JP7751802B2 - Laminate for image display device and image display device - Google Patents

Description

Embodiments of the present disclosure relate to a laminate for an image display device 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 Patent No. 5636735 specification Patent No. 5695947 specification

This embodiment provides a laminate for an image display device and an image display device that can make the presence of a wiring board within the image display device less visible.

The laminate for an image display device according to this embodiment comprises a substrate including a first surface and a second surface located opposite the first surface, a wiring board having a primer layer provided on the first surface of the substrate and a mesh wiring layer disposed on the primer layer, a dielectric layer located on the first surface side of the substrate, and an adhesive layer located on the second surface side of the substrate, wherein the substrate is transparent, a portion of the substrate is disposed between the dielectric layer and the adhesive layer, and the haze value is 3% or less.

In the laminate for an image display device according to this embodiment, the wiring board may have a radio wave transmission and reception function.

In the laminate for an image display device according to this embodiment, the wiring board may have a millimeter wave transmission/reception function.

In the laminate for an image display device according to this embodiment, the mesh wiring layer may function as an array antenna.

In the laminate for an image display device according to this embodiment, the mesh wiring layer may include a plurality of wires, the wire width of which may be 0.2 μm or more and 3.0 μm or less, the wire pitch of which may be 10 μm or more and 300 μm or less, and the wire height of which may be 0.2 μm or more and 3.0 μm or less.

In the laminate for an image display device according to the present embodiment, the wiring includes a third surface facing the first surface and a fourth surface located on the opposite side of the third surface, and in a cross section perpendicular to the longitudinal direction of the wiring, when the width of the fourth surface of the wiring is _Wx and the width of the widest part of the wiring is _Wy ,
W _y ≦1.15W _x
The following relationship may be satisfied.

In the laminate for an image display device according to this embodiment, a dummy wiring layer that is electrically independent from the mesh wiring layer may be provided around the mesh wiring layer.

In the laminate for an image display device according to this embodiment, there may be multiple mesh wiring layers, and the dummy wiring layer may be arranged to surround the multiple mesh wiring layers.

The image display device according to this embodiment includes a laminate for an image display device according to this embodiment and a display device laminated on the laminate for an image display device.

According to an embodiment of the present disclosure, the presence of a wiring board within an image display device 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. FIG. 4 is an enlarged plan view showing the mesh wiring layer of the wiring substrate. FIG. 5 is a cross-sectional view showing the wiring board (a cross-sectional view taken along line VV in FIG. 4). FIG. 6 is a cross-sectional view showing the wiring board (a cross-sectional view taken along line VI-VI in FIG. 4). 7(a) to 7(f) are cross-sectional views showing a method for manufacturing a laminate for an image display device according to one embodiment. 8(a) to 8(c) are cross-sectional views showing a method for manufacturing a laminate for an image display device according to one embodiment. FIG. 9 is a cross-sectional view showing a laminate for an image display device according to a modified example. FIG. 10 is a plan view showing a wiring board according to a first modified example. FIG. 11 is a cross-sectional view showing a wiring board according to a second modified example. FIG. 12 is a cross-sectional view showing another example of the wiring board according to the second modified example. FIG. 13 is a plan view showing a wiring board according to a third modified example. FIG. 14 is an enlarged plan view showing a wiring board according to a third modified example. FIG. 15 is a plan view showing another example of the wiring substrate according to the third modified example. FIG. 16 is a plan view showing another example of the wiring board according to the third modified example. FIG. 17 is a plan view showing a wiring board according to a fourth modified example. FIG. 18 is an enlarged plan view showing a wiring board according to a fourth modified example. FIG. 19 is an enlarged plan view showing a mesh wiring layer of a wiring substrate according to a fifth modified example.

First, one embodiment will be described with reference to Figures 1 to 8. Figures 1 to 8 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 the following embodiments, the mesh wiring layer 20 is described as having radio wave transmission and reception functionality (functioning as an antenna), but the mesh wiring layer 20 does not necessarily have to have radio wave transmission and reception functionality (functioning as an antenna).

[Configuration of image display device]
The configuration of the image display device according to this embodiment will be described with reference to FIGS.

1 and 2, the image display device 60 according to this embodiment includes a laminate 70 for an image display device and a display device (display) 61 laminated on the laminate 70 for an image display device. The laminate 70 for an image display device includes a first transparent adhesive layer (dielectric layer) 95, a second transparent adhesive layer (adhesive layer) 96, and a wiring substrate 10. The wiring substrate 10 includes a substrate 11, a primer layer 15, and a mesh wiring layer 20. The substrate 11 includes a first surface 11a and a second surface 11b located opposite the first surface 11a. The primer layer 15 is provided on the first surface 11a of the substrate 11. The mesh wiring layer 20 is disposed on the primer layer 15. A power supply unit 40 is electrically connected to the mesh wiring layer 20. 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 the communication module 63, enabling communication. The communication module 63 may include any of 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 (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 (negative side in the Z direction) of the display device 61.

The display device 61 is, for example, an organic electroluminescence (EL) 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 (not shown). A touch sensor (not shown) may be disposed on the display device 61. A wiring substrate 10 is disposed on the display device 61 via a second transparent adhesive layer 96. 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 (light emitters). The display device 61 may also be a liquid crystal display device including liquid crystal. A cover glass (surface protection plate) 75 is disposed on the wiring substrate 10 via a first transparent adhesive layer 95. 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), and then cured using ultraviolet (UV) light, for example, to obtain an OCA sheet. After bonding this 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.

