Patent Publication Number: US-2016225996-A1

Title: Display device and method of manufacturing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application of the U.S. patent application Ser. No. 14/037,242, filed Sep. 25, 2013 which claims the benefit of Korean Patent Application No. 10-2012-0143834, filed on Dec. 11, 2012, in the Korean Intellectual Property Office. The disclosures of the above-referenced applications are hereby expressly incorporated by reference. 
    
    
     BACKGROUND 
     1. Field 
     The present invention relates to a device and a method of manufacturing the device, and more particularly, to a display device and a method of manufacturing the display device. 
     2. Description of the Related Technology 
     A conventional deposition apparatus includes a substrate holder having a substrate mounted thereon, a heating crucible (or evaporation boat) containing an electroluminescent (EL) material, i.e., a deposition material, a shutter for preventing an EL material to be sublimed from rising, and a heater for heating the EL material in the heating crucible. The EL material heated by the heater is sublimed and deposited on a rotating substrate. In order to form a uniform film, the distance between the substrate and the heating crucible should typically be at least 1 meter. 
     Since precision in film formation is not high, wide gaps between different pixels may be designed, or an insulator called a bank may be formed between pixels when the manufacture of a full color flat panel display using red (R), green (G), and blue (B) light colors is considered. 
     Furthermore, the demand for full color flat panel displays with high resolution (i.e., a large number of pixels), high aperture ratio, and high reliability is increasing. However, such demand is challenging because the pitch in each organic light-emitting layer becomes finer as the resolution (number of pixels) and size (form factor) of the light-emitting device increases. Demand for high productivity and low manufacturing costs is also ever present. 
     SUMMARY OF CERTAIN INVENTIVE ASPECTS 
     The present invention provides a display device and a method of manufacturing the display device which allow strong adhesion between upper and lower films during hybrid patterning. 
     According to an aspect of the present invention, there is provided a display device, comprising: a first substrate; a light-emitting portion formed on the first substrate; and a sealing portion which is attached to the first substrate so as to protect the light-emitting portion from ambient environmental conditions wherein at least a portion of an edge of the first substrate is chamfered. 
     The edge of the first substrate has a triangular cross-section in a thickness dimension. 
     The edge of the first substrate may be chamfered from one surface of the first substrate on which the light-emitting portion is formed towards an edge thereof. 
     Alternatively, the edge of the first substrate is chamfered from the other surface of the first substrate on which the light-emitting portion is not formed towards an edge thereof. 
     Distal ends of the first substrate are respectively chamfered from both surfaces of the first substrate towards edges of the first substrate. 
     The light-emitting portion may include an organic emission layer, and wherein the organic emission layer includes at least one of a blue emission layer, a red emission layer, a green emission layer, and a white emission layer. 
     The blue emission layer is formed by using a fine metal mask process. 
     At least one of the red and green emission layers is formed by using a laser-induced thermal imaging (LITI) process. 
     The white emission layer is formed from a stack of the blue, red and green emission layers. 
     According to another aspect of the present invention, there is provided a method of manufacturing a display device, the method comprising: providing a first substrate with chamfered edges; stacking a buffer layer, an active layer, a gate insulating layer, a gate electrode, an interlayer insulating layer, a source electrode, a drain electrode, a passivation layer, a pixel-defining layer, and a pixel electrode on the first substrate in this order; and forming, by a fine metal mask process and a laser-induced thermal imaging (LITI) process, an organic emission layer on the pixel electrode in a pixel defined by the pixel-defining layer. 
     The edges of the first substrate are chamfered by using a polishing process. 
     The forming of the organic emission layer includes depositing a blue emission layer on the pixel electrode by using the fine metal mask process and transferring green and red emission layers onto the pixel electrode by using the LITI process. 
     The LITI process includes transferring the green emission layer onto the pixel electrode and then depositing the red emission layer on the pixel electrode. 
     The transferring of the green and red emission layers onto the pixel electrode by the LITI process includes: seating the first substrate on a lower film; preparing an upper film by depositing a transfer layer having one of the red and green emission layers patterned thereon on a base film; disposing the upper film on the first substrate and laminating the upper and lower films by venting; and irradiating the upper film with a laser beam and transferring the one of the red and green emission layers onto the pixel electrode. 
     The transferring of the green and red emission layers onto the pixel electrode further includes removing the upper and lower films after irradiation with the laser beam. 
     The method of manufacturing a display device further comprising forming an opposite electrode on the pixel-defining layer on which the organic emission layer has been formed and sealing the opposite electrode with a sealing portion. 
     The manufacturing method further comprising cutting the first substrate into a plurality of substrates and separating the plurality of substrates from one another. 
