Patent Application
20100019994
The present invention relates to a plasma display panel (PDP), and more particularly, to a plasma display device in which an external light shielding sheet is disposed at the front of a PDP in order to shield external light incident upon the PDP so that the bright room contrast of the PDP can be enhanced while maintaining the luminance of the PDP.
In general, plasma display panels (PDPs) display images including text and graphic images by applying a predetermined voltage to a number of electrodes installed in a discharge space to cause a gas discharge and then exciting phosphors with the aid of plasma that is generated as a result of the gas discharge. PDPs are easy to manufacture as large-dimension, light, and thin flat displays. In addition, PDPs can provide wide vertical and horizontal viewing angles, full colors and high luminance.
In the meantime, external light incident upon a PDP may be reflected by an entire surface of the PDP due to white phosphors that are exposed on a lower substrate of the PDP. For this reason, PDPs may mistakenly recognize and realize black images as being brighter than they actually are, thereby causing contrast degradation.
The present invention provides a plasma display device which can prevent light reflection by effectively shielding external light incident upon a plasma display panel (PDP) and which can improve the bright room contrast and luminance of a PDP.
According to an aspect of the present invention, there is provided a plasma display device, including a plasma display panel (PDP) and a filter which is disposed at a front of the PDP. The filter includes an external light shielding sheet which includes a base unit and a plurality of pattern units that are formed on the base unit and that have a lower refractive index than the base unit, wherein a distance between tops of a pair of adjacent pattern units is 1-3.25 times greater than a distance between bottoms of the pair of adjacent pattern units.
According to another aspect of the present invention, there is provided a plasma display device, including a PDP and a filter which is disposed at a front of the PDP. The filter includes an external light shielding sheet which includes a base unit and a plurality of pattern units that are formed on the base unit and that have a lower refractive index than the base unit, wherein a height of the pattern units is 0.89-4.25 times greater than a distance between bottoms of a pair of adjacent pattern units.
According to another aspect of the present invention, there is provided a filter having an external light shielding sheet, the external light shielding sheet including a base unit and a plurality of pattern units that are formed on the base unit and have a lower refractive index than the base unit. A distance between tops of a pair of adjacent pattern units is 1-3.25 times greater than a distance between bottoms of the pair of adjacent pattern units.
According to another aspect of the present invention, there is provided a filter having an external light shielding sheet, the external light shielding sheet including a base unit and a plurality of pattern units that are formed on the base unit and have a lower refractive index than the base unit. A height of the pattern units is 0.89-4.25 times greater than a distance between bottoms of a pair of adjacent pattern units.
The plasma display device according to the present invention includes an external light shielding sheet which is disposed at a front of a plasma display panel (PDP) and which absorbs and shields as much external light incident upon the PDP as possible. Thus, the plasma display device according to the present invention can effectively realize black images and enhance bright room contrast. Since the distance between the bottoms of a pair of adjacent pattern units is within a predetermined percentage range of the distance between the tops of the pair of adjacent pattern units, it is possible to secure an optimum opening ratio for a PDP and enhance the luminance of images displayed by a PDP.
The present invention will hereinafter be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown.
Referring to
Each of the electrode pairs includes transparent electrodes 11a and 12a and bus electrodes 11b and 12b. The transparent electrodes 11a and 12a may be formed of indium-tin-oxide (ITO). The bus electrodes 11b and 12b may be formed of a metal such as silver (Ag) or chromium (Cr) or may be comprised of a stack of chromium/copper/chromium (Cr/Cu/Cr) or a stack of chromium/aluminium/chromium (Cr/Al/Cr). The bus electrodes 11b and 12b are respectively formed on the transparent electrodes 11a and 12a and reduce a voltage drop caused by the transparent electrodes 11a and 12a which have a high resistance.
According to an embodiment of the present invention, each of the electrode pairs may be comprised of the bus electrodes 11b and 12b only. In this case, the manufacturing cost of the PDP can be reduced by not using the transparent electrodes 11a and 12a. The bus electrodes 11b and 12b may be formed of various materials other than those set forth herein, e.g., a photosensitive material.
