Piezoelectric sensor and manufacturing method thereof

Abstract

To provide a piezoelectric sensor capable of improving sensitivity.SOLUTION: A piezoelectric sensor includes a piezoelectric layer 10 having a plurality of first openings, a lower electrode 11 provided under the piezoelectric layer 10 and having a plurality of second openings, an upper electrode 12 provided on the piezoelectric layer 10 and having a plurality of third openings, a first adhesive layer 13 provided under the lower electrode 11, a first protective layer 15 provided under the first adhesive layer 13, a second adhesive layer 14 provided on the upper electrode 12, and a second protective layer 16 provided on the second adhesive layer 14. A laminate in which the first protective layer 15, the first adhesive layer 13, the second adhesive layer 14, and the second protective layer 16 are laminated in this order is provided within each of the plurality of first openings.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a piezoelectric sensor and a method for manufacturing the same. [Background technology]

[0002] Sensors using organic piezoelectric materials such as P(VDF / TrFE) are currently in use. Organic piezoelectric materials can be applied by coating, can be produced in low-temperature processes, and can be easily made into films, so attempts are being made to apply them to flexible sensors for wearable devices and large-area sensors. Various applications are being considered for organic piezoelectric materials, such as biosensors for measuring pulse waves and myoelectric signals, tactile sensors, and pyroelectric sensors, making this a technology that is attracting attention.

[0003] When a sensor using this organic piezoelectric material is attached to the body and used continuously, the piezoelectric material itself and the electrode material used in the device generally have low water vapor permeability, so the part of the body to which the sensor is attached is likely to become stuffy due to moisture such as sweat. This causes discomfort and further problems such as rashes. Patent Document 1 describes that in a piezoelectric sensor using an inorganic piezoelectric material, stuffiness is suppressed by forming multiple through holes in the piezoelectric film and electrode layer.

[0004] In addition, devices that are attached to the body are required to have elasticity to follow the movement of the body, but piezoelectric materials generally have poor elasticity, even if they are organic piezoelectric materials. Patent Document 2 describes how, in a biovibration sensor using a piezoelectric material, the flexibility and elasticity are improved by forming multiple slits in a sheet-shaped piezoelectric body, and the degree of adhesion is increased even in the case of a biosurface with a large curvature, thereby enabling accurate detection of biovibrations.

[0005] However, when openings such as through-holes and slits are formed in the organic piezoelectric material and electrode layer to improve breathability and elasticity, the area of ​​the device is reduced, which reduces the amount of charge generated during sensing and reduces the detection sensitivity.

[0006] Furthermore, when the organic piezoelectric layer is formed by a coating process such as spin coating, screen printing, or inkjet printing, a high-voltage poling process (polarization process) must be performed after the electrode layer is formed. In order to reduce the risk of short circuits (dielectric breakdown) between the electrodes, the openings in the electrode layer must be made sufficiently larger than the openings in the organic piezoelectric layer. As a result, the device area is further reduced, and the detection sensitivity is also reduced accordingly. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2015 / 064217 [Patent Document 2] International Publication No. 2018 / 168145 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention provides a piezoelectric sensor capable of improving sensitivity, and a manufacturing method thereof. [Means for solving the problem]

[0009] According to a first aspect of the present invention, there is provided a piezoelectric sensor comprising: a piezoelectric layer having a plurality of first openings; a lower electrode provided under the piezoelectric layer and having a plurality of second openings arranged so as to overlap each of the plurality of first openings in a planar view; an upper electrode provided on the piezoelectric layer and having a plurality of third openings arranged so as to overlap each of the plurality of first openings in a planar view; a first adhesive layer provided under the lower electrode, a first protective layer provided under the first adhesive layer, a second adhesive layer provided on the upper electrode, and a second protective layer provided on the second adhesive layer, wherein a laminate in which the first protective layer, the first adhesive layer, the second adhesive layer, and the second protective layer are stacked in this order is provided within each of the plurality of first openings.

[0010] According to a second aspect of the present invention, there is provided the piezoelectric sensor according to the first aspect, wherein the first adhesive layer and the second adhesive layer are made of a material having moisture permeability.

[0011] According to a third aspect of the present invention, there is provided a piezoelectric sensor comprising: a piezoelectric layer having a plurality of first openings; a lower electrode provided below the piezoelectric layer and having a plurality of second openings arranged so as to overlap each of the plurality of first openings in a planar view; an upper electrode provided on the piezoelectric layer and having a plurality of third openings arranged so as to overlap each of the plurality of first openings in a planar view; a first protective layer provided below the lower electrode; and a second protective layer provided on the upper electrode, wherein a laminate in which the first protective layer and the second protective layer are stacked in this order is provided within each of the plurality of first openings.

