Patent Publication Number: US-11653542-B2

Title: Display apparatus

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION(S) 
     This application is a continuation of U.S. patent application Ser. No. 16/916,003, filed Jun. 29, 2020, which is a continuation of U.S. patent application Ser. No. 16/734,932 filed Jan. 6, 2020, now U.S. Pat. No. 10,700,158, which is a continuation of U.S. patent application Ser. No. 16/181,283 filed Nov. 5, 2018, now U.S. Pat. No. 10,529,794, which is a continuation application of U.S. patent application Ser. No. 15/430,095 filed on Feb. 10, 2017, now U.S. Pat. No. 10,121,844, which claims priority to and the benefit of Korean Patent Application No. 10-2016-0033989, filed on Mar. 22, 2016, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein in their entirety by reference. 
    
    
     BACKGROUND 
     1. Field 
     The present disclosure relates to a display apparatus. 
     2. Description of the Related Art 
     As the display technology develops rapidly, various flat panel display apparatuses having excellent characteristics such as a slim profile, a light weight, and low power consumption have been introduced. With the recent development in display technology, flexible display apparatuses have been researched and developed, and stretchable display apparatuses that are capable of being changed to various shapes are being actively researched and developed. 
     Meanwhile, a display apparatus having a slim profile and flexible characteristics may include a thin film encapsulation layer to block infiltration of moisture, oxygen, etc. from outside. A conventional thin film encapsulation layer has a configuration in which inorganic layers and organic layers are alternately stacked. However, since the thin film encapsulation layer is integrally formed with a display apparatus, the thin film encapsulation layer may degrade the flexibility of the display apparatus, and the thin film encapsulation layer may be damaged when the shape of the display apparatus is changed. 
     SUMMARY 
     One or more embodiments of the present disclosure provide a display apparatus. 
     Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments. 
     According to one or more embodiments, a display apparatus includes a substrate; a plurality of display units disposed on the substrate, each including a thin film transistor including at least one inorganic layer, a passivation layer disposed on the thin film transistor, and a display device electrically connected to the thin film transistor; and a plurality of encapsulation layers respectively encapsulating the plurality of display units, wherein the substrate includes a plurality of islands spaced apart from one another, a plurality of connection units that are connecting the plurality of islands to one another, and a plurality of through holes penetrating through the substrate between the plurality of connection units, the plurality of display units are disposed on the plurality of islands, respectively, the at least one inorganic layer and the passivation layer extend on the plurality of connection units, the passivation layer includes a trench that exposes a portion of the at least one inorganic layer, and the encapsulation layer contacts an exposed portion of the at least one inorganic layer via the trench. 
     The trench may be disposed on a connection unit of the plurality of connection units. 
     The trench may extend across a width of the connection unit and may be aligned with a lateral surface of an island of the plurality of islands. 
     The trench may be on an island of the plurality of islands and may completely surround a display unit of the plurality of display units. 
     The at least one inorganic layer may include a first insulating layer between an active layer and a gate electrode of the thin film transistor, and a second insulating layer disposed on the gate electrode. The trench may expose a portion of the first insulating layer or the second insulating layer. 
     The encapsulation layer may contact a lateral surface of an island of the plurality of islands. 
     The encapsulation layer may include at least one of tin fluorophosphates glass, chalcogenide glass, tellurite glass, borate glass, and phosphate glass. 
     Each of the plurality of encapsulation layers may include at least one inorganic layer and at least one organic layer. The at least one inorganic layer may contact an exposed portion of the at least one inorganic layer of the thin film transistor via the trench. 
     At least one of the at least one inorganic layer and the at least one organic layer may include silicon oxide including carbon and hydrogen. 
     Each of the plurality of encapsulation layers may include a first inorganic layer, a second inorganic layer, and an organic layer between the first inorganic layer and the second inorganic layer. At least one of the first inorganic layer and the second inorganic layer may contact a lateral surface of the island and may contact an exposed portion of the at least one inorganic layer of the thin film transistor via the trench. 
     A connection unit of the plurality of connection units may include flexures disposed on at least a portion of the connection unit, and the second inorganic layer disposed on an outermost side of the encapsulation layer from among the first inorganic layer and the second inorganic layer may extend over the flexures. 
     Each of the plurality of display units may include a display region and a non-display region around the display region, and a dam unit surrounding at least a portion of the display region may be disposed in the non-display region. The first inorganic layer and the second inorganic layer may cover the dam unit and contact each other around the dam unit. 
     The thin film transistor may include an active layer, a gate electrode, a source electrode, and a drain electrode. The display device may include a first electrode, a second electrode, and an intermediate layer including an organic emission layer between the first electrode and the second electrode. The first electrode may extend from one of the source electrode and the drain electrode. Each of the plurality of display units may be disposed between the first electrode and the island and may further include a color filter including a portion overlapped by the first electrode. 
     The plurality of islands and the plurality of connection units may be one body. 
     The plurality of islands may be repeated in a first direction and a second direction that is different from the first direction. Four connection units may be connected to each of the plurality of islands. Four connection units connected to one island from among the plurality of islands may extend in different directions and may be respectively connected to four adjacent islands that surround the one island. 
     The four connection units may include a pair of first connection units on opposite sides of the one island and each extending in the first direction, and a pair of second connection units on opposite sides of the one island and each extending in the second direction. A first wiring unit may be disposed on the two first connection units, and a second wiring unit may be disposed on the two second connection units. The first wiring unit and the second wiring unit may cross on the one island. 
     The first wiring unit may include a region curved in the second direction along a through hole of the plurality of through holes, and the second wiring unit may include a region curved in the first direction along the through hole. 
     The thin film transistor may include an active layer, a gate electrode, a source electrode, and a drain electrode. The source electrode, the drain electrode, the first wiring unit, and the second wiring unit may include a same material. 
     The first wiring unit may include a first voltage line, a second voltage line, and at least one data line, and the second wiring unit may include at least one scan line. 
     The display device may include a first electrode, a second electrode, and an intermediate layer between the first electrode and the second electrode and including an organic emission layer. The first voltage line may electrically connect first electrodes respectively included in the plurality of display units and separated from one another to one another. The second voltage line may electrically connect second electrodes respectively included in the plurality of display units and separated from one another to one another. 
     Two adjacent islands among the plurality of islands may be connected to each other by one connection unit. Each of the two adjacent islands connected to the one connection unit and a direction in which the one connection unit extends may make an acute angle. 
     Each of the plurality of islands may have a quadrilateral shape, and four corners of each of the plurality of islands may be directed in the first direction and the second direction. 
     The display apparatus may further include a first protection film and a second protection film respectively disposed on an upper surface and a lower surface of the substrate. The first protection film and the second protection film may include elongation sheets. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings in which: 
         FIG.  1    is a schematic plan view of a display apparatus, according to an embodiment of the present disclosure; 
         FIG.  2    is a magnified plan view of a portion A of  FIG.  1   , according to an embodiment; 
         FIG.  3    is a schematic plan view of a unit of  FIG.  1   , according to an embodiment; 
         FIG.  4    is a cross-sectional view taken along line I-I′ of  FIG.  3   , according to an embodiment; 
         FIG.  5    is a cross-sectional view taken along line II-II′ of  FIG.  3   , according to an embodiment; 
         FIG.  6    is a cross-sectional view taken along line III-III′ of  FIG.  3   , according to an embodiment; 
         FIG.  7    is a cross-sectional view taken along line II-II′ of  FIG.  3   , according to another embodiment; 
         FIG.  8    is a schematic plan view of a unit of  FIG.  1   , according to another embodiment; 
         FIG.  9    is a cross-sectional view taken along line I-I′ of  FIG.  3   , according to another embodiment; 
         FIG.  10    is a cross-sectional view taken along line II-II′ of  FIG.  3   , according to another embodiment; 
         FIG.  11    is a cross-sectional view taken along line III-III′ of  FIG.  3   , according to another embodiment; 
         FIG.  12    is a cross-sectional view taken along line II-II′ of  FIG.  3   , according to another embodiment; 
         FIG.  13    is a cross-sectional view taken along line I-I′ of  FIG.  3   , according to another embodiment; 
         FIG.  14    is a cross-sectional view taken along line I-I′ of  FIG.  3   , according to yet another embodiment; 
         FIG.  15    is a magnified plan view of a portion A of  FIG.  1   ; 
         FIG.  16    is a cross-sectional view taken along line VI-VI′ of  FIG.  15   , according to an embodiment; 
         FIG.  17    is a cross-sectional view taken along line VII-VII′ of  FIG.  15   , according to an embodiment; 
         FIG.  18    is a schematic cross-sectional view of a display apparatus, which is a modification of the display apparatus of  FIG.  1   ; 
         FIG.  19    is a schematic cross-sectional view of a display apparatus, which is another modification of the display apparatus of  FIG.  1   ; and 
         FIG.  20    is a magnified plan view of a portion A of  FIG.  1   , according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure allows for various changes and numerous embodiments, and particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the scope of the present disclosure to particular modes of practice, and it is to be appreciated that all changes, equivalents, and substitutes that do not depart from the spirit and technical scope of the present disclosure are encompassed in the present disclosure. In the following description of the present disclosure, a detailed description of disclosed embodiments is provided to clarify exemplary features of the present disclosure. 
