JP7784066B2 - Wiring board and image display device - Google Patents

Description

Embodiments of the present disclosure relate to a wiring board and an image display device.

Currently, mobile terminal devices such as smartphones and tablets are becoming more functional, smaller, thinner, and lighter. Because these mobile terminal devices use multiple communication bands, they require multiple antennas corresponding to the communication bands. For example, mobile terminal devices are equipped with multiple antennas, such as a telephone antenna, a Wi-Fi (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, as mobile terminal devices become smaller, the space available for antenna installation is limited, limiting the freedom in antenna design. Furthermore, because antennas are built into a limited space, radio wave sensitivity is not always satisfactory.

For this reason, film antennas that can be mounted in the display area of mobile terminal devices have been developed. These film antennas are transparent antennas in which an antenna pattern is formed on a transparent substrate, and the antenna pattern is formed from a mesh-like conductive mesh layer consisting of conductor portions as formed portions of an opaque conductive layer and numerous openings as non-formed portions.

JP 2011-66610 A

For example, in conventional film antennas, one or more mesh antennas are mounted on a transparent substrate, and the transparent substrate has both areas where an antenna pattern is formed and areas where an antenna pattern is not formed. In this case, the presence of areas where an antenna pattern is not formed makes the areas where an antenna pattern is formed easily visible. For this reason, there is a demand for wiring patterns such as antenna patterns to be less visible.

This embodiment provides a wiring board and an image display device that can make the mesh wiring layer less visible.

A first aspect of the present disclosure is a wiring board comprising: a substrate including a first surface and a second surface located opposite the first surface; a primer layer disposed on the first surface of the substrate; a mesh wiring layer disposed on the primer layer; and a dark layer covering the mesh wiring layer; the substrate is transparent; the mesh wiring layer has a first metal layer disposed on the primer layer and a second metal layer disposed on the first metal layer; and the surface roughness Ra of the dark layer is 5 nm or more and 100 nm or less.

A second aspect of the present disclosure relates to a wiring board according to the first aspect described above, wherein the first metal layer and the second metal layer may have different crystal properties, and the second metal layer may have crystal properties such that the diffraction angle 2θ of the (111) plane measured using CuKα radiation as an X-ray source is less than 43.4°.

A third aspect of the present disclosure is a wiring board according to the first or second aspect described above, wherein the dielectric loss tangent of the board may be 0.002 or less.

A fourth aspect of the present disclosure is a wiring board according to any one of the first to third aspects described above, wherein when the wiring board is bent 180 degrees around a cylinder with a diameter of 1 mm and then straightened 100 times, the increase in resistance of the mesh wiring layer may be 20% or less.

A fifth aspect of the present disclosure relates to a wiring board according to each of the first to fourth aspects described above, wherein the wiring board may have a millimeter wave transmission/reception function, and the mesh wiring layer may function as an array antenna.

A sixth aspect of the present disclosure is a wiring board according to any one of the first to fifth aspects described above, wherein a dummy wiring layer electrically independent from the mesh wiring layer may be provided around the mesh wiring layer.

A seventh aspect of the present disclosure is that, in the wiring board according to the sixth aspect described above, multiple dummy wiring layers may be provided, and the aperture ratios of the mesh wiring layer and the dummy wiring layer may increase stepwise from the mesh wiring layer toward the dummy wiring layer farther from the mesh wiring layer.

An eighth aspect of the present disclosure comprises a wiring board according to any one of the first to seventh aspects described above, and a display device stacked on the wiring board.

According to embodiments of the present disclosure, the mesh wiring layer can be made less visible.

FIG. 1 is a plan view showing an image display device according to an embodiment. FIG. 2 is a cross-sectional view (cross-sectional view taken along line II-II in FIG. 1) showing the image display device according to the embodiment. FIG. 3 is a plan view showing the wiring board according to the embodiment. FIG. 4 is an enlarged plan view showing a mesh wiring layer of a wiring board according to an embodiment. FIG. 5 is a cross-sectional view (cross-sectional view taken along line VV in FIG. 4) showing the wiring board according to the embodiment. FIG. 6 is a cross-sectional view (cross-sectional view taken along line VI-VI in FIG. 4) showing the wiring board according to the embodiment. 7A to 7I are cross-sectional views showing a method for manufacturing a wiring board according to one embodiment. FIG. 8 is a plan view showing a wiring board according to a first modified example. FIG. 9 is an enlarged plan view showing a wiring board according to a first modified example. FIG. 10 is a plan view showing a wiring board according to a second modified example. FIG. 11 is an enlarged plan view showing a wiring board according to a second modified example. FIG. 12 is a plan view showing a wiring board according to a third modified example.

First, one embodiment will be described with reference to Figures 1 to 7. Figures 1 to 7 show this embodiment.

The figures shown below are schematic diagrams. Therefore, the size and shape of each part have been appropriately exaggerated to make them easier to understand. Furthermore, appropriate modifications can be made without departing from the technical concept. In the figures shown below, identical parts are given the same reference numerals, and some detailed explanations may be omitted. Furthermore, the numerical values, such as dimensions, and material names of each component described in this specification are examples of an embodiment, and are not limited to these and can be selected and used as appropriate. In this specification, terms specifying shapes or geometric conditions, such as parallel, orthogonal, and perpendicular, are interpreted to include substantially the same state in addition to their strict meaning.

In the following embodiments, the "X direction" refers to a direction parallel to one side of the image display device. The "Y direction" refers to a direction perpendicular to the X direction and parallel to another side of the image display device. The "Z direction" refers to a direction perpendicular to both the X and Y directions and parallel to the thickness direction of the image display device. The "front surface" refers to the surface on the positive side of the Z direction, which is the light-emitting surface side of the image display device and faces the viewer. The "back surface" refers to the surface on the negative side of the Z direction, which is the surface opposite the light-emitting surface of the image display device and the surface facing the viewer. Note that in this embodiment, the mesh wiring layer 20 is described as having radio wave transmission and reception functionality (i.e., functionality as an antenna), but the mesh wiring layer 20 does not necessarily have to have radio wave transmission and reception functionality.

The configuration of the image display device according to this embodiment will be described with reference to Figures 1 and 2.

As shown in Figures 1 and 2, the image display device 60 according to this embodiment includes a wiring substrate 10 and a display device 61 laminated on the wiring substrate 10. The wiring substrate 10, together with a first transparent adhesive layer 95 and a second transparent adhesive layer 96, constitutes a laminate 70 for an image display device.

The wiring board 10 includes a substrate 11, a primer layer 15, a mesh wiring layer 20, a dark layer 18, and a power supply unit 40. As shown in FIG. 2, the substrate 11 includes a first surface 11a and a second surface 11b located opposite the first surface 11a. The primer layer 15 is disposed on the first surface 11a of the substrate 11. The mesh wiring layer 20 is disposed on the primer layer 15. The mesh wiring layer 20 is covered with the dark layer 18. The power supply unit 40 is electrically connected to the mesh wiring layer 20. Furthermore, a communication module 63 is disposed on the negative Z-direction side of the display device 61. The image display device laminate 70, the display device 61, and the communication module 63 are housed in a housing 62.

The image display device 60 shown in Figures 1 and 2 can transmit and receive radio waves of a predetermined frequency via a communication module 63, enabling communication. The communication module 63 may include any of a millimeter wave antenna, a telephone antenna, a Wi-Fi antenna, a 3G antenna, a 4G antenna, a 5G antenna, an LTE antenna, a Bluetooth (registered trademark) antenna, an NFC antenna, etc. Examples of such image display devices 60 include mobile terminal devices such as smartphones and tablets.

As shown in FIG. 2, the image display device 60 has a light-emitting surface 64. The image display device 60 includes a wiring board 10 located on the light-emitting surface 64 side (i.e., the positive side in the Z direction) of the display device 61, and a communication module 63 located on the opposite side of the light-emitting surface 64 of the display device 61 (i.e., the negative side in the Z direction).

The display device 61 is, for example, an organic EL (Electro Luminescence) display device. The display device 61 may include, for example, a metal layer, a support substrate, a resin substrate, a thin film transistor (TFT), and an organic EL layer (all not shown). A touch sensor (not shown) may be disposed on the display device 61. A wiring substrate 10 is also disposed on the display device 61 via a second transparent adhesive layer 96. Note that the display device 61 is not limited to an organic EL display device. For example, the display device 61 may be another display device that has the ability to emit light itself, or may be a micro LED display device including micro LED elements. The display device 61 may also be a liquid crystal display device including liquid crystal.

