Capacitive soft sensor and capacitive sensor module

Abstract

To provide a capacitive-type soft sensor capable of suppressing damage in the vicinity of a terminal part even if a substrate sheet is made of silicone elastomer, and a capacitive-type sensor module using the same.SOLUTION: In a capacitive-type soft sensor 1, in which a detection electrode 20 for detecting a change in capacitance is provided on a flexible substrate sheet 10, a sheet composed of a silicone elastomer is used as the substrate sheet 10, a terminal part 16 is formed at the tip of a protruding part 14 protruding from a body part 12 on which the detection electrode 20 is disposed in the substrate sheet 10, and a stretch inhibiting layer 30 is provided on the side of the protruding portion 14 on which wiring 22 is formed via an adhesive layer 40 composed of a UV curable adhesive.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a capacitive soft sensor and a capacitive sensor module. [Background technology]

[0002] Capacitive touch sensors that detect operation on an operating surface from changes in capacitance are widely used in various fields, such as in-vehicle electronic devices. Among them, soft sensors, in which detection electrodes and wiring that detect changes in capacitance are provided on a flexible and stretchable substrate sheet such as a silicone elastomer, are particularly useful because they can be freely positioned to conform to curved or uneven surfaces (e.g., Patent Document 1).

[0003] Generally, external devices such as a power supply and a control board, which have a large mass and high rigidity, are not mounted on the soft sensor but are connected externally. Specifically, a strip-shaped protrusion is provided on the base sheet of the soft sensor, and a terminal is formed at the tip of the protrusion, and the terminal is electrically connected to the external device (for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-162124 [Patent Document 2] Patent No. 6676373 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in conventional soft sensors such as those described in Patent Documents 1 and 2, when connecting the terminal portion to an external device, strong stress is applied to the protruding portion of the base sheet, which may cause damage such as tearing. This is particularly likely to occur in base sheets made of silicone elastomer. Patent Documents 1 and 2 do not consider tearing near the terminal portion when connecting to an external device.

[0006] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a capacitance-type soft sensor that can suppress damage near the terminal portion even when the base sheet is made of silicone elastomer, and a capacitance-type sensor module using the same. [Means for solving the problem]

[0007] The present invention includes the following configurations. [1] A capacitance-type soft sensor having a detection electrode for detecting a change in capacitance provided on a flexible substrate sheet, the base sheet is a sheet made of a silicone elastomer, the base sheet has a main body portion in which the detection electrode is arranged, and a protruding portion protruding from at least one side of the main body portion when viewed from the side on which the detection electrode is provided, A terminal portion is formed at the tip portion of the protrusion, a wiring that connects the detection electrode and the terminal portion is formed on the protrusion; A capacitance-type soft sensor in which an extension-suppressing layer is provided on at least one of the side of the protrusion where the wiring is formed and the opposite side thereof, via an adhesive layer made of a UV-curable adhesive. [2] The capacitance-type soft sensor according to [1], wherein the thickness of the base sheet is 12 μm or more and 250 μm or less. [3] The capacitance-type soft sensor according to [1] or [2], wherein the base sheet has a breaking elongation of 100% or more and 800% or less as measured in accordance with JIS K 6251:2017. [4] The capacitance-type soft sensor according to any one of [1] to [3], wherein the silicone elastomer has a Shore A hardness of 10 or more and 90 or less, as measured in accordance with JIS K 6253. [5] The capacitance-type soft sensor according to any one of [1] to [4], wherein the tensile strength of the base sheet measured in accordance with JIS K 6251:2017 is 4 MPa or more and 12 MPa or less. [6] The capacitive soft sensor according to [1], wherein the adhesive layer has a thickness of 5 μm or more and 50 μm or less. [7] The capacitive soft sensor according to any one of [1] to [6], wherein the surface of the protruding portion on which the adhesive layer is provided is subjected to an excimer treatment. [8] A capacitive sensor module including the capacitive soft sensor according to any one of [1] to [7]. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a capacitance-type soft sensor that can suppress damage near the terminal portion even when the base sheet is made of silicone elastomer, and a capacitance-type sensor module using the same. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a plan view showing a schematic configuration of a capacitive soft sensor according to an embodiment; [Figure 2] 2 is a cross-sectional view of the capacitance type soft sensor shown in FIG. 1 along the line AA. DETAILED DESCRIPTION OF THE INVENTION

[0010] An example of an embodiment of the present invention will be described below with reference to the drawings. Note that the dimensions of the drawings shown in the following description are merely examples, and the present invention is not necessarily limited thereto. Appropriate changes can be made within the scope of the present invention.

