Abstract:
An organic light emitting diode display includes a panel assembly for displaying an image and a first surface stress enhancing member arranged on a rear surface of the panel assembly. In one embodiment, the organic light emitting diode display includes a second surface stress enhancing member arranged on a front surface of the panel assembly. In anther embodiment, the organic light emitting diode display includes a lower bezel arranged on a rear surface of the first surface stress enhancing member and a shock absorption tape arranged between the first surface stress enhancing member and the lower bezel. The structure of the organic light emitting diode display efficiently prevents damages caused by an external impact.

Description:
CLAIM OF PRIORITY 
     This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application earlier filed in the Korean Intellectual Property Office on 17 Apr. 2008 and there duly assigned Serial No. 10-2008-0035634. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present disclosure relates to an organic light emitting diode (OLED) display. More particularly, the present disclosure relates to an OLED display that has improved mechanical strength against an external impact. 
     2. Description of the Related Art 
     Generally, a typical OLED display includes a panel assembly in which a plurality of OLEDs are formed, a bezel coupled to the panel assembly at a rear side of the panel assembly, and a printed circuit board (PCB) that is electrically connected to the panel assembly by a flexible printed circuit board (FPCB). 
     Unlike the LCD including a panel assembly having two thin substrates and liquid crystal filled in a space defined between these substrates, the OLED display is designed such that empty spaces exist in an inside of the panel assembly. Therefore, a mechanical strength of the OLED display is not sufficient. 
     Particularly, only the bezel functions to protect the panel assembly. That is, the conventional OLED display does not have a shock absorption member for absorbing an external impact. Therefore, when a user drops an electronic device that is equipped with an OLED display, a large twisting load and a large bending load are suddenly applied to the bezel and thus the bezel is deformed. As a result, the twisting and bending loads are directly transferred to the panel assembly coupled to the bezel and thus the panel assembly may be easily damaged. 
     The above information disclosed in this background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY OF THE INVENTION 
     Embodiments of the present disclosure provide an OLED display that is configured to increase mechanical strength against an external impact. 
     In an exemplary embodiment of the present disclosure, an organic light emitting diode display includes a panel assembly and a first surface stress enhancing member arranged on a rear surface of the panel assembly. The panel assembly includes a display region for displaying an image and a pad region. The display region includes a plurality of organic light emitting diodes for emitting light. 
     The organic light emitting diode display may further include a shock absorption tape arranged on a rear surface of the first surface stress enhancing member. 
     The shock absorption tape may include a shock absorption layer and an adhesive layer arranged on a surface of the shock absorption layer. The shock absorption layer may include a sponge or urethane. 
     The organic light emitting diode display may further include a second surface stress enhancing member arranged on a front surface of the panel assembly and a polarizing plate arranged on a front surface of the second surface stress enhancing member. 
     The organic light emitting diode display may further include a lower bezel arranged on the rear surface of the first surface stress enhancing member and a double-sided adhesive tape arranged between the first surface stress enhancing member and the lower bezel. 
     Alternatively, the organic light emitting diode display may further include a lower bezel arranged on a rear surface of the first surface stress enhancing member and a shock absorption tape arranged between the first surface stress enhancing member and the lower bezel. 
     The organic light emitting diode display may further include a second surface stress enhancing member arranged on a front surface of the panel assembly and a polarizing plate arranged on a front surface of the second surface stress enhancing member. 
     The lower bezel includes a bottom portion covering the rear surface of the first surface stress enhancing member and a sidewall located at edge portions of the bottom portion except for an edge portion corresponding to the pad region. 
     The organic light emitting diode display may further include an upper bezel arranged in a front surface of the panel assembly. The upper bezel may cover the pad region and be provided with an opening exposing the display region. The lower and upper bezels may be formed of metal or synthetic resin. 
     Each of the first and second surface stress enhancing members may include a hard coating layer and a pressure sensitive adhesive layer arranged on a surface of the hard coating layer. 
     According to the organic light emitting diode display of the exemplary embodiments, since the surface stress enhancing members are provided on the front and/or rear surface of the panel assembly, the impact resistance of the panel assembly is enhanced and thus the damage of the panel assembly can be prevented. In addition, the mechanical strength of the organic light emitting diode display is enhanced and thus the drop impact resistance can be further enhanced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein: 
         FIG. 1  is an exploded perspective view of an OLED display according to a first exemplary embodiment of the present disclosure. 
         FIG. 2  is a perspective view of the OLED display of  FIG. 1  when it is assembled. 
         FIG. 3  is a cross-sectional view taken along line III-III of  FIG. 2 . 
         FIG. 4  is a schematic view of a sub-pixel circuit of a panel assembly depicted in  FIG. 1 . 
         FIG. 5  is a partially enlarged cross-sectional view of a panel assembly depicted in  FIG. 1 . 
         FIG. 6  is a cross-sectional view of a surface stress enhancing member of the OLED display of  FIG. 1 . 
         FIG. 7  is a schematic view of a drop jig used in a drop impact resistance test. 
         FIG. 8  is a cross-sectional view of an OLED display according to a second exemplary embodiment of the present disclosure. 
         FIG. 9  is a partially enlarged perspective view of a shock absorbing tape of the OLED display of  FIG. 8 . 
         FIG. 10  is an exploded perspective view of an OLED display according to a third exemplary embodiment of the present disclosure. 
         FIG. 11  is a cross-sectional view of the OLED display of  FIG. 10 . 
         FIG. 12  is an exploded perspective view of an OLED display according to a fourth exemplary embodiment of the present disclosure. 
         FIG. 13  is a cross-sectional view of the OLED display of  FIG. 12 . 
         FIG. 14  is a cross-sectional view of an OLED display according to a fifth exemplary embodiment of the present disclosure. 
         FIG. 15  is a cross-sectional view of an OLED display according to a sixth exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The present disclosure will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present disclosure. 
       FIG. 1  is an exploded perspective view of an OLED display according to a first exemplary embodiment of the present disclosure,  FIG. 2  is a perspective view of the OLED display of  FIG. 1 , and  FIG. 3  is a cross-sectional view taken along line III-III of  FIG. 2 . 
     Referring to  FIGS. 1 to 3 , an OLED display  101  of the present exemplary embodiment includes a panel assembly  20  having a display region A 10  and a pad region A 20 , a bezel  40  coupled to the panel assembly  20  at a rear side of the panel assembly  20 , and a printed circuit board  36  electrically connected to the panel assembly  20  via a flexible printed circuit board  32 . Images are displayed on the display region A 10  of the panel assembly  20 . 
