Originally Posted by igorsk
Can someone who has the problem check if the screen fades under direct sunlight but behind a glass window? Another way is to shine a blacklight (UV light) on the screen and see if it fades.
I have a theory that the defective screens lose the static charge that holds the ink particles because of the UV radiation. Window glass blocks most of the UV wavelengths.
I tried with slant sunlight in the evening through a glass pane, and there was a certain amount of fading. What's more interesting is the fact of the fading being almost inmediate at noon and outdoors, even in a (still) cold and sunny winter day.
By the way, thanks to everybody for your feedback!