WO2002088693A1

WO2002088693A1 - Capacitive sensor

Info

Publication number: WO2002088693A1
Application number: PCT/JP2002/004283
Authority: WO
Inventors: Tsutomu Ogura; Sachiko Obara
Original assignee: Yamatake Corporation
Priority date: 2001-04-27
Filing date: 2002-04-26
Publication date: 2002-11-07
Also published as: JP2002328110A

Abstract

A capacitance type humidity detection sensor used under a high-temperature, high-humidity environment, wherein a sensor body has a capacitor structure comprising a polymer membrane interposed between a pair of electrodes, and the sensor body is disposed on one surface of a substrate having at least one through hole penetrating in the thickness direction of the substrate holding the sensor body.

Description

Specification

Capacitive sensor technical field

The present invention relates to a capacitance sensor, and more particularly, to a capacitance sensor useful as a humidity detection sensor used in a high-temperature and high-humidity environment. Background art

Humidity detection sensors using a polymer film as a moisture-sensitive material are roughly classified into two types: capacitance type and electric resistance type. Among them, the capacitance type sensor uses the relatively large relative permittivity characteristic of water molecules of about 80, and has a good humidity response, and the humidity dependency of the humidity sensitivity is small, and the humidity and temperature The measurement range is wide. -A capacitance-type humidity detection sensor generally has the following structure.

In the sensor body, a first electrode layer is first formed on one side of the substrate that holds the sensor, then a polymer film that is electrically insulating and has moisture sensitivity is formed, and finally, a porous film is formed. A second electrode layer having a structure or a mesh structure is formed. Lead wires for extracting a detection signal from the first electrode and the second electrode are respectively drawn. As the substrate, a material with electrical insulation and moderate strength is used to ensure the strength of the entire sensor. The sensor main body formed on the substrate has a parallel plate type capacitor structure.

This type of sensor detects the humidity of the environment based on the following operating principle. When the sensor is placed in an environment with a certain relative humidity, the water vapor (hereinafter referred to as water molecule) in the environment passes through the porous or mesh-structured second electrode layer and reaches the surface of the polymer film located thereunder. Then, it penetrates into the polymer membrane and is trapped and stored. The capture and storage of water molecules by the polymer membrane continues until an equilibrium is formed between the environment and the polymer membrane. In the equilibrium state, the absorption of water molecules into the polymer membrane and the desorption of water molecules from the polymer membrane proceed at the same time at an equal number, and the polymer membrane becomes a certain amount corresponding to the relative humidity in the environment. It is in a state that occludes water molecules.

Therefore, in this state, if each lead wire drawn from each of the above-mentioned electrodes is connected to an impedance analyzer to obtain a detection signal (capacitance) of the polymer film, the detection signal (capacitance) is applied to the polymer film based on the detection signal. Of water molecules, that is, the relative humidity of the environment.

Actual humidity detection is performed as follows.

First, the humidity sensitivity of the assembled sensor is measured. That is, for example, at a temperature of 25 ° C and a relative humidity of x. , X _1; — x _n Set several reference environments, place the sensor in each reference environment, and use the impedance analyzer to detect the sensor signal (capacitance) in each reference environment c. , _{C l} , _--- c _n are measured. And the relationship between the relative humidity and the detection signal: X. vs c _0, _Xl vs, advance and stored in the measuring device ~x _{_n} vs c _n.

Next, actual humidity detection is performed. That is, this sensor is arranged in the environment of the humidity measurement target, and a detection signal at that time is obtained. If the detected signal is a if c _n, the measuring device displays the relative humidity in the environment as a chi _eta. Even when the detection signal is not the above value, it is possible to easily obtain the corresponding relative humidity by interpolating the previous data.

This detection method can also be applied to molecules having polarities other than the above-mentioned water molecules, for example, formaldehyde, acetone, alcohol and the like.

However, the capacitance type humidity detection sensor has some excellent features due to the good use of the characteristics of water molecules, and has the following problems.

