Stretchable device
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- JAPAN DISPLAY INC
- Filing Date
- 2025-11-11
- Publication Date
- 2026-07-30
Smart Images
Figure JP2025039455_30072026_PF_FP_ABST
Abstract
Description
Stretchable Device
[0001] The present invention relates to a stretchable device.
[0002] The stretchable device has a small thickness from the front surface to the back surface and is excellent in stretchability and flexibility. Such a stretchable device includes a detection substrate and two stretchable resins sandwiching the detection substrate. Hereinafter, the direction parallel to the surface of the stretchable device is referred to as the first direction. Also, the direction parallel to the surface of the stretchable device and intersecting the first direction is referred to as the second direction. The detection substrate has a plurality of body portions arranged in the first direction and the second direction, and a plurality of hinge portions connecting the body portions to each other. The hinge portion is formed in a meander shape combining a plurality of arc portions.
[0003] When a load is input to the stretchable device, the load is transmitted from the stretchable resin to the body portion, and the hinge portion connected to the body is deformed. For example, when a tensile load acts on the body portion, each arc portion of the hinge portion is deformed so that the curvature becomes smaller. As a result, the length from one end to the other end of the hinge portion increases, and the two body portions are separated.
[0004] Also, the hinge portion is divided into a first hinge portion extending in the first direction and a second hinge portion extending in the second direction. In Patent Document 1, a strain gauge is provided in each hinge portion. Then, the strain amount (load in the first direction) of the first hinge portion is detected by the strain gauge provided in the first hinge portion, and the strain amount (load in the second direction) of the second hinge portion is detected by the strain gauge provided in the second hinge portion.
[0005] Japanese Unexamined Patent Application Publication No. 2024-010575
[0006] Incidentally, the stretchable resin adheres to the hinge. Therefore, when a load in the first direction is applied to the stretchable device, the load in the first direction is transmitted from the stretchable resin to the second hinge. Then, the second hinge is compressed or stretched in the first direction, causing strain to occur in the second hinge. As a result, the strain gauge placed on the second hinge will detect the strain caused by the load in the first direction. For this reason, it may not be possible to accurately detect the load applied to the stretchable device.
[0007] The present invention aims to provide a stretchable device that can detect loads with high accuracy.
[0008] A stretchable device according to one aspect of the present disclosure comprises a detection substrate and two stretchable resins sandwiching the detection substrate. The direction in which the two stretchable resins are arranged relative to the detection substrate is defined as the stacking direction. The direction perpendicular to the stacking direction is defined as the first direction. The direction perpendicular to the stacking direction and intersecting the first direction is defined as the second direction. The detection substrate comprises a plurality of body portions arranged in the first and second directions, a plurality of meander-shaped hinge portions extending in the first or second direction, and a plurality of base portions protruding from the body portions in the first or second direction and connecting the hinge portions. The direction in which the base portions protrude from the body portions is defined as the length direction. The direction perpendicular to the length direction when viewed from the stacking direction is defined as the width direction. The base portions are larger in the length direction than in the width direction. The base portions are provided with strain gauges for detecting the amount of strain. The strain gauges are not provided on the hinge portions.
[0009] Figure 1 is a perspective view of the stretchable device according to Embodiment 1. Figure 2 is a schematic diagram showing a cross-section of the stretchable device according to Embodiment 1, and more specifically, a cross-sectional view taken along the line II-II in Figure 3. Figure 3 is a plan view of the detection substrate laminated on the first stretchable resin of Embodiment 1, viewed from the first lamination direction. Figure 4 is an enlarged view of the first hinge portion of Embodiment 1. Figure 5 is an enlarged view of the first hinge portion of Embodiment 1 when it is extended in the first direction. Figure 6 is a circuit diagram of the strain detection circuit of Embodiment 1. Figure 7 is a plan view showing the layout of the strain detection circuit of Embodiment 1 when viewed from the first lamination direction. Figure 8 is a cross-sectional view taken along the line VIII-VIII in Figure 7. Figure 9 is an enlarged view of the first base portion of Embodiment 1. Figure 10 is a cross-sectional view taken along the line X-X in Figure 9. Figure 11 is a cross-sectional view taken along the line XI-XI in Figure 9. Figure 12 is an enlarged view of the first base portion of Modified Example 1. Figure 13 is an enlarged view of the first base of the modified example 2.
