Hiroshi Kobayashi

Development of a new blue CaMgSi2O6:Eu2+ phosphor for PDPs

— A blue-light-emitting Eu2+-doped CaMgSi2O6 phosphor having a long lifetime for a plasma-display panel (PDP) was developed. The CaMgSi2O6:Eu2+(CMS:Eu) phosphors show no luminance degradation during the baking process, and an equivalent photoluminescence peak intensity compared to that of the conventional blue-phosphor BaMgAl10O17:Eu2+ (BAM) after baking. CMS: Eu shows a poor luminescent characteristic for the Xe excimer band excitation due to the lack of absorption. To introduce the absorption center for the Xe excimer band, we performed Gd-codoping of CMS: Eu as a sensitizer and found a new excitation band around 172 nm, which originated from Gd3+. The test PDPs panels using synthesized CMS: Eu phosphor and CMS: Eu, Gd phosphor were examined to investigate the luminescent and aging characteristics of a Xe-discharge excitation source. The CMS: Eu panel shows an emission peak intensity comparable to that of the BAM panel (i.e., a comparable stimuli L/CIEy, 93% of BAM), while the CMS: Eu, Gd panel shows poorer blue emission intensity compared to the BAM panel (up to 53% of total stimuli of BAM). The CMS: Eu panel and the CMS: Eu, Gd panel show less luminance degradation than the BAM panel under the aging test, and the panel retains 90% of its luminance after 300 hours of driving. It was found that CMS: Eu appears to be a candidate for a new blue PDP phosphor because of its longevity in a Xe-discharge plasma environment.

Crystallographic and Luminescent Characteristics of Red-Emitting Ba2ZnS3:Mn Thin Film Electroluminescent Devices Prepared by Electron-Beam Evaporation

The crystallographic and luminescent characteristics of Ba2ZnS3:Mn thin film electroluminescent (EL) devices have been investigated. Ba2ZnS3:Mn thin films have been prepared by electron-beam evaporation and postdeposition annealing at 600°C. It has been found that the suitable molar fraction of Ba/Zn in a deposition source pellet for suppressing impurity phases formed in thin films is about 1.8. The Ba2ZnS3:Mn EL devices show an efficient reddish-orange luminescence with the Commission Internationale de lEclairage (CIE) color coordinates of (x, y) = (0.60, 040). The luminance and efficiency at 1 kHz are 250 cd/m2 and 0.09 lm/W, respectively. Since the Ba2ZnS3:Mn thin films are crystallized even at 600°C, Ba2ZnS3:Mn is a promising red EL phosphor for a low-temperature process.