Patent Application
20090079323
The present invention relates to a plasma display panel and a plasma display panel apparatus, and in particular to a gas component filled in a discharge space.
In recent years, plasma display panel apparatuses (hereinafter, referred to as “PDP apparatus”) have come to be widely used as flat display apparatuses. There are two types of the PDP apparatuses, a direct-current type (DC-type) and an alternating-current type (AC-type). Among AC-type PDP apparatuses which possess a high technological potential for realizing a large display apparatus, an AC-type surface discharge PDP apparatus is especially favored for its advantageous lifetime characteristics.
The PDP apparatus is constituted from a panel unit that displays an image and a drive unit that drives the panel unit based on an inputted image signal. The panel unit includes a front panel and a back panel that are placed opposing each other via a gap, and is sealed at edge portions.
The front panel, one panel of the panel unit, includes a glass substrate. On a main surface of the glass substrate, a plurality of display electrode pairs (each of which is composed of a scan electrode and a sustain electrode) are formed in parallel to each other in a stripe pattern, and are covered by a dielectric layer and a protective layer in the stated order. The back panel, another panel of the panel unit, includes a glass substrate. On a main surface of the glass substrate, data electrodes are formed in a stripe pattern, and are covered by a dielectric layer. Protruding barrier ribs are provided in a stripe pattern or grid pattern on the dielectric layer. In addition, the dielectric layer and the adjoining barrier ribs form a concave portion, and a phosphor layer is formed on an inner wall surface of the concave portion.
The front and back panels are arranged such that the display electrode pairs and the data electrodes intersect three-dimensionally. A space (discharge space) between the front and back panels is filled with a gas mixture such as xenon-neon (Xe—Ne) or xenon-neon-helium (Xe—Ne—He). In the panel unit, each area at which the display electrode pairs intersect the data electrodes three-dimensionally corresponds to a discharge cell. The drive unit of the PDP apparatus is connected to the display electrode pairs and the data electrodes in the panel unit for applying a voltage pulse to the individual electrodes.
The drive unit drives the panel unit using an in-field time division gray scale display method. This method divides one field of an inputted image into a plurality of subfields each of which is constituted from a reset period, a write period, and a sustain period.
However, there has been a demand for an improvement on luminous efficiency (discharge efficiency) of the PDP apparatus, and various approaches have been made in response to the demand. One of such approaches is a study on increasing the ratio of xenon in a discharge gas. For example, suggestions have been made that the discharge gas is composed of 100[%] of an Xe gas (Patent Document 1, listed below), and that the partial pressure ratio of the Xe gas to the total pressure ratio of the discharge gas falls in a range of 10[%] to 100[%] and that a fill pressure of the discharge gas is set to be as ultrahigh as 6×104 [Pa] (Patent Document 2, listed below).
However, when the ratio of the Xe gas in the discharge gas is raised higher than that of a conventional PDP apparatus, the protective layer tends to get prominently eroded as a result of sputtering caused by the sustain discharge generated on driving. For that reason, it is conventionally thought that the high content of the Xe gas in the discharge gas is inadequate for maintaining a high and stable display quality for a long period of driving. Aside from this, it should be noted that too high a firing voltage on driving may occur when the discharge gas does not include any Ne gas as in Patent Document 1 or when the total pressure of the discharge gas is ultrahigh as in Patent Document 2. Thus, both techniques disclosed in Patent Documents 1 and 2 are inappropriate for realizing a practical PDP apparatus.
The present invention is conceived in view of the above problem, and aims to provide a plasma display panel and a plasma display panel apparatus that can maintain high luminous efficiency and a stable display quality for a long time of driving.
The present inventors have investigated a relationship between the discharge gas component and the erosion of the protective layer caused by sputtering as a result of the discharge during driving, and found the following mechanism. That is, when the partial pressure ratio of an Xe gas to the total pressure of the discharge gas is in a range of 5[%] to 30[%], though the luminous efficiency improves, the protective layer is increasingly eroded with an increase in the partial pressure ratio of the Xe gas. Furthermore, the present inventors have confirmed that the discharge gas containing more than 30[ ] of the Xe gas leads to an increase in an amount of the erosion of the protective layer to a level that is not negligible in manufacturing a practical PDP apparatus.
