Microlens Array of Inkjet Printing Technology for Light Guide Plate Applications

近年LCD (Liquid Crystal Dispaly) 市場薄型化整體模組要求為之嚴苛；所有相關製程皆要求薄型設計。因此薄型化導光板設計，對背光模組產業需求更加嚴峻。薄型化導光板在射出成形時，需要高射速、高射壓進行模穴填充，常因殘留內應力造成導光板變形、翹曲等問題。噴墨印刷製程技術(Ink-Jet Printing)的按需噴墨(Drop-on-demand)及直接書寫(Direct writing)特性，故無須製作微結構之模仁及模具，可大幅縮短開發時程，且降低成本，因此背光模組廠認為此新式製程技術相當具有潛力開發薄型化導光板。 本研究進行噴墨材料介紹、基板疏水 Primer Coating 表面處理、噴墨微透鏡成形最佳製程參數設計、光學網點設計及成品光學檢測。使用 Miyakawa MLP-850UV 設備，運用噴墨印刷製程技術進行陣列式微透鏡導光板製作，並建立噴墨列印技術製作導光板之完整製程方式。使用準高分子 UV 固化型墨水(Polyacrylamide)作為材料，搭配噴墨成形最佳製程參數，驅動電壓22 V及墨夾與基板距離0.8 mm，經第一道噴墨製程、疏水層Primer Coating表面處理後，於疏水性基板上加工第二道噴墨製程成形微透鏡 Lens 陣列排列。 使用小尺寸13.3吋機種，搭配光學網點密度設計，實際噴印為直徑70μm、高度14μm 、覆蓋率0.539 之微透鏡尺寸、並控制疏水層Primer 薄膜厚度為0.723μm、折射率為1.509。經噴墨印刷技術，成功製作出平均輝度為2419.18nits 及均齊度為87.84% 之13.3吋噴墨導光板，因而展示噴墨印刷製程技術應用於薄型導光板快速製作之能力。In the recent years, with the raise in standard of Liquid Crystal Display (LCD) thin module, thin design becomes indispensable in the manufacturing process. Therefore, the back light module industry demands stricter design in thin light guide plate. While injecting thin light guide plate, high injection speed and molding pressure are required, so the remained residual stress often causes the plate transformed and warped. To resolve this, we can apply the properties of ink-jet printing, drop-on-demand and direct writing. By introducing these properties, no microstructure mold and stampers are fabricated, so the development period and cost can be reduced dramatically. In this paper, we will introduce printing materials, surface treatment of primer coating, parameter optimization of printing microlens, optimal design and product verification. With Miyakawa MLP-850UV, ink-jet printing process is used to manufacture micro lens array light guide plate, and establish the complete process. In our design, we adopted UV polyacrylamide, optimized ink-jet printing, 22V driving voltage, and 0.8mm substrate gap. After the first printing process and the hydrophobic layer with primer coating, we proceed with the second printing process on the substrate to form the micro lens array. 13.3' machines is operated with optical design, to control the micron lens of 70μm in diameter, 14um in height, and 0.539 coverage. Film size of hydrophobic layer primer is controlled by 0.723μm in thickness and 1.509 refractive index. With ink-jet printing technique, we can successfully manufacture 13.3' ink-jet light guide plate with 2419.18 nit luminance and 87.84% luminance uniformity in average. The experiment result validates the ability of Ink-Jet printing process in manufacturing thin light guide plate.致謝.......................................................................................................................... i 中文摘要...………………………………………………….....…………………. ii Abstract....................................................................................................................iii 目錄.........................................................................................................................iv 圖目錄....................................................................................................................vii 表目錄.................................................................................................................... xi 第一章 緒論............................................................................................................1 1-1 前言........................................................................................................... 1 1-2 光電產業噴墨列印技術應用....................................................................2 1-3 背光模組結構與型式簡介....................................................................... 3 1-4 導光板作用原理與製程種類簡介........................................................... 5 1-5 研就動機…………………………............................................................6 第二章 文獻回顧....................................................................................................7 2-1 噴墨科技歷史與發展............................................................................... 7 2-2 噴墨列印技術分類………........................................................................9 2-2-1 連續式噴墨.………......................................................................10 2-2-2 隨選式噴墨.………......................................................................11 2-3 導光板形狀之光學設計…......................................................................14 2-4 導光板表面結構特性……………..........................................................15 2-5 導光板微透鏡陣列製程…………..........................................................16 第三章 光學基礎理論..........................................................................................19 3-1 折射定律(Snell law).................................................................................19 3-2 反射定律…………………......................................................................21 3-3 全內反射與臨界角………......................................................................22 第四章 實驗規劃..................................................................................................23 4-1 實驗目的…………..................................................................................23 4-2 噴墨列印材料……………......................................................................23 4-2-1 噴墨材料特性….…......................................................................23 4-2-2 噴墨材料選用….