JP2003263775A - Optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording medium having less distribution of reflectance and modulation degree in a radius direction and stable recording and reproducing characteristics. <P>SOLUTION: In the disk-shaped optical recording medium having at least one sputtering layer formed by a sputtering method, the inner periphery of the sputtering layer is positioned inside a stack ring. As the sputtering layer, a reflection layer is quoted for of a WORM (write-once-read-many) type optical recording medium such as a DVD-R and all layers except a substrate are quoted for a re-writable optical recording medium such as a DVD-RW. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium capable of recording / reproducing information using a laser beam. 2. Description of the Related Art Conventionally, optical recording media (optical disks) capable of recording information only once with laser light are known. This optical disc is a write-once CD (so-called CD-
R), and its typical structure is a transparent disk-shaped substrate in which a dye recording layer made of organic dye, a reflective layer made of metal such as gold, and a protective layer made of resin are laminated in this order. is there. Information recording on the CD-R is performed by irradiating the CD-R with near-infrared laser light (usually laser light having a wavelength near 780 nm). Information is recorded by absorbing light and increasing the temperature locally, and changing the optical characteristics of the portion due to physical or chemical changes (for example, generation of pits). On the other hand, the reading (reproduction) of information also uses a laser beam with the same wavelength as the recording laser beam.
This is performed by irradiating R, and is performed by detecting a difference in reflectance between a portion where the optical characteristics of the dye recording layer are changed (recorded portion) and a portion where the optical characteristics are not changed (unrecorded portion). . In recent years, an optical recording medium having a higher recording density has been demanded. In response to such a demand, an optical disk called a write-once digital versatile disk (so-called DVD-R) has been proposed (for example, “Nikkei New Media”, separate volume “DVD”, published in 1995). This DVD-R has a transparent disk shape in which a guide groove (pre-groove) for tracking of the irradiated laser beam is formed with a narrow groove width that is less than half of the CD-R (0.74 to 0.8 μm). A structure in which a dye recording layer containing two organic dyes, a reflective layer, and a protective layer are laminated in this order on a substrate, with the dye recording layer inside.
Alternatively, it has a structure in which a disk-shaped protective substrate having the same shape as this disk is bonded with the dye recording layer inside. Recording and reproduction of information on this DVD-R is performed using visible laser light (usually 630 nm to 680 nm).
In this case, recording with a higher density than CD-R is possible. D
The maximum recording capacity of the VD-R is when the inner diameter of the data recording area is 48 mm, the outer diameter is 116 mm, the track pitch is 0.74 μm minimum, and the linear velocity is 3.5 m / s.
70 GB. On the other hand, information recording by laser light irradiation,
An optical recording medium that can be reproduced and erased, and is a so-called phase change optical recording medium (so-called CD-R) that utilizes a transition between crystal and amorphous or between two crystal phases.
W, DVD-RW) is known. This phase change type optical recording medium includes a phase change recording layer mainly composed of chalcogen such as Te and Se, a translucent dielectric layer sandwiching the phase change recording layer from both sides, and a laser beam incident side. It is mainly composed of a reflective layer provided on the opposite side and a protective layer. In such an optical recording medium, conventionally, for example, the reflection layer is usually formed in a donut shape from the vicinity of the outer peripheral portion of the optical disk (optical recording medium) to the vicinity of the stack ring by a sputtering method. However, according to this configuration, depending on the sputtering conditions, the thickness of the reflective layer may be uneven in the radial direction, or the substrate after sputtering may be greatly deformed due to the residual stress of the sputtered film, leading to a decrease in reflectivity. Further, depending on the case, there is a problem that the dye of the recording layer is damaged by the influence of plasma during sputtering, resulting in a decrease in the degree of modulation and unevenness in the radial direction in the recording / reproducing characteristics. SUMMARY OF THE INVENTION The present invention has been made in view of the above conventional problems, and it is an object of the present invention to achieve the following objects. That is, an object of the present invention is to provide an optical recording medium having a stable recording / reproducing characteristic with a small distribution in the radial direction of reflectivity and modulation degree. Means for solving the above-mentioned problems are as follows. That is, in a disc-shaped optical recording medium having at least one sputtered layer formed by a sputtering method, the inner periphery of the sputtered layer is located inside the stack ring. is there. The sputter layer is not particularly limited as long as it is a layer formed by sputtering. For example, in a write-once type optical recording medium, a reflective layer is used. In a rewritable type optical recording medium, a substrate is used. All layers except for. In addition, as the diameter of the inner periphery of the sputter layer,
It should be smaller than the diameter of the stack ring.
