Sensor and method for manufacturing the same

Abstract

A sensor according to the present invention comprises: a piezoelectric film that has a top main surface and a bottom main surface aligned in a vertical direction; a first electrode that is provided to the top main surface of the piezoelectric film; a second electrode that is provided to the bottom main surface of the piezoelectric film; and a first curable resin layer that is provided under the second electrode and covers at least a portion of the second electrode when viewed in the vertical direction.

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, when a pressing force is repeatedly applied to the pressure sensor, a force is repeatedly applied to the pressure sensor and a member that fixes the pressure sensor to the display panel. Therefore, from the viewpoint of preventing failure of the pressure sensor, it is desired to improve the rigidity of the pressure sensor.

[0005] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a sensor having high rigidity. [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 provided on the upper principal surface of the piezoelectric film; A second electrode provided on the lower main surface of the piezoelectric film; a first cured resin layer provided under the second electrode and covering at least a portion of the second electrode when viewed in a top-bottom direction; It is equipped with: Effect of the Invention

[0007] According to the sensor of the present invention, the rigidity of the sensor 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 6. [Diagram 5] FIG. 5 is a cross-sectional view of the sensor 6a. [Figure 6] FIG. 6 is a cross-sectional view of the sensor 6b. [Figure 7] FIG. 7 is a cross-sectional view of the sensor 6c. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (Embodiment) [Electronic device structure] The configuration of an electronic device 1 including a sensor 6 according to an embodiment of the present invention will be described below 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. Fig. 4 is 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 first electrode 15a, a second electrode 15b, a substrate 16, a first cured resin layer 17, and adhesive layers 18 and 20. 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 an electric 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 first electrode 15a is a signal electrode. Therefore, a detection signal is output from the first electrode 15a. In this embodiment, the first electrode 15a is provided on the upper main surface of the piezoelectric film 14. The first electrode 15a covers the entire upper main surface of the piezoelectric film 14. The first electrode 15a includes an adhesive layer (not shown). The first 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 is provided on the lower main surface of the piezoelectric film 14. 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 substrate 16 is provided on the first electrode 15a. The substrate 16 holds the piezoelectric film 14, the first electrode 15a, and the second electrode 15b, 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.

[0024] The adhesive layer 18 fixes the piezoelectric film 14, the first electrode 15a, and the second electrode 15b 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 first electrode 15a. The adhesive layer 18 bonds the first electrode 15a 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 double-sided tape, a thermosetting adhesive, or a thermoplastic adhesive.

[0025] 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 double-sided tape, a thermosetting adhesive, or a thermoplastic adhesive.

[0026] The first cured resin layer 17 is provided under the second electrode 15b. In this embodiment, the first cured resin layer 17 is in contact with the second electrode 15b. Also, the first cured resin layer 17 covers at least a portion of the second electrode 15b when viewed in the up-down direction. In this embodiment, the first cured resin layer 17 covers the entire second electrode 15b when viewed in the up-down direction.

[0027] Here, the first cured resin layer 17 is an adhesive layer of the carrier tape 100. Specifically, as shown in FIG. 4, the carrier tape 100 is attached to the lower main surface of the second electrode 15b. The carrier tape 100 includes the first cured resin layer 17 and a base material layer 101. The material of the first cured resin layer 17 is a UV curable resin. In an uncured state, the first cured resin layer 17 bonds the base material layer 101 and the second electrode 15b. However, the base material layer 101 is peeled off from the first cured resin layer 17 after the first cured resin layer 17 is cured. At this time, the first cured resin layer 17 is not peeled off together with the base material layer 101 and remains on the lower main surface of the second electrode 15b as shown in FIG. 3.

[0028] [effect] According to the sensor 6, the first cured resin layer 17 is provided under the second electrode 15b, and thus the sensor 6 is reinforced. As a result, the rigidity of the sensor 6 is improved.

[0029] According to the sensor 6, the manufacturing cost of the sensor 6 can be reduced. More specifically, the material of the first cured resin layer 17 is a cured resin. Therefore, the first cured resin layer 17 is an adhesive layer of the carrier tape 100. In this manner, in the sensor 6, the first cured resin layer 17, which is a part of the existing carrier tape 100, is utilized as a reinforcing member. As a result, there is no need to provide a new reinforcing member to reinforce the sensor 6. Therefore, according to the sensor 6, the manufacturing cost of the sensor 6 can be reduced.

[0030] The sensor 6 improves the sensitivity of the sensor 6. More specifically, the sensor 6 has a high rigidity because the first cured resin layer 17 is provided. When the rigidity of the sensor 6 is high, the deformation of the operation panel 2 is easily transmitted to the piezoelectric film 14. That is, in the sensor 6, the amount of deformation of the piezoelectric film 14 is likely to be large, and therefore the voltage of the detection signal output by the piezoelectric film 14 is likely to be large. Therefore, the sensor 6 improves the sensitivity of the sensor 6.