[0012] According to a fourth aspect of the present invention, there is provided the piezoelectric sensor according to the first or third aspect, wherein the first protective layer and the second protective layer are made of a material having moisture permeability.

[0013] According to a fifth aspect of the present invention, there is provided a piezoelectric sensor according to the first or third aspect, wherein an area of ​​the second opening is larger than an area of ​​the first opening, and an area of ​​the third opening is larger than an area of ​​the second opening.

[0014] According to a sixth aspect of the present invention, there is provided a piezoelectric sensor according to the first or third aspect, wherein an area of ​​the second opening is larger than an area of ​​the first opening, and an area of ​​the third opening is the same as an area of ​​the second opening.

[0015] According to a seventh aspect of the present invention, there is provided the piezoelectric sensor according to the first or third aspect, wherein each of the first openings, the second openings, and the third openings is a circle.

[0016] According to an eighth aspect of the present invention, there is provided the piezoelectric sensor according to the first or third aspect, wherein the plurality of first openings are evenly arranged.

[0017] According to a ninth aspect of the present invention, there is provided a method for manufacturing a piezoelectric sensor, comprising the steps of: forming a lower electrode having a plurality of second openings on a first protective layer; forming a piezoelectric layer on the lower electrode having a plurality of first openings arranged so as to overlap each of the plurality of second openings in a planar view; forming an upper electrode on the piezoelectric layer having a plurality of third openings arranged so as to overlap each of the plurality of second openings in a planar view; forming a second protective layer on the upper electrode so as to fill the plurality of second openings, the plurality of first openings, and the plurality of third openings; and applying a voltage between the lower electrode and the upper electrode to perform a poling process on the piezoelectric layer. Effect of the Invention

[0018] According to the present invention, it is possible to provide a piezoelectric sensor capable of improving sensitivity, and a manufacturing method thereof. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a plan view of a piezoelectric sensor according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view of the piezoelectric sensor taken along the line AA′ in FIG. [Diagram 3] FIG. 3 is a plan view of a piezoelectric sensor according to a first modified example. [Figure 4] FIG. 4 is a cross-sectional view of the piezoelectric sensor taken along the line AA′ in FIG. [Diagram 5] FIG. 5 is a cross-sectional view of a piezoelectric sensor according to a second modified example. [Figure 6] FIG. 6 is a diagram for explaining the definition of the polarization direction of the piezoelectric layer. [Figure 7] FIG. 7 is a diagram illustrating the compression operation in the film thickness direction of the piezoelectric layer. [Figure 8] FIG. 8 is a diagram illustrating the in-plane expansion operation of the piezoelectric layer. [Figure 9]FIG. 9 is a schematic diagram illustrating the operation of the piezoelectric sensor. [Figure 10] FIG. 10 is a plan view of a piezoelectric sensor according to a second embodiment of the present invention. [Figure 11] FIG. 11 is a cross-sectional view of the piezoelectric sensor taken along the line AA′ in FIG. [Figure 12] FIG. 12 is a cross-sectional view of a piezoelectric sensor according to a modified example. [Figure 13] 13A to 13C are cross-sectional views illustrating a manufacturing process of the piezoelectric sensor according to the third embodiment of the present invention. [Figure 14] FIG. 14 is a cross-sectional view illustrating the manufacturing process of the piezoelectric sensor subsequent to FIG. [Figure 15] FIG. 15 is a cross-sectional view illustrating the manufacturing process of the piezoelectric sensor subsequent to FIG. [Figure 16] FIG. 16 is a cross-sectional view illustrating the manufacturing process of the piezoelectric sensor subsequent to FIG. [Figure 17] FIG. 17 is a cross-sectional view illustrating the manufacturing process of the piezoelectric sensor subsequent to FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, the embodiments will be described with reference to the drawings. However, the drawings are schematic or conceptual, and the dimensions and ratios of each drawing are not necessarily the same as those in reality. In addition, even when the same parts are shown between the drawings, the dimensional relationships and ratios of each may be different. In particular, the following embodiments are examples of devices and methods for embodying the technical idea of ​​the present invention, and the technical idea of ​​the present invention is not specified by the shape, structure, arrangement, etc. of the components. In the following description, elements having the same function and configuration are given the same reference numerals, and duplicated descriptions are omitted.

