Disk-shaped information recording medium, disk cartridge, and information recording/reproducing apparatus

A disk-shaped information recording medium having an outer diameter and an inner diameter, the information recording medium comprising:

• a substrate having a predetermined thickness;
• a first side that is one side of the substrate;
• a second side that is the other side of the substrate;
• a cylindrical portion forming a through hole formed at a center of the substrate;
• a thin portion formed so as to surround an outer diameter of the cylindrical portion, the thin portion being thinner than the predetermined thickness;
• a non-inclined surface formed at the thin portion;
• an inclined surface formed on an outer diameter side of the non-inclined surface at the thin portion, the inclined surface being inclined at a predetermined angle to the non-inclined surface and being larger than the non-inclined surface in the thin portion;
• and
• a curvature portion formed between the inclined surface and a surface of the substrate where the thin portion is not formed.

A disk-shaped information recording medium having an outer diameter and an inner diameter, the information recording medium comprising:

• a substrate having a predetermined thickness;
• a first side that is one side of the substrate;
• a second side that is the other side of the substrate;
• a cylindrical portion forming a through hole formed at a center of the substrate;
• a thin portion formed so as to surround an outer diameter of the cylindrical portion, the thin portion being thinner than the predetermined thickness;
• a non-inclined surface formed at the thin portion;
• an inclined surface formed on an outer diameter side of the non-inclined surface at the thin portion, the inclined surface being inclined at a predetermined angle to the non-inclined surface and being larger than the non-inclined surface in the thin portion;
• and
• a protuberance formed on an outer diameter side of the thin portion on at least one of the first side and the second side, the protuberance bulging from the at least one of the first side and the second side.

A disk-shaped information recording medium having an outer diameter and an inner diameter, the information recording medium comprising:

• a substrate having a predetermined thickness;
• a first side that is one side of the substrate;
• a second side that is the other side of the substrate;
• a cylindrical portion forming a through hole formed at a center of the substrate;
• a thin portion formed so as to surround an outer diameter of the cylindrical portion, the thin portion being thinner than the predetermined thickness;
• a non-inclined surface formed at the thin portion;
• an inclined surface formed on an outer diameter side of the non-inclined surface at the thin portion, the inclined surface being inclined at a predetermined angle to the non-inclined surface;
• a concavo-convex area formed on an outer diameter side of the thin portion on either one of the first side or the second side;
• a printing area formed in the concavo-convex area;
• and
• a data recording area formed on the other one of the first side or the second side,
• wherein the data recording area of one of the information recording medium is formed at a different radial position from the printing area of one other of the information recording medium when the one of the information recording medium is placed on the other one of the information recording medium.