JP7217488B2 - Humidity sensor and manufacturing method thereof - Google Patents

Description

INDUSTRIAL APPLICABILITY The present invention is a humidity sensor, especially when it is attached to a living body or object and detects humidity with electrodes using the humidity dependence of the resistance value of a semiconductor layer or a polymer layer. The present invention relates to a humidity sensor capable of monitoring with high accuracy and suitable for attachment to a living body or an object because it can be formed on a flexible base material.

A biosignal sensing device that detects electrical signals generated from tissues such as the heart and brain can be worn and carried with bioelectrodes mounted on clothing, enabling continuous monitoring of biosignals. ing. The biosignal sensing device has a moisture replenishment mechanism that automatically replenishes the biosignal receiver with an electrolyte solution or non-electrolyte liquid when the biosignal receiver is dry. The humidity sensor of the moisture replenishment mechanism is provided inside or near the surface of the biosignal receiver, and the detection part of the humidity sensor is in contact with the biosignal receiver. Patent Document 1 discloses that a porous body made of a conductive polymer represented by PEDOT:PSS is used as a biosignal receiver.

Further, Patent Document 2 discloses a humidity sensor that utilizes the principle that a humidity sensor film containing an ionic polymer compound is formed on a pair of comb-shaped electrodes, and the electrical resistance changes when the humidity sensor material absorbs water vapor in the air. It is

Further, Patent Document 3 discloses a humidity sensor using an aniline-based conductive polymer into which an acidic group or a salt thereof is introduced. According to this method, since electrolysis does not occur, the measurement circuit does not become complicated, so that it is possible to realize a humidity sensor that operates stably even with direct-current driving, which is inexpensive and highly convenient.

Non-Patent Document 1 discloses changes in the resistance value of PEDOT:PSS, which is a semiconducting polymer material that is also used in organic transistors, depending on humidity.

Then, a semiconductor polymer material PEDOT:PSS printed on paper is used as an electrode, and after printing basic polyaniline on it, it is exposed to an atmosphere of hydrochloric acid to change the insulating property to the conductive property and the humidity of the resistance. Non-Patent Document 2 discloses an inexpensive humidity sensor that uses dependence.

JP 2014-226367 A JP 2007-163449 A JP 2011-232285 A

M. Kus, S. Okur, Sensors and Actuators B 143 (2009) 177-181. R. M. Morais, et al. , IEEE Sensors Journal (2018) 2647-2651.

The biomedical electrode disclosed in Patent Literature 1 impregnates a biomedical signal receiving portion made of a porous material with an electrolyte solution or a non-electrolyte liquid. By using PEDOT:PSS for the biosignal receiver, it is possible to efficiently retain an electrolyte solution or a non-electrolyte liquid. Then, in order to prevent the electrode impedance of the biosignal receiving part from increasing due to drying of the skin, a moisture evaporation suppressing cover covering the face of the biosignal receiving part opposite to the side in contact with the living body, an electrolyte solution or a non-electrolyte liquid, is provided. A moisture replenishment mechanism is configured to replenish the Here, the humidity replenishment mechanism is provided with a humidity sensor inside or near the surface of the biosignal receiver. However, there is no specific description of the configuration of the humidity sensor.

PEDOT:PSS impregnated with an electrolyte solution or a non-electrolyte liquid is used as a humidity sensor film, and when configuring a humidity sensor that detects with electrodes using the humidity dependence of the resistance value described in Patent Document 2, Since a means for preventing evaporation and drying of the liquid is required, the device becomes complicated and large-sized.

Patent Document 3 discloses a humidity sensor using an aniline-based conductive polymer into which an acidic group of a conductive polymer or a salt thereof is introduced, and which can stably operate even when driven by direct current. However, as shown in FIGS. 1 and 2 of the literature for humidity, the correlation of resistance to humidity change is logarithmic in form of the curve. Therefore, an arithmetic circuit is required to determine the humidity from the resistance value, and since a log amp is generally used, the circuit becomes complicated and tends to be expensive, and the accuracy tends to deteriorate.

