Abstract:
The present invention relates to a plasma display panel and a manufacture method thereof in which a color mixture of emitted light can be prevented and a contrast characteristic can be improved. The plasma display panel includes: a first barrier rib for partitioning a plurality of sub-pixels; and a second barrier rib formed to function as a boundary between one unit pixel constituting of the plurality of sub-pixels and an adjacent unit pixel, and partition the unit pixels, wherein the second barrier rib has a greater width than the first barrier rib. The method includes the steps of: coating a first and second barrier rib paste on a dielectric material formed on a glass; and placing and exposing an irregular pattern mask on the first and second barrier rib paste to form a first barrier rib pattern and a second barrier rib pattern each having a different width.

Description:
This Nonprovisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No. 10-2004-0021696 filed in Korea on Mar. 30, 2004 and Patent Application No. 10-2004-0021700 filed in Korea on Mar. 30, 2004, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a plasma display panel and a manufacture method thereof, and more particularly, to a plasma display panel and a manufacture method thereof in which when the plasma display panel is driven, a color mixture of emitted light can be prevented and a contrast characteristic can be improved. 
     2. Description of the Background Art 
     In general, plasma display panel (Hereinafter, referred to as “PDP”) includes a front substrate and a rear substrate formed of soda-lime glass, and a barrier rib defining one unit cell between the front substrate and the rear substrate. When inert gas such as He—Xe and He—Ne is discharged due to a high frequency voltage in each unit cell, vacuum ultraviolet rays are generated and phosphor is excited between the barrier ribs, thereby displaying an image. 
       FIG. 1  is a schematic perspective view illustrating a structure of a conventional plasma display panel. 
     As shown in  FIG. 1 , a plasma display panel (PDP)  100  includes a front substrate  10  and a rear substrate  20 , which are spaced apart and engaged in parallel with each other. The front substrate  10  is a display surface on which the image is displayed. The rear substrate  20  is a rear surface. The front substrate  10  is formed at a lower side of the PDP. The front substrate  10  includes a pair of sustain electrodes  11  for sustaining light emission using a mutual discharge in one pixel. The sustain electrodes  11  are comprised of a transparent electrode  11   a  formed of indium-tin-oxide (ITO) and a bus electrode  11   b  formed of metal. The sustain electrodes  11  are covered with a dielectric layer  12   a , which limits a discharge current and insulates the sustain electrodes. A passivation layer  13  is formed of oxide magnesium (MgO) on the dielectric layer  12   a  to facilitate a discharge. The rear substrate  20  includes stripe-type (or well-type) barrier ribs  21  and a plurality of address electrodes  22 . The stripe-type (or well-type) barrier ribs  21  are arranged in parallel with one another to form a plurality of discharge spaces, that is, a plurality of cells. The plurality of address electrodes  22  are arranged in parallel with the barrier ribs  21  to perform an address discharge and generate vacuum ultraviolet rays at their intersection with the sustain electrodes  11 . A dielectric layer  12   b  is formed on the address electrodes  22 . Red (R), green (G), blue (B) phosphors  23  are coated on the dielectric layer  12   b  to emit a visible ray, thereby displaying the image in the address discharge. A method for expressing a gray level in the above constructed PDP is illustrated in  FIG. 2 . 
       FIG. 2  is a view illustrating a conventional method for expressing the gray level in the plasma display panel. 
     As shown in  FIG. 2 , the gray level is expressed by dividing one frame into several sub-fields each having a different number of light emission times. Each of the sub-fields is divided into a reset period for uniformly generating the discharge, an address period for selecting the discharge cell, and a sustain period for expressing the gray level depending on the number of discharge times. For example, when the image is displayed in 256 gray levels, a frame period (16.6 ms) corresponding to 1/60 second is divided into eight sub-fields (SF 1  to SF 8 ). Each of eight sub-fields is again divided into the reset period, the address period and the sustain period. The reset period and the address period are the same at each sub-field. The address discharge is generated by a voltage difference between the address electrode (data electrode) and the transparent electrode (scan electrode) to select the discharge cell. The sustain period is increased in a ratio of 2 n  (n=0,1,2,3,4,5,6,7) at each sub-field. 
     In general, in the PDP, the unit pixel is constituted of three kinds of sub-pixels emitting R, G, B lights. Each of the sub-pixels controls an amount of emitted light depending on the number of the sustain pulses, and visually juxtaposes and mixes the controlled lights, thereby expressing the color and the gray level. 
