Electronic device

Abstract

To provide an electronic apparatus with improved outputs of a piezoelectric sensor.SOLUTION: An electronic apparatus has long sides and short sides, and includes a surface panel having a front surface and a rear surface, a housing that holds the long sides and the short sides of the surface panel, a display device that has a first main surface and a second main surface and in which the first main surface is attached to the rear surface of the surface panel, a piezoelectric sensor that is attached to the second main surface of the display device and detects deflection of the surface panel and the display device, and an attaching member that attaches the piezoelectric sensor to the second main surface of the display device. The piezoelectric sensor includes a piezoelectric film, a base material that holds the piezoelectric film, and electrodes disposed on both main surfaces of the piezoelectric film, and is provided with a slit that divides the piezoelectric film, the base material, and the electrodes along a direction of the short sides.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an electronic device provided with a piezoelectric sensor.

Background Art

[0002] In the electronic device of Patent Document 1, a piezoelectric sensor is attached to the back surface of a display. The aspect ratio of the piezoelectric sensor of Patent Document 1 is 2.5 times or more. The piezoelectric sensor of Patent Document 1 is attached to the display with a double-sided tape having a modulus of elasticity of 1 MPa or more. The piezoelectric sensor detects deflection along the short side direction of the display.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the structure shown in Patent Document 1, when trying to improve the sensitivity of the piezoelectric sensor, it is conceivable to expand the width of the piezoelectric sensor (the length along the long side direction of the display) and increase the area of the piezoelectric sensor. However, when the width of the piezoelectric sensor is expanded, the sensitivity to deflection in the direction along the long side direction of the display increases. The output polarity of the piezoelectric sensor due to deflection in the long side direction of the display is opposite to the output polarity of the piezoelectric sensor due to deflection in the short side direction. Therefore, even if the width of the piezoelectric sensor is expanded, the sensitivity of the reverse polarity increases, and as a result, the sensitivity of the piezoelectric sensor does not improve.

[0005] An object of the present invention is to provide an electronic device with improved output of a piezoelectric sensor.

Means for Solving the Problems

[0006] The electronic device includes a surface panel having a long side and a short side, and a front surface and a back surface, a housing that holds the long side and the short side of the surface panel, a display having a first main surface and a second main surface, the first main surface being attached to the back surface of the surface panel, a piezoelectric sensor that is attached to the second main surface of the display and detects bending of the surface panel and the display, and an attachment member that attaches the piezoelectric sensor to the second main surface of the display. The piezoelectric sensor includes a piezoelectric film, a base material that holds the piezoelectric film, and electrodes disposed on both main surfaces of the piezoelectric film. A slit is provided that divides the piezoelectric film, the base material, and the electrodes along the short side direction.

[0007] Since the piezoelectric sensor is divided by the slit along the short side direction, it does not bend following the bending in the long side direction of the surface panel and the display. Therefore, even if the width of the piezoelectric sensor (the length along the long side direction of the surface panel and the display) is increased, the output of the reverse polarity becomes small, and the output of the piezoelectric sensor can be improved.

Advantages of the Invention

[0008] The electronic device of the present invention can improve the output of the piezoelectric sensor.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

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Figure 10

Embodiments for Carrying Out the Invention

[0010] Hereinafter, the electronic device 1 according to the embodiment of the present invention will be described. FIG. 1 is a plan view of the electronic device 1 according to the embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line A-A shown in FIG. 1.

[0011] The electronic device 1 includes a housing 11, a surface panel 12, and a piezoelectric sensor 16. The electronic device 1 is of a size that can be carried, and is, for example, an electronic device such as a tablet personal computer or a smartphone.

[0012] The housing 11 has a rectangular parallelepiped shape with an open top surface. The housing 11 has a rectangular shape having a long side direction (Y direction) and a short side direction (X direction) in plan view.

[0013] As shown in FIGS. 1 and 2, the housing 11 holds the surface panel 12 so as to close the opening surface of the housing 11. The surface panel 12 is, for example, glass. The surface (one main surface of the outermost layer of glass) of the surface panel 12 serves as an operation surface. The surface panel 12 is made of a material having translucency.

[0014] Inside the housing 11, as shown in FIG. 2, the surface panel 12, the display 13, the adhesive 14, the plate material 15, the attachment member 17, and the piezoelectric sensor 16 are arranged in order from the operation surface side along the thickness direction (Z direction).

[0015] A touch sensor (capacitive sensor) may be disposed between the surface panel 12 and the display 13. The display 13 is composed of an LCD, an OLED, or the like. The display 13 is attached to the back surface of the surface panel 12 with an adhesive or the like (not shown).

