薄壁LED照明依赖丝网印刷的微阵列导光板，但其表面油墨点阵易老化，且微结构很难优化。因此，在导光板表面设计出高斯分布的空间微槽透镜阵列，并采用数控微磨削技术对其进行加工，替代市面丝网印刷的2D微圆阵列。首先，用微光学原理模拟导光板导光效率和出光均匀度，优化微透镜阵列的形状、尺寸和分布。利用金刚石砂轮微尖端在PMMA导光板表面精密磨削出微透镜阵列，检测其导光效率及均匀性。最后，利用微磨削加工的微阵列成型钢模芯开发微透镜阵列的快速热压微成型工艺。微光学分析表明，微槽透镜阵列比微方形透镜阵列和微半球透镜阵列分别提高导光效率6%和15%。而且，微槽透镜阵列变间距高斯分布比等间距分布提高导光效率32%，提高出光均匀度73%。试验结果显示，微磨削可以控制微槽透镜阵列加工的表面质量和形状精度，应用于LED导光板后比丝网印刷的导光板提高导光效率7%和出光均匀度9%。此外，开发3 s的快速热压微成型工艺，可以加工出变间距和变深度的微槽透镜阵列，比丝网印刷的微圆阵列提高照度26%和出光均匀度49%。因此，微空间结构优化的微槽透镜阵列比丝网印刷的2D微圆阵列可附加出更高的微光学应用价值。
The thin wall LED lighting needs the screen-printed micro array light guide plate (LGP), but the ink micro-dots array on the surface age easily and the microstructure is difficultly optimized. Therefore, the spatial microgroove lens array with Gauss distribution is designed on LGP surface, and the numerical control micro-grinding technology is adopted to fabricate it for replacing the commercial screen-printed 2D micro circular array. The light transmission efficiency and uniformity of LGP is simulated by using the micro optical principle to optimize the shape, size and distribution of micro lens array. Then, micro lens array is precisely ground on the surface of PMMA LGP, and the light transmission efficiency and uniformity are tested. Finally, the rapid micro hot embossing process is developed by using the micro-ground die core. The micro-optic analyses show that the microgroove lens array increase light transmission efficiency by 6% and 15% compared with the micro square lens array and micro hemisphere lens array, respectively. Further, the variable interval Gauss distribution of microgroove lens array improves the light transmission efficiency by 32% and its uniformity by 73%, compared with the equal interval distribution, respectively. The experimental results show that the micro-grinding technology is able to control the surface quality and shape accuracy of the microgroove lens; the micro-ground LED LGP enhances the light transmission efficiency by 7% and its uniformity by 9% compared with the screen printed LGP. Furthermore, using the 3 s rapid micro hot embossing can fabricate microgroove lens array with variable interval and depth, leading to an increase 26% in illumination and an increase 49% in uniformity. As a result, the space-optimized microgroove lens array can produce higher micro-optics application value than the 2D micro circular array.
[1] LI C J, FANG Y C, CHENG M C. Prism-pattern design of an LCD light guide plate using a neural-networkoptical model[J]. Optik, 2010, 121:2245-2249.
[2] JOO B Y, KANG J J, HONG J P. Analysis of the light-scattering power of patterned dot material printed on the light guide plate in liquid crystal display[J]. Displays, 2012, 33:178-185.
[3] YANG J C, HUANG C C. Fabrication of dual brightness enhancement structures on light guide plates using UV roll-to-plate imprinting lithography[J]. Optik, 2013, 124:3324-3328.
[4] CHEN M F, HO Y S, HSIAO W T. Optimized laser cutting on light guide plates using grey relational analysis[J]. Optics and Lasers in Engineering, 2011, 49:222-228.
[5] XIE jin, ZHUO Yuanwang, TAN Tingwu. Experimental study on fabrication and evaluation of micro pyramidstructured silicon surface using a V-tip of diamond grinding wheel[J]. Precision engineering, 2011, 35(1):173-182.
[6] 谢晋,李萍,吴可可,等. 微结构表面精密磨削技术及其功能特性开发[J]. 机械工程学报, 2013, 49(23):182-190. XIE Jin, LI Ping, WU Keke, et al. Micro and precision grinding technique and functional behavior development of micro-structured surfaces[J]. Journal of Mechanical Engineering, 2013, 49(23):182-190.
[7] 赵清亮, 郭兵. 微结构光学功能元件模具的超精密磨削加工技术[J]. 机械工程学报, 2011, 47(21):177-185. ZHAO Qingliang, GUO Bing. Ultraprecision grinding technology of microstructured optical functional molds[J]. Journal of Mechanical Engineering, 2011, 47(21):177-185.
[8] XIE Jin, WU Keke, CHENG Jian, et al. The micro-optic photovoltaic behavior of solar cell along with microlens curved glass substrate[J]. Energy Conversion and Management, 2015, 96:315-321.
[9] 鲁艳军,谢晋,李青,等. 陶瓷飞行体的微沟槽结构曲表面精密磨削与减阻性能[J],机械工程学报, 2014, 50(15):180-186. LU Yanjun, XIE Jin, CHENG Jian, et al. Precision grinding and resistance reduction of micro-grooves curved surface of ceramic flying body[J]. Journal of Mechanical Engineering, 2014, 50(15):180-186.
[10] 贺永,傅建中,陈子辰. 微热压成型脱模缺陷分析及其脱模装置[J]. 机械工程学报, 2008, 44(11):53-58. HE Yong, FU Jianzhong, CHEN Zichen. Demolding defects and the design of demolding device in micro hot embossing process[J]. Chinese Journal of Mechanical Engineering, 2008, 44(11):53-58.
[11] 屠大维,吴仍茂,杨恒亮,等. LED封装光学结构对光强分布的影响[J]. 光学精密工程, 2008, 16(5):832-838. TU Dawei, WU Rengmao, YANG Hengliang, et al. Effect of optical structure on output light intensity distribution in LED package[J]. Optics and Precision Engineering, 2008, 16(5):832-838.
[12] XIE Jin, XIE Haifan, LUO Minjian, et al. Dry electrocontact discharge mutual-wear truing of micro diamond wheel V-tip for precision micro-grinding[J]. International Journal of Machine Tools and Manufacture, 2012, 60:44-51.
