JPH0828283B2 - Moisture sensitive element composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a humidity-sensitive element composition for detecting relative humidity as a change in electric resistance.

[Conventional technology]

Conventionally, moisture-sensitive element compositions include those using electrolyte salts such as lithium chloride, those utilizing organic polymer films such as polyamide and polyethylene, those using metal semiconductors such as Se and Ge, titanium oxide-based compositions. It is known to use a metal oxide sintered body such as aluminum oxide or tin oxide. Among them, the one using the metal oxide sintered body has an advantage that it is chemically and physically stable as compared with other moisture-sensitive element compositions such as organic polymer films, and thus is used as a moisture-sensitive element composition. It is said to be influential.

However, the metal oxide sintered body generally has a high specific resistance value and is not in a practical resistance value range, and the resistance of the moisture-sensitive element composition rapidly increases particularly in a low humidity region, making it difficult to measure in a low humidity region. The surface of the metal oxide sintered body has a large temperature dependency, requires temperature compensation, has a hysteresis in moisture sensitivity characteristics when adsorbing and desorbing moisture, is weak against cold thermal shock and deteriorates moisture sensitivity characteristics. However, it has a drawback in that it needs to be heated and cleaned regularly as a countermeasure against the deterioration of the moisture-sensitive property due to the adhesion of hydroxide stains.

Therefore, it has been desired to develop a highly reliable moisture sensitive element composition.

[Problems to be solved by the invention]

INDUSTRIAL APPLICABILITY The present invention has a low specific resistance value in a practical resistance value range, has extremely small temperature dependency, does not require temperature compensation, has almost no hysteresis in moisture-sensitive characteristics at the time of moisture adsorption / desorption, and has a low temperature It is intended to provide a highly reliable moisture-sensitive element composition which is resistant to impact and does not require special heat cleaning.

[Means for solving problems]

That is, the present invention relates to a moisture-sensitive element composition obtained by sintering a metal oxide, in which the chalcogen oxoacid salt represented by the general formula (I) is blended with the metal oxide and baked in the presence of molecular oxygen. during humidity sensitive element composition _{a x B y O z (I} ) ( wherein, characterized in that formed by binding, a is alkali metal, alkaline earth metal, B is sulfur, selenium or tellurium atom, O is an oxygen atom , X is 1 to 2, y is 1 to 5, and z is a number of 2 to 7).

In the present invention, the metal oxide may be any one as long as it has a moisture-sensitive property itself, and those conventionally known as the active ingredient of the moisture-sensitive element composition are suitably used. For example Mg
O, TiO ₂ , ZrO ₂ , Nb ₂ O ₅ , TaO, Ta ₂ O ₅ , Cr ₂ O ₃ , MoO ₃ , W
O ₃ , MnO ₂ , Mn ₃ O ₄ , FeO, Fe ₂ O ₃ , CoO, Co ₂ O ₃ , NiO, Ni ₂ O
₃ , Ni ₃ O ₄ , ZnO, Al ₂ O ₃ , Ga ₂ O ₃ , In ₂ O ₃ , Tl ₂ O ₃ , SiO ₂ , G
eO ₂ , SnO, SnO ₂ , oxides exemplified by PbO, Sb ₂ O ₃ , Bi ₂ O _3, etc., Mg ₂ Fe ₂ O ₄ , ZnFe ₂ O ₄ , MgAl ₂ O ₄ , MgCr ₂ O ₃ , ZnCr ₂
Examples thereof include complex oxides such as O ₃ (above, spinel) and 3Al ₂ O ₃ .2SiO ₂ (mullite). Among these, TiO ₂ , γ-Al ₂ O ₃ , ZnO, MgO, ZrO ₂ , NiO, MgAl ₂ O ₄
Etc. are particularly preferable. The metal oxide may be a product obtained by thermally decomposing a metal salt, a metal hydroxide, an alkoxide or the like.

The chalcogen oxoacid salt is represented by the following general formula (I).

_{A x B y O z (I} ) ( in the formula, A represents an alkali metal, alkaline earth metal, B is sulfur, selenium or tellurium atom, O is an oxygen atom, x is 1 to 2, y is 1 to 5, z Represents a number of 2 to 7) As sulfur oxo acid salts, specifically, sulfoxylates, sulfites, disulfites (metabisulfites, dithionates, disulfates (pyrosulfates) , Thiosulfates, and thionates, selenium oxoacid salts include selenite and selenate, and tellurium oxoacid salts include tellurite. Examples thereof include salts and tellurates.

