Display device

Abstract

The present disclosure relates to a display device. More particularly, according to one aspect of the present disclosure, a display device includes: a substrate; a thin film transistor disposed on the substrate; a planarization layer disposed on the thin film transistor; the light emitting diode is arranged on the planarization layer; and an encapsulation layer disposed to cover the plurality of light emitting diodes; and wherein the planarization layer includes a first planarization layer disposed to cover the thin film transistor and a second planarization layer disposed to cover at least a portion of the first planarization layer, the refractive index of the first planarization layer being lower than the refractive index of the second planarization layer, and the first planarization layer includes an acrylic adhesive and a (meth) acrylic-benzyl (meth) acrylic copolymer.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Korean Patent Application No. 10-2024-0029870 filed on February 29, 2024, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. Background Art Technical Field

[0003] The present disclosure relates to a display device, and more particularly, to a display device having improved reliability and excellent light extraction efficiency by introducing a low-refractive planarization layer.

[0004] Description of the Prior Art

[0005] An organic light emitting display (OLED) is a self-luminous display device. As such, OLEDs can be manufactured with a lightweight and thin design, are advantageous in terms of power consumption due to lower voltage operation, and offer advantages in terms of excellent color reproduction, response speed, viewing angle, and contrast.

[0006] Such an organic light-emitting display device can be driven in a top emission type and a bottom emission type. In the top emission type, light emitted from the organic light-emitting diode is emitted to the top of the organic light-emitting display device, and in the bottom emission type, light is emitted to the bottom of the organic light-emitting display device. That is, in a bottom emission type organic light-emitting display device, light emitted from the organic light-emitting diode is emitted toward the bottom surface of a substrate on which a thin film transistor for driving the organic light-emitting display device is formed. In such a bottom emission type organic light-emitting display device, it is necessary to extract light emitted from the organic light-emitting layer to the outside of the organic light-emitting display device. However, some light is captured in the organic light-emitting display device due to total reflection of the substrate, and another part of the light is captured in the organic light-emitting display device due to total reflection of a layer formed by a metal such as an anode. Therefore, according to the bottom emission type, it is very important to improve the efficiency of light extraction to the outside of the organic light-emitting display device to improve efficiency. Summary of the Invention

[0007] A method for forming each layer (such as a planarization layer, an anode, an organic light-emitting layer, and a cathode) of an organic light-emitting display device with a microlens array structure has been proposed to improve the light extraction efficiency of the organic light-emitting display device. However, there are difficulties in the process of forming the microlens shape of each layer, and there are problems such as rainbow spots.

[0008] Therefore, in order to provide a flat surface while improving light extraction efficiency, a structure has been proposed in which a high-refractive-index planarization layer is formed adjacent to the anode with a higher refractive index, and a low-refractive-index planarization layer is formed adjacent to the substrate. As described above, when planarization layers with different refractive indices are stacked, the difference in refractive index needs to be adjusted to 0.2 or greater to maximize light extraction efficiency.

[0009] In the prior art, fluororesins with low refractive index are used to create a planarization layer with low refractive properties. However, fluororesins are hydrophobic, which leads to poor adhesion to upper and lower layers. Furthermore, while low-refractive nanoparticles dispersed in a base resin to form a low-refractive planarization layer exhibit excellent low-refractive properties, light absorption is blocked during the photolithography process to form the microlens array structure, making it difficult to form the lens pattern. Therefore, a method has been proposed to form a low-refractive planarization layer using a silicone-acrylic fluororesin. In this case, the fluorine component results in poor adhesion to the upper and lower layers. Furthermore, during the process of forming the anode of a light-emitting diode, after depositing the electrode material, insufficient adhesion during the development process can lead to loss of electrode material, causing lighting failures. Furthermore, when forming a low-refractive planarization layer using these materials, the roughness of the low-refractive planarization layer increases as the exposure, development, and baking steps proceed, which can reduce luminous efficiency. Furthermore, the prior art low-refractive planarization layers suffer from reduced transmittance in the short wavelength range due to yellowing after high-temperature reliability testing.

[0010] Therefore, an object of the present disclosure is to provide a display device including a low-refractive planarizing layer having a low refractive index of 1.50 or less and a high-refractive planarizing layer having a higher refractive index to improve light extraction efficiency.

[0011] Furthermore, an object of the present disclosure is to provide a display device that does not include a fluorine compound having hydrophobicity but provides a low-refractive planarization layer having low-refractive properties and improved adhesion to upper and lower layers to provide excellent workability and reliability.

[0012] Furthermore, an object of the present disclosure is to provide a display device having improved workability by providing a low-refractive planarization layer that enables light patterning to easily form a lens shape.

[0013] The objects of the present disclosure are not limited to the above objects, and those skilled in the art can clearly understand other objects not mentioned above from the following description.

[0014] According to one aspect of the present disclosure, a display device includes: a substrate; a thin film transistor disposed on the substrate; a planarization layer disposed on the thin film transistor; a light emitting diode disposed on the planarization layer; and an encapsulation layer configured to cover the plurality of light emitting diodes; and wherein the planarization layer includes a first planarization layer configured to cover the thin film transistor and a second planarization layer configured to cover at least a portion of the first planarization layer, the refractive index of the first planarization layer is lower than the refractive index of the second planarization layer, and the first planarization layer includes an acrylic adhesive and a (meth)acrylic acid-benzyl (meth)acrylic acid copolymer.

[0015] Additional details of exemplary embodiments are included in the detailed description and accompanying drawings.

[0016] According to the present disclosure, there is provided a display device including a first planarization layer having a low refractive index of 1.50 or less and a second planarization layer having a higher refractive index to improve light extraction efficiency.

[0017] According to the present disclosure, the first planarization layer does not include a hydrophobic fluorine compound and low-refractive particles, but has low-refractive properties, so that the adhesion with the upper and lower layers is excellent. Therefore, a display device with excellent processability and reliability is provided.

[0018] According to the present disclosure, the first planarization layer can be photo-patterned to easily form a lens shape and form a microlens structure at the interface of the first planarization layer and the second planarization layer without difficulty in these processes, thereby providing a display device with significantly improved light extraction efficiency.

[0019] Effects according to the present disclosure are not limited to those exemplified above, and more various effects are included in this specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and other aspects, features and other advantages of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0021] Figure 1 is a cross-sectional view of a display device according to an exemplary embodiment of the present disclosure;

[0022] Figure 2 is a graph showing the results of evaluating the high-temperature and high-humidity reliability of Example 1; and

[0023] Figure 3 This is a graph showing the results of evaluating the high-temperature reliability of Comparative Example 1. DETAILED DESCRIPTION

[0024] The advantages and features of the present disclosure and the methods for achieving the same will be described in detail below and in the accompanying drawings. Figure 1 The present disclosure will become more apparent with reference to the exemplary embodiments described in detail herein. However, the present disclosure is not limited to the exemplary embodiments disclosed herein, but may be implemented in various forms. The exemplary embodiments are provided only by way of example so that those skilled in the art can fully understand the disclosure and scope of the present disclosure.

