Top Emission Type Electroluminescence Display Having Micro-cavity Structure

Abstract

This application relates to a top-emitting electroluminescent display device having a microcavity structure. The electroluminescent display device according to this application comprises a first pixel, a second pixel, and a third pixel disposed on a substrate. The first pixel comprises a first light-emitting element, a first semi-transparent layer disposed on the first light-emitting element, and a first color filter disposed on the first semi-transparent layer.

Description

Technology Field

[0001] This application relates to a top-emission type electroluminescent display device having a micro-cavity structure. In particular, this application relates to a top-emission type electroluminescent display device that implements a micro-cavity structure by adding different semi-transparent layers for each color between a color filter stacked on a cathode electrode. Background Technology

[0002] Recently, various types of display devices, such as CRTs (Cathode Ray Tubes), LCDs (Liquid Crystal Displays), PDPs (Plasma Display Panels), and Luminescent Displays, have been developed and are advancing. These diverse display devices are utilized to display image data in a wide range of products, including computers, mobile phones, ATMs, and vehicle navigation systems, each tailored to its unique characteristics.

[0003] Organic electroluminescent displays, which are self-emissive display devices, are gaining popularity as video display devices due to their excellent optical performance, such as viewing angle and color reproduction, which is gradually expanding their application fields. Due to these advantages, they are attracting attention as the most suitable display devices for realizing ultra-high resolution displays of 8K, beyond 4K. As resolution increases, the size of the pixels decreases, and the size of the light-emitting area within the pixels also decreases. When the pixel size in an electroluminescent display is reduced, it is desirable to apply a top-emitting structure to maximize the size of the light-emitting area.

[0004] In particular, a microdisplay with a resolution of 3,000 PPI (Pixels Per Inch) may have a structure in which a black matrix is ​​removed to prevent color mixing between pixels in order to achieve high resolution. However, in the absence of a black matrix, color mixing may occur between neighboring pixels that display different colors, which can lead to a problem of degraded image quality.

[0005] In addition, in structures that achieve ultra-high resolution, such as microdisplays, it is very important to increase luminous efficiency because the pixel size is very small. For example, luminous efficiency can be increased by applying a microcavity structure. Considering these various conditions, in order to achieve ultra-high resolution of 3,000 PPI or higher, it is necessary to develop an organic light-emitting display device with a new structure that can prevent color mixing without a black matrix while simultaneously implementing a microcavity. The problem to be solved

[0006] The purpose of this application is to overcome the problems of the prior art and to provide an electroluminescent display device having a structure capable of increasing luminous efficiency and preventing color mixing while realizing ultra-high resolution. Another purpose of this application is to provide an electroluminescent display device having a structure capable of realizing a microcavity structure and preventing color mixing even without a black matrix. means of solving the problem

[0007] To achieve the above objective, the electroluminescent display device according to this application comprises a first pixel, a second pixel, and a third pixel disposed on a substrate. The first pixel comprises a first light-emitting element, a first semi-transparent layer disposed on the first light-emitting element, and a first color filter disposed on the first semi-transparent layer.

[0008] For example, the second pixel includes a second light-emitting element, a first transparent layer disposed on the second light-emitting element, a second semi-transparent layer disposed on the first transparent layer, and a second color filter disposed on the second semi-transparent layer.

[0009] For example, the third pixel includes a third light-emitting element, a first transparent layer disposed on the third light-emitting element, a second transparent layer disposed on the first transparent layer, a third semi-transparent layer disposed on the second transparent layer, and a third color filter disposed on the third semi-transparent layer.

[0010] For example, each of the first light-emitting element, the second light-emitting element, and the third light-emitting element includes a first electrode, a light-emitting layer disposed on the first electrode, and a second electrode disposed on the light-emitting layer.

[0011] For example, the first transparent layer and the second transparent layer comprise a thin film layer having any one of aluminum oxide, silicon oxide, silicon nitride, polyimide, and monomer.

[0012] For example, the first color filter is a blue color filter. The second color filter is a green color filter. The third color filter is a red color filter.

[0013] For example, the first transparent layer and the second transparent layer have a refractive index smaller than the refractive index of the first color filter, the second color filter, and the third color filter.

[0014] For example, the first transparent layer is placed between the first color filter and the second color filter, and between the first color filter and the third color filter.

[0015] For example, the first transparent layer is further disposed on the upper surface of the first color filter.

[0016] For example, the second transparent layer is placed between the first color filter and the third color filter, and between the second color filter and the third color filter.

[0017] For example, a second transparent layer is further disposed on the upper surface of the first color filter and the upper surface of the second color filter.

[0018] For example, a second transparent layer is positioned at the bottom between the first color filter and the third color filter, and between the second color filter and the third color filter. An air layer is positioned at the top between the first color filter and the third color filter, and between the second color filter and the third color filter.

[0019] For example, it further includes a third transparent layer disposed between the first semi-transparent layer and the first light-emitting element.

[0020] For example, it further includes a third transparent layer disposed between the first semi-transparent layer and the first light-emitting element.

[0021] For example, the third transparent layer is thinner than the thickness of the first transparent layer.

