TWI773528B - Display device - Google Patents

Abstract

A display device includes a circuit substrate, a plurality of light-emitting elements, a glue layer and a cover layer. The light-emitting elements are disposed on and electrically connected to the circuit substrate, and include a light-emitting layer respectively. The glue layer is disposed on the circuit substrate and between the circuit substrate and the light-emitting elements. The cover layer covers the light-emitting elements and the glue layer, wherein the glue layer’ complex refractive index has a first real part n _A, the cover layer’ complex refractive index has a second real part n _B, the light-emitting layer’ complex refractive index has a third real part n _LED, and (n _A+n _B)/n _LEDranges from 1.45 to 1.75.

Description

display device

The present invention relates to a display device, and more particularly, to a display device with improved light extraction efficiency.

The Micro-LED display device directly uses the micro-LED die as the light-emitting unit, and realizes the effect of screen display by encapsulating the micro-LED die on the circuit substrate. However, due to the high refractive index of the micro-LED crystal grains, their light extraction efficiency is still low.

The present invention provides a display device with improved light extraction efficiency.

An embodiment of the present invention provides a display device, including: a circuit substrate; a plurality of light-emitting elements, located on the circuit substrate and electrically connected to the circuit substrate, respectively including a light-emitting layer; an adhesive layer, located on the circuit substrate and the circuit substrate and the plurality of light-emitting elements between the light-emitting elements; and a cover layer covering a plurality of light-emitting elements and the adhesive layer, wherein the adhesive layer has a real part of the complex refractive index n _A , the cover layer has a real part of the complex refractive index n _B , and the light-emitting layer has a real part of the complex refractive index n B . n _LED , and (n _A +n _B )/n _LED is between 1.45 and 1.75.

In an embodiment of the present invention, the above-mentioned n _A /n _LED is between 0.8 and 0.95.

In an embodiment of the present invention, the above-mentioned n _A <n _B <n _LED .

In an embodiment of the present invention, the upper surface of the above-mentioned adhesive layer is not higher than the upper surface of the light-emitting element.

In an embodiment of the present invention, the above-mentioned adhesive layer includes a dye, and the color of the dye is the same as the light color of the light-emitting element.

In an embodiment of the present invention, the above-mentioned dye includes dye particles and a dye, and the real part of the complex refractive index of the dye particles is greater than the real part of the complex refractive index of the dye.

In an embodiment of the present invention, the imaginary part of the complex refractive index of the cover layer is smaller than the imaginary part of the complex refractive index of the adhesive layer.

In an embodiment of the present invention, the above-mentioned cover layer includes a plurality of color filter structures.

In an embodiment of the present invention, the color of the above-mentioned color filter structure is the same as the light color of the corresponding light-emitting element.

In an embodiment of the present invention, the above-mentioned display device further includes an anti-reflection layer on the cover layer.

In an embodiment of the present invention, the imaginary part of the complex refractive index of the above-mentioned anti-reflection layer is close to zero.

In an embodiment of the present invention, the above-mentioned anti-reflection layer includes a destructive interference anti-reflection layer or a graded-index anti-reflection layer.

In order to make the above-mentioned features and advantages of the present invention more obvious and easy to understand, the following embodiments are given and described in detail with the accompanying drawings as follows.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. The same reference numerals refer to the same elements throughout the specification. It will be understood that when an element such as a layer, film, region or substrate is referred to as being "on" or "connected to" another element, it can be directly on or connected to the other element, or Intermediate elements may also be present. In contrast, when an element is referred to as being "directly on" or "directly connected to" another element, there are no intervening elements present. As used herein, "connected" may refer to a physical and/or electrical connection. Furthermore, "electrically connected" or "coupled" may refer to the existence of other elements between the two elements.

Furthermore, relative terms such as "lower" or "bottom" and "upper" or "top" may be used herein to describe one element's relationship to another element, as shown in the figures. It should be understood that relative terms are intended to encompass different orientations of the device in addition to the orientation shown in the figures. For example, if the device in one of the figures is turned over, elements described as being on the "lower" side of other elements would then be oriented on "upper" sides of the other elements. Thus, the exemplary term "lower" may include an orientation of "lower" and "upper", depending on the particular orientation of the figures. Similarly, if the device in one of the figures is turned over, elements described as "below" or "beneath" other elements would then be oriented "above" the other elements. Thus, the exemplary terms "below" or "beneath" can encompass both an orientation of above and below.