The first transparent adhesive layer 95 may have a visible light transmittance (light with a wavelength of 400 nm or more and 700 nm or less) 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 setting the visible light transmittance of the first transparent adhesive layer 95 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 an object is measured using a known spectrophotometer (for example, the V-670 spectrometer manufactured by JASCO Corporation), the transmittance is 85% or more across the entire wavelength range of 400 nm or more and 700 nm or less.

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.

The wiring board 10 includes a transparent substrate 11, a primer layer 15 provided on the first surface 11a of the substrate 11, and a mesh wiring layer 20 disposed on the primer layer 15. 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. 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 (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 provided 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 provided 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 has optical transparency 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.

The second transparent adhesive layer 96 may have a visible light transmittance (light with a wavelength of 400 nm or more and 700 nm or less) of 85% or more, 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 at least twice, and preferably at least 2.5 times, 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 prevents 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.

Furthermore, 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 10 times or less, and 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 ( _T3 + _T4 ) of the thickness _T3 of the first transparent adhesive layer 95 and the thickness _T4 of the second transparent adhesive layer 96 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 thicker than 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, and absorb the thickness of the substrate 11. This prevents 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 notice the presence of the substrate 11.

Furthermore, 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 both 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, 1 μm or more and 200 μm or less, 10 μm or more and 50 μm or less, and preferably 15 μm or more and 25 μm or less. By setting the thickness T1 of the substrate ₁₁ to 1 μm or more, the strength of the wiring substrate 10 can be maintained and the first directional wiring 21 and the second directional wiring 22 of the mesh wiring layer 20, which will be described later, can be made less likely to deform. Furthermore, by setting the thickness _T1 of the substrate 11 to 50 μm or less, it is possible to prevent 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.

The thickness _T3 of the first transparent adhesive layer 95 may be, for example, 1 μm or more and 500 μm or less, and preferably 10 μm or more and 250 μm or less. The thickness _T4 of the second transparent adhesive layer 96 may be, for example, 1 μm or more and 500 μm or less, and preferably 10 μm or more and 250 μm or less.

Here, the haze value of the laminate 70 for an image display device is 3% or less. Having a haze value of 3% or less for the laminate 70 for an image display device can enhance the transparency of the laminate 70 for an image display device. This makes it difficult for an observer to recognize the presence of the laminate 70 for an image display device in the image display device 60. This also makes it difficult for the substrate 11 of the wiring board 10 to be seen with the naked eye. In this case, the haze value can be measured using, for example, a haze meter (HM-150N, manufactured by Murakami Color Research Laboratory) according to a method in accordance with JIS K 7136.

As described above, the laminate 70 for an image display device is composed of the wiring substrate 10, the first transparent adhesive layer 95 having an area larger than the substrate 11 of the wiring substrate 10, and the second transparent adhesive layer 96 having an area larger than the substrate 11. In the present embodiment, such a laminate 70 for an image display device is also provided.

The cover glass (surface protection plate) 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 (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 (X direction) may be, for example, 20 mm to 500 mm, and preferably 50 mm to 100 mm.

1, the image display device 60 has a generally rectangular shape 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 (Y direction) can be selected, for example, from 20 mm to 500 mm, preferably from 100 mm to 200 mm, and the length _L5 of the image display device 60 in the lateral direction (X direction) can be selected, for example, from 20 mm to 500 mm, preferably from 50 mm to 100 mm. The corners of the image display device 60 may be rounded.

[Configuration of wiring board]
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 used in the image display device 60 described above (see FIGS. 1 and 2), and is disposed closer to the light-emitting surface 64 than the display device 61, between the first transparent adhesive layer 95 and the second transparent adhesive layer 96. Such a wiring board 10 includes a transparent substrate 11, a primer layer 15 provided on the substrate 11, and a mesh wiring layer 20 disposed on the primer layer 15. A power supply unit 40 is electrically connected to the mesh wiring layer 20.

The substrate 11 has a substantially rectangular shape in plan view, with its longitudinal direction parallel to the Y direction and its lateral direction parallel to the X direction. The substrate 11 is transparent and substantially flat, with a substantially uniform thickness overall. The length _L1 of the substrate 11 in the longitudinal direction (Y direction) can be selected, for example, from 10 mm to 200 mm, and the length L2 of the substrate ₁₁ in the lateral direction (X direction) can be selected, for example, from 3 mm to 100 mm. The corners of the substrate 11 may be rounded.

The material of the substrate 11 may be any material as long as it is transparent in the visible light range and electrically insulating.
The substrate 11 is preferably made of 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, a polyolefin resin such as a cycloolefin polymer, a cellulose resin such as triacetyl cellulose, or a fluororesin material such as PTFE or PFA. Alternatively, the substrate 11 may be made of 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.). The substrate 11 may also be made of glass, ceramics, or other suitable materials depending on the application. While the substrate 11 is illustrated as being made of a single layer, the present invention is not limited thereto and may have a structure in which multiple substrates or layers are stacked. The substrate 11 may also be in the form of a film or a plate.

