JPS5927501A - Moisture sensitive resistance 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 Technical Field The present invention relates to a moisture-sensitive resistance element using a chemical combination of zirconium silicate or zirconium oxide and phosphorus as a moisture-sensitive material.

<Prior art> As humidity-sensitive resistance elements whose electrical resistance changes in response to humidity in the atmosphere, tin oxide (SnO2),
Iron oxide (Fe203 or Fe304), titanium oxide (T
i02) and other metal oxides or sintered bodies of these composite metal oxides; ■Those using porous metal oxide films obtained by anodic oxidation of metals such as aluminum;
2) Those using electrolyte salts such as solithium chloride (Li'CI), and 2) Those using hygroscopic resins, organic polymer membranes, and thermistors are known.

In general, moisture-sensitive resistance elements using metal oxides or composite metal oxides have the advantage of having a wide moisture sensitivity range and excellent heat resistance, but on the other hand, they have instability peculiar to metal oxides. It has the disadvantage of poor reproducibility of humidity characteristics, and tends to change over time even at room temperature and humidity. In particular, in these metal oxide sintered bodies, moisture-sensitive characteristics such as sensitivity and response speed are influenced not only by the properties of the material itself but also by its microscopic structure such as pore size distribution and porosity. Therefore, it is not always easy to manufacture devices with good moisture sensitivity characteristics with good reproducibility. In addition, there is a problem in that the moisture-sensing properties deteriorate in a relatively short period of time due to the formation of hydroxide due to chemical adsorption of water on the metal oxide surface or a reduction in the moisture-sensitive surface area due to dirt. Ta.

For this reason, a method has been proposed and implemented in which chemically adsorbed water and other deposits are removed by periodically heating the humidity sensing element. Furthermore, with conventional methods, it is not always easy to obtain a humidity sensitive element having good exponential characteristics over the entire humidity range.

<Purpose> The present invention was made in order to eliminate the drawbacks of the conventional moisture-sensitive resistance elements made of metal oxides or composite sintered bodies thereof as described above. By firing zirconium silicate or zirconium oxide and a phosphorus compound with uniform particle size to obtain a sintered body, and at the same time producing a network-like chemical bond consisting of zirconium silicate or zirconium oxide and phosphorus, The present invention provides a moisture-sensitive resistance element that is characterized by excellent mechanical and thermal properties, little change over time, pleasant exponential function characteristics, and highly reproducible heat-sensitive characteristics. . The present invention will be described in detail below according to examples.

<Example> In Fig. 1, a schematic structural diagram of a humidity-sensitive resistive element according to the present invention, (1) is a humidity-sensitive resistor in which a chemical bond of zirconium silicate or zirconium oxide and phosphorus is formed at least on the surface. For example, it is created through the steps described below. Moisture-permeable electrodes (2) are formed on both sides of the moisture-sensitive resistor +11, and lead wires (3) are drawn out.

The above-mentioned moisture-sensitive resistor (1) uses zirconium silicate particles and phosphoric acid (H3PO4) as starting materials, and both are mixed at 20:
Mix in a weight ratio of 5. Further dry on a hot water bath. Next, this is molded into a pellet having a thickness of 0.3 Ill and an area of 5 x 5-. This pellet was heated at a temperature of 350℃ for about 10 minutes.
Temporarily bake for an hour. Further, this pellet was created by firing it in air at a temperature of 1000° C. for about 3 hours.

A ruthenium oxide film with an area of 4 x 4- is formed as a moisture-permeable electrode (2) on both sides of the moisture-sensitive sintered body fl+ thus obtained, and a lead wire (3) is attached to this to form a moisture-sensitive resistor. It was named Element.

FIG. 2 shows an example of the humidity-sensing characteristics (DC resistance value versus relative humidity characteristics) of the humidity-sensitive resistance element produced according to this example at an ambient temperature of 26°C. As seen in this figure, it was confirmed that it was sensitive over almost the entire humidity range and had extremely stable and good exponential characteristics against changes in relative humidity.