     While such terms as “first”, “second”, etc., may be used to describe various components, such components must not be limited to the above terms. The above terms may be used to distinguish one component from another. 
     The terms used in the present specification are merely used to describe particular embodiments, and are not intended to limit the scope of the present disclosure. An expression used in a singular encompasses the expression in a plural, unless it has a clearly different meaning in the context. In the drawings, components may be exaggerated, omitted, or schematically illustrated for convenience and clarity of explanation. In other words, sizes and thicknesses of components in the drawings may not reflect actual sizes and thicknesses thereof. 
     One or more embodiments of the present disclosure will be described below in more detail with reference to the accompanying drawings. Those components that are the same or are in correspondence are rendered the same reference numeral regardless of the figure number, and redundant explanations may be omitted. 
       FIG.  1    is a schematic plan view of a display apparatus  10 , according to an embodiment of the present disclosure, and  FIG.  2    is a magnified plan view of a portion A of  FIG.  1   , according to an embodiment. 
     Referring to  FIG.  1   , the display apparatus  10  may include a substrate  100  and display units  200  on the substrate  100 . 
     The substrate  100  may include various materials. The substrate  100  may include a material, such as glass, metal, or an organic material. 
     According to another embodiment, the substrate  100  may include a flexible material. For example, the substrate  100  may include a material that can be easily bent, folded, or rolled. The flexible substrate  100  may include a flexible material such as ultra-thin glass, metal, or plastic. When the substrate  100  includes plastic, the substrate  100  may include polyimide (PI). As another example, the substrate  100  may include another type of plastic material. 
     The substrate  100  may include a plurality of islands  101  spaced apart from one another, a plurality of connection units  102  that are connecting the plurality of islands  101  to one another, and a plurality of through holes V penetrating through the substrate  100  between the plurality of connection units  102 . As will be described with reference to  FIG.  18   , a first protection film  410  and a second protection film  420  may be respectively disposed on an upper surface and a lower surface of the substrate  100 . 
     The plurality of islands  101  may be arranged to be spaced apart from one another. For example, the plurality of islands  101  may be repeated in a first direction X and a second direction Y that is different from the first direction X to form a planar lattice pattern. For example, the first direction X and the second direction Y may intersect at 90° angle. As another example, the first direction X and the second direction Y may meet at either an acute or an obtuse angle. 
     A plurality of display units  200  may be disposed on the plurality of islands  101 , respectively. Each display unit  200  may include at least a display device to realize visible light. Each display unit  200  will be described below in detail with reference to  FIG.  4   . 
     The plurality of connection units  102  may connect the plurality of islands  101  to one another. For example, four connection units  102  of each of the island  101  are extended to be connected to each of the adjacent islands  101  in different directions such that the four connection units  102  may be respectively connected to the four adjacent islands  101  surrounding the island  101 . The plurality of islands  101  and the plurality of connection units  102  may be formed of the same material and may be connected to each other. In other words, the plurality of islands  101  and the plurality of connection units  102  may be integrally formed with each other. 
     The through holes V penetrate through the substrate  100 . The through holes V may provide separation areas between the plurality of islands  101 , reducing the weight of the substrate  100  while improving the flexibility of the substrate  100 . When the substrate  100  is bent, rolled, or the like, the shapes of the through holes V change to effectively reduce the stress generated during deformation of the substrate  100 . Thus, abnormal deformation and stress concentration of the substrate  100  under deformation may be prevented, and durability of the substrate  100  may improve. 
     The through holes V may be formed by removing selective regions of the substrate  100  via etching or the like. As another example, the substrate  100  may be manufactured to include the through holes V during the manufacture of the substrate  100 . As another example, after the plurality of display units  200  are formed on the substrate  100 , the through holes V may be formed by patterning the substrate  100 . The through holes V may be formed in the substrate  100  in various ways, and a method of forming the through holes V may not be limited to the examples described herein. 
     Hereinafter, a unit U refers to the basic unit of the substrate  100 , and a structure of the substrate  100  will be described in more detail with reference to the unit U. 
     The unit U may be repeated in the first direction X and the second direction Y. In other words, the substrate  100  may be understood as a combination of a plurality of units U repeated in the first direction X and the second direction Y. Each unit U may include an island  101  and at least one connection unit  102  connected to the island  101 . For example, four connection units  102  may be connected to one island  101 . 
     The islands  101  of two adjacent units U may be spaced apart from each other, and connection units  102  of the two adjacent units U may be connected to each other. A connection unit  102  included in a unit U may be referred to as a partial region of the connection unit  102  that is within the unit U or may be referred to as the whole of a connection unit  102  between two adjacent islands  101  that connects the two adjacent islands  101  to each other. 
     Four adjacent units U among the plurality of units U form closed curves CL between the four units U, and the closed curves CL may define an empty space herein referred to as a through hole V. The through hole V may also be referred to as a separation area V. The separation area is formed by removing one region of the substrate  100 , and may improve the flexibility of the substrate  100  while reducing stress that is generated when the substrate  100  is deformed. Each connection unit  102  may have a smaller width than a width of each island  101 , and the separation area may contact the islands  101  of the four units U. 
     Two adjacent units U among the plurality of units U may be symmetrical to each other. In detail, as shown in  FIG.  1   , one unit U may be symmetrical to another unit U adjacent to the one unit U in the second direction Y, about an axis of symmetry that is parallel to the first direction X. At the same time, one unit U may be symmetrical to another unit U adjacent to the one unit U in the first direction X, about an axis of symmetry that is parallel to the second direction Y. 
     An angle θ between a direction in which a connection unit  102  extends and a lateral surface of an island  101  to which the connection unit  102  is connected may be an acute angle. For example, when each island  101  is a quadrilateral and is disposed such that each of the four corners thereof is directed in the first direction X or the second direction Y, the connection units  102  may be connected to the island  101  at regions adjacent to the four corners and may extend in a direction parallel to the second direction Y or the first direction X. In other words, the connection units  102  connected to the corners directed to the first direction X may be directed in the second direction Y or a direction −Y that is opposite to the second direction Y, and the connection units  102  connected to the corners directed in the second direction Y may be directed in the first direction X or a direction −X that is opposite to the first direction X. 
     Thus, each of the lateral surfaces of two adjacent islands  101  connected to one connection unit  102  may respectively make acute angles with the direction in which the connection unit  102  extends. Accordingly, the islands  101  may be densely arranged, and the areas of the separation areas may be maximized by minimizing the lengths of the connection units  102 . As shown in  FIG.  2   , the substrate  100  may exhibit an elongation property. 
       FIG.  2    illustrates a shape of the substrate  100  before and after the substrate  100  is elongated both in the first direction X and the second direction Y. Referring to  FIG.  2   , when the substrate  100  is elongated, the angles formed by the connection units  102  and the lateral surfaces of the islands  101  to which the connection units  102  are connected increase (θ&lt;θ′), and thus the separation areas may enlarge. Accordingly, intervals between the islands  101  may increase, and thus the substrate  100  may be elongated both in the first direction X and the second direction Y. 
