Abstract:
Disclosed are a plasma display panel and a method of manufacturing the same. The plasma display panel includes a scan electrode and a sustain electrode formed on a glass substrate, each including a discharge ignition part for generating initial discharge and a discharge diffusion portion for diffusing discharge to the entirety using the initial discharge, and the plasma display panel includes a dielectric layer disposed on a upper side of the glass substrate to cover the scan electrode and sustain electrode.

Description:
BACKGROUND 
       [0001]    1. Field 
         [0002]    This document relates to a plasma display panel and a method of manufacturing the same. 
         [0003]    2. Description of the Background Art 
         [0004]    In a general plasma display panel, barrier ribs formed between a front panel and a real panel constitute unit cells, each of which is filled with a main discharge gas such as Ne, He, or a mixture of Ne and He and small amount of inert gases containing Xe. A discharge induced by a high frequency voltage causes the inert gases to generate vacuum ultraviolet rays, and these vacuum ultraviolet rays excite phosphors provided between barrier ribs to display images. Because this plasma display panel can be made thinner and lighter, it has been popular as a next generation display. 
         [0005]      FIG. 1  is a view illustrating a structure of a general plasma display panel. 
         [0006]    Referring to  FIG. 1 , the plasma display panel comprises a front panel  100  and a rear panel  110 , which are spaced in parallel with each other by a constant distance. The front panel  100  comprises a front glass  101  on which a plurality of sustain electrode pairs, each of which is paired by a scan electrode  102  and a sustain electrode  103 , are arranged. The rear panel  110  comprises a rear glass  111  on which a plurality of address electrodes are arranged to intersect the sustain electrode pairs. 
         [0007]    The front panel  100  comprises pairs of a scan electrode  102  and a sustain electrode  103  to cause a discharge at a discharge cell and maintain the emission of cell, the scan electrode  102  or sustain electrode  103  consisting of a transparent electrode (a) made of a transparent material, and a bus electrode (b) made of a metallic material. The scan electrode  102  and sustain electrode  103 , which restrict discharge current, are covered by an upper dielectric layer  104  serving to isolate between electrode pairs, and a protective layer  105  deposited with MgO is disposed on the upper surface of the upper dielectric layer  104  in order to mitigate discharge conditions. 
         [0008]    The rear panel  110  comprises the address electrodes  113  arranged on the rear glass  111  in the direction of intersecting the scan electrodes  102  and sustain electrodes  103  arranged in parallel on the front glass  101 , and a lower dielectric layer  115  is disposed on the upper side of the address electrodes  113 . Barrier ribs  112  are provided on the upper side of the lower dielectric layer  115  to define discharge cells, each of which is applied with a phosphor  114  to radiate visual light having any one of red, green, and blue colors upon discharge. Manufacturing processes of a front panel according to the prior art will now be described with reference to  FIG. 2 . 
         [0009]      FIG. 2  is a flow chart illustrating sequential processes for manufacturing a front panel of a plasma display panel according to the prior art. 
         [0010]    Referring to  FIG. 2 , a transparent electrode  201  made of ITO (Indium Tin Oxide) which consists of Indium oxide and Tin oxide is disposed on the upper side of a front glass  200  (Step (a)). 
         [0011]    As an example, the transparent electrode  201 , which consists of a transparent electrode  201   a  for scan and a transparent electrode  201   b  for sustain, is formed by laminating dry film photoresist on a transparent electrode film made of ITO, exposing it to light to have a predetermined pattern with a photo mask, and developing and etching it. 
         [0012]    Then, black paste is printed on the upper side of the front glass  200  formed with the transparent electrode  201   a  for scan and transparent electrode  201   b  for sustain and is dried at approximately 120□ to form a black layer (Step (b)), and ultraviolet rays are illuminated on the dried black paste, with a photo mask  205  having a given pattern placed on the black paste (Step (c)). These processes are called “photolithography”. 
         [0013]    After the photolithography process, on the upper side of the black layer  202  is applied Ag paste, printed and dried to form bus the electrodes  203   a ,  303   b  (Step (d)). 
         [0014]    Afterwards, the photo mask  206  with a given pattern is placed on the upper side of the applied Ag paste, and exposed to light (Step (e)). After the exposure process, part which has been not cured is developed and fired in a baking furnace (not shown) at a temperature above 550□ for about 3 hours, forming the bus electrode  203   a  for scan and bus electrode  203   b  for sustain (Step (f)). 
