Touch sensor

Abstract

A touch sensor (1) comprises: a base material (40) made of an insulating material; a first touch electrode (10) positioned below the base material (40); a second touch electrode (20) positioned above the base material (40); and an antenna electrode (30) positioned on the same layer as the first touch electrode (10) or below the first touch electrode (10). The second touch electrode (20) is a mesh electrode made of metal thin wires formed in a mesh shape. When the wavelength of a radio wave used by the touch sensor (1) is defined as λ, the distance between the antenna electrode (30) and the second touch electrode (20) is λ / 32 or less.

Description

Touch Sensor

[0001] The present disclosure relates to a touch sensor, and more particularly to a touch sensor having an antenna function.

[0002] Electronic devices such as mobile terminals, including smartphones and tablets, use displays (touch panels) that include a touch sensor and a display panel for detecting user input operations. Known touch sensors use a capacitance-based method to detect user input operations. A capacitance-based touch sensor detects the position touched by the user by detecting a change in capacitance, which occurs when the user's finger touches or approaches the display screen, using a touch electrode.

[0003] Furthermore, mobile terminals such as smartphones and tablets are equipped with antennas for transmitting and receiving radio waves. The antennas are typically located on the display panel of the mobile terminal's display, but as displays become thinner, smaller, and lighter, the space available for locating the antenna on the display panel is decreasing. Therefore, a technology has been proposed for a display that includes a touch sensor and a display panel, in which the antenna is mounted on the touch sensor (see, for example, Patent Document 1).

[0004] Patent No. 6421077

[0005] In a touch sensor having a touch electrode and an antenna electrode (antenna) arranged thereon, if the touch electrode is arranged on the top surface side of the touch sensor and the antenna electrode is arranged on the bottom surface side of the touch sensor, radio waves emitted from the antenna electrode are reflected by the touch electrode and are less likely to be emitted from the touch surface side to the outside of the touch sensor.

[0006] The present disclosure has been made to solve such problems, and aims to provide a touch sensor that can radiate radio waves from the antenna electrode in the forward direction of the touch sensor, even if a touch electrode that is a mesh electrode is arranged on the top surface side and an antenna electrode is arranged on the bottom surface side.

[0007] In order to achieve the above object, one aspect of the touch sensor according to the present disclosure comprises a substrate made of an insulating material, a first touch electrode located below the substrate, a second touch electrode located above the substrate, and an antenna electrode located in the same layer as the first touch electrode or below the first touch electrode, wherein the second touch electrode is a mesh electrode made of thin metal wires formed in a mesh shape, and where λ is the wavelength of the radio waves used, the distance between the antenna electrode and the second touch electrode is λ / 32 or less.

[0008] According to the present disclosure, even if a touch electrode that is a mesh electrode is arranged on the top surface side and an antenna electrode is arranged on the bottom surface side, radio waves from the antenna electrode can be radiated in the front direction of the touch sensor.

[0009] FIG. 1 is a plan view schematically illustrating a touch sensor according to an embodiment. FIG. 2 is an enlarged plan view of a touch sensor according to an embodiment. FIG. 3 is an enlarged cross-sectional view of a touch sensor according to an embodiment. FIG. 4 is a diagram illustrating the configuration of a touch sensor of a comparative example. FIG. 5 is a diagram for explaining the effects of a touch sensor according to an embodiment. FIG. 6 is a diagram illustrating models of touch sensors of a comparative example and an example used in a simulation. FIG. 7 is a diagram illustrating the electric field distribution of each of the touch sensors of the comparative example and the example shown in FIG. 6. FIG. 8 is a diagram illustrating a model and layer structure of a touch sensor used in an experiment to verify the effects of a touch sensor according to an embodiment. FIG. 9 is a diagram illustrating the configurations of five samples 1 to 5 used in an experiment to verify the effects of a touch sensor according to an embodiment. FIG. 10 is a diagram illustrating the front gain of the antenna in the five samples 1 to 5 shown in FIG. 9. FIG. 11 is a diagram illustrating the electric field distribution in the five samples 1 to 5 shown in FIG. 9. FIG. 12 is an enlarged cross-sectional view of a touch sensor according to Modification 1. FIG. 13 is an enlarged cross-sectional view of a touch sensor according to Modification 2. FIG. 14 is an enlarged plan view of a touch sensor according to Modification 3. FIG. 15 is an enlarged plan view of a touch sensor according to the fourth modification.

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that each of the embodiments described below represents a specific example of the present disclosure. Therefore, the numerical values, shapes, materials, components, the arrangement and connection of the components, processes (steps), and the order of the processes shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Therefore, among the components in the following embodiments, components that are not described in the independent claims that represent the superordinate concept of the present disclosure will be described as optional components.

[0011] Note that each figure is a schematic diagram and is not necessarily an exact illustration. Therefore, the scales and the like do not necessarily match in each figure. Furthermore, in each figure, substantially the same configuration is assigned the same reference numeral, and duplicate explanations are omitted or simplified. Furthermore, in this specification, the terms "up" and "down" do not necessarily refer to the upward direction (vertically upward) and downward direction (vertically downward) in absolute spatial recognition.

[0012] (Embodiment) First, the overall configuration of a touch sensor 1 according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a plan view schematically showing the touch sensor 1 according to the embodiment.

