JP2006196035A - Optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk capable of performing reproduction or recording/reproduction of both data of a DVD standard and a BD standard, wherein reproduction or recording/reproduction can be performed with both specifications without turning over the optical disk to reload it even when one disk is in a loaded state in a drive or the like. <P>SOLUTION: In the optical disk having a first information layer wherein reproduction or recording/reproduction is performed with a laser beam having 300 to 600 nm wavelength, a semi-transparent reflection layer and a second information layer wherein reproduction or recording/reproduction is performed with a laser beam having 600 to 700 nm wavelength sequentially from a laser beam incident surface, the semi-transparent reflection layer has ≥20% reflectance to the beam having 300 to 600 nm wavelength and ≥40% transmittance to the beam having 600 to 700 nm wavelength. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical disc such as a DVD or Blu-ray Disc that reproduces or records / reproduces information by irradiating a laser beam.

Currently, there are CD (compact disc) and DVD (digital versatile disc) as optical disc standards widely accepted in the market.
As a CD recording format, there are a read-only CD-ROM, a write-once CD-R that can record information only once, and a rewritable CD-RW that can rewrite information.
In a CD-ROM, for example, pit rows are formed on a transparent substrate having a diameter of 120 mm and a thickness of 1.2 mm with a track pitch of 1.6 μm, a recording capacity of about 650 Mbytes, and a linear velocity of 1.2. Information is reproduced by irradiating with a laser beam having a wavelength of 770 to 790 nm, which is constant at ˜1.4 m / s.

On the other hand, DVD recording formats include DVD-ROM, DVD-R, and DVD-RW, as in the case of CD.
The DVD-ROM has a recording density of about 6 to 8 times that of a CD, and has a configuration in which two substrates having a thickness of about 0.6 mm are bonded together, and pits are formed at a track pitch of 0.74 μm. The information is reproduced by irradiating a laser beam having a wavelength of 635 to 650 nm with the linear velocity kept constant at about 3.5 m / s.

  The above CD and DVD have different standards such as the wavelength of laser light used for recording and playback, lens aperture ratio (NA), disk pits, and groove track pitch, and are not compatible. And existed. Reproduction (recording) is performed by using a dedicated drive or player, or a dual-purpose drive or player that supports both CD and DVD.

  Under such circumstances, hybrid optical discs having one side of the CD standard and the other side of the DVD standard have been put on the market (see, for example, Non-Patent Document 1). This optical disk is called “DualDisc”, and can handle (reproduce) both CD information and DVD information with a single disk.

However, the DualDisc cannot be reproduced as it is even if it tries to reproduce the other side in the reproduction state or reproduction standby state of one side, and it is necessary to turn over the DualDisc and reload it.
On the other hand, since DualDisc has a layer irradiated with laser light, that is, a layer on which information is recorded, on both sides, a sufficient area cannot be secured for use as a label surface for displaying information such as the contents of an optical disc. There was a problem.

  On the other hand, the DVD plays a role as a large-capacity optical disk at present, but the demand for higher capacity and higher density is increasing, and the development of an optical disk that can meet these demands is also necessary. Therefore, development of an optical disc having a higher recording capacity by using a laser beam having a shorter wavelength than that of a DVD has been promoted. For example, a Blu-ray Disc using a blue laser beam having a wavelength of 405 nm. An optical disc called An optical disc in which the CD standard in DualDisc is replaced with the Blu-ray Disc standard using the Blu-ray Disc standard can be considered. The above-described problems can occur even in such an optical disc.

Further, as an optical disc (recording medium) having a multilayer structure with two information layers on one side and different recording densities of the first layer and the second layer, for example, the first layer is a CD and the second layer is An optical disc having a DVD structure has been proposed (see, for example, Patent Document 1). However, there is no known optical disc capable of reproducing DVD and Blu-ray Disc from one side.
JP 2004-213882 A Article (Nikkei Electronics), [online], August 26, 2004, [Search September 2, 2004], Internet, “Large Record Company To Introduce Single-Side CD, Single-Side DVD Optical Disc“ DualDisc ”” <URL: http://www.ne.nikkeibp.co.jp/members/NEWS/20040826/105123/>

An object of the present invention is to solve the above-described conventional problems and achieve the following objects. That is,
An object of the present invention is an optical disc capable of reproducing or recording / reproducing both the DVD standard and the Blu-ray Disc standard (hereinafter sometimes referred to as “BD standard”), and drives one optical disc. It is an object of the present invention to provide an optical disc that can be reproduced or recorded / reproduced in accordance with both standards without being turned over and loaded again.

The above problems are solved by the present invention described below. That is,
<1> The first information layer that is reproduced or recorded / reproduced with a laser beam having a wavelength of 300 to 600 nm, the transflective layer, and the laser beam having a wavelength of 600 to 700 nm are reproduced or recorded / reproduced in order from the laser light incident surface. The transflective layer has a reflectance of 20% or more for light having a wavelength of 300 to 600 nm and a transmittance of 40% or more for light having a wavelength of 600 to 700 nm. An optical disc characterized by the above.

