Patent Publication Number: US-6340866-B1

Title: Plasma display panel and driving method thereof

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a display device, and more particularly to an improved plasma display pane (PDP) for displaying a picture with the aid of a discharge caused by a radio frequency voltage signal. Also, this invention is directed to an improved driving method for the PDP. 
     2. Description of a Related Art 
     A conventional PDP brightens a fluorescent material by ultraviolet rays generated upon the gaseous discharge to display a picture including a character and graphic information. Then, the picture is displayed by visible rays emitted from the fluorescent material. The ultraviolet rays are emitted from gaseous particles when electrons included in the gaseous particles are excites and then transited, and are impacted to the fluorescent material. The gaseous discharge for generating such a glow discharge will be described. 
     A voltage signal is applied between a cathode  4  and an anode  6  installed into a discharge tube  2  as shown in FIG.  2 . Then, an electrical field is formed in a discharging space between the cathode  4  and the anode  6 , and electrons move from the cathode  4  toward the anode  6  in such a manner to be accelerated by the electrical field. The accelerated electron impacts into the gaseous particles, such as neutral atoms and molecules, injected in the discharging space to cause the ionization and excitation of gases. A variety pattern of luminescence appears at the glow discharge. Among the variety pattern of the luminescence, a negative glow generated in the vicinity of the cathode  4  and a positive column caused in the long region proceeding from the middle portion of the discharging space to the anode  6  affect to a brightness characteristics. Particularly, the positive column has a discharging efficiency of about 60-70 percents for the voltage that is applied between the cathode  4  and the anode  6 . The positive column appears only in the case that the cathode  4  stands apart from the anode  6  above 1 mm. In other words, the electron must be moveable the long distance of above 1 mm. However, in the conventional PDP, a distance between two electrodes for receiving a discharge voltage is set below 150 μm. Due to this, the conventional PDP must have used only the negative glow having the discharging efficiency of below 6 percents. 
     As PDP using such a negative glow, it is an alternative current type of PDP having plasma display cells as shown in FIGS. 2A and 2B. The plasma display cells are arranged in a matrix pattern. Referring to FIGS. 2A and 2B, the plasma display cell includes an upper substrate  10  and a lower substrate  12  installed apart from each other by compartment walls  14  in parallel. These upper and lower substrates and compartment walls  14  are formed a discharging space  26 . The compartment walls  14  are formed by a material reasonable for preventing an optical interference and an electrical interference between the plasma display cells, and support the upper substrate  10 . First and second sustain electrodes  16 A and  16 B, each called as a scan/sustain electrode and a sustain electrode, are installed on the upper substrate  10  in parallel with the compartment walls  14 . On the upper substrate  10  with the first and second sustain electrodes  16 A and  16 B, a dielectric material layer  18  is formed to have an even surface. The dielectric material layer  18  stores up an electric charge. Also, a protective film  20  can be disposed on the first dielectric material layer  18 . The protective film  20  protects the first dielectric material layer  18  from a spattering of gaseous particles to extend the lifetime of the PDP and to enhance an emitting rate or second electrons. The protective film  20  frees the discharge characteristics of a fireproof metal from a variation. As the protective film  20 , it is mainly used a Magnesium Oxide (MgO) film. The upper substrate  10  with the above structure is disposed on the compartment walls  14  in such a manner that the sustain electrodes  16 A and  16 B are opposite to the lower substrate  12 . Meanwhile, the lower substrate  12  has an address electrode  22  installed in such a manner to cross with the sustain electrodes  16 A and  16 B. On the lower substrate  12  with the address electrode  22 , there is disposed a fluorescent material layer  24 . The fluorescent material saver  24  excites and then transits by vacuum ultraviolet rays generated upon a gaseous discharge. The fluorescent material layer  24  emits visible rays having a primary color such as a red, a green or a blue color at a transition. The lower substrate  12  is positioned under the compartment walls  14  in such a manner that the address electrode  22  is opposite to the sustain electrodes  16 A and  16 B. These upper and lower substrates  10  and  12  and compartment walls  14  provide the discharging space  26  to be filled with discharge gases such as He, Ne, Xe and so on. 
