Multi-layered optical disc

Abstract

A multi-layered optical disc having its recording unit comprised of plural information recording layers, in which two or more information recording layers are layered on a substrate 0.3 to 1.2 mm in thickness, with the interposition of a transparent layer, to form a recording unit, a light transmitting protective layer is formed on the recording unit to a thickness of 10 to 177 μm and in which the light is illuminated from the side of the light transmitting protective layer to effect recording and/or reproduction of information signals. At least one of the information recording layers except the information recording layer formed at a remotest position from the light transmitting protective layer has a phase change material as a recording material. A refractive index nc 1 and an extinction coefficient kc 1 in the crystallized state and a refractive index na1 and an extinction coefficient ka 1 in the amorphous state of the phase change material constituting the first information recording layer as counted from the light transmitting protective layer satisfy the relationship of (nc 1 /na 1 )≦12, (kc 1 /ka 1 )≦12 and (kc 1 /ka 1 )≦5 , (nc 1 /na 1 ) where the cases of kc 1 /ka 1 ≦1 and nc 1 /na 1 ≦1 are excluded.

What is claimed is:  
     
         1 . A multi-layered optical disc in which two or more information recording layers are layered on a substrate 0.3 to 1.2 mm in thickness, with the interposition of a transparent layer, to form a recording unit, a light transmitting protective layer is formed on said recording unit to a thickness of 10 to 177 μm, and in which the light is illuminated from the side of the light transmitting protective layer to effect recording and/or reproduction of information signals, 
 wherein 
 at least one of said information recording layers except the information recording layer formed at a remotest position from the light transmitting protective layer has a phase change material as a recording material; and wherein  
 a refractive index nc 1  and an extinction coefficient kc 1  in the crystallized state and refractive index na 1 and an extinction coefficient ka 1  in the amorphous state of the phase change material constituting the first information recording layer as counted from the light transmitting protective layer satisfy the relationship of (nc 1 /na 1 )≦12, (kc 1 /ka 1 )≦12 and (kc 1 /ka 1 )≦5 (nc 1 /na 1 ), where the cases of kc 1 /ka 1 <1 and nc 1 /na 1 <1 are excluded.  
 
 
     
     
         2 . The multi-layered optical disc according to  claim 1  wherein the phase change material contains at least one of Au, Al, Ag, Bi, Cu, Cr, Co, Cd, Ce, Cs, Dy, Fe, Ge, Gd, Ga, Hf, In, K, La, Li, Mn, Mo, Ni, Nb, Nd, Na, Os, Pd, Pr, Pb, Ru, Rh, Rb, Sn, Sb, Si, Sm, Sc, Se, The, Ti, Tb, Ta, V, W, Y, Zn and Zr.  
     
     
         3 . The multi-layered optical disc according to  claim 2  wherein the phase change material is at least one selected from the group consisting of InSe based chalcogenides, SbSE based chalcogenides, InSbSe based chalcogenides, GeSbTe based chalcogenides, GeSbTeSe based chalcogenides, AgInSbTe based chalcogenides, AgInSbSeTe based chalcogenides, GeSbTeN based chalcogenides and AgInSbTeN based chalcogenides.  
     
     
         4 . The multi-layered optical disc according to  claim 3  wherein the phase change material is at least one selected from the group consisting of InSeN, InSeNO, InSeO, SbSeN, SbSeNO, SbSeO, InSbSeN, InSbSeNO, InSbSeO, GeSbTeSeN, GeSbTeSeNO, GeSbTeSeO, AgInSbSeTeN, AgInSbSeTeNO, AgInSbSeTeO, GeSbTeNO, GeSbTeO, AgInSbTeNO and AgInSbTeO.  
     
     
         5 . The multi-layered optical disc according to  claim 1  wherein the reflectance in the crystallized state of the phase change material constituting the first information recording layer as counted from the side of the light transmitting protective layer is not less than 5% and wherein the light transmittance in the crystallized and amorphous state is not less than 40%.  
     
     
         6 . The multi-layered optical disc according to  claim 1  wherein the reflectance in the amorphous state of the phase change material constituting the first information recording layer as counted from the side of the light transmitting protective layer is not less than 5% and wherein the light transmittance in the crystallized and amorphous state is not less than 40%.  
     
