JPS5967602A - 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 The present invention provides) TI02 powder with the general formula Me Z r Oa
(In the formula, Me is BA, Co, Cu, -Ll-+ M
The present invention relates to a moisture sensing element which detects changes in humidity as changes in electrical resistance by mixing powders of 0) representing g+ Mn, Ni1Pb or Sr and borosilicate glass powders and sintering the mixture at high temperatures.

Demand for environmental humidity control is increasing in various fields such as industry, general housing, and medical care.

Furthermore, with the rapid development of integrated circuit technology, microprocessors are becoming easier to obtain.As a result, there has been a demand for the development of low-cost, small-sized, and highly reliable moisture-sensitive elements. Ta. In general, the conditions that a moisture-sensitive element should meet are (1) High precision - good ci□ linearity, and no 8↓, t, etc.

(2) High reliability.

(3) Fast response time.

(4) Must be stable and have element compatibility.

(5) Impedance should be approximately 108 to 101Ω.

(6) The element does not generate heat.

In addition, it is not affected by wind speed, is small and inexpensive, etc.

The reason why the humidity sensing element has hysteresis and its response speed is slow is that moisture once adsorbed to the temperature detection part is difficult to release.

Therefore, in order to improve the hysteresis and increase the response speed, it is necessary to increase the surface area of the leaf material of the humidity detection part that comes into contact with the atmosphere, and the film thickness of the element can be reduced. However, when the film thickness of the element is reduced, impedance increases in the case of planar electrodes, and short-circuit between electrodes becomes more likely to occur in the case of opposing electrodes. To date, various attempts have been made to eliminate this problem, but there have been no successful examples, partly because coating materials with low specific electrical resistance generally have low sensitivity to humidity. . In addition, the biggest defect of all electric humidity sensing elements is that if they are left in high humidity air,
The problem is that it deteriorates quickly. There are some theories about the cause, such as ion diffusion, but so far it is not clear, and there are few countermeasures other than annealing and using rough abrasive materials. From (υ) those using inorganic salts, (2) those using metal oxide semiconductors, (3) those using conductive Toga species diffused into polymers,
(4) Classified as other.

(1) Moisture sensing elements using inorganic salts have a long history, starting with the Dunmore type sensor in 1938.
The most common type uses LiCl. Glass wool, plant pulp, etc. are used as the support for IjCl.
There are many commercially available products. This product uses LiC in a humid atmosphere.
1 is washed away, and the response speed is slow.

(2) Are moisture-sensitive elements using semiconductors such as metal oxides easy to handle? 1. This is one of the things that will develop in the future, and the present invention also belongs to this category. 0. This type of device can be further divided into four types depending on the manufacturing method and structure. The first type is one in which a moisture-sensitive material is coated on a flat electrode. A typical example is a magnetite element. This device has comb shapes and poles printed on a substrate, and magnetite colloid is deposited on top of it by spraying, etc., but the resistance value is low and the entire temperature range can be measured with one element. It was groundbreaking for such reasons. However, if you leave it in humid conditions where it repeatedly burns, it will cause severe fatigue.
There is a problem with reproducibility during manufacturing. The second type is sintered elements, which include oxides of CO, oxides of Mn and Ti, oxides of Sn and sb, oxides of Si and metals, ferrite, lithium ferrite, SIC and glass. ,
Reports on various other substances can be found. However, in each of these devices, problems with binder content and grain boundaries make device reproducibility difficult. The third is a moisture-sensitive element fabricated using a thin film obtained by vapor deposition, etc.
There are oxides of 1Ge, Sn, etc. All of these elements are characterized by their thin film thickness and fast response time, but they suffer from various problems such as aging characteristics, high reproducibility, and high impedance. The fourth type utilizes an anodic oxide film of AI. Although the porosity of the anodic oxide film of AI has been successfully applied as a moisture-sensitive element, there are 191 problems such as poor sensitivity at high humidity due to the presence of a barrier layer and deterioration over time.

(3) A moisture-sensitive element with a conductive material diffused in a polymer,
Since carbon is often used as the conductive material, it is generally called a carbon sensor. This device differs from other types of devices in that the resistance value increases as the humidity increases. This is because the polymer expands when it contains water, increasing the distance between the soil materials. This element has a resistance fI
11 is small, the resistance to dampness is not logarithmic,
Many of them are simply proportional, which makes them convenient to use. However, there are problems with slow response time and hysteresis.

(4) Other moisture-sensitive elements are less common, but we will discuss those that have been reported to date. First, as a moisture-sensitive element that utilizes ionic conduction in polymeric materials,
(Those based on an ammonium salt structure in a conductive resin, those based on hydroxyedyl cellulose)) Those made by molding ammonium metavanadate, barium nitrate, and strontium nitrate with photosensitive resin. Furthermore, as a moisture-sensitive element using surface ion current, there is one whose surface is treated by reducing the fluorine of a fluororesin. On the right, there is one that utilizes the reverse bias current at the junction between Sn oxide and Sl. In addition, the weight of madder molecular film increases due to water adsorption, and the weight jfi', jW
This is an attempt to interpret the addition as frequency hardening of the crystal oscillator. Each of these elements has structural problems, and so far they have not been put to practical use.

As mentioned above, the moisture sensing elements that have been used or are currently being researched have problems with hysteresis, IP + - processing properties, structure, etc., so they are not practical in terms of high precision, long life, and miniaturization. It wasn't good enough. In addition, as the shape of the moisture-sensitive element becomes finer, its activity increases, and some types of moisture-sensitive elements form hydroxides due to moisture absorption, which can cause deterioration of the characteristics of moisture-sensitive elements in a short period of time. .