[0031] According to the sensor 6, the first cured resin layer 17 is provided under the second electrode 15b. This allows the conductor and resin inside the sensor 6 to be protected by the first cured resin layer 17. As a result, the conductor and resin inside the sensor 6 are prevented from being deteriorated due to moisture absorption.

[0032] The presence or absence of the first cured resin layer 17 can be confirmed by FT-IR analysis (Fourier transform infrared spectroscopy). Specifically, when the material of the first cured resin layer 17 is a UV cured resin, when the sensor 6 is subjected to FT-IR analysis, a peak indicating the UV cured resin appears in the analysis result.

[0033] (First Modification) A sensor 6a according to a first modified example will be described below with reference to the drawings. Fig. 5 is a cross-sectional view of the sensor 6a.

[0034] The sensor 6a differs from the sensor 6 in the shape of the first cured resin layer 17. The first cured resin layer 17 may cover a part of the second electrode 15b when viewed in the up-down direction. That is, a part of the first cured resin layer 17 may be peeled off together with the base material layer 101, and the remaining part of the first cured resin layer 17 may remain on the lower main surface of the second electrode 15b without being peeled off together with the base material layer 101. The other structure of the sensor 6a is the same as that of the sensor 6, so 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. 6 is a cross-sectional view of the sensor 6b.

[0036] The sensor 6b differs from the sensor 6 in that the up-down direction is reversed and in the position of the first cured resin layer 17. More specifically, the up-down direction of the sensor 6b is opposite to that of the sensor 6. Therefore, in the sensor 6b, 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 first cured resin layer 17 is provided below the second electrode 115a. The first cured resin layer 17 is located between the substrate 16 and the adhesive layer 20. 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.

[0037] (Third Modification) A sensor 6c according to a third modified example will be described below with reference to the drawings. Fig. 7 is a cross-sectional view of the sensor 6c.

[0038] The sensor 6c differs from the sensor 6 in that it further includes a second cured resin layer 117. The second cured resin layer 117 is provided on the first electrode 15a. The second cured resin layer 117 is located between the substrate 16 and the adhesive layer 20. The other structures of the sensor 6c are the same as those of the sensor 6, and therefore description thereof will be omitted. The sensor 6c can achieve the same effects as the sensor 6.

[0039] (Other embodiments) The sensor according to the present invention is not limited to the sensors 6, 6a to 6c, and can be modified within the scope of the present invention. In addition, the structures of the sensors 6, 6a to 6c may be combined in any manner.

[0040] 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.

[0041] The adhesive member 5 does not necessarily have to be waterproof.

[0042] 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.

[0043] 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.

[0044] The operation panel 2 may be a resin plate.

[0045] 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.

[0046] 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.

[0047] The material of the first cured resin layer 17 may be a cured resin other than the UV cured resin. The material of the first cured resin layer 17 may be, for example, a thermosetting resin. [Explanation of symbols]

[0048] 1:Electronic equipment 2: Operation panel 3: Housing 4: Display panel 5: Adhesive material 6, 6a to 6c: Sensors 7: Plate-shaped member 14: Piezoelectric film 15a, 115b: 1st electrode 15b, 115a: 2nd electrode 16: Base material 17: First cured resin layer 117: Second cured resin layer 18,20: Adhesive layer 100: Carrier tape 101: Base material layer

Claims

1. a piezoelectric film having upper and lower principal surfaces aligned in a vertical direction; a first electrode provided on the upper principal surface of the piezoelectric film; A second electrode provided on the lower main surface of the piezoelectric film; a first cured resin layer provided under the second electrode and covering only a portion of the second electrode when viewed in a top-bottom direction; It is equipped with The first cured resin layer is an adhesive layer of a carrier tape. Sensor.

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

3. The first cured resin layer is in contact with the second electrode. The sensor according to claim 1 or 2.

4. The material of the first cured resin layer is a UV cured resin. The sensor according to claim 1 or 2.

5. The sensor includes: A second cured resin layer provided on the first electrode, In addition, The sensor according to claim 1 or 2.

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

7. a polarity of an electric charge generated by the piezoelectric film when the piezoelectric film is stretched in a left-right direction is different from a polarity of an electric charge generated by the piezoelectric film when the piezoelectric film is stretched in a front-back direction; The sensor according to claim 1 or 2.

8. A step of preparing a sensor member including a piezoelectric film having upper and lower principal surfaces aligned in a vertical direction, a first electrode provided on the upper principal surface of the piezoelectric film, and a second electrode provided on the lower principal surface of the piezoelectric film; a step of attaching a carrier tape including a first cured resin layer and a base material layer under the second electrode, and bonding the second electrode and the base material layer with the first cured resin layer; curing the first cured resin layer; After the first cured resin layer is cured, the base layer is peeled off; Equipped with How sensors are manufactured.

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