Flexible touch sensor and touch sensor module

Abstract

To provide a flexible touch sensor having a probe point for inspecting electric characteristics while protecting a detection electrode sufficiently, and configured to suppress noise or false detection through the probe point, and a touch sensor module.SOLUTION: A flexible touch sensor 1 is equipped with a substrate sheet 10 made of resin, a detection electrode 20 arranged on a first surface 10a in a thickness direction of the substrate sheet 10, and circuit wiring 30 arranged on the first surface 10a of the substrate sheet 10 and electrically connected to the detection electrode 20, to detect a conductor which is in contact or close thereto. The flexible touch sensor includes a carbon layer 40 arranged on a surface of the detection electrode 20 opposite the substrate sheet 10, and covers, with an insulating protective layer 50, a portion of the substrate sheet 10 other than a part where the carbon layer 40 is arranged on the side where the detection electrode 20 is arranged.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a flexible touch sensor and a touch sensor module. [Background technology]

[0002] Capacitive touch sensors are widely used to detect operations on the operation surface in in-vehicle electronic devices, etc. For example, by attaching a capacitive touch sensor made of a flexible printed circuit board to the circuit board side (back side) of a decorated operation panel, it is possible to detect a change in capacitance when a user touches the operation panel.

[0003] In a touch sensor, a protective layer is generally provided on the detection electrodes, so that it is not possible to test the electrical characteristics by directly contacting the electrodes with a probe. Patent Document 1 discloses a method for inspecting electrical characteristics in which a change in capacitance is obtained by calculation using a microcontroller (IC) for a capacitance sensor. Patent Document 2 discloses that an opening is provided in a part of a protective layer covering a detection electrode to serve as a probe point, allowing a probe to come into contact with the detection electrode.

[0004] Furthermore, in touch sensors, a transparent conductive material may be used for the detection electrode. In such cases, the probe point is provided near or on the outer edge of the detection electrode so as not to obstruct light transmission. Patent Document 3 discloses that a carbon material or the like is used to provide a probe point adjacent to the detection electrode on the surface of a base sheet. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-141685 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-174494 [Patent Document 3] Patent Publication No. 2021-036465 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the method using ICs as in Patent Document 1 requires time for testing and increases equipment costs. Providing an opening in a part of the protective layer that covers the detection electrode as in Patent Document 2 makes it difficult to adequately protect the detection electrode. Providing a probe point adjacent to the detection electrode as in Patent Document 3 increases the likelihood of noise due to parasitic capacitance, making false detection more likely.

[0007] In view of the above circumstances, the present invention aims to provide a flexible touch sensor and a touch sensor module that can adequately protect detection electrodes, have probe points for testing electrical characteristics, and can suppress noise and false detection due to the probe points. [Means for solving the problem]

