Yukio Murakami

Influence of defect states on the secondary electron emission yield γ from MgO surface

In order to study the dependence of the secondary electron emission yield γ on the defect states of the MgO surface in plasma display panels, cathodoluminescence (CL) spectra of MgO films, which were deposited at oxygen partial pressures of 0, 4.0×10−4, and 1.2×10−5 Torr, were measured. The CL intensities from the F (oxygen ion vacancy+one electron) and F+ (oxygen ion vacancy+one electron) centers of the MgO film that was deposited at high oxygen partial pressure (1.2×10−4 Torr), significantly increased with aging during discharge. Assuming that the probabilities of transitions are proportional to the measured CL intensities from the F and F+ bands of the MgO films, the γi values of MgO films for Ne and Xe ions, which include the F and F+ bands, were calculated. The tendencies of the breakdown voltages calculated using these γi values were consistent with those of the measured voltages of the MgO films. These calculated results suggested that the influence of the F and F+ bands on the γi values for Xe ion...

SrCaO Protective Layer for High-Efficiency PDPs

The sustain pulse voltage of the panel for 66-kPa Ne + Xe (5%-30%) is 20%-40% lower with a Sr_0.62Ca_0.38O protective layer than with a MgO protective layer. At a normal sustain voltage of 160-200 V, the luminous efficiency of the panel with the Sr_0.62Ca_0.38O protective layer for Xe (30%) is about twice as high as with the MgO protective layer for Xe (10%). The luminances of these panels are almost the same. This high efficiency at normal sustain pulse voltage and normal luminance is obtained through the combined use of the Sr_0.62Ca_0.38O protective layer and high Xe content. With regard to ion bombardment, the Sr_0.62Ca_0.38O film has a 4.5 times longer life than SrO film and nearly 80% of the life of MgO film. We also calculated the values of theoretical secondary electron emission yield gamma_imin of MgO, SrO, and CaO without energy bands in the band gap for rare gas ions and found that [ gamma_imin of MgO] les [gamma_imin of CaO] < [gamma_imin of SrO] except for the one case with He. The breakdown voltage decreases with higher gamma_imin values. As expected, the discharge voltage of the panel is much lower with the SrO protective layer than with the MgO protective layer. The discharge voltages of the panels with Sr_0.62Ca_0.38O and SrO protective layers are almost the same. These findings show that the life of the SrO protective layer can be made 4.5 times longer without any increase in the discharge voltage by adding CaO (40 at.%)

Discharge characteristics with respect to width of address electrode using three-dimensional analysis

A numerical analysis of the microdischarge in a surface-type AC plasma display cell has been made using the time-dependent, three-dimensional (3-D) fluid equations to understand the discharge characteristics. We investigate the breakdown dynamics with the width of address electrode and barrier ribs, because the typical 3-D parameters in an AC plasma display panel (AC PDP) model are the width of address electrode and the barrier ribs. It has been clarified that the width of address electrode has important role of the formation of discharge volume with the wall annihilation by barrier ribs and the accumulation of wall charges on the part of address electrode. The obtained time dependent spatial characteristics of an AC PDP discharge with the width of address electrode and the effect of wall annihilation by barrier ribs will help us to design the optimized AC PDP cells to get stable write and sustain discharges.

Spatio-Temporal Effect of Gas Pressure on Excited Xe Atoms in Ultrafine Pixel Pitch AC Plasma Display Panels

The kaleidoscopic change in the distributions of excited xenon (Xe) atom density was investigated under a high gas pressure condition in a unit microdischarge cell on a coplanar-structured alternating-current plasma display panel with an ultrafine pixel pitch by using microscopic laser absorption spectroscopy. As the gas pressure increased, the peak densities of the excited atoms not only increased but the peak position on the anode side also tended to shift toward the center of the discharge gap by expanding in width. The temporal behavior of the excited Xe atom density in the resonant state (1s4) did not change significantly with the pressure since the decay rate was mostly governed by the effective lifetime of the imprisoned resonance radiation. On the contrary, the decay rate of the excited Xe atoms in the metastable state (1s5) decreased drastically with the pressure due to an increase in the three-body collision rate. This implied that the metastable state atoms were efficiently converted to Xe excimers, leading to an increase in the vacuum ultraviolet emission.