[0025] The shapes, sizes, proportions, angles, quantities, etc. shown in the accompanying drawings for the purpose of describing exemplary embodiments of the present disclosure are merely examples, and the present disclosure is not limited thereto. Throughout the specification, similar reference numerals generally represent similar elements. In addition, in the subsequent description of the present disclosure, detailed explanations of known related arts may be omitted to avoid unnecessarily obscuring the subject matter of the present disclosure. Terms such as "including," "having," and "consisting of" used herein are generally intended to allow the addition of other components, unless these terms are used together with the term "only." Any reference to the singular may include the plural, unless otherwise expressly stated.

[0026] Even if not explicitly stated, components are interpreted as including the usual margins of error.

[0027] When terms such as "on," "above," "below," and "adjacent" are used to describe the positional relationship between two parts, one or more parts may be located between the two parts unless these terms are used with the terms "immediately" or "directly."

[0028] When an element or layer is referred to as being “on” another element or layer, the other layer or element can be directly interposed on the other element or between them.

[0029] Although the terms "first," "second," and the like are used to describe various components, these components are not limited by these terms. These terms are merely used to distinguish one component from other components. Therefore, within the technical concept of the present disclosure, the first component mentioned below may be the second component.

[0030] Like reference numbers generally refer to like elements throughout the specification.

[0031] The size and thickness of each component shown in the drawings are shown for convenience of description, and the present disclosure is not limited to the size and thickness of the components shown.

[0032] The features of the various embodiments of the present disclosure may be partially or entirely coupled or combined with each other and may be related and operated with each other in technically various ways, and these embodiments may be implemented independently of each other or in relation to each other.

[0033] Hereinafter, a display device according to an exemplary embodiment of the present disclosure will be described in detail with reference to the accompanying drawings.

[0034] Figure 1 is a cross-sectional view of a display device according to an exemplary embodiment of the present disclosure.

[0035] Reference Figure 1 The display device 100 according to an exemplary embodiment of the present disclosure includes a substrate 110, a first buffer layer 111, a light shielding layer LS, a second buffer layer 112, a thin film transistor 120, a passivation layer 131, a color filter 140, a first planarization layer 151, a second planarization layer 152 and a light emitting diode 160.

[0036] Substrate 110 supports the various components that make up display device 100. Substrate 110 can be formed of an insulating material. For example, substrate 110 can be a glass substrate, or it can be formed of a polymer material. For example, the polymer can be selected from polyethylene terephthalate, polyimide, etc., but is not limited thereto. Substrate 110 can be configured as a single layer or a multilayer structure.

[0037] Substrate 110 includes regions defined as an active area and an inactive area. The active area is the area where images are displayed. Multiple sub-pixels that display images and a driving circuit for driving the sub-pixels may be located in the active area. Each of the sub-pixels is a separate unit that emits light, and a light-emitting diode 160 is formed in each of the sub-pixels.

[0038] The plurality of sub-pixels may include, but are not limited to, red sub-pixels, green sub-pixels, and blue sub-pixels. The driving circuit may include various transistors, storage capacitors, and wiring for driving the plurality of sub-pixels. For example, the driving circuit may be configured from various components such as, but are not limited to, a driving transistor, a switching transistor, a sensing transistor, a storage capacitor, a gate line, and a data line.

[0039] The non-active region is an area surrounding the active region and does not actually display an image. Various wiring and driver ICs for driving the sub-pixels disposed in the active region are disposed in the non-active region. For example, various driver ICs, such as gate driver ICs and data driver ICs, may be disposed in the non-active region, but the present disclosure is not limited thereto.

[0040] The first buffer layer 111 may be provided on the substrate 110. The first buffer layer 111 protects the thin film transistor 120 and the light emitting diode 160 from moisture, external air, and foreign matter penetrating from the outside. In addition, the first buffer layer 111 may suppress changes in the characteristics of the thin film transistor 120 caused by hydrogen or foreign matter diffused from the substrate 110 during the formation process of the thin film transistor. The first buffer layer 111 may be formed of an inorganic insulating material. For example, the first buffer layer 111 may be formed of a material selected from a silicon oxide film, a silicon nitride film, or a silicon oxynitride film, but is not limited thereto. The first buffer layer 111 is formed into a single-layer or multi-layer structure. For example, the first buffer layer 111 may be formed of a multi-layer structure in which a silicon oxide film and a silicon nitride film are stacked, but is not limited thereto.

[0041] A light shielding layer LS may be provided on the first buffer layer 111. The light shielding layer LS blocks light such as ultraviolet rays incident from the outside of the display device 100 to suppress damage to the thin film transistor 120, particularly damage to the active layer 121, due to the light. Therefore, the light shielding layer LS is provided to overlap with the active layer 121 of the thin film transistor 120.

[0042] like Figure 1 As shown, in the thin film transistor 120 having a structure in which the gate 122 is disposed on the active layer 121, the active layer 121 may be damaged by ultraviolet rays incident from the substrate 110. A light shielding layer LS is disposed between the substrate 110 and the active layer 121 to protect the active layer 121 from ultraviolet rays.

[0043] The light shielding layer LS can be formed of a metal material. Since the light shielding layer LS is formed of a metal material, it can protect the active layer 121 from ultraviolet radiation. However, the contrast of the display device 100 may be reduced due to the high reflectivity. Therefore, to minimize the degradation of the contrast, the light shielding layer LS can be formed of a low-reflective metal. For example, the light shielding layer LS can be formed to include a metal selected from copper (Cu), molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), and niobium (Nd), but is not limited thereto.

[0044] The light shielding layer LS may be formed as a single layer or multiple layers. Figure 1 The light-shielding layer LS may include a first layer LS1 and a second layer LS2 on the first layer LS2. In this case, the first layer LS1 may be formed to include a relatively low-reflective metal to reduce the reflectivity of external light. For example, the first layer LS1 may be formed to include one or more metals selected from molybdenum (Mo), nickel (Ni), copper (Cu), and tungsten (W). Furthermore, to reduce reflectivity, the first layer LS1 may further include a metal oxide such as, but not limited to, MoO2, In2O3, SnO2, ZnO, Nb2O5, WO3, TiO2, ZrO2, and HfO2.

[0045] For example, the second layer LS2 may be formed to include one metal selected from copper (Cu), molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), and niobium (Nd), but is not limited thereto.