     The panel assembly  20  includes a first substrate  12  and a second substrate  14  that is smaller than the first substrate  12  and has a peripheral portion coupled to the first substrate  12  by a sealant. 
     The display region A 10  is defined at a portion of an overlapping region of the first and second substrates  12  and  14 , which is surrounded by the sealant. The pad region A 20  is defined at an outside of the sealant. A plurality of sub-pixels is disposed in a matrix pattern at the display region A 10  of the first substrate  12 . Scan and data drivers (not shown) for driving the sub-pixels are located between the display region A 10  and the sealant, or at the outside of the sealant. Pads (not shown) for transferring electrical signals to the scan and data drivers are located at the pad region A 20  of the first substrate  12 . 
       FIG. 4  is a circuit diagram of a sub-pixel circuit of a panel assembly depicted in  FIG. 1 , and  FIG. 5  is a partly enlarged cross-sectional view illustrating an internal structure of a panel assembly depicted in  FIG. 1 . 
     Referring to  FIGS. 4 and 5 , each of the sub-pixels of the panel assembly  20  includes an OLED L 1  and a driving circuit unit. The OLED L 1  includes an anode electrode  16 , an organic light emitting layer  18 , and a cathode electrode  22 . The driving circuit unit includes at least two thin film transistors and at least one storage capacitor C 1 . 
     The thin film transistors include at least one switching transistor T 1  and at least one driving transistor T 2 . The switching transistor T 1  is connected to scan and data lines SL 1  and DL 1  to transfer a data voltage, which is input from the data line DL 1  in accordance with a switching voltage input to the scan line SL 1 , to the driving transistor T 2 . 
     The storage capacitor C 1  is connected to a voltage line VDD as well as to the switching transistor T 1  to store a voltage corresponding to a difference between a voltage received from the switching transistor T 1  and a voltage supplied to the power line VDD. 
     The driving transistor T 2  is connected to both of the power line VDD and the storage capacitor C 1  to supply an output current I OLED , which corresponds to a square of a difference between a voltage stored in the storage capacitor C 1  and a threshold voltage, to the OLED L 1  so that the OLED L 1  can emit light activated by the output voltage I OLED . The driving transistor T 2  includes a source electrode  24 , a drain electrode  26 , and a gate electrode  28 . The anode electrode  16  of the OLED L 1  is connected to the drain electrode  26  of the driving transistor T 2 . It should be construed that the above-described structure of the sub-pixels is exemplified only and may be variously modified. 
     The second substrate  14  is coupled to the first substrate  12  by the sealant at a predetermined interval to protect the driving circuit unit and the OLEDs on the first substrate  12  from an external environment. The second substrate  14  may be an upper substrate of the panel assembly  20 . A moisture absorption agent may be applied on an inner surface of the second substrate  14 . 
     Referring again to  FIGS. 1 to 3 , an integrated circuit chip  30  is mounted at the pad region A 20  of the panel assembly  20  through a chip-on-glass (COG) method. The flexible printed circuit board  32  is mounted at the pad region A 20  of the panel assembly  20  through a chip-on-film (COF) method. 
     A protective layer  34  is formed around the integrated circuit chip  30  and the flexible printed circuit board  32  to cover and protect pads formed at the pad region A 20 . A variety of electronic elements (not shown) for processing driving signals are mounted on the printed circuit board  36 , and a connector  38  for transferring external signals to the printed circuit board  36  is also installed on the printed circuit board  36 . The printed circuit board  32  fixed at the pad region A 20  is folded toward a rear surface of the bezel  40  to face the rear surface of the bezel  40 . 
     The bezel  40  includes a bottom portion  42 , on which the panel assembly  20  is disposed, and sidewalls  44 , which extend from side edges except a side edge at which the flexible printed circuit board  32  is bent. The sidewalls  44  extend toward the panel assembly  20  to partially cover a side surface of the panel assembly  20 . 
     A double-sided adhesive tape  46  is disposed between the bottom portion  42  of the bezel  40  and the panel assembly  20  to fix the panel assembly  20  to the bezel  40 . 
     It should be understood that the above described structure of the bezel is exemplified only and may be variously modified. For example, a flange (not shown) for enhancing strength may be formed on the edge of the bottom portion  42 , at which the flexible printed circuit board  32  is bent. 
     The bezel  40  may be formed of metal having excellent strength and rigidity, such as stainless steel, cold rolled steel, aluminum, an aluminum alloy, a nickel alloy, and the like. Alternatively, the bezel  40  can be formed of a synthetic resin having excellent impact absorption/dispersion properties. For example, the bezel  40  may be formed of a polymer-based engineering plastic such as polycarbonate. 
     A surface stress enhancing member  48  for preventing the damage of the panel assembly  20  by an external impact is provided on a rear surface of the panel assembly  20  facing the bezel  40 . The surface stress enhancing member  48  is attached on an outer surface of the first substrate  12  of the panel assembly  20  by a double-sided adhesive tape. 
     The panel assembly includes two glass substrates (the first and second substrates  12  and  14 ). When an external impact is applied to the glass substrate, compression force acts on the surface of the glass substrate and tension acts in the glass substrate, thereby breaking the glass substrate. When a user drops an electronic device having the OLED display  101 , the external impact is transferred to the panel assembly  20  via the bezel  40 . At this point, the surface stress enhancing member  48  disposed between the panel assembly  20  and the bezel  40  enhances the surface stress of the first substrate  12  to suppress the tension of the first substrate  12  that is generated by the external impact. Therefore, the damage of the first substrate  12  can be prevented. That is, since the surface stress enhancing member  48  enhances the impact-resistance of the panel assembly  20 , the damage of the panel assembly  20  by the external impact can be prevented. 
       FIG. 6  illustrates the surface stress enhancing member in more detail. Referring to  FIG. 6 , the surface stress enhancing member  48  includes a hard coating layer  50 , a pressure sensitive adhesive (PSA) layer  52  arranged on a surface of the hard coating layer  50 , and a release liner  54  arranged on a surface of the PSA layer  52 . 
     During manufacturing of the OLED display, the surface stress enhancing member  48  may be coupled to the panel assembly  20  by attaching the PSA layer  52  to an outer surface of the first substrate  12  in a state where the release liner  54  is removed from the PSA layer  52 . 
     In the present exemplary embodiment, properties of the surface stress enhancing member  48  are as shown in the following table. 
                                                 Tensile strength (N/25 mm)   240           Elongation (%)   120           Transmittance of ultraviolet (UV) rays (%)   &lt;1           Transmittance (%)   89           Exterior transmittance (%)   82           Exterior reflectance (%)   8           Exterior absorption rate (%)   10           Adhesion (N/25 mm)   12                        
Here, the tensile strength may be about 200 to 300 N/25 mm and the adhesion may be about 10 to 20 N/25 mm. The surface stress enhancing member  48  including the hard coating layer  50  and the PSA layer  52  can prevent damage of the panel assembly  20  while maintaining a thickness of 0.075 to 0.15 mm.
 
