JP3036612B2 - Ozone sensor manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a sensor for controlling ozone concentration or detecting ozone in an ozone generator or an ozone utilizing device.

[0002]

2. Description of the Related Art Since ozone has a strong oxidizing effect, it is used in various fields such as water and sewage water treatment, medical care, and the food industry for the purpose of deodorization and sterilization. However, while having such useful utility value, even a very small amount of ozone is extremely harmful to the human body, so it is necessary to reliably control the amount of generated ozone and detect leaked ozone.

In such a situation, the measurement and detection of the ozone concentration have conventionally used an oxidation-reduction titration method, an absorptiometry method, and an ultraviolet absorption spectrum method. On the other hand, recently, a simpler method of measuring ozone concentration has been desired, and a semiconductor type ozone sensor has been proposed as one of the methods.

As shown in FIG. 3, a conventional semiconductor gas sensor comprises a gas sensing element formed between an at least one pair of electrodes (2) and an electrode on an insulating substrate (1) having a heating function.
It consists of (3). Metal oxides such as SnO ₂ and In ₂ O ₃ have been put to practical use as a material used as a gas sensitive body, utilizing a change in electric conductivity due to gas adsorption. As a method of forming the gas sensitive body,
A method using sintering, a thick film method such as screen printing, a thin film method such as a sputtering method or a vacuum evaporation method are used,
The thickness is about several tens nm to several tens μm. In addition, some semiconductor gas sensors have a coating layer of a metal oxide such as SiO ₂ on a gas sensitive body in order to improve gas selectivity.

[0005]

However, the conventional method of measuring the concentration of ozone generally requires a large-scale apparatus and complicated operations, and has a disadvantage that it is expensive and cannot be easily used. ing. on the other hand,
A semiconductor type ozone sensor proposed as a simple method for measuring ozone concentration has excellent sensitivity and responsiveness to ozone gas.

The functions required of an ozone sensor include:
There are sensitivity to ozone gas, selectivity, responsiveness, stability, production reproducibility and the like. Among them, the sensitivity to ozone is the most important function, but the allowable concentration of ozone gas is 0.1 ppm.
Therefore, a gas sensor having a very low sensitivity and a high sensitivity is desired. In general, the sensitivity and selectivity to the test gas vary with changes in the thickness and composition of the gas sensitizer, so the reproducibility of gas sensitizer production is closely related to the stability of the gas sensitizer thickness and composition control. ing.

[0007] As a method of forming the gas sensitizer, a thin film method such as a sputtering method or a vacuum deposition method has a problem that when the gas sensitizer is composed of multiple components, the composition tends to vary. Further, the thick film method such as screen printing has a problem that the film thickness tends to vary.

An object of the present invention is to solve the above problems and to provide a manufacturing method capable of manufacturing a highly sensitive ozone sensor with good reproducibility.

[0009]

In order to achieve the above object, a first method for manufacturing an ozone sensor according to the present invention comprises an inorganic indium salt, an organic compound capable of coordinating at least indium, and an organic material containing an active agent. A gas sensitive body is formed by applying a solution on a substrate and baking the solution.

In the above structure, the inorganic indium salt is preferably at least one salt selected from the group consisting of indium nitrate, indium sulfate, and indium chloride.

In the above structure, the coordinating organic compound may be β-diketones, α-ketone acids, β-ketone acids, esters of the ketone acids, α-amino alcohols and β-amino alcohols. It is preferably at least one compound selected from the group consisting of

Next, a second method of manufacturing an ozone sensor according to the present invention comprises applying a masking ink on a substrate, drying and curing the substrate by heat or light, and then coordinating the inorganic indium salt with at least indium. Possible organic compounds;
A gas sensitizer is formed by applying an organic solution containing an activator on a substrate and baking it.

[0013] In the above configuration, the masking ink preferably contains at least one compound selected from epoxy acrylate, epoxy methacrylate, urethane acrylate, and urethane methacrylate.

[0014]

According to the first aspect of the present invention, an organic solution containing an inorganic indium salt, an organic compound capable of coordinating with indium, and an activator is used to form a gas sensitizer. In general, inorganic indium salts often have deliquescence or are easily hydrolyzed, and it is difficult to stably produce a gas sensitive material having the same thickness and composition. For this purpose, an organic compound capable of coordinating with the indium is added to generate a coordination compound substituted with a part of the inorganic indium salt, thereby stabilizing the inorganic indium salt. The activator is a metal salt other than indium, and the addition of these salts improves the sensitivity and selectivity of the gas sensitizer to ozone gas. As a result, by applying and baking a composition for forming a gas sensitizer consisting of an inorganic indium salt, an organic compound capable of coordinating with indium, and an organic solution containing an activator, the gas sensitizer whose composition is controlled is stabilized. Can be manufactured. And, compared to physical film forming methods such as vacuum evaporation and sputtering, the gas sensitizer causes mutual diffusion with the substrate during firing,
A highly reliable ozone sensor with good adhesion to the substrate can be obtained.

