8
In order to qualify for repair due to pixel defects during the warranty period, a PDP / TFT panel in
a Plasma / LCD display must have pixel or sub-pixel defects exceeding the tolerances listed in the
following table.
Dark spots or patches may occasionally appear on some LCD panels. This is known within the industry as
Mura, which is a Japanese term for “unevenness.” It is used to describe an irregular pattern or area in
which uneven screen uniformity appears under certain conditions. Mura is a result of the deterioration of
the liquid crystal alignment layer and is most commonly caused by long-term operation under high
ambient temperatures. It is an industry-wide phenomenon and Mura is not repairable or covered by ou
warranty terms. Mura has been around since the introduction of LCD technology and with screens getting
bigger and in operation 24/7, many displays are running in low light conditions. This all adds to the
possibility of Mura affecting displays.
There are many symptoms of Mura and also multiple causes. Several of these are listed below
Impurities or foreign particles in the crystal matri
Uneven distribution of LCD matrix during manufacturin
Non-uniform luminance distribution of the backligh
Panel assembly induced stres
Flaws within the LCD cell
Thermal induced stress - high temperature operation over long periods of time
Although we can not guarantee the complete eradication of Mura every time, the appearance of Mura can
be minimized by using these methods
Lower the backlight brightnes
Use a screen save
Reduce the ambient temperature around the unit
How to Spot Mura
How to Avoid Mura
5.4. Pixel Defect Tolerances
5.5. Mura
BRIGHT DOT EFFEC
1 lit sub pixe
BLACK DOT EFFEC
1 dark sub pixe
TOTAL DOT DEFECTS
ACCEPTABLE LEVE
ACCEPTABLE LEVE
1
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