"About," "approximately," or "substantially" as used herein includes the stated value and is of ordinary skill in the art, given the measurement in question and the particular amount of error associated with the measurement (ie, limitations of the measurement system). The average within an acceptable deviation range for a specific value determined by a person. For example, "about" can mean within one or more standard deviations of the stated value, or within ±30%, ±20%, ±10%, ±5%. Furthermore, as used herein, "about", "approximately", or "substantially" may be used to select a more acceptable range of deviation or standard deviation depending on optical properties, etching properties, or other properties, and not one standard deviation may apply to all. nature.

FIG. 1A is a schematic cross-sectional view of a display device 10 according to an embodiment of the present invention. FIG. 1B is a simulation diagram of light extraction efficiency of the display device 10 according to an embodiment of the present invention. The display device 10 includes: a circuit substrate 110; a plurality of light-emitting elements 120 located on the circuit substrate 110 and electrically connected to the circuit substrate 110, respectively including a light-emitting layer EL; an adhesive layer 130 located on the circuit substrate 110 and the circuit substrate 110 and the multiple between the light-emitting elements 120; and a cover layer 140 covering the plurality of light-emitting elements 120 and the adhesive layer 130, wherein the adhesive layer 130 has a real part of the complex refractive index n _A , the cover layer 140 has a real part of the complex refractive index n _B , and emits light. Layer EL has the real part of the complex index _nLED , and (nA _{+ nB} )/ _nLED may be between about 1.45 and 1.75.

In the display device 10 according to an embodiment of the present invention, by controlling the refractive index of the adhesive layer 130 and the cover layer 140 around the light-emitting element 120 to reduce the light-emitting reflection of the light-emitting element 120, the light-emitting transmission of the light-emitting element 120 is increased at the same time, thereby Improve the light extraction efficiency of the light-emitting element. Hereinafter, with reference to FIG. 1 , the embodiment of each element of the display device 10 will be continuously described, but the present invention is not limited thereto.

In this embodiment, the circuit substrate 110 may include a bottom plate 112 and a driving circuit layer 114 . The bottom plate 112 of the circuit substrate 110 can be a transparent substrate or a non-transparent substrate, and its material can be a quartz substrate, a glass substrate, a polymer substrate or other suitable materials, but the invention is not limited thereto. The driving circuit layer 114 may include pads P1 and P2 , and the pads P1 and P2 may electrically connect the circuit substrate 110 and the light-emitting element 120 . The pads P1 and P2 may have a single-layer structure or a structure in which more than one conductive layer is stacked. For example, the pads P1, P2 may have metals such as aluminum, molybdenum, titanium, copper, and indium tin oxide (ITO), indium zinc oxide (IZO), indium gallium zinc oxide (IGZO), or other suitable conductive materials. Oxide layered structure, but the present invention is not limited to this.

In some embodiments, the driving circuit layer 114 may further include elements or lines required by the display device 10 , such as driving elements, switching elements, storage capacitors, power lines, driving signal lines, timing signal lines, current compensation lines, and detection signal lines and many more. For example, a thin film deposition process, a lithography process and an etching process can be used to form the driving circuit layer 114 on the base plate 112 , and the driving circuit layer 114 may include an array of active elements, wherein the array of active elements may include a plurality of arrays of active elements arranged in an array. The active element T, and the active element T can be electrically connected to the pad P1 or the pad P2. Specifically, the driving circuit layer 114 may include an active element T, a buffer layer I1, a gate insulating layer I2, an interlayer insulating layer I3, a flat layer I4, and pads P1 and P2. The active element T may be composed of a semiconductor layer CH, a gate electrode GE, a source electrode SE and a drain electrode DE. The region where the semiconductor layer CH overlaps the gate electrode GE can be regarded as a channel region of the active element T. The gate insulating layer I2 is located between the gate electrode GE and the semiconductor layer CH, and the interlayer insulating layer I3 is provided between the source electrode SE and the gate electrode GE and between the drain electrode DE and the gate electrode GE. The gate electrode GE and the source electrode SE can respectively receive signals from, for example, a driving element, and the drain electrode DE can be electrically connected to the pad P1 through the through hole in the flat layer I4. When the gate GE receives the signal to turn on the active element T, the signal received by the source SE can be transmitted to the pad P1 through the drain DE. In other embodiments, the driving circuit layer 114 may further include more insulating layers and conductive layers as required.

