KR20090026975A - Plasma display apparatus - Google Patents

Abstract

A plasma display apparatus is provided to improve the contrast and color temperature characteristic by comprising the pigment of the cobalt material in the glass substrates of the image filter. An image filter(110) is arranged at the front side of a plasma display panel(100). The image filter comprises a glass substrates(160), an optical shield layer(120), a colored layer(130), and an electromagnetic wave shielding layer(140). The first adhesive layer(151) is formed between the optical shield layer and the colored layer and adheres the optical shield layer and the colored layer. The second adhesive layer(152) is formed between the colored layer and the electromagnetic wave shielding layer, and adheres the colored layer and electromagnetic wave shielding layer. The image filter and the plasma display panel are adhered by the third bonding layer(150).

Description

Plasma Display Apparatus {Plasma Display Apparatus}

The present invention relates to a plasma display device.

The plasma display apparatus may include a plasma display panel having electrodes formed thereon, and a driving unit supplying driving signals to the electrodes of the plasma display panel.

In the plasma display panel, a phosphor layer is formed in a discharge cell divided by a partition, and a plurality of electrodes are formed.

When the drive signal is supplied to the electrode of the plasma display panel, the discharge is generated by the drive signal supplied in the discharge cell. Here, when discharged by a drive signal in the discharge cell, the discharge gas filled in the discharge cell generates vacuum ultraviolet rays, and the vacuum ultraviolet light emits the phosphor formed in the discharge cell to emit visible light. Generate. The visible light displays an image on the screen of the plasma display panel.

One embodiment of the present invention is to provide a plasma display device having improved contrast characteristics by reducing light reflection by a glass substrate included in an image filter.

A plasma display device according to an embodiment of the present invention includes a plasma display panel and an image filter disposed on the front surface of the plasma display panel, the image filter includes a glass substrate, and the glass substrate includes a blue pigment. do.

In addition, the content of the blue pigment is more than 0 ppm and 57 ppm or less.

In addition, the content of the blue pigment is 5 ppm or more and 32 ppm or less.

In addition, the blue pigment includes a cobalt (Co) material.

In addition, the glass substrate has a blue-based color.

In addition, a discharge gas containing xenon (Xe) is filled in the plasma display panel, and the xenon content is 10% or more and 20% or less.

In addition, the content of xenon is 12% or more and 15% or less.

Plasma display device according to an embodiment of the present invention includes a pigment of cobalt (Co) material on the glass substrate of the image filter, thereby reducing the panel reflectance, improve the contrast characteristics and improve the color temperature characteristics.

Hereinafter, a plasma display device according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a view for explaining the configuration of a plasma display device according to an embodiment of the present invention.

Referring to FIG. 1, a plasma display device according to an embodiment of the present invention includes a plasma display panel 100 for implementing an image using plasma discharge and an image filter 110 disposed on a front surface of the plasma display panel 100. It may include.

The plasma display panel 100 includes a front substrate 101 on which the scan electrodes 102 and Y and the sustain electrodes 103 and Z which are parallel to each other are disposed, and are arranged to face the front substrate 101, and are arranged to face the scan electrodes 102 and The rear substrate 111 on which the address electrode 113 intersects the sustain electrode 103 may be bonded to each other by a seal layer (not shown).

An upper dielectric layer 104 is disposed on the front substrate 101 on which the scan electrode 102 and the sustain electrode 103 are disposed, and the scan electrode 102 and the sustain electrode 103 are embedded.

The upper dielectric layer 104 limits the discharge current of the scan electrode 102 and the sustain electrode 103 and can insulate the scan electrode 102 and the sustain electrode 103 from each other.

A protective layer 105 may be disposed over the upper dielectric layer 104 to facilitate discharge conditions. The protective layer 105 may include a material having a high secondary electron emission coefficient, such as magnesium oxide (MgO).

In addition, an electrode, for example, an address electrode 113 is disposed on the rear substrate 111, and the rear substrate 111 on which the address electrode 113 is disposed covers the address electrode 113 and insulates the address electrode 113. A dielectric layer, such as lower dielectric layer 115, may be disposed.

