可溶型聚亞醯胺薄膜成膜、剝膜與延伸行為之研究

Film-Forming, Peeling and Stretching of Soluble Polyimides

王瀚毅(Han-Yi Wang)

指導教授 ： 劉大佼

國立清華大學/工學院/化學工程學系/博士(2010年)

https://doi.org/10.6843/NTHU.2010.00172

摘要

本研究主要討論以溶液鑄膜法製作可溶性聚亞醯胺薄膜之兩個技術關鍵，分別為一、薄膜剝離之相關問題；二、以延伸製程調控以熱膨脹係數為主之薄膜物性。在建立完整之理論分析工具之前，首先必須先進行對塗液出模口至乾燥前的揮發與烘箱內乾燥情況之分析，以完成兩大部分之前置預測理論模型。
本研究首先成功建立一維乾燥模型，可預測可溶性聚亞醯胺與N-甲基咯酮塗液出模具口之雙面揮發情況與塗膜在烘箱內之乾燥行為，並與乾燥實驗做比較，以確認理論工具之準確性。對於可溶性聚亞醯胺薄膜的關鍵製程技術，本研究主要探討的兩部分內容簡介如下：
一、分析解決剝膜之技術問題
　　本部分研究目的為分析並解決聚亞醯胺成膜與剝膜的相關問題，以可溶型聚亞醯胺和其溶劑N-甲基咯酮於鋼板基材為研究系統。由於塗佈於鋼板的聚亞醯胺濕膜在高溫下乾燥會有大量溶劑揮發擴散，造成乾燥缺陷進而影響剝膜製程，所以本研究於分析剝膜程序之前首先必須確定薄膜無乾燥缺陷，並依此建立薄膜厚度對乾燥溫度之操作視窗。隨後本研究以實驗分析來建構剝膜操作視窗，並建立理論模型工具與實驗結果相驗證。
剝膜操作視窗定義為可穩定且無剝膜缺陷之剝膜操作範圍。剝膜操作視窗之邊界為兩大剝膜缺陷所限：一為在高剝膜拉力下會產生脆性斷膜缺陷；二為於低剝膜拉力下則造成剝膜於鋼板基材界面產生條紋狀之黏滑剝膜缺陷。此外當溶劑殘存量低於某一臨界值時，聚亞醯胺薄膜與鋼板基材之接著性過強，使其無法順利自鋼板基材剝離。在理論工具方面，本研究參考先前文獻有關剝膜及對缺陷的預測，並加以修改延伸以符合本研究系統。
二、以延伸製程調控以熱膨脹係數為主之薄膜物性
本部分研究目的是首先以實驗確立適當之延伸範圍再於此範圍進行分析。本研究並建立理論模型預測各物性，再與實驗量測的結果相比較。
本研究發現聚亞醯胺高分子薄膜存在一延伸操作視窗，其界線分別由延伸溫度和延伸倍率所界定。延伸溫度上下限分別為再結晶溫度與玻璃轉化溫度；延伸倍率上下限為薄膜表面不平整性與頸縮現象。在建立完延伸操作視窗後，可在視窗內進行延伸製程對薄膜物性之探討，並建構延伸後的薄膜雙折射，二維楊氏係數與熱膨脹係數的理論分析工具。由於高分子薄膜物性與膜內分子排列度有高度相關，本研究可使用偏光顯微鏡偵測各延伸條件下薄膜綜觀分子排列度(fibrils structure)以解釋各薄膜物性經延伸之現象。

關鍵字

可溶性聚亞醯胺薄膜 ； 乾燥 ； 揮發 ； 剝膜 ； 操作視窗 ； 黏滑效應之條紋缺陷 ； 脆性斷膜 ； 單軸延伸 ； 雙折射率 ； 楊氏係數 ； 熱膨脹係數

並列摘要

The objective of this thesis is the investigation of drying, peeling and stretching of recyclable polyimide films. There are two important parts of this research; peeling of the polyimide film without defect and is how to control the coefficient of thermal expansion (CTE) by the stretching process. Understanding of formation, evaporation and drying of polyimide film is necessary before analyzing the two important issues.
A dimensional drying model was developed successfully to predict the residual solvent content and drying time during solvent evaporation and drying of polyimide film.
The peeling behavior of polyimide film coated on steel substrates was experimentally investigated and compared with existing models. An operating window for peeling, which is defined as a closed domain for steady and defect-free peeling, is presented in terms of peeling force vs. residual solvent content. The window is bounded by two major defects: the film becomes too brittle for peeling at high peeling force, and stick-slip striation defect appears at low peeling force. There exists a critical residual solvent content below which the adhesion between the polyimide film and the substrate is too strong, then peeling is impossible. Existing models for predicting steady peeling and the on-set of peeling defects have been modified and applied to set up the boundaries of the operating window. There also exists another operating window for drying of polyimide, and is presented in the form of drying temperature versus film thickness.
The effects of uni-axial stretching on the CTE, birefringence and Young’s modulus of a recyclable polyimide film were examined. An operating window which was bounded by two temperatures and draw ratios were found first. Inside this operating window, stable and defect-free stretching was possible. CTE, birefringence and Young’s modulus of the recyclable polyimide film were measured under stretching. Values of birefringence and Young’s modulus go up as the stretching stress in the machine direction increases. On the other hand, CTE in the machine direction decreases as the stretching stress increases. A theoretical model that relates stretching conditions to birefringence and Young’s modulus was developed. CTE can also be evaluated with the Young’s modulus vs CTE data available. Theoretically evaluated physical properties are in qualitative agreement with the experimental data.

並列關鍵字

soluble polyimide film ； drying ； evaporating ； peeling ； operating window ； stick-slip striation defect ； brittle film ； uni-axial stretching ； birefringence ； Young’s modulus ； coefficient of thermal expansion

參考文獻

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