     In the plasma display cell with such a structure, the sustain electrodes  16 A and  16 B stand apart from each other about 60-80 μm. The compartment walls  14  are formed to be below 200 μm in the height. In other words, all the distances between the electrodes  16 A,  16 B and  22  included in the plasma display cell is below 200 μm. Due to this, the alternative current type of the PDP can not use the positive column. Consequently, the discharging efficiency of the PDP drops off. Also, the alternative current type of the PDP causes a address discharge between any one of the sustain electrode  16 A and  16 B and the address electrode  22  before a display discharge (or a sustained discharge) is generated between the first and second sustain electrodes  16 A and  16 B, thereby displaying a desired picture. 
     In the next, the PDP having the above structure will be described. The address discharge is generated by any one of the sustain electrodes  16 A and  16 B and the address electrode  22  and then the sustain discharge is continuously caused by the sustain electrodes  16 A and  16 B. The vacuum ultraviolet rays generating by the sustain discharge excite and transit the fluorescent material layer  24  to emit visible rays, thereby displaying a desired picture. The visible rays are generated when the fluorescent material layer  24  is transited. In other words, the alternative current type of the PDP displays a desired picture by the sustain discharge. In order to generate the sustain discharge, a sustain pulse is applied between the sustain electrodes  16 A and  16 B. The sustain pulse has a frequency of about 200-300 kHz and a width of about 2-3 μm, as shown in FIG.  3 . Responding to the sustain pulse, the sustain discharge causes only once at the shorter moment of the period of the sustain pulse. In other words, the greater part of the period of the sustain pulse is consumed regardless of real discharge. 
     For example, if the sustain pulse is applied to the first sustain electrode  16 A, a charged particle moves from the second sustain electrode  16 B having an opposing polarity toward the first sustain electrode  16 A along a discharge path, as shown in FIG.  4 . Then, the gaseous particles are excited and transited by the charged particle. As a result, the sustain discharge is generated in vicinity or the second sustain electrode  16 B when a predetermined time have passed since the raising edge or the sustain pulse. Also, the charged particles from the electrode  16 B opposite to the first electrode  16 A are stored on the dielectric material layer  18  surrounding the surfaces of the sustain electrodes  16 A and  16 B. In other words, a wall charge is formed on the dielectric material layer  18  when the predetermined time have passed since the sustain discharge have been started. The wall charge offsets the voltage applied between the sustain electrodes  16 A and  16 B to drop down a voltage input to the discharging space, thereby reducing the sustain discharge. Consequently, the sustain discharge is generated only once during the shorter moment relative to the width of the sustain pulse. 
     As described above, in the PDP with the plasma display cell as shown FIGS. 2A and 2B, the positive column can not be caused because the distances of the electrodes are very shorter. Due to this, the discharging efficiency of the PDP decreases. Also, since the wall charge is formed at the sustain discharge, the discharge generates only once in a moment. For re-discharge, a predetermined period is required to eliminate the wall charge. Due to this, in the PDP with the plasma display cell, the period of the real discharge is very shorter than a period set up for the discharge, and the discharging efficiency decreases more. Consequently, the PDP with the plasma display cell as shown in FIGS. 2A and 2B can not provide with a sufficient brightness. Furthermore, the PDP requires an additional signal for eliminating the wall charge. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a plasma display panel that is adapted to obtain a sufficient brightness as well as to enhance a discharging efficiency, and a driving method thereof. 
     In order to achieve these and other objects of the invention, according to one aspect of the present invention there is provided with a plasma display panel comprising at least a pair of electrodes for applying a radio frequency voltage. 
     According to another aspect of the present invention, there is provided with a plasma display panel including: first electrode for applying a radio frequency voltage; second electrode for supplying a video data voltage; and a discharging space implemented with gas causing a gaseous discharge. 
     According to still another aspect of the present invention, there is provided with a plasma display panel driving method applying a radio frequency voltage into a discharge cell through at least a pair of electrodes to cause a display discharge. 
     According to still another aspect of the present invention, there is provided with a plasma display panel driving method including the steps of: applying a radio frequency voltage to a first electrode to starting simultaneously the discharge of cells; supplying a second electrode with a erasing pulse in accordance with a video data to stop selectively the discharge of the cells; and feeding a radio frequency voltage to the first electrode to maintain the discharge of the cells. 
     According to still another aspect of the present invention, there is provided with a plasma display panel driving method including the steps of: applying a first electrode with a driving signal corresponding too a video data to select discharge cells; and supplying a radio frequency voltage to a second electrode to generated continuously a display discharges in the discharge cell selected by the driving signal. 
