JPH0718833B2 - Moisture sensitive element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a moisture-sensitive element, in particular, a response characteristic is fast and hysteresis is small, and the humidity-sensitive characteristic does not deteriorate even at a high temperature of 100 ° C. or higher, and the heat resistance Therefore, the present invention relates to a humidity sensitive element which is useful as a humidity sensor in an automobile engine room, a clothes dryer, a sauna room and the like.

[Prior Art] As a humidity sensitive element, one that detects humidity from the change in electric resistance value due to humidity is widely used, and one that uses an inorganic electrolyte such as lithium chloride in the humidity sensitive part is commonly used. It is known.

Further, recently, a device using a polymer electrolyte membrane as an organic electrolyte has been developed in the moisture sensitive part, but a moisture sensitive element using this polymer electrolyte membrane has an advantage that the response speed is fast and the hysteresis is small. On the other hand, it has poor heat resistance, and generally has the drawback that when used in a high temperature atmosphere of 60 ° C. or higher, the moisture-sensitive film deteriorates to lower the sensitivity.

Further, since all of them contain an electrolyte, they are poor in water resistance, and when used in a dew-condensing atmosphere, carrier ions in the moisture-sensitive film flow out, and the sensitivity is lowered.

[Problems to be Solved by the Invention] Therefore, for the purpose of improving these drawbacks, there has been proposed a moisture-sensitive element which uses an organopolysiloxane film (see JP-A-62-247239).
However, this is because the organic electrolyte used here has a cationic quaternary ammonium group.
In a high temperature atmosphere of 0 ° C. or higher, there is a drawback that decomposition occurs and the sensitivity of the moisture sensitive element decreases.

[Means for Solving the Problem] The present invention relates to a moisture-sensitive element capable of solving the above disadvantages and drawbacks, which is formed on the surface of an electrode formed on an insulating substrate having a hydroxyl group on the surface. And an organopolysiloxane film containing a sulfone group or a salt thereof.

That is, as a result of various investigations by the present inventors to develop a moisture-sensitive element having particularly excellent heat resistance, the surface of an electrode formed on an insulating substrate having a hydroxyl group on the surface contains a sulfone group or a salt thereof. When an organopolysiloxane film is formed, it has been found that a moisture-sensitive element having excellent heat resistance can be obtained because the organopolysiloxane film has excellent heat resistance, and the feeling obtained in this way is also found. The present invention has been completed by confirming that the wet element has good response characteristics and small hysteresis.

Next, this will be described in more detail.

[Operation] The moisture-sensitive element of the present invention has the insulating substrate 1 as shown in FIG.
A comb-shaped electrode 2 is formed on the above by screen printing or the like and baked, and then an organopolysiloxane film containing a sulfone group or a salt thereof is formed on the moisture sensitive layer 3.
Then, the lead wire 5 is soldered to the electrode lead-out portion 4.

The insulating substrate 1 may be made of alumina, quartz glass, steatite, or the like, which is reacted with a silane or organopolysiloxane having a hydrolyzable group, which will be described later, to form an organopolysiloxane. Since it forms a polysiloxane film, it must have a hydroxyl group on its surface.

The electrode 2 formed on the insulating substrate 1 is made of gold,
A conductive material such as silver-palladium or ruthenium oxide may be formed by screen printing, sputtering or the like, but this shape is preferably comb-shaped, which is preferably fixed by baking. .

Next, the moisture-sensitive layer 3 formed on this electrode is an organopolysiloxane film containing a sulfone group or a salt thereof in the present invention. This organopolysiloxane film is made of an organopolysiloxane containing a sulfone group or a salt thereof, for example, a compound of the general formula R ¹ is an alkyl group such as a methyl group, an ethyl group, a propyl group or a butyl group, an alkenyl group such as a vinyl group or an allyl group, an aryl group such as a phenyl group or a tolyl group, or a carbon atom of these groups. Selected from a chloromethyl group, a trifluoropropyl group, a cyanoethyl group, etc., in which some or all of the hydrogen atoms bonded to are substituted with a halogen atom, a cyano group, etc. Substituted or substituted monovalent hydrocarbon group, R ² is an unsubstituted divalent hydrocarbon group such as alkylene group such as methylene group, ethylene group, propylene group, butylene group or a part or all of hydrogen atoms bonded to this carbon atom. A substituted divalent hydrocarbon group in which is substituted with a halogen atom or the like, or an unsubstituted or substituted group in which 1/2 or less of the unsubstituted or substituted methylene portion of these groups is replaced with an oxygen atom. Oxyalkylene group, R ³ is R ¹
An unsubstituted or substituted monovalent hydrocarbon group having 1 to 20 carbon atoms or an organic group containing a functional group such as a methacryloxy group, a vinyl group, an allyl group, an amino group, and a mercapto group,
Is a hydrogen atom or an alkali metal atom such as Na, K or Li, a is an integer of 0 ≦ a ≦ 20, and b is 1,2 or 3 formed from an organopolysiloxane.

