Display device

Abstract

To provide a display device in which generation of an afterimage can be minimized.SOLUTION: A display device 100 according to an embodiment of the present specification includes: a substrate 110 which includes a display area and a non-display area enclosing the display area; a light emitting element 130 disposed on the display area; a first inorganic encapsulation layer 141 disposed on the light emitting element 130; an organic encapsulation layer 142 disposed on the first inorganic encapsulation layer 141; a second inorganic encapsulation layer 143a disposed on the organic encapsulation layer 142; and an optical compensation layer 150a which is disposed on or below the second inorganic encapsulation layer 143a, and includes or is formed of a transition metal oxide. Therefore, the oxidation of the second inorganic encapsulation layer 143a can be minimized, and generation of an afterimage can be prevented.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present specification relates to a display device, and more particularly to a display device with improved reliability. [Background technology]

[0002] As the information society develops, the demand for display devices to display images is increasing in various forms, and various display devices such as liquid crystal displays (LCDs), plasma display panels (PDPs), organic light emitting displays (OLEDs), and quantum dot light emitting displays (QLEDs) are being used in recent years.

[0003] Among them, organic light-emitting display devices, unlike LCDs, do not require a separate light source and can be manufactured in a lightweight and thin form. Furthermore, organic light-emitting display devices are not only advantageous in terms of power consumption due to their low voltage operation, but also excel in color realization, response speed, viewing angle, and contrast ratio (CR), and are therefore being researched as next-generation displays. Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present disclosure is to provide a display device (e.g., a display panel) that can minimize the occurrence of image retention.

[0005] Another problem to be solved by the present specification is to provide a display device (for example, a display panel) capable of minimizing luminance unevenness.

[0006] The objects of this specification are not limited to the objects mentioned above, and other objects 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 an embodiment of the present specification includes a substrate including a display area and a non-display area surrounding the display area, light-emitting elements (which may be, but are not limited to, organic light-emitting elements) disposed in the display area, a first inorganic sealing layer disposed on the light-emitting elements, 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 including (or consisting of) a transition metal oxide disposed on or below the second inorganic sealing layer. This can minimize the occurrence of spots on the display device (e.g., a display panel) due to oxidation caused by light emitted from the light-emitting elements.

[0008] Further details of the embodiments are included in the detailed description and drawings.

[0009] In the present specification, an optical compensation layer is disposed on or under the second inorganic sealing layer, thereby minimizing oxidation of the second inorganic sealing layer.

[0010] The present invention can minimize the oxidation of the second inorganic sealing layer, thereby minimizing the occurrence of image retention in a display device due to the oxidation of the second inorganic sealing layer.

[0011] The present invention can minimize the problem of uneven brightness of the display device due to partial oxidation of the second inorganic sealing layer, thereby improving the display quality of the display device.

[0012] The present specification can improve the moisture resistance of a display device and improve the reliability of the display device.

[0013] The effects of this specification are not limited to the examples given above, and various other effects are included within this specification. [Brief explanation of the drawings]

[0014] [Figure 1]1 is a schematic plan view of a display device according to an embodiment of the present specification; [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II' in FIG. [Figure 3] FIG. 2 is a cross-sectional view taken along the line III-III' in FIG. [Figure 4] FIG. 10 is a cross-sectional view of a display device according to another embodiment of the present specification. [Figure 5] FIG. 10 is a cross-sectional view of a display device according to another embodiment of the present specification. DETAILED DESCRIPTION OF THE INVENTION

[0015] The advantages and features of the present invention, and methods for achieving them, will become more apparent from the following detailed description of the embodiments in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and may be embodied in various different forms. The embodiments are provided solely to ensure that the disclosure of the present invention is complete and to fully convey the scope of the present invention to those skilled in the art.

[0016] The shapes, areas, ratios, angles, numbers, etc. disclosed in the drawings for illustrating the embodiments of this specification are illustrative only and are not intended to limit the scope of this specification. The same reference symbols refer to the same elements throughout this specification. Furthermore, when describing this specification, if it is deemed that a detailed description of related prior art would unnecessarily obscure the gist of this specification, such a detailed description will be omitted. When using words such as "include," "have," and "be made" in this specification, other parts may be added unless "only" is used. When describing an element in the singular, this also includes the plural unless otherwise explicitly stated.

[0017] When interpreting elements, they are interpreted as including a margin of error even if there is no other explicit description.

[0018] When describing a positional relationship, for example, when describing the positional relationship of two parts using "above," "at the top," "below," "next to," etc., one or more other parts may be located between the two parts, as long as "immediately" or "directly" is not used.

