Display device

Abstract

To solve problems that since a plurality of LED elements of the conventional LED display device is difficult to be pressed at a predetermined uniform pressure, poor mounting occurs, display quality of the LED display device deteriorates, and production yield is decreased.SOLUTION: A display device comprises: a substrate including a first surface and a second surface opposite the first surface; a display part positioned closed to the first surface; a first wiring pad positioned close to the second surface and electrically connected to the display part; an external connection terminal positioned close to the second surface; connection wiring positioned close to the second surface and electrically connecting the first wiring pad to the external connection terminal; and a dummy conductor part positioned close to the second surface and formed as protrusion that does not overlap with any of the first wiring pad, the external connection terminal and the connection wiring in plan view.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a display device including light-emitting elements such as light-emitting diodes (LEDs). [Background technology]

[0002] 2. Description of the Related Art Display devices disclosed in, for example, Patent Documents 1 and 2 are known in the art. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-9789 A [Patent Document 2] JP 2009-231785 A Summary of the Invention

[0004] The display device of the present disclosure includes a substrate having a first surface and a second surface opposite to the first surface; A display unit located on the first surface side; a first wiring pad located on the second surface side and electrically connected to the display unit; An external connection terminal located on the second surface side; a connection wiring located on the second surface side and electrically connecting the first wiring pad and the external connection terminal; The substrate includes a convex portion that is located on the second surface side and does not overlap any of the first wiring pad, the external connection terminal, and the connection wiring in a plan view. [Brief description of the drawings]

[0005] The objects, features and advantages of the present disclosure will become more apparent from the following detailed description and drawings. [Figure 1] FIG. 1 is a diagram illustrating a schematic circuit configuration of a display device according to an embodiment of the present disclosure, and is a plan view of the first surface side of a substrate. [Diagram 2]FIG. 2 is a diagram illustrating a schematic circuit configuration of a display device according to an embodiment of the present disclosure, and is a plan view of the second surface side of the substrate. [Diagram 3] 2 is a partial cross-sectional view of a portion including an edge portion of a substrate in a display device according to an embodiment of the present disclosure, taken along line C1-C2 in FIG. 1. [Figure 4] FIG. 13 is a diagram illustrating a schematic circuit configuration of a display device according to another embodiment of the present disclosure, and is a plan view of the second surface side of the substrate. [Diagram 5] FIG. 13 is a diagram illustrating a schematic circuit configuration of a display device according to another embodiment of the present disclosure, and is a plan view of the second surface side of the substrate. [Figure 6] FIG. 13 is a diagram illustrating a schematic circuit configuration of a display device according to another embodiment of the present disclosure, and is a plan view of the second surface side of the substrate. [Figure 7] FIG. 13 is a diagram illustrating a schematic circuit configuration of a display device according to another embodiment of the present disclosure, and is a plan view of the second surface side of the substrate. [Figure 8] FIG. 13 is a diagram illustrating a schematic circuit configuration of a display device according to another embodiment of the present disclosure, and is a plan view of the second surface side of the substrate. [Figure 9] FIG. 13 is a diagram illustrating a schematic circuit configuration of a display device according to another embodiment of the present disclosure, and is a plan view of the second surface side of the substrate. [Figure 10] 11 is a graph of an example of a display device according to the present disclosure, showing the relationship between the distance between adjacent dummy conductors and the defect rate of mounting of light-emitting elements. [Figure 11] FIG. 13 is a diagram illustrating a schematic circuit configuration of a display device according to another embodiment of the present disclosure, and is a plan view of the second surface side of the substrate. [Figure 12] FIG. 13 is a diagram illustrating a schematic circuit configuration of a display device according to another embodiment of the present disclosure, and is a plan view of the second surface side of the substrate. [Figure 13] FIG. 13 is a diagram illustrating a schematic circuit configuration of a display device according to another embodiment of the present disclosure, and is a plan view of the second surface side of the substrate. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] The configuration on which the display device according to the embodiment of the present disclosure is based will be described. Patent Documents 1 and 2 disclose an LED display device having a plurality of LED elements. A manufacturing method of an LED display device includes a mounting process of mounting a plurality of LED elements on a substrate. In the mounting process, a substrate having a plurality of mounting portions on one main surface is first placed on a flat stage surface of a mounting device so that the other main surface of the substrate faces the stage surface. Next, a plurality of LED elements are placed on the plurality of mounting portions via a conductive bonding material such as an anisotropic conductive film. After that, the conductive bonding material is heated while pressing the plurality of LED elements against the substrate, thereby electrically connecting the electrodes of the LED elements to the electrode pads provided on the mounting portions.

[0007] In conventional LED display devices, the flatness of the other main surface of the substrate is low, so when pressing the multiple LED elements against the substrate, it is sometimes difficult to press the multiple LED elements uniformly with a predetermined pressure. Also, when pressing the multiple LED elements against the substrate, deformation of the substrate such as bending of the substrate occurs, so it is sometimes difficult to press the multiple LED elements uniformly with a predetermined pressure. In these cases, mounting defects of the LED elements occur, which can reduce the display quality of the LED display device or reduce the manufacturing yield.

[0008] Hereinafter, a display device according to an embodiment of the present disclosure will be described with reference to the accompanying drawings. Each of the figures referred to below shows the main components of the display device according to the embodiment. The display device according to the present embodiment may include well-known components such as a circuit board, wiring conductors, control IC, and control LSI, which are not shown. In addition, each of the figures referred to below is schematic, and the positions, dimensional ratios, etc. of the components of the display device are not necessarily accurately illustrated.

[0009] FIG. 1 is a plan view of the first surface side of the substrate, which is a schematic diagram of the circuit configuration of the display device according to an embodiment of the present disclosure. FIG. 2 is a plan view of the second surface side of the substrate, which is a schematic diagram of the circuit configuration of the display device according to an embodiment of the present disclosure. FIG. 3 is a partial cross-sectional view of a portion including an edge portion of the substrate in the display device according to an embodiment of the present disclosure. FIGS. 4 to 9 and 11 to 13 are plan views of the second surface side of the substrate, which are schematic diagrams of the circuit configuration of the display device according to another embodiment of the present disclosure. FIG. 10 is a graph of an example of the display device according to the present disclosure, which shows the relationship between the interval between adjacent dummy conductors and the defect rate of mounting of the light-emitting element. In FIGS. 2, 4 to 9, 11 to 13, the first wiring pads 4, the external connection terminals 5, and the dummy conductors 7 are hatched to facilitate illustration.

[0010] The display device 1 of the present disclosure includes a substrate 2, a display unit 3, a first wiring pad 4, an external connection terminal 5, a connection wiring (also called a first connection wiring) 6, and a dummy conductor portion 7 as a convex portion.

[0011] As shown in FIG. 2, the display device 1 of the present disclosure comprises a substrate 2 having a first surface 2a and a second surface 2b opposite the first surface 2a, a display unit 3 located on the first surface 2a side, a first wiring pad 4 located on the second surface 2b side and electrically connected to the display unit 3, an external connection terminal 5 located on the second surface 2b side, connection wiring 6 located on the second surface 2b side and electrically connecting the first wiring pad 4 and the external connection terminal 5, and a dummy conductor portion 7 located on the second surface 2b side as a convex portion that does not overlap any of the first wiring pad 4, the external connection terminal 5, and the connection wiring 6 in a planar view.