       FIGS. 3A through 3D  are views illustrating various discharge cell structures in the conventional plasma display panel.  FIG. 3A  illustrates the discharge cell structure having a stripe-type barrier rib,  FIG. 3B  illustrates the discharge cell structure having a well-type barrier rib,  FIG. 3C  illustrates the discharge cell structure having a delta-type barrier rib, and  FIG. 3D  illustrates the discharge cell structure having a honey-type barrier rib. 
     As shown in  FIGS. 3A through 3D , in sub-pixels  101   a ,  101   b  and  101   c  of the conventional PDP having the above discharge cell structure, a barrier rib  21  separates phosphors expressing each R, G, B color. The sub-pixels  101   a ,  101   b  and  101   c  constitute a unit pixel  101  with the barrier rib  21  functioning as a boundary. The unit pixel is arranged to form a predetermined shape with an adjacent unit pixel using the barrier rib  21  functioning as the boundary, to display the image. 
     In the PDP having the discharge cell structure, the barrier rib functions to prevent electrical and optical crosstalk between the sub-pixels or the unit pixels. The barrier rib is the most important element in controlling a display quality and a light emission efficiency of the PDP. In the conventional PDP, the barrier rib partitioning the unit pixel has the same width as the barrier rib functioning as the boundary between the R, G, B sub-pixels constituting the unit pixel. In the PDP where each unit pixel emits light and the emitted light is mixed and displayed, there is a drawback in that a color mixture characteristic depending on a color of the adjacent unit pixel is not good. In other words, since the barrier rib formed between the sub-pixels has the same width as the barrier rib formed between the unit pixels, when the PDP is driven, the color mixture characteristic between an inherent color of the unit pixel and the color of the adjacent unit pixel is deteriorated. 
     In the conventional PDP having the above discharge cell structure, a black matrix having a low reflectance is formed at the front substrate to separate the colors and decrease a reflectance between upper and lower unit pixels, thereby improving a contrast characteristic. 
       FIGS. 4A and 4B  are views illustrating black matrix structures disposed at the front substrate in the conventional PDP having the stripe-type discharge cell structure or the well-type discharge cell structure. 
     Referring to  FIGS. 4A and 4B , in the front substrate  10 , a black matrix  13   a  is formed only in a traverse direction of the unit pixel  101 . Such a black matrix structure has a good contrast characteristic due to color separation and reflectance reduction between the unit pixels  101  formed at upper and lower sides on the basis of the black matrix  13   a . However, it is not so in left and right unit pixels. Accordingly, in the conventional rear substrate, the barrier rib  21  partitioning the unit pixels or the sub-pixels is formed of black-color material having the low reflectance to improve the contrast characteristic. However, such a black matrix structure has a drawback in that since the transparent front substrate is provided at a predetermined thickness between an upper end of the barrier rib and the exterior, the emitted light is not fully blocked between the unit pixels, thereby deteriorating the contrast characteristic. 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of the present invention is to solve at least the problems and disadvantages of the background art. 
     An object of the present invention is to provide a plasma display panel and a manufacture method thereof in which a barrier rib partitioning a unit pixel is deformed in structure, thereby improving a visual color mixture, and concurrently the barrier rib is improved in reflectance and a black matrix is improved in structure, thereby improving a contrast characteristic. 
     To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, there is provided a plasma display panel for displaying an image, the panel including: a first barrier rib for partitioning a plurality of sub-pixels; and a second barrier rib formed to function as a boundary between one unit pixel constituting of the plurality of sub-pixels and an adjacent unit pixel, and partition the unit pixels, wherein the second barrier rib has a greater width than the first barrier rib. 
     A black-color material layer is formed on the first barrier rib and the second barrier rib. 
     In another aspect of the present invention, there is provided a plasma display panel for displaying an image, the panel including: a first barrier rib for partitioning a plurality of sub-pixels; a second barrier rib formed to function as a boundary between one unit pixel constituting of the plurality of sub-pixels and an adjacent unit pixel, and partition the unit pixels; a first black matrix formed in a vertical direction of the first barrier rib and the second barrier rib; and a second black matrix formed in an extension direction of the second barrier rib, wherein the second barrier rib has a greater width than the first barrier rib. 
     The second black matrix has a predetermined gap partitioning the unit pixel at its center portion. 
     The first barrier rib and the second barrier rib all have white-color materials. 
