Study on Photocurable Stress of Poly Urethane Acrylate for Liquid Optical Clear Adhesive of Touch Panel

現今由於手機、筆記型電腦、液晶電視、平板電腦等有關液晶顯示器在電子市場日漸成為生活用品的消費主流，如何在各方面提升產品品質、良率提升、成本控制、生產效能即扮演重要腳色，其中利用紫外光固化技術為本研究探討液態光學膠在加工貼合技術領域上，因此在觸控貼合的生產流程，成為本研究重要課題之一。本論文液態光學膠主要以聚氨酯丙烯酸樹酯、反應性單體、光起始劑及助劑為基礎組成，利用自由基激發聚合而成高分子固態，為無溶劑系統。實驗主要是利用紫外光能量提供光起始劑產生自由基，促使高反應活性單體 EM215 進行交聯反應，形成聚氨酯壓克力型複合材料。本研究定義出接著劑之物性要求低固化收縮率和低彈性模數所得到的低貼合應力(Stress)為本研究液態光學膠的動機，此為組裝製程中重要解決方案之一。本文利用萬用拉力機與收縮率測定、紫外光可見光光譜儀(UV-visible)、光量熱示差掃描分析儀(UV-DSC)、凝膠滲透層析儀(GPC)及熱重分析儀(TGA)分析，驗證出本研究配方及製程的最佳化條件達到極小貼合應力，並以液晶顯示器的 Mura 程度佐證之。本文歸納出下面兩項重要成果： (1) 對 於 光 學 性 質 最 適 化 配 方 ， 選 用 聚 氨 酯 丙 烯 酸 樹 脂50wt%(Mw:32024)，Darocure 1173 光起始劑為 0.1wt%，及月桂酸丙烯酸反應性單體 50wt%製備液態光學膠，其膠體彈性模數(Modulus)明顯從 111.64 降低至 3.17 kPa；然後，再導入不具有反應性助劑大分子量 B-204(Mw:4000)，可將膠體光固化收縮率自 5.21％降低至 1.58％且同時亦降低彈性模數至 0.74 kPa，且有效提升 60℃耐熱性質，得到收縮應力最小值為 0.01 kPa。 (2) 在曝光能量 12J 之下，由紫外光 30mW/cm2 低光照強度得知，膠體彈性模數為 61.02 kPa；而紫外光 3W/cm2 高光照強度足以克服反應活化能以加速分子有序結構的排列，明顯促進大分子交聯反應，以致大分 子間的作用力變大，造成分子鏈段較長，明顯降低膠體彈性模數，此 可改善觸控面板之貼合應力。The applications of touch panel in mobile phones, laptops, TVs, tablet PCs and so on, become daily necessities in information and communication technology. In the point of view of manufacturing, to improve the quality of product, the yield enhancement, the cost control, and the production efficiency in all aspects plays an important role. In the field of the lamination, the liquid optical clear adhesive (LOCA) which utilizes UV-curing is a critical factor, and therefore we focus this topic in our study. The LOCAs used in this study contain a urethane acrylate resin, reactive monomers, a photo-initiator and additives as a solvent-free system. Upon UV-irradiation, the photo-initiator produces free radicals to induce the polymerization and to form a polyurethane acrylate composite material. To apply the LOCAs as an adhesive, it mainly uses the stress which combines the shrinkage percentage and the modulus as the evaluation criteria. Through universal material testing machine, the measured shrinkage percentage, the UV-visible、UV-DSC、GPC and TGA analysis, it verified the composite and the process for the best condition in this study to achieve minimal stress, and it successfully supports the applied simulation to monitor the extent of the Mura. We summarized the important results as following two points : (1) For optimal optical properties of the formulation, selected urethane acrylate resin 62MU2 (Mw: 32024) 50wt% were mixed Lauryl reactive monomer 50wt%, and photo-initiator 0.1wt% to obtain the optimum optical conditions of LOCA. The elastic modulus reduced sharply from 111.64 kPa to only 3.17 kPa. The introduction of non-reactive addictive B- 204 (Mw: 4000) with high molecular weight leads to the reduction of the curing shrinkage percentage from 5.21% to 1.58%, and the elastic modulus lowered to 0.74 kPa, which obviously have a maximum elastic energy that also enhance the heat-resistance, and therefore achieves the minimal shrinkage stress value to 0.01 kPa. (2) Under the exposure energy 12J, low UV-intensity: 30mW/cm2 that elastic modulus is 61.02 kPa, while 3W/cm2 high UV-intensity is large enough to overcome activation energy of the reaction and lead to accelerated arrangement of the molecular structure, which increases crosslinking reaction of macromolecules. The macromolecules are large with a longer molecular chain and the decreased elastic modulus, this can improve the bonding stress of the touch panel.摘要 ................................................. I Abstract ........................................... III 圖目錄 ............................................. VII 表目錄 ................................................ IX 緒論 ................................................... 1 1-1 前言................................................ 1 1-2 研究動機與方法.................................... 4 第一章 理論基礎 ................................. 8 2-1 本章摘要 ........................................ 8 2-2 高分子聚氨酯丙烯酸酯材料﹙Poly Urethane Acrylate，PUA﹚ ............................ 9 2-2-1 聚氨酯丙烯酸酯預聚物的合成 ....................................................10 2-2-2 PUA 合成與固化膜製得方法: ....................................................11 2-3 紫外光固化（UV-curing）技術 .....................................................14 2-3-1 一般紫外光固化樹脂的組成配方可分為三大部份：.................................. 15 2-4 紫外光聚合反應配方組成 ..............................17 2-4-1 可聚合寡聚物(28) ...............................17 2-4-2 單體(29) ...................................17 2-4-3 光起始劑(30,31) .................................18 2-4-4 助劑(32) ................................. 19 2-5 實驗設計 ........................................20 2-6 膠黏劑收縮率 ..................................... 21 第三章 實驗方法 ........................................... 23 3-1 本章摘要 ......................................... 23 3-2 液態光學膠膠體配製 ..................................23 3-3 實驗因子及規劃 ...............................24 3-4 儀器分析 ........................................... 25 3-5 實驗藥品 ........................................ 39 3-5 實驗儀器與設備 .....................................44 第四章 結果與討論 ....................................... 45 4-1 本章摘要 ..................................... 45 4-2 膠體曝光能量驗證 ....................................46 4-3 探討影響膠體固化收縮率 ............................52 4-3-1 聚氨酯丙烯酸樹酯 ...................................52 4-3-2 光起始劑 ..................................55 4-3-3 反應單體 ..................................... 56 4-4 探討膠體固化收縮率下影響彈性模數之關係 ............................................57 4-4-1 聚氨酯丙烯酸樹酯 ..................................57 4-4-2 光起始劑 ......................................60 4-4-3 紫外光照度 ...................................65 4-5 液態光學膠組成最佳化 ...............................69 4-5-1 助劑 ................................... 69 第五章 綜合結論與未來延續方向 ............................. 72 5-1 結論 ........................................ 72 5-2 未來延續方向 .................................. 74 參考文獻................................................. 7