Origin
LCD(LiquidCrystalDisplay)maynotbeanewtermformanyusers,butthehistoryofthistechnologymayfarexceedOurimagination.Asearlyastheendofthe19thcentury,Austrianbotanistsdiscoveredliquidcrystals,thatis,liquidcrystals,whichmeansthatasubstancepossessesthefluidityofaliquidandacertainarrangementcharacteristicsimilartocrystals.Undertheactionofanelectricfield,thearrangementofliquidcrystalmoleculeswillchange,therebyaffectingitsopticalproperties.Thisphenomenoniscalledelectro-opticeffect.Usingtheelectro-opticaleffectofliquidcrystals,Britishscientistsmanufacturedthefirstliquidcrystaldisplay,orLCD,inthelastcentury.
Theworld'sfirstliquidcrystaldisplaydeviceappearedintheearly1970sandwascalledTN-LCD(twistednematic)liquidcrystaldisplay.Althoughitisamonochromedisplay,ithasbeenextendedtoelectronicwatches,calculatorsandotherfields.
Basicstructure
Liquidcrystalpanel
Theliquidcrystalpanelincludespolarizingfilm,glasssubstrate,blackmatrix,colorfilter,protectivefilm,commonelectrode,calibrationlayer,Liquidcrystallayer(liquidcrystal,spacer,sealant),capacitor,displayelectrode,prismlayer,lightscatteringlayer.
PolarizerisalsocalledPolarizer.Thepolarizerisdividedintoupperpolarizerandlowerpolarizer.Thepolarizationfunctionsoftheupperandlowerpolarizersareperpendiculartoeachother,andtheirfunctionislikeafence,blockingaccordingtorequirementsThelightwavecomponent,forexample,blocksthelightwavecomponentperpendiculartothepolarizerfence,andonlyallowsthelightwavecomponentparalleltothefencetopass.
Glasssubstratecanbedividedintoanuppersubstrateandalowersubstrateinaliquidcrystaldisplay,anditsmainfunctionistoclamptheliquidcrystalmaterialinthespacebetweenthetwosubstrates.Thematerialoftheglasssubstrategenerallyadoptsalkali-freeborosilicateglasswithexcellentmechanicalproperties,heatresistanceandchemicalcorrosionresistance.ForTFT-LCD,onelayerofglasssubstrateisdistributedwithTFTs,andtheotherlayerofglasssubstrateisdepositedwithcolorfilters.
BlackMatrixisusedtoseparatethethreeprimarycolorsofred,green,andblueinthecolorfilter(topreventcolorconfusion)bymeansofamaterialwithhighshadingperformance,andtopreventlightleakage,therebyhelpingtoimproveeachcolorThecontrastoftheblock.Inaddition,inTFT-LCD,theblackmatrixcanalsoconcealinternalelectrodetracesorthinfilmtransistors.
Colorfilter(ColorFilter)isalsocalledcolorfilterfilm,itsfunctionistoproducered,green,andblueprimarycolorsoflight,toachievethefull-colordisplayoftheliquidcrystaldisplay.
Alignmentlayer(AlignmentLayer)isalsocalledalignmentfilmoralignmentlayer,itsfunctionistoenableliquidcrystalmoleculestoachieveuniformarrangementandorientationonthemicroscopiclevel.
Thetransparentelectrodeisdividedintoacommonelectrodeandapixelelectrode,andtheinputsignalvoltageisappliedbetweenthepixelelectrodeandthecommonelectrode.Thetransparentelectrodeisusuallyformedbydepositingindiumtinoxide(ITO)materialonaglasssubstratetoformatransparentconductivelayer.
LiquidCrystalMaterial(LiquidCrystalMaterial)playsarolesimilartoalightvalveinLCD,whichcancontrolthebrightnessofthetransmittedlight,soastoachievetheeffectofinformationdisplay.
