Pressure sensor

Abstract

This pressure sensor comprises: a plurality of detection electrodes that are disposed on a substrate; a common electrode that is disposed between adjacent detection electrodes among the plurality of detection electrodes; a facing electrode that faces the plurality of detection electrodes and the common electrode in a direction perpendicular to the substrate, with space therebetween; and an elastic body that is provided between the facing electrode, and the plurality of detection electrodes and the common electrode, in the direction perpendicular to the substrate. The elastic body includes a plurality of conductive particles and a plurality of insulating particles, and has a plurality of protrusions formed on the surface thereof facing the plurality of detection electrodes and the common electrode.

Description

Pressure Sensor

[0001] The present invention relates to a pressure sensor.

[0002] Patent Document 1 discloses a pressure sensor that detects a pressing force (referred to as a load sensor in Patent Document 1). The pressure sensor of Patent Document 1 includes two cell electrodes arranged opposite to each other for sensing an external load state, and a pressure-sensitive resistive layer provided on at least one of the cell electrodes. The pressure-sensitive resistive layer has a protruding portion that protrudes toward the other cell electrode.

[0003] Japanese Unexamined Patent Application Publication No. 2006-317340

[0004] In a configuration including a pressure-sensitive resistive layer having protruding portions, repeated reproducibility decreases due to plastic deformation of the pressure-sensitive resistive layer, which may increase variation in sensor output in response to repeated loads. Alternatively, when the protruding portions are arranged randomly, variation in sensor output may occur depending on the position where the load is applied. For this reason, there is a demand for improving the detection accuracy of the pressure sensor.

[0005] The present disclosure aims to provide a pressure sensor capable of improving detection accuracy.

[0006] The pressure sensor according to one aspect of the present disclosure includes: a plurality of detection electrodes arranged on a substrate; a common electrode arranged between adjacent ones of the plurality of detection electrodes; a counter electrode facing the plurality of detection electrodes and the common electrode with a gap therebetween in a direction perpendicular to the substrate; and an elastic body provided between the plurality of detection electrodes, the common electrode, and the counter electrode in the direction perpendicular to the substrate. The elastic body includes a plurality of conductive particles and a plurality of insulating particles, and has a plurality of convex portions formed on a surface facing the plurality of detection electrodes and the common electrode.

[0007] Figure 1 is a schematic cross-sectional view of a pressure sensor according to an embodiment. Figure 2 is a schematic cross-sectional view of a pressure sensor when a pressing force is applied from the counter electrode side. Figure 3 is a diagram showing an example of the circuit configuration of the pressure sensor. Figure 4 is a timing chart showing an example of electrical control of the pressure sensor. Figure 5 is a plan view illustrating the shape of the electrodes within the detection area of ​​the pressure sensor. Figure 6 is a plan view showing an example of a wiring layer provided with power supply lines and signal lines. Figure 7 is a plan view showing an example of contact arrangement connecting the electrode layer shown in Figure 5 and the wiring layer shown in Figure 6. Figure 8 is a cross-sectional view taken along VIII-VIII' of Figure 5. Figure 9 is a graph showing the relationship between pressing force and sensor output for the pressure sensors according to the embodiment and comparative example. Figure 10 is a graph showing the repeatability of the pressure sensors according to the embodiment and comparative example. Figure 11 is a graph showing the relationship between the amount of insulating particles added and hysteresis for the pressure sensor according to the embodiment. Figure 12 is an explanatory diagram for explaining the pressure distribution when a constant pressing force is applied to a predetermined area of ​​the pressure sensor according to the embodiment. Figure 13 is an explanatory diagram illustrating the pressure distribution when a constant pressing force is applied to a predetermined area of ​​a pressure sensor according to a comparative example.

[0008] The embodiments for implementing this disclosure will be described in detail with reference to the drawings. This disclosure is not limited to the embodiments described below. 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. In addition, the components described below can be combined as appropriate. The disclosure is merely an example, and any modifications that a person skilled in the art can easily conceive while maintaining the spirit of this disclosure are naturally included within the scope of this disclosure. Furthermore, 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 this disclosure. Furthermore, in this disclosure and in each drawing, elements 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.

[0009] In this disclosure, 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.

[0010] (Embodiment) Figure 1 is a schematic cross-sectional view showing a pressure sensor according to an embodiment. The pressure sensor 1 is a so-called device substrate in which a plurality of components are stacked on a substrate 10. The plurality of components include a field-effect transistor (FET) that utilizes semiconductors. As shown in Figure 1, on the substrate 10, an insulating film 11, a first wiring layer 12, a first insulating layer 13, a semiconductor layer 14, a second wiring layer 15, a second insulating layer 16, a third wiring layer 17, a third insulating layer 18, a fourth wiring layer 19, etc. are stacked in order from the side closer to the substrate 10.

[0011] The first wiring layer 12, the second wiring layer 15, the third wiring layer 17, and the fourth wiring layer 19 are formed using conductive materials such as metal electrodes. The first insulating layer 13, the second insulating layer 16, and the third insulating layer 18 are formed using insulators including, for example, silicon oxide or silicon nitride. The semiconductor layer 14 is a semiconductor that functions as the channel of the FET. If the FET is a MOSFET (Metal Oxide Semiconductor FET), the semiconductor layer 14 is, for example, silicon (Si). Through this layered structure, FETs such as the first element 61 shown in Figure 1, and the second element 62, third element 63, and fourth element 64 shown in Figure 3 (described later) are formed on the substrate 10.