Furthermore, the dielectric dissipation factor of the substrate 11 is preferably 0.002 or less. By having the dielectric dissipation factor of the substrate 11 within this range, it is possible to reduce the loss of gain (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 preferably 2 or more and 10 or less. Having a relative dielectric constant of 2 or more 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 the loss of gain (sensitivity) 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 loss of gain (sensitivity) 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, the loss of gain (sensitivity) 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, the loss of gain (sensitivity) 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 10 mm to 20 mm in width and 50 mm to 100 mm in length. 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.

The substrate 11 is also transparent. In this specification, "transparent" means that the transmittance of visible light (light with a wavelength of 400 nm or more and 700 nm or less) is 85% or more. The substrate 11 may have a transmittance of visible light (light with a wavelength of 400 nm or more and 700 nm or less) 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. For example, polymers containing acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methacrylic acid, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl acrylate, acrylamide, acrylonitrile, hydroxyl acrylate, or the like as the main component, copolymerized with a copolymerizable monomer (e.g., styrene, divinylbenzene, acrylonitrile, etc.) can be used. Furthermore, the acrylic resin can be crosslinked and cured by adding a dimer having two acrylic or methacrylic groups per molecule, a multifunctional urethane acrylate, or an organic molecule having two or more epoxy groups per molecule, in addition to the above monomers. The cured primer layer has excellent adhesion. It can also exhibit excellent water resistance, acid resistance, alkali resistance, solvent resistance, or a combination of these. This prevents the deterioration of adhesion 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 and 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 over time. Furthermore, the primer layer 15 formed by curing a polyester polyol and a polyisocyanate and/or a polyisocyanate prepolymer exhibits excellent heat resistance. This makes it less susceptible to the effects of heat generated during various film-forming processes performed after the primer layer 15 is formed, thereby preventing heat-induced whitening and cracking of the primer layer 15.

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 can improve 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.

Next, the mesh wiring layer 20 will be described. In this embodiment, the mesh wiring layer 20 is formed as an antenna pattern that functions as an antenna. In FIG. 3, one mesh wiring layer 20 is formed on the substrate 11. Also, as shown in FIG. 3, the mesh wiring layer 20 does not need to be present over the entire surface of the substrate 11, but may be present only in a partial region on the substrate 11. This mesh wiring layer 20 corresponds to a predetermined frequency band. That is, the length (length in the Y direction) _La of the mesh wiring layer 20 corresponds to a specific frequency band. Note that 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 any of 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, a millimeter wave antenna, etc. Note that multiple mesh wiring layers 20 may be formed on the substrate 11. In this case, 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 radio wave transmission and reception functions, each mesh wiring layer 20 may perform functions such as hovering (a function that allows the user to operate the display without directly touching it), fingerprint authentication, heater, noise cutting (shielding), etc.

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 and the tip end portion 20b each have a roughly rectangular shape in a plan view. In this case, the length (Y direction distance) of the tip end portion 20b is longer than the length (Y direction distance) of the base end portion 20a, and the width (X direction distance) of the tip end portion 20b is wider than the width (X direction distance) of the base end portion 20a.

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 (Y direction) can be selected, for example, from 3 mm to 100 mm, and the width _Wa of the mesh wiring layer 20 (tip portion 20b) in the lateral direction (X direction) can be selected, for example, from 1 mm to 10 mm. In particular, when the mesh wiring layer 20 has a millimeter wave transmitting/receiving function (functions as a millimeter wave antenna), the length _La of the mesh wiring layer 20 can be selected, for example, from 1 mm to 10 mm, and more preferably, from 1.5 mm to 5 mm.

The mesh wiring layer 20 has metal wires formed in a lattice or mesh pattern, with a repeating pattern in the X and Y directions. That is, the mesh wiring layer 20 has a pattern shape consisting of a portion extending in the X direction (second-directional wiring 22) and a portion extending in the Y direction (first-directional wiring 21).

As shown in FIG. 4 , the mesh wiring layer 20 includes a plurality of first-directional wirings (antenna wirings (wiring)) 21 that function as antennas, and a plurality of second-directional wirings (antenna connecting wirings (wiring)) 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 are integrated as a whole to form a lattice or mesh shape. Each first-directional wiring 21 extends in a direction (longitudinal direction, Y direction) corresponding to the frequency band of the antenna, and each second-directional wiring 22 extends in a direction (width direction, X direction) perpendicular to the first-directional wiring 21. The first-directional wiring 21 has a length L _a (the length of the mesh wiring layer 20 described above, see FIG. 3 ) that corresponds to a predetermined frequency band, and thereby mainly functions as an antenna. 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 may be, for example, in the range of 10 μm to 1 mm, and preferably in the range of 10 μm to 80 μm. The plurality of second directional wires 22 are arranged at equal intervals, and the pitch _P2 may be, for example, in the range of 10 μm to 1 mm, and preferably in the range of 10 μm to 80 μm. By making the pitch _P1 of the first directional wires 21 and the pitch _P2 of the second directional wires 22 each 10 μm or more, the first directional wires 21 and the second directional wires 22 can be made difficult to see with the naked eye. Furthermore, by setting the pitch _P1 of the first directional wirings 21 and the pitch _P2 of the second directional wirings 22 to 80 μm or less, degradation of antenna performance can be effectively suppressed. Furthermore, by arranging the plurality of first directional wirings 21 and the plurality of second directional wirings 22 at equal intervals, the size of the openings 23 within the mesh wiring layer 20 is uniform, making the mesh wiring layer 20 less visible to the naked eye. Furthermore, 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 primer layer 15 and the transparent 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 may be, for example, in the range of 0.01 mm to 1 mm. Although the first directional wirings 21 and the second directional wirings 22 are orthogonal to each other, they may intersect at an acute or obtuse angle. The shape of the openings 23 is preferably the same shape and size over the entire surface, but it is not necessary to make it uniform over the entire surface, and it may be changed depending on the location.