[0019] When an element or layer is referred to as "on" another element or layer, it includes the case where the element or layer is directly on top of the other element or layer, or where there are other layers or elements interposed therebetween.

[0020] Furthermore, although terms such as "first," "second," etc. are used to describe various components, these components are not limited by these terms. These terms are used merely to distinguish one component from another. Therefore, a first component referred to below may be a second component within the technical concept of this specification.

[0021] Like reference numbers refer to like elements throughout the specification.

[0022] The area and thickness of each component shown in the drawings are shown for convenience of explanation, and the present specification is not necessarily limited to the area and thickness of the components shown.

[0023] The features of the various embodiments of this specification may be partially or wholly combined or combined with each other, may be technically interlocked and driven in various ways, and each embodiment may be implemented independently of the other or may be implemented together in a related relationship.

[0024] In the following, the present specification will be described with reference to the drawings.

[0025] Fig. 1 is a schematic plan view of a display device according to one embodiment of the present specification. Fig. 2 is a cross-sectional view taken along line II-II' in Fig. 1. Fig. 3 is a cross-sectional view taken along line III-III' in Fig. 1. The subpixel SP shown in Fig. 2 is a subpixel SP in the initial state or in a state where it hardly emits light in the display device 100, and the subpixel SP shown in Fig. 3 is a subpixel SP in a state where it has emitted light for a very long time.

[0026] Referring to Figures 1 to 3, a display device (which may also refer to a display panel) 100 includes a substrate 110, a transistor 120, a light-emitting element 130, a first inorganic sealing layer 141, an organic sealing layer 142, second inorganic sealing layers 143a, 143b, and optical compensation layers 150a, 150b.

[0027] 1, the substrate 110 is a component for supporting and protecting 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] The display area AA may be disposed in the center of the substrate 110 and may be an area where an image is displayed on the display device 100. Display elements and various driving elements for driving the display elements may be disposed in the display area AA. For example, the display elements may be formed of a light-emitting element 130 including a first electrode 131, a light-emitting portion 133, and a second electrode 135. In addition, various driving elements such as a transistor 120, a capacitor, wiring, etc. for driving the display elements may be disposed in the display area AA.

[0030] A plurality of pixels PX may be arranged in the display area AA. The plurality of pixels PX may be an intersection region of a plurality of gate lines arranged in a first direction and a plurality of data lines arranged in a second direction different from the first direction. Here, the first direction may be the horizontal direction in FIG. 1, and the second direction may be the vertical direction in FIG. 1, but is not limited thereto. The plurality of pixels PX may include a plurality of subpixels SP that emit light of different hues. For example, some of the plurality of subpixels SP may be red subpixels, others may be green subpixels, and still others may be blue subpixels. However, the plurality of subpixels SP may further include a white subpixel, but is not limited thereto.

[0031] A pixel PX is the smallest unit constituting a screen, and each of the plurality of pixels PX may include a light emitting element 130 and a driving element. The driving element may include a switching transistor, a driving 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, a data driver, etc., arranged in the non-display area NA.

[0032] The non-display area NA may be disposed around the substrate 110 and may be an area where no image is displayed. The non-display area NA may be disposed to surround the display area AA. Various components for driving the pixels PX disposed in the display area AA may be disposed in the non-display area NA. For example, a driving integrated circuit (IC) for supplying signals for driving the pixels PX, a driving circuit, signal wiring, a flexible film, etc. may be disposed. The driving integrated circuit (IC) may include a gate driver, a data driver, etc. The driving IC and the driving circuit may be disposed in a GIP (Gate In Panel) format, a COF (Chip On Film) format, a TAB (Tape Automated Bonding) format, a TCP (Tape Carrier Package) format, a COG (Chip On Glass) format, etc.

[0033] In the following, each of the sub-pixels SP arranged in the display area AA of the display device 100 will be described in more detail with reference to FIGS.

[0034] 2 and 3, a buffer layer 111 may be disposed on the substrate 110. The buffer layer 111 may improve adhesion between the substrate 110 and a layer formed on the buffer layer 111. The buffer layer 111 may also block alkaline components, etc., from flowing out of the substrate 110 and prevent moisture and / or oxygen that has penetrated from outside the substrate 110 from diffusing. The buffer layer 111 may be formed of a single layer or multiple layers of silicon nitride (SiNx) or silicon oxide (SiOx), but is not limited thereto. The buffer layer 111 may also 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 disposed on the buffer layer 111 and can drive the light-emitting element 130. The transistor 120 can be disposed in each of the plurality of sub-pixels SP in the display area AA. The transistor 120 disposed in each of the plurality of sub-pixels SP can be used as a driving element of the display device 100. The transistor 120 may be, for example, 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), or the like, but is not limited thereto. In the following description, it is assumed that the transistor 120 is a thin film transistor, but the present invention is not limited thereto.

