JPH0577162B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention provides a method for a humidity-sensitive material that detects the relative humidity of the atmosphere by changes in electrical resistance to obtain stable humidity detection characteristics in a relatively short time. Concerning a method for aging wet and dry materials.

[Conventional technology]

Recently, many moisture-sensitive materials, mainly ceramics and polymer electrolytes, have been proposed. The humidity-sensing mechanism of the moisture-sensitive materials using these materials is that the amount of water adsorbed on the surface of the moisture-sensitive material varies depending on the humidity of the atmosphere, so detection is performed by utilizing the change in surface electrical resistance.

However, when a humidity-sensitive element using the above-mentioned humidity-sensitive material is driven by applying AC power, it is affected by the temperature and humidity of the atmosphere in which it is used, and its humidity detection characteristics may fluctuate during use. Therefore, JP-A-57-
As shown in Japanese Patent No. 136302, there is a method of aging moisture-sensitive materials in a high humidity state, and Japanese Patent Application Laid-Open No. 162302/1983
As shown in the publication, the humidity sensitive element is heated to 40 to 60℃.
In an attempt to stabilize the resistance-relative humidity characteristics of the moisture-sensitive element, methods are used to age the element, either by leaving it in an atmosphere with a humidity of 80 to 100% RH, or by leaving it to age while applying an alternating current voltage.

[Problem that the invention seeks to solve]

In the conventional aging method for moisture-sensitive materials as described above, the optimum conditions may not be known or
When left in an RH atmosphere (Japanese Unexamined Patent Publication No. 57-136302), the humidity detection characteristics become stable after 500 hours, or when left in an atmosphere of 50°C and 85% RH (Japanese Unexamined Patent Application No. 57-162302). There was a problem that it took too long to stabilize, such as the humidity detection characteristics becoming stable after 800 hours.

The present invention was made to solve these problems, and an object of the present invention is to provide a method for aging a moisture-sensitive material by which stable humidity sensing characteristics can be obtained in a relatively short period of time.

[Means for solving problems]

The aging method for a moisture-sensitive material of the present invention includes a moisture-sensitive material containing at least one of an alkali metal and a halogen element in an atmosphere with a relative humidity of 90% RH or more at a temperature range of 70 to 85°C. 50~
The method is to leave it for 200 hours.

[Operation] In the temperature range of 70 to 85°C in this invention, 90%
When left in an atmosphere with a relative humidity higher than RH for 50 to 200 hours, the temperature is higher than before, making it easier to stabilize hydration and hydrate in a short time. In addition, since it is stably hydrated, it has good characteristics as a humidity sensor.

The alkali metal and halogen element in the present invention greatly contribute to rapid stabilization of the resistance value because they hydrate and coordinate water in a short time.

〔Example〕

As the alkali metal in this invention, at least one of sodium, potassium, lithium, etc. is used as a simple substance or as a compound.

As the halogen element in this invention, for example, at least one of fluorine, chlorine, bromine, etc. is used alone or as a compound.

Example: 1.8% by weight of Li ₂ O as a starting material for moisture-sensitive material
The SiO ₂ -MgO-based ceramics containing SiO 2 -MgO were kneaded together with an organic binder.

Ten pairs of comb-shaped electrodes were screen-printed on an alumina insulating substrate using Rt-Pd alloy paste at 0.2 mm intervals, and baked after attaching Pt lead wires. On top of this, the above-mentioned kneaded material was applied to a thickness of about 30 μm by dipping, and after pre-baking at 130°C for 20 minutes, it was fired at 1300°C for 3 hours to form a ceramic type material as shown in the example of the structure shown in Figure 3. A large number of moisture sensing elements were manufactured. In the figure, 1 is the substrate, 2 is the electrode,
3 is a moisture sensitive film, and 4 is a lead wire.

Next, after leaving the above humidity sensing element in a constant temperature and humidity chamber at 80°C and 95% RH, the humidity detection characteristics (relative humidity (%) - electrical resistance value (Ω)) at an applied voltage of 1 V AC and 50 Hz were determined. Upon investigation, it was found that the humidity detection characteristics stabilized after being left for 80 hours, and the aging time was significantly shortened compared to conventional methods.

As mentioned above, the reason why the aging method according to an embodiment of the present invention takes less time to stabilize the humidity sensing characteristics than the conventional aging method is because the alkali metals and halogen elements in the moisture-sensitive material absorb water. It is inferred that short-term hydration coordination contributes greatly.

Next, an experiment was conducted to examine the detailed conditions of the aging method of the present invention using the same moisture-sensitive element as described above. After each aging, the aging effect was evaluated based on the time it took for the resistance value to stabilize when AC 1V, 50Hz was applied.

First, the aging time must be between 50 and 200 hours. If it is less than 50 hours, the resistance value will fluctuate during use, and if it is more than 200 hours, ions in the moisture-sensitive material will elute and deteriorate, which is not preferable.

Next, Figure 1 shows the changes in the aging time (hr) necessary for the humidity sensing characteristics of the humidity sensing element to stabilize due to the atmospheric humidity (%) when the ambient temperature is 80°C, and the FIG. 2 shows the change in aging time (hr) necessary for stabilizing the temperature detection characteristics of the humidity sensitive element depending on the temperature (° C.). As can be seen from Figure 1, the atmospheric humidity during aging is around 90% RH, and if it is less than that, the aging time becomes significantly longer and is not practical. In addition, as can be seen from Figure 2, when the ambient temperature during aging is around 70℃, when the temperature is lower than that, the aging time becomes significantly longer.
Not for practical use. On the other hand, at temperatures above 70°C, the aging time becomes dramatically shorter than expected at conventional aging temperatures (less than 70°C).
Furthermore, if the temperature exceeds 85°C, the surface of the moisture-sensitive material will be altered by the high-temperature water vapor, and the humidity detection characteristics will vary greatly. Therefore, the aging atmosphere of this invention needs to be 70 to 85°C and 90% RH. Note that the above diagram was the same even when the atmospheric temperature and atmospheric humidity were changed.

Note that the same effect as that obtained in the above example can be obtained even when various moisture-sensitive materials such as other ceramic type materials and polymer electrolyte type materials are used as the moisture-sensitive material. It was done.

Furthermore, the method of the present invention may be carried out on a completed moisture-sensitive element as shown in the examples, or may be carried out on a moisture-sensitive material and used in the moisture-sensing part of the moisture-sensitive element. It was confirmed that the same effect as in the example could be obtained.

〔Effect of the invention〕

As explained above, the present invention provides a moisture-sensitive material containing at least one of an alkali metal and a halogen metal in a temperature range of 70 to 85°C.
By leaving the material in an atmosphere with a relative humidity higher than RH for 50 to 200 hours, it is possible to obtain a method for aging a moisture-sensitive material in which stable humidity sensing characteristics can be obtained in a relatively short period of time.

[Brief explanation of the drawing]

1 and 2 are characteristic diagrams of a humidity sensing element according to an embodiment of the invention, and FIG. 3 is a perspective view of the humidity sensing element used in an embodiment of the invention.

Claims (1)

[Claims] 1. A moisture-sensitive material containing at least one of an alkali metal and a halogen element is left in an atmosphere with a relative humidity of 90% RH or more at a temperature range of 70-85°C for 50-200 hours. Aging method.