Optical recording media

Abstract

An optical recording medium capable of suppressing a decrease in reproduction durability is provided. [Solution] In an optical recording medium, a first disc (10) includes at least one information signal layer (L0-Ln). The information signal layer includes a first dielectric layer (14), a recording layer (13), and a second dielectric layer (15), in that order, with the first dielectric layer being located deeper than the recording layer when viewed from a first light irradiation surface (C1). The recording layer includes Mn and O. The first dielectric layer includes Zn, Sn, Al, and O or Zn, Sn, Ti, and O, with the Al content relative to the total amount of Zn, Sn, and Al being 10 atomic % or more, and the Ti content relative to the total amount of Zn, Sn, and Ti being 10 atomic % or more.

Description

[Technical Field]

[0001] The present disclosure relates to optical recording media. [Background technology]

[0002] Optical recording media having dielectric layers on both sides of a recording layer are known. Various materials for the dielectric layers have been investigated to improve the characteristics of optical recording media with such structures. For example, Patent Document 1 discloses a dielectric layer material containing zinc (Zn) oxide, tin (Sn) oxide, and zirconium (Zr) oxide. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-167633 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the dielectric layer material described in Patent Document 1 is used, there is a risk that the reproduction durability of the optical recording medium may be reduced. When the above-mentioned dielectric layer material is used in an optical recording medium with a high recording density, there is a risk that the reproduction durability may be significantly reduced. In this disclosure, reproduction durability is an index that represents the degree of deterioration in signal quality when reproduction light is continuously irradiated onto a recording mark.

[0005] An object of the present disclosure is to provide an optical recording medium that can suppress a decrease in playback durability. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the optical recording medium according to the present disclosure comprises: At least one information signal layer is provided, the information signal layer includes a first dielectric layer, a recording layer, and a second dielectric layer in this order; the first dielectric layer is provided on the back side of the recording layer as viewed from the light irradiation surface, the recording layer contains Mn and O; the first dielectric layer comprises Zn, Sn, Al and O, or Zn, Sn, Ti and O; The content of Al relative to the total amount of Zn, Sn, and Al is 10 atomic % or more, The content of Ti relative to the total amount of Zn, Sn, and Ti is 10 atomic % or more. [Brief explanation of the drawings]

[0007] [Figure 1] Fig. 1A is a perspective view showing an example of the appearance of an optical recording medium according to a first embodiment of the present disclosure, and Fig. 1B is a cross-sectional view showing an example of the configuration of the optical recording medium according to the first embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic cross-sectional view showing an example of the configuration of each information signal layer shown in FIG. [Figure 3] FIG. 3 is a cross-sectional view showing an example of the configuration of an optical recording medium according to the second embodiment of the present disclosure. [Figure 4] FIG. 4 is a graph showing the change in error rate when the optical recording medium of Experimental Example 3 is repeatedly reproduced. [Figure 5] FIG. 5 is a diagram showing the measurement results of the return light intensity of the optical recording medium in Experimental Example 3. In FIG. [Figure 6] FIG. 6 is a graph showing the change in reflectance when the optical recording medium of Experimental Example 3 is repeatedly reproduced. [Figure 7] FIG. 7 is a graph showing the change in reflectance when the optical recording media of Experimental Examples 1-1, 2-1, and 3 are repeatedly reproduced. [Figure 8] FIG. 8 is a graph showing the change in reflectance when the optical recording media of Experimental Examples 3 to 7 are repeatedly reproduced. DETAILED DESCRIPTION OF THE INVENTION

[0008] In the present disclosure, it is preferable that at least one information signal layer is provided on a substrate, and a cover layer is provided on this at least one information signal layer. While the thickness of this cover layer is not particularly limited, since high-density optical recording media use objective lenses with high NA (Numerical Aperture), it is preferable to use a thin light-transmitting layer such as a sheet or coating layer as the cover layer, and to record and reproduce information signals by irradiating laser light from the light-transmitting layer side. In this case, it is also possible to use an opaque substrate. The incident surface of the laser light for recording or reproducing information signals can be appropriately set on at least one of the cover layer side and the substrate side, depending on the format of the optical recording medium.

[0009] In the present disclosure, when an optical recording medium has multiple information signal layers, it is preferable that all of the multiple information signal layers have the same layer structure from the viewpoint of improving productivity. More specifically, it is preferable that the first dielectric layer, the recording layer, and the second dielectric layer contain the same type of material in the multiple information signal layers from the viewpoint of improving productivity.

[0010] The embodiments of the present disclosure will be described in the following order. 1. First Embodiment 1.1 Structure of optical recording medium 1 1.2 Manufacturing method of optical recording medium 1 1.3 Effects 2. Second Embodiment 2.1 Structure of Optical Recording Medium 1A 2.2 Manufacturing Method of Optical Recording Medium 1A 2.3 Effects 3. Variations

[0011] <1 First Embodiment> [1.1 Configuration of optical recording medium 1] 1A, the optical recording medium 1 according to the first embodiment of the present disclosure has a disk shape with an opening (hereinafter referred to as a center hole) in the center. Note that the shape of the optical recording medium 1 is not limited to this example, and it can also be, for example, card-shaped.

[0012] 1B, the optical recording medium 1 is a so-called multi-layer write-once optical recording medium (for example, an AD (Archival Disc)), and includes a first disc 10, a second disc 20, and a bonding layer 30 provided between the first and second discs 10 and 20. The optical recording medium 1 is an optical recording medium that uses a method for recording data on both groove tracks and land tracks (hereinafter referred to as a "land / groove recording method").

[0013] The first disc 10 has a configuration in which an information signal layer L0, a spacer layer S1, an information signal layer L1, ..., a spacer layer Sn, an information signal layer Ln, and a light-transmitting layer 12 serving as a cover layer are laminated in this order on one main surface of a substrate 11. The second disc 20 has a configuration in which an information signal layer L0, a spacer layer S1, an information signal layer L1, ..., a spacer layer Sm, an information signal layer Lm, and a light-transmitting layer 22 serving as a cover layer are laminated in this order on one main surface of a substrate 21. Note that n and m are each independently an integer of 1 or greater, and from the viewpoint of improving recording capacity, are preferably an integer of 2 or greater, more preferably an integer of 3 or greater, and even more preferably an integer of 4 or greater. In the following description, when the information signal layers L0 to Ln and L0 to Lm are not particularly distinguished from one another, the information signal layers L0 to Ln and L0 to Lm may be referred to as information signal layer L.

