Display device

Abstract

To provide a display device with a larger light amount.SOLUTION: The display device includes: a plurality of light emitting elements equipped in an insulation substrate; a plurality of wires connected to the light emitting element; and a planarized film located between the light emitting elements and the insulation substrate. Each of the light emitting elements has a first electrode and a second electrode connected to the wires. The planarized film has a recessed part around the light emitting elements and a reflection unit made of a reflection material is provided in a side surface of the recessed part.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] FIELD An embodiment of the present invention relates to a display device. [Background technology]

[0002] 2. Description of the Related Art A known example of a display device is one in which one or more light emitting diodes (LEDs) are arranged for each of a plurality of pixels arranged on a substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent Application Publication No. 2020 / 0203392 Summary of the Invention [Problem to be solved by the invention]

[0004] This embodiment provides a display device with a high amount of light. [Means for solving the problem]

[0005] A display device according to an embodiment includes: an insulating substrate; a plurality of light-emitting elements mounted on the insulating substrate; and a plurality of wirings connected to the plurality of light-emitting elements; a planarization film provided between the light emitting element and the insulating substrate; Equipped with Each of the plurality of light-emitting elements a first electrode and a second electrode connected to the wiring; Equipped with the planarization film has a recess around the light-emitting element, A reflective portion made of a reflective material is provided on the side surface of the recess. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a perspective view showing an example of a schematic configuration of a display device. [Figure 2] FIG. 2 is a cross-sectional view showing an example of a schematic configuration of a pixel. [Figure 3] FIG. 3 is a cross-sectional view showing a detailed example of a light-emitting element. [Figure 4] FIG. 4 is a plan view showing an example of a schematic configuration of a pixel according to this embodiment. [Figure 5] FIG. 5 is a cross-sectional view showing an example of the configuration of a display device according to an embodiment. [Figure 6] FIG. 6 is a cross-sectional view showing an example of the configuration of a display device according to an embodiment. [Figure 7] FIG. 7 is a cross-sectional view showing an example of the configuration of a display device according to an embodiment. [Figure 8] FIG. 8 is a cross-sectional view showing an example of the configuration of a display device according to an embodiment. [Figure 9] FIG. 9 is a plan view showing an example of a schematic configuration of the display device of this configuration example. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, each embodiment of the present invention will be described with reference to the drawings. The disclosure is merely an example, and appropriate modifications that a person skilled in the art can easily conceive while maintaining the gist of the invention are naturally included within the scope of the present invention. Furthermore, in order to clarify the explanation, the drawings may show the width, thickness, shape, etc. of each part schematically compared to the actual embodiment, but these are merely examples and are not intended to limit the interpretation of the present invention. Furthermore, in this specification and each drawing, elements similar to those described above with reference to the previous drawings may be designated by the same reference numerals, and detailed descriptions may be omitted as appropriate. Hereinafter, a display device according to an embodiment will be described in detail with reference to the drawings.

[0008] In this embodiment, the first direction X, the second direction Y, and the third direction Z are perpendicular to one another, but may intersect at an angle other than 90 degrees. The direction toward the tip of the arrow of the third direction Z is defined as up or upward, and the direction opposite to the direction toward the tip of the arrow of the third direction Z is defined as down or downward. The first direction X, the second direction Y, and the third direction Z may also be referred to as the X direction, the Y direction, and the Z direction, respectively.

[0009] Furthermore, when the terms "second member above the first member" and "second member below the first member" are used, the second member may be in contact with the first member or may be located apart from the first member. In the latter case, a third member may be interposed between the first and second members. On the other hand, when the terms "second member above the first member" and "second member below the first member" are used, the second member is in contact with the first member.

[0010] Furthermore, it is assumed that an observation position for observing the display device is located at the tip of the arrow in the third direction Z, and viewing from this observation position toward the XY plane defined by the first direction X and the second direction Y is called planar view. Viewing a cross section of the display device in the XZ plane defined by the first direction X and the third direction Z, or in the YZ plane defined by the second direction Y and the third direction Z, is called cross-sectional view.