     The forming of the organic emission layer includes forming a white emission layer by depositing or transferring blue, green, and red emission layers. 
     The display device and the method of manufacturing the display device allow complete attachment between the upper and lower films at edges of the first substrate, thereby improving an adhesion force therebetween. 
     The display device and the manufacturing method also eliminate a portion where the upper film is not attached to the lower film due to the thickness of the first substrate to thereby prevent movement of the first substrate and allow transfer of the organic emission layer onto a precise location on the pixel-defining layer. 
     In particular, the display device thus manufactured allows the transfer of the organic emission layer onto the precise location, thereby providing increased brightness and reproducibility. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features and advantages of the disclosed technology will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: 
         FIG. 1  is a conceptual diagram of a display device according to an embodiment of the disclosed technology; 
         FIG. 2  is a cross-sectional view of a first substrate and a light-emitting portion shown in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view illustrating a process of forming an emission layer (EML) shown in  FIG. 2  according to an embodiment of the disclosed technology; 
         FIG. 4  is a cross-sectional view illustrating a process of forming the EML shown in  FIG. 2 , according to another embodiment of the disclosed technology; and 
         FIG. 5  is a cross-sectional view illustrating a process of forming the EML shown in  FIG. 2 , according to another embodiment of the disclosed technology. 
     
    
    
     DETAILED DESCRIPTION OF CERTAIN INVENTIVE EMBODIMENTS 
     Example embodiments of the invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, the exemplary embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The scope of the present invention is defined only by the appended claims. The terminology used herein is of describing particular exemplary embodiments only and is not intended to limit the invention. As used herein, 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 further understood that the terms “comprises” and/or “comprising” or “includes” and/or “including” when used in this specification, specify the presence of components, steps, operations and/or elements, but do not preclude the presence or addition of one or more other components, steps, operations, and/or elements. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. 
       FIG. 1  is a conceptual diagram of a display device  100  according to an embodiment of the disclosed technology.  FIG. 2  is a cross-sectional view of a first substrate  110  and a light-emitting portion  120  shown in  FIG. 1 .  FIG. 3  is a cross-sectional view illustrating a process of forming an emission layer (EML) shown in  FIG. 2 . 
     Referring to  FIGS. 1 through 3 , the display device  100  includes the first substrate  110 , a sealing portion  130 , a sealing member  190  and the light-emitting portion  120 . At least portions of edges of the first substrate  110  are chamfered. More specifically, the first substrate  110  may have sloped edges formed through polishing. The light-emitting portion  120  is disposed on the first substrate  110  and includes a thin-film transistor (TFT), a passivation layer  121  covering the TFT, and an organic light-emitting diode (OLED) overlying the passivation layer  121 . 
     The first substrate  110  may be made of glass, but it is not limited thereto. The first substrate  110  may be formed of a plastic material or a metallic material such as SUS or Ti. 
     Now referring, more particularly, to  FIGS. 2 &amp; 3 , for the purpose of explanation only one portion of a pixel circuit of the light emitting portion  120  will be described. However, it will be recognized that a display will typically be formed of a matrix of such pixel circuits arranged in many rows and columns. In the depicted pixel circuit portion a buffer layer  122  of an organic and/or inorganic compound may be formed over the first substrate  110 . For example, the buffer layer  122  may be made of silicon oxide (SiOx, x≧1) or silicon nitride (SiNx, x≧1). 
     An active layer  123  is arranged on the buffer layer  122  in a predetermined pattern, and buried in a gate insulating layer  124 . The active layer  123  includes a source region  123   a , a drain region  123   c , and a channel region  123   b  interposed therebetween. The active layer  123  is made of amorphous silicon, but it is not limited thereto. The active layer  123  may be formed of oxide semiconductor. For example, the oxide semiconductor may include an oxide of a material selected from the group consisting of metals in groups  12 ,  13 , and  14 , such as zinc (Zn), indium (In), gallium (Ga), tin (Sn), cadmium (Cd), germanium (Ge) and hafnium (Hf), and mixtures thereof. For example, the active layer  123  may include G-I-Z-O [(In2O3)a(Ga2O3)b(ZnO)c] where a, b, and c are real numbers satisfying a≧0, b≧0, and c&gt;0. For convenience of explanation, it is assumed herein that the active layer  123  is made of amorphous silicon. 
     Formation of the active layer  123  may include forming an amorphous silicon layer on the buffer layer  122 , crystallizing the amorphous silicon layer into a polycrystalline silicon layer, and patterning the polycrystalline silicon layer. The source and drain regions  123   a  and  123   c  in the active layer  123  are doped with n- or p-type impurities depending on the type of the TFT used, such as a driving TFT (not shown) or a switching TFT (not shown). 