[0010] Embodiments for implementing this disclosure will be described in detail with reference to the drawings. The invention of this disclosure is not limited by the contents described in the following embodiments. Furthermore, the components described below include those that can be easily conceived by a person skilled in the art, and those that are substantially the same. Moreover, the components described below can be combined as appropriate. It should be noted that the disclosure is merely an example, and any modifications that can be easily conceived by a person skilled in the art while maintaining the spirit of the invention are naturally included within the scope of the present invention. In order to make the explanation clearer, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the actual embodiment, but these are merely examples and do not limit the interpretation of the present invention. Furthermore, in this specification and each drawing, components similar to those described above with respect to previously shown drawings are denoted by the same reference numerals, and detailed explanations may be omitted as appropriate.
[0011] Furthermore, in this specification and the claims, when describing a manner in which one structure is placed on top of another structure, unless otherwise specified, the term "on top of" includes both cases: when one structure is placed directly on top of another structure so as to be in contact with it, and when another structure is placed above another structure via yet another structure.
[0012] (Embodiment 1) Figure 1 is a perspective view of a stretchable device according to Embodiment 1. As shown in Figure 1, the stretchable device 100 is formed in a flat plate shape. The stretchable device 100 has a front surface 1 and a back surface 2 (not shown in Figure 1; see Figure 2) facing opposite directions. Hereinafter, the direction parallel to each of the front surface 1 and back surface 2 will be referred to as the planar direction.
[0013] Figure 2 is a schematic diagram showing a cross-section of the stretchable device according to Embodiment 1, and more specifically, it is a cross-sectional view taken along the line II-II in Figure 3. As shown in Figure 2, the stretchable device 100 has a first stretchable resin 60, a detection substrate 10, and a second stretchable resin 70 that are stacked in order. The detection substrate 10 is sandwiched between two stretchable resins (the first stretchable resin 60 and the second stretchable resin 70) from both sides in the stacking direction.
[0014] Hereinafter, the direction in which the first stretchable resin 60, the detection substrate 10, and the second stretchable resin 70 are arranged will be referred to as the stacking direction. Furthermore, with respect to the stacking direction, the direction in which the second stretchable resin 70 is arranged as viewed from the first stretchable resin 60 will be referred to as the first stacking direction Z1, and the direction opposite to the first stacking direction Z1 will be referred to as the second stacking direction Z2. Viewing the stretchable device 100 from the first stacking direction Z1 will be referred to as a plan view.
[0015] As shown in Figure 1, the stretchable device 100 is formed in a rectangular (quadrilateral) shape in plan view. Therefore, the surface 1 of the stretchable device 100 has a pair of long sides 3 and a pair of short sides 4. Hereinafter, the direction parallel to the planar direction and parallel to the long sides 3 will be referred to as the first direction X, and the direction parallel to the short sides 4 will be referred to as the second direction Y. The first direction X is perpendicular to the stacking direction. The second direction Y is perpendicular to the stacking direction and also perpendicular (intersects) the first direction X.
[0016] In a plan view, the stretchable device 100 is divided into a detection area 5 where the strain gauge 30 (see Figure 9) is placed, and a non-detection area 6 other than the detection area 5. The detection area 5 is located in the center of the stretchable device 100 and is formed as a rectangle (quadrilateral) in a plan view. The non-detection area 6 is formed as a rectangular frame in a plan view. The detection area 5 is located inside the non-detection area 6. Note that in Figure 1, a boundary line M is drawn to make the boundary between the detection area 5 and the non-detection area 6 easier to understand.
[0017] As shown in Figure 2, the first stretchable resin 60 and the second stretchable resin 70 have insulating properties, stretchability, and flexibility. Examples of resins used as the first stretchable resin 60 and the second stretchable resin 70 include acrylic elastomers. However, the first stretchable resin 60 and the second stretchable resin 70 in this disclosure are not limited to acrylic elastomers, and may be acrylic resins, epoxy resins, urethane resins, etc., and are not particularly limited.
[0018] The first stretchable resin 60 and the second stretchable resin 70 are formed in a plate shape and extend in a planar direction. The surface of the first stretchable resin 60 in the second lamination direction Z2 constitutes the back surface 2 of the stretchable device 100. The surface 61 of the first stretchable resin 60 in the first lamination direction Z1 is adhered to the detection substrate 10.
[0019] The surface of the second stretchable resin 70 in the first lamination direction Z1 constitutes the surface 1 of the stretchable device 100. The surface 71 of the second stretchable resin 70 in the second lamination direction Z2 is adhered to the detection substrate 10.
