底(di)(di)油(you)是指在上UV光油(you)之前先(xian)在印品(pin)表(biao)面涂(tu)一層油(you)作為UV光油(you)的底(di)(di)層，UV光油(you)涂(tu)布到底(di)(di)油(you)層上而不(bu)是直接涂(tu)布紙張(zhang)表(biao)面。UV底(di)(di)油(you)有油(you)性(xing)(xing)和(he)(he)水(shui)性(xing)(xing)兩(liang)種，都是用熱干(gan)燥。油(you)性(xing)(xing)底(di)(di)油(you)特點(dian)是與油(you)墨和(he)(he)紙張(zhang)親和(he)(he)力強、干(gan)燥快，但由(you)于(yu)(yu)含60%以上的溶(rong)劑，氣味較大不(bu)利于(yu)(yu)環(huan)保。水(shui)性(xing)(xing)底(di)(di)油(you)特點(dian)是白度好，紙張(zhang)打水(shui)性(xing)(xing)底(di)(di)油(you)能增加白度，由(you)于(yu)(yu)水(shui)性(xing)(xing)底(di)(di)油(you)的溶(rong)劑大部分是水(shui)和(he)(he)乙醇，因此(ci)氣味小屬(shu)環(huan)保產(chan)品(pin)，但與紙張(zhang)和(he)(he)油(you)墨親和(he)(he)性(xing)(xing)差些。

打底油的原因有兩個：

一個(ge)是有(you)些(xie)紙(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)張(zhang)表(biao)面(mian)緊(jin)度(du)(du)不(bu)夠(gou)、平滑度(du)(du)較差(cha)，如低(di)(di)檔白紙(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)板，上UV光后不(bu)光亮(liang)(liang)或有(you)波紋。紙(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)張(zhang)緊(jin)度(du)(du)低(di)(di)的(de)情(qing)況下，涂到(dao)紙(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)表(biao)面(mian)的(de)UV光油(you)(you)(you)(you)會滲到(dao)紙(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)張(zhang)內(nei)部，結(jie)果紙(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)張(zhang)表(biao)面(mian)存留的(de)光油(you)(you)(you)(you)很(hen)少，UV光照(zhao)射時只(zhi)有(you)紙(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)張(zhang)表(biao)面(mian)很(hen)少的(de)UV油(you)(you)(you)(you)可以固(gu)化(hua)(hua)，因此光亮(liang)(liang)度(du)(du)不(bu)夠(gou)。另外(wai)若(ruo)(ruo)UV油(you)(you)(you)(you)向紙(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)滲透太深UV光照(zhao)不(bu)到(dao)紙(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)內(nei)UV油(you)(you)(you)(you)，這(zhe)些(xie)未固(gu)化(hua)(hua)的(de)uv油(you)(you)(you)(you)會反(fan)向潤濕紙(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)表(biao)面(mian)已固(gu)化(hua)(hua)的(de)uv光膜(mo)層(ceng)，使之(zhi)失去光澤，降低(di)(di)光油(you)(you)(you)(you)與紙(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)張(zhang)的(de)附(fu)著力。這(zhe)種情(qing)況下需要打底油(you)(you)(you)(you)，用(yong)底油(you)(you)(you)(you)將(jiang)松(song)散(san)的(de)紙(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)表(biao)面(mian)填(tian)密實，再(zai)上UV光油(you)(you)(you)(you)效(xiao)果極佳。平滑度(du)(du)低(di)(di)的(de)紙(zhi)(zhi)(zhi)(zhi)(zhi)(zhi)張(zhang)表(biao)面(mian)是凸凹(ao)(ao)不(bu)平的(de)，用(yong)底油(you)(you)(you)(you)可填(tian)平凹(ao)(ao)坑，再(zai)上UV光油(you)(you)(you)(you)則平整光亮(liang)(liang)。一般(ban)用(yong)水(shui)性(xing)底油(you)(you)(you)(you)可增加白度(du)(du)并且環保(bao)，若(ruo)(ruo)油(you)(you)(you)(you)墨含蠟質(zhi)過髙，水(shui)性(xing)油(you)(you)(you)(you)親和性(xing)差(cha)，在有(you)油(you)(you)(you)(you)墨的(de)地方出(chu)現(xian)(xian)水(shui)性(xing)油(you)(you)(you)(you)脫(tuo)落現(xian)(xian)象，此情(qing)況就(jiu)只(zhi)好上油(you)(you)(you)(you)性(xing)底油(you)(you)(you)(you)。

打底油(you)的第二個原因是(shi)，油(you)墨含蠟質過(guo)髙，經電(dian)暈處(chu)理UV光油(you)仍不(bu)親和，只(zhi)能先打一層(ceng)油(you)性底油(you)再上UV光油(you)。此種情況不(bu)多(duo)，如果調整油(you)墨配方(fang)就可避免打底油(you)。

底(di)(di)油(you)涂(tu)布(bu)的(de)(de)(de)厚度越薄(bo)越好(hao)，在(zai)(zai)達到目(mu)的(de)(de)(de)后涂(tu)更(geng)多也是浪(lang)費(fei)。底(di)(di)油(you)一定要干(gan)燥徹底(di)(di)，因為(wei)底(di)(di)油(you)內(nei)含的(de)(de)(de)溶劑(ji)都能將醇性(xing)的(de)(de)(de)UV光油(you)潤濕。若底(di)(di)油(you)干(gan)燥不(bu)徹底(di)(di)殘(can)留部分溶劑(ji)壓(ya)在(zai)(zai)UV膜層下面(mian)，溶劑(ji)反向潤濕UV膜層使UV膜層消光或(huo)脫落。油(you)性(xing)底(di)(di)油(you)的(de)(de)(de)稀(xi)(xi)釋比例無限制，最好(hao)用加(jia)(jia)熱桶加(jia)(jia)熱稀(xi)(xi)釋，這樣可節約稀(xi)(xi)釋劑(ji)，因為(wei)稀(xi)(xi)釋劑(ji)不(bu)成膜干(gan)燥時(shi)揮發掉(diao)純屬浪(lang)費(fei)。水性(xing)底(di)(di)油(you)也可用加(jia)(jia)熱桶加(jia)(jia)熱稀(xi)(xi)釋，但如(ru)果需添加(jia)(jia)稀(xi)(xi)釋劑(ji)比例一般不(bu)超過15%，因為(wei)水性(xing)油(you)墨(mo)是乳液(ye)，若稀(xi)(xi)釋過度會(hui)破壞乳化(hua)狀(zhuang)態出(chu)現小白顆粒狀(zhuang)或(huo)小白片(pian)狀(zhuang)物(wu)，稀(xi)(xi)釋劑(ji)中水和乙醇各(ge)占50%。

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