Sensors

Abstract

A sensor according to the present invention comprises: a piezoelectric film having an upper main surface and a lower main surface arrayed in the vertical direction; a first electrode that has an upper main surface and a lower main surface arrayed in the vertical direction, that is provided above the piezoelectric film, and that overlaps with at least a portion of the piezoelectric film as seen in the vertical direction; a second electrode that has an upper main surface and a lower main surface arrayed in the vertical direction, that is provided below the piezoelectric film, and that overlaps with at least a portion of the piezoelectric film as seen in the vertical direction; and an insulator layer that has an upper main surface and a lower main surface arrayed in the vertical direction, that is provided above the first electrode, and that overlaps with at least a portion of the first electrode as seen in the vertical direction. At least a portion of the outer edge of the upper main surface of the insulator layer, as seen in the vertical direction, does not overlap with the first electrode, and is positioned below the upper main surface of the first electrode.

Description

[Technical field]

[0001] The present invention relates to a sensor for detecting a pressing force. [Background technology]

[0002] As an example of a conventional sensor-related invention, a pressure sensor described in Patent Document 1 is known. This pressure sensor includes a piezoelectric film, a second electrode, and a third electrode. The second electrode is fixed to the upper main surface of the piezoelectric film via an adhesive layer. The third electrode is fixed to the lower main surface of the piezoelectric film via an adhesive layer. When the piezoelectric film is pressed downward, it extends in the left-right direction. When the piezoelectric film is stretched in the left-right direction, it generates an electric charge. This causes the second electrode to output a detection signal according to the pressure. A pressure sensor such as the above is attached to a display panel of an electronic device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020 / 129346 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, in the pressure sensor described in Patent Document 1, it is desired to improve the sealing performance of the electrodes.

[0005] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a sensor capable of improving the sealing performance of the electrodes. [Means for solving the problem]

[0006] A sensor according to one aspect of the present invention includes: a piezoelectric film having upper and lower principal surfaces aligned in a vertical direction; a first electrode having upper and lower principal surfaces aligned in a vertical direction, disposed above the piezoelectric film, and overlapping at least a portion of the piezoelectric film when viewed in the vertical direction; a second electrode having upper and lower principal surfaces aligned in the vertical direction, disposed below the piezoelectric film, and overlapping at least a portion of the piezoelectric film when viewed in the vertical direction; an insulator layer having upper and lower principal surfaces aligned in a vertical direction, disposed above the first electrode, and overlapping at least a portion of the first electrode when viewed in the vertical direction; It is equipped with At least a part of the outer edge of the upper main surface of the insulating layer when viewed in the up-down direction does not overlap the first electrode when viewed in the up-down direction, and is located below the upper main surface of the first electrode. Effect of the Invention

[0007] According to the sensor of the present invention, the sealing performance of the electrodes can be improved. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is an exploded perspective view of an electronic device 1. As shown in FIG. [Diagram 2] FIG. 2 is a cross-sectional view of the electronic device 1 taken along line AA. [Diagram 3] FIG. 3 is a bottom view and a cross-sectional view of the sensor 6. [Figure 4] FIG. 4 is a cross-sectional view of the sensor 6a. [Diagram 5] FIG. 5 is a cross-sectional view of the sensor 6b. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (Embodiment) [Electronic device structure] Hereinafter, a configuration of an electronic device 1 including a sensor 6 according to an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is an exploded perspective view of the electronic device 1. Fig. 2 is a cross-sectional view of the electronic device 1 taken along line AA. Fig. 3 is a bottom view and a cross-sectional view of the sensor 6.

