Indication device
By using optical compensation layers of transition metal oxides to capture external oxygen, the display device minimizes afterimages and luminance unevenness, enhancing reliability and uniformity.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- LG DISPLAY CO LTD
- Filing Date
- 2024-08-22
- Publication Date
- 2026-07-08
AI Technical Summary
Display devices, particularly organic light-emitting display devices, suffer from issues such as afterimages and luminance unevenness due to oxidation of the second inorganic encapsulation layer, which is exacerbated by light emission and temperature changes.
Incorporating an optical compensation layer made of transition metal oxides, such as cobalt or cerium oxide, above or below the second inorganic encapsulation layer to capture external oxygen and prevent its penetration, thereby minimizing oxidation and maintaining uniform color across subpixels.
The solution effectively reduces the occurrence of afterimages and luminance unevenness by maintaining consistent color and improving the reliability and moisture resistance of the display device.
Smart Images
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Abstract
Description
Technical Field
[0001] This specification relates to a display device, and more particularly to a display device with improved reliability.
Background Art
[0002] As the information society develops, the requirements for display devices for displaying images are increasing in various forms. As a result, in recent years, various display devices such as liquid crystal display devices (LCDs), plasma display devices (PDPs), organic light-emitting display devices (OLEDs), and quantum dot light-emitting display devices (QLEDs) have been utilized.
[0003] Among them, organic light-emitting display devices do not require a separate light source unlike liquid crystal display devices and can be manufactured in a lightweight and thin form. In addition, organic light-emitting display devices are not only advantageous in terms of power consumption due to low-voltage driving, but also excellent in color reproduction, response speed, viewing angle, and contrast ratio (CR), and are being studied as next-generation displays.
Summary of the Invention
Problems to be Solved by the Invention
[0004] The problem to be solved by this specification is to provide a display device (for example, a display panel) that can minimize the occurrence of afterimages.
[0005] Another problem to be solved by this specification is to provide a display device (for example, a display panel) that can minimize luminance unevenness.
[0006] The problems of this specification are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]
[0007] A display device according to one embodiment of this specification includes a substrate including a display area and a non-display area surrounding the display area, a light-emitting element (for example, an organic light-emitting element, but not limited to one) disposed in the display area, a first inorganic encapsulation layer disposed on the light-emitting element, an organic encapsulation layer disposed on the first inorganic encapsulation layer, a second inorganic encapsulation layer disposed on the organic encapsulation layer, and an optical compensation layer containing (or consisting of) a transition metal oxide disposed above or below the second inorganic encapsulation layer. Thus, the occurrence of blemishes on the display device (for example, a display panel) due to oxidation by light emitted from the light-emitting element can be minimized.
[0008] Specific details of other embodiments are included in the detailed description and drawings.
[0009] This specification describes how oxidation of the second inorganic encapsulation layer can be minimized by arranging (or incorporating) an optical compensation layer above or below the second inorganic encapsulation layer.
[0010] This specification minimizes the oxidation of the second inorganic sealing layer, thereby minimizing the occurrence of afterimages on the display device due to oxidation of the second inorganic sealing layer.
[0011] This specification can minimize the problem of brightness unevenness in the display device caused by partial oxidation of the second inorganic encapsulation layer, thereby improving the display quality of the display device.
[0012] This specification describes how the moisture resistance of a display device can be improved, thereby improving the reliability of the display device.
[0013] The effects described herein are not limited to those exemplified above, and a wider variety of effects are included within this specification. [Brief explanation of the drawing]
[0014] [Figure 1]This is a schematic plan view of a display device according to one embodiment of this specification. [Figure 2] Figure 1 shows a cross-sectional view along line II-II'. [Figure 3] Figure 1 shows a cross-sectional view along line III-III'. [Figure 4] This is a cross-sectional view of a display device according to another embodiment of this specification. [Figure 5] This is a cross-sectional view of a display device according to another embodiment of this specification. [Modes for carrying out the invention]
[0015] The advantages and features of this specification, and the methods for achieving them, will become clearer with reference to the examples described below in detail with the accompanying drawings. However, this specification is not limited to the examples disclosed below, but can be embodied in a variety of different shapes, and these examples are provided merely to make the disclosure of this specification complete and to fully inform a person with ordinary skill in the art to which this specification belongs of the scope of the specification.
[0016] The shapes, areas, proportions, angles, numbers, etc. disclosed in the drawings illustrating the embodiments of this specification are illustrative and the specification is not limited to those illustrated. Throughout the specification, the same reference numerals refer to the same components. Furthermore, in describing this specification, if it is determined that a specific explanation of related prior art would unnecessarily obscure the gist of this specification, such detailed explanation will be omitted. Where "includes," "has," "is made," etc., are used in this specification, other parts may be added unless "only" is used. When a component is expressed singularly, it includes cases where it includes multiple components unless otherwise explicitly stated.
[0017] When interpreting the constituent elements, they shall be interpreted as including a margin of error, even if not explicitly stated otherwise.
[0018] When it comes to the description of the positional relationship, for example, when the positional relationship between two parts is described such as "above ~", "at the upper part of ~", "at the lower part of ~", "next to ~", etc., as long as "immediately" or "directly" is not used, one or more other parts may be located between the two parts.
