Reflector sheet

A reflector sheet is a thin, bright white film that lines the back of an LCD's backlight. Any light that heads backward or sideways hits it and bounces toward the screen again. Good reflector sheets send back well over 90% of the light that hits them.

It's made from PET plastic, but not as clear film. Before the film is formed, tiny particles are mixed into the molten PET, such as titanium dioxide or another plastic that doesn't blend in. The melt is pressed out into a sheet and stretched in both directions. As it stretches, the PET pulls away from each particle, leaving millions of microscopic air pockets. Every boundary between plastic and air reflects a little light, and with so many of them, almost all of it is scattered back. Titanium dioxide, the same white pigment used in paint, adds to the brilliant white.

In the backlight unit, the reflector sheet lies on the steel back chassis, under the LEDs. It catches light that the prism sheets send back and recycles it, which is a big part of why LED TVs are efficient. It works by scattering light, not by mirroring it, which is why it looks white rather than silver.