TWI882265B - Flexible transparent electrode and flexible organic light-emitting diode structure using the flexible transparent electrode - Google Patents

Abstract

The present invention provides a flexible transparent electrode, the material of which is a flexible alloy layer of silver-chromium (Ag, Cr) alloy, and a transparent metal oxide conductive layer of molybdenum-doped gallium zinc oxide (Mo-doped GaZnO). The flexible alloy layer is arranged between the transparent substrate and the transparent metal oxide conductive layer to improve the conductivity of the entire first electrode layer. The present invention further provides a flexible organic light-emitting diode structure using the flexible transparent electrode, with the flexible transparent electrode as the first electrode layer. The organic light-emitting diode includes a transparent flexible plastic substrate, a first electrode layer, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer and a second electrode layer stacked on each other.

Description

Flexible transparent electrode and flexible organic light-emitting diode structure using the flexible transparent electrode

The present invention relates to a flexible transparent electrode and a flexible organic light-emitting diode structure using the same. The flexible transparent electrode comprises a flexible alloy layer and a transparent metal oxide conductive layer, and can be used as a transparent electrode of a flexible organic light-emitting device.

With the advancement of technology, the popularization of personal computers, the Internet and information communication, monitors have become an indispensable role in human-computer interaction. The continuous advancement of display technology has driven the development of the monitor industry. After the cathode ray tube screen was replaced by the thinner liquid crystal display, it was gradually replaced by the light-emitting diode (LED) display.

LED displays are made up of multiple discretely packaged LEDs. The red, green, and blue LEDs form a square module that is driven in coordination to form full-color pixels.

With the evolution of the times, another new flat panel display technology has been developed in recent years, namely organic light emitting diode display.

The basic structure of an organic light-emitting diode (OLED) consists of a transparent indium tin oxide (ITO) with semiconductor properties, connected to the positive electrode of the power, and then a layer of organic semiconductor materials with different functions, and then another metal cathode, forming a sandwich structure. The entire structure includes: hole transport layer (HTL), luminescent layer (EML) and electron transport layer (ETL). When the power is supplied to the appropriate voltage, the anode holes and cathode electrons will combine in the luminescent layer to generate photons, which will produce various colors depending on the material properties.

Common organic light-emitting diodes are composed of a cathode, an electron transport layer, a light-emitting layer, a hole transport layer, and an anode. Electrons are injected from the cathode into the electron transport layer, and holes are injected from the anode into the hole transport layer. They recombine in the light-emitting layer to emit photons. Unlike inorganic semiconductors, there is no extended state for charge carrier transport, and the energy state of the excited molecules is discontinuous. Charge is mainly transferred through carrier hopping between molecules. Therefore, in organic semiconductors, the mobility of carriers is lower than in inorganic semiconductors such as silicon, gallium arsenide, and even amorphous silicon. However, because organic materials rely on the van der Waals forces between molecules to form solid films, organic solid films are flexible and their electrical conductivity and luminescence properties will not be destroyed due to bending.

As mentioned above, displays made using organic light-emitting diode technology have the advantages of being thin and light, easy to carry, flexible, high brightness, high contrast, power-saving, wide viewing angle, and no image afterimage. They are the new trend of flat-panel displays in the future. For this reason, organic light-emitting diode flat-panel display technology has attracted the attention of the industry and academia, and has been engaged in a lot of development and research.

Due to the flexible nature of organic light-emitting diodes, bendable and foldable flexible organic light-emitting diodes have gradually been developed in flat panel displays. Common flexible organic light-emitting diodes usually use opaque metal electrodes as electrodes located on the side of the substrate, use thin metal as the upper electrode, and use the light-emitting surface to form a light-emitting element that emits light from the top. However, the organic light-emitting diode that emits light from the top will form a micro-resonance cavity because the anode and cathode are both metal electrodes, thereby increasing the light-emitting directivity of the light-emitting element. Therefore, in order to reduce the light-emitting directivity of the light-emitting element, it is necessary to use a bottom-emitting light and use a transparent metal oxide as a transparent conductive electrode.

