Daim ntawv curl thiab ntug nthwv dej (feem ntau hu ua "wrinkling" lossis "ntug yoj") yog cov deformations uas tuaj yeem cuam tshuam rau kev luam ntawv, stackability, thiab tag nrho kev siv tau. Qhov tseem ceeb, ntawv yog cov khoom siv hygroscopic uas muaj cov cellulose fibers. Nws qhov ntev stability nyob ntawm nws cov kev cuam tshuam nrog ya raws thiab sab hauv mechanical stresses. Cov teeb meem no tshwm sim thaum cov dej noo los yog kev ntxhov siab sab hauv kev faib tawm hauv cov qauv ntawv tsis sib xws.
1. Hygroscopicity (Moisture Imbalance)
Lub hauv paus ua rau daim ntawv curl thiab yoj yog qhov sib txawv ntawm qhov nqus los yog poob ntawm cov dej noo. Thaum cov ntawv fibers nqus dej noo, lawv nthuav tawm radially (ua dav), thiab thaum lawv qhuav, lawv cog lus. Yog tias qhov nthuav dav lossis kev cog lus ntawm ib sab ntawm daim ntawv ntau dua li ntawm lwm qhov, kev ntxhov siab sab hauv yuav loj tuaj.
Curl: Curl tshwm sim thaum muaj noo noo gradient nyob rau hauv thickness ntawm daim ntawv. Yog hais tias cov dej noo nyob rau sab pem hauv ntej ntawm daim ntawv siab dua nyob rau sab nraub qaum, cov fibers ntawm sab xub ntiag nthuav dav ntxiv, ua rau daim ntawv curl downward (los yog upward, nyob ntawm seb cov fiber ntau cov kev taw qhia). Qhov xwm txheej no feem ntau tshwm sim tom qab siab - luam ntawv ceev lossis laser luam ntawv, vim tias tshav kub sai sai ua kom cov dej noo tawm ntawm ib sab ntawm daim ntawv sai dua lwm qhov. Hloov pauv, yog tias daim ntawv khaws cia rau hauv qhov chaw ntub dej, qhov chaw raug nqus dej noo thiab nthuav dav, ua rau daim ntawv curling sab hauv.
Ntug Wave (Curl): Ntug nthwv dej feem ntau tshwm sim los ntawm cov dej noo nyob hauv daim ntawv. Qhov xwm txheej no feem ntau tshwm sim thaum cov npoo ntawm ib lub ream lossis yob ntawm daim ntawv raug rau cov av noo siab thaum qhov chaw tseem qhuav. Cov npoo nqus dej noo, nthuav dav, thiab ua ntev dua li qhov chaw qhuav. Txij li thaum lub chaw tsis tuaj yeem ua kom haum rau qhov kev nthuav dav no, cov npoo khoov rau hauv cov qauv wavy. Qhov no yog ib txwm muaj nyob rau hauv cov ntawv khaws cia hauv cov chaw khaws khoom huab cua tsis muaj kev tswj hwm lossis hauv ib qho ream uas tau siv ib nrab thiab tsis kaw.
2. Fiber Orientation thiab Mechanical Stress
Vim qhov kev npaj ntawm fibers thaum lub sij hawm tsim khoom, ntawv muaj kev ntxhib los mos. Kev nthuav dav thiab kev cog lus nyob rau hauv qhov kev taw qhia transverse (perpendicular mus rau kev ntxhib los mos kev taw qhia) yog ntau dua nyob rau hauv longitudinal kev taw qhia (raws li kev ntxhib los mos). Yog li ntawd, curl thiab yoj feem ntau hnyav dua nyob rau hauv cov kev taw qhia perpendicular mus rau kev ntxhib los mos kev taw qhia.
Tsis tas li ntawd, residual mechanical stress kuj tuaj yeem ua rau cov teeb meem no. Thaum lub sij hawm papermaking txheej txheem, qhov nro los ntawm winding thiab calendering (tus txheej txheem uas ua rau daim ntawv du) tuaj yeem tsim "cov tshuab curl." Yog tias daim ntawv raug mob nruj dhau ntawm cov yob lossis yog tias muaj qhov tsis sib xws ntawm qhov nro ntawm cov khaubncaws sab nraud povtseg sab saud thiab qis thaum lub sijhawm tsim khoom, daim ntawv khaws cia qhov kev nco txog ntawm kev khoov. Thaum daim ntawv raug txiav thiab raug huab cua dawb, qhov kev ntxhov siab no raug tso tawm, tshwm sim raws li curl.
3. Ib puag ncig thiab kev tuav pov hwm
Ib puag ncig plays lub luag haujlwm tseem ceeb hauv kev ua kom cov kev tsis zoo no. Daim ntawv yog rhiab heev rau qhov kub hloov pauv. Yog tias daim ntawv txias tau txav mus rau hauv qhov chaw ua haujlwm sov thiab ntub dej, cov ntaub ntawv condensation rau ntawm daim ntawv pawg, ua rau muaj qhov sib txawv ntawm cov dej noo tseem ceeb thiab tsim yoj tam sim ntawd. Kev hloov pauv sai ntawm qhov txheeb ze av noo (RH) ua rau daim ntawv tsis ruaj khov; Qhov zoo tshaj plaws, daim ntawv yuav tsum tau ua kom haum rau qhov chaw ua haujlwm luam ntawv (feem ntau 45% txog 55% RH) tsawg kawg 24 teev ua ntej siv.
4. Thaum tshav kub kub hauv txheej txheem luam ntawv
Nyob rau hauv niaj hnub digital thiab laser luam ntawv, kub kub yog siv los fuse toner rau ntawm daim ntawv. Yog tias cov dej noo ntawm daim ntawv tsis sib npaug los yog siab dhau, qhov kev thov tam sim ntawd ntawm cov cua sov ua rau cov dej noo ntawm ib sab kom evaporate sai heev. Qhov kev cog lus hauv zos tam sim no ua rau "curl ntawm lub tshav kub" cuam tshuam thaum daim ntawv tawm hauv lub tshuab.
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