KR20210089842A - Micro led display - Google Patents

Abstract

A micro LED display according to an exemplary embodiment of the present application includes a micro LED; and a light control layer provided on the micro LED. The light control layer includes a protrusion pattern layer and a planarization layer. A refractive index difference between the protrusion pattern layer and the planarization layer is 0.03 to 0.3. It is possible to increase the front brightness of the micro LED display.

Description

Micro LED DISPLAY {MICRO LED DISPLAY}

This application relates to a micro LED display.

Light emitting diodes (LEDs) can be widely used in various wavelength bands from ultraviolet to infrared. Since Nichia commercialized nitride light emitting diodes (GaN LEDs), thanks to the continuous development of semiconductor thin film technology, process technology, and device technology, GaN-LED has dramatically improved performance and reliability, and features small display devices. LED demand is increasing explosively with the launch of high-brightness, high-power applications in mobile phones, TVs, lighting, electronic signs, traffic lights, automobiles, and home appliances. In particular, as the total light efficiency increased rapidly after 2005, a huge market was formed as an LCD backlight unit in the display industry. The development is expected to increase steadily.

Recently, numerous research papers have been published that apply the effect of the degree of freedom of size adjustment, flexible characteristics, and selective emission wavelength of LED. LEDs used for lighting are mainly in the size of 1,000㎛ × 1,000㎛. If the area of these LEDs is reduced to 1/100 or less, the size becomes 100㎛ × 100㎛, which is about the thickness of a human hair. Such LEDs are called micro LEDs. These micro LEDs can be mounted on stretchable substrates, flexible substrates, and substrates with three-dimensional structures, so they are applied to various fields such as wearable displays, skin-attached medical devices, semiconductor equipment, autonomous driving sensors, and light sources for big data services. can do.

Micro LED display, which is attracting attention as a next-generation display, applies RGB micro LED with a size of 100 μm or less that emits light by itself as a pixel of the pixel. Compared to conventional OLED and LCD, it has low power consumption, high efficiency and reliability, and the unit panel is tiled. Arrangement has the advantage of being able to increase the area. Due to these advantages, active studies are being conducted to apply micro LEDs to displays.

Republic of Korea Patent Publication No. 10-2018-0009116

The present application is to provide a micro LED display device.

An exemplary embodiment of the present application is,

micro LED; and

It includes a light control layer provided on the micro LED,

The light control layer includes a protrusion pattern layer and a planarization layer, and the difference in refractive index between the protrusion pattern layer and the planarization layer is 0.03 to 0.3.

The micro LED display according to an exemplary embodiment of the present application may include a light control layer including a protrusion pattern layer and a planarization layer on the micro LED, thereby increasing the front brightness of the micro LED display.

1 to 7 are diagrams schematically showing a micro LED display according to an exemplary embodiment of the present application, respectively.
8 to 12 are diagrams illustrating luminance evaluation results of micro LED displays according to Examples and Comparative Examples of the present application, respectively.
13 is a diagram schematically illustrating a light control layer according to an exemplary embodiment of the present application.

Hereinafter, preferred embodiments of the present application will be described. However, the embodiments of the present application may be modified in various other forms, and the scope of the present application is not limited to the embodiments described below. In addition, the embodiments of the present application are provided to explain the present invention in more detail to those with ordinary knowledge in the art.

The light emission distribution of a micro LED display varies depending on the size, thickness, and reflector material of the micro LED. As the size of the micro LED becomes smaller, the side luminous effect of the LED increases, thereby increasing the brightness at the side viewing angle rather than the front side. In terms of display utilization, the brightness of the front is more important than the side, so a technology that can increase the brightness of the front is needed.

In the present application, the term "viewing side" means a surface or direction arranged to face the viewer. Conversely, "opposite the viewing side" means a side or direction disposed to face the opposite side of the viewer.

In the present application, "extension" means to lengthen while maintaining the inclination of a straight line or plane.

In the present application, the term “flat surface” means that the centerline average roughness (Ra) is less than 0.1 μm.

