For the application of transparent dielectric layer of PDP (Plasma display panel), a Pb-free glass, ZnO-B2O3-SiO2 glass, was measured for thermal and optical properties after forming thick films. Glass frit of different size (d50=1.7, 4.3㎛) and different thickness film forming process (a die coater and a screen printer) were applied to a transparent dielectric. The coated layer was determined for pore contents, size, and transmittance. As a result, the screen printing method produced non-uniform surface and increased pores with multilayer. The die coater method, however, produced more uniform surface and less pore content compared to the screen printing method. Thus it shows that the increase of pore size and contents has detrimental effects on the transmittance of thick films made by a lead-free glass, ZnO-B2O3-SiO2 glass.