Patent ID: 8264944

Claim:
A manufacturing method for an optical recording medium, the method comprising: forming an optical recording medium having a cover layer, N information recording surfaces, and N−1 intermediate layers respectively disposed between the information recording surfaces, wherein N is a positive integer of 3 or more, wherein the information recording surfaces include a first information recording surface disposed closest to a surface of the optical recording medium where light is incident, and the first information recording surface is disposed on an opposite side of the cover layer from the surface, assuming that actual thicknesses of the cover layer and first through (N−1)-th intermediate layers of the optical recording medium having refractive indexes nr 1 , nr 2 , . . . , and nrN are respectively tr 1 , tr 2 , . . . , and trN in the order from the surface of the optical recording medium where light is incident, the thicknesses tr 1 , tr 2 , . . . , and trN are converted into thicknesses t 1 , t 2 , . . . , and tN of layers having a predetermined standard refractive index “no” which makes a defocus value equal to a defocus value of the actual thicknesses tr 1 , tr 2 , . . . , and trN, a difference DFF between the sum of a thickness “ti” through a thickness “tj”, and the sum of a thickness “tk” through a thickness “tm” is set to 1 μm or more, wherein i, j, k, and m are positive integers satisfying i≦j<k≦m≦N, and the thicknesses t 1 , t 2 , . . . , and tN are calculated by products of a function f(n) expressed by the following formula (1), and the thicknesses tr 1 , tr 2 , . . . , and trN: f ( n )−1.088 n 3 +6.1027 n 2 −12.042 n+ 9.1007 (1) in the formula (1), n=nr 1 , nr 2 , . . . , and nrN.