<2> The distance from the laser light incident surface to the surface of the first information layer on the laser light incident surface side is 0.05 to 0.15 mm, and the distance from the laser light incident surface to the second information layer The optical disk according to <1>, wherein the distance to the laser light incident surface side is 0.4 to 0.8 mm.

  According to the present invention, an optical disc that can reproduce or record / reproduce both the DVD standard and the BD standard, and even if one optical disc is loaded in a drive or the like, it is not turned over and reloaded. An optical disc that can be reproduced or recorded / reproduced by both standards can be provided. In addition, since the optical disc of the present invention uses only one side for recording / reproducing information, the area of the label surface can be sufficiently secured.

  The optical disc of the present invention is reproduced or reproduced with a first information layer that is reproduced or recorded / reproduced with a laser beam having a wavelength of 300 to 600 nm, a transflective layer, and a laser beam with a wavelength of 600 to 700 nm in this order from the laser light incident surface. A second information layer for recording / reproducing, wherein the transflective layer has a reflectance of 20% or more for light having a wavelength of 300 to 600 nm and a transmittance of 40% for light having a wavelength of 600 to 700 nm. It is characterized by the above.

  More specifically, as the layer configuration of the optical disk of the present invention, for example, in order from the laser light incident surface, a cover layer, a first information layer, a transflective layer, a first substrate, a second information layer, A reflective layer, a second substrate, and a protective layer can be used. In addition, an intermediate layer can be provided between each layer, and a printed layer can be provided on the protective layer.

  The first information layer and the second information layer are a concept including a layer in which information that can be read by a laser beam is recorded, or a layer in which such information can be recorded. The concept includes a pit, a dye recording layer, a phase change recording layer, and the like. The pit is a depression formed in the substrate and does not actually constitute a layer, but in this specification, the information layer includes a pit. That is, in the case of the ROM configuration, the area where the pits are located in the substrate is regarded as the information layer. Accordingly, in the case of the ROM configuration, the first information layer is assumed to be located between the first substrate and the transflective layer in the above-described examples of the layer configuration. In the case of pits, they can be formed on the first substrate and the second substrate according to the DVD standard and the BD standard, respectively. Alternatively, without dividing into two substrates, it can be formed on one surface of one substrate by the BD standard and formed on the other surface by the DVD standard. In this case, a dummy substrate is bonded to the DVD standard side in the same manner as the well-known DVD manufacturing method.

In the present invention, the first information layer is actually an information layer of the BD standard, and the BD standard is composed of the same layer alone or in combination as the information surface in the BD-ROM, BD-R, and BD-RW. Among them, the information layer of BD-ROM or the information layer of BD-R is preferable, and the information layer of BD-ROM is most preferable.
The second information layer is actually an information layer of the DVD standard, and the DVD standard is the same layer as the information surface in DVD-ROM, DVD-R, DVD-RW, DVD-RAM alone or in combination. Among them, the information layer of DVD-ROM or the information layer of DVD-R is preferable, and the information layer of DVD-ROM is most preferable.
The first to second information layers described above may have a single layer structure or a multilayer structure.

  FIG. 1 is a diagram schematically showing the layer structure of the optical disc of the present invention. The optical disk shown in FIG. 1 has a first substrate 12 having a transflective layer 14, a first information layer 16, and a cover layer 18, a reflective layer 24, and a second information layer 22 on one side. The second substrate 20 is bonded to each other so that the side opposite to the cover layer 18 of the first substrate 12 and the reflective layer 24 side of the second substrate face each other. The first information layer 16 is a layer where information is recorded according to the BD standard, and the second information layer 22 is a layer where information is recorded according to the DVD standard. As indicated by arrows in FIG. 1, the laser light is reflected by the semi-transmissive reflective layer 14 when the wavelength is 300 to 600 nm, and is transmitted through the semi-transmissive reflective layer 14 when the wavelength is 600 to 700 nm. reflect. That is, when the laser beam having a wavelength of 300 to 600 nm is irradiated toward the first substrate 12, the laser beam is reflected by the transflective layer 16 and output as BD information. On the other hand, when laser light having a wavelength of 600 to 700 nm is irradiated, the laser light passes through the semi-transmissive reflective layer 14, is reflected by the reflective layer 24, and is output as DVD information.

  In the case of the optical disk having the configuration shown in FIG. 1, if the laser beam to be irradiated is switched between the laser beam having the wavelength used for the BD standard and the laser beam having the wavelength used for the DVD standard, if necessary, the transflective layer is made of the laser beam. The first information layer and the second information layer can be reproduced or recorded / reproduced from one surface side by selectively transmitting / reflecting the wavelength and accurately guiding each laser beam to each layer. . In other words, both the BD standard and the DVD standard can be reproduced or recorded / reproduced without turning over and loading the optical disk in the drive.

  In the optical disk of the present invention, the distance from the laser light incident surface to the surface of the first information layer on the laser light incident surface side is set to 0.05 to 0.15 mm, and the distance from the laser light incident surface to the second By setting the distance to the laser light incident surface side of the information layer to 0.4 to 0.8 mm, the BD and DVD standards (0.1 mm and 0.6 mm from the substrate surface, respectively) are satisfied. be able to. The distance from the laser light incident surface to the surface on the laser light incident surface side of the first information layer is more preferably 0.07 to 0.13 mm, and more preferably 0.09 to 0.11 mm. Further preferred. The distance from the laser light incident surface to the surface on the laser light incident surface side of the second information layer is more preferably 0.5 to 0.7 mm, and more preferably 0.55 to 0.65 mm. More preferably.

