Philips BDL6520QL - Pixel Defect Management; Dark Dot Defect Examples; Pixel Defect Proximity and Tolerances; Understanding MURA

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BDL6520QL

8.4. 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 Twoadjacentdarkdots=1pairofdarkdots Twodarkdots,specicationsdenesthe

minimumdistancebetweendarkdots

8.5. 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speciestolerancesforthe

proximityofpixeldefects.Inthetablebelowyoucanndspecications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

8.6. 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.

BRIGHTDOTEFFECT ACCEPTABLELEVEL

1litsubpixel 2

BLACKDOTEFFECT ACCEPTABLELEVEL

1darksubpixel 10

TOTALDOTDEFECTSOFALLTYPES 12

NOTE:*1or2adjacentsubpixeldefects=1dotdefect

8.7. 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

• FlawswithintheLCDcells

• Thermalinducedstress-hightemperatureoperationoverlongperiodsof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