Transparent Conductive Electrode (TCE) is a thin film material with good transmittance in the visible light range and good conductivity. It is widely used in flat display, lighting, photovoltaic industry and smart products. Organic light-emitting diodes are a kind of display lighting element that has emerged in recent years. Due to its characteristics of flexibility, self-luminescence, surface luminescence and fast response speed, it is widely used in flat panel displays, especially mobile phone screens.

However, the flexible transparent oxide conductive film electrodes used in conventional flexible organic light-emitting diodes are mostly transparent oxides of zinc-gallium oxide type, which have poor conductivity, thereby reducing the overall efficiency of the organic light-emitting diode. Therefore, the industry needs a flexible organic light-emitting diode that can overcome the poor conductivity of the flexible transparent conductive film electrode.

In view of the above problems of the prior art, the present invention provides a flexible transparent electrode, which uses a flexible transparent metal oxide as an anode and sets a flexible alloy layer between the transparent metal oxide and a transparent substrate, wherein the alloy layer is a small amount of a metal with high surface energy doped into silver, so that the alloy layer is formed at an extremely thin thickness. The extremely thin alloy layer will not significantly reduce the transmittance of the transparent metal oxide conductive layer, and can increase the conductivity of the transparent metal oxide conductive layer.

One purpose of the present invention is to provide a flexible transparent electrode, which is a flexible alloy layer disposed under a flexible transparent metal oxide conductive layer, wherein the alloy layer is a small amount of a metal with high surface energy doped into silver, further increasing the conductivity of the flexible transparent electrode to enhance the overall luminous efficiency of the organic light-emitting element.

One purpose of the present invention is to provide a flexible organic light-emitting diode structure using a flexible transparent electrode, which uses a flexible transparent metal oxide conductive layer as an anode, and a flexible alloy layer is disposed between the transparent metal oxide conductive layer and a transparent substrate, wherein the alloy layer is a small amount of a metal with high surface energy doped into silver to further increase the conductivity, thereby improving the luminous efficiency of the organic light-emitting diode.

In order to achieve the above-mentioned purposes and effects, the present invention provides a flexible transparent electrode, which is a first electrode including a flexible alloy layer and a transparent metal oxide conductive layer. The material of the flexible alloy layer is a silver-chromium (Ag, Cr) alloy, and the material of the transparent metal oxide conductive layer is molybdenum-doped gallium zinc oxide (Mo-doped GaZnO). The flexible alloy layer is arranged between the transparent substrate and the transparent metal oxide conductive layer to improve the conductivity of the first electrode layer as a whole.

In order to achieve the above-mentioned purposes and effects, the present invention provides a flexible organic light-emitting diode structure using a flexible transparent electrode, which is a flexible alloy layer and a transparent metal oxide conductive layer. The material of the flexible alloy layer is a silver-chromium (Ag, Cr) alloy, and the material of the transparent metal oxide conductive layer is molybdenum-doped gallium zinc oxide (Mo-doped GaZnO). The flexible alloy layer is arranged between the transparent substrate and the transparent metal oxide conductive layer to improve the conductivity of the first electrode layer as a whole, and can be applied to the organic light-emitting diode as the first electrode layer. The organic light-emitting diode comprises a transparent flexible plastic substrate, a first electrode layer, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer and a second electrode layer stacked on each other. When a bias is applied to the organic light-emitting diode, electrons and holes enter the light-emitting layer and recombine to emit light. The light passes through the hole transport layer, the hole injection layer, the transparent metal oxide conductive layer, the flexible alloy layer and the transparent flexible plastic substrate in sequence.

In one embodiment of the present invention, the transparent flexible substrate material is PET or any other flexible transparent plastic material or a transparent mica substrate.

In one embodiment of the present invention, the transparent alloy metal is silver-chromium (Ag, Cr) alloy, copper-silver (Ag, Cu) alloy or any other silver alloy material.

In one embodiment of the present invention, the material of the transparent metal oxide conductive layer is Mo-doped GaZnO or any other zinc-gallium oxide material.

In one embodiment of the present invention, the hole injection layer is made of HAT-CN or molybdenum trioxide (MoO ₃ ) or any other hole injection layer material.

In one embodiment of the present invention, the material of the hole transport layer is TAPC, NPB, TCTA or any other hole transport layer material.

In one embodiment of the present invention, the material of the light-emitting layer is CBP:Ir(ppy) ₃ , mCP:Firpic, CBP:Ir(piq) ₂ acac or any other material combination of the light-emitting layer.