[0012] In the following explanation, the first direction Dx is a direction in a plane parallel to the surface of the substrate 10. The second direction Dy is a direction in a plane parallel to the surface of the substrate 10 and is perpendicular to the first direction Dx. The second direction Dy may intersect the first direction Dx without being perpendicular to it. The third direction Dz is a direction perpendicular to both the first direction Dx and the second direction Dy. The third direction Dz is the normal direction to the surface of the substrate 10. Furthermore, "plan view" refers to the positional relationship when viewed from a direction perpendicular to the surface of the substrate 10.

[0013] Above the fourth wiring layer 19, a coating layer HRC, an electrode layer, and the like are further laminated. The coating layer HRC is laminated between the fourth wiring layer 19 and the electrode layer to insulate the fourth wiring layer 19 from the electrode layer. The coating layer HRC is also an organic layer. As a result, when a pressing force is applied from the opposing electrode 30 side, the coating layer HRC suppresses and protects the components below the coating layer HRC from being subjected to the pressing force.

[0014] The pressure sensor 1 includes a detection electrode 20, a counter electrode 30, a common electrode 40, and an elastic body 50. The detection electrode 20 and the common electrode 40 are arranged along the substrate 10. Specifically, the detection electrode 20 and the common electrode 40 are provided on the coating portion HRC. The detection electrode 20 and the common electrode 40 are spaced apart. Although Figure 1 shows one detection electrode 20, multiple detection electrodes 20 are arranged in a matrix (see Figure 5). The plan view configuration of the detection electrode 20 and the common electrode 40 will be described later in Figure 5 and subsequent figures.

[0015] The counter electrode 30 faces the plurality of detection electrodes 20 and the common electrode 40 with a distance between them in the third direction Dz. The counter electrode 30 is a conductive sheet, but it is sufficient if the counter electrode 30 is a sheet-like material in which at least the side facing the elastic body 50 is conductive. More specifically, the counter electrode 30 can be made of, for example, ITO (Indium Tin Oxide). The side of the counter electrode 30 opposite the elastic body 50 may be conductive, or it may be coated with an insulator such as a synthetic resin.

[0016] The elastic body 50 is provided in the third direction Dz between the plurality of detection electrodes 20 and the common electrode 40 and the counter electrode 30. The elastic body 50 is a thin film elastic member. The elastic body 50 contains a plurality of conductive particles 51 and a plurality of insulating particles 52. The elastic body 50 containing the conductive particles 51 exhibits pressure-sensitive conductivity.

[0017] The elastic body 50 has a plurality of protrusions 50t provided on its lower surface (the surface facing the plurality of detection electrodes 20 and the common electrode 40). The plurality of protrusions 50t are provided along the substrate 10 with a predetermined arrangement pitch. In addition, recesses 50u are formed between adjacent protrusions 50t. The protrusions 50t and recesses 50u are arranged alternately to form an uneven pattern.

[0018] Here, the arrangement pitch of the multiple protrusions 50t is the distance between the tops (the parts closest to the substrate 10) of adjacent protrusions 50t in a direction parallel to the surface of the substrate 10. The height H1 of the multiple protrusions 50t is the distance in the third direction Dz between the bottom of the recess 50u (the part furthest from the substrate 10) and the top of the protrusion 50t in adjacent protrusions 50t and recesses 50u.

[0019] The particle sizes of the multiple insulating particles 52 contained in the elastic body 50 are sufficiently smaller than the height H1 of the multiple protrusions 50t and the arrangement pitch of the multiple protrusions 50t. The particle sizes of the multiple insulating particles 52 are approximately 1 / 20 to 1 / 10 of the height H1 of the multiple protrusions 50t, for example, 1 μm or less.

[0020] Figure 2 is a schematic cross-sectional view showing a pressure sensor when a pressing force is applied from the counter electrode side. Note that the pressure sensor 1 shown in Figure 1 represents the state in which no pressing force is applied compared to Figure 2. As shown in Figures 1 and 2, when the pressure sensor 1 receives a pressing force in the third direction Dz from the counter electrode 30 side, the elastic body 50 is compressed in the third direction Dz. In other words, a pressing force is applied to the elastic body 50 that brings the detection electrode 20 and the counter electrode 30 closer together. As a result, some of the multiple conductive particles 51 contained in the elastic body 50 become electrically conductive between the common electrode 40 and the counter electrode 30, and between the detection electrode 20 and the counter electrode 30. This forms a conductive path that electrically connects the detection electrode 20, the counter electrode 30, and the common electrode 40.

[0021] In Figure 2, conductive particles 51a connect the common electrode 40 and the counter electrode 30, and conductive particles 51b connect the detection electrode 20 and the counter electrode 30. Conductive particles 51a and 51b are part of a plurality of conductive particles 51. When the pressing force in the third direction Dz from the counter electrode 30 side is removed, the state returns from the state shown in Figure 2 to the state shown in Figure 1, and the conductive path is lost. That is, there is no electrical conductivity between the common electrode 40 and the counter electrode 30, and between the detection electrode 20 and the counter electrode 30.

[0022] In this way, the pressure sensor 1 can detect the pressing force from the counter electrode 30 side depending on whether or not a conductive path is established. Furthermore, the common electrode 40, counter electrode 30, detection electrode 20, and elastic body 50, which form a conductive path in response to the pressing force from the counter electrode 30 side, function as a switch 80 that switches between open and closed in response to the pressing force. Note that the counter electrode 30 is in a floating state when no pressing force is applied and it is not connected to the detection electrode 20 and common electrode 40.