[0014] The optical recording medium 1 has light irradiation surfaces on both sides thereof that are irradiated with laser light for recording or reproducing information signals. More specifically, the optical recording medium 1 has a first light irradiation surface C1 that is irradiated with laser light for recording or reproducing information signals on the first disc 10, and a second light irradiation surface C2 that is irradiated with laser light for recording or reproducing information signals on the second disc 20.

[0015] In the first disc 10, the information signal layer L0 is located at the innermost position relative to the first light irradiation surface C1, and the information signal layers L1 to Ln are located in front of it. Therefore, the information signal layers L1 to Ln are configured to be able to transmit laser light used for recording or reproduction. On the other hand, in the second disc 20, the information signal layer L0 is located at the innermost position relative to the second light irradiation surface C2, and the information signal layers L1 to Lm are located in front of it. Therefore, the information signal layers L1 to Lm are configured to be able to transmit laser light used for recording or reproduction. Although not shown, the optical recording medium 1 may further include hard coat layers on the surfaces of the light transmission layers 12 and 22 (i.e., the first and second light irradiation surfaces C1 and C2).

[0016] In the optical recording medium 1, information signals are recorded on or reproduced from the first disc 10 as follows. That is, information signals are recorded on or reproduced from the first disc 10 by irradiating each of the information signal layers L0 to Ln included in the first disc 10 with laser light from the first light irradiation surface C1 on the light transmitting layer 12 side. For example, information signals are recorded on or reproduced from the first disc 10 by condensing laser light having a wavelength in the range of 350 nm to 410 nm using an objective lens with a numerical aperture in the range of 0.84 to 0.95, and irradiating the laser light onto each of the information signal layers L0 to Ln included in the first disc 10 from the light transmitting layer 12 side.

[0017] On the other hand, information signals are recorded on or reproduced from the second disc 20 as follows: That is, laser light is irradiated onto each of the information signal layers L0 to Lm included in the second disc 20 from the second light irradiation surface C2 on the light transmitting layer 22 side, thereby recording or reproducing information signals from the second disc 20. For example, laser light having a wavelength in the range of 350 nm to 410 nm is focused by an objective lens having a numerical aperture in the range of 0.84 to 0.95, and the laser light is irradiated onto each of the information signal layers L0 to Lm included in the second disc 20 from the light transmitting layer 22 side, thereby recording or reproducing information signals.

[0018] The substrates 11, 21, bonding layer 30, information signal layers L0 to Ln, L0 to Lm, spacer layers S1 to Sn, S1 to Sm, light transmitting layers 12, 22 and hard coat layer that constitute the optical recording medium 1 will be described in order below.

[0019] (substrate) The substrates 11 and 21 have, for example, a disk shape with a center hole in the center. One main surface of the substrates 11 and 21 is, for example, an uneven surface, and the information signal layer L0 is formed on this uneven surface. Hereinafter, the concave portions of the uneven surface will be referred to as lands Ld, and the convex portions will be referred to as grooves Gv.

[0020] The shapes of the lands Ld and grooves Gv include various shapes such as spiral, concentric circles, etc. Furthermore, the lands Ld and / or grooves Gv may be wobbled (meandered) to stabilize the linear velocity, add address information, etc.

[0021] The spiral directions of the first disk 10 and the second disk 20 may be reversed. In this case, simultaneous recording and reproduction are possible on an optical recording medium (double-sided disk) 1 formed by bonding the first disk 10 and the second disk 20 together, which can approximately double the data transfer speed during recording and reproduction.

[0022] The outer diameter (diameter) of substrates 11 and 21 is selected to be, for example, 120 mm. The inner diameter (diameter) of substrates 11 and 21 is selected to be, for example, 15 mm. The thickness of substrate 11 is selected in consideration of rigidity, and is preferably 0.3 mm or more and 0.545 mm or less, and more preferably 0.445 mm or more and 0.545 mm or less.

[0023] The substrates 11 and 21 may be made of, for example, a plastic material or glass, with a plastic material being preferred from the viewpoint of formability. Examples of the plastic material that may be used include polycarbonate resin, polyolefin resin, and acrylic resin, with a polycarbonate resin being preferred from the viewpoint of cost.

[0024] (Laminating layer) The bonding layer 30 is made of a cured ultraviolet curable resin. The first disc 10 and the second disc 20 are bonded together by this bonding layer 30. More specifically, the substrate 11 of the first disc 10 and the substrate 21 of the second disc substrate are bonded together with the light transmitting layers 12 and 22 facing the front surfaces.

[0025] The thickness of the bonding layer 30 is, for example, 0.01 mm or more and 0.22 mm or less. The ultraviolet curing resin is, for example, a radical polymerization ultraviolet curing resin.

[0026] (Information Signal Layer) The information signal layer L is configured to be capable of multi-level recording (for example, 5-level recording). The information signal layer L has concave tracks (hereinafter referred to as "land tracks") and convex tracks (hereinafter referred to as "groove tracks"). The optical recording medium 1 according to the first embodiment is configured to be capable of recording information signals on both the land tracks and the groove tracks. From the viewpoint of high recording density, it is preferable that the track pitch Tp between the land tracks and the groove tracks is 225 nm or less. The lower limit of the track pitch Tp is not particularly limited, but is, for example, 120 nm or more.

[0027] 2, the information signal layers L0 to Ln include, in this order, a first dielectric layer 14, a recording layer 13, and a second dielectric layer 15. By configuring the recording layer 13 to be sandwiched between the first dielectric layer 14 and the second dielectric layer 15 in this manner, it is possible to improve the durability of the recording layer 13. The information signal layers L0 to Lm can have the same configuration as the information signal layers L0 to Ln, and therefore a description thereof will be omitted.

[0028] (Recording layer 13) The recording layer 13 is configured to be capable of recording information signals by changing the reflectivity. The recording layer 13 is sandwiched between a first dielectric layer 14 and a second dielectric layer 15. The recording layer 13 contains Mn and O. The recording layer 13 may contain Mn and O as manganese oxide. The recording layer 13 preferably contains at least a portion of the manganese oxide as +4-valent Mn (i.e., MnO2). The recording layer 13 may contain manganese oxide other than MnO2 (e.g., Mn2O3, Mn3O4, etc.).

