Abstract:
A flat display panel is constructed in such a manner that weak impact resistance of a substrate, due to a step difference present on the flat display panel, is prevented. The flat display panel includes: a substrate; a facing member bonded to the substrate, and having a surface area smaller than that of the substrate; a display unit disposed between the substrate and the facing member; a bonding unit which bonds the substrate and the facing member, and which is interposed between the substrate and the facing member along outer sides of the display unit; and a buffer member included on outer sides of the bonding unit of the substrate.

Description:
CLAIM OF PRIORITY  
       [0001]     This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application filed in the Korean Intellectual Property Office on Sep. 8, 2004 and there duly assigned Serial No. 10-2004-0071589.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Technical Field  
         [0003]     The present invention relates to a flat display panel and a flat panel display device having the same and, more particularly, to a flat display panel in which the weak impact resistance of a substrate due to a step difference can be compensated, and a flat panel display device having the same.  
         [0004]     2. Related Art  
         [0005]     Flat panel display devices display images on a flat substrate such as a liquid crystal display (LCD) device, an organic light emitting display (OLED) device, or an inorganic light emitting device.  
         [0006]     A flat panel display device is generally composed of a pair of substrates, edge parts of which are bonded to each other, and a pad unit having a plurality of terminals and exposed outwardly. Internal circuits of the flat panel display device are connected to external electronic devices through the terminals in the pad unit, the terminals being bonded to a flexible printed circuit board (PCB).  
         [0007]     The sizes of the two substrates must be different since the pad unit is formed on one of the two substrates. Therefore, a predetermined step difference is present on portions corresponding to the pad unit on the flat display panel.  
         [0008]     The substrate on which the pad unit is formed is supported by a support member such as a bracket. When the substrate on which the pad unit is not formed is also supported by the support member, a predetermined space between the support member and this substrate is present due to a step difference on portions on the other substrate where the pad unit is located.  
         [0009]     The portions of the substrate located in correspondence to the predetermined space have a low resistance to an external impact.  
         [0010]     The portions of the substrate on which step differences are formed, besides the portions on which the pad unit are formed, also have a low resistance to an external impact.  
       SUMMARY OF THE INVENTION  
       [0011]     The present invention provides a flat panel display device in which a weak impact resistance of a substrate, due to a step differences formed on a flat display panel, can be prevented.  
         [0012]     According to an aspect of the present invention, there is provided a flat display panel comprising: a substrate; a facing member bonded to the substrate, and having a smaller surface area than the substrate; a display unit disposed between the substrate and the facing member; a bonding unit which bonds the substrate and the facing member, and which is interposed between the substrate and the facing member along outer sides of the display unit; and a buffer member included on outer sides of the bonding unit of the substrate.  
         [0013]     According to an aspect of the present invention, there is provided a flat display panel comprising: a pair of substrates, the surface areas of which are different, the substrates being bonded to face each other; a display unit disposed between the substrates; a bonding unit which bonds the pair of substrates, and which is disposed on an outer side of the display unit; and a planarizing member which approximately planarizes at least a portion of the step difference resulting from the surface area difference of the substrates, and which is disposed on an outer side of the bonding unit.  
         [0014]     According to an aspect of the present invention, there is provided a flat display device comprising: a flat display panel which displays predetermined images, and which has at least a step difference; a support member which supports the flat display panel; and a buffer member interposed between the support member and at least a step difference of the flat display panel. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     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:  
         [0016]      FIG. 1  is an exploded perspective view of an OLED device used as a flat panel display device according to a first embodiment of the present invention;  
         [0017]      FIG. 2  is a cross-sectional view of a panel of the OLED device of  FIG. 1 ;  
         [0018]      FIG. 3  is a cross-sectional view taken along line I-I of  FIG. 1 ;  
         [0019]      FIG. 4  is a plan view of the panel of  FIG. 2 ;  
         [0020]      FIG. 5  is a cross-sectional view of an example of the OLED device of  FIG. 1 ;  
         [0021]      FIG. 6  is a cross-sectional view of another example of the OLED device of  FIG. 1 ;  
         [0022]      FIG. 7  is a cross-sectional view of a flat display panel according to a second embodiment of the present invention;  
         [0023]      FIG. 8  is a cross-sectional view of a flat display panel according to a third embodiment of the present invention; and  
         [0024]      FIG. 9  is a cross-sectional view of a flat display panel according to a fourth embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0025]     The present invention will now be described more fully with reference to the accompanying drawings in which exemplary embodiments of the invention are shown.  
         [0026]      FIG. 1  is an exploded perspective view of an OLED device used as a flat panel display device according to a first embodiment of the present invention;  FIG. 2  is a cross-sectional view of a panel of the OLED device of  FIG. 1 ;  FIG. 3  is a cross-sectional view taken along line I-I of  FIG. 1 ;  FIG. 4  is a plan view of the panel of  FIG. 2 ;  FIG. 5  is a cross-sectional view of an example of the OLED device of  FIG. 1 ; and  FIG. 6  is a cross-sectional view of another example of the OLED device of  FIG. 1 .  
