JP2006196037A - Optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk which can perform reproduction or recording/reproduction by both CD and DVD (or HD DVD) standards and in which reproduction or recording/reproduction by both standards can be performed without turning over the optical disk to reload it even when one optical 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 can be performed with a laser beam having 600 to 700 nm wavelength, a semi-transparent reflection layer, and a second information layer wherein reproduction or recording/reproduction is performed with a laser beam having 700 to 900 nm wavelength in order from a laser beam incident surface, the semi-transparent reflection layer has ≥30% reflectance to the beam having 600 to 700 nm wavelength and ≥50% transmittance to the beam having 700 to 900 nm wavelength. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical disc, such as a CD or a DVD, 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. As an optical disk capable of satisfying such a requirement, “HD DVD” has been proposed, which can perform recording at a higher density than DVD with a laser beam having a short wavelength of 450 nm or less. An optical disc in which the DVD standard in DualDisc is replaced with the HD DVD standard using the HD DVD 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, Patent Document 1 does not clearly describe how the first layer and the second layer are configured to be read. In other words, it is unclear how CDs and DVDs with different standards have a two-layer structure.
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 CD standard and the DVD standard (or the HD DVD standard), and even if one optical disk is loaded in a drive or the like, it is turned over. Another object of the present invention is to provide an optical disc that can be reproduced or recorded / reproduced in accordance with both standards without being reloaded.

The above problems are solved by the present invention described below. That is,
<1> A first information layer that is reproduced or recorded / reproduced with a laser beam having a wavelength of 600 to 700 nm, a transflective layer, and a laser beam having a wavelength of 700 to 900 nm are reproduced or recorded in order from the laser beam incident surface. The semi-transmissive reflective layer has a reflectance of 30% or more for light having a wavelength of 600 to 700 nm and a transmittance of 50% or more for light having a wavelength of 700 to 900 nm. It is an optical disc characterized by being.

<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 0.4 to 0.8 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 0.8 to 1.4 mm.

<3> Reproduction or recording / reproduction with a third 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 700 to 900 nm in order from the laser light incident surface And a fourth information layer
The transflective layer is an optical disc characterized by having a reflectance of 10% or more for light having a wavelength of 300 to 600 nm and a transmittance of 50% or more for light having a wavelength of 700 to 900 nm.

<4> The distance from the laser light incident surface to the surface of the third information layer on the laser light incident surface side is 0.4 to 0.8 mm, and the distance from the laser light incident surface to the fourth information layer The optical disk according to <3>, wherein the distance to the laser light incident surface side is 0.8 to 1.4 mm.

  According to the present invention, an optical disc capable of reproducing or recording / reproducing both the CD standard and the DVD standard (or the HD DVD standard) is turned over even when one optical disk is loaded in a drive or the like. Thus, it is possible to provide an optical disc that can be reproduced or recorded / reproduced in accordance with both standards without being reloaded. 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.

According to the first aspect of the optical disc of the present invention, 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 600 to 700 nm, a transflective layer, and a wavelength of 700 A second information layer that is reproduced or recorded / reproduced with a laser beam of ˜900 nm, the transflective layer has a reflectance of 30% or more for light having a wavelength of 600 to 700 nm, and a wavelength of 700 to 900 nm. The light transmittance is 50% or more.
According to the second aspect, the optical disc of the present invention, in order from the laser light incident surface, a third 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 wavelength of 700 to A fourth information layer that is reproduced or recorded / reproduced by a 900 nm laser beam, the transflective layer has a reflectance of 10% or more for light having a wavelength of 300 to 600 nm, and has a wavelength of 700 to 900 nm. The light transmittance is 50% or more.

  More specifically, as the layer configuration of the optical disc according to the first aspect of the present invention, for example, a first substrate, a first information layer, a transflective layer, and a second substrate are sequentially arranged from the laser light incident surface. The second information layer, the reflective layer, and the protective layer can be used. In addition, an intermediate layer can be provided between the layers, and a printed layer can be provided on the protective layer. Further, the layer configuration of the optical disc of the second mode is the configuration in which, in the first mode, the first information layer is replaced with a third information layer, and the second information layer is replaced with a fourth information layer. is there.

  Information that can be read by laser light is recorded in the first information layer, the second information layer, the third information layer, and the fourth information layer in the first aspect and the second aspect. Or a layer that can record such information, and more specifically 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. In the case of pits, they can be formed on the first substrate and the second substrate according to the DVD standard and the CD standard, respectively. Alternatively, it is conceivable to form the second substrate on the one side according to the DVD standard and the other side on the CD standard.