…......................................................................25 4-3 實驗設備與量測儀器……......................................................................27 4-3-1 噴墨設備簡介….…......................................................................27 4-3-2 噴墨頭簡介…….…......................................................................29 4-3-3 光學顯微鏡…….…......................................................................31 4-3-4 雷射掃描式共厄焦顯微鏡….......................................................32 4-3-5 BM-7輝度檢測儀….......................................................................33 4-3-6 CCD面光源強度檢測儀................................................................34 4-3-7 F20膜厚量測儀……......................................................................35 4-4 實驗程序…………………......................................................................36 4-4-1 噴墨實驗流程….…......................................................................36 4-4-2 實驗參數……….…......................................................................37 4-5 實驗背光模組……………………..........................................................39 第五章 實驗結果與討論…..................................................................................42 5-1 噴墨導光板微透鏡成形最佳參數實驗…………………......................42 5-1-1 微透鏡成形理論.…......................................................................42 5-1-2 基材導光板改質...........................................................................43 5-1-3 噴墨成形製程參數.......................................................................45 5-1-4 噴墨頭電壓及波形圖...................................................................45 5-1-5 噴墨頭與基板之距離設計...........................................................47 5-1-6 墨滴成形之微透鏡大小點實際值...............................................48 5-2 噴墨導光板微透鏡點徑尺寸影響光學最佳參數實驗……..................51 5-2-1 噴墨網點密度設計分佈.…..........................................................51 5-2-2 噴墨微透鏡提升光學萃取效率...................................................52 5-3 噴墨導光板疏水層厚度設計最佳參數實驗……...... ...........................56 5-3-1 噴墨疏水層厚度與折射率變化實驗.…......................................56 5-3-2 噴墨疏水層厚度調整之光學最佳參數.......................................65 5-4 噴墨導光板製程穩定性實驗……...... ...................................................68 第六章 總結....................…..................................................................................70 參考文獻................................................................................................................72 圖目錄 圖1-1 背光模組結構圖[13].....................................................................................4 圖1-2 導光板光路徑示意圖[13]............... .............................................................4 圖1-3 Miyakawa以噴墨直接書寫製作導光板[14]..................................................6 圖2-1 液體從噴頭射出後滴狀形成圖[5]...............................................................8 圖2-2 液體射流為單個水滴圖像[6].......................................................................8 圖2-3 噴墨技術分類圖[12].....................................................................................9 圖2-4 連續式噴墨設備示意圖[5].........................................................................10 圖2-5 連續式雙向偏轉示意圖[5].........................................................................10 圖2-6 連續式多向偏轉示意圖[5].........................................................................10 圖2-7 熱氣泡式噴墨頭設計示意圖[5].................................................................12 圖2-8 基本的壓電陶瓷板的變形模式[5].............................................................12 圖2-9 擠壓模式壓電噴墨設計示意圖[16]...........................................................13 圖2-10 彎曲模式壓電噴墨設計示意圖[5]...........................................................13 圖2-11 推送模式壓電噴墨設計示意圖[5]...........................................................13 圖2-12 剪切模式壓電噴墨設計示意圖[5]...........................................................13 圖2-13 矩形與楔形導光板光反射比較[13].........................................................14 圖2-14 (a)楔形與(b)弧形之導光板[18]…..............................................................15 圖2-15 纖毛狀的微結構[21].................................................................................16 圖2-16 導光板微透鏡陣列SEM圖[31].................................................................18 圖3-1 折射機制示意圖[37]...................................................................................20 圖3-2 反射機制示意圖[39]....................................................................................21 圖3-3 全內反射機制示意圖[37]............................................................................22 圖4-1 不同黏度及表面張力液滴成形圖[40].......................................................24 圖4-2 噴墨用之材料疏水層Primer........................................................................25 圖4-3 噴墨用之材料微透鏡Lens..........................................................................25 圖4-4 噴墨設備 Miyakawa MLP-850UV[42].......................................................27 圖4-5 噴墨設備 Miyakawa MLP-850UV[42].......................................................27 圖4-6 Single Path 噴墨方式作動示意圖...............................................................28 圖4-7 Toshiba CE-2 噴墨頭(6-90 picoliter).............................................................29 圖4-8 壓電式噴墨列印動作示意圖[43]...............................................................30 圖4-9 光學顯微鏡............................. .............. .............. .....................................31 圖4-10 雷射掃描式共厄焦顯微鏡.......................................................................32 圖4-11 BM-7 輝度檢測儀........................... .............. ..........................................33 