[0023] More specifically, the elastic body 50 exhibits anisotropic pressure-sensitive conductivity, establishing conductivity between the common electrode 40 and the counter electrode 30, and between the detection electrode 20 and the counter electrode 30, in response to a pressing force in the direction along the third direction Dz, while preventing conductivity in other directions (such as the direction along the substrate 10). The conductive particles 51 are provided within the elastic body 50 to achieve this pressure-sensitive conductivity.

[0024] In this embodiment, since multiple protrusions 50t are provided on the lower surface of the elastic body 50, the contact area between the elastic body 50 and the detection electrode 20, and the contact area between the elastic body 50 and the common electrode 40, change according to the pressing force. As a result, the pressure sensor 1 can have a larger pressure sensitivity range compared to a configuration without multiple protrusions 50t.

[0025] Furthermore, since the elastic body 50 contains multiple insulating particles 52, the elastic modulus of the elastic body 50 can be appropriately adjusted. As a result, the pressure sensor 1 can suppress plastic deformation of the elastic body 50, thereby suppressing variations in the sensor output when repeated pressing forces are applied. In addition, the pressure sensor 1 can improve the elastic modulus of the elastic body 50, thereby suppressing hysteresis in the sensor output. The sensor output when repeated pressing forces are applied, and the hysteresis of the sensor output, will be described later in Figures 9 and 10.

[0026] The elastic body 50 of this embodiment can be formed by, for example, a printing method such as screen printing, a coating method using a bar coater, or a molding method using a mold. When forming the elastic body 50, for example, a carbon ink containing insulating particles 52 is used. Since the elastic body 50 contains a plurality of insulating particles 52, the thixotropy of the ink used when manufacturing the elastic body 50 can be appropriately adjusted. As a result, the plurality of protrusions 50t of the elastic body 50 can be formed in a shape that well reflects the mesh pattern of the screen mask used during printing, the uneven shape of the bar coater, or the uneven shape of the mold. As a result, the variation in the height H1 and arrangement pitch of the plurality of protrusions 50t of the elastic body 50 can be suppressed compared to the case where the plurality of insulating particles 52 are not included.

[0027] Therefore, since the pressure sensor 1 has small variations in the height H1 and arrangement pitch of the multiple protrusions 50t, in-plane variations in the sensor output can be suppressed. In other words, in-plane variations in the contact area between the elastic body 50 and the detection electrode 20, and between the elastic body 50 and the common electrode 40, when a predetermined pressing force is applied can be suppressed.

[0028] In this embodiment, the sheet resistance of the common electrode 40 is smaller than that of the counter electrode 30. Specifically, the electrode layers constituting the detection electrode 20 and the common electrode 40 are made of a highly conductive metal such as silver (Ag). The specific composition of the common electrode 40 is not limited to this, but it is desirable that the common electrode 40 be made of a material that is as conductive as possible and has low sheet resistance.

[0029] Figure 3 shows an example of a pressure sensor circuit configuration. The circuit shown in Figure 3 comprises an array component SC and a reset component RC.

[0030] The array component SC includes a first element 61, a second element 62, a third element 63, and the like. The first element 61, the second element 62, and the third element 63 are switching elements composed of FETs. One of the sources or drains of the first element 61 is connected to a switch 80, and the other is connected to the second element 62, the third element 63, and a capacitor 70. One of the sources or drains of the second element 62 is connected to a signal line Sig, and the other is connected to the first element 61, the third element 63, and a capacitor 70. One of the sources or drains of the third element 63 is connected to an initialization potential line Vbl, and the other is connected to the first element 61, the second element 62, and a capacitor 70.

[0031] Furthermore, the gate and back gate of the first element 61 are connected to the detection operation signal transmission line Vs. The gate and back gate of the second element 62 are connected to the scan line Gate. The gate and back gate of the third element 63 are connected to the initialization signal transmission line Vdch.

[0032] Capacitor 70 has two terminals, one of which is connected to a common potential line Vcom, and the other is connected to the first element 61, the second element 62, and the third element 63. Switch 80 is provided to switch between the source or drain of the first element 61 and the power supply line Vbias.

[0033] The reset section RC includes a fourth element 64. The fourth element 64 is a switching element composed of an FET. One of the source or drain of the fourth element 64 is connected to the signal line Sig, and the other is connected to the reset potential line VR1. In addition, the gate and back gate of the fourth element 64 are connected to the reset signal transmission line Vrst.

[0034] The array component SC is provided individually for each array capable of individually detecting pressure. The pressure sensor 1 is provided with multiple arrays Un, as illustrated in Figure 5, which will be described later. The scan line Gate is shared by multiple arrays Un aligned in the first direction Dx. The signal line Sig is shared by multiple arrays Un aligned in the second direction Dy. The detection operation signal transmission line Vs, the power supply line Vbias, the common potential line Vcom, the initialization potential line Vbl, and the initialization signal transmission line Vdch are shared by all arrays Un. The reset unit RC is shared by multiple arrays Un that share the signal line Sig. The reset potential line VR1 is shared by all reset units RC.