Black matrices are formed on the upper substrate 10. The black matrices perform a light shied function by absorbing external light incident upon the upper substrate 10 so that light reflection can be reduced. In addition, the black matrices enhance the purity and contrast of the upper substrate 10.
In detail, the black matrices include a first black matrix 15 which overlaps a plurality of barrier ribs 21, a second black matrix 11c which is formed between the transparent electrode 11a and the bus electrode 11b of each of the scan electrodes 11, and a second black matrix 12c which is formed between the transparent electrode 12a and the bus electrode 12b. The first black matrix 15 and the second black matrices 11c and 12c, which can also be referred to as black layers or black electrode layers, may be formed at the same time and may be physically connected. Alternatively, the first black matrix 15 and the second black matrices 11c and 12c may not be formed at the same time, and may not be physically connected.
If the first black matrix 15 and the second black matrices 11c and 12c are physically connected, the first black matrix 15 and the second black matrices 11c and 12c may be formed of the same material. On the other hand, if the first black matrix 15 and the second black matrices 11c and 12c are physically separated, the first black matrix 15 and the second black matrices 11c and 12c may be formed of different materials.
An upper dielectric layer 13 and a passivation layer 14 are deposited on the upper substrate 10 on which the scan electrodes 11 and the sustain electrodes 12 are formed in parallel with one other. Charged particles generated as a result of a discharge accumulate in the upper dielectric layer 13. The upper dielectric layer 13 may protect the electrode pairs. The passivation layer 14 protects the upper dielectric layer 13 from sputtering of the charged particles and enhances the discharge of secondary electrons.
The address electrodes 22 are formed and intersects the scan electrode 11 and the sustain electrodes 12. A lower dielectric layer 24 and the barrier ribs 21 are formed on the lower substrate 20 on which the address electrodes 22 are formed.
A phosphor layer 23 is formed on the lower dielectric layer 24 and the barrier ribs 21. The barrier ribs 21 include a plurality of vertical barrier ribs 21a and a plurality of horizontal barrier ribs 21b that form a closed-type barrier rib structure. The barrier ribs 21 define a plurality of discharge cells and prevent ultraviolet (UV) rays and visible rays generated by a discharge from leaking into the discharge cells.
Referring to
When the filter 100 is 10-30 μm distant apart from the PDP, the filter 100 can effectively shield external light incident upon the PDP and discharge light generated by the PDP to the outside of the PDP. In order to protect the PDP against external pressure, the distance between the filter 100 and the PDP may be set to 30-120 μm. For shock prevention, an adhesive layer which can absorb shock may be formed between the filter 100 and the PDP.
The present invention can be applied to a barrier rib structure other than that set forth herein. For example, the present invention can be applied to a differential barrier rib structure in which the height of vertical barrier ribs 21a is different from the height of horizontal barrier ribs 21b, a channel-type barrier rib structure in which a channel that can be used as an exhaust passage is formed in at least one vertical or horizontal barrier rib 21a or 21b, and a groove-type barrier rib structure in which a groove is formed in at least one vertical or horizontal barrier rib 21a or 21b. In the differential barrier rib structure, the height of horizontal barrier ribs 21b may be greater than the height of vertical barrier ribs 21a. In the channel-type barrier rib structure or the groove-type barrier rib structure, a channel or a groove may be formed in at least one horizontal barrier rib 21b.
According to the present embodiment, red (R), green (G), and blue (B) discharge cells are arranged in a straight line. However, the present invention is not restricted to this. For example, R, G, and B discharge cells may be arranged as a triangle or a delta. Alternatively, R, G, and B discharge cells may be arranged as a polygon such as a rectangle, a pentagon, or a hexagon.
The phosphor layer 23 is excited by UV rays that are generated upon a gas discharge. As a result, the phosphor layer 23 generates one of R, G, and B rays. A discharge space is provided between the upper and lower substrates 10 and 20 and the barrier ribs 21. A mixture of inert gases, e.g., a mixture of helium (He) and xenon (Xe), a mixture of neon (Ne) and Xe, or a mixture of He, Ne, and Xe is injected into the discharge space.