[0008] The present invention includes the following aspects. [1] A flexible touch sensor comprising: a base sheet made of resin; a detection electrode provided on one side of the base sheet in a thickness direction; and a circuit wiring provided on the one side of the base sheet and electrically connected to the detection electrode, the flexible touch sensor detecting contact or proximity of a conductor with the detection electrode from a change in capacitance of the detection electrode due to the conductor contacting or proximity to the detection electrode, the detecting electrode further includes at least one of a carbon layer provided on at least a part of the surface of the detecting electrode opposite to the base sheet, and a carbon layer having a volume resistivity of 1 Ω cm or less and a surface resistance of 1000 Ω / □ or less, and also serving as the detecting electrode; a flexible touch sensor, wherein a portion of the base sheet on the side where the detection electrode is provided, other than a portion where the carbon layer is provided, is covered with an insulating protective layer. [2] The flexible touch sensor according to [1], wherein a carbon layer is provided over the entire surface of the detection electrode opposite the base sheet. [3] The flexible touch sensor described in [1], wherein, when viewed in the thickness direction of the base sheet, the detection electrode is mesh-shaped and has a ring-shaped portion and partition portions that divide the inside of the ring-shaped portion into multiple regions. [4] The flexible touch sensor described in [2], wherein, when viewed in the thickness direction of the base sheet, the detection electrode is mesh-shaped and has a ring-shaped portion and partition portions that divide the inside of the ring-shaped portion into multiple regions. [5] A touch sensor module including the flexible touch sensor according to any one of [1] to [4]. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a flexible touch sensor and a touch sensor module that can adequately protect detection electrodes, have probe points for inspecting electrical characteristics, and can suppress noise and false detection due to the probe points. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a front view of a flexible touch sensor according to an embodiment, viewed from the base sheet side. [Figure 2] 2 is a cross-sectional view of the flexible touch sensor shown in FIG. 1 along the line AA. [Figure 3] 2 is a front view showing a detection electrode of the flexible touch sensor of FIG. 1. [Figure 4] FIG. 10 is a front view showing another example of the detection electrode. [Figure 5] FIG. 10 is a front view showing another example of the detection electrode. [Figure 6] 2 is a cross-sectional view showing a step in the manufacture of the flexible touch sensor of FIG. 1. [Figure 7] 2 is a cross-sectional view showing a step in the manufacture of the flexible touch sensor of FIG. 1. [Figure 8]FIG. 10 is a cross-sectional view showing a flexible touch sensor according to another example of the embodiment. [Figure 9] 1 is a cross-sectional view illustrating a touch sensor module according to an embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0011] [Flexible touch sensor] The flexible touch sensor of the present invention will be described below with reference to the drawings, showing an example. 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.

[0012] As shown in Figures 1 and 2, the flexible touch sensor 1 of the embodiment is a capacitance-type touch sensor for detecting operation on an operation surface, and includes a base sheet 10, three detection electrodes 20, circuit wiring 30, a carbon layer 40, and an insulating protective layer 50.

[0013] Three detection electrodes 20 are provided on a first surface 10a in the thickness direction of the base sheet 10, and a carbon layer 40 is provided on the surface of each detection electrode 20 opposite the base sheet 10. In addition, circuit wiring 30 electrically connected to the detection electrodes 20 is provided on the first surface 10a of the base sheet 10. An insulating protective layer 50 is provided on the side of the base sheet 10 where the detection electrodes 20, the circuit wiring 30, and the carbon layer 40 are provided, so as to cover the areas other than the area where the carbon layer 40 is provided.

[0014] The base sheet 10 is a flexible resin sheet. In the example shown in FIG. 1, the base sheet 10 has a main body portion 11 that is rectangular in plan view, and a strip-shaped portion 12 that extends so as to protrude from a part of one short side of the main body portion 11. 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.

[0015] A transparent insulating resin film can be used as the base sheet 10. Here, "insulating" means that the electrical resistance is 1 MΩ or more, preferably 10 MΩ or more. Also, "transparent" means that the light transmittance measured according to JIS K7136 is 50% or more.

[0016] Examples of materials that can be used to form the base sheet 10 include polyester (such as polyethylene terephthalate (PET)), polycarbonate (PC), acrylic resin, cyclic polyolefin resin, and triacetyl cellulose. The base sheet 10 can be formed of one type of material or two or more types of materials.

[0017] In order to ensure sufficient strength and rigidity, the average thickness of the base sheet 10 is preferably 10 μm or more, and more preferably 25 μm or more. In order to easily reduce the thickness of the flexible touch sensor 1, the average thickness of the base sheet 10 is preferably 250 μm or less, and more preferably 188 μm or less. The lower and upper limits of the average thickness of the base sheet 10 can be arbitrarily combined, and are, for example, preferably 10 to 250 μm, and more preferably 25 to 188 μm. The average thickness of the base sheet means the average value of thicknesses measured at any 10 points on the base sheet.

