Wiring board and method for manufacturing a wiring board

Abstract

To provide a wiring board and a manufacturing method for the wiring board capable of suppressing the occurrence of moire.SOLUTION: A wiring board includes a mesh wiring layer 20 and a dummy wiring layer 30. A unit pattern 20A of the mesh wiring layer 20 includes first directional wiring 21 extending along a first direction and second directional wiring 22 extending along a second direction. A dummy unit pattern 30A of the dummy wiring layer 30 includes a first dummy wiring portion 31 extending along the first direction and a second dummy wiring portion 32 extending along the second direction. A cutout portion 33 is formed in the dummy unit pattern 30A, and at least one of the position and shape of the cutout portion 33 is different from each other between the dummy unit patterns 30A adjacent to each other.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] Embodiments of the present disclosure relate to a wiring board and a method for manufacturing a wiring board.

Background Art

[0002] Currently, high functionality, miniaturization, thinning, and weight reduction of mobile terminal devices such as smartphones and tablets are progressing. Since these mobile terminal devices use multiple communication bands, multiple antennas corresponding to the communication bands are required. For example, mobile terminal devices are equipped with multiple antennas such as a telephone antenna, a WiFi (Wireless Fidelity) antenna, a 3G (Generation) antenna, a 4G (Generation) antenna, an LTE (Long Term Evolution) antenna, a Bluetooth (registered trademark) antenna, and an NFC (Near Field Communication) antenna. However, with the miniaturization of mobile terminal devices, the mounting space for antennas is limited, and the design freedom of antennas is narrowing. In addition, since the antenna is built in a limited space, the radio wave sensitivity is not always satisfactory.

[0003] For this reason, film antennas that can be mounted in the display area of mobile terminal devices have been developed. This film antenna is a transparent antenna in which an antenna pattern is formed on a transparent base material, and the antenna pattern is formed by a mesh-shaped conductor mesh layer including a conductor part as a formation part of an opaque conductor layer and a number of openings as non-formation parts.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

[0005] For example, in conventional film antennas, one or more mesh antennas are mounted on a transparent substrate, but the transparent substrate has both areas where the antenna pattern is formed and areas where the antenna pattern is not formed. In this case, the presence of areas where the antenna pattern is not formed makes the areas where the antenna pattern is formed more visible. Therefore, there is a need to make wiring patterns such as antenna patterns difficult to see.

[0006] In response to this, a dummy wiring layer containing electrically independent dummy wiring may be provided around the wiring pattern to make it difficult to see the wiring pattern. However, in mobile devices equipped with film antennas, the period of the dummy wiring and the period of the pixels may interfere, potentially causing moiré patterns (streaks of light and dark). When moiré patterns occur in this way, the visibility of images in mobile devices may be reduced.

[0007] One of the objectives of this embodiment is to provide a wiring board and a method for manufacturing a wiring board that can suppress the occurrence of moiré patterns. [Means for solving the problem]

[0008] A wiring board according to one embodiment of the present disclosure comprises a substrate, a mesh wiring layer disposed on the substrate and including a plurality of wirings, and a dummy wiring layer disposed around the mesh wiring layer and including a plurality of dummy wirings electrically independent from the wirings, wherein the substrate has a transmittance of 85% or more for light rays with a wavelength of 400 nm to 700 nm, the mesh wiring layer is composed of a predetermined repeating unit pattern, the unit pattern includes first direction wirings extending along a first direction and second direction wirings extending along a second direction different from the first direction, the dummy wiring layer is composed of a predetermined repeating dummy unit pattern, the dummy unit pattern includes a first dummy wiring portion extending along the first direction and a second dummy wiring portion extending along the second direction, and notches are formed in the dummy unit pattern, and at least one of the position and shape of the notches in adjacent dummy unit patterns is different from each other.

[0009] In a wiring board according to one embodiment of the present disclosure, the difference in aperture ratio between adjacent 500 μm square regions in the dummy wiring layer may be within 0.2%.

[0010] In a wiring board according to one embodiment of the present disclosure, the first dummy wiring portion and the second dummy wiring portion may be spaced apart from each other in the dummy unit pattern.

[0011] In a wiring board according to one embodiment of the present disclosure, the first dummy wiring portions and the second dummy wiring portions may be spaced apart from each other in adjacent dummy unit patterns.

[0012] In a wiring board according to one embodiment of the present disclosure, a plurality of the notches may be formed in the dummy unit pattern.

[0013] In a wiring board according to one embodiment of the present disclosure, the total lengths of the first dummy wiring portion and the second dummy wiring portion in adjacent dummy unit patterns may be equal to each other.

[0014] In a wiring board according to one embodiment of the present disclosure, an additional pattern spaced apart from the dummy wiring may be arranged within the dummy wiring layer.

[0015] In a wiring board according to one embodiment of the present disclosure, the dummy unit patterns may be repeatedly arranged parallel to the first and second directions.

[0016] A wiring board according to one embodiment of the present disclosure may have radio wave transmission and reception functions.

