Optical information recording medium, method for manufacturing the same, and initialization device

Abstract

An optical information recording medium includes a plurality of recording layers, a reflectance of at least one of the plurality of the recording layers in a non-initialized state with respect to a light beam for initialization being smaller than a reflectance of the same in an initialized state with respect to the light beam for initialization. The recording layers are initialized by irradiating, among the plurality of recording layers, the recording layer positioned farther from a light beam irradiation side with the light beam prior to irradiating the recording layer positioned closer to the light beam irradiation side, so that the initialized recording layers have no initialization irregularities. In initialization, at a position at a same distance in a radial direction on the optical information recording medium, the recording layer positioned farther from a light beam irradiation side is irradiated with one light beam before the recording layer positioned closer to the light beam irradiation side is irradiated with another light beam so that the plurality of recording layers are initialized at the same time by a light beam projecting operation in which the light beams are focused at different positions. This ensures the initialization without irregularities within a short time.

What is claimed is:  
     
         1 . An optical information recording medium comprising a plurality of recording layers, a reflectance of at least one of the plurality of the recording layers in a non-initialized state with respect to a light beam for initialization being smaller than a reflectance of the same in an initialized state with respect to the light beam for initialization, 
 wherein the recording layers are initialized by irradiating, among the plurality of recording layers, the recording layer positioned farther from a light beam irradiation side with the light beam prior to irradiating the recording layer positioned closer to the light beam irradiation side.    
     
     
         2 . The optical information recording medium according to  claim 1 , wherein the reflectance of at least one of the plurality of recording layers in the non-initialized state with respect to the light beam for initialization is not more than 1/2 of the reflectance in the initialized state.  
     
     
         3 . The optical information recording medium according to  claim 1 , wherein the recording layer positioned farther from the light beam irradiation side and the recording layer positioned closer to the light beam irradiation side are initialized at the same time by one light-beam-projecting operation, by focusing the light beam at different positions.  
     
     
         4 . An optical information recording medium comprising a plurality of recording layers, a reflectance of at least one of the plurality of the recording layers in a non-initialized state with respect to a light beam for initialization being smaller than a reflectance of the same in an initialized state with respect to the light beam for initialization, 
 wherein the initialized recording layers have no initialization irregularities.    
     
     
         5 . The optical information recording medium according to  claim 4 , wherein the reflectance of the at least one of the plurality of recording layers in the non-initialized state with respect to the light beam for initialization is not more than 1/2 of the reflectance in the initialized state.  
     
     
         6 . A method for manufacturing an optical information recording medium having a plurality of recording layers, comprising, for initializing the optical information recording medium: 
 projecting different light beams to the plurality of recording layers, respectively, wherein    at a position at a same distance in a radial direction on the optical information recording medium, the recording layer positioned farther from a light beam irradiation side is irradiated with one light beam before the recording layer positioned closer to the light beam irradiation side is irradiated with another light beam so that the plurality of recording layers are initialized at the same time by a light beam projecting operation in which the light beams are focused at different positions.    
     
     
         7 . The method for manufacturing an optical information recording medium according to  claim 6 , wherein 
 the light beams are emitted from a plurality of optical heads, respectively, that are provided so as to face a same surface of the recording medium, and are moved in a predetermined initialization traveling direction, and    among the plurality of recording layers, the recording layer positioned farther from the light beam irradiation side is irradiated with the light beam emitted from the optical head positioned ahead relative to the initialization traveling direction, in the initialization of the plurality of recording layers at the same time.    
     
     
         8 . The method for manufacturing an optical information recording medium according to  claim 7 , wherein the light beams emitted from at least two optical heads among the plurality of optical heads form spots different in shape from each other.  
     
     
         9 . The method for manufacturing an optical information recording medium according to  claim 6 , wherein in initializing at least one of the recording layers, a focus position control light beam different from a crystallization beam for crystallizing a recording layer is employed for controlling a focus position of the crystallization beam.  
     
     
         10 . The method for manufacturing an optical information recording medium according to  claim 6 , wherein in initializing at least one of the recording layers, at an initial stage of the initialization, a focus position of an optical head is moved up and down, with a light beam having an intensity sufficient for initialization, so that the recording layer is crystallized partially.  
     
     
         11 . The method for manufacturing an optical information recording medium according to  claim 6 , wherein in initializing at least one of the recording layers, at an initial stage of the initialization, a focus position is focused at a recording layer from which a greater reflected light amount is obtained than a reflected light amount obtained from the target recording layer, and thereafter a focus position of an optical head is moved a predetermined distance in a thickness direction of the recording medium so that the target recording layer is initialized.  
     
     
         12 . The method for manufacturing an optical information recording medium according to  claim 6 , wherein a focus position is focused at a recording layer from which a greater reflected light amount is obtained than a reflected light amount obtained from the target recording layer, with a light beam having an intensity with which the target recording layer is not crystallized, and thereafter a focus position of an optical head is moved up and down with respect to a position at a predetermined distance therefrom in a thickness direction of the recording medium so that the target recording layer is crystallized partially.  
     
     
         13 . The method for manufacturing an optical information recording medium according to  claim 6 , wherein a focus position is focused at a recording layer from which a greater reflected light amount is obtained than from the target recording layer, with a light beam having an intensity with which the target recording layer is not crystallized, and thereafter a focus position of an optical head is moved a predetermined distance in a thickness direction of the recording medium, and the intensity of the light beam is increased so as to be sufficient for initializing the target recording layer, so that the target recording layer is initialized.  
     