[0035] Figure 4 is a timing chart showing an example of electrical control of a pressure sensor. During periods other than period T1 shown in Figure 4, the third element 63 is in a state where signal transmission between source and drain is blocked (OFF). Also, during periods other than period T2, the first element 61 is in a state where signal transmission between source and drain is blocked (OFF). Also, during periods other than period T3, the second element 62 is in a state where signal transmission between source and drain is blocked (OFF). Also, during periods other than period T3, the fourth element 64 is in a state where signal transmission between source and drain is enabled (ON).

[0036] In other words, the initialization signal transmission line Vdch, detection operation signal transmission line Vs, reset signal transmission line Vrst, and scan line Gate during periods other than periods T1, T2, and T3 are set to a potential that realizes the state of the first element 61, second element 62, third element 63, and fourth element 64. The potentials of the initialization potential line Vbl, reset potential line VR1, common potential line Vcom, and power supply line Vbias are predetermined constant potentials. The constant potential C1 of the initialization potential line Vbl, the constant potential C2 of the reset potential line VR1, the constant potential C3 of the common potential line Vcom, and the constant potential C4 of the power supply line Vbias may all be different potentials, or some may be the same potential. In this embodiment, constant potentials C3 and C4 are equal.

[0037] Furthermore, multiple scan line gates are provided, corresponding to the number of arrays Un aligned in the second direction Dy. The multiple scan line gates are sequentially supplied with drive signals from a scanning circuit (not shown). The scanning circuit includes, for example, a shift register. The number of shift outputs of the shift register is the same as the number of scan line gates (n). n is a natural number greater than or equal to 2. The scanning circuit uses the shift register to sequentially shift from the first scan line gate (1) to the nth scan line gate (n) and output drive signals.

[0038] First, during period T1, the potential of the initialization signal transmission line Vdch becomes high (H). This connects the source and drain circuits of the third element 63. Consequently, the other terminal of the capacitor 70, which is connected to the other terminal of the source or drain of the third element 63, is electrically connected to the initialization potential line Vbl. By being electrically connected to the initialization potential line Vbl, the capacitor 70 releases the capacitance it held before the connection. That is, the capacitance held by the capacitor 70 becomes corresponding to the potential difference between the common potential line Vcom and the initialization potential line Vbl. This state is the reset state of the capacitor 70. As described above, the initialization signal transmission line Vdch is shared by all arrays Un, so during period T1, the capacitors 70 of all arrays Un are reset.

[0039] Next, during period T2, the potential of the detection operation signal transmission line Vs becomes high (H). This connects the source and drain circuits of the first element 61. Therefore, depending on whether the switch 80 connected to either the source or drain of the first element 61 is ON or OFF, the connection of the power supply line Vbias to one of the terminals of the capacitor 70 changes. Specifically, when the pressure sensor 1 is receiving pressure from the counter electrode 30, the power supply line Vbias is connected to one of the terminals of the capacitor 70. On the other hand, when the pressure sensor 1 is not receiving pressure from the counter electrode 30, the power supply line Vbias is not connected to one of the terminals of the capacitor 70. In this way, the capacitance stored in the capacitor 70 changes depending on whether the pressure sensor 1 is receiving pressure from the counter electrode 30 during period T2.

[0040] During period T3, the potential of the reset signal transmission line Vrst is low (L). Except for period T3 and some periods before and after period T3, the fourth element 64 is ON, so the signal line Sig and the reset potential line VR1 are connected. During the period when the fourth element 64 is ON, the potential of the signal line Sig is reset by the potential of the reset potential line VR1. The low (L) / high (H) state of the reset signal transmission line Vrst reverses before and after period T3, and as a result, the potential of the reset signal transmission line Vrst is low (L) during period T3, thus disconnecting the connection between the signal line Sig and the reset potential line VR1.

[0041] Furthermore, during period T3, the potential is controlled so that the first scan line Gate(1) to the nth scan line Gate(n) sequentially reverses between high (H) and low (L). Figure 4 shows an example in which any of the scan lines Gate(1), ..., scan line Gate(n) becomes high (H) in response to the above-mentioned drive signal. As a result, the second elements 62 of the multiple arrays Un aligned in the second direction Dy are sequentially turned ON, and the capacitor 70 is connected to the signal line Sig.

[0042] Therefore, the potential of the signal line Sig becomes a potential corresponding to the capacitance held in the capacitor 70. This allows the pressure sensor 1 connected to the signal line Sig to detect pressure. The pressure sensor 1 is a circuit that determines whether the pressure sensor 1 is receiving a pressing force from the counter electrode 30 side based on the potential of the signal line Sig.

[0043] Although not shown in the figures, the pressure sensor 1 is equipped with various circuits for performing the electrical control described with reference to Figure 4. Specifically, the pressure sensor 1 is provided with a power supply circuit that supplies potentials corresponding to high (H) / low (L) states such as the initialization signal transmission line Vdch, initialization potential line Vbl, detection operation signal transmission line Vs, and reset signal transmission line Vrst, as well as potentials corresponding to constant potentials C1, C2, C3, and C4, and a control circuit that controls the switching of high (H) / low (L) states corresponding to periods T1, T2, and T3 as described with reference to Figure 4.

[0044] Hitherto, description has been given based on the circuit configuration of FIG. 3, but the circuit configuration of the pressure sensor 1 is not limited to that shown in FIG. 3. In principle, the operation of the pressure sensor according to the present disclosure can be achieved as long as the first element 61, the second element 62, the capacitor 70, the switch 80, the connection between the sources and drains thereof, and the potential supply to the gates are provided. The third element 63 and the fourth element 64 are specific configuration examples for resetting a potential, and are not essential for pressure detection.