  As described above, the transflective layer is a layer that reflects light having a wavelength of 300 to 600 nm and transmits light having a wavelength of 600 to 700 nm. Can be configured. That is, the transflective layer is a multilayer laminate type having at least a low refractive index layer and a high refractive index layer, and the refractive index difference is 0.1 or more, preferably 0.2 or more, more preferably 0.3. Above, more preferably 0.5 or more. The total number of layers is 2 or more, preferably 3 or more, more preferably 5 or more, and even more preferably 7 or more. The upper limit of the number of layers is preferably 20 layers, more preferably 15 layers, and still more preferably 10 layers. In addition, a layer other than the low refractive index layer and the high refractive index layer (for example, a refractive index layer between the refractive index of the low refractive index layer and the refractive index of the high refractive index layer, higher than the refractive index of the high refractive index layer) A refractive index layer, a refractive index layer lower than the refractive index of the low refractive index layer) may be included. Such a transflective layer has a reflectance of light of 300 to 600 nm of 20% or more, preferably 30% or more, more preferably 35% or more, and further preferably 40% or more. If the reflectance is less than 20%, a reflectance sufficient for reproduction cannot be obtained. Further, the transmittance of light of 600 to 700 nm is 40% or more, preferably 50% or more, more preferably 70% or more, still more preferably 80% or more, and particularly preferably 90% or more. If the transmittance is less than 40%, sufficient light for reproduction to the second information layer cannot be reached.

The material constituting the low refractive index layer is Al ₂ O ₃ , BiF ₃ , CaF ₂ , CeF ₃ , Na ₃ AlF ₆ , LaF ₃ , PbF ₂ , LiF, MgF ₂ , MgO, NdF ₃ , Si ₂ O. ₃ , SiO ₂ , NaF, ThO ₂ , ThF ₄ , etc., among which Al ₂ O ₃ , CaF ₂ , CeF ₃ , LiF, MgF ₂ , MgO, Si ₂ O ₃ , SiO ₂ are preferable, Al ₂ O ₃ , MgF ₂ , Si ₂ O ₃ and SiO ₂ are preferable. The layer thickness of the low refractive index layer is preferably 10 to 5000 nm, more preferably 50 to 2000 nm, and still more preferably 100 to 1000 nm.

As the material constituting the high refractive index layer, Sb ₂ O ₃ , Sb ₂ S ₃ , Bi ₂ O ₃ , CdS, CdTe, CeO ₂ , Ge, HfO ₂ , La ₂ O ₃ , PbCl ₂ , PbTe, Nd ₂ O ₃ , Pr ₆ O ₁₁ , Sc ₂ O ₃ , Si, SiO, Ta ₂ O ₅ , TiO ₂ , TlCl ₃ , Y ₂ O ₃ , ZnS, etc., among others, Sb ₂ O ₃ , Bi ₂ are mentioned. O ₃ , CeO ₂ , HfO ₂ , La ₂ O ₃ , Si, SiO, Ta ₂ O ₅ , TiO ₂ , Y ₂ O ₃ , ZnS are preferable, and in particular, Si, SiO, Ta ₂ O ₅ , TiO ₂ , Y ₂ O ₃ and ZnS are preferred. The layer thickness of the high refractive index layer is preferably 10 to 5000 nm, more preferably 50 to 2000 nm, and even more preferably 100 to 1000 nm.

The transflective layer can be formed by sputtering and multilayering the material constituting the low refractive index layer and the material constituting the high refractive index layer.
The thickness of the transflective layer is preferably 10 to 5000 nm, more preferably 50 to 2000 nm, and still more preferably 100 to 1000 nm.

Hereinafter, each layer in the optical disc of the present invention will be described.
[First substrate, second substrate]
As the first substrate and the second substrate, various materials used as substrate materials for conventional optical recording media can be arbitrarily selected and used.
Specifically, glass; acrylic resin such as polycarbonate and polymethyl methacrylate; vinyl chloride resin such as polyvinyl chloride and vinyl chloride copolymer; epoxy resin; amorphous polyolefin; polyester; metal such as aluminum; These may be used together if desired.
Among the above materials, polycarbonate and amorphous polyolefin are preferable, and polycarbonate is particularly preferable from the viewpoints of moisture resistance, dimensional stability, and low cost. The thickness of the first substrate is preferably 0.4 to 0.8 mm, more preferably 0.5 to 0.7 mm, and still more preferably 055 to 0.65 mm. The thickness of the second substrate is preferably 0.3 to 0.7 mm, more preferably 0.4 to 0.6 mm, and still more preferably 0.45 to 0.55 mm.
On the other hand, as will be described later, one surface side of one substrate can be configured as a BD, and the other surface side can be configured as a DVD. The thickness is preferably 0.7 mm, more preferably 0.4 to 0.6 mm, and still more preferably 0.45 to 0.55 mm.