[0021] [1] First embodiment [1-1] Configuration of piezoelectric sensor 1 Fig. 1 is a plan view of a piezoelectric sensor 1 according to a first embodiment of the present invention. Fig. 2 is a cross-sectional view of the piezoelectric sensor 1 taken along line AA' in Fig. 1. The X direction in Fig. 1 is a direction along one side of the piezoelectric sensor 1, and the Y direction is a direction perpendicular to the X direction.

[0022] The piezoelectric sensor 1 includes a piezoelectric layer 10 , a lower electrode 11 , an upper electrode 12 , a lower adhesive layer 13 , an upper adhesive layer 14 , a lower protective layer 15 , and an upper protective layer 16 .

[0023] The piezoelectric layer 10 is a material that has the property of generating a potential difference when a mechanical force is applied thereto, or generating a mechanical force when a voltage is applied thereto. The piezoelectric layer 10 has, for example, a quadrangle shape. The piezoelectric layer 10 is located at the center of the piezoelectric sensor 1 in the stacking direction, and also functions as a base material of the piezoelectric sensor 1. It is desirable that the piezoelectric layer 10 has flexibility and / or stretchability. The piezoelectric layer 10 is made of, for example, an organic piezoelectric material. The piezoelectric layer 10 is made of, for example, a polymer piezoelectric material such as polyvinylidene fluoride (PVDF), polyvinylidene fluoride / trifluoroethylene copolymer (P(VDF / TrFE)), or vinylidene cyanide / vinyl acetate copolymer (P(VDCN / VAc)). In addition, in order to give stretchability to P(VDF / TrFE), an acrylic resin (PMMA: polymethyl methacrylate) may be added to P(VDF / TrFE).

[0024] A lower electrode 11 is provided under the piezoelectric layer 10. The planar shape of the lower electrode 11 is, for example, a rectangle. For example, the outer area of ​​the lower electrode 11 is smaller than the outer area of ​​the piezoelectric layer 10. The lower electrode 11 is made of a metal material or an organic conductive material. Examples of the metal material include silver (Ag), silver paste, molybdenum (Mo), aluminum (Al), chromium (Cr), and an alloy containing one of these. Examples of the organic conductive material include PEDOT / PSS and carbon paste. PEDOT / PSS is a composite of poly(3,4-ethylenedioxythiophene) (PEDOT) and polystyrene sulfonate (PSS). The lower electrode 11 may be made of a material that includes the above material and has flexibility and / or stretchability. For example, the lower electrode 11 may be made of a mixture of a conductive material and a resin that has flexibility and / or stretchability. A wiring (an extraction electrode on the lower side of FIG. 1) is connected to the lower electrode 11, and this wiring is electrically connected to a detection circuit (not shown) that detects pressure. A voltage can be applied to the lower electrode 11 using this wiring.

[0025] An upper electrode 12 is provided on the piezoelectric layer 10. The planar shape of the upper electrode 12 is, for example, a rectangle. For example, the outer area of ​​the upper electrode 12 is smaller than the outer area of ​​the piezoelectric layer 10. The upper electrode 12 can be made of the conductive material listed for the lower electrode 11 above. A wire (the lower extraction electrode in FIG. 1) is connected to the upper electrode 12, and this wire is electrically connected to a detection circuit that detects pressure. A voltage can be applied to the upper electrode 12 using this wire.

[0026] A lower adhesive layer 13 is provided under the piezoelectric layer 10 so as to cover the lower electrode 11. The area of ​​the lower adhesive layer 13 is the same as the external area of ​​the piezoelectric layer 10. The lower adhesive layer 13 has a function of adhering the layers above and below it. The lower adhesive layer 13 is desirably made of an adhesive with high moisture permeability. The lower adhesive layer 13 is made of, for example, a urethane-based, acrylic-based, or silicone-based adhesive.

[0027] A lower protective layer 15 is provided under the lower adhesive layer 13. The area of ​​the lower protective layer 15 is the same as the area of ​​the outline of the piezoelectric layer 10. The lower protective layer 15 is made of an insulating material, for example, a resin. The lower protective layer 15 is desirably made of a material having flexibility and / or stretchability. In addition, the lower protective layer 15 is desirably made of a material having high moisture permeability. The lower protective layer 15 is desirably made of a polyimide resin, a polyethylene terephthalate (PET) resin, an epoxy resin, a polyurethane resin, a polyolefin resin, a polystyrene resin, or a polyester resin, for example.