[0045] FIG. 5 is a plan view illustrating the shape of an electrode in a detection region of a pressure sensor. FIG. 6 is a plan view showing an example of a wiring layer provided with a power supply line and a signal line. FIG. 7 is a plan view showing an arrangement example of contacts connecting the electrode layer shown in FIG. 5 and the wiring layer shown in FIG. 6. FIG. 8 is a sectional view taken along line VIII-VIII' in FIG. 5.

[0046] As shown in FIG. 5, the detection electrodes 20 include an array electrode 20A, an array electrode 20B, an array electrode 20C, and an array electrode 20D. In a plan view, the detection electrodes 20 are arranged in a matrix. In the following description, when it is not necessary to distinguish between the array electrodes 20A, 20B, 20C, and 20D, they are simply referred to as the detection electrode 20.

[0047] In the pressure sensor 1, the array electrodes 20A, 20B, 20C, 20D and the common electrode 40 are provided in an array Un. Although reference numerals are omitted, FIG. 5 exemplifies a configuration in which 3×3 arrays Un arranged three in the first direction Dx and three in the second direction Dy are arranged. More arrays Un or fewer arrays Un may be arranged in the detection area SA. As described above, in the pressure sensor 1, a plurality of arrays Un are arranged in a matrix in the detection area SA in plan view.

[0048] In the array Un, the array electrode 20A and the array electrode 20B are adjacent to each other in the first direction Dx. The array electrode 20C and the array electrode 20D are adjacent to each other in the first direction Dx. The array electrode 20A and the array electrode 20C are adjacent to each other in the second direction Dy. The array electrode 20B and the array electrode 20D are adjacent to each other in the second direction Dy. The common electrode 40 is not disposed between the array electrode 20A and the array electrode 20B that are adjacent in the first direction Dx in the array Un, nor between the array electrode 20C and the array electrode 20D that are adjacent in the first direction Dx. The common electrode 40 is disposed between the array electrode 20A and the array electrode 20C that are adjacent in the second direction Dy in the array Un, and between the array electrode 20B and the array electrode 20D that are adjacent in the second direction Dy.

[0049] As described above, the common electrode 40 is continuous in a grid shape that partitions the detection electrodes 20 adjacent to each other in at least one direction (for example, the second direction Dy) among the plurality of detection electrodes 20 adjacent to each other in the array Un. The positional relationship between the plurality of detection electrodes 20 and the common electrode 40 in the array Un is not limited to this. For example, the first direction Dx and the second direction Dy may be interchanged in FIG. 5. Further, the common electrode 40 may further extend in the array Un so as to separate the array electrode 20A from the array electrode 20B and separate the array electrode 20C from the array electrode 20D.

[0050] In the present embodiment, the plurality of detection electrodes 20 (array electrodes 20A, 20B, 20C, 20D) provided in one array Un share one second element 62. Note that the opening / closing (ON / OFF) of the switch 80 in FIG. 5 refers to switching between conduction (ON) and non-conduction (OFF) among the common electrode 40, the counter electrode 30, and the detection electrodes 20 (array electrodes 20A, 20B, 20C, 20D).

[0051] As shown in FIG. 6, the connection portion 19a extends so as to correspond to the shapes and arrangements of the array electrodes 20A, 20B, 20C, 20D in a plan view. The connection portion 19a is connected to the array electrodes 20A, 20B, 20C, 20D via one or more contacts included in the contact formation regions 20P, 20Q, 20R, 20S shown in FIG. 7. The contact shown in FIG. 7 is formed so as to penetrate the covering portion HRC.

[0052] Specifically, array electrode 20A is connected to the connection part 19a shown in Figure 6 via contact 451 included in the contact formation region 20P shown in Figure 7. Array electrode 20B is connected to the connection part 19a shown in Figure 6 via contact 452 included in the contact formation region 20Q shown in Figure 7. Array electrode 20C is connected to the connection part 19a shown in Figure 6 via contact 453 included in the contact formation region 20R shown in Figure 7. Array electrode 20D is connected to the connection part 19a shown in Figure 6 via contact 454 included in the contact formation region 20S shown in Figure 7.

[0053] Multiple connection points 19a, individually connected to array electrodes 20A, 20B, 20C, and 20D, are interconnected via a common connection point 19c located near the center of array Un, for example. The common connection point 19c is provided on the same layer as the connection points 19a. The structure in Figure 1 where the connection points 19a and electrode 15a were connected corresponds to the connection between the common connection point 19c and electrode 15a (see Figure 1) in Figure 6. The specific form of the connection between the connection points 19a and electrode 15a is not limited to this and can be changed as appropriate.

[0054] Furthermore, the number and arrangement of the detection electrodes 20 (array electrodes 20A, 20B, 20C, 20D) are not limited to the example shown in Figure 5 and can be changed as appropriate. For example, in a plan view, one of the array electrodes 20A, 20B, 20C, 20D may be located above the common connection part 19c. In this case, contacts are provided to connect the array electrodes 20A, 20B, 20C, 20D to the common connection part 19c. Also, the more contacts there are connecting the connection part 19a (or common connection part 19c) to one of the array electrodes 20A, 20B, 20C, 20D, the more current paths there are between the connection configurations, which can further reduce the electrical resistance of each individual contact. For this reason, connections to the array electrodes 20A, 20B, 20C, 20D may be made using the common connection part 19c and contacts.

