Abstract:
A plasma display device includes a plurality of discharge cells each having substrates, and at least two electrodes formed on the substrates, for generating a discharge therebetween, and a shielding electrode formed between the electrodes respectively positioned in the neighboring cells, for shielding crosstalk generated between the electrodes of the neighboring cells.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a plasma display device, and more particularly, to a plasma display device with a reduced cell space by providing a crosstalk shielding electrode. 
     2. Description of the Related Art 
     In general, a plasma display device includes at least a pair of electrodes and generates discharge by a voltage applied to the electrodes. Due to excellent display characteristics such as display capacity, brightness, contrast and view angle, much attention has been paid to plasma display devices as flat display panels having almost the same performance as cathode ray tubes. 
     A plasma display panel is largely divided into a direct current (DC) plasma display panel and an alternating current (AC) plasma display panel according to its operational principles. In the DC plasma display panel, all electrodes are exposed to a discharge space, in which charges migrate directly from/to corresponding electrodes. On the other hand, the AC plasma display panel has a structure in which at least one electrode is surrounded by a dielectric material, wherein charges do not directly migrate from/to corresponding electrodes and discharging is performed by the electrical field of wall charges. The DC plasma display panel adopts both a DC driving method by which the polarity of a driving voltage does not change, and an AC driving method by which the polarity of a driving voltage changes. However, the AC plasma display panel adopts only the AC driving method. 
     Meanwhile, a plasma display panel is divided into a cross discharge type and a neighboring discharge type according to the discharge mechanism. The cross discharge type plasma display panel includes a scanning electrode opposite an address electrode, generates an addressing discharge therebetween and the addressing discharge is sustained by a sustaining discharge. The neighboring discharge type plasma display panel includes a scanning electrode and a common electrode which face an address electrode, and generates an addressing discharge between the address electrode and the common electrode and a sustaining discharge between the scanning electrode and the common electrode. 
     Referring to FIGS. 1 and 2, an example of a neighboring discharge type plasma display device will be described briefly. The plasma display device includes address electrodes  11  formed on a rear substrate  10  in a predetermined pattern, and a dielectric layer  12  covering the address electrodes  11  and the rear substrate  10 . A partition  13  formed on the dielectric layer  12  maintains a discharge distance, and a fluorescent layer  17  is formed between neighboring partitions  13 . A front substrate  16  is installed over the rear substrate  10 , and a scanning electrode  14  and a common electrode  15 , perpendicular to the address electrodes  11 , are alternately formed on the bottom of the front substrate  16 . A dielectric layer  18  is coated on the front substrate  16  and the scanning and common electrodes  14  and  15 . A protective film  20  is coated on the dielectric layer  18 . A predetermined discharge gas is injected to a discharge space S between the front substrate  16  and the rear substrate  10 . 
     Referring to FIG. 2, if a voltage is applied to the respective electrodes, ions of the discharge gas accumulate on the dielectric layer  12 . A trigger discharge is generated between the address electrode  11  and the common electrode  15  by the accumulated ions, and charged particles are formed on bottom surface of the dielectric layer  18  of the front substrate  16 . At this time, according to image signals, a sustaining discharge is generated in the discharge space S by a predetermined voltage V applied between the scanning electrode  14  and the common electrode  15 . Then, the fluorescent material is excited by the plasma formed in the discharge gas to then emit light. 
     Referring to FIG. 3, the electrodes  14  and  15  are repeatedly formed with a constant cell pitch CP on the front substrate  16 . The cell pitch CP is a constant value as a design factor determined in consideration of resolution in a given screen size. Thus, in order to improve discharge efficiency or the brightness under a given cell pitch CP, the electrode width EW must be increased. However, since the cell pitch CP is constant, increasing the electrode width EW requires a reduction in the cell space CS. Current having pulses of opposite polarities is applied to the electrodes  14  and  15  by a circuit equivalent to one as shown in FIG.  4 . In this case, if the cell space CS is small, a crosstalk discharge as well as a normal discharge is generated between the electrodes  14  and  15  positioned in the adjacent cells as shown in FIG.  5 . Thus, since the reduction in the cell space CS cannot exceed a certain limit, the electrode width EW must be unavoidably reduced, which results in the reduction in the light emission area in the discharge cell to thereby decrease brightness. Also, the plasma display requires a high voltage for normal discharge. Further, since the concentration of electrical fields is lowered during discharge, which degrades the overall discharge efficiency. 
     SUMMARY OF THE INVENTION 
     To solve the above problem, it is an objective of the present invention to provide a plasma display device having a shielding electrode, by which crosstalk discharge between cells is shielded, and thus the cell space can be reduced. 
     Accordingly, to achieve the above objective, there is provided a plasma display device including a plurality of discharge cells each having substrates, and at least two electrodes formed on the substrates, for generating a discharge therebetween, and a shielding electrode formed between the electrodes respectively positioned in the neighboring cells, for shielding crosstalk generated between the electrodes of the neighboring cells. 
     The shielding electrode is electrically floated. 
