Tactile sensor

Abstract

To provide a more sensitive tactile sensor.SOLUTION: The tactile sensor includes a first substrate and a second substrate facing the first substrate, and a first pressure-sensitive element and a second pressure-sensitive element provided between the first substrate and second substrate with a change in resistance in response to pressure changes. When shear force is applied to an external force acting portion on the outer surface of the second substrate, due to the moment generated in the external force acting portion according to the magnitude of the shear force, the resistance value of one of the first pressure-sensitive element and the second pressure-sensitive element increases, and the resistance value of the other decreases.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a tactile sensor capable of detecting pressure and shear force.

Background Art

[0002] As a tactile sensor for detecting pressure and shear force, there is known one having a structure in which a conductor layer or a resin layer is sandwiched between two opposed electrodes. This tactile sensor can detect pressure and shear force based on a change in a physical quantity between the electrodes by deforming the conductor layer or the resin layer by an external force, and changing the physical quantity between the electrodes (Patent Documents 1 to 3). Further, in a general tactile sensor, a change in resistance value between electrodes formed between two opposed substrates (upper and lower substrates) is measured via wiring connected to the electrodes.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] Depending on the application, a tactile sensor needs to detect an extremely small load or shear force.

[0005] Therefore, an object of the present invention is to provide a more sensitive tactile sensor.

Means for Solving the Problems

[0006] One aspect of the present invention for solving the above problems includes a first base material, a second base material facing the first base material, and a first pressure-sensitive element and a second pressure-sensitive element provided between the first base material and the second base material, the resistance values of which change in response to a change in pressure. When a shearing force is applied to the external force acting portion on the outer surface of the second base material, a moment is generated in the external force acting portion according to the magnitude of the shearing force, causing the resistance value of one of the first pressure-sensitive element and the second pressure-sensitive element to increase and the resistance value of the other to decrease. It is a tactile sensor.

Advantages of the Invention

[0007] According to the present invention, a more sensitive tactile sensor can be provided.

Brief Description of the Drawings

[0008]

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Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the shape and number of each component constituting the tactile sensor according to the embodiment are merely examples and do not limit the present invention. Also, for the sake of simplicity of explanation, the drawings are drawn at a ratio different from the actual dimensions, but this does not impair the gist of the technology according to the present invention.

[0010] <Embodiment> FIG. 1 is a schematic diagram showing a schematic configuration of a tactile sensor according to an embodiment of the present invention. More specifically, FIG. 1(a) is a plan view of the tactile sensor, and FIG. 1(b) is a cross-sectional view taken along the line A-A' shown in FIG. 1(a). FIG. 2 is a schematic diagram of the first substrate side of the tactile sensor. More specifically, FIG. 2(a) is a plan view of the first substrate side of the tactile sensor, and FIG. 2(b) is a cross-sectional view taken along the line B-B' shown in FIG. 2(a). FIG. 3 is a schematic diagram of the second substrate side of the tactile sensor. More specifically, FIG. 3(a) is a plan view of the second substrate side of the tactile sensor, and FIG. 3(b) is a cross-sectional view taken along the line C-C' shown in FIG. 3(a). Note that in FIGS. 1(b), 2(b), and 3(b), for the sake of convenience, the wirings described later are omitted.

[0011] The tactile sensor 100 is a sensor capable of detecting the pressure and shear force (shearing force) applied to the substrate, and includes a first substrate 1, a second substrate 2, a first pressure-sensitive element 10, a second pressure-sensitive element 20, a third pressure-sensitive element 30, a fourth pressure-sensitive element 40, and a fifth pressure-sensitive element 50 provided between the first substrate 1 and the second substrate 2, and a plurality of wirings provided on one surface of the first substrate 1. The first pressure-sensitive element 10, the second pressure-sensitive element 20, the third pressure-sensitive element 30, the fourth pressure-sensitive element 40, and the fifth pressure-sensitive element 50 are elements whose resistance value changes in response to a pressure change, and the tactile sensor 100 includes an output circuit such as a bridge circuit that converts the resistance value generated in each pressure-sensitive element into a voltage and outputs it.

[0012] The tactile sensor 100 has the first base material 1 and the second base material 2 adhered to each other via a connection layer 5 provided so as to surround all the pressure-sensitive elements. Further, if necessary, a cushioning material for inputting a load to the tactile sensor 100 may be provided on the surface of the second base material 2 opposite to the first base material 1. The cushioning material is provided in a region inside the inner circumference of the connection layer 5 in a plan view. By providing the cushioning material, the detection region of the tactile sensor 100 becomes clear, and since the input load is dispersed within the cushioning material, it becomes easier to stably apply a force to all the pressure-sensitive elements. The detection region is a region to which a load should be input for the tactile sensor 100 to perform accurate detection, and corresponds to the region of the smallest circle including all the pressure-sensitive elements in a plan view.

