Introduction
InthethirdsetofRenminbi,the1960versionof"RedOneCorner"andallbanknotesaboveoneyuanareprintedwithintaglioprintingonthefrontandback.Theremaining1,2,and5jiaobanknoteswereinitiallyintaglioprintedonthefrontandoffsetprintedontheback.Later,withtheeconomicdevelopment,thepurchasingpowerof1,2,and5jiaobanknotesbecamelowerandlower,andnoonewasgoingtoforgeit.Therefore,inordertoreduceprintingcosts,thebanknoteprintingplantchangedtheirfrontfacestolower-costoffsetplates.Theearlyintagliocornercouponsarefewinstock,andthepriceisofcoursemoreexpensivethanoffsetcornercoupons.
Thedistinctionbetween"gravure"and"offset"canbejudgedbylookingatthecolorandthree-dimensionalsenseofthepattern.Ifyoucomparethesetwobanknotes,thedifferenceisveryobviousandeasytojudge.Inaddition,forbeginners,youcanalsousethefollowingtwomethods:Thefirstis"touching".Thesixcharacters"People'sBankofChina"onthefrontoftheintagliorenminbihaveaveryobviousprotrudingfeeling.Aslongasyougentlytouchitwithyourfingerfromlefttoright,youcanclearlyfeelthateachcharacterisraised.Thesecondis"lookattheedge".Intaglioprintedcharactersandpatterns,theedgesofthelineswillhavesmall"burrs"causedbyinkdiffusion,whichcanbeseenclearlywithamagnifyingglass.Theedgesofoffsetprintinglinesaresmooth.
Principleandtechnology
Basicprinciple
Principleofimmiscibilityofoilandwater;
Principleofselectiveadsorptionofprintingplate;
Principleofdotcolorformation;
Principleofindirectprinting.
Thechoiceofoverprintingortrapping
Iftheoverprintingisnotcorrect,itiseasytoexposewhiteandaffecttheappearance,whileoverprintingiseasytosmearthebackduetothethickinklayer,sosingleWetpressanddryprintingoncolormachinestendtouseoverprinting,andwetpressandwetonmulticolormachinestendtousetrapping;
Wetpressoverprintingmusttakeintoaccountthepropertiesoftheink,andtheviscosityandadhesionofthefirstprintedinkmustbeLargerthanthepost-printedink,otherwisethepost-printedinkwillhavereverseoverprinting.Thepost-printedinkmustalsohavehighertransparency;
Whenprintinggoldinkandsilverinkoncoatedpaper,printinggoldinkandsilverinkonwhitepaperbytrappingmethodisbetterthanprintinggoldinkandsilverinkonwhitepaper.Thecolorsobtainedonotherbackgroundcolorsappearthickerandpurer;
Whenprintingblack,ifthereisonlyalargeareaofsolidimagesontheblackplate,usethemethodoftrappingtoincreasetheamountofinkontheblackplate.Theinkcolorobtainedbyprintingonpaperisthickerthanthatobtainedbyoverprintingonothersolidbackgroundcolors.However,overprintingisgenerallyusedforsmalllines.
Inordertoensurethatthetrappedplateiscoveredbytheinklayerbehind,thetrappingvolumeisusuallyincreasedby0.03~0.05mmonthebasisoftheregistrationaccuracyofthedevice.Iftheregistrationaccuracyis0.15mm,thetrappingpartisgenerally0.18~0.20mmlarger.
Four-colorprinting
Whenusingthefour-colorprintingprocess,ifthereisalargeareaofblacksolid,becausetheinksoliddensitydoesnotexceed1.8,printalargeareaofblacksolidwiththisdensity,Willlackathickvisualeffect,thecommonmethodistooverprintabout40%ofthecyanonthelargeblacksolidpart.
Angleselection
Therearefouranglesforthenetworkcabletochoosefrom,15°,45°,75°,90°.
Four-colorprinting,themaincolorisgenerally45°,theyellowversionisaweakcolor,choose90°;
Three-coloroverprinting,usually30°,60°and90°Angle;
Two-coloroverprinting,usually45°and90°;
Inspotcolorprinting,single-colorgradationprintingorsingle-colorgradationsolidprintingisused,andthegradationversionuses45°Thecornersareusuallymorebeautiful;
The45°networklinehasthebestvisualeffect.Itisgenerallyusedtoshowtheskincolorofthecharacters,andismostlyusedinmagenta;
Theskeletonthatconstitutestheentirepictureisgenerally15°,75°.