     According to still another aspect of the present invention, there is provided with a plasma display panel driving method including steps of: applying a first electrode with a driving signal corresponding to a video data to allow charged particles to be selectively injected into discharge cells; supplying a sustain voltage to additional electrodes to preserve the charged particles; and feeding a radio frequency voltage to a second electrode to generate continuously a display discharge by the charged particles. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects of the invention will be apparent from the following detailed description of the embodiments of the present invention with reference to the accompanying drawings, in which: 
     FIG. 1 is a schematic view showing a model of a conventional gaseous discharge; 
     FIGS. 2A and 2B are sectional views showing a structure of plasma display cells included in a PDP; 
     FIG. 3 is a waveform of a sustain pulse to be applied to a sustain electrode shown in FIGS. 2A and 2B; 
     FIG. 4 is a schematic view of a discharge phenomenon causing in a plasma display cell shown in FIGS. 2A and 2B; 
     FIG. 5 is a sectional view showing a construction of a plasma display cell included in a PDP according to an embodiment of the present invention; 
     FIG. 6 is a waveform of a radio frequency voltage signal to be applied to second electrode shown in FIG. 5; 
     FIG. 7 is a flow chart explaining a PDP driving method according to an embodiment of the present invention; 
     FIG. 8 is a flow chart explaining a PDP driving method according to another embodiment of the present invention; 
     FIG. 9 is a sectional view showing a construction of a plasma display cell included In a PDP according to another embodiment of the present invention; 
     FIG. 10 is a flow chart explaining a PDP driving method according to another embodiment of the present invention; and 
     FIGS. 11A to  11 C are schematic views showing discharge statuses appearing in a plasma display cell shown in FIG.  9 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A PDP according to the present invention uses a radio frequency voltage signal of several tens to several hundreds MHz to cause a display discharge, i.e., a sustain discharge. In this case, since electrons perform a vibration motion (or a swing motion), the PDP keeps a display discharge while the radio frequency voltage signal is applied. In detail, if the radio frequency voltage signal having alternatively voltage polarities is applied to any one of two electrodes opposed to each other, charged particles move toward one electrode or another electrode according to the polarity of the radio frequency voltage signal. Furthermore, the polarity of the radio frequency voltage signal is inverted before the charged particle has arrived at one electrode, the charged particle into a discharging space is moving toward the other electrode positioned at opposite direction after the charged particle goes gradually slow. The charged particle into the discharging space swings between two electrodes because the polarity of the radio Frequency voltage signal is changed before the charged particles has arrived at any to one of two electrodes. Therefore, during the supplying period of the radio frequency voltage signal, the charged particles don&#39;t eliminate and the excitation and transition of gaseous particles is continuously generated. Since the display discharge is maintained during a greater part of a set discharge period, the PDP according to the present invention enhances the discharging efficiency. Furthermore, the PDP enhances more and more the discharging efficiency as well as an energy efficiency because the radio frequency discharge has a physical characteristics equal to the positive column of the glow discharge. As a result, the PDP according to the present invention can obtain a sufficient brightness in low power. 
     The PDP using the radio frequency discharge must have at least two electrodes for applying the radio frequency voltage signal to the discharging space injected with gases. Also, the PDP must include a plurality of plasma display cells each having the discharging space in order to display a picture. To this end, each the plasma display cells building the PDP can be manufactured as shown in FIG.  5 . Furthermore, the PDP can further comprise a plurality of additional electrodes for selecting the plasma display cells and erasing the discharge. In this case, each the plasma display cells included in the PDP has a configuration as shown in FIG.  9 . 