The base unit 200 may be formed of a transparent plastic material, e.g., a UV-hardened resin-based material, so that light can smoothly transmit therethrough. Alternatively, the base unit 200 may be formed of a rigid material such as glass in order to enhance the protection of an entire surface of a PDP.
Referring to
Referring to
As described above, external light which reduces the bright room contrast of a PDP is highly likely to be incident upon a PDP from above. Referring to
Light that is emitted from a PDP 320 for displaying an image, as indicated by solid lines, is totally reflected from the slanted surfaces of the pattern units 310 to the outside of the external light shielding sheet, i.e., toward the user side.
As described above, external light is refracted into and absorbed by the pattern units 310 and light emitted from the PDP 320 is totally reflected by the pattern units 310 because the angle between the external light and each of the slanted surfaces of the pattern units 310 is greater than the angle between the light emitted from the PDP 320 and each of the slanted surfaces of the pattern units 310, as illustrated in
Therefore, the external light shielding sheet according to the present embodiment can prevent external light incident upon the PDP 320 from being reflected toward the user side by absorbing the external light and can enhance the bright room contrast of an image displayed by the PDP 320 by increasing the reflection of light emitted from the PDP 320.
In order to maximize the absorption of external light and the total reflection of light emitted from the PDP 320 in consideration of the angle of external light incident upon the PDP 320, the refractive index of the pattern units 310 may be 0.3-1 times higher than the refractive index of the base unit 300. In order to maximize the total reflection of light emitted from the PDP 320 by the slanted surfaces of the pattern units 310, the refractive index of the pattern units 310 may be set to be 0.3-0.8 times higher than the refractive index of the base unit 300 in consideration of a vertical viewing angle of the PDP 320.
In order to facilitate the manufacture of the light absorption particles 420 and the insertion of the light absorption particles 420 into the pattern units 410 and to maximize the absorption of external light, the light absorption particles 420 may be formed to have a size of 1 μm or more. In order to effectively absorb external light refracted into the pattern units 410, the pattern units 410 may contain at least 10 weight % of light absorption particles 420 having a size of 1 μm or more. In this case, the total weight of light absorption particles 420 contained in the pattern units 410 may account for at least 10% of the total weight of the pattern units 410. The light absorption particles 420 may be circular. In this case, the light absorption particles 420 may have a diameter of 1 μm or more. The light absorption particles 420 may not be circular for manufacturing reasons or for other reasons. In this case, an inscribed circle or a circumscribed circle of each of the light absorption particles 410 may have a diameter of 1 μm or more.
The light absorption particles 420 may have different sizes. In this case, the light absorption particles 420 may have an average size of 1 μm or more. In order to enhance the absorption of external light, the light absorption particles 420 may be formed on the outer surfaces of the pattern units 410.
Referring to
In order to shield external light through light absorption and to enhance the reflection of panel light through total reflection of visible light emitted from a PDP, the refractive index of the patter units 510, particularly, the refractive index of at least the slanted surfaces of the pattern units 510, may be lower than the refractive index of the base unit 500.
External light which reduces the bright room contrast of a PDP is highly likely to be incident upon a PDP from above. Referring to
Light that is emitted from a PDP for displaying an image is totally reflected from the slanted surfaces of the pattern units 510 to the outside of the external light shielding sheet, i.e., toward the user side.
As described above, external light is refracted into and absorbed by the pattern units 510 and light emitted from a PDP is totally reflected by the pattern units 510 because the angle between the external light and each of the slanted surfaces of the pattern units 510 is greater than the angle between the light emitted from the PDP and each of the slanted surfaces of the pattern units 510, as illustrated in
Therefore, the external light shielding sheet according to the present embodiment can prevent external light incident upon a PDP from being reflected toward the user side by absorbing the external light and can enhance the bright room contrast of an image displayed by a PDP by increasing the reflection of light emitted from the PDP.
In order to maximize the absorption of external light and the total reflection of light emitted from a PDP in consideration of the angle of external light incident upon the PDP, the refractive index of the pattern units 510 may be 0.3-1 times higher than the refractive index of the base unit 500. In order to maximize the total reflection of light emitted from a PDP by the slanted surfaces of the pattern units 510, the refractive index of the pattern units 510 may be set to be 0.3-0.8 times higher than the refractive index of the base unit 500 in consideration of a vertical viewing angle of the PDP.