[0022] For example, the third transparent layer comprises a thin film layer having any one of aluminum oxide, silicon oxide, silicon nitride, polyimide, and monomer. Effects of the invention

[0023] The electroluminescent display device according to this application is characterized by having a light-emitting element formed on a substrate and a color filter having a microcavity structure stacked thereon. Accordingly, this application provides a top-emitting electroluminescent display device in which luminous efficiency is maximized for each color. In particular, since the light-emitting element is arranged in overlap with the driving element, the area of ​​the light-emitting region occupied in the pixel area can be maximized. Additionally, it has a structure in which a transparent layer or an air layer with a lower refractive index than the color filter is interposed between adjacent color filters. Therefore, when light incident from the light-emitting element to the color filter diffuses in a lateral direction, total internal reflection occurs due to the transparent layer or air layer having a low refractive index, thereby preventing color mixing. The electroluminescent display device according to this application can achieve ultra-high resolution because no color mixing occurs between adjacent pixels even without a black matrix. Furthermore, by implementing a microcavity structure, luminous efficiency can be maximized. Brief explanation of the drawing

[0024] FIG. 1 is a plan view showing the schematic structure of an electroluminescent display device according to this application. FIG. 2 is a diagram showing the circuit configuration of a pixel constituting an electroluminescent display device according to this application. FIG. 3 is a planar enlarged view showing the structure of pixels arranged in an electroluminescent display device according to this application. FIG. 4 is a cross-sectional view showing the structure of an electroluminescent display device according to this application, cut along I-I' of FIG. 3. FIG. 5 is a cross-sectional enlarged view showing the structure of consecutive subpixels in an electroluminescent display device according to the first embodiment of this application, cut along II-II' of FIG. 3. FIG. 6 is a cross-sectional enlarged view showing the structure of consecutive subpixels in an electroluminescent display device according to the second embodiment of this application, cut along II-II' of FIG. 3. FIG. 7 is a cross-sectional enlarged view showing the structure of consecutive subpixels in an electroluminescent display device according to the third embodiment of this application, cut along II-II' of FIG. 3. Specific details for implementing the invention

[0025] The advantages and features of this application and the methods for achieving them will become clear by referring to the examples described below in detail together with the accompanying drawings. However, this application is not limited to the examples disclosed below but may be embodied in various different forms; the examples of this application are provided merely to ensure that the disclosure of this application is complete and to fully inform those skilled in the art of the scope of the invention to which the invention of this application belongs, and the invention of this application is defined only by the scope of the claims.

[0026] Shapes, sizes, proportions, angles, quantities, etc. disclosed in the drawings for illustrating an example of this application are exemplary and are not limited to the matters depicted herein. Throughout the specification, the same reference numerals refer to the same components. Furthermore, in describing the examples of this application, detailed descriptions of related prior art are omitted if it is determined that such detailed descriptions would unnecessarily obscure the essence of the application.

[0027] Where terms such as 'includes,' 'have,' and 'consists of' mentioned in this application specification are used, other parts may be added unless 'only' is used. Where a component is expressed in the singular, it includes cases where it is in the plural unless specifically stated otherwise.

[0028] In interpreting the components, they are interpreted to include a margin of error even in the absence of a separate explicit statement.

[0029] In the case of describing a positional relationship, for example, when the positional relationship between two parts is described using expressions such as 'on,' 'upper,' 'lower,' or 'next to,' one or more other parts may be located between the two parts unless 'immediately' or 'directly' is used.

[0030] In the case of an explanation of a temporal relationship, for example, when a temporal sequence is explained using 'after', 'following', 'next', 'before', etc., it may include cases where the sequence is not continuous unless 'immediately' or 'directly' is used.

[0031] The terms first, second, etc. are used to describe various components, but these components are not limited by these terms. These terms are used merely to distinguish one component from another. Accordingly, the first component mentioned below may be the second component within the technical scope of this application.

[0032] The term “at least one” should be understood to include all combinations that can be presented from one or more related items. For example, the meaning of “at least one of the first item, the second item, and the third item” may mean not only the first item, the second item, or the third item individually, but also all combinations of items that can be presented from two or more of the first item, the second item, and the third item.

[0033] The features of each of the various examples of this application may be combined or combined with one another, either partially or wholly, and may technically enable various interlocking and operation. Each example may be implemented independently of one another or may be implemented together in an interlocking relationship.

[0034] Hereinafter, an example of an organic light-emitting display device according to this application will be described in detail with reference to the attached drawings. In assigning reference numerals to the components of each drawing, the same components may have the same reference numeral as much as possible, even if they are shown in different drawings.

[0035] Hereinafter, this application will be described in detail with reference to the attached drawings. FIG. 1 is a drawing showing the schematic structure of an electroluminescent display device according to this application. In FIG. 1, the X-axis represents a direction parallel to the scan wiring, the Y-axis represents a direction parallel to the data wiring, and the Z-axis represents the height direction of the display device.

[0036] Referring to FIG. 1, the electroluminescent display device according to this application includes a substrate (110), a gate (or scan) driving unit (200), a data pad unit (300), a source driving integrated circuit (410), a flexible wiring film (430), a circuit board (450), and a timing control unit (500).

[0037] The substrate (110) may include an insulating material or a material having flexibility. The substrate (110) may be made of glass, metal, plastic, etc., but is not limited thereto. If the electroluminescent display device is a flexible display device, the substrate (110) may be made of a flexible material such as plastic. For example, it may include a transparent polyimide material.

[0038] The substrate (110) may be divided into a display area (DA) and a non-display area (NDA). The display area (DA) is an area where an image is displayed and may be defined in most of the area including the central part of the substrate (110), but is not limited thereto. Scan lines (or gate lines), data lines, and pixels are formed in the display area (DA). The pixels include a plurality of sub-pixels, and each of the plurality of sub-pixels may include scan lines and data lines.

[0039] The non-display area (NDA) is an area where no image is displayed and may be defined at the edge portion of the substrate (110) to surround all or part of the display area (DA). A gate driver (200) and a data pad portion (300) may be formed in the non-display area (NDA).

