JP6287166B2 - Inspection method of piezoelectric sensor - Google Patents

Description

  The present invention relates to a piezoelectric sensor inspection method for inspecting a voltage generated by being pressed.

  Conventionally, a display device including an operation panel such as a touch panel is provided with a piezoelectric sensor not only for detecting a touch position on one main surface (operation surface) of the operation panel but also for detecting a pressing amount on the operation surface. May be.

  For example, Patent Document 1 discloses a plate-like piezoelectric sensor in which a first detection electrode and a second detection electrode are provided on both surfaces of a piezoelectric sheet (piezoelectric film). For example, the piezoelectric sensor is bonded to the other main surface opposite to the operation surface of the operation plate.

  When a part of the piezoelectric sheet (piezoelectric film) is pressed, the piezoelectric sheet is bent in the thickness direction, and a voltage is generated between the first detection electrode and the second detection electrode of the piezoelectric sheet. This piezoelectric sensor can detect the pressure and the amount of pressing by detecting the voltage.

International Publication No. 2012/137897

  After the piezoelectric sensor is manufactured, it is necessary to inspect whether or not an appropriate voltage is output when the piezoelectric sensor is pressed before being bonded to the operation plate and mounted on the display device. Here, when the piezoelectric sensor outputs an appropriate voltage, it can be determined that the piezoelectric sensor is a non-defective product.

  However, the voltage output from the piezoelectric sensor by pressing a part of the piezoelectric sensor before being joined to the operation panel, and the part of the operation surface of the operation board being pressed after being joined to the operation board and mounted on the display device. As a result of measuring the voltage output from the piezoelectric sensor, the problem that the two voltages have no correlation was clarified.

  That is, even if the voltage is measured by pressing a part of the piezoelectric sensor before the piezoelectric sensor is joined to the operation plate, it is not possible to determine whether an appropriate voltage is output (that is, a non-defective product or a defective product). It became clear.

  For this reason, in the conventional method for inspecting a piezoelectric sensor, the piezoelectric sensor is bonded to an operation plate or an inspection glass plate instead of the operation plate, and then a part of one main surface of the operation plate or the inspection glass plate is pressed. Thus, it was necessary to inspect whether the piezoelectric sensor output an appropriate voltage.

  Therefore, the conventional method for inspecting a piezoelectric sensor requires a step of joining the piezoelectric sensor to an operation plate or a glass plate for inspection, which contributes to high inspection costs.

  An object of the present invention is to provide a method for inspecting a piezoelectric sensor that can reduce the inspection cost of the piezoelectric sensor as compared with the prior art.

  The present invention relates to a method for inspecting a piezoelectric sensor including a sensor unit and a detection plate. The sensor unit has a piezoelectric film in which a first detection electrode and a second detection electrode are formed on opposite surfaces. The sensor plate is attached to the first main surface of the detection plate.

  This piezoelectric sensor inspection method includes at least a fixing step and a measuring step.

In the fixing step, both ends of the detection plate are fixed to the measurement table.
In the measurement step, a part of the detection plate is pressed by a piezo actuator, and a voltage generated between the first detection electrode and the second detection electrode is measured. The piezoelectric sensor further includes a pusher mounted on the surface of the sensor unit opposite to the detection plate.

  In this inspection method, by experiment, a part of the piezoelectric sensor is pressed by a piezo actuator and the voltage output from the piezoelectric sensor and one main surface of the inspection glass plate after the piezoelectric sensor is joined to the inspection glass plate. It has been clarified that the voltage output from the piezoelectric sensor by pressing the part with a predetermined actuator has a certain correlation.

  Therefore, by inspecting the piezoelectric sensor by this inspection method, even if the piezoelectric sensor is not joined to the glass plate for inspection, an appropriate voltage is output simply by pressing a part of the piezoelectric sensor and measuring the voltage. Whether it is a good product or a defective product.

  Therefore, according to this inspection method, the inspection cost of the piezoelectric sensor can be reduced as compared with the conventional method.

  In this inspection method, by experiment, a pusher (a part of a piezoelectric sensor) is pressed by a piezoelectric actuator and output from the piezoelectric sensor, and one of the inspection glass plates after the piezoelectric sensor is joined to the inspection glass plate. It has been clarified that the voltage output from the piezoelectric sensor by pressing a part of the main surface with a predetermined actuator has a certain correlation.

  Therefore, by inspecting the piezoelectric sensor with this inspection method, whether or not to output an appropriate voltage by simply pressing the pusher and measuring the voltage without joining the piezoelectric sensor to the glass plate for inspection ( That is, it is possible to determine whether the product is good or defective.

  Therefore, according to this inspection method, the inspection cost of the piezoelectric sensor can be reduced as compared with the conventional method.

  In the present invention, the tip of the piezo actuator that contacts the pusher is preferably a flat surface.

  In this inspection method, the voltage output from the piezoelectric sensor by pressing the pusher with a piezo actuator and a part of one main surface of the inspection glass plate after bonding the piezoelectric sensor to the inspection glass plate are predetermined by experiment. It was clarified that there is a proportional relationship with the voltage output from the piezoelectric sensor by being pressed by the actuator, and having a certain correlation.

  The reason for this experimental result is that the tip of the piezo actuator that comes in contact with the pusher becomes a flat surface, so that the point transmission is changed from the point pressing to the surface pressing, and the way in which both stresses are transmitted is similar. it is conceivable that.