In the present application, it was attempted to increase the front brightness of the micro LED display by applying a light control layer including a structure for condensing light traveling at a side viewing angle to the front. The light control layer is integrated with the micro LED display, and is present on the top of the micro LED display, that is, on the side of the viewer.

A micro LED display according to an exemplary embodiment of the present application includes a micro LED; and a light control layer provided on the micro LED, wherein the light control layer includes a protrusion pattern layer and a planarization layer, and a refractive index difference between the protrusion pattern layer and the planarization layer is 0.03 to 0.3.

In the exemplary embodiment of the present application, the difference in refractive index between the protrusion pattern layer and the planarization layer may be 0.03 to 0.3, or 0.05 to 0.2. In this case, the refractive index of the higher refractive index of the protrusion pattern layer and the planarization layer may be about 1.45 to 1.7, and the refractive index of the lower refractive index may be 1.3 to 1.55. The refractive index is measured at a wavelength of 590 nm. When the refractive index difference between the protrusion pattern layer and the planarization layer is less than 0.03, the light path control effect is lowered and sufficient light collecting performance cannot be obtained.

In an exemplary embodiment of the present application, the light control layer may have a single-layer structure or a multi-layer structure. The multilayer structure means a structure in which two or more light control layers including a protrusion pattern layer and a planarization layer are stacked.

In an exemplary embodiment of the present application, the light control layer has a multilayer structure in which two light control layers are stacked, and may further include a substrate layer between the two light control layers. In addition, in an exemplary embodiment of the present application, at least one of an adhesion layer and a substrate layer may be further included between the micro LED and the light control layer.

As the adhesion layer and the base layer, those known in the art may be used, and are not particularly limited. For example, the base layer is polyester, polyacrylic, polyvinyl chloride, polycarbonate, polymethyl methacrylate, polystyrene, polyester sulfone, polybutadiene, triacetate cellulose film (TAC), cycloolefin polymer (COP), polyethylene It may be terephthalate (PET) or an acrylic film, but is not limited thereto. The acrylic film may include a (meth)acrylate-based resin, and the film including the (meth)acrylate-based resin is formed by extrusion molding a molding material containing the (meth)acrylate-based resin as a main component. can be obtained

In addition, the adhesive layer may be an adhesive layer or an adhesive layer. For example, the adhesive layer may be an optical clear adhesive (OCA) film.

In an exemplary embodiment of the present application, the protrusion pattern layer includes a first surface including a flat surface; and a second surface facing the first surface and including a plurality of protrusions, each of which may include a first inclined surface and a second inclined surface. At this time, the angle (θ ₁ ) between the first inclined surface or the extended surface of the first inclined surface and the first surface and the second inclined surface or the second inclined surface and the extended surface and the first surface are formed (θ ₂ ) may be each independently 50° to 80°, or 60° to 80°. _{In addition, the angle (θ 1} ) formed between the first inclined surface or the surface extending the first inclined surface and the first surface and the second inclined surface or the extending surface of the second inclined surface and the first surface formed by the first surface (θ ₂ ) is They may have the same angle to each other.

In the exemplary embodiment of the present application, the angle (θ) between the first inclined surface or the surface extending the first inclined surface and the second inclined surface or the second inclined surface extending surface may be 20 ° to 80 °, 20 ° to 50 °. If the angle (θ) between the first inclined surface or the surface extending the first inclined surface and the second inclined surface or the surface extending the second inclined surface is less than 20°, it is difficult to manufacture a mold for shape duplication, and it is more than 80° In this case, the light-gathering effect is reduced.

In the exemplary embodiment of the present application, the planarization layer is provided on the second surface side of the protrusion pattern layer. In another exemplary embodiment, the planarization layer is provided to be in contact with the second surface of the protrusion pattern layer.

In an exemplary embodiment of the present application, a flat surface of the protrusion pattern layer may be provided toward the micro LED. In addition, at least one of an adhesion layer and a base layer may be further included on the light control layer. Specific details of the adhesion layer and the base layer are the same as described above.

In the exemplary embodiment of the present application, the shape of the protrusion may be a prism, a pyramid, or a cone shape.

