JPH0414744B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a sensitive medium that can be used as a humidity sensor, a dew sensor, a gas sensor, etc., and a method for manufacturing the same. Conventional technologies and their problems A number of sensitive media for humidity sensors, dew condensation sensors, gas sensors, etc. made of materials such as organic polymers, ceramics, semiconductors, and fixed electrolytes have been studied, and their trial use is currently in progress. Or it has been put into practical use. However, in recent years, as measuring devices have become smaller, more accurate, and more sophisticated, there has been a demand for sensitive media with better performance and better workability. However, ceramic materials and semiconductor materials have disadvantages in that they require complicated manufacturing processes to be processed into sensitive media, have poor product yields, and are therefore expensive. Furthermore, organic polymer materials have problems in that they have poor durability and heat resistance, and lack reliability as sensitive media. Means for Solving the Problems In view of the problems of the prior art, the present inventor has conducted extensive research in order to obtain a sensitive medium with excellent performance and good processability. the result,
The electrical conductivity, light transmittance, reflectance, etc. of the thin film obtained by applying a solution of an amorphous oxide containing V ₂ O ₅ to a substrate and drying it at room temperature to 300°C are as follows: It was discovered that it responds sensitively to changes in gas and moisture content, and the present invention was completed based on this knowledge. That is, the present invention provides the following sensitive medium and method for producing the same. General formula (V ₂ O ₅ ) _1-x・(M _y O _z ) _x・nH ₂ O [in the formula,
M _y O _z is at least one of a metal oxide and a metalloid oxide, 0≦x<1, 0≦n<18. General formula (V ₂ O ₅ ) _1-x・(M _y O _z ) _x・nH ₂ O [in the formula,
M _y O _z is at least one of a metal oxide and a metalloid oxide, 0≦x<1, 0≦n<18], and an organic polymer material and/or an inorganic polymer A sensitive medium consisting of a composite material. General formula (V ₂ O ₅ ) _1-x・(M _y O _z ) _x [In the formula, M _y O _z
is at least one of a metal oxide and a metalloid oxide
A method for producing a sensitive medium, comprising applying a solution of an amorphous oxide represented by the following formula, 0≦x<1, on a substrate and drying the solution at room temperature to 300°C. General formula (V ₂ O ₅ ) _1-x・(M _y O _z ) _x [In the formula, M _y O _z
is at least one of a metal oxide and a metalloid oxide
A solution containing an amorphous oxide represented by a species, 0≦x<1] and an organic polymer material and/or an inorganic polymer material is applied onto a substrate, and the solution is heated at room temperature to
A method for producing a sensitive medium, characterized by drying at 300°C. The sensitive medium of the present invention is a thin film made of a composite oxide represented by the general formula (V ₂ O ₅ ) _1-x ·(M _y O _z ) _x ·nH ₂ O. Here, M _y O _z is at least one of a metal oxide and a metalloid oxide, and satisfies 0≦x<1, 0≦n<18. Although n varies depending on the moisture absorption of the sensitive medium, it is preferably 3.5 to 0.1 during medium production. Also, x is 0.5
It is preferable that it is below. Specifically, M _y O _z includes Li, Na, K, Cu,
Ag, Mg, Ca, Zn, Ba, Hg, B, Al, Y,
Ga, In, Ti, Zr, Si, Ge, Sn, pb, Nb, Ta,
Tl, As, Sb, Bi, Cr, Mo, W, Se, Te, Mn,
Examples include oxides of Fe, Co, Ni, Pt, Nd, Gd, Er, La, Ce, etc., and a mixture of two or more oxides may be used. The sensitive medium of the present invention can be obtained by applying a solution of an oxide having an amorphous structure represented by (V ₂ O ₅ ) _1-x (M _y O _z ) _x to a substrate and drying the solution. This solution is a sol solution using water as a medium, and can be prepared, for example, by the following method. A method of forming an amorphous oxide with the composition (V ₂ O ₅ ) _1-x (M _y O _z ) _x and dissolving or dispersing it in a solvent. In this case, the method for producing the amorphous oxide may be a known method, such as heating and melting the raw material oxide and rapidly cooling it by blowing it out onto the surface of a high-speed rotating roll or a cooling plate, heating and melting the raw material oxide, Examples include a method of atomizing with high-pressure gas and rapid cooling, and a method of evaporating, ionizing, or causing a gas phase reaction of the raw material by PVD or CVD and depositing it on a substrate. A method in which the raw material oxide is melted by heating, poured into a solvent, and rapidly cooled and dissolved at the same time. Method for preparing solutions by hydrolysis of alcoholates of panadium and other additives. A method of preparing a solution by ion exchange method using panadate. The concentration of the solution obtained in this way is 0.001 ~