[0020] With respect to their size in the planar direction, the first stretchable resin 60 and the second stretchable resin 70 are larger than the detection substrate 10. Hereinafter, when viewed from above, the portion of the first stretchable resin 60 that does not overlap with the detection substrate 10 and is located around (outside) the detection substrate 10 will be referred to as the edge portion 62. Similarly, when viewed from above, the portion of the second stretchable resin 70 that does not overlap with the detection substrate 10 and is located around (outside) the detection substrate 10 will be referred to as the edge portion 72.
[0021] The edge 72 of the second stretchable resin 70 is extruded in the second lamination direction Z2, forming a frame that surrounds the detection substrate 10. The edge 72 of the second stretchable resin 70 is adhered to the edge 62 of the first stretchable resin 60. As a result, the first stretchable resin 60 and the second stretchable resin 70 cooperate with each other to form a housing that accommodates the detection substrate 10.
[0022] The detection substrate 10 has through holes 19 that penetrate in the stacking direction. A portion of the second stretchable resin 70 is extruded in the second stacking direction Z2 and enters the through holes 19. Hereinafter, the portion of the second stretchable resin 70 that enters the through holes 19 will be referred to as a protrusion 73. The end face of the protrusion 73 in the second stacking direction Z2 is adhered to the first stretchable resin 60.
[0023] Figure 3 is a plan view of the detection substrate laminated on the first stretchable resin of Embodiment 1, viewed from the first lamination direction. Figure 4 is an enlarged view of the first hinge portion of Embodiment 1. In Figure 4, dashed lines are drawn to make the boundaries between the body portion 11, the hinge portion 12, and the base portion 20 clearer.
[0024] As shown in Figure 3, the detection substrate 10 has a plurality of body portions 11 arranged with spacing in a first direction X and a second direction Y, a plurality of hinge portions 12 extending in a plane direction in a meandering manner, and a plurality of base portions 20 protruding in the plane direction from each body portion 11. The area surrounded by the four hinge portions 12 is a through hole 19 that penetrates the detection substrate 10 in the stacking direction.
[0025] As shown in Figure 4, the body portion 11 has an octagonal shape in plan view. Multiple body portions 11 are arranged in a first direction X and a second direction Y, and are spaced apart from each other. Note that this disclosure is not limited to an octagonal shape with respect to the shape of the body portion 11 in plan view; it may also be circular or have other polygonal shapes.
[0026] As shown in Figure 3, the hinge portion 12 extends between adjacent body portions 11. There are two types of hinge portions 12: a first hinge portion 12A that extends in the first direction X, and a second hinge portion 12B that extends in the second direction Y. In a plan view, rotating the first hinge portion 12A by 90° results in the same shape as the second hinge portion 12B. In the following description of the hinge portion 12, the first hinge portion 12A will be described as a representative example, and the description of the second hinge portion 12B will be omitted.
[0027] As shown in Figure 4, the first hinge portion 12A has four bent portions 13 and extends in the first direction X in a meandering manner. Such a meandering shape is sometimes referred to as a meander shape. Each bent portion 13 in this embodiment is arc-shaped. However, the bent portions of this disclosure may be formed in an angular shape instead of an arc shape. Also, the number of bent portions is not limited to four.
[0028] The four bent sections 13 are the first arc section 14, the second arc section 15, the third arc section 16, and the fourth arc section 17, which are arranged in order in the first direction X. The first arc section 14 and the fourth arc section 17 are quarter-circular and bent at 90 degrees. The second arc section 15 and the third arc section 16 are semi-circular and bent at 180 degrees.
[0029] Figure 5 is an enlarged view of the first hinge portion of Embodiment 1 when it is extended in the first direction. As shown in Figure 5, when a tensile load in the first direction X (see arrow F in Figure 5) acts on the first hinge portion 12A, the first arc portion 14, the second arc portion 15, the third arc portion 16, and the fourth arc portion 17 deform so that their curvature decreases. As a result, the distance from one end to the other of the first hinge portion 12A increases, and the body portions 11 separate from each other.
[0030] Furthermore, although not specifically shown, when a compressive load in the first direction X acts on the first hinge portion 12A, the first arc portion 14, the second arc portion 15, the third arc portion 16, and the fourth arc portion 17 deform so that their curvature increases. As a result, the distance from one end to the other of the first hinge portion 12A decreases, and the body portions 11 come closer together.
