JPH06281610A - Humidity sensor, alcohol sensor or ketone sensor - Google Patents

Abstract

PURPOSE:To provide a humidity sensor, alcohol sensor, or ketone sensor which can be easily manufactured and has excellent responsiveness. CONSTITUTION:The sensor is constituted by successively piling up a set of an electrode and poly(1-(trimethylsilil)propyn) film on an insulating substrate. The sensor can be also constituted by successively forming a lower electrode, poly(1trimethylsilil)-1-propyn) film, and upper electrode on an insulating substrate or a poly(1-(trimethylsilil)-1-propyn) film and upper electrode on a conductive substrate which is used as a lower electrode also.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a humidity sensor, alcohol sensor or ketone sensor. For more details,
The present invention relates to a humidity sensor, an alcohol sensor, or a ketone sensor which is excellent in manufacturability and responsiveness.

[0002]

2. Description of the Related Art A humidity sensor is roughly classified according to its detection principle.
There are four types of mechanical sensors, dry and wet bulb sensors, electromagnetic sensors, and impedance change type sensors. Among these, impedance change type sensors are drawing attention, and there are two types: resistance change type and capacitance change type. There is one.

The impedance change type sensor is roughly classified into a ceramic type and a polymer type in terms of the moisture sensitive material. For ceramics, T
Oxides such as i, Sn, Zr, Mg, Cr, Si, and V are used. Therefore, they have high heat resistance and a wide operating temperature range, but their moisture-sensitive properties are derived from the porous structure of ceramics. However, it has a problem of poor reproducibility and inevitable change of adsorbed water with time due to capillary condensation.

On the other hand, examples of high molecular weight compounds include polyacrylic acid, polystyrene sulfonic acid, polymethylaminoethyl methacrylate salt, carboxylic acid (salt) derivative of styrene-divinylbenzene copolymer, and the like. It has good reproducibility because it exhibits hygroscopicity due to the hygroscopicity and ionic conductivity of the molecule itself, and has the advantage that it is resistant to contamination and is not easily affected by other gas species, but its heat resistance is low. There is a problem. Polymers having heat resistance include those using polyimide, which is applied to a substrate in the form of polyamic acid and then heated to cause a polycondensation reaction to form a polyimide, There is a problem in terms of productivity.

Further, sensor elements which have been put to practical use or studied as gas sensors such as alcohol sensors and ketone sensors are roughly classified into semiconductor type and catalytic combustion type.

The semiconductor type sensor element detects gas by utilizing the characteristic that the resistance value of the sensor changes when the test gas is adsorbed on the surface of the sensor element. The biggest problem is the change in sensitivity. It is said that the reason is that the element must be heated to about 400 ° C. before it is used, so that the sintered state and surface state of the element are thermally changed. On the other hand, the catalytic combustion type sensor element applies a change in resistance of a platinum wire to gas detection. Therefore, it has a drawback that the gas selectivity is almost nonexistent.

When using these gas sensors, it is necessary to heat them in order to improve the sensitivity of the element, and a part of heat energy is radiated to the outside of the element, resulting in a large heat loss, which is also a problem. Further, when these sensors are manufactured, many steps such as film formation on an insulating substrate of an element, firing, formation of electrodes and heaters are required.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide an impedance change type humidity sensor using a polymer type moisture sensitive material, which is excellent in manufacturability and responsiveness. It is in.

Another object of the present invention is that alcohol is selective to alcohols or ketones in various organic vapors, does not require heating of the element, and is excellent in manufacturability and responsiveness. To provide a sensor or a ketone sensor.

[0010]

The various objects of the present invention are achieved by a humidity sensor, an alcohol sensor, or a ketone sensor having the following configurations. (1) Insulating substrate, one set of electrodes and a poly [1- (trimethylsilyl) -1-propyne] coating film sequentially laminated on humidity sensor, alcohol sensor or ketone sensor (2) Insulating substrate, lower electrode, poly [ 1- (trimethylsilyl)
Humidity sensor, alcohol sensor or ketone sensor in which -1-propyne] film and upper electrode are laminated in sequence (3) Conductive substrate that also serves as lower electrode, poly [1- (trimethylsilyl) -1-propyne] film and upper electrode Humidity sensor, alcohol sensor or ketone sensor that are sequentially stacked

First, the humidity sensor of the first aspect will be described. As the insulating substrate, glass, alumina, quartz, a silicon wafer whose surface is insulated, or the like is used, and a pair of electrodes, generally a counter electrode, is formed on the substrate. As the electrode material, a conductor such as Au, Pt, or Al that can be thinned is used, and the thinning is performed by a vapor deposition method, a sputtering method, or the like. The patterning is performed by forming a resist pattern by photolithography and etching. The close distance between the pair of electrodes formed is preferably about 0.01 to 1 mm. The smaller the distance is, or the longer the total length of the adjacent portions is, the larger the resistance change or the capacitance change is, which is preferable for humidity detection, alcohol detection, or ketone detection. Therefore, the comb-shaped counter electrode is generally used.

