| 摘要 |
<p>An optical information recording medium comprising a first substrate, a second substrate and a recording layer formed between the first and second substrates, and having a land portion and a groove portion formed thereon, wherein a distance between a light source for a laser beam irradiating the optical information recording medium and the land portion is larger than that between the light source and the groove portion, the difference D between a distance from the light source to the land portion and that from the light source to the groove portion is within a range, 0 < D < μ/(4N), μ being wavelength of laser beam and N refractive index of the substrate, and the groove portion is formed on the optical information recording medium at a pitch of up to 40 νm and has either of a first state providing a first reflectance and a second state providing a second reflectance lower then the first reflectance, a reversible change-over between the first and second states being enabled by a laser beam irradiation, the difference ζ1-ζ2 between the phase ζ1 of reflection light from the portion in the first state of the groove portion and the phase ζ2 of reflection light from the portion in the second state of the groove portion when a reproducing laser beam is applied to the groove portion satisfying 2nπ - π < ζ1 - ζ2 < 2nπ (n, arbitrary integer).</p> |