The present inventors have further found that the discharge gas made of a 100[%] Xe gas with no Ne gas, as in Patent Document 1, suppresses the protective layer from being eroded as a result of sputtering caused by a discharge during driving. Furthermore, the present inventors have examined sputtering rates when the Ne gas content (partial pressure ratio) in the discharge gas is in a range of 1[%] to 10[%], and found that the smaller the content is, the smaller the erosion of the protective layer as a result of sputtering is.
The present inventors have found from these investigations that the Ne gas content in the discharge gas is an important factor that determines the amount of the erosion of the protective layer as a result of sputtering during driving.
Consequently, the present invention adopts the following features.
A plasma display panel pertaining to the present invention has a pair of substrates (a first substrate and a second substrate) that opposes each other with a space therebetween. A plurality of electrode pairs, a dielectric layer, and a protective layer are stacked in the stated order on a main surface of one of the substrates (the first substrate), and the protective layer faces the space. A phosphor layer that faces the protective layer is disposed over a main surface of another substrate (the second substrate). The space is filled with a discharge gas. The discharge gas contains a principal gas component composed of a component that emits light to excite a phosphor in the phosphor layer during a plasma discharge, and a neon gas. The principal gas component is contained at a principal ratio of the discharge gas, and the neon gas is contained at a partial pressure ratio of 8[%] or less to a total pressure of the discharge gas. The wording “(the neon gas is contained at a) partial pressure ratio” used herein refers to a value that is obtained by dividing the partial pressure of the Ne gas by the total pressure of the discharge gas.
Note that the “principal ratio” of the principal gas component in the above description means the highest partial pressure ratio to the total pressure of the discharge gas. For example, for a binary gas mixture, any ratio larger than 50[%] is the principal ratio, and for a ternary gas mixture, any ratio larger than 33.3[%] is the principal ratio.
In another aspect, the present invention provides a PDP apparatus having the above-mentioned PDP structures and a drive unit that applies, in accordance with an inputted image signal, a voltage pulse to each electrode constituting the electrode pairs of the PDP.
Since the principal gas component of the discharge gas accounts for the principal ratio as described above, the PDP and the PDP apparatus pertaining to the present invention possess high luminous efficiency (discharge efficiency). In addition, since the Ne gas is contained in the discharge gas of the PDP and the PDP apparatus, a lower firing voltage can be maintained compared with the PDP of Patent Document 1 that contains no Ne gas.
Furthermore, since the partial pressure ratio of the Ne gas is specified to 8[%] or below, the protective layer is suppressed from being eroded as a result of sputtering caused by Ne ions generated in a discharge during driving. Thus, the PDP and the PDP apparatus are able to maintain a high display quality for a long time of driving.
Accordingly, the PDP and the PDP apparatus pertaining to the present invention are advantageous for maintaining a stable display quality while keeping high luminous efficiency for a long time of driving.
In the PDP and the PDP apparatus pertaining to the present invention, the dielectric layer that has a thickness of less than 20 [μm] is desirable. The protective layer with the above thickness contributes to keep a low firing voltage on driving of the panel, therefore is favorable for suppressing damages to the protective layer as a result of sputtering caused by a discharge during driving.
In the PDP and the PDP apparatus pertaining to the present invention, the neon gas is desired to be contained at a partial pressure ratio of 5[%] or less to the total pressure of the discharge gas. The low content of the Ne gas is effective in suppressing the erosion of the dielectric layer caused by sputtering during driving without the need to specify the thickness of the dielectric layer as described above.
In the PDP and the PDP apparatus pertaining to the present invention, the neon gas that is contained at a partial pressure ratio of at least 0.2[%] to the total pressure of the discharge gas is practical. Furthermore, the neon gas is preferably contained at a partial pressure ratio of at least 3[%] to the total pressure so that the aging time in manufacturing can be as short as that required for manufacturing a PDP apparatus with a conventional panel structure.
In the PDP and the PDP apparatus pertaining to the present invention, it is desirable to contain an argon gas in the discharge gas. This is to take advantage of Penning effect of Ar atoms, which further suppresses the firing voltage and improves luminous efficiency.