In the present invention, the first information layer is actually an information layer of the DVD standard, and the DVD standard is the same layer alone as the information surface in DVD-ROM, DVD-R, DVD-RW, and DVD-RAM. In particular, 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.
Further, the second information layer and the fourth information layer are actually CD standard information layers, and the CD standard is the same layer as the information surface in CD-ROM, CD-R, CD-RW. Or it consists of a combination, and among them, CD-ROM or CD-R is preferable.
Furthermore, the third information layer is actually an information layer of the HD DVD standard, and -ROM, -R, -RW, and the like are conceivable similarly to DVD and CD.
The first to fourth 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 information layer 14, a transflective layer 16, a second substrate 18, a second information layer 20, and a reflective layer 22 laminated on a first substrate 12. Being done. The first information layer 14 is a layer where information is recorded according to the DVD standard, and the second information layer 20 is a layer where information is recorded according to the CD standard. As indicated by arrows in FIG. 1, the laser light is reflected by the semi-transmissive reflective layer 16 when the wavelength is 600 to 700 nm, and is transmitted through the semi-transmissive reflective layer 16 when the wavelength is 700 to 900 nm. reflect. That is, when the laser beam having a wavelength of 600 to 700 nm is irradiated toward the first substrate 12, the laser beam is reflected by the transflective layer 16 and output as DVD information. On the other hand, when laser light having a wavelength of 700 to 900 nm is irradiated, the laser light is transmitted through the semi-transmissive reflective layer 16, reflected by the reflective layer 22, and output as CD 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 DVD standard and the laser beam having the wavelength used for the CD standard as 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. . That is, both the DVD standard and the CD standard can be reproduced or recorded / reproduced without turning the optical disk in the drive upside down and reloading.

  The optical disc according to the first aspect of the present invention has been described above with reference to FIG. 1. The first information layer 14 in FIG. 1 is the third information layer, and the second information layer 20 is the fourth information layer. If the information layer is replaced, the second mode is obtained. However, in the second embodiment, the transflective layer 16 reflects light having a wavelength of 300 to 600 nm and transmits light having a wavelength of 700 to 900 nm.

  In the first aspect 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 0.4 to 0.8 mm, and the distance from the laser light incident surface is DVD and CD standards (0.6 mm and 1.2 mm from the substrate surface, respectively) by setting the distance to the laser light incident surface side surface of the second information layer to 0.8 to 1.4 mm Can be satisfied. The distance from the laser light incident surface to the surface of the first information layer on the laser light incident surface side is more preferably 0.5 to 0.7 mm, and more preferably 0.55 to 0.65 mm. Further preferred. The distance from the laser light incident surface to the surface of the second information layer on the laser light incident surface side is more preferably 0.9 to 1.3 mm, and more preferably 0.95 to 1.25 mm. More preferably.

  On the other hand, in the second aspect of the present invention, the distance from the laser light incident surface to the surface of the third information layer on the laser light incident surface side is set to 0.4 to 0.8 mm, and the laser light incident By setting the distance from the surface to the laser light incident surface side of the fourth information layer to 0.8 to 1.4 mm, each standard of HD DVD and CD (respectively 0.6 mm, 1 mm from the substrate surface, .2 mm) can be satisfied. The distance from the laser light incident surface to the surface of the third information layer on the laser light incident surface side is more preferably 0.5 to 0.7 mm, and more preferably 0.55 to 0.65 mm. Further preferred. The distance from the laser light incident surface to the surface of the fourth information layer on the laser light incident surface side is more preferably 0.9 to 1.3 mm, and more preferably 0.95 to 1.25 mm. More preferably.

  As described above, the transflective layer is a layer that reflects light having a wavelength of 600 to 700 nm and transmits light having a wavelength of 700 to 900 nm in the first embodiment. Can be configured as follows, for example. 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 600 to 700 nm of 30% or more, preferably 40% or more, more preferably 45% or more, and further preferably 50% or more. If the reflectance is less than 30%, sufficient reflectance for reproduction cannot be obtained. Further, the transmittance of light of 700 to 900 nm is 50% or more, preferably 60% 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 50%, sufficient light for reproduction cannot reach the second information layer.

