This application claims priority to and the benefit of Korean Patent Application number 10-2003-0086144, filed Nov. 29, 2003, the entire disclosure of which is incorporated herein by reference.
(a) Field of the Invention
The present invention relates to a plasma display panel (hereinafter, PDP), and more particularly, to a surface discharge type PDP with an electrode structure in which a pair of display electrodes are formed on one substrate and have a corresponding pair of bus electrodes within each discharge cell between two substrates to cause a display discharge.
(b) Description of the Related Art
Generally, a plasma display panel is a display device in which ultraviolet rays generated by gas discharge excite phosphors to realize predetermined images. Such a plasma display panel is popular for wide screen display devices since it enables the manufacture of large screen sizes with high resolution.
Referring to
In addition, display electrodes 102, 103 having a pair of transparent electrodes 102a, 103a and bus electrodes 102b, 103b are formed along the direction crossing the address electrodes 112 (in the Y-axis direction of the drawing) on a surface of a front substrate 100 opposing the rear substrate 110. A transparent dielectric layer 106 and a MgO protection film 108 are formed covering the display electrodes on a surface of the front substrate 100.
The region where the address electrodes 112 on the rear substrate 110 are intersected with the display electrodes 102, 103 on the front substrate 100 is to be a portion where discharge cells are formed.
An address voltage Va is applied between the address electrodes 112 and the display electrodes 102, 103 to cause address discharge, and a sustain voltage Vs is applied to a pair of the display electrodes 102, 103 to cause sustain discharge. Then, the generated vacuum ultraviolet rays excite phosphors so that they emit visible light through the front substrate 100 and thereby display PDP images.
However, the PDP having the discharge electrodes 102, 103 and the barrier ribs 115 in a stripe formation as shown in
To solve the above problems, PDPs having improved electrodes and barrier ribs as shown in
A PDP is a display using gas discharge, and its emission efficiency can be varied according to the amount of the excited atoms generated. The emission efficiency is known to increase with increasing total or partial pressure of sealed discharge gases.
If total or partial pressure is increased to improve the efficiency, the breakdown voltage necessarily increases and the discharge instability increases. Sometimes the discharge itself does not take place, and the use of high pressure resistant devices causes an increase in the unit cost of a circuit.
In an effort to lower the breakdown voltage in such a PDP, a gap between discharge electrodes can be decreased when designing discharge electrodes. However, simply decreasing the gap between discharge electrodes may cause several problems.
One problem arising when this gap is decreased is that the discharge path is decreased, thereby deteriorating the emission efficiency of panel. Furthermore, if the gap between discharge electrodes is decreased below a certain value, the breakdown voltage is increased. As shown in the Paschen curve of
Another problem which can occur when the gap between the discharge electrodes is decreased is related to insulation resistance of dielectric substances. If the gap between the discharge electrodes is decreased, a strong magnetic field is generated between two electrodes and then the possibility of destruction of insulation between the electrodes is increased. It therefore becomes necessary to improve the insulating resistance. Accordingly, these factors must be considered when designing the discharge electrodes.
a and 11b show a plan view of conventional discharge cells and a light profile graph for sustain discharge in a conventional PDP.
b shows the light emission from the portion within the dotted line in
According to one aspect of the present invention, there is provided a PDP in which emission efficiency is maximized by an efficient layout and design of the electrodes, and the circuit unit cost is decreased by lowering breakdown voltage, thereby improving the quality.
According to one exemplary embodiment of the present invention, the plasma display panel includes a first substrate and a second substrate opposing each other; address electrodes formed on the second substrate; barrier ribs arranged in the space between the first substrate and the second substrate to define a plurality of discharge cells; phosphor layers formed within each of the discharge cells; and display electrodes formed on the first substrate. The display electrodes have bus electrodes, which extend along the direction intersecting the direction of the address electrodes to form a corresponding pair within each of the discharge cells, and extension electrodes, which extend from the bus electrodes into each of the discharge cell to form an opposing pair. A pair of the display electrodes corresponding to each of the discharge cells forms a first gap G1 and a different, second gap G2. A third gap G3 is formed between the bus electrodes. In one embodiment, the second gap G2 is longer than the first gap G1, and the third gap G3 is longer than the second gap G2.