In the exemplary embodiment of the present application, a plurality of protrusions included in the second surface may be continuously disposed. When the plurality of protrusions are continuously provided, the pattern layer may be formed such that the first inclined surface of one protrusion and the second inclined surface of the other protrusion contact each other.

According to another exemplary embodiment, the plurality of protrusions may be provided non-continuously.

In the exemplary embodiment of the present application, at least one cross-section perpendicular to the first surface of the protrusion may have a triangular, quadrangular, or pentagonal shape.

When at least one cross section perpendicular to the first surface of the protrusion has a triangular shape, one end of the first inclined surface is in contact with the end of the second inclined surface, and the other end is formed to contact the first surface, An end of the second inclined surface that is not in contact with the end of the first inclined surface may be formed to contact the first surface.

When at least one cross-section perpendicular to the first surface of the protrusion has a rectangular shape, one end of the first inclined surface and one end of the second inclined surface are in contact with the first surface, and the other end of the first inclined surface and the second end of the first inclined surface are in contact with the first surface. 2 It includes a third inclined surface formed to abut the other end of the inclined surface, or one end of the first inclined surface is in contact with the first surface, and the other end is formed so as to be in contact with the end of the second inclined surface, of the first inclined surface It includes an end of the second inclined surface not in contact with the end and a third inclined surface formed to contact the first surface.

When at least one cross section perpendicular to the first surface of the protrusion has a pentagonal shape, a plurality of protrusions are continuously formed, the protrusions include a first inclined surface and a second inclined surface, and the first inclined surface of one protrusion The end of the second inclined surface of the protrusion adjacent to the end of the abuts against each other, but is formed so as not to be in contact with the first surface.

In the exemplary embodiment of the present application, the aspect ratio of each of the protrusions represented by Equation 1 below may be greater than 0.7 and less than 3.0, and may be 1.6 to 2.0. By satisfying the aspect ratio of the protrusion as described above, it is possible to more effectively increase the front brightness of the micro LED display. When the aspect ratio is 0.7 or less, it is difficult to obtain a sufficient light condensing effect, and when the aspect ratio is 3.0 or more, the difficulty of mold processing rapidly increases.

[Equation 1]

Aspect ratio of overhang = height of overhang / pitch of overhang

In the exemplary embodiment of the present application, the height of the protrusion means a vertical distance between the lowest point of the protrusion and the highest point of the protrusion, and the height of the protrusion may be 5 μm to 60 μm, or 10 μm to 30 μm. When the pitch of the protrusions is the same and the height of the protrusions is low, the angle of the apex of the protrusions is increased. Therefore, in the exemplary embodiment of the present application, the height of the protrusion is preferably 5 μm to 60 μm, and more preferably 10 μm to 30 μm.

In the exemplary embodiment of the present application, the pitch of the protrusions means a distance between the first inclined surfaces of adjacent protrusions based on the first surface, and the pitch of the protrusions may be 5 μm to 20 μm, and 10 μm to 15 μm. μm. If the pitch of the protrusion is out of the above range, it is not preferable because a micro LED display and a moire phenomenon may occur.

The height of the protrusion and the pitch of the protrusion are schematically shown in FIG. 13 below.

In an exemplary embodiment of the present application, the material of the protrusion pattern layer may be an ultraviolet curable resin, but is not limited thereto. As an example of the ultraviolet curable resin, epoxy (meth) acrylate, urethane (meth) acrylate, phenylphenol ethoxylated (meth) acrylate, trimethylol propane ethoxylated (meth) acrylate, phenoxy Benzyl (meth) acrylate, phenylphenoxyethyl (meth) acrylate, ethoxylated thiodiphenyl di (meth) acrylate, phenylthioethyl (meth) acrylate monomers or oligomers thereof, or fluorene derivative unsaturated It may include a resin, but is not limited thereto.

In the exemplary embodiment of the present application, the material of the planarization layer may be formed using an ultraviolet curable resin or an acrylate-based adhesive.

The thickness of the planarization layer may be about 1 μm to 200 μm.

