JPWO2018221288A1 - Sensor, touch panel, and electronic device - Google Patents

Abstract

Provided are a sensor, a touch panel, and an electronic device with reduced flexibility and detection sensitivity that are less affected by the position where a pressing operation is applied. The piezoelectric film (20), the first electrode (21) disposed on the first main surface of the piezoelectric film (20), and at least the first electrode (21) on the second main surface of the piezoelectric film (20) are opposed to each other. A second electrode (22) disposed at a position, the piezoelectric film (20) includes a slit (15), and the slit (15) is provided around the first electrode (21).

Description

  One embodiment of the present invention relates to a sensor that detects a pressing position or pressing information on a panel, a touch panel using the sensor, and an electronic device.

  In Patent Document 1, electrodes are formed on the first main surface and the second main surface of the polylactic acid film, and the electrodes on the first main surface are divided into at least four electrically divided portions. A touch panel that is an electrode is disclosed. In the touch panel described in Patent Document 1, transparency is improved by providing a transparent electrode on a polylactic acid film, and not only position information but also pressing information is obtained at the same time.

International Publication No. 2010/143528

  In the touch panel described in Patent Document 1, when a pressing operation is applied to a piezoelectric film made of a polylactic acid film, the entire piezoelectric film is affected by the pressing operation because the piezoelectric film is formed into a single film. For this reason, the electric charge detected may be influenced by distortion of the piezoelectric film other than the position where the pressing operation is applied. Therefore, depending on the position where the pressing operation is applied, the direction of the largest distortion differs, and accurate charge detection may be difficult. For this reason, when the distortion method is complicated, it may be difficult to accurately detect the pressing force.

  Therefore, an object of an embodiment of the present invention is to provide a sensor, a touch panel, and an electronic device that reduce the influence of a position where a pressing operation is applied and have high flexibility and detection sensitivity.

  A sensor according to an embodiment of the present invention includes a piezoelectric film, a first electrode disposed on a first main surface of the piezoelectric film, and a position facing at least the first electrode on a second main surface of the piezoelectric film. A second electrode disposed on the piezoelectric film, wherein the piezoelectric film includes a slit, and the slit is provided around the first electrode.

  In this configuration, since the piezoelectric film is provided with slits, when the piezoelectric film is deformed by a pressing operation, it is affected by the region divided by the slits. Since the slit is provided around the first electrode, the area where the first electrode is arranged follows the shape of the area divided by the slit provided around the first electrode when a pressing operation is accepted. How to distort. Thereby, the area | region where the 1st electrode is arrange | positioned carries out the same way of distortion even if any position is a case where pressing operation is received. Therefore, it is possible to reduce the influence of the position where the pressing operation is received and improve the detection sensitivity. Moreover, since the slit is provided in the piezoelectric film, the flexibility of the piezoelectric film is increased and the flexibility can be enhanced.

  According to one embodiment of the present invention, it is possible to reduce the influence of the position where the pressing operation is applied, and to improve the flexibility and detection sensitivity.

FIG. 1A is a perspective view of an electronic apparatus 1 including a press detection sensor 3 according to the first embodiment. FIG. 1B is a cross-sectional view of the electronic device 1 according to the first embodiment cut along an XZ plane. FIG. 2 is an exploded perspective view of the sensor 10 according to the first embodiment. FIG. 3A is a schematic cross-sectional view of the sensor 10 according to the first embodiment. FIG. 3B is a plan view of the sensor 10 according to the first embodiment. FIG. 4 is a view for explaining the piezoelectric film 20 according to the first embodiment. FIG. 5A is a diagram for explaining a deformation when the sensor 101 according to the related art receives a pressing operation. FIG. 5B is a diagram for explaining a deformation when the sensor 10 according to the first embodiment receives a pressing operation. FIG. 6A to FIG. 6C are diagrams for explaining a modification of the sensor 10 according to the first embodiment. FIG. 7A is a plan view of the sensor 110 according to the second embodiment. FIG. 7B is an exploded perspective view of the sensor 110 according to the second embodiment. FIG. 8 is a view for explaining the piezoelectric film 120 according to the second embodiment. FIG. 9A is a schematic diagram showing a strain distribution of the sensor 110 when a load is applied to the center of the touch panel, and FIG. It is a schematic diagram which shows the distortion distribution of the sensor 110 in the case of. FIGS. 10A to 10C are diagrams illustrating regions in which the output is 0 when the sensor 110 according to the second embodiment receives a pressing operation. FIG. 11 is a simulation model of how the touch panel is distorted. FIG. 12 is a graph showing the electrode position from the origin and the amount of shear distortion at the electrode position.