ThedriverICisactuallyasetofintegratedcircuitchipdevicesusedtoadjustandcontrolthephase,peakvalue,frequency,etc.ofthepotentialsignalonthetransparentelectrode,establishadrivingelectricfield,andfinallyrealizetheinformationdisplayoftheliquidcrystal.
Intheliquidcrystalpanel,theactivematrixliquidcrystaldisplayiscomposedofatwistednematic(TN)liquidcrystalmaterialenclosedbetweentwoglasssubstrates.Amongthem,theupperglasssubstrateclosetothedisplayscreenisdepositedwithred,green,andblue(RGB)colorfilters(orcolorfilters),ablackmatrix,andacommontransparentelectrode.Thelowerglasssubstrate(thesubstratefartherfromthedisplayscreen)isequippedwiththinfilmtransistor(TFT)devices,transparentpixelelectrodes,storagecapacitors,gatelines,signallines,etc.Analignmentfilm(oralignmentlayer)ispreparedontheinnersideofthetwoglasssubstratestoaligntheliquidcrystalmolecules.Theliquidcrystalmaterialispouredbetweenthetwoglasssubstrates,andspacersarespreadtoensuretheuniformityofthegap.Thesurroundingsarebondedbyframesealinggluetoplayasealingrole;andthecommonelectrodesoftheupperandlowerglasssubstratesareconnectedbymeansofthesilverglueprocess.
Polarizers(orpolarizingfilms)areattachedtotheoutersidesoftheupperandlowerglasssubstrates.Whenavoltageisappliedbetweenthepixeltransparentelectrodeandthecommontransparentelectrode,thearrangementstateoftheliquidcrystalmoleculeswillchange.Atthistime,theintensityofincidentlightpassingthroughtheliquidcrystalalsochangesaccordingly.Theliquidcrystaldisplayisbasedontheopticalrotationoftheliquidcrystalmaterial,coupledwiththecontroloftheelectricfield,torealizeinformationdisplay.
Backlightmodule
LCDproductisanon-activelight-emittingelectronicdevice,whichdoesnothavelight-emittingcharacteristics.Itmustrelyontheemissionofthelightsourceinthebacklightmoduletoobtaindisplayperformance.ThebrightnessoftheLCDisdeterminedbyitsbacklightmodule.Itcanbeseenthattheperformanceofthebacklightmoduledirectlyaffectsthedisplayqualityoftheliquidcrystalpanel.
Thebacklightmoduleincludesalightingsource,areflectiveplate,alightguideplate,adiffuser,abrightnessenhancementfilm(prismsheet),andaframe.ThebacklightmodulesusedinLCDscanbemainlydividedintotwocategories:edge-litbacklightmodulesanddirect-litbacklightmodules.Mobilephones,notebookcomputersandmonitors(15inches)mainlyuseedge-litbacklightmodules,whileLCDTVsmostlyusedirect-typebacklightmodulelightsources.ThebacklightmodulelightsourcemainlyusesColdCathodeFluorescentLamp(CCFL)andLightEmittingDiode(LED)asthebacklightsourceoftheLCD.
ReflectorSheet(ReflectorSheet)isalsocalledthereflector.Itsmainfunctionistocompletelysendthelightemittedbythelightsourceintothelightguideplatetoreduceuselesslossasmuchaspossible.
ThemainfunctionoftheLightGuidePlateistoguidethelightemittedbythesidelightsourcetothefrontofthepanel.
PrismFilmisalsoknownasBrightnessEnhancementFilm.Itsmainfunctionistorefractionandtotalreflectionofthescatteredlightthroughthefilmlayer,focusingonacertainangleandthenfromthebacklight.Thesourceisemittedtoachievethedisplayeffectofbrighteningthescreen.
Themainfunctionofthediffuseristocorrecttheedgelightofthebacklightmoduleintoauniformsurfacelightsourcetoachievetheeffectofopticaldiffusion.Thediffuserisdividedintoanupperdiffuserandalowerdiffuser.Theupperdiffusionsheetislocatedbetweentheprismsheetandtheliquidcrystalassemblyandisclosertothedisplaypanel.Thelowerdiffusionsheetislocatedbetweenthelightguideplateandtheprismsheet,whichisclosertothebacklightsource.
