Patent Application
20140312314
This application claims the benefit of Korean Patent Application No. 10-2013-0042421, filed on Apr. 17, 2013, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field
The disclosed technology relates to a flexible display device and a manufacturing method thereof.
2. Description of the Related Technology
Recently, along with the development of display-related technology, flexible display devices capable of being folded or rolled in a roll shape have been researched and developed.
Since an organic light-emitting display panel has good characteristics in terms of a view angle, contrast, a response speed, power consumption, and the like, the application fields thereof have been expanded from personal portable devices, such as MP3 players, portable phones, and the like, to TVs. In addition, since an organic light-emitting display panel has a self-light-emitting characteristic, a separate light source is not necessary, and thus, a thickness and weight thereof can be reduced.
Such an organic light-emitting display panel can be implemented to be flexible using a plastic substrate. In general, a flexible organic light-emitting display panel may be formed by forming an organic light-emitting diode (OLED) and other components on a carrier substrate formed of a material, such as glass or the like, and debonding the carrier substrate from a plastic substrate.
Embodiments of the disclosed technology relate to a flexible display device capable of preventing unnecessary adhesion of a substrate and a carrier substrate, and a manufacturing method thereof.
According to an aspect of the disclosed technology, a flexible display device includes: a substrate having a first surface and a second surface opposing the first surface, a light-emitting display part formed on the first surface of the substrate, an encapsulation layer formed on the light-emitting display part, and an exfoliation layer formed on the second surface of the substrate, where the exfoliation layer has a layer structure formed of a plurality of layers.
The exfoliation layer may be an inorganic material.
The exfoliation layer may be at least one of a hydrated magnesium silicate, a hexagonal boron nitride, graphite, and a molybdenum disulfide.
The exfoliation layer may be formed on substantially the entire second surface of the substrate.
A device and wiring layer may be formed between the substrate and the light-emitting display part.
The light-emitting display part may be an organic light-emitting display panel.
The exfoliation layer may be two layers and there may be a substantial van der Waals force between the two layers.
The exfoliation layer may have a small coefficient of friction.
The exfoliation layer may have a small coefficient of thermal expansion.
According to another aspect of the disclosed technology, a method of manufacturing a flexible display device includes: forming an exfoliation layer on a surface of a carrier substrate, where the exfoliation layer has a layer structure formed of a plurality of layers, disposing a surface of a substrate on the exfoliation layer, forming a light-emitting display part on the substrate, forming an encapsulation layer on the light-emitting display part, and removing the carrier substrate by splitting the exfoliation layer.
The exfoliation layer may be substantially formed of an inorganic material.
The exfoliation layer may be at least one of a hydrated magnesium silicate, a hexagonal boron nitride, graphite, and a molybdenum disulfide.
The exfoliation layer may be formed on the entire surface of the carrier substrate.
The method may further include aligning the carrier substrate and the substrate.
The bonding force between the carrier substrate and the substrate may be greater than the inter-layer bonding force of the exfoliation layer.
The exfoliation layer may be split between first and second layers in the layer structure.
The method may further include annealing at least one of the substrate or the carrier substrate.
A temperature of annealing may be about 300° C. or above.
The carrier substrate may be removed by a physical method.
The light-emitting display part may include an organic light-emitting display panel.
The above and other features and advantages of the disclosed technology will become more apparent by describing in detail certain embodiments thereof with reference to the attached drawings in which:
The disclosed technology will now be described more fully with reference to the accompanying drawings, in which certain embodiments of the invention are shown. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Generally, expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.
Referring to
The display panel part 200 has a flexible property, and accordingly, can be folded or rolled. This in turn helps to keep or carry the display panel part 200. The display panel part 200 may be an organic light-emitting display panel, a liquid crystal display panel, or the like, and is not limited thereto.
