Patent Grant
7663317
1. Field of the Invention
The present invention relates to a plasma display panel and, more particularly, to a plasma display panel capable of minimizing luminance deterioration even when employing a colored fluorescent layer and improving a bright room contrast ratio.
2. Description of the Related Art
In general, a plasma display panel is a display device that may use vacuum ultra-violet (VUV) rays emitted from plasma obtained through gas discharge so as to excite a fluorescent material. The excited fluorescent material may generate visible light of red (R), green (G), and blue (B), so that an image may be displayed.
For example, an alternating current (AC) type plasma display panel may have a structure in which address electrodes may be formed on a rear substrate and covered with a dielectric layer. Barriers may be disposed between the address electrodes on the dielectric layer in a stripe pattern. Fluorescent layers of red (R), green (G), and blue (B) may be formed at the barriers. On a front substrate facing a rear substrate, display electrodes, e.g., pairs of sustain electrodes and scan electrodes, may be formed along a direction that crosses the address electrodes. The display electrodes may be covered with a dielectric layer and an MgO protective layer. A discharge cell may be formed at a position where the address electrode on the rear substrate crosses the pair of the display electrodes on the front substrate. Millions or more unit discharge cells may be arrayed in a matrix pattern inside the plasma display panel.
In order to operate the discharge cells of the plasma display panel, memory characteristics may be used. More specifically, in order to generate discharge between the pairs of sustain and scan electrodes which may be included in the display electrode, a potential difference greater than a predetermined voltage may be required. The boundary of the voltage may be called a firing voltage Vf. When a scan voltage and an address voltage Va are applied to the scan electrode and the address electrode, respectively, discharge may occur, and plasma may be formed in the discharge cell. Electrons and ions of the plasma move toward electrodes having opposite polarities from each other.
Each electrode of the plasma display panel may be coated with a dielectric layer, so that most of the moved space charge may be accumulated on the dielectric layer having an opposite polarity. Accordingly, net space charge between the scan and the address electrodes may become lower than an address voltage Va that is applied in advance, so that discharge may be decreased, and address discharge may be terminated. In this case, a relatively small amount of electrons may be accumulated on the sustain electrode, and a relatively large amount of ions may be accumulated on the scan electrode. Charge accumulated on the dielectric layer covering the sustain and scan electrodes may be called a wall charge Qw, and space charge formed between the sustain and scan electrodes by the wall charge Qw may be called a wall voltage Vw.
In a case where a discharge sustain voltage Vs may be applied to the sustain and scan electrodes, when a value Vs+Vw of adding the discharge sustain voltage Vs and the wall voltage Vw is larger than the firing voltage Vf, sustain discharge may occur in the discharge cell. VUV generated at this time may excite a corresponding fluorescent material so as to emit visible light through the transparent front substrate.
However, when an address discharge between the scan and address electrodes does not exist, e.g., when the address voltage Va is not applied, the wall charge may not be accumulated between the sustain and scan electrodes, and as a result, the wall voltage between the sustain and scan electrodes may not exist. In this case, only the discharge sustain voltage Vs applied to the sustain and scan electrodes may be formed in the discharge cell. In addition, since the discharge sustain voltage Vs may be lower than the firing voltage Vf, gas space between the sustain and scan electrodes may not be discharged.
There have been various attempts to improve the bright room contrast ratio by increasing a black area ratio that may be a ratio of a black color in the plasma display panel operated as described above, i.e., a method of using a complementary color relation has been developed.
In the plasma display panel using the complementary color relation, the dielectric layer of the front substrate may be colored with a shade of blue, and the barriers of the rear substrate may be colored with a shade of red in order to improve the bright room contrast ratio.
In addition, in the plasma display panel using the complementary color relation, the fluorescent layers on the rear substrate may be colored with a shade of red similar to the barriers in order to further improve the bright room contrast ratio.
However, although the plasma panel display improves the bright room contrast ratio by coloring the fluorescent layers with the shade of red, a large amount of visible light generated in the discharge cell may be absorbed by the fluorescent layers colored with the shade of red, so that luminance may be decreased.
The present invention is therefore directed to a plasma display panel, which substantially overcomes one or more of the problems due to the limitations and disadvantages of the related art.
It is therefore a feature of an embodiment of the present invention to provide a plasma display panel which includes colored fluorescent layers to improve the bright room contrast ratio.
It is therefore a feature of an embodiment of the present invention to provide a plasma display panel which includes colored fluorescent layers to improve luminance.