A cover glass 75 is disposed on the wiring substrate 10 via a first transparent adhesive layer 95. Note that a decorative film and a polarizing plate (not shown) may be disposed between the first transparent adhesive layer 95 and the cover glass 75.

The first transparent adhesive layer 95 is an adhesive layer that directly or indirectly bonds the wiring substrate 10 to the cover glass 75. This first transparent adhesive layer 95 is located on the first surface 11a side of the substrate 11. The first transparent adhesive layer 95 is optically transparent and may be an OCA (Optical Clear Adhesive) layer. The OCA layer is a layer prepared, for example, as follows: First, a liquid curable adhesive layer composition containing a polymerizable compound is applied to a release film such as polyethylene terephthalate (PET). Next, the composition is cured using, for example, ultraviolet (UV) light to obtain an OCA sheet. After bonding the OCA sheet to an object, the release film is peeled off and removed to obtain the OCA layer. The material of the first transparent adhesive layer 95 may be an acrylic resin, a silicone resin, a urethane resin, or the like. In particular, the first transparent adhesive layer 95 may contain an acrylic resin. In this case, it is preferable that the second transparent adhesive layer 96 contains an acrylic resin. This effectively eliminates the difference in refractive index between the first transparent adhesive layer 95 and the second transparent adhesive layer 96, and more reliably suppresses reflection of visible light at the interface B4 between the first transparent adhesive layer 95 and the second transparent adhesive layer 96.

The first transparent adhesive layer 95 may have a visible light transmittance of 85% or more, preferably 90% or more. There is no particular upper limit to the visible light transmittance of the first transparent adhesive layer 95, but it may be, for example, 100% or less. By ensuring that the visible light transmittance of the first transparent adhesive layer 95 falls within the above range, the transparency of the image display device laminate 70 can be increased, making the display device 61 of the image display device 60 easier to see. Visible light refers to light with a wavelength of 400 nm or more and 700 nm or less. A visible light transmittance of 85% or more means that, when the absorbance of the member to be measured (e.g., the first transparent adhesive layer 95) is measured, the transmittance is 85% or more across the entire wavelength range from 400 nm to 700 nm. Absorbance measurements can be performed using a known spectrophotometer (e.g., the V-670 spectrometer manufactured by JASCO Corporation).

As described above, the wiring substrate 10 is disposed on the light-emitting surface 64 side of the display device 61. In this case, the wiring substrate 10 is located between the first transparent adhesive layer 95 and the second transparent adhesive layer 96. More specifically, a portion of the substrate 11 of the wiring substrate 10 is disposed in a portion of the area between the first transparent adhesive layer 95 and the second transparent adhesive layer 96. In this case, the first transparent adhesive layer 95, the second transparent adhesive layer 96, the display device 61, and the cover glass 75 each have a larger area than the substrate 11 of the wiring substrate 10. In this way, by disposing the substrate 11 of the wiring substrate 10 in a portion of the image display device 60 rather than over the entire surface in a plan view, the overall thickness of the image display device 60 can be reduced.

As described above, the wiring board 10 includes a transparent substrate 11, a primer layer 15 disposed on the first surface 11a of the substrate 11, a mesh wiring layer 20 disposed on the primer layer 15, and a dark layer 18 covering the mesh wiring layer 20. A power supply unit 40 is electrically connected to the mesh wiring layer 20. The power supply unit 40 is electrically connected to the communication module 63 via a power supply line (not shown). Furthermore, a portion of the wiring board 10 is not disposed between the first transparent adhesive layer 95 and the second transparent adhesive layer 96, but protrudes outward (i.e., toward the negative Y-direction) from between the first transparent adhesive layer 95 and the second transparent adhesive layer 96. Specifically, the region of the wiring board 10 where the power supply unit 40 is disposed protrudes outward. This facilitates electrical connection between the power supply unit 40 and the communication module 63. Meanwhile, the region of the wiring board 10 where the mesh wiring layer 20 is disposed is located between the first transparent adhesive layer 95 and the second transparent adhesive layer 96. Details of the wiring board 10 will be described later.

The second transparent adhesive layer 96 is an adhesive layer that directly or indirectly adheres the display device 61 to the wiring substrate 10. This second transparent adhesive layer 96 is located on the second surface 11b side of the substrate 11. Like the first transparent adhesive layer 95, the second transparent adhesive layer 96 is optically transparent and may be an OCA (Optical Clear Adhesive) layer. The material of the second transparent adhesive layer 96 may be an acrylic resin, a silicone resin, a urethane resin, or the like. In particular, the second transparent adhesive layer 96 may contain an acrylic resin. This substantially eliminates the difference in refractive index between the first transparent adhesive layer 95 and the second transparent adhesive layer 96, and more reliably suppresses reflection of visible light at the interface B4 between the first transparent adhesive layer 95 and the second transparent adhesive layer 96.

The second transparent adhesive layer 96 may have a transmittance of 85% or more for visible light (i.e., light with a wavelength of 400 nm or more and 700 nm or less), and preferably 90% or more. There is no particular upper limit to the visible light transmittance of the second transparent adhesive layer 96, but it may be, for example, 100% or less. By setting the visible light transmittance of the second transparent adhesive layer 96 within the above range, the transparency of the image display device laminate 70 can be increased, making it easier to view the display device 61 of the image display device 60.

In this laminate 70 for an image display device, the difference in refractive index between the primer layer 15 and the first transparent adhesive layer 95 is 0.1 or less, and preferably 0.05 or less. Furthermore, the difference in refractive index between the primer layer 15 and the substrate 11 is 0.1 or less, and preferably 0.05 or less. Here, the refractive index refers to the absolute refractive index, and can be determined based on Method A of JIS K-7142. For example, if the material of the first transparent adhesive layer 95 is an acrylic resin (refractive index 1.49), the refractive index of the primer layer 15 should be 1.39 or more and 1.59 or less. Examples of such materials include fluororesins, silicone resins, polyolefin resins, polyester resins, acrylic resins, polycarbonate resins, polyimide resins, and cellulose resins.

In this way, by keeping the difference between the refractive index of the primer layer 15 and the refractive index of the first transparent adhesive layer 95 to 0.1 or less, reflection of visible light at the interface B1 between the primer layer 15 and the first transparent adhesive layer 95 is suppressed, making it difficult for the observer to see the substrate 11 on which the primer layer 15 is provided with the naked eye. Furthermore, by keeping the difference between the refractive index of the primer layer 15 and the refractive index of the substrate 11 to 0.1 or less, reflection of visible light at the interface B2 between the primer layer 15 and the substrate 11 is suppressed, making it difficult for the observer to see the substrate 11 with the naked eye.

In the laminate 70 for an image display device, the difference in refractive index between the substrate 11 and the first transparent adhesive layer 95 is 0.1 or less, and preferably 0.05 or less. The difference in refractive index between the second transparent adhesive layer 96 and the substrate 11 is 0.1 or less, and preferably 0.05 or less. The difference in refractive index between the first transparent adhesive layer 95 and the second transparent adhesive layer 96 is preferably 0.1 or less, and more preferably 0.05 or less. For example, if the material of the first transparent adhesive layer 95 and the material of the second transparent adhesive layer 96 are acrylic resins (refractive index 1.49), the refractive index of the substrate 11 is set to 1.39 or more and 1.59 or less. As described above, examples of such materials include fluororesins, silicone resins, polyolefin resins, polyester resins, acrylic resins, polycarbonate resins, polyimide resins, and cellulose resins.

In this way, by keeping the difference between the refractive index of the second transparent adhesive layer 96 and the refractive index of the substrate 11 to 0.1 or less, reflection of visible light at the interface B3 between the second transparent adhesive layer 96 and the substrate 11 is suppressed, making it difficult for the observer to see the substrate 11 with their naked eyes. Furthermore, by keeping the difference between the refractive index of the first transparent adhesive layer 95 and the refractive index of the second transparent adhesive layer 96 to 0.1 or less, reflection of visible light at the interface B4 between the first transparent adhesive layer 95 and the second transparent adhesive layer 96 is suppressed, making it difficult for the observer to see the first transparent adhesive layer 95 and the second transparent adhesive layer 96 with their naked eyes.

In particular, it is preferable that the material of the first transparent adhesive layer 95 and the material of the second transparent adhesive layer 96 are the same. This reduces the difference in refractive index between the first transparent adhesive layer 95 and the second transparent adhesive layer 96, and suppresses reflection of visible light at the interface B4 between the first transparent adhesive layer 95 and the second transparent adhesive layer 96.