     In addition, by increasing the thickness of the surface stress enhancing member  48  or forming each of the hard coating layer  50  and the PSA layer  52  with two layers stacked on one another, the shock absorption effect can be maximized. Here, a total thickness of the surface stress enhancing member  48  including a thickness of the double-sided adhesive tape  46  is about 0.11 to 0.19 mm, which does not affect the slimness of the OLED display  101 . 
     The strength of the panel assembly  20  against an external impact is further enhanced by the surface stress enhancing member  48 . This will be described in more detail hereinafter. 
     The inventor of the present application made an OLED display of Comparative Example 1 in which a double-sided adhesive tape is located between a 60.96-mm (2.4-inch) panel assembly and a bezel, an OLED display of Comparative Example 2 in which an adhesive shock absorption tape is located between a panel assembly and a bezel, and an OLED display of Example 1 in which a surface stress enhancing member and a double-sided adhesive tape are located between a panel assembly and a bezel. 
     In Comparative Example 1, thickness of the double-sided adhesive tape was 0.05 mm, in Comparative Example 2, thickness of the adhesive shock absorption tape was 0.26 mm, and in Example 1, thicknesses of the surface stress enhancing member and the double-sided adhesive tape were respectively 0.75 mm and 0.05 mm. 
     The OLED displays of Comparative Examples 1 and 2 and the OLED display of Example 1 were mounted in drop jigs and a series of drop impact resistance tests were performed by dropping the jigs from a height of 1.8 m to determine if the OLEDs were damaged. 
       FIG. 7  is a schematic view of a drop jig used in a drop impact resistance test. Referring to  FIG. 7 , the drop jig  56  includes an upper case  58  and a lower case  60  that are coupled to each other by screws. The OLED display is mounted in a space defined by the upper and lower cases  58  and  60  of the drop jig  56 . The drop jig  56  was dropped in the first through sixth directions indicated by six arrows corresponding to respective sides of the hexahedron drop jig  56 . Four test samples were prepared for each of the OLED displays of Comparative Examples 1 and 2 and the OLED display of Example 1. The drop impact resistance test was performed 3 times (3 times for each of the six directions) for each of the OLED displays. 
     The following Table 1 shows test results evaluated by total points and average points for the OLED displays of Comparative Examples 1 and 2 and the OLED display of Example 1. The drop impact resistance points were calculated by giving 1 point when the panel assembly is not damage and by giving 0 points when the panel assembly is damaged. 
     
