JPH05119010A - Moisture sensor - Google Patents

Abstract

PURPOSE:To obtain a low-cost and reliable moisture sensor with a low resistance and a proper change width of the resistance by using a moisture- sensitive body with silicon oxide and manganese oxide as main constituents. CONSTITUTION:A moisture-sensitive body 1 with silicon oxide and manganese oxide as main constituents is used for this moisture sensor. For example, a colloidal silica is dipcoated and heat-treated onto an alumina substrate 4 where a Pt-Pa comb-type electrode 2 is formed by screen printing, thus enabling a porous film with silica as a main constituent to be produced. After dipping this substrate 4 into a liquid solution of manganese nitrate, it is heat-treated. The moisture sensor which is produced in this manner has a low resistance, a proper change width of resistance, has characteristics which do not change according to temperature, and has high durability and reliability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a humidity sensor for detecting humidity by changing electric characteristics of an element in response to humidity.

[0002]

2. Description of the Related Art In recent years, the number of fields requiring humidity measurement and humidity control has increased, and the importance of humidity sensors has come to be recognized.

Humidity sensors that detect humidity by varying the electrical characteristics of the element in response to humidity include electrolyte-based, metal-based, polymer-based, and ceramic-based humidity sensors, and various systems have been studied. However, what is currently put into practical use is a polymer-based and ceramic-based humidity sensor. Both of them utilize the property that the resistance value or the capacitance of the element changes due to the adsorption and desorption of water with respect to the element.

[0004]

However, the conventional humidity sensor has a high resistance value at a low humidity and a large variation range of the resistance value. Therefore, in order to manufacture a highly accurate hygrometer,
Requires advanced circuit and packaging technology.

Therefore, the present invention solves such a problem, and an object thereof is to provide a humidity sensor having a low resistance value, an appropriate change width of the resistance value, a high precision and a high reliability. There is a place to do it.

[0006]

The humidity sensor of the present invention comprises:
It is characterized by using a moisture sensitive body containing silicon oxide and manganese oxide as main components.

Manganese oxide does not have to be manganese oxide as a raw material, but may be one that decomposes to manganese oxide, for example, manganese carbonate, manganese acetate, manganese nitrate or the like. Further, it is not necessary to heat treat silicon oxide and manganese oxide at the same time. For example, a film of silicon oxide may be first formed on a substrate and heat treated, and then this may be immersed in a manganese nitrate solution and then heat treated.

[0008]

【Example】

Example 1 10 g of silica and 20 g of manganese dioxide were mixed, press-molded, and then heat-treated at 600 ° C. for 1 hour. A cube having a side of 5 mm was cut out from the obtained heat-treated product, and an electrode was attached to the cube to prepare a humidity sensor as shown in FIG. In FIG. 1, 1 is a moisture sensitive material, 2 is an electrode, and 3 is a lead wire. The humidity sensitivity characteristics of this humidity sensor are shown in FIG. From FIG. 2, the humidity sensor of the present invention has a low resistance value,
Moreover, it is easy to use because the change width of the resistance value is appropriate.

Example 2 Colloidal silica containing 30 g of silica particles having a particle size of 0.3 μm in 100 g was dip-coated on an alumina substrate on which a Pt-Pd comb-shaped electrode was formed by screen printing, and at 500 ° C. By heat treatment for 1 hour, a porous film containing silica as a main component was produced. Next, the alumina substrate on which the porous film containing silica as a main component was formed was immersed in a manganese nitrate solution (70% by weight) and then heat-treated at 200 ° C. for 1 hour.

A perspective view of the humidity sensor thus manufactured is shown in FIG. In FIG. 3, 1 is a moisture sensitive film, 2 is an electrode, and 4 is a substrate. FIG. 4 shows the humidity sensitivity characteristics of this humidity sensor. It can be seen from FIG. 4 that the humidity sensor of the present invention is easy to use because it has a low resistance value, an appropriate change width of the resistance value, and the characteristics do not change with temperature. The humidity sensor was left for 1000 hours in a constant temperature and humidity chamber at 60 ° C. and 90%, and the characteristics were measured. Therefore, it can be seen that this humidity sensor has high durability and reliability.

(Example 3) 75 ml of colloidal silica
To this, 150 ml of ethanol, 1 ml of hydrochloric acid, 25 ml of ethyl silicate, and 27 g of manganese acetate were added and stirred for 1 hour. This solution was spin-coated on a glass substrate on which a comb-shaped electrode was formed by depositing Cr and Au in this order.
It heat-processed at 00 degreeC for 1 hour.

FIG. 3 is a perspective view of the humidity sensor thus manufactured, and FIG. 5 is a humidity-sensing characteristic thereof.

[0013]

As described above, since the humidity sensor of the present invention uses the humidity sensitive material containing silicon oxide and manganese oxide as main components, it has a low resistance value and an appropriate variation range of the resistance value. It is also highly durable and reliable. Therefore, since the humidity measuring circuit can be easily manufactured, the humidity measuring circuit can be widely applied to a field requiring humidity measurement and humidity control as a low cost, highly accurate and highly reliable humidity sensor.

[Brief description of drawings]

FIG. 1 is a perspective view of a humidity sensor of the present invention.

FIG. 2 is a humidity sensitive characteristic diagram of the humidity sensor of the present invention.

FIG. 3 is a perspective view of the humidity sensor of the present invention.

FIG. 4 is a humidity sensitive characteristic diagram of the humidity sensor of the present invention.

FIG. 5 is a humidity sensitive characteristic diagram of the humidity sensor of the present invention.

[Explanation of symbols]

 1 Moisture Sensitive Body or Moisture Sensitive Film 2 Electrode 3 Lead Wire 4 Substrate

Claims (1)

[Claims] 1. A humidity sensor characterized by using a moisture sensitive material containing silicon oxide and manganese oxide as main components.