Multilayer optical recording medium
View Patent ↗The multilayer optical recording medium with six or more recording and reading layers disposed one above the other has at least two or more recording and reading layer groups. The recording and reading layer groups each include a plurality of recording and reading layers successively disposed one above the other. The reflectance of each of the recording and reading layers in a stacked state decreases in the order from a front side near a light incident surface toward a back side far from the light incident surface. A recording and reading layer nearest the front side among the recording and reading layers in the recording and reading layer group nearer the back side has a reflectance in a stacked state higher than that of a recording and reading layer nearest the back side among the recording and reading layers in the recording and reading layer group nearer the front side.
1. A multilayer optical recording medium with at least six or more recording and reading layers disposed one above the other with intermediate layers interposed therebetween, wherein information can be read by light irradiation,
the multilayer optical recording medium comprising at least two or more recording and reading layer groups each including the plurality of recording and reading layers successively disposed one above the other in an order in which the layers are stacked so that reflectance of each of the recording and reading layers in a stacked state in each of the groups decreases in the order from a front side near a light incident surface toward a back side far from the light incident surface, wherein
regarding the recording and reading layer groups adjacent to each other with any of the intermediate layers interposed therebetween, a recording and reading layer nearest the front side among the recording and reading layers in the recording and reading layer group nearer the back side has a reflectance in a stacked state higher than that of a recording and reading layer nearest the back side among the recording and reading layers in the recording and reading layer group nearer the front side.
2. The multilayer optical recording medium according to claim 1 , wherein the intermediate layer disposed between the adjacent recording and reading layer groups has a film thickness greater than those of two intermediate layers that are adjacent to recording and reading layers disposed on both sides of the intermediate layer between the two groups.
3. The multilayer optical recording medium according to claim 1 , wherein a plurality of film thicknesses are set for the intermediate layers, and
the intermediate layer disposed between the adjacent recording and reading layer groups has a maximum film thickness of the plurality of film thicknesses.
4. The multilayer optical recording medium according to claim 1 , wherein the intermediate layers disposed in the recording and reading layer groups have substantially the same film thickness in each of the recording and reading layer groups.
5. The multilayer optical recording medium according to claim 3 , wherein the intermediate layers disposed in the recording and reading layer groups have substantially the same film thickness in each of the recording and reading layer groups.
6. The multilayer optical recording medium according to claim 1 , wherein the intermediate layers include a first intermediate layer having a first film thickness and a second intermediate layer having a second film thickness greater than the first film thickness, the first and second intermediate layers being alternately disposed one above the other with the recording and reading layer interposed therebetween.
7. The multilayer optical recording medium according to claim 3 , wherein the intermediate layers include a first intermediate layer having a first film thickness and a second intermediate layer having a second film thickness greater than the first film thickness, the first and second intermediate layers being alternately disposed one above the other with the recording and reading layer interposed therebetween.
8. The multilayer optical recording medium according to claim 4 , wherein the intermediate layers include a first intermediate layer having a first film thickness and a second intermediate layer having a second film thickness greater than the first film thickness, the first and second intermediate layers being alternately disposed one above the other with the recording and reading layer interposed therebetween.
9. The multilayer optical recording medium according to claim 6 , wherein the second intermediate layer is disposed between the adjacent recording and reading layer groups.
10. The multilayer optical recording medium according to claim 1 , comprising three or more of the recording and reading layer groups, and wherein
the recording and reading layer group(s) except the recording and reading layer group nearest the front side and the recording and reading layer group nearest the back side has(have) an even number of the recording and reading layers.
11. The multilayer optical recording medium according to claim 3 , comprising three or more of the recording and reading layer groups, and wherein
the recording and reading layer group(s) except the recording and reading layer group nearest the front side and the recording and reading layer group nearest the back side has(have) an even number of the recording and reading layers.
12. The multilayer optical recording medium according to claim 4 , comprising three or more of the recording and reading layer groups, and wherein
the recording and reading layer group(s) except the recording and reading layer group nearest the front side and the recording and reading layer group nearest the back side has(have) an even number of the recording and reading layers.
13. The multilayer optical recording medium according to claim 1 , comprising two of the recording and reading layer groups.
14. The multilayer optical recording medium according to claim 3 , comprising two of the recording and reading layer groups.
15. The multilayer optical recording medium according to claim 4 , comprising two of the recording and reading layer groups.
16. The multilayer optical recording medium according to claim 1 , wherein at least one of the recording and reading layer groups includes four or more of the recording and reading layers.
17. The multilayer optical recording medium according to claim 3 , wherein at least one of the recording and reading layer groups includes four or more of the recording and reading layers.
18. The multilayer optical recording medium according to claim 1 , wherein the number of the recording and reading layers forming the farthest one of the recording and reading layer groups from the light incident surface is four or smaller.
19. The multilayer optical recording medium according to claim 3 , wherein the number of the recording and reading layers forming the farthest one of the recording and reading layer groups from the light incident surface is four or smaller.
20. The multilayer optical recording medium according to claim 1 , comprising at least eight or more of the recording and reading layers.