塑料薄膜印刷前為什么要進行電暈處理？

塑(su)(su)料(liao)(liao)(liao)薄(bo)(bo)膜在包裝印(yin)(yin)刷中(zhong)的(de)(de)(de)應用非(fei)常(chang)(chang)廣泛，但塑(su)(su)料(liao)(liao)(liao)一般是以合(he)成樹脂為基本(ben)成分的(de)(de)(de)高分子有(you)機化合(he)物，結晶度(du)高，分子結構具(ju)有(you)非(fei)極性特征(zheng)，表(biao)(biao)面(mian)(mian)(mian)張力(li)較低，表(biao)(biao)面(mian)(mian)(mian)光潔(jie)度(du)高，化學穩定(ding)性強(qiang)，常(chang)(chang)溫(wen)下一般不溶于常(chang)(chang)用溶劑(ji)(ji)(ji)，另外(wai)塑(su)(su)料(liao)(liao)(liao)中(zhong)加入的(de)(de)(de)增塑(su)(su)劑(ji)(ji)(ji)、抗氧劑(ji)(ji)(ji)等助劑(ji)(ji)(ji)會緩緩向表(biao)(biao)面(mian)(mian)(mian)遷移以及(ji)儲存過程中(zhong)空氣中(zhong)的(de)(de)(de)塵垢吸(xi)附(fu)在塑(su)(su)料(liao)(liao)(liao)表(biao)(biao)面(mian)(mian)(mian)，將(jiang)在薄(bo)(bo)膜表(biao)(biao)面(mian)(mian)(mian)形(xing)成油(you)(you)污(wu)（弱界(jie)面(mian)(mian)(mian)層(ceng)），使薄(bo)(bo)膜不易接受油(you)(you)墨(mo)。因(yin)此(ci)通常(chang)(chang)對極性較弱和表(biao)(biao)面(mian)(mian)(mian)能較低的(de)(de)(de)塑(su)(su)料(liao)(liao)(liao)薄(bo)(bo)膜進行(xing)印(yin)(yin)前表(biao)(biao)面(mian)(mian)(mian)處(chu)(chu)(chu)(chu)理(li)(li)，以滿(man)足油(you)(you)墨(mo)的(de)(de)(de)附(fu)著。塑(su)(su)料(liao)(liao)(liao)印(yin)(yin)前表(biao)(biao)面(mian)(mian)(mian)處(chu)(chu)(chu)(chu)理(li)(li)的(de)(de)(de)方(fang)法(fa)(fa)很(hen)多，如(ru)氧化處(chu)(chu)(chu)(chu)理(li)(li)法(fa)(fa)、溶劑(ji)(ji)(ji)處(chu)(chu)(chu)(chu)理(li)(li)法(fa)(fa)、電暈(yun)(yun)處(chu)(chu)(chu)(chu)理(li)(li)法(fa)(fa)、火焰處(chu)(chu)(chu)(chu)理(li)(li)、涂層(ceng)處(chu)(chu)(chu)(chu)理(li)(li)和紫外(wai)線照射(she)法(fa)(fa)等，但最常(chang)(chang)采(cai)用的(de)(de)(de)方(fang)法(fa)(fa)是電暈(yun)(yun)處(chu)(chu)(chu)(chu)理(li)(li)，為了使塑(su)(su)料(liao)(liao)(liao)薄(bo)(bo)膜印(yin)(yin)前表(biao)(biao)面(mian)(mian)(mian)處(chu)(chu)(chu)(chu)理(li)(li)具(ju)有(you)優良的(de)(de)(de)印(yin)(yin)刷適性。

塑(su)料薄(bo)膜印前電暈處理(li)原理(li)