[0019] An element or layer that is referred to as "on" another element or layer includes both the case where there is another layer or another element immediately above the other element and the case where there is another layer or another element intervening in the middle.
[0020] Also, although the first, second, etc. are used to describe various components, these components are not limited by these terms. These terms are merely used to distinguish one component from another. Therefore, the first component mentioned below may be the second component within the technical concept of this specification.
[0021] Throughout the specification, the same reference numerals refer to the same components.
[0022] The area and thickness of each configuration shown in the drawings are shown for the convenience of explanation, and this specification is not necessarily limited to the area and thickness of the shown configuration.
[0023] The respective features of the various embodiments of this specification can be partially or wholly combined or combined with each other, enabling various technical linkages and drives, and each embodiment may be implemented independently of each other or may be implemented together in a related relationship.
[0024] In the following, this specification will be described with reference to the drawings.
[0025] Figure 1 is a schematic plan view of a display device according to one embodiment of this specification. Figure 2 is a cross-sectional view taken along line II-II' in Figure 1. Figure 3 is a cross-sectional view taken along line III-III' in Figure 1. The subpixel SP shown in Figure 2 is a subpixel SP in the initial state or a state in which the display device 100 is hardly emitting light, while the subpixel SP shown in Figure 3 is a subpixel SP in a state in which it has been emitting light for a very long time.
[0026] Referring to Figures 1 to 3, the display device (which may also mean a display panel) 100 includes a substrate 110, a transistor 120, a light-emitting element 130, a first inorganic encapsulation layer 141, an organic encapsulation layer 142, a second inorganic encapsulation layer 143a, 143b, and optical compensation layers 150a, 150b.
[0027] Referring to Figure 1, the substrate 110 is a component that supports and protects various components of the display device 100. The substrate 110 may be made of a flexible plastic material. Alternatively, the substrate 110 may be made of a transparent insulating material. For example, the substrate 110 may be made of transparent polyimide (PI).
[0028] The substrate 110 includes a display area AA and a non-display area NA.
[0029] Display area AA is located in the center of the substrate 110 and may be the area where the display device 100 displays an image. Display elements and various driving elements for driving the display elements may be arranged in display area AA. For example, the display element may consist of a light-emitting element 130 including a first electrode 131, a light-emitting part 133, and a second electrode 135. In addition, various driving elements such as a transistor 120, a capacitor, and wiring for driving the display elements may be arranged in display area AA.
[0030] Multiple pixels PX may be arranged in the display area AA. Multiple pixels PX may be the intersection area of multiple gate lines arranged in a first direction and multiple data lines arranged in a second direction different from the first direction. Here, the first direction may be the horizontal direction in Figure 1, and the second direction may be the vertical direction in Figure 1, but is not limited to these. Multiple pixels PX may include multiple subpixels SP, each emitting light of a different hue. For example, some of the multiple subpixels SP may be red subpixels, some may be green subpixels, and some may be blue subpixels. However, the multiple subpixels SP may also include white subpixels, but is not limited to these.
[0031] A pixel PX is the smallest unit that constitutes the screen, and each of multiple pixel PXs may include a light-emitting element 130 and a driving element. The driving element may include a switching transistor, a drive transistor, etc. The driving element may be electrically connected to signal wiring such as gate wiring, data wiring, etc., which are connected to a gate driver, data driver, etc., located in the non-display area NA.
[0032] The non-display area NA is located in the area surrounding the substrate 110 and may be an area where no image is displayed. The non-display area NA may be arranged to surround the display area AA. Various components for driving multiple pixels PX located in the display area AA may be arranged in the non-display area NA. For example, a drive integrated circuit (IC) that supplies signals for driving multiple pixels PX, a drive circuit, signal wiring, a flexible film, etc., may be arranged. The drive integrated circuit (IC) may include a gate driver, a data driver, etc. The drive IC and drive circuit may be arranged using GIP (Gate In Panel), COF (Chip On Film), TAB (Tape Automated Bonding), TCP (Tape Carrier Package), COG (Chip On Glass), etc.
[0033] In the following, with reference to Figures 2 and 3, each of the multiple subpixels SP arranged in the display area AA of the display device 100 will be described in more detail.
[0034] Referring to Figures 2 and 3, a buffer layer 111 may be placed on the substrate 110. The buffer layer 111 can improve the adhesion between the layer formed on the buffer layer 111 and the substrate 110. In addition, the buffer layer 111 can block alkaline components etc. that flow out from the substrate 110 and prevent moisture and / or oxygen that has penetrated from the outside of the substrate 110 from diffusing. The buffer layer 111 may consist of a single layer or multiple layers of silicon nitride (SiNx) or silicon oxide (SiOx), but is not limited to these. Furthermore, the buffer layer 111 may be omitted depending on the type and material of the substrate 110, the structure and type of the transistor 120, etc.
[0035] The transistor 120 is arranged on the buffer layer 111 and can drive the light-emitting element 130. The transistor 120 may be arranged in each of the multiple sub-pixels SP of the display area AA. The transistor 120 arranged in each of the multiple sub-pixels SP can be used as a driving element of the display device 100. The transistor 120 may be, but is not limited to, a thin film transistor (TFT), an N-channel metal oxide semiconductor (NMOS) transistor, a P-channel metal oxide semiconductor (PMOS) transistor, a complementary metal oxide semiconductor (CMOS) transistor, a field effect transistor (FET), etc. In the following explanation, it will be assumed that the transistor 120 is a thin film transistor, but is not limited to this.
