| abstract |
An optical recording medium having a light absorption layer formed on a substrate having a spiral groove by means of the vacuum deposition and a reflective layer formed on the light absorption layer, wherein:(1) the groove of the substrate has a groove section of which cross section is a trapezoidal;(2) a ratio of a groove width (W) to a track pitch (TP) (W/TR) of the substrate falls within a range of 0.25 to 0.45;(3) a groove depth (D) is 20 to 80% of (lambd/4n) (wherein A is a wavelength of a laser beam, and n is a refractive index of the substrate); and(4) angles a1 and a2 formed by both side surfaces of the groove section and surfaces vertical to a groove bottom surface on cross lines between the both side surfaces of the groove section and the groove bottom surface are 45 to 80°, and a difference between a1 and a2 (a1-a2) is not more than ±10°. |