[0013] The touch sensor 1 has a function of detecting an input operation by a user. The touch sensor 1 in this embodiment is a capacitance-type touch sensor, and detects the position touched by the user by detecting a change in capacitance that occurs when the user's finger, pen, or the like touches or approaches the display screen using a touch electrode.

[0014] 1, in order to detect a position touched by a user, the touch sensor 1 includes a first touch electrode 10 and a second touch electrode 20. The first touch electrode 10 and the second touch electrode 20 are sensor electrodes that detect a position touched by a user.

[0015] Specifically, the touch sensor 1 is a mutual capacitance type touch sensor that detects a position touched by a user by detecting a change in electrostatic capacitance between the first touch electrode 10 and the second touch electrode 20. In this case, for example, the first touch electrode 10 functions as a receiving electrode (Rx electrode), and the second touch electrode 20 functions as a transmitting electrode (Tx electrode). Note that the first touch electrode 10 may function as the transmitting electrode (Tx electrode), and the second touch electrode 20 may function as the receiving electrode (Rx electrode).

[0016] 1 , the first touch electrode 10 extends along a first direction. The first touch electrode 10 extends linearly. A plurality of first touch electrodes 10 are provided. The plurality of first touch electrodes 10 are parallel to each other.

[0017] The second touch electrode 20 extends along a second direction intersecting the first direction. The second touch electrode 20 also extends linearly. A plurality of second touch electrodes 20 are provided. The plurality of second touch electrodes 20 are parallel to each other.

[0018] In this embodiment, the first touch electrode 10 and the second touch electrode 20 are orthogonal to each other. Specifically, the multiple first touch electrodes 10 extend along the column direction, and the multiple second touch electrodes 20 extend in the row direction orthogonal to the column direction. Note that the first touch electrode 10 and the second touch electrode 20 do not have to be orthogonal to each other. In other words, the angle formed by the linear first touch electrode 10 and the linear second touch electrode 20 does not have to be 90°.

[0019] As shown in FIG. 1 , the touch sensor 1 has an active area 1a (valid area) and an inactive area 1b (invalid area) that is different from the active area 1a. The active area 1a is an area located inside the inactive area 1b. The inactive area 1b is an area located outside the active area 1a. The active area 1a is a rectangular area indicated by a dashed line in FIG. 1 . In this embodiment, the inactive area 1b surrounds the entire active area 1a. Specifically, the inactive area 1b is a rectangular frame-shaped area (picture frame-shaped) that surrounds the active area 1a. The inactive area 1b is an outer peripheral area located at the outer edge of the touch sensor 1.

[0020] A flexible wiring board 2 is connected to the inactive area 1b. For example, the touch sensor 1 and the flexible wiring board 2 are joined in the inactive area 1b by a conductive joining member such as an anisotropic conductive film (ACF) or solder. The flexible wiring board 2 may be a wiring board having only a wiring function in which only a plurality of metal wires are formed, or may be a COF (chip on film) on which a semiconductor chip of a driver IC or the like is mounted in addition to the plurality of metal wires.

[0021] In this embodiment, the active area 1a is an area touched by the user (a view area viewed by the user). In other words, the active area 1a is an area that detects an input operation by the user. Therefore, the first touch electrode 10 and the second touch electrode 20 are present in the active area 1a. On the other hand, the inactive area 1b is an area that is not visible to the user. In the inactive area 1b, a plurality of metal wires (wirings) are routed to electrically connect the first touch electrode 10, the second touch electrode 20, and the antenna electrode 30 to the flexible wiring substrate 2.

[0022] 1 , the touch sensor 1 includes an antenna electrode 30 as an antenna. That is, the touch sensor 1 is a touch sensor with an antenna function. The touch sensor 1 including the antenna electrode 30 can be used in displays mounted on electronic devices such as mobile terminals such as smartphones and tablets, or car navigation systems. A display equipped with such an antenna electrode 30 is called an antenna-on-display (AOD).

[0023] The antenna electrode 30 emits radio waves into space and receives radio waves from space. The touch sensor 1 having the antenna electrode 30 can be used, for example, in devices for 3G to 5G communications. The communication frequency used by the touch sensor 1 (the communication frequency of the antenna electrode 30) is, for example, a predetermined frequency band of 0.5 GHz to 30 GHz. For example, the communication frequency of the antenna electrode 30 is the 700 MHz band / 800 MHz band / 900 MHz band, 1.5 GHz band, 1.7 GHz band, 2 GHz band, 2.5 GHz band, 3.4 GHz band / 3.5 GHz band, 3.7 GHz band / 4.5 GHz band, or 28 GHz band.

[0024] The antenna electrode 30 is formed in a predetermined pattern. In the present embodiment, the antenna electrode 30 is disposed in the active region 1 a. The antenna electrode 30 is also disposed between two adjacent first touch electrodes 10.

[0025] Next, a detailed structure of the touch sensor 1 according to the embodiment will be described with reference to Fig. 2 and Fig. 3. Fig. 2 is an enlarged plan view of the touch sensor 1 according to the embodiment. Fig. 2 is an enlarged view of an area II surrounded by a dashed line in Fig. 1. Fig. 3 is an enlarged cross-sectional view of the touch sensor 1 according to the embodiment. Fig. 3 is a cross-sectional view taken along line III-III in Fig. 2.

[0026] 2 , in the present embodiment, each of the first touch electrode 10 and the second touch electrode 20 is a mesh electrode made of thin metal wires formed in a mesh shape. That is, each of the first touch electrode 10 and the second touch electrode 20 is strip-shaped as a whole, but the strip-shaped portion has a mesh pattern.