  Therefore, by inspecting the piezoelectric sensor by this inspection method, even if the piezoelectric sensor is not bonded to the glass plate for inspection, the voltage can be appropriately measured with respect to the pressing amount by simply pressing the pusher and measuring the voltage. It can be determined whether or not to output (ie, good or defective).

  Therefore, according to this inspection method, the inspection cost of the piezoelectric sensor can be reduced as compared with the conventional method.

  In the present invention, it is preferable that the area of the tip plane of the piezo actuator that contacts the pusher is larger than the area of the surface of the pusher that contacts the piezo actuator.

  In this inspection method, the voltage output from the piezoelectric sensor by pressing the pusher with a piezo actuator and a part of one main surface of the inspection glass plate after bonding the piezoelectric sensor to the inspection glass plate are predetermined by experiment. It was clarified that there is a proportional relationship with the voltage output from the piezoelectric sensor by being pressed by the actuator, and having a certain correlation.

  The reason for this experimental result is that the area of the tip plane of the piezo actuator that contacts the pusher is larger than the area of the surface of the pusher that contacts the piezo actuator. Is considered to be almost equal.

  Therefore, by inspecting the piezoelectric sensor by this inspection method, even if the piezoelectric sensor is not bonded to the glass plate for inspection, the voltage can be appropriately measured with respect to the pressing amount by simply pressing the pusher and measuring the voltage. It can be determined whether or not to output (ie, good or defective).

  Therefore, according to this inspection method, the inspection cost of the piezoelectric sensor can be reduced as compared with the conventional method.

In the present invention, the piezoelectric sensor includes an elastic member attached to the second main surface opposite to the first main surface of the detection plate,
In the fixing step, it is preferable that both ends of the detection plate are fixed to the measurement table in a state where the elastic member is placed on the measurement table.

  In the present invention, it is preferable that the elastic member is mounted in a region overlapping the pusher on the second main surface of the detection plate when viewed from a direction perpendicular to the second main surface of the detection plate.

  In this inspection method, the detection plate bends when the pusher is pressed. When the pusher is no longer pressed, the elastic member pushes back the detection plate. As a result, when the pusher is no longer pressed, the detection plate can be returned to its original flat state.

  In the present invention, the material of the detection plate is preferably glass or stainless steel.

  In the present invention, the piezoelectric film is preferably formed of a chiral polymer.

  In this inspection method, the piezoelectric sensor can reliably detect the displacement of the piezoelectric film with high sensitivity.

  In the present invention, the chiral polymer is preferably polylactic acid.

  In this inspection method, the piezoelectric sensor can reliably detect the displacement of the piezoelectric film with high sensitivity.

  In the present invention, the polylactic acid is preferably L-type polylactic acid.

  In this inspection method, the piezoelectric sensor can reliably detect the displacement of the piezoelectric film with high sensitivity.

  According to this invention, the inspection cost of the piezoelectric sensor can be reduced.

It is a top view of the display apparatus 10 provided with the piezoelectric sensor 100 which concerns on embodiment of this invention. It is sectional drawing of the AA line shown in FIG. It is a top view of the piezoelectric sensor 100 shown in FIG. It is sectional drawing of the BB line shown in FIG. FIG. 4 is an exploded plan view of a sensor unit 16 of the piezoelectric sensor 100 shown in FIG. 3. It is sectional drawing at the time of the pressing force detection of the principal part of the display apparatus 10 shown in FIG. It is a flowchart which shows the manufacturing method of the piezoelectric sensor 100 shown in FIG. It is a top view which shows the manufacturing process of the piezoelectric sensor 100 shown in FIG. It is a top view which shows the manufacturing process of the piezoelectric sensor 100 shown in FIG. It is a top view which shows the manufacturing process of the piezoelectric sensor 100 shown in FIG. It is a top view which shows the manufacturing process of the piezoelectric sensor 100 shown in FIG. It is a top view which shows the manufacturing process of the piezoelectric sensor 100 shown in FIG. It is a top view which shows the manufacturing process of the piezoelectric sensor 100 shown in FIG. It is a top view which shows the manufacturing process of the piezoelectric sensor 100 shown in FIG. It is a back view which shows the manufacturing process of the piezoelectric sensor 100 shown in FIG. It is a side view which shows the manufacturing process of the piezoelectric sensor 100 shown in FIG. It is sectional drawing which shows a mode that the piezoelectric sensor 100 shown in FIG. 1 is test | inspected by the 1st test | inspection method. FIG. 2 is a cross-sectional view showing a state in which the piezoelectric sensor 100 is inspected in a state where the piezoelectric sensor 100 shown in FIG. It is a figure which shows the correlation of the voltage output from the piezoelectric sensor 100 shown in FIG. 17, and the voltage output from the piezoelectric sensor 100 shown in FIG. It is sectional drawing which shows a mode that the piezoelectric sensor 100 shown in FIG. 1 is test | inspected with the 2nd test | inspection method. It is a figure which shows the correlation of the voltage output from the piezoelectric sensor 100 shown in FIG. 20, and the voltage output from the piezoelectric sensor 100 shown in FIG. It is sectional drawing which shows a mode that the piezoelectric sensor 100 shown in FIG. 1 is test | inspected with the 3rd test | inspection method. It is a figure which shows the correlation of the voltage output from the piezoelectric sensor 100 shown in FIG. 22, and the voltage output from the piezoelectric sensor 100 shown in FIG.

  Hereinafter, a piezoelectric sensor according to an embodiment of the present invention will be described. FIG. 1 is a plan view of a display device 10 including a piezoelectric sensor 100 according to an embodiment of the present invention. 2 is a cross-sectional view taken along line AA shown in FIG.