[0055] As shown in Figure 6, the power supply line Vbias extends in the second direction Dy in a configuration that does not contact the connection portion 19a and the signal line Sig. Specifically, the power supply line Vbias is provided along two of the four sides of the array Un that extend in the second direction Dy, opposite the first direction Dx. The power supply line Vbias and the common electrode 40 are connected via a contact 455 included in the contact formation region 45A shown in Figure 7.

[0056] Furthermore, a dummy electrode DF, shown in Figure 6, is positioned at a location corresponding to the space between array electrodes 20A and 20C shown in Figure 5. The dummy electrode DF is connected to the common electrode 40 via a contact 456 located between contact formation region 20P and contact formation region 20R, which is included in the contact formation region 45A shown in Figure 7. The potential of the power supply line Vbias is supplied to the dummy electrode DF via the contacts of the contact formation region 45A and the common electrode 40. This makes it possible to make the electrical characteristics between array electrodes 20A and 20C and between array electrodes 20B and 20D closer, thereby improving the accuracy of pressure detection.

[0057] As shown in Figure 8, the width W1 of the detection electrode 20 (array electrode 20A) in the first direction Dx is greater than the width W2 of the common electrode 40 in the first direction Dx. The width W2 of the common electrode 40 in the first direction Dx is approximately the same as the distance Sp between the detection electrode 20 (array electrode 20A) and the common electrode 40. The arrangement pitch of the multiple protrusions 50t in the first direction Dx is smaller than the length of one of the multiple detection electrodes 20 (for example, the array electrode 20A) in the first direction Dx. As a result, variations in the contact state between the detection electrode 20 and the elastic body 50 are suppressed, and variations in the sensor output for each detection electrode 20 are suppressed.

[0058] In this embodiment, the width W1 of the detection electrode 20 (array electrode 20A) is, for example, about 435 μm. The width W2 of the common electrode 40 is, for example, about 50 μm. The spacing Sp is, for example, about 50 μm. The height H1 of the multiple protrusions 50t of the elastic body 50 is, for example, about 10 μm to 20 μm.

[0059] In Figure 7, only two representative symbols are assigned to each contact in each region (contacts 451, 452, 453, 454, 455, and 456). However, components illustrated with a similar shape to the square-shaped configurations with assigned symbols also function as contacts.

[0060] Furthermore, among the multiple arrays Un arranged in a matrix, adjacent arrays Un share the power supply line Vbias and common electrode 40 located between them.

[0061] The wiring layer shown in Figure 6 is, for example, the fourth wiring layer 19 in Figure 1, but is not limited to this and may be any other wiring layer. In that case, the contacts and contact holes for establishing connections by the contacts shown in Figure 7 extend to the other wiring layers.

[0062] In the example described with reference to Figures 5 to 8, four detection electrodes 20 (array electrodes 20A, 20B, 20C, and 20D) share one second element 62 within array Un. However, the number of detection electrodes 20 that can share one second element 62 is not limited to four; two or more are acceptable. Furthermore, the arrangement of multiple detection electrodes 20 sharing one second element 62 in a plan view and the shape of each detection electrode 20 are arbitrary.

[0063] In this embodiment, since multiple detection electrodes 20 (array electrodes 20A, 20B, 20C, 20D) share one second element 62, conductivity occurs individually between the multiple detection electrodes 20 (array electrodes 20A, 20B, 20C, 20D) and the counter electrode 30 in response to the pressing force from the counter electrode 30. For this reason, it is possible that some of the multiple detection electrodes 20 will conduct to the counter electrode 30, or that all of the multiple detection electrodes 20 will conduct to the counter electrode 30. In other words, it is possible that at least one of the multiple detection electrodes 20 will conduct to the counter electrode 30.

[0064] For example, in the configuration shown in Figure 5, where array electrodes 20A, 20B, 20C, and 20D share one second element 62, there can be a first case where none of the array electrodes 20A, 20B, 20C, and 20D are conductive to the counter electrode 30; a second case where one of the array electrodes 20A, 20B, 20C, and 20D is conductive to the counter electrode 30; a third case where two of the array electrodes 20A, 20B, 20C, and 20D are conductive to the counter electrode 30; a fourth case where three of the array electrodes 20A, 20B, 20C, and 20D are conductive to the counter electrode 30; and a fifth case where four of the array electrodes 20A, 20B, 20C, and 20D are conductive to the counter electrode 30.

[0065] The detection circuit connected to the signal line Sig has an electrical resolution capable of distinguishing between the first to fifth cases, thereby enabling gradation in the detection of pressing force at each array Un by the pressure sensor 1. In other words, by making it possible to individually detect the differences in the strength of the pressing force from the opposing electrode 30 side, it is possible to detect not only the presence or absence of pressing force, but also the degree of the pressing force strength. Here, the first to fifth cases are used as examples, but the electrical resolution of the detection circuit should be such that it corresponds to the number of detection electrodes 20 that share one second element 62.

[0066] One transistor (second element 62) is connected to two or more detection electrodes 20 (array electrodes 20A, 20B, 20C, 20D). As a result, the intensity of the signal output to the signal line Sig via the transistor (sensor output) changes according to the number of detection electrodes 20 connected to the counter electrode 30 among the two or more detection electrodes 20. This improves the detection accuracy of the pressed area and pressing force within the detection region SA.