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

In this embodiment, the line width _W1 of the first directional wiring 21 (length in the X direction, see FIG. 5 ) and the line width _W2 of the second directional wiring 22 (length in the Y direction, see FIG. 6 ) are not particularly limited and can be appropriately selected depending on the application. For example, the line width _W1 of the first directional wiring 21 can be selected from the 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 the range of 0.1 μm to 5.0 μm, and preferably from 0.2 μm to 2.0 μm. By making the line width _W1 of the first directional wiring 21 and the line width _W2 of the second directional wiring 22 each 0.2 μm or more, degradation of antenna performance can be effectively suppressed. Furthermore, by setting the line width _W1 of the first directional wiring 21 and the line width _W2 of the second directional wiring 22 to 2.0 μm or less, the first directional wiring 21 and the second directional wiring 22 can be made difficult to see with the naked eye.

The height H ₁ of the first directional wiring 21 (length in the Z direction, see FIG. 5 ) and the height H ₂ of the second directional wiring 22 (length in the Z direction, see FIG. 6 ) are not particularly limited and can be appropriately selected depending on the application. The height H ₁ of the first directional wiring 21 and the height H ₂ of the second directional wiring 22 can each be selected, for example, from a range of 0.1 μm to 5.0 μm, and preferably from 0.2 μm to 1.0 μm. By making the height H ₁ of the first directional wiring 21 and the height H ₂ of the second directional wiring 22 each 0.2 μm or more, a decrease in antenna performance can be effectively suppressed. Furthermore, by making the height H ₁ of the first directional wiring 21 and the height H ₂ of the second directional wiring 22 each 1.0 μm or less, the first directional wiring 21 and the second directional wiring 22 can be made difficult to see with the naked eye.

The material of the first directional wiring 21 and the second directional wiring 22 may be any conductive metal material. 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 metal material (including an alloy) such as gold, silver, copper, platinum, tin, aluminum, iron, or nickel. The first directional wiring 21 and the second directional wiring 22 may also be a plating layer formed by electrolytic plating.

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 wiring substrate 10 in this range, the conductivity and transparency of the wiring substrate 10 can be ensured. Note that the aperture ratio refers to the percentage of the area of the open region (the region where no metal parts such as the first directional wiring 21 and second directional wiring 22 are present and where the substrate 11 is exposed) in a unit area of a specified region (for example, the entire area of the mesh wiring layer 20).

Although not shown, a protective layer may be formed on the primer layer 15 to cover the mesh wiring layer 20. 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 conductive thin plate-like member having a substantially rectangular shape. The longitudinal direction of the power supply unit 40 is parallel to the X direction, and the lateral direction of the power supply unit 40 is parallel to the Y direction. The power supply unit 40 is disposed at the longitudinal end (the negative end in the Y direction) of the substrate 11. The power supply unit 40 may be made of a metal material (including alloys) such as gold, silver, copper, platinum, tin, aluminum, iron, or nickel. When the wiring substrate 10 is incorporated into the image display device 60 (see FIGS. 1 and 2), this power supply unit 40 is electrically connected to the communication module 63 of the image display device 60. Note that while 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. Furthermore, by forming the power supply unit 40 to be flexible, the power supply unit 40 may be able to wrap around the side or back of the image display device 60 and be electrically connected on the side or back.

[Method of manufacturing a wiring board]
Next, a method for manufacturing the laminate 70 for an image display device according to this embodiment will be described with reference to Figures 7(a) to (f) and 8(a) to (c). Figures 7(a) to (f) and 8(a) to (c) are cross-sectional views showing the method for manufacturing the laminate 70 for an image display device according to this embodiment.

First, prepare a transparent substrate 11.

Next, as shown in FIG. 7(a), 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 Figure 7(b), metal foil 51 is laminated over substantially the entire surface of primer layer 15. In this embodiment, the thickness of metal foil 51 may be 0.1 μm or more and 5.0 μm or less. In this embodiment, metal foil 51 may contain copper.

Next, as shown in Figure 7(c), a photo-curable insulating resist 52 is applied to substantially the entire surface of the metal foil 51. Examples of this photo-curable insulating resist 52 include organic resins such as acrylic resins and epoxy resins.

Next, as shown in FIG. 7(d), the insulating layer 54 is formed by photolithography. In this case, the photo-curable 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.

Next, as shown in FIG. 7(e), the metal foil 51 located on the surface of the primer layer 15 in the area not covered by the insulating layer 54 is removed. At this time, the metal foil 51 is etched so that the surface of the primer layer 15 is exposed by wet processing 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.

Next, as shown in FIG. 7(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.

In this way, a wiring board 10 is obtained, which includes a substrate 11, a primer layer 15 provided on the substrate 11, and a mesh wiring layer 20 disposed on the primer layer 15. In this case, the mesh wiring layer 20 includes first-directional wiring 21 and second-directional wiring 22. The wiring board 10 is then cut to the desired size.

