WO2020246135A1

WO2020246135A1 - Optical recording medium

Info

Publication number: WO2020246135A1
Application number: PCT/JP2020/016025
Authority: WO
Inventors: 陽太田; 紀彰西; 崇志清水
Original assignee: ソニー株式会社
Priority date: 2019-06-05
Filing date: 2020-04-09
Publication date: 2020-12-10
Also published as: JPWO2020246135A1; JP7468521B2; CN113874939A

Abstract

This optical recording medium comprises an optical recording medium main body having a first surface and a second surface, and a first uneven structural layer provided on the first surface. The first uneven structural layer includes a plurality of first structural bodies provided at a pitch equal to or less than the wavelength of light for recording or playing back an information signal. The area ratio of protrusions in the first uneven structural layer is 80% or less, and light is radiated from the first-surface side.

Description

Optical recording medium

This disclosure relates to an optical recording medium.

It is generally said that optical recording media have higher storage reliability than hard disk drives (HDD), flash memories, etc. due to their recording / playback principle. For this reason, in recent years, the demand for optical recording media as archival media has increased. Optical recording media are generally required to ensure surface smoothness.

In optical recording media, a hard coat layer is widely used for the purpose of protecting the surface of the medium. When a hard coat layer is used, the smoothness of the surface of the medium is likely to be impaired. Therefore, a technique for forming a smooth hard coat layer has been studied. For example, Patent Document 1 discloses an optical recording medium on which a hard coat layer having excellent durability such as scratch resistance, dust resistance, and stain resistance, and excellent surface smoothness at the time of coating is formed. ..

JP-A-2009-96927

However, with an optical recording medium having a smooth surface, there is a problem that the optical recording media stick to each other when a plurality of optical recording media are stacked.

An object of the present disclosure is to provide an optical recording medium capable of suppressing sticking between optical recording media when a plurality of optical recording media are stacked.

In order to solve the above-mentioned problems, the present disclosure includes an optical recording medium main body having a first surface and a second surface, and a first concavo-convex structure layer provided on the first surface. The concavo-convex structure layer includes a plurality of first structures provided at a pitch equal to or lower than the wavelength of light for recording or reproducing an information signal, and the area ratio of the convex portion of the first concavo-convex structure layer is 80. % Or less, and is an optical recording medium in which light is irradiated from the first surface side.

FIG. 1A is a perspective view showing an example of the appearance of the optical recording medium according to the first embodiment of the present disclosure. 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. FIG. 2 is a cross-sectional view showing an example of the configuration of each information signal layer shown in FIG. FIG. 3 is a plan view showing an example of arrangement of a plurality of structures. FIG. 4 is a cross-sectional view showing an example of the configuration of the optical recording medium according to the second embodiment of the present disclosure. FIG. 5 is a cross-sectional view showing an example of the configuration of the optical recording medium according to the modified example. FIG. 6A is an SEM image of the uneven structure of the optical disc of the first embodiment. FIG. 6B is an SEM image of the uneven structure of the optical disc of the second embodiment. FIG. 6C is an SEM image of the uneven structure of the optical disc of Comparative Example 2. FIG. 7 is a graph showing the frequency distribution of the uneven structure of the optical disk of the first embodiment. FIG. 8 is a schematic view for explaining a method of measuring the sticking force. FIG. 9A is a graph showing the relationship between the area ratio of the convex portion and the sticking force. FIG. 9B is a graph showing the relationship between the area ratio of the convex portion and the sliding force. FIG. 10A is a graph showing the evaluation results of the signal characteristics of the optical disc of the third embodiment. FIG. 10B is a graph showing the evaluation results of the signal characteristics of the optical disc of the fourth embodiment. FIG. 10C is a graph showing the evaluation results of the signal characteristics of the optical disc of Comparative Example 3.

The embodiments of the present disclosure will be described in the following order.
1 First embodiment 1.1 Configuration of optical recording medium 1.2 Manufacturing method of optical recording medium 1.3 Effect 2 Second embodiment 2.1 Configuration of optical recording medium 2.2 Manufacturing method of optical recording medium 2.3 Effect 3 Modification example

<1 First Embodiment>
[1.1 Configuration of optical recording medium]
As shown in FIG. 1A, the optical recording medium 1 according to the first embodiment of the present disclosure has a disk shape having an opening (hereinafter referred to as “center hole”) at the center. The shape of the optical recording medium 1 is not limited to this example, and may be, for example, a card shape. The optical recording medium 1 is a so-called multilayer write-once optical recording medium (for example, AD (Archival Disc)), and as shown in FIG. 1B, the optical recording medium main body 2, the first concave-convex structure layer 3, and the second The concavo-convex structure layer 4 is provided. The optical recording medium 1 is an optical recording medium of a method of recording data on both a groove track and a land track (hereinafter referred to as a “land / groove recording method”).

(Optical recording medium body)
The optical recording medium main body 2 includes a first disc 10, a second disc 20, and a bonding layer 30. In the first disk 10, the information signal layer L0, the spacer layer S1, the information signal layer L1, ..., The spacer layer Sn, the information signal layer Ln, and the light transmitting layer 12 which is a cover layer are one of the substrates 11 in this order. It has a structure laminated on the main surface. In the second disk 20, the information signal layer L0, the spacer layer S1, the information signal layer L1, ..., The spacer layer Sm, the information signal layer Lm, and the light transmitting layer 22 as the cover layer are one of the substrates 21 in this order. It has a structure laminated on the main surface. However, n and m are independently integers of 2 or more, and from the viewpoint of improving the recording capacity, they are preferably an integer of 3 or more, more preferably an integer of 4 or more, and even more preferably an integer of 5 or more. is there. In the following description, when the information signal layers L0 to Ln and L0 to Lm are not particularly distinguished, they are referred to as the information signal layer L.

The optical recording medium main body 2 has light irradiation surfaces on both sides to which laser light for recording or reproducing an information signal is irradiated. More specifically, the recording or reproduction of the information signal of the first disk 10 and the first light irradiation surface C1 irradiated with the laser beam for recording or reproducing the information signal of the first disk 10 and the information signal of the second disk 20. It has a second light irradiation surface C2 to be irradiated with a laser beam for performing.

In the first disk 10, the information signal layer L0 is located at the innermost position with respect to the first light irradiation surface C1, and the information signal layers L1 to Ln are located in front of the first light irradiation surface C1. Therefore, the information signal layers L1 to Ln are configured to be capable of transmitting laser light used for recording or reproduction. On the other hand, in the second disk 20, the information signal layer L0 is located at the innermost position with respect to the second light irradiation surface C2, and the information signal layers L1 to Lm are located in front of the second light irradiation surface C2. Therefore, the information signal layers L1 to Lm are configured to be capable of transmitting laser light used for recording or reproduction.