It is preferable to set it as 4 mm, and it is more preferable to set it as 16-36 mm. DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the optical recording medium of the present invention will be described below. The optical recording medium of the present invention is a disc-shaped optical recording medium having at least one sputtered layer formed by a sputtering method, and the inner periphery of the sputtered layer is located inside the stack ring. Has characteristics. FIG. 1 schematically shows a cross section of a write-once type optical recording medium 10 having a dye recording layer to which the present invention is applied. The optical recording medium 10 has a dye recording layer 1 on a substrate 12.
4, a disc-shaped optical recording medium in which a reflective layer (sputtered layer) 16 and a protective layer 18 are laminated, and a central hole 20 is formed at the center. The diameter of the center hole 20 is 15 mm, and a stack ring 22 is formed on a concentric circle of the center hole 20 and at a predetermined distance from the edge of the center hole 20. The stack ring 22 serves to prevent the optical recording media from sticking to each other when stacked. For example, when disks are stacked and the optical recording media are in close contact with each other during the manufacturing process, the reflective layer or the information reading surface is damaged immediately after forming the reflective layer, or the printed label surface is stained immediately after label printing. The information reading surface may become dirty due to a defective product, or the information reading surface may be damaged if the ink is cured. Stack ring 22
Will prevent them. In the optical recording medium 10 of the present embodiment, the reflective layer 18 is formed by sputtering, and the reflective layer 1
As shown in FIGS. 1 and 2, the inner circumference of 8 is located inside the stack ring 22. Conventionally, the inner periphery of the reflective layer was positioned in the vicinity of the stack ring. However, by positioning the inner periphery of the reflective layer on the inner side of the stack ring, the mask diameter during sputtering in the manufacturing process is reduced. be able to. When the diameter of the mask is reduced, film formation in the radial direction can be made uniform and deformation of the substrate can be reduced. Furthermore, it is possible to reduce the influence of plasma on the recording layer dye during sputtering. Therefore, the optical recording medium of the present invention has a smaller distribution in the radial direction in the recording / reproducing characteristics than the conventional optical recording medium in which the reflective layer is positioned in the vicinity of the stack ring, and stable recording / reproducing characteristics can be obtained on the entire circumference. The diameter of the mask is preferably smaller than the diameter of the stack ring and 16 mm or more. The optical recording medium 10 shown in FIG. 1 shows the case where the sputtered layer is a reflective layer. However, in the present invention, the optical recording medium 10 is not limited to the reflective layer, and may be any layer formed by a sputtering method. In addition, it is only necessary that the inner circumference is positioned inside the stack ring. The inner peripheral diameter of the sputter layer is preferably 15 to 44 mm, and preferably 16 to 36.
More preferably, it is mm. As the sputter layer, in the case of a write-once type optical recording medium such as a DVD-R, a reflective layer can be cited.
In the case of a rewritable optical recording medium such as -RW, all layers except the substrate can be mentioned. The substrate and each layer of the optical recording medium of the present invention will be described in detail below, but the present invention is not limited to the following configuration. <Substrate> As the 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. Moreover, it is preferable that the thickness of a board | substrate shall be 0.5-1.4 mm. The substrate is provided with irregularities (pre-grooves) representing information such as tracking guide grooves or address signals. The track pitch of the pregroove is not particularly limited, but is preferably 400 to 900 nm, more preferably 450 to 850 nm.