In an exemplary embodiment of the present application, the micro LED may use one known in the art. For example, the micro LED is an LED having a size of 10 μm to 100 μm. After growing a plurality of thin films of inorganic materials such as Al, Ga, N, P, As In on a sapphire substrate or a silicon substrate, the sapphire substrate or the silicon substrate It can be formed by cutting and separating. In addition, since individually separated micro LEDs can be transferred onto a large-area substrate and used, a large-area display device can be manufactured.

A micro LED display according to an exemplary embodiment of the present application is schematically shown in FIGS. 1 to 7 below. 1, the micro LED display according to an exemplary embodiment of the present application includes a micro LED (10); and a light control layer provided on the micro LED 10 , wherein the light control layer includes a protrusion pattern layer 20 and a planarization layer 30 . 2 shows a structure further including an adhesion layer 40 between the micro LED 10 and the light control layer, and FIG. 3 further includes a substrate layer 50 on the light control layer. structure is shown. In addition, the following FIG. 4 shows a structure that further includes an adhesion layer 40 between the micro LED 10 and the light control layer, and further includes a base layer 50 on the light control layer. In addition, the following FIG. 5 further includes an adhesion layer 40 and a base layer 50 between the micro LED 10 and the light control layer, and the adhesion layer 40 and the base layer ( 50) shows a structure further comprising a.

6 shows a structure in which the light control layer has a multilayer structure in which two light control layers are stacked, and further includes an adhesion layer 40 between the micro LED 10 and the light control layer. 7 shows a structure in which the light control layer has a multilayer structure in which two light control layers are stacked, and each additionally includes a base layer 50 on the light control layer.

Hereinafter, the embodiments described in the present specification are illustrated through examples. However, it is not intended that the scope of the above embodiments be limited by the following examples.

<Example>

<Example 1>

Simulation was performed by configuring a micro LED display stacked in the order of the micro LED (10)/adhesion layer (40)/protrusion pattern layer (20)/planarization layer (30) as shown in FIG. 2 . For the simulation, ZEMAX, an optical simulation S/W, was used.

1) Projection pattern layer: an angle θ between the first inclined surface and the second inclined surface is 30°, an angle θ ₁ between the first inclined surface and the first surface is 75°, and the second inclined surface is formed from the first surface Application of a prism structure with an angle (θ ₂ ) of 75° (refractive index at a wavelength of 590 nm: 1.48)

The height of the protrusions of the pattern layer was 28 μm, the pitch of the protrusions was 15 μm, and the aspect ratio of the protrusions was 1.87.

2) Planarization layer: provided on the pattern layer (refractive index at a wavelength of 590 nm: 1.61)

<Example 2>

In Example 1, as shown in FIG. 6 below, except that the light control layer including the protrusion pattern layer and the planarization layer had a multilayer structure in which two light control layers were stacked, the simulation was performed in the same manner as in Example 1 proceeded.

<Example 3>

Simulation was performed by configuring a micro LED display stacked in the order of the micro LED (10)/adhesion layer (40)/protrusion pattern layer (20)/planarization layer (30) as shown in FIG. 2 . For the simulation, ZEMAX, an optical simulation S/W, was used.

1) Projection pattern layer: an angle θ between the first inclined surface and the second inclined surface is 30°, an angle θ ₁ between the first inclined surface and the first surface is 75°, and the second inclined surface is formed from the first surface Application of a prism structure with an angle (θ ₂ ) of 75° (refractive index at a wavelength of 590 nm: 1.61)

The height of the protrusions of the pattern layer was 28 μm, the pitch of the protrusions was 15 μm, and the aspect ratio of the protrusions was 1.87.

2) Planarization layer: provided on the pattern layer (refractive index at a wavelength of 590 nm: 1.48)

<Example 4>

In Example 3, as shown in FIG. 6 below, except that the light control layer including the protrusion pattern layer and the planarization layer had a multilayer structure in which two light control layers were stacked, the simulation was performed in the same manner as in Example 1 proceeded.