In the optical recording medium 1, the information signal of the first disk 10 is recorded or reproduced as follows. That is, by irradiating the information signal layers L0 to Ln included in the first disk 10 with laser light from the first light irradiation surface C1 on the light transmitting layer 12 side, the information signal of the first disk 10 can be obtained. Recording or playback takes place. For example, laser light having a wavelength in the range of 350 nm or more and 415 nm or less is focused by an objective lens having a numerical aperture in the range of 0.84 or more and 0.95 or less, and the first disk is displayed from the light transmitting layer 12 side. By irradiating each of the information signal layers L0 to Ln included in 10, the information signal is recorded or reproduced.

On the other hand, the recording or reproduction of the information signal of the second disc 20 is performed as follows. That is, by irradiating each information signal layer L0 to Lm included in the second disk 20 with laser light from the second light irradiation surface C2 on the light transmitting layer 22 side, the information signal of the second disk 20 can be obtained. Recording or playback takes place. For example, laser light having a wavelength in the range of 350 nm or more and 415 nm or less is focused by an objective lens having a numerical aperture in the range of 0.84 or more and 0.95 or less, and a second disk is displayed from the light transmitting layer 22 side. By irradiating each information signal layer L0 to Lm included in 20, the information signal is recorded or reproduced.

Hereinafter, the

substrates

11 and 21, the bonding layer 30, the information signal layers L0 to Ln, L0 to Lm, the spacer layers S1 to Sn, S1 to Sm, and the light transmitting layers 12 and 22 constituting the optical recording medium main body 2 will be sequentially described. To do.

(substrate)
The

substrates

11 and 21 have, for example, a disk shape having a center hole provided 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 the uneven surface. In the following, the concave portion of the uneven surface is referred to as a land Ld, and the convex portion is referred to as a groove Gv.

Examples of the shapes of the land Ld and the groove Gv include various shapes such as a spiral shape and a concentric circle shape. Further, the land Ld and / or the groove Gv may be wobbled (meandering) for stabilizing the linear velocity, adding address information, and the like.

The spiral directions of the first disc 10 and the second disc 20 may be opposite to each other. In this case, the optical recording medium (double-sided disc) 1 in which the first disc 10 and the second disc 20 are bonded can be simultaneously recorded and played back, so that the data transfer speed during recording and playback is approximately doubled. be able to.

The outer diameter (diameter) of the

substrates

11 and 21 is selected to be, for example, 120 mm. The inner diameter (diameter) of the

substrates

11 and 21 is selected to be, for example, 15 mm. The thickness of the 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.

As the materials of the

substrates

11 and 21, for example, a plastic material or glass can be used, and it is preferable to use a plastic material from the viewpoint of moldability. As the plastic material, for example, a polycarbonate resin, a polyolefin resin, an acrylic resin, or the like can be used, and from the viewpoint of cost, it is preferable to use a polycarbonate resin.

(Lated layer)
The bonding layer 30 is provided between the first disc 10 and the second disc 20. The bonding layer 30 attaches the first disk 10 and the second disk 20 to each other. More specifically, the surface of the first disk 10 on the substrate 11 side and the surface of the second disk substrate on the substrate 21 side are bonded so that the light transmitting layers 12 and 22 are on the front side, respectively. ..

The bonding layer 30 is made of a cured ultraviolet curable resin. The thickness of the bonded layer 30 is, for example, 0.01 mm or more and 0.22 mm or less. The ultraviolet curable resin is, for example, a radical polymerization type ultraviolet curable resin.

(Information signal layer)
The information signal layer L has a concave track (hereinafter referred to as “land track”) and a convex track (hereinafter referred to as “groove track”). The optical recording medium 1 according to the first embodiment is configured to be capable of recording an information signal on both a land track and a groove track. From the viewpoint of high recording density, the track pitch Tp of the land track and the groove track is preferably 0.225 μm or less, more preferably less than 0.225 μm. The lower limit of the track pitch Tp is not particularly limited, but is, for example, 0.12 μm or more.

As shown in FIG. 2, the information signal layers L0 to Ln include an inorganic recording layer (hereinafter, simply referred to as “recording layer”) 13 having an upper surface (first main surface) and a lower surface (second main surface). A protective layer 14 provided adjacent to the upper surface of the recording layer 13 and a protective layer 15 provided adjacent to the lower surface of the recording layer 13 are provided. With such a configuration, the durability of the recording layer 13 can be improved. Here, the upper surface refers to the main surface of both main surfaces of the recording layer 13 on the side irradiated with the laser light for recording or reproducing the information signal, and the lower surface means the main surface irradiated with the above-mentioned laser light. The main surface on the opposite side to the side, that is, the main surface on the substrate 11 side. Since the configuration of the information signal layers L0 to Lm can be the same as that of the information signal layers L0 to Ln, the description thereof will be omitted.

(Recording layer)
The recording layer 13 is configured to be able to record an information signal by irradiating the laser beam. Specifically, the recording layer 13 is configured so that a recording mark can be formed by irradiating a laser beam. The recording layer 13 is an inorganic recording layer and contains a metal oxide as a main component as an inorganic recording material. The metal oxide includes, for example, an inorganic recording material containing manganese oxide (MnO-based material), an inorganic recording material containing palladium oxide (PdO-based material), an inorganic recording material containing copper oxide (CuO-based material), or silver oxide. It is an inorganic recording material (AgO-based material).

The MnO-based material preferably further contains one or both of tungsten oxide and molybdenum oxide and zirconium oxide in addition to manganese oxide. The MnO-based material may further contain one or both of nickel oxide and magnesium oxide with or without these oxides other than manganese oxide.

The PdO-based material preferably further contains tungsten oxide and copper oxide in addition to palladium oxide, and more preferably further contains tungsten oxide, copper oxide, and zinc oxide.

The thickness of the recording layer 13 is preferably in the range of 25 nm or more and 60 nm or less, more preferably 30 nm or more and 50 nm or less. When the thickness of the recording layer 13 is 25 nm or more, excellent signal characteristics can be obtained. On the other hand, when the thickness of the recording layer 13 is 60 nm or less, a wide recording power margin can be secured.

(Protective layer)
The protective layers 14 and 15 have a function as an oxygen barrier layer. Thereby, the durability of the recording layer 13 can be improved. In addition, the

protective layers

14 and 15 have a function of suppressing the escape of oxygen in the recording layer 13. As a result, changes in the film quality of the recording layer 13 (detected mainly as a decrease in reflectance) can be suppressed, and a preferable film quality as the recording layer 13 can be secured. The protective layers 14 and 15 also have a function of improving recording characteristics.