[0027] The antenna electrode 30 is also a mesh electrode made of thin metal wires formed in a mesh shape. That is, the antenna electrode 30 is a mesh antenna. In this embodiment, the antenna electrode 30 has two L-shapes as a whole, but each L-shape has a mesh pattern in the form of a partial mesh.

[0028] Each of the first touch electrode 10, the second touch electrode 20, and the antenna electrode 30, which are made of thin metal wires formed in a mesh shape, includes a plurality of first thin metal wires extending linearly in one direction and a plurality of second thin metal wires extending linearly in another direction that intersects with the first direction. In the present embodiment, for each of the first touch electrode 10, the second touch electrode 20, and the antenna electrode 30, the direction in which the first thin metal wires extend (one direction) and the direction in which the second thin metal wires extend (another direction) are different from the first direction in which the first touch electrode 10 extends and also different from the second direction in which the second touch electrode 20 extends, but this is not limited to this.

[0029] In each of the first touch electrode 10, the second touch electrode 20, and the antenna electrode 30, the first and second thin metal wires constituting the mesh electrode may or may not be perpendicular to each other. In each of the first touch electrode 10, the second touch electrode 20, and the antenna electrode 30, the first thin metal wires are parallel to each other, and the second thin metal wires are also parallel to each other.

[0030] In each of the first touch electrode 10, the second touch electrode 20, and the antenna electrode 30, the plurality of first thin metal wires and the plurality of second thin metal wires are formed on the same plane, and therefore the plurality of first thin metal wires and the plurality of second thin metal wires are integrated at the intersections where the first thin metal wires and the second thin metal wires intersect.

[0031] The thin metal wires (first thin metal wire, second thin metal wire) that make up the first touch electrode 10, the second touch electrode 20, and the antenna electrode 30 are fine metal wires with a line width on the order of micrometers. Specifically, the line width of the thin metal wires that make up the first touch electrode 10, the second touch electrode 20, and the antenna electrode 30 is 100 μm or less. In the present embodiment, the line width of the thin metal wires that make up the first touch electrode 10, the second touch electrode 20, and the antenna electrode 30 is 1 μm to 30 μm.

[0032] In this way, by forming the first touch electrode 10, the second touch electrode 20, and the antenna electrode 30 as mesh electrodes, the first touch electrode 10, the second touch electrode 20, and the antenna electrode 30 can be made transparent. In other words, the first touch electrode 10, the second touch electrode 20, and the antenna electrode 30 can be made less visible to the user. Therefore, the touch sensor 1 of the present embodiment is transparent enough to allow the user to see through the first touch electrode 10, the second touch electrode 20, and the antenna electrode 30, even if they are made of metal wires. Furthermore, the touch sensor 1 is in the form of a film and is flexible. Therefore, the touch sensor 1 of the present embodiment is a transparent conductive film. In the touch sensor 1 configured in this manner, the active area 1a is a transparent area. This allows a user to view an image displayed on a display panel through the transparent active area 1a, or to operate a mobile terminal or the like by touching the active area 1a with a finger. The inactive area 1b may be a transparent area or a non-transparent area. The inactive area 1b is an area that is not visible to the user because it is covered by the housing of the mobile terminal or the like.

[0033] 3 , the touch sensor 1 further includes a substrate 40, a first insulating layer 50, and a second insulating layer 60 in addition to the first touch electrode 10, the second touch electrode 20, and the antenna electrode 30. In the present embodiment, the surface on the upper side of the touch sensor 1 (the surface on the second touch electrode 20 side of the substrate 40) is the touch surface that is touched by the user.

[0034] The base material 40 is an insulating substrate made of an insulating material. Specifically, the base material 40 is an insulating resin substrate made of an insulating resin material. In the present embodiment, the base material 40 is made of a light-transmitting resin material. Specifically, the base material 40 is made of a transparent resin material.

[0035] The substrate 40 is a base substrate that serves as the base of the touch sensor 1. The substrate 40 may be a flexible sheet-like film substrate or a rigid substrate. The substrate 40 is a light-transmitting substrate that is translucent to visible light. Specifically, the substrate 40 is a transparent substrate with high transmittance that allows the other side to be seen through. The substrate 40 is a flat, planar plate with a constant thickness. The top view shape of the substrate 40 is, for example, rectangular, but is not limited to this.

[0036] Examples of the light-transmitting resin material that can be used to form the substrate 40 include polyethylene terephthalate (PET) resin, polyimide (PI) resin, polyethylene naphthalate (PEN) resin, cycloolefin resin, polycarbonate resin, and acrylic resin. In this embodiment, the substrate 40 is a transparent PET film made of PET. Alternatively, a transparent glass substrate may be used as the substrate 40.

[0037] The first insulating layer 50 is located below the base material 40. In this embodiment, the first insulating layer 50 is formed on the lower surface of the base material 40. On the other hand, the second insulating layer 60 is located above the base material 40. In this embodiment, the second insulating layer 60 is formed on the upper surface of the base material 40.

