Reversible optical information-recording medium

Abstract

Phase-change type, reversible optical information recording medium, being possible for recording, reproducing, erasing, and rewriting of information, by use of a laser beam. This invention consists of recording thin film of ternary elements, for example, containing Ge, Te, Sb/or Bi or quaternary elements containing the fourth element of Se with which a part of Te is replaced, which is established on such surface—flat substrates as glass or plastics. In this case, the component ratio of Te and Se is selected not to be excess for other elements, such as Ge, Sb/or Bi so as to be fixed as stable compounds of stoichiometric compositions of GeTe, Sb 2 Te 3 /or Bi 2 Te 3 , or GeSe, Sb 2 Se 3 /Bi 2 Se 3 when crystallized. Strictly speaking, a concentration of each component is selected to have proper ratio of the number of atomes each other so as to represent whole composition as the sum of each component. By this treatment, it is possible to have high crystallization speed and long cyclability of recording/erasing. The effect of Se is to increase the viscosity of the system and to make easily to obtain amorphous state; and moreover, by selecting of proper amount diplaced with Te, it is possible to obtain the composition of recoding film superior in both characteristics of recording (amorphization and erasing (crystallization).

What is claimed is:  
     
         1 . An optical information recording medium having a substrate and a recording thin film which produces reversible phase transition between amorphous and crystalline states by laser beam irradiation on said substrate, and said recording thin film is characterized by 
 a) having a crystalline phase containing plural stoichiometric compounds of Te or Se as main components, and    b) existing at least one stoichiometric stable compounds among said plural stoichiometric phases.    
     
     
         2 . An optical information recording medium according to    claim 1   , characterized by forming a metastable single phase at first state in crystallization.  
     
     
         3 . An optical information recording medium according to    claim 2   , characterized by metastable phase with well symmetrized crystal structure.  
     
     
         4 . An optical information-recording medium according to    claim 1   , characterized by Te-compounds of Ge and Sb/or Bi as components consisting of crystal phase.  
     
     
         5 . An optical information-recording medium according to    claim 1   , characterized by Te-compounds and Se-compounds of Ge and Sb/or Bi as components consisting of crystal phase.  
     
     
         6 . An optical information-recording medium according to claims  1  and  4 , characterized by Te, Ge and Sb/or Bi as main components in the composition of recording film, and existence of the ratio of the numbers of atoms in the area, which is surrounded by the composition points of A 1  (Te 38 , Ge 59 , Sb/or Bi 3 ), B 1  (Te 50 , Ge 2 , Sb/or Bi 48 ), C 1  (Te 70 , Ge 2 , Sb/or Bi 28 ), and D 1  (Te 63 , Ge 34 , Sb/or Bi 3 ) in a triangle diagram showing the range of composition.  
     
     
         7 . An optical information-recording medium according to claims  1  and  6 , characterized by existence of the ratio of the numbers of Te, Ge and Sb/or Bi atoms in the area, which is surrounded by the composition points of A 2  (Te 42 , Ge 55 , Sb/or Bi 3 ), B 2  (Te 53 , Ge 2 , Sb/or Bi 45 ), C 2  (Te 64.5 , Ge 2 , Sb/or Bi 33.5 ), and D 2  (Te 57 , Ge 40 , Sb/or Bi 3 ) in a triangle diagram showing the range of composition.  
     
     
         8 . An optical information-recording medium according to claims  1  and  7 , chaaracterized by existence of the ratio of the numbers of Te, Ge and Sb/or Bi atoms in the area, which is surrounded by the composition points of A 3  (Te 44.5 , Ge 52.5 , Sb/or Bi 3 ), B 3  (Te 55 , Ge 2 , Sb/or Bi 43 ), C 3  (Te 63 , Ge 2 , Sb/or Bi 35 ), and D 3  (Te 54 , Ge 43 , Sb/or Bi 3 ) in a triangle diagram showing the range of composition.  
     