     A gate electrode  125  corresponding to the active layer  123  and an interlayer insulating layer  126  burying the gate electrode  125  are formed on the gate insulating layer  124 . 
     After forming contact holes in the interlayer insulating layer  126  and the gate insulating layer  124 , a source electrode  127   a  and a drain electrode  127   b  are disposed on the interlayer insulating layer  126  so as to contact the source region  123   a  and the drain region  123   c , respectively. 
     Since the source and drain electrodes  127   a  and  127   b  also serve as a reflective layer the source and drain electrodes  127   a  and  127   b  may be formed of a material having high electrical conductivity and be thick enough to reflect light. For example, the source and drain electrodes  127   a  and  127   b  may be formed of a metallic material such as silver (Ag), magnesium (Mg), aluminum (Al), platinum (Pt), palladium (Pd), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), lithium (Li), calcium (Ca), or a compound thereof. 
     The passivation layer  121  is formed on the TFT and the reflective layer, and a pixel electrode  128   a  of the OLED is disposed on the passivation layer  121  so as to contact the drain electrode  127   b  of the TFT through a via hole H 2  ( FIGS. 2 &amp; 3 ). The passivation layer  121  may be formed of a single layer or at least two layers of an inorganic and/or organic material. The passivation layer  121  may be a planarization layer having a planarized top surface regardless of an uneven topology of the underlying layer, or may have a curved surface which follows a curvature of a surface of the underlying layer. The passivation layer  121  may also be a transparent insulator in order to achieve a resonance effect. 
     After forming the pixel electrode  128   a  on the passivation layer  121 , a pixel-defining layer  129  of an organic and/or inorganic material is formed so as to cover the pixel electrode  128   a  and the passivation layer  121 , and an opening is formed to expose the pixel electrode  128   a.    
     An organic layer  128   b  and an opposite electrode  128   c  are disposed on at least the pixel electrode  128   a.    
     The pixel electrode  128   a  and the opposite electrode  128   c  act as an anode and a cathode, respectively. However, an embodiment is not limited thereto, and the pixel electrode  128   a  and the opposite electrode  128   c  may act as a cathode and an anode, respectively. 
     The pixel electrode  128   a  may be formed of a material with a high work function, e.g., a transparent conducting material such as indium tin oxide (ITO), indium zinc oxide (IZO), indium oxide (In2O3), or zinc oxide (ZnO). 
     The opposite electrode  128   c  may be formed of a metallic material with a low work function, such as Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, or a compound thereof. Alternatively, it may be formed as a thin semi-transparent reflective layer of Mg, Ag, and Al so as to transmit light after optical resonance. 
     The pixel electrode  128   a  and the opposite electrode  128   c  are insulated from each other by the organic layer  128   b , and during operation of the display device, apply voltages of opposite polarity to the organic layer  128   b  so that light is emitted by an emission layer. 
     The organic layer  128   b  may be a low molecular weight or polymeric organic layer. When the organic layer  128   b  is a low molecular weight organic layer, the organic layer  128   b  may have a single- or multi-layered structure including a stack of a hole injection layer (HIL), a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL), and an electron injection layer (EIL). An organic material for use in the organic layer  128   b  may be copper phthalocyanine (CuPc), N,N′-Di (naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB), tris-8-hydroxyquinoline aluminum (Alq3), or other various materials. In this case, the organic layer  128   b  may be formed by vacuum deposition. Like the opposite electrode  128   c , the HIL, the HTL, and ETL which are common to red, green, and blue pixels may be formed so as to cover all the pixels. 
     On the other hand, when the organic layer  128   b  is a polymeric organic layer, the organic layer  128   b  mainly includes an HTL and an EML. poly(3,4-ethylenedioxythiophene) (PEDOT) is used as the HTL, and Poly-Phenylenevinylene (PPV)- or Polyfluorene-based polymeric organic material is used as the EML. In this case, the organic layer  128   b  may be formed by screen printing, inkjet printing, a fine metal mask method, or laser-induced thermal imaging (LITI). 
     However, the organic layer  128   b  is not limited thereto, and the organic layer  128   b  may be formed by other methods. 
     The sealing portion  130  is used to protect the materials in the light emitting portion  120  that may decay when exposed to oxygen, water and light, for example, and may be formed in a similar way to the first substrate  110 . More specifically, like the first substrate  110 , the sealing portion  130  may be made of glass. However, the sealing portion  130  is not limited thereto, and it may be made of a plastic material. The sealing portion  130  may be formed by alternately stacking at least one organic and one inorganic layer. The sealing portion  130  may include a plurality of inorganic layers and a plurality of organic layers. 