In one embodiment of the present invention, the material of the electron transport layer is B3PyMPM, TmPyPB, CN-T2T or any other electron transport layer material.

In one embodiment of the present invention, the material of the electron injection layer is lithium fluoride (LiF), 8-hydroxyquinoline-lithium (LiQ) or lithium carbonate (Li ₂ CO ₃ ) or any other electron injection layer material.

In one embodiment of the present invention, the material of the second electrode layer is aluminum (Al), silver (Ag) or silver-magnesium (Ag, Mg) alloy.

In order to enable you to have a deeper understanding and knowledge of the features and effects of the present invention, we would like to provide practical examples and accompanying explanations as follows:

In view of the above problems of the prior art, the present invention is a flexible transparent electrode, which uses a flexible transparent metal oxide conductive layer as an anode, and a flexible alloy layer is disposed between the transparent metal oxide conductive layer and a transparent substrate, wherein the alloy layer is a small amount of a metal with high surface energy doped into silver, so that the alloy layer is formed in an extremely thin film without significantly reducing the transmittance, but can increase the conductivity of the transparent metal oxide conductive layer, and further improve the overall luminous efficiency of the organic light-emitting element. The invention is applied to a flexible organic light-emitting diode, and its structure is that a first electrode layer is arranged on a transparent flexible substrate, and the first electrode layer includes a flexible alloy layer and a transparent metal oxide conductive layer. The flexible alloy layer is arranged between the transparent substrate and the transparent metal oxide conductive layer. The flexible alloy layer is used to improve the conductive efficiency and the transmittance of the first electrode layer, so as to solve the problem of poor conductivity or poor transmittance of the transparent conductive electrode of the conventional organic light-emitting diode.

Please refer to Figure 1, which is a schematic diagram of a flexible transparent electrode structure of an embodiment of the present invention. As shown in the figure, in this embodiment, it is a flexible transparent electrode 1, which includes a first electrode layer 20, and the first electrode layer 20 includes a flexible alloy layer 22 and a transparent metal oxide conductive layer 24. The transparent metal oxide conductive layer 24 is arranged on one of the flexible alloy layers 22. The flexible alloy layer 22 is used to improve the conductive efficiency of the first electrode layer 20 and maintain the light transmittance of the first electrode layer 20.

Please refer to FIG. 2, which is a schematic diagram of an organic light-emitting diode structure of an embodiment of the present invention. As shown in the figure, in this embodiment, it is a flexible organic light-emitting diode structure 2 using a flexible transparent electrode. The flexible organic light-emitting diode structure 2 using a flexible transparent electrode uses the flexible transparent electrode 1 of the above embodiment as the first electrode (anode). The flexible organic light-emitting diode structure 2 comprises a transparent substrate 10, a first electrode layer 20, a hole injection layer 30, a hole transport layer 40, a light-emitting layer 50, an electron transport layer 60, an electron injection layer 70 and a second electrode layer 80, and these layers are stacked on each other. In this embodiment, the transparent substrate 10 is a flexible substrate and allows the light emitted by the light-emitting layer 50 to pass through.

Referring to FIG. 2 again, as shown in the figure, in this embodiment, the first electrode layer 20 includes a flexible alloy layer 22 and a transparent metal oxide conductive layer 24, the flexible alloy layer 22 is disposed on one of the transparent substrates 10, the transparent metal oxide conductive layer 24 is disposed on one of the flexible alloy layers 22, the hole injection layer 30 is disposed on one of the transparent metal oxide conductive layers 24, and the hole conductive layer 30 is disposed on one of the transparent metal oxide conductive layers 24. The transport layer 40 is disposed on one of the hole injection layers 30, the light-emitting layer 50 is disposed on one of the hole transport layers 40, the electron transport layer 60 is disposed on one of the light-emitting layers 50, the electron injection layer 70 is disposed on one of the electron transport layers 60, and the second electrode layer 80 is disposed on one of the electron injection layers 70. These layers are stacked on each other to form the flexible organic light-emitting diode structure 2 using the flexible transparent electrode.