[0029] The recording layer 13 may further contain a metal other than Mn. In this case, the recording layer 13 may contain Mn and the metal other than Mn as a mixture of metal oxides or a composite oxide, or may contain both a mixture and a composite oxide. Here, metals are defined to include semimetals such as Si and Sb. The metal other than Mn includes at least one selected from the group consisting of W, Zn, Cu, Al, Ta, Hf, Nb, Si, Sn, and Sb. The thickness of the recording layer 13 is, for example, 10 nm or more and 100 nm or less.

[0030] (First dielectric layer 14) The first dielectric layer 14 has a function as a protective layer that protects the recording layer 13 and a function to adjust the reflectance of the information signal layer L. The first dielectric layer 14 is provided on the back side of the recording layer 13 when viewed from the first light irradiation surface C1. The first dielectric layer 14 includes a dielectric. More specifically, the first dielectric layer 14 includes Zn, Sn, Al and O, or Zn, Sn, Ti and O.

[0031] When the first dielectric layer 14 contains Zn, Sn, Al, and O, the first dielectric layer 14 may contain these metals Zn, Sn, and Al as a mixture containing their respective metal oxides (zinc oxide (ZnO), tin oxide (SnO2), and aluminum oxide (Al2O3)), or may contain them as a composite oxide containing the metals Zn, Sn, and Ti, or may contain them as both a mixture and a composite oxide thereof.

[0032] When the first dielectric layer 14 contains Zn, Sn, Ti, and O, the first dielectric layer 14 may contain these metals Zn, Sn, and Ti as a mixture containing their respective metal oxides (zinc oxide (ZnO), tin oxide (SnO2), and titanium oxide (TiO2)), or may contain them as a composite oxide containing the metals Zn, Sn, and Ti, or may contain them as both a mixture and a composite oxide.

[0033] (Zn, Sn, and Al content in the first dielectric layer) The lower limit of the Zn content relative to the total amount of Zn, Sn, and Al contained in the first dielectric layer 14 is preferably 15 atomic % or more, more preferably 20 atomic % or more, and even more preferably 30 atomic % or more. From the viewpoint of improving the productivity of the optical recording medium 1, it is preferable to deposit the first dielectric layer 14 using DC sputtering, which has excellent deposition speed. More specifically, it is preferable to deposit the first dielectric layer 14 by DC co-sputtering a Zn-O target, a Sn-O target, and an Al-O target. However, if the lower limit of the Zn content is less than 15 atomic %, the conductivity of the Zn-O target decreases, making it difficult to DC co-sputter the Zn-O target, a Sn-O target, and an Al-O target. In other words, it becomes difficult to deposit the first dielectric layer 14 by DC co-sputtering.

[0034] In this specification, metal atoms M1, M2, ..., M n-1 , M n and O containing targets M1-M2-···-M n-1 -M n The target is called the -O target. The target consists of metal atoms M1, M2, ..., M n-1 and M n are the oxides of metal atom M1, metal atom M2, . . . and metal atom M n-1 oxides and metal atoms M n or as a mixture of oxides of metal atoms M1, M2, . . . , M n-1 and M nIt may be contained as a composite oxide of these, or may be contained as both a mixture and a composite oxide.

[0035] The upper limit of the Zn content relative to the total amount of Zn, Sn, and Al contained in the first dielectric layer 14 is, for example, 70 atomic % or less, 60 atomic % or less, or 50 atomic % or less.

[0036] The numerical range of the Zn content relative to the total amount of Zn, Sn, and Al contained in the first dielectric layer 14 may be defined by any of the above upper limits and any of the above lower limits, for example, 15 atomic % or more and 70 atomic % or less, 20 atomic % or more and 70 atomic % or less, 30 atomic % or more and 70 atomic % or less, 30 atomic % or more and 60 atomic % or less, or 30 atomic % or more and 50 atomic % or less.

[0037] The lower limit of the Sn content relative to the total amount of Zn, Sn, and Al contained in the first dielectric layer 14 is, for example, 15 atomic % or more, 20 atomic % or more, or 30 atomic % or more.

[0038] The upper limit of the Sn content relative to the total amount of Zn, Sn, and Al contained in the first dielectric layer 14 is, for example, 60 atomic % or less, 50 atomic % or less, or 40 atomic % or less.

[0039] The numerical range of the Sn content relative to the total amount of Zn, Sn, and Al contained in the first dielectric layer 14 may be defined by any of the above upper limits and any of the above lower limits, for example, 15 atomic % or more and 60 atomic % or less, 20 atomic % or more and 60 atomic % or less, 20 atomic % or more and 50 atomic % or less, 20 atomic % or more and 40 atomic % or less, or 30 atomic % or more and 40 atomic % or less.

[0040] The lower limit of the Al content relative to the total amount of Zn, Sn, and Al contained in the first dielectric layer 14 is 10 atomic % or more, and preferably 20 atomic % or more. When the Al content is 10 atomic % or more, a decrease in playback durability can be suppressed.

[0041] The upper limit of the Al content relative to the total amount of Zn, Sn, and Al contained in the first dielectric layer 14 is, for example, 30 atomic % or less or 25 atomic % or less.

[0042] The numerical range of the Al content relative to the total amount of Zn, Sn, and Al contained in the first dielectric layer 14 may be defined by any of the upper limit values ​​and any of the lower limit values, for example, 10 atomic % or more and 30 atomic % or less, 20 atomic % or more and 30 atomic % or less, or 20 atomic % or more and 25 atomic % or less.

[0043] (Zn, Sn, Ti content in the first dielectric layer) The lower limit of the Zn content relative to the total amount of Zn, Sn, and Ti contained in the first dielectric layer 14 is preferably 15 atomic % or more, more preferably 20 atomic % or more, and even more preferably 30 atomic % or more. From the viewpoint of improving the productivity of the optical recording medium 1, it is preferable to deposit the first dielectric layer 14 using DC sputtering, which has excellent deposition speed. More specifically, it is preferable to deposit the first dielectric layer 14 by DC co-sputtering a Zn-O target, an Sn-O target, and a Ti-O target. However, if the lower limit of the Zn content is less than 15 atomic %, the conductivity of the Zn-O target decreases, making it difficult to DC co-sputter the Zn-O target, an Sn-O target, and a Ti-O target. In other words, it becomes difficult to deposit the first dielectric layer 14 by DC co-sputtering.

[0044] The upper limit of the Zn content relative to the total amount of Zn, Sn, and Ti contained in the first dielectric layer 14 is, for example, 70 atomic % or less, 60 atomic % or less, or 50 atomic % or less.