[0046] Although the light shielding layer LS is shown to have a double-layer structure in the drawings, it is not limited thereto, and the light shielding layer may be formed as a single layer, or as three or more layers.

[0047] The second buffer layer 112 is disposed on the light-shielding layer LS. The second buffer layer 112 insulates the light-shielding layer LS from the thin film transistor 120. Furthermore, during the process of forming the thin film transistor 120, the second buffer layer 112 blocks impurities flowing from the substrate 110 and the light-shielding layer LS. For example, the second buffer layer 112 may be formed of a material selected from a silicon oxide film, a silicon nitride film, or a silicon oxynitride film, but is not limited thereto.

[0048] The thin film transistor 120 is disposed on the second buffer layer 112 . The thin film transistor 120 includes an active layer 121 , a gate electrode 122 , a source electrode 123 , and a drain electrode 124 .

[0049] The active layer 121 is disposed on the second buffer layer 112. As described above, the active layer 121 is disposed on the second buffer layer 112 so as to overlap with the light shielding layer LS. Therefore, damage to the active layer 121 caused by ultraviolet rays can be suppressed. The active layer 121 can be formed of an oxide semiconductor material or polycrystalline silicon. When the active layer 121 is formed of polycrystalline silicon, the light shielding layer LS below it can be omitted. When the active layer 121 is formed of polycrystalline silicon, impurities can be doped on both edges of the active layer 121.

[0050] An insulating film ILD formed of an insulating material is provided on the active layer 121. The insulating film ILD is provided between the active layer 121 and the gate 122 to insulate the active layer 121 and the gate 122 from each other. The insulating film ILD may be formed of a material selected from a silicon oxide film, a silicon nitride film, and a silicon oxynitride film, but is not limited thereto.

[0051] A gate electrode 122 formed of a conductive material such as a metal may be disposed on the insulating film ILD. The gate electrode 122 is disposed to overlap with the channel region of the active layer 121. For example, the gate electrode 122 may be made of copper (Cu), aluminum (Al), molybdenum (Mo), nickel (Ni), titanium (Ti), chromium (Cr), or an alloy thereof, but is not limited thereto.

[0052] The source electrode 123 and the drain electrode 124 may be disposed on the insulating film ILD, similar to the gate electrode 122. The source electrode 123 and the drain electrode 124 may be made of, but are not limited to, copper (Cu), aluminum (Al), molybdenum (Mo), nickel (Ni), titanium (Ti), chromium (Cr), or alloys thereof. The source electrode 123 and the drain electrode 124 may be formed using the same material in the same process as the gate electrode 122, but are not limited thereto.

[0053] The source electrode 123 and the drain electrode 124 may each be provided to be electrically connected to the active layer 121. The source electrode 123 and the drain electrode 124 may be provided to contact both ends of the active layer 121 that are not covered by the insulating film ILD and are exposed. That is, the source electrode 123 may be provided to contact one end of the active layer 121, and the drain electrode 124 may be provided to contact the other end of the active layer 121.

[0054] The source electrode 123 or the drain electrode 124 can be arranged to contact the light shielding layer LS through a contact hole formed in the second buffer layer 112. When the light shielding layer LS is formed in an island shape so as to overlap with the active layer 121, parasitic capacitance may affect the performance of the thin film transistor 120. Therefore, the light shielding layer LS is connected to the source electrode 123 or the drain electrode 124 to apply a voltage to minimize the influence of the parasitic capacitance. However, the structure of the present disclosure is not limited to this, but can be varied according to the structure and design of the thin film transistor 120. As another example, the thin film transistor 120 can be formed as a bottom-gate thin film transistor, in which the gate electrode 122 is arranged below the active layer 121. In this case, the gate electrode 122 arranged below the active layer 121 can serve as a light shielding layer.

[0055] A passivation layer 131 is provided on the thin film transistor 120. The passivation layer 131 can suppress degradation of the thin film transistor 120 due to external moisture or oxygen. For example, the passivation layer 131 can be formed of an inorganic insulating material such as a silicon oxide film or a silicon nitride film, but is not limited thereto. If desired, the passivation layer 131 can be formed as a single layer or multiple layers as appropriate.

[0056] The display device 100 according to the exemplary embodiment of the present disclosure is driven in a bottom emission type, wherein the light emitted from the light emitting diode 160 is emitted to the bottom of the display device 100. Therefore, the color filter 140 can be provided on the passivation layer 131. The color filter 140 converts the white light emitted from the light emitting diode 160 into red light, green light and blue light. Therefore, the color filter 140 is provided to correspond to the light emitting area of ​​the light emitting diode 160. The color filter 140 converts the white light emitted from the light emitting diode 160 into light having a color corresponding to each of the plurality of sub-pixels to achieve full color and improve color reproducibility. When the light emitting diodes 160 formed in the plurality of sub-pixels emit red light, green light and blue light respectively, the color filter 140 can be omitted.

[0057] Planarization layers 151 and 152 are provided on the thin film transistor 120 and the color filter 140. The planarization layers 151 and 152 are provided on the thin film transistor 120 and the color filter 140 to provide a flat surface. Therefore, optical distortion such as rainbow spots can be suppressed.

[0058] The planarization layers 151 and 152 may include a first planarization layer 151 and a second planarization layer 152. The first planarization layer 151 is provided to cover the thin film transistor 120 and the color filter 140. The second planarization layer 152 is provided to cover at least a portion of the first planarization layer 151. For example, the second planarization layer 152 may be provided on the first planarization layer 151 so as to correspond to the light emitting area of ​​the light emitting diode 160. However, this is not limiting, and if desired, the second planarization layer 152 may be provided on the entire surface of the first planarization layer 151 as appropriate.

[0059] The first planarization layer 151 and the second planarization layer 152 will be described below.

[0060] Light-emitting diode 160 is disposed on planarization layers 151 and 152. Light-emitting diode 160 includes an anode 161, an organic light-emitting layer 162, and a cathode 163. Anode 161 of light-emitting diode 160 is electrically connected to source electrode 123 or drain electrode 124 of the thin-film transistor through a contact hole formed in planarization layers 151 and 152. Although the drawings illustrate that anode 161 is electrically connected to source electrode 123, the present disclosure is not limited thereto. Anode 161 may also be electrically connected to drain electrode 124.

[0061] The anode 161 is disposed on the planarization layers 151 and 152. The anode 161 may be formed of a conductive material having a high work function to supply holes to the organic light emitting layer 162. For example, the anode 161 may include a transparent conductive material such as indium tin oxide (ITO) and indium zinc oxide (IZO), but is not limited thereto.