塑料(liao)(liao)(liao)薄(bo)(bo)(bo)膜(mo)上圖文并(bing)茂的(de)(de)(de)效果是通過油墨(mo)(mo)(mo)在其(qi)表(biao)面(mian)(mian)的(de)(de)(de)附(fu)(fu)著(zhu)來(lai)實現的(de)(de)(de)，與油墨(mo)(mo)(mo)附(fu)(fu)著(zhu)密切相(xiang)關的(de)(de)(de)是塑料(liao)(liao)(liao)表(biao)面(mian)(mian)的(de)(de)(de)物理(li)、化(hua)學(xue)特性(xing)(xing)（潤濕(shi)、鋪展、表(biao)面(mian)(mian)極(ji)(ji)性(xing)(xing)和粗糙度(du)）。油墨(mo)(mo)(mo)附(fu)(fu)著(zhu)性(xing)(xing)的(de)(de)(de)大小用(yong)附(fu)(fu)著(zhu)力(li)來(lai)衡量(liang)。塑料(liao)(liao)(liao)薄(bo)(bo)(bo)膜(mo)上油墨(mo)(mo)(mo)的(de)(de)(de)附(fu)(fu)著(zhu)力(li)主要(yao)依賴于油墨(mo)(mo)(mo)和塑料(liao)(liao)(liao)分子(zi)(zi)(zi)間作(zuo)用(yong)力(li)和化(hua)學(xue)鍵(jian)(jian)力(li)，分子(zi)(zi)(zi)間作(zuo)用(yong)力(li)和化(hua)學(xue)鍵(jian)(jian)力(li)產生的(de)(de)(de)條件(jian)是分子(zi)(zi)(zi)或原子(zi)(zi)(zi)之間必須充分靠近，只(zhi)有油墨(mo)(mo)(mo)對塑料(liao)(liao)(liao)表(biao)面(mian)(mian)呈濕(shi)潤狀態(tai)時(shi)，它(ta)們(men)的(de)(de)(de)相(xiang)互距離才(cai)能(neng)處于引力(li)場的(de)(de)(de)范圍內，產生有效的(de)(de)(de)附(fu)(fu)著(zhu)力(li)。電暈處理(li)能(neng)實現塑料(liao)(liao)(liao)薄(bo)(bo)(bo)膜(mo)表(biao)面(mian)(mian)印刷(shua)適性(xing)(xing)要(yao)求(qiu)，其(qi)工作(zuo)原理(li)為：處理(li)機釋放高(gao)頻高(gao)壓電，產生細小密集的(de)(de)(de)電火花沖(chong)擊塑料(liao)(liao)(liao)薄(bo)(bo)(bo)膜(mo)表(biao)面(mian)(mian)，使(shi)(shi)(shi)塑料(liao)(liao)(liao)薄(bo)(bo)(bo)膜(mo)表(biao)面(mian)(mian)部分分子(zi)(zi)(zi)鏈斷(duan)裂而降解，塑料(liao)(liao)(liao)表(biao)面(mian)(mian)粗化(hua)，增(zeng)加其(qi)比表(biao)面(mian)(mian)積；另外在高(gao)壓電場中(zhong)空氣中(zhong)的(de)(de)(de)氧產生電離形成(cheng)臭氧，它(ta)能(neng)夠(gou)除去表(biao)面(mian)(mian)的(de)(de)(de)油污等弱界面(mian)(mian)層，并(bing)氧化(hua)塑料(liao)(liao)(liao)分子(zi)(zi)(zi)，在其(qi)分子(zi)(zi)(zi)鏈上生成(cheng)羥基(ji)、羧(suo)基(ji)等極(ji)(ji)性(xing)(xing)基(ji)團，使(shi)(shi)(shi)塑料(liao)(liao)(liao)薄(bo)(bo)(bo)膜(mo)轉化(hua)為極(ji)(ji)性(xing)(xing)表(biao)面(mian)(mian)，表(biao)面(mian)(mian)張力(li)提(ti)高(gao)至3.8~6.0×10-2N/m，使(shi)(shi)(shi)其(qi)對印刷(shua)油墨(mo)(mo)(mo)的(de)(de)(de)潤濕(shi)性(xing)(xing)、黏附(fu)(fu)性(xing)(xing)增(zeng)加，從而提(ti)高(gao)印跡的(de)(de)(de)牢度(du)。

塑料、印刷工藝和油墨類型對電暈處理的(de)要求(qiu)