More preferably, it is set to 00 to 800 nm. Also,
The depth of the pregroove (groove depth) is preferably 80 to 180 nm, more preferably 100 to 170 nm, and still more preferably 110 to 160 nm. Furthermore, the half width of the pregroove is 200-
400 nm is preferable, 230 to 380 nm
More preferably, the thickness is more preferably 250 to 350 nm. The aforementioned stack ring is formed on the substrate. The diameter of the stack ring is, for example, 33-4
It can be 4 mm. An undercoat layer may be provided on the substrate surface on the side where the recording layer described later is provided for the purpose of improving the flatness, improving the adhesive force and preventing the recording layer from being altered. 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. Polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer,
Examples thereof include polymer substances such as ethylene / vinyl acetate copolymer, polyethylene, polypropylene, and polycarbonate; and surface modifiers such as a silane coupling agent. The undercoat layer is prepared by dissolving or dispersing the above substance in an appropriate solvent to prepare a coating solution, and then spin-coating the coating solution.
It can be formed by applying to the substrate surface using a coating method such as dip coating or extrusion coating. The thickness of the undercoat layer is generally 0.005 to 20 μm
m, preferably 0.01 to 10 μm. <Recording layer> As the recording layer, a dye recording layer is used in the case of a write-once optical recording medium, and a phase change recording layer is used in the case of a rewritable optical recording medium. Hereinafter, each recording layer will be described. -Dye recording layer-The dye used in the dye recording layer is not particularly limited.
Examples of usable dyes include cyanine dyes, phthalocyanine dyes, azo metal complex dyes, dipyrromethene metal complex dyes, imidazoquinoxaline dyes, pyrylium / thiopyrylium dyes, azurenium dyes, squarylium dyes, Ni, Cr Metal complex dyes such as naphthoquinone dyes, anthraquinone dyes, indophenol dyes, indoaniline dyes, triphenylmethane dyes, merocyanine dyes, oxonol dyes, aminium dyes / diimmonium dyes and nitroso compounds be able to. Among these dyes, cyanine dyes, phthalocyanine dyes, oxonol dyes, azo metal complex dyes, and dipyrromethene metal complex dyes are preferable. Examples of the solvent of the coating solution for forming the dye recording layer include esters such as butyl acetate and cellosolve acetate; methyl ethyl ketone, cyclohexanone,
Ketones such as methyl isobutyl ketone; chlorinated hydrocarbons such as dichloromethane, 1,2-dichloroethane and chloroform; amides such as dimethylformamide; hydrocarbons such as cyclohexane; ethers such as tetrahydrofuran, ethyl ether and dioxane;
alcohols such as n-propanol, isopropanol, n-butanol, diacetone alcohol;
Fluorine solvents such as 3,3-tetrafluoropropanol; glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, and the like. The above solvents may be used alone or in combination of two or more in consideration of the solubility of the dye used. Preferably, it is a fluorinated solvent such as 2,2,3,3-tetrafluoropropanol. In addition, an anti-fading agent and a binder may be added to the coating liquid as desired, and various additives such as an antioxidant, a UV absorber, a plasticizer, and a lubricant are added depending on the purpose. May be. Representative examples of the antifading agent include nitroso compounds, metal complexes, diimmonium salts and aminium salts. Examples of these include, for example, JP-A-2-300288, JP-A-3-224793, and JP-A-4.
-146189 and other publications. Examples of binders include natural organic polymer materials such as gelatin, cellulose derivatives, dextran, rosin and rubber; and hydrocarbon resins such as polyethylene, polypropylene, polystyrene and polyisobutylene, polyvinyl chloride, polychlorinated Vinyl resins such as vinylidene, polyvinyl chloride / polyvinyl acetate copolymer, acrylic resins such as polymethyl acrylate, polymethyl methacrylate,
Examples include synthetic organic polymers such as polyvinyl alcohol, chlorinated polyethylene, epoxy resins, butyral resins, rubber derivatives, and initial condensates of thermosetting resins such as phenol / formaldehyde resins. When the binder is used, the amount of the binder used is generally 0.2 to 20 parts by mass, preferably 0.5 to 1 with respect to 100 parts by mass of the dye.
0 parts by mass, more preferably 1 to 5 parts by mass. The above solvents can be used alone or in combination of two or more in consideration of the solubility of the recording material used. In the coating solution, further antioxidants, UV
Various additives such as an absorbent, a plasticizer, and a lubricant may be added according to the purpose. When a binder is used, examples of the binder include natural organic polymer materials such as gelatin, cellulose derivatives, dextran, rosin and rubber; hydrocarbon resins such as polyethylene, polypropylene, polystyrene and polyisobutylene. Polyvinyl chloride, polyvinylidene chloride,
Vinyl resins such as polyvinyl chloride / 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 A synthetic organic polymer such as an initial condensate of a thermosetting resin, and the like. When a binder is used in combination as a material for the dye recording layer, the amount of binder used is generally 0.0 with respect to the recording substance.
