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.     

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.     

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.     

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.     

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.     

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 diagnosis of high Xe concentration and high‐γ protective layer in PDPs

Abstract— The high‐Xe‐concentration and high‐γ (ion‐induced secondary‐electron emission coefficient) protective layer have been diagnosed from both experimentation and simulation. The experimental results show that there is a great increase in luminance and luminous efficacy, while the breakdown voltage decreases in the high‐Xe and high‐γ discharge. In the high‐Xe discharge, the great increase in VUV radiation mainly results from an increase in excimer VUV emission. The application of high‐Xe concentration can greatly increase the luminous efficacy, while the high‐γ protective layer can promote it further. Considering that the total discharge efficiency can be divided into the electron heating efficiency, the Xe excitation efficiency, and the VUV radiation efficiency, both the electron heating efficiency and Xe excitation efficiency increased for a high‐Xe discharge; while for a high‐γ discharge, the increase in electron heating efficiency contributes to the improvement in discharge efficiency.     

Front address structure for high luminous efficacy and low address voltage in ACPDPs

Abstract— 8‐in. AC plasma display panels with front address (FA) structures were developed. Deep barrier ribs, high‐Xe‐content gas, and long sustain gaps were applied to FA structures to achieve high luminous efficacy. The FA structures have several advantages over conventional structures. Because address electrodes are closer to sustain electrodes, FA PDPs can be driven at lower address voltages, under the condition of deep barrier ribs or high‐Xe‐content gas, than conventional PDPs. A disadvantage of FA PDPs is relatively high capacitance between the sustain electrodes and address electrodes compared to that of conventional PDPs.     

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.     

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.     

Improvement of PDP discharge efficiency based on macro‐cell studies

Abstract— In this paper we explain how macro‐cells (real PDP cells scaled‐up a hundred times) with external and removable electrodes have been validated by comparison with real panels and modeling and used to optimize the luminous efficacy of real PDPs. We illustrate the application of the macroscopic PDP tool to optimize the electrode configuration of short‐gap discharges towards higher luminous efficacy, as well as its use in conjunction with 2D and 3D modeling to lower the operating voltages of high‐efficacy long‐gap discharges triggered by auxiliary electrodes.     

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.     

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‐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 luminous‐efficacy mercury‐free flat fluorescent lamp (MFFL) with local‐dimming functionality

Abstract— In order to realize high‐luminance and luminous‐efficacy mercury‐free flat fluorescent lamps (MFFLs) for LCD backlighting, the phosphor profile was optimized to enlarge the surface area. The proposed uneven profile of the rear phosphor increases the effective surface area of the phosphor, resulting in a wide luminance range from 3000 to 16,788 cd/m² with a corresponding high luminous efficacy from 66 to 34.7 lm/W, respectively. Also, a dynamic operation method for an adaptive local‐dimming and scanning operation is proposed which can be used in a 32‐in. multi‐structured configuration having one inverter system. With the deployment of the bipolar drive scheme and dual auxiliary electrodes, a stable and selective diffuse glow discharge with high luminance is possible.     

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.     

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‐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‐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.     

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.