     Since each connection unit  102  has a smaller width than a width of each island  101 , a shape change corresponding to the increase of the angle θ while an external force is applied to the substrate  100  may mainly occur in the connection units  102 , and the shapes of the islands  101  may not substantially change during elongation of the substrate  100 . Thus, the display units  200  on the islands  101  may be stably maintained even when the substrate  100  is elongated, and accordingly the display apparatus  10  may be suited for display apparatuses that require flexibility, for example, bending display apparatuses, flexible display apparatuses, or stretchable display apparatuses. 
     Moreover, since stress concentrates on connecting portions of the connection units  102  that are connected to the lateral surfaces of the islands  101  during elongation of the substrate  100 , connecting regions C of the connection units  102  may include curved surfaces to prevent tearing or the like of the connection units  102  due to the concentration of the stress. 
       FIG.  3    is a schematic plan view of a unit U of  FIG.  1   ,  FIG.  4    is a cross-sectional view taken along line I-I′ of  FIG.  3   ,  FIG.  5    is a cross-sectional view taken along line II-II′ of  FIG.  3   , and  FIG.  6    is a cross-sectional view taken along line III-III′ of  FIG.  3   , according to an embodiment.  FIG.  7    is a cross-sectional view taken along line II-II′ of  FIG.  3   , according to another embodiment.  FIG.  8    is a schematic plan view of another example of a unit U of  FIG.  1   . 
     Referring to  FIGS.  3 - 8   , a display unit  200  and an encapsulation layer  300  encapsulating the display unit  200  may be on an island  101  of a unit U. 
     The display unit  200  may be located on the island  101  and may include a display region DA and a non-display region around the display region DA. In the display region DA, at least one organic light-emitting device  230  emitting, for example, red (R), blue (B), green (G), or white (W) light, may be located. Herein, the organic light-emitting device  230  may be referred to and described as the display device. However, embodiments of the present disclosure are not limited thereto, and the display unit  200  may include various other types of display devices, such as a liquid crystal display. 
     The display unit  200  may include one organic light-emitting device  230  emitting red (R), blue (B), green (G), or white (W) light, and thus one display unit  200  may form one sub-pixel. As another example, the display unit  200  may include a plurality of organic light-emitting devices  230  that emit different lights. For example, one display unit  200  may form a pixel by including an organic light-emitting device  230  emitting red (R) light, an organic light-emitting device  230  emitting green (G) light, and an organic light-emitting device  230  emitting blue (B) light. As another example, the display unit  200  may include a plurality of pixels. 
     Organic light-emitting devices  230  within the display unit  200  may be arranged in various configurations, such as an RGB configuration, a pentile structure, and a honeycomb structure, depending on the efficiency of a material included in an organic emission layer. 
     Referring to  FIG.  4   , a buffer layer  202  may be formed on the island  101 . For example, the buffer layer  202  may be formed of an inorganic material (e.g., silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, aluminum nitride, titanium oxide, and titanium nitride), an organic material (e.g., polyimide, polyester, and acryl), or stacks of inorganic and organic materials. The buffer layer  102  may be formed on both the island  101  and the connection unit  102 . 
     A thin film transistor TFT may include an active layer  203 , a gate electrode  205 , a source electrode  207 , and a drain electrode  208 . A case of a top gate type thin film transistor TFT in which the active layer  203 , the gate electrode  205 , the source electrode  207 , and the drain electrode  208  are sequentially formed in the stated order will now be described. However, the present embodiment is not limited thereto, and various types of thin film transistors TFT, such as a bottom gate type thin film transistor TFT, may be employed. 
     The active layer  203  may include a semiconductor material, for example, amorphous silicon or polycrystalline silicon. However, the present embodiment is not limited thereto, and the active layer  203  may include various materials. According to another embodiment, the active layer  203  may include an organic semiconductor material or the like. According to another embodiment, the active layer  203  may include an oxide semiconductor material. For example, the active layer  203  may include an oxide of a material selected from Group 12, 13, and 14 metal elements (e.g., zinc (Zn), indium (In), gallium (Ga), stannum (Sn), cadmium (Cd), and germanium (Ge)) and a combination thereof. 
     A first insulating layer  204  may be formed on the active layer  203 . The first insulating layer  204  may be formed of an inorganic material, such as silicon oxide and/or silicon nitride, in a multi-layer structure or a single-layer structure. The first insulating layer  204  insulates the active layer  203  from the gate electrode  205 . The first insulating layer  204  may be formed on both the island  101  and the connection unit  102 . 
     The gate electrode  205  may be formed on the first insulating layer  204  to overlap the active layer  203 . The gate electrode  205  may be connected to a gate line (not shown) that applies an ON/OFF signal to the thin film transistor TFT. The gate electrode  205  may include a low resistance metal material. The gate electrode  205  may be formed of at least one of aluminum (Al), platinum (Pt), palladium (Pd), silver (Ag), magnesium (Mg), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), calcium (Ca), molybdenum (Mo), titanium (Ti), tungsten (W), and copper (Cu) in a single-layered or a multi-layered structure. 
     A second insulating layer  206  may be formed on the gate electrode  205  and the first insulating layer  204 . The second insulating layer  206  insulates the source electrode  207  and the drain electrode  208  from the gate electrode  205 . The second insulating layer  206  may be formed of an inorganic material in a multi-layer structure or a single-layer structure. For example, the inorganic material may be metal oxide or metal nitride. In detail, the inorganic material may include silicon oxide (SiO 2 ), silicon nitride (SiNx), silicon oxynitride (SiON), aluminum oxide (Al 2 O 3 ), titanium oxide (TiO 2 ), tantalum oxide (Ta 2 O 5 ), hafnium oxide (HfO 2 ), zirconium oxide (ZrO 2 ), or the like. 
     According to another embodiment, the second insulating layer  206  may be a single layer formed of an organic material, or may be a multi-layer structure including a plurality of organic material layers. The organic material may include a commercial polymer such as polymethyl methacrylate (PMMA) or polystyrene (PS), a polymer derivative having a phenol-based group, an acryl-based polymer, an imide-based polymer, an acryl ether-based polymer, an amide-based polymer, a fluorine-based polymer, a p-xylene-based polymer, a vinyl alcohol-based polymer, a blend thereof, or the like. A passivation layer  209  may be a stack of an inorganic insulation layer and an organic insulation layer. 
     The second insulating layer  206  may be formed on both the island  101  and the connection unit  102 . 
     The source electrode  207  and the drain electrode  208  are formed on the second insulating layer  206 . The source electrode  207  and the drain electrode  208  may be formed of at least one selected from a group including aluminum (Al), platinum (Pt), palladium (Pd), silver (Ag), magnesium (Mg), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), calcium (Ca), molybdenum (Mo), titanium (Ti), tungsten (W), and copper (Cu) in a single-layered or a multi-layered structure. The source electrode  207  and the drain electrode  208  contact the active layer  203  via contact holes formed in the second insulating layer  206  and the first insulating layer  204 . 
     The passivation layer  209  may cover the thin film transistor TFT. The passivation layer  209  may planarize steps caused by the thin film transistor TFT, thereby preventing the organic light-emitting device  230  from being damaged by unevenness. 
     The passivation layer  209  may be a single layer formed of an organic material, or may be a multi-layer structure including a plurality of organic material layers. The organic material may include a commercial polymer such as PMMA or PS, a polymer derivative having a phenol-based group, an acryl-based polymer, an imide-based polymer, an acryl ether-based polymer, an amide-based polymer, a fluorine-based polymer, a p-xylene-based polymer, a vinyl alcohol-based polymer, a blend thereof, or the like. The passivation layer  209  may be a stack of an inorganic insulation layer and an organic insulation layer. 
     The passivation layer  209  may be formed on both the island  101  and the connection unit  102 . The passivation layer  209  on the connection unit  102  may include a trench T exposing an inorganic layer under the passivation layer  209 . The inorganic layer that is exposed under the passivation layer  209  may be the buffer layer  202 , the first insulating layer  204 , and/or the second insulating layer  206 . 
     The trench T may extend across the width of the connection unit  102 . Accordingly, the trench T may reduce or prevent infiltration of external moisture into the display unit  200  via the passivation layer  209  formed of an organic material. 
     For example, as shown in  FIG.  3   , the trench T may extend across the width of the connection unit  102 , in a connecting region C where the island  101  and the connection unit  102  are connected to each other, and may be aligned with a lateral surface of the island  101 . In detail, an extension of the lateral surface of the island  101  may be within the width of the trench T. 