[0010] In addition, in this specification, directions are defined as follows. In the electronic device 1, the direction in which the upper and lower main surfaces of the operation panel 2 are aligned is defined as the up-down direction. In addition, the direction in which the long side of the operation panel 2 of the electronic device 1 extends when viewed in the up-down direction is defined as the front-rear direction. In addition, the direction in which the short side of the operation panel 2 of the electronic device 1 extends when viewed in the up-down direction is defined as the left-right direction. The up-down direction, left-right direction, and front-rear direction are mutually perpendicular. Note that the definitions of directions in this specification are merely examples. Therefore, the directions in the actual use of the electronic device 1 do not need to match the directions in this specification. In addition, the up-down direction may be reversed in FIG. 1. The left-right direction may be reversed in FIG. 1. The front-rear direction may be reversed in FIG. 1.

[0011] The electronic device 1 is a portable electronic terminal such as a smartphone, a tablet computer, etc. The electronic device 1 includes an operation panel 2, a housing 3, a display panel 4, an adhesive member 5, a sensor 6, and a plate-shaped member 7, as shown in Fig. 1 and Fig. 2.

[0012] The operation panel 2 has upper and lower main surfaces aligned in the vertical direction. When viewed in the vertical direction, the operation panel 2 has a rectangular shape with two long sides extending in the front-to-back direction and two short sides extending in the left-to-right direction. A part of the user's body or an operation member comes into contact with the upper main surface of the operation panel 2. The operation panel 2 is a transparent plate. The operation panel 2 is, for example, a glass plate.

[0013] The display panel 4 has an upper main surface and a lower main surface aligned in the vertical direction. The display panel 4 has a rectangular shape with two long sides extending in the front-rear direction and two short sides extending in the left-right direction when viewed in the vertical direction. The display panel 4 is fixed to the lower main surface of the operation panel 2. The display panel 4 is fixed to the operation panel 2 with an adhesive, double-sided tape, or the like. The entire display panel 4 overlaps with the operation panel 2 when viewed in the vertical direction. Therefore, the display panel 4 does not protrude from the outer edge of the operation panel 2 when viewed in the vertical direction. The display panel 4 is, for example, an organic EL display or a liquid crystal display. The display panel 4 may also include a touch panel for detecting the position where the user touches the operation panel 2. However, the touch panel may be included in the operation panel 2.

[0014] The plate-shaped member 7 has an upper main surface and a lower main surface aligned in the vertical direction. The plate-shaped member 7 has a rectangular shape with two long sides extending in the front-rear direction and two short sides extending in the left-right direction when viewed in the vertical direction. The plate-shaped member 7 is fixed to the lower main surface of the display panel 4. The plate-shaped member 7 is fixed to the display panel 4 by adhesive, double-sided tape, or the like. The entire plate-shaped member 7 overlaps with the display panel 4 when viewed in the vertical direction. Therefore, the plate-shaped member 7 does not protrude from the outer edge of the display panel 4 when viewed in the vertical direction. The rigidity of the plate-shaped member 7 is higher than the rigidity of the sensor 6 described later. The material of such a plate-shaped member 7 is, for example, a metal such as SUS (Stainless Used Steel). However, the material of the plate-shaped member 7 may be a material other than a metal. The material other than a metal is, for example, a resin.

[0015] The housing 3 is located below the operation panel 2. The housing 3 is a box. The housing 3 has a rectangular shape when viewed in the vertical direction. The long sides of the housing 3 extend in the front-to-rear direction. The short sides of the housing 3 extend in the left-to-right direction. The outer edge of the housing 3 when viewed in the vertical direction coincides with the outer edge of the operation panel 2 when viewed in the vertical direction. However, the top surface of the housing 3 is open. The opening Op of the housing 3 has a rectangular shape when viewed in the vertical direction.

[0016] The adhesive member 5 fixes a portion of the lower main surface of the operation panel 2 to the housing 3. More specifically, the adhesive member 5 fixes the periphery of the opening Op of the housing 3 to the vicinity of the outer edge of the operation panel 2. Thus, the adhesive member 5 has a rectangular frame shape surrounding the display panel 4 when viewed in the vertical direction. Therefore, the adhesive member 5 does not overlap with the display panel 4 when viewed in the vertical direction. The adhesive member 5 as described above is waterproof.

