Abstract:
A sealing structure and a plasma display panel employing the same. A front plate, a rear plate, and a sealing layer are all provided. Sealing strength and reliability of the sealing structure are improved by the intended position and geometric shape of the sealing layer located between the front plate and the rear plate, thereby raising plasma display panel yield.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a sealing structure, and more particularly to a sealing structure for a plasma display panel.  
         [0003]     2. Description of the Related Art  
         [0004]     Flat panel displays (FPD), such as liquid crystal displays (LCD), organic light emitting diodes (OLED) and plasma display panels (PDP), are rapidly replacing cathode ray tubes (CRT). Plasma display panels are self-emitting, highly luminous, provided wider viewing angle, and have a simpler fabrication process. Thus they are a popular choice for industry.  
         [0005]     A PDP is a display device employing charges accumulated by electrode discharge. Due to a variety of advantages, such as large scale, high capacity and full-color capability, the PDP has become one of the most popular flat panels for various applications.  
         [0006]     Typically, a front plate and a rear plate of a PDP are formed first. The front plate is thus inverted for mounting onto the rear plate. The two plates are then sealed together to form closed discharge cells. The tightness of the sealing process can affect the yield of subsequent processes that remove gases from, or inject gases into the PDP. Additionally, the sealing process may affect the isolation between each discharge cell.  
         [0007]      FIG. 1  is a perspective view illustrating a conventional method for sealing a front plate  12  and a rear plate  14  of a PDP  10 .  
         [0008]     The PDP  10  includes the front plate  12 , the rear plate  14  in parallel with the front plate  12 , and a plurality of barrier ribs  16  on a predetermined area of the rear plate  14 .  
         [0009]     In the conventional method for sealing the two plates, a sealing frit  18  is formed and surrounds the barrier ribs  16  on the rear plate  14 , and a corresponding sealing frit  18  is formed on the front plate  12 . The front plate  12  and the rear plate  14  are affixed, and the sealing frits  18  temporarily bond to each other. The front plate  12  and the rear plate  14  are then placed into an oven and heated to 450° C., and the sealing frits  18  are melted to form a sealing layer. After cooling, the front plate  12  and the rear plate  14  are tightly bonded together.  
         [0010]     The sealing strength of the PDP  10 , however depends on the position and geometric shape of the sealing layer  18 ′ located between the front plate  12  and the back plate  14 , referring to  FIGS. 2   a  to  2   c . If the sealing layer  18 ′ has an unsatisfactory geometric shape as shown in  FIGS. 2   a  to  2   c , it is probable that the PDP  0 . 10  will crack or separate during a subsequent thermal compression step due to the insufficient strength of the seal thereof, resulting in low yield.  
         [0011]     Therefore, it is necessary to further modify the position and geometric shape of the sealing layer located between the two plates, in order to improve the sealing strength of a PDP.  
       SUMMARY OF THE INVENTION  
       [0012]     Accordingly, an object of the present invention is to provide a sealing structure for plasma display panel providing improved sealing strength between the front plate and the rear plate of the plasma display panel, with increased the sealing structure reliability.  
         [0013]     Another object of the present invention is to provide a plasma display panel having the sealing structure according to the present invention. Sealing strength and reliability of the sealing structure are improved by the intended position and geometric shape of the sealing layer located between the front plate and the rear plate, thereby raising the production yield.  
         [0014]     To achieve the above objects, according to the present invention, a sealing structure with a high sealing strength comprises a first plate, a second plate under and offset from the first plate, and a sealing layer located between the first surface and the second surface providing a seal therebetween, wherein the sealing layer comprises a first region contacting the first plate and a second region contacting the second plate. Particularly, the first region extends at least to an outer edge of the underside of the first plate, and the second region extends at least to a boundary corresponding to the outer edge of the first plate.  
         [0015]     According to the present invention, the sealing layer can be formed to extend beyond a plane containing the outer edge and the boundary.  
         [0016]     In the present invention, a plasma display panel comprises a first plate, a second plate under and offset from the first plate, and a sealing layer located between the first surface and the second surface for sealing the first plate and the second plate, wherein the sealing layer comprises a first region contacting the first plate and a second region contacting the second plate. Particularly, the first region extends at least to an outer edge of the underside of the first plate, and the second region extends at least to a boundary corresponding to the outer edge of the first plate. Furthermore, the first plate or the second plate acts a front plate of the plasma display panel and the other remaining plate as a rear plate of the plasma display panel.  
         [0017]     According to the present invention, the sealing layer can be formed to extend beyond a plane containing the outer edge and the boundary.  
         [0018]     A detailed description is given in the following embodiments with reference to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     The present invention can be more fully understood by reading the subsequent detailed description in conjunction with the examples and references made to the accompanying drawings, wherein:  
         [0020]      FIG. 1  is a perspective view illustrating a method for sealing a front plate and a rear plate of a PDP according to the related art.  
         [0021]      FIGS. 2   a  to  2   c  are cross sections of a conventional sealing structure of a PDP.  
         [0022]      FIG. 3  is a cross section of a combination of a first plate and a second of the present invention.  
