Patent ID: 8451708
Filing Date: 2013-05-28
Classification: G11B,Y10T

Abstract:
1. A manufacturing method for an optical recording medium having N (where N is a positive integer of 3 or more) information recording surfaces, actual thicknesses of a cover layer and first through (N−1)-th intermediate layers of the optical recording medium having refractive indexes nr 1 , nr 2 , . . . , and nrN being respectively tr 1 , tr 2 , . . . , and trN in an order from a surface of the optical recording medium where light is incident, the manufacturing method comprising: converting the thicknesses tr setting the refractive index “no” to 1.60; setting the thicknesses t setting a difference DFF between a sum of a thickness “ti” through a thickness “tj”, and a sum of a thickness “tk” through a thickness “tm” to 1 μm or more (where i, j, k, and m are each any positive integer satisfying i≦j<k≦m≦N); and calculating the thicknesses t in the formula (1), n=nr wherein the manufacturing method produces the optical recording medium with layers having thicknesses that prevent light from forming an image on a backside of a surface of the optical recording medium, suppress coherence between reflected light from the information recording surfaces, and improve the quality of a servo signal and a reproduction signal.