[0017] The sensor 6 detects deformation of the operation panel 2. As shown in FIG. 1, the sensor 6 is fixed to the lower main surface of the plate-like member 7. More specifically, the sensor 6 has a rectangular shape when viewed in the up-down direction. The sensor 6 has a longitudinal direction extending in the left-right direction. The sensor 6 is located in the center of the plate-like member 7 in the front-rear direction when viewed in the up-down direction.

[0018] When the user presses the operation panel 2 and the operation panel 2 bends downward, the display panel 4 and the plate-like member 7 also bend downward. The sensor 6 then bends downward together with the plate-like member 7. This causes the sensor 6 to output a detection signal corresponding to the deformation of the operation panel 2 caused by the user pressing the operation panel 2. The sensor 6 will be described in detail below with reference to FIG. 3.

[0019] As shown in FIG. 3, the sensor 6 includes a piezoelectric film 14, a third electrode 15a, a second electrode 15b, a base material 16, a flexible printed circuit board 19, adhesive layers 18, 20, and an insulating layer 21. The piezoelectric film 14 has a sheet shape. Therefore, the piezoelectric film 14 has an upper main surface and a lower main surface aligned in the vertical direction. The length of the piezoelectric film 14 in the left-right direction is longer than the length of the piezoelectric film 14 in the front-rear direction. In this embodiment, the piezoelectric film 14 has a rectangular shape with long sides extending in the left-right direction when viewed in the vertical direction. The piezoelectric film 14 generates a charge according to the deformation amount of the piezoelectric film 14. In this embodiment, the piezoelectric film 14 is a PLA film. The piezoelectric film 14 will be described in more detail below.

[0020] The piezoelectric film 14 has a characteristic that the polarity of the electric charge generated when the piezoelectric film 14 is stretched in the left-right direction is opposite to the polarity of the electric charge generated when the piezoelectric film 14 is stretched in the front-back direction. Specifically, the piezoelectric film 14 is a film formed from a chiral polymer. The chiral polymer is, for example, polylactic acid (PLA), particularly L-type polylactic acid (PLLA). PLLA made of a chiral polymer has a helical structure of the main chain. PLLA has a piezoelectricity in which the molecules are oriented by uniaxial stretching. The piezoelectric film 14 has a piezoelectric constant of d14. The uniaxial stretching direction (orientation direction) of the piezoelectric film 14 forms an angle of 45 degrees with respect to each of the front-back direction and the left-right direction. This 45 degrees includes, for example, an angle including about 45 degrees ±10 degrees. As a result, the piezoelectric film 14 generates an electric charge when the piezoelectric film 14 is stretched in the left-right direction or the front-back direction. The polarity of the charge generated by the piezoelectric film 14 when it is stretched in the left-right direction is different from the polarity of the charge generated by the piezoelectric film 14 when it is stretched in the front-back direction. For example, the piezoelectric film 14 generates a positive charge when it is stretched in the left-right direction. For example, the piezoelectric film 14 generates a negative charge when it is stretched in the front-back direction. The magnitude of the charge depends on the amount of deformation of the piezoelectric film 14 due to stretching or compression. More precisely, the magnitude of the charge is proportional to the derivative of the amount of deformation of the piezoelectric film 14 due to stretching or compression.

[0021] The third electrode 15a is a signal electrode. Therefore, a detection signal is output from the third electrode 15a. The third electrode 15a has an upper main surface and a lower main surface aligned in the vertical direction. The third electrode 15a is provided above the piezoelectric film 14 and below the first electrode 17 (described in detail later). In this embodiment, the third electrode 15a is provided on the upper main surface of the piezoelectric film 14. The third electrode 15a overlaps at least a portion of the piezoelectric film 14 when viewed in the vertical direction. In this embodiment, the third electrode 15a covers the entire upper main surface of the piezoelectric film 14. The third electrode 15a includes an adhesive layer (not shown). The third electrode 15a is fixed to the upper main surface of the piezoelectric film 14 by this adhesive layer.