[0062] The bank BNK is provided on the planarization layers 151 and 152 and the anode 161. The bank BNK is provided on the planarization layers 151 and 152 so as to expose at least a portion of the anode 161. In other words, the bank BNK can be provided on the planarization layers 151 and 152 so as to cover the edge of the anode 161. The bank BNK is an insulating layer provided between multiple sub-pixels to divide the sub-pixels. In this case, the exposed area not covered by the bank BNK can be defined as a light-emitting area that emits light. The bank BNK can be formed of an organic insulating material. For example, the bank BNK can be formed of polyimide, acryl, or benzocyclobutene (BCB) resin, but is not limited thereto.

[0063] The organic light-emitting layer 162 is disposed on the anode 161. The organic light-emitting layer 162 may be an organic layer that emits light having a specific color. The organic light-emitting layer 162 may be formed as a continuous layer over the entire active area. For example, the organic light-emitting layer 162 may be configured to emit white light, but is not limited thereto. As another example, the organic light-emitting layer 162 may be patterned to correspond to each of the multiple sub-pixels. In this case, the organic light-emitting layer 162 may be configured to emit light having a color corresponding to each of the multiple sub-pixels. Furthermore, in this case, the color filter 140 may be omitted.

[0064] If necessary, the organic light emitting layer 162 may further include various layers as appropriate, such as a hole transport layer, a hole injection layer, a hole blocking layer, an electron injection layer, an electron blocking layer, or an electron transport layer.

[0065] The cathode 163 is provided on the organic light-emitting layer 162. The cathode 163 may be formed as a continuous layer over the entire active area. That is, the cathode 163 may be a common layer formed in common in a plurality of sub-pixels. The cathode 163 supplies electrons to the organic light-emitting layer 162, so that the cathode may be formed of a conductive material having a low work function. For example, the cathode 163 may be formed of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO), or a metal such as magnesium (Mg) or silver (Ag), or an alloy including the metal, and may further include a metal doping layer, but is not limited thereto.

[0066] The display device 100 according to an exemplary embodiment of the present disclosure may be driven in a bottom emission type in which light emitted from the organic light emitting layer 162 is emitted toward the bottom of the display device 100 .

[0067] As described above, in the display device 100 driven in the bottom emission type, light emitted from the light emitting diode 160 is emitted to the bottom surface of the display device 100. In order to improve light extraction efficiency by minimizing the loss of light emitted from the light emitting diode 160, the first and second planarization layers 151 and 152 may be formed to have different refractive indices.

[0068] The refractive index of anode 161 of light-emitting diode 160 is higher than that of substrate 110 and the outside of display device 100, i.e., the air. Therefore, to minimize the loss of light emitted from light-emitting diode 160 to the bottom of display device 100, the refractive index of first planarization layer 151 adjacent to substrate 110 is formed to be lower than the refractive index of second planarization layer 152 adjacent to anode 161. In other words, the refractive index of first planarization layer 151 is lower than the refractive index of second planarization layer 152. In this case, when light emitted from light-emitting diode 160 is emitted to the bottom of display device 100, the light loss generated in display device 100 is minimized, thereby improving light extraction efficiency.

[0069] For example, the refractive index of the first planarization layer 151 is 1.45 to 1.50, and the refractive index of the second planarization layer 152 is 1.6 to 2.0. Furthermore, the difference between the refractive indexes of the first planarization layer 151 and the second planarization layer 152 is desirably 0.2 or greater. When the refractive index and the refractive index difference of the first planarization layer 151 and the second planarization layer 152 are within the above ranges, the light extraction efficiency of the display device 100 is improved, thereby having excellent display quality.

[0070] The microlens array structure can be formed at the interface where the first planarization layer 151 contacts the second planarization layer 152. For example, the first planarization layer 151 can have a plurality of raised portions and a plurality of recessed portions. The raised portions of the first planarization layer 151 are arranged adjacent to the recessed portions. That is, the recessed portions and the raised portions of the first planarization layer 151 are arranged alternately. The second planarization layer 152 can be formed along the surface shape of the first planarization layer 151. Therefore, the raised portions and the recessed portions can be formed on the bottom surface of the second planarization layer 152. Although the cross-sections of the recessed portions of the first planarization layer 151 and the raised portions of the second planarization layer 152 are shown as semicircular in the figure, the present disclosure is not limited thereto.

[0071] The raised portions of second planarization layer 152 and the recessed portions of first planarization layer 151 engage with each other to form contact. Specifically, the raised portions of second planarization layer 152 overlap with the recessed portions of first planarization layer 151, and the recessed portions of second planarization layer 152 overlap with the raised portions of first planarization layer 151. Thus, a microlens array structure can be formed at the interface where first and second planarization layers 151, 152 contact each other. Therefore, when light is incident on the interface between first and second planarization layers 151, 152, the incident angle of light emitted from light-emitting diode 160 is less than the critical angle for total internal reflection. Consequently, light emitted from light-emitting diode 160 is not lost due to total internal reflection at first and second planarization layers 151, 152, but instead propagates toward the bottom surface of display device 100, i.e., color filter 140, at a nearly right angle. Consequently, the efficiency of light extraction from display device 100 is improved, thereby increasing the brightness of display device 100 and improving display quality.

[0072] As described above, planarization layers 151 and 152 provide a flat surface. That is, the microlens array structure is formed only at the interface where first planarization layer 151 and second planarization layer 152 contact each other. Furthermore, the top surface of second planarization layer 152, which is positioned to correspond to the light-emitting region of light-emitting diode 160, and the top surface of first planarization layer 151, on which second planarization layer 152 is not positioned, can be flat. Consequently, light extraction efficiency is improved without optical distortion such as rainbow spots, significantly enhancing display quality.

[0073] Hereinafter, materials constituting the first planarization layer 151 and the second planarization layer 152 will be described in detail.

[0074] First, the second planarization layer 152 is formed of a material having a higher refractive index than the first planarization layer 151. For example, the second planarization layer 152 may be formed of one of acrylic resin, epoxy resin, phenolic resin, polyamide resin, polyimide resin, unsaturated polyester resin, polyphenylene resin, polyphenylene sulfide resin, benzocyclobutene, and photoresist, but is not limited thereto.

[0075] As described above, in order to further improve light extraction efficiency, the refractive index difference between the first planarization layer 151 and the second planarization layer 152 is desirably 0.2 or greater. Therefore, the first planarization layer 151 is formed to have a low refractive index of 1.50 or less.

[0076] For example, the first planarization layer 151 can be formed by curing a composition including an acrylic adhesive, a (meth) acrylic acid-benzyl (meth) acrylic acid copolymer and an initiator. The first planarization layer 151 formed as described above does not include low-refractive particles or fluorine materials, but has a low refractive index of 1.50 or less, and has excellent adhesion to the upper and lower layers, thereby providing excellent reliability while improving the light extraction efficiency of the display device 100. In the related art, as the exposure, development and baking processes proceed, the surface roughness of the low-refractive planarization layer formed by the silicone-acrylic fluororesin increases (about 5nm level), thereby causing a problem of reduced luminous efficiency. According to the present disclosure, the first planarization layer 151 is formed to include an acrylic adhesive and a (meth) acrylic acid-benzyl (meth) acrylic acid copolymer, and its roughness is 2nm or less after the exposure, development and baking processes. Therefore, when the first planarization layer 151 according to the present disclosure is provided, it has the advantage of excellent light extraction efficiency.