[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 in which the gate electrode 122 is disposed on the active layer 121. However, the transistor 120 is not limited thereto, and may also be embodied as a thin film transistor with a bottom gate structure.

[0037] An active layer 121 of the transistor 120 may be disposed on the buffer layer 111. The active layer 121 is a region where a channel is formed when the transistor 120 is driven. The active layer 121 may be formed of, but is not limited to, an oxide semiconductor, amorphous silicon (a-Si), polycrystalline silicon (poly-Si), an organic semiconductor, or the like.

[0038] A gate insulating layer 112 may be disposed on the active layer 121. The gate insulating layer 112 may be composed of a single layer or multiple layers of inorganic silicon nitride (SiNx) or silicon oxide (SiOx). Contact holes may be formed in the gate insulating layer 112 to allow the source electrode 123 and the drain electrode 124 to contact the source region and the drain region of the active layer 121, respectively. The gate insulating layer 112 may be formed over the entire surface of the substrate 110 as shown in FIGS. 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 disposed on the gate insulating layer 112. The gate electrode 122 may be disposed on the gate insulating layer 112 so as to overlap a channel region of the active layer 121. The gate electrode 122 may be made of any one or an alloy of two or more of various metal materials, such as, but not limited to, molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd), and copper (Cu), or a multilayer thereof.

[0040] An interlayer insulating layer 113 may be disposed on the gate electrode 122. The interlayer insulating layer 113 may be composed of a single layer or multiple layers of inorganic silicon nitride (SiNx) or silicon oxide (SiOx). Contact holes may be formed in the interlayer insulating layer 113 to allow the source electrode 123 and the drain electrode 124 to contact the source region and the drain region of the active layer 121, respectively.

[0041] The source electrode 123 and the drain electrode 124 may be disposed on the interlayer insulating layer 113. The source electrode 123 and the 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 the drain electrode 124 may be made of any one of various metal materials, such as molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd), and copper (Cu), or may be an alloy of two or more of these, or a multilayer thereof, but is not limited thereto.

[0042] 2 and 3, for convenience of explanation, only the driving transistors among the various transistors 120 included in the display device 100 are shown, but other transistors such as switching transistors may also be arranged.

[0043] A passivation layer 114 for protecting the transistor 120 may be disposed on the transistor 120. A contact hole for exposing a drain electrode 124 of the transistor 120 may be formed in the passivation layer 114. Although FIGS. 2 and 3 show that a contact hole for exposing the drain electrode 124 is formed in the passivation layer 114, a contact hole for exposing the source electrode 123 may also be formed. The passivation layer 114 may be composed of a single layer or multiple layers 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 for planarizing the top of the transistor 120 may be disposed on the passivation layer 114. A contact hole for exposing the drain electrode 124 of the transistor 120 may be formed in the overcoating layer 115. Although FIGS. 2 and 3 illustrate that a contact hole for exposing the drain electrode 124 is formed in the overcoating layer 115, a contact hole for exposing the source electrode 123 may also be formed. The overcoating layer 115 may be made of one of, but is not limited to, an acrylic resin, an epoxy resin, a phenol resin, a polyamide resin, a polyimide resin, an unsaturated polyester resin, a polyphenylene resin, a polyphenylene sulfide resin, a benzocyclobutene, and a photoresist.

[0045] The light-emitting element 130 may be disposed 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 disposed on the first electrode 131, a light-emitting portion 133 disposed on the hole transport layer 132, an electron transport layer (ETL) 134 disposed on the light-emitting portion 133, and a second electrode 135 disposed on the electron transport layer 134.

[0046] The first electrode 131 may be disposed 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 a contact hole in the overcoating layer 115. For example, although not shown in FIGS. 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 disposed spaced apart from each other for each subpixel SP. The first electrode 131 may be formed of a transparent conductive material, such as, but not limited to, indium tin oxide (ITO), indium zinc oxide (IZO), etc.

[0047] Although not shown in the drawings, when the display device 100 according to an embodiment of the present disclosure is a top emission type, the first electrode 131 may further include a reflective layer so that light emitted from the light emitting unit 133 can be reflected by the first electrode 131 and more smoothly emitted upward. For example, the first electrode 131 may have a two-layer structure in which a transparent conductive layer made of a transparent conductive material and a reflective layer are sequentially stacked, or a three-layer structure in which a transparent conductive layer, a reflective layer, and another transparent conductive layer are sequentially stacked. The reflective layer may be made of silver (Ag) or an alloy containing silver, for example, silver or APC (Ag / Pd / Cu).