[0017] A method for manufacturing a wiring board according to one embodiment of the present disclosure comprises the steps of: preparing a substrate; forming a mesh wiring layer containing a plurality of wirings on the substrate; and forming a dummy wiring layer on the substrate, which is arranged around the mesh wiring layer and contains a plurality of dummy wirings electrically independent from the wirings, wherein the substrate has a transmittance of 85% or more for light rays with a wavelength of 400 nm to 700 nm; the mesh wiring layer is composed of a predetermined repeating unit pattern, the unit pattern includes a first direction wiring extending along a first direction and a second direction wiring extending along a second direction different from the first direction; the dummy wiring layer is composed of a predetermined repeating dummy unit pattern, the dummy unit pattern includes a first dummy wiring portion extending along the first direction and a second dummy wiring portion extending along the second direction; and notches are formed in the dummy unit pattern, with at least one of the position and shape of the notches being different in adjacent dummy unit patterns. [Effects of the Invention]

[0018] According to the embodiments of this disclosure, the occurrence of moiré patterns can be suppressed. [Brief explanation of the drawing]

[0019] [Figure 1] FIG. 1 is a plan view showing a wiring board according to the present embodiment. [Figure 2] FIG. 2 is an enlarged plan view (an enlarged view of part II in FIG. 1) showing a wiring board according to the present embodiment. [Figure 3] FIG. 3 is a cross-sectional view (a cross-sectional view taken along line III-III in FIG. 2) showing a wiring board according to the present embodiment. [Figure 4] FIG. 4 is a cross-sectional view (a cross-sectional view taken along line IV-IV in FIG. 2) showing a wiring board according to the present embodiment. [Figure 5] FIG. 5 is a cross-sectional view (a cross-sectional view taken along line V-V in FIG. 2) showing a wiring board according to the present embodiment. [Figure 6] FIGS. 6(a)-(f) are cross-sectional views showing a method for manufacturing a wiring board according to the present embodiment. [Figure 7] FIG. 7 is a plan view showing an image display device according to the present embodiment. [Figure 8] FIG. 8 is a plan view showing a modified example of the wiring board according to the present embodiment. [Figure 9] FIG. 9 is a plan view showing a modified example of the wiring board according to the present embodiment.

MODE FOR CARRYING OUT THE INVENTION

[0020] First, a first embodiment will be described with reference to FIGS. 1 to 7. FIGS. 1 to 7 are diagrams showing the first embodiment.

[0021] The following figures are schematic representations. Therefore, the size and shape of each part are exaggerated as appropriate for ease of understanding. Furthermore, modifications can be made as appropriate without departing from the technical concept. In the following figures, the same parts are denoted by the same reference numerals, and some detailed explanations may be omitted. Also, the numerical values ​​such as dimensions and material names of each component described in this specification are examples of embodiments and are not limiting; they can be selected and used as appropriate. In this specification, terms that specify shapes and geometric conditions, such as parallel, orthogonal, and perpendicular, are used not only in their strict sense but also to include substantially the same state.

[0022] In this embodiment, the "X direction" is the direction perpendicular to the longitudinal direction of the mesh wiring layer and perpendicular to the length direction corresponding to the frequency band of the first direction wiring. The "Y direction" is the direction perpendicular to the X direction and parallel to the longitudinal direction of the mesh wiring layer and parallel to the length direction corresponding to the frequency band of the first direction wiring. The "Z direction" is the direction perpendicular to both the X and Y directions and parallel to the thickness direction of the wiring board. Furthermore, the "front surface" refers to the surface on the positive Z direction side, which is the surface on which the first direction wiring is provided on the board. The "back surface" refers to the surface on the negative Z direction side, which is the surface on the opposite side of the board from the surface on which the first direction wiring is provided. In this embodiment, the explanation is given using the example of a mesh wiring layer 20 having a radio wave transmission and reception function (function as an antenna), but the mesh wiring layer 20 does not have to have a radio wave transmission and reception function (function as an antenna).

[0023] [Wiring board configuration] The configuration of the wiring board according to this embodiment will be described with reference to Figures 1 to 5. Figures 1 to 5 are diagrams showing the wiring board according to this embodiment.

[0024] As shown in Figure 1, the wiring board 10 according to this embodiment is, for example, placed on the display of an image display device. Such a wiring board 10 comprises a transparent substrate 11, a mesh wiring layer 20 placed on the substrate 11, and a dummy wiring layer 30 placed around the mesh wiring layer 20 on the substrate 11. A power supply unit 40 is electrically connected to the mesh wiring layer 20.

[0025] The substrate 11 is approximately rectangular in shape when viewed from above, with its longitudinal direction parallel to the Y direction and its transverse direction parallel to the X direction. The substrate 11 is transparent and approximately flat, and its thickness is approximately uniform throughout. The length L1 in the longitudinal direction (Y direction) of the substrate 11 can be selected within the range of, for example, 20 mm to 500 mm, preferably 100 mm to 200 mm, and the length L2 in the transverse direction (X direction) of the substrate 11 can be selected within the range of, for example, 20 mm to 500 mm, preferably 50 mm to 100 mm. The corners of the substrate 11 may also be rounded.

[0026] The material of the substrate 11 may be any material that has transparency in the visible light region and electrical insulation properties. In this embodiment, the material of the substrate 11 is polyethylene terephthalate, but it is not limited to this. Preferably, the material of the substrate 11 is an organic insulating material such as a polyester resin such as polyethylene terephthalate, an acrylic resin such as polymethyl methacrylate, a polycarbonate resin, a polyimide resin, or a polyolefin resin such as cycloolefin polymer, or a cellulose resin material such as triacetylcellulose. Alternatively, the material of the substrate 11 may be an organic insulating material such as a cycloolefin polymer (e.g., ZF-16 manufactured by Nippon Zeon Co., Ltd.) or a polynorbornene polymer (manufactured by Sumitomo Bakelite Co., Ltd.). In addition, glass, ceramics, etc. can be appropriately selected as the material of the substrate 11 depending on the application. Although the illustration shows an example in which the substrate 11 is composed of a single layer, it is not limited to this, and may be a structure in which multiple substrates or layers are laminated. Furthermore, the substrate 11 may be in the form of a film or a plate. Therefore, there are no particular restrictions on the thickness of the substrate 11, and it can be appropriately selected depending on the application. However, as an example, the thickness T1 of the substrate 11 (length in the Z direction, see Figure 3) can be in the range of 10 μm to 200 μm.

