Abstract:
The present invention relates to a container for encapsulating organic light emitting diodes (hereinafter, referred to as OLED) and a manufacturing method thereof, wherein a container for encapsulating OLEDs is manufactured by forming a sealant in a glass sheet using a glass frit, thereby resulting in improving the characteristic of junction between the container and the top substrate.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a container for encapsulating organic light emitting diodes (hereinafter, referred to as “OLED”) and a manufacturing method thereof, wherein a container for encapsulating OLEDs is manufactured by forming a lateral wall in a glass sheet using a glass frit, thereby resulting in improving the junction characteristic between the container and the top substrate.  
           [0003]    2. Description of the Prior Art  
           [0004]    An OLED comprises a top substrate whereon organic substance is stacked and a container for encapsulation. The top substrate has a glass substrate whereon an anode ITO, an organic thin film and a cathode are stacked. On the organic thin film are formed a hole injecting layer ‘HIL’, hole transport layer ‘HTL’, electron transport layer ‘ETL’ and electron injecting layer ‘EIL’.  
           [0005]    A container for encapsulation is formed of a metal plate using a metal mold.  
           [0006]    The OLED is formed by arranging and connecting the above-described substrate and the container for encapsulation.  
           [0007]    In the above-described conventional OLED, a container for encapsulation is formed of metal. As a result, if the surface has high roughness, the junction of the container and the top substrate is difficult or a leak may be generated. Furthermore, if the area becomes larger, the surface of the container may not have the desired roughness. Accordingly, there is a limit to enlarge the size of an OLED.  
           [0008]    In addition, the conventional container has the low junction strength because its material is metal. It is also difficult to maintain the junction condition because the container has the different thermal expansive coefficient from that of the top substrate formed of glass.  
         SUMMARY OF THE INVENTION  
         [0009]    Accordingly, the present invention has an object to provide a container for encapsulating OLEDS by forming a lateral wall on a glass sheet with a glass frit, thereby improving the junction characteristic of a container and a top substrate.  
           [0010]    To achieve the above-described object, a container for encapsulating OLEDs according to the present invention comprises a glass sheet and a lateral wall formed of a glass frit including a binder, while a getter or an absorbent is mounted between lateral walls.  
           [0011]    The lateral wall is formed by coating and burning the glass frit on the glass sheet corresponding to the size and the pattern of the top substrate to be encapsulated. A plurality of lateral walls are arranged on the glass sheet in a matrix structure. They may be formed of a stair structure.  
           [0012]    A ceramic plate is formed instead of the glass sheet. Here, it is desirable to form a buffer film to relieve the stress resulting from the thermal expansive coefficient. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    The present invention will be explained in terms of exemplary embodiments described in detail with reference to the accompanying drawings, which are given only by way of illustration and thus are not limitative of the present invention, wherein:  
         [0014]    [0014]FIG. 1 is a diagram illustrating an example of a lateral wall formed to have lines and rows on a glass sheet in order to manufacture a container for encapsulating OLEDs in accordance with the present invention;  
         [0015]    [0015]FIG. 2 a  is a cross-sectional diagram illustrating X-Y portion of FIG. 1 when a lateral wall is formed using dispensing or screen printing;  
         [0016]    [0016]FIG. 2 b  is a cross-sectional diagram illustrating X-Y portion of FIG. 1 when a lateral wall is transformed to prevent its diffusion after dispensing;  
         [0017]    [0017]FIG. 2 c  is a cross-sectional diagram illustrating X-Y portion of FIG. 1 when a lateral wall is transformed to consider taping for accepting an absorbent having powder condition;  
         [0018]    [0018]FIG. 3 a  is a cross-sectional diagram illustrating an example wherein a getter is attached to the inside of the container;  
         [0019]    [0019]FIG. 3 b  is a cross-sectional diagram illustrating an example wherein a film is taped by accepting the absorbent;  
         [0020]    [0020]FIG. 4 is a cross-sectional diagram of a top substrate; and  
         [0021]    [0021]FIG. 5 is a cross-sectional diagram of an encapsulated OLED. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]    A container for encapsulating OLEDs and a manufacturing method thereof in accordance with preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.  
