Antenna module

Abstract

An antenna module (1) is provided with a transparent conductive film (2) and a flexible wiring board (3). The transparent conductive film (2) has a first base material (41) having a first surface (41a) and a second surface (12b), an antenna (10), a first signal terminal (31), and a second ground layer (52) provided on the first surface (41a), and a first ground layer (51) provided on the second surface (41b). The flexible wiring board (3) has a second base material (42), a third ground (53), and a second signal terminal (31) provided in the second base material (42), and a second signal line (22). The second base material (42) has a first base material layer (421) and a second base material layer (422). The second signal line (22) and the second signal terminal (32) are electrically connected through a via (61) provided in the first base material layer (421).

Description

Antenna Module

[0001] The present disclosure relates to an antenna module including a transparent conductive film.

[0002] Transparent conductive films having fine conductive lines formed on a transparent substrate are known. One such type of transparent conductive film is a film antenna having an antenna formed from fine conductive lines (see, for example, Patent Document 1). Film antennas are used in mobile devices requiring an antenna, such as smartphones or tablet devices. The antenna in a film antenna is formed from fine conductive lines having a line width of 100 μm or less, which is difficult to detect with the naked eye. This allows the antenna to be made transparent, so that the antenna can be easily mounted on a mobile device even if the mobile device is made thinner and lighter, reducing the space available for component placement.

[0003] International Publication No. 2021 / 229994 Special Publication No. 2021-528902

[0004] In a transparent conductive film having an antenna, an antenna and a signal line connected to the antenna are formed on one surface of a transparent substrate, and a ground layer is formed on the other surface of the transparent substrate. In a transparent conductive film having an antenna, crosstalk occurring between the signal lines is an issue.

[0005] Furthermore, in order to connect the transparent conductive film to an external device such as a control circuit, a wiring board such as a flexible wiring board is connected to an end of the transparent conductive film (see, for example, Patent Document 2). An antenna module is constructed by connecting the transparent conductive film having an antenna to the wiring board.

[0006] However, the antenna module structure disclosed in Patent Document 2 is susceptible to noise from the installation surface of the antenna module (the surface to which the transparent conductive film is attached). For example, when the transparent conductive film of the antenna module is attached to a display, the signal lines of the wiring board joined to the transparent conductive film are susceptible to noise from the display. As a result, the performance of the antenna module deteriorates.

[0007] Therefore, it is conceivable to use a wiring board having a ground layer disposed opposite the signal lines and to bond the wiring board to the transparent conductive film so that the ground layer faces the display side.

[0008] However, in this case, in order to expose the signal lines on the wiring board, it is necessary to remove the ground layer by providing a step at the joint between the wiring board and the transparent conductive film, which causes a discontinuity in impedance between the signal lines on the wiring board and the ground layer, resulting in a large transmission loss in the antenna module.

[0009] One aspect of the antenna module according to the present disclosure includes a transparent conductive film and a wiring board connected to the transparent conductive film, wherein the transparent conductive film includes a first substrate having a first surface and a second surface facing away from the first surface, an antenna provided on the first surface, a first signal terminal provided on the first surface and electrically connected to the antenna, a first ground layer provided on the second surface, and a second ground layer provided on the first surface, and the wiring board includes a second substrate, a third ground layer provided on the second substrate, a second signal terminal provided on the second substrate, and a signal line electrically connected to the second signal terminal, and at least a portion of the wiring board is connected to the transparent conductive film. The second substrate is disposed so as to face the transparent conductive film, the first signal terminal and the second signal terminal are electrically connected, the second ground layer and the third ground layer are electrically connected, the second substrate has a first substrate layer and a second substrate layer laminated on the first substrate layer, the signal line is provided between the first substrate layer and the second substrate layer, the signal line and the second signal terminal overlap in a plan view, and the signal line and the second signal terminal are electrically connected via a first via provided in the first substrate layer.

[0010] Another aspect of the antenna module according to the present disclosure includes a transparent conductive film and a wiring board connected to the transparent conductive film, wherein the transparent conductive film includes a first substrate, an antenna provided on the first substrate, a first signal terminal provided on the first substrate and electrically connected to the antenna, a first ground layer provided on the first substrate, and a second ground layer provided on the first substrate that is a layer different from the first ground layer, the wiring board includes a second substrate, a third ground layer provided on the second substrate, a second signal terminal provided on the second substrate, and a signal line electrically connected to the second signal terminal, and at least a portion of the wiring board is connected to the transparent conductive film. The second substrate is arranged to face the film, the first signal terminal and the second signal terminal are electrically connected, the second ground layer and the third ground layer are electrically connected, the second substrate has a first substrate layer and a second substrate layer laminated on the first substrate layer, the signal line is provided between the first substrate layer and the second substrate layer, in a planar view, at least a portion of the signal line overlaps the second signal terminal, and the signal line and the second signal terminal are electrically connected via a first via provided in the first substrate layer.

[0011] According to the present disclosure, it is possible to match the impedance of the wiring board while suppressing the influence of noise received from the installation surface side of the antenna module.

[0012] 1 is a diagram schematically illustrating the configuration of an antenna module according to an embodiment. FIG. 9 is an enlarged view of an end portion of the antenna module in region II surrounded by a dashed line in FIG. 1. FIG. 10 is a cross-sectional view taken along line A-A in FIG. 2. FIG. 11 is a cross-sectional view taken along line B-B in FIG. 2. FIG. 12 is a diagram illustrating a configuration when an antenna module according to a comparative example is installed on a display. FIG. 13 is a diagram illustrating a configuration when an antenna module according to an embodiment is installed on a display. FIG. 14 is a diagram illustrating the impedance of the antenna module shown in FIG. 5. FIG. 15 is a diagram illustrating the impedance of the antenna module according to an embodiment. FIG. 16 is an enlarged view of a joint portion between a transparent conductive film and a flexible wiring board in an antenna module according to a modified example. FIG. 17 is a cross-sectional view taken along line A-A in FIG. 17. FIG. 18 is a cross-sectional view taken along line B-B in FIG. 18.

[0013] 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.

[0014] 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.