The protective layers 14 and 15 contain a dielectric. The dielectric comprises, for example, at least one selected from the group consisting of oxides, nitrides, sulfides, carbides and fluorides. As the materials of the

protective layers

14 and 15, the same or different materials can be used. As the oxide, for example, an oxide of 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. Can be mentioned. As the nitride, for example, a nitride of 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 a nitride of one or more elements selected from the group consisting of Si, Ge and Ti. Examples of the sulfide include Zn sulfide. The carbides include, for example, carbides of one or more elements selected from the group consisting of In, Sn, Ge, Cr, Si, Al, Ti, Zr, Ta and W, preferably from the group consisting of Si, Ti and W. Carbides of one or more selected elements can be mentioned. Examples of the fluoride include fluorides of one or more elements selected from the group consisting of Si, Al, Mg, Ca and La. Specific examples of these _{_{_{_{mixtures, ZnS-SiO 2, SiO 2}}}} -In 2 O 3 -ZrO 2 (SIZ), 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 (IGO), In ₂ O _3- Ga ₂ O _3- ZnO (IGZO), Sn ₂ O _3- Ta ₂ O _{_{_{5 (TTO), TiO 2 -SiO}}} 2, Al 2 O 3 -ZnO, Al 2 O 3 -BaO , and the like.

The thickness of the protective layer 15 is preferably in the range of 2 nm or more and 30 nm or less. When the thickness of the protective layer 15 is 2 nm or more, a good barrier effect can be obtained. On the other hand, when the thickness of the protective layer 15 is 30 nm or less, it is possible to suppress a decrease in the recording power margin.

The thickness of the protective layer 14 is preferably in the range of 2 nm or more and 50 nm or less. When the thickness of the protective layer 14 is 2 nm or more, a good barrier effect can be obtained. On the other hand, when the thickness of the protective layer 14 is 50 nm or less, it is possible to suppress a decrease in the recording power margin.

(Spacer layer)
The spacer layers S1 to Sn and S1 to Sm have a role of physically and optically separating the information signal layers L0 to Ln and L0 to Lm with sufficient distances, respectively, and the surface thereof is provided with an uneven surface. There is. The uneven surface forms, for example, concentric or spiral land Ld and groove Gv. The thickness of the spacer layers S1 to Sn and S1 to Sm is preferably 9 μm or more and 50 μm or less. The materials of the spacer layers S1 to Sn and S1 to Sm are not particularly limited, but it is preferable to use an ultraviolet curable acrylic resin. Further, since the spacer layers S1 to Sn and S1 to Sm serve as optical paths for laser light for recording and reproducing data in the inner layer, it is preferable that the spacer layers have sufficiently high light transmission.

(Light transmitting layer)
The light transmitting layers 12 and 22 are resin layers obtained by curing a photosensitive resin such as an ultraviolet curable resin. Examples of the ultraviolet curable resin include an ultraviolet curable acrylic resin. Further, the light transmitting layers 12 and 22 may be composed of a light transmitting sheet having a ring shape and an adhesive layer for adhering the light transmitting sheet to the information signal layers Ln and Lm. .. The light-transmitting sheet is preferably made of a material having a low absorption ability with respect to the laser light used for recording and reproduction, and specifically, it is preferably made of a material having a transmittance of 90% or more. As the material of the light transmissive sheet, for example, a polycarbonate resin or a polyolefin resin (for example, Zeonex (registered trademark)) or the like can be used. As the material of the adhesive layer, for example, an ultraviolet curable resin or a pressure-sensitive adhesive (PSA: Pressure Sensitive Adhesive) can be used.

The thickness of the light transmitting layers 12 and 22 is preferably selected from the range of 10 μm or more and 177 μm or less, for example, 57 μm. High-density recording can be realized by combining such thin light transmitting layers 12 and 22 with an objective lens having a high NA (numerical aperture) of, for example, about 0.85.

(First and second uneven structure layers)
The first and second uneven structure layers 3 and 4 impart scratch resistance to the first and second light irradiation surfaces C1 and C2, respectively. Further, the first and second uneven structure layers 3 and 4 have reflection suppression functions for suppressing the reflection of laser light for recording or reproducing an information signal on the first and second light irradiation surfaces C1 and C2, respectively. Give. The first uneven structure layer 3 is provided on the first light irradiation surface C1 of the optical recording medium main body 2. The second uneven structure layer 4 is provided on the second light irradiation surface C2 of the optical recording medium main body 2.

As the materials of the first and second concave-convex structure layers 3 and 4, for example, an acrylic resin, a silicone resin, a fluororesin, an organic-inorganic hybrid resin, or the like can be used. The first and second uneven structure layers 3 and 4 may contain fine powder of metal oxide particles such as silica particles in order to improve the mechanical strength.

The upper limit of the area ratio R of the convex portions in the first and second concave-convex structure layers 3 and 4 is 80% or less, preferably 60% or less from the viewpoint of suppressing the adhesion between the superimposed optical recording media 1. , More preferably 50% or less, even more preferably 40% or less, and particularly preferably 20% or less. On the other hand, the lower limit of the area ratio R is preferably 10% or more, more preferably 20% or more, and even more preferably 30% or more from the viewpoint of improving the reflection suppressing effect. Here, the convex portion refers to the convex portion itself when the first and second concave-convex structure layers 3 and 4 have a convex structure, and the first and second concave-convex structure layers 3 When 4 has a concave structure, it refers to a portion without a concave structure which is regarded as a convex portion with reference to the concave portion. Specifically, the area ratio R of the convex portion in the first and second uneven structure layers 3 and 4 is the ratio of the area Sb of the convex portion forming region to the area Sa of the uneven structure forming region (= (Sb / Sa)). It means × 100). The method of measuring the area ratio R will be described in Examples.

The first uneven structure layer 3 is a hard coat layer provided with a fine uneven structure (moss eye structure) on the surface. Specifically, the first concavo-convex structure layer 3 includes a base layer 3A and a plurality of structures 3B. The basal layer 3A and the plurality of structures 3B may be made of the same material or may be made of different materials. Since the second concavo-convex structure layer 4 has the same structure as the first concavo-convex structure layer 3, the description of the structure of the second concavo-convex structure layer 4 will be omitted.

The basal layer 3A is the main body of the hard coat layer and is provided on the first light irradiation surface C1. The plurality of structures 3B are provided on the basal layer 3A. The structure 3B is a so-called moth-eye structure (sub-wavelength structure), and has a convex shape with respect to the first light irradiation surface C1. The structure 3B may have a shape similar to a concave portion or a convex portion (for example, a pit) used for recording an information signal on a reproduction-only optical recording medium. In this case, as a master (mold) for forming the first concave-convex structure layer 3 (that is, a plurality of structures 3B), a master for forming a substrate of a reproduction-only optical recording medium can be used. Therefore, it is possible to omit the step of separately producing the master for forming the first concave-convex structure layer 3.