  FIG. 1A is a perspective view of an electronic apparatus 1 including a press detection sensor 3 according to the first embodiment. FIG. 1B is a cross-sectional view of the electronic device 1 cut along an XZ plane. Note that the electronic device 1 illustrated in FIGS. 1A and 1B is merely an example, and is not limited thereto, and can be changed as appropriate according to specifications.

  As shown in FIGS. 1A and 1B, the electronic apparatus 1 includes a substantially rectangular parallelepiped housing 2 having an open top surface. The electronic device 1 includes a flat plate-shaped press detection sensor 3 disposed in an opening on the upper surface of the housing 2. The press detection sensor 3 functions as an operation surface on which a user performs a pressing operation using a finger or a pen. The pressure detection sensor 3 includes a protective sheet 4, a sensor 10, and a detection unit 6. The protective sheet 4 is made of a flexible material. For this reason, when the user performs a pressing operation on the protective sheet 4, the strain applied to the protective sheet 4 is transmitted to the sensor 10. The detection unit 6 is disposed inside the housing 2 and is connected to the sensor 10 via a wiring (not shown).

  When a user performs a touch operation on the pressure detection sensor 3 using a finger or a pen, pressure is transmitted to the sensor 10. For this reason, the sensor 10 outputs a voltage corresponding to the operation received by the press detection sensor 3. The detection unit 6 detects the voltage output from the sensor 10. The detection unit 6 may be at any position as long as it is inside the housing 2. In the following description, the width direction (lateral direction) of the housing 2, that is, the press detection sensor 3 is defined as the X direction, the length direction (vertical direction) is defined as the Y direction, and the thickness direction is described as the Z direction.

  FIG. 2 is an exploded perspective view of the sensor 10 according to the first embodiment. In FIG. 2, the resin base material and wiring are omitted. As shown in FIG. 2, the sensor 10 includes a piezoelectric film 20, a first electrode 21, a second electrode 22, a first adhesive portion 23, and a second adhesive portion 24. The plurality of first electrodes 21 are arranged on the same plane. The plurality of second electrodes 22 are also arranged on the same plane. The first electrode 21 is disposed on the first main surface 11 of the piezoelectric film 20. The second electrode 22 is disposed on the second main surface of the piezoelectric film 20 that is the back side of the first main surface 11. The first adhesive portion 23 is disposed between the first electrode 21 and the piezoelectric film 20 and attaches the first electrode 21 to the piezoelectric film 20. The second adhesive portion 24 is disposed between the second electrode 22 and the piezoelectric film 20 and attaches the second electrode 22 to the piezoelectric film 20.

  A plurality of the first electrodes 21 and the second electrodes 22 are arranged with a gap therebetween. The second electrode 22 is disposed at a position facing the first electrode 21 through the piezoelectric film 20. The second electrode 22 is a so-called ground electrode. The first electrode 21 and the second electrode 22 detect charges generated from the piezoelectric film 20. By arranging a plurality of first electrodes 21 and second electrodes 22, it is possible to detect charges at necessary locations on the piezoelectric film 20 and to reduce the bulk of the sensor 10 because the electrodes can be formed small. . In addition, arrangement | positioning with respect to the piezoelectric film 20 of the 1st electrode 21 and the 2nd electrode 22 can be suitably deform | transformed according to use. For example, the distance between the first electrode 21 and the second electrode 22 or the size, number, or shape of the first electrode 21 and the second electrode 22 can be changed.

  When the sensor 10 is viewed in plan, the second electrode 22 may be completely overlapped with the piezoelectric film 20 in a top view or may be located on the inner side in the plane direction from the piezoelectric film 20. Thereby, the short circuit in the edge part of an electrode can be suppressed. The second electrode 22 only needs to be disposed at a position facing at least the first electrode 21, and may be a single electrode that covers the entire piezoelectric film 20. Thereby, since the 2nd electrode 22 is one piece, a manufacturing process becomes simple.