[0015] (Embodiment 1) An antenna module 1 according to an embodiment will be described using Figures 1 to 3B. Figure 1 is a diagram schematically illustrating the configuration of an antenna module 1 according to an embodiment. In Figure 1, (a) is a plan view of the antenna module 1, (b) is a cross-sectional view taken along line b-b in (a), and (c) is a cross-sectional view taken along line c-c in (a). Figure 2 is an enlarged view of region II surrounded by a dashed line in Figure 1, illustrating the joint between the transparent conductive film 2 and the flexible wiring substrate 3 in the antenna module 1. In Figure 2, the end of the antenna module 1 in region II is illustrated as being divided into the end of the transparent conductive film 2 and the end of the flexible wiring substrate 3. Specifically, (a) of Fig. 2 shows the end of the transparent conductive film 2 in region II (the peripheral portion of the second ground layer 52), (b) of Fig. 2 shows the end of the flexible wiring board 3 in region II (the peripheral portion of the end of the third ground layer 53), and (c) of Fig. 2 shows the end of the flexible wiring board 3 in region II (the peripheral portion of the end of the second signal line 22). Also, Fig. 3A is a cross-sectional view taken along line A-A in Fig. 2, and Fig. 3B is a cross-sectional view taken along line B-B in Fig. 2. The second ground layer 52 is not shown in (a) of Fig. 1.

[0016] The antenna module 1 is an example of an antenna device having an antenna for emitting radio waves into space and receiving radio waves from space. The antenna module 1 can be used, for example, in devices for 3G to 5G communications. The communication frequency of the antenna module 1 is, for example, a predetermined frequency band of 0.5 GHz to 30 GHz. For example, the communication frequency of the antenna module 1 is the 3.7 GHz band, the 4.5 GHz band, or the 28 GHz band.

[0017] As shown in FIG. 1( a ), the antenna module 1 includes a transparent conductive film 2 and a flexible wiring board 3 connected to the transparent conductive film 2 .

[0018] The transparent conductive film 2 is an example of a wiring substrate on which conductive lines of a predetermined shape are formed. Specifically, the transparent conductive film 2 is a flexible film-like wiring substrate that is transparent enough to allow the other side to be seen through. In this embodiment, the transparent conductive film 2 is a film antenna having an antenna made of conductive lines.

[0019] A flexible wiring board 3 is connected to the transparent conductive film 2. The flexible wiring board 3 may be a wiring board having only conductive lines formed thereon and having a wiring function only, or may be a COF (chip on film) on which a semiconductor chip such as a driver IC is mounted.

[0020] As shown in FIG. 1A, the transparent conductive film 2 has a first region, an effective region 2a (active region), and a second region, an ineffective region 2b (inactive region), which is different from the effective region 2a. The effective region 2a is a region located inside the ineffective region 2b. The ineffective region 2b is a region located outside the effective region 2a. In this embodiment, the ineffective region 2b surrounds the effective region 2a. Specifically, the ineffective region 2b is a frame-shaped region (frame region) surrounding the effective region 2a. Therefore, the effective region 2a is a rectangular region. The ineffective region 2b is a peripheral region located at the outer peripheral edge of the transparent conductive film 2.

[0021] The effective area 2a is a transparent area, and the ineffective area 2b is a non-transparent area. Therefore, for example, when the transparent conductive film 2 is placed on a display device of a mobile terminal, the effective area 2a is an area (view area) that can be seen by a user of the mobile terminal, and the ineffective area 2b is an area that is not visible to the user because it is covered by the housing of the mobile terminal or the like. The user can view an image displayed on the display device through the effective area 2a, which is a transparent area, and can operate the mobile terminal by touching the effective area 2a with their finger.

[0022] The effective area 2a is an antenna area in which the antenna 10 (antenna radiation portion) is provided. The antenna 10 is made of conductive wire. In this embodiment, the antenna 10 is a microstrip antenna (patch antenna) made of a microstrip line, which is a fine metal wire with a line width on the order of micrometers. Specifically, the line width of the metal wire that makes up the antenna 10 is 100 μm or less. As an example, the line width of the metal wire that makes up the antenna 10 is 1 μm to 30 μm. The metal wire that makes up the antenna 10 is formed in a predetermined pattern. In this embodiment, the conductive wire that makes up the antenna 10 is formed in a mesh shape. In other words, the antenna 10 is a mesh antenna.

[0023] In this embodiment, the antenna 10 is an assembly of multiple antenna elements 10a. This allows the radiation intensity of the antenna 10 to be increased and allows it to support multiple frequency bands. The multiple antenna elements 10a are formed in different regions within the effective area 2a. In this embodiment, each of the multiple antenna elements 10a is formed in a respective one of multiple island regions 2a1 that are partitioned into island-like regions within the effective area 2a. The multiple island regions 2a1 are formed in a matrix. As an example, the multiple island regions 2a1 are partitioned into 16 regions with 4 rows and 4 columns, as shown in FIG. 1A. In each island region 2a1, the antenna elements 10a are formed in a mesh pattern.

[0024] As shown in the enlarged view of FIG. 1A , the mesh-shaped antenna element 10a includes a plurality of first directional lines extending in a first direction and a plurality of second directional lines extending in a second direction intersecting the first direction. In this embodiment, the first directional lines and the second directional lines are not perpendicular to each other, but they may be perpendicular to each other. Furthermore, each of the plurality of first directional lines is parallel to each other. Similarly, each of the plurality of second directional lines is parallel to each other. The plurality of first directional lines and the plurality of second directional lines are formed on the same plane. Therefore, the plurality of first directional lines and the plurality of second directional lines are integrated at the intersections where the first directional lines and the second directional lines intersect. The first directional lines and the second directional lines may intersect at an intersection such that the first directional lines and the second directional lines do not contact each other at the intersections.

[0025] Furthermore, a first signal line 21 and a first signal terminal 31 are provided in the ineffective region 2b. Each of the first signal line 21 and the first signal terminal 31 is electrically connected to the antenna 10. Specifically, the antenna 10 and the first signal terminal 31 are electrically connected via the first signal line 21. In other words, the first signal line 21 is a connection wiring for connecting the antenna 10 and the first signal terminal 31. Furthermore, the first signal line connected to the antenna 10 functions as a transmission path. Note that the first signal terminal 31 may be a part of the first signal line 21. For example, the first signal terminal 31 may be one end of a conductive wire that constitutes the first signal line 21.

