| 摘要: | 射出成型精密光學鏡片之幾何精度是一重要的品質需求，然而即使幾何尺寸符合標準，也有可能其光學性質評估仍不合格，這是因為成型產品有雙折射的存在；若雙折射過大則會造成光學系統之光程差，不易透過組合透鏡等方法做像差矯正。所以，為使塑膠射出光學鏡片良率提高，對於成型過程所可能產生之雙折射研究就顯得非常重要。本研究運用流變學實驗，結合流變學理論，取得光學材料之流變參數與彈性參數，並運用Moldex3D模流軟體，對光學凸透鏡進行模流分析，並將目標鎖定於雙折射之分析探討。本研究分別採用三個流變模式(White-Metzner、Phan-Thien Tanner、Giesekus Models)，針對COP(Zeonex 480R)與PMMA(Kurary GH-1000S)兩種光學材料，以Moldex3D軟體作模流分析。從模擬計算之雙折射與光彈條紋的分布來看，是以流動所造成之殘留應力為主要影響因素，而且在澆口附近的雙折射最為嚴重。再與實射成品之光彈條紋實驗值比較，發現以PTT模式所得模擬結果最為接近。
本研究另針對PMMA材料，進行蠕變/回復實驗，輔以Burger模式之參數迴歸分析，探討材料之彈性效應。在PMMA這支材料上，可以發現當溫度升高時，材料彈性效應會越衰減；此外，當蠕變時間越長時，材料之彈性效應會減弱。
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. |