[0045] The numerical range of the Zn content relative to the total amount of Zn, Sn, and Ti contained in the first dielectric layer 14 may be defined by any of the above upper limits and any of the above lower limits, for example, 15 atomic % or more and 70 atomic % or less, 20 atomic % or more and 70 atomic % or less, 30 atomic % or more and 70 atomic % or less, 30 atomic % or more and 60 atomic % or less, or 30 atomic % or more and 50 atomic % or less.

[0046] The lower limit of the Sn content relative to the total amount of Zn, Sn, and Ti contained in the first dielectric layer 14 is, for example, 15 atomic % or more, 20 atomic % or more, or 30 atomic % or more.

[0047] The upper limit of the Sn content relative to the total amount of Zn, Sn, and Ti contained in the first dielectric layer 14 is, for example, 60 atomic % or less, 50 atomic % or less, or 40 atomic % or less.

[0048] The numerical range of the Sn content relative to the total amount of Zn, Sn, and Ti contained in the first dielectric layer 14 may be defined by any of the above upper limits and any of the above lower limits, for example, 15 atomic % or more and 60 atomic % or less, 20 atomic % or more and 60 atomic % or less, 20 atomic % or more and 50 atomic % or less, 20 atomic % or more and 40 atomic % or less, or 30 atomic % or more and 40 atomic % or less.

[0049] The lower limit of the Ti content relative to the total amount of Zn, Sn, and Ti contained in the first dielectric layer 14 is 10 atomic % or more, and preferably 20 atomic % or more. When the Ti content is 10 atomic % or more, a decrease in playback durability can be suppressed.

[0050] The upper limit of the content of Ti relative to the total amount of Zn, Sn, and Ti contained in the first dielectric layer 14 is, for example, 30 atomic % or less, or 25 atomic % or less.

[0051] The numerical range of the Ti content relative to the total amount of Zn, Sn, and Ti contained in the first dielectric layer 14 may be defined by any of the upper limit values ​​and any of the lower limit values, for example, 10 atomic % or more and 30 atomic % or less, 20 atomic % or more and 30 atomic % or less, or 20 atomic % or more and 25 atomic % or less.

[0052] (Thickness of the first dielectric layer 14) The thickness of the first dielectric layer 14 is preferably within the range of 15 nm to 30 nm. When the thickness of the first dielectric layer 14 is 15 nm or more, the functionality of the first dielectric layer 14 can be ensured. On the other hand, when the thickness of the first dielectric layer 14 is 30 nm or less, a decrease in the recording power margin can be suppressed.

[0053] (Second dielectric layer 15) The second dielectric layer 15 has a function as a protective layer that protects the recording layer 13 and a function to adjust the reflectance of the information signal layer L. The second dielectric layer 15 is provided on the nearer side than the recording layer 13 when viewed from the first light irradiation surface C1.

[0054] The second dielectric layer 15 includes a dielectric. The dielectric includes, for example, at least one selected from the group consisting of oxides, nitrides, sulfides, carbides, and fluorides. Examples of oxides include oxides containing one or more elements selected from the group consisting of In, Zn, Sn, Al, Si, Ge, Ti, Ga, Ta, Nb, Hf, Zr, Cr, Bi, and Mg. Examples of nitrides include nitrides containing one or more elements selected from the group consisting of In, Sn, Ge, Cr, Si, Al, Nb, Mo, Ti, Nb, Mo, Ti, W, Ta, and Zn, preferably nitrides containing one or more elements selected from the group consisting of Si, Ge, and Ti. Examples of sulfides include Zn sulfide. Examples of carbides include carbides containing one or more elements selected from the group consisting of In, Sn, Ge, Cr, Si, Al, Ti, Zr, Ta, and W, preferably carbides containing one or more elements selected from the group consisting of Si, Ti, and W. Examples of fluorides include fluorides containing one or more elements selected from the group consisting of Si, Al, Mg, Ca, and La. Specific examples of these mixtures include ZnO-SnO2-ZrO2, ZnS-SiO2, SiO2-In2O3-ZrO2 (SIZ), SiO2-Cr2O3-ZrO2 (SCZ), In2O3-SnO2 (ITO), In2O3-CeO2 (ICO), In2O3-Ga2O3 (IGO), In2O3-Ga2O3-ZnO (IGZO), Sn2O3-Ta2O5 (TTO), TiO2-SiO2, Al2O3-ZnO, and Al2O3-BaO.

[0055] The thickness of the second dielectric layer 15 is preferably in the range of 15 nm to 50 nm. When the thickness of the second dielectric layer 15 is 15 nm or more, the functionality of the second dielectric layer 15 can be ensured. On the other hand, when the thickness of the second dielectric layer 15 is 50 nm or less, a decrease in the recording power margin can be suppressed.

[0056] [1.2 Manufacturing method of optical recording medium 1] Next, an example of a method for manufacturing the optical recording medium 1 according to the first embodiment of the present disclosure will be described.

[0057] (Process for manufacturing the first disc 10) The first disk 10 is produced as follows.

[0058] (Process for forming substrate 11) First, a substrate 11 is formed with a concave-convex surface formed on one main surface thereof. As a method for forming the substrate 11, for example, an injection molding method or a photopolymer method (2P method: Photo Polymerization) can be used.

[0059] (Process of forming information signal layer L0) Next, for example, by sputtering, the information signal layer L0 is formed by sequentially laminating the first dielectric layer 14, the recording layer 13, and the second dielectric layer 15 on the substrate 11. The steps of forming the first dielectric layer 14, the recording layer 13, and the second dielectric layer 15 will be specifically described below.

[0060] (Step of forming first dielectric layer 14) First, the substrate 11 is transferred into a vacuum chamber equipped with a plurality of targets for forming the first dielectric layer, and the vacuum chamber is evacuated to a predetermined pressure. The plurality of targets for forming the first dielectric layer may be a Zn-O target, a Sn-O target, and an Al-O target, or a Zn-O target, a Sn-O target, and a Ti-O target.

[0061] Thereafter, while introducing a process gas such as Ar gas or O2 gas into the vacuum chamber, the multiple dielectric layer formation targets are sputtered to form a first dielectric layer 14 on the substrate 11. Sputtering methods that can be used include radio frequency (RF) sputtering and direct current (DC) sputtering, with DC sputtering being particularly preferred. This is because DC sputtering requires less expensive equipment and has a higher film formation rate than RF sputtering, thereby reducing manufacturing costs and improving productivity.

