| 摘要 |
PROBLEM TO BE SOLVED: To provide a high recording density information recording medium having a thin shape, a small tilt angle and excellent recording and reproducing characteristics and its manufacturing method. SOLUTION: A substrate 1, an information recording layer 2, a protective layer 3 and a counter balance film 4 are formed in such a manner that a tilt angle changing amount of a plastic substrate in an outermost circumferential recording area is in ±0.4 degree range, when the information recording medium provided with the plastic substrate 1 having <=0.8 mm thickness is left for 400 hr under the condition of 80 deg.C. The information recording medium can be manufactured by forming the plastic substrate having <=0.8 mm thickness, subjecting the plastic substrate to required film- deposition and leaving the plastic substrate after completion of the film-deposition under the condition of >=50 deg.C and <=120 deg.C to perform heat aging treatment. In this case, preferably, the heat aging treatment starts at an initial temperature of <=80 deg.C, then the temperature is increased up to an objective temperature of >=100 deg.C and <=120 deg.C spending time of 30 min or more, then the objective temperature is kept for a prescribed time and finally the plastic substrate is gradually cooled down to its completion temperature of <=80 deg.C spending time of 30 min or more. |