On the other hand, the correlation of the DC resistance value with respect to the humidity change of the single semiconductor polymer material PEDOT:PSS is shown in Fig. As indicated by 6, there is a difference in resistance value between when the humidity rises and when the humidity falls, even if the humidity is the same.

Further, the humidity sensor disclosed in Non-Patent Document 2 utilizes the resistance value of polyaniline against changes in humidity, and does not use the resistance value of PEDOT:PSS as a humidity sensor film. Furthermore, although there is a description of a low frequency, DC drive tends to cause unstable operation.

An object of the present invention is to solve the above problems, and a semiconductor polymer layer suitable for integration with a sensing circuit, a wireless communication circuit, etc. formed using an organic semiconductor is used as a moisture sensitive body, and a flexible substrate is used. It can be formed thinly and flexibly by coating on top, making it excellent for sticking to living bodies and objects.It suppresses the difference in resistance value when measuring DC voltage when the humidity rises and when the humidity falls, and the correlation between the resistance value and the humidity change is improved. To provide a humidity sensor suitable for easily and accurately monitoring changes in humidity over time because it becomes a linear type.

The present invention is a humidity sensor comprising a flexible substrate comprising plastic; a first electrode layer patterned on the substrate; a second electrode layer, a semiconductor polymer layer overlapping the first electrode layer and the second electrode layer in plan view, and an insulating polyaniline polymer layer covering at least a portion of the semiconductor polymer layer. A DC voltage is applied between the first electrode layer and the second electrode layer, and the current between the first electrode layer and the second electrode layer is measured to calculate the resistance value.

In this humidity sensor, by providing an insulating ponyaniline polymer layer that covers at least a part of the semiconductor polymer layer, the difference in resistance value that occurs when the humidity rises and when the humidity falls is suppressed. humidity changes can be monitored.

When only the semiconducting polymer layer is used as the moisture-sensitive film, a sharp rise in resistance value is observed in a high-humidity region due to the accumulation of moisture in the film. In this case, it is presumed that the permeation of moisture into the semiconductor polymer layer is adjusted, a steep increase in resistance is suppressed in a high humidity region, and a linear resistance value change is exhibited.

The present invention is a humidity sensor, wherein the semiconducting polymer layer consists of poly-3,4-ethylenedioxythiophene (PEDOT:PSS) film doped with poly-4-styrenesulfonic acid, and the insulating polyaniline polymer layer is characterized by consisting of basic polyaniline.

In particular, in the case of a laminated structure consisting of a hydrophilic PEDOT:PSS film and an insulating basic polyaniline film, the PEDOT:PSS is neutralized by the basic polyaniline in the vicinity of the lamination interface to make it hydrophobic. , a hydrophilic layer of insulating basic polyaniline, a hydrophobic layer at the lamination interface, and a three-layer structure of PEDOT:PSS serving as a conductor is formed. As a result, the permeation of moisture into PEDOT:PSS is adjusted, a steep increase in resistance is suppressed in a high-humidity region, and the resistance value changes linearly.

Furthermore, in this temperature sensor, the semiconductor polymer layer is made of PEDOT:PSS film, and the insulating film polyaniline polymer layer is made of basic polyaniline. preferable.

Since the humidity sensor of the present invention uses a semiconductor polymer layer as a moisture sensitive element, it is suitable for integration with a sensing circuit, a wireless communication circuit, or the like formed using an organic semiconductor. A thin and flexible humidity sensor can be formed by coating on a flexible base material, so it is excellent for attaching to living organisms and objects, and by measuring DC voltage, the difference in resistance value is suppressed between when the humidity rises and when the humidity falls. In addition, since the correlation of the resistance value with respect to the humidity change becomes linear, it is possible to easily and accurately monitor the change in humidity over time.