[0013] (Base material) Between the first substrate 1 and the second substrate 2, a first pressure-sensitive element 10, a second pressure-sensitive element 20, a third pressure-sensitive element 30, a fourth pressure-sensitive element 40, and a fifth pressure-sensitive element 50 are provided. On the first substrate 1, a first substrate-side pressure-sensitive element (details will be described later) that constitutes the first pressure-sensitive element 10, the second pressure-sensitive element 20, the third pressure-sensitive element 30, the fourth pressure-sensitive element 40, and the fifth pressure-sensitive element 50, and a plurality of wirings are provided. On the second substrate 2, a second substrate-side pressure-sensitive element (details will be described later) that constitutes the first pressure-sensitive element 10, the second pressure-sensitive element 20, the third pressure-sensitive element 30, the fourth pressure-sensitive element 40, and the fifth pressure-sensitive element 50 is provided. The material of the first substrate 1 is not particularly limited as long as it is a substrate on which a pressure-sensitive element and wirings can be formed on the surface. Also, the material of the second substrate 2 is not particularly limited as long as it is a substrate on which a pressure-sensitive element can be formed on the surface. The first substrate 1 and the second substrate 2 are preferably flexible sheet-like members. In this case, for example, plastic films such as polyester, polyethylene, polyethylene terephthalate, polyethylene naphthalate (PEN), polybutylene terephthalate, polyamide, polymethyl methacrylate, polypropylene, polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, polyimide, polyether ether ketone, ethylene-vinyl alcohol copolymer, cellophane, dimethyl polysiloxane of silicone rubber, and processed papers such as clean paper, coated paper, and calendar paper can be used. Also, when considering the use of the tactile sensor 100 on a living body, as the material of the substrate, polyesters made of homopolymers or copolymers such as polylactic acid, polyglycolic acid, and polycaprolactone, acrylic resins, silicones, cellulose derivatives such as cellulose acetate, cellulose propionate, and cellulose butyrate, polycarbonates, cycloolefin copolymers, styrene-butadiene-based elastomers, etc. can be used. Further, depending on the pressure to be sensed, an elastic body such as rubber may be used as a pressure buffer. When using a conductive substrate, it is desirable to coat the surface with an insulating material so as not to affect the sensor, signal line, and electrode. Also, not only a flexible substrate having flexibility but also a flat substrate that does not substantially bend may be used, and it can be appropriately selected according to the use of the tactile sensor 100 and the like.When using a plastic film as the base material, either an unstretched base material or a stretched base material may be used. Considering mechanical strength and dimensional stability, it is preferable to use a stretched base material such as a uniaxially stretched base material or a biaxially stretched base material, particularly a biaxially stretched base material.

[0014] There are no particular restrictions on the thicknesses of the first base material 1 and the second base material 2, but from the perspective of thinning, it is preferable to be thinner, while it is necessary to have a thickness capable of achieving sufficient strength as the base material. The total thickness of the first base material 1 and the second base material 2 is preferably, for example, 6 μm or more and 200 μm or less. Also, as described in FIG. 1, in this embodiment, the planar shape of the base material is a rectangle, but the planar shape is not limited to this, and shapes such as triangles and circles can be appropriately selected according to the place where the sensor is installed. However, considering mass productivity, it is preferable that the base material before cutting is a long object. Also, the materials, thicknesses, and sizes of the first base material 1 and the second base material 2 do not have to be the same.

[0015] Also, in this embodiment, the second base material 2 is the base material on the side where an external force is input. At this time, it is preferable that the input / output wiring of the tactile sensor 100 is provided only on the first base material 1 and not on the second base material 2. Thereby, the input external force can be efficiently transmitted to the pressure-sensitive element. Although details will be described later, in this embodiment, in order to provide the input / output wiring only on the first base material 1, each of the pressure-sensitive elements is composed of a pair of divided elements 11 and 12 arranged at a predetermined interval.

[0016] (Pressure-sensitive element) The first pressure-sensitive element 10, the second pressure-sensitive element 20, the third pressure-sensitive element 30, the fourth pressure-sensitive element 40, and the fifth pressure-sensitive element 50 are elements whose resistance values change in response to a pressure change. The first pressure-sensitive element 10 and the second pressure-sensitive element 20 are arranged at equal intervals with the fifth pressure-sensitive element 50 interposed therebetween. Also, the third pressure-sensitive element 30 and the fourth pressure-sensitive element 40 are arranged at equal intervals with the fifth pressure-sensitive element 50 interposed therebetween in a direction orthogonal to the alignment direction of the first pressure-sensitive element 10 and the second pressure-sensitive element 20. That is, as shown in FIG. 1, the pressure-sensitive elements are arranged such that the fifth pressure-sensitive element 50 is centered and the other four pressure-sensitive elements (the first pressure-sensitive element 10, the second pressure-sensitive element 20, the third pressure-sensitive element 30, and the fourth pressure-sensitive element 40) are rotationally symmetric four times.

[0017] The first pressure-sensitive element 10, the second pressure-sensitive element 20, the third pressure-sensitive element 30, and the fourth pressure-sensitive element 40 are pressure-sensitive elements that contribute to the detection of shear force, and the fifth pressure-sensitive element 50 is a pressure-sensitive element that contributes to the detection of pressure. When the alignment direction of the first pressure-sensitive element 10 and the second pressure-sensitive element 20 is the X-axis direction and the alignment direction of the third pressure-sensitive element 30 and the fourth pressure-sensitive element 40 is the Y-axis direction, the first pressure-sensitive element 10 and the second pressure-sensitive element 20 can detect the shear force in the X-axis direction, and the third pressure-sensitive element 30 and the fourth pressure-sensitive element 40 can detect the shear force in the Y-axis direction. Note that the pressure indicates the force component in the direction perpendicular to the sensor surface (the Z-axis direction in FIG. 1), and the shear force indicates the force component in the surface direction of the base material (the Z-axis and Y-axis directions in FIG. 1).