[0077] For example, the first planarization layer 151 can be formed by curing a composition comprising 65 to 75 weight % of a solvent, 10 to 20 weight % of an acrylic adhesive, 10 to 20 weight % of a (meth) acrylic acid-benzyl (meth) acrylic acid copolymer, and 0.2 to 10 weight % of an initiator, based on 100 weight % of the composition. In this case, light extraction efficiency is excellent while having low refractive properties, and adhesion to upper and lower layers is improved, thereby ensuring excellent reliability of the display device 100.

[0078] When the first planarization layer 151 is formed through a photolithography process, the (meth)acrylic acid-benzyl (meth)acrylic acid copolymer improves developability in a post-exposure development step and serves as a crosslinking agent for an acrylic adhesive to increase the density of the first planarization layer 151. Therefore, by improving adhesion to layers above and below the first planarization layer 151, a display device 100 having excellent reliability can be provided. Furthermore, the thermal stability of the first planarization layer 151 is improved, enabling high-temperature processes.

[0079] In addition, when the initiator content in the composition is high, the yellowing degree of the first planarization layer 151 increases during high-temperature processes, thereby reducing the transmittance. The first planarization layer 151 of the present disclosure is produced using a composition with a low initiator content of 0.2% to 10% by weight, and has the high thermal stability of the composition to improve the yellowing degree, so that the problem of reduced transmittance in the short wavelength band in the related art can be solved. In addition, there is a trend that the higher the initiator content, the higher the refractive index of the first planarization layer 151. Therefore, in order to ensure low refractive properties, it is desirable to control the initiator content within the above range.

[0080] In addition, when a predetermined level or more of the metal catalyst remains in the composition, the degree of yellowing will increase after the high-temperature process. Therefore, the residual amount of the metal catalyst in the composition is ideally kept at a low level of 0.02ppm to 0.05ppm. Within this range, the first planarization layer 151 has a high transmittance of 99% or more in a wide band of 380nm to 780nm, and has excellent optical properties with low yellowing and haze, so that the display quality of the display device 100 can be significantly improved. When the residual amount of the metal catalyst exceeds 0.05ppm, the yellowing and haze values ​​are very high, and the transmittance in the short band of 380nm is reduced, which will reduce the display quality. In addition, when the residual amount of the metal catalyst is 0.02ppm or less, there is a problem of residual film surviving after the photolithography process.

[0081] For example, the acrylic adhesive may be one or more selected from the group consisting of methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, methyl acrylate, isopropyl acrylate, cyclohexyl methacrylate, 2-methylcyclohexyl methacrylate, dicyclopentenyl acrylate, dicyclopentenyl acrylate, dicyclopentenyl methacrylate, dicyclopentanyl methacrylate, 1-adamantyl acrylate, 1-adamantyl methacrylate, dicyclopentyloxyethyl methacrylate, isobornyl methacrylate, cyclohexyl acrylate, 2-methylcyclohexyl acrylate, tricyclopentyloxyethyl acrylate, isobornyl acrylate, phenyl methacrylate, phenyl acrylate, and benzyl acrylate, but is not limited thereto.

[0082] If necessary, the acrylic adhesive may further include an acrylic multifunctional monomer. In this case, developability can be improved and residual film during the photolithography process can be minimized. For example, the acrylic multifunctional monomer can be one or more selected from the group consisting of: 1,4-butanediol diacrylate, 1,3-butanediol diacrylate, ethylene glycol diacrylate, trimethylolpropane diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, dipentaerythritol hexaacrylate, dipentaerythritol triacrylate, dipentaerythritol diacrylate, sorbitol triacrylate, bisphenol A diacrylate derivatives, dipentaerythritol polyacrylate, methacrylate, fluorinated acrylate, and fluorinated methacrylate, but is not limited thereto.

[0083] The solvent can facilitate the photolithography process by controlling the spreadability of the composition. For example, the solvent can be one or more selected from the group consisting of ethylene glycol monoalkyl ether, propylene glycol monoalkyl ether, dipropylene glycol alkyl ether, butylene glycol monomethyl ether, dibutylene glycol alkyl ether, diethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, propylene glycol propyl ether acetate, propylene glycol methyl ether propionate, propylene glycol ethyl ether propionate, propylene glycol propyl ether propionate, propylene glycol methyl ether, propylene glycol ethyl ether ... Propyl alcohol ether, propylene glycol butyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dibutyl glycol monomethyl ether, dibutyl glycol monoethyl ether, dibutyl glycol dimethyl ether, dibutyl glycol diethyl ether, diethylene glycol butyl methyl ether, diethylene glycol butyl ethyl ether, triethylene glycol dimethyl ether, triethylene glycol butyl methyl ether, diethylene glycol tert-butyl ether, tetraethylene glycol dimethyl ether, diethylene glycol ethylhexyl ether, diethylene glycol methylhexyl ether, dipropylene glycol butyl methyl ether, dipropylene glycol ethylhexyl ether and propylene glycol methylhexyl ether, but are not limited thereto.

[0084] For example, the initiator may be one or more selected from the group consisting of 1-[4-(phenylthio)phenyl]-1,2-octanedione 2-(O-benzoyl oxime), 1-{6-[4-(2,2-dimethyl-[1,3]dioxan-4-ylmethyl)benzoyl]-9-ethyl-9H-carbazol-3-yl}-ethanone oxime-O-acetate, 1-[9-ethyl-6-(4-diethylamino-4-benzoyl)-9H-carbazol-3-yl]-ethanone oxime-O-acetate, 1-[9-ethyl-6-(4-phenylsulfonyl-4-benzoyl)-9H-carbazol-3-yl]ethanone oxime-O-acetate, [9-ethyl-6-(4-(2,6-dimethylmorpholin-4-benzoyl)-9H-carbazol-3-yl]-ethanone oxime-O-acetate, 1-[9-ethyl-6-(2-methyl-benzoyl)-9H-carbazol-3-yl]-ethanone oxime-O-acetate, 1-{6-[4-(2,2-dimethyl-[1,3]dioxan-4-ylmethyl)-2-methyl-benzoyl]-9-ethyl-9H-carbazol-3-yl}-ethanone oxime-O-acetate, and 1-[9-ethyl-6-(2-methyl-4-morpholin-4-yl-benzoyl)-9H-carbazol-3-yl]-ethanone oxime-O-acetate, but are not limited thereto.