[0016] The first main surface of the plate member 15 is attached to the second main surface of the display 13 with the adhesive 14. The plate member 15 is made of, for example, SUS (stainless steel). The adhesive 14 has a function of protecting the second main surface of the display 13 and attaching the plate member 15.

[0017] The piezoelectric sensor 16 is attached to the second main surface of the plate member 15 by the attaching member 17. Thus, the piezoelectric sensor 16 is attached to the second main surface of the display 13 via the adhesive 14, the plate member 15, and the attaching member 17. Note that the adhesive 14 and the plate member 15 are not essential components of the present invention. The piezoelectric sensor 16 may be directly attached to the second main surface of the display 13 via the attaching member 17.

[0018] As shown in FIG. 1, the piezoelectric sensor 16 is long along the short side direction of the surface panel 12 and short along the long side direction. The piezoelectric sensor 16 detects the deflection of the surface panel 12 and the display 13.

[0019] FIG. 3 is a plan view of the piezoelectric sensor 16, and FIG. 4 is a cross-sectional view taken along line B-B shown in FIG. 3. As shown in FIGS. 3 and 4, the piezoelectric sensor 16 includes a piezoelectric film 31, an adhesive 91, an adhesive 92, a first electrode 34, a second electrode 35, a base material 36, and a base material 37.

[0020] The first electrode 34, the second electrode 35, the piezoelectric film 31, the base material 36, and the base material 37 each have a flat plate shape and are provided with a first main surface and a second main surface facing each other in the thickness direction. The first electrode 34 is formed on the upper surface of the base material 36. The first electrode 34 is connected to the lower surface of the piezoelectric film 31 via an adhesive 92. The second electrode 35 is formed on the lower surface of the base material 37. The second electrode 35 is connected to the upper surface of the piezoelectric film 31 via an adhesive 91. Either one of the first electrode 34 and the second electrode 35 is a reference electrode (ground electrode), and the other is a detection electrode. For example, the first electrode 34 is a detection electrode. The extraction electrode 50 is electrically connected to the first electrode 34 via a via hole provided in the base material 36.

[0021] The first electrode 34, the second electrode 35, the piezoelectric film 31, the base material 36, and the base material 37 each have an outer shape that is approximately rectangular in plan view. The base material 36 and the base material 37 are larger than the first electrode 34, the second electrode 35, and the piezoelectric film 31 in plan view.

[0022] Note that the adhesive 91 and the adhesive 92 are composed of, for example, an acrylic adhesive.

[0023] The piezoelectric film 31 is a film mainly made of a chiral polymer such as polylactic acid. The polylactic acid may be either L-type polylactic acid (PLLA) or D-type polylactic acid (PDLA).

[0024] Polylactic acid is a chiral polymer having a helical structure in the main chain and has the property of exhibiting piezoelectricity when oriented in a predetermined axial direction. This piezoelectricity is represented by the piezoelectric tensor component d14 with the thickness direction of the film as the first axis and the direction in which the polylactic acid molecules are oriented as the third axis.

[0025] If the piezoelectric film 31 is arranged such that the direction in which the molecules of polylactic acid are oriented (the stretching direction) intersects the long sides and short sides of the surface panel 12 and the display 13, polarization will occur due to the expansion and contraction in the direction of the long sides or short sides of the surface panel 12 and the display 13. For example, if the piezoelectric film 31 has a stretching direction that is approximately 45° with respect to the long sides and short sides of the surface panel 12 and the display 13, polarization will occur due to the expansion and contraction in the direction of the long sides or short sides of the surface panel 12 and the display 13, and an output will appear at the piezoelectric sensor 16.

[0026] Note that the angle of the stretching direction in the piezoelectric film 31 is not limited to exactly 45° with respect to the long sides and short sides of the surface panel 12 and the display 13, and can be any angle close to 45°. However, the closer the angle of the stretching direction is to 45° or 0° with respect to the long sides and short sides, the more efficiently the deflection of the long sides and short sides of the surface panel 12 and the display 13 can be detected.

[0027] Therefore, the approximately 45° referred to in this embodiment means an angle within a predetermined range centered around 45°, such as about 45° ± 10°. These specific angles may be appropriately determined according to the overall design based on the use of the displacement sensor and the characteristics of each part.

[0028] When the stretching direction of the piezoelectric film 31 is arranged at approximately 45° with respect to the long sides and short sides of the surface panel 12 and the display 13 as described above, the output of the piezoelectric film 31 has the opposite polarity of the output of the piezoelectric sensor due to the deflection in the long side direction of the surface panel 12 and the display 13 compared to the output polarity of the piezoelectric sensor due to the deflection in the short side direction. The piezoelectric film 31 is short along the long side direction of the surface panel 12 and the display 13 and long along the short side direction. Therefore, the piezoelectric film 31 detects the deflection in the direction along the short side direction of the surface panel 12 and the display 13 with high sensitivity.

