Short for Trinitron Flat Display
. It is a somewhat new technology from Sony
for manufacturing Trinitron
tubes that are entirely flat, instead of just vertically flat
like standard Trinitron displays. The tubes still have those two horizontal stabilizing wires that Trinitron haters always bring up, but otherwise they are much clearer and have much better image geometry
than previous tubes.
There are two challenges to building a completely flat CRT: First, you have the fact that a flat surface can't handle atmospheric pressure as well as a curved one, so the front face of the tube has to be thicker. This results in more weight, which is bad when you put a 19" Trinitron FD monitor on that flimsy desk you bought 8 years ago for $60. The second challenge is the fact that the distance from the electron gun to the front of the tube changes constantly along the current scan line; when you scan a line in 1/91,100th of a second or faster, adjusting the focus as necessary during that time is much more difficult than over the 1/70th or 1/80th of a second it takes to sweep the entire screen vertically in a Trinitron tube that is only vertically flat.