[0027] Furthermore, the dielectric loss tangent of the substrate 11 may be 0.002 or less, and preferably 0.001 or less. There is no particular lower limit for the dielectric loss tangent of the substrate 11, but it may be greater than 0. By having the dielectric loss tangent of the substrate 11 within the above range, the loss of gain (sensitivity) associated with the transmission and reception of electromagnetic waves (e.g., millimeter waves) transmitted and received by the mesh wiring layer 20 can be reduced, especially when the electromagnetic waves transmitted and received by the mesh wiring layer 20 are at high frequencies. There is no particular lower limit for the dielectric loss tangent of the substrate 11.

[0028] The dielectric loss tangent of substrate 11 can be measured in accordance with IEC 62562. Specifically, first, a test specimen is prepared by cutting out a portion of substrate 11 where the mesh wiring layer 20 is not formed. Alternatively, a portion of substrate 11 with the mesh wiring layer 20 formed on it may be cut out, and the mesh wiring layer 20 may be removed by etching or the like. The dimensions of the test specimen should be 10 mm to 20 mm in width and 50 mm to 100 mm in length. Next, the dielectric loss tangent is measured in accordance with IEC 62562. The dielectric constant and dielectric loss tangent of substrate 11 can also be measured in accordance with ASTM D150.

[0029] Furthermore, the substrate 11 may have a transmittance of 85% or more for visible light (light with a wavelength of 400 nm to 700 nm), and preferably 90% or more. There is no particular upper limit to the visible light transmittance of the substrate 11, but it may be 100% or less, for example. By setting the visible light transmittance of the substrate 11 within the above range, the transparency of the wiring board 10 can be increased, making the display 91 (described later) of the image display device 90 easier to see. Visible light refers to light with a wavelength of 400 nm to 700 nm. Furthermore, a visible light transmittance of 85% or more means that when the absorbance of the substrate 11 is measured using a known spectrophotometer (for example, a spectrometer manufactured by JASCO Corporation: V-670), the transmittance is 85% or more in the entire wavelength range of 400 nm to 700 nm.

[0030] In Figure 1, there are multiple (three) mesh wiring layers 20 on the substrate 11, each corresponding to a different frequency band. That is, the multiple mesh wiring layers 20 have a length (length in the Y direction) L a These are all different in length, and each has a length corresponding to a specific frequency band. The lower the frequency band, the longer the mesh wiring layer L. aThe length is increasing. When the wiring board 10 is placed on, for example, the display 91 of an image display device 90 (see Figure 7 described later), each mesh wiring layer 20 may have radio wave transmission and reception functionality. In this case, each mesh wiring layer 20 may correspond to one of the following: a telephone antenna, a WiFi antenna, a 3G antenna, a 4G antenna, a 5G antenna, an LTE antenna, a Bluetooth® antenna, an NFC antenna, etc. Alternatively, if the wiring board 10 does not have radio wave transmission and reception functionality, each mesh wiring layer 20 may perform functions such as hovering (a function that allows operation without the user directly touching the display), fingerprint authentication, a heater, noise reduction (shielding), etc. Furthermore, the mesh wiring layer 20 may not be present across the entire surface of the substrate 11, but only in a portion of the substrate 11.

[0031] Each mesh wiring layer 20 is approximately rectangular in shape when viewed from above. The longitudinal direction of each mesh wiring layer 20 is parallel to the Y direction, and its short direction is parallel to the X direction. The length L of the longitudinal direction (Y direction) of each mesh wiring layer 20 is... a For example, it can be selected within a range of 1 mm to 100 mm, and the width W in the short direction (X direction) of each mesh wiring layer 20. a The mesh wiring layer can be selected within a range of, for example, 1 mm to 10 mm. In particular, the mesh wiring layer 20 may be a millimeter-wave antenna. If the mesh wiring layer 20 is a millimeter-wave antenna, the length L of the mesh wiring layer 20 a This can be selected within the range of 1 mm to 10 mm, more preferably 1.5 mm to 5 mm.

[0032] The mesh wiring layer 20 is composed of a predetermined unit pattern 20A that is repeatedly arranged along a first direction (e.g., the Y direction). This unit pattern 20A is also repeatedly arranged along a second direction (e.g., the X direction) that is different from the first direction. In other words, each of the metal wires in the mesh wiring layer 20 is formed in a grid or mesh shape and has a uniform repeating pattern in the X and Y directions. That is, as shown in Figure 2, the mesh wiring layer 20 is composed of a repetition of an L-shaped unit pattern 20A (shaded portion in Figure 2) which consists of a portion extending in the X direction (part of the second direction wiring 22 described later) and a portion extending in the Y direction (part of the first direction wiring 21 described later). In other words, the unit pattern 20A includes the first direction wiring 21 described later which extends along the first direction and the second direction wiring 22 described later which extends along the second direction.

[0033] As shown in Figure 2, each mesh wiring layer 20 includes a plurality of first directional wirings (antenna wirings) 21 that function as antennas, and a plurality of second directional wirings (antenna connecting wirings) 22 that connect the plurality of first directional wirings 21. Specifically, the plurality of first directional wirings 21 and the plurality of second directional wirings 22 together form a regular grid or mesh shape. Each first directional wiring 21 extends in the direction corresponding to the antenna frequency band (longitudinal direction, Y direction), and each second directional wiring 22 extends in the direction perpendicular to the first directional wiring 21 (width direction, X direction). The first directional wiring 21 has a length L corresponding to a predetermined frequency band. a (See Figure 1 for the length of the mesh wiring layer 20 described above) it primarily functions as an antenna. On the other hand, the second directional wiring 22 connects these first directional wirings 21 to each other, thereby preventing problems such as the first directional wiring 21 being disconnected or the first directional wiring 21 losing electrical connection with the feed point 40.

