Discharge characteristics and low‐voltage driving of high‐Xe‐content PDPs

Abstract— High‐Xe‐content PDPs attain improved luminous efficiency, but with sacrifices of higher sustain and address voltages and slower discharge build‐up. By examining PDPs with 3.5–100% Xe contents, it was revealed that space‐charge priming as well as wall‐charge accumulation are effective in obtaining low‐voltage and high‐speed operation. In addition, it was found that the effectiveness is emphasized for higher‐Xe‐pressure PDPs. In this respect, erase addressing is more favorable than write addressing, especially for high‐Xe‐pressure PDPs. The formative time lag of the discharge and diffusion/drift of the space charges are shorter for high Xe contents. In this respect, high‐Xe‐content PDPs have a potential for high‐speed addressing, if driven adequately. The use of space‐charge priming, however, is limited by the duration between the priming and scan pulses. Accumulation of wall charges is limited by ignition of a self‐erase discharge with which all the wall charges are dissipated. Although the highest efficiency and luminance are attained with a 100%‐Xe panel, the optimum Xe gas content, considering the sustain pulse voltage and drive voltage margin, would be 70% Xe + Ne.     

High‐speed low‐voltage driving of high‐Xe‐content PDPs with priming particles

Abstract— Power savings, image‐quality improvement, and cost reduction are the major issues facing PDP development. High‐Xe‐content PDPs have attained improved luminous efficiency, but with sacrifices in higher switching and sustain voltages and slower discharge build‐up. By examining PDPs having 3.5%–30% Xe content, it was found that utilization of the space‐charge priming effect as well as wall‐charge accumulation are effective in obtaining a low operating voltage and a high switching speed. The improvements are enhanced for higher Xe pressures. By using space‐charge priming, the statistical time lag of the discharge triggering for the 30% Xe content is reduced significantly and becomes approximately equal to that of 3.5% Xe content. Once triggered, the formative time lag of the discharge becomes shorter and the space charge experiences diffusion/drift; hence, accumulation of the wall charge is faster for discharges with higher Xe contents. These indicate that the use of an erase addressing scheme, rather than a write addressing scheme, is preferable when driving high Xe‐content PDPs, because the erase addressing scheme provides the addressing operation with an abundant amount of priming particles. Also, the drive voltages are lower for the erase addressing scheme. In order to reduce the address voltage, it is effective to accumulate wall charges prior to addressing. It was found that there are limiting values for the charge accumulation, above which self‐erase discharges ignite and the wall charge is dissipated. The self‐erase discharge occurs at relatively low wall voltages when the Xe percentages becomes higher. The sustain pulse voltage can be reduced while keeping the luminous efficiency high by increasing the sustain pulse frequency. As the frequency is increased, a residual amount of space charge created by the preceding sustain pulse increases. Due to the priming effect of these space charge, the build‐up of the discharge current becomes faster, resulting in a lower voltage.     

Discharge analysis of high‐efficacy PDP with a luminous efficacy of 5 lm/W

Abstract— The discharge mechanism concerning the width of the display electrodes in high‐Xe‐content gas mixtures to improve the luminous efficacy of PDPs has been researched. It was found that a luminous efficacy of 5 lm/W was realized for a high‐Xe‐content gas mixture and narrower display electrodes. For a high‐Xe‐content gas mixture, the luminous efficacy increases as the display electrode becomes narrower. This phenomenon was analyzed by observing the emission from a discharge cell. The observation data indicate that a high electron heating efficiency contributes to increased luminous efficacy along with narrow electrodes for a high‐Xe‐content gas mixture as well as high excitation efficiency.     

The 121‐contiguous‐subfield addressing of high Xe‐content PDPs

Abstract— As the Xe content of PDPs is increased, the space‐charge priming becomes more effective. Also, the diffusion/drift of the space charges and accumulation of the wall charges becomes faster. These facts indicate that the use of an erase addressing is preferable for high‐Xe‐content PDPs. A 30%‐Xe green test panel was driven with contiguous subfields using erase addressing and a grouped Address‐While‐Display scheme. Crosstalk was suppressed by driving the odd and even sustain electrodes separately. The fast addressing speed of 0.283 μsec allowed for 121 subfields and 122 gray levels, with a resultant luminance of 4200 cd/m² and a dark‐room contrast of 310:1. The scan and data pulse voltages were as low as 90 and 75 V, respectively. All the subfields had an identical length of 136 μsec, but the number of sustain pulses in these subfields could be varied between 2 and 20. By selecting an adequate number of sustain pulses in the subfields, arbitrary gamma characteristics could be realized. A gray‐scale expression having a constant difference between the consecutive “perceived” luminance levels was verified throughout all the luminance levels.     

