WO2001006504A1 - Optical recording medium - Google Patents

Optical recording medium Download PDF

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Publication number
WO2001006504A1
WO2001006504A1 PCT/KR2000/000790 KR0000790W WO0106504A1 WO 2001006504 A1 WO2001006504 A1 WO 2001006504A1 KR 0000790 W KR0000790 W KR 0000790W WO 0106504 A1 WO0106504 A1 WO 0106504A1
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WO
WIPO (PCT)
Prior art keywords
layer
film
optical disc
thickness
substrate
Prior art date
Application number
PCT/KR2000/000790
Other languages
French (fr)
Inventor
Seong-Sue Kim
Du-Seop Yoon
Original Assignee
Samsung Electronics Co., Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Samsung Electronics Co., Ltd. filed Critical Samsung Electronics Co., Ltd.
Priority to AU60253/00A priority Critical patent/AU6025300A/en
Publication of WO2001006504A1 publication Critical patent/WO2001006504A1/en

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Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/24018—Laminated discs
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
    • G11B7/257—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers
    • G11B7/2578—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers consisting essentially of inorganic materials
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
    • G11B7/258—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of reflective layers
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
    • G11B7/257—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers
    • G11B2007/25705—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers consisting essentially of inorganic materials
    • G11B2007/25706—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers consisting essentially of inorganic materials containing transition metal elements (Zn, Fe, Co, Ni, Pt)
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
    • G11B7/257—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers
    • G11B2007/25705—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers consisting essentially of inorganic materials
    • G11B2007/25708—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers having properties involved in recording or reproduction, e.g. optical interference layers or sensitising layers or dielectric layers, which are protecting the recording layers consisting essentially of inorganic materials containing group 13 elements (B, Al, Ga)
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
    • G11B7/253—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of substrates
    • G11B7/2531—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of substrates comprising glass
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
    • G11B7/256—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of layers improving adhesion between layers
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/241—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material
    • G11B7/252—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers
    • G11B7/258—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of reflective layers
    • G11B7/2585—Record carriers characterised by shape, structure or physical properties, or by the selection of the material characterised by the selection of the material of layers other than recording layers of reflective layers based on aluminium

