US Patent 7981494 Optical informaton recording medium

In a write-once optical information recording medium including a substrate, a groove-shaped track such as a guiding groove, and an optical recording layer containing an organic dye material and disposed on the guiding groove, wherein information is recorded by irradiating a short-wavelength laser beam from a surface of the optical recording layer opposite the substrate, and the information can be reproduced by reading a change in the reflected light of a short-wavelength laser beam after the information recording, an unrecorded portion of the optical recording layer has a lower reflectance than a pit portion formed after recording to a portion of the optical recording layer, the optical recording layer has a refractive index n in the range of about 1.2 to about 2.1 before recording and an extinction coefficient k in the range of about 0.01 to about 0.7 before recording, and n+k is in the range of about 1.4 to about 2.1.