Continuing from the above, the material of the flexible alloy layer 22 included in the first electrode layer 20 is a silver-chromium (Ag, Cr) alloy; the thickness of the flexible alloy layer 22 is preferably less than or equal to 5 nm, so that the flexible alloy layer 22 can be bent while maintaining a transmittance greater than 80% in the visible light band.

Continuing from the above, if the flexible alloy layer 22 of pure silver is extremely thin, due to the inherent characteristics of silver, discontinuous islands and block structures will be generated and a film cannot be formed, making it difficult to increase the conductivity of the metal layer 22. If the thickness is increased to form a silver film, the light transmittance will be greatly reduced. Therefore, the present embodiment uses an alloy to solve this problem. A small amount of "high surface energy" metal is doped into the silver. The flexible alloy layer 22 adds chromium (Cr) to silver (Ag) to form a silver-chromium alloy, so that the flexible alloy layer 22 is formed at an extremely thin thickness (less than or equal to 5 nm), increasing the conductivity while maintaining the light transmittance.

Continuing from the above, the material of the transparent metal oxide conductive layer 24 is Mo-doped GaZnO. The transparent metal oxide conductive layer 24 is connected to the flexible alloy layer 22, so that the conductivity of the first electrode 20 is increased.

Continuing with the above, in one embodiment, the material of the transparent substrate 10 is PET (polyethylene terephthalate), so that the transparent substrate 10 is light-transmissive, but the embodiment is not limited thereto.

Continuing from the above, in one embodiment, the material of the hole injection layer 30 is HAT-CN (dipyrazino[2,3-f:2,3-]quinoxaline-2,3,6,7,10,11-hexacarbonitril) or molybdenum trioxide (MoO ₃ ), but the embodiment is not limited thereto.

Continuing from the above, in one embodiment, the material of the hole transport layer 40 is TAPC (di-[4-(N,N-di-p-tolylamino)phenyl]cyclohexane), NPB (N,N'-di(1-naphthyl)-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine) or TCTA (Tris(4-carbazoyl-9-ylphenyl)amine), but the present embodiment is not limited thereto.

Continuing with the above, in one embodiment, the material of the light-emitting layer 50 is CBP:Ir(ppy) ₃ , mCP:Firpic, CBP:Ir(piq) ₂ acac or any combination thereof, but the embodiment is not limited thereto.

Continuing from the above, in one embodiment, when the light-emitting layer 50 emits green light, the material of the light-emitting layer 50 may include CBP, mCP or other host materials, and may include a phosphorescent material of an Ir(ppy) ₃ (fac-tris(2-phenylpyridine)iridium) doped material or a fluorescent material including Alq ₃ (tris(8-hydroxyquinolino)aluminum), but the present embodiment is not limited thereto.

Continuing from the above, in one embodiment, when the light-emitting layer 50 emits blue light, the material of the light-emitting layer 50 may include CBP, mCP or other host materials, and may include a phosphorescent material doped with FIrpic or (4,6-F2ppy) ₂ Irpic, but the embodiment is not limited thereto.

Continuing from the above, in this embodiment, when the light-emitting layer 50 emits red light, the material of the light-emitting layer 50 may include CBP, mCP or other host materials, and may include at least one phosphorescent material of the group consisting of Ir(piq) _2acac (bis(1-phenylisoquinoline)acetylacetonate iridium), PQIr(acac) (bis(1-phenylquinoline)acetylacetonate iridium), PQIr (tris(1-phenylquinoline)iridium), and PtOEP (platinum octaethylporphyrin), or may include PBD:Eu(DBM) ₃ The fluorescent material may be phen or perylene, but the present embodiment is not limited thereto.

Continuing with the above, in one embodiment, the material of the electron transport layer 60 is B3PyMPM (bis-4,6-(3,5-di-3-pyridylphenyl)-2-methylpyrimi-dine), TmPyPB (1,3,5-tris[(3-pyridine)-phenyl-3-yl]benzene) or CN-T2T, but the present embodiment is not limited thereto.

Continuing with the above, in one embodiment, the material of the electron injection layer 70 is lithium fluoride (LiF), 8-hydroxyquinoline-lithium (LiQ) or lithium carbonate (Li ₂ CO ₃ ), but the embodiment is not limited thereto.

Continuing with the above, in one embodiment, the material of the second electrode layer 80 is aluminum (Al), silver (Ag) or silver-magnesium (Ag, Mg) alloy, but the embodiment is not limited thereto.