     The organic layer may be composed of a single layer of one of polymers, e.g., polyethylene terephthalate, polyimide, polycarbonate, epoxy, polyethylene, and polyacrylate, or a stack of multiple layers thereof. The organic layer may be formed of polyacrylate by polymerization of a monomer composition containing a diacrylate monomer and a triacrylate monomer. The monomer composition may further include monoacrylate monomer. The monomer composition may further contain a known photoinitiator such as TPO, but it is not limited thereto. 
     The inorganic layer may be composed of a single layer of metal oxide or metal nitride or a stack of multiple layers thereof. More specifically, the inorganic layer may include one of SiNx, aluminum oxide (Al2O3), silicon dioxide (SiO2), and titanium oxide (TiO2). An exposed uppermost layer in the sealing portion  130  may be an inorganic layer in order to prevent permeation of moisture into the OLED. 
     The sealing portion  130  may have at least one sandwich structure including at least two inorganic layers and at least one organic layer interposed therebetween. Alternatively, the at least one sandwich structure may include at least two organic layers and at least one inorganic layer interposed therebetween. 
     The sealing portion  130  may include a first inorganic layer, a first organic layer, and a second inorganic layer stacked in this order when viewed from the top of the light-emitting portion  120 . The sealing portion  130  may also include a first inorganic layer, a first organic layer, a second inorganic layer, a second organic layer, and a third inorganic layer sequentially stacked from the top of the light-emitting portion  120 . Alternatively, the sealing portion  130  may include a first inorganic layer, a first organic layer, a second inorganic layer, a second organic layer, a third inorganic layer, a third organic layer, and a fourth inorganic layer sequentially stacked from the top of the light-emitting portion  120 . 
     A metal halide layer containing lithium fluoride (LiF) may also be formed between the light-emitting portion  120  and the first inorganic layer to prevent damage to the light-emitting portion  120  during sputtering or plasma deposition for forming the first inorganic layer. 
     The first and second organic layers may respectively have areas smaller than those of the second and third inorganic layers. Furthermore, the second and third inorganic layers may completely cover the first and second organic layers, respectively. 
     For convenience of explanation, it is assumed herein that the sealing portion  130  is made of glass which is the same material as that of the first substrate  110 . 
     A method of manufacturing the display device  100  will now be described in detail. 
     First, a first substrate  110  is prepared with its edges chamfered by mechanical polishing. In these embodiments, the edges of the first substrate  110  may have a triangular cross-section in the thickness dimension of the first substrate  110 . In particular, the edges of one surface and the other surface of the first substrate  110  may be simultaneously chamfered. Thus, the edges of the first substrate  110  are sloped from two surfaces of the first substrate  110  towards edges thereof. 
     When the first substrate  110  is large in size, a single substrate is used as the first substrate  110 . Conversely, when the first substrate  110  is small in size, a mother substrate (not shown) including a plurality of the first substrates  110  may be used. Since the display device  100  is manufactured in a similar manner regardless of the size of the first substrate  110 , for convenience of explanation, it is assumed herein that the first substrate  110  is a single substrate. 
     The first substrate  110  may have various shapes including a circle, a rectangle, and a polygon. For convenience of explanation, the first substrate  110  is assumed to have a rectangular shape. 
     The first substrate  110  having a rectangular shape may have at least one edge chamfered in a similar way as described above. For convenience of explanation, however, it is assumed herein that all four edges of the first substrate  110  are chamfered. 
     After preparing the first substrate  110  with the chamfered edges, a buffer layer  122 , an active layer  123 , a gate insulating layer  124 , a gate electrode  125 , an interlayer insulating layer  126 , a source electrode  127   a , a drain electrode  127   b , a passivation layer  121 , a pixel-defining layer  129 , and a pixel electrode  128   a  are stacked on the first substrate  110  in this order. Since the above stacking method is performed in the same or similar manner to a method of manufacturing a general display device, a detailed description thereof is omitted. 
     After stacking the respective layers on the first substrate  110 , an EML may be formed on the pixel electrode  128   a  in a pixel defined by the pixel-defining layer  129  by using a fine metal mask method and an LITI method. The EML may be formed together with or separately from other layers described above. For convenience of explanation, it is assumed herein that the EML is formed separately from other layers. 
     When the EML is formed as described above, first, a blue EML is deposited on the pixel electrode  128   a  by using the fine metal mask, followed by formation of green and red EMLs. In such embodiments, at least one of the green and red EMLs may be transferred onto the pixel electrode  128   a  by using an LITI method. For convenience of explanation, it is assumed hereinafter that the green and red EMLs are sequentially transferred by using the LITI method. 
