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Dimensional stability yog hais txog ib daim ntawv lub peev xwm los tswj nws qhov geometric qhov ntev nyob rau hauv cov kev cuam tshuam sab nraud xws li kev nyuaj siab, thermal fluctuations, thiab ambient humidity variations. Raws li feem ntau cov ntawv-raws li substrates muaj cov khoom siv polymeric (piv txwv li, sizing agents, binders, lossis coating resins), lawv tus cwj pwm viscoelastic inherent ua rau lawv muaj kev cuam tshuam rau lub sijhawm- deformation nyob ntawm -tshwj xeeb tshaj yog nkag- nyob rau hauv cov khoom hnyav, nrog rau tus kheej. Cov kev hloov pauv loj no cuam tshuam qhov kev sau npe raug, kev ua haujlwm ntawm siab - nrawm nrawm, thiab tshaj tawm - xovxwm ua haujlwm ncaj ncees. Yog li ntawd, cov txheej txheem phiaj xwm kev cuam tshuam yog qhov tseem ceeb los txo qis qhov tsis ruaj khov. Cov ntu hauv qab no qhia txog cov txheej txheem tseem ceeb tshaj plaws - txheej, wrinkling, passive humidification, nquag humidification{14}} thiab prepress cov kev txiav txim siab uas sib sau ua ke txhim kho daim ntawv qhov ntev.
1. Daim ntawv thov txheej
Txheej txhim kho qhov sib xws ntawm qhov chaw thiab tuaj yeem ua rau qee qhov cuam tshuam qhov txawv txav los ntawm kev hloov kho daim ntawv hygroscopic teb thiab txhua yam anisotropy. Txawm li cas los xij, ib qho - sab txheej txheej qhia txog asymmetry hauv kev faib dej noo thoob plaws daim ntawv tuab. Qhov no cuam tshuam qhov sib npaug ntawm kev sib cuam tshuam ntawm fiber-dej, ua rau tsis muaj -cov kev ntxhov siab sab hauv thiab qhov sib txawv ntawm qhov sib txawv / nthuav dav ntawm cov coated thiab uncoated nto. Unmitigated, qhov kev tsis txaus ntseeg no ua rau cov curl, cockle, lossis ntug waviness - txo qis web tuav thiab kev sau npe ua haujlwm. Yog li ntawd, tom qab- txheej txheej txias (xws li, tswj rehumidification thiab calendering) yog ib qho tseem ceeb los kho qhov sib npaug ntawm qhov sib npaug.
2. Tswj Wrinkling Technology
Wrinkling yog ib qho kev xav txog kev ua haujlwm deformation ua haujlwm los txhim kho daim ntawv elongation ntawm kev so, dynamic tensile lub zog, softness, huab cua permeability, thiab kua absorbency. Nws yog dav siv nyob rau hauv cov ntaub so ntswg, huv si, thiab tshwj xeeb ntim qib. Ob txoj kev lag luam tseem ceeb yog ua haujlwm:
- Kev xav rau cov menyuam txoj kev: Siv cov engraved rollers los faib cov micro-wrinkles.
- Scraper-raws li kev ziab- lub tog raj kheej txoj kev: Ib qho scraper hu rau lub tog raj kheej kom qhuav thaum lub ntub los yog ib nrab- ntawv lub vev xaib qhuav yog tev tawm, inducing tswj buckling. Raws li daim ntawv noo noo ntawm qhov chaw ntawm wrinkling, txoj kev no yog cais raws li:
• Kev ntub dej ntub dej (40-60% noo noo): Cov yas siab ua kom muaj qhov sib txawv ntawm qhov tawv nqaij; Txawm li cas los xij, cov nplooj ntawv qhuav kawg ua rau txo qis thiab feem ntau txwv rau qib qis - cov khoom siv tu cev.
• Semi- dry wrinkling (20–40% noo noo): Muab qhov zoo sib npaug ntawm qhov sib txawv ntawm daim tawv nqaij thiab qhov muag muag; haum rau nruab nrab - mus rau - siab - cov ntaub ntawv siv cov ntaub so ntswg.
• Qhuav wrinkling (5-8% ya raws): Yuav tsum muaj cov khoom siv hluav taws xob ntau dua thiab ua rau cov wrinkles tsawg dua; tsis tshua siv industrially vim muaj fiber ntau puas.
3. Passive Humidification (Cua txias)
Daim ntawv yog cov khoom siv hygroscopic ntxeem tau: ± 0.1% kev hloov pauv hauv cov ntsiab lus noo noo (MC) tuaj yeem ua rau ntsuas qhov ntsuas qhov hloov pauv- txaus los cuam tshuam qhov tseeb ntawm kev luam ntawv ntau yam. Rau offset lithography, qhov zoo tshaj plaws MC yog 7% ± 1%, nrog radial (center- rau- ntug) sib txawv tsis tshaj 1%. Txhawm rau ua kom muaj qhov sib npaug, qhov kev xyaum ua tau zoo tshaj plaws yuav tsum ua kom muaj cov ntawv ua ntej hauv huab cua-tswj ib puag ncig sib piv rau chav xovxwm qhov kub thiab qhov txheeb ze av noo (RH) rau ≥24 teev ua ntej luam ntawv. Thaum qhov kev txwv tsis pub muaj kev txwv txuas ntxiv acclimatization, cov chav tsev humidification tshwj xeeb- khaws cia ntawm RH 6–8 feem pua ntawm cov ntsiab lus saum toj ntawm chav xovxwm- raug pom zoo. Qhov no ua kom yooj yim rau kev faib tawm sai, tsis tu ncua noo noo, txo qis cov gradients residual uas tsav tom qab- luam ntawv distortion.