     
         9 . An optical information-recording medium according to claims  1  and  8 , characterized by existence of the ratio of the numbers of Te, Ge, and Sb/or Bi atoms in the area, which is surrounded by the composition points of A 4  (Te 46.5 , Ge 41.5 , Sb/or Bi 2  ), B 4  (Te 63 , Ge 2 , Sb/or Bi 35 ), C 4  (Te 62 , Ge 4 , Sb/or Bi 34 ), and D 4  (Te 55 , Ge 39 , Sb/or Bi 6 ) in a triangle diagram showing the range of composition.  
     
     
         10 . An optical information-recording medium according to claims  1  and  9 , characterized by satisfaction of the following formula by the ratio of the numbers of Te, Ge and Sb/or Bi atoms:  
       x·50 GeTe+(1−x)·20 Sb 2 Te 3 /or (1−x)·20 Bi 2 Te 3  or Te 60-10x Ge 50x (Sb/or Bi) 40-40x    
       (wherein 0.05≦x≦0.8)  
     
     
         11 . An optical information-recording medium according to claims  1  and  5 , characterized by Te, Ge, Sb/or Bi and Se as main components and existence of the ratio of the numbers of Te, Ge, and Sb/or Bi atoms in the area, which is surrounded by the composition points of A 1  (Te 38 , Ge 59 , Sb/or Bi 3 ), B 1  (Te 50 , Ge 2 , Sb/or Bi 48 ), C 1  (Te 70 , Ge 2 , Sb/or Bi 28 ), and D 1  (Te 63 , Ge 34 , Sb/or Bi 3 ) in a triangle diagram showing the range of composition, and equipment of substrate material with the recording thin film in which the concentration (atomic %) of Se is 0≦m≦30 atomic % in the following formula of the total composition:  
       (Te x , Ge y , Sb/or Bi z ) 100-m Se m    
     
     
         12 . An optical information-recording medium according to claims  1  and  11 , characterized by existence of the ratio of the numbers of Te, Ge, and Sb/or Bi atoms in the area, which is surrounded by the composition points of A 2  (Te 42 , Ge 55 , Sb/or Bi 3 ), B 2  (Te 53 , Ge 2 , Sb/or Bi 45 ), C 2  (Te 64.5 , Ge 2 , Sb/or Bi 33.5 ), and D 2  (Te 57 , Ge 40 , Sb/or Bi 3 ) in a triangle diagram showing the range of composition.  
     
     
         13 . An optical information-recording medium according to claims  1  and  12 , characterized by existence of the ratio of the numbers of Te, Ge, and Sb/or Bi atoms in the area, which is surrounded by the composition points of A 3  (Te 44.5 , Ge 52.5 , Sb/or Bi 3 ), B 3  (Te 55 , Ge 2 , Sb/or Bi 35 ), C 3  (Te 63 , Ge 2 , Sb/or Bi 35 ), and D 3  (Te 54 , Ge 43 , Sb/or Bi 3 ) in a triangle diagram showing the range of composition.  
     
     
         14 . An optical information-recording medium according to claims  1  and  13 , characterized by existence of the ratio of the numbers of Te, Ge, and Sb/or Bi atoms in the area, which is surrounded by the composition points of A 4  (Te 46.5 , Ge 41.5 , Sb/or Bi 12 ), B 4  (Te 55 , Ge 2 , Sb/or Bi 35 ), C 4  (Te 62 , Ge 4 , Sb/or Bi 34 ), and D 4  (Te 55 , Ge 39 , Sb/or Bi 6 ) in a triangle diagram showing the range of composition.  
     
     
         15 . An optical information-recording medium according to claims  1  and  14 , characterized by constitution with quaternary elements of Te, Ge, Sb/or Bi and Se and satisfaction of the following formula by the atomic ratios:  
       x·50 Ge(Te,Se)+(1−x)·20 Sb 2 (Te,Se) 3 /or (1−x) 20 ·Bi(Te,Se) 3  or (Te,Se) 60-10x Ge 50x (Sb/or Bi) 40-40x    (wherein 0.05≦x≦0.8)    and also the Se concentration of 30 or less atomic % of total concentration.    
     
     
         16 . An otpical information-recording medium according to claims  1  and  15 , characterized by existence of concentration of Se in the range of 5≦m≦15 atomic % in the following formula of the whole composition:  
       (Te x , Ge y , Sb/or Bi z ) 100-m Se m .