Display glass

Display glass is the base every LCD panel is built on. It looks like window glass, but it's much flatter, thinner (usually about 0.5 to 0.7 mm) and chemically different. Window glass contains sodium, and sodium drifting into a transistor would ruin it. Display glass is alkali-free: it contains almost no sodium or potassium.

The recipe starts with silicon dioxide, the main glass former. Aluminum oxide adds strength and lets the glass take the heat of transistor-making without sagging. Boron trioxide lowers the melting point and adds toughness. Smaller amounts of calcium oxide, strontium oxide and magnesium oxide keep the melt from crystallizing and tune how much the glass expands when heated. The powders are melted at around 1,600 °C. Many makers then use the fusion process: molten glass overflows both sides of a long trough, and the two streams meet underneath to form a sheet whose surfaces have never touched anything. Others float the glass on molten tin. Either way, the sheet needs little or no polishing.

An LCD panel uses this glass twice: for the thin-film transistor array at the back and the color filter at the front. Sheets in the biggest plants are about 2.9 by 3.4 meters.