Abstract:
An organic light emitting diode (OLED) display device, including: a base substrate, on which OLEDs are formed; and an encapsulation substrate disposed on the base substrate, to cover the OLEDs; and a bonding member connecting the base substrate and the encapsulating substrate. The base substrate and/or the encapsulation substrate include bonding grooves, in which the bonding member is disposed.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2009-0116420, filed Nov. 30, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    An aspect of the present disclosure relates to an organic light emitting diode (OLED) display device. 
         [0004]    2. Description of the Related Art 
         [0005]    In general, flat panel displays (FPDs) are being used in place of cathode ray tube (CRT) displays, because the FPDs are thinner and lighter. Typical examples of the FPDs include liquid crystal displays (LCDs) and organic light emitting diode (OLED) display devices. OLED display devices have a higher luminance and a wider viewing angle than LCDs. Also, OLED display devices require no backlight, and thus, may be ultrathin. 
         [0006]    In an OLED display device, electrons emitted from a cathode recombine with holes emitted from an anode, in a thin organic layer, to form excitons. When the excitons transition from an excited state to a ground state, light with a specific wavelength is emitted. In order to facilitate the emission of the light, by the recombination of the electrons with the holes, the anode, into which the holes are injected, may be formed of a material having a large work function, while the cathode, into which the electrons are injected, may be formed of a material having a small work function. 
         [0007]    However, since the cathode may be highly active and chemically unstable, the cathode may react easily with external oxygen or moisture and thus, may be susceptible to oxidation or corrosion. Also, the thin organic layer may be crystallized, due to a reaction with external moisture or oxygen, so that the organic layer may be structurally changed and have degraded emission characteristics. 
         [0008]    Thus, various methods for encapsulating OLED display devices have been developed, in order to block oxygen and moisture from infiltrating OLED display devices. Among these, an encapsulation method using an encapsulation substrate has lately attracted considerable attention. 
         [0009]    According to the encapsulation method using the encapsulation substrate, a bonding member may be interposed between a base substrate, on which OLEDs are formed, and the encapsulation substrate, and pressure may be applied to bond the base substrate to the encapsulation substrate. 
         [0010]    However, since the base substrate is pressure bonded to the encapsulation substrate, the bonding member may flow out of a bonding region, according to the amount and pressure applied to the bonding member. As such, controlling the width of the bonding member becomes problematic. In addition, when an amount of pressure is controlled to prevent the bonding member from flowing out, the thickness of the bonding member may be increased or become non-uniform. 
       SUMMARY 
       [0011]    Aspects of the present disclosure provide an organic light emitting diode (OLED) display device, including a bonding member interposed between a base substrate and an encapsulation substrate, having a reduced width and thickness. 
         [0012]    According to an aspect of the present disclosure, an OLED display device includes a base substrate, on which OLEDs are formed. An encapsulation substrate is disposed on the base substrate, to cover the OLEDs, and is bonded to the base substrate, using a bonding member. The base substrate or the encapsulation substrate may include a plurality of bonding grooves, in which the bonding member is disposed. 
         [0013]    According to various aspects of the present disclosure, the bonding grooves may be disposed in edges of the base substrate or the encapsulation substrate. 
         [0014]    According to various aspects of the present disclosure, the bonding grooves may be disposed in a surface facing the base substrate or the encapsulation substrate. 
         [0015]    According to various aspects of the present disclosure, the bonding grooves may have the same width and depth or different widths and depths. 
         [0016]    According to various aspects of the present disclosure, at least one of the bonding grooves may form a closed loop, extending along edges of the base substrate or the encapsulation substrate. 
         [0017]    According to various aspects of the present disclosure, the bonding member may include a sealant or a glass frit. 
         [0018]    According to various aspects of the present disclosure, the encapsulation substrate may be formed of a plate-shaped glass material. 
         [0019]    According to another aspect of the present disclosure, an OLED display device is provided that includes a base substrate, on which a plurality of OLEDs are formed. An encapsulation substrate is disposed over the base substrate, to cover the OLEDs, and is bonded to the base substrate, using a bonding member. Each of the base substrate and the encapsulation substrate may include a plurality of bonding grooves, in which the bonding member is disposed. 
         [0020]    According to various aspects of the present disclosure, the bonding grooves may be disposed in edges of the base substrate and the encapsulation substrate. 
