JP2009277491A - Plasma display panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a PDP capable of achieving an excellent image display performance by demonstrating a high luminance efficiency in a full pressure of a low discharge gas, while controlling a rise of a discharging voltage irrespective of a cell structure of high definition by adjusting a discharge gas composition. <P>SOLUTION: In the PDP 1 of an AC plane discharge type, a Xe-Ar system discharge gas is enclosed in a discharge space 15. An Ar partial pressure in the discharge gas is set at 0.1 to 10%, and moreover a full pressure of the discharge gas is set at 20 kPa or higher and 50 kPa or lower. Furthermore, a shortest distance between adjacent barrier ribs 13 facing each other is adjusted at 80 to 170 μm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a plasma display panel used in a television or the like, and more particularly to a technique for improving luminous efficiency by a discharge gas sealed in a discharge space.

  2. Description of the Related Art In recent years, with the increase in the screen size of home television receivers, thin display devices that replace conventional CRT (Cathode Ray Tube) devices are rapidly spreading. As a display device that realizes a thin and large screen, the current mainstream along with a liquid crystal display is that discharge plasma is generated inside a minute cell corresponding to each pixel, and ultraviolet rays generated therefrom are phosphors. A plasma display panel (hereinafter referred to as PDP) that emits light by converting it into visible light.

  A typical configuration of the PDP is called a surface discharge AC type. This PDP generally has a plurality of pairs of display electrodes (scanning electrodes and sustaining electrodes) arranged on the surface, and a front panel in which a dielectric layer and a protective layer are sequentially laminated so as to cover them. A back panel in which a plurality of address (data) electrodes are arranged on the surface, a dielectric layer covering the electrodes, a plurality of barrier ribs (ribs), and a phosphor layer of each RGB color between adjacent barrier ribs is fixed. The panels are arranged opposite to each other and sealed around both panels. Glass substrates are used for the front panel and the back panel. The internal space between the panels is a discharge space for plasma discharge, and the space is filled with a discharge gas containing a predetermined rare gas component such as xenon (hereinafter referred to as “Xe”). A plurality of discharge cells are arranged on the entire panel corresponding to the region corresponding to the intersection of the pair of display electrodes and one address electrode.

  When the PDP is driven, a voltage is applied to the pair of display electrodes, the dielectric layer is dielectrically broken, and plasma discharge is generated in the discharge gas in the discharge space. The electric charge generated by this discharge accumulates in the discharge cell as wall charge, and cancels the potential of each electrode. Discharge occurs in a pulsed manner when a voltage is applied, and the electric field due to wall charges accumulated in the discharge cell is superimposed on the same polarity as the applied voltage when the potential of the applied voltage is reversed, and the applied voltage necessary to maintain the discharge is Reduced. By controlling such wall charges, it is possible to select ON / OFF of the discharge cells.

By the way, in order to give priority to the improvement of luminous efficiency, PDP originally uses Xe, which has a low excitation voltage and a long wavelength of resonance radiation ultraviolet rays, as a discharge gas to obtain ultraviolet emission. . However, when Xe is used, it is difficult to adjust the power efficiency for converting the input power into useful ultraviolet rays so as to exceed 10%.
In order to deal with such a problem, for example, as in Patent Document 1, development research has been conducted to increase the Xe partial pressure in the discharge gas and increase the total pressure of the discharge gas. By adjusting the Xe partial pressure in this way, in addition to the resonance radiation (wavelength 147 nm) from the excited Xe atom as an ultraviolet light emission source, the Xe excited dimer (hereinafter referred to as “excimer”) is simply referred to as “excimer”. It is said that a wide range of light emission centered on 172 nm can be obtained, and improvement in light emission efficiency can be expected.

This principle will be described. An excimer is a three-body reaction between an excited Xe atom and an atom in the ground state, such as Xe ^* + Xe + Xe → Xe ₂ ^* + Xe (formula 1)
Formed by. Therefore, the excimer formation probability increases rapidly as the Xe partial pressure increases. In addition, since the ground state has a repulsive potential, the excimer quickly dissociates into a single atom. Therefore, self-absorption does not occur, and high luminous efficiency can be obtained even at a relatively high gas pressure.

Xe is known to have a lower sputtering efficiency in which ions are accelerated and impact the protective layer as compared with neon and argon (hereinafter referred to as “Ne” and “Ar”, respectively). It is considered that increasing the partial pressure of Xe within this range has a positive effect on the life characteristics of the AC type PDP.
However, when Xe is used in the AC type PDP, there is a problem that the discharge voltage tends to increase.

That is, in the AC type PDP, since the display electrode pairs are sequentially covered with the dielectric layer and the protective layer, the supply of the discharge current depends on the secondary electron emission process due to the ion rush into the protective layer surface during driving. Yes.
However, Xe has a lower ionization voltage and a lower secondary electron emission coefficient than Ne or the like. Therefore, when the Xe partial pressure is increased, it is necessary to accelerate more Xe ions toward the protective layer in order to supply secondary electrons. As a result, the cathode fall voltage increases and the discharge voltage may increase. .

  An increase in the discharge voltage is not preferable because it increases the burden on the drive circuit components and increases costs such as the use of high-voltage components. In addition, as the discharge voltage rises, the ion bombardment of the buffer gas (Ne is often used) mixed with Xe on the protective layer increases, and depending on the mixing ratio, the protective layer is formed by sputtering. There is also a problem that the lifetime characteristics deteriorate due to progress of destruction.

For this problem, for example, in Patent Document 2, Ar is included in Xe instead of Ne, which has a mass number close to that of Mg atoms, to form a discharge gas. Based on the assumption that the presence of Mg ions constituting the protective layer and Ne ions having a mass number close to that of the mass number, resonance energy is transferred and the influence of sputtering becomes large, and Ne is excluded using Ar as the buffer gas. In this way, destruction of the protective layer is avoided, and both efficiency and life characteristics are achieved.
JP 2002-83543 A PCT / JP2006 / 312164

  However, in the technique described in Patent Document 1, the upper limit is to set the Xe concentration in the discharge gas to 100%, and in order to obtain a further improvement in luminous efficiency, it is necessary to increase the total pressure of the discharge gas. However, when a high-pressure discharge gas is used, the discharge voltage rises, which may cause a problem with the breakdown voltage of the drive circuit components and electrode wiring. Furthermore, a configuration that can withstand high-pressure discharge gas is required, which is difficult to realize from the viewpoint of manufacturing cost.

