| 摘要 |
PURPOSE:To avert substrate deformation with balance of a film stress, to make possible recording at a high density and to improve durability by determining the total stress of the respective layers forming the recording medium so as as to satisfy a specific equation. CONSTITUTION:The stress S1 of the thin films of the optical information recording medium formed by providing the surface of a plastic substrate 1 with protective layers 2, 4, 6, a recording layer 3 and a heat radiating reflection layer 5 is the sum of internal stress components and thermal stress components and the deformation quantity of the substrate is a function of S1. The total stress S of this time is expressed by the formula if the deformation threshold of the incident angle of a laser beam to make possible servo on the substrate is defined as + or -theta. In the equation, E: the Young's modulus of the substrate, b: the thickness of the substrate, l: (the outside diameter of the substrate-the hole diameter of the substrate) X1/2, nu: the Poisson's ratio of the substrate. Then, the respective layers are so constituted that the total stress S satisfies the equation, bv which the deformation according to the reduction in the thickness of the substrate 1 is averted by the film stress balance. The high-density recording is thus made possible and the durability is improved. |