[0048] Banks 116 may be disposed on the first electrode 131 and the overcoating layer 115. The banks 116 may divide adjacent subpixel regions. The banks 116 may also divide pixel regions PX, each of which is made up of a plurality of subpixel SP regions.

[0049] A hole transport layer 132 may be disposed on the first electrode 131. The hole transport layer 132 may be disposed 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 transporting holes to the light emitting unit 133, and may be disposed on the first electrode 131 and the bank 116 as a single layer. The hole transport layer 132 may be composed of, for example, 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), but is not limited thereto.

[0050] Meanwhile, a hole injection layer may be disposed 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 unit 133. The hole injection layer may be made of, for example, but not limited to, one or more selected from the group consisting of 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). The hole injection layer may be included or omitted depending on the structure and characteristics of the display device 100.

[0051] The light emitting unit 133 may be disposed on the hole transport layer 132. The light emitting unit 133 may be disposed on the hole transport layer 132 so as to overlap the first electrode 131. The light emitting unit 133 may be patterned between two adjacent banks 116 to form a light emitting region. The light emitting unit 133 may include a material capable of emitting light of a specific color. For example, the light emitting unit 133 may include a light emitting material capable of emitting red light, green light, blue light, or yellow-green light. However, the light emitting unit 133 is not limited thereto and may include a light emitting material capable of emitting light of other colors.

[0052] An electron transport layer 134 may be disposed on the light-emitting portion 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 disposed as 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 include a compound having electron transport properties. For example, the electron transport layer 134 may include, but is not limited to, one or more compounds selected from the group consisting of metal quinolate, 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).

[0054] The second electrode 135 may be disposed on the electron transport layer 134. The second electrode 135 may be, but is not limited to, a cathode electrode that supplies electrons to the light emitting unit 133. The second electrode 135 may include or be formed of a metal material such as magnesium (Mg), silver-magnesium (Ag:Mg), etc. In a top-emission type display device that emits light upward, the second electrode 135 may be, but is not limited to, one or more transparent conductive oxides selected from the group consisting of indium tin oxide (ITO), indium zinc oxide (IZO), indium tin zinc oxide (ITZO), zinc oxide (ZnO), and tin oxide (TiO).

[0055] Meanwhile, an electron injection layer may be disposed between the electron transport layer 134 and the second electrode 135. The electron injection layer may be an organic layer that facilitates the injection of electrons from the second electrode 135 to the light-emitting unit 133. The electron injection layer may be omitted as necessary.

[0056] A capping layer 117 may be disposed on the second electrode 135. The capping layer 117 may be made of a material with a high refractive index and light absorption rate to reduce diffuse reflection of external light. The capping layer 117 may be, for example, an organic layer made of an organic material, but is not limited thereto, and may also be made of an inorganic material. The capping layer 117 may also be omitted if necessary.

[0057] A first inorganic sealing layer 141 is disposed on the capping layer 117. The first inorganic sealing layer functions to block the penetration of oxygen or moisture from the outside. The first inorganic sealing layer 141 may include or be formed of a silicon compound such as silicon nitride (SiNx) or silicon oxide (SiOx), but is not limited thereto.

[0058] The organic encapsulation layer 142 is disposed on the first inorganic encapsulation layer 141. The organic encapsulation layer functions to planarize the upper surface of the first inorganic encapsulation layer and compensate for steps caused by foreign matter, pinholes, etc. that may be disposed below the organic encapsulation layer 142. The organic encapsulation layer 142 may be formed of an organic material such as, but not limited to, acrylic resin, epoxy resin, phenolic resin, polyamide resin, and polyimide resin.

[0059] Second inorganic sealing layers 143a and 143b are disposed on the organic sealing layer 142. The second inorganic sealing layer may be disposed as a single layer and may be disposed to cover the underlying components of the second inorganic sealing layers 143a and 143b. The second inorganic sealing layer functions to block the penetration of oxygen or moisture from the outside. The second inorganic sealing layers 143a and 143b may include or be formed of an inorganic material such as silicon nitride (SiNx) or silicon oxide (SiOx). For example, the second inorganic sealing layers 143a and 143b may include or be formed of silicon nitride (SiNx).