[0012] The display device 1 of the present disclosure has the following effects due to the above configuration. Since the second surface 2b of the substrate 2 is provided with the dummy conductors 7 that do not overlap the first wiring pads 4, the external connection terminals 5, and the connection wirings 6 in a planar view, the flatness of the second surface 2b of the substrate 2 can be improved. In addition, since the rigidity of the substrate 2 is improved, it is possible to suppress the occurrence of changes in the substrate 2, such as bending of the substrate 2, when the substrate 2 is pressed from the first surface 2a of the substrate 2 in the mounting process of the light-emitting elements 31. As a result, when the multiple light-emitting elements 31 are pressed against the substrate 2 in the mounting process, it is easy to uniformly press the multiple light-emitting elements 31 with a predetermined pressure. Therefore, it is possible to reduce mounting defects of the light-emitting elements 31, improve the display quality of the display device 1, and improve the manufacturing yield of the display device 1.

[0013] The convex portion may be made of a conductive material such as a metal, a semiconductor material, an inorganic insulating material, an organic insulating material, or the like. The conductive material may be Al, Al / Ti, Ti / Al / Ti, Mo, Mo / Al / Mo, MoNd / AlNd / MoNd, Cu, Cr, Ni, Ag, or the like. For example, "Al / Ti" means a laminated structure in which a Ti layer is laminated on an Al layer. The semiconductor material may be silicon, germanium, gallium arsenide, gallium phosphide, indium phosphide, or the like. The inorganic insulating material may be silicon dioxide (SiO2), silicon nitride (Si3N4), or the like. The organic insulating material may be acrylic resin, polycarbonate, polyethylene terephthalate (PET), or the like. The convex portion may be configured such that at least the surface layer is made of a material having a lower hardness than any of the first wiring pad 4, the external connection terminal 5, and the connection wiring 6. In the case of this configuration, when the substrate 2 is pressed from the side of the first surface 2a of the substrate 2 in the mounting process of the light emitting element 31, the convex portion is deformed and easily functions as a cushion. In order to improve this function, the convex portion may be configured such that at least the surface layer is made of the above-mentioned resin material. In this case, the convex portion may be configured such that the surface layer is made of a resin material, and the layer below the surface layer is made of the above-mentioned conductive material such as metal, semiconductor material, or the like. The resin material may have elasticity. The elastic resin material may be a silicone resin, a urethane resin, a porous urethane resin (urethane foam), an acrylic resin, or the like. The thickness of the surface layer of the convex portion may be about 5% to 50% of the height of the convex portion, but is not limited to this range. The convex portion may also be configured to be made of the same conductive material as the connection wiring 6, etc. In this case, the convex portion can be formed in the same manufacturing process as the connection wiring 6, etc. Therefore, in the following description, a configuration in which the convex portion is a dummy conductor portion 7 will be described. The dummy conductor portion 7 may also include a wiring portion, and may also include various conductive pattern portions.

[0014] As shown in Figs. 2 and 4, the substrate 2 may have a first region A1 on the second surface 2b where the first wiring pads 4, the external connection terminals 5, and the connection wirings 6 are located, and a second region A2 other than the first region A1. The dummy conductors 7 may be located in the second region A2 and occupy half or more of the area of ​​the second region A2. In this case, the flatness of the second surface 2b side of the substrate 2 can be further improved. Also, the rigidity of the substrate 2 is further improved. The ratio of the area of ​​the dummy conductors 7 to the area of ​​the second region A2 may be 60% or more and less than 100%, or may be about 70% to 95%. Note that "to" means "to", and the same applies hereinafter.

[0015] In the above configuration, the dummy conductors 7 may include a solid portion. Of course, the entire dummy conductors 7 may be solid. In this case, it is easy to adjust the area of ​​the dummy conductors 7, and it is also easier to improve the rigidity of the substrate 2.

[0016] Also, as shown in FIG. 5 and FIG. 6, the plurality of dummy conductors 7 may be uniformly distributed in the second region A2. In this case, the flatness of the second surface 2b side of the substrate 2 can be further improved. That is, for example, when the dummy conductors 7 are entirely solid, the difference in rigidity applied to the substrate 2 between the portion where the dummy conductors 7 are present and the portion where the dummy conductors 7 are not present is likely to become large. In this case, the substrate 2 tends to be easily deflected in the natural state. In the case where the plurality of dummy conductors 7 are uniformly distributed in the second region A2, the rigidity applied to the substrate 2 is distributed, so that the substrate 2 is prevented from being deflected in the natural state. In addition, since the rigidity of the substrate 2 is improved uniformly overall, it is possible to further prevent the substrate 2 from being deformed or otherwise changed when the substrate 2 is pressed from the first surface 2a side of the substrate 2 in the mounting process of the light emitting element 31.

[0017] 5, the distance g1 between adjacent dummy conductors 7 and the distance g2 between the connection wiring 6 and the dummy conductor 7 closest thereto may be equal to or less than a predetermined value. In this case, the dummy conductors 7 are densely arranged in the second region A2 of the second surface 2b of the substrate 2, so that the flatness of the second surface 2b side of the substrate can be further improved. In addition, the rigidity of the second surface 2b of the substrate 2 is improved more uniformly overall, so that the substrate 2 is prevented from bending in its natural state. In addition, the rigidity of the substrate 2 is improved more uniformly overall, so that the substrate 2 is prevented from changing in its natural state, such as bending, when the substrate 2 is pressed from the first surface 2a side of the substrate 2 in the mounting process of the light emitting element 31. The predetermined value may be about 6.5 mm, as described later.

[0018] The display device 1 of the present disclosure may have a configuration in which a plurality of dummy conductors 7 are distributed over the entire second surface 2b of the substrate 2. In this case, the dummy conductors 7 may be located in areas between the first wiring pads 4, between the external connection terminals 5, or between the connection wires 6, which has the effect of further improving the flatness of the second surface 2b side of the substrate and further distributing the rigidity applied to the substrate 2.

[0019] In the display device 1 of the present disclosure, the first wiring pads 4, the external connection terminals 5, and the first connection wirings 6 in the first region A1 are arranged in a unit area (for example, 1 mm 2 , 1cm 2 The occupied area ratio (SR1) per unit area of ​​the first region A1 (such as the area of ​​the first region A2) and the occupied area ratio (SR2) per unit area of ​​the dummy conductors 7 in the second region A2 may be substantially the same. The magnitude relationship between SR1 and SR2 may be, but is not limited to, 0.8≦SR1 / SR2≦1.2.

[0020] When comparing the size (area) of the first region A1 where the first wiring pads 4, the external connection terminals 5, and the connection wirings 6 are located with the second region A2 having the dummy conductors 7, the size of the second region A2 may be equal to or larger than the size of the first region A1. In this case, the ratio of the area of ​​the dummy conductors 7 to the second surface 2b of the substrate 2 increases, so that the flatness of the second surface 2b of the substrate can be further improved. In addition, since the rigidity of the second surface 2b of the substrate 2 is improved more uniformly overall, it is possible to suppress the substrate 2 from bending in a natural state. In addition, since the rigidity of the substrate 2 is improved more uniformly overall, it is possible to further suppress the occurrence of changes in the substrate 2, such as bending of the substrate 2, when the substrate 2 is pressed from the side of the first surface 2a of the substrate 2 in the mounting process of the light emitting element 31. The ratio of the area of ​​the second region A2 to the area of ​​the second surface 2b of the substrate 2 may be 50% or more, 70% or more, or 90% or more. The upper limit of the ratio of the area of ​​the second region A2 to the area of ​​the second surface 2b of the substrate 2 may be about 95%.

[0021] The substrate 2 is, for example, a transparent or opaque glass substrate. The substrate 2 has a first surface 2a, a second surface 2b opposite to the first surface 2a, and a third surface (also called a side surface) 2c connecting the first surface 2a and the second surface 2b. The substrate 2 may be, for example, a plastic substrate, a ceramic substrate, or the like. The substrate 2 may be a composite substrate in which a plurality of substrates made of different materials are laminated.

[0022] The substrate 2 may have a rectangular shape such as a triangular plate, a square plate, or a rectangular plate, a trapezoidal plate, a pentagonal plate, a hexagonal plate, a circular plate, an elliptical plate, or other shape. When the substrate 2 has an equilateral triangular, rectangular, or regular hexagonal shape, it is easy to configure a multi-display by tiling a plurality of display devices 1.

