Coloration due to colloidal Ag particles formed in float glass

Colloidal silver (Ag) particles are formed in a float glass by the heat-treatment with sputtered Ag film in air. This study deals with the coloration of the bottom face of float glass. The presence of those colloids in the glass gives rise to yellow coloration. Secondary ion mass spectrometry (SIMS), transmission electron microscopy (TEM) and optical spectra measurements are applied to investigate the effects on coloration from the heat treatment temperature, surface corrosion and chemical state of tin at the bottom face of the glass. It is found that the colloidal Ag particle size becomes smaller with depth, and that the Ag colloids governing the coloration mainly exist within ∼0.5 μm region of the glass surface. It is also found that the diffused Ag concentration is greater in the glass with corroded layer near surface than without the corroded layer, resulting in deeper yellow coloration. This fact may result from the difference in the ion-exchange rate between Ag+–H+and Ag+–Na+. The remarkable change is observed in the depth profile of Ag concentration. The depth of change is dependent on a hump position in tin profile of the float glass. This result is discussed in correlation with the chemical state of tin.