[0031] As shown in Figure 4, the base portion 20 has two types: a first base portion 21 that protrudes from the body portion 11 in a first direction X, and a second base portion 22 that protrudes from the body portion 11 in a second direction Y. In this embodiment, two first base portions 21 and two second base portions 22 are provided for one body portion 11. Of the two first base portions 21, one protrudes from the body portion 11 in one direction of the first direction X, and the other protrudes in the other direction of the first direction X. Of the two second base portions 22, one protrudes from the body portion 11 in one direction of the second direction Y, and the other protrudes in the other direction of the second direction Y. Further details of the base portion 20 will be described later.
[0032] As shown in Figure 2, the detection substrate 10 has a resin substrate 50 and an array layer 51. The resin substrate 50 is a substrate for manufacturing the array layer 51 and has elasticity, flexibility, and insulation properties. The resin substrate 50 is manufactured from a resin material such as polyimide.
[0033] The array layer 51 is provided on the surface of the resin substrate 50 in the first lamination direction Z1. The array layer 51 has a plurality of insulating layers (see insulating layers 52, 53, 54, and 55 in Figure 8) that are laminated in the lamination direction, and an electrical circuit whose insulation from the outside is ensured by the plurality of insulating layers. In addition, the detection region 5 of the array layer 51 includes a strain detection circuit. On the other hand, as shown in Figure 1, the non-detection region 6 of the array layer 51 includes a connection part 101, a first potential line selection circuit 104, a second potential line selection circuit 105, a first detection line selection circuit 108, and a second detection line selection circuit 109.
[0034] The strain detection circuit has strain gauges 30 provided on the array layer 51 that constitutes the base 20 (see Figure 7). The strain gauges 30 detect the amount of strain generated in the base 20. One strain detection circuit is provided for each array layer 51 that constitutes each body part 11. The basic configuration of one strain detection circuit will be described below.
[0035] Figure 6 is a circuit diagram of the strain detection circuit of Embodiment 1. The strain detection circuit includes a strain gauge 30, a first resistance section 41, a second resistance section 42, a third resistance section 43, a first potential line 44, a second potential line 45, a first detection line 48, and a second detection line 49.
[0036] The strain gauge 30 and the first resistance section 41 are connected in series. The second resistance section 42 and the third resistance section 43 are connected in series. The wiring including the strain gauge 30 and the first resistance section 41, and the wiring including the second resistance section 42 and the third resistance section 43 are connected in parallel to form a bridge circuit (Wheatstone bridge circuit).
[0037] One end of the first potential line 44 is connected to the first connection point P1 between the strain gauge 30 and the second resistance section 42. The other end of the first potential line 44 is connected to the first potential line selection circuit 104 (see Figure 1). One end of the second potential line 45 is connected to the third connection point P3 between the first resistance section 41 and the third resistance section 43. The other end of the second potential line 45 is connected to the second potential line selection circuit 105 (see Figure 1).
[0038] One end of the first detection wire 48 is connected to the second connection point P2 between the strain gauge 30 and the first resistance section 41. The other end of the first detection wire 48 is connected to the first detection wire selection circuit 108. One end of the second detection wire 49 is connected to the fourth connection point P4 between the second resistance section 42 and the third resistance section 43. The other end of the second detection wire 49 is connected to the second detection wire selection circuit 109 (see Figure 1).
[0039] As shown in Figure 1, the connection portion 101 is for connecting to a drive IC (Integrated Circuit) located outside the stretchable device 100. The drive IC may be mounted as a COF (Chip On Film) on a flexible printed circuit board or rigid circuit board (not shown) connected to the connection portion 101.
[0040] The first potential line selection circuit 104 is a switch circuit that sequentially or simultaneously selects a plurality of first potential lines 44. The first potential line selection circuit 104 connects the first potential line 44 to the driving IC based on a selection signal supplied from the driving IC. As a result, a predetermined first potential V1 (see FIG. 6) is applied to the first potential line 44.
[0041] The second potential line selection circuit 105 is a switch circuit that sequentially or simultaneously selects a plurality of second potential lines 45. The second potential line selection circuit 105 connects the second potential line 45 to the driving IC based on a selection signal supplied from the driving IC. As a result, a predetermined second potential V2 (see FIG. 6) is applied to the second potential line 45.
[0042] The first detection line selection circuit 108 is a switch circuit that sequentially or simultaneously selects a plurality of first detection lines 48. The first detection line selection circuit 108 connects the selected first detection line 48 to the driving IC based on a selection signal supplied from the driving IC. As a result, the potential V3 (see FIG. 6) at the second connection point P2 is sent to the driving IC.