     As another example, as shown in  FIG.  8   , a trench T′ may be disposed on the island  101  to completely surround the display unit  200 . Accordingly, separate passivation layers  209  may be formed on each of the islands  101 , respectively. 
     The organic light-emitting device  230  is formed on the passivation layer  209 . The organic light-emitting device  230  may include a first electrode  231 , a second electrode  232  opposite to the first electrode  231 , and an intermediate layer  233  between the first electrode  231  and the second electrode  232 . 
     The first electrode  231  may be electrically connected to either the source electrode  207  or the drain electrode  208 . The first electrode  231  may have various shapes. For example, the first electrode  231  may be patterned to have an island shape. 
     The first electrode  231  may be formed on the passivation layer  209  and may be electrically connected to the thin film transistor TFT via a contact hole formed in the passivation layer  209 . For example, the first electrode  231  may be a reflection electrode including a reflection layer formed of silver (Ag), magnesium (Mg), aluminum (Al), platinum (Pt), palladium (Pd), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), or a compound thereof. In another example, the first electrode  231  may include a transparent electrode layer on the reflection layer. The transparent electrode layer may include at least one selected from a group including indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium oxide (In 2 O 3 ), indium gallium oxide (IGO), and aluminum zinc oxide (AZO). 
     The second electrode  232  may be electrically connected to a second voltage line V 2  and may receive a second voltage ELVSS that is lower than a first voltage ELVDD that is applied to the first electrode  231 . Although the second voltage line V 2  and the second electrode  232  are shown to be connected to each other via a connection line  216  shown in  FIG.  6   , embodiments of the present disclosure are not limited thereto. For example, the second voltage line V 2  and the second electrode  232  may directly contact each other. 
     The second electrode  232  may have various shapes. For example, the second electrode  232  may be patterned to have an island shape. Thus, a portion of the second electrode  232  may be prevented from being exposed even when the second electrode  232  is completely covered with the encapsulation layer  300 , and encapsulation layers  300  are respectively formed on the islands  101 . 
     The second electrode  232  may be a transparent electrode. The second electrode  232  may include a metal thin film including Li, Ca, LiF/Ca, LiF/Al, Al, Ag, Mg, or a combination thereof. An auxiliary electrode layer or a bus electrode may be further formed on the metal thin film. The auxiliary electrode layer or the bus electrode may include a material such as ITO, IZO, ZnO, or In 2 O 3 . Accordingly, the second electrode  232  may transmit light emitted by an organic emission layer included in the intermediate layer  233 . In other words, the light emitted by the organic emission layer may travel directly toward the second electrode  232 , or may be reflected by the first electrode  231  that is formed as the reflection electrode and then travel toward the second electrode  232 . 
     In the example described above with reference to  FIGS.  3 - 8   , the display unit  200  is of a top-emission type. However, the display unit  200  according to another embodiment is not limited to the top-emission type. According to another embodiment, the display unit  200  may be a bottom-emission type in which the light emitted by the organic emission layer is emitted toward the island  101 . In this case, the first electrode  231  may be a transparent electrode, and the second electrode  232  may be a reflection electrode. The display unit  200  according to yet another embodiment may be of a dual emission type that emits light in both directions toward the top surface and the bottom surface of the display unit  200 . 
     A pixel defining layer  219  including an insulating material is formed on the first electrode  231 . The pixel defining layer  219  may be formed of at least one organic insulating material selected from the group including polyimide, polyamide (PA), acryl resin, benzocyclobutene (BCB) and a phenolic resin, by using a method such as spin coating. The pixel defining layer  219  exposes an area of the first electrode  231 . The intermediate layer  233  including an organic emission layer is formed on the exposed area of the first electrode  231 . In other words, the pixel defining layer  219  defines a pixel region of an organic light-emitting device. 
     The intermediate layer  233  may further include one or more functional layers, such as a hole transport layer (HTL), a hole injection layer (HIL), an electron transport layer (ETL), and an electron injection layer (EIL), in addition to the organic emission layer. 
     The encapsulation layer  300  encapsulating the display unit  200  may be formed on the second electrode  232 . The encapsulation layer  300  may block external oxygen and moisture and may include a single layer or a plurality of layers. 
     The encapsulation layer  300  may include at least one of an organic layer and an inorganic layer. 
     The organic layer may include PMMA, polycarbonate (PC), PS, acryl-based resin, epoxy-based resin, polyimide, and/or polyethylene. The inorganic layer may include at least one selected from a group including 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). 
     According to another embodiment, the encapsulation layer  300  may include a Low temperature Viscosity Transition (LVT) inorganic material. A viscosity transition temperature denotes a minimum temperature at which fluidity can be provided to an LVT inorganic material. The viscosity transition temperature may be less than a denaturalization temperature of a material included in the organic light-emitting device  230 . 
     The LVT inorganic material may be, for example, a low liquidus temperature (LLT) material having a glass transition temperature of 200° C. or less. In more detail, an LLT material may include at least one of tin fluorophosphates glass, chalcogenide glass, tellurite glass, borate glass, and phosphate glass. 
     For example, the tin fluorophosphates glass may include, but is not limited to, Sn of 20-80% by weight, phosphorus (P) of 2-20% by weight, oxygen (O) of 3-20% by weight, and fluorine (F) of 10-36% by weight. The aforementioned glass materials may further include tungsten (W). When tungsten (W) is added to a glass material, a more stable and uniform glass can be produced, and thus the encapsulation layer  300  may have improved chemical durability. 
     The LVT inorganic material may include Sn oxide (e.g., SnO or SnO 2 ). For example, when the LVT inorganic material includes SnO, SnO content may be 20% to 100% by weight. 
     The LVT inorganic material including Sn oxide may further include, but is not limited to, at least one of P oxide (e.g., P 2 O 5 ), boron (B) phosphate (BPO 4 ), Sn fluoride (e.g., SnF 2 ), niobium oxide (e.g., NbO), and W oxide (e.g., WO 3 ). 
     For example, the LVT inorganic material may include, but is not limited to, SnO; SnO and P 2 O 5 ; SnO and BPO 4 ; SnO, SnF 2  and P 2 O 5 ; SnO, SnF 2 , P 2 O 5  and NbO; or SnO, SnF 2 , P 2 O 5  and WO 3 . 
     The LVT inorganic material may have, but is not limited to, any of the following compositions: 
     1 SnO (100 wt %); 
     2 SnO (80 wt %) and P 2 O 5  (20 wt %); 
     3 SnO (90 wt %) and BPO 4  (10 wt %); 
     4 SnO (20-50 wt %), SnF 2  (30-60 wt %) and P 2 O 5  (10-30 wt %) (where a sum of the weights of SnO, SnF 2 , and P 2 O 5  is 100 wt %); 
     5 SnO (20-50 wt %), SnF 2  (30-60 wt %), P 2 O 5  (10-30 wt %) and NbO (1-5 wt %) (where a sum of the weights of SnO, SnF 2 , P 2 O 5  and NbO is 100 wt %); or 
     6 SnO (20-50 wt %), SnF 2  (30-60 wt %), P 2 O 5  (10-30 wt %) and WO 3  (1-5 wt %) (where a sum of the weights of SnO, SnF 2 , P 2 O 5  and WO 3  is 100 wt %). 
     Since such an encapsulation layer  300  is formed of a glass material, even when the encapsulation layer  300  does not include a plurality of layers, the encapsulation layer  300  may effectively prevent infiltration of external moisture and oxygen. 
     The encapsulation layer  300  may be formed on one island  101  to encapsulate one display unit  200 . In other words, when the display apparatus  10  of  FIG.  1    includes N display units  200 , N encapsulation layers  300  may be formed. Thus, the encapsulation layer  300  is prevented from being damaged, for example, cracked, when the display apparatus  10  is elongated or when the display apparatus  10  is deformed due to bending, rolling, or the like, thereby improving the reliability and flexibility of the display apparatus  10 . 
     The encapsulation layer  300  may contact an exposed portion of an inorganic layer of the display unit  200  in the non-display region of the display unit  200 . In this case, the inorganic layer of the display unit  200  may be at least one of the buffer layer  202 , the first insulating layer  204 , and the second insulating layer  206 . The encapsulation layer  300  may further extend beyond the island  101  and may contact the lateral surface of the island  101 . Thus, the encapsulation layer  300  may effectively prevent infiltration of external moisture and/or oxygen. 
