射出成型及模壓光學鏡片之光學特性研究

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

汪忠諺

指導教授 ： 王培仁

國立清華大學/工學院/動力機械工程學系/博士(2014年)

摘要

本世紀以來，塑膠鏡片廣泛運用於智慧手機、數位相機以及DVD讀取頭等消費性產品，其需求量與日俱增，射出成型技術具有大量生產及低成本的優點，是目前用於塑膠鏡片的主要生產技術，然而在短暫成型過程中，塑料歷經複雜熱及壓力變化，導致成型鏡片具有不同程度的翹屈及殘留應力，形狀精度及光學品質會變差，降低翹屈及減少殘留應力是塑膠光學鏡頭製造業一直努力的研究方向。
在本論文中，採用一模兩穴的光學鏡片模具，藉由水路設計使得各模穴受到水路冷卻的條件不同，再行探討水路設計對光學鏡片形狀精度的影響，並建立水路參數設計法，藉由水路與模穴間距離和模穴重要尺寸的相互關係，分析出模穴內均勻溫度場的適當參數值，最後再採用模壓成型技術為後處理製程消除成型鏡片的殘留應力之製程，並維持良好形狀精度。
綜合研究結果得到知，不良水路設計影響模具冷卻條件，多模穴模具之各模穴產出之鏡片無法具有相同之光學品質，必須重新設計水路配合適當之成型參數，達成模穴溫度場各穴均等，再搭以模穴修模補償，即可生產形狀精度達標鏡片，若無法降低充填之殘留應力，可輔以模壓成型將鏡片殘留應力完全消除，維持產品之形狀精度。

關鍵字

模壓 ； 塑膠鏡片 ； 雙折射 ； 翹屈

並列摘要

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.

並列關鍵字

Compression Molding Process ； Plastics Lenses ； Birefringence ； Warpage

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