On top of the lower dielectric layer 115, a discharge space, that is, a partition wall 112 such as a stripe type, a well type, a delta type, a honeycomb type, etc., which partitions a discharge cell, may be disposed. Can be. The barrier rib 112 may be provided with a red (R), green (G), and blue (B) discharge cell between the front substrate 101 and the rear substrate 111. In addition, in addition to the red (R), green (G), and blue (B) discharge cells, white (W) or yellow (Yellow: Y) discharge cells may be further provided.

In the discharge cell partitioned by the partition wall 112, a discharge gas such as xenon (Xe), neon (Ne), or the like may be filled.

In addition, a phosphor layer 114 that emits visible light for image display may be disposed in the discharge cell partitioned by the partition wall 112. For example, a first phosphor layer emitting red (R) light, a second phosphor layer emitting blue (B) light, and a third phosphor layer emitting green (G) light are disposed. Can be. In addition to the red (R), green (G), and blue (B) light, it is also possible to further arrange other phosphor layers emitting white (W) light or yellow (Yellow: Y) light.

In addition, the thickness of the phosphor layer 114 in at least one of the red (R), green (G), and blue (B) discharge cells may be different from other discharge cells. For example, a phosphor layer of a green (G) discharge cell, that is, a phosphor layer in a third phosphor layer or a blue (B) discharge cell, that is, a thickness of a second phosphor layer in a red (R) discharge cell, Ie thicker than the thickness of the first phosphor layer. Here, the thickness of the third phosphor layer may be substantially the same or different from the thickness of the second phosphor layer.

In addition, in the plasma display panel 100 according to an exemplary embodiment, the widths of the red (R), green (G), and blue (B) discharge cells may be substantially the same, but the red (R) and green (G) colors may be substantially the same. And at least one of the blue (B) discharge cells may be different from the widths of the other discharge cells.

For example, the width of the red (R) discharge cell is the smallest, and the width of the green (G) and blue (B) discharge cells can be made larger than the width of the red (R) discharge cell. Here, the width of the green (G) discharge cell may be substantially the same as or different from the width of the blue (B) discharge cell.

The width of the phosphor layer 114 disposed in the discharge cell is then changed in relation to the width of the discharge cell. For example, the width of the second phosphor layer disposed in the blue (B) discharge cell is wider than the width of the first phosphor layer disposed in the red (R) discharge cell, and the third disposed in the green (G) discharge cell. The width of the phosphor layer may be wider than the width of the first phosphor layer disposed in the red (R) discharge cell, thereby improving the color temperature characteristics of the image implemented.

In addition, although the red (R), green (G), and blue (B) discharge cells are each shown and described as being arranged on the same line in FIG. 1, they may be arranged in other shapes. For example, a delta type arrangement in which red (R), green (G) and blue (B) discharge cells are arranged in a triangular shape is also possible. In addition, the shape of the discharge cell is not only rectangular but also various polygonal shapes such as pentagon and hexagon.

In addition, although only the case where the partition wall 112 is formed in the rear substrate 111 is illustrated in FIG. 1, the partition wall 112 may be disposed on at least one of the front substrate 101 and the rear substrate 111.

In the above description, only one example of the plasma display panel 100 according to an exemplary embodiment of the present invention is illustrated and described. Therefore, the present invention is not limited to the plasma display panel 100 having the structure described above. For example, the above description shows only the case where the lower dielectric layer number 115 and the upper dielectric layer number 104 are one layer, but at least one of the lower dielectric layer or the upper dielectric layer is not composed of a plurality of layers. It is also possible.

In addition, although the width and thickness of the address electrode 113 disposed on the rear substrate 111 may be substantially constant, the width or thickness inside the discharge cell may be different from the width or thickness outside the discharge cell. For example, the width or thickness inside the discharge cell may be wider or thicker than that outside the discharge cell.

The image filter 110 may be formed by combining the glass substrate 160 with the light blocking layer 120, the color layer 130, and the electromagnetic shielding layer 140 that block light incident from the outside.

In addition, it is preferable that the first adhesive layer 151 is formed between the light shielding layer 120 and the color layer 130 to bond the light shielding layer 120 and the color layer 130 to the color layer 130. It is preferable that the second adhesive layer 152 is formed between the electromagnetic wave shielding layer 140 and the color layer 130 is bonded to the electromagnetic wave shielding layer 140.

In addition, a third adhesive layer 150 may be further disposed to bond the image filter 110 to the plasma display panel 100.