[0023] In this embodiment, the substrate 2 has a rectangular plate shape as shown in Figures 1 and 2. The second surface 2b of the substrate 2 has a first side 2ba, a second side 2bb, a third side 2bc, and a fourth side 2bd. The second side 2bb is a side that continues to the first side 2ba. The third side 2bc is a side that continues to the second side 2bb and faces the first side 2ba. The fourth side 2bd is a side that continues to the first side 2ba and faces the second side 2bb.

[0024] The display unit 3 is disposed on the first surface 2a side of the substrate 2. The display unit 3 includes a plurality of pixel units 3p. The plurality of pixel units 3p are arranged in a matrix, for example, as shown in FIG.

[0025] Each pixel unit 3p includes a light-emitting element 31, an electrode pad 32, and a driving circuit (not shown) for driving and controlling the light-emitting element 31. The driving circuit may be configured to include a thin film transistor (TFT) and a capacitance element. The TFT may have a semiconductor film (also called a channel) made of, for example, amorphous silicon (a-Si), low-temperature polysilicon (LTPS), or the like. The TFT may have three terminals, a gate electrode, a source electrode, and a drain electrode. The TFT functions as a switching element that switches between conduction and non-conduction between the source electrode and the drain electrode depending on a voltage applied to the gate electrode. The driving circuit may be formed using a thin film formation method such as a chemical vapor deposition (CVD) method.

[0026] The light-emitting element 31 is a self-luminous light-emitting element. The self-luminous light-emitting element may be a light-emitting diode (LED) element or a semiconductor laser (LD) element. In this embodiment, an LED element, which is a two-terminal element having an anode electrode 31a and a cathode electrode 31b, is used as the light-emitting element 31. The light-emitting element 31 may be a micro light-emitting diode element (also called a micro LED element). When the light-emitting element 31 is a micro LED element, the light-emitting element 31 may have a rectangular shape in plan view with a side length of about 1 μm to about 100 μm or about 3 μm to about 30 μm when disposed on the first surface 2a.

[0027] As shown in FIG. 3, the electrode pad 32 is connected to the light emitting element 31 and supplies a driving signal to the light emitting element 31. The electrode pad 32 includes an anode electrode pad 32a and a cathode electrode pad 32b. The anode electrode pad 32a and the cathode electrode pad 32b are made of a conductive material. The anode electrode pad 32a and the cathode electrode pad 32b may be made of a single metal layer, or may be made of a laminate of multiple metal layers. The anode electrode pad 32a and the cathode electrode pad 32b may be made of, for example, Mo / Al / Mo, MoNd / AlNd / MoNd, etc. Here, "Mo / Al / Mo" indicates a laminate structure in which an Al layer is laminated on a Mo layer, and a Mo layer is laminated on an Al layer. The same applies to the others. "MoNd" indicates an alloy of Mo and Nd. The same applies to the others. The surface of the anode electrode pad 32a and the surface of the cathode electrode pad 32b may each be covered with a transparent conductive layer 32c made of indium tin oxide (ITO), indium zinc oxide (IZO), or the like.

[0028] The anode electrode 31a and the cathode electrode 31b of the light-emitting element 31 are electrically connected to the anode electrode pad 32a and the cathode electrode pad 32b, respectively, of the electrode pad 32. The anode electrode 31a and the cathode electrode 31b may be electrically connected to the anode electrode pad 32a and the cathode electrode pad 32b, respectively, via a conductive bonding material such as an anisotropic conductive film (ACF) or solder.

[0029] Each pixel section 3p may be configured to include a plurality of light-emitting elements 31, a plurality of anode electrode pads 32a, and a single or a plurality of cathode electrode pads 32b. A plurality of anode electrodes 31a of the plurality of light-emitting elements 31 are electrically connected to the plurality of anode electrode pads 32a. When a plurality of cathode electrode pads 32b are present in each pixel section 3p, a plurality of cathode electrodes 31b of the plurality of light-emitting elements 31 may be connected to the plurality of cathode electrode pads 32b. When a single cathode electrode pad 32b is present in each pixel section 3p, a plurality of cathode electrodes 31b of the plurality of light-emitting elements 31 may be commonly connected to the single cathode electrode pad 32b. Each pixel section 3p may include a plurality of light-emitting elements 31, which may include a red light-emitting element that emits red light, a green light-emitting element that emits green light, and a blue light-emitting element that emits blue light. This allows each pixel section 3p to display full-color gradations. Each pixel unit 3p may have a light-emitting element that emits orange light, red-orange light, red-purple light, or purple light instead of the red light-emitting element, and each pixel unit 3p may have a light-emitting element that emits yellow-green light instead of the green light-emitting element.

[0030] The first wiring pads 4 are disposed on the second surface 2b side. The first wiring pads 4 may be located on the periphery of the second surface 2b in a plan view. The width of the periphery may be about 30 μm to 150 μm. In this embodiment, the first wiring pads 4 are disposed in a portion close to the first side 2ba and a portion close to the second side 2bb in a plan view, as shown in FIG. 2, for example.

[0031] The first wiring pad 4 is electrically connected to the display unit 3. In this embodiment, the first wiring pad 4 is electrically connected to the display unit 3 via a second wiring pad 8, a side wiring 9, and a second connection wiring 10, which will be described later. The first wiring pad 4 may be electrically connected to a TFT included in the pixel unit 3p, or may be electrically connected to the anode electrode pad 32a or the cathode electrode pad 32b.

[0032] The first wiring pad 4 includes a conductive material. The first wiring pad 4 may be made of a single metal layer or may be made of a laminate of multiple metal layers. The first wiring pad 4 may be made of, for example, Al, Al / Ti, Ti / Al / Ti, Mo, Mo / Al / Mo, MoNd / AlNd / MoNd, Cu, Cr, Ni, Ag, or the like. FIG. 3 shows an example in which the first wiring pad 4 is made of a single metal layer and formed on the second surface 2b. The first wiring pad 4 may be partially covered with an insulating layer (also called an overcoat layer) 6b made of a polymer material such as SiO2, Si3N4, or acrylic resin.

[0033] The plurality of external connection terminals 5 are disposed on the second surface 2b side. The external connection terminals 5 may be electrode pads for supplying a light emission control signal Sig to the pixel section 3p, may be electrode pads for supplying a power supply voltage to the pixel section 3p, or may be electrode pads for other drive signals. The light emission control signal Sig is a signal for controlling the light emission luminance of the pixel section 3p. The power supply voltage may be a first power supply voltage Vdd supplied to the anode electrode 31a of the light emitting element 31, or may be a second power supply voltage Vss lower than the first power supply voltage Vdd supplied to the cathode electrode 31b of the light emitting element 31. The potential of the second power supply voltage Vss may be a ground potential. A circuit board that outputs the light emission control signal Sig or the first power supply voltage Vdd and the second power supply voltage Vss supplied to the pixel section 3p can be connected to the external connection terminals 5. The circuit board may be a flexible printed circuit (Flexible Printed Circuits: FPC) having a drive element such as an IC (Integrated Circuit) that controls the drive of the pixel section 3p, circuit wiring, etc.

[0034] The external connection terminals 5 include a conductive material. The material and layer structure of the external connection terminals 5 may be the same as those of the first wiring pads 4.

[0035] The first connection wiring 6 is disposed on the second surface 2b side. The first connection wiring 6 electrically connects the first wiring pads 4 and the external connection terminals 5. The first connection wiring 6 has a plurality of wiring conductors 61, and each wiring conductor 61 electrically connects one first wiring pad 4 and one external connection terminal 5. Each wiring conductor 61 may be formed in a straight line connecting one first wiring pad 4 and one external connection terminal 5 in a plan view, or may be formed with at least one bent portion. In addition, when the first connection wiring 6 is a wiring for supplying a power supply voltage to the pixel unit 3p, one wiring conductor 61 may be configured to electrically connect the first wiring pads 4 and one external connection terminal 5.