For example, the material of the semiconductor layer CH may include silicon semiconductor material (such as polysilicon, amorphous silicon, etc.), oxide semiconductor material, and organic semiconductor material, and the material of the gate electrode GE, the source electrode SE, and the drain electrode DE may include Metals with good electrical conductivity, such as aluminum, molybdenum, titanium, copper and other metals or their laminates, but not limited thereto. Materials of the buffer layer I1 , the gate insulating layer I2 and the interlayer insulating layer I3 may include transparent insulating materials, such as silicon oxide, silicon nitride, silicon oxynitride or a stack of the above materials, but the invention is not limited thereto. The material of the flat layer I4 may include transparent insulating materials, such as organic materials, acrylic materials, siloxane materials, polyimide materials, epoxy materials, etc., But not limited to this. The buffer layer I1, the gate insulating layer I2, the interlayer insulating layer I3 and the flat layer I4 may also have a single-layer structure or a multi-layer structure, respectively. Combination and variation.

In this embodiment, each light-emitting element 120 may include a first electrode E1, a second electrode E2 and a light-emitting stack SS, and the first electrode E1 and the second electrode E2 are respectively electrically connected to different layers in the light-emitting stack SS . The light-emitting stack SS may include two semiconductor layers and a light-emitting layer sandwiched between the above-mentioned two semiconductor layers, and the first electrode E1 may be electrically connected to one of the above-mentioned two semiconductor layers, and the second electrode E2 may be The other one of the two semiconductor layers is electrically connected. The material of the first electrode E1 and the second electrode E2 may include metal, alloy, nitride of metal material, oxide of metal material, oxynitride of metal material or other suitable materials or a stack of metal material and other conductive materials layer or other low resistance material.

For example, the light emitting stack SS may include a first type semiconductor layer S1, a second type semiconductor layer S2, and a light emitting layer EL sandwiched between the first type semiconductor layer S1 and the second type semiconductor layer S2. One of the first type semiconductor layer S1 and the second type semiconductor layer S1 may be an N-type doped semiconductor, and the other may be a P-type doped semiconductor. In addition, the first-type semiconductor layer S1 and the second-type semiconductor layer S2 may include II-VI group materials (eg, zinc selenide (ZnSe)) or III-V nitride materials (eg, gallium nitride (GaN), Gallium Arsenide, Indium Nitride (InN), Indium Gallium Nitride (InGaN), Aluminum Gallium Nitride (AlGaN), Aluminum Indium Gallium Nitride (AlInGaN), or Aluminum Gallium Indium Phosphide (AlGaInP). For example, in this embodiment, the first-type semiconductor layer S1 is, for example, an N-type doped semiconductor layer, and the material of the N-type doped semiconductor layer is, for example, N-type gallium nitride (n-GaN), and the second-type semiconductor layer is, for example, N-type gallium nitride (n-GaN). The layer S2 is, for example, a P-type doped semiconductor layer, and the material of the P-type doped semiconductor layer is, for example, P-type gallium nitride (p-GaN), but the invention is not limited thereto. In addition, the structure of the light emitting layer EL is, for example, a multi-layer quantum well (MQW) structure. The multi-quantum well structure may include alternately stacked multi-layer indium gallium nitride (InGaN) and multi-layer gallium nitride (GaN). The ratio of indium or gallium in the light-emitting layer EL can also adjust the light-emitting wavelength range of the light-emitting layer, but the present invention is not limited to this.

The light-emitting element 120 may be fabricated on a growth substrate (eg, a sapphire substrate), and then transferred to the circuit substrate 110 through a mass transfer process, and the first electrode E1 may be electrically connected to the pad P1 and the second electrode E2 can be electrically connected to pad P2. In some embodiments, solder, conductive glue or other conductive materials may be further included between the first electrode E1 and the pad P1 and between the second electrode E2 and the pad P2.

