JP2017219336A - Pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic pressure sensor suitable for the realization of increased sensitivity.SOLUTION: Provided is a pressure sensor 1 comprising: an organic field-effect transistor 20 including laminate in which a gate electrode 21, a gate insulating film 22 and an organic semiconductor layer 23 are laminated in the order stated; a pressure sensitive unit 20 including an organic piezoelectric layer 31 and arranged opposite the gate insulating film 22 as seen from the organic semiconductor layer 23; and a power supply 41 connected to the gate electrode 21 for applying a gate voltage Vg to the gate electrode 21. In the pressure sensor 1, the organic piezoelectric substance included in the organic piezoelectric layer 31 is polarized so that the positive and negative signs of electric charges 30c closest to the organic semiconductor layer 23 that are accumulated in the pressure sensitive unit 30 due to that the pressure to be detected is applied to the pressure sensitive unit 30 and the organic piezoelectric layer 31 is compressed in its thickness direction are in inverse to those of the gate voltage Vg.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a so-called organic pressure sensor, specifically, a pressure sensor using an organic semiconductor.

  Since organic pressure sensors are rich in flexibility, they are expected to be applied to flexible large-area pressure sensors. An active organic pressure sensor, which is one of the driving methods of an organic pressure sensor, detects the pressure applied to the pressure sensing unit using an organic transistor, specifically, an organic field effect transistor (OFET) (for example, non-pressure sensor). Patent Document 1).

Y. Zang et al., "Flexible suspended gate organic thin-film transistors for ultra-sensitive pressure detection", Nature Communications, 6, 6269 (2015)

  Organic pressure sensors are required to reduce drive voltage and increase sensitivity. In particular, increasing the sensitivity is an inevitable problem in expanding the application of organic pressure sensors and promoting their practical application. Accordingly, an object of the present invention is to provide a novel organic pressure sensor suitable for realizing high sensitivity, particularly a novel organic pressure sensor capable of detecting pressure with high sensitivity even when driven at a low voltage.

As a first aspect of the present invention,
An organic field effect transistor having a laminate in which a gate electrode, a gate insulating film, and an organic semiconductor layer are laminated in this order;
A pressure-sensitive portion having an organic piezoelectric layer and disposed on the side opposite to the gate insulating film as viewed from the organic semiconductor layer;
A power source connected to the gate electrode to apply a gate voltage Vg to the gate electrode,
When the pressure to be detected is applied to the pressure sensitive part and the organic piezoelectric layer is compressed in the thickness direction, the charge closest to the organic semiconductor layer accumulated in the pressure sensitive part is the gate voltage Vg. There is provided a pressure sensor in which an organic piezoelectric body included in the organic piezoelectric layer is polarized so that the signs of the positive and negative signs are reversed.

  ADVANTAGE OF THE INVENTION According to this invention, the organic pressure sensor suitable for realization of high sensitivity can be provided.

It is sectional drawing which shows an example of the pressure sensor of this invention. It is a figure for showing the electric charge which arises in the pressure sensitive part of the pressure sensor shown in FIG. It is sectional drawing shown with the pressure sensing part produced separately as an example of the incomplete pressure sensor before a pressure sensing part is arrange | positioned. It is a figure which shows the gate voltage (Vg) -drain current (Id) characteristic of the incomplete pressure sensor (organic field effect transistor) shown to FIG. 3A. It is sectional drawing which shows an example of the pressure sensor which has arrange | positioned and comprised the pressure sensitive part on the incomplete pressure sensor shown to FIG. 3A. It is a figure which shows the Vg-Id characteristic of the pressure sensor shown to FIG. 4A. It is a figure which shows the state which applied the pressure to the pressure sensitive part of the pressure sensor shown to FIG. 4A. It is a figure which shows the Vg-Id characteristic which changes according to the pressure of the pressure sensor shown to FIG. 5A. It is a figure which shows the tendency of a Vg-Id characteristic to change with the signs of the electric charge nearest to the organic-semiconductor layer accumulate | stored in a pressure sensitive part. It is a figure which shows the example of the measured value of the Vg-Id characteristic which changes according to the pressure of the pressure sensor by this invention. It is a figure which shows the example of a measurement of the pressure responsiveness of Id of the pressure sensor by this invention.