         [0015]    Then, an upper dielectric layer  207  is formed on the upper side of the front glass  200  formed with the scan electrodes  201   a ,  203   a  and sustain electrodes  201   b ,  203   b  (Step (g)). As an example of a method for forming the dielectric layer  207 , dielectric glass paste is applied and dried, and then fired at a temperature approximately between 500□ and 600□, forming the upper dielectric layer. 
         [0016]    Finally, a protective layer  208  made of MgO is formed on the surface of the upper dielectric layer  207  using a CVD method, ion plating method, vapor deposition method, and so forth (Step (h)), completing a front panel of a plasma display panel. 
         [0017]    However, the plasma display panel and method of manufacturing the same according of the prior art have required high cost transparent electrodes, having caused manufacturing costs to increase dramatically. A fence type electrode structure, which does not use transparent electrodes, has been proposed to overcome this problem. 
         [0018]      FIG. 3  is a plan view illustrating a discharge cell having a fence type electrode structure according to the prior art. Referring to  FIG. 3 , a discharge cell  310  having a fence type electrode structure comprises a front substrate (not shown) formed with an upper discharge diffusion part  320  and a lower discharge diffusion part  340  and a rear substrate (not shown) formed with barrier ribs to define discharge cells  310 , wherein on the upper discharge diffusion part  320  and the lower discharge diffusion part  340  are not provided high cost transparent electrodes but metallic electrodes only. 
         [0019]    At this time, each of the upper discharge diffusion part  320  and lower discharge diffusion part  340  comprises three main discharge parts  320   a ,  340   a  and two connection discharge parts  320   b ,  340   b  to form a discharge gap  350  between the upper discharge diffusion part  320  and lower discharge diffusion part  340  and connect the discharge gap  350  to the connection discharge parts  320   b ,  340   b  to thereby diffuse discharge. In other words, the upper discharge diffusion part  320  and lower discharge diffusion part  340  are provided to compensate for loss of effective area which can occur due to absence of transparent electrodes. 
         [0020]    In this fence type electrode structure, however, an opaque upper discharge diffusion part and an opaque lower discharge diffusion part occupy a large area in the discharge space, which causes a problem that aperture ratio decreases upon discharge. Furthermore, this fence type electrode structure has a smaller effective area than a conventional electrode structure having transparent electrodes, which acts as a limitation to effective discharge diffusion. 
         [0021]    Accordingly, brightness is down and voltage for starting discharge upon driving is up, causing discharge efficiency to decrease. And, a gab (d) between the upper discharge diffusion part and lower discharge diffusion part in the discharge cell is too small to make it impossible to use other portions than negative glow portions in a discharge area upon driving. The afore-mentioned discharge space is shown in  FIG. 3 . 
         [0022]      FIG. 4  is a view illustrating a discharge region between electrodes. 
         [0023]    Referring to  FIG. 4 , if voltage is applied between a cathode and an anode, then secondary electrons, which are generated and released by ion-to-cathode collision, are accelerated by electric fields and crashed with neutral particles, so that new electrons are generated. As the voltage is varied more frequently, the secondary electrons are more strongly accelerated at the negative glow portions having relatively strong electric fields. The electrons generated by collision are continuously energized while ionization proceeds, and reach positive column portions, where the electrons are not energized any more and transfer energy to the neutral particles by collision. In this course, excited particles fall down to the bottom state, so that visible light and vacuum ultraviolet rays are radiated. 
         [0024]    At the positive column portions in the discharge region, only electrons whose overall energy is high rather than electrons whose energy is from electric fields excite gases to emit light. At the positive column portions, in addition, ionization rarely occurs and the amount of light emission by excitation increases, so that conversion efficiency from energy to light is generally high. 
         [0025]    Hence, if the gap between the upper discharge diffusion part and lower discharge diffusion part decreases at the discharge cell in the plasma display panel, then area of negative glow portions is not so varied while area of positive column portions is relatively greatly decreased. Therefore, there occurs a problem that emission brightness of the plasma display panel is deteriorated. 
       SUMMARY 
       [0026]    In one aspect, a plasma display panel comprises a scan electrode and a sustain electrode formed on a glass substrate, each comprising a discharge ignition part for generating initial discharge and a discharge diffusion portion for diffusing discharge to the entirety using the initial discharge, and a dielectric layer disposed on a upper side of the glass substrate to cover the scan electrode and sustain electrode. 