Book 14 relates to a moisture sensing element made of a metal oxide semiconductor using TIO□ powder, which has unprecedented performance. Generally, there are three types of TlO2 depending on their crystal forms: rutile type, anametic type, and pulchite type. Among these, the acid rutile type is promising as a moisture sensing element.
When rutile-type TlO2 powder is sintered or vacuum-deposited, a portion or most of it changes to other crystal forms depending on the heating method. Furthermore, it has been reported that when a moisture sensing element using a T'+02 film is exposed to high humidity air for a long time, the characteristics are significantly deteriorated due to the production of TlOH.

However, the humidity-sensitive element according to the present invention is produced by mixing rutile TIO powder with MeZrO3 powder as a moisture-sensing auxiliary phase and borosilicate glass powder as a binder and sintering the mixture at high temperature. The characteristics change linearly from the high humidity area to the high humidity area, the hysteresis is small, and even when left for long periods in high humidity air, the characteristics do not deteriorate such as an increase in resistance value. Rutile type T r
Moisture sensing elements made by mixing borosilicate glass powder as a binder and sintering at high temperatures have a problem with linearity; however, when mixed with MeZrO powder and sintered,
The linearity of the resistance change from the low humidity region to the high humidity region is remarkable.

Hereinafter, the moisture-sensitive layer fogging of the present invention will be described in detail based on Examples.

(Example 1) 9 g of rutile TIO I used v) and pasted it. As a substrate for a sensing element, what size? Human crab 5mmX10mmX0.6mm
An alumina substrate is prepared, Ni is vacuum-deposited on its surface, Au is vacuum-deposited on top of it, and then photo-etched to form a comb-shaped ttu with a width of jF+ 0.13 thrn.
t was formed. Figure 1 shows <LJIlt of this implementation
Shows the at key of j ball.

Next, spray the above-mentioned paste onto the surface of the board with the square-shaped electric wire, and heat it at 160°C for 1 hour per plate.
After drying, it was sintered at 830 ± 10°C with 1 hour of heat. The thickness of the wood obtained in this way was about 20 μm. Figure 2 shows the humidity of this example.
Linearity of 1μ change as well as hysteresis is shown. -2
The resistance values in the figure are the values after holding each humidity for 5 minutes and months. The broken line is a linear connection between the resistance value at low humidity 9 and the resistance value at high humidity.
It shows the children. As is clear from this, the hysteresis is small, but there is a problem with linearity.

(Example 2) Rutile TiO2 powder with an average particle size of about 0.3 μm 4.5
4. P b Z r Oa powder with average particle size of about 1 μm.
Borosilicate glass powder 1 with 5 g and average particle size of about 1 μm
g was heated in an alumina mortar for about 12 hours, and this powder was made into a paste using butyl calpitol. This paste was spray applied to the surface of the substrate with the comb-shaped electrodes described in Example 1 and subjected to the sintering operation described in Example 1. The thickness of the moisture sensitive body thus obtained is approximately 20
FIG. 3 shows the linearity and hysteresis of the change in resistance value with respect to dampness in the embodiment. Third
The resistance values in the figure are the values after being held in each humidity atmosphere for 5 minutes. The broken line in the figure shows a line that linearly connects the resistance value at low cavities and the resistance value at high humidity. As is clear from this, a remarkable improvement was observed in linearity, and it was confirmed that hysteresis was also small.

Next, FIG. 4 shows the humidity response when the humidity sensing element according to this example was left in a low humidity atmosphere for 1 hour and then left in a high temperature atmosphere, and the humidity response when the element was left in a high humidity atmosphere for 1 hour. The humidity response is shown when the sample is left in a low-humidity environment after several hours of IFf. As is clear from this, it also exhibits excellent humidity responsiveness.

Furthermore, FIG. 5 shows the humidity sensitivity in this example at 20℃ and 98℃
% relative humidity It shows the relationship between resistance value and elapsed time when left in air for a long time. As is clear from this,
Even when left in a humid atmosphere for a long time, no change in characteristics due to the resistance value is observed.

In this way, the present invention provides a reliable moisture sensing element! )l! can be built.

[Brief explanation of the drawing]

Is Figure 1 a comb? [Diagram showing the poles, FIG. 2 is a diagram showing the humidity-sensing characteristics of the humidity-sensing element according to Example 1, FIG. 3 is a diagram showing the humidity-sensing characteristics of the humidity-sensing element according to the present invention, and FIG. A diagram showing the responsiveness of the humidity sensing element, and FIG.
It is a figure which shows an example. Relative humidity (%RH)

Claims (1)

[Claims] 1. TiO powder has the general formula MeZr03 (wherein Mo
is Ea. Co, Cu, L-4-, Mg, Ni, Pb,
Represents Mn or Sr. ) are combined and sintered at high temperature using glass powder 3 as a binder, and a moisture sensing element is characterized in that a change of 0 degrees is detected as a change in electrical resistance, 2. Claim No. 2. The moisture-sensitive element according to item 1, wherein the moisture-sensitive element is a conjunctiva formed on comb-shaped electrodes on a heat-resistant support substrate. 3. The moisture sensing element according to claim 1, wherein the amount of MeZrO3 powder filled is 0.5 to 70% by weight based on the T r 02 powder. 4. The sensitizer according to claim 1, characterized in that borosilicate glass is used as the glass powder, and its filling amount is 5 to 15% by weight based on 7'+O+MsZrOa. 5. The moisture sensing element according to claim 1, characterized in that the particle diameters of the TIO powder, MeZr03 powder, and glass powder are 1 μm or less. 6. The sintering temperature is 600 to 850°C. A moisture-sensitive element according to claim 1.