       
         
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
             
             
               
                   
                   
               
               
                   
                 Drop impact resistance point 
                   
               
             
          
           
               
                   
                 Sample 
                 Sample 
                 Sample 
                 Sample 
                 Total 
                 Average 
               
               
                   
                 1 
                 2 
                 3 
                 3 
                 point 
                 point 
               
               
                   
                   
               
             
          
           
               
                 Comparative 
                 7 
                 7 
                 5 
                 1 
                 20 
                 5 
               
               
                 Example 1 
               
               
                 (double-sided 
               
               
                 adhesive tape) 
               
               
                 Comparative 
                 7 
                 10 
                 10 
                 1 
                 28 
                 7 
               
               
                 Example 2 
               
               
                 (Shock 
               
               
                 absorption tape) 
               
               
                 Example 1 
                 15 
                 3 
                 18 
                 4 
                 40 
                 10 
               
               
                 (surface stress 
               
               
                 enhancing 
               
               
                 member and 
               
               
                 double-sided 
               
               
                 adhesive tape) 
               
               
                   
               
             
          
         
       
     
     As shown in Table 1, the OLED display of Example 1 having the surface stress enhancing member and the double-sided adhesive tape that are disposed between the panel assembly and the bezel have a higher drop impact resistance point than the OLEDs of Comparative Examples 1 and 2. This indicates that the OLED display of Example 1 has a better mechanical property against drop impact than the OLEDs of Comparative Examples 1 and 2. 
     In addition, the inventor of the present disclosure prepared electronic devices each having an OLED display of Comparative Examples 3, 4, and 5 in which only a double-sided adhesive tape was located between a 55.88-mm (2.2-inch) panel assembly and a bezel and an electronic device having an OLED display of Example 2 in which a surface stress enhancing member and a double-sided adhesive tape were located between a panel assembly and a bezel. 
     Properties of the OLED displays of Comparative Examples 3, 4, and 5 and properties of the OLED display of Example 2 are illustrated in the following Table 2. For reference, the reference character “g” in  FIG. 3  indicates a distance between a top surface of the second substrate  14  and an upper end of the bezel  44 . 
     