The display device 10 includes an operation plate 12, a spacer 14A, a spacer 14B, a detection plate 15, a plate-shaped sensor unit 16, a columnar pusher 17, and a columnar cushion 21. The display device 10 includes a piezoelectric sensor 100 having a spacer 14 </ b> A and a spacer 14 </ b> B, a pusher 17, a cushion 21, a sensor unit 16 and a detection plate 15, which will be described in detail later. Further, the display device 10 includes a housing 11 having a size that is portable. The display device 10 is, for example, a tablet or a smartphone.
The cushion 21 corresponds to the “elastic member” of the present invention.

  The housing 11 has a rectangular parallelepiped shape with the top surface opened. As shown in FIGS. 1 and 2, the casing 11 is fitted with an operation plate 12 so as to close the opening surface of the casing 11. The operation plate 12 is a laminated body in which a liquid crystal panel, a touch panel, and a cover glass are laminated. One main surface of the operation plate 12 (specifically, one main surface of the outermost cover glass) serves as the operation surface 101. The operation plate 12 is made of a material having translucency.

  As shown in FIGS. 1 and 2, the operation plate 12, the pusher 17, the sensor unit 16, the detection plate 15, and the cushion 21 are arranged in this order from the operation surface 101 side in the housing 11. .

  Hereinafter, the longitudinal direction of the operation surface 101 is referred to as the X direction, the short direction of the operation surface 101 is referred to as the Y direction, and the direction perpendicular to the operation surface 101 (that is, the thickness direction of the housing 11) is referred to as the Z direction. Sometimes called.

  The spacer 14 </ b> A is disposed in the vicinity of the first side surface parallel to the X direction among the side surfaces of the housing 11. The spacer 14 </ b> B is disposed in the vicinity of the second side surface (side surface facing the first side surface) of the housing 11. The spacer 14 </ b> A and the spacer 14 </ b> B are disposed at a substantially central portion in the X direction of the housing 11. The material of the spacer 14A and the spacer 14B is, for example, PET resin.

  The material of the detection plate 15 is SUS (stainless steel). The detection plate 15 is supported inside the housing 11 by spacers 14 </ b> A, 14 </ b> B, and a cushion 21 so that the main surface on the operation surface 101 side of the detection plate 15 is parallel to the operation surface 101 of the operation plate 12. .

  Therefore, spaces are formed between the detection plate 15 and the operation plate 12 and between the detection plate 15 and the bottom surface inside the housing 11. The detection plate 15 is disposed at a substantially central portion in the X direction of the housing 11. The longitudinal direction of the detection plate 15 is parallel to the Y direction.

  The main surface opposite to the operation surface 101 of the sensor unit 16 is attached to the main surface of the detection plate 15 on the operation surface 101 side. The sensor unit 16 is arranged inside the housing 11 so that the main surface on the operation surface 101 side of the sensor unit 16 is parallel to the operation surface 101 of the operation plate 12. Although details will be described later, the sensor unit 16 is attached to the detection plate 15 and constitutes a part of the piezoelectric sensor 100 (see FIG. 3 described later).

  The pusher 17 is disposed between the operation plate 12 and the sensor unit 16 so as to contact the operation plate 12 and the sensor unit 16. The pusher 17 is disposed at a substantially central portion of the detection plate 15 in the Y direction. The pusher 17 transmits stress from the operation plate 12 to the detection plate 15 and the sensor unit 16. The material of the pusher 17 is, for example, PET resin.

  The cushion 21 is disposed between the bottom surface inside the housing 11 and the detection plate 15 so as to contact the bottom surface inside the housing 11 and the detection plate 15. The cushion 21 is disposed at a substantially central portion of the detection plate 15 in the Y direction. The cushion 21 is made of a material softer than the pusher 17. The material of the cushion 21 is, for example, a foamable film.

  The cushion 21 is disposed at substantially the same position as the pusher 17 when viewed from the Z direction (in plan view), and has substantially the same shape and size as the pusher 17. That is, the cushion 21 overlaps the pusher 17 when viewed from the Z direction (direction perpendicular to the main surface of the detection plate 15).

  The cushion 21 supports the detection plate 15 and presses the detection plate 15 against the pusher 17 via the sensor unit 16. Thereby, even if the operation plate 12 is warped, the pressure applied to the pusher 12 can be reliably transmitted to the detection plate 15 without creating a gap between the operation plate 12 and the pusher 17.

Next, the configuration of the piezoelectric sensor 100 will be described in detail.
FIG. 3 is a plan view of the piezoelectric sensor 100 shown in FIG. 4 is a cross-sectional view taken along line BB shown in FIG. FIG. 5 is an exploded plan view of the sensor unit 16 of the piezoelectric sensor 100 shown in FIG. FIG. 5A is a plan view of the piezoelectric film 31 of the sensor unit 16. FIG. 5B is a plan view of the sensor unit 16 in a state where the substrate unit 36 and the substrate unit 37 are opened and the piezoelectric film 31 is removed.

  As shown in FIGS. 3 and 4, the piezoelectric sensor 100 includes a spacer 14 </ b> A and a spacer 14 </ b> B, a detection plate 15, a sensor unit 16, a pusher 17, a cushion 21, a component mounting unit 38, and a circuit component 39. And disposed inside the housing 11. The component mounting unit 38 is a part of the flexible printed circuit board 30. The flexible printed circuit board 30 includes a substrate unit 36 and a substrate unit 37 that constitute a part of the sensor unit 16, and a component mounting unit 38. The material of the flexible printed circuit board 30 is a resin such as polyimide.