[0018] The detection electrode 20 is an electrode for detecting contact or proximity of a conductor. The detection electrode 20 may be of a self-capacitance type or a mutual-capacitance type. 3, the detection electrode 20 in this example has a mesh shape when viewed in the thickness direction of the base sheet 10, and includes a circular annular portion 21 and three linear partitions 22 that divide the inside of the annular portion 21 into multiple regions. All three partitions 22 pass through the center of the annular portion 21, dividing the inside of the annular portion 21 into six equal fan-shaped regions.

[0019] When the detection electrode 20 is mesh-shaped, even if the carbon layer 40 is provided on the entire surface of the detection electrode 20, light can pass through the area that is not blocked by the partition portion 22 inside the annular portion 21. Therefore, with the flexible touch sensor 1 attached to the back surface of the operation panel, the portion of the operation panel where the detection electrode 20 is located can be illuminated from the side opposite the operation panel from the detection electrode 20.

[0020] The shape of the detection electrode 20 is not particularly limited as long as it can ensure sufficient detection sensitivity and detection accuracy for operations on the operation surface. For example, as shown in Fig. 4, the detection electrode 20 may be a detection electrode 20A in which a plurality of linear partitions 22 are provided in a lattice pattern inside a circular ring-shaped portion 21. Alternatively, as shown in Fig. 5, the detection electrode 20B may be a detection electrode in which a plurality of linear partitions 22 parallel to each other are provided inside a circular ring-shaped portion 21. The ring-shaped portion 21 is not limited to a circular ring, and may be a ring having a rectangular, hexagonal, or other shape. The detection electrode 20 may also be a transparent solid electrode having a circular, elliptical, rectangular, or other shape. In this case, by providing the carbon layer 40 only on a portion of the surface of the detection electrode 20, the operation panel can be illuminated through the portion where the carbon layer 40 is not provided.

[0021] The detection electrode 20 can be formed by printing a conductive ink, for example, a transparent conductive film. "Conductive" means that the electrical resistance is less than 1 MΩ. Examples of conductive substances contained in the conductive ink include conductive polymers (polythiophene-based conductive polymers (PEDOT / PSS), indium-doped tin oxide (ITO), etc.), conductive nanowires (silver nanowires, gold nanowires, etc.), metal particles (silver particles, copper particles, gold particles, etc.), and conductive metal oxide particles (ITO particles, etc.). Of these, silver ink is preferred. The conductive ink may contain one type of conductive substance or two or more types of conductive substances.

[0022] In order to easily prevent disconnection, the average thickness of the detection electrodes 20 is preferably 0.05 μm or more, and more preferably 0.1 μm or more. In order to easily reduce the thickness of the flexible touch sensor 1, the average thickness of the detection electrodes 20 is preferably 30 μm or less, and more preferably 20 μm or less. The lower and upper limits of the average thickness of the detection electrodes 20 can be arbitrarily combined, and are, for example, preferably 0.05 to 30 μm, and more preferably 0.1 to 20 μm. The average thickness of the detection electrode is the average value of thicknesses measured at any 10 points on the detection electrode.

[0023] The number of detection electrodes 20 is not limited to three and can be set appropriately, and may be two or less, or may be four or more. 1, the three detection electrodes 20 are each electrically connected by circuit wiring 30 to a connection terminal 14 provided at the tip of the strip portion 12 of the base sheet 10. The connection terminal 14 can be electrically connected to a capacitance detection unit of the circuit board. This allows the flexible touch sensor 1 to detect, from a change in the capacitance of the detection electrode 20, when a conductor comes into contact with or is in proximity to the detection electrode 20.

[0024] The material of the circuit wiring 30 is not particularly limited, and may be the same as the material of the detection electrode 20, for example, and silver ink is preferred. The average thickness of the circuit wiring 30 is not limited to, but may be approximately the same as the average thickness of the detection electrodes 20, for example.