The substrate is provided with irregularities (pregrooves) representing information such as tracking guide grooves or address signals.
In the case of the DVD standard, the track pitch of the pregroove is preferably in the range of 300 to 900 nm, more preferably 350 to 850 nm, and further preferably 400 to 800 nm.
The depth of the pregroove (groove depth) is preferably in the range of 100 to 160 nm, more preferably 120 to 150 nm, and still more preferably 130 to 140 nm.
Furthermore, the half width of the pregroove is preferably in the range of 200 to 400 nm, more preferably 230 to 380 nm, and even more preferably 250 to 350 nm.

In the case of the BD standard, the track pitch of the pregroove is preferably in the range of 50 to 500 nm, the upper limit is preferably 420 nm or less, more preferably 370 nm or less, and further preferably 330 nm or less. . Further, the lower limit is preferably 100 nm or more, more preferably 200 nm or more, and further preferably 260 nm or more.
The pregroove depth (groove depth) is preferably in the range of 30 to 180 nm, more preferably 50 to 150 nm, and even more preferably 60 to 100 nm.
Further, the half width of the pregroove is preferably in the range of 25 to 250 nm, and the upper limit is preferably 200 nm or less, more preferably 170 nm or less, and further preferably 150 nm or less. Further, the lower limit is preferably 50 nm or more, more preferably 80 nm or more, and further preferably 100 nm or more.

  In addition, an undercoat layer may be provided on the surface of the substrate on which the information layer is provided for the purpose of improving flatness, improving adhesive force, and preventing deterioration of the information layer. Examples of the material for the undercoat layer include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleic anhydride copolymer, polyvinyl alcohol, N-methylol acrylamide, styrene / vinyl toluene copolymer, chlorosulfone. Polymer materials such as chlorinated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, polyethylene, polypropylene, polycarbonate; and silane coupling And a surface modifier such as an agent. The undercoat layer is prepared by dissolving or dispersing the above substances in an appropriate solvent to prepare a coating solution, and then applying the coating solution to the substrate surface using a coating method such as spin coating, dip coating, or extrusion coating. Can be formed. The thickness of the undercoat layer is generally in the range of 0.005 to 20 μm, preferably in the range of 0.01 to 10 μm.

  The substrate can be molded by the above-mentioned substrate material by injection molding, compression molding, or injection compression molding. Alternatively, the stamper can be compression-molded by attaching a stamper to one side of a molding die of a hydraulic press machine and pressing the resin heated to the vicinity of the melting point.

<Information layer (first to second information layers)>
Next, the information layer will be described. As described above, the information layer refers to a pit formed on a substrate in the form of a ROM, and a recordable optical disk includes a dye recording layer and a phase change recording layer.

(Dye recording layer)
When the first and second information layers are dye recording layers, the dye used in the dye recording layer is not particularly limited. Examples of usable dyes include cyanine dyes, phthalocyanine dyes, imidazoquinoxaline dyes, Pyryllium / thiopyrylium dyes, azurenium dyes, squarylium dyes, metal complex dyes such as Ni and Cr, naphthoquinone dyes, anthraquinone dyes, indophenol dyes, indoaniline dyes, triphenylmethane dyes, merocyanine And dyes, oxonol dyes, aminium dyes / diimonium dyes, and nitroso compounds. Among these dyes, cyanine dyes, phthalocyanine dyes, azurenium dyes, squarylium dyes, oxonol dyes, and imidazoquinoxaline dyes are preferable.
The dye recording layer may be a single layer or a multilayer. The layer thickness of the dye recording layer is generally in the range of 20 to 500 nm, preferably in the range of 30 to 300 nm, and more preferably in the range of 50 to 200 nm.

The dye recording layer is formed by first dissolving the dye in a suitable solvent together with a binder, etc. to prepare a dye solution, and then applying the dye solution to the substrate surface to form a coating film and then drying. Is done. The concentration of the dye solution is not particularly limited.
As a method for dissolving the dye, methods such as ultrasonic treatment, homogenizer, and heating can be applied.

  Solvents used for preparing the dye solution include esters such as butyl acetate, ethyl lactate, and cellosolve acetate; ketones such as methyl ethyl ketone, cyclohexanone, and methyl isobutyl ketone; chlorinated hydrocarbons such as dichloromethane, 1,2-dichloroethane, and chloroform; Amides such as dimethylformamide; Hydrocarbons such as methylcyclohexane; Ethers such as tetrahydrofuran, ethyl ether, dioxane; Alcohols such as ethanol, n-propanol, isopropanol, n-butanol diacetone alcohol; 2,2,3,3-tetra Fluorine solvents such as fluoropropanol; glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether; It can gel.

  The above solvents can be used alone or in combination of two or more in consideration of the solubility of the dye used. Various additives such as an antioxidant, a UV absorber, a plasticizer, and a lubricant may be further added to the coating solution depending on the purpose.