     The encapsulation layer  300  may contact the exposed portion of the inorganic layer including at least one of the buffer layer  202 , the first insulating layer  204 , and the second insulating layer  206  via the trench T. 
     For example, as shown in  FIG.  5   , when the second insulating layer  206  is formed of an inorganic material, the encapsulation layer  300  may contact an exposed portion of the second insulating layer  206  via the trench T. As another example, as shown in  FIG.  7   , when the second insulating layer  206  is formed of an organic material and the first insulating layer  204  below the second insulating layer  206  is formed of an inorganic material, a trench T may be formed to expose a portion of the first insulating layer  204 , and the encapsulation layer  300  may contact the exposed portion of the first insulating layer  204  via the trench T. 
     The trench T may be aligned with the lateral surface of the island  101 . The display unit  200  is entirely surrounded and encapsulated by the encapsulation layer  300  and the inorganic layer having an isolated state, therefore infiltration of external moisture and/or oxygen into the display unit  200  may be effectively reduced or prevented. 
     As another example, as shown in  FIG.  8   , when the trench T′ is formed on the island  101  and completely surrounds the display unit  200 , the encapsulation layer  300  may contact an exposed portion of the first insulating layer  204  or the second insulating layer  206  via the trench T′ and thus may effectively reduce or prevent infiltration of external moisture and/or oxygen. 
       FIG.  9    is a cross-sectional view taken along line I-I′ of  FIG.  3     FIG.  10    is a cross-sectional view taken along line II-II′ of  FIG.  3   , and  FIG.  11    is a cross-sectional view taken along line III-III′ of  FIG.  3   , according to another embodiment. 
     Referring to  FIGS.  3  and  9 - 11   , a display unit  200  and an encapsulation layer  310  are formed on an island  101 . The display unit  200  may include at least one organic light-emitting device  230  and a thin film transistor TFT that is electrically connected to the organic light-emitting device  230 . Since the island  101  and the display unit  200  are the same as those described above with reference to  FIGS.  1 - 8   , repeated descriptions thereof may be omitted, and only differences therebetween will now be focused. 
     One encapsulation layer  310  may be formed on one island  101  to encapsulate one display unit  200 . 
     The encapsulation layer  310  may include, for example, at least one inorganic layer (i.e., inorganic layers  312  and  314 ) and at least one organic layer (i.e., an organic layer  316 ) that are alternately stacked one on another. Although the encapsulation layer  310  includes the two inorganic layers  312  and  314  and the single organic layer  316  in  FIGS.  9 - 11   , embodiments of the present disclosure are not limited thereto. For example, the encapsulation layer  310  may further include a plurality of additional inorganic layers and a plurality of additional organic layers that are alternately stacked one on another, and the number of stacked inorganic layers and the number of stacked organic layers are not limited. As described above with reference to  FIG.  4   , the encapsulation layer  310  may be formed of an LVT inorganic material or may include a layer formed of an LVT inorganic material. 
     According to an embodiment, the inorganic layers  312  and  314  may include at least one selected from a group including 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). 
     The organic layer  316  may planarize steps caused by the pixel defining layer  219  and may reduce stress generated on the inorganic layers  312  and  314 . According to an embodiment, the organic layer  316  may include at least one selected from a group including PMMA, PC, PS, acryl-based resin, epoxy-based resin, polyimide, and polyethylene. 
     According to anther embodiment, the organic layer  316  may include silicon oxide including carbon and oxygen (hereinafter, referred to as SiOCH). For example, the organic layer  316  may be formed of a material having a composition formula of SiO x C y H z . 
     When the organic layer  316  is formed of SiOCH, the organic layer  316  may be formed by forming a precursor film on the first inorganic layer  312  via plasma enhanced chemical vapor deposition (PECVD) by using a raw material gas (e.g., hexamethyldisiloxane) and a reaction gas (e.g., oxygen) and then plasma-curing the precursor film. The organic layer  316  and the inorganic layers  312  and  314  may be formed using the same method within the same chamber to reduce a tack time during formation of the encapsulation layer  310 . 
     According to another embodiment, at least one of the inorganic layers  312  and  314  may include SiOCH. For example, at least one of the inorganic layers  312  and  314  may include a material having a composition formula of SiO x ′C y ′H z ′. 
     When the organic layer  316  and at least one of the inorganic layers  312  and  314  are all formed of SiOCH, a composition ratio of SiOCH used to form the at least one of the inorganic layers  312  and  314  may be different from that of SiOCH used to form the organic layer  316 . In detail, since a film formed of SiOCH has a similar property to an inorganic layer as an oxygen content ratio increases and a carbon content ratio decreases, oxygen content of SiOCH used to form at least one of the inorganic layers  312  and  314  may be more than that of SiOCH used to form the organic layer  316 , and carbon content of SiOCH used to form at least one of the inorganic layers  312  and  314  may be less than that of SiOCH used to form the organic layer  316 . 
     The oxygen and carbon contents of SiOCH may be adjusted during production of an SiOCH film. For example, the SiOCH film may be formed via PECVD by using a raw material gas (e.g., hexamethyldisiloxane) and a reaction gas (e.g., oxygen). In this case, when a flow ratio of oxygen as a reaction gas is increased, the oxygen content of the SiOCH film may be increased and the carbon content thereof may be decreased. 
     As such, when the organic layer  316  and at least one of the inorganic layers  312  and  314  are all formed of SiOCH, the inorganic layers  312  and  314  and the organic layer  316  may be consecutively formed within the same chamber by simply adjusting the flow rate of the reaction gas, leading to an improvement in the manufacturing efficiency of the encapsulation layer  310 . 
     According to one embodiment, the inorganic layers  312  and  314  may have larger areas than the organic layer  316 . The inorganic layers  312  and  314  may contact each other, around the organic layer  316 . At least one of the inorganic layers  312  and  314  may contact the inorganic layer of the display unit  200  in the non-display region of the display unit  200 . In this case, the inorganic layer may be the buffer layer  202 , the first insulating layer  204 , or the second insulating layer  206 . At least one of the inorganic layers  312  and  314  may further extend beyond the island  101  and may contact a lateral surface of the island  101 . Accordingly, bonding strength of the encapsulation layer  310  may improve, and the encapsulation layer  310  may effectively prevent infiltration of external moisture and/or oxygen into the display unit  200 . 
     The buffer layer  202 , the first insulating layer  204 , the second insulating layer  206 , and the passivation layer  209  of the display unit  200  may be formed on the connection unit  102 , and the passivation layer  209  on the connection unit  102  may include a trench T exposing a portion of the first insulating layer  204  or the second insulating layer  206  under the passivation layer  209 . In this case, at least one of the inorganic layers  312  and  314  may contact the exposed portion of the first insulating layer  204  or the second insulating layer  206  via the trench T. 
     According to another embodiment, a dam unit D surrounding at least a portion of the display region DA of the display unit  200  may be formed in the non-display region of the display unit  200 . 
     For example, the dam unit D may include a first layer formed of the material used to form the passivation layer  209 , and a second layer formed of the material used to form the pixel defining layer  219 . However, embodiments of the present disclosure are not limited thereto, and the dam unit D may include a single layer. According to some embodiments, a plurality of dam units D may be included. When a plurality of dam units D are included, each of the dam units D has a height increasing in a direction toward the edge of the island  101 . 
     The dam unit D may include the same material used to form at least one of the layers between the first insulating layer  204  and the pixel defining layer  219 . 
     During formation of the organic layer  316  of the encapsulation layer  310 , the dam unit D may block an organic material or the like used to form the organic layer  316  from flowing toward the edge of the island  101 , thereby preventing formation of an edge tail of the organic layer  316 . Thus, the organic layer  316  may face or contact an inner surface of the dam unit D. As another example, the organic layer  316  may overlap a portion of the dam unit D, but may not extend beyond the dam unit D. 
     However, the first inorganic layer  312  and the second inorganic layer  314  may contact each other around the dam unit D, and at least one of the first inorganic layer  312  and the second inorganic layer  314  may contact an exposed portion of the first insulating layer  204  or the second insulating layer  206  via the trench T and may also contact a lateral surface of the island  101 . Accordingly, bonding strength of the encapsulation layer  310  may improve, and the encapsulation layer  310  may effectively prevent infiltration of external moisture and/or oxygen into the display unit  200 . 