A pair of electrodes formed on an insulating substrate is
It is covered by a poly [1- (trimethylsilyl) -1-propyne] film. The coating film is formed by mixing poly [1- (trimethylsilyl) -1-propyne] (including a copolymer) or a mixture thereof with other alkyl-substituted polyacetylene resin with its soluble solvent such as xylene, Aromatic hydrocarbons such as toluene and benzene, n-hexane, n-heptane, n-
Aliphatic hydrocarbons such as octane, cyclohexane, cycloaliphatic hydrocarbons such as cyclopentane, halogenated hydrocarbons such as chloroform, cyclic ethers such as dioxane, etc., in an amount of about 0.1 to 5% by weight, preferably about 0.5 to 3% by weight. It is carried out by applying a solution dissolved at a concentration of% onto a substrate and drying. The thickness of the coating film formed is about 0.01-
The thickness is 100 μm, preferably about 0.1 to 10 μm, and the film thickness can be controlled depending on the solution concentration used.

In the case of the second aspect, the lower electrode, poly [1
The-(trimethylsilyl) -1-propyne] film and the upper electrode are sequentially formed on the insulating substrate in the same manner as in the above case. The upper electrode is a comb-shaped electrode or has an electrode thickness of about 0.01 to improve the contact between the outside atmosphere and the poly [1- (trimethylsilyl) -1-propyne] film.
It is desirable to secure air permeability by setting it to about 1 μm.

In the case of the third embodiment, poly [1- (trimethylsilyl)-is formed on a conductive substrate which also serves as a lower electrode.
The 1-propyne] film and the upper electrode are formed as in the second embodiment. As the conductive substrate that also serves as the lower electrode, for example, plate-shaped or film-shaped Cu, Al, Au, Ag, Pt, or the like is used.

[0015]

[Function] When a solution of poly [1- (trimethylsilyl) -1-propyne] in an organic solvent is evaporated at room temperature, a plastic non-porous film is formed. The formed poly [1- (trimethylsilyl) -1-propyne] film has a larger diffusion coefficient of gas molecules such as CO ₂ , N ₂ and O _{2 in} the film than that of the rubber-like polymer film. It is believed that this is due to the gaps between large molecular chains and bulky substituents.

Thus, poly [1- (trimethylsilyl)-
The 1-propyne] membrane diffuses substances rapidly within the membrane, has a large contact angle with water, does not swell with water, and diffuses water vapor within the membrane too. Furthermore, poly [1- (trimethylsilyl) -1-propyne] exhibits a high electrical insulating property in a bulk film state.

In the humidity sensor according to the present invention, such a characteristic of poly [1- (trimethylsilyl) -1-propyne] is effectively used, that is, poly [1- (triphenylsilyl) -1-propyne] prepared as a thin film.
When water vapor in the air is vigorously brought into contact with (trimethylsilyl) -1-propyne], the water vapor quickly diffuses into the poly [1- (trimethylsilyl) -1-propyne] film, and molecular chain gaps or microporosity in the film It is sorbed on the inner surface. The temperature of the steam to be contacted is in the range of 120 ° C. or lower at which poly [1- (trimethylsilyl) -1-propyne] is stable, preferably about 0 to 100 ° C.

Therefore, when an electric stimulus is externally applied to the film in this state, water vapor changes as an electric signal due to direct current conduction due to the propagation of protons or interfacial polarization due to the Maxwell-Wagner effect. That is, the humidity can be instantly detected. The electrical signal can be detected by any method such as direct current volume resistance, surface resistance, alternating current impedance change, and capacitance change. The water vapor sorbed inside is immediately released to the outside of the film due to its wettability and diffusibility.

Further, in the alcohol sensor or the ketone sensor according to the present invention, the characteristic of diffusion of the substance in the poly [1- (trimethylsilyl) -1-propyne] film is effectively used. That is, when alcohol gas or ketone gas is vigorously brought into contact with poly [1- (trimethylsilyl) -1-propyne] prepared as a thin film, the alcohol gas or ketone gas is introduced into the poly [1- (trimethylsilyl) -1-propyne] film. It diffuses quickly and is sorbed on the molecular chain gaps in the membrane or on the inner surface of the microporous layer. The temperature of the alcohol gas or the ketone gas to be contacted is 120 ° C. or lower, preferably in the range of about 0 to 100 ° C. as in the case of the humidity sensor, and generally at room temperature.

When an electric stimulus is externally applied to the film in this state, it becomes possible to perform sensing as a change in an electric signal according to the sorption amount of alcohol or ketone in the film.
The electrical signal can be detected by any method such as direct current volume resistance, surface resistance, alternating current impedance change, and capacitance change. The alcohol or ketone sorbed inside is released to the outside of the membrane in a relatively short time of about several seconds, which enables excellent sensing in terms of responsiveness.