Workingprinciple
LCDisadisplaythatusesliquidcrystalasitsmaterial.Liquidcrystalisatypeoforganiccompoundbetweensolidandliquid.Undernormaltemperatureconditions,itexhibitsbothliquidfluidityandopticalanisotropyofcrystals.Itwillbecomeatransparentliquidwhenheated,andwillbecomecrystallineaftercooling.Theturbidsolidstate.
Undertheactionofanelectricfield,thearrangementofliquidcrystalmoleculeswillchange,whichwillaffecttheintensityoftheincidentlightbeamthroughtheliquidcrystal.Thischangeinlightintensityisfurthermanifestedaslightanddarkthroughtheactionofthepolarizer.Thechange.Accordingly,throughthecontroloftheelectricfieldoftheliquidcrystal,thebrightnessofthelightcanbechanged,soastoachievethepurposeofinformationdisplay.Therefore,theroleoftheliquidcrystalmaterialissimilartoasmall"lightvalve."
Becausetherearecontrolcircuitsanddrivecircuitsaroundtheliquidcrystalmaterial.WhentheelectrodesintheLCDgenerateanelectricfield,theliquidcrystalmoleculeswillbetwisted,sothatthelightpassingthroughitwillberegularlyrefracted(theopticalrotationoftheliquidcrystalmaterial),andthenfilteredbythesecondlayerofpolarizeranddisplayedonthescreen.
Itisworthpointingoutthatbecausetheliquidcrystalmaterialitselfdoesnotemitlight,theLCDusuallyneedstobeequippedwithadditionallightsourcesforthedisplaypanel.Themainlightsourcesystemiscalled"backlightmodule".Amongthem,thebacklightboardisItiscomposedoffluorescentmaterial,whichcanemitlight,anditsmainfunctionistoprovideauniformbacklight.
Monochromedisplay
LCDtechnologyistofillliquidcrystalbetweentwoplaneslinedwithfinegrooves.Thegroovesonthesetwoplanesareperpendiculartoeachother(intersectat90degrees).Inotherwords,ifthemoleculesononeplanearealignednorth-south,themoleculesontheotherplanearealignedeast-west,andthemoleculesbetweenthetwoplanesareforcedintoa90-degreetwistedstate.Becausethelighttravelsalongthedirectionofthemoleculararrangement,thelightisalsotwisted90degreeswhenpassingthroughtheliquidcrystal.Whenavoltageisappliedtotheliquidcrystal,theliquidcrystalmoleculeswillrotatetochangethelighttransmittance,therebyrealizingmulti-grayscaledisplay.
LCDusuallyconsistsoftwomutuallyperpendicularpolarizers.Thepolarizeractslikeafence,blockingthelightwavecomponentasrequired.Forexample,thelightwavecomponentperpendiculartothebarrierofthepolarizerisblocked,andonlythelightwavecomponentparalleltothebarrierisallowedtopass.Naturallightradiatesrandomlyinalldirections.Twopolarizersperpendiculartoeachothershouldblockallnaturallightthatattemptstopenetrateundernormalcircumstances.However,becausethetwopolarizersarefilledwithtwistedliquidcrystals,afterthelightpassesthroughthefirstpolarizer,itwillbetwisted90degreesbytheliquidcrystalmolecules,andfinallypassthroughthesecondpolarizer.
Colordisplay
FornotebookcomputersordesktopLCDs,morecomplexcolordisplaysarerequired.
ForcolorLCDs,itisalsonecessarytohaveacolorfilterlayerthatspecializesincolordisplay,theso-called"colorfilter",alsoknownas"colorfilter."InacolorLCDpanel,eachpixelisusuallycomposedof3liquidcrystalcells,eachofwhichhasared,green,orblue(RGB)three-colorfilterinfrontofeachcell.Inthisway,thelightpassingthroughdifferentcellscandisplaydifferentcolorsonthescreen.