The dye recording layer can contain various anti-fading agents in order to improve the light resistance of the dye recording layer.
As the antifading agent, a singlet oxygen quencher is generally used. As the singlet oxygen quencher, those described in publications such as known patent specifications can be used.
Specific examples thereof include JP-A Nos. 58-175893, 59-81194, 60-18387, 60-19586, 60-19587, and 60-35054. 60-36190, 60-36191, 60-44554, 60-44555, 60-44389, 60-44390, 60-54892, JP-A-60-47069, JP-A-63-209995, JP-A-4-25492, JP-B-1-38680, JP-A-6-26028, etc., German Patent 350399, and Japan Examples include those described in Chemical Society Journal, October 1992, page 1141.

  The amount of the antifading agent such as the singlet oxygen quencher used is usually in the range of 0.1 to 50% by weight, preferably 0.5 to 45% by weight, based on the amount of the compound for recording. More preferably, it is the range of 3-40 mass%, Most preferably, it is the range of 5-25 mass%.

  Representative examples of the antifading agent include nitroso compounds, metal complexes, diimmonium salts, and aminium salts. Examples of these are described in, for example, JP-A-2-300288, JP-A-3-224793, and JP-A-4-146189.

  Examples of the binder include natural organic polymer substances such as gelatin, cellulose derivatives, dextran, rosin, rubber; and hydrocarbon resins such as polyethylene, polypropylene, polystyrene, polyisobutylene, polyvinyl chloride, polyvinylidene chloride, Vinyl resins such as polyvinyl chloride and polyvinyl acetate copolymers, acrylic resins such as polymethyl acrylate and polymethyl methacrylate, polyvinyl alcohol, chlorinated polyethylene, epoxy resins, butyral resins, rubber derivatives, phenol / formaldehyde resins And a synthetic organic polymer such as an initial condensate of a thermosetting resin. When the binder is used, the amount of the binder used is generally 0.2 to 20 parts by mass, preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass with respect to 100 parts by mass of the dye. It is.

(Phase change recording layer)
Next, the phase change recording layer will be described. The phase change type recording layer is a layer made of a material capable of repeating a phase change between a crystalline phase and an amorphous phase by irradiation with laser light.
For example, a method in which the phase change between the crystalline phase and the amorphous phase is repeated by the following method. That is, at the time of information recording, a concentrated laser light pulse is irradiated for a short time to partially melt the phase change recording layer. The melted portion is rapidly cooled by heat diffusion and solidified to form an amorphous recording mark. During erasing, the recording mark portion is irradiated with laser light, heated to a temperature below the melting point of the recording layer and above the crystallization temperature, and then cooled to crystallize the amorphous recording mark. Return to the unrecorded state.

Specific examples of the material constituting the phase change recording layer include Sb—Te alloy, Ge—Sb—Te alloy, Pd—Ge—Sb—Te alloy, Nb—Ge—Sb—Te alloy, Pd—Nb—Ge—. Sb—Te alloy, Pt—Ge—Sb—Te alloy, Co—Ge—Sb—Te alloy, In—Sb—Te alloy, Ag—In—Sb—Te alloy, Ag—V—In—Sb—Te alloy, Ag-Ge-In-Sb-Te alloy, etc. are mentioned. Among these, Ge—Sb—Te alloy and Ag—In—Sb—Te alloy are preferable because they can be rewritten many times.
The layer thickness of the phase change recording layer is preferably 10 to 50 nm, more preferably 15 to 30 nm.

  The above phase change recording layer can be formed by vapor phase thin film deposition methods such as sputtering and vacuum deposition.

<Reflective layer>
The reflective layer is preferably made of a metal alone or an alloy. Specifically, an alloy containing aluminum, silver, gold, platinum or the like alone or other metal elements is preferable. Of these, silver alone or an alloy containing other elements is most preferable. In order to obtain sufficient reflectance, the thickness of the reflective layer is preferably 30 nm or more, more preferably 50 nm or more, and even more preferably 70 nm or more. From the viewpoint of preventing warpage, the thickness is preferably 300 nm or less, more preferably 200 nm or less, and still more preferably 150 nm or less.

  In the case of forming the reflective layer, for example, the metal can be formed on the second information layer by vapor deposition, sputtering, or ion plating. In the present invention, for the purpose of improving storage stability or changing the appearance, the reflective layer may be formed by laminating the above metals as a single layer, or by laminating two or more materials in multiple layers.

<Cover layer>
The cover layer is preferably formed by bonding a transparent sheet to the first information layer side of the first substrate with an adhesive or an adhesive.
The transparent sheet used for the cover layer is not particularly limited as long as it is a transparent material; however, acrylic resins such as polycarbonate and polymethyl methacrylate; vinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymers; epoxy resins; Amorphous polyolefin; polyester; cellulose triacetate and the like are preferably used, and among them, polycarbonate or cellulose triacetate is more preferably used.
Note that “transparent” means that the transmittance is 80% or more with respect to light used for recording and reproduction.

Further, the cover layer may contain various additives as long as the effects of the present invention are not hindered. For example, a UV absorber for cutting light having a wavelength of 400 nm or less and / or a pigment for cutting light having a wavelength of 500 nm or more may be contained.
Further, as the surface physical properties of the cover layer, it is preferable that both the two-dimensional roughness parameter and the three-dimensional roughness parameter have a surface roughness of 5 nm or less.
Further, from the viewpoint of the concentration of light used for recording and reproduction, the birefringence of the cover layer is preferably 10 nm or less.

