JPH10325789A - Crystal vibrator moisture sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the moisture resistance and durability of a moisture- sensing film and hence prevent deterioration, by accumulating the single- molecular film of a cellulose dielectric where hydrophobic long chain is added to cellulose macromolecule horizontally on the electrode surface of a crystal vibrator and fixing it in a layer. SOLUTION: A monomolecular film 5 of a cellulose dielectric where a hydrophobic long chain is added to the cellulose macromolecule is horizontally accumulated and fixed in a layer on the surface of a gold electrode 3 that is deposited on both surfaces of a crystal vibrator 1 that is optically polished. In the cellulose macromolecule, one portion or entire portion of cellulose hydroxyl group is a fatty acid of for example at least one type of acetic acid, butyric acid, myristic acid, and stearic acid and is esterified fatty acid cellulose ester or its mixture. Then, the monomolecular film 5 is formed by dissolving a developed solution to a chloroform solvent and developing it onto pure water at 10-20 deg.C, and is overlapped horizontally on the surface of the gold electrode 3 of the crystal vibrator 1 that is a fixed surface one by one, and a thin film is formed in a layer and is fixed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of a quartz oscillator humidity sensor capable of measuring humidity in a high humidity environment, such as a plant incubator, a high humidity tester for measuring the growth environment of a small plant, and the like. It belongs to

[0002]

2. Description of the Related Art In a seedling production, for example, since a high humidity condition has a good effect on a growth reaction rate and a trait expression reaction from a seed stage or an early growth stage of a plant, an incubator capable of precise control of high humidity is provided. It is known that there is a need for a quartz oscillator humidity sensor that can stably measure humidity at high humidity, which is optimal for a high humidity tester for measuring the growth environment of small plants.

As a conventionally known quartz oscillator humidity sensor, for example, a method disclosed in Japanese Patent Application Laid-Open No. 2-285236, "A hydrophilic polymer having a property of adsorbing moisture is dissolved in a suitable solvent, Is applied to the surface of a quartz oscillator, and a solvent is volatilized to form a moisture-adsorbing film thereon. " Then, a dope consisting of a water-soluble inorganic halogen salt, a hydrophilic polymer and a water-soluble organic solvent is applied to the electrode surface of the quartz oscillator, and then gelled in contact with the water surface, dried, and dried. It is to manufacture sensors.

Cellulose; fatty acid cellulose triesters such as cellulose acetate, cellulose butyrate, cellulose propionate and cellulose acetate butyrate or mixtures thereof; cellulose ethers such as ethyl cellulose and methyl cellulose; and cellulose-based polymers such as nitrocellulose as hydrophilic components. Using a polymer material having a molecule and nigrosine as a hydrophobic component as a moisture-sensitive film,
That is, a quartz oscillator humidity sensor in which a polymer thin film having two properties of hydrophilic and hydrophobic contradicting each other and a polymer sensitive film moisture is formed on the quartz oscillator face is disclosed in JP-A-8-105830. I have.

[0005] A quartz oscillator humidity sensor in which a polyethersulfone moisture-sensitive film formed by a coating method is formed on the surface of a quartz oscillator is described in JP-A-7-260661.

[0006]

In any of the humidity sensors described in the above publications, since the molecular arrangement in the moisture-sensitive film is disordered, the moisture sensor absorbs too much water molecules at high humidity. There is a problem that the humidity resistance and durability of the high humidity sensor are inferior.

The present invention realizes a close-packed state of molecules by controlling the arrangement state of the molecules in the moisture-sensitive film, and suppresses the invasion of the molecules in the moisture-sensitive film. It is an object of the present invention to provide a quartz oscillator humidity sensor capable of improving the performance.

[0008]

A quartz oscillator humidity sensor according to the present invention for solving the above-mentioned problems comprises a single crystal of a cellulose derivative obtained by adding a hydrophobic long chain to a cellulose polymer on the electrode surface of the quartz oscillator. Molecular films are accumulated horizontally and fixed in layers.

The quartz oscillator in the quartz oscillator humidity sensor according to the present invention is optically polished.

The cellulose derivative in the quartz oscillator humidity sensor according to the present invention is obtained by esterifying a hydroxyl group of cellulose with a long-chain fatty acid.