In other words, when a conventional humidity detection sensor is used for a long time in a high-temperature, high-humidity environment, and then re-measured in a reference environment, for example, the relative humidity in the environment cannot be measured. The corresponding detection signal (capacitance) tends to show a detection signal corresponding to a relative humidity higher than the true relative humidity.

That is, when the not yet used in the environment of high temperature and high humidity sensors, for example, the detection signal of the sensor corresponding to the relative humidity x _n under the reference environment and were der c _n. However, when re-measured after it has been used for a long time the sensor of that in high-temperature and high-humidity environment, the detection signal even under the reference environment of the same relative humidity _Xn becomes the c _n + A c. This phenomenon is usually referred to as drift deterioration in a capacitance measurement type humidity detection sensor. Disclosure of the invention

An object of the present invention is to solve the above-mentioned problem, and an object of the present invention is to provide a structure that suppresses drift deterioration of a capacitance type humidity detection sensor.

In order to achieve the above object, the capacitance type humidity detection sensor of the present invention has a capacitor structure in which a sensor body is formed by laminating a first electrode, a polymer film, and a second electrode in this order. And a substrate that has at least one through hole in the thickness direction and holds the sensor body on one surface. It is characterized by:

Further, the capacitance-type humidity detection sensor of the present invention includes a sensor body having a capacitor structure in which a polymer film is interposed between a first electrode and a second electrode which are erected at predetermined intervals. , Two detection signal leads drawn from each electrode, and a substrate having at least one through hole in the thickness direction and holding the sensor body on one surface. . BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a sectional view showing an example A1 of the sensor of the present invention.

FIG. 2 is a cross-sectional view showing a state where a first electrode is formed on a substrate when manufacturing the sensor A1. FIG.

FIG. 3 is a cross-sectional view showing a state where a polymer film is formed.

FIG. 4 is a cross-sectional view showing a state where the second electrode is formed.

FIG. 5 is a cross-sectional view showing a state where a resist mask is formed on the back surface of the substrate.

FIG. 6 is a sectional view showing another example A2 of the sensor of the present invention.

FIG. 7 is a sectional view showing still another example A3 of the sensor of the present invention.

FIG. 8 is a partial sectional view of a circle P in FIG.

FIG. 9 is a sectional view showing still another example A5 of the sensor of the present invention.

FIG. 10 is a plan view showing another example B of the sensor of the present invention.

FIG. 11 is a cross-sectional view taken along line XX of FIG.

FIG. 12 is a sectional view showing the structure of a conventional sensor C1.

Fig. 13 is a graph showing the relationship between the sensor's standing time in a high-temperature and high-humidity environment and the relative humidity Z when the reference environment is at a temperature of 25 ° C and a relative humidity of 10% (environment (1)). . Figure 14 is a graph showing the relationship between the relative humidity Z and the time the sensor is left in a high-temperature, high-humidity environment when the reference environment is at a temperature of 25 ° C and a relative humidity of 50% (environment (Π)). . Figure 15 is a graph showing the relationship between the relative humidity Z and the time the sensor is left in a high-temperature, high-humidity environment when the reference environment is at a temperature of 25 ° C and a relative humidity of 90% (environment (III)). . BEST MODE FOR CARRYING OUT THE INVENTION

The present inventors have made the following considerations regarding the cause of drift deterioration during the course of research for achieving the above object.

(1) In general, a hygroscopic polymer film is composed of a skeletal part formed by the condensation polymerization of a polymer and a free volume part distributed three-dimensionally in the form of micropores in the skeletal part. It is composed of Occlusion of water molecules in the polymer membrane can be interpreted as a phenomenon in which water molecules permeate and are trapped in the free volume described above. Therefore, water molecules corresponding to the temperature and relative humidity of the environment are stored in the free volume. In the equilibrium state, the number of water molecules occluded from the environment in the volume and the number of water molecules that escape from the environment and escape to the environment are equal.