In the PDP and the PDP apparatus pertaining to the present invention, it is desirable to set the total pressure of the discharge gas to be from 1×104 [Pa] to 5×104 [Pa], inclusive. This is because the luminous efficiency decreases compared with that of a conventional PDP apparatus when the total pressure ratio is set lower than 1×104 [Pa]. This is also because the firing voltage becomes too high when the total pressure ratio is set higher than 5×104 [Pa], as in Patent Document 2. These phenomena are prominent especially when the partial pressure ratio of the Xe gas is high. When both partial pressure ratio of the Xe gas and total pressure of the discharge gas are high, breakdown of the dielectric layer presents a particular concern. Preferably, the total pressure of the discharge gas is from 1.7×104 [Pa] to 5×104 [Pa], inclusive.
In addition, in the PDP and the PDP apparatus pertaining to the present invention, it is desirable that each electrode that constitutes the electrode pairs is made of a metal material. This is because it is achievable to keep the surface area of the respective electrodes that constitute the display electrode pairs to a minimum area, for the PDP and the PDP apparatus pertaining to the present invention achieve high luminous efficiency as described above. Note that each electrode constituting the display electrode pairs of a conventional PDP usually has a layered structure of a transparent electrode made of ITO (indium tin oxide) and a bus electrode made of a metal material. However, an electrode made solely of the metal material is sufficient for the PDP and the PDP apparatus of the present invention, and a transparent electrode is unnecessary. Consequently, manpower that is required for manufacturing the transparent electrode can be reduced. Thus, the PDP and the PDP apparatus pertaining to the present invention are advantageous in lowering manufacturing cost when the above electrode structure is employed.
In the PDP and the PDP apparatus pertaining to the present invention, magnesium oxide is applicable for the protective layer, and one of a xenon gas and a krypton gas is applicable for the principal gas component.
Furthermore, in the PDP and the PDP apparatus pertaining to the present invention, each of the electrode pairs on the main surface of the first substrate includes two electrodes that are spaced from each other at a distance desirably from 40 [μm] to 70 [μm], inclusive, which is favorable for reducing reactive power and suppressing occurrence of spots. More specifically, when the distance is shorter than 40 [μm], the reactive power becomes impracticably high. When the distance is larger than 70 [μm], with a high partial pressure ratio of the Xe gas, an undesired strong discharge (erroneous discharge) occurs during a reset period, and subsequently in a sustain period, some of discharge cells unintentionally emit light (occurrence of spots). However, the discharge gap at the distance from 40 [μm] to 70 [μm], inclusive, as employed in the PDP and the PDP apparatus pertaining to the present invention, is favorable for decreasing the reactive power and suppressing the occurrence of spots.
When barrier ribs are each disposed on a surface of the dielectric layer on the second substrate between the electrodes that are adjacent to each other, a height from a top of each barrier rib to the surface of the dielectric layer on the second substrate is desired to be larger than the distance between the two electrodes with an object of reducing the occurrence of spots. More specifically, the height from the top of each barrier rib to the surface of the dielectric layer on the second substrate is desired to be from 75 [μm] to 120 [μm], inclusive.
In addition, when a grid-shaped barrier rib structure with the sub-barrier ribs intersecting the main barrier ribs is adopted, the height from the top of each barrier rib to the surface of the dielectric layer on the second substrate is larger than a height from a top of each sub-barrier rib to the surface of the dielectric layer on the second substrate. Moreover, a difference in the height of each barrier rib and the height of each sub-barrier rib is desired to be from 8 [μm] to 15 [μm], inclusive. Thus, the occurrence of spots is suppressed.
Note that the difference in the height of the barrier rib and the sub-barrier rib below 8 [μm] is impractical considering variance in size and exhaust efficiency in the discharge space in manufacturing the PDP. The difference in the height is preferred to be 15 [μm] or below from the point of preventing an erroneous discharge between adjoining discharge cells in a column direction (discharge cells that are adjacent to each other across a sub-barrier rib).
The following describes the best mode for carrying out the present invention using embodiments. Note that the embodiments in the following description are merely examples, and the present invention is not limited to these.