Colorfilters,blackmatrixandcommontransparentelectrodesaregenerallydepositedonthefrontglasssubstrateofthedisplayscreen.ColorLCDcancreatecolorfulimagesinhigh-resolutionenvironments.
Dynamicimagedisplay
Humanvisualorgans(eyes)perceivedynamicimageswiththeso-called"visualresidual"phenomenon,thatis,thehigh-speedmotionpicturewillformashort-terminthehumanbrainimpression.Earlycartoons,moviesandeventhelatestgameshowsappliedtheprincipleof"visualresidue",allowingaseriesofgradualimagestobedisplayedinrapidsuccessioninfrontofpeople'seyes,formingdynamicimages.
Whenmultipleimagesaregeneratedataspeedexceeding24frames/s,thehumaneyewillperceivecontinuousimages.Thisisalsotheoriginofthemovieplaybackspeedof24framespersecond.Ifthedisplayspeedislowerthanthisstandard,peoplewillobviouslyfeelthepauseanddiscomfortofthepicture.Calculatedaccordingtothisindex,thedisplaytimeofeachpictureneedstobelessthan40ms.Fastmovingpicturesaredisplayedwithhighdefinition,andthegeneralvideomovementspeedexceeds60frames/s.Thatistosay,theintervaltimeofeachframeoftheactivepictureis16.67ms.
Iftheresponsetimeoftheliquidcrystalislongerthantheintervaltimeofeachframeofthescreen,peoplewillfeelthatthescreenisalittlefuzzywhenwatchingfast-movingimages.ResponsetimeisaspecialindicatorofLCD.TheresponsetimeofLCDreferstothespeedatwhicheachpixelofthedisplayreactstotheinputsignal,whichistheresponsetimeoftheliquidcrystalfrom"darktobright"orfrom"brighttodark".Thisvalueisassmallaspossible,andasufficientlyfastresponsetimecanensurethecontinuityofthepicture.Iftheresponsetimeistoolong,itispossiblethattheLCDwillhavethefeelingoftrailingshadowswhendisplayingdynamicimages.ThegeneralresponsetimeofLCDis2～5ms.
TFTdrive
Theso-calledTFTreferstothetransistorarrayontheglasssubstrateoftheliquidcrystalpanel,sothateachpixeloftheLCDhasitsownsemiconductorswitch.Eachpixelcancontroltheliquidcrystalbetweenthetwoglasssubstratesthroughdotpulses,thatis,throughactiveswitchestoachieveindependentandprecisecontrolofeachpixel"point-to-point".Therefore,eachnodeofthepixelisrelativelyindependentandcanbecontinuouslycontrolled.
TheTFTLCDismainlycomposedofaglasssubstrate,agateelectrode,adrainelectrode,asourceelectrode,andasemiconductoractivelayer(a-Si).
TheTFTarrayisgenerallydepositedtogetherwithtransparentpixelelectrodes,storagecapacitors,gatelines,signallines,etc.ontherearglasssubstrateofthedisplayscreen(thesubstratefartherfromthedisplayscreen).Theconfigurationofsuchatransistorarrayhelpstoimprovetheresponsespeedoftheliquidcrystaldisplay,andcanalsocontrolthedisplaygraylevel,therebyensuringthattheimagecoloroftheLCDismorerealisticandthepicturequalityismorepleasingtotheeye.Therefore,mostLCDs,LCDTVsandsomemobilephonesaredrivenbyTFT,whetheritisasmallandmedium-sizedLCDwithanarrowviewingangletwistednematic(TN)mode,oralarge-sizeLCDwithawideviewingangleparallelarrangement(IPS)mode.Liquidcrystaltelevisions(LCD-TV),theyarecommonlyreferredtoas"TFT-LCD".