     
         7 . The multi-layered optical disc according to  claim 1  wherein the recording material constituting the second information recording layer as counted from the light transmitting protective layer is a phase change material and wherein the reflectance in the crystallized state of the phase change material is not less than 10%.  
     
     
         8 . The multi-layered optical disc according to  claim 7  wherein the reflectance ratio between the crystallized state and the amorphous state of the phase change material constituting the first information recording layer as counted from the light transmitting protective layer is not less than 1.5 and wherein the reflectance ratio between the crystallized state and the amorphous state of the phase change material constituting the second information recording layer is not less than 1.5  
     
     
         9 . The multi-layered optical disc according to  claim 1  wherein the wavelength of the light illuminated from said light transmitting protective layer is 380 to 450 nm.  
     
     
         10 . The multi-layered optical disc according to  claim 1  wherein the wavelength of the light illuminated from said light transmitting protective layer is 630 to 700 nm.  
     
     
         11 . A multi-layered optical disc in which two or more information recording layers are layered on a substrate 0.3 to 1.2 mm in thickness, with the interposition of a transparent layer, to form a recording unit, a light transmitting protective layer is formed on said recording unit to a thickness of 10 to 177 μmm, and in which the light is illuminated from the side of the light transmitting protective layer to effect recording and/or reproduction of information signals, 
 wherein 
 each information recording layer has a phase change material as a recording material; and wherein i 
 f, when the recording and/or reproducing light is converged on the second recording layer remote from said light transmitting protective layer, there co-exist an information recorded track and a non-information recorded track in the recording and/or reproducing light passage area in the first recording layer on the side of the light transmitting protective layer, the phase change recording material of the first recording layer satisfies the following relationship: 
 0.8≦T 1 c/T 1 a≦1.270%≧T 1 c≧40%70%≧T 1 a≧40%Alc/Ala≧1.0 
 where T 1   c  is the light transmittance of the phase change recording material of the first recording layer in the crystal state, Al c  is the absorption rate of light absorbed by the phase change recording material of the first recording layer in the crystal state, T 1   a  is the light transmittance of the phase change recording material in the amorphous state and Al a  is the absorption rate of light absorbed by the phase change recording material in the amorphous state.  
 
 
     
     
         12 . The multi-layered optical disc according to  claim 11  wherein the thickness dr of the phase change recording material of the first recording layer satisfies the following relationship: 
       dr≧5 nmexp (−4π·k 1 c·dr/λ)≧40%exp (−4π·k 1 a·dr/λ)≧40% 
       where λ is the wavelength of the laser light used for recording and/or reproduction.  
     
     
         13 . The multi-layered optical disc according to  claim 11  wherein, if the recording and/or reproducing wavelength is 385 to 450 nm, the phase change recording material of the first recording layer has a recording mode in which the reflectance of the first recording layer is higher in the amorphous state than in the crystal state of the phase change recording material of the first recording layer.  
     
     
         14 . The multi-layered optical disc according to  claim 13  wherein an anti-reflection film is formed so that the reflectance to the recording and/or reproducing light of the light transmitting layer as the outermost disc surface will be not higher than 2%.  
     
     
         15 . The multi-layered optical disc according to  claim 14  wherein the anti-reflection film is formed of a thin dielectric film transparent to the recording and/or reproducing wavelength and having a different refractive index.  
     
     
         16 . A multi-layered optical disc in which a plurality of information recording layers are layered, with a transparent intermediate layer in-between, on a supporting substrate, with a thickness of 0.3 to 1.2 mm, carrying a guide groove by a pattern of crests and recesses, and a light transmitting layer 10 to 177 μm is layered thereon, 
 wherein 
 said information recording layer has a film of a phase change material formed of a phase change material containing at least one of binary alloys, such as InSe, SbSe or SbTe, ternary alloys, such as InSbSe, GeSbTe or InSbTe, quatanary alloys, such as GeSbTeSe or AgInSbTe, quinary alloys, such as AgInSbSeTe, nitrides and oxides of these alloys, wherein  
 a crystallization promoting film and an enhancement film are formed at least on the side of said supporting substrate or on the opposite side to the supporting substrate of said film of the phase change material, wherein  
 the information recording layer closest to said supporting substrate has a reflecting film allocated to an outermost side thereof towards the supporting substrate and also has a semi-transparent enhancement film allocated to an outermost side thereof opposite to said supporting substrate, and wherein  
 said crystallization promoting film is formed of a material containing at least one of Si, SiC, Ge, GeC, Sn, SnC, Al, AIC, Ga, GaC, In, InC, chlorides and oxides thereof.  
 