The thickness of the cover layer is appropriately determined depending on the wavelength and NA of the laser beam irradiated for recording and reproduction. In the present invention, the thickness is preferably 0.05 to 0.15 mm. 0.07 to 0.13 mm is more preferable, and 0.09 to 0.11 mm is further preferable.
The total thickness of the cover layer and the layer made of an adhesive or a pressure-sensitive adhesive is preferably 0.09 to 0.11 mm, and more preferably 0.095 to 0.105 mm.
The light incident surface of the cover layer may be provided with a hard coat layer for preventing the light incident surface from being damaged when the optical disc is manufactured.

As the adhesive used for forming the cover layer, for example, a UV curable resin, an EB curable resin, a thermosetting resin or the like is preferably used, and in particular, a UV curable resin is preferably used.
When a UV curable resin is used as an adhesive, the UV curable resin may be used as it is or dissolved in an appropriate solvent such as methyl ethyl ketone or ethyl acetate to prepare a coating solution, which may be supplied from the dispenser to the barrier layer surface. . Further, in order to prevent warpage of the produced optical information recording medium, it is preferable that the UV curable resin constituting the adhesive layer has a small curing shrinkage rate. Examples of such UV curable resins include UV curable resins such as “SD-640” manufactured by Dainippon Ink and Chemicals, Inc.

For example, a predetermined amount of adhesive is applied onto the first information layer of the first substrate, a transparent sheet is placed thereon, and then the adhesive is applied by spin coating to cover the surface to be bonded and the cover. It is preferable to make it harden | cure, after extending so that it may become uniform between layers.
The thickness of the adhesive layer made of such an adhesive is preferably in the range of 0.1 to 100 μm, more preferably in the range of 0.5 to 50 μm, and still more preferably in the range of 10 to 30 μm.

  As the pressure-sensitive adhesive used for forming the cover layer, acrylic-based, rubber-based, and silicon-based pressure-sensitive adhesives can be used, and acrylic-based pressure-sensitive adhesives are preferable from the viewpoints of transparency and durability. As such an acrylic pressure-sensitive adhesive, 2-ethylhexyl acrylate, n-butyl acrylate and the like are the main components, and in order to improve cohesion, short-chain alkyl acrylates and methacrylates such as methyl acrylate, ethyl acrylate, and methyl methacrylate are used. And acrylic acid, methacrylic acid, acrylamide derivatives, maleic acid, hydroxylethyl acrylate, glycidyl acrylate, and the like, which can be crosslinking points with the crosslinking agent, are preferably used. The glass transition temperature (Tg) and the crosslinking density can be changed by appropriately adjusting the mixing ratio and type of the main component, the short chain component, and the component for adding a crosslinking point.

  As a crosslinking agent used together with the said adhesive, an isocyanate type crosslinking agent is mentioned, for example. Such isocyanate-based crosslinking agents include tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1,5-diisocyanate, o-toluidine isocyanate, isophorone diisocyanate, triphenylmethane triisocyanate, and the like. Isocyanates, products of these isocyanates with polyalcohols, and polyisocyanates formed by condensation of isocyanates can be used. Commercially available products of these isocyanates include Coronate L, Coronate HL, Coronate 2030, Coronate 2031, Millionate MR, Millionate HTL manufactured by Nippon Polyurethane; Takenate D-102 and Takenate D-110N manufactured by Takeda Pharmaceutical Co., Ltd. , Takenate D-200, Takenate D-202; Death Module L, Death Module IL, Death Module N, Death Module HL;

The pressure-sensitive adhesive may be uniformly applied on the surface of the first information layer of the first substrate by a predetermined amount, and after the cover layer is placed thereon, it may be cured, A predetermined amount may be uniformly applied to one surface of the cover layer to form an adhesive coating film, and the coating film may be bonded to the surface to be bonded, and then cured.
Moreover, you may use the commercially available adhesive film in which the adhesive layer was previously provided for the cover layer.
The thickness of the pressure-sensitive adhesive layer made of such a pressure-sensitive adhesive is preferably in the range of 0.1 to 100 μm, more preferably in the range of 0.5 to 50 μm, and still more preferably in the range of 10 to 30 μm.

<Protective layer>
A protective layer is preferably provided on the reflective layer for the purpose of physically and chemically protecting the information layer and the like. As a material for the protective layer, inorganic substances such as SiO ₂ , MgF ₂ , SnO ₂ , and Si ₃ N ₄ , organic substances such as thermoplastic resins, thermosetting resins, and UV curable resins can be used. The thickness of the protective layer is generally in the range of 0.1 to 100 μm.

  In the case of an inorganic substance, the protective layer can be formed by a method such as vacuum vapor deposition, sputtering, or coating. In the case of an organic substance, the protective layer can be formed by laminating a plastic film, coating and drying a coating solution dissolved in a solvent, or the like. Alternatively, the protective layer can be formed, for example, by laminating a film obtained by extrusion of plastic on the reflective layer via an adhesive. In the case of a thermoplastic resin or a thermosetting resin, it can also be formed by dissolving these in a suitable solvent to prepare a coating solution, and then applying and drying the coating solution. In the case of a UV curable resin, it can also be formed by preparing a coating solution as it is or by dissolving it in a suitable solvent, coating the coating solution, and curing it by irradiating with UV light. In these coating liquids, various additives such as an antistatic agent, an antioxidant, and a UV absorber may be added according to the purpose.