2 , at least one of the thickness _T3 of the first transparent adhesive layer 95 and the thickness _T4 of the second transparent adhesive layer 96 may be 1.5 times or more, preferably 2 times or more, and more preferably 2.5 times or more, the thickness _T1 of the substrate 11. By making the thickness _T3 of the first transparent adhesive layer 95 or the thickness _T4 of the second transparent adhesive layer 96 sufficiently thick relative to the thickness T1 of the substrate ₁₁ , the first transparent adhesive layer 95 or the second transparent adhesive layer 96 deforms in the thickness direction in the region overlapping with the substrate 11, absorbing the thickness of the substrate 11. This makes it possible to prevent steps from occurring in the first transparent adhesive layer 95 or the second transparent adhesive layer 96 at the periphery of the substrate 11, making it difficult for an observer to perceive the presence of the substrate 11.

At least one of the thickness _T3 of the first transparent adhesive layer 95 and the thickness _T4 of the second transparent adhesive layer 96 is preferably 10 times or less, and more preferably 5 times or less, the thickness _T1 of the substrate 11. This prevents the thickness _T3 of the first transparent adhesive layer 95 or the thickness _T4 of the second transparent adhesive layer 96 from becoming too thick, and allows the overall thickness of the image display device 60 to be thin.

2 , the thickness _T3 of the first transparent adhesive layer 95 and the thickness _T4 of the second transparent adhesive layer 96 may be the same. In this case, the thickness _T3 of the first transparent adhesive layer 95 and the thickness _T4 of the second transparent adhesive layer 96 may each be 1.5 times or more, and preferably 2.0 times or more, the thickness _T1 of the substrate 11. That is, the sum of the thickness _T3 of the first transparent adhesive layer 95 and the thickness _T4 of the second transparent adhesive layer 96 (i.e., _T3 + _T4 ) is three times or more the thickness _T1 of the substrate 11. In this way, by making the sum of the thicknesses _T3 and _T4 of the first transparent adhesive layer 95 and the second transparent adhesive layer 96 sufficiently thick relative to the thickness _T1 of the substrate 11, the first transparent adhesive layer 95 and the second transparent adhesive layer 96 deform (shrink) in the thickness direction in the region overlapping with the substrate 11. As a result, the first transparent adhesive layer 95 and the second transparent adhesive layer 96 absorb the thickness of the substrate 11. This makes it possible to prevent steps from occurring in the first transparent adhesive layer 95 or the second transparent adhesive layer 96 at the periphery of the substrate 11, making it difficult for an observer to recognize the presence of the substrate 11.

When the thickness _T3 of the first transparent adhesive layer 95 and the thickness _T4 of the second transparent adhesive layer 96 are the same, the thickness _T3 of the first transparent adhesive layer 95 and the thickness _T4 of the second transparent adhesive layer 96 may each be five times or less, and preferably three times or less, the thickness _T1 of the substrate 11. This prevents the thicknesses _T3 and _T4 of the first transparent adhesive layer 95 and the second transparent adhesive layer 96 from becoming too thick, and allows the overall thickness of the image display device 60 to be thin.

Specifically, the thickness _T1 of the substrate 11 may be, for example, 2 μm or more, 10 μm or more, and preferably 15 μm or more. By setting the thickness _T1 of the substrate 11 to 2 μm or more, the strength of the wiring substrate 10 can be maintained and the first directional wiring 21 and second directional wiring 22 (described later) of the mesh wiring layer 20 can be made less likely to deform. Furthermore, the thickness _T1 of the substrate 11 may be, for example, 200 μm or less, 50 μm or less, and preferably 25 μm or less. Setting the thickness _T1 of the substrate 11 to 200 μm or less prevents steps from occurring in the first transparent adhesive layer 95 and the second transparent adhesive layer 96 at the periphery of the substrate 11, making it difficult for an observer to recognize the presence of the substrate 11. Furthermore, by setting the thickness _T1 of the substrate 11 to 50 μm or less, the occurrence of steps in the first transparent adhesive layer 95 and the second transparent adhesive layer 96 at the periphery of the substrate 11 is further suppressed, making it more difficult for an observer to recognize the presence of the substrate 11.

The thickness _T3 of the first transparent adhesive layer 95 may be, for example, 15 μm or more, and preferably 20 μm or more. The thickness _T3 of the first transparent adhesive layer 95 may be, for example, 500 μm or less, and preferably 300 μm or less, and more preferably 250 μm or less. The thickness _T4 of the second transparent adhesive layer 96 may be, for example, 15 μm or more, and preferably 20 μm or more. The thickness _T4 of the second transparent adhesive layer 96 may be, for example, 500 μm or less, and preferably 300 μm or less, and more preferably 250 μm or less.

Referring again to FIG. 2 , the cover glass 75 is disposed directly or indirectly on the first transparent adhesive layer 95. This cover glass 75 is a light-transmitting glass member. The cover glass 75 is plate-shaped and may be rectangular in plan view. The thickness of the cover glass 75 may be, for example, 200 μm to 1000 μm, and preferably 300 μm to 700 μm. The length of the cover glass 75 in the longitudinal direction (i.e., Y direction) may be, for example, 20 mm to 500 mm, and preferably 100 mm to 200 mm. The length of the cover glass 75 in the lateral direction (i.e., X direction) may be, for example, 20 mm to 500 mm, and preferably 50 mm to 100 mm.

As shown in FIG. 1 , the shape of the image display device 60 is generally rectangular in plan view, with its longitudinal direction parallel to the Y direction and its lateral direction parallel to the X direction. The length _L4 of the image display device 60 in the longitudinal direction (i.e., the Y direction) can be selected, for example, from 20 mm to 500 mm, preferably from 100 mm to 200 mm. The length _L5 of the image display device 60 in the lateral direction (i.e., the X direction) can be selected, for example, from 20 mm to 500 mm, preferably from 50 mm to 100 mm. The planar shape of the image display device 60 may also be a rectangle with rounded corners.

Next, the configuration of the wiring board will be described with reference to Figures 3 to 6. Figures 3 to 6 are diagrams showing the wiring board according to this embodiment.

As shown in FIG. 3, the wiring board 10 according to this embodiment is a substrate used in the image display device 60 described above (see FIGS. 1 and 2). The wiring board 10 can be disposed on the light-emitting surface 64 side of the display device 61, between a first transparent adhesive layer 95 and a second transparent adhesive layer 96. As described above, such a wiring board 10 has a transparent substrate 11, a primer layer 15 disposed on the substrate 11, a mesh wiring layer 20 disposed on the primer layer 15, and a dark layer 18 covering the mesh wiring layer 20. In addition, a power supply unit 40 is electrically connected to the mesh wiring layer 20.

The shape of the substrate 11 is substantially rectangular in plan view. The substrate 11 is transparent and substantially flat, with a substantially uniform thickness overall. The length _L1 of the substrate 11 in the first direction (i.e., Y direction) can be selected, for example, from 3 mm to 300 mm. The length _L2 of the substrate 11 in the second direction (i.e., X direction) (see FIG. 1 ) can be selected, for example, from 3 mm to 300 mm. The planar shape of the substrate 11 may be a rectangle with rounded corners.

The material of the substrate 11 may be any material that is transparent in the visible light range and electrically insulating. The substrate 11 is preferably made of an organic insulating material such as polyester resin, acrylic resin, polycarbonate resin, polyimide resin, polyolefin resin, cellulose resin, or fluororesin material. The polyester resin may be polyethylene terephthalate or the like. The acrylic resin may be polymethyl methacrylate or the like. The polyolefin resin may be cycloolefin polymer or the like. The cellulose resin may be triacetyl cellulose or the like. The fluororesin material may be PTFE or PFA or the like. For example, the substrate 11 may be made of an organic insulating material such as cycloolefin polymer (e.g., ZF-16 manufactured by Nippon Zeon Co., Ltd.) or polynorbornene polymer (manufactured by Sumitomo Bakelite Co., Ltd.). The substrate 11 may also be made of glass, ceramics, or the like, depending on the application. Although the substrate 11 is illustrated as being made up of a single layer, it is not limited to this and may have a structure in which multiple base materials or layers are stacked. Furthermore, the substrate 11 may be a film-like member or a plate-like member.

The dielectric dissipation factor of the substrate 11 may be 0.002 or less, and preferably 0.001 or less. The lower limit of the dielectric dissipation factor of the substrate 11 is not particularly limited, but may be greater than 0. By having the dielectric dissipation factor of the substrate 11 within the above range, it is possible to reduce the gain loss (i.e., reduction in sensitivity) associated with the transmission and reception of electromagnetic waves, particularly when the electromagnetic waves (e.g., millimeter waves) transmitted and received by the mesh wiring layer 20 are high frequency.