This organopolysiloxane film is formed by using the above-mentioned organopolysiloxane containing a sulfone group or a salt thereof and a silane or organopolysiloxane containing a hydrolyzable group, for example, the general formula R ⁴ SiY ³ (2) R ⁴ is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms similar to R ¹ , Y is a hydroxyl group or a halogen atom, or an alkoxy group having 1 to 4 carbon atoms, an acyloxy group,
Organosilane which is a hydrolyzable group such as amino group, aminooxy group, oxime group, alkenyloxy group, or the general formula R ⁵ is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms similar to R ¹ , R ⁶ is a hydroxyl group or a halogen atom, or an alkoxy group having 1 to 4 carbon atoms, an acyloxy group, amino Groups, aminooxy groups, oxime groups, alkenyloxy groups, and other hydrolyzable groups, where m and n are 0 <m <
3, 0 <n <3, 0 <m + n ≦ 3, preferably 1 ≦ m +
A composition comprising an organopolysiloxane having a number of n ≦ 2.2 is applied to the above-mentioned substrate by a screen printing method, a spray coating method, a dipping method, etc., and dried at room temperature at 50 to 150 ° C. for 0.1 to 2 Just heat for a while
According to this, the hydrolyzable group of the silane or organopolysiloxane having this hydrolyzable group is bonded by a condensation reaction with the hydroxyl group on the surface of the insulating substrate, and this forms an organopolysiloxane film by cross-linking polymerization by heating. However, at this time, since the organopolysiloxane containing a sulfone group or a salt thereof is fixed in the organopolysiloxane film by an anchor effect, the organopolysiloxane film formed on the substrate is a sulfone group or a salt thereof. Will be included.

The moisture-sensitive element thus produced has an organopolysiloxane film containing a sulfone group or a salt thereof on the electrode surface, so it has good heat resistance and fast response characteristics.
Since it has a small hysteresis, it is advantageous in that it is easy to use and has high sensitivity. However, when the above-mentioned organopolysiloxane film is formed, the organopolysiloxane containing a sulfone group or a salt thereof is used in the above general formula. R ³ in (1) is a group having a vinyl group, and R ⁴ in the general formula (2) of a silane having a hydrolyzable group is also a group having a vinyl group, and in this reaction system, benzoyl peroxide or the like is used. Organic peroxide is added,
By chemically bonding these by radical polymerization of vinyl groups, the organopolysiloxane containing the sulfone group or its salt can be more firmly fixed to the organopolysiloxane film, further improving the heat resistance of the humidity sensitive element. be able to.

[Examples] Next, examples of the present invention will be described. The humidity-sensitive characteristics, response characteristics, and hysteresis characteristics of the humidity-sensitive element in the examples are LCR meter / H
It shows the results measured using P4284A [trade name of Yokogawa Hewlett-Packard Co.].
It shows the test results when left in a dryer at 120 ° C for 3 months.

Example 1 A comb-shaped electrode was screen-printed on a 17 mm × 7 mm × 0.635 mm alumina insulating substrate using a silver-palladium alloy-based paste, and baked to manufacture an alumina substrate with an electrode.

Then this board is expressed 10 parts by weight of organopolysiloxane and silicone varnish S coat 58 [trade name of Shin-Etsu Chemical Co., Ltd.]
It was dipped in a composition consisting of 90 parts by weight, dried at room temperature for 1 hour and then heated at 120 ° C. for 1 hour to form an organopolysiloxane film containing a sodium sulfonate group on the substrate.

Next, when a lead wire was soldered to the extraction electrode portion of this substrate, a moisture-sensitive element having an organopolysiloxane film containing a sulfone group salt formed on the electrode was obtained. When examined, the results shown in FIG. 2 were obtained, and the results shown in FIGS. 3 and 4 were obtained for the response characteristics and hysteresis characteristics. It was confirmed that it had a small and excellent characteristic, and when it was also examined its change over time, it showed the results as shown in FIG. Since it did not change, it was confirmed that the heat resistance was extremely excellent.

Example 2 A comb-shaped gold electrode was formed by sputtering on an alumina insulating substrate of 4 mm × 3 mm × 0.635 mm to prepare an alumina substrate with electrodes.

Then the formula on this board Organopolysiloxane of 30 parts by weight and formula The composition consisting of 40 parts by weight of organosilane, 29 parts by weight of methanol and 1 part by weight of benzoyl peroxide was applied by a spray coating method, dried at room temperature for 1 hour, and then heated at 150 ° C. for 1 hour. An organopolysiloxane film containing a sulfone-containing potassium salt was formed on the substrate.

Next, a lead wire was soldered to the extraction electrode portion of this substrate to form a moisture sensitive element, and when the moisture sensitive characteristics of this element were investigated, the results shown in FIG. 6 were obtained, and the change with time of this element When examined, the results shown in FIG. 7 were obtained, and it was confirmed that this was extremely excellent in heat resistance.

[Advantages of the Invention] The present invention relates to a moisture-sensitive element, which is provided with an electrode on an insulating substrate having a hydroxyl group, and an organopolysiloxane film containing a sulfone group or a salt thereof is formed on the electrode, as described above. This is because the organopolysiloxane film that becomes the moisture sensitive layer has heat resistance.
This provides an advantage that a humidity sensitive element that has a high response speed and a small hysteresis and that its humidity sensitive property hardly changes even in a high temperature atmosphere can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view of the moisture sensitive element of the present invention, FIGS. 2 to 5 are graphs showing the physical properties of the moisture sensitive element obtained in Example 1 of the present invention, and FIG. FIG. 3 shows the response characteristics, FIG. 4 shows the hysteresis characteristics, and FIG. 5 shows the change over time. FIGS. 6 to 7 show the humidity-sensitive element obtained in Example 2 of the present invention. 6 is a graph showing the physical properties, FIG. 6 shows the moisture sensitivity characteristics, and FIG. 7 shows the change with time.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 62-247239 (JP, A) JP 58-176538 (JP, A) JP 62-127661 (JP, A) JP 56- 51651 (JP, A)

Claims (1)

[Claims] 1. A moisture-sensitive element comprising an electrode formed on an insulating substrate having a hydroxyl group on the surface thereof, and an organopolysiloxane film containing a sulfone group or a salt thereof formed on the surface of the electrode.