[0028] An upper adhesive layer 14 is provided on the piezoelectric layer 10 so as to cover the upper electrode 12. The area of ​​the upper adhesive layer 14 is the same as the outer area of ​​the piezoelectric layer 10. The upper adhesive layer 14 has the function of adhering the layers above and below it. The upper adhesive layer 14 is desirably made of an adhesive with high moisture permeability. The upper adhesive layer 14 can be made of the materials listed for the lower adhesive layer 13 above.

[0029] An upper protective layer 16 is provided on the upper adhesive layer 14. The area of ​​the upper protective layer 16 is the same as the area of ​​the outline of the piezoelectric layer 10. The upper protective layer 16 is made of an insulating material, for example, a resin. The upper protective layer 16 is desirably made of a material having flexibility and / or stretchability. In addition, the upper protective layer 16 is desirably made of a material having high moisture permeability. The upper protective layer 16 can be made of the materials listed for the lower protective layer 15 described above.

[0030] Here, the piezoelectric layer 10, the lower electrode 11, and the upper electrode 12 each have a plurality of openings. Specifically, the piezoelectric layer 10 has a plurality of openings OP1. The planar shape of the plurality of openings OP1 is, for example, a circle. The plurality of openings OP1 are evenly arranged in the piezoelectric layer 10. The plurality of openings OP1 are arranged, for example, in a staggered pattern.

[0031] The lower electrode 11 has a plurality of openings OP2. The plurality of openings OP2 of the lower electrode 11 are arranged so as to overlap with the plurality of openings OP1 of the piezoelectric layer 10 in a plan view. The planar shape of the plurality of openings OP2 is, for example, a circle. The area of ​​the openings OP2 is larger than the area of ​​the openings OP1. In other words, the diameter of the openings OP2 is larger than the diameter of the openings OP1.

[0032] The upper electrode 12 has a plurality of openings OP3. The plurality of openings OP3 of the upper electrode 12 are arranged so as to overlap with the plurality of openings OP1 of the piezoelectric layer 10 in a plan view. The planar shape of the plurality of openings OP3 is, for example, a circle. The area of ​​the openings OP3 is larger than the area of ​​the openings OP2. In other words, the diameter of the openings OP3 is larger than the diameter of the openings OP2. The centers of the openings OP1 to OP3 are at the same position.

[0033] In the region where the plurality of openings OP1 of the piezoelectric layer 10 are arranged, the lower adhesive layer 13 and the upper adhesive layer 14 are in contact with each other. For example, the bottom surface of the lower adhesive layer 13 is approximately flattened. For example, the top surface of the upper adhesive layer 14 is approximately flattened. In other words, a laminate in which the lower protective layer 15, the lower adhesive layer 13, the upper adhesive layer 14, and the upper protective layer 16 are laminated in this order is provided in each of the plurality of openings OP1. The plurality of openings OP1, the plurality of openings OP2, and the plurality of openings OP3 are filled with a laminate in which the lower protective layer 15, the lower adhesive layer 13, the upper adhesive layer 14, and the upper protective layer 16 are laminated in this order.

[0034] (Modification) Next, modified examples (first and second modified examples) of the piezoelectric sensor 1 will be described.

[0035] Fig. 3 is a plan view of the piezoelectric sensor 1 according to the first modified example. Fig. 4 is a cross-sectional view of the piezoelectric sensor 1 taken along line AA' in Fig. 3. The layered structure of the piezoelectric sensor 1 according to the first modified example is the same as that in Fig. 2.

[0036] The piezoelectric layer 10 has a plurality of openings OP1. The lower electrode 11 has a plurality of openings OP2. The upper electrode 12 has a plurality of openings OP3. The area of ​​the openings OP2 is larger than the area of ​​the openings OP1. The area of ​​the openings OP3 is approximately the same as the area of ​​the openings OP2. In this way, the area of ​​the openings OP2 of the lower electrode 11 and the area of ​​the openings OP3 of the upper electrode 12 may be the same.

[0037] Fig. 5 is a cross-sectional view of the piezoelectric sensor 1 according to the second modified example. The plan view corresponding to Fig. 5 is the same as Fig. 1. The layered structure of the piezoelectric sensor 1 according to the second modified example is the same as Fig. 2. The area relationship of the openings OP1 to OP3 is the same as Fig. 2.

[0038] The thickness of the piezoelectric layer 10 in the region where the opening OP1 is provided in the piezoelectric sensor 1 is defined as t A The thickness of the region of the piezoelectric sensor 1 where the lower electrode 11, the piezoelectric layer 10, and the upper electrode 12 are laminated is called t S The thickness t A is the thickness t S Thinner.

