Abstract:
An alternating current drive type plasma display panel (AC PDP) having a discharge cell-defining barrier structure with minimized firing shrinkage distortions provided by selecting different line widths for the barrier rib row and column members, and/or adding supplementary barrier rib members adjacent the peripheral edges of the barrier rib structure, and/or reducing the zig-zag distances of the edge profile of the barrier rib structure.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to plasma display panels. More particularly, this invention relates to an alternating current drive type plasma display panel (AC PDP) having a discharge cell-defining barrier structure formed by an x-y array of T-shape ribs having minimized firing shrinkage distortions, and methods for making such a barrier structure.  
       BACKGROUND OF THE INVENTION  
       [0002]     Plasma display panels (PDPs) are rapidly becoming one of the more popular types of color display devices used for displaying color images, for example, on computers and televisions, because they are slim, lightweight, and typically have large display screens. PDPs are classified as either a direct current (DC) type or an alternating current (AC) type.  
         [0003]     As shown in  FIGS. 1A and 3C , a conventional AC PDP may include a front glass substrate  50 , a rear glass substrate  10 , and a barrier rib structure  20  formed on an inner surface of the rear substrate  10  in display area A thereof. The barrier rib structure  20  may be constructed as an x-y array of T-shaped barrier ribs  30  (best seen in  FIG. 1B ) each of which is defined by a straight row member  32  and a straight column member  34 . In an alternative embodiment, as shown in  FIG. 2 , the barrier rib structure  20 ′ may be constructed as an x-y array of Y-shaped barrier ribs  30 ′ each of which is defined by a bent row member  32 ′ and a straight column member  34 ′. The row members  32  and  32 ′ have respective line widths w r  and w r′ , and column members  34  and  34 ′ have respective line widths w c  and w c′ . The row member line widths w r  and w r′  are substantially equal to respective column member line widths w c  and w c′ . The x-y array of barrier ribs  30 ,  30 ′ define a plurality of rectangular ( FIG. 1B ) or hexagonal ( FIG. 2 ) sub-pixel spaces  40 ,  40 ′. An AC PDP similar to the one described above having rectangular sub-pixel spaces as shown in  FIG. 1B , is described in U.S. Pat. No. 6,373,195. An AC PDP similar to the one described above but with hexagonal sub-pixel spaces as shown in  FIG. 2 , is described in U.S. Pat. No. 5,317,334.  
         [0004]     The above-described barrier rib structures are typically fabricated from a compound of glass powder and oxide material. The barrier rib structure is usually fabricated in a process that includes the steps of coating or printing a layer of the glass powder and oxide compound onto the rear substrate, patterning the coating to define the x-y array of barrier ribs, and then firing the patterned coating.  
         [0005]     A problem associated with the fabrication process is that the barrier ribs experience thermal shrinkage during firing. This problem is depicted in  FIGS. 3A and 3B  wherein  FIG. 3A  shows one of the barrier ribs  30  before firing and  FIG. 3B  shows the same barrier rib  30  after firing. The vertical and column members  32 ,  34  experience substantial shrinkage in the direction of arrow S ( FIG. 3A ), which distorts the rib  30  as shown in  FIG. 3B . This distortion causes the front surface of the row member  32  of the rib  30  to project upwardly towards the front substrate  50  of the AC PDP. This problem is especially critical when very narrow line width barrier ribs are employed in the barrier rib structure. The projection problem is typically seen only on the front surface of the barrier ribs because the rear surface of the ribs are restrained by the rear substrate  10 . Thus, when the barrier ribs become distorted, the projection is usually towards the gap h 2 -h 1  between the front substrate  50  and rear substrate  10 . The projections can cause a buzzing noise especially at the edge of the display area. At the same time, the shrinkage can allow the gap h 2 -h 1  to become large enough such that an erroneous discharge will be produced in a neighboring sub-pixel cell C 1 , C 2 , C 3 , which produces cross-talk in the display area A.  
         [0006]     As shown in  FIGS. 5A-5C , the barrier rib structure  20 ,  20 ′ are patterned with a zig-zagging edge profile  22 ,  22 ′. The zig-zagging edge profiles generate substantial rib shrinkages or distortions in the directions identified by arrows S in  FIGS. 5B and 5C , which result in the rib projections described above after firing. In addition to the distortion problems, a certain number of the barrier ribs exhibit open defect problems or breaks after patterning, as shown in  FIG. 4 . Such defective ribs become distorted after firing also.  