After the mass transfer process, the adhesive layer 130 may be coated on the circuit substrate 110 around the light-emitting element 120 , and then the adhesive layer 130 may flow between the light-emitting element 120 and the circuit substrate 110 . Considering the feasibility of the actual process, the upper surface 130T of the adhesive layer 130 may not be higher than the upper surface 120T of the light emitting element 120 . For example, in this embodiment, the upper surface 130T of the adhesive layer 130 may be lower than the upper surface 120T of the light emitting element 120 , but not limited thereto. In some embodiments, the upper surface 130T of the adhesive layer 130 may be substantially flush with the upper surface 120T of the light emitting element 120 .

In general, the so-called refractive index refers to the real part of the complex refractive index of the material, and the imaginary part of the complex refractive index can also be called the extinction coefficient (Extinction coefficient), which represents the attenuation of light after entering the material. In this embodiment, it can be defined that the light emitting layer EL of the light emitting element 120 has a complex refractive index real part n _LED , and the adhesive layer 130 has an average complex refractive index real part n _A . Since the refractive index of the light-emitting layer EL may be as high as 2.4 to 3.6, n _A is designed to be smaller than n _LED , and the ratio of n _A /n _LED is preferably above 0.8, for example, n _A /n _LED can be between 0.8 and 0.95 , so as to avoid total reflection of the light emitted by the light-emitting layer EL.

In this embodiment, the cover layer 140 may cover the upper surface 120T of the light emitting element 120 and the adhesive layer 130 , and the cover layer 140 may have an average complex refractive index real part n _B . In some embodiments, n _B may be between n _A and n _LED , that is, n _A <n _B <n _LED , so as to improve the light extraction rate of the light emitting element 120 . In addition, it can be seen from the simulation result of the light extraction efficiency in FIG. 1B that when (n _A +n _B )/n _LED is between 1.45 and 1.75, the light extraction efficiency of the light-emitting element 120 can be increased to more than 11.5%; when ( When n _A +n _B )/n _LED is between 1.47 and 1.71, the light extraction efficiency of the light-emitting element 120 can reach more than 12%; and when (n _A +n _B )/n _LED is between 1.5 and 1.67 , the light extraction efficiency of the light emitting element 120 may also exceed 12.5%.

In some embodiments, the subbing layer 130 may have an average complex refractive index imaginary part k _A , the cover layer 140 may have an average complex refractive index imaginary part k _B , and k _B may be slightly smaller than k _A , that is, k _B <k _A , In order to reduce the interface reflection between the adhesive layer 130 and the cover layer 140 .

Hereinafter, other embodiments of the present invention will continue to be described with reference to FIGS. 2 to 3 , and the element numbers and related contents of the embodiment in FIG. 1A will be followed, wherein the same numbers are used to represent the same or similar elements, and the same elements are omitted. Description of technical content. For the description of the omitted part, reference may be made to the embodiment of FIG. 1A , which will not be repeated in the following description.

FIG. 2 is a schematic cross-sectional view of a display device 20 according to an embodiment of the present invention. The display device 20 includes a circuit substrate 110 , a light-emitting element 120 , pads P1 , P2 , an adhesive layer 132 and a cover layer 140 , and the light-emitting element 120 includes a first electrode E1 , a second electrode E2 and a light-emitting stack SS, wherein the light-emitting stack The light emitting layer in layer SS has a real part of the complex refractive index _nLED , the subbing layer 132 has an average real part of the complex refractive index n _A , the cover layer 140 has an average real part of the complex refractive index n _B , and (n _A +n _B )/ n _LEDs are between 1.45 and 1.75. Compared with the display device 10 shown in FIG. 1A , the display device 20 shown in FIG. 2 is different in that the adhesive layer 132 of the display device 20 further includes a dye DM.

For example, in this embodiment, the color of the dye DM is preferably the same as the light color of the light-emitting element 120, and the dye DM may include dye particles DP and dyes DS, wherein the dyes DS can help disperse the dye particles DP in the adhesive layer 132 . In addition, the real part of the complex refractive index of the dye particles DP can be slightly larger than the real part of the complex refractive index of the dye DS, so as to improve the uniformity of light color. In some embodiments, the cover layer 140 may also include a dye, and the color of the dye of the cover layer 140 is also the same as the light color of the light emitting element 120 .