Definitions

  • the present invention relates to an optical recording medium such as a compact disc or laser disc, and more particularly, to a reproduction- dedicated two-layer optical disc having a signal surface with a two-layer structure.
  • FIG. 1 is a vertical cross-sectional view of a reproduction-dedicated optical disc (hereinafter, referred to as a two-layer optical disc) having a two- layer signal surface, which is a model of an optical information medium having a multi-layer structure.
  • a conventional two-layer optical disc has first and second substrates 11 and 15 which are positioned opposite to each other.
  • the first and second substrates 11 and 15 which are typically translucent substrates formed in the shape of a disc having a predetermined thickness by injection-molding a transparent synthetic resin, have signal surfaces which are uneven because of the formation of grooves on each of the facing surfaces in a spiral or concentric circular pattern. Pits are formed on the signal surfaces for recording optical information.
  • a thin semitransparent film 12 is coated along the rugged surface of the first substrate 11 so that the film 12 has a rugged surface that is the same as the rugged surface of the first substrate.
  • the semitransparent film 12 has non- variable reflectivity and permeability, and is typically a single-layer gold film
  • 80BSTITUTESHEEr(RULE26) or a three-layer dielectricfilm In actual manufacturing, a single-layer gold film is usually used in consideration of the manufacturing cost.
  • a spacer 13 made of translucent ultraviolet hard resin or the like is deposited to a predetermined thickness on the semitransparent film 12, and thus connects the first and second substrates 11 and 15 and also reduces the cross-talk between the signal surfaces of the two substrates 11 and 15.
  • a total reflection film 14 is tightly coated along the rugged surface of the second substrate 15 so that the total reflection film 14 has a rugged surface that is the same as the rugged surface of the second substrate.
  • the total reflection film 14, which is typically a thin metal film having a high reflectivity, is usually formed of aluminum (Al) or an aluminum alloy.
  • a two-layer optical disc having such a configuration allows reproduction light beams L1 and L2 radiated from an optical pickup (not shown) to be focused on the signal surface of the first substrate 11 and that of the second substrate 15, respectively, and thus receives reflective light modulated by pits formed on each of the signal surfaces. Thus, reproduction of desired information can be achieved.
  • This two-layer disc must have small and high-density grooves and pits formed on the reflection layer, in order to record a large amount and high density of information. Since an optical pickup uses a laser beam having a short wavelength as a reproduction light source, the specification of optical discs, that is, the specification in which the reflectivities of the signal surfaces of the substrates 11 and 15 of the optical disc must have the same value of at least 18%, must be satisfied in order to achieve accurate and stable information reproduction.
  • an objective of the present invention is to provide a two-layer optical disc having a single-layer semitransparent film, in which a reflectivity of at least 18% is provided from each signal surface even when a blue laser having a short wavelength is used as a reproduction light source, so that a specification enabling accurate and stable information reproduction is satisfied.
  • the above objective of the present invention is achieved by a two-layer optical disc formed by sequentially stacking a semitransparent film, a spacer layer, a total reflection film, and a second substrate on a first substrate having a predetermined index of refraction, the optical disc characterized in that the semitransparent film is a GaP thin film layer.
  • the semitransparent GaP thin film layer is formed to a thickness of 7 to 16nm.
  • the semitransparent film can be an aluminum layer.
  • the semitransparent aluminum film is formed to a thickness of 3 to 7nm.
  • the semitransparent film can be a silver layer.
  • the semitransparent silver film is formed to a thickness of 15 to 25nm.
  • FIG. 1 is a cross-sectional view schematically illustrating the structure of a conventional two-layer optical disc
  • FIG. 2 is a cross-sectional view schematically illustrating the structure of a two-layer optical disc according to an embodiment of the present invention
  • FIG. 3 is a graph showing variation in the reflectivity of the signal surface of each substrate according to the thickness of a GaP semitransparent film, when a 410nm-wavelength blue laser beam is used as the reproduction light source of a two-layer optical disc according to an embodiment of the present invention
  • FIG. 4 is a graph showing variation in the reflectivity of the signal surface of each substrate according to the thickness of an Al layer, when a 410nm-wavelength blue laser beam is used as the reproduction light source of a two-layer optical disc according to another embodiment of the present invention in which a semitransparent film is formed of aluminum (Al); and FIG.
