US20120201992A1 - Optical information recording medium - Google Patents

Optical information recording medium Download PDF

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Publication number
US20120201992A1
US20120201992A1 US13/355,807 US201213355807A US2012201992A1 US 20120201992 A1 US20120201992 A1 US 20120201992A1 US 201213355807 A US201213355807 A US 201213355807A US 2012201992 A1 US2012201992 A1 US 2012201992A1
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layer
protective layer
oxide
information signal
optical information
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Hiroshi Tabata
Takeshi Miki
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Sony Corp
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Sony Corp
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Publication of US20120201992A1 publication Critical patent/US20120201992A1/en
Priority to US14/101,959 priority Critical patent/US8865286B2/en
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    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/2403—Layers; Shape, structure or physical properties thereof
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
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    • Y10T428/00—Stock material or miscellaneous articles
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Definitions

  • the present disclosure relates to an optical information recording medium. More specifically, the present disclosure relates to an optical information recording medium having two or more information signal layers.
  • CDs Compact Discs
  • DVDs Digital Versatile Discs
  • Mass storage optical information recording media for blue lasers such as BD (Blu-ray Disc (registered trademark)) have been developed to meet such a demand and the market for new, mass storage optical information recording media is continuing to grow.
  • optical information recording media there are rewritable optical information recording media as represented by CD-RW (Compact Disc-ReWritable), and DVD ⁇ RW (Digital Versatile Disc ⁇ ReWritable), as well as write-once optical information recording media as represented by CD-R (Compact Disc-Recordable), and DVD-R (Digital Versatile Disc-Recordable).
  • CD-RW Compact Disc-ReWritable
  • DVD ⁇ RW Digital Versatile Disc ⁇ ReWritable
  • write-once optical information recording media as represented by CD-R (Compact Disc-Recordable), and DVD-R (Digital Versatile Disc-Recordable).
  • optical information recording media is high compared to hard disk drives (HDD), flash memory and the like due to the recording and reproduction principles thereof, with the result that in recent years such media have been in more and more demand as archival media such as those which are beginning to be used to store important information.
  • HDD hard disk drives
  • an optical information recording medium having an inorganic recording layer including Pd and O is proposed.
  • an optical information recording medium, which is provided with a protective layer of a mixture (ITO) of indium oxide and tin oxide as a main component on at least one surface of the inorganic recording layer including Pd and O in order to achieve both storage reliability and good productivity is proposed.
  • an optical information recording medium including: a substrate; two or more information signal layers provided on the substrate; and a cover layer provided on the information signal layers, in which at least one layer out of the two or more information signal layers is provided with an inorganic recording layer including Pd oxide, a first protective layer provided on a first main surface of the inorganic recording layer, and a second protective layer provided on a second main surface of the inorganic recording layer, and in which at least one of the first protective layer and the second protective layer includes a compound oxide of Si oxide, In oxide, and Zr oxide as a main component.
  • an optical information recording medium recording layer that including: a substrate; two or more information signal layers provided on the substrate; and a cover layer provided on the information signal layers, in which at least one layer out of the two or more information signal layers is provided with an inorganic recording layer including Pd oxide, a first protective layer provided on a first main surface of the inorganic recording layer, and a second protective layer provided on a second main surface of the inorganic recording layer, and in which at least one of the first protective layer and the second protective layer includes a compound oxide of In oxide, Ga oxide, and Zn oxide as a main component.
  • the thickness of the cover layer is not particularly limited, and the cover layer includes the substrate, a sheet, the coating layer and the like.
  • a preferable high-density optical information recording medium there is one having a configuration in which, with the use of a high NA objective lens, a thin light transmissive layer such as a sheet or a coating layer is adopted as a cover layer, and the recording and reproduction of information signals is performed by irradiating light from the side of the light transmissive layer. In such a case, it is possible to adopt an opaque substrate as the substrate.
  • the light incidence plane for recording and reproducing the information signal is appropriately set to at least one surface of the cover layer side and the substrate side according to the format of the optical information recording medium.
  • the inorganic recording layer preferably includes W oxide, Pd oxide and Cu oxide as a main component and even more preferably includes Zn oxide in addition to these oxides.
  • one surface of either the substrate side or the cover layer side is preferably a light irradiation plane on which light for recording or reproducing an information signal on two or more information signal layers is irradiated.
  • the layer out of the first protective layer and the second protective layer which is on the opposite side to the light irradiation plane, include a compound oxide of Si oxide, In oxide, and Zr oxide, and it is preferable that both of the first protective layer and the second protective layer include a compound oxide of Si oxide, In oxide and Zr oxide as a main component.
  • At least one layer out of the information signal layers other than the information signal layer furthest to the back from the light irradiation plane is an information signal layer in which at least one of the first protective layer and the second protective layer includes a compound oxide of Si oxide, In oxide and Zr oxide as a main component.
  • the inorganic recording layer of the information signal layer which is closest to the light irradiation plane out of the two or more information signal layers is an information signal layer in which at least one of the first protective layer and the second protective layer includes a compound oxide of Si oxide, In oxide and Zr oxide as a main component.
  • the layer out of the first protective layer and the second protective layer which is the opposite side to the light irradiation plane include a compound oxide of In oxide, Ga oxide and Zn oxide and it is preferable that both the first protective layer and the second protective layer include a compound oxide of In oxide, Ga oxide, and Zn oxide as a main component.
  • At least one layer out of the information signal layers other than the information signal layer furthest to the back from the light irradiation plane be an information signal layer in which at least one of the first protective layer and the second protective layer includes a compound oxide of In oxide, Ga oxide and Zn oxide as a main component.
  • the inorganic recording layer of the information signal layer which is closest to the light irradiation plane out of the two or more information signal layers be an information signal layer in which at least one of the first protective layer and the second protective layer includes a compound oxide of In oxide, Ga oxide and Zn oxide as a main component.
  • FIG. 1A is a schematic cross-sectional view showing an example configuration of an optical information recording medium according to one embodiment of the present disclosure
  • FIG. 1B is a schematic diagram showing a configuration example of each information signal layer shown in FIG. 1A .
  • FIG. 2A is a graph showing the power margin of the optical information recording medium in Test Example 1-1 and FIG. 2B is a graph showing the power margin of the optical information recording medium in Test Example 1-2.
  • FIG. 3 is a graph showing the power margin of the optical information recording medium in Test Example 1-3.