[0085] The composition for forming the first planarization layer 151 may further include a low-refractive compound having a bulky functional group to reduce the refractive index, thereby making the first planarization layer 151 have a porous structure. For example, the low-refractive compound may be at least one of a polystyrene block copolymer, dodecyl (meth)acrylate, and acrylic acid containing a cycloolefin group.

[0086] For example, the polystyrene block copolymer may include one or more selected from the group consisting of compounds represented by Formula 1 and Formula 2 below.

[0087] [Formula 1]

[0088]

[0089] [Formula 2]

[0090]

[0091] For example, m and n in Formula 1 and x and y in Formula 2 may independently be integers of 1 to 100.

[0092] For example, the acrylic acid containing a cycloolefin group may be 5-norbornene-2-acrylic acid, but is not limited thereto.

[0093] Such a compound may have a relatively large functional group within the molecule to form a porous structure within the first planarization layer 151. Therefore, the refractive index of the first planarization layer 151 may be formed to be low.

[0094] For example, the low-refractive compound may be included in an amount of 0.1 to 50 parts by weight based on 100 parts by weight of the acrylic adhesive. Within this range, the refractive index of the first planarization layer 151 is reduced to further improve light extraction efficiency.

[0095] The composition for forming the first planarization layer 151 may further include a thermosetting monomer including at least one of an epoxy group and a hydroxyl group. This improves thermal stability, thereby facilitating high-temperature processes, and suppresses an increase in yellowing while maintaining high light transmittance.

[0096] For example, the thermosetting monomer may be a monomer including a functional group, such as oxetane or tetrahydrofuran. For example, the content of the thermosetting monomer may be 1 to 40 parts by weight based on 100 parts by weight of the acrylic adhesive. Within this range, the heat resistance of the first planarization layer 151 is excellent.

[0097] The composition used to form the first planarization layer 151 may further include one or more unsaturated carboxylic acids selected from acrylic acid, methacrylic acid, maleic acid, fumaric acid, citraconic acid, mesaconic acid, and itaconic acid. This improves the solubility of the acrylic binder, thereby providing the first planarization layer 151 with uniform physical properties. For example, the content of the unsaturated carboxylic acid may be 1 to 30 parts by weight based on 100 parts by weight of the acrylic binder. Within this range, the solubility of the acrylic binder can be improved without degrading the physical properties of the first planarization layer 151.

[0098] If necessary, the composition for forming the first planarization layer 151 may further include additives such as a coupling agent or a UV absorber. The content of the additives may be 0.1 parts by weight to 30 parts by weight based on 100 parts by weight of the acrylic adhesive, but is not limited thereto.

[0099] The coupling agent improves the adhesion to the upper layer and the lower layer. For example, the coupling agent can be one or more selected from silane coupling agents, such as (3-glycidyl propoxy) trimethoxysilane, (3-glycidyl propoxy) triethoxysilane, (3-glycidyl propoxy) methyldimethoxysilane, (3-glycidyl propoxy) methyldiethoxysilane, (3-glycidyl propoxy) dimethylethoxysilane, 3,4-epoxybutyltrimethoxysilane, 3,4-epoxybutyltriethoxysilane, 2-(3,4-epoxycyclohexyl) ethyltrimethoxysilane, 2- (3,4-Epoxycyclohexyl)ethyltriethoxysilane, aminopropyltrimethoxysilane, aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylene)propylamine, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, and (3-isocyanatepropyl)triethoxysilane, but are not limited thereto.

[0100] For example, the coupling agent may be included in an amount of 0.1 parts by weight to 10 parts by weight based on 100 parts by weight of the acrylic adhesive, and within this range, adhesion is excellent.

[0101] UV absorbers absorb unwanted ultraviolet rays to suppress degradation caused by light and improve optical properties. For example, UV absorbers may include, but are not limited to, benzophenone, triazine, benzotriazole, aniline, and the like. For example, the UV absorber may be present in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the acrylic adhesive.

[0102] The first planarization layer 151 formed as described above does not include a hydrophobic fluorine compound and low-refractive particles such as porous silica, but has low-refractive properties. Therefore, there is an advantage of excellent adhesion to the upper and lower layers of the first planarization layer 151. Therefore, a display device 100 with excellent workability and reliability is provided.

[0103] According to an exemplary embodiment of the present disclosure, the surface of the first planarization layer 151 and the surface of the second planarization layer 152 can be independently plasma-treated with a gas selected from oxygen, nitrogen, hydrogen, and helium. In this case, the surface energy of the first planarization layer 151 and the second planarization layer 152 is increased, and the contact angle is reduced, thereby increasing hydrophilicity. As a result, the adhesion between the first planarization layer 151 and the second planarization layer 152, as well as the adhesion between the first planarization layer 151, the second planarization layer 152, and the anode 161 can be further improved. Specifically, by plasma-treating with nitrogen, hydrogen, or helium, adhesion can be further improved, and defects such as cracking and / or missing of the anode 161 can be suppressed.

[0104] The display device 100 according to an exemplary embodiment of the present disclosure includes a first planarization layer 151, which includes an acrylic adhesive and a (meth) acrylic acid-benzyl (meth) acrylic acid copolymer. Even if the first planarization layer 151 of the present disclosure does not include low-refractive particles or fluorine-based materials, the first planarization layer has low-refractive properties and excellent adhesion to the upper and lower layers, and facilitates the formation of a lens shape through a photolithography process. Therefore, the display device 100 including the first planarization layer 151 according to the present disclosure has advantages in process, improves light extraction efficiency and provides excellent display quality. In addition, the adhesion of the first planarization layer 151 is improved, so that the optical properties do not change after high temperature / high humidity reliability evaluation, and defects such as missing or cracked anode 161 are improved.

[0105] Hereinafter, the effects of the present disclosure described above will be described with reference to Examples. However, the following Examples are set forth to illustrate the present disclosure, but the scope of the present disclosure is not limited thereto.

[0106] [Example 1]

[0107] A mixture is prepared by mixing 10 to 20 parts by weight of an acrylic adhesive, 20 parts by weight of a methacrylic acid-benzyl methacrylic acid copolymer, 72 parts by weight of propylene glycol monomethyl ether acetate as a solvent, 5 parts by weight of 2-(O-benzoyl oxime)-1-[4-(phenylthio)phenyl]-1,2-octanedione as an initiator, 1 part by weight of 2,4-bis(2-hydroxy-4-butoxyphenyl)-6-(2,4-dihydroxyphenyl)-1,3,5-triazine as a UN absorber, 1 part by weight of (3-isocyanatepropyl)triethoxysilane as a silane coupling agent, and 1 part by weight of a silicone surfactant. Propylene glycol monoethyl acetate is added so that the solid content of the mixture is 20 to 30 parts by weight, and the mixture is dissolved to prepare a photosensitive resin composition for a first planarization layer. The composition is used to form a low-refractive planarization layer on a substrate.