  FIG. 3A is a schematic cross-sectional view of the sensor 10. FIG. 3B is a plan view of the sensor 10. In FIG. 3B, only the first electrode 21 and the piezoelectric film 20 are shown, and other members are omitted.

  As shown in FIG. 3A, the sensor 10 may include a resin base material 25 and a resin base material 26. Thereby, the 1st electrode 21 and the 2nd electrode 22 are protected, and durability increases. Moreover, the sensor 10 can be affixed on the protective sheet 4 by further providing an adhesive portion on the outer side of one of the resin substrate 25 and the resin substrate 26.

  As shown in FIGS. 3A and 3B, the piezoelectric film 20 includes a plurality of slits 15. Each slit 15 is provided around the first electrode 21. In other words, each slit 15 is formed so as to surround the first electrode 21. Thereby, the piezoelectric film 20 can be divided by the slits 15 for each first electrode 21. Moreover, since each slit 15 is a plurality of straight lines, it is easy to form.

  In particular, when the pressure detection sensor 3 is greatly deformed, the area formed so as to be surrounded by the plurality of slits 15 is preferably larger than the first electrode 21. That is, it is preferable that the end portion of the region formed so as to be surrounded by the plurality of slits 15 in plan view is outside the end portion of the first electrode 21. If the areas of the regions formed so as to be surrounded by the first electrode 21 and the slit 15 are the same (overlapping in plan view), the first electrode 21 and the slit are slightly caused by distortion of the first electrode 21 and the slit 15. There is a possibility that the 15 positional relationships interfere with each other. When the press detection sensor 3 is pressed, if the slit 15 is slightly enlarged and the gap is widened, the area of the piezoelectric film 20 immediately below the first electrode 21 is reduced. As a result, there is a possibility that charges that should be detected are not sufficiently detected. On the other hand, when the region formed so as to be surrounded by the plurality of slits 15 is larger than the first electrode 21, a proper charge is detected without the positional relationship between the first electrode 21 and the slit 15 interfering. .

  The region divided for each first electrode 21 by the slit 15 is formed in a rectangular shape. The region divided by the slit 15 has a short side direction and a long side direction. The short side direction is a direction along the X direction, and the long side direction is a direction along the Y direction. When the piezoelectric film 20 is distorted, the piezoelectric film 20 is easily affected by the longitudinal direction. That is, the piezoelectric film 20 is easy to bend along the Y direction which is the longitudinal direction. Thus, when the user applies a pressing operation to the pressing detection sensor 3, the piezoelectric film 20 is distorted according to the shape of the region divided by the slit 15 for each first electrode 21. The region in which the first electrode 21 is arranged has the same distortion regardless of which position receives the pressing operation. By forming the slit 15, the aspect ratio of the piezoelectric film 20 can be substantially adjusted. For this reason, by adjusting how the piezoelectric film 20 is distorted, the detection sensitivity can be improved by reducing the area where the charge opposite to the charge to be detected is generated. Therefore, it is possible to reduce the influence due to the position where the pressing operation is received and improve the detection sensitivity.

  FIG. 4 is a view for explaining the piezoelectric film 20 according to the first embodiment. FIG. 4 is a plan view of the piezoelectric film 20.

  As shown in FIG. 4, the piezoelectric film 20 may be a film formed from a chiral polymer. In the first embodiment, polylactic acid (PLA), particularly L-type polylactic acid (PLLA) is used as the chiral polymer. PLLA made of a chiral polymer has a main chain with a helical structure. PLLA has piezoelectricity when uniaxially stretched and molecules are oriented. The uniaxially stretched PLLA generates a voltage when the flat plate surface of the piezoelectric film 20 is pressed. At this time, the amount of voltage generated depends on the amount of displacement by which the flat plate surface is displaced in the direction perpendicular to the flat plate surface by the pressing amount.

  In the first embodiment, the uniaxial stretching direction of the piezoelectric film 20 (PLLA) is a direction that forms an angle of 45 degrees with respect to the Y direction and the Z direction, as indicated by arrows in FIG. The 45 degrees includes an angle including about 45 degrees ± 10 degrees, for example. Thereby, a voltage is generated when the piezoelectric film 20 is pressed.