The amount of the chalcogen oxo acid salt is usually 0.01 to 99.9 based on the sum of the metal oxide and the chalcogen oxo acid salt.
It is 9 mol%, preferably 0.1 to 99.9 mol%, and in view of economy and characteristics, 50 mol% or less is particularly preferable.

The sintered body obtained by mixing the respective components in the above composition range under appropriate sintering conditions has extremely good moisture-sensitive properties as compared with the metal oxide alone.

The moisture-sensitive element composition of the present invention can be manufactured by the usual porcelain manufacturing technique as follows.

First, a predetermined amount of each component is weighed, and then these are sufficiently mixed by a dry method or a wet method using a mixed solvent such as water and methyl alcohol by a ball mill, a vibration mill or the like. Then, if necessary, the obtained mixture is dried, calcined at an appropriate temperature, and then pulverized to prepare a raw material powder. These raw material powders may be directly dry-molded, or may be kneaded with a binder such as polyvinyl alcohol or polyethylene glycol to prepare a kneaded product,
You may shape | mold after drying. This molded body is sintered in the presence of molecular oxygen (usually in air) to obtain a sintered body. Generally, the sintered body preferably has a porous structure having a porosity of 10 to 55% and a pore diameter of 1 μm or less.

The moisture-sensitive element composition of the present invention usually has a particle size of the raw material powder of 0.
1-3μ, compacting pressure 50-1000Kg / cm ² , sintering temperature of compact 500
It is obtained by setting the conditions of ~ 1200 ° C and sintering time of 0.5 ~ 3 hours.

The sintered body thus obtained is, if necessary, polished, and then an electrode is formed using a commonly used paste such as a gold paste, a platinum paste, a ruthenium oxide paste, to manufacture a moisture-sensitive element. can do. Further, it is possible to increase the mass productivity and reduce the cost by using the thick film method.

〔Example〕

 Examples will be described below.

Example 1 Titanium oxide and sodium pyrosulfate (Na ₂ S ₂ O ₇ ) were weighed so as to have a molar ratio of 96.5% and 3.5%, and were weighed with a pot mill.
Wet mixed for hours. The obtained mixture was dried at 140 ° C. for 4 hours and granulated to prepare a raw material powder. This raw material powder
Pressure molding was performed under the condition of 500 kg / cm ² to make a disk-shaped compact with a diameter of 12 mm and a thickness of about 2 mm. After this compact was sintered at 900 ° C. for 3 hours, a ruthenium oxide paste was screen-printed in a comb shape on one surface of the sintered body and baked at about 850 ° C.

The structure of the moisture sensitive element thus manufactured is shown in FIG. In FIG. 1, 1 is an electrode and 2 is a moisture sensitive element composition.

With respect to this humidity sensitive element, the ambient temperature was kept at 25 ° C in a constant temperature bath, the relative humidity was changed from 20 to 100%, and the change in resistance value at that time was examined. This result (No. 1) is shown in FIG. 2 in comparison with the change in resistance value (No. 1 ') of the humidity sensitive element consisting of only titanium oxide component. As is clear from FIG. 2, the humidity-sensitive element composition of the present invention has an ambient temperature of 25 ° C. and a relative humidity of 30%.
Shows 1.04 × 10 ⁶ Ω and relative humidity of 80% shows a low resistance change of 4.5 × 10 ³ Ω over a wide temperature range, indicating that it is in an extremely practical resistance range.

Example 2 Titanium oxide and barium selenite (BaSeO ₃ ) were weighed so that the molar ratio was 96.5% and 3.5%, and wet-mixed in a pot mill for 16 hours. The obtained mixture was dried at 140 ° C. for 4 hours and granulated to prepare a raw material powder. 50 of this raw material powder
It was pressure-molded under the condition of 0 kg / cm ² to make a disk-shaped compact with a diameter of 12 mm and a thickness of about 2 mm. After sintering this compact for 3 hours at 1000 ° C., a ruthenium oxide paste was screen-printed on one surface of the sintered body in a comb shape to form a baking electrode at about 850 ° C.

About this humidity sensitive element, the ambient temperature is 25 ° C in a constant temperature bath,
The relative humidity was changed from 20 to 100%, and the change in resistance value (humidity characteristic) at that time was examined.

