JPS5947702A - Moisture sensitive element and method of producing same - 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 The present invention relates to a humidity sensing element that detects humidity as a change in electrical resistance and is used to control humidity in air conditioners, humidifiers, microwave ovens, warehouses, printing machines, etc. .

Most conventional moisture-sensitive elements have used electrolyte materials, and others have used organic polymer oxide materials.

One using electrolyte phase 1 and 1. For example, two parallel Y and C palladium wires are wound around a cylindrical tube of polynutyroll as electrodes 5, and polyvinyl acetate and 1. +c) - There are two types, called Dammer type, in which a mixture with an aqueous solution is applied, and an impregnation type, in which vegetable fibers, porous silicon, galanutave, etc. are impregnated with LiCJ aqueous solution, but these include Ii + Since C' was used, there were drawbacks such as .

■ Since LiCJ- is deliquescent, under high humidity conditions such as during the rainy season, the concentration gradually decreases to 'f < fr, and its lifespan is short.

■ Since it sublimates over a long period of time, check whether it is necessary to calibrate it at regular intervals.

■ The measurement range varies depending on the concentration of the LiC' solution, and since the measurement range is narrow, it is necessary to combine several types of senna with different concentrations in order to measure a wide range, and therefore the number of senna is large. The problem is that the number of measurement terminals increases, making assembly and control circuits complicated.

etc.

In addition, the above-mentioned organic polymer materials and 1. For example, there is nylon, which is an alternative to traditional hair.
It detects the change in length when it swells due to moisture. This also had the following drawbacks.

■ The upper limit of the operating temperature is 60°C, which severely limits the range of use.

■ Accuracy is low due to large hysteresis during expansion and contraction.

■ Extremely slow response to changes in humidity.

etc.

The present applicant has already proposed a new moisture-sensitive element using a porous ceramic sintered body as shown in FIGS. 1(a) and 1(b), which eliminates the above-mentioned conventional drawbacks. Weigh and wet-mix fine powders of ZrO2 and MgO in predetermined mol%, dry, pressurize at a predetermined pressure to form tablets, and place the tablets in an electric furnace and heat and sinter them at a predetermined temperature for a predetermined time. After drying and cooling naturally, use a diamond blade to cut it to a specified thickness (
For example, slice into 300/1m) and each side is 4~
Porous ceramic sintered body cut into 5 squares (1)
Gold electrodes (
2+ (3) is fired and an electrode wire (4H5) is bonded thereto. By constructing the device using a porous ceramic sintered body in this way, the drawbacks of the conventional device could be eliminated.

However, even with such an element, the process of slicing the ceramic sintered body to a certain thickness (for example, 300 μm) is troublesome, and the use of gold for the electrodes makes it extremely expensive. There was a problem.

The present invention was made to solve these problems, and the base of the moisture-sensitive element is formed as a thick film on an electrically insulating substrate. In addition, in order to further improve the characteristics, it was subjected to dip coating treatment with a Na3PO4.t2MooA solution.

The present invention will be explained in detail below.

First, create the thick film moisture-sensitive paste that will be the base of the moisture-sensitive element 1! The l+4 order is as follows.

■ Z with a purity of 99.99% or more and an average particle size of 1 μm or less
Prepare fine powders of rO2 and Mho. And ZrO2
Weigh out 99 mol% of MgO and 1 mol% of MgO, put these 2S fine powders into ethanol in a plastic container, add agate balls at the same time, and wet mix in a ball mill.

■ After wet mixing, leave to stand, remove supernatant filtrate, and heat dry.

(2) This dry powder is mixed with a liquid binder to form a moisture-sensitive paste having a predetermined viscosity. As the liquid binder, a mixed solution of powdered methylcellulose, ethylcellulose, polyvinyl alcohol, etc. and α-terpineol, terpineol, etc. is used.

Next, the order of manufacturing the moisture sensitive element is as follows.