  From the second aspect of the present invention, the current I (PX) flowing in the organic semiconductor layer by applying the gate voltage Vg in a state where the pressure is applied is not applied in the state where the pressure is applied. The pressure sensor according to the first aspect, which is smaller than the current I (P0) flowing through the organic semiconductor layer by applying the gate voltage Vg, is provided.

  According to a third aspect of the present invention, there is provided the pressure sensor according to the second aspect, wherein the current I (P100) when the pressure is 100 kPa is not more than 0.1 times the current I (P0). .

  According to a fourth aspect of the present invention, there is provided the pressure sensor according to the second aspect, wherein the current I (P300) when the pressure is 300 kPa is 0.01 times or less of the current I (P0). .

  From the fifth aspect of the present invention, the current I (PMAX) when the maximum value PMAX of the pressure measurement range set for measuring the pressure is applied is 50% or less of the current I (P0). There is provided the pressure sensor according to any one of the second to fourth aspects, in which the gate voltage Vg is set.

  From the sixth aspect of the present invention, a gate voltage setting unit that sets the gate voltage Vg based on a pressure measurement range set for measuring the pressure, and the gate voltage determined by the gate voltage setting unit There is provided a pressure sensor according to any one of the second to fifth aspects, further comprising a pressure calculation unit that calculates a value of the pressure from Vg and the current I (PX).

  According to a seventh aspect of the present invention, there is provided the pressure sensor according to any one of the first to sixth aspects, wherein the absolute value of the gate voltage Vg is 5 V or less.

  According to an eighth aspect of the present invention, there is provided the pressure sensor according to any one of the first to seventh aspects, wherein the charge is a surface charge accumulated on the surface of the pressure sensitive part.

  According to a ninth aspect of the present invention, there is provided the pressure sensor according to the eighth aspect, wherein the surface of the pressure sensitive part is in contact with a gap between the organic semiconductor layer and the pressure sensitive part.

  From the tenth aspect of the present invention, there is provided the pressure sensor according to any one of the first to ninth aspects, further comprising a layer in contact with the organic piezoelectric layer and grounded.

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the accompanying drawings, but the following description is an example and does not limit the present invention.

  The pressure sensor 1 shown in FIG. 1 includes an organic field effect transistor 20 that functions as a reading unit, a pressure sensitive unit 30 disposed on the organic field effect transistor 20, and power supplies 41 and 42 connected to the organic field effect transistor 20. And. The organic field effect transistor 20 is formed on the substrate 10.

  The organic field effect transistor 20 includes a stacked body in which a gate electrode 21, a gate insulating film 22, and an organic semiconductor layer 23 are stacked in this order. The organic field effect transistor 20 further includes a source electrode 24 and a drain electrode 25. The source electrode 24 and the drain electrode 25 are disposed in contact with the organic semiconductor layer 23 and spaced apart from each other. Similarly to the organic semiconductor layer 23, the source electrode 24 and the drain electrode 25 are formed on the surface so as to be in contact with the surface of the gate insulating film 22. The source electrode 24 and the drain electrode 25 have a thickness smaller than that of the organic semiconductor layer 23, and an organic semiconductor is deposited thereon. The source electrode 24 and the drain electrode 25 are sandwiched between the gate insulating film 22 and a part of the organic semiconductor layer 23.

  A power source 41 for applying a predetermined gate voltage Vg is connected to the gate electrode 21. The source electrode 24 and the drain electrode 25 are connected to a wiring for applying a source / drain voltage. A power source 42 is disposed on this wiring. Each power source 21, 24, 25 may be constituted by, for example, a connection mechanism to a commercial power source and an AC-DC conversion circuit.