[0067] Furthermore, the common electrode 40 separates at least two or more detection electrodes 20 (array electrodes 20A, 20B, 20C, 20D) connected to one transistor (second element 62) from each other in the second direction Dy. This makes it easier to stabilize the electrical characteristics due to the positional relationship between the two or more detection electrodes 20 connected to one transistor (second element 62) via the first element 61 and the common electrode 40.

[0068] Furthermore, the common electrode 40 is electrically connected to the power supply line Vbias, which is stacked on the substrate 10 side of the common electrode 40. This allows the power supply line Vbias to be placed within the detection region SA and connected to the common electrode 40.

[0069] Furthermore, the power supply line Vbias is on the same layer as the signal line Sig. This allows the power supply line Vbias and the signal line Sig to be formed in the same process, enabling the pressure sensor 1 to be manufactured at a lower cost.

[0070] Figure 9 is a graph showing the relationship between pressing force and sensor output for the pressure sensors according to the Examples and Comparative Examples. Both the Examples and Comparative Examples of pressure sensors have an elastic body 50 having a plurality of protrusions 50t (see Figures 1 and 2). The pressure sensor 1 according to the Examples has an elastic body 50 having conductive particles 51 and insulating particles 52. The pressure sensor according to the Comparative Examples has an elastic body having conductive particles but no insulating particles.

[0071] In the graph shown in Figure 9, the horizontal axis represents the magnitude of the pressing force applied to the counter electrode 30, and the vertical axis represents the sensor output. In addition, in the graph shown in Figure 9, arrow A1 shows the sensor output profile when the pressing force is increased, and arrow A2 shows the sensor output profile when the pressing force is decreased.

[0072] As shown in Figure 9, in the comparative example pressure sensor, the variation in sensor output increases when the pressing force is increased and when it is decreased. That is, in the comparative example pressure sensor, the sensor output when the pressure is decreased is greater than the sensor output when the pressure is increased. Thus, the comparative example has a large hysteresis in the sensor output. This is because the elastic body does not have insulating particles, so the elastic modulus of the elastic body is insufficient, and even after the pressing force changes from increased to decreased, the contact state between the elastic body and the detection electrode 20 as it was when the pressure was increased is maintained. Note that the hysteresis in the sensor output represents the difference between the sensor output corresponding to a predetermined pressing force when the pressure is increased and the sensor output corresponding to a predetermined pressing force when the pressure is decreased.

[0073] In the pressure sensor 1 according to the embodiment, the variation in sensor output between pressurization and depressurization is suppressed compared to the comparative example. That is, in the pressure sensor 1 according to the embodiment, the sensor output during pressurization and the sensor output during depressurization are substantially the same. Thus, the embodiment demonstrates that the hysteresis of the sensor output is small. This is because the elastic body 50 has insulating particles 52, which improves the elastic modulus of the elastic body 50, and when the pressurization changes from pressurization to depressurization, the contact state between the elastic body 50 and the detection electrode 20 changes well in accordance with the pressurization.

[0074] Figure 10 is a graph showing the repeatability of the pressure sensors according to the examples and comparative examples. The graph in Figure 10 shows the relationship between the pressing force and the sensor output when the pressing force and depressurization are repeated four times at a predetermined pressing force for each of the examples and comparative examples. The graphs in Figure 10 all show the profile during pressing.

[0075] As shown in Figure 10, in the comparative example pressure sensor, the sensor output changes each time a pressing force is applied. Specifically, the sensor output when a pressing force is applied for the second time is larger than the sensor output when it is applied for the first time. Similarly, the sensor output increases each time a pressing force is repeatedly applied, such as for the third and fourth times. This is because, since the elastic body does not have insulating particles, the elastic body undergoes plastic deformation, and the contact state between the elastic body and the detection electrode from when the pressing force was applied in the previous instance is maintained while repeated pressing forces are applied.

[0076] In the pressure sensor 1 according to the embodiment, it was shown that the variation in sensor output was smaller compared to the comparative example, even when pressing force was repeatedly applied multiple times. This is because, since the elastic body 50 has insulating particles 52, elastic deformation becomes dominant when pressing force is applied to the elastic body 50. In other words, each time pressing force is repeatedly applied to the elastic body 50, the contact state between the elastic body 50 and the detection electrode 20 is reset to the original state (the state when no pressing force is applied).

[0077] Figure 11 is a graph showing the relationship between the amount of insulating particles added and hysteresis in the pressure sensor according to the embodiment. In the graph shown in Figure 11, the horizontal axis represents the amount of insulating particles 52 added to the elastic body 50 (wt%), and the vertical axis represents the hysteresis of the sensor output. Note that "wt%" can be replaced with "mass%". Furthermore, "hysteresis of sensor output" represents the ratio (%) of the difference between the sensor output when pressurized and when depressurized at a predetermined pressing force, relative to the maximum value of the sensor output.

[0078] As shown in Figure 11, the hysteresis of the sensor output decreases as the amount of insulating particles 52 added increases. Preferably, the amount of insulating particles 52 added is, for example, 2.5 wt% to 20 wt%. More preferably, the amount of insulating particles 52 added is, for example, 5 wt% to 10 wt%.

[0079] Specifically, when the amount of insulating particles 52 added is in the range of 2.5 wt% or more, the hysteresis of the sensor output is reduced compared to the comparative example without the addition of insulating particles 52. More preferably, when the amount of insulating particles 52 added is in the range of 5 wt% or more, the hysteresis of the sensor output is reduced more effectively.

