| 摘要 |
PURPOSE:To obtain an optical card with superior mechanical strength and high reliabil ity by a method wherein as a transparent substrate two polycarbonate resin boards each having a birefringence caused by the orientation of molecular chains are laminat ed so that the molecular chains can intersect with each other in orientation at a predetermined angle and subjected to a heating and pressurizing treatment. CONSTITUTION:With respect to the measurement of birefringence, the measured values of the same substrate depend on the measured direction (a direction A and a direction B). Namely, the measured values have reverse signs even if having approximately the same absolute value. This is caused by the orientation of molecular chains in a polycarbonate substrate 10 which is melted and extruded. Therefore, two substrates with molecular chains being oriented orthogonally to each other are overlapped, pressu rized, heated, and laminated ; in this manner, a positive/negative birefringence offset effect can be obtained in addition to a thermal relaxation effect, thereby reducing a birefringence. Therefore, an optical card using this substrate as a transparent sub strate 1 has a sufficient mechanical strength and a high S/N ratio and, thus, a high- reliable optical card is made available. Additionally, the two polycarbonate substrates to be overlapped with each other have an offset effect at the time of intersecting at an angle ranging 30-150 deg. in orientation. |