At least one of the above and other features and advantages of the present invention may be realized by providing a plasma display panel that includes a first substrate; a second substrate facing the first substrate with a predetermined gap; a plurality of barriers disposed between the first and second substrates to create a plurality of discharge cells; a plurality of fluorescent layers formed in the discharge cells; address electrodes corresponding to the plurality of discharge cells and extending in a first direction; pairs of first and second electrodes between the substrates and extending in a second direction crossing the first direction and formed on one of the substrates corresponding to the discharge cells; and a dielectric layer covering the pairs of first and second electrodes, wherein the dielectric layer is colored with a first color, the barriers are colored with a second color having a subtractive mixture relation with the first color, and wherein the fluorescent layers include first fluorescent layers formed on the barriers and the discharge cells, and second fluorescent layers formed on the first fluorescent layers in the second color.
The first and second colors may have a complementary color relation. The first color may be brown, and the second color may be blue.
The plurality of barriers may include a plurality of first barrier members extending in the first direction at a predetermined interval corresponding to a discharge cell spacing along the second direction, and a plurality of second barrier members extending in the second direction across the first barrier members at a predetermined interval corresponding to a discharge cell spacing along the first direction.
The first fluorescent layer may be thicker than the second fluorescent layer.
The fluorescent layers may overlap along a direction approximately perpendicular to the second substrate.
The fluorescent layers may include a double layer region having two overlapping colored layers with the first and second colors. The fluorescent layers may include a triple layer region having three overlapping layers that include the first and second colors.
The barriers may include a first barrier end portion formed toward the first substrate, a second barrier end portion that may be wider than the first barrier end portion and formed toward the second substrate, and inclined plane barrier portions formed between corresponding ends of the first barrier end portion and the second barrier end portion.
The double layer region may include a first double layer region corresponding to the first barrier end portion. The double layer region may include a second double layer region corresponding to a thickness of the first fluorescent layer adjacent the first barrier end portion approximately and perpendicular to the first substrate. The double layer region may include a third double layer region corresponding to a region between adjacent second barrier end portions.
The plurality of fluorescent layers may include a first fluorescent layer corresponding to one of red, green, and blue colors, and the second fluorescent layers may be formed on the first fluorescent layers.
According to another embodiment of the present invention, a plasma display panel includes a first substrate; a second substrate facing the first substrate with a predetermined gap; a plurality of barriers disposed between the first and second substrates to create a plurality of discharge cells; a plurality of fluorescent layers formed in the discharge cells; address electrodes corresponding to the discharge cells and extending in a first direction; pairs of first and second electrodes between the substrates and extending in a second direction crossing the first direction and are formed on one of the substrates corresponding to the discharge cells; and a dielectric layer covering the pairs of first and second electrodes, wherein the dielectric layer is colored with a first color, and wherein the plurality of fluorescent layers include colored fluorescent layers colored with a second color having a subtractive mixture relation with at least the first color.
The first and second colors may have a complementary color relation. The barriers may be colored with the second color. The first color may be brown and the second color may be blue.
The above and other features and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing in detail exemplary embodiments thereof with reference to the attached drawings, in which:
Korean Patent Application No. 10-2006-0028290 filed on Mar. 29, 2006 in the Korean Intellectual Property Office and entitled: “Plasma display Panel” is incorporated by reference herein in its entirety.
The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are illustrated. The invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
In the figures, the dimensions of layers and regions may be exaggerated for clarity of illustration. It will also be understood that when a layer or element is referred to as being “on” another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present. Further, it will be understood that when a layer is referred to as being “under” another layer, it can be directly under, and one or more intervening layers may also be present. In addition, it will also be understood that when a layer is referred to as being “between” two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present. Like reference numerals refer to like elements throughout.
Referring to
The barriers 16 may have a predetermined height between the front substrate 20 and rear substrate 10 and may partition a plurality of discharge cells 17. The discharge cells 17 may be filled with discharge gas, e.g., a mixture of neon (Ne) and xenon (Xe), so that they may generate vacuum ultra-violet (VUV) radiation by gas discharge, and may include fluorescent layers 19 for emitting visible light upon absorbing the VUV.
The plasma display panel according to an embodiment of the present invention may include an address electrode 11, a first electrode, e.g., a sustain electrode 31, and a second electrode, e.g., a scan electrode 32, corresponding to each discharge cell 17 between the rear substrate 10 and front substrate 20. The address electrodes 11 may be disposed on an inner surface of the rear substrate 10 and may extend in a first direction, e.g., the y-axis, to sequentially correspond to adjacent discharge cells 17 in the y-axis direction. The plurality of sustain electrodes 31 and scan electrodes 32 may be parallel to each other in a second direction, e.g., x-axis, and may cross the address electrodes 11 in order to sequentially correspond to adjacent discharge cells 17 in the x-axis direction.
