A significant point is that the phosphors on a CRT screen have their "persistence" designed to support a particular fairly narrow range of refresh rates. The phosphors could be made to have really long persistence (seconds), so there would be no serious flicker down to even maybe a 5 second refresh interval, but then, since the phosphors can only be "turned on" and not "turned off", you wouldn't be able to see motion much faster than that. (Some early CRT terminals used long-persistence phosphors, with the characters "drawn" on the screen instead of scanned. This didn't provide very fast "refresh", but it only had to be as good as a 10 CPS Teletype.)
LCDs have the property that they can be turned on or off, at some relatively high rate, and once set one way or the other they have a relatively long persistence, on the order of a second or so. For this reason they can support a wide range of refresh rates.
The upper limit on refreshing an LCD is a function of capacitance and of the fact that the L in LCD stands for "liquid" --
LCDs are "scanned" via an X-Y matrix of wires, with a pixel at each point where two wires cross. Only one pixel can be manipulated at a time. The voltage on a pixel must be maintained long enough to "charge" the pixel, so that it will hold the charge until refreshed, and all pixels must be visited on each refresh cycle.
And, in addition to the charge time, the liquid inside needs time to mechanically reorient its crystal structure (though, at a physics level, this reorientation is tied at least partially to the "charge" time). Both of these factors place an upper limit on refresh rate.
1An excellent summary of the points that I lacked time to supply. I will say though that LCDs do have a lower limit to their refresh rate. Fortunately it is down around 0.5Hz or so. – Ignacio Vazquez-Abrams – 2011-05-22T00:24:01.307
1hmm interesting stuff, especially about ghosting and the effects on motion. Thanks for that! – Kez – 2011-05-24T07:07:03.613
1Thanks! I spent a few years evaluating LCDs for a company doing film and video processing when the CRTs stopped being produced. LCDs had a really rough start :) – Itai – 2011-05-24T13:12:35.290
1I believe that you may be confusing refresh rate with frame rate. If a video source (e.g., an MPEG file) has 30 frames per second, and the screen has a refresh rate of 60 Hz, then each frame will be displayed twice. Increasing the refresh rate to 90 Hz will just result in each frame being displayed three times; I don’t see how that would give smoother motion. In fact, motion might look less smooth at 70 Hz because you no longer have an n to 1 ratio. – Scott – 2014-01-14T01:07:41.590