| 摘要 |
PROBLEM TO BE SOLVED: To enable recording and reproducing with red laser beams of 620 to 690nm wavelength and also with laser beams of 770 to 830nm wavelength. SOLUTION: When wavelengths of laser beams used for recording and reproducing are λ1, λ2 (λ1>λ2), thickness of dyestuff films of a groove part and a land part in a recording layer are dg1, dl1, depth of a pregroove part in a substrate is dsub , thicknesses of dyestuff films of the groove part and the land part in an optical interference layer are dg2, dl2, depth of the pregroove part at a reflecting layer side of the optical interference layer is dint , refractive indexes of the recording layer at wavelengths of λ1, λ2 are respectively nabs 1, nabs 2, refractive indexes of the interference layer at the wavelengths of λ1, λ2 are respectively nint 1, nint 2 and refractive index of the substrate at the wavelengths of λ1, λ2 is nsub , optical phase difference (ΔT1)=2[nsub .dsub -nabs 1(dg1-dl1)-nint 1(dg2-dl2) ]/λ1 is -0.1<=ΔT1<=0.5, optical phase difference (ΔT2)=2[nsub .dsub -nabs 2(dg1-dll)-nint 2(dg2-dl2)]/λ2 is 0.2$6hΔT2<=0.8 and further dg1+dg2<=d11+d12+dsub and dg1-dl1<=dsub . |