         [0027]    The scan electrode may be symmetrical to the sustain electrode. 
         [0028]    The scan electrode and the sustain electrode each may have a shape of ‘H’. 
         [0029]    The scan electrode and the sustain electrode each may have a shape of ‘U’. 
         [0030]    The scan electrode and the sustain electrode may be formed only of metallic electrodes. 
         [0031]    The discharge ignition part may comprise an upper discharge ignition part and a discharge ignition part, and the upper discharge ignition part and the lower discharge ignition part may be located on a upper side of barrier ribs. 
         [0032]    The discharge ignition part may comprise an upper discharge ignition part and a discharge ignition part, and a gap between the upper discharge ignition part and the lower discharge ignition part may range from 50 μm to 150 μm. 
         [0033]    The a discharge diffusion portion may comprise an upper discharge ignition part and a lower discharge ignition part, and a gap between the upper discharge diffusion part and the lower discharge diffusion part may range from 150 μm to 500 μm. 
         [0034]    A line width of each of the metallic electrodes may range from 20 μm to 70 μm. 
         [0035]    The dielectric layer may have uneven thickness so that a first part where initial discharge occurs has thinner thickness than a second part other than the first part. 
         [0036]    The dielectric layer may be formed to have a shape of a groove. 
         [0037]    An auxiliary dielectric layer may be provided on a upper side of the dielectric layer, and the auxiliary dielectric may has a higher dielectric constant than that of the dielectric layer. 
         [0038]    In another aspect, a method of manufacturing a plasma display panel comprises forming a scan electrode and a sustain electrode on a front glass substrate; forming a dielectric layer to cover the scan electrode and the sustain electrode, and forming a groove on the dielectric layer. 
         [0039]    The method may comprise forming an auxiliary dielectric layer in the groove posterior to said forming the groove. 
         [0040]    The groove may be formed on a portion where initial discharge occurs. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0041]    Further detailed description of the other embodiments will be contained in the accompanying detailed description and drawings. The above and/or other aspects and advantages of the prevent invention will become apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompany drawings, where like reference numerals refer to like elements throughout, in which: 
           [0042]      FIG. 1  is a view illustrating a structure of a general plasma display panel; 
           [0043]      FIG. 2  is a process flow view illustrating sequential processes for manufacturing a front panel of a plasma display panel according to the prior art; 
           [0044]      FIG. 3  is a plan view illustrating a discharge cell having a fence type electrode structure according to the prior art; 
           [0045]      FIG. 4  is a view illustrating a discharge region between electrodes according to the prior art; 
           [0046]      FIG. 5  is a plan view illustrating a discharge cell having a fence type electrode structure according to an embodiment of the present invention; 
           [0047]      FIG. 6  is a plan view illustrating a discharge cell having another fence type electrode structure according to another embodiment of the present invention; 
           [0048]      FIG. 7  is a view illustrating a dielectric layer having uneven thickness distribution in a plasma display panel according to an embodiment of the present invention; 
           [0049]      FIG. 8  is a view illustrating a dielectric layer having uneven thickness distribution in a plasma display panel according to an embodiment of the present invention; 
           [0050]      FIG. 9  is a process flow view illustrating sequential processes for manufacturing a front panel of a plasma display panel according to an embodiment of the present invention; and 
           [0051]      FIG. 10  is a process flow view illustrating sequential processes for manufacturing a front panel of another plasma display panel according to another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0052]    A plasma display panel according to an embodiment of the present invention will be described with reference to  FIGS. 5 to 8 .  FIG. 5  is a plan view illustrating a discharge cell having a fence type electrode structure according to an embodiment of the present invention.  FIG. 6  is a plan view illustrating a discharge cell having another fence type electrode structure according to another embodiment of the present invention. 
         [0053]    Referring to  FIGS. 5 and 6 , a plasma display panel according to an embodiment of the present invention comprises a front glass substrate (not shown) formed with scan electrodes  520 ,  620  and sustain electrodes  540 ,  640  and a rear glass substrate (not shown) formed with address electrodes (not shown) in the direction of intersecting the scan electrodes  520 ,  620  and sustain electrodes  540 ,  640 . And, barrier ribs  530 ,  630  are formed on the rear glass substrate to define discharge cells  560 ,  660 , so that positive column portions can be used when discharge occurs. 