(2) In the case of the conventional sensor structure, one of the polymer surfaces is fixed to the substrate via the first electrode and is in a constrained state. The membrane absorbs water molecules without free thermal expansion. In other words, while the skeletal portion remains constrained by the substrate, the free volume portion near the other film surface of the polymer film swells by forcibly absorbing water molecules. This causes internal stress due to excess residual water molecules in the polymer film after passing through a high temperature and high humidity environment.

A state in which the polymer film has no internal stress means a state in which water molecules can be relatively freely absorbed and dehydrated in accordance with environmental conditions while the above-mentioned skeleton portion and free volume portion maintain a relative proportional relationship. it is conceivable that. In other words, if the polymer film is in an unconstrained state, both the skeleton and the free volume part thermally expand in relative proportion, so that no internal strain occurs in the polymer film itself, and the water molecule has a relatively free volume part. You can go in and out.

Therefore, the capacitance of the conventional sensor, which is re-measured through a high-temperature, high-humidity environment, is smaller than the capacitance measured first under the reference environment. It appears as a value larger by the amount corresponding to the dielectric amount. This is A c described above.

Based on the above considerations regarding drift deterioration, the present inventors can suppress the occurrence of stress accumulation even in a high-temperature and high-humidity environment by configuring a sensor without restraining the polymer film to the substrate. With the idea that drift degradation can be suppressed, the capacitance sensor of the present invention has been developed based on this idea. Various preferred embodiments of the capacitance sensor according to the present invention will be described in detail below.

FIG. 1 shows a sensor A1 according to an embodiment of the present invention. This sensor Al has a frame-shaped substrate 10 in which one through hole 10a penetrating in the thickness direction is formed at the center. On the upper surface 10b of the substrate 10, the first electrode 11, the polymer film 12, and the second electrode 13 having a porous or mesh structure are laminated in this order so as to close the through hole 10a. A sensor body 15 having a parallel plate capacitor structure is disposed. Then, lead wires 3a and 3b are respectively connected to ends of the first electrode 11 and the second electrode 13 using, for example, a conductive adhesive.

Further, the sensor body 15 as a capacitor area has a structure in which the through hole 10a of the substrate 10 is closed and held in a hollow state. Therefore, the lower surface of the first electrode 11 in the sensor body 15 is in direct contact with the environment via the through hole 10a of the substrate 10. This sensor A1 can be manufactured as follows.

First, as shown in FIG. 2, a first electrode 11 is formed by depositing an electrode material on a substrate 10 having a predetermined shape by using, for example, a vacuum evaporation method and a sputtering method.

The substrate 10 may be made of any material having an electrical insulation property, and examples thereof include glass, quartz, silicon, silicon nitride, aluminum nitride, zirconia, sialon, and sapphire. Among them, the glass substrate is preferable from the viewpoints of cost and ease of performing the substrate processing described later.

The material of the first electrode 11 may be any conductive material, for example, Pt, Cr, A, Nb, Ru, Ti, Ta, Al, W, C, Si, Ni, Ag, pd, etc. Cu, Ru0 _2, ITO and the like. Of these, corrosion-resistant materials such as Au, Pt, Ta, Nb, Cr, and Ti are preferred, assuming that the humidity measurement environment is a corrosive environment. Pt is particularly preferred.

Although the thickness of the first electrode 11 is not particularly limited, it is usually set to about 0.02 to 1 μπι in consideration of conductivity.

Then, as shown in FIG. 3, the polymer film 12 is formed by burying the first electrode 11. When forming the polymer film 12, first, it is made of a predetermined material and adjusted to a predetermined viscosity. Prepare a conditioned resin solution. Then, the resin liquid is applied on the substrate 10 and the first electrode 11 at an appropriate temperature, for example, by a spin coating method as shown in FIG. Next, the coating film is cured by drying at an appropriate temperature to form the polymer film 12. In this process, a polymer film having a desired thickness can be obtained by adjusting the applied thickness of the resin solution.