  On the front main surface of the component mounting portion 38, a first terminal 32 and a second terminal 33, which are conductor patterns, are formed. Further, a circuit component 39 is surface-mounted on the front main surface of the component mounting portion 38. The circuit component 39 is connected to the first detection electrode 34 and the second detection electrode 35 via the first terminal 32 and the second terminal 33.

  The pusher 17 is pressed against the main surface on the operation surface 101 side in a part of the area of the sensor unit 16.

  The main surface opposite to the operation surface 101 of the sensor unit 16 is adhered to the main surface on the operation surface 101 side of the detection plate 15 with an adhesive layer 90 so that the longitudinal direction thereof is the Y direction. The pressure-sensitive adhesive layer 90 is made of, for example, an epoxy adhesive.

  As shown in FIGS. 3 to 5, the sensor unit 16 includes a piezoelectric film 31, an adhesive layer 91 and an adhesive layer 92, a first detection electrode 34, a second detection electrode 35, a substrate unit 36, and a substrate unit 37. Prepare. As described above, the flexible printed board 30 includes the board part 36 and the board part 37 that constitute a part of the sensor part 16 and the component mounting part 38.

  The first detection electrode 34, the second detection electrode 35, the piezoelectric film 31, the substrate portion 36, and the substrate portion 37 each have a flat main surface and a back main surface that are flat and face each other in the thickness direction. In addition, the upper side surface in FIG. 4 is referred to as a front main surface and the lower side surface is referred to as a back main surface.

  As shown in FIG. 4, the substrate portion 37, the second detection electrode 35, the adhesive layer 91, the piezoelectric film 31, the adhesive layer 92, the first detection electrode 34, and the substrate portion 36 are arranged in this order from the front main surface side. It is laminated over the back main surface side.

  Specifically, the second detection electrode 35 is laminated on the front main surface of the piezoelectric film 31 via the adhesive layer 91, and the substrate portion 37 is further laminated on the front main surface of the second detection electrode 35. Further, the first detection electrode 34 is laminated on the back main surface of the piezoelectric film 31 via the adhesive layer 92, and the substrate portion 36 is further laminated on the back main surface of the first detection electrode 34.

  As shown in FIG. 5, the outer shape of each of the second detection electrode 35, the first detection electrode 34, the piezoelectric film 31, the substrate portion 37, and the substrate portion 36 in a plan view is a substantially rectangular shape. Here, the outer shapes of the substrate portion 37 and the substrate portion 36 are slightly larger than the outer shape of the piezoelectric film 31.

  As shown in FIGS. 3 and 5, the substrate unit 36 and the substrate unit 37 are part of the flexible printed circuit board 30. In the flexible printed circuit board 30, a slit 18 </ b> A is provided at a position that partitions the substrate unit 37 and the substrate unit 36.

  The slit 18 </ b> A extends in parallel with the long side of the substrate unit 37 (or the long side of the substrate unit 36). In the flexible printed circuit board 30, connecting portions 18B are provided on both sides of the slit 18A in the direction in which the slit 18A extends. Each connecting portion 18 </ b> B connects the substrate portion 37 and the substrate portion 36. Note that the slit 18A and the two connecting portions 18B are not necessarily provided, and may have other shapes.

  A second detection electrode 35 is formed on the back main surface of the substrate portion 37, and a first detection electrode 34 is formed on the front main surface of the substrate portion 36. That is, the first detection electrode 34 and the second detection electrode 35 are formed side by side on the same surface of the flexible printed circuit board 30.

  As shown in FIG. 4, the piezoelectric film 31 is attached to the front main surface of the first detection electrode 34 with an adhesive layer 92. The piezoelectric film 31 is attached to the back main surface of the second detection electrode 35 with an adhesive layer 91.

  The pressure-sensitive adhesive layer 91 and the pressure-sensitive adhesive layer 92 are made of, for example, an acrylic pressure-sensitive adhesive.

  As shown in FIG. 5, one end of the first terminal 32 is connected to the first detection electrode 34. On the other hand, the other end of the first terminal 32 is connected to the circuit component 39. One end of the second terminal 33 is connected to the second detection electrode 35. On the other hand, the other end of the second terminal 33 is connected to the circuit component 39.

  Accordingly, the first detection electrode 34 and the second detection electrode 35 are electrically connected to the circuit component 39 via the first terminal 32 and the second terminal 33, respectively.

  Next, the configuration of the piezoelectric film 31 will be described in detail.

The piezoelectric film 31 is molecularly oriented in a direction 19 that forms about 45 ° with respect to the long and short sides. The piezoelectric film 31 is a film mainly composed of L-type polylactic acid (PLLA). PLLA is a chiral polymer whose main chain has a helical structure, and has a property of expressing piezoelectricity by being oriented in a predetermined axial direction. This piezoelectricity is represented by a piezoelectric tensor component d ₁₄ with the film thickness direction as the first axis and the PLLA molecule orientation direction as the third axis.

In the piezoelectric film 31 having the piezoelectric tensor component d ₁₄ is a direction intersecting the long sides and short sides in the front main surface and rear main surface, specifically about 45 ° direction with respect to the long sides and short sides, By setting the direction in which the PLLA molecules are oriented, the pressing force from the thickness direction can be detected.