       FIG.  12    is a cross-sectional view taken along line II-II′ of  FIG.  3   , according to another embodiment. 
     Referring to  FIG.  12   , a display unit  200  may be formed on the island  101 . The display unit  200  may include the thin film transistor TFT of  FIG.  4    including inorganic layers and the organic light-emitting device  230  of  FIG.  4    that is electrically connected to the thin film transistor TFT. The passivation layer  209  may be interposed between the thin film transistor TFT and the organic light-emitting device  230 . The inorganic layers of the thin film transistor TFT may be the first insulating layer  204  and the second insulating layer  206 . 
     The buffer layer  202 , the first insulating layer  204 , the second insulating layer  206 , and the passivation layer  209  formed on the island  101  may extend over the connection unit  102 . The passivation layer  209  on the connection unit  102  may include a trench T exposing a portion of the first insulating layer  204  or the second insulating layer  206  under the passivation layer  209 . 
     At least one of the inorganic layers  312  and  314  of the encapsulation layer  310  may contact the exposed portion of the first insulating layer  204  or the second insulating layer  206  via the trench T. 
     According to one embodiment, a dam unit D surrounding at least a portion of the display region DA of the display unit  200  may be formed in the non-display region of the display unit  200 . The organic layer  316  may face or contact an inner surface of the dam unit D or may overlap a portion of the dam unit D, but may not extend beyond the dam unit D. However, the inorganic layers  312  and  314  may cover the dam unit D and may contact each other around the dam unit D. 
     According to one embodiment, an outermost inorganic layer of the encapsulation layer  310  may extend over the connection unit  102 . For example, when the encapsulation layer  310  includes the two inorganic layers  312  and  314 , the second inorganic layer  314  on the outermost side of the encapsulation layer  310  may be formed on both the island  101  and the connection unit  102 . 
     In other words, the passivation layer  209  formed on the connection unit  102  may be covered with the second inorganic layer  314 . Since the passivation layer  209  may be formed of an organic material as described above, when the passivation layer  209  formed on the connection unit  102  is covered with the second inorganic layer  314  formed of an inorganic material, exposure of a surface of the passivation layer  209  to oxygen or moisture may be prevented, and thus infiltration of oxygen or moisture into the display unit  200  via the passivation layer  209  may be prevented. 
     According to one embodiment, flexures P may be formed on at least a portion of the region on the connection unit  102 . For example, the flexures P may be formed by patterning the passivation layer  209 . As another example, the flexures P may be formed using various methods, such as, by forming steps or the like on the connection unit  102 . A method of forming the flexures P is not limited thereto. 
     The flexures P may be formed at a location corresponding to the connection region C of  FIG.  3    where the island  101  and the connection unit  102  are connected to each other. The flexures P may reduce stress that may concentrate on a connecting portion between the connection unit  102  and the island  101  during elongation of the substrate  10  of  FIG.  1   . The flexures P may prevent the second inorganic layer  314  extending over the connection unit  102  from being damaged, for example, cracked. 
       FIG.  13    is a cross-sectional view taken along line I-I′ of  FIG.  3   , according to another embodiment. 
     Referring to  FIG.  13   , a display unit  200 ′ may be disposed on the island  101 , and may include a source electrode  2111 , a drain electrode  2112 , an active layer  2130 , an organic light-emitting device  2125 , a gate electrode  2140 , a light protection layer  2105 , a color filter  2106 , and an auxiliary electrode  2150 . For convenience of explanation,  FIG.  13    does not show an encapsulation layer on the display unit  200 ′. However, the display unit  200 ′ may be encapsulated by an encapsulation layer. 
     The island  101  may include the same material as the materials mentioned in the previous embodiments. A buffer layer  2102  may be formed on the island  101 . 
     The source electrode  2111  and the drain electrode  2112  may be formed on the buffer layer  2102 . A first electrode  2120  of the organic light-emitting device  2125  may also be formed on the buffer layer  2102 . In other words, the first electrode  2120  may extend from the source electrode  2111  or the drain electrode  2112 . In other words, the first electrode  2120  may include the same material used to form the source electrode  2111  or the drain electrode  2112 , and may be integrally formed with the source electrode  2111  or the drain electrode  2112 . Thus, process efficiency of the display unit  200 ′ may improve. 
     The active layer  2130  may be formed on the source electrode  2111  and the drain electrode  2112 . The active layer  2130  corresponds to a space between the source electrode  2111  and the drain electrode  2112 . 
     According to another embodiment, the active layer  2130  may contact the source electrode  2111  and the drain electrode  2112 , and, in particular, may contact respective lateral surfaces of the source electrode  2111  and the drain electrode  2112  that face each other. For example, the active layer  2130  may contact a lateral surface facing the drain electrode  2112  from among the lateral surfaces of the source electrode  2111  and may contact a lateral surface facing the source electrode  2111  from among the lateral surfaces of the drain electrodes  2112 . According to another embodiment, the active layer  2130  may contact a portion of the upper surface of the source electrode  2111  and a portion of the upper surface of the drain electrode  2112 . Accordingly, contact areas between the active layer  2130  and the source electrode  2111  and the drain electrode  2112  increase, and thus a short channel structure may be implemented. 
     The active layer  2130  may include various materials. For example, the active layer  2130  may include an oxide semiconductor material. According to another embodiment, the active layer  2130  may include a ZnO-based oxide. According to yet another embodiment, the active layer  2130  may include an oxide semiconductor material containing In, Ga, and/or Sn. 
     According to yet another embodiment, the active layer  2130  may include G-I-Z-O [(In 2 O 3 )a(Ga 2 O 3 )b(ZnO)c], wherein a, b, and c are real numbers that respectively satisfy a≥0, b≥0, and c&gt;0. 
     According to yet another embodiment, the active layer  2130  may include an oxide of a material selected from Group 12, 13, and 14 metal elements (e.g., zinc (Zn), indium (In), gallium (Ga), stannum (Sn), cadmium (Cd), germanium (Ge), and hafnium (Hf)), and a combination thereof. 
     The gate electrode  2140  has a region that overlaps at least a portion of the active layer  2130 . The gate electrode  2140  may include various highly-conductive materials. According to another embodiment, the gate electrode  2140  may include a low resistance metal material, for example, molybdenum (Mo), aluminum (Al), copper (Cu), or titanium (Ti). 
     A first insulation layer  2135  is formed between the gate electrode  2140  and the active layer  2130 . The first insulation layer  2135  electrically insulates the gate electrode  2140  from the active layer  2130 . 
     The first insulating layer  2135  may not cover at least one region of the first electrode  2120 . According to another embodiment, the first insulating layer  2135  may cover at least an edge of the first electrode  2120 . 
     The gate electrode  2140  is formed on the first insulating layer  2135 . The first insulating layer  2135  may include various insulating materials. For example, the first insulating layer  2135  may include an inorganic material, such as silicon oxide, silicon nitride, or aluminum oxide. As another example, the first insulating layer  2135  may include an organic material including a polymer. 
     A second insulation layer  2144  is formed on the gate electrode  2140 . The second insulating layer  2144  covers the gate electrode  2140 . The second insulating layer  2144  is formed on the first insulating layer  2135 . The second insulating layer  2144  may not cover at least one region of the first electrode  2120 . 
     According to another embodiment, the second insulating layer  2144  may cover the first insulating layer  2135 , in a region corresponding to an upper surface of the first electrode  2120 . 
     According to another embodiment, at least a portion of the first insulating layer  2135  may be exposed without being covered with the second insulating layer  2144 , in the region corresponding to the upper surface of the first electrode  2120 . 
     The second insulating layer  2144  may include various insulating materials. For example, the second insulating layer  2144  may include an inorganic material, such as silicon oxide, silicon nitride, or aluminum oxide. As another example, the second insulating layer  2144  may include an organic material including a polymer. 
     The auxiliary electrode  2150  may be formed on the second insulating layer  2144 . The auxiliary electrode  2150  contacts at least a portion of one of the source electrode  2111  and the drain electrode  2112 . The first insulating layer  2135  and the second insulating layer  2144  may expose at least one region of at least one of the source electrode  2111  and the drain electrode  2112 , and the auxiliary electrode  2150  may contact the exposed region. 