[0062] (Process of forming recording layer 13) Next, the substrate 11 is transferred into a vacuum chamber equipped with one or more targets for forming a recording layer, and the vacuum chamber is evacuated to a predetermined pressure. Thereafter, while a process gas such as Ar gas or O2 gas is introduced into the vacuum chamber, the one or more targets for forming a recording layer are sputtered to form a recording layer 13 on the first dielectric layer 14. Examples of sputtering methods that can be used include radio frequency (RF) sputtering and direct current (DC) sputtering, with DC sputtering being particularly preferred. As described above, DC sputtering can be used to reduce manufacturing costs and improve productivity.

[0063] (Step of forming second dielectric layer 15) Next, the substrate 11 is transferred into a vacuum chamber equipped with one or more targets for forming a dielectric layer, and the vacuum chamber is evacuated to a predetermined pressure. Thereafter, the targets are sputtered while a process gas such as Ar gas or O2 gas is introduced into the vacuum chamber, to form a second dielectric layer 15 on the recording layer 13. Examples of sputtering methods that can be used include radio frequency (RF) sputtering and direct current (DC) sputtering, with DC sputtering being particularly preferred. As described above, DC sputtering can be used because it can reduce manufacturing costs and improve productivity. In this way, the information signal layer L0 is formed on the substrate 11.

[0064] (Spacer layer S1 formation process) Next, for example, by spin coating, an ultraviolet curable resin is uniformly applied onto the information signal layer L0. After that, the concave-convex pattern of the stamper is pressed against the ultraviolet curable resin uniformly applied onto the information signal layer L0, and the ultraviolet curable resin is irradiated with ultraviolet light to harden it, and then the stamper is peeled off. As a result, the concave-convex pattern of the stamper is transferred to the ultraviolet curable resin, and a spacer layer S1 provided with, for example, lands Ld and grooves Gv is formed on the information signal layer L0.

[0065] (Process of forming information signal layers L1, L2, . . . , Ln and process of forming spacer layers S2, S3, . . . Sn) Next, in the same manner as in the above-mentioned "information signal layer forming process" and "spacer layer forming process," an information signal layer L1, a spacer layer S2, an information signal layer L2, a spacer layer S3, ..., a spacer layer Sn, and an information signal layer Ln are stacked in this order on the spacer layer S1.

[0066] (Process for forming light transmitting layer 12) Next, a photosensitive resin such as an ultraviolet curing resin (UV resin) is spin-coated onto the information signal layer Ln, for example, by spin coating, and then the photosensitive resin is irradiated with light such as ultraviolet light to harden it. This forms a light-transmitting layer 12 on the information signal layer Ln. In this way, the first disc 10 is produced.

[0067] (Second disc 20 manufacturing process) The "process for producing the second disk 20" is the same as the "process for producing the first disk 10" described above, and therefore a description thereof will be omitted.

[0068] (Laminating process) Next, an ultraviolet-curable resin is spread as an adhesive between the first and second disks 10 and 20 fabricated as described above, for example by spin coating, as follows: First, the ultraviolet-curable resin is applied in a ring shape along the periphery of the center hole on one of the two main surfaces of the second disk 20 opposite the second light-irradiated surface C2. Next, the first disk 10 is pressed against the second disk 20 via the ultraviolet-curable resin, with the one of the two main surfaces of the first disk 10 opposite the first light-irradiated surface C1 facing the one of the two main surfaces of the second disk 20 opposite the second light-irradiated surface C2.

[0069] Next, the first and second disks 10, 20 are rotated, and the UV-curable resin is spread between the first and second disks 10, 20 in the radial direction of the first and second disks 10, 20. At this time, the rotation speed is adjusted so that the thickness of the UV-curable resin becomes a predetermined thickness. This allows the UV-curable resin to spread from the inner periphery to the outer periphery of the first and second disks 10, 20 between the first and second disks 10, 20. As a result, an optical recording medium 1 having an uncured bonding layer 30 is obtained.

[0070] In the above-described stretching process of the ultraviolet curable resin, it is preferable to irradiate the outer peripheries of the first and second disks 10 and 20 with ultraviolet light to temporarily cure the ultraviolet curable resin that has been stretched to the outer peripheries. This makes it possible to prevent openings from occurring in the outer peripheries of the first and second disks 10 and 20.

[0071] Next, ultraviolet rays are irradiated from both sides of the optical recording medium 1 using an ultraviolet lamp to harden the laminating layer 30. In this way, the desired optical recording medium 1 is obtained.

[0072] [1.3 Effects] In the optical recording medium 1 according to the first embodiment, the first dielectric layer 14 contains Zn, Sn, Al, and O, or Zn, Sn, Ti, and O. When the first dielectric layer 14 contains Zn, Sn, Al, and O, the content of Al relative to the total amount of Zn, Sn, and Al is 10 atomic % or more. When the first dielectric layer 14 contains Zn, Sn, Ti, and O, the content of Ti relative to the total amount of Zn, Sn, and Ti is 10 atomic % or more. This can prevent a decrease in playback durability.

[0073] <2. Second embodiment> [2.1 Configuration of Optical Recording Medium 1A] 3, an optical recording medium 1A according to a second embodiment of the present disclosure is a so-called multi-layer write-once optical recording medium, and has a configuration in which an information signal layer L0, a spacer layer S1, an information signal layer L1, ..., a spacer layer Sn, an information signal layer Ln, and a light transmitting layer 12 serving as a cover layer are stacked in this order on one main surface of a substrate 11A. Note that in the second embodiment, parts that are the same as those in the first embodiment are given the same reference numerals, and descriptions thereof will be omitted.

[0074] The optical recording medium 1A has a light irradiation surface C on one side, onto which light for recording or reproducing an information signal is irradiated. The information signal layer L0 is located at the innermost position based on the light irradiation surface C, and the information signal layers L1 to Ln are located in front of it. Therefore, the information signal layers L1 to Ln are configured to be able to transmit laser light used for recording or reproducing.

[0075] In the optical recording medium 1A according to the second embodiment, information signals are recorded or reproduced by irradiating each of the information signal layers L0 to Ln with laser light from a light irradiation surface C on the side of the light transmitting layer 12. For example, information signals are recorded or reproduced by focusing laser light having a wavelength in the range of 400 nm to 410 nm with an objective lens having a numerical aperture in the range of 0.84 to 0.86, and irradiating the laser light onto each of the information signal layers L0 to Ln from the side of the light transmitting layer 12. An example of such an optical recording medium 1A is a multilayer Blu-ray Disc (BD: Blu-ray (registered trademark) Disc).

