Abstract:
An organic electro-luminescence display device includes a thin film transistor on a first substrate, where the thin film transistor has a drain region and a common electrode connected to the drain region. An organic electro-luminescence diode resides on a second substrate, where the organic electro-luminescence diode includes a spacer covered with a diode electrode. First and second sealant materials reside at a periphery of the first and second substrates, where the first sealant material surrounds the thin film transistor and the organic electro-luminescence diode, and the second sealant material surrounds an outer perimeter of the first sealant material. The first and second substrates are bonded together, such that the common electrode of the thin film transistor contacts the diode electrode of the organic electro-luminescence diode. The bonding process is carried out by sequentially sealing the first sealant material and the second sealant material.

Description:
RELATED APPLICATION 
     The present application claims the benefit of priority under 35 U.S.C. §119 to Korean Patent Application No. 2006-060065 filed in Korea on Jun. 30, 2006, which is hereby incorporated by reference. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to an organic electro-luminescence display device, and more particularly, to an organic electro-luminescence display device, in which a first substrate and a second substrate are attached using a frit glass, and a method for fabricating the same. 
     2. Description of the Related Art 
     An organic electro-luminescence display device displays an image using light generated when pairs of electrons and holes are created in semiconductors, or carriers excited to a high-energy state return to a stable state, i.e., a ground state. Since the organic electro-luminescence display device is a self-luminous display device, no backlight is required, unlike a liquid crystal display device (LCD). Therefore, the organic electro-luminescence display device is lightweight and slim and has low power consumption, high contrast ratio, and wide viewing angle. In addition, the organic electro-luminescence display device can be driven at a low DC voltage and has a rapid response time. Since all components of the organic electro-luminescence display device are formed of solid materials, it is robust against external impact. Moreover, the organic electro-luminescence display device can be used in a wide temperature range and can be manufactured at low cost. 
     In such an organic electro-luminescence display device, an encapsulation process is performed to attach a substrate, on which array elements and organic electro-luminescent diodes are formed, to a separate encapsulation substrate. Thus, the organic electro-luminescent diodes can be protected against external moisture and oxygen. Dark spots may occur in the organic electro-luminescence display device because it is susceptible to moisture and oxygen. The occurrence of the dark spots will reduce the lifetime of the organic electro-luminescence display device and degrade its reliability in high-temperature high-humidity environment. 
     SUMMARY 
     In one embodiment, a method for fabricating an organic electro-luminescence display device includes providing a first substrate having a thin film transistor thereon. A second substrate is provide having an organic electro-luminescence diode thereon. A first sealant material is positioned around the thin film transistor and the organic electro-luminescence diode, and a second sealant material is positioned around an outer perimeter of the first sealant material. The first and second substrates are aligned such that the thin film transistor and the organic electro-luminescence diode are in close proximity and the first and second substrates are bonded together by sequentially sealing the first sealant material and the second sealant material. 
     In accordance with another embodiment, a method for fabricating an organic electro-luminescence display device includes forming a thin film transistor on a first substrate, where the thin film transistor has a drain region and a common electrode connected to the drain region. An organic electro-luminescence diode is formed on a second substrate, where the organic electro-luminescence diode includes a spacer covered with a diode electrode. A first sealant material is formed around the thin film transistor and the organic electro-luminescence diode, and a second sealant material is formed around an outer perimeter of the first sealant material. The first and second substrates are aligned, such that the common electrode of the thin film transistor and the diode electrode of the organic electro-luminescence diode form an electrical contact. The first and second substrates are bonded together by sequentially sealing the first sealant material and the second sealant material. 
     In yet another embodiment, an organic electro-luminescence display device includes a thin film transistor on a first substrate, where the thin film transistor has a drain region and a common electrode connected to the drain region. An organic electro-luminescence diode resides on a second substrate, where the organic electro-luminescence diode includes a spacer covered with a diode electrode. First and second sealant materials reside at a periphery of the first and second substrates, where the first sealant material surrounds the thin film transistor and the organic electro-luminescence diode, and the second sealant material surrounds an outer perimeter of the first sealant material. The first and second substrates are arranged, such that the common electrode of the thin film transistor contacts the diode electrode of the organic electro-luminescence diode. 
     It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is a cross-sectional view of an organic electro-luminescence display device according to an embodiment of the present invention; and 
         FIGS. 2A to 2E  are cross-sectional views illustrating a method for fabricating an organic electro-luminescence display device according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
       FIG. 1  is a cross-sectional view of an organic electro-luminescence display device according to an embodiment of the present invention. 
