LCD panel

An LCD (liquid crystal display) panel is two sheets of glass with a liquid crystal layer a few micrometers thick between them. It makes no light of its own. Each subpixel acts as a tiny adjustable shutter for light coming from behind.

The back sheet is the thin-film transistor array, with a transistor switch for every subpixel. The front sheet is the color filter. Both are coated with a thin film of polyimide that lines up the liquid crystal molecules in one direction. A bead of epoxy resin sealant is drawn around each panel's edge, drops of liquid crystal mixture are placed inside, and the two sheets are pressed together in a vacuum. UV light and heat cure the seal. The mother glass is cut into panels, a polarizer is laminated to each face, and display driver chips on flexible film are bonded along the edges.

Light from the backlight unit passes the rear polarizer. Each subpixel's voltage sets how far its molecules turn, which decides how much light escapes through the front polarizer. A 4K panel has about 8.3 million pixels, or about 25 million subpixels.

Common types are VA (deeper blacks) and IPS (wider viewing angles). OLED panels skip the liquid crystal and backlight entirely.