A plurality of structures 3B are arranged so as to form a plurality of rows on the surface of the first light irradiation surface C1, for example. The row has, for example, a linear, concentric or curved shape. Two or more of these shapes may be combined. Examples of the curve include a curve that meanders periodically or aperiodically. Specific examples of such a curve include, but are not limited to, waveforms such as a sine wave and a triangular wave.

The arrangement of the plurality of structures 3B on the first light irradiation surface C1 may be either a regular arrangement or an irregular arrangement. As a regular arrangement, a grid-like arrangement such as a four-sided lattice, a quasi-four-sided lattice, a six-way lattice, or a quasi-hexagonal lattice is preferable. Note that FIG. 3 shows an example in which a plurality of structures 3B are arranged in a hexagonal grid pattern. Here, the four-sided grid means a square-shaped grid. A quasi-square grid is a distorted four-way grid. A hexagonal grid is a regular hexagonal grid. A quasi-hexagonal grid is a distorted hexagonal grid.

Specific shapes of the structure 3B include, for example, a cone shape, a columnar shape, a needle shape, a hemispherical shape, a semi-elliptical shape, a polygonal shape, and the like, but the shape is not limited to these shapes. Other shapes may be adopted. Examples of the cone shape include a cone shape having a sharp top, a cone shape having a flat top (so-called frustum shape), and a cone shape having a convex or concave curved surface at the top. It is not limited to the shape. Examples of the cone shape having a convex curved surface at the top include a quadric curved surface such as a parabolic surface. Further, the conical surface may be curved in a concave or convex shape.

The plurality of structures 3B provided on the first light irradiation surface C1 may all have the same size, shape and height, and the plurality of structures 3B may have different sizes, shapes or different sizes. Those having a height may be included. Further, a plurality of structures 3B may be included in which the lower parts are connected so as to overlap each other.

As shown in FIG. 3, the plurality of structures 3B are arranged at pitches P1 and P2 below the wavelength of the laser beam (for example, 350 nm or less) for recording or reproducing an information signal. The absolute value H of the height of the structure 3B is set, for example, in the range of 40 nm or more and 450 nm or less, but is not limited thereto. Here, the pitch P1 means the pitch of the structure 3B in the inter-row direction D1. Further, the pitch P2 means the pitch of the structure 3B in the row direction (row extending direction) D2.

The aspect ratio of the structure 3B is preferably 1 or more. This is because when the aspect ratio is 1 or more, an excellent reflection suppression function and transmission characteristics can be obtained. The upper limit of the aspect ratio of the structure 3B is preferably 2 or less, more preferably 1.46 or less. This is because when the aspect ratio is 2 or less, the master can be easily separated from the first concavo-convex structure layer 3 when the first concavo-convex structure layer 3 is formed. Here, the aspect ratio of the structure 3B means the aspect ratio R1 of the structure 3B in the inter-row direction D1 and the aspect ratio R2 of the structure 3B in the column direction (extending direction of the rows) D2. The aspect ratio R1 of the structure 3B in the inter-row direction D1 means the ratio (H / W1) of the height H of the structure 3B to the width W1 of the structure 3B in the inter-row direction D1 in the column direction (row). The aspect ratio R2 of the structure 3B in the extending direction (extending direction) D2 means the ratio (H / W2) of the height H of the structure 3B to the width W2 of the structure 3B in the row direction (extending direction of the row) D2. To do.

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

(Making process of the first disc)
First, the first disc 10 is manufactured as follows.

(Substrate molding process)
First, the substrate 11 having the uneven surface formed on one main surface is molded. As a method for molding the substrate 11, for example, an injection molding method or a photopolymerization method (2P method: Photopolymerization) can be used.

(Process of forming information signal layer)
Next, the information signal layer L0 is formed by sequentially laminating the protective layer 15, the recording layer 13, and the protective layer 14 on the substrate 11 by, for example, a sputtering method.

(Process of forming spacer layer)
Next, for example, the ultraviolet curable resin is uniformly applied onto the information signal layer L0 by a spin coating method. Then, the uneven pattern of the stamper is pressed against the ultraviolet curable resin uniformly applied on the information signal layer L0, the ultraviolet curable resin is irradiated with ultraviolet rays to cure it, and then the stamper is peeled off. As a result, the uneven pattern of the stamper is transferred to the ultraviolet curable resin, and for example, the spacer layer S1 provided with the land Ld and the groove Gv is formed on the information signal layer L0.

(Information signal layer forming process and spacer layer forming process)
Next, in the same manner as the above-mentioned "information signal layer forming step" and "spacer layer forming step", the information signal layer L1, the spacer layer S2, the information signal layer L3, ..., The spacer layer Sn, the information signal Layers Ln are laminated on the spacer layer S1 in this order.

(Step of forming a light transmitting layer)
Next, for example, a photosensitive resin such as an ultraviolet curable resin (UV resin) is spin-coated on the information signal layer Ln by a spin coating method, and then the photosensitive resin is irradiated with light such as ultraviolet rays to be cured. As a result, the light transmitting layer 12 is formed on the information signal layer Ln.

(Step of forming the first uneven structure layer)
Next, the first uneven structure layer 3 is formed on the first light irradiation surface C1 of the optical recording medium main body 2 by UV nanoimprint. Specifically, an ultraviolet curable resin is applied to the first light irradiation surface C1 of the optical recording medium main body 2 by a spin coating method, a master (mold) is pressed against the ultraviolet curable resin, and then ultraviolet rays are applied to the ultraviolet curable resin. Is irradiated to cure the ultraviolet curable resin. After curing, the master is released from the UV curable resin. As a result, the first uneven structure layer 3 is formed. As described above, the first disc 10 is produced.

(Production process of the second disc)
Since the "second disc manufacturing step" is the same as the above-mentioned "first disc manufacturing step", the description thereof will be omitted.

(Lasting process)
Next, the ultraviolet curable resin as an adhesive is stretched between the first and

second discs

10 and 20 produced as described above by, for example, a spin coating method as follows. First, an ultraviolet curable resin is applied in a ring shape along the peripheral edge of the center hole on the main surface of both main surfaces of the second disc 20 opposite to the second light irradiation surface C2. Next, the main surface of both main surfaces of the first disk 10 opposite to the first light irradiation surface C1 and the second light irradiation surface C2 of both main surfaces of the second disk 20 The first disc 10 is pressed against the second disc 20 via the ultraviolet curable resin so that the main surface on the opposite side faces the second disc 20.

Next, the first and

second discs

10 and 20 are rotated, and the ultraviolet curable resin is stretched in the radial direction of the first and

second discs

10 and 20 between the first and

second discs

10 and 20. To do. At this time, the thickness of the ultraviolet curable resin is adjusted to a predetermined thickness by the rotation speed. As a result, the ultraviolet curable resin is spread between the first and

second discs

10 and 20 from the inner peripheral portion to the outer peripheral portion of the first and

second discs

10 and 20. As described above, the optical recording medium main body 2 having the bonded layer 30 in the uncured state can be obtained.