         [0023]    A plurality of containers for encapsulating OLEDs are manufactured on a glass sheet having a predetermined area to have a matrix structure. After a lateral wall is formed on the glass sheet, the glass sheet is cut into unit containers and used in encapsulation of a top substrate. In another way, the glass sheet may be cut into unit panels after encapsulationg of the glass sheet.  
         [0024]    As shown in FIG. 1, a preferred embodiment in accordance with the present invention comprises a plurality of lateral walls  12  on a surface of a glass sheet  10 . The plurality of lateral walls  12  are formed on the surface of the glass sheet  10  in a matrix structure having lines and rows. The lateral wall  12  is formed by coating and burning a glass frit. Here, it is desirable to include a binder in the glass frit.  
         [0025]    The lateral wall  12  can-have various patterns.  
         [0026]    In a simpler way, the lateral wall  12  may be formed to have a cross section structure, as shown in FIG. 2 a . In other words, the glass frit is coated on the glass sheet  10  to have a plane surface as shown in FIG. 1. Thereafter, if the glass frit is burned at a high temperature, as shown in FIG. 2 a , the lateral wall  12  is formed-and the surface of the burned lateral wall  12  is polished. Here, the surface of the lateral wall  12  may be polished by a slurry made from mixing polishing powder in water or by a CMP (Chemical Mechanical Polisher) process.  
         [0027]    The glass frit used in forming the lateral wall  12  has all kinds of colors ranging from white to black. The glass sheet  10  for encapsulation has a thickness of 0.3˜3 mm.  
         [0028]    The above-described glass frit may be coated by dispensing or screen printing. Here, dispensing has a nozzle on a surface of the glass sheet  10  so that the glass frit may have a predetermined pattern and size. Screen printing is a method for printing a desired pattern on the glass sheet  10 . In this method, a desired pattern is first designed and drawn on the metal sheet having a net structure.  
         [0029]    Then, the portion without the pattern is masked using emulsion liquid, and the glass frit is planed with a squeeze. As a result, the desired pattern is printed on the glass sheet.  
         [0030]    The coatable glass frit is hardened and burned while the binder mixed at a temperature of 400˜500° C. is removed. As a result, the burned glass frit forms the lateral wall  12 . It is desirable that the surface of the lateral wall  12  should be polished to have an easy junction with the top substrate.  
         [0031]    As shown in FIG. 2 b , a lateral wall  23  is formed to prevent the diffusion after dispensing.  
         [0032]    In detail, the lateral wall  23  of FIG. 2 b  has a cross section wherein stairs are formed on the inside of outlines in rectangle. This cross section having a stair structure is formed by twice coating. That is, first, a glass frit is widely coated to have a rectangle on a glass sheet  22  using screen printing. Then, a glass frit is narrowly coated on the second coated glass frit using a dispensing method. As a result, the lateral wall  23  is formed. Here, it is desirable to bum the glass frit in each step in order to prevent the diffusion of the glass frit after dispensing.  
         [0033]    An absorbent having powder condition is injected on a glass sheet  24  between lateral walls  25  and then may be taped to be sealed. For this process, a stair surface is widely formed on the lateral wall  25 , as shown in FIG. 2 c.    
         [0034]    Referring to FIG. 3 b , an absorbent  26  having powder condition is injected on a glass sheet  24  between the lateral walls  25 . A protective film  27  is formed above the absorbent  26  to seal the absorbent  26  between the lateral walls  25 . The absorbent  26  is sealed because the end portion of the protective film  27  is taped on the stair surface of the lateral walls  25 . It is desirable to form the wide stair surface in order to attach the adhesive tape to the stair sruface easily.  
         [0035]    Unlike FIGS. 2 a  through  2   c , the height and the pattern of lateral walls may be transformed in various ways, in consideration of a getter or an absorbent to be placed in a container.  
         [0036]    A getter or an absorbent should be attached or placed in a container for encapsulating OLEDs.  
         [0037]    As shown in FIG. 3 a , in a container of OLEDS, a getter  16  may be attached to a gap formed between the lateral walls  12  using an adhesive.  
