Optical recording medium

摘要

An over-writable magneto-optical recording medium from which a superior signal characteristic and a high durability are obtained by sufficiently securing the defocus tolerance of a laser beam to be irradiated, and improving a jitter characteristic and expanding a power margin, and thereby improving a C/N characteristic and holding the surface strength of a disk even when narrowing a track pitch. An optical recording medium has a configuration in which a recording section constituted of at least a first dielectric layer (3), a first recording layer (4), a second recording layer (5), and a second dielectric layer (6) is sequentially formed and a reflective layer (7) and a protective layer are formed on the recording section. A groove is formed on the transparent substrate along a recording track, both sidewalls of the groove (2a,2b) are respectively formed into an independent wobbling shape, the relation of 0.470≤W/O≤0.610 is effectuated when assuming the width of the groove as W, the relation of 0.120≤D/( lambda /n)≤0.142 is effectuated when assuming the depth of the groove as D, and the angleθbetween wall faces of the groove is kept at 150 DEG +/- 10 DEG . In this case, O denotes the spot diameter of a laser to be irradiated, lambda denotes the wavelength of a laser beam in a vacuum state, and n denotes the refractive index of a transparent substrate. Then, an in-plane-directional refractive index is set to a value in a range of 140 to 25 (nm) and a vertical-directional double-refractive index is set to a value in a range of 200 to 300 (nm). Then, the first recording layer is made of Gd, Fe, and Co, contains 28 to 30 (at%) of Gd, and has a thickness of 50 to 100 ANGSTROM and the second recording layer is made of at least Tb, Fe, and Co, contains 22 to 24 (at%) of Tb, and has a thickness of 180 to 250 ANGSTROM . Moreover, the relation of 0.55≤(d2/d1)≤0.9 is effectuated when assuming the thickness of the first dielectric layer as d1 and that of the reflective layer as d2 and the reflective layer is made of Al, Au, and Ti and contains 20 to 40 (wt%) of Au and 0.5 to 2.0 (wt%) of Ti.