JP2019138741A - Pressure sensor - Google Patents

Abstract

To provide a pressure sensor that can be fixed to a curved surface due to its flexibility and can measure a pressure highly sensitively.SOLUTION: A pressure sensor 100 according to the present invention includes: a flexible substrate 10; an elastic layer 20 on the flexible substrate; and a first strain detection film 30 on the elastic layer 20.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pressure sensor.

In recent years, the usage scenes of sensors have expanded dramatically, and the number of scenes in which sensors are fixed not only on flat surfaces but also on curved surfaces with various curvatures has increased. For this reason, research on flexible wiring and sensor elements has been actively conducted (for example, Patent Documents 1 and 2 and Non-Patent Document 1).
In particular, paying attention to a flexible sensor element, a pressure sensor using a piezoresistance effect of a conductive polymer mixed with a material such as CNT has been researched and developed (for example, Non-Patent Document 2).

JP 2017-096863 A JP 2017-050355 A

J. van den Brand, M. de Kok, M. Koetse, M. Cauwe, R. Verplancke, F. Bossuyt, et al., "Flexible and stretchable electronics for wearable health devices," Solid-State Electronics, 2015, vol 113, pp. 116-120 M. Kaltenbrunner, T. Sekitani, J. Reeder, T. Yokota, K. Kuribara, T. Tokuhara, et al., "An ultra-lightweight design for imperceptible plastic electronics" Nature, 2013, vol. 499, pp. 458 -463

  However, a pressure sensor using a conductive polymer has a problem that the sensitivity of the sensor is inferior to that of a semiconductor sensor based on silicon. When a flexible pressure sensor is fixed on a curved surface, bending occurs to follow the curved surface. The bending-induced strain thus generated is detected by being combined with the pressure-derived strain. For this reason, the sensitivity of the pressure sensor may be deteriorated.

  The present invention has been made in view of the above problems. An object is to provide a flexible and highly sensitive pressure sensor.

  That is, this invention provides the pressure sensor of the following aspects in order to solve the said subject.

(1) A pressure sensor according to an aspect of the present invention includes a flexible substrate, an elastic layer formed on the flexible substrate, and a first strain detection film formed on the elastic layer.

(2) In the pressure sensor of (1), the elastic layer may be a layer made of an elastic material or a layer in which a gas or a liquid is enclosed.

(3) The pressure sensor of (1) or (2) may further include a strain sensor having a second strain detection film on the flexible substrate.

(4) In the pressure sensor according to any one of (1) to (3), the second strain detection film may be disposed between the flexible substrate and the elastic layer.

(5) In the pressure sensor according to any one of (1) to (4), the second strain detection film may be disposed adjacent to a laminate of the elastic layer and the first strain detection film.

(6) The pressure sensor according to (5) further includes a support layer between the flexible substrate and the second strain detection film, and the support layer is formed on a part of the surface of the second strain detection film. There may be a protrusion that contacts a part of the lower surface, and the second strain detection film can detect the shear force applied to the pressure sensor.

(7) The pressure sensor according to any one of (3) to (6) includes a first strain sensor group including a plurality of strain sensors, and each of the plurality of strain sensors in the first strain sensor group includes: The strain detection azimuths possessed may be arranged so as to be orthogonal to each other.

(8) The pressure sensor according to (7) includes the first strain sensor group and a second strain sensor group including a plurality of strain sensors, and the strain sensor of the first strain sensor group includes the second strain sensor. The strain sensors in the strain sensor group may be arranged so as to overlap each other.

(9) In the pressure sensor of (8) above, the strain detection direction of the strain sensor of the first strain sensor group and the strain detection direction of the strain sensor of the second strain sensor group form 45 ° with each other. It may be arranged in the direction.

(10) The pressure sensor according to any one of (1) to (9) may include a plurality of the first strain detection films, and may be arranged so that the detection directions of the first strain detection films are orthogonal to each other. Good.

(11) In the pressure sensor according to any one of (1) to (10), another support layer that supports the first strain detection film, having a different Young's modulus from the elastic layer, is provided on one side of the elastic layer. In addition, the first strain detection film may have a cantilever structure.

  According to the pressure sensor of the present invention, since it is flexible, it can be fixed on a curved surface, and pressure can be measured with high sensitivity.