The constituent material of the polymer film 12 may be any material having electrical insulation properties and moisture-sensitive properties, such as polyimide, polysulfone, polyethersulfone, polyetherimide, polyether, and the like. Organic macromolecules such as polyamide imide, poly phenol oxide, polycarbonate, polymethyl methacrylate, polybutylene terephthalate, polyethylene terephthalate, polyethylene ethole ketone, poly etheno ketone, cellulose acetate butyl, cellulose acetate, etc. Crosslinked polymer materials can be given.

Among them, a crosslinked polyimide which is resistant to deterioration even in a corrosive environment and has a long-term stable moisture-sensitive property is preferable.

The capacitance of the sensor having the capacitor structure has a relationship inversely proportional to the thickness of the polymer film 12. Therefore, if the thickness of the polymer film is too large, the accuracy of the detection signal is reduced. Conversely, if the thickness is too small, the homogeneity and insulation of the film will be degraded, leading to a reduction in reliability. For these reasons, it is generally preferable to set the film thickness to about 0.5 to 10 μιη.

Further, as shown in FIG. 4, a second electrode 13 having a porous structure or a network structure is formed on the polymer film 12 by using, for example, a vacuum evaporation method and a sputtering method. The three stacked portions are the sensor body 15.

Examples of the electrode material used as the second electrode 13 include Cr, Au, Pt, Nb, Ru, Ti, Ta, Al, W, C, Si, Ni, Ag, Pd, and Cu. Of these, Cr has excellent corrosion resistance, and at the same time, fine cracks occur during film formation or in later processes. It is easy to have porous structure. Therefore, it is suitable as the second electrode 13 because the humidity response of the sensor is improved.

If the thickness of the second electrode 13 is too large, the humidity responsiveness is reduced. On the other hand, if the thickness of the electrode 13 is too small, the film becomes an island-like structure and the conductivity as an electrode is reduced. Therefore, the thickness of the electrode 13 is usually set to about 10 to 300 nm.

Next, as shown in FIG. 5, the surface other than the portion where the through hole is to be formed is formed with a resist mask 14 on the lower surface 10c of the substrate 10 (the surface opposite to the surface on which the sensor body 2 is located) by using, for example, photolithography technology. Cover.

Then, the exposed lower surface 1 Ob of the first electrode 11 is applied to the lower surface 1 Ob of the first electrode 11 by using, for example, inductively-coupled plasma (ICP) dry etching. The substrate material is removed up to. Of course, depending on the substrate material, a wet etching method may be used. As a result, a through hole 10a as shown in FIG. 1 is formed in the substrate 10, and the lower surface 11a (the lower surface side in the figure) of the first electrode 11 is exposed from the upper portion.

Finally, as shown in FIG. 1, the end of the polymer film 12 is removed to expose the end surface of the first electrode 11, to which the lead wire 3 a is connected, and the second The sensor A1 is manufactured by connecting the lead wire 3b to the end of the electrode 13.

In the case of this sensor A1, the sensor main body 2 is held at the peripheral end of the substrate 10, and the first electrode 11 in the capacitor region located at the center thereof is not fixed to the substrate 10, and therefore, the capacitor The region is held hollow above the through hole 10a. When the sensor A1 is placed in a high temperature and high humidity environment, the polymer film 12 thermally expands. Since the sensor body 15 is held in the air via the first electrode 11 without being restrained by the substrate 10, the restraint on the polymer film 12 is significantly reduced.

Therefore, the thermal expansion and thermal contraction of the skeleton portion and the free volume portion also proceed while maintaining the ratio of both in the reference environment. That is, as described above, the free volume Water molecules are excessively occluded in the part, and the state does not become larger (compressive stress state) than the skeleton part. Therefore, with this sensor A1, drift deterioration in a high-temperature and high-humidity environment is suppressed.

