Patent Publication Number: US-2006012302-A1

Title: Plasma display panel

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a plasma display panel (PDP) and, more particularly, to bus electrodes and rib structures of a plasma display panel.  
      2. Description of the Related Art  
      A plasma display panel (PDP) is a thin type display, typically has a large display area. The luminescent principle of the PDP is the same as that of fluorescent lamps. A vacuum glass trough is filled with inert gas. When a voltage is applied to the glass trough, plasma occurs and radiates ultraviolet (UV) rays. The fluorescent material coated on the wall of the glass trough adsorb the UV rays, hence the fluorescent material radiates visible light including red, green and blue light. A plasma display can be described as a combination of hundreds of thousands of illuminating units, each illuminating unit has three subunits for radiating red, green and blue light, respectively. Images are displayed by mixing these three primary colors.  
      As shown in  FIG. 1 , a conventional PDP  10  has a pair of glass substrates  12 , and  14  arranged parallel and opposite to each other. A discharge space  16  is formed between the glass substrates  12 , and  14  and injected with inert gases, such as Ar, Xe or others. The upper glass substrate  12  has a plurality of transverse electrode group positioned in parallel. Each group of transverse electrode groups has a first and a second sustaining electrode  18 , and  20 , and each of which includes transparent electrodes  181 ,  201  and bus electrodes  182 ,  202 . A dielectric layer  24  is further formed to cover these transverse electrodes, and a protection layer  26  is formed on the dielectric layer  24 .  
      The lower glass substrate  14  has a plurality of barrier ribs  28  arranged in parallel and spaced apart by a predetermined distance dividing the discharge space  16  into a plurality of groups of sub-discharge spaces. Each group of sub-discharge spaces includes a red discharge space  16 R, a green discharge space  16 G, and a blue discharge space  16 B. Additionally, the lower glass substrate  14  has a plurality of lengthwise electrodes  22  disposed in parallel between two adjacent barrier ribs  28  serving as address electrodes. In addition, a red fluorescent layer  29 R, a green fluorescent layer  29 G, and a blue fluorescent layer  29 B are respectively coated on the lower glass substrate  14  and the sidewalls of the barrier ribs  28  within each red discharge space  16 R, each green discharge space  16 G, and each blue discharge space  16 B.  
      When a voltage is applied for driving these electrodes, the inert gases in the discharge space  16  are discharged to produce UV rays. The UV rays further illuminate the fluorescent layers  29 R,  29 G,  29 B to radiate visible light including red, green and blue light. After the three primary colors are mixed at different ratios, various images are formed and transmitted through the upper glass substrate  12 .  
       FIG. 2  is a plane view of a conventional PDP with close sub-pixel spaces. As shown in  FIG. 2 , bus electrodes  202  are disposed on a front substrate, extending along the profile of ribs  204  substantially in direction X to prevent them from blocking a light source of the PDP. Typically, the ribs  204  are white, such that ambient light is easily reflected by the uncovered white ribs  206 , thus reducing contrast of the PDP.  
     SUMMARY OF THE INVENTION  
      An embodiment of the invention provides a bus electrode with protrusions to cover ribs on a rear substrate, thus reducing reflection of ambient light and increasing contrast of PDP.  
      To achieve the above objects, the present invention provides a high contrast plasma display structure. A plurality of ribs are formed on a rear substrate to define a plurality of sub-pixel spaces, wherein the ribs comprise first portions extending substantially in a first direction and second portions extending substantially in a second direction perpendicular to the first direction. A front substrate is disposed opposite to the rear substrate. A sustain electrode formed on the front substrate comprises a bus electrode and a plurality of protrusions. The bus electrode extends substantially along the first portion. The protrusions extend along the second portion from the bus electrode, covering the second portion without connecting to adjacent bus electrodes.  
      A detailed description is given in the following embodiments with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:  
       FIG. 1  shows the structure of the conventional PDP.  
       FIG. 2  is a plane view of the conventional PDP with close sub-pixel spaces;  
       FIG. 3  is a plane view of PDP of the first embodiment;  
       FIG. 4  is a plane view of a PDP of the second embodiment;  
       FIG. 5  is a plane view of a PDP of the third embodiment;  
       FIG. 6  is a plane view of a PDP of the fourth embodiment;  
       FIG. 7  is a plane view of a PDP of the fifth embodiment.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      An embodiment of the invention provides a sustain electrode structure formed on a front substrate for covering ribs. The sustain rib structure comprises a bus electrode and protrusions extending thereof. The bus electrode is along ribs thereunder and extends in a direction. The exposed ribs are further covered by the protrusions.  