[0026] A plurality of first signal lines 21 are provided. Each of the plurality of first signal lines 21 is connected to each of the plurality of antenna elements 10a. That is, the plurality of first signal lines 21 and the plurality of antenna elements 10a are provided in a one-to-one correspondence. Each of the plurality of first signal lines 21 is formed in a predetermined shape in the ineffective region 2b. The ineffective region 2b is a wiring region in which the first signal lines 21 are routed.

[0027] A plurality of first signal terminals 31 are provided to be connected to the first signal line 21. The number of first signal terminals 31 also corresponds to the number of antenna elements 10a. In other words, there is a one-to-one correspondence between the first signal terminals 31 and the antenna elements 10a.

[0028] The multiple first signal terminals 31 are provided in a connection terminal portion 31a in the ineffective region 2b. Therefore, the multiple first signal lines 21 connected to the multiple first signal terminals 31 are concentrated in the connection terminal portion 31a. Each of the multiple first signal terminals 31 is formed in an elongated shape and extends toward the end of the transparent conductive film 2. The multiple first signal terminals 31 are arranged in parallel.

[0029] The connection terminal portion 31a, which is an area where a plurality of first signal terminals 31 are provided, is a pad portion to which the flexible wiring board 3 is connected. The flexible wiring board 3 is connected to the ineffective area 2b of the transparent conductive film 2. Specifically, the flexible wiring board 3 is connected to the transparent conductive film 2 at the connection terminal portion 31a in the ineffective area 2b.

[0030] The flexible wiring board 3 and the transparent conductive film 2 are joined by a conductive joining member (not shown) such as an anisotropic conductive film (ACF) or solder. In this embodiment, the flexible wiring board 3 and the transparent conductive film 2 are joined by the anisotropic conductive film. In (a) of Figure 1, an ACF region 4a surrounded by a dashed line is a region where the anisotropic conductive film is disposed.

[0031] The flexible wiring board 3 has a second signal line 22 and a second signal terminal 32. The second signal line 22 is made of a conductive wire such as a metal wire, and is electrically connected to the second signal terminal 32. As an example, the second signal line 22 and the second signal terminal 32 are made of copper.

[0032] A plurality of second signal lines 22 and a plurality of second signal terminals 32 are provided. The plurality of second signal lines 22 and the plurality of second signal terminals 32 are provided in a one-to-one correspondence. The plurality of second signal lines 22 are arranged in parallel. The plurality of second signal terminals 32 are also arranged in parallel.

[0033] 1(a) and 1(b), the plurality of second signal terminals 32 face the plurality of first signal terminals 31 of the transparent conductive film 2. The plurality of second signal terminals 32 and the plurality of first signal terminals 31 may be the same in number and provided in one-to-one correspondence, or they may not be the same in number.

[0034] The flexible wiring board 3 is provided with a connector 5. The connector 5 is provided at an end of the second signal line 22 opposite to the second signal terminal 32 side. A connector of an external device such as a control circuit is connected to the connector 5. The plurality of second signal terminals 32 are electrically connected to the external device such as the control circuit via the connector 5.

[0035] As shown in FIGS. 1 to 3B, the transparent conductive film 2 has a first substrate 41, a first ground layer 51, and a second ground layer 52.

[0036] 1B and 1C, the first substrate 41 has a first surface 41a and a second surface 41b facing away from the first surface 41a. In other words, the second surface 41b is the surface opposite to the first surface 41a. In FIGS. 1B and 1C, the first surface 41a is the upper surface of the first substrate 41, and the second surface 41b is the lower surface of the first substrate 41.

[0037] The first base material 41 has a base material layer 411 and a resin layer 412 laminated on the base material layer 411. In (b) and (c) of Figure 1, the resin layer 412 is disposed above the base material layer 411. In other words, the base material layer 411 is located below the resin layer 412. The upper surface of the resin layer 412 is a first surface 41a which is the upper surface of the first base material 41, and the lower surface of the base material layer 411 is a second surface 41b which is the lower surface of the first base material 41.

[0038] The antenna 10, the first signal line 21, and the first signal terminal 31 are provided on the first surface 41a of the first base material 41. Specifically, the antenna 10, the first signal line 21, and the first signal terminal 31 are provided on the resin layer 412 of the first base material 41. An insulating film may be formed to cover the antenna 10, the first signal line 21, and the first signal terminal 31.

[0039] The substrate layer 411 is a substrate that serves as a base film for the transparent conductive film 2. Specifically, the substrate layer 411 is a flexible sheet-like film substrate. The substrate layer 411 is a light-transmitting substrate that is transparent to visible light. Specifically, the substrate layer 411 is a transparent substrate with such high transmittance that the other side can be seen through it.

[0040] The base material layer 411 is made of a resin material. In this embodiment, the base material layer 411 is made of a translucent resin material. Specifically, the base material layer 411 is made of a transparent resin material. The base material layer 411 is also an insulating substrate made of an insulating material. Therefore, the base material layer 411 is made of a transparent insulating resin material. The base material layer 411 is a flat, planar plate with a constant thickness. The top view shape of the base material layer 411 is, for example, rectangular, but is not limited to this.

[0041] Examples of the light-transmitting resin material that can be used to form the base layer 411 include polyethylene terephthalate (PET) resin, polyimide (PI) resin, polyethylene naphthalate (PEN) resin, cycloolefin resin, polycarbonate resin, and acrylic resin. In this embodiment, the base layer 411 is a transparent PET film made of PET. Alternatively, a transparent glass substrate may be used as the base layer 411.

[0042] The resin layer 412 is located above the base material layer 411. In the present embodiment, the resin layer 412 is laminated on one surface of the base material layer 411. Specifically, the resin layer 412 is formed directly on the base material layer 411. Therefore, the upper surface of the base material layer 411 is in contact with the lower surface of the resin layer 412.