[0108] [Comparative Example 1]

[0109] A low-refractive planarizing layer was formed on a substrate using a photosensitive resin composition for a first planarizing layer, wherein the composition included an acrylic binder but did not include the methacrylic acid-benzyl methacrylic acid copolymer in Example 1.

[0110] [Comparative Examples 2 to 6]

[0111] A low-refractive planarization layer was formed on a substrate using a photosensitive resin composition for a first planarization layer. The composition included a silicone adhesive and an acrylic adhesive in proportions as shown in Table 1 below.

[0112] [Experimental Example 1]

[0113] The refractive index and surface roughness of each sample of Example 1 and Comparative Example 1 were measured, and the results are shown in Table 1 below.

[0114] [Table 1]

[0115]

[0116] Referring to Table 1, it was confirmed that the low-refractive layer formed of the composition for forming the first planarization layer according to Example 1 had a low refractive index and low surface roughness. Therefore, it can be understood that when the low-refractive planarization layer according to the present disclosure is included, light extraction efficiency can be improved.

[0117] Unlike Example 1, it was confirmed that the low-refractive planarizing layer of Comparative Example 1, which did not include the methacrylic acid-benzyl methacrylic acid copolymer, had a higher refractive index and higher surface roughness than those of Example 1.

[0118] [Experimental Example 2]

[0119] The refractive index and surface roughness of each sample of Example 1 and Comparative Examples 2 to 6 were measured, and the results are shown in Table 2 below.

[0120] [Table 2]

[0121]

[0122] Referring to Table 2, it was confirmed that the low-refractive layer formed of the composition for forming the first planarization layer according to Example 1 had a low refractive index and low surface roughness. Therefore, it can be understood that when the low-refractive planarization layer according to the present disclosure is included, light extraction efficiency can be improved.

[0123] Referring to Comparative Examples 2 to 6 together, it was confirmed that when the acrylic adhesive and the silicone adhesive were mixed, the higher the content of the silicone adhesive, the lower the refractive index, but the surface roughness increased significantly.

[0124] As can be seen from Comparative Examples 2 to 6 above, refractive index and roughness have a complementary relationship. Therefore, it can be understood that the low-refractive planarization layer of Example 1, formed from a composition including a methacrylic acid-benzyl methacrylic acid copolymer and not including a silicone-based adhesive, has the lowest surface roughness and low refractive index, effectively reducing reflectivity.

[0125] [Experimental Example 3]

[0126] Experimental Example 3 was conducted to find out the electro-optical characteristics of a unit cell including the low-refractive planarizing layer of each of Example 1 and Comparative Examples 1 and 7. Comparative Example 7 was prepared using a low-refractive planarizing layer including a fluorine-containing acrylic resin. The results are shown in Table 3 below.

[0127] [Table 3]

[0128]

[0129] Referring to Table 3, it was confirmed that the unit cell equipped with the low-refractive planarization layer according to Example 1 had excellent color reproducibility and the highest luminous efficiency.

[0130] As described above, the low-refractive flattening layer according to Example 1 of the present disclosure has the advantages of a lower refractive index and low surface roughness than the low-refractive flattening layer of Comparative Example 1. Therefore, according to Example 1, it was confirmed that the adhesion between the low-refractive flattening layer and its upper layer was improved, thereby having a higher luminous efficiency than that of Comparative Example 1. When a fluorine-containing acrylic resin, which is a material used for a low-refractive flattening layer in the related art, is included, the refractive index is low due to the fluorine component, but it is hydrophobic and thus provides poor adhesion to the upper layer. Therefore, it was confirmed that in Comparative Example 7, the refractive index of the low-refractive flattening layer is lower than that of the low-refractive flattening layer of Example 1, but the efficiency is lower than that of Example 1.

[0131] [Experimental Example 4]

[0132] The high temperature and high humidity reliability of the low refractive index planarizing layer according to Example 1 was evaluated. The high temperature and high humidity reliability was evaluated by measuring the transmittance after storing the sample of Example 1 under the conditions of a temperature of 85 degrees and a relative humidity of 85% for 0 to 1000 hours. The results are shown in Figure 2 For comparison, the evaluation results of the high temperature reliability of the low refractive index planarizing layer of Comparative Example 1 are shown to Figure 3 middle.

[0133] Figure 2 This is a graph showing the results of evaluating the high-temperature (85° C.) and high-humidity (85%) reliability of Example 1. Figure 3 This is a graph showing the results of evaluating the high-temperature (60° C.) reliability of Comparative Example 1.

[0134] Reference Figure 2 , it was confirmed that the light transmittance did not change even when the low-refractive flattening layer according to Example 1 was stored under high-temperature and high-humidity conditions for 1000 hours.

[0135] In comparison, reference Figure 3 Even if the low-refractive flattening layer according to Comparative Example 1 is not stored under high temperature conditions (0 hours), the transmittance in the short wavelength band of 380nm to 430nm is reduced. In addition, even when the low-refractive flattening layer according to Comparative Example 1 is tested under a temperature condition of 60 degrees, which is lower than that of Example 1, the transmittance in the short wavelength band is significantly reduced.

[0136] Therefore, it can be understood that the low-refractive planarization layer formed according to the present disclosure has excellent reliability for a high-temperature and high-humidity environment.

[0137] Exemplary embodiments of the present disclosure may also be described as follows:

[0138] According to one aspect of the present disclosure, a display device is provided. The display device includes: a substrate; a thin film transistor disposed on the substrate; a planarization layer disposed on the thin film transistor; and a light-emitting diode disposed on the planarization layer, wherein the planarization layer includes a first planarization layer disposed to cover the thin film transistor and a second planarization layer disposed to cover at least a portion of the first planarization layer, wherein the first planarization layer has a lower refractive index than the second planarization layer, and the first planarization layer includes an acrylic adhesive and a (meth)acrylic acid-benzyl (meth)acrylic acid copolymer.

[0139] The display device may further include: a passivation layer disposed to cover the thin film transistor; and a color filter disposed on the passivation layer to correspond to a light emitting region of the light emitting diode, wherein the planarization layer may be disposed to cover the color filter.

[0140] The refractive index of the first planarization layer may be 1.45 to 1.50, and the refractive index of the second planarization layer may be 1.6 to 2.0.

[0141] The second planarization layer may be disposed on the first planarization layer to correspond to a light emitting region of the light emitting diode.

