How LCD screens are made

Pattern transistors on glass

A large sheet of glass is coated with thin films and etched into a grid of thin-film transistors, one for each subpixel, with transparent electrodes of indium tin oxide.

Print the color filters

On a second glass sheet, black photoresist is applied first, exposed to ultraviolet through a mask and washed to leave a black grid. Red, green and blue resists then fill the holes in turn. Their pigment particles are just 40 nm wide.

40 nm pigment particles

Glue the sheets with crystal inside

The two sheets are glued together with spacers and liquid crystal sandwiched between. In a twisted nematic panel, alignment layers on the inside surfaces make the molecules lie in a twist when no voltage is applied.

Cut the big sheet

Several finished cells share one large pair of sheets, and they are cut apart into individual screens.

Stick on polarizers

Polarizing sheets go on the front and back with their axes crossed. A pixel then passes light only when the liquid crystal twists its polarization.

Add the LED backlight

Liquid crystals do not make light. A row of white LEDs along the edge shines into a light guide plate, usually of acrylic, which spreads it evenly behind the panel.