| 摘要 |
A groove is present in a surface of a disc substrate. A part of the groove is curved toward another groove adjacent to the groove to thereby form a land pre-pit. The following relations hold among DG, DP and r: <paragraph lvl="0"><in-line-formula>0.267<=(DP/DG)2.r<=0.701; and </in-line-formula><paragraph lvl="0"><in-line-formula>3.185<=(DP/DG)/r<=8.553, </in-line-formula>where DG: depth of the groove 4B, DP: depth of the land pre-pit 5A, r [mum]: distance between the center of the land pre-pit 5A and the center line of the groove 4B having the curved land pre-pit 5A.
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