Further, as disclosed in Patent Document 2, when Ar is added to the discharge gas composition at a relatively large mixing ratio, the amount of Xe added must be reduced by that amount, and the effect of the above-described excimer is reduced. sell.
For this reason, the improvement in efficiency by increasing the partial pressure of Xe aiming at high efficiency in a high-definition cell has been limited to the discharge gas of Xe 100% in the conventional technology. In order to increase the efficiency further, it is necessary to increase the total pressure of the discharge gas. However, increasing the total pressure causes an increase in discharge voltage, which causes a problem of withstand voltage of drive circuit components and electrode wiring, and is difficult from the viewpoint of manufacturing cost.

  As another problem, in recent years, with the spread of high-definition television broadcasting such as terrestrial digital high-definition broadcasting, there is an increasing demand for higher definition display devices. High-definition displays inevitably involve an increase in the number of discharge cells and a reduction in the size of the discharge cells, but if the PDP discharge cells are simply reduced in size, the relative plasma wall loss due to increased bipolar diffusion Increase in the discharge voltage, and there is a risk that the discharge voltage will increase and the luminance and luminous efficiency will decrease significantly. Therefore, in manufacturing such a PDP, a discharge gas design having a high luminous efficiency and a low discharge voltage is indispensable.

As described above, in the current PDP, there is still a room to be solved for improving the light emission efficiency and suppressing the discharge voltage.
The present invention has been made in view of the above problems, and by adjusting the discharge gas composition, high luminous efficiency can be achieved at a low total pressure of the discharge gas while suppressing an increase in the discharge voltage even in a high-definition cell structure. An object of the present invention is to provide a PDP that can realize an excellent image display performance by exhibiting.

  In order to solve the above problems, the present invention is a plasma display panel in which a first substrate in which a plurality of pairs of display electrodes are disposed is opposed to a second substrate across a discharge space, The discharge space is filled with a discharge gas composed of Xe and Ar, the Ar partial pressure in the discharge gas is 0.1% to 10%, and the total pressure of the discharge gas is 20 kPa to 50 kPa. The configuration was set as follows.

  Here, when the total pressure of the discharge gas is further set to 20 kPa or more and 35 kPa or less, a suitable effect can be obtained in a relatively large discharge cell size. As the PDP in this case, each of the second substrates has a configuration in which a plurality of partition walls are provided on the surface facing the first substrate, and each of the partition walls adjacent to each other at the top of the partition walls facing the first substrate. The shortest distance between the partition walls can be set to be 80 μm or more and 170 μm or less.

  It has also been found that if the total pressure of the discharge gas is further set to 30 kPa or more and 50 kPa or less, a higher effect can be obtained in a high-definition cell. As the PDP in this case, each of the second substrates has a configuration in which a plurality of partition walls are provided on the surface facing the first substrate, and each of the partition walls adjacent to each other at the top of the partition walls facing the first substrate. The shortest distance between the partition walls can be set to be 270 μm or more and 350 μm or less.

  The Ar partial pressure in the discharge gas is preferably set to 0.1% or more and 2.0% or less in any of the above cases.

  In the PDP of the present invention having the above configuration, the Ar partial pressure in the discharge gas is adjusted to a ratio in the range of 0.1% to 10%, and the total pressure of the discharge gas is in the range of 20 kPa to 50 kPa. Since it has been adjusted, it is possible to expect an effective rise suppression effect of the discharge voltage while exhibiting good light emission efficiency as compared with the prior art. The total pressure and Ar partial pressure of the discharge gas of the present invention that can achieve both such high luminous efficiency and the effect of suppressing the increase in discharge voltage are numerical ranges found by experiments as a result of intensive studies by the present inventors.

In the PDP of the present invention, first, Xe in the discharge gas is a main component having a high concentration, and a very small amount of Ar having a partial pressure of 10% or less is added thereto, whereby a discharge gas in which the luminous efficiency in the PDP is composed only of Xe It can be improved compared to the case where it is used.
Furthermore, in the present invention, since the total pressure of the discharge gas is kept lower than a conventional value (for example, 66.5 kPa to 101 kPa), a special configuration for withstanding a high gas pressure is unnecessary, which is almost the same as the conventional one. There is an advantage that can be realized by the configuration of the PDP. Therefore, the present invention can be realized relatively easily even in the next generation PDP having a large number of discharge cells and a fine discharge cell structure.

Each embodiment of the present invention will be described below. However, the present invention is not limited to these embodiments, and can be implemented with appropriate modifications without departing from the technical scope thereof.
<Embodiment 1>
(PDP configuration example)
FIG. 1 is a schematic diagram of a discharge cell structure that is a discharge unit of PDP 1 according to Embodiment 1 of the present invention.

Here, the PDP 1 is set to a next generation high vision standard (4K2K) of 4096 × 2060 (number of pixels) with a screen size of 50 inches diagonal.
As shown in FIG. 1, the configuration of the PDP 1 is roughly divided into a first substrate (front panel 2) and a second substrate (back panel 9) that are arranged with their main surfaces facing each other.
A front panel glass 3 serving as a substrate of the front panel 2 has a pair of display electrodes 6 (scanning electrodes 5 and sustaining electrodes 4) disposed on one main surface thereof with a predetermined discharge gap (75 μm). It is formed over multiple pairs. Each display electrode pair 6 is in consideration of strip-shaped transparent electrodes 51 and 41 (thickness 0.1 μm, width 150 μm) made of a transparent conductive material such as ITO, ZnO, SnO ₂ in consideration of light extraction during driving. , Bus lines 52 and 42 (thickness: 7 μm, thickness: 2 μm to 10 μm), Al thin film (thickness: 0.1 μm to 1 μm), Cr / Cu / Cr laminated thin film (thickness: 0.1 μm to 1 μm), etc. The width is 95 μm). The sheet resistance of the transparent electrodes 51 and 41 is lowered by the bus lines 52 and 42.