[0036] In this embodiment, as shown in FIG. 2, the first wiring pads 4 and the external connection terminals 5 are disposed in a portion closer to the first side 2ba and a portion closer to the second side 2bb in a plan view. In this case, the wiring length of the wiring conductor 61 connecting the first wiring pads 4 and the external connection terminals 5 can be shortened. As a result, the delay and waveform dullness of the light emission control signal Sig, or the potential fluctuation of the first power supply voltage Vdd and the second power supply voltage Vss, caused by the electrical resistance of the wiring conductor 61, the parasitic capacitance between the wiring conductor 61 and other wiring conductors of the display device 1, can be reduced. As a result, the display quality of the display device 1 can be improved.

[0037] As shown in FIG. 3, the first connection wiring 6 includes a conductive layer 6a made of a conductive material. The material and layer structure of the conductive layer 6a may be the same as those of the first wiring pad 4. The first connection wiring 6 may further include an insulating layer (also called an overcoat layer) 6b made of an insulating material, and for example, the insulating layer 6b may cover the conductive layer 6a. The insulating layer 6b may be made of, for example, SiO2, Si3N4, a polymer material such as an acrylic resin, or the like. The insulating layer 6b may at least partially cover the surface of the conductive layer 6a other than the surface facing the substrate 2, in which case the risk of short-circuiting between the wiring conductors 61 can be reduced.

[0038] The dummy conductor portion 7 is disposed on the second surface 2b side. The dummy conductor portion 7 is disposed so as not to overlap any of the first wiring pad 4, the external connection terminal 5, and the connection wiring 6 in a plan view. In other words, the dummy conductor portion 7 is disposed in the second area A2 in which the first wiring pad 4, the external connection terminal 5, and the connection wiring 6 are not disposed in a plan view. The dummy conductor portion 7 may be electrically insulated from the connection wiring 6. In addition, when the connection wiring 6 includes a ground wiring conductor 61 to which a ground potential is applied, the dummy conductor portion 7 may be electrically connected to the ground wiring conductor 61. This makes it possible to stabilize the ground potential by the wide-area dummy conductor portion 7, and as a result, it is possible to improve the display quality of the display device 1. The dummy conductor portion 7 may be electrically floating. For the same purpose, the dummy conductor portion 7 may be electrically connected to the ground external connection terminal 5 or the electrically floating external connection terminal 5.

[0039] The dummy conductor 7 may include a conductor layer 7a made of a conductive material and an insulating layer (also called an overcoat layer) 7b covering the conductor layer 7a. The material and layer structure of the conductor layer 7a may be the same as those of the conductive layer 6a of the first connection wiring 6. The insulating layer 7b may be made of a polymer material such as SiO2, Si3N4, or acrylic resin. The insulating layer 7b may at least partially cover the surfaces of the conductor layer 7a other than the surface facing the substrate 2. In this case, the dummy conductor 7 functions as a protective layer and can reduce the risk of short-circuiting with the first wiring pad 4, the external connection terminal 5, the first connection wiring 6, and the like.

[0040] The display device 1 may be housed in a housing (not shown) having a heat dissipation structure such as a cooling fan, heat dissipation fins, etc. In this case, the dummy conductors 7 may face or be in contact with the heat dissipation structure. This allows the heat generated by the light emitting elements 31 to be effectively dissipated to the outside, thereby improving the display quality of the display device 1.

[0041] The display device 1 further includes a plurality of second wiring pads 8, a plurality of side wirings 9, and second connection wirings .

[0042] The display device 1 having the side wiring 9 is suitable for forming a composite display device (multi-display). That is, since the display device 1 can be made to have a narrow frame, the joints between the display devices 1 in the composite display device are less noticeable. When a composite display device is fabricated by tiling a plurality of display devices 1, the front side and the back side of each display device 1 are electrically connected by the side wiring 9 made of Ag or the like. The composite display device is constructed by joining (tiling) the sides of one display device 1 and another display device 1 adjacent thereto. This configuration ensures the continuity of the display image at the joint, and prevents the viewer from feeling uncomfortable about the display image and the joint from being easily visible. The joint member for joining the sides of the plurality of display devices 1 may be a resin adhesive, a resin adhesive with a color that has a light-shielding property such as black, or the like. The joint member may also be a mechanical joint member such as a screw. Also, a fitting method may be used in which a convex portion formed at the end of one substrate 2 is fitted into a concave portion formed at the end of the other substrate 2 and having a shape complementary to the convex portion. A plurality of display devices 1 may be installed on a base substrate. Each display device 1 may be fixed to the base substrate via a resin adhesive, or each display device 1 may be fitted into a frame, and the frame may be fixed to the base substrate by a resin adhesive or screws.

[0043] The second wiring pads 8 are located on the first surface 2a side, as shown in FIG. 1 for example. At least a portion of the second wiring pads 8 may overlap with the first wiring pads 4 in a plan view. This configuration may be applied to all of the second wiring pads 8. The second wiring pads 8 are electrically connected to the pixel unit 3p of the display unit 3 via second connection wirings 10, as shown in FIG. 1 for example.

[0044] The second wiring pad 8 is made of a conductive material. The material and layer structure of the second wiring pad 8 may be the same as those of the first wiring pad 4. Fig. 3 shows an example in which the second wiring pad 8 is made of laminated metal layers 82, 88 and is disposed on insulating layers 83, 84 formed on the first surface 2a. The back surface of the second wiring pad 8 is connected to a connection wiring 81 that is electrically connected to the TFT, the light emitting element 31, etc.

[0045] When the second wiring pad 8 is formed by laminating a plurality of metal layers 82, 88, an insulating layer 87 may be disposed in a portion between the metal layers 82, 88, as shown in FIG. 3, for example. Also, insulating layers 85, 86 may be disposed at the end of the second wiring pad 8 on the inner side (the right side in FIG. 3). This can prevent the second wiring pad 8 from shorting with the wiring conductors disposed on the inner side. The insulating layers 83, 84, 85, 86, 87 are made of polymer materials such as SiO2, Si3N4, acrylic resin, etc. The metal layer 88 on the surface side of the second wiring pad 8 may be a transparent conductive layer made of ITO, IZO, etc.

[0046] The second connection wiring 10 is located on the first surface 2a side. The second connection wiring 10 may be made of, for example, Mo / Al / Mo, MoNd / AlNd / MoNd, etc. The second connection wiring 10 may be a scanning signal line, an image signal line, a light emission control signal line, etc., which connects the thin film transistor included in the pixel portion 3p and the second wiring pad 8. The second connection wiring 10 may be a power supply wiring which connects the anode electrode pad 32a or the cathode electrode pad 32b and the second wiring pad 8. The anode electrode pad 32a or the cathode electrode pad 32b connected to the second connection wiring 10 may be formed as a part of the second connection wiring 10. The second connection wiring 10 may be a linear or strip-shaped conductor pattern, or may be a planar conductor pattern. When the second connection wiring 10 is a power supply wiring for Vss and connects the cathode electrode pad 32b and the second wiring pad 8, the second connection wiring 10 may be a planar conductor pattern.

[0047] The side wirings 9 are located from the first surface 2a, through the side surface 2c, to the second surface 2b. The side wirings 9 connect the second wiring pads 8 and the first wiring pads 4.