[0011] 1 is a perspective view showing an example of a schematic configuration of a display device DSP. The display device DSP includes a display panel PNL, a first circuit board PC1, and a second circuit board PC2. In one example, the display panel PNL has a rectangular shape. In the illustrated example, the short side EX of the display panel PNL is parallel to the first direction X, and the long side EY of the display panel PNL is parallel to the second direction Y. The third direction Z corresponds to the thickness direction of the display panel PNL. The main surface of the display panel PNL is parallel to the XY plane defined by the first direction X and the second direction Y. The display panel PNL has a display area DA and a non-display area NDA other than the display area DA. In the illustrated example, the non-display area NDA is an area outside the display area DA and surrounds the display area DA. The non-display area NDA has a terminal area MT.

[0012] The display area DA is an area for displaying an image, and in the display area DA, for example, a plurality of pixels PX are arranged in a matrix in the first direction X and the second direction Y. In this embodiment, the shape of the display area DA is a rectangle, but is not limited to this and may be a polygon other than a rectangle, a circle, or the like. Furthermore, the size of the display area DA is larger than the size of the non-display area NDA, but is not limited to this and the size of the display area DA may be smaller than the size of the non-display area NDA.

[0013] Each pixel PX is provided with a micro light emitting diode (hereinafter referred to as a micro LED) which is a self-emitting element. In this embodiment, such a display device DSP is called a micro LED display device.

[0014] The terminal area MT is provided along the short side EX of the display panel PNL, and is used to connect the display panel PNL to an external device. It includes terminals for electrically connecting to the above.

[0015] The first circuit board PC1 is mounted on the terminal area MT and electrically connected to the display panel PNL. The first circuit board PC1 is, for example, a flexible printed circuit board (FPC). The first circuit board PC1 includes a panel driver DRV, which is a driving IC chip that drives the display panel PNL. In the illustrated example, the panel driver DRV is mounted on the first circuit board PC1, but it may also be mounted below the first circuit board PC1. Alternatively, the panel driver DRV may be mounted on a location other than the first circuit board PC1, for example, on the display panel PNL or the second circuit board PC2. The second circuit board PC2 is, for example, a printed circuit board (PCB). The second circuit board PC2 is connected to the first circuit board PC1, for example, below the first circuit board PC1.

[0016] The panel driver DRV is connected to a control board (not shown), for example, via a second circuit board PC2. The panel driver DRV controls the display of an image on the display panel PNL by driving a plurality of pixels PX based on a video signal output from the control board, for example.

[0017] The display panel PNL may have a bending area BA indicated by diagonal lines. The bending area BA is an area that is bent when the display device DSP is housed in a housing. The bending area BA is located on the terminal area MT side of the non-display area NDA. When the bending area BA is bent, the first circuit board PC1 and the second circuit board PC2 are disposed below the display panel PNL so as to face the display panel PNL.

[0018] 2 is a cross-sectional view showing an example of a schematic configuration of a pixel. The pixel PX includes an insulating substrate BP, a planarization film FL, a transparent adhesive layer AD, wiring WL, a light-emitting element LS that is a micro LED, and reflection portions REF1 and REF2. The light-emitting element LS includes a semiconductor layer SC, a first electrode LP, and a second electrode LN.

[0019] The insulating substrate BP includes, for example, a thin film transistor (TFT) provided on an insulating base material, etc. The thin film transistor functions as a driving element for driving the light emitting element LS.

[0020] A planarization film FL is provided on the insulating substrate BP. The planarization film FL is a resin layer with high transmittance. The planarization film FL is formed of, for example, acrylic, epoxy, or silicone resin. The thickness of the planarization film FL should be as thick as possible, for example, between 1 μm and 100 μm.