■ As shown in Figure 2, 10 sections x 15 sections m x 0.3+
An electrically insulating substrate (6) made of alumina or the like having a temperature of about +s is prepared.

■ On this substrate (6), comb-shaped electrodes (71 (8)) are arranged at a predetermined distance from each other (d=5ooμm, 250μm, etc.).
Formed with. As the electrode (71f8), for example, the substrate (61
1, dried, and then fired at 850°C. Note that the impedance can be adjusted by changing the spacing ((1)) between the electrodes (7) and (8), but this point will be described later.

(2) Next, the moisture sensitive paste is applied onto the electrode (71 (81) and the substrate (6) to form a thick moisture sensitive layer (9).

That is, this thick film moisture sensitive N (9) is made by printing the moisture sensitive paste leaving the terminal part of the electrode (7081), drying it, and then baking it at about 900°C.The thickness varies from several tens of μm to several tens of μm depending on the purpose It may be applied multiple times to achieve a thickness of up to several hundred μm.

■ Next, when further improving the properties, sodium phosphotungstate (Na, PO, .12MoO3
) (hereinafter referred to as SPM). Specifically, add 10cc of deionized water, 4ff of SPM, 40”P, 400W9.4t each on a scale 11r.
Add L and te and stir to give 0,04.0.4.
4. Make a 0.40% by weight aqueous solution. The element formed as shown in FIG. 2 is immersed in an aqueous solution adjusted to these concentrations.

(2) Take out the element from the bead and remove moisture by heating or air drying to obtain a moisture-sensitive element (10).

(2) An annealing treatment is performed to improve the characteristics of this moisture-sensitive element (10).

Feelings formed as above 2! In order to test whether the 1000000 has the desired characteristics, as shown in FIG.
signal source (1υ, resistance 02 (e.g. IOKΩ)
A voltmeter H is further connected in parallel with this resistor (12).

Next, the measurement results will be explained based on FIGS. 5 and 6.

■ Figure 5 shows the distance between the electrodes (%l (81) ((1)
These are the R-H characteristics when changed to 00 μm (dotted line characteristic) and 250 μm (solid line characteristic). In the experiment shown in FIG. 5, the mixing ratio of ZrO2 and MgO in the thick film moisture sensitive layer (9) was 99:
1 (molar ratio). Also, the property (()((') is S
No PM treatment, (b) (d) is 0.4% by weight, (c) (
/1 was treated with an 8tM solution of 4.0% by weight, and C) was treated with a 40% by weight 8tM solution.

From this characteristic diagram, widening the distance (d) between the electrodes (7) (81) will increase the resistance value, while narrowing it will lower the resistance value.
Moreover, it can be seen that the relative humidity is 10-b. Therefore, in order to obtain the desired resistance value, it is sufficient to change the interval (d) between the electrodes (71 (81). Also, from this characteristic diagram, from (a) no SPM treatment to (to)
) 0.4, (c) 4.0, to) 40% by weight and gradually 8t
It can be seen that as the M concentration increases, the resistance value moves approximately in parallel and becomes smaller. In particular, when the relative humidity is 40% by weight (/44.0), the relative humidity changes approximately linearly in the range of 10 to 90% RH, and a wide range of measurement is possible with one element. From the above points, the 8tM concentration is most preferably in the range of 0.5 to 5.0% by weight.

■ Figure 6 shows that treated with an aqueous solution of SPM 4.0%
This is the R-H characteristic when the mixing ratio of MgO to ZrO2 is varied when the spacing (d) between the electrodes (7) (81) is 500 μm. That is, (/9 is Z r
o2:Mg0-=99:1 (MoA/ratio), (e)) is ZrO2:MgO=95:5 (mole ratio) (f) is ZrO2:Mg0z 90:10 (Mo/L/ratio) )
ZrO2:Mg0 = 85:15 (molar ratio)
, h) are the respective characteristics of ZrO2:MgO=80:20 (mole ratio). From this characteristic diagram, it can be seen that both exhibit a substantially linear change in the relative humidity range of 10 to 90% I'L)i, and that a sufficiently wide range of measurement is possible with one element.