The cellulose derivative monomolecular film in the quartz oscillator humidity sensor according to the present invention is prepared by dissolving a developing solution in a chloroform solvent and developing the solution on pure water at 10 ° C. to 20 ° C.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a quartz oscillator humidity sensor according to the present invention will be described with reference to the drawings. As shown in FIGS. 2
A gold electrode 3 is vapor-deposited on both surfaces of the substrate, and a monolayer 5 of a cellulose derivative obtained by adding a hydrophobic long chain to a cellulose polymer is horizontally fixed on the surface of the gold electrode 3 in a layered manner.

The quartz oscillator 1 is optically polished, and the cellulose derivative is obtained by esterifying a hydroxyl group of cellulose with a long-chain fatty acid. The cellulose derivative monomolecular film 5 is prepared by dissolving a developing solution in a chloroform solvent and developing the solution on pure water at 10 ° C to 20 ° C. Cellulose-based polymer, a part or all of the hydroxyl groups of cellulose is one or more acetic acid,
Butyric acid, myristic acid, fatty acids such as stearic acid,
It is an esterified fatty acid cellulose ester or a mixture thereof.

The immobilization of the monomolecular film 5 of a cellulose derivative obtained by adding a hydrophobic long chain to a cellulosic polymer on the surface of the gold electrode 3 of the crystal unit 1 in the present invention is performed by a Langmuir film called a monomolecular accumulation method. That is, the monolayer 5 of the cellulose derivative formed on the water surface is horizontally stacked one by one on the surface of the gold electrode 3 of the crystal unit 1 which is the fixed surface, and a thin film is formed and fixed in layers. Produced.

A molecule having a hydrophilic group at the end of a hydrophobic group, for example, stearic acid (CH ₃ (CH ₂ ) ₁₆ COOH) has a property of forming a monomolecular layer with the hydrophilic group —COOH facing downward on the water surface. This monomolecular layer is a two-dimensional system and becomes a “gas film”, “liquid film” or “solid film” depending on the size of the intermolecular distance. Then, there are roughly two methods for transferring the monomolecular layer to the solid surface. One is "vertical breach method"
By raising and lowering the solid base across the water surface and applying sufficient surface pressure to maintain the solid membrane,
The monomolecular layers are stacked one by one, and the orientation of the film forming molecules is reversed between the lifting process and the erosion process. The resulting Langmuir film is a Y-type having a layered structure with two molecular layers as unit cells. A film structure can be formed.

The other is the "horizontal attachment method" in which the substrate is held horizontally and adhered to the water surface and then transferred. In this method, the orientation of the film-forming molecules is not changed, and the hydrophobic groups are removed. An X-type membrane structure having a monolayer facing the substrate as a unit cell can be formed. The invention relied on a vertical dipping method and a horizontal deposition method.

FIG. 4 shows a feedback oscillation circuit 1 using a CMOS inverter used for measuring the oscillation frequency of the crystal unit 1.
It shows an example, and as shown in the figure, is composed of a crystal oscillator 1, an inverter 6, a resistor R, and a capacitor C,
It is connected to a microwave counter 7 which displays the measured values. This circuit uses the crystal unit 1 as an inductive reactance element and forms a transmission circuit between the two capacitors C so that the mechanical vibration of the crystal unit 1 can be stably converted into an electric signal. .

After one layer of stearic acid is accumulated on the 15 MHz quartz oscillator 1 on which the gold electrode 3 is deposited, the monolayer 5 of the cellulose derivative is accumulated and fixed horizontally in a layered manner by a known vertical immersion method and a horizontal attachment method. Have been.

In order to improve the adhesion with the gold electrode 3, first, a monomolecular film of stearic acid is accumulated. Thereafter, a developing solution in which palmitoyl cellulose was dissolved in chloroform solvent at 1 mmol glucose / 1 was spread on pure water at a water temperature of 10 ° C. to 20 ° C., and two layers on one side were formed into a cumulative film having a thickness of about 40 ° by a horizontal adhesion method. did.

FIG. 4 shows a quartz oscillator transmitting circuit using one quartz oscillator 1 having a palmitoyl cellulose moisture-sensitive film formed on the surface in this manner. The measured frequency is a microwave counter. The frequency measuring device 8 measured by 7 was installed in a constant temperature and constant humidity water bath at 10 ° C. to 20 ° C., and the frequency change with respect to the relative humidity was measured.

