Optical recording medium and optical recording/reproducing method

An optical recording/reproducing method, comprising the steps of:

• providing an optical recording medium comprising at least a supporting substrate;
• a recording layer on the supporting substrate, the recording layer containing an organic compound as a major component;
• a dielectric layer on the recording layer;
• and a light-transmitting layer on and directly in contact with the dielectric layer, the light-transmitting layer having a thickness of 1 to 150 μm and being capable of transmitting laser light with a wavelength of 390 to 420 nm for recording and reproducing information, wherein the organic compound in the recording layer includes a trimethine cyanine dye that has the minimum value nmin of its refractive index n (real part of the complex refractive index) within the range of 370 to 425 nm and has a refractive index n of 1.2 or lower with respect to the wavelength of the recording/reproducing laser light, and the organic compound, when absorbing the laser light, melts or degrades to bring about a change in the refractive index and wherein the trimethine cyanine dye contains a trimethine chain with two nitrogen-containing heterocyclic rings positioned on ends of the trimethine chain, one of the two nitrogen-containing heterocyclic rings being benzoxazole, and the other of the two heterocyclic rings being selected from the group consisting of benzoxazole, benzimidazole and indolenine;
• irradiating a recording laser light of 390 to 420 nm onto the optical recording medium from the light-transmitting layer side thereof to effect recording of the information, whereupon the refractive index n of the organic compound with respect to the wavelength of reproducing laser light of 390 to 420 nm is raised in the area irradiated with the recording laser light;
• and
• subsequent to the recording step, irradiating the reproducing laser light of 390 to 420 nm onto the optical recording medium from the light-transmitting layer side thereof to effect reproducing of the information
• wherein lands and grooves are formed on the supporting substrate with the grooves being 60 to 150 nm in depth, and having a pitch of 290 to 350 nm
• wherein only the land area serves as a recording area.