The content may be about 10% by weight, but in order to form a uniform thin film, it is preferably about 0.001 to 5.0% by weight. If the concentration is less than 0.001% by weight, uneven coating tends to occur, and if it exceeds 5.0% by weight, unevenness in the thickness of the coating film tends to occur, which is not preferable. In the present invention, if the substrate to which the solution is applied has poor hydrophilicity, an organic solvent may be added to the solution in order to improve the compatibility between the solution and the substrate. Common organic solvents may be used,
Typical examples include methanol, ethanol, acetone, dimethylformamide, dimethyl sulfoxide, and the like. The amount of the organic solvent added may be about 0.01 to 10 times the amount of the above solution.
Further, a polymer material may be added to the solution in order to make the viscosity of the solution uniform, form a homogeneous coating film, and improve adhesion to the substrate.
As the polymeric material, for example, organic materials such as polyvinyl alcohol, polyacrylamide, polyacrylic acid, polyethyglycol, and methylcellulose, and inorganic materials such as polyphosphoric acid and water glass can be used. Furthermore, polymethyl methacrylate, polyethylene, polycarbonate, polyester, etc. can also be used in combination with an organic solvent. The amount of polymer material added is
The amount may be about 0.01 to 10% based on the solution. In the present invention, stabilizers, PH adjusters, emulsifiers, and the like may be added to these solutions to improve the stability of the solutions. To prepare the sensitive medium of the present invention, first, a solution obtained by the above method is applied onto a substrate. The coating method is not particularly limited, and may be, for example, a dipping method, a coating method, a spray method, a spinner method, a roll coater method, or the like. The substrate may be made of glass, plastic, ceramics, etc., and may be in the form of a plate, sheet,
Various shapes such as film, porous, etc. can be used. Next, the solution applied on the substrate was heated from room temperature to 300°C.
The sensitive medium of the invention is obtained by drying at a temperature in the range of .degree. By adjusting the drying conditions, the amount of water in the sensitive medium can be adjusted to an appropriate amount. A transmission electron micrograph (15,000 times, acceleration voltage 75 KV) of the obtained sensitive medium is shown in FIG. From FIG. 1, it can be seen that the sensitive medium of the present invention has a width of 10 in the matrix.
It can be seen that the structure has many fine fibers with lengths of several 100 to several 1000 Å. According to electron beam diffraction, the fine fibers have a layered structure. Further, both the matrix and the fine fibers of the sensitive medium are estimated to be composed of (V ₂ O ₅ ) _1-x ·(M _y O _z ) _x ·nH ₂ O. The reason why the sensitive medium having the structure described above responds sensitively to moisture and gas concentrations is not clear, but it is presumed as follows. In other words, the medium base absorbs moisture and gas in the atmosphere depending on its concentration.
It has the function of absorption and excretion, the so-called respiratory function.
The absorbed moisture and gas then enter between the layers of fine fibers having a layered structure. Therefore, the interlayer spacing of the fine fibers varies depending on the moisture and gas concentration in the atmosphere, which appears as a change in the characteristics of the sensitive medium. Therefore, changes in moisture or gas concentration are detected as changes in the electrical conductivity of the sensitive medium. Further, the medium has a property of transmitting light in the ultraviolet to infrared wavelength range, and therefore, changes in moisture or gas concentration can also be detected as changes in light reflectance or transmittance. Experimental results are shown graphically in FIG. 2 which also show that the interlayer spacing of the fine fibers in the sensitive media of the present invention accurately responds to changes in relative humidity. The sensitive medium used in the measurement was (V ₂ O ₅ ) _0.85・(TiO ₂ ) _0.15 , and the fine fiber layer in the sensitive medium was changed when the relative humidity in the test room was changed between 30% and 90%. Changes in spacing were measured by X-ray diffraction. From FIG. 2, it can be seen that the change in the interlayer spacing of the fine fibers in the sensitive medium responds with good reproducibility to changes in the relative humidity in the test chamber. In the present invention, in order to adjust the electrical conductivity etc. of the sensitive medium to appropriate values, (V ₂ O ₅ ) _1-x・(M _y O _z ) _x・nH ₂ O and inorganic It can be composited with a polymeric material and/or an organic polymeric material. Normally, the electrical conductivity of a sensitive medium consisting only of (V ₂ O ₅ ) _1-x・(M _y O _z ) _x・nH ₂ O is 1 to 1 at room temperature.
