Method of manufacturing flexible display

A flexible display and method of manufacturing the same are disclosed. In one aspect, the method includes forming a metal peroxide layer over a supporting substrate, forming a metal layer over the metal peroxide layer and forming a flexible substrate over the metal layer. The method also includes forming a display layer over the flexible substrate, irradiating the supporting substrate with laser light in a direction from the supporting substrate to the flexible substrate so as to form a metal oxide layer and separating the supporting substrate from the flexible substrate with the metal oxide layer as a boundary between the supporting substrate and the flexible substrate.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

This application claims the benefit of Korean Patent Application No. 10-2014-0141196, filed on Oct. 17, 2014, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND

Field

The described technology generally relates to a flexible display and a method of manufacturing the same, and more particularly, to a flexible display having a flexible substrate that is easily detachable from a supporting substrate and a method of manufacturing the flexible display.

Description of the Related Technology

Organic light-emitting diode (OLED) displays are being noted as next-generation displays due to their associated advantages such as wide viewing angles, excellent contrast, and fast response times.

In general, an OLED display has thin film transistors and OLEDs formed on a substrate and the OLEDs display images by emitting light. OLED displays can be used as the display of portable devices such as cell phones and can also be used as the display of large-sized products such as televisions.

SUMMARY OF CERTAIN INVENTIVE ASPECTS

One inventive aspect is a flexible display having a flexible substrate easily detachable from a supporting substrate.

Another aspect is a method of manufacturing the flexible display having a flexible substrate easily detachable from a supporting substrate.

Another aspect is a method of manufacturing a flexible display including forming a metal peroxide layer on a supporting substrate; forming a metal layer on the metal peroxide layer; forming a flexible substrate on the metal layer; forming a display layer on the flexible substrate; irradiating laser light in a direction from the supporting substrate to the flexible substrate, thereby forming a metal oxide layer; and separating the supporting substrate and the flexible substrate with the metal oxide layer as a boundary between the supporting substrate and the flexible substrate.

The forming of the metal peroxide layer may be forming the metal peroxide layer including an alkali metal.

The forming of the metal oxide layer may include: irradiating the laser light on the supporting substrate in the direction from the supporting substrate to the flexible substrate; and as oxygen spreads from the metal peroxide layer to the metal layer by heat of the laser, combining the spread oxygen with the metal layer.

The irradiating of the laser and the combining of the oxygen with the metal layer may be performed simultaneously.

The separating of the supporting substrate and the flexible substrate may be separating the supporting substrate and the flexible substrate such that at least a portion of the metal oxide layer remains on one side of the flexible substrate.

The method may further include forming a barrier layer between the forming of the metal layer and the forming of the flexible substrate.

The forming of the display layer may be forming the display layer including a thin film transistor and an organic light-emitting device electrically connected to the thin film transistor.

The method may further include forming an encapsulation layer formed such that an organic film and an inorganic film are alternated on the display layer.

Another aspect is a flexible display includes a flexible substrate; a metal oxide layer formed on at least a portion of one side of the flexible substrate; a display layer formed on the other side of the flexible substrate; and a barrier layer formed between the flexible substrate and the metal oxide layer.

The display layer may include a thin film transistor and an organic light-emitting device electrically connected to the thin film transistor.

The apparatus may further include an encapsulation layer formed such that an organic film and an inorganic film are alternated on the display layer.

Another aspect is a method of manufacturing a flexible display, the method comprising forming a metal peroxide layer over a supporting substrate; forming a metal layer over the metal peroxide layer; forming a flexible substrate over the metal layer; forming a display layer over the flexible substrate; irradiating the supporting substrate with laser light in a direction from the supporting substrate to the flexible substrate so as to form a metal oxide layer; and separating the supporting substrate from the flexible substrate with the metal oxide layer as a boundary between the supporting substrate and the flexible substrate.

In exemplary embodiments, the metal peroxide layer comprises an alkali metal. The irradiating of the supporting substrate can comprise heating the metal peroxide layer with the laser light so as to spread oxygen from the metal peroxide layer to the metal layer and combine the oxygen with the metal layer. The irradiating of the laser light and the combining of the oxygen with the metal layer can be performed simultaneously. The separating of the supporting substrate from the flexible substrate can comprise separating the supporting substrate from the flexible substrate such that at least a portion of the metal oxide layer remains on one side of the flexible substrate.