     In a further aspect of the present invention, there is provided a plasma display panel for displaying an image, the panel including: a first barrier rib for partitioning a plurality of sub-pixels; and a second barrier rib formed to function as a boundary between one unit pixel constituting of the plurality of sub-pixels and an adjacent unit pixel, and partition the unit pixels, wherein the first barrier rib and the second barrier rib are all formed of black-color material, and wherein the second barrier rib has a greater width than the first barrier rib. 
     In the plasma display panel, the first barrier rib and the second barrier rib form at least one of stripe-type, well-type, delta-type, and honey-type discharge cell structures. 
     In a further another aspect of the present invention, there is provided a method for manufacturing a plasma display panel for displaying an image, the method including the steps of: coating a first and second barrier rib paste on a dielectric material formed on a glass; and placing and exposing an irregular pattern mask on the first and second barrier rib paste to form a first barrier rib pattern and a second barrier rib pattern each having a different width. 
     The method further includes the step of: after the coating of the first and second barrier rib paste, forming a black-color material layer on the first and second barrier rib paste. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described in detail with reference to the following drawings in which like numerals refer to like elements. 
         FIG. 1  is a schematic perspective view illustrating a structure of a conventional plasma display panel; 
         FIG. 2  is a view illustrating a conventional method for expressing a gray level in a plasma display panel; 
         FIGS. 3A through 3D  are views illustrating various discharge cell structures in a conventional plasma display panel; 
         FIGS. 4A and 4B  are views illustrating black matrix structures disposed at front substrates in a conventional plasma display panel having a stripe-type discharge cell structure or a well-type discharge cell structure; 
         FIGS. 5A and 5B  are views illustrating barrier rib structures of discharge cell structures in a plasma display panel according to a first embodiment of the present invention; 
         FIGS. 6A and 6B  are views illustrating barrier rib structures and black matrix structures of discharge cell structures in a plasma display panel according to a second embodiment of the present invention; 
         FIGS. 7A and 7B  are views illustrating black matrix structures of discharge cell structures in a plasma display panel according to the present invention; 
         FIGS. 8A and 8B  are views illustrating barrier rib structures of discharge cell structures in a plasma display panel according to a third embodiment of the present invention; 
         FIGS. 9A through 9D  are views sequentially illustrating a method for manufacturing a barrier rib in a plasma display panel according to an embodiment of the present invention; and 
         FIGS. 10A through 10D  are views sequentially illustrating a method for manufacturing a barrier rib in a plasma display panel according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention will be described in a more detailed manner with reference to the drawings. 
     &lt;First Embodiment&gt; 
       FIGS. 5A and 5B  are views illustrating barrier rib structures of discharge cell structures in a plasma display panel according to a first embodiment of the present invention. In other words,  FIG. 5A  illustrates the barrier rib structure in a stripe-type discharge cell structure according to the present invention, and  FIG. 5B  illustrates the barrier rib structure in a well-type discharge cell structure according to the present invention. 
     As shown in  FIGS. 5A and 5B , the inventive plasma display panel includes a first barrier rib  31  and a second barrier rib  31 ′ each disposed at a rear substrate. The first barrier rib  31  partitions red (R), green (G) and blue (B) sub-pixels  201   a ,  201   b  and  201   c . The second barrier rib  31 ′ partitions a unit pixel  201 , which is constituted of the R, G, B sub-pixels  201   a ,  201   b  and  201   c , and an adjacent unit pixel. On the assumption that the first barrier rib  31  partitioning the R, G, B sub-pixels  201   a ,  201   b  and  201   c  has a width of “b” and the second barrier rib  31 ′ partitioning the unit pixel  201  and the adjacent unit pixel has a width of “a”, the width “a” is much greater than the width “b”. In other words, the width “a” of the second barrier rib  31 ′ functioning as a boundary between the unit pixel and the adjacent unit pixel is greater than the width “b” of the first barrier rib  31  functioning as a boundary between the sub-pixels. A black-color material layer is formed on the first barrier rib  31  and the second barrier rib  31 ′. 
     The inventive barrier rib can be manufactured using not only a sand blasting method but also any one of a screen printing method, an additive method and a photosensitive paste method. The inventive barrier rib is applicable not only to the stripe-type and well-type discharge cell structures of  FIGS. 5A and 5B , but also to a delta-type or honey-type discharge cell structure. 
     As such, in the inventive plasma display panel having the barrier rib structure, a unit pixel color combined due to light emission of the R, G, B sub-pixels is more spaced apart from an adjacent unit pixel color, thereby improving a visual color mixture. 
