Image persistence, or image retention, is the

LCD A liquid-crystal display (LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers. Liquid crystals do not emit light directly but in ...

and

plasma display A plasma display panel (PDP) is a type of flat panel display that uses small cells containing plasma: ionized gas that responds to electric fields. Plasma televisions were the first large (over 32 inches diagonal) flat panel displays to be release ...

equivalent of

screen burn-in Screen burn-in, image burn-in, or ghost image, is a permanent discoloration of areas on an electronic display such as a cathode ray tube (CRT) in an old computer monitor or television set. It is caused by cumulative non-uniform use of the scre ...

. Unlike screen burn, the effects are usually temporary and often not visible without close inspection. Plasma displays experiencing severe image persistence can result in screen burn-in instead. Image persistence can occur as easily as having something remain unchanged on the screen in the same location for a duration of even 10 minutes, such as a web page or document. Minor cases of image persistence are generally only visible when looking at darker areas on the screen, and usually invisible to the eye during ordinary computer use.

Cause

Liquid crystal Liquid crystal (LC) is a state of matter whose properties are between those of conventional liquids and those of solid crystals. For example, a liquid crystal may flow like a liquid, but its molecules may be oriented in a crystal-like way. T ...

s have a natural relaxed state. When a

voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to m ...

is applied they rearrange themselves to block certain

light wave In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visible) ligh ...

s. If left with the same voltage for an extended period of time (e.g. displaying a pointer or the

Taskbar A taskbar is an element of a graphical user interface which has various purposes. It typically shows which programs are currently running. The specific design and layout of the taskbar varies between individual operating systems, but generally a ...

in one place, or showing a static picture for extended periods of time), 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 Color (American English) or colour (British English) is the visual perceptual property deriving from the spectrum of light interacting with the photoreceptor cells of the eyes. Color categories and physical specifications of color are associ ...

off by a slight degree, which causes the image to look like the traditional "burn-in" on phosphor based displays. In fact, the root cause of LCD image persistence is the same as phosphor burn-in, namely, non-uniform usage of the display's pixels. The cause of this tendency is unclear. It might be due to accumulation of ionic impurities inside the LCD, electric charge building up near the electrodes,

parasitic capacitance Parasitic capacitance is an unavoidable and usually unwanted capacitance that exists between the parts of an electronic component or circuit simply because of their proximity to each other. When two electrical conductors at different voltages a ...

, or "a DC voltage component that occurs unavoidably in some display pixels owing to anisotropy in the dielectric constant of the liquid crystal".

Prevention and treatment

Image persistence can be reversed by allowing the liquid crystals to relax and return to their relaxed state, such as by turning off the monitor for a sufficiently long period of time (at least a few hours). For most minor cases, simply continuing to use the computer as usual (and thus allowing other colors to "cover" the affected regions) or turning off the monitor for the night is more than enough. One strategy for users looking to avoid image persistence artifacts is to vary the activities performed on a computer to avoid static colors and hide elements on the screen which are displayed perpetually (such as an OS's

). Another strategy is the usage of a

screensaver A screensaver (or screen saver) is a computer program that blanks the display screen or fills it with moving images or patterns when the computer has been idle for a designated time. The original purpose of screensavers was to prevent phosphor ...

to help during times the computer is left unattended. Covering the entire display area with pure white for an extended period of time is also a useful proactive solution.{{Cite web , url=https://www.necdisplay.com/documents/UserManuals/EA275UHD_CD_EN_UserManual.pdf , title=Archived copy , access-date=2018-10-05 , archive-date=2020-09-21 , archive-url=https://web.archive.org/web/20200921003733/https://www.necdisplay.com/documents/usermanuals/ea275uhd_cd_en_usermanual.pdf , url-status=dead

References

External links

Article on LCD image persistence
Display technology Liquid crystal displays