Display device

Abstract

According to an aspect of the present disclosure, there is provided a display device including: a substrate including a display area and a non-display area surrounding the display area; a light emitting element such as a light emitting diode on the display area; a first inorganic encapsulation layer on the light emitting element; an organic encapsulation layer on the first inorganic encapsulation layer; a second inorganic encapsulation layer on the organic encapsulation layer; and an optical compensation layer disposed on or below the second inorganic encapsulation layer, and including or formed of a transition metal oxide. Thus, oxidation of the second inorganic encapsulation layer can be minimized and occurrence of afterimage can be suppressed.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority from Korean Patent Application No. 10-2024-0028164 filed on February 27, 2024, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. Technical Field

[0003] The present disclosure relates to a display device, and more particularly, to a display device with enhanced reliability. Background Art

[0004] With the development of the information society, people's demand for display devices to display images has increased in various ways. Accordingly, various display devices such as liquid crystal display (LCD) devices, plasma display panel (PDP) devices, organic light emitting display (OLED) devices, and quantum dot light emitting display (QLED) devices have been used recently.

[0005] Among these display devices, organic light-emitting display devices (OLEDs) can be manufactured to be lightweight and thin because they do not require additional light sources like liquid crystal displays (LCDs). Furthermore, due to their low-voltage drive, OLEDs offer advantages in power consumption and are superior in color realization, response speed, viewing angle, and contrast ratio (CR). Consequently, OLEDs are being researched as the next generation of display devices. Summary of the Invention

[0006] An object to be achieved by the present disclosure is to provide a display device in which the occurrence of afterimages on the display device (eg, a display panel thereof) is reduced to the greatest extent.

[0007] Another object to be achieved by the present disclosure is to provide a display device in which the uneven brightness of the display device (eg, a display panel thereof) is reduced to the greatest extent.

[0008] The objects to be achieved by the present disclosure, means for achieving the objects, and the effects of the present disclosure described above do not specify essential features of the claims, and therefore, the scope of the claims is not limited to the disclosed contents of the present disclosure.

[0009] According to one aspect of the present disclosure, a display device is provided. The display device includes: a substrate, the substrate including a display area and a non-display area surrounding the display area; a light-emitting element (for example, a light-emitting diode, in particular an organic light-emitting diode, but not limited thereto) on the display area (or arranged at the display area); a first inorganic encapsulation layer on the light-emitting element; an organic encapsulation layer on the first inorganic encapsulation layer; a second inorganic encapsulation layer on the organic encapsulation layer; and an optical compensation layer, the optical compensation layer being arranged on the second inorganic encapsulation layer or below the second inorganic encapsulation layer and including a transition metal oxide (in other words, an oxide of a transition metal) or being formed of a transition metal oxide. Therefore, the occurrence of afterimages of the display device (or its display panel) caused by oxidation due to light emitted from the light-emitting element (for example, a light-emitting diode) can be minimized.

[0010] Additional details of exemplary embodiments are included in the detailed description and accompanying drawings.

[0011] According to the present disclosure, an optical compensation layer is disposed (or included) on an upper side or a lower side of the second inorganic encapsulating layer, thereby minimizing oxidation of the second inorganic encapsulating layer.

[0012] According to the present disclosure, oxidation of the second inorganic encapsulating layer is minimized, thereby minimizing the occurrence of an afterimage on a display device due to oxidation of the second inorganic encapsulating layer.

[0013] According to the present disclosure, a brightness unevenness state of the display device due to partial oxidation of the second inorganic encapsulating layer is minimized, thereby enhancing the display quality of the display device.

[0014] According to the present disclosure, the moisture-proof (or humidity-proof) function of the display device is enhanced, thereby improving the reliability of the display device.

[0015] The effects according to the present disclosure are not limited to those exemplified above, and further various effects can be provided in the present disclosure.

[0016] The effects of the present disclosure are not limited to the above-described effects, and include other various effects in the detailed description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic plan view of a display device according to an exemplary embodiment of the present disclosure.

[0018] Figure 2 It is along Figure 1 A cross-sectional view taken along line II-II'.

[0019] Figure 3 It is along Figure 1 A cross-sectional view taken along line III-III'.

[0020] Figure 4 is a cross-sectional view of a display device according to another exemplary embodiment of the present disclosure.

[0021] Figure 5 is a cross-sectional view of a display device according to another exemplary embodiment of the present disclosure. DETAILED DESCRIPTION

[0022] The advantages and features of the present disclosure and methods for achieving these advantages and features will become clear by referring to the exemplary embodiments described in detail below in conjunction with the accompanying drawings. However, the present disclosure is not limited to the exemplary embodiments disclosed herein, but may be implemented in various forms. The exemplary embodiments are provided only by way of example so that those skilled in the art can fully understand the disclosure and scope of the present disclosure.

[0023] The shapes, sizes, proportions, angles, and quantities illustrated in the accompanying drawings for describing exemplary embodiments of the present disclosure are merely examples, and the present disclosure is not limited thereto. In addition, in the following description of the present disclosure, detailed explanations of known related arts may be omitted to avoid unnecessarily obscuring the subject matter of the present disclosure. Terms such as "including," "having," and "consisting of" used herein are generally intended to allow for the addition of other components unless these terms are used with the term "only." Unless expressly stated otherwise, any reference to the singular may include the plural.