  • FIG. 4A is a graph showing the power margin of the optical information recording medium in Test Example 1-4 and FIG. 4B is a graph showing the power margin of the optical information recording medium in Test Example 1-5.
  • FIG. 5 is a graph showing the power margin of the optical information recording medium in Test Example 2.
  • FIG. 6 is a graph showing the power margin of the optical information recording media in Test Examples 3-3 to 3-4.
  • FIG. 7A is a graph showing the relationship between the variable x and the transmittance in the optical information recording media of Test Examples 4-1 to 4-13 and FIG. 7B is a graph showing the relationship between the transmittance and the optimal recording power Pwo in the optical information recording media of Test Examples 4-1 to 4-13.
  • FIG. 8 is a graph showing the composition ratio of the inorganic recording layer in the optical information recording media of Test Examples 4-1 to 4-13.
  • FIG. 9A is a graph showing the relationship between the i-MLSE of the L 0 layer and the reflectance of the L 0 layer in the optical information recording media of Test Examples 5-1 to 5-12
  • FIG. 9B is a graph showing the relationship between the reflectance of the L 1 layer and the reflectance of the L 0 layer in the optical information recording media of Test Examples 5-13 to 5-24
  • FIG. 9C is a graph showing the relationship between the transmittance of the L 1 layer and the i-MLSE of the L 0 layer in the optical information recording media of Test Examples 6-1 to 6-9.
  • FIG. 1A is a schematic cross-sectional view showing an example configuration of an optical information recording medium according to one embodiment of the present disclosure.
  • the optical information recording medium 10 is a so-called write-once optical information recording medium, and, as shown in FIG. 1A , has a configuration in which an information signal layer L 0 , an intermediate layer S 1 , an information signal layer L 1 , an intermediate layer S 2 , an information signal layer L 2 , an intermediate layer S 3 , an information signal layer L 3 , and a light transmissive layer 2 which is a cover layer are laminated in such an order on the main surface of the substrate 1 .
  • a hard coat layer 3 may further be provided on the surface of the light transmissive layer 2 .
  • a barrier layer 4 may further be provided on the surface of the substrate 1 side.
  • information signal layer L is used where no particular distinction is made between the information signal layers L 0 to L 3 .
  • recording and reproduction of the information signal is performed by irradiating the laser beam from the surface C of the light transmissive layer 2 side to each of the information signal layers L 0 to L 3 .
  • recording and reproduction of the information signal is performed by condensing a laser beam having a wavelength range of 400 nm to 410 nm with an objective lens having a numerical aperture range of 0.84 to 0.86, and irradiating the laser beam from the side of the light transmissive layer 2 to each of the information signal layers L 0 to L 3 .
  • BD-R may be exemplified.
  • the surface C which is irradiated by the laser beam for recording or reproducing the information signal on the information signal layers L 0 to L 3 is called the light irradiation plane C.
  • the substrate 1 the information signal layers L 0 to L 3 , intermediate layers S 1 to S 3 , light transmissive layer 2 , hard coat layer 3 , and barrier layer 4 configuring the optical information recording medium 10 will be described in order.
  • the substrate 1 for example, has a circular shape in which an opening is formed in the center (hereinafter, called the center hole).
  • the main surface of the substrate 1 for example, is concavo-convex, and the information signal layer L 0 is deposited on such a concavo-convex surface.
  • concavo-convex surface concave portions are referred to as in-grooves Gin and convex portions are referred to as on-grooves Gon.
  • the shape of the in-groove Gin and the on-groove Gon for example, various shapes may be exemplified such as spiral shapes and concentric circles. Further, the in-grooves Gin and/or the on-grooves Gon, for example, are made to wobble (meander) in order to add linear velocity stability and address information.
  • the diameter of the substrate 1 may be selected as 120 mm for example.
  • the thickness of the substrate 1 is selected while taking the stiffness into account and is preferably 0.3 mm to 1.3 mm, more preferably 0.6 mm to 1.3 mm; for example, 1.1 mm may be selected. Further, the diameter of the center hole may be selected as 15 mm, for example.
  • a plastic material or glass may be used, and, from a cost standpoint, it is preferable to use a plastic material.
  • a plastic material for example, polycarbonate resins, polyolefin resins, acrylic resins, or the like may be used.
  • FIG. 1B is a schematic diagram showing a configuration example of each information signal layer shown in FIG. 1A .
  • the information signal layers L 0 to L 3 are provided with an inorganic recording layer 11 having an upper side surface (second main surface) and a lower side surface (first main surface), a first protective layer 12 provided adjacently to the lower side surface of the inorganic recording layer 11 , and a second protective layer 13 provided adjacently to the upper side surface of the inorganic recording layer 11 .
  • an inorganic recording layer 11 having an upper side surface (second main surface) and a lower side surface (first main surface)
  • first protective layer 12 provided adjacently to the lower side surface of the inorganic recording layer 11
  • a second protective layer 13 provided adjacently to the upper side surface of the inorganic recording layer 11 .
  • the upper side surface refers to the main surface irradiated with a laser beam for recording or reproducing an information signal and the lower side surface refers to the main surface opposite to the side irradiated with the above-described laser beam, that is, the main surface of the substrate side.
  • the main component of the inorganic recording layer 11 is preferably an inorganic recording material including Pd oxide (hereinafter referred to as “PdO-based material”).
  • PdO-based materials for example, it is possible to use a material having a main component having a two-elemental compound oxide of In oxide and Pd oxide; however, the use of a three-elemental compound oxide of W oxide, Pd oxide and Cu oxide (hereinafter referred to as “WCPO”) is preferable and the use of a four-elemental compound oxide in which Zn oxide is further added to the WCPO (hereinafter referred to as “WZCPO”) is more preferable.
  • WCPO three-elemental compound oxide of W oxide, Pd oxide and Cu oxide
  • WZCPO four-elemental compound oxide in which Zn oxide is further added to the WCPO
  • WCPO As the PdO-based materials, it is possible to achieve excellent transmission characteristics while satisfying the characteristics asked for the recording layer of the optical information recording medium.
  • WZCPO As the PdO-based materials, it is possible to achieve excellent transmission characteristics while satisfying the characteristics asked for the recording layer of the optical information recording medium and it is possible to reduce the content of W oxide, Pd oxide, and Cu oxide. By reducing the content of W oxide, Pd oxide, and Cu oxide, in particular, Pd oxide, it is possible to reduce the cost of the optical information recording medium 10 .