The glass substrate 160 may provide a space in which the light blocking layer 120, the color layer 130, and the electromagnetic shielding layer 140 may be formed.

The glass substrate 160 may include a blue pigment of cobalt (Co) material.

The glass substrate 401 includes a blue pigment in a glass material, and has a blue-based color by the blue pigment.

Glass material is not particularly limited, but PbO-B ₂ 0 ₃ -SiO ₂ -based glass, P ₂ O ₆ -B ₂ O ₃ -ZnO-based glass, ZnO-B ₂ O ₃ -RO (RO is BaO, SrO, La ₂ O ₃ , Bi ₂ O ₃ , P ₂ O ₃ , SnO-based glass, ZnO-BaO-RO (RO is SrO, La ₂ O ₃ , Bi ₂ O ₃ , P ₂ O ₃ , SnO One) -based glass, ZnO-Bi ₂ O ₃ -RO (RO may be any one of the SrO, La ₂ O ₃ , P ₂ O ₃ , SnO) -based glass material or a mixture of two or more.

The blue pigment is not particularly limited as long as the blue pigment is included in the glass substrate so that the glass substrate has a blue-based color. However, in view of ease of manufacture, color, manufacturing cost, and reflectance of the glass substrate, cobalt (Co) It may be desirable to be a material.

The content and effect of this blue pigment will be described in more detail later.

The above description has described an example of the image filter 110 included in the plasma display device according to an embodiment of the present invention, and the present invention is not limited to FIG. 1.

For example, among the glass substrate 160, the light shielding layer 120, the color layer 130, and the electromagnetic wave shielding layer 140, the light shielding layer 120, the color layer 130, and the electromagnetic wave excluding the glass substrate 160 may be used. It is also possible that one or more of the shielding layers 140 are omitted.

In addition to the above-described light blocking layer 120, color layer 130, and electromagnetic wave shielding layer 140, an anti-glare layer, a near-infrared shielding layer, an anti-reflective layer that prevents reflection of external incident light, and a plasma display panel It is also possible to further include a variety of functional layers, such as the optical characteristic layer having a different transmittance for each color depending on the characteristics of.

In addition, in the image filter 110 described above, the positions of the light blocking layer 120, the color layer 130, the electromagnetic shielding layer 140, and the glass substrate 160 may be changed. For example, the electromagnetic shielding layer 140 is disposed on the glass substrate 160, the color layer 130 is disposed on the electromagnetic shielding layer 140, and the light shielding layer is disposed on the color layer 130. It is also possible to arrange 120.

2 is a view for explaining an example of the operation of the plasma display device according to an embodiment of the present invention. 2 illustrates an example of a method of operating a plasma display panel according to an embodiment of the present invention. The present invention is not limited to FIG. 2, and the plasma display panel according to an embodiment of the present invention. How to operate the can be variously changed.

Referring to FIG. 2, a reset signal may be supplied to a scan electrode in a reset period for initialization. The reset signal may include a ramp-up signal and a ramp-down signal.

For example, in the set-up period, the voltage gradually increases from the second voltage V2 to the third voltage V3 after the voltage rises rapidly from the first voltage V1 to the second voltage V2 with the scan electrode. Rising rising ramp signals may be supplied. Here, the first voltage V1 may be a voltage of the ground level GND.

In this setup period, a weak dark discharge, that is, setup discharge, occurs in the discharge cell by the rising ramp signal. By this setup discharge, some wall charges can be accumulated in the discharge cells.

In the set-down period after the setup period, the rising ramp signal may be supplied to the scan electrode after the rising ramp signal in the opposite polarity direction.

Here, the falling ramp signal may gradually fall from the peak voltage of the rising ramp signal, that is, the fourth voltage V4 lower than the third voltage V3 to the fifth voltage V5.

As the falling ramp signal is supplied, a weak erase discharge, that is, a setdown discharge, occurs in the discharge cell. By this set-down discharge, wall charges such that address discharge can be stably generated in the discharge cells remain uniformly.

In the address period after the reset period, a scan bias signal that substantially maintains the lowest voltage of the falling ramp signal, that is, a voltage higher than the fifth voltage V5, for example, the sixth voltage V6, is supplied to the scan electrode.

In addition, a scan signal falling from the scan bias signal may be supplied to the scan electrode.

