Abstract:
A low-discharge-voltage high-brightness high-efficiency flat discharge lamp includes: a container; first and second electrodes arranged in the container, the second electrode including a plurality of discharge elements having different respective discharge distances with respect to the first electrode; and at least one discharge delay element respectively electrically connected to at least one of the plurality of discharge elements, each of the at least one discharge delay elements having different delay times. A high-brightness low-discharge-voltage high-efficiency PDP includes: a discharge space; first and second electrodes arranged in the discharge space, the second electrode including a plurality of discharge elements having different discharge distances with respect to the first electrode; and at least one discharge delay element respectively electrically connected to at least one of the discharge elements, each of the at least one discharge delay elements having different delay times. Accordingly, it is possible to initiate a discharge at a low discharge voltage and sustain a long-distance discharge.

Description:
CLAIM OF PRIORITY  
       [0001]     This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C.§119 from an application entitled  FLAT LAMP AND PLASMA DISPLAY PANEL,  earlier filed in the Korean Intellectual Property Office on 30 Dec. 2004 and there duly assigned Serial No. 10-2004-0117011.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a flat discharge lamp and a Plasma Display Panel (PDP), and more particularly, to a low-discharge-voltage high-efficiency flat discharge lamp and PDP.  
         [0004]     2. Description of the Related Art  
         [0005]     Plasma Display Panels (PDPs) are classified into facing and surface discharge PDPs. The present invention particularly relates to surface discharge PDPs. Surface discharge PDPs are disclosed in U.S. Pat. Nos. 4,638,218 and 5,661,500. In a surface discharge PDP, a pair of discharge sustaining electrodes is provided on the same front substrate, and discharge is generated between two electrodes in the direction parallel to the front substrate.  
         [0006]     The discharge generated in the direction parallel to the substrate is called the surface discharge. In the surface discharge PDP, the discharge sustain electrodes are provided on the front substrate, light passing portions are made of a light transparent material such as Indium Tin Oxide (ITO). The ITO is a transparent conductive material used for transparent electrodes. Since it has a high resistance, the light transparent material such as ITO is partially used in the plasma discharge region. Bus lines made of a low-resistance metal is used to transmit signals to the ITO electrodes.  
         [0007]     A PDP includes first and second substrates. A plurality of discharge sustain electrode pairs are disposed on an inner surface of the first substrate. The discharge sustain electrodes are made of a transparent material. A dielectric layer and a protective layer are stacked in this order to cover the discharge sustain electrodes. A plurality of barrier ribs are provided over an inner surface of the second substrate in the direction perpendicular to the discharge sustain electrodes. A plurality of address electrodes are disposed on the inner surface of the second substrate between the barrier ribs. A dielectric layer is provided to cover the address electrodes. Fluorescent layers are coated on side walls of the barrier ribs and upper surfaces of the dielectric layer between the barrier ribs. The discharge sustain electrodes are disposed in the direction perpendicular to the address electrodes and the barrier ribs.  
         [0008]     In the surface discharge PDP, an initial discharge is generated by one discharge sustain electrode and one address electrode. The discharge is then sustained by the discharge sustain electrodes. Ultra-violet (UV) light emitted by a discharge region irradiates the fluorescent layers. Visible light is emitted from the excited fluorescent layers. The visible light is used for illumination by the flat discharge lamp or for display by the PDP.  
         [0009]     In such a PDP, the discharge distance is short, and there is a limitation as to the electrode arrangement. Therefore, the discharge efficiency of such a PDP is disadvantageously low. In addition, since the discharge is generated close to the first substrate (front substrate), plasma ions collide with the protective layer. Therefore, the protective layer can rapidly deteriorate, so that lifetime of the PDP is shortened. On the other hand, the fluorescent layers are separated from the second substrate (rear substrate) by a relatively long distance. Therefore, a relatively large amount of the UV light emitted by the discharge region of the first substrate is not absorbed by the fluorescent layers. As a result, the brightness of the PDP is reduced.  