[0039] In the second modified example, the lower adhesive layer 13 has approximately the same thickness overall. The upper adhesive layer 14 has approximately the same thickness overall. The lower protective layer 15 has approximately the same thickness overall. The upper protective layer 16 has approximately the same thickness overall. In this configuration, the lower protective layer 15 has a recess in the area where the opening OP1 is provided. The upper protective layer 16 has a recess in the area where the opening OP1 is provided.

[0040] In the second modified example, the area of ​​the opening OP3 in the upper electrode 12 may be approximately the same as the area of ​​the opening OP2 in the lower electrode 11, as in the first modified example.

[0041] [1-2] Operation Next, the operation of the piezoelectric sensor 1 configured as above will be described.

[0042] First, the characteristics of the piezoelectric layer will be described. The piezoelectric layer is composed of P(VDF / TrFE). Figure 6 is a diagram for explaining the definition of the polarization direction of the piezoelectric layer. Any direction in the plane of the piezoelectric layer is defined as direction "1". A direction perpendicular to direction "1" in the plane of the piezoelectric layer is defined as direction "2". Directions "1" and "2" are both in-plane directions. A direction perpendicular to the plane of the piezoelectric layer is defined as direction "3". Direction "3" is the film thickness direction.

[0043] Fig. 7 is a diagram for explaining the compression operation in the thickness direction of the piezoelectric layer. Fig. 7 shows how a force is applied to the piezoelectric layer in the thickness direction, causing the piezoelectric layer to be compressed in the thickness direction. The dashed square in Fig. 7 shows the piezoelectric layer before deformation, and the solid square shows the piezoelectric layer after deformation.

[0044] When the piezoelectric layer is compressed in the film thickness direction, the polarization direction of the piezoelectric layer becomes the upward direction (direction "3") in the drawing. A positive charge is generated on the upper side of the piezoelectric layer. The plus in Figure 7 means a positive charge. When the piezoelectric layer is compressed in the film thickness direction, the piezoelectric strain constant is d 33 The number on the left of the piezoelectric strain constant indicates the polarization direction, and the number on the right indicates the deformation direction. The compression in the film thickness direction is called d 33 Also called mode.

[0045] Fig. 8 is a diagram for explaining the in-plane expansion of the piezoelectric layer. Fig. 8 shows the state in which the piezoelectric layer is pulled in the in-plane direction and the piezoelectric layer expands in the in-plane direction. The dashed square in Fig. 8 shows the piezoelectric layer before deformation, and the solid square shows the piezoelectric layer after deformation.

[0046] When the piezoelectric layer is stretched in the in-plane direction, the polarization direction of the piezoelectric layer becomes the upward direction (direction "3") in the drawing. A positive charge is generated on the upper side of the piezoelectric layer. The plus in Figure 8 means a positive charge. When the piezoelectric layer is stretched in the in-plane direction, the piezoelectric strain constant is d 31 Or d 32 The in-plane stretching motion is d 31 Mode or d 32 Also called mode.

[0047] 7 and 8, the piezoelectric layer generates charges of the same polarity when it is compressed in the film thickness direction and expanded in the in-plane direction. That is, the piezoelectric sensor 1 generates output voltages of the same polarity when it is compressed in the film thickness direction and expanded in the in-plane direction.

[0048] 9 is a schematic diagram for explaining the operation of the piezoelectric sensor 1. In explaining the operation, the piezoelectric sensor 1 according to the second modified example shown in FIG.

[0049] The piezoelectric sensor 1 can be used by being attached to a part of the body. In Fig. 9, pressure is applied from the body to the upper surface of the piezoelectric sensor 1. Pressure is applied to the piezoelectric sensor 1 from the body in the film thickness direction. The following explanation of the operation corresponds to the action centered on the position where the piezoelectric sensor 1 receives the pressure.

[0050] In the region where the opening OP1 is provided, the lower protective layer 15, the lower adhesive layer 13, the upper adhesive layer 14, and the upper protective layer 16 are laminated in this order, and the lower protective layer 15 and the upper protective layer 16 are adhered to each other by the lower adhesive layer 13 and the upper adhesive layer 14. That is, in the region where the opening OP1 is provided, the lower protective layer 15 and the upper protective layer 16 deform integrally (in conjunction with each other).