Meanwhile, the pulse width of the scan signal Scan supplied to the scan electrode in the address period of at least one subfield may be different from the pulse width of the scan signal of another subfield. For example, the width of the scan signal in the subfield located later in time may be smaller than the width of the scan signal in the preceding subfield. In addition, the reduction of the scan signal width according to the arrangement order of the subfields can be made gradually, such as 2.6 Hz (microseconds), 2.3 Hz, 2.1 Hz, 1.9 Hz, or 2.6 Hz, 2.3 Hz, 2.3 Hz, 2.1 Hz. .... 1.9 ㎲, 1.9 ㎲ and so on.

As such, when the scan signal is supplied to the scan electrode, the data signal may be supplied to the address electrode corresponding to the scan signal.

When the scan signal and the data signal are supplied, an address discharge may be generated in the discharge cell to which the data signal is supplied while the voltage difference between the scan signal and the data signal and the wall voltage generated by the wall charges generated in the reset period are added. .

Here, the sustain bias signal may be supplied to the sustain electrode in order to prevent the address discharge from becoming unstable due to the interference of the sustain electrode in the address period.

The sustain bias signal can keep the sustain bias voltage Vz smaller than the voltage of the sustain signal supplied in the sustain period and larger than the voltage of the ground level GND.

Subsequently, in the sustain period for displaying an image, a sustain signal may be supplied to at least one of the scan electrode and the sustain electrode. For example, a sustain signal may be alternately supplied to the scan electrode and the sustain electrode.

When such a sustain signal is supplied, the discharge cell selected by the address discharge is added with the wall voltage in the discharge cell and the sustain voltage Vs of the sustain signal, and a sustain discharge, i.e., display between the scan electrode and the sustain electrode when the sustain signal is supplied. Discharge may occur.

Meanwhile, in the at least one subfield, a plurality of sustain signals are supplied in the sustain period, and the pulse width of at least one sustain signal of the plurality of sustain signals may be different from the pulse widths of other sustain signals. For example, the pulse width of the sustain signal that is supplied first of the plurality of sustain signals may be larger than the pulse width of other sustain signals. Then, the sustain discharge can be more stabilized.

3 is a view for explaining the color coordinate characteristics of the plasma display device according to an embodiment of the present invention.

In FIG. 3, a first type panel Type 1 containing 15 ppm of cobalt (Co) material as a blue pigment and a second type panel (Type 2) containing no pigment are prepared on a glass substrate of an image filter. The graph shows the color coordinates measured using the MCPD-1000 with the panel supplying the same drive signal.

Referring to FIG. 3, the color coordinate P1 of green G is about 0.272 on the X axis and about 0.672 on the Y axis in the second type without the pigment. The color coordinate P2 of the red color R is approximately 0.630 in the X axis and approximately 0.357 in the Y axis. In addition, the color coordinate P3 of the blue color B is approximately 0.190 in the X axis and approximately 0.115 in the Y axis.

In the case of the first type panel, the color coordinate P10 of green (G) is approximately 0.270 in the X axis and approximately 0.670 in the Y axis. In addition, the color coordinate P20 of the red color R is approximately 0.610 in the X axis and approximately 0.350 in the Y axis. In addition, the color coordinate P30 of blue (B) is approximately 0.150 in the X axis, and approximately 0.060 in the Y axis.

Here, it can be seen that the triangle connecting the P10, P20 and P30 of the first type panel is moved in the blue (B) direction on the color coordinates compared to the triangle connecting the P1, P2 and P3 of the second type panel. This means that the color temperature of the first type panel is higher than the color temperature of the second type panel, so that the viewer can feel that the image of the first type panel is clearer than the image of the second type panel.

As such, when cobalt (Co) is included as a pigment in the glass substrate and the glass substrate has a blue-based color, the glass substrate can absorb light incident from the outside, thereby reducing the reflectance of the glass substrate. It can improve the contrast characteristic.

4 is a view for explaining the transmittance according to the content of the blue pigment contained in the glass substrate.

Figure 4 shows the data for the transmittance measured in each case varying the content of the blue pigment contained in the glass substrate between 0ppm and 70ppm.

Here, a cobalt material was used as the blue pigment, and all other conditions such as the thickness of the glass substrate and the amount of irradiated light were all the same, and the transmittance was measured while only changing the content of the pigment.

