JPH0736008B2 - Moisture sensitive element - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to an improvement of a moisture sensitive element.

[Technical Background of the Invention and Problems Thereof] As a humidity sensitive element (humidity sensor) for measuring or detecting humidity in the atmosphere, various types of humidity sensitive elements have been proposed and put into practical use. In particular, in recent years, various types of humidity-sensitive elements that directly detect humidity have been proposed. Such a humidity-sensitive element has attracted attention because it has a feature that not only humidity detection but also humidity control can be easily processed by an electric signal.

By the way, since the above-mentioned moisture-sensitive element measures the humidity in the atmosphere, moisture in the atmosphere is physically adsorbed on the surface of the moisture-sensitive element body constituting the element, and the electrical resistance of the element surface at this time is measured. Generally read. As the moisture-sensitive element body of such a moisture-sensitive element, a polymer substance, a sintered body of a metal oxide, or a sintered body of a metal oxide has been conventionally used. However, there is a drawback that it is difficult to detect a wide range of humidity with a humidity sensitive element having such a moisture sensitive element.
For example, when a high molecular substance or a metal oxide is used, the resistance value of the humidity sensitive element in the low humidity region becomes extremely large as 1 MΩ to 10 MΩ or more, and therefore the humidity can be easily detected by a normal electric detection circuit. I can't. Further, a humidity sensitive element using a certain kind of metal oxide has a low sensitivity in a low humidity region, which makes it difficult to detect humidity. As described above, it has been difficult for the conventional humidity sensitive element to detect the low humidity region with high accuracy.

[Object of the Invention]

An object of the present invention is to provide a humidity sensitive element which has a constant and high sensitivity over a wide range from a high humidity region to a low humidity region and has a resistance value which is easy to use even in a low humidity region.

[Outline of Invention]

The present invention is a moisture-sensitive element comprising a moisture-sensitive element body and a pair of electrodes connected to the moisture-sensitive element body, wherein the moisture-sensitive element body is made of a sintered body having a large number of fine pores, The particles constituting the sintered body have a spinel skeleton, the surface of which is covered with glass made of CuO and MZnVO ₄ (M is Li, Na, K), and the sintered body is
The total volume of pores formed by fine pores of 0.1 μm or less is 1.0
For the total volume of pores formed by micropores of less than μm
The moisture-sensitive element is characterized by being distributed at a rate of 15% or less.

The moisture-sensitive element of the present invention having the above-mentioned configuration is used in an extremely wide range of humidity range of about 700 kΩ in an atmosphere of 25 ° C. and a relative humidity of 5% and about 20 kΩ in an atmosphere of a relative humidity of 95% at the same temperature. It has a resistance value that can be controlled, has a high sensitivity, has a constant sensitivity in the entire humidity range, and has an excellent moisture sensitivity characteristic that can be easily applied to a detection circuit. Such an excellent humidity characteristic is that the moisture-sensitive element is composed of a sintered body having a large number of fine pores, the particles constituting the sintered body are composed of a spinel skeleton, and the surface thereof is CuO and MZnVO ₄ It is presumed that this is because the sintered body is covered with a glass made of (M represents Li, Na, K) and the sintered body has a fine pore distribution, but its detailed behavior is still unknown. Possibly, fine pores of 0.1 μm or less are different from the fine pores having a larger diameter in adsorbing moisture, and the glass covering the surface of the particles constituting the sintered body affects the adsorption of moisture. It is considered that the moisture-sensitive element provided with the moisture-sensitive element body having the above-described excellent moisture-sensitive property can be obtained by selecting the diameter of the fine pores and the interaction of the glass covering the particles.

The reason for limiting the fine pore distribution of the sintered body that constitutes the moisture-sensitive element is that if it is less than 15% with respect to the total volume of pores formed by fine pores of 0.1 μm or less, it is The resistance value becomes high, and it becomes impossible to obtain the above-mentioned moisture-sensitive property.