     Referring to  FIG. 1 , the organic electro-luminescence display device includes first and second substrates  100  and  200  and an organic electro-luminescent diode E. The first and second substrates  100  and  200  are spaced apart from each other by a predetermined distance, and the organic electro-luminescent diode E is formed between the first substrate  100  and the second substrate  200 . First and second sealants  300  and  400  are formed in the periphery of the first substrate  100  or the second substrate  200  and seal the organic electro-luminescent diode E. In addition, the first and second sealants  300  and  400  attach the first substrate  100  to the second substrate  200 . 
     The first sealant  300  is formed of ultraviolet (UV) curable resin, and the second sealant  400  is formed of frit glass having good moisture tolerance and adhesive property. Therefore, the organic electro-luminescent diode can be protected against external moisture and oxygen, thereby increasing the lifetime and reliability of the organic electro-luminescence display device. 
     The second sealant  400  is formed outside the first sealant  300 . Specifically, the second sealant  400  seals the first sealant  300  and the organic electro-luminescent diode E and attaches the first substrate  100  to the second substrate  200 . The second sealant  400  includes an organic binder as well as the frit glass. Outgassing generated during the curing process of the second sealant  400  damages an organic emission layer of the organic electro-luminescent diode. This may reduce the lifetime of the organic electro-luminescent diode and generate dark spots. 
     The first sealant  300  serves as a barrier layer that prevents the outgas generated during the curing process of the second sealant  400  from flowing into the organic electro-luminescent diode. 
     A thin film transistor (TFT) Tr is formed on the first substrate  100 , and the organic electro-luminescent diode E is formed on the second substrate  200 . 
     Specifically, a plurality of gate lines cross a plurality of data lines over the first substrate  100 . The TFT Tr is formed in a subpixel defined by the crossing of the gate lines and the data lines. The TFT Tr includes a gate electrode  101 , a semiconductor layer  102 , and source/drain electrodes  103   a  and  103   b . A gate insulating layer  110  overlies first substrate  100  and separates gate electrode  101  from semiconductor layer  102 . Characteristics of the TFT Tr can be improved by increasing a channel length of the TFT, such as an area corresponding to the source electrode  103   a  and the drain electrode  103   b . That is, the source electrode  103   a  is formed to surround the periphery of the drain electrode  103   b.    
     A passivation layer  120  is formed over the first substrate  100  where the TFT Tr is formed. A connection electrode  104  is formed on the passivation layer  120  to contact the drain electrode  103   b  of the TFT Tr. The TFT Tr is electrically connected to the organic electro-luminescent diode E through the connection electrode  104 . That is, the TFT Tr is electrically connected to a second electrode  230  of the organic electro-luminescent diode E. 
     A common voltage pad P is formed on the first substrate  100  to receive a common voltage from an external circuit and provide the received common voltage to the organic electro-luminescent diode E. The common voltage pad P includes a power electrode  111  and a power contact electrode  112 . The power electrode  111  is electrically connected to a common voltage line formed in the first substrate  100 , and the power contact electrode  112  is electrically connected to a first electrode  210  of the organic electro-luminescent diode formed on the second substrate  200 . 
     A dummy pattern  113  is formed between the power electrode  111  and the power contact electrode  112 . The dummy pattern  113  has the same height difference as that of the TFT Tr. 
     The organic electro-luminescent diode E including the first electrode  210 , an organic emission layer  220 , and the second electrode  230  is formed under the second substrate  200 . 
     The first electrode  210  is formed on the second substrate  200  using a transparent conductive material, for example, indium tin oxide (ITO), indium zinc oxide (IZO), and the like. 
     An auxiliary electrode  205  may be further formed between the second substrate  200  and the first electrode  210 . The auxiliary electrode  205  reduces the resistance of the first electrode  210 . At this point, the auxiliary electrode  205  is formed of a low-resistance metal and is mostly opaque. Therefore, the auxiliary electrode  205  is preferably formed at a region corresponding to a non-emission region. 
     The organic emission layer  220  may further include at least one of a hole injection layer (HIL), a hole transport layer (HTL), a hole blocking layer (HBL), an electron transport layer (ETL), and an electron injection layer (EIL) under or above the organic emission layer  220 . Therefore, electrons and holes can be more readily injected into the organic emission layer  220  because energy levels can be appropriately adjusted at boundaries of the first electrode  210 , the organic emission layer  220 , and the second electrode  230 . Hence, the luminous efficiency of the organic electro-luminescence display device can be significantly improved. 
     A separator  225  is disposed on a buffer layer  215  formed in the periphery of a subpixel. The second electrode  230  is automatically patterned in each subpixel by the separator  225 . In addition, the second electrode  230  is formed to surround the periphery of a first spacer  235   a  that constantly maintains a cell gap between the first substrate  100  and the second substrate  200 . Due to the first spacer  235   a,  a portion of the second electrode  230  protrudes toward the first substrate  200 . The protrusion of the second electrode  230  contacts the connection electrode  104 . 