[0011] [Capacitive soft sensor] Fig. 1 is a plan view of a capacitance type soft sensor 1 (hereinafter also referred to as "soft sensor 1") according to an embodiment, as viewed from the side where detection electrodes and wiring are provided. Fig. 2 is a cross-sectional view of the soft sensor 1 taken along line AA in Fig. 1.

[0012] The soft sensor 1 according to this embodiment includes a base sheet 10, a detection electrode 20, wiring 22, an extension suppressing layer 30, and an adhesive layer 40.

[0013] 1 has a main body 12 that is rectangular in plan view, and strip-shaped protruding portions 14, 14 that extend so as to protrude from both short sides of the main body 12. Terminal portions 16, 16 are formed at the tip portions of the respective protruding portions 14, 14. The planar shape of the base sheet 10 is not limited to the shape in this example, and can be set appropriately depending on the application. For example, the base sheet 10 may have only one protrusion 14.

[0014] The base sheet 10 is a flexible sheet made of silicone elastomer. The Shore A hardness of the silicone elastomer is preferably 10 or more, more preferably 30 or more. If the Shore A hardness is equal to or greater than the lower limit, the base sheet 10 is less likely to be damaged, such as torn, when connected to an external device. The Shore A hardness of the silicone elastomer is preferably 90 or less, more preferably 60 or less. If the Shore A hardness is equal to or less than the upper limit, the soft sensor 1 is improved in its ability to conform to a three-dimensional shape. The preferred lower and upper limits of the Shore A hardness of the elastomer can be arbitrarily combined, and for example, a range of 10 to 90 is preferred. The Shore A hardness is a type A durometer hardness measured according to JIS K 6253 with a test piece having a thickness (height) of 1 cm.

[0015] The thickness of the base sheet 10 is preferably 12 μm or more, more preferably 50 μm or more. If the thickness of the base sheet 10 is equal to or greater than the above-mentioned lower limit, the base sheet 10 is less likely to be damaged, such as torn, when connected to an external device. The thickness of the base sheet 10 is preferably 250 μm or less, more preferably 100 μm or less. If the thickness of the base sheet 10 is equal to or less than the above-mentioned upper limit, the soft sensor 1 is improved in its ability to conform to a three-dimensional shape. The preferred lower and upper limits of the thickness of the base sheet 10 can be arbitrarily combined, and for example, 12 to 250 μm is preferred.

[0016] The breaking elongation of the base sheet 10 is preferably 100% or more, more preferably 500% or more. If the breaking elongation of the base sheet 10 is equal to or greater than the lower limit, the soft sensor 1 will have improved conformability to a three-dimensional shape. The breaking elongation of the base sheet 10 is preferably 800% or less, more preferably 600% or less. If the breaking elongation of the base sheet 10 is equal to or less than the upper limit, peeling or breakage of the detection electrodes 20 and wiring 22 due to excessive elongation can be easily prevented. The preferable lower and upper limits of the breaking elongation of the base sheet 10 can be arbitrarily combined, and for example, 100 to 800% is preferred. The breaking elongation is measured in accordance with JIS K 6251:2017 using a dumbbell No. 2 test piece at a tensile speed of 500 mm / min.

[0017] The tensile strength of the base sheet 10 is preferably 4 MPa or more, more preferably 8 MPa or more. If the tensile strength of the base sheet 10 is equal to or greater than the lower limit, the base sheet 10 is less likely to be damaged, such as torn, when connected to an external device. The tensile strength of the base sheet 10 is preferably 12 MPa or less, more preferably 10 MPa or less. If the tensile strength of the base sheet 10 is equal to or less than the upper limit, the soft sensor 1 is more likely to be able to conform to a three-dimensional shape. The preferred lower and upper limits of the tensile strength of the base sheet 10 can be arbitrarily combined, and for example, a range of 4 to 12 MPa is preferred. The tensile strength is measured in accordance with JIS K 6251:2017 using a dumbbell No. 2 test piece at a tension speed of 500 mm / min.

[0018] In this example, four detection electrodes 20 are provided at intervals along the long side direction of the main body 12 on the first surface 10a side of the main body 12 of the base sheet 10. Wiring 22 is electrically connected to each detection electrode 20, and two of the wiring 22 are formed to reach two terminal portions 16, respectively.