[0018] Each of the first pressure-sensitive element 10, the second pressure-sensitive element 20, the third pressure-sensitive element 30, the fourth pressure-sensitive element 40, and the fifth pressure-sensitive element 50 is composed of a first base material side pressure-sensitive element provided on one surface of the first base material 1 and a second base material side pressure-sensitive element provided on the surface of the second base material 2 facing the first base material 1 so as to face each of the pressure-sensitive elements on the first base material 1 side. The first base material side pressure-sensitive elements of the first pressure-sensitive element 10, the second pressure-sensitive element 20, the third pressure-sensitive element 30, the fourth pressure-sensitive element 40, and the fifth pressure-sensitive element 50 are respectively the first detection element X1, the second detection element X2, the third detection element Y1, the fourth detection element Y2, and the fifth detection element O, and the second base material side pressure-sensitive elements are respectively the first detection element X1', the second detection element X2', the third detection element Y1', the fourth detection element Y2', and the fifth detection element O'.

[0019] The first detection element X1, the second detection element X2, the third detection element Y1, the fourth detection element Y2, and the fifth detection element O are provided on one surface of the first base material 1 (the surface facing the second base material 2), and wirings are connected to the respective detection elements. Further, the first detection element X1', the second detection element X2', the third detection element Y1', the fourth detection element Y2', and the fifth detection element O' are provided on the surface of the second base material 2 facing the one surface of the first base material 1.

[0020] As shown in FIG. 2(a), each of the first detection element X1, the second detection element X2, the third detection element Y1, the fourth detection element Y2, and the fifth detection element O is composed of a pair of divided elements 11 and 12 arranged at a predetermined interval. Each of the divided elements 11 and 12 has, in order from the first base material 1 side, a first small electrode 10a and a first small pressure-sensitive layer 10b laminated on the first small electrode 10a.

[0021] As shown in FIG. 3(a), each of the first detection element X1', the second detection element X2', the third detection element Y1', the fourth detection element Y2', and the fifth detection element O' has, in order from the second base material 2 side, a second electrode 20a, a second small pressure-sensitive layer 21 laminated on one end portion of the second electrode 20a, and a second small pressure-sensitive layer 22 laminated on one end portion of the second electrode 20a. The second small pressure-sensitive layers 21 and 22 are arranged at a predetermined interval and are electrically connected by the second electrode 20a. Each of the pair of second small pressure-sensitive layers 21 and 22 overlaps both of the pair of divided elements 11 and 12 arranged at opposing positions in a plan view. In the present embodiment, the second small pressure-sensitive layers 21 and 22 are arranged at a predetermined interval, but instead of the pair of second small pressure-sensitive layers 21 and 22, one second small pressure-sensitive layer may be provided.

[0022] (Small electrode) The first small electrode 10a is provided on one surface of the first base material 1 (the surface facing the second base material 2). The second electrode 20a is provided on the surface of the second base material 2 facing the one surface of the first base material 1 so as to overlap each of the first small electrodes 10a. Hereinafter, the first small electrode 10a and the second electrode 20a are also simply referred to as "electrodes". Further, the second electrode 20a electrically connects each of the pair of second small pressure-sensitive layers 21 and 22 (FIG. 3). As a result, when the split elements 11 and 12 come into contact with the second small pressure-sensitive layers 21 and 22 facing each other, a series current path is formed with each of the first small electrodes 10a included in the pair of split elements 11 and 12 arranged on the first base material 1 side as both ends and passing through the second electrodes 20a included in the pair of second small pressure-sensitive layers 21 and 22 arranged on the second base material 2 side. That is, it is a current path in which the current input from the first base material 1 side once flows to the second base material 2 side and then returns to the first base material 1 side again. For this reason, since it is not necessary to provide wiring for signal extraction for the second base material 2, the wiring design is simple, the sensor can be easily miniaturized, and the formation defect of the wiring can also be reduced.

[0023] The resistivity of the electrode is preferably 1.0×10 -3 Ω·cm or less. Further, the thickness of each electrode is not particularly limited, but is preferably 0.01 μm or more and 30 μm or less, and more preferably 0.05 μm or more and 20 μm or less. When it is less than 0.01 μm, the formed film is likely to be a discontinuous film, and sufficient conductivity cannot be obtained. When it exceeds 30 μm, there is a risk that the electrode will crack when the tactile sensor 100 formed on the flexible base material is bent. Further, the shape and area of the overlapping portion of the upper and lower opposing electrodes may be the same shape and area, but it is preferable that one electrode has an area larger than the overlapping portion (FIGS. 5 to 6). The area of the overlapping portion is preferably 1 / 5 or more and 2 / 3 or less of the area of the electrode having a relatively large area. If it is less than 1 / 5, the sensitivity of the tactile sensor 100 will decrease. If it exceeds 2 / 3, it will be difficult to align the two electrodes.