Since the observed change in the electric signal is derived from the OH group of alcohol or the CO group of ketone, the type of alcohol or ketone is not particularly limited.

[0022]

The humidity sensor, alcohol sensor or ketone sensor of the present invention is made of poly [1- (trimethylsilyl) -1-
According to the characteristics of propyne, humidity or selectively alcohol gas or ketone gas can be measured quickly and with good reproducibility, and a complicated process is not required, and the manufacturing cost can be reduced. Furthermore, unlike conventional polyimide moisture sensitive films, it does not require heat treatment when it is formed,
No deformation due to moisture absorption. Further, when used as an alcohol sensor or a ketone sensor, it is not necessary to heat it to a high temperature.

[0023]

EXAMPLES The present invention will now be described with reference to examples.

Example 1 A pair of opposed comb-shaped gold electrodes (thickness: about 0.5 μm) were formed on an alumina substrate (5 × 5 × 0.5 mm) by vapor deposition, and a gold lead wire was formed at one end of each electrode. It was fixed with gold paste. Poly [1- (trimethylsilyl) -1-
3 drops of a 1 wt% toluene solution of propyne] were dropped and naturally dried at room temperature to form a counter-comb-shaped electrode coating film (thickness: about 1 μm). The direct current resistance of the obtained device at room temperature was 520 MΩ.

(1) When steam of 85 ° C. was sprayed on this element, its resistance value decreased to 50 MΩ in about 2 seconds. When air (relative humidity 95%) at room temperature was brought into contact with this device, the resistance value decreased to 170 MΩ in about 0.2 seconds after the contact. This operation was repeated every 1 minute for 1 hour, and the reproducibility was good.

(2) When air containing 10% methanol vapor was vigorously blown onto this device for 5 seconds at room temperature, the result was about 0.2.
The surface resistance value decreased to 30 MΩ in seconds. When the blowing of the air containing methanol vapor was stopped, the surface resistance value returned to about 520 MΩ in about 5 seconds. This operation was repeated every 1 minute for 10 hours, and the reproducibility was good.

(3) When air containing 10% acetone vapor was vigorously blown onto the device for 5 seconds at room temperature, the surface resistance value decreased to 100 MΩ in about 0.2 seconds. When the blowing of the air containing acetone vapor is interrupted, the surface resistance value is about 520 in about 5 seconds.
Returned to MΩ. This operation was repeated every 1 minute for 10 hours, and the reproducibility was good.

Comparative Example The element obtained in Example 1 was vigorously blown with air containing 15% n-hexane vapor at room temperature, but no change was observed in the surface resistance value.

Example 2 A comb-shaped gold electrode (having a thickness of about 0.5 μm) was formed as a lower electrode on an alumina substrate (5 × 5 × 0.5 mm) by a vapor deposition method, and then the same procedure as in Example 1 was performed. Poly covering the comb-shaped gold electrode
After forming the [1- (trimethylsilyl) -1-propyne] coating film, a comb-shaped gold electrode (thickness: about 0.5 μm) in a positional relationship orthogonal to the lower comb-shaped electrode is formed as the upper electrode, Each gold lead was attached.

The DC resistance of the obtained device at room temperature was 60.
When it was 0 MΩ and 85 ° C steam was sprayed on it, the resistance value decreased to 50 MΩ in about 2 seconds.

Claims (9)

[Claims] 1. An insulating substrate, a pair of electrodes and poly [1-
(Trimethylsilyl) -1-propyne] A humidity sensor made by sequentially laminating coating films. 2. A humidity sensor comprising an insulating substrate, a lower electrode, a poly [1- (trimethylsilyl) -1-propyne] film, and an upper electrode, which are sequentially laminated. 3. A conductive substrate also serving as a lower electrode, poly [1-
(Trimethylsilyl) -1-propyne] film and upper electrode are laminated in this order. 4. An insulating substrate, a pair of electrodes and poly [1-
(Trimethylsilyl) -1-propyne] An alcohol sensor formed by sequentially laminating coating films. 5. An alcohol sensor comprising an insulating substrate, a lower electrode, a poly [1- (trimethylsilyl) -1-propyne] film, and an upper electrode, which are sequentially laminated. 6. A conductive substrate also serving as a lower electrode, poly [1-
(Trimethylsilyl) -1-propyne] film and an upper electrode are laminated in this order. 7. An insulating substrate, a pair of electrodes and poly [1-
(Trimethylsilyl) -1-propyne] A ketone sensor formed by sequentially laminating coating films. 8. A ketone sensor formed by sequentially laminating an insulating substrate, a lower electrode, a poly [1- (trimethylsilyl) -1-propyne] film, and an upper electrode. 9. A conductive substrate also serving as a lower electrode, poly [1-
(Trimethylsilyl) -1-propyne] film and an upper electrode are laminated in this order.