It exists in the range of 1 times amount-50 times amount (mass ratio), Preferably it exists in the range of 0.1-5 times amount (mass ratio). The concentration of the recording material in the coating solution thus prepared is generally 0.
It is in the range of 01-10% by mass, preferably 0.1-5
It is in the range of mass%. Examples of the coating method include a spray method, a spin coating method, a dip method, a roll coating method, a blade coating method, a doctor roll method, and a screen printing method. 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.
More preferably, it exists in the range of 50-100 nm. Also,
There is no particular problem if the coating temperature is 23 to 50 ° C., preferably 24 to 40 ° C., more preferably 25.
~ 37 ° C. 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 are disclosed in JP-A-5.
Nos. 8-175693, 59-81194,
60-18387, 60-19586, 60-19588, 60-35054, 60-36190, 60-36191
Publication No. 60-45554 Publication No. 60-4455
No. 5, No. 60-44389, No. 60-443
No. 90, No. 60-54892, No. 60-47
No. 069, No. 63-209995, JP-A-4
-25492, JP-B-1-38680, and JP-A-6-26028, German Patent 3
No. 50399, and Journal of the Chemical Society of Japan, 1992 1
The thing described in 0th issue, page 1141, etc. can be mentioned. 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 0.8%, based on the amount of the compound for recording.
The range is 5 to 45% by mass, more preferably 3 to 40% by mass, and particularly preferably 5 to 25% by mass. -Phase change recording layer- The phase change recording layer is a layer made of a material capable of repeating a phase change between a crystalline phase and an amorphous phase by laser light irradiation. 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
Alloys, etc. Among these, Ge-Sb-Te alloy, Ag-In can be rewritten many times.
-Sb-Te alloy is preferred. The layer thickness of the phase change recording layer is 10-50.
Preferably, the phase change recording layer is formed by a vapor phase thin film deposition method such as a sputtering method or a vacuum vapor deposition method. <Reflective layer> A reflective layer is provided on the recording layer for the purpose of improving the reflectance, particularly when reproducing information.
The light-reflective substance that is the material of the reflective layer is a substance that has a high reflectivity with respect to laser light.
Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo,
W, Mn, Re, Fe, Co, Ni, Ru, Rh, P
d, Ir, Pt, Cu, Ag, Au, Zn, Cd, A
l, Ga, In, Si, Ge, Te, Pb, Po, S
Mention may be made of metals such as n and Bi, metalloids and stainless steel. Of these, preferred are
Cr, Ni, Pt, Cu, Ag, Au, Al, and stainless steel. These substances may be used alone or
Or you may use it in combination of 2 or more types. Or you may use as an alloy. Particularly preferred is Au, Ag or an alloy thereof. The reflective layer can be formed on the recording layer by using, for example, the above-described light reflective material by a vapor-phase thin film deposition method such as sputtering or vacuum evaporation. The thickness of the reflective layer is generally in the range of 10 to 800 nm, preferably in the range of 20 to 500 nm, more preferably in the range of 50 to 300.
It is provided in the range of nm. <Protective layer> The protective layer is formed in order to prevent moisture from entering into the optical recording medium and is not particularly limited as long as it is a transparent material, but is preferably polycarbonate, UV curable resin, or the like, more preferably. Is 23 ° C 50%
A material having a moisture absorption rate of 5% or less at RH. Note that “transparent” means that the recording light and the reproduction light are so transparent that the light is transmitted (transmittance: 90% or more). The thickness of the protective layer is preferably 1 to 30 μm.