圖4-12 CCD 面光源強度檢測儀示意圖..............................................................34 圖4-13 F20 膜厚量測儀[44]………………............................................................35 圖4-14 噴墨製程流程圖…......................................................................................36 圖4-15 噴墨製程光學設計流程圖................... .......................................................37 圖4-16 Toshiba CE2 噴墨頭解析度300DPI 示意圖................................................38 圖4-17 噴墨製程微透鏡覆蓋率示意圖....................... .......................................38 圖4-18 10.1吋背光模組圖面[53]...........................................................................39 圖4-19 10.1吋背光模組圖…………………............................................................39 圖4-20 13.3吋背光模組圖面[53]….......................................................................40 圖4-21 13.3吋背光模組圖圖..................................................................................40 圖5-1 接觸角與表面張力關係圖.........................................................................42 圖5-2 親水性及疏水性接觸角示意圖[47]............................................................43 圖5-3 疏水層Primer攤平於導光板基材示意圖...................................................44 圖5-4 微透鏡Lens於疏水層Primer矩陣排列示意圖...............................................44 圖5-5 不同波型圖噴印後之差異圖[52]...............................................................46 圖5-6 電壓波形圖.................................................................................................46 圖5-7 不同操作電壓下觀察墨滴滴下情況.........................................................46 圖5-8 噴墨頭與基板(導光板)距離示意圖..........................................................47 圖5-9 不同噴墨頭與基板距離下之噴墨成形圖(OM圖).....................................48 圖5-10 透鏡大小網點成形原因示意圖...............................................................49 圖5-11 不同大小微透鏡網點成形Confocal圖....................................................50 圖5-12 噴墨網點密度設計分佈示意圖...............................................................51 圖5-13 背光模組13點點位光學檢測位置圖[53]…….…….….............................53 圖5-14 Level.1(32.5μm)微透鏡13點點位光學輝度分佈圖…................................53 圖5-15 Level.7(70μm) 微透鏡13點點位光學輝度分佈圖....................................53 圖5-16 Level.7(70μm) CCD Analysis圖...................................................................54 圖5-17 Level.7(70μm) 背光模組光學品味圖........................................................54 圖5-18 疏水層Primer薄膜厚度9點檢測點位圖....................................................57 圖5-19 疏水層Primer Level.4薄膜厚度與折射率檢測圖……………...…............57 圖5-20 疏水層Primer Level.4薄膜厚度9點分佈圖…………………………..........58 圖5-21 疏水層Primer Level.5薄膜厚度與折射率檢測圖……………...…............58 圖5-22 疏水層Primer Level.5薄膜厚度9點分佈圖…………………………..........59 圖5-23 疏水層Primer Level.6薄膜厚度與折射率檢測圖……………...…............59 圖5-24 疏水層Primer Level.6薄膜厚度9點分佈圖…………………………..........60 圖5-25 疏水層Primer Level.7薄膜厚度與折射率檢測圖……………...…............60 圖5-26 疏水層Primer Level.7薄膜厚度9點分佈圖…………………………..........61 圖5-27 疏水層Primer Level.4~ Level.7折射率變化圖…………….........…............61 圖5-28 疏水層Primer Level.4~ Primer Level.7光學效益比較曲線圖…...…..........65 圖5-29 5點光學輝度表現曲線圖…......................................................................68 圖5-30 5點光學輝度均勻性表現曲線圖..............................................................69 圖5-31 13點光學輝度均勻性表現曲線圖……………………………................69 表目錄 表4-1 噴墨用之材料疏水層Primer.......................................................................26 表4-2 噴墨用之材料微透鏡Lens..........................................................................26 表4-3 噴墨機台規格表.........................................................................................28 表4-4 Toshiba CE-2 噴墨頭規格表........................................................................30 表4-5 光學顯微鏡規格表.....................................................................................31 表4-6 雷射掃描式共厄焦顯微鏡規格表.............................................................32 表4-7 BM-7輝度檢測儀規格表……….................................................................33 表4-8 CCD面光源強度檢測儀規格表..................................................................34 表4-9 F20膜厚量測儀[44].............................. ..................... .................................35 表4-10 微透鏡噴印階數規格表..............................................................................38 表4-11 10.1吋背光模組光學規格表[53]…................ ...........................................41 表4-12 13.3吋背光模組光學規格表[53]...............................................................41 表5-1 Level.1微透鏡13點光學輝度表現表...........................................................55 表5-2 Level.7微透鏡13點光學輝度表現表............................................................55 表5-3 疏水層Primer Level.4薄膜厚度9點量測表.................................................62 表5-4 疏水層Primer Level.5薄膜厚度9點量測表.................................................62 表5-5 疏水層Primer Level.6薄膜厚度9點量測表.................................................63 表5-6 疏水層Primer Level.7薄膜厚度9點量測表.................................................63 表5-7 疏水層Primer Level.4 ~ Level.7薄膜厚度與各波長折射率量測表............64 表5-8 疏水層Primer Level.4 13點輝度表現表......................................................66 表5-9 疏水層Primer Level.5 13點輝度表現表......................................................66 表5-10 疏水層Primer Level.6 13點輝度表現表....................................................67 表5-11 疏水層Primer Level.7 13點輝度表現表....................................................67 表5-12 疏水層Primer Level.4~Level.7 13點輝度比較表.......................................6