[0024] The electrode is not limited in terms of material or formation method as long as it is a conductive material suitable for the specifications of the sensor element to be used. For example, as the material, metals such as Au, Pt, Ag, Cu, Ni, Cr, Rh, Pd, Zn, Co, Ru, W, Os, Ir, Fe, Mn, Ge, Sn, Ga, In, etc., and conductive metal oxides such as ITO (indium tin oxide), ZnO (zinc oxide), SnO2 (tin oxide), etc. can be used. As the formation method, methods using printing methods such as inkjet printing method, screen printing method, offset printing method, gravure offset printing method, reverse offset printing method, etc., or methods of forming a film on the entire surface of a substrate using vapor deposition methods such as vacuum evaporation method, sputtering method, etc. and patterning it by an etching method can be used. When using a printing method, a material obtained by mixing the electrode material with a resin and inkifying it so that it can be applied by each printing method can be used. In the case of a vapor deposition method, it may be formed by depositing the material only at a predetermined position using a metal mask. Also, a general vinyl wire or the like may be fixed on the substrate with an adhesive or the like. Any other general signal extraction line and electrode formation method may be used. The electrode may be manufactured in the same process as the wiring. In this embodiment, the shape of the first small electrode 10a is a shape obtained by dividing an annular ring in the circumferential direction and a shape in which one side of a rectangular shape is curved outward (FIGS. 2(a) and 3(a)), but it may be a rectangle, a square, a circle, etc., and the shape of the second electrode 20a is also appropriately designed accordingly.

[0025] (Small pressure-sensitive layer) The first small pressure-sensitive layer 10b is laminated on each of the first small electrodes 10a. The second small pressure-sensitive layers 21 and 22 are laminated so as to overlap both ends of each of the second electrodes 20a. The first small pressure-sensitive layer 10b completely covers the first small electrode 10a and is formed so as to be separated from the first small pressure-sensitive layer 10b laminated on an adjacent first small electrode 10a. In plan view, it is preferable that the sizes of the small pressure-sensitive layers are the same. Also, the pair of second small pressure-sensitive layers 21 and 22 may be separated from each other (FIG. 2), but instead of the pair of second small pressure-sensitive layers 21 and 22, one second small pressure-sensitive layer may be provided so as to cover the second electrode 20a.

[0026] The thickness of the small pressure-sensitive layer is preferably 1 μm or more and 100 μm or less, and more preferably 5 μm or more and 50 μm or less. When the small pressure-sensitive layer is less than 1 μm, it becomes difficult to sufficiently cover the electrodes, and the upper and lower electrodes conduct without passing through the small pressure-sensitive layer, resulting in poor sensor operation. When the small pressure-sensitive layer exceeds 100 μm, the deformation in response to the change in the pressing force becomes dull, or the time until the pressing force is evenly transmitted to all the small pressure-sensitive layers increases, so the detection accuracy of the pressure and shear force decreases. Also, from the perspective of thinning, the first small electrode 10a, the first small pressure-sensitive layer 10b, the second electrode 20a, and the second small pressure-sensitive layer 21 (or the second small pressure-sensitive layer 22) are preferably formed to have a total thickness of 260 μm or less.

[0027] Since the tactile sensor 100 according to this embodiment detects pressure and shear force based on the change in the resistance value between the opposing electrodes, the small pressure-sensitive layer is formed of a conductive material. However, it is necessary to use a material with a higher resistivity than that of the electrodes. The resistivity of the small pressure-sensitive layer is preferably 1.0×10 -1 Ω·cm or more and 1.0×10 6 Ω cm or less. In this case, the change amount of the conduction resistance value with respect to the change in the pressing force is suitable, and the detection accuracy of the tactile sensor 100 is good.

[0028] Also, the tactile sensor 100 can detect the input pressing force by the change in the contact resistance of the contact surface between the first small pressure-sensitive layer 10b and the second small pressure-sensitive layers 21, 22 due to the input pressing force. When the pressing force is input, the upper and lower small pressure-sensitive layers come into contact with each other, the unevenness on the surface is slightly deformed, and the contact area increases. And since the resistance value changes according to the change in the contact area, the input pressing force can be detected. In this case, it is preferable to use a material that deforms in response to the pressing force for the small pressure-sensitive layer. For example, conductive carbon or conductive nanocarbon can be used. Also, unevenness on the order of several μm can be formed on the surface of each small pressure-sensitive layer to make the change in the contact area prominent and make it easier to detect the change in the resistance value. As a method of forming unevenness on the surface of the small pressure-sensitive layer, for example, a method of printing and forming conductive carbon ink using screen printing can be used.