In some embodiments, the display device 20 further includes an anti-reflection layer AR, and the anti-reflection layer AR may be located on the cover layer 140 . The anti-reflection layer AR can reduce reflectivity, thereby improving light transmittance and light extraction efficiency. In some embodiments, the imaginary part of the complex refractive index of the anti-reflection layer AR can be close to zero, so as to improve the light extraction rate by reducing the attenuation of the incoming light.

In some embodiments, the antireflection layer AR may be a destructive interference antireflection layer. For example, the thickness of the anti-reflection layer AR can be half the wavelength of light, so that the phase of the light reflected by the anti-reflection layer AR after penetrating the anti-reflection layer AR can be opposite to the incident light, so that the reflected light and the incident light Destructive interference occurs, thereby reducing reflectivity.

In some embodiments, the antireflection layer AR may be a graded index antireflection layer. For example, the anti-reflection layer AR may include a material with a lower refractive index, such as air bubbles or other suitable materials. When the distribution concentration of air bubbles increases from the side C1 of the anti-reflection layer AR close to the cover layer 140 to the opposite side C2, a refractive index decreasing from the side C1 to the side C2 can be formed in the anti-reflection layer AR , which is conducive to light output. In some embodiments, the antireflection layer AR may comprise a graded refractive index multilayer structure.

FIG. 3 is a schematic cross-sectional view of a display device 30 according to an embodiment of the present invention. The display device 30 includes a circuit substrate 110 , a light-emitting element 120 , pads P1 , P2 , an adhesive layer 130 and a cover layer 143 , and the light-emitting element 120 includes a first electrode E1 , a second electrode E2 and a light-emitting stack SS, wherein the light-emitting stack The light emitting layer in layer SS has a real part of the complex refractive index _nLED , the subbing layer 130 has an average real part of the complex refractive index n _A , the cover layer 143 has an average real part of the complex refractive index n _B , and (n _A +n _B )/ n _LEDs are between 1.45 and 1.75. Compared with the display device 10 shown in FIG. 1A , the display device 30 shown in FIG. 3 is different in that: the cover layer 143 of the display device 30 may include a plurality of color filter structures CF, and the upper layer of the adhesive layer 130 The surface 130T may be substantially flush with the upper surface 120T of the light emitting element 120 .

In this embodiment, the orthographic projections of the plurality of color filter structures CF on the circuit substrate 110 may overlap the orthographic projections of the plurality of light-emitting elements 120 on the circuit substrate 110 respectively, so as to filter the light from the corresponding light-emitting elements 120 respectively. , and the color of the color filter structure CF may be the same as the light color of the corresponding light-emitting element 120 . For example, when the corresponding light-emitting element 120 is a blue light-emitting diode, the color filter structure CF can be a blue color filter; when the corresponding light-emitting element 120 is a green light-emitting diode, the color filter structure CF CF may be a green color filter; and when the corresponding light emitting element 120 is a red light emitting diode, the color filter structure CF may be a red color filter.

In this embodiment, the display device 30 may further include a plurality of light-shielding structures BM and a light-transmitting cover plate CV, wherein the color filter structures CF and the light-shielding structures BM may be alternately formed on the surface of the light-transmitting cover plate CV close to the light-emitting element 120 . above, and the color filter structure CF, the light-shielding structure BM and the light-transmitting cover plate CV can constitute the color filter substrate CS. By placing the light-shielding structures BM between the color filter structures CF respectively, and the orthographic projection of the light-shielding structure BM on the circuit substrate 110 is located outside the orthographic projection of the light-emitting element 120 on the circuit substrate 110 , it is possible to avoid affecting the light output, and at the same time, it is possible to reduce the amount of light emitted. Dark-state brightness and improved color contrast.

To sum up, the display device of the present invention can effectively improve the light extraction efficiency of the light-emitting element by controlling the complex refractive index of the adhesive layer and the cover layer around the light-emitting element.

Although the present invention has been disclosed above by the embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, The protection scope of the present invention shall be determined by the scope of the appended patent application.