[0080] Furthermore, when the amount of insulating particles 52 added is in the range of 7.5 wt% or more, the slope (decrease rate) of the sensor output hysteresis becomes smaller and almost constant. Preferably, the amount of insulating particles 52 added is 20 wt% or less. More preferably, the amount of insulating particles 52 added is 10 wt% or less.

[0081] If the amount of insulating particles 52 added exceeds 20 wt%, the relationship between pressing force and sensor output (see Figure 9) may change. Specifically, since the amount of insulating particles 52 contained between the detection electrode 20, the counter electrode 30, and the common electrode 40 increases, the resistance of the conductive path formed when pressing force is applied from the counter electrode 30 side may increase. Alternatively, in the example shown in Figure 9, the sensor output changes continuously and smoothly according to the magnitude of the pressing force, but if the amount of insulating particles 52 added increases, the conductive path may not be formed properly, and the sensor output may change discontinuously in a stepwise manner.

[0082] Figure 12 is an explanatory diagram illustrating the pressure distribution when a constant pressing force is applied to a predetermined area of ​​the pressure sensor according to the embodiment. Figure 13 is an explanatory diagram illustrating the pressure distribution when a constant pressing force is applied to a predetermined area of ​​the pressure sensor according to the comparative example.

[0083] In measuring the pressure distribution shown in Figures 12 and 13, a pressing member having a rectangular shape in plan view, with a width Wx in the first direction Dx and a width Dy in the second direction of 25 mm, was used. The pressing member was made of, for example, urethane. Figures 12 and 13 show the pressure distribution, i.e., the distribution of sensor output for each detection electrode 20, when the pressing member is placed on the pressure sensor 1 and a pressing force is applied by placing, for example, a 1 kg weight on it. In Figures 12 and 13, the lower the pressure, the closer the density is to black, and the higher the pressure, the closer the density is to white.

[0084] As shown in Figure 13, the pressure sensor of the comparative example, which uses an elastic material without insulating particles, exhibits a larger pressure distribution. Specifically, in a region where a constant pressing force is applied, areas of high pressure and areas of low pressure are generated.

[0085] In contrast, the pressure sensor 1 of the embodiment using an elastic body 50 having insulating particles 52 exhibits a more uniform pressure distribution compared to the comparative example. That is, the pressure sensor 1 of the embodiment can suppress variations in the sensor output within the detection region SA when a predetermined pressing force is applied. This is because, in the pressure sensor 1 of the embodiment, the elastic modulus of the elastic body 50 is improved because the elastic body 50 has insulating particles 52, and the arrangement pitch and height H1 of the multiple protrusions 50t are formed to be constant.

[0086] It should be noted that the graphs and pressure distribution data shown in Figures 9 to 13 are merely examples and are not limiting.

[0087] While preferred embodiments of this disclosure have been described above, this disclosure is not limited to such embodiments. The contents disclosed in the embodiments are merely examples, and various modifications are possible without departing from the spirit of this disclosure. Any modifications made without departing from the spirit of this disclosure will naturally fall within the technical scope of this disclosure. At least one of various omissions, substitutions, and modifications of components can be made without departing from the gist of each embodiment and each modification described above.

[0088] 1 Pressure sensor 10 Substrate 20 Detection electrodes 20A, 20B, 20C, 20D Array electrodes 30 Counter electrodes 40 Common electrode 50 Elastic body 51 Conductive particles 52 Insulating particles 50t Convex portion 50u Recessed portion HRC Coating portion Un Array

Claims

1. A pressure sensor comprising: a plurality of detection electrodes arranged on a substrate; a common electrode arranged between adjacent plurality of detection electrodes; a counter electrode facing the plurality of detection electrodes and the common electrode with a distance between them in a direction perpendicular to the substrate; and an elastic body provided between the plurality of detection electrodes, the common electrode and the counter electrode in a direction perpendicular to the substrate, wherein the elastic body contains a plurality of conductive particles and a plurality of insulating particles and has a plurality of protrusions formed on the surface facing the plurality of detection electrodes and the common electrode.

2. The pressure sensor according to claim 1, wherein the particle size of the plurality of insulating particles is smaller than the height of the plurality of protrusions in the direction perpendicular to the substrate.

3. The pressure sensor according to claim 2, wherein the particle size of the plurality of insulating particles is 1 / 20 or more and 1 / 10 or less of the height of the plurality of protrusions.

4. The pressure sensor according to claim 1, wherein the arrangement pitch of the plurality of protrusions in the first direction is smaller than the length of one of the plurality of detection electrodes in the first direction.

5. The pressure sensor according to claim 1, wherein the amount of the plurality of insulating particles added to the elastic body is 2.5 wt% or more and 20 wt% or less.

6. The pressure sensor according to claim 1, wherein the amount of the plurality of insulating particles added to the elastic body is 5 wt% or more and 10 wt% or less.

7. The pressure sensor according to claim 1, wherein the plurality of conductive particles electrically connect the detection electrode and the counter electrode when a pressing force is applied to the elastic body that brings the detection electrode and the counter electrode close together.

8. The pressure sensor according to any one of claims 1 to 7, wherein the plurality of detection electrodes are arranged in a matrix on the substrate, and the common electrode is continuously provided in a grid pattern that separates adjacent detection electrodes in at least one direction among the plurality of detection electrodes.

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