JPS6161521B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a mixed component of a resistor with excellent sensitivity for use in a moisture-sensitive resistance element. Conventionally, the electrical resistance of molded bodies without Al ₂ O ₃ powder depends on humidity, so high purity powder with a particle size of 1 to 5 μm is used.
Water is added to the Al ₂ O ₃ powder and stirred to form a slurry, which is applied thinly to the surface of an insulating substrate such as a glass plate with a balanced electrode, air dried, and then dried at 100°C to form a thin oxide film. The ivy humidity sensor was known. This was further improved to produce Al ₂ O ₃ powder with a particle size of 1 to 5μ.
Glass containing 60-90% by weight and transition metal elements 40-10
Japanese Patent Publication No. 10677/1983 describes a mixture prepared by press-molding and firing a mixture with % by weight. However, the former has low mechanical strength and the moisture-sensitive resistor easily peels50.
% relative humidity (hereinafter abbreviated as "RH"), the electrical resistance was as high as 10 ⁴ MΩ, and it was impossible to measure at low humidity. The latter also contains glass as a binder, so even at high humidity levels such as 90% RH, it is 5 x 10 ⁵
In order to create a resistor that has high electrical resistance (Ω) and practical mechanical strength, a large amount of glass must be added, which inevitably results in small changes in resistivity due to humidity and slow response. In addition, there was the problem that hysteresis remained when changing from high humidity to low humidity. The present invention has been made to improve these problems, and is characterized by molding a mixture of oxide fine powder obtained by hydrolyzing Al alkoxide and Ti alkoxide, and calcining it at 800 to 1300°C. The present invention provides a humidity resistance element, and the humidity sensitive resistor component thereof is comprised of 5 to 99 mol% _{Al2O3 and 1} to 95 mol% TiO2. Since the present invention does not use a binder and the firing is completed before crystal growth progresses, a microcrystalline and uniform porous body can be obtained, and a moisture-sensitive resistance element with high sensitivity and quick response can be obtained. I can do it. Addition of TiO ₂ to Al ₂ O ₃ contributes to lowering the resistance of the element and further increasing the range of change, which makes it more superior in practice. The method of obtaining fine oxide powder and making a mixture by hydrolyzing Al alkoxide and Ti alkoxide has the following characteristics: high purity with no impurities introduced during the manufacturing process, and uniform ultrafine particles of approximately 100 Å in size. It can be sintered at relatively low temperatures, from 800 to 1,300 degrees Celsius. Furthermore, by simultaneously hydrolyzing the alkoxide mixed solution using a common solvent, an extremely homogeneous composition having an arbitrary composition ratio can be easily obtained, and the reproducibility is high even though the composition ratio is high and the range of variation is high. In addition, because the particles are fine particles that do not contain glass as a binder, they have a large specific surface area, are active, have high sensitivity, and are free from hysteresis during dehumidification, which is also due to this method. The reason why we limited the firing temperature to 800 to 1300℃ is that
℃ or below, rutile type TiO ₂ cannot be formed in a composition containing 1 mol% or more of TiO ₂ and an amorphous or anatase type structure is formed.
Al ₂ O ₃ is also mostly amorphous and has low strength and is unstable. This is because at temperatures above 1300°C, crystals grow and become larger, becoming insensitive to humidity changes and losing linearity between humidity and resistance changes. In addition, the reason for limiting the moisture-sensitive resistor components to 5 to 99 mol% of Al ₂ O ₃ and 1 to 95 mol% of TiO ₂ is as follows.
At Al ₂ O ₃ 99 mol% or more (TiO ₂ 1 mol% or less),
This is because the range of change in resistance of the fired body is small, and if Al ₂ O ₃ is less than 5 mol % (TiO ₂ is more than 95 mol %), the linearity of the resistance of the fired body is lost, making it impractical. A more specific explanation will be given below with reference to Examples. Example Al(isoOC ₃ H ₇ ) ₃ and Ti(nOC ₄ H ₉ ) ₄ were weighed to have the mol% shown in Table 1 below, dissolved in ethanol, and added to a solution heated to a temperature of 60°C or higher.
(isoOC ₃ H ₇ ) ₃ and Ti(nOC ₄ H ₉ ) ₄ are added in a molar amount or more of pure water, and the mixture is allowed to react for 1 hour while stirring.
A mixed solution of Al and Ti alkoxides of any composition can be easily hydrolyzed simultaneously using a common solvent. After the hydrolyzed oxide fine powder is separated and dried, the particle size is approximately 100 Å, uniform, and the specific surface area is small.
280 to 350 m ² /g can be obtained. This fine powder was press-molded without a binder into a size of 0.5 mm in thickness and 1.0 mm in diameter, and fired at a temperature of 1100° C. for 2 hours.