Effects of Xe content on wall‐voltage variation during address period in AC plasma‐display panel

Abstract— To investigate the influence of the gas condition, especially xenon (Xe) gas, on the wall‐voltage variation in relation to the electric‐field intensity during the address period, the wall voltages were measured under various Xe‐gas content ranging from 11 to 20% by using the V^t closed curve analysis method. It was observed that under a weak electric‐field intensity between the scan and address electrodes, the change in Xe content did not affect the wall‐voltage variation, even at a higher panel temperature of 65δC. However, under a strong electric‐field intensity, the wall‐voltage variations were reduced with an increase in the Xe content, confirming that a higher electric‐field intensity would be required to induce the wall‐voltage variation at a higher Xe content during the address period.     

High‐efficacy plasma‐display designs achieving 5 lm/W

Abstract— Under high‐Xe‐content conditions, the luminous characteristics were evaluated for the sustaining electrode width and the sustaining pulse cycle. It was recognized that the proper designs for them in a high‐Xe‐content gas mixture make it possible to obtain high luminous efficacy. In this research, it was found that narrower electrodes can gain higher luminous efficacy in high‐Xe‐content conditions. The dependency of the luminous characteristics on the electrode width was analyzed and the differences of discharge phenomena from low‐Xe‐content conditions, which explain the dependency on the electrode width, were recognized. In an 8‐in. test panel, 5.2 lm/W of the maximum white efficacy was obtained. The found phenomenon that narrower electrodes are more advantageous for the luminous efficacy is favorable in high‐definition PDPs.     

High‐frequency drive of high‐Xe‐content PDPs for high efficiency and low‐voltage performance

Abstract— It has been well known that the luminous efficiency of PDPs can be improved by increasing the Xe content in the panel. For instance, the efficiency is improved by a factor 1.7 when the Xe content is increased from 3.5% to 30%. The sustain pulse voltage, however, increases from 180 to 230 V by a factor 1.3. It was found that the increase in the sustain pulse voltage can be suppressed by increasing the sustain pulse frequency. The high‐frequency operation further increases the luminous efficiency. If the Xe content is increased from 3.5% to 30% and the drive pulse frequency is increased from 147 to 313 kHz, the luminous efficiency becomes 2.7 times higher and the luminance 4.5 times higher. Furthermore, the increase in the sustain pulse voltage is suppressed 1.1 times, from 180 to 200 V. A mechanism of attaining high efficiency and low‐voltage performance can be considered as follows. A train of pulses is applied during a sustain period. As the sustain pulse frequency is increased, the pulse repetition rate becomes faster and a percentage of the space charge created by the previous pulse remains until the following pulse is applied. Due to the priming effect of these space charge, the discharge current build‐up becomes faster, the width of the discharge current becomes narrower, ion‐heating loss is reduced, and the effective electron temperature is optimized so that Xe atoms are excited more efficiently. The intensity of Xe 147‐nm radiation, dominant in low‐pressure Xe dis‐charges, saturates with respect to electron density due to plasma saturation. This determines the high end of the sustain pulse frequency.     

New high‐luminance 50‐ and 43‐in. ACPDPs with an improved panel structure

New 50‐ and 43‐in. ACPDPs, which have been developed and commercialized in 2001, show high luminance with improved cell structure and higher Xe‐content gas. The specific features of the cell structure are “T”‐shaped electrodes and waffle‐structured ribs, which are same as those of the previous model. Both the cell structure and gas conditions have been optimized. New green and blue phosphors have also been adopted. As a result, the luminous efficacy has been improved up to 1.8 lm/W by using a black stripe. The peak luminance of the 50‐ and 43‐in. PDPs have reached 900 and 1000 cd/m², respectively, while the power consumption of the 50‐in. PDP has been decreased to 380 W, which is 20% lower than that of our previous 50‐in. PDP.     

