Optical recording method and optical recording medium

Abstract

An optical recording method for recording mark length-modulated information on a recording medium by using a plurality of recording mark lengths. The optical recording method comprises the steps of: when a time length of one recording mark is denoted nT (T is a reference clock period equal to or less than 25 ns, and n is a natural number equal to or more than 2), (i) dividing the time length of the recording mark nT into η 1 T, α 1 T, β 1 T, α 2 T, β 2 T, . . . , α i T, β i T, . . . , α m T, β m T, η 2 T  in that order (m is a pulse division number; Σ i (α i +β i )+η 1 +η 2 =n; α i (1≦i≦m) is a real number >0; β i (1≦i≦m−1) is a real number>0; β m is a real number ≧0; and η 1 is a real number of −2≦η 1 ≦2 and η 2 is a real number of −2≦η 2 ≦2); radiating recording light with a recording power Pw i in a time duration of α i T (1≦i≦m), and radiating recording light with a bias power Pb i in a time duration of β i T (1≦i≦m), the bias power being Pb i <Pw i and Pb i <Pw i+1 ; and (ii) changing m, α i , β i , η 1 , η 2 , Pw i and Pb i according to n of the time length nT of the recording mark; wherein the pulse division number m is 2 or more for the time duration of at least one recording mark and meets n/m ≧1.25 for the time length of all the recording marks.

What is claimed is: 
     
       1. An optical recording method for recording mark length-modulated information with a plurality of recording mark lengths by irradiating a recording medium with a light, the optical recording method comprising the steps of:
 when a time length of one recording mark is denoted nT (T is a reference clock period equal to or less than 25 ns, and n is a natural number equal to or more than 2),   dividing the time length of the recording mark nT into
   η 1 T, α 1 T, β 1 T, α 2 T, β 2 T, . . . , α i T, β i T, . . . , α m T, β m T, η 2 T
 
    in that order (m is a pulse division number; Σhd i(α i +β i )+η 1 +η 2 =n; α i  (1≦i≦m−1) is a real number larger than 0; βi (1≦i≦m−1) is a real number larger than 0; β m  is a real number larger than or equal to 0; α i +β i  (2≦i≦m−1) or β i −1+α i  (2≦i≦m−1) is kept constant independently of said real number i; and η 1  and η 2  are real numbers between −2 and 2);   radiating recording light with a recording power Pw i  in a time duration of α i T (1≦i≦m); and   radiating recording light with a bias power Pb i  in a time duration of β i T(1≦i≦m−1), the bias power being Pb i <Pw i  and Pb i <Pw i+1 ;   wherein the pulse division number m is 2 or more for the time duration of at least one recording mark and meets n/m≧1.25 for the time length of all the recording marks,   further wherein when the same pulse division number m is used on at least two recording marks with different n values, a difference mark length is formed by changing at least one of β 1 , β m−1 , and βm.   
     
     
       2. An optical recording method according to  claim 1 , wherein α i +β i  (2≦i≦m−1) or β i −1+α i  (2≦i≦m−1) is 2 independently of said real number i. 
     
     
       3. An optical recording method according to  claim 1 , wherein α i  is kept constant as a constant value αc where said is (2≦i≦m−1). 
     
     
       4. An optical recording method according to  claim 1 , wherein α i  (2≦i≦m−1) is kept constant in the time length of the recording mark with having a pulse division number m being at least 3. 
     
     
       5. An optical recording method according to  claim 1 , wherein when performing a mark length modulation scheme recording on the same recording medium by using a plurality of linear velocities v while keeping v×T constant,
 for m equal to or greater than 2, (α i +β i ) in 2≦i≦m−1 is kept constant independently of the linear velocity, Pw 1 , Pb i  and Pe in each i are kept almost constant independently of the linear velocity, and α i  (2≦i≦m) is decreased as the linear velocity lowers. 
 
     
     
       6. An optical recording method according to  claim 1 , wherein when performing a mark length modulation scheme recording on the same recording medium by using a plurality of linear velocities v while keeping v×T constant,
 for m equal to or greater than 2, (β i −1+α i ) in 2≦i≦m are kept constant independently of the linear velocity, Pw 1 , Pb 1  and Pe in each i are kept almost constant independently of the linear velocity, and α i  (2≦i≦m) are decreased as the linear velocity lowers. 
 
     
     
       7. An optical recording according to  claim 5  or  6 , wherein α i T (2≦i≦m−1) is kept almost constant independently of the linear velocity. 
     
     
       8. An optical recording method according to  claim 1 , the phase change type optical recording medium having a recording layer made of M z Ge y (Sb x Te 1-x ) 1-y-z  alloy (where 0≦ z ≦0.1, 0< y ≦0.3, 0.8≦x; and
 M is at least one of In, Ga, Si, Sn, Pb Pd, Pt, Zn, Au, Ag, Zr, Hf, V, Nb, Ta, Cr, Co, Mo, Mn, Bi, O, N and S). 
 