This is because the moisture-sensitive resistor (1) is created through a process of adding a phosphorous compound (phosphoric acid in the above example) to zirconium silicate and sintering it. This is thought to be due to the formation of a network structure on the surface of the zirconium silicate particles in which zirconium thorine (or ions) are chemically bonded via oxygen atoms. Since the moisture-sensitive resistance element of the above embodiment operates in response to only the physically adsorbed water contained in the moisture-sensitive sintered body, its moisture-sensitive characteristics exhibit extremely good exponential characteristics with respect to relative humidity. Since reformation due to moisture absorption of surface hydroxyl groups does not easily occur, it is stable with little change over time.

The humidity-sensitive resistor (+), which is sintered by adding all the phosphorus compounds to the above-mentioned zirconium silicate, shows the relationship between resistance value and relative humidity as shown in the curve in Figure 2 even after being left at room temperature and humidity for 1 degree. There is almost no change in the properties, and the properties are stable with no changes over time.

Incidentally, the moisture-sensitive characteristics of a moisture-sensitive resistance element produced in the same manner as in the above example without adding phosphoric acid but with aluminum oxide particles at an ambient temperature of 25°C are as follows. Shown in the figure for reference. In Figure 3, curve (a) is
These are the initial characteristics of pellets that were fired for 3 hours at a firing temperature of 1000°C. Curve (b) is curve 1 (a
) These are the characteristics of the humidity-sensitive resistance element shown after being left at room temperature and humidity for about 4 days.

In this way, it was confirmed that the moisture sensitivity characteristics of the material to which phosphorus was not added changed in a relatively short period of time even in an atmosphere of normal temperature and normal humidity.

As is clear from FIG. 2, the humidity sensitivity of the humidity-sensitive resistance element of the above embodiment is extremely high, and the resistance changes by 6 to 7 orders of magnitude over the entire humidity range.

In the above example, 7nium silicate particles were used as one of the starting materials, but zirconium oxide may also be used.

Furthermore, the other starting material is not limited to phosphoric acid (H3PO4), and phosphorus compounds such as niline trioxide and ammonium phosphate may also be used.

As detailed above, according to the present invention, a moisture-sensitive resistance element having stable and excellent moisture-sensitive characteristics over the entire humidity range can be easily produced with good reproducibility.

[Brief explanation of the drawing]

FIG. 1 is a structural diagram of a humidity-sensitive resistance element according to the present invention, and FIG. 2 is an example of humidity-sensitive characteristics of a humidity-sensitive resistance element according to an embodiment of the present invention. FIG. 3 shows an example of the humidity-sensitive characteristics of a humidity-sensitive resistance element not according to the present invention. 1: Moisture-sensitive resistor 2: Moisture-permeable electrode 3: Lead wire agent Patent attorney Yoshihiko Fukushi (and 2 others) No.

Claims (1)

[Scope of Claims] 1) In a moisture-sensitive resistance element comprising a moisture-sensitive element whose electrical resistance value changes in response to relative humidity or absolute humidity, silicon is added to the entire or surface layer of the moisture-sensitive element. A moisture-sensitive resistor characterized by forming a chemical bond with zirconium oxide or zirconium oxide. 2) In a method for manufacturing a humidity-sensitive resistor comprising a humidity-sensitive element whose electrical resistance value changes in response to relative humidity or an absolute humidity layer, a mixture of zirconium silicate or zirconium oxide and phosphorus is fired at a high temperature. A method for manufacturing a moisture-sensitive resistor, characterized in that: 3) The method for manufacturing a moisture-sensitive resistance element according to claim 2, wherein the phosphorus is a phosphate such as phosphoric acid, niphosphorus trioxide, or ammonium phosphate. 4) The amount of the phosphoric acid or phosphate salt added is 30% by weight
The method for manufacturing a moisture-sensitive resistance element according to claim 3, characterized in that: 5) The temperature of the high temperature firing is 350°C or more and 1800°C
A method for manufacturing a moisture-sensitive resistor according to claim 2, which is set as follows.