  • At least one layer of the inorganic recording layer 11 among the information signal layers L 1 to L 3 other than the information signal layer L 0 furthest to the back from the light irradiation plane C include WCPO as a main component.
  • the ratio of W, Pd, and Cu included in the WCPO preferably satisfies the relationship 0.17 ⁇ x 1 , more preferably 0.37 ⁇ x 1 , still more preferably 0.37 ⁇ x 1 ⁇ 1.26, and most preferably 0.56 ⁇ x 1 ⁇ 1.26.
  • the characteristics asked for the information signal layer of the optical information recording medium are, for example, low i-MLSE, wide power margin, high reproduction durability, suppression of changes in transmittance after recording, and the like.
  • the inorganic recording layers 11 of the information signal layers L 0 to L 3 include WCPO as a main component.
  • the ratio of the W, the Pd, and the Cu that are included in the WCPO preferably satisfies the relationship 0.17 ⁇ x 1 , more preferably satisfies the relationship 0.37 ⁇ x 1 , still more preferably satisfies the relationship 0.37 ⁇ x 1 ⁇ 1.26, and most preferably satisfies the relationship 0.56 ⁇ x 1 ⁇ 1.26.
  • the value of the variable x 1 of the inorganic recording layer 11 of the information signal layers L 0 to L 3 is preferably a value as great as that of the information signal layer L close to the light irradiation plane C. The reason is that it is preferable to set the transmittance to be as high as the information signal layer L close to the light irradiation plane C.
  • the atomic ratio a of W with respect to the total of W, Pd, and Cu is preferably within a range between 10 atomic % and 70 atomic %, and more preferably within a range between 14.2 atomic % and 31.8 atomic %. If the atomic ratio a is less than 10 atomic %, the transmittance tends to be low. On the other hand, if the atomic ratio a exceeds 70 atomic %, the transmittance is high but the recording sensitivity tends to be insufficient.
  • the atomic ratio b of Pd with respect to the total of the W, the Pd, and the Cu is preferably within a range between 2 atomic % and 50 atomic %, and more preferably within a range between 4.4 atomic % and 32.2 atomic %. If the atomic ratio b is less than 2 atomic %, the recording power margin tends to become narrow. On the other hand, if the atomic ratio b exceeds 50 atomic %, the transmittance tends to be low.
  • the atomic ratio c of Cu with respect to the total of the W, the Pd, and the Cu is preferably within a range between 10% atomic % and 70% atomic %, and more preferably within a range between 28.5 atomic % and 68.1 atomic %. If the atomic ratio c is less than 10 atomic %, the reproduction durability tends to decrease. On the other hand, if the atomic ratio c exceeds 70 atomic %, the transmittance tends to be low.
  • the inorganic recording layer 11 of at least one layer out of the information signal layers L 1 to L 3 other than the information signal layer L 0 that is furthest to the back of the light irradiation plane C include WZCPO, in which Zn oxide is added to WCPO, as a main component.
  • the ratio of the W, the Pd, the Cu, and the Zn that are included in the WZCPO preferably satisfies the relationship 0.17 ⁇ x 2 , more preferably satisfies the relationship 0.37 ⁇ x 2 , still more preferably satisfies the relationship 0.37 ⁇ x 2 ⁇ 1.26, and most preferably satisfies the relationship 0.56 ⁇ x 2 ⁇ 1.26.
  • d atomic ratio (atomic %) of Zn with respect to the total of W, Pd, Cu, and Zn
  • the inorganic recording layers 11 of the information signal layers L 0 to L 3 include WZCPO as a main component.
  • the ratio of the W, the Pd, and the Cu that are included in the WZCPO preferably satisfies the relationship 0.17 ⁇ x 2 , more preferably satisfies the relationship 0.37 ⁇ x 2 , still more preferably satisfies the relationship 0.37 ⁇ x 2 ⁇ 1.26, and most preferably satisfies the relationship 0.56 ⁇ x 2 ⁇ 1.26.
  • the value of the variable x 2 of the inorganic recording layer 11 of the information signal layers L 0 to L 4 is preferably a value as great as that of the information signal layer L close to the light irradiation plane C. The reason is that it is possible to increase the transmittance to be as high as the information signal layer L close to the light irradiation plane C.
  • the atomic ratio a of W with respect to the total of W, Pd, Cu, and Zn is preferably within a range between 10 atomic % and 70 atomic %, and more preferably within a range between 14.2 atomic % and 31.8 atomic %. If the atomic ratio a is less than 10 atomic %, the transmittance tends to be low. On the other hand, if the atomic ratio a exceeds 70 atomic %, the recording sensitivity tends to be insufficient.
  • the atomic ratio b of Pd with respect to the total of the W, the Pd, the Cu, and the Zn is preferably within a range between 2 atomic % and 50 atomic %, and more preferably within a range between 4.4 atomic % and 32.2 atomic %. If the atomic ratio b is less than 2 atomic %, the recording power margin tends to become narrow. On the other hand, if the atomic ratio b exceeds 50 atomic %, the transmittance tends to be low.
  • the atomic ratio c of Cu with respect to the total of the W, the Pd, the Cu, and the Zn is preferably within a range between 10% and 70%, and more preferably within a range between 28.5 atomic % and 43.4 atomic %. If the atomic ratio c is less than 10 atomic %, the reproduction durability tends to weaken. On the other hand, if the atomic ratio c exceeds 70 atomic %, the transmittance tends to be low.
  • the atomic ratio d of Zn with respect to the total of the W, the Pd, the Cu, and the Zn is preferably within a range between 5% and 60%, and more preferably within a range between 17 atomic % and 41 atomic %. If the atomic ratio d is less than 5 atomic %, the cost reducing effect tends to weaken. On the other hand, if the atomic ratio d exceeds 60 atomic %, there is a tendency for storage reliability to deteriorate.
  • the material of the information signal layers L 1 to L 3 other than WCPO or WZCPO for example, it is also possible to use a material in which the main component is a mixed oxide of In oxide and Pd oxide. However, from the viewpoint of achieving excellent transmission characteristics while satisfying the characteristics asked for the information signal layer of the optical information recording medium, it is preferable to use WCPO or WZCPO.
  • the material of the information signal layer L 0 furthest to the back from the light irradiation plane C for example, it is also possible to use a material in which the main component is a mixed oxide of In oxide and Pd oxide. However, from the viewpoint of a wide recording power margin, it is preferable to use the above-described WCPO or WZCPO.