[0051] Pressure from above on the piezoelectric sensor 1 compresses the piezoelectric layer 10 in the film thickness direction. Furthermore, pressure from above on the piezoelectric sensor 1 causes the upper protective layer 16 to extend laterally (in the in-plane direction of the piezoelectric sensor 1). Since the upper protective layer 16 and the lower protective layer 15 deform in the same direction in conjunction with each other, when the upper protective layer 16 extends in the lateral direction, the lower protective layer 15 also extends in the lateral direction. When the upper protective layer 16 and the lower protective layer 15 extend in the lateral direction, the piezoelectric layer 10 is pulled in the in-plane direction in conjunction with this deformation.

[0052] That is, the piezoelectric layer 10 generates compressive stress in the film thickness direction when pressure from above on the piezoelectric sensor 1 acts directly on the piezoelectric layer 10, and tensile stress in the in-plane direction caused by deformation of the upper protective layer 16 and the lower protective layer 15. As described above, compression of the piezoelectric layer 10 in the film thickness direction and expansion of the piezoelectric layer 10 in the in-plane direction generate voltages of the same polarity in the piezoelectric layer 10. Thus, by applying compressive stress and tensile stress to the piezoelectric layer 10, these signals reinforce each other, and the sensitivity of the piezoelectric sensor 1 can be further improved. Sensitivity is the change in output voltage per unit change in pressure.

[0053] [1-3] Effects of the first embodiment According to the first embodiment, when stress is applied to the piezoelectric sensor 1, compressive stress and tensile stress can be generated in the piezoelectric layer 10. The signals are strengthened by the compressive stress and the tensile stress, so that the sensitivity of the piezoelectric sensor 1 can be improved.

[0054] In addition, the piezoelectric layer 10, the lower electrode 11, and the upper electrode 12 each have a plurality of openings. This improves the moisture permeability of the piezoelectric sensor 1. This makes it possible to prevent the body from becoming stuffy when the piezoelectric sensor 1 is attached to the body.

[0055] Furthermore, since the piezoelectric layer 10, the lower electrode 11, and the upper electrode 12 each have a plurality of openings, it is possible to improve the flexibility of the piezoelectric sensor 1. As a result, when the piezoelectric sensor 1 is attached to a curved portion of the body, the piezoelectric sensor 1 can be in close contact with the body.

[0056] Furthermore, by forming the lower protective layer 15 and the upper protective layer 16 from a material with high moisture permeability, when the piezoelectric sensor 1 is worn on the body, it is possible to prevent the area where the sensor is worn from becoming stuffy.

[0057] Furthermore, by constructing the piezoelectric layer 10, the lower protective layer 15, and the upper protective layer 16 from highly elastic materials, when the piezoelectric sensor 1 is attached to a part of the body with a large curvature, the degree of adhesion can be improved and physical information can be detected more accurately.

[0058] [2] Second embodiment In the second embodiment, a laminated structure constituting a piezoelectric element is provided on a substrate.

[0059] Fig. 10 is a plan view of a piezoelectric sensor 1 according to a second embodiment of the present invention, and Fig. 11 is a cross-sectional view of the piezoelectric sensor 1 taken along line AA' in Fig. 10.

[0060] The piezoelectric sensor 1 includes a lower protective layer 15 , a lower electrode 11 , a piezoelectric layer 10 , an upper electrode 12 , an upper adhesive layer 14 , and an upper protective layer 16 .

[0061] The lower protective layer 15 is used as a base material of the piezoelectric sensor 1. The lower protective layer 15 is provided over the entire piezoelectric sensor 1. The planar shape of the lower protective layer 15 is, for example, a rectangle.

[0062] The lower electrode 11 is provided on the lower protective layer 15. The planar shape of the lower electrode 11 is, for example, a rectangle. For example, the outer area of ​​the lower electrode 11 is smaller than the area of ​​the lower protective layer 15. The lower electrode 11 has a plurality of openings OP2.

[0063] The piezoelectric layer 10 is provided on the lower protective layer 15 and the lower electrode 11. The piezoelectric layer 10 is provided so as to cover the lower electrode 11. The outer area of ​​the piezoelectric layer 10 is the same as the area of ​​the lower protective layer 15. The piezoelectric layer 10 has a plurality of openings OP1. The piezoelectric layer 10 in the second embodiment can be formed using a coating process.

[0064] An upper electrode 12 is provided on the piezoelectric layer 10. The planar shape of the upper electrode 12 is, for example, a rectangle. For example, the outer area of ​​the upper electrode 12 is smaller than the outer area of ​​the piezoelectric layer 10. The upper electrode 12 has a plurality of openings OP3.