  However, the angle of the direction 19 in the piezoelectric film 31 is not limited to an accurate 45 ° with respect to the long side and the short side, and can be any angle close to 45 °. As the angle in the direction 19 is closer to 45 ° with respect to the long side and the short side, the pressing force from the thickness direction can be detected more efficiently.

  Accordingly, the term “approximately 45 °” as used in the present invention refers to an angle within a predetermined range centered on 45 °, for example, about 45 ° ± 10 °. These specific angles may be appropriately determined according to the overall design based on the use of the displacement sensor, the characteristics of each part, and the like.

  The piezoelectric film 31 is not limited to a film mainly composed of PLLA, and may be a film mainly composed of D-type polylactic acid (PDLA) or polyvinylidene fluoride (PVDF). However, the piezoelectricity of the piezoelectric film 31 mainly composed of a chiral polymer such as PLLA or PDLA is not expressed by the polarization of ions like ferroelectrics such as PVDF and PZT, and is characteristic of molecules. It is derived from the spiral structure.

  Therefore, the chiral polymer does not need to exhibit piezoelectricity by poling treatment like other polymers such as PVDF and piezoelectric ceramics using a piezoelectric crystal thin film, and PVDF or the like has a piezoelectric constant over time. Although fluctuations are observed and in some cases the piezoelectric constant may be significantly reduced, the piezoelectric constant of the chiral polymer is very stable over time.

  Furthermore, the chiral polymer does not generate pyroelectricity that occurs in other ferroelectric piezoelectric materials. Therefore, the piezoelectric film 31 mainly composed of a chiral polymer can obtain a detection voltage corresponding only to the pressing force without depending on the temperature at the detection position at the time of pressing detection.

  In addition, since the chiral polymer is a polymer and has flexibility, it is not damaged by a large displacement unlike piezoelectric ceramics. Therefore, the piezoelectric film 31 mainly composed of a chiral polymer is not damaged even if the displacement amount is large, and the displacement amount can be reliably detected.

Since PLLA has a very low relative dielectric constant of about 2.5, the piezoelectric output constant (= piezoelectric g constant, g = d / ε ^T ) is large when d is a piezoelectric constant and ε ^T is a dielectric constant. Value. Here, the piezoelectric g constant of PVDF having a dielectric constant ε ₃₃ ^T = 13 × ε ₀ and a piezoelectric tensor component d ₃₁ = 25 pC / N is g ₃₁ = 0.2172 Vm / N from the above formula.

On the other hand, when the piezoelectric g constant of PLLA having a piezoelectric tensor component d ₁₄ = 10 pC / N is converted to g ₃₁ , d ₁₄ = 2 × d ₃₁ , so that d ₃₁ = 5 pC / N, and the piezoelectric g constant Is g ₃₁ = 0.2258 Vm / N. Therefore, sufficient sensor sensitivity similar to PVDF can be obtained with PLLA having a piezoelectric tensor component d ₁₄ = 10 pC / N.

The inventor of the present invention has experimentally obtained PLLA with d ₁₄ = 15 to 20 pC / N. If the PLLA film is used, the piezoelectric sensor 100 can be configured with very high sensitivity.

  6 is a cross-sectional view of the main part of the display device 10 shown in FIG. 1 when a pressing force is detected. In addition, in FIG. 6, in order to demonstrate a mode that the operation board 12, the sensor part 16, and the detection board 15 bend, these bending is emphasized and shown.

  The user presses the operation surface 101 of the operation plate 12 as shown in FIG. As a result, the sensor unit 16 and the detection plate 15 of the piezoelectric sensor 100 are pressed in the thickness direction from the operation plate 12 via the pusher 17, and are bent in the thickness direction to generate charges in the piezoelectric film 31.

  That is, between the first detection electrode 34 and the second detection electrode 35, the detection voltage having a voltage value corresponding to the magnitude of the pressing force (the amount of expansion of the piezoelectric film 31) is a voltage polarity corresponding to the direction of the pressing force. It occurs in. This detection voltage is input to the circuit component 39 via the first terminal 32 and the second terminal 33 as a press detection signal (see FIG. 3).

  Next, an example of a method for manufacturing the piezoelectric sensor 100 will be described. FIG. 7 is a flowchart showing a manufacturing method of the piezoelectric sensor 100 shown in FIG. 8-16 is a top view which shows the manufacturing process of the piezoelectric sensor 100 shown in FIG. In the implementation, a plurality of piezoelectric sensors 100 are manufactured in a lump. However, in this embodiment, a scene in which one piezoelectric sensor 100 is manufactured will be described in order to simplify the description.

  First, as shown in FIG. 8, a sheet-like flexible printed board 3 having a copper foil 50 formed on the entire surface of one main surface is prepared (S1). In the implementation, the flexible printed circuit board 3 may be formed with copper foil on the entire main surface in order to provide the sensor unit 30 with a shield electrode layer that shields noise.

  Next, as shown in FIG. 9, a conductor pattern is formed on one main surface of the flexible printed circuit board 3 by etching or the like (S2). Accordingly, the first detection electrode 34 connected to the first terminal 32 and the second detection electrode 35 connected to the second terminal 33 are formed side by side on the same surface of the flexible printed circuit board 3.

  Next, the flexible printed circuit board 3 is punched with a press die to form the flexible printed circuit board 30 having the shape shown in FIG. 10 (S3). Thereby, the flexible printed circuit board 30 in which the slit 18A, the connecting portion 18B, the substrate portion 36, and the substrate portion 37 are formed is prepared.