[0019] Each terminal 16 can be electrically connected to an external device such as a power supply, a control board, etc. As a result, when a conductor comes into contact with or near the detection electrode 20 while each terminal 16 is electrically connected to the external device, the soft sensor 1 can detect this from a change in the capacitance of the detection electrode 20. The number of detection electrodes 20 is not limited to four, but can be set appropriately, and may be three or less, or five or more.

[0020] The detection electrode 20 is an electrode for detecting contact or proximity of a conductor by detecting a change in capacitance. The detection of the change in capacitance by the detection electrode 20 may be a self-capacitance type or a mutual capacitance type. The detection electrode 20 may be in the form of, for example, a solid electrode, a comb-tooth electrode, a mesh electrode, a checkered electrode pattern, a diamond pattern, or the like. The planar shape of the detection electrode 20 is rectangular in the example shown in FIG. 1, but may be circular, elliptical, or the like.

[0021] An example of the material constituting the detection electrode 20 is paste ink containing a metal filler. Examples of the metal filler include silver filler, copper filler, and gold filler, with silver filler being preferred. The paste ink may contain one type of metal filler or two or more types of metal fillers.

[0022] The paste ink constituting the detection electrode 20 may contain other conductive materials such as conductive polymers (polythiophene-based conductive polymers (PEDOT / PSS), indium-doped tin oxide (ITO), etc.), conductive nanowires (silver nanowires, gold nanowires, etc.), conductive metal oxide particles (ITO particles, etc.), etc. The material for forming the detection electrode 20 is preferably silver paste ink, and particularly preferably silver paste ink in which silver filler is added to acrylic resin.

[0023] The thickness of the detection electrode 20 is preferably 1 μm or more, and more preferably 5 μm or more. If the thickness of the detection electrode 20 is equal to or greater than the above-mentioned lower limit, peeling or breakage of the detection electrode 20 is easily suppressed. The thickness of the detection electrode 20 is preferably 20 μm or less, and more preferably 10 μm or less. If the thickness of the detection electrode 20 is equal to or less than the above-mentioned upper limit, it is easy to make the soft sensor 1 thinner. The preferred lower and upper limits of the thickness of the detection electrode 20 can be arbitrarily combined, and for example, 1 to 20 μm is preferred.

[0024] The material of the wiring 22 is not particularly limited, and may be the same as the material of the detection electrode 20, for example. Silver paste ink is preferable, and silver paste ink in which silver filler is added to acrylic resin is particularly preferable.

[0025] The thickness of the wiring 22 can be, for example, approximately the same as the thickness of the detection electrode 20, and is preferably 1 μm or more, more preferably 5 μm or more, and is preferably 20 μm or less, more preferably 10 μm or less. The preferred upper and lower limits of the thickness of the wiring 22 can be arbitrarily combined, and for example, 1 to 20 μm is preferred.

[0026] An extension suppressing layer 30 is provided on the first surface 10a side of the protruding portion 14 of the base sheet 10 so as to cover the wiring 22. The extension suppressing layer 30 is adhered to the protruding portion 14 of the base sheet 10 via an adhesive layer 40. By providing the extension suppressing layer 30 on the protruding portion 14 of the base sheet 10, the protruding portion 14 of the base sheet 10 is less likely to be extended excessively even when connecting the terminal portion 16 to an external device, and stress applied to the protruding portion 14 can be reduced. As a result, the protruding portion 14 of the base sheet 10 is less likely to be damaged, such as torn. The stretch-restricting layer 30 may be attached via an adhesive layer 40 to the second surface 10b of the protruding portion 14 of the base sheet 10, which is opposite to the first surface 10a.

[0027] The stretch-suppressing layer 30 may be made of any material that reduces the stretching of the protruding portion 14 of the base sheet 10 when the terminal portion 16 is connected to an external device, and may be made of, for example, a polyethylene terephthalate (PET) film, a polyethylene naphthalate film, a polybutylene terephthalate film, a polybutylene naphthalate film, or a polypropylene (PP). The film that constitutes the stretch-suppressing layer 30 may be a single-layer film or a multilayer film. The stretch-control layer 30 is preferably made of a PET film or polypropylene (PP) because of its high strength (it is difficult to stretch) and low cost.