[0029] Further, the tactile sensor 100 may detect the input pressing force based on a change in the resistance value between the upper and lower small pressure-sensitive layers caused by a change in the thickness of the small pressure-sensitive layer generated by the input pressing force. In this case, it is preferable to use a material having a piezoresistive effect in which the resistivity changes due to deformation for the small pressure-sensitive layer. For example, conductive polymers such as polyethylene dioxythiophene, polyaniline, and polypyrrole, carbon pastes using graphite or carbon nanotubes, and materials obtained by mixing these with a modifier such as a medium to adjust the resistivity can be used, and can be formed using known printing methods such as inkjet printing, screen printing, and offset printing, or known coating methods such as spray coating. Further, it may be formed entirely using a vapor deposition method such as a vacuum evaporation method, a sputtering method, a thermal chemical vapor deposition method, or a plasma chemical vapor deposition method and then formed by an etching method. In this case, it can also be formed by depositing a material only at a predetermined position using a metal mask.

[0030] The resistivity of the small pressure-sensitive layer is preferably adjusted according to the magnitude of the assumed pressing force. When the assumed pressing force is large, it is preferable to select a material with a gentle change in resistivity, and when the assumed stress is small, it is preferable to select a material with a steep change in resistivity.

[0031] (Connection layer) The connection layer 5 is provided between the first base material 1 and the second base material 2 so as to surround all the pressure-sensitive elements, and connects the first base material 1 and the second base material 2. The thickness of the connection layer 5 is preferably less than the thickness of the pressure-sensitive element (see FIG. 5). Further, there is no particular limitation on the material of the connection layer 5, and it is sufficient if it has good adhesion to the base material. For example, adhesives such as rubber-based, acrylic-based, and silicone-based adhesives are preferably used. Further, a double-sided tape or the like may be used as the connection layer 5.

[0032] The connection layer 5 is preferably in an annular shape as shown in FIG. 1 with the center of the detection region (corresponding to the center of the fifth pressure-sensitive element 50) as the center. When the center of the annular connection layer 5 coincides with the center of the detection region, the distances between the pressure-sensitive elements (the first pressure-sensitive element 10, the second pressure-sensitive element 20, the third pressure-sensitive element 30, the fourth pressure-sensitive element 40) that contribute to shear force detection and the connection layer 5 are all equal. In this case, the repulsive force of the connection layer 5 when a shear force is applied becomes constant regardless of the direction of the shear force, and the dependence on the application direction of the shear force is reduced, so the detection accuracy is further improved. Also, from the viewpoint of detection accuracy, the connection layer 5 preferably has a radius larger than that of the detection region. Note that the connection layer 5 is not limited to an annular shape and may be square.

[0033] As a method for forming the connection layer 5, for example, in the case of a printing method, an inkjet printing method, a screen printing method, or an offset printing method can be used. Also, it may be formed by bonding a double-sided tape processed into a desired shape to the formation position of the connection layer 5. The double-sided tape is preferably used when it is not desired to apply an excessive thermal load to the base material or when it is desired to avoid uneven adhesion due to printing variations.

[0034] (Wiring) Referring further to FIG. 4, the wiring structure according to the present embodiment will be described. FIG. 4 is a schematic circuit diagram of the tactile sensor according to the embodiment. A plurality of wirings are provided on one surface of the first base material 1 and are respectively connected to each detection element on the first base material 1. Note that "fixed R" shown in FIG. 4 represents a fixed resistor.

[0035] Here, in order to compare with the wiring structure of the tactile sensor 100 according to the present embodiment, as a reference example, a wiring structure generally considered in a tactile sensor for detecting shear force will be described. FIG. 11 is a schematic diagram of the first base material side of the tactile sensor according to the reference example, and FIG. 12 is a schematic circuit diagram of the tactile sensor according to the reference example.

[0036] Generally, as shown in FIGS. 11 and 12, one output wiring (X, Y, Z) is connected to each of the first detection element X1, the second detection element X2, the third detection element Y1, the fourth detection element Y2, and the fifth detection element O. Hereinafter, such a wiring structure in which one output wiring is provided for one detection element is referred to as "one active wiring". Further, in the tactile sensor employing one active wiring, the voltage between the output wirings X, Y, and Z and the common wiring COM is detected.

[0037] On the other hand, in the wiring structure according to the present embodiment, as shown in FIGS. 2(a) and 4, output wirings (corresponding to the first output wiring X and the second output wiring Y described later, respectively) are provided between the first detection element X1 and the second detection element X2, and between the third detection element Y1 and the fourth detection element Y2. Hereinafter, such a wiring structure in which one output wiring is provided between two pairs of detection elements is referred to as "two active wirings". In the two active wirings, the first output wiring X can output the potential between the first detection element X1 and the second detection element X2, and the second output wiring Y can output the potential between the third detection element Y1 and the fourth detection element Y2. That is, in the tactile sensor 100 employing two active wirings, the voltage between the output wirings X, Y, and Z and the ground wiring GND is detected.

[0038] The wiring in the present embodiment employing two active wirings can be designed, for example, as shown in FIG. 2(a). The power supply wiring COM is commonly connected to the divided element 11 of the second detection element X2, the divided element 11 of the fourth detection element Y2, and the divided element 11 of the fifth detection element O. The first ground wiring Gx is connected to the divided element 11 of the first detection element X1. The first output wiring X is connected to the divided element 12 of the first detection element X1 and the divided element 12 of the second detection element X2. The second ground wiring Gy is connected to the divided element 11 of the third detection element Y1. The second output wiring Y is connected to the divided element 12 of the third detection element Y1 and the divided element 12 of the fourth detection element Y2. The third output wiring Z is connected to the divided element 12 of the fifth detection element O.