IPS
IPSscreen(In-PlaneSwitching,in-planeswitching)technologyisaliquidcrystalpaneltechnologylaunchedbyHitachiin2001,commonlyknownas"SuperTFT".IPSscreenisatechnologybasedonTFT,anditsessenceisTFTscreen.IPSsolvestheviewingangleproblembymakingtheapparentlengthofthemoleculesthesameinalldirections.
ThereasonwhytheIPShardscreenhasaclearandsuperstabledynamicdisplayeffectdependsonitsinnovativehorizontalconversionmoleculararrangement,whichchangestheverticalmoleculararrangementoftheVAsoftscreen,thushavingamorerobustandstableliquidcrystalstructure.Notinthesuperficialsense,thehardscreenistoaddahardprotectivefilmtotheLCDpanel,inordertopreventtheLCDscreenfrombeingdamagedbyexternalhardobjects.
SLCD
S-LCDpanelisPVApanel,Samsung’smainPVAmodewideviewingangletechnology,S-LCDpaneladoptsPVAtechnology,whichusestransparentITOelectrodelayer,soItshigherapertureratiocanobtainbrightnessoutputbetterthanMVA;PVAtechnologyalsohasahighcontrastratioof500:1andaprimarycolordisplaycapacityofupto70%.
Technicalparameters
Brightness
Themaximumbrightnessofliquidcrystaldisplaysisusuallydeterminedbythebacklightsource.Technicallyitcanachievehighbrightness,butthisdoesnotmeanbrightnessThehigherthevalue,thebetter,becauseadisplaywithtoohighbrightnessmayhurttheviewer'seyes.LCDisasubstancebetweensolidandliquid.Itcannotemitlightbyitselfandrequiresadditionallightsources.Therefore,thenumberoflampsisrelatedtothebrightnessoftheliquidcrystaldisplay.
Resolution
Resolutionreferstothenumberofpixelsdisplayedperunitarea.Thephysicalresolutionoftheliquidcrystaldisplayisfixed.FortheCRTdisplay,aslongasthedeflectionvoltageoftheelectronbeamisadjusted,differentresolutionscanbechanged.However,itismuchmorecomplicatedtoimplementinaliquidcrystaldisplay,andthedisplayeffectmustbesimulatedthroughcalculations,andtheactualresolutionhasnotchanged.Sincenotallpixelsarezoomedinatthesametime,thereisazoomerror.Whentheliquidcrystaldisplayisusedinanon-standardresolution,thetextdisplayeffectwilldeteriorate,andtheedgesofthetextwillbeblurred.
Colorfulness
ThemostimportantthingaboutLCDiscolorperformance.Weknowthatanycolorinnatureiscomposedofthreebasiccolors:red,greenandblue.Forexample,anLCDpanelwitharesolutionof1024×768isdisplayedby1024×768pixels,andthecolorofeachindependentpixeliscontrolledbythreebasiccolorsofred,green,andblue(R,G,B).MostmanufacturersproduceLCDmonitors,eachbasiccolor(R,G,B)reaches6bits,thatis,64kindsofexpression,theneachindependentpixelhas64×64×64=262144kindsofcolors.Therearealsomanymanufacturersthatusetheso-calledFRC(FrameRateControl)technologytoexpressfull-colorimagesinasimulatedmanner,thatis,eachbasiccolor(R,G,B)canreach8bits,thatis,256expressions.,Theneachindependentpixelhasasmanyas256×256×256=16777216colors.
Contrast
Contrastisdefinedastheratioofthemaximumbrightnessvalue(fullwhite)dividedbytheminimumbrightnessvalue(fullblack).ThecontrolIC,filterandorientedfilmandotheraccessoriesusedinLCDmanufacturingarerelatedtothecontrastofthepanel.
Responsetime
Theresponsetimereferstotheresponsespeedoftheliquidcrystaldisplaytotheinputsignal,thatis,theresponsetimeoftheliquidcrystalfromdarktobrightorfrombrighttodark,usuallyinmillisecondsAsaunit.Ofcourse,thesmallerthevalue,thebetter.Iftheresponsetimeistoolong,itispossiblethattheliquidcrystaldisplaywillhavethefeelingoftrailingshadowswhendisplayingdynamicimages.