  The pressure sensitive unit 30 includes an organic piezoelectric layer 31 and a layer 32, and the organic piezoelectric layer 31 is disposed on the organic semiconductor layer 23 side. Layer 32 is preferably grounded to reduce electrical noise, at least when measuring pressure.

  The pressure-sensitive part 30 is formed by depositing the organic piezoelectric layer 31 on the layer 32. After this deposition, the organic piezoelectric layer 31 is placed on the organic semiconductor layer 23 with the organic piezoelectric layer 31 side. And stacked. For this reason, unlike the case where the organic piezoelectric layer 23 is formed by applying an organic piezoelectric body on the organic semiconductor layer 23, the organic semiconductor layer 23 and the pressure-sensitive portion 30 are not completely adhered to each other. . That is, a minute gap is interposed between the organic semiconductor layer 23 and the pressure sensitive part 30, and the surface 30 s of the pressure sensitive part 30 is in contact with this gap.

  The organic piezoelectric body included in the organic piezoelectric layer 31 is previously polarized by a voltage applied along the thickness direction of the layer 31. In the organic piezoelectric material, when an external pressure is applied to the organic piezoelectric material layer 31 along the thickness direction, the charge acting on the organic semiconductor layer 23 from the pressure-sensitive portion 30 is opposite in sign to the gate voltage. That is, the polarization processing is performed so as to be positive in the present embodiment. As the pressure increases, the degree of charge acting on the organic semiconductor layer 23 increases.

  This charge may not substantially act on the organic semiconductor layer 23 in a state where no pressure is applied to the pressure-sensitive portion 30, or may act on the organic semiconductor layer 23 even in this state. May be. Specifically, the degree of the action of electric charges on the organic semiconductor layer 23 can be described by the influence on the current between the source and the drain of the organic field effect transistor 20 (drain current Id).

  The charge acting on the organic semiconductor layer 23 from the pressure-sensitive portion 30 is a charge accumulated at a position closest to the organic semiconductor layer 23 of the pressure-sensitive portion 30, specifically, the organic semiconductor layer 23 of the organic piezoelectric layer 31. This is the surface charge 30c accumulated on the side surface 30s. Although the surface charge 30 c is enlarged for illustration in FIG. 2, the surface charge 30 c exists in the gap between the organic semiconductor layer 23 and the organic piezoelectric layer 31. The surface charge 30 c may be accumulated on the surface of a layer different from the organic piezoelectric layer 31, for example, a layer added to the organic semiconductor layer 23 side of the organic piezoelectric layer 31.

  In FIG. 2 that also shows the charges accumulated in the pressure-sensitive portion 30, the surface charge 31c is indicated by positive and negative signs surrounded by a circle, and the charge or polarization state inside the organic piezoelectric layer 31 is indicated by a circle. It is indicated by a positive or negative sign that is not enclosed. The organic piezoelectric layer 31 is polarized so that the lower side of the organic semiconductor layer 23 on the side of the organic semiconductor layer 23 is negatively polarized, and positive charges are supplied from the surrounding environment by this polarization processing to accumulate the surface charge 30c. . In the illustrated form, the negative surface charge existing above the pressure-sensitive portion 30 is accumulated on the surface of the layer 32 that is a semiconductor layer.

  Pressure detection by the pressure sensor 1 is performed in a state where a gate voltage Vg for flowing a current in the organic semiconductor layer 23 is applied to the gate electrode 21, that is, in a state where the organic field effect transistor 20 is turned on. In this state, as the external pressure applied to the organic piezoelectric layer 31 increases from 0, the influence of the charge 30c on the channel formed in the organic semiconductor layer 23 increases, and the drain current Id Will decrease.

