Optical data storage medium and use of such medium

Abstract

A multi-stack optical data storage medium for recording and reading using a focused radiation beam entering through an entrance face of the medium has a first substrate with a first guide groove having a depth G L0 <80 nm and a full half maximum width W L0 <350 nm, where a first recording stack is formed over the first substrate and includes a recordable type recording layer formed in the first guide groove. A first reflective layer is present between the first recording layer and the first substrate. A second recording stack has a recordable type recording layer formed a second guide groove of a second substrate, where the second recording stack is present at a position closer to the entrance face than the first recording stack. A transparent spacer layer is sandwiched between the first and second recording stacks. The first L 0 guide groove has a depth G L0 <100 nm.

1 . A multi-stack optical data storage medium with two recording stacks separated by a transparent spacer layer for recording and reading using a focused radiation beam entering through an entrance face of the medium during recording and reading, comprising:
 a first substrate located on a side farthest from the entrance face, the first substrate having a first guide groove formed on a substrate surface facing the entrance face;   a second substrate located on a side nearest to the entrance face, the second substrate having a second guide groove formed on a substrate surface facing away from the entrance face;   a first reflective layer located on the first guide groove;   a first recording layer formed on the first reflective layer;   a dielectric layer located over the first recording layer;   the transparent spacer layer located over the dielectric layer;   a second reflective layer located on the second guide groove;   a second recording layer formed in the second guide groove and located on the second reflective layer,   wherein the transparent spacer layer separating the two recording stacks including the first and second recording layers is directly between the dielectric layer and the second reflective layer.   
     
     
         2 . The multi-stack optical data storage medium of  claim 1 , wherein the first guide groove has a depth G L0 <19 nm and a full half maximum width W L0 <350 nm. 
     
     
         3 . The multi-stack optical data storage medium of  claim 1 , wherein the dielectric layer located over the first recording layer has a thickness between 5 to 19 nm. 
     
     
         4 . The multi-stack optical data storage medium of  claim 1 , wherein the first guide groove has a depth G L0 <100 nm, the first recording layer comprises a dye and has a thickness & between 70 nm and 150 nm on land portion of the first guide groove, and a parameter L defined as L=(d G −d L )/G is between 0.2 and 0.5, d G  being a thickness of the dye on a groove portion of the first guide groove, and G is a groove depth of the groove portion. 
     
     
         5 . The multi-stack optical data storage medium of  claim 1 , wherein the second reflective layer has a thickness between 5 to 13 nm. 
     
     
         6 . The multi-stack optical data storage medium of  claim 1 , wherein the second reflective layer mainly comprises a metal selected from the group of Ag, Au, Cu, Al. 
     
     
         7 . The multi-stack optical data storage medium of  claim 1 , wherein the effective reflection level of the stacks is at least 0.18 at a radiation beam wavelength of approximately 655 nm. 
     
     
         8 . The multi-stack optical data storage medium of  claim 1 , wherein the multi-stack optical data storage medium has a modulation M of 75% and a reflection level of 70%, and wherein the modulation is M=(R no-mark −R mark )/R no-mark , R mark  and R no-mark  being reflection levels from a read out laser beam when respectively a written mark and no mark are present. 
     
     
         9 . The multi-stack optical data storage medium of  claim 1 , wherein a thickness of the transparent spacer layer is between 40 μm to 70 μm. 
     
     
         10 . The multi-stack optical data storage medium of  claim 1 , further comprising a third recording stack formed over the second recording stack, wherein the third recording stack includes a third guide groove in the first substrate, the third guide groove having a thickness from 25 nm to 40 nm, a dye layer formed over the third guide groove and having a thickness from 90 nm to 160 nm, and a third reflective layer formed over the dye layer and having a thickness of 100 nm. 
     
     
         11 . A multi-stack optical data storage medium for recording and reading using a focused radiation beam entering through an entrance face of the medium during recording and reading, comprising:
 a first substrate located on a side farthest from the entrance face, the first substrate having a first guide groove formed on a substrate surface facing the entrance face;   a second substrate located on a side nearest to the entrance face, the second substrate having a second guide groove formed on a substrate surface facing away from the entrance face;   a first reflective layer located on the first guide groove;   a first recording layer formed on the first reflective layer;   a dielectric layer located over the first recording layer;   a transparent spacer layer located over the dielectric layer;   a second reflective layer located on the second guide groove;   a second recording layer formed in the second guide groove and located on the second reflective layer,   wherein the first guide groove has a depth G L0 <19 nm and a full half maximum width W L0 <350 nm.   
     
     
         12 . The multi-stack optical data storage medium of  claim 11 , wherein the dielectric layer located over the first recording layer has a thickness between 5 to 19 nm. 
     
     
         13 . The multi-stack optical data storage medium of  claim 11 , wherein the first guide groove has a depth G L0 <100 nm, the first recording layer comprises a dye and has a thickness & between 70 nm and 150 nm on land portion of the first guide groove, and a parameter L defined as L=(d G −d L )/G is between 0.2 and 0.5, d G  being a thickness of the dye on a groove portion of the first guide groove, and G is a groove depth of the groove portion. 
     
     
         14 . The multi-stack optical data storage medium of  claim 11 , wherein the second reflective layer has a thickness between 5 to 13 nm. 
     
     
         15 . A multi-stack optical data storage medium for recording and reading using a focused radiation beam having a wavelength of 655 nm entering through an entrance face of the medium during recording and reading, comprising:
 a first substrate having, on a side thereof, a first recording stack comprising a first recording layer comprising a dye, and formed in a first guide groove, and a first reflective layer present between the recording layer and the first substrate;   a second substrate having, on a side thereof, a second recording stack comprising a second recording layer, said second recording stack being at a position closer to the entrance face than the recording stack and being formed in a second guide groove;   a transparent spacer layer sandwiched between the first and second recording stacks; and   a dielectric layer present at a side of the recording layer opposite from the side where the first reflective layer is present,   wherein the dielectric layer has a thickness in the range of 5 nm to 19 nm.   
     
     
         16 . The multi-stack optical data storage medium of  claim 15 , wherein the first guide groove has a depth G L0 <19 nm and a full half maximum width W L0 <350 nm. 
     
     
         17 . The multi-stack optical data storage medium of  claim 15 , wherein the first guide groove has a depth G L0 <100 nm, the first recording layer has a thickness & between 70 nm and 150 nm on land portion of the first guide groove, and a parameter L defined as L=(d G −d L )/G is between 0.2 and 0.5, d G  being a thickness of the dye on a groove portion of the first guide groove, and G is a groove depth of the groove portion. 
     
     
         18 . The multi-stack optical data storage medium of  claim 15 , further comprising a second reflective layer having a thickness between 5 to 13 nm and being located on the second guide groove formed on a substrate surface of the second substrate, the substrate surface facing away from the entrance face. 
     
     
         19 . The multi-stack optical data storage medium of  claim 18 , further comprising a third recording stack formed over the second recording stack, wherein the third recording stack includes a third guide groove in the first substrate, the third guide groove having a thickness from 25 nm to 40 nm, a dye layer formed over the third guide groove and having a thickness from 90 nm to 160 nm, and a third reflective layer formed over the dye layer and having a thickness of 100 nm. 
     
     
         20 . The multi-stack optical data storage medium of  claim 15 , wherein a thickness of the transparent spacer layer is between 40 μm to 70 μm.