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                   
                 Distance 
                   
                   
               
               
                   
                   
                   
                 between top 
               
               
                   
                   
                   
                 surface of 
                   
                 Thickness of 
               
               
                   
                   
                 Thickness of 
                 second 
                 Thickness of 
                 surface stress 
               
               
                   
                 Thickness of 
                 second 
                 substrate and 
                 double-sided 
                 enhancing 
               
               
                   
                 first substrate 
                 substrate 
                 upper end of 
                 adhesive tape 
                 member 
               
               
                   
                 (mm) 
                 (mm) 
                 bezel (mm) 
                 (mm) 
                 (mm) 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Comparative 
                 0.4 
                 0.4 
                 0.1 
                 0.05 
                 0 
               
               
                 Example 3 
               
               
                 Comparative 
                 0.5 
                 0.5 
                 0.1 
                 0.05 
                 0 
               
               
                 Example 4 
               
               
                 Comparative 
                 0.5 
                 0.5 
                 0 
                 0.05 
                 0 
               
               
                 Example 5 
               
               
                 Example 2 
                 0.4 
                 0.4 
                 0.03 
                 0.05 
                 0.07 
               
               
                   
               
             
          
         
       
     
     Four test samples were prepared for each of the electronic devices having the OLED displays of Comparative Examples 3, 4, and 5 and the electronic device having the OLED display of Example 2. The drop impact resistance test was performed by dropping the samples from heights of 1.2 m and 1 m. The following Table 3 illustrates the test results. 
     
       
         
               
               
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                 Dropping 
                 Comparative 
                 Comparative 
                 Comparative 
                   
               
               
                 height 
                 Example 3 
                 Example 4 
                 Example 5 
                 Example 2 
               
               
                   
               
             
             
               
                 1.2 m 
                 Two of four 
                 Three of four 
                 Two of four 
                 No sample 
               
               
                   
                 samples were 
                 samples were 
                 samples were 
                 was 
               
               
                   
                 damaged 
                 damaged 
                 damaged 
                 damaged 
               
               
                   1 m 
                 No sample was 
                 Three of four 
                 One of four 
                 No sample 
               
               
                   
                 damaged 
                 samples were 
                 samples was 
                 was 
               
               
                   
                   
                 damaged 
                 damaged 
                 damaged 
               
               
                   
               
             
          
         
       
     