     
         14 . The method for manufacturing an optical information recording medium according to  claim 6 , wherein a positional relationship of the optical heads is set so as to satisfy a relationship expressed as: 
         z >( x/ 2)+( y /2)+( d ·tan θ) 
       where 
 x represents a spot width of a light beam for initializing the recording layer positioned closer to the light beam irradiation side,  
 y and θ represent a spot width and an incident angle, respectively, of a light beam for initializing the recording layer positioned farter from the light beam irradiation side,  
 z represents a distance between the light beams, and  
 d represents a distance between the recording layers.  
 
     
     
         15 . A method for manufacturing an optical information recording medium having a plurality of recording layers, comprising initializing an optical information recording medium wherein, in initializing at least one of the recording layers, a focus position control light beam different from a crystallization beam for crystallizing a recording layer is employed for controlling a focus position of the crystallization beam.  
     
     
         16 . The method for manufacturing an optical information recording medium according to  claim 15 , wherein among the plurality of recording layers, the recording layer positioned farther from a light beam irradiation side is initialized prior to initializing the recording layer positioned closer to the light beam irradiation side.  
     
     
         17 . The method for manufacturing an optical information recording medium according to  claim 15 , wherein, while a plurality of optical heads provided to face a same surface of the recording medium are moved in a predetermined initialization traveling direction, the recording layer positioned farther from the light beam irradiation side among the plurality of recording layers is irradiated with a light beam emitted from the optical head positioned ahead relative to the initialization traveling direction, in the initialization of the plurality of recording layers at the same time.  
     
     
         18 . An initialization device for initializing an optical information recording medium having a plurality of recording layers, comprising: 
 a plurality of optical heads provided to face a same surface of a recording medium for irradiating different recording layers with light beams, respectively; and    a transfer system for moving the optical heads in a predetermined initialization traveling direction,    wherein among the plurality of optical heads, the optical head for irradiating a recording layer positioned farther from a light beam irradiation side among a plurality of recording layers is positioned ahead relative to the initialization traveling direction.    
     
     
         19 . The initialization device according to  claim 18 , wherein a positional relationship of the optical heads is set so as to satisfy a relationship expressed as: 
         z >( x /2)+( y /2)+( d ·tan θ) 
       where 
 x represents a spot width of a light beam for initializing the recording layer positioned closer to the light beam irradiation side,  
 y and θ represent a spot width and an incident angle, respectively, of a light beam for initializing the recording layer positioned farther from the light beam irradiation side,  
 z represents a distance between the light beams, and  
 d represents a distance between the recording layers.  
 
     
     
         20 . The initialization device according to  claim 18 , wherein the light beams emitted from at least two optical heads among the plurality of optical heads form spots different in shape from each other.  
     
     
         21 . The initialization device according to  claim 18 , further comprising a spindle motor for rotating the recording medium, 
 wherein the transfer system includes a transfer mount on which the optical heads are mounted and the transfer system moves the transfer mount so as to move the optical heads to the predetermined position,    wherein the plurality of optical heads are arranged so that light beams emitted from the optical heads are projected to the recording medium at different positions in a radial direction of the recording medium.    
     
     
         22 . The initialization device according to  claim 21 , wherein the plurality of optical heads are mounted on one transfer mount.  
     
     
         23 . The initialization device according to  claim 21 , wherein 
 optimal substrate thicknesses for the optical heads are different from each other, the optimal substrate thicknesses being obtained by optimizing substrate thicknesses, through which the light beams emitted from the optical heads pass while being converged to form spots on the recording layers, respectively, so as to make the formed spots have minimum diameters, respectively.    
     
     
         24 . The initialization device according to  claim 18 , wherein at least one of the plurality of optical heads includes a driving system for moving an objective lens equipped in the optical head, a counter for counting up-and-down movements of the objective lens, and a controller for controlling an intensity of the light beam emitted from the optical head and for controlling the driving system.  
     
     
         25 . An initialization device comprising at least one optical head and a transfer system for moving the optical head in a predetermined initialization traveling direction, 
 wherein at least one of the optical heads includes an objective lens that is a single lens, a light source for emitting a crystallization beam for crystallizing a recording layer, and a light source for emitting a focus position control beam with an intensity with which the recording layer is not crystallized.    
     
     
         26 . The initialization device according to  claim 25  comprising a plurality of optical heads provided facing a same surface of the recording medium and projecting light beams to different recording layers, respectively, 
 wherein, among the plurality of optical heads, the optical head for irradiating the recording layer positioned farther from a light beam irradiation side among the plurality of recording layers is positioned ahead relative to the initialization traveling direction.  
 
     
     
         27 . The initialization device according to  claim 25 , wherein the optical head includes an objective lens and a plurality of light sources, 
 the initialization device further comprising an optical path correction system positioned on an optical path of one light beam emitted from at least one of the optical sources.    
     
     
         28 . The initialization device according to  claim 27 , wherein the optical path correction system is a liquid crystal element or a lens.  
     
     
         29 . The initialization device according to  claim 27 , wherein the light sources emit light beams with different wavelengths from each other.