In the above-mentioned stretching step of the ultraviolet curable resin, it is preferable to irradiate the outer peripheral portions of the first and

second discs

10 and 20 with ultraviolet rays to temporarily cure the ultraviolet curable resin stretched to the outer peripheral portions. As a result, it is possible to suppress the occurrence of opening in the outer peripheral portions of the first and

second discs

10 and 20.

Next, the bonded layer 30 is cured by irradiating ultraviolet rays from both sides of the optical recording medium main body 2 with an ultraviolet lamp. As a result, the target optical recording medium 1 can be obtained.

[1.3 Effect]
The optical recording medium 1 according to the first embodiment described above is provided with first and second uneven structure layers 3 and 4, respectively, on the first and second light irradiation surfaces C1 and C2. As a result, when a plurality of optical recording media 1 are superposed, the contact area of the superposed optical recording media 1 can be reduced. Therefore, sticking of the superimposed optical recording media 1 to each other can be suppressed. In addition, the sliding force of the superimposed optical recording media 1 can be reduced.

The first and second uneven structure layers 3 and 4 are composed of structures arranged at a pitch equal to or lower than the wavelength of laser light (for example, 350 nm or less) for recording or reproducing an information signal. As a result, the amount of reflected light can be reduced as compared with a flat light irradiation surface.

In the method of forming the first and second uneven structure layers on the first and second light irradiation surfaces of the optical recording medium main body by using the ultraviolet curable resin to which fine particles such as nanoparticles are added, the uneven shape is formed. It is difficult to control. When the uneven shape of the first and second uneven structure layers cannot be controlled, optical interference is caused in a region having a large uneven shape, and the signal quality is deteriorated. On the other hand, in the method for manufacturing the optical recording medium 1 according to the first embodiment, the uneven shape of the master is transferred to the ultraviolet curable resin to transfer the first and second light irradiation surfaces C1 of the optical recording medium 1. Since the first and second concavo-convex structure layers 3 and 4 are formed on C2, respectively, it is easy to control the concavo-convex shape of the first and second concavo-convex structure layers 3 and 4. Therefore, interlayer interference can be stably reduced over the entire surface of the optical recording medium 1.

<2 Second embodiment>
[2.1 Configuration of optical recording medium]
As shown in FIG. 4, the optical recording medium 101 according to the second embodiment of the present disclosure is a so-called multi-layer write-once optical recording medium, in which the optical recording medium main body 102 and the first uneven structure layer 3 are formed. Be prepared. In the second embodiment, the same reference numerals are given to the same parts as those in the first embodiment, and the description thereof will be omitted.

In the optical recording medium main body 102, the information signal layer L0, the spacer layer S1, the information signal layer L1, ..., The spacer layer Sn, the information signal layer Ln, and the light transmission layer 12 which is the cover layer are one of the substrates 11A in this order. It has a structure laminated on the main surface.

The optical recording medium 101 has a light irradiation surface C on one side, which is irradiated with light for recording or reproducing an information signal. The information signal layer L0 is located at the innermost position with respect to the light irradiation surface C, and the information signal layers L1 to Ln are located in front of the information signal layer L0. Therefore, the information signal layers L1 to Ln are configured to be capable of transmitting laser light used for recording or reproduction.

In the optical recording medium 101 according to the second embodiment, information signals are recorded or reproduced by irradiating each information signal layer L0 to Ln with laser light from the light irradiation surface C on the light transmission layer 12 side. .. For example, laser light having a wavelength in the range of 400 nm or more and 415 nm or less is focused by an objective lens having a numerical aperture in the range of 0.84 or more and 0.86 or less, and each information signal layer L0 is focused from the light transmitting layer 12 side. By irradiating ~ Ln, information signals are recorded or reproduced. Examples of such an optical recording medium 101 include a multi-layer Blu-ray disc (BD: Blu-ray (registered trademark) Disc).

The optical recording medium 101 is typically a groove recording type optical recording medium, but may be an optical recording medium such as a land / groove recording type.

The diameter (diameter) of the substrate 11A is selected to be, for example, 120 mm. The thickness of the substrate 11A is selected in consideration of rigidity, preferably 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 (diameter) of the center hole is selected to be, for example, 15 mm. The material of the substrate 11A is the same as that of the substrate 11 in the first embodiment described above.

[2.2 Manufacturing method of optical recording medium]
An example of the method for manufacturing the optical recording medium 101 according to the second embodiment of the present disclosure will be described.

First, the optical recording medium main body 102 is manufactured in the same manner as in the "first disk manufacturing step" in the first embodiment described above. Next, the first concave-convex structure layer 3 is formed on the light irradiation surface C of the optical recording medium main body 102 by UV nanoimprint. As a result, the target optical recording medium 101 can be obtained.

[2.3 effect]
The optical recording medium 101 according to the second embodiment described above can obtain the same effect as that of the first embodiment. For example, by reducing the amount of reflected light as compared with a flat light irradiation surface, it is possible to provide four or more information signal layers L within the range of the thickness (100 μm) of the light transmission layer 12 of the BD standard.

<3 Modification example>
In the first and second embodiments described above, the information signal layer L is provided adjacent to the recording layer 13, the protective layer 14 provided adjacent to the upper surface of the recording layer 13, and the lower surface of the recording layer 13. Although the configuration including the protective layer 15 has been described, the configuration of the information signal layer L is not limited to this. For example, the protective layer may be provided only on either the upper surface or the lower surface of the recording layer 13. Further, the information signal layer L may be composed of only the recording layer 13 single layer. With such a simple configuration, the

optical recording media

1 and 101 can be reduced in cost and their productivity can be improved. This effect becomes more remarkable as the number of layers of the information signal layer L is larger.

In the first and second embodiments described above, the case where all the multilayer information signal layers L have the same layer structure (three-layer structure) has been described, but the characteristics (for example, optics) required for each information signal layer L have been described. The layer structure may be changed according to the characteristics, durability, etc.). However, from the viewpoint of productivity, it is preferable that all the information signal layers L have the same layer structure.

The optical recording medium to which the present disclosure is applicable is not limited to those having the configurations according to the first and second embodiments. For example, a plurality of layers of information signal layers and protective layers are laminated in this order on a substrate, and information signals can be recorded or reproduced by irradiating the plurality of layers of information signal layers with laser light from the substrate side. It has a configuration in which a plurality of layers of information signal layers are provided between an optical recording medium (for example, a CD (Compact Disc)) or two substrates, and a plurality of layers of laser light are emitted from the side of at least one substrate. The present disclosure is also applicable to an optical recording medium (for example, a DVD (Digital Versatile Disc)) in which an information signal is recorded or reproduced by irradiating the information signal layer.