[0021] A recess CAV is provided in the planarization film FL. The cross-sectional shape of the recess CAV is an inverted tapered shape with the upper side longer than the lower side. In a cross-sectional view, the side surface of the recess CAV forms an angle of 5° or more and 85° or less with the third direction Z. The recess CAV does not overlap with the light-emitting element LS, described later, particularly the semiconductor layer SC, in a planar view. Also, as shown in FIG. 4, in a planar view, the recess CAV of the planarization film FL is provided around the light-emitting element LS and is formed in a ring-shaped or rectangular shape so as to surround the outline of the light-emitting element LS.

[0022] The recess CAV constitutes the reflecting portions REF1 and REF2. Although both the reflecting portions REF1 and REF2 are provided in Fig. 2, only the reflecting portion REF1 or only the reflecting portion REF2 may be provided. The reflecting portions REF1 and REF2 are also referred to as first reflecting portions. The reflective portion REF1 has a recess CAV and a reflective material RL filled in the recess CAV. In the reflective portion REF1, the recess CAV may not be filled with the reflective material RL, but a layer of wiring material RL may be formed on the side surface of the recess CAV, and the inside of the recess CAV may be hollow. The reflecting portion REF2 has a recess CAV, a filling member FIL, and a reflective material RL formed on the side surface of the recess CAV. The filling member FIL may be formed of, for example, the same material as the transparent adhesive layer AD described below. The reflective material RL may be formed of the same material as the wiring WL. Alternatively, the reflective material RL may be a white resin material that reflects light.

[0023] To form the reflective material RL on the side surface of the recess CAV, if the reflective material RL is the same material as the wiring WL, the material may be deposited by sputtering, etc. If the reflective material RL is a resin material, the reflective material RL may be applied by inkjet, spin coating, slit coating, etc.

[0024] A transparent adhesive layer AD is provided on the planarization film FL at a position overlapping the reflective portions REF1 and REF2. The transparent adhesive layer AD is a resin layer with high transmittance. The transparent adhesive layer AD is formed of, for example, acrylic, epoxy, or silicone resin. The transparent adhesive layer AD should be as thin as possible, for example, with a thickness of 1 μm or more and 50 μm or less.

[0025] A micro LED, which is a light-emitting element LS, is provided on the transparent adhesive layer AD. That is, the light-emitting element LS is mounted on the insulating substrate BP with the transparent adhesive AD sandwiched therebetween. The micro LED has a square shape in a plan view, with the length of each side being 100 μm or less. However, the micro LED may have a shape other than a square, such as a rectangle. In the case of a shape other than a square, it is sufficient that the length of the longest side is 100 μm or less.

[0026] Wiring WL is provided in contact with each of the first electrode LP and second electrode LN of the light emitting element LS. The wiring WL is made of a reflective conductive material, for example, a metal thin film. The light emitted from the light-emitting element LS is reflected by the wiring WL and emitted in the opposite direction to the third direction Z, i.e., downward. The display device DSP is a downward emission type display device. The downward emitted light is referred to as LT.

[0027] An example of the structure of the light emitting element LS will now be described. Fig. 3 is a cross-sectional view showing a detailed example of the light emitting element.

[0028] As shown in FIG. 3, the light-emitting element LS is a flip-chip type light-emitting diode element. The light-emitting element LS includes a transparent substrate SUB having insulating properties. The substrate SUB is, for example, a sapphire substrate. A semiconductor layer SC (crystal layer) is formed on a bottom surface BTM of the substrate SUB, in which an n-type semiconductor layer SCN, an active layer (light-emitting layer) SCA, and a p-type semiconductor layer SCP are laminated in this order. In the semiconductor layer SC, a region containing P-type impurities is the p-type semiconductor layer SCP, and a region containing N-type impurities is the n-type semiconductor layer SCN. The material of the semiconductor layer SC is not particularly limited, but the semiconductor layer SC may include gallium nitride (GaN) or gallium arsenide (GaAs).