The base unit 500 may be formed of a transparent plastic material, e.g., a UV-hardened resin-based material, so that light can smoothly transmit therethrough. Alternatively, the base unit 500 may be formed of a rigid material such as glass in order to enhance the protection of an entire surface of a PDP.
Referring to
In order to facilitate the manufacture of light absorption particles and the insertion of the light absorption particles into the pattern units 510 and to maximize the absorption of external light, the light absorption particles may be formed to have a size of 1 μm or more. In order to effectively absorb external light refracted into the pattern units 510, the pattern units 510 may contain at least 10 weight % of light absorption particles having a size of 1 μm or more. In this case, the total weight of light absorption particles contained in the pattern units 510 may account for at least 10% of the total weight of the pattern units 510.
When the thickness T of the external light shielding sheet is 20-250 μm, the manufacture of the external light shielding sheet can be facilitated and the transmissivity of the external light shielding sheet can be optimized. The thickness T may be set to 100-180 μm in order to effectively absorb and shield external light refracted into the pattern units 510 and to enhance the durability of the external light shielding sheet.
Referring to
The height h of the pattern units 510 is set to 80-170 μm in consideration of the bottom width P1. Thus, the pattern units 510 can form a gradient that can effectively absorb external light and reflect light emitted from a PDP. In addition, the pattern units 510 can be prevented from being short-circuited.
In order to achieve a sufficient opening ratio to display images with optimum luminance through discharge of light emitted from a PDP toward the user side and to provide an optimum gradient for the pattern units 510 for enhancing the external light shielding efficiency and the reflection efficiency of an external light shielding sheet, the distance D1 between the bottoms of a pair of adjacent pattern units 510 may be set to 40-90 μm, and the distance D2 between the tops of the pair of adjacent pattern units 510 may be set to 60-130 μm. An optimum opening ratio for displaying images can be obtained when the distance D1 is 1.1-5 times greater than the bottom width P1. In order to obtain an optimum opening ratio and to optimize the external light shielding efficiency and the reflection efficiency of an external light shielding sheet, the distance D1 may be set to be 1.5-3.5 greater than the bottom width P1.
When the height h is 0.89-4.25 times greater than the distance D1, external light that is diagonally incident upon the external light shielding sheet from above can be prevented from being incident upon a PDP. In order to prevent the pattern units 510 from being short-circuited and to optimize the reflection of light emitted from a PDP, the height h may be set to be 1.5-3 times greater than the distance D1.
When the distance D2 is 1-3.25 times greater than the distance D1, a sufficient opening ratio to display images with optimum luminance can be obtained. In order to maximize the total reflection of light emitted from a PDP by the slanted surfaces of the pattern units 510, the distance D2 may be set to be 1.2-2.5 times greater than the distance D1.
Referring to
Referring to
Referring to
Referring to
Referring to
When the height h is within the range of 80-170 μm, the manufacture of an external light shielding sheet can be facilitated, an optimum opening ratio can be obtained, and the shielding of external light and the reflection of light emitted from a PDP can be maximized.
The height h can be varied according to the thickness T. In general, external light that considerably affects the bright room contrast of a PDP is highly likely to be incident upon a PDP from above. Therefore, in order to effectively shield external light, the height h may be within a predetermined percentage range of the thickness T.
Referring to
Table 1 presents experimental results obtained by testing a plurality of external light shielding sheets having the same thickness T and different pattern unit heights (h) for whether they cause dielectric breakdown and whether they can shield external light.
Referring to Table 1, when the thickness T is 120 μm and the height h is greater than 115 μm, pattern units in the external light shielding sheet are highly likely to dielectrically break down, thereby increasing defect rates. When the height h is less than 115 μm, the pattern units are less likely to dielectrically break down, thereby reducing defect rates. When the height h is less than 85 μm, the external light shielding efficiency of the pattern units is likely to decrease. When the height h is less than 60 μm, external light is likely to be directly incident upon a PDP.