Among constituent elements of a PDP apparatus 1 in a first embodiment of the present invention, a structure of a panel unit 10 is described as follows with reference to
As shown in
As shown in
The front substrate 111 is made of, for example, high-strain-point glass or soda-lime glass. Each scan electrode Scn and each sustain electrode Sus is made of a metal material (e.g. Ag), and does not include any of ITO (tin-doped indium oxide), SnO2 (tin oxide), and ZnO (zinc oxide) as a constituent material. Note, however, that it is possible for the scan electrode Scn and the sustain electrode Sus to include such constituent materials as ITO, SnO2, and ZnO.
Additionally, the dielectric layer 113 is made of a non-lead and low-melting glass material, and the thickness is designed to be approximately 25 [μm]. The protective layer 114 is made of MgO (magnesium oxide).
Note that a black stripe may be provided between the adjacent display electrode pairs 112 on the surface of the front substrate 111 in order to prevent light of discharge cells from leaking to the adjoining discharge cells.
The back panel 12 has a plurality of data electrodes Dat on a main surface (facing upward in
A phosphor layer 124 is formed on inner walls of a plurality of concave portions that are surrounded by the dielectric layer 122 on the bottom, two main barrier ribs 1231 and two sub-barrier ribs 1232 on the side. The concave portions of each row in the X direction all have the same one of three colors of the phosphor layers. In the Y direction shown in
As with the front substrate 111, the back substrate 121 of the back panel 12 is made of high-strain-point glass or soda-lime glass. The data electrodes Dat are made of a metal material such as Ag similarly to the scan electrode Scn and the sustain electrode Sus. Note that the data electrodes Dat may be made of any other metal material such as gold (Ag), chromium (Cr), copper (Cu), nickel (Ni), and platinum (Pt), or may have a layered structure of combination of the metal materials.
The dielectric layer 122 is made of non-lead and low-melting glass, basically similar to the dielectric layer 113 of the front panel 11. However, aluminum oxide (Al2O3) or titan oxide (TiO2) may also be contained. The barrier ribs 123 are made of, for example, a glass material.
Each color of the phosphor layers, 124R, 124G, and 124B is made of the following phosphors alone or in combination.
Red (R) phosphor; (Y, Gd) BO3: Eu
Green (G) phosphor; Zn2SiO4: Mn
Blue (B) phosphor; BaMgAl10O17: Eu
As shown in
A discharge gas made up of a xenon (Xe) gas and a neon (Ne) gas is enclosed in the discharge space 13, where a total pressure of the discharge gas is adjusted to 5×104 [Pa]. In the panel unit 10 of the present embodiment, the partial pressure ratio of the Ne gas to the total pressure ratio of the discharge gas is set to 5[%]. That is to say, the partial pressure ratio of the Xe gas to the total pressure ratio in the discharge gas is 95[%] in the panel unit 10. The Xe gas, which is the principal gas component, in the discharge gas emits vacuum ultraviolet rays which excite respective phosphors constituting the phosphor layers 124 caused by a discharge during driving.
In the panel unit 10, each area at which the display electrode pairs 112 intersect the data electrodes three-dimensionally corresponds to a discharge cell (unillustrated), and the plurality of the discharge cells are arranged in a matrix.
The PDP apparatus 1 including the above panel unit 10 is described with reference to
As shown in
In addition, m data electrodes Dat (1) to Dat (m) are arranged in a column direction in the panel unit 10. A discharge cell of the panel unit 10 is formed in an area corresponding to an area at which a pair of the scan electrode Scnk (k=1−n) and the adjacent sustain electrode Susk (k=1−n) intersects a data electrodes Datl (l=1−m). Thus, the entire panel unit 10 includes (m×n) discharge cells.
As shown in
The A/D converter 25 of the display drive unit 20 converts the inputted image signal VD into a digital signal representing image data, and outputs the converted image data to the scan number converter 26 and the APL detector 28. After receiving the image data corresponding one screen from the A/D converter 25, the APL detector 28 calculates, based on the image data indicating the grayscale level of each discharge cell in the screen, a total of the grayscale levels in the screen, and obtains a value by dividing the total value by the total number of discharge cells. After that, the APL detector 28 obtains an average picture level (APL value) by calculating a percentage of the above division result value to a maximum grayscale level (e.g. 256), and outputs the APL value to the timing generator 24. The higher the APL value is, the whiter the screen is, and the lower the APL value is, the darker the screen is.
