Luminous efficacy evaluation of XeI excimer for ACPDP

We demonstrate for the first time a luminous efficacy of a XeI excimer PDP comparable to that of a conventional Xe/Ne‐mixture PDP using 6‐in. ACPDPs. For the conventional PDP as a reference, a mixture of Xe: Ne = 4:96(%) with a total gas pressure of 60.0 kPa (450 torr) was used. For the XeI PDP, Ne‐buffered mixtures with the same total gas pressure were tried, and a mixture of I₂:Xe: Ne = 0.02:7.1:92.88 (%) showed an efficacy as high as that of the conventional Xe PDP.     

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 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.     

DIA‐PDP with high luminous efficacy and increased vertical resolution

Abstract— A PDP utilizing a new cell configuration to improve the vertical resolution and luminous efficacy is proposed. In this configuration, a delta subpixel arrangement is adopted because it reduces the vertical pixel pitch by half and increases the vertical resolution. In this configuration, R, G, B subpixels form triangles which are diamond shaped, the rational for calling this technology “DIAPDP.” High luminous efficacy is achieved by reducing the reflectivity of the panel. The lower reflectivity enables increased transmittivity of the light‐reduction filter which is part of the PDP panel, thus ensuing sufficient contrast under bright conditions. The higher transmittivity increases the luminous efficacy with the filter. Results obtained for a 46‐in. panel demonstrate a 33% increase in the luminous efficacy when using the filter. The DIA cell configuration is further modified to be a “clustered DIA” in order to improve the color mixing. Through subjective evaluation, the color mixing was compared with that of panels based on a trio subpixel arrangement and DIA, and the effect on color mixing was confirmed. The luminous efficacy of clustered DIA is also shown to be equal to that of DIA.     

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.     

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.     

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.     

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.     

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.     

Development of a high‐definition 32‐in. PDP

We developed the world's smallest‐profile 32‐in. HDTV PDP. By improving the luminous efficiency, a luminance of 650 cd/m² and power consumption (discharge and driving circuit) of 200 W or less was achieved. Moreover, incorporating an advanced color compensating (ACC) filter improved the PDP's color‐reproduction capability, better than that of CRTs.     

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.     

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.     

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.     

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.     

Influence of wavelength red‐shift on color‐rendering index and luminous efficacy of LEDs

Abstract— The peak wavelength of light‐emitting‐diodes(LEDs) shifts towards the longer wavelengths when the temperature of the LED chip increases. The color‐rendering index (CRI) and luminous efficacy may change with the peak wavelength of the LED, and it is not expected to do so when the LEDs are used in fields which require a high CRI and luminous efficacy. A mathematical model of the LED spectrum was used to analyze the influence of the wavelength shift on the CRI and luminous efficacy of three‐ and four‐chip‐packaged LEDs, respectively. The results show that the CRI decreases with the peak wavelengths shifting towards longer wavelength for both three‐ and four‐chip LEDs; especially, the CRI of the four‐chip LEDs decreases more for a green‐color wavelength shift than for other colors. The luminous efficacy increases with a green‐color wavelength shift and decreases with a red‐color wavelength shift.     

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‐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.     

Investigation of the firing voltage in a shadow‐mask PDP

Abstract— A numerical method was used to investigate the firing characteristics of the discharge cell in an AC shadow‐mask PDP (SM‐PDP). The firing voltages for the various discharge paths in the addressing and sustaining periods were calculated, and the effects of the metal barrier rib and the dielectric layer in the discharge cell on the firing characteristics were studied. Furthermore, the advantages of the SM‐PDP in terms of the firing characteristics will be discussed.     

New electrode structure for reducing power consumption of PDPs

Abstract— A new electrode structure for plasma‐display panels (PDPs) is proposed, which decreases the panel capacitance by effectively decreasing the electrode area and increasing the discharge efficacy. Although the electrode area is decreased, the proposed structure does not require an increase in operating voltage and can improve the discharge efficacy by limiting the discharge current. The effect of panel capacitance reduction of the suggested electrode structure contributes to power‐consumption reduction in the entire PDP system by reducing the dissipative power due to the charging current of the panel capacitance. The effects of panel‐capacitance reduction by using the new electrode structure were confirmed by comparing the charging‐current waveforms and directly measuring the capacitances of various panels with conventional and new electrode structures.     

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.