JPS58135602A - 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] [Technical field in which the invention pertains] The present invention provides a moisture-sensitive element, more specifically, a moisture-sensitive element that has a resistance value that exhibits little deterioration over time, is highly reliable, and is easy to use in a wide range of humidity. The present invention relates to a moisture-sensitive element having a moisture-sensitive element.

[Prior art and its problems]

There are various types of devices that measure and detect humidity in the atmosphere, ranging from wet and psychrometric hygrometers to devices that use alpha rays.

In recent years, various methods have been proposed that can directly detect humidity in the atmosphere using electrical signals. A method that can detect humidity directly with an electrical signal makes it easy to not only measure humidity but also control it1.
It is attracting attention for its ease of handling. Among these, one that can directly electrically detect humidity in a fairly wide humidity range and is inexpensive is one that adsorbs and desorbs moisture from the atmosphere onto the surface of a humidity sensing element, thereby increasing the resistance or capacitance value. It takes advantage of change. In these humidity sensing elements, a sintered body of a metal oxide or a polymer is usually used as a humidity sensing element body. By the way, the humidity sensing elements that have been proposed so far with the above functions have relatively low humidity in high humidity regions, regardless of whether they use sintered metal oxides or molecules as the humidity sensing element. Although it exhibits a resistance value that is easy to use, in low humidity areas (below 20-30% RH), the resistance value of the humidity sensing element is extremely high, exceeding IOMΩ, and requires an extremely expensive circuit to accurately detect low humidity. It had the disadvantage that it was necessary.

In addition, conventional moisture-sensing elements that adsorb and desorb water molecules on their surfaces have the drawback of large deterioration over time and poor reliability. In order to eliminate this drawback, in the case of moisture-sensitive elements made of sintered bodies of metal oxides, a method called heating cleaning has been introduced to put them into practical use, taking advantage of their excellent heat resistance. . This heating cleaning is a method of repairing the deterioration of the humidity sensing element by heating the humidity sensing element to about 450 degrees Celsius at regular intervals. Although it is not possible to detect humidity automatically, it requires a heating circuit, which has the drawbacks of complicated operation and high cost.

[Object of the Invention] The present invention eliminates these drawbacks, and provides a moisture-sensitive element that exhibits little deterioration over time, is highly reliable, and has a resistance value that is easy to use in a wide range of humidity. The purpose is to

[Summary of the invention]

The present invention uses zinc oxide: 10 to 80 mol% and titanium oxide (I).
V): I 5-70 mol% and chromium oxide (1):
A moisture-sensitive element characterized in that a porous sintered body consisting of 5 to 20 mol% supports at least one element or oxide selected from phosphorus and sulfur, or both. The supported amount of at least 1 M of a simple substance or oxide selected from sulfur and sulfur is 0.1 to 2 in terms of phosphorus and sulfur based on the weight of the sintered body.
．． In a moisture sensitive element, it is preferable that the content be 0% by weight.

The reasons for limiting each composition in the present invention will be described below. If zinc oxide exceeds 80 mol%, titanium oxide (
When IV) exceeds 70 mol% and when chromium oxide is less than 5 mol%, the change over time becomes unfavorable. Furthermore, if chromium (1) oxide exceeds 20 mol%, zinc oxide is less than 10 mol%, and titanium (IV) oxide is less than 15 mol%, the resistance value of the moisture-sensitive element will increase. It becomes impossible to detect low humidity open areas with a simple circuit.

Next, when the amount of phosphorus or sulfur supported is less than 0.1% by weight, the change over time becomes unfavorable, and when the amount supported exceeds 2 to 1% by weight, the resistance value as a moisture sensing element becomes high.

The sintered leaf body according to the present invention can usually be obtained by the following method. That is, first, zinc oxide, titanium oxide (■)
, chromium oxide powder is weighed and blended to a predetermined composition ratio of 1 mol %), and this is wet-mixed with a non-aqueous solvent such as ethyl alcohol or ethyl alcohol.

The mixed powder thus obtained is dried, adjusted by mixing a predetermined amount of a binder, and then pressure-molded using a mold to obtain a molded body. Thereafter, this molded body is sintered by a conventional method to obtain a sintered body. At this time, it is desirable that the sintered body be porous.

A conductive paste such as gold paste, platinum paste, or ruthenium oxide paste is applied to opposing surfaces or the same surface of the sintered body thus obtained, and then baked to provide a pair of electrodes, and then the surface of the sintered body is Then, phosphorus, sulfur, etc. are baked and supported in the internal pores to obtain a moisture-sensitive element of the present invention.