  The transflective layer in the second embodiment is a layer that reflects light having a wavelength of 300 to 600 nm and transmits light having a wavelength of 700 to 900 nm. Examples of such a functioning layer include the following. Can be configured. That is, the transflective layer has at least a low refractive index layer and a high refractive index layer, and the refractive index difference thereof is 0.1 or more, preferably 0.2 or more, more preferably 0.3 or more, and further preferably Is 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, for example, a reflectance of light of 300 to 600 nm of 10% or more, preferably 20% or more, more preferably 35% or more, still more preferably 40% or more, and 700 to 900 nm. The light transmittance is 50% or more, preferably 60% or more, more preferably 70% or more, still more preferably 80% or more, and particularly preferably 90% or more.

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. Further, the thickness of the first substrate and the thickness of the second substrate are both preferably 0.4 to 0.8 mm, more preferably 0.5 to 0.7 mm. More preferably, it is 55 to 0.6 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 CD standard, the track pitch of the pregroove is preferably in the range of 1.2 to 2.0 μm, more preferably 1.4 to 1.8 μm, and 1.55 to 1.65 μm. More preferably.
The depth of the pregroove (groove depth) is preferably in the range of 100 to 250 nm, more preferably 150 to 230 nm, and even more preferably 170 to 210 nm.
The half width of the pregroove is preferably in the range of 400 to 650 nm, more preferably 480 to 600 nm, and further preferably 500 to 580 nm.

In the case of the HD DVD 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. preferable. 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 fourth 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 to fourth information layers are dye recording layers, the dye used in the dye recording layer is not particularly limited, but 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.

<Protective layer>
A protective layer is preferably provided on the reflective layer or the information layer (first to fourth information layers) 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 the second information layer described above and the reflective 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 0.6-mm-thick first substrate having a DVD-ROM pit (first information layer) formed on one side is produced by injection molding.
(2) On the pit surface of the first substrate produced in the above (1), the above-described material of the semi-transmissive reflective layer is formed by sputtering to form a multilayer semi-transmissive reflective layer.
(3) A second substrate having a thickness of 0.6-α mm in which CD-ROM pits (second information layer) are formed on one side is manufactured by injection molding (α is formed in a later step). It is the thickness of the adhesive layer.)
(4) The first substrate on which the transflective layer produced in (2) is formed and the second substrate produced in (3) are arranged so that the transflective layer and the CD-ROM pit surface face each other. Then, they are bonded together with an ultraviolet curing adhesive and irradiated with ultraviolet rays to cure the ultraviolet curing adhesive. At this time, it is preferable to irradiate ultraviolet rays from both sides. Moreover, it is preferable that the transflective layer side is balanced by increasing the irradiation amount of ultraviolet rays. The adhesive layer made of an ultraviolet curable adhesive is preferably α mm (α = 1 to 100 μm, preferably 5 to 60 μm, more preferably 10 to 40 μm).
(5) A reflective layer (for example, silver) is formed on the CD-ROM pit surface by sputtering.
(6) An ultraviolet curable protective layer is applied on the reflective layer by spin coating, and cured by irradiation with ultraviolet rays.
(7) A printing layer is formed alone or in multiple layers with ultraviolet curable ink.

[Production Method B]
(1) A first substrate having a thickness of 0.6 mm in which a DVD-ROM pit (first information layer) is formed on one surface and a CD-ROM pit (second information layer) is formed on the other surface. Is produced by injection molding.
(2) On the DVD-ROM pit surface of the substrate produced in (1), the above-described material of the semi-transmissive reflective layer is formed by sputtering to form a multilayer semi-transmissive reflective layer.
(3) A 0.6-α mm thick substrate on which both sides are not formed with pits is injection molded (α is the thickness of the adhesive layer formed in a later step).
(4) Both substrates so that the transflective layer of the substrate on which the transflective layer obtained in (2) is formed and one surface of the substrate obtained in (3) face each other. Paste together. The adhesive layer is preferably α mm (α = 1 to 100 μm, preferably 5 to 60 μm, more preferably 10 to 40 μm).
(5) A reflective layer (for example, silver) is formed on the pit surface of the CD-ROM by sputtering.
(6) An ultraviolet curable protective layer is applied on the reflective layer by spin coating, and cured by irradiation with ultraviolet rays.
(7) A printing 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.