     Referring to FIG. 5, there is illustrated a plasma display cell included in a PDP according to an embodiment of the present invention. The plasma display cell includes an upper substrate  30  and a lower substrate  32  installed apart from each other by compartment walls  34  in parallel. The compartment walls  34  are formed by a material reasonable for preventing an optical interference and an electrical interference between the plasma display cells, and support the upper substrate  30 . First electrode  36  is installed on the upper substrate  30  in parallel with the compartment walls  34 . On the upper subs-rate  30  with the first electrode  36 , first dielectric material layer  38  is formed to have an even surface. The first dielectric material layer  38  has a function of storing electric charges. Also, a protective film  40  can be disposed on the first dielectric material layer  38 . The protective film  40  is not necessary because almost gaseous particles are not impacted to the first dielectric material layer  38 . This result from that the gaseous particles lighten relative to the electrons are in almost stop state. However, the protective layer  40  is used to enhance an emitting rate or second electrons. The upper substrate  30  with the above structure is disposed on the compartment walls  34  in such a manner that the first electrode  36  is opposite to the lower substrate  32 . Meanwhile, the lower substrate  32  has second electrode  42  installed in such a manner to cross with the first electrode  16 . On the lower substrate  32  with the second electrode  42 , there is sequentiality disposed a second dielectric material layer  44  and a fluorescent material layer  46 . Similarly to the first dielectric Material layer  38 , the second dielectric material layer  44  also stores up the electric charges. The fluorescent material layer  46  excites and then transits by vacuum ultraviolet rays generated during tile gaseous discharge. The fluorescent material layer  46  emits visible rays having a primary color such as a red, a green or a blue color, at a transition. The lower substrate  32  is positioned under the compartment walls  34  in such a manner that the second electrode  42  is opposite to the first electrode  16 . These upper and lower substrates  30  and  32  and compartment walls  34  provide the discharging space  26  to be filled with discharge gases such as He, Ne, Xe and so on. Also, any one of the first and second electrodes is formed by a transparent material (for example, ITO(Indium Tin Oxide)) according to whether any one of the upper and lower substrates  30  and  32  is used as a display face. In other words, the electrode on the substrate used as the display face is formed by the transparent material. 
     In the plasma display cell with such a structure, the discharge is started by where an alternative current voltage pulse of a low frequency as described in the related art or the radio frequency voltage signal of about 200-300 MHz as shown in FIG. 6 is supplied to the second electrode  42 . The started discharge is maintained daring feeding of the radio frequency voltage signal. As a radio frequency voltage signal, a sine wave, a square wave, a sawtooth wave and so on can be used. Similarly, the plasma display cell as above described can be driven in two methods as shown in FIGS. 7 and 8. 
     In FIG. 7, a PDP driving method allows a radio frequency voltage signal of about 200-300 MHz to be temporally applied to the second electrode  42 . A display discharge is started at all the plasma display cells on a line or on entire panel. An erasing pulse having a constant level and a specific shape is selectively supplied to the first electrodes  36  according to a video data, These Fire erased the display discharges from the plasma display cells receiving the erasing pulse. In the next, the radio frequency voltage signal is continuously applied to the second electrode  42 . While the radio frequency voltage signal is applied to the second electrode  42 , the display discharge is continuously generated at each the plasma display cells which the erasing pulse are not applied. 
     FIG. 8 illustrates a PDP driving method according to another embodiment of the present invention. The method of FIG. 8 allows a low frequency pulse to be selectively fed to the first electrodes  36  in accordance with a video data, thereby injected selectively the charged particles into the plasma display cells on one line. Then, the display discharge is started at each the plasma display cells which the charged particles are injected. In the next, a radio frequency voltage signal is continuously applied to the second electrode  42 . The plasma display cells injected with the charged particles each keep the stated display discharge while the radio frequency voltage signal is applied. 
     As described above, in PDP according to an embodiment of the present invention, since the radio frequency discharge is maintained while the radio frequency voltage signal is applied, a real discharging period is almost equal to the set discharge period. Also, the radio frequency discharge has a physical characteristics equal to the positive column into the glow discharge. As a result, the PDP according an embodiment of the present invention enhances a discharging efficiency and energy efficiency and is obtained a sufficient brightness. 