The relative dielectric constant of the substrate 11 is not particularly limited, but is preferably between 2 and 10. Having a relative dielectric constant of 2 or greater for the substrate 11 allows for a wider range of material options for the substrate 11. Furthermore, having a relative dielectric constant of 10 or less for the substrate 11 reduces gain loss associated with the transmission and reception of electromagnetic waves. That is, if the relative dielectric constant of the substrate 11 increases, the thickness of the substrate 11 has a greater effect on the propagation of electromagnetic waves. Furthermore, if there is an adverse effect on the propagation of electromagnetic waves, the dielectric loss tangent of the substrate 11 increases, which can result in a greater gain loss associated with the transmission and reception of electromagnetic waves. In contrast, having a relative dielectric constant of 10 or less for the substrate 11 reduces the effect of the thickness of the substrate 11 on the propagation of electromagnetic waves. Therefore, gain loss associated with the transmission and reception of electromagnetic waves can be reduced. In particular, when the electromagnetic waves (e.g., millimeter waves) transmitted and received by the mesh wiring layer 20 are high frequency, gain loss associated with the transmission and reception of electromagnetic waves can be reduced.

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

In this embodiment, the substrate 11 is transparent. In this specification, "transparent" means that the transmittance of visible light (i.e., light with a wavelength of 400 nm or more and 700 nm or less) is 85% or more. The substrate 11 may have a visible light transmittance of 85% or more, and preferably 90% or more. There is no particular upper limit to the visible light transmittance of the substrate 11, but it may be, for example, 100% or less. By setting the visible light transmittance of the substrate 11 within the above range, the transparency of the wiring substrate 10 can be increased, making it easier to view the display device 61 of the image display device 60.

Next, the primer layer 15 will be described. The primer layer 15 serves to improve adhesion between the mesh wiring layer 20 and the substrate 11. In this embodiment, the primer layer 15 is provided over substantially the entire first surface 11a of the substrate 11. This eliminates the need to pattern the primer layer 15, thereby reducing the number of process steps. The primer layer 15 may also be provided only in the area of the first surface 11a of the substrate 11 where the mesh wiring layer 20 is provided.

This primer layer 15 contains a polymer material, which effectively improves adhesion between the mesh wiring layer 20 and the substrate 11. In this case, a colorless and transparent polymer material can be used as the material for the primer layer 15.

The primer layer 15 preferably contains an acrylic resin or a polyester resin. This more effectively improves adhesion between the mesh wiring layer 20 and the substrate 11. When the primer layer 15 contains an acrylic resin, examples of the acrylic resin include polymers containing acrylic acid, methacrylic acid, and their derivatives as monomer components. Examples of acrylic resins include polymers whose main components are acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methacrylic acid, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl acrylate, acrylamide, acrylonitrile, and hydroxyl acrylate, and copolymerized with a copolymerizable monomer (e.g., styrene, divinylbenzene, acrylonitrile, etc.). In addition to the above-mentioned monomers, dimers containing two acrylic or methacrylic groups per molecule, or polyfunctional urethane acrylates, etc., may be added to the resin as the main component. Organic molecules containing two or more epoxy groups per molecule may also be added to the resin as the main component. This crosslinks the acrylic resin, hardening it to form the primer layer 15. The cured primer layer exhibits excellent adhesion. It can also exhibit excellent water resistance, acid resistance, alkali resistance, solvent resistance, or a combination of these. This prevents the adhesion between the mesh wiring layer 20 and the substrate 11 from decreasing during wiring formation or over time.

Furthermore, when the primer layer 15 contains a polyester-based resin, the primer layer 15 can be formed, for example, by crosslinking and curing a hydroxyl-containing polyester-based resin with a curing agent that reacts with hydroxyl groups. Examples of hydroxyl-containing polyester-based resins include polyester polyols, and examples of curing agents include polyisocyanates and/or polyisocyanate prepolymers. The primer layer 15 formed by curing a polyester polyol with a polyisocyanate and/or a polyisocyanate prepolymer exhibits excellent adhesion. It can also exhibit excellent water resistance, acid resistance, alkali resistance, solvent resistance, or a combination of these. This prevents deterioration of adhesion between the mesh wiring layer 20 and the substrate 11 over time. Furthermore, the primer layer 15 formed by curing a polyester polyol with a polyisocyanate and/or a polyisocyanate prepolymer exhibits excellent heat resistance. This makes it less susceptible to the effects of heat generated during the various film-forming processes that are carried out after the primer layer 15 is formed, and prevents the primer layer 15 from whitening or cracking due to heat.

Preferred examples of polyisocyanates and/or polyisocyanate prepolymers include IPDI-based, XDI-based, and HDI-based polyisocyanates and/or polyisocyanate prepolymers. Using these can prevent the primer layer 15 from yellowing. Here, "IPDI-based" refers to isophorone diisocyanate and its modified forms, "XDI-based" refers to xylylene diisocyanate and its modified forms, and "HDI-based" refers to hexamelletin diisocyanate and its modified forms. Examples of modified forms include trimethylolpropane (TMP) adducts, isocyanurates, biuret forms, and allophanates.

The polymer material of the primer layer 15 may also be cured by crosslinking it through irradiation with visible light, ultraviolet light, X-rays, electron beams, alpha rays, beta rays, gamma rays, or the like. This improves the scratch resistance and heat resistance of the primer layer 15.

The primer layer 15 may also have a visible light (light with a wavelength of 400 nm or more and 700 nm or less) transmittance of 85% or more, preferably 90% or more. There is no particular upper limit to the visible light transmittance of the primer layer 15, but it may be, for example, 100% or less. By ensuring that the visible light transmittance of the primer layer 15 falls within the above range, the transparency of the wiring substrate 10 can be increased, making it easier to view the display device 61 of the image display device 60.

The thickness _T2 of the primer layer 15 (length in the Z direction, see FIG. 5) is preferably 0.05 μm or more and 0.5 μm or less. When the thickness _T2 of the primer layer 15 is 0.05 μm or more, the adhesion between the mesh wiring layer 20 and the substrate 11 can be effectively improved. Furthermore, when the thickness _T2 of the primer layer 15 is 0.5 μm or less, the transparency of the wiring substrate 10 can be ensured.

In this embodiment, the mesh wiring layer 20 is made up of an antenna pattern that functions as an antenna. This mesh wiring layer 20 functions as an array antenna. In this way, when the mesh wiring layer 20 functions as an array antenna, it is possible to improve the performance of the millimeter wave antenna, which transmits and receives millimeter waves with high linearity. Note that an array antenna is an antenna in which multiple antenna elements (radiating elements) are regularly arranged, and in which the amplitude and phase of the excitation of the elements can be controlled independently.

Three mesh wiring layers 20 are formed on the substrate 11 (see FIG. 1). As shown in FIG. 3, the mesh wiring layers 20 may be present only in a partial region of the substrate 11, rather than over the entire surface of the substrate 11. Each mesh wiring layer 20 may have the same shape. In this case, it is preferable that the error in the length (i.e., length in the Y direction) _La and the error in the width (length in the X direction) _Wa of each mesh wiring layer 20 are within 10%. This effectively improves the millimeter wave antenna performance.

This mesh wiring layer 20 corresponds to a specific frequency band. That is, the length (length in the Y direction) _La of the mesh wiring layer 20 corresponds to a specific frequency band. The lower the corresponding frequency band, the longer the length _La of the mesh wiring layer 20. The mesh wiring layer 20 may correspond to a millimeter-wave antenna, a telephone antenna, a Wi-Fi antenna, a 3G antenna, a 4G antenna, a 5G antenna, an LTE antenna, a Bluetooth (registered trademark) antenna, an NFC antenna, or the like. The multiple mesh wiring layers 20 may have different lengths and correspond to different frequency bands. Alternatively, if the wiring board 10 does not have a radio wave transmission/reception function, each mesh wiring layer 20 may perform functions such as a hovering function, fingerprint authentication, a heater, and noise reduction (shielding). The hovering function refers to a function that allows a user to operate the display without directly touching it.

The mesh wiring layer 20 has a base end portion 20a on the power supply unit 40 side and a tip end portion 20b connected to the base end portion 20a. The base end portion 20a is connected to the power supply unit 40. The base end portion 20a and the tip end portion 20b each have a substantially rectangular shape in a plan view. In this case, the length of the tip end portion 20b (i.e., the distance in the Y direction) is longer than the length of the base end portion 20a (i.e., the distance in the Y direction), and the width of the tip end portion 20b (i.e., the distance in the X direction) is wider than the width of the base end portion 20a (i.e., the distance in the X direction).