[0038] The first insulating layer 50 and the second insulating layer 60 are made of an insulating material. The first insulating layer 50 and the second insulating layer 60 are resin layers made of a resin material. In this embodiment, the first insulating layer 50 and the second insulating layer 60 are made of a light-transmitting insulating resin material. Specifically, the first insulating layer 50 and the second insulating layer 60 are transparent layers made of a transparent insulating resin material. The resin material making up the first insulating layer 50 and the second insulating layer 60 is a thermosetting resin or an ultraviolet-curing resin. Specifically, the resin material making up the first insulating layer 50 and the second insulating layer 60 may be, for example, an acrylic resin, a PET resin, a polyimide resin, a cycloolefin resin, or a polycarbonate resin. In this embodiment, the first insulating layer 50 and the second insulating layer 60 are made of a transparent acrylic resin. The first insulating layer 50 and the second insulating layer 60 each have a uniform thickness. Furthermore, the thickness of the first insulating layer 50 and the thickness of the second insulating layer 60 may be the same or different.

[0039] The first touch electrode 10 is provided on the first insulating layer 50 located below the substrate 40. Therefore, the first touch electrode 10 is located below the substrate 40. The antenna electrode 30 is also provided on the first insulating layer 50. Therefore, the antenna electrode 30 is also located below the substrate 40, similar to the first touch electrode 10. In the present embodiment, the first touch electrode 10 and the antenna electrode 30 are both provided on the first insulating layer 50, and therefore the antenna electrode 30 is provided in the same layer as the first touch electrode 10. In other words, the first touch electrode 10 and the antenna electrode 30 are arranged on the bottom surface side (the first insulating layer 50 side of the substrate 40) of the touch sensor 1, which is the surface facing the display.

[0040] The thin metal wires constituting the first touch electrode 10 and the antenna electrode 30 are made of a metal material such as copper or silver. In the present embodiment, the thin metal wires constituting the first touch electrode 10 and the thin metal wires constituting the antenna electrode 30 are made of the same metal material. Specifically, the thin metal wires constituting the first touch electrode 10 and the thin metal wires constituting the antenna electrode 30 are both copper wirings containing copper as a main material. Furthermore, the first touch electrode 10 and the antenna electrode 30 are formed in the same process. Note that the thin metal wires constituting the first touch electrode 10 and the thin metal wires constituting the antenna electrode 30 may be made of different metal materials or may be formed in different processes. Furthermore, the first touch electrode 10 may be made of a transparent conductive material such as ITO (indium tin oxide) instead of a metal material.

[0041] The thin metal wires constituting the first touch electrode 10 and the thin metal wires constituting the antenna electrode 30 are embedded in grooves provided in the first insulating layer 50. Specifically, the thin metal wires constituting the first touch electrode 10 and the thin metal wires constituting the antenna electrode 30 are embedded in the grooves of the first insulating layer 50 so that their surfaces are exposed.

[0042] The grooves provided in the first insulating layer 50 are linear recesses formed so as to recess the surface of the first insulating layer 50. The first insulating layer 50 provided with grooves can be formed by an imprinting method. In this case, the first insulating layer 50 is an imprint layer, and the first insulating layer 50 with grooves formed therein can be formed by pressing a die member (mold) having protrusions corresponding to the grooves against the first insulating layer 50.

[0043] The first insulating layer 50 having grooves can also be formed by a method other than the imprinting method. For example, after forming a flat first insulating layer 50, grooves can be formed in the first insulating layer 50. In this case, the grooves can be formed by cutting or etching the surface of the flat first insulating layer 50 using laser scribing or the like. Also, the first touch electrode 10 may be formed on the flat surface of the first insulating layer 50 without forming grooves in the first insulating layer 50.

[0044] Meanwhile, the second touch electrode 20 is provided on the second insulating layer 60 located above the substrate 40. Therefore, the second touch electrode 20 is located above the substrate 40. In other words, the second touch electrode 20 is arranged on the top surface side (the second insulating layer 60 side of the substrate 40) of the touch sensor 1, which is the operation side surface. In this way, the second touch electrode 20 is provided on a layer separate from the layer on which the first touch electrode 10 and the antenna electrode 30 are provided.

[0045] The thin metal wires constituting the second touch electrode 20 are made of a metal material such as copper or silver. The thin metal wires constituting the second touch electrode 20 may be made of the same metal material as the thin metal wires constituting the first touch electrode 10, or may be made of a different metal material. In this embodiment, the thin metal wires constituting the second touch electrode 20 are copper wirings mainly made of copper, similar to the first touch electrode 10. Note that the second touch electrode 20 may be made of a transparent conductive material such as ITO (indium tin oxide) instead of a metal material.

[0046] Furthermore, the thin metal wires constituting the second touch electrode 20 are embedded in grooves provided in the second insulating layer 60. Specifically, the thin metal wires constituting the second touch electrode 20 are embedded in the grooves of the second insulating layer 60 so that the surfaces thereof are exposed.

[0047] The grooves provided in the second insulating layer 60 are linear recesses formed so as to recess the surface of the second insulating layer 60. The second insulating layer 60 provided with the grooves can be formed by an imprinting method, similar to the first insulating layer 50. In this case, the second insulating layer 60 is an imprint layer, and the second insulating layer 60 with the grooves formed therein can be formed by pressing a die member (mold) having protrusions corresponding to the grooves against the second insulating layer 60.

[0048] The second insulating layer 60 having grooves can also be formed by a method other than the imprinting method. For example, after forming a flat second insulating layer 60, grooves may be formed in the second insulating layer 60 by cutting or etching using laser scribing or the like. Alternatively, the second touch electrode 20 may be formed on the flat surface of the second insulating layer 60 without forming grooves in the second insulating layer 60.