Having received the image data from the A/D converter 25, the scan number converter 26 converts the image data into pieces of image data that corresponds to the number of pixels of the panel unit 10, and outputs the converted image data pieces to the subfield converter 27. The subfield converter 27 is provided with a subfield memory (unillustrated) and converts the image data pieces transferred from the scan number converter 26 into pieces of subfield data and temporarily stores the subfield data in the subfield memory. Each piece of the subfield data is a set of binary data indicating ON/OFF of the discharge cell in each subfield that is used for displaying gradation of the image data on the panel unit 10. The subfield converter 27 then outputs the subfield data to the data driver 21 in accordance with a timing signal received from the timing generator 24.
The data driver 21 converts the image data for each subfield into signals corresponding to each of the data electrodes Dat (1) to Dat (m), and individually drives the data electrodes Dat. The data driver 21 is provided with a publicly known driver IC and the like.
The timing generator 24 generates a timing signal based on the inputted horizontal sync signal H and the vertical sync signal V, and outputs the generated signal to the drivers 21, 22, and 23. The timing generator 24 judges, based on the APL value inputted by the APL detector 28, whether each reset period of subfields constituting one field is an entire-cell or a selective-cell reset period, and controls the number of times of application to the entire-cell reset period in one field.
The scan driver 22 applies a driving voltage to the scan electrodes Scn (1) to Scn (n) in accordance with the timing signal received from the timing generator 24. The scan driver 22 is provided with a publicly known driver IC, as with the data driver 21.
The sustain driver 23 is provided with a publicly known driver IC, and applies a driving voltage to the sustain electrodes Sus (1) to Sus (n) in accordance with the timing signal received from the timing generator 24.
A driving method of the PDP apparatus 1 with the above structure is described with reference to
As shown in
To drive the PDP apparatus 1, first in the reset period T1, a reset discharge is generated in all the discharge cells of the panel unit 10, thereby eliminating the effect of the discharge having or not having been generated in the individual discharge cells in the preceding subfield and absorbing any variance in the discharge properties. In the reset period T1, as shown in
In the write period T2 subsequent to the above reset period T1, the Scan electrodes Scn (1) to Scn (n) are sequentially scanned line by line in accordance with the subfield data, and a write discharge (weak discharge) is generated between the scan electrodes Scn and the data electrodes Dat in each discharge cell that is intended to have a sustain discharge in the subsequent sustain period of the subfield. In the discharge cell in which the write discharge has been generated between the scan electrodes Scn and the data electrodes Dat, wall charges are accumulated on a surface of the protective layer 114 on the front panel 11, the surface facing the discharge space 13.
Subsequently, in the sustain period T3, a rectangular waveform sustain pulse of a specified cycle (e.g. 6 μsec.) and of a specified voltage (e.g. 180 V) is applied to the sustain electrodes Sus (1) to Sus (n) and the scan electrodes Scn (1) to Scn (n). The waveform of the sustain pulse applied to the sustain electrodes Sus (1) to Sus (n) and the waveform of the sustain pulse applied to the scan electrodes Scn (1) to Scn (n) have the same cycle, and are out of phase by a half cycle. The sustain pulses are applied simultaneously to all the discharge cells in the panel unit 10.
By applying the pulses as shown in
In the PDP apparatus 1 pertaining to the present embodiment, the binary gas mixture (Xe—Ne) fills the discharge space 13 of the panel unit 10 and the ratio of the Ne gas in the discharge gas (the partial pressure ratio of the Ne gas to the total pressure) is set to 5[%]. That is to say, the ratio of the Xe gas in the discharge gas is as high as 95[%]. This ensures the PDP apparatus 1 of the present embodiment to have high luminous efficiency (discharge efficiency), as described above. In addition, 5[%] of the Ne gas contained in the discharge gas in the PDP apparatus 1 effectively keeps the low firing voltage, unlike the discharge gas composed of 100[%] Xe gas disclosed in Patent Documents 1 or the discharge gas having the ultrahigh total pressure in Patent Document 2.
In the PDP apparatus 1 pertaining to the present embodiment, since the Ne gas in the discharge gas is set to 5[%], erosion of the protective layer 114 as a result of sputtering induced by the discharge during driving is unlikely to occur, which leads to the effect of realizing the PDP apparatus with a long life. The reason for this is described later.