Surface Charges in a Coplanar-Electrode Microgap Discharge Measured at Various Gas Pressures Using an Electrooptic Crystal

The surface voltage and charge on the dielectric barrier in a plasma display panel (PDP)-like microdischarge have been measured using an electrooptic crystal. The initiation of discharge starts the accumulation of surface charges and the charges spread uniformly over the entire region of the electrode surface under the condition of a time resolution of 0.1 µs. For the case of a gas mixture of Ne+Xe (10%), the plasma light emission at the cathode side is much stronger than that at the anode, however, the quantity of surface charges accumulated at both electrodes are the same. The surface charges at various gas pressures are also measured as functions of externally applied voltage and total charge flowing in an external circuit estimated from the discharge current. These characteristics for the microdischarge are compared with the results obtained for macrodischarge. It is found that the voltage difference on the barrier surface between the ground and high-voltage electrodes, caused by the accumulated charges, is an important factor in determining the barrier discharge.

Gap Length-Dependent Excited Xe-Atom Density Distribution in Superfine-Pitch Discharge Cells for Coplanar-Structure Plasma Display Panels

In order to investigate the vacuum ultraviolet emission characteristics in a superfine-pixel-pitch plasma display panel, we visualize the spatiotemporal behavior of the density of excited Xe atoms as a streak image. We use microscopic laser absorption spectroscopy to estimate the density of the excited atoms in a microdischarge cell; the density varies according to the discharge gap length. Long gaps produce a new excited atoms generation area which is formed in the discharge gap region.

49.1: Invited Paper: Development of 0.3mm‐Pixel‐Pitch Ultra‐High‐Resolution PDP for “Super Hi‐Vision” Broadcasting System

The 0.3 mm-pixel-pitch ultra-high-resolution PDP is being developed for use in the “Super Hi-Vision” broadcasting system with over 4,000 scanning lines. In this study, we used three-dimensional discharge simulation to compare the vacuum ultraviolet (VUV) radiation characteristics of box- and stripe-type cells in the PDP in order to improve the luminous efficiency and VUV crosstalk. The luminous efficiency of the box-type cell was 22% higher than that of stripe-type cell in a gas composition of Ne-Xe (5 %) at 67 kPa (500 Torr) due to the lower discharge current. The stripe-type cell had 19% VUV crosstalk to the phosphor surfaces of the neighboring vertical cells. Use of the box-type cell, which can intercept the VUV crosstalk, is most effective for achieving high resolution and enhancing efficiency.

Discharge Luminescence Characteristics of Ultrahigh-Resolution Plasma Display Panels with a 0.3-mm Pixel Pitch

We experimentally investigated the effect of increased generation efficiency of excited Xe atoms on ultrahigh-resolution plasma display panels (PDPs). At a horizontal cell pitch of 0.1 mm, the sustain voltage increased; however, the generation efficiency was equal to or higher than that obtained at the conventional 0.22-mm cell pitch. We investigated the luminous efficiency of fine-pitch discharge cells, which are fabricated with fine-grain colour phosphors. The absolute luminous efficiency of the experimental fine pitch panel is estimated to be 0.68 lm/W.

A Method of Visualizing the Energy Translation Process of Excited Xe Atoms in the Microdischarge Cells of Plasma Display Panels

We propose a new method for effectively visualizing the energy translation of excited Xe atoms. Understanding the translation process between power consumption and visible light emission is important for improving the device performance of plasma display panels (PDPs). The new method can describe the Xe* (1s4) density, energy input, energy consumption, rate of radiative transition, and energy loss, thereby presenting a composite picture of the entire energy translation process in Xe* (1s4). We have applied the new method to the results of a 3-D discharge simulation for PDP, and the findings are described in this paper.