[0142] At least a portion of the surface of the second planarization layer in contact with the first planarization layer may include a convex portion, at least a portion of the surface of the first planarization layer in contact with the second planarization layer may include a concave portion corresponding to the convex portion, and the convex portion and the concave portion may engage with each other to contact each other.

[0143] The first planarization layer may be a cured material of a composition including an acrylic adhesive, a (meth)acrylic acid-benzyl (meth)acrylic acid copolymer, and an initiator.

[0144] The composition may further include at least one low refractive compound of a polystyrene block copolymer, dodecyl (meth)acrylate, and acrylic acid containing a cycloolefin group.

[0145] The polystyrene block copolymer may include one or more compounds selected from the group consisting of the compounds represented by the following Formula 1 and Formula 2:

[0146] [Formula 1]

[0147]

[0148] [Formula 2]

[0149]

[0150] (wherein m and n in Formula 1 and x and y in Formula 2 are independently integers of 1 to 100).

[0151] The composition may further include a thermosetting monomer including at least one of an epoxy group and a hydroxyl group.

[0152] The composition may further include one or more unsaturated carboxylic acids selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, fumaric acid, citraconic acid, mesaconic acid, and itaconic acid.

[0153] The composition may include 65 to 75 wt % of a solvent, 10 to 20 wt % of an acrylic binder, 10 to 20 wt % of a (meth)acrylic acid-benzyl (meth)acrylic acid copolymer, and 0.2 to 10 wt % of an initiator, based on 100 wt % of the composition.

[0154] The low refractive compound may be included in an amount of 0.1 parts by weight to 50 parts by weight based on 100 parts by weight of the acrylic adhesive.

[0155] The thermosetting monomer may be included in an amount of 1 to 40 parts by weight based on 100 parts by weight of the acrylic adhesive.

[0156] The unsaturated carboxylic acid may be present in an amount of about 1 part by weight to about 30 parts by weight based on about 100 parts by weight of the acrylic adhesive.

[0157] The surface of the first planarization layer and the surface of the second planarization layer may be plasma-treated with a gas selected from oxygen, nitrogen, hydrogen, and helium.

[0158] Although the exemplary embodiments of the present disclosure have been described in detail with reference to the accompanying drawings, the present disclosure is not limited thereto and can be embodied in a variety of different forms without departing from the technical concept of the present disclosure. Therefore, the exemplary embodiments of the present disclosure are provided for illustrative purposes only and are not intended to limit the technical concept of the present disclosure. The scope of the technical concept of the present disclosure is not limited thereto. Therefore, it should be understood that the above-mentioned exemplary embodiments are illustrative in all aspects and do not limit the present disclosure. The scope of protection of the present disclosure should be interpreted based on the following claims, and all technical concepts within the equivalent scope of the present disclosure should be interpreted as falling within the scope of the present disclosure.

Claims

1. A display device comprising: substrate; a thin film transistor disposed on the substrate; a planarization layer disposed on the thin film transistor; and A light emitting diode is provided on the planarization layer, wherein the planarization layer comprises a first planarization layer arranged to cover the thin film transistor and a second planarization layer arranged to cover at least a portion of the first planarization layer, and The first planarizing layer has a lower refractive index than the second planarizing layer, and includes an acrylic adhesive and a (meth)acrylic acid-benzyl (meth)acrylic acid copolymer.

2. The display device according to claim 1, further comprising: A passivation layer configured to cover the thin film transistor; and a color filter disposed on the passivation layer to correspond to a light emitting area of ​​the light emitting diode, The planarization layer is configured to cover the color filter. 3 . The display device according to claim 1 , wherein a refractive index of the first planarization layer is 1.45 to 1.50, and a refractive index of the second planarization layer is 1.6 to 2.

0. 4 . The display device according to claim 1 , wherein the second planarization layer is provided on the first planarization layer to correspond to a light emitting region of the light emitting diode.

5. The display device according to claim 1 , wherein at least a portion of a surface of the second planarization layer in contact with the first planarization layer includes a convex portion, and At least a portion of a surface of the first planarization layer in contact with the second planarization layer includes a concave portion corresponding to the convex portion, and The convex portion and the concave portion engage with each other to contact each other. 6 . The display device according to claim 5 , wherein a microlens array structure is formed on an interface where the first planarization layer and the second planarization layer contact each other. 7 . The display device according to claim 1 , wherein the first planarization layer is a cured material of a composition including the acrylic adhesive, the (meth)acrylic acid-benzyl (meth)acrylic acid copolymer, and an initiator. 8 . The display device according to claim 7 , wherein the composition further comprises at least one low-refractive compound selected from the group consisting of a polystyrene block copolymer, dodecyl (meth)acrylate, and acrylic acid containing a cycloolefin group.

9. The display device according to claim 8, wherein the polystyrene block copolymer comprises one or more compounds selected from the group consisting of compounds represented by the following Formula 1 and Formula 2: [Formula 1] [Formula 2] wherein m and n in Formula 1 and x and y in Formula 2 are independently integers of 1 to 100. 10 . The display device according to claim 7 , wherein the composition further comprises a thermosetting monomer comprising at least one of an epoxy group and a hydroxyl group. 11 . The display device according to claim 7 , wherein the composition further comprises one or more unsaturated carboxylic acids selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, fumaric acid, citraconic acid, mesaconic acid, and itaconic acid. 12 . The display device according to claim 7 , wherein the composition further comprises at least one additive selected from the group consisting of a coupling agent and a UV absorber.

13. The display device according to claim 7, wherein: The composition includes 65 to 75 weight % of a solvent, 10 to 20 weight % of the acrylic adhesive, 10 to 20 weight % of the (meth)acrylic acid-benzyl (meth)acrylic acid copolymer, and 0.2 to 10 weight % of the initiator, based on 100 weight % of the composition. 14 . The display device according to claim 8 , wherein the low-refractive compound is present in an amount of 0.1 parts by weight to 50 parts by weight based on 100 parts by weight of the acrylic adhesive. 15 . The display device according to claim 10 , wherein the content of the thermosetting monomer is 1 part by weight to 40 parts by weight based on 100 parts by weight of the acrylic adhesive. 16 . The display device according to claim 11 , wherein the content of the unsaturated carboxylic acid is 1 part by weight to 30 parts by weight based on 100 parts by weight of the acrylic adhesive. 17 . The display device according to claim 1 , wherein a surface of the first planarization layer and a surface of the second planarization layer are plasma-treated with a gas selected from oxygen, nitrogen, hydrogen, and helium.

18. The display device according to claim 2, further comprising: a first buffer layer disposed on the substrate, a light shielding layer disposed on the first buffer layer, and a second buffer layer disposed on the light shielding layer, a color filter disposed on the passivation layer to correspond to a light emitting area of ​​the light emitting diode, The passivation layer is configured to cover the color filter.

Images