In the panel unit 10 pertaining to the present embodiment, MgO is used as a constituent material of the protective layer 114 of the front panel 11. Although MgF2 (magnesium fluoride) may be used as the constituent material, MgO is the optimum material for the protective layer considering its secondary electron emission coefficient and its sputtering resistance. Thus, the panel unit 10 having the protective layer 114 made of MgO is advantageous for its high luminous efficiency and its sputtering resistance during driving.
In addition, in the panel unit 10, since each of the scan electrodes Scn and the sustain electrodes Sus constituting the display electrode pairs 112 is made of only a metal material such as Ag, the panel unit 10 obtains an advantage in terms of manufacturing cost, compared with a conventional panel unit that has a layered-structure of a transparent electrode made of ITO and a bus electrode made of a metal material. It should be noted that the reason why the electrodes Scn and Sus can be made solely of a metal material is because the PDP apparatus 1 of the present embodiment has excellent luminous efficiency so that each width of the electrodes Scn and Sus can be narrowed down. Since the electrodes Scn and Sus are made of a metal material, a sputtering method may be used to form the electrodes so that thin and low-resistant electrodes can be achieved.
Note that different variations can be adopted for the PDP apparatus 1 of the present embodiment. In the panel unit 10, the Xe gas is adopted as the principal gas component in the discharge gas. However, a krypton (Kr) gas, for example, may be adopted instead. The total pressure of the discharge gas is set to 5×104 [Pa] in the structure of the panel unit 10. However, the total pressure in a range of 1×104 [Pa]-5×104 [Pa], inclusive, may be favorably adopted in view of suppressing a firing voltage on driving the PDP apparatus 1. When the fill pressure is set below 1×104 [Pa], the luminous efficiency of the panel unit 10 becomes lower than that of a conventional panel unit.
Conversely, when the fill pressure is higher than 5×104 [Pa], a firing voltage rises as with the panel unit of Patent Document 2. In a panel unit having a basically identical structure with the panel unit 10, when the fill pressure is increased to 6×104 [Pa], for example, a firing voltage rises to approximately 700 [V].
Furthermore, although the Ne gas content in the discharge gas is set to 5[%] in this embodiment, any value of the content is acceptable as long as the value is 8[%] or below. Note that a gas composition with no Ne gas content should be avoided for the above reasons.
Based on the structure of the panel unit 10, samples were prepared with different Xe gas and Ne gas contents to investigate changes in a firing voltage and a sputtering rate of the protective layer 114 caused by a discharge during driving of the panel.
As shown in
When the sputtering rate rises, the protective layer gets eroded so that the panel unit cannot be used for a long period. In other words, the high sputtering rate shortens a life of the PDP apparatus and thus lowers its reliability. For that reason, there is an upper limit to the acceptable sputtering rate.
The results shown in
Note that too high a partial pressure ratio of the Xe gas, as with Patent Document 1, causes an increase in a firing voltage. Therefore, the Ne gas needs to be added to the discharge gas so as to suppress the firing voltage even a little.
Subsequently, a relationship between the partial pressure ratio of the Ne gas and the firing voltage is described with reference to
Generally speaking, a pressure increase results in a firing voltage increase. However, this does not hold in a case that the Ne gas is added to the Xe gas. As shown in
As shown in
Accordingly, the discharge gas is desirably the Xe/Ne gas mixture, and the partial pressure ratio of the Ne gas is 5[%] or below. Thus, high luminous efficiency (discharge efficiency) is achieved, erosion of the protective layer 114 because of sputtering is suppressed, and the firing voltage is decreased.
Although data of a neon-gas-free discharge gas (partial pressure ratio of Ne gas=0%) is not plotted in
Note that although the Xe gas is adopted as the principal gas component of the discharge gas in this embodiment, a krypton gas may be adopted instead. No change would be observed in the experimental results in
Subsequently, a PDP apparatus pertaining to a second embodiment of the present invention is described as follows.
A structure of a panel unit of the second embodiment is basically identical with that of the first embodiment shown in
In addition, the partial pressure of the Ne gas in the discharge gas is set to 8[%] in this embodiment. A description of other structural parts of the panel unit and the PDP apparatus of this embodiment is omitted, as these parts are basically identical with those described in the first embodiment.