      Embodiments with various ribs and corresponding sustain electrode structures will be described in the following, but the invention is not limited thereto.  
      Examples with rectangular discharge spaces arranged triangularly and corresponding sustain electrode structures are illustrated in the first embodiment. Examples in the second embodiment have similar rib structures with the first embodiment, but the sustain electrode structures differ. The third embodiment illustrates rectangular discharge spaces arranged in a matrix, and corresponding sustain electrode structures. The fourth embodiment illustrates hexagonal discharge spaces arranged triangularly, and corresponding sustain electrode structures. The fifth embodiment illustrates saw-shaped ribs extending along direction Y. The saw-shaped ribs form hexagonal discharge spaces, and further with dark regions.  
     FIRST EMBODIMENT  
       FIG. 3  is a plane view of a PDP of the first embodiment. As illustrated in  FIG. 3 , a rib structure formed on a rear substrate includes first portions  302  and second portions  304 . The first portions  302  are arranged in parallel and the second portions  304  in parallel to perpendicularly intersect the first portions  302 , thereby defining rectangular sub-pixel spaces  306 . The rectangular sub-pixel spaces  306  are arranged triangularly. In the preferred embodiment, the first portions  302  extend along direction X and the second portions  304  along direction Y. Address electrodes (not shown) are formed under sub-pixel spaces  306  and the second portions  304 . The ribs  304  and  306  are formed by depositing thick film on the rear substrate, followed by sandblasting and sintering process. The preferable thickness of the ribs  304  and  306  is about 120˜150 μm. Red, green and blue phosphor layers are respectively disposed on the rectangular sub-pixel spaces  306  in a delta configuration, thus forming delta color pixels.  
      A plurality of sustain electrodes are formed on the front substrate opposite the rear substrate, and cover the ribs  302  and  304  on the rear substrate. Each of the sustain electrode comprises a bus electrode  308  extending along the first portions  302  and a plurality of protrusions  310  extending along the second portions  304 . Thus, the second portions  304  along the direction Y are covered by the protrusions  310 . The bus electrodes  308  are preferably formed of non-transparent materials  308 , such as Cr, Cu, Ag or their combination. Consequently, the white ribs  302  and  304  are covered by the non-transparent bus electrodes  308  and protrusions  310 . The electrodes comprise metal having low resistance.  
      The bus electrodes  308  and the protrusions  310  can be formed with the same process step, such as depositing and patterning a metal layer. Consequently, additional process steps are not required. Wing portions  312  extending from corresponding bus electrodes  308  respectively protrude out and toward the phosphor-coated sub-pixel spaces  306 . Preferably, wing portions are formed of transparent materials, such as ITO, to increase light emission.  
      Adjacent protrusions  310  along a second rib  304  are separated by a predetermined distance, for example 70 μm, to prevent crosstalk. Preferably, the first gap  314  between two adjacent protrusions  310  in the Y direction is large than the second gap  316  between two adjacent wing portions  312  to avoid arcing, and the width of the protrusions  310  is 0.7˜1.2 times that of the second portions  304 , such that the second portions  304  can be covered by protrusions to reduce reflection of ambient light.  
      Because the protrusions  310  are preferably formed at the same time as the bus electrodes, addition process steps, such as photo lithography and etching, are not required for forming protrusions  310 . Additionally, because the bus electrodes  308  and the protrusions  310  are formed of non-transparent materials, the first portions  302  covered by the bus electrodes  308  and the second portions  304  covered by the protrusions  310  cannot reflect ambient light. Specifically, the second portions  304  on the rear substrate are covered by the protrusion  310  to reduce reflection of ambient light and increase contrast of PDP.  
     SECOND EMBODIMENT  
       FIG. 4  is a plane view of a PDP of the second embodiment. Referring to  FIG. 4 , the rib structure and the bus electrodes are the same as in the first embodiment, only the structure of the protrusions  402  differs.  
      In this embodiment, a protrusion  404  extends from a bus electrode  410  in a direction Y, covering a second portion  408  of the rib structure, and the adjacent protrusion  408  extends from the opposite electrode  406 . The second portions  412  of the rib structure on the rear substrate are also covered by the protrusion  404  and  408  that reflection of ambient light is eliminated and contrast of PDP is increased.  