[0040] The gate driver (200) supplies scan (or gate) signals to the scan lines according to the gate control signal input from the timing control unit (500). The gate driver (200) may be formed in a non-display area (NDA) outside one side of the display area (DA) of the substrate (110) in a GIP (gate driver in panel) manner. The GIP method refers to a structure in which the gate driver (200) is formed directly on the substrate (110).

[0041] The data pad section (300) supplies data signals to the data wires according to a data control signal input from the timing control section (500). The data pad section (300) is manufactured as a driving chip and mounted on a flexible wiring film (430), and can be attached to a non-display area (NDA) outside one side of the display area (DA) of the substrate (110) using a tape automated bonding (TAB) method.

[0042] The source driving integrated circuit (410) receives digital video data and a source control signal from the timing control unit (500). The source driving integrated circuit (410) converts the digital video data into analog data voltages according to the source control signal and supplies them to the data wires. When the source driving integrated circuit (410) is manufactured as a chip, it can be mounted on a flexible wiring film (430) using a COF (chip on film) or COP (chip on plastic) method.

[0043] In the flexible wiring film (430), wirings connecting the data pad section (300) and the source driving integrated circuit (410), and wirings connecting the data pad section (300) and the circuit board (450) may be formed. The flexible wiring film (430) is attached to the data pad section (300) using an anisotropic conducting film, thereby allowing the wirings of the data pad section (300) and the flexible film (430) to be connected.

[0044] The circuit board (450) can be attached to flexible wiring films (430). The circuit board (450) may have a number of circuits implemented with driving chips mounted on it. For example, a timing control unit (500) may be mounted on the circuit board (450). The circuit board (450) may be a printed circuit board or a flexible printed circuit board.

[0045] The timing control unit (500) receives digital video data and timing signals from an external system board through a cable of the circuit board (450). Based on the timing signals, the timing control unit (500) generates a gate control signal for controlling the operation timing of the gate driver (200) and a source control signal for controlling the source driver integrated circuits (410). The timing control unit (500) supplies the gate control signal to the gate driver (200) and supplies the source control signal to the source driver integrated circuits (410). Depending on the product, the timing control unit (500) may be formed with the source driver integrated circuit (410) and a single driver chip and mounted on the substrate (110).

[0046] FIG. 1 is a plan view showing the schematic structure of an electroluminescent display device according to this application. FIG. 2 is a diagram showing the circuit configuration of a pixel constituting the electroluminescent display device according to this application. FIG. 3 is a planar enlarged view showing the structure of pixels arranged in the electroluminescent display device according to this application. FIG. 4 is a cross-sectional view showing the structure of the electroluminescent display device according to this application, cut along I-I' in FIG. 3. In FIG. 2 to 4, an organic light-emitting display device, which is a type of electroluminescent display device, is described as an example.

[0047] Referring to FIGS. 2 to 4, a pixel of an organic light-emitting display device includes a scan line (SL), a data line (DL), and a driving current line (VDD). Additionally, a pixel of the organic light-emitting display device includes a switching thin-film transistor (ST), a driving thin-film transistor (DT), an organic light-emitting diode (OLE), and an auxiliary capacitance (Cst). A high potential voltage is applied to the driving current line (VDD) to drive the organic light-emitting diode (OLE).

[0048] For example, a switching thin-film transistor (ST) may be placed at the intersection of a scan line (SL) and a data line (DL). The switching thin-film transistor (ST) includes a switching gate electrode (SG), a switching source electrode (SS), and a switching drain electrode (SD). The switching gate electrode (SG) may branch off from the scan line (SL) or be part of the scan line (SL) as shown in FIG. 3. The switching source electrode (SS) is connected to the data line (DL), and the switching drain electrode (SD) is connected to a driving thin-film transistor (DT). The switching thin-film transistor (ST) functions to select a pixel to be driven by applying a data signal to the driving thin-film transistor (DT).

[0049] The driving thin-film transistor (DT) functions to drive the organic light-emitting diode (OLE) of a pixel selected by the switching thin-film transistor (ST). The driving thin-film transistor (DT) includes a driving gate electrode (DG), a driving source electrode (DS), and a driving drain electrode (DD). The driving gate electrode (DG) is connected to the switching drain electrode (SD) of the switching thin-film transistor (ST). The driving source electrode (DS) is connected to the driving current line (VDD), and the driving drain electrode (DD) is connected to the anode electrode (ANO) of the organic light-emitting diode (OLE). An auxiliary capacitance (Cst) may be formed between the switching drain electrode (SD) of the driving thin-film transistor (DT) and the anode electrode (ANO) of the organic light-emitting diode (OLE).

[0050] The driving thin-film transistor (DT) is placed between the driving current wiring (VDD) and the organic light-emitting diode (OLE). The driving thin-film transistor (DT) adjusts the amount of current flowing from the driving current wiring (VDD) to the organic light-emitting diode (OLE) according to the magnitude of the voltage at the gate electrode (DG) of the driving thin-film transistor (DT) connected to the drain electrode (SD) of the switching thin-film transistor (ST).

[0051] FIG. 4 illustrates a structure in which thin-film transistors (ST, DT) of a top-gate structure are formed. A top-gate structure refers to a structure in which gate electrodes (SG, DG) are disposed on semiconductor layers (SA, DA). That is, the top-gate structure has a structure in which semiconductor layers (SA, DA) are first formed on a substrate (110), and gate electrodes (SG, DG) are formed on a gate insulating film (GI) covering the semiconductor layers (SA, DA). As another example, a thin-film transistor of a bottom-gate structure may be provided. A bottom-gate structure is a structure in which a gate electrode is first formed on a substrate, and a semiconductor layer is formed on a gate insulating film covering the gate electrode. However, in order to achieve ultra-high density resolution, the electroluminescent display device according to this application preferably has a thin-film transistor of a top-gate structure to increase the aperture ratio, which is the ratio of the light-emitting region to the pixel region.

