Abstract:
A design for a plasma display panel (PDP). The novel PDP has two separate layers of fluorescent material. One layer of fluorescent material can generate long wavelength from VUV rays and the other fluorescent layer can convert either of VUV or long wavelength ultraviolet rays into visible rays. Such a PDP improves the luminance efficiency by more efficiently using the UV and VUV rays generated during plasma 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 for PLASMA DISPLAY PANEL earlier filed in the Korean Intellectual Property Office on 24 Nov. 2003 and there duly assigned Serial No. 2003-83617.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a plasma display panel (PDP), and more particularly, to a design for a PDP resulting in improved luminous efficiency.  
         [0004]     2. Description of the Related Art  
         [0005]     A PDP generates visible rays of a predetermined wavelength from a fluorescent material energized by ultraviolet rays in a plasma discharge. The amount of visible rays depends on a discharge distance. However, there is a limit as to the size of the discharge distance within a small discharge area of a PDP. In order to display images of high luminance, a large amount of ultraviolet rays are required and it is necessary to efficiently activate the fluorescent material by using the ultraviolet rays. However, a significant amount of the generated ultraviolet rays never reach and activate the fluorescent material leading to waste.  
         [0006]     Turning now to the figures,  FIG. 1  is a sectional view illustrating a surface discharge type PDP according to the prior art. The PDP of  FIG. 1  is similar to  FIG. 2  of U.S. Pat. No. 5,959,403 to Lee. The PDP illustrated in  FIG. 1  can also be derived from U.S. Pat. No. 4,638,218 to Shinoda et al. Referring to  FIG. 1 , predetermined barrier walls  9  are located between a front plate  1  and a rear plate  2 . First and second sustain electrodes  3   a  and  3   b  are formed on the surface of the front plate  1  facing the rear plate  2 , and a first dielectric layer  4   a  and a protection layer  5  are formed over the first and second sustain electrodes  3   a  and  3   b . An address electrode  6  is formed on the surface of the rear plate  2  facing the front plate  1  to correspond to the first and second sustain electrodes  3   a  and  3   b , and a second dielectric layer  4   b  is formed over the address electrode  6 . A fluorescent layer  7  is formed on the sidewalls of the barrier walls  9  and on the surface of the rear plate  2  facing the front plate  1 .  
         [0007]     A discharge method for the surface discharge type PDP is disclosed in U.S. Pat. No. 4,638,218 to Shinoda et al. In the surface discharge type PDP, an initial discharge is induced by one sustain electrode and one address electrode, and then the initial discharge is maintained by the sustain electrodes. The ultraviolet rays generated in a discharge area  8  are absorbed in the fluorescent layer  7  to activate the fluorescent layer  7 . The ultraviolet rays produced in discharge area  8  are radiated in every direction and thus some rays never reach the fluorescent layer, producing wasted energy. Also, vacuum ultraviolet rays (VUV) are also produced in the discharge area  8 . These VUV rays have a shorter wavelength than ultraviolet rays. However, the fluorescent layer  7  may not be able to convert the VUV rays into visible light, further producing waste. In other words, a large amount of radiation generated in the discharge area is not converted into visible light. Thus, in order to improve the luminance efficiency, a design for a PDP that converts VUV rays into visible light and converts more of the generated ultraviolet rays into visible light is needed.  
       SUMMARY OF THE INVENTION  
       [0008]     It is therefore an object of the present invention to provide for an improved design for a plasma display panel.  
         [0009]     It is also an object to provide a design for a plasma display panel that improves on the luminance efficiency.  
         [0010]     It is further an object of the present invention to provide a plasma display where shorter wavelength VUV rays can also be converted to visible images.  
         [0011]     These and other objects can be achieved by a PDP that more efficiently converts ultraviolet rays generated from a plasma into visible images of high luminance. According to an aspect of the present invention, there is provided a PDP that includes a container having a gas discharge area and a discharge generating unit generating a discharge in the discharge area, the discharge area includes a first fluorescent layer converting both ultraviolet rays and shorter wavelength vacuum ultraviolet rays (VUV) into visible rays, and a second fluorescent layer converting VUV rays into longer wavelength ultraviolet rays.  
         [0012]     According to another aspect of the present invention, there is provided a PDP having a front plate and a rear plate forming a discharge area, barrier walls arranged between the front plate and the rear plate with a predetermined distance therebetween and having a predetermined height, a first fluorescent layer arranged at one side of the discharge area converting VUV and ultraviolet rays into visible rays, and a second fluorescent layer arranged at the other side of the discharge area that converts VUV rays into longer wavelength ultraviolet rays.  
