The effects of injection molding conditions on replication, birefringence and optical properties of microscopic V-groove structures in injection molded parts were examined for polycarbonate (PC) with different molecular weight. For optical properties, luminance and its distribution at the surface of the V-groove were measured. The micro-scale structure size was a continuous V-groove of 20μm in depth and 50μm in width. For injection molding conditions, melt temperature, mold temperature, injection velocity and holding pressure were varied at three levels. Birefringence decreased according as the degree of replication increased at higher melt temperature and higher mold temperature. This trend was more remarkable when higher molecular weight PC was used. It was found that the contrast value of luminance increased in proportion to higher degree of replication, but not significantly to birefringence.