Optical recording medium

A recording/retrieving apparatus, in which a disk-shaped rewritable optical recording medium is mounted, and in a state of rotating said rewritable optical recording medium a recording beam is applied onto said rewritable optical recording medium for recording information, where said rewritable optical recording medium having a phase-change recording layer in which a crystalline state of the phase-change recording layer is used as an unrecorded/erased state and recording marks in an amorphous state with various time lengths nT (where T is a reference clock period and n is an integer not less than 2) are formed in the unrecorded/erased state;

• said recording/retrieving apparatus has three recording beam radiation modes;
• a rewritable recording mode, a write-once recording mode and a DC erasing mode;
• (A-1) in said rewritable recording mode, recording on the rewritable optical recording medium is performed;
• rotating said rewritable optical recording medium so that a linear velocity at a radial position of said rewritable optical recording medium for recording information therein is within a range of recording velocity at which said rewritable optical recording medium can be rewritten,
• a plurality of recording marks with the time length nT are formed;
• dividing said time length nT into n T, α1T, β1T, α2T, β2T, . . . , αiT, βiT, . . . , αmT, βmT and η2T (where m is a pulse dividing number, i is an integer not less than 1 and not larger than m, Σi(αi+βi)+η1+η2=n, αi (1≦i≦m) is a real number larger than 0, βi (1≦i≦m−1) is a real number larger than 0, βm is a real number not less than 0, and η1 and η2 are real numbers not less than −2 and not larger than 2) in this order, where said pulse dividing number m for the time length of at least one recording mark is not less than 2, and the every time length of recording marks satisfies n/m≧1.25;
• applying a recording beam having a recording power Pwi (1≦i≦m) during a time period of αiT;
• applying a recording beam having a bias power Pbi (1≦i≦m, Pbi<Pwi, Pbi<Pwi+1) during a time period of βiT;
• applying a recording beam having an erasing power Pe (Pe is a value not less than any values of m Pbi's where 1≦i≦m, and is a value smaller than any values of m Pwi's where 1≦i≦m) on the spaces between said plural recording marks,
• (A-2) in said write-once recording mode, recording on said rewritable optical recording medium is performed;
• rotating said rewritable optical recording medium so that the linear velocity at a radial position of said rewritable optical recording medium for recording information therein is higher than the recording velocity range in which recorded information in said rewritable optical recording medium can be rewritten;
• forming a recording mark with a time length nT with one block pulse in which a recording beam having a recording power PwH and a recording beam having a bias power PbH can be applied;
• (A-3) in said DC erasing mode, recorded information in said rewritable optical recording medium is erased;
• rotating said rewritable optical recording medium so that the linear velocity at a radial position of said rewritable optical recording medium in which recorded information is to be erased is within the range of recording velocity in which said rewritable optical recording medium can be rewritten,
• applying a recording beam having an erasing power PDC;
• and
• (A-4) when executing said write-once recording mode after executing said rewritable recording mode, or when again executing said write-once recording mode after executing said write-once recording mode,
• said DC erasing mode is executed to erase recorded information in said rewritable optical recording medium.