         [0021]    According to various aspects of the present disclosure, the bonding grooves may be disposed in surfaces of the base substrate and the encapsulation substrate, which are disposed opposite each other. 
         [0022]    According to various aspects of the present disclosure, the bonding grooves included in the base substrate may be disposed in positions vertically corresponding to the bonding grooves included in the encapsulation substrate. 
         [0023]    According to various aspects of the present disclosure, the bonding grooves included in the base substrate may be disposed in positions that vertically alternate with positions of the bonding grooves included in the encapsulation substrate. 
         [0024]    According to various aspects of the present disclosure, the bonding member may include a sealant or a glass frit. 
         [0025]    According to various aspects of the present disclosure, the bonding grooves included in the base substrate and the encapsulation substrate may be symmetrical to one another. 
         [0026]    According to various aspects of the present disclosure, the bonding grooves included in each of the base substrate and the encapsulation substrate may have the same width and depth, or different widths and depths. 
         [0027]    According to various aspects of the present disclosure, at least one of the bonding grooves may form a closed loop, along edges of the base substrate or the encapsulation substrate. 
         [0028]    According to various aspects of the present disclosure, the encapsulation substrate may be formed of a plate-shaped glass material. 
         [0029]    Additional aspects and/or advantages of the present disclosure will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0030]    These and/or other aspects and advantages of the present disclosure will become apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompanying drawings, of which: 
           [0031]      FIG. 1  is a cross-sectional view of an organic light emitting diode (OLED) display device, according to an exemplary embodiment of the present disclosure; 
           [0032]      FIG. 2  is a cross-sectional view of a unit OLED, according to an exemplary embodiment of the present disclosure; 
           [0033]      FIG. 3  is a cross-sectional view of portion “A” of  FIG. 1 ; 
           [0034]      FIG. 4  is a plan view of a base substrate of the OLED display device of  FIG. 1 ; 
           [0035]      FIG. 5  is a cross-sectional view of an OLED display device, according to another exemplary embodiment of the present disclosure; 
           [0036]      FIG. 6  is a cross-sectional view of an OLED display device, according to still another exemplary embodiment of the present disclosure; 
           [0037]      FIGS. 7A and 7B  are plan views of a base substrate and an encapsulation substrate of the OLED display device of  FIG. 6 ; and 
           [0038]      FIG. 8  is a cross-sectional view of portion “B” of  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION 
       [0039]    Reference will now be made in detail to the exemplary embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The exemplary embodiments are described below, in order to explain the present disclosure, by referring to the figures. 
         [0040]      FIG. 1  is a cross-sectional view of an organic light emitting diode (OLED) display device  100 , according to an exemplary embodiment of the present disclosure, and  FIG. 2  is a cross-sectional view of a unit OLED, according to an exemplary embodiment of the present disclosure.  FIG. 3  is a cross-sectional view of portion “A” of  FIG. 1 , and  FIG. 4  is a plan view of a base substrate of the OLED display device  100 . 
         [0041]    Referring to  FIG. 1 , the OLED display device  100  includes a base substrate  110  and an encapsulation substrate  120 . The base substrate  110  may include a plurality of first bonding grooves  114 , and the encapsulation substrate  120  may be disposed on the base substrate  110 . 
         [0042]    Specifically, the base substrate  110  may include a pixel region  117  and a bonding region  115  disposed around the pixel region  117 . The pixel region  117  may include a plurality of OLEDs, and the bonding region  115  may have the first bonding grooves  114 . 
         [0043]    The OLED display device  100  may be a top-emitting or bottom-emitting OLED display device. The present exemplary embodiment will be described using a top-emitting OLED display device of  FIG. 2 , for convenience. 
         [0044]    Referring to  FIG. 2 , a buffer layer  140  may be disposed on the base substrate  110 , and a semiconductor layer  146 , having source and drain regions  142  and a channel region  144 , may be disposed on the buffer layer  140 . A gate insulating layer  148  covering the semiconductor layer  146  may be disposed on the base substrate  110 , and a gate  150  may be disposed on the gate insulating layer  148 . An interlayer insulating layer  152  covering the gate  150  may be disposed on the gate insulating layer  148 . Source and drain electrodes  154  and  156  may be disposed on the interlayer insulating layer  152  and respectively connected to the corresponding source and drain regions  142 . A planarization layer  158  covering the source and drain electrodes  154  and  156  may be disposed on the interlayer insulating layer  152 . The planarization layer  158  may have a stacked structure of an inorganic layer and an organic layer. 