[0043] The resin layer 412 is an insulating layer made of an insulating resin material. In the present embodiment, the resin layer 412 is made of an insulating resin material having light-transmitting properties. Specifically, the resin layer 412 is made of a transparent insulating resin material. The resin material making up the resin layer 412 is a thermosetting resin or an ultraviolet-curing resin. Specifically, the resin material making up the resin layer 412 may be, for example, a PET resin, a polyimide resin, a cycloolefin resin, a polycarbonate resin, or an acrylic resin.

[0044] The resin layer 412 is provided with the conductive wires that make up the antenna 10, the first signal line 21, and the first signal terminal 31. The conductive wires that make up the antenna 10 have a smaller line width than the first signal line 21. In other words, the line width of the first signal line 21 is larger than the line width of the conductive wires that make up the antenna 10. This allows the resistance of the first signal line 21 to be reduced. As an example, the line width of the first signal line 21 is 5 μm to 200 μm, and is 20 μm in this embodiment.

[0045] The conductive wires, first signal line 21, and first signal terminal 31 that constitute antenna 10 may be made of the same metal material. For example, the conductive wires, first signal line 21, and first signal terminal 31 that constitute antenna 10 may be copper wiring mainly made of copper. Furthermore, the conductive wires, first signal line 21, and first signal terminal 31 that constitute antenna 10 may be formed in the same process. However, the conductive wires, first signal line 21, and first signal terminal 31 that constitute antenna 10 may be made of different metal materials or may be formed in different processes.

[0046] The conductive wires, first signal line 21, and first signal terminal 31 that constitute antenna 10 are embedded in grooves provided in resin layer 412. The conductive wires, first signal line 21, and first signal terminal 31 that constitute antenna 10 are embedded in the grooves of resin layer 412 so that their upper surfaces are exposed.

[0047] The grooves provided in the resin layer 412 are linear recesses formed so as to indent the surface of the resin layer 412. The resin layer 412 with the grooves provided therein is formed by an imprinting method. That is, the resin layer 412 is an imprinted layer. In this case, the resin layer 412 with the grooves provided therein can be formed by pressing a die member (mold) having protrusions corresponding to the grooves against the resin layer 412. Note that the resin layer 412 with the grooves can also be formed by a method other than the imprinting method. Specifically, the resin layer 412 with the grooves provided therein can be formed by forming a flat resin layer 412 and then forming the grooves in the resin layer 412. For example, the grooves can be formed by cutting out the surface of the flat resin layer 412 using a laser scriber or the like.

[0048] 1B and 1C, the first ground layer 51 is provided on the second surface 41b of the first substrate 41. Specifically, the first ground layer 51 is provided on the surface of the substrate layer 411 of the first substrate 41 opposite to the resin layer 412 side.

[0049] The first ground layer 51 faces the antenna 10 provided in the effective area 2a. Therefore, the first ground layer 51 is provided in the effective area 2a. In this embodiment, the first ground layer 51 faces all of the antenna elements 10a. In other words, in a plan view, the first ground layer 51 encompasses the entire antenna 10 and overlaps all of the multiple antenna elements 10a.

[0050] The first ground layer 51 is provided not only in the effective area 2 a but also in the ineffective area 2 b. For example, the first ground layer 51 may be provided over the entire effective area 2 a and the entire ineffective area 2 b. In this case, the first ground layer 51 may be a solid film formed over the entire second surface 41 b of the first substrate 41.

[0051] The first ground layer 51 provided in the ineffective region 2b overlaps the first signal terminal 31 as shown in Fig. 1B, and also overlaps the first signal line 21 as shown in Fig. 1C. In other words, in a plan view, the first ground layer 51 overlaps both the first signal terminal 31 and the first signal line 21.

[0052] 2 and 3A, the second ground layer 52 is provided on the first surface 41a of the first substrate 41. Specifically, the second ground layer 52 is provided on the surface of the resin layer 412 of the first substrate 41 opposite the substrate layer 411 side. As shown in Fig. 3A, in this embodiment, the second ground layer 52 is embedded in a groove provided in the resin layer 412, similar to the first signal terminal 31. The second ground layer 52 is embedded in the groove of the resin layer 412 so that the upper surface thereof is exposed.

[0053] 2A, the second ground layer 52 is provided in the ineffective region 2b. Specifically, the second ground layer 52 is provided in the ACF region 4a in the ineffective region 2b. Therefore, the second ground layer 52 is provided at the end of the first substrate 41 on the flexible wiring board 3 side.

[0054] 2A, in this embodiment, the second ground layer 52 has a comb-like shape in plan view, and includes a base ground portion 52a and a side ground portion 52b located on either side of the first signal terminal 31.

[0055] The base ground portion 52a is an end ground portion located at an end of the first substrate 41. The base ground portion 52a extends in the arrangement direction of the multiple first signal terminals 31. The base ground portion 52a has a portion located between the end of the first signal terminal 31 and the edge 41c of the first substrate 41, and extends along the edge 41c of the first substrate 41. In the present embodiment, the side edge of the base ground portion 52a coincides with the edge 41c of the first substrate 41, but this is not limited thereto. Specifically, the side edge of the base ground portion 52a may be located at a position set back from the edge 41c of the first substrate 41.

[0056] The side ground portion 52b is provided so as to protrude from the base ground portion 52a in a plan view. The side ground portion 52b extends in a direction away from the edge 41c of the first substrate 41. In this embodiment, the side ground portions 52b are provided side by side along the direction in which the first signal terminals 31 are arranged. The base ground portion 52a connects the side ground portions 52b together. The side ground portions 52b and the first signal terminals 31 are provided alternately one by one.

[0057] The first ground layer 51 and the second ground layer 52 are made of a conductive material such as metal. For example, the first ground layer 51 and the second ground layer 52 are copper layers made of copper. The conductive material that makes up the first ground layer 51 and the conductive material that makes up the second ground layer 52 may be the same or different.

[0058] A specific voltage such as a ground potential (earth potential) may be applied to the first ground layer 51 and the second ground layer 52, but no specific voltage may be applied thereto. In other words, the first ground layer 51 and the second ground layer 52 may be in an electrically floating state.