Viewingangle
TheviewingangleoftheLCDissymmetrical,butnotnecessarilyupanddown.Forexample,whentheincidentlightfromthebacklightpassesthroughthepolarizer,liquidcrystal,andalignmentfilm,theoutputlighthasspecificdirectionalcharacteristics,thatis,mostofthelightemittedfromthescreenhasaverticaldirection.Ifwelookatacompletelywhitepicturefromaveryobliqueangle,wemayseeblackorcolordistortion.Generallyspeaking,theupanddownangleshouldbelessthanorequaltotheleftandrightangle.Iftheviewingangleis80degreestotheleftandright,itmeansthatthescreenimagecanbeclearlyseenatthepositionof80degreesfromthenormallineofthescreen.However,becausepeoplehavedifferentvisionranges,ifyoudon'tstandwithinthebestviewingangle,youwillseeerrorsincolorandbrightness.
Viewablearea
ThesizemarkedontheLCDisthesameastheactualscreenrangethatcanbeused.Forexample,a15.1-inchLCDmonitorisapproximatelyequaltothevisualrangeofa17-inchCRTscreen.
AdvantagesandDisadvantages
Advantages
Themainprincipleofliquidcrystaldisplayistostimulatetheliquidcrystalmoleculestogeneratedots,linesandsurfacestoformapicturewiththebacklighttube.IthasThefollowingfourfeatures:
(1)Thebodyisthinandsavesspace.ComparedwiththemorebulkyCRTmonitor,theLCDmonitoronlyneedsone-thirdofthespaceoftheformer;
(2)Itsaveselectricityanddoesnotgeneratehightemperature.Itisalowpowerconsumptionproduct.ComparedwithCRTmonitors,itcanbecompletelynon-hot;(3)Noradiation,whichisgoodforhealth,andLCDmonitorsarecompletelyfreeofheat.Radiation;
(4)Thescreenissoftanddoesnothurttheeyes.UnlikeCRTtechnology,theLCDscreenwillnotflicker,whichcanreducethedamagetotheeyesofthedisplayandmaketheeyeslessfatigued.
Disadvantages
(1)Thevisualdeflectionangleissmall;
(2)Itiseasytoproduceimagetailingphenomenon(suchastherapidshakingofthemousepointer),whichisSinceordinaryLCDscreensaremostly60Hz(display60framespersecond),thisproblemmainlyoccursingameswhenLCDmonitorswerejustpopular(ie"screentearing");
(3)LCDmonitorsThebrightnessandcontrastarenotverygood;
(4)LCD"deadpixels"problem;
(5)Lifeislimited;
(6)WhendistinguishingWhentheresolutionislowerthanthedefaultresolutionofthemonitor,thepicturewillbeblurred;
(7)Whentheresolutionisgreaterthanthedefaultresolutionofthemonitor(mandatorysoftwaresettingisrequired),thecolorinthedetailswillbelost.
Commonsenseofmaintenance
Safeandclean
Ifthereisdustonthemonitorscreenpanel,pleasefollowtheadviceofprofessionalmaintenancepersonneltooperate,personallydonotjustfindarag,Orroughthingstowipe,becauseitiseasytodamagetheLCDscreenduetoimproperpersonaloperation,thecorrectmethodofwipingshouldchoosearelativelycleanandsoftclothtowipe,sothatitwillnotcausedamagetothedisplayscreenpanel.Duringthewipingprocess,donotspraywaterordetergentdirectlyonthescreen.Youcandipalittlespecialdetergentonasoftclothandwipethescreengently,whichpreventsthedetergentfromflowingintothescreenandcausingashortcircuit.Whenwipingthemonitorscreenpanel,becarefultouselightforce,letalonescratchthepanelwithhardobjects.Donotletanyliquidenterthegapofthemonitorboundary.Therearemanyexamplesofdamagetothemonitorcausedbytheliquidenteringthegapaccidentally.