Here, the “thick film” refers to a film formed by various thick film methods formed by applying a paste containing a conductive material and baking it. The “thin film” means a film formed by various thin film methods using a vacuum process including a sputtering method, an ion plating method, an electron beam evaporation method and the like.
The display electrode pair 6 may be composed of only a metal electrode from the viewpoint of cost, and a known transparent conductive material such as a ZnO-based material or a SnO ₂ -based material may be used as the transparent electrode material.

The front panel glass 3 on which the display electrode pair 6 is disposed has lead glass (PbO), bismuth oxide (Bi ₂ O ₃ ), or phosphorus oxide (PbO) having a glass softening point of about 550 ° C. to 600 ° C. over the entire main surface. A low-melting glass (thickness 35 μm) mainly composed of PO ₄ ) or a dielectric layer 7 made of SiO ₂ is formed by a screen printing method or the like.
The dielectric layer 7 has a current limiting function (charge barrier function against discharge current) peculiar to the AC type PDP, and is an element that realizes a longer life than the DC type PDP.

A protective layer 8 is disposed on the surface of the dielectric layer 7. The protective layer 8 is composed of an MgO film produced by sputtering, ion plating, vapor deposition, or the like, and protects the dielectric layer 7 from ion bombardment during discharge and reduces the discharge start voltage. For this reason, it consists of a material excellent in sputtering resistance and secondary electron emission coefficient γ.
A back panel glass 10 serving as a substrate of the back panel 9 has an Ag thick film (thickness 2 μm to 10 μm), an Al thin film (thickness 0.1 μm to 1 μm) or a Cr / Cu / Cr laminated thin film (thickness) on one main surface. A plurality of data electrodes 11 having a width of 40 μm, such as 0.1 μm to 1 μm, are arranged in parallel in a striped manner at regular intervals (95 μm) in the y direction with the x direction as the longitudinal direction so as to contain the data electrodes 11 A dielectric layer 12 having a thickness of 10 μm is coated over the entire surface of the back panel glass 9.

  On the dielectric layer 12, a partition wall having a predetermined height formed by molding and firing a low melting point glass paste (height: about 110 μm, width at the top on the front panel side: about 20 μm. The width of the top portion is about 40 μm) 13 is formed by combining the pattern portions 1231 and 1232 having a cross pattern. In this case, the pattern portion 1231 is arranged in the x direction of the panel, and the pattern portion 1232 is arranged in the stripe direction in the y direction. The barrier ribs 13 prevent the occurrence of erroneous discharge and discharge crosstalk between adjacent discharge cells 20. Here, the surface of each partition wall 13 at the top of the partition wall 13 facing the front panel 2 in the partition walls 13 facing each other and adjacent to each other (that is, between the adjacent pattern portions 1231 or the pattern portions 1232). That is, the shortest distance between (that is, the surface of the partition wall 13 excluding the phosphor layer 14) is adjusted to be 80 μm or more and 170 μm or less.

On the side surface of the partition wall 13 and the surface of the dielectric layer 19 therebetween, the phosphor layers 14 (corresponding to red (R), green (G), and blue (B) for color display using the three primary colors of light ( 14R, 14G, 14B) are formed.
The dielectric layer 12 is not essential, and the data electrode 11 may be directly enclosed by the phosphor layer 14.

The front panel glass 3 and the back panel glass 10 can be made of soda lime glass, but other translucent materials such as refractory glass such as borosilicate glass can also be used. Further, it is possible to improve the shape and accuracy by using a photosensitive paste material as the material of the partition wall 13.
The front panel 2 and the back panel 9 are disposed to face each other so that the longitudinal directions of the data electrode 11 and the display electrode pair 6 are orthogonal to each other, and the outer peripheral edges of both the panels 2 and 9 are sealed with glass frit.

  A discharge space 15 formed between the front panel 2 and the back panel 9 is filled with a Xe—Ar-based discharge gas. Here, as a feature of the first embodiment, the Ar partial pressure in the discharge gas is adjusted to a ratio in the range of 0.1% to 10% (for example, 1%), and the total pressure of the discharge gas is 20 kPa. It is adjusted to a range of 50 kPa or less (as an example, 30 kPa).

  Between the front panel 2 and the back panel 9, a space surrounded by the cross-shaped partition walls 13 is a discharge space 15. As shown by the dotted lines in FIG. 1, a pair of adjacent display electrodes 6 and one data electrode 11 correspond to each of the phosphor layers 14R, 14G, and 14B and pass through the center of the partition wall 13 in the thickness direction. A substantially rectangular parallelepiped region where the three-dimensionally intersect with the discharge space 15 interposed therebetween is the discharge cell 20 (20R, 20G, 20B). The dimensions of the discharge cell 20 are 285 μm in the x direction and 95 μm in the y direction as viewed from the center in the thickness direction (dotted line in the figure) of the barrier ribs 13 extending in the xy direction. Thus, one square pixel ((285 μm × 285 μm)) is formed by the three discharge cells 20 corresponding to the adjacent RGB colors.

As shown in FIG. 2, scan electrode driver 111, sustain electrode driver 112, and data electrode driver 113 are connected to scan electrode 5, sustain electrode 4 and data electrode 11 as drive circuits, respectively, as shown in FIG.
(PDP drive example)
The PDP 1 having the above-described configuration has an arbitrary AC voltage of several tens of kHz to several hundreds of kHz applied to the gap between the display electrode pairs 6 by a known driving circuit (not shown) including the drivers 111 to 113. A discharge is generated in the discharge cell 20, and the phosphor layer 14 is excited by ultraviolet rays from the excited Xe atoms to drive visible light emission.

  As a driving method, there is a so-called intra-field time division gradation display method. In this method, a field to be displayed is divided into a plurality of subfields (SF), and each subfield is further divided into a plurality of periods. One subfield further includes (1) an initialization period in which all display cells are initialized, and (2) each discharge cell 20 is addressed, and a display state corresponding to input data is selected and input to each discharge cell 20. The data writing period is divided into four periods: (3) a sustain discharge period for causing the discharge cells 20 in the display state to emit light, and (4) an erase period for erasing wall charges formed by the sustain discharge.