      Alternatively, the bus electrodes comprise a first bus electrode  410  and a second bus electrode  406 . The protrusions comprise a first protrusion  404  and a second protrusion  408 . The first protrusion  404  is connected to the first bus electrode  410 . The second protrusion  408  is connected to the second bus electrode  406 . The first protrusion  404  is separated from the second bus electrode  406 , and the second protrusion  408  is separated from the first bus electrode  410 .  
      In the embodiment, because the third gap  416  between the protrusion  404  and the opposite bus electrode  406  is spaced apart from the discharge region  414 , the third gap  416  can be smaller than the first gap  314  in  FIG. 3  of the first embodiment without arcing problem. The advantage of the embodiment is the third gap  416  is far enough from the discharge region  414  that arcing and cross talk do not easily occur.  
     THIRD EMBODIMENT  
      As shown in  FIG. 5 , a rib structure includes first portions  502  and second portions  504 . The PDP of this embodiment comprises a rear substrate formed with first portions  502  arranged in parallel, second portions  504  arranged in parallel perpendicularly intersecting the first portions  502 , thereby defining rectangular sub-pixel spaces  506  arranged in a matrix.  
      A plurality of bus electrodes  508 , preferably formed of non-transparent material, such as Cr, Cu, Ag or their combination, are disposed on the front substrate. Each extends along the first portions  502  and has protrusions  510  extended along the second portions  504  from the bus electrodes  508  to cover the second portions  504  on the rear substrate. Accordingly, the white, first and second portions  502 , and  504  arranged in a matrix are covered by the non-transparent bus electrodes  508  and protrusions  510 , reducing reflection of ambient light.  
     FOURTH EMBODIMENT  
      As shown in  FIG. 6 , a rib structure includes first portions  602  and second portions  604 . In this embodiment, a PDP comprises a rear substrate formed with first portions  602  arranged in a zigzag shape, second portions  604  arranged in parallel intersecting the first portions  602 , thereby defining hexagonal sub-pixel spaces  606  arranged in a delta configuration.  
      A plurality of bus electrodes  608 , preferably formed of non-transparent materials, such as Cr, Cu, Ag or their combination, are disposed on a front substrate. Each bus electrode  608  extends along the first portions  610  also in a zigzag shape to avoid covering light emitted from discharge space  606 . The bus electrodes are formed with protrusions  610  extending along the second portions  604 , covering the second portions  604  on the rear substrate. Accordingly, the white, first and second portions  602  and  604  arranging hexagonal sub-pixel spaces  606  are covered by the non-transparent bus electrodes  608  and protrusions  610 , reducing reflection of ambient light. In more detail, the zigzag-shaped first portions  602  are covered by the bus electrodes  608 , and the second portions  604  by the protrusions  610 .  
     FIFTH EMBODIMENT  
      As shown in  FIG. 7 , a plurality of ribs  702  are formed on the rear substrate and extend substantially in a direction Y. Adjacent ribs  704  spaced apart by corresponding channels define respective sub-pixel spaces and dark regions. The ribs  702  and  704  have a zigzag configuration such that each channel, between adjacent ribs  702  and  704 , varies periodically in width in a direction Y between first width  705  and second width  707  becoming respectively smaller than and at least as large as a width required for supporting discharges. The sub-pixel spaces  706  are of the second width  707  and the dark regions  713  are of the first width  705 , wherein the second width  707  is larger than the first width  705 . For each pixel, the ribs comprise a first portion  709  along X direction and a second portion  711  along Y direction.  
      A plurality of sustain electrodes are formed on a front substrate opposite a rear substrate, covering the ribs on the rear substrate. The sustain electrodes comprise a plurality of bus electrodes  710  and protrusions  712 . The bus electrodes cover the first portions  709  of the rib structure and extend substantially in the direction X. The protrusions  712  cover the second portions  711  of the rib structure and extend substantially in the direction Y. The first portions  709  of the ribs  702  and  704  are covered by the bus electrodes  710 . The second portions  711  of the rib structure extending along the direction Y are covered by the protrusions  712 .  
      Additionally, each bus electrode  710  contains protrusions  712  extending in a direction Y from the corresponding bus electrodes  710  to cover the adjacent second portions  711  and the dark regions  713  therebetween. Each dark region  713  is defined by the second portions of the sub-pixel  706  and the one of neighboring sub-pixels  716 . The dark regions  713  and the second portions  711  of the rib structure on the both sides are covered by the protrusions  712 .  
      According to embodiments of the invention described, the white ribs are covered by bus electrodes and further with protrusions on the front substrate to eliminate light reflection, thus increasing contrast of the PDP.  
      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 thee appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.