     The auxiliary electrode  2150  may not face at least a portion of the entire region of the first electrode  2120  that is not covered with the first insulating layer  2135  and the second insulating layer  2144 . 
     The auxiliary electrode  2150  improves electrical characteristics of the source electrode  2111  and the drain electrode  2112 . In particular, when the source electrode  2111  and the drain electrode  2112  are formed of a light transmitting material, electrical resistances of the source electrode  2111  and the drain electrode  2112  may increase. This problem may be compensated by forming the auxiliary electrode  2150  of a material having low resistivity to improve electrical properties of the source electrode  2111  and the drain electrode  2112 . 
     The auxiliary electrode  2150  may include various conductive materials, for example, a highly-conductive metal material. According to another embodiment, the auxiliary electrode  2150  may include Cu, Ag, Al, Mo, or Au. According to one embodiment, the auxiliary electrode  2150  is formed to be spaced apart from the active layer  2130  to prevent a component of the auxiliary electrode  2150  from being diffused into the active layer  2130  and damaging the active layer  2130 . 
     According to one embodiment, the auxiliary electrode  2150  may be formed on a different level from the level of the gate electrode  2140  on the second insulating layer  2144 , thereby minimizing interference in the gate electrode  2140  and enabling precise patterning of the gate electrode  2140  and the auxiliary electrode  2150 . However, according to another embodiment, the auxiliary electrode  2150  may be formed on the first insulating layer  2135  on the same level as that of the gate electrode  2140 . 
     A passivation layer  2145  is formed on the second insulating layer  2144 . The passivation layer  2145  covers the auxiliary electrode  2150 . The passivation layer  2145  may not cover at least one region of the first electrode  2120 . 
     According to one embodiment, the passivation layer  2145  may cover the second insulating layer  2144  in the region corresponding to the upper surface of the first electrode  2120 . According to another embodiment, at least a portion of the second insulating layer  2144  may be exposed without being covered with the passivation layer  2145  in the region corresponding to the upper surface of the first electrode  2120 . 
     The passivation layer  2145  may be a single layer formed of an organic material, or may be a multi-layer structure including a plurality of organic material layers. The organic material may include a commercial polymer such as PMMA or PS, a polymer derivative having a phenol-based group, an acryl-based polymer, an imide-based polymer, an acryl ether-based polymer, an amide-based polymer, a fluorine-based polymer, a p-xylene-based polymer, a vinyl alcohol-based polymer, a blend thereof, or the like. The passivation layer  2145  may be a stack of an inorganic insulation layer and an organic insulation layer. 
     The first insulating layer  2135 , the second insulating layer  2144 , and the passivation layer  2145  may also be formed on the connection unit  102  of  FIG.  3   . The first insulating layer  2135  or the second insulating layer  2144  may be exposed via the trench T of  FIG.  3   . The exposed first insulating layer  2135  or the exposed second insulating layer  2144  may contact the encapsulation layer  300  of  FIG.  3   . 
     An intermediate layer  2123  is formed on an upper surface of the first electrode  2120 . The intermediate layer  2123  may include an organic emission layer to generate visible light. The intermediate layer  2123  may generate various colors of lights. In other words, the intermediate layer  2123  may generate red (R), green (G), and blue (B) lights, for example. According to another embodiment, the intermediate layer  2123  may generate white (W) light. 
     A second electrode  2122  is formed on the intermediate layer  2123 . The second electrode  2122  may include various conductive materials, for example, Li, Ca, LiF/Ca, LiF/Al, Al, Mg, and Ag. 
     The light protection layer  2105  faces the active layer  2130 . The light protection layer  2105  may face a surface opposite to a surface facing the gate electrode  2140  among the surfaces of the active layer  2130 . Accordingly, the active layer  2130  may be prevented from being damaged by light. 
     According to one embodiment, an over-coating layer  2103  may be formed on a substrate to cover the light protection layer  2105 . The over-coating layer  2103  may be formed below the buffer layer  2102 . 
     The color filter  2106  faces at least one region of the first electrode  2120 . In detail, the color filter  2106  may face a region of the first electrode  2120  that is overlapped by the intermediate layer  2123 . The color filter  2106  may be disposed between the first electrode  2120  and the substrate. 
     According to one embodiment, the color filter  2106  may be formed on the substrate, and the over-coating layer  2103  may be formed to cover the color filter  2106 . The over-coating layer  2103  may be formed below the buffer layer  2102 . 
     The color filter  2106  may face the first electrode  2120 , and thus a display apparatus generating various colors may be realized. 
     While the color filter  2106  is being formed, the light protection layer  2105  may also be formed of a color filter material based on one color, for example, a red (R) color. In other words, after the light protection layer  2105  and the color filter  2106  are formed on the substrate, the over-coating layer  2103  may be formed to cover the light protection layer  2105  and the color filter  2106 . 
       FIG.  14    is a cross-sectional view taken along line I-I′ of  FIG.  3   , according to yet another embodiment. 
     Referring to  FIGS.  3  and  14   , a display unit  200  may be disposed on the island  101 , and may include at least one organic light-emitting device  230  and a thin film transistor TFT that is electrically connected to the organic light-emitting device  230 . The organic light-emitting device  230  may include a first electrode  231 , an intermediate layer  233 , and a second electrode  232 . A passivation layer  209  may be disposed between the organic light-emitting device  230  and the thin film transistor TFT. For convenience of explanation,  FIG.  14    does not show an encapsulation layer on the display unit  200 . However, the display unit  200  may be encapsulated by an encapsulation layer. 
     A pixel defining layer  219  exposes an area of the first electrode  231  and defines a pixel region of the organic light-emitting device  230 . A light blocking layer BL may be disposed on a remaining region except for the pixel region defined by the pixel defining layer  219 . 
     For example, when the display unit  200  is of a top-emission type, the light blocking layer BL may be formed on an upper surface of the pixel defining layer  219 . However, embodiments are not limited thereto, and the pixel defining layer  219  or the passivation layer  209  may include a material that is capable of blocking light. On the other hand, when the display unit  200  is of a bottom-emission type, the light blocking layer BL may be disposed between the island  101  and the thin film transistor TFT. 
       FIG.  15    is a magnified plan view of a portion A of  FIG.  1   .  FIG.  16    is a cross-sectional view taken along line VI-VI′ of  FIG.  15   , and  FIG.  17    is a cross-sectional view taken along line VII-VII′ of  FIG.  15   , according to an embodiment. 
     Referring to  FIGS.  15 - 17   , the display apparatus  10  may include a plurality of islands  101 , a plurality of connection units  102  that are connecting the plurality of islands  101  to one another, and a plurality of display units  200  respectively disposed on the plurality of islands  101 . Inorganic layers and a passivation layer  209  of the display units  200  may be consecutively formed on the islands  101  and the connection units  102 . The inorganic layers may be the buffer layer  202 , the first insulating layer  204 , and the second insulating layer  206  included in the thin film transistor TFT of  FIG.  4   , respectively. 
     Each of the plurality of display units  200  may be encapsulated by the encapsulation layer  300  of  FIG.  4   . The encapsulation layer  300  may contact an exposed portion of the first insulating layer  204  or the second insulating layer  206  via the trench T. 
     Four connection units  102  are connected to one island  101 . In detail, a pair of first connection units  102   a  positioned on opposite sides of one island  101  and each extending in the first direction X, and a pair of second connection units  102   b  positioned on opposite sides of the island  101  and each extending in the second direction Y may be connected to the island  101 . 
     A first wiring unit may be positioned on the two first connection units  102   a , and a second wiring unit may be positioned on the two second connection units  102   b . For example, the first wiring unit may include a first voltage line V 1 , a second voltage line V 2 , and at least one data line DL, and the second wiring unit may include at least one scan line SL. 
     The first wiring unit and the second wiring unit may cross each other on the island  101 . 
     The first wiring unit may extend in the first direction X and may include a region curved along a through hole V in the second direction Y. Since the first wiring unit may extend in the first direction X and may repeat a curved shape at regular intervals, non-uniformity of brightness or the like between the display units  200  due to the first wiring unit may be reduced or prevented. A plurality of first wiring units extending in the same direction may be formed not to overlap each other to thereby minimizing interferences therebetween. 