         [0010]     The lengthening of the discharge distance in the limited discharge space is one of the main development subjects for the flat discharge lamp as well as the PDP. Since there is a limitation to the discharge space, it is difficult to design the flat discharge lamp and the PDP. On the other hand, the lengthening of the discharge distance results in increase in the discharge voltage. In case of lengthening of the discharge distance in the limited discharge space, the reducing of the discharge voltage must be taken into consideration.  
         [0011]     Therefore, there is a need for a discharge mechanism used for a low-discharge-voltage high-brightness high-efficiency flat discharge lamp or PDP.  
       SUMMARY OF THE INVENTION  
       [0012]     The present invention provides a low-discharge-voltage high-brightness high-efficiency flat discharge lamp or Plasma Display Panel (PDP).  
         [0013]     The present invention also provides a low-discharge-voltage high-brightness high-efficiency flat discharge PDP.  
         [0014]     According to one aspect of the present invention, a flat discharge lamp is provided including: a container; first and second electrodes arranged in the container, the second electrode including a plurality of discharge elements having different respective discharge distances with respect to the first electrode; and at least one discharge delay element respectively electrically connected to at least one of the plurality of discharge elements, each of the at least one discharge delay elements having different delay times.  
         [0015]     The at least one discharge delay element includes a magnetic switch.  
         [0016]     A discharge delay element having a longest delay time is preferably electrically connected to a discharge element having a greatest discharge distance with respect to the first electrode.  
         [0017]     The discharge delay elements are preferably respectively electrically connected to the plurality of discharge elements such that the delay times of the discharge delay elements are proportional to the discharge distances with respect to the first electrode of the plurality of discharge elements.  
         [0018]     According to another aspect of the present invention, a Plasma Display Panel (PDP) is provided including: a discharge space; first and second electrodes arranged in the discharge space, the second electrode including a plurality of discharge elements having different discharge distances with respect to the first electrode; and at least one discharge delay element respectively electrically connected to at least one of the discharge elements, each of the at least one discharge delay elements having different delay times.  
         [0019]     The at least one discharge delay element preferably includes a magnetic switch.  
         [0020]     A discharge delay element having a longest delay time is preferably electrically connected to a discharge element having a greatest discharge distance with respect to the first electrode.  
         [0021]     The discharge delay elements are preferably respectively electrically connected to the plurality of discharge elements such that the delay times of the discharge delay elements are proportional to the discharge distances with respect to the first electrode of the plurality of discharge elements. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     A more complete appreciation of the present invention and many of the attendant advantages thereof, will be readily apparent as the present invention becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein:  
         [0023]      FIG. 1  is a schematic perspective view of a Plasma Display Panel (PDP);  
         [0024]      FIG. 2  is a schematic cross-sectional view of the PDP of  FIG. 1 ;  
         [0025]      FIG. 3  is a view of a discharge mechanism according to an embodiment of the present invention;  
         [0026]      FIG. 4  is a perspective view of a magnetic switch used for the discharge mechanism according to an embodiment of the present invention;  
         [0027]      FIG. 5  is a schematic cross-sectional view of a flat discharge lamp according to an embodiment of the present invention;  
         [0028]      FIG. 6  is a schematic perspective view of a PDP according to another embodiment of the present invention; and  
         [0029]      FIG. 7  is a schematic cross-sectional view of the PDP of  FIG. 6 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0030]      FIG. 1  is a schematic perspective view of a Plasma Display Panel (PDP).  FIG. 2  is a schematic cross-sectional view of the PDP of  FIG. 1 .  
         [0031]     The PDP includes first and second substrate  10  and  20 . A plurality of discharge sustain electrode pairs  13   a  and  13   b  are disposed on an inner surface of the first substrate  10 . The discharge sustain electrodes  13   a  and  13   b  are made of a transparent material. A dielectric layer  11  and a protective layer  12  are stacked in this order to cover the discharge sustain electrodes  13   a  and  13   b.  A plurality of barrier ribs  21  are provided over an inner surface of the second substrate  20  in the direction perpendicular to the discharge sustain electrodes  13   a  and  13   b.  A plurality of address electrodes  22  are disposed on the inner surface of the second substrate  20  between the barrier ribs  21 . A dielectric layer  23  is provided to cover the address electrodes  22 . As shown in  FIG. 2 , fluorescent layers  24  are coated on side walls of the barrier ribs  21  and upper surfaces of the dielectric layer  23  between the barrier ribs  21 . As shown in  FIG. 1 , the discharge sustain electrodes  13   a  and  13   b  are disposed in the direction perpendicular to the address electrodes  22  and the barrier ribs  21 . However, in  FIG. 2 , in order to show all the components in the single figure, the discharge sustain electrodes  13   a  and  13   b  are depicted in a direction parallel to the address electrodes  22  and the barrier ribs  21 .  