FIG. 6 shows a sensor A2 according to another embodiment of the present invention.

In the case of this sensor A2, the first electrode 21 and a part of the polymer film 22 have a structure directly exposed to the environment. This is shown by the exposed portion 22a of the polymer film 22.

In the sensor A2, since the sensor body 2 is held hollow in the through hole 20a, the stress accumulation (water molecule accumulation) in the polymer film 22 due to thermal expansion in a high-temperature and high-humidity environment is performed similarly to the sensor A1. Is alleviated. Furthermore, since the polymer film 22 is in direct contact with the environment not only from the second electrode 23 side but also from the exposed surface 22a through the through hole 20a, the water molecules excessively occluded in the free volume portion described above. Is easily released from the environment, so that even after passing through a high-temperature, high-humidity environment, the moisture-sensitive characteristics under the standard environment can be easily reproduced. The sensor A2 also has the effect of shortening the time required to reach an equilibrium state with the relative humidity of the environment, that is, improving the humidity response of the sensor.

In addition, when the first electrode 21 has a porous structure or a mesh structure, the responsiveness from the through hole 20a side can be further improved. This method is similarly effective for the sensor A1, and the responsiveness can be further improved by using cracking Cr for both the first electrode 11 and the second electrode 13, for example. In the case of the sensor A1, since the opening formed by the through hole 10a is entirely closed by the first electrode 11 and protects the polymer film 12 from the environment, the stability of the electrical characteristics of the sensor A1 is low. Better than A2.

The sensor Al and the sensor A2 described above both have a case in which one through hole 10a, 20a is formed in the substrate 10, 20. The present invention is not limited to this embodiment. For example, FIG. As shown, the sensor A3 may have a plurality of through holes 30a formed in the substrate 30. In this case, although not shown in the drawing, the entire upper surface 30b of the substrate opened by the through hole 30a may reach the lower surface 31a of the first electrode 31, or a part of the upper surface 30b may be partially omitted. The lower surface 31a of the first electrode 31 (the lower surface side in the drawing) and the remainder may reach the lower surface 32a of the polymer film 32 (the lower surface side in the drawing). FIG. 8 shows a partial cross-sectional view thereof.

Further, as shown in FIG. 9, a structure in which a sensor body 55 having a triangular shape in a plan view, for example, is held in a hollow state on one side of a frame-shaped substrate 50 may be employed. Of course, a square or other sensor body shape is also possible, and the frame shape can be circular or otherwise.

Next, the sensor B according to the present invention will be described with reference to FIGS.

The sensors Al, A2, A3, and A5 shown in FIGS. 1 to 9 all had a multilayer structure in which the polymer body was sandwiched between two electrode layers, but the sensor body 65 of the sensor B was It has a structure in which a polymer film 62 is embedded in two thin film electrodes 61 and 63.

More specifically, as shown in FIG. 10, the sensor B has a square shape in plan view. The substrate 60 of the sensor B includes a frame 60d having a square outer shape, and a space surrounded by the frame 60d forms a rectangular through hole 60a. A sensor body 65 is formed on the substrate 60 so as to extend over one surface (upper surface) 60b of the frame 60d.

The pair of thin-film electrodes 61 and 63 of the sensor body 65 have substantially the same shape, and have a large number of comb-like teeth. In addition, the teeth are arranged with a predetermined space therebetween. The polymer film 62 is formed so as to fill a gap formed between the teeth of the electrodes 61 and 63. Therefore, as shown in the cross-sectional view of FIG. 11, the first electrode 61, the polymer film 62, and the second electrode 63 have a structure repeated many times, and the two electrode films 61, 63 and the high The molecular film 62 is formed flat with respect to the substrate surface 60b.

