Plastic substrate with high performance using a new polycarbonate with addition of an antiplasticizer. II [optical disc storage]

Abstract

The author found that higher transcribability, better flow property, higher stiffness, lower birefringence, and lower water absorption, while maintaining transparency, were created by the addition of a small amount of antiplasticizer to a conventional bisphenol A backboned polycarbonate (PC) for an injection molded optical disk substrate. At ODS 2001 (M. Ueda, Proc. SPIE, vol. 4342, p. 39, 2002), it was shown that addition of m-tPh (meta-terphenyl) to PC resulted in the excellent performance described above. This technology would be advantageous for production of optical disk substrates without significant increase in material cost. However, such an additive may act as an impurity for an extra pure PC, which may cause poor signal quality. If the additive acts like an impurity, white spots are generated inside the polycarbonate substrate and the transmittance is depressed. In this paper, the author investigated life test performance for substrates made from PC with m-tPh addition. Also, the improved surface hardness induced by m-tPh addition was demonstrated. This nature is preferable for a transparent thin cover layer, since it can avoid a scratch marks. Finally, the ideal viscoelastic property behavior for a resin to achieve higher transcribability, lower birefringence, and lower tilt angle, is proposed.