[0059] The first ground layer 51 and the second ground layer 52 may be electrically connected via a via or a connecting line provided in the first substrate 41. This allows a return current generated in the first ground layer 51 to flow to the third ground layer 53 of the flexible wiring board 3 via the second ground layer 52, thereby suppressing crosstalk between signal lines.

[0060] As shown in FIGS. 1 to 3B, the flexible wiring board 3 has a second substrate 42 and a third ground layer 53 .

[0061] 1(b) and 1(c), the second substrate 42 has a third surface 42a and a fourth surface 42b facing away from the third surface 42a. In other words, the fourth surface 42b is the surface opposite to the third surface 42a. In FIG. 1(b) and 1(c), the third surface 42a is the lower surface of the second substrate 42, and the fourth surface 42b is the upper surface of the second substrate 42.

[0062] The second substrate 42 is a substrate that serves as the base film of the flexible wiring board 3. The second substrate 42 is a flexible sheet-like film substrate. In the present embodiment, the second substrate 42 has a first substrate layer 421 and a second substrate layer 422 laminated on the first substrate layer 421. The surface of the first substrate layer 421 opposite to the second substrate layer 422 side (the bottom surface in FIGS. 3A and 3B ) is a third surface 42a of the second substrate 42. The surface of the second substrate layer 422 opposite to the first substrate layer 421 side (the top surface in FIGS. 3A and 3B ) is a fourth surface 42b of the second substrate 42.

[0063] The first base material layer 421 and the second base material layer 422 are insulating layers made of an insulating resin material. For example, the first base material layer 421 and the second base material layer 422 are made of polyimide resin, polyester resin, or the like. The insulating resin material making up the first base material layer 421 and the insulating resin material making up the second base material layer 422 may be the same or different. Furthermore, the first base material layer 421 and the second base material layer 422 may or may not be light-transmitting. The thickness of the first base material layer 421 and the thickness of the second base material layer 422 may be the same or different.

[0064] In the flexible wiring board 3, the second signal terminal 32 is provided on the third surface 42a of the second base material 42. The second signal terminal 32 is provided at an end of the second base material 42 on the transparent conductive film 2 side. In the present embodiment, the second signal terminal 32 is provided on the first base material layer 421. Specifically, the second signal terminal 32 is formed so as to be embedded in the first base material layer 421, but this is not limitative. The second signal terminal 32 may be formed in a predetermined pattern on the surface of the first base material layer 421 (second base material 42).

[0065] 3B , the second signal line 22 is provided between the first base material layer 421 and the second base material layer 422 of the second base material 42. In other words, the second signal line 22 and the second signal terminal 32 are formed in different wiring layers. Specifically, the first base material layer 421 is present between the second signal line 22 and the second signal terminal 32.

[0066] Furthermore, the second signal line 22 extends from the end on the transparent conductive film 2 side toward the end on the connector 5 side. In a plan view, the second signal line 22 and the second signal terminal 32 overlap. Specifically, the second signal terminal 32 overlaps with the end of the second signal line 22. Therefore, the second signal line 22 extends from the position of the second signal terminal 32 to the position of the connector 5. In the present embodiment, the longitudinal edge of the second signal line 22 on the transparent conductive film 2 side and the longitudinal edge of the second signal terminal 32 on the transparent conductive film 2 side coincide with each other, but this is not limited to this.

[0067] The second signal line 22 and the second signal terminal 32 are electrically connected via a via 61 provided in the first base material layer 421. The via 61 is provided in a through hole that penetrates the first base material layer 421. Note that the via 61 is, for example, a via hole, but may also be a buried via formed to fill the through hole provided in the first base material layer 421.

[0068] The via 61 is provided at the end of the second substrate 42 on the transparent conductive film 2 side, between the second signal line 22 and the second signal terminal 32. The via 61 is also provided in a connection terminal portion 31 a where the transparent conductive film 2 and the flexible wiring board 3 are connected. Specifically, when the transparent conductive film 2 and the flexible wiring board 3 are connected, the via 61 is located in the ACF region 4 a. In this embodiment, a plurality of vias 61 are provided.

[0069] 3A , the third ground layer 53 is provided on the third surface 42 a of the second substrate 42, similar to the second signal terminal 32. Specifically, the third ground layer 53 is provided on the first substrate layer 421 of the second substrate 42. In the present embodiment, the third ground layer 53 is formed so as to be embedded in the first substrate layer 421, but this is not limitative. The third ground layer 53 may also be formed in a predetermined pattern on the surface of the first substrate layer 421 (second substrate 42).

[0070] The third ground layer 53 has a base ground portion 53 a and a side ground portion 53 b located on the side of the second signal terminal 32 .

[0071] The base ground portion 53a of the third ground layer 53 is located inside the second signal terminal 32. In other words, the second signal terminal 32 is located between the base ground portion 53a and the edge 42c of the second substrate 42. In the present embodiment, the base ground portion 53a extends in the same direction as the second signal line 22. As shown in FIG. 1B , the base ground portion 53a extends, for example, to the vicinity of the connector 5.

[0072] Additionally, the side ground portion 53b of the third ground layer 53 is provided so as to protrude from the base ground portion 53a in a plan view. The side ground portion 53b extends in a direction approaching the edge 42c of the second substrate 42. In this embodiment, the side ground portions 53b are arranged in the same direction as the second signal terminals 32. The base ground portion 53a connects the side ground portions 53b together. The side ground portions 53b and the second signal terminals 32 are arranged alternately.

[0073] In a plan view, at least a portion of the base ground portion 53a of the third ground layer 53 overlaps with the base ground portion 52a of the second ground layer 52. Furthermore, at least a portion of the lateral ground portion 53b of the third ground layer 53 overlaps with the lateral ground portion 52b of the second ground layer 52. In the present embodiment, the lateral ground portion 53b of the third ground layer 53 has the same shape in a plan view as the lateral ground portion 52b of the second ground layer 52.

[0074] The third ground layer 53 is made of a conductive material such as a metal. For example, the third ground layer 53 is a copper layer made of copper. The conductive material of the third ground layer 53 may be the same as or different from the conductive materials of the first ground layer 51 and the second ground layer 52 in the transparent conductive film 2.