10, 20, 30: Display device

110: circuit substrate

112: Bottom plate

114: Driver circuit layer

120: Light-emitting element

120T: Upper surface

130, 132: Adhesive layer

130T: Upper surface

140, 143: Overlay

AR: Anti-Reflection Layer

BM: shading structure

C1, C2: side

CF: Color filter structure

CH: semiconductor layer

CS: Color Filter Substrate

CV: translucent cover

DE: drain

DM: Dye

DP: Dye Particles

DS: dye

E1: The first electrode

E2: Second electrode

EL: light-emitting layer

GE: gate

I1: Buffer layer

I2: gate insulating layer

I3: Interlayer insulating layer

I4: flat layer

P1, P2: pads

S1: first type semiconductor layer

S2: Second type semiconductor layer

SE: source

SS: Light Emitting Laminate

T: Active element

FIG. 1A is a schematic cross-sectional view of a display device 10 according to an embodiment of the present invention. FIG. 1B is a simulation diagram of light extraction efficiency of the display device 10 according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a display device 20 according to an embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of a display device 30 according to an embodiment of the present invention.

10: Display device

110: circuit substrate

112: Bottom plate

114: Driver circuit layer

120: Light-emitting element

120T: Upper surface

130: Adhesive layer

130T: Upper surface

140: Overlay

CH: semiconductor layer

DE: drain

E1: The first electrode

E2: Second electrode

EL: light-emitting layer

GE: gate

I1: Buffer layer

I2: gate insulating layer

I3: Interlayer insulating layer

I4: flat layer

P1, P2: pads

S1: first type semiconductor layer

S2: Second type semiconductor layer

SE: source

SS: Light emitting stack

T: Active element

Claims (11)

A display device includes: a circuit substrate; a plurality of light-emitting elements located on the circuit substrate and electrically connected to the circuit substrate, respectively including a light-emitting layer; an adhesive layer located on the circuit substrate and the circuit substrate and the circuit substrate between the plurality of light-emitting elements; and a cover layer covering the plurality of light-emitting elements and the adhesive layer, wherein the adhesive layer has a real part of a complex refractive index n _A , and the cover layer has a real complex refractive index part n _B , the light-emitting layer has a real part of the complex refractive index n _LED , and (n _A +n _B )/n _LED is between 1.45 and 1.75, the imaginary part of the complex refractive index of the cover layer is smaller than that of the glue The imaginary part of the complex refractive index of the layer. The display device of claim 1, wherein n _A /n _LED is between 0.8 and 0.95. A display device includes: a circuit substrate; a plurality of light-emitting elements located on the circuit substrate and electrically connected to the circuit substrate, respectively including a light-emitting layer; an adhesive layer located on the circuit substrate and the circuit substrate and the circuit substrate between the plurality of light-emitting elements; and a cover layer covering the plurality of light-emitting elements and the adhesive layer, wherein the adhesive layer has a complex refractive index real part n _A , and the cover layer has a complex refractive index real part n A . Part n _B , the light emitting layer has a real part of the complex refractive index n _LED , and (n _A +n _B )/n _LED is between 1.45 and 1.75, n _A <n _B <n _LED . A display device includes: a circuit substrate; a plurality of light-emitting elements located on the circuit substrate and electrically connected to the circuit substrate, respectively including a light-emitting layer; an adhesive layer located on the circuit substrate and the circuit substrate and the circuit substrate between the plurality of light-emitting elements; and a cover layer covering the plurality of light-emitting elements and the adhesive layer, wherein the adhesive layer has a real part of a complex refractive index n _A , and the cover layer has a real complex refractive index part n _B , the light-emitting layer has a real part of the complex refractive index n _LED , and (n _A +n _B )/n _LED is between 1.45 and 1.75, the upper surface of the adhesive layer is not higher than the light-emitting element the upper surface. The display device of claim 1, 3 or 4, wherein the subbing layer includes a dye, and the color of the dye is the same as the light color of the light-emitting element. The display device of claim 5, wherein the dye comprises dye particles and a dye, and the real part of the complex refractive index of the dye particles is greater than the real part of the complex refractive index of the dye. The display device of claim 1, 3 or 4, wherein the cover layer includes a plurality of color filter structures. The display device according to claim 7, wherein the color of the color filter structure is the same as the light color of the corresponding light-emitting element. The display device of claim 1, 3 or 4, further comprising an anti-reflection layer on the cover layer. The display device of claim 9, wherein an imaginary part of the complex refractive index of the anti-reflection layer is close to zero. The display device of claim 9, wherein the antireflection layer comprises a destructive interference antireflection layer or a graded index antireflection layer.

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