[0036] The transistor 120 may include an active layer 121, a gate electrode 122, a source electrode 123, and a drain electrode 124. The transistor 120 shown in Figures 2 and 3 is a thin-film transistor with a top-gate structure, where the gate electrode 122 is located on the active layer 121. However, it is not limited thereto, and the transistor 120 may also be embodied as a thin-film transistor with a bottom-gate structure.
[0037] The active layer 121 of transistor 120 may be located on the buffer layer 111. The active layer 121 is the region where a channel is formed when transistor 120 is driven. The active layer 121 may be formed from an oxide semiconductor, amorphous silicon (a-Si), polycrystalline silicon (poly-Si), or organic semiconductor, but is not limited to these materials.
[0038] A gate insulating layer 112 may be disposed on the active layer 121. The gate insulating layer 112 may consist of a single or multiple layer of an inorganic material, such as silicon nitride (SiNx) or silicon oxide (SiOx). Contact holes may be formed in the gate insulating layer 112 for the source electrode 123 and the drain electrode 124 to contact the source region and drain region of the active layer 121, respectively. The gate insulating layer 112 may be formed across the entire surface of the substrate 110, as shown in Figures 2 and 3, and may be patterned to have the same width as the gate electrode 122, but is not limited thereto.
[0039] The gate electrode 122 may be positioned on the gate insulating layer 112. The gate electrode 122 may be positioned on the gate insulating layer 112 so as to overlap with the channel region of the active layer 121. The gate electrode 122 may, but is not limited to, a variety of metallic materials, such as one or more alloys of molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd), and copper (Cu), or multiple layers thereof.
[0040] An interlayer insulating layer 113 may be placed on the gate electrode 122. The interlayer insulating layer 113 may consist of a single layer or multiple layers of an inorganic material, such as silicon nitride (SiNx) or silicon oxide (SiOx). Contact holes may be formed in the interlayer insulating layer 113 for the source electrode 123 and the drain electrode 124 to contact the source region and drain region of the active layer 121, respectively.
[0041] The source electrode 123 and drain electrode 124 may be arranged on the interlayer insulating layer 113. The source electrode 123 and drain electrode 124 may be electrically connected to the active layer 121 through contact holes in the gate insulating layer 112 and the interlayer insulating layer 113. The source electrode 123 and drain electrode 124 may consist of one of various metallic materials, such as molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd), and copper (Cu), or an alloy of two or more of these, or a multilayer thereof. However, they are not limited to these.
[0042] In Figures 2 and 3, for the sake of explanation, only the drive transistors among the various transistors 120 included in the display device 100 are shown, but other transistors such as switching transistors may also be included.
[0043] A passivation layer 114 may be placed on the transistor 120 to protect it. The passivation layer 114 may have contact holes to expose the drain electrode 124 of the transistor 120. While Figures 2 and 3 show that the passivation layer 114 has contact holes to expose the drain electrode 124, contact holes to expose the source electrode 123 may also be formed. The passivation layer 114 may consist of a single or multiple layer of silicon nitride (SiNx) or silicon oxide (SiOx). However, the passivation layer 114 may be omitted depending on the embodiment.
[0044] An overcoating layer 115 may be placed on the passivation layer 114 to flatten the top of the transistor 120. A contact hole may be formed in the overcoating layer 115 to expose the drain electrode 124 of the transistor 120. In Figures 2 and 3, a contact hole for exposing the drain electrode 124 is shown to be formed in the overcoating layer 115, but a contact hole for exposing the source electrode 123 may also be formed. The overcoating layer 115 may be, but is not limited to, one of acrylic resin, epoxy resin, phenol resin, polyamide resin, polyimide resin, unsaturated polyester resin, polyphenylene resin, polyphenylene sulfide resin, benzocyclobutene, and photoresist.
[0045] The light-emitting element 130 may be placed on the overcoating layer 115. The light-emitting element 130 is formed on the overcoating layer 115 and includes a first electrode 131 electrically connected to the drain electrode 124 of the transistor 120, a hole transport layer (HTL) 132 placed on the first electrode 131, a light-emitting portion 133 placed on the hole transport layer 132, an electron transport layer (ETL) 134 placed on the light-emitting portion 133, and a second electrode 135 placed on the electron transport layer 134.
[0046] The first electrode 131 may be placed on the overcoating layer 115. The first electrode 131 may be an anode electrode configured to supply holes to the light-emitting portion 133, but is not limited thereto. The first electrode 131 may be electrically connected to the transistor 120 through contact holes in the overcoating layer 115. For example, although not shown in Figures 2 and 3, the first electrode 131 may be electrically connected to the source electrode 123 of the transistor 120. The first electrode 131 may be placed separately from each subpixel SP. The first electrode 131 may be formed of a transparent conductive material, such as indium tin oxide (ITO), indium zinc oxide (IZO), etc., but is not limited thereto.