         [0027]     Referring to FIGS.  1  thru  4 , an organic light emitting display (OLED) device includes an organic light emitting unit  3  (see  FIGS. 3, 5 , and  6 ) which includes an organic light emitting element and a facing member  4  which seals the organic light emitting unit  3  on a substrate  2 .  
         [0028]     The substrate can be a transparent glass material, such as acryl, polyimide, polycarbonate, polyester, mylar, or other plastic materials.  
         [0029]     The organic light emitting unit  3  for displaying predetermined images is formed on the substrate  2  and has an organic light emitting element.  
         [0030]     The organic light emitting element included in the organic light emitting unit  3  can be formed in various configurations, that is, it can be a passive matrix (PM) type organic light emitting element (i.e., a simple matrix type) or an active matrix type organic light emitting element which includes a TFT layer.  
         [0031]     Referring to  FIG. 5 , a buffer layer  21  formed of SiO2, a first electrode layer  31  in a predetermined form, an organic layer  33 , and a second electrode layer  34  are sequentially formed on the substrate  2 . An insulating layer  32  can be interposed between the first electrode layers  31 , and the second electrode layer  34  can be patterned so as to have a pattern perpendicular to the pattern of the first electrode layer  31 . Although it is not shown in  FIG. 5 , an additional insulating layer perpendicular to the first electrode layer  31  can be included for the purpose of patterning the second electrode layer  34 .  
         [0032]     The organic layer  33  can be a low molecular weight organic layer or a polymer layer. When the organic layer  33  is a low molecular weight film, the organic layer  33  may be a Hole Injection Layer (HIL), a Hole Transport Layer (HTL), an Emission Layer (EML), an Electron Transport Layer (ETL), an Electron Injection Layer (EIL), or a combination of these layers, and can be composed of copper phthalocyanine (CuPc), N,N′-Di(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB), or tris-8-hydroxyquinoline aluminum (Alq3). The low molecular weight organic film can be formed using an evaporation method.  
         [0033]     If the organic layer  33  is a polymer organic film, the organic layer  33  can be an HTL or an EML. The HTL can be formed of poly-(2,4)-ethylene-dihydroxy thiophene (PEDOT), and the EML can be formed of Poly-Phenylenevinylene (PPV), Soluble PPV&#39;s, Cyano-PPV, or Polyfluorene, and can be formed using screen printing or inkjet printing.  
         [0034]     The first electrode layer  31  functions as an anode and the second electrode layer  34  functions as a cathode. Of course, the polarity of the first and second electrode layers can be reversed.  
         [0035]     The first electrode layer  31  can be used as a transparent electrode or as a reflection electrode. When the first electrode layer  31  is used as a transparent electrode, the first electrode layer  31  can be formed of ITO, IZO, ZnO or In 2 O 3 .  
         [0036]     When the first electrode layer  31  is used as a reflection electrode, the first electrode layer  31  can be formed of ITO, IZO, ZnO or In 2 O 3  on a reflection film after forming the reflection film using Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, or a compound of these metals.  
         [0037]     The second electrode layer  34  can also be used as a transparent electrode or a reflection electrode. When the second electrode layer  34  is used as a transparent electrode, an auxiliary electrode layer or a bus electrode line formed of the same material as the transparent electrode, such as ITO, IZO, ZnO or In 2 O 3 , can be included on a material layer after depositing the material layer formed of a metal having a low work function, such as Li, Ca, LiF/Ca, LiF/Al, Al, Ag, Mg, or a compound of these metals, so as to face the organic layer  33  since the second electrode layer  34  is used as the cathode. When the second electrode layer  34  is used as a reflection electrode, the second electrode layer  34  is formed by entirely depositing Li, Ca, LiF/Ca, LiF/Al, Al, Ag, Mg, or a compound of these metals.  
         [0038]      FIG. 6  is a cross-sectional view of another example of the OLED device of  FIG. 1 , and specifically, an AM type organic light emitting unit. Each of the pixels in the organic light emitting unit  3  has a TFT structure, as depicted in  FIG. 6 , and an organic light emitting element which is a light emission element.  
         [0039]     The present invention is not limited to the structure of the TFT depicted in  FIG. 6 . The AM type organic light emitting unit of  FIG. 6  will now be described in detail.  
         [0040]     Referring to  FIG. 6 , a buffer layer  21  formed of SiO 2  is disposed on a glass substrate  2 , and a TFT having the above-described structure is disposed on a buffer layer  21 .  
         [0041]     The TFT comprises an active layer  22 , a gate insulating film  23 , and a gate electrode  24  sequentially formed on the buffer layer  21 .  
         [0042]     The active layer  22  can be formed of an amorphous silicon thin film or a poly silicon thin film, but it is not limited thereto. An organic semiconductor layer can also be used. The semiconductor active layer has source and drain regions which are highly doped with an N type or P type dopant.  