[0076] The optical recording medium 1A is typically an optical recording medium of a groove recording system, but may also be an optical recording medium of a land / groove recording system or the like.

[0077] The diameter of substrate 11A is selected to be, for example, 120 mm. The thickness of substrate 11 is selected in consideration of rigidity and is preferably selected to be 0.3 mm or more and 1.3 mm or less, more preferably 0.6 mm or more and 1.3 mm or less, for example, 1.1 mm. The diameter of the center hole is selected to be, for example, 15 mm. The material of substrate 11A is the same as that of substrate 11 in the first embodiment described above.

[0078] The information signal layers L0 to Ln in the optical recording medium 1A are the same as the information signal layers L0 to Ln in the optical recording medium 1 according to the first embodiment.

[0079] [2.2 Manufacturing method of optical recording medium 1A] The method for manufacturing the optical recording medium 1A according to the second embodiment of the present disclosure is similar to the "first disc manufacturing process" in the first embodiment described above.

[0080] [2.3 Effects] The information signal layers L0 to Ln in the optical recording medium 1A according to the second embodiment are similar to the information signal layers L0 to Ln in the optical recording medium 1 according to the first embodiment, and therefore, deterioration in reproduction durability can be suppressed.

[0081] <3 Variations> In the above-described first and second embodiments, the information signal layer L includes the recording layer 13 having a single-layer structure, but the configuration of the information signal layer L is not limited to this. For example, the information signal layer L may include a recording layer 13 having a stacked structure made up of a first layer, ..., n-th layer (n is an integer of 2 or more) having different compositions. In this case, at least one of the first layer, ..., n-th layer 、 It has the same composition as the recording layer 13 in the first embodiment.

[0082] In the above-described first and second embodiments, the case where a plurality of information signal layers L are provided has been described, but a single information signal layer L may also be provided.

[0083] Furthermore, in the above-described first and second embodiments, the case where all of the multiple information signal layers L have the same layer structure (three-layer structure) has been described, but the layer structure may be changed depending on the characteristics (e.g., optical characteristics, durability, etc.) required for each information signal layer L. However, from the viewpoint of productivity, it is preferable that all of the information signal layers L have the same layer structure.

[0084] Furthermore, optical recording media to which the present disclosure can be applied are not limited to those having the configurations of the first and second embodiments. For example, the present disclosure can also be applied to optical recording media having a configuration in which multiple information signal layers and protective layers are stacked in this order on a substrate, and in which information signals are recorded or reproduced by irradiating the multiple information signal layers with laser light from the substrate side, or optical recording media having a configuration in which multiple information signal layers are provided between two substrates, and in which information signals are recorded or reproduced by irradiating the multiple information signal layers with laser light from the side of at least one of the substrates.

[0085] Furthermore, in the case of a multi-layer recording layer configuration, the recording layer of the present disclosure may be combined with a recording layer other than a write-once type.The present disclosure is also applicable to optical recording media in which a recording area using read-only pits or the like is partially provided.

[0086] [Experimental Example] Hereinafter, the present disclosure will be specifically explained using experimental examples, but the present disclosure is not limited to these experimental examples.

[0087] [Experimental Examples 1-1 to 1-5] (Substrate formation process) First, a polycarbonate substrate with a thickness of 1.1 mm was formed by injection molding. At this time, spiral lands and grooves were formed on the polycarbonate substrate as recording tracks. The track pitch Tp was set to 180 nm.

[0088] (First dielectric layer forming step) Next, a first dielectric layer containing Zn, Sn, Al, and O and having a thickness of 18 nm was formed on the polycarbonate substrate by DC co-sputtering using a Zn-O target, a Sn-O target, and an Al-O target. The DC co-sputtering conditions were adjusted so that the composition ratio (atomic percentage ratio) of Zn, Sn, and Al in the first dielectric layer was as shown in Table 1. However, in Experimental Example 1-4, the first dielectric layer could not be formed by DC co-sputtering.

[0089] (Recording layer formation process) Next, a 40-nm-thick recording layer containing Mn, W, Zn, Cu, Al, Ta, and O was formed on the first dielectric layer by DC co-sputtering using an Mn-O target, a W-Zn-O target, and a Cu-Al-Ta-O target. The DC co-sputtering conditions were adjusted so that the composition ratio (atomic percentage) of Mn, W, Zn, Cu, Al, and Ta was 13:18:25:13:5:26.

[0090] (Step of forming second dielectric layer) Next, a Zn-O target, an Sn-O target, and a Zr-O target were DC co-sputtered to form an 18-nm-thick second dielectric layer on the recording layer, containing Zn, Sn, Zr, and O. The DC co-sputtering conditions were adjusted so that the composition ratio (atomic percentage) of Zn, Sn, and Zr was Zn:Sn:Zr 40:40:20.

[0091] Next, a UV-curable resin was uniformly applied onto the second dielectric layer by spin coating, and then cured by irradiating it with UV light to form a light-transmitting layer with a thickness of 100 μm, thereby obtaining the desired optical recording medium.

[0092] [Experimental Examples 2-1 to 2-6] Except for the step of forming the first dielectric layer, optical recording media were obtained in the same manner as in Experimental Example 1-1. In Experimental Examples 2-1 to 2-6, the step of forming the first dielectric layer was carried out as follows.

[0093] A first dielectric layer having a thickness of 18 nm and containing Zn, Sn, Ti, and O was formed on a polycarbonate substrate by DC co-sputtering using a Zn-O target, an Sn-O target, and a Ti-O target. The DC co-sputtering conditions were adjusted so that the composition ratios (atomic percentages) of Zn, Sn, and Ti were as shown in Table 1. However, in Experimental Example 2-5, it was not possible to form a first dielectric layer by DC co-sputtering.

[0094] [Experimental Example 3] An optical recording medium was obtained in the same manner as in Experimental Example 1-1, except for the step of forming the first dielectric layer. In Experimental Example 3, the step of forming the first dielectric layer was carried out as follows.

[0095] A first dielectric layer containing Zn, Sn, Zr, and O and having a thickness of 18 nm was formed on a polycarbonate substrate by DC co-sputtering using a Zn-O target, an Sn-O target, and a Zr-O target. The DC co-sputtering conditions were adjusted so that the composition ratios (atomic percentages) of Zn, Sn, and Zr were as shown in Table 1.

[0096] [Experimental Example 4] An optical recording medium was obtained in the same manner as in Experimental Example 1-1, except for the step of forming the first dielectric layer. In Experimental Example 4, the step of forming the first dielectric layer was carried out as follows.