[0047] Although not shown in the drawings, if the display device 100 according to one embodiment of this specification is a top emission type, the first electrode 131 may further include a reflective layer so that the light emitted from the light-emitting part 133 can be reflected by the first electrode 131 and emitted more smoothly in the upward direction. For example, the first electrode 131 may be a two-layer structure in which a transparent conductive layer and a reflective layer made of a transparent conductive material are stacked in order, or a three-layer structure in which a transparent conductive layer, a reflective layer and a transparent conductive layer are stacked in order. The reflective layer may be made of silver (Ag) or a silver-containing alloy, for example, silver or APC (Ag / Pd / Cu).
[0048] A bank 116 may be arranged on the first electrode 131 and the overcoating layer 115. The bank 116 can separate adjacent subpixel regions. The bank 116 can also separate a pixel PX region composed of multiple subpixel SP regions.
[0049] A hole transport layer 132 may be placed on the first electrode 131. The hole transport layer 132 may be placed on the first electrode 131 and the bank 116 so as to cover them. The hole transport layer 132 is an organic layer for smoothly transferring holes to the light-emitting part 133 and may be placed in a single layer on the first electrode 131 and the bank 116. The hole transport layer 132 may consist of, but is not limited to, one or more selected from the group consisting of NPD (N,N'-bis(naphthalene-1-yl)-N,N'-bis(phenyl)-2,2'-dimethylbenzidine), TPD (N,N'-bis-(3-methylphenyl)-N,N'-bis-(phenyl)-benzidine), s-TAD (2,2',7,7'-tetrakis(N,N-dimethylamino)-9,9-spirofluorene), and MTDATA (4,4',4''-Tris(N-3-methylphenyl-N-phenyl-amino)-triphenylamine).
[0050] On the other hand, a hole injection layer may be placed between the first electrode 131 and the hole transport layer 132. The hole injection layer may be an organic layer that facilitates the injection of holes from the first electrode 131 to the light-emitting section 133. The hole injection layer may consist of one or more selected from the group consisting of, for example, HAT-CN(dipyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile), CuPc(phthalocyanine), and NPD(N,N'-bis(naphthalene-1-yl)-N,N'-bis(phenyl)-2,2'-dimethylbenzidine), but is not limited thereto. The hole injection layer may or may not be included depending on the structure and characteristics of the display device 100.
[0051] The light-emitting portion 133 may be placed on the hole transport layer 132. The light-emitting portion 133 may be placed on the hole transport layer 132 so as to overlap with the first electrode 131. Alternatively, the light-emitting portion 133 can form a light-emitting region by patterning between two adjacent banks 116. The light-emitting portion 133 may include a material capable of emitting light of a specific color. For example, the light-emitting portion 133 may include a light-emitting material capable of emitting red, green, blue, or yellow-green light. However, it is not limited to this and may include a light-emitting material capable of emitting light of other colors.
[0052] An electron transport layer 134 may be placed on the light-emitting section 133.
[0053] The electron transport layer 134 may be an organic layer that transfers electrons to the light-emitting portion 133. The electron transport layer 134 may be arranged in a single layer along the upper surfaces of the light-emitting portion 133 and the hole transport layer 132. The electron transport layer 134 may contain a compound having electron transport properties. For example, it may consist of one or more selected from the group consisting of metal quinolates, PBD (2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4oxadiazole), TAZ (3-(4-biphenyl)4-phenyl-5-tert-butylphenyl-1,2,4-triazole), spiro-PBD, and BCP (2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline), but is not limited thereto.
[0054] The second electrode 135 may be placed on the electron transport layer 134. The second electrode 135 may be a cathode electrode that supplies electrons to the light-emitting part 133, but is not limited thereto. The second electrode 135 may contain or be formed from a metallic substance such as magnesium (Mg) or silver-magnesium (Ag:Mg). In a top-emission type display device that emits light upward, the second electrode 135 may be one or more transparent conductive oxides selected from indium tin oxide (ITO), indium zinc oxide (IZO), indium tin zinc oxide (ITZO), zinc oxide (ZnO), and tin oxide (TiO), but is not limited thereto.
[0055] On the other hand, an electron injection layer may be placed between the electron transport layer 134 and the second electrode 135. This layer may be an organic layer that facilitates the injection of electrons from the second electrode 135 to the light-emitting portion 133. The electron injection layer may be omitted if necessary.
[0056] A capping layer 117 may be placed on the second electrode 135. The capping layer 117 may be made of a material with a high refractive index and light absorption rate in order to reduce diffuse reflection of external light. The capping layer 117 may be, for example, an organic layer made of organic material, but is not limited to this, and may also be made of inorganic material. The capping layer 117 may also be omitted if necessary.
[0057] A first inorganic sealing layer 141 is placed on the capping layer 117. The first inorganic sealing layer serves to block the penetration of oxygen or moisture from the outside. The first inorganic sealing layer 141 contains, but is not limited to, silicon compounds such as silicon nitride (SiNx) or silicon oxide (SiOx).
[0058] An organic encapsulation layer 142 is placed on the first inorganic encapsulation layer 141. The organic encapsulation layer flattens the upper part of the first inorganic encapsulation layer and compensates for any steps caused by foreign matter, pinholes, etc., which may be located below the organic encapsulation layer 142. The organic encapsulation layer 142 may be formed from, but is not limited to, organic materials such as acrylic resin, epoxy resin, phenolic resin, polyamide resin, and polyimide resin.