When the thickness T is 1.01-2.25 times greater than the height h, it is possible to prevent the upper portions of the pattern units from dielectrically breaking down and to prevent external light from being incident upon a PDP. In order to prevent dielectric breakdown of the pattern units and infiltration of external light into a PDP, to increase the reflection of light emitted from a PDP, and to secure optimum viewing angles, the thickness T may be 1.01-1.5 times greater than the height h.
Table 2 presents experimental results obtained by testing a plurality of external light shielding sheets having different pattern unit bottom width-to-bus electrode width ratios for whether they cause the moire phenomenon and whether they can shield external light, when the width of bus electrodes that are formed on an upper substrate of a PDP is 90 μm.
Referring to Table 2, when the bottom width P1 of pattern units is 0.2-0.5 times greater than the bus electrode width, the moire phenomenon can be prevented and the amount of external light incident upon a PDP can be reduced. In order to prevent the moire phenomenon, to effectively shield external light, and to secure a sufficient opening ratio to discharge light emitted from a PDP, the bottom width P1 may be 0.25-0.4 times greater than the bus electrode width.
Table 3 presents experimental results obtained by testing a plurality of external light shielding sheets having different pattern unit bottom width-to-vertical barrier rib width ratios for whether they cause the moire phenomenon and whether they can shield external light, when the width of vertical barrier ribs that are formed on a lower substrate of a PDP is 50 μm.
Referring to Table 3, when the bottom width P1 is 0.3-0.8 times greater than the vertical barrier rib width, the moire phenomenon can be prevented and the amount of external light incident upon a PDP can be reduced. In order to prevent the moire phenomenon, to effectively shield external light, and to secure a sufficient opening ratio to discharge light emitted from a PDP, the bottom width P1 may be 0.4-0.65 times greater than the vertical barrier rib width.
Referring to
The EMI shielding sheet 1020 includes a base sheet 1022 which is formed of a transparent plastic material and an EMI shielding layer 1021 which is attached onto an entire surface of the base sheet 1022 and shields EMI generated by a PDP so that the EMI can be prevented from being released externally. The EMI shield layer 1021 may be formed of a conductive material in a mesh form. In order to properly ground the EMI shielding layer 1021, an invalid display zone on the EMI shielding sheet 1020 where no images are displayed is covered with a conductive material.
An external light source is generally located over the head of a user regardless of an indoor or outdoor environment. The external light shielding sheet 1030 effectively shields external light so that black images can be rendered even blacker by a PDP.
An adhesive layer 1040 is interposed between the AR/NIR sheet 1010, the EMI shielding sheet 1020, and the external light shielding sheet 1030 so that the filter 1000 including the AR/NIR sheet 1010, the EMI shielding sheet 1020, and the external light shielding sheet 1030 can be firmly attached onto a PDP. In order to facilitate the manufacture of the filter 1000, the base sheets 1013 and 1022 may be formed of the same material.
Referring to
Referring to
At least one of the base sheets 1013 and 1022 illustrated in
A filter according to an embodiment of the present invention may also include a diffusion sheet. The diffusion sheet can diffuse light incident upon a PDP so that the brightness of the PDP can be uniformly maintained. In addition, the diffusion sheet can widen vertical and horizontal viewing angles of a display screen by uniformly diffusing light emitted from a PDP. Moreover, the diffusion sheet can hide patterns formed on an external light shielding sheet. Furthermore, the diffusion sheet can uniformly enhance the luminance of a PDP through collection of light in a direction corresponding to a vertical viewing angle, and can enhance the antistatic property of a PDP.
The diffusion sheet may be comprised of a transparent or reflective diffusion film. In general, the diffusion sheet may be comprised of a polymer base sheet containing small glass particles. The diffusion sheet may also be comprised of a polymethyl-methacrylate (PMMA) base sheet. In this case, the diffusion sheet is thick and highly heat-resistant and can thus be applied to large-scale display devices which generate a considerable amount of heat.
While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2006-0089170 | Sep 2006 | KR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/KR06/04597 | 11/6/2006 | WO | 00 | 10/6/2009 |