  That is, in the pressure sensor 1, the drain current I (PX) in the organic semiconductor layer 23 that flows by applying the gate voltage Vg in a state where the pressure PX is applied is (P = 0) in a state where the pressure is not applied (P = 0). It becomes smaller than the drain current I (P0) in the organic semiconductor layer 23 that flows by application of the gate voltage Vg (of the same magnitude). This corresponds to the fact that as the pressure PX increases, the charge 30c of the pressure-sensitive portion 30 acts on the organic semiconductor layer 23 as a gate voltage having a sign opposite to that of the gate voltage Vg.

  When the pressure sensitive part 30 is arranged on the organic field effect transistor 20 (FIG. 4A), a curve (Vg-Id curve) showing a gate voltage (Vg) -drain current (Id) characteristic of the transistor 20 (FIG. 3A) before arrangement. FIG. 3B) shifts so that the absolute value of the so-called threshold voltage increases (FIG. 4B). When the pressure 50 is applied to the pressure sensing unit 10 (FIG. 5A), the Vg-Id curve shifts to the left side in the figure so that the absolute value of the threshold voltage is further increased (FIG. 5B). The Vg-Id curve moves to the left in the figure as the pressure increases. From FIG. 5B, in a state where a predetermined gate voltage is applied, the drain current I (PX) is a one-to-one function of the pressure PX applied to the pressure-sensitive portion 30, in other words, the drain current I (PX). It can be understood that the magnitude PX of the pressure 50 can be specified by measuring.

  The Vg-Id curve (FIG. 4B) of the pressure sensor 1 in the state where the pressure 50 is not applied (FIG. 4A) is the Vg-Id curve (FIG. 3B) of the organic field effect transistor 20 measured without the pressure-sensitive portion 30. ) May be substantially the same.

  As the pressure 50 increases, the polarization of the organic piezoelectric body in the organic piezoelectric layer 31 increases, and as a result, the amount of surface charge increases (FIG. 5A). For this reason, the drain current decreases as the pressure 50 is applied. In addition, the gap between the organic semiconductor layer 23 and the organic piezoelectric layer 31 is narrowed by the application of the pressure 50, and the surface charge 30 c becomes closer to the organic semiconductor 23. It is considered that the narrowing of the air gap also contributes to the reduction of the drain current.

  Contrary to the above-described embodiment, when the sign of the surface charge 30c is the same negative as the gate voltage, the Vg-Id curve is shifted to the right side in the drawing as the pressure is applied. An example of actual measurement is shown in FIG. In FIG. 6, the measurement curve A in the state where there is no influence of the charge 30c shifts in the direction of the arrow C as the pressure increases when the sign of the charge 30c is the same as the gate voltage. FIG. 6 shows a plurality of sets of Vg-Id curves measured by applying the same magnitude of pressure with the charges 30c having opposite signs.

  There is a limit to the amount of charge accumulated in the pressure-sensitive portion 30 as the organic piezoelectric layer 31 is compressed. For this reason, even if a pressure is applied exceeding a predetermined limit value, the Vg-Id curve does not shift any more. Referring to FIG. 6, in order to realize a higher sensitivity of the pressure sensor by changing the drain current more greatly by applying a predetermined pressure, a charge having a sign opposite to that of the gate voltage Vg is applied to the organic semiconductor layer 23. It can be seen that it is advantageous to act to shift the Vg-Id curve in the direction of arrow B.

  According to the pressure sensor 1, for example, the drain current Id (P100) when the pressure 50 applied to the pressure sensing unit 30 is 100 kPa flows by applying the same gate voltage Vg in a state where no pressure is applied. The drain current Id (P0) can be reduced to 0.1 times or less. According to the pressure sensor 1, for example, the drain current Id (P300) when the pressure 50 applied to the pressure sensing unit 30 is 300 kPa can be 0.01 times or less of the drain current Id (P0). Moreover, the absolute value of the gate voltage Vg necessary for detecting the pressure 50 with such high sensitivity is sufficient to be 5 V or less.

  The gate voltage Vg applied to the gate electrode 21 may be 5 V or less, further 3 V or less, particularly 1 V or less.