         [0043]     The gate insulating film  23 , formed of SiO 2 , is disposed on the active layer  22 , and the gate electrode  24 , which is a conductive film formed of MoW or Al/Cu, is formed on a predetermined region of the gate insulating film  23 . The gate electrode  24  is connected to a gate line that applies an ON/OFF signal to the TFT. The region on which the gate electrode  24  is formed corresponds to a channel region of the active layer  22 .  
         [0044]     An inter-insulator  25  is formed on the gate insulating film  23 , and a source electrode  26  and a drain electrode  27  are each formed so as to contact the source and drain regions, respectively, of the active layer  22  through contact holes.  
         [0045]     A passivation film  28 , formed of SiO 2 , is formed on the source electrode  26  and drain electrode  27 , and a planarizing film  29  formed of acryl or polyimide is formed on the passivation film  28 .  
         [0046]     Although not shown in the drawing, at least one capacitor is connected to the TFT. A circuit which includes the TFT is not limited to the circuit depicted in  FIG. 6 .  
         [0047]     The drain electrode  27  is connected to the first electrode layer  31 , which functions as the anode of an organic light emitting element. The first electrode layer  31  is formed on the passivation film  28 , and a pixel defining film  29 , which is an insulating film, is formed on the passivation film  28 . The organic light emitting element of  FIG. 6  is formed after forming a predetermined opening in the pixel defining film  29 .  
         [0048]     The organic light emitting element displays predetermined image information by generating lights of red, green, and blue colors according to a current flow, and comprises a first electrode layer  31  which receives positive power from the drain electrode  27 , a second electrode layer  34  which covers all pixels and which supplies negative power to the pixels, and an organic layer  33  which generates light and which is disposed between the first electrode layer  31  and the second electrode layer  34 .  
         [0049]     The material for forming the first electrode layer  31  and the first electrode layer  31  can be the same as the material for forming the PM organic light emitting unit.  
         [0050]     As described above, the organic light emitting unit  3  formed on the substrate  2  is sealed by a facing member  4 , as depicted in  FIG. 3 . The facing member  4  can be formed of glass or plastic material as is the substrate  2 , and can also be formed of a metal cap.  
         [0051]     The substrate  2  and the facing member  4  are bonded by a sealant  51 . The sealant  51  is coated on edges of the facing member  4  on an outer side of the organic light emitting unit  3 , and, as depicted in  FIGS. 1 through 4 , the facing member  4  on which the sealant  51  is coated is bonded to the substrate  2 . The portion on which the sealant  51  is formed forms a bonding portion which bonds the substrate  2  and the facing member  4 .  
         [0052]     As depicted in  FIGS. 2 through 4 , a pad unit  61  exposed to an outer side of the facing member  4  is disposed at least on an edge of the substrate  2 . A plurality of terminals (not shown) is disposed in the pad unit  61 , and a flexible PCB  6  is connected to the terminals.  
         [0053]     In the present invention, the weak impact resistance of the substrate  2  at portions where step differences are present is compensated by attaching a buffer member  7  on these portions. That is, as depicted in  FIGS. 2 and 3 , a space between the substrate  2  and the support member  8  is filled by attaching the buffer member  7  to the flexible PCB  6  when the support member  8  is mounted on the panel  1  so as to face the facing member  4 , thereby compensating for the weak impact resistance of the substrate  2 .  
         [0054]     As depicted in  FIG. 4 , the buffer member  7  may be formed so as to cover the entire surface of the pad unit  61 , and the thickness of the buffer member  7  may be greater than the sum of the thicknesses of the facing member  4  and the sealant  51 . This is for the purpose of making the buffer member  7  contact the support member  8  closely when the panel  1  is mounted on the support member  8 .  
         [0055]     The buffer member  7  can be made of any material as long as it can support the substrate  2  when it is disposed as shown in the  FIG. 3 . The buffer member  7  can be a material that can absorb an impact, such as a polymer, but is not limited thereto, and can also be silicon or a metal.  
         [0056]     As depicted in  FIG. 2 , the entire surface of the panel  1  can be planarized by the buffer member  7 . Therefore, the buffer member  7 , as depicted in  FIG. 7 , can be attached to a portion where the step difference is formed besides attaching it to the portion where the pad unit  61  is formed, as depicted in  FIGS. 1 through 4 .  
         [0057]     Also, as depicted in  FIG. 8 , the buffer member  7  can be attached to a portion corresponding to the support member  8 .  
         [0058]     In addition, the buffer member  7  can be formed in a particular shape as described in the above embodiments, but the present invention is not limited thereto, and can be formed of a coating material.  
         [0059]     That is, as depicted in  FIG. 9 , if the facing member  4  which seals the organic light emitting unit  3  is in a film shape, the buffer member  7  can be coated on an edge portion of the facing member  4  by plating.  
         [0060]     The embodiments of the present invention are not limited to organic light emitting display devices, but they can be applied to various display devices, such as LCD devices, inorganic light emitting display devices, and electron emission display devices.  
         [0061]     The panel according to the present invention improves the impact resistance of the panel since the step difference formed in the flat display panel is removed.  
         [0062]     Also, the panel can be safely supported when the panel is bonded to a support member, like a bracket.  
         [0063]     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 detail may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.