[0052] In addition, in the case of the top-gate structure illustrated in FIG. 4, the switching source electrode (SS), the switching drain electrode (SD), the driving source electrode (DS), and the driving drain electrode (DD) are formed on the same layer as the gate electrodes (SG, DG). That is, while the source electrodes (SS, DS) and the drain electrodes (SD, DD) are formed on the same layer as the scan wiring (SL) and the gate electrodes (SG, DG), the data wiring (DL) and the driving current wiring (VDD) can be formed on a different layer from the scan wiring (SL). An intermediate insulating film (ILD) is laminated over the gate electrodes (SG, DG), the source electrodes (SS, DS), and the drain electrodes (SD, DD). The data wiring (DL) and the driving current wiring (VDD) are disposed on the intermediate insulating film (ILD).

[0053] An organic light-emitting diode (OLE) comprises an anode electrode (ANO), an organic light-emitting layer (EL), and a cathode electrode (CAT). The organic light-emitting diode (OLE) emits light according to a current controlled by a driving thin-film transistor (DT). In other words, since the amount of light emitted by the organic light-emitting diode (OLE) is controlled according to the current controlled by the driving thin-film transistor (DT), the brightness of the electroluminescent display device can be controlled. The anode electrode (ANO) of the organic light-emitting diode (OLE) is connected to the driving drain electrode (DD) of the driving thin-film transistor (DT), and the cathode electrode (CAT) is connected to a low power supply wiring (VSS) to which a low potential voltage is supplied. That is, the organic light-emitting diode (OLE) is driven by a low potential voltage and a high potential voltage controlled by the driving thin-film transistor (DT).

[0054] A protective film (PAS) is laminated on the surface of a substrate (110) on which thin-film transistors (ST, DT) are formed. It is preferable that the protective film (PAS) be formed from an inorganic film such as silicon oxide or silicon nitride. A planarization film (PL) is laminated on the protective film (PAS). The planarization film (PL) is a thin film intended to flatten the surface of the substrate (110) on which thin-film transistors (ST, DT) are formed, as the surface may not be uniform. To make the height difference uniform, the planarization film (PL) may be formed from an organic material. Pixel contact holes (PH) are formed in the protective film (PAS) and the planarization film (PL) to expose a portion of the drain electrode (DD) of the driving thin-film transistor (DT).

[0055] An anode electrode (ANO) is formed on the upper surface of the planarization film (PL). The anode electrode (ANO) is connected to the drain electrode (DD) of the driving thin-film transistor (DT) through a pixel contact hole (PH). The components of the anode electrode (ANO) may vary depending on the light-emitting structure of the organic light-emitting diode (OLE). For example, in the case of a bottom-emitting type that provides light toward the substrate (110), it may be formed of a transparent conductive material. As another example, in the case of emitting light in the upward direction facing the substrate (110), it may be formed of a metallic material with excellent light reflectivity. For example, the anode electrode (ANO) may be made of any one material selected from silver (Ag), aluminum (Al), molybdenum (Mo), gold (Au), magnesium (Mg), calcium (Ca), or barium (Ba), or an alloy of two or more materials. Alternatively, the top-emitting type anode electrode (ANO) may have a structure comprising a metal layer with excellent light reflectivity and a transparent conductive material laminated on the metal layer.

[0056] In the case of this application, it is desirable to have a top-emission structure suitable for realizing ultra-high resolution. In the top-emission structure, it is desirable to form the anode electrode (ANO) to have the maximum area in the pixel region defined by the data line (DL), the driving current line (VDD), and the scan line (SL). In this case, thin-film transistors (ST, DT) may be arranged to overlap the anode electrode (ANO) under the anode electrode (ANO). Additionally, the data line (DL), the driving current line (VDD), and the scan line (SL) may also be arranged to partially overlap the anode electrode (ANO).

[0057] A bank (BA) is formed on the anode electrode (ANO). The bank (BA) covers the edge region of the anode electrode (ANO) and is positioned to expose most of the central region. Most of the central region exposed by the bank (BA) on the anode electrode (ANO) is defined as a light-emitting region.

[0058] An organic light-emitting layer (EL) is laminated over the anode electrode (AN0) and the bank (BA). The organic light-emitting layer (EL) may be formed over the entire display area (DA) of the substrate (110) to cover the anode electrode (ANO) and the bank (BA). An organic light-emitting layer (EL) according to one example may include two or more vertically laminated light-emitting parts to emit white light. For example, the organic light-emitting layer (EL) may include a first light-emitting part and a second light-emitting part for emitting white light by mixing a first light and a second light.

[0059] As another example, the organic light-emitting layer (EL) may include any one of a blue light-emitting part, a green light-emitting part, and a red light-emitting part for emitting light corresponding to the color set in the pixel. In this case, the organic light-emitting layer (EL) may be placed only within the light-emitting area defined by the bank (BA). Additionally, the organic light-emitting diode (OLE) may further include a functional layer to improve the light-emitting efficiency and / or lifespan of the organic light-emitting layer (EL).

[0060] The cathode electrode (CAT) is laminated to make surface contact with the organic light-emitting layer (EL). The cathode electrode (CAT) is formed across the entire substrate (110) to be commonly connected to the organic light-emitting layer (EL) formed in all pixels. In the case of the top-emitting type, it is preferable that the cathode electrode (CAT) be formed from a transparent conductive material such as indium-tin-oxide (ITO) or indium-zinc-oxide (IZO).

