JPS61147143A - Production of moisture sensitive material - Google Patents

Abstract

PURPOSE:To obtain a material having a stable moisture sensing characteristic for a long period of time by applying at least one of alkali ion and halogen ion to at least one of SiO2 and zeolite then kneading the same with a binder and calcining the kneaded matter. CONSTITUTION:Comb-shaped electrodes 2 are formed of Pt-Pd alloy paste by acreen printing on an insulating base plate 1 consisting of alumina and are calcined after Pt lead wires 4 are attached thereto. The kneaded matter prepd. by dipping the powder obtd. by pulverizing a commercially marketed silica gel as SiO2 for about 15sec in an aq. sonl. of about 10% NaCl then kneading the same with aluminum phosphate at about 1:1 by weight is coated on the plate 1 to about 50mum thickness by a dipping treatment and is calcined for about 70min at a about 370 deg.C to obtain a moisture sensitive film 3. The moisture sensor is manufactured by using such moisture sensitive material. The material having the long-term moisture sensing characteristic is manufactured even with out the provision of the heater for preventing the deterioration with age.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a moisture-sensitive material for a humidity sensor that detects the relative humidity of an atmosphere based on changes in electrical resistance.

[Conventional technology]

Recently, metal oxide ceramics, which are physically and chemically stable in the atmosphere and have high strength, have been most often used as moisture-sensitive materials having the above-mentioned functions. The moisture-sensing mechanism of conventional ceramics is that the concentration of hydrogen ions (H") produced when water vapor dissociates on the porous ceramic surface varies depending on the surrounding relative humidity. This method takes advantage of the fact that the electrical resistance value changes.As shown in the following publication, when the relative humidity is low, this H+ is oxidized by hopping on the hydroxyl groups that are generated on the surface of the 9. However, when the relative humidity is high, hydrated cod is said to conduct water films as well as in an aqueous solution (Publications, i.e., J.
L. Anderson and G.

A, Parks magazine base: J, Phys, C
hem, volume 72.

Page 3662, published in 1968) c.

[Problem that the invention seeks to solve]

Those made of conventional ceramics as mentioned above.

It utilizes electrical conduction due to H+, and in order to have a sensitivity that is as good as that which can be measured, its electrical resistance value must have a lower limit (approximately 500 KΩ at 50% relative humidity, 9
When the humidity sensor using the above ceramic is used for applications such as automatic humidity control by an air conditioner.

In terms of ease of use in the drive and detection circuits, there was a problem in that the electric resistance value was high and it was difficult to obtain a sensor that was easy to use.

In addition, in most conventional ceramic moisture-sensitive materials that utilize electrical conduction through H+, when water (moisture) is repeatedly adsorbed and desorbed when used in the air or left unattended, OH groups become stabilized by chemical adsorption on the surface. As a result, it is unavoidable that the resistance value of the sensor changes greatly over time, so in order to restore this to its initial characteristic, the following methods are disclosed. Japanese Patent Publication No. 5
2-61788゜54-701195.54-1013
99.55-87941゜56-2542.56-10
As seen in Publication No. 9044.56-160649, heaters are provided around the moisture-sensitive material, in the cover, inside the substrate, on the electrodes, etc., and the characteristics changed by heating the moisture-sensitive material t-5oo to 600C with electricity are evaluated. There was a problem in that it was necessary to restore the initial characteristics.

This invention was made to solve this problem, and provides a method for producing a moisture-sensitive material that has stable moisture-sensitive characteristics for a long period of time without necessarily requiring a heating device (heater) for preventing deterioration over time. The purpose is to

[Means to solve all problems]

The method for producing a moisture-sensitive material of the present invention is a method in which at least one of 5i02 and zeolite is given at least one of alkali ions and halogen ions, then kneaded with a binder, and the kneaded product is fired. .

[Effect]

The applied alkali ions and halogen ions in the present invention are called out by the adsorbed water on the surface of the moisture sensitive part and participate in surface electrical conduction, thereby lowering the resistance value of the moisture sensitive material.

Moreover, S i02 and zeolite in this invention are
This allows alkali ions and halogen ions to stably exist in the pore structure, and allows them to move in and out smoothly depending on the presence or absence of adsorbed water.

〔Example〕

The alkali ions used in this invention include at least one of potassium ions, sodium ions, lithium ions, and the like.

The ions Fi according to the present invention include at least one of chlorine ions and fluorine ions.

Examples of binders used in this invention include those that become porous upon firing, such as methyl silicone, methyl phenyl silicone, aluminum phosphate, ethyl silicate polymer, and water glass.
Acts as a binder for 5i02 and zeolite. Also, due to its porous nature, the moisture-sensitive material according to the embodiment of the present invention has
The above effects of 5i02 and zeolite clearly appear.

Since the amount of adsorbed water increases, a moisture-sensitive material with a lower resistance value can be obtained.

Among them, the use of organosilicon compound polymers as binders is advantageous because of its excellent water resistance and water resistance, which makes it possible to create moisture-sensitive materials that have good water resistance and have particularly little change in moisture-sensitive characteristics in high humidity environments. Because you can get it.

Particularly preferred.