     Furthermore, the EML may further include various other color EMLs. In particular, the EML may include a white EML, and in such embodiments, the white EML may include blue, green, and red EMLs. 
     The white EML may be formed by using various methods. For example, the white EML may be formed by forming a blue EML by using a fine metal mask process and then stacking green and red EMLs on the blue EML by using an LITI method. The white EML may also be formed by stacking blue, green, and red EMLs during a fine metal mask process. Alternatively, the white EML may be formed by transferring blue, green, and red EMLs using an LITI method. However, for convenience of explanation, it is assumed hereinafter that only blue, green, and red EMLs are formed instead of a white EML. 
     In order to form the green EML, first, an upper film  140  is prepared. The upper film  140  may be formed by preparing a base film  141  and transferring a transfer layer  143  having the green EML patterned thereon onto the base film  141 . The upper film  140  may further include a light-to-heat conversion layer  142  disposed between the base film  141  and the transfer layer  143 . For convenience of explanation, it is assumed hereinafter that the upper film  140  includes the base film  141 , the light-to-heat conversion layer  142 , and the transfer layer  143 . 
     Light emitted by a light source is absorbed in the light-to-heat conversion layer  142  on the base film  141  and converted into thermal energy. The thermal energy may cause a change in adhesion force among the first substrate  110  and the light-to-heat conversion layer  142  and the transfer layer  143  so that the material of the transfer layer  143  overlying the light-to-heat conversion layer  142  is transferred to the first substrate  110 . Thus, an EML is patterned on the first substrate  110 . 
     Simultaneously with preparing the upper film  140  as described above, a lower film  150  on which the first substrate  110  is seated is prepared. The upper film  140  may be disposed on the first substrate  110 . 
     After completing the above-described arrangement, the upper and lower films  140  and  150  may be laminated with each other by venting. In this case, since the upper and lower films  140  and  150  have greater planar dimensions than the first substrate  110 , they may be bonded to each other where they extend over the edges of the first substrate  110 . 
     When the upper film  140  is attached to the lower film  150  as described above, the upper and lower films  140  and  150  may be bent to follow the chamfered shapes of the edges of the first substrate  110 . 
     Of particular note, when upper and lower films are attached to each other according to conventional methods whereby an edge of a first substrate is not chamfered, the upper and lower films may not completely adhere to each other at edges of the first substrate. 
     Conversely, according to embodiments of the disclosed technology, the upper and lower films  140  and  150  can completely attach to each other at the edges of the first substrate  110  thereby substantially preventing their separation due to external shocks. 
     After completing adhesion between the upper and lower films  140  and  150  as described above, a laser beam is irradiated from above the upper film  140  to thereby transfer the green EML onto the pixel electrode  128   a.    
     Following the above thermal transfer, the upper and lower films  140  and  150  are separated from the first substrate  110 . Since a process of removing the upper and lower films  140  and  150  is performed in a similar manner to a general LITI process, a detailed description thereof will be omitted. 
     After transferring the green EML as described above, the red EML may be transferred by using a similar process to that for transferring the green EML. Thus, a detailed description thereof will be omitted. 
     Upon completion of the transfer of the green and red EMLs as described above, the opposite electrode  128   c  is formed on the pixel-defining layer  129 . Since the opposite electrode  128   c  is formed in the same manner as generally known methods, a detailed description thereof will be omitted. 
     After forming the opposite electrode  128   c , the first substrate  110  is attached to the sealing portion  130  by forming a sealing member  190  between the first substrate  110  and the sealing portion  130  and pressing together the first substrate  110  and the sealing portion  130  to form an airtight seal. Since the first substrate  110  is sealed to the sealing portion  130  by the sealing member  190  in a similar manner as a general sealing method used in manufacturing a display device, a detailed description thereof will be omitted. 
     When the sealing portion  130  is formed as a thin film as described above, lamination may be used. 
     In another embodiment, the display device  100  may be manufactured by performing the above-described process on a mother substrate including a plurality of the first substrates  110  and separating the plurality of the first substrates  110  from one another. Since a method of separating the first substrates  110  is the same as generally known separation methods, a detailed description thereof will be omitted. 
     As described above, the method of manufacturing the display device  100 , according to the present embodiment, allows complete attachment between the upper and lower films  140  and  150  at edges of the first substrate  110 , thereby improving the adhesive force therebetween. 
     The method also eliminates a portion where the upper film  140  is not attached to the lower film  150  due to the thickness of the first substrate  110  to thereby prevent movement of the first substrate  110  and allow transfer of an EML onto a precise location on the pixel-defining layer  129 . 
     In particular, such precise EML can increase the brightness and reproducibility of the display device  100 . 
