A Study on the Hot Embossing Process of Plastic Microlens Arrays

• Main Authors: Chun-Hua Chang, 張俊樺
• Other Authors: Shi-Chang Tseng
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/60269611505668495113

碩士 === 國立雲林科技大學 === 機械工程系碩士班 === 102 === The present study focused on the fabrication of 4×4 plastic microlens arrays via the contactless embossing process. Polycarbonate, which possesses good light transmitting and mechanical properties, was used for the molding material. The process of hot embossing has the advantages of having low material flow and large processing surface, which are desirable attributes for optical lens fabrication. ANSYS POLYFLOW was used for simulation. The cross law model was employed to analyze the effects of embossing speed, embossing time and material temperature on material flow during filling. To verify the accuracy of the simulation, hot embossing experiment was carried out. The experiment produced microlens of 216.221μm in height and 172.7μm in radius of curvature. The fabrication process involved mold insert arrays with openings of 300μm in diameter, and was carried out under the conditions of 160°C in material temperature, 10μm/s in embossing speed and 3.5sec in embossing time. With the same parameters, ANSYS POLYFLOW simulation resulted in microlens of 220.87μm in height and 173.134μm in radius of curvature. Results from the ANSYS POLYFLOW simulation showed that with the same embossing time and material temperature, the velocity, pressure and local shear rate of the molding material increased with increases in embossing speeds. The viscosity of the molding material was found to be inversely proportional to embossing speed. Flow field distribution simulated by ANSYS POLYFLOW were verified by MOLDEX3D ICM simulations. In terms of the distributions of pressure, velocity, shear rate, viscosity and velocity vector, the two software programs gave almost identical simulation results. However, the material temperature definition in MOLDEX3D ICM was above the melting temperature (Tm) whereas ANSYS POLYFLOW was able to simulate near glass transition temperature (Tg). It was found that simulation results from ANSYS POLYFLOW resembled more closely to the actual fabrication process.