High‐efficacy drive of spatial positive‐column‐discharge PDP with delayed D pulses

Abstract— A thick‐film ceramic‐sheet PDP provides a long sustain discharge gap of 0.45 mm, enabling the use of positive column discharges. The discharges are established in the middle of the discharge space and are completely free from touching the surface of substrates. This allows for the reduction in diffusion losses of the charged particles. To further improve the efficacy, delayed D pulses are applied to the address electrodes during the sustain period. Although the pulses only draw a little current, they perturb the electric field, reducing the peak discharge current and hence resulting in higher efficacy and luminance. The efficacy and luminance increase by 35% and 38%, respectively, with the delayed D pulses. These pulses are incorporated into the contiguous‐subfield erase‐addressing drive scheme for TV application. A short gap of 70 μm between the sustain and data electrodes generates a fast‐rising discharge and allows a high‐speed addressing of 0.25 μsec. This provides 18 contiguous subfields for the full‐HD single‐scan mode, with 70% light emission duty. A luminous efficacy of 6.0 lm/W can been attained using Ne + 30% Xe 47 kPa, a sustain voltage of 320 V, and a sustain frequency of 3.3 kHz, when the luminance is 157 cd/m². Alternatively, the panel can achieve 4.2 lm/W and 1260 cd/m² by increasing the sustain frequency to 33 kHz.     

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.     

Characteristics of a high‐Xe‐concentration 4‐in. PDP

The performance of two 4‐in. color PDP test panels with a default and a high‐Xe‐concentration gas mixture will be discussed. The default panel with a gas mixture of 3.5% Xe in Ne and a filling pressure of 665 hPa was compared with a panel containing a gas mixture of 13.5% Xe in Ne and a filling pressure of 800 hPa. The panels contain a green phosphor, YBO₃:Tb, which showed less saturation at high UV load compared with a Willemite phosphor. The panel performance was compared in addressed conditions. For the default panel, a white luminance of 710 cd/m² and an efficacy of 1.6 lm/W was found, while for the high‐Xe‐partial‐pressure panel, a white luminance of 2010 cd/m² and an efficacy of 3.8 lm/W was realized. The increase of the driving voltages, about 20–30 V, is moderate. Finally, color saturation is improved at high Xe partial pressure.     

Laser Thomson scattering and optical emission studies of striated PDP micro‐discharge plasmas

Abstract— Properties of a plasma‐display‐panel (PDP) like discharge were examined by emission and laser Thomson scattering (LTS) measurements. Emission measurements were performed using an intensified CCD camera. By varying several external parameters such as the amplitude of the input voltage, gas composition, and pressure, the influence of these parameters on the discharge behavior was studied. Results of emission measurements showed that they were in good agreement with similar emission measurements on real PDP cells. LTS measurements were performed for the striated PDP‐like discharge at a pressure of 100 Torr and the results showed clear modulations in both profiles of electron density and electron temperature.     

Investigation of the discharge process in a shadow‐mask PDP cell using fluid models

Abstract— Two fluid models, LFA (local field approximation) and EME (electron mean energy), were applied to simulate the discharge process of a novel PDP with a shadow mask. In order to consider the variation of the secondary electron emission coefficient under different electric‐field and gas content, the secondary electron emission coefficient was calculated as a function of the energy of incident ions. The variation of the mean density of different particles as a function of time, electron temperature, and their space distributions in the discharge cell will be presented. And the simulation results of these two models are also compared in this paper. Then the EME model was used to investigate the relation between the discharge efficiency and the structure of the shadow mask, the xenon concentration, and the pressure.     

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.     

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.     

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.     

A high‐luminous‐efficacy PDP having multi‐anodes for reduction of ionic effect (MARI)

Abstract— We propose a PDP having a new structure and driving scheme. An auxiliary electrode was inserted between X and Y electrodes. Driving and discharge stability was determined using a test panel. A 42‐in. SD (852 × 480) panel and a 42‐in. HD (1366 × 768) panel were also made having this new structure, and we verified the increase in luminous efficacy and the reduction of ionic losses. We achieved a luminous efficacy of 2.35 lm/W in an SD panel and 1.97 lm/W in a HD panel. Finally, we investigated the characteristics and merits of the new structure.     