It is the section schematic diagram showing the pressure sensor of a 1st embodiment. (A) is a pressure sensor when the second strain detection film is disposed so as to be separated from the elastic layer, and (b) is a pressure sensor when the second strain detection film is disposed between the flexible substrate and the elastic layer. FIG. It is the figure which expanded the principal part of the cross-sectional schematic of the pressure sensor of this embodiment. (A) shows a state where no pressure is applied, and (b) shows a state where pressure is applied. It is the cross-sectional schematic of the pressure sensor which showed the principal part about the location which can detect a pressure. (A) shows the case where a pressure is applied to the protective layer. (B) shows the case where a pressure is applied to the flexible substrate. FIG. 6 is a schematic cross-sectional view of a pressure sensor in which a first strain detection film is disposed such that a neutral axis of the pressure sensor passes through the first strain detection film. It is a plane schematic diagram from the upper surface of a pressure sensor provided with a plurality of first strain detection films. It is the cross-sectional schematic which showed the pattern which responds to a pressure, when the pressure sensor which has arrange | positioned the strain sensor so that it may separate from an elastic layer was fixed to the curved surface. It is a plane schematic diagram from the upper surface of the pressure sensor by which the some strain sensor is arrange | positioned. (A) is the cross-sectional schematic shown about the pressure sensor of 2nd Embodiment. (B) is a plane schematic diagram from the upper surface of a shear force detection part. (A) is the plane schematic diagram shown about the deformation | transformation at the time of a pressure being applied about the pressure sensor of 2nd Embodiment. (B) is the plane schematic diagram shown about the deformation | transformation at the time of a shear force being applied about the pressure sensor of 2nd Embodiment. It is the cross-sectional schematic which showed the various suitable example of the 2nd distortion | strain detection film | membrane support layer 61 with which a shearing force detection part is provided. 1 is a schematic cross-sectional view showing a flow for producing a pressure sensor of Example 1. FIG. It is the photograph which image | photographed the flexible substrate used for Example 1 in which the copper electrode was formed in the polyimide board. In Example 1, it is the photograph which image | photographed the pressure sensor in preparation when the elastic layer by a silicone rubber was produced on the flexible substrate. In Example 1, it is the photograph which image | photographed the pressure sensor under manufacture when the silicon piezoresistive element was transcribe | transferred on the elastic layer. In Example 1, it is the photograph which image | photographed the pressure sensor under manufacture when the silicon piezoresistive element was directly transcribe | transferred to the exposed flexible substrate. In Example 1, it is the photograph which image | photographed the pressure sensor in preparation when the electrode on a flexible substrate and a silicon piezoresistive element were connected using the conductive adhesive. It is the photograph at the time of bending the pressure sensor produced in Example 1 with a finger. 2 is a photograph of a silicon piezoresistive element used in Example 1. It is a graph which shows the result of having measured the rate of resistance change to pressure by fixing the pressure sensor of Example 1 on a plane and a curved surface, and performing a pressure load test. It is a graph which shows the output of a pressure sensor and a distortion sensor at the time of pressing on the surface of a pressure sensor with a finger a plurality of times when fixed on a plane. It is a graph which shows the output of a pressure sensor and a distortion sensor at the time of pressing the surface of a pressure sensor with a finger a plurality of times when fixed on a curved surface.

Hereinafter, the pressure sensor of the present invention will be described in detail with reference to the drawings as appropriate.
In the drawings used in the following description, in order to make the characteristics of the present invention easier to understand, the characteristic parts may be shown in an enlarged manner for the sake of convenience, and the dimensional ratios of the respective components are different from actual ones. Sometimes. In addition, the materials, dimensions, and the like exemplified in the following description are examples, and the present invention is not limited to these, and can be appropriately modified and implemented without changing the gist thereof. Furthermore, the present invention is not limited only to the embodiments described below.

(First embodiment)
With reference to FIGS. 1-6, the pressure sensor of 1st Embodiment is demonstrated.

FIG. 1 is a schematic cross-sectional view of the pressure sensor according to the present embodiment. FIG. 1A is a schematic cross-sectional view of the pressure sensor when the second strain detection film 40 is disposed so as to be separated from the elastic layer 20. FIG. 1B is a schematic cross-sectional view of the pressure sensor when the second strain detection film 40 is disposed between the flexible substrate 10 and the elastic layer 20.
FIG. 2 is an enlarged view of a main part of a schematic cross-sectional view of the pressure sensor of the present embodiment. 2A shows a state where no pressure is applied, and FIG. 2B shows a state where pressure is applied.