  • FIG. 5 is a graph showing variation in the reflectivity of the signal surface of each substrate according to the thickness of an Ag layer, when a 410nm-wavelength blue laser beam is used as the reproduction light source of a two-layer optical disc according to still another embodiment of the present invention in which a semitransparent film is formed of silver (Ag).
  • a reproduction-dedicated optical disc having a two-layer structure according to the present invention shown in FIG. 2 has substantially the same structure as a conventional two-layer optical disc shown in FIG. 1 , except for the material and thickness of a semitransparent film.
  • the two-layer optical disc according to the present invention is characterized in that a blue laser beam having a wavelength ranging from 400 to 500nm is used as a reproduction light beam emitted onto the signal surface of each substrate.
  • the two-layer optical disc according to the present invention has first and second substrates 21 and 25 which are positioned to face each other.
  • the first and second substrates 21 and 25 are typically translucent substrates formed in the shape of a disc having a predetermined thickness by injection-molding a transparent synthetic resin, and have uneven signal surfaces with grooves formed on each of the facing surfaces in a spiral or concentric circular pattern. Pits are formed on the signal surfaces for recording optical information.
  • a thin semitransparent film 22 is coated along the rugged surface of the first substrate 21 so that the film 22 has a rugged surface that is the same as the rugged surface of the first substrate 21.
  • the material and thickness of the semitransparent film 22 determine the reflectivity of the signal surface of each of the first and second substrates 21 and 25.
  • the semitransparent film 22 is formed of GaP to be a thin single layer having a thickness of 7nm to 16nm.
  • the thickness of a GaP layer which satisfies the specification in which the reflectivities of the signal surfaces of the two substrates 21 and 25 must be the same value of at least 18%, is between 7nm and 16nm.
  • the thickness of the GaP layer is 10.4nm.
  • formation of the GaP semitransparent film to a thickness of about 10.4 nm is optimal.
  • the GaP thin single layer, which is the semitransparent film 22, is formed to have a thickness of 7 to 16nm.
  • the semitransparent film 22 is a thin single layer formed of aluminum (Al).
  • the thickness of the Al layer which satisfies the specification in which the reflectivities of the signal surfaces of the two substrates 21 and 25 must be the same value of at least 18%, is between 3nm and 7nm.
  • the thickness of the Al layer is 4.8nm.
  • formation of the Al semitransparent film to a thickness of about 4.8 nm is optimal.
  • the Al thin single layer, which is the semitransparent film 22, is formed to have a thickness of 3 to 7nm.
  • the semitransparent film 22 is a thin single layer formed of silver (Ag).
  • the thickness of the Ag layer which satisfies the specification in which the reflectivities of the signal surfaces of the two substrates 21 and 25 must be the same value of at least 18%, is between 15nm and 25nm.
  • the thickness of the Ag layer is 19.3 nm.
  • formation of the Ag semitransparent film to a thickness of about 19.3 nm is optimal.
  • the Ag thin single layer, which is the semitransparent film 22, is formed to have a thickness of 15 to 25 nm.
  • the semitransparent film 22 can be a thin single layerformed of GaP, Al or Ag to a thickness of 7 to 16nm, 3 to 7nm, or 15 to 25nm, respectively. Accordingly, even when a 410nm-wavelength blue laser beam is used as a reproduction light source, the specification in which the reflectivities of the signal surfaces of the substrates 21 and 25 must have the same value of at least 18%, is satisfied, thereby achieving accurate and stable information reproduction.
  • a spacer 23 made of translucent ultraviolet hard resin or the like is deposited to a predetermined thickness on the semitransparent film 22 as in conventional two-layer optical discs, and thus connects the first and second substrates 21 and 25, and also reduces the cross-talk between the signal surfaces of the two substrates 21 and 25.
  • a total reflection film 24 is tightly coated along the rugged surface of the second substrate 25 so that the film 24 has a rugged surface that is the same as the rugged surface of the second substrate.
  • the total reflection film 24, which is typically a thin metal film having a high reflectivity, is usually formed of aluminum (Al) or an aluminum alloy.
  • reproduction light beams L1 and L2 radiated by an optical pickup are made to be focused on the signal surface of the first substrate 21 and that of the second substrate 25, respectively, so that light reflected and modulated by pits formed on each of the signal surfaces is received.
  • reproduction of desired information can be achieved.
  • the specification in which the reflectivities of the signal surfaces of the substrates 21 and 25 must have the same value of at least 18%, can be satisfied by the material and thickness of the semitransparent film 22 described above.
  • the signal surface of each substrate can provide a reflectivity of at least 18% even when a blue laser beam having a short wavelength between 400nm and 500nm is used as a reproduction light source, so that accurate and stable reproduction of information can be achieved.