[0061] After the cathode electrode (CAT) is stacked to complete the organic light-emitting diode (OLE), a color filter (CF) having a microcavity structure is further formed on the cathode electrode (CAT). For example, FIG. 4 shows a blue pixel, in which case a first semi-transparent layer (HT1) is formed on the cathode electrode (CAT). The first semi-transparent layer (HT1) can transmit some of the incident light and reflect the rest. For example, the first semi-transparent layer (HT1) may be an ultrathin metal layer formed with a thickness of 10 nm to 20 nm using a metallic material such as aluminum (Al), silver (Ag), gold (Au), or magnesium (Mg).

[0062] The distance between the anode electrode (ANO) and the first semi-transparent layer (HT1), specifically the distance between the upper surface of the anode electrode (ANO) and the lower surface of the first semi-transparent layer (HT1), may be an integer multiple of the wavelength of light emitted from the blue pixel. The thickness of the organic light-emitting layer (EL) and the cathode electrode (CAT) can be adjusted so that the distance between the anode electrode (ANO) and the first semi-transparent layer (HT1) corresponds to the resonance distance. Additionally, if the anode electrode (ANO) is composed of a metal layer and a transparent conductive material layer stacked thereon, the resonance distance may be further finely adjusted by adjusting the thickness of the transparent conductive material layer.

[0063] For example, the distance corresponding to the sum of the thicknesses of the organic light-emitting layer (EL) and the cathode electrode (CAT) may correspond to an integer multiple of the wavelength of light emitted from the blue pixel. In the case of such thickness, due to the microcavity effect, when light emitted from the organic light-emitting layer (EL) passes through the cathode electrode (CAT) and the first semi-transparent layer (HT1), the light reflected from the interface between the cathode electrode (CAT) and the first semi-transparent layer (HT1) is reflected again by the anode electrode (ANO), the amount of light is not lost and can be reflected back toward the cathode electrode (CAT). Otherwise, if the distance between the anode electrode (ANO) and the first semi-transparent layer (HT1) does not correspond to an integer multiple of the wavelength of light emitted from the blue pixel, the amount of light may be reduced when the light reflected from the first semi-transparent layer (HT1) is reflected again by the anode electrode (ANO).

[0064] In some cases, if the distance between the anode electrode (ANO) and the first semi-transparent layer (HT1) is not an integer multiple of the wavelength of light emitted from the corresponding pixel, a transparent layer may be further included to secure a resonance distance for a microcavity effect between the cathode electrode (CAT) and the first semi-transparent layer (HT1).

[0065] Here, the first semi-transparent layer (HT1) and / or the transparent layer for the microcavity is in contact with the cathode electrode (CAT), but it is preferable to form the transparent layer with a non-conductive material so that it does not have electrical conductivity.

[0066] A blue color filter (CFB) may be laminated on the first semi-transparent layer (HT1). 50% of the light emitted from the organic light-emitting layer (EL) is directed toward the cathode electrode (CAT), and the remaining 50% is directed toward the anode electrode (ANO). A portion of the light directed toward the cathode electrode (CAT) passes through the cathode electrode (CAT) and the first semi-transparent layer (HT1) and is incident on the blue color filter (CFB). The remaining portion of the light directed toward the cathode electrode (CAT) is reflected at the interface between the first semi-transparent layer (HT1) and the cathode electrode (CAT) and is directed toward the anode electrode (ANO).

[0067] Light directed toward the anode electrode (ANO) is reflected from the anode electrode (ANO) and directed back toward the cathode electrode (CAT). At this time, the light reflected at the interface between the first semi-transparent layer (HT1) and the cathode electrode (CAT) is reflected while maintaining maximum light intensity, particularly at the anode electrode (ANO). Through this optical path, most of the light generated from the organic light-emitting layer (EL) is incident on the blue color filter (CFB). The light incident on the blue color filter (CFB) transmits only the blue wavelength light and emits it outward.

[0068] The electroluminescent display device according to this application may further comprise a light-blocking layer (LS). The light-blocking layer (LS) may be placed below the semiconductor layer (SA, DA) to prevent light from entering from the outside into the semiconductor layer (SA, DA) and changing the channel characteristics of the semiconductor channel region. For example, after forming the light-blocking layer (LS) at the location where the semiconductor layer (SA, DA) is to be placed on the substrate (110), a buffer layer (BUF) may be applied over the entire surface of the substrate (SUB).

[0069] In addition to preventing external light from penetrating the semiconductor layers (SA, DA), the light-blocking layer (LS) can also be used as a repair element to connect a defective pixel to an adjacent normal pixel to enable normal operation. Alternatively, the light-blocking layer (LS) can be used as a data line (DL) and a driving current line (VDD). As another example, since the light-blocking layer (LS) overlaps with the semiconductor layers (SA, DA), it can also be used as a gate electrode to implement a thin-film transistor having a double-gate structure.

[0070] The microcavity structure is a structure designed to maximize the light emission efficiency of light having a specific color emitted from an organic light-emitting layer (EL). Accordingly, the following embodiments describe various embodiments of structures of consecutive pixels emitting blue, green, and red light.

[0071] <First Embodiment>

[0072] Hereinafter, a first embodiment of the present application will be described with reference to FIG. 5. FIG. 5 is a cross-sectional enlarged view showing the structure of consecutive subpixels in an electroluminescent display device according to the first embodiment of the present application, cut along II-II' of FIG. 3.

[0073] A buffer layer (BUF) is laminated on a substrate (110). A gate insulating film (GI) is laminated on the buffer layer (BUF). A protective film (PAS) is laminated on the gate insulating film (GI). A planarization film (PL) is laminated on the protective film (PAS). For convenience, the components of the thin-film transistor are not shown in FIG. 5.

[0074] Anode electrodes (ANO) are formed on the planarization film (PL). One anode electrode (ANO) is assigned to each blue pixel (PB), green pixel (PG), and red pixel (PR).