[0043] The second detection line selection circuit 109 is a switch circuit that sequentially or simultaneously selects a plurality of second detection lines 49. The second detection line selection circuit 109 connects the selected second detection line 49 to the driving IC based on a selection signal supplied from the driving IC. As a result, the potential V4 at the fourth connection point P4 is sent to the driving IC.
[0044] Next, a detection method by the strain detection circuit will be described. Let the variable resistance value of the strain gauge 30 when the base 20 is not deformed be Rg. Also, the first resistance value R1 of the first resistor 41, the second resistance value R of the second resistor 42, and the third resistance value R3 of the third resistor 43 are each the same as the variable resistance value Rg (Rg = R1 = R2 = R3). Further, the first resistor 41, the second resistor 42, and the third resistor 43 are provided in the array layer 51 that constitutes the body portion 11. Therefore, even when a load is input to the stretchable device 100, the first resistor 41, the second resistor 42, and the third resistor 43 do not change, and the change amount of the resistance value is zero.
[0045] When detecting the amount of strain, a detection signal which is a predetermined first potential V1 is supplied to the first potential line 44. Also, a second potential V2 which is lower than the first potential V1 is supplied to the second potential line 45 (V2 > V1). The second potential V2 in the present embodiment is 0 V. Therefore, the potential of the first connection point P1 becomes the first potential V1.
[0046] When the base portion 20 is not deformed, the resistance value of the strain gauge 30 remains the variable resistance value Rg. And the variable resistance value Rg of the strain gauge 30, the first resistance value R1 of the first resistance portion 41, the second resistance value R2 of the second resistance portion 42, and the third resistance value R3 of the third resistance portion 43 are equal to each other. Therefore, the potential V3 of the second connection point P2 read by the first detection line 48 and the potential V4 of the fourth connection point P4 read by the second detection line 49 are equal.
[0047] On the other hand, when the base portion 20 is deformed (strain occurs), the variable resistance value Rg of the strain gauge 30 changes. As a result, the potential V3 of the second connection point P2 changes. And a potential difference occurs between the second connection point P2 and the fourth connection point P4. From the above, by detecting the potential V3 and the potential V4, the change amount of the resistance value of the strain gauge 30 is detected. Also, based on the detected change amount of the resistance value of the strain gauge 30, the amount of strain (load input to the base portion 20) generated in the base portion 20 is calculated.
[0048] Next, the layout of the strain detection circuit of Embodiment 1 will be described. As shown in FIG. 3, the strain gauge 30 has a first strain gauge 31 disposed on the first base portion 21 and a second strain gauge 32 disposed on the second base portion 22. The first strain gauge 31 is for detecting a load in the first direction X. The second strain gauge 32 is for detecting a load in the second direction Y. Hereinafter, the strain detection circuit including the first strain gauge 31 will be described, and the description of the strain detection circuit including the second strain gauge 32 will be omitted.
[0049] Figure 7 is a plan view showing the layout of the strain detection circuit of Embodiment 1 when viewed from the first stacking direction. Figure 8 is a cross-sectional view taken along the line VIII-VIII in Figure 7. In Figure 8, hatching is applied to each layer to make it easier to distinguish each wire of the strain detection circuit. The hatching applied in Figure 8 is common to each insulating layer to which the wires are stacked. In other words, for example, the wires stacked on the first insulating layer have the same hatching. Also, the circles in Figure 7 indicate connections with wires of other layers.
[0050] In the following description, the four sides of the body portion 11 that are not connected to the base portion 20 will be referred to as the first side 201, second side 202, third side 203, and fourth side 204 in a counterclockwise direction in a plan view (Figure 8). The orientation of each component may be described using these four sides.
[0051] The first resistor 41, third resistor 43, and second resistor 42 are arranged in the order of the third side 203 of the body portion 11 toward the first side 201. The first resistor 41, second resistor 42, and third resistor 43 have the same shape in plan view. Therefore, in describing the shape of the resistors, the first resistor 41 will be described as a representative example, and the descriptions of the second resistor 42 and third resistor 43 will be omitted.
[0052] The first resistance section 41 has a plurality of straight wirings 210 and a plurality of crossing wirings 220, and is meandering in plan view. The straight wirings 210 extend linearly along the planar direction and are parallel to the first side 201 and the third side 203. The crossing wirings 220 connect the ends of the straight wirings 210. The crossing wirings 220 are also parallel to the second side 202 and the fourth side 204.