In exemplary embodiments, the method further comprises forming a barrier layer between the forming of the metal layer and the forming of the flexible substrate. The forming of the display layer can comprise forming a thin film transistor and an organic light-emitting diode (OLED) electrically connected to the thin film transistor. The method can further comprise forming an encapsulation layer comprising an organic film and an inorganic film that are alternated stacked on the display layer.

Another aspect is a flexible display comprising a flexible substrate; a metal oxide layer formed on at least a portion of one side of the flexible substrate; a display layer formed on the other side of the flexible substrate; and a barrier layer interposed between the flexible substrate and the metal oxide layer.

In exemplary embodiments, the display layer comprises a thin film transistor and an organic light-emitting diode (OLED) electrically connected to the thin film transistor. The flexible display can further comprise an encapsulation layer comprising an organic film and an inorganic film that are alternated stacked on the display layer.

These general and specific embodiments may be implemented by using a system, a method, a computer program, or a combination thereof.

DETAILED DESCRIPTION OF CERTAIN INVENTIVE EMBODIMENTS

One type of OLED display, that is flexible displays, are being actively researched. In order to manufacture such a flexible display, instead of using a traditional glass substrate, a flexible substrate formed of a material such as synthetic resin is used. Flexible substrates can have a problem in that it is not easy to handle such substrates in a manufacturing process because of their flexible properties. Accordingly, in order to solve this problem, a flexible substrate can be formed on a supporting substrate having sufficient rigidity, and after several processes, the flexible substrate is separated from the supporting substrate.

These standard flexible displays and methods of manufacturing the same have problems where a material used as a sacrificial layer is relatively expensive and is not easy to handle in a manufacturing process. Further, it is difficult to fix such a flexible substrate onto a supporting substrate because of a weak adhesive strength between the supporting substrate and the flexible substrate.

As the described technology allows for various changes and numerous embodiments, exemplary embodiments will be illustrated in the drawings and described in detail in the written description. The effects and features of the described technology and methods of accomplishing the same will become apparent from the following description of the embodiments in detail, taken in conjunction with the accompanying drawings. The described technology may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein.

Hereinafter, the described technology will be described in detail with reference to the accompanying drawings, in which exemplary embodiments of the described technology are shown Like reference numerals in the drawings denote like elements, and thus repeated descriptions thereof will be omitted.

While such terms as “first” and “second” may be used to describe various components, such components must not be limited to the above terms. The above terms are used only to distinguish one component from another. Also, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

It will be understood that the terms such as “including,” “comprising,” and “having” used herein specify the presence of stated features or components, but do not preclude the presence or addition of one or more other features or components. It will be further understood that when a layer, region, or component is referred to as being “formed on” another layer, region, or component, it can be directly or indirectly formed on the other layer, region, or component. That is, for example, intervening layers, regions, or components may be present.

Sizes of components in the drawings may be exaggerated for the sake of clarity. In other words, since the sizes and thicknesses of components in the drawings may be exaggerated, the following embodiments are not limited thereto.

FIGS. 1 through 3are cross-sectional views schematically illustrating a process of manufacturing a flexible display according to an embodiment.

Referring toFIG. 1, in order to manufacture a flexible display according to an embodiment, a first operation of forming a metal peroxide layer20on a supporting substrate10is performed. The supporting substrate10may be formed of various materials such as glass having sufficient rigidity or a metal material. As a flexible substrate100itself has flexible properties, the supporting substrate10serves to support the flexible substrate100while various kinds of layers which will be described in the following are formed on the flexible substrate100.

As described above, the metal peroxide layer20may be formed on the supporting substrate10prior to the flexible substrate100. The metal peroxide layer20may include alkali metals such as lithium (Li), sodium (Na), or potassium (K). Accordingly, the metal peroxide layer20may be Li2O2, Na2O2, or K2O2; however, the present embodiment is not limited thereto. The metal peroxide layer20can be formed to have a thickness of about 10 nm to about 100 nm, and more particularly, a thickness of about 20 nm to about 50 nm.