[0034] In each mesh wiring layer 20, multiple openings 23 are formed by being surrounded by adjacent first-directional wirings 21 and adjacent second-directional wirings 22. Furthermore, the first-directional wirings 21 and second-directional wirings 22 are arranged at equal intervals. That is, the multiple first-directional wirings 21 are arranged at equal intervals, and their pitch P1 (see Figure 2) can be, for example, in the range of 0.01 mm to 1 mm. Similarly, the multiple second-directional wirings 22 are arranged at equal intervals, and their pitch P2 (see Figure 2) can be, for example, in the range of 0.01 mm to 1 mm. In this way, because the multiple first-directional wirings 21 and multiple second-directional wirings 22 are arranged at equal intervals, there is no variation in the size of the openings 23 within each mesh wiring layer 20, making the mesh wiring layer 20 difficult to see with the naked eye. Also, the pitch P1 of the first-directional wirings 21 is equal to the pitch P2 of the second-directional wirings 22. Therefore, each opening 23 is approximately square in plan view, and the transparent substrate 11 is exposed through each opening 23. By increasing the area of ​​each opening 23, the overall transparency of the wiring board 10 can be increased. The length L3 of one side of each opening 23 (see Figure 2) can be, for example, in the range of 0.01 mm to 1 mm. Although each first directional wiring 21 and each second directional wiring 22 are orthogonal to each other, they are not limited to this and may intersect each other at acute or obtuse angles. Furthermore, each opening 23 may have a shape such as approximately rectangular in plan view. In addition, it is preferable that the shape and size of the openings 23 be the same across the entire surface, but they do not have to be uniform across the entire surface, for example, by varying them in different locations.

[0035] As shown in Figure 3, each first-directional wiring 21 has a roughly rectangular or roughly square cross-section perpendicular to its longitudinal direction (cross-section in the X direction). In this case, the cross-sectional shape of the first-directional wiring 21 is roughly uniform along its longitudinal direction (Y direction). Also, as shown in Figure 4, the shape of the cross-section perpendicular to the longitudinal direction (cross-section in the Y direction) of each second-directional wiring 22 is roughly rectangular or roughly square, and is roughly the same as the cross-sectional shape (cross-section in the X direction) of the first-directional wiring 21 described above. In this case, the cross-sectional shape of the second-directional wiring 22 is roughly uniform along its longitudinal direction (X direction). The cross-sectional shapes of the first-directional wiring 21 and the second-directional wiring 22 do not necessarily have to be roughly rectangular or roughly square; for example, they may be roughly trapezoidal in shape, where the front side (positive Z direction side) is narrower than the back side (negative Z direction side), or they may have curved sides on both sides in the width direction.

[0036] In this embodiment, the line width W1 of the first directional wiring 21 (length in the X direction, see Figure 3) and the line width W2 of the second directional wiring 22 (length in the Y direction, see Figure 4) are not particularly limited and can be appropriately selected according to the application. For example, the line width W1 of the first directional wiring 21 can be selected in the range of 0.1 μm to 5.0 μm, and is preferably 0.2 μm to 2.0 μm. Similarly, the line width W2 of the second directional wiring 22 can be selected in the range of 0.1 μm to 5.0 μm, and is preferably 0.2 μm to 2.0 μm. By setting the line width W1 of the first directional wiring 21 to 5.0 μm or less, even if moiré patterns occur, the density of the moiré can be reduced, and by setting the line width W1 to 2.0 μm or less, the density of the moiré can be further reduced. Similarly, if the line width W2 of the second direction wiring 22 is 5.0 μm or less, the density of the moiré pattern can be reduced even if it occurs, and if the line width W2 is 2.0 μm or less, the density of the moiré pattern can be reduced even further.

[0037] Furthermore, the height H1 (length in the Z direction, see Figure 3) of the first directional wiring 21 and the height H2 (length in the Z direction, see Figure 4) of the second directional wiring 22 are not particularly limited and can be appropriately selected depending on the application. For example, they can be selected in the range of 0.1 μm to 5.0 μm, and preferably 0.2 μm to 2.0 μm.

[0038] The material for the first directional wiring 21 and the second directional wiring 22 can be any conductive metallic material. In this embodiment, the material for the first directional wiring 21 and the second directional wiring 22 is copper, but it is not limited to this. For example, the material for the first directional wiring 21 and the second directional wiring 22 can be a metallic material (including alloys) such as gold, silver, copper, platinum, tin, aluminum, iron, or nickel.

[0039] Referring again to Figure 1, the dummy wiring layer 30 is provided so as to surround each mesh wiring layer 20, and is formed to surround the entire circumferential area (positive X direction, negative X direction, positive Y direction) of each mesh wiring layer 20, excluding the side facing the power supply unit 40 (negative Y direction). In this case, the dummy wiring layer 30 is on the substrate 11 and is arranged over substantially the entire area excluding the mesh wiring layer 20 and the power supply unit 40. Unlike the mesh wiring layer 20, this dummy wiring layer 30 does not substantially function as an antenna.

[0040] As shown in Figure 2, the dummy wiring layer 30 is composed of a predetermined dummy unit pattern 30A (a combination of the shaded and diagonal areas in Figure 2) arranged in a repeating pattern. This dummy unit pattern 30A is arranged in a repeating pattern along a first direction (e.g., the Y direction) and a second direction (e.g., the X direction). In the illustrated example, the dummy unit pattern 30A is L-shaped and arranged in a repeating pattern parallel to the first direction (Y direction) and the second direction (X direction). In other words, the dummy wiring layer 30 is composed of a repeating pattern of dummy wiring 30a having a predetermined unit pattern. That is, the dummy wiring layer 30 contains multiple dummy wirings 30a, each of which is electrically independent from the mesh wiring layer 20 (first-direction wiring 21) and the power supply section 40. Furthermore, the multiple dummy wirings 30a are regularly arranged throughout the entire area of ​​the dummy wiring layer 30. Each dummy wire 30a is formed from metal wires in a grid or mesh shape, and has a uniform repeating pattern in the X and Y directions. That is, as shown in Figure 2, each dummy wire 30a includes a first dummy wire portion 31 extending along a first direction (Y direction) and a second dummy wire portion 32 extending along a second direction (X direction). The first dummy wire portion 31 has a predetermined length L4 (length in the Y direction), and the second dummy wire portion 32 has a predetermined length L5 (length in the X direction).