[0053] The strain detection circuit of this embodiment has a plurality of connecting wires that connect the resistive parts, including the strain gauge 30. The plurality of connecting wires are a first connecting wire 231, a second connecting wire 232, and a third connecting wire 233. The first connecting wire 231, the second connecting wire 232, and the third connecting wire 233 each extend in a direction parallel to the first side 201.
[0054] The first connection wire 231 connects the first connection point P1 to one end 42a of the second resistor 42. The second connection wire 232 connects the other end 42b of the second resistor 42 to the fourth connection point P4 (one end 43a of the third resistor 43). The third connection wire 233 connects the other end 43b of the third resistor 43 to the third connection point P3 (one end 41a of the first resistor 41).
[0055] The first strain gauge 31 is positioned on the first base 21. The first connecting wiring 231 has an extension wiring 35 that extends from the first connection point P1 to the first base 21. One end 31a of the first strain gauge 31 is connected to the extension wiring 35.
[0056] A first potential line 44 is connected to the first connection point P1. The first potential line 44 extends along the fourth side 204 of the body portion 11. The first potential line 44 extends across multiple body portions 11, multiple second hinge portions 12B, and multiple second base portions 22, and is drawn out from the body portion 11 in one direction of the second direction Y and connected to the first potential line selection circuit 104.
[0057] Furthermore, the other end 31b of the first strain gauge is connected to the strain wiring 36 and extends to the second connection point P2 (the other end 41b of the first resistance section 41).
[0058] The first detection line 48 is connected to the second connection point P2. The first detection line 48 extends along the fourth side 204 of the body portion. The first detection line 48 extends across multiple body portions, multiple first hinge portions 12A, and multiple first base portions 21, so that the first detection line 48 is drawn out from the body portion 11 in one direction X and connected to the first detection line selection circuit 108.
[0059] A second potential line 45 is connected to the third connection point P3. The second potential line 45 extends along the second side 202. The second potential line 45 extends across multiple body parts 11, multiple second hinge parts 12B, and multiple second base parts 22, and is drawn out from the body part 11 to the other side of the second direction Y and connected to the second potential line selection circuit 105.
[0060] The second connection wiring 232 extends further from the fourth connection point P4 toward the second side 202, forming the second detection line 49. The second detection line 49 extends along the second side 202. The second detection line 49 extends across multiple body parts 11, multiple first hinge parts 12A, and multiple first base parts 21, and is drawn out from the body parts 11 toward the other side of the first direction X and connected to the second detection line selection circuit 109.
[0061] In addition, the base 20 and the body 11 are positioned next to each other, and the temperatures of the base 20 and the body 11 are approximately the same. In other words, the strain gauge 30 positioned on the base 20 and the first resistance section 41, second resistance section 42, and third resistance section 43 positioned on the body 11 also have approximately the same temperature.
[0062] Furthermore, as shown in Figure 8, the strain gauge 30, the first resistance section 41, the second resistance section 42, and the third resistance section 43 are arranged on the same layer of the array layer 51. As a result, there is almost no temperature difference between the strain gauge 30, the first resistance section 41, the second resistance section 42, and the third resistance section 43.
[0063] According to this, for example, if the variable resistance value Rg is also large because the temperature of the strain gauge 30 is high, the temperatures of the first resistance section 41, the second resistance section 42, and the third resistance section 43 are also high. In other words, the values of the first resistance value R1, the second resistance value R2, and the third resistance value R3 are also large. Therefore, it is avoided that the variable resistance value Rg becomes relatively large (or small) compared to the first resistance value R1, the second resistance value R2, and the third resistance value R3. As a result, the change in resistance value (noise) due to the temperature difference of the strain gauge 30 is not detected. Thus, the amount of strain in the base 20 can be detected with high accuracy.
[0064] Next, the details of the base 20 and strain gauge 30 of Embodiment 1 will be described. Note that when the first base 21 is rotated 90° in a plan view, it becomes identical in shape to the second base 22. In the following description of the base 20, the first base 21 and the first strain gauge 31 will be described as representative examples, and the description of the second base and the second strain gauge will be omitted. Also, in the following description of the base 20, the direction in which the first base 21 protrudes from the body portion 11 (first direction X) will be referred to as the length direction. Also, the direction perpendicular to the length direction when viewed from the stacking direction (second direction Y) will be referred to as the width direction.