  The gate voltage Vg may be determined based on the range of pressure to be detected. Specifically, the drain current Id (PMAX) when the maximum value PMAX of the pressure measurement range set for measuring the pressure is applied is the drain current Id (P0) when no pressure is applied. It is preferable to set it to be 50% or less, further 10% or less, particularly 5% or less, particularly 1% or less. However, when it is sufficient to measure a pressure in a very limited range, the gate voltage Vg may be set to such an extent that Id (PMAX) is 90% or less of Id (P0). The gate voltage Vg is such that the drain current Id (PMAX) is 0.0001% or more, further 0.001% or more, particularly 0.01% or more of the drain current Id (P0) when no pressure is applied. It is preferable to set so that.

  The pressure sensor 1 may further include a gate voltage setting unit for setting the gate voltage Vg to an appropriate value. Based on the pressure measurement range set to measure the pressure to be detected, the gate voltage setting unit, for example, so that the value of the drain current Id (PMAX) at the maximum value PMAX in the range falls within the preferable range described above. Is set to the gate voltage Vg. The gate voltage setting unit is, for example, a switching device that connects a single or a plurality of power supplies selected from a plurality of power supplies to the gate electrode, a transformer device for changing the voltage of the power supply to a predetermined value, and the like. Since the configuration necessary for the gate voltage setting unit is well known, further description is omitted here.

  The gate voltage setting unit may set the gate voltage Vg based on the pressure measurement range input or selected by the user using the measurement range setting unit that the pressure sensor 1 may further include.

  The pressure sensor 1 preferably further includes a pressure calculation unit that calculates the applied pressure 50 from the measured drain current I (PX). For example, the pressure calculation unit calculates the magnitude of the pressure PX based on the gate voltage Vg, the drain current I (PX), and the current-pressure conversion table. The pressure calculation unit can be configured using, for example, a CPU (Central Processing Unit), an information storage device including various memories, and the like. Since this kind of calculation mechanism is also well known, further explanation is omitted here.

  Hereinafter, modifications of the pressure sensor 1 will be described. In the pressure sensor 1, there is a gap between the organic semiconductor layer 23 and the pressure sensitive part 30. That is, the organic piezoelectric layer 31 is formed on the layer 32 in advance, and the layer 32 is used as one electrode to apply a voltage along the thickness direction of the layer, followed by polarization treatment, and then the organic semiconductor layer 23. It is arranged above. The pressure-sensitive layer 30 can be fixed on the organic semiconductor layer 23 without requiring an adhesive or the like due to electrostatic force caused by the surface charge 30c. However, the present invention is not limited thereto, and the organic semiconductor layer 23 and the pressure sensitive part 30 may be in close contact with each other. In this case, for example, the organic piezoelectric layer 31 may be formed not on the layer 32 but on the organic semiconductor layer 23. For example, the organic piezoelectric layer 31 directly formed on the organic semiconductor layer 23 can be polarized by applying a voltage between the layer 31 and the gate electrode 21. In this case, the charge generated in the organic piezoelectric layer 31 is closest to the organic semiconductor layer 23 and becomes a charge acting on the layer 23. Therefore, the polarization process is performed so that a charge opposite to the gate voltage is generated below the organic piezoelectric layer 31. However, in the aspect in which the organic piezoelectric layer 31 is formed in advance on the layer 32, the surface charge 30c can be used, and the organic piezoelectric layer can be easily thickened. It is advantageous because it can be easily prevented and is suitable for film formation by a solution process.

  The organic field effect transistor (OFET) 20 has a so-called bottom gate / bottom contact structure. However, the present invention is not limited to this, and a top gate type or top contact type OFET may be used. When a top gate type OFET is used, a pressure sensitive part is disposed between the substrate and the OFET. However, the embodiment using the bottom gate / bottom contact structure OFET is advantageous in that the direct contact between the organic piezoelectric layer 31 and the source / drain electrodes 24 and 25 can be surely prevented.