Next, the first transparent adhesive layer 95, the wiring substrate 10, and the second transparent adhesive layer 96 are laminated together. To do this, first, as shown in FIG. 8(a), an OCA sheet 90 is prepared, which includes, for example, a polyethylene terephthalate (PET) release film 91 and an OCA layer 92 (first transparent adhesive layer 95 or second transparent adhesive layer 96) laminated on the release film 91. The OCA layer 92 may be formed by applying a liquid curable adhesive layer composition containing a polymerizable compound onto the release film 91 and curing it using, for example, ultraviolet (UV) light. This curable adhesive layer composition contains a polar group-containing monomer.

Next, as shown in Figure 8(b), the OCA layer 92 of the OCA sheet 90 is bonded to the wiring board 10. This sandwiches the wiring board 10 between the OCA layers 92.

Then, as shown in Figure 8(c), the release film 91 is peeled off and removed from the OCA layer 92 of the OCA sheet 90 bonded to the wiring substrate 10, thereby obtaining the first transparent adhesive layer 95 (OCA layer 92), wiring substrate 10, and second transparent adhesive layer 96 (OCA layer 92) laminated together.

In this way, a laminate 70 for an image display device is obtained, comprising a first transparent adhesive layer 95, a second transparent adhesive layer 96, and a wiring substrate 10.

Then, by laminating a display device 61 on the laminate 70 for an image display device, an image display device 60 is obtained, which comprises the laminate 70 for an image display device and the display device 61 laminated on the laminate 70 for an image display device.

[Operation of this embodiment]
Next, the operation of this embodiment having the above-described configuration will be described.

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, a portion of the substrate 11 is disposed in a portion between the first transparent adhesive layer 95 and the second transparent adhesive layer 96. Furthermore, the haze value of the laminate 70 for an image display device is 3% or less. This makes it difficult for an observer to see the laminate 70 for an image display device with the naked eye when observing the image display device 60 from the light-emitting surface 64 side. Therefore, when an observer observes the image display device 60 from the light-emitting surface 64 side, the substrate 11 of the wiring substrate 10 can be difficult to see with the naked eye. In particular, when the first transparent adhesive layer 95 and the second transparent adhesive layer 96 each have a larger area than the substrate 11, the outer edge of the substrate 11 can be difficult to see with the naked eye, preventing the observer from noticing the presence of the substrate 11.

Also, according to this embodiment, the wiring board 10 comprises a substrate 11, a primer layer 15 provided on the substrate 11, and a mesh wiring layer 20 disposed on the primer layer 15. The substrate 11 is transparent. Furthermore, the mesh wiring layer 20 has a conductor portion as a forming portion of an opaque conductive layer and a mesh pattern with numerous openings. 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 of the mesh wiring layer 20, and the visibility of the display device 61 is not obstructed.

[Modification]
Next, a modified example of the laminate 70 for an image display device will be described.

Figure 9 shows a modified example of a laminate for an image display device. The modified example shown in Figure 9 differs in that a protective layer 17 is formed on the primer layer 15 to cover the mesh wiring layer 20 and the power supply section 40, but the other configuration is substantially the same as the embodiment shown in Figures 1 to 8 described above. In Figure 9, the same parts as those shown in Figures 1 to 8 are designated by the same reference numerals and detailed description will be omitted.

In the modified example shown in Figure 9, a protective layer (dielectric layer) 17 is formed on the surface of the primer layer 15 to cover the mesh wiring layer 20 and the power supply section 40. The protective layer 17 protects the mesh wiring layer 20 and the power supply section 40, and may be formed over substantially the entire surface of the primer layer 15.

The thickness _T5 of the protective layer 17 (see FIG. 9 ) may be 0.05 μm or more and 1.8 μm or less. When the thickness _T5 of the protective layer 17 is 0.05 μm or more, the scratch resistance and weather resistance of the protective layer 17 can be improved. Furthermore, when the thickness _T5 of the protective layer 17 is 1.8 μm or less, the thickness of the laminate 70 for an image display device does not become too thick, and the overall thickness of the image display device 60 can be made thin. Note that in this specification, the thickness _T5 of the protective layer 17 refers to the distance in the Z direction from the surface of the power supply unit 40 to the surface of the protective layer 17.

Furthermore, the dielectric loss tangent of the protective layer 17 is 0.005 or less. This effectively prevents the protective layer 17 from affecting the transmission and reception of radio waves in the mesh wiring layer 20. This prevents a decrease in antenna performance. The dielectric loss tangent of the protective layer 17 can be measured in accordance with IEC 62562 or ASTM D150 using the same method used to measure the relative dielectric constant of the substrate 11.

Materials that can be used for the protective layer 17 include acrylic resins such as polymethyl (meth)acrylate and polyethyl (meth)acrylate, and their modified resins and copolymers; polyester resins; polyvinyl resins such as polyvinyl alcohol, polyvinyl acetate, polyvinyl acetal, and polyvinyl butyral, and their copolymers; polyurethane resins; epoxy resins; polyamide resins; and colorless, transparent insulating resins such as chlorinated polyolefins.

It is particularly preferable that the protective layer 17 contains an acrylic resin or a polyester resin. This can further improve adhesion between the first directional wiring 21 and the second directional wiring 22, or adhesion between the first directional wiring 21 and the second directional wiring 22 and the primer layer 15, and can increase the abrasion resistance and weather resistance of the first directional wiring 21 and the second directional wiring 22. Furthermore, invisibility and antenna performance can be maintained.