[0025] The carbon layer 40 is provided on the surface of each of the three detection electrodes 20 opposite the base sheet 10. In the example shown in Fig. 1 and Fig. 2, the carbon layer 40 is provided on the entire surface of each detection electrode 20 opposite the base sheet 10. Note that the carbon layer 40 is not limited to being provided on the entire surface of the detection electrode 20, and the carbon layer 40 may be provided on only a portion of the surface of the detection electrode 20.

[0026] The carbon layer 40 is a film containing carbon, and can be formed from a carbon material such as carbon black, graphite, or carbon ink containing carbon nanotubes. The carbon layer 40 provided on the surface of the detection electrode 20 can serve as a probe point to which a probe is brought into contact when testing electrical characteristics. That is, by bringing a probe into contact with the carbon layer 40, the electrical characteristics of the flexible touch sensor 1 can be tested after its manufacture.

[0027] The carbon layer 40, which is made of a carbon material, is strong and does not corrode. Therefore, the portion of the detection electrode 20 covered with the carbon layer 40 is sufficiently protected without the need for a protective layer. Therefore, there are no restrictions on where the carbon layer 40 can be provided on the surface of the detection electrode 20 opposite the base sheet 10, and the carbon layer 40 can be provided freely. When the detection electrode 20 has a pattern such as a grid or mesh, in the past, inspecting whether the pattern was formed properly required visual inspection of whether the lines were thick or thin, blurred, or broken. However, if a carbon layer 40 is provided on the entire surface of the detection electrode 20, or if the carbon layer 40 is provided at multiple locations to serve as probe points, it becomes possible to inspect whether the pattern is formed properly more accurately and easily by contacting the probe. The carbon layer may be further formed on the connection terminal 14 of the circuit wiring 30. This also makes it possible to protect the contact points of the circuit wiring 30.

[0028] In order to adequately protect the detection electrodes 20 and to prevent damage due to contact with a probe during testing, the average thickness of the carbon layer 40 is preferably 0.1 μm or more, and more preferably 1.0 μm or more. In order to easily reduce the thickness of the flexible touch sensor 1, the average thickness of the carbon layer 40 is preferably 50 μm or less, and more preferably 25 μm or less. The lower and upper limits of the average thickness of the carbon layer 40 can be arbitrarily combined, and are, for example, preferably 0.1 to 50 μm, and more preferably 1.0 to 25 μm. The average thickness of the carbon layer is the average value of thicknesses measured at any 10 points on the carbon layer.

[0029] The insulating protective layer 50 is a film made of an insulating material. The insulating protective layer 50 is provided on the first surface 10a side of the base sheet 10 so as to cover the entire surface except for the portion where the carbon layer 40 is provided.

[0030] The insulating material constituting the insulating protective layer 50 is not particularly limited, but a resist ink is preferable. Examples of insulating resins contained in the resist ink include acrylic resin, polyester resin, polystyrene resin, polyamide resin, chlorinated polyolefin resin, chlorinated ethylene-vinyl acetate copolymer, chlorinated vinyl-vinyl acetate copolymer, cyclized rubber, and coumarone-indene resin. Among these, acrylic resin, which has good light transmittance, is preferable in terms of easy bending and taking advantage of the advantages of a transparent film. The insulating resin constituting the insulating protective layer 50 may be one type or two or more types.

[0031] In order to ensure sufficient strength and rigidity and to adequately protect the circuit wiring 30, the average thickness of the insulating protective layer 50 is preferably 5 μm or more, and more preferably 10 μm or more. In order to easily reduce the thickness of the flexible touch sensor 1, the average thickness of the insulating protective layer 50 is preferably 250 μm or less, and more preferably 100 μm or less. The lower and upper limits of the average thickness of the insulating protective layer 50 can be arbitrarily combined, and are, for example, preferably 5 to 250 μm, and more preferably 10 to 100 μm. The average thickness of the insulating protective layer is the average value of thicknesses measured at any 10 points on the insulating protective layer.