         [0054]    At this time, the scan electrodes  520 ,  620  and the sustain electrodes  540 ,  640  are symmetrical to each other. It is desirable that the scan electrodes  520 ,  620  and the sustain electrodes  540 ,  640  are formed to have a shape of ‘H’ (see  FIG. 5 ) or ‘U’ (see  FIG. 6 ). 
         [0055]    Forming the scan electrodes  520 ,  620  and sustain electrodes  540 ,  640  in the shape of ‘H’ or ‘U’ enables wall charges to accumulate sufficiently while securing aperture ratio as much as possible. 
         [0056]    At this time, it is desirable that the scan electrodes  520 ,  620  and sustain electrodes  540 ,  640  are composed only of metallic electrodes. Although the metallic electrode generally has narrower width than that of the transparent electrode in a discharge space, the metallic electrode can replace the transparent electrode, which is relatively more expensive than the metallic electrode, by modifying the design, and this can reduce dramatically costs for manufacturing scan electrodes and sustain electrodes. 
         [0057]    The metallic electrodes  520 ,  540 ,  620 ,  640  comprise upper discharge ignition portions  520   a ,  620   a  and lower discharge ignition portions  540   a ,  640   a , which are located along the barrier ribs  530 ,  630  defining discharge cells  560 ,  660  to cause initial discharge, and upper discharge diffusion portions  520   b ,  620   b  and lower discharge diffusion portions  540   b ,  640   b , which radiate light at a positive column portion in the discharge cells  560 ,  660  using the initial discharge and diffuse light to the entire discharge cell regions  560 ,  660 . 
         [0058]    At this time, it is desirable that the metallic electrodes  520 ,  540 ,  620 ,  640  each have a line width of more than 20 μm and less than 70 μm. 
         [0059]    And, it is desirable that a gap between the upper discharge ignition portion  520   a ,  620   a  and the lower discharge ignition portion  540   a ,  640   a  ranges from 50 μm to 150 μm. 
         [0060]    In addition, it is desirable that a gap between the upper discharge diffusion portion  520   b ,  620   b  and the lower discharge diffusion portion  540   b ,  640   b  ranges from 150 μm to 500 μm 
         [0061]    Here, the upper discharge ignition portions  520   a ,  620   a  and lower discharge ignition portions  540   a ,  640   a  are placed at the upper part than the barrier ribs because the discharge ignition portions  520   a ,  620   a ,  540   a ,  640   a  cause only weak discharge which can&#39;t generate plasma, so that aperture ratio can be deteriorated. 
         [0062]    The discharge ignition portions  520   a ,  620   a ,  540   a ,  640   a  can easily cause discharge even with low discharge voltage because of short discharge gap  550   a ,  650   a . At this time, since once discharge starts it diffuses to the discharge diffusion portions  520   b ,  620   b ,  540   b ,  640   b , even low discharge voltage can generate discharge well. 
         [0063]    Accordingly, providing the discharge ignition portions  520   a ,  620   a ,  540   a ,  640   a  enables high efficiency even with relatively low discharge start voltage. 
         [0064]    In general, a plasma display panel has the same structure as a capacitor. Therefore, as the distance between electrodes increases more, capacitance becomes smaller, and this lowers reactive power, thus improving discharge efficiency. 
         [0065]    As such, making the discharge gaps  550   b ,  650   b  long enables allows for high discharge efficiency. 
         [0066]    A dielectric layer having uneven thickness distribution is shown in  FIGS. 7 and 8 , which can reduce the discharge voltage of the plasma display panel and improve the discharge efficiency of the plasma display panel. 
         [0067]      FIG. 7  is a schematic view illustrating a dielectric layer having uneven thickness distribution in a plasma display panel according to an embodiment of the present invention.  FIG. 8  is a schematic view illustrating a dielectric layer having uneven thickness distribution in a plasma display panel according to an embodiment of the present invention. 
         [0068]    Referring to  FIG. 7 , the dielectric layer  730 , which has uneven thickness distribution, restricts the discharge current between a scan electrode  710  and a sustain electrode  720  and isolates therebetween. In addition, a protective layer  750  deposited with MgO is provided on the upper surface of the dielectric layer  730  to mitigate discharge conditions. 
         [0069]    At this time, the dielectric layer  730  is uneven in its thickness distribution, and is formed to have a depression part depressed by a predetermined depth at the center of the discharge cell. Here, it is desirable that the depression part is located between metallic electrodes (see  FIG. 7   c ). In addition, it is also desirable that the depression part is located only on the discharge ignition portions among the discharge electrodes (see  FIG. 7   d ). 