The mesh wiring layer 20 has a longitudinal direction parallel to the Y direction and a lateral direction parallel to the X direction. The length _La of the mesh wiring layer 20 in the longitudinal direction (i.e., the Y direction) can be selected, for example, from 3 mm to 100 mm. The width W _a of the tip portion 20 b of the mesh wiring layer 20 in the lateral direction (i.e., the X direction) can be selected, for example, from 1 mm to 10 mm. In particular, the mesh wiring layer 20 may be a millimeter wave antenna. When the mesh wiring layer 20 is a millimeter wave antenna, the length _La of the mesh wiring layer 20 can be selected in the range of 1 mm or more, more preferably 1.5 mm or more. When the mesh wiring layer 20 is a millimeter wave antenna, the length _La of the mesh wiring layer 20 can be selected in the range of 10 mm or less, more preferably 5 mm or less.

The mesh wiring layer 20 has a pattern in which metal wires are arranged in a grid or mesh pattern. This pattern is repeatedly arranged in the X and Y directions. That is, the mesh wiring layer 20 has a pattern consisting of a portion extending in a first direction (e.g., the Y direction) (i.e., first-directional wiring 21) and a portion extending in a second direction (e.g., the X direction) (i.e., second-directional wiring 22).

As shown in FIG. 4 , the mesh wiring layer 20 has two or more wires. Specifically, the mesh wiring layer 20 has a plurality of first directional wires 21 that function as antennas and a plurality of second directional wires 22 that connect the plurality of first directional wires 21. The plurality of first directional wires 21 and the plurality of second directional wires 22 are integrated as a whole to form a lattice or mesh-like shape. Each first directional wire 21 extends linearly in the longitudinal direction (i.e., Y direction) of the mesh wiring layer 20. Each second directional wire 22 extends linearly in the width direction (i.e., X direction) of the mesh wiring layer 20. The first directional wire 21 has a length L _a (see FIG. 3 ) corresponding to a predetermined frequency band, thereby mainly functioning as an antenna. Here, length L _a is the length of the mesh wiring layer 20 described above. On the other hand, the second directional wiring 22 plays a role in preventing problems such as the first directional wiring 21 being broken or the first directional wiring 21 and the power supply section 40 losing electrical connection by connecting these first directional wirings 21 together.

In the mesh wiring layer 20, a plurality of openings 23 are formed by being surrounded by adjacent first directional wires 21 and adjacent second directional wires 22. The first directional wires 21 and the second directional wires 22 are arranged at equal intervals. That is, the plurality of first directional wires 21 are arranged at equal intervals, and the pitch _P1 can be, for example, in the range of 0.01 mm to 1 mm. The plurality of second directional wires 22 are arranged at equal intervals, and the pitch _P2 can be, for example, in the range of 0.01 mm to 1 mm. Since the plurality of first directional wires 21 and the plurality of second directional wires 22 are arranged at equal intervals, the size of the openings 23 within the mesh wiring layer 20 is uniform, making the mesh wiring layer 20 difficult to see with the naked eye. The pitch _P1 of the first directional wires 21 is equal to the pitch _P2 of the second directional wires 22. Therefore, each opening 23 has a substantially square shape in a plan view, and the transparent primer layer 15 and substrate 11 are exposed through each opening 23. Therefore, by increasing the area of each opening 23, the transparency of the wiring substrate 10 as a whole can be increased. The length _L3 of one side of each opening 23 can be, for example, in the range of 0.01 mm to 1 mm. While the first directional wirings 21 and the second directional wirings 22 are orthogonal to each other, this is not a limitation and they may intersect at an acute or obtuse angle. The shape of the openings 23 is preferably the same across the entire surface, but it does not have to be uniform across the entire surface; for example, it may vary depending on the location.

As shown in FIG. 5, each first directional wiring 21 has a cross section perpendicular to its longitudinal direction (i.e., X-direction cross section) that is approximately rectangular or approximately square. In this case, the cross-sectional shape of the first directional wiring 21 is approximately uniform along the longitudinal direction of the first directional wiring 21 (i.e., Y-direction). As shown in FIG. 6, each second directional wiring 22 has a cross section perpendicular to its longitudinal direction (i.e., Y-direction cross section) that is approximately rectangular or approximately square, and has approximately the same shape as the cross-sectional shape (i.e., X-direction cross section) of the first directional wiring 21 described above. In this case, the cross-sectional shape of the second directional wiring 22 is approximately uniform along the longitudinal direction of the second directional wiring 22 (i.e., X-direction). The cross-sectional shapes of the first directional wiring 21 and the second directional wiring 22 do not necessarily have to be approximately rectangular or approximately square. For example, the cross-sectional shapes of the first directional wiring 21 and the second directional wiring 22 may be substantially trapezoidal, with the front side (i.e., the positive Z-direction side) narrower than the back side (i.e., the negative Z-direction side), or may have curved sides on both widthwise sides.

In this embodiment, the line width _W1 of the first directional wiring 21 (see FIG. 5 ) and the line width _W2 of the second directional wiring 22 (see FIG. 6 ) are not particularly limited and can be appropriately selected depending on the application. Here, the line width _W1 of the first directional wiring 21 is the width in a cross section perpendicular to its longitudinal direction (i.e., the length in the X direction), and the line width _W2 of the second directional wiring 22 is the width in a cross section perpendicular to its longitudinal direction (i.e., the length in the Y direction). For example, the line width _W1 of the first directional wiring 21 can be selected from a range of 0.1 μm to 5.0 μm, and preferably from 0.2 μm to 2.0 μm. Furthermore, the line width _W2 of the second directional wiring 22 can be selected from a range of 0.1 μm to 5.0 μm, and preferably from 0.2 μm to 2.0 μm.

The height _H1 of the first directional wiring 21 (see FIG. 5) and the height _H2 of the second directional wiring 22 (see FIG. 6) are not particularly limited and can be appropriately selected depending on the application. Here, the height _H1 of the first directional wiring 21 and the height _H2 of the second directional wiring 22 are each lengths in the Z direction. The height _H1 of the first directional wiring 21 and the height _H2 of the second directional wiring 22 can each be selected, for example, within a range of 60 nm to 5.0 μm.

Here, as shown in Figures 5 and 6, the mesh wiring layer 20 has first metal layers 21a and 22a arranged on the primer layer 15, and second metal layers 21b and 22b arranged on the first metal layers 21a and 22a. That is, the first directional wiring 21 has a first metal layer 21a arranged on the primer layer 15, and a second metal layer 21b arranged on the first metal layer 21a. Furthermore, the second directional wiring 22 has a first metal layer 22a arranged on the primer layer 15, and a second metal layer 22b arranged on the first metal layer 22a.

Of these, the first metal layers 21a and 22a serve to improve adhesion between the substrate 11 and the mesh wiring layer 20. The first metal layers 21a and 22a also serve as seed layers when the second metal layers 21b and 22b are formed by electrolytic plating. The first metal layers 21a and 22a are preferably formed by sputtering or vapor deposition, with sputtering being particularly preferred.

The thicknesses _d1a and _d2a of the first metal layers 21a and 22a may be 10 nm or more and 1000 nm or less, preferably 30 nm or more and 500 nm or less, and more preferably 50 nm or more and 300 nm or less. When the thicknesses _d1a and _d2a of the first metal layers 21a and 22a are 10 nm or more, the second metal layers 21b and 22b can be effectively supported when they are formed on the first metal layers 21a and 22a. Furthermore, when the thicknesses _d1a and _d2a of the first metal layers 21a and 22a are 1000 nm or less, the formation time of the mesh wiring layer 20 can be shortened.

The second metal layers 21b, 22b serve to increase the height _H1 of the first directional wiring 21 and the height _H2 of the second directional wiring 22. This reduces the resistance values of the first directional wiring 21 and the second directional wiring 22. The second metal layers 21b, 22b are preferably formed by a plating method or the like, and are particularly preferably formed by an electrolytic plating method.

The thicknesses _d1b and _d2b of the second metal layers 21b and 22b may be 50 nm or more and 4990 nm or less, preferably 100 nm or more and 2000 nm or less, and more preferably 200 nm or more and 1800 nm or less. When the thicknesses _d1b and _d2b of the second metal layers 21b and 22b are 50 nm or more, the height _H1 of the first directional wiring 21 and the height _H2 of the second directional wiring 22 can be increased, and the resistance values of the first directional wiring 21 and the second directional wiring 22 can be reduced. When the thicknesses _d1b and _d2b of the second metal layers 21b and 22b are 4990 nm or less, the formation time of the mesh wiring layer 20 can be shortened.