Refer to FIG. 2 and FIG. 3 again. FIG. 3 is a schematic diagram of the light path of an embodiment of the present invention. As shown in the figure, in this embodiment, a light ray L1 is emitted from one side (the lower side) of the light-emitting layer 50. After the light ray L1 passes through the hole transport layer 40 and the hole injection layer 30, the light ray L1 passes through the transparent metal oxide conductive layer 24 and the flexible alloy layer 22. Finally, the light ray L1 passes through the transparent substrate 10 and is emitted, forming the flexible organic light-emitting diode structure 2 using the flexible transparent electrode for downward light emission.

Continuing with the above, in this embodiment, the flexible alloy layer 22 of the first electrode layer 20 and the transparent metal oxide conductive layer 24 are used as anodes, and the second electrode layer 80 is used as cathodes.

Continuing from the above, since the metal of the cathode of the organic light-emitting diode must have the characteristics of low work function in order to effectively inject electrons into the organic layer, the material of the second electrode layer 80 can be magnesium, silver or their alloys as mentioned above, wherein the work function of magnesium is low enough (about 3.5 eV) and is also quite stable, which fully meets the requirements of the cathode of the organic light-emitting diode. When magnesium and silver form an alloy in a ratio of ten to one, a small amount of silver can provide a nucleating site for magnesium, so that magnesium can smoothly form a film on the organic layer. However, metallic lithium (Li) (work function of about 1.4 eV) and its compounds such as lithium fluoride (LiF) and aluminum oxide (Li ₂ O) and metallic aluminum (Al) (work function of about 3.4 eV) and its compounds may also be used.

Continuing from the above, the material of the anode of the organic light-emitting diode must be a material with high work function and light transmittance. Therefore, in this embodiment, molybdenum-doped gallium zinc oxide (Mo-doped GaZnO) is used as the material of the transparent metal oxide conductive layer 24, which has stable properties and high light transmittance.

Continuing from the above, in the light-emitting layer 50 of the flexible organic light-emitting diode structure 2 using the flexible transparent electrode, the number of holes is usually greater than the number of electrons. If the number of the two in the light-emitting layer can be properly adjusted, it will help to improve the recombination rate and also show higher efficiency and brightness. Therefore, the electron injection layer 70 and the electron transport layer 60 are provided to allow more electrons to enter the light-emitting layer 50; and the hole injection layer 20 is provided to reduce the number of holes entering the light-emitting layer 50, and the hole transport layer 30 is provided to extend the time that the holes stay in the light-emitting layer 50.

Please refer to FIG. 4, which is a schematic diagram of the light reflection path of an embodiment of the present invention. As shown in the figure, in this embodiment, after the light ray L1 is emitted from the other side (upper side) of the light emitting layer 50, the light ray L1 passes through the electron transport layer 60 and the electron injection layer 70, and then the light ray L1 is projected to the second electrode layer 80. The second electrode layer 80 reflects the light ray L1 to form a reflected light L2, and the reflected light L2 passes through the electron injection layer 70, the electron transport layer 60, the electron injection layer 7 ... The electron transport layer 60, the light-emitting layer 50, the hole transport layer 40, the hole injection layer 30, the first electrode layer 20 and the transparent substrate 10, and finally the reflected light L2 is emitted from the transparent substrate 10; the present embodiment utilizes the thicker second electrode layer 80 to form an opaque layer and reflect the light L1 of the light-emitting layer 50 on the other side to improve the light extraction efficiency of the flexible organic light-emitting diode structure 2 using the flexible transparent electrode.

In summary, the present invention provides a flexible transparent conductive layer as an anode, with a flexible alloy layer disposed between a transparent metal oxide conductive layer and a transparent substrate, wherein the alloy layer is a small amount of a metal with high surface energy doped into silver, further increasing the conductivity of the transparent metal oxide conductive layer, and using this flexible electrode as the anode of an organic light-emitting diode, and then stacking a hole injection layer, a hole transport layer, a light-emitting layer, and an electron transport layer. The invention relates to a flexible organic light-emitting diode (OLED) structure that is flexible and has a transparent electrode, an electron injection layer, and a metal cathode. The invention also solves the problem that the transparent flexible conductive electrode used in the conventional flexible organic light-emitting diode has poor conductivity and the thick metal anode also has poor transmittance, which results in a decrease in the overall luminous efficiency of the organic light-emitting diode or the generation of a micro-resonant cavity.