[0039] (Detection principle) First, the pressure detection of the tactile sensor 100 according to the present embodiment will be described. In the present embodiment, the pressure can be detected by the fifth pressure-sensitive element 50 (the fifth detection element O and the fifth detection element O' facing it).

[0040] FIG. 5 is a partial cross-sectional view of the tactile sensor during pressure measurement. In FIG. 5, the case where the first small electrode 10a is larger than the overlapping portion of the first small electrode 10a and the second electrode 20a is shown, but they may have the same size. When no pressure is applied, the contact area between the fifth detection element O and the fifth detection element O' is small, or the upper and lower small pressure-sensitive layers are not in contact with each other, so the electrical resistance value between the fifth detection element O and the fifth detection element O' is large (FIG. 5(a)). By applying the pressure F1, the uneven shape of the surface of the upper and lower small pressure-sensitive layers is slightly deformed, and the contact area increases (FIG. 5(b)). When the contact area increases, the conduction paths between the first small electrode 10a of the fifth detection element O on the first base material 1 and the second electrode 20a of the fifth detection element O' on the second base material 2 increase, so the electrical resistance value decreases. Therefore, the pressure can be detected based on the electrical resistance value between the fifth detection element O on the first base material 1 and the fifth detection element O' on the second base material 2. The conversion from the electrical resistance value to the pressure is performed based on the relationship between the pressure obtained in advance as a calibration curve and the resistance value between the fifth detection element O and the fifth detection element O'.

[0041] Next, the shear force detection of the tactile sensor 100 according to the present embodiment will be described. In the present embodiment, the shear force in the X-axis direction is detected by the first pressure-sensitive element 10 and the second pressure-sensitive element 20 (the first detection element X1, the second detection element X2, and the first detection element X1', the second detection element X2' facing them), and the shear force in the Y-axis direction can be detected by the third pressure-sensitive element 30 and the fourth pressure-sensitive element 40 (the third detection element Y1, the fourth detection element Y2, and the third detection element Y1', the fourth detection element Y2' facing them). When a shear force is applied to the external force acting portion on the outer surface of the second base material 2, due to the moment generated in the external force acting portion according to the magnitude of the shear force, the resistance value of one of the first pressure-sensitive element 10 and the second pressure-sensitive element 20 increases, and the resistance value of the other decreases.

[0042] When two active wirings are adopted as in this embodiment, the first output wiring X can output the potential between the first pressure-sensitive element 10 and the second pressure-sensitive element 20, and the second output wiring Y can output the potential between the third pressure-sensitive element 30 and the fourth pressure-sensitive element 40 (Fig. 4). At this time, when a shearing force is input in the alignment direction (X-axis direction) of the first pressure-sensitive element 10 and the second pressure-sensitive element 20, the resistance value of either the first pressure-sensitive element 10 or the second pressure-sensitive element 20 increases, and the resistance value of the other decreases. Then, the output value changes according to the ratio of the change amounts of the resistance values of the first pressure-sensitive element 10 and the second pressure-sensitive element 20, and the shearing amount can be directly obtained from the change in the output value (potential change). Also, when a shearing force is input in the alignment direction (Y-axis direction) of the third pressure-sensitive element 30 and the fourth pressure-sensitive element 40, the resistance value of either the third pressure-sensitive element 30 or the fourth pressure-sensitive element 40 increases, and the resistance value of the other decreases, and the output value changes according to the ratio of the change amounts of the resistance values of the third pressure-sensitive element 30 and the fourth pressure-sensitive element 40, and the shearing amount can be directly obtained from the change in the output value (potential change).

[0043] The detection of the shearing force will be described in more detail with reference to Figs. 6 to 8. Fig. 6 is a cross-sectional view of the tactile sensor when measuring the shearing force. Fig. 7 is a diagram for explaining the detection of the shearing force in the X-axis direction. Fig. 8 is a graph showing the relationship between the shearing displacement and the output value in the X-axis direction when two active wirings are adopted. In the shearing displacement of Fig. 7, the positive direction is the right direction on the paper surface in Fig. 1 (the positive direction of the X-axis), and the negative direction is the left direction on the paper surface in Fig. 1 (the negative direction of the X-axis). Here, the detection of the shearing force in the X-axis direction will be described, but the detection method of the shearing force in the Y-axis direction can also be detected by the same principle.

[0044] Taking the case where no load is applied to the tactile sensor 100 as the initial state, the resistance values of the first detection element X1 and the second detection element X2 at this time are respectively set as R1 and R2 (Fig. 7(a)).

[0045] When only a predetermined pressure is applied to the tactile sensor 100 (Fig. 6(a)), the loads applied to the first detection element X1 and the second detection element X2 are the same (Fig. 7(b)). At this time, if the change amounts of the resistance values from the initial states in the first detection element X1 and the first detection element X2 are ΔR1 and ΔR2 respectively, then ΔR1 and ΔR2 are equal. That is, the resistance values of the first detection element X1 and the second detection element X2 are equal (R1 + ΔR1 = R2 + ΔR2), and the potential of the first output wiring X (the potential between the first detection element X1 and the second detection element X2) does not change from the initial state (Fig. 8). From this, it is required that the shear displacement is 0 μm. Note that both ΔR1 and ΔR2 are negative values.