[0029] The light reflecting film REM is made of a conductive material and is formed on the p-type semiconductor layer SCP. The p-electrode ELP is formed on the light reflecting film REM. The n-electrode ELN is formed on the n-type semiconductor layer SCN. The pad PAD2 covers the n-electrode ELN and is electrically connected to the n-electrode ELN. The protective layer PRL covers the n-type semiconductor layer SCN, the active layer SCA, the p-type semiconductor layer SCP, and the light reflecting film REM, and also covers a part of the p-electrode ELP. The pad PAD1 covers the p-electrode ELP and is electrically connected to the p-electrode ELP.

[0030] In this embodiment, the combined structure of the pad PAD1 and the p-electrode ELP, the pad PAD1 alone, or the p-electrode ELP alone is referred to as the first electrode LP. The combined structure of the pad PAD2 and the n-electrode ELN, the pad PAD2 alone, or the n-electrode ELN alone is referred to as the second electrode LN.

[0031] Returning to Figure 2, reflection of light generated in the semiconductor layer SC will be described. Of the light generated in the semiconductor layer SC, light L0 irradiated upward is reflected by the first electrode LP or the second electrode LN, or both, and emitted downward (in the direction opposite to the third direction Z), becoming emitted light L1. The light reflected by the first electrode LP or the second electrode LN, or both, is further reflected by the reflective material RL of the reflective portion REF1 or REF2 and emitted downward. The light reflected by the reflective portions REF1 and REF2 is referred to as emitted light L2 and L3, respectively. The emitted light LT includes emitted light L1, L2, and L3. Although not described in detail, light emitted laterally (in the first direction X and the second direction Y) from the light generated in the semiconductor layer SC is reflected by the wiring WL and emitted downward as the emitted light LT, similar to the emitted light L1, L2, and L3. The wiring WL and the semiconductor layer SC are insulated from each other by, for example, a protective layer PRL shown in FIG. 3.

[0032] Consider the case where the reflectors REF1 and REF2 are not provided. The downward emitted light LT is only the emitted light L1. Without the reflectors REF1 and REF2, the light would escape in an oblique direction via the planarizing film FL and insulating substrate BP. Because the emitted light LT does not include the emitted light L2 and L3, there is a risk that the amount of light will be reduced. However, since the light-emitting element LS of this embodiment includes the reflectors REF1 and REF2 below the semiconductor layer SC, it is possible to increase the spectral intensity of the emitted light L2 and L3. This embodiment can provide a display device DSP with a high light intensity, particularly in the front luminance.

[0033] Fig. 4 is a plan view showing an example of a schematic configuration of a pixel of this embodiment. Fig. 2 is a cross-sectional view taken along the line A1-A2 of the pixel PX shown in Fig. 4. If the width of the first electrode LP and the second electrode LN is W1 and the width of the wiring WL is W2, then the width W1 is longer than the width W2. However, this is not limiting and the width W1 and the width W2 may be equal.

[0034] In Fig. 4, a recess CAV in the planarization film FL and a reflective portion REF (REF1, REF2) formed within the recess CAV are formed around the light-emitting element LS so as to surround the light-emitting element LS. As described above, either the reflective member REF1 or the reflective member REF2 may be provided in the recess CAV formed so as to surround the light-emitting element LS in a ring-like or rectangular shape, or a combination of both the reflective members REF1 and REF2 may be provided. Although not shown in Fig. 4, the transparent adhesive layer AD shown in Fig. 2 is formed larger than the outer shape of the reflective member REF, reliably insulating the reflective member REF from the wiring WL and fixing the light-emitting element LS to the planarization film FL.

[0035] <Configuration example 1> Fig. 5 is a cross-sectional view showing another example of the configuration of the display device according to the embodiment. The example of the configuration shown in Fig. 5 differs from the example of the configuration shown in Fig. 2 in that there is a step between the first electrode and the second electrode. In the light emitting element LS shown in FIG. 5, a step is generated in the semiconductor layer SC, which causes a step in the first electrode LP and the second electrode LN.

[0036] Alternatively, even when the pads PAD1 and PAD2 shown in FIG. 3 are not provided and the p-electrode ELP and n-electrode ELN are used as the first electrode LP and second electrode LN, respectively, steps are generated in the first electrode LP and second electrode LN.