  The material of each member which comprises the pressure sensor 1 is illustrated below. As the substrate 10, resin, ceramics, glass, semiconductor, or the like may be used. When the pressure sensor 1 is required to have flexibility, it is preferable to use a material having excellent flexibility for the substrate 10 as well. The electrodes 21, 24, and 25 may be formed using various metals and semiconductors, but a metal material is more suitable. The gate insulating film 22 may be formed of an inorganic insulating material typified by an oxide, but it is preferable to use organic materials such as various resins. An example of a preferable organic insulating material is PVC described later. For the layer 32 to be grounded at the time of pressure measurement, use of a semiconductor or metal is suitable. For the organic semiconductor layer 23 and the organic piezoelectric layer 31, it is suitable to use an organic semiconductor material and an organic piezoelectric material that are more flexible than the inorganic semiconductor and the inorganic piezoelectric body, respectively.

  The organic semiconductor material for forming the organic semiconductor layer 23 may be n-type or p-type. Organic semiconductor materials include, for example, pentacenes such as 6,13-bis (triisopropylsilylethynyl) pentacene (TIPS-pentacene), tetramethylpentacene, perfluoropentacene, TES-ADT, diF-TES-ADT (2,8 Anthradithiophenes such as -difluoro-5,11-bis (triethylsilylethynyl) anthradithiophene), benzothienobenzothiophenes such as DPh-BTBT and Cn-BTBT, and dinaphthothienothiophenes such as Cn-DNTT, Dioxaanthanthrenes such as perixanthenoxanthene, rubrenes, fullerenes such as C60 and PCBM, phthalocyanines such as copper phthalocyanine and fluorinated copper phthalocyanine, polythiophenes such as P3RT, PQT, P3HT and PQT, poly [ A 5- bis (3-dodecyl-2-yl) thieno [3,2-b] thiophene] polythienothiophenes such as (PBTTT), an example of a preferred organic semiconductor material is TIPS- pentacene. The organic piezoelectric material for forming the organic piezoelectric layer 31 is polyvinylidene fluoride (PVDF), polyvinylidene fluoride trifluoride ethylene copolymer (P (VDF-TrFE)), and a preferable organic piezoelectric material is P (VDF-TrFE).

  Hereinafter, an example of manufacturing a pressure sensor will be described. First, an Al film having a thickness of 30 nm is vacuum-deposited as a gate electrode 21 on a glass substrate prepared as the substrate 10, and then a PVC (Poly (vinyl cinnamate)) film having a thickness of 320 nm is spin-coated as a gate insulating film 22. Crosslinked by UV irradiation. Subsequently, an Ag film having a thickness of 50 nm was vacuum-deposited as the source electrode 24 and the drain electrode 25, and the surface was modified by dipping in an ethanol solution of pentafluorothiophenol (Pentafluorothiophenol). Further, a mixed semiconductor layer of TIPS-pentacene (6,13-bis (triisopropyl-silylethylenyl) pentacene) and polystyrene (PS) having a thickness of 100 nm is formed by spin coating to form an organic semiconductor layer 23, and an organic field effect transistor (OFET) was produced.

  The pressure sensitive part 30 was produced separately from the OFET 20. Specifically, a polyvinylidene fluoride trifluoride ethylene copolymer (P (VDF-TrFE)) film having a thickness of 8 μm is blade-coated on a silicon substrate 32 to form an organic piezoelectric layer 31, which is polarized by contact poling. . The contact polling voltage was 1 kV. Next, the piezoelectric film 31 side of the pressure sensitive unit 30 was placed on the OFET 20 to form a pressure sensor.

  With respect to the pressure sensor 1 manufactured by the above process, −5V is applied as the drain voltage and −1.8V is applied as the gate voltage, and the silicon substrate 32 of the pressure-sensitive part 30 is grounded to the pressure-sensitive part 30 from above. 50 was applied and the drain current Id was measured. The stress was increased by 100 kPa from 0 kPa to 400 kPa. The obtained results are shown in FIG. Moreover, the result of having measured pressure responsiveness is shown in FIG.