[0041] In this embodiment, the dummy wiring 30a has a shape in which a part of the unit pattern 20A of the mesh wiring layer 20 described above is missing. That is, the shape of the dummy wiring 30a is the L-shaped unit pattern 20A of the mesh wiring layer 20 with the notch portion 33 described later removed. In other words, the shape obtained by combining the dummy wiring 30a of the dummy wiring layer 30 and the notch portion 33 corresponds to the grid shape or mesh shape that forms the mesh wiring layer 20. In this way, because the dummy wiring 30a of the dummy wiring layer 30 has a shape in which a part of the unit pattern 20A of the mesh wiring layer 20 is missing, it is possible to make it difficult to visually recognize the difference between the mesh wiring layer 20 and the dummy wiring layer 30, and to make the mesh wiring layer 20 placed on the substrate 11 less visible.

[0042] In Figure 2, the mesh wiring layer 20 and the dummy wiring layer 30 are adjacent to each other in the Y direction. Near the boundary between the mesh wiring layer 20 and the dummy wiring layer 30, the first dummy wiring portion 31 is formed on the extension of the first directional wiring 21. Therefore, in the Y direction, the difference between the mesh wiring layer 20 and the dummy wiring layer 30 is difficult to see with the naked eye. In addition, the first dummy wiring portion 31 is parallel to the first directional wiring 21 of the unit pattern 20A of the mesh wiring layer 20. In this way, because the first dummy wiring portion 31 is parallel to the first directional wiring 21, glare due to light reflection can be effectively suppressed even when the first dummy wiring portion 31 of the dummy unit pattern 30A is arranged irregularly, as will be described later.

[0043] Furthermore, although not shown in the diagram, the mesh wiring layer 20 and the dummy wiring layer 30 are adjacent to each other in the X direction. Near the boundary between the mesh wiring layer 20 and the dummy wiring layer 30, the second dummy wiring portion 32 is formed on the extension of the second directional wiring 22. As a result, the difference between the mesh wiring layer 20 and the dummy wiring layer 30 is difficult to see with the naked eye in the X direction. In addition, the second dummy wiring portion 32 is parallel to the second directional wiring 22 of the unit pattern 20A of the mesh wiring layer 20. In this way, because the second dummy wiring portion 32 is parallel to the second directional wiring 22, glare due to light reflection can be effectively suppressed even when the second dummy wiring portion 32 of the dummy unit pattern 30A is arranged irregularly, as will be described later.

[0044] As shown in Figure 5, the first dummy wiring portion 31 of each dummy wiring 30a has a roughly rectangular or roughly square cross-section (cross-section in the X direction) perpendicular to its longitudinal direction (Y direction). Also, as shown in Figure 4, the second dummy wiring portion 32 of each dummy wiring 30a has a roughly rectangular or roughly square cross-section (cross-section in the Y direction) perpendicular to its longitudinal direction (X direction). In this case, the cross-sectional shape of the first dummy wiring portion 31 is roughly the same as the cross-sectional shape of the first direction wiring 21, and the cross-sectional shape of the second dummy wiring portion 32 is roughly the same as the cross-sectional shape of the second direction wiring 22.

[0045] In this embodiment, the line width W3 (length in the X direction, see Figure 5) of the first dummy wiring portion 31 is approximately the same as the line width W1 of the first direction wiring 21, and the line width W4 (length in the Y direction, see Figure 4) of the second dummy wiring portion 32 is approximately the same as the line width W2 of the second direction wiring 22. Furthermore, the height H3 (length in the Z direction, see Figure 5) of the first dummy wiring portion 31 and the height H4 (length in the Z direction, see Figure 4) of the second dummy wiring portion 32 are approximately the same as the height H1 of the first direction wiring 21 and the height H2 of the second direction wiring 22, respectively.

[0046] In this embodiment, a notch 33 is formed in the dummy unit pattern 30A. Furthermore, in adjacent dummy unit patterns 30A, at least one of the position and shape of the notch 33 is different from each other. In other words, the notches 33 are formed randomly (irregularly) in the dummy unit pattern 30A. This allows the first dummy wiring portion 31 and the second dummy wiring portion 32 of the dummy unit pattern to be arranged irregularly. As a result, the pitch of the moiré pattern generated due to the regularity (periodicity) of the dummy unit pattern 30A and the regularity (periodicity) of the pixels (not shown) of the image display device 90, which will be described later, can be reduced to a level that is not visible to the naked eye.

[0047] Furthermore, in the illustrated example, the position and shape of the notches 33 differ between adjacent dummy unit patterns 30A. Specifically, the length L4 of the first dummy wiring portion 31 differs between adjacent dummy unit patterns 30A. Also, the length L5 of the second dummy wiring portion 32 differs between adjacent dummy unit patterns 30A.

[0048] Furthermore, a dummy unit pattern 30A may have multiple notches 33 formed therein. This allows the first dummy wiring portion 31 and the second dummy wiring portion 32 to be arranged more irregularly. In this case, in one dummy unit pattern 30A, the notches 33 may be formed to divide the first dummy wiring portion 31 (second dummy wiring portion 32). The dummy wiring layer 30 may also be provided with dummy unit patterns 30A having multiple notches 33 formed therein, and dummy unit patterns 30A having a single notch 33 formed therein.

[0049] In the dummy unit pattern 30A, the first dummy wiring portion 31 and the second dummy wiring portion 32 may be spaced apart from each other. That is, a notch 33 may be formed between the first dummy wiring portion 31 and the second dummy wiring portion 32. This allows the first dummy wiring portion 31 and the second dummy wiring portion 32 to be arranged more irregularly.