As a result, the moisture sensitivity characteristic (No. 1) shown in FIG. 3 was obtained. For comparison, the humidity-sensitive characteristic of the humidity-sensitive element made of titanium oxide is shown as No. 1 '. As is apparent from FIG. 3, the humidity sensitive element composition of the present invention has an ambient temperature of 25 ° C.
At 30% relative humidity, 8.0 × 10 ⁵ Ω, at 80% relative humidity, 5.
It shows a low resistance value change over a wide temperature range of 0 × 10 ⁴ Ω, indicating that the resistance value range is extremely practical.

Examples 3 to 11 The compositions shown in Table 1 were sintered in the same manner as in Example 1 above, and the moisture sensitivity characteristics of the sintered bodies were examined. The results are shown in Table 1. For comparison, Table 1 also shows the moisture sensitivity characteristics (Comparative Example 1) of a sintered body containing only a titanium oxide component.

Examples 12 to 13 The compositions shown in Table 2 were sintered in the same manner as in Example 2 above, and the moisture sensitivity characteristics of the sintered bodies were examined. Table 2 shows the results. For comparison, Table 2 also shows the moisture-sensitive characteristics (Comparative Example 1) of the sintered body containing only the titanium oxide component.

Example 14 In the same manner as in Example 1, titanium oxide and potassium selenite (K ₂ SeO ₃ ) were sintered at a composition of 96.5% and 3.5% in terms of mol%, and the moisture-sensitive property of the sintered body was sintered. I checked. The results are shown in Table 3.

Example 15 In the same manner as in Example 2, a composition of titanium oxide and calcium tellurite (CaTeO ₃ ) in mol% of 96.5% and 3.5% was sintered, and the moisture-sensitive property of the sintered body was examined. It was Table 4 shows the results.

Examples 16 to 28 In the same manner as in Example 1, the compositions shown in Table 5 were sintered, and the moisture-sensitive characteristics of the sintered bodies were examined. The result is the fifth
Shown in the table.

Examples 29 to 41 In the same manner as in Example 2, the compositions shown in Table 6 were sintered, and the moisture sensitivity characteristics of the sintered bodies were examined. The result is No. 6
Shown in the table.

Examples 42 to 44 In the same manner as in Example 1, the compositions shown in Table 7 were sintered, and the moisture sensitivity characteristics of the sintered bodies were examined. The result is No. 7
Shown in the table. The results of Example 9 are also shown in Table 7.

Examples 45 to 47 In the same manner as in Example 2, the compositions shown in Table 8 were sintered, and the moisture sensitivity characteristics of the sintered bodies were examined. The result is No. 8
Shown in the table. The results of Example 2 are also shown in Table 8.

Example 48 The sintered body of the moisture-sensitive element composition used in Example 9 was subjected to an ambient temperature of 25 ° C, 40 ° C, 60 ° C and 80 ° C and a relative humidity of 20 to 100.
%, And the moisture sensitivity characteristics at that time were investigated. The results are shown in FIG.

In Fig. 4, numbers 1, 2, 3, and 4 are ambient temperatures of 25 ℃, 40 ℃, and 6 ℃.
Moisture-sensitive property at 0 ℃ and 80 ℃. The conventional product is shown by a dotted line in FIG. 4 for reference. The dotted line numbers 1'and 2'indicate the moisture sensitivity characteristics at ambient temperatures of 25 ° C and 40 ° C, respectively. As is clear from FIG. 4, it can be seen that the temperature dependency is extremely small and the temperature compensation is not required at the ambient temperature of 25 ° C to 40 ° C. The moisture-sensitive element composition of the present invention has an ambient temperature
It can be seen that the total amount of change in the humidity-sensitive property at 25 to 80 ° C corresponds to the amount of change in the humidity-sensitive property at the atmospheric temperature of 25 to 40 ° C of the conventional product, and that the temperature characteristic is significantly smaller than that of the conventional product.