[0048] The side wiring 9 can be formed by applying a conductive paste containing conductive particles such as Ag, Cu, Al, stainless steel, etc., a resin component such as uncured epoxy resin, an alcohol solvent such as ethyl alcohol, water, etc., to desired locations on the side 2c, the first surface 2a, and the second surface 2b, and then by a method such as a heating method, a photocuring method in which the paste is cured by irradiation with light such as ultraviolet light, a photocuring heating method, etc. The side wiring 9 can also be formed by a thin film formation method such as plating, vapor deposition, and CVD. A groove may be formed in advance in the location on the side 2c where the side wiring 9 is to be formed. This makes it easier to place the conductive paste that becomes the side wiring 9 in the desired location on the side 2c.

[0049] When the first wiring pads 4 are located on the periphery of the second surface 2b and the second wiring pads 8 are located on the periphery of the first surface 2a, the first wiring pads 4 may at least partially overlap the second wiring pads 8 in a plan view. This configuration may be applied to all of the first wiring pads 4. In this case, the wiring length of the side wiring 9 connecting the first wiring pads 4 and the second wiring pads 8 can be shortened to reduce resistance. In addition, it is possible to prevent the side wiring 9 from coming into contact with other wiring pads, wiring conductors, etc. of the display device 1 and causing a short circuit.

[0050] The size (area) of the first wiring pad 4 located on the second surface 2b side may be larger than the size (area) of the second wiring pad 8 located on the first surface 2a side. The second wiring pad 8 is difficult to enlarge because it is located in the frame portion around the display unit 3, which is desired to be as narrow as possible. In particular, when the pixel pitch is narrow, it is difficult to enlarge the second wiring pad 8. On the other hand, the first wiring pad 4 is located on the second surface 2b side, where there is basically no restriction on size. Therefore, by making the size of the first wiring pad 4 larger than the size of the second wiring pad 8, the contact resistance between the side wiring 9 and the first wiring pad 4 can be reduced, and the conductivity of the signal transmitted through the side wiring 9 can be improved. The size of the first wiring pad 4 may be more than one time and about two times the size of the second wiring pad 8, but is not limited to this range.

[0051] The first wiring pad 4 and the second wiring pad 8 can be connected using a penetrating conductor such as a through hole that penetrates the substrate 2 from the first surface 2a to the second surface 2b. When the first wiring pad 4 and the second wiring pad 8 are connected using a penetrating conductor, for example, it is necessary to secure an area in which the penetrating conductor can be formed on the periphery of the substrate 2, making it difficult to reduce the area of ​​the frame region (also called the non-display region) of the display device 1. By connecting the first wiring pad 4 and the second wiring pad 8 using the side wiring 9, it becomes easy to realize a display device 1 with a reduced area of ​​the frame region.

[0052] In the display device 1 of this embodiment, the dummy conductors 7 are arranged so as not to overlap the first connection wirings 6 in a plan view, and therefore the flatness of the back surface side of the substrate 2 is improved. In addition, in the mounting step of the light emitting elements 31 in the manufacturing method of the display device 1, both the first connection wirings 6 and the dummy conductors 7 can be brought into contact with the flat stage surface of a mounting device. As a result, bending, deformation, etc. of the substrate 2 when pressing the multiple light emitting elements 31 against the substrate 2 can be suppressed, and mounting defects of the light emitting elements 31 can be reduced. In turn, the display quality of the display device 1 can be improved, and the manufacturing yield of the display device 1 can be improved.

[0053] The first connection wiring 6 and the dummy conductor 7 may have the same height (thickness) from the second surface 2b. In this case, in the mounting process, both the first connection wiring 6 and the dummy conductor 7 can be brought into good contact with the flat stage surface of the mounting device. As a result, it is possible to further suppress bending, deformation, etc. of the substrate 2 when pressing the plurality of light-emitting elements 31 against the substrate 2, and further reduce mounting defects of the light-emitting elements 31. In addition, it is possible to improve the display quality of the display device 1 and to improve the manufacturing yield of the display device 1. Note that the height of the first connection wiring 6 from the second surface 2b refers to the height from the second surface 2b of the surface of the first connection wiring 6 opposite to the surface facing the substrate 2. The height of the dummy conductor 7 from the second surface 2b is defined in the same manner.

[0054] The thickness of each of the first connection wiring 6 and the dummy conductors 7 may be about 3 to 10 μm, but is not limited to this range. When there is an insulating layer (also called an overcoat layer) 6b covering the conductive layer 6a of the first connection wiring 6, the thickness of the insulating layer 6b may be about 5 μm to 15 μm, but is not limited to this range.

[0055] The thickness of the first wiring pad 4 and the thickness of the dummy conductor 7 may be the same. In this case, bending, deformation, etc. of the substrate 2 when the plurality of light-emitting elements 31 are pressed against the substrate 2 can be further suppressed, and mounting defects of the light-emitting elements 31 can be further reduced. Furthermore, on the second surface 2b, the distances of the plurality of first wiring pads 4 located along the first side 2ba from the first side 2ba, the distances of the plurality of first wiring pads 4 located along the second side 2bb from the second side 2bb, the distances of the dummy conductors 7 from the third side 2bc, and the distances of the dummy conductors 7 from the fourth side 2bd may be substantially the same. In this case, the film-like portions on the second surface 2b are more likely to be distributed uniformly. As a result, bending, deformation, etc. of the substrate 2 when the plurality of light-emitting elements 31 are pressed against the substrate 2 can be further suppressed, and mounting defects of the light-emitting elements 31 can be further reduced. Note that the distances being substantially the same means, for example, that the difference from the reference distance is about ±10% or less.

[0056] The first connection wiring 6 and the dummy conductor 7 may be higher from the second surface 2b than the first wiring pads 4 and the external connection terminals 5. In this case, by simply placing the substrate 2 on which the first wiring pads 4, the external connection terminals 5, the first connection wiring 6, and the dummy conductor 7 are arranged on the second surface 2b, on a flat stage surface of a mounting device, both the first connection wiring 6 and the dummy conductor 7 can be brought into good contact with the stage surface of the mounting device. As a result, it is possible to further suppress bending and deformation of the substrate 2 when pressing the light-emitting elements 31 against the substrate 2, and to further reduce mounting defects of the light-emitting elements 31. In addition, it is possible to improve the display quality of the display device 1 and to improve the manufacturing yield of the display device 1. The height of the first wiring pads 4 from the second surface 2b refers to the height of the surface of the first wiring pads 4 opposite to the surface facing the substrate 2 from the second surface 2b. The height of the external connection terminals 5 from the second surface 2b is defined in the same manner. In the above configuration, there is an insulating layer 6b on the surface of the first connection wiring 6, and since the multiple first wiring pads 4 and the multiple external connection terminals 5 are electrical connection parts, they may be configured so that they do not have the insulating layer 6b on their surface.

[0057] The dummy conductor 7 may include a solid portion 71, as shown in FIG. 2, for example. The solid portion 71 may have a polygonal, circular, elliptical, oval, or other shape in a plan view. Here, the "polygonal" may be a triangular, rectangular (square or rectangular), pentagonal, hexagonal, octagonal, or other shape. When the dummy conductor 7 includes the solid portion 71, the ratio of the planar area of ​​the dummy conductor 7 to the planar area of ​​the second surface 2b can be easily increased. This makes it possible to increase the ratio of the support area of ​​the stage surface on the second surface 2b when pressing the plurality of light-emitting elements 31 against the substrate 2 in the mounting process, and as a result, it is possible to effectively suppress bending, deformation, and the like of the substrate 2 and effectively reduce mounting defects of the light-emitting elements 31. This in turn makes it possible to improve the display quality of the display device 1 and to improve the manufacturing yield of the display device 1.