  PLLA generates piezoelectricity by molecular orientation treatment such as stretching, and does not need to be subjected to poling treatment unlike other polymers such as PVDF and piezoelectric ceramics. That is, the piezoelectricity of PLLA that does not belong to ferroelectrics is not expressed by the polarization of ions like ferroelectrics such as PVDF or PZT, but is derived from a helical structure that is a characteristic structure of molecules. is there. For this reason, the pyroelectricity generated in other ferroelectric piezoelectric materials does not occur in PLLA. Since there is no pyroelectricity, the influence of the temperature of the user's finger or frictional heat does not occur, and the press detection sensor 3 can be formed thin. Further, PVDF or the like shows a change in piezoelectric constant over time, and in some cases, the piezoelectric constant may be remarkably reduced, but the piezoelectric constant of PLLA is extremely stable over time. Therefore, it is possible to detect displacement due to pressing with high sensitivity without being affected by the surrounding environment.

  The piezoelectric film 20 may be made of a film made of a ferroelectric material in which ions are polarized, such as PVDF or PZT subjected to poling treatment, instead of PLLA.

  As the first electrode 21 and the second electrode 22 formed on both main surfaces of the piezoelectric film 20, metal electrodes such as aluminum and copper can be used. When the electrode is required to be transparent, the first electrode 21 and the second electrode 22 can be made of a highly transparent material such as ITO or PEDOT. By providing the first electrode 21 and the second electrode 22 as described above, the charge generated by the piezoelectric film 20 can be acquired as a voltage, and a pressing amount detection signal having a voltage value corresponding to the pressing amount can be output to the outside. .

  Next, deformation of the piezoelectric film 20 when the sensor 10 receives a pressing operation will be described. FIG. 5A is a diagram for explaining a deformation when the sensor 101 according to the related art receives a pressing operation. FIG. 5B is a diagram for explaining a deformation when the sensor 10 receives a pressing operation. 5A and 5B, only the piezoelectric film 20, the first adhesive portion 23, and the second adhesive portion 24 are shown, and the other members are omitted.

  As shown in FIG. 5A, the piezoelectric film 20 of the sensor 101 according to the prior art has no slit 15 and is continuous in the X direction. In this configuration, when the sensor 101 receives a pressing operation in the direction indicated by the arrow 902 in FIG. 5A, that is, in the −Z direction, the piezoelectric film 20, the first adhesive portion 23, and the second adhesive portion 24 are each − Distorted in the Z direction. Since the piezoelectric film 20 is continuous in the X direction, the entire piezoelectric film 20 is distorted. For this reason, it is influenced by a region other than the vicinity of the center that has undergone the pressing operation. The piezoelectric film 20 is affected by tensile stress, and the flexibility as a whole decreases. As described above, in the sensor 101 according to the related art, the detection accuracy when a pressing operation is received may decrease.

  On the other hand, as shown in FIG. 5B, the piezoelectric film 20 of the sensor 10 is provided with a slit 15. The piezoelectric film 20 is divided into regions of a piezoelectric film 201, a piezoelectric film 202, and a piezoelectric film 203 in the X direction by the slit 15.

  When the sensor 10 receives a pressing operation in the direction indicated by the arrow 902 in FIG. 5B, that is, in the −Z direction, the piezoelectric film 20, the first adhesive portion 23, and the second adhesive portion 24 are each distorted in the −Z direction. . Since the piezoelectric film 20 is divided by the slit 15, the piezoelectric film 20 is distorted in the −Z direction for each divided area. The piezoelectric film 201, the piezoelectric film 202, and the piezoelectric film 203 can move freely at the end on the slit 15 side. For this reason, the piezoelectric film 20 as a whole is easily bent and rich in flexibility. Therefore, the degree of freedom when bending the sensor 10 can be increased. For example, even when the sensor 10 is used for an electronic device or the like that performs a flexible operation, the piezoelectric film 20 can be distorted for each electrode. Become.

  FIGS. 6A to 6C are views for explaining modifications 1 to 3 of the sensor according to the first embodiment. 6 (A) to 6 (C), only the first electrode 21 and the piezoelectric film 20 are shown, and the other members are omitted. In the description of the first to third modifications, only the configuration different from that of the sensor 10 will be described, and the rest will be omitted.

