I'm using a 320x240 monochrome LCD with a built-in high voltage generator. As is probably standard, the LCD bias is provided out of the module, and I have to use a resistive divider to provide this voltage back into the module for contrast adjustment. This simple two- resistor circuit is given in the datasheet. The LCD contains a controller if that helps (RA8835).
Up until now, I've always simply turned the main 5V supply on and off with no regard to power sequencing. The only odd thing I've noticed is on power-down, one dark horizontal line in a random location will appear for maybe one second. (Incidentally, my TI-89 calculator does the same thing!) If I immediately power the module back up, the horizontal row of pixels where that dark line was looks slightly lighter in contrast than other pixels that have been turned on via the attached microcontroller. After a second or two, there is no noticable contrast differences.
Is this bad for the liquid crystal material? I'm surprised the datasheet for this specific module makes no mention of any of this, but another module's datasheet from the same company (Densitron) does talk about sequencing. How damaging would this behavior be to the LC material in the glass panel? I've been using it like this for some time and haven't noticed any detrimental effects, but maybe I'm slowly killing it.