[0058] 2, the solid portion 71 may be disposed on the second surface 2b near a corner 2d between the third side 2bc and the fourth side 2bd. In this case, the first connection wiring 6 and the dummy conductors 7 are disposed in a wide range on the second surface 2b, so that when the light-emitting elements 31 are pressed against the substrate 2 in the mounting process, the bias of the support points due to the stage surface on the second surface 2b can be reduced. As a result, the bending, deformation, etc. of the substrate 2 can be effectively suppressed, and mounting defects of the light-emitting elements 31 can be effectively reduced. As a result, the display quality of the display device 1 can be improved, and the manufacturing yield of the display device 1 can be improved.

[0059] The solid portion 71 may have a triangular shape, for example, as shown in Fig. 4. In this case, the dummy conductors 7 can be arranged so as to include a portion along most of the third side 2bc and a portion along most of the fourth side 2bd on the second surface 2b, and the ratio of the planar area of ​​the dummy conductors 7 to the planar area of ​​the second surface 2b can be increased. As a result, bending, deformation, etc. of the substrate 2 when the plurality of light-emitting elements 31 are pressed against the substrate 2 in the mounting process can be effectively suppressed, and mounting defects of the light-emitting elements 31 can be effectively reduced. As a result, the display quality of the display device 1 can be improved, and the manufacturing yield of the display device 1 can be improved.

[0060] 5, the dummy conductor 7 may have a plurality of small island-shaped portions (also called small piece-shaped portions) 74 dispersed in the second region A2. Each island-shaped portion 74 may have a shape such as a polygonal shape, a circular shape, an elliptical shape, or an oval shape in a plan view. The island-shaped portions 74 may have the same shape as each other, or the shape of at least one island-shaped portion 74 may be different from the shapes of the remaining island-shaped portions 74.

[0061] In addition, the island-shaped portions 74 may be configured such that the size of the island-shaped portions (also called side island-shaped portions) 74p in the portion along the third side 2bc and the fourth side 2bd, which is the portion facing the first region A1 on the second surface 2b, is larger than the size of the remaining island-shaped portions 74. In this case, the total area of ​​the first wiring pads 4, the external connection terminals 5, and the first connection wirings 6 densely present in the first region A1 can be made closer to the area of ​​the side island-shaped portion 74p. As a result, the rigidity of the first region A1 in the substrate 2 can be made closer to the rigidity of the portion where the side island-shaped portion 74p is located, and deformation such as bending can be suppressed from occurring in the substrate 2 in a natural state. In addition, bending, deformation, etc. of the substrate 2 when the light-emitting elements 31 are pressed against the substrate 2 in the mounting process can be effectively suppressed, and mounting defects of the light-emitting elements 31 can be effectively reduced. The size of the side island portion 74p may be more than one time and not more than about two times the size of the remaining island portion 74, but is not limited to this range.

[0062] When the solid portion 71 covering more than half of the area of ​​the second surface 2b is formed by a printing method such as screen printing, the thickness of the solid portion 71 may be easily varied. When the dummy conductor portion 7 has a plurality of solid portions 71, the dummy conductor portion 7 can be arranged over a wide range of the second surface 2b while reducing the variation in the thickness of the dummy conductor portion 7. As a result, it is possible to effectively suppress the bending and deformation of the substrate 2 when the plurality of light-emitting elements 31 are pressed against the substrate 2 in the mounting process, and effectively reduce mounting defects of the light-emitting elements 31. As a result, it is possible to improve the display quality of the display device 1 and improve the manufacturing yield of the display device 1.

[0063] The solid portions 71 such as the island portions 74 may be arranged so that each solid portion 71 overlaps at least one light emitting element 31 in plan view. In this case, when the light emitting element 31 is pressed against the substrate 2 in the mounting process, the solid portion 71 functions as a support portion for the light emitting element 31, and the pressing force is easily applied to the light emitting element 31. As a result, the bending, deformation, etc. of the substrate 2 due to the pressing force can be effectively suppressed, and mounting defects of the light emitting element 31 can be effectively reduced. In addition, the display quality of the display device 1 can be improved, and the manufacturing yield of the display device 1 can be improved. A solid portion 71 such as one island portion 74 may overlap one light emitting element 31 in plan view. When there are multiple light emitting elements 31, each of the multiple light emitting elements 31 may be configured to overlap one solid portion 71 in plan view. In this configuration, the pressing force is easily applied to each light emitting element 31. Also, in a plan view, the area of ​​the solid portion 71 may be larger than the area of ​​the light-emitting element 31, and the solid portion 71 may enclose the light-emitting element 31. In this configuration, the solid portion 71 effectively functions as a support for the light-emitting element 31, and the pressing force is more easily applied to the light-emitting element 31. The area of ​​the solid portion 71 may be more than 1 time and up to about 5 times the area of ​​the light-emitting element 31, but is not limited to this range.

[0064] The dummy conductors 7 may include a stripe-shaped portion 72 as shown in FIG. 6. The stripe-shaped portion 72 is made of a plurality of strip-shaped conductors 72a extending parallel to each other. The plurality of strip-shaped conductors 72a may extend along the longitudinal direction of the substrate 2 (the left-right direction in FIG. 6) as shown in FIG. 6, or may extend along a direction intersecting the longitudinal direction of the substrate 2 (the short-side direction of the substrate 2, the up-down direction in FIG. 6). When the dummy conductors 7 have the stripe-shaped portion 72, the dummy conductors 7 can be disposed over a wide range of the second surface 2b while reducing the variation in thickness of the dummy conductors 7. As a result, it is possible to effectively suppress bending, deformation, etc. of the substrate 2 when the plurality of light-emitting elements 31 are pressed against the substrate 2 in the mounting process, and effectively reduce mounting defects of the light-emitting elements 31. This in turn improves the display quality of the display device 1 and improves the manufacturing yield of the display device 1.

[0065] The pitch P2 between the adjacent strip conductors 72a may be approximately equal to the pixel pitch P1 of the display unit 3. The interval g3 between the strip conductors 72a may be uniform (constant). In this case, the stripe-shaped portions 72 can be arranged such that each strip conductor 72a overlaps at least one light emitting element 31 in a plan view. In this case, when the light emitting element 31 is pressed against the substrate 2 in the mounting process, the stripe-shaped portions 72 function as a support portion for the light emitting element 31, and the pressing force is easily applied to the light emitting element 31. As a result, the bending, deformation, etc. of the substrate 2 due to the pressing force can be effectively suppressed, and mounting defects of the light emitting element 31 can be effectively reduced. In addition, the display quality of the display device 1 can be improved, and the manufacturing yield of the display device 1 can be improved.

[0066] The dummy conductors 7 may include a lattice portion 73 as shown in FIG. 7. When the dummy conductors 7 have the lattice portion 73, the dummy conductors 7 can be arranged over a wide range of the second surface 2b while reducing the variation in thickness of the dummy conductors 7. As a result, bending, deformation, etc. of the substrate 2 when pressing the light-emitting elements 31 against the substrate 2 in the mounting process can be effectively suppressed, and mounting defects of the light-emitting elements 31 can be effectively reduced. As a result, the display quality of the display device 1 can be improved, and the manufacturing yield of the display device 1 can be improved.

[0067] The lattice pitch P3 of the lattice portion 73 may be approximately equal to the pixel pitch P1 of the display unit 3. In this case, the lattice portion 73 can be disposed so that each lattice point overlaps one light-emitting element 31 in a plan view. In this case, when the light-emitting element 31 is pressed against the substrate 2 in the mounting process, the lattice portion 73 functions as a support portion for the light-emitting element 31, and the pressing force is easily applied to the light-emitting element 31. As a result, it is possible to effectively suppress bending, deformation, etc. of the substrate 2 due to the pressing force, and effectively reduce mounting defects of the light-emitting element 31. In turn, it is possible to improve the display quality of the display device 1 and improve the manufacturing yield of the display device 1.