[0049] In this way, in the touch sensor 1, the second touch electrode 20 is arranged on the top surface side (touch surface side) of the touch sensor 1, and the first touch electrode 10 and the antenna electrode 30 are arranged on the bottom surface side of the touch sensor 1.

[0050] As described above, each of the first touch electrode 10, the second touch electrode 20, and the antenna electrode 30 is a mesh electrode made of thin metal wires formed in a mesh shape. In this case, the pitch of the thin metal wires constituting the first touch electrode 10, the pitch of the thin metal wires constituting the second touch electrode 20, and the pitch of the thin metal wires constituting the antenna electrode 30 may be the same or different.

[0051] 3, in the present embodiment, the pitch of the thin metal wires that make up the second touch electrode 20 is larger than the pitch of the thin metal wires that make up the first touch electrode 10, and is also larger than the pitch of the thin metal wires that make up the antenna electrode 30. Furthermore, in the present embodiment, the pitch of the thin metal wires that make up the first touch electrode 10 and the pitch of the thin metal wires that make up the antenna electrode 30 are the same.

[0052] In addition, the line width and thickness of the thin metal wires that make up the first touch electrode 10, the line width and thickness of the thin metal wires that make up the second touch electrode 20, and the line width and thickness of the thin metal wires that make up the antenna electrode 30 may be the same or different.

[0053] In the touch sensor 1 configured in this manner, if the wavelength of the radio waves used by the touch sensor 1 (the radio waves transmitted and received by the antenna electrode 30) is λ, the distance d (distance in the thickness direction) between the antenna electrode 30 and the second touch electrode 20 is λ / 32 or less. For example, if the communication frequency used by the touch sensor 1 is in the 3.5 GHz band, the wavelength of the radio waves used by the touch sensor 1 is 85.655 mm. In this case, the distance d between the antenna electrode 30 and the second touch electrode 20 should be approximately 2.68 (85.655 / 32) mm or less. Furthermore, the shorter the distance d between the antenna electrode 30 and the second touch electrode 20, the better, and d = λ / 64 or less is preferable, and d = λ / 128 or less is even better.

[0054] Furthermore, in this embodiment, the distance d (distance in the thickness direction) between the antenna electrode 30 and the second touch electrode 20 is smaller than the distance (distance in the lateral direction) between the antenna electrode 30 and the first touch electrode 10. For example, the distance d between the antenna electrode 30 and the second touch electrode 20 is about 100 μm, and the distance between the antenna electrode 30 and the first touch electrode 10 is about 1 mm. In other words, the distance d between the antenna electrode 30 and the second touch electrode 20 is about 1 / 10 of the distance between the antenna electrode 30 and the first touch electrode 10.

[0055] 4 and 5, the effects of the touch sensor 1 according to the present embodiment will be described, including how the technology of the present disclosure was achieved, while comparing it with a touch sensor 1X of a comparative example. Fig. 4 is a diagram showing the configuration of the touch sensor 1X of the comparative example. Fig. 5 is a diagram for explaining the effects of the touch sensor 1 according to the embodiment.

[0056] In recent years, technology has been studied to mount an antenna (antenna electrode) on a touch sensor having a touch electrode. In this case, if the antenna electrode is disposed on the top surface of the touch sensor, which is the touch surface side, in a touch sensor in which an antenna electrode and a touch electrode are disposed, there is a risk that the touch function will be impaired.

[0057] Therefore, it is conceivable to arrange the touch electrode on the top surface side of the touch sensor and the antenna electrode on the bottom surface side of the touch sensor. For example, as in the comparative touch sensor 1X shown in Figure 4, it is conceivable to form the first touch electrode 10 and the antenna electrode 30 on a first insulating layer 50X located below the substrate 40X, and form the second touch electrode 20 on a second insulating layer 60X located above the substrate 40X. Note that in the comparative touch sensor 1X, if the wavelength of the radio waves used by the touch sensor 1X (the radio waves transmitted and received by the antenna electrode 30) is λ, the distance d between the antenna electrode 30 and the second touch electrode 20 is d = λ / 4.

[0058] However, when the antenna electrode 30 is disposed on the bottom surface side of the touch sensor 1X as in the comparative example shown in Fig. 4, it has been found that radio waves emitted from the antenna electrode 30 are reflected by the second touch electrode 20 disposed on the top surface side, making it difficult for the antenna electrode 30 to radiate radio waves in the front direction of the touch sensor 1X (upward in the paper of Fig. 4) as shown in Fig. 4. In particular, when the second touch electrode 20 is a mesh electrode, the radio waves from the antenna electrode 30 are reflected by the second touch electrode 20 and are not radiated in the front direction of the touch sensor 1X.

[0059] For example, in Figure 4, if the distance d between the antenna electrode 30 and the second touch electrode 20 is set to approximately d = λ / 4 as described above, the spacing (mesh pitch) between the metal fine wires of the second touch electrode 20 as seen from the antenna electrode 30 becomes sufficiently shorter than the wavelength, so the radio waves (radial electric field) emitted from the antenna electrode 30 cannot pass through the second touch electrode 20 and most of them are reflected by the second touch electrode 20.As a result, in Figure 4, the radio waves cannot pass through upward.

[0060] As a result of intensive research by the present inventors into these issues, they discovered that whether or not the radio waves from the antenna electrode pass through the mesh-shaped touch electrode without being reflected by it depends on the distance between the antenna electrode and the touch electrode, and found that even if a touch electrode that is a mesh electrode is placed on the top surface side and an antenna electrode is placed on the bottom surface side, the radio waves from the antenna electrode can be radiated in the forward direction of the touch sensor.