[0028] The thickness of the stretch-inhibiting layer 30 is preferably 10 μm or more, more preferably 20 μm or more. If the thickness of the stretch-inhibiting layer 30 is equal to or greater than the above-mentioned lower limit, it is easy to prevent damage such as tearing from occurring in the protruding portion 14 of the base sheet 10 when connecting to an external device, etc. The thickness of the stretch-inhibiting layer 30 is preferably 50 μm or less, more preferably 30 μm or less. If the thickness of the stretch-inhibiting layer 30 is equal to or less than the above-mentioned upper limit, it is possible to reduce the thickness while suppressing stretching, thereby increasing the degree of freedom in design. The preferred lower and upper limits of the thickness of the stretch-inhibiting layer 30 can be arbitrarily combined, and for example, 20 to 30 μm is preferred.

[0029] The material that forms the adhesive layer 40 is a UV-curable adhesive. The UV-curable adhesive is not particularly limited, and any known UV-curable adhesive can be used without limitation, such as an acrylic UV-curable adhesive or an epoxy UV-curable adhesive. The adhesive layer 40 may contain one type of UV-curable adhesive or two or more types of UV-curable adhesives.

[0030] The thickness of the adhesive layer 40 is preferably 5 μm or more, more preferably 30 μm or more. If the thickness of the adhesive layer 40 is equal to or greater than the lower limit, it becomes easy to bond the protrusions 14 of the base sheet 10 and the stretch-suppressing layer 30 with sufficient adhesive strength. The thickness of the adhesive layer 40 is preferably 50 μm or less, more preferably 40 μm or less. If the thickness of the adhesive layer 40 is equal to or less than the upper limit, it becomes possible to make the adhesive layer 40 thinner while maintaining adhesive strength, thereby increasing the degree of freedom in design. The preferred lower and upper limits of the thickness of the adhesive layer 40 can be arbitrarily combined, and for example, 5 to 40 μm is preferred.

[0031] The surface of the base sheet 10 on which the adhesive layer 40 is provided in the protruding portions 14 is preferably subjected to an excimer treatment, which allows the protruding portions 14 of the base sheet 10 and the stretch-suppressing layer 30 to be bonded with even higher adhesive strength.

[0032] The method for manufacturing the soft sensor 1 is not particularly limited. For example, the base sheet 10 can be produced by using a known molding method such as press molding, extrusion molding, or calendar molding. The detection electrodes 20, wiring 22, extension suppression layer 30, and adhesive layer 40 can be sequentially formed in a predetermined pattern on the base sheet 10 by, for example, screen printing. When the detection electrodes 20, wiring 22, and adhesive layer 40 are formed by screen printing, optical surface treatment or application of an easy-adhesion coating (primer) may be performed on the first surface 10a of the base sheet 10 as a pre-processing step before the screen printing. It is preferable to perform excimer treatment on the first surface 10a of the base sheet 10 on which the adhesive layer 40 is to be provided in the protruding portion 14.

[0033] As described above, the soft sensor 1 uses a base sheet made of a highly flexible silicone elastomer, which provides excellent conformability to curved and uneven surfaces and is less likely to wrinkle. Furthermore, the extension suppression layer 30 is provided on the protruding portion 14 of the base sheet 10, which has the terminal portion 16 at its tip. Therefore, even when connecting the terminal portion 16 to an external device, excessive stress is less likely to be applied to the protruding portion 14 of the base sheet 10, making it less likely to tear or otherwise break. Furthermore, while it is difficult to obtain sufficient adhesive strength with non-UV-curable adhesives such as acrylic adhesives, the use of a UV-curable pressure-sensitive adhesive allows the protruding portion 14 of the base sheet 10 to be bonded to the extension suppression layer 30 with sufficient adhesive strength.

[0034] [Capacitive sensor module] The capacitance type sensor module of the present invention is a module equipped with the capacitance type soft sensor of the present invention. The capacitance type sensor module of the present invention can adopt any known configuration except for including the capacitance type soft sensor of the present invention. For example, an example of a capacitance type sensor module is one in which an adhesive layer is provided on the second surface 10b side of the base sheet 10 of the soft sensor 1, and the soft sensor 1 is attached to an object having a three-dimensional shape such as a curved surface or an uneven surface via the adhesive layer.

[0035] The material for forming the adhesive layer when attaching the soft sensor 1 to the object is not particularly limited, and may be, for example, the UV-curable adhesive exemplified for the adhesive layer 40.

[0036] The present invention is not limited to the above-described embodiment. For example, in the capacitive soft sensor of the present invention, a GND electrode may be provided on the base sheet in addition to the detection electrode. Furthermore, in soft sensor 1, the extension suppression layer was provided only on the side of the protruding portion of the base sheet where the wiring was formed, but it may be provided on both the side where the wiring of the protruding portion is formed and the opposite side, or it may be provided only on the side opposite to the side where the wiring of the protruding portion is formed.