1 is a cross-sectional view for explaining the configuration of a humidity sensor according to the present invention; FIG. FIG. 4 is a diagram showing the time change of the resistance value with respect to the humidity change of the humidity sensor according to the present invention; FIG. 4 is a diagram showing the correlation between humidity change and resistance value of the humidity sensor according to the present invention; FIG. 4 is a cross-sectional view for explaining the configuration of a humidity sensor having only a semiconductor polymer layer as a comparative example. FIG. 4 is a diagram showing the time change of the resistance value with respect to the humidity change of a humidity sensor having only a semiconductor polymer layer as a comparative example. FIG. 4 is a diagram showing the correlation between humidity change and resistance value of a humidity sensor having only a semiconductor polymer layer as a comparative example. FIG. 4 is a graph showing the correlation between the humidity change and the resistance value of a humidity sensor having only a semiconductor polymer layer as a comparative example in semi-logarithm.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. A humidity sensor according to the present invention comprises a flexible substrate comprising plastic, a first electrode layer patterned on the substrate, and a second electrode layer patterned on the substrate spaced apart from the first electrode layer. Consists of a two-electrode layer, a semiconductor polymer layer overlapping the first electrode layer and the second electrode layer in plan view, and an insulating polyaniline polymer layer covering at least a portion of the semiconductor polymer layer, A DC voltage is applied between the first electrode layer and the second electrode layer, and the current between the first electrode layer and the second electrode layer is measured to calculate the resistance value.

FIG. 1 illustrates the basic configuration of a humidity sensor according to the present invention. A first electrode layer 2 and a second electrode layer 3 are formed on the surface of a base material 1, a semiconductor polymer layer 4 overlapping the first electrode layer 2 and the second electrode layer 3, and finally a semiconductor polymer layer 4. A humidity sensor is constructed by forming an insulating polyaniline polymer layer 5 covering the .

A DC voltage is applied to the first electrode layer 2 and the second electrode layer 3 via a power source (not shown), and the resistance value is calculated from the detected current value to correspond to the humidity.

Examples of materials for the base material 1 include resins such as polyethylene naphthalate, polyethylene terephthalate, polyethylene, polyimide, and polyparaxylylene (parylene (registered trademark)), paper, and the like.

Examples of materials that can be used for the first electrode layer 2 and the second electrode layer 3 include gold, silver, copper, platinum, aluminum, carbon, and indium tin oxide (ITO). By using gold, it is possible to form a thin and flexible film in the process of vacuum-depositing the gold-containing material, and it is stable against oxidation-reduction, which is preferable. Alternatively, by using silver, it is possible to print a silver nanoparticle-dispersed ink to form a film in a low-temperature process, which broadens the selection of substrates, and is also excellent in mass productivity, which is preferable.

As a material for the semiconductor polymer layer 4, for example, poly-3,4-ethylenedioxythiophene (PEDOT:PSS) doped with poly-4-styrenesulfonic acid, polyaniline, polypyrrole, or the like can be used. PEDOT:PSS is suitable for integration with a circuit formed using an organic semiconductor, and can be easily formed into a film by coating or printing, so it is preferable.

As the material for the insulating polyaniline polymer layer 5, basic polyaniline is preferable because it can be expected to have a hydrophobizing effect by neutralization at the interface with PEDOT:PSS.

EXAMPLES The present invention will now be described in more detail based on examples, but the present invention is not limited to the following examples.

FIG. 1 is a cross-sectional view for explaining the configuration of a humidity sensor according to the present invention. Gold (thickness: 50 nm) was vapor-deposited on a polyethylene naphthalate (PEN) film (thickness: 120 μm) of the base material 1 using a vacuum vapor deposition apparatus through a through-hole mask to form the first electrode layer 2 and the second electrode layer 2 . A pattern with the electrode layer 3 was produced. The shape of the electrode pattern is not limited to this, but the electrode width of the first electrode layer 2 and the second electrode layer 3 is 1 to 3 mm, and the distance between the first electrode layer 2 and the second electrode layer 3 is 2 mm. and

Poly-4-styrenesulfonic acid-doped poly-3,4-ethylenedioxythiophene (PEDOT :PSS) and baked at 120° C. for 60 minutes to form a semiconductor polymer layer 4 having a thickness of 5 μm. Finally, using a dispenser device (manufactured by Musashi Engineering Co., Ltd.) so as to cover the semiconductor polymer layer 4, basic polyaniline is applied and baked at 100 to 120° C. for 60 minutes to form an insulating polyaniline having a thickness of 1 to 5 μm. A polymer layer 5 was formed.