[0037] Even when a step occurs between the first electrode LP and the second electrode LN, the amount of light LT emitted downward can be increased by providing a reflecting portion. Fig. 5 shows an example in which only the reflecting portion REF1 is formed to surround the periphery of the light-emitting element LS, but this configuration example is not limited to this. The reflecting portions REF1 and REF2 shown in Fig. 2 may be combined to surround the light-emitting element LS, or the reflecting portion REF2 may be used to surround the light-emitting element LS instead of the reflecting portion REF1. This configuration example also has the same configuration as the embodiment.

[0038] <Configuration example 2> Fig. 6 is a cross-sectional view showing another example of the configuration of the display device according to the embodiment. The example of the configuration shown in Fig. 6 differs from the example of the configuration shown in Fig. 5 in that an insulating layer RFT is provided in contact with the semiconductor layer. The light-emitting element LS shown in Fig. 6 has, as the semiconductor layer SC, an n-type semiconductor layer SCN, an active layer SCA, and a p-type semiconductor layer SCP, which are stacked in this order. The semiconductor layer SC in Fig. 6 is the same as the semiconductor layer SC shown in Fig. 3. That is, the semiconductor layer SC shown in Fig. 6 also has a step, and steps are generated in the first electrode LP and the second electrode LN. The length of the n-type semiconductor layer SCN in the direction perpendicular to the third direction Z is longer than the lengths of the active layer SCA and the p-type semiconductor layer SCP. The length of the active layer SCA and the length of the p-type semiconductor layer SCP are the same.

[0039] An insulating layer RFT is provided in contact with the upper surface of the n-type semiconductor layer SCN, the side surfaces of the active layer SCA and the p-type semiconductor layer SCP, and part of the upper surface of the p-type semiconductor layer SCP. In other words, the insulating layer RFT is provided so as to cover the stepped portion of the semiconductor layer SC. The insulating layer RFT is formed of, for example, acrylic, epoxy, silicone resin, or the like. When the insulating layer RFT is made of, for example, a reflective insulating material, such as a white resin material, the insulating layer RFT can also be called a second reflecting portion. By providing the insulating layer RFT adjacent to the active layer SCA, which is a light-emitting layer, it is possible to prevent a short circuit between the first electrode LP and the second electrode LN. Furthermore, when the insulating layer PFT is made of a white resin material and functions as a second reflecting member, it is possible to reflect downward the light that passes through between the two wirings WL, allowing for more efficient use of the generated light, thereby increasing the amount of emitted light LT.

[0040] In the display device DSP shown in FIG. 6, a reflective portion REF1 is provided on the planarizing film FL, and this configuration example also achieves the same effects as the embodiment. Furthermore, the insulating layer RFT reflects light passing between the first electrode LP and the second electrode LN while the insulating layer PFR reliably insulates the pads PAD1 and PAD2 described in Fig. 3 or while the insulating layer PFT reliably insulates the p-electrode ELP and the n-electrode ELN. The step in the semiconductor layer SC shown in Fig. 6 is not necessarily required, and a structure in which the insulating layer RFT is provided between the first electrode LP and the second electrode LN shown in Fig. 2 may also be used.

[0041] <Configuration example 3> Fig. 7 is a cross-sectional view showing another example of the configuration of the display device according to the embodiment. The example of the configuration shown in Fig. 7 differs from the example of the configuration shown in Fig. 4 in that the width of the wiring is longer than the width of the electrode. 7, the width W2 of the wiring WL is longer than the width W1 of the first electrode LP and the second electrode LN. This increases the overlapping area between the wiring WL and the semiconductor layer SC. Since more light generated in the semiconductor layer SC is reflected by the wiring WL, the amount of downward emitted light LT is further increased. This configuration example also provides the same effects as the embodiment.

