超薄注塑中的局部剪切流及混排导光板设计

Local Shear Flow in Ultra-Thin Injection Molding and Design of Mixed-Row Light Guide Plate

针对超薄导光板背光模组注塑中出现"暗痕"缺陷,分析了缺陷成因,剖析了局部剪切流流动特性,发现局部剪切流可以提升熔体剪切速率,降低黏度,增强流动性,特别指出了局部剪切流侧向剪切对熔体黏度的影响不容忽略。对于局部剪切流的良好充模能力及其导致成型缺陷的两面性,在超薄导光板设计中,提出了不同微特征混排设计方案;混排设计方案在充模平面内形成规则局部剪切流,不但增强了熔体充模能力,同时保证了充模前沿的平衡性,避免了成型缺陷。在模拟及成型试验中,印证了混排设计方案的可行性与正确性。

In view of the "dark mark" defect of the backlight module of the ultra-thin light guide plate in the injection molding, this paper analyzes the cause of the defect and the flow characteristics of the local shear flow, and finds that the local shear flow can improve the shear rate, reduce the viscosity and enhance the fluidity of the melt, especially points out that the influence of the lateral shear of the local shear flow on the melt viscosity can’t be ignored. For the two sides of the good filling ability and forming defectsat the local shear flow, in the design of ultra-thin light guide plate, mixed design schemes with different micro characteristics arrangement are proposed. The mixed design scheme forms regular local shear flow in the filling plane, which not only enhances the filling ability of melt, but also ensures the balance of filling front and avoids forming defects. In the simulation and forming test, the feasibility and correctness of the mixed design scheme are confirmed.