Philips Pixel Defect Policy - Philips BDL5587XL Service Manual

16 BDL5587XL LCD
Philips' Flat Panel Displays Pixel Defect Policy
Philips strives to deliver the highest quality products. We use some of the
industry's most advanced manufacturing processes and practice stringent
quality control. However, pixel or sub-pixel defects on the PDP / TFT panels
used in Plasma- & LCD- displays are sometimes unavoidable. No
manufacturer can guarantee that all panels will be free from pixel defects,
but Philips guarantees that any Plasma- & LCD- displays with an
unacceptable number of defects will be repaired during the warranty period
in line with your local guarantee conditions. This notice explains the different
types of pixel defects and defines the acceptable defect level for the
BDL4651VH LCD screen. In order to qualify for repair under warranty, the
number of pixel defects must exceed a certain level which is given in the
reference table. If the LCD screen is within specification a warranty
exchange / claim back will be refused. Additionally, because some types or
combinations of pixel defects are more noticeable than others, Philips sets
even higher quality standards for those.
Pixels and Sub pixels
A pixel, or picture element, is composed of three sub-pixels in the primary
colors of red, green and blue. Many pixels together form an image. When all
sub-pixels of a pixel are lit, the three colored sub-pixels together appear as a
single white pixel. When all are dark, the three colored sub-pixels together
appear as a single black pixel. Other combinations of lit and dark sub-pixels
appear as single pixels of other colors.
Types of Pixel Defects + Dot Definition
Pixel and sub-pixel defects appear on the screen in different ways. There are
three categories of pixel defects and several types of sub-pixel defects within
each category.
Dot definition = What is a defective "Dot"? : One or more defective,
adjacent sub-pixel are defined as one "dot". The no. of defective sub-pixels
are not relevant to define a defective dot. This means that a defective dot
can consist of one, two or three defective sub-pixels which can be dark or lit.
Bright Dot Defects
Bright dot defects appear as pixels or sub-pixels that are always lit or "on".
These are the examples of bright dot defects:
One lit red, green or Two adjacent lit
blue sub-pixel sub-pixels:
- Red + Blue = Purple
- Red + Green = Yellow
- Green + Blue = Cyan
(Light Blue)

Philips Pixel Defect Policy

Dark Dot Defects
Black dot defects appear as pixels or sub-pixels that are always dark or "off".
These are the examples of black dot defects
One dark dot l
Proximity of Pixel Defects
Because pixel and sub-pixels defects of the same type that are nearby one
another may be more noticeable, Philips also specifies tolerances for the
proximity of pixel defects. In the table below you can find specifications
about:
• Allowed amount of adjacent dark dots = (adjacent dark dots =1 pair of dark
dots)
• Minimum distance between dark dots
• Total no. of all defective dots
Pixel Defect Tolerances
In order to qualify for repair due to pixel defects during the warranty period, a
PDP / TFT panel in a Philips Plasma / LCD- display must have pixel or
sub-pixel defects exceeding the tolerances listed in the following table.
MODEL
1 lit sub pixel
1 dark sub pixel
TOTAL DOT DEFECTS OF ALL TYPES
Note: * 1 or 2 adjacent sub pixel defects = 1 dot defect
MURA
Dark spots or patches may occasionally appear on some liquid crystal
display (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.
It is also not covered by our 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.
HOW TO SPOT MURA
There are many symptoms of Mura and also multiple causes. Several of
these are listed below:
• Impurities or foreign particles in the crystal matrix
• Uneven distribution of LCD matrix during manufacturing
• Non-uniform luminance distribution of the backlight
• Panel assembly induced stress
Three adjacent lit
• Flaws within the LCD cells
sub-pixels (one white
• Thermal induced stress - high temperature operation over long periods of
dot)
time
HOW TO AVOID MURA
Although we can not guarantee the complete eradication of Mura every time,
in general the appearance of Mura can be minimized by these methods:
• Lower the backlight brightness
• Use a screen saver
• Reduce the ambient temperature around the unit
Two adjacent dark
dots = 1 pair of dark
dots
BRIGHT DOT EFFECT
BLACK DOT EFFECT
Two dark dots,
specifications defines
the minimum distance
between dark dots
ACCEPTABLE LEVEL
BDL5587XL
2
ACCEPTABLE LEVEL
10
12