[0024] Even if not explicitly stated, components are interpreted as including the usual margin of error.

[0025] When terms such as "on," "over," "below," and "near" are used to describe the positional relationship between two components, one or more components may be located between the two components, unless these terms are used together with the terms "immediately" or "directly."

[0026] When one element or layer is disposed on another element or layer, the other element or layer may be directly interposed on the other element or layer or interposed therebetween.

[0027] Although the terms "first," "second," etc. are used to describe various components, these components are not limited by these terms. These terms are only used to distinguish one component from other components. Therefore, the first component mentioned below can be the second component in the technical concept of the present disclosure.

[0028] Like reference numbers generally refer to like elements throughout the description.

[0029] The size and thickness of each component illustrated in the drawings are illustrated only for convenience of description, and the present disclosure is not limited to the size and thickness of the components shown.

[0030] The features of the various embodiments of the present disclosure may be partially or entirely adhered to or combined with each other, and may be technically related and operated with each other in various ways, and these embodiments may be implemented independently of or in association with each other.

[0031] Hereinafter, a display device according to exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0032] Figure 1 is a schematic plan view of a display device according to an exemplary embodiment of the present disclosure, Figure 2 It is along Figure 1 A cross-sectional view taken along line II-II', and Figure 3 It is along Figure 1 A cross-sectional view taken along line III-III'. Figure 2 The sub-pixel SP of FIG. 1 shows the initial state of the display device 100 or the sub-pixel in the state of almost no light emission, and Figure 3 The sub-pixels SP of φ show the sub-pixels SP of the display device 100 that are in a light-emitting state for a considerable period of time.

[0033] refer to Figures 1 to 3 The display device 100 (or its display panel as is well known in the art) includes a substrate 110, a transistor 120, a light emitting diode 130, a first inorganic encapsulation layer 141, an organic encapsulation layer 142, a second inorganic encapsulation layer 143a and 143b, and optical compensation layers 150a and 150b.

[0034] refer to Figure 1 The substrate 110 is configured to support and protect the various components of the display device 100. The substrate 110 may be formed of a flexible plastic material. Alternatively, the substrate 110 may be formed of a transparent insulating material. For example, the substrate 110 may be formed of transparent polyimide (PI).

[0035] The substrate 110 includes a display area AA and a non-display area NA.

[0036] The display area AA may be provided at the central portion of the substrate 110 and may be a region where an image is displayed in the display device 100. Light emitting elements (or display elements) and various driving elements for driving the light emitting elements (or display elements) may be provided in the display area AA. Figure 2 and Figure 3As shown, the light-emitting element (or display element) may be configured as a light-emitting diode 130 including a first electrode 131, a light-emitting unit 133, and a second electrode 135. In addition, various driving elements such as a transistor 120 for driving the light-emitting element (or display element), a capacitor, and wiring (circuit) may be provided at the display area AA.

[0037] A plurality of pixels PX may be provided at the display area AA. The plurality of pixels PX may be provided at intersections between a plurality of gate lines provided in a first direction and a plurality of data lines provided in a second direction different from the first direction. Here, the first direction may be Figure 1 The horizontal direction, and the second direction can be Figure 1 The vertical direction of the plurality of pixels PX is not limited thereto. Each of the plurality of pixels PX may include a plurality of sub-pixels SP for emitting light of different colors. For example, some of the plurality of sub-pixels SP may be red sub-pixels, some of the plurality of sub-pixels SP may be green sub-pixels, and other sub-pixels of the plurality of sub-pixels SP may be blue sub-pixels. The plurality of sub-pixels SP may further include a white sub-pixel, but the present disclosure is not limited thereto.

[0038] The pixel PX is the smallest unit constituting the screen, and each of the plurality of pixels PX may include a light-emitting diode 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 a signal line, such as a gate line and a data line connected to a gate driver, a data driver, etc. provided in the non-display area NA.

[0039] The non-display area NA may be an area provided at the periphery (or periphery) of the substrate 110, in other words, an area where no image is displayed. The non-display area NA may be provided to surround the display area AA. Various components for driving the plurality of pixels PX provided at the display area AA may be provided at the non-display area NA. For example, a driver integrated circuit IC, a driver circuit, a signal line, a flexible film, etc. may be provided to supply signals to drive the plurality of pixels PX. The driver integrated circuit IC may include a gate driver, a data driver, etc. The driver integrated circuit IC and the driver circuit may be provided in a gate-in-panel (GIP) manner, a chip-on-film (COF) manner, a tape automated bonding (TAB) manner, a tape carrier package (TCP) manner, a chip-on-glass (COG) manner, etc.

[0040] In the following, reference will be made to Figure 2 and Figure 3 Each of the plurality of sub-pixels SP provided at the display area AA of the display device 100 is explained in more detail.