塑(su)(su)料(liao)(liao)(liao)(liao)(liao)(liao)(liao)種類不(bu)(bu)(bu)同(tong)(tong)(tong)，其化學(xue)結構和塑(su)(su)料(liao)(liao)(liao)(liao)(liao)(liao)(liao)表(biao)(biao)(biao)(biao)面(mian)(mian)(mian)(mian)印(yin)(yin)(yin)(yin)(yin)(yin)(yin)刷(shua)(shua)(shua)(shua)(shua)適(shi)(shi)(shi)(shi)性(xing)(xing)(xing)(xing)不(bu)(bu)(bu)同(tong)(tong)(tong)，不(bu)(bu)(bu)是所(suo)有塑(su)(su)料(liao)(liao)(liao)(liao)(liao)(liao)(liao)薄膜(mo)都需表(biao)(biao)(biao)(biao)面(mian)(mian)(mian)(mian)處(chu)理(li)或適(shi)(shi)(shi)(shi)合電(dian)暈處(chu)理(li)，即(ji)使同(tong)(tong)(tong)是電(dian)暈處(chu)理(li)，其處(chu)理(li)程度也不(bu)(bu)(bu)同(tong)(tong)(tong)，這主(zhu)(zhu)要取決于塑(su)(su)料(liao)(liao)(liao)(liao)(liao)(liao)(liao)分(fen)(fen)(fen)(fen)子(zi)極(ji)(ji)(ji)性(xing)(xing)(xing)(xing)的(de)(de)(de)(de)(de)強(qiang)弱與表(biao)(biao)(biao)(biao)面(mian)(mian)(mian)(mian)張(zhang)力的(de)(de)(de)(de)(de)大(da)(da)小、印(yin)(yin)(yin)(yin)(yin)(yin)(yin)刷(shua)(shua)(shua)(shua)(shua)工(gong)藝(yi)以(yi)及所(suo)用(yong)油(you)(you)(you)(you)墨(mo)(mo)(mo)(mo)(mo)的(de)(de)(de)(de)(de)性(xing)(xing)(xing)(xing)質。對于分(fen)(fen)(fen)(fen)子(zi)鏈(lian)中(zhong)帶(dai)有極(ji)(ji)(ji)性(xing)(xing)(xing)(xing)基團的(de)(de)(de)(de)(de)塑(su)(su)料(liao)(liao)(liao)(liao)(liao)(liao)(liao)，其分(fen)(fen)(fen)(fen)子(zi)偶極(ji)(ji)(ji)矩（ч）不(bu)(bu)(bu)等，其所(suo)表(biao)(biao)(biao)(biao)現的(de)(de)(de)(de)(de)極(ji)(ji)(ji)性(xing)(xing)(xing)(xing)強(qiang)弱不(bu)(bu)(bu)同(tong)(tong)(tong)，一般分(fen)(fen)(fen)(fen)子(zi)偶極(ji)(ji)(ji)矩的(de)(de)(de)(de)(de)大(da)(da)小可(ke)作(zuo)為衡量(liang)分(fen)(fen)(fen)(fen)子(zi)極(ji)(ji)(ji)性(xing)(xing)(xing)(xing)強(qiang)弱的(de)(de)(de)(de)(de)標準，極(ji)(ji)(ji)性(xing)(xing)(xing)(xing)越(yue)大(da)(da)，印(yin)(yin)(yin)(yin)(yin)(yin)(yin)刷(shua)(shua)(shua)(shua)(shua)適(shi)(shi)(shi)(shi)性(xing)(xing)(xing)(xing)越(yue)好(hao)(hao)(hao)。例如弱極(ji)(ji)(ji)性(xing)(xing)(xing)(xing)塑(su)(su)料(liao)(liao)(liao)(liao)(liao)(liao)(liao)的(de)(de)(de)(de)(de)印(yin)(yin)(yin)(yin)(yin)(yin)(yin)刷(shua)(shua)(shua)(shua)(shua)適(shi)(shi)(shi)(shi)性(xing)(xing)(xing)(xing)好(hao)(hao)(hao)于非極(ji)(ji)(ji)性(xing)(xing)(xing)(xing)塑(su)(su)料(liao)(liao)(liao)(liao)(liao)(liao)(liao)，極(ji)(ji)(ji)性(xing)(xing)(xing)(xing)和強(qiang)極(ji)(ji)(ji)性(xing)(xing)(xing)(xing)印(yin)(yin)(yin)(yin)(yin)(yin)(yin)刷(shua)(shua)(shua)(shua)(shua)適(shi)(shi)(shi)(shi)性(xing)(xing)(xing)(xing)更好(hao)(hao)(hao)。