         [0038]    In other words, the getter  16  is placed on the container wherein the lateral walls  12  having the cross section of FIG. 2 a  are formed. Here, it is desirable to design the height of the lateral walls  12  in consideration of that of the getter  16 .  
         [0039]    As shown in FIG. 3 b , the absorbent  26  may be placed on the container wherein the lateral walls  25  having the cross section of FIG. 2 c  are formed.  
         [0040]    Here, the absorbent  26  is injected on the glass sheet  24  between the lateral walls  25 . The protective film  27  as an adhesive tape is taped between the stair surface of the lateral walls  25  to seal the absorbent having powder condition. The protective film  27  may be formed of porous cloth to help the function of the absorbent  26 . The protective film  27  may also be formed of a built-in adhesive tape. Materials in powder condition such as barium oxide or zeolite may be used as the absorbent  26 .  
         [0041]    The container as described above in FIGS. 1 through 3 b  is manufactured as an OLED while the top substrate having the cross section of FIG. 4 is encapsulated.  
         [0042]    The top substrate of FIG. 4 has a stacked structure wherein an anode  41 , a hole injecting layer  42 , a hole transport layer  43 , an organic film  44 , an electron transport layer  45 , an electron injecting layer  46  and a cathode  47  are sequentially stacked on a glass substrate  40 .  
         [0043]    The transparent anode  41  formed of indium tin oxide ‘ITO’ is first formed on the glass substrate  40 . Then, an insulating film (not shown) and an auxiliary electrode (not shown) are formed. A separating film for determining the separation of RGB pictures and the pattern of cathode electrodes is formed of negative polyimide photo resist to have a reverse picture sidewall.  
         [0044]    Thereafter, a hole injecting layer  42 , a hole transport layer  43 , an organic film  44 , an electron transport layer  45 , an electron injecting layer  46  and a cathode.  47  are sequentially in a vacuum chamber.  
         [0045]    The top substrate having the above-described structure is encapsulated as a container in accordance with various preferred embodiments of the present invention. For example, the top substrate of FIG. 4 is encapsulated as a container wherein a getter  16  is attached to a glass sheet  10 , as shown in FIG. 5.  
         [0046]    In other words, an adhesive  13  is coated on the top substrate of FIG. 4 and the surface of the lateral wall  12  in a container for encapsulation of FIG. 3 a . Then, the top substrate of FIG. 4 and the lateral wall  12  of the glass sheet  10  of FIG. 3 a  are connected using the adhesive  13  in a chamber having a inactive gas as shown in FIG. 5. Such kinds of adhesives as adhesive  14  used in mounting the getter  16  may be used as the adhesive  13 . Here, it is desirable to use an adhesive for attaching the object using ultraviolet hardening as the adhesive  13 .  
         [0047]    In another way, an OLED may be manufactured by connecting the top substrate of FIG. 4 and the container wherein the absorbent  26  of FIG. 3 b  or  3   c  is injected.  
         [0048]    A container wherein a lateral wall is formed on a ceramic plate instead of the above-described glass sheet using a glass frit in consideration of thermal expansive coefficient may be used in encapsulation. Here, a buffer layer may be formed between the lateral wall and the ceramic plate to buffer the difference of thermal expansive coefficient in the ceramic and the glass.  
         [0049]    According to the present invention, a lateral wall can be formed without deformation of a glass sheet using a glass frit. Various patterns of lateral walls may also be formed to improve the adhesiveness on the glass sheet. The process where a lateral wall is formed in a container for encapsulating OLEDs is simple. The cost can be reduced in forming various patterns of lateral walls.  
         [0050]    In addition, it is possible to prevent generation of leaks resulting from the stress due to the difference of thermal expansive coefficient because the thermal expansive coefficient is the same or similar in the container for encapsulation and the top substrate. Accordingly, the durability of OLEDs can be improved.  
         [0051]    While the invention is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and described in detail herein. However, it should be understood that the invention is not limited to the particular forms disclosed. Rather, the invention covers all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined in the appended claims.