In the panel unit of the PDP apparatus pertaining to the present embodiment, the dielectric layer of the front panel is made of oxide silicon of which a dielectric constant is lower than that made of low-melting glass in the first embodiment. Therefore, if a capacity that can store electric charges in the discharge space is set as high as that of the panel unit 10, the dielectric layer can be from one half to one third as thick as the original layer of the first embodiment. For that reason, in the panel unit pertaining to the present embodiment, it is possible to thin down the thickness of the dielectric layer to 20 [μm] which is thinner by 5 [μm] than the dielectric layer 113 with the thickness of 25 [μm] of the panel unit 10. The reduction of the thickness contributes to a decrease in a discharge voltage.
In addition to the advantages possessed by the PDP apparatus 1 of the first embodiment, the PDP apparatus and the panel unit having the above structure are able to reduce damages to the protective layer because of sputtering as a result of a discharge during driving. More specifically, the reduction of the thickness of the dielectric layer serves to lower the discharge voltage, which leads to reduce energy of ions colliding to the protective layer even if the partial pressure ratio of the Ne gas in the discharge gas is 8[%].
Following describes a confirmatory experiment conducted to verify the above advantages of the PDP apparatus pertaining to the present embodiment with reference to
As shown in
Also, as shown in
These results show that by specifying the partial pressure ratio of the Ne gas in the discharge gas to be 8[%] or below in the panel unit of the present embodiment, the PDP apparatus can achieve both high luminous efficiency and a long life. Note that, also in this embodiment, there is a precondition that the discharge gas contains Ne gas (e.g. 0.2%) even if an amount thereof may be small.
Note that, in the PDP apparatus pertaining to the present embodiment as well, the total pressure of the discharge gas may be set in the range of 1×104 [Pa]-5×104 [Pa], inclusive, and respective electrodes Scn and Sus composing the display electrode pairs may be made of Ag. The reasons for these are similar to those disclosed in the first embodiment. Each of the electrodes Scn and Sus is preferred to be thin so as to prevent breakdown of the dielectric layer because of the thinness of the dielectric layer.
Instead of the Xe gas, a krypton gas may be used as the principal gas component of the discharge gas, which also shows the similar superiority to that in the first embodiment.
Following is a description of a PDP apparatus and a panel unit pertaining to a third embodiment of the present invention.
The PDP apparatus and the panel unit of the present embodiment have a basically identical structure with that in the second embodiment. A difference between the second and the present embodiments is the composition of the discharge gas. That is, an Xe—Ne—Ar ternary gas mixture is used as the discharge gas in the panel unit of the present embodiment. The respective partial pressure ratios of the Ne gas and the Ar gas in the discharge gas are set to 5[%]. The total pressure of the discharge gas is set to 3.5×104 [Pa], as in the second embodiment. Other structural parts than these are basically identical with those in the second embodiment.
The panel unit of the present embodiment contains an Ar gas in the discharge gas for the following reason. Ar ions are less likely to cause sputtering than Ne ions, therefore Ar gas addition does not influence a life of the panel unit. Moreover, the Ar gas addition to the discharge gas is expected to cause Xe excitation. Therefore, the PDP apparatus of the present embodiment further improves the luminous efficiency compared with the PDP apparatus of the second embodiment.
In addition, the Ar ions cause a larger secondary electron emission coefficient of the protective layer than Xe ions do, therefore a decrease in a firing voltage of the PDP apparatus of the present embodiment can be expected.
Accordingly, the PDP apparatus of the present embodiment is even more advantageous than the PDP apparatus of the first and second embodiments in achieving high luminous efficiency (discharge efficiency), in suppressing erosion of the protective layer caused by sputtering, and in decreasing a firing voltage.
As shown in
Note that different variations can be adopted for the PDP apparatus and the panel unit pertaining to the present embodiment, as with the first and second embodiments.