 
     
     
         17 . A multi-layered optical disc in which a plurality of information recording layers are layered, with a transparent intermediate layer in-between, on a supporting substrate, with a thickness of 0.3 to 1.2 mm, carrying a guide groove by a pattern of crests and recesses, and a light transmitting layer 10 to 177 μm is layered thereon, 
 wherein 
 said information recording layer has a film of a phase change material formed of a phase change material containing at least one of binary alloys, such as InSe, SbSe or SbTe, ternary alloys, such as InSbSe, GeSbTe or InSbTe, quatanary alloys, such as GeSbTeSe or AgInSbTe, quinary alloys, such as AgInSbSeTe, nitrides and oxides of these alloys, wherein  
 a crystallization promoting film and an enhancement film are formed at least on the side of said supporting substrate or on the opposite side to the supporting substrate of said film of the phase change material, wherein  
 the information recording layer closest to said supporting substrate has a reflecting film allocated to an outermost side thereof towards the supporting substrate and also has a semi-transparent enhancement film allocated to an outermost side thereof opposite to said supporting substrate, and wherein  
 said enhancement film is formed of a material containing at least one of ZnS, ZnS—SiO 2 , SiO 2  and MgF 2 .  
 
 
     
     
         18 . A multi-layered optical disc in which a plurality of information recording layers are layered, with a transparent intermediate layer in-between, on a supporting substrate, with a thickness of 0.3 to 1.2 mm, carrying a guide groove by a pattern of crests and recesses, and a light transmitting layer 10 to 177 μm is layered thereon, 
 wherein 
 said information recording layer has a film of a phase change material formed of a phase change material containing at least one of binary alloys, such as InSe, SbSe or SbTe, ternary alloys, such as InSbSe, GeSbTe or InSbTe, quatanary alloys, such as GeSbTeSe or AgInSbTe, quinary alloys, such as AgInSbSeTe, nitrides and oxides of these alloys, wherein  
 a crystallization promoting film and an enhancement film are formed at least on the side of said supporting substrate or on the opposite side to the supporting substrate of said film of the phase change material, wherein  
 the information recording layer closest to said supporting substrate has a reflecting film allocated to an outermost side thereof towards the supporting substrate and also has a semi-transparent enhancement film allocated to an outermost side thereof opposite to said supporting substrate, and wherein  
 said semi-transparent enhancement film is formed of a material containing at least one of Au, an AuCo alloy, Si, an Ag alloy, SiO x , ZnS—SiO x , an Au—SiO 2  mixture and an Au—ZnS—SiO 2  mixture, with x≦2.  
 
 
     
     
         19 . A multi-layered optical disc in which a plurality of information recording layers are layered, with a transparent intermediate layer in-between, on a supporting substrate, with a thickness of 0.3 to 1.2 mm, carrying a guide groove by a pattern of crests and recesses, and a light transmitting layer 10 to 177 μm is layered thereon, 
 wherein 
 said information recording layer has a film of a phase change material formed of a phase change material containing at least one of binary alloys, such as InSe, SbSe or SbTe, ternary alloys, such as InSbSe, GeSbTe or InSbTe, quatanary alloys, such as GeSbTeSe or AgInSbTe, quinary alloys, such as AgInSbSeTe, nitrides and oxides of these alloys, wherein  
 a crystallization promoting film and an enhancement film are formed at least on the side of said supporting substrate or on the opposite side to the supporting substrate of said film of the phase change material, wherein  
 the information recording layer closest to said supporting substrate has a reflecting film allocated to an outermost side thereof towards the supporting substrate and also has a semi-transparent enhancement film allocated to an outermost side thereof opposite to said supporting substrate, and wherein  
 said reflective film is formed of a material containing one of an Al alloy, a BiSb alloy, an Ag alloy, Au, an Au alloy.  
 