         [0070]    It is desirable that the dielectric layer  730  is formed to have a shape of a groove. The groove comprises a ‘U’ shape, a trapezoid shape, a semicircle shape, and so forth. 
         [0071]    In addition, it is desirable that on the upper side of the dielectric layer  730  there is further provided another dielectric layer  740  having relatively a higher dielectric constant than that of the dielectric layer  730  (see  FIG. 7   b ). 
         [0072]    It is desirable that the depression part is located to cover part of ends of the metallic electrodes between the metallic electrodes (see  FIG. 8   c ). 
         [0073]    It is desirable that the dielectric layer  830  is formed to have a shape of a groove. The groove comprises a ‘U’ shape, a trapezoid shape, a semicircle shape, and so forth. 
         [0074]    In addition, it is desirable that on the upper side of the dielectric layer  830  there is further provided another dielectric layer  840  having relatively a higher dielectric constant than that of the dielectric layer  830  (see  FIG. 8   b ). 
         [0075]    These dielectric layers  730 ,  830  and the auxiliary dielectric layers  740 ,  840  increase the electric fields generated when the plasma display panel is driven, so that even more wall charges can be accumulated, which can reduce driving voltage upon plasma surface discharge, thus making it possible to improve the discharge efficiency. 
         [0076]    Processes of manufacturing a front panel in a plasma display panel according to an embodiment of the present invention will be described with reference to  FIGS. 9 and 10 .  FIG. 9  is a process flow view illustrating sequential processes for manufacturing a front panel of a plasma display panel according to an embodiment of the present invention.  FIG. 10  is a process flow view illustrating sequential processes for manufacturing a front panel of another plasma display panel according to another embodiment of the present invention. 
         [0077]    Referring to  FIG. 9 , Ag paste is applied on the upper side of a front glass  600 , printed, and dried so as to form metallic electrodes  601  on the front glass  600  (Step (a)). Then, a photo mask  604  formed with a predetermined pattern is placed on the upper side of the Ag paste, and exposed to light (Step (b)). Next, part not cured is developed and then fired in a baking furnace (not shown) at a temperature over 550□ for about 3 hours, completing metallic layers  601  (Step (c)). 
         [0078]    Then, a dielectric layer  602  is formed to cover the metallic electrodes  601  and the front glass  600  (Step (d)). At this time, the dielectric layer  602  is formed to have uneven thickness distribution, so that the thickness at the gap between the metallic electrodes  601  is different from the thickness at the part other than the gap. 
         [0079]    As an example for forming the dielectric layer  602 , firstly a dielectric layer is provided on the front glass  600  to have a predetermined thickness, and secondly the dielectric layer is etched at a given depth using as a mask a photosensitive film patterned to have a predetermined pattern, so that a groove is formed to have a discharge space. 
         [0080]    Finally, a protective layer  603  made of MgO is formed on the surface of the dielectric layer  602  using a CVD method, ion plating method or vapor deposition method, completing a front panel of a plasma display panel. 
         [0081]    At this time, it is desirable that the groove of the dielectric layer  602  is formed at the portion where initial discharge occurs. 
         [0082]    In addition, it is desirable that an auxiliary dielectric layer  704  having a given pattern is formed on the upper side of the dielectric layer  702  after Step (d) in  FIG. 9 , as shown in  FIG. 10 . 
         [0083]    At this time, it is desirable that the groove of the dielectric layer  702  is formed at the portion where initial discharge occurs. 
         [0084]    It is to be understood by those skilled in the art that the invention may be embodied in several forms without departing from the spirit of essential characteristics thereof. The scope of the present invention is defined by the appended claims rather than by the description preceding them, and all changes that fall within meets and bounds of the claims, or equivalence of such meets and bounds are therefore intended to embrace by the claims. 
         [0085]    As mentioned above, the present invention forms scan electrodes and sustain electrodes only with metallic electrodes without forming transparent electrodes, so that manufacturing costs for the scan electrodes and sustain electrodes can be saved, and the present invention can assure high efficiency or reduce discharge voltage by selecting either a long discharge gap or a short discharge gap. In addition, the present invention can reduce driving voltage upon plasma surface discharge by providing a dielectric layer having uneven thickness distribution and an auxiliary dielectric layer, thus making it possible to improve the discharge efficiency.