[0060] 2 and 3, the color of the second inorganic sealing layers 143a and 143b may vary depending on the degree of oxidation of the second inorganic sealing layers 143a and 143b in each of the subpixels SP. The color of the second inorganic sealing layers 143a and 143b may be yellowish (e.g., yellow) before oxidation occurs and may change to transparent white as oxidation progresses. The oxidation of the second inorganic sealing layers 143a and 143b is accelerated by temperature increases due to heat generated during long-term operation of the light emitting device 130 and energy absorption due to light emission from the light emitting device 130. Therefore, the degree of oxidation of each of the subpixels SP may vary depending on the degree of operation of the light emitting device 130. For example, as shown in FIG. 2, oxidation of the second inorganic sealing layer 143a may be relatively less in some subpixels SP where the light emitting device 130 is driven less frequently. The color of the second inorganic sealing layer 143a in the subpixels SP where oxidation of the second inorganic sealing layer 143a occurs relatively less may be yellowish. 3, oxidation of the second inorganic sealing layer 143b may occur relatively frequently in some sub-pixels SP where the light emitting device 130 is driven frequently. In this case, in the sub-pixels SP where oxidation of the second inorganic sealing layer 143b occurs frequently, the color of the second inorganic sealing layer 143b may be a transparent white-based color (e.g., transparent white).

[0061] Optical compensation layers 150a and 150b may be disposed 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, function to block the penetration of moisture or oxygen from the outside, and at the same time, compensate for discoloration of the second inorganic sealing layers, thereby solving the problem of image retention.

[0062] The optical compensation layer may be arranged as a single layer and may be arranged to cover the lower components of the optical compensation layer. In this case, at least one surface of the optical compensation layer 150a, 150b may be in contact with one surface (e.g., the upper surface) of the second inorganic sealing layer 143a, 143b. For example, the lower surface of the optical compensation layer 150a, 150b may be in contact with the upper surface of the second inorganic sealing layer 143a, 143b.

[0063] The optical compensation layers 150a and 150b may include or be formed of a transition metal oxide. 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 a blue-series transition metal. 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 be made of at least one of cobalt oxide, cerium oxide, and chromium oxide. Specifically, the optical compensation layers 150a and 150b may be made of cobalt oxide or cerium oxide.

[0064] The optical compensation layers 150a and 150b can be formed by depositing the above-mentioned transition metal oxide on the second inorganic sealing layers 143a and 143b using a method such as physical vapor deposition (PVD), but are not limited to this. In this case, the transition metal oxide has an oxygen-deficient structure and actively undergoes an oxidation reaction with external oxygen. This captures external oxygen and prevents external oxygen from penetrating into the second inorganic sealing layers 143a and 143b. This reduces oxidation of the second inorganic sealing layers 143a and 143b.

[0065] 2 and 3, the color of the optical compensation layers 150a and 150b may vary depending on the degree of oxidation of the optical compensation layers 150a and 150b in each of the subpixels SP. The color of the optical compensation layers 150a and 150b may be blue-based before oxidation occurs and may change to transparent white as oxidation progresses. The oxidation of the optical compensation layers 150a and 150b is accelerated by an increase in temperature due to heat generated when the light emitting device 130 is driven for a long period of time and energy absorption due to light emission from the light emitting device 130. Therefore, the degree of oxidation of each of the subpixels SP may vary depending on the driving frequency of the light emitting device 130. For example, as shown in FIG. 3, the oxidation of the optical compensation layer 150a may be relatively small in some subpixels SP where the light emitting device 130 is driven less frequently. In this case, the color of the optical compensation layer 150a may be blue-based. In contrast, as shown in FIG. 3, the oxidation of the optical compensation layer 150b may be relatively large in some subpixels SP where the light emitting device 130 is driven more frequently. In this case, in the sub-pixel SP where the optical compensation layer 150b is largely oxidized, the color of the optical compensation layer 150b may be transparent white-based (for example, transparent white).

[0066] Therefore, in the display device 100 according to an embodiment of the present specification, the second inorganic encapsulating layers 143a, 143b and the optical compensation layers 150a, 150b may have different colors in each of the subpixels SP. For example, the second inorganic encapsulating layer 143b and the optical compensation layer 150b of the subpixel SP shown in FIG. 3, where oxidation is relatively strong among the subpixels SP, may be white-based. In contrast, the second inorganic encapsulating layer 143a of the subpixel SP shown in FIG. 2, where oxidation is relatively weak among the subpixels SP, may be yellow-based, and the optical compensation layer 150a may be blue-based. In this case, the color density (or intensity) of the second inorganic encapsulating layers 143a, 143b, and the optical compensation layers 150a, 150b may vary depending on the degree of oxidation. For example, the second inorganic encapsulating layer 143a of the subpixels SP that are relatively less oxidized among the subpixels SP may be more yellow-based, and the optical compensation layer 150a may also be more blue-based. Furthermore, the more oxidation occurs in each of the subpixels SP, the lower the color density of the second inorganic sealing layer 143a and the optical compensation layer 150a. In this case, the color density refers to the degree of darkness or lightness of the color. For example, a high color density means that the color is dark, and a low color density means that the color is light.

