JPS6184001A - Moisture-sensitive 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 the Zr01 series, Z r Ox + Yt Os
The present invention relates to a ceramic moisture-sensing element using a Y2O3-based moisture-sensitive material and a Y2O3-based moisture-sensitive material, and in particular, Li, co, and v, 0. The present invention relates to a moisture-sensitive element having a low resistance value, excellent stability over time, and good humidity response, which is characterized by adding at least one of the above.

Background of the Invention 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 electrical resistance, and there are many types of moisture-sensitive materials used, including electrolyte materials such as lithium chloride, organic polymer materials, ceramic materials, and light. has been proposed. As an electrical resistance type moisture sensing element, basically,
It is required to have low electrical resistance, good linearity in resistance-humidity characteristics, have an appropriate operating range, and not deteriorate in the usage environment. Material-based moisture-sensitive materials are in the spotlight.

There have been many proposals for ceramic moisture-sensitive materials, but the important properties are (a) low electrical resistance (the higher the current, the better the sensitivity), and (b) resistance-humidity characteristics. (c) Good linearity and (c) Good responsiveness are required. The present inventors believe that (1) yt is a ceramic moisture-sensitive material that basically satisfies these characteristics.
os, (2) Yt Os + Z r Ox (old 11~
99.00. %), (3) Yt O@ + (Ca
O+ M g O+ B a O+ T i02 +
Ta 10s +Nb! 'O, and VtOs)
at least -74 ((l, 01~9 9.0 0%), (4) Zr0t + (CaO, MgO, Bad,'
rio,s TatOs.

At least one of Nb, O, and VtOs (0,
01-9 9. OO%) etc., 0. It was concluded that Yz 0B + Z r Os series, and Zr01 series ceramics are good. In particular, the YtOs+ZrOt ceramic exhibits stable and favorable properties.

The form of the humidity sensing element may be a Nordic type in which a pair of electrodes are provided on opposing surfaces of the ceramic sintered body, but a preferred form is that an electrode layer is formed on at least one surface of the ceramic substrate, and It is of a thin film type, in which a mixture of the ceramic and a binder is coated on the electrode layer, and a moisture sensitive layer is formed by drying and sintering the mixture. 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 α2 (its or less). Good results can be obtained by setting the comb tooth spacing to 120B or less.

However, such Y, 0. system, y, o, +Z
There is still a lot of room for improvement in the performance of rO2-based and Zr01-based ceramic humidity sensing elements, and trials are currently being carried out. One of the points to be improved is the prevention of deterioration over time, and it is also desired to further reduce the resistance value. It is desirable to further shorten the humidity response time.

YtOs system, Y, 0°-
)-In order to obtain ZrOs-based and ZrO-based ceramics, many studies have been made, including the addition of additives to the humidity-sensitive part, firing methods, surface post-treatment methods, etc. . There is no guarantee that additives, firing methods, and surface post-treatment methods suitable for one type of moisture-sensitive material will be compatible with another type of moisture-sensitive material, and selection thereof can be difficult.

SUMMARY OF THE INVENTION The present inventor has developed a ZrO system, Z r Ox + Yt O
In the s-based and YtOs-based ceramic humidity sensing elements, Li2Co and v, 0. It has been found that when at least one of these is included, significant improvements can be made in low resistance, stability over time, and humidity responsiveness. These additives enable low temperature firing and form a very stable moisture sensitive part. Furthermore, KOE or Nag 0
It was also found that performance was further improved when used in combination with 03 surface treatment.

Thus, the present invention provides ZrO, system, ZrO2+Y10s
Li,
Provided is a moisture sensitive element characterized in that at least one of Co and VtOs is added. Furthermore, the present invention provides ZrO, system, Z r Ot + Y, Os system and Y, 0. Li, CO is added to the moisture sensing part, which is mainly made of moisture-sensitive materials.
The present invention also provides a moisture sensing element characterized in that at least one of No. 3 and VtOs is cooled and surface treated with KOH or NatCOs.

Although the moisture-sensitive element used in the present invention can be realized in a so-called bulk type in which a pair of electrodes are formed on opposing surfaces of a ceramic sintered body, it is preferably in a thin-film type in which a moisture-sensitive film is formed on a substrate. will be produced. 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).

Ceramics such as Autos, 5i02, ZrO, etc. are used as the substrate. Formation of the electrode layer on the substrate involves, for example, depositing nickel or the like as an under electrode, then depositing gold, platinum, or the like as an upper electrode for rust prevention, and forming a desired electrode pattern using photo-etching technology. The ruthenium electrode can also be formed by a screen printing method 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 electrode pattern is preferably one in which a pair of comb-shaped electrode teeth are interlocked alternately, 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 have been obtained using comb spacings of 0.05-0.20 mx.