[0065] Figure 9 is an enlarged view of the first base of Embodiment 1. The first side surface 24 and the second side surface 25 of the first base 21 extend linearly in the longitudinal direction (first direction X). Therefore, the first base 21 is formed in a rectangular shape in plan view. One end of the first base 21 in the longitudinal direction is connected to the body portion 11, and the other end in the longitudinal direction is connected to the first hinge portion 12A.
[0066] The first strain gauge 31 is located only on the first base portion 21. In other words, the first strain gauge 31 is not located on the first hinge portion 12A. Therefore, the first strain gauge 31 detects the strain generated in the first base portion 21, but does not detect the strain generated in the first hinge portion 12A. Furthermore, the amount of strain generated in the first base portion 21 is as follows.
[0067] Figure 10 is a cross-sectional view taken along the line X-X in Figure 9. Figure 11 is a cross-sectional view taken along the line XI-XI in Figure 9. Note that the first strain gauge 31 inside the first base portion 21 is not shown in Figures 10 and 11. The length of the first base portion 21 is L. The width of the first base portion 21 is W. The length L is larger than the width W. Also, as shown in Figures 10 and 11, the size H in the stacking direction of the detection substrate 10 is constant at each point on the detection substrate 10. Therefore, the cross-sectional area S1 (see Figure 10) when the first base portion 21 is cut along the length is larger than the cross-sectional area S2 (see Figure 11) when the first base portion 21 is cut along the width.
[0068] Here, regarding the stress acting on an object, the larger the cross-sectional area of the object facing the applied load, the smaller the stress acting per unit cross-sectional area of the object. Also, the relationship between stress per unit area and strain is proportional. From the above, the amount of strain generated when a load in the width direction (see arrow A2 in Figure 10) is applied to the first base 21 is less than the amount of strain generated when a load in the length direction (see arrow A1 in Figure 10) is applied. Therefore, even when a load in the second direction Y (tensile load, compressive load) is applied to the first base 21, the load component in the second direction Y detected by the first strain gauge 31 is also small, improving the detection accuracy of the first strain gauge 31.
[0069] Furthermore, it is preferable that the length L of the base 20 is 10 times or more than the width W. In this case, the amount of change in the length of the base 20 when a load is applied in the length direction will be 10 times the amount of change in the width direction of the base 20 when a load of the same magnitude is applied in the width direction, and the detection accuracy of the strain gauge 30 will be significantly improved.
[0070] In addition to tensile and compressive loads, bending loads may also act on the first base portion 21 (see arrow A3 in Figure 9). Bending loads occur when one load in the second direction Y acts on one end of the first base portion 21 in the longitudinal direction, and the other load in the second direction Y acts on the other end of the first base portion 21 in the longitudinal direction. When these bending loads are applied, a lot of strain occurs near the first side surface 24 and the second side surface 25 of the first base portion 21 (see the area enclosed by the dashed line D in Figure 9). On the other hand, the amount of strain that occurs in the central part of the first base portion 21 in the width direction is small.
[0071] As shown in Figure 9, the imaginary line K extends in the longitudinal direction from the center of the widthwise portion of the first base 21. The first strain gauge 31 extends linearly in the longitudinal direction (first direction X). The first strain gauge 31 overlaps with the imaginary line K and is positioned in the center of the widthwise portion of the first base 21. Therefore, even if a bending load is applied to the first base 21, the amount of strain detected by the first strain gauge 31 is small. In other words, since the first strain gauge 31 is positioned in a location where it is difficult to detect the bending load, the detection accuracy is improved.
[0072] Furthermore, the first strain gauge 31 is symmetrical with respect to the imaginary line K. When a bending load is applied to the first base 21, the stresses generated near the first side surface 24 and the second side surface 25 (see the area enclosed by the dashed line D in Figure 9) are one compressive stress and the other tensile stress. If the first strain gauge 31 is positioned near the first side surface 24 and the second side surface 25, it will detect both the stress acting near the first side surface 24 (e.g., compressive stress) and the stress acting near the second side surface 25 (e.g., tensile stress). As a result, both the increase in resistance due to tensile stress and the decrease in resistance due to compressive stress occur in the first strain gauge 31 and cancel each other out. Therefore, even if the first strain gauge 31 detects strain due to a bending load, the noise component (bending load component) included in the detected current value is small, improving detection accuracy.
[0073] Embodiment 1 has been described above. Next, a modified example in which a part of Embodiment 1 has been altered will be described.
