Patent ID: 8054727

Claim:
An information recording medium having a substrate, and a recording unit capable of recording three-dimensionally a recording pits onto the substrate: wherein the recording unit includes n number of recording layers, where n is an integer equal to or larger than 4, on which information is recorded by using a two photon absorption phenomenon, and a plurality of intermediate layers laminated one on another with each of the recording layers; wherein the recording layer includes a recording material capable of recording at a photon mode; wherein the plurality of intermediate layers are substantially transparent at a wavelength λ 1 of the recording light and at a wavelength λ 2 of the reproduction light, respectively; wherein a light intensity of recording light incident onto a recording layer nearest to the substrate is more than 0.707 fold as much as a light intensity of recording light incident onto a recording layer farthest from the substrate; wherein an absorptivity A 1 per layer of an unrecorded region of the recording layers and an absorptivity A 2 per layer of a recorded region of the recording layers are different from each other at the wavelength λ 1 of the recording light; wherein a difference between a refractive index of the unrecorded region of the recording layers and a refractive index of the intermediate layers is larger than a difference between a reflective index of the recorded region of the recording layers and a refractive index of the intermediate layers at the wavelength λ 1 of the recording light; wherein a transmittance T 1 per layer of the unrecorded region at the wavelength λ 1 of the recording light satisfies conditions of the following relation: T 1≧0.707 1/(n-1) where n is an integer equal to or larger than 4, which represents the number of recording layers; and wherein the absorptivity A 1 and the absorptivity A 2 satisfy conditions of the following relation: A 1< A 2≦1− T 2 provided that T 2 is a transmittance per layer of the recorded region at the wavelength λ 1 of the recording light.