For example, baking and supporting phosphorus or sulfur as a simple substance or oxide is carried out as follows. The sintered body obtained as described above is impregnated with a solution containing at least one selected from phosphorus and sulfur, and is supported by heating and thermal decomposition at a predetermined temperature. Examples of phosphorus solutions include organic phosphoric acid compound solutions such as triethyl phosphite and trimethyl phosphate, and inorganic phosphoric acid solutions such as phosphoric acid, ammonium phosphate, and orthophosphoric acid. Examples include organic sulfur compound solutions.

〔Effect of the invention〕

The moisture-sensitive element according to the present invention obtained in this way has a temperature of 10% at 25°C.
It has a resistance value of about 2MΩ at RH and about 10Ω at 90% ELH, which is easy to use in a wide range of humidity and has a large change in resistance.Compared to conventional humidity sensing elements, the resistance value is about 1 digit at low humidity. It's getting lower. Furthermore, it was also confirmed that the deterioration over time was extremely good, and that even after s, ooo of time had elapsed, the deterioration was extremely small, at less than ±5% FLH.

[Embodiments of the invention]

The moisture sensitive element of the present invention will be explained in detail below based on examples.

First, fine powders of zinc oxide, titanium oxide + m-chromium oxide (seal) were used as starting materials, and were weighed to give 50 mol%, 40 mol%, and 10 mol%, respectively. Thereafter, wet mixing with ethyl alcohol was performed for 24 hours using a Teflon pot.

This mixed powder was then dried at 85°C. After that, 10% by weight of a 5% solution of polyvinyl alcohol was added to this dry powder, and the mixture was kneaded for about 30 minutes using a Raikai machine. Added molding. The molded product thus obtained was heated at 1200°C for 2
Time sintering was performed to obtain a sintered body.

Thereafter, the sintered body was polished using 8iC abrasive, and as shown in Fig.
1). Both sides of this disc-shaped element (1) have a diameter of 8.0 mm.
The screen electrodes (2) were formed by screen printing and baking using ruthenium oxide paste. (1) Next, the element body thus obtained was immersed in a triethyl phosphite solution and held and impregnated in a vacuum (IQ-''Tart) for 30 minutes.After this, the element body was taken out and 5 I
A heat treatment was performed for 30 minutes at s O''C to obtain a moisture sensitive element.

The moisture-sensitive characteristics of the moisture-sensitive element thus obtained are shown in FIG.

The R value was measured using an impedance meter at an ambient temperature of 25°C and relative humidity.

The measurement frequency at this time is IKH. ! J3 figure 5
．． The moisture sensitivity characteristics after being left in the atmosphere for 000 hours are shown.

As is clear from this result, the relative humidity is 10 to 90% RH.
It was confirmed that the resistance value was easy to use, with a maximum value of 1.5 MΩ, and the change was large, and the change over time was within ±5%RH even after s, ooo hours had passed, indicating extremely high reliability.

Table 1 shows the initial moisture sensitivity characteristics (R value of 10% FLH, 90%
R value of RH) and moisture sensitivity characteristics after 5,000 hours (109
1H (7) R value, 9096RH (73fL[) Te is shown.

As is clear from the results shown in the margins below, it is clear that the humidity sensing element of the present invention has a resistance value that is easy to use over a wide range of humidity, can be varied widely, and is highly reliable. .

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a moisture-sensitive element according to the present invention.
lk#lV$lu/is Fig. 2: A curve diagram showing the initial moisture sensitive characteristics of the humidity sensing element according to Example 1 of the present invention; Fig. 3: Atmospheric group 1i of the humidity sensing element according to Example 1 of the present invention.
A curve diagram showing moisture sensitivity characteristics after 5,000 hours. (1) Rao Shao Yi Feng Q) Electrode agent Patent attorney Nori Chika Kensuke (1 other person)

Claims (2)

[Claims] (1) Zinc oxide = 10 to 80 mol% and titanium oxide (IV
): 15-70 mol% and chromium oxide rl): 5
1. A moisture-sensing element characterized in that a porous sintered body comprising 20 mol % of IN supports at least a simple substance or an oxide of IN selected from phosphorus and sulfur, or both. (2) The supported amount of at least one element or oxide selected from phosphorus and sulfur is 01 to 2.0% by weight in terms of phosphorus and sulfur based on the weight of the sintered body. The moisture sensitive element according to claim I, item 1. −