[0041] refer to Figure 2 and Figure 3 , a buffer layer 111 may be provided on the substrate 110. The buffer layer 111 may be configured to enhance the bonding force between the layer formed on the buffer layer 111 and the substrate 110. In addition, the buffer layer 111 may block alkali components and the like leaked from the substrate 110, and may suppress the diffusion of moisture and / or oxygen introduced from outside the substrate 110. The buffer layer 111 may be formed of a single layer of silicon nitride (SiNx) or silicon oxide (SiOx) or a multilayer thereof. However, the present disclosure is not limited thereto. Alternatively, the buffer layer 111 may be omitted based on the type and material of the substrate 110, the structure and type of the transistor 120, and the like.

[0042] The transistor 120 may be provided on the buffer layer 111 to drive the light emitting diode 130. The transistor 120 may be provided at each of the plurality of sub-pixels SP in the display area AA. The transistor 120 provided at each of the plurality of sub-pixels SP may serve as a driving element of the display device 100. For example, the transistor 120 may be 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 transistor (CMOS), a field effect transistor (FET), or the like. However, the present disclosure is not limited thereto. In the following, the present disclosure will be explained under the assumption that the transistor 120 is a thin film transistor, but is not limited thereto.

[0043] The transistor 120 may include an active layer 121 , a gate electrode 122 , a source electrode 123 , and a drain electrode 124 . Figure 2 and Figure 3 The transistor 120 is a top-gate thin film transistor in which a gate electrode 122 is provided on the active layer 121. However, the present disclosure is not limited thereto, but may be configured as a bottom-gate thin film transistor.

[0044] The active layer 121 of the transistor 120 may be provided 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 an oxide semiconductor, amorphous silicon (a-Si), polycrystalline silicon (poly-Si), an organic semiconductor, etc., but the present disclosure is not limited thereto.

[0045] The gate insulating layer 112 may be provided above the active layer 121. The gate insulating layer 112 may be formed of a single layer or a multilayer of silicon nitride (SiNx) or silicon oxide (SiOx), which are inorganic materials. Contact holes may be formed in the gate insulating layer 112 for allowing the source electrode 123 and the drain electrode 124 to contact the source region and the drain region of the active layer 121, respectively. Figure 2 and Figure 3As shown, the gate insulating layer 112 may be formed over the entire surface of the substrate 110 and may also be patterned to have the same width as the gate electrode 122. However, the present disclosure is not limited thereto.

[0046] 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 with the channel region of the active layer 121. The gate electrode 122 may be formed of one of various metal materials, such as molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd), and copper (Cu). Alternatively, the gate electrode 122 may be formed of an alloy of two or more of these metal materials or a multilayer thereof, but the present disclosure is not limited thereto.

[0047] An interlayer insulating layer 113 may be provided on the gate electrode 122. The interlayer insulating layer 113 may be formed of a single layer or a multilayer of silicon nitride (SiNx) or silicon oxide (SiOx), which are inorganic materials. Contact holes may be formed in the interlayer insulating layer 113 for allowing the source electrode 123 and the drain electrode 124 to contact the source region and the drain region of the active layer 121, respectively.

[0048] The source electrode 123 and the drain electrode 124 may be provided on the interlayer insulating layer 113. The source electrode 123 and the drain electrode 124 may be electrically connected to the active layer 121 via contact holes of the gate insulating layer 112 and the interlayer insulating layer 113. The source electrode 123 and the drain electrode 124 may be formed of one of various metal materials, such as molybdenum (Mo), aluminum (Al), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd), and copper (Cu). Alternatively, the source electrode 123 and the drain electrode 124 may be formed of an alloy of two or more of these metal materials or a multilayer thereof, but the present disclosure is not limited thereto.

[0049] For ease of explanation, Figure 2 and Figure 3 Only driving transistors are illustrated among various types of transistors 120 included in the display device 100. However, other transistors such as switching transistors may be provided.

[0050] A passivation layer 114 for protecting the transistor 120 may be provided on the transistor 120. A contact hole may be formed in the passivation layer 114 for exposing a drain electrode 124 of the transistor 120. Figure 2 and Figure 3The figure shows that the contact hole for exposing the drain electrode 124 is formed in the passivation layer 114. However, the contact hole for exposing the source electrode 123 may be formed in the passivation layer 114. The passivation layer 114 may be configured as a single layer or a multilayer of silicon nitride (SiNx) or silicon oxide (SiOx). However, according to an exemplary embodiment of the present disclosure, the passivation layer 114 may be omitted.

[0051] An over coating layer 115 for planarizing an upper portion 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 over coating layer 115. Figure 2 and Figure 3 The figure shows that the contact hole for exposing the drain electrode 124 is formed in the cover coating 115. However, the contact hole for exposing the source electrode 123 may be formed in the cover coating 115. The cover coating 115 may be formed of one of acrylic resin, epoxy resin, phenolic resin, polyamide resin, polyimide resin, unsaturated polyester resin, polyphenylene resin, polyphenylene sulfide resin, benzocyclobutene, and photoresist. However, the present disclosure is not limited thereto.

[0052] The light emitting diode 130 may be disposed on the overcoat layer 115. The light emitting diode 130 includes a first electrode 131 formed on the overcoat layer 115 and 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 unit 133 disposed on the hole transport layer 132, an electron transport layer (ETL) 134 disposed on the light emitting unit 133, and a second electrode 135 disposed on the electron transport layer 134.