Referring to
The substrate 210 may be formed of a plastic material, such as, for example, acryl, polyethylene etherphthalate, polyethylene naphthalate, polycarbonate, polyarylate, polyetherimide, polyether sulfone, polyester, mylar, polyimide, or the like, so that the light-emitting display part OLED 220 has a flexible property. However, the substrate 210 is not limited thereto, and may also be formed of various other flexible materials.
The barrier film 240 may be disposed on the substrate 210. The barrier film 240 prevents foreign substances, such as for example, humidity, moisture and oxygen, from permeating a driving thin-film transistor TFT and/or the light-emitting display part OLED 220, by passing through the substrate 210.
The device and wiring layer 250 may be disposed on the barrier film 240 and may include the driving thin-film transistor TFT for driving the light-emitting display part OLED 220, a switching thin-film transistor (not shown), a capacitor, and wirings connected to the thin-film transistors and the capacitor.
The driving thin-film transistor TFT includes an active layer 251, a gate electrode 253, and source and drain electrodes 255a and 255b.
The light-emitting display part OLED 220 is disposed on the device and wiring layer 250. The light-emitting display part OLED 220 includes a pixel electrode 221, an organic light-emitting layer 222 disposed on the pixel electrode 221, and an opposing electrode 223 formed on the organic light-emitting layer 222.
In one embodiment, the pixel electrode 221 is an anode, and the opposing electrode 223 is a cathode. However, the disclosed technology is not limited thereto, and according to a method of driving the light-emitting display part OLED 220, the pixel electrode 221 may be a cathode, and the opposing electrode 223 may be an anode. Holes and electrons from the pixel electrode 221 and the opposing electrode 223 are doped into the organic light-emitting layer 222. When excitons obtained by bonding the doped holes and electrons drop from an excited state to a base state, light is emitted.
The pixel electrode 221 is electrically connected to the driving thin-film transistor TFT formed in the device and wiring layer 250.
Although a structure in which the light-emitting display part OLED 220 is disposed on the device and wiring layer 250 is set forth in one embodiment, the disclosed technology is not limited thereto, and can be modified in various forms, such as a structure in which the pixel electrode 221 of the light-emitting display part OLED 220 is formed in the same layer as the active layer 251 of the driving thin-film transistor TFT, a structure in which the pixel electrode 221 is formed in the same layer as the source and drain electrodes 255a and 255b, and so forth.
In addition, although the gate electrode 253 of the driving thin-film transistor TFT is disposed on the active layer 251 in one embodiment, the disclosed technology is not limited thereto, and the gate electrode 253 may be disposed below the active layer 251.
The pixel electrode 221 included in the light-emitting display part OLED 220 may be a reflective electrode, and may include a reflective film formed of one of: silver (Ag), magnesium (Mg), aluminum (Al), platinum (Pt), palladium (Pd), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chrome (Cr), or a compound thereof, and a transparent or translucent electrode layer formed on the reflective film.
The transparent or translucent electrode layer may include at least one of an indium tin oxide (ITO), an indium zinc oxide (IZO), a zinc oxide (ZnO), an indium oxide (In2O3), an indium gallium oxide (IGO), or an aluminum zinc oxide (AZO).
The opposing electrode 223 disposed to face the pixel electrode 221 may be a transparent or translucent electrode and may be formed by a metal thin film having a small work function, which may include lithium (Li), calcium (Ca), lithium fluoride/calcium (LiF/Ca), lithium fluoride/aluminum (LiF/Al), silver (Ag), magnesium (Mg), or a compound thereof. In addition, an auxiliary electrode layer or a bus electrode of a transparent electrode forming material (not shown), such as an ITO, an IZO, a ZnO, or an In2O3, may be further formed on the metal thin film. Thus, the opposing electrode 223 may transmit light emitted by the organic light-emitting layer 222.
The organic light-emitting layer 222 is disposed between the pixel electrode 221 and the opposing electrode 223, and may be formed of a low-molecular organic material or a high-molecular organic material.
In addition to the organic light-emitting layer 222, intermediate layers, such as a hole transport layer (HTL), a hole injection layer (HIL), an electron transport layer (ETL), an electron injection layer (EIL), and the like, may be selectively disposed between the pixel electrode 221 and the opposing electrode 223.