Example 49 The sintered body of the moisture-sensitive element composition used in Example 2 was subjected to an ambient temperature of 25 ° C, 40 ° C, 60 ° C and 80 ° C and a relative humidity of 20 to 100.
%, And the moisture sensitivity characteristics at that time were investigated. The results are shown in FIG. In FIG. 5, reference numerals 1, 2, 3, and 4 indicate moisture-sensitive characteristics at ambient temperatures of 25 ° C, 40 ° C, 60 ° C, and 80 ° C.
The conventional product is shown by a dotted line in FIG. 5 for reference. The dotted line numbers 1'and 2'indicate the moisture sensitivity characteristics at ambient temperatures of 25 ° C and 40 ° C, respectively. As is clear from FIG. 5, it is understood that the temperature dependency is extremely small and the temperature compensation is not necessary at the ambient temperature of 25 ° C to 40 ° C. Further, in the humidity-sensitive element composition of the present invention, the total change amount of the humidity-sensitive property at the ambient temperature of 25 to 80 ° C corresponds to the change amount of the moisture-sensitive property of the conventional product at the ambient temperature of 25 to 40 ° C. It can be seen that the temperature characteristics are remarkably small.

Example 50 A composition having a molar ratio of titanium oxide and potassium selenite (K ₂ SeO ₃ ) of 89.5% and 10.5% was sintered in the same manner as in Example 1.

After leaving the obtained sintered body in an atmosphere with an ambient temperature of 25 ° C and a relative humidity of 98% for 24 hours, the ambient temperature was adjusted to the relative humidity.
Hysteresis of moisture sensitivity was investigated in the range of 20-80%. Further, the hysteresis of the moisture-sensitive property was examined for the composition sintered body of Example 9 in the same manner as above.

The result is shown in FIG. In FIG. 6, numbers 1 and 2 show the results of Examples 9 and 50, respectively. As is apparent from FIG. 6, the hysteresis in the moisture sensitivity characteristics of these composition sintered bodies is about ± 3% RH, and the relative humidity is 98%,
It can be seen that the hysteresis is extremely small despite the load of leaving for 24 hours.

Example 51 The composition sintered bodies used in Examples 2 and 13 were allowed to stand in an atmosphere having an ambient temperature of 25 ° C. and a relative humidity of 98% for 24 hours, and then at the same ambient temperature, a relative humidity of 20 to 80%. The hysteresis of the moisture sensitivity characteristic was investigated in the range of.

The results are shown in FIG. In FIG. 7, the numbers 1 and 2 show the results of Examples 2 and 13, respectively. As is clear from FIG. 7, the hysteresis in the moisture sensitivity characteristics of these composition sintered bodies is within ± 2% RH, relative humidity 98%,
It can be seen that the hysteresis is extremely small despite the load of leaving for 24 hours.

Example 52 The moisture-sensitive element composition of Example 9 was heated to an ambient temperature of 85 ° C.
After being left for 30 minutes, a 50-cycle thermal shock test was conducted with one cycle of being left at an ambient temperature of -25 ° C for 30 minutes, and the humidity-sensitive characteristics of the humidity-sensitive element composition before and after the thermal shock test were the same as in Example 1 above. I looked it up.

The results are shown in FIG. In FIG. 8, reference numeral 1 indicates the moisture-sensitive property before the above test, and number 2 indicates the moisture-sensitive property after the above test. For comparison, the moisture sensitivity characteristics of the conventional product before and after the above test are shown by dotted line numbers 1'and 2 ', respectively. As is clear from FIG. 8, the humidity-sensitive element composition of the present invention has a humidity-sensitive property change before and after the thermal shock test of 3% or less,
It can be seen that it is much more resistant to thermal shock than conventional products.

Example 53 The composition sintered body used in Example 13 was heated to an ambient temperature of 85.
After leaving it at ℃ for 30 minutes, leave it at ambient temperature -25 ℃ for 30 minutes.
As a cycle, a 50-cycle thermal shock test was conducted, and the moisture sensitivity characteristics before and after the thermal shock test were examined in the same manner as in Example 2 above.

The results are shown in FIG. In FIG. 9, number 1 indicates the moisture sensitivity characteristic before the above test, and number 2 indicates the moisture sensitivity characteristic after the above test. For comparison, the moisture sensitivity characteristics of the conventional product before and after the above test are shown by dotted line numbers 1'and 2 ', respectively. As is clear from FIG. 9, the humidity-sensitive element composition of the present invention has a change in humidity-sensitive property before and after the thermal shock test of 3% or less,
It can be seen that it is much more resistant to thermal shock than conventional products.