Referring to FIG. 4, when the content of the blue pigment included in the glass substrate is 0 ppm, the pigment is not contained, and the panel transmittance is very high as 89.5% because the glass substrate hardly absorbs the light incident from the outside. .

In addition, when the content of the blue pigment is 5ppm or more and 32ppm or less, the transmittance is 88.3% to 80.7% to maintain a relatively high transmittance.

In addition, when the content of the blue pigment is 35ppm or more and 57ppm or less, the transmittance is 78.5% ~ 70.2%, while the content of the blue pigment is reduced than 5ppm or more and 30ppm or less, but maintains a good transmittance.

On the other hand, when the content of the blue pigment is 60 ppm or more, the content of the blue pigment contained in the glass substrate is excessively high, so that the glass substrate absorbs the light incident from the outside so much that the transmittance is significantly lowered to 67.8% or less. It can also fall excessively.

Next, FIG. 5 is a view for explaining the luminance and reflectance according to the content of the blue pigment contained in the glass substrate.

Referring to FIG. 5, as described with reference to FIG. 4, the relationship between the reflectance and the luminance is shown in relation to the transmittance according to the content change of the blue pigment.

Here, FIG. 5 shows the relationship between the luminance and the reflectance observed while changing the content of the blue pigment contained in the glass substrate from 0 ppm to 70 ppm, and a cobalt material was used as the blue pigment.

Indicates that the brightness of the image is high enough to be very good, or that the contrast property of the image to be implemented is very good due to high reflectance, ○ is relatively good, and X is relatively low due to low brightness or low reflectance. Indicates poor.

First, looking at the brightness according to the content of the blue pigment, the brightness is very good (◎) when the content is more than 0ppm or less than 32ppm. The reason is that the luminance is also sufficiently high as the content of the blue pigment is sufficiently small and the light transmittance of the glass substrate is increased.

Further, when the content of the blue pigment is 35 ppm or more and 57 ppm or less, the luminance is relatively good (○). In this case, the transmittance is low, but the luminance of the image may be reduced, but the degree may be insignificant.

On the other hand, when the content of the blue pigment is 60ppm or more, the brightness is very poor (X). This is because the content of the blue pigment is excessively high and the luminance is excessively lowered as the transmittance of the glass substrate decreases.

Next, looking at the side of the reflectance, the reflectance is very poor (X) when the content of the blue pigment is 0ppm. This is because the glass substrate does not contain a blue pigment and thus cannot sufficiently absorb light incident from the outside, so that the reflectance can be excessively increased and the contrast characteristics of the glass substrate can be reduced.

On the other hand, when the content of the blue pigment is 3 ppm, the reflectance is relatively good (○). In this case, although the reflectance is low, the contrast characteristic may be degraded, but the degree may be insignificant.

In addition, when the content of the blue pigment is 5 ppm or more, the reflectance is very good (?). This is because the glass substrate sufficiently contains a blue pigment to sufficiently absorb light incident from the outside, and thus the reflectance can be lowered, whereby the contrast characteristics of the glass substrate can be improved.

4 and 5, the content of the blue pigment may be preferably 0 ppm or more and 57 ppm or less in order to reduce the reflectance to improve the contrast characteristic and to prevent the luminance from being excessively reduced due to excessively low transmittance. It may be more preferably 5 ppm or more and 32 ppm or less.

On the other hand, xenon (Xe) contained in the discharge gas of the plasma display panel can increase the luminance by increasing the amount of vacuum ultraviolet rays in the discharge cell, thereby increasing the brightness.

Therefore, it is also possible to adjust the content of xenon (Xe) contained in the discharge gas to compensate for the luminance which can be reduced by the glass substrate containing a blue pigment of cobalt material. This will be described with reference to FIGS. 6A to 6B.

6A to 6B are views for explaining the content of xenon contained in the discharge gas.

6A to 6B, xenon (Xe) is included in the discharge gas while the glass substrate of the image filter contains a blue pigment of cobalt material, and the content of xenon (Xe) is changed from 5% to 25%. Data showing luminance when the 25% window pattern image is displayed on the screen, and measuring a discharge start voltage (Firing Voltage) between the scan electrode and the sustain electrode are shown.