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  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Optical Record Carriers And Manufacture Thereof (AREA)

Abstract

A two-layer optical disc formed by sequentially stacking a semitransparent film, a spacer layer, a total reflection film, and a second substrate on a first translucent substrate having a predetermined index of refraction, in which the semitransparent film is a thin single layer formed of GaP, Al or Ag to a thickness of 7 to 16nm, 3 to 7 nm, or 15 to 25nm, respectively. Accordingly, even when a blue laser beam having a wavelength between 400nm and 500nm is used as a reproduction light source, the specification in which the reflectivities of the signal surfaces of the two substrates must have the same value of at least 18%, is satisfied.

Description

OPTICAL RECORDING MEDIUM
Technical Field
The present invention relates to an optical recording medium such as a compact disc or laser disc, and more particularly, to a reproduction- dedicated two-layer optical disc having a signal surface with a two-layer structure.
Background Art Reproduction-dedicated optical discs such as compact discs (CD), laser discs (LD) and digital versatile discs (DVD) are well known as representative optical recording media. Recently, these discs are manufactured to be, so-called, multi-layer optical discs in which a reflective layer having pits and grooves on which necessary information is recorded is formed to have a multi-layer structure.
FIG. 1 is a vertical cross-sectional view of a reproduction-dedicated optical disc (hereinafter, referred to as a two-layer optical disc) having a two- layer signal surface, which is a model of an optical information medium having a multi-layer structure. Referring to FIG. 1 , a conventional two-layer optical disc has first and second substrates 11 and 15 which are positioned opposite to each other.
The first and second substrates 11 and 15, which are typically translucent substrates formed in the shape of a disc having a predetermined thickness by injection-molding a transparent synthetic resin, have signal surfaces which are uneven because of the formation of grooves on each of the facing surfaces in a spiral or concentric circular pattern. Pits are formed on the signal surfaces for recording optical information.
A thin semitransparent film 12 is coated along the rugged surface of the first substrate 11 so that the film 12 has a rugged surface that is the same as the rugged surface of the first substrate. The semitransparent film 12 has non- variable reflectivity and permeability, and is typically a single-layer gold film
80BSTITUTESHEEr(RULE26) or a three-layer dielectricfilm. In actual manufacturing, a single-layer gold film is usually used in consideration of the manufacturing cost.
A spacer 13 made of translucent ultraviolet hard resin or the like is deposited to a predetermined thickness on the semitransparent film 12, and thus connects the first and second substrates 11 and 15 and also reduces the cross-talk between the signal surfaces of the two substrates 11 and 15.
A total reflection film 14 is tightly coated along the rugged surface of the second substrate 15 so that the total reflection film 14 has a rugged surface that is the same as the rugged surface of the second substrate. The total reflection film 14, which is typically a thin metal film having a high reflectivity, is usually formed of aluminum (Al) or an aluminum alloy.
A two-layer optical disc having such a configuration allows reproduction light beams L1 and L2 radiated from an optical pickup (not shown) to be focused on the signal surface of the first substrate 11 and that of the second substrate 15, respectively, and thus receives reflective light modulated by pits formed on each of the signal surfaces. Thus, reproduction of desired information can be achieved.
This two-layer disc must have small and high-density grooves and pits formed on the reflection layer, in order to record a large amount and high density of information. Since an optical pickup uses a laser beam having a short wavelength as a reproduction light source, the specification of optical discs, that is, the specification in which the reflectivities of the signal surfaces of the substrates 11 and 15 of the optical disc must have the same value of at least 18%, must be satisfied in order to achieve accurate and stable information reproduction.
However, in a conventional two-layer optical disc having a semitransparent single-layer gold film as described above, when a laser for emitting blue light having a wavelength between 410nm and 650nm is used as a reproduction light source, both the reflectivity and permeability of the single-layer gold film are reduced. In fact, a reflectivity of 14% or higher cannot be obtained from the signal surface of each of the substrates 11 and 15. This failure in meeting the above-described specification prevents accurate and stable reproduction of information.
Disclosure of the Invention To solve the above problem of conventional two-layer optical discs, an objective of the present invention is to provide a two-layer optical disc having a single-layer semitransparent film, in which a reflectivity of at least 18% is provided from each signal surface even when a blue laser having a short wavelength is used as a reproduction light source, so that a specification enabling accurate and stable information reproduction is satisfied.
The above objective of the present invention is achieved by a two-layer optical disc formed by sequentially stacking a semitransparent film, a spacer layer, a total reflection film, and a second substrate on a first substrate having a predetermined index of refraction, the optical disc characterized in that the semitransparent film is a GaP thin film layer.
Here, the semitransparent GaP thin film layer is formed to a thickness of 7 to 16nm.
Also, the semitransparent film can be an aluminum layer. In this case, preferably, the semitransparent aluminum film is formed to a thickness of 3 to 7nm.
Also, the semitransparent film can be a silver layer. In this case, preferably, the semitransparent silver film is formed to a thickness of 15 to 25nm.
In a two-layer optical disc according to the present invention having such a structure, a blue laser beam having a wavelength between 400nm and 500nm, which is used as a reproduction light beam, is emitted onto the signal surface of each of the first and second substrates, thereby reproducing information.
Brief Description of the Drawings
FIG. 1 is a cross-sectional view schematically illustrating the structure of a conventional two-layer optical disc;
