JPS61204901A - Moisture sensing element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a ZrO2-YtO3 based ceramic moisture sensing element, and in particular ZrO2-YtO3 based ceramic moisture sensitive elements.
01-Y, O, by using powder that becomes a solid solution,
Furthermore, by adding a small amount of LiC0, in addition to that, 60°C, which is representative of the atmosphere used in air conditioning equipment, etc.
Good Accuracy Under Humidity Before and After Arc, Background of the Invention In recent years, moisture sensing elements have come to be used in many fields. In household products, it is often used to control food cooking in microwave ovens, to detect dryness in clothes dryers, to control humidity in room air conditioners, to detect condensation in V'rR cylinders, and in industrial applications. It is widely used for humidity control in the manufacture of various electronic parts.In addition, attempts are being made to use it for air conditioning in agriculture and for preventing dew condensation in rear windows in automobiles.Food cooking In addition to temperature control, humidity control has become essential in various automated systems such as air conditioning, drying, etc., and there is a demand for the development of moisture-sensitive elements that operate with high reliability.

As a response to these demands, electrical resistance type moisture sensing elements have been put into practical use.This detects changes in humidity as changes in electrical resistance.The humidity material used is lithium chloride. Representative electrolyte materials, organic polymer materials, and ceramic materials Pu! 8m noodles's book sparrow description is basically as a reiki resistance type moisture sensing element.
It is required to have low electrical resistance, good linearity of resistance-humidity characteristics, have an appropriate operating range, and not deteriorate in the usage environment. Ceramic moisture-sensitive materials are in the spotlight.

There have been many proposals for ceramic moisture-sensitive materials, but the important characteristics are (a) moderately low electrical resistance (the higher the current, the better the sensitivity), and (b) resistance. It is required to have good linearity of humidity characteristics, (c) good sensitivity, (d) good accuracy, and (e) good stability, and various ceramic moisture-sensitive materials are used to make up the moisture-sensing part. materials have been studied. Among them, Zr02-YzOs ceramics are considered promising.

The form of the wet element can be a bulk type in which a pair of electrodes are provided on opposite surfaces of the ceramic sintered body, but
A preferred form is a thin-film type book in which an electrode layer is formed on at least one surface of a ceramic substrate, a mixture of the above-mentioned ceramic and a binder is applied on the electrode layer, and a moisture-sensitive layer is formed by drying and sintering the electrode layer. be. It is preferable to form the coating film by screen printing. More importantly, the electrode pattern in the electrode layer should be formed so that the spacing between the electrodes is as small as possible, equal to or less than α20fi. For example, good results can be obtained by interlocking the comb teeth of a pair of comb-shaped electrodes and making the interval between the comb teeth equal to or less than α'1Qssa.

However, these ceramic moisture sensing elements still have
There is a lot of room for improvement in terms of performance, and research is currently being carried out.

Moisture sensing elements are used in the various applications listed above, but in air conditioning equipment, etc., the operating atmosphere humidity of humidity sensing elements is 60%.
There is a need for a moisture sensing element that exhibits good stability, accuracy and sensitivity, particularly under such humidity conditions. Needless to say, the linearity is good.

SUMMARY OF THE INVENTION The present inventor has solved the above request by
, addressed the issue of improving the reproducibility and sensitivity of yarn moisture-sensitive elements.

Conventionally, in manufacturing a Zr02-Y,on type moisture sensitive element, for example, in the case of a thin film type, separately manufactured Zr(% powder and Y,os powder were mixed together with the addition of ethyl acetate. The moisture sensitive part is created by grinding and mixing, then adding butyl calpitol and epoxy resin paint to form a moisture sensitive paste, applying it on the electrode layer, and then performing a baking process. These, ZrO, and Y2
When using a mechanically mixed powder with O3, the structure of the moisture-sensitive part after firing is not sufficiently homogeneous, and we thought that this would be used as a starting powder with poor stability, accuracy, and sensitivity, and we tried it. Good results were obtained. Furthermore, the addition of LICOs in the range of 10-4 mol% has also been found to be very effective.

To provide a humidity sensing element characterized by having a static/humidity sensing part.

DETAILED DESCRIPTION OF THE INVENTION The moisture sensing element used in the present invention comprises a pair of 1! Although it can be realized in a so-called bulk type in which a pole is formed, it is preferably produced as a thin film type in which a moisture sensitive film is formed on a substrate. FIG. 1 shows an example of a thin film type moisture sensitive element.

An electrode layer 3 is formed on one or both surfaces of the substrate 1, and a moisture sensitive layer 5 is formed thereon (the moisture sensitive layer is partially omitted).