According to the second aspect of the present invention, in order to form a gas sensitive body in a predetermined pattern, a masking ink is applied to an unnecessary portion of the gas sensitive body on a substrate, dried, and then heated or lighted. By curing, the solvent resistance of the masking resin film is improved, the gas sensitizer forming composition is applied, and the heat treatment is performed. A gas sensitive body is formed at the bottom. When forming a masking resin film of an unnecessary portion of these gas sensitizers, screen printing or offset printing is used, and the application of the gas sensitizer forming composition uses a dip coating method, a spin coating method, or the like. The variation in the film thickness of the gas sensing element is small, and a highly reliable ozone sensor can be obtained.

[0016]

Embodiments of the present invention will be described below in detail.
FIG. 1 is a schematic sectional view of the ozone sensor of the present invention. FIG.
In the figures, 1 is an insulating substrate such as alumina or mullite, 2 is an electrode made of a metal such as gold, silver or platinum, and 3 is a gas sensitive body made of a metal oxide represented by the following chemical formula (1).

[0017]

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As the substrate (1), any substrate can be used as long as it has an insulating surface and has a heating function, and the material and the configuration are not limited. The main purpose of the electrode (2) is to apply a voltage to the gas sensitive body (3) and measure its electric resistance, and there is no limitation on the material, configuration, pattern, manufacturing method and the like of the electrode.

Next, according to the first manufacturing method of the present invention, the gas sensitive body (3) can be formed as follows. After forming a film of the composition for forming a gas sensitive body on a substrate, it is baked at a temperature of several 100 ° C. or more to form a gas sensitive body. The gas sensitizer forming composition can be applied by a screen printing method, a roll coating method, a dip coating method, a spin coating method, or the like, but the dip coating method and the spin coating method are preferred. The firing temperature may be 400 ° C. or higher as long as it is higher than the temperature at which the composition for forming a gas sensitive body is decomposed and lower than the deformation temperature of the substrate.
700 ° C. is preferred. Here, the composition for forming a gas sensitive body is synthesized as follows.

First, an inorganic indium salt is mixed with an organic compound capable of coordinating with indium. Here, the inorganic indium salt is an organic compound capable of coordinating with indium,
What is necessary is just to have the ligand which can be substituted. For example, indium nitrate, indium chloride, and indium sulfate are mentioned, and those having crystallization water are preferable. In addition, the organic compound capable of coordinating with indium is necessary for coordinating one part with indium to stabilize the inorganic indium salt and to have solubility in an organic solvent. For example, β-diketones, α- Or β-ketone acids, esters of the ketone acids, and α- or β-amino alcohols.

Next, an organic solvent and an activator are added to the solution,
The organic solutions are heat-treated. Here, the activator is a metal salt added for the purpose of improving the sensitivity or gas selectivity of the gas sensitizer, such as a metal magnesium salt, a metal calcium salt, a metal strontium salt, or an alkaline earth metal salt such as metal barium. , Transition metal salts such as metal titanium salts, metal zirconium salts, metal vanadium salts, metal chromium salts, metal manganese salts, metal iron salts, metal cobalt salts, metal nickel salts, metal copper salts, metal zinc salts, metal lead salts, Metal cadmium salts, metal tin salts, metal antimony salts and the like. The compound is relatively stable at room temperature, but may be easily decomposed by heat treatment, and may be an inorganic salt or an organic salt. For example, for inorganic salts, nitrates, sulfates,
Chloride salts and the like, and organic salts include carboxylate and dicarboxylate. The organic solvent may be any solvent that dissolves the organic compound or inorganic compound used in the present invention. For example, toluene, aromatic hydrocarbons such as xylene, ethanol, alcohols such as isopropanol,
Examples thereof include acetates such as ethyl acetate and butyl acetate, ketones such as acetone and diethyl ketone, ethers such as methoxyethanol and ethoxyethanol, and tetrahydrofuran. Further, when the activator is hardly soluble at room temperature, an inorganic indium salt, an organic compound capable of coordinating with indium, and an organic solution containing the activator are subjected to heat treatment at or near the reflux temperature of the organic solution. You may.