  • the thickness of the inorganic recording layer 11 is preferably within a range of 25 nm to 60 nm, and more preferably 30 nm to 50 nm. If the thickness is less than 25 nm, there is a tendency for the i-MLSE to deteriorate, the modulation rate to be low and the signal properties to deteriorate. On the other hand, if the thickness exceeds 60 nm, the recording power margin tends to become narrow.
  • dielectric layers or transparent conductive layers as the first protective layer 12 and the second protective layer 13 , and it is possible to use a dielectric layer for one of the first protective layer 12 and the second protective layer 13 and a transparent conductive layer for the other. Because the dielectric layers or the transparent conductive layers function as oxygen barrier layers, it is possible to improve the durability of the inorganic recording layers 11 . Further, by suppressing oxygen from escaping from the inorganic recording layers 11 , it is possible to suppress changes (particularly observable as a decrease in the reflectance) in the film quality of the recording film, and it is possible to secure the necessary characteristics of the inorganic recording layers 11 . Furthermore, by providing dielectric layers or transparent conductive layers, it is possible to improve the recording properties.
  • At least one of the first protective layer 12 and the second protective layer 13 include as a main component the three-elemental compound oxides of Si oxide, In oxide, and Zr oxide (SiO 2 —In 2 O 3 —ZrO 2 is below referred to as “SIZ”) as a compound oxide, or the three elemental oxides of In oxide, Ga oxide, and Zn oxide (In 2 O 3 —Ga 2 O 3 —ZnO is below referred to as “IGZO”). In such a manner, it is possible to obtain a favorable power margin.
  • both the first protective layer 12 and the second protective layer 13 may include SIZ or IGZO as a main component; however, without being limited to this example, one of the first protective layer 12 and the second protective layer 13 may include SIZ as a main component and the other may include IGZO as a main component.
  • the inorganic recording layer 11 it is preferable that, as the inorganic recording layer 11 , a layer including WCPO as a main component be adopted and more preferable that a layer including WZCPO, in which Zn oxide is added to WCPO, as a main component be adopted.
  • a more favorable power margin may be obtained compared to a case where the inorganic recording layer 11 has a PdO-based material other than WCPO or WZCPO as a main component.
  • the inorganic recording layer 11 has WZCPO as a main component, it is possible to further obtain the advantage that the optical information recording medium 10 is reduced in cost.
  • the reason for this is that, by making the WCPO further include Zn oxide, it is possible to thin the entirety of the WZCPO with the Zn oxide, and, as a result, decrease the content of Pd, which is a precious metal material.
  • At least one layer out of the information signal layers L 1 to L 3 other than the information signal layer L 0 that is furthest to the back of the light irradiation plane C it is preferable that at least one layer of the first protective layer 12 and the second protective layer 13 adopt a configuration that has SIZ or IGZO as a main component and more preferable that both layers of the first protective layer 12 and the second protective layer 13 adopt a configuration that has SIZ or IGZO as a main component.
  • the high transmittance may be maintained and it is possible to increase the light quantity of laser beam that reaches the information signal layer L 0 .
  • At least one layer of the first protective layer 12 and the second protective layer 13 adopt a configuration that has SIZ or IGZO as a main component and more preferable that both layers of the first protective layer 12 and the second protective layer 13 adopt a configuration that has SIZ or IGZO as a main component.
  • At least one layer of the first protective layer 12 and the second protective layer 13 of the information signal layer L 3 preferably has SIZ or IGZO with a low extinction coefficient as a main component and, more preferably, both layers have SIZ or IGZO as a main component.
  • the reason for maintaining the transmittance of the information signal layer L 3 closest to the light irradiation plane C in the information signal layers L 1 to L 3 as high as possible is that, generally, in the balancing of the transmittance and the recording sensitivity which is inversely proportional thereto, when a single layer of the information signal layer L 3 is set with a high transmittance and a low recording sensitivity, for a multi-layer layered medium, which is configured by a combination such that the transmittance is set as low as that of the information signal layer far from the light irradiation plane C of one side and the sensitivity of a single layer is high, it is possible to approximately fix the recording sensitivity of each layer set as a multi-layer medium by combining transmittance and sensitivity.
  • both the first protective layer 12 and the second protective layer 13 include SIZ or IGZO as the main component.
  • SIZ or IGZO is set as the main component of one of the first protective layer 12 and the second protective layer 13
  • the first protective layer 12 provided on the lower side surface of the inorganic recording layer 11 have SIZ or IGZO as the main component.
  • SIZ or IGZO as the main component in the first protective layer 12 provided on the lower side surface of the inorganic recording layer 11 , it is possible to further increase the power margin in comparison to a case in which SIZ or IGZO is included as the main component in the first protective layer 12 provided on the upper side surface of the inorganic recording layer 11 .
  • oxides for example, one or more oxides of chemical elements selected from the group consisting of In, Zn, Sn, Al, Si, Ge, Ti, Ga, Ta, Nb, Hf, Zr, Cr, Bi, and Mg may be exemplified.
  • nitrides for example, one or more nitrides of chemical elements selected from the group consisting of In, Sn, Ge, Cr, Si, Al, Nb, Mo, Ti, Nb, Mo, Ti, W, Ta, and Zn, preferably, one or more nitrides of chemical elements selected from the group consisting of Si, Ge and Ti, may be exemplified.
  • sulfides for example, Zn sulfide may be exemplified.
  • carbides for example, one or more carbides of chemical elements selected from the group consisting of In, Sn, Ge, Cr, Si, Al, Ti, Zr, Ta, and W, preferably, one or more carbides of chemical elements selected from the group consisting of Si, Ti and W, may be exemplified.
  • fluorides for example, one or more fluorides of chemical elements selected from the group consisting of Si, Al, Mg, Ca and La may be exemplified.
  • ZnS—SiO 2 , SiO 2 —Cr 2 O 3 —ZrO 2 (SCZ), In 2 O 3 —SnO 2 (ITO), In 2 O 3 —CeO 2 (ICO), In 2 O 3 —Ga 2 O 3 (ITO), Sn 2 O 3 —Ta 2 O 5 (TTO), TiO 2 —SiO 2 , and the like may be exemplified.