<Intermediate layer>
For example, an intermediate layer may be formed between each layer for the purpose of protecting the dye recording layer. The material constituting the intermediate layer, as long as the material transmits the laser beam is not particularly limited, is preferably a dielectric, and more _{specifically, ZnS, TiO 2, SiO 2} , ZnS-SiO ₂ , GeO ₂ , Si ₃ N ₄ , Ge ₃ N ₄ , MgF ₂ , and other inorganic oxides, nitrides, and sulfides. ZnS—SiO ₂ or SiO ₂ is preferable. The thickness of the intermediate layer is preferably 1 to 100 nm.

When forming the intermediate layer, sputtering is performed with inorganic oxides, nitrides, sulfides such as ZnS, TiO ₂ , SiO ₂ , ZnS—SiO ₂ , GeO ₂ , Si ₃ N ₄ , Ge ₃ N ₄ , MgF ₂ , It can be formed by ion plating or the like.

<Print layer>
In the optical disk of the present invention, the printed layer formed on the side opposite to the laser light incident surface is generally used as an index of recorded information. The printing layer is usually provided by screen printing, and is printed by overlapping one layer and two layers.
The printing layer is preferably made of a material that can be easily printed later. Specifically, materials such as acrylate-based ultraviolet curable ink and urethane-based ultraviolet curable ink can be used.
As with the protective layer described later, the printed layer can be formed by dissolving the above materials in an appropriate solvent to prepare a coating solution, and then applying the coating solution and drying or curing. It can also be formed by laminating a printing layer.
The thickness of the printing layer is preferably 3 to 50 μm, and more preferably 5 to 30 μm.
The pattern of the print layer is preferably formed over the entire print area so that the base is not visible.
In the optical disc of the present invention, the laser beam irradiation during reproduction or recording / reproduction is only from one side, so the printing layer is assigned to the entire surface of one side of the optical disc without being constrained by the laser beam irradiation region. be able to.

<Optical disk production method>
Next, a method for producing the optical disk of the present invention will be described. Hereinafter, two examples of creation methods A and B will be described. However, the present invention is not limited to these examples.

[Production Method A]
(1) A first substrate having a thickness of 0.55-α mm in which BD-ROM pits (first information layer) are formed on one side is produced by injection molding (α is the thickness of the adhesive layer). ).
(2) On the other hand, a second substrate having a thickness of 0.6 mm in which pits (second information layer) of a DVD-ROM are formed on one side is produced by injection molding.
(3) A reflective layer (for example, silver) is formed by sputtering on the DVD-ROM pit surface of the second substrate produced in (2).
(4) The first substrate manufactured in (1) and the second substrate manufactured in (2) are arranged on the side where the pits of the first substrate are not formed, the reflective layer of the second substrate, Are bonded with an ultraviolet curable adhesive so as to face each other, and irradiated with ultraviolet rays to cure the ultraviolet curable adhesive. At this time, it is preferable to irradiate ultraviolet rays from both sides, and in this case, it is preferable to balance the increase in temperature by irradiating a large amount of ultraviolet rays on the reflective layer side. The occurrence of warpage can be suppressed by balancing the temperature rise (equalizing on both sides). In addition, when irradiating an ultraviolet-ray from only one side, it is preferable to irradiate from the side without a reflection layer. The amount of the adhesive is adjusted so that the thickness of the adhesive layer made of the ultraviolet curable adhesive is α mm. α is preferably 1 to 100 μm, preferably 5 to 60 μm, and more preferably 10 to 40 μm.
(5) The material of the above-described transflective layer is formed on the BD-ROM pit surface of the first substrate by sputtering to form a multilayer transflective layer.
(6) A cover layer is formed on the transflective layer.
(7) On the surface opposite to the cover layer (on the reflective layer), a print layer is formed alone or in multiple layers with ultraviolet curable ink.

[Production Method B]
(1) A substrate having BD-ROM pits (first information layer) on one side and DVD-ROM pits (second information layer) on the other side is manufactured by injection molding.
(2) A reflective layer (for example, silver) is formed on the pit surface of the DVD-ROM by sputtering.
(3) A 0.6-α mm substrate (dummy substrate) whose both surfaces are flat (pits are not formed) is produced.
(4) The reflective layer side of the substrate produced in (1) and the dummy substrate produced in (3) are bonded together with an ultraviolet curable adhesive, and the ultraviolet curable adhesive is cured by irradiating with ultraviolet rays. At this time, it is preferable to irradiate ultraviolet rays from both sides, and in this case, it is preferable to balance the increase in temperature by irradiating a large amount of ultraviolet rays on the reflective layer side. The occurrence of warpage can be suppressed by balancing the temperature rise (equalizing on both sides). In addition, when irradiating an ultraviolet-ray from only one side, it is preferable to irradiate from the side without a reflection layer. The amount of the adhesive is adjusted so that the thickness of the adhesive layer made of the ultraviolet curable adhesive is β mm. β is preferably 1 to 100 μm, preferably 5 to 60 μm, and more preferably 10 to 40 μm. At this stage, since the pit forming surface of the BD-ROM is not a light incident surface, α and β may not be the same numerical value.
(5) The material of the above-described transflective layer is formed on the BD-ROM pit surface of the substrate by sputtering to form a multilayer transflective layer.
(6) A cover layer is formed on the transflective layer.
(7) On the surface opposite to the cover layer (on the reflective layer), a print layer is formed alone or in multiple layers with ultraviolet curable ink.