In each subfield, after the wall charge of the entire screen is initialized (reset) in the initialization period, address discharge is performed so that the wall charge is accumulated only in the discharge cells 20 to be lit in the address period, and in the subsequent discharge sustain period. By applying alternating voltage (sustain voltage) to all the discharge cells 20 at once, the discharge is maintained for a certain period of time, thereby displaying light.
Here, FIG. 3 shows an example of a driving waveform in the mth subfield in the field. As shown in FIG. 3 showing the driving waveform of the mth subfield in the field, each subfield is assigned an initialization period, an address period, a discharge sustain period, and an erase period.

  The initialization period is a period in which the wall charges of the entire screen are erased (initialization discharge) in order to prevent the influence of the previous lighting of the cells (the influence of the accumulated wall charges). In the waveform example shown in FIG. 3, a voltage higher than that of the data electrode 11 and the sustain electrode 4 is applied to the scan electrode 5 to discharge the gas in the cell. Since the charges generated thereby are accumulated on the cell wall so as to cancel the potential difference among the data electrode 11, the scan electrode 5, and the sustain electrode 4, a negative charge is applied to the surface of the protective layer 8 near the scan electrode 5 as a wall charge. Accumulated as. Further, positive charges are accumulated as wall charges on the surface of the phosphor layer 14 near the data electrode 11 and the surface of the protective layer 8 near the sustain electrode 4. Due to the wall charges, potentials formed by wall charges having a predetermined value are generated between the scan electrode 5 and the data electrode 11 and between the scan electrode 5 and the sustain electrode 4.

  The address period is a period for performing addressing (lighting / non-lighting setting) of a cell selected based on the image signal divided into subfields. In this period, when the cell is turned on, a voltage lower than that of the data electrode 11 and the sustain electrode 4 is applied to the scan electrode 5. That is, a voltage is applied to scan electrode 5 -data electrode 11 in the same direction as the potential formed by the wall charge, and a data pulse is applied in the same direction as the potential formed by the wall charge between scan electrode 5 and sustain electrode 4. Is applied to generate an address discharge (address discharge). As a result, negative charges are accumulated on the surface of the phosphor layer 14 and the surface of the protective layer 8 near the sustain electrode 4, and positive charges are accumulated on the surface of the protective layer 8 near the scan electrode 5 as wall charges. Thus, a predetermined potential is generated between sustain electrode 4 and scan electrode 5.

  The discharge maintaining period is a period in which the lighting state set by the address discharge is expanded and the discharge is maintained in order to ensure the luminance corresponding to the gradation. Here, in the discharge cell 20 in which the wall charges are present, a sustain discharge voltage pulse (for example, a rectangular wave voltage of about 200 V) is applied to each of the pair of scan electrodes 5 and the sustain electrodes 4 in different phases. As a result, a pulse discharge is generated every time the voltage polarity changes in the discharge cell 20 which is a display cell in which the display state is written.

  By this sustain discharge, a resonance line of 147 nm is emitted from the excited Xe atoms in the discharge space 15, and a molecular beam mainly composed of 173 nm is emitted from the excited Xe molecules. The surface of the phosphor layer 14 is irradiated with the resonance line / molecular beam, and display light is emitted by visible light emission. Then, multi-color / multi-gradation display is performed by a combination of sub-field units for each color of RGB. In the discharge cell 20 of the non-display cell in which the wall charge is not written in the protective layer 8, the sustain discharge does not occur and the display state is black.

In the erasing period, a gradual erasing pulse is applied to the scanning electrode 5 to erase wall charges.
(PDP discharge process)
A discharge process when the PDP 1 having the configuration of FIGS. 1 and 2 is driven based on the drive waveform of FIG. 3 will be described.

  When the PDP 1 is driven, when a predetermined AC rectangular wave pulse voltage is applied between the sustain electrode 4 and the scan electrode 5 in the display electrode pair 6, the discharge gas causes dielectric breakdown of the dielectric layer 7 in the discharge space 15. Wake up to generate plasma discharge. Positive ions (mainly Xe ions) in the plasma are directed to an electrode (for example, the sustain electrode 4) operating as an instantaneous cathode, and electrons are operated as an instantaneous anode (in this case) To the scanning electrode 5), each is accelerated and moved by the electric field. However, since the front surface of each electrode is covered with the dielectric layer 7 and the protective layer 8 that act as a charge barrier, neither electrons nor positive ions can flow into both electrodes as a conduction current. Therefore, positive ions accumulate on the surface of the protective layer 8 as wall charges having a polarity opposite to the electrode potential. The electric field created by the accumulated charges cancels out the electric field due to the voltage applied to the electrodes, so that the electric field contributing to the discharge does not exist effectively in the discharge cell 20 and the discharge stops.

  On the other hand, as shown in FIG. 3, since the pulse voltage is alternately applied to the sustain electrode 4 and the scan electrode 5 at a constant cycle, the sustain electrode 4 becomes an instantaneous anode and the scan electrode 5 becomes an instantaneous cathode after a half cycle. It becomes. At this time, the electric field generated by the charge accumulated in the previous discharge has the same polarity as the potential of the electrode, and thus is superimposed on the applied voltage. That is, at the time of voltage reversal, a voltage corresponding to the sum of the applied voltage and the voltage due to wall charges is applied inside the discharge cell 20.

As a result, the voltage applied to the discharge cell 20 can be lower than the voltage actually required for sustaining the discharge, and the pixel selection operation by the address discharge using the data electrode 11 can be performed to turn on / off with a small number of signals. Lighting control is possible.
In the PDP 1 having the above configuration, the Ar partial pressure in the Xe-Ar-based discharge gas is adjusted to a ratio in the range of 0.1% to 10% (for example, 1%), and the total pressure of the discharge gas Is adjusted to a range of 20 kPa to 50 kPa (for example, 30 kPa). For this reason, it is possible to expect an effect of suppressing a rise in the discharge voltage while exhibiting better light emission efficiency than the conventional one. The total pressure and Ar partial pressure of such a discharge gas are numerical ranges found by experiments as a result of intensive studies by the inventors of the present application.