  The substrates can be bonded together by applying an ultraviolet curable resin to the substrate and curing it by irradiating ultraviolet rays from the laser light incident surface. At this time, it is preferable to irradiate ultraviolet rays from the opposite side at the same time because the temperature rise is well balanced on both sides and the occurrence of warpage is suppressed.

  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 CD recording surface (the side opposite to the laser light incident side) by spin coating on the reflective layer 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]
MgF ₂ (108 nm), TiO ₂ (62 nm), MgF are formed on a 0.6 mm-thick injection molded substrate (first substrate) having a DVD-ROM pit (first information layer) formed on one side by vacuum film formation. ₂ layers (74 nm), TiO ₂ (44 nm), and MgF ₂ (41 nm) were deposited to form a semi-transmissive reflective layer (the thickness in parentheses indicates the thickness of each layer). The transflective layer had a reflectance of 54% at a wavelength of 650 nm and a transmittance of 90% at a wavelength of 780 nm.

Separately, a silver alloy reflective layer is formed on a 0.6 mm-thick injection molded substrate (second substrate) having CD-ROM pits (second information layer) formed on one side, and an ultraviolet curable resin is formed thereon. Was coated to form a protective layer.
The above two substrates are pasted using a transparent ultraviolet curable resin as an adhesive so that the transflective layer of the first substrate and the surface of the second substrate opposite to the protective layer face each other. By combining, 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 CD-ROM pit at a position 1.2 mm was produced. The optical disk of Example 1 was produced.

[Example 2]
_Two layers of MgF ₂ (67 nm) and TiO ₂ (24 nm) are formed on a 0.6 mm-thick injection-molded substrate having HD DVD-ROM pits formed on one side by vacuum film formation. A film was formed. The transflective layer had a reflectance of 50% at a wavelength of 405 nm and a transmittance of 94% at a wavelength of 780 nm. Otherwise, the optical disk of Example 2 was produced in the same manner as Example 1.

[Example 3]
MgF ₂ (106 nm), TiO ₂ (37 nm), MgF ₂ (17 nm), TiO ₂ (68 nm), MgF are formed on a 0.6 mm-thick injection-molded substrate having HD DVD-ROM pits on one side by vacuum film formation. ₂ (133 nm) 5 layers were formed to form a transflective layer. The transflective layer had a reflectance of 50% at a wavelength of 405 nm and a transmittance of 94% at a wavelength of 780 nm. Otherwise, the optical disk of Example 3 was produced in the same manner as in Example 1.

  The manufactured optical discs of Examples 1 to 3 are loaded into drives capable of reproducing CDs and DVDs (or HD DVDs) and reproduced as CDs and DVDs (or HD DVDs). When reproduced as a CD, laser light having a wavelength of 780 nm is transmitted through the transflective layer, and a signal corresponding to the CD-ROM pit can be read. When reproduced as a DVD (HD DVD), laser light having a wavelength of 650 nm (405 nm) is reflected by the transflective layer and can read DVD-ROM pits (HD DVD-ROM pits). That is, playback can be performed from one side without turning over the CD standard and the DVD standard (HD DVD standard).

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

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical disk 12 1st board | substrate 14 1st information layer 16 Transflective layer 18 2nd board | substrate 20 2nd information layer 22 Reflective layer

Claims (4)

A first information layer that is reproduced or recorded / reproduced with a laser beam having a wavelength of 600 to 700 nm, a transflective layer, and a first information layer that is reproduced or recorded / reproduced with a laser beam having a wavelength of 700 to 900 nm. Two information layers,
An optical disc, wherein the transflective layer has a reflectance of 30% or more for light having a wavelength of 600 to 700 nm and a transmittance of 50% or more for light having a wavelength of 700 to 900 nm.   The distance from the laser light incident surface to the surface of the first information layer on the laser light incident surface side is 0.4 to 0.8 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 0.8 to 1.4 mm. In order from the laser light incident surface, a third 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 fourth information layer that is reproduced or recorded / reproduced with a laser beam having a wavelength of 700 to 900 nm. With an information layer of
An optical disc, wherein the transflective layer has a reflectance of 10% or more for light having a wavelength of 300 to 600 nm and a transmittance of 50% or more for light having a wavelength of 700 to 900 nm.   The distance from the laser light incident surface to the surface of the third information layer on the laser light incident surface side is 0.4 to 0.8 mm, and the laser light incident on the fourth information layer from the laser light incident surface 4. The optical disk according to claim 3, wherein the distance to the surface on the surface side is 0.8 to 1.4 mm.

Images