In the first embodiment described above, the case where the first and

second disks

10 and 20 each include a plurality of layers of information signal layers L has been described, but the first and

second disks

10 and 20 have single layers, respectively. The information signal layer L of the above may be provided.

In the second embodiment described above, the case where the optical recording medium 101 includes a plurality of layers of information signal layers L has been described, but the optical recording medium 101 may include a single layer information signal layer L.

In the above-described first embodiment, the case where the uneven structure layer is provided on both the first light irradiation surface C1 and the second light irradiation surface C2 of the optical recording medium main body 2 has been described, but the optical recording medium. A concavo-convex structure layer may be provided on either the first light irradiation surface C1 or the second light irradiation surface C2 of the main body 2. However, in order to make the reflectance and the transmittance of the first light irradiation surface C1 and the second light irradiation surface C2 the same, as in the first embodiment described above, the first light recording medium main body 2 It is preferable that the uneven structure layer is provided on both the light irradiation surface C1 and the second light irradiation surface C2.

In the above-described first embodiment, the case where the structure 3B has a convex shape with respect to the first light irradiation surface C1 has been described, but as shown in FIG. 5, the structure 3C has the first light irradiation surface. It may have a concave shape with respect to C1. In this case, the absolute value of the depth D of the concave structure 3C can be treated in the same manner as the absolute value of the height H of the convex structure 3B in the first embodiment. Similarly, in the second embodiment described above, the structure 3B may have a concave shape with respect to the light irradiation surface C.

In the first and second embodiments described above, the case where the recording layer 13 is an inorganic recording layer has been described, but the recording layer 13 may be an organic recording layer.

In the first and second embodiments described above, the case where the

optical recording media

1 and 101 are write-once type has been described, but the

optical recording media

1 and 101 may be play-only type or rewritable type.

In the second embodiment described above, the case where the optical recording medium 101 has a configuration capable of recording or reproducing the information signal from only one side has been described, but the optical recording medium 101 records the information signal from both sides. Alternatively, it may have a configuration that can be reproduced. In this case, a plurality of layers of information signal layers L and light transmitting layers 12 are provided on both sides of the substrate 11A. Further, the uneven structure layer may be provided on both sides.

In the first and second embodiments described above, the case where the first uneven structure layer 3 is a hard coat layer including the basal layer 3A and the plurality of structures 3B has been described, but the first uneven structure layer 3 has been described. May not include the basal layer 3A and may be composed of only a plurality of structures 3B.

In the first embodiment and the second embodiment, the

structures

3B and 3C included in the first and second concavo-convex structure layers 3 and 4 (specifically, the first and second concavo-convex structure layers 3 and 4). ) May have information. For example, information may be provided to the first and second uneven structure layers 3 and 4 by thinning out moth eyes, BD pits, or the like, or by CD pits themselves. The information given to the first and second concave-convex structure layers 3 and 4 includes disc-specific information such as that given to BCA (Burst Cutting Area) and two-dimensional barcodes, and for piracy prevention and copy protection. Encrypted information, security information such as bootlegs, etc. can be mentioned.

For the detection of the above information, an optical system for signal detection of the information signal layer L may be used, or an optical system using a light source having a wavelength different from that may be used. Further, after the images of the first and second uneven structure layers 3 and 4 are acquired by using an image sensor or the like, the images may be detected by image recognition of the images.

In the first embodiment, one of the first light irradiation surface C1 and the second light irradiation surface C2 has a concavo-convex structure layer, while the other is a surface (smooth surface) without the concavo-convex structure layer. There may be. In this case, it is possible to determine the front and back sides of the optical recording medium 1 depending on the presence or absence of the uneven structure layer. The specifications (for example, the structure) of the first concavo-convex structure layer 3 of the first light irradiation surface C1 and the second concavo-convex structure layer 4 of the second light irradiation surface C2 may be different. In this case, the front and back surfaces of the optical recording medium 1 can be discriminated by the difference in specifications between the first concavo-convex structure layer 3 and the second concavo-convex structure layer 4. Similarly, in the second embodiment described above, a concavo-convex structure layer having different specifications may be provided on the light irradiation surface C and the back surface on the opposite side to the light irradiation surface C.

The front and back of the optical recording medium 1 may be discriminated by using an optical system or image recognition, as in the case of detecting the information of the first and second uneven structure layers 3 and 4.

In the first embodiment described above, the first and second concavo-convex structure layers 3 are formed on the first and second light irradiation surfaces C1 and C2 of the first and

second disks

10 and 20, respectively, before the bonding step. Although the case of forming 4 and 4 has been described, the first and second uneven structure layers 3 and 4 are formed on the first and second light irradiation surfaces C1 and C2 of the optical recording medium main body 2 after the bonding step, respectively. You may try to do it.

Hereinafter, the present disclosure will be specifically described with reference to Examples, but the present disclosure is not limited to these Examples.

Examples of the present disclosure will be described in the following order.
i Examples and comparative examples in which sticking force and sliding force are evaluated
ii Examples and Comparative Examples for Evaluating the Effect of Concavo-convex Structure on Signal Characteristics

<Examples and Comparative Examples in which Sticking Force and Sliding Force were Evaluated>
An optical disc having a fine uneven structure formed on the light irradiation surface was produced as follows, and the sticking force and the sliding force were evaluated.

[Example 1]
By UV nanoimprint, a fine concavo-convex structure (Mosseye) consisting of a concave structure on both light irradiation surfaces (both signal surfaces) of the optical disc body (BD-DSD, same specifications as the recording capacity of 200 GB except for the formation of concavo-convex structure by UV nanoimprint) Structure) was formed. At this time, the pitches P1 and P2 of the structure, the widths W1 and W2 of the structure, and the depth D of the structure (see FIG. 5) were set to the values shown in Table 1. The pitches P1 and P2 are set to be equal to or lower than the wavelength of the laser beam for recording or reproducing the information signal. From the above, the target optical disc was obtained.

[Example 2]
BD2T pits (2T pits on a 3-layer 100GB disc of ULTRA HD Blu-ray (registered trademark) arranged at predetermined intervals) were formed as a fine concavo-convex structure. At this time, the pitches P1 and P2 of the concave-convex structure, the widths W1 and W2 of the structure, and the height H of the structure (see FIG. 3) were set to the values shown in Table 1. The pitches P1 and P2 are set to be equal to or lower than the wavelength of the laser beam for recording or reproducing the information signal. An optical disk was obtained in the same manner as in Example 1 except for the above.

[Comparative Example 1]
The optical disc of Comparative Example 1 was used as it was without forming a fine uneven structure on both light irradiation surfaces (both signal surfaces) of the optical disc body (BD-DSD, recording capacity 200 GB).