The first metal layers 21a, 22a and the second metal layers 21b, 22b may have different crystal characteristics. The first metal layers 21a, 22a and the second metal layers 21b, 22b may differ from each other in at least one of the crystal fraction, crystal structure, crystallite size, and crystal plane spacing. For example, the diffraction angle 2θ of the (111) plane of the first metal layers 21a, 22a measured using CuKα radiation as an X-ray source may be larger than the diffraction angle 2θ of the (111) plane of the second metal layers 21b, 22b. For example, the first metal layers 21a, 22a may have crystal characteristics such that the diffraction angle 2θ of the (111) plane measured using CuKα radiation as an X-ray source is 43.430° or less. This improves adhesion between the substrate 11 and the first metal layers 21a, 22a. In this case, the diffraction angle 2θ is preferably 43.420° or less, and more preferably 43.410° or less. The lower limit of the diffraction angle 2θ is not particularly limited, but may be 43.250° or more, preferably 43.300° or more, and more preferably 43.350° or more. The diffraction angle can be measured using an X-ray diffraction device (manufactured by Rigaku Corporation, Smart Lab, 9 kW type). The diffraction angle 2θ of the (111) plane of the first metal layers 21a and 22a and the diffraction angle 2θ of the (111) plane of the second metal layers 21b and 22b are each measured at the power supply unit 40. As described below, the power supply unit 40 is formed simultaneously with the first metal layers 21a, 22a and the second metal layers 21b, 22b by a portion of the first metal film 51 constituting the first metal layers 21a, 22a and a portion of the second metal film 52 constituting the second metal layers 21b, 22b. Therefore, the power supply unit 40 can measure the diffraction angle 2θ of the (111) plane of the first metal layers 21a, 22a and the diffraction angle 2θ of the (111) plane of the second metal layers 21b, 22b. In this case, the diffraction angle _{2θ of} the (111) plane of the first metal layers 21a, 22a can be measured more accurately than when measuring the diffraction angle 2θ of the (111) plane of the first metal layers 21a, 22a in a mesh wiring layer 20 having relatively narrow line widths W1 and W2. The measurement conditions are as follows:
Measurement mode: 2θ/θ measurement (out-plane)
X-ray source: Cu-Kα 45kV-50mA
Optical system: Concentration method Incident side optical system 1: Soller slit 5 deg
Incident side optical system 2: variable slit (IS) 1 deg
Length limit slit: 10 mm
Receiving optical system 1: variable slit (RS1) 1 deg, (RS2) 0.3 mm
Receiving optical system 2: PSA OPEN/solar slit 5 deg
Detector: Scintillation counter Measurement range: 35-80 deg
Step: 0.02 deg
Measurement time: 2.0 deg/min

The second metal layers 21b, 22b may have crystalline properties such that the diffraction angle 2θ of the (111) plane measured using CuKα radiation as an X-ray source is less than 43.4°. This improves the formability of the second metal layers 21b, 22b when they are formed by etching. The diffraction angle 2θ of the (111) plane of the second metal layers 21b, 22b may be 43.390° or less, preferably 43.380° or less, and more preferably 43.370° or less.

The material of the first directional wiring 21 and the second directional wiring 22 may be any metallic material having electrical conductivity. In other words, the material of the first metal layers 21a, 22a and the second metal layers 21b, 22b may be any metallic material having electrical conductivity. In this embodiment, the material of the first directional wiring 21 and the second directional wiring 22 is copper, but is not limited to this. The material of the first directional wiring 21 and the second directional wiring 22 may be, for example, a metallic material such as gold, silver, copper, platinum, tin, aluminum, iron, or nickel, or an alloy containing these metals.

The overall aperture ratio At of the mesh wiring layer 20 may be, for example, in the range of 87% or more and less than 100%. By setting the overall aperture ratio At of the mesh wiring layer 20 in this range, the conductivity and transparency of the wiring substrate 10 can be ensured. The overall aperture ratio At of the mesh wiring layer 20 is preferably in the range of 95% or more and less than 100%. This allows the transparency of the wiring substrate 10 to be increased while ensuring the conductivity of the wiring substrate 10. The aperture ratio refers to the percentage (%) of the area of the open region in a unit area of a specified region (e.g., the entire mesh wiring layer 20). The open region refers to a region where no metal parts such as the first directional wiring 21 and second directional wiring 22 are present and the substrate 11 is exposed.

When a bending resistance test is performed on the wiring substrate 10, the increase in the resistance value of the mesh wiring layer 20 may be 20% or less, or may be 10% or less. The bending resistance test is a test in which a cylindrical mandrel bending tester is used to bend the wiring substrate 10 180° around the circumference of a cylinder with a diameter of 1 mm, and then straighten it 100 times.

Specifically, the test is performed as follows. First, the electrical resistance between both ends of the mesh wiring layer 20 in the longitudinal direction is measured. The resistance value at this time is defined as R0 (Ω). Next, the wiring substrate 10 is wrapped around the cylinder of a cylindrical mandrel bending tester so that both ends of the wiring substrate 10 in the longitudinal direction are oriented in opposite directions by 180°. The wiring substrate 10 is then removed from the cylinder and flattened. This process is repeated 100 times. Thereafter, the electrical resistance between both ends of the mesh wiring layer 20 in the longitudinal direction is measured again. The resistance value at this time is defined as _R1 (Ω). The value calculated by (( _R1 - _R0 ) / _R0 ) x 100 (%) is defined as the increase in resistance. If this increase in resistance is 20% or less, the durability of the wiring substrate 10 can be improved when the wiring substrate 10 is used while being curved or bent.

Next, the dark layer 18 will be described. As shown in Figures 5 and 6, a dark layer (blackening layer) 18 is formed on the mesh wiring layer 20 of the wiring substrate 10. This dark layer 18 is a layer that suppresses reflection of visible light by the mesh wiring layer 20, making the mesh wiring layer 20 less visible to the naked eye. The dark layer 18 covers the entire mesh wiring layer 20. This dark layer 18 may also cover the entire power supply section 40.

The dark layer 18 may be a layer of a dark color, such as black. The dark layer 18 may also be a layer with a roughened surface.

The surface roughness Ra of the dark layer 18 is 5 nm or more and 100 nm or less. A surface roughness Ra of 5 nm or more of the dark layer 18 reduces reflection of visible light on the surface of the dark layer 18. This makes it difficult for an observer to see the mesh wiring layer 20 covered by the dark layer 18 with their naked eyes. A surface roughness Ra of 100 nm or less of the dark layer 18 prevents the haze value of the dark layer 18 from becoming too high. This makes it difficult for an observer to recognize the presence of the dark layer 18. This makes it difficult for an observer to see the mesh wiring layer 20 covered by the dark layer 18 with their naked eyes. In this case, the surface roughness Ra can be determined in accordance with JIS B 0601:2013 using a laser microscope (manufactured by Keyence Corporation, VK-X250 (controller), VK-X260 (measuring unit), laser wavelength 408 nm)).

The dark layer 18 may be formed from a portion of the mesh wiring layer 20 or the power supply unit 40, for example, by subjecting a portion of the metal material that constitutes the mesh wiring layer 20 or the power supply unit 40 to a darkening treatment (blackening treatment). In this case, the dark layer 18 may be formed as a layer made of metal oxide or metal sulfide. The dark layer 18 may also be formed on the surface of the mesh wiring layer 20 or the power supply unit 40 as a coating of a dark material or a plating layer of nickel, chromium, or the like. Furthermore, the dark layer 18 may be formed by roughening the surface of the mesh wiring layer 20 or the power supply unit 40.

Although not shown, a protective layer may be formed on the primer layer 15 to cover the mesh wiring layer 20 and the dark layer 18. The protective layer protects the mesh wiring layer 20 and is formed to cover at least the mesh wiring layer 20 of the substrate 11. Materials that can be used for the protective layer include acrylic resins such as polymethyl (meth)acrylate and polyethyl (meth)acrylate, modified resins thereof, copolymers thereof, polyvinyl resins such as polyester, polyvinyl alcohol, polyvinyl acetate, polyvinyl acetal, and polyvinyl butyral, copolymers thereof, polyurethane, epoxy resin, polyamide, chlorinated polyolefin, and other colorless and transparent insulating resins.