  The order of the steps in the manufacturing methods A and B described above is not necessarily limited to the order described. Moreover, you may provide the other process (The process of forming the protective layer of a light-incidence surface, or the process of forming an intermediate | middle layer) in the middle. In the above manufacturing methods A and B, the manufacturing method A is preferable in terms of easy manufacturing.

  Unlike the Dual Disc in which the information layers are arranged on both sides, the optical disc of the present invention can be provided with a label surface on the side opposite to the incident side of the laser beam, so that the disc information can be printed or used as a printable layer. You can use it freely. Specifically, it can be formed by applying an ultraviolet curable resin on the reflective layer on the side opposite to the laser light incident side by spin coating and curing the ultraviolet rays. Thereafter, it is preferable to apply (draw) ultraviolet curable ink by screen printing or the like to obtain a design surface.

  Hereinafter, the optical disk of the present invention will be described with reference to examples. However, the optical disk of the present invention is not limited to the following examples. In the following examples, the transflective layer is described as if it was actually formed, but was not actually formed, and was simulated by thin film reflectance calculation software (manufactured by TFcalc / Software Spectra Inc.). Is. The transflective layer has the significance of having a certain level of transmittance and reflectance for light of a specific wavelength, even if it is the transmittance and reflectance obtained by simulation. It is thought that the result is obtained as it is or close to it.

[Example 1]
On the pit formation surface of an injection molded substrate (first substrate) having a thickness of 0.5 mm on which BD-ROM pits (first information layer) are formed on one side, MgF ₂ (60 nm), TiO ₂ ( 39 nm), MgF ₂ (45 nm), TiO ₂ (28 nm), and MgF ₂ (84 nm) to form a semi-transmissive reflective layer (the thicknesses in parentheses indicate the thickness of each layer). The transflective layer had a reflectance of 40% at a wavelength of 405 nm and a transmittance of 100% at a wavelength of 650 nm.
Separately, a reflective layer made of a silver alloy (AgNdCu = 98: 1: 1) is formed on the pit forming surface of a 0.6 mm-thick injection-molded substrate having DVD-ROM pits (second information layer) formed on one side. A protective layer was formed by coating a UV curable resin thereon.
Using the first substrate and the second substrate as described above, a transparent ultraviolet curable resin is used as an adhesive so that the surface side of the first substrate where the pits are not formed and the reflective layer of the second substrate face each other. Used together. Next, a cover layer of 0.1 mm was formed on the transflective layer.
The optical disk of Example 1 having a BD-ROM pit at a position 0.1 mm from the light incident surface (cover layer side) and a DVD-ROM pit at a position 0.6 mm from the light incident surface was manufactured.

[Example 2]
An optical disk of Example 2 was manufactured in the same manner as Example 1 except that the semi-transmissive reflective layer was formed as a _two- layer film of MgF ₂ (76 nm) and TiO ₂ (23 nm). The transflective layer had a reflectance of 33.3% at a wavelength of 405 nm and a transmittance of 88.8% at a wavelength of 650 nm.

  The manufactured optical discs of Examples 1 and 2 are loaded into drives capable of reproducing DVD and BD, respectively, and reproduced as DVD and BD. When reproduced as a DVD, a laser beam having a wavelength of 650 nm is transmitted through the transflective layer, and a signal corresponding to the DVD-ROM pit can be read. When reproduced as a BD, the laser beam having a wavelength of 405 nm is reflected by the transflective layer and can read the BD-ROM pits. That is, playback can be performed from one side without turning over the DVD standard and the BD standard.

It is a schematic diagram which shows the layer structure of one Embodiment of the optical disk of this invention.

Explanation of symbols

10 optical disk 12 first substrate 14 transflective layer 16 first information layer 18 cover layer 20 second substrate 22 second information layer 24 reflective layer

Claims (2)

In order from the laser light incident surface, a first information layer that is reproduced or recorded / reproduced with a laser beam having a wavelength of 300 to 600 nm, a transflective layer, and a second information layer that is reproduced or recorded / reproduced with a laser beam having a wavelength of 600 to 700 nm. With an information layer of
An optical disc, wherein the transflective layer has a reflectance of 20% or more for light having a wavelength of 300 to 600 nm and a transmittance of 40% or more for light having a wavelength of 600 to 700 nm.   The distance from the laser light incident surface to the surface on the laser light incident surface side of the first information layer is 0.05 to 0.15 mm, and the laser light incident on the second information layer from the laser light incident surface 2. The optical disk according to claim 1, wherein the distance to the surface side surface is 0.4 to 0.8 mm.

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