| 摘要 |
PROBLEM TO BE SOLVED: To obtain a medium having excellent surface properties and excellent electromagnetic conversion characteristics by forming a lower base layer and an upper base layer by using a coating material for the lower base layer and a coating material for the upper base layer each of which is controlled to have specified viscoelasticity. SOLUTION: The coating material for the lower base layer and the coating material for the upper base layer are prepared in such a manner that the storage elastic modulus G'(1) at 1% strain and 1 rad/see angular frequency and the storage elastic modulus G' (10) at 1% strain and 10 rad/sec angular frequency of the both coating materials measured by using a strain-controlling type viscoelasticity measuring instrument satisfy the relation of formula I, formula II and formula III. Further, the complex elastic modulus G*(0) at 1% strain and 2πrad/sec angular frequency at 0 sec which is just after the initial shear is added at 1000% strain and 2 rad/sec angular frequency for 60 sec., and the complex elastic modulus G*(120) at 1% strain and 2πrad/sec angular frequency at the time after 120 sec from 0 sec satisfy the relation of formula IV.
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