Information recording medium and its manufacturing method

Abstract

A phase change recording medium comprising an as-deposited first recording layer configured to undergo a reversible phase change between an amorphous state and a crystalline state due to light irradiation and thereby change an optical characteristic. The as-deposited first recording layer includes a plurality of fine nuclei having an average size of 0.5 nm to 4 nm in the amorphous state.

What is claimed is:  
     
         1 . A phase change recording medium comprising an as-deposited first recording layer configured to undergo a reversible phase change between an amorphous state and a crystalline state due to light irradiation and thereby change an optical characteristic, wherein said as-deposited first recording layer includes a plurality of fine nuclei having an average size of 0.5 nm to 4 nm in said amorphous state.  
     
     
         2 . A phase change recording medium as set forth in  claim 1 , wherein said as-deposited first recording layer is configured to form a crystal part including a plurality of crystal grains in the crystalline state when said as-deposited first recording layer is irradiated with an erasing light beam, said plurality of crystal grains having grain sizes whose crystal grain size distribution has at least two maxima.  
     
     
         3 . A phase change recording medium as set forth in  claim 2 , wherein: 
 said at least two maxima has a first maximum for a grain size of greater than 4 nm and less than 20 nm and a second maximum for a grain size of greater than 20 μm and less than 100 nm; and    said crystal part comprises 75% or more of all crystal grains in a first distribution centered on said first maximum and a second distribution centered on said second maximum.    
     
     
         4 . A phase change recording medium as set forth in  claim 1 , further comprising: 
 a second recording layer configured to undergo a reversible phase change between an amorphous state and a crystalline state due to light irradiation and thereby change a second recording layer optical characteristic; and    a separation layer provided between said as-deposited first recording layer and said second recording layer.    
     
     
         5 . A phase change recording medium as set forth in  claim 1 , wherein said as-deposited first recording layer comprises at least one of Kr and Xe in a range of between 0.25 at % to 10 at %.  
     
     
         6 . A phase change recording medium as set forth in  claim 1 , wherein said as-deposited first recording layer includes a continuous amorphous state band between adjacent tracks after said recording layer is irradiated with a recording light beam having a spot size of a e −2  diameter greater than a track pitch.  
     
     
         7 . A phase change recording medium as set forth in  claim 2 , wherein said as-deposited first recording layer includes a continuous amorphous state band between adjacent tracks after said recording layer is irradiated with a recording light beam having a spot size of a e −2  diameter greater than a track pitch.  
     
     
         8 . A phase change recording medium comprising a first recording layer configured to undergo a reversible phase change between an amorphous state and a crystalline state due to light irradiation and thereby change an optical characteristic, wherein said first recording layer forms a crystal part including a plurality of crystal grains and having a crystal grain size distribution with at least two maxima.  
     
     
         9 . A phase change recording medium as set forth in  claim 8 , wherein: 
 said at least two maxima has a first maximum for a first grain size of greater than 4 nm and less than 20 nm and a second maximum for a second grain size of greater than 20 nm and less than 100 nm; and    said crystal part comprises 75% or more of all crystal grains in a first distribution centered on said first maximum and a second distribution centered on said second maximum.    
     
     
         10 . A phase change recording medium as set forth in  claim 8 , wherein said first recording layer becomes the amorphous state when said first recording layer is irradiated with a recording light beam, and forms an amorphous part comprising a plurality of fine nuclei having an average size of from 0.5 nm to 4 nm.  
     
     
         11 . A phase change recording medium as set forth in  claim 8 , further comprising: 
 a second recording layer configured to undergo a reversible phase change between an amorphous state and a crystalline state due to light irradiation and thereby change an optical characteristic; and    a separation layer provided between said first recording layer and said second recording layer.    
     
     
         12 . A phase change recording medium comprising an as-deposited recording layer configured to undergo a reversible phase change between an amorphous state and a crystalline state due to light irradiation and thereby change an optical characteristic, said as-deposited recording layer having an amorphous state thermal conductivity of from 0.8 W/mK to 6 W/mK.  
     
     
         13 . A phase change recording medium as set forth in  claim 12 , wherein said as-deposited recording layer comprises a plurality of fine nuclei having an average size of from 0.5 nm to 4 nm when the as-deposited recording layer is in the amorphous state.  
     