[0075] Banks (BA) are formed covering the edges of the anode electrode (ANO) and exposing most of the central portion. An organic light-emitting layer (EL) is laminated over the banks (BA) and the anode electrode (ANO). The organic light-emitting layer (EL) can be formed in a structure that connects all pixel regions (PB, PG, PR) as a single layer over the entire surface of the substrate (110), as shown in FIG. 5. As another example, an organic light-emitting layer emitting a different color can be placed for each pixel region. For example, a blue organic light-emitting layer can be placed for the blue pixel (PB), a green organic light-emitting layer for the green pixel (PG), and a red organic light-emitting layer for the red pixel (PR).

[0076] A cathode electrode (CAT) is laminated on the organic light-emitting layer (EL). It is preferable that the cathode electrode (CAT) be formed as a common single layer connecting all pixel regions (PB, PG, PR) on the entire surface of the substrate (110). By laminating the cathode electrode (CAT), an organic light-emitting diode (OLE) is completed in which the anode electrode (ANO), the organic light-emitting layer (EL), and the cathode electrode (CAT) are laminated.

[0077] On the cathode electrode (CAT), a first semi-transparent layer (HT1) is formed in the blue pixel (PB) region. Additionally, a blue color filter (CFB) is formed on the first semi-transparent layer (HT1). It is preferable that the first semi-transparent layer (HT1) and the blue color filter (CFB) be patterned to have the same width. In the blue pixel (PB), an organic light-emitting layer (EL) and a cathode electrode (CAT) are stacked between the anode electrode (ANO) and the first semi-transparent layer (HT1), and the stacking thickness has a thickness corresponding to the resonance distance of the blue light.

[0078] A first transparent layer (A1) is laminated over the entire surface of a substrate (110) on which a blue color filter (CFB) is formed. The first transparent layer (A1) may include aluminum oxide (Al2O3). Aluminum oxide is a non-conductive and transparent material, and is a desirable material for securing resonance distance. However, the first transparent layer (A1) is not necessarily limited to aluminum oxide and may be a thin film composed of silicon oxide, silicon nitride, polyimide, or monomer.

[0079] On the first transparent layer (A1), a second semi-transparent layer (HT2) is formed in the green pixel (PG) region. Additionally, a green color filter (CFG) is formed on the second semi-transparent layer (HT2). It is preferable that the second semi-transparent layer (HT2) and the green color filter (CFG) be patterned to have the same width. In the green pixel (PG), an organic light-emitting layer (EL), a cathode electrode (CAT), and the first transparent layer (A1) are stacked between the anode electrode (ANO) and the second semi-transparent layer (HT2), and the stacked thickness has a thickness corresponding to the resonance distance of the green light.

[0080] A second transparent layer (A2) is laminated over the entire surface of the substrate (110) on which the green color filter (CFG) is formed. The second transparent layer (A2) may include aluminum oxide (Al2O3). Aluminum oxide is a non-conductive and transparent material, and is a desirable material for securing resonance distance.

[0081] On the second transparent layer (A2), a third semi-transparent layer (HT3) is formed in the red pixel (PR) region. Additionally, a red color filter (CFR) is formed on the third semi-transparent layer (HT3). It is preferable that the third semi-transparent layer (HT3) and the red color filter (CFR) be patterned to have the same width. In the red pixel (PR), an organic light-emitting layer (EL), a cathode electrode (CAT), a first transparent layer (A1), and a second transparent layer (A2) are stacked between the anode electrode (ANO) and the third semi-transparent layer (HT3), and the stacked thickness has a thickness corresponding to the resonance distance of the red light.

[0082] Thus, the electroluminescent display device according to the first embodiment of this application secures a unique resonance distance for each pixel, so that blue light, green light, and red light each have maximum light emission efficiency.

[0083] Additionally, a first transparent layer (A1) is interposed between the blue color filter (CFB) and the green color filter (CFG). A second transparent layer (A2) is interposed between the green color filter (CFG) and the red color filter (CFR). Additionally, the first transparent layer (A1) and the second transparent layer (A2) are interposed between the red color filter (CFR) and the blue color filter (CFB). For example, a transparent insulating thin film layer made of aluminum oxide is disposed between each color filter (CF). However, the material of the transparent insulating thin film layer is not limited to aluminum oxide, and may be a thin film made of silicon oxide, silicon nitride, polyimide, or monomer.

[0084] A transparent insulating thin film layer made of aluminum oxide has a lower refractive index than the color filters, namely the blue color filter (CFB), green color filter (CFG), and red color filter (CFR). As a result, light traveling laterally within the color filter (CF) undergoes total reflection at the interface between the sidewall of the color filter (CF) and the transparent insulating thin film layer made of aluminum oxide, re-enters the color filter (CF), and is eventually emitted upward. That is, colors are not mixed between neighboring color pixels, and light is emitted within the area of ​​each color pixel. The electroluminescent display device according to the first embodiment of this application facilitates the realization of ultra-high resolution because no color mixing occurs between pixels, even without a black matrix placed between each pixel.

[0085] <Second Embodiment>

[0086] Hereinafter, a second embodiment of the present application will be described with reference to FIG. 6. FIG. 6 is a cross-sectional enlarged view showing the structure of consecutive subpixels in an electroluminescent display device according to the second embodiment of the present application, cut along II-II' of FIG. 3.

[0087] FIG. 6, which illustrates a second embodiment of this application, has a structure almost identical to that of FIG. 5, which illustrates a first embodiment. Therefore, redundant descriptions that are not strictly necessary for the explanation are omitted. An important difference is that the second embodiment has a structure in which the first transparent layer (A1) and / or the second transparent layer (A2), which are laminated on the surfaces of the blue color filter (CFB) and the green color filter (CFR) in the first embodiment, are removed.