     As illustrated in Table 3, it can be noted that all of the four samples of Example 2 where the OLED displays have the surface stress enhancing member were not damaged. This shows that the OLED display of Example 2 has a better mechanical property than the OLED displays of Comparative Examples 3, 4, and 5. As described above, the surface stress enhancing member  48  enhances the shock absorption effect of the panel assembly  20 . Therefore, in the OLED display  101  of the present exemplary embodiment, damage of the panel assembly  20  by an external impact can be more effectively prevented. 
       FIG. 8  is a cross-sectional view of an OLED display according to a second exemplary embodiment of the present disclosure. Referring to  FIG. 8 , an OLED display of a second exemplary embodiment is the same as the OLED display of the first exemplary embodiment except that an adhesive shock absorption tape is used instead of the double-sided adhesive tape. In the first and second exemplary embodiments, like reference numerals are used to refer to like parts. 
     The shock absorption tape  62 , as shown in  FIG. 9 , includes a shock absorption layer  64  having a shock absorption function, a pair of adhesive layers  66  formed on front and rear surfaces of the shock absorption layer  64 , and release liners  68  located on outer surfaces of the adhesive layers  66 . The release liners  68  are removed later so that one of the adhesive layers  66  is attached on the surface stress enhancing member  48  and the other of the adhesive layers  66  is attached on a bottom portion  42  of a bezel  40 . The shock absorption layer  64  may include a sponge or urethane. The shock absorption tape  62  is thicker than the double-sided adhesive layer of the first exemplary embodiment. 
     In the present exemplary embodiment, as the OLED display  102  includes both the surface stress enhancing member  48  and the shock absorption tape  62 , the impact resistance thereof is further enhanced, and damage by an external impact can be minimized. 
       FIGS. 10 and 11  illustrate an OLED display according to a third exemplary embodiment of the present disclosure. Referring to  FIGS. 10 and 11 , an OLED display  103  of the present exemplary embodiment includes a first surface stress enhancing member  48  located on a rear surface of a panel assembly  20  and a second surface stress enhancing member  70  located on a front surface of the panel assembly  20 . 
     A double-sided adhesive tape or a shock absorption tape may be located between the first surface stress enhancing member  48  and a bezel  40 . In  FIGS. 10 and 11 , the double-sided adhesive tape  46  is exemplarily located between the first surface stress enhancing member  48  and the bezel  40 . 
     The second surface stress enhancing member  70  is attached on an outer surface of the second substrate  14 . As the surface stress of the second substrate  14  is enhanced, the tensile force of the second substrate  14 , which is generated when the external force is applied, is suppressed, and thus the damage of the second substrate  14  can be prevented. The internal structure of the second surface stress enhancing member  70  is the same as that of the first surface stress enhancing member  48  described in the first exemplary embodiment. 
     Meanwhile, a polarizing plate  72  may be located on a front surface of the second surface stress enhancing member  70 . The polarizing plate  72  polarizes incident light from an external side and functions to suppress a phenomenon that the polarized light is reflected in the OLED display and is subsequently transmits to the external side. Therefore, the OLED display  103  having the polarizing plate  72  prevents the reflection of the external light, thereby improving a visual perception. 
       FIGS. 12 and 13  illustrate an OLED display according to a fourth exemplary embodiment of the present disclosure. Referring to  FIGS. 12 and 13 , an OLED display  104  of the present exemplary embodiment includes a lower bezel  40  arranged on a rear surface of a panel assembly  20  and an upper bezel  74  arranged on a front surface of the panel assembly  20 . That is, the present exemplary embodiment is identical to the first through third exemplary embodiments except that the present exemplary embodiment further includes the upper bezel  74 .  FIGS. 12 and 13  show a structure that is exemplarily the same as that of the first exemplary embodiment except for the upper bezel  74 . 
     The upper bezel  74  is formed of a plate having a predetermined thickness. The upper bezel  74  may have the same size as the first substrate  12  of the panel assembly  20 . The bezel  74  may be formed of the same material as the lower bezel  40 . 
     The panel assembly  20  may further include a first double-sided adhesive tape located between the panel assembly  20  and the lower bezel  40 , and a second double-sided adhesive tape for attaching the bezel  74  to a front surface of the second substrate  14 . 
     The bezel  74  and the second double-sided adhesive tape  76  are respectively provided with openings  741  and  761  for exposing the display region. 
     According to the OLED display  104  of the present exemplary embodiment, since the upper bezel  74  covers and protects the pad region A 20  of the panel assembly  20 , the mechanical strength of the OLED display  104  can be further enhanced. Particularly, the mechanical strength of the pad region A 20  can be further enhanced. 
       FIG. 14  illustrates an OLED display according to a fifth exemplary embodiment of the present disclosure. Referring to  FIG. 14 , an OLED display of the present exemplary embodiment does not include a bezel but is constructed to suppress an external impact applied to the panel assembly  20  by providing a surface stress enhancing member  48  to a rear surface of the panel assembly  20 . 
     A shock absorption tape  62 ′ may be located on an outer surface of the surface stress enhancing member  20 . The shock absorption tape  62 ′ includes a shock absorption layer  64  having a shock absorption function and an adhesive layer  66  located on a surface of the shock absorption layer  64  facing the surface stress enhancing member  48 . 
       FIG. 15  illustrates an OLED display according to a sixth exemplary embodiment of the present disclosure. Referring to  FIG. 15 , an OLED display of the present exemplary embodiment does not include a bezel. The OLED display is configured to suppress an external impact applied to a panel assembly by providing a first surface stress enhancing member  48  on a panel assembly  20  and a second surface stress enhancing member  70  on a front surface of the panel assembly  20 . 
     A shock absorbing tape  62 ′ may be located on a rear surface of the first surface stress enhancing member  48 . A polarizing plate  72  may be located on a front surface of the second surface stress enhancing member  70 . 
     In the OLED displays  105  and  106  of the respective fifth and sixth exemplary embodiments, the impact resistance of the panel assembly  20  can be enhanced by the surface stress enhancing member  48  or the first and second surface stress enhancing members  48  and  70  without using the bezel. Therefore, the OLED displays  105  and  106  can be manufactured to be slimmer. 
     While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.