Example 54 The moisture-sensitive element composition of Example 50, with an ambient temperature of 85 ° C.,
The humidity-sensitive element composition was allowed to stand for 1 month in an environment having a relative humidity of 80%, and the humidity-sensitive properties before and after standing were examined in the same manner as in Example 1 above.

The results are shown in Table 9. As is clear from Table 9, the humidity-sensitive element composition of the present invention has been left in a severe environment of high temperature and high humidity for a long period of time, but its humidity-sensitive property changes little. Therefore, it can be seen that under normal atmosphere, it can be used for a long time without special heat cleaning.

Example 55 The composition sintered bodies used in Examples 2 and 13 were immersed in distilled water at a temperature of 25 ° C. for 1 month and then air-dried, and the feeling before and after the leaving test was performed in the same manner as in Example 2. Wet properties were investigated.

In FIG. 10, reference numerals 1 and 1'represent the moisture-sensitive characteristics of the sintered body of Example 2 before and after the above test, and number 2 and 2'indicate the moisture-sensitive characteristics of the sintered body of Example 13 before and after the above test. Indicates.

As is clear from FIG. 10, there is almost no change in the moisture sensitivity characteristics of these sintered compositions of the composition before and after the above-mentioned test, and it is understood that the water resistance is extremely good. Therefore, it can be seen that the moisture-sensitive element composition of the present invention can be used for a long period of time without requiring special heat cleaning because there is no fear of deterioration of moisture-sensitive characteristics even under a severe environment of dew condensation.

〔effect〕

According to the present invention, compared with the conventional moisture-sensitive element composition,
It has a low specific resistance value and is in a practical range, its temperature dependence is extremely small, temperature compensation is not necessary, there is almost no hysteresis in the moisture sensitivity characteristics when absorbing and desorbing moisture, and it is resistant to thermal shock and It is possible to provide a highly reliable moisture-sensitive element composition which does not require any heat cleaning.

When an alkaline earth metal salt is used as the chalcogen oxo acid salt, a moisture sensitive element composition having excellent water resistance can be provided.

[Brief description of drawings]

FIG. 1 is a front view showing one form of a moisture sensitive element using the moisture sensitive element composition of the present invention. 2 to 10 are graphs showing the characteristics of the humidity-sensitive element composition of the present invention, FIGS. 2 to 3 are humidity-sensitive characteristics, FIGS. 4 to 5 are temperature dependence of humidity-sensitive characteristics, and 6-
Fig. 7 shows the hysteresis of the humidity-sensitive property after leaving it at high humidity, 8th to 9th.
FIG. 10 is a graph showing the moisture sensitivity characteristics before and after the thermal shock test, and FIG. 10 is a graph showing the moisture sensitivity characteristics before and after the water resistance test. In the figure, 1 indicates an electrode and 2 indicates a moisture-sensitive composition.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Osamu Kondo 6-1, 1-1 Shinjuku, Katsushika-ku, Tokyo Yoshio Imai Examiner, Research Center, Mitsubishi Gas Chemical Co., Ltd.

Claims (7)

[Claims] 1. A moisture-sensitive element composition obtained by sintering a metal oxide, which comprises adding a chalcogen oxoacid salt represented by the general formula (I) to the metal oxide and baking the mixture in the presence of molecular oxygen. during humidity sensitive element composition _{a x B y O z (I} ) ( wherein, characterized in that formed by binding, a is alkali metal, alkaline earth metal, B is sulfur, selenium or tellurium atom, O is an oxygen atom , X is 1-2, y is 1-5, and z is 2-7). 2. The amount of chalcogen oxoacid salt compounded is 0.01 based on the sum of the metal oxide and the chalcogen oxoacid salt.
Moisture-sensitive element composition according to claim 1, wherein the composition is from about 99.99 mol% 3. The moisture-sensitive element composition according to claim 1, wherein the chalcogen oxoacid salt is an alkali metal salt. 4. The moisture-sensitive element composition according to claim 1, wherein the chalcogen oxoacid salt is a tellurium salt. 5. The metal oxide is TiO ₂ , γ-Al ₂ O ₃ , ZnO, Mg.
The moisture-sensitive element composition according to claim 1, which is at least one selected from the group consisting of O, ZrO ₂ , NiO, and MgAl ₂ O ₄ . 6. The moisture-sensitive element composition according to claim 1, wherein the metal oxide is TiO ₂ . 7. Claim 1 in which the sintering temperature is 500 to 1200 ° C.
Moisture sensitive element composition