[0032] The manufacturing method of the flexible touch sensor 1 is not particularly limited, and known methods can be used. For example, as shown in FIG. 6, silver ink or the like is used for screen printing on the first surface 10a of the base sheet 10 to form the detection electrodes 20 and circuit wiring 30. Next, as shown in FIG. 7, carbon ink is used for screen printing on the surface of the detection electrodes 20 to form a carbon layer 40. Next, resist ink is printed on the first surface 10a of the base sheet 10 in areas other than the area where the carbon layer 40 is provided, to form an insulating protective layer 50. In this way, the flexible touch sensor 1 is obtained.

[0033] As described above, in the flexible touch sensor 1, the carbon layer 40 is provided on the surface of the detection electrode 20 opposite the base sheet 10, and the portion of the base sheet 10 on the side where the detection electrode 20 is provided other than the portion where the carbon layer 40 is provided is covered with the insulating protective layer 50. This allows the detection electrode 20 to be adequately protected while allowing electrical characteristics to be inspected using the carbon layer 40 as a probe point. Furthermore, in the flexible touch sensor 1, because the carbon layer 40 is laminated on the surface of the detection electrode 20, noise due to parasitic capacitance is less likely to occur compared to when probe points are provided close to the periphery of the detection electrode, and false detection can be suppressed.

[0034] The flexible touch sensor of the present invention is not limited to the flexible touch sensor 1 described above. For example, it may be the flexible touch sensor 2 illustrated in Fig. 8. The same parts in Fig. 8 as those in Fig. 2 are denoted by the same reference numerals, and the description thereof will be omitted. The flexible touch sensor 2 is similar to the flexible touch sensor 1, except that a carbon layer 40 is provided on a part of the surface of the detection electrode 20 opposite the base sheet 10, and the remaining part of the surface of the detection electrode 20 is covered with an insulating protective layer 50.

[0035] [Touch sensor module] The touch sensor module of the present invention is a touch sensor module equipped with the flexible touch sensor of the present invention. The touch sensor module of the present invention can adopt any known embodiment except that it is equipped with the flexible touch sensor of the present invention. In the touch sensor module of the present invention, for example, the flexible touch sensor of the present invention is attached to the back surface of an operation panel. An example of the touch sensor module of the present invention will be described below.

[0036] As shown in FIG. 9, the touch sensor module 100 (hereinafter also referred to as "module 100") of the embodiment includes an operation panel 110 having an operation surface 112, a frame member 120, an internal light source 130, and a flexible touch sensor 1.

[0037] The operation panel 110 and the frame member 120 are fixed to each other by springs 140 while being spaced apart from each other. Fixing is not limited to using springs, and the operation panel 110 and the frame member 120 may also be fixed to each other by positioning pins, screws, or the like. The flexible touch sensor 1 is attached to the back surface of the operation panel 110 via an adhesive layer 60 provided on the second surface 10b of the base sheet 10. In the module 100, the surface of the operation panel 110 opposite to the flexible touch sensor 1 serves as the operation surface 112. A touch operation on the operation surface 112 of the operation panel 110 can be detected by a change in the capacitance of the detection electrodes 20 of the flexible touch sensor 1.

[0038] The method for attaching the flexible touch sensor 1 to the operation panel 110 is not particularly limited, and examples include a diaphragm method and a roller method. Among these, the diaphragm method is preferred because it is easy to prevent air bubbles from being mixed in between the flexible touch sensor 1 and the operation panel 110 and it is easy to attach the flexible touch sensor 1 neatly.

[0039] There are no particular limitations on the operation panel 110, and an example thereof is one that includes a panel body and a decorative layer formed on the surface of the panel body. Examples of materials that form the panel body include resins such as PC and acrylic resin, and glass.

[0040] The decorative layer is a layer on which any decoration such as ornaments, letters, figures, symbols, patterns, or combinations of these, or combinations of these with colors, is applied. The decorative layer can be formed, for example, by printing on the panel body. Note that the operation panel 110 does not necessarily have to have a decorative layer.