In the PDP of the present invention, a discharge gas (using 100% Xe) in which the luminous efficiency of the PDP is composed only of Xe was used by first containing Xe in the discharge gas as a main component of high concentration and adding a small amount of Ar thereto. The case has been improved.
On the other hand, by adding a very small amount of Ar having a smaller mass number than Xe and a large secondary electron emission coefficient in the discharge gas, low secondary electron emission characteristics due to Xe alone can be obtained. Complemented by the release characteristics. As a result, it is possible to effectively suppress an increase in discharge voltage when the PDP is driven. This eliminates the need for circuit components such as a pressure-resistant IC and contributes to the reduction of manufacturing costs.

Furthermore, in the present invention, the total pressure of the discharge gas is suppressed to be lower than the conventional value (for example, 66.5 kPa to 101 kPa), so that it is not necessary to take a configuration for withstanding the high pressure gas. Therefore, there is an advantage that the present invention can be easily realized even in the configuration of the PDP similar to the conventional one.
In addition, according to the present invention, since it can be realized by appropriately adjusting the discharge gas composition and the total pressure of the discharge gas, the next generation type having a huge number of discharge cells and an extremely fine discharge cell structure. Even a PDP can be realized relatively easily. Therefore, even in these next-generation PDPs, production of PDPs having excellent high-definition image display performance can be expected by obtaining high luminous efficiency and suppressing increase in discharge voltage.
(Performance measurement experiment)
Hereinafter, a performance measurement experiment is performed on the characteristics and luminous efficiency of the discharge gas in the PDP, and the results obtained thereby will be described.

In the sample PDP used in the experiment, the size of the discharge cell was set to 285 μm × 95 μm corresponding to a 4K2K display device having a diagonal size of 50 inches. Luminous efficiency (arbitrary unit) when Xe-Ar-based discharge gas is sealed and Ar partial pressure (%) is changed at a predetermined discharge gas total pressure (20, 25, 30, 40, 50 kPa) , Maintenance voltage (V), and relative efficiency were measured.
These results are shown in FIGS. 4, 5 and 7, “efficiency 1” or “relative efficiency 1” indicates a value when Xe 100% is used as the discharge gas, and all other numerical values are expressed as relative values of the above values. . Further, the “minimum sustain voltage” indicates a minimum voltage value necessary for normal sustain discharge in all the discharge cells of the sample PDP.

In each experiment, the Ar partial pressure and the total pressure of the discharge gas were changed independently.
FIG. 4 is a graph showing the results of plotting the change in the light emission efficiency of the PDP when the Ar partial pressure is changed for each total pressure of the discharge gas in the Xe-Ar discharge gas. In the figure, when “efficiency” is 1 or more, it indicates that the luminous efficiency is better than usual.

In the graph shown in FIG. 4, it can be confirmed that the luminous efficiency increases as the total pressure of the discharge gas increases, regardless of the Ar partial pressure. In particular, good luminous efficiency is obtained when the Ar partial pressure is in the range of 0.1% to 10%. Further, it can be confirmed that in the region where the total pressure of the discharge gas is 30 kPa or more and 50 kPa or less, as the Ar partial pressure is higher, the luminous efficiency is significantly reduced.
Here, as a notable result of this experiment, when Xe is 100% in a region where the amount of Ar added to Xe is very small, that is, in a region where the Ar partial pressure in the discharge gas is 0.1% or more and 2% or less. It became clear that there was a region with higher luminous efficiency.

  FIG. 5 shown next is an enlarged graph of a portion where the Ar partial pressure is low in the graph of FIG. As shown in the figure, when the total pressure of the discharge gas is in the range of 30 kPa to 50 kPa, the Ar partial pressure is in the range of 0.1% to 10%, preferably in the range of 0.1% to 2.0%. , The luminous efficiency is particularly improved as compared with the case of 100% Xe discharge gas not containing Ar, and the peak is about 1%. In this case, the luminous efficiency is improved by about 10% at the maximum. On the other hand, such a systematic change in the luminous efficiency could not be remarkably confirmed in a region where the discharge gas has a total pressure of less than 20 kPa.

  From these results, considering only the effect on the light emission efficiency, it is considered that good results can be obtained even when the total pressure of the discharge gas exceeds 50 kPa. However, it has been found that when such a high-pressure discharge gas is used, another problem of increasing the discharge voltage occurs. Therefore, as the total pressure of the discharge gas in the present invention, the upper limit is set to 50 kPa or less to balance the discharge voltage.

  Considering the problem of the increase in the discharge voltage, it is desirable that both the maintenance of the light emission efficiency and the effect of suppressing the increase in the discharge voltage can be achieved even if the light emission efficiency is somewhat lower than in the past. From this viewpoint, in the present invention, it is preferable to set the total pressure of the discharge gas in a range of 20 kPa to 50 kPa. In this range, particularly a range of 30 kPa or more and 50 kPa or less provides a remarkable effect on the discharge efficiency.

Next, FIG. 6 is a graph plotting changes in the sustaining voltage with respect to the Ar partial pressure at a predetermined total pressure of the discharge gas in the Xe—Ar-based discharge gas. As shown in the figure, no particular increase in the discharge voltage was observed in the Ar partial pressure range (1% or more and 10% or less) in which the luminous efficiency increased.
FIG. 7 shows the “efficiency improvement rate” at each total pressure of the discharge gas for each Ar partial pressure in the range of 30 kPa to 50 kPa in total pressure in which the improvement in luminous efficiency was confirmed in the graph of FIG. The result of calculating the average value (when time is the reference) is shown. In the figure, error bars attached to each data point are standard deviations of variations in efficiency improvement rate at each total pressure. Table 1 shows a list of average values of efficiency improvement rates.

