Blue‐light emitting vacuum fluorescent display using Te‐doped ZnS phosphors

Abstract

AbstractZinc sulfide (ZnS), which is one of the wide‐gap II‐VI compound semiconductors, has been used as the blue phosphor for vacuum fluorescent displays (VFD). Because the ZnS phosphor has a high resistivity, it is usually mixed with a conductive powder such as In2O3. ZnS crystals grown from Sb2Te3 solutions showed a blue emission at room temperature due to the Te impurities (the isoelectronic centers of the Te‐Te pair) and had relatively low resistivities (about 105 Qcm), due to the presence of Sb impurities. The VFDs prepared directly from these crystals as phosphors without use of conductive powder were investigated. The VFDs emitted light at an anode voltage higher than 15 V. The luminance increased linearly with the anode voltage. For VFDs employing crystals with 0.2 at.% Te, the luminance was 530 cd/m2 and the luminous efficiency was 0.30 lm/W at an anode voltage of 60 V. The emission had a peak at 460 nm and a chromaticity coordinate of (0.15, 0.15) that was independent of the anode voltage. The luminance decreased with increasing temperature and at 80°C was 3 percent of that at 25°C. The luminance and the luminous efficiency improved with increasing Te concentration in the phosphor crystal.