[0061] Specifically, it was found that even if the first touch electrode 10 and the antenna electrode 30 are arranged below the substrate 40 and the second touch electrode 20 is arranged above the substrate 40, as in the touch sensor 1 shown in Fig. 5 , by setting the distance d between the antenna electrode 30 and the second touch electrode 20 to d = λ / 32 or less and making the distance d between the antenna electrode 30 and the second touch electrode 20 sufficiently shorter than the wavelength of the radio waves, the radio waves radiated from the antenna electrode 30 are less likely to be reflected by the second touch electrode 20 arranged on the top surface side and are transmitted through the second touch electrode 20, as shown in Fig. 5. In particular, it was found that by setting d = λ / 32 or less, even if the second touch electrode 20 is a mesh electrode, the radio waves from the antenna electrode 30 are transmitted through the second touch electrode 20 and are radiated in the front direction of the touch sensor 1 (upward in the plane of Fig. 5 ).

[0062] For example, in Fig. 5, when the distance d between the antenna electrode 30 and the second touch electrode 20 is d = λ / 32 or less, the apparent spacing (mesh pitch) of the thin metal wires of the second touch electrode 20 as seen from the antenna electrode 30 appears sufficiently wide compared to the wavelength, so that the radio waves (radial electric field) radiated from the antenna electrode 30 are less likely to be reflected by the second touch electrode 20, and as a result, the radio waves tend to pass upward in Fig. 5. This was discovered by the present inventors and is a finding not previously known.

[0063] A simulation was performed to confirm this effect, and the results of the simulation will be described with reference to Fig. 6 and Fig. 7. Fig. 6 is a diagram showing models of the touch sensors of the comparative example and the example used in the simulation. Fig. 7 is a diagram showing the electric field distribution of each of the touch sensors of the comparative example and the example shown in Fig. 6.

[0064] In this simulation, the distance between the mesh-shaped antenna electrode and the mesh-shaped touch electrode in the touch sensor was changed to obtain the electric field distribution, and it was confirmed whether the radio waves from the antenna electrode could penetrate the touch electrode. Note that the pitch of the touch electrodes (mesh pitch) was set to 600 μm.

[0065] As shown in (a) of Figure 6, in the touch sensor of the comparative example, the antenna electrode and the touch electrode are separated to increase the distance between them. In this simulation, a communication frequency of 3.5 GHz (wavelength λ = 85.655 mm) is assumed, and in the touch sensor of the comparative example, the distance between the antenna electrode and the touch electrode is set to λ / 4. In other words, the distance between the antenna electrode and the touch electrode is set to approximately 21 mm (≒ 85.655 / 4).

[0066] 6B, in the touch sensor of the example, the antenna electrode and the touch electrode are brought closer to each other to reduce the distance between them. Specifically, in the touch sensor of the example, the distance between the antenna electrode and the touch electrode is set to 0.1 mm.

[0067] As a result, as shown in (a) of Fig. 7, in the touch sensor of the comparative example, no electric field exists below the touch electrode, and radio waves from the antenna electrode do not penetrate the touch electrode. On the other hand, as shown in (b) of Fig. 7, in the touch sensor of the example, an electric field exists not only above the touch electrode but also below the touch electrode. In other words, in the touch sensor of the example, radio waves from the antenna electrode penetrate the touch electrode.

[0068] Next, an experiment was conducted to confirm the effect of the pitch (mesh pitch) of the mesh-shaped touch electrode in the touch sensor on the antenna gain, and the results of the experiment will be described using FIGS. 8 to 11. FIG. 8 is a diagram showing the model and layer structure of the touch sensor used in the experiment. FIG. 9 is a diagram showing the configurations of five samples 1 to 5 used in the experiment. FIG. 10 is a diagram showing the front gain of the antenna in the five samples 1 to 5. FIG. 11 is a diagram showing the electric field distribution in the five samples 1 to 5. FIG. 11 shows the electric field distribution in the cross section indicated by the dashed line in FIG. 8. In addition, in (a) to (e) of FIG. 11, the arrow (→) indicates the position of the touch electrode.

[0069] As shown in FIG. 8, the touch sensor model in this experiment includes a 100 μm thick transparent substrate made of PET (corresponding to base material 40), an antenna (corresponding to antenna electrode 30) located on the transparent substrate, a touch electrode (corresponding to second touch electrode 20) located below the transparent substrate, and a 1100 μm thick glass substrate placed on the antenna via a 100 μm thick optically clear adhesive sheet (OCA; Optically Clear Adhesive).

[0070] As shown in FIG. 9, in all of Samples 1 to 5, the antenna was a mesh electrode (pitch: 200 μm) made of copper (Cu) with a thickness of 1.5 μm.

[0071] In addition, Sample 1 did not have a touch electrode, and only the antenna was used instead of the touch electrode and antenna. In Sample 2, the touch electrode was a flat, solid electrode (Cu film) made of copper (Cu) with a thickness of 1.1 μm. In Samples 3 to 5, the touch electrode was a mesh electrode made of copper (Cu) with a thickness of 1.1 μm, and the pitch of the mesh electrode was 200 μm, 400 μm, and 600 μm, respectively.