  In the results shown in FIG. 7 and Table 1, the luminous efficiency is the highest when the Ar partial pressure is around 1%, and the Ar partial pressure is about 0.1% or more (clearly 0.5% or more) and 2% or less. An improvement in luminous efficiency was obtained in the range. The tendency of the luminous efficiency gradually decreases as the Ar partial pressure increases, and settles to a luminous efficiency almost equal to that when Ar is not used (when Xe is 100%) when the Ar partial pressure is around 10%.

Therefore, in the present invention, the Ar partial pressure in the discharge gas is considered to be preferably in the range of 0.1% to 10%.
(Discussion about discharge gas)
Regarding the discharge gas, a conventional discharge process by Xe atoms and a discharge process by Xe atoms and Ar atoms of the present invention will be considered in order.

In the AC type PDP, the discharge cell 20 constitutes one pixel in the display (one pixel includes discharge cells of RGB colors and constitutes one of them). Therefore, the discharge cell is very small as a discharge light emitter.
For this reason, the electrode gap in the display electrode pair 6 is very narrow in the discharge cell. According to a well-known relational expression (Paschen's law) between the product of the discharge gap and the discharge gas pressure with respect to the discharge start voltage, in general, the gas pressure must be increased to suppress the discharge voltage. The pressure is on the order of 10 ² kPa.

In such a gas pressure region, the excited atom of Xe is a three-body collision process with another atom. Xe ^* + Xe + M → Xe ₂ ^* + M (Equation 2)
Is likely to be an excimer. Here, M is an atom in the ground state of the same Xe, or an atom in the ground state of another gas contained in the discharge, for example, Ne or Ar.
The excimer Xe ₂ ^* thus formed radiates broadband ultraviolet light having a peak near the wavelength of 172 nm (molecular beam) with high efficiency. Further, the lower level Xe ₂ radiating ultraviolet rays is unstable because it has a repulsive potential, and quickly dissociates into two Xe atoms. Accordingly, there is no loss of ultraviolet rays due to self-absorption as seen in the resonance emission line.

As is clear from (Equation 2), the excimer generation probability increases rapidly in proportion to the gas pressure, so that the emission efficiency of ultraviolet rays increases as the total pressure of the discharge gas increases. The generation probability is highest when the atoms M are the same Xe, and the efficiency increases as the Xe partial pressure increases under the same total pressure condition. Therefore, it is considered that the luminous efficiency is the highest when Xe is 100%.
However, since Xe atoms have a very low secondary electron emission coefficient with respect to magnesium oxide as a general protective layer material, the discharge voltage rises in proportion to the partial pressure of Xe. To avoid this, there is a method of adding a rare gas having a mass number smaller than that of Xe, such as Ne having a relatively high secondary electron emission coefficient with respect to magnesium oxide.

On the other hand, when a rare gas such as Ne is usually added, the amount of Xe is reduced by that amount, so that the excimer generation probability is lowered and the luminous efficiency can be lowered.
FIG. 4 of Patent Document 2 shows a result in which the Ar partial pressure is proportional to the efficiency. At first glance, it seems to contradict the relationship discussed above. However, this is because, as a result of increasing the Ar partial pressure with respect to a constant partial pressure of Xe, the total pressure of the discharge gas increased and the excimer generation efficiency increased (M in (Equation 2) becomes Ar). Yes, it should be interpreted as a result of an increase in total pressure. Further, the increase in excimer generation efficiency in this case is smaller than that in the case where the discharge gas is composed of Xe 100% and the total pressure is increased.

  Therefore, in the conventional AC type PDP, in order to give priority to the light emission efficiency, a configuration in which the discharge gas pressure is increased as much as possible after the discharge gas is configured with Xe 100% is ideal. On the other hand, when the discharge gas pressure is increased, the discharge voltage of the PDP tends to increase, and it is necessary to consider toled off with the life characteristics. Such a problem related to the design of the discharge gas is an important matter, particularly in the case of an AC type PDP having an ultra-high-definition cell size such as 4K2K, which is related to a substantial decrease in luminous efficiency.

Next, the discharge process of the discharge gas of the present invention will be described. When a small amount of Ar is added to Xe, there is a mechanism in which the efficiency increases only in a specific range where the Ar partial pressure is small. This mechanism will be discussed below with reference to FIGS.
FIG. 8 is a diagram schematically showing energy levels of Xe atoms and reaction processes (A) to (F). FIG. 9 is a diagram schematically showing the energy levels of Xe atoms and Ar atoms and the reaction process (G).

The Xe atom is ionized when energy of 12.13 eV is obtained from the electron by collision with the electron, and becomes Xe ion. This reaction is the direct (collision) ionization process shown by the reaction process (A) in FIG.
Xe + e → Xe ⁺ + 2e (Equation 3)
It is represented by

In addition, the excitation level group having the lowest energy represented by 6s in FIG. 8 includes high-efficiency including ultraviolet light having a wavelength of 147 nm called a resonance line and ultraviolet light having a wavelength of 172 nm derived from an excimer called a molecular beam. Of particular importance for generating luminescence. This is usually the direct (collision) excitation process indicated by the reaction process (B) in FIG. 8 Xe + e → Xe ^* (6s) + e (4)
Excited by

  By the way, the ionization energy of the Xe atom is 12.13 eV, and the excitation energy of the lowest excitation level group 6s is also about 8.4 eV. For example, this is a cause of lower luminous efficiency than mercury (ionization energy 10.38 eV, excitation energy about 4.8 eV) often used in fluorescent lamps for general illumination. Therefore, in order to maintain plasma discharge with good luminous efficiency in the PDP, it is necessary that a high energy electron group exists in the discharge space.

For this reason, plasma acts to lower the electron density and increase the average electron energy (electron temperature) by itself, so that the probability of the reaction process (B) occurring as a result is increased, and high ultraviolet light emission efficiency is obtained. It is done.
However, when the voltage applied to the PDP is increased, the density of excited level atoms increases as the current increases. The Xe atom is characterized in that the energy difference between the lowest energy level 6s and 6s' and the level immediately above is small. In FIG. 8, for example, the difference between the 6s ′ and 6p levels is 1 eV or less. Therefore, even in collisions with low energy electrons, the Xe atoms are in the multi-stage excitation process shown in the reaction process (C) of FIG. 8 (where Xe ^** is a higher level than Xe ^* ).
^{Xe * + e → Xe ** +} e · · · ( Equation 5)
The probability of being excited to a higher energy excitation level is high.