[Comparative Example 2]
A CD pit (pit used in a CD-ROM substrate) is formed as a fine uneven structure, and the pitches P1 and P2 of the uneven structure, the widths W1 and W2 of the structure, and the height H of the structure H (see FIG. 3). Was set to the values shown in Table 1. The pitches P1 and P2 are set to be larger than the wavelength of the laser light for recording or reproducing the information signal. An optical disk was obtained in the same manner as in Example 1 except for the above.

(Area ratio of convex parts)
First, an SEM image of the light irradiation surface (signal surface) of the optical disc obtained as described above was acquired. 6A, 6B, and 6C show SEM images of the uneven structure of Examples 1, 2 and Comparative Example 2, respectively. Next, the contrast data for each pixel was acquired from the acquired SEM image, and the frequency distribution was created. FIG. 7 shows the frequency distribution of the uneven structure of the optical disk of Example 1. Next, each of the low contrast (concave) group and the high contrast group (convex) was fitted (Gaussian fitting) with an optimum function (Gaussian function), and the intersection P of the fitting function was obtained. The integrated value of the raw data of the group having the pixel contrast lower than the intersection P was defined as the area of the concave portion, and the integrated value of the raw data of the group having the pixel contrast higher than the intersection P was defined as the area of the convex portion. Next, the ratio of the area of the convex portion to the sum of the area of the concave portion and the area of the convex portion was obtained, and this ratio was defined as the area ratio R [%] of the convex portion on the light irradiation surface (signal surface) of the optical disk.

(Reflectance)
The reflectance of the light irradiation surface (signal surface) of the optical disc obtained as described above is measured using an evaluation machine manufactured by Pulsetec Co., Ltd. (ODU-1000, wavelength λ = 405 nm, objective lens NA = 0.85) as follows. It was measured simply as follows. First, the expander position was adjusted so that the spherical aberration was optimized near the L2 layer. Next, the objective lens was searched in the optical axis direction, and the total signal of the reflected return light from the optical disk was acquired. In the acquired sum signal, the peak that appears first corresponds to the surface of the optical disc, so the voltage value of that peak was acquired. Next, the reflectance of the light-irradiated surface of the optical disk was obtained using the acquired surface voltage value with reference to the reflectance of the L2 layer (voltage value of the total signal) acquired by applying the focus servo in advance. The reflectance based on the voltage value on the surface is slightly deviated because the spherical aberration is optimal for the L2 layer, but since the conditions are the same in all of the above Examples and Comparative Examples, there is no problem in relative comparison.

(Attachment force)
FIG. 8 is a schematic view for explaining a method of measuring the sticking force. First, two optical discs obtained as described above were prepared and superposed on a measuring table so that the light irradiation surface (signal surface) was on the upper surface and a part of them overlapped. Next, a load of 30 to 40 kg was applied to the two superposed optical disks, and then the load was released. Subsequently, while applying a load of 290 g to the two superposed optical discs, the optical disc located on the upper side is pulled by a force gauge in a direction horizontal to the surface of the measuring table, and the tensile force at which the optical discs start to move is measured. The maximum value of the force was taken as the sticking force. FIG. 9A shows the relationship between the area ratio of the convex portion and the sticking force.

(Sliding power)
First, two optical discs were superposed on the measuring table in the same manner as in the evaluation of the sticking force described above. Next, while applying a load of 290 g to the two superposed optical discs, the optical disc located on the upper side is pulled by a force gauge in a direction horizontal to the surface of the measuring table, and the tensile force is measured, and the maximum of this tensile force is measured. The value was used as the sliding force. FIG. 9B shows the relationship between the area ratio of the convex portion and the sliding force.

The configuration and evaluation result of the concave-convex structure of the optical discs of Examples 1 and 2 and Comparative Examples 1 and 2 are shown.

The following can be seen from FIGS. 9A, 9B and Table 1.
An optical disc (Examples 1 and 2 and Comparative Example 2) in which a fine uneven structure is formed on a light irradiation surface (signal surface) is pasted as compared with an optical disc (Comparative Example 1) in which the light irradiation surface (signal surface) is smooth. Attaching force and sliding force are reduced.
An optical disk (Examples 1 and 2) in which a plurality of structures are provided on a light irradiation surface (signal surface) at a pitch equal to or lower than the wavelength of laser light for recording or reproducing an information signal records or reproduces an information signal. The sticking force and the sliding force are reduced as compared with an optical disk (Comparative Example 2) in which a plurality of structures are provided on a light irradiation surface (signal surface) at a pitch larger than the wavelength of the laser beam for the purpose.

In an optical disk (Examples 1 and 2) in which a plurality of structures are provided on an optical irradiation surface (signal surface) at a pitch equal to or lower than the wavelength of laser light for recording or reproducing an information signal, the light irradiation surface (signal surface) The reflectance is reduced as compared with an optical disc having a smooth surface (Comparative Example 1). On the other hand, in the optical disk (Comparative Example 2) in which a plurality of structures are provided on the light irradiation surface (signal surface) at a pitch larger than the wavelength of the laser light for recording or reproducing the information signal, the light irradiation surface (signal surface) The reflectance may be increased depending on the state of diffraction on the light irradiation surface (signal surface) as compared with the smooth disk (Comparative Example 1).

<Examples and comparative examples in which the influence of the uneven structure on the signal characteristics is evaluated>
An optical disk in which a fine uneven structure was formed on a light irradiation surface (signal surface) was produced as follows, and the influence of the uneven structure on the signal characteristics was evaluated.

[Example 3]
By UV nanoimprint, the same fine concavo-convex structure (moth-eye structure) as in Example 1 is applied to both light irradiation surfaces (both signal surfaces) of the optical disc body (AD, the same specifications as the recording capacity of 300 GB except for the formation of concavo-convex structure by UV nanoimprint). Was formed. From the above, the target optical disc was obtained.

[Example 4]
A three-layer 100GB disc with a fine concavo-convex structure (BD2T pit (ULTRA HD Blu-ray (registered trademark)) similar to that in Example 2 on both light irradiation surfaces (both signal surfaces) of the optical disc body (AD, recording capacity 300 GB). An optical disk was obtained in the same manner as in Example 3 except that the 2T pits in (1) were formed at predetermined intervals.

[Comparative Example 3]
The optical disc of Comparative Example 3 was used as it was without forming a fine uneven structure on both light irradiation surfaces (both signal surfaces) of the optical disc body (AD, recording capacity 300 GB).