         [0032]     In the surface discharge PDP, an initial discharge is generated by one discharge sustain electrode and one address electrode. The discharge is then sustained by the discharge sustain electrodes  13   a  and  13   b.  Ultra-violet (UV) light emitted by a discharge region  8  irradiates the fluorescent layers  24 . Visible light is emitted from the excited fluorescent layers  24 . The visible light is used for illumination by the flat discharge lamp or for display by the PDP.  
         [0033]     In such a PDP, the discharge distance is short, and there is a limitation as to the electrode arrangement. Therefore, the discharge efficiency of such a PDP is disadvantageously low. In addition, since the discharge is generated close to the first substrate (front substrate)  10 , plasma ions collide with the protective layer  12 . Therefore, the protective layer  12  can rapidly deteriorate, so that lifetime of the PDP is shortened. On the other hand, the fluorescent layers  24  are separated from the second substrate (rear substrate)  20  by a relatively long distance. Therefore, a relatively large amount of the UV light emitted by the discharge region  8  of the first substrate  10  is not absorbed by the fluorescent layers  24 . As a result, the brightness of the PDP is reduced.  
         [0034]     A flat discharge lamp and a Plasma Display Panel (PDP) according to embodiments of the present invention are described in detail below with reference to the accompanying drawings.  
         [0035]      FIG. 3  is a view of a discharge mechanism according to an embodiment of the present invention.  
         [0036]     The flat discharge lamp (or the PDP) according to an embodiment of the present invention includes first and second electrodes  131  and  132  separated from each other. The second electrode  132  includes a plurality of discharge elements  132   a  to  132   c.    
         [0037]     A power supply  150  is connected to the first and second electrodes  131  and  132 . A discharge delay unit  141  is connected to the discharge elements  132   a,    132   b,  and  132   c  of the second electrode  132 . The discharge delay unit  141  delays discharges of the discharge elements  132   a,    132   b,  and  132   c.    
         [0038]     The discharge delay unit  141  includes discharge delay elements  141   a,    141   b,  and  141   c  connected to the respective discharge elements  132   a,    132   b,  and  132   c.    
         [0039]     The discharge elements  132   a,    132   b,  and  132   c  are separated from the first electrode  131  by different distances. The discharge delay elements  141   a,    141   b,  and  141   c  delay discharges D 1 , D 2 , and D 3  of the discharge elements  132   a,    132   b,  and  132   c  by different delay times, so that the closer discharge element initiates a discharge earlier than the further away discharge element. Namely, the closest discharge element  132   a  first initiates a discharge, and the furthest away discharge element initiates the last discharge. Therefore, the discharges D 1 , D 2 , and D 3  are initiated in this order.  
         [0040]     The discharge delay elements  141   a,    141   b,  and  141   c  can include a magnetic switch or a semiconductor switch, which is generally used for a PDP or discharge lamp. The semiconductor switch is arranged on a circuit board. The magnetic switch is constructed with an inductor. The magnetic switch delays the discharge with a discharge delay time, that is, a voltage maintaining time T H  described later.  
         [0041]     The discharge D 1  is first generated by the closest discharge element  132   a  at the lowest discharge voltage with a low discharge efficiency. Charged particles such as plasma ions generated in the discharge D 1  enable the second discharge element  132   b  to easily generate the subsequent discharge D 2 . In turn, the charged particles generated in the discharges D 1  and D 2  also enable the third discharge element  132   c  to easily generate the subsequent discharge D 3 . Here, since the third discharge element  132   c  has the longest discharge distance, the discharge efficiency of the discharge D 3  is highest.  