[0037] In addition, within the scope of the spirit of the present invention, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described modifications may be combined as appropriate. [Example]

[0038] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following descriptions.

[0039] [Experimental Example 1] A film-like test piece was molded from a silicone elastomer (manufactured by Shin-Etsu Polymer Co., Ltd., model number: KE-971T-U) by a known method, and the surface of the test piece was subjected to excimer treatment. The excimer treatment was carried out using a UV wavelength of 172 nm and an illuminance of 50 mW / cm. 2 The distance between the test piece and the lamp (irradiation distance) was set to 3 mm, and irradiation was carried out for 2 seconds. A UV-curable adhesive (acrylic, manufactured by Kyoritsu Chemical Industries, model number: 3990) was applied by screen printing to the excimer-treated surface of the test piece to a dry thickness of 40 μm, and after drying, a PET film (thickness: 25 μm, manufactured by Toray Industries, model number: Lumirror S10) was attached to produce a sample.

[0040] [Experimental Example 2] A sample was produced in the same manner as in Experimental Example 1, except that the surface of the test piece to which the PET film was to be attached was not subjected to excimer treatment.

[0041] [Reference example 1] A reference sample was prepared by attaching an acrylic double-sided tape (manufactured by 3M, model number: 467MP) to one side of a PET film (thickness 25 μm, manufactured by Toray Industries, model number: Lumirror S10).

[0042] [Adhesion strength measurement] The samples obtained in each example were subjected to the following tensile test to measure the adhesive strength (N / cm 2 ) was measured. Specifically, a tensile test was carried out using a tensile tester at a speed of 300 mm / min. The results are shown in Table 1.

[0043] [Table 1]

[0044] As shown in Table 1, the sample of Experimental Example 1, which underwent excimer treatment, had a higher adhesive strength between the silicone elastomer film and the PET film than the sample of Experimental Example 2, which did not undergo excimer treatment, and the adhesive strength was almost the same as that of the sample of Reference Example 1 to which the double-sided tape was attached. [Explanation of symbols]

[0045] 1...capacitive soft sensor, 10...base material sheet, 10a...first surface, 10b...second surface, 12...main body portion, 14...protrusion portion, 16...terminal portion, 20...detection electrode, 22...wiring, 30...extension suppression layer, 40...adhesive layer.

Claims

1. A capacitance-type soft sensor having a detection electrode for detecting a change in capacitance provided on a flexible substrate sheet, the base sheet is a sheet made of a silicone elastomer, the base sheet has a main body portion in which the detection electrode is arranged, and a protruding portion protruding from at least one side of the main body portion when viewed from the side on which the detection electrode is provided, A terminal portion is formed at the tip portion of the protrusion, a wiring that connects the detection electrode and the terminal portion is formed on the protrusion; A capacitance-type soft sensor in which an extension-suppressing layer is provided on at least one of the sides of the protrusion where the wiring is formed and the opposite side thereof via an adhesive layer made of a UV-curable adhesive, and the protrusion and the extension-suppressing layer are adhered together by the adhesive force of the adhesive layer.

2. A capacitive soft sensor as described in claim 1, wherein the extension suppression layer is provided via the adhesive layer on the side opposite to the side on which the wiring is formed in the protrusion.

3. A capacitance type soft sensor as described in Claim 1, wherein the wiring is formed on the base sheet so that one end is electrically connected to the detection electrode and extends to a terminal portion.

4. The capacitive soft sensor according to claim 1, wherein the thickness of the base sheet is 12 μm or more and 250 μm or less.

5. The capacitance-type soft sensor according to claim 1, wherein the base sheet has a breaking elongation of 100% or more and 800% or less, as measured in accordance with JIS K 6251:2017.

6. 2. The capacitive soft sensor according to claim 1, wherein the silicone elastomer has a Shore A hardness of 10 or more and 90 or less, measured in accordance with JIS K 6253.

7. The capacitive soft sensor according to claim 1, wherein the tensile strength of the base sheet measured in accordance with JIS K 6251:2017 is 4 MPa or more and 12 MPa or less.

8. The capacitive soft sensor according to claim 1 , wherein the adhesive layer has a thickness of 5 μm or more and 50 μm or less.

9. The capacitive soft sensor according to claim 1 , wherein an excimer treatment is performed on a surface of the protruding portion on which the adhesive layer is provided.

10. A capacitance type sensor module comprising the capacitance type soft sensor according to any one of claims 1 to 9.

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