[0050] Furthermore, in adjacent dummy unit patterns 30A, the first dummy wiring portions 31 and the second dummy wiring portions 32 may be spaced apart from each other. That is, the first dummy wiring portion 31 of one dummy unit pattern 30A and the first dummy wiring portion 31 of the other dummy unit pattern 30A adjacent to that one dummy unit pattern 30A may be spaced apart from each other. Similarly, the second dummy wiring portion 32 of one dummy unit pattern 30A and the second dummy wiring portion 32 of the other dummy unit pattern 30A adjacent to that one dummy unit pattern 30A may be spaced apart from each other. Even in this case, the first dummy wiring portions 31 and the second dummy wiring portions 32 can be arranged more irregularly.

[0051] Furthermore, it is preferable that the total length (L4 + L5) of the first dummy wiring portion 31 and the second dummy wiring portion 32 are equal in adjacent dummy unit patterns 30A. This suppresses variations in the aperture ratio, which will be described later, in the dummy wiring layer 30. As a result, the dummy wiring layer 30 can be made difficult to recognize with the naked eye.

[0052] The material of the dummy wiring 30a in such a dummy wiring layer 30 can be the same metallic material as the material of the first direction wiring 21 and the material of the second direction wiring 22.

[0053] In this embodiment, the mesh wiring layer 20 and the dummy wiring layer 30 each have a predetermined aperture ratio. The aperture ratios of the mesh wiring layer 20 and the dummy wiring layer 30 can be, for example, in the range of 85% to 99.9%.

[0054] Furthermore, the overall aperture ratio of the mesh wiring layer 20 and the dummy wiring layer 30 (the combined aperture ratio of the mesh wiring layer 20 and the dummy wiring layer 30) can be, for example, in the range of 87% or more and less than 100%. By setting the overall aperture ratio of the wiring board 10 within this range, the conductivity and transparency of the wiring board 10 can be ensured.

[0055] Furthermore, in the dummy wiring layer 30, it is preferable that the difference in aperture ratio between adjacent 500 μm square regions is within 0.2%. This makes the dummy wiring layer 30 difficult to recognize with the naked eye.

[0056] The aperture ratio refers to the ratio (%) of the area of ​​the opening region (the region where there are no metal parts such as the first-direction wiring 21, second-direction wiring 22, dummy wiring 30a, etc., and the substrate 11 is exposed) to the unit area of ​​a predetermined region (mesh wiring layer 20, dummy wiring layer 30, or mesh wiring layer 20 and dummy wiring layer 30).

[0057] Referring again to Figure 1, the power supply unit 40 is electrically connected to the mesh wiring layer 20. This power supply unit 40 consists of a roughly rectangular conductive thin plate-like member. The longitudinal direction of the power supply unit 40 is parallel to the X direction, and the short direction of the power supply unit 40 is parallel to the Y direction. The power supply unit 40 is located at the longitudinal end (negative Y-direction end) of the substrate 11. The material of the power supply unit 40 can be a metallic material (including alloys) such as gold, silver, copper, platinum, tin, aluminum, iron, or nickel. When the wiring board 10 is incorporated into the image display device 90 (see Figure 7), this power supply unit 40 is electrically connected to the wireless communication circuit 92 of the image display device 90. Although the power supply unit 40 is provided on the surface of the substrate 11, it is not limited to this, and part or all of the power supply unit 40 may be located outside the periphery of the substrate 11.

[0058] [Manufacturing method for wiring boards] Next, the method for manufacturing a wiring board according to this embodiment will be described with reference to Figures 6(a)-(f). Figures 6(a)-(f) are cross-sectional views showing the method for manufacturing a wiring board according to this embodiment.

[0059] First, a transparent substrate 11 is prepared, as shown in Figure 6(a).

[0060] Next, a mesh wiring layer 20 containing a plurality of first-directional wirings 21 and a dummy wiring layer 30 containing a plurality of dummy wirings 30a arranged around the mesh wiring layer 20 and electrically independent from the first-directional wirings 21 are formed on the substrate 11.

[0061] In this process, first, as shown in Figure 6(b), a metal foil 51 is laminated over substantially the entire surface of the substrate 11. In this embodiment, the thickness of the metal foil 51 may be 0.1 μm or more and 5.0 μm or less. In this embodiment, the metal foil 51 may contain copper.

[0062] Next, as shown in Figure 6(c), a photocurable insulating resist 52 is supplied to substantially the entire surface of the metal foil 51. Examples of photocurable insulating resists 52 include organic resins such as acrylic resins and epoxy resins.

[0063] Next, as shown in Figure 6(d), the insulating layer 54 is formed by photolithography. In this case, the photocurable insulating resist 52 is patterned by photolithography to form the insulating layer 54 (resist pattern). At this time, the insulating layer 54 is formed so that the metal foil 51 corresponding to the first directional wiring 21 and the second directional wiring 22 is exposed.

[0064] Next, as shown in Figure 6(e), the metal foil 51 located on the surface of the substrate 11 that is not covered by the insulating layer 54 is removed. In this process, the metal foil 51 is etched so that the surface of the substrate 11 is exposed by performing a wet treatment using ferric chloride, cupric chloride, strong acids such as sulfuric acid and hydrochloric acid, persulfates, hydrogen peroxide, aqueous solutions thereof, or combinations thereof.

[0065] Next, as shown in Figure 6(f), the insulating layer 54 is removed. In this case, the insulating layer 54 on the metal foil 51 is removed by wet treatment using a permanganate solution, N-methyl-2-pyrrolidone, an acid or alkaline solution, or by dry treatment using oxygen plasma.

[0066] In this way, a wiring board 10 is obtained having a substrate 11 and a mesh wiring layer 20 and a dummy wiring layer 30 arranged on the substrate 11. In this case, the mesh wiring layer 20 includes first-direction wiring 21 and second-direction wiring 22, and the dummy wiring layer 30 includes dummy wiring 30a.