Whencleaning,itisrecommendedthatthepoweranddatacablesarephysicallyseparatedfor20minutes,andthenthedisplayshouldbeplacedflat(toavoidliquidflowingintothegapduetogravity),andthescreenwipingclothshouldbeslightlymoistened.Payattentiontotheboundarywhenwipinggently.Neverspraycleanerorwaterdirectlyonthescreen(avoidformingliquidandflowingintothegap).Whentheliquidevaporates,itcanbeusedlater.
Avoidgettingwater
NeverletanythingwithmoistureentertheLCDdisplay.Ofcourse,oncethishappens,don’tpanic.Ifyoufindthatthereisonlyafogonthesurfaceofthescreenbeforeturningiton,justwipeitoffwithasoftcloth.IfthemoisturehasenteredtheLCDdisplay,thenputtheLCDdisplayinaventilatedanddryplace.Themoistureinsidewillgraduallyevaporate.Ifthescreen"flooding"ismoreserious,itisbetterforordinaryuserstocalltheserviceproviderforhelp,becausethemoreseriousmoisturewilldamagethecomponentsoftheLCDdisplay.Causestheliquidcrystalelectrodetocorrode,causingpermanentdamage.Inaddition,alwaystrytoavoidusingLCDmonitorsinhumidenvironments.
Avoidbumps
LCDdisplaysarerelativelyfragile,soyoushouldbecarefulnottobe"breached"byotherdevicesduringnormaluse.Alsopayattentionwhenusingthecleaner.Donotspraythecleanerdirectlyonthescreen.Itmayflowintothescreenandcauseashortcircuit.Thecorrectwayistouseasoftclothtostickthecleanerandgentlywipethescreen.Remember,Theabilityofliquidcrystaldisplaystoresist"shocks"isverysmall.Manycrystalsandsensitiveelectricalcomponentswillbedamagedwhentheyarehit,sopleasehitsharpobjectsinahurry.
Timework
Thepixelsofliquidcrystaldisplaysarecomposedofmanyliquidcrystals.Continuoususeforalongtimewillcausethecrystalstoageorburnout.Oncedamageoccurs,Itispermanentandirreparable.Generallyspeaking,donotleavetheLCDdisplayonforalongtime(continuouslymorethan72hours),andturnoffthedisplaywhenitisnotinuse.
OverloadworkofLCDmonitormainlyincludesthefollowingpoints:
(1)Longworkinghours;
(2)Highbrightness;
(3)Carelesslyturnoffthepower;
(4)Continuouslydisplayafixedcontentforalongtime.
Protectionmeasures:
(1)LettheLCDdisplaydisplayacompletelywhitescreencontent;
(2)ReducethebrightnessoftheLCDdisplaySmalltoarelativelydarklevel;
(3)oftenchangethedisplaycontentontheLCDscreenatdifferenttimeintervals;
(4)pleaseturnoffthedisplaywhenyouareokay.
Airrequirements
Generally,ifthehumidityismaintainedbetween30%and80%,thedisplaycanworknormally,butoncetheindoorhumidityishigherthan80%,thedisplaywillcauseinternalproblems.Exposurephenomenon.Theinternalpowertransformerandothercoilsarealsopronetoleakagewhentheyaredamp,andmayevencauseashortcircuitintheconnection.Therefore,LCDdisplaysmustbeprotectedfrommoisture.Displaysthatarenotusedforalongtimecanbeenergizedforaperiodoftime,sothattheheatgeneratedbythedisplaywilldriveoutthemoistureinthemachine.
