Abstract:
An OLED package structure includes: a substrate, on which an organic light-emitting element is provided, and a cover plate having an annular groove surrounding the organic light-emitting element thereon. A packaging adhesive, partly inside the groove and partly outside the groove, adheres the cover plate to the substrate to seal the organic light-emitting element. In the OLED package structure according to the present invention, the thickness of the spacer can be smaller, so as to eliminate color mixture during an evaporation process and to prevent a Newton ring phenomenon in the OLED package structure.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims priority to Chinese patent application No. 201210567658.1 titled “ORGANIC LIGHT-EMITTING DIODE PACKAGE STRUCTURE AND METHOD FOR FORMING THE SAME” and filed with State Intellectual Property Office of PRC on Dec. 24, 2012, which is incorporated herein by reference in its entirety. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to display technology, and in particular to an organic light-emitting diode package structure and a method for forming the same. 
       BACKGROUND OF THE INVENTION 
       [0003]    Organic light-emitting diode (OLED) display, which is also referred to as organic electroluminescence display (OELD), is a most promising display technology due to its advantages such as good color contrast, active light-emitting, wide viewing angle, thinness, fast response speed and low power consumption. However, in an OLED device, it is possible for an organic light-emitting layer and an electrode to fail if they encounter with water or oxygen. Accordingly, thereby service life of the OLED device is affected greatly. Thus the OLED device generally needs to be well sealed. In an early packaging method, since it has been impossible to ensure a good sealing, typically a desiccant or drier sheet has been provided inside the OLED device. However, it has been unnecessary to use the desiccant or drier sheet inside the OLED device since frit sealing has been used as a packaging adhesive, as the frit is heated and melted by using a moving laser beam and can form a seal structure with good air-tightness. 
         [0004]    However, there is a new problem for the OLED package structure using a frit as the packaging adhesive. 
         [0005]    As shown in  FIG. 1 , an OLED package structure  100  using the frit as the packaging adhesive includes a substrate  110 , a cover plate  120  and a frit packaging adhesive  130 . An organic light-emitting element  111  is formed on the substrate  110 . Typically, there is a spacer  112  inside the package structure for keeping a uniform distance between the substrate  110  and the cover plate  120  of the OLED. 
         [0006]    Generally, the spacer should not be too thick. This is because, as shown in  FIG. 2 , evaporation is needed during the manufacture of the OLED. During the evaporation, a mask  240  is typically used for protection, and an organic film layer  213  (and an inorganic film layer) is formed on the substrate through an opening of the mask  240  by the evaporation. During the evaporation process, the mask  240  contacts the spacer  212 . Thus, if the spacer  212  is too thick, unwanted evaporation material develops on the left side and the right side of the organic film layer  213 . The unwanted evaporation material may cause poor display quality, such as poor color mixture of the display device. 
         [0007]    Therefore, it is typically required to manufacture a thinner spacer. Moreover, the frit used as the packaging adhesive is also required to be thinner. This is because, as shown in  FIG. 3 , if the thickness of the frit  330  is not reduced, the frit  330  on the left side and the right side of the OLED package structure  300  is thicker and the spacers  312  in the middle are thinner, the cover plate  320  may be warped. In this case, a Newton ring effect which affects image quality of the finally formed display device may be generated between the cover plate  320  and the substrate  310 . However, the frit  330  has to be sufficiently thick to ensure packaging requirements. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    One implementation is an organic light-emitting diode package structure, including a substrate, on which an organic light-emitting element is provided, and a cover plate including an annular groove along a periphery of an inner surface of the cover plate, where the annular groove surrounds the organic light-emitting element. The organic light-emitting diode package structure also includes a packaging adhesive having a thickness greater than a depth of the groove, where a portion of the packaging adhesive is located inside the groove of the cover plate, a portion of the packaging adhesive extends outside the groove of the cover plate, and the cover plate and the substrate are adhered to each other by the packaging adhesive, so as to seal the organic light-emitting element. 