As a substrate, AhOs, sio,, Zr02
Ceramics such as are used. Formation of the electrode layer on the substrate can be carried out by, for example, vaporizing nickel or the like as an under electrode.
Next, gold, platinum, etc. can be vaporized on top of it as an upper electrode for rust prevention, and a desired electrode pattern can be formed by photo-etching technology, and silthenium can be formed by screen printing using ruthenium paste. Electrodes can also be formed. Recently, multi-tK microfabrication techniques for manufacturing printed circuit boards for electronic circuits have been put into practical use, and by applying these techniques, fine electrode patterns can be formed. For example, sputtering is also a useful method. The electrode pattern is preferably one in which a pair of comb-shaped electrodes are interlocked with comb teeth as shown in FIG. The smaller the interval between the comb teeth, the lower the resistance value, so the sensitivity of the moisture sensing element can be increased. Good results were obtained using a comb spacing of α05-0.20 vts.

Furthermore, an electrode layer using a neutral electrode has recently been proposed by the present applicant. This arranges a neutral electrode between each pair of toothed electrodes.

The neutral electrode is formed from a metal and/or a metal compound that is the same as the conductive material constituting the electrode or has a smaller tendency to ionize than hydrogen. Although the neutral electrode is called an electrode, it does not perform a current-carrying function, but serves to suppress the tendency of ions that favor m-temperature characteristics to segregate and move toward the original electrode.

After the electrode layer is formed in this way, on top of it! The moisture sensitive layer constituting the lA wet part is ZrO2-Y2O3 [iS! The solution powder was added to a mixture of Zr0Ch and YCl at a predetermined ratio.
A coprecipitation reaction is caused using an alkali such as H, (ammonia), etc., and Y and Os are solid-dissolved in zrOf at the stage of raw material powder, resulting in a nine-yen mixed powder. In addition to the above-mentioned coprecipitation method, such solid solution powders can be produced by hydrolysis method, alkoxy F method,
It can be manufactured by a melting method or the like. In the case of the coprecipitation method, the coprecipitate is filtered, washed, dried, and then finely ground to -500 mesh. 03 is 5-4
A proportion of 0 mol-+ is added. Low resistance of moisture sensing element,
The above range is good from a comprehensive viewpoint of linearity, stability, etc.

After the Zr01-YtOs solid solution powder is mixed with conventionally known auxiliary additives, if desired, the viscosity of the resin paint is determined. A moisture sensitive paste is prepared. As auxiliary additives, Cab, MgO1BadST 102
,'Ta20g.

1'Jb2oS, V2O6, etc. are known.

Furthermore, according to the invention, LIC in the range 1 to 4 mol%
It has been found that the addition of O, is effective.

The addition of Ll'L:01 is effective for improving stability, precision and sensitivity, which are the main objectives of the present invention, and for that purpose, the addition of 1 mol%
or more is required. If the amount exceeds 4 mol%, the moisture sensitive paste of the mixed powder may be added to a film thickness of 5 to 200 mm on the electrode layer.
It is preferably applied by screen printing so that the thickness is 1 μm1, preferably 40 to 120 μmW.

Thereafter, after preliminary drying at a temperature of 130-190° C. for 0.2-2 hours, a firing treatment is performed at a temperature lower than conventionally. The firing process sinters the ceramic particles to form the skeletal structure of the IWA wet film and provide structural strength. Conventionally, a predetermined structural strength could be obtained, but it was found that such high-temperature firing actually worsened the characteristics, particularly the resistance characteristics, of the produced moisture-sensitive element. In the present invention, 50
Firing is performed at a temperature of 0 to 870°C, typically 700 to 870°C. Firing holding time is 5 minutes to 9°0 minutes,
Usually 8 to 20 minutes is sufficient.

In this way, a low-resistance moisture-sensitive element is produced, and in order to stabilize its resistance properties, a KOH surface treatment is carried out by immersion in a KOH-containing liquid.

The immersion treatment in the KOH-containing liquid is performed by
by immersion in the liquid for a suitable period of time, such as 120 minutes. The appropriate KOH concentration is 10 to 30% by weight. If it is less than 10%, it will take a long time for impregnation, and if it exceeds 50%, harmful effects such as increased hysteresis due to a large degree of surface modification will occur.

After the dipping treatment, the device is preferably fired at a temperature of 600-870°C. The firing temperature is 600 to 870℃ to prevent the KO0 surface treatment agent from dripping due to dew condensation and to ensure stable modification.
This is preferable in order to prevent an increase in electrical resistance (as described above).

