ANALYSIS OF OPTICAL PROPERTIES IN INJECTION MOLDED AND COMPRESSION MOLDED OPTICAL LENSES

• Main Author: 汪忠諺
• Other Authors: 王培仁
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/19836039506551143496

博士 === 國立清華大學 === 動力機械工程學系 === 102 === In the past decade, plastic lenses have been extensively applied to many modern consumer products, such as smart mobile phones, digital still cameras, and pick-up head in DVD drives. In the products, due to the requirements on low cost and compact design, injection molding technology has been the principal process in mass-production in the optics industry. However, residual stresses and warpage are produced in the injection-molded lenses due to the complex thermal-mechanical history experienced during the manufacture process; hence, problems in form accuracy and optical properties are common. Evidently, it is essential to carefully study the process for reaching the goal of perfect form accuracy and near-zero residual stresses in the lenses. In this dissertation, numerical mold-flow simulations and experimental measurements for injection-molded lenses have been investigated in form accuracy on a two-cavity mold with various process conditions. First, form profiles of the molded lenses have been measured together with simulations in the corresponding mold temperature distribution and displacement distribution of lens in z direction. Flow-through type layout of cooling channels has been devised for balance of mold temperature distribution in mold cavities with various parametric distances for assessments in uniformity of temperature distribution. Finally, a compression molding process is proposed for relieving residual birefringence and maintaining form accuracy. In conclusions, only balanced design of cooling channels plus optimized process conditions could provide uniform mold temperature distributions so that molded lenses meeting the requirements are possible. Ultimately, the profile deviations in molded lenses could be further compensated by profile diamond-turning processes so that post-compression molding process could make birefringence-free plastic lenses with good form accuracy.