Characterization of micro‐cell discharge in AC‐PDPs by spatio‐temporal optical emission spectroscopy

Abstract— We have developed highly resolved spatio‐temporal optical emission spectroscopy to investigate the discharge characteristics of coplanar type ac plasma‐display panels (AC‐PDPs). Spatio‐temporal emission profiles were measured for relevant lines of atomic He, Ne, Xe, and ionic Xe in He‐Xe and Ne‐Xe systems with various Xe concentrations and total gas pressures. The surface‐discharge behavior in coplanar PDPs has been clarified.     

Discharge properties and chemical stability of SrZrO films

Abstract— MgO thin film is currently used as a surface protective layer for dielectric materials because MgO has a high resistance during ion sputtering and exhibits effective secondary electron emission. The secondary‐electron‐emission coefficient γ of MgO is high for Ne ions; however, it is low for Xe ions. The Xe content of the discharge gas of PDPs needs to be raised in order to increase the luminous efficiency. Thus, the development of high‐γ materials replacing MgO is required. The discharge properties and chemical surface stability of SrO containing Zr (SrZrO) as the candidate high‐γ protective layer for noble PDPs have been characterized. SrZrO films have superior chemical stability, especially the resistance to carbonation because of the existence of a few adsorption sites due to their amorphous structure. The firing voltage is 60 V lower than that of MgO films for a discharge gas of Ne/Xe = 85/15 at 60 kPa.     

Protective layer for high‐efficiency PDPs driven at low voltage

Abstract— The sustain pulse voltage of a panel for 66‐kPa Ne + Xe (5–30%) with an (SrCa)O protective layer is 20–40% lower than that with an MgO protective layer. The luminous efficiency of the panel with a Ne + Xe (30%) (SrCa)O protective layer is 1.5 times that of the conventional panel with a Ne + Xe (10%) MgO protective layer; the sustain pulse voltages of these panels are almost the same. The power loss caused by panel capacitance is proportional to the second power of the sustain pulse voltage. Using the (SrCa)O protective layer for Xe (5–30%), the power loss is reduced by 35–60% compared with the MgO protective layer. It follows that, using the (SrCa)O protective layer, we can increase the Xe content with little power loss and thus achieve high‐efficiency PDPs. As for MgO and CaO with Xe ions, electrons are probably ejected from only the defect states. On the other hand, as for the SrO with Xe ions, it is likely that electrons can be ejected from not only defect states but also the valance band. This seems to be the reason why the driving voltage is lower with the (SrCa)O protective layer than with the MgO protective layer.     

Electron‐beam deposition of MgO on plastic substrate and manufacturing flexible flat fluorescent lamp

Abstract— A flexible fluorescent lamp that utilizes the same plasma discharge mode as in PDPs has been manufactured. The structure of the flexible lamp is simple and easy to manufacture. All‐plastic materials including plastic substrates, barrier ribs (spacers), and sealants for low‐temperature manufacturing processing have been adopted except for the phosphor and MgO thin film. The MgO thin films were coated on the plastic substrates as a protection layer against the plasma discharge. The adhesion and biaxial texture of MgO thin film deposited on the plastic substrates, poly‐ethyle‐nenaphthalate (PEN) and polycarbonate (PC), at low temperature (100–180°C) has been characterized. The MgO film on PEN shows good adhesion under a repeated bending test. The manufactured flexible lamp consists of two plastic substrates of about 3 in. on the diagonal, barrier rib (spacer), and external ITO electrodes. The Ne‐Xe (5%) gas mixture at 100–200 Torr was used for the discharge gas. A maximum surface luminance of about 100 cd/m² was achieved for a 1 ‐kHz AC pulse.     