[0053] The first electrode 131 may be provided on the overcoating layer 115. The first electrode 131 may be an anode electrode configured to supply holes to the light emitting unit 133, but the present disclosure is not limited thereto. The first electrode 131 may be electrically connected to the transistor 120 via a contact hole of the overcoating layer 115. For example, although Figure 2 and Figure 3 Although not shown in the figure, the first electrode 131 can be electrically connected to the source electrode 123 of the transistor 120. The first electrodes 131 can be arranged to be spaced apart from each other according to each sub-pixel SP. The first electrode 131 can be formed of a transparent conductive material. For example, the first electrode 131 can be formed of indium tin oxide (ITO), indium zinc oxide (IZO), etc., but the present disclosure is not limited thereto.

[0054] Although not shown in the drawings, in the case where the display device 100 according to the exemplary embodiment of the present disclosure is a top emission type (which is a top emission type), the first electrode 131 may further include a reflective layer so that the light emitted from the light emitting unit 133 can be emitted more smoothly in an upward direction by being reflected by the first electrode 131. For example, the first electrode 131 may have a two-layer structure in which a transparent conductive layer and a reflective layer formed of a transparent conductive material are sequentially stacked on each other, or may have a three-layer structure in which a transparent conductive layer, a reflective layer, and a transparent conductive layer are sequentially stacked on each other. The reflective layer may be formed of silver (Ag) or an alloy including silver, and may be formed of silver or APC (Ag / Pd / Cu), for example.

[0055] The bank 116 may be provided on the first electrode 131 and the cover coating 115. The bank 116 may be configured to separate adjacent sub-pixel regions from each other. In addition, the bank 116 may be configured to separate pixel PX regions from each other, and the pixel region is composed of the regions of multiple sub-pixels SP.

[0056] The hole transport layer 132 may be provided on the first electrode 131. The hole transport layer 132 may be provided on the first electrode 131 and the bank 116 so as to cover them. The hole transport layer 132 may be an organic layer for smoothly transporting holes to the light emitting unit 133 and may be provided as a single layer on the first electrode 131 and the bank 116. For example, the hole transport layer 132 may be formed of at least one material 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). However, the present disclosure is not limited thereto.

[0057] Meanwhile, a hole injection layer may be provided between the first electrode 131 and the hole transport layer 132. The hole injection layer may be an organic layer for smoothly injecting holes from the first electrode 131 into the light emitting unit 133. For example, the hole injection layer may be formed of at least one selected from the following group, 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). However, the present disclosure is not limited thereto. The hole injection layer may be included or omitted depending on the structure or characteristics of the display device 100.

[0058] 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 with the first electrode 131. The light-emitting unit 133 may be patterned between two adjacent embankments 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 present disclosure is not limited thereto. That is, the light-emitting unit 133 may include a material capable of emitting light of other colors.

[0059] The electron transport layer 134 may be disposed on the light emitting unit 133 .

[0060] The electron transport layer 134 may be an organic layer for transporting electrons to the light emitting unit 133. The electron transport layer 134 may be provided as a single layer along the top surface of the hole transport layer 132 and the light emitting unit 133. The electron transport layer 134 may include a compound having an electron transport function. For example, the electron transport layer 134 may be formed by at least one selected from the following groups, the group consisting of metal quinolinate, PBD (2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole), 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). However, the present disclosure is not limited thereto.

[0061] The second electrode 135 may be provided on the electron transport layer 134. The second electrode 135 may be a cathode electrode for supplying electrons to the light emitting unit 133, but the present disclosure is not limited thereto. The second electrode 135 may include a metal material such as magnesium (Mg), silver-magnesium (Ag:Mg) or be formed of a metal material such as magnesium (Mg), silver-magnesium (Ag:Mg). In the case of a top emission type display device that emits light in an upward direction, the second electrode 135 may be a transparent conductive oxide based on one or more of indium tin oxide ITO, indium zinc oxide IZO, indium tin zinc oxide ITZO, zinc oxide ZnO, and tin oxide TiO. However, the present disclosure is not limited thereto.

[0062] The electron injection layer may be provided between the electron transport layer 134 and the second electrode 135. The electron injection layer may be an organic layer for smoothly injecting electrons from the second electrode 135 into the light emitting unit 133. The electron injection layer may be omitted if necessary.

[0063] A coating layer (or cap layer) 117 may be provided on the second electrode 135. The coating layer 117 may be formed of a material having a high refractive index and a high light absorptivity to reduce diffuse reflection of external light. For example, the coating layer 117 may be an organic material layer formed of an organic material. However, the present disclosure is not limited thereto. That is, the coating layer 117 may be formed of an inorganic material. The coating layer 117 may be omitted if necessary.

[0064] The first inorganic encapsulation layer 141 is provided on the coating layer 117. The first inorganic encapsulation layer 141 is used to block oxygen or moisture from penetrating from the outside. The first inorganic encapsulation layer 141 may include a silicon compound such as silicon nitride (SiNx) or silicon oxide (SiOx) or be formed of a silicon compound such as silicon nitride (SiNx) or silicon oxide (SiOx). However, the present disclosure is not limited thereto.