Furthermore, preferably, the element after KOHOH surface treatment and firing is subjected to an aging treatment. As the aging treatment method, since the humidity sensitive element of the present invention is intended to be used at a humidity of around 60%, the aging treatment is performed at a humidity of 60% for a long time, for example, 50 hours. The aging temperature is 50-90°C, preferably 60-85°C. Another effective method is to alternately expose the cod to a low-humidity atmosphere for a certain period of time and to a high-humidity atmosphere for a certain period of time. The aging process produces a stable moisture sensitive part that exhibits little deterioration under normal conditions.

Since a homogeneous mixed state can be obtained, the characteristics of the moisture sensitive element can be improved and stabilized. In particular, it is possible to obtain a moisture-sensitive element that exhibits good stability, precision, sensitivity, and linearity under a humidity of around 60%, which is required for use in air conditioning equipment, etc. It was ground into a mesh and used as a starting material. . To this, LICO,
After adding 15 mol %, a moisture sensitive paste was prepared by mixing under the addition of ethyl acetate and then adding the organic resin paint.

On the other hand, 18m + 11 length x 9m 11 and width 120. Square-shaped electrodes were formed on the substrate by double-screen printing, and the interval between each comb tooth was α2mm, and an electrode row was printed over a length of 12mm.

The moisture-sensitive paste was applied onto the electrode layer by screen printing and dried at a temperature of 170° C. for 1 hour.

Thereafter, an m-humidity element was produced through the process of firing at 800°C, 12 minutes running KOH surface treatment (KOH 15%), firing at 800°C, aging at 60% humidity for 12 minutes, and 80°C for 50 hours.

Thereafter, it was left to stand at 80° C. and 30% humidity for 48 hours, and then left to stand at 80° C. and 90% humidity for 12 hours, after which the resistance-humidity characteristics were measured. The three curves in the graph in Figure 2 are ■80
Characteristics after the above aging for 50 hours at ℃ x 60% humidity (solid line) ■ Characteristics after 48 hours at 80℃ x 30% humidity (point M), and ■ Further after that at 80℃ x 90% humidity Characteristics after 12 hours (dotted chain line) are shown. (2) and (2) mean that the device was left at low humidity and high humidity after being left at 40% humidity in (2). The smaller the difference between (1) and (2), the better the stability and accuracy of the humidity sensing element against changes in humidity.

The graph in FIG. 2 confirms that the difference between ■ and ■ is small, as will be seen when compared with the comparative example later. Further, the resistance value is small and the linearity is good at humidity of 50% or more.

FIG. 3 shows the responsiveness after aging processing.

This shows that very good responsiveness can be obtained. Thus, curve lsB represents the case where the humidity changed from 85% to 55%. Comparative Example 1 Except that separately obtained z r O2 powder and Y2O3 powder were mechanically mixed in the same proportion as in Example 1. Example 1
A moisture-sensitive element was fabricated using the same procedure as described above, and the resistance-humidity characteristics were measured in the same manner. The results are shown in Figure 4.

Three curves (■, ■, and ■) corresponding to Example 1 are shown. ■
It is clear that the gap between (1) and (2) is much larger than in the example.

Comparative Example 2 Y, 0. A moisture-sensitive element was prepared in the same manner as in Example 1 except that the amount was changed to 2.7 mol %, and the resistance-humidity characteristics were measured in the same manner. The measurement was carried out under the same conditions, and the obtained curves ①, ② and ② are shown in FIG. There is a large gap between curves ■ and ■. Therefore, it can be seen that when Yz9sjjk is small, stability and accuracy against humidity fluctuations deteriorate.

A moisture-sensitive element was prepared in the same manner as in Comparative Example 5, and the resistance-humidity characteristic curves (■, ■, and ■) were determined under the same conditions. The results are shown in FIG. 7 shows that the higher the amount of LICOs, the higher the resistance.

In order to suppress the resistance to a predetermined level, it is necessary to set the upper limit of the amount added to LIC to 4%.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a thin film type moisture sensitive element, Figs. 2 and 3 are graphs showing resistance-humidity characteristics and responsiveness in connection with Example 1, and Fig. 4 is a resistance-temperature graph of Comparative Example 1. Graphs showing the characteristics, Figure 5 is the same graph for Comparative Example 2, and Figure 6 is the same graph for Comparative Example 3. 1: Substrate 3: Electrode layer 5: Moisture sensitive layer Procedure Amendment Book 1985 3J- 1190

Claims (1)

[Scope of Claims] 1) A moisture sensing element comprising a moisture sensing portion made of sintered powder that easily becomes a ZrO_2-Y_2O_3 solid solution. 2) Zr containing 1.0 to 4.0 mol% LiCo_3
A moisture sensing element comprising a moisture sensing portion made of an O_2-Y_2O_3 solid solution.