The address electrodes 11 may be covered with a dielectric layer 13 that may also cover the inner surface of the rear substrate 10. The dielectric layer 13 may prevent damage to the address electrodes 11 through positive ions and electrons directly colliding with the address electrodes 11 during discharge. The dielectric layer 13 may form and accumulate wall charges as well. The address electrodes 11 may be disposed on the rear substrate 10 so that they may not interrupt visible light emitting toward the front substrate 20. Thus, the address electrodes 11 may be opaque, e.g., the address electrodes 11 may be made of a metal having a high electroconductivity.
The plurality of barriers 16 may partition the plurality of discharge cells 17 disposed on the dielectric layer 13. The barriers 16 may include first barrier members 16a extending in the y-axis direction and second barrier members 16b extending in the x-axis direction to form the discharge cells 17 in a matrix structure.
Alternatively, the barriers 16 may include only first barrier members 16a extending in the y-axis direction to form the discharge cells in a stripe pattern. In this case, the discharge cells 17 may be continuous along the y-axis direction.
A fluorescent layer 19 may be formed in each discharge cell 17 by coating a fluorescent material on a side wall of the barrier 16 and a surface of the dielectric layer 13 between the barriers 16 and processing the layer, e.g., drying, exposing, developing, and firing.
The fluorescent layers 19 in the discharge cells 17 that may be disposed along the same row in the y-axis direction may have a fluorescent material with the same color. The fluorescent layers 19 in the discharge cells 17 disposed along the same row in the x-axis direction may repeatedly alternate between red (R), green (G), and blue (B) fluorescent materials.
Referring to
The sustain electrode 31 and scan electrode 32 may be disposed between the front substrate 20 and rear substrate 10 and may correspond to each discharge cell 17 to form an opposed-discharge structure (not shown).
Each sustain electrode 31 and each scan electrode 32 may include a transparent electrode 31a, 32a for generating discharge, respectively. Each sustain electrode 31 and each scan electrode 32 may include a bus electrode 31b, 32b for applying a voltage signal, respectively. The transparent electrodes 31a, 32a may generate surface-discharge in the discharge cell 17 and may be made of a transparent material, e.g., Indium Tin Oxide (ITO), in order to guarantee an acceptable aperture ratio of the discharge cell 17. The bus electrodes 31b, 32b may be made of a metal material having a high electroconductivity in order to compensate for a high electric resistance of the transparent electrodes 31a, 32a.
The transparent electrodes 31a and 32a may have widths W31 and W32, respectively, and may extend from opposing edges toward a center of a discharge cell 17 along the direction of the y-axis and may form the surface-discharge structure with a discharge gap G in the center of the discharge cell 17. The bus electrodes 31b, 32b may be disposed on the transparent electrodes 31a, 32a, respectively. Therefore, when the bus electrodes 31b, 32b may be applied with a voltage signal, each transparent electrode 31a or 32a connected to each bus electrode 31b or 32b, respectively, may also be applied with the voltage signal.
Returning to
During operation of the plasma display panel, during a reset period, reset discharge may occur by a reset pulse that may be applied to the scan electrode 31. In an address period that may follow the reset period, address discharge may occur by a scan pulse applied to the scan electrode 32 and an address pulse applied to the address electrode 11. Thereafter, in a sustain period, sustain discharge may occur by a sustain pulse applied to the sustain electrode 31 and the scan electrode 32.
The sustain electrode 31 and the scan electrode 32 may apply the sustain pulse needed for the sustain discharge, the scan electrode 32 may apply the reset pulse and the scan pulse, and the address electrode 11 may apply the address pulse. The functions of the sustain electrode 31, scan electrode 32, and address electrode 11 may be changed according to voltage waveforms applied thereto, so that the functions are not limited thereto.
The plasma display panel according to an embodiment of the present invention may select a discharge cell 17 to turn on by address discharge through an interaction between the address electrode 11 and the scan electrode 32. The plasma display panel may operate the selected discharge cell 17 by sustain discharge through an interaction between the sustain electrode 31 and the scan electrode 32 in order to create an image.
According to an embodiment of the present invention, the dielectric layer 21 may be colored with a first color, and the barriers 16 may be colored with a second color in order to improve a bright room contrast ratio and luminance. The colors used may have a complementary relation to increase a black area ratio.
The first and second colors may have a subtractive mixture relation and may further have a complementary color relation for representing a black color, e.g., the first color may be brown, and the second color may be blue. The barrier 16 may be colored brown, and the dielectric layer 21 of the front substrate 20 may be colored blue.