[0065] The organic encapsulation layer 142 is disposed on the first inorganic encapsulation layer 141. The organic encapsulation layer 142 is used to flatten the upper portion of the first inorganic encapsulation layer and to compensate for steps caused by foreign matter, pinholes, etc. that may be present on the lower side of the organic encapsulation layer. The organic encapsulation layer 142 may be formed of an organic material such as an acrylic resin, an epoxy resin, a phenolic resin, a polyamide resin, and a polyimide resin. However, the present disclosure is not limited thereto.

[0066] The second inorganic encapsulation layer 143a and 143b are provided on the organic encapsulation layer 142. The second inorganic encapsulation layer can be provided as a single layer so as to cover the components provided on the lower side of the second inorganic encapsulation layer. The second inorganic encapsulation layer is used to block oxygen or moisture from penetrating from the outside. The second inorganic encapsulation layers 143a and 143b may include an inorganic material such as silicon nitride (SiNx) or silicon oxide (SiOx) or be formed of an inorganic material such as silicon nitride (SiNx) or silicon oxide (SiOx), and in particular may include, for example, silicon nitride (SiNx) or be formed of, for example, silicon nitride (SiNx).

[0067] refer to Figure 2 and Figure 3 , the second inorganic encapsulation layers 143a and 143b may have different colors according to their oxidation degree at each of the multiple sub-pixels SP. The second inorganic encapsulation layers 143a and 143b may have a yellow color scheme before oxidation (in other words, may appear yellow), and may have a color change toward transparent white as oxidation proceeds. Here, the oxidation of the second inorganic encapsulation layers 143a and 143b is accelerated by the temperature increase due to heat generation that occurs when the light-emitting diode 130 is driven for a long time, the energy absorption due to the light emission of the light-emitting diode 130, and the like. Therefore, the oxidation degree of each of the multiple sub-pixels SP may be variable according to the driving degree of the light-emitting diode 130. For example, as Figure 2As shown, at some sub-pixels SP where the driving frequency (number of times) of the light emitting diode 130 is small (or low), the oxidation (or oxidation degree) of the second inorganic encapsulation layer 143a may be relatively small (or low). Here, at the sub-pixels SP where the oxidation (or oxidation degree) of the second inorganic encapsulation layer 143a is relatively small (or low), the second inorganic encapsulation layer 143a may have a yellow color. On the other hand, as Figure 3 As shown, oxidation of the second inorganic encapsulating layer 143a may be relatively significant at some sub-pixels SP where the driving frequency (number) of the light emitting diode 130 is high. Here, at the sub-pixels SP where oxidation of the second inorganic encapsulating layer 143b is relatively significant, the second inorganic encapsulating layer 143b may have a transparent white color (in other words, may appear transparent white).

[0068] The optical compensation layers 150a and 150b may be disposed on the second inorganic encapsulation layers 143a and 143b. The optical compensation layers 150a and 150b may block oxygen or moisture from penetrating from the outside together with the second inorganic encapsulation layers 143a and 143b, and may solve the afterimage problem by compensating for color changes of the second inorganic encapsulation layers.

[0069] The optical compensation layer may be provided as a single layer so as to cover the components provided on the lower side of the optical compensation layer. Here, at least one surface of the optical compensation layers 150a and 150b may contact the surface (e.g., top surface) of the second inorganic encapsulation layers 143a and 143b. For example, the bottom surfaces of the optical compensation layers 150a and 150b may contact the top surfaces of the second inorganic encapsulation layers 143a and 143b.

[0070] The optical compensation layers 150a and 150b may include a transition metal oxide or be formed of a transition metal oxide. Here, the transition metal in the transition metal oxide may have an energy band gap of 2.18eV to 3.10eV (e.g., 2.48eV to 2.76eV). In addition, the transition metal may include a blue-colored transition metal. For example, the transition metal may include at least one of cobalt (Co), cerium (Ce), and chromium (Cr). More specifically, the transition metal may include cobalt (Co) or cerium (Ce). Therefore, the optical compensation layers 150a and 150b may be formed of at least one of cobalt oxide, cerium oxide, and chromium oxide. More specifically, the optical compensation layers 150a and 150b may be formed of cobalt oxide or cerium oxide.

[0071] The optical compensation layers 150a and 150b can be formed by depositing the aforementioned transition metal oxide on the second inorganic encapsulation layers 143a and 143b using a method such as physical vapor deposition (PVD). However, the present disclosure is not limited thereto. Here, due to the oxygen defect (or oxygen deficiency) structure, the transition metal oxide can actively (or positively) undergo an oxidation reaction with external oxygen. Therefore, external oxygen is collected, which can inhibit external oxygen from penetrating into the second inorganic encapsulation layers 143a and 143b. This can reduce the oxidation of the second inorganic encapsulation layers 143a and 143b.