[Table] The characteristics shown in Table 1 above are 2 at a temperature of 1100℃.
It is a porous material that has been fired for hours and has a crystal grain size of 0.1 to 1.0μ and a vaporization rate of 30 to 40, although it varies depending on the composition. Silver electrodes are baked on the top and bottom surfaces at a temperature of 700℃,
A lead wire was attached to create a moisture-sensitive resistance element. Its side view is shown in FIG. In the figure, 1 is a humidity sensitive resistor, 2 is a silver electrode, and 3 is a lead wire. AC1V for each sample above
Figures 2 and 3 show the changes in the relationship between humidity and resistance when applying The curves and straight lines in the figure are No. 10, 9, 8, 7,
It is 6. The samples of the present invention excluding No. 1 and No. 10 are
10 ⁴ Ω at 90%RH, 10 ⁸ Ω at 20%RH,
It had a large range of variation and linearity in a highly practical resistance range, and no hysteresis was observed during dehumidification. However, No. 1 and 10, which are outside the scope of the present invention, are 90%RH.
It is 10 ⁵ Ω at 20% RH, and 10 ⁷ Ω at 20%RH, showing a small resistance change range, and especially No. 10 has no linearity.
Regarding the responsiveness at an air temperature of 30℃, as shown in Figure 4, samples Nos. 2 to 9 showed almost the same values.
It became stable and fast within 30 seconds, which is thought to be due to the effect of the homogeneous fine particle porous material, which does not contain a binder. The broken line in the figure is RH90%
If the RH is changed to 50%, the solid line will change from RH20%.
This is the relative indicated humidity when changing to 50%.
Figure 5 shows the change over time at a temperature of 20°C and a humidity of 70%. Samples Nos. 2 to 9 of the present invention show almost no change, and are shown as solid lines, indicating that organic matter on the surface of the humidity-sensitive resistor. Contamination caused by adhesion was slow, and the change in resistance after 400 hours was approximately 1.5 times the initial resistance and stable. In contrast, the broken line represents the electrical resistance of the conventional product, clearly demonstrating the superiority of the product of the present invention. In this example, the raw materials were Al(isoOC ₃ H ₇ ) ₃ ,
Ti _{(nOC4H9)4 was used} , but Al( _OCH3 ) ₃ , Al
( _OC2H5 ) ₃ , Al _{( nOC4H9} ) ₃ , Ti( _{OC2H5 ) 4} , _Ti
(isoOC ₃ H ₉ ) ₄ , Ti [OCH ₂ CH (C ₂ H ₅ ) C ₄ H ₉ ] ₄ , or other aluminum or titanium alkoxides can of course be used.

[Brief explanation of the drawing]

Figure 1 is a side view of a humidity-sensitive resistance element, Figures 2 and 3 are the relationship between humidity and resistance in the examples and comparative examples of the present invention, and Figure 4 is the relationship between elapsed time and humidity in response of the present invention. FIG. 5 shows the relationship between the time of change over time and the resistance of the product of the present invention and the conventional product.

Claims (1)

[Claims] 1 In terms of oxide moles, Al ₂ O ₃ 5~99% and TiO ₂ 1~
Mix Al alkoxide and Ti alkoxide so that it is 95%, hydrolyze it, and after molding, 800~
A method for manufacturing a moisture-sensitive resistance element characterized by firing at 1300°C.