In this humidity sensor, the semiconductor polymer layer 4 is made of PEDOT:PSS, and the insulating polyaniline polymer layer 5 is made of basic polyaniline.

Since the first electrode layer 2 and the second electrode layer 3 are formed by vapor deposition of gold, they are very stable against heat, humidity, oxygen, and chemical corrosion caused by acids, alkalis, etc. It is preferable because an electrode with excellent conductivity can be formed.

FIG. 4 is a cross-sectional view for explaining the configuration of a humidity sensor as a comparative example. The only difference from the embodiment of the humidity sensor shown in FIG. 1 is that the insulating polyaniline polymer layer 5 is not provided.

Next, a detection method using the humidity sensor of the present invention will be described in detail. Control of the voltage between the first electrode layer 2 and the second electrode layer 3 and measurement of the current between the first electrode layer 2 and the second electrode layer 3 were performed using a 2400 Source Meter device (manufactured by KEITHLEY). gone. A DC voltage was used as the voltage to be applied. By using a direct current voltage, the circuit configuration can be simplified, which is advantageous because it is cheaper and more convenient, and the device can be made smaller and wearable.

FIG. 2 is a diagram showing the time change of the resistance value with respect to the humidity change of the humidity sensor of the embodiment, FIG. 3 is a diagram showing the correlation between the humidity change and the resistance value of the humidity sensor according to the present invention, and FIG. FIG. 6 is a graph showing the time change of the resistance value with respect to the humidity change of the humidity sensor with only the molecular layer, FIG. 6 is a graph showing the correlation between the humidity change and the resistance value of the humidity sensor with only the semiconductor polymer layer as a comparative example, and FIG. 7 is the comparative example. is a diagram showing the correlation between the humidity change and the resistance value of the humidity sensor having only the semiconductor polymer layer as a semi-logarithm. All show measurement data at an environmental temperature of 35°C.

First, FIGS. 2 and 5 will be described in detail. The humidity sensors of Examples and Comparative Examples were installed in a Temperature & Humidity Chamber device (manufactured by ESPEC), the humidity was increased from 20%rh to 80%rh at intervals of 10%rh, and then from 80%rh to 20%rh. Humidity was lowered at intervals of 10%rh to . A DC voltage of 0.1 V was applied between the first electrode layer 2 and the second electrode layer 3, and the current between the first electrode layer 2 and the second electrode layer 3 was measured to calculate the resistance value. .

Since the digits of the resistance value differ between the example and the comparative example, the difference in the resistance value when the humidity rises and when the humidity falls at 20%rh is expressed as a ratio using the following formula for comparison.
H = (|Rr−Rf|/Rr)×100
H: ratio, Rr: resistance value of 20%rh when rising, Rf: resistance value of 20%rh when falling

As a result, with the humidity sensor of the comparative example shown in FIG. It was reduced to a difference of 2.3 when the humidity was increased and when the humidity was decreased. This means that, in the humidity sensor of the embodiment, by providing the insulating polyaniline polymer layer 5, it is possible to suppress the difference in the resistance value of the semiconductor polymer layer 4 between when the humidity rises and when the humidity falls. In other words, it can be seen that the change in resistance due to humidity can be prevented from becoming unstable. Therefore, since it is possible to suppress the difference in the resistance value between when the humidity rises and when the humidity falls, it is possible to accurately monitor changes in humidity over time.

3 and 6 will now be described in detail. 2 shows the correlation between the humidity change and the resistance value when the humidity rises and when the humidity falls for the humidity sensors of the example and the comparative example. The humidity sensor of the comparative example shown in FIG. 6 shows a curve with a different curvature when the humidity rises and when the humidity falls when the change in resistance value with respect to humidity changes. Since the correlation of the resistance value with respect to the humidity change is a logarithmic curve, it can be linearized as shown in FIG. 7 by semi-logarithmizing the resistance value. The result is 0.999, and the correlation between when the humidity rises and when the humidity falls is not good. For this reason, an arithmetic circuit for obtaining the humidity from the resistance value is required, and since a log amp or the like is generally used, the circuit becomes complicated, expensive, and tends to deteriorate in accuracy. On the other hand, the resistance value of the humidity sensor of the embodiment shown in FIG. A correlation was observed. Therefore, since the correlation of the resistance value with respect to the humidity change becomes linear, the humidity can be obtained easily and accurately from the resistance value with a simple circuit.