[0072] refer to Figure 2 and Figure 3 , the optical compensation layers 150a and 150b may have different colors according to their oxidation degree at each of the plurality of sub-pixels SP. The optical compensation layers 150a and 150b may have a blue color before oxidation, and may have a color change toward transparent white as oxidation proceeds. Here, the oxidation of the optical compensation layers 150a and 150b is accelerated by a temperature increase due to heat generation that occurs when the light emitting diode 130 is driven for a long time, energy absorption due to the light emission (brightness) of the light emitting diode 130, and the like. Therefore, the oxidation degree of each of the plurality of sub-pixels SP may be variable according to the driving degree of the light emitting diode 130. For example, as Figure 2 As shown, at some sub-pixels SP where the driving frequency (number) of the light emitting diode 130 is low, oxidation of the optical compensation layer 150a may be relatively low. Here, the optical compensation layer 150a may have a blue color. On the other hand, as Figure 3 As shown, oxidation of the optical compensation layer 150a may be relatively significant at some sub-pixels SP where the driving frequency (number) of the light emitting diode 130 is high. Here, at the sub-pixels SP where oxidation of the optical compensation layer 150a is relatively high, the optical compensation layer 150a may have a transparent white color (in other words, may appear transparent white).

[0073] Therefore, in the display device 100 according to an exemplary embodiment of the present disclosure, the second inorganic encapsulation layers 143a and 143b and the optical compensation layers 150a and 150b may have different colors at each of the plurality of sub-pixels SP. Figure 3 At the sub-pixel SP shown (where oxidation proceeds relatively high or significantly), the second inorganic encapsulation layer 143b and the optical compensation layer 150b may have a white color. Figure 2At the sub-pixel SP shown (where oxidation proceeds relatively slowly or less), the second inorganic encapsulation layer 143a may have a yellow hue, and the optical compensation layer 150a may have a blue hue. Here, the color concentration (or intensity) of the second inorganic encapsulation layers 143a and 143b and the optical compensation layers 150a and 150b may vary according to the degree of oxidation. For example, at some sub-pixels SP where oxidation proceeds relatively slowly among the plurality of sub-pixels SP, the second inorganic encapsulation layer 143a may have a higher concentration of yellow hue, and the optical compensation layer 150a may also have a higher concentration of blue hue. As oxidation proceeds at each of the plurality of sub-pixels SP, the color concentration of each of the second inorganic encapsulation layer 143a and the optical compensation layer 150a may decrease. Here, color concentration refers to the degree of lightness or darkness of a color. For example, a high color concentration means a dark color, while a low color concentration means a light color.

[0074] Organic light-emitting diodes generally have a structure including an anode, a cathode, and an organic material layer disposed between the anode and the cathode. The organic material layer generally has a multilayer structure formed of different materials in order to enhance the efficiency and stability of the organic light-emitting diode. For example, the organic material layer may be composed of a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer, and the like. In this structure of an organic light-emitting diode, when a voltage is applied between two electrodes (i.e., an anode and a cathode), holes from the anode and electrons from the cathode are injected into the organic material layer. When the injected holes and electrons meet, excitons are formed. When the excitons fall back to the bottom state, light is generated. Such organic light-emitting diodes are the next generation of light sources with self-luminous properties and have advantages over liquid crystals in terms of viewing angle, contrast, response speed, power consumption, etc.

[0075] However, as mentioned above, organic light emitting diodes are very susceptible to the effects of water (H2O) or oxygen (O2) because they include an organic material layer. More specifically, if water or oxygen penetrates into an organic light emitting diode including two electrodes and an organic light emitting layer disposed therebetween, the lifespan is shortened due to various types of defects, such as dark spots and pixel shrinkage due to oxidation of the electrodes or degradation of the organic material. "Pixel shrinkage" refers to a defect in which a pixel changes color from its edge to black as the interface between the electrode and the organic light emitting layer is oxidized or degraded due to the penetration of moisture or oxygen. When pixel shrinkage continues for a long time, it may deteriorate into a dark spot in which the pixel completely changes color to black, thereby seriously affecting the reliability of the organic light emitting display device.

[0076] Therefore, in order to prevent moisture or oxygen from penetrating into the organic light emitting diode, an encapsulation unit including a first inorganic encapsulation layer, an organic encapsulation layer, and a second inorganic encapsulation layer is provided on the organic light emitting diode. Here, the second inorganic encapsulation layer provided at the uppermost portion requires high-density physical properties in order to enhance moisture-proof function, oxygen (gas)-proof function, and physical strength. In order to meet this requirement, the second inorganic encapsulation layer is generally formed of a silicon-rich (Si-rich) inorganic material such as silicon nitride (SiNx). The Si-rich second inorganic encapsulation layer is generally light yellow because it absorbs light of blue wavelengths. Therefore, the color coordinates of the organic light emitting display device are shifted. In particular, Si-rich inorganic materials such as silicon nitride (SiNx) are oxidized by the temperature increase caused by heat generation when the light emitting diode is driven for a long time and the energy absorption caused by light emission. In addition, the second inorganic encapsulation layer (i.e., the layer provided at the uppermost portion) is most affected by moisture or oxygen from the outside. Therefore, the second inorganic encapsulation layer is oxidized faster than other layers. Once the second inorganic encapsulating layer is oxidized, the moisture-proof function is reduced, and the second inorganic encapsulating layer changes color from yellow to white.