[0072] As a result, as can be seen from comparing Sample 2 with Samples 3 to 5, as shown in Figure 10, the front gain of the antenna is improved by using a mesh electrode as the touch electrode. Furthermore, as can be seen from Samples 3 to 5, the front gain of the antenna is also improved by increasing the pitch of the mesh-shaped touch electrode. The front gain of the antenna in Figure 10 refers to the antenna gain on the back side (the PET touch electrode side) in Figure 8.

[0073] 11(c) to (d), by increasing the pitch of the mesh-shaped touch electrode, the electric field distribution on the underside (back side) of the touch electrode spreads, and the proportion of radio waves from the antenna electrode that pass through the touch electrode increases. However, as can be seen by comparing (d) and (e) of FIG. 11, even if the touch electrode pitch is increased from 400 μm to 600 μm, the proportion of radio waves from the antenna electrode that pass through the touch electrode does not increase significantly, and the electric field distribution remains almost unchanged. In other words, the touch electrode pitch should be 400 μm or more.

[0074] As described above, the touch sensor 1 according to the present embodiment includes the first touch electrode 10 and the antenna electrode 30 located below the substrate 40, and the mesh-like second touch electrode 20 located above the substrate 40. If the wavelength of the radio waves used by the touch sensor 1 is λ, then the distance between the antenna electrode 30 and the second touch electrode 20 is λ / 32 or less.

[0075] As a result, even if the second touch electrode 20 is a mesh electrode, the radio waves from the antenna electrode 30 can pass through the second touch electrode 20. In other words, even if the second touch electrode 20 is located closer to the top surface (touch surface side) than the antenna electrode 30, the radio waves from the antenna electrode 30 are radiated toward the top surface side without being obstructed by the second touch electrode 20. Thus, according to the touch sensor 1 of the present embodiment, even if the second touch electrode 20, which is a mesh electrode, is arranged on the top surface side and the antenna electrode 30 is arranged on the bottom surface side, the radio waves from the antenna electrode 30 can be radiated in the front direction of the touch sensor 1.

[0076] In addition, in touch sensor 1 according to the present embodiment, the pitch of the thin metal wires constituting second touch electrode 20, which is a mesh electrode, is equal to or greater than the pitch of the thin metal wires constituting antenna electrode 30, which is also a mesh electrode.

[0077] In this way, by increasing the pitch of the second touch electrodes 20, even if the second touch electrodes 20 are located closer to the top surface (touch surface side) than the antenna electrode 30, it is possible to further prevent the radio waves from the antenna electrode 30 from being blocked by the second touch electrodes 20. Therefore, the radio waves from the antenna electrode 30 can be radiated more efficiently in the front direction of the touch sensor 1.

[0078] In this case, the pitch of the thin metal wires constituting the second touch electrode 20 is preferably 200 μm or more, and more preferably 400 μm or more.

[0079] This allows the radio waves from the antenna electrode 30 to sufficiently penetrate the second touch electrode 20. Therefore, the radio waves from the antenna electrode 30 can be radiated in the front direction of the touch sensor 1 more efficiently.

[0080] In this embodiment, the first touch electrode 10 and the antenna electrode 30 are provided in the same layer, resulting in a double-sided single-layer structure in which only one metal layer (first touch electrode 10, antenna electrode 30) is formed on one side of the substrate 40 and only one metal layer (second touch electrode 20) is formed on the other side of the substrate 40, but this is not limited to this.

[0081] Specifically, as shown in FIG. 12 , the touch sensor 1A may have a single-sided, two-layer structure in which the first touch electrode 10 and the antenna electrode 30 are provided on different layers, thereby forming two metal layers (the first touch electrode 10 and the antenna electrode 30) on one side of a substrate 40. In this case, as shown in FIG. 12 , the touch sensor 1A may have a configuration in which a touch sensor substrate 100 on which a touch electrode is formed and an antenna substrate 200 on which an antenna is formed are bonded together with a transparent adhesive layer 300. The touch sensor substrate 100 includes a substrate 40, an antenna electrode 30 embedded in a first insulating layer 50 formed on one side of the substrate 40, and a first touch electrode 10 embedded in a second insulating layer 60 formed on the other side of the substrate 40. The antenna substrate 200 on the touch surface side includes a substrate 70 and a second touch electrode 20 embedded in an insulating layer 80 formed on one side of the substrate 70.

[0082] In addition, in the present embodiment, the first touch electrode 10, the second touch electrode 20, and the antenna electrode 30 are mesh electrodes, but the present invention is not limited to this.

[0083] Specifically, as in the touch sensor 1B shown in Fig. 13, the second touch electrode 20 may remain a mesh electrode, and the first touch electrode 10B and the antenna electrode 30B may be solid electrodes made of metal films. Note that, although both the first touch electrode 10B and the antenna electrode 30B are solid electrodes in Fig. 13, this is not limitative. In other words, at least one of the first touch electrode 10B and the antenna electrode 30B may be a solid electrode, and the remaining may be a mesh electrode.

[0084] (Modification) Although the touch sensor according to the present disclosure has been described above based on the embodiment, the present disclosure is not limited to the above embodiment.

[0085] For example, in the above embodiment, the antenna electrode 30 is disposed between two adjacent first touch electrodes 10, but this is not limiting. Specifically, as in a touch sensor 1C shown in Fig. 14, the antenna electrode 30 may be disposed in the active area 1a near the inactive area 1b. In Fig. 14, the antenna electrode 30 is disposed outside the first touch electrode 10 located at the outermost end of the multiple first touch electrodes 10.