Furthermore, an electrode layer using a neutral electrode has recently been proposed by the present applicant. As shown in FIG. 2, a neutral electrode 4 is arranged between each pair of comb-like 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, which lead to advantageous moisture-sensitive characteristics, to segregate and migrate toward the original electrode. That is, in the moisture sensitive layer, ions which advantageously lead to moisture sensitive properties due to the adsorption of water in the IJ lux are initially uniformly distributed. However, due to the difference in ionization tendency between metals, ions that advantageously lead to moisture-sensitive characteristics move toward each electrode side of the electrode layer over time.

The ions that lead to advantageous moisture-sensitive characteristics include the ceramic material used, the binder, and if surface treatment such as dipping treatment or pre-additive treatment has been performed, the treatment agent or pre-additive to the sintered body (IJ Lux) These are ions such as Li, Na, Ca, etc. introduced. For example, in the case of a comb-shaped electrode, these ions in the moisture-sensitive layer move toward the comb-shaped electrode, and the uniform distribution of these ions between the comb-shaped electrodes is impaired. Due to the presence of the neutral electrode, the above-mentioned ions also move around the neutral electrode, so even if ion movement occurs, the uniform dispersion of ions at the beginning of Todoroki as a whole will not be affected as much. . Such a neutral electrode is useful for preventing the above-mentioned segregation and movement of ions toward the electrode, thereby suppressing changes in the characteristics of the moisture-sensitive element over time. The neutral electrode is not limited to a straight line as shown in the figure, but may be formed in a dot array or any other arbitrary shape.

! By screen printing the polar layer, the neutral electrode can be easily formed at the same time.

After forming the electrode layer in this way, the Zr
O2 system, Y, 0. A moisture sensitive layer consisting of a mixture of a Y, O, + ZrO2 moisture sensitive material and a binder is formed thereon.

As a moisture-sensitive material, (1) Yt o, alone.

(2) YtOs+Zr0t(0,01~99.00
%).

(3) YtO3+ (C&OI MgO* B a
o* T 102 + T at Os +Nb, O
, and V, O,) and morphi(0,01~9ρ0
0chi) (a) Zr0v + (CaO, MgO+
Bad, Ti1t+TatOs+Nb,
O, and V, O8) At least four types (n, o1 to 9
700%) etc. can be preferably used.

According to the invention, the binders include Li, CO3 and V2
It is constituted as a common species among O3.

A combination of both is preferred. Lt, co3 is 1 to 10 moA/
It is preferable that H, V, and O are used in an amount of 10 mol or less, and the total of both is in the range of 1 to 10 mol.

Alternatively, conventional binders may be used, including lead-free borosilicate glass KLi, CO, and V,0. may be added and mixed. A preferred composition for use as lead-free borosilicate has a sodium oxide content of 10 to 1.
5% by weight, potassium oxide content 2-5% by weight, calcium oxide content 5-10% by weight, magnesium oxide content (L5-3% by weight, aluminum oxide content 5-10% by weight) weight i%, silicon dioxide content is 30~
45% by weight, and the content of boron oxide is 20-50% by weight. This binder is preferable because it has a higher content of alkali metal and alkaline earth metal oxides and a lower melting point than general lead-free borosilicate glass.

Generally, a moisture-sensitive paste is prepared by pulverizing and kneading the mixture of the ceramic and binder, and then adjusting the viscosity with a resin paint.

It has been found that the preparation of a moisture-sensitive paste in the following manner leads to good results when using only as a binder.

(1) Ceramic (Zr011 Yz Os) and Li1CO.

and are stirred under addition of an organic binder.

(n) After the organic binder is evaporated and removed, primary firing is performed at a temperature of around 800°C.

GiD The fired product is crushed with the addition of an organic binder.

(ψ After removing the organic binder by evaporation, add V, O5 and resin paint.

M: Knead and adjust viscosity to form a moisture-sensitive paste.

After the moisture-sensitive paste has been prepared, the moisture-sensitive layer is coated by screen printing so that the thickness of the moisture-sensitive layer is about 5 to 200 μm, preferably about 40 to 120 μm.

The thicker the film, the lower the electrical resistance of the final product.

Thereafter, after preliminary drying at a temperature of 130 to 190° C. for 11.2 to 2 hours, a firing treatment is performed at a temperature lower than conventional.

Since LL, CO, and V, O, have low melting points, their use as binders or their presence in binders allows low temperature firing. The firing process sinters the ceramic particles to form the skeleton structure of the moisture sensitive membrane and to provide structural strength. Conventionally, a minimum temperature of 900°C was required to obtain a certain level of structural strength.
However, it has been found that such high temperature firing actually deteriorates the characteristics, particularly the resistance characteristics, of the produced moisture-sensitive element. In the present invention, 500 to 87
Calcining is carried out at a temperature of 0°C, preferably between 550 and 700°C. The firing holding time may be 5 minutes to 1 hour, typically several tens of minutes.

