JPH01183439A - Production of humidity sensor - Google Patents

Abstract

PURPOSE:To make it possible to produce a sensor having high precision in good productivity, by dispersing a carbon particle into sol obtained by hydrolyz ing silicon alkoxide with a specific amount of water, gelling the sol on an insulating substrate and drying and sintering the resultant gel. CONSTITUTION:For example, 50ml ethanol and 0.02 N hydrochloric acid [of amounts satisfying H2O/Si(OC2H5)4 of 0.5-2] are added to 50 ml tetraethoxysilane [Si(OC2H5)4] and the mixture is stirred for 1hr and hydrolyzed to provide a sol. 10.8g carbon black is added to the sol and the mixture is stirred to uniformly dispersed. The resultant carbon-dispersed sol is gelled into film shape on a glass substrate 4, dried at 60 deg.C for 1 day and then sintered at 450 deg.C for 1hr to afford a sintered film on the substrate 4. Then electrodes 2 are attached to the sintered film 1 to prepare the humidity sensor. The sensor has good linearity of logarithm of resistance value to relative humidity and exhibits resistance value capable of readily measuring also in low humidity and further is simple in production and also has excellent productivity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a humidity sensor that detects humidity as a change in the electrical characteristics of an element.

[Conventional technology]

In recent years, the number of fields requiring humidity measurement and humidity control has increased.
The importance of humidity sensors is now recognized.

Humidity sensors that detect humidity as changes in the electrical characteristics of elements include electrolyte-based, polymer-based, and gold M-based sensors.

There are ceramic-based humidity sensors, and various systems are being researched, but the ones currently in practical use are polymer-based and ceramic-based humidity sensors. both,
This takes advantage of the property that the resistance value or capacitance of the element changes due to adsorption and desorption of water.

[Problem that the invention seeks to solve]

However, conventional humidity sensors have the disadvantage that they have poor accuracy in high humidity and low humidity, and deteriorate when used for long periods in high temperature and high humidity environments. In particular, resistance value detection type humidity sensors have poor accuracy at low humidity, and deterioration under high temperature and high humidity tends to be noticeable in polymer humidity sensors. For ceramic humidity sensors, the element is heated to several hundred degrees Celsius at regular intervals.
There is a product equipped with a mechanism called Heating 7 Ressie, which restores deteriorated properties by heating the product. In this case, aging can be reduced by heating and refreshing, but since the element becomes high temperature, it cannot be used in places where flammable gas or dust is present due to the risk of explosion or fire. It is no exaggeration to say that there are currently no humidity sensors with such satisfactory characteristics.

The present invention is intended to solve these problems, and its purpose is to provide a method for manufacturing a humidity sensor with high precision and high mass productivity.

[Means for solving problems]

The method for manufacturing a humidity sensor of the present invention includes dispersing carbon particles in a sol obtained by hydrolyzing silicon alkoxide with moles of silicon alkoxide and water, and gelling the sol into a film on an insulating substrate. It is characterized by drying and sintering.

A humidity sensor can be obtained by dispersing carbon particles in a sol obtained by hydrolyzing silicon alphoxide, gelling the sol into a film on an insulating substrate, drying and sintering. (Our N125959 silicon alkoxide has four alkyl groups bonded to it, and during hydrolysis, one water molecule reacts with each alkyl group. 1. In order to completely hydrolyze silicon alkoxide, 4 moles of water are required for 1 mole of silicon alkoxide, and it can be hydrolyzed with such an amount of water.However, if silicon alkoxide is completely hydrolyzed, the gel will shrink significantly during sintering. The gel sometimes peeled off from the substrate.As a result of various experiments, reducing the amount of water used for hydrolysis reduces the shrinkage of the gel during sintering and improves the adhesion between the substrate and the sintered film. However, if the amount of water is reduced too much, the hydrolysis will be incomplete and the mechanical strength of the sintered film will decrease. !,)4)
A uniform sol with a brightness of 50% was obtained. Carbon black 1 [L8t] was added to this sol and stirred for 30 minutes to disperse the carbon black, resulting in a black and uniform sol. This sol was gelled into a film on a glass substrate, and 6
After drying at 0°C for 1 day, sintering was performed at 450°C for 1 hour, and a sintered film was obtained on the glass substrate. Electrodes were attached to the obtained sintered film to produce the humidity sensor shown in FIG. In Fig. 1, 1 is a sintered film, 2 is an electrode, 3 is a lead wire,
4 is a substrate. The humidity sensitivity characteristics of this humidity sensor are shown in Figure 2. From FIG. 2, it can be seen that the linearity of the logarithm of the resistance value with respect to relative humidity is good, and the resistance value is easy to measure even at low humidity, so that it can be used as a highly accurate humidity sensor.

Example λ Upon hydrolysis, a transparent and uniform sol was obtained. When 4t of carbon black S was added to this sol and stirred for 50 minutes to disperse the carbon black, a black and uniform sol was obtained. This sol was gelled into a film on an alumina substrate, dried at 60°C for one day, and then sintered at 400°C for 5 hours, resulting in a sintered film on the alumina substrate. Electrodes were attached to the obtained sintered film, and the humidity sensor shown in FIG. 1 was manufactured. The humidity sensitivity characteristics of this humidity sensor are shown in Figure 3.

Example 5 was added and stirred for 1 hour to hydrolyze tetraethoxysilane, yielding a transparent and uniform sol. When 21.6 f of activated carbon was added to this sol and stirred for 30 minutes to disperse carbon black, a black and uniform sol was obtained. This sol was gelled into a film on an alumina substrate, dried at 60°C for one day, and then sintered at 500°C for 30 minutes, resulting in a sintered film on the alumina substrate. Electrodes were attached to the obtained sintered film to produce the humidity sensor shown in FIG. The humidity sensitivity characteristics of this humidity sensor are shown in FIG. 4. As shown, this humidity sensor has good characteristics, and furthermore, since the manufacturing method is simple, it is also excellent in mass production.

〔Effect of the invention〕

As described above, the method for manufacturing a humidity sensor of the present invention involves dispersing carbon particles in a sol obtained by hydrolyzing silicon alkoxide with a similar amount of water, and dispersing the sol on an insulating substrate. Since it is gelled into a film, dried and sintered, the logarithm of the resistance value against relative humidity has good linearity.
Furthermore, since the resistance value is easy to measure even at low humidity, it can be used as a highly accurate humidity sensor. Furthermore, since the manufacturing method is simple, mass productivity is excellent. Therefore, it can be widely applied to fields requiring humidity measurement and humidity control.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of the configuration of a humidity sensor according to the present invention. 1... Sintered film 2... Electrode 3... Lead wire 4... Substrate 2nd 3 and 4 are humidity sensitivity characteristic diagrams of the humidity sensor of the present invention. Applicant Seiko Epson Co., Ltd. Agent Mogami Ben-shi (and 1 other person) Q 150 100 Aigara t4<9 Figure 2 Oy0 1o0 L (%) Figure 3

Claims (1)

[Claims] Silicon alkoxide (Si(OR)_4, R: alkyl group) is mixed with an amount of water such that the molar ratio of silicon alkoxide and water (H_2O) is {H_2O/Si(OR)_4}=0.5 to 2. A method for manufacturing a humidity sensor, which comprises dispersing carbon particles in a sol that has been hydrolyzed in step 1, gelling the sol into a film on an insulating substrate, drying, and sintering the sol.