Specifically, a method of forming the metal peroxide layer20can start from forming a metal film such as an alkali metal film on the supporting substrate10. The alkali metal film can be formed by using methods such as sputtering, physical vapor deposition (PVD), or chemical vapor deposition (CVD). After the alkali metal film is formed on the supporting substrate10, the alkali metal film is annealed in an oxygen atmosphere. Through this process, the metal peroxide layer20may be formed.

For example, when the alkali metal film is formed by using sodium, the alkali metal film can be annealed at a temperature of about 130° C. to about 200° C. so as to combine with oxygen through the reaction process shown below.
4Na+O2→2Na2O
2Na2O+O2→2Na2O2

Through the above process, a sodium peroxide layer can be formed. However, the present embodiment is not limited thereto, and a sodium amalgam can also be used to form the sodium peroxide layer. In this case, the sodium peroxide layer can be formed by using a sodium amalgam diluted solution of about 0.1 mol % to about 0.5 mol % at a temperature of about 0° C. to about 20° C.

Next, an operation of forming a metal layer30on the metal peroxide layer20can be performed. The metal layer30may include molybdenum (Mo), iron (Fe), tungsten (W), or chromium (Cr); however, the described technology is not limited thereto. On the metal peroxide layer20, the metal layer30can be formed to have a thickness of about 10 nm to about 100 nm, preferably a thickness of about 20 nm to about 50 nm, and more preferably a thickness of about 15 nm to about 25 nm. The metal layer30can be formed on the metal peroxide layer20by using methods such as sputtering, PVD, CVD, or electron beam (EB) deposition.

After the metal layer30is formed, an operation of forming the flexible substrate100on the metal layer30can be performed. The flexible substrate100, which has flexible properties, can be formed of various materials, for example, metal materials, or plastic materials such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyester (PES), polyetheretherketone (PEEK), polycarbonate (PC) or polyimide (PI). Thin metal foil such as steel use stainless (SUS) can also be used as a material of the flexible substrate100.

In some embodiments, a barrier layer40can be further formed between the metal layer30and the flexible substrate100. The barrier layer40can prevent impurities from penetrating through the flexible substrate100. The barrier layer40may be formed of an inorganic film and may include silicon oxide (SiOx), silicon nitride (SiNx), silicon oxynitride (SiOxNy), aluminum oxide (Al2O3), aluminum nitride (AlN), or aluminum oxynitride (AlOxNy).

On the flexible substrate100, a display layer300can be formed. Although not illustrated inFIG. 1, the display layer300can include a thin film transistor, and an OLED electrically connected to the thin film transistor. For example, the display layer300can be an OLED display layer including a plurality of thin film transistors and pixel electrodes connected thereto. Alternatively, the display layer300can be a liquid crystal display layer. A detailed structure of the display layer300will be described with reference toFIG. 4.

Meanwhile, on the display layer300, an encapsulation layer400can be formed. The encapsulation layer400can be formed on an opposite electrode of the display layer300which will be described later and can be formed on the entire surface of the flexible substrate100. The encapsulation layer400covers the display layer300and a portion of the encapsulation layer400can be in direct contact with an edge of the flexible substrate100. The encapsulation layer400can be formed such that an organic film and an inorganic film are alternately arranged. The encapsulation layer400serves to prevent impurities, moisture, or the like from penetrating through the display layer300from the environment.

The organic film forming the encapsulation layer400may include, for example, one or more materials selected from the group consisting of an acrylic resin, a methacrylic resin, polyisoprene, a vinyl resin, an epoxy resin, a urethane resin, a cellulose resin, and a perylene resin. Also, the inorganic film forming the encapsulation layer400may include, for example, one or more materials selected from the group consisting of silicon nitride, aluminum nitride, zirconium nitride, titanium nitride, hafnium nitride, tantalum nitride, silicon oxide, aluminum oxide, titanium oxide, tin oxide, cerium oxide, and silicon oxynitride (SiON).