Furthermore, it is preferable that the protective layer 17 contains silicon dioxide. Silicon dioxide may be added to the resin as a powder. Alternatively, it may be formed as a film that is substantially free of resin using techniques such as vapor deposition, sputtering, or CVD. This improves the slipperiness of the surface of the protective layer 17 and the anti-reflection properties of the protective layer 17.

Methods for forming such a protective layer 17 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.

In this modified example, a laminate 70 for an image display device is composed of a wiring substrate 10, a protective layer 17, and a second transparent adhesive layer 96 having an area larger than that of the substrate 11. This embodiment also provides such a laminate 70 for an image display device.

In this modified example, the haze value of the laminate 70 for an image display device is 3% or less, making it difficult for an observer to see the laminate 70 for an image display device with the naked eye when observing the image display device 60 from the light-emitting surface 64 side. This makes it difficult for an observer to see the substrate 11 of the wiring board 10 with the naked eye when observing the image display device 60 from the light-emitting surface 64 side.

Next, we will explain modified examples of wiring boards.

(First Modification)
Fig. 10 shows a first modified example of the wiring board. The modified example shown in Fig. 10 differs in that the mesh wiring layer 20 functions as an array antenna, but other configurations are substantially the same as those shown in Figs. 1 to 9 described above. In Fig. 10, the same parts as those shown in Figs. 1 to 9 are designated by the same reference numerals, and detailed description thereof will be omitted.

In the wiring board 10 shown in Figure 10, the 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.

As shown in Fig. 10, four mesh wiring layers 20 are formed on the substrate 11. The mesh wiring layers 20 are present only in a partial region on the substrate 11. The mesh wiring layers 20 may have the same shape as each other. In this case, it is preferable that the errors in the length (length in the Y direction) _La and width (length in the X direction) _Wa of each mesh wiring layer 20 are each within 10%. This can effectively improve the millimeter wave antenna performance.

(Second Modification)
Fig. 11 shows a second modified example of the wiring board. The modified example shown in Fig. 11 differs in that the cross-sectional shapes of the first-directional wirings 21 and the second-directional wirings 22 are not substantially rectangular or substantially square, but the other configurations are substantially the same as those shown in Figs. 1 to 10 described above. In Fig. 11, the same parts as those shown in Figs. 1 to 10 are designated by the same reference numerals, and detailed description thereof will be omitted.

In the wiring board 10 shown in Figure 11, the cross-sectional shape of the first directional wiring 21 and the second directional wiring 22 is a generally trapezoidal shape in which the front side (positive side in the Z direction) is narrower than the back side (negative side in the Z direction). In this case, the first directional wiring 21 (second directional wiring 22) includes a third surface 25a facing the first surface 11a of the substrate 11, and a fourth surface 25b located on the opposite side of the third surface 25a.

In this modification, in a cross section (X-direction cross section (Y-direction cross section)) perpendicular to the longitudinal direction of the first directional wiring 21 (second directional wiring 22), when the width of the fourth surface 25 b of the first directional wiring 21 (second directional wiring 22) is _Wx and the width of the widest portion (hereinafter simply referred to as wide portion) 26 of the first directional wiring 21 (second directional wiring 22) is _Wy ,
W _y ≦1.15W _x
It is preferable to satisfy the following relationship. This makes it possible to shorten the length along the X direction (Y direction) of the surface 25c extending between the fourth surface 25b and the wide portion 26 in a cross section (X direction cross section (Y direction cross section)) perpendicular to the longitudinal direction of the first directional wiring 21 (second directional wiring 22). This makes it possible to suppress scattering of visible light incident on the surface 25c from the fourth surface 25b side into the first directional wiring 21 (second directional wiring 22). As a result, it is possible to suppress an increase in the haze value of the laminate 70 for an image display device.

In the example shown in Figure 11, the wide portion 26 forms the third surface 25a. However, this is not limited to this. For example, as shown in Figure 12, the wide portion 26 may be located between the third surface 25a and the fourth surface 25b in the Z direction.

According to this modified example, the haze value of the laminate 70 for an image display device can be prevented from increasing, making it difficult for an observer to see the laminate 70 for an image display device with the naked eye when observing the image display device 60 from the light-emitting surface 64 side. Therefore, when an observer observes the image display device 60 from the light-emitting surface 64 side, it makes it difficult for an observer to see the substrate 11 of the wiring board 10 with the naked eye.

(Third Modification)
Figures 13 and 14 show a third modified example of the wiring board. The modified example shown in Figures 13 and 14 differs in that a dummy wiring layer 30 is provided around the mesh wiring layer 20, but other configurations are substantially the same as the embodiment shown in Figures 1 to 12 described above. In Figures 13 and 14, the same parts as those shown in Figures 1 to 12 are given the same reference numerals and detailed descriptions thereof will be omitted.

In the wiring substrate 10 shown in Figure 13, a dummy wiring layer 30 is provided along the periphery of the mesh wiring layer 20. Unlike the mesh wiring layer 20, this dummy wiring layer 30 does not actually function as an antenna.

As shown in FIG. 14, 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 (first directional wiring 21 and second directional wiring 22). The multiple dummy wirings 30a are also 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. 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 (see Figure 4) of the mesh wiring layer 20 described above 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 it difficult to see the mesh wiring layer 20 arranged on the substrate 11. 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 preferably close to the aperture ratio of the mesh wiring layer 20.

In this way, by arranging the dummy wiring layer 30, which 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.