另外油(you)(you)(you)(you)墨(mo)(mo)(mo)(mo)(mo)如能在塑(su)(su)料(liao)(liao)(liao)(liao)(liao)(liao)(liao)表(biao)(biao)(biao)(biao)面(mian)(mian)(mian)(mian)很好(hao)(hao)(hao)附著(zhu)，印(yin)(yin)(yin)(yin)(yin)(yin)(yin)刷(shua)(shua)(shua)(shua)(shua)用(yong)油(you)(you)(you)(you)墨(mo)(mo)(mo)(mo)(mo)的(de)(de)(de)(de)(de)表(biao)(biao)(biao)(biao)面(mian)(mian)(mian)(mian)張(zhang)力必低(di)于塑(su)(su)料(liao)(liao)(liao)(liao)(liao)(liao)(liao)的(de)(de)(de)(de)(de)表(biao)(biao)(biao)(biao)面(mian)(mian)(mian)(mian)張(zhang)力，由于印(yin)(yin)(yin)(yin)(yin)(yin)(yin)刷(shua)(shua)(shua)(shua)(shua)工(gong)藝(yi)不(bu)(bu)(bu)同(tong)(tong)(tong)，所(suo)用(yong)油(you)(you)(you)(you)墨(mo)(mo)(mo)(mo)(mo)不(bu)(bu)(bu)同(tong)(tong)(tong)，即(ji)使同(tong)(tong)(tong)種印(yin)(yin)(yin)(yin)(yin)(yin)(yin)刷(shua)(shua)(shua)(shua)(shua)工(gong)藝(yi)，也可(ke)用(yong)不(bu)(bu)(bu)同(tong)(tong)(tong)類型油(you)(you)(you)(you)墨(mo)(mo)(mo)(mo)(mo)，所(suo)以(yi)應根據印(yin)(yin)(yin)(yin)(yin)(yin)(yin)刷(shua)(shua)(shua)(shua)(shua)工(gong)藝(yi)及所(suo)用(yong)油(you)(you)(you)(you)墨(mo)(mo)(mo)(mo)(mo)的(de)(de)(de)(de)(de)不(bu)(bu)(bu)同(tong)(tong)(tong)對塑(su)(su)料(liao)(liao)(liao)(liao)(liao)(liao)(liao)表(biao)(biao)(biao)(biao)面(mian)(mian)(mian)(mian)適(shi)(shi)(shi)(shi)當處(chu)理(li)。例如水性(xing)(xing)(xing)(xing)油(you)(you)(you)(you)墨(mo)(mo)(mo)(mo)(mo)主(zhu)(zhu)要的(de)(de)(de)(de)(de)溶(rong)劑(ji)(ji)為水，水的(de)(de)(de)(de)(de)表(biao)(biao)(biao)(biao)面(mian)(mian)(mian)(mian)張(zhang)力比(bi)有機溶(rong)劑(ji)(ji)大(da)(da)，因此水性(xing)(xing)(xing)(xing)油(you)(you)(you)(you)墨(mo)(mo)(mo)(mo)(mo)的(de)(de)(de)(de)(de)表(biao)(biao)(biao)(biao)面(mian)(mian)(mian)(mian)張(zhang)力較大(da)(da)（水性(xing)(xing)(xing)(xing)墨(mo)(mo)(mo)(mo)(mo)3.8×10-2N/m，溶(rong)劑(ji)(ji)型墨(mo)(mo)(mo)(mo)(mo)3.3~3.6×10-2N/m），要使水性(xing)(xing)(xing)(xing)油(you)(you)(you)(you