  The pressure sensor 100 according to the first embodiment includes a flexible substrate 10, an elastic layer 20, a first strain detection film 30, a second strain detection film 40, a protective layer 50, a first electrode Ea1, and a second electrode. Eb1. An elastic layer 20 is provided between the flexible substrate 10 and the first strain detection film 30. The first electrode Ea1 is electrically connected to the first strain detection film 30. The second electrode Eb1 is electrically connected to the second strain detection film 40.

  When pressure is applied to the sensor surface, the first strain detection film 30 disposed between the elastic layer 20 and the protective layer 50 is deformed into a convex shape toward the flexible substrate 10 due to a difference in Young's modulus between the elastic layer 20 and the protective layer 50. (FIG. 2B). As a result, distortion (change in length) occurs in the first strain detection film 30. As will be described later, the first strain detection film 30 converts the strain generated inside as a change in electrical properties. By measuring (measuring) these, the pressure applied to the surface of the pressure sensor 100 can be detected (measured).

  The flexible substrate 10 is a flexible substrate. For example, the category includes plastic substrates, paper, cloth, glass thin films, silicon thin films, and the like. Examples of the material of the flexible substrate 10 include plastics such as polynorbornene having a polar group, polyethylene terephthalate (PET), polyethersulfone (PES), polyethylene naphthalate (PEN), polycarbonate (PC), nylon, and polyether. Ether ketone (PEEK), polysulfone (PSF), polyetherimide (PEI), polyarylate (PAR), polybutylene terephthalate (PBT), polyimide, and the like can be used. The thickness of the glass thin film or silicon thin film is preferably 50 μm or less. As a flexible substrate, it can have practically sufficient flexibility.

The elastic layer 20 is a layer having elasticity. As the elastic layer 20, for example, a layer made of an elastic material can be used. A known material can be used as the elastic material. Examples thereof include silicone rubber and elastic plastic. Silicone rubber is a two-component mixed material and can be preferably used as the material of the elastic layer 20 because the Young's modulus can be adjusted by the mixing ratio of the main agent and the curing agent.
Further, a layer in which a gas or a liquid is enclosed in the elastic layer 20 can be used. For example, air, nitrogen, or argon can be used as the gas. Nitrogen and argon can be preferably used as a material to be enclosed in the elastic layer 20 in order to prevent oxidation of the material. Examples of the liquid include water, silicon oil, and ionic liquid. Silicon oil or ionic liquid has a low vapor pressure, and is kept as a liquid without being evaporated even in a vacuum. Therefore, it is compatible with a semiconductor process often performed in a vacuum atmosphere. Therefore, it can be preferably used for the elastic layer 20 as a material sealed in the elastic layer 20.

  The thickness of the elastic layer 20 is preferably 5% or more and 20% or less of the length of the first strain detection film 30 described later. When the thickness of the elastic layer 20 is 5% or more of the length of the first strain detection film 30, there is a large range of strain in the direction of the flexible substrate 10 when pressure is applied to the first strain detection film 30. Become. Therefore, the pressure can be detected with better sensitivity. Further, if the thickness of the elastic layer 20 is 20% or less of the length of the first strain detection film 30, the amount of strain of the flexible substrate and the strain of the first strain detection film 30 are practically sufficient. Can be regarded as equivalent. For this reason, the distortion amount can be corrected with high accuracy. Therefore, the pressure can be detected with better sensitivity.

  The strain detection film refers to a film made of a material whose electrical properties change due to internal strain. Thereby, externally applied forces such as pressure and shear force can be detected as electrical signals.

  For example, a material having piezoresistance characteristics can be used for the first strain detection film 30 and the second strain detection film 40 as a piezoresistance film. By measuring the resistance value changed by the strain, the force applied from the outside can be detected. A known material having a piezoresistance characteristic can be used for the strain detection film. A piezoresistive film made of silicon is preferably used because of its high sensitivity to static strain. As the silicon piezoresistive element, for example, an element obtained by ion-implanting P (phosphorus) or As (arsenic) into p-type silicon can be preferably used. A strain gauge using copper or a nickel-based alloy is preferable because a very high gauge ratio of about 50 to 100 is obtained compared to a gauge ratio of about 2. For example, a material having piezoelectricity can be used for the first strain detection film 30 and the second strain detection film 40 as a piezoelectric film. Thereby, dynamic distortion can be measured suitably. Moreover, the force applied from the outside can be detected by measuring the electromotive force generated by the distortion. A known material having piezoelectricity can be used for the strain detection film. For example, PZT (lead zirconate titanate) and AlN (aluminum nitride) can be suitably used.