       SUMMARY  
       [0007]     A method is described for making a sub-pixel barrier structure for a plasma display panel having an array of intersecting barrier rib row and column members. The method comprises the steps of: forming a layer of dielectric material over a substrate; selecting a line width for each of the barrier rib row and column members which minimizes fired shrinkage distortions in the barrier structure; patterning the barrier rib row and column members of the selected line widths in the layer; and firing the substrate.  
         [0008]     A method is described for making a sub-pixel barrier structure for a plasma display panel having an array of intersecting barrier rib row and column members. The method comprise the steps of: forming a layer of dielectric material over a substrate; patterning the barrier rib row and column members in the layer; and patterning supplementary barrier rib members in the layer adjacent at least one edge of the barrier structure; and firing the substrate.  
         [0009]     A sub-pixel barrier structure is described for a plasma display panel. The barrier structure comprises: a plurality of barrier rib row members, each of the row members having a line width; and a plurality of barrier rib column members intersecting the barrier rib row members, each of the column members having a line width; wherein the line widths of the barrier rib row and column members are selected to minimize fired shrinkage distortions in the barrier structure.  
         [0010]     A plasma display panel is described. The plasma display panel comprises: a sub-pixel barrier structure comprising: a plurality of barrier rib row members, each of the row members having a line width; and a plurality of barrier rib column members intersecting the barrier rib row members, each of the column members having a line width; wherein the line widths of the barrier rib row and column members are selected to minimize fired shrinkage distortions in the barrier structure.  
         [0011]     A sub-pixel barrier structure is described for a plasma display panel. The barrier structure comprises: a plurality of barrier rib row members; a plurality of barrier rib column members intersecting the barrier rib row members; and supplementary barrier rib members adjacent at least one edge of the barrier structure for minimizing fired shrinkage distortions in the barrier structure.  
         [0012]     A plasma display panel is described. The plasma display panel comprises a sub-pixel barrier structure comprising: a plurality of barrier rib row members; a plurality of barrier rib column members intersecting the barrier rib row members; and supplementary barrier rib members adjacent at least one edge of the barrier structure for minimizing fired shrinkage distortions in the barrier structure. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1A  is a plan view of a rear substrate of a conventional AC PDP with an enlarged view of an inner section of an embodiment of a barrier rib structure.  
         [0014]      FIG. 1B  is a further enlarged, plan view of the section of the barrier rib structure shown in  FIG. 1A .  
         [0015]      FIG. 2  is a plan view of an inner section of another embodiment of a conventional barrier rib structure.  
         [0016]      FIG. 3A  is a plan view of a barrier rib of the conventional barrier rib structure of  FIG. 1B  before firing.  
         [0017]      FIG. 3B  is a plan view of the barrier rib of  FIG. 3A  after firing.  
         [0018]     FIG. 4 is a plan view of a defective barrier rib of the conventional barrier rib structure of  FIG. 1B  before and after firing.  
         [0019]      FIG. 5A  is a plan view of a rear substrate of the AC PDP of  FIG. 1A  with an enlarged view of a peripheral section of the barrier rib structure.  
         [0020]      FIG. 5B  is a further enlarged, plan view of the peripheral section of the barrier rib structure shown in  FIG. 5A .  
         [0021]      FIG. 2  is a plan view of a peripheral section of the embodiment of the barrier rib structure shown in  FIG. 2 .  
         [0022]      FIG. 6  is a perspective view of an embodiment of an AC PDP according to the present invention.  
         [0023]      FIG. 7A  is a plan view of an embodiment of a barrier rib according to a first aspect of the present invention.  
         [0024]      FIG. 7B  is a plan view of another embodiment of a barrier rib according to the first aspect of the present invention.  