     Also, alternatively, the substrates include front and rear substrates facing each other, the electrodes include a first electrode formed on the upper surface of the rear substrate in a predetermined pattern, and a second electrode formed on the bottom surface of the front substrate to be perpendicular to the first electrode, wherein the shielding electrode is formed between the second electrodes positioned in the neighboring cells, respectively. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above objectives and advantages of the present invention will become more apparent by describing in detail a preferred embodiment thereof with reference to the attached drawings in which: 
     FIG. 1 is an exploded perspective view of a conventional neighboring discharge type plasma display device; 
     FIG. 2 is a cross-sectional view taken along line II—II of FIG. 1; 
     FIG. 3 is a cross-sectional view showing a portion of FIG. 2; 
     FIG. 4 is an equivalent circuit diagram, in which power is applied to electrodes shown in FIG. 3; 
     FIG. 5 illustrates an equipotential surface formed by the electrodes shown in FIG. 3; 
     FIG. 6 is an exploded perspective view of a neighboring discharge type plasma display device according to an embodiment of the present invention; 
     FIG. 7 is a partially cross-sectional view taken along line VII—VII of FIG. 6; 
     FIG. 8 is an equivalent circuit diagram, in which power is applied to electrodes shown in FIG. 7; 
     FIG. 9 illustrates an equipotential surface formed by the electrodes shown in FIG. 7; 
     FIG. 10 is a cross-sectional view of a plasma display device according to another embodiment of the present invention; and 
     FIG. 11 is a cross-sectional view of a plasma display device according to still another embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIGS. 6 and 7 showing a neighboring discharge type plasma display device according to an embodiment of the present invention, address electrodes  61  are formed on a rear substrate  60  in a predetermined pattern, and a dielectric layer  62  covers the address electrodes  61  and the rear substrate  60 . A partition  63  formed on the dielectric layer  62  maintains a discharge distance, and a fluorescent layer  67  is formed between neighboring partitions  63 . A front substrate  66  is installed over the rear substrate  60 , and a scanning electrode  64  and a common electrode  65 , perpendicular to the address electrodes  61 , are alternately installed on the bottom of the front substrate  66 . The scanning electrode  64  and a common electrode  65  define an unit cell together with the neighboring partitions  63 . 
     According to the characteristics of the present invention, a shielding electrode  69  is formed between the neighboring cells, that is, on the front substrate  66  between the scanning electrode  64  positioned in a cell and the common electrode  65  positioned in another adjacent cell. 
     To prevent a voltage drop, a bus electrode (not shown) may be provided in the respective electrodes  64 ,  65  and  69 . A dielectric layer  68  is coated on the front substrate  66  and these electrodes  64 ,  65  and  69  formed on the bottom of the front substrate  66 . A protection layer  70  made of, for example, MgO may be further coated on the dielectric layer  68 . A predetermined discharge gas is injected to the discharge space between the front substrate  66  and the rear substrate  60 . The discharging operation has been described above. 
     The shielding electrode  69  shields a crosstalk discharge occurring between the common electrode  65  of a cell and the scanning electrode  64  of another adjacent cell. Therefore, the cell space CS can be reduced, which enables the increase in the electrode width EW. 
     The shielding electrode  69  is made of a conductive material, preferably, an argentum (Ag) paste having a black color, for improving contrast by suppressing outer light reflection. 
     As shown in FIG. 8 which is an equivalent circuit diagram showing power being applied to the electrodes  64 ,  65  and  69 , it is preferred that the shielding electrode  69  is electrically floated. Otherwise, an average DC voltage Va of voltages V applied to the electrodes  64  and  65  adjacent to the shielding electrode  69  may be applied to the shielding electrode  69 . 
     FIG. 9 illustrates an equipotential surface formed by the respective electrodes to which power is applied. If the average voltage Va is applied to the shielding electrode  69 , since a potential difference between neighboring cells is buffered by the equipotential surface formed by the average voltage of the shielding electrode, crosstalk discharge between neighboring cells is shielded. Similarly, if the shielding electrode  69  is floated, capacitive coupling of the electrodes  64  and  65  adjacent to the shielding electrode  69  affects the shielding electrode  69  as the average voltage of the electrodes  64  and  65  is applied thereto, which generates the equipotential surface preventing crosstalk discharge. 
     According to FIG. 10 showing another embodiment of the present invention, a shielding electrode  89  may be formed on the dielectric layer  68  or the protection layer  70  coated on the dielectric layer  68 . 
     Although a three-electrode sheet discharge type AC plasma display device has been described in the present invention, the present invention is not limited thereto. Also, in two-electrode/three-electrode type, neighboring/cross discharge type, and DC/AC plasma display devices, crosstalk discharge can also be suppressed by providing a shielding electrode between neighboring cells using the same principle and structure as described above. 
     For example, referring to FIG. 11, a shielding electrode  99  may be formed between electrodes  94  positioned respective cells to thereby shield crosstalk between the cells. Reference numeral  96  indicates a front substrate or a rear substrate. 
     As described above, according to the plasma display device of the present invention, since crosstalk discharge between the neighboring cells is prevented by a shielding electrode, the cell space between neighboring cells can be reduced, and electrode width can be increased. Accordingly, the discharge area can be increased, which causes a discharge voltage applied to the electrode to decrease, thereby improving discharge efficiency. Also, since an equipotential surface is formed by the shielding electrode, the electrical field of a discharge electrode is concentrated, thus improving the discharge efficiency.