Referring toFIG. 2, a metal oxide layer50can be formed by irradiating laser light L in a direction from the supporting substrate10to the flexible substrate100. In some embodiments, forming the metal oxide layer50includes irradiating laser light L on the supporting substrate10in the direction from the supporting substrate10to the flexible substrate100. That is, the laser light L is irradiated on one side of the supporting substrate10which conducts heat to the metal peroxide layer20formed on the other side of the supporting substrate10. The metal peroxide layer20is exposed to high-temperature heat by the irradiated laser light L. In the process, oxygen combined in the metal peroxide layer20is separated therefrom and spreads to the metal layer30. Depending on the thickness of the metal peroxide layer20, a portion of the metal peroxide layer20that is in contact with the flexible substrate100may remain unaltered.

For the oxygen combined in the metal peroxide layer20to spread well, a temperature of equal to or greater than about 500° C. needs to be applied to the metal peroxide layer20, and more particularly, a temperature of equal to or greater than 600° C. can be applied. When a temperature of less than about 500° C. is applied, as the oxygen does not sufficiently spread, and thus, the metal layer30partially becomes a metal oxide and the rest of the metal layer30is unaltered. Thus, it may be not easy to detach the flexible substrate100from the supporting substrate10.

As such, when the oxygen combined in the metal peroxide layer20is separated by the laser light L irradiated to the metal peroxide layer20and combines with the metal layer30, the metal layer30becomes the metal oxide layer50. For example, the metal oxide layer50may be formed of molybdenum oxide (MoOx), tungsten oxide (WOx), chromium oxide (CrOx), or iron oxide (FeOx) (x=4, 5, 6).

As described above, the operation of irradiating the laser light L and the operation of oxygen combining with the metal layer30can be performed simultaneously. Since the laser light L needs to be irradiated onto a sacrificial layer in order to detach the flexible substrate100from the supporting substrate10, the metal layer30can be formed as the metal oxide layer50by heating the metal layer30and the metal peroxide layer20with the laser light L, thereby streamlining process operations. Also, when metal oxide is directly formed as a sacrificial layer without going through such an operation, the adhesive strength between the flexible substrate100and the supporting substrate10is weak, and thus defects such as the flexible substrate100falling off of the supporting substrate10may occur when handling the flexible substrate100during a manufacturing process. On the contrary, in a method of manufacturing a flexible display according to the present embodiment, after the metal peroxide layer20is formed on the supporting substrate10and the metal layer30is formed thereon, the metal layer30is formed as the metal oxide layer50by the heat of the laser light L irradiated in separating the flexible substrate100and the supporting substrate10. Thus, a process of manufacturing the flexible display can be streamlined and the flexible substrate100can also be firmly bonded to the supporting substrate10until the flexible substrate100is detached from the supporting substrate10.

Referring toFIG. 3, after the metal oxide layer50is formed by irradiating the laser light L, an operation of separating the flexible substrate100from the supporting substrate10with the metal oxide layer50as a boundary between the supporting substrate10and the flexible substrate100can be performed. On one side of the flexible substrate100, at least a portion of a second metal oxide may remain. As such, the metal oxide layer50remaining on the one side of the flexible substrate100may serve as a protection film for protecting a lower portion of the flexible substrate100.

While a method of manufacturing a flexible display has been mainly described, exemplary embodiments are not limited thereto. For example, a flexible display manufactured by using the method of manufacturing such a flexible display is also within the scope of the described technology.

FIG. 4is a schematic cross-sectional view of a flexible display manufactured by the manufacturing process ofFIGS. 1 through 3.

Referring toFIG. 4, a flexible display includes a flexible substrate100, a thin film transistor layer190and an OLED200which are formed on one side of the flexible substrate100. The flexible display also includes a barrier layer40and a metal oxide layer50which are formed on the other side of the flexible substrate100. The display layer300described inFIGS. 1 through 3includes the thin film transistor layer190and the OLED200. Although it is illustrated inFIG. 4that the OLED200is formed on the thin film transistor layer190, the described technology is not limited thereto. When the flexible display is bottom-emission type display, the OLED200can also be formed directly on the flexible substrate100.

The flexible substrate100has flexible properties and can be formed of various materials, for example, metal materials, or plastic materials such as PET, PEN, or polyimide.