       FIG. 4  is a cross-sectional view illustrating a process of forming the EML shown in  FIG. 2 , according to another embodiment of the disclosed technology. Hereinafter, like numbers refer to like elements. 
     Referring to  FIG. 4 , a display device (not indicated in  FIG. 4 ) includes a first substrate  210 , a sealing portion (not shown), and a light-emitting portion (not shown). Since the sealing portion and the light-emitting portion have the same or similar functions and structures as described above, detailed descriptions thereof will be omitted. 
     At least one edge of the first substrate  210  may be chamfered. More specifically, the first substrate  210  may have a sloped edge formed through a polishing process. In particular, the edge of the first substrate  210  may be sloped from one surface of the first substrate  110  on which the light-emitting portion is disposed towards an edge thereof. 
     A method of manufacturing the display device having the above-described structure will now be described in detail with reference to  FIG. 4 . 
     Referring to  FIG. 4 , first, the first substrate  210  is prepared with its edges chamfered by mechanical polishing. In this case, the edges of the first substrate  210  may have a triangular cross-section in a thickness direction of the first substrate  210 . In particular, the edges of one surface of the first substrate  210  may be chamfered. Thus, the edges of the first substrate  210  may be sloped from the one surface of the first substrate  210  towards edges thereof. 
     When the first substrate  210  is large in size, a single substrate is used as the first substrate  210 . Conversely, when the first substrate  210  is small in size, a mother substrate (not shown) including a plurality of the first substrates  210  may be used. Since the display device is manufactured in a similar manner regardless of the size of the first substrate  210 , for convenience of explanation, it is assumed hereinafter that the first substrate  210  is a single substrate. 
     The first substrate  210  may have various shapes including a circle, a rectangle, and a polygon. For convenience of explanation, the first substrate  210  is assumed to have a rectangular shape. 
     The first substrate  210  having a rectangular shape may have at least one edge chamfered in a similar manner as described above. For convenience of explanation, however, it is assumed herein that all four edges of the first substrate  210  are chamfered. 
     Once the first substrate  210  with the chamfered edges is prepared, a buffer layer  222 , an active layer  223 , a gate insulating layer  224 , a gate electrode  225 , an interlayer insulating layer  226 , a source electrode  227   a , a drain electrode  227   b , a passivation layer  221 , a pixel-defining layer  229 , and a pixel electrode  228   a  are stacked on the first substrate  210  in this order. Since the above stacking method is performed in the same or similar manner to a method of manufacturing a general display device, a detailed description thereof is omitted. 
     After stacking the respective layers on the first substrate  210 , an EML may be formed on the pixel electrode  228   a  in a pixel defined by the pixel-defining layer  229  by using a fine metal mask method and an LITI method. The EML may be formed together with or separately from other layers described above. For convenience of explanation, it is assumed herein that the EML is formed separately from other layers. 
     When the EML is formed as described above, first, a blue EML is deposited on the pixel electrode  228   a  by using the fine metal mask, followed by formation of green and red EMLs. 
     In this case, at least one of the green and red EMLs may be deposited on the pixel electrode  228   a  by using an LITI method. For convenience of explanation, it is assumed hereinafter that the green and red EMLs are sequentially transferred by using the LITI method. 
     Furthermore, the EML may further include various other color EMLs. The EML may include a white EML, and in this case, the white EML may include blue, green, and red EMLs. Since the white EML is formed in the same manner as described above, a detailed description thereof is omitted. 
     In order to form the green EML, first, an upper film  240  is prepared. The upper film  240  may be formed by preparing a base film  241  and transferring a transfer layer  243  having the green EML patterned thereon onto the base film  241 . The upper film  240  may further include a light-to-heat conversion layer  242  disposed between the base film  241  and the transfer layer  243 . For convenience of explanation, the upper film  240  is assumed hereinafter to include the base film  241 , the light-to-heat conversion layer  242 , and the transfer layer  243 . 
     Light emitted by a light source is absorbed in the light-to-heat conversion layer  242  on the base film  241  and converted into thermal energy. The thermal energy may then cause a change in an adhesion force between the first substrate  210  and the light-to-heat conversion layer  242  and the transfer layer  243  so that a material of the transfer layer  243  overlying the light-to-heat conversion layer  242  is transferred to the first substrate  210 . Thus, an EML is patterned on the first substrate  210 . 
     Simultaneously with preparing the upper film  240  as described above, a lower film  250  on which the first substrate  210  is seated is prepared. The upper film  240  may be disposed on the first substrate  210 . 