[0059] Second inorganic sealing layers 143a and 143b are arranged on the organic sealing layer 142. The second inorganic sealing layer is arranged as a single layer and may be arranged to cover the lower components of the second inorganic sealing layers 143a and 143b. The second inorganic sealing layer serves to block the penetration of oxygen or moisture from the outside. The second inorganic sealing layers 143a and 143b may contain or be formed from inorganic materials such as silicon nitride (SiNx) or silicon oxide (SiOx), for example, they may contain or be formed from silicon nitride (SiNx).
[0060] Referring to Figures 2 and 3, the color of the second inorganic encapsulation layers 143a and 143b may differ in each of the multiple subpixels SP depending on the degree of oxidation of the second inorganic encapsulation layers 143a and 143b. Before oxidation occurs, the color of the second inorganic encapsulation layers 143a and 143b may be in the yellow series (e.g., yellow), and as oxidation progresses, it may change to transparent white. In this case, the oxidation of the second inorganic encapsulation layers 143a and 143b is promoted by the temperature increase due to heat generated during long-term operation of the light-emitting element 130 and the energy absorption due to the light emission of the light-emitting element 130, so the degree of oxidation of each of the multiple subpixels SP may vary depending on the degree of operation of the light-emitting element 130. For example, as shown in Figure 2, in some subpixels SP where the operation frequency of the light-emitting element 130 is low, oxidation of the second inorganic encapsulation layer 143a may occur relatively little. In this case, the color of the second inorganic encapsulation layer 143a in subpixels SP where oxidation of the second inorganic encapsulation layer 143a occurs relatively little may be in the yellow series. In contrast, as shown in Figure 3, oxidation of the second inorganic encapsulation layer 143b may occur relatively frequently in some subpixels SP where the light-emitting element 130 is driven frequently. In this case, in subpixels SP where oxidation of the second inorganic encapsulation layer 143b has occurred frequently, the color of the second inorganic encapsulation layer 143b may be in the transparent white series (for example, transparent white).
[0061] Optical compensation layers 150a and 150b may be placed on the second inorganic sealing layers 143a and 143b. The optical compensation layers 150a and 150b, together with the second inorganic sealing layers 143a and 143b, serve to block the penetration of moisture or oxygen from the outside, and at the same time compensate for discoloration of the second inorganic sealing layer, thereby solving the problem of afterimages.
[0062] The optical compensation layer may be arranged as a single layer and positioned to cover the lower components of the optical compensation layer. In this case, at least one surface of the optical compensation layers 150a, 150b may be in contact with one surface (e.g., the top surface) of the second inorganic sealing layer 143a, 143b. For example, the lower surfaces of the optical compensation layers 150a, 150b may be in contact with the upper surfaces of the second inorganic sealing layer 143a, 143b.
[0063] The optical compensation layers 150a and 150b contain or can be formed from transition metal oxides. In this case, the transition metal in the transition metal oxide may have an energy band gap of 2.18 eV to 3.10 eV, for example, 2.48 eV to 2.76 eV. The transition metal may also include transition metals of the blue series. For example, the transition metal may include at least one of cobalt (Co), cerium (Ce), and chromium (Cr), specifically cobalt (Co) or cerium (Ce). Therefore, the optical compensation layers 150a and 150b may consist of at least one of cobalt oxide, cerium oxide, and chromium oxide. Specifically, the optical compensation layers 150a and 150b may consist of cobalt oxide or cerium oxide.
[0064] The optical compensation layers 150a and 150b can be formed by depositing the aforementioned transition metal oxide onto the second inorganic sealing layers 143a and 143b using methods such as PVD (Physical Vapor Deposition), but are not limited to this. In this case, the transition metal oxide has an oxygen-deficient structure and actively undergoes oxidation reactions with external oxygen. Through this, external oxygen is captured, preventing it from penetrating the second inorganic sealing layers 143a and 143b. Therefore, oxidation of the second inorganic sealing layers 143a and 143b can be reduced.
[0065] Referring to Figures 2 and 3, the color of the optical compensation layers 150a and 150b may differ in each of the multiple sub-pixels SP depending on the degree of oxidation of the optical compensation layers 150a and 150b. Before oxidation occurs, the color of the optical compensation layers 150a and 150b may be in the blue range, and as oxidation progresses, it may change to transparent white. At this time, the oxidation of the optical compensation layers 150a and 150b is promoted by the temperature increase due to the heat generated when the light-emitting element 130 is driven for a long time and by the energy absorption due to the light emission of the light-emitting element 130. Therefore, the degree of oxidation of each of the multiple sub-pixels SP may vary depending on the degree of driving of the light-emitting element 130. For example, as shown in Figure 3, in some sub-pixels SP where the driving frequency of the light-emitting element 130 is low, oxidation of the optical compensation layer 150a may occur relatively little. At this time, the color of the optical compensation layer 150a may be in the blue range. In contrast, as shown in Figure 3, in some sub-pixels SP where the driving frequency of the light-emitting element 130 is high, oxidation of the optical compensation layer 150b may occur relatively much. In this case, in subpixels SP where a lot of oxidation of the optical compensation layer 150b has occurred, the color of the optical compensation layer 150b may be in the transparent white series (for example, transparent white).