It should be noted that the moisture-sensitive material according to the embodiment of the present invention contains the following inorganic material powders such as metal oxides as additives for the purpose of film-forming effect, acceleration of drying and hardening, prevention of cracks, and improvement of adhesion to the underlying substrate. It may contain as.

The present invention will be explained in detail by showing Examples below, but the present invention is not limited thereto.

Embodiment 1 FIG. 1 is a perspective view of a humidity sensor using a moisture-sensitive material according to an embodiment of the present invention. In FIG. 9, (1) is an insulating substrate, (2) is an electrode, and (3) is a sensitive Wet film, (4) is a lead wire.

That is, on an alumina insulating substrate (1), 10 pairs of comb-shaped electrodes (2) are screen-printed with a Pt-Pd alloy paste at a spacing of 0.2 mm, and Pt lead wires (4) are printed.
The mounting was done by post-baking.

Next, commercially available silica gel was pulverized as 5i02 and the powder was immersed in a 101 NaC11 aqueous solution for 15 seconds, and then kneaded with aluminum phosphate at a weight ratio of 1:1, and the kneaded product was applied to the above substrate. It was applied to a thickness of about 50 μm by dipping treatment and baked at 370C for 70 minutes to obtain a moisture-sensitive film (3), which produced a humidity sensor using a moisture-sensitive material according to an embodiment of the present invention as shown in FIG. was produced.

A humidity sensor using a moisture-sensitive material according to an embodiment of the present invention manufactured in this way and a moisture-sensitive film with a weight of 1250 tons:
Using AI 203-MgO-ZnO ceramics sintered for 4 hours at Excellent) - Electrical resistance (Ω))
When we compared and measured its change over time, we obtained the results shown in Figure 2. Note that the applied voltage was AC IV, 50 Hz. In fig.

Curves (A1) and (A2) show the moisture sensitivity characteristics of the conventional type at the initial stage and after being left indoors for 6 months, respectively.

Curves (B1) and (B2) are the moisture sensitivity characteristics of a sample using a moisture sensitive material according to an embodiment of the present invention, respectively, at the initial stage and after being left indoors for 6 months.

As is clear from this figure, the humidity sensor using conventional H10 conduction type ceramics as the moisture-sensitive material shows that after being left unused for 6 months, the resistance device becomes two orders of magnitude more sensitive than the initial one. In contrast, the humidity sensor using a moisture-sensitive material according to an embodiment of the present invention has a lower humidity function.
After leaving it for 6 months, the resistance value decreased only slightly.

No decrease in moisture sensing function was observed. Furthermore, as can be seen by comparing the initial moisture-sensitive characteristic curves (A1) and (B1), the resistance value of the material using the moisture-sensitive material according to an embodiment of the present invention is one order of magnitude lower than that of the conventional material. It is easy to use in terms of one circuit.

Example 2 Another example of the present invention was carried out in the same manner as Example 1 except that methylphenyl silicone was used instead of aluminum phosphate as the binder in Example 1, toluene was added, and crosstalk was performed. Moisture sensitive material? What humidity sensor did you use? When manufactured and examined for moisture sensitivity characteristics, it was confirmed that it exhibited excellent moisture sensitivity characteristics similar to Example 1, had good water resistance, and did not further decrease in resistance in high humidity.

In the above example, the case where alkali ions were applied was described, but the same effect can be obtained when all of the norogen ions, alkali ions, and halogen ions are applied, and the application method may be, for example, ion implantation, vapor deposition, The same effect can be obtained regardless of the method, such as immersion in a solution containing the ions or leaving in the ion vapor.

Furthermore, the above effects are the same when using zeolite or S i02 and zeolite, and alkali ions,
The same applies when the types of halogen ions and binders are changed.

〔Effect of the invention〕

As explained above, this invention is made by adding at least one of alkali ions and halogen ions to at least one of 5to2 and zeolite, kneading it with a binder, and firing the kneaded product. It is possible to obtain a method for producing a moisture-sensitive material with stable moisture-sensing characteristics over a long period of time without necessarily requiring a heating device (heater) for preventing deterioration over time.9 It is useful for example in humidity sensors.

[Brief explanation of drawings]

FIG. 1 shows one embodiment of the invention. FIG. 2 is a perspective view of a humidity sensor using a moisture-sensitive material, and is a humidity-sensing characteristic diagram comparing a humidity sensor using a moisture-sensitive material according to an embodiment of the present invention with a conventional humidity sensor. (1) is an insulating substrate, (2) is an electrode, (3)
is a moisture-sensitive film, (4) is a lead wire, (AI), (A
2) is the moisture sensitivity characteristic of the comparative conventional example, (B1)l (
B2) shows the moisture sensitivity characteristics of a humidity sensor using the moisture sensitive material gold according to an embodiment of the present invention.

Claims (2)

[Claims] (1) A method for producing a moisture-sensitive material, which comprises adding at least one of alkali ions and halogen ions to at least one of SiO_2 and zeolite, then kneading it into a binder, and firing the kneaded product. (2) The method for producing a moisture-sensitive material according to claim 1, wherein the binder is an organosilicon compound polymer.