[0068] As shown in FIG. 11, the dummy conductor 7 may include a concentric ring portion 75. In this configuration, the area of ​​the dummy conductor 7 can be made smaller than when the dummy conductor 7 includes a solid portion 71 (shown in FIG. 2). As in the case where the dummy conductor 7 is the solid portion 71, the bending, deformation, etc. of the substrate 2 when the light emitting elements 31 are pressed against the substrate 2 in the mounting process of the light emitting elements 31 can be effectively suppressed, and mounting defects of the light emitting elements 31 can be effectively reduced. The outer shape of the outermost ring portion of the concentric ring portion 75 may be similar to the second surface 2b of the substrate 2. In this case, the pressing force when the light emitting elements 31 are pressed against the substrate 2 in the mounting process of the light emitting elements 31 can be easily uniformly distributed.

[0069] In the display device 1, the area of ​​the dummy conductors 7 (area in plan view) may be 20% or more and 60% or less of the area of ​​the second surface 2b (area in plan view). If the area of ​​the dummy conductors 7 is less than 20% of the area of ​​the second surface 2b, there is a risk that bending, deformation, etc. of the substrate 2 cannot be sufficiently suppressed. If the area of ​​the dummy conductors 7 is more than 60% of the area of ​​the second surface 2b, there is a risk that the thickness of the dummy conductors 7 may easily vary, or the interval between the first connection wiring 6 and the dummy conductors 7 may become narrow, making it easier for the first connection wiring 6 and the dummy conductors 7 to be short-circuited. By setting the area of ​​the dummy conductors 7 in plan view to 20% or more and 60% or less of the area of ​​the second surface 2b, it is possible to suppress bending, deformation, etc. of the substrate 2 while suppressing the variation in the thickness of the dummy conductors 7 and the short-circuit between the first connection wiring 6 and the dummy conductors 7.

[0070] 8, the dummy conductors 7 may be disposed between adjacent wiring conductors 61. In this case, the first connection wirings 6 and the dummy conductors 7 can be distributed substantially uniformly in the portion on the second surface 2b where they are disposed, so that bending, deformation, etc. of the substrate 2 when the light-emitting elements 31 are pressed against the substrate 2 in the mounting process can be effectively suppressed, and mounting defects of the light-emitting elements 31 can be effectively reduced. As a result, the display quality of the display device 1 can be improved, and the manufacturing yield of the display device 1 can be improved.

[0071] As shown in FIG. 12, the second surface 2b of the substrate 2 may be a polygon such as a rectangle, and the dummy conductor 7 may include portions (also referred to as corner dummy conductors) 76a, 76b, and 76c located at the corners of the second surface 2b. In this configuration, bending, deformation, and the like of the substrate 2 when the light-emitting elements 31 are pressed against the substrate 2 in the mounting process of the light-emitting elements 31 can be more effectively suppressed, and mounting defects of the light-emitting elements 31 can be more effectively reduced. The corner dummy conductors 76a, 76b, and 76c may be located at at least one corner of the second surface 2b, or may be located at all corners. When there are a plurality of corner dummy conductors 76a, 76b, and 76c, they may have the same shape and the same area. In this case, the pressing force when the light-emitting elements 31 are pressed against the substrate 2 in the mounting process of the light-emitting elements 31 is more likely to be applied uniformly to the entire second surface 2b. The corner dummy conductors 76a, 76b, 76c may be in a shape such as a circle, an ellipse, a triangle, a rectangle, a polygon such as a pentagon, an L-shape, etc. The corner dummy conductors 76a, 76b, 76c may be in a shape similar to that of the second surface 2b. In this case, the pressing force when pressing the multiple light-emitting elements 31 against the substrate 2 in the mounting process of the multiple light-emitting elements 31 is easily applied uniformly to the entire second surface 2b.

[0072] 13, the dummy conductor 7 may include a portion (also referred to as an edge dummy conductor) 77 located on the edge of the second surface 2b. In this configuration, bending, deformation, etc. of the substrate 2 when the light-emitting elements 31 are pressed against the substrate 2 in the mounting process of the light-emitting elements 31 can be more effectively suppressed, and mounting defects of the light-emitting elements 31 can be more effectively reduced.

[0073] In the display device 1, the shapes, dimensions, etc. of the members may be within the following numerical values ​​and ranges, but are not limited to these numerical values ​​and ranges. For example, the substrate 2 may be a square with a side length of about 10 mm to 1000 mm. The pressing plate pressing the substrate 2 may be a square with a side length equal to or greater than that of the substrate 2. The pressure of the pressing plate may be about 10 MPa to 100 MPa. The temperature during the thermal bonding of the anisotropic conductive film may be a general value of about 150° C. to 200° C. If the dummy conductors 7 are striped, they may have a width of about 1 mm to 10 mm and an interval of about 1 mm to 20 mm. EXAMPLES

[0074] First, a plurality of display device precursors were fabricated, each having the same configuration as the display device 1 shown in FIG. 9, except that the light-emitting element 31 was not mounted. In the display device 1 shown in FIG. 9, the substrate 2 is a square with a side length of 60 mm, and the dummy conductor portion 7 is composed of a plurality of vertically elongated stripe-shaped portions 72. The stripe-shaped portions 72 are uniformly distributed in the second region A2. The stripe conductors 72a are 5 mm wide, and the interval g3 between adjacent stripe conductors 72a is uniform. The dummy conductor portion 7 occupies about 70% of the area of ​​the second region A2. The interval g3 between adjacent stripe conductors 72a is different for each of the plurality of display device precursors, and the interval g3 was changed in the range of 3.5 mm to 16 mm. The pressing plate pressing the substrate 2 is a square with a side length of 100 mm, and the pressing force is about 70 MPa.

[0075] The display device precursor was placed on a stage surface such that the second surface 2b of the substrate 2 faced the stage surface of the mounting device. Next, a plurality of light-emitting elements (micro LED elements) 31 were placed on the electrode pads 32 via an anisotropic conductive film. Thereafter, while the anisotropic conductive film was heated, the plurality of light-emitting elements 31 were pressed against the substrate 2 by a pressing plate, and the plurality of light-emitting elements 31 were mounted on the display device precursor, thereby producing the display device 1.

[0076] A predetermined light emission control signal Sig, a first power supply voltage Vdd, and a second power supply voltage Vss were supplied to a plurality of external connection terminals 5, and the luminance value of the light emitted from the plurality of light emitting elements 31 was detected to measure the number of light emitting elements 31 in which mounting defects occurred. FIG. 10 is a graph showing the results of measuring the ratio (also called defect rate) of light emitting elements 31 in which mounting defects occurred among the total number of light emitting elements 31. In this embodiment, the total number of light emitting elements 31 was set to 1000. In this embodiment, the step between the portion where the dummy conductor portion 7 is provided and the portion where the dummy conductor portion 7 is not provided was set to 4 to 12 μm. The horizontal axis of FIG. 10 indicates the interval g3 between the adjacent dummy conductor portions 7, and the vertical axis of FIG. 10 indicates the defect rate. In FIG. 10, the black circles indicate the measured defect rate, and the solid line is a line approximating the measured defect rate.

[0077] 10, when the distance between adjacent dummy conductors 7 was about 6.5 mm or less, the defect rate was 0.1% or less. As a comparative example, a display device similar to the display device 1 of the embodiment except that it did not have dummy conductors 7 was fabricated, and the defect rate was measured. In some cases, the defect rate exceeded 50%.

[0078] According to the display device of the present disclosure, the flatness of the second surface side of the substrate can be improved. In addition, the rigidity of the substrate can be improved to suppress the occurrence of changes in the substrate, such as bending of the substrate. As a result, when pressing a plurality of light-emitting elements against the substrate in the mounting process, it becomes easy to uniformly press the plurality of light-emitting elements with a predetermined pressure. Therefore, it is possible to reduce mounting defects of the light-emitting elements, improve the display quality of the display device, and improve the manufacturing yield of the display device.