[0046] When a shear force is applied to the tactile sensor 100 in the positive direction of the X-axis (the right direction of the paper surface in Fig. 1) in addition to the pressure (Fig. 6(b)), a larger load is applied to the second detection element X2 than to the first detection element X1 (Fig. 7(c)). At this time, if the change amounts from the state of Fig. 7(b) (the state where only pressure is applied) in the first detection element X1 and the first detection element X2 are ΔR1' and ΔR2' respectively, then |ΔR1'| = |ΔR2'| (however, ΔR1' is a positive value and ΔR2' is a negative value). Also, the resistance value of the first detection element X1 becomes larger than the resistance value of the second detection element X2 (R1 + ΔR1 > R2 + ΔR2), and the output value from the first output wiring X (the potential between the first detection elements X1 and X2) becomes smaller. And since the output value from the first output wiring X changes from the initial state according to the ratio of the change amounts ΔR1 and ΔR2 of the resistance values of the first detection element X1 and the second detection element X2, the shear force can be obtained from the relationship between this potential and the potential and shear force obtained in advance as a calibration curve. Thus, as the shear force in the positive direction of the X-axis increases, the potential also decreases from 2.5 V (Fig. 8).

[0047] When a shearing force is applied to the tactile sensor 100 in the negative direction of the X-axis (the left direction on the paper surface in FIG. 1) in addition to the pressure, a larger load is applied to the first detection element X1 than to the second detection element X2 (FIG. 7(d)). At this time, assuming that the amounts of change from the state of FIG. 7(b) (the state where only pressure is applied) in the first detection element X1 and the first detection element X2 are ΔR1’ and ΔR2’ respectively, |ΔR1’| = |ΔR2’| (however, ΔR1’ is a negative value and ΔR2’ is a positive value). Also, the resistance value of the first detection element X1 becomes smaller than the resistance value of the second detection element X2 (R1 + ΔR1 < R2 + ΔR2), and the output value from the first output wiring X (the potential between the first detection elements X1 and X2) becomes larger. At this time, since the potential of the first output wiring X changes from the initial state according to the ratio of the change amounts ΔR1 and ΔR2 of the resistance values of the first detection element X1 and the second detection element X2, the shearing force can be obtained from the relationship between this potential and the potential and the shearing force obtained in advance as a calibration curve. Thus, as the shearing force in the negative direction of the X-axis increases, the potential also increases from 2.5 V (FIG. 8).

[0048] FIG. 9 is a graph showing the relationship between the shearing displacement and the output value in the X-axis direction when one active wiring is adopted. FIG. 10 is a graph showing the relationship between the shearing displacement and the output value in one active wiring and two active wirings. In the case of two active wirings, since the change amounts ΔR1’ and ΔR2’ of the resistance values of the first detection element X1 and the second detection element X2 change with opposite signs to each other, for example, when the absolute values of the change amounts ΔR1’ and ΔR2’ are the same, the output change becomes twice as large as when taking outputs from the first detection element X1 and the second detection element X2 respectively as in the case of one active wiring, and the sensitivity is improved. On the other hand, when one active wiring is simply adopted, since the direction and magnitude of the applied shearing force are detected based on the outputs of the first detection element X1 and the second detection element X2 respectively, the sensitivity is lower than in the case of two active wirings (FIGS. 9 and 10).

[0049] In addition, when one active wiring is adopted, the direction and magnitude of the shearing force input based on the outputs of the first pressure-sensitive element 10 and the second pressure-sensitive element 20 (or the third pressure-sensitive element 30 and the fourth pressure-sensitive element 40) will be detected. Also in this case, when a shearing force is applied to the external force application part on the outer surface of the two base materials 2, a moment is generated in the external force application part according to the magnitude of the shearing force, causing the resistance value of one of the first pressure-sensitive element 10 and the second pressure-sensitive element 20 (or the third pressure-sensitive element 30 and the fourth pressure-sensitive element 40) to increase and the resistance value of the other to decrease. Further, when one active wiring is adopted, even if the fifth pressure-sensitive element 50 is omitted, the pressure can be calculated based on the average value of the resistance values of the first pressure-sensitive element 10, the second pressure-sensitive element 20, the third pressure-sensitive element 30, and the fourth pressure-sensitive element 40.

[0050] <Modification Example> FIGS. 13 and 14 are plan views of the first base material side and the second base material side of the tactile sensor according to the modification example. More specifically, FIGS. 13(a) and 14(a) are plan views of the first base material side of the tactile sensor according to the modification example, and FIGS. 13(b) and 14(a) are plan views of the second base material side of the tactile sensor according to the modification example.

[0051] In this embodiment, five pressure-sensitive elements, namely the first pressure-sensitive element 10, the second pressure-sensitive element 20, the third pressure-sensitive element 30, the fourth pressure-sensitive element 40, and the fifth pressure-sensitive element 50, are used to detect the pressure in the Z-axis direction and the shearing forces in the X and Y-axis directions. However, for example, when pressure detection is not required, the fifth pressure-sensitive element 50 that contributes to pressure detection and the wiring connected to the fifth pressure-sensitive element 50 in the embodiment may be omitted (FIG. 13).