     After completing the above-described arrangement, the upper and lower films  240  and  250  may be laminated with each other through venting. In such embodiments, since the upper and lower films  240  and  250  have larger planar dimensions than the first substrate  210 , they may be bonded to each other where they extend beyond the edges of the first substrate  210 . 
     When the upper film  240  is attached to the lower film  250  as described above, the upper film  240  is bent to follow the chamfered shapes of the edges of the first substrate  210  while the lower film  250  is straight like a lower surface of the first substrate  210 . 
     In particular, when upper and lower films are attached to each other according to conventional methods whereby an edge of a first substrate is not chamfered, the upper and lower films may not completely adhere to each other at edges of the first substrate. 
     Conversely, according to embodiments of the disclosed technology, the upper and lower films  240  and  250  can be completely attached to each other at the edges of the first substrate  210  to thereby substantially preventing their separation due to external shocks. 
     After completing adhesion between the upper and lower films  240  and  250  as described above, a laser beam is irradiated from above the upper film  240  to thereby transfer the green EML onto the pixel electrode  228   a.    
     Following the above thermal transfer, the upper and lower films  240  and  250  are separated from the first substrate  210 . Since a process of removing the upper and lower films  240  and  250  is performed in a similar manner to a general LITI process, a detailed description thereof is omitted. 
     After transferring the green EML as described above, the red EML may be transferred by using a similar process to that for transferring the green EML. 
     Upon completion of the stacking of the green and red EMLs as described above, an opposite electrode (not shown) may be disposed on the pixel-defining layer  229 . Since the opposite electrode is formed in the same manner as generally known methods, a detailed description thereof will be omitted. 
     After forming the opposite electrode, the first substrate  210  is sealed to the sealing portion in the same manner as described above. 
     In another embodiment, the display device may be manufactured by performing the above-described process on a mother substrate including a plurality of the first substrates  210  and separating the plurality of the first substrates  210  from one another. Since a method of separating the first substrates  210  is the same as a general separation method, a detailed description thereof will be omitted. 
     As described above, the method of manufacturing the display device according to the present embodiment allows complete attachment between the upper and lower films  240  and  250  at the edges of the first substrate  210 , thereby improving the adhesive force therebetween. 
     The method also eliminates a portion where the upper film  240  is not attached to the lower film  250  due to the thickness of the first substrate  210  to thereby prevent movement of the first substrate  210  and allow transfer of the EML onto a precise location on the pixel-defining layer  229 . 
     Of particular note, the display device thus manufactured includes the precise transfer of the EML, thereby providing increased brightness and reproducibility. 
       FIG. 5  is a cross-sectional view illustrating a process of forming the EML shown in  FIG. 2 , according to another embodiment of the disclosed technology. Hereinafter, like numbers refer to like elements. 
     Referring to  FIG. 5 , a display device (not indicated in  FIG. 5 ) includes a first substrate  310 , a sealing portion (not shown), and a light-emitting portion (not shown). Since the sealing portion and the light-emitting portion have the same or similar functions and structures as described above, detailed descriptions thereof will be omitted. 
     At least one edge of the first substrate  310  may be chamfered. More specifically, the first substrate  310  may have a sloped edge formed through a polishing process. In particular, the edge of the first substrate  310  may be sloped from the other surface of the first substrate  310  on which the light-emitting portion is not formed towards an edge thereof. 
     A method of manufacturing the display device having the above-described structure will now be described in detail with reference to  FIG. 5 . 
     Referring to  FIG. 5 , first, the first substrate  310  is prepared with its edges chamfered by mechanical polishing. In this case, the edges of the first substrate  310  may have a triangular cross-section in a thickness direction of the first substrate  310 . In particular, the edges of the other surface of the first substrate  310  may be chamfered. Thus, the edges of the first substrate  210  may be sloped from the other surface of the first substrate  310  towards edges thereof. 
     When the first substrate  310  is large in size, a single substrate is used as the first substrate  310 . Conversely, when the first substrate  310  is small in size, a mother substrate (not shown) including a plurality of the first substrates  310  may be used. Since the display device is manufactured in a similar manner regardless of the size of the first substrate  310 , for convenience of explanation, it is assumed hereinafter that the first substrate  310  is a single substrate. 
     The first substrate  310  may have various shapes including a circle, a rectangle, and a polygon. For convenience of explanation, the first substrate  310  is assumed to have a rectangular shape. 
     The first substrate  310  having a rectangular shape may have at least one edge chamfered in a similar manner as described above. For convenience of explanation, however, it is assumed herein that all four edges of the first substrate  310  are chamfered. 