[0065] The area relationship between the opening OP1 in the piezoelectric layer 10, the opening OP2 in the lower electrode 11, and the opening OP3 in the upper electrode 12 is the same as in the first embodiment.

[0066] An upper adhesive layer 14 is provided on the lower protective layer 15, the piezoelectric layer 10, and the upper electrode 12. The area of ​​the upper adhesive layer 14 is the same as the area of ​​the outline of the piezoelectric layer 10. An upper protective layer 16 is provided on the upper adhesive layer 14. The area of ​​the upper protective layer 16 is the same as the area of ​​the outline of the piezoelectric layer 10. A laminate consisting of the upper adhesive layer 14 and the upper protective layer 16 is configured to fill the multiple openings OP1, the multiple openings OP2, and the multiple openings OP3.

[0067] Fig. 12 is a cross-sectional view of a piezoelectric sensor 1 according to a modified example. The plan view corresponding to Fig. 12 is the same as Fig. 10. The layered structure from the lower protective layer 15 to the upper electrode 12 is the same as Fig. 11.

[0068] An upper protective layer 16 is provided on the lower protective layer 15, the piezoelectric layer 10, and the upper electrode 12. The upper protective layer 16 is configured to fill the multiple openings OP1, the multiple openings OP2, and the multiple openings OP3. The upper protective layer 16 can be formed using a coating process.

[0069] According to the second embodiment, the same effects as those of the first embodiment can be obtained.

[0070] [3] Third embodiment The third embodiment relates to a method for manufacturing the piezoelectric sensor 1. In the method for manufacturing the piezoelectric sensor 1, a poling process is performed on the piezoelectric layer.

[0071] Hereinafter, a method for manufacturing the piezoelectric sensor 1 will be described with reference to the drawings. The configuration of the piezoelectric sensor 1 is the same as that of the second embodiment shown in Figs. 10 and 11. The plan view corresponding to the partial cross-sectional view for explaining the manufacturing method of the third embodiment is the same as Fig. 10.

[0072] 13, a lower protective layer 15 having a predetermined area is prepared. The lower protective layer 15 is used as a base material of the piezoelectric sensor 1. Next, a lower electrode 11 is formed on the lower protective layer 15, and the lower electrode 11 is patterned. The lower electrode 11 is patterned to have a plurality of openings OP2.

[0073] 14, a piezoelectric layer 10 is formed on the lower protective layer 15 and the lower electrode 11 using a coating process, and the piezoelectric layer 10 is patterned. The piezoelectric layer 10 is formed so as to cover the lower electrode 11. The piezoelectric layer 10 is patterned so as to have a plurality of openings OP1. The coating process includes spin coating, screen printing, and inkjet printing. The piezoelectric layer 10 is made of P(VDF / TrFE).

[0074] 15, the upper electrode 12 is formed on the piezoelectric layer 10, and then the upper electrode 12 is patterned. The upper electrode 12 is patterned so as to have a plurality of openings OP3.

[0075] The diameter of the opening OP3 in the upper electrode 12 is set to be larger than the diameter of the opening OP1 in the piezoelectric layer 10 and larger than the diameter of the opening OP2 in the lower electrode 11. The distance between the edge of the upper electrode 12 on the opening OP3 side and the edge of the piezoelectric layer 10 on the opening OP1 side is referred to as L.

[0076] 16, the upper adhesive layer 14 is formed by coating on the lower protective layer 15, the piezoelectric layer 10, and the upper electrode 12. Then, the upper protective layer 16 is attached onto the upper adhesive layer 14. The upper protective layer 16 is made of a film.

[0077] Next, as shown in FIG. 17, a power source 17 is connected between the lower electrode 11 and the upper electrode 12, and an AC voltage is applied between the lower electrode 11 and the upper electrode 12. Specifically, the power source 17 is connected to a wiring drawn from the lower electrode 11 and a wiring drawn from the upper electrode 12. Then, a poling process is performed on the piezoelectric layer 10. The poling process (also called a polarization process) is a process in which an electric field is applied from the outside to cause spontaneous polarization in the material. In the poling process, an AC voltage is applied so that the electric field becomes 100 V / μm or more. A DC voltage may be used for the poling process. By performing the poling process on the piezoelectric layer 10, spontaneous polarization occurs in the piezoelectric layer 10, and a large piezoelectricity is generated.

[0078] In this manner, the piezoelectric sensor 1 according to the third embodiment is manufactured.