[0075] A specific voltage such as a ground potential (earth potential) may be applied to the third ground layer 53. However, no specific voltage may be applied to the third ground layer 53. In other words, the third ground layer 53 may be in an electrically floating state.

[0076] The third ground layer 53 and the second signal terminal 32 formed on the same first base layer 421 may be formed in the same process. In this case, the third ground layer 53 and the second signal terminal 32 are made of the same metal material. The third ground layer 53 and the second signal terminal 32 may be made of different metal materials or may be formed in different processes. Furthermore, an insulating film may be formed on the first base layer 421 so as to cover the second signal line 22 and the second signal terminal 32 formed on the first base layer 421.

[0077] The flexible wiring board 3 is connected to the transparent conductive film 2 with the third surface 42a of the second substrate 42 facing the first surface 41a of the first substrate 41 of the transparent conductive film 2. In this case, as described above, the transparent conductive film 2 and the flexible wiring board 3 are joined with a conductive bonding member such as an anisotropic conductive film. This electrically connects the first signal terminal 31 of the transparent conductive film 2 and the second signal terminal 32 of the flexible wiring board 3. Therefore, although not shown, a conductive bonding member such as an anisotropic conductive film is interposed between the first signal terminal 31 and the second signal terminal 32.

[0078] Furthermore, by joining the transparent conductive film 2 and the flexible wiring board 3 with a conductive bonding material such as an anisotropic conductive film, the second ground layer 52 of the transparent conductive film 2 and the third ground layer 53 of the flexible wiring board 3 are also electrically connected.

[0079] Next, the effects of the antenna module 1 according to this embodiment will be described, including how the technology of the present disclosure was developed.

[0080] The antenna module 1X shown in FIG. 4 is a comparative example of the antenna module 1 of the present disclosure. The antenna module 1X shown in FIG. 4 includes a first substrate 41X composed of a resin layer 412X and a substrate layer 411X on which a first signal terminal 31X and a first signal line 21X are provided, and a transparent conductive film 2X having a first ground layer 51X provided on the back surface of the first substrate 41X. The antenna module 1X also includes a flexible wiring board 3X including a first substrate layer 421X on which a second signal terminal 32X and a second signal line 22X are provided, a second substrate layer 422X laminated on the first substrate layer 421X, and a third ground layer 53X provided between the first substrate layer 421X and the second substrate layer 422X. In the antenna module 1X, the flexible wiring board 3X is bonded to the transparent conductive film 2X so that the second signal line 22X is closer to the transparent conductive film 2X than the third ground layer 53X.

[0081] When the antenna module 1X configured in this manner is installed on the display 100, as shown in Fig. 4, if the transparent conductive film 2X is installed on the display 100 with the surface of the transparent conductive film 2X facing the first ground layer 51X as the installation surface, the second signal line 22X of the flexible wiring board 3X joined to the transparent conductive film 2X will be affected by noise from the display 100. As a result, the performance of the antenna module 1X will deteriorate.

[0082] Therefore, it is conceivable to join the flexible wiring board 3X shown in FIG. 4 to the transparent conductive film 2X so that the third ground layer 53X is located closer to the display 100 than the second signal line 22X.

[0083] In this case, the second signal terminal 32X of the flexible wiring board 3X and the first signal terminal 31X of the transparent conductive film 2X must be joined using an ACF or the like, so a step must be provided at the joint between the flexible wiring board 3Y and the transparent conductive film 2X, as in the antenna module 1Y shown in FIG. 5 . That is, the third ground layer 53X and the second base layer 422X at the end of the flexible wiring board 3Y must be removed to form the step and expose the second signal terminal 32X. As a result, a discontinuity in impedance occurs between the second signal line 22X and the third ground layer 53X in the flexible wiring board 3Y. This results in increased transmission loss in the antenna module 1Y.

[0084] As a result of extensive research into these problems, the present inventors have discovered an antenna module that can match the impedance of a flexible wiring board while suppressing the influence of noise from the installation surface of the antenna module.

[0085] Specifically, in the flexible wiring board 3 of the antenna module 1 according to this embodiment, the second signal line 22 and the second signal terminal 32 overlap each other, and are electrically connected to each other through a via 61 provided in the first base layer 421 of the second base material 42. This allows the second signal line 22 and, in particular, the third ground layer 53 to be disposed in a state where their positional relationship is maintained up to the point where the second signal line 22 and the second signal terminal 32 are connected. This eliminates impedance discontinuity between the second signal line 22 and the third ground layer 53 in the flexible wiring board 3, and enables impedance matching of the flexible wiring board 3.

[0086] When the antenna module 1 configured in this manner is installed on the display 100, the transparent conductive film 2 is installed on the display 100 with the surface of the transparent conductive film 2 facing the first ground layer 51 as the installation surface, as shown in Figures 6A and 6B. Figures 6A and 6B are diagrams showing the configuration when the antenna module 1 according to the embodiment is installed on the display 100. Figure 6A corresponds to the cross section of Figure 3A, and Figure 6B corresponds to the cross section of Figure 3B.

[0087] 6A and 6B , by installing the antenna module 1 on the display 100, the flexible wiring board 3 bonded to the transparent conductive film 2 has the third ground layer 53 positioned closer to the display 100 than the second signal line 22. This allows the flexible wiring board 3 to block noise from the display 100 with the third ground layer 53. This makes it possible to prevent performance degradation of the antenna module 1 due to noise from the display 100.

[0088] As described above, according to the antenna module 1 of this embodiment, it is possible to match the impedance of the flexible wiring board 3 while suppressing the influence of noise received from the installation surface side of the antenna module 1.

[0089] Here, the impedances of the antenna module 1 according to this embodiment and the antenna module 1Y having the structure shown in Fig. 5 were measured, and the measurement results will be explained using Fig. 7 and Fig. 8. Fig. 7 shows the impedance of the antenna module 1Y shown in Fig. 5, and Fig. 8 shows the impedance of the antenna module 1 according to this embodiment.

[0090] As shown in Fig. 7, in the antenna module 1Y shown in Fig. 5, the impedance becomes high around 230 picoseconds (the area indicated by the dashed circle), indicating that an impedance mismatch occurs in the flexible wiring board 3X. On the other hand, as shown in Fig. 8, in the antenna module 1 according to this embodiment, the impedance is suppressed around 230 picoseconds, indicating that the impedance of the flexible wiring board 3 is matched.