Subsequently, a relationship between the sputtering rate and the thickness of the dielectric layer is described as follows with reference to
As shown in
Furthermore, as shown in
These results show that, for the panel unit and the PDP apparatus, the thickness of the dielectric layer is preferred to be 20 [μm] or below, providing that the partial pressure ratio of the Ne gas is 8[%] or below. However, when the partial pressure ratio of the Ne gas is 5[%], as evident from
The following describes a relationship between a content of the Ne gas and an aging time in a manufacturing process with reference to
As shown in
Following is a description of a characteristic chart showing a relationship between occurrence of spots and a distance (discharge gap) between the scan electrodes Scn and the sustain electrode Sus of the front panel 11 with reference to
As shown in
Note that the discharge gap smaller than 40 [μm] results in too large reactive power during driving. The discharge gap larger than 70 [μm] results in occurrence of spots when a driving time is long.
Accordingly, the desirable width of the discharge gap is in a range of 40 [μm]-70 [μm], inclusive, in consideration of decreasing the reactive power and suppressing the occurrence of spots for a long driving hours.
Following describes a relationship between a height of the barrier ribs 123 and occurrence of the spots with reference to
In this investigation, a difference in height between the main barrier ribs 1231 and the sub-barrier ribs 1232 is set at two levels.
The difference is set at 8 [μm] or 15 [μm]. In either case, as shown in
In addition, when the main barrier ribs 1231 are 120 [μm] or below, the frequency of spot occurrence indicates 0.5 or below, which is able to suppress the occurrence of spots when the total driving time is long. Thus, the height of the main barrier ribs 1231 ranging from 75 [μm] to 120 [μm], inclusive, is desirable from a perspective of suppressing both the firing voltage and occurrence of spots when the total driving time is long.
The above embodiments only provide examples to describe the configuration of the PDP and the PDP apparatus pertaining to the present invention and the effects obtained therewith. Accordingly, the present invention is not restricted to these except for the characterizing aspects. For example, the first and second embodiments use the Xe—Ne binary gas mixture as the discharge gas, and the third embodiment uses the Xe—Ne—Ar ternary gas mixture. However, a discharge gas that contains the Ne gas in the above range to principal gas component can be adopted. Also, a gas mixture containing any of a Kr—Ne, Kr—Ne—Ar, Xe—Ne—He, Xe—Ne—He—Ar, and Kr—Ne—He—Ar is applicable for the discharge gas.
In addition, although phosphor materials constituting each of the phosphor layers 124R, 124G, and 124B are provided as examples in the first embodiment and the like, other than those, each of the following phosphor materials can also be used.
R phosphor; (Y, Gd) BO3: Eu
G phosphor; a mixture of (Y, Gd) BO3: Tb and Zn2SiO4: Mn
B phosphor; BaMg2Al14O24: Eu
Furthermore, in the above embodiments, a gas component such as an Xe gas and a Kr gas that emits ultraviolet rays with a wavelength of 147 [nm] or 173 [nm] responding to a discharge is adopted as the principal gas component. However, the component may be changed according to the constituent materials of the phosphor layer 124 of the back panel 12.
Additionally, in the first, second and third embodiments, the PDP apparatus has the structure shown in
Furthermore, the thickness of the dielectric layer is 25 [μm] in the first embodiment and 20 [μm] in the second and third embodiments. However, the thickness may be changed to any other value. Note that the value needs to be set in consideration of the relationship between the firing voltage on driving the PDP apparatus and the breakdown of the dielectric layer.
Furthermore, the scan electrodes Scn and the sustain electrodes Sus that constitute the display electrode pairs are made of Ag in the first embodiment, and Al—Nd in the second and third embodiments. However, the present invention is not limited to those embodiments. For example, an electrode with a layered structure of a transparent electrode made of ITO and a bus line made of a metal material can be used, as been adopted by the conventional PDP apparatus, and a layered product of Cu—Cr—Cu can be adopted as well. In addition, since the structure of the present invention enables the PDP apparatus and the panel unit to have high luminous efficiency mentioned as above, the display electrode pairs can be made of a different metal material than Ag, or Al—Nd, and the transparent electrode made of ITO and the like is unnecessary.
The present invention can maintain a stable display quality for a long time of driving without sacrificing high luminous efficiency. Thus, it is possible to apply the present invention to a large high-definition television, a large display apparatus and the like.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-162875 | Jun 2005 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2006/310987 | 6/1/2006 | WO | 00 | 11/15/2007 |
