使用皮秒雷射雕刻玻璃導光板之微結構

Use Pico-Laser to Engrave Glass Light Guide Plate with Microstructures

蔡閎丞(Tsai Hung-Cheng)

指導教授 ： 鄧敦建

國立臺灣師範大學/科技與工程學院/機電工程學系/碩士(2018年)

https://doi.org/10.6345/THE.NTNU.DME.013.2018.E08

摘要

近來，大尺寸的超薄液晶顯示器(Liquid Crystal Display, LCD)已成為主流。為了降低厚度，除了採用更薄的導光板外，側入式背光模組中的其他支撐部件也都被移除或簡化以進一步降低整體厚度；這將導致由PMMA製成的導光板(Light Guide Plate, LGP)材料強度不足以支撐背光。相比之下，由玻璃製成的導光板比PMMA導光板具有更高的材料強度，因此被視為潛在的解決方案。然而，目前除了網版印刷之外，很難直接在玻璃LGP上形成微結構；然而網版印刷的使用在玻璃材料上仍有其限制。另一方面，由於皮秒雷射(Picosecond Laser, Pico-Laser)具有非線性光子吸收特性和低熱影響區而適用於加工玻璃材料，所以我們試圖用皮秒雷射來製造微結構玻璃導光板，並且研究雷射加工參數對微結構玻璃導光板出光行為的影響。在本研究中，我們使用532 nm的皮秒雷射直接在康寧玻璃基板(Iris glass)表面雕刻出凹面微結構，以評估實際製造微結構玻璃導光板的可行性，包括皮秒雷射製程參數（包括焦點位置，功率，掃描速度和填滿間距）對雕刻表面形貌以及出光行為的影響。此外，在製程的後處理部分採用熱回流(Thermal reflow)和HF化學濕蝕刻兩種不同製程來平滑樣品的微結構輪廓，減少因表面粗糙造成的雜散光，進而改善出光特性。最後，我們展示了6英吋的微結構玻璃導光板樣品。實驗結果顯示：在最佳製程條件下，經過微結構圖案密度分布最佳化所設計製作的樣品，其出光平均輝度與均齊度可分別達到1.03 x 103 cd/m2與0.793。

關鍵字

雷射燒蝕 ； 雷射雕刻 ； 微結構玻璃導光板 ； 皮秒雷射

並列摘要

Recently, the large-sized, ultra-slim Liquid-Crystal Display(LCD) has become the mainstream. Therefore, the light guide plate (LGP) is becoming thinner, and the supporting components in the edge-lit backlight are removed to further reduce the entire thickness, which led the LGP made of PMMA too weak to support the backlight. In contrast, the LGP made of glass has much higher stiffness than that of PMMA and thus has become a potential solution. However, it is difficult to form microstructures directly on the glass LGP except screen-printing, but screen-printing has the limit for glass material. Because the Picosecond Laser (pico-laser) has the characteristics of nonlinear photon absorption and low heat affected zone suitable to machine the glass material, we tried to use the laser to fabricate a sample of the microstructure glass LGP and investigate the effects of the process parameters of the laser on the optical behaviors of the LGP. In this study, we tried to use a pico-laser of 532 nm to engrave a glass substrate (Iris glass, Corning) with concave microstructures to evaluate the feasibility of practically fabricating a LGP, and investigated the effects of laser processing parameters, including focus position, power, scanning speed, and scanning pitch on the morphology of engraving surface. In addition, we adopted two kinds of post-processing, thermal reflow and HF chemical wet etching, to smooth the microstructure of the sample and reduce stray light caused by surface roughness, thereby improving the light-emitting characteristics. Finally, we demonstrated a sample of the 6-inch glass LGP and verified the feasibility of fabricating a microstructure glass LGP using ablation by the pico-laser. With the optimal process parameters and distribution of pattern density, the average luminance and uniformity of the LGP sample is 1.03 x 103 cd/m2 and 0.793.

並列關鍵字

laser ablation ； laser engraving ； mircostructure glass light guide plate ； pico-laser

參考文獻

[1] 液晶顯示器，https：//zh.wikipedia.org/wiki/液晶显示器

[2] 張國順，鄭壽昌，“現代雷射製造技術”，初版，新文京開發出版股份有限公司，台灣，2008/1。

[3] Y. Kondo, M. Inoue, K. Ishikawa, K. Mori, “ Glass light guide plate for ultrathin large-sized television,” SID 2016 DIGEST, Japan, 1094-1097 (2016).

[4] S. Burdette, D. Joshi, A. Tremper, H. Vepakomma, “Mechanics of Ultra-slim Television Sets with Glass Light Guide Plate,” SID 2017 DIGEST, Japan, 1209-1212 (2017).

[5] Y. Arai, M. Inoue, K. Ishikawa, T. Yokote, Y. Kondo, K. Mori, “Evolution of the glass light guide plate and its peripheral technologies for large size TV application,” SID 2017 DIGEST, Japan, 1663-1666 (2017).