     Once the first substrate  310  with the chamfered edges is prepared, a buffer layer  322 , an active layer  323 , a gate insulating layer  324 , a gate electrode  325 , an interlayer insulating layer  326 , a source electrode  327   a , a drain electrode  327   b , a passivation layer  321 , a pixel-defining layer  329 , and a pixel electrode  328   a  are stacked on the first substrate  310  in this order. Since the above stacking method is performed in the same or similar manner to generally known methods of manufacturing a display device, a detailed description thereof will be omitted. 
     After stacking the respective layers on the first substrate  310 , an EML may be formed on the pixel electrode  328   a  in a pixel defined by the pixel-defining layer  329  by using a fine metal mask method and an LITI method. The EML may be formed together with or separately from other layers described above. For convenience of explanation, it is assumed herein that the EML is formed separately from other layers. 
     When the EML is formed as described above, first, a blue EML is deposited on the pixel electrode  328   a  by using the fine metal mask, followed by formation of green and red EMLs. In this case, at least one of the green and red EMLs may be deposited on the pixel electrode  328   a  by using an LITI method. For convenience of explanation, it is assumed hereinafter that the green and red EMLs are sequentially transferred by using the LITI method. 
     More specifically, in order to form the green EML, first, an upper film  340  is prepared. The upper film  340  may be formed by preparing a base film  341  and transferring a transfer layer  343  having the green EML patterned thereon onto the base film  341 . The upper film  340  may further include a light-to-heat conversion layer  342  disposed between the base film  341  and the transfer layer  343 . For convenience of explanation, the upper film  340  is assumed hereinafter to include the base film  341 , the light-to-heat conversion layer  342 , and the transfer layer  343 . 
     Light emitted by a light source is absorbed by the light-to-heat conversion layer  342  on the base film  341  and converted into thermal energy. The thermal energy may then cause a change in an adhesion force between the first substrate  310  and the light-to-heat conversion layer  342  and the transfer layer  343  so that a material of the transfer layer  343  overlying the light-to-heat conversion layer  342  is transferred to the first substrate  310 . Thereby, an EML is patterned on the first substrate  310 . 
     Simultaneously with preparing the upper film  340  as described above, a lower film  350  on which the first substrate  310  is seated is prepared. The upper film  340  may be disposed on the first substrate  310 . 
     After completing the above-described arrangement, the upper and lower films  340  and  350  may be laminated with each other through venting. In such embodiments, since the upper and lower films  340  and  350  are larger than the first substrate  310 , they may be bonded to each other at edges of the first substrate  310 . 
     When the upper film  340  is attached to the lower film  350  as described above, the upper film  340  is bent to follow the chamfered shapes of the edges of the first substrate  310  while the lower film  350  is straight like an upper surface of the first substrate  310 . 
     In particular, when upper and lower films are attached to each other according to conventional methods whereby an edge of a first substrate is not chamfered, the upper and lower films may not completely adhere to each other at edges of the first substrate. 
     Conversely, according to embodiments of the disclosed technology, the upper and lower films  340  and  350  can be completely attached to each other at the edges of the first substrate  310  to thereby substantially prevent their separation due to external shocks. 
     After completing adhesion between the upper and lower films  340  and  350  as described above, a laser beam is irradiated from above the upper film  340  to thereby transfer the green EML onto the pixel electrode  328   a.    
     Following the above thermal transfer, the upper and lower films  340  and  350  are separated from the first substrate  310 . Since a process of removing the upper and lower films  340  and  350  is performed in a similar manner to a general LITI process, a detailed description thereof is omitted. 
     After transferring the green EML as described above, the red EML may be transferred by using a similar process to that for transferring the green EML. 
     Upon completion of the stacking of the green and red EMLs as described above, an opposite electrode (not shown) may be disposed on the pixel-defining layer  329 . Since the opposite electrode is formed in the same manner as a general method, a detailed description thereof will be omitted. 
     After forming the opposite electrode, the first substrate  310  is sealed to the sealing portion in the same manner as described above. 
     In another embodiment, the display device may be manufactured by performing the above-described process on a mother substrate including a plurality of the first substrates  310  and separating the plurality of the first substrates  310  from one another. Since a method of separating the first substrates  310  is the same as generally known separation methods, a detailed description thereof will be omitted. 
     As described above, the method of manufacturing the display device according to the present embodiment allows complete attachment between the upper and lower films  340  and  350  at the edges of the first substrate  310 , thereby improving the adhesive force therebetween. 
     The method also eliminates a portion where the upper film  340  is not attached to the lower film  350  due to the thickness of the first substrate  310  to thereby prevent movement of the first substrate  310  and allow transfer of the EML onto a precise location on the pixel-defining layer  329 . 
     In particular, the display device thus manufactured includes the precise EML transfer, thereby providing increased brightness and reproducibility. 
     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.