Note that the energy interval between atomic levels becomes narrower as the energy level increases between excited levels. Therefore, every time an atom repeats the reaction process (C), it is excited to a higher energy, and finally the accumulated ionization process shown in the reaction process (D) Xe ^** + e → Xe ⁺ + 2e. 6)
It is ionized through. As shown in FIG. 8, 2 eV or less is sufficient for the electron energy in the process of such multistage excitation → accumulation ionization of atoms.

By the way, in the AC type PDP in the present invention, the Xe partial pressure is set high (90% or more and 99.9% or less) in order to maintain the luminous efficiency as described above. For this reason, collisions between Xe atoms and ions frequently occur in the plasma, and the Xe ions are converted into the ion conversion process shown in the reaction process (E) Xe ⁺ + 2Xe → Xe ²⁺ + Xe (7)
Through the Xe molecular ion Xe ²⁺ . Xe molecular ions eventually dissociate and recombine with electrons (reaction process (F)).
Xe ²⁺ + e → Xe ^** + Xe (Equation 8)
Then, the Xe atom returns to the Xe atom, but at that time, it becomes a high-energy excited level atom in the vicinity of the lowest energy level (about 11-12 eV) of the Xe molecular ion. Since this level of energy is close to ionization energy (12.13 eV), it can be easily re-ionized by collision with low-energy electrons. In addition, the ionization is due to the high Xe gas pressure, auto-ionization process Xe ^** + Xe due to the collision between the excited level atom ^{* → Xe + + Xe · ·} · ( Equation 9)
Also happens. In this ionization process, no electrons are required.

By passing through each of these ionization processes, the plasma discharge can be satisfactorily maintained by the cycle (referred to as cycle II) shown by the broken line in FIG. 8 in the PDP of the present invention.
In cycle II, high energy electrons are not required to form ion-electron pairs as described above. Therefore, the electron temperature in the plasma decreases and the electron density increases. As a result, the direct excitation process to the 1s level important for ultraviolet light emission is less likely to occur, and if the discharge gas is composed of Xe 100%, the light emission efficiency may be reduced.

However, in the Xe-Ar discharge gas of the present invention in which a small amount of Ar is present in Xe, it can be inferred that a phenomenon different from the above occurs. As shown in the energy level of the Ar atom in FIG. 9, the lowest excited level group of the Ar atom is in the vicinity of 11.5 eV, and the energy level of the Xe atom recombined just by the above-described reaction process (F). Close to. Between these energetically close states, the resonance excitation process shown in reaction process of FIG. ^{9 (G) Xe ** + Ar} → Xe + Ar * · · · ( Equation 10)
Can happen.

  When the reaction of (Formula 10) occurs, even if the Xe molecular ion is recombined, the high energy excited level atom passes energy to Ar and returns to the ground state, so it is high to be ionized again from there. Energy electrons are needed. Therefore, to maintain the plasma discharge, the electron density must be lowered and the electron temperature raised. As a result, it is considered that the excitation efficiency to the 6s level of Xe increases (because the electron temperature increases and the number of high energy electrons relatively increases), and the luminous efficiency increases.

  In order to confirm the validity of the above consideration, the present inventors conducted a discharge experiment using krypton (about 10 eV) whose lowest excitation energy is lower than that of Ar. When krypton was added, the excitation level energy was considerably lower than the excitation energy after recombination of the Xe molecular ions, and resonance excitation was unlikely to occur, so it was expected that the same effect as Ar could not be obtained. From the experimental results, no increase in efficiency was observed as expected.

This resonance excitation process is limited to extremely low density of atoms (Ar in the present application) that obtain energy from excited atoms, such as the Penning effect of (Ar + mercury) mixed gas in a fluorescent lamp. It can be expected that the effect is expressed only at the mixing ratio. However, it is not easy to theoretically estimate the range, and it is only possible to determine the range in which the effect of the present invention can be obtained only after actually making a sample and conducting a number of experiments.
(Embodiment 2)
The PDP according to the second embodiment will be described focusing on differences from the first embodiment.

  The basic structure of the PDP of the second embodiment is the same as that of the PDP 1, but the discharge cell size is relatively large. The dimensions of the discharge cell 20 are 675 μm × 300 μm, which corresponds to a 42-inch diagonal HD (720p) display device, and each pixel has a size of 675 μm × 900 μm. In the second embodiment, each of the partition walls 13 that face each other and are adjacent to each other (that is, the pattern parts 1231 that face each other adjacent to each other or the pattern parts 1232), each at the top of the partition wall 13 that faces the front panel 2. The shortest distance between the surfaces of the barrier ribs 13 (that is, the surface of the barrier ribs 13 excluding the phosphor layer 14) is adjusted to be 270 μm to 350 μm.

Further, the total pressure of the Xe-Ar discharge gas is in the range of 20 kPa to 35 kPa, and the Ar partial pressure in the discharge gas is 0.1% to 10% (particularly 0.1% to 2. A range of 0% or less is preferable.
In the PDP according to the second embodiment having such a configuration, the total pressure of the discharge gas can be further reduced as compared with the PDP 1, while exhibiting excellent light emission efficiency and suppressing an increase in the discharge voltage as with the PDP 1. Both effects can be achieved.

  Here, in order to consider the reason why the effect of the second embodiment can be obtained, the Xe-Ar discharge gas is sealed in the sample PDP (discharge cell size is set to 675 μm × 300 μm) as in the above performance measurement experiment. Then, the luminous efficiency (arbitrary unit) and relative efficiency when the Ar partial pressure (%) and the total pressure of the discharge gas were changed were measured. The measurement results regarding the Ar partial pressure dependency are shown in FIGS. In each experiment, the Ar partial pressure and the total pressure of the discharge gas were changed independently.

