Medium and method for providing a desirable direct overwriting characteristic for optical data recorded at different linear recording velocities

Abstract

It is an object of the present invention to provide a method for recording information in an optical recording medium with a good direct overwriting characteristic. The method for recording information in an optical recording medium according to the present invention forms record marks in a recording layer containing a phase change material by modulating the power of a laser beam between a plurality of power levels including a recording power Pw, an erasing power Pe and ground power Pb. The erasing power Pe is set to a level within a region where a reflection coefficient of a region between neighboring record marks approaches a reflection coefficient of the record mark as the erasing power Pe increases. As a result, a good overwriting characteristic can be obtained when data are recorded at a high linear velocity.

1 . A method for recording data in an optical recording medium including a recording layer containing a phase change material by projecting a laser beam thereonto, the method comprising steps of projecting the laser beam onto the recording layer so that the portion of the recording layer onto which the laser beam impinges is continuously moved and modulating the power of the laser beam between a plurality of power levels including at least an erasing power, thereby recording a plurality of record marks in the recording layer, the level of the erasing power being set to a level within an area where a reflection coefficient of a region between neighboring record marks approaches a reflection coefficient of the record mark as the erasing power increases.  
   
   
       2 . A method for recording data in an optical recording medium in accordance with  claim 1  wherein the plurality of power levels includes a recording power whose level is higher than that of the erasing power and a ground power whose level is lower than that of the erasing power.  
   
   
       3 . A method for recording data in an optical recording medium in accordance with  claim 1  wherein the optical recording medium is constituted as a “high-to-low type and the level of the erasing power is set to a level within which the reflection coefficient of a region between neighboring record marks decreases as the erasing power increases.  
   
   
       4 . A method for recording data in an optical recording medium in accordance with  claim 2  wherein the optical recording medium is constituted as a “high-to-low type and the level of the erasing power is set to a level within which the reflection coefficient of a region between neighboring record marks decreases as the erasing power increases.  
   
   
       5 . A method for recording data in an optical recording medium including a recording layer containing a phase change material by projecting a laser beam thereonto, the method comprising steps of projecting the laser beam onto the recording layer so that the portion of the recording layer onto which the laser beam impinges is continuously moved and modulating the power of the laser beam between a plurality of power levels including at least an erasing power, thereby recording a plurality of record marks in the recording layer, the level of the erasing power being set to higher than a level within an area where the reflection coefficient of the region between the neighboring record marks is not substantially changed even if the erasing power increases and lower than a level within an area where the reflection coefficient of the region between the neighboring record marks moves away from that of the record mark as the erasing power increases.  
   
   
       6 . A method for recording data in an optical recording medium in accordance with  claim 5  wherein the optical recording medium is constituted as a “high-to-low type and the level of the erasing power is set to a level lower than a level within an area where the reflection coefficient of the region between the neighboring record marks increases as the erasing power increases.  
   
   
       7 . A method for recording information in an optical recording medium for forming record marks in a recording layer containing a phase change material by modulating the power of a laser beam between a plurality of power levels including at least erasing power, the method comprising a step of setting the level of the erasing power to a level within a region where the reflection coefficient of the region between the neighboring record marks approaches the reflection coefficient of the record mark as the erasing power increases.  
   
   
       8 . A method for recording information in an optical recording medium in accordance with  claim 7  wherein the plurality of power levels includes a recording power whose level is higher than that of the erasing power and a ground power whose level is lower than that of the erasing power.  
   
   
       9 . A method for recording information in an optical recording medium in accordance with  claim 7  wherein the optical recording medium is constituted as a “high-to-low type and the level of the erasing power is set to a level within which the reflection coefficient of a region between neighboring record marks decreases as the erasing power increases.  
   
   
       10 . A method for recording information in an optical recording medium in accordance with  claim 8  wherein the optical recording medium is constituted as a “high-to-low type and the level of the erasing power is set to a level within which the reflection coefficient of a region between neighboring record marks decreases as the erasing power increases.  
   
   
       11 . A method for recording information in an optical recording medium for forming record marks in a recording layer containing a phase change material by modulating the power of a laser beam between a plurality of power levels including at least erasing power, the method comprising a step of setting the level of the erasing power to a level higher than a level within an area where the reflection coefficient of the region between the neighboring record marks is not substantially changed even if the erasing power increases and lower than a level within an area where the reflection coefficient of the region between the neighboring record marks moves away from that of the record mark as the erasing power increases.  
   
   
       12 . A method for recording information in an optical recording medium in accordance with  claim 11  wherein the optical recording medium is constituted as a “high-to-low type and the level of the erasing power is set to a level lower than a level within an area where the reflection coefficient of the region between the neighboring record marks increases as the erasing power increases.  
   
   
       13 . A method for recording data in an optical recording medium for forming record marks in a recording layer containing a phase change material by modulating the power of a laser beam between a plurality of power levels including at least erasing power wherein the erasing power is set to a first level when data are to be recorded at a first linear velocity and the erasing power is set to a second level different from the first level when data are to be recorded at a second linear velocity higher than the first linear velocity.