[0097] A first dielectric layer containing Zn, Sn, Ga, and O was formed on a polycarbonate substrate by DC co-sputtering using a Zn-O target, a Sn-O target, and a Ga-O target. The DC co-sputtering conditions were adjusted so that the composition ratios (atomic percentages) of Zn, Sn, and Ga were as shown in Table 1.

[0098] [Experimental Example 5] An optical recording medium was obtained in the same manner as in Experimental Example 1-1, except for the step of forming the first dielectric layer. In Experimental Example 5, the step of forming the first dielectric layer was carried out as follows.

[0099] A first dielectric layer containing Zn, Sn, Nb, and O and having a thickness of 18 nm was formed on a polycarbonate substrate by DC co-sputtering using a Zn-O target, a Sn-O target, and a Nb-O target. The DC co-sputtering conditions were adjusted so that the composition ratios (atomic percentages) of Zn, Sn, and Nb were as shown in Table 1.

[0100] [Experimental Example 6] An optical recording medium was obtained in the same manner as in Experimental Example 1-1, except for the step of forming the first dielectric layer. In Experimental Example 6, the step of forming the first dielectric layer was carried out as follows.

[0101] A first dielectric layer containing Zn, Sn, Si, and O was formed on a polycarbonate substrate by DC co-sputtering using a Zn-O target, a Sn-O target, and a Si-O target. The DC co-sputtering conditions were adjusted so that the composition ratios (atomic percentages) of Zn, Sn, and Si were as shown in Table 1.

[0102] [Experimental Example 7] An optical recording medium was obtained in the same manner as in Experimental Example 1-1, except for the step of forming the first dielectric layer. In Experimental Example 7, the step of forming the first dielectric layer was carried out as follows.

[0103] An 18-nm-thick first dielectric layer containing Sn, In, and O was formed on a polycarbonate substrate by DC co-sputtering using an Sn-O target and an In-O target. The DC co-sputtering conditions were adjusted so that the composition ratio (atomic percentage) of Sn and In was as shown in Table 1.

[0104] (evaluation) The error rate was evaluated for the optical recording medium of Experimental Example 3 obtained as described above. The reproduction durability was also evaluated for the optical recording media of Experimental Examples 1-1 to 1-3, 1-5, 2-1 to 2-4, 2-6, and 3 to 7 obtained as described above. These evaluations of the error rate and reproduction durability were specifically carried out as follows.

[0105] (error rate) Using an optical recording medium evaluation device, signals were recorded on the groove tracks of the optical recording medium of Experimental Example 3, and the error rate was measured by repeating the reproduction of the recorded signals from the groove tracks 1.5 million times. The measurement results are shown in Figure 4.

[0106] (Reproduction durability) Using an optical recording medium evaluation device, signals were recorded on groove tracks of the optical recording media of Experimental Examples 1-1 to 1-3, 1-5, 2-1 to 2-4, 2-6, and 3-7, and the recorded signals from the groove tracks were reproduced over one million times to measure the return light intensity of the laser beam. Next, the ratio of the return light intensity after n reproductions to the return light intensity after one reproduction was calculated, and this ratio was used as the reflectance. The measurement results of the return light intensity of the optical recording medium of Experimental Example 3 after one reproduction are shown on the left side of Figure 5, and the measurement results of the return light intensity of the optical recording medium of Experimental Example 3 after 500,000 reproductions are shown on the right side of Figure 5. In Figure 5, region R1 represents the region where a recording mark is formed, and region R2 represents the region where no recording mark is formed. Level L0 represents the reference light intensity. Figure 6 shows the change in reflectance when the optical recording medium of Experimental Example 3 was repeatedly reproduced. Figure 7 shows the change in reflectance when the optical recording media of Experimental Examples 1-1, 2-1, and 3 were repeatedly reproduced. FIG. 8 shows the change in reflectance when the optical recording media of Experimental Examples 3 to 7 were repeatedly read.

[0107] Next, the read durability of the optical recording medium was evaluated based on the amount of decrease in reflectance after 1 million reads (reproduced light irradiations) from the reflectance after one read (reproduced light irradiations). The results are shown in Table 1. ⊚: The amount of reflected light reduced by 5% or less after 1 million irradiations with reproducing light. ◯: The reduction in the amount of reflected light after 1 million irradiations with reproducing light is more than 5% and 8% or less. ×: The amount of reflected light reduced by more than 8% after 1 million irradiations with reproducing light. The evaluation result symbol "◎" indicates that the playback durability is very good, the evaluation result symbol "◯" indicates that the playback durability is good, and the evaluation result symbol "×" indicates that the playback durability is poor. In Table 1, a "-" in the "Composition ratio of first dielectric layer" column indicates that the corresponding component is not contained. In Table 1, a "-" in the "Evaluation result of playback durability" column indicates that the playback durability was not evaluated.

[0108] [Table 1]

[0109] The following can be seen from Figure 4: In optical recording media whose first dielectric layer contains Zn, Sn, Zr, and O, the error rate increases significantly after the number of read cycles exceeds 500,000. In other words, the read durability decreases significantly after the number of read cycles exceeds 500,000. The following can be seen from Figure 5. In areas where recording marks are formed, the intensity of the returned light hardly changes even when reproduction is repeated. In contrast, in areas where no recording marks are formed, the intensity of the returned light decreases with repeated reproduction. The decrease in reproduction durability described above is thought to be due to this decrease in the intensity of the returned light in areas where no recording marks are formed. The following can be seen from Figure 6: In optical recording media whose first dielectric layer contains Zn, Sn, Zr, and O, the reflectivity drops significantly after the number of reads exceeds 500,000. It is believed that there is a correlation between the increase in error rate and the drop in reflectivity.

[0110] The following can be seen from Table 1, Figures 7 and 8. When the first dielectric layer contains Zn, Sn, Al, and O and the content of Al relative to the total amount of Zn, Sn, and Al is 10 atomic % or more, sufficient reproduction performance can be ensured even after 1 million reproduction cycles (see the evaluation results of Experimental Examples 1-1 to 1-3 and 1-5). If the Zn content relative to the total amount of Zn, Sn, and Al is 15 atomic % or less, the conductivity of the Zn-O target decreases, making it difficult to perform DC sputtering on the Zn-O target (see the evaluation results of Experimental Example 1-4). When the first dielectric layer contains Zn, Sn, Ti, and O and the content of Ti relative to the total amount of Zn, Sn, and Ti is 10 atomic % or more, sufficient reproduction performance can be ensured even after 1 million reproduction cycles (see the evaluation results of Experimental Examples 2-1 to 2-4 and 2-6). If the Zn content relative to the total amount of Zn, Sn, and Ti is 15 atomic % or less, the conductivity of the Zn-O target decreases, making it difficult to perform DC sputtering of the Zn-O target (see the evaluation results of Experimental Example 2-5). If the first dielectric layer does not contain Zn, Sn, Al and O, or Zn, Sn, Ti and O, it is difficult to ensure sufficient reproduction performance at 1 million reproduction cycles (see the evaluation results of Experimental Examples 3 to 7).