     &lt;Second Embodiment&gt; 
       FIGS. 6A and 6B  are views illustrating barrier rib structures and black matrix structures of discharge cell structures in a plasma display panel according to a second embodiment of the present invention. In other words,  FIG. 6A  illustrates the barrier rib structure and the black matrix structure in a stripe-type discharge cell structure, and  FIG. 6B  illustrates the barrier rib structure and the black matrix structure in a well-type discharge cell structure. 
     In  FIGS. 6A and 6B , the inventive barrier rib structures are the same as those of the first embodiment and therefore, their descriptions are omitted. However, in the inventive plasma display panel, a black matrix having a predetermined pattern is formed at a front substrate. It is desirable that a barrier rib has a white-color material to compensate for luminance reduction caused by the black matrix of the front substrate in the PDP. 
     Like a conventional art, in the inventive plasma display panel having the stripe-type and well-type discharge cell structures, a first black matrix  13   a  is formed at the front substrate to be in a vertical direction of a first barrier rib  31  and a second barrier rib  31 ′. A second black matrix  13   b  is formed in an extension direction of the second barrier rib  31 ′ partitioning unit pixels. In other words, the second black matrix  13   b  is extended from the second barrier rib  31 ′ and formed on the front substrate. The second barrier rib  31 ′ has a greater width than the first barrier rib  31  partitioning sub-pixels. In some cases, the black matrix can be formed in the extension direction of the first barrier rib  31  partitioning the sub-pixels. However, there is a drawback in that a luminance characteristic can be deteriorated, and there is a process difficulty in maintaining an alignment characteristic between the barrier rib of the rear substrate and the black matrix of the front substrate. Therefore, it is desirable that the black matrix is formed in the extension direction of the second barrier rib  31 ′ partitioning the unit pixels  201 . 
     The black matrix is formed of paste in a screen-printing method and the like. The paste employs a metallic compound such as chrome (Cr) or a nonmetallic compound. In the black matrix formed of metallic compound, reflectance can be decreased due to poor transparency, thereby improving the contrast characteristic. However, when a voltage is applied to a plurality of electrodes formed at the front substrate, a dielectric material covering the electrodes is broken down in dielectricity, thereby conducting the black matrix in a cell discharge. Accordingly, there is a drawback in that an erroneous cell discharge is caused in the PDP. 
       FIGS. 7A and 7B  are views illustrating the black matrix structures of the discharge cell structures in the plasma display panel according to the present invention. 
     As shown in  FIGS. 7A and 7B , the black matrixes  13   a  and  13   b  are almost the same as those of  FIGS. 6A and 6B . However, the second black matrix  13   b  is formed in the extension direction of the second barrier rib  31 ′ to have a predetermined gap (d) partitioning the unit pixel  201  at its center portion. In other words, the black matrix is short-circuited to secure electrical insulation. The barrier rib structure is the same as that of the first embodiment of the present invention. 
     In the inventive PDP having the barrier rib structure and the black matrix structure according to the second embodiment of the present invention, the color mixture caused by light emission of each unit pixel can be improved and concurrently, the reflectance against external light and internal transmitted light can be decreased, thereby improving the contrast characteristic. 
     &lt;Third Embodiment&gt; 
       FIGS. 8A and 8B  are views illustrating barrier rib structures of discharge cell structures in a plasma display panel according to a third embodiment of the present invention. In other words,  FIG. 8A  illustrates the barrier rib structure of a stripe-type discharge cell structure, and  FIG. 8B  illustrates the barrier rib structure of a well-type discharge cell structure. 
     In  FIGS. 8A and 8B , the barrier rib structures are the same as those of the first embodiment of the present invention and therefore, their descriptions are omitted. However, the barrier rib structures are all formed of black-color material. 
     As such, in the inventive PDP having the barrier rib structure, color mixture caused by light emission of each unit pixel can be improved, and the barrier rib can be formed of black-color material, thereby decreasing reflectance against external light and improving a contrast characteristic. 
       FIGS. 9A through 9D  are views sequentially illustrating a method for manufacturing the barrier rib in the plasma display panel according to an embodiment of the present invention. 
