| 摘要 |
PURPOSE:To obtain a medium which does not crack even after repetitive recording and reproducing or is usable with substantially no decrease in S/N even if a crack arises in the medium by maintaining the compressive modulus of a high polymer base plate in the thickness direction thereof in a specific range. CONSTITUTION:A high polymer base plate 2 is exemplified by polyester, polyolefin, cellulose deriv., polycarbonate, PVC, polyamide, polyimide, etc. and in the case of having an undercoating layer, said layer regarded inclusively as the plate 2. A limitation is given to the mechanical characteristic of the plate 2 in the thickness direction thereof. More specifically, the compressive modulus in the thickness direction is made >=400kg/mm.<2>. Cracking is thereby obviated even in the abnormal stress concentration in a traveling system and even if the medium is cracked, the crack is not developed to the permanent set to the extent of decreasing S/N. The selection of the material having >=400kg/mm.<2> compressive modulus in the thickness direction as the conditions for the base plate is accomplished by selecting material or selecting particularly the conditions for heat managing in the stage of forming the film even if the same material is used.
|