  As shown in FIG. 6A, in the sensor 70 according to the first modification, the piezoelectric film 20 includes a slit 151. The slits 151 are continuously formed so as to surround the three directions around each first electrode 21. As a result, the slits 151 surrounding the first electrodes 21 in the same row can be formed in one step, which facilitates the manufacturing process.

  In the sensor 70, the region R1 for each first electrode 21 divided by the respective slits 151 is generally rectangular like the region indicated by the oblique lines shown in FIG. In the region R1, the Y direction is the long direction, and the X direction is the short direction. For this reason, when the first electrode 21 receives the pressing operation, the region of the piezoelectric film 20 divided by each slit 151 is easily affected by the Y direction. Thereby, the sensor 70 can obtain the same effect as the sensor 10.

  As shown in FIG. 6B, in the sensor 71 according to the second modification, the piezoelectric film 20 includes a slit 152. A plurality of slits 152 are formed so as to surround two directions around each first electrode 21. Thereby, since the shape of each slit 152 is a simple structure, it becomes easy to form the slit 152 in a required location.

  In the sensor 71, the region R2 for each first electrode 21 divided by the respective slits 152 is substantially rectangular like the region indicated by the oblique lines shown in FIG. 6B, similarly to the region R1. For this reason, the sensor 71 can obtain the same effect as the sensor 10.

  As shown in FIG. 6C, in the sensor 72 according to the modification 3, the piezoelectric film 20 includes a slit 153. The slits 153 are continuously formed so as to surround three directions around each first electrode 21. The slit 153 is not formed to the end of the piezoelectric film 20 as compared with the slit 151. For this reason, since the piezoelectric film 20 is not divided | segmented into a fine area | region at the time of manufacture, handling becomes easy.

  In the sensor 72, the region R3 for each first electrode 21 divided by the respective slits 153 is substantially rectangular like the region indicated by the oblique lines shown in FIG. In the region R3, the X direction is the longitudinal direction and the Y direction is the short direction. For this reason, when the first electrode 21 receives the pressing operation, the region of the piezoelectric film 20 divided by each slit 151 is easily affected by the X direction. Thereby, the sensor 72 can obtain the same effect as the sensor 10.

  Hereinafter, the touch panel according to the second embodiment will be described. FIG. 7A is a plan view of a pressure detection sensor according to the second embodiment. FIG. 7B is an exploded perspective view of the press detection sensor according to the first embodiment. In the touch panel according to the second embodiment, only the difference in configuration from the sensor 10 according to the first embodiment will be described. In FIG. 7A, the electrodes are indicated by broken lines.

  As shown in FIGS. 7A and 7B, the touch panel according to the second embodiment includes a sensor 110. The sensor 110 includes a first electrode 121, a second electrode 122, and a piezoelectric film 120. The piezoelectric film 120 may not have a slit.

  A plurality of first electrodes 121 and second electrodes 122 are formed in pairs. That is, in the present embodiment, the sensor 110 includes a first electrode pair 61 and 63 and a second electrode pair 62 and 64 each including a first electrode 121 and a second electrode 122. Hereinafter, although described in detail, the sensor 110 includes a plurality of electrode pairs, so that the pressing loads at a plurality of locations can be calculated. The first electrode 121 is disposed on the first main surface 11 of the piezoelectric film 120. The second electrode 122 is disposed on the second main surface of the piezoelectric film 120 that is the back side of the first main surface 11.

  FIG. 8 is a diagram for explaining the piezoelectric film 120 according to the second embodiment, and is a diagram in which the piezoelectric film 120 is viewed in plan.

  As shown in FIG. 8, in the second embodiment, the uniaxial stretching direction of the piezoelectric film 120 (PLLA) is a direction that forms an angle of 90 degrees with respect to the Y direction, as indicated by an arrow 902 in FIG. A similar effect can be obtained even in a direction that forms an angle of 0 degrees with respect to the Y direction. The 90 degrees or 0 degrees includes an angle including about ± 10 degrees.

  As shown in FIG. 7A, the first electrode pair 61, 63 and the second electrode pair 62, 64 are preferably arranged at symmetrical positions from the center of the sensor 110. Furthermore, the first electrode pair 61, 63 and the second electrode pair 62, 64 are more preferably arranged at the corners of the sensor 110. Thereby, it becomes easy to detect the output from the pair of the first electrode pair 61, 63 and the second electrode pair 62, 64. On the other hand, when the first electrode pair 61, 63 or the second electrode pair 62, 64 is arranged at the center of the sensor 110, the output becomes close to zero. This makes it difficult to read the output accurately. Hereinafter, detection of the sensor 110 will be described.