In one embodiment, the first gap G1 is formed to be in the range of 50 to 80 μm. The second gap G2 can be formed between the centers of the opposite end portions of the extension electrodes, and can be in the range of 75 to 120 μm. In one embodiment, the third gap G3 is in the range of 500 to 800 μm. The first gap G1, the second gap G2, and the third gap G3 can be also formed to have a ratio of G1:G2=1:1.5 and G1:G3=1:10.
Each of the extension electrodes becomes narrower further from the center of the discharge cells. Furthermore, the barrier ribs arranged in the space between the first substrate and the second substrate can define non-discharge regions in addition to the plurality of discharge cells, and the non-discharge region can be formed in an area encompassed by discharge cell abscissas that pass through centers of adjacent discharge cells and discharge cell ordinates that pass through centers of adjacent discharge cells in a direction that intersects the direction of the abscissas.
A non-discharge region can be formed to have independent cell structures defined by the barrier ribs, and each of the discharge cells becomes narrower further from their centers.
The extension electrodes of a pair of display electrodes corresponding to each of the discharge cells form different gaps G1 and G2 from each other. The optimum values for these gaps can be determined together with the gap G3 between the bus electrodes to improve the discharge efficiency.
a is a drawing of a PDP extension electrode according to one embodiment of the present invention.
b is a drawing of a PDP extension electrode with an excessive concave portion according to one embodiment of the present invention.
a, 6b, and 6c are plan views of a PDP with varying the length of the third gap G3 between the bus electrodes within a discharge cell.
a is an image for discharge cells of a conventional PDP.
b is a light profile for sustain discharge of a conventional PDP.
As shown in
A plurality of the address electrodes 21 are formed along one direction (the X-axis direction, as shown) of the second substrate 20 on a surface of the second substrate 20 opposing the first substrate 10. The address electrodes 21 are formed in a stripe pattern and spaced apart from the adjacent address electrodes 21 at a predetermined distance and parallel to one another. A dielectric layer 23 is also formed on the second substrate 20 where the address electrodes 21 are provided. The dielectric layer 23 is formed on an entire surface of the substrate covering the address electrodes 21. It should be noted that, although the address electrodes of the stripe type are mentioned above, the type of the address electrodes is not limited to this pattern and may be formed in various ways.
Barrier ribs 25 are arranged in the space between the first substrate 10 and the second substrate 20 to define a plurality of discharge cells 27R, 27G, 27B and non-discharge regions 26. Preferably, the barrier ribs 25 are established on the top surface of the dielectric layer 23 formed on the second substrate 20. The discharge cells 27R, 27G, 27B designate areas in which discharge gas is provided and where gas discharge is expected to take place with the application of an address voltage and a discharge sustain voltage. The non-discharge region 26 is an area where a voltage is not applied so that gas discharge, i.e. illumination, is not expected to take place therein. It is preferable that the non-discharge region 26 is formed to have a region with a width which is greater than the width of the top portion of the barrier ribs 25.
The non-discharge region 26 defined by the barrier ribs 25 is formed in an area encompassed by discharge cell abscissas H and ordinates V that pass through centers of each of the discharge cells 27R, 27G, 27B and that are respectively aligned with direction Y and direction X. In one embodiment, non-discharge region 26 is centered between adjacent abscissas H and adjacent ordinates V. Stated differently, in one embodiment, each pair of discharge cells 27R, 27G, 27B adjacent to one another along direction X has a common non-discharge region 26 with another such pair of discharge cells 27R, 27G, 27B adjacent along direction Y. The non-discharge region 26 of the present invention is formed to have an independent cell structure respectively by the barrier ribs 25.
The discharge cells 27R, 27G, 27B are formed to share at least one barrier rib with the adjacent one in the direction of the display electrodes 12, 13, and they are formed to accommodate the widths of both end portions thereof (in the direction of the display electrode, i.e. in the Y-axis direction of the drawing) placed in the direction of the address electrodes (in the X-axis direction of the drawing) becoming narrower further from the center of the discharge cells 27R, 27G, 27B. That is, with reference to
Red (R), green (G) and blue (B) phosphors are coated respectively within the inside of the discharge cells 27R, 27G, 27B to form phosphor layers 29R, 29G, 29B.