As shown in FIG. 15, when multiple (four) mesh wiring layers 20 are present on the substrate 11, dummy wiring layers 30 that are electrically independent from the mesh wiring layers 20 may be arranged around each mesh wiring layer. Also, as shown in FIG. 16, the dummy wiring layers 30 may be arranged to surround multiple mesh wiring layers 20. In the illustrated example, a single dummy wiring layer 30 surrounds all (four) mesh wiring layers 20. Although not shown, multiple dummy wiring layers 30 may be provided. In this case, the number of mesh wiring layers 20 surrounded by each dummy wiring layer 30 may differ from each other.

(Fourth Modification)
17 and 18 show a fourth modified example of the wiring substrate. The modified example shown in Figures 17 and 18 differs in that a plurality of dummy wiring layers 30A, 30B having different aperture ratios are provided around the mesh wiring layer 20, but other configurations are substantially the same as those shown in Figures 1 to 16 described above. In Figures 17 and 18, the same parts as those shown in Figures 1 to 16 are designated by the same reference numerals, and detailed description thereof will be omitted.

In the wiring substrate 10 shown in FIG. 17, multiple (in this case, two) dummy wiring layers 30A, 30B (first dummy wiring layer 30A and 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. Unlike the mesh wiring layer 20, these dummy wiring layers 30A, 30B do not actually function as antennas.

As shown in FIG. 18, 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. Furthermore, 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, and makes it difficult to see the mesh wiring layer 20 arranged on the substrate 11. The aperture ratio of the first dummy wiring layer 30A is greater than the aperture ratio of the mesh wiring layer 20, and the aperture ratio of the first dummy wiring layer 30A is greater than the aperture ratio of the second dummy wiring layer 30B.

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. Also, three or more dummy wiring layers with different aperture ratios may be provided. In this case, it is preferable that the aperture ratio of each dummy wiring layer gradually increase from those closest to the mesh wiring layer 20 to those farther away.

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 more 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.

Although not shown, when multiple mesh wiring layers 20 are present on the substrate 11, dummy wiring layers 30A, 30B that are electrically independent from the mesh wiring layer 20 may be arranged around each mesh wiring layer. Furthermore, the dummy wiring layers 30A, 30B may be arranged to surround multiple mesh wiring layers 20. In this case, multiple dummy wiring layers 30A, 30B may be provided, and the number of mesh wiring layers 20 surrounded by each dummy wiring layer 30A, 30B may be different.

(Fifth Modification)
Fig. 19 shows a fifth modified example of the wiring board. The modified example shown in Fig. 19 differs in the planar shape of the mesh wiring layer 20, but other configurations are substantially the same as those shown in Figs. 1 to 18 described above. In Fig. 19, the same parts as those shown in Figs. 1 to 18 are designated by the same reference numerals, and detailed description thereof will be omitted.

Figure 19 is an enlarged plan view showing a mesh wiring layer 20 according to one modified example. In Figure 19, the first directional wiring 21 and the second directional wiring 22 intersect at an angle (not at a right angle), and each opening 23 is formed in a diamond shape 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.

[Example]
Next, a specific example of this embodiment will be described.

Example 1
A laminate for an image display device having the configuration shown in FIG. 2 was fabricated. In this case, a polyethylene terephthalate substrate having a thickness of 100 μm was used as the substrate for the wiring board. A polyester resin having a thickness of 0.1 μm was used as the primer layer. Copper wiring having a line width of 1.0 μm and a height of 1.0 μm was formed on the polyester resin as the first directional wiring and the second directional wiring, with a pitch of 100 μm. Furthermore, an acrylic resin OCA layer having a thickness of 25 μm was used as the first transparent adhesive layer 95 and the second transparent adhesive layer 96. In this case, the _Wy / _Wx ratio for the first directional wiring and the second directional wiring was 1.052.

(1) Haze Value Measurement Test Next, a haze value measurement test was carried out to measure the haze value of the laminate for an image display device 70. At this time, the haze value of the laminate for an image display device was measured using a haze meter (HM-150N, manufactured by Murakami Color Research Laboratory) by a method in accordance with JIS K 7136.

(2) Visibility Evaluation Test Next, the visibility of the wiring board in the laminate for an image display device was confirmed. At this time, first, 10 experimenters were randomly selected. Then, the selected experimenters observed the laminate for an image display device.

(3) Antenna Performance Evaluation Test Next, an antenna performance evaluation test was conducted. First, the wiring board to be evaluated was attached to the input terminal of a network analyzer (KEYSIGHT E5080B ENA Vector Network Analyzer), and a 28 GHz helical antenna (Candox Systems) was attached as a standard antenna to the output terminal. Next, S21 at 28 GHz was measured. The standard antenna was also attached to the input and output terminals, and S21 at 28 GHz was measured. Then, the extent to which S21 changed when a wiring board was attached to the input terminal was evaluated, using the standard antenna attached to the input and output terminals as a reference.

Example 2
A laminate for an image display device was produced in the same manner as in Example 1, except that W _y /W _x was 1.121, and a haze value measurement test, a visibility evaluation test, and an antenna performance evaluation test were carried out.

Example 3
A laminate for an image display device was produced in the same manner as in Example 1, except that the line width was 2.0 μm and W _y /W _x was 1.138, and a haze value measurement test, a visibility evaluation test, and an antenna performance evaluation test were performed.