         [0009]    Another implementation is a method for forming an organic light-emitting diode package structure. The method includes providing an entire substrate having a plurality of substrate units, each substrate unit including an organic light-emitting element. The method also includes providing an entire cover plate having a plurality of cover plate units, each cover plate unit including an annular groove surrounding the organic light-emitting element thereon, and forming a packaging adhesive in the groove of each of the cover plate units, where a portion of the packaging adhesive is located inside the groove of each of the cover plate units and a portion of the packaging adhesive extends outside the groove of each of the cover plate units. The method also includes pressing the entire cover plate and the entire substrate together, where the cover plate units our adhered to the substrate units with the packaging adhesive to seal each organic light-emitting element, and cutting the adhered entire cover plate and entire substrate to obtain a plurality of organic light-emitting diode package structures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a schematic diagram illustrating an existing OLED package structure using frit as a packaging adhesive; 
           [0011]      FIG. 2  is a schematic diagram illustrating the OLED package structure illustrated in  FIG. 1  during an evaporation process; 
           [0012]      FIG. 3  is a schematic diagram illustrating an existing OLED package structure in which a Newton ring occurs; 
           [0013]      FIG. 4  is a schematic diagram illustrating an OLED package structure according to an embodiment of the present invention; and 
           [0014]      FIG. 5  to  FIG. 7  are schematic diagrams illustrating structures corresponding to steps in a method for forming an OLED package structure according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A First Embodiment 
       [0015]    As shown in  FIG. 4 , an OLED package structure  400  according to an embodiment is shown. The OLED package structure  400  includes a substrate  410 , a cover plate  420  and a packaging adhesive  430 . On the substrate  410 , an organic light-emitting element  411  including an OLED (not shown in the Figure) is provided. An annular groove is on the periphery of the inner surface of the cover plate  420  and surrounds the organic light-emitting element  411 . As shown, the groove is located where the packaging adhesive  430  extends into the cover plate  420 . The thickness of the packaging adhesive  430  is greater than the depth of the groove, so that a portion of the packaging adhesive  430  is in the groove of the cover plate  420 , and a portion of the packaging adhesive  430  extends outside the groove of the cover plate  420 . The cover plate  420  and the substrate  410  are adhered to each other by the packaging adhesive  430 , so as to seal the organic light-emitting element  411 . 
         [0016]    It should be noted that, in other embodiments according to the present invention, multiple grooves may also be similarly used. The frit is filled in each of the grooves, and the adhering is performed, so that the effect of sealing and adhering between the cover plate  420  and the substrate  410  is improved. 
         [0017]    In some embodiments, multiple spacers  412  (only one is shown in  FIG. 4 ) are provided between the organic light-emitting element  411  and the cover plate  420 . In the OLED package structure  400  according to the embodiment shown, a portion of the packaging adhesive  430  is fixed in the groove of the cover plate  420 . Therefore, the distance between the cover plate  420  and the substrate  410  adhered with the packaging adhesive  430  can be reduced with the packaging being not affected, and thus the thickness of the spacer  412  may be smaller. Since the thickness of the spacers  412  is smaller, evaporated materials at undesirable places may be reduced or eliminated. Accordingly, a color mixture phenomenon is prevented from occurring in the OLED package structure  400 . Moreover, since the thickness of the spacers  412  is equal to the distance between the cover plate  420  and the substrate  410 , in this case the spacers  412  may ensure a uniform distance between the cover plate  420  and the substrate  410 , so that the Newton ring phenomenon is prevented form occurring in the entire OLED package structure  400 . 
         [0018]    In some embodiments, the thickness of the spacer is typically above 2.5 μm. However, in other embodiments, the thickness of the spacer  412  is much smaller and may be below about 2.0 μm. For example, the thickness of the spacer may be about 1.5 μm or about 1.0 μm. 
         [0019]    In the embodiment, the substrate  410  may be either a transparent substrate  410  or a semitransparent or nontransparent substrate  410 . In some embodiments, the substrate  410  is a glass substrate  410 . 
         [0020]    The cover plate  420  may be transparent. The cover plate  420  may be made of a glass material or a plastic material. In order to be used with the packaging adhesive  430 , the depth of the may be between about 1 μm and about 4 μm, and the width thereof may be between about 0.8 μm and about 2 μm. 
         [0021]    The packaging adhesive  430  may be frit. The frit can not be manufactured because the frit can not have a good sealing and adhering effect if to thin. The thickness of the frit may be between about 5 μm and about 9 μm. With a thickness in such a range, a portion of the frit may extend into the groove of the cover plate  420  and another portion of the frit is exposed outside the groove to adhere to the substrate  410 . It should be noted that, other packaging adhesives which are capable of ensuring good sealing for the OLED package structure  400  may also be applicable in other embodiments according to the present invention. 
         [0022]    The OLED may be an active matrix OLED and the organic light-emitting element  411  may be an active matrix organic light-emitting element  411 . Thus the formed OLED package structure  400  may be an active matrix OLED package structure. 
       A Second Embodiment 
       [0023]    A method for forming an OLED package structure, including Step S 1  to Step S 5  is described below. It should be noted that, in the method, the steps are named as S 1  to S 5  for distinguishing the steps conveniently and not for limiting the sequencing of the steps. In different embodiments according to the present invention, the sequencing of the steps may be adjusted. Steps S 1  to S 5  are described in conjunction with  FIG. 4  to  FIG. 7 . The OLED package structure  400  as shown in  FIG. 4  is formed with Steps S 1  to S 5  (corresponding to structures shown in  FIG. 5  to  FIG. 7 ) in the embodiment. 