[0066] Therefore, in the display device 100 according to one embodiment of this specification, the second inorganic sealing layers 143a, 143b and the optical compensation layers 150a, 150b may be different colors for each of the multiple subpixels SP. For example, the second inorganic sealing layer 143b and optical compensation layer 150b of the subpixel SP shown in Figure 3, where relatively more oxidation occurred in multiple subpixels SP, may be in the white series. In contrast, the second inorganic sealing layer 143a of the subpixel SP shown in Figure 2, where relatively less oxidation occurred in multiple subpixels SP, may be in the yellow series, and the optical compensation layer 150a may be in the blue series. In this case, the density (or intensity) of the colors of the second inorganic sealing layers 143a, 143b and the optical compensation layers 150a, 150b may vary depending on the degree of oxidation. For example, the less oxidation occurred in some of the multiple subpixels SP, the more concentrated the yellow series the second inorganic sealing layer 143a may be, and the more concentrated the blue series the optical compensation layer 150a may also be. Furthermore, the color density of the second inorganic sealing layer 143a and the optical compensation layer 150a may decrease as oxidation occurs in each of the multiple subpixels SP. In this case, color density refers to the degree to which a color is dark or light. For example, high color density means that the color is dark, and low color density means that the color is light.
[0067] Organic light-emitting diodes generally have a structure that includes an organic layer between a positive electrode and a negative electrode, and between the positive and negative electrodes. The organic layer is often a multilayer structure composed of different materials to enhance the efficiency and stability of the organic light-emitting diode, and can consist of, for example, a hole injection layer, a hole transport layer, an emissive layer, an electron transport layer, and an electron injection layer. When a voltage is applied between two electrodes (e.g., a positive electrode and a negative electrode) in such an organic light-emitting diode, holes are injected into the organic layer at the positive electrode, and electrons are injected into the organic layer at the negative electrode. When the injected holes and electrons meet, an exciton is formed, and when this exciton returns to the ground state, light is emitted. Such organic light-emitting diodes are next-generation light sources with self-luminance properties and have superior advantages over liquid crystals in terms of viewing angle, contrast, response speed, and power consumption.
[0068] However, as mentioned above, organic light-emitting elements are extremely vulnerable to moisture (H2O) or oxygen (O2) because they contain an organic layer. Specifically, when moisture or oxygen penetrates the interior of an organic light-emitting element, which includes two electrodes and an organic light-emitting layer placed between them, various defects such as dark spots and pixel shrinkage due to oxidation of the electrodes or deterioration of the organic material occur, leading to a reduced lifespan. Pixel shrinkage is a defect in which the edges of a pixel turn black due to oxidation or deterioration of the interface between the electrode and the organic light-emitting layer caused by the penetration of moisture or oxygen. If pixel shrinkage persists for a long time, it can worsen into a dark spot defect where the entire pixel turns black, seriously affecting the reliability of the organic light-emitting display device.
[0069] Therefore, to block the penetration of moisture or oxygen into the organic light-emitting element, a sealing section consisting of a first inorganic sealing layer, an organic sealing layer, and a second inorganic sealing layer is arranged on the organic light-emitting element. In this case, the second inorganic sealing layer, which is placed on the topmost layer, requires high density to enhance moisture resistance, oxygen resistance, and physical strength. To satisfy this, the second inorganic sealing layer is mainly composed of silicon-rich inorganic materials such as silicon nitride (SiNx). Because this silicon-rich second inorganic sealing layer absorbs light in the blue wavelength range, it mainly takes on a yellowish tint. As a result, a color coordinate shift occurs in the organic light-emitting device, and especially during long-term operation, the silicon-rich inorganic material such as silicon nitride (SiNx) oxidizes due to the temperature increase caused by heat generation and energy absorption due to light emission. Furthermore, the second inorganic sealing layer is the topmost layer and is most affected by moisture and oxygen from the outside. As a result, oxidation progresses faster in the second inorganic sealing layer compared to the other layers. When the second inorganic sealing layer oxidizes in this way, its moisture resistance decreases, and the color of the second inorganic sealing layer changes from yellow to white.
[0070] On the other hand, an organic light-emitting display device consists of multiple subpixels, each of which emits a different color, such as white, blue, green, and red. The organic light-emitting display device transmits images of various hues by combining these multiple subpixels that emit different colors. In this process, the light emission frequency of each of the multiple subpixels changes as the organic light-emitting display device transmits an image.
[0071] Therefore, as the emission frequency of each subpixel changes, the frequency of light reaching the second inorganic encapsulation layer on the light-emitting element also changes for each subpixel. That is, the second inorganic encapsulation layer located on a frequently emitting subpixel is more affected by the light emitted from the light-emitting element, thereby accelerating the oxidation of the second inorganic encapsulation layer. Conversely, the second inorganic encapsulation layer located on a relatively infrequently emitting subpixel is less affected by the light emitted from the light-emitting element, thereby delaying the oxidation of the second inorganic encapsulation layer. As described above, the color of the second inorganic encapsulation layer changes from yellow to white depending on the degree of oxidation, depending on its constituent components. Therefore, if the degree of oxidation of the second inorganic encapsulation layer changes for each subpixel, differences will also occur in the color change of the second inorganic encapsulation layer for each subpixel. That is, the second inorganic encapsulation layer located on a frequently emitting subpixel will become white due to relatively more oxidation, while the second inorganic encapsulation layer located on a relatively infrequently emitting subpixel will become yellow due to relatively less oxidation. Thus, the color of the second inorganic sealing layer changes in each of the multiple subpixels, resulting in the problem of patchy afterimages that cannot be restored.