High‐Xe‐content high‐efficacy PDPs

Abstract— The trade‐off between PDP efficacy improvement and driving voltages was investigated for several design factors. It was found that for a proper combination of an increased Xe content, cell design, and the use of a TiO₂ layer combined with “non‐saturating” phosphors, a large increase in both efficacy and luminance can be realized at moderately increased drive voltages. In a 4‐in. color test panel, a white efficacy of 5 lm/W and a luminance of 5000 cd/m² was obtained for sustaining at 260 V in addressed condition.     

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.     

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.     

Surface‐discharge electrode design methods for ACPDPs

Abstract— In order to lower development costs and to shorten development time, small panels, under 10‐in on the diagonal, are used for the experiments to improve the luminous efficiency of plasma‐display panels. However, it is difficult to show the same results as those of large panels, over 40 in. on the diagonal. In this paper, first, we show that the luminous efficiency and the voltage margin of mini‐panels are not obtained with large panels by using an actual 46‐in. PDP. The reason is that the resistance in the large panels is larger than that in the mini panels and the voltage drop in the large panels are larger than in mini‐panels. Therefore, we conclude that the bus electrode width and the transparent electrode width are important factors in the design of large PDPs. Next, we show the technique of designing large panels by using a database obtained from mini‐panels. The estimated cell‐design results show good agreement with an actual 46‐in. PDP in luminous efficiency and minimum sustain voltage. We show that a desired large PDP can be obtained by using the cell design proposed in the present paper.     

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.     

Improvement of luminous efficiency using high helium content in full‐HD plasma‐display panels

Abstract— The influence of the Xe (15%) and He (70%) fractions on the discharge and driving characteristics was compared in 50‐in. full‐HD plasma‐display panels. The same improvement in the luminous efficacy was obtained when increasing either the Xe or He fraction. However, the discharge current with a high He fraction was smaller than that with a high Xe fraction. While the breakdown voltage was hardly influenced by an increase in the He fraction, it was significantly changed when increasing the Xe fraction. The formative and statistical time lags were only slightly changed with a high He fraction, yet significantly increased with a high Xe fraction. In addition, the relatively low luminance and driving‐margin characteristics with a high He fraction were compensated for by controlling the capacitance of the upper dielectric layer.     

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.     

PDP picture‐quality enhancement based on human‐visual‐system relevant features

The success of a new display technology such as plasma is strongly related to the final picture quality assessed by the customer's eyes. The human visual system (HVS) characteristics enable the definition of new cost‐efficient methods to significantly reduce the visibility of all plasma‐specific artifacts. Simple optimized encoding methods based on the luminance perception will be presented as well as more‐complicated algorithms based on motion perception.     

High‐luminous‐efficacy structure for plasma tubes

Abstract— The plasma‐tube‐array display is expected to become a wall‐sized display with very high luminous efficacy. The cell design for high luminous efficacy was investigated. Also, discharging in the plasma tube was observed in order to investigate the structure for high luminous efficacy. As the result, a high luminous efficacy of 5.4 lm/W was achieved.     

Space and time evolution of the plasma in a PDP cell: Comparisons between simulations and experiments

We have used a macroscopic discharge cell to study the space and time evolution of the plasma in geometry similar to real matrix and coplanar PDP cells with a scaling factor of around 100 (dimensions 100 times larger, pressure 100 times smaller, i.e., 1‐cm gap length, 5‐torr pressure). Discharges in pure neon and in a xenon‐neon mixture with 10% xenon have been investigated. The measurements have been compared with results from a two‐dimensional fluid model of the discharge.     

Effect of intensified discharge in the vicinity of ribs on PDP performance

It was determined that the discharge in the vicinity of ribs should be intensified to obtain low‐voltage, high‐luminous efficacy, and high module efficiency. One possible way is to increase the space between ribs and the discharge surface. Even if the amount of space increases by only 2 or 3 µm, it still results in low discharge voltage, large discharge current, and high luminous efficacy. For that reason it might be important to control the micron‐sized particles included in the MgO crystal dispersed layers. Another preferable way is to use ribs with a low electric permittivity (ε) that are represented by porous ribs. Moreover, low‐ε ribs diffuses the high‐energy spots in plasma, resulting in a high luminous efficacy. They feature a significantly lower sustain voltage and a smaller parasitic capacitance as well to facilitate a help high module efficiency. Also, highly porous ribs are expected to increase their practical use in aspects of mechanical strength and impurity gas exhaustion.