Optical recording medium

Claim 1

A reflection-type optical recording medium having, on a surface thereof on which track guide grooves are formed, a layer of a recording material which has an increased energy reflection coefficient data is written therein, wherein the track guide grooves are formed such that a depth φ 0 thereof given by: φ.sub.0 =2·n·d/λ·2π (where n is a refractive index of the medium which covers said track guide grooves and which transmits input/output read light therethrough, d is an actual step of said track guide grooves, and λ is a wavelength of the read light) satisfies: (i) sin φ 0 <0 for θ 2 -θ 1 >0, or (ii) sin φ 0 >0 for θ 2 -θ 1 <0 where θ 1 is the phase of the reflected light before data is written on the recording material θ 2 is the phase of the reflected read light after data has been written on said recording material and which are defined by the equations: r.sub.1 =R.sub.1 expiθ.sub.1 r.sub.2 =R.sub.2 expiθ.sub.2 R 1 <R 2 (where r 1 is a complex reflection coefficient before data has been written on said recording material and r 2 is a complex reflection coefficient after data has been written on said recording material, and R 1 is an absolute value of the complex reflection coefficient before data has been written on said recording material and R 2 is an absolute value of the complex reflection coefficient after data has been written on said recording material).