Spotcolorprinting
Oneproductusesfour-colorprintingandspot-colorprintingatthesametime:thefour-colorprintingpartcancorrectlyrestorethepicturebycontrollingthesoliddensity,andthebackgroundcolorpartisincreasedbyappropriatelyincreasingtheinkTheamountofinktoobtainauniformandthickvisualeffect.
IftheelectronicfileorfilmprovidedbythecustomerisinadditiontotheCMYKfourcolorsplus2~3spotcolors,andoneofthespotcolorinkscoversasmallarea,itiseasytomatchwithCMYK,youcanSubtractthisspotcolor.IftheoriginalmanuscriptprovidedbythecustomerisonlyCMYKfour-coloroverprinting,butitshueisdifficulttocontrolinactualprinting,suchascyanandmagentaoverprintingintopurple,iftheamountofcyaninkislarge,itwillbecomeblue,andiftheamountofmagentainkislarge,itwillbecomered.Atthistime,youmaywishtochangethistoaspotcolorpurpleversion.Althoughthereisonemoreversion,theprintingpreparationtimeisshortened,theprintingspeedisincreased,andthehuecontrolisstabilized.
Waterlessoffsetprinting
Principleofpositivetypewaterlessoffsetprinting:Itiscomposedofaluminumplatebase,bottomlayer,photosensitiveresinlayer,silicagellayerandcoverfilm.Afterexposure,thesilicagellayerinthelight-visiblepart(blankpart)oftheprintingplateundergoesabridgingreactionforphoto-crosslinking;whilethesilicagellayerinthenon-lightpart(pictureandtextpart)isremovedundertheactionofthedeveloperandexposedThelowerphotosensitiveresinlayer.Sincethephotosensitiveresinlayerisink-friendly,andthesilicagellayerinthenon-graphicpartrepelstheink,theselectiveadsorptionoftheinkiscompleted.
Waterlessoffsetprintingisverydemandingontheenvironment:thetemperatureoftheprintingworkshopis23~25℃,andtheinkwillsolidifywhenthetemperatureislow;ifthetemperatureishigh,thepastefailurewilloccur.Inaddition,itisdifficulttodecontaminatethewaterlessoffsetprintingplateafteritgetsdirty.
Goldandsilverinkprinting
Whenfour-coloroffsetprinting,usemedium-hardlining,andputtheshorttoneandthinprintinginklayeronthepreviousunitofthegoldandsilverinkatthesametime.Largeinkvolume;
Usingmonochromeoffsetprinting"wetpressdry"hasmoreadvantages:fastdrying,strongglossofprintedproducts,goodvisualeffects,etc.Neutralorsoftliningcanbeused,usingneutrallining,withdomesticrubbercloth,plusliningclothorcardboard(hardnessisbetter),thepressureisslightlyincreasedandtheeffectisverygood.However,thesemi-finishedproductshouldnotbeleftforalongtime,otherwiseitwilleasilycausecrystallization,whichwillcausethesubsequentcolorinktofailtobeprinted;
Redpotionshouldnotbeusedforthedampeningtoavoidoxidationreaction,and"Lide"powdercanbeusedinstead;Itisbesttousealcoholtodamptheplate;
Theinfluenceofprintingspeedonprintingpressure
Tomaketheink-coatedgraphicsontheprintingplateclearTransfertothesurfaceofthesubstrate.Theremustbesufficientprintingpressure.However,theappliedprintingpressureshouldnotbetoolarge.Excessiveprintingpressurewillcausethesubstratetocontinuetodeform,thickentheprint,mergethedots,andpastetheplate,whichwillaffecttheclarityofthegraphicsandtext.Atthesametime,itwillincreasetheabrasionoftheprintingplate.Theprintingenduranceoftheprintingplatedecreases.Whentheprintingpressureisinsufficient,thereisnotsufficientandreliablecontactbetweentheprintingplateandtheblanket,andtheimprintwillbecomelighter,whichwillaffecttheclarityoftheimageandtext.
Printingcolorsequencearrangement
Generallyinthecaseofwetpressure,thecoloroftheinkprintedfirstisdominant.Forexample,ifthecolorisprintedfirst,thecoloroftheoverprintwillbeblue.;Printmagentafirstandthencyan,theoverprintcolorwillbereddish.Inthecaseofwetpressinganddrying,thecolorofthepost-printedinkisdominant.Fromanopticalpointofview,CMYKcolorsequenceshouldbeusedforwetpressandwetprinting.