         [0024]    In Step S 1 , an entire substrate including multiple substrate units is provided. Each substrate unit includes an organic light-emitting element. 
         [0025]    With reference to  FIG. 5 , the entire substrate  510  includes multiple substrate units. As shown in  FIG. 5 , in this embodiment, only a portion of one substrate unit of the entire substrate  510  is shown for convenience of illustration. On the substrate unit, an organic light-emitting element  511  including an OLED is provided. Various processes for forming the organic light-emitting element  511  on the entire substrate  510  are known and are not described herein. 
         [0026]    Still referring to  FIG. 5 , a spacer  512  is provided on the organic light-emitting element  511  and the thickness of the spacer  512  is much less than that in conventional displays, and may be less than 2.0 μm. In some embodiments, the thickness of the spacer  512  may be only about 1.5 μm or about 1.0 μm. 
         [0027]    In Step S 2 , an entire cover plate is provided. The entire cover plate includes multiple cover plate units. One or more annular grooves are formed in the inner surface of each of the cover plate units to surround the organic light-emitting element. 
         [0028]    In the shown embodiment, the entire cover plate  520  (referring to  FIG. 6 ) corresponding to the entire substrate  510  is provided. The entire cover plate  520  includes multiple cover plate units. Similarly, as shown in  FIG. 6 , only a portion of one cover plate unit of the entire cover plate  520  is shown for convenience of illustration. The cover plate unit matches and aligns with the substrate unit. Accordingly, each cover plate unit covers one substrate unit. An annular groove  521  is provided in the inner surface of each of the cover plate units surrounding the organic light-emitting element. It should be noted that, in other embodiments of the invention, multiple annular grooves may be used. 
         [0029]    The entire cover plate  520  may be a transparent cover plate. In some embodiments, the entire cover plate  520  is made of a glass material or a plastic material. The depth of the groove  521  may range from about 1 μm to about 4 μm and the width thereof may range from about 0.8 μm to about 2 μm, so that a portion of a packaging adhesive can fill in the groove  521 . 
         [0030]    In Step S 3 , the packaging adhesive is formed in the groove of the cover plate unit. A portion of the packaging adhesive is located inside the groove of the cover plate and a portion of the packaging adhesive extends outside the groove of the cover plate. 
         [0031]    Referring to  FIG. 7 , the packaging adhesive  530  may be a frit. The frit may be formed in the groove  521  by using, for example, a screen printing process. Moreover, the thickness of the frit packaging adhesive  530  may range from about 5 μm to about 9 μm to fit the size of the groove  521 . The depth of the groove  521  may range from about 1 μm to about 4 μm and the width thereof may range from about 0.8 μm to about 2 μm. It should be noted that other packaging adhesives which are capable of ensuring good sealing for the OLED package structure may also be applicable in other embodiments according to the present invention. 
         [0032]    In Step S 4 , the entire cover plate and the entire substrate are pressing together, and the cover plate units are adhered to the substrate units using the packaging adhesive, so as to seal each organic light-emitting element. 
         [0033]    In Step S 4 , multiple seal structure units are formed as a whole. Therefore, the entire cover plate  520  and the entire substrate  510  are pressed together with the cover plate units being adhered to the substrate units using the packaging adhesive  530 , and each organic light-emitting element  511  is sealed. Although the formed entire OLED package structure is not shown in the figure, the structure in  FIG. 4  may be referred to.  FIG. 4  may be regarded as a schematic diagram illustrating a portion of one unit of the OLED package structures formed as a whole. The frit may be melted by laser to adhere the cover plate units with the substrate units. 
         [0034]    In Step S 5 , the adhered entire cover plate and entire substrate are cut, to obtain multiple OLED package structures. 
         [0035]    The OLED package structures formed as a whole are cut into individual OLED package structures. The adhered entire cover plate and entire substrate are cut to obtain multiple OLED package structures. For the OLED package structure, the OLED package structure  400  shown in  FIG. 4  may be referred to. The OLED may be an active matrix OLED and the organic light-emitting element may be an active matrix organic light-emitting element. Thus, the finally formed OLED package structure may be an active matrix OLED package structure. 
         [0036]    The above described characteristics are only specific embodiments of the present invention. However, the scope of protection of the present invention is not limited thereto. Changes may be made to the embodiments by those skilled in the art in light of the spirit of the present invention without deviation from the scope of protection of the present invention.