  Next, as shown in FIG. 11, the main surface on the side opposite to the operation surface 101 of the main portion (the portion that becomes the sensor portion 16) of the flexible printed circuit board 30 is the first main surface on the operation surface 101 side of the detection plate 15. Affixed to the surface with an adhesive (S4). Thereby, the sensor part 16 is affixed on the detection board 15 with an adhesive agent, and the composite_body | complex of the sensor part 16 and the detection board 15 is created. You may connect with the above-mentioned shield electrode layer using a conductive adhesive for this adhesive agent.

  Next, as shown in FIG. 3, the circuit component 39 is surface-mounted on the front main surface of the component mounting portion 38 (S5). Accordingly, the first detection electrode 34 and the second detection electrode 35 are connected to the circuit component 39 via the first terminal 32 and the second terminal 33.

  Next, as shown in FIG. 12, the piezoelectric film 31 is stuck on the first detection electrode 34 of the substrate portion 36 with an adhesive (S6). This pressure-sensitive adhesive may be a conductive pressure-sensitive adhesive.

  Next, as shown in FIG. 13, the substrate portion 37 is folded, the second detection electrode 35 is attached to the piezoelectric film 31 with an adhesive, and the piezoelectric film 31 is interposed between the first detection electrode 34 and the second detection electrode 35. (S7). This pressure-sensitive adhesive may be a conductive pressure-sensitive adhesive. Since the flexible printed board 30 is flexible and can be greatly deformed, the board portion 37 is easily folded back.

  Next, as shown in FIG. 14, the main surface of the pusher 17 on the side opposite to the piezoelectric film 31 in a part of the region of the substrate portions 36 and 37 (that is, the sensor portion 16) sandwiching the piezoelectric film 31. (S8).

  Next, as shown in FIG. 15, when viewed from the direction perpendicular to the second main surface opposite to the operation surface 101 of the detection plate 15, the cushion 21 is pushed by the pusher 17 on the second main surface of the detection plate 15. (S9).

  Next, as shown in FIG. 16, spacers 14A and 14B are mounted on both surfaces of both ends of the detection plate 15 (S10).

  The piezoelectric sensor 100 of this embodiment can be manufactured through the manufacturing steps S1 to S10 described above. After the piezoelectric sensor 100 is manufactured, it is necessary to inspect whether or not an appropriate voltage is output when the piezoelectric sensor 100 is pressed before being bonded to the operation plate 12 and mounted on the display device 10. Here, when an appropriate voltage is output when the piezoelectric sensor 100 is pressed, the piezoelectric sensor 100 can be determined as a non-defective product.

  In the present embodiment, a first inspection method, a second inspection method, and a third inspection method will be described as examples of the inspection method of the piezoelectric sensor 100.

First, the first inspection method will be described.
FIG. 17 is a cross-sectional view showing a state in which the piezoelectric sensor 100 shown in FIG. 1 is inspected by the first inspection method.

  First, as shown in FIG. 17, both end portions of the detection plate 15 are fixed to fixed rods 126 provided on the measurement table 125 (S <b> 11).

  Then, as shown in FIG. 17, the pusher 17 is pressed by the tip 121 of the piezo actuator 120, and the voltage generated between the first detection electrode 34 and the second detection electrode 35 is measured (S12). A measurement terminal is connected to the circuit component 39 to which this voltage is input, and the voltage is measured.

  FIG. 18 is a cross-sectional view showing a state in which the piezoelectric sensor 100 is inspected with the piezoelectric sensor 100 shown in FIG.

  Here, in S12, a voltage output from the piezoelectric sensor 100 when a part of the piezoelectric sensor 100 (the pusher 17) is pressed by the piezoelectric actuator 120 as shown in FIG. 17, and the piezoelectric sensor as shown in FIG. After mounting 100 on the measuring device 190, a part of one main surface of the inspection glass plate 112 is pressed by the electric actuator 920, and the voltage output from the piezoelectric sensor 100 is compared. For this comparison, the measuring device 190 will be described.

  The measuring device 190 is a device that artificially configures the state where the piezoelectric sensor 100 is mounted on the display device 10. The measurement apparatus 190 includes a measurement table 113 on which the piezoelectric sensor 100 is placed, a housing 111 that houses the measurement table 113, and an inspection glass plate 112 that is placed on the housing 111 while being joined to the piezoelectric sensor 100. .

  The casing 111 has a rectangular parallelepiped shape with the top surface opened. As shown in FIG. 18, an inspection glass plate 112 is placed on the casing 111 so as to close the opening surface of the casing 111. The material of the casing 111 is aluminum. The material of the measuring table 113 is also aluminum.

  The electric actuator 920 is driven by a motor. Therefore, the pressing amount of the electric actuator 920 cannot be set more finely than the pressing amount of the piezo actuator 120. The pressing amount of the electric actuator 920 is set, for example, at intervals of 0.6N, 1.5N, 2.4N, and 3.3N.

  On the contrary, since the piezo actuator 120 is driven by the piezo piezoelectric effect, the pressing amount of the piezo actuator 120 should be set very finely compared with the pressing amount of the electric actuator 920 by changing the voltage applied to the piezo element. Can do. Therefore, it becomes possible to give a sinusoidal displacement at a predetermined frequency. Here, for example, assume that a displacement of ± 10 μm is given at 1 Hz.

  FIG. 19 is a diagram illustrating a correlation between the voltage output from the piezoelectric sensor 100 illustrated in FIG. 17 and the voltage output from the piezoelectric sensor 100 illustrated in FIG.