  FIG. 9A is a schematic diagram showing a strain distribution of the sensor 110 according to the second embodiment when a load is applied to the center of the touch panel, and FIG. It is a schematic diagram which shows the distortion distribution of the sensor 110 at the time of applying a load to the center. FIGS. 10A and 10B are diagrams showing a region where the output is 0 when one point of the sensor 110 receives a pressing operation. FIG. 10C is a diagram illustrating a region where the output is 0 when two points of the sensor 110 are subjected to a pressing operation.

  As shown in FIGS. 9A and 9B, the direction of distortion of the sensor 110 extends toward the point where the load is applied. In the deformation of the corners of the sensor 110, when a load is applied to the center, and when a load is applied to the end, the deformation is also substantially in the direction of 45 degrees obliquely. Here, how to deform the corners of the sensor 110 will be described. In the vicinity of the two sides sandwiching the corners of the corners of the sensor 110, the sensor 110 is close to the fixed side, and thus is difficult to be displaced in the Z direction (the direction perpendicular to the paper surface). On the other hand, the vicinity of the center of the two sides of the opposing sensor 110 is not strongly restrained in the Z direction because the distance from the corner of the sensor 110 of interest to the fixed side is long. For example, when a load is applied to the pressing point P2 shown in FIG. 9B, since the pressing point P2 is far from the upper and lower sides along the X direction, the pressing point P2 is easily deformed in the Z direction. That is, when the corner portion of the sensor 110 is viewed locally, the sensor 110 can be approximated to a structure in which only two sides sandwiching the corner are fixed. Such a structure is most easily displaced on a diagonal line extending from the corner. Further, on the diagonal line of the sensor 110, distortion occurs in a direction of approximately 45 degrees with respect to the fixed side. The method of distortion of the sensor 110 on the diagonal line is the same regardless of where the sensor 110 is pressed on the diagonal line. Therefore, when a load is applied to the center or when a load is applied to the end, the end of the sensor 110 is generally distorted in a 45-degree oblique direction.

  A piezoelectric film (PLLA), which is a chiral polymer, generates a piezoelectric effect due to shear stress in the orientation direction of the polymer. For this reason, the piezoelectric effect is obtained from the corner of the piezoelectric film in the sensor 110 regardless of the position where the load is applied. Therefore, the load applied to the main surface of the touch panel can be detected by setting the orientation direction of the piezoelectric film to 0 or 90 degrees with respect to the Y-axis and arranging the electrode pair at the corner. At this time, no matter which position on the touch panel is pressed, a shear stress is generated at the corner, so that the sensor can stably obtain an output regardless of where it is pressed.

  Next, the arrangement of electrode pairs will be described. As shown in FIG. 9, the corner of the sensor 110 is distorted in an oblique direction. The direction of distortion at the corners is reversed left and right or up and down. That is, there is always a portion where the distortion direction is 0 degree or 90 degrees between the left and right corners or the upper and lower corners. The part where the distortion is 0 degree or 90 degrees depends on the pressed part.

  For example, when a load is applied to the center of the touch panel (when the pressing point P1 is pressed), as shown in FIG. 9A, the distortion is symmetrical vertically and horizontally around the pressing point P1. Therefore, the portion where the distortion direction is 0 degree or 90 degrees is a cross area A1 extending perpendicularly to the X axis and the Y axis from the depression point indicated by the depression point P1 in FIG. When a load is applied to the center of the long side edge of the touch panel (when the pressing point P2 is pressed), as shown in FIG. The distribution is such that the direction of distortion gradually goes to the pressing point P2. Therefore, a portion where the distortion is 0 degree or 90 degrees is as shown in a region A2 in FIG.

  Accordingly, there is a portion where the piezoelectric effect cannot be obtained without applying shear stress to the piezoelectric film whose orientation direction is set to 0 degree or 90 degrees depending on the pressed position. For this reason, it is necessary to optimize the arrangement of the electrode pairs so that the zero point of the sensor output does not occur no matter where the touch panel is pressed. Hereinafter, optimization of the arrangement of the electrode pairs will be described.

