Patent ID: 6959447

Claim:
An optical information recording medium comprising a recording layer, and a protective layer including at least first to mth layers (m≧2), wherein when i is an integer satisfying 1≦i≦m; a refractive index of the ith layer in the protective layer at a wavelength of 405 nm is n i ; and a thickness of the ith layer is d i , and when (a) a combined refractive index n of one layer which is substantially equivalent to the plurality of layers constituting the protective layer and substituted for the plurality of layers is specified as n=((n 1 d 1 +n 2 d 2 + . . . +n m d m )/(d 1 /n 1 +d 2 /n 2 + . . . +d m /n m )) 0.5 ; (b) a combined thickness d of said one layer is specified as d=((n 1 d 1 +n 2 d 2 + . . . +n m d m )×(d 1 /n 1 +d 2 /n 2 + . . . +d m /n m )) 0.5 ; and (c) an expression f(n): f(n)=−109.8n 3 +577.2n 2 −985.5n+648.6 is specified as a design criterion relating to the combined thickness of the protective layer, the refractive index n i of the ith layer and the combined refractive index n is equal to or larger than 1.45 and equal to or smaller than 1.65, and a difference d−f(n) between the combined thickness and the design criterion is equal to or larger than −10 μm and equal to or smaller than 10 μm.