用于超薄MiniLED背光模组的光学膜设计

Design of optical film for ultra-thin MiniLED backlight modules

为了降低背光模组厚度,设计了用于MiniLED背光模组的表面具有微结构的光学膜。首先分析了基于扩散粒子和折射式透镜的两种扩散原理,发现在混光距离(OpticalDistance,OD)很小的情况下,两种方式都无法直接将光源进行充分扩散以满足均匀性要求。然后基于全反射原理将扩展光源离散为点光源,分析单个点光源返回灯板的能量,并对所有离散点光源的返回能量累计,得出扩展光源经微结构全反射后的能量达到最大时的微结构形貌。仿真结果表明:将双层微结构光学膜放置在MiniLED芯片上表面,仿真的亮度均匀性为79.9%,在OD=0.9 mm位置再添加一层扩散膜,可以将亮度均匀性提升到89.2%。采用无掩模直写光刻技术制备了光学膜样片。实验结果表明:将双层微结构光学膜放置在MiniLED芯片上表面的亮度均匀性为79.6%,在OD=0.9 mm位置添加一层扩散膜后亮度均匀性提升为88.7%。本文设计的微结构光学膜实现了背光模组超薄化,使用时无需精确对位,实用性强。

An optical film with microstructures for use in MiniLED backlight modules is designed to reduce the backlight module thickness.First,two diffusion principles based on the diffusion particle and refraction lens are analyzed.It is found that when the optical distance(OD)is very small,none of the principles are effective in ensuring that the light is fully diffused in order to meet the requirement on uniformity.Then,based on the principle of total reflection,the surface source is discreted to a cluster of point sources,the energy returned by a single point source to the lamp board is analyzed,and the energy returned by all the discrete point sources is accumulated.Notably,the profile of a microstructure can be decided when the energy returned by the surface source is maximum.The simulation results show that when the double-layer microstructure optical film is placed on the surface of a MiniLED chip,the brightness uniformity is 79.9%,which can be further increased to 89.2%by adding a diffusion film at an OD of 0.9 mm.Maskless direct writing lithography is used to prepare a sample optical film.The experimental results show that the brightness uniformity of the double-layer microstructure optical film placed on the surface of the MiniLED chip is 79.6%,which can be increased to 88.7%by adding a diffusion film at OD=0.9 mm.The optical film thus designed can be used to realize the ultrathin backlight module without the requirement of a precise position and therefore presents strong practicability.