The display electrodes 12, 13 formed on the first substrate 10 are formed with bus electrodes 12b, 13b arranged in a corresponding pair within each of the discharge cells 27R, 27G, 27B along the direction (in the Y-axis direction of the drawing) intersecting the direction of the address electrodes 21. Each the display electrodes 12, 13 also has a pair of extension electrodes 12a, 13a extending from the bus electrodes 12b, 13b into the inside of each of the discharge cells towards each other to form an opposing pair. The extension electrodes 12a, 13a have a role in causing plasma discharge within the discharge cells 27R, 27G, 27B, and they may be formed with Indium Tin Oxide (ITO) of a transparent electrode in order to obtain a desired brightness. However, they are not limited thereto so that they can be formed with an opaque electrode like metal electrodes.
A pair of the display electrodes 12, 13 corresponding to each of the discharge cells 27R, 27G, 27B forms a first gap G1 and a second gap G2 having different distances from each other between the extension electrodes 12a, 13a opposing each other, and forms a third gap G3 between the bus electrodes 12b, 13b. The second gap G2 is longer than the first gap G1, and the third gap G3 is longer than the second gap G2. As shown in
Since the first gap G1 of the extension electrodes 12a, 13a enables closing of the distance between the ends of the opposing extension electrodes 12a, 13a without deterioration of the aperture ratio, the voltage necessary for discharge can be lowered. The second gap G2 has a role in stably discharging by concentrating the discharge at the center thereof.
The gap necessary for starting the discharge is designed to lower the breakdown voltage, and the other electrode gaps are designed to improve the efficiency. That is, a significant factor for the first gap G1 is the lowest breakdown voltage and a significant factor for the second gap G2 and the third gap G3 is the improvement of the discharge efficiency.
Each of the extension electrodes 12a, 13a is formed to accommodate the width in the direction of the bus electrodes 12b, 13b (in the Y-axis direction in the drawing) becoming narrower as a back end portion thereof adjacent to the bus electrodes 12b, 13b is further from the center of the discharge cells 27R, 27G, 27B. Since the portion where the extension electrodes 12a, 13a are connected to the bus electrodes 12b, 13b makes little contribution to the discharge efficiency, the width thereof can be formed to be narrower than that of the ends to improve the discharge efficiency and to secure the aperture ratio.
Determination of the optimum values for the three gaps G1, G2, G3 formed by a pair of display electrodes 12, 13 corresponding each of the discharge cells 27R, 27G, 27B will now be described.
With reference to
The second gap G2 is longer than the first gap G1. As the second gap G2 is increased from the value of the first gap G, the efficiency is gradually increased. Although the discharge is diffused around the edge after the start of the discharge and the discharge itself is decreased, restriction of the discharge current increases its effect. That is, since the discharge efficiency is directly proportional to the brightness and inversely proportional to the active power dissipation, the restriction of discharge current means that the active power dissipation is decreased and the discharge efficiency inversely proportional to it is increased.
If the value of the second gap G2 is increased to exceed a certain value (the maximum value for the efficiency of the second gap), however, the discharge efficiency is decreased. This is because the discharge itself is weakened and a sufficient diffusion of the discharge does not occur. That is, as shown in
a, 6b, and 6c are plan views of a PDP with varying lengths of the third gap G3 due to positioning of the bus electrodes within a discharge cell. If the third gap G3 is short, as shown in
If the bus electrodes are positioned as shown in
As described above, the most optimum efficiency can be achieved when the first gap G1 and the second gap G2 formed between the extension electrodes 12a, 13a of the opposite display electrodes 12, 13, and the third gap G3 formed between the bus electrodes 12b, 13b are designed to have a ratio of G1:G2=1:1.5, and G1:G3=1:10.
Although embodiments of the present invention have been described in detail hereinabove in connection with certain exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary is intended to cover various modifications and/or equivalent arrangements included within the spirit and scope of the present invention, as defined in the appended claims.
Number | Date | Country | Kind |
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10-2003-0086144 | Nov 2003 | KR | national |