The characteristics of antiplasticized polycarbonates (PC) and their optical disk substrates were investigated. Meta-terphenyl (m-tPh) was chosen as an antiplasticizer. Blends of PC with small amounts of added m-tPh were injection molded to form optical disk substrates. The flow properties of the blends were significantly improved by the common plasticizing effect of antiplasticizer at the melt state. The effect also induced reduction in internal stress, causing birefringence of the substrate. The increased stiffness and decreased glass transition temperature of the antiplasticized PC caused better flatness of the substrate and better microreplication of the groove geometry, respectively. It also resulted in embrittlement of the substrates, known to be a typical characteristic of antiplasticization. The antiplasticizer decreased the water absorption of the blends and also caused increased stiffness of the blends. The increased stiffness was associated with the elimination of secondary mechanical loss transition at low temperatures. From these results, the ideal viscoelastic property behavior of a polymer for an optical disk substrate to achieve better microreplication, better flatness, and low birefringence was proposed, that is, exhibiting lower modulus above glass transition temperature and higher modulus at the regions below glass transition temperature for the polymer of interest. (C) 2004 Society of Plastics Engineers.