     The organic electro-luminescence display device further includes a second spacer  235   b  having the same height as the first spacer  235   a . The second spacer  235   b  electrically connects the common voltage pad P to the first electrode  210 . Specifically, the second spacer  235   b  is formed in a region corresponding to the region where the power contact electrode  112  is formed. At this point, a second electrode dummy pattern  240  separated from the second electrode  230  is formed to surround the second spacer  235   b . The second electrode dummy pattern  240  surrounding the second spacer  235   b  contacts the power contact electrode  112 . The second electrode dummy pattern  240  separated from the second electrode  230  is electrically connected to the first electrode  210 . The first electrode  210  and the power contact electrode  112  are electrically connected by the second spacer  235   b,  so that the common voltage can be applied to the first electrode  210 . In addition, the second spacer  235   b  is formed to correspond to the dummy pattern  113  having the same height difference as the TFT Tr. 
     Because the first substrate  100  and the second substrate  200  are attached to each other by the double seal patterns, the organic electro-luminescent diode can be completely protected against outgas generated during the curing process of the second sealant  400 , as well as external moisture and oxygen. Therefore, the lifetime and reliability of the organic electro-luminescence display device can be significantly improved. 
     Although the dual-panel type organic electro-luminescence display device has been described above, the present invention is not limited thereto. For example, the organic electro-luminescent diode E electrically connected to the TFT Tr may be formed on the first substrate  100 . 
       FIGS. 2A to 2E  are cross-sectional views illustrating a method for fabricating an organic electro-luminescence display device according to an embodiment of the present invention. 
     Referring to  FIG. 2A , a first substrate  100  is prepared, and a TFT Tr is formed on the first substrate  100 . 
     Specifically, a conductive layer is formed on the first substrate  100  and is patterned to form a gate line (not shown) and a gate electrode  101 . At this point, the gate line is formed in one direction and the gate electrode  101  is branched from the gate line. Simultaneously, a power electrode  111  may be formed such that it receives a common voltage from an external signal and applies the received common voltage to an organic electro-luminescent diode, which will be described later. In addition, a first dummy pattern  113   a  is formed spaced apart from the power electrode  111  by a predetermined distance. 
     A gate insulating layer  110  is formed over the first substrate  100  where the gate electrode  101  is formed. The gate insulating layer  110  may be formed of a silicon oxide layer, a silicon nitride layer, or a stacked layer thereof, which is deposited using a chemical vapor deposition (CVD) process. 
     A semiconductor layer  102  is formed on a portion of the gate insulating layer  110  that corresponds to the gate electrode  101 . Simultaneously, a second dummy pattern  113   b  corresponding to the first dummy pattern  113   a  may be further formed on the gate insulating layer  110 . 
     A first conductive layer (not shown) is formed oh the semiconductor layer  102  and the gate insulating layer  110  and is patterned to form a data line (not shown) crossing the gate line (not shown). Simultaneously, a drain electrode  103   b  is formed on a center portion of the semiconductor layer  102 , and a source electrode  103   a  is formed in an annular shape to surround the periphery of the drain electrode  103   b . Therefore, characteristics of a TFT Tr can be improved by increasing a channel region of the TFT Tr, such as an area corresponding to the source electrode  103   a  and the drain electrode  103   b . A third dummy pattern  113 C may be further formed on the second dummy pattern  113   b.    
     In this way, the TFT Tr including the gate electrode  101 , the semiconductor layer  102  and the source/drain electrodes  103   a  and  103   b,  and the dummy pattern  113  having the same height difference as the TFT Tr are formed. 
     A passivation layer  120  is formed over the TFT Tr and the gate insulating layer  110 . The passivation layer  120  may be formed of an organic layer or an inorganic layer. For example, the organic layer may be benzo-cylco-butene (BCB), polyimide (PI), or Novolac resin, and the inorganic layer may be a silicon oxide layer, a silicon nitride layer, or a stacked layer thereof. 
     Contact holes are formed in the passivation layer  120  to expose a portion of the drain electrode  103   b  of the TFT Tr and a portion of the power electrode  111 , respectively. 
     A conductive layer is formed on the passivation layer  120  where the contact holes are formed, and is patterned to form a connection electrode  104  electrically connected to the drain electrode  103   b . Simultaneously, a power contact electrode  112  may be formed. The power contact electrode  112  is disposed on the first to third dummy patterns  113   a,    113   b  and  113   c,  so that it has a height difference like the connection electrode  104 . 
     Referring to  FIG. 2B , a second substrate  200  where an organic electro-luminescent diode E is formed is prepared. 