[0067] [Operation of this embodiment] Next, we will describe the operation of this embodiment, which has the above configuration.

[0068] As shown in Figure 7, the wiring board 10 is incorporated into an image display device 90 having a display 91. The wiring board 10 is placed on the display 91. Examples of such image display devices 90 include mobile terminal devices such as smartphones and tablets. The mesh wiring layer 20 of the wiring board 10 is electrically connected to the wireless communication circuit 92 of the image display device 90 via the power supply unit 40. In this way, radio waves of a predetermined frequency can be transmitted and received via the mesh wiring layer 20, and communication can be performed using the image display device 90. The dummy wiring layer 30 is separated from the mesh wiring layer 20 and is electrically independent. Therefore, even if the dummy wiring layer 30 is provided, it does not affect the transmission and reception of radio waves.

[0069] According to this embodiment, the wiring board 10 has a substrate 11 and a mesh wiring layer 20 disposed on the substrate 11 and including a plurality of first directional wirings 21. Since the substrate 11 has a transmittance of 85% or more for light rays with wavelengths of 400 nm to 700 nm, the transparency of the wiring board 10 is ensured. As a result, when the wiring board 10 is placed on the display 91, the display 91 can be viewed through the openings 23 of the mesh wiring layer 20, so the visibility of the display 91 is not obstructed.

[0070] Furthermore, a dummy wiring layer 30 containing multiple dummy wirings 30a that are electrically independent from the first directional wiring 21 is arranged around the mesh wiring layer 20.

[0071] Incidentally, in the image display device 90, the dummy wiring layer 30 of the wiring board 10 is arranged to overlap the pixels (not shown) of the image display device 90 in the Z direction. Therefore, moiré patterns may occur due to the regularity (periodicity) of the dummy unit pattern 30A of the dummy wiring layer 30 and the regularity (periodicity) of the pixels.

[0072] In contrast, in this embodiment, notches 33 are formed in the dummy unit pattern 30A of the dummy wiring layer 30. Furthermore, in adjacent dummy unit patterns 30A, at least one of the position and shape of the notches 33 is different from each other. As a result, when viewed from the Z direction, the first dummy wiring portion 31, the second dummy wiring portion 32, and the pixels of the dummy unit pattern 30A are arranged irregularly. Therefore, the pitch of the moiré pattern generated due to the regularity (periodicity) of the dummy unit pattern 30A and the regularity (periodicity) of the pixels can be reduced to a level that is not visible to the naked eye.

[0073] Furthermore, the unit pattern 20A includes a first-direction wiring 21 extending along the Y direction (first direction) and a second-direction wiring 22 extending along the X direction (second direction), and the dummy unit pattern 30A includes a first dummy wiring portion 31 extending along the Y direction (first direction) and a second dummy wiring portion 32 extending along the X direction (second direction). That is, the first-direction wiring 21 and the first dummy wiring portion 31 extend along the Y direction, and the second-direction wiring 22 and the second dummy wiring portion 32 extend along the X direction. As a result, even if the first dummy wiring portion 31 and the second dummy wiring portion 32 of the dummy unit pattern 30A are arranged irregularly, glare due to light reflection can be suppressed. In addition, in this embodiment, the first dummy wiring portion 31 and the second dummy wiring portion 32 are parallel to the first-direction wiring 21 and the second-direction wiring 22. This effectively suppresses glare caused by light reflection, even when the first dummy wiring portion 31 and the second dummy wiring portion 32 of the dummy unit pattern 30A are arranged irregularly.

[0074] Furthermore, according to this embodiment, in the dummy unit pattern 30A, the first dummy wiring portion 31 and the second dummy wiring portion 32 are spaced apart from each other. That is, a notch 33 is formed between the first dummy wiring portion 31 and the second dummy wiring portion 32. This allows the first dummy wiring portion 31 and the second dummy wiring portion 32 to be arranged more irregularly. As a result, the resulting moiré pattern can be made less visible.

[0075] Furthermore, according to this embodiment, in adjacent dummy unit patterns 30A, the first dummy wiring portions 31 and the second dummy wiring portions 32 are spaced apart from each other. Even in this case, the first dummy wiring portions 31 and the second dummy wiring portions 32 can be arranged more irregularly, making the resulting moiré patterns less visible.

[0076] Furthermore, according to this embodiment, a plurality of notches 33 are formed in the dummy unit pattern 30A. In this case as well, the first dummy wiring portion 31 and the second dummy wiring portion 32 can be arranged more irregularly, making the resulting moiré pattern less visible.

[0077] Furthermore, according to this embodiment, in adjacent dummy unit patterns 30A, the total length (L4 + L5) of the first dummy wiring portion 31 and the second dummy wiring portion 32 are equal. This suppresses variations in the aperture ratio in the dummy wiring layer 30. As a result, the dummy wiring layer 30 can be made difficult to recognize with the naked eye.

[0078] Furthermore, according to this embodiment, the dummy unit pattern 30A is repeatedly arranged parallel to the Y direction (first direction) and the X direction (second direction). This makes it possible to more effectively suppress glare caused by light reflection, even when the first dummy wiring portion 31 and the second dummy wiring portion 32 of the dummy unit pattern 30A are arranged irregularly.

[0079] [Differentiation] Next, a modified image display device and a wiring board will be described. Figures 8 and 9 show a modified wiring board. The modified form shown in Figures 8 and 9 differs in the planar shape of the mesh wiring layer 20, but the other configurations are substantially the same as those of the embodiments shown in Figures 1 to 7 described above. In Figures 8 and 9, the same reference numerals are used for parts that are the same as those shown in Figures 1 to 7, and detailed descriptions are omitted.