         [0023]      FIGS. 4   a  to  7   e  are cross sections of the sealing structures according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0024]     The present invention improves the sealing strength and reliability of a sealing structure through the specific position and geometric shape of the sealing layer thereof. While a PDP is used to illustrate the invention, numerous modifications and variations will be apparent to those skilled in the art.  
         [0025]      FIG. 3  is a cross section of a combination of a first plate and a second plate without a sealing layer, illustrating the positional relationship between each element of the sealing structure of a PDP. The PDP  100  comprises a first plate  104  and a second plate  102  parallel to and offset from the first plate  104 , wherein the first plate  104  has a first surface  114  and the second plate  102  has a second surface  112  facing the first surface  114 . A plurality of barrier ribs  110  are disposed between the two plates  104  and  102  for forming a discharging space. The first surface  114  of the first plate  104  has an outer edge P 1 , and the second plate  102  extends to a perpendicular plane containing the outer edge P 1  of the first plate  104 . Furthermore, the second plate  102  contains a boundary P 2  corresponding to the outer edge P 1  of the first plate  104 , and a plane  122  containing the outer edge P 1  and the boundary P 2  is perpendicular to the second plate  102 . The distance between the two plates  102  and  104  is about 50 μm to 250 μm.  
         [0026]      FIGS. 4   a  to  4   e  are cross sections illustrating sealing structures with a high sealing strength of the PDP according to the present invention.  
         [0027]     Referring to  FIG. 4   a , the PDP  100  comprises a sealing layer  120  formed between the first plate  104  and the second plate  102  for sealing a peripheral region of the first plate  104  and the second plate  102 , wherein the sealing layer  120  comprises a first region  134  contacting the first plate  104  and a second region  132  contacting the second plate  102 . Moreover, the first region  134  contains a first edge A 1  and the second region  132  contains a second edge B 1  and a third edge B 2 , as shown in  FIG. 4   a . The first plate  104  or the second plate  102  acts a front plate of the plasma display panel and the other acts as a rear plate of the plasma display panel. The sealing layer  120  can be a sealing frit or an adhesive. Specifically, the position and geometric shape of the sealing layer  120 , located between the two plates  102  and  104 , according to the present invention is defined in the following.  
         [0028]     The first region  134  of the sealing layer  120  extends at least to an outer edge P 1  of the first surface  114 , and the second region  132  of the sealing layer  120  extends at least to a boundary P 2  corresponding to the outer edge P 1 . Moreover, the sealing layer  120  can be formed to extend beyond the plane  122  containing the outer edge P 1  of the first surface  114  and the boundary P 2 , as shown in  FIGS. 4   b  to  4   e . Furthermore, the vertical distance between the first edge A 1  and the second edge B 1  is not less than the distance between the outer edge P 1  and the boundary P 2 , and the horizontal distance between the second edge B 1  and the third edge B 2  is not less than the distance between the boundary P 2  and the third edge B 2 . Accordingly, the vertical distance between the first edge A 1  and the second edge B 1  can be equal to the distance between the outer edge P 1  and the boundary P 2 , as shown in  FIGS. 4   a  and  4   c . Additionally, the vertical distance between the first edge A 1  and the second edge B 1  can be more than the distance between the outer edge P 1  and the boundary P 2 , as shown in  FIGS. 4   b ,  4   d  and  4   e.    
         [0029]     In the PDP  100  of the present invention, the peripheral side surface  116  of the first plate  104  can be planar and perpendicular to the first surface  114 , as shown in  FIGS. 4   a  to  4   e . In another aspect, the peripheral side surface  116  of the first plate  104  can intersect with the first surface  114  to form an acute angle, as shown in  FIGS. 5   a  to  5   e . In still another aspect, the peripheral side surface  116  of the first plate  104  can intersect with the first surface  114  to form an obtuse angle, as shown in  FIGS. 6   a  to  6   e . The peripheral side surface  116  of the first plate  104  can also be a cambered surface as shown in  FIGS. 7   a  to  7   e , or a curved surface.  
         [0030]     The thermal compression yields of conventional PDPs and the PDPs according to the present invention are respectively shown in Table 1. Accordingly, the crack loss of conventional PDPs is more than 30%. To the contrary, the crack loss of the sealing structure according to the present invention is less than 0.1%. Therefore, the sealing strength thereof is improved.  
                                                     TABLE 1                                       Yield   Crack           Sealing structure   (%)   loss (%)                                    Conventional   {overscore (B1B2)} &lt; {overscore (P2B2)}   H2 = H1     60%     40%       PDPs   {overscore (B1B2)} &lt; {overscore (P2B2)}   H2 &gt; H1     70%     30%       PDPs of the   {overscore (B1B2)} ≧ {overscore (P2B2)}   H2 ≧ H1   99.9%   0.01%       present       invention                 {overscore (B1B2)}: horizontal distance between B1 and B2;            {overscore (P2B2)}: horizontal distance between P2 and B2;            H1: vertical distance between P1 and P2; and            H2: vertical distance between A1 and P2.             
 
         [0031]     Accordingly, the sealing structure of the present invention provides improved sealing strength and increased reliability, when compared to the related art.  
         [0032]     Moreover, the sealing structure is suitable not only for PDPs, but also for other FPDs such as OLEDs or LCDs is eliminating instability resulting from glass crack or separation.  
         [0033]     While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.