[0072] Therefore, the display device 100 according to one embodiment of this specification includes an optical compensation layer 150a, 150b made of or containing a transition metal oxide on top of the second inorganic sealing layer 143a, 143b. In this case, the oxygen-deficient structure of the transition metal oxide collects external oxygen, thereby delaying the oxidation of the second inorganic sealing layer 143a, 143b. Thus, the oxidation resistance and moisture permeability reliability of the display device 100 can be improved.
[0073] Furthermore, the display device 100 according to one embodiment of this specification can minimize the occurrence of unrecovered afterimages.
[0074] As described above, by delaying the oxidation of the second inorganic encapsulation layers 143a and 143b, the difference in the degree of oxidation of the second inorganic encapsulation layers 143a and 143b in each of the multiple subpixels SP can be reduced. Through this, the difference in color change of the second inorganic encapsulation layers 143a and 143b in each of the multiple subpixels SP can be reduced, thereby improving the afterimage of the drive.
[0075] As shown in Figure 2, the display device 100 according to one embodiment of this specification can have an optical compensation layer 150a having a complementary color to the second inorganic encapsulation layer 143a placed on top of it. Through this, the color of the second inorganic encapsulation layer 143a, which appears in the yellow series when not oxidized, can be compensated to white. Therefore, when the display device 100 is viewed in an unoxidized state, the color of the corresponding area can be seen as white. Also, as shown in Figure 3, the color density of both the second inorganic encapsulation layer 143b and the optical compensation layer 150b can become lighter as oxidation occurs, resulting in white. Therefore, the afterimage caused by the discoloration of the second inorganic encapsulation layer 143b and the optical compensation layer 150b generated by the operation of the display device 100 can be improved. That is, since the second inorganic encapsulation layer 143a, 143b and the optical compensation layers 150a, 150b can be seen as white in all subpixels regardless of the degree of oxidation, the occurrence of unrecovered afterimages can be minimized.
[0076] In the following, other embodiments of the display device 400 according to this specification will be described with reference to Figures 4 and 5.
[0077] Figure 4 is a cross-sectional view of a display device according to another embodiment of this specification. Figure 5 is a cross-sectional view of a display device according to another embodiment of this specification. The subpixel SP shown in Figure 4 is the subpixel SP in the initial state or when it is hardly emitting light, and the subpixel SP shown in Figure 5 is the subpixel SP when it has been emitting light for a very long time. The display device 400 in Figures 4 and 5 differs from the display device 100 in Figures 1 to 3 only in the arrangement order of the second inorganic sealing layer 443a, 443b and the optical compensation layer 450a, 450b, and the other configurations are substantially the same, so redundant explanations are omitted.
[0078] Referring to Figures 4 and 5, in other embodiments of this specification, the display device 400 may have optical compensation layers 450a and 450b positioned below the second inorganic encapsulation layers 443a and 443b. Specifically, the optical compensation layers 450a and 450b may be positioned between the organic encapsulation layer 142 and the second inorganic encapsulation layers 443a and 443b. The optical compensation layers 450a and 450b may be positioned to cover the entire top and side surfaces of the organic encapsulation layer 142. For example, the optical compensation layers 450a and 450b may be positioned over a larger area than the organic encapsulation layer 142.
[0079] Other embodiments of the display device 400 according to this specification may include optical compensation layers 450a, 450b beneath the second inorganic encapsulation layers 443a, 443b. Through this, the transfer of heat or luminescence energy generated in the light-emitting element 130 to the second inorganic encapsulation layers 443a, 443b can be blocked. Therefore, the oxidation of the second inorganic encapsulation layers 443a, 443b can be delayed.
[0080] Furthermore, the display device 400 according to other embodiments of this specification contains a transition metal oxide with excellent oxygen collection ability, or collects ambient oxygen through optical compensation layers 450a and 450b made of such oxides, thereby delaying the oxidation of the second inorganic sealing layers 443a and 443b. In addition, since the penetration of moisture or oxygen into the light-emitting element 130 can be prevented, the oxidation resistance and moisture permeability reliability of the display device 400 can be improved.
[0081] As shown in Figure 4, the display device 400 according to another embodiment of the present invention can have a second inorganic encapsulation layer 443a having a complementary color to the color of the optical compensation layer 450a placed on the optical compensation layer 450a. Therefore, the color of the second inorganic encapsulation layer 443a, which appears in the yellow series when not oxidized, can be compensated to white. Through this, the problem of the color coordinates of the display device 400 being shifted can be prevented. Also, as shown in Figure 5, the colors of both the optical compensation layer 450b and the second inorganic encapsulation layer 443b can become transparent white series (e.g., transparent white) even as oxidation occurs. Through this, the display device 400 according to one embodiment of this specification can be viewed as having a uniform color in each of the multiple subpixels SP, regardless of the degree of oxidation of the second inorganic encapsulation layers 443a and 443b. Therefore, the hue difference between the multiple subpixels SP can be minimized.
