Optical recording medium and production process for the medium

Abstract

An optical information recording medium is provided in which the active layer is a phase change material capable of absorbing energy and being converted between a substantially amorphous state and a substantially crystalline state. The active layer contains nitrogen, which may be in the form of a nitride or nitrides of the constituent elements of the active layer, or may be a nitrided surface thereof. The inclusion of nitrogen inhibits localized shifting of the active material, which leads to degradation of the recording/erase properties of the medium. The optical recording medium includes a substrate, onto which is deposited in sequence a first dielectric layer, a nitrogen-containing active layer, a second dielectric layer, and a metallic reflecting layer. The second dielectric layer is made thin, so that the cooling rate of the active layer is increased to form a more uniform amorphous state.

We claim: 
     
       1. An optical recording medium having a recording layer capable of absorbing energy and being converted between a substantially non-crystalline state and a substantially crystalline state, wherein said recording layer comprises a ternary alloy of Te-Ge-Sb and at least one nitride or Te, Ge, or Sb. 
     
     
       2. An optical recording medium comprising: a) a substrate;   b) a first dielectric layer formed on one surface of said substrate;   c) a recording layer formed on said first dielectric layer, said recording layer capable of absorbing energy and being converted between a substantially non-crystalline state and a substantially crystalline state, wherein said recording layer includes a ternary alloy of Te-Ge-Sb and at least one nitride of Te, Ge, or Sb;   d) a second dielectric layer formed on said recording layer having a thickness substantially less than the thickness of said first dielectric layer; and   e) a reflecting layer formed on said second dielectric layer.   
     
     
       3. An optical recording medium in accordance with claim 2, wherein said second dielectric layer has a thickness of 30 nm or less. 
     
     
       4. An optical recording medium in accordance with claim 2, wherein said first and second dielectric layers comprise a mixture of ZnS and SiO 2  in which SiO 2  is n a concentration range of 5-40 mol %. 
     
     
       5. An optical recording medium comprising a recording layer which includes a ternary alloy or Te-Ge-Sb and at least one nitride of Te, Ge or Sb. 
     
     
       6. An optical recording medium comprising: a) a substrate;   b) a first dielectric layer formed on one surface of said substrate;   c) a recording layer formed on said first dielectric layer, said recording layer capable of absorbing energy and being converted between a substantially non-crystalline state and a substantially crystalline state, wherein said recording layer includes a ternary alloy or Ge-Te-Sb and germanium nitride;   d) a second dielectric layer formed on said recording layer having a thickness substantially less than the thickness of said first dielectric layer; and   e) a reflecting layer formed on said second dielectric layer.   
     
     
       7. An optical recording medium in accordance with claim 6, wherein said second dielectric layer has a thickness of 30 nm or less. 
     
     
       8. An optical recording medium in accordance with claim 6, wherein said first and second dielectric layers comprise a mixture of ZnS and SiO 2  in which SiO 2  is in a concentration range of 5-40 mol %. 
     
     
       9. An optical recording medium comprising a recording layer which includes a ternary alloy of Te-Ge-Sb dispersed in a matrix selected from the group consisting of Te nitride, Ge nitride and Sb nitride. 
     
     
       10. An optical recording medium having a recording layer comprising a ternary alloy composition of Sb, Sb 2  Te 3 , and GeTe, said composition further including at least one nitride of Ge, Te, or Sb. 
     
     
       11. An optical recording medium in accordance with claim 10, wherein the mole ratio of GeTe to Sb 2  Te 3  is greater than 0.5 and less than 3.0. 
     
     
       12. An optical recording medium comprising: a) a substrate;   b) a first dielectric layer formed on one surface of said substrate;   c) a recording layer formed on said first dielectric layer, said recording layer capable of absorbing energy and being converted between a substantially non-crystalline state and a substantially crystalline state, wherein said recording layer includes a ternary alloy of GeTe, Sb 2  Te 3 , Sb and at least one nitride of Ge, Te, or Sb;   d) a second dielectric layer formed on said recording layer having a thickness substantially less than the thickness of said first dielectric layer; and   e) a reflecting layer formed on said second dielectric layer.   
     
     
       13. An optical recording medium in accordance with claim 12, wherein said second dielectric layer has a thickness which is 30 nm or less. 
     
     
       14. An optical recording medium in accordance with claim 12, wherein said first and second dielectric layers comprise a mixture of ZnS and SiO 2  in which SiO 2  is in a concentration range of 5-40 mol %. 
     
     
       15. An optical recording medium in accordance with claim 12, wherein the mole ratio of GeTe to Sb 2  Te 3  is greater than 0.5 and less than 3.0. .Iadd. 
     
     
       16.  The optical recording medium of claim 1, wherein said at least one nitride of Te, Ge or Sb is present only as a nitrided surface layer formed as at least one surface of said recording layer. .Iaddend..Iadd.17. The optical recording medium of claim 2, wherein said at least one nitride of Te, Ge or Sb is present only as a nitrided surface layer formed as at least one surface of said recording layer. .Iaddend..Iadd.18. The optical recording medium of claim 1, wherein at least one surface of said recording layer includes said at least one nitride of Te, Ge or Sb. .Iaddend..Iadd.19. The optical recording medium of claim 2, wherein at least one surface of said recording layer includes said at least one nitride of Te, Ge or Sb. .Iaddend.