In the above embodiment, the electrodes (7) and (8) were shaped like a comb, as shown in FIG. In addition, it may be bent in a curved line or in a straight line. In addition, although the electrodes (71 (81) are provided on the same surface in FIG. 2, they may be provided on both sides with the thick film moisture sensitive layer in between. Specifically, as shown in FIG. A refresh heater (141) is provided on the back side of 6), and a porous lower electrode (7), a thick film moisture-sensitive layer (9), and a porous upper electrode (8) are laminated in this order on the upper surface. It's okay.

In this case, the area of the electrode (71 (8), the thick film moisture sensitive layer (9)
Of course, the RH characteristics change depending on the thickness. With such a shape, the shape of the element can be made small.

As described above, the present invention uses a thick film as the parent body of the moisture-sensitive element, so it has excellent workability and is inexpensive. Additionally, a single element can measure humidity over a wide range and has a long lifespan. Furthermore, when 8PM processing is performed, the effect is further increased. Moreover, even if the mutual spacing of the electrodes is changed, the S
Characteristics (device impedance) even if the concentration of PM solution is changed
It is possible to move in parallel.

[Brief explanation of drawings]

Fig. 1(a) is a front view of an element using a ceramic sintered body, Fig. 1(b) is a side view of the same, and Fig. 2 is an example of a thick film type element with a pair of electrodes provided on one side. A partially cutaway front view, and Figure 3 is an exploded perspective view of a J9 membrane type element with a pair of electrodes provided on both sides. P, Figure 4 is an electric circuit diagram for measuring characteristics, Figure 5 is a characteristic diagram when changing the electrode spacing and 8PM concentration, and Figure 6 is a diagram of characteristics when changing the electrode spacing and 8PM concentration.
The figure is a characteristic diagram when the mixing ratio of ZrO2 and MgO is changed. (6)... Electrical insulating substrate, (7) (81... Electrode, (9)... Thick film moisture sensitive layer, aOl... Moisture sensitive element, (
11)...Signal source, (121...Resistor, (13)...
...% pressure 1tl-1041...Refresh heater. Patent applicant: General Co., Ltd. Figure 1 (a) (b) Figure 4

Claims (1)

[Scope of Claims] (1) An electrically insulating substrate, at least one pair of electrodes provided on the substrate at a predetermined distance from each other, and ZrO2 and Mg provided so as to fill the gap between the electrodes.
1. A moisture-sensitive element comprising a thick moisture-sensitive layer formed mainly of a mixture of O. (2. A moisture sensing element as described in claim 1, in which the mixing ratio of ZrO2 and MgO is 99=1 to 80:20 (molar ratio). (3) Claim 1 or 2 (4) A moisture-sensing element according to claim 3, in which the W desensitizing layer is dip-coated with an aqueous solution of N-PO, .12MoOs.
A moisture sensing element using an O4.12MoOs aqueous solution having a concentration of 0.5 to 5.0% by weight. (5) The moisture sensing element according to claim 1, wherein the pair of electrodes are provided on one side of a thick film moisture sensitive layer with a space between them. (6) The moisture-sensitive element according to claim 1, wherein the pair of electrodes are provided on both sides of the thick-film moisture-sensitive layer so as to sandwich the thick-film moisture-sensitive layer. (7) A moisture-sensitive paste made of a mixture of ZrO□ and MgO made viscous by a binder solution, and this moisture-sensitive paste is placed on at least one row of electrodes on an electrically insulating M plate. A method for producing a moisture-sensitive element, which comprises coating and baking to form a thick moisture-sensitive layer, followed by dip coating treatment I7 with an aqueous Na3PO4.12MoO++ solution. (8) The method for producing a moisture-sensitive element according to claim 7, wherein the binder solution is powdered methyl cellulose, and the ethyl cellulose material is polyvinyl alcohol mixed and dissolved with α-terpineol or terpineol.