[0022] The second electrode 15b is a ground electrode. The second electrode 15b is connected to a ground potential. The second electrode 15b has an upper main surface and a lower main surface aligned in the vertical direction. The second electrode 15b is provided below the piezoelectric film 14. The second electrode 15b is provided on the lower main surface of the piezoelectric film 14. The second electrode 15b overlaps at least a portion of the piezoelectric film 14 when viewed in the vertical direction. In this embodiment, the second electrode 15b covers the entire lower main surface of the piezoelectric film 14. The second electrode 15b includes an adhesive layer (not shown). The second electrode 15b is fixed to the lower main surface of the piezoelectric film 14 by this adhesive layer.

[0023] The flexible printed circuit board 19 has upper and lower main surfaces aligned in the vertical direction. The flexible printed circuit board 19 is provided above the third electrode 15a. The flexible printed circuit board 19 overlaps with the third electrode 15a when viewed in the vertical direction.

[0024] The flexible printed circuit board 19 includes a first electrode 17 and flexible layers 19a and 19b. The flexible layers 19a and 19b are laminated in this order from top to bottom. The flexible layers 19a and 19b are made of an insulating material such as resin.

[0025] The first electrode 17 is a ground electrode. The first electrode 17 is connected to a ground potential. The first electrode 17 has an upper main surface and a lower main surface aligned in the vertical direction. The first electrode 17 is provided above the piezoelectric film 14. In this embodiment, the first electrode 17 is provided between the flexible layer 19a and the flexible layer 19b. The first electrode 17 overlaps at least a portion of the piezoelectric film 14 when viewed in the vertical direction. In this embodiment, the first electrode 17 is within the outer edge of the piezoelectric film 14 when viewed in the vertical direction.

[0026] The insulator layer 21 is a resist layer that is a protective layer. The insulator layer 21 has an upper main surface and a lower main surface aligned in the vertical direction. The insulator layer 21 is provided above the first electrode 17. In this embodiment, the insulator layer 21 is provided on the upper main surface of the flexible printed circuit board 19. The insulator layer 21 overlaps at least a portion of the first electrode 17 when viewed in the vertical direction. In this embodiment, the insulator layer 21 overlaps the entire first electrode 17 when viewed in the vertical direction. At least a portion of the outer edge E of the upper main surface of the insulator layer 21 when viewed in the vertical direction does not overlap the first electrode 17 when viewed in the vertical direction, and is located below the upper main surface of the first electrode 17. In this embodiment, the entire outer edge E of the upper main surface of the insulator layer 21 when viewed in the vertical direction does not overlap the first electrode 17 when viewed in the vertical direction, and is located below the upper main surface of the first electrode 17. The vertical position of the outer edge E of the upper main surface of the insulator layer 21 when viewed in the vertical direction is the same as the vertical position of the first electrode 17. In this specification, the upper main surface of the insulator layer 21 is a portion of the surface of the insulator layer 21 having a normal line that includes an upward component. The material of the insulator layer 21 as described above is, for example, polyimide.

[0027] The substrate 16 is provided on the insulating layer 21. The substrate 16 holds the piezoelectric film 14, the third electrode 15a, the second electrode 15b, the flexible printed circuit board 19, and the insulating layer 21, and thereby deforms together with the piezoelectric film 14. The substrate 16 has a sheet shape. The substrate 16 has an upper main surface and a lower main surface. The length of the substrate 16 in the left-right direction is longer than the length of the substrate 16 in the front-rear direction. The material of the substrate 16 is, for example, polyurethane or PET.

[0028] The adhesive layer 18 fixes the piezoelectric film 14, the third electrode 15a, the second electrode 15b, the flexible printed circuit board 19, and the insulator layer 21 to the substrate 16. More specifically, the adhesive layer 18 is provided on the lower main surface of the substrate 16. The adhesive layer 18 covers the entire lower main surface of the substrate 16. The adhesive layer 18 also covers the entire upper main surface of the insulator layer 21. The adhesive layer 18 bonds the insulator layer 21 to the substrate 16. As a result, the deformation of the substrate 16 is transmitted to the piezoelectric film 14 via the adhesive layer 18. The material of the adhesive layer 18 is, for example, a thermosetting adhesive or a thermoplastic adhesive.