     Referring to  FIG. 9A , a dielectric material  41  is formed on a lower substrate  40  having an address electrode (not shown) mounted thereon. After that, a barrier rib paste  31  is formed at a predetermined thickness on the dielectric material  41 . Next, the barrier rib paste  31  is formed of black-color material in a printing method or a coating method so as to reduce the reflectance against the external light. After that, a dry film resin (Hereinafter, referred to as “DFR”)  42  is formed on the barrier rib paste  31  in a laminating process. Next, a photo mask  43  is aligned on the DFR  42 , and light is irradiated on the photo mask  43 . The photo mask  43  has a pattern of irregular intervals (d 1  and d 2 ) between a light blocking unit  43   a  and a light transmitting unit  43   b . This is to differentiate the barrier ribs in width, that is, the barrier rib functioning as the boundary between the R, G, B sub-pixels and the barrier rib functioning as the boundary between the unit pixels constituted of the R, G, B sub-pixels. 
     Referring to  FIG. 9B , after the DFR  42  is exposed, a developing process is performed. In the developing process, a DFR  42  region not exposed to light (Hereinafter, referred to as “non-exposure region”) remains on the barrier rib paste  31  to form a DFR  42  pattern, whereas a DFR  42  region exposed to light (Hereinafter, referred to as “exposure region”) is etched out. 
     Referring to  FIG. 9C , a sand blasting device  44  is placed and driven over the developed barrier rib paste  31  and the DFR  42  to spray sand particles onto the barrier rib paste  31 . At this time, the barrier rib paste  31  is cut out due to sputtering of the sand particles whereas the barrier rib paste  31  corresponding to the barrier rib is protected by the DFR  42  pattern. 
     Referring to  FIG. 9D , after the barrier rib paste  31  is protected and patterned by the DFT  42  in a sand blasting process, the DFR  42  is peeled off in a peeling-off process. Next, the barrier rib paste  31  is plasticized, thereby completing the barrier rib. As a result, a discharge space is concavely provided between the barrier ribs. 
     In the inventive barrier rib of the PDP manufactured through the above processes, when the PDP is driven, the visual color mixture of the discharge cell is improved and concurrently, the barrier rib paste is formed of the black-color material, thereby reducing the reflectance against the external light and improving the contrast characteristic. 
       FIGS. 10A through 10D  are views sequentially illustrating a method for manufacturing a barrier rib in a plasma display panel according to another embodiment of the present invention. 
     Referring to  FIG. 10A , a dielectric material  41  is formed on a lower substrate  40  having an address electrode (not shown) mounted thereon, and then a white-color barrier rib paste  31  is formed at a predetermined thickness on the dielectric material  41 . After that, a photosensitive black-color paste  31   a  is layered on the barrier rib paste  31  in a printing method or a coating method. After that, a dry film resin (DFR)  42  is formed on the photosensitive black-color paste in a laminating process. A photo mask  43  is aligned on the DFR  42  and then, light is irradiated on the photo mask  43 . At this time, the photo mask has a pattern of irregular intervals (d 1  and d 2 ) between a light blocking unit  43   a  and a light transmitting unit  43   b . This is to differentiate the barrier ribs in width, that is, the barrier rib functioning as the boundary between the R, G, B sub-pixels and the barrier rib functioning as the boundary between the unit pixels constituted of the R, G, B sub-pixels. 
     Referring to  FIG. 10B , after the DFR  42  is exposed, a developing process is performed. In the developing process, a DFR  42  region not exposed to light (Hereinafter, referred to as “non-exposure region”) remains on the photosensitive black-color paste  31   a  to form a DFR  42  pattern, whereas a DFR  42  region exposed to light (Hereinafter, referred to as “exposure region”) is etched out. 
     Referring to  FIG. 10C , a sand blasting device  44  is placed and driven over the developed barrier rib paste  31 , the photosensitive black-color paste  31   a  and the DFR  42  to spray sand particles onto the barrier rib paste  31 . At this time, the barrier rib paste  31  is cut out due to sputtering of the sand particles whereas the barrier rib paste  31  corresponding to the barrier rib is protected by the DFR  42  pattern. 
     Referring to  FIG. 10D , after the barrier rib paste  31  is protected and patterned by the DFT  42  in a sand blasting process, the DFR  42  is peeled off in a peeling-off process. Next, the barrier rib paste  31  is plasticized, thereby completing the barrier rib. As a result, a discharge space is concavely provided between the barrier ribs. 
     In the inventive barrier rib of the PDP manufactured through the above processes, the luminance characteristic is not only improved, but also the contrast characteristic is improved. 
     As described above, the present invention has an effect in that the color mixture caused by the light emission of each unit discharge cell is improved in the PDP, and the reflectance against the external light and the internal light is reduced, thereby improving the contrast characteristic. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.