[0091] Furthermore, in the antenna module 1 according to this embodiment, when viewed in a plane, the base ground portion 53 a of the third ground layer 53 of the flexible wiring board 3 and the base ground portion 52 a of the second ground layer 52 of the transparent conductive film 2 overlap, and the lateral ground portion 53 b of the third ground layer 53 of the flexible wiring board 3 and the lateral ground portion 52 b of the second ground layer 52 of the transparent conductive film 2 overlap.

[0092] This configuration makes it possible to easily match the impedance of the flexible wiring board 3 .

[0093] Furthermore, in the antenna module 1 according to this embodiment, the transparent conductive film 2 is provided with a plurality of first signal terminals 31 and a plurality of side ground portions 52b of the second ground layer 52, arranged alternately one by one. Furthermore, the flexible wiring board 3 is provided with a plurality of second signal terminals 32 and a plurality of side ground portions 53b of the third ground layer 53, arranged alternately one by one.

[0094] This configuration makes it possible to more easily match the impedance of the flexible wiring board 3 .

[0095] In the antenna module 1 according to the above embodiment, the flexible wiring board 3 is provided with only the third ground layer 53 as a ground layer (i.e., a single ground layer), but this is not limited thereto. For example, as in the antenna module 1A shown in FIGS. 9, 10A, and 10B, the flexible wiring board 3A may be provided with multiple ground layers. FIG. 9 is an enlarged view of the joint between the transparent conductive film 2 and the flexible wiring board 3A in an antenna module 1A according to a modified example. In FIG. 9, (a) shows the end of the transparent conductive film 2 (the area surrounding the second ground layer 52), (b) shows the end of the flexible wiring board 3A (the area surrounding the end of the third ground layer 53), and (c) shows the end of the flexible wiring board 3A (the area surrounding the end of the second signal line 22 and the fourth ground layer 54). FIG. 10A is a cross-sectional view taken along line A-A in FIG. 9, and FIG. 10B is a cross-sectional view taken along line B-B in FIG. 9. Note that FIG. 9 corresponds to the enlarged view of FIG. 2.

[0096] 9, 10A, and 10B, the antenna module 1A of this modification differs from the antenna module 1 of the above embodiment in that the flexible wiring board 3A has a fourth ground layer 54 and a fifth ground layer 55. Note that, like the antenna module 1 of the above embodiment, the antenna module 1A of this modification has the flexible wiring board 3A in which the second signal line 22 and the second signal terminal 32 are electrically connected via the via 61 (first via).

[0097] The fourth ground layer 54 is laminated on the third ground layer 53 via the first substrate layer 421 of the second substrate 42. In other words, the first substrate layer 421 is present between the third ground layer 53 and the fourth ground layer 54. The third ground layer 53 and the fourth ground layer 54 are electrically connected via a via 62 (second via) provided in the first substrate layer 421.

[0098] The fourth ground layer 54, like the second signal line 22, is provided between the first substrate layer 421 and the second substrate layer 422 of the second substrate 42. As shown in Fig. 9C, the fourth ground layer 54 extends linearly along the longitudinal direction of the second signal line 22. A plurality of fourth ground layers 54 are provided, and the plurality of fourth ground layers 54 and the plurality of second signal lines 22 are provided alternately one by one.

[0099] The fifth ground layer 55 is provided on the fourth surface 42b of the second substrate 42. As an example, the fifth ground layer 55 is formed on the entire fourth surface 42b of the second substrate 42, but is not limited to this. The fifth ground layer 55 is connected to the fourth ground layer 54 through a via 63 (third via) provided in the second substrate layer 422 of the second substrate 42.

[0100] The fourth ground layer 54 and the fifth ground layer 55 are made of a conductive material such as metal. For example, the fourth ground layer 54 and the fifth ground layer 55 are copper layers made of copper. Note that, like the third ground layer 53, the fourth ground layer 54 and the fifth ground layer 55 may have a specific voltage such as a ground potential (earth potential) applied to them, or may be in an electrically floating state without any specific voltage applied to them.

[0101] In the antenna module 1A configured in this manner, similar to the antenna module 1 according to the above embodiment, the second signal line 22 and the second signal terminal 32 overlap on the flexible wiring board 3A, and the second signal line 22 and the second signal terminal 32 are electrically connected via the via 61.

[0102] As a result, similarly to the antenna module 1 according to the above embodiment, it is possible to match the impedance of the flexible wiring board 3A while suppressing the influence of noise received from the installation surface side of the antenna module 1A.

[0103] In addition, in the antenna module 1A according to this modification, a fourth ground layer 54 is provided on the flexible wiring board 3A.

[0104] This makes it possible to effectively suppress crosstalk between the second signal lines 22 in the flexible wiring board 3A.

[0105] In addition, in the antenna module 1A according to this modification, a fifth ground layer 55 is provided on the flexible wiring board 3A.

[0106] This makes it possible to more effectively suppress crosstalk between the second signal lines 22 in the flexible wiring board 3A.

[0107] (Other Modifications) The transparent conductive film and antenna module according to the present disclosure have been described above based on the embodiments, but the present disclosure is not limited to the above-described embodiments.

[0108] For example, in the above embodiment, the conductive wires, first signal line 21, and first signal terminal 31 that constitute antenna 10 are embedded in the grooves of resin layer 412 of first base material 41, but this is not limiting. Specifically, the conductive wires, first signal line 21, and first signal terminal 31 that constitute antenna 10 may be formed on the flat upper surface of resin layer 412 without forming grooves in resin layer 412.

[0109] Furthermore, in the transparent conductive film 2 of the above embodiment, the antenna 10, the first signal terminal 31, and the second ground layer 52 are provided on the first surface 41a of the first substrate 41, but this is not limiting. The antenna 10, the first signal terminal 31, and the second ground layer 52 may be provided inside the first substrate 41, rather than on the exposed surface of the first substrate 41. Similarly, in the transparent conductive film 2, the first ground layer 51 is provided on the second surface 41b of the first substrate 41, but this is not limiting. The first ground layer 51 may be provided inside the first substrate 41, rather than on the exposed surface of the first substrate 41.