The space between the polymer film and the thickness of the thin film electrode is optimally determined in consideration of the number of teeth of the comb, that is, the detection sensitivity as a capacitor that depends on the total area of the two electrodes in contact with the polymer film. Designed. Therefore, the thickness of the thin film is increased (the thickness is increased) In this case, a plating method may be used instead of the above-described vacuum evaporation method / sputtering method. The sensor B is manufactured as follows. First, masking is performed on the upper surface 60b of the flat substrate 60 to form the electrodes 61 and 63 having the above shapes, and if necessary, etching is performed to form two electrodes having the shapes shown in FIG. 10 described above. Next, a polymer liquid is applied between the electrodes 61 and 63 by applying a resin liquid by, for example, a spin coat, and then hardening the resin liquid, thereby completing the sensor body 65. Then, the lower surface 60c of the substrate 60 is etched until it reaches the surface of the sensor main body 65 to form a through hole 60a.

As described above, in the sensor B, since one capacitor structure is formed by the electrodes 61 and 63 and the polymer film 62 interposed therebetween, the static electricity of the polymer film 62 accompanying occlusion and dehydration of water molecules from the environment is obtained. A change in capacitance can be extracted as a detection signal.

In this case, the polymer film 62 in the sensor body 65 behaves completely differently from the case of the polymer film 12 in the sensor A1. That is, when the sensor B is placed in a high-temperature and high-humidity environment, the polymer film 62 tends to thermally expand, but the thermal expansion is uniformly suppressed by the electrodes 61 and 63 on both sides. In other words, while the skeleton and free volume of the polymer maintain the same structure as in the reference environment, only the free volume becomes relatively larger than the skeleton even in a high-temperature, high-humidity environment. Absent.

In the case of sensor B, the thermal expansion of the polymer film is almost uniformly restrained as a whole, so that the polymer shape under the standard environment is maintained, so that only the free volume part does not increase in a high temperature environment. it is conceivable that. According to the experiment, large residual stress did not occur in the free volume even after sensor B passed through the high temperature and high humidity environment. That is, the drift deterioration of the sensor B is suppressed similarly to the sensor A.

On the other hand, since the polymer film 62 is in direct contact with the environment both from above in FIG. 11 and from below through the through-hole 60a, much more water molecules are compared to the polymer film of the sensor A. Occlusion and release easily occur. Therefore, sensor B has excellent humidity response to the environment. become.

An example of the sensor Al shown in FIG. 1 was manufactured as follows.

Pt is deposited on a glass substrate 10 having a thickness of 0.5 mm by a vacuum deposition method to form a first electrode 11 having a thickness of 500 nm (FIG. 2). C was heat-treated to form a 5 μπι-thick crosslinked polyimide polymer film 12 (Fig. 3). Then, Cr was deposited on the film 12 by sputtering to form a second electrode 13 having a thickness of 100 nm, and the sensor body 15 was disposed on the upper surface 10b of the glass substrate 10 (FIG. 4).

Next, after applying a resist to the lower surface 1 Oc of the glass substrate 10, photolithography was performed, and a frame-shaped resist mask 14 was formed at the end of the lower surface 10 c (FIG. 5).

Next, using an ICP dry etching apparatus, the structure was completely removed by etching from the exposed lower surface 10c to the lower surface 11a of the first electrode 11, and the sensor body 15 was held in the air by the glass substrate 10. Then, a part of the polyimide film 12 is removed to expose the end of the first electrode 11, and the lead wires 3a and 3b made of Cu are electrically connected to this end and the end of the second electrode 13, respectively. By connecting with an adhesive, the sensor A1 shown in FIG. 1 was manufactured.

For comparison, a sensor having a conventional structure in which the sensor body 15 is disposed on the upper surface 10b of the substrate 10 without performing the etching process on the glass substrate 10 was manufactured. This is sensor C1 (Fig. 11).

An experimental result of measurement and comparison between the sensor A1 and the sensor C1 will be described below. The measurement procedure is as follows.

