The Influence of Polymer Viscoelasticity on the Optical Features for the Injected Optical Lens

• Main Authors: De-Lung Lai, 賴德隆
• Other Authors: Gwo-Geng Lin
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/85833972472435363912

碩士 === 淡江大學 === 化學工程與材料工程學系碩士班 === 104 === For the injected optical lens, the geometric precision is really an important quality requirement. But, even standard geometry, the optical properties are probably assessed to be unsatisfactory, because of the existence of the part birefringence. Severe birefringence in the optical part could cause the optical path difference in the optical system, which is not easy to be overcome through the optical aberration correction or other methods. Therefore, in order to improve the yield of the injected optical lenses, the investigation of the induced birefringence generated during the molding process is very important. In this study, the rheological measurements along with the theoretical models were firstly used to obtain the material parameters, and then the commercial Moldex3D software was applied to numerically simulate the injection molding process of the concave lens, focusing on the analysis of the birefringence inside the molded part. Three kinds of rheological models ( White-Metzner, Phan-Thien Tanner and Giesekus Models) and one kind of creep equation ( Burger Model ) were employed in the software with the COP (Zeonex 480R) and PMMA(Kurary GH-1000S) material. The creep/recovery experiment were conducted to discuss the factors which impact the elastic effect. It resulted that elastic effects of PMMA would be more obvious with the rise of the temperature; however, increasing the creep time would weak the elastic effect. From the simulated birefringence and the photoelastic fringes, it was found that the flow-induced, rather than the thermal-induced, residual stress is the major factor to bring about the birefringence, and it was the most serious near the gate. It was also found that the simulated photoelastic fringes by using the PTT model can show the most agreements with the experimental results among the three models in this study.