As described above, in the humidity sensor of the embodiment, by providing the insulating polyaniline polymer layer 5, the resistance of the semiconductor polymer layer 4 is prevented from being different between when the humidity rises and when the humidity falls. Since the resistance value can be suppressed and the correlation of the resistance value to the humidity change becomes linear, the change in humidity over time can be monitored with high accuracy, and the humidity can be easily and accurately obtained from the resistance value with a simple circuit.

Here, the first electrode layer 2 and the second electrode layer 3 are formed by printing silver nanoparticle-dispersed ink, and the substrate 1 is made of polyethylene terephthalate (PEN), which has lower heat resistance than polyethylene naphthalate (PEN). A humidity sensor was produced in the same manner as in the above example, except that PET) was used. Also in this humidity sensor, it is possible to suppress the difference in the resistance value between when the humidity rises and when the humidity falls, as in the case of the embodiment, and the correlation between the humidity change and the resistance value is also good as in the case of the embodiment. It was confirmed that it was linear.

By forming the first electrode layer 2 and the second electrode layer 3 by printing silver nanoparticle-dispersed ink, the treatment temperature in the process can be lowered, so the heat resistance restriction of the base material 1 is relaxed, and polyethylene terephthalate ( PET) film or the like can be used, and can be provided at a low cost.

Since the humidity sensor described above can be formed on the flexible base material 1, it is excellent in attachment to a living body or object, and the difference in resistance value when the humidity rises and when the humidity falls is measured by DC voltage measurement. is suppressed, and the correlation of the resistance value with respect to the humidity change becomes linear, so the change in humidity over time can be monitored easily and accurately. In addition, the humidity sensor substrate 1 can be effectively integrated with a sensing circuit, a wireless communication circuit, or the like using an organic semiconductor.

1 base material 2 first electrode layer 3 second electrode layer 4 semiconductor polymer layer 5 insulating polyaniline polymer layer

Claims (4)

A DC voltage is applied between the first electrode layer and the second electrode layer on the base material,
A humidity sensor for calculating a resistance value of a semiconductor polymer layer by measuring a current between the first electrode layer and the second electrode layer,
a flexible substrate comprising plastic;
a first electrode layer patterned on the substrate;
a second electrode layer patterned on the substrate spaced apart from the first electrode layer;
a semiconductor polymer layer overlapping the first electrode layer and the second electrode layer in plan view;
an insulating polyaniline polymer layer covering at least a portion of the semiconductor polymer layer;
A humidity sensor consisting of: The humidity sensor of claim 1, wherein
The semiconducting polymer layer consists of a poly-3,4-ethylenedioxythiophene (PEDOT:PSS) film doped with poly-4-styrenesulfonic acid,
The humidity sensor, wherein the insulating polyaniline polymer layer is made of basic polyaniline. A DC voltage is applied between the first electrode layer and the second electrode layer on the base material,
A humidity sensor manufacturing method for calculating a resistance value of a semiconductor polymer layer by measuring a current between the first electrode layer and the second electrode layer,
forming a patterned first electrode layer on a flexible substrate comprising plastic;
forming a patterned second electrode layer spaced apart from the first electrode layer;
forming a semiconductor polymer layer overlapping the first electrode layer and the second electrode layer in plan view;
forming an insulating polyaniline polymer layer covering at least a portion of the semiconductor polymer layer;
A method of manufacturing a humidity sensor comprising: In the method for manufacturing a humidity sensor according to claim 3,
The step of forming the semiconductor polymer layer includes applying poly-3,4-ethylenedioxythiophene (PEDOT:PSS) doped with poly-4-styrenesulfonic acid,
The method for manufacturing a humidity sensor, wherein the step of forming the insulating polyaniline polymer layer includes the step of applying basic polyaniline.

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