Therefore, this invention is novel, progressive and can be used in the industry. It should undoubtedly meet the patent application requirements of the Patent Law of our country. Therefore, we have filed an invention patent application in accordance with the law and pray that the Bureau will approve the patent as soon as possible. I am deeply grateful.

However, the above is only an embodiment of the present invention and is not intended to limit the scope of the present invention. Therefore, all equivalent changes and modifications based on the shape, structure, features and spirit described in the patent application scope of the present invention should be included in the patent application scope of the present invention.

1: Flexible transparent electrode 2: Flexible organic light-emitting diode structure using flexible transparent electrode 10: Transparent substrate 20: First electrode layer 22: Flexible alloy layer 24: Transparent metal oxide conductive layer 30: Hole injection layer 40: Hole transport layer 50: Luminescent layer 60: Electron transport layer 70: Electron injection layer 80: Second electrode layer L1: Light L2: Reflected light

Figure 1: It is a schematic diagram of the flexible transparent electrode structure of one embodiment of the present invention; Figure 2: It is a schematic diagram of the organic light-emitting element structure of one embodiment of the present invention; Figure 3: It is a schematic diagram of the light path of one embodiment of the present invention; and Figure 4: It is a schematic diagram of the light reflection path of one embodiment of the present invention.

2: Flexible organic light-emitting diode structure using flexible transparent electrode

10:Transparent substrate

20: First electrode layer

22: Flexible alloy layer

24: Transparent metal oxide conductive layer

30: Hole injection layer

40: Hole transport layer

50: Luminous layer

60:Electron transmission layer

70:Electron injection layer

80: Second electrode layer

Claims (8)

A flexible organic light-emitting diode structure using a flexible transparent electrode comprises: A transparent mica substrate; A first electrode layer, which is composed of a flexible alloy layer and a transparent metal oxide conductive layer, the flexible alloy layer is disposed on one of the transparent mica substrates, the material of the flexible alloy layer is a silver-chromium (Ag, Cr) alloy, and the thickness of one of the flexible alloy layers is less than 5nm, the transparent metal oxide conductive layer is disposed on one of the flexible alloy layers, and the material of the transparent metal oxide conductive layer is molybdenum-doped gallium zinc oxide (Mo-doped GaZnO); A hole injection layer, which is disposed on one of the transparent metal oxide conductive layers; A hole transport layer disposed above one of the hole injection layers; A light-emitting layer disposed above one of the hole transport layers; An electron transport layer disposed above one of the light-emitting layers; An electron injection layer disposed above one of the electron transport layers; and A second electrode layer disposed above one of the electron injection layers. A flexible organic light-emitting diode structure using a flexible transparent electrode as described in claim 1, wherein the transparent mica substrate is a flexible substrate. A flexible organic light-emitting diode structure using a flexible transparent electrode as described in claim 1, wherein the material of the hole injection layer is HAT-CN or molybdenum trioxide (MoO ₃ ). A flexible organic light-emitting diode structure using a flexible transparent electrode as described in claim 1, wherein the material of the hole transport layer is TAPC, NPB or TCTA. A flexible organic light-emitting diode structure using a flexible transparent electrode as claimed in claim 1, wherein the material of the light-emitting layer is CBP:Ir(ppy) ₃ , mCP:Firpic, CBP:Ir(piq) ₂ acac or any combination thereof. A flexible organic light-emitting diode structure using a flexible transparent electrode as described in claim 1, wherein the material of the electron transport layer is B3PyMPM, TmPyPB or CN-T2T. The flexible organic light-emitting diode structure using a flexible transparent electrode as claimed in claim 1, wherein the material of the electron injection layer is lithium fluoride (LiF), 8-hydroxyquinoline-lithium (LiQ) or lithium carbonate (Li ₂ CO ₃ ). A flexible organic light-emitting diode structure using a flexible transparent electrode as described in claim 1, wherein the material of the second electrode layer is aluminum (Al), silver (Ag) or silver-magnesium (Ag, Mg) alloy.

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