A display layer300is formed on the flexible substrate100. In certain embodiments, the display layer300includes a thin film transistor TFT and a capacitor CAP and the OLED200electrically connected to the thin film transistor TFT. The thin film transistor TFT includes a semiconductor layer120including amorphous silicon, polycrystalline silicon, or an organic semiconductor material, a gate electrode140, a source electrode160, and a drain electrode162. Hereinafter, a general structure of the thin film transistor TFT will be described in detail.

First, a buffer layer110formed of silicon oxide, silicon nitride, or the like can be formed on the flexible substrate100in order to planarize a surface of the flexible substrate100or prevent impurities and the like from penetrating through the semiconductor layer120of the thin film transistor TFT, and the semiconductor layer120can be positioned on the buffer layer110.

The gate electrode140is formed over the semiconductor layer120, and the source electrode160and the drain electrode162are electrically connected to each other according to a signal applied to the gate electrode140. In consideration of the distance to an adjacent layer, the surface flatness of a layer to be stacked, processability, and the like, the gate electrode140, for example, may be formed of one or more materials from the following: aluminum (Al), platinum (Pt), palladium (Pd), silver (Ag), magnesium (Mg), gold (Au), nickel (Ni), neodymium (Nd), iridium (Jr), chromium (Cr), lithium (Li), calcium (Ca), molybdenum (Mo), titanium (Ti), tungsten (W), and copper (Cu) as a single layer or multiple layers.

A gate insulating film130formed of silicon oxide and/or silicon nitride, or the like can be formed between the semiconductor layer120and the gate electrode140to electrically insulation the semiconductor layer120from the gate electrode140.

An interlayer insulating film150can be formed over the gate electrode140and the interlayer insulating film150can be formed of materials such as silicon oxide or silicon nitride as a single layer or multiple layers.

The source electrode160and the drain electrode162are formed over the interlayer insulating film150. The source electrode160and the drain electrode162are respectively electrically connected to the semiconductor layer120via contact holes formed in the interlayer insulating film150and the gate insulating film130. In consideration of conductivity and the like, the source electrode160and the drain electrode162, for example, may be formed of one or more materials from the following: Al, Pt, Pd, Ag, Mg, Au, Ni, Nd, Jr, Cr, Li, Ca, Mo, Ti, W, and Cu as a single layer or multiple layers.

Although not illustrated inFIG. 4, a protection film (not shown) can be formed to cover the thin film transistor TFT for protection of the thin film transistor TFT having the above described structure. The protection film (not shown), for example, may be formed of inorganic materials such as silicon oxide, silicon nitride, or silicon oxynitride.

Meanwhile, a first insulating film170can be formed on the flexible substrate100. The first insulating film170can be a planarization film and may also be a protection film. When the OLED200is formed over the thin film transistor TFT, the first insulating film170serves to substantially planarize an upper surface of the thin film transistor TFT and protect the thin film transistor TFT and different kinds of devices. The first insulating film170, for example, can be formed of an acrylic organic material, benzocyclobutene (BCB), or the like. As shown inFIG. 4, the buffer layer110, the gate insulating film130, the interlayer insulating film150, and the first insulating film170can be formed on the entire surface of the flexible substrate100.

Meanwhile, a second insulating film180can be formed over the thin film transistor TFT. The second insulating film180can be a pixel defining layer. The second insulating film180can be positioned on the first insulating film170and may have an opening. The second insulating film180serves to define a pixel region on the flexible substrate100.

The second insulating film180, for example, can be provided as an organic insulating film. The organic insulating film can include an acrylic polymer such as poly(methyl methacrylate) (PMMA), polystyrene (PS), a polymer derivative having a phenol group, an imide-based polymer, an aryl ether-based polymer, an amide-based polymer, a fluorine-based polymer, a p-xylene based polymer, a vinyl alcohol-based polymer, and a mixture thereof.

Meanwhile, the OLED200can be formed on the second insulating film180. The OLED200can include a pixel electrode210, an intermediate layer220including an emission layer (EML), and an opposite electrode230.