  As can be understood from FIG. 7, the voltage (−1.8 V) applied as the gate voltage Vg is an appropriate value when the pressure of about 400 kPa is set as the maximum measurable pressure using the manufactured pressure sensor 1. It can also be seen that if the maximum measurable pressure is less than this, the absolute value of the appropriate gate voltage Vg may be smaller. For example, when the maximum pressure that can be measured is 100 kPa, an appropriate gate voltage Vg is about −1.4V. In this case, by applying a pressure of 100 kPa, the drain current Id (P100) is reduced to a value not more than 0.1 times the drain current Id (P0) in a state where no pressure is applied.

  As shown in FIG. 8, the pressure responsiveness of the drain current Id of the manufactured pressure sensor 1 was sufficiently rapid, and the measured values were reproducible.

1 Pressure Sensor 10 Substrate 20 Organic Field Effect Transistor 21 Gate Electrode 22 Gate Insulating Film 23 Organic Semiconductor Layer 24 Source Electrode 25 Drain Electrode 30 Pressure Sensitive Part 30c Surface Charge of Pressure Sensitive Part (Charge Closest to Organic Semiconductor Layer)
30 s Pressure-sensitive part surface 31 Organic piezoelectric layer 32 (grounded) layer 41, 42 Power supply

Claims (10)

An organic field effect transistor having a laminate in which a gate electrode, a gate insulating film, and an organic semiconductor layer are laminated in this order;
A pressure-sensitive portion having an organic piezoelectric layer and disposed on the side opposite to the gate insulating film as viewed from the organic semiconductor layer;
A power source connected to the gate electrode to apply a gate voltage Vg to the gate electrode,
When the pressure to be detected is applied to the pressure sensitive part and the organic piezoelectric layer is compressed in the thickness direction, the charge closest to the organic semiconductor layer accumulated in the pressure sensitive part is the gate voltage Vg. The organic piezoelectric body included in the organic piezoelectric layer is polarized so that the positive and negative signs are reversed.
Pressure sensor.   By applying the gate voltage Vg in a state where the pressure is applied, a current I (PX) flowing in the organic semiconductor layer is applied by applying the gate voltage Vg in a state where the pressure is not applied. The pressure sensor according to claim 1, wherein the pressure sensor is smaller than a current I (P 0) flowing through the organic semiconductor layer.   The pressure sensor according to claim 2, wherein the current I (P100) when the pressure is 100 kPa is 0.1 times or less of the current I (P0).   The pressure sensor according to claim 2, wherein the current I (P300) when the pressure is 300 kPa is 0.01 times or less of the current I (P0).   The gate voltage Vg is set so that the current I (PMAX) when the maximum value PMAX of the pressure measurement range set for measuring the pressure is applied is 50% or less of the current I (P0). The pressure sensor according to claim 2, wherein the pressure sensor is provided.   A gate voltage setting unit for setting the gate voltage Vg based on a pressure measurement range set for measuring the pressure; the gate voltage Vg and the current I (PX) determined by the gate voltage setting unit; The pressure sensor according to any one of claims 2 to 5, further comprising a pressure calculation unit that calculates a value of the pressure from the pressure sensor.   The pressure sensor according to any one of claims 1 to 6, wherein an absolute value of the gate voltage Vg is 5 V or less.   The pressure sensor according to claim 1, wherein the charge is a surface charge accumulated on a surface of the pressure-sensitive portion.   The pressure sensor according to claim 8, wherein the surface of the pressure sensitive part is in contact with a gap between the organic semiconductor layer and the pressure sensitive part.   The pressure sensor according to claim 1, wherein the pressure sensitive part further includes a layer that is in contact with the organic piezoelectric layer and is grounded.

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