Next, FIGS. 2A to 2C are schematic sectional views of a method for manufacturing an ozone sensor according to a second manufacturing method of the present invention. 2 (a) to 2 (c), reference numeral 1 denotes an insulating substrate such as alumina or mullite, 2 denotes an electrode made of a metal such as gold, silver or platinum, and 3 denotes a metal oxide represented by the following chemical formula (1). Reference numeral 4 denotes a masking resin, and reference numeral 5 denotes a film of the gas-sensitive body forming composition. In the case of a thermal decomposition method such as dip coating, the gas sensitive body can be patterned as described below. First, after printing and curing a masking resin (4) on the unnecessary part of the gas sensitive body on the electrode (2), the substrate (1)
A film (5) of the composition for forming a gas sensitive body is formed thereon. Here, the masking resin only needs to be insoluble in the composition for forming a gas sensitive body after being cured by heat or ultraviolet rays, and epoxy acrylate, epoxy methacrylate, urethane acrylate, and urethane methacrylate are preferred.
Next, the substrate is fired at a temperature of several hundred degrees Celsius or more to form a gas sensitive body. In addition, the coating of the composition for forming a gas sensitive body, a screen printing method, a roll coating method, a dip coating method, a spin coating method and the like can be used,
Dip coating and spin coating are preferred. Also,
The firing temperature may be at least the temperature at which the composition for forming a gas sensitive body decomposes and at most the deformation temperature of the substrate.
0-700 ° C is preferred.

The patterning of the gas sensitive body is performed by subjecting the gas sensitive body formed by a thermal decomposition method such as dip coating, a thin film method such as a sputtering method or a vacuum evaporation method to photolithography or resist printing / curing / etching. It can also be made.

Hereinafter, the present invention will be described with reference to more detailed examples, but the present invention is not limited to these examples. Example 1 In a 1-liter Erlenmeyer flask, 45 g of indium nitrate (Chemical Formula 2) was weighed, and 50 g of acetylacetone was added.
They were mixed and dissolved at room temperature. (Equation 1) is 5mo
Nitrate of various metals M, acetone and 10 g of glycerin weighed to 1% were added, stirred and mixed to obtain a desired composition for forming a gas sensitive body.

[0025]

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[0026]

(Equation 1)

[0027] The composition for forming a gas sensible body was prepared to have a thickness of 0.4 m.
After coating by dip coating on an alumina substrate having a thickness of m 2, the resultant was baked at 600 ° C. for 1 hour to form a gas sensitive body having a thickness of 50 nm and comprising a metal oxide containing indium as a main component. An organic metal compound paste of gold was applied on the substrate by screen printing and dried, and then fired at 560 ° C. to form an electrode layer. Next, the response characteristic to ozone was measured using the manufactured sensor element. The sensor element is fixed in a quartz glass measuring tube, the element temperature is controlled to 300 ° C by a heater, and the change in the resistance of the sensor element when air and air containing 1 ppm of ozone alternately flow through the sensor element is measured. It was measured. The sensor element resistance in air was changed to R _A and air containing ozone was changed to R _G1 , and the sensor element resistance after one minute was determined as R _G1 to obtain R _G1 / R _A, which was defined as the sensor sensitivity.
Table 1 shows the sensitivities obtained by the sensors of the respective compositions thus obtained.
Listed in

[0028]

[Table 1]

Example 2 A gold organometallic compound paste was applied on a 0.4 mm-thick alumina substrate by screen printing and dried.
It was fired at 800 ° C. to form an electrode layer. Next, a masking ink composed of urethane acrylate, an organic vehicle, and an organic solvent was applied on the substrate by screen printing, and cured by ultraviolet rays. Further, a film of the composition for forming a gas sensitive body was formed by spin coating, and baked at 650 ° C. for 1 hour to form a gas sensitive body made of ITO having a thickness of 40 nm. Others are the same as Example 1. The sensor sensitivity (R _G1 / R _A ) was 3.9.

Example 3 A gold organometallic compound paste was applied on a 0.4 mm-thick alumina substrate by screen printing, dried, and fired at 800 ° C. to form an electrode layer. Next, a masking ink comprising an epoxy acrylate, an organic vehicle, and an organic solvent was applied on the substrate by screen printing, dried at 60 ° C. for 5 minutes, and cured by heating at 130 ° C. for 30 minutes. Further, a film of the composition for forming a gas sensitive body is formed by spin coating, and baked at 700 ° C. for 1 hour to form a film.
A gas sensitive body made of 40 nm ITO was formed. Others are the same as Example 1. The sensor sensitivity (R _G1 / R _A ) was 3.6.