[0067] Organic light-emitting devices typically have a structure including an anode and a cathode, and an organic material layer between the anode and cathode. To enhance the efficiency and stability of the organic light-emitting device, the organic material layer is often a multi-layer structure composed of different materials. For example, it can consist of a hole injection layer, a hole transport layer, an emission layer, an electron transport layer, and an electron injection layer. When a voltage is applied between two electrodes (e.g., an anode and an electrode) in such an organic light-emitting device, holes are injected into the organic material layer from the anode and electrons are injected into the organic material layer from the cathode. When the injected holes and electrons meet, excitons are formed. When these excitons fall back to the ground state, light is emitted. Such organic light-emitting devices are next-generation light sources with self-luminance properties and offer superior advantages over liquid crystals in terms of viewing angle, contrast, response speed, and power consumption.

[0068] However, as mentioned above, organic light emitting devices are highly vulnerable to moisture (H2O) or oxygen (O2) because they contain organic material layers. Specifically, when moisture or oxygen penetrates into an organic light emitting device, which includes two electrodes and an organic light emitting layer disposed between them, various defects such as dark spots and pixel shrinkage caused by oxidation of the electrodes or deterioration of the organic material can occur, resulting in a reduced lifespan. Pixel shrinkage refers to a defect in which the edge of a pixel turns black due to oxidation or deterioration at the interface between the electrode and the organic light emitting layer caused by the penetration of moisture or oxygen. If pixel shrinkage continues for a long period of time, it can worsen into a dark spot defect in which the entire pixel turns black, seriously affecting the reliability of the organic light emitting display device.

[0069] Therefore, to prevent moisture or oxygen from penetrating into the organic light-emitting device, an encapsulation unit consisting of a first inorganic encapsulation layer, an organic encapsulation layer, and a second inorganic encapsulation layer is disposed on the organic light-emitting device. The second inorganic encapsulation layer, which is disposed on the top, is required to have high density to enhance moisture permeability, oxygen resistance, and physical strength. To meet this requirement, the second inorganic encapsulation layer is primarily made of a silicon-rich inorganic material such as silicon nitride (SiNx). The silicon-rich second inorganic encapsulation layer absorbs light in the blue wavelength range, resulting in a predominantly yellow color. This causes a color coordinate shift in the organic light-emitting display device, particularly during long-term operation. Silicon-rich inorganic materials such as silicon nitride (SiNx) are oxidized due to temperature increases caused by heat generation and energy absorption by light emission. Furthermore, since the second inorganic encapsulation layer is the topmost layer, it is most susceptible to external moisture and oxygen. As a result, oxidation of the second inorganic encapsulation layer proceeds more rapidly than other layers. When the second inorganic sealing layer is oxidized in this manner, the moisture resistance performance decreases and the color of the second inorganic sealing layer changes from yellow to white.

[0070] An organic light emitting display (OLED) includes a plurality of sub-pixels, each of which emits a different color, such as white, blue, green, or red. The OLED displays images of various colors by combining the sub-pixels emitting different colors. When the OLED displays images, the frequency of emission of each of the sub-pixels varies.

[0071] Therefore, as the emission frequency of each of the subpixels varies, the frequency with which light reaches the second inorganic sealing layer on the light-emitting element in each of the subpixels also varies. That is, the second inorganic sealing layer disposed in the subpixels that emit light more frequently is more affected by the light emitted from the light-emitting element, thereby accelerating the oxidation of the second inorganic sealing layer. In contrast, the second inorganic sealing layer disposed in the subpixels that emit light less frequently is less affected by the light emitted from the light-emitting element, thereby delaying the oxidation of the second inorganic sealing layer. As described above, the color of the second inorganic sealing layer changes from yellow to white depending on the degree of oxidation of its constituent components. Therefore, as the degree of oxidation of the second inorganic sealing layer varies in each of the subpixels, the color change of the second inorganic sealing layer in each of the subpixels also varies. That is, the second inorganic sealing layer disposed in the subpixels that emit light more frequently is white due to the relatively high degree of oxidation, while the second inorganic sealing layer disposed in the subpixels that emit light less frequently is yellow due to the relatively low degree of oxidation. As described above, the color of the second inorganic sealing layer changes in each of the plurality of sub-pixels, which causes a problem of spots, which are non-restoring afterimages.

