Optical recording medium

Claim 1

A high density optical recording medium adapted to have an information signal recorded thereon in a corresponding pattern of changes in optical characteristics in a transparent substrate and adapted to reproduce the recorded information signal by detecting a reflection of reproducing light being applied perpendicularly thereto through the transparent substrate and moved and scanned over the transparent substrate, said high density recording medium consisting essentially of: a transparent substrate; a high refractive index layer comprising a sintered mixture of ZnS and SiO 2 disposed on said substrate having a refractive index including a real portion refractive index of about 1.8 or higher and having a layer thickness of about λ/4n 1 ±10%, wherein λ is the wavelength of reproducing light and n 1 is the refractive index of the high refractive index layer; a saturable absorption dye containing layer disposed on said high refractive index layer comprising a naphthalocyanine-based saturable absorption dye and a polymeric binder, said dye having a molecular extinction coefficient ε of 10 4 or greater at a wavelength, λ, of reproducing light and a relaxation time τ in a range of from greater than or equal to about 1 nanosecond to less than or equal to about 100 nanoseconds, the saturable absorption dye layer having a thickness dimension of about λ/4n 2 , where λ is the wavelength of the reproducing light and n 2 is the refractive index of the saturable absorption dye containing layer; and a reflecting layer disposed on said saturable absorption dye layer having a reflectivity of 70% or higher on an air boundary thereof.