[0029] The adhesive layer 20 is provided on the upper main surface of the base material 16. The adhesive layer 20 fixes the base material 16 to the lower main surface of the plate-like member 7. The material of the adhesive layer 20 is, for example, a thermosetting adhesive or a thermoplastic adhesive.

[0030] The substrate 16 and the adhesive layers 18, 20 are, for example, double-sided tape.

[0031] [effect] According to the sensor 6, the sealing performance of the first electrode 17 can be improved. More specifically, the insulator layer 21 is provided above the first electrode 17. At least a part of the outer edge E of the upper main surface of the insulator layer when viewed in the vertical direction does not overlap with the first electrode 17 when viewed in the vertical direction, and is located below the upper main surface of the first electrode 17. This allows the insulator layer 21 to prevent moisture that penetrates into the sensor 6 from reaching the first electrode 17. Therefore, according to the sensor 6, the sealing performance of the first electrode 17 can be improved.

[0032] According to the sensor 6, the sealing performance of the first electrode 17 can be further improved. The entire outer edge E of the upper main surface of the insulator layer 21 does not overlap with the first electrode 17 when viewed in the vertical direction, and is located below the upper main surface of the first electrode 17. This allows the insulator layer 21 to further prevent moisture that penetrates into the sensor 6 from reaching the first electrode 17. Therefore, according to the sensor 6, the sealing performance of the first electrode 17 can be further improved.

[0033] (First Modification) A sensor 6a according to a first modified example will be described below with reference to the drawings. Fig. 4 is a cross-sectional view of the sensor 6a.

[0034] The sensor 6a differs from the sensor 6 in that the vertical direction is inverted, the first electrode 17 and the flexible layers 19a and 19b are not present, and the position of the insulator layer 21. More specifically, the vertical direction of the sensor 6a is opposite to that of the sensor 6. Therefore, in the sensor 6a, the first electrode 115b is located above the piezoelectric film 14. The first electrode 115b is connected to a ground potential. The second electrode 115a is located below the piezoelectric film 14. A detection signal is output from the second electrode 115a. The insulator layer 21 is provided on the first electrode 115b. In this embodiment, the insulator layer 21 is provided on the upper main surface of the first electrode 115b and the upper main surface of the piezoelectric film 14. The entire outer edge E of the upper main surface of the insulator layer 21 when viewed in the vertical direction does not overlap the first electrode 115b when viewed in the vertical direction, and is located below the upper main surface of the first electrode 115b. The other structure of the sensor 6a is the same as that of the sensor 6, and therefore a description thereof will be omitted. The sensor 6a can achieve the same effects as the sensor 6.

[0035] (Second Modification) A sensor 6b according to a second modified example will be described below with reference to the drawings. Fig. 5 is a cross-sectional view of the sensor 6b.

[0036] The sensor 6b differs from the sensor 6 in that the third electrode 15a and the flexible layers 19a and 19b are not present, and in the position of the first electrode 17 and the position of the insulator layer 21. More specifically, the first electrode 17 is provided on the upper main surface of the piezoelectric film 14. The first electrode 17 is a signal electrode. Therefore, a detection signal is output from the first electrode 17.

[0037] The insulator layer 21 is provided on the upper main surface of the first electrode 17 and the upper main surface of the piezoelectric film 14. The entire outer edge E of the upper main surface of the insulator layer 21 when viewed in the vertical direction does not overlap with the first electrode 17 when viewed in the vertical direction, and is located below the upper main surface of the first electrode 17. The other structure of the sensor 6b is the same as that of the sensor 6, so a description thereof will be omitted. The sensor 6b can achieve the same effects as the sensor 6.