     Specifically, the second substrate  200  is prepared, and a first electrode  210  is formed as a common electrode on the second substrate  500 . The first electrode  210  is formed of a transparent conductive material having a high work function. For example, the first electrode  210  may be formed of ITO or IZO. 
     A buffer layer  215  is formed to define pixel regions on the first electrode  210 . The buffer layer is formed of an insulating layer. A separator  225  is formed on the buffer layer  215 . The separator  225  may be formed in a shape of a reversely tapered partition wall. The separator  225  may be formed of an organic insulating material. In addition, an island-shaped buffer layer  215  is further formed in a subpixel, and a first spacer  235   a  is formed on the buffer layer  215 . Simultaneously, a second separator is formed to have the same height as that of the first spacer  235   a.    
     An organic emission layer  220  and a second electrode  230  are sequentially formed over the first spacer  235   a  and the first electrode  210 . The second electrode  230  is automatically separated in each subpixel by the separator  225 . In addition, because the second electrode  230  extends while surrounding the periphery of the first spacer  235   a,  a portion of the second electrode  230  is protruded upwards by the first spacer  235   a.    
     At the same time, a second electrode dummy pattern  240  is formed in the periphery of the second substrate  200  and contacts the first electrode  210 . Because the second electrode dummy pattern  240  is formed to surround the periphery of the second spacer  235   b,  a portion of the second electrode dummy pattern  240  is protruded upwards. At this point, the second electrode dummy pattern  240  is separated from the second electrode  200 . 
     Before forming the organic emission layer  220 , a hole injection layer and/or a hole transport layer may be further formed. In addition, after forming the organic emission layer  220 , at least one of a hole blocking layer, an electrode transport layer and an electrode injection layer may be further formed. 
     Referring to  FIG. 2C , a first sealant  300  and a second sealant  400  are formed in a periphery of the first substrate  100  where the TFT Tr is formed or a periphery of the second substrate  200  where the organic electro-luminescent diode E is formed. At this point, the second sealant  400  is formed outside the first sealant  300 . The first sealant  300  is formed of UV curable resin, and the second sealant  400  is formed of frit glass. 
     Referring to  FIG. 2D , the first substrate  100  and the second substrate  200  are aligned, such that the TFT Tr and the common voltage pad P are in electrically contact with the organic electro-luminescent diode E. That is, the connection electrode  104  contacts the second electrode  230  overlying the first spacer  235   a . In addition, the power contact electrode  112  corresponding to the dummy pattern  113  is electrically contacted with the second electrode dummy pattern  240  overlying the second spacer  235   b.    
     The first sealant  300  is cured by irradiating UV light thereon. At this point, a first mask  500  is placed on the rear of the second substrate  200  such that the UV light can be irradiated only onto the first sealant  300 . 
     Referring to  FIG. 2E , the second sealant  400  is cured by irradiating a laser beam generated from a laser device onto the second sealant  400 . Although outgas may be generated from the second sealant  400 , the first sealant  300  can prevent the generated outgas from moving toward the organic electro-luminescent diode. In addition, a second mask  600  is placed on the rear of the second substrate  200  such that the laser beam can be irradiated only onto the second sealant  400 . 
     In addition, the second sealant  400  can be cured using a beam heater. The beam heater may have a wavelength ranging from about 0.1 μm to about 200 μm. Because the beam heater can irradiate light onto the second sealant  400  in a line type or a rectangular type, the curing time of the second sealant  400  can be reduced. Consequently, time during which the organic electro-luminescent diode E is exposed to high-temperature heat is reduced, the degradation of the organic electro-luminescent diode E can be reduced and the deformation of the first substrate  100  or the second substrate  200  can be prevented. 
     In using the laser device or the beam heater to cure the second sealant  400 , the second sealant  400  is cured by supplying energy only to the region where the second sealant  400  is formed. Therefore, the influence on the organic electro-luminescent diode E can be reduced. 
     In this way, the organic electro-luminescent diode E can be prevented from being degraded and protected against oxygen or moisture, thereby increasing the lifetime and reliability of the organic electro-luminescence display device. 
     In addition, the reduction of a defect ratio and the increase of a production yield can be expected by forming the TFT Tr and the organic electro-luminescent diode E on the different substrates and attaching the two substrates to each other. Accordingly, the organic electro-luminescence display device having the extended lifetime and improved reliability can be provided through an encapsulation process using the frit glass having good tolerance against oxygen and moisture. 
     Furthermore, the organic electro-luminescent diode can be prevented from being damaged due to outgassing generated during the encapsulation process using the frit glass. 
     Moreover, the influence on the organic electro-luminescent diode, such as the degradation of the organic electro-luminescent diode, can be prevented by irradiating energy only to the region where the sealant is formed. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.