FIG. 2 is a cross-sectional view schematically illustrating the structure of a two-layer optical disc according to an embodiment of the present invention; FIG. 3 is a graph showing variation in the reflectivity of the signal surface of each substrate according to the thickness of a GaP semitransparent film, when a 410nm-wavelength blue laser beam is used as the reproduction light source of a two-layer optical disc according to an embodiment of the present invention; FIG. 4 is a graph showing variation in the reflectivity of the signal surface of each substrate according to the thickness of an Al layer, when a 410nm-wavelength blue laser beam is used as the reproduction light source of a two-layer optical disc according to another embodiment of the present invention in which a semitransparent film is formed of aluminum (Al); and FIG. 5 is a graph showing variation in the reflectivity of the signal surface of each substrate according to the thickness of an Ag layer, when a 410nm-wavelength blue laser beam is used as the reproduction light source of a two-layer optical disc according to still another embodiment of the present invention in which a semitransparent film is formed of silver (Ag).
Best mode for carrying out the Invention
A reproduction-dedicated optical disc having a two-layer structure according to the present invention shown in FIG. 2 has substantially the same structure as a conventional two-layer optical disc shown in FIG. 1 , except for the material and thickness of a semitransparent film. The two-layer optical disc according to the present invention is characterized in that a blue laser beam having a wavelength ranging from 400 to 500nm is used as a reproduction light beam emitted onto the signal surface of each substrate.
Referring to FIG. 2, the two-layer optical disc according to the present invention has first and second substrates 21 and 25 which are positioned to face each other. The first and second substrates 21 and 25 are typically translucent substrates formed in the shape of a disc having a predetermined thickness by injection-molding a transparent synthetic resin, and have uneven signal surfaces with grooves formed on each of the facing surfaces in a spiral or concentric circular pattern. Pits are formed on the signal surfaces for recording optical information.
A thin semitransparent film 22 is coated along the rugged surface of the first substrate 21 so that the film 22 has a rugged surface that is the same as the rugged surface of the first substrate 21. The material and thickness of the semitransparent film 22 determine the reflectivity of the signal surface of each of the first and second substrates 21 and 25.
In a two-layer optical disc according to an embodiment of the present invention, the semitransparent film 22 is formed of GaP to be a thin single layer having a thickness of 7nm to 16nm.
Referring to FIG. 3, it can be seen that the thickness of a GaP layer, which satisfies the specification in which the reflectivities of the signal surfaces of the two substrates 21 and 25 must be the same value of at least 18%, is between 7nm and 16nm. In particular, in a case when the reflectivity is the highest, 28.3%, while satisfying the above specification, the thickness of the GaP layer is 10.4nm. Thus, in this embodiment of the present invention, formation of the GaP semitransparent film to a thickness of about 10.4 nm is optimal. Preferably, the GaP thin single layer, which is the semitransparent film 22, is formed to have a thickness of 7 to 16nm.
In a two-layer optical disc according to another embodiment of the present invention, the semitransparent film 22 is a thin single layer formed of aluminum (Al).
Referring to FIG. 4, it can be seen that the thickness of the Al layer, which satisfies the specification in which the reflectivities of the signal surfaces of the two substrates 21 and 25 must be the same value of at least 18%, is between 3nm and 7nm. In particular, in a case when the reflectivity is the highest, 25.8%, while satisfying the above specification, the thickness of the Al layer is 4.8nm. Thus, in this embodiment of the present invention, formation of the Al semitransparent film to a thickness of about 4.8 nm is optimal. Preferably, the Al thin single layer, which is the semitransparent film 22, is formed to have a thickness of 3 to 7nm.
In a two-layer optical disc according to still another embodiment of the present invention, the semitransparent film 22 is a thin single layer formed of silver (Ag).
Referring to FIG. 5, it can be seen that the thickness of the Ag layer, which satisfies the specification in which the reflectivities of the signal surfaces of the two substrates 21 and 25 must be the same value of at least 18%, is between 15nm and 25nm. In particular, in a case when the reflectivity is the highest, 28.3%, while satisfying the above specification, the thickness of the Ag layer is 19.3 nm. Thus, in this embodiment of the present invention, formation of the Ag semitransparent film to a thickness of about 19.3 nm is optimal. Preferably, the Ag thin single layer, which is the semitransparent film 22, is formed to have a thickness of 15 to 25 nm.
In a two-layer optical disc according to the present invention, as described above, the semitransparent film 22 can be a thin single layerformed of GaP, Al or Ag to a thickness of 7 to 16nm, 3 to 7nm, or 15 to 25nm, respectively. Accordingly, even when a 410nm-wavelength blue laser beam is used as a reproduction light source, the specification in which the reflectivities of the signal surfaces of the substrates 21 and 25 must have the same value of at least 18%, is satisfied, thereby achieving accurate and stable information reproduction.
In the structure of a two-layer optical disc of the present invention as described above, a spacer 23 made of translucent ultraviolet hard resin or the like is deposited to a predetermined thickness on the semitransparent film 22 as in conventional two-layer optical discs, and thus connects the first and second substrates 21 and 25, and also reduces the cross-talk between the signal surfaces of the two substrates 21 and 25. Also, a total reflection film 24 is tightly coated along the rugged surface of the second substrate 25 so that the film 24 has a rugged surface that is the same as the rugged surface of the second substrate. The total reflection film 24, which is typically a thin metal film having a high reflectivity, is usually formed of aluminum (Al) or an aluminum alloy.
According to the two-layer optical disc of the present invention having such a configuration, reproduction light beams L1 and L2 radiated by an optical pickup are made to be focused on the signal surface of the first substrate 21 and that of the second substrate 25, respectively, so that light reflected and modulated by pits formed on each of the signal surfaces is received. Thus, reproduction of desired information can be achieved. At this time, the specification in which the reflectivities of the signal surfaces of the substrates 21 and 25 must have the same value of at least 18%, can be satisfied by the material and thickness of the semitransparent film 22 described above.
Industrial Applicability
In a two-layer optical disc according to the present invention, the signal surface of each substrate can provide a reflectivity of at least 18% even when a blue laser beam having a short wavelength between 400nm and 500nm is used as a reproduction light source, so that accurate and stable reproduction of information can be achieved.