  In order to obtain the optimal position of the electrode pair arrangement, the strain on a 100 mm × 100 mm flat plate simulating a touch panel was simulated by stress analysis using a finite element method.

  FIG. 11 is a simulation model of how the touch panel is distorted. The touch panel was a 100 mm × 100 mm flat plate, and the four sides of the flat plate had zero displacement in the Z-axis direction. Further, the simulation was performed under the condition that a force of 1 N is applied to the main surface of the flat plate in the −Z-axis direction.

  FIG. 12 is a graph showing the electrode position from the origin and the amount of shear distortion at the electrode position when the size of the electrode pair is 5 mm × 5 mm. The position of the electrode is moved on a diagonal line, and the position on the X-axis and the Y-axis is the same, so the electrode position is indicated by a position on the X-axis. Similarly, the pressed position was simulated at a position of X, Y = 30 mm or X, Y = 40 mm on the diagonal line.

  As a result of the simulation, as shown in FIG. 12, when X, Y = 30 mm is pressed, if the electrodes are arranged at X, Y = 30 mm, the shear distortion is reduced, but the output is not zero. On the other hand, when X, Y = 40 mm is pressed, if the electrodes are arranged at X, Y = 40 mm, the shear distortion is reduced by 1/10 or more, making it difficult to design the dynamic range of the amplifier circuit. For this reason, the electrode is preferably arranged on the inner side of 30 mm with respect to the side having a width of 100 mm, that is, on the inner side of 30% of the length of the side.

  Next, the principle of detecting pressing at a plurality of locations when a plurality of electrode pairs are provided will be described. For convenience of explanation, it is assumed that there are two pressed points and two electrode pairs. FIG. 10C shows the load at two points and the positions of the two first electrode pairs 61 and 63 and the second electrode pairs 62 and 64. The first electrode pair 61, 63 and the second electrode pair 62, 64 are arranged at the corners at positions that are point-symmetric with respect to the center of the touch panel.

  When the load applied to the first pressing point P3 is fixed and the load applied to the second pressing point P4 is changed, the shear distortion applied to the piezoelectric film at the corner is applied to the second pressing point P4. Distortion according to the load. Similarly, when the load applied to the second pressing point P4 is fixed and the load applied to the first pressing point P3 is varied, the shear distortion applied to the piezoelectric film at the corner is the first pressing point. It becomes distortion according to the load concerning P3.

  As described above, when the sensor is pressed at two points, the shear strain generated at the corner is the sum of the applied load applied to the pressed point P3 or the applied strain applied to the pressed point P4. That is, the sensor output at the corner is a linear function of the load applied to the pressing point P3 or the pressing point P4 and the pressing position, and the pressing point P3 and the pressing point P4 can be calculated individually. Therefore, when detecting the load of 2 points | pieces, what is necessary is just to form an electrode in an at least 2 or more edge part. According to the same principle, when detecting three or more pressing points, it is sufficient to provide three or more electrode pairs. When detecting the load pressing point as one point, one electrode pair may be used.

  Here, the signal amplification circuit of the sensor 110 will be described. Although not shown, the signal detection circuit of the sensor 110 includes an I / V conversion circuit that converts the current in the previous stage into a voltage, and one or more voltage amplification circuits in the subsequent stage. When a plurality of electrodes for detecting charges generated in the piezoelectric film 120 are provided in the sensor 110, if an I / V conversion circuit and a voltage amplification circuit are provided for each electrode, the mounting area of the sensor 110 increases. Here, when one voltage amplification circuit is connected to a plurality of electrodes, a switch is provided between the I / V conversion circuit and the plurality of electrodes, and switching is performed to switch the connection between the electrode and the I / V conversion circuit. Thus, the mounting area of the sensor 110 can be kept small. In addition, when an I / V conversion circuit is provided for each electrode and each I / V conversion circuit is connected to one voltage amplification circuit, a switch is provided between each I / V conversion circuit and the voltage amplification circuit. Thus, the connection with the subsequent voltage amplification circuit can be switched by switching. Alternatively, the electrodes of the sensor 110 may be connected to a current detection type capacitance detection IC. In order to increase the sensitivity of the sensor 110, a capacitor may be connected between the signal electrode and the signal detection circuit of the sensor 110 and between the reference electrode (GND electrode) and the signal detection circuit of the sensor 110. Thereby, the capacitor can increase the sensitivity of the sensor 110 by charging the electric charge generated in the piezoelectric film 120 of the sensor 110 and flowing the charged electric charge to the detection circuit.