[0029] On the other hand, since the output of the piezoelectric film 31 depends on the surface area of the piezoelectric film 31, it is preferable that the area of the piezoelectric film 31 is larger. However, when the piezoelectric sensor is expanded in the width direction of the piezoelectric film 31 (the long side direction of the surface panel 12 and the display 13), the polarization of the opposite polarity increases, so the sensitivity does not improve only by expanding the width of the piezoelectric film 31.

[0030] Therefore, the piezoelectric sensor 16 of the present embodiment is provided with a slit 18 that divides the piezoelectric film 31, the base material 36, the base material 37, the first electrode 34, and the second electrode 35 along the short side direction of the surface panel 12 and the display 13. In the example shown in FIG. 3, the slit 18 divides the piezoelectric film 31, the base material 36, the base material 37, the first electrode 34, and the second electrode 35 along the short side direction except for the location where the extraction electrode 50 is provided.

[0031] However, the structure of the piezoelectric sensor 16 shown in FIGS. 3 and 4 has a portion where the base material and the electrodes are connected in plan view. Specifically, in the portion where the extraction electrode 50 is provided, the base material 36, the base material 37, and the first electrode 34 are not divided by the slit 18.

[0032] Since the piezoelectric sensor 16 is divided by the slit 18 along the short side direction, it does not bend following the bending in the long side direction of the surface panel 12 and the display 13. Therefore, even if the width of the piezoelectric sensor 16 (the length along the long side direction of the surface panel 12 and the display 13) is expanded, the output of the opposite polarity becomes smaller.

[0033] FIG. 5 is a top view of the electronic device 1. Points 1 to 25 in FIG. 5 indicate the pressing positions on the upper surface of the surface panel 12. FIG. 6 is a graph showing the relationship between the pressing position of the surface panel 12 and the integrated value of the charge generated by the piezoelectric sensor. FIG. 6 shows the integrated value of the charge when there is no slit 18 as a reference example and when there is a slit 18 in the present embodiment. FIG. 7 is a diagram showing the strain in the X direction and the strain in the Y direction when the position of point 12 is pressed.

[0034] As shown in Fig. 6, when the piezoelectric sensor 16 has the slit 18 of the present embodiment, the output value of the piezoelectric sensor 16 is greatly improved particularly when pressing the positions of points 11 to 15 as compared with the case where there is no conventional slit 18.

[0035] For example, as shown in Fig. 7, when the piezoelectric sensor 16 having the slit 18 of the present embodiment presses the position of point 12, the strain in the X direction is substantially unchanged, while the strain in the Y direction decreases by about 60% compared with the case where there is no conventional slit 18.

[0036] In this way, since the piezoelectric sensor 16 of the present embodiment is divided by slits along the short side direction, even if the width of the piezoelectric sensor 16 (the long side direction of the surface panel and the display) is expanded, the strain in the Y direction becomes smaller and the output of the reverse polarity becomes smaller. Therefore, the slit 18 of the present embodiment can improve the output of the piezoelectric sensor.

[0037] Next, Fig. 8 is a plan view of the piezoelectric sensor 16A according to Modification 1. The structure of the piezoelectric sensor 16 shown in Figs. 3 and 4 had a portion where the base material and the electrodes were connected in a plan view. Specifically, in the portion where the extraction electrode 50 was provided, the base material 36, the base material 37, and the first electrode 34 were not divided by the slit 18. On the other hand, the slit 18A shown in Fig. 8 divides the piezoelectric film, the base material, and the electrodes in all portions along the X direction. Therefore, in the example of Fig. 8, the extraction electrode is divided into a first extraction electrode 50A and a second extraction electrode 50B. Further, the piezoelectric film 31 is divided into a first piezoelectric film 31A and a second piezoelectric film 31B. Further, the base material 37 is divided into a first base material 37A and a second base material 37B. In addition, the first electrode 34, the second electrode 35, and the base material 36 shown in Fig. 4 are also divided by slits.

[0038] In this way, the slit may divide the piezoelectric film, the base material, and the electrodes in all portions along the X direction.

[0039] Note that the integrated value of the charge shown in FIG. 6 and the strain shown in FIG. 7 correspond to the structure having the portion where the base material and the electrode are connected as viewed in plan (the structures shown in FIGS. 3 and 4). In FIGS. 3 and 4, for the sake of explanation, the length of the slit 18 in the X direction is shown to be long, but the length along the X direction of the portion where the base material and the electrode are connected is 1 / 5 or less of the length along the X direction of the piezoelectric sensor 16.