         [0042]     In the present invention, an initial discharge is generated by a shortest-discharge-distance discharge element (the closest discharge element), and then, the subsequent discharges are generated. As a result, it is possible to obtain a high-efficiency discharge.  
         [0043]      FIG. 4  is a perspective view of the magnetic switch used for the discharge mechanism according to an embodiment of the present invention. The magnetic switch is a kind of choke. The magnetic switch includes a ring-type core  140   a  and a wire  140   b  wound around the ring-type core  140   a.  The discharge delay time, that is, the voltage maintaining time T H  obtained by the magnetic switch is represented by Equation 1 below.  
                 ∫             T   H       ⁢       V   ⁡     (   t   )       ⁢           ⁢     ⅆ   t         =       Am   ·   Nt   ·   Δ     ⁢           ⁢   B             Equation   ⁢           ⁢   1                 L   MS     =       μ   r     ⁢     μ   o     ⁢     Am   Im     ⁢     Nt   2               Equation   ⁢           ⁢   2                 V   MS     =       -     L   MS       ⁢       ⅆ   l       ⅆ   t                 Equation   ⁢           ⁢   3               
         [0044]     The ring-type core  140   a  and the wire  140   b  constitute an inductor that is the magnetic switch. The ring-type core  140   a  is made of a ferromagnetic material. The wire  140   b  is made of a conductor. The inductor&#39;s inductance L MS  is represented by Equation 2 below. A counter electromotive force V MS  induced to the inductor is represented by Equation 3 below. The counter electromotive force V MS  is proportional to the relative permeability of the inductor. The counter electromotive force V MS  changes according to the change of relative permeability. The magnetic switch is a device using the change in the counter electromotive force V MS  according to the change in the relative permeability μ r  after the voltage maintaining time T H  of the Equation 1.  
         [0045]     Here, μ r  is a relative permeability, μ 0  is a permeability in vacuum, V(t) is an applied voltage, Am is a magnetic cross-sectional area, Nt is turns of wire, B is a magnetic flux density, ΔB is a change in the magnetic flux density B, lm is a magnetic length, and di/dt is a current change rate.  
         [0046]     In addition, the magnetic switch is a passive device. Therefore, at the time of designing the magnetic switch, an operating timing of the magnetic switch must be taken into consideration. The operating time can be defined by the magnetic field intensity proportional to the current flowing through the inductor, that is, the magnetic switch. In particular, since the operating timing cannot be externally controlled, the operating time must be determined at the time of designing the magnetic switch. More specifically, the operating time is determined by the voltage maintaining time T H  of Equation 1.  
         [0047]     According to an experiment, an inductor having an inductance of 8.1 μH has a delay time of about 5 μs at a voltage of 3 kV. In the experiment, the magnetic cross-sectional area Am is 3 cm 2 , the turns of wire Nt is 500, the change ΔB in magnetic field density is 0.1 T, and the magnetic length lm is 11.6 cm.  
         [0048]     By taking the delay time, that is, the voltage maintaining time T H  into consideration, the inductances of the discharge delay elements  141   a,    141   b,  and  141   c  are suitably adjusted.  
         [0049]     When using the magnetic switches (inductors) as a discharge element, the magnetic switches are manufactured separately from the discharge lamp or the PDP. The discharge delay elements, that is, the inductors, are then mounted on the discharge delay lamp or the PDP. When using the semiconductor switches as a discharge element, the semiconductor switches are formed on the discharge lamp or the PDP together with other circuit element.  
         [0050]      FIG. 5  is a schematic cross-sectional view of a flat discharge lamp according to an embodiment of the present invention.  
         [0051]     The flat discharge lamp includes first and second substrates  201  and  202  which define a discharge space  203 . First and second discharge electrodes  211  and  212  are disposed on an inner surface of the second substrate  202  within the discharge space  203 .  