(1) Capacitance measurement per 1% relative humidity between sensor A1 and sensor C1

Rere shift even when the temperature force ^S 25. In C, create an environment that is managed at 9 levels of 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90% of the humidity vs. humidity. A sensor is placed at the point where the capacitance is measured. The measurement was performed with an LCZ meter (measurement conditions: frequency 100 kHz, applied voltage 1.0 V).

The obtained capacitance value is plotted on the vertical axis, and the relative humidity is plotted on the horizontal axis. Measurement Since the constant temperature is relatively low at 25 ° C, a straight line was obtained in which the relative humidity and the detected value (capacitance) had a clear proportional relationship. The slope of this straight line indicates the amount of change in capacitance V detected by the sensor when the relative humidity changes by 1%, and its unit is (capacitance pFZl% relative humidity). As a result of the measurement, the variation V obtained for the sensor A1 and the sensor C1 was 0.2 in both cases.

(2) Capacitance comparison of sensor maintained in standard environment and high temperature and high humidity environment

From the above 9 levels of environment, the environment of temperature 25 ° C> 10% relative humidity (1), the environment of temperature 25 ° C and relative humidity 50% (11), the environment of temperature 25 ° C and relative humidity 90% ( III) was set as the reference environment and HX Ah was performed.

Sensor A1 and sensor C1 were placed in three environments, and the capacitance at that time was measured. Both sensor A1 and sensor C1 showed the same values as 192DF in the case of environment (1), 200pF in the case of environment (II), and 208pF in the case of environment (III).

Then, the sensor A1 and the sensor C1 were moved from the environment (I), (II), and (III) to a high-temperature and high-humidity environment with a temperature of 40 ° C and a relative humidity of 90%. After 1000 hours, each sensor was taken out and returned to the reference environment (I), (II), (III), and the capacitance was measured under that environment.

Then, the amount of increase in capacitance (pF) due to the history of the high-temperature and high-humidity environment and the change in capacitance per 1% relative humidity obtained in (1) above, 0.2 (pF), are used. Then, the relative humidity value Z in the reference environment after being placed in the high-temperature and high-humidity environment was calculated as follows.

For environment (I):

Z = {(Capacitance at 10% relative humidity after standing in a high temperature and high humidity environment-Capacitance at 10% relative humidity before standing in a high temperature and high humidity environment) ZO. 2} +1

0

For environment (II): Z = {(Capacitance at 50% relative humidity after standing in a high temperature and high humidity environment—Capacitance at 50% relative humidity before leaving in a high temperature and high humidity environment) /0.2} + Five

0

For environment (III):

Z = {(Capacitance at 90% relative humidity after storage in a high temperature and high humidity environment-Capacitance at 90% relative humidity before storage in a high temperature and high humidity environment) /0.2} + 9

0

The above results are shown in Fig. 13 for environment (I), Fig. 14 for environment (II), and Fig. 15 for environment (II).

In FIGS. 13 to 15, the values on the vertical axis at the zero point on the horizontal axis are the values before the sensor is left in a high-temperature, high-humidity environment in environment (1), environment (II) or environment (III). Relative humidity (% RH). This value is the same because both sensor Al and sensor C1 use the same type of polymer film.

However, after the force sensors A1 and C1 have been left in a high-temperature, high-humidity environment, they both behave as follows.

For example, in Fig. 13, after leaving sensor A1 for 200 hours, returning to the environment (I) again and measuring the capacitance, the Z value shows about 10.5, while the sensor C1 shows a Z value of about 12.1. Is shown. In other words, when the sensor Al and the sensor C1 are both left in a high-temperature and high-humidity environment for 200 hours, the detected capacitance increases as compared to before being left in a high-temperature and high-humidity environment. Z value is the reference value Z in environment (I). (Z value at the zero point on the horizontal axis) The larger the difference between the sensors, the larger the residual amount of water molecules in the polymer film.

