almost the same and the cost is greatly reduced. Is possible. As a result, it is possible to expand the application range of the humidity detection sensor in a harsh environment.

[Brief description of the drawings]

FIG. 1A is a configuration diagram of a humidity detection sensor of the present invention. FIG. 1B is a sectional view of the humidity detection sensor of the present invention.

[Explanation of symbols]

 1 Alumina substrate 2,3 Comb type carbon electrode 4 Moisture sensitive resin film 5,6 Lead wire 7 Protective film

Claims (5)

[Claims] 1. A humidity sensor mainly comprising a combination of an insulating substrate, a moisture sensitive film and an electrode, wherein the humidity detecting sensor has a protective film formed on the surface of the moisture sensitive film. 2. The humidity detecting sensor according to claim 1, wherein the protective film is an emulsion of an acrylic acid ester monomer and an acrylic acid ester monomer copolymer containing a siloxane skeleton. 3. The method for manufacturing a humidity detecting sensor according to claim 1, wherein the protective film is formed by applying the emulsion onto the humidity sensor and then heat treating the emulsion. 4. A humidity detecting sensor in which a protective film according to claim 2 is formed on the surface of a moisture-sensitive film obtained by containing a conductive powder in a hygroscopic resin. 5. A humidity detecting sensor in which the protective film according to claim 2 is formed on the surface of a hygroscopic film using a polymer electrolyte.