Use of self‐erase discharges for high‐speed and low‐voltage addressing of PDPs

Abstract— A technique called “self‐erase‐discharge addressing” has been incorporated with a address‐while‐display driving scheme, contiguous subfield, and erase addressing to obtain high‐speed and low‐voltage addressing of PDPs. The technique uses a relatively high X‐sustain pulse voltage VXsus, which produces a weak self‐erase discharge at its trailing edge. An application of a data pulse Vdata synchronous to a weak self‐erase discharge results in full erase discharge and eliminates all the wall charges. The technique assures a wider operating‐voltage margin since it provides identical amounts of priming charges as well as wall charges to all the horizontal scan lines just prior to addressing. The priming charges are generated by the weak self‐erase discharges, resulting in low Vdata of 30 V and a high addressing speed of 0.66 μsec for a Ne + 10% Xe PDP. V_Xsus = 245 V, and the voltage margins of Vdata and VXsus were 35 and 16 V, respectively. For a 30% Xe PDP, Vdata and VXsus were 30 and 335 V, respectively, with an addressing speed of 1.0 μsec. In order to obtain high dark‐room contrast, it is essential to use ramp reset pulses, with which erase addressing cannot be achieved. By adopting the write addressing only to the first subfield and the self‐erase‐discharge addressing to the subsequent subfields, a peak and background luminance in green of 3100 and 0.22 cd/m², respectively, were obtained with a dark‐room contrast of 14,000:1. The number of subfields was 28, and the light emission duty was 83%. The number of ramp reset pulse drivers could be reduced to 12 by adopting the common reset pulse technique.     

Influence of He‐Ne‐Xe gas composition on vacuum ultraviolet ray spectra in plasma‐display panels

The vacuum ultraviolet (VUV) ray emission characteristics for plasma‐display panels (PDPs) were studied with respect to various three‐component (He‐Ne‐Xe) and two‐component (He‐Xe and Ne‐Xe) gas systems. In the 4% Xe‐25% Ne‐He balance and 4% Xe‐He balance, an increase in the pressure contributed to an increase in the 147‐nm atomic emission, and above a certain point this decreased, while in the 4% Xe‐Ne balance it was saturated. The 172‐nm dimer emission showed a nearly linear increasing behavior with pressure and Xe content irrespective of its composition. In the various Xe with 25% Ne‐He balance gases, it was shown that total integrated VUV intensity can directly represent the luminance of real panels with the same gas compositions. Xe‐content variation showed similar characteristics of VUV emission as pressure variation both in two‐component (various Xe‐Ne balance) and three‐component (various Xe‐25% Ne‐He balance) systems. Therefore, different compositions with the same Xe partial pressure showed nearly the same optical properties. For the case of Ne content variation with 4% Xe, the 147‐nm peak increased and the 172‐nm peak decreased to 85% Ne, but above this point both intensities decreased.     

High‐efficiency PDP micro‐discharges

Abstract— High‐efficiency plasma‐display‐panel micro‐discharge characteristics will be discussed. An increase in the discharge efficiency for a higher‐Xe‐content gas mixture is well known. In this article, the interdependency of the capacitive design, the sustain voltage, and the Xe content will be discussed. A high panel efficacy was obtained, especially for the design and driving conditions that govern the development of a fast discharge. A fast discharge was observed for a higher discharge field at sustain voltages higher than 200 V. A +C‐buffer design, where the extra capacitance acts as a local on the panel power source that lowers the voltage decrease inherent to the discharge of the discharge capacitance upon firing, and efficient priming of the discharge at higher sustain frequency, also stimulates a fast‐discharge development. Apparently, a “high‐efficiency fast‐discharge mode” exists. It is proposed that in this mode the cathode sheath is not, or incompletely, formed during the increase in the discharge current, and the electric field in the discharge cell is dominated not by the space charges but by the externally applied voltage. The effective discharge field is lowered, resulting in a lower effective electron temperature and more efficient Xe excitation. Also, under a fast discharge build‐up condition, the electron‐heating efficiency increases, due to a decrease in the ion heating losses in the cathode sheath. In a 4‐in. color plasma‐display test panel, operating in a high‐efficiency discharge mode and containing a 50%Xe in Ne gas mixture, a panel efficacy of 5 lm/W concurrent with a luminance of 5000 cd/m² was realized. This result was obtained at a sustain voltage of 260 V. These data compare favorably with alternative high‐efficacy panel design approaches.     

