Fund Project:Project supported by National Natural Science Foundation of China (Grant No. 61275167) and Shenzhen Science and Technology Development Funds, China (Grant Nos. JCYJ20140418095735591, JCYJ20130329103020637).
Received Date:10 September 2018
Accepted Date:04 December 2018
Available Online:01 February 2019
Published Online:05 February 2019
Abstract:The microstructure distribution on the bottom surface of the partial integrated light guide plate (PILGP) is the key to affecting the uniformity of the output light from the backlight module (BLM), which is one of the important factors in the BLM design. Based on the development trend of the BLM in light-weight and integration, many research institutes have realized the requirement for high luminance and luminance uniformity in the BLM by setting micro-prism structure on the surface of the light guide plate (LGP). In most of these studies, the length of the micro-prism structure is the same as the width of the LGP, and the optimization of the micro-prism distribution is performed only in the length direction of the LGP, which is a one-dimensional distribution. So, the long strip micro-prism structure cannot modulate the light in the axial direction, resulting in large area identity in the width direction of the LGP, thereby the luminance uniformity of the BLM is affected. In this paper, a design idea of two-dimensional distribution of the micro-prism on the bottom surface of the PILGP, which improves the luminance uniformity of the BLM, is proposed to solve the problem that the luminance uniformity is affected by large area identity caused by one-dimensional distribution design of the micro-prism. The small length micro-prism structure is used to break the limit of the axial distribution of the long strip micro-prism structure, and it can modulate the light in the axial direction. The Lighttools software is used to optimize the two-dimensional distribution of the micro-prism on the bottom surface of a 5.0-inch PILGP. Comparing with the PILGP with one-dimensional distribution of the micro-prism on the bottom surface, the simulation results show that the utilization of light energy, illuminance uniformity and luminance uniformity in the BLM with optimized two-dimensional distribution of the micro-prism on the bottom surface of the PILGP respectively reach 92.03%, 87.07% and 91.94%, which meet industry standards. And the illuminance uniformity increases by 10%. Meanwhile, the luminance diagram shows that the overall luminance uniformity of the BLM is improved effectively. Moreover, the distribution principle of the micro-prism on the bottom surface of the PILGP is analyzed and the physical mechanism is reasonably explained . The simulation results above show that the design concept of the two-dimensional distribution of micro-prism is feasible. The study results have a certain referential value for the development of the BLM in light-weight and integration. Keywords:optical design/ partial integrated light guide plate/ two-dimensional distribution/ micro-prism
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3.集成化导光板下表面微棱镜二维分布的优化设计为了探究高性能参数下PILGP下表面微棱镜结构二维分布的可行性, 首先利用光学软件Lighttools建立5.0英寸(1 in = 2.54 cm)集成化背光模组初始模型, 建模参数如表1所列.
6.6646 lm, 朗伯分布, 发散角110°, 1.2 mm × 2.5 mm × 0.4 mm
LED数量和间隔
10个, 6.56 mm, 等间距分布于PILGP的短边
RF反射率
95%
表1集成化背光模组结构参数 Table1.Structural parameters of partial integrated backlight module.
由表1中的建模参量可知, 设置在导光板下表面的内凹微棱镜结构单元的长度为0.1 mm, 远小于导光板的宽度数值; 这样的设置使得微棱镜结构单元可在PILGP的下表面形成二维分布模式. 为了实现背光模组出光面的均匀发光, 利用Lighttools软件中的背光图案优化模块对微棱镜分布进行优化. 评价函数设置原则为通过调整微棱镜分布使背光模组出光面的照度均匀性和亮度均匀性达到较高, 具体实施过程中采用了分步优化策略. 首先以较高的照度均匀性为目标, 优化得到PILGP下表面微棱镜二维分布的初始模型; 再以较高的亮度均匀性为目标, 进而得到较佳的PILGP下表面微棱镜二维分布. 优化过程中, 将微棱镜的最小间隔作为约束条件, 避免出现微棱镜重叠现象. 优化后的PILGP下表面微棱镜二维分布如图2所示, 图2(a)—(c)分别表示PILGP下表面近光源区、中间区域和远光源区的微棱镜分布图, 图中的红点表示微棱镜单元. 从图2可以看出, 微棱镜沿着导光板长度方向(x轴)的分布, 近光源区域间隔较大, 远光源区域间隔较小, 间隔变化过渡比较平滑, 这符合导光板微结构分布的一般规律[26]. 微棱镜沿着导光板宽度方向(y轴)的分布, 近光源处和远光源处的微棱镜在其轴向方向上分布的数量和位置各不相同, 相比于长条状微棱镜的一维分布增加了一个自由度, 消除了一维分布中存在的大面积同一性问题. 在表1其他建模参数不变的情况下, 仅改变PILGP下表面微棱镜结构单元的长度及微棱镜结构阵列的分布, 建立另一款微棱镜具有较佳一维分布的5.0英寸集成化背光模组模型[25]. 该背光模组中, PILGP下表面微棱镜结构单元长度为导光板宽度数值(68.7 mm). 利用Lighttools软件仿真得到上述两款集成化背光模组的出射光照度图和亮度图, 如图3所示; 对应的性能参数如表2所列. 图 2 优化后的PILGP下表面微棱镜二维分布图 (a)近光源区; (b)中间区; (c)远光源区 Figure2. Optimized two-dimensional distribution diagram of micro-prism on the bottom surface of PILGP: (a) Near the LEDs; (b) in the middle area; (c) far from the LEDs
图 3 PILGP下表面微棱镜分布分别为一维、二维时, 背光模组的出射光照度图、亮度图 (a), (b)微棱镜一维分布时的照度图和亮度图; (c), (d)微棱镜二维分布时的照度图和亮度图 Figure3. Simulation results of illuminance and luminance diagram of the output light from partial integrated backlight module with one-dimensional and two-dimensional distribution of micro-prism on the bottom surface of PILGP: (a) and (b) is respectively illuminance and luminance diagram with one-dimensional distribution of micro-prism; (c) and (d) is respectively illuminance and luminance diagram of two-dimensional distribution of micro-prism.
性能参数
微棱镜分布模式
一维
二维
光能利用率/%
91.61
92.03
平均照度/Lux
8519.0
8571.0
平均亮度/Nit
6859.7
6394.6
照度均匀性/%
76.71
87.07
亮度均匀性/%
91.14
91.94
表2PILGP下表面微棱镜分布为一维、二维时的背光模组仿真结果 Table2.Simulation results of partial integrated backlight modules with one-dimensional and two-dimensional distribution of micro-prism on the bottom surface of PILGP.