The organic light-emitting layer 222 may be a top-emission type in which the light emitted by the organic light-emitting layer 222 is directly emitted towards the opposing electrode 223, or is reflected by the pixel electrode 221, which is a reflective electrode, and is emitted towards the opposed electrode 223.
However, the light-emitting display part OLED 220 is not limited to the top-emission type, and the OLED 220 may be a bottom-emission type in which the light emitted by the organic light-emitting layer 222 is emitted towards the substrate 210. In this case, the pixel electrode 221 may be a transparent or translucent electrode, and the opposing electrode 223 may be a reflective electrode.
An encapsulation layer 230 may be disposed on the opposing electrode 223. The encapsulation layer 230 may be formed by a thin film including a multi-layer inorganic film, or including an inorganic film and an organic film. The encapsulation layer 230 may be formed by alternately laminating one or more organic layers, and one or more inorganic layers. The encapsulation layer 230 functions to prevent permeation of external humidity, moisture, oxygen, and the like, into the light-emitting display part OLED 220.
Returning to
A layer structure of the hexagonal boron nitride is shown in
The exfoliation layer 100 may be formed in a layer structure in which two layers 101 and 102 are laminated. Although the two layers 101 and 102 are shown in
In addition, the van der Waals force is relatively weaker than a force of the covalent bond or the electrical interaction between ions. Thus, the exfoliation layer 100, which can have a layer structure based on the van der Waals force, may have a small coefficient of friction. Accordingly, the exfoliation layer 100 may have a lubricant ability. In this case, the carrier substrate (300 of
The exfoliation layer 100 may be formed on the whole substrate 210.
Hereinafter, a method of manufacturing the flexible display device 10, according to an embodiment of the disclosed technology, is be described with reference to
First, as shown in
The carrier substrate 300 is formed of a material, such as glass or the like, capable of withstanding a high temperature. In addition, the carrier substrate 300 is formed of a material that has a sufficient mechanical strength not to be deformed even when various devices or layers are formed thereon.
The exfoliation layer 100 may be formed by coating a material, such as a hydrated magnesium silicate, a hexagonal boron nitride, graphite (C), a molybdenum disulfide, or the like, on the carrier substrate 300 by spin coating, dip coating, slit coating, or the like. The exfoliation layer 100, which can have a layer structure by the van der Waals force, may have a small coefficient of friction. Accordingly, the exfoliation layer 100 may have a lubricant ability. In this case, the carrier substrate 300 may be easily covered by the exfoliation layer 100.
The exfoliation layer 100 may have a layer structure in which a first layer 103 and a second layer 104 are included. An attractive force acts between the first layer 103 and the second layer 104. The attractive force of each of the first 103 and second 104 layers may be the van der Waals force. Although
The exfoliation layer 100 may be formed on the whole substrate 210. Conventionally, when a temperature of the substrate 210 or the carrier substrate 300 reaches about 300° C. or above, permanent bonding of the substrate 210 and the carrier substrate 300 may occur. By forming the exfoliation layer 100 on the whole substrate 210, the substrate 210 and the carrier substrate 300 can be generally debonded from each other. Accordingly, the bonding between the substrate 210 and the carrier substrate 300 can be prevented.
Next, as shown in
The substrate 210 may be formed of a plastic material, such as acryl, polyethylene etherphthalate, polyethylene naphthalate, polycarbonate, polyarylate, polyetherimide, polyether sulfone, polyester, mylar, polyimide, or the like.
After disposing the substrate 210 on the exfoliation layer 100, the substrate 210 and the carrier substrate 300 are aligned. Since the exfoliation layer 100 has a layer structure, the exfoliation layer 100 may have a lubricant ability. Accordingly, the substrate 210 and the carrier substrate 300 can be aligned without scratching or injuring the substrate 210 or the carrier substrate 300.