The sintered body is composed of a spinel skeleton such as ZnO, ZnO and MgO, or ZnCr ₂ O ₄ . The surface of particles having such a spinel skeleton is in the form of being coated with glass of CuO and MZnVO ₄ (where M represents Li, Na, and K). The moisture-sensitive element including the moisture-sensitive element body made of the sintered body having such a form is
The change in resistance value can be read by the humidity sensitivity of the glass.
At this time, the fine pore state of the skeleton (particles) such as ZnCr ₂ O ₄ and the coating of the glass with the particles have a great influence on the moisture-sensitive characteristics of the entire device.

The sintered body forming the moisture-sensitive element body of the moisture-sensitive element according to the present invention described above, for example, Cr ₂ O ₃ 21 ~ 73 mol%, ZnO and
At least one 25-55 mol% of MgO, CuO0.5~8.0 mol%, V ₂ O ₃ 0.5 to 8.0 mol%, Li ₂ O, alkali metal oxides 0.5 to 8.0 mol selected from Na ₂ O and K ₂ O % Of the composition as a starting material, and then the calcined powder is sufficiently crushed, and the resulting material is molded and sintered.

Example of Invention

 Hereinafter, examples of the present invention will be described in detail.

Example 1 First, fine powders of chromium oxide, zinc oxide, magnesium oxide, copper oxide, sodium carbonate, lithium carbonate and vanadium oxide were used as starting materials, and these starting materials were made of Cr.
₂ O ₃ , ZnO, MgO, CuO, Li ₂ O, V ₂ O _{3 in} a molar ratio of 45, 43,
Weigh it to 1, 3, 4, 4 and then in a pot mill
Wet mixed for 24 hours. Subsequently, this mixture was heated at 120 ° C for 1 hour.
After drying for 2 hours, it was calcined at 800 ° C. Subsequently, the calcined product was wet pulverized with a pulverizer for 1.5 hours and then dried again at 120 ° C. for 12 hours to prepare a raw material powder.

Next, 2% by weight of polyvinyl alcohol (binder) was added to the raw material powder and granulated with a liquor machine, and the granulated product was pressure molded under the condition of 500 Kg / cm ₂ to have a diameter of 10 mm and a thickness of A 2 mm disk-shaped compact was formed. Subsequently, this molded body was fired at a temperature of 1300 ° C. for 2 hours, and then both main surfaces of the sintered body were polished to prepare a moisture-sensitive element body having a thickness of 1 mm. Subsequently, a ruthenium oxide paste was screen-printed on both main surfaces of this moisture-sensitive element, followed by baking at about 700 ° C. to form an electrode having a diameter of 7 mm, and the moisture-sensitive element shown in FIG. 1 was manufactured. In FIG. 1, 1 is a moisture sensitive element and 2 is an electrode.

Examples 2 and 3 The pulverization time of the calcined product in Example 1 was set to 1 hour and 2
A moisture sensitive element was manufactured in the same manner as in Example 1 except that the operation was performed for a time.

Comparative Example 1 A moisture sensitive element was manufactured by the same method as in Example 1 except that the calcination time in Example 1 was changed to 30 minutes.

Then, the moisture-sensitive element bodies made of the sintered bodies of Examples 1 to 3 and Comparative Example 1 were measured for their fine pore distribution with a mercury porosimeter, and the results shown in Table 1 below were obtained.

Further, when the humidity characteristics of the moisture sensitive elements of Examples 1 to 3 and Comparative Example 1 were examined at an ambient temperature of 25 ° C., the characteristic diagram shown in FIG. 2 was obtained. In FIG. 2, A _{1 to} A ₃ are characteristic lines of the moisture sensitive elements of Examples 1 to 3, and B ₁ is a characteristic line of the moisture sensitive element of Comparative Example 1. As is clear from FIG. 2, the humidity-sensitive elements of Examples 1 to 3 have a low resistance value from the low humidity region to the high humidity region, high sensitivity, and constant sensitivity, which is extremely easy to use. It turns out that For example, in the humidity sensitive element of Example 1, 650 kΩ and 95% relative humidity at a relative humidity of 5%.
% Shows 23 kΩ.