[0074] (Modification 1) Figure 12 is an enlarged view of the first base of Modification 1. As shown in Figure 12, the first base 21A (base 20A) of Modification 1 differs from Embodiment 1 in that the widthwise size W1 of the first side surface 24 and the second side surface 25 decreases as it approaches the first hinge portion 12A (hinge portion 12). In other words, the first base 21A (base 20A) is trapezoidal in plan view.
[0075] Therefore, the width of the first base portion 21A is largest in the portion closer to the body portion 11, with a maximum width of W2. Also, even in the first base portion 21A of the modified example 1, the lengthwise size L (see Figure 10) is larger than the maximum width W2. In other words, the first base portion 21A (base portion 20A) is formed to be larger in the lengthwise direction than in the widthwise direction, just like in Embodiment 1.
[0076] From the above, even with the first base portion 21A of the modified example 1, the amount of strain generated when a load in the width direction is applied is small, just like in the embodiment 1. In other words, the load component in the second direction Y detected by the first strain gauge 31 is small, and the detection accuracy of the first strain gauge 31 is improved.
[0077] Although Modification 1 has been described above, the base of the present disclosure only needs to have a length greater than its width. Therefore, the shape of the base 20 when viewed from above is not limited to the rectangle described in Embodiment 1 or the trapezoid described in Modification 1.
[0078] (Modification 2) Figure 13 is an enlarged view of the first base of Modification 2. In Figure 13, the strain gauge is shown with a solid line for easier visibility. The first strain gauge 31B (strain gauge 30B) of Modification 2 differs from that of Embodiment 1 in that it meanders in the width direction. More specifically, the first strain gauge 31B comprises a plurality of first wirings 330 extending in the length direction and a plurality of second wirings 340 extending in the width direction and connecting the first wirings 330 to each other. Even with such a first strain gauge 31B, the amount of strain generated in the first base 21 can be detected in the same way as in Embodiment 1.
[0079] Furthermore, the first strain gauge 31B is symmetrical with respect to the imaginary line K. Therefore, when a bending load is applied to the first base 21, the first strain gauge 31B detects both the stress acting near the first side surface 24 (see the area enclosed by the dashed line D in Figure 9) and the stress acting near the second side surface 25 (see the area enclosed by the dashed line D in Figure 9). As a result, even if the first strain gauge 31B detects strain due to the bending load, the noise component (bending load component) included in the detected current value is small, improving detection accuracy.
[0080] Although the second modification has been described above, the strain gauge of this disclosure only needs to have the base portion 20. Therefore, the strain gauge of this disclosure does not need to be symmetrical with respect to the imaginary line K.
[0081] 5 Detection area 6 Non-detection area 10 Detection substrate 11 Body part 12 Hinge part 13 Bending part 19 Through hole 20, 20A Base part 21, 21A First base part 22 Second base part 24 First side part 25 Second side part 30, 30B Strain gauge 31, 31B First strain gauge 32 Second strain gauge 41 First resistance part 42 Second resistance part 43 Third resistance part 44 First potential line 45 Second potential line 48 First detection line 49 Second detection line 50 Resin substrate 51 Array layer 60 First stretchable resin 70 Second stretchable resin 100 Stretchable device 231 First connection wiring 232 Second connection wiring 233 Third connection wiring
Claims
1. A stretchable device comprising: a detection substrate; and two stretchable resins sandwiching the detection substrate, wherein the direction in which the two stretchable resins are arranged relative to the detection substrate is defined as the stacking direction, the direction perpendicular to the stacking direction is defined as the first direction, and the direction perpendicular to the stacking direction and intersecting the first direction is defined as the second direction, the detection substrate comprising: a plurality of body portions arranged in the first and second directions; a plurality of meander-shaped hinge portions extending in the first or second direction; and a plurality of base portions protruding from the body portions in the first or second direction and connecting the hinge portions, wherein the direction in which the base portions protrude from the body portions is defined as the length direction, the direction perpendicular to the length direction when viewed from the stacking direction is defined as the width direction, the base portions are larger in the length direction than in the width direction, strain gauges for detecting strain are provided on the base portions, and the strain gauges are not provided on the hinge portions.
2. The stretchable device according to claim 1, wherein the strain gauge is formed symmetrically with respect to an imaginary line passing through the central part of the base in the width direction in the length direction.
3. The stretchable device according to claim 1 or claim 2, wherein the base portion is formed in a rectangular shape when viewed from the stacking direction.
4. The stretchable device according to any one of claims 1 to 3, wherein the strain gauge comprises a first strain gauge for detecting the amount of strain in the first direction and a second strain gauge for detecting the amount of strain in the second direction.