         [0013]     The first and second fluorescent layers are formed so that the visible light is emitted in a direction normal to the layers. The first fluorescent layer may be formed on a surface of the front plate that faces the rear plate and the second fluorescent layer may be formed on a surface of the rear plate that faces the front plate. Sustain electrodes may be formed on the inner walls of the barrier walls to face each other. Address electrodes may be formed on the surface of the rear plate that faces the front plate, the address electrodes thus being between the barrier walls. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same 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:  
         [0015]      FIG. 1  is a sectional view illustrating the structure of a prior art plasma display panel (PDP);  
         [0016]      FIG. 2  is a sectional view a PDP according to the present invention illustrating the locations of the two fluorescent layer;  
         [0017]      FIG. 3  is a sectional view illustrating a DC PDP according to a first embodiment of the present invention;  
         [0018]      FIG. 4  is a sectional view illustrating an AC PDP according to a second embodiment of the present invention; and  
         [0019]      FIG. 5  is a perspective view illustrating a rear plate of a PDP according to a third embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]     Turning now to  FIG. 2 ,  FIG. 2  is a sectional view for explaining a method of generating visible rays by using ultraviolet rays including vacuum ultraviolet rays (VUV) that are generated in a discharge area according to the present invention. Referring to  FIG. 2 , a front plate  10  and a rear plate  20  are arranged at both sides of a gas plasma discharge area, and a first fluorescent layer  70   a  is formed on the surface of the front plate  10  facing the rear plate  20  and a second fluorescent layer  70   b  is formed on the surface of the rear plate  20  facing the front plate  10 .  
         [0021]     The first fluorescent layer  70   a  is formed of a fluorescent material is able to convert both the ultraviolet rays and the shorter wavelength VUV rays into visible light. The second fluorescent layer  70   b  is formed of a fluorescent material that converts VUV into ultraviolet rays having a longer wavelength than VUV. The ultraviolet rays and the VUV generated in the discharge area progress in every direction, and the VUV and the ultraviolet rays arriving at the first fluorescent layer  70   a  activate the first fluorescent layer  70   a  to generate visible rays. The VUV rays arriving at the second fluorescent layer  70   b  activate the second fluorescent layer  70   b  to generate the ultraviolet rays of the longer wavelength. The ultraviolet rays generated from the second fluorescent layer  70   b  progress to the first fluorescent layer  70   a  to activate the first fluorescent layer  70   a , resulting in the generation of the visible rays. Thus, by designing the two fluorescent layers as in  FIG. 2 , the VUV and more of the generated ultraviolet light can be converted into visible light resulting in a higher luminance.  
         [0022]     Turning now to  FIG. 3 ,  FIG. 3  illustrates a sectional view of PDP  300  according to a first embodiment of the present invention. PDP  300  of  FIG. 3  is a DC type PDP. Referring to  FIG. 3 , the discharge area may extend to the planar directions of first and second fluorescent layers  70   a  and  70   b , thus sustain electrodes  30   a  and  30   b  are arranged on barrier walls  90  between front plate  10  and rear plate  20 . Sustain electrodes  30   a  and  30   b  face each other. The sustain electrodes  30   a  and  30   b  form a surface discharge type (or coplanar type) instead of a facing discharge type (or opposed discharge type). A surface discharge type PDP is characterized in that a pair of sustain electrodes are formed on a substrate, typically a front substrate. Meanwhile, a facing discharge type PDP is characterized in that one electrode is formed on a front substrate and the other is formed on the rear substrate so that the discharge occurs between electrodes located on opposite plates.  
         [0023]     According to a first embodiment of the present invention, the discharge area extends between the front plate  10  and the rear plate  20  in the z direction and between the sustain electrodes  30   a  and  30   b  in the x direction. Such a design improves discharge efficiency and results in a large amount of ultraviolet rays being generated. An address electrode  60  is formed on the surface of the rear plate  20  facing the front plate  10 , a dielectric layer  40  covers the address electrode  60 , and the second fluorescent layer  70   b  is formed on the dielectric layer  40 . In the DC PDP  300  of  FIG. 3 , a material for protecting the sustain electrodes  30   a  and  30   b  from ion impacts may be coated on the sustain electrodes  30   a  and  30   b . Thus, an address discharge occurs in any one of areas between the address electrode  60  and the sustain electrodes  30   a  and  30   b , and a DC plasma discharge is maintained between the sustain electrodes  30   a  and  30   b.    