High‐luminance and highly luminous‐efficient AC‐PDP with DelTA cell structure

To improve PDP performance, we developed an AC‐PDP with the Delta Tri‐Color Arrangement (DelTA) cell structure and arc‐shaped electrodes. The experimental panel has a pixel pitch of 1.08 mm and luminous efficacy of 3 lm/W at a luminance of 200 cd/m² despite its conventional gas mixture of Ne and Xe (4%) and conventional phosphor set. Moreover, its peak luminance can be greater than 1000 cd/m². The strong dependence of luminous efficacy on the sustain voltage is also discussed in this paper.     

ALIS method for high‐resolution color PDPs

This paper describes the Alternate Lighting of Surfaces (ALIS) method as a promising drive technology which can lead to high‐resolution plasma‐display panels (PDPs). This technology provides a resolution of more than 1000 scanning lines without lowering luminance, thus enabling the essential requirements of HDTV. Moreover, it allows the number of scanning electrodes to be halved in comparison with the conventional method, as well as the circuit scale to be minimized due to the use of the single scanning drive. The ALIS method is expected to be a key technology that will help PDPs penetrate the TV market.     

Dependency of PDP efficacy on gas pressure

The dependency of the efficacy of an alternating‐current surface‐discharge plasma‐display panel (PDP) on the gas pressure was investigated for several Xe‐Ne gas mixtures. Also, the sustain voltage was varied. Monochrome 4‐in. test panels, with a design which resembles the one used in mainstream commercial products, were used. The experimental panel efficacy and emission characteristics were compared to the results of a numerical discharge model. A strong increase in the efficacy for increasing voltage was found in high‐gas‐pressure mixtures with a high Xe concentration. An increase in the electron‐heating efficiency and of the Xe‐excitation efficiency contribute, about equally, to the increase in efficacy. The increase in the Xe‐excitation efficiency is due to an increase in the excitation in the lower Xe levels induced by a lowering of the electron temperature. The contribution of the increasing Xe‐dimer radiation fraction to the efficacy improvement is relatively small. These results imply an efficient panel design comprised of the combination of a high Xe concentration, a high gas pressure, and a high sustain voltage. A high luminance and a high efficacy are concurrent for such a design. A 4‐in. test panel containing a mixture of 13.5% Xe in Ne at 800 hPa has been realized, demonstrating a white luminance of 2600 cd/m² and an efficacy of 3.1 lm/Wfor continuous operation at 50 kHz and 230 V.     

Influence of barrier‐rib morphologies on PDP efficacy

Abstract— In this study, the effects of barrier‐rib morphology on the luminance efficacy of PDPs were examined. Barrier ribs such as stripe, waffle, rectangular, honeycomb, SDR, and inverse SDR types were prepared using the capillary molding process. By using rear plates with such barrier ribs, the luminance and its efficacy were measured. The results demonstrated the feasibility of a capillary molding process in fabricating high‐efficacy PDP discharge cells.     

Time‐averaged spatial profile of Xe excitation efficiency in PDPs

Abstract— The Xe excitation efficiency for various Xe content was analyzed by monitoring the panel luminance and IR emission intensity. It was found that dependences of the Xe excitation efficiency and luminous efficacy on the sustain voltage show almost the same tendency. A decrease for increasing sustaining voltage was found in a low‐Xe‐content panel and an increase was found in a high‐Xe‐content panel. A reduction in the effective electron temperature and a reduction in plasma saturation contribute to the efficacy improvement. The time‐averaged spatial profile of the Xe excitation efficiency in PDPs was investigated by measuring the distribution of IR and blue‐phosphor emissions. The results show that the Xe excitation efficiency is similar in the cathode and anode regions even though the spatial and time development of the discharge in these regions is very different. An extended theory that takes into account not only the radiative transition process but also the collisional de‐excitation process from Xe** to Xe* is proposed for investigating the pressure dependence of the Xe excitation efficiency. By using the proposed theory, it was found that Xe excitation efficiency increases, attains a maximum value at 30% Xe, then decreases as the Xe content is increased, when the rate coefficient of the collisional de‐excitation process is less than 1.0 × 10^?10 cm³/sec.