10 ^-2 (Ωcm) ^-1 , which is why it is sometimes difficult to detect changes in moisture or gas concentration as changes in electrical conductivity. In such cases, (V ₂ O ₅ ) _1-x・(M _y O _z ) _x・nH ₂ O can be combined with an appropriate inorganic polymer material and/or organic polymer material. , it is possible to adjust the electrical conductivity to be easily detected according to the object to be measured. Preferred polymeric materials are substances that have the effect of improving sensitivity to changes in gas and moisture content and increasing the electrical resistance of the sensitive medium. Examples of organic polymeric materials include polyacrylic acid, polyvinyl alcohol, and polyacrylamide. , cellulose, cellulose acetate, ethylcellulose, methylcellulose, carboxymethylcellulose, nitrocellulose, vinyl acetate, etc., and copolymers of these can also be used. Furthermore, a crosslinking agent can be used in combination if necessary. Examples of inorganic polymer materials include colloidal silica, phosphate polymers, and phosphazene polymers. The inorganic polymer material and the organic polymer material may be used alone or in combination as appropriate. ( _{V 2} O ₅ ) _{1 - x}・( _{M y O z} ) A polymeric material may be added to a solution of an amorphous substance of M _y O _z ) _x , dissolved or dispersed, and then applied to a substrate and dried. The coating method, drying conditions, etc. may be the same as in the case of using a solution of (V ₂ O ₅ ) _1-x ·(M _y O _z ) _x alone. The amount of polymeric material in solution is
(V ₂ O ₅ ) _1-x・(M _y O _z ) _x 0.01 to 1 part by weight
The amount is about 100 parts by weight, preferably about 0.01 to 20 parts by weight. If the polymeric material exceeds 100 parts by weight,
This is not preferable because the sensitivity and electrical conductivity of the sensitive medium decrease too much. (V ₂ O ₅ ) _1-x・(M _y O _z ) _x・nH ₂ O _and a polymer material are combined into a sensitive medium, (V ₂ O ₅ ) _{1- x} Similar to the sensitive medium consisting only of _x ·nH ₂ O, it has a structure in which a large number of fine fibers exist in the matrix, and it is presumed that the polymer material exists in the matrix. Examples of methods for measuring moisture and gas concentrations in the atmosphere using the sensitive medium of the present invention include a method of measuring electrical conductivity of the sensitive medium, a method of measuring optical reflectance and transmittance, and the like. To measure electrical conductivity, it is sufficient to form an electrode at an appropriate position on the front or back surface of a sensitive medium according to a conventional method. A medium may be formed. FIG. 3 shows a cross-sectional view of an example of a sensor using the sensitive medium of the present invention. In FIG. 3, 1 is a substrate,
2 and 4 are sensitive media, and 3 is an electrode. In addition, the optical reflectance and transmittance can be measured using conventional methods.
You can irradiate the sensitive medium with gas laser light or semiconductor laser light such as Ne laser, Ar laser, He-Cd laser, etc., measure the intensity of reflected light and transmitted light with a photodetector, and read the changes. . Effects of the Invention The present invention provides the following effects. The sensitive medium of the present invention has excellent responsiveness to changes in moisture and gas concentrations, and can be used as a humidity sensor, a dew sensor, an organic gas sensor, an inorganic gas sensor, etc. Since it can be manufactured by a coating method, sensors with many shapes and large sensors with a large area can be easily manufactured. Moisture and gas concentrations can be measured by various methods such as electrical conductivity measurement, optical reflectance and transmittance measurement, so it has a wide range of uses. With a combination of a composite oxide and a polymer material, the electrical conductivity can be adjusted to any desired range, making it possible to measure with high precision. Examples The features of the present invention will be described in more detail with reference to Examples below. Example 1 V ₂ O ₅ and M _y O _z (each oxide shown in Table 1) were used as raw materials, and after thoroughly mixing them, they were filled into a PT tube with a slit nozzle at the bottom and heated with high frequency. After melting in a furnace, the melt was sprayed onto the surface of a high-speed rotating roll to produce an amorphous (V ₂ O ₅ ) _1-x (M _y O _z ) _x ribbon. The quenching rate at this time was 1×10 ⁵ to 2×10 ⁶ ° C./sec. The obtained amorphous oxide ribbon was dissolved in water, and 2
After preparing a sol-like solution of % by weight, this solution was applied to a glass substrate and dried to produce a sensitive medium of the present invention, and then electrodes were formed on the medium by vacuum evaporation to produce a sensor. Drying conditions, media film thickness, and electrode materials are shown in Table 1.

