Thermal, Optical, and Dielectrical Characteristics of Oxide Dielectrics with Low Permittivity for Emissive Display Device

Abstract

The subject of this dissertation is regarding the optical, thermal, and dielectrical properties of the transparent dielectric materials with low permittivity for emissive display devices (plasma display panels, PDPs) to improve the luminous efficacy and substitute PbO and Bi2O3 glass systems. In this study, a ZnO-B2O3-SiO2-Al2O3 glass containing alkaline-earth oxides and an alkali oxide was fabricated as a candidate Pb- and Bi-free transparent dielectric layer with a low dielectric constant. The thermal, electrical and optical properties of these glasses were characterized. The changes of the properties in this glass system were investigated according to the alkaline-earth oxides (RO) / alkali oxide (R2O) ratio. The glass transition temperature (Tg), the coefficient of thermal expansion (CTE) and the dielectric constant of the glasses varied from 480 to 540oC, 7.9 to 10.6×10-6/K and 7.4-8.2, respectively. As the RO/R2O ratio was increased, the Tg value increased, the CTE and transmittance decreased, and the dielectric constant increased slightly. The Tg or CTE can be calculated from other known values in these system glasses without requiring numerous experiments. The Tg and CTE are in inversely proportional to each other and a constant was obtained by multiplying the two values. Furthermore, the optical property was examined to improve a color temperature using transparent dielectric layers with variation of the transition metal oxides in the PDP. In this work, ZnO-B2O3-SiO2-Al2O3 glasses with variations of the Co3O4 content (0, 0.5, 1.0, 1.5, 2.0wt%) were fabricated and the optical properties of these glasses were characterized. As the content of Co3O4 increased, the transmittance of the red region (form 580nm to 780nm) decreased more than of the blue region (from 380nm to 500nm). This change of the transmittance induced the transition of the coordination of the color temperature toward the blue region. Therefore, the addition of 2wt% Co3O4 could improve the color temperature from 6087K to 7378K and the result was confirmed using a simulation. The optical properties of transparent dielectric layers with other metal oxides (CeO2, CuO, Fe2O3, MnO2, and NiO) in the PDP were also investigated. ZnO-B2O3-SiO2-Al2O3 glasses with various metal oxides were fabricated and the optical properties of these glasses were examined . As the metal oxides were added in the glasses, the visible transmittances of the dielectric layers decreased and the transmittances in special wavelength regions were reduced with the different rate. The change of the transmittance in each wavelength range induced the variation of the visible emission spectra and the change of the color temperature in the PDP. the additions of CuO are able to improve the color temperature from 6087K to 7057K. However, the others reduced the color temperature in the PDP. As a result, It is suggested that the inclusion of the transition metal in the transparent dielectric material glass could control the color temperature without employing asymmetric cell structures and the change of the driving scheme.