From Wikipedia, the free encyclopedia

TFT display showing persistence artifacts

Image Persistence is the term used for the LCD equivalent to "burn-in". Unlike burn-in, however, the effects are generally temporary.

Liquid crystals have a natural relaxed state, when a voltage is applied they rearrange themselves to block certain light waves. If left with the same voltage for an extended period of time (from, for example, displaying the mouse cursor in one place, or the Taskbar), the liquid crystals can develop a tendency to stay in one position. This ever so slight tendency to stay arranged in one position can throw the requested color off by a slight degree, which causes the image to look like the traditional "burn-in" on phosphor based displays.

The actual cause for this tendency is unclear. It might be due to accumulation of ionic impurities inside the LCD [1], or electric charge building up near the electrodes [2], or parasitic capacitance [3], or "a dc voltage component that occurs unavoidably in some display pixels owing to anisotropy in the dielectric constant of the liquid crystal" [4].

This is easily preventable and can be reversed by allowing the liquid crystals to return to their relaxed state. In other words, turning off a LCD computer monitor for as little as 15 minutes a day will relax the crystals and help prevent image retention. It is also ideal to rotate desktops, and hide away elements on the screen which normally would be displayed perpetually (like the Taskbar). The usage of a screensaver that has a constantly changing image can help as well.

The fastest remedy for Image Persistence is to leave the monitor off for an extended period of time. This time can range anywhere from hours to days. Another useful approach to removing LCD image persistence is to first create a plain black background image and display the image as a screensaver for an extended period of time.

• Article on LCD Image Persistence