Claims

What is claimed is:
1. A two-layer optical disc formed by sequentially stacking a semitransparent film, a spacer layer, a total reflection film, and a second substrate on a first translucent substrate having a predetermined index of refraction, the optical disc characterized in that the semitransparent film is a GaP thin film layer.
2. The two-layer optical disc of claim 1 , wherein the GaP thin film layer is formed to a thickness of 7 to 16nm.
3. A two-layer optical disc formed by sequentially stacking a semitransparent film, a spacer layer, a total reflection film, and a second substrate on a first translucent substrate having a predetermined index of refraction, the optical disc characterized in that the semitransparent film is an aluminum layer having a thickness of 3 to 7nm.
4. A two-layer optical disc formed by sequentially stacking a semitransparent film, a spacer layer, a total reflection film, and a second substrate on a first translucent substrate having a predetermined index of refraction, the optical disc characterized in that the semitransparent film is a silver layer having a thickness of 15 to 25nm.
PCT/KR2000/000790 1999-07-21 2000-07-21 Optical recording medium WO2001006504A1 (en)

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KR1019990029532A KR20010010565A (en) 1999-07-21 1999-07-21 Optical recording medium

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1770695A1 (en) * 2004-07-16 2007-04-04 Sony Corporation Multilayer optical recording medium and manufacturing method thereof

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002342980A (en) * 2001-05-14 2002-11-29 Sharp Corp Optical information recording medium
JP2002352469A (en) * 2001-05-25 2002-12-06 Pioneer Electronic Corp Multilayer information recording medium and information recording/reproducing device

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09237438A (en) * 1996-02-29 1997-09-09 Sanyo Electric Co Ltd Optical recording medium
JPH09293270A (en) * 1996-04-24 1997-11-11 Pioneer Electron Corp Double layer optical disk
US5777969A (en) * 1995-06-08 1998-07-07 Matsushita Electric Industrial Co., Ltd. Dual-layered optical disc and pickup head

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100402169B1 (en) * 1995-04-27 2004-03-10 닛폰콜롬비아 가부시키가이샤 Multi-layer structure photo information media
JPH1031844A (en) * 1996-07-17 1998-02-03 Hitachi Ltd Maltilayered optical information medium
JPH10188342A (en) * 1996-12-19 1998-07-21 Nippon Columbia Co Ltd Optical information recording medium and reproducing device therefor
JPH10302314A (en) * 1997-04-23 1998-11-13 Hitachi Ltd Multilayer structure optical information medium

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5777969A (en) * 1995-06-08 1998-07-07 Matsushita Electric Industrial Co., Ltd. Dual-layered optical disc and pickup head
JPH09237438A (en) * 1996-02-29 1997-09-09 Sanyo Electric Co Ltd Optical recording medium
JPH09293270A (en) * 1996-04-24 1997-11-11 Pioneer Electron Corp Double layer optical disk

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1770695A1 (en) * 2004-07-16 2007-04-04 Sony Corporation Multilayer optical recording medium and manufacturing method thereof
EP1770695A4 (en) * 2004-07-16 2008-12-24 Sony Corp Multilayer optical recording medium and manufacturing method thereof

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