  The first strain detection film preferably has a thickness of 50 μm or less. If the film thickness is larger than 50 μm, the strain detection film may be broken by bending.

  A first strain detection film 30 is disposed on the elastic layer 20. As a result, when pressure is applied to the sensor surface, the first strain detection film 30 disposed between the elastic layer 20 and the protective film 50 protrudes toward the flexible substrate 10 due to the difference in Young's modulus between the elastic layer 20 and the protective film 50. It is deformed into a shape (FIG. 2B). As a result, distortion (change in length) occurs in the first strain detection film 30. The first strain detection film 30 converts the strain generated inside as a change in electrical properties. For example, when the first strain detection film 30 is a piezoresistive film, the strain is converted into a resistance change. For example, when the first strain detection film 30 is a piezoelectric film, the strain is converted into an electromotive force. By measuring (measuring) these, the pressure applied to the surface of the pressure sensor 100 can be detected (measured).

  The second strain detection film 40 is disposed on the flexible substrate 10. Thus, the second strain detection film 40 (strain sensor) can detect the strain derived from the bending generated in the pressure sensor 100 by distinguishing it from the strain derived from the pressure. Further, the second strain detection film 40 (strain sensor) can correct the pressure detected by the first strain detection film 30 by using the strain derived from bending generated in the pressure sensor 100. Thereby, the pressure sensor 100 can detect the pressure with better accuracy.

  For example, the second strain detection film 40 (strain sensor) can be disposed so as to be separated from the elastic layer 20 (FIG. 1A). As a result, the distance between the flexible substrate 10 and the first strain detection film 30 can be made smaller than when the second strain detection film 40 is disposed between the flexible substrate 10 and the elastic layer 20. Therefore, the strain amount of the first strain detection film 30 and the strain amount of the flexible substrate 10 that are generated when the flexible substrate 10 is distorted by bending become closer. For this reason, when the distortion derived from the bending which arose in the pressure sensor 100 is correct | amended from the distortion derived from a pressure with a distortion sensor, the deterioration of the detection accuracy of a pressure can be prevented.

  For example, the 2nd distortion detection film | membrane 40 can also be arrange | positioned between the flexible substrate 10 and the elastic layer 20 (FIG.1 (b)). Thereby, the first strain detection film 30 and the second strain detection film 40 can be superimposed on the flexible substrate 10. Therefore, the number of the first strain detection films 30 and the second strain detection films 40 per unit area can be increased. Therefore, the range in which the pressure is detected can be refined.

  FIG. 3 shows a schematic cross-sectional view of the pressure sensor 100, showing the locations where pressure can be detected. FIG. 3 shows a main part of the pressure sensor 100. (A) shows the case where a pressure is applied to the protective layer 50. (B) shows the case where pressure is applied to the flexible substrate 10. For example, the pressure applied to the protective layer 50 from the outside can be suitably detected (FIG. 3A). For example, the pressure applied to the flexible substrate 10 from the outside can also be detected suitably (FIG. 3B).

  When a force is applied to bend a flexible member, there are locations where compressive stress is generated, locations where tensile stress is generated, and locations where a strain does not occur due to the balance between compressive stress and tensile stress (neutral axis). . It is preferable that the neutral shaft of the pressure sensor 100 is disposed so as to pass through elements and wirings included in the pressure sensor 100. For example, the first strain detection film 30 can be arranged such that the neutral axis of the pressure sensor 100 passes through the first strain detection film 30. Thereby, the stress which generate | occur | produces in the 1st distortion detection film | membrane 30 can be reduced (FIG. 4). Therefore, it is possible to prevent the first strain detection film 30 from being broken or cracked. Here, the first strain detection film 30 has been described as an example, but other elements, electrodes, wirings, and the like may be disposed on the neutral axis of the pressure sensor 100.