As described above, according to the embodiment of the present invention, an organic solution containing an inorganic indium salt, an organic compound capable of coordinating with indium, and an activator is used for forming a gas sensitizer. In general, inorganic indium salts often have deliquescence or are easily hydrolyzed, and it is difficult to stably produce a gas sensitive material having the same thickness and composition. For this purpose, an organic compound capable of coordinating with the indium is added,
A coordination compound substituted with a part of the inorganic indium salt is generated to stabilize the inorganic indium salt. The activator is a metal salt other than indium, and the addition of these salts improves the sensitivity and selectivity of the gas sensitizer to ozone gas. As a result, by applying and baking a composition for forming a gas sensitizer consisting of an inorganic indium salt, an organic compound capable of coordinating with indium, and an organic solution containing an activator, the gas sensitizer whose composition is controlled is stabilized. Can be manufactured. Then, as compared with a physical film forming method such as vacuum deposition or sputtering, the gas sensitizer causes mutual diffusion with the substrate at the time of baking, so that a highly reliable ozone sensor with good adhesion to the substrate can be obtained.

[0032]

As described above, according to the first production method of the present invention, according to the first production method, a gas-sensitive substance comprising an organic solution containing an inorganic indium salt, an organic compound capable of coordinating with indium, and an active agent is formed. By applying and baking the composition for
It is possible to stably produce a gas sensitive body whose composition is controlled. Then, as compared with a physical film forming method such as vacuum deposition or sputtering, the gas sensitizer causes mutual diffusion with the substrate at the time of baking, so that a highly reliable ozone sensor with good adhesion to the substrate can be obtained.

According to the second manufacturing method of the present invention, since the gas sensitive body is formed in a predetermined pattern, masking ink is applied to the unnecessary portions of the gas sensitive body on the substrate.
By drying and hardening by heat or light, the solvent resistance of the masking resin film is improved, and the gas sensitizer forming composition is applied and heat-treated, so that the masking resin in an unnecessary portion of the gas sensitizer is heated. The gas sensor is decomposed to form a gas sensitive body only at a necessary portion, and the thickness of the gas sensitive body has a small variation, so that a highly reliable ozone sensor can be obtained.

The present invention also provides an ozone sensor which is compact, lightweight, inexpensive and has excellent gas detection characteristics, and is suitable for use in ozone concentration control or ozone detection in ozone generators and equipment utilizing ozone.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of an ozone sensor of the present invention.

FIGS. 2A, 2B and 2C are schematic sectional views showing another embodiment of the method for manufacturing an ozone sensor according to the present invention.

FIG. 3 is a schematic sectional view of a conventional semiconductor gas sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Electrode 3 Gas sensitive body 4 Masking resin 5 Film of composition for forming gas sensitive body

────────────────────────────────────────────────── ─── Continuation of the front page (72) Nobuyuki Yoshiike, Inventor 1006 Kazuma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-4-152258 (JP, A) JP-A-4- 152259 (JP, A) JP-A-4-5559 (JP, A) JP-A-59-92341 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 27/12

Claims (5)

(57) [Claims] 1. An ozone characterized by forming a gas sensitizer by applying an inorganic solution containing an inorganic indium salt, an organic compound capable of coordinating at least indium, and an activator on a substrate and firing the solution. Manufacturing method of sensor. 2. The method according to claim 1, wherein the inorganic indium salt is indium nitrate,
The method for manufacturing an ozone sensor according to claim 1, wherein the at least one salt is at least one salt selected from the group consisting of indium sulfate and indium chloride. 3. The organic compound capable of coordination is selected from the group consisting of β-diketones, α-ketone acids, β-ketone acids, esters of the ketone acids, α-amino alcohols and β-amino alcohols. The method for manufacturing an ozone sensor according to claim 1, wherein the ozone sensor is at least one compound selected. 4. After applying a masking ink on a substrate, drying and curing with heat or light, an inorganic indium salt, an organic compound capable of coordinating at least to indium,
A method for manufacturing an ozone sensor, wherein an organic solution containing an activator is applied on a substrate and baked to form a gas sensitive body. 5. The method according to claim 4, wherein the masking ink contains at least one compound selected from epoxy acrylate, epoxy methacrylate, urethane acrylate, and urethane methacrylate.