More preferably, it is the range of 3-20 micrometers, More preferably, it is the range of 3-10 micrometers. In the optical recording medium of the present invention, for example, a light transmission layer for improving adhesion to the recording layer is provided between the reflective layer and the recording layer in accordance with the characteristics of the recording layer. Also good. Any material can be used as the light transmission layer as long as it has a transmittance of 90% or more at the laser wavelength. The light transmission layer can be formed by a conventionally known method, and the thickness of the light transmission layer is preferably 2 to 50 nm. EXAMPLES Examples of the present invention will be described in detail below, but the present invention is not limited thereto. Example 1 First, polycarbonate resin having a stack ring with a diameter of 36 mm (manufactured by Teijin Limited,
A resin substrate made by trade name: Panlite AD5503) was produced by injection molding. Next, 1.0 g of dye A represented by the following structural formula and 0.5 g of dye B represented by the following structural formula
Are mixed with 100 cm ³ of 1,1,2,2-tetrafluoro-1-propanol, and an ultrasonic vibrator (1800
W) was used to dissolve the dye over 2 hours to prepare a recording layer coating solution. The recording layer coating liquid is applied to the surface of the polycarbonate substrate having the pregroove at a rotational speed of 300.
It was applied by spin coating while changing to ˜4000 rpm, and dried to form a dye recording layer (thickness (in pre-groove): about 150 nm). The forming conditions of the dye recording layer are as follows: atmosphere temperature: 23 ° C., humidity: 50% RH, coating solution temperature: 23 ° C., substrate temperature: 23 ° C., pumping speed:
It was 0.1 m / sec. ## STR1 ## Next, the substrate on which the dye recording layer was formed was replaced with 6
It was stored for 2 hours in a dry environment at 0 ° C. to remove the residual solvent in the dye recording layer. Next, Ag was sputtered onto the dye recording layer to form a reflective layer having a thickness of 150 nm so that the inner peripheral diameter was 22 mm. Furthermore, on the reflective layer,
A UV curable resin (manufactured by Dainippon Ink & Chemicals, Inc., trade name: SD318) was applied by a spin coating method while changing the rotation speed to 50 to 5000 rpm. After coating, an ultraviolet ray was irradiated from above with a high-pressure mercury lamp and cured to form a protective layer of 8 μm. The write-once type optical recording medium A composed of the substrate, the dye recording layer, the reflective layer, and the protective layer was produced by the above steps. Next, Ag is sputtered on the substrate formed in the same manner as the above-mentioned substrate, a layer having a thickness of 150 nm is formed, a protective layer is formed with a UV curable resin, and a dummy substrate B for bonding is formed. And the optical recording medium A and the dummy substrate B were bonded together to obtain the optical recording medium of Example 1. Comparative Example 1 An optical recording medium was fabricated in the same manner as in Example 1 except that the reflective layer was formed so that the inner periphery of the reflective layer coincided with the position of the stack ring. (Evaluation) With respect to the optical recording media of Examples and Comparative Examples obtained as described above, the inner circumference (radius 24 mm) and the intermediate portion (radius 40 mm) in terms of the warpage, modulation degree, and reflectance of the disc. ) And the outer periphery (radius 55 mm) for each region. The results are shown in Table 1. The evaluation method for each evaluation is as follows. [Distortion of disk] DLD manufactured by Japan EM
The amount of warpage of the completed optical recording medium was measured using 4000. [Modulation Degree] DDU1000 manufactured by Pulse Tech
Were recorded with the same recording strategy, and the 14T modulation degree was measured. [Reflectance] DDU1000 manufactured by Pulstec
Was used to measure the reflectance after recording. [Table 1] From Table 1, the optical recording medium of the embodiment has a smaller warp of the disk than the optical recording medium of the comparative example, and the reflectance and the modulation degree are particularly high in the inner peripheral portion, and the inner peripheral portion and the intermediate portion. ,
The difference in characteristics at the outer periphery is reduced. According to the present invention, it is possible to provide an optical recording medium having a stable recording / reproducing characteristic with a small radial distribution of reflectance and modulation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic sectional view of an optical recording medium to which the present invention is applied. FIG. 2 is a partial cross-sectional perspective view of an optical recording medium to which the present invention is applied. [Explanation of Symbols] 10 Optical Recording Medium 12 Substrate 14 Dye Recording Layer 16 Reflective Layer (Sputtering Layer) 18 Protective Layer 20 Center Hole 22 Stack Ring

Claims (1)

1. A disk-shaped optical recording medium having at least one sputtered layer formed by a sputtering method, wherein an inner periphery of the sputtered layer is located inside a stack ring. An optical recording medium characterized by the above.