[0077] An organic light-emitting display device includes multiple sub-pixels, each of which emits light of a different color (e.g., white, blue, green, and red). The organic light-emitting display device transmits images of various colors by combining the multiple sub-pixels that emit different colors. When the organic light-emitting display device transmits an image, the brightness (light emission) frequency of each of the multiple sub-pixels is variable.

[0078] Since the brightness frequency of each of the multiple sub-pixels is variable, the number of times (frequency) that light reaches the second inorganic encapsulation layer on the light-emitting diode at each of the multiple sub-pixels is also variable. That is, the second inorganic encapsulation layer arranged at the sub-pixel that emits light at a higher frequency is more affected by the light emitted from the light-emitting diode, so its oxidation is accelerated. On the other hand, the second inorganic encapsulation layer arranged at the sub-pixel that emits light at a lower frequency is less affected by the light emitted from the light-emitting diode, so its oxidation is delayed. As mentioned above, the second inorganic encapsulation layer changes color from yellow to white according to the degree of oxidation. Therefore, if the degree of oxidation of the second inorganic encapsulation layer is variable at each of the multiple sub-pixels, the color of the second inorganic encapsulation layer is also variable at each of the multiple sub-pixels. That is, the second inorganic encapsulation layer arranged at the sub-pixel that emits light at a higher frequency is white because it oxidizes more. On the other hand, the second inorganic encapsulation layer arranged at the sub-pixel that emits light at a lower frequency is yellow because it oxidizes less. As such, since the second inorganic encapsulating layer has a different color at each of the plurality of sub-pixels, there is a problem in that stain, which is a non-restorative afterimage, occurs.

[0079] Therefore, the display device 100 according to an exemplary embodiment of the present disclosure includes optical compensation layers 150a and 150b on the second inorganic encapsulation layers 143a and 143b, which have (or include) transition metal oxides or are formed of transition metal oxides. Here, external oxygen is collected by the oxygen defect structure of the transition metal oxide. This can result in delayed oxidation of the second inorganic encapsulation layers 143a and 143b. Therefore, the reliability of the anti-oxidation function and moisture-proof (waterproof) function of the display device 100 can be enhanced.

[0080] Furthermore, the display apparatus 100 according to an exemplary embodiment of the present disclosure may minimize the occurrence of non-restoring afterimages.

[0081] As previously described, by delaying the oxidation of the second inorganic encapsulating layers 143a and 143b, the difference in the degree of oxidation of the second inorganic encapsulating layers 143a and 143b at each of the plurality of sub-pixels can be reduced. This can reduce the difference in color change of the second inorganic encapsulating layers 143a and 143b at each of the plurality of sub-pixels. As a result, driving afterimages can be improved.

[0082] like Figure 2 As shown, the display device 100 according to an exemplary embodiment of the present disclosure may include an optical compensation layer 150a disposed on the second inorganic encapsulation layer 143a and having a complementary color relationship with the second inorganic encapsulation layer 143a. This can compensate the color of the second inorganic encapsulation layer 143a, which is viewed as yellow when not oxidized, to white. Therefore, when the display device 100 is observed in a non-oxidized state, the color of the corresponding area can be viewed as white. Figure 3 As shown, as oxidation progresses, the second inorganic encapsulation layer 143b and the optical compensation layer 150b may have a white color as their color concentration becomes lighter (or lower). This can improve the afterimage caused by the discoloration of the second inorganic encapsulation layer 143b and the optical compensation layer 150b, which occurs as the display device 100 is driven. That is, regardless of the degree of oxidation, the second inorganic encapsulation layers 143a and 143b and the optical compensation layers 150a and 150b can be seen as white at all sub-pixels. As a result, the occurrence of non-restorative afterimages can be minimized.

[0083] In the following, reference will be made to Figure 4 and Figure 5 A display device 400 according to another exemplary embodiment of the present disclosure is explained.

[0084] Figure 4 is a cross-sectional view of a display device according to another exemplary embodiment of the present disclosure. Figure 5 is a cross-sectional view of a display device according to another exemplary embodiment of the present disclosure. Figure 4The sub-pixel SP is a sub-pixel in an initial state or a state in which almost no light is emitted in the display device 400 . Figure 5 The sub-pixel SP of the display device 400 is a sub-pixel SP that is in a light-emitting state for a considerable period of time. Figures 1 to 3 Compared with the display device 100, except for the arrangement order of the second inorganic encapsulation layers 443a and 443b and the optical compensation layers 450a and 450b, Figure 4 and Figure 5 The display device 400 has the same configuration. Therefore, the same explanation will be omitted.

[0085] refer to Figure 4 and Figure 5 , a display device 400 according to another exemplary embodiment of the present disclosure may include optical compensation layers 450a and 450b below the second inorganic encapsulation layers 443a and 443b. More specifically, the optical compensation layers 450a and 450b may be disposed between the organic encapsulation layer 142 and the second inorganic encapsulation layers 443a and 443b. The optical compensation layers 450a and 450b may be disposed so as to completely cover the top and side surfaces of the organic encapsulation layer 142. For example, the optical compensation layers 450a and 450b may be disposed to have a larger area than the organic encapsulation layer 142.