[0079] The present disclosure can be implemented in the following aspects (1) to (16).

[0080] (1) a substrate having a first surface and a second surface opposite the first surface; A light emitting element located on the first surface side; a first wiring pad located on the second surface side and electrically connected to the light emitting element; An external connection terminal located on the second surface side; a connection wiring located on the second surface side and electrically connecting the first wiring pad and the external connection terminal; a convex portion located on the second surface side and not overlapping any of the first wiring pad, the external connection terminal, and the connection wiring in a plan view;

[0081] (2) the substrate has, on the second surface side, a first region in which the first wiring pads, the external connection terminals, and the connection wirings are located, and a second region other than the first region, The wiring board according to (1) above, wherein the convex portion is located in the second region and occupies an area of ​​at least half of an area of ​​the second region.

[0082] (3) The wiring board according to (2) above, wherein the plurality of convex portions are uniformly distributed in the second region.

[0083] (4) The wiring board according to (3) above, wherein the distance between adjacent ones of the plurality of convex portions and the distance between the connection wiring and the convex portion closest thereto are equal to or less than a predetermined value.

[0084] (5) The wiring board according to any one of (1) to (4) above, wherein at least a surface layer of the convex portion is made of a material having a lower hardness than any of the first wiring pad, the external connection terminal, and the connection wiring.

[0085] (6) The display device according to (5) above, wherein at least the surface layer of the convex portion is made of a resin material.

[0086] (7) The wiring board according to (6) above, wherein the resin material has elasticity.

[0087] (8) The wiring board according to any one of (1) to (7) above, wherein the convex portion includes at least one of an island portion, a solid portion, a stripe portion, and a lattice portion.

[0088] (9) The wiring board according to any one of (1) to (7) above, wherein the convex portion includes a concentric annular portion.

[0089] (10) The second surface of the substrate is polygonal, The wiring board according to any one of (1) to (7) above, wherein the convex portion includes a portion located at a corner of the second surface.

[0090] (11) The wiring board according to any one of (1) to (10) above, wherein the convex portion has an area that is 20% to 60% of the area of ​​the second surface.

[0091] (12) The wiring board according to any one of (1) to (11) above, wherein the connection wiring and the convex portion are higher from the second surface than the first wiring pad and the external connection terminal.

[0092] (13) The wiring board according to (12), wherein the connection wiring and the convex portion are at the same height from the second surface.

[0093] (14) A display device including the wiring board according to any one of the above configurations (1) to (13), The light emitting device is provided in each of a plurality of pixel units arranged in a matrix, The display device, wherein the convex portion overlaps at least one of the plurality of light-emitting elements in a plan view.

[0094] (15) The display device according to (14), wherein the light-emitting element includes a micro light-emitting diode element.

[0095] (16) A display device including the wiring board according to any one of the above configurations (1) to (13), a second wiring pad located on the first surface side and electrically connected to the light emitting element; A display device comprising: a side wiring that is located from the first surface side, through a third surface that connects the first surface and the second surface, to the second surface side, and connects the first wiring pad and the second wiring pad.

[0096] Although each embodiment of the present disclosure has been described in detail above, the present disclosure is not limited to the above-described embodiments, and various modifications and improvements are possible within the scope of the gist of the present disclosure. It goes without saying that all or part of the components of each of the above-described embodiments can be appropriately combined within the scope of not being inconsistent. [Industrial Applicability]

[0097] The display device of the present disclosure can be applied to various electronic devices, such as automobile route guidance systems (car navigation systems), ship route guidance systems, aircraft route guidance systems, instrument indicators for vehicles such as automobiles, instrument panels, smartphone terminals, mobile phones, tablet terminals, personal digital assistants (PDAs), video cameras, digital still cameras, electronic organizers, electronic books, electronic dictionaries, personal computers, copiers, game console terminals, televisions, product display tags, price display tags, industrial programmable display devices, car audio, digital audio players, facsimiles, printers, automated teller machines (ATMs), vending machines, medical display devices, digital display wristwatches, smart watches, guidance display devices installed in stations and airports, and advertising signage (digital signage). [Explanation of symbols]

[0098] 1 Display device 2. Board 2a 1st page 2b 2nd side 2ba First Side 2bb Second side 2bc Third Side 2bd 4th side 2c 3rd side (side) 2d corner 3 Display section 3p pixel section 31 Light emitting element 31a Anode electrode 31b Cathode electrode 32 Electrode Pads 32a Anode pad 32b Cathode pad 32c transparent conductive layer 4 1st wiring pad 5 External connection terminal 6 Connection wiring (first connection wiring) 6a conductive layer 6b Insulating layer 61 Wiring conductor 7 Dummy conductor part (convex part) 7a conductive layer 7b Insulating layer 71 Solid part 72 Striped section 72a Strip conductor 73 Grid part 74 Island 74p Island (edge ​​island) 75 Concentric annular section 76a, 76b, 76c Corner dummy conductor 77 Edge dummy conductor 8 Second wiring pad 81 Connection wiring 82,88 Metal layer 83,85,87 Insulating layer 9 Side wiring 10 Second connection wire

Claims

1. a substrate having a first surface and a second surface opposite the first surface; A light emitting element located on the first surface side; a first wiring pad located on the second surface side and electrically connected to the light emitting element; An external connection terminal located on the second surface side; a connection wiring located on the second surface side and electrically connecting the first wiring pad and the external connection terminal; a convex portion located on the second surface side and not overlapping any of the first wiring pad, the external connection terminal, and the connection wiring in a plan view; The convex portion is a dummy conductor portion.

2. the substrate has, on the second surface side, a first region in which the first wiring pads, the external connection terminals, and the connection wirings are located, and a second region other than the first region; The wiring board according to claim 1 , wherein the convex portion is located in the second region and occupies an area equal to or greater than half of an area of ​​the second region.

3. The wiring board according to claim 2 , wherein the plurality of convex portions are uniformly distributed in the second region.

4. 4. The wiring board according to claim 3, wherein a distance between adjacent ones of the plurality of convex portions and a distance between the connection wiring and the convex portion closest thereto are equal to or less than a predetermined value.

5. 5. The wiring board according to claim 1, wherein the surface layer of the convex portion is made of a material having a lower hardness than any of the first wiring pad, the external connection terminal, and the connection wiring.

6. The wiring board according to claim 5 , wherein the surface layer of the convex portion is made of a resin material.

7. The wiring board according to claim 6 , wherein the resin material has elasticity.

8. 8. The wiring board according to claim 1, wherein the convex portion includes at least one of an island portion, a solid portion, a stripe portion, and a lattice portion.

9. The wiring board according to claim 1 , wherein the convex portion includes a concentric ring portion.

10. the second surface of the substrate is polygonal; 8. The wiring board according to claim 1, wherein the convex portion includes a portion located at a corner of the second surface.

11. 11. The wiring board according to claim 1, wherein the convex portion has an area that is 20% to 60% of an area of ​​the second surface.

12. 12. The wiring board according to claim 1, wherein the connection wiring and the convex portion are higher from the second surface than the first wiring pad and the external connection terminal.

13. The wiring board according to claim 12 , wherein the connection wiring and the convex portion are at the same height from the second surface.

14. A display device comprising the wiring board according to any one of claims 1 to 13, The light emitting device is provided in each of a plurality of pixel units arranged in a matrix, The display device, wherein the convex portion overlaps with at least one of the plurality of light-emitting elements in a plan view.

15. The display device of claim 14 , wherein the light emitting elements include micro light emitting diode elements.

16. A display device comprising the wiring board according to any one of claims 1 to 13, a second wiring pad located on the first surface side and electrically connected to the light emitting element; A display device comprising: a side wiring located from the first surface side, through a third surface connecting the first surface and the second surface, to the second surface side, and connecting the first wiring pad and the second wiring pad.

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