[0072] Therefore, the display device 100 according to one embodiment of the present specification includes optical compensation layers 150a and 150b containing or made of a transition metal oxide on the second inorganic sealing layers 143a and 143b. The oxygen-deficient structure of the transition metal oxide allows it to capture external oxygen, thereby delaying the oxidation of the second inorganic sealing layers 143a and 143b. This improves the oxidation resistance and moisture permeation resistance reliability of the display device 100.

[0073] Furthermore, the display device 100 according to an embodiment of the present disclosure can minimize the occurrence of non-restored image retention.

[0074] As described above, by delaying the oxidation of the second inorganic sealing layers 143a and 143b, the difference in the degree of oxidation of the second inorganic sealing layers 143a and 143b in each of the sub-pixels SP can be reduced, thereby reducing the difference in color change of the second inorganic sealing layers 143a and 143b in each of the sub-pixels SP, thereby improving driving afterimages.

[0075] As shown in FIG. 2, the display device 100 according to an embodiment of the present disclosure may include an optical compensation layer 150a having a complementary color to the second inorganic encapsulation layer 143a. This compensates for the color of the second inorganic encapsulation layer 143a, which appears yellowish when not oxidized, to white. Therefore, when the display device 100 is viewed in an unoxidized state, the color of the corresponding area may appear white. Furthermore, as shown in FIG. 3, as oxidation occurs, the color densities of the second inorganic encapsulation layer 143b and the optical compensation layer 150b both become lighter, resulting in a white appearance. This may reduce image retention due to discoloration of the second inorganic encapsulation layer 143b and the optical compensation layer 150b when the display device 100 is driven. That is, the second inorganic encapsulation layers 143a, 143b and the optical compensation layers 150a, 150b appear white in all subpixels regardless of the degree of oxidation, thereby minimizing the occurrence of non-restoration image retention.

[0076] A display device 400 according to another embodiment of the present specification will be described below with reference to FIGS.

[0077] FIG. 4 is a cross-sectional view of a display device according to another embodiment of the present specification. FIG. 5 is a cross-sectional view of a display device according to another embodiment of the present specification. The subpixel SP shown in FIG. 4 is a subpixel SP in an initial state of the display device 400 or in a state where it hardly emits light, and the subpixel SP shown in FIG. 5 is a subpixel SP in a state where it has emitted light for a very long time. The display device 400 of FIGS. 4 and 5 differs from the display device 100 of FIGS. 1 to 3 only in the arrangement order of the second inorganic sealing layers 443a, 443b and the optical compensation layers 450a, 450b, and the other configurations are substantially the same, so redundant description will be omitted.

[0078] 4 and 5, in a display device 400 according to another embodiment of the present specification, optical compensation layers 450a and 450b may be disposed below second inorganic sealing layers 443a and 443b. Specifically, the optical compensation layers 450a and 450b may be disposed between the organic sealing layer 142 and the second inorganic sealing layers 443a and 443b. The optical compensation layers 450a and 450b may be disposed to cover the entire top and side surfaces of the organic sealing layer 142. For example, the optical compensation layers 450a and 450b may be disposed over an area larger than that of the organic sealing layer 142.

[0079] The display device 400 according to another embodiment of the present specification may include optical compensation layers 450a and 450b below the second inorganic encapsulation layers 443a and 443b, which may prevent heat or light-emitting energy generated in the light-emitting element 130 from being transferred to the second inorganic encapsulation layers 443a and 443b. This may delay oxidation of the second inorganic encapsulation layers 443a and 443b.

[0080] Furthermore, the display device 400 according to another embodiment of the present specification can delay oxidation of the second inorganic sealing layers 443a and 443b by capturing surrounding oxygen through the optical compensation layers 450a and 450b containing or made of a transition metal oxide having excellent oxygen capturing ability. Furthermore, since the permeation of moisture or oxygen into the light emitting element 130 can be prevented, the oxidation resistance and moisture permeation resistance reliability of the display device 400 can be improved.

