JPS60195055A - Humidity 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 Yttrium oxide (yttrium oxide) has excellent resistance-humidity properties.
tom) type ceramic moisture sensitive element.

In recent years, moisture sensitive 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 VTR cylinders, and in industrial applications, it is used in various electronic components. Widely used for humidity control during manufacturing. In addition, attempts are being made to use it for air conditioning in agricultural houses and for preventing dew condensation on automobile rear windows. Humidity control is essential in addition to temperature control in various automated systems for food cooking, air conditioning, drying, etc., and there is a need for the development of moisture-sensitive elements that operate with high reliability.

In order to meet these demands, electrical resistance type moisture sensing elements have been put into practical use. This detects changes in humidity as changes in thermal resistance, and the moisture-sensitive leaf materials used include electrolyte materials such as lithium chloride, organic polymer materials, and ceramic materials of equal length. Something similar has been proposed. Electrical resistance type moisture sensing elements are basically required to have a low electrical resistance value, good linearity of resistance-humidity characteristics, have an appropriate operating range, and not deteriorate in the usage environment. Recently, ceramic material-based moisture-sensitive leaf materials have been attracting attention as a material that comprehensively satisfies these requirements.

Up until now, ceramic material-based moisture-sensitive leaf materials have mainly been made of zirconium oxide (ZrO2) (e.g. ZrO2).
rQ, +MgO), iIgCr2o, -Ti
There are many proposals such as OH system, T 102 +V204, Ta1O=, etc. Ceramic moisture-sensitive materials will increasingly be used in the future as: (1) low electrical resistance (the higher the current, better sensitivity); (2) good linearity of resistance-humidity characteristics; and (3) responsiveness. There is a demand for materials with even better performance than the ceramic moisture-sensitive materials that have been proposed so far.

Although there are attempts to apply additional coating treatments on ceramics,
This is not a preferable solution since the coating process is costly and time consuming. For example, the matrix is a Zr01-MgO powder sintered body with electrode pairs on the front and back sides, and Na1PO4.12
A moisture-sensitive element subjected to dip coating treatment with an aqueous solution of MoO has been proposed (Japanese Patent Application Laid-Open No. 134401/1983). Although this device exhibits low resistance and good linearity, the dip coating process described above is burdensome.

Under these circumstances, the present inventors investigated moisture-sensitive materials and found that yttrium oxide is an extremely suitable moisture-sensitive material. Yttrium oxide alone has never been used as a moisture-sensitive material, and this is the first time that the excellent moisture-sensing effect of yttrium oxide has been discovered. It can be applied to various types of devices such as thin film type and bulk type.

Thus, the present invention proposes a moisture sensing element characterized by using yttrium oxide as a moisture sensing material, and furthermore, a moisture sensing element using yttrium oxide as a moisture sensing material.
ad, Ta1O1'ZrO2, NbzOs and v!
A moisture sensing element characterized by using a material containing one or more of OIl as a moisture sensing material, further comprising an electrode layer formed on at least one surface of a ceramic substrate, and yttrium oxide mixed with a binder on the electrode layer. The present invention will now be described in detail.

FIG. 1 is a perspective view of a specific example of a moisture sensitive element according to the present invention. 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, AI, 0. .

Ceramics such as 5IOI, ZRO, etc. are used.

To form an electrode layer on the substrate, for example, nickel or the like is deposited as an under electrode, then gold, platinum, etc. is deposited on top of it as an upper electrode for rust prevention, and a desired electrode pattern is formed using photo-etching technology. It can be shaped, and a ruthenium electrode can also be formed by screen printing using ruthenium paste. Recently, many microfabrication techniques for manufacturing printed circuit boards for electronic circuits have been put into practical use, and by applying them, it is possible to form fine electrode patterns. For example, sputtering is also a useful method. The preferred electrode pattern is one in which a pair of comb-shaped electrodes are interlocked with the comb teeth as shown in Figure 1. <LThe smaller the spacing between the teeth, the lower the resistance value, so the resistance value of the moisture sensing element is lower. High sensitivity can be achieved. Q, 05~α2
Good results were obtained using a comb spacing of 0fi 1 ml.

After forming the electrode layer in this way, yttrium oxide (y,
A moisture-sensitive layer is formed using the moisture-sensitive material as the moisture-sensitive material. It is preferable to use a binder for sintering at low humidity.