In order to make the humidity-sensitive element even more stable, it has been proposed to subject the sintered humidity-sensitive element to an aging treatment, followed by a heat treatment, and this does not preclude its use.

In this way, a moisture-sensitive element with low resistance and high sensitivity and stability is produced, although the stabilization and low resistance can be further improved by preferably carrying out a subsequent surface treatment. . There are various proposals for surface treatment methods, but the preferred methods in the present invention are KOH or NatCO.
This is an immersion treatment in a liquid containing No. 3.

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. Appropriate KOH strength is 10 to 30 degrees. If it is less than 10%, it will take a long time for impregnation, and if it exceeds 50%, the degree of surface modification will increase, causing harmful effects such as increased hysteresis.

After the dipping treatment, the device is preferably fired at a temperature of 600-870°C. The calcination is necessary to prevent the KOH surface treatment agent from dripping during condensation and to produce a stable modified surface. The reason why the firing temperature range is preferably 600 to 870°C is to prevent an increase in electrical resistance, as described above.

In the case of Na and Co treatments, it can be carried out in substantially the same manner as above.

Example 18 A1 frame length x 1 m width. O. A comb-shaped ruthenium coffin as shown in FIG. 1 was formed on the substrate by screen printing. The spacing of each electrode comb tooth is α20mx, 121m
printed over a length of .

Zr0t:Y,O,=s o : 15 moles of Li2Co were added to the mixed ceramic in a weight ratio of 50 and stirred under addition of ethyl acetate. After evaporating ethyl acetate, the mixture was calcined at 800° C. for 1 hour. Crushing was carried out under the addition of ethyl acetate, the ethyl acetate was evaporated, and then v, o, o, s mol, butyl calpitol and epoxy resin paint were added, and the viscosity was adjusted after mixing to prepare a moisture sensitive paste. .

The moisture-sensitive paste was applied onto the electrode by screen printing so that the thickness of the moisture-sensitive layer was 40 μm, and dried at a temperature of 170° C. for 1 hour. Thereafter, low temperature phosphorization was performed at 600° C. for 15 minutes.

Subsequently, immerse in a 20-inch KOH aqueous solution for 5 minutes, and then a.
Post-treatment was performed by firing at OO°C for 20 minutes.

Humidity-resistance characteristics, humidity responsiveness (90% response, 55'% RH - 455% RH and 8
5cm RH → 55cm RH) and stability over time (standing at 80° C. and various humidity conditions) were investigated. Results in section 3.4
and Figure 5 respectively.

It can be seen from graph 27 in FIG. 3 that the resistance value is very low and the linearity is maintained as before. From FIG. 4, it can be seen that the response characteristics are extremely good (10 seconds). FIG. 5 shows that the stability over time is also good. It can be seen that the present invention provides a moisture-sensitive element that is overall excellent.

Example 2 A moisture sensitive layer was coated on an electrode layer having a neutral electrode as shown in FIG. 2 in the same manner as in Example 1 to form a moisture sensitive element. As shown in FIG. 3, the resistance value is only somewhat low, and the response is good as shown in FIG. 4. The stability over time was measured in the same manner as in FIG. The results are shown in Figure 6. Very good stability over time has been obtained.

In addition, in the above test example, the resistance value is measured at a measurement frequency of 1000
Hz and the measurement voltage was 1 V.

Effects of the Invention The present invention provides a moisture sensing element with extremely low resistance, excellent stability over time, and extremely good response characteristics, which is superior to various moisture sensing elements currently on the market or proposed. Overall, it is excellent.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an example of a coated humidity sensing element, FIG. 2 is a plan view of an electrode pattern using a neutral electrode, and FIG. Graph showing resistance characteristics,
FIG. 4 is a graph showing the humidity responsiveness, FIG. 5 is a graph showing the stability over time of the humidity sensing element of Example 1, and FIG.
The figure is a graph showing the stability over time of the humidity sensitive element of Example 2. 1: Substrate 5: Electrode 4: Neutral electrode 5: Moisture sensitive layer

Claims (1)

[Claims] 1) ZrO_2 system, ZrO_2+Y_2O_3 system, and Y
Li_2C in the moisture sensing part, which is mainly made of _2O_3 moisture-sensitive material.
A moisture-sensitive element characterized by adding at least one of O_3 and V_2O_3. 2) ZrO_2 series, ZrO_2+Y_2O_3 series and Y
Li_2C in the moisture sensing part, which is mainly made of _2O_3 moisture-sensitive material.
1. A moisture-sensitive element characterized in that at least one of O_3 and V_2O_3 is added and the surface is treated with KOH or Na_2CO_3.