A monolayer film 5 of a cellulose derivative obtained by adding a hydrophobic long chain to a cellulose polymer is horizontally accumulated on the surface of the gold electrode 3 of the crystal unit 1 of the crystal unit humidity sensor according to the present invention. As shown in FIG. 5 which shows the film quality when fixed to the relationship between the occupied area and the surface pressure, the temperature of the developing solution
At 7 ° C., the surface pressure decreases linearly between 30 mN / m and 5 mN / m, indicating good film quality during accumulation.

When the developing solution temperature is 25 ° C., the surface pressure decreases linearly between 25 mN / m and 15 mN / m. Can be said to have good film quality.

As shown in FIG. 6, a good linear relationship between the relative humidity of the quartz oscillator humidity sensor thus produced and the weight of the moisture-sensitive film (determined from the change in the resonance frequency). Was brought. In addition, 100 ℃
For 24 hours, no change was observed in its moisture absorption properties.

As a result, as shown in FIG.
In the range of 2 to 95%, about 10% relative humidity and about 10%
The Hz frequency shift amount changes, and there is a good correlation between the relative humidity and the frequency shift amount. It can be seen that the quartz resonator having the moisture-sensitive film functions sufficiently as a humidity sensor.

The humidity resistance test of the quartz oscillator humidity sensor is performed by immersing the quartz oscillator humidity sensor in primary distilled water for 30 minutes,
Repeated moisture resistance experiments were performed three times: air-drying and measuring sensitivity to humidity again.

As a result of the three experiments, as shown in FIG. 7, the change in the measured value of the humidity sensitivity of the palmitoyl cellulose cast film humidity sensor (indicated by a triangle in the graph) decreases as the number of tests increases. This indicates that the cast film peeled off from the surface of the gold electrode 3, thereby lowering the moisture adsorption rate and deteriorating the humidity sensitivity of the cast film humidity sensor. Cellulose moisture-sensitive film humidity sensor (marked with ○ in the graph) does not peel off the film like the cast film quality sensor, and therefore, there is no change in the humidity resistance of the humidity sensor, and it has excellent moisture resistance. Recognize. In FIG. 7, X0 indicates the initial value of the measured value of the frequency, and X indicates the measured value of the frequency after the test.

As described above, the quartz oscillator humidity sensor has a relative humidity of 95% R. H. After confirming that the device operates stably at a relative humidity of 30% R. H. Momentarily exposed to the atmosphere. As a result, as shown in FIG. 8, the light was focused to a constant value in about 20 seconds. From this, it can be understood that the response to the humidity change is extremely good.

[0028]

The quartz oscillator humidity sensor according to the present invention has the following features.
It is more excellent in terms of water resistance, and has an effect that stable humidity measurement at high humidity is possible.

[Brief description of the drawings]

FIG. 1 is a plan view showing one embodiment of a quartz oscillator humidity sensor according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is an enlarged sectional view taken along a dashed line indicated by B in FIG. 2;

FIG. 4 is a diagram showing one embodiment of a crystal oscillator transmission circuit using a crystal oscillator humidity sensor according to the present invention.

FIG. 5 is a graph showing the film quality when monolayers are horizontally accumulated and fixed in a layered form according to the present invention in relation to occupied area and surface pressure.

FIG. 6 is a graph showing an example of a hygrometer using a quartz oscillator humidity sensor according to the present invention in a relationship between a frequency shift amount and a relative humidity.

FIG. 7 is a graph showing the results of a moisture resistance test of the quartz oscillator humidity sensor according to the present invention in the relationship between the measured value change amount and the number of tests.

FIG. 8 is a graph showing the dehumidification time of the quartz oscillator humidity sensor according to the present invention in relation to the frequency shift amount.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Quartz crystal oscillator 2 Quartz surface 3 Gold electrode 5 Monomolecular film

Claims (4)

[Claims] 1. A quartz oscillator humidity sensor comprising a monolayer of a cellulose derivative obtained by adding a hydrophobic long chain to a cellulose polymer and horizontally fixed on a surface of an electrode of the quartz oscillator in a layered manner. . 2. The quartz oscillator humidity sensor according to claim 1, wherein the quartz oscillator is optically polished. 3. The quartz oscillator humidity sensor according to claim 1, wherein the cellulose derivative is obtained by esterifying a hydroxyl group of cellulose with a long-chain fatty acid. 4. The monomolecular film of a cellulose derivative is prepared by dissolving a developing solution in a chloroform solvent and developing the solution on pure water at 10 ° C. to 20 ° C. Quartz crystal humidity sensor.