[0111] Although the embodiments and modifications of the present disclosure have been specifically described above, the present disclosure is not limited to the above embodiments and modifications, and various modifications based on the technical concepts of the present disclosure are possible. For example, the configurations, methods, steps, shapes, materials, and numerical values ​​described in the above embodiments and modifications are merely examples, and different configurations, methods, steps, shapes, materials, and numerical values ​​may be used as necessary. The configurations, methods, steps, shapes, materials, and numerical values ​​of the above embodiments and modifications can be combined with each other as long as they do not deviate from the spirit of the present disclosure.

[0112] The chemical formulas of the compounds exemplified in the above embodiments and modifications are representative, and are not limited to the valences described, etc., as long as they are the general names of the same compounds. In the numerical ranges described in stages in the above embodiments and modifications, the upper or lower limit of a numerical range in one stage may be replaced with the upper or lower limit of a numerical range in another stage. Unless otherwise specified, the materials exemplified in the above embodiments and modifications can be used alone or in combination of two or more.

[0113] The present disclosure may also employ the following configuration. (1) At least one information signal layer is provided, the information signal layer includes a first dielectric layer, a recording layer, and a second dielectric layer in this order; the first dielectric layer is provided on the back side of the recording layer as viewed from the light irradiation surface, the recording layer contains Mn and O, the first dielectric layer comprises Zn, Sn, Al and O, or Zn, Sn, Ti and O; the content of Al relative to the total amount of Zn, Sn, and Al is 10 atomic % or more, the content of the Ti relative to the total amount of the Zn, the Sn, and the Ti is 10 atomic % or more; Optical recording media. (2) the content of the Zn relative to the total amount of the Zn, the Sn, and the Al is 15 atomic % or more, the content of the Zn relative to the total amount of the Zn, the Sn, and the Ti is 15 atomic % or more; The optical recording medium according to (1). (3) the content of Al relative to the total amount of Zn, Sn, and Al is 20 atomic % or more, the content of the Ti relative to the total amount of the Zn, the Sn, and the Ti is 20 atomic % or more; The optical recording medium according to (1) or (2). (4) the content of the Zn relative to the total amount of the Zn, the Sn, and the Al is 30 atomic % or more and 70 atomic % or less, the content of the Sn relative to the total amount of the Zn, the Sn, and the Al is 20 atomic % or more and 40 atomic % or less, the content of Al relative to the total amount of Zn, Sn, and Al is 10 atomic % or more and 30 atomic % or less, the content of the Zn relative to the total amount of the Zn, the Sn, and the Ti is 30 atomic % or more and 70 atomic % or less, the content of the Sn relative to the total amount of the Zn, the Sn, and the Ti is 20 atomic % or more and 50 atomic % or less, the content of Ti relative to the total amount of Zn, Sn, and Ti is 10 atomic % or more and 30 atomic % or less; The optical recording medium according to (1). (5) The at least one information signal layer includes a plurality of information signal layers. The optical recording medium according to any one of (1) to (4). (6) The thickness of the first dielectric layer is 15 nm or more and 30 nm or less. The optical recording medium according to any one of (1) to (5). (7) the information signal layer is configured to be capable of multi-value recording; The optical recording medium according to any one of (1) to (6). [Explanation of symbols]

[0114] 1. 1A Optical recording media 10 Disc 1 20 Disc 2 30 Bonding layer 11, 11A, 21 board 12, 22 Light transmission layer 13 Recording layer 14, 15 Protective layer L0~Ln, L0~Lm information signal layer S1~Sn, S1~Sm spacer layer C Light irradiation surface C1 1st light irradiation surface C2 Second light irradiation surface Gv Groove Ld Land Tp Track Pitch

Claims

1. At least one information signal layer is provided, the information signal layer includes a first dielectric layer, a recording layer, and a second dielectric layer in this order; the first dielectric layer is provided on the back side of the recording layer as viewed from the light irradiation surface, the recording layer contains Mn and O, the first dielectric layer comprises Zn, Sn, Al and O, or Zn, Sn, Ti and O; the content of Al relative to the total amount of Zn, Sn, and Al is 10 atomic % or more; the content of Ti relative to the total amount of Zn, Sn, and Ti is 10 atomic % or more; Optical recording media.

2. the content of the Zn relative to the total amount of the Zn, the Sn, and the Al is 15 atomic % or more; the content of the Zn relative to the total amount of the Zn, the Sn, and the Ti is 15 atomic % or more; 2. The optical recording medium according to claim 1.

3. the content of Al relative to the total amount of Zn, Sn, and Al is 20 atomic % or more; the content of Ti relative to the total amount of Zn, Sn, and Ti is 20 atomic % or more; 2. The optical recording medium according to claim 1.

4. the content of the Zn relative to the total amount of the Zn, the Sn, and the Al is 30 atomic % or more and 70 atomic % or less, the content of the Sn relative to the total amount of the Zn, the Sn, and the Al is 20 atomic % or more and 40 atomic % or less, the content of Al relative to the total amount of Zn, Sn, and Al is 10 atomic % or more and 30 atomic % or less, the content of the Zn relative to the total amount of the Zn, the Sn, and the Ti is 30 atomic % or more and 70 atomic % or less, the content of Sn relative to the total amount of Zn, Sn, and Ti is 20 atomic % or more and 50 atomic % or less, the content of Ti relative to the total amount of Zn, Sn, and Ti is 10 atomic % or more and 30 atomic % or less; 2. The optical recording medium according to claim 1.

5. the at least one information signal layer includes a plurality of information signal layers; 2. The optical recording medium according to claim 1.

6. The thickness of the first dielectric layer is 15 nm or more and 30 nm or less.

2. The optical recording medium according to claim 1.

7. the information signal layer is configured to be capable of multi-value recording; 2. The optical recording medium according to claim 1.

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