  • the first protective layer 12 and the second protective layer 13 be included as the main component of one of the first protective layer 12 and the second protective layer 13 and that ITO be included in the other and it is more preferable that the first protective layer 12 include ITO as a main component and the second protective layer 13 include SIZ or IGZO as a main component.
  • the first protective layer 12 include ITO as a main component
  • the second protective layer 13 include SIZ or IGZO as a main component.
  • layers other than the innermost layer are information signal layers for transmission and the balance between high transmittance and transmittance variance after recording may be achieved according to the desired characteristics of each layer.
  • the In oxide content in SIZ may be 20 mol % or more, and from the viewpoint of storage reliability, is preferably 70 mol % or less. Further, in order that the SI oxide and the Zr oxide function as a compound oxide, amounts of 15 mol % or more and 50 mol % or less are preferable.
  • the thickness of the first protective layer 12 is preferably within a range of 2 nm to 20 nm. If the thickness is less than 2 nm, there is a tendency for the barrier effect to the recording layer to be reduced. On the other hand, if the thickness exceeds 20 nm, there is a tendency for the recording power margin to be reduced.
  • the thickness of the second protective layer 13 is preferably within a range of 2 nm to 50 nm. If the thickness is less than 2 nm, there is a tendency for the barrier effect to the recording layer to be reduced. On the other hand, if the thickness exceeds 50 nm, there is a tendency for the recording power margin to be reduced.
  • the L 1 layer which is close to the innermost layer having small x 1 and x 2 in composition ratio and asked to have a high sensitivity, is likely to have large transmittance fluctuations after recording as the amounts of Pd and Cu are likely to be large.
  • a first protective layer 12 and a second protective layer 13 with an extinction coefficient of 0.05 or more and suppress transmittance fluctuations.
  • the transmittance fluctuations after recording are small but the power margin is likely to become narrow.
  • the L 2 layer uses a combination of the L 1 layer and the L 3 layer, it is possible to make the power margin and transmittance fluctuation suppression characteristics of each layer uniform even when the material of the recording layer, the desired sensitivity and the transmittance are different.
  • First protective layer 12 ITO
  • Inorganic recording layer 11 WCPO (0.4 ⁇ x 1 ⁇ 0.6), preferably WZCPO (0.4 ⁇ x 2 ⁇ 6)
  • Second protective layer 13 ITO
  • First protective layer 12 material with an extinction coefficient k in a range of 0.05 to 0.6, preferably ITO
  • Inorganic recording layer 11 WCPO (0.5 ⁇ x 1 ⁇ 0.9), preferably WZCPO (0.5 ⁇ x 2 ⁇ 0.9)
  • Second protective layer 13 material with an extinction coefficient k in a range of 0.05 to 0.6, preferably ITO
  • First protective layer 12 material with an extinction coefficient k in a range of 0.05 to 0.6, preferably ITO
  • Inorganic recording layer 11 WCPO (0.8 ⁇ x 1 ⁇ 1.2), preferably WZCPO (0.8 ⁇ x 2 ⁇ 1.2)
  • Second protective layer 13 SIZ or IGZO
  • First protective layer 12 SIZ or IGZO
  • Inorganic recording layer 11 WCPO (0.8 ⁇ x 1 ⁇ 1.2), preferably WZCPO (0.8 ⁇ x 2 ⁇ 1.2)
  • Second protective layer 13 SIZ or IGZO
  • the intermediate layers S 1 to S 3 fulfill a role of separating the L 0 , L 1 , L 2 , and L 3 so as to have a sufficient physical and optical distance, are provided with a concavo-convex surface on the surfaces thereof, and form concentric circle or spiral shaped grooves (in-groove Gin and on-groove Gon).
  • the material of the intermediate layers S 1 to S 3 is not particularly limited, but it is preferable to use an ultraviolet curable acrylic resin, in addition, it is preferable that the intermediate layers S 1 to S 3 have a sufficiently high light transmittance since they will be optical paths for laser beam for the purpose of recording and reproducing data to and from the inner layers.
  • the light transmissive layer 2 is a resin layer formed by curing a photosensitive resin such as an ultraviolet curable resin.
  • a photosensitive resin such as an ultraviolet curable resin.
  • ultraviolet curable acrylic resins may be exemplified.
  • the light transmissive layer 2 may be configured of a light transmitting sheet having a circular shape and an adhesive layer for making the light transmitting sheet adhere to the substrate 1 . It is preferable that the light transmitting sheet be material with low absorbance with respect to the laser beam used in recording and reproduction, specifically, a material with a transmittance of 90% or more is preferable.
  • the material of the light-transmitting sheet for example, a polycarbonate resin material, a polyolefin resin (for example, ZEONEX (registered trademark)), and the like may be used.
  • a polycarbonate resin material for example, a polyolefin resin (for example, ZEONEX (registered trademark)), and the like may be used.
  • ZEONEX registered trademark
  • the material of the adhesive layer for example, an ultraviolet curable resin, a pressure sensitive adhesive (PSA: Pressure Sensitive Adhesive), or the like, may be used.
  • the thickness of the light transmissive layer 2 is preferably selected from a range of 10 ⁇ m to 177 ⁇ m, for example, set as 53.5 ⁇ m.
  • the hard coat layer 3 is for conferring anti-scratching properties and the like on the light irradiation plane C.
  • an acrylic resin, a silicone resin, a fluorine resin, an organic inorganic hybrid resin, or the like may be used.
  • the barrier layer 4 is for suppressing outgassing (moisture release) from the back face of the substrate 1 during the film forming process. Further, the barrier 4 also functions as a moisture-proof layer that suppresses the absorption of moisture on the back face of the substrate 1 .
  • the material that configures the barrier layer 4 is not particularly limited as long as the outgassing (moisture release) from the back face of the substrate 1 is able to be suppressed, to give an example, a dielectric with low gas transmission may be used. As such a dielectric, for example, SiN, SiO 2 , TiN, AlN, ZnS—SiO 2 , or the like may be used.
  • the thickness of the barrier layer 4 is preferably set to between 5 nm and 40 nm.
  • the thickness is less than 5 nm, the barrier function of suppressing outgassing from the substrate back face tends to decrease. This is because, on the other hand, if the thickness is greater than 40 nm, there is hardly any difference in the barrier function of suppressing outgassing compared to a case when the thickness is lower, and further, productivity tends to decrease. It is preferable that the moisture transmittance of the barrier 4 be equal to or less than 5 ⁇ 10 ⁇ 5 g/cm 2 per day.
