工業傾角狹縫塗佈製程之塗佈技術分析

Coating Window Study in Industrial Angled Slot Coating

秦志平(Chih-Ping Chin)

指導教授 ： 吳和生

元智大學/工程學院/化學工程與材料科學學系/碩士(2007年)

https://doi.org/10.6838/YZU.2007.00031

摘要

狹縫式精密塗佈廣泛的應用於現今各種塗佈產品的製程之上，為預計量式塗佈的一種。而預計量式塗佈方式，是指塗佈液膜厚度可依產品的品質要求，預先由流量及塗佈速度估算決定的塗佈方式並與其他的製程變數無關。此種狹縫式塗佈方式的主要操作限制為最低流量限制及塗佈視窗兩種，最低流量限制是指在已知塗佈速度狀況下，可得之最小塗膜厚度；塗佈視窗則是可以顯示特定種類塗料的最適操作範圍。
此次研究中所謂的傾角狹縫式塗佈，則是藉由傾斜模具使得塗液與基材形成不再只是垂直於基材的角度變化。過去在於預計量式塗佈相關的文獻中，所用的流體多為低黏度的牛頓流體及高分子非牛頓流體，但在實際工業製程上所採用的大部分多為高黏度非牛頓流體，且為了配合產品要求及後段處理速度，往往並非以最大速度進行操作。因此，此次研究主要是利用光學保護膜製程中的光硬化膜塗料及矽膠塗料，藉由傾角塗佈及改變模具組成方式建立出一可操作的塗佈區間及最小膜厚分佈，加以分析討論之。
從實驗結果發現，傾角塗佈的方式研究中發現，會使得沾濕線的接觸角亦產生變化，進而延遲塗佈缺陷的產生使得塗佈視窗得以提升至高流量或高速的方向。藉由改變模具幾何形狀，不需加以輔助設備即可產生類似的真空效應及刮刀效應，進而因此穩定液珠即有助於塗膜厚度的均勻化，並可藉此提升塗佈速度及延遲最低流量限制的發生時機。並由實驗結果發現塗佈速度可因此提升至原塗佈速度的兩倍，塗膜均勻度可由標準差±1μm縮減至±0.5μm。經由將實驗求得之最適化操作參數，經實際量產測試時除品質上膜厚均勻度提升外，產量亦提升至原操作參數狀況下的1.5倍以上，也因此驗證實驗可靠性。

關鍵字

狹縫式塗佈； 預計量式塗佈； 擠壓式塗佈； 塗佈缺陷；塗佈視窗

並列摘要

Slot die coating is a common method in the manufacture of a wide variety of products. It belongs to a class of coating method known as pre-metered coating: the thickness of the coated liquid layer in principle is set by the flow rate fed to the die and the speed of the substrate moving past, and is independent of other process variables. Thus, pre-metered methods are ideal for high precision coating. The important operating limits of slot coating are the minimum thickness that can be coated at a given substrate speed, generally referred to as the low-flow limit and coating window which is used to reflect the flexibility in suitable operation condition range.
The coating flow examined as labeled angled slot die coating, was that where a substrate contacts a sheet of liquid forming an angled flows with the vertical to the substrate, so that it intersects the liquid along a wetting line which was not perpendicular to the direction of its motion. Although most of the liquids coated industrially are polymeric solutions and dispersions that are not Newtonian, previous analyses of the low-flow limit and coating window in slot coating dealt only with Newtonian liquids. The experiments were carried out with various kinds of liquids hard coating and polysilica solution which are Newtonian fluid and power law fluid and both are used in real industrial coating process to determine the coating effect on the substrate velocity when coating defects appeared.
It was observed that coating defects are delayed to higher speeds and expanded to larger flow rate, as this angle of the die departs from vertical. The experiment data show that the speed which is relevant to coating defects is not the velocity of the substrate itself but its component normal to the wetting line. Variation of the die geometry also can influence the coating window and its coatability, and even shift the low-flow-limit in higher speed and give thinner film thickness. The experiment data show that Bead vacuum effect and blade effect are formed by changing the die geometry without using any assistant equipment, which can make the coating bead stable and uniform the film thickness. These results have important practical implications and suggest that these fundamental principles are also applicable to other coating flows.

並列關鍵字

slot die ； Pre-metered coating ； Extrusion coating ； Coating window ； Air entrainment

參考文獻

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