)墨(mo)(mo)(mo)(mo)(mo)在塑(su)(su)料(liao)(liao)(liao)(liao)(liao)(liao)(liao)表(biao)(biao)(biao)(biao)面(mian)(mian)(mian)(mian)良(liang)好(hao)(hao)(hao)附著(zhu)，需要塑(su)(su)料(liao)(liao)(liao)(liao)(liao)(liao)(liao)有較大(da)(da)的(de)(de)(de)(de)(de)表(biao)(biao)(biao)(biao)面(mian)(mian)(mian)(mian)張(zhang)力，所(suo)以(yi)，對于表(biao)(biao)(biao)(biao)面(mian)(mian)(mian)(mian)張(zhang)力界(jie)于3.6~3.8×10-2N/m的(de)(de)(de)(de)(de)塑(su)(su)料(liao)(liao)(liao)(liao)(liao)(liao)(liao)薄膜(mo)，用(yong)溶(rong)劑(ji)(ji)型油(you)(you)(you)(you)墨(mo)(mo)(mo)(mo)(mo)印(yin)(yin)(yin)(yin)(yin)(yin)(yin)刷(shua)(shua)(shua)(shua)(shua)時可(ke)以(yi)不(bu)(bu)(bu)需表(biao)(biao)(biao)(biao)面(mian)(mian)(mian)(mian)處(chu)理(li)，但用(yong)水性(xing)(xing)(xing)(xing)油(you)(you)(you)(you)墨(mo)(mo)(mo)(mo)(mo)或UV墨(mo)(mo)(mo)(mo)(mo)印(yin)(yin)(yin)(yin)(yin)(yin)(yin)刷(shua)(shua)(shua)(shua)(shua)時需表(biao)(biao)(biao)(biao)面(mian)(mian)(mian)(mian)處(chu)理(li)。為了使印(yin)(yin)(yin)(yin)(yin)(yin)(yin)刷(shua)(shua)(shua)(shua)(shua)油(you)(you)(you)(you)墨(mo)(mo)(mo)(mo)(mo)能很好(hao)(hao)(hao)附著(zhu)在塑(su)(su)料(liao)(liao)(liao)(liao)(liao)(liao)(liao)表(biao)(biao)(biao)(biao)面(mian)(mian)(mian)(mian)上，處(chu)理(li)后(hou)塑(su)(su)料(liao)(liao)(liao)(liao)(liao)(liao)(liao)的(de)(de)(de)(de)(de)表(biao)(biao)(biao)(biao)面(mian)(mian)(mian)(mian)張(zhang)力值一般應比(bi)油(you)(you)(you)(you)墨(mo)(mo)(mo)(mo)(mo)的(de)(de)(de)(de)(de)表(biao)(biao)(biao)(biao)面(mian)(mian)(mian)(mian)張(zhang)力值高出(chu)約1×10-2N/m。

不同塑料(liao)表(biao)(biao)面(mian)(mian)性(xing)(xing)能不同，是否需電暈處(chu)(chu)(chu)理或處(chu)(chu)(chu)理的(de)程度也(ye)不同。對(dui)于表(biao)(biao)面(mian)(mian)張(zhang)力是3.9~4.5×10-2N/m的(de)極(ji)性(xing)(xing)塑料(liao)，不需表(biao)(biao)面(mian)(mian)處(chu)(chu)(chu)理，對(dui)于本身(shen)無(wu)極(ji)性(xing)(xing)或極(ji)性(xing)(xing)較弱(ruo)，表(biao)(biao)面(mian)(mian)張(zhang)力較低的(de)塑料(liao)，電暈處(chu)(chu)(chu)理的(de)程度較深，以(yi)獲得與印刷油墨相適應的(de)表(biao)(biao)面(mian)(mian)性(xing)(xing)能。

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