  • the optical information recording medium 10 having the above configuration, when the laser beam is irradiated to the inorganic recording layer 11 , Pd oxide is heated and decomposed by the laser beam to release oxygen and bubbles are generated in the parts irradiated with laser beam. In this manner it is possible to irreversibly record the information signal.
  • the substrate 1 in which a concavo-convex surface is formed on the principal surface is formed.
  • an injection method, a photopolymerization method (2P method), and the like may be used.
  • the information signal layer L 0 is formed by sequentially laminating the first protective layer 12 , the inorganic recording layer 11 , and the second protective layer 13 on the substrate 1 by a sputtering method, for example.
  • the formation process of the first protective layer 12 , the inorganic recording layer 11 , and the second protective layer 13 will be described below in detail.
  • the substrate 1 is transported into a vacuum chamber in which a target for the first protective layer formation, and the inside of the vacuum chamber is vacuumed until the vacuum chamber reaches a predetermined pressure.
  • the first protective layer 12 is then formed on the substrate 1 by sputtering the target while introducing a process gas such as Ar gas or O 2 gas into the vacuum chamber.
  • a radio frequency (RF) sputtering method or a direct current (DC) sputtering method for example, may be used as the sputtering method, the direct current sputtering method is particularly preferable. The reason is that since the direct current sputtering method has a high film forming rate compared to the radio frequency sputtering method, it is possible to improve productivity.
  • the substrate 1 is transported into a vacuum chamber in which a target for inorganic recording layer film formation use is provided, and the inside of the vacuum chamber is vacuumed until the vacuum chamber reaches a predetermined pressure.
  • the inorganic recording layer 12 is then formed on the first protective layer 11 by sputtering the target while introducing a process gas such as Ar gas or O 2 gas into the vacuum chamber.
  • the substrate 1 is transported into a vacuum chamber in which a target for second protective layer film formation use is provided, and the inside of the vacuum chamber is vacuumed until the vacuum chamber reaches a predetermined pressure.
  • the second protective layer 13 is then formed on the inorganic recording layer 12 by sputtering the target while introducing a process gas such as Ar gas or O 2 gas into the vacuum chamber.
  • a process gas such as Ar gas or O 2 gas
  • the sputtering method it is possible to use a high-frequency (RF) sputtering method, a direct current (DC) sputtering method, or the like; however, the direct current sputtering method is preferable. The reason is that since the direct current sputtering method has a high film forming rate compared to the radio frequency sputtering method, it is possible to improve productivity.
  • the information signal layer L 0 is formed on the substrate 1 .
  • an ultraviolet curable resin is evenly coated over the information signal layer L 0 by a spin coating method, for example.
  • the stamper is removed.
  • the concavo-convex pattern of the stamper is transferred on the ultraviolet curable resin, and for example, the intermediate layer 51 on which the in-grooves Gin and the on-grooves Gon are provided is formed over the information signal layer L 0 .
  • the target for inorganic recording layer film formation the target for the first protective layer formation, and the target for second protective layer formation will be described.
  • the target for the inorganic recording layer film formation may be a WCP metal target with W, Cu, and Pd as main components, may be a WCPO oxide target with W oxide, Cu oxide, and Pd oxide as main components, and, in consideration of productivity, the use of a metal target, which has main components of W, Cu, and Pd for which DC sputtering capable of a comparatively rapid film formation rate is possible, is preferable.
  • the ratio of W, Pd, and Cu included in the target preferably satisfies a relationship of 0.17 ⁇ x 1 , more preferably 0.37 ⁇ x 1 , still more preferably 0.37 ⁇ x 1 ⁇ 1.26, and most preferably 0.56 ⁇ x 1 ⁇ 1.26.
  • the target for the inorganic recording layer film formation may be a WZPC metal target with W, Cu, Pd, and Zn as main components, may be a WZCPO oxide target with W oxide, Cu oxide, Pd oxide and Zn oxide as main components, and, furthermore, may be a target mixing WZCPO of metal and oxide.
  • a metal target which has main components of W, Cu, Pd and Zn for which DC sputtering capable of a comparatively rapid film formation rate is possible, is preferable.
  • the ratio of W, Pd, Cu and Zn included in the target preferably satisfies a relationship of 0.17 ⁇ x 2 , more preferably 0.37 ⁇ x 2 , still more preferably 0.37 ⁇ x 2 ⁇ 1.26, and most preferably 0.56 ⁇ x 2 ⁇ 1.26.
  • the WCP target for inorganic recording layer film formation the WCPO target and the WZCP and WZCPO targets, ones having the same composition as the inorganic recording layer 11 are preferable.
  • At least one of the target for forming the first protective layer and the target for forming the second protective layer preferably includes SIZ or IGZO as a main component and it is more preferable that both targets include SIZ or IGZO.
  • the target for forming the first protective layer and the target for forming the second protective layer include SIZ or IGZO as a main component.
  • SIZ or IGZO as the main component in the first protective layer 12 provided on the lower side surface of the inorganic recording layer 11 , it is possible to further increase the power margin in comparison to a case in which SIZ or IGZO is included as the main component in the first protective layer 12 provided on the upper side surface of the inorganic recording layer 11 . Further, when SIZ is used, if the amount of highly conductive In oxide is great, DC sputtering becomes possible and productivity becomes high; however, conversely, if the amount of In oxide is too great, the extinction coefficient of thin film becomes great and the transmittance of the information signal layer is lowered.
  • the In oxide ratio is not particularly limited; however, it is preferable that the ratio be adjusted according to the desired characteristics and productivity of the information signal layer.
  • the IGZO since both In oxide and ZnO oxide have conductivity, when the total amount of In oxide and ZnO oxide is great, DC sputtering is possible and productivity is high, which is thus preferable.
  • the amount of In oxide is too large, for the same reasons mentioned above similarly to SIZ, since the transmittance of the information signal layer deteriorates, it is preferable that the ratio be adjusted according to the desired characteristics of the information signal layer.
  • the information signal layer L 1 , the intermediate layer S 2 , the information signal layer L 2 , the intermediate layer S 3 , and the information signal layer L 3 are sequentially laminated over the intermediate layer S 1 in such an order.
  • the film formation conditions or the target composition as appropriate, the thicknesses or the compositions of the first protective layer 12 , the inorganic recording layer 11 , and the second protective layer 13 that configure the information signal layers L 1 to L 3 may be adjusted as appropriate.
