INFORMATION RECORDING MEDIUM, RECORDING DEVICE, REPRODUCTION DEVICE, AND REPRODUCTION METHOD

摘要

Provided is an information recording medium having N (N is an integer not smaller than 3 ) information layers where information can be recorded.  When a laser beam is applied, information is recorded to each of the information layers and information is reproduced from each of the information layers.  The N information layers include: the N-th information layer, the N-1-th information layer, the N-2-th information layer, ..., the second information layer, and the first information layer which are arranged in this order from the laser beam input side.  The N-th information layer has a refraction index RN.  The M-th information layer (M is an integer satisfying the relationship: N > M = 1) has a refraction index RM.  The laser beam applied to the N-th information layer upon reproduction of the information recorded on the N-th information layer has the uppermost reproduction power PrNmax.  The laser beam applied to the M-th information layer upon reproduction of the information recorded on the M-th information layer has the uppermost reproduction power PrMmax.  The laser beams simultaneously satisfy the following Expressions [1] and [2]. RN > RM ... [1] PrNmax Mmax ... [2]