The pressure sensor 100 can be preferably provided with a plurality of first strain detection films 30. The range in which the first strain detection film 30 is disposed in the pressure sensor can be expanded, and the range in which pressure is detected can be expanded. Further, by increasing the number of first strain detection films 30 to be arranged with respect to the unit area of the pressure sensor, it is possible to refine the pressure detection range.
Further, the orientation of the first strain detection film 30 can be arranged in various ways. For example, as shown in FIG. 5, a plurality of first strain detection films 30 having a rectangular shape may be arranged so that the long side direction intersects perpendicularly.

  6A to 6C are schematic cross-sectional views showing patterns that respond to pressure when the pressure sensor 100 in which the strain sensor is arranged is fixed to a curved surface so as to be separated from the elastic layer 20. It is. Compensating the bending-derived strain obtained from the second strain detection film 40 with respect to the strain obtained from the first strain detection film 30, thereby increasing the detection accuracy of the pressure applied to the pressure sensor 100. it can.

  The thickness of the second strain detection film 40 is preferably 50 μm or less. If the film thickness is larger than 50 μm, the strain detection film may be broken by bending.

A material having flexibility (flexibility) can be preferably used for the protective layer 50. For example, a plastic substrate, paper, cloth, etc. are included in the category. Examples of the material of the flexible substrate 10 include plastics such as polynorbornene having a polar group, polyethylene terephthalate (PET), polyethersulfone (PES), polyethylene naphthalate (PEN), polycarbonate (PC), nylon, and polyether. Ether ketone (PEEK), polysulfone (PSF), polyetherimide (PEI), polyarylate (PAR), polybutylene terephthalate (PBT), polyimide, and the like can be used. For the protective layer 50, a known material having flexibility (flexibility) can be used.
It is preferable that the Young's modulus of the material of the protective layer 50 is higher than the material of the elastic layer 20. In addition, the greater the difference in hardness (Young's modulus) between the protective layer 50 and the elastic layer 20, the greater the amount of strain with respect to the pressure of the first strain detection film, so that the sensitivity of the pressure sensor can be increased.

  The thickness of the protective layer 50 is preferably 10 times or less the length of the first strain detection film 30. When the thickness is 10 times or less the film thickness of the first strain detection film 30, dispersion of the pressure applied to the pressure sensor 100 can be suppressed and the pressure can be sufficiently transmitted to the first strain detection film 30. For this reason, the accuracy of distortion detection can be improved.

  The protective layer 50 can be provided on one side of the flexible substrate (FIG. 1). It can also be provided on both sides of the flexible substrate.

A plurality of first electrodes Ea1 are formed so as to be electrically connected to one first strain detection film 30. Thereby, the first strain detection film 30 can be incorporated in the circuit. In addition, each of the plurality of first electrodes Ea1 can be electrically connected to an external signal processing device. Thereby, the signal generated from the first strain detection film 30 can be processed by an external signal processing device.
The first electrode Ea1 only needs to be made of a conductive material. A known conductive material can be used. Also, a known method can be used as a method for producing the first electrode Ea1. For example, it can be produced by applying a stretchable conductive adhesive. Moreover, it can also produce using the method of screen-printing a silver paste.

  A plurality of second electrodes Eb1 are formed so as to be electrically connected to one second strain detection film 40. Thereby, the second strain detection film 40 can be incorporated in the circuit. In addition, each of the plurality of second electrodes Eb1 can be electrically connected to an external signal processing device. Thereby, the signal generated from the second strain detection film 40 can be processed by an external signal processing device.