After aligning the substrate 210 and the carrier substrate 300, the exfoliation layer 100 is bonded to the carrier substrate 300 and the substrate 210. That is, one surface of the exfoliation layer 100 is bonded to the substrate 210, and the other surface of the exfoliation layer 100 is bonded to the carrier substrate 300. The substrate 210 and the carrier substrate 300 are temporarily bonded to each other by interposing the exfoliation layer 100 therebetween. According to an embodiment of the disclosed technology, when a hydrated magnesium silicate (Mg3Si4O10(OH)2) is used for the exfoliation layer 100, since the —OH groups of the exfoliation layer 100 react with the —OH groups of the substrate 210 and the carrier substrate 300, the exfoliation layer 100 can be bonded to the carrier substrate 300 and the substrate 210.
A bonding force between the exfoliation layer 100 and the substrates 210 and 300 is preferably greater than an attractive force between every two layers in the layer structure. That is, the bonding force between the exfoliation layer 100 and the substrates 210 and 300 is preferably greater than the attractive force between the first layer 103 and the second layer 104.
The light-emitting display part OLED 220 is formed on the substrate 210 by sequentially forming a pixel electrode 221, an organic light-emitting layer 222, and an opposing electrode 223, and the encapsulation layer 230 is formed on the light-emitting display part OLED 220 to cover the light-emitting display part OLED 220. The encapsulation layer 230 may be formed by a thin film including a multi-layer inorganic film or including an inorganic film and an organic film. In addition, the encapsulation layer 230 may be formed by alternately laminating one or more organic layers and one or more inorganic layers.
In the process of sequentially forming the pixel electrode 221, the organic light-emitting layer 222, and the opposing electrode 223, a process of annealing the substrate 210 or the carrier substrate 300 may be included. A temperature of the substrate 210 or the carrier substrate 300 may be about 300° C. or above by the annealing process. Conventionally, when a temperature of the substrate 210 or the carrier substrate 300 is about 300° C. or above, the permanent bonding of the substrate 210 and the carrier substrate 300 may occur. According to an embodiment of the disclosed technology, by disposing the exfoliation layer 100 of a layer structure between the substrate 210 and the carrier substrate 300, the permanent bonding of the substrate 210 and the carrier substrate 300 does not occur even though a temperature of the substrate 210 or the carrier substrate 300 is at about 300° C. or above.
In addition, the exfoliation layer 100 may have a small coefficient of thermal expansion. In more detail, the hexagonal boron nitride may have a coefficient of thermal expansion that is less than about 0. Since the exfoliation layer 100 has a small coefficient of thermal expansion, deformation of the exfoliation layer 100 due to heat is small, and thus, the process of annealing the substrate 210 or the carrier substrate 300 may be carried out without any problem due to thermal expansion of the exfoliation layer 100.
Next, as shown in
The carrier substrate 300 may be debonded from the substrate 210 in a physical method.
The exfoliation layer 100 has a layer structure and includes the first layer 103 and the second layer 104, and the bonding force between the substrates 210 and 300 may be greater than the attractive force between the first layer 103 and the second layer 104. Accordingly, the bonding between the first and second layers 103 and 104 of the exfoliation layer 100 may be debonded by a physical method, thereby debonding the carrier substrate 300 from the substrate 210. That is, when the inter-layer bonding in the layer structure of the exfoliation layer 100 is debonded, the exfoliation layer 100 is divided into two, thereby easily separating the carrier substrate 300. Accordingly, the detachment yield of the carrier substrate 300 may be improved.
The configuration and method of the embodiments described above is not limitedly applied to the flexible display device 10 according to the disclosed technology, and the embodiments may be formed by selectively combining all or a portion of the embodiments so that various modifications are made.
According to an embodiment of the disclosed technology, by forming an exfoliation layer on one surface of a substrate, the permanent bonding of the substrate and a carrier substrate can be prevented.
While the present invention has been particularly shown and described with reference to certain embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2013-0042421 | Apr 2013 | KR | national |