4. Active Humidification (Pre-Moisturization)
Nyob rau hauv offset thiab UV- kho kom zoo luam ntawv, ntawv absorbs cov dej ntws los yog cov dej tsis zoo thaum lub sij hawm kev xav, ua rau lub sij hawm o - ua raws li lub cev qhuav dej sai nyob rau hauv siab - siv IR / UV kom qhuav. Qhov cuam tshuam ntawm cov dej noo no ua rau tsis tuaj yeem thim rov qab, tshwj xeeb tshaj yog tom qab lamination lossis tawm -kab varnishing, qhov twg thermal raug exacerbates seem contraction. Txhawm rau tiv thaiv qhov no, "dej- khiav" (piv txwv li, khiav daim ntawv los ntawm cov xovxwm yam tsis muaj number case, siv cov tshuaj dampening nkaus xwb) ua ntej kev luam ntawv tiag tiag yog kev tswj xyuas ua ntej -moisturization kauj ruam. Qhov no tso cai rau daim ntawv mus rau qhov pib o thiab tom qab ib feem sib npaug, yog li txo qhov loj ntawm - txheej txheem deformation. Nyob rau hauv cov xwm txheej hnyav dhau los-lamination shrinkage, lub hom phiaj rehumidification- ntawm kev tswj RH raug- tuaj yeem rov qab qhov qub qhov ntev, txawm tias tag nrho rov qab yog feem ntau tsis tuaj yeem ua tiav vim muaj fiber ntau compaction.
Prepress txheej txheem optimization
Tshaj li kev kho substrate, qhov ruaj khov ntawm qhov yuav tsum tau hais txog kev ua haujlwm thaum lub sijhawm npaj ua ntej:
– Sheet Format Selection: Layout Dimensions yuav tsum suav rau daim ntawv -txhim kho deformation coefficients. Highly hygroscopic los yog xoob cov ntaub ntawv (piv txwv li, uncoated woodfree qib) muaj ntau dua qhov sib txawv; cov layouts loj loj ua kom pom kev sau npe yuam kev. Thaum tag nrho - ntawv luam ntawv txhim kho kev ua tau zoo, nws tuaj yeem cuam tshuam cov txheej txheem hauv qab (piv txwv li, tuag- txiav, folding, ntawv nyiaj stamping) yuav tsum muaj kev sau npe nruj. Ib txoj hauv kev sib npaug-txhim kho daim ntawv loj rau cov khoom tshwj xeeb, cov txheej txheem kev xav tau ntawm cov saw hlau, thiab kev txo qis qis dua{11}} yog li qhia.
- Grain Direction Alignment: Daim ntawv nthuav tawm cov lus teb anisotropic dimension: longitudinal (tshuab-kev taw qhia) fibers swell/shrink ntau dua cross-direction fibers. Txhawm rau kom zoo rau kev tso npe ruaj ntseg, cov duab luam tawm yuav tsum tau taw qhia thaum uas tig mus rau cov lus taw qhia cov nplej -ie, ua raws li lub tog raj kheej axis thaum lub vev xaib lossis cov ntawv luam tawm. Nkag siab txog kev sib raug zoo ntawm cov dej noo thiab qhov hloov pauv (piv txwv li, los ntawm kev ntsuas TAPPI T 402 lossis ISO 187 tus qauv) ua rau cov ntaub ntawv -tsav tshwj xeeb ntawm chav xovxwm RH setpoints thiab cov txheej txheem txias.
- Overprint Pattern Placement: Rau cov khoom uas yuav tsum tau embellishments theem nrab (xws li, kub ntawv nyiaj stamping, embossing), overprint lub hom phiaj yuav tsum tau positioned strategically. Vim qhov zoo tshaj qhov sib xws ntawm sab nraub qaum (piv rau cov ntawv luam tawm pem hauv ntej), cov ntawv sib dhos thiab cov hom phiaj sau npe yuav tsum muab tso rau ntawm qhov thim rov qab thaum twg ua tau -tshwj xeeb tshaj yog rau cov khoom loj - hom ntim. Tsis tas li ntawd, cov txheej txheem tsim qauv pom zoo kom taw qhia cov ntawv nplej perpendicular mus rau qhov ntev tshaj plaws ntawm lub thawv ntim kom ua kom tawg thiab tawg tsis kam. Txawm li cas los xij, qhov kev taw qhia no tuaj yeem cuam tshuam nrog kev sau npe zoo tshaj; Yog li, kev sib koom tes tsim kev tshuaj xyuas ntawm cov kws tsim khoom ntim khoom thiab pab pawg tsim khoom yog qhov tseem ceeb rau kev sib koom ua ke ntawm cov qauv kev ncaj ncees nrog kev ncaj ncees.
Sib sau ua ke, cov txheej txheem no qhia meej tias qhov kev ruaj ntseg ntawm qhov ntev tsis yog cov cuab yeej hauv lub cev tab sis qhov kev tswj hwm qhov ntsuas tsis tau- tswj hwm los ntawm cov khoom muaj pes tsawg leeg, kev tswj hwm ib puag ncig, kev ua tshuab, thiab kev npaj ua ntej. Lub tswv yim sib koom ua ke, kev sib koom ua ke- ncua kev xaiv cov khoom siv raw, hloov pauv kev ua haujlwm, kev tswj ib puag ncig, thiab digital workflow calibration- yog qhov tseem ceeb rau kev ua tiav cov txiaj ntsig zoo ib yam, siab - cov txiaj ntsig luam tawm.