【table】

【table】

[Table] Using the obtained sensor, we measured the relationship between the relative humidity in a constant temperature and humidity chamber (manufactured by Tabai Seisakusho) and the electrical resistance value when 1V DC was applied. (manufactured by Card Co., Ltd.). As a result, all of the sensors using the sensitive media of Samples No. 1 to 45 above showed excellent responsiveness to changes in relative temperature, and the measurement results were within the shaded area in Figure 4, making them effective as humidity sensors and dew condensation sensors. It could be used for Example 2 (V ₂ O ₅ ) _0.75・produced in the same manner as Example 1
(GeO ₂ ) _0.25 Each polymeric material shown in Table 2 below is added to a 2% by weight sol solution of the amorphous ribbon, mixed, the solution is applied onto the substrate material, and heated and dried to form a sensitive medium. I got it. Next, Au was deposited on the sensitive medium using a vacuum evaporation method to form an electrode.

[Table] Using the obtained sensor, the relationship between relative humidity and electrical resistance when 1 V DC was applied was measured in the same manner as in Example 1. The results are shown in FIG. Furthermore, using the sensor of sample No. 47, the relationship between relative humidity and electrical resistance when 5 V AC was applied was measured, and the results are shown in FIG. The AC electrical resistance values were measured at AC frequencies of 1 KHz, 10 KHz, and 100 KHz. It can be seen from FIGS. 5 and 6 that the sensor using the sensitive medium of the present invention can be used as a humidity sensor and a dew sensor by measuring DC resistance or AC resistance. In addition, using the sensor of sample No. 47, we measured the SO gas concentration in the closed chamber and the AC 5V (10KHz).
Figure 7 shows the results of measuring the relationship between hydrazine gas concentration and electrical resistance (AC 5V,
Fig. 8 shows the results of measuring the relationship with 10KHz applied). It can be seen from FIGS. 7 and 8 that the sensor using the sensitive medium of the present invention can be used as a gas sensor. Furthermore, sample No. 46 was placed in a constant temperature and humidity chamber, and a He-Ne laser (λ = 633 nm) was applied.
[Beam diameter 1.0 mmφ, output 1 mW] Light was irradiated, the transmitted light was received by a photodiode, the output current was measured with an oscilloscope, and the relationship between the relative humidity inside the chamber and the output current was determined. 9th result
As shown in the figure. It can be seen from FIG. 9 that the sensitive medium of the present invention can be used as a humidity sensor by measuring transmitted light.

[Brief explanation of drawings]

Figure 1 is a transmission electron micrograph of the sensitive medium of the present invention, Figure 2 is a graph of the relationship between the layer spacing of fine fibers and relative humidity in the sensitive medium of the present invention, and Figure 3 is a photograph of the sensitive medium of the present invention. A cross-sectional view of the sensor, FIG. 4 is a graph of the relationship between DC electrical resistance and relative humidity of the sensitive medium of the present invention, FIG. 5 is a graph of the relationship between DC electrical resistance and relative humidity of the sensitive medium of the present invention, and FIG. 7 is a graph of the relationship between the AC electrical resistance value and the relative humidity of the sensitive medium of the present invention, FIG. 7 is a graph of the relationship between the AC electrical resistance value of the sensitive medium of the present invention and SO gas concentration, and FIG. FIG. 9 is a graph of the relationship between AC electrical resistance and hydrazine gas concentration, and FIG. 9 is a graph of the relationship between the intensity of transmitted light and relative humidity of the sensitive medium of the present invention. In FIG. 3, 1 is a substrate, 2 and 4 are sensitive media, and 3 is an electrode.

Claims (1)

[Claims] 1 General formula (V ₂ O ₅ ) _1-x・(M _y O _z ) _x・nH ₂ O [in the formula,
M _y O _z is at least one of a metal oxide and a metalloid oxide, 0≦x<1, 0≦n<18. 2 General formula (V ₂ O ₅ ) _1-x・(M _y O _z ) _x・nH ₂ O [in the formula,
M _y O _z is at least one of a metal oxide and a metalloid oxide, 0≦x<1, 0≦n<18], and an organic polymer material and/or an inorganic polymer A sensitive medium consisting of a composite material. 3 General formula (V ₂ O ₅ ) _1-x・(M _y O _z ) _x [In the formula, M _y O _z
is at least one of a metal oxide and a metalloid oxide
A method for producing a sensitive medium, comprising applying a solution of an amorphous oxide represented by the following formula, 0≦x<1, on a substrate and drying the solution at room temperature to 300°C. 4 General formula (V ₂ O ₅ ) _1-x・(M _y O _z ) _x [In the formula, M _y O _z
is at least one of a metal oxide and a metalloid oxide
A solution containing an amorphous oxide represented by a species, 0≦x<1] and an organic polymer material and/or an inorganic polymer material is applied onto a substrate and dried at room temperature to 300°C. A method for producing a sensitive medium characterized by: