Effects of aperture structure on residual stress of precision injection molded microlens arrays

The optical quality of plastic microlens arrays is very sensitive to the presence of residual stress induced during the molding process. In this paper, the effects of aperture structures on the maximum value of residual stress have been investigated. The results from numerical simulation indicate that the geometrical configuration of the aperture can profoundly influence the levels of residual stress in precision injection molded microlens arrays. The five aperture structures present similar trends to the change of mold temperature, packing pressure, packing time and cooling time. With regard to melt temperature and flow rate, the trends of maximum value of residual stress exhibit differences with different aperture structures. It is shown that the cooling time has the least effect on the residual stress. The aperture structure of microlens arrays should be considered the effects on final quality of product at the initial stage of optical design.