[0038] (Other embodiments) The sensor according to the present invention is not limited to the sensors 6, 6a, and 6b, and may be modified within the scope of the present invention. In addition, the structures of the sensors 6, 6a, and 6b may be arbitrarily combined.

[0039] In the electronic device 1, the piezoelectric film 14 may be a PVDF (polyvinylidene fluoride) film. The piezoelectric film 14 may be a piezoelectric ceramic. The piezoelectric film 14 may be a strain sensor.

[0040] The adhesive member 5 does not necessarily have to be waterproof.

[0041] In addition, the two sides extending in the front-rear direction may be short sides, and the two sides extending in the left-right direction may be long sides.

[0042] The sensor 6 may be provided at a position other than the center of the plate member 7 in the front-rear direction when viewed in the up-down direction.

[0043] The operation panel 2 may be a resin plate.

[0044] The sensor 6 does not necessarily have a longitudinal direction extending in the left-right direction, but may have a longitudinal direction extending in the front-rear direction.

[0045] Although the electronic device 1 is described as having a touch panel, it may be a touch pad. In this case, the display panel 4 is not necessary. Moreover, the operation panel 2 does not have to be made of a transparent material.

[0046] In addition, the outer edge E of the upper main surface of the insulator layer 21 when viewed in the vertical direction may include a portion that does not overlap the first electrode when viewed in the vertical direction and is not located below the upper main surface of the first electrode.

[0047] The flexible printed circuit board 19 may further include a conductor layer other than the first electrode 17. The conductor layer other than the first electrode 17 is, for example, a wiring conductor layer.

[0048] The base material 16 and the adhesive layers 18, 20 (double-sided tape) are larger than the sensor 6 when viewed in the vertical direction. However, the sensor 6 may be larger than the base material 16 and the adhesive layers 18, 20 (double-sided tape) when viewed in the vertical direction.

[0049] The substrate 16 and the adhesive layer 20 are not essential components. The double-sided tape may include only the adhesive layer 18. [Explanation of symbols]

[0050] 1:Electronic equipment 2: Operation panel 3: Housing 4: Display panel 5: Adhesive material 6, 6a, 6b: Sensor 7: Plate-shaped member 14: Piezoelectric film 15a: 3rd electrode 15b, 115a: 2nd electrode 16: Base material 17,115b: 1st electrode 18: Adhesive layer 19: Flexible printed circuit board 19a, 19b: Flexible layer 20: Adhesive layer 21: Insulator layer E: Outer edge

Claims

1. a sensor having a longitudinal direction extending in a left-right direction, which is a direction in which a short side of an operation panel of an electronic device extends, the sensor detecting deformation of the operation panel, a piezoelectric film having upper and lower principal surfaces aligned in a vertical direction; a first electrode having upper and lower principal surfaces aligned in a vertical direction, disposed above the piezoelectric film, and overlapping at least a portion of the piezoelectric film when viewed in the vertical direction; a second electrode having upper and lower principal surfaces aligned in the vertical direction, disposed below the piezoelectric film, and overlapping at least a portion of the piezoelectric film when viewed in the vertical direction; an insulator layer having upper and lower principal surfaces aligned in a vertical direction, provided above the first electrode, and overlapping at least a portion of the first electrode when viewed in the vertical direction; Equipped with an outer edge of an upper main surface of the insulator layer when viewed in the vertical direction does not overlap with the first electrode when viewed in the vertical direction and is located below the upper main surface of the first electrode, the first electrode is shorter than the second electrode in the left-right direction, The upper principal surface and the side surface of the first electrode are in contact with the insulator layer. Sensor.

2. The first electrode is connected to a ground potential; A detection signal is output from the second electrode. The sensor of claim 1 .

3. the polarity of the electric charge generated by the piezoelectric film when the piezoelectric film is stretched in the left-right direction is different from the polarity of the electric charge generated by the piezoelectric film when the piezoelectric film is stretched in the front-rear direction, which is the direction in which the long sides of the operation panel extend; The sensor according to claim 1 or 2.

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