As the binder, substances known as sintering aids can be used, but lead-free borosilicate glass is particularly suitable. The binder is used in an amount of 5 to 15%, preferably 7 to 12% of the total moisture sensitive material. After crushing and kneading the mixture of yttrium oxide and binder, the viscosity is adjusted with resin paint.
After that, the film thickness of the moisture sensitive layer is 5 to 50 μm, preferably 20 μm.
A moisture sensitive layer is coated and formed by screen printing so as to have a thickness of around m. Also, as an additive, Cab.

Mg0SBaO1TalO1, ZrO2, Nb20B and v,0. It may contain one or more of these. After that, after pre-drying for 0.2-2 hours at a temperature of 130-190℃,
Sintering is performed at a temperature of ℃ for several tens of minutes. Thereafter, lead wires are attached to the pad portions of the electrode layer to complete the moisture sensing element.

Example 18 - A comb-shaped ruthenium electrode as shown in FIG. 1 was formed by screen printing on an AI, O, substrate having a length of X9W+width. The spacing between each electrode comb was 0-15 m, and printing was performed over a length of 12 hazes. Y, Q, 95% on the electrode layer
A moisture sensitive layer was formed consisting of a 7% mixture of lead-free borosilicate glass. The moisture-sensitive layer was formed as follows: The above-mentioned mixture was crushed and kneaded in an automatic mortar made of alumina, and the viscosity was adjusted with butyl calpitol and epoxy resin paint so that the thickness of the moisture-sensitive layer was approximately 20 μm. It was applied by screen printing. After that, pre-drying at a temperature of 170°C for 1 hour,
Sintering was performed at a temperature of 850±10° C. for 30 minutes.

The change in resistance value of the humidity sensitive element thus produced with respect to humidity was measured at a measurement frequency of 1000 Hz and a measurement voltage of 1 V. The obtained characteristic curve is shown as X in FIG.

Figure 2 also shows some characteristics of commercially available products for comparison. The materials and structure of the commercially available product are as follows.

Comparison sample Material Fu Zouya I MgCr204-TiOj Bulk type 2 A ho
s + T 10x Thin film/comb 5 T 101 +
VlOs” 4 Resin system #I 5 Zr01-MgO pyp type Na1PO4・12Mo01 Dip coating treatment The resistance-humidity characteristics of the present invention are lower than commercial products 1 to 4, and Zr02-MgO subjected to dip coating treatment. It exhibits properties comparable to those of the Zr-based Zr system.Incidentally, Zr without dip coating treatment
01-MgO system exhibits worse characteristics than Samples 6 and 4 Next, the moisture sensitivity response of the device of the present invention is shown in FIG.

Curve A shows the response when the relative humidity is changed from 85% to 30%, and curve B shows the response when the relative humidity is changed from 30% to 85%. Although the response is good, curves A and B both show a sufficiently short response time. As explained above, Y, 0. By using a single moisture-sensitive leaf material, an electric resistance ceramic moisture-sensitive element with low resistance, good linearity, and good response can be obtained without the need for post-sintering treatment such as dip coating treatment. . Since it is ceramic-based, it can be used in a high temperature range and has little deterioration in the usage environment. Therefore, the humidity sensing element of the present invention is useful as a high performance humidity sensor for various uses.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the structure of the present moisture-sensitive element, FIG. 2 is a graph showing the resistance-humidity characteristics of the present invention and commercially available humidity-sensitive elements, and FIG. 3 is a graph showing the responsiveness of the present invention. This is a graph showing. 18 Substrate 3: Electrode layer 5: Moisture sensitive layer Name of agent Motoi Kurauchi J:! 2B + Kurahashi Figure 1

Claims (1)

[Scope of Claims] 1) A moisture-sensitive element characterized by using yttrium oxide as a moisture-sensitive material. 2) Cao, MgO, B based on yttrium oxide
ao. A moisture-sensitive element characterized in that a moisture-sensitive material containing one or more of Ta106, ZrO2, NJ03, and V2O is used as a moisture-sensitive material. 3) A moisture-sensitive layer in which an electrode layer is formed on at least one surface of a ceramic substrate, and a mixture of indium oxide mixed with a binder is coated on the electrode layer and sintered. 2- A moisture-sensitive element characterized by being made of a pre-formed material.