Glasses in the $Bi_{2}O_3-SiO_2-ZnO$ glasses system were examined as a potential replacement for lead-oxide glass frits with low firing temperature ($500sim600^{circ}C$) for the dielectric layer of a plasma display panel (PDP). The glasses were evaluated for glass transition temperature($T_{g}$) and thermal expansion coefficient(${alpha}$). After forming transparent thick films by a screen-printing method, it was evaluated for the optical properties. The transmittance of thick films fired at $500-600^{circ}C$ showed above $80\%$, which was not dependent on the firing temperature. As a result, many pores were observed at samples fired at low temperature, while the number of pores from samples prepared at high temperature decreased and the pores size increased.