[0088] For example, on the cathode electrode (CAT) of an organic light-emitting diode (OLE), a first semi-transparent layer (HT1) and a blue color filter (CFB) are sequentially stacked in the blue pixel (PB) region. It is preferable that the first semi-transparent layer (HT1) and the blue color filter (CFB) be patterned to have the same width.

[0089] A first transparent layer (A1) is laminated over the entire surface of a substrate (110) on which a blue color filter (CFB) is formed. The first transparent layer (A1) may include aluminum oxide (Al2O3).

[0090] On the first transparent layer (A1), a second semi-transparent layer (HT2) and a green color filter (CFG) are sequentially stacked in the green pixel (PG) region. It is preferable that the second semi-transparent layer (HT2) and the green color filter (CFG) be patterned to have the same width.

[0091] A second transparent layer (A2) is laminated over the entire surface of the substrate (110) on which the green color filter (CFG) is formed. The second transparent layer (A2) may include aluminum oxide (Al2O3).

[0092] On the second transparent layer (A2), a third semi-transparent layer (HT3) and a red color filter (CFR) are sequentially stacked in the red pixel (PR) region. It is preferable that the third semi-transparent layer (HT3) and the red color filter (CFR) be patterned to have the same width.

[0093] Thus, the electroluminescent display device according to the first embodiment of this application secures a unique resonance distance for each pixel, so that blue light, green light, and red light each have maximum light emission efficiency.

[0094] In the structure formed in this way, the first transparent layer (A1) and / or the second transparent layer (A2) stacked on the upper surface of the blue color filter (CFB) and the green color filter (CFG) are etched and removed. As a result, the upper surfaces of the blue color filter (CFB), the green color filter (CFG), and the red color filter (CFR) are all exposed. Although the first transparent layer (A1) and the second transparent layer (A2) are transparent materials, even if their transparency is high, they do not have 100% transmittance, so the transmittance may be slightly reduced. However, in the second embodiment of this application, the upper surface and part of the side of the color filters have a structure exposed to the air layer. Therefore, more light can be secured in the upward direction.

[0095] Here, when the first transparent layer (A1) and the second transparent layer (A2) are made of aluminum oxide, an etching process using a potassium hydroxide (KOH) solution can be used. At this time, it is preferable to etch the first transparent layer (A1) and the second transparent layer (A2) to be removed such that the remaining upper end is positioned higher than the height of the first semi-transparent layer (HT1), the second semi-transparent layer (HT2), and the third semi-transparent layer (HT3). By doing so, damage to the semi-transparent layer due to the etching of the transparent layer can be prevented.

[0096] Additionally, a first transparent layer (A1) and an air layer are interposed between the blue color filter (CFB) and the green color filter (CFG). A second transparent layer (A2) and an air layer are interposed between the green color filter (CFG) and the red color filter (CFR). Additionally, a first transparent layer (A1), a second transparent layer (A2), and an air layer are interposed between the red color filter (CFR) and the blue color filter (CFB). That is, between each color filter (CF), a transparent insulating thin film layer is disposed at the bottom, and an air layer is disposed at the top.

[0097] The transparent insulating thin film layer and the air layer have a lower refractive index than the color filters, namely the blue color filter (CFB), green color filter (CFG), and red color filter (CFR). As a result, light traveling laterally within the color filter (CF) undergoes total reflection at the interface between the sidewall of the color filter (CF) and the transparent insulating thin film layer, and at the interface between the sidewall of the color filter (CF) and the air layer, re-enters the color filter (CF), and is eventually emitted upward. That is, colors are not mixed between adjacent color pixels, and light is emitted within the area of ​​each color pixel. The electroluminescent display device according to the second embodiment of this application facilitates the realization of ultra-high resolution because no color mixing occurs between pixels, even without a black matrix placed between each pixel.

[0098] <Third Embodiment>

[0099] Hereinafter, a third embodiment of the present application will be described with reference to FIG. 7. FIG. 7 is a cross-sectional enlarged view showing the structure of consecutive subpixels in an electroluminescent display device according to the third embodiment of the present application, cut along II-II' of FIG. 3.

[0100] FIG. 7, which illustrates a third embodiment of this application, has a structure almost identical to that of FIG. 6, which illustrates a second embodiment. Therefore, redundant descriptions that are not strictly necessary for the explanation are omitted. Focusing on the important differences, in the third embodiment, a third transparent layer (A3) is further laminated between the first semi-transparent layer (HT1) and the cathode electrode (CAT) in the blue pixel (PB) of the second embodiment.

[0101] In the green pixel (PG), a first transparent layer (A1) is laminated to secure a resonance distance between the anode electrode (ANO) and the second semi-transparent layer (HT2). Additionally, in the red pixel (PR), a first transparent layer (A1) and a second transparent layer (A2) are laminated to secure a resonance distance between the anode electrode (ANO) and the third semi-transparent layer (HT3).

[0102] On the other hand, in the blue pixel (PB), the resonance distance between the anode electrode (ANO) and the first semi-transparent layer (HT1) is determined by the organic light-emitting layer (EL) and the cathode electrode (CAT). However, the thickness of the organic light-emitting layer (EL) and the cathode electrode (CAT) may not be determined to satisfy the resonance distance of the blue light. In this case, it is necessary to further form a third transparent layer (A3) between the first semi-transparent layer (HT1) and the cathode electrode (CAT) to secure the resonance distance of the blue light.