     
         14 . A phase change recording medium as set forth in  claim 12 , wherein said as-deposited recording layer comprises: 
 an address part substantially in the as-deposited recording layer in the amorphous state; and    a data part.    
     
     
         15 . A phase change recording medium as set forth in  claim 12 , wherein said as-deposited recording layer comprises at least one of Kr and Xe in a range of between 0.25 at % to 10 at %.  
     
     
         16 . A phase change recording medium comprising an as-deposited recording layer configured to undergo a reversible phase change between an amorphous state and a crystalline state due to light irradiation and thereby change a recording layer optical characteristic, said as-deposited recording layer including a continuous amorphous state band between adjacent tracks after said as-deposited recording layer is irradiated with a recording light beam having a spot size of a e −2  diameter greater than a track pitch.  
     
     
         17 . A phase change recording medium as set forth in  claim 16 , wherein the continuous amorphous state band comprises a plurality of fine nuclei with an average size of from 0.5 nm to 4 nm.  
     
     
         18 . A phase change recording medium as set forth in  claim 16 , wherein said as-deposited recording layer comprises at least one of Kr and Xe in a range of between 0.25 at % to 10 at %.  
     
     
         19 . A method for producing a phase change recording medium including a first recording layer part configured to undergo a reversible phase change between an amorphous state and a crystalline state due to light irradiation, and a second recording layer part and configured to undergo a reversible phase change between an amorphous state and a crystalline state due to said light irradiation, comprising: 
 depositing said first recording layer part on a first substrate;    forming a separation layer on said first recording layer part;    depositing said second recording layer part on a second substrate;    irradiating said first recording layer part with an initial crystallizing beam;    irradiating said second recording layer part substantially simultaneously with the crystallizing step of said first recording layer part by using part of the initial crystallizing beam passing through said first recording layer; and    sticking said first and second substrates together via said separation layer after said crystallizing steps so that said first recording layer part and said second recording layer part oppose each other.    
     
     
         20 . A method for producing a phase change recording medium having a substrate and an as-deposited recording layer including nuclei therein, comprising: 
 raising a recording layer temperature to a temperature higher than a room temperature using an infrared lamp; and    maintaining a temperature of said substrate less than a substrate thermal deformation temperature during the raising step by supporting said substrate on a material configured to absorb substantially no light emitted from said infrared lamp during or after deposition of said recording layer on said substrate.    
     
     
         21 . A method for producing a phase change recording medium as set forth in  claim 20 , wherein said material for supporting said substrate is substantially transparent to the light emitted from the infrared lamp.  
     
     
         22 . A phase change recording medium comprising an as-deposited first recording layer configured to undergo a reversible phase change between an amorphous state and a crystalline state due to light irradiation and thereby change a first recording layer optical characteristic, the as-deposited first recording layer in the crystalline state having a crystal grain size distribution having at least two maxima and crystal grains of the at least two maxima randomly arranged in the as-deposited first recording layer.  
     
     
         23 . A method for producing a phase change recording medium including a first recording layer part configured to undergo a reversible phase change between an amorphous state and a crystalline state due to light irradiation, a separation layer formed on said first recording layer part, and a second recording layer part formed on said separation layer and configured to undergo a reversible phase change between an amorphous state and a crystalline state due to said light irradiation, comprising: 
 providing a convergent optical system between said first and second recording layer parts to irradiate said second recording layer part with a condensed crystallizing light beam, said convergent optical system being configured to condense a light beam;    irradiating said first recording layer part with an initial crystallizing light beam to crystallize initially; and    irradiating said second recording layer part with part of said initial crystallizing light beam passing through said first recording layer part and condensed by said convergent optical system to crystallize initially substantially simultaneously with said first recording layer part.    
     
     
         24 . A phase change recording medium produced by a process comprising sputter depositing a recording layer onto a substrate with a relationship between a dc voltage (V dc ) applied to a target and a sputter threshold voltage (V th ) of a target forming element set to be (V th )<(V dc )≦10(V th ).  
     
     
         25 . A phase change recording medium produced by a process as set forth in  claim 24 , further comprising having an ion density (N i ) in a negative glow plasma produced in a vicinity of said target during said sputter depositing in the range of (N i )>10 11 .  
     
     
         26 . A phase change recording medium produced by a process as set forth in  claim 24 , wherein the recording layer includes Te.  
     
     
         27 . A phase change recording medium produced by a process as set forth in  claim 24 , wherein the recording layer includes Te and Sb.