(Signal characteristics)
The signal characteristics of the optical discs of Examples 3, 4 and Comparative Example 3 obtained as described above were evaluated as follows. Using a drive capable of recording and reproducing AD with a recording capacity of 300 GB, optical discs were reproduced by 64 RUBs (Recording Unit Blocks) at intervals of 0.1 mm. Then, the maximum value Max, the minimum value Min, and the average value Ave of the SER (Symbol Error Rate) at the time of 64RUB reproduction are acquired over the entire surface at intervals of 0.1 mm, and the maximum value Max, the minimum value Min, and the average value Ave are respectively obtained. The average value was calculated. The results are shown in FIGS. 10A, 10B and 10C. From this evaluation result, it was found that even if a fine uneven structure (moss eye structure and BD pit) is provided on the light irradiation surface (signal surface) of AD having a recording capacity of 300 GB, the SER does not deteriorate.

In addition, using a drive capable of recording and reproducing AD with a recording capacity of 300 GB, optical discs were reproduced by 64 RUB at 0.1 mm intervals, and i-MLSE (Integrated-Maximum Likelihood. Sequence Error) was evaluated. From this evaluation result, it was found that even if a fine uneven structure (moth-eye structure and BD pit) was provided on the light irradiation surface (signal surface) of AD having a recording capacity of 300 GB, i-MLSE did not deteriorate.

[Examples 5 and 6, Comparative Example 4]
An optical disc was obtained in the same manner as in Examples 3 and 4 and Comparative Example 4 except that an AD having a recording capacity of 500 GB was used as the optical disc main body.

[Examples 7 and 8, Comparative Example 5]
An optical disk was obtained in the same manner as in Examples 1 and 2 and Comparative Example 1.

(Signal characteristics)
The signal characteristics of the optical discs of Examples 5 to 8 and Comparative Examples 4 and 5 obtained as described above were evaluated in the same manner as the signal characteristics of the optical discs of Examples 3, 4 and Comparative Example 3. As a result, even if a fine uneven structure (moth-eye structure and BD pit) is provided on the light irradiation surface (signal surface) of an AD having a recording capacity of 500 GB and a BD-DSD having a recording capacity of 200 GB, the signal characteristics (SER, i-MLSE) It turns out that does not get worse.

Although the embodiments of the present disclosure have been specifically described above, the present disclosure is not limited to the above-described embodiments, and various modifications based on the technical idea of the present disclosure are possible.

The configurations, methods, processes, shapes, materials, numerical values, etc. mentioned in the above-described embodiments are merely examples, and different configurations, methods, processes, shapes, materials, numerical values, etc. may be used as necessary. ..

The configurations, methods, processes, shapes, materials, numerical values, etc. of the above-described embodiments can be combined with each other as long as they do not deviate from the gist of the present disclosure.

In the numerical range described stepwise in the above embodiment, the upper limit value or the lower limit value of the numerical range of one step may be replaced with the upper limit value or the lower limit value of the numerical range of another step.

Unless otherwise specified, the materials exemplified in the above-described embodiments can be used alone or in combination of two or more.

The present disclosure may also adopt the following configuration.
(1)
An optical recording medium body having a first surface and a second surface,
It is provided with a first concavo-convex structure layer provided on the first surface.
The first concavo-convex structure layer includes a plurality of first structures provided at a pitch equal to or lower than the wavelength of light for recording or reproducing an information signal.
The area ratio of the convex portion of the first concave-convex structure layer is 80% or less.
An optical recording medium in which the light is irradiated from the first surface side.
(2)
The optical recording medium according to (1), wherein the area ratio of the convex portion of the first concave-convex structure layer is 50% or less.
(3)
The optical recording medium according to (2), wherein the area ratio of the convex portion of the first concave-convex structure layer is 20% or less.
(4)
The optical recording medium according to any one of (1) to (3), wherein the first uneven structure layer is a hard coat layer.
(5)
The optical recording medium according to any one of (1) to (4), wherein the first structure has a shape similar to a concave portion or a convex portion used for recording a signal on an optical recording medium.
(6)
Further provided with a second concavo-convex structure layer provided on the second surface,
The second concavo-convex structure layer includes a plurality of second structures provided at a pitch equal to or lower than the wavelength of the light.
The optical recording medium according to any one of (1) to (5), wherein the light is irradiated from the second surface side.
(7)
The optical recording medium body is
The first disc and
With a second disc
The first disk and the second disk are
With the board
The information signal layer provided on the substrate and
A cover layer that covers the information signal layer is provided.
The optical recording medium according to any one of (1) to (6), wherein the surface of the first disk on the substrate side and the surface of the second disk on the substrate side are bonded to each other.
(8)
The optical recording medium body is
With the board
The information signal layer provided on the substrate and
A cover layer that covers the information signal layer is provided.
The optical recording medium according to any one of (1) to (6), wherein the first surface is a surface on the cover layer side.

1,101 Optical recording medium 2,102 Optical recording medium body 3 First uneven structure layer 4 Second uneven structure layer

3A Base layer

3B, 3C structure 10 First disk 20 Second disk 30 Laminated

layer

11 , 11A, 21

Substrates

12, 22 Light transmission layer 13

Recording layer

14, 15 Protective layer L0 to Ln, L0 to Lm Information signal layer S1 to Sn, S1 to Sm Spacer layer C Light irradiation surface C1 First light irradiation surface C2 Second light irradiation surface Gv groove Ld land Tp track pitch

Claims

An optical recording medium body having a first surface and a second surface,
It is provided with a first concavo-convex structure layer provided on the first surface.
The first concavo-convex structure layer includes a plurality of first structures provided at a pitch equal to or lower than the wavelength of light for recording or reproducing an information signal.
The area ratio of the convex portion of the first concave-convex structure layer is 80% or less.
An optical recording medium in which the light is irradiated from the first surface side.
The optical recording medium according to claim 1, wherein the area ratio of the convex portion of the first uneven structure layer is 50% or less.
The optical recording medium according to claim 2, wherein the area ratio of the convex portion of the first uneven structure layer is 20% or less.
The optical recording medium according to claim 1, wherein the first uneven structure layer is a hard coat layer.
The optical recording medium according to claim 1, wherein the first structure has a shape similar to a concave portion or a convex portion used for recording a signal on an optical recording medium.
Further provided with a second concavo-convex structure layer provided on the second surface,
The second concavo-convex structure layer includes a plurality of second structures provided at a pitch equal to or lower than the wavelength of the light.
The optical recording medium according to claim 1, wherein the light is irradiated from the second surface side.
The optical recording medium body is
The first disc and
With a second disc
The first disk and the second disk are
With the board
The information signal layer provided on the substrate and
A cover layer that covers the information signal layer is provided.
The optical recording medium according to claim 1, wherein the surface of the first disk on the substrate side and the surface of the second disk on the substrate side are bonded to each other.
The optical recording medium body is
With the board
The information signal layer provided on the substrate and
A cover layer that covers the information signal layer is provided.
The optical recording medium according to claim 1, wherein the first surface is a surface on the cover layer side.