[0110] In the flexible wiring board 3 according to the above embodiment, the third ground layer 53 and the second signal terminal 32 are provided on the third surface 42 a of the second base material 42, but this is not limiting. The third ground layer 53 and the second signal terminal 32 may be provided inside the second base material 42, rather than on the exposed surface of the second base material 42.

[0111] In the above embodiment, the antenna 10 is a mesh antenna, but this is not limiting, and the antenna 10 may be formed in a pattern other than a mesh.

[0112] In addition, the present disclosure also includes embodiments obtained by applying various modifications to the above-described embodiments that would occur to a person skilled in the art, and embodiments realized by arbitrarily combining the components and functions of the embodiments within the scope of the present disclosure. Furthermore, the present disclosure also includes any combination of two or more claims from among the multiple claims set forth in the claims at the time of filing, within the scope of technical compatibility. 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 technical compatibility, the present disclosure also includes any combination of all claims included in that multiple claim or multiple multiple claims.

[0113] The transparent conductive film and antenna module according to the present disclosure can be used in various electrical devices such as mobile terminals.

[0114] REFERENCE SIGNS LIST 1, 1A Antenna module 2 Transparent conductive film 2a Effective area 2a1 Island area 2b Ineffective area 3, 3A Flexible wiring board 4a ACF area 5 Connector 10 Antenna 10a Antenna element 21 First signal line 22 Second signal line 31 First signal terminal 31a Connection terminal portion 32 Second signal terminal 41 First substrate 411 Substrate layer 412 Resin layer 41a First surface 41b Second surface 41c Edge 42 Second substrate 421 First substrate layer 422 Second substrate layer 42a Third surface 42b Fourth surface 42c Edge 51 First ground layer 52 Second ground layer 52a Base ground portion 52b Side ground portion 53 Third ground layer 53a Base ground portion 53b Side ground portion 54 Fourth ground layer 55 Fifth ground layer 61, 62, 63 Vias 100 Display

Claims

1. A wiring board connected to the transparent conductive film, wherein the transparent conductive film comprises: a first substrate having a first surface and a second surface facing away from the first surface; an antenna provided on the first surface; a first signal terminal provided on the first surface and electrically connected to the antenna; a first ground layer provided on the second surface; and a second ground layer provided on the first surface; the wiring board comprises: a second substrate; a third ground layer provided on the second substrate; a second signal terminal provided on the second substrate; and a signal line electrically connected to the second signal terminal; wherein at least a portion of the wiring board is disposed to face the transparent conductive film; the first signal terminal and the second signal terminal are electrically connected; and the second ground layer and the third ground layer are electrically connected; the second substrate comprises a first substrate layer and a second substrate layer laminated on the first substrate layer; and the signal line is provided between the first substrate layer and the second substrate layer; An antenna module, wherein in a plan view, the signal line and the second signal terminal overlap, and the signal line and the second signal terminal are electrically connected to each other through a first via provided in the first base layer.

2. The antenna module described in claim 1, wherein the second base material has a third surface and a fourth surface facing away from the third surface, the third ground layer and the second signal terminal are provided on the third surface, and the wiring board is disposed on the transparent conductive film with the third surface facing the first surface.

3. The antenna module described in claim 2, wherein the wiring board further has a fourth ground layer laminated on the third ground layer via the first base material layer, and the third ground layer and the fourth ground layer are electrically connected via a second via provided in the first base material layer.

4. The antenna module according to claim 3, wherein the wiring board further has a fifth ground layer provided on the fourth surface.

5. The antenna module according to claim 1 or 2, wherein the second ground layer has a base ground portion and a side ground portion located on a side of the first signal terminal, the third ground layer has a base ground portion and a side ground portion located on a side of the second signal terminal, the side ground portion of the second ground layer protrudes from the base ground portion of the second ground layer in a direction away from the edge of the first substrate, and the side ground portion of the third ground layer protrudes from the base ground portion of the third ground layer in a direction approaching the edge of the second substrate, and in a planar view, the base ground portion of the third ground layer overlaps with the base ground portion of the second ground layer and the side ground portion of the third ground layer overlaps with the side ground portion of the second ground layer.

6. The ground layer further includes a plurality of side ground portions and the third ground layer further includes a plurality of side ground portions, each of the plurality of first signal terminals is the first signal terminal, each of the plurality of second signal terminals is the second signal terminal, each of the plurality of side ground portions of the second ground layer is the lateral ground portion of the second ground layer, each of the plurality of lateral ground portions of the third ground layer is the lateral ground portion of the third ground layer, the plurality of first signal terminals are arranged side by side, the plurality of second signal terminals are arranged side by side, the plurality of lateral ground portions of the second ground layer are arranged side by side, the plurality of lateral ground portions of the third ground layer are arranged side by side, the plurality of first signal terminals and the plurality of lateral ground portions of the second ground layer are arranged alternately one by one, 6. The antenna module according to claim 5, wherein each of the second signal terminals faces a corresponding one of the first signal terminals, and the second signal terminals and the side ground portions of the third ground layer are arranged alternately one by one.

7. A transparent conductive film and a wiring board connected to the transparent conductive film, wherein the transparent conductive film has: a first substrate, an antenna provided on the first substrate, a first signal terminal provided on the first substrate and electrically connected to the antenna, a first ground layer provided on the first substrate, and a second ground layer provided on the first substrate which is a layer different from the first ground layer; the wiring board has: a second substrate, a third ground layer provided on the second substrate, a second signal terminal provided on the second substrate, and a signal line electrically connected to the second signal terminal, wherein at least a portion of the wiring board is disposed to face the transparent conductive film, the first signal terminal and the second signal terminal are electrically connected, and the second ground layer and the third ground layer are electrically connected; the second substrate has a first substrate layer and a second substrate layer laminated on the first substrate layer, and the signal line is provided between the first substrate layer and the second substrate layer, An antenna module, wherein, in a plan view, at least a portion of the signal line overlaps with the second signal terminal, and the signal line and the second signal terminal are electrically connected through a first via provided in the first base layer.

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