         [0045]    A first electrode  160  may be disposed on the planarization layer  158 . The first electrode  160  may be connected to the drain electrode  156  and operate as an anode. A pixel defining layer  162  exposing a portion of the first electrode  160  may be disposed on the planarization layer  158 . An organic thin layer  164  may be disposed on the exposed portion of the first electrode  160  and a portion of the pixel defining layer  162 . A second electrode  166  operates as a cathode and may be disposed on the pixel defining layer  162  and the organic thin layer  164 . A passivation layer  168  may be disposed on the second electrode  166 . The passivation layer  168 , which is formed of a transparent material, may block external moisture and oxygen. 
         [0046]    Referring to  FIG. 3  and  FIG. 4 , which shows a top surface  111  of the base substrate  110  of  FIG. 1 , the bonding region  115  of the base substrate  110  may be disposed at edges of the base substrate  110 , surrounding the pixel region  117 . 
         [0047]    First bonding grooves  114   a,    114   b,  and  114   c  may be disposed in the top surface  111  of the base substrate  110 , in the bonding region  115 , facing the encapsulation substrate  120 . During the bonding of the base substrate  110  and the encapsulation substrate  120 , the first bonding grooves  114   a,    114   b,  and  114   c  may be filled with a portion of the bonding member  130 , to prevent the bonding member  130  from flowing out of the bonding region  115 . 
         [0048]    Various numbers of the first bonding grooves  114   a,    114   b,  and  114   c  may be provided, in consideration of, for example, the coated amount of and bonding pressure applied to the bonding member  130 , and the shapes of the base and encapsulation substrates  110  and  120 . The first bonding grooves  114   a,    114   b,  and  114   c  may have the same or different widths and depths. For example, the first bonding grooves  114   a,    114   b,  and  114   c  may have the same width and different depths or different widths and the same depth. The first bonding grooves  114   a,    114   b,  and  114   c  may be spaced apart from one another by the same interval or at different intervals. 
         [0049]    At least one of the first bonding grooves  114   a,    114   b,  and  114   c  may be formed as a closed loop extending along the edge of the base substrate  110 . All the first bonding grooves  114   a,    114   b,  and  114   c  may be formed as closed loops extending along the edges of the base substrate  110 . When at least one of the first bonding grooves  114   a,    114   b,  and  114   c  is a closed loop, the other first bonding grooves may be closed loops disposed inside or outside thereof. 
         [0050]    Referring to  FIGS. 1 and 3 , the encapsulation substrate  120  may be disposed on the base substrate  110 . The encapsulation substrate  120  may protect the pixel region  117  and OLEDs disposed therein, and may prevent external moisture and oxygen from contacting the OLEDs. The encapsulation substrate  120  may be formed of, for example, a plate-shaped glass material. 
         [0051]    The base substrate  110  and the encapsulation substrate  120  may be bonded to each other with the bonding member  130 , which is interposed between the bonding region  115  and a portion of the encapsulation substrate  120  facing the bonding region  115 . The bonding member  130  may include, for example, a sealant or a glass frit, and a paste obtained by mixing a ceramic material, such as silicon dioxide, with an organic binder. 
         [0052]    The bonding of the base substrate  110  and the encapsulation substrate  120  may include coating the bonding member  130 , applying pressure to adhere the base substrate  110  and the encapsulation substrate  120 , and curing the bonding member  130 . In this case, during the application of the pressure the first bonding grooves  114   a,    114   b,  and  114   c  may prevent the bonding member  130  from flowing out of the bonding region  115 , due to the pressure. In other words, a portion of the bonding member  130  may flow into the first bonding grooves  114   a,    114   b,  and  114   c,  during the bonding process, thereby preventing the bonding member  130  from flowing out of the bonding region  115 . 
         [0053]    Thus, the width of the bonding member  130  may be easily controlled. Also, since the first bonding grooves  114   a,    114   b,  and  114   c  are filled with any excess amount of the bonding member  130 , the base substrate  110  and the encapsulation substrate  120  may be bonded to each other under a high pressure. Therefore, the distance between the base substrate  110  and the encapsulation substrate  120  may be reduced, and the bonding member  130  may be formed to a uniform thickness. 