[0086] The display device 400 according to another exemplary embodiment of the present disclosure may include optical compensation layers 450a and 450b below the second inorganic encapsulation layers 443a and 443b. In this configuration, heat or luminous energy generated by the light-emitting diode 130 can be prevented from being transferred to the second inorganic encapsulation layers 443a and 443b. As a result, oxidation of the second inorganic encapsulation layers 443a and 443b can be delayed.

[0087] In addition, in the display device 400 according to another exemplary embodiment of the present disclosure, peripheral (or ambient) oxygen is collected by optical compensation layers 450a and 450b including or formed of a transition metal oxide having an excellent oxygen (gas) collection function. As a result, oxidation of the second inorganic encapsulating layers 443a and 443b can be delayed. In addition, since the penetration of moisture or oxygen into the light-emitting diode 130 is suppressed, the reliability of the anti-oxidation function and the moisture-proof function of the display device 400 can be enhanced.

[0088] like Figure 4As shown, the display device 400 according to another exemplary embodiment of the present disclosure may include a second inorganic encapsulation layer 443a provided on the optical compensation layer 450a and having a complementary color relationship with the optical compensation layer 450. This can compensate the color of the second inorganic encapsulation layer 443a, which is considered yellow when not oxidized, to white. Therefore, the color coordinate shift of the display device 400 can be suppressed. In addition, as Figure 5 As shown, when oxidation progresses, the optical compensation layer 450b and the second inorganic encapsulation layer 443b may have a transparent white color (in other words, may appear transparent white). In this configuration, the display device 400 according to an exemplary embodiment of the present disclosure can be viewed as a uniform color at each of the plurality of sub-pixels SP, regardless of the degree of oxidation of the second inorganic encapsulation layers 443a and 443b. This can minimize color differences between the plurality of sub-pixels SP.

[0089] Exemplary embodiments of the present disclosure may also be described as follows:

[0090] According to one aspect of the present disclosure, a display device is provided. The display device includes: a substrate including a display area and a non-display area surrounding the display area; a light-emitting element such as a light-emitting diode on (or disposed at) the display area; a first inorganic encapsulation layer on the light-emitting element; an organic encapsulation layer on the first inorganic encapsulation layer; a second inorganic encapsulation layer on the organic encapsulation layer; and an optical compensation layer disposed on or below the second inorganic encapsulation layer and including or formed of a transition metal oxide.

[0091] The light emitting element may be configured as an organic light emitting diode.

[0092] The optical compensation layer may be disposed on the second inorganic encapsulating layer and contact a top surface of the second inorganic encapsulating layer.

[0093] The optical compensation layer may be disposed between the organic encapsulating layer and the second inorganic encapsulating layer.

[0094] The optical compensation layer may contact a bottom surface of the second inorganic encapsulation layer.

[0095] The optical compensation layer may be provided to completely cover the top and side surfaces of the organic encapsulation layer.

[0096] The optical compensation layer may be provided to have a larger area than the organic encapsulation layer.

[0097] The transition metal in the transition metal oxide may have an energy band gap of 2.18 eV to 3.10 eV.

[0098] The transition metal may have an energy band gap of 2.48 eV to 2.76 eV.

[0099] The transition metal oxide may include at least one of cobalt oxide, cerium oxide, manganese oxide, and chromium oxide.

[0100] The transition metal oxide may include cobalt oxide or cerium oxide.

[0101] The optical compensation layer may have a complementary color relationship with the second inorganic encapsulating layer.

[0102] The optical compensation layer may have a blue hue.

[0103] The second inorganic encapsulating layer may have a yellow color.

[0104] The second inorganic encapsulating layer may include or be formed of silicon nitride (SiNx).Regardless of the degree of oxidation, the optical compensation layer and the second inorganic encapsulating layer may be viewed as white.

Claims

1. A display device comprising: a substrate comprising a display area and a non-display area surrounding the display area; a light-emitting element on the display area; a first inorganic encapsulation layer on the light-emitting element; an organic encapsulation layer on the first inorganic encapsulation layer; a second inorganic encapsulation layer on the organic encapsulation layer; as well as An optical compensation layer is provided on or below the second inorganic encapsulating layer and includes or is formed of a transition metal oxide.

2. The display device according to claim 1, wherein The light emitting element is configured as an organic light emitting diode.

3. The display device according to claim 1, wherein The optical compensation layer is disposed on the second inorganic encapsulating layer and contacts a top surface of the second inorganic encapsulating 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 contacts a bottom surface of the second inorganic encapsulation layer. The display device according to claim 4 , wherein: The optical compensation layer is disposed to completely cover the top surface and side surfaces of the organic encapsulation layer.

7. The display device according to claim 4, wherein The optical compensation layer is configured to have a larger area than the organic encapsulation layer.

8. 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. The display device according to claim 5, 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 and the second inorganic encapsulation layer have a complementary color relationship.

13. The display device according to claim 1, wherein The optical compensation layer has a blue color.

14. The display device according to claim 1, wherein The second inorganic encapsulating layer has a yellow color.

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

16. The display device according to claim 1, wherein Regardless of the degree of oxidation, the optical compensation layer and the second inorganic encapsulation layer are viewed as white.

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