  Here, FIG. 19 shows a voltage output from the piezoelectric sensor 100 when a part (the pusher 17) of the piezoelectric sensor 100 is pressed by the piezoelectric actuator 120 as shown in FIG. 17, and a piezoelectric sensor as shown in FIG. A plurality of samples are measured while changing a pressing amount of a voltage output from the piezoelectric sensor 100 by pressing a part of one main surface of the inspection glass plate 112 with the electric actuator 920 after mounting 100 on the measuring device 190. The experimental results are shown.

  According to the experiment, in the piezoelectric sensor 100 shown in FIG. 18, when a part of one main surface of the inspection glass plate 112 is pressed with a predetermined pressing amount (for example, pressing from the initial state 2.4N to 3.3N) A voltage of 03V or higher is output from the piezoelectric sensor 100, whereas in the piezoelectric sensor 100 shown in FIG. 17, when a part of the piezoelectric sensor 100 is pressed with the predetermined pressing amount, a voltage of 0.58V or higher is applied. The output from the piezoelectric sensor 100 became clear.

  From this experimental result, a voltage output from the piezoelectric sensor 100 by pressing a part of the piezoelectric sensor 100 with a predetermined pressing amount as shown in FIG. 17 and the piezoelectric sensor 100 mounted on the measuring device 190 as shown in FIG. After that, it has been clarified that there is no correlation between the voltage output from the piezoelectric sensor 100 by pressing a part of one main surface of the inspection glass plate 112 with a predetermined pressing amount.

Next, the second inspection method will be described.
20 is a cross-sectional view showing a state in which the piezoelectric sensor 100 shown in FIG. 1 is inspected by the second inspection method. FIG. 21 is a diagram illustrating a correlation between the voltage output from the piezoelectric sensor 100 illustrated in FIG. 20 and the voltage output from the piezoelectric sensor 100 illustrated in FIG.

  The second inspection method is different from the first inspection method shown in FIG. 17 in that both ends of the detection plate 15 are fixed to the measurement table 113 while the cushion 21, the spacer 14A, and the spacer 14B are placed on the measurement table 113. And the shape of the tip 221 of the piezo actuator 220. The tip of the piezo actuator 220 that contacts the pusher 17 is a flat surface. Since the other points are the same, the description is omitted.

  Here, FIG. 21 shows a voltage output from the piezoelectric sensor 100 when a part (the pusher 17) of the piezoelectric sensor 100 is pressed by the piezoelectric actuator 220 as shown in FIG. 20, and a piezoelectric sensor as shown in FIG. A plurality of samples are measured while changing a pressing amount of a voltage output from the piezoelectric sensor 100 by pressing a part of one main surface of the inspection glass plate 112 with the electric actuator 920 after mounting 100 on the measuring device 190. The experimental results are shown.

  According to the experiment, in the piezoelectric sensor 100 shown in FIG. 18, the voltage output from the piezoelectric sensor 100 increases as the pressing amount to a part of one main surface of the inspection glass plate 112 increases. In the piezoelectric sensor 100 shown in FIG. 20, it has been clarified that the voltage output from the piezoelectric sensor 100 increases as the pressing amount to a part of the piezoelectric sensor 100 increases.

  That is, the voltage output from the piezoelectric sensor 100 by pressing a part of the piezoelectric sensor 100 as shown in FIG. 20, and the inspection glass plate 112 after the piezoelectric sensor 100 is mounted on the measuring device 190 as shown in FIG. Compared with FIG. 19, it became clear that the voltage output from the piezoelectric sensor 100 by pressing a part of one of the main surfaces has a strong correlation.

  The reason for this experimental result is that the tip of the piezo actuator 220 in contact with the pusher 17 becomes a flat surface, so that the point is changed from a point push to a surface push, and both stresses are transmitted compared to the first inspection method. This is thought to be due to the fact that they have become similar.

  Therefore, by inspecting the piezoelectric sensor 100 by the second inspection method, even if the piezoelectric sensor 100 is not bonded to the glass plate 112 for inspection, the pressure is measured only by pressing a part of the piezoelectric sensor 100 and measuring the voltage. It is possible to determine whether or not an appropriate voltage is output with respect to the quantity (that is, whether it is a good product or a defective product).

  Therefore, according to the second inspection method, the inspection cost of the piezoelectric sensor 100 can be reduced as compared with the conventional method.

Next, the third inspection method will be described.
FIG. 22 is a cross-sectional view showing a state in which the piezoelectric sensor 100 shown in FIG. 1 is inspected by the third inspection method. FIG. 23 is a diagram illustrating a correlation between the voltage output from the piezoelectric sensor 100 illustrated in FIG. 22 and the voltage output from the piezoelectric sensor 100 illustrated in FIG.

  The third inspection method is different from the second inspection method shown in FIG. 20 in the shape of the tip 321 of the piezo actuator 320. The area of the tip plane of the piezo actuator 320 that contacts the pusher 17 is larger than the area of the surface of the pusher 17 on the side that contacts the piezo actuator 320. Since the other points are the same, the description is omitted.

  Here, FIG. 23 shows a voltage output from the piezoelectric sensor 100 when a part (the pusher 17) of the piezoelectric sensor 100 is pressed by the piezoelectric actuator 320 as shown in FIG. 22, and a piezoelectric sensor as shown in FIG. A plurality of samples are measured while changing a pressing amount of a voltage output from the piezoelectric sensor 100 by pressing a part of one main surface of the inspection glass plate 112 with the electric actuator 920 after mounting 100 on the measuring device 190. The experimental results are shown.