Example 4 First, as starting materials, fine powders of chromium oxide, zinc oxide, magnesium oxide, copper oxide, sodium carbonate, potassium carbonate and vanadium oxide were used.
₂ O ₃ , ZnO, MgO, CuO, Na ₂ O, K ₂ O, V ₂ O _{3 in} a molar ratio of 45, 4
After weighing so as to be 3, 1, 3, 2, 2, 4, the mixture was wet-mixed in a pot mill for 24 hours. Then, this mixture
After drying at 120 ° C for 12 hours, it was calcined at 800 ° C. Subsequently, the calcined product was wet pulverized with a pulverizer for 1.5 hours and then dried again at 120 ° C. for 12 hours to prepare a raw material powder.

Next, 2% by weight of polyvinyl alcohol (binder) was added to the raw material powder and granulated with a liquor machine, and the granulated product was pressure molded under the condition of 500 Kg / cm ₂ to have a diameter of 10 mm and a thickness of A 2 mm disk-shaped compact was formed. Subsequently, this molded body was fired at a temperature of 1300 ° C. for 2 hours, and then both main surfaces of the sintered body were polished to prepare a moisture-sensitive element body having a thickness of 1 mm. Subsequently, after ruthenium oxide paste was screen-printed on both main surfaces of this moisture-sensitive element, baking was performed at about 700 ° C to form an electrode with a diameter of 7 mm, and a moisture-sensitive element having the same structure as in Fig. 1 was formed. Manufactured.

Examples 5 and 6 The calcined product of Example 4 was crushed for 1 hour and 2
A moisture-sensitive element was manufactured by the same method as in Example 4 except that the operation was performed for a time.

Comparative Example 2 A moisture sensitive element was manufactured by the same method as in Example 4 except that the calcination time in Example 4 was changed to 30 minutes.

Then, the moisture-sensitive element bodies made of the sintered bodies of Examples 4 to 6 and Comparative Example 2 were measured for their fine pore distribution with a mercury porosimeter, and the results shown in Table 2 below were obtained.

Further, when the humidity characteristics of the moisture sensitive elements of Examples 4 to 6 and Comparative Example 2 were examined at an ambient temperature of 25 ° C., the characteristic diagram shown in FIG. 3 was obtained. In FIG. 3, A _{4 to} A ₆ are characteristic lines of the moisture sensitive elements of Examples 4 to 6 and B ₂ are characteristic lines of the moisture sensitive element of Comparative Example 2. As is apparent from FIG. 3, the humidity-sensitive elements of Examples 4 to 6 have a low resistance value from the low humidity region to the high humidity region, high sensitivity, and constant sensitivity, which is extremely easy to use. It turns out that For example, in the humidity sensitive element of Example 4, 570 kΩ and 95% relative humidity at a relative humidity of 5%.
% Indicates 14 kΩ.

〔The invention's effect〕

As described in detail above, according to the present invention, it is possible to detect humidity with low resistance and uniform sensitivity over a wide range from a high humidity region of 5 to 95% relative humidity to a low humidity region. However, it is possible to provide a moisture sensitive element having a resistance value that is easy to use.

[Brief description of drawings]

FIG. 1 is a perspective view of a humidity sensitive element showing an embodiment of the present invention, and FIG. 2 is a characteristic diagram showing the relationship between relative humidity and resistance value in the humidity sensitive elements of Examples 1 to 3 and Comparative Example 1. FIG. 3 is a characteristic diagram showing the relationship between the relative humidity and the resistance value in the moisture sensitive elements of Examples 4 to 6 and Comparative Example 2. 1 ... Moisture-sensitive element, 2 ... Electrode.

Claims (1)

[Claims] 1. A moisture sensitive element comprising a moisture sensitive element and a pair of electrodes connected to the moisture sensitive element, wherein the moisture sensitive element comprises a sintered body having a large number of fine holes. The particles constituting the sintered body have a spinel skeleton, and the surface thereof is covered with glass made of CuO and MZnVO ₄ (M is Li, Na, K), and the sintered body is
The total volume of pores formed by fine pores of 0.1 μm or less is 1.0
For the total volume of pores formed by micropores of less than μm
A moisture-sensitive element characterized by being distributed at a rate of 15% or less.