  • the thicknesses of the intermediate layers S 2 to S 3 may be adjusted as appropriate.
  • UV resin ultraviolet curable resin
  • the desired optical information recording medium is obtained by the above processes.
  • the information signal layers of the multi-layer optical information recording medium will be referred to as the L 0 layer, the L 1 layer, the L 2 layer . . . in order from the substrate side toward the laser irradiation plane side.
  • test examples will be described in the following order.
  • a polycarbonate substrate with a thickness of 1.1 mm was formed by injection molding.
  • a concavo-convex surface with grooves was formed on the polycarbonate substrate.
  • the first protective layer (lower side), the inorganic recording layer, and the second protective layer (upper side) were sequentially laminated over the polycarbonate substrate, thereby forming an L 0 layer.
  • each layer of the L 0 layer was as follows.
  • ultraviolet curable resin manufactured by Sony Chemical & Information Device Corporation, product name: SK5500B
  • SK5500B ultraviolet curable resin
  • the first protective layer, the inorganic recording layer, and the second protective layer were sequentially stacked on the intermediate layer, thereby forming the L 2 layer. Furthermore, the formation of the L 1 layer was omitted.
  • an ultraviolet curable resin was evenly coated over the L 2 layer by a spin coating method and cured by the irradiation of ultraviolet rays, whereby a resin layer having the same hardness as the intermediate layer and a thickness of 31.0 ⁇ m was formed.
  • a two-layer optical information recording medium having an L 0 layer and an L 2 layer was obtained.
  • the L 2 layer state is set to the state of the L 2 layer of a four-layer optical information recording medium in a simulated manner.
  • An optical information recording medium was obtained in the same manner as in Test Example 1-1 apart from the materials, thicknesses and film formation methods of the first protective layer and the second protective layer of layer L 2 as shown below.
  • An optical information recording medium was obtained in the same manner as in Test Example 1-1 apart from the materials, thicknesses and film formation methods of the first protective layer and the second protective layer of layer L 2 as shown below.
  • An optical information recording medium was obtained in the same manner as in Test Example 1-1 apart from the materials, thicknesses and film formation methods of the first protective layer and the second protective layer of layer L 2 as shown below.
  • An optical information recording medium was obtained in the same manner as in Test Example 1-1 apart from the materials, thicknesses and film formation methods of the first protective layer and the second protective layer of layer L 2 as shown below.
  • the initial state of the power margin of the L 2 layer of the optical information recording media of Test Examples 1-1 to 1-5 obtained in the above-described manner was calculated as below.
  • a disc tester manufactured by Pulstec Industrial Co., Ltd., product name: ODU-1000
  • 1-7 modulation data with a density of 32 GB per layer was recorded and reproduced with a recording wavelength of 405 nm and a recording linear velocity of 7.69 m/s, and the random symbol error rate (SER) was calculated.
  • Such an SER was calculated with respect to the recording power, a low side with recording power in excess of 4 ⁇ 10 ⁇ 3 was set as Pwl, a high side was set as Pwh, and the optimal power between Pwl and Pwh was set as Pwo.
  • the power margin PM was calculated from Formula 1 below.
  • an SER of 4 ⁇ 10 ⁇ 3 is the upper limit value of the SER at which error correction does not fail. If the upper limit value is exceeded, defects are generated in the reproduction data and the signal quality particularly deteriorates.
  • Table 1 shows the evaluation results of the optical information recording media of Test Examples 1-1 to 1-5.
  • the power margin may be set as 30% or more.
  • the power margin is 30%, it is possible to sufficiently absorb the influence of the precision of the recording power of a consumer drive, variation of in-plane sensitivity of the optical information recording medium, temperature of the optical information recording medium, and a decrease in the actual recording power accompanying warping due to humidity, thereby enabling favorable recording with a low error rate.
  • SIZ is used as the material of the first protective layer and the second protective layer, it is possible to further widen the power margin in comparison to a case where IGZO is used.
  • SIZ or IGZO as the material of the first protective layer and the second protective layer, it is possible to improve the transmittance of the information signal layer. Accordingly, it is possible to increase the light quantity of the laser beam reaching the L 0 layer positioned furthest to the back of the light irradiation plane.
  • SIZ and IGZO as the material of the first protective layer and the second protective layer adjacent to the inorganic recording layer and particularly preferable to use IGZO.
  • the content ratio of In oxide with respect to SIZ be set to 40 mol % or more; however, since the transmittance of the information signal layer deteriorates due to the extinction coefficient of the SIZ thin layer becoming large when such a content ratio is excessive, it is preferable to select the ratio of the In oxide and the like in accordance with the transmittance and productivity desired for the information signal layer.
  • a polycarbonate substrate with a thickness of 1.1 mm was formed by injection molding.
  • a concavo-convex surface with grooves was formed on the polycarbonate substrate.
  • the first protective layer (lower side), the inorganic recording layer, and the second protective layer (upper side) were sequentially laminated over the polycarbonate substrate, thereby forming an L 0 layer.
  • each layer of layer L 0 was as follows.
  • ultraviolet curable resin manufactured by Sony Chemical & Information Device Corporation, product name: SK5500B
  • SK5500B ultraviolet curable resin
  • layer L 1 was formed.
  • each layer of layer L 1 was as follows.
  • ultraviolet curable resin manufactured by Sony Chemical & Information Device Corporation, product name: SK5500B
  • SK5500B ultraviolet curable resin
  • layer L 2 was formed.
  • each layer of layer L 2 was as follows.
  • ultraviolet curable resin manufactured by Sony Chemical & Information Device Corporation, product name: SK5500B
  • SK5500B ultraviolet curable resin
  • the L 3 layer was formed.
  • the material, the thickness and the film formation method of each layer of the L 3 layer were as follows.
  • the initial state of the power margin of layers L 1 to L 3 of the optical information recording medium of Test Example 2 obtained in the above-described manner was calculated in the same manner as Test Examples 1-1 to 1-5. The results are shown in FIG. 5 .
  • An optical information recording medium was obtained in the same manner as in Test Example 1-4.
  • An optical information recording medium was obtained in the same manner as in Test Example 3-1 apart from the materials, thicknesses and film formation methods of the first protective layer and the second protective layer of layer L 2 as shown below.
  • An optical information recording medium was obtained in the same manner as in Test Example 3-1 apart from the materials, thicknesses and film formation methods of the first protective layer and the second protective layer of layer L 2 as shown below.