     Referring now to FIG. 9, there is shown a plasma display cell included in a PDP according to another embodiment of the present invention. The plasma display cell of FIG. 9 includes an upper substrate  50  and a lower substrate  52  installed apart from each other by compartment walls  54  in parallel. The compartment walls  54  are formed by a material reasonable for preventing an (optical interference and an electrical interference between the plasma display cells, and support the upper substrate  50 . An address electrode  56  is installed on the upper substrate  50  in parallel with the compartment walls  54 . On the upper substrate  50  with the address electrode  56 , an insulating layer  58  is formed to have an even surface. First and second sustain electrodes  60 A and  60 B are also Installed on the insulating layer  58 . On the insulating layer  58  with the first and second electrodes  60 A and  60 B, a dielectric material layer  62  is disposed to have an even surface. These address electrode  56 , first and second sustain electrodes  60 A and  60 B are formed wish a transparent material such as an ITO (Indium Tin Oxide and so on when the upper substrate  50  is used as a display face. The dielectric material lager  62  , as a function of storing electric charges. Furthermore, a protective film can be overlaid on the dielectric material layer  62 . The protective layer is used to enhance an emitting rate of second electrons. Such an upper substrate  50  with the above structure is disposed on the compartment walls  54  in such a manner that the address electrode  56  is opposite to the lower substrate  52 . Meanwhile, the lower substrate  52  has a metal electrode  64  installed in such a manner to cross with the address electrode  56 . The metal electrode  64  is formed with the transparent material, i.e., ITO, when the lower substrate  52  is used as a display Face. On the lower substrate  52  with the metal electrode  56 , There is overlaid a fluorescent material layer  66 . The fluorescent material layer  66  excites and then transits by vacuum ultraviolet rays generated during gaseous discharging. The fluorescent material layer  66  emits visible rays having a primary color such as a red, a greets or a blue color, at a transition. The lower substrate  52  is positioned under the compartment wall  54  in such a manner that the metal electrode  64  is opposite to the address electrode  56 . These upper and lower substrates  50  and  52  and compartment walls  54  provide the discharging space  68  to be injected with discharge gases such as He, Ne, Xe and so on. 
     The PDP having the plasma display cell with such a structure is driven by a driving method as shown in FIG.  10 . The PDP driving method of FIG. 10 applies an address signal between the address electrode  56  and any one of two sustain electrodes  60 A and  602  to cause an address discharge. For example, if the address signal is applied between the address electrode  56  and the first sustain electrode  60 A, the address discharge appears at the left and top portion of a discharging space  68  adjacent to the first sustain electrode  60 A, as shown in FIG.  11 A. Then, the charged particles are developed at the left and top potion of the discharging space  68 . The address signal is sequentially applied to all lines on a panel. To this end, the plasma display cells on each line is selectively discharged responding to the address signal. As a result, the address discharge is generated only at a part of the plasma display cells on the PDP. 
     Also, a sustain voltage signal is supplied between the sustain electrodes  60 A and  60 B until the address signal has been applied to all the lines on the panel. Then, a sustain discharge is generated in vicinity of the surface of a dielectric material layer  62  positioned between the sustain n electrodes  60 A and  60 B. Therefore, the charged particles are originally existing at the discharging space  68 . 
     When the address signal have been applied to all the lines on the panel, a radio frequency voltage signal is supplied to the metal electrode  64 . Whereas, the address electrode  56  and the sustain electrodes  60 A and  60 B receive a bias voltage or a ground voltage. Then, the charged particles into the discharging space  68  swing between the metal electrode  64  and the sustain electrodes  60 A and  60 B according to the polarity of the radio frequency voltage signal to excite and transit continuously the gaseous particles such as gaseous atoms and molecules. In other words, a radio frequency discharge is continuously generated at the center portion of the discharging space  68 , as shown in FIG.  11 C. Also, the fluorescent material layer  66  excites and then transits by vacuum ultraviolet rays emitted from the gaseous particles. When the fluorescent material layer  66  is transited, visible rays are emitted toward an external through the upper substrate  50 . The amount of the visible rays passing through the upper substrate  50  determines brightness and/or chromaticity. Since such a radio frequency discharge is continuously generated while the radio frequency voltage is applied, the real discharging period of the PDP is almost equal to a set discharging period. Also, the radio frequency discharge has a physical characteristics equal to the positive column in the glow discharge. As a result, the PDP according to another embodiment of the present invention enhances a discharging efficiency and energy efficiency and is obtained a sufficient brightness in low power. 
     As described above, in the PDP and driving method thereof according to the present invention, the electrons swing into the discharging space by the radio frequency voltage signal of about several tens to several hundreds MHz higher than the prior pulse signal of several hundreds KHz. The electrons don&#39;t eliminated during applying with the radio frequency voltage signal. To this end, a display discharge is continuously generated during applying pith the radio frequency voltage signal, and furthermore the display discharge has a physical characteristics equal to the positive column in the glow discharge. As a result, the PDP according an embodiment of the present invention enhances a discharging efficiency and energy efficiency. Also, a sufficient brightness is obtained because an amount of vacuum ultraviolet rays is enlarged. 
     Although the present invention has been explained by the embodiments shown in the drawings described above, it should be understood to the ordinary skilled person in the art that the invention is not limited to the embodiments, but rather that various changes or modifications thereof are possible without departing from he spirit of the invention. Accordingly, the scope of the invention shall be determined only by the appended claims and their equivalents.