  When two second electrodes Eb1 are in contact with one second strain detection film 40, the strain sensor 40 is derived from the bending generated in the direction (strain detection azimuth) connecting the second electrodes Eb1. Detect distortion. For this reason, as for the strain sensor 40, it is preferable that the some strain sensor 40 is arrange | positioned in the various directions in a pressure sensor. FIG. 7 is a diagram illustrating an example of the pressure sensor 100 in which a plurality of strain sensors 40 are arranged. For example, as shown in FIG. 7A, a plurality of strain sensors 40 (a strain sensor group) can be arranged so that strain detection directions are orthogonal to each other. In this case, the distortion generated in the vertical direction and the horizontal direction in FIG. 7A can be detected. In addition, for example, a plurality of strain sensor groups can be arranged such that the strain sensors included in each group overlap each other. FIG. 7B is a schematic diagram when the second strain sensor group is superimposed on the first strain sensor group with the strain detection orientations of the strain sensors included in the second strain sensor group overlapping each other. The strain detection azimuths included in each of the plurality of strain sensor groups can be, for example, orthogonal, parallel, and 45 ° directions. Further, the strain detection azimuth can be arbitrarily adjusted as necessary. Furthermore, for example, the strain sensor group shown in FIG. 7A can be combined with a plurality of superimposed strain sensor groups shown in FIG. 7B (FIG. 7C). The strain sensor group shown in FIG. 7C includes a plurality of strain sensors shown in FIG. 7A and strain sensors arranged so that strain detection directions of the strain sensor 40 are orthogonal to each other and overlap each other. The groups are overlapped so that the mutual strain detection directions (vertical direction and horizontal direction in FIG. 7A) are positioned in the 45-degree rotation direction. Such a strain sensor group can measure strain in the torsional direction in addition to the bending direction. In addition, for example, the strain sensor group shown in FIG. 7C and the first strain detection film 30 can be combined (FIG. 7D). Thereby, the pressure sensor 100 can compensate the distortion of a bending direction and a twist direction, and can detect a pressure more accurately. FIG. 7D shows a case where the orientations of the plurality of first strain detection films 30 are orthogonal to each other, but the orientations can be arbitrarily adjusted as necessary. For example, the directions may be orthogonal to each other, parallel, and rotated by 45 °.

(Second Embodiment)
A pressure sensor according to the second embodiment will be described with reference to FIGS. FIG. 8A shows a schematic cross-sectional view of the pressure sensor of the present embodiment. FIG. 8B is a schematic plan view from the upper surface of the shearing force detection unit provided in the pressure sensor of the present embodiment.
The pressure sensor 101 of the second embodiment includes a flexible substrate 11, an elastic layer 21, a first strain detection film 31, a second strain detection film 41, a protective layer 51, and a second strain detection film support layer 61. The first electrode Ea2 and the second electrode Eb2.
An elastic layer 21 is provided between the flexible substrate 11 and the first strain detection film 31. Further, the first strain that supports one side of the first strain detection film 31 so that the protective layer 51 fills the void formed by the elastic layer 21, the first strain detection film 31, and the flexible substrate 11. A detection film support layer 51a is provided.
A second strain detection film support layer 61 is provided between the flexible substrate 11 and the second strain detection film 41.
The first electrode Ea2 is electrically connected to the first strain detection film 31. The second electrode Eb2 is electrically connected to the second strain detection film 41.

Both the elastic layer 21 and the first strain detection film support layer 51 a can be provided between the flexible substrate 11 and the first strain detection film 31. With this configuration, the first strain detection film 31 can be supported by the elastic layer 21 and the first strain detection film support layer 51a. By providing a difference in hardness (Young's modulus) between the elastic layer 21 and the first strain detection film support layer 51a, the first strain detection film 31 can be suitably used as a cantilever. By having this structure, the first strain detection film 31 can detect the pressure applied to the pressure sensor 101.
The first strain detection film 31 is supported by an elastic layer 21 having different hardness (Young's modulus) and a first strain detection film support layer 51a. Therefore, the first strain detection film 31 is bent by the pressure so that the portion of the first strain detection film 31 supported by the soft layer approaches the direction of the flexible substrate 11. FIG. 9A shows an example in which the elastic layer 21 is softer (lower Young's modulus) than the first strain detection film support layer 51a. In this way, the first strain detection film 31 functions as a cantilever, and a strain is generated at a portion corresponding to the root of the cantilever. By detecting this strain as an electrical signal, it is possible to detect a strain due to pressure. By measuring (measuring) the strain generated in the first strain detection film 31 as a change in electrical properties, the pressure applied to the surface of the pressure sensor 101 can be detected (measured).

  The second strain detection film support layer 61 has a protrusion 61 a on a part of its surface, and the protrusion 61 a is in contact with the lower surface of the second strain detection film 41. The end 41A of the second strain detection film 41 has a cantilever structure that rises with the protrusion 61a as a fulcrum. The plurality of second electrodes Eb2 are provided so as to constitute a circuit in which the end portion 41A of the second strain detection film is incorporated between them. For example, such a circuit can be configured by providing an insulating layer between the plurality of second electrodes Eb2 (FIG. 8B). Thereby, the second strain detection film 41 can detect the shear force applied to the pressure sensor 101. By having the above configuration, the second strain detection film 41 and the protrusion 61a function as a shear force detection unit of the pressure sensor 101.