         [0025]      FIGS. 8A, 8B ,  9 A- 9 D,  10 A,  10 B,  11 A,  11 B,  12 A- 12 F, and  13 A- 13 C are plan views showing peripheral sections of various embodiments of a barrier rib structure according to a second aspect of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]      FIG. 6  shows an exemplary embodiment of an AC PDP  200  according to the present invention. The AC PDP  200  comprises a rear glass substrate  210  having formed on an inner surface thereof a barrier rib structure  220  defined by an x-y array of T-shaped (shown in  FIG. 6 ) or Y-shaped barrier ribs  230  each of which is defined by a row member  232  and column member  234 . The barrier rib row members  232  are arranged parallel to one another, and the barrier rib column members  234  are arranged parallel to one another, and perpendicular to and intersecting the barrier rib row members  232 , thereby defining a plurality of square, rectangular (shown in  FIG. 6 ) or hexagonal sub-pixel spaces  240 . Address electrodes (not shown) are formed under the sub-pixel spaces  240  and the barrier rib column members  234 , and red, green, and blue phosphor layers  260   a,    260   b,    260   c  are disposed in adjacent sub-pixel spaces  240  in a delta configuration. Each delta configured group of sub-pixel spaces  240  with red, green, and blue phosphor layers  260   a,    260   b,    260   c  forms a color pixel  270 . The AC PDP  200  further comprises a transparent front glass substrate  250  having bus electrodes  280  corresponding to and along the barrier rib row members  232 , and sustain electrodes  290  disposed over the phosphor-coated sub-pixel spaces  240 .  
         [0027]     In accordance with a first aspect of the present invention, the barrier ribs  230  of the barrier rib structure  220  may be patterned to provide row members and column members of different line widths.  FIG. 7A  shows an embodiment a barrier rib  330  according to the present invention wherein the barrier rib row member  332  has a line width w r  which is greater than the line width w c  of the barrier rib column member  334 .  FIG. 7B  shows another embodiment of a barrier rib  430  wherein the line width w c  of the column rib member  434  is greater than the line width w r  of the barrier rib row member  432 .  
         [0028]     Patterning the barrier rib row and column members with different line widths reduces firing shrinkage distortion of the barrier ribs. This in turn reduces the barrier rib projection problem associated with prior art barrier rib structures. Accordingly, the gaps between the front surfaces of the barrier ribs and the front substrate are minimized such that erroneous discharges caused by overly large gaps are substantially reduced or eliminated between neighboring sub-pixel cells resulting in a corresponding reduction or elimination of gap related cross-talk in the display area.  
         [0029]     The reduction in firing shrinkage distortion realized from patterning the barrier rib row and column members with different line widths, also reduces the front surface projection problem of prior art barrier rib structures. Hence, the buzzing noise associated with barrier rib front surface projection problems is substantially reduced or eliminated.  
         [0030]     Patterning the barrier rib row and column members with different line widths is especially effective for reducing shrinkages and distortions within the inner areas of the barrier rib structure. However, the zig-zagging edge profile of the barrier rib structure generates additional rib shrinkage and distortion problems, because the barrier rib row and column members along the edges of the barrier rib structure are unrestrained, unlike the barrier rib row and column members disposed within the inner areas of the structure.  
         [0031]     Hence, in accordance with a second aspect of the invention, the unrestrained barrier rib row and column members forming the edge profile of the barrier rib structure may be restrained by adding supplementary barrier rib members which reduce or eliminate shrinkage and distortion along the periphery thereof after firing. The following discussion provides a few examples of supplementary barrier rib members.  
         [0032]     In the rectangular sub-pixel space embodiment of the barrier rib structure shown in  FIG. 8A , the barrier rib row and column members forming the edge profile of the barrier rib structure may be restrained by adding supplementary column members  500  to close off open sub-pixel spaces along the edge of the barrier rib structure, thus providing a straight edge profile.  
         [0033]     The barrier rib row and column members (including the supplementary column members) forming the edge profile of the barrier rib structure may have different line widths w r  and w c  as shown in  FIG. 10A . In another embodiment, as shown in  FIG. 10B , the barrier rib row and column members (including the supplementary column members) forming the edge profile of the barrier rib structure may have respective line widths w re  and w ce  that are each different (greater than in the shown embodiment of  FIG. 10B ) from the line width w ri  of the row members and/or line width w ci  of the column members defining the inner portion of the barrier rib structure.  
         [0034]     In the hexagonal sub-pixel space embodiment shown in  FIG. 8B , the barrier rib row and column members forming the edge profile of the barrier rib structure may be restrained by: 1) adding supplementary column members  500 ′ to close off open sub-pixel spaces along the side edges of the barrier rib structure, thus providing a straight edge profile along this edge, and/or 2) adding an elongated row member  510  along the zig-zagging, outermost row of barrier rib row members, thus providing a straight edge profile along this edge.  