[0041] In order to easily obtain sufficient strength, the average thickness of operation panel 110 is preferably 0.05 mm or more, and more preferably 2 mm or more. In order to easily prevent module 100 from becoming excessively thick, the average thickness of operation panel 110 is preferably 10 mm or less, and more preferably 5 mm or less. The lower and upper limits of the average thickness of operation panel 110 can be arbitrarily combined, and for example, a range of 0.05 to 10 mm is preferable, and a range of 2 to 5 mm is more preferable. The average thickness of the operation panel is the average value of thicknesses measured at any 10 points on the operation panel.

[0042] Examples of materials that can be used to form the frame member 120 include resin, glass, and inorganic materials. Examples of resins that can be used to form the frame member 120 include the same resins that are exemplified as resins that can be used to form the panel body.

[0043] In the module 100, an internal light source 130 is disposed on the flexible touch sensor 1 side of the frame member 120, on the opposite side of the carbon layer 40 from the operation panel 110. As a result, in the module 100, light emitted from the internal light source 130 passes through the detection electrode 20 and the inside of the annular portion of the carbon layer 40, illuminating characters and the like on the operation surface 112 of the operation panel 110.

[0044] The technical scope of the present invention is not limited to the above-described embodiment. For example, if the carbon layer has a sufficiently low resistance, instead of laminating the detection electrode 20 and the carbon layer 40, only the carbon layer 40 that also serves as the detection electrode 20 may be provided. Similarly, when forming a carbon layer in the portion of the connection terminal 14 of the circuit wiring 30, instead of laminating the circuit wiring 30 and the carbon layer, only the carbon layer that also serves as the circuit wiring 30 may be formed. In such a case, a flexible touch sensor can be manufactured by simply forming a carbon layer without providing a protective layer, and the probe points can also be set freely. Note that "sufficiently low resistance" refers to a volume resistivity of 1 Ω·cm or less and a surface resistivity of 1000 Ω / □ or less.

[0045] Also, a capacitance detection unit (IC) may be provided on the surface of the frame member 120 on the flexible touch sensor 1 side, and the frame member 120 may serve as a control board. Furthermore, the control board may be connected to the flexible touch sensor 1 via a connector. 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. [Explanation of symbols]

[0046] 1, 2...flexible touch sensor, 10...base material sheet, 10a...first surface, 10b...second surface, 20...detection electrode, 30...circuit wiring, 40...carbon layer, 50...insulating protective layer, 60...adhesive layer, 100...touch sensor module, 110...operation panel, 120...frame member, 130...internal light source, 140...spring.

Claims

1. A flexible touch sensor comprising: a base sheet made of resin; a detection electrode provided on one side in a thickness direction of the base sheet; and circuit wiring provided on the one side of the base sheet and electrically connected to the detection electrode, the flexible touch sensor detecting contact or proximity of a conductor with the detection electrode from a change in capacitance of the detection electrode caused by the conductor coming into contact with or proximity to the detection electrode, The electrode further includes at least one of a carbon layer provided on at least a part of the surface of the detection electrode opposite to the base sheet, and a carbon layer having a volume resistivity of 1 Ω cm or less and a surface resistance of 1000 Ω / □ or less, and also serving as the detection electrode; the carbon layer is made of a carbon material, the carbon layer is provided on the entire surface of the detection electrode opposite to the base sheet, a flexible touch sensor, wherein a portion of the base sheet on the side where the detection electrode is provided, other than a portion where the carbon layer is provided, is covered with an insulating protective layer.

2. The flexible touch sensor according to claim 1 , wherein, when viewed in the thickness direction of the base sheet, the detection electrode is in a mesh shape having an annular portion and partition portions that divide the inside of the annular portion into multiple regions.

3. A touch sensor module comprising the flexible touch sensor according to claim 1 or 2.

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