[0042] <Configuration Example 4> Fig. 8 is a cross-sectional view showing another example of the configuration of the display device according to the embodiment. The example of the configuration shown in Fig. 8 differs from the example of the configuration shown in Fig. 2 in that a reflective layer is provided to cover the entire light-emitting element LS. 8, an insulating layer IL is provided to cover the entire light-emitting element LS and the wiring WL. The insulating layer IL is made of a highly light-transmitting insulating material. The insulating layer IL is preferably made of a material with a low specific heat, in other words, a high thermal conductivity, so that heat generated in the light-emitting element LS can be efficiently transferred to the metal layer HM described below.

[0043] A metal layer HM is provided covering the insulating layer IL. It can be said that the metal layer HM covers the entire light-emitting element LS and the wiring WL. The metal layer HM has the function of dissipating heat generated in the light-emitting element LS to the outside. The metal layer HM may be formed from the same material as the wiring WL. The surface of the metal layer HM may be provided with minute irregularities. This is because providing irregularities further increases the heat dissipation effect.

[0044] Fig. 9 is a plan view showing an example of a schematic configuration of a display device of this configuration example. The display device DSP shown in Fig. 9 has a plurality of pixels PX. The plurality of pixels PX include a pixel PXR that emits red light, a pixel PXG that emits blue light, and a pixel PXB that emits green light. The pixels PXR, PXG, and PXB form one pixel unit SX. Note that the pixel unit SX may also be simply called a pixel, and the pixels PXR, PXG, and PXB may also be called sub-pixels.

[0045] A metal layer HM is provided to cover the pixels PX. The metal layer HM may be a metal film that is continuously and integrally formed across the pixels PX, a so-called solid film. Forming a continuously and integrally formed metal film increases the heat dissipation effect compared to when each light-emitting element LS is covered with a metal film. This configuration example also provides the same effects as the embodiment.

[0046] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0047] BP...insulating substrate, CAV...recess, DSP...display device, ELN...n-electrode, ELP...p-electrode, FIL...filling member, FT...planarizing film, HM...metal layer, L0...light, L1...emitted light, L2...emitted light, LN...second electrode, LP...first electrode, LS...light-emitting element, LT...emitted light, PAD1...pad, PAD2...pad, PNL...display panel, PX...pixel, REF1...reflective portion, REF2...reflective portion, RFT...reflective portion, RL...reflective material, SC...semiconductor layer, SCA...active layer, SCN...n-type semiconductor layer, SCP...p-type semiconductor layer, SX...pixel unit, WL...wiring.

Claims

1. an insulating substrate; a plurality of light-emitting elements mounted on the insulating substrate; and a plurality of wirings connected to the plurality of light-emitting elements; a planarization film provided between the light emitting element and the insulating substrate; Equipped with Each of the plurality of light-emitting elements a first electrode and a second electrode connected to the wiring; Equipped with the planarization film has a recess around the light-emitting element, The display device further comprises a reflecting portion made of a reflective material provided on a side surface of the recess.

2. A filling member is provided inside the recess, The display device according to claim 1 , wherein the filling member is any one of acrylic, epoxy, and silicone resin.

3. The display device according to claim 1 , wherein the inside of the recess is hollow.

4. 2. The display device according to claim 1, wherein the planarization film is made of any one of acrylic, epoxy, and silicone resin.

5. 5. The display device according to claim 4, wherein the thickness of the planarization film is 1 [mu]m or more and 100 [mu]m or less.

6. The display device according to claim 1 , wherein the recess and the reflecting portion are formed in a ring-like or rectangular shape so as to surround the outer shape of the light-emitting element in a plan view.

7. The display device according to claim 6 , wherein the light emitting element is adhered to the planarizing film by a transparent adhesive layer.

8. the transparent adhesive layer is formed to be larger than the recess formed in the annular or rectangular shape in a plan view, The display device according to claim 7 , wherein the wiring and the reflective portion are insulated from each other by the transparent adhesive layer.

9. The display device according to claim 1 , further comprising a metal layer covering the light-emitting elements and the wiring.

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