  In the embodiment, the slit 15 is configured to penetrate the piezoelectric film 20. However, any slit may be used as long as it increases the flexibility of the piezoelectric film 20. For example, the slit 15 may be a groove formed in the piezoelectric film 20.

  Although the present embodiment relates to a sensor that detects a pressing force, for example, a touch sensor is provided between the protective sheet 4 and the sensor 10 in FIG. A touch panel that detects the pressing force can be formed by arranging the display devices.

  In addition, arrangement | positioning of the said touch panel is an example, For example, arrangement | positioning like a press sensor / touch sensor / display apparatus or a touch sensor / display apparatus / press sensor from the operation surface side may be sufficient.

DESCRIPTION OF SYMBOLS 1 ... Electronic device 2 ... Housing | casing 3 ... Press detection sensor 4 ... Protection sheet 6 ... Detection part 10,70,71,72,101,110 ... Sensor 11 ... 1st main surface 15,151,152,153 ... Slit 21 , 121 ... the first electrode 22, 122 ... the second electrode 20, 120, 201, 202, 203 ... the piezoelectric film 23 ... the first adhesive part 24 ... the second adhesive part 61, 63 ... the first electrode pair 62, 64 ... the first Two-electrode pair 902 ... arrow

As shown in FIGS. 7A and 7B, the touch panel according to the second embodiment includes a sensor 110. The sensor 110 includes first electrodes 61 and 62 , second electrodes 63 and 64 , and a piezoelectric film 120. The piezoelectric film 120 may not have a slit.

A plurality of first electrodes 61 and 62 and second electrodes 63 and 64 are formed in pairs. In other words, in the present embodiment, the sensor 110 includes a first electrode pair 121 and a second electrode pair 122 including the first electrodes 61 and 62 and the second electrodes 63 and 64 . Hereinafter, although described in detail, the sensor 110 includes a plurality of electrode pairs, so that the pressing loads at a plurality of locations can be calculated. The first electrodes 61 and 62 are disposed on the first main surface 11 of the piezoelectric film 120. The second electrodes 63 and 64 are disposed on the second main surface of the piezoelectric film 120 that is the back side of the first main surface 11.

As shown in FIG. 7A, the first electrode pair 121 and the second electrode pair 122 are preferably arranged at symmetrical positions from the center of the sensor 110. Furthermore, the first electrode pair 121 and the second electrode pair More preferably, the electrode pair 122 is disposed at a corner of the sensor 110. Thereby, it becomes easy to detect the output from the pair of the first electrode pair 121 and the second electrode pair 122 . On the other hand, when the first electrode pair 121 or the second electrode pair 122 is arranged at the center of the sensor 110, the output becomes close to zero. This makes it difficult to read the output accurately. Hereinafter, detection of the sensor 110 will be described.

Next, the principle of detecting pressing at a plurality of locations when a plurality of electrode pairs are provided will be described. For convenience of explanation, it is assumed that there are two pressed points and two electrode pairs. FIG. 10C shows the load at two points and the positions of the two first electrode pairs 121 (first electrodes 61 and 62) and the second electrode pair 122 (second electrodes 63 and 64) . The first electrode pair 121 and the second electrode pair 122 are arranged at the corners at points symmetrical with respect to the center of the touch panel.

Claims (7)

Piezoelectric film,
A first electrode disposed on a first main surface of the piezoelectric film;
A second electrode disposed at a position facing at least the first electrode of the second main surface of the piezoelectric film;
With
The piezoelectric film includes a slit,
The slit is a sensor provided around the first electrode.   The sensor according to claim 1, wherein the slit is provided so as to surround the first electrode.   3. The sensor according to claim 1, wherein a region of the piezoelectric film divided by the slit provided around the first electrode has a longitudinal direction and a lateral direction.   The sensor according to claim 1, wherein the slit is formed to be continuous.   The sensor according to any one of claims 1 to 3, wherein a plurality of the slits are formed.   A touch panel comprising the sensor according to claim 1.   An electronic device comprising the touch panel according to claim 6.

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