  FIG. 10 is a graph showing the results of measuring the Ar partial pressure dependence of the luminous efficiency for each total pressure in a PDP using a Xe—Ar-based discharge gas, as in FIG. 4. FIG. 11 is a graph showing the relationship between Ar partial pressure and relative efficiency in the PDP. First, in the graph of FIG. 10, unlike the small discharge cell shown in FIG. 4, the discharge gas has a lower total pressure (that is, a region of 20 kPa to 35 kPa) and an Ar partial pressure of 0.1. It can be seen that in the region of 1% or more and 10% or less, the luminous efficiency is relatively higher than when Xe 100% is used (Ar is not used). Here, FIG. 10 does not show a curve when the total pressure of the discharge gas is “35 kPa”, but considering the region between the curves of 20 kPa and 40 kPa, the upper limit of 35 kPa is set as the total pressure. Is reasonable.

In addition, as shown in the graph of FIG. 11, such a tendency in luminous efficiency can be confirmed notably in the region where the Ar partial pressure is 0.1% or more and 2.0% or less.
On the other hand, in FIG. 4, a remarkable improvement in luminous efficiency was seen at a high discharge gas total pressure of 40 kPa or higher. However, such a tendency was not seen in FIG. 10, and became gentle particularly in a range higher than 35 kPa. Yes.

  The reason why such an experimental result was obtained will be considered. In the PDP of the second embodiment, since the discharge cell 20 is relatively large, the distance between the plasma generated in the discharge space 15 and the partition wall 13 is increased, and it is considered that the loss of ions due to bipolar diffusion is small. In this case, if the discharge gas has the same total pressure, the longer the dimension of the discharge cell 20, the longer the time during which ions are present in the plasma. On the other hand, since the loss due to ambipolar diffusion decreases as the total pressure increases, the time during which ions exist in the plasma also increases. If ions are present for a long period of time, the secondary electron emission characteristics are enhanced, and the increase in discharge voltage can be expected. Further, since ultraviolet rays are abundantly generated, good results can be obtained in terms of luminous efficiency.

  Therefore, in the PDP of the second embodiment, in order to make the existence ratio of ions in plasma equal to that of PDP 1 so that the reaction of (Equation 10) assumed in the discharge cell 20 occurs efficiently, the total pressure is set to Lowering to increase loss due to ion diffusion. As a result, the PDP achieves good image display performance in terms of improving the luminous efficiency and suppressing the increase of the discharge voltage in the same manner as the PDP 1 under the conditions of the low total pressure of the discharge gas and the Ar partial pressure. It is a thing.

In addition, as described above, in the energy transfer process such as the resonance excitation process assumed in the present invention, the balance of the density of each ion or atom is important, and these are in a limited appropriate range. Only has an effect.
By taking such a balance, the PDP of the second embodiment having a relatively large discharge cell 20 exerted a remarkable effect on the improvement of the light emission efficiency and the discharge voltage in the region where the total pressure of the discharge gas is low. It is considered a thing.

  The PDP of the present invention can be used for a display device used for a television apparatus and a computer display in a transportation facility, public facility, home, etc., and in particular, a PDP for an ultra-high-definition video display device that requires high luminous efficiency. Available to:

It is a schematic diagram which shows the structure of AC type PDP which concerns on Embodiment 1 of this invention. It is a schematic diagram which shows the relationship between each electrode and a driver. It is a figure which shows the drive waveform example of PDP. FIG. 6 is a graph showing a result of plotting, for each total pressure of a mixed gas, a change in light emission efficiency of the PDP of Embodiment 1 when an Ar partial pressure is changed in a Xe—Ar-based discharge gas. It is the graph which expanded the part with low Ar partial pressure in FIG. 6 is a graph plotting a change in discharge sustaining voltage with respect to an Ar partial pressure at a predetermined total pressure of a discharge gas in a Xe-Ar discharge gas. In the graph of FIG. 5, it is a graph which shows the result of having calculated the average value of the efficiency improvement rate in each total pressure of discharge gas for every Ar partial pressure in the range whose discharge gas total pressure is 30 kPa or more and 50 kPa or less. It is a figure which shows typically the energy level and reaction process of Xe atom for demonstrating the effect of this invention. It is a figure which shows typically each energy level and reaction process of Xe atom and Ar atom for demonstrating the effect of this invention. 6 is a graph showing the results of measuring the Ar partial pressure dependence of luminous efficiency for each total pressure in the PDP of Embodiment 2. 6 is a graph showing the relationship between Ar partial pressure and relative efficiency in the PDP of the second embodiment.

Explanation of symbols

1 PDP
2 Front panel 4 Sustain electrode 5 Scan electrode 6 Display electrode pair 7, 12 Dielectric layer 8 Protective layer
9 Back panel 11 Data electrode 13 Bulkhead 14 Phosphor layer 15 Discharge space

Claims (6)

The first substrate in which a plurality of pairs of display electrodes are disposed is a plasma display panel disposed to face the second substrate across the discharge space,
The discharge space is filled with a discharge gas composed of Xe and Ar,
A plasma display panel, wherein an Ar partial pressure in the discharge gas is 0.1% to 10% and a total pressure of the discharge gas is 20 kPa to 50 kPa. The plasma display panel according to claim 1, wherein a total pressure of the discharge gas is 20 kPa or more and 35 kPa or less. The plasma display panel according to claim 1, wherein a total pressure of the discharge gas is 30 kPa or more and 50 kPa or less. The second substrate is provided with a plurality of partition walls on the surface facing the first substrate,
3. The plasma display panel according to claim 2, wherein, in the partition walls facing each other, the shortest distance between each partition wall surface at the top of the partition wall facing the first substrate is 80 μm or more and 170 μm or less. The second substrate is provided with a plurality of partition walls on the surface facing the first substrate,
4. The plasma display panel according to claim 3, wherein, in the partition walls facing each other and adjacent to each other, the shortest distance between each partition wall surface at the top of the partition wall facing the first substrate is 270 μm or more and 350 μm or less. The plasma display panel according to any one of claims 1 to 5, wherein an Ar partial pressure in the discharge gas is 0.1% or more and 2.0% or less.

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