The pixel electrode210can be formed as a (semi)transparent electrode or a reflective electrode. When the pixel electrode210is formed as a (semi)transparent electrode, the pixel electrode210, for example, may be formed of indium tin oxide (TTO), indium zinc oxide (IZO), zinc oxide (ZnO), indium oxide (In2O3), indium gallium oxide (IGO), or aluminum zinc oxide (AZO). When the pixel electrode210is formed as a reflective electrode, the pixel electrode210may have a reflective film formed of Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Jr, Cr, a compound thereof and the like, and a layer formed of ITO, IZO, ZnO, In2O3, IGO, or AZO. However, the described technology is not limited thereto. The pixel electrode210can be formed of various materials, and the structure of the pixel electrode210may have various modifications such as a single layer or multiple layers.

The intermediate layer220can be formed in the pixel region defined by the second insulating film180. The intermediate layer220includes the EML that can emit light based on an electrical signal. The intermediate layer can also include a hole injection layer (HIL) and a hole transport layer (HTL) which are formed between the EML and the pixel electrode210, and an electron transport layer and an electron injection layer which are formed between the EML and the opposite electrode230as a single or complex structure. However, the intermediate layer220is not limited thereto and may have various structures.

The opposite electrode230facing the pixel electrode210while covering the intermediate layer220which includes the EML can be formed over the entire surface of the flexible substrate100. The opposite electrode230can be formed as a (semi)transparent electrode or a reflective electrode.

When the opposite electrode230is formed as a (semi)transparent electrode, the opposite electrode230may have a layer formed of Li, Ca, LiF/Ca, LiF/Al, Al, Ag, and Mg, which are metals having a low work function, and a compound thereof and may have a (semi)transparent conductive layer formed of ITO, IZO, ZnO, In2O3, or the like. When the opposite electrode230is formed as a reflective electrode, the opposite electrode230can have a layer formed of Li, Ca, LiF/Ca, LiF/Al, Al, Ag, Mg, and a compound thereof. However, the structure and the material of the opposite electrode230are not limited thereto and may have various modifications.

An encapsulation layer400can be formed on the display layer300. The encapsulation layer400can be formed on the opposite electrode230and can be formed over the entire surface of the flexible substrate100. The encapsulation layer400covers the display layer300and a portion of the encapsulation layer400can be in direct contact with an edge of the flexible substrate100. The encapsulation layer400can be formed to include an organic film and an inorganic film that are alternately stacked. The encapsulation layer400serves to prevent impurities, moisture, or the like from penetrating through the display layer300from the environment.

Additionally, the barrier layer40and the metal oxide layer50are formed on a lower surface of the flexible substrate100. That is, it can be understood that the metal oxide layer50is formed on the lower surface of the flexible substrate100and the barrier layer40is formed between the flexible substrate100and the metal oxide layer50.

The barrier layer40can prevent impurities from penetrating through the flexible substrate100. The barrier layer40may be formed of an inorganic film and may include, for example, SiOx, SiNx, SiOxNy, Al2O3, AlN, or AlOxNy.

As described above, as oxygen which is separated from a metal peroxide layer20formed under a metal layer30spreads to the metal layer30, the metal oxide layer50can be formed. The metal oxide layer50, for example, may be formed of MoOx, WOx, CrOx, or FeOx (x=4, 5, 6); however, the metal oxide layer50is not limited thereto.

In at least one embodiment, since a laser light L needs to be irradiated to a sacrificial layer in order to detach the flexible substrate100from a supporting substrate10in the manufacturing process, the metal layer30can be formed as the metal oxide layer50by heat of the laser light L, thereby streamlining process operations. Also, when metal oxide is directly formed as a sacrificial layer without going through such an operation, the adhesive strength between the flexible substrate100and the supporting substrate10is weak, and thus defects such as the flexible substrate100falling off of the supporting substrate10may occur when handling the flexible substrate100during the manufacturing process. On the contrary, according to the method of manufacturing the flexible display according to at least one embodiment, after the metal peroxide layer20is formed on the supporting substrate10and the metal layer30is formed thereon, the metal oxide layer50is formed by the heat of the laser light L irradiated in separating the flexible substrate100and the supporting substrate10. Thus, the manufacturing process can be streamlined and the flexible substrate100can also be firmly bonded to the supporting substrate10until the flexible substrate100is detached from the supporting substrate10.

As described above, according to one or more of the above exemplary embodiments, a flexible display having a flexible substrate easily detachable from a supporting substrate and a method of manufacturing the flexible display are disclosed. However, no limitation of the scope of the described technology is intended by such an effect.