<Comparative Example 1>

In Example 1, the structure of the adhesion layer 40/protrusion pattern layer 20/planarization layer 30 was not applied, and only the micro LED was evaluated.

<Experimental Example 1>

Simulations were performed by configuring the micro LED display devices of the Examples and Comparative Examples. For the simulation, optical simulation S/W ZEMAX was used, 10 million ray was applied, and intensity and luminance distribution for each viewing angle were calculated using a polar detector.

The front luminance of the micro LED display device was measured, and the results are shown in Table 1, respectively. In addition, the vertical (V)/horizontal (H) luminance of the micro LED display device was measured, and the results are shown in FIGS. 8 to 12 below. 8 shows the results of Comparative Example 1, FIG. 9 shows the results of Example 1, and FIG. 10 shows the results of Example 2. In addition, the following FIG. 11 shows the result of Example 3, and the following FIG. 12 shows the result of Example 4.

[Table 1]

In Table 1, "display-prism direction arrangement" means an angle generated between the horizontal and vertical lengths of the result display of the prism. For example, in the case of Example 1, it means that the grain of the prism is arranged parallel to the long axis, which is the horizontal axis of the display. In the case of Example 2, the angle with the horizontal axis of the result display of the prisms of the two layers in the light control layer of the multilayer structure is ±30°, respectively, and the angle between the grains of the prisms of the two layers is 60°.

In addition, in FIGS. 8 to 12, vertical (V) luminance means luminance according to the vertical viewing angle of the display, and horizontal (H) luminance means luminance according to the left and right viewing angle of the display. 8 to 12 , a horizontal axis indicates a viewing angle, and a vertical axis indicates luminance.

As described above, the micro LED display according to an exemplary embodiment of the present application includes a light control layer including a protrusion pattern layer and a planarization layer on the micro LED, thereby increasing the front brightness of the micro LED display.

10: micro LED
20: protrusion pattern layer
30: planarization layer
40: adhesion layer
50: base layer
60: the first surface of the protrusion pattern layer
70: second surface of the protrusion pattern layer
80: the height of the protrusion
90: pitch of protrusions

Claims (12)

micro LED; and
It includes a light control layer provided on the micro LED,
The light control layer includes a protrusion pattern layer and a planarization layer, and the difference in refractive index between the protrusion pattern layer and the planarization layer is 0.03 to 0.3. The micro LED display according to claim 1, wherein the light control layer has a single-layer structure or a multi-layer structure. The method according to claim 2, wherein the light control layer is a multi-layer structure in which two light control layers are stacked,
The micro LED display further comprising a substrate layer between the two light control layers. The micro LED display according to claim 1, further comprising at least one of an adhesion layer and a base layer between the micro LED and the light control layer. The method according to claim 1, wherein the protrusion pattern layer is a first surface including a flat surface; and a second surface facing the first surface and including a plurality of protrusions,
Each of the protrusions includes a first inclined surface and a second inclined surface,
The first inclined surface or the first inclined surface on one side and the first surface is an angle (θ ₁₎ and the second angle a surface extending the inclined surface or the second inclined surface and the first surface forms (θ ₂₎ extending each independently A micro LED display of 50 ° to 80 °. The micro LED display according to claim 5, wherein an angle (θ) between the first inclined surface or the surface extending the first inclined surface and the second inclined surface or the extending surface of the second inclined surface is 20° to 80°. The micro LED display according to claim 5, wherein the flat surface of the protrusion pattern layer is provided toward the micro LED. The micro LED display according to claim 7, further comprising at least one of an adhesion layer and a base layer on the light control layer. The micro LED display according to claim 5, wherein the protrusion has a shape of a prism, a pyramid or a cone. The micro LED display according to claim 5, wherein the aspect ratio of each of the protrusions represented by the following Equation 1 is greater than 0.7 and less than 3.0:
[Equation 1]
Aspect ratio of overhang = height of overhang / pitch of overhang The micro LED display according to claim 5, wherein the height of the protrusion is 5 μm to 60 μm. The micro LED display according to claim 5, wherein the protrusion has a pitch of 5 μm to 20 μm.

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