[0052] Also, when omitting the fifth pressure-sensitive element 50, a dummy pressure-sensitive element 60 may be provided instead of the fifth pressure-sensitive element 50 (FIG. 14). The dummy pressure-sensitive element 60 includes a dummy detection element d provided on one surface of the first base material 1, and a dummy detection element d' provided on the surface of the second base material 2 facing the first base material 1 and facing the dummy detection element d on the first base material 1 side. By providing the dummy pressure-sensitive element 60, the area of the pressure-sensitive elements occupying the detection region increases, and the load is more likely to be evenly applied to each pressure-sensitive element, so that the detection non-uniformity caused by the arrangement of the pressure-sensitive elements can be reduced.

[0053] Also, if it is sufficient to detect only one of the shearing forces in the X and Y-axis directions, the pressure-sensitive elements that contribute to the detection of the shearing force in the X or Y-axis direction may be omitted as appropriate. Further, when the detection of pressure is not required, the fifth pressure-sensitive element 50 that contributes to the detection of pressure may be omitted, or, as described above, a dummy pressure-sensitive element 60 may be provided instead of the fifth pressure-sensitive element 50.

Industrial Applicability

[0054] The present invention can be applied to a tactile sensor capable of detecting pressure and shearing force.

Explanation of Signs

[0055] 1: First base material 2: Second base material 10: First pressure-sensitive element 10a: First small electrode 10b: First small pressure-sensitive layer 20: Second pressure-sensitive element 20a: Second electrode 21: Second small pressure-sensitive layer 22: Second small pressure-sensitive layer 30: Third pressure-sensitive element 40: Fourth pressure-sensitive element 50: Fifth pressure-sensitive element 60: Dummy pressure-sensitive element 100: Tactile sensor O: Fifth detection element O’: Fifth detection element X: First output wiring X1: First detection element X1’: First detection element X2: Second detection element X2’: Second detection element Y: Second output wiring Y1: Third detection element Y1’: Third detection element Y2: Fourth detection element Y2’: Fourth detection element Z: Third output wiring

Claims

1. A first substrate, a second substrate facing the first substrate, and a first pressure-sensitive element and a second pressure-sensitive element provided between the first substrate and the second substrate and having a resistance value that changes in response to a change in pressure. When a shearing force is applied to an external force application portion on the outer surface of the second substrate, a moment is generated in the external force application portion according to the magnitude of the shearing force, causing the resistance value of one of the first pressure-sensitive element and the second pressure-sensitive element to increase and the resistance value of the other to decrease. A tactile sensor.

2. The tactile sensor according to claim 1, further comprising a first output wiring connected to the first pressure-sensitive element and the second pressure-sensitive element and outputting a potential between the first pressure-sensitive element and the second pressure-sensitive element.

3. The first pressure-sensitive element and the second pressure-sensitive element have a pair of opposed small pressure-sensitive layers, and when a shearing force is applied, the contact resistance of the contact surface of the pair of small pressure-sensitive layers changes. The tactile sensor according to claim 1.

4. The potential of the first output wiring increases as the shearing force applied in a direction parallel to the alignment direction of the first pressure-sensitive element and the second pressure-sensitive element increases, and decreases as the shearing force applied in a direction opposite to the one direction increases. The tactile sensor according to claim 2.

5. Between the first substrate and the second substrate, a third pressure-sensitive element and a fourth pressure-sensitive element arranged side by side in a direction orthogonal to the alignment direction of the first pressure-sensitive element and the second pressure-sensitive element and having a resistance value that changes in response to a change in pressure, and a second output wiring connected to the third pressure-sensitive element and the fourth pressure-sensitive element and outputting a potential between the third pressure-sensitive element and the fourth pressure-sensitive element. When a shearing force is applied in the alignment direction of the third pressure-sensitive element and the fourth pressure-sensitive element, the resistance value of one of the third pressure-sensitive element and the fourth pressure-sensitive element increases and the resistance value of the other decreases. The tactile sensor according to claim 1.

6. The third pressure-sensitive element and the fourth pressure-sensitive element have a pair of opposed small pressure-sensitive layers, and when a shearing force is applied, the contact resistance of the contact surface of the pair of small pressure-sensitive layers changes. The tactile sensor according to claim 5.

7. The tactile sensor according to claim 1, wherein the total thickness of the first substrate and the second substrate is 200 μm or less.

8. The tactile sensor according to claim 5, wherein pressure is calculated based on an average value of resistance values of the first pressure-sensitive element, the second pressure-sensitive element, the third pressure-sensitive element, and the fourth pressure-sensitive element.

9. The tactile sensor according to claim 1 or 5, wherein a dummy pressure-sensitive element is formed between the first pressure-sensitive element and the second pressure-sensitive element.

10. The tactile sensor according to claim 1 or 5, wherein a fifth pressure-sensitive element whose resistance value changes in response to a pressure change is formed between the first pressure-sensitive element and the second pressure-sensitive element.

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