Multi-stack optical storage medium

A method of manufacturing a multi-stack optical storage medium in a disk format with at least one stack receiving a radiation beam through another stack, the method comprising acts of:

• providing a semi-transparent first substrate having a thickness within a range of 0.56 mm and 0.60 mm, an entrance face and a pre-grooved face on the opposite bottom side of the semi-transparent substrate from the entrance face, the entrance face is configured to receive a radiation beam having a wavelength (λ) less than or approximately equal to 655 nm;
• forming a higher recording layer having a thickness on groove greater than 28 nm and less than 115 nm and a variation of the thickness on groove between recorded and unrecorded areas within a first range by depositing an organic dye onto the pre-grooved face of the semi-transparent substrate by spin-coating, wherein the first range is 0.06λ to 0.08λ;
• applying a first metal reflector layer under the higher recording layer by sputtering;
• applying a spacer layer under the first metal reflector layer by applying a UV-curable lacquer to the first metal reflector layer by spin coating, the spacer layer having a thickness within a range of 0.03 mm and 0.07 mm;
• forming grooves in the UV-curable lacquer of the spacer layer, by pressing a stamper into the UV-curable lacquer, to replicate the grooves in the semi-transparent substrate;
• curing the UV-curable lacquer by exposing the UV-curable lacquer to UV;
• depositing a lower recording layer by depositing an organic dye onto the grooves of the spacer layer by spin-coating;
• applying a second metal reflector layer below the lower recording layer by sputtering, the second metal reflector layer is sufficiently thicker than the first metal reflector layer to reduce the wave front phase variation when a radiation beam traveling through the first metal reflector layer records data on the lower recording layer at the second metal reflector layer;
• and
• applying a second substrate to the second metal reflector layer,
• wherein the data is recorded on the higher recording layer through the entrance face alone and on the lower recording layer through the entrance face and through the higher recording layer without causing deterioration in optical properties of the radiation beam and the recorded areas on the lower recording layer.

A multi-stack optical storage medium in a disk format with at least one stack receiving a radiation beam through another stack, comprising:

• a semi-transparent first substrate having a thickness within a range of 0.56 mm and 0.60 mm, an entrance face and a pre-grooved face on the opposite bottom side of the semi-transparent first substrate from the entrance face the entrance face is configured to receive a radiation beam having a wavelength (λ) less than or approximately equal to 655 nm ;
• a higher recording layer of organic dye below the semi-transparent first substrate, the organic dye coating the grooves and having a thickness on groove greater than 28 nm and less than 115 nm and a variation of the thickness on groove between recorded and unrecorded areas within a first range of 0.06 λ to 0.08 λ;
• a first metal reflector layer below the higher recording layer;
• a spacer layer below the first metal reflector layer and having grooves on a bottom surface that replicate the grooves in the pre-grooved face of the semi-transparent first substrate, the spacer layer having a thickness within a range of 0.03 mm and 0.07 mm;
• a lower recording layer of organic dye below the spacer layer, the organic dye coating the grooves;
• a second metal reflector layer below the lower recording layer, the second metal reflector layer is sufficiently thicker than first metal reflector layer to reduce the wave front phase variation when a radiation beam traveling through the first metal reflector layer writes data on the second recording layer at the second metal reflector layer;
• and
• a second substrate to the second metal reflector layer,
• wherein the entrance face enables recording of data on the higher recording layer through the entrance face alone and on the lower recording layer through the entrance face and through the higher recording layer without causing deterioration in optical properties of the radiation beam and the recording areas on the lower recording layer.

A method of operating a multi-stack optical storage medium in a disk format with at least one stack receiving a radiation beam through another stack, comprising:

• providing a semi-transparent substrate with an entrance face and pre-grooved face on the opposite side of the semi-transparent substrate from the entrance face;
• providing a higher stack and a lower stack, separated by a spacer having a thickness within a range of 0.03 mm and 0.07 mm extending from the pre-grooved face of the semi-transparent substrate and including respective recording layers, the recording layer of the higher stack having a thickness on groove and a variation of thickness on groove between recorded and unrecorded areas equal to a first range of 0.06 λ to 0.08 λ;
• and
• receiving through the entrance face, the radiation beam having a wavelength (λ) less than or approximately equal to 655 nm and a wave front phase variation of within the first range for recording data on the recording layers, wherein data is recorded on the recording layer of the higher stack by the beam passing through the entrance face alone and on the recording layer of the lower stack by the beam passing through the entrance face and through the recording layer of the higher stack,
• wherein the recording layer of the higher stack comprises an organic dye material having:
• the thickness on groove greater than 28 nm and less than 115 nm.