Referring to FIG. 6A, when the content of xenon (Xe) in the discharge gas is about 5%, the luminance of the implemented image is 329 [cd / m ² ], and when 9% is about 346 [cd / m ² ]. , Relatively small.

On the other hand, when the content of xenon (Xe) is 10%, the luminance increases to approximately 353 [cd / m ² ]. As such, as the content of xenon (Xe) is increased, the brightness is increased. If the content is increased, the amount of light generated in the discharge cell increases.

In addition, when the content of xenon (Xe) is 11%, the luminance is about 359 [cd / m ² ], and when the content of xenon (Xe) is about 12% or more and 15% or less, the brightness is 373 [cd / m ^2]. ] Has a high value of not less than 390 [cd / m ² ].

In addition, when the content of xenon (Xe) is 16% or more, the luminance is approximately 396 [cd / m ² ] or more.

Referring to the data of FIG. 6A, when the xenon (Xe) content is in the range of 10% or more and 20% or less, as the xenon (Xe) content is increased, the luminance of the implemented image is gradually increased.

If the content of xenon (Xe) is more than 25% it can be seen that the effect of improving the brightness is insignificant.

Next, referring to FIG. 6B, when the content of xenon (Xe) in the discharge gas is about 5%, the discharge start voltage between the scan electrode and the sustain electrode is about 135V, and when it is 9%, it is about 136V, which is relatively small.

On the other hand, when the content of xenon (Xe) is 10%, the discharge start voltage increases to approximately 137V.

In addition, when the content of xenon (Xe) is 11%, the discharge start voltage is about 137V, and when the content of xenon (Xe) is about 12% or more and 15% or less, the discharge start voltage is about 138V or more and 140V or less.

In addition, when the content of xenon (Xe) is 16% or more and 20% or less, the discharge start voltage is approximately 141V or more and 143V or less, and when the content of xenon (Xe) is 25% or more, the discharge start voltage rapidly rises to approximately 153V or more. can do.

As described above, even when the glass substrate of the image filter includes a blue pigment of cobalt material, when the xenon (Xe) content is increased, the brightness of the image is increased, and conversely, the discharge between the scan electrode and the sustain electrode It can be seen that the starting voltage rises.

Therefore, the discharge gas filled between the front substrate and the rear substrate to prevent excessive increase in the discharge start voltage between the scan electrode and the sustain electrode while maintaining a sufficiently high luminance of the image to be realized is 10% of xenon (Xe). It may be preferable to include more than 20%, more preferably more than 12% may include 15% or less.

As such, the technical configuration of the present invention described above can be understood by those skilled in the art that the present invention can be implemented in other specific forms without changing the technical spirit or essential features of the present invention.

Therefore, the exemplary embodiments described above are to be understood as illustrative and not restrictive in all respects, and the scope of the present invention is indicated by the appended claims rather than the foregoing detailed description, and the meaning and scope of the claims are as follows. And all changes or modifications derived from the equivalent concept should be interpreted as being included in the scope of the present invention.

1 is a view for explaining the configuration of a plasma display device according to an embodiment of the present invention.

2 is a view for explaining an example of the operation of the plasma display device according to an embodiment of the present invention.

3 is a view for explaining the color coordinate characteristics of the plasma display device according to an embodiment of the present invention.

4 is a view for explaining the transmittance according to the content of the blue pigment contained in the glass substrate.

5 is a view for explaining the luminance and reflectance according to the content of the blue pigment contained in the glass substrate.

6A to 6B are views for explaining the content of xenon contained in the discharge gas.

<Explanation of symbols for the main parts of the drawings>

100: plasma display panel 110: image filter

160: glass substrate

Claims (7)

Plasma display panel, An image filter disposed in front of the plasma display panel; The image filter includes a glass substrate, The glass substrate comprises a blue pigment (pigment). The method of claim 1, The content of the blue pigment is more than 0ppm 57ppm or less plasma display device. The method of claim 1, The content of the blue pigment is a plasma display device of 5ppm or more and 32ppm or less. The method of claim 1, The blue pigment includes a cobalt (Co) material plasma display device. The method of claim 1, The glass substrate is a plasma display device having a blue-based color. The method of claim 1, The plasma display panel is filled with a discharge gas including xenon (Xe), The xenon content is 10% or more 20% or less plasma display device. The method of claim 6, The xenon content is 12% or more 15% or less plasma display device.

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