         [0052]     The first and second electrodes  211  and  212  are separated from each other. The second electrode  212  is divided into three discharge elements  212   a,    212   b,  and  212   c.  A discharge delay unit  213  is coupled to the discharge elements  212   a,    212   b,  and  212   c  of the second electrode  212 . The discharge delay unit  213  includes discharge delay elements  213   a,    213   b,  and  213   c  coupled to the respective discharge elements  212   a,    212   b,  and  212   c.  The discharge delay elements  213   a,    213   b,  and  213   c  are constructed with inductors having different inductances and voltage maintaining times T H . A power supply  205  is connected to the first electrodes  211  and the discharge delay element  213 . Alternatively, in another embodiment, a dielectric layer (not shown) covers the first and second electrodes  211  and  212 .  
         [0053]     Although a single one discharge space  203  is provided in the embodiment of  FIG. 5 , the discharge space can be partitioned into a plurality of discharge spaces. In this case, a plurality of first and second electrodes are provided to the respective discharge spaces. On the other hand, since the closest discharge element  212   a  first initiates a discharge, the discharge need not be delayed. Therefore, the discharge delay element  213   a  coupled to the closest discharge element  212   a  can be omitted.  
         [0054]      FIG. 6  is a schematic perspective view of a PDP according to another embodiment of the present invention.  
         [0055]     The PDP includes first and second substrates  301  and  302 , which define a discharge space. In addition, the discharge space is partitioned into a plurality of discharge cells by barrier ribs  306 . A plurality of first and second electrodes  311  and  312  are disposed on an inner surface of the first substrate  301 . The first and second electrodes  311  and  312  are made of a transparent material. The first and second electrodes  311  and  312  serve as discharge sustain electrodes, which are parallel to each other. A dielectric layer  303  and a protective layer  304  are stacked in this order on the first and second electrodes  311  and  312 . The protective layer  304  is made of MgO.  
         [0056]     The second electrode  312  is divided into a plurality of discharge elements. In the embodiment, three discharge elements  312   a,    312   b,  and  312   c  are provided. A discharge delay unit  313  is coupled to the discharge elements  312   a,    312   b,  and  312   c.  The discharge delay unit  313  includes three discharge delay elements  313   a,    313   b,  and  313   c  coupled to the respective discharge elements  312   a,    312   b,  and  312   c.  The discharge delay elements  313   a,    313   b,  and  313   c  can be shared by other discharge cells.  
         [0057]     On the other hand, since the closest discharge element  312   a  first initiates a discharge, the discharge need not be delayed. Therefore, the discharge delay element  313   a  coupled to the closest discharge element  312   a  can be omitted.  
         [0058]     A plurality of the barrier ribs  306  are provided over an inner surface of the second substrate  302  in the direction perpendicular to the first and second electrodes  311  and  312 . A plurality of address electrodes  308  are disposed on the inner surface of the second substrate  302  between the barrier ribs  306 . A dielectric layer  305  is provided to cover the address electrodes  308 . As shown in  FIG. 7 , fluorescent layers  307  are coated on side walls of the barrier ribs  306  and upper surfaces of the dielectric layer  305  between the barrier ribs  306 . As shown in  FIG. 6 , the first and second electrodes  311  and  312  are disposed in the direction perpendicular to the address electrodes  308  and the barrier ribs  306 . However, in  FIG. 7 , in order to show all the components in the single figure, the first and second electrodes  311  and  312  are depicted in the direction parallel to the address electrodes  308  and the barrier ribs  306 .  
         [0059]     The operation of the PDP according to the present invention is generally similar to that of a conventional PDP. The difference therebetween is the operation associated with the plurality of the discharge elements of the second electrodes  312  and the discharge delay elements coupled thereto.  
         [0060]     When using the semiconductor switches as a discharge element, there is need for a driving circuit for the semiconductor switches. The driving circuit can be implemented by those of ordinarily skill in the art.  
         [0061]     According to a discharge lamp and Plasma Display Panel (PDP) of the present invention, it is possible to initiatea discharge at a low discharge voltage and generate a sustain discharge through a long discharge path. Therefore, it is possible to reduce the production costs of the discharge lamp or the PDP. In addition, it is possible to improve the discharge efficiency due to the long discharge path.  
         [0062]     In addition, a discharge mechanism according to the present invention can be used for a low-discharge-voltage high-efficiency apparatus such as a discharge lamp or a PDP.  
         [0063]     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various modifications in form and detail can be made therein without departing from the spirit and scope of the present invention as defined by the appended claims.