[0079] Now, assume that a poling process is performed immediately after the manufacturing process of FIG. 15 (in a state in which the upper electrode 12 is exposed). In the configuration of FIG. 15, unless the distance L is increased, there is a high risk of a short circuit occurring between the lower electrode 11 and the upper electrode 12. When a poling process is performed, the distance L is preferably 300 μm or more. In this case, the area of ​​the opening OP3 of the upper electrode 12 needs to be increased, which reduces the sensitivity of the piezoelectric sensor.

[0080] In this embodiment, the poling process is not performed immediately after the manufacturing process of FIG. 15, but is performed after the opening OP3 of the upper electrode 12 is filled with the upper protective layer 16. This makes it possible to suppress the occurrence of a short circuit between the lower electrode 11 and the upper electrode 12.

[0081] Furthermore, even if misalignment occurs between the openings of the piezoelectric layer 10, the lower electrode 11, and the upper electrode 12, the occurrence of a short circuit between the lower electrode 11 and the upper electrode 12 can be suppressed.

[0082] The manufacturing method for carrying out the poling process can also be applied to the piezoelectric sensors 1 according to other embodiments.

[0083] The present invention is not limited to the above-mentioned embodiment, and various modifications can be made in the implementation stage without departing from the gist of the invention. In addition, the embodiments may be implemented in appropriate combination, and in that case, the combined effect can be obtained. Furthermore, the above-mentioned embodiment includes various inventions, and various inventions can be extracted by combinations selected from the multiple components disclosed. For example, if the problem can be solved and the effect can be obtained even if some components are deleted from all the components shown in the embodiment, the configuration from which the components are deleted can be extracted as an invention. [Explanation of symbols]

[0084] 1...piezoelectric sensor, 10...piezoelectric layer, 11...lower electrode, 12...upper electrode, 13...lower adhesive layer, 14...upper adhesive layer, 15...lower protective layer, 16...upper protective layer, 17...power supply, OP1 to OP3...openings.

Claims

1. a piezoelectric layer having a plurality of first openings; a lower electrode provided under the piezoelectric layer, the lower electrode having a plurality of second openings arranged to overlap the plurality of first openings in a plan view; an upper electrode provided on the piezoelectric layer, the upper electrode having a plurality of third openings arranged to overlap the plurality of first openings in a plan view; a first adhesive layer provided under the lower electrode; a first protective layer provided under the first adhesive layer; A second adhesive layer provided on the upper electrode; a second protective layer provided on the second adhesive layer; Equipped with A laminate in which the first protective layer, the first adhesive layer, the second adhesive layer, and the second protective layer are laminated in this order is provided within each of the first openings. Piezoelectric sensor.

2. The first adhesive layer and the second adhesive layer are made of a moisture-permeable material. The piezoelectric sensor according to claim 1 .

3. a piezoelectric layer having a plurality of first openings; a lower electrode provided under the piezoelectric layer, the lower electrode having a plurality of second openings arranged to overlap the plurality of first openings in a plan view; an upper electrode provided on the piezoelectric layer, the upper electrode having a plurality of third openings arranged to overlap the plurality of first openings in a plan view; a first protective layer provided under the lower electrode; A second protective layer provided on the upper electrode; Equipped with A laminate in which the first protective layer and the second protective layer are laminated in this order is provided within each of the first openings. Piezoelectric sensor.

4. The first protective layer and the second protective layer are made of a material having moisture permeability. The piezoelectric sensor according to claim 1 or 3.

5. The area of ​​the second opening is larger than the area of ​​the first opening, The area of ​​the third opening is larger than the area of ​​the second opening. The piezoelectric sensor according to claim 1 or 3.

6. The area of ​​the second opening is larger than the area of ​​the first opening, The area of ​​the third opening is the same as the area of ​​the second opening. The piezoelectric sensor according to claim 1 or 3.

7. Each of the first openings, the second openings, and the third openings is a circle. The piezoelectric sensor according to claim 1 or 3.

8. The plurality of first openings are evenly spaced. The piezoelectric sensor according to claim 1 or 3.

9. forming a lower electrode having a plurality of second openings on the first protective layer; forming a piezoelectric layer on the lower electrode, the piezoelectric layer having a plurality of first openings arranged to overlap the plurality of second openings in a plan view; forming an upper electrode on the piezoelectric layer, the upper electrode having a plurality of third openings arranged to overlap the plurality of second openings in a plan view; forming a second protective layer on the upper electrode so as to fill the second openings, the first openings, and the third openings; applying a voltage between the lower electrode and the upper electrode to perform a poling process on the piezoelectric layer; A method for manufacturing a piezoelectric sensor comprising the steps of:

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