Referring again to FIG. 3, the power supply unit 40 is electrically connected to the mesh wiring layer 20. This power supply unit 40 is made of a substantially rectangular conductive thin plate. The longitudinal direction of the power supply unit 40 is parallel to the X direction, and the transverse direction of the power supply unit 40 is parallel to the Y direction. The power supply unit 40 is disposed at the longitudinal end of the substrate 11 (i.e., the negative end in the Y direction). The power supply unit 40 may be made of a metal material such as gold, silver, copper, platinum, tin, aluminum, iron, or nickel, or an alloy containing these metals. When the wiring substrate 10 is incorporated into the image display device 60 (see FIGS. 1 and 2), the power supply unit 40 is electrically connected to the communication module 63 of the image display device 60 via a power supply line (not shown). Note that, although the power supply unit 40 is provided on the first surface 11a of the substrate 11, this is not limiting, and part or all of the power supply unit 40 may be located outside the periphery of the substrate 11. Additionally, the power supply unit 40 may be configured to be flexible so that it can wrap around the side or back of the image display device 60. In this case, the power supply unit 40 may be electrically connected to the communication module 63 on the side or back of the image display device 60.

Next, a method for manufacturing the wiring substrate 10 according to this embodiment will be described with reference to Figures 7(a)-7(i).

First, as shown in FIG. 7(a), a substrate 11 is prepared, which includes a first surface 11a and a second surface 11b located on the opposite side of the first surface 11a. The substrate 11 is transparent.

Next, as shown in FIG. 7(b), a primer layer 15 is formed on the substrate 11. In this case, the primer layer 15 may be formed over substantially the entire first surface 11a of the substrate 11. Methods for forming the primer layer 15 include roll coating, gravure coating, gravure reverse coating, microgravure coating, slot die coating, die coating, knife coating, inkjet coating, dispenser coating, kiss coating, spray coating, screen printing, offset printing, and flexographic printing.

Next, a mesh wiring layer 20 including a plurality of first directional wirings 21 and a plurality of second directional wirings 22 connecting the plurality of first directional wirings 21 is formed on the primer layer 15.

In this case, first, as shown in FIG. 7(c), a first metal film 51 is laminated over substantially the entire surface of the primer layer 15. The first metal film 51 may be formed by, for example, a sputtering method. The thickness of the first metal film 51 may be 10 nm or more and 1000 nm or less. In this embodiment, the first metal film 51 may contain copper.

Next, as shown in FIG. 7(d), a second metal film 52 is laminated on the first metal film 51. The second metal film 52 may be formed using electrolytic plating, using the first metal film 51 as a seed layer. The thickness of the second metal film 52 may be 50 nm or more and 4990 nm or less. In this embodiment, the second metal film 52 may contain copper.

Next, as shown in FIG. 7(e), a photo-curable insulating resist 53 is applied to substantially the entire surface of the second metal film 52. Examples of this photo-curable insulating resist 53 include organic resins such as acrylic resins and epoxy resins.

Next, as shown in FIG. 7(f), the insulating layer 54 is formed by photolithography. In this case, the photo-curable insulating resist 53 is patterned by photolithography to form the insulating layer 54 (i.e., the resist pattern). At this time, the insulating layer 54 is formed so that the second metal film 52 corresponding to the first directional wiring 21 and the second directional wiring 22 is exposed.

Next, as shown in FIG. 7(g), the second metal film 52 and the first metal film 51 located on the first surface 11a of the substrate 11 in the portion not covered by the insulating layer 54 are removed. At this time, a wet process is performed using ferric chloride, cupric chloride, a strong acid such as sulfuric acid or hydrochloric acid, persulfate, hydrogen peroxide, or an aqueous solution of these, or a combination of these, to etch the second metal film 52 and the first metal film 51 so as to expose the first surface 11a of the substrate 11.

Next, as shown in FIG. 7(h), the insulating layer 54 is removed. In this case, the insulating layer 54 on the second metal film 52 is removed by wet processing using a permanganate solution, N-methyl-2-pyrrolidone, an acid or alkaline solution, or by dry processing using oxygen plasma.

Next, as shown in FIG. 7(i), the dark layer 18 is formed. In this case, the dark layer 18 may be formed by subjecting a portion of the first metal film 51 and the second metal film 52 to a darkening treatment (blackening treatment). Alternatively, the dark layer 18 may be formed on the surfaces of the first metal film 51 and the second metal film 52 as a coating of a dark material or a plating layer of nickel, chromium, or the like. Furthermore, the dark layer 18 may be formed by roughening the surfaces of the first metal film 51 and the second metal film 52.

In this way, a wiring substrate 10 is obtained, which includes a substrate 11, a primer layer 15 provided on the first surface 11a of the substrate 11, a mesh wiring layer 20 disposed on the primer layer 15, and a dark layer 18 covering the mesh wiring layer 20. In this case, the mesh wiring layer 20 includes first-directional wiring 21 and second-directional wiring 22. In this case, the power supply section 40 may be formed by a portion of the first metal film 51 and the second metal film 52.

Then, the display device 61 is laminated onto the wiring substrate 10 via the first transparent adhesive layer 95 and the second transparent adhesive layer 96, thereby obtaining an image display device 60 comprising the wiring substrate 10 and the display device 61 laminated onto the wiring substrate 10.

Next, we will describe the operation of this embodiment configured as described above.

As shown in Figures 1 and 2, the wiring board 10 is incorporated into an image display device 60 having a display device 61. At this time, the wiring board 10 is placed on the display device 61. The mesh wiring layer 20 of the wiring board 10 is electrically connected to the communication module 63 of the image display device 60 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 60.

According to this embodiment, the mesh wiring layer 20 has first metal layers 21a and 22a disposed on the primer layer 15, and second metal layers 21b and 22b disposed on the first metal layers 21a and 22a. This effectively increases the height _H1 of the first directional wiring 21 and the height _H2 of the second directional wiring 22. This reduces the resistance values of the first directional wiring 21 and the second directional wiring 22.

Furthermore, according to this embodiment, the surface roughness Ra of the dark layer 18 is 5 nm or more and 100 nm or less. This makes it possible to suppress reflection of visible light on the surface of the dark layer 18. It also prevents the haze value of the dark layer 18 from becoming too high, making it difficult for an observer to notice the presence of the dark layer 18. As a result, it is possible to make it difficult for an observer to see the mesh wiring layer 20 covered with the dark layer 18 with the naked eye.

Furthermore, according to this embodiment, the wiring board 10 comprises a substrate 11, a primer layer 15 disposed on the substrate 11, a mesh wiring layer 20 disposed on the primer layer 15, and a dark layer 18 covering the mesh wiring layer 20. The substrate 11 is transparent. The mesh wiring layer 20 has a conductor portion as a forming portion of the opaque conductive layer and a mesh pattern consisting of numerous openings 23. This ensures the transparency of the wiring board 10. As a result, when the wiring board 10 is placed on a display device 61, the display device 61 can be seen through the openings 23 in the mesh wiring layer 20, and the visibility of the display device 61 is not obstructed.

Next, we will explain modified examples of wiring boards.

Figures 8 and 9 show a first modified example of a wiring board. The modified example shown in Figures 8 and 9 differs in that a dummy wiring layer 30 is provided around the mesh wiring layer 20, but the other configuration is substantially the same as the embodiment shown in Figures 1 to 7 described above. In Figures 8 and 9, parts that are the same as those shown in Figures 1 to 7 are given the same reference numerals and detailed descriptions are omitted.

In the wiring substrate 10 shown in Figure 8, a dummy wiring layer 30 is provided along the periphery of the mesh wiring layer 20. The dummy wiring layer 30 may be covered with a dark color layer 18. Unlike the mesh wiring layer 20, this dummy wiring layer 30 does not actually function as an antenna.

As shown in FIG. 9, the dummy wiring layer 30 is composed of repeated dummy wirings 30a each having a predetermined unit pattern shape. That is, the dummy wiring layer 30 includes multiple dummy wirings 30a of the same shape, and each dummy wiring 30a is electrically independent from the mesh wiring layer 20 (i.e., the first directional wiring 21 and the second directional wiring 22). The multiple dummy wirings 30a are regularly arranged throughout the dummy wiring layer 30. The multiple dummy wirings 30a are spaced apart from each other in the planar direction and are arranged to protrude above the substrate 11. That is, each dummy wiring 30a is electrically independent from the mesh wiring layer 20, the power supply section 40, and other dummy wirings 30a. The shape of each dummy wiring 30a is approximately L-shaped in plan view.

In this case, the dummy wiring 30a has a shape in which a portion of the unit pattern shape of the mesh wiring layer 20 described above (see Figure 4) is missing. This makes it difficult to visually distinguish the difference between the mesh wiring layer 20 and the dummy wiring layer 30, and makes the mesh wiring layer 20 arranged on the substrate 11 less visible.