         [0035]      FIGS. 9A-9D  show other supplementary barrier rib members for restraining the unrestrained barrier rib row and column members forming the edge profile of the barrier rib structure to reduce or eliminate shrinkage and distortion along the periphery thereof after firing. The embodiment shown in  FIG. 9A  is similar to the embodiment of  FIG. 8A , except that supplementary column members  600  are added in the space between the outermost barrier rib column members. The line widths w cs  of the supplementary barrier rib column members  600  may be different (greater than, as shown in  FIG. 9A ) from w c  of the column members.  
         [0036]     The embodiment shown in  FIG. 9B  is similar to the embodiment shown in  FIG. 8B , except that the barrier rib row members forming the edge profile of the barrier rib structure may be restrained by adding supplementary column members  700  along the outermost row of barrier rib row members, the ends of which are connected together with supplementary elongated row member  710 .  
         [0037]     The embodiment shown in  FIG. 9C  is also similar to the embodiment shown in  FIG. 8B , except that the barrier rib row members forming the edge profile of the barrier rib structure may be restrained by adding alternating long and short supplementary column members  800 ,  801  along the outermost row of barrier rib row members, the ends of which are connected together with a supplementary elongated row member  810 . The supplementary column members  800  and  801  may have different line widths w c1  and w c2 , respectively.  
         [0038]     In the embodiment of  FIG. 9D , the barrier rib row members forming the edge profile of the barrier rib structure may be restrained by adding very short supplementary column members  900  along the outermost row of barrier rib row members, the ends of which are connected together with a supplementary elongated row member  910 . The barrier rib row and column members forming the zig-zagging edge profile of the barrier rib structure may be restrained by adding longer supplementary row members  911 , the ends of which are connected together with an elongated column member  912 .  
         [0039]     The embodiments shown in  FIGS. 11A and 11B  are similar to the respective embodiments of  FIGS. 8A and 9B , except that one or more of the corner positions of the barrier rib structure are open, instead of closed to accommodate pumping apertures in the rear substrate  210 , which allow air, disposed in the space between the front substrate  250  and the rear substrate  210 , to be evacuated.  
         [0040]     The embodiments shown in  FIGS. 12A-12F  are similar to the embodiment of  FIG. 8A , except these embodiments further include a restraining lattice structure formed by: one or more supplementary elongated column members  1100  connected by one or more supplementary row members  1110  (FIGS.  12 A- 12 C); supplementary large radius curved members  1200  and supplementary row members  1210  ( FIG. 12D ); supplementary small radius curved members  1300  ( FIG. 12E ); and supplementary arrow-head shaped members  1400  ( FIG. 12F ).  
         [0041]     In accordance with a third aspect of the invention, the barrier rib row and column members forming the zig-zagging edge profile can be restrain during firing by reducing the distance a of the zig-zag ( FIG. 5B ) as shown in  FIG. 13A . The outermost row column members forming the zig-zagging edge profile have a shortened zig-zag distance a′.  
         [0042]     The embodiment shown in  FIG. 1   3 B is similar to the embodiment of  FIG. 12E , except that the curved members  1300 ′ of the lattice structure define a zig-zagging edge profile which has a shortened zig-zag distance a′. Similarly, the embodiment shown in  FIG. 13C  is similar to the embodiment of  FIG. 12F , except that the arrow-head members  1400 ′ of the lattice structure define a zig-zagging edge profile which has a shortened zig-zag distance a′.  
         [0043]     The barrier rib structures of the present invention may be fabricated from a dielectric material comprising, for example, a compound of glass powder, e.g., SiO 2 , and oxide material, e.g., Al 2 O 3 , B 2 O 3 , PbO, ZnO, and combinations thereof. The barrier rib structures may be fabricated in a process that includes the steps of coating or printing a layer of the glass powder and oxide compound onto the rear substrate  210 , patterning the coating to define the x-y array of barrier ribs, and then firing the patterned coating. The firing may be conducted in an air atmosphere at about 550° C. for about 30 minutes. The firing process can be adjusted according to the composition of the dielectric material.  
         [0044]     While the foregoing invention-has been described with reference to the above embodiments, various modifications and changes can be made without departing from the spirit of the invention. Accordingly, all such modifications and changes are considered to be within the scope of the appended claims.