[0081] As shown in FIG. 4, a display device 400 according to another embodiment of the present invention may include a second inorganic encapsulation layer 443a having a color complementary to that of the optical compensation layer 450a disposed on the optical compensation layer 450a. Therefore, the color of the second inorganic encapsulation layer 443a, which appears yellowish when not oxidized, can be compensated to white. This prevents the color coordinates of the display device 400 from shifting. Furthermore, as shown in FIG. 5, the colors of the optical compensation layer 450b and the second inorganic encapsulation layer 443b may both become transparent white (e.g., transparent white) as oxidation occurs. As a result, the display device 400 according to an embodiment of the present disclosure may appear to have a uniform color in each of the subpixels SP, regardless of the degree of oxidation of the second inorganic encapsulation layers 443a and 443b. This minimizes the hue difference between the subpixels SP.

[0082] Display devices according to various embodiments of the present disclosure can be described as follows.

[0083] A display device according to one embodiment of the present 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 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 on top or bottom of the second inorganic sealing layer and containing or consisting of a transition metal oxide.

[0084] According to other embodiments herein, the light emitting device may be an organic light emitting device.

[0085] According to still another embodiment of the present specification, the optical compensation layer may be disposed on the second inorganic sealing layer and contact the top surface of the second inorganic sealing layer.

[0086] According to still other embodiments herein, the optical compensation layer may be disposed between the organic encapsulation layer and the second inorganic encapsulation layer.

[0087] According to still another embodiment of the present specification, the optical compensation layer may be in contact with the lower surface of the second inorganic sealing layer.

[0088] According to yet another embodiment of the present disclosure, the optical compensation layer may be disposed to completely cover the top and side surfaces of the organic encapsulation layer.

[0089] According to another embodiment of the present specification, the optical compensation layer may be disposed over a larger area than the organic sealing layer.

[0090] According to still another embodiment of the present disclosure, 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 still another embodiment of the present specification, the transition metal may have an energy band gap of 2.48 eV to 2.76 eV.

[0092] According to another embodiment of the present disclosure, the transition metal oxide may include at least one of cobalt oxide, cerium oxide, manganese oxide, and chromium oxide.

[0093] According to still other embodiments herein, the transition metal oxide may include cobalt oxide or cerium oxide.

[0094] According to still another embodiment of the present specification, the optical compensation layer may have a complementary color relationship with the second inorganic sealing layer.

[0095] According to yet another embodiment of the present specification, the optical compensation layer may be blue-based.

[0096] According to still another embodiment of the present disclosure, the second inorganic sealing layer may be yellow-based.

[0097] According to yet another embodiment of the present disclosure, the second inorganic encapsulation layer may include or be formed of silicon nitride (SiNx).

[0098] According to still another embodiment of the present specification, the optical compensation layer and the second inorganic sealing layer may be white regardless of the degree of oxidation.

[0099] Although the embodiments of the present specification have been described in more detail above with reference to the accompanying drawings, the present specification is not necessarily limited to such embodiments and may be variously modified within the scope of the technical concept of the present specification. Therefore, the embodiments disclosed in the present specification are for illustrative purposes only and do not limit the technical concept of the present specification. Therefore, the embodiments described above should be understood to be illustrative in all respects and not restrictive.

Claims

1. 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 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 on or under the second inorganic sealing layer and including or formed of a transition metal oxide; A display device comprising:

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 an upper surface of the second inorganic sealing layer.

4. The display device of claim 1 , wherein the optical compensation layer is disposed between the organic sealing layer and the second inorganic sealing layer.

5. The display device according to claim 4 , wherein the optical compensation layer is in contact with a lower surface of the second inorganic sealing layer.

6. The display device according to claim 4 , wherein the optical compensation layer is disposed so as to completely cover an 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 disposed over an area larger than that of the organic sealing layer.

8. 2. The display device according to claim 1, wherein the transition metal in the transition metal oxide has an energy band gap of 2.18 eV to 3.10 eV.

9. 9. The display device according to claim 8, wherein the transition metal has an energy band gap of 2.48 eV to 2.76 eV.

10. 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.

11. The display device according to claim 10 , wherein the transition metal oxide includes cobalt oxide or cerium oxide.

12. The display device according to claim 1 , wherein the optical compensation layer has a complementary color to the second inorganic sealing layer.

13. The display device of claim 1 , wherein the optical compensation layer is blue-based.

14. The display device according to claim 1 , wherein the second inorganic sealing layer is yellow-based.

15. The display device of claim 1 , wherein the second inorganic sealing layer includes or is formed of silicon nitride (SiNx).

16. The display device of claim 1 , wherein the optical compensation layer and the second inorganic sealing layer are white regardless of the degree of oxidation.

17. The display device according to claim 1 , wherein the optical compensation layer is disposed so as to completely cover an upper surface of the organic sealing layer.

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