[0082] The various embodiments of this specification may be described as follows.
[0083] A display device according to one embodiment of this specification includes a substrate including a display area and a non-display area surrounding the display area, a light-emitting element disposed in the display area, a first inorganic encapsulation layer disposed on the light-emitting element, an organic encapsulation layer disposed on the first inorganic encapsulation layer, a second inorganic encapsulation layer disposed on the organic encapsulation layer, and an optical compensation layer disposed above or below the second inorganic encapsulation layer and containing or made of a transition metal oxide.
[0084] According to other embodiments of this specification, the light-emitting element may be an organic light-emitting element.
[0085] According to yet another embodiment of this specification, the optical compensation layer is disposed on a second inorganic encapsulation layer and may be in contact with the upper surface of the second inorganic encapsulation layer.
[0086] According to yet another embodiment of this specification, the optical compensation layer may be placed between the organic encapsulation layer and the second inorganic encapsulation layer.
[0087] According to other embodiments of this specification, the optical compensation layer may be in contact with the lower surface of the second inorganic encapsulation layer.
[0088] According to other embodiments of this specification, the optical compensation layer may be arranged to completely cover the top and sides of the organic encapsulation layer.
[0089] According to other embodiments of this specification, the optical compensation layer may be arranged over an even larger area than the organic encapsulation layer.
[0090] According to other examples of this specification, the transition metal in the transition metal oxide may have an energy band gap of 2.18 eV to 3.10 eV.
[0091] According to other embodiments of this specification, the transition metal may have an energy band gap of 2.48 eV to 2.76 eV.
[0092] According to other examples herein, the transition metal oxide may include at least one of cobalt oxide, cerium oxide, manganese oxide, and chromium oxide.
[0093] According to other examples herein, the transition metal oxide may include cobalt oxide or cerium oxide.
[0094] According to other embodiments of this specification, the optical compensation layer may be in a complementary color relationship with the second inorganic sealing layer.
[0095] According to other embodiments of this specification, the optical compensation layer may be in the blue series.
[0096] According to other embodiments of this specification, the second inorganic encapsulation layer may be of the yellow series.
[0097] According to other embodiments of this specification, the second inorganic encapsulation layer may contain or be formed of silicon nitride (SiNx).
[0098] According to other embodiments of this specification, the optical compensation layer and the second inorganic sealing layer may be white regardless of the degree of oxidation.
[0099] Although embodiments of this specification have been described in more detail above with reference to the attached drawings, this specification is not necessarily limited to these embodiments and can be modified and implemented in various ways within the scope of the technical concept of this specification. Accordingly, the embodiments disclosed herein are for illustrative purposes only, not to limit the technical concept of this specification, and the scope of the technical concept of this specification is not limited by such embodiments. Therefore, the embodiments described above should be understood in all respects as illustrative and not restrictive.
Claims
1. A substrate including a display area and a non-display area surrounding the display area, A light-emitting element arranged in the display area, A first inorganic sealing layer disposed on the light-emitting element, An organic sealing layer disposed on the first inorganic sealing layer, A second inorganic sealing layer disposed on the organic sealing layer, and An optical compensation layer disposed above or below the second inorganic sealing layer and formed of a transition metal oxide having an oxygen-deficient structure. Includes, The aforementioned transition metal oxide contains a transition metal that is blue before oxidation and changes to transparent white as oxidation progresses. The transition metal in the transition metal oxide has an energy band gap of 2.18 eV to 3.10 eV, and is used in a display device.
2. The display device according to claim 1, wherein the light-emitting element is an organic light-emitting diode.
3. The display device according to claim 1, wherein the optical compensation layer is disposed on the second inorganic sealing layer and is in contact with the upper surface of the second inorganic sealing layer.
4. The display device according to claim 1, wherein the optical compensation layer is disposed between the organic encapsulation layer and the second inorganic encapsulation layer.
5. The display device according to claim 4, wherein the optical compensation layer is in contact with the lower surface of the second inorganic sealing layer.
6. The display device according to claim 4, wherein the optical compensation layer is arranged to completely cover the upper surface and at least one side surface of the organic sealing layer.
7. The display device according to claim 4, wherein the optical compensation layer is arranged to have a larger area than the organic sealing layer.
8. The display device according to claim 1, wherein the transition metal has an energy band gap of 2.48 eV to 2.76 eV.
9. The display device according to claim 1, wherein the transition metal oxide includes at least one of cobalt oxide, cerium oxide, manganese oxide, and chromium oxide.
10. The display device according to claim 9, wherein the transition metal oxide includes cobalt oxide or cerium oxide.
11. The display device according to claim 1, wherein the optical compensation layer is in a complementary color relationship with the second inorganic sealing layer.
12. The display device according to claim 1, wherein the optical compensation layer is in the blue series.
13. The display device according to claim 1, wherein the second inorganic sealing layer is of the yellow series.
14. The display device according to claim 1, wherein the second inorganic encapsulation layer contains or is formed of silicon nitride (SiNx).
15. The display device according to claim 1, wherein the second inorganic sealing layer appears white regardless of the degree of oxidation.
16. The display device according to claim 1, wherein the optical compensation layer is arranged to completely cover the upper surface of the organic sealing layer.