The plasma display panel may apply the complementary colors and may decrease the luminance and improve the bright room contrast ratio by increasing the black area ratio, e.g., the blue dielectric layer 21 of the front substrate 20 may increase a color temperature. The blue-colored dielectric layer 21 and the brown-colored barrier 16 may increase the black area ratio of a non-discharge region in the plasma display panel.
In addition, in order to increase the black area ratio of a discharge region along with the non-discharge region, the fluorescent layer 16 may have a plurality of layers including a fluorescent layer colored with the second color, which may have a subtractive mixture relation or a complementary color relation with the first color.
Referring to
The second fluorescent layer 19b and the barrier 16 may be colored brown to increase the black area ratio of the entire plasma display panel. The second fluorescent layer 19b may increase the black area ratio, however, the second fluorescent layer 19b may absorb visible light emitting onto the front substrate 20. In order to reduce the absorption of visible light, the first fluorescent layer 19a may have a first thickness T1, and the second fluorescent layer 19b may have a second thickness T2. The second thickness T2 may be smaller than the first thickness T1. Accordingly, the second thickness T2 of the second fluorescent layer 19b may cause an increase in the black area ratio of a portion corresponding to the discharge cell 19 so as to increase the bright room contrast. In addition, the absorption of visible light that occurs correspondingly may be reduced, to maintain luminance.
The fluorescent layers 19 may include a plurality of fluorescent layers corresponding to a red, green, or blue color. The second fluorescent layer 19b may be formed on only a single fluorescent layer from among the plurality of fluorescent layers.
Referring to
The cross-sectional shape of the first barrier member 16a may be the same as that of the second barrier member 16b. Thus, for convenience, only the cross-sectional shape of the first barrier member 16a is exemplified and described with reference to
The barrier 16 may have a predetermined height H and may include a first end portion E1, a second end portion E2 and inclined planes IP. The first end portion E1 may be formed toward the front substrate 20, and a second end portion E2, which may be wider than the first end portion E1, e.g., along the x-axis, may be formed toward the rear substrate 10. Inclined planes IP may be formed between adjacent ends of the first end portions E1 and second end portions E2.
The double layer region DL may include first, second and third double layer regions DL1, DL2, and DL3. The first double layer DL1 region may correspond to the first end portion E1. The first double layer region DL1 may form a black color by using a complementary color of the dielectric layer 21 and the barrier 16, shown in
The second double layer region DL2 may correspond to a thickness Tx of the first fluorescent layer 19a in the x-axis direction against the first end portion E1. The second double layer region DL2 may form a black color by using a complementary color of the dielectric layer 21 and the barrier 16, with the first fluorescent layer 19a interposed therebetween, so that the black area ratio of the outer portion of the discharge region may increase. In addition, the forward emission of visible light from the rear substrate 10 may not be interrupted.
The third double layer region DL3 may be formed between the second end portions E2 of adjacent barriers 16. The third double layer region DL3 may form a black color by using a complementary color of the dielectric layer 21 and the second fluorescent layer 19b. Therefore, the third double layer region DL3 may increase the black area ratio of the center of the discharge region. The forward emission of visible light may be partially interrupted by the second fluorescent layer 19b.
As described above, the third double layer region DL3 may partially absorb the visible light emitting forward from the discharge cell 17. However, since the thickness T1 of the first fluorescent layer 19a may be thicker than the thickness T2 of the second fluorescent layer 19b, the absorption of visible light may be reduced, and the black area ratio in the discharge region may be increased.
The triple layer TL may be formed between the second double layer region DL2 and the third double layer region DL3. The triple layer TL may include the first and second fluorescent layers 19a, 19b and may form a black color by using a complementary color of the second florescent layer 19b, the dielectric layer 21, and the barrier 16. The triple layer TL may increase the black area ratio of the outer portion of the discharge region.
The triple layer TL may partially absorb visible light emitting forward from the discharge cell 17. However, since the thickness T2 of the second fluorescent layer 19b may be thinner than the thickness T1 of the first fluorescent layer 19a, the absorption of visible light emitting forward may be reduced. Additionally, the three-layered structure of the barrier 16, the second fluorescent layer 19b, and the dielectric layer 31 may increase the black area ratio.
Accordingly, the second fluorescent layer 19b having thickness T2 may be thinner than the first fluorescent layer 19a having thickness T1 which emits visible light. Therefore, the plasma display panel according to an embodiment of the present invention may increase the black area ratio with a minimum amount of the second fluorescent layer 19b colored. In addition, the plasma display panel may also have a luminance similar to that of a plasma display panel having an uncolored fluorescent layer while increasing the bright room contrast.
Exemplary embodiments of the present invention have been disclosed herein, and although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. Accordingly, it will be understood by those of ordinary skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present invention as set forth in the following claims.
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