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.     

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.     

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.     

Discharge characteristics of a new ACPDP structure using Thick‐Film Ceramic Sheet technology

Abstract— We have proposed a counterelectrode PDP structure in which the sustain and scan electrodes are embedded face to face in the ribs by applying Thick‐Film Ceramic Sheet technology. An advantage of the counterelectrode PDP is low discharge voltage, which does not depend on the dielectric thickness. A positive column is observed at a longer gap, and the luminous efficacy reaches 3.7 lm/W at Ne‐30%Xe at a 450‐μm discharge gap.     

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.     

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‐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.     

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.     

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.     

Performance of the efficacy enhancement layer using nano‐particles in PDPs

Abstract— A nano‐particle dielectric layer was experimentally placed between a conventional dielectric layer and a MgO thin film. This greatly reduces the discharge current and enhances high luminous efficacy. The current reduction might reflect a capacitance reduction in the entire dielectric layer due to the extremely low permittivity of the nano‐particle layer which includes a large amount of space. The luminous efficacy is improved more than what is expected because of the reduction in capacitance. The layer affects the MgO film properties such as crystal growth size, orientation, cathode luminescence, and exo‐electron emission. As a result, it improves the statistical delay in addressing. This might be caused by the large crystal growth of MgO due to the surface roughness of the nano‐particle layer underneath. The particle size required to optimize the roughness of the large growth is about 10–50 nm. The rise in the discharge voltage accompanied by the nano‐particle layer insertion is improved when the layer is properly patterned. A reduction in luminance is prevented when it is patterned in narrow lines along the X—Y gaps while the improvement in address delay strongly depends on the areal ratio of the nano‐particle layer.     

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.     

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.     

Improvement in luminance,luminous efficiency,driving margin,and operational lifetime of HD PDPs by using discharge deactivation film

Abstract— We have improved our 116‐cm HD PDP in many respects by using DDF formed on MgO around the display line boundaries. The DDF allows an extremely narrow inter‐pixel gap even for a stripe‐rib structure because it prohibits vertical crosstalk discharge. The DDF combined with a stripe‐rib structure results in the best address discharge response. Thus, a very wide driving margin area is achieved, allowing for a high percentage of Xe. The preferable sustain electrode shape follows the CAPABLE DDF style, where the principal discharge portion is separated from the bus via a slim bridge. This cell configuration proved to be excellent in operational life testing with respect to DDF as well as in manufacturing process margin. By employing both a thinner dielectric layer and a TiO₂reflective underlayer for phosphor, the address response is further improved so that Xe15% vol. is available from the viewpoint of the driving margin. Thus, we achieved a white peak luminance of 1220 cd/m² and a luminous efficiency of 2.16 lm/W simultaneously despite of an applied sustain voltage as low as 185 V. We foresee that they will be soon as high as 1400 cd/m² and 2.5 lm/W by modifying the sustain electrode style.     

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.     

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.     

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.     

High‐speed and low‐voltage write addressing of plasma display panels by use of extremely weak discharge

Although the priming effect shortens address period and reduces address voltage, it is difficult to use the priming effect for the conventional write addressing method because the ramp reset pulses provide little priming effect. An extremely weak discharge for priming has been incorporated with write addressing method. The extremely weak discharge is generated by priming pulse applied just prior to the scan pulse. In the 4‐in‐diagonal test panel containing Ne + 10%Xe mixture gas, infrared emission intensity of the discharge is 900 times smaller than that of sustain discharge. Therefore, there is no degradation of dark room contrast ratio. Because the priming discharge generates a very small amount of charges, there is little reduction in the amount of wall charge accumulated during reset period. Namely, increase in address voltage can be avoided. Although the discharge intensity is extremely low, it provides sufficient priming particles for high‐speed and low‐voltage addressing. When priming pulse voltage is 70 V and width is 10 µs, the address discharge delay is reduced to less than half. When the scan voltage margin is 10 V, the data voltage is reduced to 17 V, which is 20 V lower than that of conventional method.     

Address pulses during sustain period for increasing luminous efficiency

Abstract— A new driving method using a short pulse applied to the address electrode (i.e., address pulse) during a sustain period is proposed to improve the luminous efficiency. In this method, short pulses are additionally applied to the address electrode during the rising or falling edge of the sustain pulses. In the case of a small sustain gap, address pulses synchronized with a rising edge of the sustain pulse can help the expansion of the discharge volume toward the address electrode, whereas address pulses synchronized with a falling edge of the sustain pulse produce a self‐erasing discharge, which improves the luminous efficiency. In the case of a large sustain gap, the application of the address pulse can produce a stable sustain discharge at a low sustain voltage level, generating an efficient discharge even in the case of the long discharge path.     

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.