Example 4
A laminate for an image display device was produced in the same manner as in Example 1, except that the pitch was 80 μm and W _y /W _x was 1.144, and a haze value measurement test, a visibility evaluation test, and an antenna performance evaluation test were carried out.

Example 5
A laminate for an image display device was produced in the same manner as in Example 1, except that the height was 0.3 μm and W _y /W _x was 1.022, and a haze value measurement test, a visibility evaluation test, and an antenna performance evaluation test were carried out.

Example 6
A laminate for an image display device was produced in the same manner as in Example 1, except that the height was 0.7 μm and W _y /W _x was 1.030, and a haze value measurement test, a visibility evaluation test, and an antenna performance evaluation test were carried out.

(Comparative Example 1)
A laminate for an image display device was produced in the same manner as in Example 1, except that the height was 0.3 μm and W _y /W _x was 1.180, and a haze value measurement test, a visibility evaluation test, and an antenna performance evaluation test were carried out.

(Comparative Example 2)
A laminate for an image display device was produced in the same manner as in Example 1, except that the pitch was 50 μm and W _y /W _x was 1.086, and a haze value measurement test, a visibility evaluation test, and an antenna performance evaluation test were carried out.

The results are shown in Table 1. In the visibility column of Table 1, "◎ (excellent)" means that three or fewer out of ten test subjects noticed glare from the wiring board. "× (poor)" means that seven or more out of ten test subjects noticed glare from the wiring board.

In the performance column of Table 1, "◎ (excellent)" means that the S21 at 28 GHz was not significantly degraded compared to the standard antenna. "○ (good)" means that the S parameter (S21) at 28 GHz was slightly degraded compared to the standard antenna. "× (poor)" means that the S parameter (S21) at 28 GHz was significantly degraded compared to the standard antenna.

As a result, as shown in Table 1, the laminates for image display devices according to Comparative Examples 1 and 2 had haze values of 3% or more, and more than 7 out of 10 test subjects noticed glare from the wiring board. In contrast, the laminates for image display devices according to Examples 1 to 6 had haze values of 3% or less, and 3 out of 10 test subjects noticed glare from the wiring board. This demonstrates that the laminates for image display devices according to this embodiment can make the wiring board less visible to the naked eye.

Furthermore, as shown in Table 1, the laminate for an image display device according to Comparative Example 1 exhibited a significantly deteriorated S parameter (S21) at 28 GHz compared to the standard antenna. In contrast, the laminates for image display devices according to Examples 1 to 6 were able to suppress the deterioration of the S parameter (S21) at 28 GHz compared to the standard antenna. In particular, the laminates for image display devices according to Examples 1 to 4 did not exhibit significant deterioration of S21 at 28 GHz compared to the standard antenna. Therefore, it was found that the laminate for an image display device according to this embodiment can effectively suppress the deterioration of antenna performance.

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.

REFERENCE SIGNS LIST 10 Wiring substrate 11 Substrate 11a First surface 11b Second surface 15 Primer layer 17 Protective layer 20 Mesh wiring layer 21 First direction wiring 22 Second direction wiring 25a Third surface 25b Fourth surface 26 Wide portion 30 Dummy wiring layer 30A First dummy wiring layer 30B Second dummy wiring layer 60 Image display device 61 Display device 70 Laminate for image display device 95 First transparent adhesive layer 96 Second transparent adhesive layer

Claims (9)

a wiring board including a substrate including a first surface and a second surface located opposite to the first surface, a primer layer provided on the first surface of the substrate, and a mesh wiring layer disposed on the primer layer;
a dielectric layer located on the first surface side of the substrate;
an adhesive layer located on the second surface side of the substrate,
The substrate is transparent,
a portion of the substrate is disposed in a portion of the region between the dielectric layer and the adhesive layer;
the dielectric layer is directly bonded to the adhesive layer in a region between the dielectric layer and the adhesive layer other than a region where a partial region of the substrate is disposed;
A laminate for an image display device, having a haze value of 3% or less. The laminate for an image display device according to claim 1, wherein the wiring substrate has a radio wave transmission/reception function. The laminate for an image display device according to claim 2, wherein the wiring substrate has a millimeter wave transmission/reception function. The laminate for an image display device according to any one of claims 1 to 3, wherein the mesh wiring layer functions as an array antenna. The laminate for an image display device according to any one of claims 1 to 4, wherein the mesh wiring layer includes a plurality of wires, the wire width of the wires being 0.2 μm or more and 2.0 μm or less, the wire pitch being 10 μm or more and 80 μm or less, and the wire height being 0.2 μm or more and 1.0 μm or less. The wiring includes a third surface facing the first surface and a fourth surface located on the opposite side of the third surface, and in a cross section perpendicular to the longitudinal direction of the wiring, when the width of the fourth surface of the wiring is _Wx and the width of the widest part of the wiring is _Wy ,
W _y ≦1.15W _x
The laminate for an image display device according to claim 5 , which satisfies the following relationship: The laminate for an image display device according to any one of claims 1 to 6, wherein a dummy wiring layer electrically independent from the mesh wiring layer is provided around the mesh wiring layer. The laminate for an image display device according to claim 7, wherein there are multiple mesh wiring layers, and the dummy wiring layer is arranged to surround the multiple mesh wiring layers. The laminate for an image display device according to any one of claims 1 to 8,
and a display device laminated on the laminate for an image display device.