Undernormalcircumstances,forwarm-tonedprintsthataremainlyportraitpaintings,thecolorsequenceshouldbeblack,cyan,magenta,andyellow;
Forthecolor-basedprinting,theprintingcolorsequenceshouldbeblack,magenta,cyan,andyellow;
Theprintingcolorsequenceofthetwo-colormachineiscyan+magenta,black+yellow,andthecolorsequenceofthemonochromaticmachineprintingThencyan,magenta,yellow,blackorblack,cyan,magenta,yellow(usuallywhentheblackplateisaskeletonplate,blackisprintedbefore);
Inordertofacilitateoverprinting,presstheinklayerArrangethecolororderindescendingorderofthickness,suchasblackink0.8um—cyanink0.9um—magentaink1.0um—yellowink1.1um;
ArrangetheinkviscosityindescendingorderPrintingcolorsequence,suchasblackink1188Pa.s—cyanink488Pa.s—magentaink477Pa.s—yellowink147Pa.s.Iftheinkviscositycannotmeetthearrangementrequirements,theinkviscositycanbeadjustedinadvance;
Theinkwithasmallcoverageareashouldbeprintedfirst,andthedarkinkshouldbeprintedfirst(becauseofitshighviscosityandlargehidingpowertoavoidsmearingontheback);
WhenprintingwithUVink,becauseofitsThedegreeofabsorptionofUVphotonsisdifferent,resultingindifferentcuringspeeds,sothecolorsequenceshouldbeblack-cyan-yellow-magentaduringprinting.
Mattersneedingattention
a.Trytoavoidselectingdotsthataretoosmallforthecolorblockoverprinting,suchasflatdotsbelow20%.Becausethecolorblockscomposedofsmalldotsarelikelytobepartiallyexposedtolightduetoinsufficientairabsorptionortheadhesionofsmallparticlesontheglassofthenegativefilmandtheglassoftheexposuremachineduringprinting;excessivewatercontentduringprintingislikelytocausetheblankettolightup.Dirtyorabrasionoftheprintingplatecausestheplatetodrop.Theabovetworeasonswillcausetheinkcolorofthecolorblocktobeuneven.Asforthedotsbelow5%,theordinaryoffsetprintingprocessisdifficulttorestore,andshouldbeavoided.
b.Atthesametime,theoverprintingcolorofthecolorblockshouldtrytoavoidusingalargepercentageofdots,suchasflatdotsabove80%.Becausethecolorblockscomposedoflargedotsareeasytopasteintheprintingprocess,thewatersupplyisslightlyinsufficientortheblanketgetsdirty.Asformorethan95%oftheoutlets,itshouldbeavoided.
c.Itisnecessarytoavoidoverprintingcolorblockswithtoomanycolorsorhighpercentagedots,asitiseasytosmudgethebacksideduetothethickinklayer.
d.Whenusingspotcolorprintingprocess,trynottochoosecolorblocksthatrequiretoomanybasiccolorinks.Mixingtoomanykindsofinkswillgreatlyincreasethedifficultyofblendinginks,whichnotonlyincreasestheinkblendingtime,butalsomakesitdifficulttoblendcolorswithsimilarhue.
e.Whenusingspotcolorstoprintalargeareaofacertaincolor,trytoavoidusingthatcolortoprintsmallreversedtextandlinesatthesametime.Becauseprintingalargeareaofsolidlandtendstoincreasethethicknessoftheinklayer,thethickerinklayeriseasytospread,butitwillcausesmallinvertedtextandlinestopaste.
f.Forthetext,inthemiddleofthefield,printsmallreversewhitecharacters,andweshouldtryourbesttorecommendthatcustomerschooseboldfonts.
g.Whentheprintingisfullandsolid,theprintingplateleftafterthelastprintingcanbeusedtostopthewatersupplyinsteadofspecialplatemaking.However,becausethephotoresistinthegraphicpartofthePSplateandthealuminaintheblankparthaveaslightlydifferentinkadsorptioncapacity,itisbesttouseacompletelyhollowfoldwhenprintingcolorswithstrongcolorrenderingproperties(suchasdarkblue)onthefullpage.Printingplate.