Fabrication of Stampers by UV Resin Dispensing & Curing Method and The Vario-Thermal Mold System for injection Molding Light Guide Plates

• Main Authors: Yeong-Sheng Kuo, 郭永昇
• Other Authors: Shi-Chang Tseng
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/25434661162227119976

碩士 === 國立雲林科技大學 === 機械工程系碩士班 === 93 === A BSTRACT Chemical etching process is often used in the mold fabrication for light guide plates (LGP), but the surface roughness of the micro structures (micro lens) is relatively rough in the micro scale. This will affect the brightness of the LGP. This study develops micro lens array by UV resin dispensing and curing method. And the stamper for LGP can be duplicated by the electroforming process. It is believed to be low cost and to have better surface quality of the micro optic devices. And it is expected to improve the brightness of LGP and avoid using time consuming lithography process. In order to improve the performance of micro injection molding, a vario-thermal mold system was developed. It was assembled with heat insulation system and the stamper for micro structural replication. The vario-thermal molding can provide the micro injection molding with higher mold temperature (even higher than glass transition temperature) during the injection stage. So the polymer melt can flow into the micro structures more easily than the conventional one. And then it can be immediately cooled down by circulating cold oil to shorten the cycle time. The effects of different processing conditions of the vario-thermal molding on the brightness, surface, roughness and warpage were studied. Because of the surface tension effect, the half-spheres were formed during UV resin dispensing. After exposure of UV light, they were cured into micro half-spherical lens array. The diameters of micro lens can be controlled by adjusting the process parameters during dispensing. Different resins and substrates were used to get better factors combination for smaller diameters. So far the best condition in this study is to obtain the diameter as small as 38μm. But while the diameter is smaller than 100μm, the sphere is unstable and may collapse suddenly. The surface roughness of molded LGP by UV dispensing and curing stamper is about Ra 0.0718μm. And it is much lower than the one by the etching process, which is Ra 0.5772μm. In order to achieve better processing conditions and reduce the times of experiments, Taguchi’s design of experiments was used. The injections molding experimental results reveal that for the vario-thermal injection molding (VTIM), the most important factor for LGPs’ brightness is the initial mold temperature. And the brightness by VTIM is higher than the one by convention injection molding (CIM). The degrees of replication near the gate are found to be higher than those far from the gate. And overall degrees of replication of VTIM are higher than those of CIM. But the warpage of CIM is smaller than the VTIM one. Key words : Light guide plate(LGP), Brightness, UV resin dispensing and curing method, Micro injection molding, Vario-thermal mold system for injection molding, Surface roughness