  As shown in FIG. 9A, when pressure is applied to the pressure sensor 101 downward from the top of the paper, the elastic layer 21 is compressed and deformed. As described above, the first strain detection film 31 functions as a cantilever, and its tip bends downward to cause distortion at the base. By detecting this strain as an electrical signal, it is possible to detect a strain due to pressure. Further, the pressure can be detected by processing the electrical signal generated by the first strain detection film 31 with, for example, a signal processing device. On the other hand, since the entire second strain detection film 41 moves downward, it is possible to suppress the occurrence of strain in the inside. For this reason, the second strain detection film 41 does not respond to a practically sufficient level when pressure is applied to the pressure sensor 101.

As shown in FIG. 9B, when a shearing force is applied to the pressure sensor 101 from the left to the right in the drawing, the entire first strain detection film 31 moves in the horizontal direction. Generation of general distortion can be suppressed. For this reason, the first strain detection film 31 does not respond to a practically sufficient degree when a shearing force is applied to the pressure sensor 101.
On the other hand, the second strain detection film 41 is deformed by the applied shear force so that the raised tip portion moves in the right direction on the paper surface, and the amount of movement in the horizontal direction increases as it approaches the tip portion. For this reason, in the second strain detection film 41, the force acting on the tip portion acts on the portion near the root through the protrusion 61a via the fulcrum, and distortion occurs. By detecting this strain as an electrical signal, it is possible to detect a strain derived from a shearing force applied from the outside. In addition, the shearing force can be detected by processing the electrical signal generated by the second strain detection film 41 with, for example, a signal processing device.

  A known material having flexibility (flexibility) can be preferably used for the second strain detection film support layer 61. For example, the same material as the elastic layer 21 can be suitably used (FIG. 10A). For example, the same material as the protective layer 51 can be used suitably (FIG.10 (b)). Further, for example, the flexible substrate 11 provided with the protrusion 11a can be used as the second strain detection film support layer 61 having the protrusion 61a (FIG. 10C).

Example 1
A flexible pressure sensor was produced according to the flow shown in FIG. The photograph which image | photographed the produced flexible pressure sensor is shown in FIGS. On a flexible substrate (FIG. 11) on which a copper electrode (Ec in FIG. 11) is formed on the polyimide plate shown in FIG. 11 (a), silicone having a thickness of 0.3 mm as shown in FIG. 11 (b). An elastic layer made of rubber was produced (FIG. 13). Next, as shown in FIG. 11 (c), the elastic layer was cut out with a scalpel to expose the copper electrode. Next, as shown in FIG. 11D, a silicon piezoresistive element was transferred onto the elastic layer (FIG. 14). As the silicon piezoresistive element, an ultrathin silicon piezoresistive element (FIG. 18) having a width of 1 mm, a depth of 5 mm, and a thickness of 5 μm was used. Next, a part of the elastic layer was cut off with a scalpel to expose a part of the flexible substrate. Next, an ultrathin silicon piezoresistive element was directly transferred to the exposed flexible substrate as a strain sensor for strain compensation (FIG. 15). Next, as shown in FIG. 11 (e), an electrode on a flexible substrate and a silicon piezoresistor are formed using a conductive adhesive (Cemedine Co., Ltd., low temperature curable flexible conductive adhesive [SX-ECA48] 120%). The elements were connected. Next, as shown in FIG. 11 (f), a protective layer of 0.3 mm silicone rubber was formed on the surface of the flexible substrate (FIG. 16). With the above flow, a pressure sensor with high sensitivity of silicon composed only of a flexible material was produced. The manufactured pressure sensor was very thin with a thickness of about 0.7 mm. Further, since it is composed only of a flexible material, as shown in FIG. 17, the wiring and the sensor element did not break or break even when bent with a finger.

