Information recording medium comprising recording layer capable of recording under-exposure to recording laser beam

In an information recording medium comprising at least a substrate, a recording layer deposited on said substrate directly or through a protective layer to record the information under exposure to a recording laser beam and a reflective layer deposited on said recording layer directly or through other protective layers,

• wherein said information recording medium has a reflectivity, a with respect to the laser beam coming from the substrate, of at least 65 percent on the unrecorded mark and not more than 45 percent on the recorded mark, or not more than 45 percent on the unrecorded mark and at least 65 percent on the recorded mark, while the reflectivity of said reflective layer, with respect to the reproduction laser beam is at least 85 percent and electric resistance at the temperature of 298K of said reflective layer is at least 7 .mu..OMEGA..multidot.cm.

An information recording medium comprising at least a substrate, a lower dielectric protective layer, a recording layer comprising an inorganic substance whose optical constant changes due to change of atomic arrangement when exposed to a laser beam without deformation, an upper dielectric protective layer and an upper reflective layer provided successively on said substrate;

• wherein the reflectivity of the said medium with respect to the reproduction laser beam coming from the substrate side is at least 65 percent on the unrecorded mark and not more than 45 percent on the recorded mark, or not more than 45 percent on the unrecorded mark and at least 65 percent on the recorded mark;
• and
• wherein the reflectivity of said reflective layer with respect to the reproduction laser beam is at least 85 percent and electric resistance at the temperature of 298K of said reflective layer is at least 7 .mu..OMEGA..multidot.cm.

An information recording medium comprising at least a substrate, a lower reflective layer, a lower dielectric protective layer, a recording layer comprising an inorganic substance whose optical constant changes due to change of atomic arrangement when exposed to a laser beam without deformation, an upper dielectric protective layer and an upper reflective layer provided successively on said substrate;

• wherein the reflectivity of the said medium with respect to the reproduction laser beam coming from the substrate side is at least 65 percent on the unrecorded mark and not more than 45 percent on the recorded mark, or not more than 45 percent on the unrecorded mark and at least 65 percent on the recorded mark;
• and
• wherein the reflectivity of said reflective layer with respect to the reproduction laser beam is at least 85 percent and electric resistance at the temperature of 298K of said reflective layer is at least 7 .mu..OMEGA..multidot.cm.