[0080] (First variation) In Figure 8, the first directional wiring 21 and the second directional wiring 22 intersect at an angle (not perpendicular), and each opening 23 is formed in a rhombus shape in plan view. Neither the first directional wiring 21 nor the second directional wiring 22 are parallel to either the X or Y direction, but either one of the first directional wiring 21 or the second directional wiring 22 may be parallel to either the X or Y direction.

[0081] Furthermore, the first dummy wiring portion 31 of the dummy wiring layer 30 may extend parallel to the first directional wiring 21. Similarly, the second dummy wiring portion 32 of the dummy wiring layer 30 may extend parallel to the second directional wiring 22.

[0082] In this modified example, notches 33 are formed in the dummy unit pattern 30A of the dummy wiring layer 30. Furthermore, in adjacent dummy unit patterns 30A, at least one of the position and shape of the notches 33 differs from one another. As a result, when viewed from the Z direction, the first dummy wiring portion 31, the second dummy wiring portion 32, and the pixels of the dummy unit pattern are arranged irregularly. Therefore, the pitch of the moiré pattern generated due to the regularity (periodicity) of the dummy unit pattern 30A and the regularity (periodicity) of the pixels can be reduced to a level that is not visible to the naked eye.

[0083] (Second variation) In Figure 9, in this modified example, additional patterns 34 are arranged within the dummy wiring layer 30, spaced apart from the dummy wiring 30a of the dummy wiring layer 30. In this case, the additional patterns 34 are spaced apart in both the X and Y directions from the multiple first dummy wiring portions 31 and the multiple second dummy wiring portions 32. In this case, each additional pattern 34 extends linearly parallel to either the first dummy wiring portion 31 or the second dummy wiring portion 32. Furthermore, multiple (two) additional patterns 34 are arranged for each dummy wiring 30a. It is preferable that the total area of ​​these multiple (two) additional patterns 34 approaches the area of ​​the notch portion 33 of each dummy wiring 30a. The material of the additional patterns 34 can be the same metal material as the material of the dummy wiring 30a.

[0084] In this way, by placing the additional pattern 34 within the dummy wiring layer 30, the difference between the aperture ratio of the dummy wiring layer 30 and the aperture ratio of the mesh wiring layer 20 can be brought close to zero. Specifically, this difference can be set to a range of 0% to 1%. This makes the boundary between the mesh wiring layer 20 and the dummy wiring layer 30 unclear, making the mesh wiring layer 20 difficult to recognize with the naked eye.

[0085] Although not shown in the diagram, each additional pattern 34 may extend linearly and non-parallel to the first dummy wiring section 31 or the second dummy wiring section 32. Alternatively, the additional patterns 34 may not extend linearly but have a dot shape (point shape) in plan view.

[0086] The multiple components disclosed in the above embodiments and each of the variations can be combined as needed. Alternatively, some components may be removed from all the components shown in the above embodiments and each of the variations. [Explanation of Symbols]

[0087] 10 Wiring board 11 circuit boards 20 mesh wiring layers 20A unit pattern 21 1st direction wiring 22 2nd direction wiring 30 Dummy Wiring Layers 30A Dummy Unit Pattern 30a dummy wiring 31. First dummy wiring section 32. Second dummy wiring section 33 Notch 34 Additional Patterns

Claims

1. A wiring board, A transparent substrate, A mesh wiring layer, which includes multiple wirings, is arranged on the aforementioned substrate. A dummy wiring layer comprising a plurality of dummy wires electrically independent from the aforementioned wiring, The mesh wiring layer is composed of a repeating arrangement of unit patterns. The dummy wiring layer is composed of a repeating arrangement of dummy unit patterns. A notch is formed in the dummy unit pattern. In the adjacent dummy unit patterns, at least one of the position and shape of the notches is different from one another. The dummy unit pattern includes a first dummy wiring portion extending along a first direction and a second dummy wiring portion extending along a second direction different from the first direction. A wiring board in which the first dummy wiring portion and the second dummy wiring portion are spaced apart from each other in the dummy unit pattern.

2. The wiring substrate according to claim 1, wherein the difference in aperture ratio of adjacent 500 μm square regions in the dummy wiring layer is within 0.2%.

3. The wiring board according to claim 1 or 2, wherein in adjacent dummy unit patterns, the first dummy wiring portions and the second dummy wiring portions are spaced apart from each other.

4. The wiring board according to any one of claims 1 to 3, wherein a plurality of the notches are formed in the dummy unit pattern.

5. The wiring board according to any one of claims 1 to 4, wherein in adjacent dummy unit patterns, the total length of the first dummy wiring portion and the second dummy wiring portion are equal to each other.

6. The wiring board according to any one of claims 1 to 5, wherein an additional pattern spaced apart from the dummy wiring is arranged within the dummy wiring layer.

7. The wiring board according to claim 6, wherein the additional pattern extends non-parallel to the first dummy wiring portion or the second dummy wiring portion.

8. The wiring board according to any one of claims 1 to 7, wherein the dummy unit pattern is repeatedly arranged parallel to the first direction and the second direction.

9. A wiring board according to any one of claims 1 to 8, having a radio wave transmission and reception function.

10. A method for manufacturing a wiring board, A process for preparing a transparent substrate, The process includes forming a mesh wiring layer containing a plurality of wirings and a dummy wiring layer containing a plurality of dummy wirings electrically independent from the aforementioned wirings on the substrate, The mesh wiring layer is composed of a repeating arrangement of unit patterns. The dummy wiring layer is composed of a repeating arrangement of dummy unit patterns. A notch is formed in the dummy unit pattern. In the adjacent dummy unit patterns, at least one of the position and shape of the notches is different from one another. The dummy unit pattern includes a first dummy wiring portion extending along a first direction and a second dummy wiring portion extending along a second direction different from the first direction. A method for manufacturing a wiring board, wherein in the dummy unit pattern, the first dummy wiring portion and the second dummy wiring portion are spaced apart from each other.

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