 
     
     
         20 . The multi-layered optical disc according to  claim 16   wherein 
 said information recording layer closest to said supporting substrate is comprised of said reflecting film, enhancement film, film of the phase change material, crystallization promoting film, enhancement film and said semi-transparent enhancement film, layered sequentially looking from the supporting substrate side.  
   
     
     
         21 . The multi-layered optical disc according to  claim 17   wherein 
 said information recording layer closest to said supporting substrate is comprised of said reflecting film, enhancement film, film of the phase change material, crystallization promoting film, enhancement film and said semi-transparent enhancement film, layered sequentially looking from the supporting substrate side.  
   
     
     
         22 . The multi-layered optical disc according to  claim 18   wherein 
 said information recording layer closest to said supporting substrate is comprised of said reflecting film, enhancement film, film of the phase change material, crystallization promoting film, enhancement film and said semi-transparent enhancement film, layered sequentially looking from the supporting substrate side.  
   
     
     
         23 . The multi-layered optical disc according to  claim 19   wherein 
 said information recording layer closest to said supporting substrate is comprised of said reflecting film, enhancement film, film of the phase change material, crystallization promoting film, enhancement film and said semi-transparent enhancement film, layered sequentially looking from the supporting substrate side.  
   
     
     
         24 . The multi-layered optical disc according to  claim 16   wherein 
 said information recording layer closest to said supporting substrate is comprised of said reflecting film, enhancement film, crystallization promoting film, film of the phase change material, enhancement film and said semi-transparent enhancement film, layered sequentially looking from the supporting substrate side.  
   
     
     
         25 . The multi-layered optical disc according to  claim 17   wherein 
 said information recording layer closest to said supporting substrate is comprised of said reflecting film, enhancement film, crystallization promoting film, film of the phase change material, enhancement film and said semi-transparent enhancement film, layered sequentially looking from the supporting substrate side.  
   
     
     
         26 . The multi-layered optical disc according to  claim 18   wherein 
 said information recording layer closest to said supporting substrate is comprised of said reflecting film, enhancement film, crystallization promoting film, film of the phase change material, enhancement film and said semi-transparent enhancement film, layered sequentially looking from the supporting substrate side.  
   
     
     
         27 . The multi-layered optical disc according to  claim 19   wherein 
 said information recording layer closest to said supporting substrate is comprised of said reflecting film, enhancement film, crystallization promoting film, film of the phase change material, enhancement film and said semi-transparent enhancement film, layered sequentially looking from the supporting substrate side.  
   
     
     
         28 . The multi-layered optical disc according to  claim 16   wherein 
 said information recording layer closest to said supporting substrate is comprised of said reflecting film, enhancement film, crystallization promoting film, film of the phase change material, crystallization promoting film, enhancement film and said semi-transparent enhancement film, layered sequentially looking from the supporting substrate side.  
   
     
     
         29 . The multi-layered optical disc according to  claim 17   wherein 
 said information recording layer closest to said supporting substrate is comprised of said reflecting film, enhancement film, crystallization promoting film, film of the phase change material, crystallization promoting film, enhancement film and said semi-transparent enhancement film, layered sequentially looking from the supporting substrate side.  
   
     
     
         30 . The multi-layered optical disc according to  claim 18   wherein 
 said information recording layer closest to said supporting substrate is comprised of said reflecting film, enhancement film, crystallization promoting film, film of the phase change material, crystallization promoting film, enhancement film and said semi-transparent enhancement film, layered sequentially looking from the supporting substrate side.  
   
     
     
         31 . The multi-layered optical disc according to  claim 19   wherein 
 said information recording layer closest to said supporting substrate is comprised of said reflecting film, enhancement film, crystallization promoting film, film of the phase change material, crystallization promoting film, enhancement film and said semi-transparent enhancement film, layered sequentially looking from the supporting substrate side.