Before being left in a high-temperature and high-humidity environment, that is, considering that the Z value in environment (I) was 10.0 for both sensor A1 and sensor C1, they were left in a high-temperature and high-humidity environment for 200 hours. As a result, the Z value of the sensor A1 increases by about 0.5 (= 10.5-10.0), and the Z value of the sensor C1 increases by 1.6 (= 12.1-10.5). That is, 0.5% R for sensor A1 It has an error of H and sensor C1 has an error of 1.6% RH. That is, it is understood that the drift deterioration of the sensor A1 is considerably suppressed as compared with the sensor C1.

It is clear from FIGS. 14 and 15 that the more the reference environment is set to the high humidity side (50%, 90%), the more the sensor A1 has a greater stress relaxation effect than the sensor C1. is there.

As is clear from the above results, the capacitance sensor of the present invention can obtain a highly reproducible relative humidity signal which does not easily cause drift deterioration even in a high temperature and high humidity environment. This is because a through-hole 10a that reaches the sensor body 15 is provided in the substrate 10 on which the sensor body 15 is disposed, so that the degree of freedom of thermal expansion of the polymer film 12 of the sensor body 15 is ensured. This is the effect of designing the sensor structure so that the free volume in the film does not easily accumulate stress due to water molecules. Similarly, a similar effect can be obtained in the sensor B.

In the above embodiment, the number of sensor bodies is limited to one. However, a plurality of sensor bodies are formed on one substrate, and each sensor body has at least one through hole. You may.

The present invention is not limited to the embodiment described above. The above description has been made on the case where the measurement target is the humidity in the environment. However, the capacitance sensor of the present invention is not limited to this. Gases that change the temperature (for example, formaldehyde, acetone, and alcohol) can be used as sensors to detect them. In short, the present invention can be implemented with various modifications without departing from the scope of the invention. Industrial applicability

ADVANTAGE OF THE INVENTION According to the present invention, it is possible to suppress drift deterioration of a conventional humidity detection sensor, and an extremely high temperature and high humidity environment such as humidity detection in a fuel cell, horticulture cultivation in facilities, weather, and food storage and drying is required. It is effective in fields such as

Claims

The scope of the claims

1. Capacitive humidity sensor consisting of:

A sensor body having first and second surfaces, the sensor body including first and second electrodes, and a polymer film interposed between the first electrode and the second electrode;

A substrate having one surface, the substrate having at least one through hole in a thickness direction; the sensor main body is held and arranged on the one surface of the substrate, and a first surface of the sensor main body is provided with the through hole. The second side is directly exposed to the environment through the holes.

2. In the sensor body, the first electrode is stacked on the one surface of the substrate, the polymer film is stacked on the first electrode, and the second electrode is stacked on the polymer film. The humidity detection sensor according to claim 1, wherein the humidity detection sensor has a laminated structure formed by

3. The humidity detection sensor according to claim 1, wherein at least one of the first electrode and the second electrode has a porous structure or a mesh structure.

4. The humidity detection sensor according to claim 1, wherein at least one of the first electrode and the second electrode is a chromium material.

5. The humidity detection sensor according to claim 1, wherein a part of the polymer film is exposed in the through hole.

6. The humidity detection sensor according to claim 1, wherein a part of a peripheral portion of the sensor main body is held by the substrate.

7. In the sensor body, the first electrode, the second electrode, and the polymer film are all formed on the one surface of the substrate, and the polymer film is filled between the first electrode and the second electrode. 2. The humidity detection sensor according to claim 1, wherein the humidity detection sensor has a flat film structure formed.

8. The humidity detection sensor according to claim 7, wherein at least one of the first electrode and the second electrode has a porous structure or a mesh structure.

9. at least one of the first electrode and the second electrode is a chromium material, The humidity detection sensor according to claim 7.

10. The humidity according to claim 1, wherein the sensor body has a plurality of the sensor bodies, the substrate holds the plurality of sensor bodies, and has at least one or more through holes corresponding to each of the sensor bodies. Detection sensor.