         [0024]     Turning now to  FIG. 4 ,  FIG. 4  illustrates a PDP  400  according to a second embodiment of the present invention. In  FIG. 4 , the PDP  400  is an AC type PDP. Referring to  FIG. 4 , a front plate  10  and a rear plate  20  are separated by barrier walls  90  having a predetermined height, and a discharge area is formed between the front plate  10  and the rear plate  20 . Sustain electrodes  30   a  and  30   b  are formed on the inner walls of the barrier walls  90 . Dielectric layers  91  are formed over the sustain electrodes  30   a  and  30   b  to help sustain an AC discharge between the sustain electrodes  30   a  and  30   b . An address electrode  60  is arranged on the surface (+z surface) of the rear plate  20  facing the front plate  10 , and a dielectric layer  40  covers on the address electrode  60 . A second fluorescent layer  70   b , that converts VUV to longer wavelength ultraviolet light, is formed on the dielectric layer  40 . A first fluorescent layer  70   a , which generates visible rays from the ultraviolet rays of any wavelength (i.e., long wavelength ultraviolet and the shorter VUV), is formed on the surface of the front plate  10  facing the rear plate  20 . An address discharge occurs in any one of areas between the address electrode  60  and the sustain electrodes  30   a  and  30   b  for a short time, and an AC plasma discharge is maintained between the sustain electrodes  30   a  and  30   b . In the PDPs illustrated in  FIGS. 3 and 4 , a protection layer, such as an MgO layer or MgF 2  layer, may also be formed on the surface of the first fluorescent layer  70   a  to protect the first fluorescent layer  70   a  from ion impact in the first and second embodiments of the present invention.  
         [0025]     Turning now to  FIG. 5 ,  FIG. 5  is a perspective view illustrating a rear plate  20  on which barrier walls  90  are formed in a lattice type. In the first and second embodiments of the present invention, the barrier walls are formed in a stripe shape. In the present invention, the barrier ribs may instead be formed in a lattice or matrix formation instead of the stripe formation. The lattice formation serves to prevent crosstalk between pixels. The barrier walls  90  include first portions  90   a  running in the y direction parallel to the address electrodes  60  and having sustain electrodes  30   a  and  30   b  formed thereon. The second portions  90   b  are preferably perpendicular to the first portions  90   a  and run in the x direction and define unit pixel areas together with the first portions  90   b . It is to be appreciated that the barrier walls need not be perpendicular to each other as other configurations, such a honey comb are not outside the scope of the present invention.  
         [0026]     Unlike  FIGS. 3 and 4 , the PDP illustrated in  FIG. 5  shows the sustain electrodes  30   a  and  30   b  as being perpendicular to the address electrodes  60 , in order to emphasize that the principles of the present invention can apply to a large range of PDP structures. In  FIGS. 5 , second fluorescent layers  70   b  are formed on portions of the rear plate  20  where the barrier walls  90  are not formed, and the address electrodes  60  and an insulating layer for protecting the address electrodes  60  are formed under the second fluorescent layers  70   b . The sustain electrodes  30   a  and  30   b  are illustrated in  FIG. 5  as not being covered by dielectric layer, however the present invention can use the matrix or lattice shaped barrier ribs where a dielectric layer covers the sustain electrodes  30   a  and  30   b  as in  FIG. 4 .  
         [0027]     It is to be appreciated that the present invention is not limited to the exact configurations of  FIGS. 1 through 5  but other configurations and combinations of configurations are also within the scope of the present invention. For example, the sustain electrodes and the address electrodes in  FIGS. 1, 3 , and  4  are illustrated as being parallel to each other running in the y direction however the present invention is in no way limited in this way. Also in the embodiments of the present invention, instead of being formed on the barrier walls, the sustain electrodes can be formed on a front plate as in  FIG. 1 .  
         [0028]     As described above, a PDP according to the present invention includes one fluorescent layer that converts both long wave ultraviolet rays and VUV rays into visible rays and another fluorescent layer that converts VUV rays into longer wavelength ultraviolet rays. Such a design results in a more efficient use of the ultraviolet rays and VUV generated from a plasma discharge. Accordingly, the luminance of the PDP may be improved.  
         [0029]     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details maybe made therein without departing from the spirit and scope of the present invention as defined by the following claims.