         [0054]      FIG. 5  is a cross-sectional view of an OLED display device  200 , according to another exemplary embodiment of the present disclosure. The OLED display device  200  may include substantially the same components as the OLED display device  100 . Thus, a repeated description of similar components will be omitted. 
         [0055]    Referring to  FIG. 5 , the OLED display device  200  includes a base substrate  110  and an encapsulation substrate  170  disposed on the base substrate  110 . The encapsulation substrate  170  includes a plurality of second bonding grooves  172 . 
         [0056]    The second bonding grooves  172  may be disposed at edges of the encapsulation substrate  170 , facing a bonding region  115  of the base substrate  110 . The second bonding grooves  172  may be disposed on an inner surface  171  of the encapsulation substrate  170 , which faces the base substrate  110 . 
         [0057]    Various numbers of the second bonding grooves  172  may be provided. For example, the second bonding grooves  172  can include second bonding grooves  172   a,    172   b,  and  172   c,  in consideration of the coated amount and bonding pressure of a bonding member, and the shapes of the base substrate  110  and the encapsulation substrate  170 . The second bonding grooves  172   a,    172   b,  and  172   c  may have the same width and depth or different widths and depths. The second bonding grooves  172   a,    172   b,  and  172   c  may be spaced apart by the same interval or by different intervals. 
         [0058]    At least one of the second bonding grooves  172   a,    172   b,  and  172   c  may be formed as a closed loop, along the edges of the encapsulation substrate  170 . For example, all the second bonding grooves  172   a,    172   b,  and  172   c  may be formed as closed loops, along the edges of the base substrate  110 . When at least one of the second bonding grooves  172   a,    172   b,  and  172   c  is a closed loop, the second bonding grooves disposed inside or outside thereof, may be formed as separate closed loops. 
         [0059]      FIG. 6  is a cross-sectional view of an OLED display device  300 , according to still another exemplary embodiment of the present disclosure.  FIGS. 7A and 7B  are plan views of a base substrate  110  and an encapsulation substrate  170  of the OLED display device  300 , and  FIG. 8  is a cross-sectional view of portion “B” of  FIG. 6 . 
         [0060]    The OLED display device  300  includes substantially the same components as the OLED display device  100 . Thus, a repeated description of similar components will be omitted. 
         [0061]    Referring to  FIG. 6 , the OLED display device  300  includes the base substrate  110  and the encapsulation substrate  170 , which is disposed on the base substrate  110 . The base substrate  110  may have a plurality of first bonding grooves  114 , while the encapsulation substrate  170  may have a plurality of second bonding grooves  172 . The base substrate  110  and the encapsulation substrate  170  may be disposed such that the first bonding grooves  114  face the second bonding grooves  172 . 
         [0062]    Specifically, referring to  FIGS. 7A and 7B , which illustrate inner surfaces  111  and  171  of the base substrate  110  and the encapsulation substrate  170 , the base substrate  110  may include a pixel region  117  and a first bonding region  115 . The pixel region  117  may be a region where a plurality of OLEDs are formed. The encapsulation substrate  170  may include a second bonding region  119 . 
         [0063]    The first bonding region  115  may be disposed in the inner surface  111 , at edges of the base substrate  110 , so as to surround the pixel region  117 . The first bonding grooves  114   a,    114   b,  and  114   c  may be disposed in a portion of the base substrate  110  facing the first bonding region  115 . 
         [0064]    The second bonding region  119  may be disposed in the inner surface  171 , at edges of the encapsulation substrate  170 . The second bonding grooves  170  may include second bonding grooves  172   a,    172   b,  and  172   c  disposed in a portion of the encapsulation substrate  170  facing the second bonding region  119 . The second bonding region  119  may face the first bonding region  115  of the base substrate  110 . 
         [0065]    As shown in  FIG. 7A , the first bonding grooves  114   a,    114   b,  and  114   c  may be disposed facing the second bonding grooves  172   a,    172   b,  and  172   c.  Alternatively, as shown in  FIG. 7B , the first bonding grooves  114   a,    114   b,  and  114   c  and the second bonding grooves  172   a,    172   b,  and  172   c  may be offset from one another, i.e., so as not to directly face one another. 