  The manufactured pressure sensor was fixed on a flat surface and a curved surface, and a resistance change rate with respect to pressure was measured by performing a pressure load test. In addition, the surrounding wall of the acrylic pipe of diameter 5.5cm was used as a curved surface. FIG. 19 shows the resistance change rate with respect to the pressure, which was measured on the flat surface and the curved surface, respectively. When fixed on a plane (in FIG. 19, “when fixed on a plane”) and when fixed on a curved surface (in FIG. 19, “when fixed on a curved surface”), linearly with respect to the applied pressure, The resistance change rate showed a response. Furthermore, it was confirmed by measurement that the same sensitivity to pressure was exhibited on both flat and curved surfaces. Further, it was found that the resistance change rate of the pressure sensor fixed to the curved surface is larger than the sensor fixed to the flat surface by the amount of distortion caused by the distortion of the sensor. As a result, it was confirmed that the pressure applied to the sensor can be correctly measured even when fixed on a curved surface by performing distortion compensation using the response of the strain sensor manufactured at a position close to the pressure sensor. .

  Moreover, the response of the pressure sensor and the strain sensor when the sensor was pressed with a finger was measured using a pressure sensor fixed on a plane. In addition, using a pressure sensor fixed on a peripheral wall (curved surface) of an acrylic pipe having a diameter of 5.5 cm, responses of the pressure sensor and the strain sensor when the sensor was pressed with a finger were measured. FIG. 20 shows a case where the output of the pressure sensor and the strain sensor when the sensor surface is pressed a plurality of times with a finger is fixed on a plane, and FIG. 21 shows a case where the output is fixed on a curved surface. In both cases, the pressure sensor showed an output in response to finger contact. Moreover, when it fixed on the curved surface, the distortion sensor output steadily. This is due to distortion caused by bending to follow the curved surface. Thereby, it was confirmed that the strain sensor is insensitive to the pressure in common in both the case of fixing on a flat surface and the case of fixing on a curved surface. From the above, it was confirmed that the produced pressure sensor can reliably detect the applied pressure both when fixed on a flat surface and when fixed on a curved surface.

  Since the pressure sensor of the present invention is flexible, it can be fixed on a curved surface, and can measure pressure with high sensitivity.

100, 101, 100A: pressure sensors 10, 11, 10A: flexible substrate 11a: protrusions 20, 21, 20A: elastic layers 30, 31, 30A: first strain detection films 40, 41, 40A: second strain detection films 50, 51, 50A: protective layer 51a: first strain detection film support layer 61a: second strain detection film support layer Ea1, Ea2, EaA: first electrode Eb1, Eb2, EbA: second electrode Ec: copper electrode

Claims (11)

A flexible substrate;
An elastic layer formed on the flexible substrate;
And a first strain detection film formed on the elastic layer.   The pressure sensor according to claim 1, wherein the elastic layer is a layer made of an elastic material or a layer in which a gas or a liquid is sealed.   The pressure sensor according to claim 1, further comprising a strain sensor having a second strain detection film on the flexible substrate.   The pressure sensor according to claim 3, wherein the second strain detection film is disposed between the flexible substrate and the elastic layer.   The pressure sensor according to claim 3, wherein the second strain detection film is disposed adjacent to a laminate of the elastic layer and the first strain detection film. Further comprising a support layer between the flexible substrate and the second strain detection film,
The support layer has a protrusion that contacts a part of the lower surface of the second strain detection film on a part of the surface thereof, and the second strain detection film can detect a shear force applied to the pressure sensor. The pressure sensor according to claim 5, wherein A first strain sensor group comprising a plurality of strain sensors;
The pressure sensor according to any one of claims 3 to 6, wherein the plurality of strain sensors of the first strain sensor group are arranged so that strain detection orientations of the plurality of strain sensors are orthogonal to each other. The first strain sensor group, and a second strain sensor group comprising a plurality of the strain sensors,
The pressure sensor according to claim 7, wherein the strain sensors of the second strain sensor group are arranged so as to overlap the strain sensors of the first strain sensor group.   The strain detection azimuth possessed by the strain sensors of the first strain sensor group and the strain detection azimuth possessed by the strain sensors of the second strain sensor group are arranged in a direction forming 45 ° with each other. Pressure sensor. A plurality of the first strain detection films;
The pressure sensor as described in any one of Claims 1-9 arrange | positioned so that the detection direction which the said 1st strain detection film | membrane has may mutually orthogonally cross.   The elastic layer further comprises another support layer supporting the first strain detection film having a different Young's modulus from the elastic layer, and the first strain detection film has a cantilever structure. The pressure sensor as described in any one of 1-10.