     
     
       9. An optical information recording medium having a recording layer, containing excessive Sb in SbTe eutectic point, in which phase change is made reciprocally between a crystal state and amorphous state with optical characteristic being differed from each other by irradiation of an optical beam, wherein said crystal condition is defined as polycrystal made of a substantial single crystal phase of a hexagonal crystal. 
     
     
       10. An optical information recording medium according to  claim 9 , wherein said recording layer is made of M z Ge y (Sb x Te 1-x ) 1-y-z  alloy (where 0≦z≦0.1 0<y≦0.3, 0.8≦x; and
 M is at least any one of In, Ga, Si, Sn, Pb, Pd, Pt, Zn, Au, Ag, Zr, Hf, V, Nb, Ta, Cr, Co, Mo, Mn, Bi, O, N and S). 
 
     
     
       11. An optical information recording medium according to  claim 9  or  10 , wherein said crystal state of said recording layer is defined as an unrecorded state and an erased state, while said amorphous state thereof is defined as a recorded state and an erased state, while said amorphous state thereof is defined as a recorded state so as to performed recording or erasing of information. 
     
     
       12. A method of manufacturing an optical information recording medium having a recording layer, containing excessive Sb in SbTe eutectic point, in which phase change is made recriprocally between a crystal state and amorphous state with optical characteristic being differed from each other by irradiation of an optical beam, wherein
 an initialization step is performed with another optical beam having an elliptical beam shape of which minor axis is 0.1-10 μm after forming at least said recording layer on a substrate, by scanning said another optical beam to the recording layer in a direction of said minor axis so as to make the recording layer in the crystal state, further wherein   said scanning of said optical beam is performed in a speed in a range of 50-80% of a maximum usable linear velocity for over-writing of the recording layer.   
     
     
       13. An optical recording method for recording mark length-modulated information with a plurality of recording mark lengths by irradiating a recording medium with a light, the optical recording method comprising the steps of:
 when a time length of one recording mark is denoted nT (T reference clock period equal to or less than 25 ns, and n is a natural number equal to or more than 2), dividing the time length of the recording mark nT into
   η 1 T, α 1 T, β 1 T, α 2 T, β 2 T, . . . , α m T, β m T, η 2 T
 
   
       in that order (m is a pulse division number; Σ i (α i +β i )+η 1 +η 2 =n; α i  (1≦i≦m) is a real number larger than 0; β i  (1≦i≦m−1) is a real number larger than 0; β m  is a real number larger than or equal to 0; α i +β i  (2≦i≦m−1) or β i−1 +α i  (2≦i≦m−1) is kept constant independently of said real number i; and η 1  and η 2  are real numbers between −2 and 2);
 radiating recording light with a recording power Pw i , in a time duration of α i T (1≦i≦m); and 
 radiating recording light with a bias power Pb i , in a time duration of β i T(1≦i≦m−1), the bias power being Pb i <Pw i  and Pb i <Pw 1+1 ; 
 wherein the pulse division number m is 2 or more for the time duration of at least one recording mark and meets n/m≧1.8 for the time length of all the recording marks, 
 further wherein when the same pulse division number m is used on at least two recording marks with different n values, a difference mark length is formed by changing at least one of β 1 , β m−1 , and β m .  
 
     
     
       14. An optical recording method according to claim 13, wherein α i +β i  (2≦i≦m−1) or β i−1 +α i  (2≦i≦m−1) is 2 independently of said real number i.  
     
     
       15. An optical recording method according to claim 13, wherein α i  is kept constant as a constant value αc where said i is (2≦i≦m−1).  
     
     
       16. An optical recording method according to claim 13, wherein α i  (2≦i≦m−1) is kept constant in the time length of the recording mark with having a pulse division number m being at least 3.  
     
     
       17. An optical recording method according to claim 13, wherein when performing a mark length modulation scheme recording on the same recording medium by using a plurality of linear velocities v while keeping v×T constant,
 for m equal to or greater than 2, (α i +β i ) in 2≦i≦m−1 is kept constant independently of the linear velocity, Pw i , Pb i  and Pe in each i are kept almost constant independently of the linear velocity and α i  (2≦i≦m) is decreased as the linear velocity lowers.  
 
     
     
       18. An optical recording method according to claim 13, wherein when performing a mark length modulation scheme recording on the same recording medium by using a plurality of linear velocities v while keeping v×T constant,
 for m equal to or greater than 2, (β i−1 +α i ) in 
 2≦i≦m are kept constant independently of the linear velocity, Pw i , Pb i  and Pe in each i are kept almost constant independently of the linear velocity, and α i  (2≦i≦m) are decreased as the linear velocity lowers.  
 
     
     
       19. An optical recording method according to claim 17 or 18, wherein α i T (2≦i≦m−1) is kept almost constant independently of the linear velocity.  
     
     
       20. An optical recording method according to claim 13, the phase change type optical recording medium having a recording layer made of M z Ge y (Sb x Te 1 -x) 1-y-z  alloy (where 0≦z≦0.1, 0<y≦0.3, 0.8≦x; and
 M is at least one of In, Ga, Si, Sn, Pb Pd, Pt, Zn, Au, Ag, Zr, Hf, V, Nb, Ta, Cr, Co, Mo, Mn, Bi, O, N and S).