[0040] Next, FIG. 9 is a plan view of the piezoelectric sensor 16B according to the second modification. FIG. 10 is a cross-sectional view taken along line B-B shown in FIG. 9. In the piezoelectric sensor 16B shown in FIGS. 9 and 10, the lengths of the first electrode 34 and the second electrode 35 in the X direction are shorter than those of the piezoelectric sensor 16 shown in FIGS. 3 and 4. In other words, a portion where no electrode is formed exists at the X-direction end of the piezoelectric sensor 16B. On the other hand, the piezoelectric film 31, the base material 37, and the attachment member 17 are also arranged at the X-direction ends of the piezoelectric sensor 16.

[0041] When pressing near the center in the Y direction (the position where the piezoelectric sensor 16 is arranged), the strain in the X direction becomes larger than that near the end in the Y direction, but at the same time, the strain in the Y direction also becomes larger. For example, the strain in the Y direction when pressing points 11 and 15 shown in FIG. 5 is larger than the strain in the Y direction when pressing other positions (for example, points 6, 10, 16, and 20). Therefore, as shown by the charges at points 11 and 15 in FIG. 6, the output when pressing both ends in the X direction is lower than the output when pressing other positions (for example, points 6, 10, 16, and 20).

[0042] On the other hand, the piezoelectric sensor 16B according to Modification 2 has a portion where no electrode is formed at the end in the X direction. Therefore, it is configured not to detect charges of opposite polarities due to strain in the Y direction at both ends in the X direction. On the other hand, since the piezoelectric film 31, the base material 37, and the attachment member 17 are also arranged at the end in the X direction of the piezoelectric sensor 16, the piezoelectric sensor 16 is distorted in conjunction with the strain in the X direction of the surface panel 12 and the display 13. Therefore, the piezoelectric sensor 16B according to Modification 2 can suppress a decrease in output when pressing near the end in the X direction near the center in the Y direction (the position where the piezoelectric sensor 16 is arranged). Note that the piezoelectric sensor 16B according to Modification 2 may be in a mode where only one of the first electrode 34 or the second electrode 35 is not formed at the end in the X direction. Even in this case, the piezoelectric sensor 16B according to Modification 2 can obtain the same effect as the mode where neither the first electrode 34 nor the second electrode 35 is formed at the end in the X direction.

[0043] Finally, it should be considered that the descriptions of the above embodiments are illustrative in all respects and not restrictive. The scope of the present invention is indicated not by the above embodiments but by the claims. Further, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the claims.

[0044] For example, the number of slits is not limited to one. The piezoelectric film, the base material, and the electrodes may be divided by two or more slits.

Description of Reference Numerals

[0045] 1: Electronic device 11: Housing 12: Surface panel 13: Display 14: Adhesive 15: Plate material 16: Piezoelectric sensor 16A: Piezoelectric sensor 16B: Piezoelectric sensor 17: Attachment member 18: Slit 18A: Slit 31: Piezoelectric film 31A: First piezoelectric film 31B: Second piezoelectric film 34: First electrode 35: Second electrode 36: Substrate 37: Substrate 37A: First substrate 37B: Second substrate 50: Extraction electrode 50A: First extraction electrode 50B: Second extraction electrode 91: Adhesive 92: Adhesive

Claims

1. A surface panel having a long side and a short side, and having a front surface and a back surface; A housing that holds the long side and the short side of the surface panel; A display having a first main surface and a second main surface, the first main surface being attached to the back surface of the surface panel; A piezoelectric sensor attached to the second main surface of the display for detecting deflection of the surface panel and the display; An attachment member for attaching the piezoelectric sensor to the second main surface of the display; Comprising: The piezoelectric sensor includes a piezoelectric film, a base material that holds the piezoelectric film, and electrodes disposed on both main surfaces of the piezoelectric film; A slit is provided for dividing the piezoelectric film, the base material, and the electrodes along the short side direction; The piezoelectric sensor has a portion at an end in the short side direction where at least one of the electrodes disposed on both main surfaces is not formed; The attachment member is also disposed at an end in the short side direction of the piezoelectric sensor; An electronic device.

2. The piezoelectric sensor has a portion where the base material and the electrodes are connected as viewed in plan; The electronic device according to Claim 1.

3. The length along the short side direction of the connected portion is 1 / 5 or less of the length along the short side direction of the piezoelectric sensor; The electronic device according to Claim 2.

4. The piezoelectric film is also disposed at an end in the short side direction of the piezoelectric sensor; The electronic device according to any one of Claims 1 to 3.

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