     Similarly, since the second wiring unit may extend in the second direction Y, and a curved shaped in the first direction X may be repeated at regular intervals, non-uniformity of brightness or the like between the display units  200  due to the second wiring unit may be reduced or prevented. A plurality of second wiring units extending in the same direction may be formed not to overlap each other to thereby minimizing interferences therebetween. 
     The first wiring unit and the second wiring unit may include the same material. For example, the first wiring unit and the second wiring unit may have a stacked structure of Ti/Al/Ti and may include the same material used to form the source electrode  207  and the drain electrode  208 , which are highly flexible. 
       FIG.  16    illustrates an example in which a scan line SL is formed on a second connection unit  102   b . The buffer layer  202 , the first insulating layer  204 , the second insulating layer  206 , and the passivation layer  209  may be sequentially stacked on the second connection unit  102   b  in the stated order, and the scan line SL may be formed on the passivation layer  209 . Since the scan line SL is connected to the gate electrode  205  of the thin film transistor to apply a scan signal to the thin film transistor, the scan line SL and the gate electrode  205  of the thin film transistor may be electrically connected to each other via a contact hole. 
       FIG.  17    illustrates an example in which the first voltage line V 1 , the data line DL, and the second voltage line V 2  are formed on a first connection unit  102   a . The buffer layer  202 , the first insulating layer  204 , the second insulating layer  206 , and the passivation layer  209  may be sequentially stacked on the first connection unit  102   a  in the stated order, and the first voltage line V 1 , the data line DL, and the second voltage line V 2  may be formed on the passivation layer  209 . 
     The data line DL may be connected to the drain electrode  208  of the thin film transistor to apply a data signal to the thin film transistor. The first voltage line V 1  may electrically connect first electrodes  231  of  FIG.  4    respectively included in a plurality of display units  200  and separated from one another to one another. 
     According to embodiments of the present disclosure, since the plurality of display units  200  respectively include separated second electrodes  232  of  FIG.  4   , to electrically connect the separated second electrodes  232  to one another, the second voltage line V 2  may have the same pattern as or a similar pattern to the first voltage line V 1 , and the second voltage line V 2  may be electrically connected to the second electrode  232  via a contact hole. 
       FIG.  18    is a schematic cross-sectional view of a display apparatus  20 , which is a modification of the display apparatus  10  of  FIG.  1   . 
     Referring to  FIG.  18   , the display apparatus  20  may include a substrate  100  including a plurality of islands  101  and a plurality of connection units  102  that are connecting the plurality of islands  101  to one another, a plurality of display units  200  respectively disposed on the plurality of islands  101 , a plurality of encapsulation layers  300  respectively encapsulating the plurality of display units  200 , and a first protection film  410  and a second protection film  420  respectively disposed on an upper surface and a lower surface of the substrate  100 . The substrate  100  may include a plurality of through holes V of  FIG.  1    that penetrate through the substrate  100  between the connection units  102 . 
     Since the substrate  100 , the display unit  200 , and the encapsulation layer  300  are the same as those described above in the previous embodiments, repeated descriptions thereof may be omitted herein. 
     The first protection film  410  and the second protection film  420  may prevent external foreign materials or the like from permeating the display apparatus  20 . The first protection film  410  and the second protection film  420  are formed of elongation sheets, and thus may be elongated or changed in shape when the display apparatus  20  is elongated or changed in shape. For example, the first protection film  410  and the second protection film  420  may be biaxially oriented polypropylene films, biaxially oriented polyethylene terephthalate films, or the like. According to another embodiment, the first protection film  410  and the second protection film  420  may include, but is not limited to, polydimethylsiloxane (PDMS). 
       FIG.  19    is a schematic cross-sectional view of a display apparatus  30 , which is another modification of the display apparatus  10  of  FIG.  1   . 
     Referring to  FIG.  19   , the display apparatus  30  may include a substrate  100 , a plurality of display units  200  disposed on the substrate  100 , a plurality of encapsulation layers  300  respectively encapsulating the plurality of display units  200 , a first protection film  410  and a second protection film  420  respectively disposed on an upper surface and a lower surface of the substrate  100 , and a functional layer  500  on the second protection film  420 . 
     The substrate  100  may include a plurality of islands  101 , a plurality of connection units  102  that are connecting the plurality of islands  101  to one another, and a plurality of through holes V penetrating through the substrate  100  between the plurality of connection units  102 . 
     The plurality of display units  200  may be respectively disposed on the plurality of islands  101 . The encapsulation layers  300 , respectively encapsulating the plurality of display units  200 , may also be disposed on the plurality of islands  101 . 
     As described above with reference to  FIG.  18   , the first protection film  410  and the second protection film  420  may prevent external foreign materials or the like from permeating the display apparatus  30 . 
     The functional layer  500  may include at least one of a polarization layer and a touch screen layer. The functional layer  500  may further include an optic film for external light reflection and a protection layer. The functional layer  500  is elongatable, and may be elongated when the display apparatus  30  is elongated. 
       FIG.  20    is a magnified plan view of a portion A of  FIG.  1   , according to another embodiment. 
     Referring to  FIG.  20   , the substrate  100  may include a plurality of islands  101  spaced apart from one another, a plurality of connection units  102  that are connecting the plurality of islands  101  to one another, and a plurality of through holes V penetrating through the substrate  100  between the plurality of connection units  102 . 
     A plurality of display units  200  may be disposed on the plurality of islands  101 , respectively. Each display unit  200  may include at least a display device to realize visible light. The display device may be an organic light-emitting device. The plurality of display units  200  may be independently encapsulated by a plurality of encapsulation layers  300 . 
     The plurality of connection units  102  may connect the plurality of islands  101  to one another. For example, four connection units  102  are connected to each of the plurality of islands  101  and extend adjacent to the island  101  in different directions, and thus the four connection units  102  may be respectively connected to other four adjacent islands  101  surrounding the island  101 . 
     The plurality of islands  101  and the plurality of connection units  102  may be formed of the same material and may be connected to each other. In other words, the plurality of islands  101  and the plurality of connection units  102  may be integrally formed to have one body. 
     The inorganic layers and the passivation layer  209  of  FIG.  4    of the display units  200  may be consecutively formed on the islands  101  and the connection units  102 . The inorganic layers may include the buffer layer  202  and the first insulating layer  204  and the second insulating layer  206  included in the thin film transistor TFT of  FIG.  4   , The encapsulation layer  300  may contact an exposed portion of the first insulating layer  204  or the second insulating layer  206  via the trench T. Accordingly, the encapsulation layer  300  may reduce or prevent infiltration of external moisture and oxygen into the display units  200  via the passivation layer  209  that may be formed of an organic material. 
     Wiring units that are electrically connected to the display units  200  may be disposed on the plurality of islands  101 . 
     Referring to  FIG.  20   , each connection unit  102  has at least one curved portion. Accordingly, the shape of the at least one curved portion changes when the substrate  100  is elongated, and intervals between the plurality of islands  101  may increase. Thus, the shape of the display apparatus  10  of  FIG.  1    may change two-dimensionally or three-dimensionally. 
     The through holes V penetrate through the substrate  100 . The through holes V may provide separation areas between the plurality of islands  101 , reduce the weight of the substrate  100 , and improve the flexibility of the substrate  100 . When the substrate  100  is bent, rolled, or the like, the shapes of the through holes V change, and thus stress generated during deformation of the substrate  100  is effectively reduced. Thus, abnormal deformation of the substrate  100  may be prevented, and durability of the substrate  100  may improve. Accordingly, convenience and usability of the display apparatus  10  may improve, and the display apparatus  10  may be suitably applied to bending display apparatuses, flexible display apparatuses, or stretchable display apparatuses. 
     According to embodiments of the present disclosure, even when the shape of a display apparatus changes, an encapsulation layer may be prevented from being damaged, and infiltration of external moisture and oxygen may be effectively prevented, thereby improving the reliability of the display apparatus. It should be understood that the scope of the present disclosure is not restricted by this effect. 
     It should be understood that embodiments described herein should be considered in a descriptive sense and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments. 
     While one or more embodiments have been described with reference to the figures, 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 disclosure.