I guess at the end of the day, we're dealing with a capacitor with an oil dielectric. It would appear that any change in voltage leads to some kind of negative spike which pulls the TiO2 quickly down to the lower electrode (leaving the black oil - very X-Files !) followed by a relatively slow relaxation to the newly applied voltage where the TiO2 drifts back to the surface electrode. Hence my assertion that only changing the pixels which require changing might potentially alleviate the effect. I imagine white to black would be quite fast whereas black to white would be slightly slower. But at least that would be a fade rather than a 'flash'. P.S. Apologies for the geek attack displayed in this reply