         [0066]    The first bonding grooves  114   a,    114   b,  and  114   c  and the second bonding grooves  172   a,    172   b,  and  172   c  may be symmetrically shaped. The first bonding grooves  114   a,    114   b,  and  114   c  and the second bonding grooves  172   a,    172   b,  and  172   c  may be provided in various numbers, in consideration of, for example, the coated amount and bonding pressure of a bonding member, and the shapes of the base substrate  110  and the encapsulation substrate  170 . The first bonding grooves  114   a,    114   b,  and  114   c  and the second bonding grooves  172   a,    172   b,  and  172   c  may have the same or different widths and depths. For example, the first bonding grooves  114   a,    114   b,  and  114   c  and the second bonding grooves  172   a,    172   b,  and  172   c  may have the same width and different depths, or different widths and the same depth. Furthermore, the first bonding grooves  114   a,    114   b,  and  114   c  may be spaced apart by the same interval or by different intervals, and the second bonding grooves  172   a,    172   b,  and  172   c  may be spaced apart by the same interval or by different intervals. 
         [0067]    At least one of the first bonding grooves  114   a,    114   b,  and  114   c  may be formed as a closed loop, along edges of the base substrate  110 . Also, at least one of the second bonding grooves  172   a,    172   b,  and  172   c  may be formed as a closed loop, along edges of the encapsulation substrate  110 . For example, all the first bonding grooves  114   a,    114   b,  and  114   c  and the second bonding grooves  172   a,    172   b,  and  172   c  may all be formed as closed loops, along the edges of the base substrate  110  and the encapsulation substrate  170 , respectively. When at least one of the first bonding grooves  114   a,    114   b,  and  114   c  and at least one of the second bonding grooves  172   a,    172   b,  and  172   c  is a closed loop, the bonding grooves disposed inside or outside thereof may be separate closed loops. 
         [0068]    The first bonding grooves  114   a,    114   b,  and  114   c  may be closed loops, while the second bonding grooves  172   a,    172   b,  and  172   c  may be closed loops. Alternatively, the first bonding grooves  114   a,    114   b,  and  114   c  may be separate closed loops, while the second bonding grooves  172   a,    172   b,  and  172   c  may be closed loops. 
         [0069]    Referring to  FIGS. 6 and 8 , the base substrate  110  and the encapsulation substrate  170  may be bonded to each other, by a bonding member  130  interposed between the first bonding region  115  having the first bonding grooves  114   a,    114   b,  and  114   c,  and the second bonding region  119  having the second bonding grooves  172   a,    172   b,  and  172   c.  The first bonding grooves  114   a,    114   b,  and  114   c  and the second bonding grooves  172   a,    172   b,  and  172   c  may prevent a portion of the bonding member  130  from flowing out of the first and second bonding regions  115  and  119 , during the bonding process. In other words, an excess amount of the bonding member  130  may fill the first bonding grooves  114   a,    114   b,  and  114   c  and the second bonding grooves  172   a,    172   b,  and  172   c,  during the bonding process, so that the bonding member  130  does not flow out of the first and second bonding regions  115  and  119 . 
         [0070]    According to the present disclosure, a plurality of bonding grooves may be formed in a base substrate, on which OLEDs are formed, or in an encapsulation substrate encapsulating the base substrate. Also, a plurality of bonding grooves may be formed in each of the base substrate and the encapsulation substrate. 
         [0071]    As a result, an excess amount of the bonding member may fill the bonding grooves during the bonding of the base substrate with the encapsulation substrate, thereby preventing the bonding member from flowing out of the bonding region. Accordingly, the width of the bonding member can be easily controlled. 
         [0072]    Furthermore, by filing the bonding grooves with a portion of the bonding member, the base substrate and the encapsulation substrate can be bonded under a high pressure. Therefore, a distance between the base substrate and the encapsulation substrate can be reduced, and the bonding member can be formed to a uniform thickness. 
         [0073]    As explained thus far, the present disclosure provides an OLED display device in which a plurality of bonding grooves are formed in a base substrate, on which OLEDs are formed, or in an encapsulation substrate for encapsulating the base substrate. Also, the present disclosure provides an OLED display device, in which bonding grooves are formed in each of a base substrate and an encapsulation substrate. 
         [0074]    Although a few exemplary embodiments of the present disclosure have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these exemplary embodiments, without departing from the principles and spirit of the present disclosure, the scope of which is defined in the claims and their equivalents.