  • An optical information recording medium was obtained in the same manner as in Test Example 1-1.
  • SIZ be used as the material of one of the first protective layer and the second protective layer, in particular, as the material of the first protective layer (lower side) and more preferable that SIZ be used as the material of both the first protective layer and the second protective layer.
  • a polycarbonate substrate with a thickness of 1.1 mm was formed by injection molding.
  • a concavo-convex surface with grooves was formed on the polycarbonate substrate.
  • the first protective layer, the inorganic recording layer, and the second protective layer were sequentially laminated over the polycarbonate substrate by the sputtering method.
  • the specific configurations of each layer were as follows.
  • the target compositions were manufactured for each of Test Examples 4-1 to 4-15 so that the atomic ratios c, d, b, and a of each of Cu, Zn, Pd and W in the WZCPO of the inorganic recording layer became the values shown in Table 2.
  • each coefficient was determined by multiplying a coefficient by each ratio so that the square of a determination coefficient R is the greatest with the sum of each ratio of the W oxide and the Zn oxide with relatively small extinction coefficients as the numerator and the sum of each ratio of the Pd oxide and the Cu oxide with relatively large extinction coefficients as the denominator.
  • y indicates the transmittance [%] and x indicates (0.1d+a)/(b+0.8c).
  • Table 2 illustrates the composition ratios and the transmittances of the inorganic recording layers of Test Examples 4-1 to 4-15.
  • FIG. 8 is a graph that illustrates the composition ratios of the inorganic recording layers of Test Examples 4-1 to 4-13.
  • variable x be equal to or greater than 0.17.
  • variable x be equal to or greater than 0.37.
  • variable x be equal to or greater than 0.56.
  • variable x be equal to or less than 1.26.
  • the transmittances of information signal layers equal to or higher than the L 1 layer (L 1 layer, L 2 layer, L 3 layer, . . . ) be equal to or greater than 55%.
  • the reason why a transmittance equal to or greater than 55% is preferable will be described later.
  • the transmittance of the L 1 layer be equal to or greater than 50%.
  • the optimum recording power Pwo it is preferable that the transmittance be equal to or less than 78%.
  • the optimum recording power Pwo: 20 mW is the upper limit value of the optimum recording power Pwo of a consumer drive device. If the upper limit value is exceeded, the recording power becomes insufficient and the signal properties deteriorate.
  • a polycarbonate substrate with a thickness of 1.1 mm was formed by injection molding.
  • a concavo-convex surface with grooves was formed on the polycarbonate substrate.
  • the first protective layer, the inorganic recording layer, and the second protective layer were sequentially laminated over the polycarbonate substrate by the sputtering method, whereby an L 0 layer was produced.
  • the L 0 layer is for use as a two-layer optical information recording medium.
  • the i-MLSE of the optical information recording media of Test Examples 5-1 to 5-12 obtained as described above was calculated as below.
  • the reflectance of a single-layer optical information recording medium manufactured using only the L 0 layer of a two-layer optical information recording medium is referred to as the reflectance of the L 0 layer alone.
  • Table 3 shows the measurement results of the i-MLSE and reflectances of the optical information recording media of the Test Examples 5-1 to 5-12.
  • FIG. 9A is a graph that illustrates the relationship between the i-MLSE and the reflectances calculated as described above. It is seen from FIG. 9A that for the i-MLSE value of the L 0 layer to be equal to or less than 11%, it is important for the reflectance of the L 0 layer to be equal to or less than 14%.
  • the i-MLSE value 11% is the upper limit value that is said to be error correctable by a consumer drive device.
  • the reflectance was able to be improved by causing one or a combination of the first protective layer, the inorganic recording layer, and the second protective layer to be thinner than the above film thicknesses, the i-MLSE values would then deteriorate. It is presumed that the i-MLSE values deteriorate since the formation of bubbles during recording becomes inappropriate as a result of changes in the heat accumulation or heat release of the inorganic recording layer.
  • Table 4 illustrates the reflectances of the L 0 layers alone, the transmittances of the L 1 layers, and the reflectances of the L 0 layers of the optical information recording media of Test Examples 5-13 to 5-24.
  • the reflectance 4% of the L 1 layer is the lower limit value that is demanded for an information signal to be reproduced using a consumer two-layer compatible drive device.
  • the i-MLSE of the L 0 layer was measured when the transmittance of the L 1 layer alone of a four-layer optical information recording medium was made to vary. The results are illustrated in Table 5 and FIG. 9C .
  • adjustment of the transmittance of the L 1 layer was performed by the adjustment of the thickness of the inorganic recording layer according to the below conditions.
  • Table 5 illustrates the transmittances of the L 1 layer, and the i-MLSE values of the L 0 layers of the optical information recording media of Test Examples 6-1 to 6-9.
  • the i-MLSE value of the L 0 layer is important for the transmittance of the L 1 layer to be equal to or greater than 55%.
  • the i-MLSE value 11% is the upper limit value that is error correctable by a consumer drive device. The reason is that in a case when the transmittance of the L 1 layer is low, since the signal amount of the L 0 layer decreases, it is thought that sufficient S/N for reproduction is not obtained. Therefore, the higher the transmittance of the L 1 layer, the better the signal properties of the L 0 layer.
  • the transmittances of information signal layers equal to or higher than the L 1 layer (L 1 layer, L 2 layer, L 3 layer, . . . ) be equal to or greater than 55%.
  • the number of layers of the information signal layer is not limited thereto, and it is possible for the information signal layer to have an arbitrary number of two or more layers.
  • the present disclosure is able to be applied to an optical information recording medium with a configuration in which two or more information signal layers and a protective layer are laminated in such an order on a substrate and in which recording or reproduction of information signals is performed by irradiating laser beam on the two or more information signal layers from the substrate side or to an optical information recording medium with a configuration in which two or more information signal layers are provided between two substrates and in which recording or reproduction of information signals is performed by irradiating laser beam on the information signal layers from the side of one of the substrates.
  • the film formation method is not limited thereto, and other film formation methods may be used.
  • CVD methods Chemical Vapor Deposition: technique in which a thin film is separated from vapor using a chemical reaction
  • heat CVD plasma CVD
  • light CVD PVD methods
  • Physical Vapor Deposition technique in which a thin film is formed by agglomerating a material that is physically vaporized in a vacuum on a substrate
  • vacuum deposition plasma-assisted deposition, or ion plating

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