  According to the experiment, in the piezoelectric sensor 100 shown in FIG. 18, the voltage output from the piezoelectric sensor 100 increases as the pressing amount to a part of one main surface of the inspection glass plate 112 increases. In the piezoelectric sensor 100 shown in FIG. 22, it has been clarified that the voltage output from the piezoelectric sensor 100 increases as the pressing amount to a part of the piezoelectric sensor 100 increases.

  That is, the voltage output from the piezoelectric sensor 100 by pressing a part of the piezoelectric sensor 100 as shown in FIG. 22, and the inspection glass plate 112 after the piezoelectric sensor 100 is mounted on the measuring device 190 as shown in FIG. It is clear that the voltage output from the piezoelectric sensor 100 by pressing a part of one of the main surfaces is substantially proportional, and has a stronger correlation than FIG.

  The reason for this experimental result is that the area of the tip plane of the piezo actuator 320 in contact with the pusher 17 is larger than the area of the surface of the pusher 17 on the side in contact with the piezo actuator 320. This is probably because the way stress is transmitted is almost equal.

  Therefore, by inspecting the piezoelectric sensor 100 by the third inspection method, even if the piezoelectric sensor 100 is not joined to the glass plate 112 for inspection, the pressure is measured only by pressing a part of the piezoelectric sensor 100 and measuring the voltage. It is possible to determine whether or not an appropriate voltage is output with respect to the quantity (that is, whether it is a good product or a defective product).

  Therefore, according to the third inspection method, the inspection can be performed with better accuracy at the same cost as the second inspection method.

  In the above-described embodiment, the planar shape of the piezoelectric film 31 is a rectangular shape, but is not limited thereto. In implementation, the planar shape of the piezoelectric film may be other planar shapes such as a square shape, a circular shape, a trapezoidal shape, a parallelogram shape, a polygonal shape of quadrilateral or more, an elliptical shape, an oval shape, or the like.

  Moreover, in the said embodiment, although the material of the detection plate 15 is SUS (stainless steel), it is not restricted to this. In implementation, the material of the detection plate 15 may be a glass plate, for example.

  Moreover, in the said embodiment, although the piezoelectric sensor 100 has the pusher 17, the cushion 21, and spacer 14A, 14B, it is not restricted to this. In implementation, the piezoelectric sensor 100 may not have the pusher 17, the cushion 21, or the spacers 14A and 14B.

  Finally, the description of each of the embodiments should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

DESCRIPTION OF SYMBOLS 3 ... Flexible printed circuit board 10 ... Display apparatus 11 ... Housing | casing 12 ... Operation board 14A, 14B ... Spacer 15 ... Detection board 16 ... Sensor part 17 ... Pusher 18A ... Slit 18B ... Connection part 19 ... Direction 21 ... Cushion 30 ... Flexible Printed circuit board 31 ... piezoelectric film 32 ... first terminal 33 ... second terminal 34 ... first detection electrode 35 ... second detection electrode 36 ... board part 37 ... board part 38 ... component mounting part 39 ... circuit component 50 ... copper foil 90 ... adhesive layer 91 ... adhesive layer 92 ... adhesive layer 100 ... piezoelectric sensor 101 ... operating surface 111 ... housing 112 ... inspection glass plate 113 ... measurement table 120 ... piezo actuator 121 ... tip 125 ... measurement table 126 ... Fixed rod 190 ... measuring device 220 ... piezo actuator 221 ... tip portion 320 ... piezo actuator 321 ... tip portion 920 ... electric Actuator

Claims (9)

In a method for inspecting a piezoelectric sensor, comprising: a sensor unit having a piezoelectric film having a first detection electrode and a second detection electrode formed on opposite surfaces; and a detection plate having the sensor unit attached to a first main surface. ,
A fixing step of fixing both ends of the detection plate to a measurement table;
A measurement step of pressing a part of the detection plate with a piezoelectric actuator and measuring a voltage generated between the first detection electrode and the second detection electrode;
Only including,
The piezoelectric sensor further includes a pusher attached to a surface of the sensor unit opposite to the detection plate .
Inspection method of piezoelectric sensor. The method for inspecting a piezoelectric sensor according to claim 1 , wherein a tip of the piezoelectric actuator that contacts the pusher is a flat surface. The area of the distal end plane of the piezoelectric actuator, the contact to the piezoelectric actuator wider than the area of the surface of the pusher side, inspection method of a piezoelectric sensor according to claim 1 or claim 2 in contact with the pusher. The piezoelectric sensor includes an elastic member attached to a second main surface facing the first main surface of the detection plate,
The fixing step, the elastic member is fixed to both ends of the detecting plate in a state of being placed on the measuring table to the measuring table, the piezoelectric sensor according to any one of claims 1 to 3 Inspection method. The elastic member is viewed from a direction perpendicular to the second major surface of said detection plate is mounted in a region which overlaps with the pusher in the second major surface of said detection plate, according to claim 4 Inspection method of piezoelectric sensor. The method for inspecting a piezoelectric sensor according to any one of claims 1 to 5 , wherein a material of the detection plate is glass or stainless steel. The piezoelectric film is formed by a chiral polymer, inspection method of a piezoelectric sensor according to any one of claims 1 to 6. The method for inspecting a piezoelectric sensor according to claim 7 , wherein the chiral polymer is polylactic acid. The method for inspecting a piezoelectric sensor according to claim 8 , wherein the polylactic acid is L-type polylactic acid.

Images