[0086] Furthermore, in the above embodiment, the shape of the antenna electrode 30 is a pattern of two L-shapes, but this is not limited thereto. For example, as in the touch sensor 1D shown in FIG. 15 , the shape of the antenna electrode 30D may be a single linear pattern. Note that the shape of the antenna electrode 30 is not limited to an L-shape or a linear pattern. The antenna electrode 30 may also be a combination of multiple patterns. The antenna electrode 30 may also be formed in multiple locations on the touch sensor 1. In this case, multiple antenna electrodes 30 may be formed only in the active region 1a, or multiple antenna electrodes 30 may be formed in both the active region 1a and the inactive region 1b.

[0087] In the above embodiment, the first touch electrode 10 is embedded in the groove of the first insulating layer 50, but this is not limiting. Specifically, the first touch electrode 10 may be formed on the flat upper surface of the first insulating layer 50 without forming a groove in the first insulating layer 50. Similarly, the second touch electrode 20 may be formed on the flat upper surface of the second insulating layer 60 without forming a groove in the second insulating layer 60.

[0088] In the above embodiment, the first and second thin metal wires constituting the mesh-shaped first touch electrode 10 are formed to be integrated at their intersections, but this is not limited thereto. For example, two first insulating layers 50 may be stacked, with the first thin metal wires formed in one of the two first insulating layers 50 and the second thin metal wires formed in the other of the two first insulating layers 50, and the first and second thin metal wires may be arranged to intersect at different levels so as not to contact each other at their intersections. Similarly, the second touch electrode 20 and antenna electrode 30 formed in a mesh shape may also be arranged to intersect at different levels so as not to contact each other at their intersections.

[0089] Furthermore, in the above embodiment, the touch sensor is a mutual capacitance type that detects a change in capacitance between two touch electrodes (Rx electrode, Tx electrode) of the first touch electrode 10 and the second touch electrode 20 when a touch object such as a finger or a pen touches the touch sensor, but this is not limited to this. For example, the technology disclosed herein can also be applied to a self-capacitance type touch sensor that detects a change in capacitance between a touch object and the touch electrode (Rx electrode) when a touch object such as a finger or a pen touches the touch sensor. In this case, for example, a self-capacitance type touch sensor can be realized by using only the second touch electrode 20 without using the first touch electrode 10 of the first touch electrode 10 and the second touch electrode 20, as shown in FIG. 3 .

[0090] In addition, the present disclosure also includes forms obtained by applying various modifications to the above-described embodiments that would occur to those skilled in the art, and forms realized by arbitrarily combining the components and functions of the embodiments within the scope of the present disclosure. The present disclosure also includes any combination of two or more claims from the multiple claims set forth in the claims at the time of filing, provided that there is no technical contradiction. For example, when a dependent claim set forth in the claims at the time of filing is made into a multiple claim or multiple multiple claims that cite all of the superordinate claims within the scope of the technical contradiction, the present disclosure also includes all combinations of claims included in that multiple claim or multiple multiple multiple claims.

[0091] The touch sensor according to the present disclosure can be used in various electrical devices, including electronic devices such as mobile terminals such as smartphones and tablets, and displays mounted on car navigation systems, etc.

[0092] REFERENCE SIGNS LIST 1, 1A, 1B, 1C, 1D Touch sensor 1a Active area 1b Inactive area 2 Flexible wiring substrate 10, 10B First touch electrode 20 Second touch electrode 30, 30B, 30D Antenna electrode 40, 70 Base material 50 First insulating layer 60 Second insulating layer 80 Insulating layer 100 Touch sensor substrate 200 Antenna substrate 300 Adhesive layer

Claims

1. A touch sensor comprising: a substrate made of an insulating material; a first touch electrode located below the substrate; a second touch electrode located above the substrate; and an antenna electrode located in the same layer as the first touch electrode or below the first touch electrode, wherein the second touch electrode is a mesh electrode made of thin metal wires formed into a mesh shape, and wherein the distance between the antenna electrode and the second touch electrode is λ / 32 or less, where λ is the wavelength of the radio waves used.

2. The touch sensor according to claim 1, wherein the antenna electrode is a mesh electrode made of thin metal wires formed in a mesh shape.

3. The touch sensor according to claim 2, wherein the first touch electrode is a mesh electrode made of thin metal wires formed in a mesh shape.

4. The touch sensor according to claim 3, wherein the pitch of the thin metal wires constituting the second touch electrode is equal to or greater than the pitch of the thin metal wires constituting the antenna electrode.

5. The touch sensor according to claim 4, wherein the pitch of the thin metal wires constituting the second touch electrode is 200 μm or more.

6. The touch sensor according to any one of claims 1 to 5, wherein the antenna electrode is located below the first touch electrode.

7. The touch sensor according to any one of claims 1 to 5, wherein the touch sensor has an active area and a non-active area outside the active area, and the antenna electrode is disposed in the active area.

8. The touch sensor according to claim 7, wherein the antenna electrode is disposed between two adjacent first touch electrodes.

9. The touch sensor according to claim 7, wherein the antenna electrode is disposed in the active area adjacent to the inactive area.

10. The touch sensor according to claim 3, wherein the first touch electrodes are provided in a plurality of lines along a first direction, and the second touch electrodes are provided in a plurality of lines along a second direction intersecting the first direction.

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