Faultsandrepairs
Whitescreen
Thewhitescreeniscausedbythenormalbacklightandthescreendidnotreceivethesignalfromthemotherboardcorrectly,whichmeanshighvoltagePartofitisgood.ThewhitescreenisbecausetheT-CONboardontheupperpartoftheLCDscreenstopsworkingorworksabnormally.ItmaybecausedbytherelatedfailureofthecircuitthatpowerstheLCDT-CONboardonthedriverboard(thevoltageisgenerally5V,andafewLCDscreensuse12Vor3.3Vpowersupply)orthedisplaymotherboardcontrolmainchipandMCUhavepoorordamagedcharacteristics.TherearechipsonthemarketthathavebeenwrittenintovarioustypesofMCUprograms.Aslongasyouremovetheoriginalchiponthemaincontrolboardandreplacethenewchipwiththeprogram,thisfailurecanbesolved.
Blackscreen
Intheactualmaintenanceprocess,theblackscreenismostlythecase,andtheblackscreenisdividedintothreetypes:thepowerlightflashes,thepowerlightisonoroff.
(1)Liquidcrystaldisplaypowersupplylightflashes.Powersupplylightflashesaremostlyshort-circuitedintheback-stageswitchtubeofthehigh-voltageboardduringmaintenance.WhentheLCDdriverboardsendsoutthecontrolvoltagetoturnonthehigh-voltageboard,theboostcircuitstartstowork,Butoneorapairofswitchtubesareshort-circuitedtotheground,andthemainpowersupplyispulleddown,whichcausesthepowersupplyoftheLCDdriverboardtobepulleddown.Theboardvoltageoutputreturnstonormalagain.Therefore,thepowerlightwillturnonandoffagainandagain.Replacementofthecorrespondingfaultycomponentfailureshouldbeabletosolveit.
(2)Thepowerlightoftheliquidcrystaldisplayisonforalongtimetoconfirmthatthepowersupplypartisnormal,mainlybecausethefinalstageofthehigh-voltageinvertercircuitorthepowersupplystagecomponentsgeneratealargeamountofheat,andlong-termworkcausesavirtualweldingspot.Cause;themostpronetofailureofthiscircuitistheboostcoil,whichisgenerallyaproblemofpoorcontact,andthecircuitshouldbechecked.
(3)ThepowerlightoftheLCDmonitorisnoton.Thepowerlightisnoton.Thepowersupplyshouldbechecked.Themainthingistocheckwhetherthe12Vand5Vvoltageisnormal.Thepowerlightisoff.Checkwhethertheswitchtubehaspoorthermalstability,orthebaseelectrodeissoldered,andthecapacitorisbulging.Inaddition,thepulsewidthmodulationmonolithicswitchingpowersupply,thepulsewidthmodulationintegratedcontrollerusedgenerallyincludesSG6841,UC3842,andUC3843.Componentswithahigherfailurerate.
Backlightfailure
Inadditiontotheabovefailures,LCDbacklightfailuresarealsocommon,whicharemainlymanifestedasagingandcompletedamage,thatis,nolight.Afterthebacklightisaging,youcanseethattheimagebecomesyellow.Adjustingthecolortemperatureandwhitebalancecannotbesolvedwell.Atthesametime,adjustingthescreenbrightnesstothemaximumisdifficulttomeettherequirementsofuse,whichremindsyouthatitistimetochangethelight.
Afterthesingle-tubestructuredisplayisdamaged,youcanseethedimgraphicdisplaywhenyouturnonthescreenandsquintinthesun.Thenewmulti-lampdisplayshowsunevenimagebrightnesswhenacertainlampisdamaged.Forexample,iftheupperpartisdim,thatmeanstheupperlampisdamaged.Touchthepositionofthelamponthedisplaybyhand,andyoucanjudgewhetherthelampisornotbycomparingthetemperature.Damaged,thetemperatureofthenormaldisplaylamptubepositionshouldbethesame.However,sincemostofthenewdisplayshavehigh-voltagebalanceprotectioncircuits,itisnotthatthebrightnessofalampisunbalanced,butthatthedisplaycannotbeturnedonorthescreenisblackafterturningon.Thisdependsonthespecificdisplaycircuit.