[0103] Blue light has a wavelength range of 450 nm to 490 nm, green light has a wavelength range of 490 nm to 570 nm, and red light has a wavelength range of 630 nm to 750 nm. Considering this, the distance between the first semi-transparent layer (HT1) placed in the blue pixel (PB) and the cathode electrode (CAT) is the smallest, the distance between the third semi-transparent layer (HT3) placed in the red pixel (PR) and the cathode electrode (CAT) is the largest, and the distance between the second semi-transparent layer (HT2) placed in the green (PG) and the cathode electrode (CAT) may have an intermediate size. At this time, the thickness of the third transparent layer (A3) placed in the blue pixel (PB) may be thinner than the thickness of the first transparent layer (A1) placed in the green pixel (PG).

[0104] As a result, the electroluminescent display device according to the third embodiment of this application has a microcavity structure, thereby maximizing light emission efficiency. Furthermore, since there are no transparent layers on top of the color filters, the light emission efficiency can be further improved. Moreover, a transparent thin film layer and / or an air layer with a lower refractive index than the color filters are interposed between the color filters, so that color mixing does not occur between pixels even without a black matrix. As a result, an electroluminescent display device can be provided that achieves ultra-high resolution and maximizes light emission efficiency and light emission efficiency.

[0105] The features, structures, effects, etc. described in the various embodiments of this application described above are included in at least one example of this application and are not necessarily limited to only one example. Furthermore, the features, structures, effects, etc. exemplified in at least one example of this application may be combined or modified and implemented in other examples by a person skilled in the art to which this application pertains. Therefore, details regarding such combinations and modifications should be interpreted as being included within the scope of this application.

[0106] It will be obvious to those skilled in the art to which this application pertains that the above-described application is not limited to the aforementioned embodiments and attached drawings, and that various substitutions, modifications, and alterations are possible within the scope of the technical details of this application. Therefore, the scope of this application is defined by the claims set forth below, and all modifications or variations derived from the meaning and scope of the claims and equivalent concepts thereof should be interpreted as being included within the scope of this application. Explanation of the symbols

[0107] OLE: Organic Light Emitting Diode ANO: Anode electrode EL: Organic Light-emitting Layer CAT: Cathode Electrode ST: Switching thin-film transistor DT: Driving thin-film transistor SA: Switching semiconductor layer DA: Driving semiconductor layer SG: Switching gate electrode DG: Driving gate electrode SS: Switching source electrode DS: Driving source electrode SD: Switching drain electrode DD: Driving drain electrode LS: Shading layer HT1: First semi-transparent layer HT2: Second semi-transparent layer HT3: Third semi-transparent layer A1: First transparent layer A2: Second transparent layer A3: Third transparent layer

Claims

Claim 1 An electroluminescent display device comprising: a first pixel, a second pixel, and a third pixel disposed on a substrate; wherein the first pixel comprises a first light-emitting element; a first semi-transparent layer in contact with the upper surface of the first light-emitting element; and a first color filter in contact with the upper surface of the first semi-transparent layer; wherein the second pixel comprises a second light-emitting element; a first transparent layer in contact with the upper surface of the second light-emitting element; a second semi-transparent layer in contact with the upper surface of the first transparent layer; and a second color filter in contact with the upper surface of the second semi-transparent layer; and wherein the third pixel comprises a third light-emitting element; the first transparent layer in contact with the upper surface of the third light-emitting element; a second transparent layer in contact with the upper surface of the first transparent layer; a third semi-transparent layer in contact with the upper surface of the second transparent layer; and a third color filter in contact with the upper surface of the third semi-transparent layer. Claim 2 delete Claim 3 delete Claim 4 In claim 1, each of the first light-emitting element, the second light-emitting element, and the third light-emitting element comprises: a first electrode; a light-emitting layer disposed on the first electrode; and a second electrode disposed on the light-emitting layer. Claim 5 In claim 1, the first transparent layer and the second transparent layer comprise a thin film layer formed from any one of aluminum oxide, silicon oxide, silicon nitride, polyimide, and monomer. Claim 6 An electroluminescent display device according to claim 1, wherein the first color filter is a blue color filter, the second color filter is a green color filter, and the third color filter is a red color filter. Claim 7 In claim 1, the first transparent layer and the second transparent layer have a refractive index smaller than the refractive index of the first color filter, the second color filter, and the third color filter, in an electroluminescent display device. Claim 8 In claim 1, the first transparent layer is an electroluminescent display device disposed between the first color filter and the second color filter, and between the first color filter and the third color filter. Claim 9 In claim 8, the first transparent layer is an electroluminescent display device further disposed on the upper surface of the first color filter. Claim 10 In claim 8, the second transparent layer is an electroluminescent display device disposed between the first color filter and the third color filter, and between the second color filter and the third color filter. Claim 11 In claim 10, the second transparent layer is an electroluminescent display device further disposed on the upper surface of the first color filter and the upper surface of the second color filter. Claim 12 In claim 8, the second transparent layer is disposed at the bottom between the first color filter and the third color filter and between the second color filter and the third color filter, and an air layer is disposed at the top between the first color filter and the third color filter and between the second color filter and the third color filter. Claim 13 In claim 1, the first transparent layer is disposed at the bottom between the first color filter and the second color filter, and an air layer is disposed at the top between the first color filter and the second color filter, in an electroluminescent display device. Claim 14 An electroluminescent display device according to claim 1, further comprising a third transparent layer disposed between the first semi-transparent layer and the first light-emitting element. Claim 15 In claim 14, the third transparent layer is an electroluminescent display device that is thinner than the thickness of the first transparent layer. Claim 16 In claim 14, the third transparent layer comprises a thin film layer formed from any one of aluminum oxide, silicon oxide, silicon nitride, polyimide, and monomer, in an electroluminescent display device.

Images