As shown in FIG. 9 , the dummy wiring 30a extends parallel to the first directional wiring 21 or the second directional wiring 22. Specifically, the dummy wiring 30a includes a first portion 31a extending parallel to the first directional wiring 21 and a second portion 32a extending parallel to the second directional wiring 22. The first portion 31a has a shape in which a portion of the first directional wiring 21 is missing. The second portion 32a has a shape in which a portion of the second directional wiring 22 is missing. Note that other configurations of the first portion 31a and the second portion 32a are similar to the configurations of the first directional wiring 21 and the second directional wiring 22, so detailed description will be omitted here. In this way, by having the dummy wiring 30a extend parallel to the first directional wiring 21 or the second directional wiring 22, the mesh wiring layer 20 arranged on the substrate 11 can be made even less visible. The aperture ratio of the dummy wiring layer 30 may be the same as or different from the aperture ratio of the mesh wiring layer 20, but it is preferable that it be close to the aperture ratio of the mesh wiring layer 20.

In this way, by providing a dummy wiring layer 30 that is electrically independent from the mesh wiring layer 20 around the mesh wiring layer 20, the outer edge of the mesh wiring layer 20 can be made unclear. This makes the mesh wiring layer 20 less visible on the surface of the image display device 60, making it more difficult for a user of the image display device 60 to recognize the mesh wiring layer 20 with the naked eye.

Figures 10 and 11 show a second modified example of a wiring substrate. The modified example shown in Figures 10 and 11 differs in that two or more dummy wiring layers 30A, 30B with different aperture ratios are provided around the mesh wiring layer 20, but the other configuration is substantially the same as the embodiment shown in Figures 1 to 9 described above. In Figures 10 and 11, parts that are the same as those shown in Figures 1 to 9 are given the same reference numerals and detailed explanations are omitted.

In the wiring substrate 10 shown in FIG. 10, multiple (in this case, two) dummy wiring layers 30A, 30B (i.e., a first dummy wiring layer 30A and a second dummy wiring layer 30B) with different aperture ratios are provided along the periphery of the mesh wiring layer 20. Specifically, the first dummy wiring layer 30A is arranged along the periphery of the mesh wiring layer 20, and the second dummy wiring layer 30B is arranged along the periphery of the first dummy wiring layer 30A. The dummy wiring layers 30A, 30B may be covered with a dark layer 18. Unlike the mesh wiring layer 20, these dummy wiring layers 30A, 30B do not actually function as antennas.

As shown in FIG. 11, the first dummy wiring layer 30A is composed of repeated dummy wirings 30a1 each having a predetermined unit pattern shape. The second dummy wiring layer 30B is composed of repeated dummy wirings 30a2 each having a predetermined unit pattern shape. That is, the dummy wiring layers 30A and 30B each include multiple dummy wirings 30a1 and 30a2 of the same shape, and each dummy wiring 30a1 and 30a2 is electrically independent from the mesh wiring layer 20. The dummy wirings 30a1 and 30a2 are regularly arranged throughout the entire dummy wiring layers 30A and 30B, respectively. The dummy wirings 30a1 and 30a2 are spaced apart from each other in the planar direction and are arranged to protrude above the substrate 11. Each dummy wiring 30a1 and 30a2 is electrically independent from the mesh wiring layer 20, the power supply section 40, and the other dummy wirings 30a1 and 30a2. The shape of each of the dummy wirings 30a1 and 30a2 is approximately L-shaped in plan view.

In this case, the dummy wirings 30a1 and 30a2 have a shape in which a portion of the unit pattern shape (see FIG. 4) of the mesh wiring layer 20 described above is missing. This makes it difficult to visually recognize the difference between the mesh wiring layer 20 and the first dummy wiring layer 30A, and the difference between the first dummy wiring layer 30A and the second dummy wiring layer 30B, making the mesh wiring layer 20 arranged on the substrate 11 less visible. As shown in FIG. 11, the dummy wirings 30a1 and 30a2 extend parallel to the first directional wiring 21 or the second directional wiring 22. Specifically, the dummy wiring 30a1 includes a first portion 31a1 extending parallel to the first directional wiring 21 and a second portion 32a1 extending parallel to the second directional wiring 22. The dummy wiring 30a2 includes a first portion 31a2 extending parallel to the first directional wiring 21 and a second portion 32a2 extending parallel to the second directional wiring 22.

The area of each dummy wiring 30a1 in the first dummy wiring layer 30A is larger than the area of each dummy wiring 30a2 in the second dummy wiring layer 30B. In this case, the line width of each dummy wiring 30a1 is the same as the line width of each dummy wiring 30a2, but this is not limited to this, and the line width of each dummy wiring 30a1 may be wider than the line width of each dummy wiring 30a2. The other configurations of the dummy wirings 30a1 and 30a2 are the same as the configuration of the dummy wiring 30a in the first modified example, so detailed explanations will be omitted here.

In this modified example, the aperture ratios of the mesh wiring layer 20 and the two or more dummy wiring layers 30A, 30B preferably increase stepwise from the mesh wiring layer 20 toward the dummy wiring layers 30A, 30B furthest from the mesh wiring layer 20. In other words, the aperture ratio of each dummy wiring layer preferably increases gradually from that closest to the mesh wiring layer 20 to that furthest from it. In this case, the aperture ratio of the first dummy wiring layer 30A is preferably greater than that of the mesh wiring layer 20. The aperture ratio of the second dummy wiring layer 30B is preferably greater than that of the first dummy wiring layer 30A. This makes it possible to further obscure the outer edges of the mesh wiring layer 20 and the dummy wiring layers 30A, 30B. This makes it possible to make the mesh wiring layer 20 even less visible on the surface of the image display device 60.

In this way, by arranging dummy wiring layers 30A and 30B that are electrically independent from the mesh wiring layer 20, the outer edge of the mesh wiring layer 20 can be made less clear. This makes the mesh wiring layer 20 less visible on the surface of the image display device 60, making it more difficult for users of the image display device 60 to recognize the mesh wiring layer 20 with the naked eye. Note that three or more dummy wiring layers with different aperture ratios may be provided around the mesh wiring layer 20.

Figure 12 shows a third modified example of the wiring board. The modified example shown in Figure 12 differs in the planar shape of the mesh wiring layer 20, but the other configuration is substantially the same as the embodiment shown in Figures 1 to 11 described above. In Figure 12, the same parts as those shown in Figures 1 to 11 are designated by the same reference numerals, and detailed explanations will be omitted.

Figure 12 is an enlarged plan view showing a mesh wiring layer 20 according to a third modified example. In Figure 12, the first directional wiring 21 and the second directional wiring 22 intersect at an angle (i.e., not at a right angle), and the shape of each opening 23 is a rhombus in plan view. The first directional wiring 21 and the second directional wiring 22 are not parallel to either the X direction or the Y direction, but either one of the first directional wiring 21 and the second directional wiring 22 may be parallel to the X direction or the Y direction.

The multiple components disclosed in the above embodiments and modifications may be combined as needed. Alternatively, some components may be omitted from all of the components shown in the above embodiments and modifications.

Claims (8)

A wiring board,
a substrate including a first surface and a second surface opposite the first surface;
a primer layer disposed on the first surface of the substrate;
a mesh wiring layer disposed on the primer layer;
a dark layer covering the mesh wiring layer,
The substrate is transparent,
The mesh wiring layer includes:
a first metal layer disposed on the primer layer;
a second metal layer disposed on the first metal layer;
the surface roughness Ra of the dark color layer is 5 nm or more and 100 nm or less;
The wiring board , wherein the primer layer contains an acrylic resin . The wiring board of claim 1, wherein the first metal layer and the second metal layer have different crystal properties, and the second metal layer has crystal properties such that the diffraction angle 2θ of the (111) plane measured using CuKα radiation as an X-ray source is less than 43.4°. The wiring board according to claim 1, wherein the dielectric loss tangent of the substrate is 0.002 or less. The wiring board described in claim 1, wherein when the wiring board is bent 180 degrees around a cylinder with a diameter of 1 mm and then straightened 100 times, the increase in resistance of the mesh wiring layer is 20% or less. The wiring board according to claim 1, wherein the wiring board has a millimeter wave transmitting and receiving function, and the mesh wiring layer functions as an array antenna. The wiring board according to claim 1, wherein a dummy wiring layer electrically independent from the mesh wiring layer is provided around the mesh wiring layer. The wiring board of claim 6, wherein a plurality of dummy wiring layers are provided, and the aperture ratios of the mesh wiring layer and the dummy wiring layer increase stepwise from the mesh wiring layer toward the dummy wiring layer farthest from the mesh wiring layer. The wiring substrate according to claim 1 ,
a display device laminated on the wiring substrate.